bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of the electron and one pair of phonons interaction on Holstein polaron
Authors: Ren Xue-Zao  , Liao Xu  , Liu Tao  , Wang Ke-Lin  ,   (1)西南科技大学理学院，绵阳  621010; (2)中国科学技术大学近代物理系，合肥  230026
Published: December 2020

This paper set out from Holstein model of the quantization, by means of the method of incoherent state expansion, get the non-Linear Schrdinger equation of the polaron in ground state of one-dimensional molecular crystal, and get the soliton solution of fixed state,the ground state energy, the lattice displacement.
Depth-dependent elastic strain in ZnO/Zn0.9Mg0.1O/ZnO heterostructure studied by Rutherford backscattering/channeling
Authors: Wang Kun  , Yao Shu-De  , Hou Li-Na  , Ding Zhi-Bo  , Yuan Hong-Tao  , Du Xiao-Long  , Xue Qi-Kun  ,   (1)北京大学物理学院，北京  100871; (2)中国科学院物理研究所表面物理国家重点实验室，北京  100080
Published: December 2020

ZnO/Zn0.9Mg0.1O/ZnO heterostructure was grown by radio frequency plasma-assisted molecular beam epitaxy on a sapphire (0001) substrate. By using RBS/C, the depth-dependent elastic strain was deduced. The strain changes from negative to positive from interface to surface, and the value is higher at the depth close to the interface (also at the interface between ZnO and Zn0.9Mg0.1O) and decreases towards the surface. The negative tetragonal distortion was explained by considering the lattice mismatch and thermal mismatch between ZnO and sapphire substrate, and the positive distortion is due to the tensile strain in the parallel direction of Zn0.9Mg0.1O and the gradual release of the strain.
Effect of high pressures on structural, electronic and optical properties of BN nanotube
Authors: He Kai-Hua  , Zheng Guang  , Lü Tao  , Chen Gang  , Ji Guang-Fu  ,   (1)中国地质大学数学与物理学院,武汉  430074; (2)中国工程物理研究院流体物理研究所冲击波物理与爆轰物理国防重点实验室,绵阳  621900
Published: December 2020

The structural,electronic and optical properties of BN(5,5) nanotube under high pressures were studied by means of quantum-mechanical calculations based on the density functional theory and pseudopotential method. It was found that the geometric structure has large distortion under pressures. Differences exist between BN(5,5) nanotube and zinc blende structure BN: firstly, the band gap of BN(5,5) nanotube increases with pressure with a slope of -0.01795eV/GPa; secondly, the absorption spectrum does not “blue shift”, but stretches in the direction of infrared； yet these two structures have same electronic transfer direction. The electron density map indicated that BN(5,5) has stronger ionicity, which weakens with pressure increasing.
Molecular dynamics simulation of the growth and structural properties of ultra-thin diamond-like carbon films
Authors: Ma Tian-Bao  , Hu Yuan-Zhong  , Wang Hui  ,   清华大学摩擦学国家重点实验室，北京  100084
Published: December 2020

Molecular dynamics simulations are performed to study the growth of diamond-like carbon (DLC) films with a thickness of 2—3nm on diamond (100) substrate. Some important structural properties characterizing the quality of the deposited films, such as sp3 hybridization fraction, film density, radial distribution function, are analyzed which turn out to be consistent with experimental results. The incident energy has significant influence on the structural properties, and hence film properties. Optimal properties are obtained when kinetic energy of the incident atoms is in the range 20—60eV. The incidence of energetic species is prerequisite for growing homogeneous, continuous and compact films. A steady-state intrinsic region is required to guarantee outstanding mechanical properties of the thin film.
Density of defect states in low-k porous SiO2:F film researched by SCLC method
Authors: Gou Jie  , He Zhi-Wei  , Pan Guo-Hui  , Wang Yin-Yue  ,   兰州大学物理系，兰州  730000
Published: December 2020

The porous fluorine doped silica (SiO2:F) films were prepared by sol-gel method. The densities of the states (DOS) of the SiO2:F films and the effect of the dose of the F dopant were studied by space charge limited current(SCLC) techniques. Distribution of defect states N(E) in the vicinity of Fermi level in SiO2:F films was determined to be about 7×1015cm-3·eV-1. The dangling bounds on the surface of the porous film were the primary cause of the DOS.
Effect of optical phonon on magnetic excitation of two-dimensional Heisenberg ferromagnetic system
Authors: Cheng Tai-Min  , Xianyu Ze  , Gang Tie-Chen  ,   (1)东北大学理学院物理系，沈阳  110004; (2)沈阳化工学院数理系，沈阳  110142
Published: December 2020

A magnon-phonon interaction model is built in the two-dimensional double square ferromagnetic system. By using Matsubara Green function theory, we study magnetic excitation of the system, and calculate the magnon dispersion curve on the main symmetric points and lines in the Brillouin zone. The influences of optical phonon and acoustic phonon on the magnetic excitation of the system are compared, and the influences of the parameter change on the magnon softening are also studied. It is concluded that the coupling of the optical phonon and magnon has predominant effect on the magnon softening, especially the longitudinal optical phonon has the greatest effect on the magnon softening, and the effect of nonmagnetic ion on magnon softening is stronger than that of magnetic ion.
Electrons-phonons collision velocity in films radiated by laser
Authors: Xia Zhi-Lin  , Fan Zheng-Xiu  , Shao Jian-Da  ,   (1)中国科学院上海光学精密机械研究所,上海  201800; (2)中国科学院上海光学精密机械研究所,上海  201800;中国科学院研究生院,北京  100039
Published: December 2020

Avalanche ionization is a dominant damage mechanism of optical films if laser power density reaches to TW/cm2 level. In order to study avalanche ionization mechanism, it is inevitable to deal with rates of electrons absorbing and losing energy. Both of these relate to the rate of collision between electrons and phonons. So it is important to study the collision of electrons and phonons. In this paper, we discuss the effect of truncating the maximum phonon vector on collision rate, and find the relation between scattering rate and electron kinetic energy. The conclusion is consistent with that obtained from other theories and experiments. At the same time, we also modify the coupling parameter, and obtain the connection of the coupling parameter with phonon vector. After modification, the curve shape of scatter rate versus electronic energy does not change, but the overall value decreases.
The exchange bias in ferromagnetic/antiferro-magnetic bilayers under the stress field
Authors: Pan Jing  , Tao Yong-Chun  , Hu Jing-Guo  ,   (1)南京师范大学物理科学与技术学院，南京  210097; (2)扬州大学物理科学与技术学院，扬州  225002
Published: December 2020

Using a method in which the free energy is minimized, the exchange bias for ferromagnetic(FM)/antiferromagnetic(AFM) bilayers under the stress field is studied. The thin FM film is considered as a single crystal with cubic and uniaxial magnetocrystalline anisotropies, while the AFM film has only uniaxial magnetocrystalline anisotropy. In the semi-infinite approximation for the AFM layer, the analytical expressions have been derived for effective exchange bias and pinning angle. Numerical calculations show that the effective exchange bias depends on the angle of applied magnetic field, but not on its magnitude. However, the effective exchange bias depends not only on the angle of the stress field but also on its magnitude. The reason is that both the magnitude and angle of the stress field affect the pinning angle.
Phase behavior and thermal dynamic properties of free volume on SMMA/SMA copolymer blend studied by PALS method
Authors: Jiang Zhong-Ying  , Yu Wei-Zhong  , Huang Yan-Jun  , Xia Yuan-Fu  , Ma Shu-Xin  ,   (1)南京大学物理系，南京  210093; (2)清华大学物理系，北京  100084; (3)伊犁师范学院物理系，伊宁  835000; (4)伊犁师范学院物理系，伊宁  835000;南京大学物理系，南京  210093
Published: December 2020

The temperature dependence of the free volume in SMMA/SMA (30/70) blend was investigated by the positron annihilation life spectroscopy (PALS) at different heating rates according to the free volume theory, and the thermodynamics characteristics of the phase behavior of the polymer blends was also explored. At temperatures above Tg, we found from the positron annihilation life spectra that when the structural relaxation time is comparable with the retention time, the temperature dependence of the free volume parameters obviously departs from the linear relation. Based upon the change tendency of the free volume concentration I3 with temperature, it is postulated that there is a growing stage of the phase separation in the same temperature range.
A delayed sea-air oscillator coupling model for the ENSO
Authors: Mo Jia-Qi  , Wang Hui  , Lin Wan-Tao  ,   (1)安徽师范大学,芜湖  241000;上海高校计算科学E-研究院上海交通大学研究所，上海  200240; (2)中国科学院大气物理研究所,北京  100029; (3)中国气象科学研究院,北京  100081
Published: December 2020

A time delay sea-air oscillator model is studied. Using the perturbation theory and corresponding method, the asymptotic expansion of the solution for the sea-air oscillator model is obtained.
Integrating factors and conservation theorems of Lagrange’s equations for generalized nonconservative systems in terms of quasi-coordinates
Authors: Zheng Shi-Wang  , Qiao Yong-Fen  ,   (1)东北农业大学工程学院，哈尔滨  150030; (2)商丘师范学院物理系，商丘  476000
Published: December 2020

The conservation theorems of the Lagrange's equations for generalized nonconservative systems in terms of quasi-coordinates are studied by using the method of integrating factors. The differential equations of motion of systems are written. The definition of integrating factors is given. The necessary conditions for the existence of the conserved quantity are studied in detail. Finally, the conservation theorem and its inverse are established, and an example is given to illustrate the application of the result.
New type of exact solitary wave solutions for dispersive long-wave equation and Benjamin equation
Authors: Taogetusang  , Sirendaoreji  ,   内蒙古师范大学数学学院，呼和浩特  010022
Published: December 2020

On the basis of homogeneous balance method, tanh-function method and auxiliary equation method, new types of exact solitary wave solutions of the dispersive long-wave equation and Benjamin equation are constructed by using a new auxiliary equation and with the aid of computer algebraic system Mathematica in this paper. This method also can be used to find new solitary wave solutions of other nonlinear evolution equations.
Single N-dimensional quNit quantum secret sharing
Authors: Yang Yu-Guang  , Wen Qiao-Yan  , Zhu Fu-Chen  ,   (1)北京邮电大学理学院，北京  100876; (2)现代通信国家重点实验室，成都  610041
Published: December 2020

A single N-dimensional quNit quantum secret sharing scheme is proposed. In this scheme, extending two bases and four states used in Bennett and Brassard protocol(BB84) to multi-bases and multi-states,a distributor sends the encoded N-dimensional quantum system to one of his two recipients. After receiving the quNit, the recipient makes a unitary operation on it using a N-dimensional cloning machine, and then sends it to the other recipient. After being informed that the second recipient has received the quNit, the distributor announces his preparing base, and then the two recipients perform measurements on their systems using the same base as the distributor and obtain the sent quantum state after collaboration. The security of the scheme is based on quantum non-cloning principle. In addition, this scheme has the features of great information flux and high efficiency. At last, the generalization from two recipients to N recipients is discussed.
Quantum measurement of single electron state by a quantum point contact
Authors: Hu Xue-Ning  , Li Xin-Qi  ,   中国科学院半导体研究所 超晶格和微结构国家重点实验室,北京  100083
Published: December 2020

Closely related to the quantum information processing in solid states, we study the quantum measurement of single electron state by a mesoscopic charge-sensitive detector, namely the quantum point contact (QPC). We find that the conventional Lindblad-type master equation is not appropriate for describing the underlying measurement dynamics. The treatment developed in this work properly accounts for the energy-exchange between the detector and the measured system, and its role on the detailed-balance relation. A valid description for the QPC measurement dynamics is provided which may have impact on the study of quantum measurement and quantum feedback control in solid states.
Solution of the ground state wave function of Bose-condensed gas in a harmonic trap based on the Gross-Pitaevskii function
Authors: Xu Zhi-Jun  , Shi Jian-Qing  , Li Zhen  , Cai Ping-Gen  ,   (1)浙江工业大学应用物理系，杭州  310032; (2)浙江工业大学应用物理系，杭州  310032;波谱与原子分子物理国家重点实验室，武汉  430071
Published: December 2020

Based on the Gross-Pitaevskii(G-P) energy functional and variational method, we present a new method to find the ground state wave function for Bose-condensed gas in a harmonic trap at zero temperature. With this method we are able to find the analytic expression of ground state wave function and explore the relevant quantities, such as energy, chemical potential and so on. These results agree well with previous ground state numerical solutions of the G-P equation given by Dalfovo et al. Under the large number of particles N limit for repulsive interaction, our results and Thomas-Fermi approximation model approach to reaching unanimity. This new method is simple compared to other methods used to solve numerically the G-P equation, and one can obtained the analytic and reliable results.
Entropy of Dirac field in a generalized non-stationary spherically symmetric black hole with charge
Authors: Zheng Yuan-Qiang  ,   阆中治平中学物理研究组，阆中  637400
Published: December 2020

Using the improved brick-wall film model， we calculated the entropy of Dirac field in a generalized non-stationary spherically symmetric black hole with charge. From the point of view of the model， these entropies are nothing but the entropy of the black hole. The result showed that this entropy is proportion to the area of event horizon.
A switch-modulated method for hyperchaotic digital secure communications based on drive functions
Authors: Sun Lin  , Jiang De-Ping  ,   (1)长沙理工大学物理与电子科学系，长沙  410077; (2)中南林业科技大学电子与信息工程学院，长沙  410004
Published: December 2020

In this paper, a scheme for digital secure communications is proposed by using different drive functions of hyperchaotic systems based on APD approach. Two different drive functions can be alternately sent according to the transmission of binary signal “0" and “1", which will enhance the complexity and decrease the correlation of transmitted signals. Meanwhile, by designing compound nonlinear function transformation for transmitted signals to further intercalate the secret key, a determined intruder is very difficult to retrieve the contents of message signal using forecasting method. Theoretical analysis and numerical simulation results show that this method is effective.
Emulation of multi-scroll chaotic attractors in four-dimensional systems
Authors: Wang Fa-Qiang  , Liu Chong-Xin  , Lu Jun-Jie  ,   西安交通大学电气工程学院，西安  710049
Published: December 2020

A new type of four-dimensional chaotic system is studied by constructing a new nonlinear function. The characteristic of this chaotic systems is that the 2n+2 scroll chaotic attractors are found in our computer simulation with the natural number n increasing, and the bounds of the chaotic attractors is modified by changing the control parameter k. Finally, the circuit is designed and emulated on EWB platform.
A new three-dimensional quadratic chaotic system and its circuitry implementation
Authors: Wang Guang-Yi  , Qiu Shui-Sheng  , Xu Zhi-Yi  ,   (1)杭州电子科技大学电子信息学院，杭州  310037; (2)华南理工大学电信学院，广州  510640
Published: December 2020

In order to generate complex chaotic attractors, we construct a new three-dimensional quadratic autonomous chaotic system, in which each equation contains a single quadratic cross-product term and a system parameter. Basic dynamic properties of the new system are investigated via theoretical analysis and numerical simulation using the Lyapunov exponent spectrum and bifurcation diagram. Our results show that this system has five equilibria, therefore is not topologically equivalent to the Lorenz, Rsslor or the Chen and Lü systems, and the new system is chaotic when its parameters satisfy certain conditions. Compared with the systems mentioned above, the proposed system has larger positive Lyapunov exponent，displays a complex attractor and some other interesting properties. An electronic circuit was designed to realize the new chaotic system. Experimental chaotic behaviors of the system were found to be identical to the dynamic properties predicted by theoretical analysis and numerical simulations.
Non-autonomous feedback control for a class of chaotic systems
Authors: Jiang Shu-Min  , Tian Li-Xin  ,   江苏大学非线性科学研究中心，镇江  212013
Published: December 2020

This paper proposes a method of non-autonomous feedback control, and proves its validity by the stability theory. This method is used in numerical emulation of energy resource chaotic system and Arneodo system. The result indicates that it is correct and feasible.
Investigation of the bottleneck in high speed traffic caused by a bridge
Authors: Xiao Shi-Fa  , Liu Mu-Ren  , Kong Ling-Jiang  ,   (1)广西师范大学物理与信息工程学院, 桂林  541004; (2)湛江师范学院物理系, 湛江  524048
Published: December 2020

A cellular automaton model for the bottleneck in high speed traffic caused by a bridge is proposed. It takes the initial density apart into six regions. Based on the mean field theory and the results of definitive NS model, the relations of car density of every line are given. The simulation results show that the theoretical model is correct.
A WKB solution of excess carriers in conductivity modulation base with non-uniform lifetime
Authors: Fang Jian  , Lin Wei  , Zhou Xian-Da  , Li Zhao-Ji  ,   电子科技大学微电子与固体电子学院,成都  610054
Published: December 2020

Base on the establishment of an ambipolar transport equation of conductivity modulation base with non-uniform lifetime, WKB solutions of excess carrier profiles under different boundary conditions have been obtained by using Liouville-Green transform. The results can be used in modeling of conductivity modulation power devices under localized lifetime control.
Theoretical calculation of the modulation transfer function in a femoto-second electron diffraction system
Authors: Tian Jin-Shou  , Zhao Bao-Sheng  , Wu Jian-Jun  , Zhao Wei  , Liu Yun-Quan  , Zhang Jie  ,   (1)中国科学院物理研究所,北京  100080; (2)中国科学院西安光学精密机械研究所瞬态光学与光子学国家重点实验室, 西安  710068
Published: December 2020

This article has introduces the basic components and characteristics of a femoto-second electron diffraction system, i.e. the photo-cathode, magnetic lens, deflector and detector with doubled MCP etc., and demonstrated our design method and results. The photo-cathode is an Ag film deposition on a sapphire disk and the femtosecond electron pulses are accelerated to 50 keV through an extraction electric field of 10kV/mm between the photocathode and the extraction mesh. After extraction, the electron pulses are reshaped in size by a 100 μm pinhole, which screens out electrons with larger elevation angle and makes the passed electrons flying almost parallel to the axis, which results in a reduced electron beam spot. The beam is collimated with a magnetic lens and positioned to the sample by a pair of deflection plates for diffraction measurements. The electron diffraction images are recorded with a two-dimensional imaging system composed of a Chevron-type microchannel plate and a P20 phosphor screen on an optical-fiber faceplate. The initial position, kinetic energy and angle distribution of the photoelectrons is sampled with Monte Carlo method. The electric field is calculated with finite difference formula, and the magnetic flux of the focus region is calculated with finite elements methods, and the electron trajectory is traced with Runge-Kutta method. We analysized the temporal and spatial distribution of 3000 electrons when they reached the prime plane and give out the temporal and spatial modulation transfer function of the femoto-diffraction system.
Calculation of diamagnetic spectrum of Rydberg hydrogen atom using B-spline basis sets
Authors: Kang Shuai  , Liu Qiang  , Zhong Zhen-Xiang  , Zhang Xian-Zhou  , Shi Ting-Yun  ,   (1)河南师范大学物理与信息工程学院，新乡  453002; (2)中国科学院武汉物理与数学研究所波谱与原子分子物理国家重点实验室，武汉  430071; (3)中国科学院武汉物理与数学研究所波谱与原子分子物理国家重点实验室，武汉  430071；河南师范大学物理与信息工程学院，新乡  453002; (4)中国科学院武汉物理与数学研究所波谱与原子分子物理国家重点实验室，武汉  430071;中国科学院研究生院，北京  100049
Published: December 2020

The energy spectrum and oscillator strength of hydrogen atom in static magnetic field have been calculated using basis set method. Both the radial and angular wave-functions are expanded in terms of B-spline functions. The resultant size of Hamiltonian matrix is reduced considerably, which enables the calculations to be carried out in personal computer. Diamagnetic spectrum of Rydberg hydrogen atom from -40cm-1 to the field free ionization threshold was obtained with high accuracy. The results have been compared with those of most accurate ones in the literature. The method presented in this paper can be extended easily to the region with positive energy and to the cases of non-hydrogen atoms and the crossed field problem.
Laser phase determination and transfer equation to directly measure the temporal structure of narrow bandwidth attosecond XUV pulse
Authors: Ge Yu-Cheng  ,   北京大学技术物理系，北京  100871
Published: December 2020

A laser phase determination method and a transfer equation which makes use of the proportional term of the measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow bandwidth attosecond XUV pulse. The method is based on the spectrum measurement of electrons generated by XUV photo-ionization interacting with a femtosecond laser field. The results of the study suggest that the measurement should be taken at 0° or 180° with respect to the linear laser polarization. The method has a temporal measurement range of about half a laser oscillation period. The temporal resolution also depends on the jitter and control precision of the laser and XUV pulses.
A two-level atom in a cavity with a moving mirror
Authors: Qu Zhao-Jun  , Liu Sheng-Dian  , Yang Chuan-Lu  , Ma Xiao-Guang  ,   烟台师范学院物理系,烟台  264000
Published: December 2020

It has great meaning to study the effect of a moving mirror in a cavity on the dynamic behavior of a two-level atom injected in the cavity. In this paper, for a system composed of a two-level injected atom and a single-mode field and a moving mirror in the cavity (the moving mirror to be regarded as a quantum harmonic oscillator with frequency ωm), the time-evolution of its state is obtained by means of complete quantum theory in the interaction picture. The time-evolution of the atomic population is derived on the basis of former investigations. It is found that the atomic population oscillates near its initial value. The result shows that the periodic motion of the mirror has a periodic effect on the atomic population.
Array of micro-optical traps for cold atoms or cold molecules using a Damman grating
Authors: Ji Xian-Ming  , Lu Jun-Fa  , Mu Ren-Wang  , Yin Jian-Ping  ,   (1)教育部光谱学与波谱学重点实验室，华东师范大学物理系，上海  200062; (2)教育部光谱学与波谱学重点实验室，华东师范大学物理系，上海  200062;东华理工学院物理系，抚州  344000; (3)南通大学理学院，南通  226007; (4)南通大学理学院，南通  226007;教育部光谱学与波谱学重点实验室，华东师范大学物理系，上海  200062
Published: December 2020

We propose a novel scheme to produce an array of micro-optical traps by using an optical system composed of a Damman grating and a spherical lens, which is illuminated by a red detuned Gaussian laser beam. We derive formulas to calculate the periodical structures of the micro-optical well arrays, and characteristics of each well, such as the spatial intensity distribution, intensity gradient, and geometrical parameters. Applications of our micro-optical traps in the fields of atom and molecule optics are briefly discussed. Our study shows that the proposed array of micro-optical wells can be used to trap cold atoms or cold molecules more efficiently than previous optical traps, even to prepare novel optical lattices.
Optimization of the method to measure d electron occupancy in transition elements from electron energy loss spectrum
Authors: Yang Wei-Guo  , Zhang Xiao-Zhong  , Yuan Jun  ,   清华大学材料科学与工程系电子显微镜实验室，北京  100084
Published: December 2020

A “floating window method” is proposed to optimize the existing methods of calculating d electron occupancy in alloys from electron energy loss spectrum (EELS) with high accuracy. This method is free of some systematic errors that are serious in previous approaches. The application of this method will throw new light on the understanding of the change of d electron occupancy in alloys and the relationship between the electronic structure and properties of materials.
Molecular structure of AlHn(n=1—3) and thermodynamic stability of AlH3
Authors: Sheng Xiao-Hong  , Zhu Zheng-He  , Gao Tao  , Luo Shun-Zhong  ,   (1)四川大学原子分子物理研究所,成都  610065; (2)西华大学物理实验中心,成都  610039；四川大学原子分子物理研究所,成都  610065; (3)中国工程物理研究院,绵阳  621900
Published: December 2020

Geometric configurations and harmonic frequencies of AlHn(n=1—3) molecule, their univalent cation and univalent anion have been calculated by means of b3lyp and qcisd methods at 6-311++g** level with Gaussian03 software packages. Dissociation energies, first vertical ionization energies, electron affinities of the neutral molecules are studied. We compared the above theoretical values with experimental values and other theoretical values from literatures, and found that the values from qcisd method are closer to experimental values, the bond length of AlHn(n=1—3) and their univalent cation shorten with the H atom numbers increasing in AlHn molecule. That is to say, the Al atom attracts H atoms stronger as the number of the H atoms increases and electronic cloud are closer to aluminum atom. The computational results show that the equilibrium pressure of AlH3 is higher than that of NiH, but it is rather low still. For the AlH3 molecule we have the results: De=9.3705eV,ΔG0=-163.373kJ at 298.15K, so the AlH3 molecule is more stable thermodynamically. The problem is that AlH3 molecule is easier to dissociate and produce hydrogen gas. It may be stable if preserved in hydrogen gas environment.
The effect of ion oscillation on the self-sustenance of low pressure electronegative discharge
Authors: Wu Yan-Qing  , Xiao Ti-Qiao  ,   中国科学院上海应用物理研究所上海光源同步辐射实验部,上海  201800
Published: December 2020

It is a common way to obtain ion-ion plasmas from pulsed electronegative discharges. The pumping pulse can excite ion oscillation at the early active glow stage of a pulsed electronegative discharge. To study the ion oscillation and its influence on the self-sustaining condition of the discharge, a global model was developed to describe the interaction between ion oscillation and a small amount of electrons in a low-pressure ion-ion plasma. A parameter r was introduced in this model to describe the momentum residual/loss of the electrons after the collision with the electrodes. It was found a critical value r=rc that differentiates two electron loss mechanisms. Another critical value r=4rc determines two different threshold of the electron density growth. Thus, the threshold of the electron density growth is non-monotonously depend on r. Therefore, there might be a gap existing in the parameter space of the self-sustaining condition. The above result has been examined by a particle-in-cell simulation with Monte-Carlo collision (PIC-MCC).
SO-FDTD method and its application to the calculation of electromagnetic wave reflection coefficients of plasma
Authors: Yang Hong-Wei  , Chen Ru-Shan  , Zhang Yun  ,   (1)南京理工大学通信工程系,南京  200094; (2)南京理工大学通信工程系,南京  200094；南京农业大学物理系,南京  200095; (3)南京农业大学物理系,南京  200095
Published: December 2020

The dielectric property of dispersive media is written as rational polynomial function, the relation between D and E is derived in time domain. It is named shift operator FDTD (SO-FDTD) method. The high accuracy and efficiency of this method is confirmed by computing the reflection coefficients of electromagnetic waves by a collisional plasma slab. The reflection coefficients between plasma and the atmosphere or vacuum can be calculated by using the SO-FDTD method.The result is that the reflection coefficients are affected by plasma thickness, electron numerical density, the distributing orderliness of electron density, and incidence wave frequency.
Simulation electro-optic switch of plasma-electrode Pockels cells driven by one-pulse process
Authors: Guo Wen-Qiong  , Zhou Xiao-Jun  , Zhang Xiong-Jun  , Sui Zhan  , Wu Deng-Sheng  ,   (1)电子科技大学光电信息学院，成都  610054; (2)电子科技大学光电信息学院，成都  610054;中国工程物理研究院激光聚变中心,绵阳  621900; (3)中国工程物理研究院激光聚变中心,绵阳  621900
Published: December 2020

In this paper, a fluid model of electro-optic switch of plasma-electrode Pockels cells (PEPC) driven by one-pulse process is proposed. The model includes a simplified set of fluid continuity equations, Poisson's equation and the electron average energy equation, and these equations are numerically solved with the exponential difference scheme, the classical successive over relaxation method (SOR) and the classical fourth-order Runge-Kutta method, respectively. The evolving characteristics of density of charged particles, electronic temperature, electric field, discharge current, charging voltage of the KDP crystal and the switching efficiency of PEPC are simulated. The model for PEPC, which reveals the relationship between the microcosmic physical processes of gaseous discharge plasma and macrocosmic parameters of PEPC, is very useful for the design of large aperture electro-optic switches.
Structure and magnetic properties of (Nd1－xGdx)3 Fe27.31Ti1.69 compounds
Authors: Wang Wen-Quan  , Xu Shi-Feng  , Xu Qin-Ying  , Zhang Wen-Liang  , Chen Dong-Feng  ,   (1)吉林大学第一临床医院,长春  130021; (2)吉林大学物理学院，长春  130023; (3)中国原子能科学研究院,北京  102413
Published: December 2020

The structure and magnetic properties of (Nd1-xGdx)3Fe27.31Ti1.69 compounds have been investigated by means of X-ray diffraction and magnetic measurements. All compounds with x in the range of x≤0.6 crystallize in Nd3(Fe, Ti)29-type structure. Substitution of Gd for Nd leads to a contraction of unit-cell volume. The Curie temperature TC and anisotropy field Ba of the (Nd1-xGdx)3Fe27.31Ti1.69 compounds increases monotonically with increasing Gd content. Saturation magnetization Ms of the (Nd1-xGdx)3Fe27.31Ti1.69 compounds decreases with increasing x. As temperature lowers from room temperature to 5K, a spin reorientation from the easy plane to the easy cone occurs for (Nd1-xGdx)3Fe27.31Ti1.69 compounds. Spin phase diagrams have been constructed for (Nd1-xGdx)3Fe27.31Ti1.69 compounds.
The structure analysis of novel Ti: LiAlO2 crystal
Authors: Zou Jun  , Huang Tao-Hua  , Wang Jun  , Zhang Lian-Han  , Zhou Sheng-Ming  , Xu Jun  ,   (1)中国科学院上海光学精密机械研究所，上海  201800; (2)中国科学院上海光学精密机械研究所，上海  201800；中国科学院研究生院，北京  100049
Published: December 2020

The structure of novel LiAlO2 crystal with Ti concentration of 0.2 at% was studied by measuring the absorption, luminescence and IR spectra. It was found that the crystal has the 196nm typical quarivalent Ti absorption peak, and also the 384nm typical quarivalent Ti emission peak when excited by 235nm light. A color-center model successfully explains the four small peaks in the range of 660—820nm, which disappeared when the samples were annealed in air or Li-rich atmosphere. Compared to the pure LiAlO2, we can find that the intensity and situation of ［LiO4］ are unchanged. Combined with the ICP results, we can count the number of Li vacancies to be about 5.5×1020 for the Ti: LiAlO2 with dimensions of 50mm×1mm.
Monte Carlo simulation of the SRAM single event upset
Authors: Li Hua  ,   暨南大学物理系，广州  510632
Published: December 2020

The process of deposited energy in sensitive volumes in a static random access memory (SRAM) chip induced by 10—20MeV neutrons is simulated using the Monte Carlo method. In the simulation, the physical parameters related to the single event upset (SEU) of the SRAM chip are calculated. The results provide detailed statistical data for the SEU process induced by 10—20MeV incident neutrons, and reference information for the deface reinforcement of the SRAM chip.
Study of thermal conduction of carbon nanotube by molecular dynamics
Authors: Bao Wen-Xing  , Zhu Chang-Chun  ,   (1)西安交通大学电子与信息工程学院,西安  710049; (2)西安交通大学电子与信息工程学院,西安  710049;西北第二民族学院计算机系,银川  750021
Published: December 2020

Based on the molecular dynamics method and improved reactive empirical bond order potential, Green-Kubo function is used to calculate the thermal conductivity of carbon nanotube. The overlapping method is used which shortens the simulation time greatly. The result shows that the most significant contribution to the thermal conductivity is presented by the auto correlation of interactive force of atoms. The thermal conductivity decreases as the tube diameter increases. The thermal conductivity increases as the temperature increases for temperature lower than 300K and converges to a constant when the temperature rises above 300K. The thermal conductivity of the single-walled carbon nanotube ranges from 1000W/mK to 4000W/mK, and the results are in good agreement with the experimental data.
Structural and electronic properties of C72 and La2@C72
Authors: Tang Chun-Mei  , Yuan Yong-Bo  , Deng Kai-Ming  , Yang Jin-Long  ,   (1)南京理工大学应用物理系和材料化学实验室,南京  210094; (2)中国科学技术大学化学选键实验室,合肥  230032
Published: December 2020

The geometric and electronic properties of the three isomers for C72 and La2@C72 have been studied using the generalized gradient approximation in density functional theory (DFT). It is found that C72(D6d) which satisfies the isolated-pentagon rule is the most stable structure among the three isomers of C72, while La2@C72 (#10611) is the most stable structure and La2@C72 (D6d) is the most unstable structure among the three isomers of La2@C72. It is also found from the analysis of energy levels as well as the density of states that the stability change is due to the mixing of La atomic orbital with C atomic orbital in C72. From Milliken populations, we find that there are about three electrons transferring from the two encaged La atoms to C72 cage so the electronic configuration of La2@C72 (#10611) can be described as La3+2@C3-72. We also come to the conclusion from the net spins of La as well as of La2@C72 that the magnetic moments of La have been completely quenched so La2@C72 (#10611) shows no magnetism.
A new method to grow high quality GaN film by MOCVD
Authors: Peng Dong-Sheng  , Feng Yu-Chun  , Wang Wen-Xin  , Liu Xiao-Feng  , Shi Wei  , Niu Han-Ben  ,   (1)深圳大学光电子学研究所，深圳  518060; (2)中国科学院西安光学精密机械研究所，西安  710068;中国科学院研究生院，北京  100049;深圳大学光电子学研究所，深圳  518060
Published: December 2020

Patterned c-plane sapphire substrate is prepared by chemical etching. GaN films are grown by LP-MOCVD on surface treated sapphire substrate and common c-plane sapphire substrate. The structure and properties of the GaN films are analyzed by high-resolution double crystal X-ray diffraction(DCXRD), scanning electron microscope(SEM) and atomic force microscope(AFM).The results indicate that the quality of GaN film grown on sapphire substrate prepared by surface treatment is superior to that grown on common c-plane sapphire substrate. High-resolution double crystal X-ray diffraction shows that for the GaN grown on surface treated sapphire substrate,the (0002) and (1012) reflections have full-width at half-maximum as low as 208.80arcsec and 320.76 acrsec, respectively. The shortcomings of procedure complexity and high crystallographic tilt in conventional lateral epitaxial overgrowth are overcome by using the new method.
The localized electronic states and transmission spectra in N-layer superlattice with structural defects in finite magnetic fields
Authors: Wang Xin-Jun  , Wang Ling-Ling  , Huang Wei-Qing  , Tang Li-Ming  , Chen Ke-Qiu  ,   湖南大学应用物理系，长沙  410082
Published: December 2020

Within the framework of effective-mass approximation, the properties of the localized electronic states in a N-layer superlattice (SL) with structural defects in finite magnetic fields are investigated by utilizing the transfer matrix and effective barrier-height methods. When the mismatch of electron effective mass in different constituent layers is considered, an external magnetic field will lead to the magneto-coupling. The numerical results show that the magneto-coupling brings about not only quantization of localized electron levels but also the degree of the strong dependence of the localized levels on Landau indices and magnetic fields, especially for the localized levels in higher energy region. In addition, we demonstrate in detail the correlations between the localized electronic states inside the minigaps of the infinite SL with structural defect layer and the resonant transmission peaks in dips of the finite SL. A good coincidence between the localized states and transmission peaks is found, which provides a theoretical basis for experimental observation of the localized electronic states in SLs.
2-D threshold voltage model for short-channel MOSFET with quantum-mechanical effects
Authors: Li Yan-Ping  , Xu Jing-Ping  , Chen Wei-Bing  , Xu Sheng-Guo  , Ji Feng  ,   华中科技大学 电子科学与技术系,武汉  430074
Published: December 2020

A threshold condition different from the classical one is proposed for MOSFET with quantum effects, by means of self-consistent numerical solution of the Schrdinger's and Poisson's equations, and thus an accurate 1-D threshold-voltage model is obtained with good agreements between simulated results and measurement data. Based on this 1-D model, an accurate 2-D quantum-modified threshold-voltage model for small-scale MOSFET is developed by solving the quasi-2D Poisson's equation and taking short-channel effects and quantum-mechanical effects into consideration. The model can also be used for simulation of electrical properties and design of structural parameters for deep-submicron MOSFETs with high-k materials as gate dielectric.
Electrical polarization and charge dynamics of cellular polypropylene ferroelectret films
Authors: Wang Fei-Peng  , Xia Zhong-Fu  , Qiu Xun-Lin  , Shen Jun  ,   (1)上海同济大学波耳固体物理研究所,200092; (2)同济大学波耳固体物理研究所,200092  上海
Published: December 2020

In this work, the polarization of the ferroelectret was first estimated based on the experimental results of charging current by a corona charging with a grid in combination with the reverse-polarity corona charging compensation method. The experimental results indicated that the polarization drastically increases with the rise of grid voltage accompanying the breakdown of gas in the void. Also, by means of the charging method mentioned above and analyzing the thermally stimulated discharging spectra, the charge dynamics of macroscope dipoles with space charges and their compensation charges near the free surface of the film during thermal depolarization were discussed. A geometric distribution of trap levels trapping two kinds of charges was discovered, that is, the space charges formed in the macroscopic dipoles were trapped in shallow- and deep- energy level traps respectively, while the space charges located near the free surface of the film were trapped in medium energy level traps.
Ferroelectric and dielectric properties of Mo-doped SrBi4Ti4O15 ceramics
Authors: Jin Can  , Zhu Jun  , Mao Xiang-Yu  , He Jun-Hui  , Chen Xiao-Bing  ,   扬州大学物理科学与技术学院，扬州  225002
Published: December 2020

The ferroelectric ceramics samples of SrBi4-x/3Ti4-xMoxO15(x=0.00, 0.003, 0.012, 0.03, 0.06, 0.09) have been prepared by the conventional solid-state reaction method. X-ray diffraction analysis shows that the crystal structure of SrBi4Ti4O15 (SBTi) is not affected by Mo-doping. The scanning electronics microscope (SEM) images indicate that all the samples consist of sheet grains and the grain size is reduced by Mo-doping while the ferroelectric properties are improved significantly. The remanent polarization (2Pr) increases at first，then decreases with the increasing Mo content. At x=0.06, the 2Pr maximizes at a value of 26.5 μC/cm2, which about 117% higher in comparison with that of SBTi. And the coercive field of SBTi is increased only about 20%. The Curie temperature of the samples varied slightly after doping, which implies that the good thermal stability of SBTi is not sacrificed.
Poly-SiGe films prepared by metal-induced growth using UHVCVD system
Authors: Wu Gui-Bin  , Ye Zhi-Zhen  , Zhao Xing  , Liu Guo-Jun  , Zhao Bin-Hui  ,   浙江大学硅材料国家重点实验室，杭州  310027
Published: December 2020

Poly-SiGe films were prepared by a metal-induced growth technique with ultrahigh vacuum chemical vapor deposition(UHVCVD) at low temperature. The crystal quality and morphology of poly-SiGe films were characterized by XRD and SEM. The influences of varying the thickness of Ni prelayer and the growth parameters on poly-SiGe films were investigated. It is shown that thicker Ni(≥10nm) has an obvious effect on poly-SiGe growth at 420—500℃. And for the samples with 60nm thick Ni layers, poly-SiGe deposition yields a continuous, highly crystalline film with good morphology.
Preparation and Raman spectra of high quality ZnO nano-bulk materials
Authors: Qin Xiu-Juan  , Shao Guang-Jie  , Liu Ri-Ping  , Wang Wen-Kui  , Yao Yu-Shu  , Meng Hui-Min  ,   (1)北京科技大学材料学院，北京  100080; (2)燕山大学亚稳材料科学与技术重点实验室，秦皇岛  066004; (3)燕山大学亚稳材料科学与技术重点实验室，秦皇岛  066004;北京科技大学材料学院，北京  100080; (4)燕山大学亚稳材料科学与技术重点实验室，秦皇岛  066004;中国科学院物理研究所，北京  100080; (5)中国科学院物理研究所，北京  100080
Published: December 2020

ZnO nano-bulk materials with high density and low brittleness is prepared on CS-1B 6×8000kN cubic high pressure apparatus. Grain sizes and microstructures of the samples have been characterized by X-ray diffraction and field emission scanning electron microscopy. The Raman spectra of polar semiconductor ZnO are studied by Raman spectrophotometer in the range of 50—500cm-1. No obvious size confinement effect is found in the polar semiconductor oxide.
In-situ polymerization and third-order nonlinear optical properties of polyaniline/carbon natotube composite
Authors: Feng Wei  , Yi Wen-Hui  , Feng Yi-Yu  , Wu Zi-Gang  , Zhang Zhen-Zhong  ,   (1)天津大学材料科学与工程学院，天津  300072; (2)西安交通大学电子与信息工程学院，西安  710049
Published: December 2020

The composites of polyaniline/multi-walled carbon natotubes (PANI/MWCNT) were prepared by electrostatic interaction between MWCNT and aniline via in situ polymerization. The results of Fourier transform infrared spectroscopy, Raman spectroscopy and ultraviolet-visible absorption spectroscopy indicated that aniline molecules were adsorbed and polymerized on the surface of MWCNTs. The composite dimensions were observed by scanning electron microscope and transmission electron microscope, the diameter of PANI/MWCNT was measured to be about 40—70 nm, and the thickness of the coated polyaniline was about 15—20 nm. Third-order optical nonlinear susceptibility of PANI/MWCNT composites were measured by degenerate four-wave mixing. The results showed that the resulting PANI/MWCNT composites exhibited larger third-order optical nonlinear susceptibilities than that of pure PANI, which can be ascribed to the π-electron coupling between the PANI and the MWCNTs.
Influence of magnetic field on the morphology of Zn electrodeposits grown on filter paper
Authors: Luo Cheng-Lin  , Yang Bing-Chu  , Rong Mao-Hua  ,   中南大学物理科学与技术学院，长沙  410083
Published: December 2020

The effect of an applied magnetic field on the growth patterns of Zn electrodeposits on filter paper was investigated using an optical microscope and an atom force microscope. It was found that the concentration of electrolyte and the fibre of filter paper influenced strongly the morphology of Zn electrodeposits obtained in unsaturated electrolyte. No evidence indicated that the magnetic field affected the morphology of electrodeposits obtained in unsaturated electrolyte. The branches of Zn electrodeposits obtained in saturated electrolyte grew in two layers, and the thin layer that adhered to the filter paper grew faster than the thick layer. In the case of saturated electrolyte, the 0.40T magnetic field made the branched electrodeposits grow into a spiral pattern. On the basis of these experimental results and the related theories, it was proposed that the magnetic field influenced the morphologies of the branched Zn electrodeposits grown on filter paper through the Hall effect.
Two comprehensions on Noether symmetry
Authors: Wu Hui-Bin  , Mei Feng-Xiang  ,   北京理工大学理学院,北京  100081
Published: December 2020

This paper presents two ways of comprehending the Noether symmetry for the Lagrange system.One is based on invariance of the Lagrangian, the other is based on invariance of the action. This paper proves that these two comprehensions are different from each other. We give the condition under which the invariance of the Lagrangian can become the invariance of the action,and the condition under which the invariance of the action can become the invariance of the Lagrangian is obtained. It is suitable that the Noether symmetry is comprehended as the invariance of the action.
A new type of adiabatic invariants for Birkhoffian system
Authors: Zhang Yi  ,   苏州科技学院土木工程系，苏州  215011
Published: December 2020

The perturbation of symmetries and adiabatic invariants for Birkhoffian system are studied. The exact invariants in the form of Hojman conserved quantities introduced by the Lie symmetries of Birkhoffian system without perturbations are given. Based on the definition of high-order adiabatic invariants of a mechanical system, the perturbation of Lie symmetries for Birkhoffian system under the action of small disturbance is investigated, and a new type of adiabatic invariants of the system are obtained. An example is given to illustrate the application of the results.
Methods of analytical mechanics for dynamics of the Kirchhoff elastic rod
Authors: Xue Yun  , Liu Yan-Zhu  , Chen Li-Qun  ,   (1)上海大学力学系，上海  200436; (2)上海交通大学工程力学系，上海  200030; (3)上海应用技术学院机械与自动化工程学院，上海  200235
Published: December 2020

A cross section of the rod is taken as object of investigation. The freedom of the section in free or constraint case is analyzed and the definition of virtual displacement of the section is given, which can be expressed by a variational operation. Assuming the variational and partial differential operations has commutativity, based on the hypothesis about surface constraint subjected to the rod, the freedom of the section on constraint surface is discussed and the equations satisfied by virtual displacements of the section are given. Combining D'Alembert principle and the principle of virtual work, D'Alembert-Lagrange principle is established. When constitutive equation of material of the rod is linear, the principle can be transformed to Euler-Lagrange form. From the principle, a dynamical equation in various forms such as Kirchhoff, Lagrange, Nielsen and Appell equation can be derived. For the case when a rod is subjected to a surface or a nonholonomic constraint, Lagrange equation with undetermined multipliers is obtained. Integral variational principle of dynamics of a super-thin elastic rod is also established, from which Hamilton principle formulation is obtained when the material of the rod is linear. Finally, canonical variables to describe the state of the section and Hamilton function are defined, and Hamilton canonical equation is derived. The analytical methods of dynamical modeling of a super-thin elastic rod have been constructed, which can serve as a theoretical framework of analytical dynamics of a super-thin elastic rod with two independent variables.