bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic tissue characterization of skin tissue using doublet mechanics method
Authors: Ouyang Ling  , Liu Xiao-Zhou  , Liu Jie-Hui  , Gong Xiu-Fen  ,   Key Laboratory of Modern Acoustics of Ministry of Education, Institute of Acoustics, Nanjing University, Nanjing 210093, China
Published: December 2020

Doublet mechanics (DM) is applied to materials with dispersing property. The wave equation in multi-layered skin tissue is obtained through the method of DM in this article. By changing the Poisson ratio in melanoma skin tissue, the growth and spread of melanoma (Breslow thickness), the internode distance, the reflection coefficients of the longitudinal waves incident vertically in the multi-layered skin model are calculated. And the acoustic velocity and acoustic attenuation coefficient changing with tissue parameters are also calculated. The results show that we can synthesize the change of the number of the minimal reflection coefficient, acoustic velocity and attenuation coefficient to discriminate cancerous skin from normal skin within a certain frequency.
Measurements of granular pressure in silo：Janssen behaviour and deviation
Authors: Li Zhi-Feng  , Peng Zheng  , Jiang Yi-Min  ,   School of Physics and Electronics, Central South University, Changsha 410083, China
Published: December 2020

Variations of pressure along the vertical direction in a cylindrical silo are measured, of which the side wall is comprised of two separated up and down parts. The deviation of the measured results from the so-called Janssen model of silo stress is discussed. The measurements show that certain deviations from the model are always observed, no matter whether the slowly downward motion of silo bottom by “fully mobilized friction” as suggested by Vanel et al is carried on. Moreover without mobilizing the friction, the deviation may increase considerably if a tiny sink of the upper side-wall caused by weight of filled grains is present. The effect can be however eliminated by the friction mobilized. These indicate that distributions of grain weight at the bottom and lateral wall are complex and variant, and dependent on preparation manner and deformation of experiment setup. So stress boundary conditions need to be taken into account in the nonlinear elastic theory for analyzing static stress distribution of granular matter.
Wettability alteration simulation of modified hydrophobic solid surface by lattice Boltzmann method
Authors: Liu Qiu-Zu  , Kou Zi-Ming  , Jia Yue-Mei  , Wu Juan  , Han Zhen-Nan  , Zhang Qian-Qian  ,   College of Mechanical Engineering, Taiyuan University of Technology, Taiyuan 030024, China;,   Mine Fluid Control Engineering Laboratory of Shanxi Province, Taiyuan 030024, China;,   College of Mechanics, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

Based on the wettability alteration caused by the modified hydrophobic solid surface, the phenomenon of wettability alteration is simulated numerically in terms of linear and instantaneous modification by using the lattice Boltzmann method which can properly reflect the interaction of solid-liquid molecules, combined with the volume of fluid method to dispose the quality of interface layer. Results show that the wettability changes smoothly in the process of linear modification, the time needed for wetting significantly decreases, and the relationship between the contact angle and attractive coefficient of solid-liquid accord well with literature data. The more greatly the amplitude of instantaneous modification changes, the stronger the force of solid acting on droplet is, which is reflected by the obvious change of wettability. It is also found that the contact angle changes exponentially with time after instantaneous modification, which is in good agreement with the existing conclusions. Further investigation shows that the liquid oscillation exists in the whole spreading process. The vibration peak is associated with the modified amplitude of linear modification. And liquid film velocity increases suddenly at sometime after instantaneous modification, which is associated with entrained air.
Eigen model of randomness in species evolution
Authors: Qiao Li-Hua  , Zhao Tong-Jun  , Gu Jian-Zhong  , Zhuo Yi-Zhong  ,   Institute of Biophysics, School of Science, Hebei University of Technology, Tianjin 300401, China;,   Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413, China;,   School of Basic Medicine, Heibei Medical University, Shijiazhuang 050017, China
Published: December 2020

We modify the deterministic Eigen model of species evolution into a randomized model in order to render the Eigen model more realistic for the description of species evolution. In the framework of the Eigen model, we regard the locus mutation rate of a genetic sequence as a Gaussian distributed random variable. Thus the Eigen model turns into a random model. In this randomized model, we can see that when the fluctuation strength of the mutation rate is small, the error threshold of the quasispecies changes slightly and still serves as a phase transition point. However, when the fluctuation strength becomes large, the error threshold shifts from a phase transition point into a crossover region. Since the error threshold in the real species evolution is a crossover region, we should consider the upper limit of the crossover region when dealing with practical problems.
Noise assisted signal decomposition method based on complex empirical mode decomposition
Authors: Qu Jian-Ling  , Wang Xiao-Fei  , Gao Feng  , Zhou Yu-Ping  , Zhang Xiang-Yu  ,   Naval Aeronautical Engineering Institute Qingdao Branch, Qingdao 266041, China;,   Naval Aeronautical Engineering Institute, Yantai 264001, China
Published: December 2020

The ensemble empirical mode decomposition has been proposed in order to alleviate mode mixing in empirical mode decomposition, but the ensemble average in it can always result in new mode mixing, spectrum losing, and computational cost increasing, which can affect the analysis and extraction of signal physical characteristics. To tackle these problems, a noise-assisted signal decomposition method based on complex empirical mode decomposition is proposed, in which the mode mixing is reduced by taking the projection of intrinsic mode functions decomposed from white noise as basis functions for signal extrema extraction. While the problems result from ensemble average are reduced because the effects of noise projection are eliminated in the process of calculating the envelope barycenter. Simulation results show that our method has further reduced mode mixing, and speeded up the operation rate visibly and alleviated spectrum losing to a certain degree.
Quantum dissipation of the density matrix of mesoscopic RLC circuit
Authors: Fan Hong-Yi  , He Rui  ,   Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

For the first time, as far as we know, we use the approach of solving the amplitude-decaying master equation of density matrix to study the quantum dissipation of a mesoscopic RLC circuit, and thus find out the attenuation law of circuit energy. We then use the entangled state representation and the technique of integration within an ordered product of operators to explore this problem.
Effects of different Dzyaloshinskii-Moriya interaction and magnetic field on entanglement and fidelity intrinsic decoherence in a spin system
Authors: Qin Meng  , Li Yan-Biao  , Bai Zhong  , Wang Xiao  ,   College of Sciences, PLA University of Science and Technology, Nanjing 211101, China;,   Department of Physics, Nanjing University, Nanjing 210008, China
Published: December 2020

Using the Milburn equation, we have studied the properties of the entanglement and fidelity dynamics in a spin system with different Dzyaloshinskii-Moriya interaction and magnetic field in detail. Effects of different Dzyaloshinskii-Moriya interaction, different magnetic fields, and the initial states on the entanglement and fidelity are discussed. Results show that entanglement decoherence can be suppressed by inhomogeneous magnetic fields. Initial state affects greatly the entanglement, and a proper entanglement can be obtained by adjusting the directions of Dzyaloshinskii-Moriya interaction. For a particular initial state, an optimal fidelity is obtained by changing the direction of the Dzyaloshinskii-Moriya interaction. Moreover, no matter how homogeneous or inhomogeneous the magnetic fields are, they cannot enhance the fidelity. The dependence of entanglement and fidelity on the angle of initial state shows periodicity. Hence we can select an optimal initial state for a specific condition according to requirement.
Quantum discord in the system of two atoms trapped in weak coherent state cavities connected by an optical fiber
Authors: Lu Dao-Ming  , Qiu Chang-Dong  ,   College of Mechanic and Electronic Engineering, Wuyi University, Wuyishan 354300, China
Published: December 2020

Geometrical quantum discord (GQD) is an effective measure of quantum correlation in quantum systems. We study GQD dynamics in an atom-cavity-fiber system. GQD between atoms and that between cavities are investigated. The influences of coupling constant between cavity and fiber and the intensity of the cavity field on GQD are discussed. Results show that GQD between atoms and that between cavities all display periodical evolutions, and their evolution frequencies increase with increasing coupling constant between cavity and fiber. On the other hand, the GQD between atoms and that between cavities are all strengthened with increasing intensity of the cavity field.
Klein tunneling in spin-orbit coupled Bose-Einstein condensate scattered by cusp barrier
Authors: Li Zhi  , Cao Hui  ,   Department of physics, Beijing Institute of technology, Beijing 100081, China;,   National Laboratory of Science and Technology on Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

The scattering process when spin-orbit coupled Bose-Einstein condensate gets through cusp barrier is numerically simulated by adopting time-split spectrum method; the Klein tunneling phenomena exist in the scattering process. The regions of Klein block and Klein tunneling will appear at higher barrier height as compared to the scattering process on getting through Gaussian barrier. In the Klein tunneling region, the transmission coefficient oscillates with the barrier height, and the oscillation amplitude decreases with increasing barrier height. Besides, the effect of non-linear atomic interaction has been discussed for different barrier heights as well.
Differential invariants for CDG equation and coupled KDV-MKDV equations
Authors: Ding Qi  , Hao Ai-Jing  ,   School of Mathematical Sciences.Dalian University of Technology, Dalian 116024, China
Published: December 2020

In this paper, the differential invariants of Lie symmetry groups of the CDG equation and the coupled KdV-MKdV equations are obtained. Their syzygies and recurrence relations are classified, which are based on the algorithms of equivariant moving frames.
A car-following model with considering control signals from front and rear
Authors: Ge Hong-Xia  , Cui Yu  , Cheng Rong-Jun  ,   Faculty of Maritime and Transportation, Ningbo University, Ningbo 315211, China;,   Faculty of Science, Ningbo University, Ningbo 315211, China;,   Department of Fundamental Course, Ningbo Institute of Technology, Zhejiang University, Ningbo 315200, China
Published: December 2020

A new control method to suppress traffic jams is proposed by considering headway of the front and rear. With the control signals or not the stability conditions are derived. It is shown that the vehicle speed fluctuation by the simulations disappears when the feedback control signals are introduced. Therefore, serious congestion will not occur in the system. Illustration shows that the feedback control signal can effectively suppress and alleviate the traffic congestion.
A vehicle magnetic noise compensation method for the tetrahedron magnetic gradiometer
Authors: Yu Zhen-Tao  , Lü Jun-Wei  , Bi Bo  , Zhou Jing  ,   Department of Control Engineering, Naval Aeronautical and Astronautical University, Yantai 264001, China;,   Naval Unit 92474, Sanya 572018, China
Published: December 2020

The magnetic noise of a vehicle has a strong impact on the magnetic gradiometer, so a vehicle magnetic noise compensation method is proposed. Based on the production mechanism of the vehicle magnetic noise, a mathematic model for vehicle magnetic noise on the tetrahedron magnetic gradiometer is proposed, in which the difference algorithm of the magnetic gradiometer is used to fuse the magnetic noise of each vector magnetometer. In terms of this mathematic model, we propose the noise compensation algorithm and the compensation coefficients recognition method by using the mathematic relations of the 9 components of the magnetic gradient tensor. Simulation results show that the proposed method can efficiently compensate 95.9% vehicle magnetic noise on the magnetic gradiometer. This method can compensate vehicle magnetic noise on the magnetic gradiometer output directly by the compensation coefficients, and realize the holistic noise compensation of the magnetic gradiometer theoretically.
The polarization-difference interference imaging spectrometer-I. concept, principle, and operation
Authors: Mu Ting-Kui  , Zhang Chun-Min  , Li Qi-Wei  , Wei Yu-Tong  , Chen Qing-Ying  , Jia Chen-Ling  ,   Institute of Space Optics, Ministry of Education Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

A static, compact, high optical throughput polarization-difference interference imaging spectrometer is presented. It is based on the combination of the angular shear of Wollaston prism and the lateral shear of Savart polariscope. Its remarkable characteristic is the simultaneous acquisition of the interferograms and two-dimensional images for the orthogonal polarization components of targets. Polarization spectral images of the components can be reconstructed using the algorithms of Fourier transformation and image fusion. A summation of the orthogonal polarization spectral images is equivalent to that of the conventional intensity spectral image. The difference is that the orthogonal polarization spectral images is named as polarization-difference spectral image. A higher contrast of the polarization-difference spectral image can not only provide more detailed texture information for the targets, but also can derive the size, concentration, and refractive index of elastic-scattered particles. The principle of polarization-difference interference imaging spectrometer is demonstrated in this paper. Expressions for interference intensities and theoretical simulation are presented. The mode for acquiring data is described. Approximate paraxial conditions of Fourier imaging lens for the formation of straight fringes are analyzed by using the Young's interference mode; and the influence factors for the visibility of fringes are analyzed. For the realization of a more compact system, the relationship between the collimating lens and imaging lens is analyzed in terms of optical field diffraction theory. The feasibility of the system is demonstrated by numerical simulation. This research can provide a novel development strategy for imaging spectropolarimeter.
Diode laser cavity ring-down spectroscopy for atmospheric NO3 radical measurement
Authors: Hu Ren-Zhi  , Wang Dan  , Xie Pin-Hua  , Ling Liu-Yi  , Qin Min  , Li Chuan-Xin  , Liu Jian-Guo  ,   Anhui Institute of Optics and Fine Mechanics, Key Laboratory of Environmental Optics and Technology, Chinese Academy of Sciences, Hefei 230031, China;,   School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China, Hefei 230026, China;,   Institute of Electric and Information Technology, Anhui University of Science and Technology, Huainan 232001, China
Published: December 2020

This article presents an external modulation diode laser (with wavelength 661.85 nm and line width 0.3 nm) cavity ring-down spectrometer for measurement of NO3 radical in the atmosphere. The output spectrum of the diode laser is optimized by changing the external modulation signal; the effective cross-section of the instrument is a convolution of the measured cross-section and the laser spectrum. Interference of other gases (O3, NO2, and water vapor)in NO3 radical detection has also been investigated. Considering the loss from the PFA tube wall collision and the membrane filtration, NO3 radical inlet transmission efficiencies of the system is about 70% through the preliminary quantitative analysis. When the time resolution is 7 s, the laboratory detection limit of the system is 2.0 pptv. This instrument was deployed in the night atmosphere to measure the NO3 radical. NO3 concentration varied from 17.9 to 51.7 pptv with an average level of 36.3 pptv. A typical detection sensitivity in the night atmosphere is 3.5 pptv. Because of the uncertainty in the inlet transmission efficiencies and other factors, the total uncertainty of the measured NO3 radicals is about 8%(1 ). Experimental results show that the diode laser cavity ring-down spectroscopy can achieve high sensitivity in insitu detection of NO3 radicals in the atmosphere.
An analytical model for skylight polarization pattern with multiple scattering
Authors: Wu Liang-Hai  , Zhang Jun  , Fan Zhi-Guo  , Gao Jun  ,   School of Computer and Information, Hefei University of Technology, Hefei 230009, China
Published: December 2020

To solve the issues in the modeling of skylight polarization, we build a new analytical model of skylight polarization patterns, which is based on the classic Rayleigh scattering and takes into consideration the multiple scattering properties of atmospheric particles, especially the aerosol. In this paper, we first build the model by the combination of single Rayleigh scattering and classic Perez sky models. Then we analyze the influence of secondary scattering by solving scattering phase function of different particle sizes and components of aerosol in OPAC data. Finally, the integral function for secondary scattering is simplified with the preferences of scattering phase function in forward direction. Compared with the Rayleigh model, our model can depict the existence of neutral points in the sky. The comparisons between our model and the measured results of clear sky further validate that the model not only exhibits characters of measured skylight polarization, such as the variation tendency, neutral points and the pattern symmetry, but also consists with the acquired values than the single scattering model; for example, the degree of similarity of polarization can be up to 75%.
Effect of oxygen pressure on structure and optical band gap of gallium oxide thin films prepared by sputtering
Authors: Ma Hai-Lin  , Su Qing  ,   National Engineering Research Center of Green Coating Technology and Equipment, Lanzhou Jiaotong University, Lanzhou 730070, China;,   Department of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China
Published: December 2020

Gallium oxide (Ga2O3) thin films are deposited on silicon and quartz glass substrates by reactive DC magnetron sputtering under different oxygen pressure η (η =O2/[Ar+O2]), and the effect of oxygen pressure on the structure and optical band gap (Eg) is investigated. X-ray diffraction (XRD) and Raman scattering reveal that the products are beta-gallium oxide after heat treatment at 900 ℃, and that the grain size and optical band gap of gallium oxide are increased, the band gap Eg varies from 4.68 to 4.85 eV when tested by a room-temperature ultraviolet-visible (UV-VIS) spectrophotometer, and the (Eg) has also been calculated by using Tauc formula while the oxygen pressure η gradually increases.
Research of thermal expansion coefficient of topological insulator Bi2Te3
Authors: Li Ping-Yuan  , Chen Yong-Liang  , Zhou Da-Jin  , Chen Peng  , Zhang Yong  , Deng Shui-Quan  , Cui Ya-Jing  , Zhao Yong  ,   Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Superconductivity and New Energy R & D Center, Southwest Jiaotong University, Chengdu 610031, China;,   School of Materials Science and Engineering, University of New South Wales, Sydney 2052 NSW, Australia
Published: December 2020

Topological insulator Bi2Te3 crystals were grown and their thermal expansion was studied with X-ray diffraction at various temperatures. It was shown that the linear thermal expansion coefficients, || and , which reflect, respectively, the thermal expansion within and out-off a-a plane of the Bi2Te3 crystal, exhibit quite different temperature dependent features. The obeys the Debye law in a relatively wide temperature range, while || deviates qualitatively from the Debye law at 100 K. Possible mechanisms behind the observed phenomena were explained using the crystal structure and the bonding features between the atoms in Bi2Te3 crystal.
Calculation of absorption spectrum of silver-gold bimetallic nanoparticles
Authors: Li Si-Qi  , Qi Wei-Hong  ,   School of Materials Science and Engineering, Central South University, Changsha 410083, China;,   State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;,   Key Laboratory of Non-ferrous Materials Science and Engineering, Ministry of Education, Changsha 410083, China
Published: December 2020

Optical properties of nanoparticles are related to their surface plasmon resonance. In this work, we use Mie theory to compute the extinction, absorption, and scattering properties of noble metal nanoparticles. The calculated results agree well with the experimental values. With increasing particle size, particle dipole absorption peak will be red-shifted; and the peak position and the size of the nanoparticles have a linear relationship. It is found that the ratio of core to shell size determines the absorption properties of spherical Au/Ag core/shell nanoparticles. When the Au shell is thin, the optical properties vary with the adjustable shell. When the Au shell is thick, its optical properties are similar to the pure Au nanoparticle. Through the calculation and analysis we made, the Mie theory can be generalized to nanocavity structures when the shell thickness reaches a certain value. Furthermore, it is found that the absorption peaks of alloy nanoparticles have a linear relationship with the alloy composition.
Study of Cu45Zr55-xAlx (x=3, 7, 12) bulk metallic glasses by ab-initio molecular dynamics simulation
Authors: Wei Hong-Qing  , Long Zhi-Lin  , Xu Fu  , Zhang Ping  , Tang Yi  ,   Civil Engineering and Mechanics College, Xiangtan University, Xiangtan 411105, China;,   Department of Physics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Local structural changes from liquid to amorphous state in three Cu45Zr55-xAlx (x=3, 7, 12) ternary metallic glasses have been investigated by the ab initio molecular dynamics simulation. The atomic structure of the glasses has been analyzed by means of bond-type index method in Honeycutt-Andersen and Voronoi tessellation method. Al-centered icosahedral clusters are identified as the basic local structural units and these Al-centered stable clusters play a key role in the structural heterogeneity and glass-forming ability of the Cu-Zr-Al bulk metallic glasses.
Study on a novel dual-band metamaterial absorber by using fractal Koch curves
Authors: Ma Yan-Bing  , Zhang Huai-Wu  , Li Yuan-Xun  ,   State Key Laboratory of Electronic Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China;,   Institute of Electronic and Information Engineering, University of Electronic Science and Technology of China, Dongguan 523808, China
Published: December 2020

In this paper we present a novel dual-band metamaterial absorber (MA), which is composed of a periodically arranged 2nd order Koch curve array and a metal ground separated by a dielectric spacer. By employing the fractal characteristic of space-filling, more compact unit cell with a size reduction of 17.5% has been achieved as compared with the conventional square-shaped MA. The dual-band operation is not originated from the hybrid or stacked methods as reported before, but from the two distinct resonance modes of the 2nd order Koch curves induced by the incident electromagnetic wave, and can be realized within a single unit cell. Due to its rotationally symmetric pattern, the absorptivity of the above presented MA is insensitive to the polarization of the incident waves and can perform well in a wide range of incident angles. The effective medium theory has been employed to investigate the underlying physical mechanism of the fractal MA, and good agreements between simulation and experimental results have been achieved.
Influence and mechanism of H2 in the epitaxial growth of ZnO using metal-organic chemical vapor deposition method
Authors: Zhu Shun-Ming  , Gu Ran  , Huang Shi-Min  , Yao Zheng-Grong  , Zhang Yang  , Chen Bin  , Mao Hao-Yuan  , Gu Shu-Lin  , Ye Jian-Dong  , Zheng You-Dou  ,   School of Electronic Science & Engineering and Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210046, China
Published: December 2020

This paper focuses on the influence and mechanism of H2 in the eptaxial growth of ZnO using metal-organic chemical vapor deposition method. Studies show that hydrogen has a significant influence on the structure and properties of ZnO films. Hydrogen produces a mainly negative impact on crystal quality, surface structure, and optical properties of ZnO films when tert-butanol (t-BuOH) is used as the O sources. Raman scattering shows that hydrogen has a very good effect on the suppression of carbon contamination. When nitrous oxide is used as the O sources, the surface of ZnO films becomes smooth, and the crystal quality and optical property are improved. It is shown that hydrogen can play a positive role when N2O is used as O source. In this paper we highly estimate hydrogen's ability of reducing the surface growth energy, improving the migration of the surface atoms and the corrosion effect on the surface. Studies show that the optimization of hydrogen has a significant effect during the epitaxial growth of ZnO using the MOCVD method.
Imaging algorithm for missile-borne SAR using the fractional Fourier transform
Authors: Chen Yong  , Zhao Hui-Chang  , Chen Si  , Zhang Shu-Ning  ,   School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;,   School of Physics and Electronic Electrical Engineering, Huaiyin Normal University, Huaian 223300, China
Published: December 2020

Since the Doppler parameters vary according to the slant distance, the resolution is lower when using an imaging algorithm of traditional pulse compression in processing raw echo data of the missile-borne synthetic aperture radar (SAR). Moreover, an algorithm is proposed to solve these problems, which is based on the fractional Fourier transform (FrFT) for missile-borne SAR imaging. Firstly, an echo signal model is built for the terminal guidance stage of the missile-borne SAR. Secondly, the chirp rate of the echo signal is measured through the local optimum processing and obtains the optimum angles for the FrFT, and then the entire SAR image can be obtained by using FrFT with the optimum azimuth angles and operating range. Finally, the performances of the algorithms are assessed using simulated and real Radarsat-1 data sets. Results confirm that the FrFT-based missile-borne SAR processing methods can provide enhanced resolution that yields both lower-side lobes effects and improved target detection. The method introduced in this paper has important theoretical significance in detection and recognition of military targets and for precision guidance.
Structure design and frequency characteristics of SOI SiGe HBT
Authors: Song Jian-Jun  , Yang Chao  , Zhu He  , Zhang He-Ming  , Xuan Rong-Xi  , Hu Hui-Yong  , Shu Bin  ,   Key Lab of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

Lately much interest is focused on SOI SiGe HBT in high-speed low-power BiCMOS applications. The frequency characteristics of the core device, SOI SiGe HBT in BiCMOS, determine its operating speed. So, this paper studies the frequency characteristics of SOI SiGe HBT on the basis of our proposed device structure, and analyzes the frequency characteristics in terms of the collector capacitance model we established. It is found that: 1) The characteristic frequency of SOI SiGe HBT increases with increasing doping concentration in the collector; 2) variations between the characteristic frequency and collector current of SOI SiGe HBT are consistent with those of the traditional SiGe HBT; 3) under the normal operating conditions, the maximum oscillation frequency of SOI SiGe HBT (a collector region with 3×1017 cm-3 dopant) is greater than 140 GHz, and the characteristic frequency is greater than 60 GHz. Compared with the traditional SiGe HBT, the maximum value of the characteristic frequency is increased by 18.84%. The conclusions above can provide important references to the design and research of SOI SiGe HBT and BiCMOS.
double-porosity medium
Authors: Liang Bao-Jun  ,   BGP OFFSHORE, Tianjin 300280, China
Published: December 2020

A new algorithm for P-wave reverse time migration (RTM) in a fracture-induced TTI double-porosity medium is proposed in this paper, by combining RTM with the method of P-and S-wave field separation in high-order staggered grid finitedifference scheme. Simulation results show that for the fracture-induced TTI double-porosity medium the conventional migration with a background velocity without fractures would cause the imaging position to be under the true interface. To study the influence of fracture parameters, the phase velocity formulae are derived from Christoffel equations, and the effects of fracture angles and density are analyzed. In the 2D case, the imaging position gets closer to the real interface along with increasing fracture dip angles, while a bigger fracture density can cause much more deviation.
Plateau surface energy balance components and interannual variability in response to climate fluctuations
Authors: Xia Lu  , Zhang Qiang  ,   College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;,   Institute of Arid Meteorology, China Meteorological Administration, Key Laboratory of Arid Climatic Change and Disaster Reduction of CMA, Lanzhou 730020, China;,   Gansu Provincial Meteorological Bureau, Lanzhou 730020, China
Published: December 2020

In this paper land surface observations and meteorological data are received from Semiarid Climate and Environment Observatory of Lanzhou University (SACOL) and Yuzhong Station from 2006 to 2012. The climate changes of temperature and precipitation in the seven years are analyzed in Yuzhong, and the inter-annual variation of the components of surface energy balance in land surface is discussed. The Bowen ratio and the energy inter-annual fluctuation imbalance are also studied. Explorations of surface energy balance components as well as the land surface process parameters feedback on the temperature, precipitation interannual fluctuations on the Loess Plateau are carried out. Results show that the surface energy components are responsible to the fluctuations of the climate background. But the sensitivity varies; the net radiation and air temperature are more relevant to each other, and the sensible heat and latent heat have a better correlation with precipitation. Discussions are divided into summer and winter half year results, in which the winter half year balance component surface has a better correlation with climatic fluctuations. In the winter half year, each component has a high degree of correlation with temperature, showing that in this area each component of the land surface energy balance component corresponding to the change of temperature is more remarkable The rising trend of Bowen ratio is corresponding to the reduction of precipitation, indicating that the drought is deepened The change of the energy closure shows that the deepening of energy balance unclosure is due to the change of the climate background.
Simulation of small space debris impact inducing discharge using laser-induced plasma method
Authors: Li Hong-Wei  , Han Jian-Wei  , Cai Ming-Hui  , Wu Feng-Shi  , Zhang Zhen-Long  ,   Center for Space Science and Applied Research, CAS, Beijing 100190, China
Published: December 2020

Small space debris impact that induces discharge can trigger disturbance of a spacecraft, which is a big threat to the safety of it. Research on this effect has already been carried out, but due to the limit of the facilities the research is also restricted. Since the primary cause of small space debris impact that induces discharge is to induce the plasma, similar to the laser inducing the plasma, this paper tries to simulate the space debris impact inducing discharge using a laser-induced discharge method. The analysis and experimental results are given, and they prove that this method is reliable.
A new chaotic attractor graphics drawing method based on the curved iteration
Authors: Yu Wan-Bo  , Zhao Bin  ,   College of Information Engineering, Dalian University, Dalian 116622, China
Published: December 2020

In this paper, we continue to study the chaotic characteristics of two curved surface mapping which forms a function in a unit area, and find that when one of the two curved surfaces is a standard curved surface and subjected to strong oscillation, and the other is randomly generate, the occurrence of chaos is more prone. Many different chaotic attractors are drawn by this method, adjusting the random surface to become subjective, the probability of chaotic attractor appearing can reach a half or more, which means that when certain conditions are meet, chaos is extremely common. Through calculating Lyapunov exponent and drawing the bifurcation diagram to analyze characteristics of chaos of the function, according to the bifurcation diagram of parameters and the Lyapunov exponent curve to look for more chaotic mapping function, a lot of chaotic attractors can be obtained. Finally a three-dimensional trigonometric function and two randomly generated three-dimensional polynomial functions are iterated, and many fancy three-dimensional attractors are obtained.
Coherence resonance of nonlinear piezoelectric energy harvester under broadband random excitation
Authors: Li Hai-Tao  , Qin Wei-Yang  ,   Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

With the development of micro electromechanical systems, many researchers focus their attention on nonlinear energy harvesting device. The stochastic equivalent linearization method is used to analyze an energy harvesting system under ambient noise. First, according to the bistability of beam axially loaded, a model of bistable nonlinear vibration energy harvester under the stochastic condition is proposed. A close-form approximation expression for the ensemble average of harvested power is derived and the numerical simulation of the system shows stochastic resonance. The results show that it is possible to optimally design system such that the harvest power is maximized for a given density or variance of random excitation.
An exact discrete-time model and the bifurcation performance of single phase grid-connected inverter with L-filter considering dead-time nonlinearity
Authors: Xie Rui-Liang  , Hao Xiang  , Wang Yue  , Yang Xu  , Huang Lang  , Wang Chao  , Yang Yue-Hong  ,   State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Grid-connected inverter system is recognized as a time-varying nonlinear system, and it has complex nonlinear behaviors in practice. However, the introduction of dead-time nonlinearity can make the nonlinear behaviors of the system more complex and harder to predict. In this paper, the proportional control single-phase grid-connected inverter with L-filter considering dead-time nonlinearity is investigated. The observation of current waveforms under fixed controller parameter and different dead-time parameters shows that the bifurcation phenomenon occurs with the increase of dead-time. According to the features of dead-time nonlinearity and the zero current clamping phenomenon caused by dead-time, an exact and complete discrete-time model is established by comprehensively considering the system from various aspects. And the theoretical analysis of bifurcation behaviors of system is carried out based on the proposed model. Moreover, the stability judgment has engineering significance. However, with the consideration of dead-time nonlinearity, analytical methods are difficult to use and the graphic methods do not have satisfactory accuracy. Therefore, a stability criterion based on equivalent duty ratio is proposed in this paper, which can accurately judge the stability boundary and provide reliable references for the parameter design of controller and dead-time.
An equivalent approach to modeling aperture array with considering size effect of apertures
Authors: Ren Dan  , Du Ping-An  , Nie Bao-Lin  , Cao Zhong  , Liu Wen-Kui  ,   School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
Published: December 2020

In order to reduce the number of numerical meshes and simplify aperture array modeling, an equivalent method of modeling aperture array in which the size effect of apertures is taken into account, is presented in the paper. In this method, the aperture array is replaced by a single aperture which has the same area as the original aperture array, then the scaling factor of the aperture is obtained according to the number of apertures. The empirical relations between the number of apertures and scaling factor are proposed based on theoretical derivation and curve fitting method respectively. The comparison with the commercial software HFSS indicates that the formula based on curve fitting method has a higher accuracy. The applicability of the method is verified by varying the interference source, monitoring point, total area and position of aperture array, shape of aperture and cavity size. As shown by the numerical results, the equivalent modeling approach can significantly reduce the number of meshes, which can serve as a simplified approach to numerical simulation of shielding characteristics of complex cavity.
Spectroscopic properties of BCl (X1Σ+, a3Π, A1Π) molecule
Authors: Liu Hui  , Xing Wei  , Shi De-Heng  , Sun Jin-Feng  , Zhu Zun-Lüe  ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China;,   College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The X1Σ+, a3Π and A1Π states of BCl molecule are studied using the highly accurate valence internally contracted multireference configuration interaction approach including the Davidson modification. The Dunning's correlation-consistent basis sets, aug-cc-pV6Z and aug-cc-pV5Z, are used in the study. To obtain more reliable results, the potential energy curves (PECs) of three electronic states are extrapolated to the complete basis set limit by the two-point total-energy extrapolation scheme. The effects of the core-valence correlation and relativistic corrections on the PECs are taken into account. By fitting these PECs, the spectroscopic parameters (Te, Re, ωe, ωexe, Be, αe and De) of the X1Σ+, a3Π and A1Π states of BCl are determined. These parameter values coincide with the experimental results. In addition, the whole vibrational states for X1Σ+, a3Π and A1Π states at J =0 (J is the rotational quantum number) are determined by numerically solving the radical Schrödinger equation of the nuclear motion of diatomic molecules. For each vibrational state, the vibrational level and inertial rotation constants are obtained, which are in excellent accordance with the experimental results. With the potential energy curves obtained at MRCI+Q/56+CV+DK level and the MRCI wave functions, the Franck-Condon factors, radiative lifetime of transition from a3Π and A1Π to the ground state are computed.
Full circuit model for coupling pulsed power driver with Z-pinch load
Authors: Xue Chuang  , Ding Ning  , Sun Shun-Kai  , Xiao De-Long  , Zhang Yang  , Huang Jun  , Ning Cheng  , Shu Xiao-Jian  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

In order to study the transportation and conversion of the electromagnetic energy from the pulsed power driver to Z-pinch load, a circuit model for the driver is analyzed, and coupled with magneto-hydrodynamics model for the load plasma. Our simulation results are compared with those obtained from circuit software and experimental results based on the “Qiangguang-I” facility. The simulated voltage and current waveform coincide well with the experimental results. Results show that the pulse width decreases and the peak increases as the pulse transmits from the storage capacitors to the pulse transmission line. When the storage capacitors are initially charged at 35 kV, the peak of electric powers at the transfer capacitor, the pulse forming line and the pulse output line are 0.23, 0.80 and 1.46 TW, respectively, and their rise-times (10%-90%) are 550, 160 and 45 ns, respectively. The load current is 1.5 MA and the X-ray radiation power is 0.58 TW.
Deduction of temperature and density spatial profile for implosion core by multi-objective optimization
Authors: Dong Jian-Jun  , Deng Bo  , Cao Zhu-Rong  , Jiang Shao-En  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The spatial profiles of implosion core temperature and density are very important to check the theoretical simulation codes and understand the implosion physics in depth. A method is presented that the temperature and density profiles are evaluated by multi-objective optimization, where the normalized intensity profile is calculated from implosion core X-ray images. Two models, i.e., the model with considering absorption and the model without considering absorption, are studied. The results indicate that the temperature profile from the model without considering absorption is about twice that from the model with considering absorption. The density profiles evaluated by the two models are almost the same in the fuel zone, but the density from the model without considering absorption is more than ten times smaller than that from the model with considering absorption in the ablator zone.
Experimental studies of low-convergence-ratio implosions
Authors: Pu Yu-Dong  , Kang Dong-Guo  , Huang Tian-Xuan  , Gao Yao-Ming  , Chen Jia-Bin  , Tang Qi  , Song Zi-Feng  , Peng Xiao-Shi  , Chen Bo-Lun  , Jiang Wei  , Yu Bo  , Yan Ji  , Jiang Shao-En  , Liu Shen-Ye  , Yang Jia-Min  , Ding Yong-Kun  ,   Research Center of Laser Fusion, Mianyang 621900, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

Indirectly driven low-convergence-ratio implosion experiments are conducted on SGIII prototype laser facility. Neutron yield, ion temperature and bangtime, and also their variation laws with the increase of ablator thickness are measured. These results are analyzed quantitatively and qualitatively, and the difference between the measurements and the calculations is discussed. The degradation of neutron yield is attributed to the hydrodynamic instabilities and implosion asymmetries.
The characteristics of excited states for HF+ ion under spin-orbit coupling
Authors: Li Gui-Xia  , Jiang Yong-Chao  , Ling Cui-Cui  , Ma Hong-Zhang  , Li Peng  ,   Science and Information Science College, Qingdao Agriculture University, Qingdao 266109, China;,   College of Science, China University of Petroleum, Qingdao 266580, China
Published: December 2020

The characteristics of ground state X2Πi and the first excited state A2Σ+ of HF+ under spin-orbit coupling are studied by using the multi-configuration quasi-degenerate perturbation theory. The vertical excited energy is v[2Π1/2 (v = 0)→ X2Π3/2(v = 0)] = 285.176 cm-1, and the potential energy curves of the splitting electronic states X2Π3/2, 2Π1/2 of X2Πi are obtained. The analytical potential functions of these states are derived by employing the Murrell- Sorbie function (M-S) and the least-square fitting method, and then the spectroscopic constants for X2Π3/2, 2Π1/2 and A2Σ+ are derived from the M-S function. All the spectroscopic data and the analytical potential functions for states X2Π3/2 and 2Π1/2 are given for the first time in our calculation.
Effect of the trench shape on the electrical properties of silicon based trench barrier schottky diode
Authors: Zhai Dong-Yuan  , Zhao Yi  , Cai Yin-Fei  , Shi Yi  , Zheng You-Dou  ,   School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China;,   Hangzhou QP Chip Technology Co. Ltd, Hangzhou 311121, China
Published: December 2020

With the globally enhancing demand for the energy saving and environmental protection of electronic products, the requirement for Schottky diode which is widely used in electronic products becomes higher and higher. The trench metal-oxide-semiconductor barrier Schottky (TMBS) diode is more and more favored because of its excellent performance. The shape of the trench plays an important role in determining the electrical properties of the Schottky diode. However, there is no intensive study on this point. In this study, we propose two novel trench structures, i. e., filleted corner trench and ladder trench. By performing the simulation with Medici, it is found that compared with the traditional trench TMBS diode, the filleted corner trench TMBS diode has a breakdown voltage with 15.8% increase under the conditions of the same leakage current and the forward turn-on voltage. Also, the ladder trench TMBS diode can reduce the leakage current by 35%, while have a breakdown voltage not smaller than the right angle trench TMBS and a forward turn-on voltage only a little bit higher than the right angle trench TMBS.
Curie temperature mechanism in La(Fe, Si)13 compound
Authors: Wang Fang  , Wang Jin-Zhi  , Feng Tang-Fu  , Sun Ren-Bing  , Yu Sheng  ,   Ningbo University of Technology, Ningbo 315211, China
Published: December 2020

In NaZn13 type La(Fe,Si)13 compound, the phase transition nature varies from the first order to the second order, the cell volume contracts, the saturated magnetization decreases and the Curie temperature increases with increasing Si content. In this paper, the relation between the Curie temperature and the cell volume is investigated systematically by introducing the interstitial carbon atoms, which is an efficient method to control the cell volume and the Curie temperature. It is found that the relation between the Curie temperature and the cell volume is consistent with the Jaccarino-Walker model, in which only 5% or less 3d electrons are considered as the itinerant electrons and the others are regarded as the localized ones. With the polarized itinerant electrons used as a medium, the interaction between the 3d localized electrons is similar to Ruderman-Kittel-Kasuya-Yosida interaction, whose sign and magnitude oscillate periodically with distance. The number of the itinerant electrons of the La (Fe,Si)13 increases with the increase of Si content. The Curie temperature is dependent on both the cell volume and the number of itinerant electrons.