bluuebunny/crossref_metadata_2025 huggingface dataset:
Research and application of multi-chamber heart magnetic field model
Authors: Zhu Jun-Jie  , Jiang Shi-Qin  , Wang Wei-Yuan  , Zhao Chen  , Wang Yong-Liang  , Li Wen-Sheng  , Quan Wei-Wei  ,   School of Electronics and Information Engineering, Tongji University, Shanghai 201804, China;,   Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China;,   Digital Medical Research Center, Shanghai Medical College of Fudan University, Shanghai Key Laboratory of Medical Imaging Computing and Computer Assisted Intervention, Shanghai 200032, China;,   Department of Cardiology, Rui Jin Hospital and College of Medicine, Shanghai Jiao Tong University, Shanghai 200025, China
Published: December 2020

A multi-chamber heart magnetic field model with two atria and two ventricles, boundaries of which were picked up from a magnetic resonance imaging, was established based on the boundary element method (BEM). Moreover, the model-based 36-channel cardiac magnetic field data and magnetic field maps at a specific time were analyzed. We also studied the heart electrical activity during ST-T segment from patients with complete right bundle branch block (CRBBB) and complete left bundle branch block (CLBBB) by the model, respectively. Results show that the model-based magnetic field map generated by the electrical excitation with a moving single current dipole in single bundle branch is similar to the magnetocardiogram (MCG) of the CRBBB/CLBBB patient acquired using a superconducting quantum interference device (SQUID) in cardiac repolarization. It demonstrates that the multi-chamber heart BEM model can be used to study cardiac magnetic inverse problem of CLBBB/CRBBB patient. In addition, two evaluation criteria are given as follows: the ratio of the maximum on the magnetic field strength measurement plane in the multi-chamber model to that in the single-chamber model; and the ratio of root mean squares of the magnetic field strength at the 36 measurement points of the two models. This result indicates that the magnetic field maps generated by the multi-chamber heart model are close to the measured MCG maps. In this model, the strength and topography of the magnetic field lie in the conductivity parameters of cardiac tissues, the position and the number of the equivalent current dipoles.
The distribution of large-scale drought/flood of summer in China under different configurations of monsoon and polar vortex
Authors: Ji Fei  , Zhao Jun-Hu  , Shen Qian  , Zhi Rong  , Gong Zhi-Qiang  ,   College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;,   Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China
Published: December 2020

From the view of warm and cold system configuration, an East Asian summer monsoon (EASM) index and the Asian polar vortex area (APVA) index in July were selected, and their climatic characteristics and relationships with the distribution of summer rainfall over China were analyzed. On this basis, the relationships between the EASM and APVA in July from 1951 to 2010 were divided into four types: type A, stronger monsoon and bigger polar vortex area; type B, stronger monsoon and smaller polar vortex; type C, weaker monsoon and bigger polar vortex; type D, weaker monsoon and smaller polar vortex. Based on the method of composite analysis, we found that on the seasonal scale, large-scale distributions of summer droughts and floods over China showed multi-faceted characteristics in different configurations of the EASM and the APVA in July. In A type years, the summer rainfall of China was overall less than normal, the region between eastern parts of Northwest and the western parts of North China, and the eastern regions of Northeast suffered from flood, while Yangtze River valley suffered from drought; in B type years, it had flood in South and drought in North, and the precipitation in the south/north of northern regions in the Yangtze River valley was more/less than normal; in C type years, North China was flooded and South of China suffered from drought, while the precipitation in the northern parts of the Huaihe River valley was more than normal; and in the middle and lower reaches of Yangtze River and to its south the precipitation was less than normal; in D type years, the overall summer rainfall was more than normal, with the precipitation core lying in the middle and lower reaches of Yangtze River. Thus, it can be seen that the distribution of summer rainfall is not only related to the EASM, but also to the PAVA in July. Under different configurations of the both, the precipitation and its distribution display obvious difference and regularity, which, to some extent, have effects on predicting the total trend of summer rainfall. Besides, by discussing the anomaly characteristics of atmospheric circulation due to different configurations and by analyzing the influences of different meteorological factors on the relationship between the monsoon and the polar vortex, we can conclude that the difference and regularity of summer rainfall directly depend on the configurations of circulation. Among them, the western Pacific subtropical high and the blocking situation in the mid and high latitudes are the overriding factors.
Rain attenuation prediction at Ka band based on difference stationary timeseries
Authors: Zhang Yi  , Da Xin-Yu  ,   School of Information and Navigation, Air Force Engineering University, Xi’an 710077, China
Published: December 2020

To cope with the issue of multi-parameter and intricate calculation of classical models in predicting rain attenuation in Ka band, a method is presented to reduce the complexity by utilizing difference stationary time-series. By this method, a prediction model is established based on the difference transform of leader rain attenuation data, and parameters of stationary time-series are estimated to compute the rain attenuation at each frequency point in Ka band for achieving linear prediction. Simulations show that the prediction precision depends on prediction interval, the number of time-series and the frequency of difference. Compared with Dissanayake-Allaut-Haidara model, the proposed model has a prediction error of less than 10-3 when prediction interval is 0.1 GHz and the number of time-series is 20 with quadratic difference. Furthermore, the simulation results also indicate that the proposed method is simple and practical due to the fact that influence of polarization mode on model parameters may be ignored.
Tripartite entanglement properties of coupled three atoms in cavity quantum electrodynamics
Authors: Lu Dao-Ming  ,   College of Mechanic and Electronic Engineering, Wuyi University, Wuyishan 354300, China
Published: December 2020

In this paper we consider the case that three identical two-level atoms are trapped in a single-mode cavity which is in a weak coherent state initially, and there is an interaction between two atoms. The tripartite entanglement dynamics among atoms is studied. The influences of atom-atom coupling constant and intensity of the cavity field on the tripartite entanglement among atoms are discussed. The results obtained using the numerical method show that the tripartite entanglement among atoms is strengthened with the increase of intensity of the cavity field; on the other hand, it is weakened with the increase of the coupling constant between atoms.
Stochastic response of smooth and discontinuous oscillator under additive and multiplicative Poisson white noise excitation
Authors: Yue Xiao-Le  , Xu Wei  , Zhang Ying  , Wang Liang  ,   Department of Applied Mathematics, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

The stochastic response of the smooth and discontinuous (SD) oscillator under additive and multiplicative Poisson white noise excitation is studied by the generalized cell mapping method. Based on the digraph analysis algorithm, the attractors, basins of attraction, basin boundaries, saddles and invariant manifolds of the SD oscillator can be obtained. The transient and stationary responses of the SD oscillator under Poisson white noise excitation are computed based on the matrix analysis algorithm. It can be found that there is a close relationship between the evolution direction of probability density and the unstable manifold. Monte Carlo results are used to verify the efficiency and accuracy of the matrix analysis algorithm.
Theoretical and static experiment research on all optical solid state streak camera
Authors: Liang Ling-Liang  , Tian Jin-Shou  , Wang Tao  , Li Fu-Li  , Gao Gui-Long  , Wang Jun-Feng  , Wang Chao  , Lu Yu  , Xu Xiang-Yan  , Cao Xi-Bin  , Wen Wen-Long  , Xin Li-Wei  , Liu Hu-Lin  , Wang Xing  ,   Xi’an Institute of Optics and Precision Mechanics of Chinese Academy of Sciences, State Key Laboratory of Transient Optics and Photonics, Xi’an 710119, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100039, China;,   Xi’an Transportation University, Science College, Xi’an 710049, China
Published: December 2020

All optical solid state streak camera is to carry out the process of deflecting and scanning of the signal light which is coupled into the core of the waveguide, with spatially-modulated pump pulse exciting the light deflector, through precisely controlling the time delay between signal light and pump light. Not only can it solve the problems existing in the traditional photoelectron streak camera such as the decrease of the dynamic range caused by space charge effect and incapability of detecting the infrared light signal for photoelectric cathode, but also it has the advantages of simple structure, systemic stability. And the theoretical temporal resolution can reach up to picosecond scale even sub picosecond scale. For the AlxGa1-xAs/GaAs/AlxGa1-xAs planar waveguide light deflector, we discuss in detail the change of the refractive index of the GaAs with time under the common influences of band filling, band gap shrinkage and free carrier absorption effect; when the change of the refractive index is on the order of 0.01 and the ratio of the signal spot size to the width of the waveguide p=0.5, the theoretical temporal resolution can reach 2 ps; finally, the theoretical spatial resolution is calculated to be 17 lp/mm according to the condition of static experiment, while the experimental results show that spatial resolution is 9 lp/mm.
Design and theoretical research of an ultrafast time-resolved velocity interferometer
Authors: Fan Wei  , Gu Yu-Qiu  , Zhu Bin  , Shui Min  , Shan Lian-Qiang  , Du Sai  , Xin Jian-Ting  , Zhao Zong-Qing  , Zhou Wei-Min  , Cao Lei-Feng  , Zhang Xue-Ru  , Wang Yu-Xiao  ,   Department of Physics, Harbin Institute of Technology, Harbin 150001, China;,   Science and Technology on Plasma Physics Laboratory, Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

In single-shot, ultrafast time-resolved measurements, the combination of linear chirp pulse and spectrometer is a common way. In this paper, according to the time-frequency mapping relationship of linear chirp pulse and utilizing an imaging spectrometer as a recording system, we design a chirped pulse velocity interferometer for the ultrafast measurement of free surface velocity. Theoretical research on the principle and applicability shows that picosecond resolution is achievable and the velocity sensitivity is easily adjustable, which greatly widens applications of the velocity interferometer. The numerical simulation of the measurement process shows that reconstructed velocity signal is well consistent with the given velocity, further confirming the feasibility of the chirped pulse velocity interferometer.
Theory of density-density correlations between ultracold Bosons released from optical lattices
Authors: Li Yan  ,   School of Physics and Electronics, Hunan University of Arts and Science, Changde 415000, China
Published: December 2020

The density-density correlations of ultracold Bosons released from a two-dimensional square optical lattice are investigated based on the quantum phase field U (1) rotor field. With the effects of the particle number fluctuations and the phase degrees of freedom taken into consideration, the theory can be used to describe the cold atom system with strong interaction. Using this theory, the characteristics of ultracold atom gas in the process in which the superfluid state of optical lattice transits to insulating state, are well described. The results show that in the patterns of the density-density correlations, the continuous diagonal lines gradually transit to scattered peaks. The results match the experimental ones. In addition, the effects of the quantum depletion on the density-density correlation are also included in the result, and the relevant conclusions are also consistent with the existing theoretical and experimental results.
Quantum confinement effect on electronic and optical properties of SnS
Authors: Wu Qiong  , Liu Jun  , Dong Qian-Min  , Liu Yang  , Liang Pei  , Shu Hai-Bo  ,   College of Optical and Electronic Technology, China Jiliang University, Hangzhou 310018, China
Published: December 2020

The structural stabilities, electronic and optical properties of SnS bulk, monolayer, and multilayers are systematically studied by using the first-principles calculations within the density-functional theory. Our calculated results indicate that monolayer SnS can be exfoliated from its bulk, and the process is similar to the fabrication of graphene. With the reduction of layer number, the structural stabilities of SnS nanostructures become weak and their band gaps increase due to the quantum confinement effect and the layer interactions. Therefore, the optical properties of SnS can be controlled by adjusting the layer number due to the fact that the optical properties of materials depend on their electronic structures. The main optical absorption peaks of SnS bulk and nanostructures originate from the electron transitions among the orbitals of Sn-5s, 5p and S-2p. Moreover, the optical absorption peaks of SnS show obvious blue shift when SnS structure transforms from its bulk to monolayer. The present study will contribute to the application of SnS materials in the solar cells.
The electronic structure and optical properties of P-doped silicon nanotubes
Authors: Yu Zhi-Qiang  , Zhang Chang-Hua  , Lang Jian-Xun  ,   Department of Electrical Engineering, Hubei University for Nationalities, Enshi 445000, China;,   Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

We perform first-principles calculations in the framework of density-functional theory to determine the effects of P doping on the electronic structure and optical properties of single-walled armchair silicon nanotubes. The calculated results indicate that the band-gap of single-walled armchair silicon nanotubes changes from indirect to direct one, with the P element doped. The top of valence band is determined mainly by the Si-3p electrons, and the bottom of conduction band is occupied by the Si-3p electrons and Si-3s electrons. Moreover, the band gap of single-walled armchair silicon nanotubes decreases and the optical absorption is red-shifted, with the P element doped. The results provide useful theoretical guidance for the applications of silicon nanotubes in optical detectors.
Multilevel switching mechanism for resistive random access memory based on Cu/SiOx/Al structure
Authors: Chen Ran  , Zhou Li-Wei  , Wang Jian-Yun  , Chen Chang-Jun  , Shao Xing-Long  , Jiang Hao  , Zhang Kai-Liang  , Lü Lian-Rong  , Zhao Jin-Shi  ,   School of Electronics Information Engineering, Tianjin Key Laboratory of Film Electronic and Communication Devices, Tianjin University of Technology, Tianjin 300384, China
Published: December 2020

In this paper, resistive switching device based on Cu/SiOx/Al structure is fabricated to examine its resistive switching characteristics and explore its resistive switching mechanisms. By adjusting limiting current, four stable resistance states are obtained. All of the resistive ratios between adjacent resistance states are over than 10. Moreover, the retention data of these four states at room temperature keep stable up to 1000 s. The temperature-dependent measurement and I-V curves fitting results show that the resistive switching mechanisms of the four states are different: resistance states 1 and 2 are due to Ohmic conduction mechanism, resistance state 3 is due to Pool-Frenkel emission, and resistance state 4 is due to Schottky emission mechanism. Subsequently, a resistive switching model for Cu/SiOx/Al structure is proposed.
Ionization parameters of high power microwave flashover on dielectric window surface calculated by particle-in-cell simulation for fluid modeling
Authors: Dong Ye  , Dong Zhi-Wei  , Zhou Qian-Hong  , Yang Wen-Yuan  , Zhou Hai-Jing  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

The particle-in-cell (PIC) simulation method is used to get the reliable ionization parameters of high power microwave flashover and breakdown on dielectric surface for fluid modeling. Firstly, the PIC method is presented briefly, including dynamic equations, secondary emission and Monte-Carlo collision (MCC) between electron and gas atom. Secondary, the fluid global model (GM) is introduced including continuity and energy conservation functions. Finally, by using a 1D3V PIC-MCC code programmed by the authors, the ionization parameters are calculated under different microwave electric-field values, microwave frequencies, gas types and pressures for fluid modeling, including ionization frequency, breakdown delay time, average electron energy, electron energy distribution function (EEDF). The numerical results could be concluded as follows. Average electron energy is unrelated to EEDF type. At middle and low gas pressures, electron energy satisfies Maxwell distribution, and ionization parameters are unrelated to EEDF type. At middle and high gas pressures, ionization parameter is related to EEDF type, and the relevant coefficient X of EEDF tends to be of high older. Different gases have different EEDF types, and the relevant coefficient X of EEDF should be corrected by PIC simulation. The value of X is also related to microwave electric-field value and frequency, and its value increases with the increase of microwave electric-field value and the decrease of microwave frequency. In a fixed range (microwave electric-field value below 7 MV/m, and microwave frequency below 40 GHz), at middle and low gas pressures, the average electron energy increases with the increase of electric-field value and the decrease of microwave frequency rapidly, and the ionization frequency increases and then decreases with the increase of microwave electric-field value and frequency respectively; at high gas pressure, the average electron energy increases with the increase of electric-field value slowly, the ionization frequency increases with the increase of electric-field value, and the average electron energy and ionization frequency are unrelated to microwave frequency.
Optimal closed-loop bandwidth of tip-tilt correction loop in adaptive optics system
Authors: Guo You-Ming  , Ma Xiao-Yu  , Rao Chang-Hui  ,   Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;,   The Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, Chengdu 610209, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Based on the most widely used proportional-integrator controller of the tip-tilt correction loop in an adaptive optical system, the relationship between the optimal closed-loop bandwidth and the atmosphere turbulence as well as the sensor noise is analyzed. Numerical simulation is also performed by using the time serial signals that follow the power spectrum density of the global tilt of Kolmogorov turbulence. Results show that with different atmosphere turbulences and sensor noises, the correction capability of the tip-tilt correction loop can be brought into full play by choosing appropriate closed-loop bandwidth and the residual variance can be reduced.
Effect of stability of X-ray pulsar profiles on range measurement accuracy in X-ray pulsar navigation
Authors: Sun Hai-Feng  , Bao Wei-Min  , Fang Hai-Yan  , Li Xiao-Ping  ,   School of Aerospace Science and Technology, Xidian University, Xi’an 710071, China
Published: December 2020

The Crab pulsar is an isolated rotation-powered pulsar which emits large X-ray fluxes, making it a candidate source for carrying out the X-ray pulsar navigation (XNAV). The long-term stable profiles are considered as the foundation of XNAV. However, systematic studies of the long-term stability of the X-ray pulsar profile and its effect on range accuracy in XNAV are lacking. In this paper, we use the X-ray band (2–16 keV) data monitored by Rossi X-ray timing explorer (RXTE) spacecraft over the latest 11 years, to first investigate the stability of the Crab pulsar including the profiles after the glitches. Furthermore, some measurements of the long-term profile shape, including Pearson correlation coefficient, standard deviation and spectral entropy, are presented both in the time domain and in the frequency domain. In the data processing, the Fourier analysis and cross-correlation are used to deal with the 191 RXTE data sets. With the help of the Cramer-Rao theory, the effect of the profile variation on the error of the range determination in XNAV is studied. Furthermore, after analyzing those errors, the effect of the stability of the Crab pulsar on range determination is confined to more narrow limits. The results demonstrate that the 2–16 keV profiles are almost constant during the period 2001–2012. The profiles after the glitches show no significant discrepancy. The variation of Crab profile inevitably has an influence on the navigation precision to a certain extent. The calculated range error along the pulsar line-of-sight due to the stability of the pulsar profile is 34 m±25 m.
Research on biomolecule-gate AlGaN/GaN high-electron-mobility transistor biosensors
Authors: Li Jia-Dong  , Cheng Jun-Jie  , Miao Bin  , Wei Xiao-Wei  , Zhang Zhi-Qiang  , Li Hai-Wen  , Wu Dong-Min  ,   International Laboratory for Adaptive Bio-nanotechology, Suzhou institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, China;,   Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, China;,   Heifei instituts of physical science, Chinese Academy of Sciences, Hefei 230031, China;,   Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, China
Published: December 2020

In order to enhance the performance of AlGaN/GaN high electron mobility transistor (HEMT) biosensor, millimeter grade AlGaN/GaN HEMT structure have been designed and successfully fabricated. Factors influencing the capability of the AlGaN/GaN HEMT biosensor are analyzed. UV/ozone is used to oxidize GaN surface and then 3-aminopropyl trimethoxysilane (APTES) self-assembled monolayer can be bound to the sensing region. This serves as a binding layer in the attachment of prostate specific antibody (anti-PSA) for prostate specific antigen detection. The millimeter grade biomolecule-gated GaN/AlGaN HEMT sensor shows a quick response when the target prostate specific antigen in a buffer solution is added to the antibody-immobilized sensing area. The detection capability of this biomolecule-gate sensor estimated to be below 0.1 pg/ml level using a 21.5 mm2 sensing area, which is the best result of GaN/AlGaN HEMT biosensor for PSA detection till now. The electrical result of the biomolecule-gated GaN/AlGaN HEMT biosensor suggests that this biosensor might be a useful tool for the prostate cancer screening.
Stochastic resonance in an overdamped monostable system with multiplicative and additive α stable noise
Authors: Jiao Shang-Bin  , Ren Chao  , Li Peng-Hua  , Zhang Qing  , Xie Guo  ,   School of Automation and Information Engineering, Xi’an University of Technology, Xi’an 710048, China
Published: December 2020

In this paper we combine α stable noise with a monostable stochastic resonance (SR) system to investigate the overdamped monostable SR phenomenon with multiplicative and additive α stable noise, and explore the action laws of the stability index α (0 α ≤ 2) and skewness parameter β (-1 ≤ β ≤ 1) of the α stable noise, the monostable system parameter a, and the amplification factor D of the multiplicative α stable noise against the resonance output effect. Results show that for different distributions of α stable noise, the single or multiple low-and high-frequency weak signals detection can be realized by adjusting the parameter a or D within a certain range. For a or D, respectively, there is an optimal value which can make the system produce the best SR effect. Different α or β can regularly change the system resonance output effect. Moreover, when α or β is given different values, the evolution laws in the monostable SR system excited by low-and high-frequency weak signals are the same. The conclusions drawn for the study of single-and multi-frequency monostable SR with α stable noise are also the same. These results will be the foundation for realizing the adaptive parameter adjustment in the monostable SR system with α stable noise.
Single zeptosecond pulse generation from muonic atoms under two-color XUV fields
Authors: Li Zhi-Chao  , Cui Sen  , He Feng  ,   Key Laboratory for Laser Plasma (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

We use the Lewenstein model to study the high harmonic generated for a μp atom exposed to two-color XUV pulses. Calculated results show a super continuum plateau in high harmonic spectrum which is formed when the time delay is 0 and XUV frequencies are 5 and 2.5. By synthesizing the continuous high harmonic spectra, a pulse as short as 130 zeptosecond is obtained. Such a single zeptosecond pulse may work as an ultrafast camera to capture ultrafast processes occurring inside nuclei.
Optical bottle beam generated by a new type of light emitting diode lens
Authors: He Xi  , Du Tuan-Jie  , Wu Feng-Tie  ,   College of Information Science and Engineering, Huaqiao University, Fujian Key Laboratory of Optical Beam Transmission and Transformation, Xiamen, 361021, China
Published: December 2020

A new method for generating a single bottle beam directly by light emitting diode (LED) with a secondary optical lens is proposed for the first time, so far as we know. Firstly, in the aspect of geometrical optics, we analyze the principle of generation of a single bottle beam by the LED spot light with a secondary optical lens. Then, we calculate the expression of the length and the radius of the biggest dark region of the bottle beam. After that, a new type of a secondary optical lens is calculated numerically and simulated by numerical recipes software Matlab, three-dimensional modeling software Solidworks and optical simulation software Tracepro. Meanwhile, the minimum size of the bottle beam and the scattering force for trapping particles are calculated. The result shows that the designed secondary optical lens can produce a single bottle beam, the length and the radius of the biggest dark region of the generated bottle beam are in accordance with the theoretical calculations. This result offers a practical and available method for generating a bottle beam with light emitting diode at a low cost.
New transverse Zeeman effect method for mercury detection based on common mercury lamp
Authors: Li Chuan-Xin  , Si Fu-Qi  , Zhou Hai-Jin  , Liu Wen-Qing  , Hu Ren-Zhi  , Liu Feng-Lei  ,   University of Science and Technology of China,Dept.of Optics and Optical Engineering, HeFei 230026, China;,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The accurate background correction can determine the minimum limit of trace mercury measurement in atmosphere by the cold vapor atomic absorption method. This paper studies a new method of mercury detection using the common mercury lamp as sources which correct the background according to the transverse Zeeman effect. The resonance spectral line (253.65 nm) of the meccury lamp generates σ-, σ+, and π linear polarized light in the vertical direction of the magnetic field. This study obtains mercury absorbance of σ-, σ+, and π light in different magnetic field intensity by using ultra-high resolution spectrometer, then gets the minimum field intensity of the method. We discuss the existing possible interference caused by benzene with narrow-band absorption and acetone with broadband absorption under 1.78 T magnetic field intensity. Taking σ- and σ+ as background light, and π as absorption light, we quantify the saturated mercury vapor cell with different lengths. With the accurate background correction, the R value of absorption fitting curve can achieve 0.99. Results indicate that the method can accomplish the job of accurate background correction and can be applied to trace mercury measurement in atmosphere.
Influence of coupling coefficient on sparseness of slope response matrix and iterative matrix
Authors: Cheng Sheng-Yi  , Chen Shan-Qiu  , Dong Li-Zhi  , Liu Wen-Jin  , Wang Shuai  , Yang Ping  , Ao Ming-Wu  , Xu Bing  ,   The Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;,   University of Chinese Academy of Sciences, Beijing 100049, China;,   Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, Chengdu 610209, China;,   University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

Based on a 529-actuator adaptive optic (AO) system, the sparseness of slope response matrix from deformable mirror to Hartmann wavefront sensor and the sparseness of iterative matrix in wavefront reconstruction are analyzed. The influence of actuator coupling coefficient on the slope response matrix sparseness, the iterative matrix sparseness, and the AO system correction quality are also studied under the condition of constant actuator spacing. Larger coupling coefficient results in a lower sparseness of slope response matrix and an iterative matrix. Too large or too small coupling coefficient will lead to lower stability and correction quality of AO system. Finally, the optimal range of coupling coefficient is provided by the balancing correction quality, sparseness of slope response matrix, and stability.
Study on the gain characteristics of terahertz surface plasma in optically pumped graphene multi-layer structures
Authors: Liu Ya-Qing  , Zhang Yu-Ping  , Zhang Hui-Yun  , Lü Huan-Huan  , Li Tong-Tong  , Ren Guang-Jun  ,   College of Electronic Information Engineering, Tianjin University of Technology, Tianjin 300384, China;,   Qingdao Key Laboratory of Terahertz Technology, College of Electronic Communication and Physics, Shandong University of Science and Technology, Qingdao 266510, China
Published: December 2020

Based on the developed optically pumped graphene multilayer terahertz surface plasma structures, this paper calculates the real part of propagation index and amplification coefficient in optically pumped graphene multilayer structures, discusses the inluences of momentum relaxation time, temperature, numbers of grapheme layers, and the quasi-Fermi energy in the topmost grapheme layer on the real part of propagation index and amplification coefficient. It is shown that when the real part of dynamic conductivity becomes negative in the terahertz range of frequencies in the optically pumped graphene multilayer structures, the surface plasma of graphene layers can achieve gain. By comparing the peeling-graphene-structure with the graphene structure that has a high conducting bottom graphene layer in optically pumped scheme, it can be said that the surface plasma of the peeling-graphene-structure can get a high efficient amplification. Meanwhile, the structure having properly numbers of graphene layers can get a larger amplification than the simple graphene structure in an optically pumped scheme at low temperatures.
Three-dimensional modelling and numerical simulation on segregation during Fe-Pb alloy solidification in a multiphase system
Authors: Wang Zhe  , Wang Fa-Zhan  , Wang Xin  , He Yin-Hua  , Ma Shan  , Wu Zhen  ,   College of Material and Mineral Resources, Xi’an University of Architecture and Technology, Xi’an 710055, China;,   School of Mechanical and Electrical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China
Published: December 2020

The three-dimensional mathematical model for a three-phase flow during its horizontai solidification is studied using fluid dynamics method based on Eulerian-Eulerian and volume of fraction methods, in which the mass, momentum, species, and enthalpy conservation equations of the Fe-Pb alloy solidification process are solved simultaneously. Effects of Pb area quadratic gradient (∇ (∇SPb)) and Pb concentration quadratic gradient (∇ (∇CPb)) on the segregation formation are investigated. Results show that the segregation mode is manifested as X-segregates in the upper and V-segregates in the lower part during flow-solidification of liquid phase and gas phase. The X-segregates result from the phase transformation driving force of gas phase and “scattering” is due to the orientation of phase transition. When t >tc the lower ∇ (∇SPb) and ∇ (∇CPb) curves cause a larger yielding rate of Pb with a larger down angle of X-segregates and a smaller up angle of X-segregates and V-segregates. All these are favorable for the formation of a well-dispersed microstructure. In addition, the gas-liquid two-phase flow interaction term has an effect on channel segregation, showing that channels occur only in the region where the flow-phase transition interaction term (ul·∇cl and ug·∇cg) is negative. With a negative flow-phase transition interaction term the increase in flow velocity due to the flow perturbation and flow-phase transition interaction becomes more negative, thus the channel continues to grow and tends to be stable. Calculated results show good agreement with experimental data.
Atomistic simulation study on the local strain fields around an extended edge dislocation in copper
Authors: Shao Yu-Fei  , Yang Xin  , Li Jiu-Hui  , Zhao Xing  ,   Institute of Applied Physics and Technology, Liaoning Technical University, Huludao 125105, China;,   College of Sciences, Liaoning University of Technology, Jinzhou 121001, China
Published: December 2020

The local strain fields around an extended edge dislocation in copper are studied via the quasicontinuum multiscale simulation method combined with the virial strain calculation techniques. Results show that in the regions, tens of nanometers away from the dislocation, atoms are experiencing infinitesimal strain; virial strain calculation results are consistent with the predictions from elastic theory very well. In the regions near the dislocation, the virial strain fields can outline the core areas of Shockley partial dislocations precisely, which are in the shape of ellipse with a longer axis 7b1 and a shorter axis 3b1, where b1 is the length of burgers vector of the partial dislocation.
Influences of electrode separation on structural properties of μc-Si1-xGex：H thin films
Authors: Cao Yu  , Zhang Jian-Jun  , Yan Gan-Gui  , Ni Jian  , Li Tian-Wei  , Huang Zhen-Hua  , Zhao Ying  ,   Electrical Engineering College, Northeast Dianli University, Jilin 132012, China;,   Institute of Photo-electronic Thin Film Devices and Technique of Nankai University, Key Laboratory of Photo-electronics Thin Film Devices and Technique of Tianjin, Key Laboratory of Optoelectronics Information Science and Technology,Chinese Ministry of Education, Tianjin 300071, China
Published: December 2020

Hydrogenated microcrystalline silicon germanium (μc-Si1-xGex:H) thin films have been prepared by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) using a mixture of SiH4 and GeH4 as the reactive gases. Effects of electrode separation on the structural properties of μc-Si1-xGex:H thin films have been investigated. Results show that reduction of the electrode separation can increase the Ge content in the films. Moreover, μc-Si1-xGex:H thin film deposited at a lower electrode separation of 7 mm possesses not only a stronger (220) orientation and a larger grain size, but also a lower microstructural factor. Then, the decomposition characteristics of the reactive gases are analyzed according to the variation of the structural properties of the μc-Si1-xGex:H thin films. It is found that the increase of the Ge content is due to the decrease of the SiH4 decomposition rate in the plasma. While the better film quality obtained at the lower electrode separation is attributed to the enhancement of the diffusibility of the Ge precursors caused by improving the proportion of GeH3 radicals
First-principles study on p-type ZnO codoped with F and Na
Authors: Deng Sheng-Hua  , Jiang Zhi-Lin  ,   School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, China
Published: December 2020

The first-principles calculations based on the density functional theory have been performed to investigate the doping behaviors of Na and F dopants in ZnO. It turns out from the calculated results of the band structure, density of states, and effective masses that in the F mono-doping case, the impurity states are localized and the formation energy is up as high as 4.59 eV. In the Na mono-doping case, the impurity states are delocalized and the formation energy decreases as low as -3.01 eV. One cannot obtain p-type ZnO in both instances On the contrary, in the Na-F codoping case, especially when the ratio of F and Na is 1:2, the Fermi-level shifts to the valence bands, the corresponding effective masses are small (0.7m0) and the formation energy is the lowest (-3.55 eV). These may indicate the formation of p-type ZnO having a good conductivity.
Analyses of wavelength dependence of the electro-optic overlap integral factor for LiNbO3 channel waveguides
Authors: Li Jin-Yang  , Lu Dan-Feng  , Qi Zhi-Mei  ,   State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Wavelength dependence of the electro-optic overlap integral factor (Γ) for a single-mode LiNbO3 (LN) channel waveguide was analyzed experimentally and theoretically. By measuring the half-wave voltage (Vπ) of the LN waveguide at different wavelengths and then substituting the measured values into a formula that describes the relationship between Vπ and Γ, the quantitative dependence of Γ on wavelength was obtained; and it showed that Γ rapidly decreases with increasing wavelength. On the other hand, numerical simulations of the modulating electric field distribution, the modal field distribution, and Γ at different wavelengths were carried out; the calculated relationship between Γ and wavelength is in good agreement with the measured results. Further simulations indicate that as the wavelength increases, the center of the modal field profile gradually moves toward the weak electric field side from the waveguide surface, thus leading to a smaller Γ at a longer wavelength. Such a relationship between Γ and wavelength is partially responsible for the nonlinear dependence of Vπ on wavelength obtained experimentally. This would be useful for designing and optimization of LN waveguide-based devices.
Synthesization and luminescent properties of blue emitting phosphor Ba2Ca(PO4)2：Eu2+
Authors: Wang Zhi-Jun  , Liu Hai-Yan  , Yang Yong  , Jiang Hai-Feng  , Duan Ping-Guang  , Li Pan-Lai  , Yang Zhi-Ping  , Guo Qing-Lin  ,   College of Physics Science & Technology, Hebei University, Baoding 071002, China;,   Industrial & Commercial college, Hebei University, Baoding 071002, China;,   Key Laboratory of Road Safety, Ministry of Communications PRC, Beijing 100088, China
Published: December 2020

A blue emitting phosphor Ba2Ca(PO4)2:Eu2+ is synthesized by a high temperature solid state method. Effect of the conditions is inverstigated, such as preparation temperature and time, the ratio of Ba/Ca, and Eu2+ concentration, on the phase and luminescent property. Results show that Ba2Ca(PO4)2 and Ba2Ca(PO4)2:Eu2+ have been achieved by selecting the appropriate conditions, such as the temperature 900/1200 ℃ and the time 4 h. The compound Ba2Ca(PO4)2:Eu2+ produces an asymmetric emission band centered at 454 nm under 343 nm UV excitation. For the 454 nm emission, the excitation spectrum extends from 200 to 450 nm with a peak at 343 nm, and has an obvious excitation band in the range of 350–410 nm. With increasing Eu2+ concentration, there occur the concentration quenching effect and redshift phenomenon. With decreasing ratio of Ba/Ca, there has an obvious enhancement in the green region, and the emission color gradually turns from blue to cyan. It is shown that the Eu2+ ion not only can occupy the Ba2+ site but also the Ca2+ site. Therefore, different luminescence centers of Eu2+ can exist in Ba2Ca(PO4)2, and affect its luminescence.
Bluish-green high-brightness long persistent luminescence materials Ba4(Si3O8)2：Eu2+Pr3+, and the afterglow mechanism
Authors: Wang Peng-Jiu  , Xu Xu-Hui  , Qiu Jian-Bei  , Zhou Da-Cheng  , Liu Xue-E  , Cheng Shuai  ,   Key Laboratory of Advanced Materials of Yunnan Province, College of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Published: December 2020

A bluish-green long persistent luminescence material Ba4(Si3O8)2:Eu2+, Pr3+, was synthesized by traditional solid state method in a reductive atmosphere According to the photoluminescence and afterglow spectra measurement, the emission center is the cation Eu2+ in the photoluminescence and afterglow procedure. The Pr3+ co-doped sample forms new defects which could capture current carriers after excitation. On the basis of thermoluminescence and afterglow decay measurement, the afterglow intensity of Pr3+ co-doped sample sharply enhances as compared with Eu2+ doped one, the reason is that the lower depth traps are generated in the shallow trap areas (T1 region). At the same time, the Pr3+ co-doped sample have longer afterglow decay than that doped with only Eu2+; the reason is that the deep traps concentration decreases in the deep trap areas (T2 region). The afterglow mechanism of Pr3+ co-doped sample have two different excitation paths, path 1: the electron of the host is directly projected to traops at 268 nm excitation; path 2 the electron of the Eu2+ corresponds to the transitions from the ground state to the 5d excited state at 330 nm excitation. Then the different afterglow mechanism of phosphor was produced.
Structured analysis of iron-based amorphous alloy coating deposited by AC-HVAF spray
Authors: Ye Feng-Xia  , Chen Yan  , Yu Peng  , Luo Qiang  , Qu Shou-Jiang  , Shen Jun  ,   Chongqing Key Laboratory of Photo-Electric Functional Materials, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, China;,   School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Published: December 2020

The uniform and compact Fe-based amorphous alloy coating was prepared by active combustion high velocity air fuel (AC-HVAF) spray method. By tuning the parameters of AC-HVAF spray process, the influence of the spraying gun length, spraying distance, and powder feed rate on non-crystallization has been studied carefully. Results indicate that spraying gun length is the key factor in forming perfect amorphous coating. Spraying distance and powder feed rate may determine the thickness and formation rate of the coating. The prepared coatings have a tight adhesion with the substrate, low porosity, and good non-crystallization, which would effectively maintain the excellent mechanical properties of the Fe-based amorphous alloy. The coating can provide a good protection for the substrate material.
Nematic ordering pattern formation in the process of self-organization of microtubules in a gravitational field
Authors: Hu Jian  , Qiu Xi-Jun  ,   Department of Mathematics and Physics Teaching, Shanghai Institute of Technology, Shanghai 200235, China;,   College of Sciences, Shanghai University, Shanghai 200444, China
Published: December 2020

By virtue of a functional scaling, the free energy for cytoskeletal microtubule (MT) solution system in the gravitational field has been proposed theoretically, and on this basis the influence of gravitational field on MT’s self-organization process is studied. A concentration gradient coupled with orientational order characteristic of nematic ordering pattern formation is the new feature emerging in the presence of gravity. Theoretical calculation results show that gravity facilitates the isotropic to nematic phase transition, which is reflected in a significantly broader transition region and the phase coexistence region increases with increasing g or MT concentration. We also discuss the numerical results obtained due to local MT concentration changing with the height of the vessel and some phase transition properties.
Mass segmentation in mammogram based on SPCNN and improved vector-CV
Authors: Han Zhen-Zhong  , Chen Hou-Jin  , Li Yan-Feng  , Li Ju-Peng  , Yao Chang  , Cheng Lin  ,   School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China;,   Center of Breast Disease, Peking University People’s Hospital, Beijing 100044, China
Published: December 2020

Mass segmentation plays an important role in computer-aided diagnosis (CAD) system. The segmentation result seriously affects classifying mass as benign and malignant. By combining the simplified pulse coupled neural network (SPCNN) and the improved vector active contour without edge (vector-CV), a novel method of mass segmentation in mammogram is proposed in this paper. First, the parameters and termination conditions of SPCNN are obtained through mathematical analysis and the initial contour is segmented by SPCNN. Then, the vector CV model is accordingly modified to overcome the shortcomings of traditional CV model. Finally, combined with the initial contour, the improved vector-CV is used to segment the mass contour. The experiments implemented on the public digital database for screening mammography (DDSM) and the clinical images which are provided by the Center of Breast Disease of Peking University People’s Hospital indicate that the proposed method is better than the existing methods, especially when dealing with the dense breasts of Oriental female.