bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic and structural investigation of tetracene adsorbed on Ru(1010) surface
Authors: Dou Wei-Dong  , Huang Han  , Zhang Han-Jie  , Song Fei  , Li Hai-Yang  , He Pi-Mo  , Bao Shi-Ning  , Chen Qiao  , Zhou Wu-Zong  ,   (1)圣安德鲁斯大学联合化学学院，英国; (2)浙江大学物理系，杭州 310027; (3)浙江大学物理系，杭州 310027;绍兴文理学院物理与电子信息系，绍兴 312000
Published: December 2020

The electronic states of tetracene adsorbed on Ru (1010) surface as well as their adsorption sites and directions has been studied by using ultraviolet photoelectron spectroscopy (UPS), angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and scanning tunneling microscopy (STM). The UPS measurements show that the six peaks from the tetracene are 2.1, 3.5, 4.8, 6.0, 7.1 and 9.2 eV below the Fermi level. The ARUPS measurements suggest that the plane of tetracene molecule is parallel to the Ru(1010) surface. The STM image shows that the tetracene molecule is adsorbed on Ru (1010) surface with its longer axis lying in the direction of either ［0001］ or ［1210］. The adsorption structure was confirmed with an ab initio calculation based on density functional theory (DFT). The short-bridge site and the hollow site are the most favorable sites when the molecule has its longer axis oriewted along ［0001］ and ［1210］, respectively.
Thermodynamic quantities of the spin fields near the event horizon in Taub-NUT spacetime
Authors: Liu Xiao-Ying  ,   湛江师范学院物理系，湛江 524048
Published: December 2020

The entropy density，energy density and pressure of the spin fields near the event horizon in Taub-NUT spacetime are investigated by using the Wentzel-Kramers-Brillouin approximation. It is shown that any one of the thermodynamic quantities has three terms. The first term has the same form as that in flat spacetime, the second and the third terms are spin-dependent terms due to the spin fields.
Associative memory and segmentation in the neural system under stimulation of stochastic or chaotic perceptual singals
Authors: Peng Jian-Hua  , Yu Hong-Jie  ,   (1)华东理工大学信息科学与工程学院，上海 200237; (2)上海交通大学工程力学系，上海 200240
Published: December 2020

We present in this paper some results on the temporal segmentation and retrieval of stored memories or patterns using neural networks composed of spiking neurons. Respecting the working environment，we present the network with stochastic or chaotic stimuli as their extremely working conditions and also with noise. We attempt to give an explanation to the function of memory retrieval of the brain system, where the stimuli usually may not be constant, sinusoidal or periodic, but rather chaotic or stochastic. For an input pattern which is a superposition of several stored patterns, it is shown that the proposed neuronal network model is capable of segmenting out each pattern one after another as synchronous firings of a subgroup of neurons，and if a corrupted input pattern is presented, the network is shown to be able to retrieve the perfect one，that is it has the function of associative memory. By thorougly adjusting the parameters, such as the coupling strength and the intensity of the noise, the temporal segmentation attains its optimal performance at intermediate noise intensity，which reminds of the stochastic resonance observed in the coupled spiking neuronal networks.
Bandwidth enhancement of semiconductor laser as a chaotic transmitter by external light injection
Authors: Wang Yun-Cai  , Zhang Geng-Wei  , Wang An-Bang  , Wang Bing-Jie  , Li Yan-Li  , Guo Ping  ,   太原理工大学物理系，太原 030024
Published: December 2020

A semiconductor laser that generates a chaotic signal with optical feedback can be treated as a chaotic transmitter. Based on single mode rate equations of semiconductor laser with optical feedback and external injection, the numerical simulation shows that the bandwidth of the transmitter is expanded by external optical injection. When the injection index kinj is 0.39, the bandwidth is increased from the value of 2.7 GHz without optical injection to 14.5GHz. The results also reveal that, under the same injection strength, the enhancement of bandwidth depends evidently on the frequency detuning between the external injection laser diode and the chaotic carrier transmitter. The maximum bandwidth of the chaotic transmitter can be obtained when the frequency detuning is in the range from 2 to 4GHz. The bandwidth of the chaotic transmitter can also be enhanced by increasing the bias current.
Absolute differential, elastic integral and moment transfer cross sections for electron scattering by SO2 at intermediate and high energies
Authors: Shi De-Heng  , Sun Jin-Feng  , Zhu Zun-Lue  , Yang Xiang-Dong  , Liu Yu-Fang  , Ma Heng  ,   (1)河南师范大学物理与信息工程学院,新乡 453007; (2)河南师范大学物理与信息工程学院,新乡 453007;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

Taking into consideration the overlapping effect of electron clouds between two bonded atoms in a molecule, a modificed potential method is presented which can be used to accurately calculate various cross sections for electron scattering by molecules at intermediate and high energies. The modified complex optical potential is directly employed to calculate the absolute differential, elastic integral and moment transfer cross sections for electron scattering by SO2 in the energy range 100—1000 eV by using the additivity rule at Hartree-Fork level. The quantitative results are compared with those obtained by measurement and other theories wherever available. It is shown that the additivity rule model together with the modified complex optical potential can give the encouraging results, which are much closer to the measurements than the unmodified ones.
Study of far field distribution of fiber amplifier arrays
Authors: Xiao Rui  , Hou Jing  , Jiang Zong-Fu  ,   国防科学技术大学光电科学与工程学院，长沙 410073
Published: December 2020

In this paper, according to the analytical equation of the far-field intensity distribution in coherent combination of fiber laser arrays, we investigate the influence of fill factor of the laser arrays, elements and phase errors on the far-field patterns, the energy and angular width of the main lobe. At last, we describe the experimental study of the coherent combining of three-element fiber-laser arrays based on ytterbium polarization-maintaining single-mode power amplifiers with the fill factor of 12.5%.
Wave coupling theory of optical activity in birefringent crystal
Authors: Xu Jie  , Chen Li-Xiang  , Zheng Guo-Liang  , Wang Hong-Cheng  , She Wei-Long  ,   中山大学光电材料与技术国家重点实验室，广州 510275
Published: December 2020

Different from the traditional treatment, we use the third-order tensor κ(2)jkl to describe the optical activity and take the corresponding polarization as a perturbation, and directly derive a wave coupling equation for the phenomenon from Maxwell's equations. The analytic solution of the coupling equation, which involves the results from the previous macroscopic theory of optical activity, describing the propagation of monochromatic light in arbitrary polarization state traveling in any direction in an optical active crystal belonging to any point group, is given in this paper. Finally, as an application of this theory, the influence of the wave-vector mismatch on the optical rotation in quartz crystal is studied in detail by analyzing the polarization state of the output light.
Characteristics of total reflection at interface between left-handed and right-handed materials
Authors: Shi Gang  , Cen Jie-Ping  , Fan Li  , Liu Yong-Jun  ,   扬州大学物理科学与技术学院,扬州 225000
Published: December 2020

Characteristics of total reflection at the interface between left-handed and right-handed materials are derived from electromagnetic theory, and the phase is researched. The experimental idea of observing interference fringes of evanescent waves, when total reflection takes place at the interface is discussed, and the distribution of interference fringes is calculated from electromagnetic theory.
A novel photonic crystal fiber with high birefringence
Authors: Zhang Xiao-Juan  , Zhao Jian-Lin  , Hou Jian-Ping  ,   西北工业大学光信息科学与技术研究所，陕西省光信息技术重点实验室,西安 710072
Published: December 2020

A novel high birefringence photonic crystal fiber (PCF) was proposed and the properties of this type of PCF were investigated with full vector finite difference frequency domain method. According to the results of numerical analysis, the two orthogonally polarized states of the fundamental mode become non-degenerate in the fiber and show strong linear polarization. The polarization properties are strongly dependent on the structure parameters of this PCF. Through choosing suitable relative structure parameters, it may exhibit birefringence as high as the order of 10-2, at least one order of magnitude higher than that of the conventional D-type and panda-type polarization-maintaining fiber. It is shown that it may also exhibit ideal dispersion effect in a properly designed geometrical structure of PCF. So this type of PCF can be effectively used to fabricate polarization-preserving fiber and correlative fiber elements with special dispersion and polarization characteristics.
The drag force experienced by a projectile in granular medium under gravity
Authors: Zhang Quan-Yi  , Peng Zheng  , He Run  , Liu Rui  , Lu Kun-Quan  , Hou Mei-Ying  ,   (1)中国科学院物理研究所北京凝聚态物理国家实验室，北京 100080; (2)中国科学院物理研究所北京凝聚态物理国家实验室，北京 100080;铜仁学院物理系，铜仁 554300; (3)中国科学院物理研究所北京凝聚态物理国家实验室，北京 100080;中南大学物理科学与技术学院，长沙 410083
Published: December 2020

To describe different behaviors of a projectile into a granular media, a model with both viscous drag and hydrostatic drag has been suggested. Analyses show that the parameter Γ plays a key role in determining the forms of the solutions to this model. When ΓΓ≥2, the viscous drag is dominant. In these two cases, the projectile moves in the granular media with reverse deceleration variances. Experiments have been performed to verify this argument, and the obtained u(t) curves confirm this prediction.
Force transmission in three-dimensional hexagonal-close-packed granular arrays submitted to a point load
Authors: Miao Tian-De  , Yi Chen-Hong  , Qi Yan-Li  , Mu Qing-Song  , Liu Yuan  ,   兰州大学土木工程与力学学院,兰州 730000
Published: December 2020

In this article, the aluminium-plastic board and carbon paper technique are combined to investigate the contact force at bottom boundary of three-dimensional ordered granular arrays in response to a point load. Arching effects were observed with all arrays, and the force distribution markedly depends on the crystal structure and has a 120°-symmetry at every layer of the crystals， while the heterogeneity in force distribution in the pure hcp arrays is minimal of all the arrays. Non-main force chains were observed to have the “focalization" phenomena. These results can be explained by a force-transmission model.
Effect of rise-time patterns on dynamics of sheath expansion during plasma immersion ion implantation
Authors: Huang Yong-Xian  , Tian Xiu-Bo  , Yang Shi-Qin  , Ricky Fu  , Paul Chu K.  ,   (1)哈尔滨工业大学现代焊接生产技术国家重点实验室，哈尔滨 150001; (2)哈尔滨工业大学现代焊接生产技术国家重点实验室，哈尔滨 150001;深圳市复合材料重点实验室，深圳国际技术创新研究院，深圳 518057; (3)香港城市大学物理及材料科学系，香港九龙
Published: December 2020

Plasma immersion ion implantation (PIII) has been developed as a low_cost and efficient surface modification technique of irregularly-shaped objects. The effect of six pulse waves with different rise_time patterns on the spatio-temporal evolution of plasma sheath, energy and dose of ion implantation has been simulated by particle-in-cell modeling. Statistical results may be obtained through assuming the Boltzmann distribution of electrons, and solving Poisson and Newton equations for tracing each ion in the plasma sheath. The results show that rise_time pattern has a critical influence on the evolution of plasma sheath. There exists maximum thickness difference of plasma sheath for different waveforms. The acceleration of ions is non_uniform due to the non-uniformity of electrical field strength. The maximum gradient of electrical field appears near the edge of plasma sheath. The results also show that optimization of dose and energy of incident ions may be achieved through modification of rise_time pattern. The numerical simulation of sheath expansion can be effectively used to provide a scientific basis for optimizing the PIII process.
Dynamic relaxation of polystyrene/poly(ethylene oxide) blends above glass transition temperature
Authors: Wu Xue-Bang  , Shang Shu-Ying  , Xu Qiao-Ling  , Shui Jia-Peng  , Zhu Zhen-Gang  ,   中国科学院固体物理研究所,中国科学院材料物理重点实验室,合肥 230031
Published: December 2020

A series of blends with different compositions were prepared by melt-mixing on the basis of polystyrene and poly(ethylene oxide). Using the relative energy dissipation method, the dynamic behavior of the blends above the glass transition temperature was investigated. Two relaxational dissipation peaks (α and α′) were observed. It is suggested that peak α is associated with the glass transition of polystyrene and peak α′ with the liquid-liquid transition. The relaxation time τ of both relaxations does not satisfy the Arrhenius law. The effect of composition on the dynamic relaxation of the blends were also discussed qualitatively.
Research of the Ga and Al double-impurity doping technique for making fast switching thyristor
Authors: Wang Gong-Tang  , Liu Xiu-Xi  ,   山东师范大学物理与电子科学学院,济南 250014
Published: December 2020

We describe a novel technique for producing the p-type semiconductor. The homogeneous impurity doping of Ga and Al in the n-type silicon wafer is achieved by means of the combination of two technical processes namely aluminum emulsion coating and vaporizing Ga. This Ga-Al double-impurity doping technique, as well as its effect on the quality of the produced semiconductor devices, is investigated theoretically and tested in practice. The principle of the doping technique is also discussed in detail. By using SRP, four-probe needle and thyristor analyzer, we have examined the Ga-Al impurity concentration distribution within the silicon wafer, thin layer resistance RS, and other useful parameters of the fast switching thyristors made by this technique. The turn-off time of the fast switching thyristors, toff is 31.2—38.6 μs, turn-on time ton is 4.6—5.9 μs, and the forward voltage drop VTM measured is 1.9—2.1 V. Both experiment and some real applications indicated that this technique may obviously improve the semiconductor device in the overall performance, the electrical parameter uniformity and the end product rate. It provides a feasible technique for making fast switching thyristors.
Synthesis of diamond nanocrystals by double ions (40Ar+,C2H+6) bombardment
Authors: Wang Zhen-Xia  , Pan Qiang-Yan  , Hu Jian-Gang  , Yong Zhen-Zhong  , Hu Yong-Qing  , Zhu Zhi-Yuan  ,   中国科学院上海应用物理研究所，上海 201800
Published: December 2020

We demonstrate experimentally that an irradiation-induced transformation of multiwalled carbon nanotubes to diamond nanocrystals (DNC) can be realized with double ions (40Ar+，C2H+6) bombardment. This approach is expected to form a new route for synthesis of DNC. The idea of multi-ion irradiation may also be valid for other materials and be used for fabricating nanostructures.
First principles studies of low-compressibility of transition-metal compounds OsB2 and OsO2
Authors: Liang Yong-Cheng  , Guo Wan-Lin  , Fang Zhong  ,   (1)南京航空航天大学纳米科学研究所,南京 210016; (2)南京航空航天大学纳米科学研究所,南京 210016;中国科学院物理研究所北京凝聚态物理国家实验室,北京 100080; (3)中国科学院物理研究所北京凝聚态物理国家实验室,北京 100080
Published: December 2020

By the first principles plane-wave pseudopotential calculations based on the density functional theory, we studied the equations of states and structural properties of transition metal compounds OsB2 and OsO2 and the possible high pressure phase transitions of OsO2. Three (rutile, pyrite and fluorite) phases of OsO2 are studied under high pressure. The calculated results support the opinion that OsB2 and the fluorite phase of OsO2 should be potential ultralow-compressible hard materials. The microscopic mechanism of large bulk modulus and high hardness can be understood from the calculated electronic structures. It is therefore suggested that incorporating light elements (boron, oxygen, carbon or nitrogen) into transition metals with high valence electron densities is possibly a new way to prepare superhard materials.
Energy levels of a polaron in wurtzite nitride parabolic quantum well under external electric field
Authors: Zhao Feng-Qi  , Zhou Bing-Qing  ,   内蒙古师范大学物理与电子信息学院，呼和浩特 010022
Published: December 2020

采用改进的Lee-Low-Pines中间耦合方法研究纤锌矿氮化物抛物量子阱材料中极化子能级,给出极化子基态能量、第一激发态到基态的跃迁能量以及不同支长波光学声子模对极化子能量的影响随阱宽L和外电场F变化的函数关系.在计算中考虑了纤锌矿氮化物GaN和AlxGa1-xN构成的抛物量子阱材料中准LO和准TO声子模的各向异性、电子有效带质量、介电常数、声子频率等随空间坐标z变化(SD)效应以及外电场作用对极化子能量的影响.结果表明，纤锌矿氮化物抛物量子阱材料中电子-声子相互作用、SD效应和外电场对极化子能量有明显影响，它们都使极化子能量降低.SD效应随阱宽L增大而减小，阱宽越大，SD效应越小，最后趋近于零.阱宽较大时，定域准LO声子对极化子能量的影响较大，而半空间准LO声子的影响较小；阱宽较小时，则正好相反.在阱宽L变化的整个范围，氮化物抛物量子阱材料中电子-声子相互作用对极化子基态能量的贡献(约为28—42 meV)比GaAs/AlxGa1-xAs抛物量子阱中的相应值(约为0.5—3.2 meV)大得多.而准TO声子对极化子基态能量的贡献比较小，要远远小于LO声子对极化子基态能量的总贡献.因此，讨论氮化物抛物量子阱(GaN/AlxGa1-xN)中电子态问题时要考虑电子与准LO声子相互作用，而可以忽略准TO声子的作用.
Structural and photoluminescence properties for SnO2:Sb films prepared on Al2O3 substrate
Authors: Feng Xian-Jin  , Ma Jin  , Ge Song-Hua  , Ji Feng  , Wang Yong-Li  , Yang Fan  , Ma Hong-Lei  ,   (1)青岛科技大学物理系，青岛 266061; (2)山东大学物理与微电子学院，济南 250100
Published: December 2020

The SnO2:Sb films have been prepared on sapphire (0001) substrates by radio frequency magnetron sputtering method. The structural and photoluminescence (PL) properties of the films were investigated. The prepared samples are polycrystalline films with rutile structure of pure SnO2. The photoluminescence of the samples was measured at room temperature. An ultraviolet luminescence peak near 334 nm was observed for the first time and the corresponding PL mechanism was investigated.
Spin-dependent electroresistance in Nd0.67Sr0.33MnOy(y<3.0)
Authors: Yang Chang-Ping  , Chen Shun-Sheng  , Dai Qi  , Guo Ding-He  , Wang Hao  ,   湖北大学物理学与电子技术学院,铁电压电材料与器件湖北省重点实验室，武汉 430062
Published: December 2020

Spin-dependent electroresistance (ER) was observed in polycrystalline Nd0.67Sr0.33MnOy (y=3.00, 2.95, 2.90, 2.85, 2.80) samples, which were synthesized by solid-state reaction. For the sample with stoichiometry y=3.0, the I-V characteristic shows ohmic linearity over the whole range of measuring temperature. For the samples with oxygen-deficiency, i.e. yI-V curve is linear when temperature is above a certain point, similar to the case of y=3.0. However, the electric resistance strongly depends on load current, decreasing remarkably with increasing current load when temperature falls below the critical temperature. For the sample of y=2.85, the ER ratio reaches 80% when the load current increases from 1 to 30 μA. The spin-dependent ER effect should be strongly related with the oxygen-deficiency and grain boundary effect.
Optical transparency of z-cut LiF, Al2O3 and LiTaO3 single crystals under strong shock compression
Authors: Zhou Xian-Ming  , Wang Xiao-Song  , Li Sai-Nan  , Li Jun  , Li Jia-Bo  , Jing Fu-Qian  ,   中国工程物理研究院流体物理研究所，冲击波与爆轰物理重点实验室，绵阳 621900
Published: December 2020

In this paper, a comparative experimental study on optical transparency of z-cut LiF, sapphire and LiTaO3 under 1011 Pa shock compression at our two-stage light-gas gun facility is presented. In our experiments, intensity contrast variation of light emitted from a modified experimental setup of Mallory-type was monitored by a high-speed electronic camera. The results demonstrated that the LiF under the shock pressure of 102 GPa retains its initial transparency in the whole observation time interval, which is in good agreement with the common view of good sustained transparency of LiF. The LiTaO3 became basically opaque at 139 GPa. Sapphire at 131 GPa shock pressure showed a continuous transparency degradation till became completely darkened when the shock wave was arriving at the free-surface.
The effect of polarization and non-uniform carrier distribution in the GaN-based light emitting diodes
Authors: Gu Xiao-Ling  , Guo Xia  , Wu Di  , Xu Li-Hua  , Liang Ting  , Guo Jing  , Shen Guang-Di  ,   北京工业大学北京市光电子技术实验室，北京 100022
Published: December 2020

GaN-based green light emitting diodes was designed and fabricated. We calculated the internal electric field using the coupled method on the basis of analyzing the effect of the spontaneous polarization and the piezoelectric polarization. Taking into consideration of the effect of non-uniform carrier distribution in the active region, we obtained the fractions of the carriers and the rate of the recombination in different wells by calculating the steady state rate equation and Poisson equation. It was found that the calculation data are consistent with the experimental data for the changes of the peak wavelength, the light power and the halfwidth with the current in the range of 10—70 mA.
Molecular dynamics simulation of methane hydrate dissociation by thermal stimulation
Authors: Yan Ke-Feng  , Li Xiao-Sen  , Chen Zhao-Yang  , Li Gang  , Tang Liang-Guang  , Fan Shuan-Shi  ,   中国科学院广州能源研究所,广州 510640
Published: December 2020

Thermal stimulation on dissociation of methane hydrate was investigated with molecular dynamics simulation. The dissociation mechanism of methane hydrate with structure Ⅰ was investigated systematically by injecting heated, liquid water of 340 K. The results showed that when the water molecules on hydrate surface are made in contact with high temperature liquid water, they obtain heat energy, and with the obtained energy the water molecules move intensively, breaking the hydrogen bond between water molecules, and destroy the clathrate structure. In addition, methane molecules that have obtained heat energy, break away from the clathrate and diffuse into liquid. Due to heat energy being transferred into inside layer from outside layer through collision between molecules, the hydrate is dissociated layer by layer. Comparing the effects of liquid water with different temperatures of 340 and 277 K on hydrate dissociation, it is concluded that the thermal stimulation promotes dissociation of the hydrate.
Elliptic function propagating wave for Maccari system
Authors: Huang Wen-Hua  , Liu Yu-Lu  ,   (1)湖州师范学院理学院,湖州 313000;上海大学应用数学和力学研究所，上海 200072; (2)上海大学应用数学和力学研究所，上海 200072
Published: December 2020

Based on the exact solution by multi-linear variable separation approach and introducing Jacobi elliptic functions in the variable separation functions, two types of doubly periodic propagating wave patterns for the Maccari system are derived. When the moduli of elliptic functions are set different, these periodic waves show different features with interesting properties. Especially, in the limiting case, the elliptic function waves may degenerate to dromion and peakon excitations. Graphical investigation of the interaction of elliptic function waves shows it to be inelastic.
Unified symmetry of mechanico-electrical systems
Authors: Li Yuan-Cheng  , Xia Li-Li  , Zhao Wei  , Hou Qi-Bao  , Wang Jing  , Jing Hong-Xing  ,   中国石油大学(华东)物理科学与技术学院,东营 257061
Published: December 2020

The unified symmetry of mechanico-electrical systems are studied in this paper. The definition and criterion of unified symmetry of mechanico-electrical systems are derived from the Lagrange-Maxwell equations. The Noether conserved quantity, Hojman conserved quantity and a new conserved quantity deduced from the unified symmetry are obtained. An example is given to illustrate the application of the results.
Methods of analytical mechanics for integrating the Emden-Fowler equation
Authors: Mei Feng-Xiang  , Xie Jia-Fang  , Gang Tie-Qiang  ,   北京理工大学理学院力学系,北京 100081
Published: December 2020

The methods of analytical mechanics for solving the Emden-Fowler equation are presented in this paper, including the Hamilton-Poisson method, the Lagrange-Noether method, the Lie-Hojman method and the Hamilton-Jacobi method.
The extended expansion method for Jacobi elliptic function and new exact periodic solutions of Zakharov equations
Authors: Wu Guo-Jiang  , Zhang Miao  , Shi Liang-Ma  , Zhang Wen-Liang  , Han Jia-Hua  ,   安徽大学物理与材料科学学院,合肥  230039
Published: December 2020

We generalized the Jacobi elliptic function expansion method and obtained some new exact periodic solutions of Zakharov equations, thus replenished the known results of the equation using this method.
Detection of weak square wave signals based on the chaos suppression principle with nonresonant parametric drive
Authors: Chen Long  , Wang De-Shi  ,   海军工程大学兵器工程系,武汉 430033
Published: December 2020

Based on the principle of chaos suppression with nonresonant parametric drive in autonomous chaotic systems, detection of weak square wave signals in strong noise is realized. Firstly a square wave signal whose frequency is far higher than the system characteristic frequency is introduced as the system internal drive signal. According to the parametric equivalent relation between the controlled system and the original system obtained by the averaging method, the critical value of the detection parameter is determined, which marks the sudden change from chaos state to periodic orbit of the system. Numerical simulations show that extremely low signal-to-noise ratio limit in detection can be attained by the proposed system. Compared with the known weak signal detection methods based on the parametric resonant perturbation principle, this method gives more accurate estimates of the detection parameter through strict theoretical analysis, which enables its generalization and application in related fields.
The numbers of participants and nucleon-nucleon collisions in high-energy heavy-ion collisions
Authors: Jiang Zhi-Jin  ,   上海理工大学理学院，上海 200093
Published: December 2020

By using the Glauber model of nucleus-nucleus collision, we present the distribution equations for the numbers of participants and nucleon-nucleon collisions versus the impact parameter in high-energy heavy-ion collisions, and analyze with them the centrality dependence of both numbers in \{sNN\}1/2=200GeV Au+Au collisions. The results fit well with those given by PHENIX Collaboration.
Geometric structures, electronic properties, and magnetism of M2Sn17(M=Ni，Mn)and their anions
Authors: Chen Xuan  , Lu Gong-Li  , Tang Chun-Mei  , Deng Kai-Ming  , Tan Wei-Shi  ,   南京理工大学应用物理系,南京 210094
Published: December 2020

The geometric structures and magnetism of the three probable isomers for Ni2Sn17，Mn2Sn17，［Ni2Sn17］4- and ［Mn2Sn17］2-　have been studied using the generalized gradient approximation based on density functional theory. It was found that the D2d structures of Ni2Sn17，Mn2Sn17，［Ni2Sn17］4- and ［Mn2Sn17］2- are the most stable structures among the three possible isomers. The study shows that the D2d structure and the D4d structure of Ni2Sn17 have spin-splitting, leading to the magnetic moment 4μB and 2μB， respectively, and there is weak ferromagnetic interaction between the Ni and Sn atoms for the D2d structure and the D4d structure. However, there is no magnetic moment in the D4h structure. On the other hand, the D2d, D4d, and D4h Mn2Sn17 have 2μB，6μB and 2μB magnetic moments, respectively. It is interesting that there is weak antiferromagnetic interaction and weak ferromagnetic interaction between Mn and Sn atoms for the D2d and D4h structures, respectively, while there is not only weak ferromagnetic interaction but also weak antiferromagnetic interaction between Mn and Sn atoms in the D4d structure. Finally, It is worth noting that all their anion counterparts of ［Ni2Sn17］4- and ［Mn2Sn17］2- have closed electronic configurations, showing no magnetic moment.
Modeling the evolution of atomic population of two different atoms interacting in two-mode cavity field
Authors: Piao Hong-Guang  , Ma Xiao-Ping  , Zhang Shou  ,   (1)淮海工学院数理科学系,连云港 222005; (2)延边大学理学院物理系,延吉 133002
Published: December 2020

The evolution of atomic population in the model of two different atoms interacting with two-mode field are investigated. The effect of the relative coupling constant (R=g1／g2) and initial two-mode cavity field on the inversion of atomic population are discussed.
THz wave radiation in periodically poled lithium niobate during on optical rectification
Authors: Zhang Kai-Chun  , Liu Sheng-Gang  ,   电子科技大学物理电子学院THz研究中心，成都 610054
Published: December 2020

THz wave radiation in periodically poled lithium niobate (PPLN) during optical rectification induced by femtosecond pulse is studied theoretically in this paper. Attention is focused mainly on the distribution of fields in the frequency domain and time domain, and the spectrum width of THz wave radiation. The radiation field pulse duration, the amplitude and the spectrum width varying with the length of crystal and the angle of radiation are also discussed in detail.
Calculation of dispersion relation and radiation pattern of plasma antenna
Authors: Zhao Guo-Wei  , Xu Yue-Min  , Chen Cheng  ,   (1)中国科学院空间科学与应用研究中心，北京 100080; (2)中国科学院空间科学与应用研究中心，北京 100080;中国科学院研究生院，北京 100080
Published: December 2020

We investigated some important plasma antenna parameters, such as the transmission characteristics of a microwave propagating along the cylindrical symmetric plasma antenna, dispersion relations, radiation pattern and gain. By analyzing the dielectric constant of the tube material, the outer and inner radius, the density of the plasma and the collision frequency, we found that to minimize the attenuation of wave propagation along the plasma antenna, one should increase the density of the plasma, decrease the collision frequency, increase the radius of the plasma, increase the thickness of tube，and decrease the dielectric constant. We also calculated the radiation pattern of the plasma antenna and the change of gain under different conditions. These results are useful for the design of plasma antenna.
Plasma power and impedance measurement in silicon thin film deposition
Authors: Zhang Xiao-Dan  , Zhang Fa-Rong  , Elefterious Amanatides  , Dimitris Mataras  , Zhao Ying  ,   (1)Plasma Technology Laboratory Department. Chem. Engineering,Patras University,Patra,26500,Greece; (2)南开大学光电子薄膜器件与技术研究所，天津 300071;南开大学光电子薄膜器件与技术天津市重点实验室，天津 300071
Published: December 2020

Plasma impedance and power consumption were measured by modified voltage-current method at different applied voltages on the substrate electrode. The results indicated that discharge current increases with the increase of applied voltage on the substrate electrode when the applied voltage of RF electrode is fixed. As a result, plasma impedance decreases. In addition, only a small part of power was used by the plasma and a large part of power was consumed on the matching network and cables. Through the analysis of plasma electrical properties, it was found that the deposition rate of thin films will be increased with the increase of applied voltage on the substrate electrode so long as there is enough silane.
The dynamic process of thin films damage induced by femtosecond laser
Authors: Zhang Hong-Ying  , Wu Shi-Gang  ,   山东理工大学材料科学与工程学院，淄博 255049
Published: December 2020

A dynamic model of plasma explosion is put forward. The inertia factor is considered daring plasma expansion, and the dynamic simulation is carried out. The dynamic mechanism of film damage induced by plasma blast is discussed.
Plasma boundary identification in HL-2A by means of the movable current filaments method
Authors: You Tian-Xue  , Yuan Bao-Shan  , Li Fang-Zhu  ,   (1)核工业西南物理研究院,成都 610041; (2)核工业西南物理研究院,成都 610041;西南交通大学，成都 610031
Published: December 2020

Based on the Shafranov current moment theory, reconstruction of the plasma boundary in HL-2A is studied by using the movable current filament (VCF) method. Compared with the fixed current filament (FCF) method and the finite current element (FCE) method that we've used before, this method has the advantage of accurately rebuilding the fast evolving plasma boundary by using only 1—3 filaments, which offsets the drawbacks of the FCF and the FCE methods. Combining the movable current filament method with the FCF or the FCE method, the plasma boundary can be displayed in real time and the plasma shape can be controlled during the whole discharge process.
Research on intense pulsed emission of carbon nanotube cathode
Authors: Liao Qing-Liang  , Zhang Yue  , Xia Lian-Sheng  , Huang Yun-Hua  , Qi Jun-Jie  , Gao Zhan-Jun  , Zhang Huang  ,   (1)北京科技大学材料物理与化学系，北京 100083; (2)北京科技大学材料物理与化学系，北京 100083;北京科技大学新金属材料国家重点实验室，北京 100083; (3)中国工程物理研究院流体物理研究所，绵阳 621900
Published: December 2020

Two different carbon nanotube (CNT) cathodes have been made by using screen-printing and also by coating. Pulse emission properties of the two cathodes were studied, and the cathode's surface morphology was characterized. Research results show that the CNT cathode is capable of generating pulsed beams of a few kilo-amperes. The pulsed field emission properties of the cathode were tested in a diode structure powered by a high-voltage generator(under conditions of 2×10-3 Pa, 100ns, 1.64MV). The results reveal that the emission current of the cathode made by coating can attain 5.11 kA, and the highest emission current density is 260 A/cm2. The stability of cathode made by screen-printing is better than that made by coating. The pulsed emission mechanism of carbon nanotubes is shown to be explosive electron emission. This carbon nanotube cathode appears to be suitable for high-power microwave device applications.
A study on resistive transition and anisotropy of MgB2/Al2O3 superconducting thin films
Authors: Shi Li-Bin  , Ren Jun-Yuan  , Zhang Feng-Yun  , Zhang Guo-Hua  , Yu Zeng-Qiang  ,   (1)北京大学物理学院，北京 100871; (2)北京科技大学应用科学学院物理系，北京 100083; (3)渤海大学物理系,锦州 121000
Published: December 2020

MgB2 thin films were deposited by e-beam on Al2O3(001)substrates. Resistive transition of the MgB2/Al2O3 was investigated in different magnetic fields applied parallel or perpendicular to the ab plane of the films by the standard four-probe method. An activation energy model is suggested to analyze quantitatively the activation energy of flux lines and resistive transition in whole transition temperature range. The anisotropy parameter γ=Hc2ab(0)/Hc2c(0)=2.26 was obtained by analyzing the upper critical field using the polynomial Hc2(t)=Hc2(0)+At+Bt2.
First-principle study on the electronic structure and p-type conductivity of ZnO
Authors: Zhang Jin-Kui  , Deng Sheng-Hua  , Jin Hui  , Liu Yue-Lin  ,   北京航空航天大学物理系，北京 100083
Published: December 2020

We have investigated the electronic structure of p-type ZnO by adopting the ab-initio study of plane wave ultra-soft pseudo potential technique based on the density function theory (DFT). The cell parameters, total density of states (TDOS) and partial density of states (PDOS) of N atoms were obtained after optimizing the structure of ZnO. It was shown that the volume of the primitive cell decreases with increasing content of the dopant. The p-type conductivity was realized easily by codoping with N and Al in the ratio of 2∶1, compared with doping with N alone. As the doping proportion increases, the carrier concentration was increased and the mobility was enhanced, which leads to the improvement of the conductivity.
The Interaction between Pd and CeO2(111) surface: A first-principle study
Authors: Lu Zhan-Sheng  , Luo Gai-Xia  , Yang Zong-Xian  ,   河南师范大学物理信息与工程学院,新乡 453007
Published: December 2020

The adsorption properties of Pd on CeO2(111) surface are studied using the first principle projector-augmented-wave (PAW) method based density functional theory (DFT) within generalized gradient approximation (GGA) and with the inclusion of on-site Coulomb interaction (DFT+U). It is found that there exist different adsorption features for different coverages of Pd: (1) For one monolayer (ML) Pd adsorption on CeO2(111) surface, Pd prefers to be adsorbed on the atop O site leaning toward the Ce-bridge site; while, for the 1/4 ML adsorption, Pd prefers to be adsorbed on the O-bridge site leaning toward the atop subsurface O site. (2) The interaction between the adsorbed Pd atoms is very strong when the coverage is one ML; on the other hand, there is almost no interaction between the Pd atoms for the 1/4 ML Pd adsorption, correspondingly, the interaction between Pd adatoms and CeO2(111) substrate is stronger for lower coverage adsorption (1/4 ML) than that for higher coverage adsorption (1 ML). (3) The adsorption of Pd disturbes the CeO2(111) surface structure in the vicinity of the adsorption site. (4) The Pd adsorption makes the Pd/CeO2 more active as compared with the clean CeO2(111) and bulk Pd metal, and there may exist some active sites at the Pd/CeO2 interface. These studies may lead to a better understanding for the Pd/CeO2 catalysts and give some hints to improve the efficiency of TWC.
Shock-induced phase transformations of iron studied with molecular dynamics
Authors: Shao Jian-Li  , Wang Pei  , Qin Cheng-Sen  , Zhou Hong-Qiang  ,   北京应用物理与计算数学研究所，北京 100088
Published: December 2020

Molecular dynamics simulations are used to investigate the shock-induced phase transformation of iron at a certain initial temperature, which shows that the temperature lowers the threshold pressure of shock-induced phase transformation. Also, the evolution of the loading and unloading waves is calculated and analyzed, and it is found that the velocity of the inverse phase transformation wave(during ε phase →α phase)equals the longitudinal sound speed of the wave front and is less than that of the wave rear. The pressure and density of unloading traces is also calculated, which affords a good explanation to the evolution of the unloading waves, and the phase transformation band of unloading is obtained, which shows the hysteresis in the reverse transformation.
The ab-initio study of diamond growth on its (111) surface
Authors: Liu Yi-Liang  , Kong Fan-Jie  , Yang Bin-Wei  , Jiang Gang  ,   (1)四川大学原子与分子物理研究所,成都 610065; (2)中国工程物理研究院，绵阳 621900
Published: December 2020

The adsorption of carbon on Ni (111) surface is studied with density functional theory in this paper. The adsorption energy and density of states is calculated. We analyzed the density of states of carbon on diamond (111) surface and carbon adsorbed on Ni(111) surface, the result shows that they have similar electronic structure, namely, they both have nonbonding and bonding sp3 hybridized electrons. Furthermore, it is found that the carbon atoms on diamond (111) surface and those adsorbed on Ni(111) surface are prone to bonding and form a diamond-like structure.
Strain-driven alloy decomposition of In0.15Ga0.85As well layers in InAs/In0.15Ga0.85As dots-in-a-well structure
Authors: Wang Chong  , Liu Zhao-Lin  , Chen Ping-Ping  , Cui Hao-Yang  , Xia Chang-Sheng  , Yang Yu  , Lu Wei  ,   (1)云南大学工程技术研究院，昆明 650091; (2)云南大学工程技术研究院，昆明 650091;中国科学院上海技术物理研究所红外物理国家重点实验室，上海 200083; (3)中国科学院上海技术物理研究所红外物理国家重点实验室，上海 200083
Published: December 2020

Two InAs/In0.15Ga0.85As quantum dots-in-a-well (DWELL) samples have been grown by solid source molecular beam epitaxy (MBE). The increased size of InAs dots and more homogeneous dot-size distribution have been found in one InAs DWELL sample with growth optimized by changing both the growth temperature and the thickness in In0.15Ga0.85As well layers. The improved optical properties of this sample have also been confirmed by photoluminescence (PL) and piezomodulated reflectance (PzR) spectra. The numerical calculations based on effective mass approximation indicate that the increase of dot size and the improved optical properties are dominantly due to the strain driven alloy decomposition of In0.15Ga0.85As well layers.
Study of the dark current in very long wavelength quantum well infrared photodetectors
Authors: Xiong Da-Yuan  , Li Ning  , Xu Wen-Lan  , Zhen Hong-Lou  , Li Zhi-Feng  , Lu Wei  ,   (1)华东师范大学信息科学技术学院，上海 200062; (2)中国科学院上海技术物理研究所红外物理国家重点实验室，上海 200083
Published: December 2020

A study of the carrier transport performance of GaAs/AlGaAs very long wavelength quantum well infrared photodetectors (peak wavelength: 15 μm; period: >40) has been carried out based on quantum wave transport theory. It was shown that the thermoexcitation effect dominates in the devices. By the current continuity and self-consistent calculation based on Schrdinger equation and Poisson equation, we found that the main feature resulting from the model is the redistribution of the carriers and the electric field along the whole structure being made uneven to maintain current conservation. The high-field region extends over a few barriers near the emitter contact, which takes up a considerable part of the applied voltage. The conventional flat band model assumes that the applied voltage drops linearly across the structure, leading to the numerical value of dark current to be far from the experiments, especially at small bias. The numerical result of self-consistent calculation well explains the measurement data.
Effect of implantation of nitrogen into SIMOX buried oxide on its fixed positive charge density
Authors: Zheng Zhong-Shan  , Zhang En-Xia  , Liu Zhong-Li  , Zhang Zheng-Xuan  , Li Ning  , Li Guo-Hua  ,   (1)济南大学物理系，济南 250022;中国科学院半导体研究所，北京 100083; (2)中国科学院半导体研究所，北京 100083; (3)中国科学院上海微系统与信息技术研究所，上海 200050
Published: December 2020

In order to obtain greater radiation hardness for SIMOX (separation by implanted oxygen) materials, nitrogen was implanted into SIMOX BOX (buried oxide). However, it has been found by the C-V technique employed in this work that there is an obvious increase of the fixed positive charge density in the nitrogen-implanted BOX with a 150 nm thickness and 4×1015cm-2 nitrogen implantation dose, compared with that unimplanted with nitrogen. On the other hand, for the BOX layers with a 375　nm thickness and implanted with 2×1015 and 3×1015cm-2 nitrogen doses respectively, the increase of the fixed positive charge density induced by implanted nitrogen has not been observed. The post-implantation annealing conditions are identical for all the nitrogen-implanted samples. The increase in fixed positive charge density in the nitrogen-implanted 150 nm BOX is ascribed to the accumulation of implanted nitrogen near the BOX/Si interface due to the post-implantation annealing process according to SIMS results. In addition, it has also been found that the fixed positive charge density in initial BOX is very small. This means SIMOX BOX has a much lower oxide charge density than thermal SiO2 which contains a lot of oxide charges in most cases.
Configuration of the antiferromagnetic magnetization and the exchange anisotropy in exchange-biased bilayers
Authors: Xu Xiao-Yong  , Pan Jing  , Hu Jing-Guo  ,   扬州大学物理科学与技术学院,扬州 225002
Published: December 2020

The phases of the antiferromagnetic magnetization and the corresponding exchange bias and coercivity in exchange-biased bilayers(FM/AF) with interface quadratic and biquadratic exchange coupling have been studied comprehensively. The results show that there are four possible cases for the antiferromagnetic magnetization, namely the reversible recovering case, irreversible half-rotating case, irreversible reversing and irreversible half-reversing cases. However, the realization of the cases strongly depends on interface quadratic coupling, interface biquadratic coupling and AF thickness. In the reversible recovering case the exchange coupling between FM and AF results in the exchange bias, and there is no exchange bias in the other cases. Specially, for exchange-biased bilayers without interface quadratic coupling, there exists a critical value of the biquadratic coupling constant J2crit=0.1σw(σw denotes AF domain wall energy), below which the positive exchange bias appears, otherwise there is no exchange bias, and the coercivity can be enhanced. For the FM/AF bilayers with interface quadratic and biquadratic coupling, the interface biquadratic coupling can weaken or eliminate the exchange bias, but always enhances the coercivity.
Design of spectral reflective properties of the stealth coating
Authors: Zhang Shuan-Qin  , Shi Yun-Long  , Huang Chang-Geng  , Lian Chang-Chun  ,   (1)山西大同大学，大同 037000; (2)山西大同大学，大同 037000;总装工程兵科研一所，无锡 214035; (3)总装工程兵科研一所，无锡 214035
Published: December 2020

Based on the mutual interaction between the electromagnetic wave and pigment, the theoretical model is formulated. The influence of various factors, such as the size of the pigment, the volume ratio of pigment, and the optical constants, on the spectral reflective properties is systematically analyzed. Experiment has been performed to testify the theoretical model. The theoretical design for the spectral reflective properties of the stealth coating is further proposed.
Thermally induced Fe atom transition from substitutional to interstitial sites in InP and its influence on material property
Authors: Zhao You-Wen  , Miao Shan-Shan  , Dong Zhi-Yuan  , Lü Xiao-Hong  , Deng Ai-Hong  , Yang Jun  , Wang Bo  ,   (1)四川大学物理学院应用物理系，成都 610065; (2)中国科学院半导体研究所，北京 100083
Published: December 2020

As-grown Fe-doped semi-insulating InP single crystal has been converted into n-type low-resistance material after high temperature annealing. Defects in the InP materials have been studied by conventional Hall effect measurement, thermally stimulated current spectroscopy, deep level transient spectroscopy and X-ray diffraction respectively. The results indicate that Fe atoms in the InP material change from the substitutional to the interstitial sites under thermal activation. Consequently, the InP material loses its deep compensation centers which results in the change in types of conduction. The mechanism and cause of the phenomena have been analyzed through comparison of the sites of Fe atom occupation and activation in doping, diffusion and ion implantation processes of InP.
Polarization and variations of Blazar
Authors: Liu Yun  , Zhang Xiong  , Zheng Yong-Gang  , Wang Xiao-Min  , Bao Yu-Ying  ,   云南师范大学物理与电子信息学院，昆明 650092
Published: December 2020

Blazar is an extreme subset of AGNs，constituting less than a few percent of the known AGN population. While Blazar have some properties in common with other AGNs，they have some characteristics that set them apart. The observation properties are probably the cause of strong beaming effect，and these properties would be mutually correlated. The relationship between the polarization and the magnitude variation in brightness，as well as the core-dominance parameter are derived and used statistically to compare with the observational data of Blazar smaples. The result suggests that the polarization, variation and the core-dominance parameters are possible indications of the beaming effect.
Study on the transition from filamentary to uniform discharge in dielectric barrier discharge
Authors: Li Xue-Chen  , Jia Peng-Ying  , Liu Zhi-Hui  , Li Li-Chun  , Dong Li-Fang  ,   河北大学物理科学与技术学院，保定  071002
Published: December 2020

The transition from filamentary discharge to uniform discharge in a device with water electrodes is studied in air by electrical method and emission spectroscopy. Results show that discharge can transit from filamentary mode to uniform mode by increasing the applied voltage or decreasing the gas pressure. The discharge mechanism at high pressure is the streamer and that at low pressure is glow discharge. The relations of the number of high-energy electons and experimental parameters were studied by optical emission spectroscopy. The results show that high-energy electrons increases in number with decreasing gas pressure and decreases with increasing applied voltage. The experimental results are explained qualitatively based on the theory of wall charge. The results are of value for the study of uniform discharge in dielectric barrier discharge.