Table of contents

E D V-Niño¹

¹Materials Science and Technology Research Group, Foundation of Researchers in Science and Technology of Materials, Colombia

E-mail: deydannv@gmail.com, foristom@gmail.com

These proceedings present the written contributions of the participants of the 5th International Meeting for Researchers in Materials and Plasma Technology (5th IMRMPT) which was held from 28 to May 31, 2019, at the San José de Cúcuta city, Colombia, organized by Foundation Of Researchers In Science and Technology Of Materials (FORISTOM). This was the fourth version of biennial meetings that began in 2011.

The proceedings consist of 148 contributions that were presented as plenary talks at the conference. The abstracts of all participants contributions were published in the Abstract Book with ISSN 2422-3824. The website of the conference is available at http://foristom.org/5imrmpt/index.html.

The fifth-day scientific program of the 5th IMRMPT consisted of 17 Magisterial Conferences, 111 Oral Presentations, 131 Poster Presentations, 3 Courses and 1 Discussion Panel with the participation of undergraduate and graduate students, professors, researchers and entrepreneurs from Colombia, Russia, Spain, Unite Kingdom, Mexico, Argentina, Uruguay, Brazil, Ecuador, Venezuela, among others. Moreover, the objective of IMRMPT was to bring together national and international researchers in order to establish a network of scientific cooperation with a global impact in the area of the science and the technology of materials; to promote the exchange of creative ideas and the effective transfer of scientific knowledge, from fundamental research to innovation applied to industrial solutions and to advance in the development of new research allowing to increase the lifetime of the materials used in the industry by means of efficient transference of the knowledge between sectors academia and industry.

List of Organizing Committee / Comité Organizador Local, National Scientific Committee / Comité Académico Nacional, International Scientific Committee / Comité Académico Internacional, Invited Speakers / Conferencistas Invitados, Sponsor, Partners are available in this pdf.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The low interlaminar tensile strength of fiber reinforced composite materials presents serious challenges in the design of structures with a considerable radius of curvature, which is commonly found in a wide range of fields such as aeronautics, civil engineering, maritime industry, energy industry, among others. The objective of the present research was to analyze the interlaminar tensile strength, in the interlaminar layer of a material composed of fiberglass as reinforcement in nylon matrix, using a curved beam elaborated by additive manufacturing. To achieve this, tests were carried out according to ASTM Standard, and to determine which parameters significantly influence the failure of the composite material, variations were made in the thickness of the test specimens, which were manufactured following the criteria of the standard. The results obtained allow the assessment of interlaminar tensile strength and specimen behavior after failure.

Additive manufacturing makes possible to overcome the limitations of subtractive manufacturing and supposes a transformation with respect to the traditional processes, allowing to manufacture complex geometries by controlled deposition of material. In the automotive industry, the application of continuous fiber reinforcement, in combination with shape optimization for additive manufacturing, can produce parts with higher mechanical performance. This paper reports the shape optimization problem of a suspension control arm to be produced by additive manufacturing with fiber reinforcement, using finite element analysis. First, the current material, loading conditions and constraints to which the control arm is subjected were determined, considering its traditional design. Then, a numerical model of the part was developed considering its current material and shape to obtain the total deformation and von Mises stress distributions. Afterwards, the new material model was defined, and the shape optimization was performed with the goal of maximizing stiffness. Finally, the results from the optimization process were validated by manufacturing and testing the part.

Commercial Portland cement is the most used construction material in the world, due its durability, versatility and economy generated in civil works, which follows a growth trend; however, a large amount of energy is required for its production, which generates a large amount of greenhouse gas emissions and air pollutants. Consequently, a large part of research has focused on mitigating these effects by partially replacing supplementary cementitious materials. Therefore, this research aims to evaluate the performance of commercial cement paste, partially replacing it with fly ash and blast furnace slag, characterized by scanning electron microscopy, X-ray fluorescence, surface area to establish variations of setting times and heat of hydration in hardening process. The results established that fly ash and blast furnace slag didn't generate sufficient capacities to develop stable cementation reactions and therefore higher strengths, due to their compositions surface area and the high content of alternative cements present in the commercial Portland cement since its manufacture. Nevertheless, the fly ash and blast furnace slag are alternatives in mitigating the environmental effect generated by commercial cements.

Composite materials are joined in many occasions with adhesive joints due to the condition of the materials, the ease of repair, the loading conditions, the affectation by corrosion and chemical attacks. However, the efficiency of these bonding schemes is related to multiple factors, among them, the length and the width of the adhesion zone and the thickness of the adhesive. In this work, we analyze the factors associated with the surface contact of the substrates. We define a numerical model using the finite element method and study the parameters related to the physical condition, considering optimal results based on the data of the strength provided by the suppliers of adhesives.

The organic composite materials are very competitive due to their low density and good flexibility by design, suitable for certain working conditions such as installations where high mechanical strength at a low weight is required. Additionally, they contribute to the environment by taking advantage of organic components that are currently waste. The composite proposed in this work consists of an epoxy matrix reinforced with African palm rachis fibers. The specimens were manufactured under the manual rolling process due to the nature of the reinforcement. Moreover, the variation of the interlaminar tensile strength was investigated, using a four-point flexion testing and varying the thickness of the specimen in order to evaluate the feasibility of the organic reinforcement. The experimental analysis was performed with a curved beam geometry and low flexion.

The importance of coatings in engineering has been predominant throughout the development of the new industrial era. The competitiveness of the field has led to the development of better materials that achieve superior properties. The purpose of this research is evaluating the adhesion to the surfaces coated by magnetron sputtering technique. The adherence quality of the deposited coatings on specimens was evaluated adhesion by scratch and indentation tests guided according to standards, using the Tribolab UMT at constant load. The results obtained allow validating of the additive manufacturing process as possible mechanicals applications.

Additive manufacturing of composites parts reinforced with continuous fibers is emerging as a versatile process, capable of producing complex computer-aided design models by fabricating parts adding material layer by layer. Fused deposition modelling using polymeric materials has been used to produce prototypes, with the constraint of the strength of the material. Recently, the use of continuous fiber reinforcement has provided an alternative for the production of load-bearing functional parts. Current international standards for the characterization of composite materials from mechanical tests are established for parts manufactured by conventional methods, such as, manual molding, injection or coatings. Moreover, the standards do not specify procedures for composite materials produced by additive manufacturing. The objective of this work is to evaluate the performance of the reinforced composite materials produced by additive manufacturing for tensile tests under ISO and ASTM standards, and compare the results in terms of the topology of the material configuration. Average values of the tensile strength for composite materials having a triangular nylon matrix reinforced with fiberglass were obtained within the range of 205 MPa to 234 MPa, with deformations no greater than 0.020 mm. These values are higher than the strength provided by additive manufacturing using materials such as polylactic acid and acrylonitrile butadiene styrene.

The titanium oxide nanotubes have generated great interest in recent years because to the wide variety of applications in which they are used. The reason for this is the excellent surface properties that this material gets after of grow in the anodizing process. These properties can easily modify the electrochemical anodizing process. For this reason, we have analyzed the effect of electrolyte on the morphology and corrosion resistance of titanium oxide nanotubes grown at glycerol with 0.3% w/w ammonium fluoride and 2% v/v distilled water at 30 volts for 1 hour and ethylene glycol with 0.3% w/w ammonium fluoride and 2% v/v distilled water at 40 volts for 30 minutes. The morphology of the surfaces is observed by scanning electron microscopy. The resistance to corrosion of the samples is evaluated by potentiodynamic polarization curves in Hanks solution at 37 °C. The results of the nanotubes grew in glycerol have a length of 0.7 μm with a morphology of the bamboo type, while the nanotubes grown in ethyleneglycol they have a length of 3.3 μm and their morphology is smooth wall. Regarding the corrosion rate, it was determined that the nanotubes grown in glycerol have a higher corrosion rate. Because to these low corrosion rates it is considered that the two surfaces can be used as alternatives to modify orthopedic implant materials.

Composite materials of polymer – carbon nanotubes have been widely studied for biomedical applications due to the versatility of polymers in this field and the excellent mechanical, thermal and electrical properties of carbon nanotubes. However, carbon nanotubes are materials which can provide some toxicity in biological systems, since they have low solubility in water and organic solvents, tend to form aggregates in solution, are bioincompatible and limited compatibility with polymeric matrices. For this reason, carbon nanotubes considered for biomedical applications must comply with this basic requirement of solubility. To improve the compatibility of the carbon nanotubes, they were exposed to treatment with HNO₃, NaOH and HCl to eliminate impurities and improve the solubility in other solvents. Polycaprolactone coatings at 2.5% w/v and multi-wall carbon nanotubes (0.5, 1.0 and 1.5 g/L) were developed to evaluate the electrochemical and bioactive properties. Techniques such as infrared spectroscopy, contact angle, scanning electron microscopy, atomic force microscopy, electrochemical impedance spectroscopy using simulated body fluid as electrolyte and the bioactivity of human osteoseosarcoma cells (HOS ATCC® CRL-1543) by alkaline phosphatase were used. From the reported characterizations, it was observed that the resistance to polarization increases according to the degree of dispersion of carbon nanotubes present in the polymer matrix, decreasing the degradation rate of the material.

Titanium and its alloys are currently the main materials for prosthetics, despite the fact that they, like other metals, have significant drawbacks: they cause metallosis, can provoke the formation of fibrous tissues and bone resorption in the contact zone, are toxic and, in some cases, allergenically dangerous. The noveday trend in implant technology is the prevention of direct contact of living tissues with the metal surface. For this reason, various types of protective coatings are used, usually on the base of ceramics or carbon. It is known that in the contact zone it is preferable to create a well-developed or even porous surface with osteoconductive and osseointegrative properties. This paper discusses the combined technology of modification of titanium. Implant surface treatment includes two main stages: 1) growing a porous protective layer of titanium dioxide deep into the material surface and 2) filling the pores formed on the surface of titanium dioxide with hydroxyapatite to ensure high osseointegrative properties. The formation of a layer of titanium dioxide is provided by micro arc oxidation processing with controllable density of pulsed current; then the pores are filled with crystalline hydroxyapatite by detonation spraying. The results of studying the structure and surface properties of the modified titanium samples are presented and discussed.

The procedure for obtaining electrodes modified with poly(3,4-ethylenedioxythiophene) has been widely studied for its multiple applications. This study evaluates the potential contribution of electrodes modified with poly(3,4-ethylenedioxythiophene) for desalination of seawater. Potentiostatic electropolymerization of 3,4-ethylenedioxythiophene was conducted on 6 cm² steel electrodes by using a supporting electrolyte consisting of lithium perchlorate in acetonitrile. This modified electrode was used in the extraction of anions and cations from samples of synthetic seawater by means of 20 extraction cycles (optimal cycles) and using a combination of p-type and n-type doping. A total of 140 extractions (number of optimal extractions) were carried out, which led to desalination of synthetic seawater by about 80-90%, as evidenced by the decrease in the conductivity of the solution containing the ions. Therefore, this procedure could become an alternative for seawater desalination.

A hydrophobic pH sensitive nanocontainer was fabricated using smart surfaces covalently attached to a porous alumina support. The smart surface was synthesized using a mixture of aliphatic and aminated silanes and optimized to be hydrophobic at pH<7 and hydrophilic at pH<5. The hydrophobic nanocontainer thus synthesized was able to retain a cargo of the model molecule safranine at neutral pH. When pH decreased, safranine was liberated at a high rate due to the large pores of the alumina. It is expected that the nanocontainer here presented could constitute the basis of a cancer treatment as an effective drug delivery system in chemotherapy.

With the advent of nanotechnology, graphene has gained relevance in the last two decades, due to its exceptional mechanical, electrical and thermal properties. This material being one of the thinnest existing, has at the same time great mechanical strength, flexibility, is transparent, in addition to very good conductor of electricity, much better than copper or any other known material. These properties are due to its structure constituted by a flat monoatomic sheet of carbon atoms arranged cyclically with the same structure of benzene. Several layers (>10) of superimposed graphene constitute the well-known graphite structure. To obtain it, among other methods, plasma enhanced chemical vapor deposition has been used, which uses electric discharges in the radiofrequency regime. In this work, the formation of graphene in the plasma of the abnormal glow discharge of direct current is reported. For this purpose, a mixture of 60% Ar, 5% C₂H₂ and 35% H2 is used as gas atmosphere, at a pressure of 2.0 torr. Electrolytic copper sheets were used as substrate. Temperature of the process was 600 °C and the formation time was 5 s. Deposits characterization was made by infrared spectroscopy and Raman spectroscopy.

The extensive use of smartphones is increasingly generating technological waste, such as the spent lithium-ion spent batteries, which contains potentially toxic metals that may affect the environment. These metals can be recovered and used as raw material for new industrial applications, such as the production of metal coatings. In this work, a sample of spent lithiumion batteries was manually disassembled, to extract transition metal-rich cathodes. The cathodes were separated and crushed in a blade mill, to obtain a cobalt-rich concentrate powder by sieving. The powder was leached using a 1.11 M citric acid solution amended with hydrogen peroxide (1.25% volume), at 74°C under stirring at 300 rpm. The obtained polymetallic liquor was analyzed for Co, Li, Mn, and Ni, then it was submitted for electrolysis to produce metal coatings over pure copper substrates. This electrochemical electrodeposition was studied by means of cyclic voltammetry and chronoamperometry, using electrolytic Cu as a working electrode (substrate), a reference electrode Ag/AgCl and an auxiliary graphite electrode. The visual appearance of the obtained coatings was analyzed by an Olympus SZ61 stereoscope, with images at a magnification of 120x. The results showed that by applying a -950 mV vs Ag/AgCl electrodeposition potential, a homogeneous coating with good adhesion and better visual appearance was obtained. In addition, at this potential, there was little influence of the reaction of hydrogen evolution reaction during the production of the coatings.

Graphene oxide and reduced graphene have been exfoliated from graphite oxide synthesized by Hummer's method. In order to establish a comparison, the exfoliation process was performed using two different methods, high energy ball milling and sonication. Each one was studied in two different media, organic solvent N-methyl 2 pyrrolidone and deionized water, obtaining four different products. The quality of the graphene and graphene oxides was studied using Raman spectroscopy. Structural characterization was performed using X-ray diffraction technique. The presence of oxygen-containing functional groups was determined by Fourier transform infrared spectra, while the morphology was investigated by scanning electron microscopy and energy-dispersive spectroscopy. The aim of this work is present a process to obtain graphene and graphene oxide of high quality at lower cost and better environmental conditions.

In the industry of hard coatings, the vacuum arc evaporator is one of the commonly used devices due to its high productivity, reliability and ability to operate in a non-gaseous medium. Apart from this, the imposition of an external magnetic field allows to control the localization of the arc spots both on the simple and sectioned (i.e. made from different materials) cathode surfaces. Another important feature of the vacuum arc evaporators is their capability to generate multi-charged ions. Applying a high voltage negative bias to the substrate, there can be formed the coatings with high adhesion due to the implantation effect. This paper presents some results of the study of the plasma flows generated by an industrial vacuum arc evaporator with a sectioned disk cathode composed of a zirconium in its central part with a titanium ring surrounding it. The mode of evaporator functioning is such that the arc spot motion gets limited by the zirconium disk, which results in producing the zirconium plasma flow. The quantitative characteristics and the energy distribution function of ions have been measured by a multigrid probe with a retarding potential. It has been proved that the multiply charged ions make up a significant part of the flow. The relations between the detected ion components are found as 87.4% Zr⁺, 10.6% Zr²⁺, 1.5% Zr³⁺ and 0.3% Zr⁴⁺. The presence of multi-charged ions is also confirmed by optical spectrometry measurements.

Chromium silicon nitride coatings were deposited via physical vapor deposition using a reactive sputtering magnetron, on steel specimens, with a chromium silicate target, purity of 99.5% and argon/nitrogen gas ratio (%) of 80/20. The coating characterization was carried out by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and nano hardness. The erosion-corrosion analysis was performed with a pin on disc tribometer, with a zircon pin, load of 1 N, applying three rotation speeds of the system (250 rpm, 400 rpm and 500 rpm) with an electrolyte composed of water, silica sand (0.05 mm, 0.1 mm and 0.15 mm) and 1% of sodium chloride. The electrochemical techniques used were resistance to polarization, electrochemical impedance spectroscopy and potentiodynamic polarization. The coating decreases the rate of substrate wear between 32% and 56%. The coefficient of friction decreases by almost 50% with the application of the film. Finally, the coating reduces by an order of magnitude the corrosion rate of steel in systems subject to wear and in 3 orders of magnitude in steel systems in static conditions, increasing the useful life of industrial facilities.

Sol-gel synthesis has been used since 1950 to prepare oxides. The method is attractive because the processes of obtaining the oxides are developed at room temperature; products with high purity and homogeneity are obtained, and allow the combination of several types of oxides: silicon, zirconium, titanium, aluminum, bismuth, and cerium. Sol-gel has been used to make ceramic composites with anticorrosive properties on stainless steel substrates. A class of stainless steel widely used in biomedical applications, especially in the treatment of fractures, 316L is its low economic cost relative to other materials such as titanium. Once the steel implant is inside the human body it comes into contact with body fluids that contain chloride ions. The fluid-implant interaction develops a corrosive process on the metal surface. The corrosive products of iron diffuse in the body causing tissue damage. As a possible solution to this problem, the objective of the investigation was to obtain a bismuth-titanium oxide using the sol-gel method and apply it on 316L stainless steel substrates. Bismuth nitrate pentahydrate and titanium tetrabutoxide were used as precursors. The anticorrosive response was evaluated in a simulated physiological solution, Ringer's solution, by electrochemical impedance spectroscopy and potentiodynamic polarization curves. It is concluded that the coatings function as a corrosion barrier preventing the chloride ions Ringer's solution reach the metal surface.

The bismuth silicate compound was synthesized by the sol-gel method from bismuth nitrate pentahydrate and tetraethoxysilane, as precursors. The sol-gel method is attractive because the processes for obtaining oxides are developed at room temperature. In addition, it allows precise control over the composition, homogeneity, and deposition of coatings. The impact of bone-related diseases and trauma has increased significantly, in recent decades in developed and developing countries. There are materials such as bioactive glasses, especially silica compounds, which are called to play a very important role in this area, due to properties such as osteoconductivity, osteoproduction, and osteoinduction. For 20 years, the sol-gel method and the supramolecular chemistry of surfactants have been incorporated into the field of bioceramics, which allows the control, on a nanometric scale, of porosity in bioglasses. The sol-gel method has allowed obtaining bioactive materials with high surface area and high porosity. The study consisted of shaping soles by varying the molar concentrations of tetraethoxysilane and assessing the effect on aging, viscosity, determining the presence of specific functional groups and establishing the transformations that take place as a function of temperature. The results allowed characterizing each of the sol for possible application in bioglasses.

The objective of this research is to perform a topographic characterization by atomic force microscopy of the surface of bismuth titanate (Bi/Ti) coatings varying the number of layers deposited on the substrates, considering that there were not results of reported studies in which these precursors were used. It is important to analyze the surface behavior of these coatings as a first phase of future researches to establish the viability of possible uses and applications in biomedical industry. The films were synthesized by the sol-gel method from bismuth nitrate pentahydrate and titanium tetrabutoxide. Subsequently, by means of the spin- coating technique, the coatings were deposited on 316L stainless steel in monolayer and bi- layer, as this type of steel has been widely used for medical applications due to its good compatibility. The roughness values of each of the coatings were also determined. It is concluded that there is a relationship between the topography of the surface and the roughness values of the films with respect to the concentration of the precursors, the number and the speed of centrifugation of the layers deposited on the substrate. High concentrations of titanium tetrabutoxide effect on the good densification characteristics of the coatings.

316 stainless steel low carbon vacuum melted, used for surgical implants, has good corrosion resistance, but it is degraded in the body fluids presence, generating problems for the receiver, therefore it is necessary to apply coatings that improve their biocompatibility. In the current work hydroxyapatite and tricalcium beta phosphate coatings were applied on 316 stainless steel substrates, by the radio frequency magnetron sputtering technique, with a 2 m thickness for possible biomedical applications. The coatings characterization was performed, using scanning electron microscopy, found the Ca/P ratio of 1.639 for hydroxyapatite and 1.515 for phosphate, the friction coefficient was additionally evaluated by pin on disk tribometer, with a lower coefficient of beta tricalcium phosphate in relation to hydroxyapatite. The corrosion evaluation was carried out using the electrochemical polarization technique Tafel, in Ringer lactate, as simulated biological fluid. It was observed that the coatings improve the steel electrochemical behavior and between the two coatings the one that best behaves is the tricalcium beta phosphate, with a corrosion low rate.

Tungsten carbide is used in the production of cutting tools for steel and as protection against wear due to its extremely high hardness. High speed oxygen fuel spraying process has been widely used to deposit WC-Co coatings. However, the decomposition and oxidation of WC-Co has been reported during the process, where carbon and tungsten are released, resulting in the formation of an amorphous matrix with the cobalt of the compound. This is attributed to the high heating and cooling rates suffered by the raw material. An alternative method is the thermal spray by flame, which allows controlling the working temperature and the residence time of the particles in the hot flame, avoiding the decomposition of tungsten carbide, on the other hand, it is a versatile and a low cost method. In this study projection parameters of a WC-18Co coating sprayed with a thermal flame spraying process from a commercial feedstock powder were determined to decide the conditions under which compact coatings are obtained with low porosity, avoiding dissociation of the tungsten carbide. The composition of the powders and substrates was determined by X-ray fluorescence microscopy and optical emission, respectively, X-ray diffraction studies were performed to characterize compositions and microstructures the coatings sprayed; the morphology was by scanning electron microscope. It was found that the best condition for this type of coatings is a neutral flame at a projection distance of 12 cm.

The metal alloys used for prostheses with high mechanical requirements are bioinerts, it means they have low integration with bone tissue, therefore, bioactive coatings are used in order to improve this integration. Hydroxyapatite is one of the most studied materials for this application with good results, however, sometimes there are problems due to wear or tear of the coating leading prostheses loss. Tricalcium phosphate, Ca₃(PO₄)₂, in its different phases shows osteoconductivity and higher solubility than hydroxyapatite, however, few studies have been carried out to determine its behavior as a coating for this type of applications. In this work, a study of the behavior of tricalcium phosphate as a coating on Ti6Al4V substrates obtained by flame spraying was carried out. As raw material were used tricalcium phosphate powders obtained by precipitation from calcium nitrate and ammonium phosphate dihydrogen solution, and subsequent calcination at 1,100°C. The Ca/P molar ratio obtained is 1.48 and the only present crystalline phase is beta -tricalcium phosphate. The coatings obtained have alpha tricalcium phosphate as only crystalline phase, they have compact morphology with low porosity and good wettability with the substrate, which is an index of good adhesion and good mechanical behavior. The transformation from beta- to alpha- tricalcium phosphate is product of the high temperatures used in the process, which are higher than 1,125°C where this transformation occurs.

The research addresses an analysis of the level of contamination generated by the gases produced when applying low-pressure cold plasma in a cleaning process of metal sheets used in the manufacture of white goods. A mixture of argon and oxygen ionized gases at 50% was utilized to break down the lubricating oil molecules deposited on the surface of the sheet metal. A statistically significant number of samples were selected, with different volumes of oil on the surface, between 6 ml and 34 ml. The samples were later subjected to a plasma discharge with a time of 72 s, a gas pressure of 0.6 bar and 50% power to determine the correlation of the oil volume with the levels of gases generated by the discharge, maintaining the degree of surface cleanliness, as given by contact angle values between 67.5 and 79 degrees, constant. For the analysis of results a Pearson correlation was applied for each detected gas. An analysis was later conducted of the relationship between the degree of cleanliness of the metallic surface, as given by contact angles at 16, 36 and 53 degrees, with the levels of the gases generated by the plasma discharge, keeping the volume of the lubricating oil on the surface constant at 5 ml. For the analyses, statistical tests were carried out to find the correlation between the predictor variables and the dependent variable to establish a multivariate linear statistical model. The results allowed the behavior of the level of contamination to be determined, establishing that the volume of oil does not influence the level of the gases generated by the use of low-pressure cold plasma. The results obtained allow us to understand the relationship between the contact angle that represents the quality of surface cleaning of oil-impregnated sheet metal and the level of contamination generated in the process.

Depositing the solid waste generated by wastewater treatment in landfills presents an environmental problem due to the leaching of nitrogen and subsequent eutrophication and contamination of aquafers. Glass is a material with a wide array of uses which is often disposed of after completing its use. This study evaluates an alternative to the production of bricks by replacing clay for recycled glass and sludge ash in proportions of 10% and 20%. The physical properties of the fabricated bricks (compressive strength, water absorption, and the initial rate of absorption) were then measured. The temperature used in the firing process was 950 °C. The fabricated bricks utilizing the proposed mixtures complied with the Colombian technical code for structural and non-structural brick exceeding 20 MPa. This alternative method of brick fabrication reduces the environmental impact of glass and solid waste on the ecosystem and reduce freshwater contamination. It will also solve the issue of the sludge waste produced by wastewater treatment plants.

We investigate the effects of increasing in the concentration of Cr atoms on the structural and electronic properties of Nb_1-xCr_xN alloys in the concentrations (x = 0.0,0.125,0.25,0.50,0.75 and 1.0) in the NiAs phase. For NbN and CrN in all concentrations, the calculations were carried out using the Quantum ESPRESSO code through the pseudopotential method within the framework of density functional theory. Regarding the structural properties, it was found that the lattice constant of the alloys decreases while the concentration of Cr increases. The bulk modulus of the alloys changes slightly compared to the bulk modulus of the binary NbN compound. Furthermore, the density of states calculations shows that the incorporation of Cr into the NbN matrix gives magnetic properties to the NbN. All the alloys have a metallic-ferromagnetic character.

We report the results of a study with Ti-doped AlN and GaN in the cubic-zincblende phase of the Al_0.9375Ti_0.0625N and Ga_0.9375Ti_0.0625N concentrations. All calculations were carried out using the Quantum ESPRESSO code through the pseudopotential method within the framework of density functional theory. The structural results show that the lattice constants of the Al_0.9375Ti_0.0625N and Ga_0.9375Ti_0.0625N compounds do not change compared to pure forms of c-AlN and c-GaN, yet the bond length of Ti-N increases compared to the bond length of Ga-N in pure c-AlN and c-GN. The electronic analyses reveal that both the Al_0.9375Ti_0.0625N and Ga_0.9375Ti_0.0625N compounds are ferromagnetic. The Al_0.9375Ti_0.0625N compound exhibits a metallic behavior with a total magnetic moment of 0.85 μ_β/cell, whereas Ga_0.9375Ti_0.0625N exhibits a halfmetallic character with a magnetic moment of 1.0 μ_β/cell. The magnetic effect in the Al_0.9375Ti_0.0625N and Ga_0.9375Ti_0.0625N compounds is the result of a strong hybridization between Ti-3d and N-2p. It is concluded that the Ga_0.9375Ti_0.0625N compound is a suitable candidate for a diluted magnetic semiconductor with potential use in applications such as spintronics, spin injection or magnetic memories.

In this paper, Ab-initio calculations are reported on the electronic and magnetic behavior of a 1x1-MnN/GaN superlattice in the wurtzite structure under hydrostatic pressure. The calculations were performed using the formalism of density functional theory with the generalized gradient approximations in the Perdew, Burke and Ernzerhof model, as well as the Wien2k computational package. The density of state shows that the electronic structure and the magnetic moment are affected by the hydrostatic pressure, because there is an abrupt change in the magnetic moment, which goes from 0 to 2.86 μ_β/cell under a pressure of ∼ 24.45 GPa. When the pressure decreases to 0 GPa, the magnetic moment of the superlattice rises to 4.0 μ_β/cell. Therefore, the superlattice exhibits a half-metallic behavior for a pressure of 0 GPa, while it acquires a metallic behavior when pressure surpasses 24.45 GPa.

In this numerically work, we study the effects of edges on the electronic properties of graphene lattices in the quantum Hall regime using a proposed quantity called participation ratio, that is employed to analyze the localization properties of edge states. We use the tight- binding model to include the effects of the magnetic field and disorder. The effect of the edges on the energy levels of the system is studied through Hofstadter's butterfly-like spectrum. Using the participation ratio and analyzing the contributions of the armchair and zigzag edges separately, we find that there are energy regions where the wave functions are clearly more localized in a specific edge type. The zigzag preferential localization is a reminiscence of the case without magnetic field and the armchair localization which is dependent on the disorder and the strength of the magnetic field, comes from the presence of magnetic field in the system. The results obtained contribute to the understanding of the localization properties of graphene lattices with edges.

Composite materials reinforced with organic fibers have attracted great interest in the area of mechanical engineering in recent decades due to the wide variety of industrial applications where these materials can be used, and the low impact on the environment, compared with traditional materials. In this work, experimental and numerical tests are carried out to investigate the mechanical response to a tensile load of a composite material with an epoxy matrix, reinforced with sugar cane fibers. Mechanical tests under the ASTM standard for tensile loads were performed. Then, a numerical model to investigate the mechanical response of the composite is done by finite element analysis. Results indicate that this composite material has good performance under axial loading conditions, and can be used for structural applications.

A study of the mechanical behavior of self-compacting concrete mixtures under sand replacement (as fine aggregate) by iron slag (residue from industrial machining) from 0.0% to 50.0% of mass, variations of water/cementitious material ratio between 0.3 and 0.5 and nano SiO₂ incorporation between 0.0% and 2.0% by mass of cementitious materials is presented. Fresh state tests of slump flow were performed, and the main rheological parameters: static yield stress and plastic viscosity were determined from a rheometer. For the hardened state, compressive strength tests were performed. The study of iron slag incorporation and water/cementitious materials ratio variation was developed based on a statistical methodology of central composite design from axial points based on a 2^k factorial with central points, besides a posterior analysis of variance and Tukey's multiple comparison tests. The optimization of these variables was developed using response surface methodology on 7 days compressive strength results, from the statistical design, besides the posterior determination of nano SiO₂ effects on the optimized proportions. Among the most relevant results regarding the presence of iron slag, an increase in the early age compressive strength was found, with the optimized mixture strength being more than 100% higher than mixtures without iron slag at 7 days of curing. Regarding the effect of nano SiO₂ addition to the optimized mixture, a detriment of the rheological parameters and a consequent reduction of the workability were the most remarkable findings. With the obtained results, iron slag proves to be a feasible sand replacement in self-compacting concrete mixtures.

The boom in the construction of infrastructure works has encouraged the demand for materials such as steel and natural aggregates, which in turn has generated an increase in the exploitation of materials and the generation of residual iron and steel. This situation has caused double the environmental impact due to the accumulation of these residual materials and the indiscriminate exploitation of non-renewable natural resources. This study was carried out with the aim of analyzing the possibility of using blast furnace dust to improve the properties of granular materials used in the construction of roads, as an alternative to mitigate the environmental problems caused by poor disposal and accumulation of this waste, affecting the areas of influence of these companies. To achieve this objective the physical and chemical properties of fine blast furnace dust was determined and mixtures of materials with a granular base with 0, 2, 4, 6, 8, and 10 percent blast furnace dust were analyzed to find the properties of resistance (California Bearing Ratio and resilient module), plasticity and expansion in the presence of water. The results of this study indicate that blast furnace dust can be used to improve some properties of natural aggregates for use in road construction.

During the last thirty years, there has been a growth in the study and analysis of composite materials for automotive and aerospace industry which require lightweight materials with demanding mechanical properties. textile reinforce composite materials have advantages with respect to laminated composite materials such as better formability and out-of-plane properties. Therefore, the purpose of this research is to determine the mechanical behavior for uniaxial testing of a carbon fiber of a composite material reinforced with a quadriaxial carbon fiber woven in order to decrease the anisotropy of the woven composite material. Five specimens for each of the different orientations at 0, 30, 45, and 90 degrees; In addition, six specimens of a plain woven (the most common on the market) were tested, two specimens per orientation at 0, 45 and 90 degrees, in order to contrast the behavior of these with the proposed tissue. It was obtained that the properties in the composite materials change according to the direction in which the fibers are oriented; therefore, the results showed that the quadriaxial tissue and the stress value are less than the plain tissue, by 39%, only in the zero degrees orientation, then the plaint woven has a greater number of fibers in that orientation, the orientation of ninety degrees is higher by 17%, and in the case of forty-five degrees orientation, the value is 82% higher. In the same way, when we study the orientations in there is no fiber, in the plain woven of the direction in which there is no fiber, is forty-five degrees' orientation and in the proposed tissue it is the thirty-degree one 30 degrees and it can be seen that, in this case, in the behavior of the quadriaxial tissue is greater the stress value by 66%.

This study reports the production of an adsorbent material derived from extracted coffee residues using phosphoric acid and zinc chloride as activating agents. The structural features of the materials were characterized using different analytical techniques. The BET surface areas were found between 3.81 m².g⁻¹ y 176.27 m².g⁻¹, while the FTIR analysis showed the formation of oxygenated functional groups, which are active in the adsorption process. These materials were evaluated as adsorbents for the removal of methylene blue from aqueous solution. Batch adsorption tests were performed at room temperature and the effects of contact time and, initial dye concentration was investigated. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 15.92 mg.g⁻¹. Adsorption kinetics studies indicated that the pseudo second order model yielded the best fit for the kinetic data. This typical dependence of methylene blue uptake on kinetic studies indicated the adsorption process to be both chemisorption and diffusion controlled. The experimental data obtained in the present study indicate that coffee residues are suitable candidates for use as adsorbents in the removal of cationic dyes.

This work reports the production of an adsorbent material obtained by H₃PO₄ chemical activation of oil palm waste (fiber). The experiments were carried out to explore methylene blue uptake by this adsorbent. The influence of initial dye concentration and adsorbent dosage was investigated. The adsorption equilibrium data of methylene blue onto the adsorbent material were best fitted to the Langmuir model. The maximum adsorption capacity monolayer was of 20.85 mg g⁻¹, which showed to be high compared to other adsorbent materials reported in the literature. Adsorption of methylene blue onto adsorbent material followed pseudo-second order model. The structural and chemical characterization of the adsorbent material was carried out by using various analytical techniques. FTIR showed the formation of oxygenated functional groups on the surface, which are very important for adsorption applications because they act as active sites capable of interacting with dye molecules.

This research work presents an analysis of the injection molding process of a natural fiber-reinforced composite, from the characterization of its rheological properties by the technique of capillary rheometry. Two of the main parameters of injection molding were estimated: the injection pressure and the clamping force. The rheological coefficients obtained were used as inputs in analytical and finite element models, for the prediction of the injection parameters. The results were compared, and it was observed that there is good agreement between them. The percentage errors between the two estimation methods were less than 5% for injection pressure and less than 10% for the clamping force. Also, the behavior of the material using different natural reinforcing contents (compositions of 20%, 30% and 40% fiber with a coupling agent at 4% and 8%) and the effect of its rheological properties on both the injection pressure and clamping force were evaluated. The study is of particular interest given that from the rheological characterization, the experimental values were adjusted to the Cross-WLF viscosity model and the adjustment coefficients, which contain both the reinforcing and coupling agent effects, were fed into the two methods of estimation of the injection parameters. The methodology used and the results obtained allow the prediction of the main parameters of injection molding of new bio-based composites, facilitating their use on an industrial scale.

Carbazole and their derivatives are compounds that have a great importance in the industry because their potential applications in solid-state lighting technologies. These materials have photorefractive and photoconductive properties, it is charge transporter (hole) and it is employed in organic light emission diodes. Therefore, with the aim of to contribute in the art state of this type of materials was done the synthesis of a carbazole-based material, from carbazole and bromobenzyl alcohol, employing as catalyzer sodium hydroxide and as solvent sulfoxide dimethyl. The material obtained was characterized by hydroxyl value, infrared analysis, nuclear magnetic resonance, thermogravimetric, X ray diffraction and ultraviolet- visible analyses. By infrared and proton nuclear magnetic resonance analyses was evidenced the formation of the carbazole-based material. The carbazole-based material presented fluorescent properties, since when was taken to ultraviolet lamp, this material emitted light. The thermal stability exhibited by this material may facilitate its use under conditions of high temperature. The results obtained in this study are very important since so many fluorescent materials such as organic light emission diodes are doing imported in Colombia. Therefore, the carbazole-based material may be an alternative for substitution of importations of this type of materials.

Heavy metal pollution in the effluent water due to industrial waste product of various economic activities is not adequately regulated in Colombia, this is because the agencies do little control track discharge and easily granting environmental licenses. As a result of this little regulation currently they do not have updated figures that provide real information on the amount of waste that ends up in the resort, causing health effects of living beings. In the tanning industry, in particular, there cadmium residual concentration higher than the maximum allowed by the Ministry of the environment. This work considers the use of a geopolymeric material based on pumice stone, to capture cadmium ions present in wastewater and thus reduce its concentration in the water resource in order to reduce the population's exposure to diseases that are associated with accumulation of cadmium in the body. The synthesis of geopolymer began from the alkaline activation of pumice stone with commercial sodium silicate, the use of sand:pumice stone in a 1:1 ratio and 31 hours of reaction, these proportions were defined in a previously work by the authors. The morphological and crystallographic characterization of the sorbent geopolymeric material was performed by scanning electron microscopy and X-ray diffraction. To assess the sorption process, a study of the geopolymer's contact time with a known solution of cadmium was performed. Cadmium concentration was determined using atomic absorption spectroscopy and the geopolymer was characterized after removal.

In this work a geopolymeric material was synthesized by alkaline activation of calcined coal gangue at 700 °C using a solution 1:9 of NaOH:Na₂SiO₃, as a sorbent to remove rhodamine B from aqueous solutions. X-ray diffraction, fourier-transform infrared spectroscopy and scanning electron microscopy were used to characterize the material structurally and morphologically; removal efficiency and rhodamine B sorption capacity were evaluated by using ultraviolet-visible spectrophotometry. Sorption tests were performed to evaluate the effect of the dose of geopolymeric material and the contact time of this material with rhodamine B solution in a range from 0.5 to 30 hours, interval in which the best sorption was observed. Removal efficiencies and sorption capacity to 80.4% and 1.035 mg/g respectively were found, these values show the usefulness of the material for the removal of rhodamine B in aqueous solution, making it an interesting alternative for water decontamination and object of study for future works. Removal efficiency increased by increasing geopolymer dosage and contact time.

Carbon is the great constituent of all organic matter and a key element of the compounds that make up the enormous and very complex discipline of organic chemistry. It was already known in antiquity to be obtained as a by-product of the incomplete combustion of organic materials. At present the properties of this atom constitutes a potential source for research due to its promising application in nanotechnology and new materials because of its unique mechanical, electrical and optical properties. Carbon has several structural configurations that are known as allotropes, these allotropes have the same basic component, but its molecular conformation is different. Other elements of the fourth column of the periodic table such as silicon, germanium and tin have characteristics similar to those of carbon, however, this is unique in the variety of its allotropes. The different allotropes of carbon can be produced, among other methods, by the chemical vapor deposition method, however, the energy cost of this type of growth is relatively high. Another technique that would allow to obtain deposits of carbon in the laboratory is the plasma of the glow discharge of direct current in abnormal regime, which also offers a wide range of applications in plasmo-chemistry and in the thermochemical treatment of materials. The application of the abnormal glow discharge in the deposition of synthetic materials is a recent technique that represents a decrease in the time and in the energy consumption of the process, because the heating is carried out directly by the bombardment of the ions and neutral atoms on the surface of the cathode where the sample is usually located. The technique of abnormal glow discharge was used in this work with the objective of studying the possibility of formation of carbon deposits, in a copper substrate, from an atmosphere of argon, hydrogen and acetylene. Thus, in the temperature of 600 °C, deposits of graphite, graphene and an acetylene polymer compound were obtained. These were identified by infra-red spectrometry and Raman spectrometry.

Graphite is made up of flat sheets of carbon atoms that form a periodic system of hexagonal rings of six atoms. Along the perpendicular direction of the sheets it has a low electrical conductivity, whereas this is greater throughout them. The possibility of separating the constituent sheets of the graphite and obtaining individual layers of it has led to the current scientific and technological revolution. Graphite can be produced synthetically in the laboratory, with low energy consumption, through the plasma of the abnormal glow discharge in direct current. In this work the abnormal glow discharge graphite formation is reported. The glow was initiated throughout a gaseous atmosphere containing acetylene, utilizing direct current power. In plasma generated in this type of discharge the secondary electrons, coming from the cathode, transfer their kinetic energy to the neutral molecules of the hydrocarbon causing dissociation, ionization and excitation of them. These processes generate active species that react with each other and with the substrate, producing carbon deposits on it. Under controlled conditions of temperature, acetylene content and deposition time, carbon deposits, with the characteristic structure of graphite, in abnormal glow discharge can be obtained. For this purpose, the abnormal glow discharge was established in an atmosphere composed of a mixture of 20% acetylene, 60% argon and 20% hydrogen at low pressure, in a temperature range from 400 °C to 900 °C. Under these conditions, on a copper substrate, a time of 15 minutes was used to obtain the carbon deposits. These deposits were analyzed by infra-red spectroscopy, Raman spectroscopy and scanning electron microscopy, identifying the structure of the graphite and observing the morphology of the deposits on the copper substrate.

A metal matrix composite based copper with ceramic reinforcement at 1% w/w of titanium carbide had been studied under variable titanium at 10%, 15% and 20%, in order to evaluate the microstructure and tribological properties (coefficient of friction and wear rate) in the composite material after abnormal glow discharge sintering. The metal matrix composite was manufactured by powder metallurgy process that included: mechanical and ultrasonic mixing in a suspension of 2-propanol, compaction at 200 MPa and sintering by abnormal glow discharge in an atmosphere of 10% nitrogen and 90% argon. As a result, a differentiation in the morphology and properties had been found due to the temperature, this effect was related with diffusion phenomena and energy provide by the plasma process. The final porosity of the samples at 750 °C decreases with titanium increments, reach to 2.6% with 20%. Additionally, in the grain limits of the titanium particles were detected CuTi and CuTi₂ phases. On the other hand, at 850 °C the porosity increased with concentration of titanium, a value of 16.8% was shown at 20%. Furthermore, intermetallic phases as Cu₃Ti, Cu₄Ti, CuTi₂ had been identified in the sintered at 850°C. Tribological properties had evidenced that the samples at 750 °C with Ti contents of 20% presented a wear rate value of 7.2x10⁻⁸ mm³.N⁻¹.m⁻¹, despite the porous morphology of the compound at 850 °C was estimated in 2.0x10⁻⁸ mm³.N⁻¹.m⁻¹ with concentration of 20%.

Plasma polymerization is a technique that allows obtaining polymer of any type of hydrocarbon, including the non-polymerizable by standard methods. This because of in the plasma state the activation energy can be reduced for the realization of reactions difficult to be presented under standard experimental conditions. For plasma polymerization only the implementation of different types of discharges in the radio frequency regime has been reported, leaving aside the application of direct current discharges for this process. The acetylene polymer consists of carbon chains with alternation of single and double covalent bonds. The formation of this polymer has been reported using radio frequency discharges in the abnormal regime. The paper reports the formation of polymer from acetylene using the abnormal glow discharge in the direct current regime, a novel process not yet reported in the literature. The deposition of the polymer is carried out at different times on a polycrystalline copper substrate previously treated in a glow discharge of argon and hydrogen. For the generation of this polymer an atmosphere of 60% Ar+35% H₂+5% C₂H₂ at 2 torr pressure and a temperature of 600 °C is used. The structural and morphological analysis of the deposits is carried out by infrared spectroscopy and scanning electron microscopy, respectively.

Direct synthesis of methanol and other oxygenated compounds (ethanol, propanol, acetaldehyde, formic acid, acetic acid and propanoic acid) was carried out through the partial oxidation of methane process using carbon dioxide (greenhouse gas) and water in liquid phase (water has only been used in the form of steam). The activation process was carried out with dielectric barrier discharge plasma (sinusoidal power) and in the presence of a catalyst. A Colombian natural zeolite, glass wool and a material composed of magnesium oxide and alumina were used in this scientific investigation as catalysts. Tests in the presence/absence of catalyst, presence/absence of liquid water and combinations of the previous tests were carried out in order to establish which conditions allow to obtain the highest conversion of reagents and selectivity to oxygenated compounds. It was evidenced that the glass wool allows to obtain the highest levels of reagent conversion, followed by the magnesium catalyst and finally the natural zeolite. Regarding selectivity, the natural zeolite showed to be efficient for the obtaining of oxygenated compounds. It was also established that the presence of liquid water in the reactor decreases the conversion of the reactants, but favors the formation of carbon monoxide, hydrogen and especially oxygenated compounds.

Application of titanium alloys for orthodontic implants have increase in last years and it has generated a great amount of titanium chips which are disposed as metal scrap. Titanium carbide has high hardness and can be applied as coating reinforcement against wear. Chips of titanium alloys were processed and used in the fabrication of experimental hardfacing consumables for improving the resistance of wear of mechanical components. Coatings were produced in cast steel specimens using the gas tungsten arc welding process. Microstructure was investigated by means of scanning electron microscopy. Microhardness of the coatings was analyzed by a dynamic ultra-micro hardness tester. The microstructure of the welding metal was composed of circular particles of titanium carbide surrounded by a ferritic matrix. The measures made by electron dispersive spectroscopy showed a variation in titanium amount trough the weld, where larger contents of titanium were found, and the matrix. The crystallographic analyses reinforced the formation of titanium carbides embedded in a ferrite matrix into welding metal.

Clays are of great importance at the industrial level because they can be used to make masonry products such as blocks, roof tiles, bricks, and tiles, among others. Currently, many companies in the ceramic sector get a lot of waste due to the lack of technical analysis of the raw material to forecast the behavior of the ceramic mixtures and to improve the quality of the final product. In this paper, the physical and chemical characterization of the clay used in one of the companies dedicated to the manufacture of masonry products for construction in Ocaña, Norte de Santander, Colombia was conducted. The development of the investigation was achieved by means of the execution of physical and chemical tests to the sample of selected clay from different points of the production process with which the granulometry, index of plasticity and the mineralogical composition were determined. The results obtained show that the clays currently used by the company are at a low level for masonry products for construction. This is why the addition of other clays is considered, with which an optimum mixture is achieved with which can meet the requirements of the current regulations in force. It is essential to technologically characterize the clays to optimize the mix and thus avoid defective products. It will obviously improve the company's environmental and economic resources.

The mechanical properties of a biodegradable composite material made with Colombian coconut fibers were studied. The study was carried out considering a random distribution of fibers within the composite material for three fiber/matrix compositions (10, 20 and 30) in weight-to-weight percentage. Each of these was subjected to tensile tests to evaluate the effect of the fibers in each composition, taking into account the mechanical properties of ultimate tensile strength and elastic modulus that allow selecting the composition of greater rigidity and subsequently evaluating its properties under the effects of compression forces. The results obtained show that the more rigid composite material corresponds to the fiber/matrix 20 percent composition, which presented a tensile strength of 13.83 MPa and an elastic modulus of 924.46 MPa comparable with those reported in the literature. This composition is the most fragile with a percentage of elongation is 2.27% and with low tenacity to withstand impact efforts. Finally, the behavior of the more rigid material was compared with the mechanics of Ramberg-Osgood and Hollomon, the latter being the most adjusted allowing to predict the properties of this type of materials. The results obtained expand the uses of Colombian coconut fibers as a biodegradable composite.

Composite materials with comparable properties and low environmental impact have been at the forefront of research. In the present work, the mechanical, physics and chemical properties that allow knowing the potential applications of Musa Paradisiaca fibers are evaluated, through an experimental process that starts from the selection of the binder and its fiber/binder ratio through tensile tests. The finally formed material is composed of a matrix of gelatin type C and glycerin and a reinforcement of banana fibers. The compound obtained was characterized by infrared spectroscopy by the Fourier transform, thermogravimetry, scanning electron microscopy and mechanical tensile and hardness tests. The results obtained from this study allowed confirming the presence of lignin and hemicellulose and evidencing the presence of good mechanical properties with a modulus of elasticity equivalent to 0.57 MPa, a percentage of elongation of 56%, an ultimate tensile strength of 3.5 MPa and a hardness of 82 Shore A, which allows us to consider a biodegradable composite material for applications in which soft gums and elastomers perform. The results obtained allow us to consider other alternatives for the use of Colombian banana fibers, in addition to their use as a biodegradable compound.

Thixotropy is a distinctively rheological (time-dependent) phenomenon, which is found in many complex materials, especially colloidal systems as fine-grained soils. Clays are materials that can recover their initial strength after remoulding. The estimation of such recovering allows optimising the designs of geotechnical structures and then reducing the construction costs. This paper presents the results of a study that evaluates the thixotropy phenomenon of clayey soils. The work methodology involved an experimental plan composed of five phases: (i) extraction of samples; (ii) physical and mechanical characterisation of the undisturbed samples; (iii) remoulding of samples after testing; (iv) storage of remoulded samples; and (v) evaluation of undrained shear strength recovering for 0, 15, 30, and 60 days after remoulding. Undisturbed samples were collected using Shelby tube from the municipality of Madrid, near Bogotá, in Colombia. Results were analysed in terms of sensitivity degree because this parameter allows estimating the shear strength recovering. Findings show that clayey soils from lacustrine deposits of Bogota high plateau do not loss completely all of their original mechanical properties after remoulding and exhibit a medium sensitive behaviour. Conclusions indicate there is a recovering of undrained shear strength along the time, in which the samples will recover their original state about one year after remoulding.

In the present work, experimental tests are carried out to determine the tensile strength of the fiber obtained from the African palm clusters. The tests were performed on a MTS BIONIX universal test machine under the ASTM standard, which characterizes the tensile strength and stiffness of the fiber in relation to its weight. Once the mechanical properties of the fiber are characterized, it is proposed to carry out studies as a reinforcement material in composite materials, reducing the amount of waste which generates health problems in this industry. Organic fibers have mechanical properties such as lightness, high mechanical strength and durability, for these reasons it has been used as a reinforcing element in polymeric matrices, being a potential replacement for some materials in the industry in general. By 2015, Colombia had 466000 hectares of African palm planted, highlighting the potential for acquiring this fiber in Colombia, to achieve positive results in the application of the fiber, a whole series of new industrial products can be developed with the social and economic impact that this represents.

The hydrogen economy is a concept focused on this element as a carrier of clean and cheap energy, one of the keys is the storage of this gas safely. In this sense, TiCrV-based alloys have great capacity to store hydrogen. In the present working studied the influence of the process of mechanical milling of high energy in the storage capacity of hydrogen of TiCr_1.1 V_0.9 alloy. The alloy was synthesized by arc fusion and manually crushed. The effects of mechanical milling were studied for periods of time of 1 hour and 3 hours at 300 revolutions per minute with a weight/weight ratio of the sample 10: 1. The x-ray diffraction analyzes revealed solid phase formation of body center cubic phase, characteristic of TiCrV base alloys, and formation of TiCr_1.8H_5.3 hydrides and TiH₂ hydrides with orthorhombic structure and body center cubic, respectively. The hydrogen storage capacity of the TiCr_1.1 V_0.9 alloy decreased with the increase in grinding time. The reasons for the drop in hydrogen storage capacity are mainly two: contamination of the surface of the alloy powder and changes in the microstructure generated by the plastic deformation in the grinding process. However, an increase in absorption kinetics was observed at longer milling times because the surface area increases since the crystallite size decreases. This phenomenon can be explained by the catalytic effect produced by the decrease in the particle size of the samples. The differential scanning calorimetry analysis was able to determine that the TiCr_1.8H_5.3 hydride stored a greater amount of hydrogen and has a lower desorption temperature compared to the TiH₂ hydride.

The present article analyzes some physical and chemical properties, which can influence the behavior of the diatoms present in the eastern part of the city of Tunja, by identifying and exploring three outcrops arranged in the territory, three characteristics to be evaluated and defined their respective laboratory tests were carried out in order to be able to estimate their behavior, analyzing parameters such as the dispersive effect using the pinhole test, acidity with hydrogen potential measurement and suction using the filter paper method. Prior to this, general characterization tests were developed, that is: Atterberg limits, specific gravity and hydrometer granulometry, carried out according to the respective regulations, the analysis of the results obtained and the pertinent recommendations are made in a particular way for each outcrop and in general form for the deposit of the city, defining the predominant values of the characteristics considered.

This article contains the research results in the evaluation of a mathematical model for the determination of the compressibility coefficient of the soils of the lacustrine deposit of the city of Tunja, Colombia, through the execution of one-dimensional consolidation tests, complementary with soil classification tests characterizing its index properties, stories as a ratio of voids, porosity, specific gravity and consistency limits, where a selection of different sites located covering the general area of the lake deposit is made, taking soil samples unaltered at different depths, where processed these soil samples for later geotechnical evaluation. A series of mathematical expressions were generated to determine the approximate shape of the compression coefficient, depending on the index properties, discretizing according to the type of soil, where for this case clays of low and high plasticity were found as silt of high plasticity. These models will serve as a tool to determine the approximate and preliminary form of the magnitude of the main compressibility coefficients.

The mudrocks are weatherable materials, an intrinsic condition of mineralogy and sedimentary formation. In the Eastern Cordillera of the Colombian Andes lies this rocky material, which implies the degradation of physical and mechanical properties in the face of environmental factors, such as changes in humidity and temperature that are intensively propitiated in the tropical climate of the region, factors not considered in the design of civil works. The present study determines an experimental procedure in laboratory to reproduce the effect of the cycles of wetting/drying and heating/cooling in conditions and periods similar to the original ones of the geomaterials, by means of the steam equilibrium technique and thermal change, the processes were carried out on rock cores extracted from the Lutitas de Macanal formation that emerges in the municipality of Pajarito, Boyacá, Rancheria sector, Colombia. The results quantitatively determined the degradation of Young's module and the resistance to uniaxial compression with the applied treatments, having a greater effect on the heating/cooling cycles in a period equal to that of wetting/drying generating greater damage to the rock due to pronounced cracking.

In this work, a reactive melting procedure was implemented for the inertization of the manganese-containing cathodes of spent alkaline batteries. The process consisted of adding the cathode powder mixed with borax on top of molten aluminum at 1000 °C. By means of an aluminothermic reaction, manganese oxides are reduced and incorporated into the alloy. The presence of borax in the reactive mixture was found to be fundamental to obtain the Al-Mn alloy. The characterization of the metal phase and the slag phase by scanning electron microscopy and X-ray diffraction showed that manganese is reduced to form manganese borides in the slag and Al-Mn intermetallics in the alloy. This process could make feasible to use aluminum casting shops as processors of spent alkaline batteries.

We analyzed the effect of the curvature of the path on the energy spectrum of an electron confined in a closed nanoscopic loop in the presence of magnetic and electric external fields has been studied. The system was modeled using the stationary Schrödinger equation in the framework of the approximation of effective mass and enveloping function, which was solved using the finite element method. The closed loop has been modeled theoretically as a flat waveguide, whose width is small compared to the length of the path. These geometries allowed putting in evidence the variation in the confinement potential of the electron due to changes in the curvature. The variation of the electronic spectrum and the electronic densities for some low-lying energy states were analyzed as a function of the intensity of a magnetic field applied in the direction of growth and an electric field applied in the structural plane. The results demonstrate, with clarity, the high sensitivity of the electronic spectrum of a closed nanoscopic loop in the presence of changes in the curvature of the path, which translates into high sensitivity in electronic, magnetic and optical properties.

In the development of the productive process of stone aggregates, during the stage of washing and extraction of sludge from the decanter wells, a "cienego" sand is produced in an approximate quantity of 24.75 tons per day, of which only 10% per day is commercialized, the remaining 90% must be discarded, causing financial detriment, impact on the environment in terms of pollution by handling the product that is discarded, occupation of useful areas and landscape degradation, among other impacts negatively affecting the companies in the sector, and their environment. The objective of this research was to evaluate a fertilizer based on cienego and three native microorganisms (Azotobacter sp, 1 Azotobacter sp, 2 and Pseudomonas sp) in corn seeds. For this purpose, three native strains of diazotrophic bacteria were isolated from soil samples of oil palm crops in Tibú, located at Norte de Santander, Colombia, which were biochemically identified using traditional culture media. These isolates were inoculated into corn seeds in trays with sterile soil plus ciénego at 70/30 ratio respectively, and the plant growth-promoting effect was recorded every 4 days, by measuring morphological variables such as height, number of leaves, number of roots, length and germination rate. The results showed that Azotobacter sp, 2 treatment presented a higher production of roots, reached greater height (cm), number of leaves and germination rate in comparison to control treatment after 12 days of monitoring, besides directly influencing the percentage of organic matter in the substrate and elements such as calcium, potassium and phosphorus, allowing greater productivity and corn seed yield once these were germinated.

The antibacterial effectiveness of Origanum vulgare and Ruta chalepensis essential oils cultivated in three municipalities of Norte de Santander, Colombia, on gram positive and gram-negative bacteria was determined in vitro. The oil extraction process was carried out at zoey perfumery company by the steam dragging method from 5 kg of vegetable material, the oil yield obtained compared with the vegetable material collected was calculated using mathematical formulas and its chemical composition was determined by mass spectrometry since is an analytical technique with great potential that allows to elucidate the structure and chemical properties of molecules. For the determination of the minimum inhibitory concentration and the minimum bactericidal concentration of the extracted oils, the mother solution of 2.5 g/mL was prepared and from this solution, the different dilutions at concentrations from 1000 mg/mL up to 15.62 mg/mL were made. A suspension equal to tube 0.5 of the McFarland scale of each of the microorganisms (Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853) was then prepared with sterile saline solution and inoculated in microplates with volumes of diluted solution, soy tripticasa broth and dimethyl sulfoxide, was then incubated at 37 °C for 18 hours and proceeded to inoculate in Müeller-Hinton agar to verify its minimum bactericidal concentration. The results show that the yield of Origanum vulgare essential oil was 0.8% and for Ruta chalepensis 0.1%. The chemical analysis of the oils revealed the major components of Origanum vulgare such as β-mircene 1.6%, ∝-terpinene 15.7%, 1.8-cineol 3.8%, yterpineno 2.6%, terpine-4-ol 1.1%, timol methyl ether 17.4%, timol 30.6%, carvacrol 8.1%, trans-β-caryophyllene 6.3%, ∝-humulene 1%, cariophylene oxide 3.1% and Ruta chalepensis as nonanone 37.1%, undecanone 39.4%, nonanyl acetate 2.2%, decanone 2.8%. The results obtained show that essential oil of Ruta chalepensis at concentration of 500 mg/mL stop growth of Escherichia coli and seudomonas aeruginosa and at a concentration of 1000 mg/mL stop growth of S. aureus while the essential oil of Origanum vulgare was the most effective for the inhibition of all the microorganisms evaluated, requiring a concentration of 15.62 mg/mL for Escherichia coli and Staphylococcus aureus and for Pseudomonas aeruginosa, a concentration of 125 mg/mL was necessary. It is concluded that according to the chemical composition, materials of vegetable origin such as Ruta chalepensis and Origanum vulgare essential oils can be taken for the elaboration of products with potential in artisanal cosmetics and even in pharmaceutical products.

The correlation between the maturity index and the compressive strength of concrete is validated for mixtures with strengths of 2000, 2500, 3000 and 3500 PSI, which are the most used in the civil engineering field. Temperature probes DS18B20 connected by the 1-Wire protocol to the Raspberry Pi 3 card were used to census the data and calculate the maturity index. The concrete mixtures presented A/C ratios of 0.820, 0.748, 0.680 and 0.623, which are consistent with those used in the construction industry. Compressive strength tests were performed every 24 hours during a 28-day test scenario in order to understand the behavior of concrete throughout the curing process. From the values of mechanical resistance to compression obtained in the control ages of 7 and 14 days it is inferred that the concrete has a normal hardening, likewise when comparing the experimental results of the resistance to compression, with those found using the method of maturity, it was possible to identify that at early ages (less than 10 days) they present uncertainties greater than 10% while at ages greater than 10 days of curing this error does not exceed 5%. In general, it was evidenced that the assembly carried out with the Raspberry pi 3 card and DS18B20 probes reliably allowed the monitoring, recording and storage of temperature and time data during the entire curing process.

Metal hydrides are considered an easy and safe way to store hydrogen. Storage is one of the keys to the large-scale implementation of the so-called hydrogen economy, which will undoubtedly revolutionize the new vision of sustainable development towards a more environmentally friendly world. This paper presents a general review of some alloys based on TiCrV and TiCrVZr showing their advantages and challenges that must be developed for their implementation. The capacity of absorption and desorption as a function of time is shown using a Sieverts type device, the structure is studied by means of X-ray diffraction as well as its morphology by means of scanning electron microscopy. This paper shows the advantages and disadvantages of alloy synthesis methods based on transition metals, it is observed that hydrogen capacity increases in the process of fusion synthesis and decreases in the process by mechanical grinding, however the capacity desorption is not optimal at room temperature.

It was studied the production of gold nanoparticles from a gold target by pulsed laser ablation in liquid medium. This technique allows replacing conventional methods of preparing nanoparticles without the need for precursors, where gold is used in its metallic state. Experimental tests were performed to determine the appropriate synthesis conditions to achieve small particle sizes. The variables studied were water volume, ablation time and ablation energy. Gold nanoparticles with spherical geometry, in metallic, and nanocrystalline state were obtained without the need to use precursors and stabilizers. Ablation energy is the most influential variable on the particle size, because it was observed that when is increased the ablation energy is generate greater particle sizes.

In this study, a target population of hardware stores that sell paint in the city of Bucaramanga, Colombia was determined. Through a survey, we proceeded to investigate in business the different uses that give expanded polystyrene that generally serves as a product packaging element. A univariate and bivariate analysis of the variables used in this study was carried out with statistical package for the social sciences to make a diagnosis of the different uses of expanded polystyrene and its use in construction materials. Therefore, use the expanded polystyrene to reduce the volume in sanitary landfills through the creation of waterproofing paint. The gradual process of industrialization of the new paint based on expanded polystyrene EPS will allow mitigating the transit of these wastes to sanitary landfills to reduce environmental impact, will allow the emergence of a new production chain as a commitment to a social industry that will receive economic benefits for the improvement of the quality of life of the actors that will intervene in said productive chain. It has not been implemented because some scientists believe that the inputs required to mix expanded polystyrene are expensive and the industry would not be willing to take on. It is observable that the scientific community is also not interested in exploring limonene alternatives so that the criteria of a mixture with environmentally friendly expanded polystyrene are maintained.

Elastomers are natural or synthetic polymers used in the automotive, mining, mold, assembly and other industries, due to their mechanical resistance in a wide temperature range from 60 °C to 320 °C; however, the waste generated is not disposed of properly, especially in the manufacture of tires, which generates environmental problems like inadequate final disposal, generation of toxic gases and public health problems; Therefore, in order to recycle these wastes, the present investigation modified elastomers superficially in order to produce strong adhesion with inorganic compounds like cement, through oxidation and sulfonation processes. For this purpose, NaOH and KMnO₄ solutions were prepared at a concentration of 5% and then impregnated in saturated NaHSO₃ solution. Subsequently, the modified elastomer was morphologically characterized by scanning electron microscope, thermogravimetrically by differential scanning calorimeter; compositionally by infrared spectroscopy, Raman spectroscopy, X-ray fluorescence, energy dispersive X-ray analysis and hydrophobic tests using contact angle techniques, in order to establish morphological and chemical compatibility with inorganic compounds. Results evidenced inclusion of functional groups OH, C = O and SO₃, the reduction of carbon present in weak bonds and the presence of inorganic components such as potassium, sodium, manganese and sulfur were evident. The scanning electron microscope shows an increase in the roughness and contact surface of the elastomer as a function of the inclusion of polar functional groups by surface chemical treatment. These characteristics are to generate greater inclusion and compatibility of elastomers of an organic nature in inorganic compounds like cement matrices.

The development and characterization of a functional graded composite material based on the biomimicry of the human intervertebral disc is reported in this research. The material consists of concentric radial polyurethane layers, synthesized using a condensation polymerization chemical reaction, found on methylene diphenyl diisocyanate, glycerol and castor oil as reagents. The proportions in the components of the polyol, glycerol and castor oil, were modified to generate a change in the degrees of cross-linking in the chains of the material, resulting in slightly rigid layers, as in the structure of the intervertebral disc. Two radial gradations were made through a rotating assembly and the complex modulus of the constituent polyurethane layers was used as the gradation criteria since the complex modulus provides a general description of the mechanical behaviour. After the gradation process, the graded material was characterized by means of a dynamic mechanical analysis that determines its viscoelastic properties, like storage modulus, loss modulus, complex modulus and tan δ. Moreover, with its behavioural pattern to compression and flexion, we performed a comparative analysis of the improvement of the mechanical properties of its constituent materials. The development of this study under biomechanical and chemical guidelines came together with two proposals of graded materials with high versatility and functionality in terms of frugality and stability for temperatures changes, as well as absorption and dissipation of mechanical energy. Furthermore, it serves as a tool for the elaboration of machines elements under combined load of compression and flexion at a low cost.

The compressive strength of concrete mixtures with accelerator additives designed for structural elements with strength of 5000 psi was correlated with the maturity index of concrete at an early age. The design of the mixture was made by adding the quantity of additives according to the specifications of the supplier. The maturity index was calculated using the thermal profile of the concrete dependent of the setting time, which was obtained through an automated adiabatic system. The number of thermal sensors required for temperature measurement dependent of setting time (1, 3, 7, 14 and 28 days) was determined by a factorial experimental design of two factors. The correlation coefficient was 0.96, so the logarithmic model adequately explains the variability of the compressive strength. The equation obtained was validated by means of the values of resistance to compression measured by the standard method for each age of the concrete; all values are within the calibration range of the resistances estimated by the maturity method.

This paper deals with the vitrification processing of the wastes of glass and phosphor powder obtained after the vacuum crushing of spent fluorescent lamps. Both materials were characterized by means of scanning electron microscopy and X-ray fluorescence chemical analysis. The vitrification tests were performed at 1,100°C and 20 wt % borax was added to the samples as fluxing aid. Four formulations (batches) of glasses were made, the first one consisted only of spent lamp glass, the second one of spent lamp glass plus borax, the third one was the same as the second, but incorporating 20% weight of spent phosphor powder. The fourth one, a control, was made combining soda-lime glass cullet and borax. All four batches were chemically analyzed by X-ray fluorescence and no Hg was found on them. Rare earth elements were detected in the third batch glass prepared. The chemical stability of all batches was tested by contacting tests of the glasses with distilled water. As indicative of the stability, pH and electrical conductivity of the supernatants was measured. It was found that the more stable glasses were those incorporating only borax and spent lamp glass.

This study is based on the synthesis and characterization of a hybrid perovskite based on tin chloride and methylammonium (CH₃NH₃SnCl₃) as an absorbent layer in solar cells. Preparation of the hybrid material was carried out using the wet method from a precursor of methylammonium chloride CH₃NH₃Cl and tin chloride (II) (SnCl₂). The solid obtained was heated to a temperature of 60°C in order to obtain the final product. The hybrid material was then characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The structural and morphological results showed the characteristic traits corresponding to the material. The formation of conglomerates with irregular spherical geometry and cubic forms associated with the precursor of tin chloride were also present. The application of this type of perovskite in solar cells is preferable due to its environmentally friendly impact, making it a promising material for photovoltaic technology.

This experimental study was carried out with the aim of establishing and analyzing the thermal, structural, morphological, and rheological properties of a polyethylene functionalized with a maleinized hyperbranched polyester. This area of study has scarcely been reported. It is important to study the properties of this material, since it can be employed as functionalizing agent in blends of low density polyethylene and hydrophilic polymers. In addition, it also may be used as alternative for replacing the importation of polyethylene functionalized with maleic anhydride in our country. Therefore, in this experimental study, dicumyl peroxide was utilized to catalyze a functionalization reaction between low density polyethylene and maleinized hyperbranched polyester. In the experiment, dicumyl peroxide concentrations were maintained at 0.50 wt%, 1.0 wt%, 1.5 wt%, and 2.0 wt%. The resultant material after of the functionalization was characterized by various analytic methods including infrared analysis, contact angle, thermogravimetric analysis, X ray diffraction, rheological analysis and scanning electronic microscopy. The functionalization degree of the polyethylene functionalized with a maleinized hyperbranched increased with the dicumyl peroxide amount and in all cases it was higher than 8 weight percent.

This work takes thermodynamic modelling through computer science for incubation process at domestic birds, that has presented energy consumption significantly high than energy used in processes. Thus, a data analysis was applied upon variables of temperature and relative humidity for heating zones, trying to know how much energy supplied by source was used, as well as, voltage and current variables are measured in the same moment that temperature and relative humidity are acquired. Then, data analysis was done using artificial neural networks models with samples obtained from sensors, where real process is highly time- variant, fixing environment conditions at the moment required. Therefore, with this system has been obtained an air flow of 3.4375 10⁻² m³/J using a anemometer respect to electrical energy supplied by fans, giving 9.4818 W of average power using ceramics resistances, and testing an adaptive controller where its variables are fitted using equations obtained from data analysis. In contrast, colombian farmers have decreased economic conditions to maintain them productions due to free trade agreements implemented lastly, indeed this system was developed using open- source software and hardware to avoid costs in acquisition by licensing politicians or periodic subscription to a specific product developed by companies.

In order to highlight the implementation of fly ash and hydrated lime in replacement of a % of the weight of the cementitious material traditionally used for the elaboration of mortar mixtures, a conventional mixture was made for mortars where the materials that compose this type of mixtures were previously selected, analyzed and implemented. The evaluations of the materials were carried out under the standards indicated by the Norma Técnica Colombiana that guarantee the reliability of the resulting mixture. The fly ash that was used was obtained from the power plant Termotasajero of the Municipality of San Cayetano located in the department of north Santander-Colombia. The hydrated lime was obtained in the municipality of Malaga located in the department of Santander-Colombia. The experimental mixtures presented a replacement of 40%, 50%, 60% and 70% of the weight of the cementitious material traditionally used in the city. At the same time, 10%, 20% and 30% of hydrated lime was added to the experimental mixtures in relation to the weight of the added fly ash. With each one of the elaborated mixtures, both traditional and experimental, 3 cubes were made as indicated in the Norma Técnica Colombiana for this purpose. After the 21 days of its elaboration to each one of the cubes their resistance to compression was determined by means of their respective test in the ibertest machine property of the Francisco de Paula Santander university located in the city of San Jose de Cucuta-Colombia. The data obtained in the tests were compared determining the viability of the addition of fly ash and hydrated lime in the mixtures for paste mortar, with the incorporation of a %. additional water in their designs. Thus generating a positive environmental, social and economic impact through the final disposal and marketing of an industrial waste, fly ash, and the use of a natural material, hydrated lime, in mixtures with cementitious matrix for mortars.

The increase in the world population has caused cities to grow vertically, increasing the amount of high-rise buildings, which is why there is a need to develop building materials with greater efficiency, that is, resistant and with less density to the conventional. The objective is to analyze the mechanical behavior of buildings with portico system when being designed with lightweight concrete mixtures made with thermally expanded clay from materials in the San José de Cúcuta metropolitan area, Colombia. Eight structural models were made using the finite element method with the Etabs® software, varying the building height and the concrete type that was used, in order to compare the properties and lightweight concrete characteristics contrasted with the conventional concrete. The modeled buildings were located on land with a capacity of 200 KPa and residential use. The San José de Cúcuta city is located on an area of high seismic threat according to the Colombian construction of resistant earthquake. It was determined that lightweight concrete manufactured with materials from the San José de Cúcuta metropolitan area, Colombia, is structural since it has a compressive strength at 28 days of 26 MPa on average and equilibrium density of 1646.16 Kg/m³ complying with the requirements minimums required by the Colombian regulation of resistant earthquake construction for a concrete to be considered light and structural. It was found that when using lightweight structural concrete in the design of joists and slabs, there is a 10% decrease in dead loads that reach the foundations of the structure, which implies a reduction in the dimensions of the foundations.

This paper presents the requirements specification of artificial muscles based on smart materials for a robotic finger prosthesis. The first part introduces the robotic finger, designed to mimic human precision grasping. A methodology to determine three critical parameters (strain, frequency and force) is presented. The methodology uses experimental data combined with kinematics and dynamics. Obtained values are calculated using the developed finger; as a result, we define that main requirements are: (i) Minimum active strain 5.5% for extension-based actuation or 60% bending-based actuation, (ii) Frequency (8.89 Hz, 22.2 Hz), and (iii) Force (4.80 N, 6.74 N) for bending-based actuation or force (17.81 N, 25.11 N) for extension-based actuation. Finally, a review of smart materials is presented with the aim of choosing the group of materials that can be used as artificial muscles for robotic hands. We show that shape memory Alloys can fulfill the established specifications. We also stand out Ionic polymer metal composites as a very promising actuation solution for robotic hands, due to their active strain and settling time, even though the blocking force is below the requirements.

A comparative study is presented, based on density functional theory, of the influence that the different approximations of the exchange-correlation functional have on the structural and electronic properties of titanium dioxide in the rutile phase. In this work, the method of plane waves and pseudopotentials, as implemented in the Quantum Espresso package was used. The approximations to the exchange-correlation functional that were considered are the local density approximation, the generalized gradient approximation in the form of Perdew- Burke-Ernzerhof, the Perdew-Burke-Ernzerhof for solids, and the Perdew-Wang 91. For each case, the effects due to the inclusion of spin (spin polarization), and the correction of Hubbard (U = 4.2 eV for Ti) were also studied. We found that the Perdew-Burke-Ernzerhof for solids functional offers the best results for the calculation of the lattice parameters and bond lengths, followed by the Perdew-Burke-Ernzerhof and Perdew-Wang 91. For the bond angles, the best description was obtained with the Perdew-Burke-Ernzerhof and Perdew-Wang 91 approximations. The density analysis of states showed that the functional PW91 and PBE, better describe the band gap compared with the functional PBEsol and LDA when the Hubbard correction it is not been included, however, when this is included all the functional show the same deviation with respect to the experimental value (E_gap = 3.0 eV). With and without the Hubbard correction (U = 4.2), all functionals underestimate the band gap.

The production, use, and poor management of polymers, and especially of expanded polystyrene, have resulted in various environmental challenges, such as large-scale waste generation, accumulation of toxic substances, and the pollution of natural resources, chiefly of water and soil. Consequently, nations around the world are investing considerable research effort into developing waste treatment and reduction solutions. Some areas have even enacted bans against the use of the material, however, in the Colombian case, it continues to be highly represented in the industry, and given the low cost of this packaging, little effort has been made to find a replacement. Expanded polystyrene is a thermoplastic polymer with low weight, low thermal conductivity, low cost, and low water absorption; factors which have made it a less attractive target for recycling. It has, however, excellent resistance to mechanical compression, which makes it viable for study in other applications such as those considered in the present study, offering advantages in terms of environmental protection without the need to completely eliminate the use of the material. The present study analyses the effects of integrating waste expanded polystyrene into the process of creating waterproofing paint. The research is divided into three major phases: the first focusing on the determination of the paint's technical requirements using previous research and by means of initial testing; the second, on elimination tests to validate the properties of various samples before preparing the final paint mixture; and finally, a third phase of final tests required for a waterproof paint. The final formula is applied to common materials in the construction sector, such as wood, metal, glass, and concrete, to validate each of the required properties. Among the main results, technical viability was identified in the second sample, which demonstrated the best results at a ratio of 1: 2.5: 2.5 of waste expanded polystyrene, D-limonene and methyl acetate, respectively.

Hydroxyapatite nanoparticulate materials have received a great deal of scientific attention due to their dental and orthopedic applications but simple strategies to control particle characteristics (e.g., surface area, shape and size distribution) are still needed. Among several hydroxyapatite structures, one-dimensional nanoscale materials such as nanowires, nanorods and nanobelts can be synthesized in the presence of specific surfactants added during synthesis in order to alter the particle growth. This contribution is aim to explore strategies to obtain one dimensional hydroxyapatite crystals without the use of surfactants. Particularly, we study the effect of several variables such as temperature, reaction time and pH on shape and size of hydroxyapatite crystals produced under hydrothermal conditions. The results obtained show the formation of hydroxyapatite nanorods as well as some interesting insights about how to control particle sizes in samples obtained at temperatures between 180 °C and 220 °C. These results have potential benefits at the time of producing one dimensional hydroxyapatite crystals in a simple and not expensive way.

The clay is used in the area of constructions, ceramics and industrial applications: insecticides, pharmaceutical industry, cosmetics and painting, for its physical and chemical properties that are suitable for different civil projects (roads, public services network, constructions); the dosage is a technique to modify and improve the conditions of the soil-cement in reference to the resistance, conditions of insolubility, impermeability, durability and appearance. In this study, high plasticity clay was evaluated through different laboratory tests (humidity test, soil liquid limit, plasticity index, granulometric analysis, California Bearing Ratio) for three samples and specifying the methodology used in each step, with the objective of knowing its structure and functioning in rural roads in combination with soil-cement, looking for a more profitable and lasting option in this sector, in order to benefit the people surrounding these sectors, improving the income of the sector and seeking to mitigate the environmental impact.

The need to improve people's living conditions starts from the reality of the durability of rural road constructions, which have a short useful life and have a negative impact on the inhabitants of these regions. This project aims to improve access to rural areas, rural economic development and thus improve the quality of life of people in the sector; taking into account that at the moment of building a rural road, has a better resistance and durability in time, this was done by analyzing the properties of the clay mixture of low plasticity in the dosage of soil-cement that were tested by tests to determine the liquid limit of soils, determination of the plastic limit, plasticity index, moisture test, classification of soil by sieving, granulometric analysis, unit weight-humidity relations in soils, soil support relationship in the laboratory; in order to find the best dosage that provides greater strength, long-term durability and risk reduction. The results indicate that this type of clay requires an improvement with cement, due to its bearing capacity of 2% and 4%, which gives it a very poor quality to be used in the construction of rural roads.

Dosage is a technique to modify and improve the conditions of the soil-cement that comply with the conditions of the "Instituto Nacional de Vías" standard and in the same way, is economic to be implemented in different types of clay. The clay was classified depending on its plasticity (high plasticity and low plasticity) and the behavior at loads; making laboratory tests of modified proctor, compaction and CBR% for the clays with 4% of soil cement; at the same time, the results of CBR% of soil cement of 4% with natural soils, of 6% of cement and 1 were compared. In this way, was made a proposal of the elaboration of each type of soil-cement with its respective percentage, concluding that the clay of high plasticity can be used for subgrade and the one of low plasticity has a weak bearing capacity.

The aim of this study was to investigate the effect of the hyperbranched polyester polyol from second generation content on the structural, thermal, rheological, morphological and mechanical properties of recycled polyvinyl chloride/hemp fiber/hyperbranched polyester polyol obtained from second generation blends. In all blends, the amounts of recycled polyvinyl chloride and hemp fiber were 70 wt% and 30 wt% respectively. The blends were obtained in a torque rheometer. The proportions of hyperbranched polyester polyol regards to those of the polyvinyl chloride and hemp fibers were 5 wt%, 10 wt%, 15 wt% and 20 wt%. Additionally, a recycled polyvinyl chloride/hemp fiber blend was prepared to be used as control blend. Infrared analysis was then used to evidence the interaction between components of the blends. The thermal stability of the recycled polyvinyl chloride/hemp fiber/hyperbranched polyester polyol blends was lower than that of the polyvinyl chloride. Furthermore, it was not observed a trend in the thermal behavior of the recycled polyvinyl chloride blends. Hyperbranched polyester polyol increased the glass transition temperature of the blends. Additionally, rheological analysis results indicated that the hyperbranched polyester polyol reduced the viscosity of the blends.

It is presents the characterization of the clays from the algodonal formation and the mechanical properties of the products manufactured in brickyard "Hora", located in Ocaña, Norte de Santander, Colombia.Tests of scanning electron microscopy, thermal gravimetric analysis, differential scanning calorimetry, initial rate of absorption, 24-hour immersion, compressive strength, and modulus of rupture were performed. The results indicate that the clay contains a considerable amount of silico-aluminate, while the products have low mechanical strength and high percentage of water absorption. The clays used present difficulty in the process of shaping and compacting the products. None of the samples comply with the values established in the standard and do not allow their use as non-structural masonry products for interior or exterior use.

The study of the physical-chemistry properties of dispersions are very importants in the coating industry, since of it depend the application and stability of these systems. Therefore, the aim of this investigation was evaluated the influence of the dispersion rate and titanium dioxide content in the rheological (steady and dynamic analyses), colloidal, morphological, films, and thermal properties of waterborne dispersions based on polyvinyl acrylic resin, carboxymethyl cellulose and titanium oxide. In this work were used two proportions of titanium oxide (5.51 wt% and 10.44 wt%) and the following dispersion rates: 900 rpm, 1200 rpm, 1500 rpm and 1725 rpm. The materials were characterized by rheological, dynamic light scattering, scanning electronic microscopy, adherence, hardness, flexibility and thermogravimetric analyses.

Polymers have become one of the most recognized materials in the industry, due to their good physical properties and the efficiency of their production process, in addition to the versatility and breadth of their fields of application in the aerospace, automotive, construction, textile and adhesive industries. In the case of cellulose acetate, it is used in a wide variety of everyday products such as photographic films, varnishes and cigarette filters, which makes it a factor that negatively affects the environment, since this material takes a long time to decompose and in the process contaminates the place where it is located with particles, on the other side are the agricultural residues that are manipulated in an inappropriate way, generating contamination in landfills and water sources, the following bibliometric analysis was carried out in order to provide a solution to the worrisome situation of this polymer contamination and the agricultural residues contamination, in order to encourage the development of studies focused on producing degradable materials. Therefore, this article presents a bibliometric analysis on the various alternatives to replace cellulose acetate, focusing on the collection methodology and comparison of studies with a tool known as HitsCite. The articles have been investigated by bibliometric, trend and cluster analysis in a sample of 361 articles. The research has been carried out in one of the most recognized databases such as web of science and has allowed to identify the main trends and dynamics of the scientific literature. This in order to mitigate the environmental problems that are present in our environment and being a starting point to support monetary studies that implement environmentally friendly materials, being a topic that can create a positive and innovating impact in the industries commercial sectors.

This research is articulated from the clay framework as material wealth of the region of Norte de Santander, Colombia, and seeks to structure attributes of passive thermal cooling in a ceramic piece for low cost masonry type block cooked with physical, mechanical and thermals feasible characteristics for warm tropical weather conditions of 33 °C on average. This work is based on previous studies that explores the partitions structure morphology in Blocks H10 establishing a model of 6 horizontal cavities for low thermal conductivity and having oblique geometry partitions to interrupt heat conduction by direct thermal bridge inside of the constructive unit called Form-C, which is taken as the object of analysis, adding 5% organic coffee cisco additive in the 95% clay mixture to increase the porosity with a proportion that does not affect the deterioration of the mechanical properties and allow to optimize the thermal insulation capacity regarding to a traditional product. Methodologies: in the first phase, prototypes of Block H10 with Form-A are manufactured by extrusion at the laboratory level as a comparative witness of the properties of a standard piece and Form-C as a piece with thermo-insulating strategies to execute physical-ceramic, geometric evaluations of mechanical resistance and water absorption applying the Norma Técnica Colombiana 4017 for masonry units. In the second stage, simulations of temperature distribution and heat flow are prepared by finite element method in ANSYS R16 software to determine the incidence of the variables in the mixture on heat transfer. The results obtained from thermal simulations show an energy decrease of 1.5 °C on average in relation to Form-A. In conclusion, the use of agro industrial scraps and the implementation of passive design techniques in the ceramic piece generate added value in a product that can be industrialized with improvements in technological properties from a thermal efficiency perspective in construction ceramics.

Three mixtures were made for conventional concrete with different additions of cement, 300 kg/m³, 350 kg/m³ and 400 kg/m³, being these the 3 designs of mixtures more used for the elaboration of simple concretes. For each of the conventional mixtures, the % of water used for mixing was varied, which constituted 60%, 65% and 70% of the weight of the cementitious material. These % were taken in gradual increase to the one traditionally used in each of the mixing designs made. The aggregates used were assigned by Transmateriales S.A, located in the city of San José de Cúcuta, Colombia. The analysis of the materials of the mixtures, were carried out under the standards of the "Normas Tecnicas Colombianas" and the Tests of the "Instituto Nacional de Vías". 40% of the concrete mix cementitious material was replaced by fly ash and hydrated lime. In order to determine the mechanical behavior of the mixtures resulting from partial addiction. The ash was collected from the thermoelectric Termotasajero S.A, located in the city of San José de Cúcuta, Colombia. The hydrated lime was recovered from the municipality of Malaga located in the department of Santander, Colombia. Of the % of cementitious material replaced, 30% corresponded to lime and 70% to ash, as an experimental basis for the production of unconventional mixtures. Having the % of cementitious material to replace and the % of substitute material, 3 designs of experimental mixtures were made taking as base each one of the designs of conventional mixtures made, with equal % of water for its mixing. Twenty-seven cylinders were manufactured for the experimental mixtures and the same number for conventional mixtures, a figure that corresponded to the production of 3 specimens per % of water added in each of the established mixture designs. The compressive strength of the cylinders made in the materials resistance laboratory of the Universidad Francisco de Paula Santander, San José de Cúcuta, Colombia was tested. It was concluded in the influence of the % of water in the mechanical resistance of the experimental mixtures and the viability of the use of this type of mixtures in the elaboration of nonstructural concretes, data of importance with which the construction costs would be reduced considerably, generating in turn, a positive environmental impact by means of the inclusion of residual materials in the concrete mixtures.

Steel reinforced concrete is the most commonly used composite material in construction; however, large amounts of energy, natural resources are required for its manufacture and is susceptible to corrosion in the presence of aggressive environments. However, there are alternatives aimed at sustainable development, through the gradual replacement of ordinary cement with other Supplementary cementitious materials. Consequently, the present investigation evaluates the effect of fly ash and granulated blast furnace slag on the electrochemical phenomena of steel bars, embedded in a cement paste matrix, characterized by scanning electron microscopy, X-ray fluorescence and area surface to establish variations in electrochemical phenomena evaluated by Tafel extrapolation curves, half-cell potential, resistance to linear polarization and electrochemical impedance spectroscopy. The electrochemical conditions show that the surface areas and composition affect the passivation degree; therefore, mixtures with FA generate passive protection and on the contrary, the mixture with GBFS does not present any type of corrosion protection.

In order to analyze corrosion resistance and wear behavior, steel cylinders were coated with chromium silicon nitride via physical vapor deposition, using a reactive sputtering magnetron, with base and working pressures of 4*10⁻⁶ mbar and 8*10⁻³ mbar respectively. The diffraction patterns correspond to chromium nitride and the amorphous phase of silicon nitride, hardness of 6.52 GPa, thickness of 3 μm and chemical composition characterized by nitrogen, silicon and chromium. The corrosion behavior was determined with a rotating cylinder electrode, rotating at different speeds and connected to a Gamry potentiostat galvanostat, using the techniques of polarization resistance, electrochemical impedance spectroscopy and dynamic potentiation polarization. The tests were carried out in solutions composed of water, 1% of sodium chloride and silica sand, with temperatures of 25 °C and 45 °C. Limiting current density behavior was evidenced. The coating corrosion rate was reduced by up to two orders of magnitude compared to that found for steel samples and was affected by the system rotation speed, particle size and electrolyte temperature.

In sewerage systems, the corrosion process caused by microorganisms, has been studied. This affects the structural integrity of the concrete drainage pipes and the sewage treatment plants, This article is a review of research which focuses on the study of how to reduce the production of hydrogen sulfide, how to improve the resistance of concrete through the use of additives and the implementation of antimicrobial techniques to reduce bacterial growth, This review allowed us to find a way to improve the physical simulation of exposure to the corrosive medium through chemical tests, as well as the optimization and choice of the type of zeolite that would be incorporated into the mixture with which concrete pipes are normally manufactured. for sewers in Colombia improving their durability conditions.

Research studies on the kinetics of the corrosion process that attacks concrete coincide in the amount of variables that interfere with the process, such as the impact of the pH levels of the corrosive environment and the surface of the concrete and the concentrations of biogenic sulfuric acid at the site. For this reason, it is vitally important to know the resistance of concrete to this attack in controlled laboratory conditions, defining a methodology that contributes to the development of new research related, for example, to the degradation of concrete in component elements of a sewer system.

Steels are part of the basic equipment of most of the industrial framework, including very diverse sectors such as the oil, chemical and automotive industries. However, steels are susceptible to wear phenomena limiting their life in use and losing efficiency in the applications to which it is intended leading to a technological and economic problem. In mechanical systems, lubrication requires effective strategies to ensure that the increase in critical contact voltages does not cause material failure during operation. Although there are different ways to avoid the wear of steel parts, the development of material technology has allowed the manufacture of new alloys with anti-wear properties. Replacing steels with other higher cost materials is very unfeasible. For this reason, one of the alternatives of greatest interest to reduce wear is based on the surface modification of the metal through the use of coatings. The sol-gel method allows the manufacture of coatings on steel parts to reduce wear. The objective of this work was to manufacture, using sol-gel, bismuth-titanium coatings on 316 L stainless steel substrates in order to analyze the mechanical wear of the system and evaluate its wear rates and friction coefficients. The study focused on determining the effect of precursor concentration on performance as a film to reduce wear. It was determined that the friction coefficients show significant variations due to adhesive wear processes. With respect to wear, it is concluded that the coatings offer substrate protection by indicating wear rates lower than those reported for 316 L stainless steel substrates without coating.

The well-known scientific problem about global warming and less cost energy requirement, has been boosting to the petrochemical sector to implement eco-efficiency strategies by promoting the use of critical conditions throughout the traditional chain process of oil refining. In addition, many industrial combustion processes are developed using as energy source a mixture of natural and recovery gases, which added to high temperatures generate potential corrosion atmospheres. Thus, this research aims to try to reduce the pipeline degradation that take place in combustion environments by evaluating an yttrium oxide as coating for the ferritic 9Cr-1Mo steel. This coating was deposited on the substrate by plasma laser deposition, and several growth times were implemented to evaluate its thickness effect. On the other hand, in order to obtain the real combustion atmosphere, a flue gas model composition was selected, which was useful to calculate the theoretical oxidation products by simulation. Finally, those coatings were evaluated at 650 °C and testing times from 1 hour to 100 hours inside the calculated oxidation environment. The main results indicated that even with the tested coatings, the evaluated alloy had a severe corrosion velocity, but lower than without them.

Rotodynamic pump is a commercial machine and very used in the factories so the use of centrifugal pumps or rotodynamic pump operating as turbines or motor machine offers a technically and economically viable alternative to traditional turbines, the selection and implementation of a pump that functions as a turbine is a subject that is still under development. In this investigation the process of selection and implementation of the centrifugal pump is performed where centrifugal pump works in reverse mode, as a turbine, and mechanical adaptations are made for proper operation. The hydraulic system consists mainly of a forced pipe and a tank at a height of 13.3 m. In the built equipment a maximum efficiency of 58% was obtained at 890 rpm and an electric power of 45 W with a consistent load of a 120 V and 70 W bulb. The results obtained in this case study are comparable with the results of conventional turbines.

This work sought to estimate the economic and environmental potential of palm kernel shell for hydrogen production as energy vector in Norte de Santander, Colombia. A field research determined that the department generates monthly 14082 t of palm biomass of which 12501 of palm kernel shell remain available for their use. The proximate and ultimate analyses of the palm kernel shell report high heating value (19.53 MJ/kg) compared with other agro-industrial biomasses, high content of volatile material (69.82% w/w) and fixed carbon (21.68% w/w), promoters of chemical reactions in pyrolysis and gasification processes, respectively. In the Aspen Plus^® simulation process of the palm kernel shell gasification at 900 °C and steam/biomass ratio of 1.5, a yield is obtained of hydrogen production of 40.7%, equivalent to a monthly production in Norte de Santander of 51.6 t. Using H₂ in the generation of electric power permits producing 470.9 MWh/month that represent theoretical utilities of US$27734.5. In another scenario, 55848.8 gal/month of gasoline are substituted, equivalent to US$11708.6 through the sale of carbon credits. Regarding diesel, 45905.1 gal are replaced per month, which add US$9725.4 through the commercial transaction in the carbon market. It is concluded that using palm kernel shell as primary source to obtain H₂, has, in principle, a favorable economic and environmental impact for sustainable development of the department of Norte de Santander, besides contributing to the knowledge base on the penetration of this vector in Colombia's energy matrix; however, more detailed technical and economic studies are needed to conclude regarding the economic viability of this energy conversion process.

The current work reports the synthesis and characterization of a photovoltaic material based on the CuIn_1−xGa_XSe₂(X = 0.3 y 0.5) system, making use of the doctor blade method. For this purpose, homogeneous inks were obtained and worked under previous stoichiometry arrangement. The deposition process of thin films, were made in a heating plate on conventional glass substrates, previously washed and treated for this purpose. Once the layers of Cu, In, and Ga were deposited by chemical bath, a thermal treatment was performed at 550 °C for 30 min in a conditioned oven, in which the selenization process was performed. The obtained films were characterized by X-ray diffraction, Raman spectroscopy, solid-state impedance spectroscopy, UV spectroscopy and scanning electron microscopy techniques. The identification of the main crystalline phase could be corroborated, as well as the conductive and optoelectronic behavior of the solids in accordance with reported in literature. Simultaneously, it was checked that the method used allows obtaining layers of an optimum thickness, in order to be used as an absorbent layer in the design of solar devices.

This paper addresses the design of an algorithm that estimates the irradiance and the selective layer temperature of the all-glass vacuum tube as a function of the ambient temperature in Bucaramanga, Northern Colombia. A Matlab code to meteorological National Aeronautics and Space Administration data processing and to find a linear relationship between the irradiance and ambient temperature on the location of study, was developed. The behavior of this relationship for several hours of the day was studied, and it was found that it is possible to use this relationship as a reliable preliminary approach in water heating systems design using all-glass vacuum tube. This facilitates the design calculations and would encourage the use of solar energy in water heating systems in Colombia.

This research was conducted to identify two acceptable precursors and methods of synthesis for the manufacture of photovoltaic cells. The kesterite Cu₂ZnSnSe₄, a promising material for solar cell applications, was synthesized from metal salts of Cu, Zn, Sn, and Se, by two low-cost routes: the direct dissolution of metal nitrates, and coprecipitation of selenites. In both cases, inks were obtained and deposited as thin-films by the Doctor Blade technique on glass substrates coated with molybdenum. The films were annealed in an oven at 550 °C by 30 minutes. The phases of each thin film were analyzed by X-ray diffraction and Raman scattering. The morphology and the thickness of the layers were observed using a scanning electron microscope. The optical band gap was determined by ultraviolet-visible spectroscopy and the Tauc equation. The results confirmed the main phase of kesterite material, consistent with a tetragonal crystalline system oriented along the plane (112). These values are consistent with those found by Raman spectroscopy, where the main vibrational mode was identified at 173 cm⁻¹ and 196 cm⁻¹, characteristic of mode A vibration, and 243 cm⁻¹ of mode B vibration; typical of kesterite. Simultaneously, a band gap of 0.89 eV was identified. These results demonstrate the effectiveness of the selenite's coprecipitation method for synthesis of kesterite, without evidence of secondary phases. This determines the possibility of using this material in solar cell applications.

The present work describes the obtaining of semiconductor materials with kesterite structure by a hydrothermal methodology. The obtained kesterite has a structural modification of the conventional Cu₂ZnSnS₄ structure with the insertion of titanium instead of tin, in order to obtain Cu₂ZnTiS₄. The precursors of this material, metallic salts of copper, zinc acetate, titanium butoxide and thiourea were added in a hermetic steel reactor, controlling time (24 hours, 48 hours and 72 hours) and temperature (200 °C — 300 °C). To evaluate the synthesis, the materials obtained were analysed by different characterization techniques (X-ray diffraction, scanning electron microscopy, solid state impedance). The results show that material with the conditions of synthesis 48 hours and 300 °C, exhibit the best textural and electrical results in terms of economy process. The X-ray diffraction analysis shows secondary phases, which can possibly be eliminated with a thermal treatment, since most of the secondary phases (such ZnS and Cu₂S) can be eliminated by combustion in an inert atmosphere. The results showed that the increase in the temperature of synthesis decreases the formation of amorphous agglomerates, improving the morphology of the material. The characterization of the materials showed that the Cu₂ZnSnS₄ phase is possible to obtain by hydrothermal synthesis.

The present study examines the technical and economic feasibility of a biodigester to generate biogas from organic waste, such as human and food residues, generated during construction projects. Based on existing data and the scaling model selected, the quantity of such waste was estimated on a per-worker basis over a period of 30 days; yielding a daily average of 86 grams of food waste, 250 grams of stool, and 1.5 liters of urine. These estimates are scalable for the calculation of periods of greater or lesser duration. The data, variables, and calculations were analyzed using a technological tool developed for this study, such that other users or parties interested in the use of a biodigester for the management of organic wastes and biogas generation in construction projects can enter the relevant data for their project and generate scaling and cost data as an output. The use of a biodigester for construction projects is based on real-life experience in various sectors, for the most part in rural areas and domestic applications; while factors such as space, maintenance, and safety, among others, have hindered the use of this technology in the construction sector. Nevertheless, its implementation in new construction projects drives positive social, environmental, and economic impacts, as it reduces the volume of organic wastes for disposal, and substitutes for the use of fossil fuels. The latter results in a reduction of pollution, and improves the environment, with corresponding positive effects upon human health and wellbeing. It also represents an opportunity to reduce the cost of gas consumed during the construction process of residential buildings.

The purpose of this study is to design an autonomous solar system as an alternative to the electrical energy use of San Agustín building in the municipality of Ocaña, Colombia. The building has 8 floors of which the commercial and administrative zones consume 2447.2 Wh per month. Considering that electricity costs are high, the project focuses on lowering energy consumption in the billing. The research is carried out with the development of the phases of analysis, diagnosis, and design, in order to encourage the use of renewable energy in the building. The academic study is limited to providing the design of the autonomous system to the owners of the building to continue with the investment phase. The results are based on establishing the structural and energy parameters and validating the implementation of the solar power system taking into account electricity prices, which results in the use of 15 panels of 275 Watt and 7 panels of 325 Watt with a saving of approximately 1.500.000 Colombian pesos.

The proper disposal and management of the waste generated from the agro-industrial activity in Colombia constitute a problem with environmental, economic and social implications, such that its solution constitutes a matter of national interest. Thus, the objective of this work is to estimate the potential of biomethane production by biochemical conversion of selected agro-industrial waste and, its use is proposed in vehicular transport currently moved by natural gas. Methodologically, the study relies on official statistics of the national entities that report the volume of crops and waste generated yearly, Three crops were selected, applying criteria of abundance, geographic distribution, and energy properties: sugarcane, palm oil, and rice; the waste considered for each of them were sugarcane bagasse, empty fruit bunches of palm oil and rice straw. The conversion of said waste to energy vectors is by anaerobic digestion producing biogas, and from its purification, biomethane. The volume of biomethane obtained was 1,290x10⁶ m³/year. This important value was compared with studies from other countries. The prospects for the final use of biomethane as vehicle fuel are promising. So, biomethane is a potentially attractive develop option in Colombia, which would make it necessary to carry out more specific and detailed studies include economic, environmental and social aspects that would positively impact the route to the sustainable development of the country.

The present work carried out the analysis of seven natural gas liquids removal and recovery technologies, evaluating ten decision criteria to identify the technology with the highest technical and economic potential to be implemented at the gas plant "El Centro", Colombia. The technical criteria evaluated took into account: the chemical composition of the natural gas processed; the flow, pressure and temperature of the system; the efficiency in the removal of natural gas liquids and the technology adaptability against fluctuations that may occur in the operating conditions. On the other hand, the economic criteria evaluated included the purchase of high–cost supplies and equipment, as well as space and maintenance requirements for their implementation. Based on the analysis, the triethylene glycol improved absorption process was established as the technology with the greatest potential to be implemented at the gas plant "El Centro", Colombia, so it was evaluated in a pilot test where a reduction of 30 °F on the cricondentherm point was observed, associated to the removal of higher molecular weight hydrocarbons from the natural gas stream.

The present work carried out the internal inspection of the pipeline that allows the natural gas transport from the "Compresora Lisama" to the gas plant "El Centro" in Santander, Colombia, establishing the current pipeline conditions and defining the actions that must be taken to maintain the safety of the process. The internal inspection was carried out using Magnetic Flux Leakage technology, which allowed identifying in a single run the different types of anomalies that may occur in the 8" diameter steel pipeline during natural gas transport. The anomalies identified during the internal inspection inherent to natural gas transport through water bodies and unstable soils of variable height corresponded to thickness losses, dents, and programmed anomalies with estimated repair factor greater than 1. These anomalies were grouped into a total of 41 sections of the "Lisama–El Centro" gas pipeline that require replacement to guarantee the correct operation of the "Compresora Lisama" and the gas plant "El Centro", preventing unscheduled plant shutdowns that may lead to shortages in communities and companies that require daily the natural gas.

A magneto-dielectric material composed of a polyester resin-based microstrip (P115A), copper sheets and magnetite powders was designed in concentrations of 10, 20 and 30% Wt and with filters of 200, 325 and 500. The particles were aligned vertically and horizontally during the curing process using 300 mT magnetic fields. From a complete factorial design of 3³, 27 microstrip-type circuits of 4 mm width, 70 mm length and 0.93 mm thickness were manufactured, characterized by scanning electron microscopy and vector network analysis. The cross-matrix analysis determined an optimal circuit response from the magneto-dielectric material with a concentration of 20% magnetite and an average particle size of 21.48 μm in horizontal alignment to the applied magnetic field and to the transmission line, obtaining a relative dielectric constant of Er 3.88 with a low dielectric loss of 0.054, within an operating range of 150 KHz to 4 GHz.

The action of the microorganisms upon the integrity of the constructing material is termed Biodeterioration, concrete resistance to the action of the microorganisms is considered an indirect measurement of its durability and could be used as a marker of the integrity of the structure. In Colombia, the studies considering this parameter are rare. The objective of this study was to isolate and characterize the microbial communities present in areas with evident deterioration in the selected buildings. To accomplish this, isolation, culturing and molecular identification of the isolates was performed. Results showed that Cladosporium spp, Aspergillus spp, Mucor spp, Penicillium spp, Penicillium spp, Rhizopus spp, Fusarium spp, Geotrichum spp, and bacterial genera such as Bacillus spp and Amphibacillus spp, coexist within the biofilms sampled. This study is a description and a starting point to deepen the characterization of these communities and to understand the role they perform in the integrity of the building materials considering the climatic and environmental conditions.

The studies related to the Structural Health Monitoring have been important to evaluate the operation condition of structures, and let reduce the maintenance costs. The modal strain energy method has been used for this goal. This method requires to compare the information of mechanical vibrations acquired from the structure vs the same structure in initial conditions, called structure in health condition. This work is focused on developing a methodology that differs from the traditional modal strain energy. The methodology allows us to identify and evaluate the damage severity using a severity indicator.The methodology has been implemented in an offshore structure. The results have been satisfactory for the damage quantification for single and multiple damages.

Luminescent powders have attracted the attention of scientists, boosting properties as specific as mechanoluminescence, thermoluminescence, and photoluminescence among other characteristics. The uses of these properties have grown exponentially from recreational uses in luminescent paints, toys, plasticines, and other industry-specific uses, such as crack sensors, flaw detectors, and radiation meters in medicine. These uses have grown proportionately with their more economical and efficient manufacturing methods and processes, generating more economical fluorescent pigments. This paper characterizes and compares a low-cost luminescent pigment with those reported by different authors, its chemical composition was characterized by X-ray energy dispersion spectrometry, X-ray fluorescence, and Raman spectroscopy. Its morphology was analyzed by scanning electron microscopy, and its particle size with a laser meter its structural condition with X-ray diffraction, the powder obtained was presented as a strontium alumínate doped with divalent europium and trivalent dysprosium (Al2O4: Eu2+, Dy3+) one of the most efficient powders around persistence and luminance intensity at present. The structure of the strontium aluminate was determined by the main peaks of the diffractogram showing a monoclinic system. The elemental composition helped to determine the doping of the strontium aluminate corroborating them with the obtained with Raman spectroscopy and the scanning electron microscopy images.

Electromagnetic radiation (known as electromagnetic emissions) related to processes of loading and fracture in different types of materials (from metals to rocks) has been widely reported. The physical mechanisms behind these emissions are still under discussion, however, it is commonly accepted that they are created by some of the micro-cracks that appear in the sample during fracture processes. Nucleation and growing of micro-cracks generate mechanical waves (acoustic emissions), therefore, each electromagnetic emission should be linked with some acoustic event. Furthermore, it is expected that the electromagnetic and acoustic activities (number of emissions per second) have the same general characteristics. Contrary to what is usually reported, we find that there are significant differences between acoustic and electromagnetic emissions in loading processes on rocks. These differences were detected during the compression of a typical laboratory-scale sample of granite when it is compressed at a rate of around 20 kPa/s. We found two important discrepancies: i) There were at least 20 electromagnetic bursts (out of around 200) that were not coincident with any acoustic event. ii) The electromagnetic activity in general shows its maximum value when acoustic activity is very low. Both emissions just coincide at the moment of the final collapse. These results strongly suggest the existence of a non-fracture mechanism related to the origin of electromagnetic emissions. This could have important consequences for the field of non-destructive assessment of materials and even in the study of earthquake precursors and forecasting.

In this paper the strategy of the expectation maximization algorithm is developed in order to solve the problem of maximization of the likelihood which becomes a complex problem when it is expected to estimate multiple parameters at the same time. All this will be achieved with the introduction of basic concepts of statistical estimators and will be verified by simulations carried out in the MATLAB software.

In this paper we describe the qualitative analysis of the dynamic model of a solid-state laser. Initially a brief description of the theory of dynamic systems is made, the part concerning the qualitative solutions of non-linear models, the obtaining of fixed points for second-order systems and the determination of the stability of these points. Later, the dynamic model of the solid-state laser is exposed, where all its inherent parameters and the behavior that follows will be described. Then, the qualitative analysis is developed where the model will be converted to dimensionless equivalent that contains two parameters that condense to all the others. The results obtained are verified with numerical analysis, there clarifies the veracity of the qualitative analysis in conjunction with the description of the behavior of the solid-state laser, to finish with the conclusions obtained from the whole development.

In this document, the finite element method is developed in three dimensions to find the potential field in a region composed of hemispherical shells defining subregions with different materials, the numerical solution is made by FlexPDE software version 7.12 and the general process to solve is shown Problems of three-dimensional differential equations using the Galerkin criterion to approximate functions by the linear combination of functions of form, thus, the differential problem is reduced to solve a set of algebraic equations to find the coefficients of the linear combination.

In this work, we report the behavior of the tunneling current in a semiconductor nanostructure of (Ga, Al)As/GaAs which takes into account the behavior of the electrons and the Rashba's spin orbit interaction in the presence of embedded quantum dots of different geometries (lens, pyramid and ring) in voltage function, magnetic field, and the different values of the interaction spin orbit (π/2, π/4 and 3π/4). The results that were obtained show, that the intensity of the current presents appreciable changes when is changed the configuration of the quantum dot as the intensities of external fields and spin polarization as well. All these internal and external effects that are studied in our model, significantly modify the transport of information of the semiconductor nanostructure, our results show that the spin effects and the quantum dot configuration contribute to the quantum memories efficiency and the spin filter devices of actual use on nanoscience and nanotechnology.

The braking system of a car must work safely and predictably in any circumstance, which implies having a stable level of friction, in any condition of temperature, humidity and salinity of the environment. For a correct design and operation of the brake discs, it is necessary to consider different aspects, such as the geometry, the type of material, the mechanical resistance, the maximum temperature, the thermal deformation, the cracking resistance, among others. The objective of this study was to analyze the behavior of temperature, velocity and heat flow, in the ventilation duct of an automotive disc brake with ventilation pillars different from conventional using computational fluid dynamics. The SolidWorks Simulations design software was used to analyze the behavior of the fluid (air) in terms of speed and heat dissipation capacity. The numerical results for the heat flow through the ventilation channels were compared with the results obtained mathematically. The numerical results showed that the discs performed well under severe operating conditions. In the design of the brake disc is very important to select the appropriate geometry, particularly the number and the cross section of the ducts in addition to that, the type of material. Numerical methods offer advantages through the software tools for selecting geometry and material and for modeling fluid flow to optimize heat dissipation to provide maximum performance for properly maintained components.

Medical image segmentation is one of the bases of development in the field of personalized medicine, which allows the reconstruction of parts of the human body to produce virtual models by classifying pixels to create a surface or volume with similar properties. This work is focused on image segmentation through open-source software for bone structure analysis using the finite element method. According to this approach, the aim of this study is to investigate the sequential process, based on the features and requirements of the reconstruction software, to assess the segmentation tools and provide a comparative analysis. The methodology focuses on the software that has been documented for the anatomical reconstruction of organs and tissues, accounting for algorithms of manual, semi-automatic and automatic handling. Three segmentation packages are analyzed: 3D Slicer with a semi-automatic process called Region Growing, ITK-Snap with its interactive mechanism Active Contour segmentation mode, and, finally, In Vesalius with its automatic segmentation technique that identifies types of tissues and a simplified user-machine interface. A comparison is proposed based on the ease of the workflow, time for completion, the robustness of the tool, and precision of the semi-automatic and automatic methods, as opposed to the manual process, by statistic deviations and volume error obtained with Cloud Compare. The segmentation of a vertebra obtained from a DICOM© file in a computerized axial tomography was completed, and performance indicators were evaluated. The results showed that 3D Slicer - Grow from seeds is the best option to make the segmentation with a 9.59% of volume error and the fastest process among others.

In this work, the mechanical behavior of a connecting rod of a two-stroke single-cylinder engine is studied by means of finite element analysis to reduce its weight. We investigated the static and dynamic stresses on the parts of the connecting rod, considering the boundary conditions of the Jovaj theory for the design of automotive conrods. Then, the maximum stresses of the models were compared to perform the optimization of the weight of the connecting rod, evaluating the sensitivity of the prototype, and geometry restrictions. For the study using finite element analysis, a connecting rod prototype designed at Universidad Industrial de Santander was used, within the project of reengineering the connecting rod of a two-stroke engine of small displacement for agricultural applications. The mechanical response of the designed conrod was evaluated, taking into account the mechanical stresses to which it is subjected during the operation of the engine. Finally, the design was revised to propose preliminary improvements in the geometry using topology optimization.

The interest in developing experiments and processes in general through mathematical modelling or simulation, has been growing considerably in recent decades; the previous, insofar as it offers highly reliable results that have an impact on advantages such as reduction of the risk associated with the execution of costly or difficult to reproduce experiments since they handle many variables or even the elimination of times associated with the execution of said experiments. For its part, the study of hydrogen storage alloys represents a fundamental element in the so-called hydrogen economy, which seeks the integration of hydrogen as an alternative solution to dependence on fossil fuels, due that this energy vector has a high energy density when is compared to the gasoline and the only residue of this process is water vapor that will undoubtedly reduce CO₂ emissions. Thus, in this study a simulation of the evolution of the microstructure of hydrogen storage alloys based on TiCrV is developed, using ternary systems at different temperatures; this evolution is the result of the phase change when the elements are subjected from high temperatures to room temperature, obtaining a body-centered cubic structure. Likewise, the solidification process of the components present in the alloy is studied to corroborate the final structure with experimental data. In preliminary results, it is observed that the simulation throws a body centered structure, and in the solidification process, a remnant of a compact hexagonal structure is observed. This Ti-Cr-V system is widely studied due to its large hydrogen storage capacity, which can be used for technological purposes.

Soils with a tendency to show phenomena of collapsibility generally have a susceptibility to be controlled by partial saturation, due to its structural configuration which reveal in some cases bonds of cementing minerals, that can be broken in process of wetting. This cementation is governed by the lateritic genesis, as well as for a microporal predominance. Laboratory tests that intend to reproduce the unsaturated condition, need a suction control to simulate properly the levels of stress required in the sample, according with the in-situ stresses presents in the soil mass. However, these tests are difficult to have access to given that they have a complicated assembly and can last several days (even months), due to the benefit in the resistance imposed by the suction on the soil. For this reason, it is extremely important to validate numerically by means of an appropriate constitutive law, at least at the laboratory level, the unsaturated response of a material. In this case a collapsible porous clay of lateritic origin, cause the high dependency of specialized laboratory tests can lead to non-necessaries delayed researches, that can impact in the economy of any project. In this research, an emphasis is placed on the numerical simulation of partially saturated tests through a hypoplastic constitutive model that involves suction in its mathematical formulation. The results are oriented to show the dependence of the suction with the shear strength of the material.

This work presents a practical approach to obtain the dispersion curves for a plate via numerical modelling using the commercial software ANSYS. The method is based on the dynamic analysis of the waveguide to extract the mode shapes (eigenvectors) for each resonant frequency (eigenvalue) from the natural frequency response without damping. Each eigenvalue provides a frequency and the dimensions of the model (wavelength), which are the basis of the dispersion curves. Then, an algorithm is developed in MATLAB to stack the different mode solutions with its respective frequencies using the modal assurance criterion. The data obtained is compared with the dispersion curves provided by the GUIGW software.

The oil and gas exploration and production sector are one of the most significant methane emitters through fossil fuel combustion and fugitive emissions. In Brazil, there are few studies focused on the mitigation of methane in the oil sector. The objective of the present work is to use a multicriteria analysis methodology to compare different methane mitigation technologies applicable to offshore oil and gas platforms. In the study, six different mitigation options were compared through the analytic hierarchy process methodology, considering environmental, financial and operational criteria. The results were calculated for each mitigation option considering the scores of each criterion and their respective relative weights, obtained in the prioritization of the elements. This unique score obtained through the analytic hierarchy process made it possible to compare the mitigation alternatives. The alternative that received the best score considering the evaluated criteria was the recovery of vapor from cargo tanks associated with methane reuse, being highlighted mainly due to its high potential for mitigation.

A method which is based on quantum scattering theory and, particularly, on the Jost functions, is presented for solving the bound states problem of helium atom. Within this approach, the energies of bound states of helium atom were obtained as the sum of energies of a hydrogen atom and the energies that one electron needs to bind to an ionized helium atom in a collision process. We calculated the ground state energy and the energies of the first excited states of helium atom, and obtained remarkable results, This method could then be used as basis to study atoms with more electrons.

Physics is a science that studies the laws and properties of the universe and everything in it. However, it is more interesting when it is applied to the solution of problems that influence economic and social development. In our case, applied to beekeeping to ensure the purity of honey. Some producers or intermediaries add sugar or water to honey to reduce costs and improve their income affecting the final consumer. Therefore, in this research work, an experimental methodology was proposed combined with the development of software to determine the viscosity of honey with aggregates (sugar and water) and without those, considering that the experimental methodology used here, does not alter the properties of honey. With a ball viscometer and using honey as a viscous medium, times that took metal spheres to pass through the sample tube with different densities were measured. The times were analyzed and synthesized with the application to obtain the viscosity in real-time of the different types of honey, allowing to discern which ones were pure and which had water or sugar aggregates.

The problem of bound states of atoms with many electrons does not have an analytic solution; therefore, standard methods of approximation are utilized to solve it, and among them, we can find the variational method, the perturbation method and the Hartree Fock method. Said methods may be very difficult to implement and may take a great amount of computational time, even when they are applied to the lithium atom. An alternative method that is considerably easier to implement is proposed in this paper. This involves considering the Hamiltonian for the lithium atom as a collision between an electron and an ionized lithium atom; in this way, the energy of the lithium atom is the sum of energies of a helium atom (with nuclear charge Z = 3) and the energy that an electron needs to be bound to an ionized lithium atom in a collision process. The Quantum Collision Theory under the focus of Jost function was used to calculate the bound state energies of one electron with an ionized lithium atom. Using this approach, we calculated the ground state energy of lithium atom with an error with respect to the experimental value of 0.3%. This error is very low; therefore, the proposed method produces very good results and it can be taken as basis to study atoms with more electrons. Hopefully, In the future, this method could be part of quantum physics books because it is a novel method to observe the formation of atoms.

The glow discharge is the basis of conventional techniques used to improve the tribological properties of materials, such as the generation of thin films using ionic beams and the sputtering process for the treatment of surfaces. This work focuses on the numerical study of the glow discharge in a system composed of a cylindrical quartz chamber containing argon gas, whose length and radius are 20 cm and 2.5 cm, respectively. Said chamber is limited by two copper electrodes whose potentials are 0 V (Anode) and -500 V(Cathode), respectively. In order to analyze this time-independent discharge, the generation of secondary electrons allowing the discharge to be self-sustained as well as the manifestation of fixed regions, among others, numerical modeling is carried out by using the Plasma Module of COMSOL Multiphysics software. The presented results in this paper can be useful to understand, design and build new technologies focused on the area of treatment of surfaces.

As a contribution to the study of the resonant interaction between of an electron and the transverse electric field of a stationary electromagnetic wave in the presence of a static homogeneous magnetic field in this work we develop a numerical study of the acceleration of electrons by cylindrical mode TE₀₁₁. In order to get a better understanding of the particle-wave interaction, the electric field of the microwave mode is decompose as the superposition of a left-and a right-hand circularly polarized standing wave because electrons interact effectively only with right-handed circular polarized wave. The trajectory, energy and phase-shift between the electron transverse velocity and the electric field are determined by the numerical solution of the relativistic Newton-Lorentz equation using a finite difference scheme. For an electron injected longitudinally with an energy of 5 keV and that starts at the radial midpoint of the cavity, it is accelerated up to an energy of about 90 keV using an electric field amplitude of 14 kV/cm and a frequency of 2.45 GHz. These results are compared with those obtained for another two points of injection located in different radial positions. This levels of energy can be used to produce soft X-ray which has some important medical applications like imageology. The results suggest that the particle-wave interaction using the cylindrical mode TE₀₁₁ could be optimized through the application of a external magnetic field which is gradually growing in time to preserve the resonance condition and sustain the phase stability.

The magnetohydrodynamic equilibrium is the starting point to study macro- instabilities in a confined plasma; for the particular case, where the system is axially symmetric, the static and stationary equilibrium is due by the Grad-Shafranov equation. We present the equilibrium state for a toroidal plasma confined by a spherical Tokamak with aspect ratio A ∼1.6, total plasma current 1.3 MA and beta parameter β ∼0.35. The Grad-Shafranov equation is solved numerically in a rectangular region of the poloidal plane, using the finite differences method under a successive over-relaxation scheme. Profiles of poloidal magnetic flux, pressure, safety factor and magnetic field are presented. Subsequently, by using the resistive magnetohydrodynamic model, said equilibrium is subjected to perturbations in the velocity to study the dynamics of the plasma in the linear regime. The plasma dynamics simulation is carried out under a fourth order finite difference scheme for the spatial derivatives and implementing the Runge-Kutta algorithm as a temporal integrator. The results show that the perturbations are located in the plasma outer edge; however, some poloidal modes move toward the central zone around the magnetic axis.

The spatial auto-resonant acceleration scheme consists in the acceleration of an electrons beam by the transverse electric field component of a standing microwave field and an external inhomogeneous magnetostatic field, whose longitudinal profile is fitted to maintain the electron cyclotron resonance condition along of its helical trajectories. In practice, the external magnetic profile can be generated by a system of current coils. In order to save energy and the possibility to reduce space, we study the option to replace the coils by a magnetic rings system of uniform axial magnetization. In this work, we present both, the results of the magnetostatic field generated by a magnets system, which is calculated from the magnetization currents using the Biot-Savart law, and the acceleration of an electrons beam in the spatial auto-resonant acceleration regime employing said magnetostatic field. The electron trajectory, its velocity and energy are obtained from the numerical solution of the relativistic Newton-Lorentz equation, showing that is possible to accelerate electrons injected with energies about of some electronvolts to values about of 250 keV.

The aim of this research is to describe the temperature effect on the water absorption, linear shrinkage, density and compressive strength of ceramic composites produced by mixing clay with additions of foundry sand waste from 20% to 40% wt. Previous studies have shown that foundry sands can be recycled due to the high content of SiO2 on its chemical composition, therefore, in this research is proposed as an alternative raw material in ceramic bodies. Prototypes were shaped by uniaxial pressing method and fired at three different temperatures (850°C, 950°C and 1,050°C) in order to promote the formation of the ceramic phases. Physical and mechanical properties were measured based on the procedures specified by standard ASTM C373 and ASTM C773-88. It was found that at 1,050°C properties such as mechanical strength and density reach its maximum values, effect that might be associated to the reduction in pore size inside the microstructure during calcination. The main merit of the models obtained is offer a valuable tool to set up a proper thermal process in order to obtain eco-friendly ceramic samples with physical and mechanical properties at its optimum values, reducing environmental problems related to landfill disposal and minimizing costs of manufacturing.

The magnetron sputtering of cathode material is one of the ways of producing a thin film deposition on solid surfaces and maintaining the cathode system under a certain potential. Recently, some experimental study of a magnetron sputtering system with the segmented cathode at different electric potential on each segment has been conducted. It allows the system productivity regarding the rate of deposition to be over the volt-ampere current limitations imposed on each segment. The physical processes associated with generating and sustaining it in this system are complex and have not been explained so far from a theoretical point of view. In this work, we present a computational study of the electron dynamics in the simple particle approximation which is found in a two-segments magnetron discharge under the influence of both the magnetic field and the segment electric potentials of 750 V and 500 V. The fields are calculated by using comsol multiphysics ®. The particle dynamics is studied through numerical solution of the Newton-Lorentz equation. The simulations show that the Hall current symmetry is determined by the electrode segments geometry. The obtained results are checked through the simulations fulfilled to maintain the cathode system at the same potential.

Determining the charged particle trajectories in the inhomogeneous electric and magnetic fields is the common problem in the plasma physics. For the tokamak plasma, the orbits of the captured fast ions are affected both by the curvature and gradient of the magnetic field. In the present work, the fast ion trajectories and their guiding-centre orbits in a mega ampere spherical tokamak reactor are found with employing the numerical code, that was elaborated by our team, together with the leap-frog and Runge-Kutta techniques. The magnetic field is calculated by solving the Grad-Shafranov equation at the fixed boundaries on the non-homogeneous mesh grid. The obtained results show that the ions with the energies in the range 20 keV - 80 keV can describe the typical banana orbits as well as the passing trajectories in the poloidal plane. Finally, the numerical simulation scheme stability is tested.

Aqueduct systems help to record water consumption, being a connection between nature and the population, allowing water to be transported continuously; a good design of aqueduct networks is necessary to meet the purpose of providing the community with a technical report that can serve as a starting point to carry out a construction of the aqueduct for the public battery. This research presents the simulation of an aqueduct system by means of the epanet software according to the daily maximum flow, pressure, velocities of the distribution network, pumping time, with respect to the different pressures and diameters, diagnosing the routes, nodes, forms of access, restrictions and limitations that may affect the proper functioning of the system; In this way, the advantages and the magnitude of beneficiaries who will have this new access and improved service to meet the needs of the inhabitants are evident, according to the technical requirements of drinking water and sanitation of the technical regulation of the drinking water and basic sanitation sector, where it can be implemented by any public company in the country.

The demand for cooling and heating systems to adapt spaces is a critical environmental problem due to the high energy consumption required for its operation. For this reason, the offer of products for architectural facades should consider constructive solutions that mitigate the heating of buildings. Thermal behavior of building materials is an elementary factor in the energy consumption of buildings. This paper presents the comparative thermal analysis of 4 ceramic product designs for masonry, of which, one represents the traditional multi perforated brick and the others, are proposed to prove whether shape affects the heat transfer processes. The research methodology is divided into 2 stages: product design and thermal validation by transfer and heat fluxes in the ANSYS R16 software using the finite element method. For the design process, modification of the internal cells and elimination of the thermal bridge was implemented. Simulations were configured under the highest values of solar radiation recorded in the city of San José de Cúcuta, Colombia to know the products performance in the most extreme conditions of the city. The results indicate that design varies energy performance of the product, since it reduces the temperature of the inner surface to 1.23 °C or increase it to 2.25 °C. The results show that the modification of cells distribution and elimination of thermal bridges are passive strategies for the reduction of heat transfer in the design of ceramic product for masonry. This research is a breakthrough for future research that develops constructive units focused on improving the quality of life of people from thermal comfort, energy efficiency and the use of local resources and technologies.

This research work presents an experimental and numerical analysis of three-dimensional behavior to the compression of masonry prisms with solid brick, in pieces built-in artisanal ovens used in the municipality of Ocaña, Colombia, with the objective to determining deterministically the resistance to uniaxial compression and determine numerical models for structural design purposes. The experimental methodology consisted of determining statistically for solid clay brick units, the initial rate of absorption, final absorption, rupture modulus and resistance to uniaxial compression, and in masonry prisms, to uniaxial compression resistance and modulus of elasticity. The behavior observed in the uniaxial compression test in masonry prisms were validated in a commercial code of finite element modeling. The efficiency of the model makes it possible to predict the uniaxial compressive strength of masonry prisms in solid bricks built in artisan ovens. Allowing to reduce the number of tests in the future and perform probabilistic analysis.

The segmentation of the human body organ called liver is a highly challenging problem due to the noise, artifacts and the low contrast exhibited by the anatomical structures located around the liver and that are present in digital images, generated by any modality of medical images. The main modalities are: ultrasound, nuclear emission, magnetic resonance and the gold standard called multi-slice computed tomography. In this paper, with the objective of to address this problem, we consider multi-slice computed tomography images and we propose an automatic strategy based on two phases. In the first phase, a digital filtering bank is used for diminishing the noise effect and the artifacts impact in the quality of images. In the second phase, called liver detection, we use a smart operator based on least squares support vector machines for generating both the morphology and the volume of liver. The application of this strategy allows generating the morphology of the liver in a precise and efficient manner as it was demonstrated by the metrics used to assess its performance. These results are very important in clinical-surgical processes where both the shape and volume of liver are vital for monitoring some liver diseases that can affect the normal liver physiology.

The left atrial appendage is one of the anatomical places where most frequently blood thrombi occur. When migrating from the appendage, these thrombi, become blood emboli that, potentially, can compromise the physiology and/or anatomy of cardiac or cerebral blood vessels, being able to generate cerebrovascular events. The left atrial appendage segmentation is very difficult due, mainly, to its location and the identical densitometric information presents into of this appendage and around of the left atrium. In this paper, an automatic technique is proposed to segment this appendage with the purpose of generating important information to the procedure called left atrial appendage surgical closure. This information is linked to the volume and the diameters of the left atrial appendage. The technique consists of a digital pre-processing stage, based on filtering processes and definition of a region of interest and, of one segmentation stage that considers a clustering method. The results are promising and they allow us to calculate useful quantitative variables when characterizing the most lethal appendix of the human body represented by the mentioned appendage. These results are very important in clinical processes where both the shape and volume of this appendage are vital for detecting and monitoring some vascular diseases such as cardiac embolism, arterial hypertension and stroke, among others.

In the presence of pulmonary pathologies such as chronic obstructive pulmonary disease, diffuse pulmonary disease and cystic fibrosis, among others, it is common to require the removal or replacement of a portion of lungs. There are several requirements for both donors and organ receivers (recipients) established in the literature. May be the main one is the volume that the donor's lungs occupy in the thoracic cavity. This parameter is vital because if the volume of the lungs exceeds the thoracic cavity of the recipients the transplant, logically, is unfeasible for physical reasons such as the incompatibility between the receiver lung volume and the donor lung volume. In this sense, the present paper proposes the creation of a hybrid technique, based on digital image processing techniques application to raise the quality of the information related to lungs captured in three-dimensional sequences of computed tomography and for generating the morphology and the volumes of the lungs, belonging to a patient. During the filtering stage median, saturated and gradient magnitude filters are applied with the purpose of addressing the noise and artefacts images problems; whereas during the segmentation stage, methods based on clustering processes are used to extract the lungs from the images. The values obtained for the metric that assesses the quality of the hybrid computational technique reflect its good performance. Additionally, these results are very important in clinical processes where both the shapes and volumes of lungs are vital for monitoring some lung diseases that can affect the normal lung physiology.

Leishmaniasis is a complex group of diseases caused by obligate unicellular and intracellular eukaryotic protozoa of the leishmania genus. Leishmania species generate diverse syndromes ranging from skin ulcers of spontaneous resolution to fatal visceral disease. These syndromes belong to three categories: visceral leishmaniasis, cutaneous leishmaniasis and mucosal leishmaniasis. The visceral leishmaniasis is based on the reticuloendothelial system producing hepatomegaly, splenomegaly and lymphadenopathy. In the present article, a semiautomatic segmentation strategy is proposed to obtain the segmentations of the evolutionary shapes of visceral leishmaniasis called parasites, specifically of the type amastigote and promastigote. For this purpose, the optical microscopy images containing said evolutionary shapes, which are generated from a blood smear, are subjected to a process of transformation of the color intensity space into a space of intensity in gray levels that facilitate their subsequent preprocessing and adaptation. In the preprocessing stage, smoothing filters and edge detectors are used to enhance the optical microscopy images. In a complementary way, a segmentation technique that groups the pixels corresponding to each one of the parasites, presents in the considered images, is applied. The results reveal a high correspondence between the available manual segmentations and the semi-automatic segmentations which are useful for the characterization of the parasites. The obtained segmentations let us to calculate areas and perimeters associated with the parasites segmented. These results are very important in clinical context where both the area and perimeter calculated are vital for monitoring the development of visceral leishmaniasis.

Chrysopogon zizanioides is a plant with adaptability characteristics in a variety of soils and climatic conditions, improves quality of wastewater and industrial water, due to the root system, allows the consumption of organic matter and capture pollutants. One of the water quality indicators is the amount of dissolved oxygen present. To analyze the recovery behavior of dissolved oxygen in wastewater, an artificial subsurface flow wetland was designed with stone as a filter material with dimensions 0.9 m wide, 2.5 m long and 0.60 m deep and 30 Vetiver plants. These dimensions and quantity of plants were considered appropriate in terms of space and low cost in order to replicate in rural and semi-urban areas, because in some of these they do not have an appropriate aqueduct, then this strategy becomes an option for people residing in these places. The water treated in this wetland is domestic wastewater from a rural house in the municipality of Floridablanca, Colombia. For 4 weeks the data of the dissolved oxygen present in said water was recorded using a multiparameter probe, to observe how effective the process is in a shorter time and using fractal dimension the volatility of this time series was observed.

Mathematical models allow evaluating air pollutants effects to the environment, being a relevant tool for planning and regulatory purposes. The present study aims to evaluate the air quality of Volta Redonda, Brazil, due to particulate matter emitted by stationary point sources of a large steel plant using meteorological data from three monitoring stations. A mathematical model was developed linking Matlab® and RStudio®, using the Gaussian dispersion equation and Google Maps to visualize the results. Observed data revealed southern, north-western and northern light prevailing winds that were used to simulate stable and unstable atmosphere conditions according Pasquill-Guifford classification. Results have exposed elevated concentrations of particulate matter in ambient air, reaching particularly Santa Cecilia neighbourhood. National air quality standards recently updated were partially met however numerous violations were indicated, considerably higher in Santa Cecilia station (47.98%), followed by Belmonte (6.69%) and Retiro (4.17%), indicating a forthcoming need for an update of the technologies and processes that emit particulate matter to improve the city air quality, preventing from environmental and human health effects.

In this paper is proposed an ontology framework for an autonomic reflective middleware for the management of nanodevices, which is based on the ontology-driven architecture paradigm. In this paper are presented the different levels of the ontology driven architecture model. At the first level, the computation independent model level defines the different ontologies of the nanotechnology domain, like a taxonomy of nanodevices, among others. The second level is the platform independent model level, where are defined the different ontologies for the deployment of the platform, which are the autonomic computation for the autonomous behavior of the middleware, data analytics that describes the analysis process of nanodata, and service-oriented architecture because the autonomic reflective middleware is defined as a multi-agent system oriented by services.

Searching to encourage and increase the desire of students to seek a vocation in the study of engineering and science, we wanted to implement and validate experimentally and numerically, the study of the movement of a mechanical oscillator using, in this case, a physical pendulum, formed by a bar and a disk. In this article has done the study the physical pendulum, combining a methodology that involves an experimental arrangement and the implementation of simulations developed in Python, with the aim objective of offering to students a visual and interactive experience, so that they can understand in a simpler way topics covered in the theoretical physics course, in such a way that is different from the typical physical-mathematical formalism. This study was carried out with low cost materials and easy access, in addition to the great social impact that I had against the acceptance and assessment by the students with whom this work was applied. This work was developed in three phases: first, to measure the period of oscillation of a physical pendulum experimentally. Second, the approach of the analytical model to compare with the experimental results. Third, the development of a dynamic simulator according to the predictions of the theoretical model. The students found a didactic and different way of studying the physical pendulum. Finally, it was possible to demonstrate a self-consistency between the experimental and numerical results of the system studied in this work.

The implementation of research intervention strategies is presented as the main theme of this longitudinal study, within the framework of the application of the research agenda of engineering programs. Classroom work, training practices, business practices, classroom projects, and research group projects are proposed as training scenarios. The strategies are actions that are applied in three productive processes of interest for the engineering, such as: (i) productive process of object systems (ii) primary biomass productive process and (iii) primary artisanal cosmetics production process. The objective is to show the results of the research agendas application as an academic process planning tool for form research competencies. Three cases have presented that show the knowledge construction and the research intervention traceability in different the engineer fields in his training process. The three production processes become application centers of an area of the engineer research interest, as is the supply chain optimization. In the results, the planning methods of the agenda highlight, with the collective construction of knowledge of the training process, the targeting of the area of research interest, the linking of actors, the articulation of research lines of the program, and the scope of the strategies of intervention and didactics by scenarios. The study shows training relevant processes in the economic, social and environmental fields, promoting collective learning opportunities and fostering innovation through inclusive industrialization.

This study calculated the volume of capturable rainwater over a three-month period at the Alberto Santos Buitrago school in the municipality of El Socorro, Colombia. Rainwater is frequently an under-developed natural resource, due to the minimal investment by public entities, and to the lack of awareness and education of the local inhabitants in this regard. Due to the significant climatic changes occurring across Colombia, however, new interest has arisen in utilizing this resource. The Universidad de Santander, Bucaramanga, Colombia, and the Universidad Libre in El Socorro, Colombia, have joined forces to promote projects focused upon the use of these resources to ameliorate the condition of vulnerable green areas, which tend to deteriorate during dry summer months, as occurred during this study, due to local geographic conditions and the impacted population; in these case young, low-income students of this rural municipality. Such a water storage and distribution system could also serve a valuable role in the school's sanitary facilities, and for cleaning public areas, with a total of 35.01 m³ of rainwater collected on school roofs. Nevertheless, upon the delivery of the results of the current study, a significant lack of interest was evident on the part of the directors of public institutions in implementing this type of sanitary system. It is thus necessary for the community itself to commit to incentivizing and promoting the implementation and improvement of these new mechanisms.

This article presents a guide to good practices around internet safety of things for devices that get involved with smart homes. It is chosen to use a quantitative methodology of descriptive approach, taking into account that it is a topic that is in incursion and it is necessary to begin to establish the elements that are going to incorporate in the guide. The starting point is a study of the internet layers of things, the open web application security project and the components that make up the guide. This research allows to make a contribution with an analysis of the future of the internet of things and to expose the considerations on the security that involve these devices, taking as guide the tools, documents and information that the project proposes for the development of systems of high quality in security.

The Colombian ministry of information and communications technologies is leading a digital revolution to bring computer and internet equipment to rural areas, taking into account that in these areas there are educational establishments that do not have equipment and materials for the performance of laboratories or experimental demonstrations. Therefore, this project proposed the development of a virtual learning laboratory for the study of the elastic modulus, obtained from real tensile-compression tests. It is important to clarify that there is not theoretical procedure to obtain stress-strain curves out of their linear regime. The virtual laboratory was developed in python language. The simulation allows the students to manipulate tensile-compression test for different materials. Also, they can visualization of the procedure, the stress-strain curve, and the Young modulus, all with the aim of transferring the conceptual and procedural knowledge of the physical phenomenon to the student.

This research work aimed to analyze through research results in some sports how the application of technology affects the diagnosis and planning of sports training. within the methodology, different types of theoretical methods were used, such as analysis and synthesis, the logical history that, through the findings found in different specialized databases, allowed us to find different positions and theoretical references that allow us to affirm that winning in national and international competitions is the product of conducting a well-planned interdisciplinary work, the use of methods such as quasi-experimental that is based on the pre-test, the pedagogical intervention and the post-test was carried out through the use of the technological implementation used in sport as it is through sport machines such as contact platforms, linear encoders, sports preparation software, tablets, and mobile devices that facilitate the roles of the coach and his interdisciplinary group that through technology demonstrates have better results in the data processing, evaluations, and treatment of injuries of their athletes. The work allows managing evaluative information of different sports disciplines about the level of physical, technical, and tactical preparation and other aspects of sports preparation that access to identify characteristics of sports performance of the athlete. A descriptive and application research approach was assumed that through a training plan allows to capture and generate key information for the identification and characterization of the most important aspects of the control and monitoring of the athlete as they are actors (individual, institutional, corporate), that includes elements of personal data, results of physical, technical, tactical tests and thus, having reliable data that allow us to predict results in different sports competitions As results the specific requirements expressed in user stories were obtained and the strengths and weaknesses of the athletes understudy taking into account that the social impact is to be able to use sports development mechanisms that help the orientation and selection of sports talent found in the different slums and neighborhoods of the region which will allow through sport a comprehensive education and environmental care through a sports and pedagogical process that allows it to grow economically not only in the sale of services that can be generated with the use of state of the art technology but with the economic projection of what can be worth a high-performance athlete. In conclusion, reliable information was obtained, for the realization and control of different training plans generating inputs for decision-making in the approach of different possibilities seeking to solve very particular aspects of the computerized and disciplinary management of sport, the use of technology applied to sports training represents a significant advance in reducing costs, time and processes in the training of athletes with a view to professional sports.

The competitive programming contests are competitions where the programming capacity and algorithm of the participants are measured. The objective of this work was to develop and implement a framework to formalize the working methodology of the competitive programming study group of the Universidad Francisco de Paula Santander and to develop a web-based training platform to monitor the work carried out within the study group. The intention with this platform is to give the students the tools they need to carry out their training, from the platform the student can study, can practice, can compete, and can improve their skills both in competitive programming, as well as in areas of programming and computer science. This work was carried out following an iterative methodology composed of the following phases: initially, the project has been formalized, analysis of the problem, preliminary details, and formation of the state of the art and theoretical reference. Then, the initial state of the group is diagnosed, a solution is proposed. After refining this solution proposal. Once implemented, information and metrics are gathered and the results are analyzed, already with a functional framework and a web platform, to detect problems and improvements, restarting the phases, for improving in each step those aspects that can be enhanced. The results obtained in the national and international contest have improved considerably and the participation and satisfaction of the students who are part of the study group were increased. The technological platform developed constitutes a confluence point for the study group, and a clear guideline to follow to advance in the process of continuous improvement that allows the university to achieve the best results in national and international programming competitions.

This article describes the impact of collaborative work to teach Mathematics in Seventh graders (70 students) at the school Isidro Caballero Delgado, Ocaña, Colombia. Led godt education system and fischertechnik allowed a great interaction and participation and provided the tools to incorporate robotics in the classroom. Moreover, these tools are used as a learning strategy to achieve understanding and analysis in the solving problems teaching math. Students became more critical and responsible facing daily solutions and a better understanding of basic problems of geometry, math and statistics. Students also learnt about and improved interpersonal abilities and improved social interaction. It also allowed making learning effective creating a better environment to improve the acquisition of mathematical concepts.

This paper presents the results obtained from the categorization of the social representations of farmer groups on the effects of climate change on the biodiversity of their farms, developed in a rural area of the Colombian Andes. A mixed methodology was used throughout the analysis of the behavior of rainfall and temperature between the years 2010-2017 and the implementation of an open survey on 144 farmers, of which its data was analyzed using descriptive and inferential statistics through descriptive estimators and an analysis of variance and multiple comparison mean tests, respectively. Furthermore, a qualitative analysis, supported by Corbin and Strauss' Grounded Theory, was carried out on 18 farmer families using semi-structured interviews. The hypothesis testing determined the existence of significant differences between the mean temperatures of the years observed when obtaining a value of F_c = 3.50, highly significant at 1%, and a value of F_c = 2.79, significant at 5%, P<0.05, for the mean rainfall. In the descriptive analysis, farmers' perception of the negative effects of climate change was evident in the decrease in the availability of water from natural sources (80.6%), deterioration in water quality (50.0%), variations in rainfall intensity (82.0%) and in local bimodal rainfall patterns (79.0%). The inferential analysis determined that the proportion of farmers reporting a disappearance of species due to intense heat or rainfall differs significantly from the level of p<0.05, over those who reported that these conditions have not caused variations in flora and fauna. The qualitative analysis verified the effects of climate change on rural biodiversity resources, which were expressed in 4 emerging categories: 1) Biodiversity resources in the process of extinction, 2) resilient resources, 3) emerging biodiversity, and 4) new agricultural business opportunities. The findings reveal that from a farmers' perspective climatic variations are affecting species of fauna and flora in rural communities.

This study was carried out at the "Universidad de Santander", in Bucaramanga, Colombia, to calculate the volume of rainwater capturable from the roofs of five campus buildings, as the blueprints for these surfaces were available to obtain their areas. Roof areas were first obtained for the Guane, Motilón, Arhuaco, Chibcha and Yariguíes buildings, from which rainwater can be captured. Intensity, duration, and frequency curves from the "Instituto de Hidrología, Meteorología y Estudios Ambientales" were then used to calculate a design flow, yielding the diameter of the pipe necessary to evacuate the water captured. In addition, data from the "Universidad de Santander" meteorological station was evaluated to obtain monthly rainfall figures. The highest-yielding structure was the Motilón building, with approximately 80 m³ in the months of May and November, 2018, as this structure has the largest roof area, and the area experienced its greatest quantity of rain during these months. The total accumulation predicted by the study was 1837.96 m³ annually, sufficient to suggest the possibility of its use in restrooms, gardens, and floor washing at the "Universidad de Santander", Bucaramanga, Colombia. The volume of water calculated is variable on a yearly basis, and was estimated by means of one year of rainfall readings from the university's meteorological station. Hydraulic structures designed for the purpose of capturing this water would require a specific study, taking into account the records of other nearby meteorological stations, and making necessary provision for the storage of water in excess of expected volumes.