bluuebunny/crossref_metadata_2025 huggingface dataset:
Light emission mechanism of sapphire under shock loading from 40 to 60 GPa
Authors: Zhang Ning-Chao  , Liu Fu-Sheng  , Peng Xiao-Juan  , Chen Yuan-Fu  , Wang Jun-Guo  , Zhang Ming-Jian  , Xue Xue-Dong  ,   Laboratory of High Pressure Physics, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

The spontaneous spectroscopic and radiation pyrometer techniques are combined together to study the light emission of shocked sapphire and its time dependence under a compression of 41—87 GPa. The results are confirmed that the shock induced light emission from sapphire can be attributed to the thermal radiation from the shear bands because of partial dislocation damage. The spectral distribution matches well with the equilibrium thermal radiation of Planck grey-body feature. The fact that of the radiation color temperature is close to the corresponding melting temperature can be explained reasonably by the thermal equations of the plastic flow.
Scanning tunneling mircroscopy and X-ray photoelectron spectroscopy studies of MnSi film and MnSi1.7 nanowires grown on Si substrates
Authors: Shi Gao-Ming  , Zou Zhi-Qiang  , Sun Li-Min  , Li Wei-Cong  , Liu Xiao-Yong  ,   Instrumental Analysis Center, Shanghai Jiaotong University, Shanghai 200240, China;,   Department of Physics, Shanghai Jiaotong University, Shanghai 200240, China
Published: December 2020

Manganese silicides are promising industrial materials in optoelectronics and microelectronics fields. The study of electronic structures of manganese silicide film and nanowires is essential for a deeper understanding of their properties. In this paper, MnSi film and MnSi1.7 nanowires are prepared by molecular beam epitaxy method, and then observed by scanning tunneling microscopy (STM). The Mn 2p and Si 2p of MnSi film and MnSi1.7 nanowires are comprehensively studied using X-ray photoelectron spectroscopy (XPS). The results demonstrate that MnSi film with ～ 0.9 nm high is √3 × √3 reconstruction, and that the MnSi1.7 nanowires are about ～ 3 nm high, 16—18 nm wide and 500—1500 nm long. The binding energies of the Mn 2p1/2 level and Mn 2p3/2 level for MnSi film are 649.7 and 638.7 eV, respectively, which coincide with those of MnSi1.7 nanowires. The Mn 2p3/2 and Mn 2p1/2 peaks which are located at 640—645 eV and ～653.8 eV indicate that an oxide layer formed on the surfaces of film and nanowires because of short-time exposure to the atmosphere. The negative chemical shifts for MnSi film and MnSi1.7 nanowires from Si2p spectra indicate that with the formation of manganese silicides, the chemical state of Si is changed.
Synthesis and properties of multiple boride Pr1-xCexB6 cathodes by reactive spark plasma sintering
Authors: Li Xiao-Na  , Zhang Xin  , Zhang Jiu-Xing  , Bao Li-Hong  , Zhang Ning  , Zhang Fan-Xing  ,   Key Laboratory of Advanced Functional Materials Ministry of Education College of Materials Science and Engineering Beijing University ofTechnology Beijing 100124, China
Published: December 2020

The polycrystalline Pr1-xCexB6 (x = 0.2, 0.4, 0.6, 0.8) hexaborides are prepared by the reactive spark plasma sintering (SPS) method using mixed powder of CeH2, PrH2 and B. The effects of Ce doping on the phase composition, the mechanical properties and the thermionic emission properties of the hexaboride are investigated. The single-phased hexaborides CexPr1-xB6 bulks are sintered at a temperature of 1450℃, pressure of 50MPa and holding time of 5 min, and the sintered samples show high value of Vickers hardness (24.34 GPa) and bend strength (226.02 MPa). The thermionic emission results show that with the increase of Ce content, the thermionic emission current density increases linearly and the maximum value of Pr0.4Ce0.6B6 reaches 47.3 A·cm-2 under an applied voltage of 950 V at 1973 K, which is much higher than that obtained by traditional method. Thus, the SPS technique represents a suitable method to synthesize the dense rare-earth hexaborides with excellent properties.
Spectroscopic properties of cerium doped YVO4 crystals and analysis on valence state of cerium ion
Authors: Wang You-Fa  , Wu Zhou-Li  , Li Wen-Run  , Wang Shuai  , Tong Hong-Shuang  , Ruan Yong-Feng  ,   Science School of Tianjin University, Tianjin 300072, China
Published: December 2020

High-quality cerium doped YVO4 crystals are grown by the Czochralski method in a furnace heated by medium frequency induction. Cerium carbonate and ceria of 2 at% are respectively doped into the different crystals. The X-ray diffraction spectra show that all samples present YVO4 crystallographic phase. The absorption spectra, excitation spectra and photoluminescence spectra of the samples are measured. It is found that the spectroscopic properties of the samples doped with the different cerium impurities are similar. The two kinds of the samples each radiate a wideband blue light centered at 440 nm when excited by 325 nm light. This blue light emission is due to the 5d → 4f intrinsic emission of Ce3+ ions. In addition, the two kinds of the samples each radiate a wideband red light centered at 620 nm when excited by 460 nm light. The X-ray photoelectron spectroscopy (XPS) show that the O(1s) peak splits into two peaks at 529.8 eV and 531.8 eV, which indicate that there are two types of coordinate oxygen ions in the crystal. One kind of coordinate oxygen ion is normal coordinated oxygen ion (O2-) and another kind of coordinate oxygen ion is a hole (O-). According to recorded 5 peaks of Ce(3d) XPS, it is deduced that the Ce3+ ions and Ce4+ ions coexist in each of these samples. It is considered that the wideband red light emission of Ce:YVO4 crystal is due to the charge transfer transition of the Ce4+-O2- ion pairs, and Ce:YVO4 powders may become a novel red phosphor used for white LED.
Effect of surface tension anisotropy on the growth patterns of cellulars in directional solidification
Authors: Zhang Yun-Peng  , Lin Xin  , Wei Lei  , Wang Meng  , Peng Dong-Jian  , Huang Wei-Dong  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

The growth patterns of cellulars in directional solidification are investigated numerically using the cellular automata (CA) model in two dimensions. A criterion which determine whether the cellulars reach stable state is derived from the analysis of simulated results. The simulated results also show that it is easy for tip splitting to appear for cellulars when the surface tention anisotropy is very small. So it is hard to obtain stable cellular arrays. However, if the amplitude of surface tention anisotropy is strong enough, it is easy to obtain stable cellular arrays. And the intensity of surface energy anisotropy can considerably influence the stable cellular patterns. The stronger the surface energy anisotropy, the smaller the stable cellular spacing and the cellular tip radius are, and the smaller the ratio between tip radius and cellular spacing, the smaller the tip concentration and the tip undercooling are.
Investigation of suppression of non-working mode oscillation in a high gain relativistic klystron amplifier
Authors: Chen Yong-Dong  , Jin Xiao  , Li Zheng-Hong  , Huang Hua  , Wu Yang  ,   Graduate School of China Academy of Engineering Physics, Beijing 100084, China;,   Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Because non-working modes are very easy to excit in the high gain relativistic klystron amplifier, and seriously affect the beam-wave interactive action, the suppressing of non-working modes is very important. These modes can seriously degrade klystron performance and cause the pulse shortening, the normal operation of HGRKA will be affected greatly. This paper deals with the mechanism of non-working mode self-excitation by the PIC simulation, and it is obvious that the coupling between cavities is the main cause of non-working mode self-excitation. The coupling can form the positive feedback loop. The formula for starting current of non-working mode self-excitation is developed according to the coupling between cavities, and the corresponding measures are taken to avoid non-working mode self-excitation. Then the corresponding simulations and optimization are conducted. Finally non-working mode control is realized in the HGRKA experimentally when driven power is only few kilowatts. The RF output has a power of 0.98 GW and pulse width of 100 ns.
0—1 integer linear programming for actively shielded magnetic resonance image (MRI) superconducting magnet design
Authors: Zhang Guo-Qing  , Du Xiao-Ji  , Zhao Ling  , Ning Fei-Peng  , Yao Wei-Chao  , Zhu Zi-An  ,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China;,   Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Here introduced is an optimization design method for actively shielded magnetic resonance image (MRI) superconducting magnet based on the integer linear programming. The feasible coil space is densely divided by an array of candidate squares and, its size is determined by the size of actual superconducting wire. The 0—1 integer linear programming method is adopted to obtain the initial wire concentrated region of coils by comprehensivly considering superconductivity wire consumption, magnetic field intensity inside the superconductors, homogeneity in imaging region and the range of leak fields. Then by reasonably adjusting the position and section size of the wire concentrated region for the next calculation, the final MRI superconducting magnet structure with rectangular section coils is obtained. The method is based on the full size of the superconducting wire, which makes the MRI superconducting magnet design more feasible and has greater advantage for the actual fabriction. With different constraints, the method can also be used for other superconducting magnet design. Finally an example of the MRI magnet optimal design is presented.
Calibration of optical tweezers using time of flight method
Authors: Zhou Dan-Dan  , Ren Yu-Xuan  , Liu Wei-Wei  , Gong Lei  , Li Yin-Mei  ,   Department of Optics and Optical Engineering, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

Conventional method of calibrating optical trap stiffness is applicable for microspheres whose diameters range from hundreds of nanometer to several micrometers, but only have a slight advantage for those microspheres with diameters lager than five micrometers. To compensate this, we experimentally develop a time of flight method for measuring optical trap stiffness with larger microspheres. By comparing the optical trap stiffness of microspheres with different sizes and different materials at different laser powers, the time of flight method is confirmed to be more accurate and practical for microspheres larger than 5 μm; the result is of the same order of magnitude as the results of Brownian noise based analysis of 5 μm polystyrene bead. The results are higher than theoretical values due to the limited bandwidth of the camera. In comparison, the time of flight method is superior to other methods and does make sense in the fast calibration of optical trap stiffness on cell level. This method can be applied to optical traps with special field distributions. In the measurement of mechanical properties of cells, it can avoid using microspheres as force probe, thus providing a novel approach to the study of sophisticated single molecule process on the membrane of cells.
Analysis on positive effect of time-delay on a class of second-order oscillatory systems with unit negative feedback
Authors: Zhang Yong  ,   College of Information and Control Engineering, China University of Petroleum (East China), Qingdao 266580, China
Published: December 2020

The stability analysis on a class of oscillatory systems whose controlled object has a standard form of second-order systems is presented. The effect of the signal transmission delay on the performance of the closed loop control system with unit negative feedback is discussed. The relationship between the time-delay and the stability of closed loop control system is obtained via drawing and analyzing the Nyquist plots in the different regions of the relative damping coefficient. The simulation example of unit step response for each case is processed and the simulation results show that the analysis is correct.
Dynamics of Bose-Einstein condensate trapped in a triple-well with synthetic gauge field
Authors: Wang Qiang  , Ye Chong  ,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;,   National Laboratory of Science and Technology on Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

We study bosonic atoms trapped in a triple-well with synthetic gauge field. The energy spectrum of the system can be tuned by an effective magnetic field. For a non-interacting system, eigen-states with different momenta will be the ground state with the magnetic field varying. In the full quantum scheme, we find the critical ratio between the tunneling and interaction strength for localization of system under the repulsive interaction. We also discuss the macro-rotation effect induced by the magnetic field and the boundary effect of the temporal evolution for a non-interacting system.
Control and modeling of chaotic dynamics for a free-floating rigid-flexible coupling space manipulator based on minimal joint torque's optimization
Authors: Wang Cong-Qing  , Wu Peng-Fei  , Zhou Xin  ,   College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;,   State Key Laboratory for Manufacturing Systems Engineering , Xi’an Jiaotong University, Xi’an 710049, China
Published: December 2020

The dynamic model of a planar free-floating rigid-flexible redundant space manipulator with tree joints is derived by the assumed mode method, Lagrange principle and momentum conservation. Based on minimal joint torque optimization, the state equations of chaos motion for the free-floating redundant space manipulator are built. Then chaotic numerical method is used to analyze chaotic dynamic characteristics of the model. The robust Proportional-Derivative(PD) compensatory control, the delayed feedback control and the optimal control are designed in work space, joint space and mode space respectively. The composite control can assure the trajectory tracking, chaotic suppression and vibration control. The experimental results show the effectiveness of the presented methods.
Multiscale permutation entropy analysis of oil-in-water type two-phase flow pattern
Authors: Du Meng  , Jin Ning-De  , Gao Zhong-Ke  , Zhu Lei  , Wang Zhen-Ya  ,   School of Electrical Engineering & Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

We investigate the dynamic characteristics of vertical upward water-dominant oil-water two-phase flow by multiscale permutation entropy algorithm. We first measure the two-phase flow conductance fluctuation signals in a 20 mm inner-diameter pipe. Then we calculate the multiscale permutation entropies for different water-dominant flow patterns. The results indicate that multiscale permutation entropy rate and average of mutiscale permutation entropy can be used as quantitative parameters for measuring complexity of water dominant oil-water two-phase flow. In addition, we propose a new approach to identify different water-dominant flow patterns by using the joint distribution of multiscale permutation entropy rate and cumulant of increment series.
Oscillation-localization transition behavior of bright-bright solitons in two species Bose-Einstein condensates
Authors: He Zhang-Ming  , Wang Deng-Long  , Ding Jian-Wen  , Yan Xiao-Hong  ,   Department of Physics, Xiangtan University, Xiangtan 411105, China;,   College of Electronic Science Engineering, Nanjing University of Post & Telecommunication, Nanjing 211106, China
Published: December 2020

Considering the time-dependent interspecies interactions, we study the dynamic behaviors of bright-bright solitons in two species Bose-Einstein condensates in the harmonic external potentials. In the presence of unchanged attractive interspecies and intraspecies interactions, bright-bright solitons exhibit periodic oscillations. When the attractive intraspecies interactions are fixed but the attractive interspecies interactions are increased exponentially, interestingly, a transition behavior from oscillation to localization is observed. Meanwhile, this transition behavior can be controlled by tuning the transverse trapping frequency of harmonic potential. Furthermore, an experimental protocol is designed to observe the transition behavior in the current experimental conditions.
Unlike-pair interactions of detonation products at high pressure and high temperature
Authors: Zhao Yan-Hong  , Liu Hai-Feng  , Zhang Qi-Li  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

In this paper, we present a method that unlike-pair interactions are determinated by explosive detonation data. The unlike-pair interaction parameters kN2-H2O= 1.03, kN2-CO2= 1.035, kH 2O-CO2= 0.96 are deduced from the calculated results of explosive RX-23-AB,HNB and PETN with our statistical mechanical chemical equilibrium code CHEQ-like. At the same time, the theoretical Hugoniots of explosive PBX9404 are calculated with these parameters. The results in better agreement with the experimental data show that the parameters and method are reliable.
Greatly enhanced visual density measurement level of the national standard densitometer
Authors: Liu Zi-Long  , Chen Rui  , Liao Ning-Fang  , Li Zai-Qing  , Wang Yu  ,   National Professional Laboratory of Color Science and Engineering, Beijing Institute of Technology, Beijing 100081, China;,   Optical Division, National Institute of Metrology, Beijing 100013, China
Published: December 2020

The national standard densitometer can be used for calibrating photographic film and visual photo. The development of biomedical image and space technology need large measurement range and high uncertainty of visual density. A newly designed equipment using hemispherical emitter with optic fiber can enhance the diffuse coefficient of the light to 0.945 which is higher than the other national standards (0.02-0.03). Thus the measurement range can be increased to 0-6.0 and the combined uncertainties are 0.0015 (0 D D < 6.0). On the other hand, the structure design for the whole equipment can realize the reciprocal fixing between the light module and the detect module. So the validity of Helmholtz reciprocity for transmittance measurement can be examined and proved on this new equipment.
Laser intensity dependence of nonsequential double ionization of argon atoms by elliptically polarized laser pulses
Authors: Yu Ben-Hai  , Li Ying-Bin  ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China
Published: December 2020

With a classical ensemble model, we investigate the intensity dependence of nonsequential double ionization (NSDI) of argon atoms by elliptically polarized laser pulses. The results show that the correlated behavior of two electrons along the long axis of the laser polarization plane depends on the laser intensity. At the relatively high intensity, the correlated electron momentum spectrum displays a correlated behavior and shows V-like structures in the first and third quadrants. At the relatively low intensity, the correlated electron momentum spectrum shows a strongly anticorrelated behavior. For the different laser intensities, the momentum spectra of two electrons along the short axis of the laser polarization plane all show strongly anticorrelated behaviors. The analysis of the classical trajectories of NSDI shows that the final-state electron repulsion plays a decisive role in both the V-like shape along the long axis of the laser polarization plane and the anticorrelated behavior along the short axis of the laser polarization plane.
Tunable high efficiency broadband second-harmonic conversion in quasi-phase matching
Authors: Yin Ming  , Zhou Shou-Huan  , Feng Guo-Ying  ,   School of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China;,   North China Research Institute of Electro-Optics, Beijing 100015, China
Published: December 2020

High efficiency broadband second-harmonic conversion plays an important role in communication, signal processing, spectroscopy and so on. In general, the study of high efficiency broadband second-harmonic conversion focuses on a few of wavelengths. For obtaining tunable high efficiency broadband second-harmonic conversion in quasi-phase matching, the group-velocity and quasi-phase matched condition are analyzed. The temperature effect on high-efficiency broadband second-harmonic conversion in types 0 and Ⅰ quasi-phase matched condition for 5 mol% periodically poled LiNbO3 and periodically poled LiNbO3 is studied. The results show that 15 nm and 341 nm tunable high efficiency broadband second-harmonic conversions are obtained in types 0 and Ⅰ quasi-phase matched conditions for 5 mol% periodically poled LiNbO3; 44 nm and 98 nm tunable high efficiency broadband second-harmonic conversions are obtained in types 0 and Ⅰ quasi-phase matched condition for periodically poled LiNbO3. The range of high efficiency broadband second-harmonic conversion wavelength is expanded.
Numerical simulation on mixing process of ejecta and gas
Authors: Wang Pei  , Sun Hai-Quan  , Shao Jian-Li  , Qin Cheng-Sen  , Li Xin-Zhu  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China;,   National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Ejecta mixing takes place at the interface between metal and gas under shock loading, i.e., the transport process of ejecta from metal surface appears in the gas. In this paper, adopting disperse particles instead of the initial ejecta, we simulate the ejection mixing process according to two-phase flow of gas and particle. We give the numerical results of the evolution process of the mixing, and analyze the effects of initial gas pressure and particle size on the mixing zone. The pneumatic break is observed from the numerical simulations, which can lead to evident reduction of the particle and then become an important factor affecting the evolution of mixture; also, our simulations are consistent with the corresponding measurements, showing that the gas and particle two-phase flow model is an effective method to simulate the ejection mixing.
Numerical simulation of energy deposition and extraction efficiency of the volume produced negative hydrogen ions
Authors: Yang Chao  , Liu Da-Gang  , Wang Hui-Hui  , Yang Yu-Peng  , Liao Fang-Yan  , Liu La-Qun  , Peng Kai  , Xia Meng-Zhong  ,   School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

In this paper, the negative hydrogen ion transportation and energy deposition mechanism are investigated deeply, and the collisions between negative hydrogen ions with other particles are treated by the three-dimensional Monte Carlo method. The storage of the particles and the constraint function of magnetic field are disposed by particle-in-cell (PIC) technology under the CHIPIC software. Based on this, negative hydrogen ion transportation and scattering case in the JAERI 10 A multicusp ion source are simulated. The influences of pressure and filter magnetic field on negative hydrogen ion transportation and extraction characteristics are analyzed and discussed. Results show that the greater the pressure, the bigger the collision loss of the volume produced negative hydrogen ions, and also the smaller the number of negative hydrogen ions reaching the wall and extracted is; in the lower discharge case, the more intensively the negative hydrogen ion extraction is influenced by the filter magnetic field, and also the stronger the filter magnetic field, the worse the extraction effectiveness is.
First principles caculations of h-BN monolayer with group IA/IIA elements replacing B as impurities
Authors: Liu Yue-Ying  , Zhou Tie-Ge  , Lu Yuan  , Zuo Xu  ,   College of Information Technical Science, Nankai University, Tianjin 300071, China
Published: December 2020

Using the first principles calculations based on the density-functional theory, we study the geometric structures, magnetisms, and electronic structures of h-BN monolayer with group IA/I!IA elements (Li, Na, K, B, Mg and Ca) replacing B as impurities. It is shown that the nonmagnetic substitutional impurities can induce spin polarization in nonmagnetic BN monolayer. For Li, Na and K impurities, the total magnetic moment of the supercell is 2 μB; for Mg and Ca, it is 1 μB. The magnetic moments are mainly localized on the nearest neighbor N atoms. The magnetic moment of the supercell with Be impurity is 0.705 μB, distributed over all N atoms. Spin polarized densities of states are presented, including total density of states and orbital-projected partial density of states. The origin of local magnetic moments and impurity energy level are explained. It is also found that the Mg and Ca doped systems are half metallic.
Anisotropy and isotropy of hole effective mass of strained Ge
Authors: Dai Xian-Ying  , Yang Cheng  , Song Jian-Jun  , Zhang He-Ming  , Hao Yue  , Zheng Ruo-Chuan  ,   School of Microelectronic, State Key Discipline Laboratory of Wide Bandgap Semiconductor Technologies, Xidian University, Xi’an 710071, China
Published: December 2020

In this paper, the hole effective mass along arbitrarily k wavevector direction and the hole isotropic effective masses in strained Ge/(001)(101)(111)Si1-xGex are obtained with in the frame work of kp theory. It is found that the hole effective mass of the top valence band along [010] wave vector decreases obviously with stress increasing and its absolute value is smallest. The hole effective mass of the second valence band tends to gently decrease with stress increasing, and is not significant in magnitude. Compared with the existing isotropic effective quality, the result obtained in this paper is proved to be correct.
Effects of random pores on the thermoelectric properties of Si100P2.5 (GaP)1.5 bulk
Authors: He Qin-Yu  , Luo Hai-Jin  , Wang Yin-Zhen  , Li Wei  , Su Jia-Bin  , Lei Zheng-Da  , Chen Zhen-Rui  , Zhang Yong  ,   Laboratory of Advanced Material, Institution of Electronic Information Material and Apparatus, Laboratory of Quantum Information Technology, School of Physics & Telecommunication Engineering, South China Normal University, Guangzhou 510006, China
Published: December 2020

SiGe, as a reliable and most efficient high-temperature thermoelectrics, has been utilized in special fields for many years, but there is no large-scale commercial application due to its high cost and low efficiency. Therefore, it is necessary to improve the dimensionless figure of merit ZT of a Si-based system, free of Ge which is expensive and rare earth, thereby becoming competitive in cost and efficiency for the commercial application. Since pure silicon possesses rather low ZT, for example 0.01 at room temperature, we have developed doped and nano-structured Si100P2.5 (GaP)1.5 bulk material and obtained ZT 0.47. In this work, a new approach to inducing random pores with four size distributions of 50 nm, 100 nm, 300 nm, and 1-2 μm is applied to the Si100P2.5 (GaP)1.5 bulk material, and ZT is improved by 32%. The increase of ZT can be attributed to the enhancement of the electrical conductivity and the Seebeck coefficient, and the reduction of the lattice thermal conductivity. The enhancement of electrical conductivity is ascribed to the doping effect of a small amount of Sb, while the increase of Seebeck coefficients stems mainly from the filter of low-energy carriers, and the reduction of lattice thermal conductivity arises mainly from phonons scattering. It is proved in this work that inducing random pores is an effective approach to improving the figure of merit of Si-based system.
Magneto-resistance for two-dimensional electron gas in GaN/AlxGa1-xN heterostructure
Authors: Wang Wei  , Zhou Wen-Zheng  , Wei Shang-Jiang  , Li Xiao-Juan  , Chang Zhi-Gang  , Lin Tie  , Shang Li-Yan  , Han Kui  , Duan Jun-Xi  , Tang Ning  , Shen Bo  , Chu Jun-Hao  ,   College of Physics Science and Technology, Guangxi University, Nanning 530004, China;,   National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China;,   Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241, China;,   State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
Published: December 2020

The magnetotransport measurement is performed on a GaN/AlxGa1-xN heterostructure sample in a low temperature range of 1.4-25 K and at magnetic fields ranging from 0 T up to 13 T. Magnetoresistance of a two-dimensional electron gas confined in the heterostructure is investigated. The negative magnetoresistivity in the whole magnetic field range originates from the electron-electron interactions (EEIs), while the positive magnetoresistivity in the high field range results from the parallel conductance. The EEI correction terms, as well as the concentration and mobility of the parallel channel are obtained by fitting the experimental data. Furthermore, another method of calculation is used to check their accuracy.
Temperature-dependant growth and properties of W-doped ZnO thin films deposited by reactive magnetron sputtering
Authors: Zhang Chi  , Chen Xin-Liang  , Wang Fei  , Yan Cong-Bo  , Huang Qian  , Zhao Ying  , Zhang Xiao-Dan  , Geng Xin-Hua  ,   Institute of Photo-Electronic Thin Film Devices and Technology, Tianjin Key Laboratory of Photo-Electronic Thin Film Devices and Technology, Tianjin Key Laboratory of Opto-Electronic Information Science and Technology for Ministry of Education, Nankai University, Tianjin 300071, China
Published: December 2020

W-doped ZnO (WZO) thin films for thin film solar cells have been deposited by pulsed direct-current reactive magnetron sputtering. The microstructures, surface morphologies, optical and electrical properties of WZO thin films are investigated at different substrate temperatures. The experimental results indicate that a proper substrate temperature is the key factor for fabricating high-quality WZO thin films. The surface roughness of WZO thin films increases firstly from 15.65 nm to 37.60 nm, and then decreases from 37.60 nm to 11.07 nm with the increase of substrate temperature. Higher Hall mobility deposited at the higher temperatures is attributed to the compact structure and good crystallization quality. The WZO thin film prepared at the temperature of 325 ℃ presents excellent optical and electrical properties with an average transmittance of 85.7% in the wavelength range from 400 nm to 1500 nm, a low resistivity of 9.25× 10-3 Ω·cm, a sheet resistance of 56.24 Ω /sq and a high Hall mobility of 11.8 cm2·V-1·s-1.
Electrical behavior research of silicon-on-insulator SiGe heterojunction bipolar transistor
Authors: Zhang Bin  , Yang Yin-Tang  , Li Yue-Jin  , Xu Xiao-Bo  ,   Key Laboratory for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

The paper deals with the design optimization of SiGe heterojunction bipolar transistor (HBT) on thin film silicon-on-insulator (SOI). The basic DC and AC current characteristics are obtained and the differences between the SOI and bulk SiGe HBT are analyzed. As the incorporation of SOI substrate makes the SOI SiGe HBT a four-terminal device, the influences of the substrate bias on Gummel plot, output current and avalanche current are studied emphatically. Finally, the physical parameters of material and geometric parameters of the device are discussed by changing the frequency characteristics. Compared with the bulk counterpart, the SOI SiGe HBT is designed and fabricated with a great degree of freedom for better performance. This systematic analysis of SOI SiGe HBT provides a valuable reference for the SOI SiGe BiCMOS circuit design and simulation.
The network model of mobile agents with the human mobility
Authors: Ding Yi-Min  , Yang Chang-Ping  ,   Faculty of Physics and Electronic Engineering, Hubei University, Wuhan 430062, China
Published: December 2020

Based on the research of the human mobilety patterns, a random-walker network model is used to explain the empirical results on the networks of mobile agents, and shows a possible evolution mechanism of these networks. The simulation results show that the degree distribution of this network takes Poisson distribution, and it exhibits the small-world behavior. Moreover, we present a numerical investigation on the displacements of the mobile agents, and find that the distribution of displacements takes power-law. Our numerical results are in good agreement with the empirical results on the human travel from the trajectories of human bank notes.
Influence complex network centrality on disaster spreading
Authors: Li Ze-Quan  , Zhang Rui-Xin  , Yang Zhao  , Zhao Hong-Ze  , Yu Jian-Hao  ,   School of Resource and Safety Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China;,   Communication and Information Center, State Administration of Work Safety, Beijing 100013, China
Published: December 2020

Based on a general dynamical model for disaster spreading, in different network structures, i.e. in Erdos-Renyi network, scale-free network and small world network, the influences of network centrality on the speed and trend of disaster spreading are analyzed by simulation. By changing the initial spreading condition, the influence of initial state on the spreading efficiency is analyzed. In this paper the differences between final disaster spreading state are mainly discussed based on four initial vertex-choosing strategies. For the four strategies, it is shown that there are apparent differences. Complex network has a strong ability to resist random attacks but is is fragile to resist intentional attacks. However, the three networks show different degrees of fragility. And then, the theoretical analysis results are verified in an actual network.
Raman optical activity of chiral trans-2, 3-epoxybutane molecule
Authors: Zhao Yan-Mu  , Wang Pei-Jie  , Fang Yan  , Wu Guo-Zhen  ,   Department of Physics, Beijing Key Lab for Nano-Photonics and Nano-Structure, Capital Normal University, Beijing 100048, China;,   State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

In this article, Raman bond polarizability of trans-2,3-epoxybutane is derived from its Raman intensity, and the charge distribution of its Raman excited virtual state is obtained. The differential bond polarizability is also obtained from its Raman optical activity (ROA) intensity. The Raman chirality is explained via the coupling between the dipole moment induced by the C-H bond around the chiral center and the magnetic dipole moment which is caused by the electronic current generated in the Raman process. Further analysis shows that the differential bond polarizabilities on the two opposite sides of the C-H bond around the chiral center are of opposite sign. This demonstrates the local asymmetry of this chiral molecule. The symmetric and antisymmetric coordinates are also analyzed, and their results are explained via the irreducible representations of C2 group.
Grid multi-scroll chaotic attractors in hybrid image encryption algorithm based on current conveyor
Authors: Lin Yuan  , Wang Chun-Hua  , Xu Hao  ,   College of Information Science and Engineering, Hunan University, Changsha 410082, China;,   College of Electrical & Information Engineering, Hunan Institute of Engineering, Xiangtan 411104, China
Published: December 2020

In this paper we propose a novel grid-scroll chaotic attractor generator based on the second generation current conveyor(CCII), which is used for hybrid image encryption of physical chaos encryption and advanced encryption standard (AES) encryption algorithm, because CCII has a higher speed and larger dynamic range than ordinary operational amplifier and can generate multiscroll physical chaotic signal with higher frequency and more complex dynamics properties. The hybrid encryption system of multiscroll physical chaos encryption and AES encryption based on the CCII, does not assure the relationship between plaintext and ciphertext, and the statistical characteristics of ciphertexts in this algorithm should be better than those of any other encryption system. The difference in statistical property of cipher text between the two cases is studied. One case is that the ciphertexts come from different schemes, i. e. the hybrid and the single stage ones, respectively, and the other is that the ciphertexts are generated by chaotic signals with different numbers of scrolls in the same algorithm. We design and implement the chaos circuit based on CCII, and simulat the encryption system. The results shown that they are in agreement with the theoretical analyses, and that the bigger number of scrolls chaotic system causes the weaker correlation of ciphertexts.
Complicated behaviors as well as the mechanism of the switching circuit
Authors: Ma Xin-Dong  , Bi Qin-Sheng  ,   Faculty of Civil Engineering and Mechanics, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

Switching electrical circuit with switcher between different types of Jerk systems is established. Based upon the analysis of equilibrium states, stable focus as well as periodic oscillations via Hopf bifurcation can be observed in the two subsystems as parameters varies. Complicated behavior caused by the periodic switcher is investigated in detail, and the point/circle and circle/circle switching periodic oscillations as well as the mechanism are presented. In the different types of switching oscillations, the number of the switching points on the trajectory may increase doubly with the variation of the parameter, which may lead to the cascade of period-doubling bifurcation to chaos. Furthermore, the variation of the parameter may influence the amplitude of the periodic oscillation of the subsystem and therefore the structure of the attractor of the whole switching system.
Long range absolute distance measurement based on femtosecond laser balanced optical cross-correlation
Authors: Qin Peng  , Chen Wei  , Song You-Jian  , Hu Ming-Lie  , Chai Lu  , Wang Ching-Yue  ,   Key Laboratory of Opto-electronic Information Science and Technology of Ministry of Education, College of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

High-precision distance measurement in a long range is critical for many advanced applications, such as satellite formation flying, free space optical communication and large scale machining. A 52 m absolute distance measurement in free space based on time of flight of femtosecond laser is demonstrated. The timing offset between target-reflected and the reference pulses is precisely characterized by balanced optical cross-correlation method. The balanced cross correlation signal is used for the feedback control of the cavity length and tightly locks the distance under test to multiple of pulse separation. As a result, the time of flight of the target-reflected pulse is determined by the repetition rate of the femtosecond laser, which effectively avoids the loss of timing resolution caused by direct access of pulse time-of-flight from photo-detection. In the experiment, a Yb -doped high repetition rate mode-locked fiber laser working at 1.04 μm is used as a femtosecond laser source, and a measurement precision of 12 nm is achieved in an average time of one second.
Gate length dependence of SOI NMOS device response to total dose irradiation
Authors: Peng Li  , Zhuo Qing-Qing  , Liu Hong-Xia  , Cai Hui-Min  ,   Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Education, School of Microelectronics, Xidian, University, Xi'an 710071, China
Published: December 2020

The gate length dependence of PD SOI NMOS device on total dose irradiation is investigated, which is exposed to 60Co gamma ray at a dose rate of 50 rad(Si)/s. The result shows that the transistor with shorter gate length shows larger radiation-induced interface trap density, which leads to the maximum transconductance degradation. The local floating body effect induces the output characteristic variation of irradiated MOSFET with gate length. After irradiation, the breakdown voltage of short channel SOI device decreases. Due to the buried oxide, the radiation-induced degradation of short channel SOI device is much serious compared with that of long channel SOI device.
Monte-Carlo simulation of secondary electron emission from solid metal
Authors: Chang Tian-Hai  , Zheng Jun-Rong  ,   School of Electronic, Information Engineering, South China University of Technology, Guangzhou 510000, China
Published: December 2020

The secondary electron emission is widely used in production practice, but it is difficult to measure accurately because the measuring result is severely affected by the experimental environment and equipment. A model of secondary electron emission is proposed in this paper. The model has three sections: the generation of secondary electrons, the motions of secondary electrons inside the solid and the escape of secondary electrons from the solid surface. Based on Monte-Carlo method, the relationship between the secondary electron emission coefficient and the range of energy with the energy and angle of the incident electrons is also analyzed. Simulation results show that the model proposed in this paper is corresponding to the actual condition very well. The relation between the secondary electron emission coefficient and the range of energy with the energy and angle of the incident electron is obtained.
Measurement of fine structure spectra in high-stripped states laser-produced Mo plasma
Authors: Wang Rui-Rong  , Xiong Jun  , Wang Wei  , An Hong-Hai  , Fang Zhi-Heng  , Jia Guo  ,   Shanghai Institute of Laser Plasma, Shanghai 201800, China
Published: December 2020

The fine structure spectra from very highly stripped ions of the medium and high-Z elements have important applications in plasma diagnostics and the atomic structure calculations. Therefore, on the SG-II laser facility, the X-ray emission spectra from highly stripped plasma of Molybdenum (Mo) are observed by focusing an Nd-glass frequency-tripled (0.35 m) laser beam onto the surface of the Mo target. The fine structure spectra of Mo ions in a range of 0.320.58 nm are measured by a high-resolution elliptically bent crystal spectrometer. Some of resonance transitions and inner-shell transitions of the type 42 and 32 in the C-like, O-like, F-like and Ne-like iso-electronic sequence and the lines from H-like and He-like Mo ions are identified and classified. In addition, the full widths at half maximum (FWHM) of wavelengths are also analyzed. Wavelengths are measured within an uncertainty of 0.0005 nm. A comparison shows that they are in good agreement with computational results of Hartree-Fock-Relativistic (HFR) method. This work is very helpful for enriching the spectra of Mo ions.
Structures, stabilities and electronic properties of InAs double-walled tubelike clusters and nanotubes
Authors: Wu Peng  , Liu Li-Ren  , Zhu Heng-Jiang  , Zou Yan-Bo  , Liu Zhi-Feng  ,   School of Physics and Electronic Engineering, Xinjiang Normal University, Urumuchi 830054, China;,   Condensed Matter Physics Research Institute, College of Physics, Chongqing University, Chongqing 401331, China
Published: December 2020

The structure evolutions and electronic properties of InAs Double-Walled tubelike clusters and nanotubes are studied by first-principles theory. Tubelike clusters, In(3pk+4p)/2As(3pk+4p)/2 (p=6, 8, 10, k=3-11), and the counterpart nanotubes, (m,n)@(2m,2n) (m=n=3,4,5), are analyzed. All geometric structures of clusters and nanotubes are optimized by using density functional theory with generalized gradient approximation, and they obey the Euler formula. The tube diameter formula is obtained. Size-dependent properties of clusters and nanotubes, such as binding energy, HOMO-LUMO gaps, density of state and energy band structures are calculated and discussed. The results show that both [6,k]@[12,k+2] and (3,3)@(6,6) possess relatively high stabilities in the corresponding systems. They also explain why the long and stable tublike clusters can be successfully obtined, and why InAs nanotubes can be synthesized experimentally. All of the double-walled tubelike clusters and nanotubes possess the characteristics of semiconductor.
Research on collision ionization process of Be atom by proton
Authors: Hu Ya-Hua  , Ye Dan-Dan  , Qi Yue-Ying  , Liu Xiao-Ju  , Liu Ling  ,   Jiaxing University, Jiaxing 314001, China;,   Institute of Plasma Physics, Chinese Academy of Sciences, 1126, Hefei 230031, China;,   The Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

The impact ionization process of Be by H+ is investigated using the continuum-distorted-wave and the eikonal-initial-state (CDW-EIS) approximation in this paper. The single and double differential cross sections are calculated for the projectile energies ranging from 50keV/u to 10000 keV/u. The total cross sections are consistant well with the previous results. The ionization mechanism of soft-collision, electron captured to continuum states and binary-encounter collisions are discussed. The soft-collision ionization mechanism is the most important contributor to the total cross section. Auger process for Be(1s2s2) is under study by adopting the FAC code.
Electric field of a static electric dipole in three-layer medium model using secondary equivalent method
Authors: Chen Cong  , Li Ding-Guo  , Jiang Zhi-Guo  , Liu Hua-Bo  ,   College of Sciences, Navy University of engineering, Wuhan 430033, China
Published: December 2020

In three-layer-parallel-medium mode, the method of secondary equivalent is proposed to derive the analytic expression of the electric field produced by a static electric dipole based on the uniqueness theorem when the source point is located in the middle layer but the field point is located in other layer. That is, the distribution of the electric field is solved when the source point and the field point are located in the same medium using the first equivalent method. Then the three-layer model is equivalent to two-layer model using the second equivalent method. Finally, the mirror image theory is used to obtain the field distribution. The expression of the scalar electric potential is proved to satisfy the boundary conditions, so the derivation results are proved to be effective. In order to prove the correctness of the expression of the scalar electric potential, a three-layer-parallel-medium mode, that is air-seawater-seabed, is simulated in laboratory, and the scalar electric potentials in the space of seawater and in the space of seabed are measured respectively. Some theoretical analyses are performed and the results of the analyses are in accordance with the experimental measurements, so the correctness of the solution is validated. The research results provide a theoretical base for the actual application such as modeling and characteristic analysis of electric field whose basic simulator is the static electric dipole.