Table of contents

The International Scientific Conference on Communications, Information, Electronic and Energy Systems (CIEES'2021) was held virtually in Ruse, Bulgaria from 25 to 27 November, 2021. The CIEES'2021 was organized by the Association CIEES with the following partners: University of Ruse (Bulgaria), Politehnica University of Bucharest (Romania), the Union of Scientists in Ruse (Bulgaria) and Encon Services Ltd (Bulgaria).

In light of the current situation related to the coronavirus (COVID-19) and regarding to the internal government regulations from the Bulgarian Ministry of Health, the Organizing Committee took the decision to turn CIEES'2021 in a virtual format – online conference on the same period.

The goal of the CIEES'2021 conference is to provide an international forum for researchers, academics, people in industry, and students to address recent research results and to present and discuss their ideas, theories, technologies, systems, tools, applications, work in progress and experiences on all theoretical and practical issues arising in telecommunications, electronics, signal processing and applications, information technologies and energy.

List of CIEES 2021 Organizing Committee, CIEES 2021 International Scientific Committee are avilable in the pdf.

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

• Type of peer review: Single-blind

• Conference submission management system: Microsoft CMT - https://cmt3.research.microsoft.com/

• Number of submissions received: 28

• Number of submissions sent for review: 28

• Number of submissions accepted: 17

• Acceptance Rate (Number of Submissions Accepted / Number of Submissions Received X 100): 60.71%

• Average number of reviews per paper: 2

• Total number of reviewers involved: 31

• Any additional info on review process: All manuscripts submitted to the CIEES'2021 conference were single-blind peer-reviewed and are carried out to meet the scientific criteria of novelty and academic excellence. The review process was conducted according to the review policy of IOP conference series - each paper was reviewed by at least two reviewers involving both national and international reviewers. During the discussion phase, International Scientific Committee members and the Programme Committee members discussed the reviews in detail. The rebuttals from the authors were also seriously considered. The final decision to accept a paper was entirely based on quality and not its length.

• Contact person for queries: Assoc. Prof. Teodor Iliev, PhD, Department of Telecommunications, University of Ruse, Bulgaria, E-mail: tiliev@uni-ruse.bg

Cloud computing is a new technology that is undergoing tremendous development today. People who use it are not able to separate the reasonable from the unreasonable arguments that come with the security requirements in the cloud. The claim that cloud computing is hereditarily insecure is as absurd as the claim that cloud computing does not create new security problems. Cloud computing is a way to dynamically increase resources without the need for in-depth knowledge of a brand new infrastructure, without training new workers or designing new software solutions. The article aims to analyse the different cloud security issues and models of cloud architectures. Some of the main problems with security in virtualization, concerns about storing data in the cloud and the assessment of risk tolerance in cloud computing are presented. Legal and regulatory issues for the protection of personal data are addressed.

Meeting the energy demands and sustainable development goals in Nigeria requires investigation of potentials of alternative energy sources and possible challenges to their reliability. In this study, we investigated the impact of four (4) teleconnection patterns on the solar energy potential within different climatic zones of Nigeria. Our results indicate that there are weak and insignificant correlation between the studied teleconnection patterns and solar energy potential on the long run. However, monthly analysis suggests significant correlation values between all the teleconnection patterns studied and solar energy production within all the climatic regions of the country. Therefore, it is important to consider the role of teleconnection pattern in energy planning and forecasting within the region.

With the development of modern technologies, opportunities for an exchange of the increasing amount of information at ever higher speeds are created. The use of smart systems in electric power engineering creates conditions for improving the systems for monitoring, archiving, analysis and management. It is necessary to collect the basic information about the emergency modes automatically for analysis of the operation of the equipment and the parameters of the regimes in the power grids. The main questions to be decided are: what type of information is needed, how to use this information and at what are the different access levels, what should be the systems - local or global, how to exchange data. Smart systems for power grids and switchgears have been developed on a modular basis by almost all global manufacturers, as well as by many companies on individual assignments. The publication discusses the existing types of smart systems and the data they process. Suggestions have been made for the volume and structure of data that are needed for the analysis process.

The report presents an analysis of luxury charter yachts which are a specific class of vessels that, in order to meet the schedules and increased requirements of the owners regarding the luxury of the services offered, have relatively high energy consumption for their gross tonnage, compared to other passenger ships. The study focuses on the analysis of energy efficiency of luxury yachts by calculating the energy efficiency index (EEDI). This involves comparing different parameters that affect the value of the EEDI and can lead to energy savings. The report presents theoretical and experimental studies of the energy costs of a 70-meter luxury yacht for charter trips. With the use of the design data of the ship's electrical equipment at different operating modes, at different routes, under different conditions, dependences for analysis of the optimal modes of movement are obtained, which leads to the realization of maximum savings of electricity and primary energy.

The report presents an analysis of modern technical solutions for shore power supply of a specific class of passenger ships - luxury yachts for charter trips. The design data of a motor yacht in its different operating modes are considered, as well as the energy mix related to the fuel consumption at shore supply of the yacht during its stay at the port. The use of modern technical systems for shore supply includes the application of specific frequency converters, through which compatibility between the different voltage standards and the frequency for different shore power supply systems is realized. The costs of onshore power, compared to those of marine fuel, can be calculated from the current prices of onshore electricity and the energy produced from its own generators. The analysis of the basic design data of the motor yacht and the assessment of the energy costs on board, fuel economy and emission reductions will provide a clear answer to the advantages of the power supply from the shore of the vessel.

The study is based on a one-year field experiment (2019) in the land of the Chirpan region located in central Bulgaria. The agrotechnical operations of plowing and cultivation, applied in technology for the production of sunflower, are studied. Four models (Linear, Exponential, Logarithmic, and Quadratic) were compared at p < 0.05, defining the relation between soil moisture, aggregate speed, and the uniformity of the soil index Tillage depth during plowing and cultivation. It was found that in plowing at a speed of 4 km/h the Quadratic model described the relation between soil moisture and tillage depth with the highest coefficient of determination (R² = 0.682). Relating to plowing at a speed of 4.5 km/h the most suitable is the Exponential model (R² = 0.729), i.e. about 68.2% and 72.9% of the variations in tillage depth are due to the influence of the moisture of the soil. The coefficients of determination, calculated when cultivating at speeds of 8 km/h (R² = 0.526) and 9 km/h (R² = 0.557), show that the Quadratic model most strongly (52.6% and 55.7%) determines the relation between soil moisture and tillage depth. The developed models could be used to optimize the control systems of agricultural machinery.

Paper concerns a mathematical model developed for working process observation of a fan system squirrel-cage induction motor electric drive. The electric motor in question is designed for permanent, uninterruptible operation. The system of differential equations is converted and processed with the help of appropriate software. The impact of external factors is assessed – supply voltage deflection and variation of rates of mechanical quantities involved in the motion equation. Electrical power losses in steady-state regime and energy losses at start-up are calculated. The results obtained are practical oriented when considering methods to start and control the rotational frequency to imrove energy efficiency.

Since the charging processes of electric vehicles are stochastic and time-dependent, the paper views an approach based on a statistical analysis of real data on electricity consumption at charging station connection points. Other types of data (geographical, public sites, distance between individual charging stations, etc.) are also taken into account when making the analysis. Multiplicative models are the most suitable for studying and forecasting time series with pronounced cyclicity and seasonality. Their application allows us to consider the correlation of the load in the consuming nodes with regional features, climatic factors and seasonality. The method and approach discussed in this paper make possible the processing of a large amount of data and the detection of load cyclicity in the load schedule of electricity facilities. The results of the model will identify the requested charging power in a developing charging infrastructure.

The mathematical model is developed for a virtual training system (simulator) of the power unit electrical part operators of a thermal (nuclear) power plant. The model is used to simulating the main operating conditions of the power unit electrical part: generator idling, generator synchronization with the power system, excitation shifting from the main unit to the backup one and vice versa, switching in the power unit auxiliary system, and others. Furthermore, it has been implemented modelling some probable emergency conditions within a power plant: incomplete phase switching, damage to standard power unit equipment, synchronous oscillations, asynchronous mode, etc. The model of the power unit electrical part consists of two interacting software units: models of power equipment (turbine, generator with excitation systems, auxiliary system) and models of its control systems, automation, relay protection and signalling. The models are represented by the corresponding algebraic-differential equations that provide real-time mapping power unit processes at the operator's request. The developed model uses optimal solving algebraic-differential equations to ensure the virtual process behaviour in real-time. In particular, the implicit Euler method is used to solve differential equations, which is stable when simulating processes in significant disturbances, such as accidental disconnection of the unit from the power system, tripping and energizing loads, generator excitation loss, etc.

It was shown that the traditional approaches to understanding the notion of "energy" as a work or a physical quantity are outdated. For example, R. Feynman noted that "today's physics does not know what energy is." Therefore, even now, some researchers believe that "by and large, the concept of energy... is artificial, because unlike matter, of which we can say that it exists, energy is the fruit of human thought." In contrast to these ideas, the authors showed that energy, like matter, objectively exists in various forms (energy continuum), which differ in structure, and is able to perform different types of work, to determine the forms of interaction and movement of matter in various material systems (substances, material bodies and megamaterial systems). A new scientific foundation for systematization and quantitative evaluation of energy characteristics of chemical compounds was proposed. It is based on a comprehensive assessment of contribution of chemical compounds' composition and chemical bond type in line with a chemical bond's unified model and the "System of chemical bonds and compounds" (SCBC). As a result of using this basic scientific innovation, the symbiosis of Mendeleev's periodic table of atoms (composition – property) and SCBC (composition - chemical bond and structure – property) was realized for the first time. The foundation was laid for creating a database on systemic digitalization and evaluation of energy stored in various chemicals (natural gas, coal, oil, peat, wood, etc.) and the most effective ways of extracting it from these.

This paper shows the problem with heat exchange depending on units of thermal power plant equipment. The type of structures is determined and the heat flow for different pressures is proposed. Studies are developed for the condition of the heat exchange surface. Devices with porous coatings eliminate the development of cracks in the components and units of TPP equipment have been suggested. The research is applicable to gas turbine units of TPP. Comparable capillary-porous and flow systems have high reliability, but the former allowed the reduction of coolant consumption dozens up to 80 times. The results show that at higher heat loads it is suitable to use in porous surfaces to control the cooling surface. Evaluation of capillary-porous structures has shown their advantages over traditional cooling systems.

In this paper we analized and investigated the heat exchange crisis of boiling in porous structures, applicable in thermal power plants. Then we describe the heat exchange processes mechanism and determined the ideal sizes and thicknesses of porous structures. The designed porous structures can be implemented in gas turbine's nozzles and combustion chambers. From an environmental point of view, the consumption coolant liquid is reduced by ten times in comparison the standard flow system. It's effectively to develop mesh structures to allow the extension of the critical loads and manage the surface border.

A new type of semiconductor power device was devised in the early '90s as an alternative to the classic Gate Turn-Off (GTO) thyristor. Because the low-doped n-base was replaced by a low-doped p-base, it was called the p-GTO. Its main advantage is a higher possible control voltage when the device is switched off, leading to the possibility of a higher blocking anode current (IATO) and a lower turn-off time. The studies and techniques employed with the help of SILVACO-TCAD simulation software Athena and Atlas show that the p-GTO has higher breakdown voltages compared with its classic counterpart and similar on-state voltage (VT) and switching characteristics when replacing the GTO in the same circuit. Specific circuit improvements, like an affordable higher turn-off gate voltage, will drive the p-GTO into even faster switching operation.

The article deals with the analysis of methods for assessing the energy efficiency of data centers according to the Power Usage Effectiveness method. The demand for data centers which consumes a large amount of electricity is growing with the growth of digitalization and the accumulation of big data in the network. The energy consumption of the cooling system for the machine room accounts for a significant part of the operating costs of the building. Free cooling in a refrigeration system reduces energy consumption much more than operating systems with a vapor-compression cycle. In 2006 according to The Green Grid, the assessment method of Power Usage Effectiveness has become an international standard for measuring energy efficiency and is widely used in the design and operation of data centers. In this regard, the operation principles of free-cooling chillers are considered. The calculation example of the system payback in free-cooling is also given.

Corruption is one of the main problems in many developing countries. However, the complexity of measuring corruption and its consequences does not allow for its complete study and implementation of measures. The factors and indicators currently known worldwide cannot measure corruption on time scales and depend on a narrow circle of experts in this area. Thus, corruption is easily confused with institutional gaps. In modern society, where the technologies such as Data Science and Predictive Analytics play a huge role, corruption is still omnipresent. The article examines the priority areas of combating corruption using new digital technologies. The main direction of the article is defined as an analysis of the advantages and disadvantages of the digitalization in the areas of solving social conflicts. The article presents the comparative analysis of technologies of digital anti-corruption compliance in developing countries, on the example of Kazakhstan. At the same time, according to the results, the article discusses the disadvantages of using proposed models due to the peculiarities of the legislation.

In this paper one of the recently developed metaheuristic algorithms, the Cuckoo Search algorithm is used for the optimization of the operation of a large hydropower plant in Kurdistan, Iraq. The optimization problem is to realize an annual planned energy generation with monthly imposed fractions. The obtained results are excellent, nevertheless, there are some limitations of the algorithm determined by the initial level into the reservoir and a certain correlation between the type of the year, the starting level and the planned energy to be realized.

In this paper HEC-ResSim is applied for a complex hydropower development formed by five reservoirs and related hydropower plants. There were considered characteristics of five existing hydropower developments in Romania, for which three reservoirs are with annual regulation and two with daily regulation. The objective function was the realization of a planned energy generation for one year (the mean hydrological year). Obtained results are very close to those obtained applying linear programming, a revised simplex algorithm.