bluuebunny/crossref_metadata_2025 huggingface dataset:
A high efficiency highly oriented pyrolitic graphite X-ray spectrometer
Authors: Yan Wen-Chao  , Su Lu-Ning  , Lin Xiao-Xuan  , Du Fei  , Yuan Da-Wei  , Liao Guo-Qian  , Liu Cheng  , Shen Zhong-Wei  , Chen Li-Ming  , Li Yu-Tong  , Ma Jing-Long  , Lu Xin  , Wang Xuan  , Wang Zhao-Hua  , Wei Zhi-Yi  , Sheng Zheng-Ming  , Zhang Jie  ,   Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080, China;,   Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

A novel design of X-ray spectrometer is implemented, using a high efficiency HOPG (highly oriented pyrolitic graphite) Bragg crystal. The spectral resolution of it can reach above 350 with energy ranging from 6.891 to 9.193 keV, theoretically. And the efficiency are 3 order of magnitude higher than the ordinary X-ray crystal spectrometer. Application of this instrument is demonstrated in high intensity laser-foil interaction experiments. It is shown that HOPG spectrometer has much lower threshold of X-ray intensity than ordinary one. The spectral resolution for 8.048 keV (Cu Kup -line) can reach 40 eV, which gives the spectral resolution 200.
Influence of gain on propagation properties of slow light in one-dimensional periodic structures
Authors: Shen Yun  , Fu Ji-Wu  , Yu Guo-Ping  ,   Department of Physics, Nanchang University, Nanchang 330031, China;,   Department of Physics, Wuhan University, Wuhan 430072, China
Published: December 2020

Recently, studies by Jure Grgic et al. (Phys. Rev. Lett. 108 183903, 2012) show that in a periodic structure, the large gain can be eventually turned to decreasing the effect of slow light on the structure. In this paper, one-dimensional periodic structures are taken as an instance, and the influences of gain on slow light are further investigated. It is shown that different influences can exhibit in the finite-length and infinite-length one-dimensional periodic structures. For the infinite-length structures, the addition of gain can decrease the slow light effect, whereas for finite-lengh structures, the compensation of gain can, to a certain degree, increase the slow light effect. Our results verify a feasible way in the application of such a periodic structure, as a slow-light device, and especially as the tunable slow-light devices, in the high-density integration of optical circuits.
Influence of temperature and pressure on absorption spectrum of around 1.6 m for differential absorption lidar
Authors: Zhu Xiang-Fei  , Lin Zhao-Xiang  , Liu Lin-Mei  , Shao Jun-Yi  , Gong Wei  ,   College of Electronics and Information Engineering, South-central university for nationalities, Wuhan 430074, China;,   State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China
Published: December 2020

In order to improve the inversion precision of CO2 lidar, the fine structure in CO2 absorption spectrum (at around 1.572 m) has been detected accurately, with tunable diode laser absorption spectroscopy (TDLAS) technique in a double beam differential system. Differences between absorption spectra were analyzed. The five kinds of pressure-broadened coefficients and absorption cross sections are obtained respectively at 287, 297, 311, 315 and 324 K. The temperature-dependent exponents of CO2 are also calculated, these parameters would be a series of corrections and supplements for the existing database. These results may help improve the detection capability of CO2 lidar.
Influence of granular coefficient of rolling friction on accumulation characteristics
Authors: Han Yan-Long  , Jia Fu-Guo  , Tang Yu-Rong  , Liu Yang  , Zhang Qiang  ,   Department of Engineering Northeast Agricultural University, Harbin 150030, China;,   College of Mechanic and Electrical Engineering, Tarim University, Alar 843300, China
Published: December 2020

The influence of friction coefficient, in terms of fixed static friction coefficient (sfc) and different rolling friction coefficients (rfc), on the accumulation characteristics of particle, including the angle of repose and accumulation body, is simulated using the discrete element method. The sfc of a particle is measured with a home-made cant instrument, and a linear equation is developed to describe the relationship between the rfc and the angle of repose. Results show that rfc has obviously an influence on the accumulation characteristics of particles: the angle of repose of particles increases as rfc increases, the gap between the boundary circle and the continuous circle decreases with increasing rfc. Based on the change of rotational kinetic energy in the process of accumulation of particles, the above results can be explained. And the linear equation can provide ideas for numerical measure of granular rfc. For some difficultly measured parameters of bulk materials, the simulation of accumulation process is a valid virtual calibration test.
Phasic discharge characteristics in high power pulsed magnetron sputtering
Authors: Wu Zhong-Zhen  , Tian Xiu-Bo  , Li Chun-Wei  , Ricky K. Y.  , Fu  , Pan Feng  ,   School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China;,   State Key Laboratory of Advanced Welding Production and Technology, Harbin Institute of Technology, Harbin 150001, China;,   Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
Published: December 2020

As one of the burgeoning physical vapor deposition (PVD) techniques, high power pulsed magnetron sputtering (HPPMS), which boasts high ionization rates of sputtered materials and does not suffer from macro-particles, has been investigated extensively recently. Herein, a new method to break down the discharge current into different characteristic components is employed to study the changes of the various parameters as the target voltage is increased at different pressure. Results show a phasic HPPMS discharge when the target voltage is increased, exhibiting an alternate rise of the peak and the platform of the target current. A small change at the discharge stage is observed with increasing pressure, and some stages are missing in some instances. Five discharge stages are found to correspond to the discharge of Ar atoms, Cr atoms, Ar ions, Cr ions, as well as multiply-charged Ar and Cr ions, respectively, according to the optical emission spectra obtained from the HPPMS discharge plasma. Adjacent discharge stages are also found to overlap under certain discharge conditions.
Investigation of the prediction model of IGBT junction temperature based on the rate of voltage change
Authors: Liu Bin-Li  , Tang Yong  , Luo Yi-Fei  , Liu De-Zhi  , Wang Rui-Tian  , Wang Bo  ,   National Key Laboratory of Vessel Integrated Power System Technology, Naval University of Engineering, Wuhan 430033, China
Published: December 2020

Based on semiconductor physics and the essential structure of insulated gate bipolar transistor (IGBT), the model of dV_{CE}/\d t is established through reasonable simplification and theoretical derivation. The influencing factors and temperature characteristics of dV_{CE}/\d t are studied in depth. It is concluded that dV_{CE}/\d t increases linearity with the increase of voltage or current, and decreases with the increase of junction temperature also linearly. On the basis of the model for dV_{CE}/\d t, the prediction model of junction temperature is established. Results of simulations and experiments verify the correctness and accuracy of the models. It is significant in theory and practical application for realizing IGBT junction temperature monitoring on-line and improving the reliability of IGBT module and power electronic equipment.
Influence of shadowing effect on morphology and microstructure of silicon thin film in chemical vapor deposition
Authors: Zhang Hai-Long  , Liu Feng-Zhen  , Zhu Mei-Fang  ,   College of Materials Science and Opto-electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Influences of gas incident angle () on surface morphology and microstructure of hydrogenated amorphous silicon (a-Si:H) thin films are investigated, which were grown using an oblique angle hot wire chemical vapor deposition (OAD-HWCVD) technique. An exponential relationship between the tan and RMS roughness is observed. The film surface morphology transforms from a self-affine surface into a mounded surface when the incident angle is larger than a critical angle c(60 c 75). Influences of on the microstructural properties of silicon thin films are characterized using Raman scattering and FT-IR measurements. As c, owing to the qusai-local shadowing effect, increasing increases the quantity and size of micro-voids, leading to the decrease of film density and quality. For c, the nonlocal shadowing effect causes the formation of large voids or cracks and the proportion of multi-hydride (SiHn, n 2) increases. Combined with the scaling theory, the relationship between the shadowing effect and the surface morphologies and microstructures of amorphous silicon thin films is discussed.
Whispering gallery modes in a bent ZnO microwire
Authors: Qiu Kang-Sheng  , Zhao Yan-Hui  , Liu Xiang-Bo  , Feng Bao-Hua  , Xu Xiu-Lai  ,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Micro-cavities play an important role in the light-matter interaction. The cross section of wurtzite-structured ZnO microwire is a hexagon, which gives a high quality factor. Exciton-polariton, micro-and nanowire lasers and polariton condensation have been investigated using the micro-cavities of ZnO microwires at room temperature. Strain, which changes the dielectric index of a material, is one of the methods to tune the interaction between the light and the matter. In this work, the photoluminescence spectra of strain free and bent ZnO microwires are measured across the wires, and the modes shifts are observed only in the bent one near the band edge. Shifting of the cavity modes across the wire can be observed in both TE and TM polarized spectra. For a bent ZnO microwire, the microcavity can be modified by the strain from bending, and the exciton energies may shift due to the strain. The shifted exciton energy induces a change of dielectric constant, resulting in the shifting of the cavity modes across the microwire.
Quantum control of K2 molecule in an intense laser field：Selective population of dressed states
Authors: Yao Hong-Bin  , Li Wen-Liang  , Zhang Ji  , Peng Min  ,   Department of Basic Courses, Xinjiang Institute of Engineering, Urumqi 830091, China
Published: December 2020

Control of molecular dynamics in an intense laser field has been studied by employing the time-dependent wave packet approach. A system of K2 molecule in three states (ground state|X, excited state |B and ionized state|X+) serves as a prototype which interacts with pump-probe laser fields. Interacting with an intense pump field, the excited state |B splits into two substates: | and |. Information of the energies and probability distributions of dresses states | and | can be obtained by analysing the photoelectron spectra (PES) of K2 molecule. Meanwhile, the scheme of selective population of dressed states (SPODS) has been put forward according to the dressed states theory of K2 molecule. It is found that regulating the laser intensity can control the dressed state energies, and altering the laser wavelength can make the high selectivity of the dressed state population readied.
Accuracy comparison between implicit and explicit single-diode models of photovoltaic cells and modules
Authors: Gao Xian-Kun  , Yao Chuan-An  , Gao Xiang-Chuan  , Yu Yong-Chang  ,   Key Laboratory of New Materials and Facilities for Rural Renewable Energy, Ministry of Agriculture, Henan Agricultural University, Zhengzhou 450002, China;,   School of Information Engineering, Zhengzhou University, Zhengzhou 450001, China
Published: December 2020

Accurate physical modeling and parameter extraction for the nonlinear current-voltage (Ⅰ-Ⅴ) characteristics of photovoltaic (PV) cells and modules are essential prerequisites for the design calculation, performance analysis, and optimal control of PV generation systems. In contrast to the traditional implicit single-diode models, this paper first derives the explicit single-diode models of PV cells and modules using the Lambert Wfunction, and then proposes a simple and efficient parameter extraction method on the basis of restarting the bound constrained Nelder-Mead simplex method (rbcNM). For comparing and analyzing the accuracy of implicit and explicit single-diode models, experimental data of the two typical PV cells and modules are tested and verified. Simulation results indicate that the proposed rbcNM method can rapidly and accurately extract the optimal parameters of implicit and explicit single-diode models, the simulation data produced by the extracted parameters of rbcNM method are in very good agreement with the experimental data in all cases. Comparison results show that the accuracy of rbcNM method is quite promising and outperforms the existing methods reported in the literature. Furthermore, the accuracy of explicit single-diode models is significantly higher than that of implicit single-diode models, and thus fit the Ⅰ-Ⅴ characteristic curves better.
Dynamic magnetic imaging by alternating force magnetic force mmicroscopy
Authors: Li Zheng-Hua  , Li Xiang  ,   School of Physics and Materials Engineering, Dalian Nationalities University, Dalian 116600, China;,   School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Published: December 2020

Recently, magnetic force microscope (MFM) for dynamic imaging of AC magnetic field has attracted considerable attention due to its potential applications and special requirements in industry. In this paper, we develop an alternating force MFM technique based on the frequency modulation of MFM tip oscillation, which provides a powerful tool for the development of key technologies in magnetic information storage industry. Different from conventional MFM, the main points of the present work are: 1) the investigation of the frequency-modulation phenomenon; 2) optimization of the MFM tip parameter, and introduction of the MFM signal processing apparatus; 3) observation of the AC magnetic field. For dynamic evaluation of AC magnetic field, we need to theoretically analyze the mechanical and magnetic properties of MFM tips, to technically develop the MFM signal processing apparatus, and to experimentally image the dynamic magnetic signals. Finally, we demonstrate the alternating force MFM technique, which can measure and analyze the nano-scale magnetic domain structures in advanced magnetic materials.
An anisotropic diffusion filtering method for speckle reduction of synthetic aperture radar images
Authors: Zhu Lei  , Han Tian-Qi  , Shui Peng-Lang  , Wei Jian-Hua  , Gu Mei-Hua  ,   Electronics and Information College, Xi'an Polytechnic University, Xi'an 710048, China;,   National Lab of Radar Signal Processing, Xidian University, Xi'an 710071, China
Published: December 2020

An anisotropic diffusion filtering method is proposed to reduce multiplicative speckle noise in synthetic aperture radar images. A new anisotropic diffusion equation, which can effectively smooth speckles near the edges and reduce blocking artifacts in homogeneous regions, is established by embedding the mean curvature motion controlled by an adaptive coupling function into a traditional speckle reducing anisotropic diffusion equation. Moreover, a new direction-constrained diffusion function formed by combining the local directional ratios with the improved Frost filtering is introduced into the new anisotropic diffusion equation, so that it can further reduce blocking artifacts and obviously improve the edge distortion problem in the despeckled synthetic aperture radar images. Experimental results show that the proposed method can obviously reduce blocking artifacts, sufficiently smooth speckle noise in homogeneous regions and near the edges while preserving edges, and effectively improve the edge distortion problem. Visual quality and performance indexes of the despeckled images show that the proposed method outperforms several despeckling methods.
Non linear wavelength dependence of electron localization in strong-field dissociation of D2+
Authors: Ji Ling-Ling  , Tong Ming-Qiang  , Wang Yu-Hua  ,   Department of Applied Physics, Wuhan University of Science and Technology, Wuhan 430081, China
Published: December 2020

The wavelength dependence of the electron localization in dissociating molecular ion D2+ is investigated via solving the time-dependent Schrödinger equation of the two-state model of the molecular ion. Our results reveal an anomalous dependence of the electron localization on the laser wavelength. Overall, the degree of the electron localization shows a growing trend with the increase of wavelength, but it drops off obviously at some wavelengths. It is found that the localization asymmetries for some vibrational states become opposite in phase when the wavelength is changed, leading to the decline of the electron localization. Further analysis shows that the nuclear and electronic motions that determine the electron localization respond inconsistently to the variation of the wavelength, ultimately resulting in the non-linear dependence of the electron localization on the laser wavelength.
Evolution of the quantum fidelity in a system of multimode light field interacting resonantly with a two-level atom through degenerate multi-photon process
Authors: Wang Ju-Xia  ,   Engineering Research Center of Photoelectric Detection, School of Physics and Electric Engineering, Weinan Normal University, Weinan 714099, China
Published: December 2020

The time evolution properties of the quantum fidelity in a system of multi-mode coherent light field resonantly interacting with a two-level atom via any Nj-degenerate N∑-photon transition process are studied by the fully quantum theory and numerical calculations. The analytical expressions of the quantum fidelity of field and atom, and the numerical calculation results for three-mode field interacting with the atom are obtained. Our attention focuses on the discussion of the influences of the initial average photon number, the atomic distribution angle, the phase angle of the atom dipole, the field excitation angle, and the atomic degeneracy on the evolution of the quantum fidelity. The results obtained from the numerical calculation indicate that the above factors lead to the quantum fidelity changing with oscillation behavior. The quantum fidelity of field and atom will drastically decrease as the initial light increases, which is correlated sensitively with the fidelity. The speed change of quantum fidelity is strongly dependent on the atomic degeneracy and the intensity coupling between atoms and fields. The value and frequency of the quantum fidelity change lightly with the atomic distribution angle and the angle of light field excitation as well. The phase angles of the atom dipole almost have no influences on the quantum fidelity of field and atom. According to these properties of the quantum fidelity, we can control the speed and value of quantum fidelity in the system by these constraint conditions.
First principles study on the electronic structures and optical properties of Na2Ge2Se5
Authors: Cheng Xu-Dong  , Wu Hai-Xin  , Tang Xiao-Lu  , Wang Zhen-You  , Xiao Rui-Chun  , Huang Chang-Bao  , Ni You-Bao  ,   Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Science, Hefei 230031, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The optimized crystal structure, electronic structure and optical properties of Na2Ge2Se5, an excellent nonlinear crystal, are investigated by using pseudo-potential plane-wave method based on the first principles. The band structure, density of states, bond population, dielectric function, reflection spectrum, absorption spectrum, and codex refractive index of optimized structure of Na2Ge2Se5 are calculated. The results indicate that Na2Ge2Se5 is indirect wide-band semiconductor. The electronic transitions are mainly composed of Ge-4s, Ge-4p, Se-4s and Se-4p. The optical properties are determined by the interaction between Ge and Se, while Na contributes little. The reflectance spectrum and absorption spectrum indicate that there is strong absorption to ultraviolet radiation and static refractive index is 2.133. Na2Ge2Se5 possesses moderate birefringence. The results indicate that Na2Ge2Se5 is a good candidate for the optical crystals in the infrared region.
Absolute distance measurement by high resolution frequency modulated continuous wave laser
Authors: Shi Guang  , Zhang Fu-Min  , Qu Xing-Hua  , Meng Xiang-Song  ,   State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China
Published: December 2020

Large-scale high-accuracy measurement plays an important role in many applications, such as large-scale equipment manufacturing, space technology and national defense industry. High-accuracy absolute distance measurement by laser is an important research topic in the field of large-scale high-accuracy measurement. And frequency modulated continuous wave (FMCW) laser ranging is a hot point of research nowadays. Because this method is better than pulsed time-of-flight method in measurement resolution, and the problem of ambiguity in measurement, which is the main disadvantage of phase-related method, does not exist. In this paper, the principle of FMCW laser ranging and the main factors reducing the measurement resolution are analyzed. In order to improve the ranging resolution, the method using an auxiliary interferometer to sample the signal in equal intervals of optical frequency is employed. A dual interferometer FMCW laser ranging system is designed and the experiments are carried out. The experimental results show that the measurement resolution is 50 μm at a distance of 10 m.
First-principles study of the effect of S impurity on the adhesion of Fe/Al2O3 interface
Authors: Tang Jie  , Zhang Guo-Ying  , Bao Jun-Shan  , Liu Gui-Li  , Liu Chun-Ming  ,   College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China;,   Shenyang Siasun Robot & Automation Company Limited, Shenyang 110168, China;,   College of Constructional Engineering, Shenyang University of Technology, Shenyang 110023, China;,   School of Materials and Metallurgy, Northeastern University, Shenyang 110819, China
Published: December 2020

The effect of S impurity on adhesion of Fe(110)/Al2O3(0001) interface is studied by the first-principles plane wave pseudopotential method within the density functional theory. It is shown that S impurity prefers to occupy the site of Fe3 at Fe(110)/Al2O3(0001) interface substitutionally due to the smallest interface segregation energy. The adhesion of Fe(110)/Al2O3(0001) interface is mainly governed by the interaction between Fe and O atoms on both sides of interface. The calculation results of the partial density of states, Mulliken overlap population and the electron density all suggest that Fe-O interaction is weakened by the segregated S impurity at Fe/Al2O3 interface, and the presence of S impurity gives rise to stronger electrostatic repulsion between Fe and O atoms across Fe/Al2O3 interface, which all leads to a reduced adhesion for Fe/Al2O3 interface. As a result, the results obtained by the first principles can give us a deeper understanding of the mechanism of a reduced interface adhesion and the oxidation film spallation by the segregation of S impurity at FeCrAl alloy interface.
Simulation of dendritic competitive growth during directional solidification using modified cellular automaton method
Authors: Chen Rui  , Xu Qing-Yan  , Liu Bai-Cheng  ,   School of Materials Science and Engineering, Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Tsinghua University, Beijing 100084, China
Published: December 2020

Investigating the dendritic competitive growth mechanism is of great importance for directional solidification, and the numerical simulation technique is regarded as an effective approach to a description of microstructural evolution. Therefore, a modified cellular automaton model with decentered square algorithm is developed for quantitatively simulating the dendritic competitive growth process. The model takes into account the simplified thermal field, solute diffusion, growth kinetics, etc., and the solid fraction increment calculation is achieved through local level rule method. The model is successfully used to describe the dendrites with various growth orientations and its availability in simulating dendritic competitive growth is verified by comparing with the experimental results of transparent alloy. For the nickel-based superalloy, the simulated results reveal that in the case of converging dendrites, the unfavorably oriented dendrite is able to overgrow the favorably oriented dendrite, which is dependent on the preferential growth angle. For the divergence case, the favorably oriented dendrite can overgrow the unfavorably oriented dendrite through side branching at the grain boundary. The competitive growth process is mainly controlled by the pulling rate and the preferential growth angle. Furthermore, the model is successfully extended to the simulation of three-dimensional dendritic competitive growth.
Stochastic resonance in a two-mode laser system driven by colored cross-correlation noises
Authors: Wang Zhi-Yun  , Chen Pei-Jie  , Zhang Liang-Ying  ,   School of Physics and Electronic Engineering, Hubei University of Arts and Science, Xiangyang 441053, China
Published: December 2020

Considering a gain-noise model for two-mode laser system driven by a periodic signal and two-color cross-correlation noises, we calculate the power spectrum and signal-to-noise ratio (SNR) of an output signal by means of linear approximation method, and discuss the influence of the system coefficients on SNR. Results show that under a certain condition satisfied by the coefficients of the system and input signals, the stochastic resonance phenomenon may be detected in the evolution of SNR, and also at certain intensities of noise, saturation coefficient c2, cross coupling coefficient b, and input signal frequency Ω.
Supercontinuum generation in photonic crystal fiber and tapered single-mode fiber
Authors: Zhang Long  , Han Hai-Nian  , Hou Lei  , Yu Zi-Jiao  , Zhu Zheng  , Jia Yu-Lei  , Wei Zhi-Yi  ,   Institute of Physics, Chinese Academy of Sciences, Key Laboratory of Optical Physics, Beijing 100190, China;,   China University of Petroleum, College of Science, Qingdao 266580, China
Published: December 2020

Supercontinuum generation has received extensive attention because of the innovation of high nonlinear fiber, which makes the supercontinuum system more simple, compact, and efficient. Nonlinear effects are enhanced greatly during the strong interaction between the light and matter in high nonlinear fiber, and the spectrum will be broadened effectively. In this paper, we demonstrate the supercontinuum generation in a photonic crystal fiber and a conventional tapered single-mode fiber pumped by the mode-locked Yb fiber laser. Through the experimental comparison of the supercontinuum spectrum between two kinds of the high nonlinear fibers, the spectral flatness, Raman perturbation, and dispersion wave radiation are discussed for studying the characteristics of supercontinuum generation. Finally, the octave supercontinuum-based both kinds of high nonlinear fibers could be achieved. In particular, the employment of tapered single-mode fiber is proven to be an appropriate candidate for supercontinuum generation and further application.
Experimental study on the characteristics of a two-electrode plasma synthetic jet actuator
Authors: Wang Lin  , Xia Zhi-Xun  , Luo Zhen-Bing  , Zhou Yan  , Zhang Yu  ,   Science and Technology on Scramjet Laboratory, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Performance of a two-electrode plasma synthetic jet actuator has been experimentally studied by discharge measurements with high-speed shadowgraphy technology. Results show that the breakdown voltage and the peak discharge current of the actuator may be decreased by decreasing the ambient pressure and increasing the discharge frequency. The discharge developed in the actuator cavity is a spark-arc discharge. In the actuator could be created a strong “precursor shock” and a high kinetic energy jet. During the development of the plasma synthetic jet, the speed of the “precursor shock” is invariable and the jet propagates with an approximately local sonic velocity (350 m/s). But with decreasing jet exit diameter and ambient pressure, the increase of the cavity volume and the discharge frequency could lead to decreasing strength of the “precursor shock”. Heating efficiency of the gas in the cavity will decrease with the increase of the cavity volume and discharge frequency, and the jet velocity is decreased as well. The jet exit diameter and the ambient pressure can have their optimal values for affecting the velocity of the jet. Under all the working conditions we have studied, the plasma actuator may create a strong “precursor shock” and a high-speed jet, and also may have the potential to be used in high-speed active flow control.
Use of velocity source immersed boundary-lattice Boltzmann method to study bionic micro-fluidic driving model
Authors: Liu Fei-Fei  , Wei Shou-Shui  , Wei Chang-Zhi  , Ren Xiao-Fei  ,   School of Control Science and Engineering, Shandong University, Jinan 250061, China;,   school of Information Science and Engineering, University of Jinan, Jinan 250002, China
Published: December 2020

Bionic micro-fluidic driving model is built in this paper based on the velocity source immersed boundary-lattice Boltzmann method. In order to avoid the transformation between the velocity and the force, this method introduces an immersed boundary into the lattice Boltzmann equation as the velocity source, which can reduce the computational expense. Firstly, the effects of the traveling waves produced by the elastic filament on the velocity and pressure of the flow field are studied. Secondly, the paper focuses on the influences of parameters on the flow rate. Results show that the flow rate increases with increasing frequency, wave amplitude, and filament length. Relationships between the flow rate and the other parameters of the model, such as the position of filament, wavelength, and kinematic viscosity of the fluid, are shown to be nonlinear and complicated.
Calculation of single event upset based on Monte Carlo and device simulations
Authors: Wang Xiao-Han  , Guo Hong-Xia  , Lei Zhi-Feng  , Guo Gang  , Zhang Ke-Ying  , Gao Li-Juan  , Zhang Zhan-Gang  ,   The 5th Electronics Research Institute of the Ministry of Industry and Information Technology, Science and Technology on Reliability Physics and Application of Electronic Component Laboratory, Guangzhou 510610, China;,   Northwest Institute of Nuclear Technology, Xi'an 710024, China;,   China Institute of Atomic Energy, Beijing 102413, China
Published: December 2020

An extraction method for single event upset cross section based on Monte Carlo code and device simulation is proposed, which can be used to calculate single event effects and sensitive regions in memories accurately. Single event upset cross sections of domestic static random access memory (SRAM) and field programmatic gate array (FPGA) devices are calculated, and results agree well with these from heavy ion test. Simulation results reveal the physical mechanism of the relationship between single event upset sensitivity and surface area of off-state NMOSFET and PMOSFET. Sensitive regions of single event upset under different linear energy transfer (LET) values are obtained. The radial ionization profiles of heavy ions with different energy, but the same LET, are also calculated using the Monte Carlo method. The track radius of high-energy ion is significantly larger than that of low-energy ion, while the charge density at the track center of low-energy ion is higher by two or three orders of magnitude. With decreasing technology scaling, the impact of these differences on single event effects will be more pronounced, and the threshold LET and saturated cross-section will not be capable of describing the single event response completely.
Rate-dependent characteristics of copper under plate impact
Authors: Peng Hui  , Li Ping  , Pei Xiao-Yang  , He Hong-Liang  , Cheng He-Ping  , Qi Mei-Lan  ,   State Key Laboratory of Explosion and Technology, Beijing Institutive of Technology, Beijing 100081, China;,   National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, Mianyang 621900, China;,   School of Science, Wuhan University of Technology, Wuhan 430070, China
Published: December 2020

In this paper, the rate-dependent characteristics of oxygen-free high-purity copper (OFHC) under plate-impact loading is investigated experimentally. The velocity of flyers is measured by magnetic measurement system, and the free surface velocity of targets is measured by Doppler pins system (DPS). Characteristic parameters of free surface velocity are calculated using the measured data. Results show that the spall strength of OFHC is enhanced with the increase in strain rate. It is indicated that the rate from the minima to the spall peak grows slowly at low stain rate, but steeply at high strain rate. The slope as it appears, from the minima to the spall peak is very different as the strain rate increases, The interaction of shock waves in the copper samples is systematically analysed to access the slope characteristics.
An imaging algorithm for missile-borne spotlight SAR based on subband compensation
Authors: Jiang Huai  , Han Min  , Zhao Hui-Chang  , Zhang Shu-Ning  ,   School of Electronic & Optical, Nanjing University of Science & Technology, Nanjing 210094, China;,   State key Laboratory of Milimeter Wave, South East University, Nanjing 210094, China
Published: December 2020

The missile-borne synthetic aperture radar (SAR) often use nonlinear scaling algorithm to improve the focusing effect. However, the nonlinear scaling algorithm cannot be used in missile-borne spotlight SAR because of its own limitations. Aiming at this problem, this paper first puts forward a new method named “sub-band compensation” and combineds it to the missile-borne SAR spotlight imaging algorithm. This new algorithm does not introduce the three phases of operation, so the Doppler frequency rate can be effectively compensated under low PRF. Simulation results and analysis show that compared with the nonlinear chirp scaling algorithm, the proposed one has advantages in computation, results obtained, and applicability.
HighTcSQUID low frequency receiver and through-wall receving experiments
Authors: Zheng Peng  , Liu Zheng-Hao  , Wei Yu-Ke  , Zhang Chen  , Zhang Yan  , Wang Yue  , Ma Ping  ,   Applied Superconductivity Research Center of Peking University; State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Peking University; Department of Physics, Beijing 100871, China
Published: December 2020

System and methods for wireless communication that could go through hydrous rocks, seawater, and even soil are investigated. The key components of the system are the high sensitive receivers of commercial HighTcSQUID and high-speed signal acquisition and processing systems. Within the frequency band of 30 Hz to 100 kHZ, the intrinsic noise spectral density of commercial HTcSQUID could be as good as 100 fT/Hz1/2, so that with commercial software, signals could be accurately modulated, collected,demodulated and processed. In the low frequency end, with the features of long penetration depth of electromagnetic wave and high sensitive, small size of HTcSQUID magnetometer, the feasibility of the implementation of portable low-frequency wireless communication system which could be used both under ground and water is discussed preliminarily. Using a 1 m2 square coil as test signal transmitting antenna, with the HTcSQUID magnetometer receiving sensor placed in an electromagnetic shielding cavity which could provide considerable electromagnetic attenuation, the 99 Hz AM signal emitted by the transmitting antenna is successfully collected. The result proves that with the technology of HTcSQUID, practical wireless communications can be realized between the earth's surface and a depth of hundreds of meters underground.
Influence of front and back grating period on light trapping of dual-grating structure thin film solar cell
Authors: Liang Zhao-Ming  , Wu Yong-Gang  , Xia Zi-Huan  , Zhou Jian  , Qin Xue-Fei  ,   School of Physical Science and Engineering, Tongji University, Shanghai 200092, China
Published: December 2020

In this paper, the influence of different front and back grating period ratio on the optical absorption property of a dual-grating structured thin film solar cell is analyzed using finite difference time domain method. Grating height, fill factor, and thickness of silicon layer are optimized, and the resonance modes that contribute to the absorption enhancement are studied. Results show that light leakage effect exists in the conformal grating structure with grating period ratio of 1:1, the structure with grating period ratio deviating from 1:1 suppresses the light leakage from the silicon active layer. The effective excitation and propagation of waveguide modes in the silicon active layer play an important role in the absorption enhancement of the structure with the front grating period smaller than the back grating period, while the excitation and propagation of the plasmonic modes in the active layer dominate the absorption enhancement of the structure with the front grating period larger than the back grating period. The light leakage effect also exists in the structure with grating period ratio of 1:2 and 1:3 when the silicon active layer is thick. As a result, the structure with the best absorption property deviates from the structures with these grating period ratios.
Research on microphysical property of snowfall based on particle imaging velocimetry technology
Authors: Liu Xi-Chuan  , Gao Tai-Chang  , Liu Lei  , Zhai Dong-Li  ,   College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;,   Ying EnTe Environment Technique Co. LTD, Nanjing 211101, China
Published: December 2020

In order to obtain the microphysical features of snowflakes under the natural conditions by using the self-developed sensor, precipitation microphysical characteristics, capture probability, and space distribution retrieve algorithm based on the velocity of snowflakes are discussed; and the shape, size, velocity, axial ratio, orientation and the space distribution of snowflakes are investigated by the field observation. Results show that the snowlakes may take needles, flakes, and oblate ellipsoids shapes; the falling velocity of snowflakes will increase slightly with inereasing diameter, their axial ratio may increase linearly with the diameter, and their orientations are easily influenced by the wind; the canting angle may be 0.9° and tends to be nearly symmetric with a standard deviation around 13.2°. Empirical equations of velocity and diameter, and of axial ratio and diameter are fitted by nonlinear fitting and linear fitting of observed data respectively. Compared with previous model proposed by authors abroad, this paper further provides the microphysical characteristics of snowflakes with localization features. The above conclusions can be of significance for the research on cloud precipitation physics, ground validation of weather radar, assessment of precipitation-induced microwave attenuation, etc.
Influence of the heat reservoir boundary on the performance of Brownian heat engine
Authors: Xiao Yu-Ling  , He Ji-Zhou  , Cheng Hai-Tao  ,   Department of Physics, Nanchang University, Nanchang 330031, China
Published: December 2020

In this paper we study the thermodynamic performance of a Brownian heat engine, which is driven by temperature difference. Brownian particles move in a periodic single-barrier sawtooth potential under the action of an external load force, and contact an alternating hot and cold reservoir. The kinetic energy change of the Brownian particles and the heat leak between hot and cold reservoir are considered simultaneously. The dynamics of the Brownian particle is governed by the Smoluchowski equation. The expressions for heat flow, power output and efficiency are derived analytically. The influences of the height of barrier, the external load force and the heat reservoir boundary on efficiency and power output are discussed by numerical calculation. It is shown that the Brownian heat engine is irreversible when the irreversible heat flow caused by the kinetic energy change and the heat leak exist. The curve of the power output versus the efficiency is a loop-shaped one. When the barrier boundary coincides with the heat reservoir boundary, the heat engine has a maximum power output. The efficiency of the heat engine is enhanced, but the power output is reduced when the heat reservoir boundary is changed.
An adaptive compressed sensing method based on selective measure
Authors: Kang Rong-Zong  , Tian Peng-Wu  , Yu Hong-Yi  ,   College of Information Engineering, Information Engineering University, Zhengzhou 450002, China
Published: December 2020

An adaptive compressed sensing architecture based on selective measure is proposed in this paper, in order to reduce the effects of non-sparse noise component on the performance of existing compressed sensing reconstruction algorithm. Firstly, in this paper we analyze and deduces the statistics characteristic of the measured noise and its influence on the reconstruction performance; then we propose a compressive-domain projection filter combined with iterative noise detector method to obtain the location information of noise subspace based on minimal output energy criteria; thirdly, we measure matrix adaptively with the location information, and focus on the signal subspace directly without sensing the noise component in analog part. Simulation results show that compared with the existing compressed sensing procedures, our method can obviously improve the performance of reconstruction of signals with noise, and can be used to perform the front-end spectrum analysis of absorbing materials and better detect the active channels in cognitive radio.
A time-difference fluxgate with Gauss noise and weak sinusoidal signal excitation
Authors: Yang Bo  , Bu Xiong-Zhu  , Wang Xin-Zheng  , Yu Jing  ,   School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

A novel time-difference fluxgate sensor with weak sinusoidal and Gauss noise excitation is presented in this paper. Expression of the transition rate is derived according to the bistable peculiarity and the Fokker-Planck equation of the soft magnetic material. Relationships among transition rate, external magnetic field, amplitude of the excitation field, and noise intensity are discussed through numerical simulation. By converting the periodic transition rate signal to the square signal, the time difference between the high level and the low level of the square signal can be related with the external magnetic field. And the expression of the sensor's sensitivity is derived. Simulation results show that the sensitivity is inversely proportional to the amplitude and frequency of the excitation magnetic field, and the measuring range is proportional to the amplitude of the excitation magnetic field. Experiments have been carried out on a fluxgate prototype with a measuring range of ±10.7 A/m. The minimum sensitivity could achieve 9.8696 ms/(A/m), and the novel time-difference fluxgate can be of great interest in the detection of quasi-static extremely weak magnetic field.
System design and performance simulation of ground-based differential absorption lidar for water-vapor measurements
Authors: Ge Ye  , Shu Rong  , Hu Yi-Hua  , Liu Hao  ,   Key Laboratory of Space Active Opto-Electronics Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China;,   State Key Laboratory of Pulsed Power Laser Technology, Electronic Engineering Institute, Hefei 230037, China
Published: December 2020

In order to obtain water-vapor profiles in the lower troposphere with a high accuracy and a temporal-spatial resolution, an improved ground-based differential absorption lidar system for water-vapor measurements is demonstrated. The key components of the system and the errors possibly existing in the system are described in detail. A real-time differential absorption cross-section measurement device that can compensate for measuring error caused by laser transmitter is presented. Combined with the water-vapor concentrations of different seasons in Shanghai, the differential optical thickness, the relationship between the gain of avalanche photo-diodes and the signal to noise ratio of received signal, and the statistical error in detection of four absorption lines in the 935 nm H2O absorption band are simulated in detail. The result shows that a particular absorption line can be selected, which depends on season and meteorological condition, to achieve the best outcome. With a time resolution of 5 min and a vertical resolution of 300 m, the statistical error of water vapor concentration is no more than 18% in a range of 300-5000 m.
Ramp-induced oblique detonation wave with an incoming boudary layer effect
Authors: Liu Yu  , Zhou Jin  , Lin Zhi-Yong  ,   Science and Technology on Scramjet Laboratory, National University of Defense Technology, Changsha 410073, China
Published: December 2020

The behavior of reacting shock wave in supersonic premixed flow with the effect of incoming boundary layer is investigated experimentally. A supersonic premixed flow at a Mach number of 3 encounters a ramp, and an oblique detonation wave (ODW) is produced. Four ramp angles (θ) are designed from 36° to 45° (interval of 3 degree) and the equivalence ratio (Φ) can be varied. At a lower equivalence ratio, the ODW cannot be initiated and instead the shock-induced combustion (SIC) comes into being. It is discovered that the overall flow field presents more significant unsteadiness for SIC than for inert shock wave because the separation region is greatly enlarged for SIC due to heat release by chemical reactions in the separation region. As for the ODW, it is prone to propagating upstream after initiated for current experimental conditions. For 39° ramp, the separation region of boundary layer is relatively small, and the ODW presents an abrupt pattern for which a transverse wave exists. However, larger separation region for 42° ramp and its unsteadiness make the transverse wave intermittently appear. For 45° ramp, the even larger separation region makes the transverse wave thoroughly disappear and the ODW presents a smooth pattern.
Calculation of transport coefficients of a xenon plasma
Authors: Chen Yan-Qiu  ,   China Academy of Civil Aviation Science and Technology, Beijing 100028, China
Published: December 2020

The viscosities, thermal conductivities and electrical conductivities of xenon plasma are obtained using Chapman-Enskog method expanded up to a higher approximation in a computation range from 300 to 40000 K under different pressures. In the local thermodynamic equilibrium regime, the results are compared with published experimental and computational results, showing that they are in good agreement with each other, which validates the accuracy of the computational method. The transport properties of xenon plasma are further obtained under the chemical equilibrium and thermal nonequilibrium, in which the electron temperature Te is different from that of heavy species Th. The evolutions of the transport properties with pressure and thermal nonequilibrium parameters (θ=Te/Th) are presented and analyzed.