bluuebunny/crossref_metadata_2025 huggingface dataset:
Real-time data processing of remote measurement of air pollution by infrared passive scanning imaging system
Authors: Jiao Yang  , Xu Liang  , Gao Min-Guang  , Jin Ling  , Tong Jing-Jing  , Li Sheng  , Wei Xiu-Li  ,   Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 China
Published: December 2020

Infrared passive remote sensing allows remote monitoring and early warning of air pollution. The key to the quantitative resolution is to obtain the background radiation in application process. The existing methods (such as measuring the background and atmosphere radiance spectrum in the same condition or uptake) need in advance or at the same time to measure the background spectrum without target. So, they are difficult to satisfy the demand for rapid response in the practical application. According to the infrared radiation transmission model analysis and by studying the principle of measured spectrum in the 800-1200 cm-1 band containing the target, background and environmental radiation, we propose a real-time spectrum extraction algorithm that does not require to measure the background target feature. The method is applied to the developed polluting gas scanning imaging passive FTIR system. The remote sensing of SF6 is done. Concentration data and the data obtained by the method at the same condition are compared, and the results show that the correlation coefficient squared value reaches 0.99, indicating that the method is feasible, which can effectively improve the response speed of the system and the scope of application.
Research on the characteristics of tunable structure nanowire-grid polarizer
Authors: Ling Jin-Zhong  , Huang Yuan-Shen  , Wang Zhong-Fei  , Wang Qi  , Zhang Da-Wei  , Zhuang Song-Lin  ,   School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China;,   Shanghai Key Laboratory of Modern Optics System, Shanghai 200093, China
Published: December 2020

Nanowire-grid polarizer is of a periodic sub-wave structure of metallic nanowire on the substrate, fabricated by nanoimprint technology. Different from traditional polarization prism and dichroic polarizer, the nanowire-grid polarizer has many advantages such as compact size, easy integration and high polarization performance. However, in the ultraviolet and visible regions, it is infeasible to improve the performance of single layer nanowire structure by reducing the character size of nanowire because of the bottleneck of lithographic process. The double-layer nanowire-grid structure could improve the polarization characteristics at some special wavelengths but not full-wave band of ultraviolet and visible regions. In this paper, we propose a tunable double-layer structure to enhance the extinction ratio and transmission at each wavelength by tuning the distance between two nanowire-grid polarizers through adjusting the voltage applied to PZT. To calculate the transmittance and transmission extinction ratio of tunable structure, software VirtualLab is employed and the Fourier model method is used. The numerical simulation results show that the tunable structure have a higher polarization characteristic in ultraviolet and visible regions than single layer structure and double layers structure.
A high resolution robust localization approach of high speed target based on vector sonar
Authors: Liang Guo-Long  , Ma Wei  , Fan Zhan  , Wang Yi-Lin  ,   Key Laboratory of Underwater Acoustic Technology, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Based on high speed moving target robust high-resolution direction of arrival (DOA) estimation problem under low signal-to-noise ratio and a small number of snapshots in the underwater acoustic vector signal processing framework, a novel spatial spectrum model combined with compressive sensing method is proposed. By studying the acoustic vector sensor structure, a generalized temporal filtering method based on sound pressure and particle velocity combined treatment is presented. According to the matrix spatial prefiltering theory, a new spatial filter with stopband constraint and mean square error min-max principle in passband is proposed which is used as vector sonar spatial prefiltering algorithm. Based on the methods above, a novel time-space domain jointly filtering high-resolution DOA estimation algorithm based on compressive sensing is proposed. The mathematical model, physical interpretation, and specific implement are explained in detail. Theoretical analysis and computer simulation results show that the new method has a lower dual-target distinguishing threshold and a higher estimation accuracy in solving the vector sonar high speed moving target robust DOA estimation problem under a small number of snapshots (single snapshot) condition. The higher robustness and better results of the proposed method are verified in the lake experiment.
First-principles study on cation-doped Lu2Si2O7
Authors: Lin Ling  , Zhu Jia-Jie  , Fang Hong  ,   Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian 350002, China;,   Department of Physics, Tongji University, Shanghai 200092, China;,   Department of Earth Sciences, Fitzwilliam College University of Cambridge, Cambridge CB4 3JL, the United Kingdom
Published: December 2020

Lu2Si2O7: Ce (LPS: Ce) is a well-known scintillator due to its excellent scintillation properties such as high light yield and fast decay time. However, the oxygen vacancies would degrade its scintillation properties. In this paper, we perform first-principles investigation on the stabilities of Li, Na, Mg and Ca in LPS and their influences on the oxygen vacancy. We focus on the defect formation energies and densities of states. It is found that the dopants occupy interstitial sites under oxygen-poor limit. They can suppress oxygen vacancies due to the requirement of charge balance. We discuss the influence of dopants on the density of states of perfect LPS.
Design and study of optically transparent band-pass frequency selective surface
Authors: Zhang Jian  , Gao Jin-Song  , Xu Nian-Xi  ,   Key Laboratory of Optical System Advanced Manufacturing Technology, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   University of the Chinese Academy of Sciences, Beijing 100039, China
Published: December 2020

Radar and optical dual band-pass film material can be fabricated by the method of loading frequency selective surface into metallic mesh substrate. In this paper its electromagnetic characteristics are analyzed and calculated by the vector mode matching method. Using substrate, metallic mesh and frequency selective surface integration design method, its electromagnetic characteristics are optimized. The calculated and measured results show that optically transparent frequency selective surface which is designed by the integration design method can not only quickly obtain the electric field basis functions but also accurately predict the resonant size, therefore, the computational efficiency is improved and the occurence of the modal interaction null is avoided. With integration design method, optically transparent band-pass frequency selective surface having a stable filter characteristic is obtained in this paper.
Optimization of nuclear magnetic resonance refocusing pulses to enhance signal intensity in gradient B0 field
Authors: Li Xin  , Xiao Li-Zhi  , Liu Hua-Bing  , Zhang Zong-Fu  , Guo Bao-Xin  , Yu Hui-Jun  , Zong Fang-Rong  ,   State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, China;,   Sinopec Research Institute of Petroleum Engineering, Beijing 100101, China
Published: December 2020

It is an efficient protocol to use the refocusing flip angle pulse optimization technique to solve special engineering technical problems in nuclear magnetic resonance (NMR) measurements. By reducing RF pulse duration, the low refocusing flip angle pulses can consume lower power, satisfy specific absorption rate of samples, and improve signal-to-noise ratio as well. To further analyze the function mechanism of pulse angles, the dependence of signal intensity on RF pulse is studied in homogenous magnetic field and constant gradient magnetic field respectively. Afterwards, echo amplitudes with various tip angles and flip angles ranging from 0° to 180° are compared with conventional sequence of 90° pulse followed by 180° pulses theoretically and experimentally. For the constant gradient field, the refocusing pulse of flip angle can be as low as 140°, defined as the optimum herein, to obtain the strongest signal intensity, enhanced by 13% compared with that of 180°. Moreover, T1 distributions measured by the conventional and optimal sequences for distilled water at room temperature are compared, and good conformances of T1 between the two pulse sequences are obtained, which demonstrates the optimal refocusing pulse can be directly applied to T1 measurement. The results provide constructive suggestion for designing pulse sequences for signal intensity enhancement in NMR logging while drilling and NMR online quick analysis.
Analysis on urban traffic status based on improved spatio-temporal Moran's I
Authors: Chen Shao-Kuan  , Wei Wei  , Mao Bao-Hua  , Guan Wei  ,   MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology, School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

An improved Moran's I method is proposed to describe the spatio temporal features of road traffic flow based on the traditional Moran's I. The spatio temporal distribution classification of road traffic status including homogenous congested and uncongested traffic, heterogeneous congested and uncongested traffic is then given through Moran plotting graph. To verify the applicability of the proposed method, the traffic flow data along the second ring-shape urban expressway in Beijing is introduced for analysing the spatio temporal distribution and evolution of road traffic status from global and local autocorrelation through using the proposed method.
Retrieval of liquid cloud microphysical properties from spaceborne active and passive sensor data based on optimal estimation theory
Authors: Han Ding  , Yan Wei  , Cai Dan  , Yang Han-Le  ,   Institute of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

In order to meet the urgent requirement for accurate retrieval of liquid cloud microphysical properties, integrating the detecting advantages of active and passive sensors and combining radar reflectivity and optical depth information from CloudSat and Aqua, a new retrieval algorithm of liquid cloud microphysical parameters is proposed according to the optimal estimation theory. By assuming the lognormal size distribution of cloud droplets and establishing functional relationships between measurement and retrieval variables based on forward physical model, with the prior information about spectral distribution parameters, the optimal solutions of spectral parameters are obtained after iteratively calculating, then the microphysical parameters of liquid cloud could be retrieved based on forward physical model, and the uncertainty can be calculated according to error propagation theory. By designing retrieval scheme and using measured case data, the retrieval results are compared with the data published by CloudSat official institutions and those retrieved using empirical algorithms, showing that retrievals of liqiud cloud microphysical parameters based on optimal estimation theory by using combined active and passive sensor data are well consistent with official released data, which makes up for the disadvantages of empirical algorithms that have large error and poor expansibility and gives some important references for retrieval research of liquid cloud microphysical parameters based on domestic spaceborne and airborne W-band millimeter-wave radar data.
Characteristics plasma environment isolated conductor surface charging time domain
Authors: Cao He-Fei  , Liu Shang-He  , Sun Yong-Wei  , Yuan Qing-Yun  ,   Electrostatic and Electromagnetic Protection Institute, Ordnance Engineering College, Shijiazhuang 050003, China;,   Department of Physics, Shijiazhuang College, Shijiazhuang 050035, China
Published: December 2020

Spacecraft surface charging and discharging in a plasma environment are affected by many factors, and the charging time is an important factor to influence the discharging frequency. In this paper, considering microstructure and material parameters of the plasma characteristics, appling the principles of mechanics to each particle, and using statistical methods, the expression of isolated conductor ball surface charging potential time-domain is deduced. Using the general expression of voltage, we deduce the expression of the time domain of electrostatic charging quantity of isolated conducting sphere and the expression of the time domain of the electrostatic field energy. Taking low earth orbit and geosynchronous orbit for example, we discuss the potential of isolated conducting sphere, static load and the characteristics of the electrostatic field energy. The influences of space environment parameters and the size of the conducting sphere radius on surface charging are analyzed. The laws of the time domain of isolated conductor surface charging in plasma environment are summarized.
Two-dimensional electron Gas in ZnMgO/ZnO heterostructures
Authors: Zhang Yang  , Gu Shu-Lin  , Ye Jian-Dong  , Huang Shi-Min  , Gu Ran  , Chen Bin  , Zhu Shun-Ming  , Zhen You-Dou  ,   Nanjing National Laboratory of Microstructures & Dept. of Electronic science and engineering, Nanjing University, Nanjing 210093, China
Published: December 2020

Based on the band structure and related theoretical model of two-dimensional electron gas (2DEG), the dependence of the distribution of 2DEG on the thickness of ZnMgO barrier and related Mg content in ZnMgO/ZnO heterostructures has been computed by self-consistently solving the coupled Schrodinger and Poisson equations. Computation results reveal a critical thickness of the ZnMgO barrier for 2DEG formation, with no 2DEG occurring as the barrier thickness is below the critical value. When the thickness is above the value, the density of the 2DEG increases linearly with the thickness of ZnMgO barrier and saturates finally. The density of the 2DEG also shows a strong dependence on the Mg content in the ZnMgO barrier, with an obvious increase obtained as the Mg content enhances. At the same time, we compare the computed results with experimental data reported in the references with a certain degree of consistence obtained. Explanations and discussions of the above comparison have been presented in the study from the views of polarization effects and band structure.
Fault diagnosis for permanent magnet synchronous generator under chaos conditions：LMI approach
Authors: Wu Zhong-Qiang  , Yang Yang  , Xu Chun-Hua  ,   Key Lab of Industrial Computer Control Engineering of Hebei Province, College of Electric Engineering, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

The permanent magnet synchronous wind power generator is investigated, and its mathematical model is established in two-phase synchronous rotating coordinates. By a time scaling transformation and a linear affine transformation, the chaos model is obtained, and the chaos phenomena occur when the model parameters are in a certain range and under running conditions. Then, an uncertain nonlinear model of permanent magnet synchronous wind power generator is established, and a fault observer is designed. When faults occur, the fault observer can estimate the fault quickly and accurately. Simulation results show that the fault observer based on linear matrix inequality approach can diagnosis the fault rapidly and accurately.
Terminating spiral waves and spatiotemporal chaos in heart by synchronous repolarization
Authors: Zhou Zhen-Wei  , Wang Li-Li  , Qiao Cheng-Gong  , Chen Xing-Ji  , Tian Tao-Tao  , Tang Guo-Ning  ,   College of Physical Science and Technology, Guangxi Normal University, Guilin 541004, China
Published: December 2020

In order to simulate the phenomenon that electric shock defibrillation shortens action potential duration, the synchronous repolarization process is introduced into Luo-Rudy phase I model of cardiac tissue. Effects of synchronous repolarization on dynamics of spiral waves and spatiotemporal chaos are investigated. Numerical results show that when the control period is small, the synchronous repolarization can effectively eliminate spiral waves and spatiotemporal chaos. However, the synchronous repolarization can only eliminate spiral waves or spatiotemporal chaos under some control parameters. When spiral waves cannot be controlled, the transition from spiral wave to spatiotemporal chaos or the spiral wave with longer period and wavelength is observed. The control mechanism is analyzed.
Nonlinear prediction of small scale network traffic based on local relevance vector machine regression model
Authors: Meng Qing-Fang  , Chen Yue-Hui  , Feng Zhi-Quan  , Wang Feng-Lin  , Chen Shan-Shan  ,   School of Information Science and Engineering, University of Jinan, Jinan 250022, China; Shandong Provincial Key laboratory of Network Based Intelligent Computing, Jinan 250022
Published: December 2020

Based on the nonlinear time series local prediction method and the relevance vector machine regression model, the local relevance vector machine prediction method is proposed and applied to predict the small scale traffic measurement data, and the BIC-based neighbor point selection method is used to choose the number of nearest-neighbor points for the local relevance vector machine regression model. We also compare the performance of the local relevance vector machine regression model with the feed-forward neural network optimized by particle swarm optimization for the same problem. Experimental results show that the local relevance vector machine prediction method whose neighboring points have been optimized can effectively predict the small scale traffic measurement data, can reproduce the statistical features of real small scale traffic measurements, and the prediction accuracy of the local relevance vector machine regression model is superior to that of the feedforward neural network optimized by PSO and the local linear prediction method.
Influence of central beamstop on ptychographic coherent diffractive imaging
Authors: Liu Hai-Gang  , Xu Zi-Jian  , Zhang Xiang-Zhi  , Guo Zhi  , Tai Ren-Zhong  ,   Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

A beamstop is commonly used in coherent diffractive imaging (CDI) experiments to collect more high-angle diffraction signals. But it causes the low-frequency signals missed, which can make CDI reconstruction unstable or even fail. In this work, a systematic simulation investigation of the effects of the missing low-frequency signals on the quality of reconstructed images of ptychographic CDI (PCDI) is performed using the ptychographic iterative engine algorithm. We found that the robustness of PCDI to the beamstop is much higher than that of the plane-wave CDI, and a smaller incident probe or a larger probe overlap ratio ( 70%) can further decrease the negative influence of missing low-freqency signals on the reconstruction image. The probe scanning position error will be the main degrading factor of PCDI instead of the beamstop in the higher overlap cases, and needs to be corrected in experiments by using high precision motors or adopting the position refinement algorithms. Our results provide quantitative guidelines for the usage of beamstops in ptychographic CDI experiments.
Effect of carrier envelope phase on the above threshold ionization under resonant condition
Authors: Tian Yuan-Ye  , Wei Shan-Shan  , Guo Fu-Ming  , Li Su-Yu  , Yang Yu-Jun  ,   Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
Published: December 2020

By solving the three-dimensional time-dependent Schrödinger equation, we have theoretically investigated the variation of photoelectron spectroscopy and angular distribution of hydrogen atom with carrier envelope phase (CEP) under the resonant condition. The results show that the intensity of photoelectron spectroscopy is strongly dependent on CEP near the resonant position; and the angular momentum quantum number of resonant initial-ionized state can be determined by further analyzing each partial wave. In addition, we can detect the information of initial phase of multi-cycle pulses with high accuracy by utilizing the information of angular distribution of photoelectron.
Theoretical analysis of scanning spectral filter method for coherent intensity contrast enhancement in femtosecond laser system
Authors: Ma Zai-Ru  , Sui Zhan  , Zhou Gui-Yong  , Sun Nian-Chun  , Wang Yi-Shan  , Wang Xiang-Ling  , Zhang Bin  , Zhang Rong-Zhu  ,   College of Physics and Chemistry, Xihua University, Chengdu 610064, China;,   Research Center of Laser Fusion CAEP, Mianyang 621900, China;,   College of Electronics Information, Sichuan University, Chengdu 610064, China;,   Xi’an Institute of Optics and precision Mechanics, state Key Laboratory of Transient Optics and Photonics, Xi’an 710119, China
Published: December 2020

A scanning spectral filter method is proposed for improving the intensity contrast originating from the phase ripple in the femtosecond chains, which is made using the character that the instantaneous frequency varies with the time approximately linearly for the chirped pulse in the time-frequency domain. The scanning spectral filtering for reducing the pre-pulse and post-pulse intensity is analyzed in the time-frequency domain by using the short-time Fourier transformation method. Results show that the coherent intensity pulse contrast can be improved by 0.41F2 for the chirped pulse or the compressed pulse, and the transmission efficiency of the chirped pulse can exceed 90% when the synchronizing time of the jitter ranges from -2 ps to 2 ps and the chirp rate p from 0.9C/T2 to 1.1C/T2.
The Noether conserved quantity of Lie symmetry for discrete difference sequence Hamilton system with variable mass
Authors: Xu Rui-Li  , Fang Jian-Hui  , Zhang Bin  ,   College of Science, China University of Petroleum, Qingdao 266555, China
Published: December 2020

In this paper the Lie symmetry and Noether conserved quantity of a discrete difference sequence Hamilton system with variable mass are studied. Firstly, the difference dynamical equations of the discrete difference sequence Hamilton system with variable mass are built. Secondly, the determining equations and the definition of Lie symmetry for difference dynamical equations of the discrete difference sequence Hamilton system under infinitesimal transformation groups are given. Thirdly, the forms and conditions of Noether conserved quantities to which Lie symmetries will lead in a discrete mechanical system are obtained. Finally, an example is given to illustrate the application of the results.
Theoretical and experimental study of plasma directional antenna array
Authors: Huang Fang-Yi  , Shi Jia-Ming  , Yuan Zhong-Cai  , Wang Jia-Chun  , Xu Bo  , Chen Zong-Sheng  , Wang Chao  ,   State Key Laboratory of Pulsed Power Laser Technology, Key Laboratory of Anhui Province of Infrared and Low Temperature Plasma, Electronic Engineering Institute, Hefei 230037, China
Published: December 2020

Domestic scholars are often concerned with the characteristics of the plasma cylindrical antenna and the plasma reflector antenna. However, foreign scholars have begun to study the plasma array antenna and used it to design smart antenna. In order to understand this new design idea, based on the plasma electromagnetic scattering theory, a theoretical and experimental study on the directive circular antenna array with a center element driving is presented. A sixteen-element plasma passive oscillator circular array, the mechanism of whose single-beam and multi-beam is transmitting, is established. And an experimental system is established to test the radiation result of circular antenna array. The measured results of radiation patterns are in good agreement with the computational values, verifying that electromagnetic waves can be directional and multi-beam transmitted in this circular antenna array. The advantages of this antenna array are fast switching of the radiation parameters, rapid reconstruction, radar stealth and so on.
Investgation of gas puffing and supersonic molecular beam injection density feedback expriments on EAST
Authors: Zheng Xing-Wei  , Li Jian-Gang  , Hu Jian-Sheng  , Li Jia-Hong  , Cao Bin  , Wu Jin-Hua  ,   Institute of Nuclear Science and Technology, USTC, Hefei 230027, China;,   Institute of Plasma Physics, Hefei 230031, China
Published: December 2020

To achieve desirable plasma density control, supersonic molecular beam injection (SMBI) feedback control system has been developed on EAST tokamak recently. The performance of SMBI is compared with that of gas puffing feedback system. The performance of pulse width mode is better than that of pulse amplitude mode when gas puffing is used for density feedback control. In one-day experiment scenario, the variation of gas input and wall retention can be clarified into two stages. In the first stage the retention ratio is as high as 80%–90%, and the gas input is of about the order of 1022. However, in the second stage, the retention ratio is in a range of 50%–70%. The gas input of a single discharge is small and the net wall retention grows slowly. The result of SMBI feedback control experiment is also analyzed. The shorter delay time of SMBI makes it more quickly to feedback control the plasma density. Result shows that, compared with gas puffing, the gas input of SMBI decreaseds ～ 30% and the wall retention is reduced ～ 40%. This shows SMBI’s advantage for the long pulse high-density discharges in EAST.
Preliminary experimental study on implosion dynamics and radiation character of Z-pinch dynamic hohlraum
Authors: Jiang Shu-Qing  , Ning Jia-Min  , Chen Fa-Xin  , Ye Fan  , Xue Fei-Biao  , Li Lin-Bo  , Yang Jian-Lun  , Chen Jin-Chuan  , Zhou Lin  , Qin Yi  , Li Zheng-Hong  , Xu Rong-Kun  , Xu Ze-Ping  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The Z-pinch dynamic hohlraum (ZPDH), as implemented on qiangguang-1 facility at NINT, is composed of an annular tungsten plasma that implodes onto a coaxial foam convertor. The collision between tungsten Z pinch and foam convertor launches a strong shock. The shock generates a strong radiation pulse, referred as the first radiation power peak, then the radiation is trapped by the tungsten Z pinch. As pinch diameter decreases, the second radiation power pulse rises and acts as the main power peak. The radiation and dynamic characteristics do not show obvious difference between the 8 mm and 12 mm wire array configurations. Hence, it is important to notice that the foam reduces the influence of global instability generated by MRT instability on stagnated pinch, especially reduces the growth of m=0 and m=1 MHD instability.
Serial ferroelectric memory ionizing radiation effects and annealing characteristics
Authors: Zhang Xing-Yao  , Guo Qi  , Lu Wu  , Zhang Xiao-Fu  , Zheng Qi-Wen  , Cui Jiang-Wei  , Li Yu-Dong  , Zhou Dong  ,   Xinjiang Technical Institute of Physics & Chemistry, CAS., Urumuqi 830011, China;,   Xinjiang Key Laboratory of Electric Information Materials and Devices, Urumuqi 830011, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Ferroelectric random memory was irradiated and annealed by 60Co-rays, total ionizing dose (TID) failure mechanism and annealing characteristics of the device were analyzed. DC, AC and function parameters of the memory were tested in radiation and annealing by very large scale integrated cicuit (VLSI) test system, the radiation-sensitive parameters were obtained through analyzing the test data. Ionizing radiation produced a large number of oxide trapped charges, leading MOS transistor threshold to the negative drift in memory peripheral control circuit. Additional electric field was introduced in the ferroelectric film, and leakage current was produced since the Schottky emission or space-charge-limited current occurred. The number of shallower levels and metastable state oxide trapped charges are more than the deep level oxide trapped charge, so that the device functions and the radiation-sensitive parameters were restored in the annealing.
Study on early stage of phase-separation process with low volume ratio using lattice gas model in three dimensions
Authors: Zheng Hui  , Zhang Chong-Hong  , Sun Bo  , Yang Yi-Tao  , Bai Bin  , Song Yin  , Lai Xin-Chun  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China;,   Institute of Modern Physics, China Academy of Science, Lanzhou 730000, China;,   National Key Laboratory for Surface Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621907, China
Published: December 2020

The phase separation process in a three-dimensional lattice gas model with a low volume ratio c=0.01 was studied. Using Monte Carlo simulation, the evolution behaviors of sc, fcc, bcc lattices, and 5 relative temperatures T/Tc=0.450.85 were simulated. It was found that the structure factor functions did not satisfy the scaling relationship, and the growth index was 1/6, less than the value of Lifshitz-Slyozov theory.
Behaviors of lattice distortions in the spin 1/2 antiferromagnetic XY model with quasiperiodic modulation
Authors: Li Peng-Fei  , Cao Hai-Jing  , Zheng Li  , Jiang Xiu-Li  ,   Department of Mathematics and Physics, Shanghai University of Electric Power, Shanghai 200090, China
Published: December 2020

The behaviors of lattice distortions in the spin 1/2 antiferromagnetic XY model with Thue-Morse quasiperiodic modulation are investigated by the method of exact diagonalization. It is found that the lattice distortion at each site has the character intermediate between the periodic and random systems. For weaker or stronger quasiperiodic modulation, the lattice distortion may increase or decrease with strengthening of the modulation amplitude, respectively. The results also indicate that the energy gaps of ground states are strongly affected by the quasiperiodic modulation
Microstructure and magnetic-field-induced strain in Mn70Fe30-xCox (x=0,2,4) alloys
Authors: Guo Qi-Yun  , Peng Wen-Yi  , Yan Ming-Ming  , Guo Feng-Li  ,   School of Materials Science and Engineering, Nanchang University, Nanchang 330031, China
Published: December 2020

Mn70Fe30-xCox (x=0, 2, 4) alloys were prepared using non-consumable vacuum arc furnace smelting followed by subsequently solution treatment. The effect of Co content on the property of magnetic-field-induced strain (MFIS) was studied by means of X-ray diffraction (XRD), photomicrograph, differential scanning calorimetry (DSC), and resistance strain gauge method. Result shows that Mn70Fe30-xCox (x=0, 2, 4) alloys are of singe phase at room temperature. With the increase of Co content, the Nel temperatures of alloys decrease, which are all higher than room temperature, i.e., the alloys exhibit antiferromagnetic austenite microstructure at room temperature after quenching from high temperatures. Alloys possess much larger MFIS with the increase of Co content, and taking Mn70Fe26Co4 as an example, when the magnetic field strength is 1.1 T, the MFIS is at its maximum, 610-5.
Secondary electron emission from carbon Foils by Ne2+ near Bohr velocity
Authors: Yu Yang  , Zhao Yong-Tao  , Wang Yu-Yu  , Wang Xing  , Cheng Rui  , Zhou Xian-Ming  , Li Yong-Feng  , Liu Shi-Dong  , Lei Yu  , Sun Yuan-Bo  , Zeng Li-Xia  ,   Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

We have measured secondary electron emission yields in forward and backward directions from the carbon foils with different thicknesses, which are penetrated by Ne2+ ion of an energy from 2 to 25 keV/u. In the experiment, the contributions of projectile potential energy deposition, electronic energy loss and recoil atom to the forward and backward electron emission yields have been studied systematically by changing the projectile ions energy. Results show that the ions potential energy deposition only have the impact on the backward electron emission yield, while the forward and backward electron emission yields increase approximately linearly with the increase of the electron energy loss at the exit and entrance surfaces of the thin film respectively. When the electron energy loss is low, the impact of recoil atoms on the electron emission cannot be neglected.
Effects of different substrates and CdCl2 treatment on the properties of CdS thin films deposited by magnetron sputtering
Authors: Zhang Chuan-Jun  , Wu Yun-Hua  , Cao Hong  , Gao Yan-Qing  , Zhao Shou-Ren  , Wang Shan-Li  , Chu Jun-Hao  ,   National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083, China;,   Shanghai Center for Photovoltaics, Shanghai 201201, China
Published: December 2020

CdS films were deposited on corning 9059 glass, FTO, ITO and AZO substrates by r.f. magnetron sputtering, and annealed at 380 ℃ in CdCl2+ dry air. Effects of different types of substrate and thermal annealing on the morphology, structure and optical properties were investigated. Field emission scanning electron microscope shows: the morphology of as-deposited and annealed CdS thin films on different substrates is different, grain size and surface roughness increase significantly with annealing. XRD diffraction patterns show: the structure of as-deposited and annealed CdS thin films on different substrates are mixed phase structure of hexagonal and cubic phases, there is a preferential orientation of the crystallits with the hexagonal (002) and cubic (111) peak for as-deposited and annealed CdS films on corning 9059 glass, FTO, and AZO substrates, for as-deposited CdS film on ITO substrate there is no preferentially oriented diffraction peaks, but has highly oriented with hexagonal (002) or cubic (111) peak after annealing; UV-Vis spectrophotometer spectrum analysis shows: the average transmittance in visible spectrum of CdS thin films deposited on AZO, FTO, ITO and Corning 7059 glass substrates in turn decreases, annealing increases the corresponding substrate of CdS films in visible light transmittance, reduces the optical absorption coefficient; annealing significantly increases the band gap of CdS films on different substrates. Analysis reveals that the performance comes from the result of different types of substrate and annealing process for morphology and structure of CdS thin films, and the band tail states changes, due to variation of doping concentration.
Transition control of bifurcated frequencies in inductive power transfer systems through time delay perturbation
Authors: Tang Chun-Sen  , Sun Yue  , Dai Xin  , Wang Zhi-Hui  , Su Yu-Gang  , Hu Aiguo  ,   College of Automation, Chongqing University, Chongqing 400044, China;,   School of Engineering, The University of Auckland, Auckland 1010, New Zealand
Published: December 2020

Frequency bifurcation is the most typical nonlinear phenomenon in inductive power transfer (IPT) systems. Two stable and one unstable resonant frequencies exist in a bifurcated IPT system while the unstable one lies between the two stable frequencies. To achieve the transition control of the bifurcated frequencies, this paper proposes an orbit shift method through a time delay perturbation, which is applied to the feedback signal. The phase trajectory can be shifted among the stable limit cycle attractors by adjusting the parameters of the time delay perturbation. The operation principle and implementation of the proposed method have been investigated in detail on an example IPT system with series tuned primary and secondary circuits. Both simulation and experimental results have verified the validation of the proposed method. The research results can provide useful theoretical reference for transition control of other similar multiple-attractor bifurcation behaviors.
Design and simulation of W-band BWO based on slotted single-grating and cylindrical beam
Authors: Xie Wen-Qiu  , Wang Zi-Cheng  , Luo Ji-Run  , Liu Qing-Lun  , Dong Fang  ,   Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

A slotted rectangular single-grating with a cylindrical electron beam was proposed as the beam-wave interaction circuit of a W-band backward wave oscillator (BWO). Analysis on the slow-wave characteristics of the structure was done utilizing three-dimensional electromagnetic field simulation software CST-MWS. Results are as follows: The new structure can have a much larger coupling impedance than traditional one; the bandwidth of the fundamental mode can be broadened and the fundamental mode is unlikely to compete with the high-order mode. The loss caused by the skin effect is reduced. The structure was applied to design a W-band backward wave oscillator whose band center is 94 GHz. A simple slow-wave transition part, and the output coupler and terminal matching attenuator were designed, the parameters of which were optimized to obtain good signal transmission. Using CST-PS’s PIC solver, a three-dimensional large-signal particle simulation was done. After setting a suitable electron current and other parameters, watts scale peak output power was obtained within a wide frequency band by adjusting the working voltage, and the electronic efficiency in the band was greater than 1%.
Magnetic charge constrained the mass-radius ratio of neutron star
Authors: Sun Xu-Dong  , Chen Ju-Hua  , Wang Yong-Jiu  ,   Institute of Physics, Hunan Normal University, Changsha 410081, China
Published: December 2020

In this paper, we use the wave equation of charged mass point to prove the existence of magnetic monopole. And according to Rubakov-Callan model there could be a lot of magnetic monopoles in neutron stars. Then using the structure equation of neutron stars we obtain upper limit and lower limit of mass-radius ratio for magnetic charged neutron star.
Application of mean value theorem of integrals in the efficiency callibration technology of radioactive xeon sample
Authors: Tian Zi-Ning  , Ouyang Xiao-Ping  , Zeng Ming  , Cheng Zhi-Wei  ,   Key Laboratory of Particle and Radiation Imaging of Ministry of Education, Department of Engineering Physics, Tsinghua University, Beijing 100084, China;,   Research Center for Radiation Detection, Northwest Institute of Nuclear Technology, Xi’an 710024, China
Published: December 2020

The radioxenon from environmental samples is usually measured by the HPGe detector. The relative measurement method is used in the analysis process. However, the half-life of radioactive isotopes of xenon is too short to be used as a standard, so the calibration of the HPGe detector is difficult. In order to resolve this problem, the mixed disk sources are used to simulate the efficiencies of four radioactive xenon isotopes, and the mean value theorem of integrals is adopted, thereby improving the accuracy and simplifying the process. The samples are obtained by the xenon system under environment of high activity of radon, then the γ spectrum with regions of interest for 133Xe are obtained by the sample measurement. The activity of 133Xe is given by using the detection efficiency of disk source at a certain source-detector distance. The detection efficiency simulated by disk source is consistent with the detection efficiency of gas cell. Therefore, the simulated technology of disk source and mean value theorem of integrals are identified to be correct and effective.
Interactional potential of helium atom and hydrogen halide molecules
Authors: Wang Xiao-Lu  , Linghu Rong-Feng  , Song Xiao-Shu  , Lü Bing  , Yang Xiang-Dong  ,   School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, China;,   School of Physics and Electronic Science, Guizhou Normal College, Guiyang 550018, China;,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
Published: December 2020

According to ab initio calculations, the differential scattering cross sections between He and HF, HCl, HBr are calculated and compared with experimental data. The results show that the calculation method can calculate comparatively accurate interactional potential. As halogen atom radius increases, at 0°, the minimum of interactional potential shallows, the position of potential well moves into the distance, and anisotropic property becomes prominent, while at 180°, the minimum of interactional potential depens, the position of potential well moves into the distance, and the isotropic property becomes obvious. The potential well depth under T structure is larger than that of linear structure. With the increases of halogen atoms radius, a more spherical symmetry is exhibited, and it can be seen obviously that contributions of radial coefficients V0, V1, V2, V3, ··· decrease gradually, which is important to understand the study of excited state dynamics.
A theoretical study on impulse approximation of (e, 2e) reactions
Authors: Xue Si-Min  ,   School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070, China
Published: December 2020

The triple differential cross sections for electron impact ionization hydrogen (e, 2e) reactions are calculated as an example by use of the impulse approximation and Born approximation model at different coplanar asymmetric geometries. The results of the present work are compared with experimental data. The structures of the cross sections and the physical nature of these structures are discussed in detail. Moreover, the exchange effect contribution to the cross section is also discussed, which supports our earlier conclusions.
A new conformal technique of inhomogeneous cells based on electric field strength weighted values
Authors: Sun Ya-Xiu  , Jiang Qing-Hui  ,   College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

In this paper, a new method of using the electric field numerical weight to process the inhomogeneous cells is proposed, which is to resolve the problems such as high errors and parallel direction excluded in the existing finite-difference time-domain method. Instead of deriving average dielectric constant, the new method weights the electric field strength, which is the true solving variables, according to the mean value theorem, and then the length of the integral path is multiplied by the weight. In the new method both the discontinuous effects of inhomogeneous Ampere cell and the ones of inhomogeneous Faraday cell are taken into account, so it is accurate, easy to implement, versatile, and applicable to any of the various positional relationships between the dielectric interface and the electric field strength variable. A numerical model of dielectric filled circular waveguide is used for the numerical calculation and simulation, in which the deviations of the characteristic roots in two-dimensional TE mode solved by different methods from the theoretical ones are compared, and the anisotropies of different methods are also compared. The numerical result shows that the characteristic roots solved by the presented method are closer to the theoretical ones and the anisotropy caused by the proposing method is lower, which proves that this method is more efficient to process the inhomogeneous cells.
A diagnosis of gas-phase processes in a high pressure DC CH4/H2 plasma
Authors: Zheng Shi-Jian  , Ding Fang  , Xie Xin-Hua  , Tang Zhong-Liang  , Zhang Yi-Chuan  , Li Huan  , Yang Kuan  , Zhu Xiao-Dong  ,   CAS key Laboratory of Basic Plasma Physics, Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

In this work, gas phase processes in a high pressure (～100 Torr) DC hydrocarbon plasma are investigated in situ by optical emission spectroscopy and mass spectroscopy. In the high pressure plasma, optical emission characteristics of glow layers are obviously different. C2, CH dominated band spectra and discrete spectra are distinctively observed in the positive column, whereas the emission intensity is found to decrease in the anode region. In the cathode region, a large number of complicated spectra are detected, which indicates the intensive interaction between the cathode and plasma under high pressure induces complicated atomic and molecular processes. With the the increase of pressure, electron excitation temperature decreases while gas rotational temperature goes up. High methane concentration causes increases in C2, C2H2 and C2H4 but a reduction in C2H6. Those suggest that the effect of gas temperature on gas phase process is significantly enhanced under high pressure.
Simulation study of effect of initial melt temperature on microstructure evolution of liquid metal Ni during solidfication process
Authors: Deng Yang  , Liu Rang-Su  , Zhou Qun-Yi  , Liu Hai-Rong  , Liang Yong-Chao  , Mo Yun-Fei  , Zhang Hai-Tao  , Tian Ze-An  , Peng Ping  ,   School of Physics and Microelectronics Science, Hunan University, Changsha 410082, China;,   College of Materials Science and Engineering, Hunan University, Changsha 410082, China
Published: December 2020

A molecular dynamics simulation study is performed on the effect of the thermal history of initial melt temperature on the microstructure evolution in solidification process of liquid metal Ni by means of quantum Sutton-Chen n-body potential. The pair distribution function g(r) curves, the bond-type index method, the cluster-type index method and the three-dimensional (3D) visualization method are used to analyze the microstructure evolution in the solidification process. It is found that the initial melt temperature plays a critical role in the evolution of microstructures, but it is not obvious in liquid and supercooled states and the effects can be fully displayed only near the crystallization transition temperature Tc. The 1421 and 1422 bond-types or the FCC (12 0 0 0 12 0) and HCP (12 0 0 0 6 6) cluster in the system play the critical role in the microstructure evolution. The results show that at a cooling rate of 11012 K/s with different initial melt temperatures, the solidification structures of liquid metal Ni are always crystallized, but the numbers of the main bond-types and clusters have a vast varying range, and it does not vary linearly with the decrease of initial melt temperature. However, the system energy changes linearly with the decrease of initial melt temperature. Through the 3D visualization method, it is also found that atoms of the same cluster are gathered in the same layer when the system has a higher initial temperature, and these layers would be scattered when the initial melt temperature decreases. The 3D visualization method would help to deeply investigate the evolution mechanisms of microstructures in liquid metals during solidification.