bluuebunny/crossref_metadata_2025 huggingface dataset:
Modal characteristic frequency in a range-dependent shallow-water waveguide and its application to passive source range estimation
Authors: Qi Yu-Bo  , Zhou Shi-Hong  , Zhang Ren-He  , Zhang Bo  , Ren Yun  ,   State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China;,   College of Physics, University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In order to implement robust passive source ranging in a range-dependent shallow-water waveguide, the modal characteristic frequencies are theoretically analyzed based on warping transform. Formulae of the modal spatiotemporal arrival structure and instantaneous phase are derived in the waveguide with an absolute hard bottom. The relationship between the characteristic frequency and the source-receiver range is developed. With the relationship, a modified passive source-range estimation approach is presented in a range-dependent shallow-water waveguide. Simulation and experiment verify the theory and the approach.
Numerical analysis for the characteristics of flow control around a circular cylinder with a turbulent boundary layer separation using the electromagnetic force
Authors: Yin Ji-Fu  , You Yun-Xiang  , Li Wei  , Hu Tian-Qun  ,   State Key Laboratory of Ocean Engineering, Shanghai Jiaotong University, Shanghai 200240, China
Published: December 2020

A detached eddy simulation method with the turbulent separation is presented to simulate and analyze the characteristics for the flow around a circular cylinder with a turbulent boundary layer separation and its lift/drag coefficients in a weakly conductive fluid at a high subcritical Reynolds number 1.4×105 under an electromagnetic force. The results show that the electromagnetic force can increase the fluid kinetic energy near the turbulent boundary layer, delay the turbulent boundary layer separation of the flow around the circular cylinder, and weaken the intensity of the large-scale eddy in the turbulent flow around the circular cylinder in the streamwise and spanwise directions, reduce the time-average drag, and inhibit the lift fluctuation amplitude on the circular cylinder. Moreover, after the electromagnetic force parameter reaches a certain critical value, the turbulent boundary layer separation disappears and the jet phenomenon appears in the wake of the circular cylinder, so that the electromagnetic force produces the thrust action on the circular cylinder and the negative drag occurs, and the lift fluctuation amplitude declines to almost zero and the lift phenomenon on the circular cylinder disappears.
Molecular dynamics simulation of effect of tilt angle on mechanical property of magnesium bicrystals
Authors: Wang Chen  , Song Hai-Yang  , An Min-Rong  ,   School of Science, Xi'an University of Posts and Telecommunications, Xi'an 710121, China
Published: December 2020

The effects of grain boundary on the deformation behavior of magnesium bicrystals under tensile loading are investigated using molecular dynamics simulation method. Deformation mechanisms of both asymmetric and symmetric magnesium bicrystals are studied. The results show that the twist angle could exert a significant influence on the flow stress in the plastic stage. It is found that the plastic property of symmetric magnesium bicrystal is much better than that of asymmetric counterpart. In addition, for bicrystalline metal with large twist angle, its plastic response is better than that with small angle, owing to the dislocation nucleation activity in the grain boundary region.
Effect of superconducting magnet remanence on the soft magnetic material measurements
Authors: Yu Hong-Yun  ,   Center for Testing and Analyzing of Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

The superconducting magnet is used to provide magnetic field in a magnetic property measurement system (SQUID-VSM, Quantum Design), since it can provide high magnetic field up to 7 T. Due to the pinned magnetic flux, there is residual magnetic field as the magnetic field is set to be 0 from high field. There appears an error between the reported filed and the real filed. Sometimes, the residual magnetic field can be more than 30 Oe. It is so large that it may provide incorrect experiment data, such as Hc, Mr and inverted hysteresis loops. The effect of residual magnetic field on the soft magnetic material measurements should not be neglected. The residual magnetic field is dependent on initial magnetic field. The experimental data must be corrected by measuring the standard sample. In the paper we investigate the origin and the regular pattern of the residual magnetic field. The effects on the measurement results and the correction method are presented.
Research on polarization effect for relaxor ferroelectrics by spherical random bond-random field model
Authors: Qu Shao-Hua  , Cao Wan-Qiang  ,   Key Laboratory of Low Dimension Photoelectric Material and Device of Hubei Province, School of Physics and Electronic Engineering, Hubei University of Arts and Science, Xiangyang 441053, China;,   Collaborative Innovation Center for Advanced Organic Chemical Materials of Hubei Province, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
Published: December 2020

Based on spherical random bond-random field model, micro-macro domain mechanism under electric field, and the fuzzy domain boundary with fractal dimension of electric field, the mechanism of polarization effect is analyzed. The results show that the effect of electric field on polarization effect of increment of domain dipoles leads to an unsaturated electric hysteresis loop and its associated big electrostrictive effect. But the variation of binding energy, when dipole couples to the increment of domain dipoles induced by electric field, has a little influence on electric hysteresis loop in a low electric field, and has almost no influence in a high electric field. The initial size of the micro domain is very important for electric hysteresis loop: small micro domain can lead to a long electric hysteresis loop and better linear relationship between electric field and electrostriction.
An optimization method for ion etching yield modeling based on etching velocity matching
Authors: Gao Yang-Fu  , Song Yi-Xu  , Sun Xiao-Min  ,   State Key Laboratory on Intelligent Technology and Systems, Tsinghua National Laboratory for Information Science and Technology, Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China
Published: December 2020

With the constant development of the microelectronics industry, the etching scale has come up to nanoscale, which makes the plasma etching mechanism attract more and more attention. The profile surface simulation is one of the most significant technologies for the study of ion etching. In the process of ion etching surface simulation, the ion etching yield model serves as an important model for the study of etching mechanism as well as the basic foundation of some simulations such as cellular automata. In order to solve the problem that it is difficult to achieve accurate parameters of etching yield model by adopting the traditional method, the paper proposes an optimization method for ion etching yield modeling based on etching velocity matching. Aiming at reducing the mean square error between the simulated etching velocity and the real etching velocity, it optimizes the parameters of ion etching yield modeling by using the decomposition-based multi-object evolution algorithm, which then is applied to etching simulation process on the basis of cellular automata. And the validity of the proposed method was verified by the experimental results.
Relation between the 3-base periodicity of P53 gene and codon usage bias
Authors: Wang Qi-Qiang  , Tan Cheng-Jie  , Zhu Ping  ,   School of Science, Jiangnan University, Wuxi 214122, China
Published: December 2020

To further study the properties of P53 suppressor gene, the 3-base periodicity of P53 coding sequence (CDS) and the corresponding mRNA are analyzed. And the codon biases of P53 CDS and mRNA are discussed through analyzing their relative synonymous codon usage and quasi relative synonymous codon usage values. The results show that the CDS of P53 exhibits 3-base periodicity, whereas the corresponding mRNA of P53 does not, and that the P53 CDS has a stronger bias towards C and G ending codons than the mRNA. This suggests that the 3-base periodicity is closely related to the codon usage bias of P53 gene, and the degree of codon bias has an effect on the 3-base periodicity, which further explains the difference in 3-base periodicity between P53 CDS and mRNA from the point of view of biology. This characteristic of P53 gene may be useful in increasing the correct rate of gene recognition and the extensive investigation of P53 gene.
An optimal direction strategy of diffusion sensitive gradient mangnetic fields in magnetic resonance diffusion tensor imaging based on generalized Fibonacci sequence
Authors: Gao Song  , Zhu Yan-Chun  , Li Shuo  , Bao Shang-Lian  ,   Beijing Key Laboratory of Medical Physics and Engineering, School of Physics, Peking University, Beijing 100871, China;,   Medical Imaging Physics Laboratory, Health Science Center of Peking University, Beijing 100191, China
Published: December 2020

In order to accurately investigate the directionally anisotropic diffusion information of water molecule in tissue, the diffusion sensitive gradient fields need to be applied alone many directions in order to obtain corresponding diffusion coefficients in diffusion tensor imaging (DTI) and high angular resolution diffusion imaging (HARDI) experiments. The problems facing to current diffusion sensitive gradient magnetic fields encoding schemes include the spatial uniformity of directions needs to be improved, there is no general direction design for arbitrary number of directions, flaw in any directions will cause failure or defect of the whole dataset. In this paper, we provide a generalized Fibonacci number based direction encoding scheme. This scheme can generate nearly uniform distribution for arbitrary number of directions and satisfy the spatial uniformity using partial directions from one raw data set. Besides, the diffusion sensitive gradients of neighboring directions are nearly opposite, which will reduce eddy current induced by rapid varying gradient magnetic fields.
Properties of complex network between atmospheric teleconnection and the key areas of SST in winter
Authors: Zuo Dong-Dong  , Gong Zhi-Qiang  , Feng Ai-Xia  , Zhi Rong  ,   Department of Physics, Yangzhou University, Yangzhou 225002, China;,   Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China;,   Data Service Space, National Meteorological Information Center, China Meteorological Administration, Beijing 100081, China
Published: December 2020

Based on the index of atmospheric teleconnection and the key areas of the sea, taking the relationship between the average of the height fields of the key areas and the average of the key areas of SST as boundary condition, the associated network that embodies the interaction between atmospheric teleconnection areas and the key areas of SST is constructed. Then the image of the interaction between atmospheric and ocean is given. Based on the structural characteristics of network, the basic nature of the network and the key nodes of the interaction network are studied and the influence of the key nodes on network is analysed. The Results show that the associated network belongs to the small world that has a smaller average path length and a lager clustering coefficient. Besides, the average path length has a stable value in the threshold less than 0.4. In other words, in this case the characteristics of network remain unchanged, and then it is proved that using the correlation 0.19 as the condition of edge connection is effective. The single node characteristic is analysed in the network and the results show that the areas of the East Asia-Pacific 1 and 2 and the Pacific/North American pattern 1 and 4 have lager node degrees. That is to say, these four atmosphere regions have stronger effect than other regions in the atmosphere and sea, the North Pacific Oscillation 1 and the East Asia-Pacific 3 have low node degrees, so these two regions have low effects on the region interaction. In addition, it is proved that the network has certain robustness by removing nodes in turn. The study is of significance to grasp some important areas of the teleconnection and the sea, and also it provides a new method to study air-sea interaction.
Chaotic characteristics of blazar object S5 0716+714
Authors: Ou Jian-Wen  , Zhang Hao-Jing  , Zheng Yong-Gang  , Zhang Xiong  ,   School of Physics and Electronic Information Technology, Yunnan Normal University, Kunming 650500, China
Published: December 2020

Long-term observations show that blazar object S5 0716 +714 has complicated behavious on multiband. In this paper, the light curves in the radio, V-band and X-ray bands of four outbursts are studied by the chaos theory. We calculate their correlation dimensions and Lyapunov exponents and find that 1) these two values are in a range between a stochastic system and a pure chaotic system; 2) the phase locus of S5 0716 +714 is a chaotic system similar to the Rossler attractor. Various internal or external factors may produce noises, resulting in the fact that the correlation dimension and Lyapunov exponent may be higher than those of the Rossler attractor and the phase locus might be orderless. According to our analysis, we conclude that the light curves of S5 0714+716 show some chaotic features and the variability of this source may be a chaotic phenomenon.
Conformal symmetry and Mei conserved quantity for ageneralized Hamilton system
Authors: Liu Hong-Wei  ,   School of Sciences Northeast Dianli University, Jilin 132012, China
Published: December 2020

In this paper, the conformal invariance and Mei symmetry for a generalized Hamilton system under infinitesimal transformations are discussed in details. A necessary and sufficient condition for conformal invariance of systems to be Mei symmetry is given. We get the Mei conserved quantities of the conformal invariance. Finally, an example is given to illustrate the application of the result.
Blind source separation of chaotic signals in wireless sensor networks
Authors: Huang Jin-Wang  , Feng Jiu-Chao  , Lü Shan-Xiang  ,   School of Electronic and Information engineering, South China University of Technology, Guangzhou 510641, China
Published: December 2020

Chaotic signal is essentially a nonlinear and non-Gaussian signal, which involves signal quantization when used in wireless sensor networks (WSNs). It makes the blind source separation of chaotic signal in WSNs more difficult to address. To solve the problem, we propose a new source separation algorithm based on cubature Kalman particle filter (CPF) in this paper. First the probability density function of the observed signal is derived and the optimal quantization is used; this can achieve the optimal quantization of signal under the limited budget of quantization bits. After that, the algorithm uses cubature Kalman filter (CKF) to generate the important proposal distribution of the particle filter (PF), integrating the latest observation and improving the approximation to the system posterior distribution, which will improve the performance of the signal separation. Simulation results show that the algorithm can separate mixed chaotic signal effectively, it is superior over the unscented Kalman particle filter (UPF) counterpart in accuracy and computation overhead. The running time is 88.77% compared to the UPF counterpart.
Effect of coupling modes and initial structures on the synchronization of a ring network with fractional order bistable oscillators
Authors: Wang Li-Ming  , Wu Feng  ,   Department of physics, Langfang Teachers College, Langfang 065000, China;,   Department of Physics, Tianjin University of Technology, Tianjin 300191, China
Published: December 2020

A ring network with fractional-order bistable oscillators is proposed, and the relationship between synchronization and parameters, such as coupling modes and the initial structural conditions, etc., is investigated. Based on the bistable characteristics of P-R oscillator, the effects of the coupling strength and the structures in initial conditions on the dynamic behaviors of the ring network are investigated by analyzing the largest conditional Lyapunov exponents, the largest Lyapunov exponents and the bifurcation diagrams, etc. Further investigation reveals that the ring network can be controlled to form chaotic synchronization, chaotic non-synchronization, synchronous amplitude death, synchronous non-amplitude death, etc. by changing the initial conditions and the coupling strength. Furthermore, the contours of the largest conditional Lyapunov exponents and the largest Lyapunov exponents also show how the dynamic behaviors of the network are influenced by the competition between couplings along directions of y and z, strongly relies on the initial structural conditions of network.
A least square support vector machine prediction algorithm for chaotic time series based on the iterative error correction
Authors: Tang Zhou-Jin  , Ren Feng  , Peng Tao  , Wang Wen-Bo  ,   School of Information and Communication Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

This paper analyzes the error characteristic of traditional support vector machine prediction algorithm, where the error series are smooth and regular. This is because a single prediction model is incapable of fitting chaotic system mapping function and omitting some deterministic component. On this basis, a prediction algorithm that consists of an iterative error correction and a least square support vector machine (LSSVM) is proposed. The algorithm creats multiple predictive models via the method of iterative error correction to approximate the chaotic system mapping function and obtain significant improvements of predictive performance. In addition, the optimal parameters of the prediction model are automatically obtained from the pattern search algorithm which is simple and effective. Experiment conducted on Lorenz time series and MackeyGlass time series indicates that the proposed algorithm has a much better performance than that recorded in the literature.
Automatic detection of epileptic EEG based on recurrence quantification analysis and SVM
Authors: Meng Qing-Fang  , Chen Shan-Shan  , Chen Yue-Hui  , Feng Zhi-Quan  ,   School of Information Science and Engineering, University of Jinan, Jinan 250022, China;,   Shandong Provincial Key laboratory of Network Based Intelligent Computing, Jinan 250022, China
Published: December 2020

Automatic detection and classification of epileptic EEG signals have been a significance method for the clinical diagnosis and treatment of epilepsy. The recurrence quantification analysis (RQA) based on the recurrence plot could visualize the recurrence behaviors of dynamical systems from the nonlinear time series and analysis of the recurrence properties. This paper presents a new feature extraction method for epileptic EEG signals based on the recurrence quantification analysis. Experimental results show that the seizure detection directly based on recurrence quantification analysis features has a higher detection performance; especially the classification accuracy based on the deterministic feature can be up to 90.25%. This paper also combines the RQA features with the variation coefficient and fluctuation index, and then puts the feature vectors into a support vector machine (SVM) to automatically detect the epileptic EEG from EEG recordings. Experimental results shows that the proposed methods could achieve a great classification accuracy of 99%.
Band inversion in half Heusler-type Na1-xCsxAlGe(0 x 1)
Authors: Wang Xiao-Tian  , Dai Xue-Fang  , Jia Hong-Ying  , Wang Li-Ying  , Zhang Xiao-Ming  , Cui Yu-Ting  , Wang Wen-Hong  , Wu Guang-Heng  , Liu Guo-Dong  ,   School of physics and electronic engineering, Chongqing normal university, Chongqing 400044, China;,   School of Material Sciences and Engineering, Hebei University Technology, Tianjin 300130, China;,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The influences of doping whit congeners on the band topology in half Heusler-type of NaAlGe alloys are investigated using the first-principles calculations. It is found that the Na1-xCsxAlGe alloys with a normal band order are converted into topological nontrivial phases when x is up to 0.125. We argue that it is the degree of hybridization between Al and Ge determine the band order at the Fermi level. The Na or Cs only plays a role of the valence electron contributor and influences the lattice parameter.
Accuracy study for excited atoms (ions)：A new variational method
Authors: Xiong Zhuang  , Wang Zhen-Xin  , Naoum C. Bacalis  ,   Space Science and Technology Research Institute, Southeast University, Nanjing 210096, China;,   Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, Southeast University, Nanjing 210096, China;,   Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Vasileos Constantinou 48, GR-116 35 Athens, Greece
Published: December 2020

For the computation of excited states, the traditional solutions of the Schredinger equation, using higher roots of a secular equation in a finite N-dimensional function space, by the Hylleraas-Undheim and MacDonald (HUM) theorem, we found that it has several restrictions which render it of lower quality, relative to the lowest root if the latter is good enough. In order to avoid the variational restrictions, based on HUM, we propose a new variational function and prove that the trial wave function has a local minimum in the eigenstates, which allows to approach eigenstates unlimitedly by variation. In this paper, under the configuration interaction (CI), we write a set of calculation programs by using generalized laguerre type orbitals (GLTO) to get the approximate wave function of different states, which is base on the HUM or the new variational function. By using the above program we get the approximate wave function for 1S (e), 1P (o) state of helium atoms (He) through the different theorems, the energy value and radial expectation value of related states. By comparing with the best results in the literature, the theoretical calculations show the HUM's defects and the new variational function's superiority, and we further give the direction of improving the accuracy of excited states.
Slow ions 84Kr15+, 17+ bombardment on GaAs
Authors: Yang Bian  , Yang Zhi-Hu  , Xu Qiu-Mei  , Guo Yi-Pan  , Wu Ye-Hong  , Song Zhang-Yong  , Cai Xiao-Hong  ,   Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

We have investigated surface morphology and visible light emission from slow ions Kr15+, 17+ colliding with GaAs (100). The surface disorder of GaAs films mainly depends on the charge state of incident ions. The two spectral lines of target atom Ga belong to transitions of GaⅠ 4p 2P1/2o5s 2S1/2 at 403.2 nm and 4p 2P3/2o5s 2S1/2 at 417.0 nm. Light emissions of target species depend on the energy of the incident ions deposited on the target surface atoms. During the neutralization process, the four spectral lines of Kr+ respectively can be attributed to the transitions of Kr Ⅱ 4d 4F7/25p 2D5/2o at 410.0 nm, 5s 2P3/25p 4S3/2o at 430.4 nm, 5p 4D3/2o4d 2D3/2 at 434.0 nm and Kr Ⅱ 4d 4D1/25p 2S1/2o at 486.0 nm. They are induced by cascade de-excitation after many electrons of the conductions band of the solid surface captured in highly excited states of the incident ion. Intensities of these six spectral lines from incident ions Kr17+ are obviously larger than Kr15+'s.
Optimization of the light-induced-fluorescence signals of single atoms and efficient loading of single atoms into a magneto-optical trap
Authors: Wang Jie-Ying  , Liu Bei  , Diao Wen-Ting  , Jin Gang  , He Jun  , Wang Jun-Min  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices (Shanxi University), and Institute of Opto-Electronics, Shanxi University, Taiyuan 030006
Published: December 2020

In our experiment, firstly, we carry out the loading of single atoms in the magneto-optical trap (MOT) by increasing the quadrupole magnetic field gradient, improving the background vacuum, and reducing the diameters of the cooling and trapping laser beams. Secondly, we get the single atomic fluorescence signal of a high signal-to-background ratio in the MOT by means of reducing the detuning of cooling light and increasing its intensity appropriately, and using the polarization spectroscopy locking technique to suppress the fluctuations of cooling laser. In addition, with the real-time feedback on quadrupole magnetic field gradient, we demonstrate a probability of loading single atoms in the MOT as high as 98%. We also measure the statistical properties of the single atomic fluorescence which is excited by continuous light in the MOT; the measured second-order correlation is g(2)( = 0) = 0.09.
Study on wide-band scattering from rectangular cross-section above rough land surface with exponential type distribution using FDTD
Authors: Zhu Xiao-Min  , Ren Xin-Cheng  , Guo Li-Xin  ,   School of Physics and Electronic Information, Yanan University, Yan'an 716000, China;,   School of Physics and optoelectronic engineering, Xidian University, Xi'an 710071, China
Published: December 2020

The dielectric property of the actual land surface is expressed using the four-component model of dielectric constant of soil, the actual rough land surface is simulated with model of exponential type distribution rough surface and Monte Carlo method, the wide-band electromagnetic scattering from column with rectangular cross-section above rough land surface under Gaussian differential pulse irradiation is studied using FDTD, the curves of frequency distribution of back composite scattering coefficient is obtained, the back composite scattering coefficient varying with the root-mean-square of height fluctuation, the correlation length of rough land surface, the moisture capacity of soil, the geometric parameter of the target, such as height, size, tilt and dielectric parameter of the target is calculated in details, the characteristics of the wide-band composite scattering from object above rough land surface with exponential type distribution are obtained.
Research on the fabrication and property of hydrophobic antireflective infrared window
Authors: Zhang Ran  , Cao Xiao-Wen  , Xu Wei-Wei  , Haraguchi Masanobu  , Gao Bing-Rong  ,   State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China;,   College of Mechanical Science and Engineering, Jilin University, Changchun 130022, China;,   Department of Optical Science and Technology, University of Tokushima, 7708506, Japan
Published: December 2020

We proposed a facile approach for rapid and maskless production of zinc sulfide microstructure used as antireflective and hydrophobic surface by direct laser interference ablation. This surface could improve the infrared transmittance from 75% to 92%; and the problem of bad film adhesion, corrosion resistance, and the thermal expansion mismatch in the antireflective coating membrane were solved. By this method a quick and simple fabrication, and a large-area production as well as the hydrophobic properties with a contact angle of 145° can be realized. Hence this approach can have future broad applications in areas of optoelectronics, solar energy, aerospace, and infrared guidance etc.
Generation of 266 nm continuous-wave with elliptical Gaussian beams
Authors: Chen Guo-Zhu  , Shen Yong  , Liu Qu  , Zou Hong-Xin  ,   Department of Physics, National University of Denfense Technology, Changsha 410073, China
Published: December 2020

The 266 nm continuous-wave coherent radiation is generated by the second harmonic generation of a β-BBO crystal placed inside an external enhancement cavity. Its fundamental beam is a 532 nm laser from commercial production of Coherent Company. Impact of focusing shape of the crystal on the conversion efficiency is simulated detailedly. Theoretical and experimental results show that the elliptical focusing can decrease the walk-off effect and improve conversion efficiency of the second harmonic generation (SHG). We obtain experimentally the 266 nm radiation output of 180 mW with elliptical focusing in a BBO crystal using bowtie cavity when the fundamental wave input 1 W . The SHG conversion efficiency reaches 18%.
Research on prediction and methods of evaluating sound exposure from a mixture of multiple single sources
Authors: Yan Liang  , Chen Ke-An  , Ruedi Stoop  ,   College of Marine Engineering, Northwestern Polytechnical University, Xi'an 710072, China;,   Institute of Neuroinformatics, Swiss Federal Institute of Technology Zurich, Zurich 8057, Switzerland
Published: December 2020

In this paper, the prediction and the way for calculating the total exposure level (to be denoted by LTotal) from a mixture of multiple single sources are proposed, on the premise that each single exposure level from every component single source (to be denoted by Li, where i denotes the number of single sources and i=1, 2, , K) is known. Firstly, a novel method for sound exposure level evaluation, based on a short-term exposure level in the duration of the sound event, is proposed. Using this method, each single exposure level obtained from all the single sound samples and the total exposure level obtained from every artificially combined sound samples are evaluated. Then, we lay special stress on analyzing the quantitative relationships between LTotal and Li (i=1, 2, , K) measured in three types of sound exposure indicators. All analytical results indicate that our anticipative gain of the total exposure level LTotal from a mixture of multiple single sources can be predicted on the premise that each single exposure level from every componential single source is known. To modify the predicted results, we just need to know the number of specific independent components K and the range of the single exposure levels .
Evaluation of vortex criteria by virtue of the quadruple decomposition of velocity gradient tensor
Authors: Li Zhen  , Zhang Xi-Wen  , He Feng  ,   School of Aerospace, Tsinghua University, Beijing 100084 China;,   Mathematical Sciences Center, Tsinghua University, Beijing 100084 China
Published: December 2020

Vortices play a crucial role in fluid dynamics, which is closely related to fluid diffusion mixing, force, heat, and noise. Five widely-used vortex identification criteria, i.e. the -criterion, Q-criterion, -criterion, ci-criterion, and 2-criterion are analyzed, and four of them are compared with each other based on the velocity-gradient-tensor decomposition method. A new quadruple decomposition method (QDM) is introduced for the first time, so far as we know, to decompose fluid motions into four fundamental components: dilatation, axial deformation along the principal axes of the strain-range sensor, planar motion, and pure shearing. This method helps make the kinematic implications of the four vortex identification criteria more clear. It is found that the mean rotation of fluid elements always contains the pure shearing motion. Non-zero mean rotation does not guarantee the existence of the spiraling streamlines, e.g. in a typically parallel shear flow. A positive Q value indicates the strength of the pure rotation of a fluid element in the 2D complex eigenvalue plane on top of the axial deformation, which however is a sufficient but not a necessary condition for the existence of pure rotation. The -criterion can correctly tell the existence of pure rotation, but cannot accurately determine its strength. The ci-value represents the absolute strength of the pure rotation, which is the combined effect of the canonical rotation in the complex eigenvector plane and the pure shearing. The proposed QDM enables us to achieve a deeper understanding of vortices and motions in fluid dynamics.
Study of far-field pressure wavelet of air-gun bubble based on potential flow theory
Authors: Ye Ya-Long  , Li Yan-Qing  , Zhang A-Man  ,   School of Shipbuilding Engineering, Harbin Engineering University, Harbin 150001, China;,   China Oilfield Services Limited Geophysical, Tianjin 300451, China
Published: December 2020

The study of far-field pressure wavelet of air-gun bubble is the basic research of air-gun sources. In this paper, a boundary element bubble model is established to simulate the dynamics of bubble, and an energy equivalent method is put forward to solve the bottleneck of bubble jet. In our simplified model, the bubble model takes into consideration the thermodynamic factors such as heat transfer and gas release, and the numerical results agree with the data of Nucleus software well. Based on the established model, the influence of heat transfer coefficient, air-gun firing time, and specific heat at constant volume on the pressure wavelet are studied. Finally, the three-dimensional bubble merging numerical method is put forward, which is an expansion of the axisymmetric model. Thus, the preliminary study of coherent air-gun is conducted, especially the influence of the space between two bubbles on the wavelet. This paper provides a reference for the research of air-gun.
Impact of (Al, Ga, In) and 2N preferred orientation heavy co-doping on conducting property of ZnO
Authors: Hou Qing-Yu  , Liu Quan-Long  , Zhao Chun-Wang  , Zhao Er-Jun  ,   College of Sciences, Inner Mongolia University of Technology, Hohhot 010051
Published: December 2020

At present, although there is some studies about the theoretical calculation studies of Zn1-xTMxO1-yNy(TM=Al, Ga, In) p-type doped have been reported. But, they are random doping and without considering the asymmetry of ZnO preferred orientation to doping. Therefore, Six different supercell models Zn1-xTMxO1-yNy (TM = Al, Ga, In. x = 0.0625, y = 0.125) which proportion is TM:N = 1:2 and preferred orientation to co-doped have been constructed based on the first-principles plane wave ultra-soft pseudo potential method of density function theory, in this study.Then calculate the geometric optimization, State density distribution and Band structure distribution for all models, respectively. Results indicate that with the condition of heavily doped and preferred orientation to co-doped, in the same kind of preferred orientation co-doping systems, the electrical conductivity of the system which TM-N bond along the c-axis direction is greater than it perpendicular to the c-axis. In the different kinds co-doping ZnO systems which TM-N bond along the c-axis direction, The co-doping systems of In-N bond along the c-axis direction has the strongest conductivity and the lowest ionization energy and the largest Bohr radius. It is more favorable for electrical conductivity of p-type ZnO. This study can be a theoretical guidance for improve the electrical conductivity of which design and preparation TM:N=1:2 ratio preferred orientation co-doping ZnO systems.
First-principle study on the effect of high Pr doping on the optical band gap and absorption spectra of TiO2
Authors: Mao Fei  , Hou Qing-Yu  , Zhao Chun-Wang  , Guo Shao-Qiang  ,   College of Sciences, Inner Mongolia University of Technology, Hohhot, 010051 China
Published: December 2020

Nowadays, the studies on band gap and absorption spectrum of TiO2 doped with Pr lead to opposite conclusions. Two experimental results about red-shift and blue-shift are reported in the literature. We have set up models for pure TiO2 and different doping concentrations of Pr-doped TiO2 to calculate the electronic structure and absorption spectrum based on the first-principle plane-wave ultrasoft pseudopotential in terms of the density functional theory (DFT) to slove the above problem. Results indicate that under the condition of heavy doping Pr, compared with the pure TiO2, as the Pr concentration increases the atomic charge of the doped system reduces and the total energy of the doped system becomes higher, and its formation energy will be greater. This makes the stability decline, the band gap narrowed, the absorption spectrum red-shift, and the absorption strength more significant. The results of the calculation is in agreement with the experimental data.
Breakdown voltage analysis for the new Al0.25 Ga0.75N/GaN HEMTs with the step AlGaN layers
Authors: Duan Bao-Xing  , Yang Yin-Tang  ,   Key Laboratory of the Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

In order to optimize the surface electric field of AlGaN/GaN high electron mobility transistors (HEMTs), a novel AlGaN/GaN HEMT has been grown with a step AlGaN layer, made for the first time as far as we know, to improve the breakdown voltage. The discipline of the 2DEG concentration varying with the thickness of the AlGaN epitaxy layer has been applied to the new AlGaN/GaN HEMTs with AlGaN/GaN heterostructure. By thinning the AlGaN layer near the gate edge, the 2DEG concentration in the channel is made to form the low concentration region near the gate edge. New electric field peak has appeared at the corner of the step AlGaN layer. The high electric field has been decreased effectively due to the emergence of new electric field peak; this optimizes the surface electric field of the new AlGaN/GaN HEMTs. Then the breakdown voltage is improved to 640 V in the new AlGaN/GaN HEMTs with the step AlGaN layer as compared with 446 V for the conventional structure. In order to let the breakdown curve consistent with the test results, a certain concentration of the acceptor-like traps is added to the GaN buffer to capture the leaking current coming from the source electrode. Simulation results verify the causes for doping acceptor type ions to the GaN buffer, given by foreign researchers. The breakdown curves have been obtained which are consistent with the test results in this paper.
Effect of magnetic capacitance in the Fe3O4 nanopartides and polydimethylsiloxane composite material
Authors: Li Sheng-Kun  , Tang Jun  , Mao Hong-Qing  , Wang Ming-Huan  , Chen Guo-Bin  , Zhai Chao  , Zhang Xiao-Ming  , Shi Yun-Bo  , Liu Jun  ,   Key Laboratory of Instrumentation Science and Dynamic Measurement, Ministry of Education, State Key Laboratory of Science and Technology on Electronic Test and Measurement, North University of China, Taiyuan 030051, China
Published: December 2020

In this paper, a parallel plate structure for the magnetic capacitor applications is presented, which consists of hybrid materials of Fe3O4 nanoparticles with polydimethylsiloxane (PDMS) as the dielectric medium. By changing the nanoparticle sizes and concentrations in PDMS, the magnetic-capacitance effect of the designed structure is investigated, and some key factors which may affect the performances are studied. It can be concluded from the results that a clear magnetic-capacitance coupling effect is observed by putting the designed Fe3O4 nanoparticles and PDMS hybrid material in or out of a magnetic field. Meanwhile, as we increase the concentration of the nanoparticles, an increase of capacitance variation may be observed. If the nanoparticle sizes are bigger than the critical dimension of the super-paramagnetic effect, the capacitance variations is increased as the nanoparticle size increases.
Terahertz absorption of graphene enhanced by one-dimensional photonic crystal
Authors: Xie Ling-Yun  , Xiao Wen-Bo  , Huang Guo-Qing  , Hu Ai-Rong  , Liu Jiang-Tao  ,   Department of Physics, Nanchang University, Nanchang 330031, China;,   School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China;,   Key Lab of Non destructive Test (Ministry of Education), Nanchang Hang Kong University, Nanchang 330063, China;,   Nanoscale Science and Technology Laboratory, Institute for Advanced Study, Nanchang University, Nanchang 330031, China
Published: December 2020

The terahertz (THz) radiation absorption of graphene layers in a pseudomagnetic field, prepared on top of a one-dimensional photonic crystal (1DPC), is investigated theoretically. Discrete Landau levels can be found in graphene in a pseudomagnetic field. Strong THz transitions may be found between the discrete Landau levels. The THz absorption of graphene can also be tuned by varying either pseudomagnetic field or the distance between the graphene and the 1DPC.
Study of mini-themionic electron sources for vacuum electron THz devices
Authors: Liang Wen-Long  , Wang Yi-Man  , Liu Wei  , Li Hong-Yi  , Wang Jin-Shu  ,   School of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

THz technology has attracted great attention for decades of years. Among the wide research areas of THz technologies, vacuum electron terahertz radiation sources have obvious advantages in high power region. For the THz vacuum electro devices (VED), high current density electron beams with small dimensions are required. Nanosized scandia doped dispenser (SDD) cathodes have the capability to operate stably at pulsed current densities of over 100 A/ cm2 at 950 ℃ so it becomes the most promising cathodes to meet the requirements for THz VEDs. In this paper, we report a new approach for developing miniaturized electron beam sources on normal SDD cathodes. An electron beam of 400 μm in diameter has been directly generated on an SDD cathode by deposition of a Zr/W double-layer anti-emission film and followed by a focused ion beam (FIB) milling. Results indicate that the electron beam is able to provide a space charge limited (SCL) current density of over 50 A/cm2 at the operating temperature of 950 ℃ with proper laminarity and works stably for more than 1000 hours. The beam emission characteristics and the function of the anti-emission film have been discussed and related to the surface analysis results. The approach opens a new way for producing high emission mini-electron sources to satisfy the requirment of THz VEDs.
Correlation between fracture mechanism and fracture toughness in metallic glasses
Authors: Wu Fei-Fei  , Yu Peng  , Bian Xi-Lei  , Tan Jun  , Wang Jian-Guo  , Wang Gang  ,   Chongqing Key Laboratory of Photo-Electric Functional Materials, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, China;,   Laboratory for Microstructures, Shanghai University, Shanghai 200444, China
Published: December 2020

Three metallic glasses Zr41.25Ti13.75Ni10Cu12.5Be22.5, Ce68Al10Cu20Co2 and Fe41Co7Cr15Mo14Y2C15B6(all in at.%), were compressed experimentally, and the fractured samples were investigated by scanning electron microscope. It was found that they exhibit different fracture modes. In three-point bending tests of the three pre-notched metallic glass samples, a digital speckle technique is adopted to in-situ observe the elastic strain field evolution in front of the crack tip. Accroding to the yield criterion of metallic glasses, the mechanism of different fracture processes in metallic glasses with various fracture toughnesses are elucidated.
Single-channel source separation of radar fuze mixed signal using advanced adaptive decomposition
Authors: Zhu Hang  , Zhang Shu-Ning  , Zhao Hui-Chang  ,   School of Electronic and Optical Engineering, NUST, Nanjing 210094, China;,   Unit 73015 of PLA, Huzhou 313000, China
Published: December 2020

An advanced method of signal decomposition-advanced adaptive chirplet decomposition(AACD) is presented to separate the radar fuze mixed signal in single-channel. The method adds curvature factor to the adaptive Gauss chirplet decomposition (AGCD), thus it can be used to decompose nonlinear time varying components. It uses the fast algorithm and trust region method to optimize arithmetic process, then all the parameters can be solved accurately and quickly, and the mixed signal's time-frequency distribution without cross terms is obtained. In the simulation, the advanced method is used to improve the time-frequency distribution of complex mixed signals, then it can separate all the components and calculate the mixing coefficients. Results indicate that the proposed method has higher effectiveness and strong performance of anti-noise
Symmetry in the vibration spectrum of complicated molecule
Authors: Yang Li-Hua  , Yang Bo-Jun  ,   School of E-learning (Continuing Education), Beijing University of Posts and Telecommunications, Beijing 100088, China;,   School of Sciences, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

The vibration spectra of complicated molecule are generally divided into group frequency and ridge frequency. The ridge frequency has a certain symmetry in the vibration spectra of some complicated molecules, such as the ridge frequency of malachite green isothiocyanate (MGITC) molecule which is a molecular probe and has a U(5) symmetry. In this article the U(5) symmetry of molecular vibration spectrum is introduced and tested for its fitting to the low excitation spectrum of MGITC, we find that the theoretical value conforms to the experimental results.
A new method to obtain first order approximate conserved quantities of second-ordinary dynamics system containing nonlinear perturbation terms
Authors: Lou Zhi-Mei  ,   Department of Physics, Shaoxing University, Shaoxing 312000, China
Published: December 2020

We consider the perturbed system as the combination of unperturbed system and perturbed term according to the characteristic of the first order approximate conserved quantities, and we suggest a new method to obtain the first order approximate conserved quantities by three steps: first, we select a suitable method to obtain the conserved quantity I0 of unperturbed system, second, we calculate the influence of perturbed terms on conserved quantity I0, and finally we obtain the first order approximate conserved quantities of the system by using the characteristic of the first order approximate conserved quantities. An actual two-dimensional nonlinear dynamics perturbed system is studied in this paper, and four stable first order approximate conserved quantities are obtained by using this new method. The expressions of first order approximate solution of the system are also obtained by transforming coordinates and using the perturbation method, and four special cases are discussed in this paper.
Asymptotic expressions of path curve for a class of Fermi gases in nonlinear disturbed mechanism
Authors: Shi Lan-Fang  , Chen Xian-Feng  , Han Xiang-Lin  , Xu Yong-Hong  , Mo Jia-Qi  ,   College of Mathematics and Statistics, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   Department of Mathematics, Shanghai Jiaotong University, Shanghai 200240, China;,   Department of Mathematics, Huzhou Teachers College, Huzhou 313000, China;,   Department of Mathematics and Physics, Bengbu College, Bengbu 233030, China;,   Department of Mathematics, Anhui Normal University, Wuhu 241003, China
Published: December 2020

The model of nonlinear disturbed mechanism for one-dimensional Fermi gas is investigated. Firstly, the corresponding functional is constructed; secondly, its Lagrange operator is selected; using the modified generalized variational iteration method, the approximate analytic solutions of corresponding path curves are obtained. A simple example is given, and the approximation accuracy obtained by using the modified generalized variational iteration method is shown to be better. The aim of this article is to provide a valid method of solving the nonlinear physical problems.