bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarization characteristics of coherent partially Airy beams propagating in atmospheric turbulence
Authors: Yang Ai-Lin  , Lin Qiang  ,   Institute of Optics, Department of Physics, Zhejiang University, Hangzhou 310027, China;,   College of Science, Zhejiang University of Technology, Hangzhou 310023, China
Published: December 2020

The degree of polarization of partially coherent Airy beams propagating through atmospheric turbulence is studied in this paper. Polarization fidelity of the beams is used to judge the propagation effect. It is shown that the degree of polarization of partially coherent Airy beams propagating through atmospheric turbulence tends to its initial value after it has propagated over a sufficient distance, and in free space the degree of polarization retains a certain value. The polarization distribution alone the symmetry axis is an Airy function if the propagation distance is not so long and evolves into a Gaussian-like profile when propagating at sufficient long distance in atmospheric turbulence. The polarization fidelity of the beams with larger waist width ω0 and larger coherence length σ0 is better. There is an exponential truncation factor which badly degrades the polarization fidelity. The results obtained in this paper are very useful for communication of Airy beams.
Effects of incomplete modal sampling on the underwater target detetion and performance improvement method
Authors: Li Ming-Yang  , Sun Chao  , Shao Xuan  ,   School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The generalized likelihood ratio test (GLRT) detector and its theoretical detection performance for an underwater narrowband source with an unknown position are both given in this paper. Via the eigenvalue decomposition of the mode correlation matrix (MCM), the GLRT detector is decomposed into different spectrum components corresponding to the eigenvalues of the MCM. Based on the derived statistical property of each component, the spatial processing gain of each spectrum component with respect to the input signal is obtained, which is proportional to the corresponding eigenvalue. As there are several eigenvalues of the MCM approaching to zero when the modal information is incompletely sampled, the components corresponding to these small eigenvalues contribute much less spatial processing gain to the input signal than other components. By discarding the components corresponding to these small eigenvalues, the effective spectrum detector (ESD) is proposed, of which the target signal component in the output is approximately identical to that of the GLRT detector, and the noise in the ESD output is much less. Therefore, a much more robust detection performance is obtained by ESD than by the GLRT detector. Numerical simulations in a typical shallow water environment demonstrate that 1) the theoretical analyses, derivations and the effectiveness of the proposed ESD are verified; 2) the more incomplete the modal information sampling is, the more significant performance improvement of ESD over the GLRT detector can be acquired; 3) the numerical stability of the ESD is better than that of the GLRT detector.
Influence of laser-induced plasma on stimulated Raman scatting of OH stretching vibrational from water molecules
Authors: Wang Sheng-Han  , Li Zhan-Long  , Sun Cheng-Lin  , Li Zuo-Wei  , Men Zhi-Wei  ,   College of Physics, Jilin University, Changchun 130012, China
Published: December 2020

532 nm pulse beam is used to induce the stimulated Raman scatting of water molecules. Different Stocks and anti-Stocks characteristic peaks of OH stretching vibrational from water molecules are obtained when the position of the focal spot is changed. The unique ± 3400 cm-1 Stokes characteristic peak with its anti-Stokes is present when the distance between focal spot and interface is fixed to be over 20 mm; both ±3000 cm-1 and ±3400 cm-1 with their anti-Stokes exist when the distance is reduced under 20 mm; both characteristic peaks are enhanced especially the 3000 cm-1 peak whose change is more remarkable when the spot continues to move up. Experimental results indicate that laser-induced plasma generated from water molecules enhances the stimulated Raman scattering of OH stretching vibrational from water molecules by affecting hydrogen bonds between water molecules and OH from single water molecules.
Spectroscopic study on the time evolution behaviors of the laser-induced breakdown air plasma
Authors: Liu Yu-Feng  , Ding Yan-Jun  , Peng Zhi-Min  , Huang Yu  , Du Yan-Jun  ,   State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;,   School of Control and Computer Engineering, North China Electric Power University, Baoding 071003, China
Published: December 2020

The time-resolved spectra of the air-breakdown plasma generated by the nanosecond pulsed 1064 nm beam of a Nd:YAG laser are investigated by using a PI-MAX-II ICCD with nano-time-resolved features. The results show that the laser-induced plasma spectrum in atmospheric environment is widely distributed in a range of 300-900 nm, and it is superimposed by continuous spectra and sharp line spectra. The spectral lines of oxygen, nitrogen and hydrogen are identified according to the National Institute of Standards and Technology database of atomic emission. The intuitive figures of laser-induced breakdown atmospheric plasma spectra with time resolution are given. The electron temperature and electron density are calculated according to the emission spectra. The results have scientific significance for improving the accuracy and precision of the on-line measurement in the atmospheric environment.
First-principles study of the electronic structure and NO2-sensing properties of Ti-doped W18O49 nanowire
Authors: Qin Yu-Xiang  , Liu Mei  , Hua De-Yan  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

The geometry and band structures as well as the density of states of Ti-doped nonstoichiometric W18O49 nanowire are studied by employing the ab-initio plane-wave ultra-soft pseudo potential technique based on the density functional theory. Meanwhile, the adsorption and NO2-sensing properties of the doped nanowire are analyzed by further calculating the adsorption energy, planar averaged charge density difference and atomic Mulliken charge population of the NO2/Ti-W18O49 nanowire adsorption system. The results reveal that Ti-doping modifies the electronic structure and then the gas sensitivity of W18O49 nanowire obviously. After Ti-doping, new electronic states are introduced and the band structure near Fermi level (EF) is changed obviously, resulting in the variation of the band gap and EF position and then the increase of electronic conductivity. The adsorbed NO2 molecule acts as a charge accepter to extract electrons from the conduction band of W18O49 nanowire, causing the gas-sensing response due to the conductivity change of the nanowire. NO2 adsorption on Ti-doped W18O49 nanowire can cause more electrons to transfer from nanowire to NO2 molecule than the case on pure W18O49 nanowire, theoretically suggesting the validity of Ti-doping that can improve the sensitivity of W18O49 nanowire. The population calculations on different gas molecules adsorbed on Ti-doped W18O49 nanowire further indicate the much good sensitivity and selectivity of the doped nanowire to NO2 gas.
First-principles investigation of iodine doped rutile TiO2(110) surface
Authors: Wang Tao  , Chen Jian-Feng  , Le Yuan  ,   State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
Published: December 2020

The formation energy and electronic structure of iodine (I)-doped rutile TiO2(110) surface are investigated using the first-principles method based on the density functional theory. The results indicate that I prefers to replace the five-coordinated Ti in the oxidation environment and the bridging O could be replaced by I preferentially in the reducing environment. Whether I replaces O or Ti can reduce the band gap and cause the red shift of the absorption band edge or produce the absorption in the visible light. The band gap narrows most obviously when I replaces the bridging O. The absorption spectrum shows that I doping could not only improve its visible light response but also enhance its absorption peak of UV-light, leading to the improvement in photocatalytic performance under visible and UV light.
Low frequency magnetoelectric response analysis of magnetoelectric laminate material based on energy conversion principle
Authors: Dai Xian-Zhi  ,   College of Physics and Electronic Information, China West Normal University, Nanchong 637009, China
Published: December 2020

A low frequency magnetoelectric (ME) response model of magnetostrictive/piezoelectric laminate composite is presented based on energy conversion principle, and ME response characteristics of different laminate structures are compared in this paper. In this model it is assumed that the energy transfer between the layers of the composite laminates is achieved by the interlayer shear force. The stresses and strains of the magnetostrictive and piezoelectric layers are analyzed by the stress function method. While the strain and stored magnetic energy of magnetostrictive layers and the strain and electric field energy of piezoelectric layers are solved. Under open-circuit conditions, the interlayer shear force and the low frequency ME response model of laminate composites are obtained by using Hamilton principle of minimum energy. The theoretical results show that the ME voltage coefficient is related to the Poisson ratio, magnetic permeability, magnetomechanical coupling coefficient of magnetostrictive material, Poisson ratio, and electromechanical coupling coefficient of piezoelectric material. The influences of these parameters are analyzed. The magnetoelectric characteristics of two- and three-tier laminated structures are compared in this paper, showing that different laminated structures have different formulas for ME coefficient and calculation errors will be smaller when the corresponding ME coefficient formula is used. The experimental results show that the analytical error is smaller than 6% and the model can better describe the low frequency ME response characteristics of laminated magnetoelectric materials.
Ultrathin metallic subtractive color filters based on surface plasmon primitives
Authors: Wu Qing-Jun  , Wu Fan  , Sun Li-Bin  , Hu Xiao-Lin  , Ye Ming  , Xu Yue  , Shi Bin  , Xie Hao  , Xia Juan  , Jiang Jian-Zhong  , Zhang Dong-Xian  ,   State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China;,   International Center for New-Structured Materials, Zhejiang University, Hangzhou 310027, China
Published: December 2020

Based on the surface plasmon primitives, subtractive color filters fabricated from ultrathin metallic film nanogratings, have many advantages, such as reliability, easy fabrication and high transmittance. In this work, color filter behaviors of films of four metals, i.e., silver, copper, aluminum and nickel, with one-dimensional nanogratings are systematically studied. We obtain their transmission spectra, the chromaticity coordinates and the empirical formulas of the relationship of the wavelength of transmission minimum with film thickness and period. It is found that nickel has a poor ability to select waves, which is not an ideal material for color filter. Silver, copper and aluminum perform better in selecting the wavelength. They have different transmission spectra, specifically, silver has a wide range of wavelength selection, copper is appropriate for the long wavelength filtering, and aluminum for short wavelength filtering. To verify the simulation results, we fabricate some one-dimensional nanogratings with different materials by using a direct-current magnetron sputtering system and focused ion beam machine. The experimentally observed colors for all fabricated Ag, Cu, and Al film nanogratings are consistent with their simulation results. Both simulation and experimental results reveal that different metal materials and different nanostructures exhibit lager differences in color filter behavior. The obtained results here are useful for designing desirable color filters by selecting the appropriate material and nanostructure.
Multimode steady-state theory for Gyro-TWT and simulation of mode competition
Authors: Peng Shu-Yuan  , Wang Qiu-Shi  , Zhang Zhao-Chuan  , Luo Ji-Run  ,   Key Laboratory of High Power Microwave Source and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In this paper, a multimode steady-state theory for Gyro-TWT is established. Effects of the input power and guiding center radius on backward wave oscillation in a TE11 Gyro-TWT are studies by this theory. The result shows that either of the two effects can reduce the output power of the backward wave oscillation to a certain extent, while both of them simultaneously can more effectively improve the output characteristics and the stability of the TE11 mode.
Influence of charge imbalance on breakdown voltage of 4H-SiC semi-superjunction VDMOSFET
Authors: Yang Shuai  , Tang Xiao-Yan  , Zhang Yu-Ming  , Song Qing-Wen  , Zhang Yi-Men  ,   Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China;,   School of Advanced Materials and Nanotechnology, Xidian University, Xi'an 710071, China
Published: December 2020

SiC semi-superjunction vertical double diffused MOS (VDMOSFET) has higher breakdown voltage than conventional SiC VDMOSFET with the same on-resistance. The ion implantation to form p pillar region on N-type epilayer is a key process to form semi-superjunction stucture. The influences of charge imbalance induced by ion implantation on breakdown voltages of 4H-SiC superjunction and semi-superjunction VDMOSFET are investigated through two-dimensional numerical simulation, and the largest breakdown voltage is obtained when charge imbalance is 30%. With the same structure parameters of devices, when breakdown voltage decreases by 15% due to the deviation of doping concentration in P pillars, the tolerance of doping concentration for the semi-superjunction VDMOSFET is 69.5% higher than for superjunction VDMOSFET which means that less precise process control of ion implantation for semi-superjunction VDMOSFET, will be required with less difficulty in the manufacture of pillars.
Design and analysis of high speed and high saturation uni-traveling-carrier photodetector
Authors: Zang Ge  , Huang Yong-Qing  , Luo Yang  , Duan Xiao-Feng  , Ren Xiao-Min  ,   State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

In this paper, an InP-based mesa-structure uni-traveling-carrier photodetector is designed. By adopting Gaussian doping scheme in the absorption layer and incorporating an appropriate cliff layer, high speed and high saturation current characteristics are both achieved simultaneously. For the device with a 14 μm2 active area, the simulated results indicate that the bandwidth reaches 58 GHz and DC saturation current increases up to 158 mA at a reverse bias of 2 V. Under high optical injection, the bandwidth degradation and current saturation are studied, which are caused by energy band shift and electric field collapse.
Algorithm of high-dynamic fusion image gray characterization based on variable energy
Authors: Chen Ping  , Yin Xiao-Gang  , Pan Jin-Xiao  , Han Yan  ,   Key Laboratory of Instrumentation Science and Dynamic Measurement of Ministry of Education, Shanxi Key Laboratory of Signal Capturing and Processing, National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan 030051, China;,   Key Laboratory of Molecular Imaging, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

X-ray imaging based on variable energy can expand the dynamic range of the imaging system and perfectly show the structure information of the detection objects, by acquiring and fusing the image sequences. However, the fusion method is ordinarily based on image quality optimization, and neglects the gray mapping accuracy of the actual high dynamic imaging. It cannot guarantee the physical matching between the image information and actual structure information. Therefore, in this paper we propose an X-ray image gray characterization algorithm of high dynamic fusion based on variable energy. First, take a standard wedge block as test object, and use the fusion image of low dynamic image sequences as input data. The output data are the actual high dynamic image. Then establish the X-ray imaging gray characterization model by neural network training. At the same time, because the attenuation coefficients of different heterogeneous materials are different, a modified model of physical characterization is established to achieve a correct characterization of real object. Finally, experiments by 12 bit and 16 bit imaging systems acquire the variable voltage image sequences using 12 bit detector. After image fusion, image mapping and gray level correction, the output image not only achieves the same effect of 16 bit detector, but also satisfies the gray relation. Also this method can effectively expand the dynamic range of the imaging system.
Analytical formulation for electromagnetic leakage from an apertured rectangular cavity
Authors: Jiao Chong-Qing  , Li Yue-Yue  ,   State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
Published: December 2020

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. The “closed cavity” field is obtained by using the mode-expansion method. In this formulation, the leakage field can be expressed as a function of the frequency, the source point, the field point, and the position of the aperture. The formulation then is employed to analyze the influences of the above factors on the shielding effectiveness and the corresponding physical mechanisms are also illuminated. Comparison with the full wave simulation software CST has verified the formulation over a very broad frequency range. It is shown that the near-field shielding effectiveness is smaller than the far-field one, and the electric shielding effectiveness is different from the magnetic one in the near-field zone.
Research on the facet model of electromagnetic scatterings from rough sea surface with foams
Authors: Fan Tian-Qi  , Guo Li-Xin  , Jin Jian  , Meng Xiao  ,   School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, China
Published: December 2020

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 the result of electromagnetic scatterings from the facets of the rough sea surface. Meanwhile, with increasing wind speed above the sea surface, the influence of the sea foam layer on the scatterings will increase. In this paper, the facet-model is considered, and taking into account the impact of the foam layer on the scatterings at a large angle incidence, the backscattering coefficient is calculated for different wind speeds; and the result of numerical simulation is compared with the experimental data to verify the accuracy of our method.
Effect of Raman gain on the self-steepening characteristic in isotropic fibers
Authors: Liu Bao-Lin  , Jia Wei-Guo  , Wang Yu-Ping  , Qiao Hai-Long  , Wang Xu-Dong  , Ke Neimule  ,   School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China;,   Academic Affairs Office, Inner Mongolia Radio & TV University, Hohhot 010010, China
Published: December 2020

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 the result is compared with the self-steepening effect without taking into consideration the Raman gain when the pulse propagate in the isotropic optical fiber. Raman gain specific impact on the self-steepening of the Gaussian pulse has been obtained under different conditions. Results show that the Raman gain may affect the Gaussian pulse broadening, pulse peak attenuation as well as the oscillation of the edge. These influences depend on the parameters of self-steepening, input power, and dispersion coefficient.
Mode coupling and energy transfer in a range-dependent waveguide
Authors: Mo Ya-Xiao  , Piao Sheng-Chun  , Zhang Hai-Gang  , Li Li  ,   Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China;,   College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

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 rapidly. According to the coupled mode models, the transfer of energy is expounded for the forward pressure field in the waveguide with varying topography. Meanwhile, the mechanism is explained by the ray-mode theory for variation of energy distribution caused by variation of topography. Numerical simulations show that the coupling between normal modes and the energy transfer may occur remarkably when the imaginary parts of eigenvalues take on a huge modification, and the propagation direction of sound field will be changed to the increasing direction of sea depth due to variation of topography. In the energy transfer and the modification of propagation direction, the energy of sound field tends to remain in the waveguide, rather than to leak to the seafloor. Meanwhile, the energy distribution will be affected by the compression or sparseness so that interference structures such as ellipse, will be produced.
A novel phase difference frequency estimator based on forward and backward sub-segmenting
Authors: Huang Xiang-Dong  , Meng Tian-Wei  , Ding Dao-Xian  , Wang Zhao-Hua  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

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 are the biased estimators, which are incapable of providing quantitative estimates of variance expression. To enhance the accuracy of the direct frequency estimator and derive the closed-form theoretic expression of the estimated error variance, this paper proposes a novel phase difference frequency estimator based on the forward and backward sub-segmenting. This estimator implements forward and backward fast Fourier transform (FFT) on the given samples separately, and then extracts the phase difference from the peak FFT bins of these two sub-segments to estimate the frequency. And it is emphasized that the proposed method is an unbiased frequency estimator, whose closed-form theoretic expression of the frequency estimated error variance is also derived. Moreover, simulation not only verifies the correctness of this closed-form expression but also proves that the proposed frequency estimator's mean square error is closer to the Cramer-Rao lower bound than that of apFFT/FFT phase difference estimator and Candan estimator. In conclusion, the proposed estimator has higher accuracy in measuring frequencies and has a wide application prospect.
Numerical simulation of flow around two elongated rectangles in tandem arrangement using an immersed boundary method
Authors: Yang Qing  , Cao Shu-Yang  , Liu Shi-Yi  ,   StateKey Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
Published: December 2020

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 range 200–300, a vortex shedding of front rectangle is under control of two separated shear layers. The vortex between the two rectangles belongs to Karman type, which is hindered by small spacings thus symmetric vortices are formed. Shielding effects is mainly reflected by the phenomenon that mean drag coefficients of the rear rectangle is smaller than the front one. At the critical spacing ratio, a vortex sheet between the two rectangles is fully established. The mean drag coefficient also has a jump at this spacing ratio, which is still less than that of the front rectangle. In this phase, as Reynolds number increases, the vortex regime, the jump and the critical spacing all become minimized. When Re=400, the vortex shedding of front rectangle is characterized by an impinging-shear-layer, and thw drag coefficient is no longer a regular oscillation. After that as Reynolds number rises, an impinging-shear-layer is established gradually. More vortices on the surface are produced by flow separation of the front rectangle, which leads to a less magnitude of wake vortex. Shielding effect will disappear at this time. A fluctuation impact on the rear rectangle is induced by drastic vortex shedding from the front rectangle. But proper spacing between the two rectangles can make the drag coefficient of the rear rectangle jump, which is larger than that of the front rectangle.
Study on diffusion of permeable particles in concentrated suspensions
Authors: Yang Wei-Guo  , Zhong Cheng  , Xia Hui  ,   School of Physics and Electronics, Central South University, Changsha 410083, China
Published: December 2020

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
Authors: Zhang Cheng-Bin  , Xu Zhao-Lin  , Chen Yong-Ping  ,   Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China
Published: December 2020

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.
Computer simulation of electric properties of metal-ferroelectric-substrate structured ferroelectric field effect transistor under ionizing radiation
Authors: Wu Chuan-Lu  , Ma Ying  , Jiang Li-Mei  , Zhou Yi-Chun  , Li Jian-Cheng  ,   Faculty of Materials, Optoelectronics and Physics, Xiangtan University, Xiangtan 411105, China;,   Key Laboratory of Low Dimensional Materials & Application Technology, Ministry of Education, Xiangtan 411105, China;,   School of Electronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China
Published: December 2020

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
Authors: Wang Yue  , Zhang Feng-Xia  , Wang Chun-Jie  , Gao Chun-Xiao  ,   College of New Energy, BoHai University, Jinzhou 121013, China;,   State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
Published: December 2020

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 different pressures. Results show that ZnSe undergoes a semiconductor to metal transition at 12 GPa. AC data also proves the above results. The pressure dependence of grain and grain boundary resistances indicates that the cinnabar is close to an isotropic material.
Barrier-dependent tunneling magnetoresistance reversal effect in spin field effect transistors
Authors: Yang Jun  , Zhang Xi  , Miao Ren-De  ,   Institute of Sciences, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

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
Authors: Wang Ri-Xing  , Xiao Yun-Chang  , Zhao Jing-Li  ,   College of Electrical and Information Engineering, Hunan University of Arts and Science, Changde 415000, China
Published: December 2020

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 frequency and resonant magnetic field on the magnitude and direction of dc current density and dc magnetic field are shown. The effective damping of the system can be minimized through adjusting the magnitude and the direction of current density.
Research on the nonlinear conductivity characteristics of nano-SiC/silicone rubber composites
Authors: Wang Fei-Feng  , Zhang Pei-Hong  , Gao Ming-Ze  ,   College of Electrical and Electronic Engineering, Harbin University of Science and Technology, State Key Laboratory Cultivation Base of Dielectrics Engineering, Harbin 150080, China
Published: December 2020

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 strength is obtained by experiments. Nonlinear conductivity mechanisms of the composites are analyzed, and their breakdown properties and dielectric spectröscopy characteristics of composites are studied. In order to know the effect of nonlinear SiC/silicone rubber composites on homogenizing electric field, the electric ströss distribution of cables termination and composite insulators are simulated by the COMSOL Multiphysics software. Results show that the maximum electric field strength at cable termination and the end of the composite insulators decreases efficiently when the nano-SiC/silicone rubber composites are used.
Study on luminescent properties of Yb3+-doped phosphosilicate microsphere
Authors: Wu Tian-Jiao  , Huang Yan-Tang  , Ma Jing  , Huang Jing  , Huang Yu  , Zhang Pei-Jin  , Guo Chang-Lei  ,   College of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China;,   School of Information Science and Engineering, Xiamen University, Xiamen 361005, China
Published: December 2020

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.
Analysis on relative transfer of entropy based on improved epileptic EEG
Authors: Wang Ying  , Hou Feng-Zhen  , Dai Jia-Fei  , Liu Xin-Feng  , Li Jin  , Wang Jun  ,   Image Processing and Image Communications Key Lab., Nanjing Univ. of Posts & Telecomm., Nanjing 210003, China;,   School of Science, China Pharmaceutical University, Nanjing 210009, China;,   Nanjing General Hospital of Nanjing Military Command, Nanjing, 210002, China;,   College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China
Published: December 2020

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
Authors: Xu Zhong-Hua  , Chen Wei-Bing  , Ye Wei-Qiong  , Yang Wei-Feng  ,   School of Computer and Communication, Hunan University of Technology, Zhuzhou 412007, China
Published: December 2020

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%
Dynamic interplay between epidemics and cascades:Epidemic outbreaks in uncorrelated networks
Authors: Ouyang Bo  , Jin Xin-Yu  , Xia Yong-Xiang  , Jiang Lu-Rong  , Wu Duan-Po  ,   Department of Information Science and Electronic Engineering, Zhejiang University, Hongzhou 310027, China
Published: December 2020

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 , 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.
Consensus analysis for a class of heterogeneous multi-agent systems in fixed and switching topology
Authors: Sun Yi-Jie  , Zhang Guo-Liang  , Zhang Sheng-Xiu  , Zeng Jing  ,   Department Three, The Second Artillery Engineering University, Xi'an 710025, China;,   College of Science, The Second Artillery Engineering University, Xi'an 710025, China;,   The United 96211, People's Liberation Army, Honghe 654300, China
Published: December 2020

The consensus problem of heterogeneous multi-agent systems composed of first-order agents and second-order agents in directed graph is investgated. A linear consensus protocol is proposed for solving such a consensus problem. The sufficient conditions for achieving consensus are established by using the graph theory and matrix theory in fixed and switching topology respectively, and these conditions are dependent on control gain and communication topology. Consensus equilibrium point is derived in the fixed topology. It is proved that only root nodes in the interaction topology can make contributions to the equilibrium point. Numerical examples are provided to prove the correctness of the theorems.
Chaotic robust control of permanent magnet synchronous motor system under uncertain factors
Authors: Hao Jian-Hong  , Wang Xiao-Wei  , Zhang Heng  ,   School of Electrical and Electronic Engineering, North China Electric Power University, Beijing 102206, China
Published: December 2020

In this paper, targeting the permanent magnet synchronous motor chaotic system, we consider the system influenced by uncertain factors. We use the method of the exact feedback linearization which is based on differential geometry theory to establish the nonlinear robust control model and design the robust controller for realizing the robust stabilization and output tracking control of the permanent magnet synchronous motor chaotic system. Numerical simulation results demonstrate the effectiveness of the proposed method and the robustness of the controller.
Derivation of cardinalized probability hypothesis density filter via the physical-space approach
Authors: Zhai Dai-Liang  , Lei Hu-Min  , Li Hai-Ning  , Zhang Xu  , Li Jiong  ,   School of Air and Missile Defense, Air Force Engineering University, Xi'an 710051, China
Published: December 2020

In order to make the cardinalized probability hypothesis density filter well understood, its function is deduced with the Bayes theorem and the total probability theorem based on the physical-space model made by Ozgur Erdin. The derivation is detailed and clear, and the results of the derivation are identical to those in the literature. This paper will provide the theory basis for the application and the performance improvement of the cardinalized probability hypothesis density filter in target tracking.
Fault-tolerantly implementing dense rotation operations based on non-stabilizer states
Authors: Wu Xiang-Yan  , Xu Yan-Ling  , Yu Ya-Fei  , Zhang Zhi-Ming  ,   Laboratory of Nanophotonic Functional Materials and Devices (SIPSE) Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China
Published: December 2020

Based on the quantum error-correction codes and concatenation, quantum logical gates can be implemented transversally, which is called the fault-tolerant quantum computation. Clifford gates can be directly and fault-tolerantly performed, but they cannot reach universal quantum computation. How to implement the non-Clifford gate fault-tolerantly is a vital technique in fault-tolerant universal quantum computation. Here the magic state is selected to help the implementing of the non-Clifford gate transversally. Based on the non-stabilizer state cos θi|0>+sinθi|1>, circuits which can execute 2θi rotation around X-axis and Z-axis fault-tolerantly are proposed. Then new non-stabilizer states in this form are developed and produced from the distilled magic state. By using these states, a number of non-Clifford gates can be performed transversally, which makes profound implication in fault-tolerant quantum computation. We calculate the number of the non-stabilizer states needed for simulating the desired rotation operations, which is less than that in previous protocols.
Decoherence characterization of three-dimensional transmon
Authors: Zhao Hu  , Li Tie-Fu  , Liu Qi-Chun  , Zhang Ying-Shan  , Liu Jian-She  , Chen Wei  ,   Institute of Microelectronics, Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China;,   Beijing Computational Science Research Center, Beijing 100084, China
Published: December 2020

The decoherence time of superconducting qubit is one of the main parameters that determine whether superconducting quantum computation can be realized. This paper mainly focuses on three-dimensional (3D) transmon. The sample is fabricated on SiO substrate, and measured in 10 mK temperature. By measuring Rabi oscillation, energy relaxation, Ramsey oscillation and spin echo, the decoherence time constants of 3D transmon are characterized. The results show that the decoherence time is around several hundred nanoseconds. Based on the relationship of different decoherence time constant, we have the concludes that the possible reason to diminish the decoherence time is the defect in SiO substrate, but not the low frequency noises.
Directional Lyapunov exponent and its application to fault detection of the single input single output system
Authors: Yang Dong-Dong  , Ma Hong-Guang  , Xu Dong-Hui  , Liu Hao-Miao  ,   The Second Artillery Engineering University, Xi'an 710025, China
Published: December 2020

In this paper, for the fault detection of a single-input single-output (SISO) system, we use chaotic oscillator to generate the excitation of the system under test (SUT), and use non-uniform method to reconstruct the phase space of the output time series. Directional Lyapunov exponent is defined around the equilibrium point in the phase space, and it is used to analyze the eigen-structure of the output phase space around its equilibrium point, thus the fault detection of the SISO system is realized. The simulation results show that parameter changes of the SUT will affect the phase space structure around its equilibrium point, and the directional Lyapunov exponent is sensitive to these changes.
Second derivative of Voigt function
Authors: Yang Chen-Guang  , Kan Rui-Feng  , Xu Zhen-Yu  , Zhang Guang-Le  , Liu Jian-Guo  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

In high-temperature high-pressure environment, the measurement precisions of tunable diode laser absorption spectroscopy and other laser spectrum technologies are influenced by spectral overlap because of Doppler and Lorentz broadenings. One of the potential methods to improve precision is to use the second derivative spectral signal, which has less overlap. This paper deals with the second derivative of Voigt function. The integration of its second derivative from negative to positive infinity is proved to be zero. And the analytical results of its second derivative minimum and the maxima or minima of its even-order derivatives are obtained. It is also shown that there is the relationship between the ratio of second derivative maximum point location to zero point location and the ratio of Lorentz half-width to Doppler half-width. These results provide the basis for inversing precision information from second derivative spectral signal.