bluuebunny/crossref_metadata_2025 huggingface dataset:
Second-harmonic generation of the Bessel sound beam of several lobes
Authors: Dai Yu-Rong  , Ding De-Sheng  ,   Department of Physics, Southeast University, Nanjing 210096, China;,   School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
Published: December 2020

By the Gaussian expansion approach we investigate fundamental- and second-harmonic generation in practical Bessel beams of several lobes. The analysis is based on the integral solutions of the Khokhlov-Zabolotskaya-Kuznetsov equation under the quasilinear approximation. The influence of the medium attenuation on beam profile is considered. Numerical results show that the absorption parameter has a significant effect on the beam profile of the second harmonic. Under certain circumstances, the second harmonic of a practical Bessel beam with several lobes still has the main properties of an ideal Bessel beam of infinite aperture when it propagates within its depth of field.
Numerical simulation of NOx species behaviour in atmosphere plasma
Authors: Pang Xue-Xia  , Deng Ze-Chao  , Jia Peng-Ying  , Liang Wei-Hua  ,   College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

A zero-dimensional model is used for studying the behaviors of NOx in atmosphere plasmas with different ionization degrees. The temporal evolutions of NOx (including NO, NO+, NO2, NO2+, N2O, N2O+, NO3 and N2O5), N and O3, the main important reactants which influence the producing and the consuming of NOx, are obtained in different initial densities for afterglow plasmas. The results show that the removal rates of NO and NO2 are higher when ne0=109 cm-3, and the total nitrogen oxide density is lower, so it is suited for the removal of the pollution of NOx. Some important reactants such as N and O3 varying with the increase of ionization degree are also analyzed.
Molecular dynamics study of small helium cluster diffusion in titanium
Authors: Chen Min  ,   School of National Defense Science and Technology, Southwest University of Science and Technology, Mianyang 621010, China
Published: December 2020

The diffusions of He atom and small He clusters in Ti at different temperatures are simulated by molecular dynamics. The prefactors and the activation energies of diffusion coefficients are calculated. It can be concluded that the diffusion is anisotropic. Simulations show that prefactors of diffusion coefficients are different from those of He species diffusing in different directions, but the activation energies are the same. The result demonstrates that it is insufficient to predict the diffusion behavior of He in metal when only the energy barrier in static lattice is considered. Dynamics calculations are necessary to obtain the correct prefactors. Another counterintuitive observation is that He-dimer migrates more quickly than single He atom does at room temperature. The results emphasize the importance of dynamics simulations in predicting diffusion behavior of He in metals.
Pressure threshold and dynamics of nucleation for Si nano-crystal grains prepared by pulsed laser ablation
Authors: Deng Ze-Chao  , Luo Qing-Shan  , Ding Xue-Cheng  , Chu Li-Zhi  , Liang Wei-Hua  , Chen Jin-Zhong  , Fu Guang-Sheng  , Wang Ying-Long  ,   Key Laboratory of Photo-Electronics Information Materials of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

Si nano-crystal grains are prepared by pulsed laser ablation in low pressure Ar at room temperature through changing the gas pressure and the distance between target and substrate. The morphologies and compositions of samples are characterized by scanning electron microscopy images, Raman scattering spectra and X-ray diffraction spectra.The pressure threshold for Si grain formation is obtained to be 0.6 Pa at a laser fluence of 4 J/cm2, distance between target and substarate of 3 cm, and room temperature.Combining the fluid mechanics model and the nucleation division model, the dynamics process of nucleation is analyzed.The Monte Carlo simulation shows that the nucleation of nano-crystal grains is determined jointly by temperature and supersaturated density.
The effect of stacked graphene flakes on the electronic transport of zigzag-edged graphene nanoribbons
Authors: Zhang Mi  , Chen Yuan-Ping  , Zhang Zai-Lan  , Ouyang Tao  , Zhong Jian-Xin  ,   Institute for Quantum Engineering and Micro-Nano Energy Technology, Xiangtan University, Xiangtan 411105, China
Published: December 2020

The effect of stacked graphene flakes (GFs) on the electronic transport property of zigzag-edged graphene nanoribbon (ZGNR) is investigated. By using the Greens function method, we calculate the conductances of ZGNRs with two different stacked-type GFs. It is found that the coupling effect between ZGNRs and GFs can induce dips at the conductance profiles in two different stacked-types. For both stacked-types, the dips far away from the Fermi level are nearly overlapped. However, the position of conductance dip near the Fermi level depends on the stacked-type. In addition, we discuss the effect of geometric size of GF on the electronic transport property. The results show that with the increase of the size of GF, the dips far away the Fermi level in two stacked-types gradually move toward the Fermi level, while the discrepancy of the dips near the Fermi level is much evident. Our results indicate that the stacked GFs can effectively tune the electronic transport of ZGNR.
Responses of electronic structure and magnetism to tetragonal distortion and their influence on pressure for the Heusler alloy Mn2 NiAl
Authors: Luo Li-Jin  , Zhong Chong-Gui  , Fang Jing-Huai  , Zhao Yong-Lin  , Zhou Peng-Xia  , Jiang Xue-Fan  ,   School of Science, Nantong University, Nantong 226007, China;,   Key Laboratory of Advanced Functional Materials of Jiangsu Province, Changshu Institute of Technology, Changshu 215500, China
Published: December 2020

The change rules of electronic structure and magnetism in the process of transform from a cubic structure to a tetragonal structure and their responses to pressure for Hg2CuTi-type Mn2NiAl are studied by first principles method based on the density functional theory. The study shows that in the process of transform from a cubic austenite phase to a tetragonal martensite phase, the shift of the density of states of occupied state to ward lower energy in the martensitic phase results from the enhanced Ni-Mn(A) hybridization caused by a decrease in the Ni-Mn(A) distance, and it is the reason for the stabilization of the martensitic phase. In the process of transform from the austenite phase to the martensite phase, the bonding interaction becomes stronger, owing to energy band broadening, and it can improve the stabilization in the martensitic phase. In the process of tetragonal distortions, the change of total magnetic moment is determined by the change of magnetic moment of Ni atom. The bulk modulus at zero pressure of Mn2NiAl is calculated to be 125.69 GPa, so that we expect Mn2NiAl to be the more compressible material than the familiar Heusler alloys.
The effect of Eu2+ doping concentration on luminescence properties of Ca2-xMgSi2O7∶x Eu2+ green phosphor
Authors: Cao Shi-Xiu  , Han Tao  , Tu Ming-Jing  ,   Research Center for Material Interdisciplinary Science, Chongqing University of Arts and Sciences, Chongqing 402168, China
Published: December 2020

The Ca2-xMgSi2O7∶xEu2+ green phosphor is synthesized by chemical coprecipitation. X-ray diffraction and the fluorescence spectrophotometry are used to investigate the structural and the luminescent properties of the Ca2-xMgSi2O7∶xEu2+ green phosphor. The result shows that the excitation spectrum of the Ca2-xMgSi2O7∶xEu2+green phosphor extends from 300 nm to 480 nm, and the peaks appear around 389 and 430 nm, thus the phosphor can be excited effectively by InGaN chip in a range of 360480 nm. The peak of the emission spectrum appears around 531 nm. The emission spectrum intensity first increases and then decreases with Eu2+ doping concentration increasing. The strongest emission intensity is obtained when Eu2+doping concentration reaches 0.04. The concentration self-quenching is attributed to the d-d interaction according to the Dexter theory.
Investigations of microstructure and ionic conductivity for (PEO)8-ZnO-LiClO4 polymer nanocomposite electrolytes
Authors: Wang Jun-Jun  , Gong Jing  , Gong Zhen-Li  , Yan Xiao-Li  , Gao Shu  , Wang Bo  ,   School of Physics, Wuhan University, Wuhan 430072, China
Published: December 2020

The effects of nanosized ZnO on the microstructure, the free volume and the ionic conductivity of poly ethylene oxide (PEO) nanocomposite electrolytes (PEO)8-ZnO-LiClO4 are systematically studied by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy (PALS), respectively. The experimental results show that the presence of the nanosized ZnO brings about a reduction in the crystallinity of the PEO phase and a very marked increase in ionic conductivity. PALS discrete analysis shows that the free volume size, the free volume concentration and the relative free volume fraction significantly increase with the increase of nano-ZnO. Specially, it is the first time to observe the occurrence of peaks of the free volume distribution split after nano-ZnO has been filled, which indicates that the ZnO added into (PEO)8-LiClO4 has an important effect on the microstructure for nanocomposites due to the interaction between the nano-ZnO and matrix. A direct correlation between the free volume fraction and the ionic conductivity is observed, and the ionic conductivity mechanism is discussed.
The theory and computer simulation of beam-loading conductance in the double-gap coupled cavity
Authors: Huang Chuan-Lu  , Ding Yao-Gen  , Wang Yong  ,   Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In a double-gap coupled cavity of klystrons, the electrons exchange energy with the electric field in each gap through beam-wave interaction process, and different beam-loading effects take place in each gap. However in this case the traditional beam-loading model does not hold true. To solve this problem, we present a novel model according to the space-charge-wave theory to calculate the beam-loading conductance in each gap of the coupled-cavity, and also derive the formulations. Moreover, we perform a simulation study using a three-dimensional particle-in-cell code. The results obtained by the model show good agreement with the simulation results. In comparison with the traditional model, the new model can be used to calculate the beam-loading conductances in diffident regions of the coupled-cavity, and then it can be used to study the beam-wave interactions in the gaps and analyze the mode stability in the coupled-cavity in a high accuracy.
Simulation investigation of the 2 mode operating tunable relativistic magnetron with axial radiation
Authors: Li Wei  , Liu Yong-Gui  ,   College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

A tunable relativistic magnetron with axial radiation operating at 2 mode is investigated by three-dimensional particle-in-cell simulation in this paper. The tuning is realized by filling solid dielectric material into the cavities of the interaction region. The effects of changing the relative permittivity and the inner radius of the dielectric material on the operating frequency, the average output power and the efficiency are analyzed. Then the principle of the tuning is demonstrated. The simulation results show that under the unchanged structure parameters and the work point, the relativistic magnetron realizes the tuning from S band to L band by varying the relative permittivity or the inner radius of the solid dielectric material. Furthermore, with inserting the dielectric material, the output capability of the relativistic magnetron is improved. When the relative permittivity is 615 and the radius is 4.184.40 cm, the increase in efficiency can reach 80%, the decreased frequency range is less than 55%.
Non-spherical symmetric inversion of ionospheric occultation data
Authors: Hong Zhen-Jie  , Liu Rong-Jian  , Guo Peng  , Dong Nai-Ming  ,   College of Mathematics and Information Science, Wenzhou University, Wenzhou 325035, China;,   Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China
Published: December 2020

The Abel inversion based on a spherical symmetry of the ionospheric electron density distribution is a traditional inversion method of ionospheric occultation. However, the real ionosphere is not strictly spherically symmetric, which can cause error in inversion process of ionospheric occultation data. In this paper, we develop a non-spherically symmetric ionospheric occultation inversion method, in which the gradient information about international reference ionosphere three-dimensional ionospheric model is used to correct total electron content (TEC), thus the ionospheric electron density can be reconstructed from the corrected TEC by the spherical symmetric Abel inversion method. The inversion results retrieved from the measurements data of Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ionospheric occultation are compared with the ionosonde data, showing that the result obtained from the new method is well coincident with the ionospheric electron density profile.
Global structure and variation of mesospheric and lower thermospheric zonal wind in 120 °E meridian
Authors: Ling Chao  , Chen Ze-Yu  , Chen Hong-Bin  ,   Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Multiyear (2002-2011) wind observations from TIMED Doppler Interferometer (TIDI) onboard the thermosphere ionosphere mesosphere energetics and dynamics (TIMED) satellite are used for studying the typical structures and variations of mesospheric and lower thermospheric (MLT) mean zonal wind from 80 to 105 km in 120 °E meridian. Comparisons between TIDI measurements and empirical models indicate that TIDI is in good agreement with models in the extratropic regions especially in the middle and high latitudes, but significant differences occur mainly in the tropic regions. In the altitudes of TIDI's coverage from 80 to 105 km, monthly zonal winds are always westward over the tropical regions, forming an easterly band centered at the equator. Results from multiyear observations show complicated variations in the MLT tropical easterlies. The averaged width of easterlies is 37.5 degrees and corresponding variation is about 14 degrees.
Detection of weak target signal with least-squares support vector machine and generalized embedding windows under chaotic background
Authors: Xing Hong-Yan  , Cheng Yan-Yan  , Xu Wei  ,   Jiangsu Key Laboratory of Meteorological Observation and Information Processing, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   College of Electronic and Information Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China
Published: December 2020

To extract weak signal from the chaotic background, in this paper we analyze the theory of state space reconstruction of complicated nonlinear system, and put forward an estimation method utilizing the least-squares support vector machine (LS-SVM) based on a generalized window function. In the algorithm the generalized embedded window is taken as a foundation and the correlation function method is used to determine the embedded dimension and time delay of Lorenz system and so the state space reconstruction is realized and by combining the error forecasting model in which the LS-SVM is used to estimate the errors, the detection of the weak target signal, such as transient and periodic signal, is achieved. It is illustrated in the simulation experiments that the model proposed can detect the weak signals effectively from a chaotic background and reduce the influence of noise on the target signals, which possesses minor forecasting error. Compared with those conventional methods, this method has a remarkable advantage in reducing detection threshold and improving the accuracy of prediction. When the signal-to-noise ratio is -87.41 dB in the chaotic noise background, the new method can reduce the root mean square error nearly two orders of magnitude, reach 0.000036123, while the traditional SVM can only reach 0.049 under the condition of -54.60 dB.
Measurement and analysis of neutron capture rate of U-238 in an alternate depleted uranium/polyethylene system
Authors: Yan Xiao-Song  , Liu Rong  , Lu Xin-Xin  , Jiang Li  , Wang Mei  , Lin Ju-Fang  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

In order to check the conceptual design of subcritical reactor, an alternate depleted uranium/polyethylene-shell simulation device was established, to carry out uranium-238 neutron capture rate experiment using activation technique. The depleted uranium foils were activated at 90o to the incident. By measuring the 277.6 keV -ray emitted from 239Np generated by 238U (n, ) 239U reaction and correcting self-absorption of uranium experimentally, the 238U (n, ) reaction rate with an uncertainty between 3.5% and 3.7% and a total neutron capture of 2.24 0.09 of the system were obtained. The experiment was simulated using MCNP5 code with ENDF libraries. The simulations and measurements accord within 5% for the 238U (n, ) reaction rate and within 1% for the total neutron capture rate of 238U.
Study of the focusing properties of Laue bent crystal by ray-tracing
Authors: Chen Can  , Tong Ya-Jun  , Xie Hong-Lan  , Xiao Ti-Qiao  ,   Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 201800, China;,   Graduate University of Chinese Academy of Science, Beijing 100049, China
Published: December 2020

The laue bent crystal is the most effective optical element of focusing, collimating and monochromating of high flux density hard X-rays (above 30 keV) from the insertion device radiation, because of reducing the high heat load effectively. So the study of the focusing optical properties is important for developing high performance and stability laue bent crystal monochromator. We give a systematic research of the focusing properties of laue bent crystal by X-ray trace program self-developed, analyze the effects of the mode of incident beam and crystal parameter on focusing spot size, focal length, diffracted beam divergence, etc., and obtain the following results: the higher the diffracted energy, the smaller the spot size is and the spot size tends to be a constant; the smaller the bend radius of crystal, the smaller the spot size is, and the spot size reaches a minimum when the bend radius is a threshold, then as the bend radius decreases, the spot size becomes larger because of aberration; the spot size is linearly directly proportional to the thickness of crystal. For the divergence of diffracted beam, it becomes smaller as the diffracted energy is high, and tends to be a constant; it is linearly directly proportional to the curvature of bent crystal. Also we obtain a reasonable range of bent crystal parameters from the study by ray-tracing.
Single photon wavelength modulation absorption spectrum of acetylene for 1.5 m laser wavelength stabilization
Authors: Wang Xiao-Bo  , Ma Wei-Guang  , Wang Jing-Jing  , Xiao Lian-Tuan  , Jia Suo-Tang  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Laser Spectroscopy Laboratory, Shanxi University, Taiyuan 030006, China
Published: December 2020

We describe a kHz single photon wavelength modulation technology to realize the locking reference signal of the laser frequency. By detecting the single photon acetylene gas absorption spectrum and by amplifying the lock-in the discrete single photon response pulse, we achieve the laser frequency stabilized in real time. The 1.5 m distribution feedback semiconductor laser output frequency is stabilized at acetylene gas absorption peaks, and the typical laser frequency fluctuation is less than 25 MHz within 175 s. This single photon wavelength modulated absorption spectrum technology eliminates the high background noise in low frequency range and can be used in the quantum communication system and optical wavelength division multiplex.
Investigation on FM-to-AM conversation of the optical flat plates in complex laser systems
Authors: Wang Yu-Lei  , Zhang Yun  , Fu Wan-Qin  , Lü Zhi-Wei  , Zhou Yu  , Deng Qing-Hua  , Ding Lei  ,   School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China;,   National Key Laboratory of Science and Technology on Tunable Laser, Institute of Opto-Electronics, Harbin Institute of Technology, Harbin 150080, China;,   Research Center of Laser Fusion,China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

At present, in most high-power laser drivers the phase modulation is used to suppress the effect of stimulated Brillouin scattering and meet the requirement for target surface light intensity uniformity. However, the modulated pulses show intense FM-to-AM effect after transmitted through a complex laser system. Analyzing the source of this effect is essential to the improvement of the output performance of whole laser system. In this paper, the theoretical analysis and the numerical simulation of the FM-to-AM conversion of the optical flat plates are investigated, which has been ignored by many researchers. The simulation results show that the more the laser passes through the optical flat plates, the deeper the modulation will be (for example, the modulation depth will be as high as 22.2% when transmitting ten times), and it follows a linearly increasing trend. What's more, the different flat optical elements have different spectral filtering effects. When the central wavelength of the front-end is chosen to be 1054 nm, the spectral filtering effect is very weak. To our knowledge, the reduction of the FM-to-AM conversion by changing the central wavelength is presented for the first time.
Normal force distribution in two-dimensional granular system of compositional disorder
Authors: Zhang Xing-Gang  , Hu Lin  ,   College of Science, Guizhou University, Guiyang 550025, China
Published: December 2020

Point defects are implanted in an ordered granular system by randomly selecting granules and changing their stiffness coefficients. The discrete element method is used to research the normal force probability distribution. Simulation result shows that force network is almost homogeneous without defects whereas force network will become inhomogeneous with defects. The concepts of primary normal force and secondary normal force are proposed and their statistics are analyzed separately. As the rate of defects increases, the changing process of primary normal force distribution is complex, whereas the secondary normal force distribution is always exponential distribution. Our simulation shows that normal force distributions are different between randomly packing system and compositional disordered system of low defect rate. But when defect rate is large, the distributions are similar. These results are beneficial to the understanding of the relationship between inhomogeneous force network and disordered system.
Theoretical computation studies for transport properties of air plasmas
Authors: Wang Wei-Zong  , Wu Yi  , Rong Ming-Zhe  , Yang Fei  ,   School of Electrical Engineering, Xi'an Jiaotong University, State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an 710049, China;,   Department of Electrical Engineering and Electronics, The University of Liverpool, Brownlow Hill, Liverpool L69 3GJ, UK
Published: December 2020

The thermophysical properties of arc plasma provide reliable micro-theoretical foundations and parameter inputs for the numerical simulation of the air arc discharge process. Based on the assumption of the local thermodynamic equilibrium, the computation of transport properties including electron diffusion coefficient, viscosity, thermal conductivity and electrical conductivity is performed by using the Chapman-Enskog method and expanding the sonine polynomial up to the third-order approximation (second-order for viscosity) in a pressure (0.120 atm) and temperature range (30040000 K) conditions which satisfy most thermal plasma modelling requirements. The most recent data on potential interactions and elastic differential cross sections for interacting particles are utilized to determine the collision integrals, resulting in more accurate and reliable values of transport properties than those given in the previous literature.
Research on the total dose irradiation effect of partial-depletion-silicon-on insulator static random access memory
Authors: Li Ming  , Yu Xue-Feng  , Xue Yao-Guo  , Lu Jian  , Cui Jiang-Wei  , Gao Bo  ,   Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011, China;,   Xinjiang Key Laboratory of Electronic Information Materials and Devices, Urumqi 830011, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In this paper, the changes of electrical parameters and their functional errors with the total radiation dose are studied, when the PDSOI static random access memory (SRAM) is irradiated under different total doses. After the SOI SRAM is irradiated by the 60Co-γ ray, the total dose radiation damage mechanism and the correlation between the changes of device parameters and function errors are discussed. For the large-scale SOI integrated circuits, this provides a possible method to further study the total dose radiation hardening and the radiation damage assessment of the devices. It is indicated that the increase of current consumption is due mainly to the radiation-induced leakage current from both field oxygen and buried oxide. The drift of threshold voltage creates the decline in output high level, the slight increase in output low level, the significant reduction in peak-peak value, and the increase of transmission delay. When the total dose accumulates and reaches a certain amount of dose, the logic mutation error emerges, resulting in the failure of shutdown function. There is a certain correlation between the transmission delay, the output high and the logic error.
Study on transport characteristics of CNTFET with HALO-LDD doping structure based on NEGF quantum theory
Authors: Liu Xing-Hui  , Zhang Jun-Song  , Wang Ji-Wei  , Ao Qiang  , Wang Zhen  , Ma Ying  , Li Xin  , Wang Zhen-Shi  , Wang Rui-Yu  ,   College of Physics, Liaoning University, Shenyang 110036, China
Published: December 2020

A transport model of CNTFET is built by solving the Poisson equation and Schrödinger equation within the non-equilibrium Green's function theory. The simulation method can relate the CNTFET transport properties directly with the chiral index of CNT. For the first time, the influences of single HALO and double LDD (HLL) doping structures on the CNTFET are investigated. The results show that under the same gate-source and drain-source voltages, HLL-CNTFET reduces significantly the leakage current and the subthreshold swing and increases on-off current ratio as compared with conventional CNTFET, indicating that this new structure has better gate control ability than conventional CNTFET. HLL-CNTFET possesses a smaller drain-source conductance so that it is more suitable for analog integrated circuits application, and has a smaller threshold voltage shift so shat it can better suppress DIBL effect. The increase of channel electric field strength near the source is beneficial to the increase of the electron transport rate; and the reduction in electric field near the drain is more conductive to the suppression of hot electron effects. This study is helpful for understanding the working mechanism and exploring new features of CNTFET.
Effects of random external fields on the dynamics of the one-dimensional Blume-Capel model
Authors: Li Yin-Fang  , Shen Yin-Yang  , Kong Xiang-Mu  ,   Shandong Provincial Key Laboratory of Laser Polarization and Information Technology, Department of Physics, Qufu Normal University, Qufu 273165, China
Published: December 2020

The dynamical properties of quantum spin systems have received a great deal of theoretical and experimental attention in the past decades. Only recently, has much attention been paid to the random quantum spin systems. In this paper the effect of random external field on the dynamics of one-dimensional Blume-Capel model with s = 1 in the high-temperature limit is investigated by using the recurrence relations method. The spin autocorrelation function as well as the corresponding spectral density of the system is calculated in the presence of the field that satisfies two types of distributions. When the single-ion anisotropy takes 0, for the bimodal distribution, the dynamics of the system behaves as a crossover from a central peak behavior to a collective mode one. For the Gaussian distribution, when the standard deviation is small, the dynamical behavior of the system also exhibits a crossover; when the standard deviation is large enough, the system only shows a disordered behavior. We also discuss the effect of the single-ion anisotropy on the dynamical property of the system, and find that the collective-mode behavior becomes weaker as the single-ion anisotropy exists.
Study of concentration dependence of luminescent properties for Eu3+ doped CaWO4 red phosphors
Authors: Meng Qing-Yu  , Zhang Qing  , Li Ming  , Liu Lin-Feng  , Qu Xiu-Rong  , Wan Wei-Long  , Sun Jiang-Ting  ,   Key Laboratory of Semiconductor Nanocomposite Materials, Ministry of Education, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025, China
Published: December 2020

Eu3+ doped CaWO4 phosphors of different concentrations are prepared by a co-precipitation method. The X-ray diffraction patterns and field emission scanning electron microscopy images are investigated. The excitation spectra, emission spectra and the curves of fluorescence decays of the samples are measured. The Judd-Ofelt (J-O) parameters, quantum efficiencies of the 5D0 level of Eu3+ and color coordinates are calculated. The dependences of relative intensity of charge transfer band, J-O parameter and quantum efficiency on doping concentration are discussed. The photoluminescence properties of Eu3+ doped CaWO4 luminescent material are studied. The results indicate that the 616 nm red emission of Eu3+5D07F2 transition can be effectively excited by 394.5 nm and 465 nm with high excitation efficiency and the concentration quenching is high. So the CaWO4: Eu red phosphor may have a potential application for white light emitting diode.
Simulation of morphological evolution and crystallographic tilt in heteroepitaxial growth using phase-field crystal method
Authors: Chen Cheng  , Chen Zheng  , Zhang Jing  , Yang Tao  ,   State Key Laboratory of Solidification Processing, Northwestern Ploytechnical University, Xi'an 710072, China
Published: December 2020

The phase-field crystal (PFC) model is employed to study the morphological evolution and the crystallographic tilt of heteroepitaxial growth on vicinal substrates. The results are as follows: for heterostructures with large misfit (ε > 0.08) the crystallographic tilt of epitaxial layer is approximately proportional to the substrate miscut angle, while the elastic strain energy of the film will lead to the nucleation of dislocation, which contributes to step-flow growth mode. As for the heterostructures with small misfit (ε < 0.04) the elastic strain energy will be released in the form of surface energy, and the surface profile of epitaxial film is dislocation-free island. When exposed to high undercooling, the substrate with large misfit and miscut angle will result in small-angle grain boundary between the substrate and the epitaxial layer. The small-angle grain boundary is composed of arranged dislocations, and it significantly changes the growth orientation of epitaxial layer.
The third independent conserved quantity and its symmetry of the two-dimensional anisotropic harmonic oscillator
Authors: Lou Zhi-Mei  , Mei Feng-Xiang  ,   Department of Physics, Shaoxing University, Shaoxing 312000, China;,   Department of Mechanics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

The energy and the two partial energies of two-dimensional anisotropic harmonic oscillator are conserved quantities, but only two of them are independent. The system possesses the third independent conserved quantity when the 1/2 is a rational number. The extended Prelle-Singer method is used to find the third independent conserved quantity for the five typical two-dimensional anisotropic harmonic oscillators. The Noether symmetry and the Lie symmetry of the third independent conserved quantities are also discussed.
The study of finite-time stability active control method for Lorenz-Haken laser chaotic system
Authors: Zhao Jian-Li  , Wang Jing  , Wang Hui  ,   National Engineer Research Center of Advanced Rolling, University of Science and Technology Beijing, Beijing 100083, China;,   Department of Information Security Engineering, Chinese People's Public Security University, Beijing 100038, China
Published: December 2020

In this paper, the problem of finite-time stability for Lorenz-Haken laser chaotic system is studied by active control method. On the basis of the study for terminal attractor, and the consideration fo the uncertainties, an active control method with dynamic active compensation based on terminal attractor is proposed, which makes the controlled Lorenz-Haken laser chaotic system achieve the finite-time stability approximately. Meantime, in order to solve the uncertainties, a new observer is designed, which makes the estimate value follow the real value of uncertainties in a very short time. The approximate finite-time stability of the closed-loop system is analyzed in detail by introducing a singular perturbation theory. Simulation results show the effectiveness of the active control method and observer.
Net thrust measurement of propellantless microwave thruster
Authors: Yang Juan  , Wang Yu-Quan  , Li Peng-Fei  , Wang Yang  , Wang Yun-Min  , Ma Yan-Jie  ,   College of Astronautics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

According to the classic theory of electromagnetic (EM) fields, we develop a propellantless microwave thruster system that can convert microwave power directly into thrust without the need of propellant. It is expected to be useful for spacecraft. Different from conventional space plasma propulsion, the system can obviate a large propellant storage tank and the issues related to plasma plume interference with the spacecraft surface. Different from huge solar sails and microwave-propelled sails, the system uses a cylindrical tapered resonance cavity as a thruster and uses an integrated microwave source to generate continuous EM wave so that the EM wave is radiated into and then reflected from the thruster to form a pure standing wave with amplified wave amplitude. The pure standing wave produces a non-uniform EM pressure distribution on the inner surface of the thruster. Consequently, a non-zero net EM thrust exerting on the symmetric axis and directing to the minor end plate of the thruster appears. In experiments a magnetron is used as a microwave source with an output microwave power of 2.45 GHz frequency. The generated net EM thrust is measured using a force-feedback test stand. The developed thruster system is experimentally demonstrated to produce thrust from 70 to 720 mN when the microwave output power is from 80 to 2500 W.
New Hermite-polynomial-operator identities and their application in quantum squeezing
Authors: Fan Hong-Yi  , Zhan De-Hui  , Yu Wen-Jian  , Zhou Jun  ,   Department of Material Science and Engineering, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

By introducing the Hermite-polynomial-operator Hn(X), where X is the coordinate operator (or the quadrature operator in quantum optics theory), and combining the technique of integration within an ordered product of operators, we derive some new operator identities about quantum squeezing, which are useful for studying the squeezed number state.
Estimating parameters for coupled air-sea model with variational method
Authors: Song Jun-Qiang  , Cao Xiao-Qun  , Zhang Wei-Min  , Zhu Xiao-Qian  ,   School of Computer Science, National University of Defense Technology, Changsha 410073, China
Published: December 2020

In this paper a method is presented to estimate the unknown parameters of nonlinear El Nio/La Nio-Southern Oscillation model based on the variational principle. Firstly, the equation of the coupled air-sea model is included into the objective functional. Secondly, the formulas of the adjoint equation and the functional gradient for unknown parameters are derived using the variational method. Finally, the algorithm to estimate unknown parameters of air-sea oscillator system is designed according to the above formulas. The numerical simulation results show that the proposed method is very effective and feasible to estimate the unknown parameters of nonlinear air-sea coupled dynamical system.
Acceleration effect in the gravitational field of black hole involving a global monopole
Authors: Shao Jian-Zhou  , Wang Yong-Jiu  ,   Institute of Physics, Hunan Normal University, Changsha 410081, China
Published: December 2020

In this paper, we provide the analytical expression of acceleration of neutral experimental particle in the gravitational field of black hole involving a global monopole and discuss the contribution of global monopole to acceleration effect. The results indicate that the repulsion effect takes place due to the global monopole, and when v c, neutral particle in the gravitational field is subjected to a repulsive force, which does not exist in Newtonian mechanics.
The global attractor of nonlinear thermoelastic coupled Sine-Gordon system
Authors: Zhang Jian-Wen  , Ren Yong-Hua  , Wu Run-Heng  , Feng Tao  ,   College of Mathematics, Taiyuan University of Technology, Taiyuan 030024, China;,   College of Science, North China University of Technology, Beijing 100041, China
Published: December 2020

The dynamical behavior of a class of coupled system to the Sine-Gordon equations with the Peierls-Nabarro force is considered in this paper. First, the existence of the continuous solution is shown in the semi-group approach, under the certain initial-boundary value condition. Then, using the decomposing technique of semi-group, we construct the compact positively invariant sets, and the global attractor is proved.
Analysis and synchronization of a novel chaotic system based on Chen's system
Authors: Zhang Guo-Shan  , Niu Hong  ,   School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

In this paper, a new three-dimensional autonomous chaotic system is constructed by adding a product term with variable coefficient to the first equation of Chen's system. The new system with different groups of coefficients can be chaotic or not by adjusting the variable coefficient, that is, by adjusting the variable coefficient, chaos occurs in new system when Chen's system is not chaotic, or chaos is suppressed in new system even if Chen's system is chaotic. The characteristics of the new chaotic system are analyzed in detail and the synchronization of new system is considered. Moreover, the simulation results are also presented.
Research on the single-particle resonant states by the complex scaling method
Authors: Liu Ye  , Chen Shou-Wan  , Guo Jian-You  ,   School of Physics and Material Science, Anhui University, Hefei 230039, China
Published: December 2020

In the framework of the relativistic mean field (RMF) theory, the single-particle resonant states for spherical nuclei are studied by the complex scaling method. Taking 122Zr for example, we demonstrae the calculated details, and the obtained energies, widths, and wave functions for all the possiable resonant states. The results are in good agreement with those from the analytic continuation in the coupling constant method and the scattering phase shift method. Furthermore, we investigate the resonant states for all the Zr isotopes. The results are in satisfactory agreement with those from the scattering phase-shift method.
Line-imaging optical recording velocity interferometer at Shenguang-II laser facility and its applications
Authors: Shu Hua  , Fu Si-Zu  , Huang Xiu-Guang  , Ye Jun-Jian  , Zhou Hua-Zhen  , Xie Zhi-Yong  , Long Tao  ,   Shanghai Institute of Laser Plasma, Shanghai 201800, China;,   Beijing Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

A line-imaging optical recording velocity interferometer (VISAR) is implemented at the Shenguang II laser facility. The spatial resolution is ～ 7 m, the effective field of view in the target plane is ～ 1 mm. We propose a new illumination method with increasing three times the luminosity of such a diagnostic. The VISAR is applied to experiments of laser-driven equation of state shockless compression, and shocktiming.
The study on optical transfer function of silver superlens
Authors: Xiao Xiao  , Zhang Zhi-You  , Xiao Zhi-Gang  , Xu De-Fu  , Deng Chi  ,   College of Physics and Electronic Engineering, Leshan Normal University, Leshan 614004, China;,   Institute of Nanophotonics Technology, School of Physical Science and Technology, Sichuan University, Chengdu 610064, China
Published: December 2020

Silver superlens has a great influence on super-resolution lithography, imaging and the biosensing based on surface plasmon polaritons. In this paper, the surface plasmon resonance and the imaging of silver film are discussed in detail with optical transfer function of silver superlens. And the imaging process of silver superlens has also been simulated with the finite difference time domain. The simulation results are in agreement with those from the theoretical formulas, which fully proves the optical transfer function to be reliable. This may be an effective method of rapid parameter optimization for sensors, super-resolution imaging and enhance the interference lithography based on surface plasmon polaritons.
Investigation of self-pulsing and self-mode-locking in ytterbium-doped fiber laser
Authors: Han Xu  , Feng Guo-Ying  , Wu Chuan-Long  , Jiang Dong-Sheng  , Zhou Shou-Huan  ,   College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China;,   School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000, China;,   North China Research Institute of Electro-Optics, Beijing 100015, China
Published: December 2020

The output characteristics of a continuous-wave diode pumped free-running double-clad ytterbium-doped fiber laser are investigated. In the experiment, not only self-pulsing is observed, but also self-mode-locking is observed for the first time in the free-running fiber laser. The physical mechanism responsible for these phenomena is analyzed. The analysis reveals that the signal is absorbed in the weakly pumped or non-pumped part of the active fiber, which leads the self-pulsing to be present, and self-mode-locking is induced by axial mode beating and self-phase modulation, which are enhanced by nonlinear effects, stimulated Raman scattering, and stimulated Brillouin scattering. The pulse width of self-pulsing decreases as pump power increases. The pulse width of self-mode-locking pulses becomes narrow with the increase of the pump power. When the pump power is higher than 8 W, self-pulsing and self-mode-locking disappear. The interval between adjacent self-mode-locking pulses is 224 ns, corresponding to the cavity round-trip time. The maximum and the minimum durations (full width at half maximum) of self-mode locked pulses are about 35.0 ns and 6.3 ns respectively, and the maximum and minimum spectral widths (full width at half maximum) of signal light are about 7.05 nm and 2.01 nm respectively.
Design and characterization of a terahertz microcavity structure
Authors: Ma Feng-Ying  , Chen Ming  , Liu Xiao-Li  , Liu Jian-Li  , Chi Quan  , Du Yan-Li  , Guo Mao-Tian  , Yuan Bin  ,   School of Physical Engineering, Zhengzhou University, Zhengzhou 450001, China;,   College of Mechanical and Electrical Engineering, Jiaozuo University, Jiaozuo 454000, China
Published: December 2020

The complex refractive indices of the Cr film are obtained by terahertz time-domain spectroscopy. The penetration depth the Cr film is calculated based on the complex refractive indices, and then the effective cavity length and the emitted spectrum of the structure Cr/GaAs/Cr are simulated. The resonant frequencies are located at 0.32, 0.65, 0.98, 1.31 and 1.65 THz, respectively. The peak intensity of the cavity photo-conductive resource at 0.32 THz is 25 times higher than that of non-cavity one and the full width at half maximum is greatly narrowed. The relation between the emitting dipoles and the standing wave field in the cavity is also discussed. The results show that the emission intensity is enhanced when the emitting dipoles are located at the nodes of the standing wave field, but greatly suppressed at antinodes.
Study on stimulated Brillouin scatting energy transfer to amplify laser pulses for shock ignition in laser fusion facilities
Authors: Yuan Qiang  , Wei Xiao-Feng  , Zhang Xiao-Min  , Zhang Xin  , Zhao Jun-Pu  , Huang Wen-Hui  , Hu Dong-Xia  ,   Research Center of Laser Fusion, Chinese Academy of Engineering Physics, Mianyang 621900, China;,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

Shock ignition is considered as a relatively robust way to achieve the efficient fuel burn in inertial confinement fusion. However it requires intense laser pulses of sub-ns to launch strong convergent shock to ignite the pre-compressed target. Here we present a novel method, which has a substantially high extraction efficiency, to amplify laser pulses of ～200 ps for shock ignition. In this method, stacking pulse with a Stokes light of ～200 ps in the front and a pump light of ～5 ns following, is employed to propagate in the amplifier to extract the stored energy, then in the final system after harmonic conversion, laser energy is transferred from pump pulse to probe pulse by stimulated Brillouin scattering. Because of employing long pulse in the main amplifier, an output laser energy of 1520 kJ is achievable at fundamental frequency. Simulations show that the energy transfer efficiency is up to 75%, considering harmonic conversion efficiency of 60%80%, implying that 510 kJ laser pulses of ～200 ps can be produced using this scheme. As a result, only ～20 beams are required to generate the ignitor, reducing the cost for realizing the shock ignition.