bluuebunny/crossref_metadata_2025 huggingface dataset:
Chaotic time series prediction using filtering window based least squares support vector regression
Authors: Zhao Yong-Ping  , Zhang Li-Yan  , Li De-Cai  , Wang Li-Feng  , Jiang Hong-Zhang  ,   Zndy of Ministerial Key Laboratory, Nanjing University of Scinece and Technology, Nanjing 210094, China;,   State Owned 121 Factory, Mudanjiang 157013, China
Published: December 2020

When the traditional strategy of sliding window (SW) deals with the flowing data, the data far from current position are mechanically and briefly moved out of the window, and the nearest ones are moved into the window. To solve the shortcomings of this forgetting mechanism, the strategy of filtering window (FW) is proposed, in which adopted is the mechanism for selecting the superior and eliminating the inferior, thus resulting in the data making more contributions to the will-built model to be kept in the window. Merging the filtering window with least squares support vector regression (LSSVR) yields the filtering window based LSSVR (FW-LSSVR for short). As opposed to traditional sliding window based LSSVR (SW-LSSVR for short), FW-LSSVR cuts down the computational complexity, and needs smaller window size to obtain the almost same prediction accuracy, thus suggesting the less computational burden and better real time. The experimental results on classical chaotic time series demonstrate the effectiveness and feasibility of the proposed FW-LSSVR.
Design and analysis of new spectroscopic system of Raman lidar for detection of atmospheric water vapor
Authors: Wang Hong-Wei  , Hua Deng-Xin  , Wang Yu-Feng  , Gao Peng  , Zhao Hu  ,   School of Mechanical and Precision Instrument Engineering, Xi’an University of Technology, Xi’an 710048, China
Published: December 2020

A new ultraviolet Raman lidar system is proposed and developed for detecting atmospheric water vapor and aerosol study. The combination of dichroic mirrors and narrow-band interference filters is used as high-performance spectroscopic system to obtain the fine-separation and high-efficiency extraction of Mie-Rayleigh scattering signals, the vibrational Raman scattering signal of H2O and N2. By the American standard model and a set of atmospheric scattering signal model, the signal-to-noise ratio (SNR) and the water vapor measurement error are simulated and analyzed. The preliminary experiments are carried out at nighttime in Xi'an area for detecting the atmospheric water vapor and aerosols. Taking a set of the atmospheric returned signals measured under cloudy weather for example, the profiles of atmospheric backscatter ratio and water vapor mixing ratio are retrieved, and the SNR profiles of the three channels are discussed and verify that this configuration can achieve a high rejection rate (10-7) to Mie-Rayleigh scattering. The theoretical and experimental results show that water vapor detection error of less than 15% can be obtained under a backscatter ratio of 17, which demonstrates the feasibility of the system for the atmospheric aerosol and water vapor measurements.
First-principles study of field emission properties for ZnO nanotuber capped and codoped with N-M(Cd, Mg)
Authors: Wang Xin  , Wang Fa-Zhan  , Lei Zhe-Feng  , Wang Bo  , Ma Shan  , Wang Zhe  , Wu Zhen  ,   College of Material and Mineral Resources, Xi’an University of Architecture and Technology, Xi’an 710055, China;,   School of Mechanical and Electrical Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China;,   School of Material Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

The first-principles density-functional theoretical calculations are performed to investigate the effects of N doped and N, M (Cd, Mg) codoped on the geometrical structures and field emission properties of capped (9, 0) zinc oxide nanotubes (ZnONT). The results show that the N could improve the stability of the structure of capped side. With the increase of the applied electric field, the density of states (DOS) shifts towards the low energy position, the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap and the effective work function decrease drastically, and the electrons congregate to the capped side. The analyses of DOS/local DOS, HOMO/LUMO, and Mulliken population indicate that the field emission properties of N, Cd-Codoped ZnONT are improved, but those of N, Mg-codoped ZnONT are worsened.
Photodetached electron flux of H- in magnetic field near a metal surface
Authors: Tang Tian-Tian  , Zhang Chao-Min  , Zhang Min  ,   Department of Basic Education, Yantai Nanshan University, Yantai 265713, China
Published: December 2020

The photodetached electron flux of H- in magnetic field near a metal surface is studied with a semi-classical open theory, and the relation between the electron flux distribution and classical trajectory is also revealed. The electron flux distributions are calculated at various magnetic field strengths, with a ion-surface distance given. The results show that with the increase of magnetic field strength, the interference pattern in the flux distribution becomes much more complicated because the number of the classical trajectories of the detached electrons contributing to the electron flux distribution increases. In addition, we find that as the energy of detached electron changes, the detached-electron flux distribution changes accordingly. Therefore, the interference pattern in the detached-electron flux distribution can be controlled by adjusting the magnetic field strength and the energy of detached electron. Our study will provide a new understanding of photo-detachment microscopy of anion in external field and surface, and can be used to guide the future experimental research on the anion photo-detachment microscopy.
Voigt profile function and its maximum
Authors: Yin Zeng-Qian  , Wu Chen  , Gong Wan-Yu  , Gong Zhi-Ke  , Wang Yong-Jie  ,   Department of Mathematics and Physics, North China Electric Power University, Baoding 071003, China
Published: December 2020

The Voigt profile function which is the convolution of the Doppler and Lorentzian function is investigated analytically and its maximum is obtained. The results indicate that the maximum of the Voigt profile function is smaller than maxima of Doppler and Lorentzian profile function, which is determined by the half-widths of Doppler and Lorentzian profile function. The Voigt profile function is a symmetric function about the central frequency. A new technique is presented, with which the Doppler and Lorentzian profile function can be obtained by using the maximum and half-width of the Voigt profile function, and the technique is verified by the Monte Carlo method.
Design of ultra-thin broadband metamaterial absorber and its application for RCS reduction of circular polarization tilted beam antenna
Authors: Li Si-Jia  , Cao Xiang-Yu  , Gao Jun  , Liu Tao  , Yang Huan-Huan  , Li Wen-Qiang  ,   Information and Navigation College, Air Force Engineering University, Xi’an 710077, China
Published: December 2020

In order to reduce the radar cross section (RCS) of antenna, a wideband-enhanced ultra-thin metamaterial absorber is designed by reducing the distance between the two absorption peaks due to the double resonances. The absorber is composed of two metallic layers separated by a lossy dielectric spacer. The top layer consists of a single-square loop with four splits on the four sides and a square metal patch in the center and the bottom one is of a solid metal. A dipole resonance and an LC resonance are caused by the structure of the metamaterial absorber. By fine adjusting geometry parameters of the structure, we can obtain a polarization-insensitive and wide-incident-angle ultra-thin absorber whose absorption values are 91.6% and 96.5%. On condition that thickness is less than 0.01λ the absorber has a full-width at half-maximum of 8.2%. The absorber is applied to the circularly polarized tilted beam antenna for reducing RCS. Simulated and experimented results show that the RCS reduction of antenna is above 3 dB within the operation band from 5.5 GHz to 6.5 GHz, the gain is not changed and the bandwidth is increased due to the improvement of axial ratio. At the resonance, the most reduction values exceed 8 dBsm and 11 dBsm while the absorber has a good characteristic of RCS reduction at the boresight direction from -36° to +36°.
Study on remote sensing of carbon dioxide column concentration in the atmosphere by direct-sun infrared absorption spectroscopy
Authors: Cheng Si-Yang  , Xu Liang  , Gao Min-Guang  , Jin Ling  , Li Sheng  , Feng Shu-Xiang  , Liu Jian-Guo  , Liu Wen-Qing  ,   Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The concentration of carbon dioxide in the atmosphere has been increasing continuously. This is a big concern with respect to the environment and climate changes and so on. A kind of ground-based low-resolution remote sensing system and a real-time spectral inversion method are presented for the real-time remote sensing column concentration of carbon dioxide. Based on continuous observation of this system in Hefei, the total atmospheric transmittance is real-timely obtained from the solar absorption spectrum. The column concentrations of carbon dioxide and oxygen are inversed from total atmospheric transmittance by line-by-line nonlinear least squares spectral inversion algorithm. The column concentration of oxygen is used as internal standard function to obtain the column average volume mixing ratio of carbon dioxide in total dry air column, and the precision is better than 3%.The average volume mixing ratio of carbon dioxide in dry-air column, from 12: 00 to 15:00 on September 25, 2012, is compared with observation results by Japanese greenhouse-gases satellite over the site in this period, showing that the relative deviation is less than 1%. Obviously, it is an effective way to measure greenhouse gases concentration with high precision and accuracy.
Study on measuring the exposure of sound samples in subjective experiments
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

The traditional measurements for environmental noise exposure-dose are inapplicable to the sound samples with fixed playing duration used in subjective evaluation experiment. In this paper, we propose a method for exposure-dose measurement of sound samples with fixed duration. The method based on the short-term exposure-dose values during the playing time of the sound samples. An entire analysis on the potential influencing factors are carried out, including the short-term analysis period, the statistical properties of the short-term exposure-dose values and four different frequency weightings. Then 11 indices are used to measure the exposure-dose of the fixed duration sound sample, which lays the groundwork for establishing the dose-annoyance relationships via subjective evaluating experiments.
Numerical simulation of deformation process of viscous liquid drop based on the incompressible smoothed particle hydrodynamics
Authors: Qiu Liu-Chao  ,   Department of Applied Mechanics, China Agricultural University, Beijing 100083, China
Published: December 2020

A projection-based incompressible smooth particle hydrodynamics (ISPH) is applied to the simulation of the deformation process of viscous liquid drop. In our numerical computation, the particle shifting technique is used to overcome particle clustering due to the tensile instability in SPH. In order to verify the proposed ISPH, numerical simulations of a viscous circle drop stretching and a viscous square drop rotating are carried out. The pressure distribution in the drop is obtained, and the deformation process of viscous liquid drop is correctly captured. Comparisons between numerical results and the analytical solutions in the literature are presented. The simulation results show that the projection-based ISPH with particle shifting technique can be used to simulate the deformation process of viscous liquid drop with stability and accuracy.
Simulation studies on fluid density distribution of micro-flows in a nano-channel
Authors: Hu Hai-Bao  , Bao Lu-Yao  , Huang Su-He  ,   College of Marine, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

The flow in microchannel involves many microscale effects, because of its large ratio of superficial area to volume. And it further causes the density profiles of flow in microchannel to be greatly different from in the macro-channel. In this paper we investigate the effects of three factors (εLL, σLL, σLS) on density profile of micro-flow via the Poiseuille flow in a nanochannel using none-equilibrium molecular dynamics simulation method. In our study, we selected NVE as the statical ensemble, LJ/126 model as the potential energy function. We also adopt the Rigid-atom model to describe the wall and the temperature thermostat through using the time/rescale methods. The motion equations are solved using Verlet algorithm. The results show that as the interaction between flow atoms decreases, the oscillation degree of density profiles near the wall increases. The balance distance (σLL) between flow atoms affects the existence state and density profiles of flow in the micro channel: the greater σLL causes the flow atoms to be arranged as the fcc structure liking a solid, while smaller σLL results in the flow atoms moving as a changeable "cluster". The balance distance (σLS) between wall atoms and flow atoms also has a significant influence on flow density. As σLS increases, the oscillation degrees of density profile near the wall and the distance between the starting point of density profile and wall increase. Besides, we analyze the mechanism of effects of the interaction between the flow atoms on density distribution based on the "capture-escape " behavior of atoms adjoining the wall.
Comparative analysis of quantitative method on heavy metal detection in water with laser-induced breakdown spectroscopy
Authors: Wang Chun-Long  , Liu Jian-Guo  , Zhao Nan-Jing  , Ma Ming-Jun  , Wang Yin  , Hu Li  , Zhang Da-Hai  , Yu Yang  , Meng De-Shuo  , Zhang Wei  , Liu Jing  , Zhang Yu-Jun  , Liu Wen-Qing  ,   Key Laboratory of Environment Optics and Technology, Institute of Anhui Optics Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The quantitative analysis models of multiple linear regression, neural network regression and support vector machine regression with laser-induced breakdown spectroscopy are established in this paper. Heavy metal Ni in water selected as research object is tested and comparativly analyzed. The average relative standard deviations of multiple linear regression, neural network regression and support vector machine regression are 7.60%, 4.86% and 2.35%, and the maximum standard deviations are 23.35%, 15.20% and 8.29% respectively, the average relative errors are 25.98%, 10.58% and 2.72%, and the maximum relative errors are 116.47%, 47.38% and 9.89% respectively. Methods and reference data are provided for the further study of fast measurement of tracing heavy metals in water by laser induced breakdown spectroscopy technique.
Experimental studies on the opacity of dense aluminum compressed by a laser-driven shock waves
Authors: Wang Rui-Rong  , Wang Wei  , Fang Zhi-Heng  , An Hong-Hai  , Jia Guo  , Xie Zhi-Yong  , Meng Xiang-Fu  ,   Shanghai Institute of Laser Plasma, Shanghai 201800, China
Published: December 2020

The high-precise opacity of the dense plasma has important applications in the design and simulation of fusion research, and in plasma diagnostics. Base on the novel technique of point-projection backlighting, a broadband high-resolution elliptical crystal X-ray spectrometer, which is used to measure simultaneously the self-emission spectrum, the backlighting source spectrum, and the transmission spectrum in one shot, is designed on the Shengguang-II laser facility. The process of the colliding-shock-compressed sample by laser-driven shock waves is also investigated using a one-dimensional radiation hydrodynamics code MULTI. In the measurement, the dense plasma, produced in aluminum by colliding shocks driven by laser beams, reaches a peak density several times that of a solid, and the short backlighting from the 3d-4f transition bands of ytterbium is used as an absorption source for time- and space-resolving diagnostics. Several experimental results are obtained, they are the X-ray source spectrum, the transmission spectrum, and the self-emission spectrum of the dense Al sample in one shot obtained by using the point-projection method, as well as X-ray-absorption fine-structure spectra, and the changes in the K-shell photo-absorption edge of aluminum as it was compressed by a laser-driven shock waves. The transmissivity distribution and red- shift around 80 m (with respect to the cold value of 1.56 keV) of the dense aluminum are also obtained. The data obtained are further analysed. As a result, a new theoretical model is developed.
Simulation of 0.14 THz relativistic backward-wave oscillator filled with plasma
Authors: Wang Yu  , Chen Zai-Gao  , Lei Yi-An  ,   School of Physics, Peking University, Beijing 100871, China;,   Northwest Institute of Nuclear Technology, Xi'an 710024, China
Published: December 2020

In this paper, a 0.14 THz relativistic backward-wave oscillator (RBWO) filled with neutral argon gas is simulated by using the UNIPIC code. The effects of plasma on the output power, frequency, and the start-oscillation time of the RBWO filled with different-pressure gases are studied. The simulation result shows that the background plasma can cause the pulse-shortening and new frequency appearing in the 0.14 THz RBWO. Appropriate plasma infusion can reduce the start-oscillation time and increase the output power of 0.14 THz RBWO.
Enhanced optical transmission through metallic slits embedded with rectangular cavities
Authors: Qin Yan  , Cao Wei  , Zhang Zhong-Yue  ,   School of Physical Science and Technology, Southwest University, Chongqing 400715, China;,   School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China
Published: December 2020

The non-resonantly enhanced optical transmission phenomenon of sub-wavelength metallic slits on a thin film is significant for broadband light harvesting devices. To improve the efficiency of transmission, in this paper, we propose a compound structure of the tapered metallic slit embedded with rectangular cavity, and its optical properties are investigated by the finite element method. The results show that the compound structure leads to a higher transmission than the tapered metallic slit without rectangular cavity. In addition, the effects of the structure parameters and the position of the rectangular cavity on the transmission property are also studied. These results would be helpful for designing metallic slits with high transmission.
Interaction and assembly of non-magnetic spheres and magnetic nanoparticles dispersed in magnetic fluid
Authors: Deng Hai-Dong  , Li Hai  ,   Department of Applied Physics, College of Science, South China Agricultural University, Guangzhou 510642, China
Published: December 2020

In this paper, we systematically investigate the dynamics of non-magnetic spheres (polystyrene spheres) and magnetic nanoparticles dispersed in Fe3O4 magnetic colloid under an externally applied magnetic field. It is found that the polystyrene spheres form chain-like structures when the direction of magnetic field is parallel to the sample cell. The whole dynamic process of polystyrene spheres in the magnetic field can be characterized by a fast interaction between polystyrene spheres and magnetic nanoparticles and a slow interaction among polystyrene chain-like structures respectively. When a magnetic field is applied in the direction perpendicular to the sample cell, polystyrene spheres can be assembled into a short-range ordered two-dimensional structure due to the repulsive interaction among polystyrene spheres. Once the applied magnetic field excesses a critical level, a flower-shaped complex structure can be formed due to the attractive interaction between the polystyrene sphere and the magnetic cluster.
Random field effect of polarization and dielectric permittivity in ferroelectric transitions
Authors: Gan Yong-Chao  , Cao Wan-Qiang  ,   School of Physics and Electronic Engineering, Hubei University, Wuhan 430062, China;,   School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
Published: December 2020

Based on reversion motion of dipoles in ferroelectrics under the electric field in the random field Ising model, the relationship between electric field and polarization in order-disorder transition is investigated, and the function tanh(x) for the electric field in order-disorder transition is coincident with the experimental relationship between electric field and polarization in the second order ferroelectric transition. Therefore, increases in polarization and internal poling field are due to the collective motion of dipoles, where electric field and temperature are critical in the polarization and Gibbs free energy. By distinguishing the contributions between optic mode and polarization portion with a gaussian-type distribution of Curie-temperature, and considering a complex dispersion form of dielectric permittivity contributed by dipoles, the relationships between dielectric permittivity and temperature, as well as frequency, are derived.
Node importance measurement based on the degree and clustering coefficient information
Authors: Ren Zhuo-Ming  , Shao Feng  , Liu Jian-Guo  , Guo Qiang  , Wang Bing-Hong  ,   Complex Systems Science Research Center, University of Shanghai for Science and Technology, Shanghai 200093, China
Published: December 2020

The node importance measurement plays an important role in analyzing the robustness of the network. Most researchers use the degree or clustering coefficient to measure the node importance. However, the degree can only take into account the neighbor size, regardless of the clustering property of the neighbors. The clustering coefficient could only measure the closeness among the neighbors and neglect the activity of the target node. In this paper, we present a new method to measure the node importance by combining neighbor and clustering coefficient information. The robustness results measured by the network efficiency through removing the important nodes for the US Air network, the power grid of the western United States and Barabasi-Albert networks show that the new method can more accurately evaluate the node importance than the degree, neighbor information and k-shell indices.
A study on precipitation trend and fluctuation mechanism in northwestern China over the past 60 years
Authors: Dai Xin-Gang  , Wang Ping  , Zhang Kai-Jing  ,   Key Laboratory of Regional Climate-Environment for East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   Chinese Academy of Meteorological Sciences, Beijing 100081, China;,   Qingdao Meteorological Agency, Qingdao 266003, China
Published: December 2020

This paper focuses on the mechanism of the trend and oscillation in precipitation records in northwestern China over the past 60 years. The results from regression and orthogonal wavelet decomposition show a clearly ascending in annual precipitation since 2000, which is contributed mostly by significant increase in autumn and winter precipitations, while almost no trend can be identified in spring and summer time, which shows a weak descending in non-linear form. This may be in connection with different warming rates in seasons. There is a significant anti-correlation between the precipitation and the North Atlantic oscillation (NAO) on the inter-annual scale. About 80% of their variances concentrate on inter-annual and multi-decadal scales. The multi-decadal components of NAO index have a phase leading about 10 years to corresponding precipitation, about 4-5 years leg for AMO. Hence, NAO index can be used as an indicator for inter-decadal change of the precipitation. Other results from combination-difference analysis show that the NAO in extreme negative phase could lead to the precipitation increase in central Asia and northwestern China, owing to increase in eastward water-vapor transport from south Europe to Northwestern China, which causes an increase in column water vapor content in the above areas, and meanwhile the transient eddy activity becomes intensified in the areas or north with a further south route moving from Europe, Central Asia throughout northwestern China. On the contrary, a dry climate might appear in the areas when meet extreme positive phase of NAO. Thus, NAO's oscillation is one of the most important mechanisms for inter-annual change in precipitation of northwestern China.
Research on the method of variational fusion of altimeter wind speed and radiometer wind speed
Authors: Jiang Zhu-Hui  , You Xiao-Bao  , Xiao Yi-Guo  ,   Beijing Institute of Applied Meteorology, Beijing 100029, China
Published: December 2020

In order to realize the fusion of altimeter wind speed and radiometer wind speed, the Kriging method is used to interpolate radiometer wind speed to the altimeter path to obtain the altimeter wind speed observation operator, a cost function is established, and then the variational method is adopted to construct and analyze wind speed and derive fusion results. Simulation tests are carried out when only altimeter wind speed contains error, only radiometer wind speed contains error, both altimeter and radiometer wind speed contain error. The results show that through the variational fusion, the accuracy is improved, especially in the altimeter path. The Jason-1 altimeter cycle 241 wind speed data and spatial temporally matched Special Sensor Microwave Imager Sounder wind speed data (carried by Defense Meteorological Satellite Program F17) are selected to carry out the real test, and the results show that the fused wind speed is more close to the buoy observation, so it is confirmed that the variational fusion method is effective, statics shows that 60% altimeter and radiometer data matched, which means that fusion is an important theory and has application value. The variational fusion method can be applied to the fusion of HY-2 satellite altimeter and radiometer wind inversion results.
Analysis on periodic variations of the radio flux of OJ 287 with ensemble empirical mode decomposition
Authors: Tang Jie  ,   School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001, China
Published: December 2020

BL Lacertae object OJ 287 is one of the Blazars, which shows convincing evidence of periodic variations. We have collected the 4.8, 8.0 and 14.5 GHz data for OJ 287 from the University of Michigan Radio Observatory database over three decades. Due to the complexity of the variability data, some algorithms for period searching are not ideal yet. An alternative to traditional periodicity analysis is the ensemble empirical mode decomposition (EEMD). This method can analyze the cyclic components of complicated nonlinear and non-stationary processes. Using the EEMD analysis, the light curve of OJ 287 at radio frequency can be resolved into six independent intrinsic mode functions that have different average periods and trends. We find possible periods of 18.9, 11.9, 5.7 and 2.4 years in 4.8 GHz, 12.2 , 5.2 and 2.4 years in 8.0 GHz and 21.8, 12.0, 4.3 and 2.4 years in 14.5 GHz. The most common periods are 12.0 years and 2.4 years, which imply that the emissions in these bands may originate from the same radiative process. The results also confirm that a radio variability period of OJ 287 is in agreement with the optical variability period of about 12.0 years. The result shows that the components of different variability periods can be separated properly with the EEMD that is a nonlinear and non-stationary signal processing method.
Node influence calculation mechanism based on Bayesian and semiring algebraic model in social networks
Authors: Zhao Jia  , Yu Li  , Li Jing-Ru  ,   Wuhan Natlonal Lab of Optoelect ronics, Wuhan 430074
Published: December 2020

In social networks, many applications and spreading depend on the nodes with high influence to do viral marketing, which indicates that nodes' influence should be measured in a comprehensive and reasonable way. The appearance of fake fans results in change of network topology and brings new challenge to topology-based traditional methods. This paper incorporates both the network topology and interactions among nodes into our new distribution mechanism of node influence calculation in social networks. Considering the similarity of node behaviors in time domain and several key factors, this paper presents by a discounted Bayesian model for direct influence between nodes at first. Then a semi-ring-based aggregation implements for indirect influence and the composite influence are obtained by the combination of both direct and indirect influences. Simulation shows that this mechanism not only performs well against fake fans attack and restrains the fluctuation of nodes' influence, but also spreads to more nodes when we choose several nodes with high influence under our method to be source nodes.
An algorithm of equivalent curcuit of FDTD and its application to designing metamaterial structure
Authors: Liu Li-Guo  , Wu Wei-Wei  , Wu Li-Lin  , Mo Jin-Jun  , Fu Yun-Qi  , Yuan Nai-Chang  ,   School of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China;,   Dept. of Basic Courses, Bengbu Automobile NCO Acade, Bengbu 233011, China
Published: December 2020

A novel finite-difference time domain (FDTD) algorithm named equivalent circuit FDTD (EC-FDTD) is realized, which introduces lumped elements from transmission line theory into Yee cell. It includes lumped elements such as series inductance and shunt capacitance in the right-handed materials, as well as shunt inductance and series capacitance in the left-handed materials. Due to its promising physical thoughts, it can be easily generalized to arbitrary dispersive materials including frequency selective surfaces and metamaterials. The technology of streaming single-instruction multiple-data (SIMD) extensions (SSE) was proposed by Intel and is currently utilized in personal computers. SSE is a kind of parallel speedup technology in one core. The speedup can be achieved four times in principle without changing hardware. Combined with SSE, the EC-FDTD can be apparently accelerated. Twice speedup is achieved in the tests of this paper. The algorithm of EC-FDTD is utilized to design the wideband metamaterials absorbers by employing the single square and double square loops loaded with the lumped resistors. The invisible radome has a great impact on reducing the radar cross section of the antenna out of band. The radome is designed with operating frequency to be 1 GHz and the absent bandwidth from 3 GHz to 9 GHz by the algorithm. And then these prototypes are fabricated and measured. From the comparative results, the correctness of EC-FDTD and the speedup of the SSE are both verified.
Simulation of the projectile dynamics in granular media
Authors: He Ke-Jing  , Zhang Jin-Cheng  , Zhou Xiao-Qiang  ,   School of Computer Science and Engineering, South China University of Technology, Guangzhou 510641, China
Published: December 2020

The three-dimensional (3D) dynamics of a projectile in granular media is simulated using DEM (discrete element method). Periodic boundary conditions are adopted, and the effects of gravity, contact forces, damping and friction are taken into account. The 3D simulation results fit the experiment results very well. Simulation results show that the heaver the projectile, the deeper the penetration depth. The impact depth grows linearly when the projectile quality increases. And when the density of granular media decreases, the penetration depth also increases. Splash of granular particles is also observed in the impact simulation.
Self-trapping and periodic modulation of beam propagation in semiconductor photorefractive medium
Authors: Xing Yao-Liang  , Yang Zhi-An  ,   School of Physics and Technology, University of Jinan, Jinan 250022, China
Published: December 2020

We have deduced a two-level form of beam evolution in photonic lattices of semiconductor photorefractive medium and its classical canonical form of the two-level equation. We analytically calculate the fixed points of the classical canonical aligns, analyze its stability and calculate the critical value of topology changes. According to the classical canonical form of the two-level equation, we make space phase diagram, further analyze the self-trapping of beam propagation in semiconductor photorefractive medium and find two kinds of self-trapping: 1) Both the population difference and the relative phase in energy levels oscillate near an equilibrium point in the phase space. 2) The population difference in energy levels oscillate near an equilibrium point while the relative phase increases monotonously. From the three aspects of high frequency, low frequency, and intermediate frequency, we investigate how an external periodic field influences the self-trapping and find that the external high frequency periodic field may dramatically modulate the critical points at which the transition to self-trapping occurs. It makes the self-trapping occur with small nonlinear effect when the beam propagates in semiconductor photorefractive medium.
Quantum key distribution system based on combined modulation
Authors: Guo Bang-Hong  , Yang Li  , Xiang Chong  , Guan Chong  , Wu Ling-An  , Liu Song-Hao  ,   Laboratory of Nanophotonic Functional Materials and Devices School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510631, China;,   State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing 100093, China;,   Laboratory of optical physicas, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
Published: December 2020

We suggest a combined modulation quantum key distribution (QKD) system which encodes each single-photon signal with both phase modulation and polarization modulation. With the aid of dual-velocity protocol of hybrid QKD system, we construct a scheme to realize this combined modulation QKD which generates two-bit key with one signal for increasing the efficiency of QKD. We also develop a combined modulation Michelson QKD system, then solve the stability problem of the combined modulation QKD system in principle.
Synchronization of chaotic systems with variable coefficients
Authors: Niu Hong  , Zhang Guo-Shan  ,   School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

In this paper, a novel method, to synchronize two identical or different chaotic/hyperchaotic systems with variable coefficients, is proposed based on the strictly positive real transfer function matrix. By adding a synchronization controller to the response system, the nonlinear parts of the error system derived from the synchronized systems are identified as the inputs of the error system, and the error state variables are identified as the outputs of the error system. Then the transfer function matrix of the error system can be strictly positive real. As a result, the error system can be asymptotically stable at the origin, i.e., the two chaotic/hyperchaotic systems can reach stable synchronization. Moreover, the designed synchronization controllers are linear, clear in parameter selections and robust to the changes of the coefficients of the error system. The specific design processes of the synchronization controllers and the corresponding results are presented in the paper. Also, the numerical simulation results are given to verify the feasibility and effectiveness of this method.
A model for rp-process within the (p,)-(,p) equilibrium approximation and its application
Authors: Zhang Jia-Ming  , Xu Xiao-Dong  , Sun Bao-Hua  ,   School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, China;,   Department of Physics, Beijing Normal University, Beijing 100875, China;,   International Research Center for Nuclei and Particles in the Cosmos, Beijing 100191, China
Published: December 2020

Many of the stable nuclei at the neutron-deficient side of the beta-stability valley cannot be synthesized in the neutron-capture processes. The origin of the so-called p-nuclei has been a long standing question in the nuclear astrophysics. The rapid-proton capture process (rp-process) proposed in the 1980s was one of the possible mechanisms to be responsible for some light p-nuclei. In this work, a model for rapid-proton capture process (rp-process), within the (p,)-(,p) equilibrium approximation, is established. In the framework of this model, the influence of astrophysical conditions (i.e., proton number density, temperature, and proton irradiation time) on the rp-abundance pattern is investigated. In addition, the recent-measured mass data of neutron-deficient atomic nuclei by using the storage ring mass spectrometry at IMP, Lanzhou, are employed in our calculation. It is found that the abundance at A=41 is increased by two orders of magnitude when using the new by determined mass of 41Ti, while the uncertainty of the computed abundance is reduced by almost two orders of magnitude.
Eye gaze tracking based on dark pupil image
Authors: Zhang Tai-Ning  , Meng Chun-Ning  , Liu Run-Bei  , Chang Sheng-Jiang  ,   Institute of Modern Optics, Nankai University, Tianjin 300071, China
Published: December 2020

The accurate localization of iris center is difficult since the outer boundary of iris is often occluded significantly by the eyelids. In order to solve this problem, an infrared light source un-coaxial with the camera is used to produce dark pupil image for pupil center estimation. Firstly, the 3D position of the center of cornea curvature, which is used as translational movement information of eyeball, is computed using two cameras and the coordinates of two cornea reflections on the cameras' imaging planes. Then, the relative displacement of pupil center from the projection of the cornea curvature center on 2D image is extracted, describing the rotational movement of the eyeball. Finally, the feature vector is mapped into coordinates of gazing point on the screen using artificial neural network. As for the eye region detection problem, two wide-view webcams are used, and adaptive boosting+active appearance model algorithm is adopted to limit the region of interest within a small area. The result of our experiment shows that the average root-mean-square error is 0.62 in horizontal direction and 1.05 in vertical direction, which demonstrates the effectiveness of our solution in eye gaze tracking.
Movement of a droplet on a structured substrate: A dissipative particle dynamics simulation study
Authors: Yao Yi  , Zhou Zhe-Wei  , Hu Guo-Hui  ,   Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai Key Laboratory of Mechanics in Energe Engineering, Shanghai 200072, China
Published: December 2020

The last decade has witnessed the explosive development of microfluidic systems. Droplet manipulation is one of the crucial technologies in design and optimization of microfluidic devices. In the present study, dissipative particle dynamics is applied to investigate the movement of a liquid droplet actuated by a constant force on structured substrate with different wetting properties ranging from hydrophilic to hydrophobic. By monitoring the variation of the advancing contact angle and the front position of droplet, the characteristics of the droplet motion is analyzed in detail. Results indicate that there exists an optimal structure for which the droplet has a largest speed. Additionally, the influences of wettability gradient, thermal fluctuation and external force are discussed. We find thermal fluctuation is helpful for the movement of droplet.
The use of T-matrix method for determining coagulation rate of colloidal particles in light scattering measurement
Authors: Mi Li  , Zhou Hong-Wei  , Sun Zhi-Wei  , Liu Li-Xia  , Xu Sheng-Hua  ,   Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;,   College of Chemistry, Chemical Engineering and Material Science, Shandong Normal University, Jinan 250014, China
Published: December 2020

The coagulation rate is an important parameter for colloids, which is very useful for evaluating the colloidal stability. Both static light scattering and dynamic light scattering are commonly used methods for measuring the coagulation rate. By using these methods, the light scattering properties of single particles and aggregates of two particles are needed. Therefore, one may need both the static and dynamic light scattering data to avoid the calculation of the relevant scattering properties. Usually, when only static or dynamic light scattering data are available, various approximations are used to solve the problems related to the light scattering properties of particles and aggregates. However, due to the limitation of size and shape of colloidal particles in these approximations, the results were not always satisfactory. Since the T-matrix method can be used to precisely calculate the characteristic of light scattering without approximation of particle size or shape, we use this method in the determination of coagulation rate in static or dynamic light scattering measurement in this study. The comparison of our results with those measured by simultaneous static and dynamic light scattering method confirms that the T-matrix method is suitable for the light scattering measurement of coagulation rate. Therefore, this study simplifies the coagulation rate measurement by light scattering methods and extends their applications.
Enhanced flux pinning in MOD-YBCO films with co-doping of BaCeO3 and Y2O3 nanoparitcles
Authors: Ding Fa-Zhu  , Gu Hong-Wei  , Zhang Teng  , Wang Hong-Yan  , Qu Fei  , Peng Xing-Yu  , Zhou Wei-Wei  ,   Key Laboratory of Applied Superconductivity, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Enhancing the critical-current density of YBCO films is essential to gain a deeper understanding of the vortex pinning mechanisms and enable commercial applications of high-temperature superconductivity. Combined BaCeO3 and Y2O3 nanoparticles have been achieved to be co-doped in YBa2Cu3O7-x (YBCO) films by metalorganic deposition using trifluoroacetates (TFA-MOD). The formation of integrated nanoparticles increases the critical current density (Jc) of Y2O3/BaCeO3 doped-YBCO films while keeping the critical transition temperature (Tc) close to that in the pure YBCO films. YBCO film containing BaCeO3 and Y2O3 showed Tc value of 91 K and Jc value of 5 MA/cm2 at self-field (0 T, 77 K). The strongly enhanced flux pinning over a wide range of magnetic field may be attributed to the combined BaCeO3 and Y2O3 created by optimized TFA-MOD conditions.
Luminescent properties and energy transfer in Ca4Y6 (SiO4)6F2: Ce3+, Mn2+ phosphor
Authors: Mi Rui-Yu  , Xia Zhi-Guo  , Liu Hai-Kun  ,   School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China
Published: December 2020

In this paper, a series of Ca4-xY5.95 (SiO4)6F2: 0.05Ce3+, xMn2+ phosphors with an apatite structure were synthesized by the high-temperature solid phase method; their photoluminescence properties and energy transfer behavior were investigated. The obtained phosphors exhibit a broad excitation band ranging from 200 to 375 nm and also broad emission bands with two peaks centered at 408 and 602 nm monitored at 325 nm excitation, which originate from 5d→4f transition of Ce3+ and 4T1 (4G)→6A1 (6S) transition of Mn2+, respectively. The energy transfer from Ce3+ to Mn2+ was confirmed by spectral overlap phenomenon and decay curve measurements. Based on the analysis of the energy level structure of Ce3+and Mn2+, the existence of the energy transfer from Ce3+→Mn2+ was further confirmed.
The effect of pressure on thermal decomposition of solid nitromethane via MD simulation
Authors: Zhang Li  , Chen Lang  ,   State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

The thermal decomposition of solid nitromethane (NM) is studied by ReaxFF molecular dynamics simulations to obtain the time evolution of the mechanism of NM under high temperature and pressure. It is determined that the initial decomposition mechanism of NM is dependent on pressure effect. In the 0–3 GPa pressure regime, the initial reactions is the C–N bond dissociation and the unimolecular rearrangement connecting between NM and methyl nitrite isomers; in the 4–7 GPa, the initial pathways of NM are the intermolecular proton transfer and C–N, C–O bond rupture. In the secondary reactions step, several fragments, like H2O, NO, NO2, HONO, play a role of catalysis. The product decomposition of NM contains many different structures of carbon clusters, and the configuration of cluster is dependent on pressure.
Timing equation in X-ray pulsar autonomous navigation
Authors: Zhou Qing-Yong  , Ji Jian-Feng  , Ren Hong-Fei  ,   State Key Laboratory of Geo-information engineering, Xi'an 710054, China;Xi'an Research Institute of Surveying and Mapping, Xi'an 710054
Published: December 2020

The timing equation is the basic theory of dealing with the observable data of pulsar. The pulse timing model is studied; the transformation equation of pulsar photon time of arrival in 1PN approximation is derived, the existing transformation equations are compared and analyzed; the transformation of the proper time from the spacecraft to TCB is also obtained. The process dealing with the observable data of RXTE is achieved by software, the pulsar period is estimated and pulse profile is replicated, the validity of timing equation is approved. The result of software is compared with that of Heasoft, the reason of difference between them is analyzed. Finally, the effects of the planet ephemeris error and the pulsar ephemeris error on data processing are achieved.
Pulsar signal detection based on S-transform
Authors: Wang Lu  , Xu Lu-Ping  , Zhang Hua  , Luo Nan  ,   School of Electronic Engineering, Xidian University, Xi'an 710071, China
Published: December 2020

In order to increase the detection speed and to improve the detection rate in low signal-to-noise ratio, a novel detection algorithm for pulsar integrated pulse profile is proposed based on S-transform. We prove that the local S-transform spectrum of Gaussian white noise follows chi-square distribution with two degrees of freedom in this paper, and based on this, threshold processing is operated on the S-transform power spectra of cumulative signal; then, the total energy of the time-frequency power spectral after threshold processing is accumulated to construct the detecting statistics to obtain the statistic decision. Moreover, the time-frequency power spectra after threshold processing can also be used to measure the time delay of pulsar signal. The simulation result verifies the effectiveness of the proposed method which is superior to a similar method based on the Gaussian distribution; in addition, it can give the time delay with a certain accuracy.