bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study of digital holographic tomography by a few projections
Authors: Zhou Wen-Jing  , Hu Wen-Tao  , Guo Lu  , Xu Qiang-Sheng  , Yu Ying-Jie  ,   Department of Precision Mechanical Engineering, Shanghai University, Shanghai 200072, China
Published: December 2020

Digital holographic tomography by a few projections is developed. A section of fiber with symmetrical structure and a plaster head model with nonsymmetrical structure are used as test samples. Both simulation analysis and experimental results are analyzed. Simulation analysis shows that the weighted coefficientwij and the relaxation factor λ affect evidently the quality of the reconstructed image, in addition, the relaxation factor λ also influences the computer speed. Thus the weighted coefficient wij is evaluated by using a nonlinear method and the relaxation factor λ is selected appropriately by comparing several simulation reconstructions. Experimental results reveal the feasibility and the availability of digital holographic tomography by a few projections for symmetrical samples and nonsymmetrical one. In the next work, the real time digital holographic tomography based on three projections and single hologram will be developed to reconstruct the multi-refractive index of biological samples.
Phase control of electromagnetically induced absorption in four-level atomic system
Authors: Wang Li  , Li Gen-Quan  , Xiao Shao-Wu  , Zheng Chang-Bo  ,   College of Physics and Electronics Engineering, Nanyang Normal University, Nanyang 473061, China
Published: December 2020

In this paper, we have calculated the absorption of the probing field in a N-type four-level atomic system with three dipole transitions using density matrix equation. The results indicate that the absorption or amplification of the probing field depends on the Rabi phases of the control field and signal field under introducing laser field Rabi phase, and the absorption or amplification periodically changes with the Rabi phases of the control field and the signal field at a period of 2π. The Rabi phase change of the probe field has no effect on the absorption. In addition, the effect of the signal field Rabi phase on absorption is the same as that of the control field Rabi phase on absorption. Rabi phase has an effect mainly on atomic coherence but little on atomic population.
Entanglement and preparation for an atom interacting with two-mode coherent strong field via intensity-dependent coupling multiphoton processes
Authors: Liu Xiao-Juan  , Liu Yi-Man  , Zhou Bing-Ju  ,   Department of Physics, Hunan University of Science and Technology, Xiangtan 411201, China
Published: December 2020

In this paper, effective Hamiltonian of the two-mode multiphoton Jaynes-Cummings model is given via the intensity-dependent coupling in the rotating wave approximation. Under strong field, the atom-field entanglement and the entanglement between two modes of coherent field, according to the above model, are investigated by using the quantum reduced entropy and the quantum relative entropy, respectively. It is showed that properties of these two types of entanglements are considerably relevant to the absorption or emission photon number k, per atomic transition. Different properties of entanglements in the processes of two-photon (k=1) and mutiphoton (k>2) are revealed respectively. The preparation of entangled states is discussed. The Einstein-Podolsky-Rosen states of atom-field irrelevant to time, as well as entangled states between two models of the coherent field are prepared, respectively.
Study on current spreading of photonic crystal vertical cavity surface emitting lasers
Authors: Wang Bao-Qiang  , Xu Chen  , Liu Ying-Ming  , Xie Yi-Yang  , Liu Fa  , Zhao Zhen-Bo  , Zhou Kang  , Shen Guang-Di  ,   Beijing Optoelectronic Technology Laboratory, Beijing University of Technology, Beijing 100124, China
Published: December 2020

The distribution of injected current in the active region of external cavity oxide-confined photonic crystal vertical cavity surface emitting lasers is studied extensively. An advanced three-dimensional model of current distribution is used to analyse the effects of photonic crystal structures on current density distribution and series resistance of the device. It is found that the deeper the photonic crystal holes are, the worse the circular symmetry of the current density distribution is and the higher the series resistance is,especially when the ethching depths of holes are larger than 2 μm. Different patterns of photonic crystal structures have a great imfluence on current density distribution and circular symmetry. The results are beneficial to the research and the design of external cavity oxide-confined photonic crystal vertical cavity surface emitting lasers.
The characteristic of the stero-coupling high-Q photonic crystal slab cavity
Authors: Jiang Bin  , Liu An-Jin  , Chen Wei  , Xing Ming-Xin  , Zhou Wen-Jun  , Zheng Wan-Hua  ,   Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

Inspired by the idea of the stero-coupling, we propose a new sandwich-like photonic crystal microcavity which is composed of double layer photonic crystal slabs H1 (DLPCS-H1) cavity with an air layer in between. We calculate the electromagnetic field distribution and the quality factor of the dipole mode by the three-dimensional finite-difference time-domain method and the Padé approximation method. Through carefully analyzing the effect of the air layer height on the quality factor of the dipole mode, we obtain an optimized DLPCS-H1 cavity in which the height of intermediate air layer is about 0.5a (a is the lattice constant, a=420 nm). In this cavity, the quality factor of the dipole mode is 4 times as large as that of the conventional single layer photonic crystal slab H1 cavity. Furthermore, we study the three-layer photonic crystal slabs H1 cavity, and the quality factor of its dipole mode is increased over 7 times.
Electromagnetic resonance in nanosandwich photonic metamaterial
Authors: Fu Fei-Ya  , Chen Wei  , Zhou Wen-Jun  , Liu An-Jin  , Xing Ming-Xin  , Wang Yu-Fei  , Zheng Wan-Hua  ,   Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

The magnetic plasmon (MP) modes in metal-dielectric-metal nanosandwich structures are investigated numerically using finite-difference time-domain method. We demonstrate the law of the quality factor in this kind of resonator.According to the MP modes in the nanosandwich structures, we design a series of resonators of this kind in order to investigate how to tune the resonante frequencies of MP modes through tuning the geometrical parameters and the dielectric layer refractive index of resonators, and the obtained result is well consonant with our analysis by the equivalent inductance capacitance circuit. We also investigate the electromagnetic energy confinement of the nanosandwich resonators, and analyse the Q factors of these structures from thermal and radiant points of view, which will guide one in designing new waveguides and lasers based on MP modes.
Fiber grating Fabry-Perot cavity studied by V-I transmission matrix method
Authors: Li Zhuo-Xuan  , Pei Li  , Qi Chun-Hui  , Peng Wan-Jing  , Ning Ti-Gang  , Zhao Rui-Feng  , Gao Song  ,   Key Laboratory of All Optical Network and Advanced Telecommunication Network of Ministry of Education, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

Fast and efficient access to spectral characteristics of multi-cascaded fiber grating Fabry-Perot (F-P) cavity, is an important foundation and premise to ensure optimizing the design of cascade multi-wavelength lasers, amplifiers and other optical devices, and complex distributed sensing network based on the F-P structure. V-I transmission matrix method is presented first in this paper to analyze the reflection spectral characteristics of fiber grating F-P cavity and then the V-I transmission matrix model is established. Spectral characteristics of three different structures of fiber grating F-P cavity at different parameters are analyzed based on the V-I transmission matrix model. Compared with multi-layer method, V-I transmission matrix method can save the computation time apparently under the premise of ensuring analysis accuracy. The experimental results show that for analyzing the spectral characteristics of fiber grating F-P cavity, the V-I transmission matrix method is more accurate than the coupled-mode method.
Multibeam optical pulse generation system based on time division multiplexing
Authors: Lin Hong-Huan  , Zhang Rui  , Deng Ying  , Li Ming-Zhong  , Zhou Shou-Huan  , Wang Jian-Jun  , Xu Dang-Peng  ,   (1)Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China; (2)School of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China; (3)School of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China;Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

By time division multiplexing (TDM) technique, an all-solid-state all-fiber multibeam optical pulse generation system used for an inertial confinement fusion driver is developed. The continuous wave signal is provided by a single longitudinal mode oscillator. The TDM technique and he high speed electro-optic modulation technique are utilized to realize the train pulse and arbitrary pulse-shaping. The polarization independent acoustooptic modulation technique is adopted to independently output the multibeam. Eight sub-pulses which may be shaped arbitrarily are included in each train pulse, and the time delay between adjacent sub-pulses is 120 ns. A single pulse selection module is used so that each beam turns into an independent output beam and then each beam is amplified and transmitted to output. Finally, it is successfully verified that the train pulse can be produced by the TDM technique, and its sub-pulse can be shaped arbitrarily and independently. The each beam energy is 1.275 μJ.
Influences of gas flow on gas temperature and discharge mode in dielectric barrier discharge of nitrogen at atmospheric pressure
Authors: Wang Li-Ming  , Liang Zhuo  , Guan Zhi-Cheng  , Luo Hai-Yun  , Wang Xin-Xin  ,   (1)Shenzhen Graduate School, Tsinghua University, Shenzhen 518055, China; (2)State Key Laboratory of Power System, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Dielectric barrier discharge in nitrogen at atmospheric pressure is studied with the spectroscopy and the fast photography of the discharge. By the introduction of a nitrogen flow into the discharge gap, the homogeneous discharge in a 2 mm gap can be maintained. Based on the waveform of the discharge current characterized by a current pulse per half cycle of the applied voltage and the 1 μs exposure discharge photograph showing a luminous layer covering the entire surface of the anode, the homogeneous discharge is identified with a Townsend discharge. The instrumental broadening of the spectrometer used in the experiment is calibrated with a helium-neon laser. The data relevant to the instrumental broadening are input into a code called Specair for calculating the spectrum profiles of 0—2 band in the second positive system of nitrogen molecules at different gas temperatures. By fitting the calculated spectrum profiles to the experimental one, the rotational temperature of the nitrogen molecules is determined. The results show that the dielectric barrier Townsend discharge in nitrogen at atmospheric pressure cannot heat the nitrogen to a high temperature (ΔTg≤50 K) and the small rising in temperature does not induce the thermal instability that leads to the transition of the Townsend discharge to a filamentary discharge. By the addition of a gas flow into the discharge gap, the nitrogen is indeed cooled down to a lower temperature. However, it is not the reason for the Townsend discharge to be maintained. By comparing the discharge spectra with and without the gas flow, it could be concluded that the gas flow much reduces the density of the impurity oxygen desorbed from the dielectric by the discharge and makes it possible for more nitrogen metastables to survive to the beginning time of the next discharge and to provide sufficient seed electrons which are necessary for Townsend discharge.
One-dimensional simulation of low pressure xenon dielectric barrier discharge
Authors: Shao Xian-Jun  , Ma Yue  , Li Ya-Xi  , Zhang Guan-Jun  ,   State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering,Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

A self-consistent one-dimensional fluid coupled model is built to describe the low pressure xenon dielectric barrier discharge (DBD). And the finite-element method is employed to investigate gas voltages, discharge currents and the time evolutions of surface charges on dielectric barrier under different applied voltage amplitudes and frequencies. The spatial and temporal distributions of electrons, ions, excited, resonance, metastable particles and spatial electrical field are also achieved. The simulation results show that the surface charges accumulated on the dielectric barriers play a key role in the ignition and the extinguishment of the discharge. And based on the variation of gas voltage, the surface charging can be divided into six stages in one discharge cycle. With the increase of applied voltage amplitude, the gas gap breakdown moves ahead of the zero-crossing point of applied voltage gradually, and the discharge becomes more and more intense. Furthermore, with the increase of applied voltage frequency, the gas voltage decreases gradually, gas gap tends to breakdown, and discharge becomes uniform. Finally, spatiotemporal distributions of particles and electric field indicate that the xenon DBD is a typical glow discharge.
High luminance carbon nanotube field emission cold cathode based on indium tin oxide/Ti composite electrode
Authors: Pan Jin-Yan  , Gao Yun-Long  , Zhang Wen-Yan  ,   (1)College of Information Engineering, Jimei University, Xiamen 361021, China; (2)Northwest Institute for Nono-ferrous Metal Research, Xi'an 710016, China; (3)State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Carbon nanotube (CNT) cathode with an indium tin oxide (ITO)/Ti composite electrode is successfully fabricated using both magnetron sputtering technology and screen-printed technology which can improve adhesive performance between electrode and CNT cathode of transplanted-type CNT cold cathode, thus eliminating the effects of interface barrier and non-ohmic contact on field emission uniformity and stability of CNT cathode. Microstrcture of ITO/Ti-based CNT cathode is studied by X-ray diffraction and field emission scanning electron microscopy. The results show that TiC phase forms in ITO/Ti-based CNT cathode, thereby a strong interaction system is created between CNT and Ti substrate which reduces, or even eliminates the interface barrier between electrode and CNT, and increases the probability of forming ohmic contact. The resistivity measurement by four probe technology shows that the ITO/Ti-based CNT cathode has performance of resistances in parallel and electric conductivity of CNT cathode increases. Characteristic test of ITO/Ti-based CNT cathode shows that field emission current reaches 384 μA/cm2 which significantly increases compared with that of ITO-based CNT cathode, and that the tested anode can be induced to emit stable, uniform and high luminance. So the ITO/Ti composite electrode is an effective way to make a CNT cathode with stable and uniform field emission and low power.
Study on thermal conductivity of porous silicon thermal isolation layer based on micro-structure mathematical model
Authors: Xu Lu-Jia  , Hu Ming  , Yang Hai-Bo  , Yang Meng-Lin  , Zhang Jie  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Porous silicon can be used as a thermal isolation layer because of its low thermal conductivity. Different from other models based on the mechanism that the thermal conductivity of porous silicon is attributed to complex microcosmic thermal conductivity through such as boundary scattering, the model used in this paper is based on the mechanism that the low conductivity of the porous silicon material is due to its structure factors, such as the existence and distribution of pores and porous silicon is viewed as a compound microstructure piece, which is constructed by both silicon continuous material and pore continuous material medium, connecting in parallel and series patterns. Therefore, the authors give a more understandable and simpler reason why the conductivity of such a material is at such a low level. It is pointed out that the influence of porosity on equivalent thermal conductivity can be divided into two parts: vertical and horizontal, thereby giving semi-quantitative relationships between the porosity and equivalent thermal conductivity for different pore structures and distributions. A comparison between the calculated results and experimental results shows the validity of this model, thus supporting the reason why the thermal conductivity of porous silicon material is relatively low.
Structure transition of two-dimensional hexagonal BN under large uniaxial strain
Authors: Li Jin  , Gui Gui  , Sun Li-Zhong  , Zhong Jian-Xin  ,   Key Laboratory for Quantum Engineering and Micro-Nano Energy Technology of Institution of Higher Education of Hunan Province, Department of Physics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Using the first-principles method, we have studied the structure transition of two-dimensional hexagonal boron nitride (2D h-BN) under large uniaxial strain. The strain is applied by changing the values of Lx and Ly, which correspond to the lengths of primitive cell in the directions perpendicular and parallel to B—N bonds, respectively. For the large asymmetrical tensile strain perpendicular to B—N bonds, the rhombic structure is stable when Lx≤0.3388 nm. As the strain increases, the system transforms from the rhombic structure to a rectangular structure consisting of interlaced interacting BN chains, which becomes stable when Lx≥0.3488 nm. When the strain further increases, the system finally changes into the one comprised of isolated BN chains. For the 2D h-BN with large asymmetrical tensile strain distribution parallel to B—N bonds, there is no stable rectangular structure and the system becomes the one composed of isolated BN chains when Ly>0.571 nm.
Plastic deformation of single-crystalline copper films with surface orientation [001] : molecular dynamics simulations
Authors: He An-Min  , Shao Jian-Li  , Wang Pei  , Qin Cheng-Sen  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

Molecular dynamics simulations are performed to study the plastic deformation behavior of single-crystalline copper film subjected to biaxial tensile strain. The unltrathin film is oriented normal to the [001] crystallographic direction. Beyond a critical value, the film deforms plastically through nucleation, motion and interaction of dislocations. The progress of twinning formed by the motion of Shockley partial dislocations in successive atomic planes is analyzed. Additional stacking faults bounded by twin boundaries are formed in some large newborn twins to release residual strain.
Eeffects of split-level energy on optoelectronic transport in nanocrystalline silicon
Authors: Chen Jing  , Jiang Zhen-Zong  , Lu Jia-Jia  , Liu Yong-Sheng  , Zhu Yan-Yan  ,   (1)Department of Physics and Mathematics, Shanghai University of Electric Power, Shanghai 200090, China; (2)Department of Physics, Shanghai Jiaotong University, Shanghai 200240, China
Published: December 2020

Considering the coexisting of electron resonant tunneling and miniband transport processes in a split-level energy system, and the effect of photogenerated carrier, we propose an optoelectronic transport theoretical model for the nanosilicon structure. We employ this model to calculate current density, electric field and electron density distribution under illumination, and the results show that resonant tunneling plays a major role in transporting the photogenerated electrons in a nanosilicon structure. Furthermore, we study the relationship between the photocurrent and the absorption coefficients, the applied bias, and the number of nanolayers. It is found that under certain conditions, hopping phenomenon occurs with photocurrent increasing, which is due to the redistribution of electric field inside the nanosilicon structure.
Effects of substrate resistivity and interface defect density on performance of solar cell with silicon heterojunctions
Authors: Zhou Jun  , Di Ming-Dong  , Sun Tie-Tun  , Sun Yong-Tang  , Wang Hao  ,   (1)Changzhou Yijing Optical-electronic Company Limited, Changzhou 213223, China; (2)Department of Optical Engineering, Jiangsu University, Zhenjiang 212013, China; (3)Institute of Optics and Optoelectronics, Ningbo University, Ningbo 315211, China;Department of Optical Engineering, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

For silicon heterojunction solar cell with p-type a-Si:H back surface field, the effects of substrate resistivity on the performance of solar cell with different defect densities on the front and the rear surfaces of the p-type c-Si wafer are investigated numerically by computer simulation. The results indicate that the optimized resistivity of the substrate (ρop) is related to the interface defect density on the front surface of c-Si wafer (Dit1), and ρopincreases with the increase of Dit1.The value scale of resistivity of substrate is influenced greatly by the interface defect density on the rear surface of c-Si wafer (Dit2) for ρ>ρop, and the larger the value of Dit2, the smaller will the range of acceptable ρ value be.
Porosity effects on depoling characteristics of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics under shock wave load
Authors: Feng Ning-Bo  , Gu Yan  , Liu Yu-Sheng  , Nie Heng-Chang  , Chen Xue-Feng  , Wang Gen-Shui  , He Hong-Liang  , Dong Xian-Lin  ,   Key Laboratory of National Defense Science and Technology for Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China;,   Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;,   Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;Key Laboratory of National Defense Science and Technology for Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang
Published: December 2020

Four kinds of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics with different porosities are prepared, and the porosity effects on the depoling characteristics of those samples under shock wave load are investigated. The results show that under short circuit condition, the releasing current waveforms are in the form of square pulse for all samples. The amplitude of the current pulse decreases, but the width increases with the porosity increasing. The releasing charge decreases with the porosity increasing, which is consistent with the measurement by P-E loop. Porous ceramics has lower shock impedance, which improves the impedance match to the encapsulation medium. The depoling characteristics of those samples under high resistance load are simulated well by Lysne model. The results reveal that the dielectric constant of the sample is 4—5 times larger than that under static state, moreover, it decreases with porosity increasing. After the shock wave passing through the sample, the discharging time constant increases with porosity increasing. As the load increases, the rising edge becomes less steep for the restrain of the ferroelectric phase-antiferroelectric phase transformation under high electric field, and the breakdown happens to the dense ceramics.
Protective performance and protective mechanism of SiO2 aerogel under explosive loading
Authors: Yang Jie  , Li Shu-Kui  , Yan Li-Li  , Wang Fu-Chi  ,   School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

The propagation character of shock wave in SiO2 aerogel under explosive loading is studied using a polyvinylidene fluoride piezoelectric sensor. The propagation character of shock wave in aluminum foam is also determined for comparison. The results show that the peak stress of the shock wave follows the exponential attenuation relation with the propagation distance of the shock wave in SiO2 aerogel. The shock wave attenuates more obviously in SiO2 aerogel than in aluminum foam. The special nano-porous network structure of SiO2 aerogel results in better attenuation effect of shock wave in aerogel. The shock wave velocity in SiO2 aerogel is extremly low, thus the chase of the unloading wave leads to the further attenuation of shock wave.
A new approach to adjusting sea surface wind using altimeter wind data by variational regularization method
Authors: Jiang Zhu-Hui  , Huang Si-Xun  , Du Hua-Dong  , Liu Bo  ,   Institute of Meteorology, University of Science and Technology of Chinese People’s Liberation Army, Nanjing 211101, China
Published: December 2020

To adjust non-divergent and divergent background wind fields by altimeter wind data, a novel approach, the variational regularization method, is presented. Numerical simulation results show that it is positive to use altimeter wind speed to adjust the background wind field, particularly effective in the altimeter track region. At the same time, the radar backscattering cross-section sensitivity is evaluated, when the backscattering cross-section contains noise, and the result proves that the above method can be used to suppress the noise. Finally, a real case shows that the above method is feasible and effective. This approach is an effective and reliable method of using the altimeter wind data to adjust the sea surface wind.
Distribution of cloud-to-ground lightning electromagnetic pulse fields under the ground
Authors: Yang Bo  , Zhou Bi-Hua  , Meng Xin  ,   Engineering Institute of Corps of Engineers, University of Science and Technology of Chinese People’s Liberation Army, Nanjing 210007, China
Published: December 2020

In order to find out the distribution of lightning electromagnetic pulse (LEMP) fields under the ground, the two-dimensional finite-difference time-domain method is used to calculate LEMP under the ground. The distributions of LEMP under the ground are calculated in the cases of different distances from the lightning channel, different ground conductivities, different ground permittivities and different depths. The attenuations of lightning fields in the ground are compared with those of other high-power electromagnetic environments. The calculated results show the following points: the LEMP dramatically attenuates as the distance increases; the attenuation of the electric component is significant when the ground conductivity is reasonably high; the change of ground permittivity mainly causes the change of vertical electric field component, which decreases as the ground permittivity increases; the attenuation of the high frequency electric component increases and that of the low frequency electric component invisibly changes as the depth increases.
A valid method to compute the segment size in detrended fluctuation analysis
Authors: Yang Jie  , Yang Ping  , Hou Wei  , Zhang Da-Quan  ,   (1)Institute of Urban Meteorology of Beijing, China Meteorological Administration, Beijing 100089, China; (2)National Climate Center, Beijing 100081, China;College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China; (3)National Climate Center, Beijing 100081, China;Key Laboratory of Regional Climate Environment Research for Temperature East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Published: December 2020

We develop a method to compute the segment size in the detrended fluctuation analysis (DFA), which is based on the basic concept of the information theory, and verify the method effectiveness by numerical experiment. This method is freed from the problem of subjectivity in the former process to choose the segment size which usually leads to false result. We Change the length of sequence with dynamics being the same, the results remain stable. The results indicate that when the length of sequence is too short, even the optimal selection of segment size is not enough for the portrait of the overall dynamic system, thus the DFA cannot be used in this circumstance. The method we developed in this paper can enhance the reliability of DFA results by judging whether the sequences analyzed meet the requirements of DFA. We also obtain the DFA index from 1961 to 2000 of China through DFA method and analyze its spatial characteristics of distribution.
Control of Hopf bifurcation in the one-cycle controlled Boost converter and its experimental implementation
Authors: Ma Wei  , Wang Ming-Yu  , Nie Hai-Long  ,   State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China
Published: December 2020

The one-cycle controlled Boost converter is analyzed by using its averaged model. The results show that the one-cycle controlled Boost converter loses stability via a supercritical Hopf bifurcation, which may jeopardize the performance of the converter. A washout filter is proposed in this paper to suppress the Hopf bifurcation. This method can be easily implemented due to the structure of the one-cycle controlled Boost converter. The averaged model of the washout filter-aided one cycle controlled Boost converter is derived. Two new parameters in the washout filter can be chosen by Routh-Hurwitz stability criterion. The washout filter-aided method is verified by simulation and experiment.
Multiscale simulation of nanometric cutting of single crystal Cu based on bridging domain method
Authors: Liang Ying-Chun  , Pen Hong-Min  , Bai Qing-Shun  , Lu Li-Hua  ,   School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

One of the significant methods of multiscale simulation named bridging domain method which is a mixed atomistic-continuum formulation is reviewed. The mode related to atomistic/continuum coupling is introduced. The coupled method with the treatment of the overlapping subdomain is discussed, in which different scaling parameters (weigh factors) are adopted to calculate the energy of the system in the overlapping subdomain and to constrain the atomic and the continuum displacements by the Lagrange multiplier method. A bridging domain model is set up to investigate the effect of cutting speed on chip and workpiece atom force distribution in the nanometric cutting of single crystal copper. Simulation results show the cutting deformation coefficient decreases and the workpiece atom force increases with the increase of cutting speed. In addition, the machined surface qualities at different cutting speeds are investigated. The multiscale model and simulation of nanometric cutting are accomplished based on the bridging domain method, which lays a theoretical foundation for exploring the trans-scale simulation of nanometric cutting.
Bi-directional pedestrian flow model with traffic convention
Authors: Yang Ling-Xiao  , Zhao Xiao-Mei  , Gao Zi-You  , Zheng Jian-Feng  ,   School of Traffic and Transportation, Beijing Jiaotong University, Beijing 100044, China;Key Laboratory for Urban Transportation Complex Systems Theory and Technology of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

In this paper, we extend a cellular-automata model recently proposed by Baek et al. to simulate traffic dynamics of the bi-direction pedestrians. And we present two improved strategies for the moving rules of the pedestrians. Numerical studies of average velocity-density diagram, spatial density distribution and position distribution of the pedestrians are given. We find that the two improved strategies can not only increase the average velocity of pedestrian flow, but also improve the utilization of the road, especially for the central region, reduce the degree of congestion, and avoid the occurrence of serious congestion. The two improved strategies have more comprehensive considerations of psychological and behavioral characteristics of pedestrians, which are also proper to simulate bi-directional pedestrian dynamics under a high traffic density.
A chaotic system with invariable Lyapunov exponent and its circuit simulation
Authors: Zhou Xiao-Yong  ,   Department of Electric and Information Engineering, Jangsu Teachers University of Technology, Changzhou 213001, China
Published: December 2020

A novel three-dimensional chaotic system with invariable Lyapunov exponent is proposed. The new system contains six system parameters, one quadratic cross-product term, and one square term. The dynamic properties of the new system are investigated via theoretical analysis, numerical simulation, Lyapunov dimension, Poincare diagrams, Lyapunov exponent spectrum, and bifurcation diagrams. The different dynamic behaviors of the new system are analyzed when each system parameter is changed. When the parameter of the square term varies, the Lyapunov exponent spectrum keeps invariable, the amplitudes of the signals of the first two dimensions change each as a power function with a minus half index, but the third one keeps its amplitude in the same range. Finally, the circuit of this new chaotic system is designed and realized by Multisim software, which confirms that the chaotic system can be achieved.
Nonlinear propagation and supercontinuum generation of a femtosecond pulse in silicon waveguide
Authors: Qiao Li  , Feng Ming  , Liu Zu-Xue  , Meng Jie  , Lü Ke-Cheng  ,   The Key Laboratory of Weak Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China
Published: December 2020

Propagation of femtosecond pulse and supercontinuum generation in silicon waveguide are investigated numerically by solving the generalized nonlinear Schrdinger equation. The effects of dispersive effect and nonlinear loss on supercontinuum generation are simulated and analyzed. It is found that soliton fission is the main mechanism of supercontinuum generation in silicon waveguide. The relative position between the central wavelength of femtosecond pulse and zero-dispersive wavelength (ZDW) of silicon waveguide significantly affects the generation of supercontinuum. When the input pulse falls in the anomalous dispersion regime, soliton fission phenomenon is most obvious. It is also found that the high-order dispersion plays an important role in supercontinuum generation. When the absolute value of third-order dispersion is smaller, a broader supercontinuum can be obtained. Besides, two-photon absorption (TPA) effect in silicon induces high loss, and reduces the spectral width of the supercontinuum.
Dynamics of a novel chaotic neural firing pattern discovered in experiment and simulated in mathematical model
Authors: Gu Hua-Guang  , Zhu Zhou  , Jia Bing  ,   College of Life Science, Shaanxi Normal University, Xi’an 710062, China
Published: December 2020

A special chaotic firing pattern lying between period-1 and period-2 firing pattern simulated in theoretical neuronal firing model, Hindmarsh-Rose (HR) model, has not been adequately understood for a long time. The non-periodic neural firing patterns lying between period-1 and period-2 firing pattern discovered in the biological experiments on neural pacemakers of rats are identified to be chaotic bursting and divided into three styles in appearance, according to the deterministic structures of the first return map and the short-term predictability of nonlinear predication. One style of the experimental chaos exhibits characteristics similar to the numerical simulations of the theoretical model, verifying the theoretical participation of HR model, while other styles display different characteristics. The characteristics of the three styles and the relationship and distinction among 3 styles of the chaotic rhythms are identified, and compared with those lying between period-2 and period-3 firing pattern, and between period-3 and period-4 firing pattern. In addition, the distinction between the transition procedure from period-1 to chaos and then to period-2 and other bifurcation scenarios from period-1 to period-2 firing pattern is also identified. The results confirm the novel chaos lying between period-1 and period-2 and the corresponding novel bifurcation scenario, enriching the kinds of the chaotic rhythms and bifurcation scenarios of neural firing. Finally simulations of the diversity and non-smooth characteristics of the chaotic rhythms discovered in the experiment and identification of the routine to chaos are also discussed.
Fractal characteristics of characteristic parameter statistical distributions of typical random signals
Authors: Yang Juan  , Bian Bao-Min  , Yan Zhen-Gang  , Wang Chun-Yong  , Li Zhen-Hua  ,   Department of Information Physics and Engineer, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

A two-parameter statistical model of the pulsed signals which can be used to describe the basic structural characteristics of the random signals is established in this paper. As a result, the random signal counting distributions of amplitude q(lV) and width p(l), as well as the different signal subset counting distributions under given width l(lV) and amplitude lV(l), all match well with the form of the lognormal distribution with a natural numberused as an independent variable. Besides, it is also found that there are internal relations between the counting distribution statistical characteristic parameters lnV, ln, lnV, ln and the corresponding signal characteristic parameters lV and l. In essence, these relations are the representations of random signal fractal characteristics. In a word, two characteristic parameter statistical distributions of the random signals each have a non-integral dimensional fractal feature.
Transient synchronization mutation of ring coupled Duffing oscillators driven by pulse signal
Authors: Wu Yong-Feng  , Zhang Shi-Ping  , Sun Jin-Wei  , Peter Rolfe  , Li Zhi  ,   School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The dynamic behavior of ring coupled Duffing oscillators driven by non-periodic signal is investigated, a phenomenon is discovered, which shows that when ring coupled Duffing oscillators are in the period-doubling bifurcation phase state and one of the oscillators is driven by pulse signal under certain parameter conditions, this oscillator and the other oscillators suddenly change from synchronization to transient non-synchronization and then rapidly return to synchronization, which is defined as transient synchronization mutation. This phenomenon can be used to accurately detect weak pulse signal in strong noise environments, which can further extend the weak signal detection range based on the Duffing oscillator.
Effect of temperature gradient on grain growth behavior from phase field simulations
Authors: Wei Cheng-Yang  , Li Sai-Yi  ,   School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China;,   School of Materials Science and Engineering, Central South University, Changsha 410083, China
Published: December 2020

A 2D model is developed to investigate the grain growth behavior under the influence of temperature gradient using the phase field method. The model is used to simulate the effect of temperature gradient on the nonuniform and directional grain growth behavior during annealing of polycrystalline materials. The results show that the static temperature gradient leads to the nonumiform grain growth, and that the grain growth exponent deviates from that of normal grain growth. In the case of annealing with a moving temperature gradient, the columnar grains may develop towards the locations with the highest temperature in the heated zone. Moreover, the grain growth behavior is closely related to the moving speed of the moving heated zone. Columnar grains occur only when the moving speed of the heated zone is higher than the minimum grain growth rate but lower than the maximum grain growth rate.
Analysis of comprehensive effects of piston error and sub-aperture aberrations on the image quality of sparse-optical-synthetic-aperture system
Authors: Liu Zheng  , Wang Sheng-Qian  , Huang Lin-Hai  , Rao Chang-Hui  ,   College of Opto-Electronics Science and Engineering, National University of Defense Technology, Changsha 410073, China;,   The Laboratory on Adaptive Optics, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;,   The Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, Chengdu 610209, China
Published: December 2020

To improve the image quality of sparse-optical-synthetic-aperture system, the effects of sub-aperture self aberrations and piston errors among different sub-apertures should be considered comprehensively. Based on the pupil of sparse-optical-synthetic-aperture system, the system Strehl Ratio (SR) is deduced using the principle of Fourier optics, which leads to the theoretical result of the systems SR metric with the form of separated sub-aperture aberration and piston error. As for the bi-aperture system, the variances of the system SR metric are calculated and analyzed with different sub-apertures aberrations for conditions of corrected piston error and un-corrected piston error. Therefore, the comprehensive effects of sub-aperture aberrations and the piston errors among different sub-apertures on the system image quality are analyzed theoretically. From these analyses, the physical mechanism for the comprehensive effect of sub-aperture aberration and the piston error on the sparse-optical-synthetic-aperture system image quality is revealed, and it could be seen that the compensation of piston error is meaningful only if the sub-aperture self aberration is corrected to be in a certain limit.
Mass spectrum and mixing angle of axial-vector mesons
Authors: Lü Jian  , Yang Guang  ,   College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou 450011, China;,   Basic Teaching Department, Jiaozuo University, Jiaozuo 454000, China
Published: December 2020

In this work, using the formula for hyperfine splittings, we first calculate the mass of the bottomonium member for the axial-vector multiplet (11P1). Then, the masses of the axial-vector mesons Bc1,(ss and K1B are extracted in Regge phenomenology. After that, we estimate the nonet mixing angle and the mixing angle for K1A - K1B. We suggest restudying h1(1380) near 1478 MeV and searching Bc1(1P) near 6774 MeV. The predictions may be useful for the discovery of the unobserved doubly heavy meson Bc1 and useful for understanding the K1A - K1B mixing and the axial-vector (11P1) nonet mixing.
Particle-in-cell simulation of outer magnetically insulated transmission line of Z-pinch accelerator
Authors: Guo Fan  , Li Yong-Dong  , Wang Hong-Guang  , Liu Chun-Liang  , Hu Yi-Xiang  , Zhang Peng-Fei  , Ma Meng  ,   Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049,China
Published: December 2020

In order to implement the particle-in-cell(PIC) simulation of four outer magnetically insulated transmission lines(MITL) of Z-pinch accelerator, we adopt the backward-going transmission line voltage wave at the double post-hole convolute(DHPC) travelling in the outer MITL direction, which is gained in circuit simulation to model the part from DHPC to Z-pinch load. For the purpose of enhancing the accuracy of equivalent circuit model of DHPC and Z-pinch load, the backward-going transmission line voltage wave that is computed by circuit simulation is rescaled by PIC simulation. The insulator voltage and current waves that are obtained in the PIC simulation of four outer MITLs of PBFA Z can match the electrical measurements better than those obtained by the circuit simulation. Moreover, the influence of Z-pinch load implosion on the process of pulsed power coupling in the outer MILT is analyzed and explained.
Experimental study of the secondary neutron angular spectra emitted from polyethylene slabs with D-T neutron source
Authors: Yan Jie  , Liu Rong  , Jiang Li  , Lu Xin-Xin  , Zhu Tong-Hua  , Lin Ju-Fang  , Wang Mei  , Wen Zhong-Wei  , Wang Yi-Fu  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

An experimental method of measuring the secondary neutron angular spectrum from polyethylene slab assembly with D-T neutron source based on the proton-recoil method is developed. In order to ensure the energy linearity of the detector and obtain a good neutron-gamma discrimination capability in the case of a low effective neutron threshold (0.5MeV), neutron energy spectrum is measured in two parts: one is in a high energy region and the other in a lower energy region. The pulse shape discrimination (PSD) and the pulse height distribution (PH) two-dimensional information of the secondary neutron and the associated gamma rays are recorded event-by-event simultaneously. The selection and the deduction of the gamma ray events and the joining of the two-segment energy spectra are carried out by using the off-line data analysis programs written in the ROOT data analysis framework. Furthermore, an artificial neural network technique is used to accomplish the unfolding of the neutron spectra successfully. The experimental results of the second neutron angular spectra from 9cm and 18cm thick polythene slab assemblies with D-T neutron source in an energy region of 0.5 MeV to 15 MeV are obtained. The Monte Carlo calculations of the experimental models are accomplished by using the MCNP5 code with ENDF-VI data library. The experimental results are in agree ment with the calculation results within the experimental uncertainties.
Study on geometrical structure and spectrum ofpolymerization borohydride (BH3)n(n=13)
Authors: Wu Dong-Lan  , Xie An-Dong  , Wan Hui-Jun  , Ruan Wen  ,   College of Mathematic and Physical, Jinggangshan University, Ji’an 343009, China
Published: December 2020

The possible geometrical structures of polymerization borohydride (BH3)n(n=13) are optimized in computation, based on different methods of B3P86、B3LYP,MP2,LSDA and by combining the Dunning relevant and consistent base group cc-PVTZ. The configuration geometric parameter, the electronic structure, the vibrational frequency and spectrum of the most stable structure are obtained, and the total energy (ET), binding energy (EBT), the average binding energy (Eav), the ionization potential (EIP), the energy crack (Eg), the Fermi level (EF) and so on are also given. The results indicate that the total energy is lowest and its value is close to the reported values from B3P86 method. The ground state of the three kinds of borohydride are all singlet states, the ir electronic states respectively are 1A',1A, and 1A. The stable geometry configuration of BH3 molecule is the planar triangle, B2H6 has a symmetrical ethylene type D2h spatial structure, and between H-B produces the hydrogen bridge type with three-center double electronic key, B3H9 has a C3spatial structure, also produces a hydrogen bridge type of three-center double electronic key, but the three hydrogen bridge types are isolated from each other. Finally the infrared and the Raman spectrum, the average binding energy, the ionization potential, the energy gap, Fermi level and so on are analyzed. B2H6 is shown to be the most stable molecule in (BH3)n(n=13), the H-B bridge bond key long is longer than the terminal lond, the infrared intensity of strongest peak is a maximal value.