bluuebunny/crossref_metadata_2025 huggingface dataset:
Lattice dynamics of graphene ribbon
Authors: Liang Wei  , Xiao Yang  , Ding Jian-Wen  ,   湘潭大学物理系，湘潭  411105
Published: December 2020

Based on lattice dynamics theory and force constant model, we calculated phonon dispersion relation, density of states, and specific heat of graphene ribbons.It is shown that the characteristics of phonon spectra behaves as those of a system between one_dimensional carbon nanotube and two-dimensional graphene. The high and intermediate phonon branches of armchair and zigzag nanoribbons resemble those of zigzag and armchair carbon nanotubes, respectively. With the ribbon width increasing, interestingly, it is found that the low frequency peaks in density of states shifted to lower frequency, indicating a phonon confinement effect. At both low and high temperature,specific heat decreased with the increase of the band width,showing up as a singular quantum size effect.The specific heat at 300K can be fitted by CV=CVg+A/n, where CVg is specific heat of graphene and the A/n term represents the effect of edge on specific heat of ribbons.
The kinematic and dynamic nonlinear effects in the exciton-soliton motion in one-dimensional molecular crystals
Authors: Luo Zhi-Hua  , Yu Chao-Fan  ,   广东教育学院物理系，广州  510303
Published: December 2020

Based on the static interaction potential and the (electrical) dipole-dipole interaction between neighboring molecules, the Hamiltonian model of the exciton system in one-dimensional molecular crystal can be expressed by means of the molecular projection operators. In the case of approximate resonance, according to our findings with respect to the kinematics and dynamics effects of the exciton motion, the Klein-Gordon-type equation set for the time evolution of the exciton_soliton and lattice motion has been obtained. With regard to the solitary wave function , it was found that the kinematics and dynamics effects of exciton motion not only greatly contributed to its nonlinear terms 3 and 2{2}\{ξ2}, but also led to its important high-order nonlinear terms. We solved its 5 and 7　nonlinear equation in an analytical form. In particular the solitary wave solution for the 5-nonlinear equation has been studied in detail under the Bell-type and kink-type boundary conditions. Then we found that the kinematics and dynamics effects of exciton motion contributed remarkably to the increase of exciton effective mass, and makes further negative correction to the exciton-soliton energy Ω. As for the Bell-type soliton movement in supersonic speed v＞cs and the Kink-type soliton movement in subsonic speed v＜cs, and the types of the soliton bound states appear to be situated at the bottom and the top of the exciton energy band respectively.
Hydrogen-induced changes in optical and electrical properties of LaMg2Ni alloy film
Authors: Fang Fang  , Zheng Shi-You  , Zhou Guang-You  , Chen Guo-Rong  , Sun Da-Lin  ,   复旦大学材料科学系，上海  200433
Published: December 2020

A 375nm thick LaMg2Ni alloy thin film was prepared by electron beam evaporation using LaNi, Mg and Ni targets, and followed by vacuum annealing at 350℃. Upon hydrogen loading/unloading, the reversible conversion from a metallic, reflecting state to a semiconducting, color-neutral transparent state was observed in the as-prepared film. The contrast ratios in both the transmission (400—900nm) and the resistivity between the reflecting state and the transparent state are over four orders of magnitude. The surface and the cross-section of the alloy films before and after hydrogenation were observed by scanning electron microscope and atomic force microscope, which showed that the lower reflection observed in the dehydrogenated film is due to the rough surface originating from the first hydrogenation.
Dynamics model for electrical tree propagation in cross-linked polyethylene cable insulation under high frequency voltage
Authors: Xie An-Sheng  , Li Sheng-Tao  , Zheng Xiao-Quan  ,   (1)西安交通大学电力设备电气绝缘国家重点实验室,西安  710049; (2)西安交通大学电力设备电气绝缘国家重点实验室,西安  710049；长安大学环境科学与工程学院,西安  710064
Published: December 2020

In this paper we investigated the structures and propagation characteristics of electrical trees observed in the high volatage cross-linked polyethylene (XLPE) cable insulation samples under high volatage of 10kV at frequency of 1000—2000Hz. Based on the specific tree growth mechanism and the fractal nature of tree structures, a dynamic model has been developed to qualitatively predict the electrical tree growth characteristics in XLPE cable insulation when subjected to an electrical stress under high frequency voltage, and then the tree growth rate equation and life formula of tree growth to breakdown are derived.We performed electrical tree growth tests in XLPE cable insulation samples at high frequency and compared the results, which showed that the proposed model was in good agreement with the expreriment.So,it seems that the proposeed model can be applied to the qualitative analysis of aging law of electrical tree in XLPE cable insulation.
Study of injection and relaxation of electron spins in InGaN film by time-resolved absorption spectroscopy
Authors: Chen Xiao-Xue  , Teng Li-Hua  , Liu Xiao-Dong  , Huang Qi-Wen  , Wen Jin-Hui  , Lin Wei-Zhu  , Lai Tian-Shu  ,   中山大学光电材料与技术国家重点实验室，物理科学与工程技术学院，广州  510275
Published: December 2020

The injection and relaxation of electron spins in In0.1Ga0.9N film were studied by femtosecond time-resolved circularly polarized pump-probe spectroscopy. An initial degree of spin polarization of 02 was obtained, which agrees with 3∶1 ratio of heavy- to light-hole valence bands in transition strength, but not with the 1∶1 or 1∶0.94 ratios. A spin relaxation lifetime of 490±70ps was obtained at room temperature. The spin relaxation mechanism is discussed qualitatively, and is thought to be dominated by BAP mechanism here.
Fabrication and optical properties of Au nanoparticle array
Authors: Wang Kai  , Yang Guang  , Long Hua  , Li Yu-Hua  , Dai Neng-Li  , Lu Pei-Xiang  ,   华中科技大学武汉光电国家实验室激光科学与技术研究部,武汉  430074
Published: December 2020

Using nanosphere lithography and pulsed laser deposition, Au nanoparticles with different height have been fabricated on quartz substrates. The surface images of Au particles were observed by scanning electron microscopy, and the results showed that the prism-shaped Au particles form a periodical array. In the U-V-visible absorption spectrum, strong absorption peaks due to the surface plasmon resonance of Au nanoparticles were observed. Furthermore, theoretical calculation based on the discrete dipole approximation was performed. The experimental and theoretical results show that the absorption peaks of the Au nanoprism shifted to the blue side as the out-of-plane height increases.
A quasi-dynamics method for searching for cluster isomers
Authors: Zhou Shi-Yun  , Wang Yin  , Ning Xi-Jing  ,   (1)复旦大学现代物理研究所,上海  200433；复旦大学物理系,上海  200433; (2)复旦大学现代物理研究所,上海  200433；教育部应用离子束物理重点实验室
Published: December 2020

A quasi-dynamics method is developed to search for cluster isomers and can quickly produce isomers which are probable in gas-phase growth under common experimental conditions. We studied the spectrum of C21 isomers by the method and performed molecular dynamics simulations on the clustering processes of 21 isolated carbon atoms in helium buffer, showing that the isomers formed in the dynamical process at higher probabilities are all contained in the isomer spectrum obtained by the method. The potential energy of the most stable configuration in our spectrum is much lower than that obtained by the genetic algorithm ［Chem. Phys. Lett. 364 213，2002］.
The performance of solar cell based on blends of MEH-PPV and PCBM of various compositions
Authors: Yu Huang-Zhong  , Peng Jun-Biao  , Zhou Xiao-Ming  ,   (1)华南理工大学高分子光电材料及器件研究所,特种功能材料教育部重点实验室,广州  510640; (2)华南理工大学物理科学与技术学院,广州  510640; (3)华南理工大学物理科学与技术学院,广州  510640；华南理工大学高分子光电材料及器件研究所,特种功能材料教育部重点实验室,广州  510640
Published: December 2020

The solar cells based on the blend of MEH-PPV (poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylene vinylene) as the donor and PCBM(1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6)C61) as the acceptor are fabricated. We analyzed the influence of composition on the performance of the device by measurements of atomic force microscopy, photoluminescence spectroscopy, dark current density-voltage(J-V) curve of charge-only device, wavelength response of photoconductiveity and J-V curve. The highest efficiency is achieved at the 1∶4 (MEHPPV:PCBM) weight ratio. The good performance is attributed to reasons such as the optimized interpenetrating network, effective charge separaption and rapid charges transport in bicontinuous path. We obtained an open circuit voltage of 0.8V, short circuit current density of 3.47mA/cm2 and fill factor of 55.9% under 100mW/cm2 Air-Mass 1.5 solar simulator illumination, yielding a 1.55% power conversion efficiency.
The decadal variability and its cause of the extreme drought in china
Authors: Hou Wei  , Yang Ping  , Feng Guo-Lin  ,   (1)兰州大学大气科学学院,兰州  730000；中国科学院大气物理研究所,东亚区域气候环境重点实验室,北京  100029; (2)中国科学院大气物理研究所,东亚区域气候环境重点实验室,北京  100029；国家气候中心,中国气象局气候研究开放实验室,北京  100081
Published: December 2020

This paper investigates the probability of extreme drought in four regions of China during the 1470—2000 A.D., and analyzes the δ18O record in Guliya ice core. By wavelet analysis, we find that the probability of drought in the four regions has the quasi-cycle of 350a, like the δ18O record in Guliya ice core. When the δ18O record is high, the temperature of Qinghai-Xizang Plateau is high too, and the probability of drought is low, and vice versa. This paper also analyzes the Pacific decadal oscillation and finds the quasi-cycle of 80a is weakening but the quasi-cycle of 50a is enhancing. When either of them is strong, the probability of drought is high, and the probability is low when the two quasi-cycles are alternating.
Reliability analysis of double random Duffing system
Authors: Zhang Yi-Min  , Zhang Xu-Fang  ,   东北大学机械工程与自动化学院，沈阳  110004
Published: December 2020

By using of Gegenbauer orthogonal polynomials，an effective numerical method for the reliability analysis of double random Duffing system with large coefficient of variation is presented. On the basis of the first passage model，the fourth-moment technique，the Edgeworth series approximation theory and the orthogonal polynomial expansion method are employed to develop a reliability analysis method systematically. The dynamic reliability and mean reliability of the system is discussed. The results obtained by this method are verified by Monte-Carlo simulations.
Adaptive nonlinear channel equalization based on combination neural network for chaos-based communication systems
Authors: Zhao Hai-Quan  , Zhang Jia-Shu  ,   西南交通大学信号与信息处理四川省重点实验室，成都  610031
Published: December 2020

For nonlinear channel distortions of chaos-based communication systems，based on the analysis of the theory of chaotic signal reconstruction and the characteristics of transversal filter and functional link neural network (FLNN)，a novel nonlinear adaptive equalizer with the architecture of combination of transversal filter and functional link neural network (CFFLNN) is proposed in this paper. The novel nonlinear equalizer fully utilizes faster convergence characteristics of transversal filter and the nonlinear approximation capability of FLNN by function expansion due to enhanced input space. Furthermore，the performance of the novel nonlinear adaptive equalizer is also improved. Finally，the proposed equalizer is designed and its adaptive algorithm is deduced by the low complexity normalized least mean square (NLMS) method. And an analysis of stability and convergence for the derived algorithm is provided. To illustrate the analysis，results obtained from the computer simulation are also provided for both linear and nonlinear channels in chaos-based communication system.
Two novel methods for generating spatiotemporal chaotic pseudorandom-bit sequences based on one way coupled map lattices
Authors: Fu Zhi-Jian  , Zeng Yi-Cheng  , Xu Mao-Lin  ,   (1)北京信息工程学院，应用数学研究室，北京  100101; (2)湘潭大学材料与光电物理学院，湘潭  411105
Published: December 2020

Two novel methods for generating spatiotemporal chaotic pseudorandom-bit sequences (PRBS) based on the one way coupled map lattices (OCML) model are proposed. In the first one，the symbolic sequences are generated by a partition，which is based on the statistic property of the state of the one way coupled map lattice. And in the other，the sequences are obtained by comparing the two consecutive state values of a single lattice of the OCML. We compareed the performance of these two types of sequences with the conventional ones. The numerical experiments demonstrated that the sequences have ideal randomicity, excellent correlation and run-length distribution，and they are good candidates for information security，cryptography and spread-spectrum communications.
The digraph cell mapping method based on composite cell space
Authors: He Qun  , Xu Wei  , Li Shuang  , Xiao Yu-Zhu  ,   西北工业大学理学院应用数学系，西安  710072
Published: December 2020

In order to improve the accuracy and efficiency，an iterative digraph cell mapping method is presented through introducing the notion of composite cell space. This iterative method can refine any interesting region of cell state space. Because the refining process is performed by algebraic operation，the computer memory does not be increased additionally. Furthermore，the digraph dynamical properties can be preserved in the refining process. In order to implement it easily，an effective algorithm is designed. As an example，the Henon map is taken to demonstrate the validity and efficiency of this method.
Quantum interference effects of coherent instantaneous states and Berry phase
Authors: Ma Rui-Qiong  , Li Yong-Fang  , Shi Jian  ,   (1)陕西师范大学，物理学与信息技术学院，西安  710062; (2)西安邮电学院，电子与信息工程系，西安  710061
Published: December 2020

We present the analytic expressions for different types of quantum interference effects in coherent instantaneous state quantum system, and discuss the behaviors of the optics and quantum interference, respectively. The important role that the geometrical phase plays in quantum interference is analyzed in detail for the first time. It is demonstrated theoretically that the measurement of the geometrical phase can be realized by appropriately choosing the pulse area of the pump field. The valid control of the quantum interference is achieved by manipulating the chirped pump field.
Experimental studies of spallation in nanocrystalline copper film by laser irradiation
Authors: Wang Yong-Gang  , He Hong-Liang  , Boustie Michel  , Sekine Toshimori  ,   (1)Advanced Materials Laboratory ,National Institute of Materials Science,Tsukuba  30520044,Japan; (2)Laboratoire de Combustion et de Détonique,1 Av. Clément Ader,Chasseneuil Cedex 86961,France; (3)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实验室,绵阳  621900; (4)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实验室,绵阳  621900；宁波大学工学院力学与材料科学研究中心,宁波  315211
Published: December 2020

The spall behavior of nanocrystalline copper film synthesized by electrodeposition technique is investigated by laser irradiation. The push-pull type VISAR with sub-nanosecond time resolution is used to measure the rear free surface velocity profile of the sample. The spall strength in nanocrystalline copper film is calculated from the measured free surface velocity profile as a function of tensile strain rate. Results show that the dynamic tensile strength of nanocrystalline copper film is about 3 GPa, which is much higher than that of polycrystalline bulk copper, but lower than that of single crystal copper. This difference may be attributed to the effective obstacles to dislocation motion by the presence or more grain boundaries in nanocrystalline copper.
Influence of He isotope on the differential cross section for He-NO collision system
Authors: Wang Rong-Kai  , Shen Guang-Xian  , Song Xiao-Shu  , Linghu Rong-Feng  , Yang Xiang-Dong  ,   (1)贵州师范大学理学院,贵阳  550001; (2)贵州师范大学理学院,贵阳  550001；四川大学原子与分子物理研究所,成都  610065; (3)四川大学原子与分子物理研究所,成都  610065
Published: December 2020

The total differential cross section, elastic differential cross section and inelastic differential cross section for collision between He isotopic atoms and NO molecule have been calculated by using close-coupling approximation method. The influence of He isotope on the differential cross section for He-NO collision system has been given. The calculated result shows that the total differential cross section at 0 degree increases, and rainbow phenomenon of collision of He isotopic atoms with NO molecule is more evident along with increase of incident He isotope mass at identical incident energy. At the same time, the effect of increased reduced mass is larger than the effect of diminished relative velocity of collision between He atom and NO molecule, and enables the scattering spacing of the oscillation to gradually decrease.
DFT study on the Mg-doped TinMg (n=1—10) clusters
Authors: Sheng Yong  , Mao Hua-Ping  , Tu Ming-Jing  ,   (1)四川大学材料科学与工程学院,成都  610065; (2)重庆三峡学院科技处,万州  404000
Published: December 2020

The possible geometrical and electronic structures of small TinMg (n=1—10) clusters have been optimized by using B3LYP method of density functional theory (DFT). The binding energies, energy level distribution, energy gaps, electron affinities, dissociation energy and second difference in energy are calculated and discussed. The resulting geometries show that the magnesium atom remains on the surface of clusters. The geometric effect and electronic effect clearly indicate the Ti5Mg cluster to be endowed with special stability.
Recent results of SMBI on the HL-2A tokamak with divertor configuration
Authors: Yao Liang-Hua  , Feng Bei-Bin  , Chen Cheng-Yuan  , Feng Zhen  , Li Wei  , Jiao Yi-Ming  ,   核工业西南物理研究院，成都  610041
Published: December 2020

Supersonic molecular beam injection (SMBI) can penetrate the separatrix of the HL-2A plasma and result in the increase of important plasma parameters, such as the plasma storage energy, the βp, the line averaged electron density, the central electron density and temperature. During deuterium plasma ECRH and deuterium SMBI, the neutron account rapidly increases along with the electron density and temperature increments. SMBI was considered as an alternate fuelling technique, which may provide a higher particle source at the pedestal top for ITER. A mean velocity for hydrogen SMBI of about 1.7km/s was detected in HL-2A torus and the measured result was compared with that for the effusion in vacuum.
First-principles study of the NiMgn (n=1—12) clusters
Authors: Yao Jian-Gang  , Wang Xian-Wei  , Wang Yuan-Xu  , Jing Qun  , Luo You-Hua  ,   (1)河南大学计算材料科学研究所，河南大学物理与电子学院，开封  475004; (2)河南大学计算材料科学研究所，河南大学物理与电子学院，开封  475004；华东理工大学理学院,上海  200237
Published: December 2020

The geometrical structure, frequency and electronic properties of the NiMgn(n=1—12) clusters have been studied with the generalized gradient approximation (GGA) based on the density functional theory (DFT) with the consideration of spin multiplicity. The results indicate that: when n is 1 or 2, the spin multiplicity of the ground state structures of the clusters is triplet while it is singlet from n≥3. The ground state structures of the host clusters are changed obviously due to the encapsulation of Ni atom for n≤8, the growth patterns of the ground state structures of the NiMgn clusters are dominated by the trigonal bipyramidal, as well as the octahedron structures. The evolution behaviors of the ground state structures based on the trigonal prism of the host clusters are partly modified from n≥9. The Ni atom completely falls into the center of the host clusters as n≥6. The doping of Ni atoms increases the average binding energy, but reduces the energy gap of the host clusters. n=4, 6 and 10 are the magic numbers. The 3d and 4p orbitals of the Ni atom for different sized clusters play distinct roles in the s-p-d orbital hybridization. The NiMg6 cluster with higher symmetry Oh not only possesses improved stability, but also has the smallest energy gap (just about 0.25eV) of all of the NiMgn clusters.
Research on the continuations of magnetic field of magnetic object based on integral equation method and singular value decomposition
Authors: Guo Cheng-Bao  , Xiao Chang-Han  , Liu Da-Ming  ,   海军工程大学电气与信息学院,武汉  430033
Published: December 2020

The continuation of magnetic field of magnetic object is studied, and a novel method based on integral equation method and singular value decomposition is presented. In the implementation of the new method, the magnetic object's structure only needs to be coarsely partitioned as some elements by integral equation method, thus a linear system of equations can be obtained with the magnetic field measurements at a large plane below the magnetic object. The system of equations can be solved regularly by the truncated singular value decomposition technique and the modified singular value decomposition technique based on singular value decomposition, then the 3D magnetic fields reconstruction the upward and downward continuation of the magnetic object's magnetic field are realized. The precision and reliability of the new method are higher than the conventional ones; especially, the difficulty of the upward continuation in certain ranges is surmounted.
Design and analysis of double layer resonant grating filters in the visible spectral region
Authors: Ma Jian-Yong  , Liu Shi-Jie  , Wei Chao-Yang  , Jin Yun-Xia  , Zhao Yuan-An  , Shao Jian-Da  , Fan Zhen-Xiu  ,   (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

Guide-mode resonances of double-layer gratings are analyzed with the Fourier modal method and the relationship between spectral characteristics of resonant gratings such as peak diffraction efficiency, linewidth and side-band reflectance and depth, period and fill ratio of grating are illustrated in detail. It is shown that the diffraction efficiency of resonant gratings will be higher than 99.5 percent when the groove depth tolerance is in the range of 15 percent, and mean while the relative error of line width will reach to 7 and 60 percent respectively for the negative and positive conditions. Compared with the position of resonant wavelength, the line width of resonant grating filters is relatively sensitive to the error of groove depth and residual thickness of waveguide layer when they deviate from designed values. Moveover, the resonant wavelength and width of spectrum do vary as a function of period and fill ratio.
Influence of astigmatism on the diffraction property of the axicon and its correction
Authors: Jiang Xin-Guang  , Wu Feng-Tie  ,   华侨大学信息科学与工程学院,泉州  362021
Published: December 2020

The diffraction field will show aberration if an axicon has astigmatism for beams incident at an angle. In this paper, the diffractional optical field expression of an axicon with astigmatism was derived based on the diffraction integral theory. The influence of the astigmatism on the diffraction property of the axicon was analyzed through the numerical simulation of the diffraction pattern with different astigmatism and the optical intensity distribution along the propagation direction for a given astigmatism. The method of correcting the beam aberration caused by the astigmatism is proposed and realized by the experiment using a precise tunable rotator. Experimental results agree with the theoretical analysis. The result extends the field of applications of the axicon.
Electromagnetically induced left handedness in inverted Y-type four level atomic system
Authors: Zheng Jun  , Liu Zheng-Dong  , Zeng Fu-Hua  , Fang Hui-Juan  ,   (1)南昌大学近代物理研究所，南昌  330031；南昌大学纳米技术工程研究中心，南昌  330047; (2)南昌大学近代物理研究所，南昌  330031；南昌大学纳米技术工程研究中心，南昌  330047；南昌大学材料科学与工程学院，南昌  330031
Published: December 2020

The system of inverted Y-type four-level atoms interacting with multi-mode light fields is discussed. Through the mechanism of quantum interference, the relative dielectric permittivity and the relative magnetic permeability will changed remarkably. Using appropriately chosen parameters, the real parts of both the relative dielectric permittivity and the relative magnetic permeability will be negative, and then the left handedness effect happens and the left-handed material is realized. The properties of left-handed materials such as the range of frequencies of the negative refractive index can be manipulated via changing certain parameters of the system.
Study of ultraviolet single photon imaging system
Authors: Zhang Xing-Hua  , Zhao Bao-Sheng  , Miao Zhen-Hua  , Zhu Xiang-Ping  , Liu Yong-An  , Zou Wei  ,   (1)中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安   710119; (2)中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安   710119；中国科学院研究生院，北京  100049
Published: December 2020

An ultraviolet single photon imaging system was built and its structure,working principle and spatial resolution are reported. Ultraviolet single photon can be obtained by ultraviolet lighr emitted by a mercury lamp and is attenuated by filters. Single photon irradiates on the microchannel plate directly, producing the multiplied electrons. The multiplied electrons are collected by wedge and strip anode. The charge signal coming from the anode is transformed to voltage signal by a charge_sensitive preamplifier. Then the voltage signal is filtered and shaped by a main amplifier. The output wave signal is collected by high speed data collection card continuously and processed with software. Finally, a ten-minute counting image of ultraviolet single photon is acquired and its revised image is obtained by image processing. The spatial resolution of this system can reach 150 micrometers as tested with the self-designed resolution board. The system can be used widely for very faint luminescence detecting/imaging, biological luminescence and space environment weak light detection.
Automatic pathological voice evaluation based on auditory model
Authors: Wang Di  , Fu Qiang  , Yang Lin  , Yu Ping  , Yan Yong-Hong  , Feng Ji  ,   (1)中国科学院声学研究所中科信利语音实验室，北京  100080; (2)中国科学院物理研究所，北京  100190; (3)中国科学院物理研究所，北京  100190；中国科学院声学研究所中科信利语音实验室，北京  100080; (4)中国人民解放军总医院，北京  100853
Published: December 2020

Sustained vowel analysis is an important method in pathological voice evaluation system. In view of the fact that conventional methods generally analyzes the hand-cut samples in FFT frequency domain, an auditory model is proposed as an accurate and robust method for use in pathological vowel analysis. An automatic sample cutting method increases the stability of analysis. Expertiment showed this method is more effective and robust.
Theoretical and numerical investigations of the acoustic field excited by submarine explosion
Authors: Tang Li-Guo  , Xu Xiao-Mei  , Liu Sheng-Xing  ,   厦门大学海洋学系,厦门  361005；厦门大学水声通信与海洋信息技术教育部重点实验室,厦门  361005
Published: December 2020

This paper simulates and analyzes numerically the dispersion characteristics of the waves propagating in the shallow-ocean overlying a semi-infinite elastic solid. The analytical solution of the acoustic field in the shallow-ocean, excited by an explosive point source in the solid bottom, is derived by using the theories for sound propagation in liquid and solid. The time-domain waveforms of transient acoustic field are simulated with the above analytical solution. The dispersion characteristics of the transient acoustic field are analyzed by using the smoothed pseudo Wigner-Ville distribution.
Analysis of the impact factors on the accuracy of sound field reconstruction based on wave superposition
Authors: Li Jia-Qing  , Chen Jin  , Yang Chao  , Jia Wen-Qiang  ,   上海交通大学振动、冲击、噪声研究所，上海  200240
Published: December 2020

Wave superposition is a numerical method for calculating sound radiation based on the principle of equivalent source. However, the principle does not indicate definitely how to collocate these equivalent sources. So, it is necessary to evaluate its reconstruction accuracy and analyze the impact factors when wave superposition is applied to sound field reconstruction. The purpose of this study is to find some rules for improving the reconstruction accuracy. A number of impact factors on the precision of sound field reconstruction have been analyzed through theoretical analysis and numerical simulation. It has been proved that the equivalent sources have to be collocated inside of a radiator; moreover, it is best for them to conform to the radiator's shape. However, the measurement plane needs not to conform to the radiator's shape, and even does not need to measure in near-field. In addition, it has been shown that Tikhonov and TSVD regularization method can work well with wave superposition when applied to sound field reconstruction. On the basis of these rules, wave superposition can be used to perform better sound field reconstruction; and also its application range can be extended.
Dispersion analysis of Lamb waves with narrow frequency bands
Authors: Li Fu-Cai  , Meng Guang  ,   上海交通大学机械系统与振动国家重点实验室，上海  200240
Published: December 2020

Dispersion is the intrinsic characteristic of Lamb waves, which influences the effective applications of Lamb waves in plate-like structures. The continuous wavelet transform (CWT) was applied to the Lamb wave signals with narrow frequency band captured from aluminium structures. The CWT-based contour and ridge were therefore searched in the time-scale domain. The unavoidable dispersion characteristic was used in this paper to distinguish the mode of each wave package and pinpoint these packages at each scale for determining the actual group velocities of dispersion curves. Analysis results demonstrate that the proposed approach is effective in dispersion analysis and wave mode differentiation.
Realization of homogenous discharge at atmospheric pressure in air using wire mesh covered by PET films
Authors: Luo Hai-Yun  , Wang Xin-Xin  , Mao Ting  , Liang Zhuo  , Lü Bo  , Guan Zhi-Cheng  , Wang Li-Ming  ,   (1)清华大学电机系，北京  100084; (2)清华大学深圳研究生院，深圳  518055
Published: December 2020

Homogenous discharges were produced in a 2-mm air gap at atmospheric pressure by using 325# fine wire mesh as electrodes covered with 0.1 mm PET films and 50Hz line power source paralleled with a discharge-stabilizing capacitor. For obtaining such a homogeneous discharge it is important to attach tightly the wire mesh together with the PET film on the surface of a Rogowski electrode. The experiments show that the commonly used method to distinguish a homogenous discharge from a non-homogeneous one by the waveforms of discharge current and transferred charge is not always reliable since the waveforms could tell only the discharge simultaneity rather than the discharge homogeneity. A fast image of discharge with an exposure time not longer than 100ns should be used instead to judge the discharge homogeneity. It is the first time in the experiments of atmospheric pressure discharge using wire mesh electrode covered by PET film such fast images were obtained, which indicates that the homogeneous discharge is a Townsend discharge rather than a glow discharge.
Experimental studies on the properties of the discharge modes in a cylindrical radio frequency inductively coupled plasma
Authors: Ding Zhen-Feng  , Yuan Guo-Yu  , Gao Wei  , Sun Jing-Chao  ,   大连理工大学三束材料改性国家重点实验室，大连  116023
Published: December 2020

In this paper, Z-scan, current and voltage probe were used to measure rf discharge power, coupling coil rf current, voltage and dc plasma floating voltage in RF inductive dischargr, and the effects of impedance matching network, coil coupling intensity and the source ground area on the properties of E,H mode and the mode transition are investigated. The positive and negative feedback regions are put forth on the basis of the influence of the series capacitance in a Γ-type impedance matching network on RF output power of the RF power source. It is experimentally founded that under identical experimental parameters, the discharge mode evolution is apt to be discontinuous and continuous in the positive and negative feedback regions, respectively. In addition, the threshold coil RF current (or plasma absorbed power) corresponding to the mode transition, the hysteresis loop width, the difference in plasma absorbed power during the discharge mode transition vary evidently with the series capacitance of the impedance matching network. The threshold coil RF current of E-H mode transition is not necessarily higher than that of H-E mode transition. In combination with the influences of impedance matching network and discharge pressure, the modes of transition are diversified for different ground areas.
Structural study of MnxSi1-x magnetic semiconductor thin films
Authors: Ren Peng  , Liu Zhong-Liang  , Ye Jian  , Jiang Yong  , Liu Jin-Feng  , Sun Yu  , Xu Peng-Shou  , Sun Zhi-Hu  , Pan Zhi-Yun  , Yan Wen-Sheng  , Wei Shi-Qiang  ,   中国科学技术大学国家同步辐射实验室，合肥  230029
Published: December 2020

The structure of MnxSi1-x magnetic semiconductor thin films prepared by molecular beam epitaxy(MBE) on Si(100) substrate at 600 ℃ has been studied by X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) technique. The XRD results show that in the MnxSi1-x thin films with high Mn doping concentrations (x=0.08 and 0.17), only diffraction peaks of crystalline Mn4Si7 are observed. XANES results indicate that all the Mn K-edge XANES spectra of MnxSi1-x thin films with different Mn doping concentrations (x=0.007, 0.03, 0.08 and 0.17) show the similar feature. XANES calculation based on multiple-scattering theory further reveals that the experimental spectra for samples with different Mn doping concentrations are reproduced by the calculated Mn4Si7 spectrum. These results reveal that for the MnxSi1-x magnetic semiconductor thin films, Mn atoms mainly exist in the Si thin film substrate in the form of Mn4Si7 nanocrystalline grains, the substitutional or interstitial Mn atoms scarcely exist.
Rapid solidification of undercooled Cu60Sn30Pb10 monotectic alloy
Authors: Yin Han-Yu  , Lu Xiao-Yu  ,   西北工业大学应用物理系，西安  710072
Published: December 2020

Rapid solidification of bulk Cu60Sn30Pb10 monotectic alloy was investigated. The obtained undercooling varied from 37 to 173 K. Solidification microstructures showed obvious macroscopic segregation. X-ray diffraction analysis revealed that the top of sample is a ternary_phase section composed of Sn and Pb solid solution phases and ε(Cu3Sn) intermetallic compound phase, the bottom is a Pb-rich solid solution phase section. With the increase of undercooling, ε(Cu3Sn) intermetallic compound phase in the ternary phase section showed a transition from bulk dendrites to refined lamellar microstructure; in addition, while the lamellar spacing was also decreasing. The experiment indicted that the Sn and Pb phases exist as seperated eutectoids. There is a small amount of ε(Cu3Sn) dendrites in the Pb-rich phase. The ε(Cu3Sn) dendrites increase in length with the increase of undercooling and break into pieces under the condition of great undercooling. The Sn solid solution phase always accretes the circumference of ε(Cu3Sn) intermetallic compound phase. Their shape resembles the peritectic microstructure.
Structure and thermal stability of gold nanowire encapsulated in carbon nanotube
Authors: Zhang Kai-Wang  , Meng Li-Jun  , Li Jun  , Liu Wen-Liang  , Tang Yi  , Zhong Jian-Xin  ,   湘潭大学物理系，湘潭  411105
Published: December 2020

The structure and thermal stability of gold nanowire encapsulated in single-walled carbon nanotube (SWCNT) were studied by molecular dynamics simulations. A (8,8) SWCNT was used as a model system and the simulated annealing method was employed to find the stable structure of the gold nanowire at room temperature. Ourresults show that the gold nanowire encapsulated in a (8,8) SWCNT has a cylindrical shape and a helical shell structure. The helical-shell nanowire is thermally stable at temperatures much higher than the melting temperature of its bulk counterpart and is different from the gold nanowire formed in free space without the nanotube envelope. We also found that the spiral nanowire undergoes structural changes at higher temperatures.
Theoretical studies on the structure and He interstitial diffusion of LaNi5He compounds
Authors: Zhang Chuan-Yu  , Gao Tao  , Zhang Yun-Guang  , Zhou Jing-Jing  , Zhu Zheng-He  , Chen Bo  ,   (1)四川大学原子与分子物理研究所，成都  610065; (2)四川大学原子与分子物理研究所，成都  610065；四川大学物理科学与技术学院，成都  610065; (3)中国工程物理研究院核物理与化学研究所，绵阳  621900
Published: December 2020

Based on the generalized gradient approximation (GGA) of density function and the full-potential linearized augmented plane wave (FLAPW) method, the micro-arrangement of He atoms after tritium decay in LaNi5He have been modeled for theoretical study. The energy curves between 1b-6m-2d, 4h-2d-4h, 6m-12o-12n and 12n-3f-12n interstitial sites for LaNi5He are worked out theoretically. The results indicate that 1b site is most stable for He occupation in LaNi5He among the seven nonequivalent interstices. The potential barrier doesn't exist when He atoms migrate from 6m site to 1b site, but there is a potential barrier of height 1.55eV between 2d site and 1b site. And He atoms which lie in the 12n sites can easily go throngh the 12o sites to get to the 6m sites finally. Helium atoms can freely migrate between the 4h sites. By getting through a 13.6eV potential barrier, He atoms are able to directly migrate between the 12n sites. Finally, the density of states (DOS), charge density (CD) and potential distribution for characteristic interstitial LaNi5He and LaNi5H are plotted and compared with each other in detail.
Effects of the concentration of oxygen vacancy of anatase on electric conducting performance studied by frist principles calculations
Authors: Hou Qing-Yu  , Zhang Yue  , Chen Yue  , Shang Jia-Xiang  , Gu Jing-Hua  ,   北京航空航天大学材料科学与工程学院，北京  100083
Published: December 2020

Based on the density of stales calculation of the concentration of oxygen vacancy in anatase semi-conductor, the model of anatase with different sizes and proper concentrations of oxygen vacancy were studied under the same condition.It was found that the anatase with relatively low oxygen vacancy shows better electric conducting performance by comparison of the relative average number of electrons in the conduction band , mobility and conductivity. So we arive at the conclusion that the lower the concentration of oxygen the better anatase can be prepared with heavy doping, and under the conditions of low tempeature and heavy oxygen vacancy, the conductivity of anatase semi-conductor is closely related to the concentration of oxygen vacancies, average number of electrons in the conduction band and the conductivity caused by scattering of oxygen vacancies.
Polaron-soliton squeezed states , ground state and quantum fluctuation in one-dimensional molecular crystals
Authors: Yu Chao-Fan  , Liang Guo-Dong  , Cao Xi-Jin  ,   (1)广东教育学院物理系，广州  510303; (2)华南师范大学物理系，广州  510006; (3)暨南大学光电工程系，广州  510632
Published: December 2020

On the basis of the Hamiltonian of the Holstein one_dimensional molecular crystals, using the squeezed_coherent state expansion method, the influence of the electron_two phonon interaction on the properties of the ground state and quantum fluctuation for the polaron_soliton system were investigated by including the quantum correlation between the polarons and the squeezed phonons, and the renormalized displacement correction.The nonlinear Schringer equation for one_dimensional polaron_soliton state has been found in a closed form.By the use of the nonlinear expansion, we have given the analytical solution of the corresponding nonlinear equation so as to obtain the ground state energy,the quantum fluctuation and the polaron energy of the polaron_soliton system in analytical form. We have found that, when the electron_two phonon coupling strength g1g12n〉 and 〈Δ2p〉〈Δ2q〉 for the two-phonon effect are larger than the one_phonon one and the polaron energy for the two_phonons effect is more negative compared with the one_phonon one.
Solid-state reaction synthesis and electrical properties of Sm0.9Sr0.1AlO3-δ perovskite oxide
Authors: Xiang Jun  , Wang Xiao-Hui  ,   (1)江苏科技大学数理学院，镇江  212003; (2)江苏科技大学数理学院，镇江  212003；江苏大学材料科学与工程学院，镇江  212013
Published: December 2020

The Sm0.9Sr0.1AlO3-δ samples were prepared by solid-state reaction. Their microstructure, morphology, electrical properties and transport mechanism were studied by X-ray diffraction(XRD), scanning electron microscopy(SEM), alternating current impedance technology and oxygen concentration cell method, respectively. The relationship between sintering technology, relative density and conductivity was studied. The experimental results show that the Sm0.9Sr0.1AlO3-δ perovskite oxides with single tetragonal phase can be obtained when they are sintered at 1650℃. Among all the samples, Sm0.9Sr0.1AlO3-δ sample sintered at 1650℃ for 16h has the highest relative density of 96.7% and electrical conductivity of 1.3×10-2 S/cm at 900℃. The curves of ln(σT) against 1000/T reveal two straight lines intersecting at 670 ℃, showing the activation energy of conduction in the high temperature range(T>670℃) is lower than that in the low temperature range(T0.9Sr0.1AlO3-δ is a mixed conductor of oxygen ion and hole in air. Its oxygen ionic transference number is around 0.7 in the measuring temperature region, and slightly increases with increasing temperature. By means of oxygen ionic transference numbers measured in air, the relative contributions of ionic and electronic conduction are separated, and the results reveal that activation energy for oxygen ionic conduction of 0.95eV is lager than that for hole conduction of 0.84eV, and Sm0.9Sr0.1AlO3-δ has an oxygen ionic conductivity of 9.65×10-3 S/cm at 900℃.
Electronic theoretical study on the corrosion and passivation mechanism of Ti metal
Authors: Liu Gui-Li  ,   沈阳工业大学建筑工程学院，沈阳  110023
Published: December 2020

The atomic cluster models of the crack in αTi formed by dislocation accumulation were set up. The electronic structure of Ti was calculated by using recursion method, and the influence of O, Cl, and Pd on the electronic structure of Ti was studied. The calculated results show that, the total density of states near Fermi level is lowerd due to the existence of O, which leads to the decrease of the chemical activity of Ti. The binding energy of Ti is reduced by oxygen. The affinity between O and Ti is large, so O is easy to react with Ti to form the oxide film. The stability of Cl in Ti and the affinity with Ti are not as good as O. Cl is difficult to substitute the O atom on the surface of Ti, so the oxide film of Ti is very stable, the phenomenon of over passivation can not occur. The environment-sensitive embedding energy of Pd in the crack is smaller than in αTi grain, so Pd is easy to diffuse to the crack and makes the environment sensitive embedding energy of H rise obviously, which leads to the weakening of H diffusion to the crack and the improvement of the stress-corrosion resistance of Ti.
Martensitic transformation and magnetocaloric effect in Ni50Mn35In15 Heusler alloy
Authors: Jing Chao  , Chen Ji-Ping  , Li Zhe  , Cao Shi-Xun  , Zhang Jin-Cang  ,   上海大学物理系，上海  200444
Published: December 2020

Polycrystalline Ni50Mn35In15 alloy was fabricated by arc-melting, and its martensitic transformation and magnetocaloric effect were systematically investigated with magnetic property measurement. The experimental results indicated that, with decrease of temperature, the second-order magnetic transition and the martensitic transition with characteristic of the first-order structural transition happened successively near room temperature, leading to an abrupt change of magnetization. At the same time, exchange bias was found by means of hysteresis loop measurement at low temperature, which clearly suggested coexistence of ferromagnetic and anti-ferromagnetic phases at low temperatures. In addition, a large magnetic entropy change during martensitic transition was calculated from Maxwell equations. Its value can reach 22.3 J/kg K at 309K in applied field of 5T.
The relation between green-band luminescence of 4H-SiC homoepitaxial layer and defects
Authors: Jia Ren-Xu  , Zhang Yi-Men  , Zhang Yu-Ming  , Guo Hui  , Luan Su-Zhen  ,   西安电子科技大学微电子学院，宽禁带半导体材料与器件教育部重点实验室，西安  710071
Published: December 2020

The Green-band luminescence (GL) from an Al-doped 4H-SiC Homoepitaxial layer prepared by using chemical vapur deposition (CVD) has been observed and studied. The deep pattern obtained by SEM and the buffer layer can be found in the interface between SiC substrate and epilayer. The deep profiles of Si atom in 4H-SiC epilayers obtained by using the secondary ion mass spectrometry (SIMS) and the X-ray photoelectron spectroscopy (XPS) show the relative distribution of Si and C. The results strongly suggest that the vacancy of C and the extended defects (point defects, threading dislocations, et al) from buffer layer are responsible for the GL emission. The full width at half maximum (FWHW) of GL indicates the distributions of VC and its complex defects. The quality of crystals and the distribution of defects in epitaxial layers can be characterized by the intensity and the wavelength of GL obtained from samples at room temperature.
Stark effect of donor impurity states in strained heterojunctions under pressure
Authors: Zhang Min  , Ban Shi-Liang  ,   (1)内蒙古大学物理科学与技术学院物理系，呼和浩特  010021; (2)内蒙古大学物理科学与技术学院物理系，呼和浩特  010021；内蒙古师范大学物理与电子信息学院，呼和浩特  010022
Published: December 2020

A modified variational method is adopted to investigate the binding energies of the shallow impurity states near the interface of a strained GaN/AlxGa1-xN heterojunction by using a simplified coherent potential approximation. The relations between the impurity binding energies and pressure, the impurity position, electric field strength and the Al components are calculated for strained zinc-blende GaN/AlxGa1-xN heterojunctions with (001) and (111) orientations respectively. The result indicates that the binding energy of impurity state nearly linearly increases with pressure. The Stark effect on the binding energy as a function of electric field shows blue or red shift in the spectra for different impurity positions. The results corresponding to (001) and (111) orientations are compared. It is found that the effect on the binding energy of Al component is obvious. For an impurity located in the channel side and comparatively far from the interface, a monotonic increase of the binding energies will appear with increasing Al content due to the stronger two-dimensional properties of the electrons, and pressure enhances the increase of amplitude. Whereas for an impurity located in the barrier side, the increase of Al content will weaken the bound between the impurity and the electron to decrease the binding energy.
Mechanism and impact of the double-hump substrate current in high-voltage double diffused drain MOS transistors
Authors: Wang Jun  , Wang Lei  , Dong Ye-Min  , Zou Xin  , Shao Li  , Li Wen-Jun  , Steve Yang  ,   (1)上海宏力半导体制造有限公司，上海  201203; (2)中国科学院上海微系统与信息技术研究所,上海  200050；中国科学院研究生院，北京  100049；上海宏力半导体制造有限公司，上海  201203
Published: December 2020

A 30-volt double diffused drain MOS (DDDMOS) is fabricated with standard 0.15μm CMOS process. The substrate current of this DDDMOS is investigated and the two-humps of Ib-Vg curves is observed. The origin of these two humps of substrate current is demonstrated by experiments and TCAD simulation. The cause of first peak is the same as that in conventional MOS device; the second hump is caused by the impact ionization under high electric field in the drift region far away from the channel edge. The correlation between the electric field and the device parameters is studied through the Poisson's Equation and Current continuity equation. Based on the mechanism of the second hump of Ib, its impaction on device reliability is studied.