bluuebunny/crossref_metadata_2025 huggingface dataset:
A new mini-magnetic lens proposal for coverging the clod atoms
Authors: Xu Xin-Ping  , Zhang Hai-Chao  , Wang Yu-Zhu  ,   Key Laboratory for Quantum Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Center for Cold Atom Physics, Chinese Academy of Sciences, Shanghai 201800, China
Published: December 2020

A mini-magnetic lens for laser-cooled rubidium atoms is experimentally demonstrated in this paper. The key component of the mini-magnetic lens is a mini-coil with a radius of 2 mm. When the cold atomic clouds are transported in the vicinity of the coil along its axial, they are compressed in the longitudinal direction due to the interaction with the non-uniform magnetic field of the coil. Given a current carrying time of about 10 ms, the atomic clouds tend to be gradually compressed in the axial direction with the increase of the coil current. When the coil current is greater than 0.9 A, the atomic clouds begin to expand. At a threshold value of 0.9 A, the focus length of the mini-magnetic lens is determined to be about 1.3 mm. Compared with the case that no current passes through the mini-coil, the dimension of the focused atom clouds is one order of magnitude smaller. Moreover, the focus length can be controlled by both the coil current and its carrying time. Numerical simulations are also given which are in agreement with the experimental results.
Large-diameter multi-level diffractive optical elements with high energy efficiency
Authors: Wu Rong  , Hua Neng  , Zhang Xiao-Bo  , Cao Guo-Wei  , Zhao Dong-Feng  , Zhou Shen-Lei  ,   National Laboratory on High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Shanghai 201800, China;,   National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Published: December 2020

When large-diameter (100 mm) multi-level diffractive optical elements are applied to high-power laser systems in order to solve the problem of low energy efficiency, the energy efficiency can be greatly improved within uniform focal spot by reducing high diffraction orders. In this paper, we show both theoretically and experimentally that more than 90% energy can be focused into a desired spot as predicted previously by theoretical estimation.
The effects of stacking fault and temperature on deformation mechanism of nanocrystalline Mg
Authors: Song Hai-Yang  , Li Yu-Longi  ,   School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China;,   School of Science, Xi’an University of Posts and Telecommunications, Xi’an 710121, China
Published: December 2020

The effects of stacking fault (SF) and temperature on the mechanical properties of nano-polycrystal Mg under tension loading are investigated by molecular dynamics simulations. The interatomic potential of embedded atom method (EAM) is used as the Mg-Mg interaction. The computational results show that the yield strength of nano-polycrystal Mg can be obviously enhanced when stacking fault is introduced into grains, and the effect of SF on the Young's modulus of nano-polycrystal Mg is very small. The results also show that tensile twins and new grain at 300.0 K are nucleated and initiated at grain boundaries, growing continuously with the increase of strain. The dihedral angel between the (1000) plane of new grain and the X-Y plane is about 35. In other words, the nucleation and the growth of twins and new grains are the predominant deformation mechanism for nano-polycrystal Mg at 300.0K. We also find that at 10.0K the dislocation nucleation and slip are the predominant modes of the plastic deformation for nano-polycrystal Mg.
Study on the structural and magnetic properties of La-doped barium ferrites
Authors: Li Jie  , Zhang Huai-Wu  , Li Yuan-Xun  , Li Qiang  , Qin Jun-Feng  ,   State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

Magnetic properties of La doped M-type barium ferrites are studied. The samples are prepared by the standard solid state reaction method. The influences of La3+ on structures and magnetic properties of barium ferrites (Ba1-xLaxFe12O19) are investigated. Single-phase M-type barium ferrites with chemical composition of Ba1-xLaxFe12O19 (x=0.0—0.6) are formed by sintering at 1100—1175 ℃ in air. Scanning electron microscopy (SEM) reveals that the La doping has no effect on the structure of barium ferrite. Vibrating sample magnetometer (VSM) shows that with the valaue of x increasing, the saturation magnetization (Ms) increases, reaching a maximum at x=0.2 and then decreases and the coercivity of the sample increases continuously. The value of Ms reaches a maximum value of 62.8 emu/g at x=0.2 and 1175 ℃, and the Hc reaches a maximum value of 3911.5 Oe at x=0.6 and 1125℃.
Influence of initial entanglement on entanglement evolution under phase damping channel
Authors: Liu Qi-Gong  , Ji Xin  ,   Department of Physics, College of Science, Yanbian University, Yanji 133002, China
Published: December 2020

The influence of initial entanglement on entanglement evolution under phase damping channel in noninertial frame is investigated. Compared with the scenario of amplitude damping channel, when the state parameter α has different values with the same intial entanglement, the evolution curves are identical. When the Unruh single particle state has right and left components, there is more serious quantum decoherence than the case where the Unruh single particle state has only right component with the sudden death of entanglement taking place early, and the time of sudden death of entanglement is independent of initial entanglement.
A novel detection of periodic phenomena of binary chaotic sequences
Authors: Zheng Yan-Bin  , Song Yu  , Du Bao-Xiang  , Pan Jing  , Ding Qun  ,   Key Laboratory of Electronic Engineering, Heilongjiang University, Harbin 150080, China;,   School of Computer Science and Technology, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

For any digital chaotic sequence generator, evaluating periodic characteristics which exist in only part of domains of binary chaotic sequences is extremely difficult. In this paper, we present a method which we name the binary sequence period detection (BSPD). The BSPD is a novel detection which evaluates the periodicity in a binary chaotic sequence, by which both the accurate-periodic phenomena and periodic phenomena in part of domains can be detected. Moreover, any periodic phenomenon pattern of a binary sequence can be located by the BSPD method. The experimental results show that the BSPD can detect and extract the periodic phenomena of the classical Logistic chaotic sequence generators.
A fission neutron detector based on helium scintillator
Authors: Zhang Xiao-Dong  , Qiu Meng-Tong  , Zhang Jian-Fu  , Ouyang Xiao-Ping  , Zhang Xian-Peng  , Chen Liang  ,   Radiation Detection Research Center of Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

A new neutron detector is designed. Two 235UO2 target foils are used as radiators, and the 4He gas is used as scintillator in the detector. The detector combines the features of 235U and 4He fully, so it has some excellent performances, such as flat energy response to neutrons, better n/γ discrimination, etc. It can be used well to detect neutrons in a pulsed mixture radiation field. In this paper, the principle and structure of the detector are introduced. The energy depositions of different energies of neutrons and γ -rays in 4He gas are calculated. The neutron sensitivity, γ ray sensitivity, n/γ discrimination, and time response of the detector are investigated theoretically and experimentally. The neutron sensitivity is about 10-15 C·cm2, γ ray sensitivity is about 10-17 C·cm2, and time response is about 33.1 ns.
Temperature measurements based on tunable diode laser absorption spectroscopy
Authors: Xu Zhen-Yu  , Liu Wen-Qing  , Liu Jian-Guo  , He Jun-Feng  , Yao Lu  , Ruan Jun  , Chen Jiu-Ying  , Li Han  , Yuan Song  , Geng Hui  , Kan Rui-Feng  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics of Chinese Academy of Sciences, Hefei 230031, Chnia
Published: December 2020

The thermometry based on absorption spectroscopy and developing of a temperature sensor is introduced, in which temperature is retrieved by measuring line strength ratio between a pair of absorptions of water vapor near 1.4 μm. The temperature sensor is first calibrated on a tubular furnace and then used to verify measurement results with the heating tube whose both sides are open, an average fluctuation of about 50 K is obtained at each temperature setpoint. Some new absorption lines of H2O near one absorption (centered at 7153.7 cm -1) of the selected line pair are observed during demonstration measurements for CH4/air flat flame burner. These absorption lines overlapping with 7153.7 cm-1, are not listed in HITRAN08 database while HITEMP data give absorption information about these wave number positions. But line center of the other absorption (centered at 7154.354 cm-1) in HITEMP seems different from our measurement and HITRAN database. A combination of our calibrated results from tubular furnace and line parameters of new features from HITEMP is chosen and some results measured at different equivalence ratios on the burner are shown here.
M-ary code shift keying spread spectrum underwater acoustic communication
Authors: Yu Yang  , Zhou Feng  , Qiao Gang  ,   National Laboratory of Underwater Acoustic Technology, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Aiming at the low data rate of traditional direct sequence spread spectrum, M-ary spread spectrum and code shift keying underwater acoustic spread spectrum communication, a new combine method of M-ary code shift keying underwater acoustic spread spectrum communication is proposed based on the small Kasami sequence with good self and mutual correlation. Different sequence information and the same sequence code phase information are used in this method. The influences of self and mutual correlation function on M-ary code shift keying underwater acoustic spread spectrum communication over gaussian and fading channel are analyzed. The performances under the two kinds of channels are simulated. The simulation shows that the ability for M-ary code shift spread spectrum to overcome the noise is better than for the direct sequence spread spectrum, M-ary spread spectrum and code shift keying spread spectrum. The comparative experiment is conducted to compare the M-ary spread spectrum, code shift keying spread spectrum and M-ary code shift keying spread spectrum in the pool. The M-ary code shift keying communication rate of 256.3 bps with no transmitting error in 104 bit data volume is realized.
Acoustic probing of the granular solid system under direct shear
Authors: Zhang Qi  , Li Yin-Chang  , Liu Rui  , Jiang Yi-Min  , Hou Mei-Ying  ,   Key Laboratory Artificial Micro-and Nano-structure of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China;,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;,   School of Physical Science and Technology, Central South University, Changsha 410083, China
Published: December 2020

Acoustic signal is used to study the mechanical properties of dense granular system under direct shear. In the process of direct shearing, it is found that the velocity of the sound wave decreases rapidly with the increase of shear stress. After the yield point of stress, with the increase of strain, the velocity of the propagating wave decreases gradually and attains a constant. The net reduction in velocity is found to be less than 20%, which differs from the fact that acoustic wave (especially the transverse wave) could not propagate through the shear band. This is because the direct shear strain rate is far smaller than the frequency of sound wave, and particles under shear can be regarded as quasi-static elastic-plastic solid. Effective medium theory and granular dlastic theory are employed for explaining these results.
Groove angle effect on micro-jet from shocked metal surface
Authors: Wang Pei  , Shao Jian-Li  , Qin Cheng-Sen  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

According to smoothed particle hydrodynamics, we investigate numerically the micro-jets from grooved surfaces of different metals, where the velocities of jet head and material sources are discussed in detail. Our simulation results suggest that the jetting factor reaches its maximum at the half angle 45 degree, and the jetting factor reduces with the increase or decrease of the groove angle; also, the maximum velocity of jet shows a linear reduction with the increase of groove angel. Those results are consistent with the corresponding experimental results. The jetting material source and its dynamical process are analyzed. It is shown that with the increase of groove angel, the jet material sources transfer to the bottom of groove from two-side layer, while at the groove angel near 45 degree, a homogenous source layer throughout the groove comes into being. Finally, we further explain the jetting dynamics from different grooves by particle trajectory and its mechanical quantity history.
The largest Lyapunov exponent and the turbulent fluctuation of the time series from air turbulent jets
Authors: Yao Tian-Liang  , Liu Hai-Feng  , Xu Jian-Liang  , Li Wei-Feng  ,   Key Laboratory of Coal Gasification and Energy Chemical Engineering, Ministry of Education, East China University of Science and Technology, Shanghai 200237, China
Published: December 2020

The velocity time series of round air jets are acquired with the hot-wire anemometer. We compute the largest Lyapunov exponent and the turbulent incoherent perturbation of the velocity signals at 939 ≤ Re ≤ 3758 using an analytical method of chaotic time series which is based on the invariant of the largest Lyapunov exponent. The results show that the largest Lyapunov exponent increases with exit Reynolds number, and decreases with the distance away from nozzle exit. The reciprocal of the largest Lyapunov exponent is positively correlated with correlation time. The incoherent perturbation of turbulence increases either with exit Reynolds number or with the distance away from nozzle exit. The incoherent perturbation of turbulence is negatively correlated with Kolmogorov scale.
Energy band properties and phase stability of Be1-xMgxO alloy
Authors: Zheng Shu-Wen  , Fan Guang-Han  , Li Shu-Ti  , Zhang Tao  , Su Chen  ,   Institute of Opto-electronic Materials and Technology, South China Normal University, Guangzhou 510631, China
Published: December 2020

The lattice constants, energy band properties and phase stabilities of wurtzite (WZ) and rocksalt (RS) Be1-xMgxO alloys are investigated by the plan-wave pseudopotential method in the generalized gradient approximation based on the density functional theory. The theoretical results show that the lattice constants of WZ and RS Be1-xMgxO alloys increase and their bandgaps decrease as the content x of Mg increases from 0 to 1. For the same Mg content values, the bandgap of RS Be1-xMgxO alloy is greater than that of WZ Be1-xMgxO alloy. The WZ phase will transit to the RS phase when the Mg content is about 0.89. In order to obtain the theoretical values in accordance with the experimental results, the bandgaps of WZ and RS Be1-xMgxO alloys are corrected and the values of bandgap bowing parameter b are 3.451 eV and 4.96 eV for WZ Be1-xMgxO and RS Be1-xMgxO respectively. The reason of large band gap bowing parameter b is attributed to a large difference in ionic radius between Be and Mg. Besides, the relations among energy bandgap, bowing parameter and lattice constant of wurtzite BeO-ZnO-CdO ternary alloy are analyzed.
DC characteristic research based on surface potential for a-Si:H thin-film transistor
Authors: Chen Xiao-Xue  , Yao Ruo-He  ,   School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510640, China
Published: December 2020

In this paper, based on the surface potential model, taking into account both the deep and tail state distributions simultaneously, and using the simplified Fermi-Dirac function, a unified local-state model is obtained. Using the effective characteristic temperature, the unified current-voltage (I-V) model for a-Si:H thin-film transistor a-Si:H TFT is developed. This model can describes all operating regions including subthreshold region, linear area and saturated zone through a single equation. By comparison with the experimental data, it is shown that this model can accurately describe the current voltage characteristic of the a-Si:H TFT.
First principles calculations of the electronic structure and optical properties of pure and (Nb, N) co-doped anatase
Authors: Cheng Liang  , Gan Zhang-Hua  , Liu Wei  , Zhao Xing-Zhong  ,   School of Science and Technology, Wuhan University, Wuhan 430072, China;,   School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430000, China
Published: December 2020

Titanium dioxide (TiO2), as a kind of excellent photocatalyst, has been widely researched and applied. The geometry structures, band structures, densities of states and absorption coefficients of three possible (Nb, N) co-doped anatase are studied by the density functional theory based on GGA+U method, and the results are compared with those of the single doped (Nb/N) anatase. It is shown that the introduction of dopants leads to the lattice distortion. Besides, compared with undoped TiO2, (Nb, N) co-doped TiO2 has small band gap and absorption edge, and the level of N 2p state changes from partially occupied to occupied, which reduces the recombination of electron-hole pairs. In addition, the smaller formation energy of co-doped anatase indicates that it is more stable than the N doped anatase. Therefore, (Nb, N) co-doping anatase is a kind of stable photocatalyst and it has better photocatalytic performance in visible light band than pure TiO2.
Investigation on influence of antisite defects on electronic structure and optical properties of silicon carbide nanotube
Authors: Song Jiu-Xu  , Yang Yin-Tang  , Guo Li-Xin  , Wang Ping  , Zhang Zhi-Yong  ,   School of Science, Xidian University, Xi’an 710071, China;,   School of Electronic Engineering, Xi’an Shiyou University, Xi’an 710065, China;,   Key Laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China;,   Information Science and Technology Institution, Northwest University, Xi’an 710127, China
Published: December 2020

Electronic structure and optical properties of a (5, 5) single-walled silicon carbide nanotube are studied with first principles calculation based on density functional theory. Depression and salient are formed near CSi defect and SiC defect in the surface of the nanotube. Defect energy levels are formed near the bottom of conduction band, which results in an n-type conductivity for nanotubes with antisite defects. In dielectric functions parallel and perpendicular to the axis of the nanotube, novel resonance peak is formed from transitions between top of the conduction band and the defect energy level.
Positron annihilation spectrum study in non-ferroelectric piezoelectricity SrTiO3-Bi12TiO20 (ST-BT) composite ceramics
Authors: Zhang Li-Juan  , Wang Li-Hai  , Liu Jian-Dang  , Li Qiang  , Cheng Bin  , Zhang Jie  , An Ran  , Zhao Ming-Lei  , Ye Bang-Jiao  ,   Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China;,   School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
Published: December 2020

The positron annihilation lifetime spectroscopy, combined with X-ray diffraction and scanning electron microscopy is used to measure a new type of non-ferroelectric piezoelectricity SrTiO3-Bi12TiO20 (ST-BT) composite ceramic, which is prepared by conventional solid-state reaction in Shandong University. The structural characteristics and sinter process for ST-BT composite ceramic are systematically studied. A large number of crystal defects are observed in ST-BT composite ceramic with the sintering temperature being between 860 to 940 ℃. The large scale defects are formed due to the Bi12TiO20 phase decomposed when the sintering temperature rises to 980 ℃. The experimental results indicate that the structural characteristic and piezoelectricity of ST-BT composite ceramic shows good stability with the sintering temperature being between 920 to 940 ℃.
Magnetic properties of Bi2Fe4O9 synthesized by electrospinning
Authors: Zhang Ming-Qi  , Wang Yu-Hua  , Dong Peng-Yu  , Zhang Jia  ,   School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China
Published: December 2020

The Bi2Fe4O9 fibrous precursor is successfully synthesized through electrospinning technique, and the single-phase claviform Bi2Fe4O9 is obtained after calcining the precursor. The UV-vis absorption spectrum shows that the absorption range of the as-prepared Bi2Fe4O9 is wide, which indicates that the as-prepared Bi2Fe4O9 could be a photocatalyst with visible-light-driven photocatalytic activity. In addition,the result of magnetic hysteresis loop for Bi2Fe4O9 shows weak ferromagnetism and good soft magnetic properties, which indicate that the as-prepared Bi2Fe4O9 has a good application in soft magnetic material.
The propagation and inhibition of rumors in online social network
Authors: Gu Yi-Ran  , Xia Ling-Ling  ,   College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210046, China
Published: December 2020

In this paper, a new rumor spreading SEIR model is proposed with considering both the spreading characteristics of rumors in the real online social network and the epidemic dynamics models with latency. First, the dynamical evolution equations based on the SEIR model are established. Then an efficient immunization strategy—important acquaintance immunization strategy, is given for the inhibition of rumor spreading. Finally, based on the user datasets of Facebook, the SEIR model and its dynamical evolution equations with various immunization strategies including important acquaintance immunization strategy are utilized in the computer simulation for the evolution process of rumor spreading before and after immunization. Simulation results show that SEIR model conforms to propagation characteristics of the real online social network, and the important acquaintance immunization strategy is an optimal scheme to solve the inhibition of rumor spreading in the online social network.
Decoherence by a classically small influence
Authors: Zhao Wen-Lei  , Wang Jian-Zhong  , Dou Fu-Quan  ,   School of Physics, Beijing Institute of Technology, Beijing 100081, China;,   National Key Laboratory of Science and Technology on Computation Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China;,   HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100084, China
Published: December 2020

Via a system of two kicked particles that are coupled in an infinite square well, we numerically show that the interaction with a particle of very small mass is able to lead to a quantum-to-classical transition on condition that the corresponding classical dynamics is almost unaffected. With the decrease of the mass of one of the particles, its effect on the classical dynamics of the other one decreases. Such an effect is even negligible if the mass of the particle is small enough. The classically chaotic dynamics of this small particle is effective for promoting the decoherence of the heavy particle. Therefore its quantum behavior exhibits the transition from the dynamical localization to the classically chaotic diffusion with the decrease of the effective Planck's constant ħ. Under the perturbation from the small particle, the linear entropy is rapidly saturated as time passes by. With the decrease of ħ, the time-averaged linear entropy exponentially increases from zero to almost unity.
Thermal entanglement of mixed spin XY systems
Authors: Wang Lu-Shun  , Jiang Hui  , 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

In this article, we investigate thermal entanglements of the two-site, three-site and four-site mixed spin (1/2,1) XYsystems. The entanglement versus temperature and external magnetic field is discussed. It is found that the entanglements decrease monotonically as temperature increases in the presence and absence of a weak external magnetic field. For the two-site and four-site XY systems, thermal entanglements disappear at the same temperature which is called critical temperature no matter in the ferromagnetic case or antiferromagnetic. It also shows that the critical temperature is independent of external magnetic field. For the three-site system, the corresponding critical temperature is also irrelevant to external magnetic field, while the critical temperature for the ferromagnetic case is higher than that for the antiferromagnetic case. The entanglement of XY systems can develop a few stable platform in an environment of low temperature, but the entanglement vanishes when external magnetic field exceeds some critical value. In this article, we also analyze the difference in thermal entanglement between mixed-spin system and single-spin system, and find that there exists multi-level level crossing in the mixed-spin system.
Effect of air damping on dynemical behaviors of a completely inelastic bouncing ball
Authors: Jiang Ze-Hui  , Han Hong  , Li Xiao-Ran  , Wang Fu-Li  ,   Department of Physics, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

A ball dropped on a vertically vibrating table exhibits intricate dynamical behaviors including period-doubling bifurcations and chaos. If the collision between the ball and the table is completely inelastic, the motion of the ball is always periodic, and the plateaus caused by saddle-node instability and clumping structures for periodic trajectories occur in the bifurcation diagram. Here the effect of air damping on the dynamics of the ball with zero elasticity is analyzed. The air damping is treated as linear viscous one. It is shown that a weak air damping does not change the sequence of bifurcations, but makes the bifurcation points shift to larger values and broadens the transverse dimensions of the plateaus and the clumping zones in the diagrams. However, when the air damping becomes larger, overlapping between the plateaus and clumping zones takes place. In the overlapping section, the mechanism originally leading to periodic motion is destroyed, and chaos is introduced.
Weak signal estimation in chaotic clutter using selective support vector machine ensemble
Authors: Xing HongYan  , Qi ZhengDong  , 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

A method of detecting weak signals embedded in chaotic noise by selective support vector machine ensemble based on the theory of phase space reconstruction of the complicated nonlinear system is presented. For improving the generalization ability of support vector machine ensemble, K-means algorithm is used to select the most accurate individual support vector machine from every cluster for ensembling It is established a one-step predictive model that detects the weak signal, including transient signal and period is signals, from the predictive error in the chaotic sequences. It is illustrated in the experiment which is conducted to detect weak signals from Lorenz chaotic background and IPIX Sea Clutter, that the proposed method is highly effective to detect weak signal from a chaotic background and to minimize the influence of noise on weak signals, Compared wich the RBF neural network and SVM model, the new method presents great value in predicting accuracy and detection threshold.
Effects of high pressure on microstructure and properties of bulk (PrNd)xAl0.6Nb0.5Cu0.15B1.05Fe97.7-x alloys
Authors: Tang Jie  , Yang Li-Rong  , Wang Xiao-Jun  , Zhang Lin  , Wei Cheng-Fu  , Chen Bo-Wei  , Mei Yang  ,   School of Chemistry and Chemical Engineering, Mianyang normal university, Mianyang 621000, China;,   Research Center of Laser Fusion; CAEP, Mianyang 621900, China
Published: December 2020

According to nominal composition (PrNd)xAl0.6Nb0.5Cu0.15B1.05Fe97.7-x(weight percentage), the sintered NdFeB magnets are prepared by melting processing, milling processing, moulding processing and sintering processing. Microstructures and properties of these bulk samples at different high pressures are tested. It is shown that with pressure increasing, appearance and microstructure of samples are destroyed, but their inoxidizability at high temperature is increased, although their flexure strength is badly reduced. On the other hand, there are more excellent magnetic properties of bulk NdFeB samples pressed at high pressures (1.5 GPa and 3.0 GPa) than those of this bulk samples without being pressed. For example, values of their maximum magnetic energy products are increased by 7.69 kJ·m-3 and 0.94 kJ·m-3 respectively, and values of their remanence are increased by 0.02 T and 0.01 T respectively, in addition, the values of their intrinsic coercive force are increased by 20.06 kA·m-1 and 30.33 kA·m-1 respectively. It is ind that high pressure has some effects on microstructure, mechanical and magnetic property of the bulk NdFeB alloy.
Numerical simulation of temporal and spatial distribution of X-ray ionization with high-altitude nuclear explosion
Authors: Ouyang Jian-Ming  , Ma Yan-Yun  , Shao Fu-Qiu  , Zou De-Bin  , Liu Jian-Xun  ,   College of Science, National University of Defense Technology, Changsha 410073, China
Published: December 2020

The X-ray radiation ionization processes at different altitudes of atmosphere with high-altitude nuclear explosions are numerically simulated, and the temporal and spatial distribution curves of electrons are shown in this paper. The electron density has one maximal point with 1 kt equivalent explosion at 80 kilometers, which is near the explosion point. It is different from the explosion point above 80 kilometers, and the electron density has two maximal points in that case. One is near the explosion point, and the other is near 90 km altitude, where the ionization effect range of high-altitude nuclear explosion is widest. The X-ray of high-altitude nuclear explosion has no effect at below 70 km altitude. With the increase of radiation angle, the altitude of the second electron density maximal point increases, and the cut-off altitude of X-ray increases too.
Analysis and improvement for UHF RFID reading region in real environments
Authors: Zuo Lei  , He Yi-Gang  , Li Bing  , Zhu Yan-Qing  , Fang Ge-Feng  ,   College of Electrical and Information Engineering, Hunan University, Changsha 410082, China;,   School of Electrical and Automation Engineering, Hefei University of Technology, Hefei 230009, China;,   National Key Laboratory of National Defense Science&Technology on Electronic Test & Measurement, The 41st Research Institute of China Electronics Technology Group Corporation, Qingdao 266555, China
Published: December 2020

The reading region of ultra high frequency radio-frequency identification (UHF RFID) system is affected by polarization mismatch, reader antenna height, coherent interference and so on. Based on the principles of RFID technology and ray-tracing method, a complete propagation model in real environments is derived. Utilizing recognition rate of target region (RRTR), a method of evalualing the performances of a system is presented. In order to obtain the maximization of RRTR, two solutions including tag diversity and phase switch are proposed, which combines the theories of electromagnetic propagation and coherent interference suppression. The values of RRTR under different parameters are measured in outdoor and indoor environments with a commodity hardware. The measurement results show that the values of RRTR can be enhanced by 10% and 7.6% with the two solutions respectively.
The surface modes loss control of hollow-core photonic crystal fibers
Authors: Cheng Sheng-Fei  , Peng Jing-Gang  , Li Jin-Yan  , Cheng Lan  , Jiang Zuo-Wen  , Li Hai-Qing  , Dai Neng-Li  , Jiang Fa-Gang  , Yang Xiao-Bo  ,   Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China;,   Tongji medical school affiliate union medical college hospital, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

In this paper, the influences of fiber core structure on photonic band gap and transmission loss for hollow-core photonic crystal fiber are investigated, and the proper fiber core structure of fiber preparation technology is obtained. First, the band gap structure of triangular lattice of hollow core photonic crystal fiber with a fixed duty ratio is calculated by using plane wave expansion method. When the transmission wavelength λ=1.55 μm, the structural parameters of the optical fiber are figured out. The value range of the core diameter is given by simulating the influences of core diameter on the band gap location and size, and the value of core wall thickness is obtained through analyzing the leak loss characteristics. Then the fiber end view drawing is designed according to the analytical results. The mode field distributions are simulated by the full-vectorial finite element method under different core diameters. Through the contrast analysis the best fiber core radius with R=1.6 Λ—1.75 Λ is obtained. The results indicate that choosing appropriate core structure not only can meet the photonic band gap and loss characteristics of hollow-core photonic crystal fiber, but also can properly reduce the difficulty in the preparation technology of fiber.
Studies of terahertz wave propagation in non-magnetized plasma
Authors: Zheng Ling  , Zhao Qing  , Liu Shu-Zhang  , Xing Xiao-Jun  ,   School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The space crafts, such as spaceship, space shuttle and so on, will face a famous blackout problem when they re-enter the earth's atmosphere at high velocity. The plasma sheath severely affects the propagation of the incident electromagnetic wave and causes severe electromagnetic wave attenuation, which results in the communication failures between the space crafts and the ground control center. It is important to study the properties of terahertz wave propagation in non-magnetized plasma, for using the terahertz wave communication is an alternative method to solve the reentry blackout problem. The terahertz wave propagation characteristics in non-magnetized plasma are studied in this paper. The variations of the terahertz wave propagation properties with the terahertz wave frequency, plasma density, plasma collision frequency and the thickness of the plasma are acquired. Some new phenomena are found i.e., there appears periodic oscillation on the reflectivity curve with the increase of terahertz wave frequency, and the period of oscillation is 0.03THz. The oscillation amplitude increases with the increase of terahertz frequency, decreases with the increase of plasma density, and increases with the increase of plasma collision frequency. The oscillation is attributed to the multiple reflections of the electromagnetic wave at the interfaces at z=0 and z=-d. The terahertz wave propagation properties in plasma are studied experimentally with the shock tube, and the experimental results match well with the theoretical ones. Both the theoretical and experimental results indicate that using terahertz wave communication is an effective way to solve the reentry blackout problem.
Degradation mechanism of SOI NMOS devices exposed to 60Co γ-ray at low dose rate
Authors: Shang Huai-Chao  , Liu Hong-Xia  , Zhuo Qing-Qing  ,   Key Laboratory of Ministry of Education for Wide Band-Gap Semiconductor Material and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

The total dose effect of 0.8 μm SOI NMOS device with H-gate is analyzed. The device is exposed to 60Co γ-ray at low dose rate. The result shows that the irradiation effect is more serious at low dose rate for the same total irradiation dose. The threshold voltage shift in on state is lower than in off state. Irradiation leads to the increased drain voltage VD of kink effect. Because the number of effective interface traps varies with gate bias, interface trap has different influences on sub-threshold slope and transconductance.
Progress in the theory of grain boundary anelastic relaxation
Authors: Zheng Zong-Wen  , Xu Ting-Dong  , Wang Kai  , Shao Chong  ,   Superalloy Department, Central Iron & Steel Research Institute, Beijing 100081, China
Published: December 2020

In the middle of last century, some scientists discovered grain-boundary anelastic relaxation (GAR) peaks by means of torsional pendulum. Later, various models about the origin of GAR peaks are established through further research. However, its micro-mechanism is still unclear. Recently, according to the results of solute grain boundary segregation or dilution caused by elastic stress, a micro-mechanism of GAR which is grain-boundary absorbing or emitting vacancies has been proposed. Then, the equilibrium equations and the kinetic equations of GAR are established, and the process of GAR is expressed analytically. Furthermore, it has successfully elaborated the intermediate temperature embrittlement peak movement which exists widely in metals. Those developments of GAR theory are reviewed in the present paper.
Preliminary study of the characteristic of multi-beam in intense multi-beam relativistic klystron
Authors: Liu Zhen-Bang  , Jin Xiao  , Huang Hua  , Chen Huai-Bi  , Wang Gan-Ping  ,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China;,   Institute of Applied Electronics, Science and Technology on High Power Microwave Laboratory, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Compared with the conventional klystron, high power multi-beam klystron makes use of many low perveance beams, then it has a high output efficiency and low operating voltage, but it brings new problems. There fore, the multi-beam intense relativistic electron beam transmission in the multi-beam klystron is investigated by experiment and simulation. The results show that the multi-beam rotates around the center of the system due to the interaction of the multi-beam, and simultaneously the multi-beam rotates around its own center due to the space charge effect of each beam's own. All the process can result in electron beams loss.
Berry phase and Hannay's angle of an electromagnetic mode system driven by harmonic field with Born-Oppenheimer approximation
Authors: Liu Hao-Di  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

In this paper, we investigate the Berry phase and Hannay's angle of an electromagnetic mode system driven by harmonic field with Born-Oppenheimer approximation and obtain their algebraic expressions by theoretical calculation. The semiclassical relation between Berry phase and Hannay's angle is discussed. We find that besides the usual connection term, the Berry phase of BO hybrid system contains a novel term brought forth by the coupling induced effective gauge potential. This quantum modification can be viewed as an effective Aharonov-Bohm effect. Moreover, a similar phenomenon is founded in the Hannay's angle of classical BO hybrid system, which indicates that the Berry phase and Hannay's angle possess the same relation as the usual one. Besides, our theory can also be used to generate Artificial gauge potentials for neutral atoms.
Quantum nondemolition measurement of two-photon Bell-state and three-photon Greenberger-Horne-Zeilinger-state based on weak nonlinearities
Authors: Ding Dong  , Yan Feng-Li  ,   Department of Basic Curriculum, North China Institute of Science and Technology, Beijing 101601, China;,   College of Physics Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China
Published: December 2020

The scheme for quantum nondemolition measurement of two-photon Bell-state and three-photon Greenberger-Horne-Zeilinger (GHZ)-state is proposed based on weak nonlinearities and linear-optics elements. We first describe a scheme of the symmetry analyzer for two-photon Bell-state by using beam splitters and cross-Kerr nonlinear medium. According to this symmetry analyzer for two-photon Bell-state and the controlled-NOT gates we construct a three-photon state analyzer which can completely and nondestructively discriminate eight three-photon GHZ states.
Chaos control with unknown parameter of attitude motion of perturbed spacecraft
Authors: Jia Fei-Lei  , Xu Wei  , Li Heng-Nian  , Hou Li-Qiang  ,   State Key Laboratory of Astronautic Dynamics, Xi’an 710043, China;,   Xi'an Satellite Control Center, Xi'an 710043, China;,   Northwestern Polytechnical University, School of Science, Xi'an 710072, China
Published: December 2020

The Euler's dynamical equation which describes the attitude motion of a perturbed rigid spacecraft is studied. A series of chaos systems is found from Euler's dynamical equation by selecting different parameter matrixes of perturbed torque. Based on the Lyapunov function, adaptive controller is designed such that the chaos control of unknown parameters of this system is accomplished, the state variables go to any appointed equilibrium points, and the unknown parameters are estimated simultaneously. Finally, the Newton-Leipnik system as an example is considered here to demonstrate the proposing technique. Simulation results show the feasibility and efficiency of this method.
Analyses of electromagnetic scattering characteristics for 3D time-varying plasma medium
Authors: Yang Li-Xia  , Shen Dan-Hua  , Shi Wei-Dong  ,   Department of Communication Engineering, Jiangsu University, Zhenjiang 212013, China;,   Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

To analyze the time-varying plasma, a modified finite-difference time-domain (LTJEC-FDTD) algorithm is derived. By using Laplace transform and inverse Laplace transform, we can deduce the FDTD iteration expression for calculating 3D time-varying problem from Maxwell equation and plasma constitutive equation. The iteration expression is proven to be correct by mode-coupling theory, while the correctness of the relevant boundary is tested by calculating the radar cross-section (RCS) of plasma sphere. So, the method is suitable to the calculation of time-varying plasma. Then, the RCS of complex time-varying plasma object is also analyzed.
Nonlinear interaction between modulated electron beam and the intermediate cavity of RKA
Authors: Chen Yong-Dong  , Wu Yang  , Xie Hong-Quan  , Li Zheng-Hong  , Zhou Zi-Gang  ,   College of Science, Sichuan University of Science and Engineering, Zigong 643000, China;,   Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900, China;,   College of Science, Southwest University of Science and Technology, Mianyang 621010, China
Published: December 2020

In the relativistic klystron driven by intense relativistic electron beam, due to the influences of intense current and high electric field, especially the high Q value for the intermediate cavity, the nonlinear interaction between the intermediate cavity and the electron beam is very strong. It will significantly affect the performance of the device. According to the Maxwell equations and one-dimensional motion equation of electron, the self-consistent equation of the beam-wave interaction is obtained in the intermediate cavity. Based on these equations, the influences of the modulation depth and the modulation frequency on the amplitude and phase of gap voltage are studied respectively. The voltage amplitude obtained by the self-consistent equation is close to the voltage amplitude of particle in cell simulation, especially under the higher modulation depth compared with that obtained from the equivalent circuit model of conventional klystron. Meanwhile, the bandwidth of device becomes wide with the increase of the modulation depth. Finally, an S-band high-gain RKA is designed, and the corresponding experiments are done on the LTD accelerator. The output power with 1.1 GW is obtained, the gain is 49 dB.
Effect of Ramam gain on the characteristic of soliton propagation
Authors: Qiao Hai-Long  , Jia Wei-Guo  , Liu Bao-Lin  , Wang Xu-Dong  , Menke Neimule  , Yang Jun  , Zhang Jun-Ping  ,   School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
Published: December 2020

Using the nonlinear Schrödinger equation (NLSE) including Raman gain effect but ignoring fiber loss situation, the linear operator and nonlinear operator specific expression are obtained based on MATLAB fractional Fourier numerical algorithm. They are applied to the NLSE including Raman gain, and the evolutions of soliton pulse are simulated in optical fiber through changing parameters. The result shows that soliton propagation stability is destroyed compared with the case considering no Raman gain, leading to the rapid attenuation of optical soliton. The influence degree depends on input soliton pulse peak power. The effects of Raman gain on ground state soliton and high order soliton are not the same.
Reconstruction of incoherent source Bessel beam
Authors: Fan Dan-Dan  , Wu Feng-Tie  , Cheng Zhi-Ming  , Zhu Jian-Qiang  ,   College of Information Science and Engineering, Huaqiao University, Fujian Key Laboratory of Optical Beam Transmission and Transformation, Xiamen 361021, China;,   Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
Published: December 2020

Based on the Hankel wave theory, reconstruction property of Bessel beam generated by incoherent source is analyzed. The section light intensity distribution of Bessel beam after on-axis circular obstacle is simulated by optical design software ZEMAX. Light emitting diode (LED) has a certain spectrum width, therefore we describe it by using a continuous spectrum with a certain range of spectral width. From the simulation results we can see visually that Bessel beam gradually realizes the reconstruction after circular obstacles on-axial shelter. It is proved that LED has the reconstruction property. We use LED and axcion element to generate Bessel beam. This Bessel beam passes though an on-axis circular obstacle and an on-axis square obstacle. We take the pictures of the section light intensity distribution at different positions. The reconstruction properties of the LED incoherent source are verified. Experimental results accord well with the simulation results.