bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetism research on CuMnAl, CoMnAl and CuCoMnAl alloys by KKR-CPA-LDA calculation
Authors: Tang Xiao-Dan  , Qian Jin-Feng  , Wu Guang-Heng  , Meng Fan-Bin  , Liu He-Yan  , Luo Hong-Zhi  , Li Yang-Xian  , Feng Lin  , Zhu Zhi-Yong  , Zhu Wei  , Liu En-Ke  ,   (1)Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (2)School of Material Science and Engineering, Hebei University of Technology, Tianjin 300130, China
Published: December 2020

Comparing with the experimental data, the composition dependence of atomic moment and Co-Mn exchange interaction in CuMnAl, CoMnAl and CuCoMnAl alloys have been investigated by KKR-CPA-LDA calculation. It has been found that, due to the different surrounding environments, the magnetic moment of excess Mn atom occupying Al sites is larger than that of the original Mn atoms on B sites in Cu50Mn25+xAl25-x alloys. When the Mn content increases in Co50Mn25+xAl25-x alloys, the moment of Co atom increases monotonically, while the Mn moment almost has the same value. In Cu50-xCoxMn25Al25 alloys, it has been revealed that the moment of Co decreases resulting from the decrease of the moment of Mn atom with the substitution of Co for Cu. These results indicate that the atomic moments of Mn and Co atoms are positively related. It has also been found that the Co-Mn exchange interaction can be enhanced by increasing Mn content and its strength comes not only from the added Co but also from the contribution of Mn.
The chaotic vibration of a metal plate with large deflection under a transverse magnetic field
Authors: Shu Xue-Feng  , Xue Chun-Xia  , Zhang Shan-Yuan  ,   (1)College of Science, North university of China, Taiyuan 030051, China; (2)Institute of Applied Mechanics, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

By using Karman’s plate theory of large deflection, the nonlinear equation of motion of a thin metal plate with the coaction of a transverse uniform magnetic field and a transverse load is established. These equations consider the magnetic Lorentz force induced by the eddy current. Based on the Bubnov-Galerkin method, the nonlinear partial differential equation is transformed into a third-order nonlinear ordinary differential equation. By using the sub-harmonic orbit Melnikov function method, the criterion of the Smale-horseshoe chaos is also acquired. Furthermore, the chaotic motion is numerically simulated with Matlab. The bifurcation diagram, the phase curve, the Poincaré map and the evolution curve are calculated. The digital characteristics of the chaotic motions are provided based on the analysis. The analysis results show that the magnetic induction intensity and the external load may affect the vibration of the system.
Synthesis and temperature dependence of permittivity of Ba1-xSrxTiO3 and Ba0.6-xPbxSr0.4TiO3 ceramics
Authors: Wang Meng  , He Jian-Long  , Yang Wei-Ming  , Wu Yun-Yi  , Li Jian-Jun  , Lei Qiang  , Yu Jun  ,   Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

Ba1-xSrxTiO3 (BST) and Ba0.6-xPbxSr0.4TiO3 (BPST) ceramics were prepared by conventional solid-state reaction method. The analysis of XRD, FESEM and Raman spectroscopy showed the effects of Pb-doping on the crystal lattice,phase transition and surface morphology of Ba0.6Sr0.4TiO3, respectively. And the temperature dependence of permittivity (ε-T properties)for all ceramics were measured at a frequency of 10 kHz. The mechanism that Curie temperature and the peak value of permittivity are modulated by Sr and Pb content in BST and BPST perovskite has been revealed. In addition, all samples exhibit a diffused phase transition (DPT), especially for the ceramic Ba0.5Pb0.4Sr0.1TiO3, which can improve its temperature stability of tunability as phase shifter than others. Some ferroelectric parameters are calculated to interpret the DPT by adopting Smolenski’s theory and Curie-Wise law. For example, the values of diffuseness exponent α,Curie constant and transition region have changed from 1.29 to 1.73, from 1.25×105 to 2.87×105 K, and from 13.2 ℃ to 22.3 ℃, respectively.
Size effect on phase transition temperature of epitaxial ferroelectric films
Authors: Zhang Chun-Zu  , Zhang Ying  , Zhou Zhi-Dong  ,   (1)Department of Civil Engineering, School of Architecture and Civil Engineering, Xiamen University, Xiamen 361005, China; (2)Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005, China
Published: December 2020

In this paper the phase transition temperature of epitaxial ferroelectric thin film is analyzed and discussed systematically via the dynamic Ginzburg-Landau (DGL) equation by taking the effective interior stress, surface eigenstrain relaxation and depolarization field. When the thickness of ferroelectric film is changed, external and internal factors, which affect phase transition temperature of ferroelectric thin films,are presented to explain the experimental observations. There is a good quantitative agreement between the theoretical results and experimental data for BaTiO3 thin film epitaxially grown on SrTiO3 substrate.
All-optical switching effect of the excited state proton transfer molecule 2-(2'-hydroxyphenyl) benzothiazole in different polar solvents
Authors: Zheng Jia-Jin  , Lu Yun-Qing  , Li Pei-Li  , Chen Tao  ,   Nanjing University of Posts and Telecommunications, College of Optoelectronics Engineering, Institute of Optical Communication, Nanjing 210003, China
Published: December 2020

An all-optical switching model system comprising a single pulsed pump beam at 355 nm and a cw He-Ne signal beam at 632.8 nm was demonstrated with 2-(2'-hydroxyphenyl) benzothiazole(HBT) in five different polar solvents. The origin of the optical switching effect was discussed, and it was verified that fast excited state intramolecular proton transfer (ESIPT) of HBT and the slow thermal effect of solvent together induced the change of the refractive index of HBT solutions, which lead to the signal beam deflection and dominated the optical switching "off" and "on" states, respectively. The slow thermal effect of solvent results in the "tail" phenomenon of the optical switching recovery, and reducing the signal beam waist radius is a viable means for accelerating the recovery of the optical switching. The results indicated that the HBT molecule could be an excellent candidate for high-speed and high-sensitivity optical switching devices. This work provides a theoretical as well as experimental basis for the production of ultra-fast all-optical switching device.
Spectroscopic properties and up-conversion luminescence Er3+/Yb3+ co-doped TeO2-WO3-Bi2O3 glass
Authors: Liu Li-Sha  , Lü Shu-Chen  , Sun Jiang-Ting  ,   Harbin Normal University, Institute of Physics and Electronic Engineering, Harbin 150025, China
Published: December 2020

Er3 + /Yb3 + co-doped TeO2-WO3-Bi2O3 (TWB) glass has been prepared.The absorption spectra, fluorescence spectra and up-conversion luminescence of the glass were measured. The strength parameters of Er3+ in glass were calculated according to the Judd-Oflet theory. Along with Bi2O3 content increasing, Ω2 increases, Ω4, and Ω6 gradually decrease. The broad 1.5 μm fluorescence was observed under 976 nm excitation, and its full width at half maximum (FWHM) was 96 nm. The stimulated emissiow was calculated using the McCumber theory, and the peak emission cross-section was 0.70 × 10-20cm2 at 1.5 μm. The product of stimulated emission cross section and fluorescence of FWHM was 60.2 cm2 nm. At the same time, there is an obvious phenomenon of fluorescence up-conversion of Er3 +/Yb3 + co-doped TeO2-WO3-Bi2O3 glass under 976 nm pump, and the intensity of the conversion gradually weakened with the increasing of Bi2O3 content.
The role of magnetic fields on the efficiency of OLED of double quantum well structures
Authors: Jiang Wen-Long  , Meng Zhao-Hui  , Cong Lin  , Wang Jin  , Wang Li-Zhong  , Han Qiang  , Meng Fan-Chao  , Gao Yong-Hui  ,   College of Information and Technology, Jilin Normal University, Siping 136000, China
Published: December 2020

The organic light emitting diodes with the structure of ITO/NPB(60 nm)/ Alq3 ∶Rubrene(1wt%,20 nm)/Alq3(3 nm)/Alq3:Rubrene(1wt%,20 nm)/ Alq3(20 nm)/LiF/Al, which have multiple quantum well structures (MQW), were fabricated and the magnetic field effects on the efficiency and current of the OLEDs were measured. The experiment showed that the current decreased monotoniocally, i.e. the resistance of the device increased under the magnetic field. At the same time, the magnetic field effect on efficiency was achieved. The changing ratio of efficiency increased 9.13% maximally when the magnetic field was below 20 mT. The changing ratio of efficiency decreased with the magnetic field increasing when the magnetic field was higher than 20 mT.
Study of annihilation behavior of positronium in porous silicon in different atmospheres
Authors: Li Zhuo-Xin  , Wang Dan-Ni  , Wang Bao-Yi  , Xue De-Sheng  , Wei Long  , Qin Xiu-Bo  ,   Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education,Lanzhou University, Lanzhou 730000, China;,   Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education,Lanzhou University, Lanzhou 730000, China;Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics,Chinese Academy of Sciences, Beijing 100049, China;,   Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics,Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Porous silicon (PS) prepared by electrochemical etching method has been studied by positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) measurement in different atmospheres. The longest lifetime component in PALS results is ascribed to the annihilation of positronium in cavities of PS sample. It is found that 80% of the positrons implanted in PS film have formed positronium atoms. PALS results show that the lifetime of ortho-positronium has smaller value when the sample was in oxygen gas medium compared with those in other medium. AMOC results reveal that S parameter of three lifetime components in oxygen are all bigger than that in nitrogen atmosphere. These are probably caused by the oxygen leading to the spin-conversion of positronium atoms.
Linear analysis of the dielectric-loaded folded waveguide traveling-wave tube amplifier
Authors: Zhang Chang-Qing  , Gong Yu-Bin  , Wei Yan-Yu  , Wang Wen-Xiang  ,   National Key Laboratory of High Power Vacuum Electronics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

In this paper a dielectric-loaded folded waveguide slow-wave circuit is presented. The "hot" dispersion relation for slow wave interaction between the traveling wave and linear beam is derived from the fluid dynamical treatment. In the special case where εr=1, the dispersion relation can be simplified with a closed form of the conventional Pierce’s small-signal equation, which confirms the validity of the derivations. By giving the specific parameters, the effects of dielectric loading on the small-signal gain have been studied. The results indicated that in the case of "weak loading" (where d/a<0.1), the gain is flattened and there is no need to readjust the structure parameters beyond a slight adjustment of beam parameters. By considering that the "weak loading" can reduce the ohmic loss of the conductor, this study will be also a guide to the research of the THz folded waveguide traveling-wave tube.
Linear theory of the beam-wave interaction in a ridge-loaded folded slow-wave structure
Authors: He Jun  , Wei Yan-Yu  , Gong Yu-Bin  , Duan Zhao-Yun  , Lu Zhi-Gang  , Wang Wen-Xiang  ,   Vacuum Electronics National Laboratory, School of Physical Electronics, University of Electronic Science and Technology of China,Chengdu 610054, China
Published: December 2020

A novel mm-wave high power microwave device, the ridge-loaded folded waveguide traveling wave tube (TWT), is presented and its linear gain properties are investigated. The perturbed dispersion equation is derived and the small signal growth rate is calculated for different dimensions of ridge and parameters of electron beam. For a cold beam, the linear theory predicts a gain of 1.15 dB/period and a 3-dB small-signal gain bandwidth of 18.51% in Kα-band. The investigation reveals that, with the same beam parameters, the novel slow-wave structure (SWS) has advantage over the folded waveguide SWS in its gain and efficiency. The dimensions of ridge and the beam current may be increased in order to raise the gain.
Microstructure and themoelectric properties of p-type filled skutterudite Ce0.3Fe1.5Co2.5Sb12 prepared by melt-spinning method
Authors: Guo Quan-Sheng  , Li Han  , Su Xian-Li  , Tang Xin-Feng  ,   State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology,Wuhan 430070,China
Published: December 2020

Polycrystalline nanostructured bulk samples of p-type filled skutterudite Ce0.3Fe1.5Co2.5Sb12 have been prepared by melt-spinning (MS) method combined with spark plasma sintering (SPS). The effects of melt-spinning process on their microstructure and thermoelectric properties have been investigated. The results indicate that the ribbons have finer microstructure with the increasing cooling rate for melt-spun ribbons, resulting from the increasing copper wheel speed and decreasing ejection pressure. Compared with the sample prepared by traditional method, the samples prepared by MS-SPS method have higher power, factor due to the enhanced thermopower, despite the slightly reduced electrical conductivity. Meanwhile, the lattice thermal conductivity of the MS-SPS samples is significantly suppressed. Hence, the thermoelectric performance of the MS-SPS samples is greatly improved, and the figures of merit reach about 0.55 at 750 K.
Kinetics of diffusion-limited aggregation-annihilation processes on small-world networks
Authors: Shen Wei-Wei  , Li Ping-Ping  , Ke Jian-Hong  ,   College of Physics and Electronic Information Engineering, Wenzhou University, Wenzhou 325035, China
Published: December 2020

Kinetics of diffusion-limitied aggregation-annihilation processes on NW small-world networks is investigated by Monte Carlo simulation. In the system, if two clusters of the same species meet at the same node, they will aggregate and form a large one; while if two clusters of different species meet at the same node, they will annihilate each other. Simulation results show that, if the value of p (a parameter that quantifies the number of shortcuts) is large or small enough, the concentration of clusters c(t) and the concentration of particles g(t) follow power laws at large times, i.e.c(t)∝t-α and g(t)∝t－β. Moreover, the relation between the exponents α and β is found to satisfy α=2β. However, if p is of medium value, the concentration of clusters and the concentration of particles do not follow the power laws exactly. Our simulation results agree with the reported theoretical analysis very well.
Study of the multi-system compatible receiver’s frequency selection problem based on fixed point theory and its genetic algorithm realization
Authors: Song Dan  , Zhang Xiao-Lin  ,   School of Electronic and Information Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Published: December 2020

The problem of multi-system compatible receiver’s frequency selection is studied based on fixed point theory, and genetic algorithm is applied to resolve the problem. In the frequency space Banach fixed point theory was used to explain the fixed point physical property, which is presented through the evolution of the frequency set in the frequency space. By adequate reciprocal action of the frequency space operator any iterative sequence source frequency set in the frequency space will finally converge to the unique fixed-point object frequency set, the object frequencies of which are the frequency selection problem’s optimal solution. The study of and the solution to the frequency selection problem has been accomplished by a genetic algorithm. Simulation shows that the algorithm can resolve the problem of the multi-system compatible receiver’s frequency selection effectively.
Topological horseshoe analysis for a three-dimensional four-wing autonomous chaotic system
Authors: Ye Fei  , Chen Zeng-Qiang  , Jia Hong-Yan  ,   (1)Department of Automation, Nankai University, Tianjin 300071, China; (2)Department of Automation, Tianjin University of Science and Technology, Tianjin 300222, China;Department of Automation, Nankai University, Tianjin 300071, China; (3)Department of Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

Based on topological horseshoe map theory, the paper analyses the existence of topological horseshoe in a 3-D four-wing chaotic system. As the chaotic system is continuous, the paper first choses a Poincaré section, then under which defines a first return Poincaré map. A conclusion that the Poincaré map is semi-conjugate to 2-shift map can be obtained by utilizing computer-assisted verification, showing that the topological entropy of the 3-D four-wing system is larger than or equal to ln2, which further verifies the chaotic characteristic of the system.
Bistatic scattering from three-dimensional target on perfectly conducting rough surface by using G-SMFSIA/CAG
Authors: Ji Wei-Jie  , Tong Chuang-Ming  ,   (1)Missile Institute of Air Force Engineering University, Sanyuan 713800, China; (2)Missile Institute of Air Force Engineering University, Sanyuan 713800, China; State Key Lab. of Millimeter Waves,Nanjing 210096, China
Published: December 2020

This paper presents a novel and powerful numerical technique called general sparse-matrix flat-surface iterative approach-canonical grid (G-SMFSIA/CAG), which combines the sparse-matrix flat-surface iterative approach-canonical grid (SMFSIA/CAG) for 2D conducting rough surface and the method of moment (MoM) based on Rao-Wilton-Glisson (RWG) function for PEC target, to compute the electromagnetic scattering from a three-dimensional PEC target on conducting rough surface. The coupling surface integral equations (SIEs) for the composite model are derived based on Huygens surface equivalence principle. The SMFSIA/CAG is applied to solve the SIE of rough surface, and the targets’ SIE is solved using MoM. The iteration of SMFSIA/CAG and MoM takes account the interactions between target and the rough surface. Combining the PM(Pierson-Moskowitz)sea surface generated using Monte-Carlo method, the bistatic scattering coefficient for different targets on sea surface are computed. Convergence and effectivity of the G-SMFSIA/CAG is numerically validated. The bistatic scattering coefficient from ship on sea surface is calculated finally,and the dependence of bistatic scattering pattern upon the wind speed is discussed.
Using Josephson charge qubits system to realize the transfer of a special kind of quantum state
Authors: Wu Shi-Hai  , Hu Ming-Liang  , Li Ji  , Xi Xiao-Qiang  ,   School of Science, Xi'an University of Posts and Telecommunications, Xi'an 710061, China
Published: December 2020

A type of Josephson charge qubit circuit is constructed in this paper, and properties of four-qubit quantum state transfer through this system is also investigated. By modulating the external magnetic flux, we show that ideal transfer of an excited state 1〉 from the first qubit to the fourth qubit can be realized for both homogeneous and inhomogeneous transmission channels. Moreover, the average fidelity of state transfer across this system is also analyzed, the result revealed that it cannot be used to transfer an arbitrary quantum state.
Complex subharmonic oscillation phenomenon of peak current controlled buck converter with current source load
Authors: Zhou Guo-Hua  , Xu Jian-Ping  , Bao Bo-Cheng  , Wang Jin-Ping  , Jin Yan-Yan  ,   (1)School of Electrical and Information Engineering, Jiangsu Teachers University of Technology, Changzhou 213001, China; (2)School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

Peak current controlled buck converter with current source load shows the complex phenomenon of fast-scale and slow-scale subharmonic oscillations. Its piecewise smooth switching model and discrete iterative map model are established in this paper. According to its discrete iterative map model, the effects of circuit parameters on the nonlinear dynamic behaviors of buck converter are analyzed by numerical simulation. It is found that attractive regions of fast-scale and slow-scale subharmonic oscillations and dual tori phenomena exist in the bifurcation diagram and Poincaré mapping, respectively. Time-domain simulation waveforms and phase portraits of buck converter are obtained by Runge-Kutta algorithm using the piecewise smooth switching model. The research results indicate that n-type subharmonic oscillation constituted by subharmonic oscillation and frequency-reduced subharmonic oscillation exists in the inductor current, and sine-type subharmonic oscillation constituted by fast scale and low scale exists in the output voltage, respectively. Analysis and simulation results are verified by experimental results.
Hybrid control of bifurcation in a predator-prey system with three delays
Authors: Zhang Li-Ping  , Xu Min  , Wang Hui-Nan  ,   (1)College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;Collge of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; (2)Collge of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; (3)Collge of Information Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Published: December 2020

The problem of Hopf bifurcation control for a predator-prey system with three delays is considered. A new hybrid strategy is proposed to control the Hopf bifurcation, in which the state feedback and parameter perturbation are used to delay the onset of an inherent bifurcation or make the bifurcation disappear. The stability and the existence of bifurcation are researched. In particular, the formulae determining the direction of the bifurcations and the stability of the bifurcating periodic solutions are derived by using the normal form theory and center manifold theorem. Finally, numerical simulation results confirm that the new hybrid controller is efficient in controlling Hopf bifurcation.
Bifurcation and dual-parameter characteristic of the coupled dynamos system
Authors: Wu Shu-Hua  , Sun Yi  , Hao Jian-Hong  , Xu Hai-Bo  ,   (1)Institute of Applied Physics and Computational Mathematics, Beijing 100088, China; (2)School of Electric and Electronic Engineering, North China Electric Power University, Beijing 102206, China; (3)School of Electric and Electronic Engineering, North China Electric Power University, Beijing 102206, China;Department of Physics and Electrical Information Engineering, Shijiazhuang Normal College, Shijiazhuang 050035, China
Published: December 2020

Based on the comprehensive analysis of the basic dynamic characters of the coupled dynamos system, we have calculated the Lyapunov exponent spectra, bifurcation diagrams and so on, and discussed the chaotic bifurcation and mutative characteristic thoroughly in the periodic windows of the system, and the dual-parameter characteristic is also analyzed. It is found that a boundary line is absent in period-doubling bifurcations and a complicated bifurcation structure appears in 2D parameter space, the influences of two control parameters to the dynamic behavior are different.
The fractal character of two-parameter pulse model for random signal
Authors: Yang Juan  , Bian Bao-Min  , Peng Gang  , Li Zhen-Hua  ,   Department of Information Physics and Engineer, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

For studying the statistical character of the random signal, the width and amplitude of two relatively independent characteristic parameters are used to establish the two-parameter pulse model of the random signal. On the basis of this, the counting distributions of random signal for aerosol’s scattering pulse and background noise of photoelectric sensor are statistically analyzed by using the high-speed data acquisition card PCI-9812. The experimental results show that the counting distributions of amplitude and width subsets for the random pulse signals match well with the form of the lognormal distribution while using the natural number as the independent variable. Further more, the calculating results indicate that the amplitude and width of the distribution have nonlinear transform relation in the field of definition of them for pulsed signal. Namely, the two parameters' statistical distributions have the fractal character with non-integral dimension.
Nonresonant parametric control of Chens system
Authors: Wang Meng-Jiao  , Zeng Yi-Cheng  , Chen Guang-Hui  , He Juan  ,   (1)Department of Physics and Information Engineering, Hunan Institute of Humanities, Science and Technology, Loudi 417000, China; (2)School of Material Science and Photoelectronic Physics, Xiangtan University, Xiangtan 411005, China; (3)School of Material Science and Photoelectronic Physics, Xiangtan University, Xiangtan 411005, China;Department of Physics and Information Engineering, Hunan Institute of Humanities, Science and Technology, Loudi 417000, China
Published: December 2020

In this paper, nonfeedback chaos control of Chens system is realized with nonresonant parametric drive. A periodic signal whose frequency is far higher than the systems mean frequency is used as the input. And the system variables of the controlled system are decomposed into slowly varying variables which change according to the systems mean frequency and fast varying variables which change according to the frequency of periodic signal. Then, by averaging method, a slowly varying dynamics is obtained. According to the dynamical characteristics of the slowly varying dynamics, the available control parameter range is obtained. Numerical simulation results show that this method can lead the controlled system to the target state rapidly, even when the control signal is disturbed by noise in certain SNR ranges, so the proposed method is feasible.
Active radial basis function sliding mode controller for unified chaotic system with disturbance and uncertainties
Authors: Guo Hui-Jun  , Liu Ding  , Zhao Guang-Zhou  ,   (1)Department of Automation and Information Engineering, Xi'an University of Technology, Xi'an 710048, China; (2)Department of System Science and Engineering, Zhejiang University,Hangzhou 310027, China
Published: December 2020

An adaptive active radial basis function (RBF) sliding mode controller is designed to control a unified chaotic system with parametric uncertainties under external disturbance. The controlled system is divided into a controllable subsystem and a free subsystem. Based on the controllable canonical form of controllable sub-systems state errors at the target points, a sliding surface is defined as the only input to the RBF controller. The weight of the controller is tuned on-line based on the sliding mode reaching law. The simulation results show that this method is applicable and effective, and the robustness to parametric uncertainties and external disturbance is provided. And the chattering of conventional sliding controls doesn’t occur.
Heteoclinic orbit and backstepping control of a 3D chaotic system
Authors: Wang Zhen  , Li Yong-Xin  , Xi Xiao-Jian  , Lü Lei  ,   Department of Foundation, Xijing University, Xi'an 710123, China
Published: December 2020

The existence of heteoclinic loop which connects the saddle focus equilibrium points is analyzed for a three-dimensional differential system based on heteoclinic orbit Shilnikov method, which proves the system possesses "horseshoe" chaos. Then the system bifurcation, Lyapunov exponent, Poincare mapping are studied by numerical analysis. In addition, adaptive backstepping design is used to control this system with three unknown key parameters, and an algorithm of this controller is presented. Finally, we make some numerical simulations of the system in order to verify the analytic results.
A new approach to deal with diffusivity factor
Authors: Shen Zhong-Ping  , Zhang Feng  , Wei Xiao-Dong  , Zhang Hua  ,   (1)Chinese Academy of Meteorological Sciences, Beijing 100081,China; (2)Chinese Academy of Meteorological Sciences, Beijing 100081,China;National Climate Center, China Meteorological Administration, Beijing 100081,China; (3)National Climate Center, China Meteorological Administration, Beijing 100081,China; (4)Shanghai Climate Center, Shanghai 200030,China
Published: December 2020

In this paper, a new scheme, which is more precise in comparison with the previous ones in dealing with diffusivity factor is presented. The new scheme and the previous ones are applied to a radiative transfer model to calculate the atmospheric heating rate. The results show that the new scheme is generally better than previous ones, especially in the upper atmosphere al a height of more than 45 km.
Study of neutron radiation behavior for RF heating on HT-7
Authors: Li Xiao-Ling  , Lin Shi-Yao  , Hu Li-Qun  , Xu Ping  , Duan Yan-Min  , Mao Song-Tao  , Zhang Ji-Zhong  , Wang Xiang-Qi  , Zhong Guo-Qiang  ,   (1)Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China; (2)School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230029,China; (3)School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230029,China;Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Neutron radiation was specially correlated with the type and the power of the radio frequency (RF) heating for deuterium plasma on HT-7 tokamak. We hare researched the production mechanism of the fast neutron under different RF heating conditions by the fast time-resolved neutron flux measurement system make up of BF3 and 3He proportional counters. Lower power of LHW heating was apt to bring abont runaway discharge and produce a mass of photoneutrons. The rate of fusion neutron and the total neutron yield will rapidly increase with the ion cyclotron resonance heating at the special frequencies of (27 MHz and 24 MHz).
Theoretical calculation of the vib-rotational interaction potential and the partial wave cross sections for He-H2(D2, T2) system
Authors: Wang Rong-Kai  , Yang Xiang-Dong  , Shen Guang-Xian  , Linghu Rong-Feng  ,   (1)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; (2)School of Chemistry and Material Science, Guizhou Normal University, Guiyang 550001, China; (3)School of Physics and Electronic Sciences, Guizhou Normal University, Guiyang 550001, China; (4)School of Physics and Electronic Sciences, Guizhou Normal University, Guiyang 550001, China;Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
Published: December 2020

The interaction potential surfaces of He-H2(D2, T2)have been calculated by employing supermolecule method and the single and double excitation coupled-cluster with a noniterative perturbation treatment of triple excitation CCSD(T) approach using a large basis set containing the atomic centre Gaussian function and the 3s3p2d1f key function when the key-lengths of H2 was different. The vib-rotational interaction potentials of He-H2(D2, T2)system were fitted using the Tang-Toennies potential function and nonlinear least square method in a center of mass coordinate system. The partial wave cross sections at the energies of 60,90 and 120 meV have been calculated by using the quantum close-coupling method. On the basis of the above results, the change rules of the partial wave cross sections with change of quantum number have been obtained. Furthermore, corresponding connection and scattering characteristics of partial wave cross sections and scattering parameter were discussed in combination with classical collision theory.
The afterglow and thermoluminescence properties of Y3Al5O12∶ Ce3+
Authors: Mu Zhong-Fei  , Wang Yin-Hai  , Hu Yi-Hua  , Wu Hao-Yi  , Deng Liu-Yong  , Xie Wei  , Fu Chu-Jun  , Liao Chen-Xing  ,   (1)School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China; (2)School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China;Experiment Teaching Center, Guangdong University of Technology, Guangzhou 510006, China
Published: December 2020

Cerium-doped yttrium aluminium garnet (Y3Al5O12, YAG) samples were synthesized by the conventional solid state reaction method. The structure, photoluminescence and thermoluminescence properties were studied. The prepared samples are identified as pure garnet structure by the XRD results. The doping of a small amount of cerium ions has no influence on the structure of the host. Fluorescence spectra show that in the process of the preparation of Y2.95Al5O12 ∶Ce4+0.05 there is self reduction of Ce4+ when calcined in air, Which makes Y2.95Al5O12 ∶Ce4+0.05 emit yellow light peaking at 531 nm when excited by blue light, because a part of Ce4+ have been reduced into Ce3+. Y2.95Al5O12 ∶Ce3+0.05 prepared in weak reducing atmosphere has long yellow afterglow lasting for 35 minutes after it is excited by ultraviolet light. Thermoluminescence measurements show that YAG samples doped with Ce3+ can emit light at higher temperature. There are two obvious thermoluminescence peaks located at 112 ℃ and 256 ℃ in the thermoluminescence curve of Y2.95Al5O12 ∶Ce3+0.05 prepared in weak reducing atmosphore while there is only one located at 128 ℃ in the thermoluminescence curve of Y2.95Al5O12 ∶Ce4+0.05 prepared in air. A conclusion that the thermoluminescence of YAG ∶Ce3+ originates mainly from the Ce3+ trapped by defect energy level can be made out by comparing the cases of doped samples and the un-doped ones.
Optimization of shell model potential parameters of BaTiO3 by genetic algorithm
Authors: Hu Xiao-Qin  , Xie Guo-Feng  ,   Faculty of Materials Optoelectronics and Physics, Xiangtan University, Key Laboratory of Low Dimensional Materials and Application Technology, Ministry of Education, Xiangtan 411105, China
Published: December 2020

Shell model potential is widely applied to molecular dynamics simulations of ionic crystal, and the parameters of shell model potential function are crucial to the simulation veracity. The parameters of shell model of multi-oxide are numerous, and the optimization is a challenging task. In this paper, the sensitivity analysis is applied to find the key parameters which affect structure and properties mostly in all the shell model potential parameters of BaTiO3. Whereafter, the genetic algorithm is applied to optimize the key parameters, and the insignificant parameters are kept constant in optimization. The results show that the structures, physical properties and phase transition of BaTiO3 simulated by the optimized potential agree well with the experimental data.
Structural, electronic, and optical properties of Li-n-1, Lin and Li+ n+1(n=20, 40) clusters by first-principles calculations
Authors: Guo Zhao  , Lu Bin  , Jiang Xue  , Zhao Ji-Jun  ,   (1)School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China; (2)School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China;College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

The lowest-energy structures of Li-n-1, Lin and Li+n+1 clusters (n=20, 40) were determined from first-principles simulated annealing followed by geometry optimization within the density functional theory. The growth mechanism of Lin clusters is based on nested multiple polyhedron. Other atoms form pentagonal pyramid centered on the core polyhedron. From our first-principles calculations, the molecular orbital levels can be divided into several groups, which are in good agreement with the electron shells described by structureless jellium model. With the same amount of valence electrons, the number of ions and charge states in the Li clusters have only little effect on the electronic structures. Li-19, Li20, Li+21 and Li-39, Li40, Li+41 exhibit similar energy level distributions, respectively, indicating that the momentum order is the dominating factor for these clusters. The optical absorption spectra of Li-n-1, Lin and Li+n+1 (n=20, 40) clusters from time-dependent density functional theory calculations show giant resonance phenomenon and the simulated resonance peaks agree with experimental values. With same amount of valence electrons, the polarizability decreases with the number of ions and the optical resonance peaks blueshift as the ionic number increases.
Study on the dispersion relations of a relativistic annular electron beam guided by a finite axial magnetic field
Authors: Yuan Xue-Song  , Yan Yang  , Liu Sheng-Gang  ,   Terahertz Research Center, College of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The relativistic annular electron beam guided by a finite axial magnetic field is studied in this paper, in which the electron beam is considered as a special media. Making use of the constitutive transformation and the Lorentz transformation in the four-dimensional space, the permittivity tensor of the stationary magnetized plasma, the permittivity tensor, the permeability tensor and the chiral tensor of the electron beam in the rest (laboratory) frame are acquired. And the boundary conditions, including the surface current density due to the ripple of the beam, have been obtained. As an example of the applications of this approach, the dispersion relations of a relativistic annular electron beam guided by a finite axial magnetic field in a waveguide has been studied. The results of numerical calculation show that the present approach is more accurate and can provide clearer mode information for the electron beam. In addition, the results also show the axial magnetic field can affect the dispersion curves of space charge wave via the surface current density of an electron beam. Thus this approach can be exploited in a number of electron beam-wave interaction systems, including some kinds of free electron devices, plasma filled Cherenkov radiated free electron lasers and masers.
Self-consistent nonlinear theory of gyrotron oscillator with photonic-band-gap cavity
Authors: Luo Yao-Tian  , Tang Chang-Jian  ,   School of Physical Science and Technology, Sichuan University, Chengdu 610065, China
Published: December 2020

The effective radius of photonic-band-gap cavity (PBGC) is defined, the validity of using it to treat PBGC as a mode selective cylindrical metal cavity is demonstrated, the guiding role of it in the design of PBGC is revealed, and a self-consistent nonlinear theory is established for gyrotron oscillator with PBGC (PBG gyrotron) based on it. The results of theoretical analysis and numerical calculation show that the azimuthal polarized form (traveling wave or standing wave) of RF field has an obvious effect on the beam-wave interacting process and the device operating at second harmonic can achieve higher electron efficiency than that working at fundamental wave under TE-32 mode, which means PBG gyrotron is capable of operating at both high order electromagnetic mode and high order electronic cyclotron harmonic effectively owing to the excellent mode selective ability of PBGC. This gives a new clue to the research of gyrotron oscillator.
Modeling of four-wave mixing and supercontinuum with long pulses in photonic crystal fibers
Authors: Wang Yan-Bin  , Xiong Chun-Le  , Hou Jing  , Lu Qi-Sheng  , Peng Yang  , Chen Zi-Lun  ,   (1)College of Optoelectric Science and Engineering, National University of Defense and Technology, Changsha 410073, China; (2)School of Physics, University of Sydney, Sydney 2006, Australia
Published: December 2020

We numerically investigated four-wave mixing (FWM) and supercontinuum generation in photonic crystal fibers (PCFs) in the long pump pulse scheme for the first time. We showed that simply based on phase-matching condition and energy conservation with quasi-continuous-wave approximation, one can theoretically determine the FWM signal and idler wavelengths with pump in the normal-dispersion regime, and the two symmetrical modulation instability sidebands with pump in the anomalous-dispersion regime. Using adaptive split-step Fourier method, we quantitatively simulated FWM and supercontinuum generation in PCFs with different dispersion profiles when pumping with a 1064 nm sub-nanosecond laser. Our simulation results agree with the experimental results very well.
The dependence of radiation characteristics of random laser on the size and arrangement of crystal grains in PCs
Authors: Wang Yi-Fan  , Yu Ao-Lie  , Wang Hui-Qin  , Fang Li-Guang  ,   (1)Physics Department, Nanchang University, Nanchang 330031,China; (2)Physics Experiment Center, Nanchang University, Nanchang 330031,China
Published: December 2020

The modulation on radiation characteristics of random laser caused by photonic crystals(PCs) was studied, and its dependence on the size and arrangement of the crystal grains was analyzed. For a random medium, if it is covered by different photonic crystals on its upper and lower surfaces respectively, its output characteristics should be different. The results showed that the grain size of the PCs has a great effect on the radiation characteristics of the system. The PC with a suitable grain size plays a better role in trapping the energy in the system and it can modulate the laser modes effectively. It leads the light to oscillate back and forth, enhancing the interaction between the random gain medium and the light to achieve a greater amplification, and conseguently reducins the lasing threshold. It also controls the spontaneous emission and leads it to the target frequency in the emission spectra. However, if crystal grain size daeznot match the structure of random gain medium, the laser modes could not be modulated as we wish and the energy of the light field could not be localized effectively in the system, thus the laser system has a higher lasing threshold. The arrangement of crystal grains should affect the output characteristics also. In short, there exists an optimum PC/ random medium combination for lasing, for which the lasing threshold reaches a minimum.
Spiral spectrum of Laguerre-Gaussian beams propagating in turbulent atmosphere
Authors: Li Fang  , Tang Hua  , Jiang Yue-Song  , Ou Jun  ,   School of Electronic and Information Engineering, BeiHang University, Beijing 100191, China
Published: December 2020

An analysis of the propagation of Laguerre-Gaussian beam in fluctuation turbulent atmosphere is performed. Under the Rytov approximation, the integral expression of the spiral spectrum of the beam at the receiver aperture is obtained. It is found that the atmospheric turbulence will induce the spread of the spiral spectrum. With increasing topological charge, propagation distance, refractive index structure constant and radius of receiver aperture, the spectrum spread becomes more serious. It is also shown that the dimensionless variance describing the degree of the spread is a quadratic function of the refractive index structure constant and the radius of receiver aperture respectively, while it is an 11th order function of the topological charge and a 6th order function of the propagation distance. The analytical expression of the spiral spectrum is derived by taking account of the simulation results that both radial index and waist radius have little effect on the spiral spectrum.
Polarization characteristics of the wave reflection at the interface of vacuum and Faraday chiral medium
Authors: Tang Qi  , Meng Fan-Yi  , Zhang Kuang  , Wu Qun  , Li Le-Wei  ,   (1)Dept. Microwave Engineering, Harbin Institute of Technology (HIT), Harbin 150001, China; (2)Dept. Microwave Engineering, Harbin Institute of Technology (HIT), Harbin 150001, China;State Key Laboratory of Millimeter Waves, Nanjing 210096, China
Published: December 2020

This paper rigorously derives the formulas of reflection coefficients originating from Maxwell’s equations. The relationship between the polarization characteristics of the reflected wave and the constitutive parameters of the Faraday chiral medium is analyzed for all polarization states. Special polarization cases in the research are calculated, and the results are in good agreement with theoretical expectations.
First-principles calculations of electronic structure, optical and elastic properties of LiGaX2(X=S, Se, Te)
Authors: Yang Li-Jun  , Chen Hai-Chuan  ,   (1)College of Electrical Engineering and Information Technology, Xihua University, Chengdu 610039, China;College of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China; (2)College of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China
Published: December 2020

The density of states, electronic structure, optical and elastic properties of LiGaX2 (X=S, Se, Te) are investigated by the first-principles plane-wave pseudopotential density functional theory within the generalized gradient approximation (GGA). The results show that the band gaps of LiGaX2 (X=S, Se, Te) are 4.146 eV, 3.301 eV and 2.306 eV, respectively. It can be confirmed that the valence bands are mainly composed of X-np or Ga-4p states. The complex dielectric functions, reflectivity, index of refraction and elastic property are precisely calculated by band structure and density of states. The obtained results are in agreement with the available experimental data.
Comparative study on the spectroscopic and laser propertiesof mixed vanadates Ybt:Y x Gd1-t-x VO4with different compositions
Authors: Xavier Mateos  , Valentin Petrov  , Zhang Huai-Jin  , Wang Ji-Yang  , Liu Jun-Hai  , Han Wen-Juan  ,   (1)College of Physics, Qingdao University, Qingdao 266071, China; (2)Física i Cristal·lografia de Materials, Universitat Rovira i Virgili, C/Marcel.li Domingo, s/n, E-43007 Tarragona, Spain; (3)Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy, 2A Max-Born-Str., D-12489 Berlin, Germany; (4)State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
Published: December 2020

The room-temperature polarized absorption and emission spectra of Yb doped mixed vanadates Yb0.005:Y0.298Gd0.697VO4, Yb0.007:Y0.407Gd0.586VO4, and Yb0.009:Y0.575Gd0.416VO4 have been studied. The results show that the strongest absorption and emission, occurring at wavelength of 985 nm, correspond to the π polarization, depending on the composition the maximum absorption cross section ranges from 4.8 to 8.5×10-20 cm2, with bandwidths of 9.5—9.9 nm, whereas the maximum stimulated emission cross section varies in the range of 5.8—10.3×10-20 cm2. Continuous-wave laser operation has been realized at room temperature with the mixed crystals through longitudinal pumping with a diode laser. It was found that the laser oscillation behavior differs significantly from one mixed crystal to another:in the case of T=2% (T is the output coupling of the resonator), the coexistence and switching of σ, π polarization states occur on reducing the pump power in the laser oscillation of Yb0.005:Y0.298Gd0.697VO4 and Yb0.009:Y0.575Gd0.416VO4, while the laser oscillation of Yb0.007:Y0.407Gd0.586VO4 is capable of maintaining its π polarization state. In the case of T=5%, however, the laser oscillation generated with Yb0.009:Y0.575Gd0.416VO4 is purely σ-polarized, whereas the laser behavior of Yb0.005:Y0.298Gd0.697VO4 is similar to that exhibited in the case of T=2%.