A class of solar-forced recharge oscillator model for the El Niño /Southern Oscillation (ENSO) is considered. By transforming the ENSO model equations into the van der Pol-Duffing oscillator with periodic forcing, we obtain the Hopf bifurcation conditions by the harmonic balance method. Numerical simulations also show that the 11-yr solar-cycle forced ENSO system undergoes a transition from the qu...
Recognition of micro-motion characteristics has important research values in target detection field, which can be realized by employing the dynamic speckle technology. Based on the rough surface scattering theory, this paper studies the dynamic speckle time correlation function for rotating rough convex targets, and provides the dynamic speckle time correlation function for rotating cones. Compari...
This paper presents a digital image tamper detection and recovery algorithm, which uses the dither and chaos technology. Certification of generated image and the repair information gained by low frequency sub-diagram and dither technology after wavelet transform can effectively reduce the amount of data. At the same time, the watermark is embedded in high frequency sub-diagram, so as to make the w...
This paper presents a class of quadratic nonlinear system by introducing a linear term x of the third equation into the second equation of a chaotic system based on analyzing and studying some chaos. Using nonlinear dynamics method we analyze the steady, quasi-periodic and chaotic transition process when the system parameter varies. Experiment results are in good agreement with the Matlab simulati...
In this paper, we study the stochastic resonance in a piecewise nonlinear system driven by a periodic signal and colored noises, which is described by multiplicative and additive colored noises with colored cross-correlation. Using the two-state theory and the unified colored approximation, we can derive the analytical expressions of the steady-state probability density and the signal-to-noise rat...
The coded aperture imaging spectrometer system based on the double-Amici-prism is designed in this paper, which includes the telescope objective, the coded template, the double-Amici-prism, the collimator lens and the imaging lens. This optical system can obtain a high diffraction efficiency. Compared to the imaging spectrometer system with a slit for this kind of system, the field of view is a tw...
In this paper, a corrected smoothed particle hydrodynamics (SPH) method is proposed to solve the problems of non-isothermal non-Newtonian viscous fluid. The proposed particle method is based on the corrected kernel derivative scheme under no kernel derivative and incompressible conditions, which possesses higher accuracy and better stability than the traditional SPH method. Meanwhile, a temperatur...
The following steps are given to search for new solutions to equations of sine-Gordon type. Step one, according to function transformation, the solving of sine-Gordon equation and sinh-Gordon equation is changed into the solving of two kinds of nonlinear ordinary differential equations. Step two, two kinds of nonlinear ordinary differential equations and quasi-Bcklund transformation of the first k...
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
According to the charging equation and charge conservation, the charging frequency (electric relaxation rate) is deduced and the formulation of charging electric current of the weakly ionized dust plasma is given according to the double Maxwellian distribution. It is shown that the directional speed have an influence on charging frequency; the charging frequency will decrease with the increase of ...
Polarization smoothing is a technique for reducing speckle pattern contröst on a target by overlaying two uncorrelated speckle patterns with orthogonal polarizations, and it can reduce focal spot contröst by a factor of 1/√2. Improvement of focal spot contröst by using traditional polarization wedge for polarization smoothing is usually concentrated at some special spatial frequency and is lack of...
It is important to diagnose electron density of a plasma irradiated by lasers for inertial confinement fusion, in high energy density physics and related fields, especially for measuring high-Z plasma near the interface. Use of soft X-ray laser as a probe is an important method in diagnosis of plasma electron density distribution. However, it is difficult to carry out the research in high-Z laser ...
Since X-ray pulsar signals cannot be detected on the ground, the pulsar signals need be simulated using the ground experiments. In this paper,two new simulation methods to obtain the time of arrival are put forward. The first method is based on a statistical physics model, which should overcome the shortcomings of narrow adaptation, low speed, and low time resolution in normal simulation method. T...
The physical mechanism of earthquake remains a challenging issue to be clarified. Seismologists used to attribute shallow earthquake to the elastic rebound of crustal rocks. The seismic energy calculated following the elastic rebound theory and on the basis of experimental results of rocks, however, shows a large discrepancy with measurementa fact that has been dubbed the heat flow paradox. For th...
ELECTROMAGENTISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
An analytical formulation has been developed for the electromagnetic leakage from an apertured rectangular cavity excited internally by an electric dipole. The leakage fields are represented by the equivalent electric and magnetic dipoles located at the aperture center with their dipole moments related to the “closed cavity” field within the framework of the Bethe's small aperture coupling theory....
Based on terahertz time-domain spectrscopy (THz-TDS) technology, a broad-band time domain terahertz radar system can be used to do research on scattering characteristics of objects. At present, the optical structure and mechanism of this system-showing the radar detection principle and imaging mechanism-has attracted a lot of interest in the terahertz research field. Based on the femtosecond Ti: s...
These years, with the development of material fabrication technology, some new synthetic materials that have unique electromagnetic properties have come out, one of which, the gradient meta-surface constructed into a special topological structure, gains rising popularity among experts. This paper establishes a refractive index gradient meta-surface and discusses its physical mechanism in optics. N...
The properties of off-center Gaussian vortex beams focused by a high numerical aperture are investigated on the basis of vector Debye integral. A complex amplitude of off-center Gaussian vortex beams through a high numerical aperture objective is derived and numerical calculation is performed to analyze the intensity and phase distributions of the beams in the focal plane. It is shown that the int...
We report a wave-locked 878.6 nm diode-laser-pumped multi-segmented Nd:YVO4 laser operating at 1064 nm, which is compared with the high doping concentration and the low doping concentration monolithic Nd:YVO4 lasers. Experimental results show that the configuration of the wave-locked 878.6 nm diode-laser-pumped multi-segmented crystals not only can reduce thermal effects of the laser but also can ...
Profile of a dark hollow beam in sub-diffraction -limit imaging is of crucial importance for its spatial resolution when using the coherent anti-Stokes Raman scattering microscopy, as far as the imaging quality is concerned. Therefore, the generation of dark hollow beams through a vortex phase plate will be theoretically analyzed based on the Fresnel diffraction theory. Influences of different inc...
Oxygen A-band is an ideal inversion channel. Absorption coefficient is one of the important parameters, its precision determines the accuracy of inversion result. The influence factor for the absorption of oxygen A-band is analyzed using HITRAN2012 database and temperature profiles of atmosphere. The temperature dependence is deduced for each influence factor, and then for the absorption coefficie...
The distribution of population inversion has been obtained by solving the rate equations of a Tm and Ho codoped laser system. A giant pulse laser output of 88.4 mJ with pulse duration of 426 ns has been predicted at 0.1% duty cycle of LD pump source. In a 2 m ring resonator, the Tm, Ho:LuLF laser material has been side-pumped from three directions and Q-switched for acoustic-optic device. The slop...
Under the condition that the light pulses meet the slowly varying function pulses, the higher-order nonlinear Schrödinger equation has been deduced by taking into consideration the Raman gain. The linear operator and nonlinear operator specific expressions are obtained using split-step Fourier numerical method. The Raman gain on the self-steepening of the Gaussian pulse has been simulated and then...
This paper utilizes a kinetic theory model to gain the accurate electromagnetic (EM) wave characteristics in the plasma region, based on the solution of Maxwell-Boltzmann (MB) equation system. The system is solved by finite-difference time-domain (FDTD) algorithm, which gives the results of the electric field intensity and particle velocity distribution function. Furthermore, the validity and effe...
Saturated fluid convective heat transfer in ordered three-dimensional porous media has been investigated numerically using a CFD software. Spherical particles with diameters dp equal to respectively 14, 9.4, 7 mm have orderly arrangements constituting the porous media skeleton. There is a copper plate of constant heat flux density above the porous skeleton. The distribution of temperature and loca...
Under the steady condition, the spherical geostrophic wind relationship in spherical coordinates (λ,φ,r) is applied to illustrate that when isobars take the simplest zonal distribution, the Antarctic is at a low ambient pressure, while the Arctic is at high. However, when friction is incorporated into the geostrophic wind relationship, the closed vortex over Antarctic and Arctic will turn to a spi...
The traditional method of calculating electromagnetic scatterings from the rough sea surface, which does not need a geometrical sample of sea surface, considers mainly the total scattering echoes by average assembling of different incident parameters. With the development of synthetic aperture radar and radar imaging, it is important to fully describe the sea surface at every point, and to obtain ...
Acoustic scattering from the submerged finite periodically ribbed two concentric cylindrical shells, insonified by an incident plane wave, is studied. Motion of the shell is described by Donnell equations, while the motion of the disks is described by thin plate motion equations and plane ströss equations ignoring the effects of axial forces on the disks. Through angle-frequency spectra, besides t...
The mode coupling and energy transfer are studied by considering the influences of variation in topography on sound energy transmission and structures of interference in a range-dependent waveguide. A larger level-stepped coupled mode model and a three-dimensional coupled mode model for the wedge bottom are obtained such that the mode coupling and energy transfer may be analyzed efficiently and ra...
Matched-field replica vector should be calculated using parabolic equation in a range-dependent waveguide, this means that the matched-field localization is too computationally intensive, hence its engineering application is seriously hindered. A virtual time-reversal method for passive source localization for a range-dependent waveguide is presented. The number of parabolic equation computational...
In engineering applications, many measurements of physical quantities can be converted into the problems of frequency estimation. The current frequency estimators are mainly divided into two categories: iterative approaches and direct approaches. However, iterative approaches are not suitable for rapid physical measurement occasions due to its complicated process. But most of the direct approaches...
Granular coal is a kind of multilayer and structured solid matter, which consists of a large assemblage of individual granular solids and has dual characters of coal and granular materials. Its crack propagation law can be studied using the coal mechanics and multi-scale characteristics. First of all, the linear elastic material may be damaged under compression; and the cause of crack propagation ...
In this paper, the microscale non-equilibrium gas flow, and the oscillating Couette and Poiseuille flows, have been investigated by an effective MRT-LBM. The Knudsen layer model is introduced into lattice Boltzmann method (LBM) for the relaxation time correction. In the simulations the plate or external force oscillates in the form of sine curve, and the Couette flow contains a singular oscillatio...
This paper investigates the capillary flows in variable interior corners along the axis when a microgravity environment and the Concus-Finn condition are satisfied. The governing equation for capillary-driven flows in variable interior corners is established, and an approximately analytic solution is obtained. Then we compare the approximately analytic solution with the numerical simulation result...
Fluid flow and heat transfer in a microstructure may depart from the traditional behavior due to the scale effect, and its velocity slip and temperature jump will occur at the fluid-solid interface. A molecular dynamics model of coupled fluid flow and heat transfer in rough nanochannels is developed to investigate the effect of surface roughness on nanoscale fluid flow and heat transfer, as well a...
Based on the immersed boundary concept that the border may be constructed by feedback force, a numerical simulation is carried out by modifying previous inner fluid treatment and incorporating it with non-equidistant grid. Flow around two elongated rectangles in tandem arrangement is computed in the range of Reynolds numbers from 200 to 103. Results indicate that when the Reynolds number is in the...
We have studied the effective diffusion coefficient of permeable particles with different radii at different permeability and volume fractions by using the numerical simulation results of short-time diffusion dynamics of permeable particles in concentrated suspensions and the combination of Cohen-de Schepper and Percus-Yevick approximations. As a result, the diffusivity of particles having the sam...
We demonstrate an efficient tunable phase-stabilized near-infrared optical parametric amplifier (OPA) made from a BBO (β -BaB2O4) single crystal in this paper. By using the seeded white-light continuum produced by CEP(carrier envelop phase)-stabilized femtosecond laser amplifier system which is seeded into the two stages of a type II OPA system, the pump-to-signal conversion efficiency of 34% can ...
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Considering Rashba spin orbit interaction and spin quantum transport in the spin field effect transistor, we study the influence of the barrier strength on the spin coherence transport in spin field effect transistors. It is found that when the barrier strength is weak, the tunneling junction conductance exhibits oscillatory phenomenon obviously with increasing Rashba spin orbit interaction streng...
The freewheeling diode in power electronic converters may generate a voltage peak on the load during the reverse recovery process, and the peak voltage becomes larger when the forward conduction time is smaller, which very likely induces the over-voltage failure of the power devices. To effectively guide the reliability design of power electronic devices, the switching transition mechanism of the ...
Positron annihilation lifetime spectroscopy, which takes positron lifetime as a detected object, has been widely applied to the study on micro-defects of semiconductors and other materials, and is very sensitive to the type of crystal structure, defect types, and temperature, and so on. Therefore, the analysis of fast and accurate calculation of positron lifetime theoretically combined with the ex...
The organic phosphorescent OLED (PhOLED) has been widely studied because its inner quantum efficiency can reach 100%, but there has been much debate about the internal luminescence mechanism and process, mainly because they are explained using the luminescence theory of inorganic LED. In this paper, we set up a transient electroluminescence (EL) and delay EL measurement system, and for the first t...
Structure and stability of the Li-adsorbed silicene under a biaxial strain are studied by using the first-principles plane-wave pseudopotential method based on the density functional theory. Results show that Li-adsorbed silicenes keep their original configurations basically when the tensile and certain compressive strains are applied, while the silicene plane bulges towards the Li atom when a lar...
Molybdenum disulphide (MoS2), a layered quasi-two dimensional (2D) chalcogenide material, is a subject of intense research because of its electronic, optical, mechanical and physicochemical properties. Since the monolayer MoS2 is a direct-gap seminconductor, it is widely used in the field of light-emitting area. However, its photoluminescence (PL) efficiency is very low due to excessive doping in ...
Nano-silicon carbide/silicone rubber composites with nonlinear conductivity characteristics have been made by mixing nano-sized silicon carbide (SiC) into silicone rubber. In this paper, the nonlinear conductivity characteristics of composites made by mixing 5 wt%, 15 wt%, 30 wt% and 45 wt% of nano-SiC and silicone rubber are investigated. The relationship between conductivity and electric field s...
Cooperative luminescence, down-conversion laser oscillation and cascaded Raman laser in Yb3+-doped 55.93P2O5-3.57Al2O3-15Na2CO3-20SiO2 phosphosilicate glass are studied in the biconical fiber-microsphere coupling system in this paper. A single-mode semiconducter laser with the center wavelength at 976 nm and line-width 0.15 nm is used as a pump source. The blue-shifted cooperative luminescence cen...
GaN-based light-emitting diode (LED) thin films grown on Si(111) substrates are successfully detached and transferred to copper and silicon submounts, and then become 40mil high power vertical structure LED chips. Electroluminescence properties of the two kinds of chips with the same expitaxial structure are investigated at different forward current densities and ambient temperatures. The obtained...
A theoretical study is presented on the magnetic-field-excited and adjusted ferromagnetic resonance in the spin valve structures with perpendicular anisotropy. Through linearizing the Landau-Lifshitz-Gilbert equation including the spin-transfer torque term, the magnetic-field-excited and adjusted ferromagnetic resonant spectra are obtained. The dependences of the resonant linewidth, resonant frequ...
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Epidemics and cascades are independently studied topics in network science, but in practice, there are cases where they interact and neither of their effects can be ignored, e.g., when a digital virus spreads in a communication network that is transferring data. We have built a model to study their interplay in previous works. Here we present the epidemic threshold criteria of this model. When the...
Technical parameter design is an effective approach to improve marine environment sounding capability for fully polarimetric synthetie apertuer radar (SAR). By analyzing geophysical contact between noise-equated backscattering coefficient and marine environment sounding, and that between radiometric resolution and marine environment sounding, we present the key technical parameters design method f...
EEG (electroencephalogram) is generated by the brain activity and is present in the central nervous system of spontaneous electrical activity, which is an important biological signal. EEG is a very weak and nonlinear as well as irreversible signal. This paper presents a new method to describe it based on the relative entropy of transition probability for the forward and reverse sequences. Besides,...
Based on the condition of inhibiting traffic flow instability, this paper studies the effects of comprehensive information of the nearest following vehicle obtained by drivers' rear view behavior on traffic flow instability. Research shows that in the real practice the probability of paying attention to the information of the preceding vehicle is greater than that of paying attention to the inform...
A tandem solar cell, composed of a MEH-PPV:PCBM bulk heterojunction front sub-cell and a CuPc/PCBM small molecule back sub-cell, is fabricated by spin-coating and vacuum evaporating methods. Measurement results show that an optimal tandem solar cell with 50 nm MEH-PPV:PCBM active layer thickness and 0.5 nm Ag inter-layer thickness can be obtained with a power conversion efficiency of 1.86%
Ca0.64WO4:Eu0.24 also crystalizes in the phase of CaWO4 with about 12 mol% of Schottky defects on Ca2+-sites in the crystal lattice of CaWO4. The question whether such a phase is well stable at high temperatures remains to be studied, so the impacts of over-sintering on the structure of Ca0.64WO4:Eu0.24 ceramics are examined. The probable origins resulting in the phase transition at high temperatu...
Vanadium dioxide (VO2) thin film have been fabricated on the ZnO-doped Al conductive glass (AZO) substrates by DC magnetron sputtering and after thermal annealing. Effect of different annealing temperature and time olunation on the VO2/AZO composite films has been studied, then the structure, components and optical-electrical properties of the composite films are tested and analyzed by suitable in...
Among the three methods (B3LYP, BP86 and B3LYP*) in density functional theory (DFT), the best tools for predicting the ground state of metal hydride, the B3LYP method for predicting the harmonic frequencies and geometric parameters of the ground state of FeH2 gives result in good accordance with the experimental data; so it is employed to optimize the structure of molecules FeH and FeH2 in possibl...
We propose a new scheme for molecular mirror with a blue-detuned surface plasmon ploariton field excited on a microstructural metal film and study the dynamic process of reflection of cold molecules by Monte Carlo simulation. Our study shows that this mirror can realize a reflection of cold iodine molecular beam with a longitudinal temperature of 10 mK and a transverse temperature of 1 mK with a r...
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
Specimens of 6H-SiC were irradiated by 300keV He ions at temperatures of RT, 450, 600 and 750 ℃ with fluences ranging from 11015 to 11017 cm-2. Post-irradiation, virgin and irradiated 6H-SiC specimens are measured and studied by microscopic laser confocal Raman spectrometer and UV-visible transmission apparatus. Analyses of both experimental results shown that production and recovery of defects ca...
This article uses the Miller model to simulate the ferroelectric polarization of the metal-ferroelectrics-insulator-substrate (MFIS) structured ferroelectric field effect transistor (FeFET), interfacial charge concentration, and charge migration rate under ionizing radiation. The capacitance and source-drain current at different total dose and different dose rate are calculated. Results show that ...
The pressure dependence of electrical properties of ZnSe was observed by means of in situ high pressure DC electrical resistivity measurement and AC impedance spectrum methods in a range of 0–35 GPa. Two structure phase transitions have been observed corresponding to the wurtzite-cinnabar-rocksalt transitions. The temperature dependence of the electrical resistivity of ZnSe is measured under diffe...
We have studied the vibration behavior of a water droplet vibrated on a superhydrophobic surface via a high-speed camera. The resonance frequencies of the droplet satisfy the Rayleigh equation, suggesting that the droplet on a superhydrophobic surface can be regarded as a free droplet. Its real oscillation frequency is half of the driving frequency when it is vibrated at low frequencies(<200 Hz). ...