Analysis of one-dimensional electromagnetic wave transmission characteristics of plasma based on a kinetic theory model
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 effectiveness of the proposed method is verified by comparing the results of reflection coefficient and transmission coefficient of the wave that impinges on plasma plate region with that of the analytic solution.
Broad-band time domain terahertz radar cross-section research in scale models
Based on terahertz time-domain spectröscopy (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: sapphire osillators pumped terahertz time-domain spectröscopy system, this paper constructs the first terahertz radar system in this country (0.1–1.3 THz). System calibration is carried out by measurements on standard metallic spheres. Three military scale models are measured by the Radar system. The shapes of the models are retrieved by the improved back projection algorithm, which verifies the new imaging mechanism based on time domain scattering signal. With high frequency broad band spectrum and high imaging resolution, the terahertz radar would make great contribution to stealth military units design and become a new research platform on terahertz scattering characteristics.
Analytical formulation for electromagnetic leakage from an apertured rectangular cavity
Research on the facet model of electromagnetic scatterings from rough sea surface with foams
Studies on the mechanism of refractive index gradient surface
Tight focusing properties of off-center Gaussian vortex beams
High efficient CEP-stabilized infrared optical parametric amplifier made from a BBO single crystal
Study on the temperature dependence of oxygen A-band absorption coefficient
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 coefficient. It is found that the influence of temperature on the coefficient is poor for HWHM (half width at half maximum) of the spectral line, but the HWHM of the line is greatly influenced by the temperature. The linetype function has two changes during the variation of temperature: The function value decreases with increasing temperature beyond the HWHM; it, however, slowly increases from the center frequency to HWHM of the line. The line intensity is strongly dependent on the temperature. Using the line by line integral algorithm, the absorption of oxygen A-band is calculated. The temperature dependences are considered to come from the pressure broadening effect, spectral line intensity, and HWHM. A conclusion is given that the temperature dependence of absorption of oxygen A-band comes from line intensity, and especially the center frequency. While, the temperature dependence of the linetype function with Lorentzian is not obvious. Finally, the absorption of oxygen A-band is measured at 63m using BRUKER spectrometer with 1 cm-1. The error is less than 0.83% as compared with that in theoretical model under the same condition. The correctness of the temperature calibration model is thus verified.
Theoretical and experimental researches on Tm and Ho codoped Q-switching laser
A 28.2-W wave-locked 878.6 nm diode-laser-pumped multi-segmented Nd:YVO4 laser operating at 1064 nm
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 improve the optical-to-optical conversion efficiency. We have achieved an output power of 28.2 W at 1064 nm with an incidence pump power of 40 W, corresponding to the optical-to-optical efficiency of 70.5%, slope efficiency of 70.6%. For absorbed pump power, the optical-to-optical efficiency is 76% and the slope efficiency is 76.4%. The laser also has an excellent output stability while the temperature is varied from 10 ℃ to 40 ℃.
Effect of Raman gain on the self-steepening characteristic in isotropic fibers
Acoustic scattering from the finite periodically ribbed two concentric cylindrical shells
Mode coupling and energy transfer in a range-dependent waveguide
A virtual time reversal method for passive source localization in a range-dependent waveguide
A novel phase difference frequency estimator based on forward and backward sub-segmenting
Numerical study of convection heat transfer in ordered three-dimensional porous media
Generation of dark hollow beams used in sub-diffraction-limit imaging in coherent anti-Stokes Raman scattering microscopy
Granular coal crack propagation study under uniaxial compression based on J integral
From Arctic high, Antarctic low to three-dimensional heteroclinic orbit connecting south pole and north pole
Numerical simulation of flow around two elongated rectangles in tandem arrangement using an immersed boundary method
Lattice Boltzmann modeling of microscale oscillating Couette flow
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 oscillation and a double-plate oscillation. It is revealed that the corrected MRT-LBM model can well handle the simulation of microscale non-equilibrium gas flow. For the Couette flow, the wall slip phenomenon is obvious for a larger Kn number, and the streamwise velocity profiles appear to be of a nonliner character when St number increases. When the two plates oscillate, the streamwise velocity profiles almost overlap with each other at small Kn and St. In the Poiseuille flow case, the extent of phase lag decreases as St exceeds a certain value. Compared to the Kn number, St has a bigger impact on the emerging of phase lag in the oscillating Couette and Poiseuille flows.
A study of capillary flow in variable interior corners under microgravity
Study on diffusion of permeable particles in concentrated suspensions
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 same radius will increase monotonically with increasing permeability to a certain volume fraction, and decrease linearly with increasing volume fraction to a certain permeability. While the effect of particle radius on the measured effective diffusion coefficients for the permeable particles with larger wave-numbers at the same ratio of particle radius to the hydrodynamic penetration depth may be neglected.
Molecular dynamics simulation on fluid flow and heat transfer in rough nanochannels
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 as velocity slip and temperature jump at the fluid-solid interface. The fluid microscopic structure, velocity and temperature distributions, interfacial velocity slip and temperature jump in a rough nanochannel are evaluated and compared with the corresponding smooth nanochannel. Effects of solid-liquid interaction and wall stiffness on the velocity slip and temperature jump are analyzed. Results indicate that the velocity of the fluid flow under an external force in a nanochannel in a bulk region is of a parabolic distribution, and the viscous dissipation due to shear flow induces the fourth-order temperature profile in the nanochannel. And the velocity slip and temperature jump will occur at the fluid-solid interface. The presence of roughness may introduce an extra viscous dissipation in shear flow, leading to a reduction of overall velocity and an increase in temperature in the nanochannel when compared with the smooth nanochannel. In addition, the degree of velocity slip and temperature jump at a rough liquid-solid interface is smaller than that at a smooth interface. In particular, the increase in fluid-solid interaction strength and reduction in wall stiffness will lead to a small velocity slip and temperature jump.
Spectra study of He-irradiation induced defects in 6H-SiC
Specimens of 6H-SiC were irradiated by 300keV He ions at temperatures of RT, 450, 600 and 750 ℃ with fluences ranging from 1×1015 to 1×1017 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 caused by irradiation are directly related to the fluences and temperatures. Amorphization of 6H-SiC irradiated at RT occurrs, which is reflected by the disappearance of the Raman peaks and the saturation of the relative Raman intensity(simultaneously a strong Si-Si peak appears). Recovery of defects may exist in high-temperature irradiation, when helium bubbles do not exist, so that irradiation-induced defects can be easily recovered during irradiation process at elevated temperatures; but when helium bubbles are present, they can inhibit defects to recover, as shown in the trend of slopes of curves representing the relative Raman intensity and the relative absorption coefficients. This paper mainly focuses on the effects of helium bubbles on defect accumulation and recovery under the condition of high temperature irradiation, and then the comparison with the results of 6H-SiC irradiated by Si ions at elevated temperatures.
Computer simulation of electric properties of metal-ferroelectric-substrate structured ferroelectric field effect transistor under ionizing radiation
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 total dose of 0.1 MGy changes slightly the source leakage current and capacitance of the FeFET, and the total dose of 1 MGy leads to a larger variation in these quantities. When the radiation dose rate is varied, the minimal changes in the drain-source current and capacitance are observed. These results suggest that FeFET has a relatively large radiation hardness.
DC and AC electrical properties of ZnSe under high pressure
Stick-slip transition of a water droplet vibrated on a superhydrophobic surface
Effect of strain on Li adsorption on silicene
Investigation into the reverse recovery voltage peak mechanism of freewheeling diode at a switching transition
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 PIN freewheeling diode is discussed thoroughly based on semiconductor physics and the essential structure of power diodes. The law of reverse recovery voltage peak variation with switching transition time is deduced by methods of stored charge analysis, which shows that the peak voltage is larger for shorter conduction time and decreases abruptly as the transient conduction time increases. Experiments are carried out using the two-level half-bridge inverter unit with insulated-gate bipolar transistors and PIN diodes. Results show that the reverse recovery voltage peak decreases with the increase of the transition time, following an exponential rule, and tends to be constant after the freewheeling current becomes stable and finally approaches a steady state as the steady forward conduction current vanishes, thus proving the correctness of the presented analysis. This paper shows the theoretical and application values in the optimization of the reverse recovery mechanism of power diodes and the reliability improvement of power converters.
Barrier-dependent tunneling magnetoresistance reversal effect in spin field effect transistors
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 strength. The conductance exhibites barrier-dependent “conductive switching effect” as the barrier strength increases. When the barrier strength gradually increases, parallel conductance exhibits a monotonicall decreasing trend, while the anti-parallel conductance fluctuates, and such a fluctuation leading to the tunneling magnetoresistance also exhibits oscillatory phenomenon with the variation of barrier strength . For a suitable thickness of quasi one-dimensional electron gas, the tunneling magnetoresistance value can produce positive and negative inversion, and the effect will shed light on the application of spin information storage electronic device.
Ferromagnetic resonance in spin valve structures with perpendicular anisotropy
Research on the emission process of doped PhOLED by transient EL and delay luminescence measurement
PL enhancement of MoS2 by Au nanoparticles
Research on the nonlinear conductivity characteristics of nano-SiC/silicone rubber composites
Anylasis and comparison of several methods for calculation of positron bulk lifetime in perfect crystals
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 experimental data is particularly necessary. In this paper, the superposed neutral atom model, the pseudo-potential model, and the full-potential model are used to deal with the positron local potential. While the positron wave function is solved self-consistently by the finite difference method, the positron-electron correlation potential and its enhancement factor are handled within the frame work of the local density approximation and the generalized gradient approximation. We have respectively calculated the positron bulk lifetime of three kinds of single crystal solid: the alpha iron of a body-centered cubic structure, the aluminum of a face-centered cubic structure, and the silicon of a double face-centered cubic structure. Calculation results agree well with the published experimental data. At the same time, the impact on positron bulk lifetime due to electron density grid point accuracy, positron-electron correlation potential and enhancement factor is analyzed carefully. Finally, we discuss the advantages and disadvantages of the three methods for calculating the positron bulk lifetime. In summary, an effective and reasonable calculation for the positron bulk lifetime should take into account the electron density, positron-electron correlation potential, and enhancement factor, etc. especially the enhancement factor.
Study on luminescent properties of Yb3+-doped phosphosilicate microsphere
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 centered at 476.1 nm is obtained in the Yb3+-doped phosphosilicate microsphere. And a suitable model may be applied to explain the reason for the 11.9 nm blue-shift in this process. Meanwhile, the single-mode laser (at 1058.26 nm) and multimode laser oscillations (from 1060.02 to 1126.08 nm) have also been obtained as the result of resonant oscillation in microsphere cavity. In addition, for the first time so far as we know a self-stimulated cascaded Raman laser is observed in the same phosphosilicate microsphere, which is generated by the down-conversion laser of Yb3+. When the pump power is 8.53 mW, a two-order cascade Raman laser is generated, which extends the laser wavelength to near 1300 nm.
Electroluminescence properties of vertical structure GaN based LED on silicon and copper submount at different temperatures and current densities
Fabrication and optical-electrical properties of VO2/AZO composite films
Mechanism of phase transition induced by high temperatures and its influences on the luminescence of Ca0.64WO4:Eu0.24 ceramics
Simulation study on the design of key technical parameters in marine environment sounding with fully polarimetric synthetic aperture radar based on ocean surface scattering model
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 for fully polarimetric SAR. We first calculate radar backscattering coefficient in different marine environments by using the fully polarimetric ocean surface scattering model, and accordingly determine the noise-equated backscattering coefficient of fully polarimetric SAR ocean sounding. Then the noise-equated backscattering coefficient is used as an input parameter in SAR equation, and the function relationship between radiometric resolution and signal to noise ratio is used as a constraint condition, we thus can carry out technical parameter design, such as for signal to noise ratio, radiometric resolution and system power aperture product. By simulation calculation of fully polarimetric ocean surface scattering, we find that the noise-equated backscattering coefficient of ocean sounding is designed to -35.0 dB, which can meet the needs of fully polarimetric SAR sounding in different marine environments. Studying the function relationship between radiometric resolution and signal to noise ratio, we find that the optimal signal to noise ratio of ocean sounding is 8.0 dB. Results of C-band airborne fully polarimetric SAR design show that the above method can make technical parameter of fully polarimetric SAR meet both the need for marine environment application and system design, because of taking into account the needs of marine environment sounding.
Analysis on relative transfer of entropy based on improved epileptic EEG
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, we may apply this method to study the normal EEG and epileptic EEG irreversibility, and the experimental results show that the EEG irreversibility of patients who suffer from epilepsy is significantly less than that of normal people. This shows that the relative transfer entropy can be used as aparameter to detect the irreversible degree of EEG for recognizing whether a patient is suffering from epilepsy or not, which may be a positive index for clinical diagnosis.
A Study of tandem structure organic solar cells composed of polymer and small molecular sub-cells
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%
Effects of comprehensive information of the nearest following vehicle on traffic flow instability
Dynamic interplay between epidemics and cascades:Epidemic outbreaks in uncorrelated networks
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 infectivity is fixed, the tolerance parameter α, in capturing the capacity of nodes, must be larger than a critical value to fulfill the criteria, and at equilibrium the fraction of nodes both uninfected and un-failed is the largest at this critical point. So the the presentation of the epidemic threshold criteria is of significance.
Hopf bifurcation and chaos in the solar-forced El Niño /Southern Oscillation recharge oscillator model
New infinite sequence solutions to equations of sine-Gordon type
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-Bäcklund transformation of the first kind of elliptic equation are obtained. Finally, new infinite sequence solutions to equations of sine-Gordon type are constructed by applying Bäcklund transformation and new solutions of the first kind of elliptic equation.
A corrected smoothed particle hydrodynamics approach to solve the non-isothermal non-Newtonian viscous fluid flow problems
Recognition technology for obtaining micro-motion characteristics of rotating rough targets
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. Comparison of the simulation results with those obtained under the experimental conditions confirms the validity of target time correlation length for cone targets. The angular velocity and line-of-sight angle for rotating cones are inversed by adopting particle group algorithm. Results show that this method is capable to identify the line-of-sight angle within 20°–90° and the angular velocity within 0.5–6 r/min for rotating cones, thus providing theoretical and experimental bases for recognition of micro-motion characteristics.
Stochastic resonance in a piecewise nonlinear system driven by colored correlated additive and multiplicative colored noises
Analysis on a class of double-wing chaotic system and its control via linear matrix inequality
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 simulation results. The Lyapunov exponent of the system with absolute value operation is larger than the original system, and the absolute value operation makes the wing of the original system doubled. Based on Takagi-Sugeno (T-S) fuzzy model and linear matrix inequality, a robust fuzzy controller is designed for the double-wing chaotic system being in asymptotical stability. Simulation results are provided to illustrate the effectiveness of the proposed scheme.
A novel image authentication and recovery algorithm based on dither and chaos
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 watermark invisible. Chaos technology is used to complete watermark embedding and encryption; and combined with the Chinese remainder theorem, the impact on the image quality can further be reduced. Experimental results show that the algorithm's watermark has high invisibility and robustness, and also can repair tampered images. So it has a high practical significance in the image authentication and recovery.
Optical system design of the coded aperture imaging spectrometer
Spin polarization and potential energy function of FeH2
Theoretical study on a novel molecular mirror with a surface plasmon polariton field
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 reflectivity of 55.89% when the incident laser is of a 10 ns pulse width and its intensity is I0=1.0 × 109 W/cm2; and the molecular reflectivity increases with increasing incident laser intensity.
Theoretical study on charging equation of dust plasmas in double Maxwellian distribution
Polarization smoothing design for improving the whole spatial frequency at focal spot
Diagnosis of high-Z plasma with soft X-ray laser probe
On the mechanism of earthquake
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 measurement–a fact that has been dubbed “the heat flow paradox”. For the intermediate-focus and deep-focus earthquakes, both occurring in the region of the mantle, there is not any reasonable explanation yet. The current article will discuss the physical mechanism of earthquake from a new perspective, starting from the fact that both the crust and the mantle are discrete collective systems of matters with slow dynamics, as well as from the basic principles of physics, especially some new concepts of condensed matter physics emerging in recent years. 1. Ströss distribution in earth's crust: Without taking the tectonic force into account, according to the rheological principle that “everything flows”, the vertical and the horizontal strösses must be in balance due to the effect of gravitational pressure over a long period of time, thus no differential ströss in the original crustal rocks is to be expected. The tectonic force is successively transferred and accumulated via stick-slip motions of rocky blocks to squeeze the fault gouges, and then applied to other rocky blocks. The superposition of such additional horizontal tectonic force and the original ströss gives rise to the real-time ströss in crustal rocks. The mechanical characteristics of fault gouge are different from rocks as it consists of granular matters. Thus the elastic modulus of the fault gouge is much lower than that of rocks, and will become larger with increasing pressure. This character of the fault gouge leads to a tectonic force that increases with depth in a nonlinear fashion. The distribution and variation of tectonic ströss in the crust are then specified. 2. Strength of crust rocks: The gravitational pressure can initiate the transition from elasticity to plasticity in crust rocks. A method for calculating the depth dependence of elasticity-plasticity transition is formulated, and demonstrated by exemplar systems. According to the actual situation analysis the behaviors of crust rocks fall into three typical zones: elastic, partially plastic and fully plastic. As the proportion of plastic parts in the partially plastic zone reaches about 10%, plastic interconnection may occur and the variation of shear strength of rocks is mainly characterized by plastic behavior. The equivalent coefficient of friction for the plastic slip is smaller by an order of magnitude, or even less, than that for brittle fracture, thus the shear strength of the rocks for plastic sliding is much less than that for brittle breaking. Moreover, with increasing depth a number of other factors can further reduce the shear yield strength of rocks. On the other hand, since earthquake is a large-scale damage, the rock breaking must occur along a weakest path. Therefore, the actual fracture strength of rocks in a shallow earthquake is assuredly lower than the normally observed average shear strength of rocks. The typical distributions of averaged strength and actual fracture strength in crustal rocks varying with depth are schematically illustrated in the paper. 3. Conditions and mechanisms of earthquake: An earthquake will lead to large volume expansion, and the expansion must break through the obstacles. The condition for an earthquake to occur may be as follows: the tectonic force should exceed the sum of (a) the fracture strength of rocks, (b) the friction force of fault boundary, and (c) the resistance from obstacles. Therefore, the shallow earthquake is characterized by plastic sliding of rocks that break through the obstacles. Accordingly, four possible patterns for shallow earthquakes are put forward. Deep-focus earthquakes are believed to result from a wide-range rock flow that breaks the jam. Both shallow earthquakes and deep-focus earthquakes are the slip or flow of rocks following a jamming-unjamming transition. 4. Energetics and precursors of earthquake: The energy of earthquake is the kinetic energy released from the jamming-unjamming transition. Calculation shows that the kinetic energy of seismic rock sliding is comparable to the total work for rocks' shear failure and for overcoming the frictional resistance. There will be no heat flow paradox. More importantly, some valuable seismic precursors are likely to be identified by observing the accumulation of additional tectonic forces, local geological changes, as well as the effect of rock state changes, etc.
A new method for the pulsar signals simulation
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. This method has a high time-resolution and rapid simulation for any random pulse signals. 23 Another one is for the optimization of statistical models that satisfy signals in non-homogeneous Poisson process. The is second method has an improved simulation speed at least 30 times higher than the common Poisson model, even achieves four orders of magnitude greater than that for low flow pulsars, and this method also achieves a nanosecond time resolution simulation.