In this paper, the process of the free dendritic growth of Mg-0.5 wt.%Al alloy in the basal plane (0001) is simulated in two-dimensional system by using a quantitative phase-field model. A convergence study is carried out to choose the optimal coupling parameter λ and grid width Δx/W0 in simulation. Then we systematically discuss the effects of the anisotropic strength ε and the supersaturation Ω ...
As one of the most popular numerical methods, the method of moments (MoM) is known for its high accuracy. Besides, MoM has other advantages. For example, the integral equations satisfy the Sommerfeld radiation condition automatically, the additional boundary conditions are not needed., etc. But if the wide angle problem, especially the composite electromagnetic back scattering from a ship place on...
By using the imaginary-time propagation method, we study the ground state structure of a two-component dipolar Bose-Einstein condensate confined in a coupled annular potential. The effects of contact and dipole-dipole interaction on the ground state density distribution of such a system are investigated in detail. The results show that the dipole-dipole interaction, acting as a new degree of freed...
This article aims at studying the stochastic P-bifurcation of tri-stable van der Pol-Duffing oscillator subjected to multiplicative colored noise. First, the stationary probability density of amplitude is derived by using the stochastic averaging method. Then the critical parameter conditions of stochastic P-bifurcation are obtained based on the singularity theory. And the different types of stati...
This paper focuses on the piezoelectric cantilever energy harvesting system with an externally applied magnetic field. The calculation method and model for the magnetic force are proposed from the magnetizing current method, and the calculation results are compared with a set of experimental data. The study shows that there is a deviation in the calculation model derived by the magnetizing current...
Aiming at the blind angle in detecting weak signals of the same frequency by Duffing oscillator, a novel method of dephasing for the driving signals is proposed to eliminate the blind angle. According to the characteristic of weak signals, expression of blind angle is analyzed, and then the range of blind angle is found out, which corresponds to the amplitude of a new driven signal synthesized fro...
In order to remain the structure of the neural network in the process of the optimization unchanged, taking the hysteretic chaotic neuron and the hysteretic chaotic neural network as controlled plants, a novel control strategy based on the filtered tracking error is proposed to perform the stability control for the single hysteretic chaotic neuron or the hysteretic chaotic neural network. Especial...
The simulation of pedestrian push-force in evacuation with arched congestion before exit is presented based on cell automata. The generation, absorption, transfer and gather of pedestrian push-force are analyzed. Initial push-force facing to exit is generated based on the distance between pedestrian and exit. The scalar and vector sum of push-force are introduced to respectively describe the push ...
We present a new realization of weak electrostatic force based on Kelvin capacitor, which, compared with the conventional realization, simplifies the mechanical design without synchronously moving the central and guard-ring electrodes. However, a residual force due to the edge effect of the capacitor should be accurately known. In this paper, an analytic model of the electrostatic force generated ...
In the division of time imaging polarimetry, polarization information of field under measurement (I, Q, U), is obtained by rotating the analyzer. In the process of measurement, the beam deviation caused by the wedge of the analyzer reduces the spatial resolution and polarization accuracy of imaging polarimetry. In this paper we present that the beam deviation above can be reduced or even compensat...
In this paper, the time-dependent wave-packet method is used to study the three-dimensional dynamical properties of the H+Li2 reactive system on its ground state potential energy surface. The reaction probabilities for J=0 with different vibrational quantum numbers v=0, 1, 2, 3 and for v=0 with different total rotational quantum numbers, integral cross sections and rate constants are calculated fo...
A density functional method DFT/B3P86 with relativistic effective core potential basis for U and 6-311+G(d) basis for N is used to study the energy gap and harmonic frequency of UN2 ground state molecule under the action of the uranium-produced spontaneous radiation fields ranging from -0.005 to 0.005 a.u.. The results show that UN2 has an anti-symmetry expansion vibrational frequency ν3 (σg) that...
The geometric parameters are optimized at the B3LYP and CI levels under the constraints of the C2v, C2v and C2h symmetry point groups for the three isomers of dichloroethylene. The theoretical two-dimensional electron momentum distributions and momentum profiles of four core orbitals for iso-dichloroethylene, cis-dichloroethylene and trans-dichloroethylene are calculated by non-relativistic densit...
ELECTROMAGENTISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
In this paper, the characteristics of the azimuthally polarized non-diffracting beam (APB) propagating in the free space and obstruction space are investigated theoretically and experimentally. The variations in intensity distribution and polarization characteristics of the APB in propagation process are simulated. In the experiment, the APB is generated by using the polarization converter and axi...
The formation environment and the evolution of dark soliton with environment parameters are investigated by using the electromagnetically induced transparency effect produced high dispersion and nonlinearity. To improve the stability and operability, a dual-well semiconductor is used. Combining the quantum theory and the classical field theory, we derive the nonlinear Schrodinger equation to descr...
In image processing, in order to well preserve corners, peaks, and thin edges of the image, a new biharmonic diffusion model is established, which takes into account the stress balance of the biharmonic equation and local maximum values of higher-order partial derivatives. If the noise is very strong in the image, some isolated spots will leave on the processed image, and texture of the image has ...
A test system including light path system and software system is built for measuring the refractive index of fiber by using the digital holographic tomography technology. Based on the phase distribution curve of object wave the optimal hologram is recorded. The spectral range corresponding to the object wave is selected accurately based on the optimization of the spectrum. The phase distribution i...
In this paper, we investigate the spectrum properties of the lasing without population inversion in a three-level atomic system under an action of an externally applied microwave field. The probed absorption spectrum is obtained by solving the density matrix equation of this system. The results show that the absorption profile has a multi-peak structure, and exhibits obviously negative absorption ...
We demonstrate a high-repetition-rate Er-doped all fiber laser with nonlinear-polarization-rotation mode-locking. The highest repetition rate of the laser is 217 MHz. The fiber laser has a very simple and compact structure and can output a stable mode-locking pulse only by using one polarization-dependent isolator and a polarization controller. The pulse width, spectral width and signal-to-noise r...
The transmission spectra of the model of photonic double quantum well consisting of two photonic crystals with two different single-negative materials are calculated by the transfer matrix method. It is found that these resonance modes split into pairs, owing to a coupling between two photonic wells. The distance of resonant modes can be controlled by the coupling strength between the two wells. I...
Photonic crystal not only can be used to inhibit the spontaneous emission and redistribute the energy into useful forms, but also can be designed to control and confine photons. Since the concept was introduced by John and Yablonovitch in 1987, there have been discussed the machinery of broadening the band bap and a quest for the optimal structure. Band structures of two-dimensional photonic cryst...
We propose a two-dimensional photonic crystal structure with low rotational symmetry and investigate its band structure characteristics over the whole first Brillouin zone by the plane wave expand method. The physical mechanism of broadband all-angle self-collimation effect and the influence of aspect ratio on the bandwidth are clarified. Furthermore, we obtain the existence criterion for self-col...
With the rapid development of all-optical communication, the wavelength division multiplexing transmission system cannot meet the requirements of high capacity in optical networks, while mode division multiplexing uses the limited stability modes as independent channels to transmit information, improving the system capacity and spectrum efficiency, which is one of the key technologies in the const...
Based on the theoretical model of optical wave propagation in parity-time (PT) symmetric waveguide, the transmission and control of bright solitons in PT symmetric Kerr nonlinear planar waveguide with Gaussian distribution are studied numerically. The PT symmetric waveguide requires that the refractive index distribution of waveguide should have to be an even symmetry, whereas the gain/loss distri...
Two different types of few mode fibers (FMFs) are considered: a graded-core with a cladding FMF and a multi-step-index FMF. The characteristics of mode field distribution and the effective index are analyzed based on Comsol software. Then differential mode delay is analyzed. The structure and profile parameters are optimized in order to achieve the lowest possible differential mode delay (DMD). Un...
Fiber-optic surface plasmon resonance sensor (SPR) plays an important role in the fields of high sensitivity sensor and online real time monitor. We propose a novel six-fold symmetric photonic quasi-crystal fiber SPR sensor with two large semi circular channels. Its sensing properties and influence of fiber structure are simulated numerically by the finite element method. Numerical results demonst...
To solve the problem of poor performance of the traditional l2-norm channel estimation, a sparse channel estimation approach based on basis pursuit denoising (BPDN) is proposed in orthogonal frequency division multiplex underwater acoustic communication. Owing to the sparsity of the underwater acoustic channel, only a few observations are needed to recover the channel impulse response with a high ...
The components of the underwater target scattering waves alias together in time domain and frequency domain realistically. They are affected by the incident angle, and show great differences under different angles. It is necessary to build an analytical model of scattering waves under all-direction incident angles theoretically. The analytical expressions of geometrical scattering components chang...
Chaotic motion of a kind of nonlinear relative rotation system with load Coulomb frictional damping is investigated. Based on the Lagrange equation of a dissipative system, the dynamic equation of a kind of nonlinear relative rotation system with two pieces of mass is established, which contains a kind of nonlinear load Coulomb frictional damping. The eigenvalue of the autonomous system is discuss...
Form invariance and Mei conserved quantity for generalized Hamilton systems after adding additional terms are studied. By introducing infinitesimal transformation group and its infinitesimal transformation vector of generators, the definition and determining equations of the Mei symmetry for generalized Hamilton systems after adding additional terms are provided. By means of the structure equation...
The fine flow structure over backward facing step with supersonic injection at the free-stream Mach number of 3.4 is investigated via nano-tracer planar laser scattering (NPLS). The Mach number of injection is measured to be 2.45 actually, even though designed to be 2.5 nominally. The shock wave, shear layer, mixing layer, Kelvin-Helmholtz vortex, horn-like vortex, coherent structures, etc, are cl...
The problem of calculating the equation of state (EOS) of a material mixture often comes from fluid-dynamical system containing multiple materials. Generally, the EOS of a material mixture is a system of nonlinear equations which are usually solved by the tabular method and the Newton iterative method. However, the former has poor accuracy, and the later has a finite radius of convergence and henc...
In recent years, the motion of nanodroplets on energy gradient surface on a microscale has attracted widespread attention, however, experimental studies are still irrealizable. In this work, the motions of nanodroplets driven by the energy gradient on surfaces with different microstructures are studied by molecular dynamics method. The results show that: the groove-shaped and post-shaped microstru...
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
Thermodynamics basic and alloy phase evolution of Mg-Sn-Si alloy are studied. The results indicate that for Mg-Sn-Si alloy, the specific heat of alloy phase increases with temperature, and it changes quickly at low temperature while gently at high temperature. In the range of low temperature, its thermal expansion increases exponentially with the increase of temperature, and in the range of high t...
The Ni50-xFexMn37In13(x=1, 3, 5) polycrystalline samples are prepared by arc melting method. The martensitic transformations and crystal structures for Ni50-xFexMn37In13(x=1, 3, 5) samples are systematically analyzed by measuring the structure and magnetism. The results show that the three samples present different structures at room temperature. In the mean time, with the increase of the content ...
The sliding friction between a rigid tip and an amorphous polymer film is studied using large scale molecular dynamics simulation. We focus on the changes of surface microstructure on the polymer film caused by friction, and study the effects of the interaction between tip and substrate, the sliding speed and the molecular chain length on the change of surface microstructure. When there is an adhe...
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Nowadays although the In–N co-doping effects on the optical band gap and absorption spectrum of ZnO are studied extensively, all of the In–N co-doped ZnO materials are of random doping, and the preferred orientation doping using the unpolarized structure of ZnO has not been considered so far. Therefore, in this paper, based on the density functional theory using first principles plane-wave ultraso...
The electronic structures and optical properties of boron/phosphorus mono- and co-doped β silicon nitride are studied by the first-principles plane-wave ultrasoft pseudopotential method with the generalized gradient approximation. The results are obtained as follows. The B-doped system has a better stability than the P-doped system, while the P-doped structure has a stronger ionicity. The mono-dop...
Within the framework of the Su-Schrieffer-Heeger model modified to include uniform disorder and an external electric field, the polaron transport process in conjugated polymer material is simulated using a nonadiabatic evolution method. It is found that the polaron dynamic mechanism is determined by both the electric field and the uniform disorder. The effect of uniform disorder is not obvious and...
We theoretically investigate the electromagnetic properties of the multilayer graphene-dielectric composite materials based on the effective medium theory. It is found that the structure exhibits hyperbolic isofrequency wavevector dispersions at THz and far-infrared frequencies, hence thereby realizing the effective graphene-based hyperbolic metamaterials (HMM). The frequncy band of the hyperbolic...
Frequency selective surface based on metallic mesh can realize the physical properties of both high infrared transmittance and millimeter-wave band-pass filter. In order to improve the optical transmittance, reduce surface resistance and suppress the effect of high order diffraction energy on the imaging quality of the optical system, a new design of frequency selective surface based on hybrid per...
Nickle ohmic contacts on the Si-face of n-type 4H-SiC are prepared by both rapid thermal annealing (RTA) and laser spark annealing (LSA). The effects of the different annealing procedures on the cathode surface morphology, cathode/substrate cross sectional morphology, element composition, microscopic structure of carbon clusters in the SiC substrate near surface, are characterized by scanning elec...
In order to design the power devices with the low loss required for the power integrated circuits (PIC), a new folded silicon LDMOS with the folding step oxide layer (SOFLDMOS) is proposed in this paper for the first time. In this structure, the step oxide layer is covered on the folded silicon surface with a periodic distribution. The surface electric field is optimized to be uniform by introduci...
The capacitance model is fundamental for the transient analysis, AC analysis and noise analysis of uniaxially strained Si MOSFET device and circuit. Firstly, the 16-differential capacitance model for uniaxially strained Si NMOSFET is developed. Secondly, the simulation results from that model match the experimental results well, which validates the accuracy of the model. Meanwhile the simulated re...
The polycrystalline samples of two-layered perovskite manganites (La1-xGdx)4/3Sr5/3Mn2O7 (x=0, 0.025) are prepared by traditional solid state reaction method. X-ray diffraction measurements show that both samples are of the Sr3Ti2O7 -type tetragonal phase (space groups I4/mmm). Magnetic measurements show that Gd3+ doping reduces the magnetic transition temperature (TC3D) and magnetization (M) of t...
The Fe-Ni nano-polycrystalline thin films of 21 nm and 235 nm in thickness are prepared by molecular beam vapor deposition in the absence and the presence of a magnetic field as high as 6 T. The results show that in the absence of the magnetic field, the 21-nm-thick thin films are formed by the grain stacks, and the sizes of grains are about 6-7 nm. In the presence of 6 T, the 5-nm-thick flat laye...
SiNx films are synthesized on Si substrates in a home-made linear microwave plasma enhanced chemical vapor deposition system at different microwave powers, duty cycles, substrate temperatures, and ratios of silane (SiH4) flow to ammonia (NH3) gas flow. The effects of technological parameters on morphology of film surface, stoichiometric proportion, refractive index and deposition rate of SiNx film...
In this paper, by a radio frequency magnetron sputtering equipment, the ZnO/Pt nanoparticles/ZnO thin film structure is fabricated on a SiO2 substrate via three-step. And the metal-semiconductor-metal (MSM) structured ultraviolet (UV) photodetectors are built up. It is studied that the Pt nanoparticles in different depths of the layer of ZnO thin film affect the photoresponse performances of the M...
This article first gives a brief review of magnetic structures, magnetic domains and topological magnetic textures and their relations. On the one hand, the magnetic domains are determined by the magnetic structures, the intrinsic magnetic properties and the micro-structural factors of a material. On the other hand, the magnetic domains could control the magnetization and demagnetization processes...
Recently, Cu2ZnSnS4 (CZTS) has emerged as one of the most promising thin film materials due to its being environment friendly, abundant in storage and low cost. To date, solar cell with up to 12.6% efficiency have been reached with using Cu2ZnSn(S, Se)4 (CZTSSe) absorber by hydrazine solution method. In this paper, the structural, optical, electrical, interface layer properties of CZTS thin films ...
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
InAs/InAlAs/InP(001) nanostructure materials are grown using solid-source molecular beam epitaxy equipment. Effect of As pressure-modulated InAlAs superlattice on the morphology of InAs nanostructure is investigated. The results show that As pressure-modulated InAlAs superlattice can suppress the quantum wires formation and results in quantum dot growth with a uniform size distribution. The analys...
The influences of medium and temperature on the shear thickening behavior of silica colloids are investigated. The nano fumed silica colloids in four media (ethylene glycol, polyethylene glycol 400, propylene glycol, and polypropylene glycol 400) exhibit continuous or discontinuous shear thickening behaviors. With the increase of temperature, the medium viscosity decreases, thus the apparent visco...
Terahertz (THz) spectra for different palm leaves are measured by Fourier transformed infrared spectroscopy-attenuated total reflection, and the physical morphologies and chemical compositions of the leaves are characterized by scanning electron microscopy and infrared spectroscopy, respectively. Accordingly, the THz fingerprint peaks of chlorophyll and carotenoid are experimentally identified. In...
Biological memory is a ubiquitous phenomenon, which could be found in a variety of biological subsystems. Based on a model of dual feedback gene regulatory circuit, in this paper we investigate the influence of time delay on memory time. The results show that the memory time is enhanced dramatically due to the existence of time delay, and the memory time increases linearly with increase of time de...
In this paper, we discuss the applications of random balance design Fourier amplitude sensitivity test (RBD-FAST) and extended Fourier amplitude sensitivity test (EFAST) in the parameter sensitivity analysis of land surface process model. We use the common land model and data of Tongyu station, which is a reference site of CEOP in the semi-arid regions, use five model outputs (sensible heat flux, ...
Radiation belt energetic electrons can interact with very low frequency (VLF) electromagnetic wave due to wave-particle resonance; then the particles are imposed to enter into the loss cone and sink to dense atmosphere resulting from changing of its pitch angle. To investigate the diffusion mechanism of interaction of VLF electromagnetic wave with radiation belt energetic electrons, according to q...