Table of contents

By a series of transformations, the (2+1)-dimensional variable coefficient nonlinear Schrödinger equation can turn to the Klein–Gordon equation. Many new double travelling wave solutions of the Klein–Gordon equation are obtained. Thus, the new solitary solutions of the variable coefficient nonlinear Schrödinger equation with an external potential can be found.

We study the perturbation to symmetries and adiabatic invariants of a generalized Birkhoff system. Based on the invariance of differential equations under infinitesimal transformations, Lie symmetries, laws of conservations, perturbation to the symmetries and adiabatic invariants of the generalized Birkhoff system are presented. First, the concepts of Lie symmetries and higher order adiabatic invariants of the generalized Birkhoff system are proposed. Then, the conditions for the existence of the exact invariants and adiabatic invariants are proved, and their forms are given. Finally, an example is presented to illustrate the method and results.

To achieve robust gate operations on superconducting charge qubits, we theoretically propose a feasible scheme to realize geometric quantum computation via coherent pulses. Only by adiabatically tuning the microwave pulses applied to the gate capacitance can the Berry phases associated with the system be acquired, from which we construct a universal set of geometric gates. Combining the geometric approach with the coherent pulse technique, robust quantum operations aimed at combating noise errors may be implemented experimentally.

We introduce a character matrix for the N-qubit subsystem of a 2N-qubit state and show the criterion for genuine entanglement channel existing between two N-qubit subsystems in the state. The criterion allows us to check conveniently whether genuine quantum channels exist or not in the 2N-qubit state without calculating its N-qubit reduced density matrices.

We report a simple Hermitian operator whose eigenspace corresponding to the maximum eigenvalue defines the symmetric universal cloning machines. It opens up therefore the possibility of implementing universal quantum cloning machines via adiabatic evolution.

The Lamb–Dicke (LD) approximation (LDA) is usually utilized to simplify the treatments for the dynamics of ion-trap systems, where the so-called LD parameters should be sufficiently small. In this Letter, based on the quantum dynamics of a single trapped ion beyond the LDA, we discuss the fidelities of the control-NOT (CNOT) gate generated by performing the usual LDA. It is shown that the fidelity of the generated CNOT gate under the LDA is sufficiently high for the current LD experiments, e.g., it reaches 99.9% for η = 0.20. The validity of the LDA is also discussed by calculating these fidelities for slightly larger LD parameters, e.g., η = 0.4, etc.

We study the generation and evolution of continuous-variable entanglement in a holographic laser. The two-level atomic medium is trapped in a ring cavity, and couples with two counter-propagating modes. By simulating the dynamics of the system, our numerical results show that the two-mode continuous variable (CV) entanglement can be realized in the present system even in the presence of cavity loss. This investigation provides a research clue for realizing CV entanglement in a two-level atomic medium, which is simpler than the previous works.

The energy eigenvalues and the corresponding eigenfunctions of the one-dimensional Klein–Gordon equation with q-parameter Pöschl–Teller potential are analytically obtained within the position-dependent mass formalism. The parametric generalization of the Nikiforov–Uvarov method is used in the calculations by choosing a mass distribution.

We propose a scheme to teleport an unknown single-qubit state by using a high-dimensional entangled state as the quantum channel. As a special case, a scheme for teleportation of an unknown single-qubit state via three-dimensional entangled state is investigated in detail. Also, this scheme can be directly generalized to an unknown f-dimensional state by using a d-dimensional entangled state (d > f) as the quantum channel.

Based on the concept and principles of quantum computing and the principle of the immune clonal selection, a new algorithm for multi-objective 0/1 knapsack problems is introduced. In the algorithm, for the novel representation, qubit antibodies in the antibody population are updated by applying a new chaos update strategy. A quantitative metric is used for testing the convergence to the Pareto-optimal front. Simulation results on the 0/1 knapsack problems show that the new algorithm, in most cases, is more effective.

In the frame of quantum mechanics, we consider an ensemble of spin-½ neutral particles passing through a Stern–Gerlach apparatus and explore how their motions depend on the initial phase difference between two internal spin states. Assuming the particles moving along y-axis, due to the initial phase difference between spin states, they not only split along the longitudinal direction (z-axis) but also separate along the lateral direction (x-axis). The dependence of the lateral displacement on the initial phase difference reminds one of the picture of a quantum interference. This generalized interference provides an alternative approach to measuring the initial phase difference. The experimental realization with ultracold atoms or Bose–Einstein condensates is also discussed.

The properties of the neutron star rotating at 619Hz (which is the spin frequency of 4U 1608–52 neutron star) are investigated by using an equation of state (EOS) of the nuclear matter in the relativistic σ-ω-ρ model. It is shown that the EOS in the relativistic σ-ω-ρ model is supported by the observational mass and radius of the 4U 1608–52 neutron star. Moreover, a strict constraint on the polar redshift of 4U 1608–52 neutron star is obtained.

The association between intrinsic noises and deterministic descriptions/properties of the rate equations for chemical reactions is analyzed using the linear noise approximation of the master equation. We illustrate that the effect of intrinsic noise is determined in combination by three components: the system size, the matrix associated with reaction kinetics, and the eigenvalues associated with the system's dissipation. Generally, a more attractive dynamics tends to attenuate the internal fluctuations more significantly because intrinsic noises are inversely proportional to the absolute value of the real part of the eigenvalues. In addition, a higher reaction rate and larger stoichiometry coefficients will give rise to stronger intrinsic noise.

Taking account of the Ca²⁺-activated degradation of inositol trisphosphate (IP₃), a one pool model of cytosolic calcium oscillation is considered to investigate the effect of the calcium pump on the Ca²⁺ bursting oscillation behavior. In order to give the oscillation domain, a two-parameter bifurcation analysis of the fast subsystem is performed in the parameter plane. Different types of bursting are presented with the variation of the pump parameter, and fast-slow dynamics is used to analyze the types and generation mechanisms of the bursting oscillations. The results are instructive for understanding the role of the calcium pump played in complex intracellular calcium activities.

We propose a new passivity based synchronization scheme for chaotic behavior in nonlinear Bloch equations. Based on the Lyapunov theory and linear matrix inequality (LMI) approach, for the first time, the passivity based controller is presented to guarantee stable synchronization. The proposed controller can be obtained by solving a convex optimization problem represented by an LMI. A numerical example is given to demonstrate the effectiveness of the proposed synchronization scheme.

The cytoplasmic Ca oscillations are investigated under the effect of CRAC channels in non-excitable cells (especially in T cells). The oscillatory Ca²⁺ signals can be modulated as the amplitude-, frequency- and mixed amplitude-frequency modulation modes dependent on the different IP₃R gating models. Bifurcation analyses show that Ca²⁺ signals in the single positive feedback loop model is a mixed modulation mode. In contrast, Ca²⁺ signals in the Mak–McBride–Foskett model demonstrates approximately the frequency modulation mode only with slight amplitude shifts.

Submerging the sub-wavelength Cu wire grating in liquid water, we prove that the transmission ration can be changed pronouncedly from 0.1 THz to 1.7 THz. The modulation of terahertz responses by liquid water is explained by the increasing effective electron mass in the plasmon picture. Due to this response, we extract the index of liquid water, and our results provide a potential application of using metal grating to detect real solvated condition biomaterials in the THz frequency range.

We use the first-order approximate solutions to the nonlinear system of Klein–Gordon–Maxwell–Einstein equations describing the minimally coupled charged spin-less field to a spherically symmetric spacetime to analyze a becoming boson star. In the far future and long-range approximation, we derive an analytical time-dependent charge which allows us to point out several significant moments in the evolution of the boson nebula.

In the frame of the constituent quark model with screened color confinement, non-strange baryon spectra are studied by using non-relativistic and semi-relativistic Faddeev equations in momentum space. The results show that a qualitative description of the high-energy baryon spectra can be obtained, especially for states at excitation energies from 1 to 1.5 GeV. Compared with the linear confinement potential, the discrepancy between non-relativistic and semi-relativistic approaches becomes smaller in the present model with screened color confinement.

Type-III seesaw scenario predicts the existence of the heavy charged leptons, which might generate observable signals in future collider experiments. We consider the contributions of these new particles to the process e⁺e⁻ → HH. We find that, for the large mixing between the light and heavy leptons, these new particles can indeed generate significant contributions to this process.

The yrast bands of the even-even dysprosium isotopes ^164–174Dy are calculated up to high angular momentum 34ħ based on the projected shell model. Our calculations are in good agreement with the experiments quantitatively. They predict that an energy minimum of the first 2⁺ state in these isotopes exists around the neutron mid-shell N = 104, implying the maximum collectivity in ₆₆¹⁷⁰Dy₁₀₄, however, the energy ratio R₄ = E(4⁺₁)/E(2⁺₁) reaches a saturation at N = 102. Meanwhile, the back-bending plots of these yrast bands are examined carefully. It is found that the sharpness of the back-bending has a gradual shift along the dysprosium isotopic chain, namely, the slope of the back-bending becomes steeper as the neutron number increases except for an irregularity of a decreasing dip angle in the double mid-shell nucleus ¹⁷⁰Dy. We suggest that ¹⁷⁰Dy undergoes a dual alignment with midshell high-j protons and neutrons aligning simultaneously at spin I ≈ 16ħ, which probably results in the distinctive back-bending behavior.

Whether the mixing of scalar meson exists or not is an interesting question. We consider the mixing of scalar meson and further study the nucleon-nucleon interaction in the chiral SU(3) quark model by solving the resonating group method equation. The results are analyzed and compared with no mixing, ideal mixing and general mixing. It seems that the nucleon-nucleon interaction and binding energy of deuteron can be reasonably described with the different mixing of scalar meson.

The decay rate variation of ⁷Be implanted into platinum and aluminum host materials has been measured via detecting the 478 keV γ-rays from the first excited state of ⁷Li populated in the electron capture decay of ⁷Be. The result (λPt – λ_A1)/λ₀ = (–0.17 ± 0.13)% is obtained. It is smaller than the theoretical estimate from the TB-LMTO calculation (0.38%). This is quite different from our previous study which showed a larger decay rate variation ((0.8 ± 0.2)%) than the TB-LMTO calculation (0.30%) of ⁷Be in palladium and gold. It is suggested that the effective quasi-free electron density near the implanted ions in different metal host materials may play an important role in ⁷Be EC decay rate variation in addition to the electronic affinity and crystal structure of different host materials.

The microscopic optical potential for deuteron is obtained by folding the microscopic optical potentials of its constituent nucleons. The optical potential is used to predict the reaction cross sections and the elastic scattering angular distributions for some spherical target nuclei, and the results of theoretical calculation are compared with the experimental data available.

In order to extract the information of the momentum-dependent interaction of kaons under the extreme condition, the properties of the positively charged kaons produced in a heavy ion collision are studied via a simple model which has an invariable nucleon's velocity. Our special attention is focused on the observation of the dependence of the kaon's properties on the motion of nucleons in a hot and dense nuclear environment. Starting from two kinds of kaon quasiparticle models defined in transport theories for simulating heavy ion collisions, we calculate the effective mass and potential of the K⁺ 's produced in the collisions and find that these properties not only depend closely on the velocity of nucleons but the dependence varies with kaon's quasiparticle model. It is clearly shown that the motion of nucleons reduces the momentum of K⁺ 's at a given rapidity and thus weakens the rapidity distribution of K⁺ 's directed flow in realistic nuclear collisions.

Using the time dependent local density approximation, applied to valence electrons, coupled non-adiabatically to molecular dynamics of ions, the collision process between ethylene and fast charged projectiles is studied in the microscopic way. The impact of ionic motion on the ionization is explored to show the importance of treating electronic and ionic degrees of freedom simultaneously. The number of escaped electrons, ionization probabilities are obtained. Furthermore, it is found that the ionic extensions in different directions show the different patterns.

The collapse and revival of evolution with photon number of population inversion in the case of an atomic beam with velocity distribution interacting with a single-mode and Fock-state light field is investigated by full quantum theory. Compared to the previously reported coherent state case [Li B and Chen J B Chin. Phys. Lett. 26 (2009) 123203], which was induced by evolution with coupling strength of population inversion, in the case under consideration there exists Poisson distribution of photon numbers and atomic velocity distribution in the beam. Moreover, we prove that above, the collapse and revival have an analogy with conventional collapse and revival [Eberly J H et al. Phys. Rev. Lett. 44 (1980) 1323] in both the mathematical expression and physical significance.

⁴⁰Ca⁺ ions are trapped and laser cooled in a miniature Paul trap. The secular motion was observed by the radio-frequency resonance of the ion cloud and Zeeman profile sidebands of a single ion experimentally. The trap stability parameters a and q are determined with an uncertainty under 1 % by the secular motion frequency measurement. The trap efficiency is 0.75. A practicable suggestion is given for the benefits of a new trap design.

The absorption spectra of lycopene in n-hexane and CS₂ are measured under high pressure and the results are compared with β-carotene. In the lower pressure range, the deviation from the linear dependence on the Bayliss parameter (BP) for β-carotene is more visible than that for lycopene. With the further increase of the solvent BP, the 0–0 bands of lycopene and β-carotene red shift at almost the same rate in n-hexane; however, the 0–0 band of lycopene red shifts slower than that of β-carotene in CS₂. The origins of these diversities are discussed taking into account the dispersion interactions and structures of solute and solvent molecules.

The positron-impact excitation of hydrogen atoms embedded in plasma environments is investigated using the close-coupling approximation from the low to intermediate energy region without including any positronium formation channel, and the excitation cross sections for 1s → 2s, 1s → 2p and 2s → 2p processes are calculated in a wide Debye parameter range. The screening interactions, described by the Debye–Hückel model, decrease the coupling matrix elements, resulting in the reduction of the excitation cross sections from a few percent to one magnitude of ten. This will alter remarkably the spectroscopy of hydrogen in intensity and position, which should be considered in the simulation and diagnostics under some specific plasma conditions.

Numerical modeling on the composite electromagnetic (EM) scattering from a two-dimensional (2-D) object located on a rough surface is presented by using the efficient method of fundamental solution (MFS). The proposed special choice of the MFS is an interesting alternative to the onerous mesh generation in the traditional numerical methods, particularly for the method of moment (MoM). There is no mesh scheme and singularity analysis, the field to be solved can be obtained directly in terms of the fundamental solutions of the appropriate wave equations. The numerical results are obtained and compared with the traditional MoM results, to demonstrate the accuracy and effectiveness of this technique.

We concentrate on describing the important influence and physical law of the split resonant ring (SRR) based left-handed materials on patch antennae. The finite-difference time-domain method, together with the finite element method is used to study the characteristics of patch antennae based on composite rectangular SRRs. A novel composite rectangular SRR system is formed by assembling the conventional patch antennae and SRRs, it is found that electromagnetic wave resonance occurs near f = 3.15 GHz, the equivalent permittivity and permeability are both negative, and the electromagnetic wave's tunnel effect and evanescent waves' enhancing effect are formed, which can improve the localization extent of electromagnetic wave's energy apparently. Such effects can improve the antenna's radiation gain and its matching condition. The phenomenon indicates that such composite rectangular patch antennae are promising in wireless communications such as mobile phones, satellite communication and aviation.

A wide-angle, split-step finite-difference method with the classical local one-dimensional scheme is presented to analyze the 3-D semi-vectorial wave equation. The method requires only matrix multiplication for beam propagation. To validate the effectiveness, numerical results for the eigen-mode propagation in tilted step-index channel waveguides are studied, and results show that the method has high accuracy and numerical efficiency.

The multimode evolution, optical losses and wavelength response of non-adiabatic micro/nano-fiber (MNF) tapers are numerically simulated using a three-dimensional finite-difference beam propagation method. For a non-adiabatic MNF taper, it is illustrated that optical losses vary with the transition region length and the optical wavelength. We explain how the complicated multimode evolutions result in the complicated optical loss and wavelength response properties, especially when the waist diameters are large enough to allow much higher-order modes. These results may offer valuable references for trapping and guiding cold atoms in atom optics and practical application of micro/nano-devices.

A new means of generating all-optically high-repetition-rate pulse trains is proposed and numerically demonstrated in an optical fiber. Our numerical simulations show that, due to the modulation instability effect, the initial continuous-wave with a weak optical pulse instead of conventional weak sinusoidal modulation imposed on it can gradually evolve into high-repetition-rate pulse trains. However, the generated pulse trains take on different features from the conventional case in terms of their widths, intensities, intervals, numbers, and pedestals.

We present the simple designs of metamaterial absorbers which are composed of a periodic array of copper annular (or circular) patches, FR4 substrate, and copper film. With appropriate geometrical parameters, these metamaterials can provide the electric and magnetic resonances overlapping in the given frequency range, and the experiments demonstrate the absorptivities of 97.6% and 96.7% with only a single layer of the metamaterial absorber. The surface currents and field distributions of these metamaterials are discussed to look straight into the resonance mechanism. Furthermore, our numerical simulations confirm that these metamaterial absorbers could be operated at wide angles of incidence. The simple and highly symmetric structures of the metamaterial absorbers proposed would greatly accelerate the practical applications in optics and electromagnetics.

We demonstrate our experiment of controlling spatial displacements of the probe beam induced by the cross-Kerr effect in a three-level V-type atomic system. By increasing the atomic density or the intensity of strong control laser beams, spatial displacements are enhanced. We further study the difference of effects from the atomic density and the laser intensity. In addition, the spatial displacement efficiencies of the probe beam in different energy level atomic systems are compared. Such studies of controlling spatial displacements can have potential applications in soliton deflection, spatial optical switch and generating spatially correlated (entangled) laser beams in multi-level EIT systems.

We report a period continuously tunable, efficient, mid-infrared optical parametric oscillator (OPO) based on a fan-out periodically poled MgO-doped congruent lithium niobate (PPMgLN). The OPO is pumped by a Nd:YAG laser and a maximum idler output average power of 1.65 W at 3.93 μm is obtained with a pump average power of 10.5 W, corresponding to the conversion efficiency of about 16% from the pump to the idler. The output spectral properties of the OPO with the fan-out crystal are analyzed. The OPO is continuously tuned over 3.78–4.58 μm (idler) when fan-out periods are changed from 27.0 to 29.4 μm. Compared with temperature tuning, fan-out period continuous tuning has faster tuning rate and wider tuning range.

An efficient high power long wave infrared laser based on ZnGeP₂ optical parametric oscillator pumped by a 2.09 μm Tm:YLF/Ho:YAG laser at 10KHz pulse repetition rate is reported. The pump to idler conversion efficiency is 8% at 15.6 W Ho pump power level and a quantum efficiency of 31 % when the 1'idler wavelength is tuned at 8.08 μm. The wavelength tuning range from 8–9.1 μm is also achieved by rotating the ZGP crystal.

A kind of double-cladding photonic crystal fiber (DC-PCF) with high birefringence and two zero-dispersion wavelengths is proposed. It is found that the birefringence of DC-PCF with inner cladding air holes pitch 1.0 μm and diameter 0.8 μm is 1.001 × 10⁻² in the optical communication band at wavelength 1.55 μm by the multipole method. It is demonstrated that two zero dispersion wavelengths can be achieved in the optical communication band between 0.8 μm and 1.7 μm, and the first zero-dispersion wavelength is in the working wave band of the Ti:sapphire oscillator, which contributes to the frequency conversion of the Ti:sapphire femtosecond laser. PCF with two zero-dispersion wavelengths can make strong power supercontinuum spectral in the near infrared band.

Sb is a classic material of a super-resolution near field structure (super-RENS) mask layer in which the optical switch formation is often realized by nanosecond laser pulse stimulation. We achieve fast and repeatable optical switching driven by picosecond laser pulses in a proper fluence range on Sb thin films. The optical properties of Sb thin films before and after switching are studied by surface-sensitive micro-area ellipsometry. The change of optical constants after switching is less than 2% in the whole visible range. The Sb mask layer is shown to be very promising for ultrafast super-resolution optical storage applications.

We report the fabrication of an optical fiber Bragg grating assisted mismatched coupler based on the fused biconical tapered technology. The investigation of the spectrum properties shows that the coupler has a good filtering property. The drop filtering efficiency as much as 94.2% at 1553.5 nm is achieved. Furthermore, using the fabricated coupler, a wavelength de-multiplexing transmission experiment is carried out in a 10 Gbps system with NRZ optical signals. Experimental results show that the coupler basically realizes the function of wavelength de-multiplexing.

We employ a sample of cold ⁸⁷Rb atoms in a magneto-optical trap to study the impulse responses and spatial characters of backward conjugate waves in a four-wave mixing process. We measure the slow and superluminal group velocities of backward conjugate waves, and find the sensitive variation of the spatial mode of backward waves with the probe-pump detuning and the dependence of the reflectance on the magnetic field, while the trapping magnetic field exists.

The quantum entropy of the damping Jaynes–Cummings model is investigated in different decay coefficients under detuning conditions. The results indicate that the larger the decay coefficient is, the more quickly the entropy decays. The detuning of the atom and field frequencies reduce the entanglement maximum in short time regions, but delays the damping process of the entanglement. The sine modulation enhances the entanglement in short time regions.

Mode competitions between modes with different output coupling efficiencies can result in optical bistability under certain asymmetric nonlinear gain. For a GaInAsP/InP equilateral triangle microlaser with the side length of 10 μm, the drop of the output power with the increase of the injection current is observed corresponding to transverse mode transitions. Furthermore, the measured laser spectra up to 270 K show that lasing modes coexist with the wavelength interval of 39 nm at 240 K. The emission at 5.2 THz can be expected by the mode frequency beating with the 39 nm interval.

Levitation stability is a crucial factor that influences acoustic levitation capability. We present two sample-including models for a single-axis acoustic levitator with either a rigid or elastic reflector. Numerical analysis shows that, with the rigid reflector, both the decay time from initial disturbance and the vibration amplitude increase with sample density, which is unfavorable for levitation stability. However, with the elastic reflector, the decay time and the vibration amplitude are greatly reduced by choosing appropriate parameters of the reflector. Experimental results agree well with theoretical predictions, indicating that levitation stability can be remarkably enhanced by replacing the rigid reflector with an elastic reflector.

A modified Lattice–Boltzmann method is proposed by considering the Klinkenberg effect and adsorbability-desorbability for the purpose of simulating methane gas seepage in fissured coal. The results show that the Klinkenberg effect has a little influence on methane gas seepage in fissured coal, so it can be neglected in engineering computations for simplicity. If both the Klinkenberg effect and the adsorbability-desorbability are considered, the Klinkenberg influence on gas pressure decreases as the Darcy coefficient increases. It is found by gas drainage simulations that near a drainage hole, the effect of adsorption and desorption cannot be neglected, and the location of the drainage hole has a great influence on drainage efficient λ when the hole is just located at the mid-zone of the coal seam, λ is 0.691808; when the hole is excursion down to 1.0 m from the mid-zone of coal seam, λ decreases to 0.668631; when the hole is excursion up or down to 2.0 m from the mid-zone of coal seam, λ decreases to 0.632917. The simulations supply an effective approach for optimizing the gas drainage hole location.

The method of Lie group transformation is used to obtain an approximate analytical solution to the system of first-order quasilinear partial differential equations that govern a one-dimensional unsteady planer, cylindrically symmetric and spherically symmetric motion in a non-ideal gas, involving strong shock waves. Invariance groups admitted by the governing system of partial differential equations, which are indeed continuous group of transformations under which the system of partial differential equations remains invariant, are determined, and the complete Lie algebra of infinitesimal symmetries is established. The infinitesimal generators are used to construct the similarity variables. These similarity variables are used to reduce the governing system of partial differential equations into a system of ordinary differential equations.

The Bond counting rule is proved to be an important and effective criterion for searching low-energy metastable structures for ternary boron carbon nitrogen (B-C-N) compounds. The Bond counting rule, however, has its limitations for the binary diamond-like or ternary B-C-N polymorphs with the same bond ratio. First-principles calculations validate that the Mulliken charge difference may serve as an indication of low-energy crystal structures, and clarify the energy difference among those polymorphs to some extent. For example, we predict two ground state phases of superhard BC₅ (named as I-BC₅ and I-BC₅), which are 0.28 and 0.27 eV/formula lower in energy than the P3m1 structure reported recently in the literature [Calandra et al. Phys. Rev. Lett. 101 (2008) 016401], respectively. The charge transfer analysis reveals that the smaller Mulliken charge difference for the same kind of element will result in more stable structures.

By introducing internal degree, the deformation of hexagonal noncentrosymmetric crystal sheet can be described by the revised Cauchy–Born rule based on atomic potential. The instability criterion is deduced to investigate the inhomogeneous dislocation nucleation behavior of the crystal sheet under simple loading. The anisotropic characters of dislocation nucleation under uniaxial tension are studied by using the continuum method associated with the instability criterion. The results show a strong relationship between yield stress and crystal sheet chirality. The results also indicate that the instability criterion has sufficient ability to capture the dislocation nucleation site and expansion. To observe the internal dislocation phenomenon, the prediction of the dislocation nucleation site and expansion domain is illustrated by MD simulations. The developed method is another way to explain the dislocation nucleation phenomenon.

We report on the evaluation of thermal degradation damage in metal material using the nonlinear effect of Lamb wave propagation. A "mountain-shape" change in the second harmonic of Lamb wave propagation versus the level of thermal degradation in the specimens is observed. It is attributed to the precipitations in the early stage and the microvoids after long-term service in terms of metallographic studies. The results show that the nonlinear Lamb wave is very sensitive to the microstructure evolution and is a good potential for quantitative evaluation of the thermal damaged materials.

Employing the transfer matrix method, we investigate the property of the interface optical-phonon modes (IOPMs) in a finite superlattice with a cap layer and a structural defect layer in the dielectric continuum approximation. In the present structure, there exist two types of defect IOPMs: localized modes and surface modes. The evolution of extended, localized and surface IOPMs can be clearly tracked with the thickness of the defect or cap layer. In some cases, degeneracy between surface IOPMs may occur, but the conservation of the total number of the IOPMs is always kept for every value of the transversal wave number. These results show that the spectra of these localized or surface IOPMs can be engineered by adjusting structural parameters.

A thermodynamic cavitation model is developed to simulate the cavitating water flow in a wide temperature range. The thermal effect on bubble growth during cavitation is introduced in the developed model by considering both pressure difference and heat transfer between the vapor and liquid phase. The cavitating turbulent flow over a NACA0015 hydrofoil has been simulated at various temperatures from room temperature to 150°C by using the present cavitation model, which has been validated by the experimental data. It is seen that the thermodynamic effects of cavitation, vapor depression and temperature depression are much more predominant in high temperature water compared with those in room temperature water. These results indicate that the proposed thermodynamic cavitation model is reasonably applicable to the cavitating water flow in a wide temperature range.

The static equation of state (EOS) of tantalum (Ta) is determined by in situ energy-dispersive synchrotron powder x-ray diffraction in a diamond anvil cell (DAC) up to 133 GPa. The body-centered-cubic (bcc) phase of Ta is found to be stable over the entire pressure range investigated. The bulk moduli and its first pressure derivative of Ta are constrained by fitting the determined pressure-volume data to Vinet form EOS: B₀ = 192.65 ± (3.08) GPa and B'₀ = 3.58 ± (0.11). For the sake of avoiding the affect of non-hydrostatic stress, argon is used as a pressure media. A careful checking of the stress state of the sample is presented simultaneously.

The adsorption and reaction of CO on SrTiO₃ (100) surface with and without surface oxygen vacancy are investigated by the first-principles calculation based on the density functional theory. The calculated results reveal that the oxygen vacancy site prefers to the activation of the C-O bond. The adsorption energies increase to 1.0855 and 0.3245 eV for defect-CO and defect-OC orientations, respectively. Particularly the C-O bond is elongated by about 0.1285 Å in the defect-OC orientation compared with that in the Ti-OC one without surface oxygen vacancies. There is predominantly a chemisorption mechanism between the CO molecule and the surface in the defect-CO orientation.

P-type conduction is a great challenge for the full utilization of ZnO due to low dopant solubility and high acceptor ionization energy. We investigate formation energies and transition levels of the defect complex mAl_Zn – nN_O in ZnO by the first principles. The formation and ionization energies for isolated N_O in ZnO are 1.17eV and 0.439 eV, respectively. Among all complexes investigated here, formation and ionization energies of the complex Al_Zn −2N_O can be reduced to 0.632eV and 0.292eV, respectively, which indicates that the defect complex is a relative better candidate for p-type ZnO. However, the results calculated from density of states show that 4Al_Zn – N_O doped ZnO takes on n-type conduction.

The influence of Rashba spin-orbit interaction (SOI) and polaronic effect on the ground-state energy of electrons in semiconductor quantum rings (QRs) are studied by means of the Lee-Low-Pines variational method. Numerical calculations for GaAs QRs are performed and the results show that the ground-state energy of electrons splits into two branches as E(↑) and E(↓) under the Rashba SOI, which correspond to the spin-up state and spin-down state, respectively. The contribution of the Rashba SOI effect to the ground-state energy of electrons is related to the spin state of electrons and is closely linked to the inner and outer radii of a QR. However, it is independent of the height of the QR. The ground-state energy of electrons decreases due to the polaronic effect in QRs. The energy shift Δ_e–LO of the ground-state of the electron induced by the polaronic effect decreases monotonically with increase of the height of a QR. and fluctuates with the changes of the radii of QRs. The amplitude of the fluctuation is very sensitive and remarkable to the changes of the inner radius R₁ and the outer radius R₂.

Sb-doped ZnO thin films are deposited on c-plane sapphire substrates by pulsed laser deposition. Hall results indicate that the conductivity of the Sb-doped ZnO thin films is strongly dependent on the substrate temperature. The sample deposited at the temperature of 550°C exhibits p-type conductivity. It gives a resistivity of 15.25 Ω · cm, with a Hall mobility of 1.79cm²V⁻¹s⁻¹ and a carrier concentration of 2.290 × 10¹⁷ cm⁻³ at room temperature. The x-ray diffraction indicates that the Sb-doped ZnO thin films deposited in the range of 450–650°C are high c-axis oriented. Low-temperature photoluminescence spectra indicate that the sample deposited at 550°C shows the strong acceptor-bound exciton (A⁰X) emission.

Quantum well intermixing (QWI) by the impurity-free vacancy disordering (IFVD) technique is an important and effective approach for the monolithic integration of optoelectronic devices based on InGaAs/InP quantum well structures. We experimentally investigate the influence of the capping layer SiO₂ and Si₃N₄ on the QWI by IFVD. The results show that for all the samples with three-types differently doped (P, N and I) top InP layers, Si₃N₄ can always induce a larger photoluminescence blueshift than SiO₂ in the IFVD QWI process, which attributes more to the group III and V vacancies point defects created in the interface of Si₃N₄-InP than that of SiO₂-InP, proved by the SIMS measurements. The inherent mechanisms for explaining these properties are further discussed.

We have fabricated organic Schottky barrier diodes with Cu/LiF/C₆₀/Al sandwiched construction. Cu and Al are selected as the cathode and the anode, respectively. C₆₀ is used as the organic layer and LiF as the buffer layer inserted between the cathode and C₆₀. After the annealing process, Schottky contact is well formed at the Al/C₆₀ interface and Ohmic contact is formed at the (Cu/LiF)/C₆₀ interface. The current density-voltage (J – V) measurements of the diodes present nonlinear behavior. As a result, the rectification ratio reaches 1 × 10³. The characteristics of the diodes have been analyzed using the energy band diagram. The values of Schottky barrier height Φ_B, ideality factor n and reverse saturation current density J_s are extracted according to the standard thermionic emission model.

We extensively explore the experimentally proposed metallic structure of hcp P6₃ for the hydrogen rich compound, SiH₄. It is found that the lattice dynamic of this structure is severely unstable. By freezing the soften mode, an orthorhombic Pbcn structure is discovered to be dynamically stable up to 226 GPa. Within the conventional BCS theory, the calculated critical temperature T_c within the proposed Pbcn structure is 16.5K at 188GPa, in good agreement with the experimental result (17.5K). Thus, we propose that the current predicted orthorhombic phase is a better candidate for the metallic phase of SiH₄.

The sputtering parameter mediated composition (SPMC) effect of 3.0-μm-thick SmCo-based films is experimentally and theoretically studied. The experimental results give a clear indication that the Sm concentration increases with the decreasing sputtering power or with the increasing Ar gas pressure, which are in agreement with the calculated values when the preferential sputtering effect is disregarded. The SPMC effect provides an opportunity for the same composite target to fabricate films with an Sm concentration varying from 13.8 at.% to 17.3 at.%, which is reasonable for the magnetic phase transformation (Sm₂Co₁₇ → SmCo₇ → SmCo₅) and the enhanced coercivity.

Mn_0.5Zn_0.5Fe₂O₄ Magnetic nanofibers were fabricated by calcining electrospun polymer/inorganic composite nanofibers and characterized by thermogravimetric and differential thermal analysis, x-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy and a vibrating sample magnetometer. The experimental results show that the pure spinel structure is basically formed when the composite nanofibers are calcined at 450°C for 2h. With the increasing calcination temperature, both the saturation magnetization and coercivity of nanofiber samples increase initially along with the growth of Mn_0.5Zn_0.5Fe₂O₄ nanocrystals contained in the nanofibers. However, when the calcination temperature reaches 550°C, the saturation magnetization of nanofibers starts to dramatically decrease owing to the formation of the α-Fe₂O₃ phase at this temperature. The prepared Mn_0.5Zn_0.5Fe₂O₄ nanofibers calcined at 500°C for 2h have diameters ranging from 100 to 200nm. Their saturation magnetization and coercivity are 12.37 emu/g and 4.81 kA/m at room temperature, respectively.

We investigate the electron paramagnetic resonance (EPR) of VO²⁺ ions in bis (glycinato) Mg (II) monohydrate single crystals at room temperature. Detailed EPR. analysis indicates the presence of only one VO²⁺ site. The vanadyl complexes are found to take up the substitutional position. The angular variation of the EPR spectra in three planes a*b, be and ca* are used to determine principal g and A tensors. The values of spin Hamiltonian parameters are g_x = 2.1447×10⁻⁴, g_y = 1.9974×10⁻⁴, g_z = 1.9131×10⁻⁴, A_x = 49×10⁻⁴, A_y = 60×10⁻⁴, A_z = 82×10⁻⁴ cm⁻¹. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental data. By correlating EBB. and optical data, different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.

The phase structures of lead-free (K_0.48Na_0.52)_0.945 Li_0.055Sb_0.05Nb_0.95O₃ piezoceramics are studied based on the measurements of ferroelectric and dielectric properties as well as the analyses of x-ray diffraction pattern and energy dispersive spectroscopy. The poled samples exhibit orthorhombic structure whereas the surface and interior for unpoled samples exhibit tetragonal and tetragonal-orthorhombic coexistent structures, respectively. These results are in agreement with the relative permittivity-temperature curves and demonstrate that phase transitions can be induced by Na volatilization and poling process. The remnant polarization P_r measured at 20°C increases continuously with the increase of electric held in the range of 2000–4000 V/mm. This indicates that the polymorphic structure is more beneficial to the rotation or reorientation of dipoles than either the orthorhombic or the tetragonal structure. The randomly oriented domains may be the essential reason for the continuous rotation or reorientation and not good thermal stability.

A ferroelectric bilayer model considering depolarization field and interfacial coupling is proposed and the expression of the depolarization field is derived. The spatial profiles of spontaneous polarization and hysteresis loops are calculated using the numerical method with and without considering the depolarization field. The effects of the depolarization field and interfacial coupling on the polarization of second-order ferroelectric bilayers are studied systematically. When interfacial coupling is ferroelectric coupling, the interface spontaneous polarization increases and the area of hysteresis loop becomes larger with increasing coupling. When interfacial coupling is antiferroelectric coupling, the depolarization field makes the central loop become smaller and the shape of the hysteresis loop becomes steep. Meanwhile, as interfacial coupling increases, the outer loops stretch further out horizontally and the size of the central loop widens.

A beam optical focusing structure with double subwavelength metal slits surrounded by tapered surface dielectric gratings is proposed and demonstrated numerically. In the proposed structure, just with the regulation of the surface gratings, the radiation fields of surface plasmon polaritons (SPPs) can be controlled effectively to make a beam spot at several times the wavelength distance from the slit. Two methods for the control of focal length and width are proposed, and the simulation results verify that both the methods are effective for the design of nano-optical focusing devices.

The complex refractive indices and the dielectric function of GaN for frequencies ranging from 0.25 to 1.22 THz are obtained using THz time-domain spectroscopy. The real part of the dielectric function first decreases from 0.25 to 0.42 THz and then oscillates from 0.42 to 1.22 THz, whereas the imaginary part of the dielectric function is oscillating within the whole range of frequency. The simple Drude model is extended to take into account the effect of defects on the dielectric function. The extended model is in agreement with the experimental data.

Giant negative temperature coefficient of resistance (TCR) was observed in ZnO/Si (111) thin films. The films were grown using the pulsed laser deposition (PLD) technique, taking Si (111) wafer as substrates, with a substrate at the temperature below 450°C in the PLD. It is found that both TCP-temperature behavior and TCP, value are strongly affected by deposition temperature. The maximal TCP, value over −10.9%K⁻¹ can be observed at the deposition temperature from 20°C to 350°C and reaches to −13%K⁻¹ at deposition temperature 20°C where the film shows X-ray diffraction amorphous. The results suggest that the ZnO/Si films demonstrate great potentials when used in a low-cost, high-performance, non-cooling and highly sensitive bolometer.

Prefer-oriented and fine grained polycrystalline GaN films are prepared by plasma enhanced metal organic chemical vapour deposition on nucleation surfaces of freestanding thick diamond films. The characteristics of the GaN films are characterized by x-ray diffraction, reflection high energy electron diffraction and atomic force microscopy. The results indicate that the structure and morphology of the films are strongly dependent on the deposition temperature. The most significant improvements in morphological and structural properties of GaN films are obtained under the proper deposition temperature of 400°C.

The concentration and temperature dependence of the viscosity is observed for some aqueous dispersions of Carbopol. The experimental data are analyzed with the power model, and reveal non-Newtonian behavior (shear thinning) of the samples.

We demonstrate an optical switching in a middle infrared continuous-wave quantum cascade laser operated in single mode by illuminating its front facet with a near infrared laser. A decrease in the laser net gain is observed in the amplified spontaneous emission spectrum. This is attributed to an increase of the carrier concentration caused by the near infrared excitation. The net gain reduction allows the quantum cascade laser to be completely switched off from single mode lasing. This optical switching can be used to convert near infrared signals into middle infrared signals for free space communication.

The technique of surface acoustic waves (SAWs) is a very promising method for determining film properties such as Young's modulus, density and film thickness nondestructively and accurately. The dispersion property of SAWs is also affected largely from the adhesion property of films, which is revealed by the bonding spring assumption described. This SAW method could offer a quantitative evaluation of the film adhesion from the curvature of SAW dispersion lines affected by the normal and shear spring constants. The method is applied to numerically characterize the adhesion property of the typical ultra-large-scale integrated circuit interconnect layered structure of a thin Cu film deposited on the Si substrate as well as a SiO₂ thin film on a Si substrate.

A nonvolatile memory effect was observed in an organic thin-film transistor by introducing a Boating gate structure. The Boating gate was composed of an Al film in a thickness of nanometers, which was thermally deposited on a SiO2 insulator and exposed to air to spontaneously oxidize. It can be seen that the transistors exhibit significant hysteresis behaviors and storage circles in current-voltage characteristics in the dark and under illumination, indicating that the transistors may act as a nonvolatile memory element. The operational mechanism is discussed in the cases of dark and illumination via charge trapping by the Al floating gate.

A fundamental tenet in theoretical ecology is the competitive exclusion principle. Two competitive species for a limited resource cannot coexist and thus one of the species will be driven to extinction. However, we show that noise can revise this principle in a resonance-like manner, which makes coherence resonance in the system. Our obtained results well enrich the findings in the interaction of populations in ecosystems, which may explain some filed observations in the real world.

The Small world model has been successfully used to explore the abnormal pattern of brain information processing in some neuropsychiatric diseases, but not engaged in the study of cognitive functions. We apply the small-world measures: the clustering coefficient and average path length, to evaluate multi-channel event-related potential activity during the generation of global and local imagery. Results show that the brain functional networks of the global and local imagery generation are both small-world ones. In addition, the local imagery generation has a larger clustering coefficient, while the global imagery generation has a shorter average path length. These results support the global precedence in the global-local imagery generation, and reflect the different processing modes in which global imagery emphasizes particularly on global integration, while local imagery on local specialization. Our results indicate that small-world measures could be applied to quantify the difference of brain activities in different cognitive tasks, and further provide some explanations for cognitive behavior.

Electrostatic solitary waves (ESWs) are observed in the vicinity of the magnetic null of the widely studied magnetic reconnection taking place at the near-earth tail when current sheet becomes dramatic thinning during substorm time on 1 October 2001. We use the Imada method for the 2-D reconnection model and study the characteristics of ESWs near the X-line region and the magnetic null points. The result shows that the amplitude of the observed ESWs in the vicinity of X-line region ranges from 0.1 mV/m to 5 mV/m, and the amplitude is larger near the magnetic null points. The generation mechanism and the role of ESWs associated with magnetic reconnection are also discussed.

Previous particle-in-cell simulations have evidenced that supercritical, quasi-perpendicular shocks are non-stationary. By separating the incident ions into reflected (R) and directly transmitted (DT) parts, we investigate the ion distributions in a non-stationary perpendicular shock. The upstream ion distributions have two parts corresponding to the R and incident ions respectively, while the R ions have higher energy. The downstream ions have a corering distribution. The core and ring parts correspond to the DT and R, ions, respectively. The ion distributions depend largely on the non-stationary shock structure. The percentage of the reflected ions cyclically varies in time with a period equal to the shock self-reformation cycle, and the number of the R ions increases with the steepness of the shock ramp.