bluuebunny/crossref_metadata_2025 huggingface dataset:
Defect microstructures in polycrystalline pure copper induced by high-current pulsed electron beam——the vacancy defect clusters and surface micropores
Authors: Wang Xue-Tao  , Guan Qing-Feng  , Qiu Dong-Hua  , Cheng Xiu-Wei  , Li Yan  , Peng Dong-Jin  , Gu Qian-Qian  ,   College of Material Science and Engineering, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

In this paper, high-current pulsed electron beam (HCPEB) was used to irradiate the polycrystalline pure copper. The vacancy defect clusters of the irradiated surface layer have been investigated by using transmission electron microscopy. Very dense vacancy defect clusters involving square cells, vacancy dislocation loops and stacking fault tetrahedra were formed after HCPEB irradiation. It suggests that the very high stress and high strain rate induced by rapid heating and cooling due to HCPEB irradiation could cause the shifting of whole atomic planes synchronously, which is the probable mechanism of the formation of the vacancy defect clusters. Additionally, it was established by scanning electron microscopy investigations that dense, fine and dispersed micropores on the irradiated surface of pure copper can be successfully fabricated by using HCPEB irradiation. The dominating formation mechanism of surface micropores should be attributed to the formation of supersaturation vacancies within the near-surface introduced during HCPEB irradiation and vacancy migration along grain boundaries and (or) dislocations towards the irradiated surface. The present results indicate that HCPEB technique may become a new method for rapid synthesis of surface porous materials.
Heat conduction in one-dimensional Fibonacci chain with on-site potential
Authors: Xu Hui  , Cui Mai-Ling  , Ma Song-Shan  ,   College of Physical Science and Technology, Central South University, Changsha 410083, China
Published: December 2020

By making use of the method of transfer matrix, we study the behaviors of heat conduction in one-dimensional Fibonacci chain under the influence of on-site potential (including transmission coefficient, Lyapunov coefficient and heat conduction). The results show that, with the on-site potential increasing while fixing the ratios of atom mass and force constant, the transmission coefficient of the low-frequency region decreases, and the corresponding Lyapunov coefficient increases, and the transmission spectrum moves to the higher frequency region. Meanwhile, with the increasing of on-site potential, the heat conductivity of the system decreases. When the on-site potential is large enough, the thermal conductivity of the system will tend to zero. In the curve of κ-ω2, the thermal conductivity shows a slowly increasing trend in steps, and tends to a certain value in the high-frequency region.
First-principles study of optical and electronic properties of N-doped SnO2
Authors: Yu Feng  , Wang Pei-Ji  , Zhang Chang-Wen  ,   School of Science, University of Jinan, Jinan 250022, China
Published: December 2020

Using first-principles full potential linearized augmented plane wave method (FP-LAPW), we present the isosurface of spin density, total density of states and optical properties of undoped SnO2, substitutional N for O and substitutional N for Sn in SnO2. The results show that the band gap in two kinds of N-doped SnO2 is wider than that of SnO2 eigenstate, and the imaginary part of the dielectric function makes a blue shift corresponding to the increasing band gaps. It points out the relationship between electronic structure and optical properties in theory.
Effect of spin polarization on the ground state of Kondo system
Authors: Li Huan  , Guo Wei  ,   School of Physics, Peking University, Beijing 100871, China
Published: December 2020

The effect of spin polarization on the ground state of Kondo type system is a fundamental issue in study of Anderson model. By using variational and diagonal methods we analysis the stability of Kondo singlet state in s-d model and Zhang-Rice singlet state in two-component model for high Tc superconductivity when Cu site spin polarization is considered.
High temperature annealing of enhancement-mode AlGaN/GaN high-electron-mobility transistors
Authors: Wang Chong  , Quan Si  , Ma Xiao-Hua  , Hao Yue  , Zhang Jin-Cheng  , Mao Wei  ,   Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, The School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

The high temperature annealing effect of DC characteristics of the different enhancement-mode AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. The threshold voltage shifted from 0.12 V to 0.57 V and the gate leakage current was reduced one order after the recessed-gate enhancement-mode AlGaN/GaN HEMTs were annealed at 500 ℃ for 5 min in N2 atmosphere. The threshold voltage shifted from 0.23 V to -0.69 V and the gate leakage current increased after the F-implantation enhancement-mode AlGaN/GaN HEMTs were annealed at 400 ℃ for 2 min in N2 atmosphere. The height of Schottky barrier increased in annealing process that enhanced the depletion of gate to channel electrons, so that the threshold voltage shifted in the positive direction of x axis, the gate leakage current was reduced and the device can work at higher gate voltage. The depletion of F ions and the increased barrier height of F ions were weakened after annealing, so that the threshold voltage shifted in negative direction of x axis and the gate leakage current increased. The channel electron mobility of F-implantation enhancement-mode AlGaN/GaN HEMTs increased obviously after annealing process.
Design and study of second-order Y-loop frequency selective surfaces
Authors: Gao Jin-Song  , Wang Shan-Shan  , Feng Xiao-Guo  , Xu Nian-Xi  , Zhao Jing-Li  , Chen Hong  ,   (1)Key Laboratory of Optical System Advanced Manufacturing Technology, Changchun Institute of Optics and Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (2)Key Laboratory of Optical System Advanced Manufacturing Technology, Changchun Institute of Optics and Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China, Graduate University of the Chinese Academy of Science, Beijing 100039,
Published: December 2020

The multiband properties of self-similar fractals can be used to design multiband single-layer frequency selective surfaces (FSS). Combined with Floquet periodic boundary conditions, the moments method is applied to characterize the second-order Y-loop fractal FSS frequency response to different valuses of iterative scaling factor F and lattice as the incidence varies, and then the estimated empirical constant is obtained. Experimental results show good correlation to the calculations, indicating that the resonant frequencies are mainly determined by the iteration factor and the initial unit size,while the lattice impacts the transmission coefficient and bandwidth apparently.
Calculation of positron wave function in the single crystal solid
Authors: Xiong Tao  , Zhang Jie  , Chen Xiang-Lei  , Ye Bang-Jiao  , Du Huai-Jiang  , Weng Hui-Min  ,   Department of Modern Physics, University of Science and Technology of China, Hefei 230026
Published: December 2020

In this paper, we first introduce two basic methods for calculating the positron wave function: the finite differential method and the plane wave method (PW). Then taking Si as an example, we calculate the positron wave function from the wave function, and get the positron density distribution in silicon. Then we obtain the bulk positron lifetime from the positron density. The calculation result agrees with our latest experimental result of 220 ps. At last, we discuss the respective advantages and disadvantages of the two methods.
Preparation of nano-particle carbonates emission materials
Authors: Wang Qi-Fu  , Wang Xiao-Xia  , Luo Ji-Run  , Zhao Qing-Lan  ,   (1)Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics,Chinese Academy of Sciences, Beijing 100190, China; (2)Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics,Chinese Academy of Sciences, Beijing 100190, China, Graduate University of Chinese Academy of Sciences, Beijing 100039, China
Published: December 2020

Oxide cathode has been widely used as electron emission source in vacuum electronic devices. Emission of an oxide cathode is dependent upon the ratio of the three kinds of ingredients and the microscopic shape of alkaline earth carbonates on the cathode surface. The synthesizing method plays a key role in dctermining the shape and ingredient of the carbonates. A gas-liquid synthetic method has been used to prepare the carbonate in this paper. The influences of temperature, concentration of constituents and whisk velocity were investigated. A nano-particle carbonate is synthesized by optimizing temperature and concentration.
Influence of annealing on the microstructure and electrochemical properties of B-doped nanocrystalline diamond films
Authors: Pan Jin-Ping  , Hu Xiao-Jun  , Lu Li-Ping  , Yin Chi  ,   College of Chemical Engineering and Material Science, Zhejiang University of Technology, Hangzhou 310014, China
Published: December 2020

The annealing under different temperatures was performed on boron-doped nanocrystalline diamond films synthesized by hot filament chemical vapor deposition (HFCVD). The effects of annealing on the microstructure and electrochemical properties of films were systematically investigated. The results show that there are four peaks at 1157,1346,1470 and 1555 cm-1 in Raman spectra of the unannealed sample. When the films were annealed at temperatures above 800 ℃, there are only two peaks of D and G band, indicating that the hydrogen in grain boundaries significantly decreased. The area-integrated intensity ratio of D band to G band (ID/IG) reaches minimum value, revealing that the cluster number or cluster size of sp2 phase was reduced. The G peak position shifts to lower wave number, indicating an decrease in the ordering of graphitic component. The electrode exhibits the widest potential window and the highest oxygen evolution potential, and the quasi-reversible reaction occurs on the surface of the samples. The D peak is quite sharp and its intensity increases when the sample was annealed at 1000 ℃. The ID/IG value attains to the maximum value and the G peak position clearly shifts to higher value. The electrode exhibits the narrowest potential window and the lowest oxygen evolution potential, and the reversible electrochemical reaction occurs in the surface of the sample. The above results reveal that the cluster number or cluster size of sp2 phase, the amounts of trans-polyacetylene related to hydrogen in the grain boundaries, the disordering of graphitic components and the boron diffusion in the nanocrystalline diamond films give contributions to the complex change in electrochemical properties of the films with the annealing temperature increasing.
Compression properties of rare gases in region of ionization
Authors: Zheng Jun  , Gu Yun-Jun  , Chen Qi-Feng  , Chen Zhi-Yun  ,   National Key Laboratory of Shock Wave and Detonation Physics Research, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The equations of state and ionization degrees of helium, neon, argon, krypton, and xenon in the region of ionization have been presented based on the Saha equation with the Debye-Hückel correction. The calculated results were compared with the experimental data and other calculations and the reliability of this model has been validated. The compressibility and the regularity of ionization were discussed by the calculated isotherms and shock compression curves of the rare gases. The results indicate that xenon has better compression resistance among the gases cousidered.
A new type of conserved quantity induced by Mei symmetry of Appell equation
Authors: Zhang Yao-Yu  , Jia Li-Qun  , Yang Xin-Fang  , Xie Yin-Li  , Cui Jin-Chao  ,   (1)Electric and Information Engineering College, Pingdingshan University, Pingdingshan 467002, China; (2)School of Science, Jiangnan University, Wuxi 214122, China
Published: December 2020

A New type of conserved quantity induced by Mei symmetry of Appell equations for a holonomic system is studied. The definition and the criterion of Mei symmetry of Appell equations for a holonomic system are given. A new type of conserved quantity induced by Mei symmetry of Appell equations expressed by Appell functions is obtained. And an example is given to illustrate the application of the results.
Analytical time-domain model of transient eddy current field in pulsed eddy current testing
Authors: Cao Bing-Hua  , Yang Xue-Feng  , Fan Meng-Bao  ,   (1)College of Information and Electrical Engineering, China University of Mining and Technology Xuzhou 221116, China; (2)College of Mechanical and Electrical Engineering; Uinversity of Mining and Technology Xuzhou 221116, China
Published: December 2020

The transient eddy current field is analytically modeled by applying inverse Laplace transform to pulsed eddy current testing. The closed-form solution to transient eddy current field in a complex domain is obtained by using the truncated region eigenfunction expansion (TREE) method and the theory of reflection and transmission of electromagnetic waves. After extensive algebraic transform, the poles of the developed model and corresponding residues are able to be calculated. As a result, partial fraction expansion can be used to split up the complicated complex-domain model into the forms that are listed in the Laplace Transform table. Therefore, it is easy to derive the time-domain solutions to transient eddy current field with step and exponential current excitations respectively. The derived time-domain model not only has some advantages in the sense of implementation and efficiency, but also removes the Gibbs phenomenon. Finally, the inverse Fourier transform of induced voltage in the probe is performed and the good agreement demonstrates the validity of the established model.
Feedback iterative decoding of sparse quantum codes
Authors: Wang Yun-Jiang  , Bai Bao-Ming  , Wang Xin-Mei  ,   State Key Laboratory of Integrated Service Networks, Xidian University, Xi’an 710071, China
Published: December 2020

Decoding sparse quantum codes can be accomplished by syndrome-based decoding through using the sum-product algorithm (SPA). We significantly improve this decoding scheme by developing a new feedback adjustment strategy for the standard SPA. In our feedback strategy, we exploit not only the syndrome but also the values of the frustrated checks on individual qubits of the code and the channel model. Consequently, our decoding algorithm, on the one hand, can break the symmetric degeneracy, and on the other hand, can feed back more useful information to the SPA decoder to help the decoder determine a valid output, thereby significantly improving the decoding ability of the decoder. Moreover, our algorithm does not increase the measurement complexity compared with the previous method, but takes full advantage of the measured information.
Precise planement of all Lyapunov exponents for discrete-time dynamical systems
Authors: Chen Xu  , Qiu Shui-Sheng  ,   School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510640, China
Published: December 2020

In this paper, a new algorithm for all Lyapunov Exponents precisely configuraling a discrete-time dynamical system is proposed. A given deterministic discrete-time dynamical system can be chaotified by the algorithm. A new feed-back controller is designed via moduling operation. All Lyapunov Exponents of the controlled system are equal to a given set of ones. The new controller is simple and can be used to control or anti-control a chaotic system . The corresponding proof as well as two illustrative examples are presented. The simulation results show the effectiveness of the algorithm.
Bifurcations and chaos of coupled Jerk systems
Authors: Chen Zhang-Yao  , Bi Qin-Sheng  ,   Faculty of Science, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

Upon the analysis of the equilibrium points as well as the stabilities in coupled Jerk systems, bifurcation sets in parameter space are derived, which divide the parameter space into several regions associated with different forms of dynamics. The dynamical evolution of the coupled system is investigated with the variation of different parameters and specially, the influence of the coupling strength on the dynamics of the system is explored in details. The mechanism of some nonlinear phenomena such as the coexistence of multiple behaviors as well as the sequence of period-doubling bifurcations are presented.
Computation of invariant manifolds with self-adaptive parameter and trajectories continuation method
Authors: Jia Meng  , Fan Yang-Yu  , Li Hui-Min  ,   (1)Department of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, China; (2)Department of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, China;Department of Electrical Engineering, Xinxiang College, Xinxiang 453000, China
Published: December 2020

Most work on manifold study focuses on two-dimensional manifolds and there have been proposed some good computing methods. However, the computation of two-dimensional manifold is still a hot research field. In this paper the two-dimensional manifold of hyperbolic equilibria for vector fields is computed by combining self-adaptive parameter with trajectories continuation, approximating the local manifold with an ellipse around the equilibria, extending the trajectory with equal distance, and adjusting the trajectory with self-adaptive parameter. This method is more accurate than the "trajectories and arc-length method", and better shows the trend of the manifolds than the "box covering method".
Measurements of energy spectra for high energy pulsed X-ray
Authors: Su Zhao-Feng  , Yang Hai-Liang  , Qiu Ai-Ci  , Sun Jian-Feng  , Cong Pei-Tian  , Wang Liang-Ping  , Lei Tian-Shi  , Han Juan-Juan  ,   Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

The basic principle and the experimental results of measuring energy spectra of high energy pulsed X-ray are reported. The Monte-Carlo code is developed to calculate the energy deposition of high energy photons in each sensitive cell of the energy spectrometer. The intensity of high energy pulsed X-ray created on the Qiangguang-Ⅰ accelerator is measured by using the energy spectrometer. According to the deposited energy and the integral data, the time-resolved high pulsed x-ray energy spectrum is obtained. By using the voltage waveform and the current waveform of the diode, the energy spectrum is calculated in details. The results are in agree with the measured values from the experimental energy spectrum.
Study of structural and electronic properties of Cu-adsorbed (SiO2)n(n=1—8) clusters with the DFT
Authors: Sun Jian-Min  , Zhao Gao-Feng  , Wang Xian-Wei  , Yang Wen  , Liu Yan  , Wang Yuan-Xu  ,   Institute of Computational Materials Science, Henan University, Kaifeng 475004, China
Published: December 2020

Equilibrium geometries, charge distributions, stabilities, and electronic properties of the Cu-adsorbed (SiO2)n (n=1—8) clusters are investigated by using the density functional theory in the generalized gradient approximation for exchange-correlation functional. The results show that the Ag atom preferably binds to silicon atom with dangling bond, and the incoming Ag atoms tend to cluster on the existing Ag cluster leading to the formation of Ag islands. Therefore the ability for Si to lose electron is weaker, while the ability for Si to gain electron is stronger. In addition, the energy gaps between the highest occupied and the lowest unoccupied molecular orbitals remarkably decrease compared with the pure (SiO2)n (n=1—8) clusters, eventually approaching the near infrared radiation region.
Coherent control of atom dipole squeezing and violation of Cauchy-Schwarz inequality
Authors: Zhao Jia-Qiang  , Lu Huai-Xin  ,   Shandong Provincial Key Laboratory of Multi-photon Entanglement and Manipulation, Department of Physics and Electronic Sciences, Weifang University, Weifang 261061, China
Published: December 2020

By studying the interaction of isolated two-level atom with two-mode entangled coherent state optical field, the time evolution of dipole squeezing quantum effect in the system is investigated in detail. The results show that the properties of interaction coherent mode determine the degree of atom dipole squeezing. Parameter ΔV of violation of Cauchy-Schwarz inequality of the interaction system is defined. Time evolution of parameter ΔVis studied, and it can be seen evidently from the results that the degree of violation of Cauchy-Schwarz inequality accords with the nonclassical property of interaction system. Through tuning the parameter of the coherent field, we can easily perform the remote control of the noncommercial properties.
Theoretical analysis of characteristics for silica based Tm3+ doped fiber laser
Authors: Yan Feng-Ping  , Ji Ye-Nan  , Wang Lin  , Gong Tao-Rong  , Liu Peng  , Tao Pei-Lin  , Wang Wen-Jie  ,   (1)Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044,China; (2)Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044,China;Key Laboratory of All Optical networks and Advanced Communications Networks, Ministry of Education, Beijing 100044,  China
Published: December 2020

In this paper, a theoretical model of Tm3+ doped silica fiber laser(TDSFL) for 3H6—3H4 pumping mechanism is established based on the rate-equation theory, and the numerical simulation is performed by using the Runge-Kutta algorithm. The introcavity power distributions of the TDSFL are obtained for both pump and laser, and the effects of Tm3+ doped fiber length and Tm3+ concentration on laser performance are analyzed.
Analysis of flexural vibration thick disk
Authors: Pan Xiao-Juan  , He Xi-Ping  ,   Institute of Applied Acoustics, Shaanxi Normal University, Xi’an 710062, China
Published: December 2020

The flexural vibration of thick disk is studied in this paper. The general solutions of radial displacement and transverse displacement for flexural vibration thick disk under the Mindlin theory are derived. The resonance frequency equations are derived when the boundary conditions are free, simply supported and clamped, and The results obtained from the analyticae method are in good agreement with those from the finite element method and also with the experimental results. These results can serve as reference for the design of flexural vibration thick disk radiator.
Simulation study of evolution mechanisms of microstructures during rapid solidification of liquid Mg7Zn3 alloy
Authors: Liang Yong-Chao  , Liu Rang-Su  , Zhu Xuan-Min  , Zhou Li-Li  , Tian Ze-An  , Liu Quan-Hui  ,   School of Physics and Microelectronics Science, Hunan University, Changsha 410082, China
Published: December 2020

A simulation study has been performed for the rapid solidification process of liquid Mg7Zn3 alloy by using molecular dynamics method. The pair distribution function g(r) curves, the bond-type index method of Honeycutt-Andersen (H-A), the cluster-type index method and the genetic tracking method have been used to analyze the formation and evolution properties of cluster structures during the solidification process. The results show that the bonding probability between Zn-Zn atoms is increased obviously during the solidification process at cooling rate of 1×1012 K ·s-1. The amorphous structures are formed mainly with the 1551, 1541 and 1431 bond-types, and the turning point of the relation curve of the characteristic 1551 bond-type with temperature is corresponding to the glass transition temperature Tg, thus it maybe become a new method to determine Tg. The basic cluster (12 0 12 0) consisting of 1551 bond-type plays a key role in forming amorphous structure, and becomes the main body of the large clusters which are formed by the combination of some middle and small clusters with distinctly different sizes, through mutual competition by unceasing annex and evolution in a seesaw manner (in turn of obtaining and losing).
Preparation and mechanism analysis of hollow microspheres/reticulated composite carbon foam
Authors: Lü Hui-Min  , Shi Zhen-Hai  , Zhao Chao  , Wei Ping  ,   (1)Applied Chemistry Department, Xi’an University of Technology, Xi’an 710048, China; (2)Applied Physics Department, Xi’an University of Technology, Xi’an 710048, China
Published: December 2020

On the basis of the ligamental reticulated carbon foam by Klett in 2000 and hollow microsphere carbon foam by Bruneton in 2002, a hollow microsphere/ reticulated composite carbon foam is prepared by microstructural optimization, carbonization and graphitization sequentially. The scanning electron microscope (SEM) and stereo microsccope tests demonstrate that both reticulated ligament and globe cavity show obvious spacial periodicities. Diffraction peak of X-ray diffraction (XRD) at 26°indicates that the sample features graphitization. Besides, the forming mechanism is also analyzed.
First principles study of electronic properties of carbon/silicon carbide nanotube heterojunction
Authors: Zhang Hai-Bo  , Wang Zhi-Guo  , Zu Xiao-Tao  , Yang Ding-Yu  , Zhu Xing-Hua  ,   (1)Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, China; (2)School of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, China; (3)School of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, China;Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

Using the first-principles method, the electronic properties of the armchair and the zigzag C/SiC nanotube heterojunctions are investigated. Both heterjunctions exhibit semiconducting behaviors with a direct energy band. For the armchair heterojunction, type I heterojection is formed at the interface between the C and the SiC nanotubes, and the electrons and holes are confined in the C nanotube part. In the zigzag heterojunction, the electrons are localized in the C nanotube part, whereas the holes are distributd in the heterojunction uniformly. These heterojunctions can be good candidates for the future nano-devices.
Accurate determination of electronic transition energy of carbon nanotubes from the resonant behavior of radial breathing modes and their overtones
Authors: Zhang Jun  , Tan Ping-Heng  , Zhao Wei-Jie  ,   State Key Laboratory of SupperLattices and Microstructures, Institute of Semiconductor, Chinese Academy of Science, Beijing 100083,China
Published: December 2020

The resonant Raman behavior of the radial breathing modes are very useful to analyze the electronic property of carbon nanotubes. We investigated the resonant behaviors of Stokes and anti-Stokes radial breathing mode and its overtone of a metallic nanotube, and show how to accurately determine the electronic transition energy of carbon nanotubes from radial breathing modes and their overtones. Based on the present results, the previously reported resonant Raman behavior of the radial breathing modes of SWNT bundles can be interpreted very well.
First-principles study on the catalytic role of Ti in the hydrogenation of Al(110) surfaces
Authors: Cao Yi-Jie  , Ren Bao-Xing  , Chen Yu-Hong  ,   (1)School of Science, Lanzhou University of Technology,Lanzhou 730050,China; (2)State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050,China;School of Science, Lanzhou University of Technology,Lanzhou 730050,China
Published: December 2020

First-principles calculation is used to study the hydrogen molecule adsorbed on Ti-doped Al(110) surface and pure Al(110) surface separately. We find an adsorption path of hydrogen molecule for decomposing hydrogen atoms and forming TiH2 with Ti atoms on top site. Afterwards, the TiH2 molecule moves to hollow site and approaches to the Al(110) surface. The analyses of density of state and Milliken overlap population show that there is covalence interaction between hydrogen atoms and Al atoms of surface, which gives rise to the formation of Al-H, Na3AlH6 and NaAlH4. Hydrogen molecule is unable to decompose hydrogen atoms on pure Al(110) surface.These results contribute further towards the understanding of the improved observation in recycling of hydrogen with Ti-doped NaAlH4.
GaN grown on AlN/sapphire templates
Authors: Wang Lai  , Wang Lei  , Ren Fan  , Zhao Wei  , Wang Jia-Xing  , Hu Jian-Nan  , Zhang Chen  , Hao Zhi-Biao  , Luo Yi  ,   State Key Laboratory on Integrated Optoelectronics/Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Properties of unintentionally-doped GaN re-grown on molecular beam epitaxy grown AlN/Sapphire templates by metal organic vapor phase epitaxy (MOVPE) are studied in this article. X-ray diffraction (XRD), transmission electron microscope (TEM), and atomic force microscope are used to investigate the influence of the crystal quality and surface morphology of AlN on the GaN. It is found that when surface roughness of AlN is small, the GaN has a full width at half maximum (FWHM) values of XRD rocking curves (200—300 and 400—500 arcsec for (002) and (102) plane ω-scan, respectively) and surface roughness (0.1—0.2 nm), which are comparable to those grown on sapphire substrates by using "two-step" method, although the FWHMs of (102) plane XRD ω-scan curves of AlN are 900—1500 arcsec. The reason for dislocation reduction in GaN shown by TEM image is that a part of dislocations in AlN are eliminated in the interface between AlN and GaN. This is probably due to the lattice restoration from Ga atoms for their large size. On the other hand, when surface roughness of AlN is large, the surface migration of Ga atoms is nestricted during the MOVPE growth, which results in a poor GaN quality. Moreover, the resistivity of GaN confirmed with Van der Pauw method is between 105 and 106 Ω ·cm, which is about six orders of magnitude higher than that in GaN grown on sapphire substrates. This is attributed to the replacement of low temperature GaN buffer layer by the AlN.
InNSb single crystal films prepared on GaAs (001) substrates by molecular beam epitaxy
Authors: Zhang Yan-Hui  , Chen Ping-Ping  , Li Tian-Xin  , Yin Hao  ,   National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
Published: December 2020

InNSb alloy films are prepared on GaAs (001) substrates by the N2 radio frequency plasma-assisted molecular beam epitaxy ( RF-MBE). The N composition and the micro-structure of the samples are characterized by atom force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The measurement results reveal that the films have smooth surfaces and good crystalline quality, the N composition can reach 0.84%(from XRD) and most of the N atoms in the samples are at the sites of Sb atoms. The transport properties of the samples are also characterized, and the results demonstrate that our samples have lower carrier concentrations and higher mobilities. Owing to the introduction of N, a condside rable reduction of room-temperature magnetoresistance is observed.
Effect of distances from source or drain to the gate on the robustness of sub-micron ggNMOS ESD protection circuit
Authors: Zhang Bing  , Chai Chang-Chun  , Yang Yin-Tang  ,   Key Laboratory of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices,School of Microelectronics,Xidian University,Xi'an 710071,China
Published: December 2020

In this paper,based on the research of the features about high voltage and high current under electrostatic discharge(ESD),the new 3D model of 0.6 μm gate-grounded NMOS(ggNMOS) ESD protection circuit with CSMC 6S06DPDM-CT02 CMOS technology have been derived from the optimization of lattice self-heating drift/diffusion model and its thermal model; systematic study about the effect of drain contact to gate spacing(DCGS)and the source contact to gate spacing(SCGS)on the relative protection circuit robustness index(turn-on voltage,breakdown voltage,self-heating peak,etc)have been done based on this model. The simulation results show that turn-on voltage and thermal balance are not influenced by the change of DCGS and SCGS,and compared to SCGS,DCGS is more sensitive to the breakdown voltage and the self-heating peak value of protection circuit. To improve the robustness of ESD protection circuit,it is not appropriate to monotonic increase the DCGS and SCGS for the reason that the breakdown voltage cannot be increased and the self-heating peak value of devices cannot be reduced by increasing DCGS and SCGS continuously. Compared to the TLP test results of 0.5 μm and 0.6 μm CMOS,a better reflection about the trend of electrical and heating features is derived from the simulation results,and the conclusions and test results are fully consistent. The reference for sub-micrometer ggNMOS ESD protection circuit layout parameter can be provided by the study.
Mechanism of high-temperature exchange-coupling interaction of FeCo-based nanocrystalline alloy
Authors: Yang Jing  , Wang Zhi  , Jia Yun-Yun  , Han Ye-Mei  ,   School of Science,Tianjin University,Tianjin 300072,China
Published: December 2020

Temperature dependence of initial permeability is investigated for nanocrystalline Fe38.4Co40Si9B9Nb2.6Cu alloy annealed at 500 and 600℃,and the initial permeability of 600℃-annealed sample is observed not to drop sharply at the Curie temperature of the residual amorphous phase,which is a new magnetic phenomenon in dual-phase nanocrystalline alloys. The origin of the above phenomenon is explored by estimating the Curie temperature of amorphous ribbons which have the same compositions with the residual amorphous phase in annealed nanocrystalline alloys. The results indicate that the Curie temperature of the intergranular amorphous region can be enhanced drastically up to the Curie temperature of the crystalline phase (TAC=TαC) when the exchange-field between adjacent nanograins penetrates through the amorphous interphase thoroughly. Furthermore, the effective exchange penetration length of FeCo-based nanocrystalline alloys (LFeCo) is evaluated to be 0.61 nm much larger than that of Fe-based nanocrystalline alloys, which may be the main reason of the higher permeability of FeCo-based alloys at elevated temperature.
An all-proton spin quantum gate in semiconductor spin magnetic resonance force system
Authors: Ren Da-Nan  , Ren Ren  , Xu Jin  ,   (1)Department of Mathematics , North-West University, Xian 710069, China; (2)Department of Physics, BME Institute , Xian JiaoTong University, Xian 710049, China
Published: December 2020

We report on a kind of all-proton spin quantum gate realized by fabric silicon cantilever in a semiconductor spin magnetic resonance microscopy system. In the paper, the Rf pulse sequence control and the spin rotate frame system are adopted according to spin-lattice and spin-spin relaxation times,and the small resonance force, the sensitivity and the spin density matrix are studied. The results show that all-proton spin quantum gates have high Q controlling and detecting sensitivity, and gain the effective force oscillating through the resonance slice and fiber interferometer. The system has advantages of MRI and AFM characteristics. In addition, the calculation indicates that it is powerful tool of magnetic resonance force technology and useful way to achieve quantum computation and quantum information.
Effect of H3BO3 on preparation and luminescence properties of submicron green-emitting Ca3Sc2Si3O12 ∶Ce phosphor
Authors: Liu Yuan-Hong  , Zhuang Wei-Dong  , Gao Wen-Gui  , Hu Yun-Sheng  , He Tao  , He Hua-Qiang  ,   National Engineering Research Center for Rare Earth Materials General Research Institute for Nonferrous Metals, and Grirem Advcanced Materials Co., Ltd., Beijing 100088,China
Published: December 2020

Green-emitting Ca3Sc2Si3O12:Ce3+ phosphors for white LED are successfully synthesized by a gel-combustion method. The as-synthesized phosphors are investigated by XRD, SEM, and fluorescence spectrophotometer. The results indicate that the crystal structure of the phosphor is pure. The particle morphology of the sample is basically spherical in shape. The particle size is smaller than 1μm. The emission spectrum shows a broad band emission, and the main emission peak locates at 505 nm. Bright green-emission broadening is attributed to the characteristic emissions 5d-2F5/2 and 5d-2F7/2 transitions of Ce3+. The optimal doping concentration of Ce in Ca3-xSc2Si3O12:Ce is x=0.1. The thermal stability and the luminescence intensity of the Ca3Sc2Si3O12:Ce3+ are significantly improved compare with those of YAG:Ce.
Influence of LiF and AlF3 on optical, spectroscopic, crystallization and structrural properties of Tm3+ doped fluorophosphate glass
Authors: Zhang Li-Yan  , Tian Ying  , Zhang Jun-Jie  , Hu Li-Li  ,   Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences, Shanghai 201800,China
Published: December 2020

To balance the requirements for lifetime, cross section and crystallization stability in rare-earth-doped fluorophosphate(FP) glass, we studied the influence of LiF and AlF3 on the properties of FP. Results indicate that LiF plays an important role in improving the radiative lifetime of Tm3+, and the glass performs good crystallization stability with LiF proportion as high as 30mol%. Crystallization stability in high AlF3 glass is excellent but the radiative lifetime of Tm3+decreases fast. Emission cross section changes mildly with the variation of LiF and AlF3 proportions, so lifetime, cross section and crystallization stability can achieve their batter values through the ajustment of LiF and AlF3 proportions.Comparations between J-O parameters and several properties of the Tm3+ doped FP glass show that with AlF3 increasing, the overlap integral of 4f and 5d orbitals of the rare earth ions increases. Raman spectra testify the great variation of glass structure when LiF and AlF3 contents change largely.
Magnetic-field-induced strains in polycrystalline Mn1-xCux(0.1≤x≤0.3) alloys
Authors: Peng Wen-Yi  , Qin Jin  , Zhang Ai-Sheng  , Yan Ming-Ming  ,   School of Materials Science and Engineering, Nanchang University, Nanchang 330031,China
Published: December 2020

Magnetic-field-induced strain(MFISs) in polycrystalline Mn1-xCux(0.1≤x≤0.3, atomic fraction) alloys are studied by means of X-ray, photomicrograph, DSC, resistance strain gauge method at room temperature. The results show that Mn1-xCux alloys consist of fcc (γ) and fct (γ’) phases after a long period of homogenization because of fcc(γ)→fct(γ’) martensitic transformation in the cooling process. The volume proportion of γ’ phase increases with the increase of Mn content, so that the samples possess much better MFIS performance. At room temperature, the MFIS in Mn0.9Cu0.1 sample reaches 91 ppm in 0.9 T magnetic field.
Minimum-energy frame of discrete signal space and its de-noising application to rectangular pulse signal
Authors: Yang Wei  , Zhang Yu  , Xie Ying-Hai  ,   (1)State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, Beijing 100876, China; (2)State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

The minimum-energy (wavelet) frame has an extensive application prospect in the field of signal processing, but now it can be applied only to continuous signals. In order to solve the problem, we define a minimum-energy frame in the discrete signal space, and then prove that it has some good properties. In the actual application, we propose a new de-noising algorithm which is special for the binary rectangular pulse signal polluted by the additive gaussian noise and obtain better processing effect by using a minimum-energy frame in the discrete signal space to denoise the sampled sequence of receiving waveform. The simulation results show that if a pre-processing link is used to denoise the receiving waveform through using the algorithm, the receiver can reduce the bit error rate and achieve a 3.4 dB performance gain at 4 dB signal-to-noise ratio.
Period estimation method for weak pulsars based on coherent statistic of cyclostationary signal
Authors: Li Jian-Xun  , Ke Xi-Zheng  ,   Automation and Information Engineering School, Xi'an University of Technology, Xi'an 710048, China
Published: December 2020

The importance of period estimation for pulsars in pulsar searching was discussed. In the paper, the radiation signal from pulsars was modeled as second-order cyclostationary process,and corresponding simulation was done to verify its reasonableness. Based on the model, a novel method was proposed to estimate pulsars’ cyclo-period by the coherent statistic of bispectrum, and then one robust strategy for periodicity searches was provided in order to eliminate its sensitivity to data amount. Using the method, the period of PSR J0437-4715 with single pulse was estimated based on original signal, and the period of PSR B1821-24 with double pulses was also estimated based on simulated signal. Results show that, compared with the classical Fourier-transform method, the algorithm is intuitive, effective, of good performance even in case of lower SNR,and also appropriate for the noncontinuous observing data. The method, though with higher computation complexity, can provide a powerful reference for period estimation of weak pulsar signal.
Controlling the entanglement among three atoms by quantum-jump-based feedback
Authors: Chen Yu  , Zou Jian  , Li Jun-Gang  , Shao Bin  ,   Department of Physics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

We consider a model consisting of three two-level atoms in a heavily damped cavity. We show that the quantum-jump-based feedback can be used to generate a steady entangled state of three atoms against decoherence. When the feedback acts on just one of the atoms, it can protect a maximally entangled state of other two atoms. When the feedback acts on three atoms, by choosing appropriate parameters we can obtain a decoherence-free subspace spanned by two vectors, and by using quantum trajectory Monte Carlo wave function method we find that the maximally entangled state of three atoms in this decoherence-free subspace can be obtained for some specific initial conditions.
A new switched four-scroll hyperchaotic system and its circuit implementation
Authors: Liu Yang-Zheng  , Lin Chang-Sheng  , Wang Zhong-Lin  ,   (1)Department of Physics and Electronics, Binzhou University, Binzhou 256603, China; (2)Institute of Nonlinear Physics, Nanjing Institute of Technology, Nanjing 211167, China
Published: December 2020

A new switched four-scroll hyperchaotic system with two subsystems which are interconnected and can be switched to each other, is generated. The two subsystems are analyzed in detail by presenting the bifurcation diagram, the feature of equilibrium, the phase portraits of chaotic attractor, the Lyapunov exponent and the evolution course of the dynamical action. A practical circuit is designed to conveniently realize two subsystems for the hyperchaotic systems each with only smooth quadratic nonlinearity. Based on time-dependent switching law and state-dependent switching law, the two subsystems can be switched from one to another either randomly or independently, just by using this special circuit.
Controlling hyperchaos and periodic state synchronization of degenerate optical parametric oscillators
Authors: Feng Xiu-Qin  , Yao Zhi-Hai  , Tian Zuo-Lin  , Han Xiu-Yu  ,   (1)School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun 130022, China; (2)School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

Hyperchaotic control and periodic synchronization between two degenerate optical parametric oscillators are presented by mutual coupling parameter modulation, based on the nonlinear kinetic characteristic of degenerate optical parametric oscillator. Theoretical results show that the two degenerate optical parametric oscillators in hyperchaotic state can be controlled into periodic output by mutual couple, no matter whether the two degenerate optical parametric oscillators are identical. It is also shown that the periodic states can result in identical synchronization or anti-synchronization only in the case where the largest Lyapunov exponent of the system is negative. Thus synchronization type and evolution process of synchronization are determined by modulating coefficient and initial conditions.
Characteristic of hybrid single electron transistor and metal oxide semiconductor structure in Chua’s circuit
Authors: Feng Chao-Wen  , Cai Li  , Zhang Li-Sen  , Yang Xiao-Kuo  , Zhao Xiao-Hui  ,   College of Science, Air Force Engineering University, Xi’an 710051, China
Published: December 2020

The negative differential resistance (NDR) characteristic equation of single electron transistor and metal oxide semiconductor (SETMOS) hybrid structure is simplified by a fitting method. And a new approach to designing multi-scroll chaotic circuit with SETMOS is proposed. The effect of NDR characteristic on the equilibrium point of multi-scroll Chua’s circuit is analyzed both qualitatively and quantitatively. The results show that the unidirectional motions of radial contract and axial tension occur in the negative sections of multi-scroll Chua’s circuit, whereas in the positive sections appear the scroll motions of radial tension and axial contract. The result provides theoretical basis for the construction of multi-scroll chaotic circuits and the further study of their complex dynamical behaviors.
A time-dependent theory for helix traveling wave tubes in beam-wave interaction
Authors: Peng Wei-Feng  , Hu Yu-Lu  , Yang Zhong-Hai  , Li Jian-Qing  , Lu Qi-Ru  , Li Bin  ,   Key Laboratory of National Defense of Science and Technology for High Power Microwave Electronics Vacuum Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

A time-dependent theory for helix traveling wave tubes in beam-wave interaction is presented. The effect of wave on electrons is described by radio frequency (RF) field equations and space charge (SC) field equations, while the effect of electrons on waves is described by electron dynamic equations. The RF field equations are achieved from Ampere’s law and Faraday law, combined with sheath helix model RF field. The SC field equations are achieved from a space charge wave model. The electron dynamic equations are achieved by substituting the RF field equations and the SC field equations into the Lorenz force equation. Using coupling impedance to treat exciting sources of RF field equations, the RF and the SC field equations can be solved with the help of high frequency simulation software, such as HFSS or HFCS, which makes this time-dependent theory more flexible. The feasibility of this theory is proved by numerical simulation.