bluuebunny/crossref_metadata_2025 huggingface dataset:
A tracking algorithm based on orthogonal cubature Kalman filter with TDOA and FDOA
Authors: Lu Zhi-Yu  , Wang Da-Ming  , Wang Jian-Hui  , Wang Yue  ,   PLA Information Engineering University, Zhengzhou 450000, China
Published: December 2020

In a passive target tracking system, the position and velocity of a target can be estimated based on time difference of arrival (TDOA) and frequency difference of arrival (FDOA) received by different stations. But TDOA and FDOA equations are nonlinear, which make the target tracking become a nonlinear estimation problem. To solve the nonlinear estimation problem, the most extensive research algorithms are those of extended Kalman filter (EKF), particle filter (PF), unscented Kalman filter (UKF), quadrature Kalman filter (QKF), and cubature Kalman filter (CKF). But the existing algorithms all come up with shortcoming in some way. EKF only retains the first order of the nonlinear function by Taylor series expansion, which will bring large error. PF has to face the degeneracy phenomenon and the problem of large computational complexity. The standard UKF is easy to become divergence in a high dimensional state estimation. QKF is sensitive to the dimension of state, and the calculation is of exponential growth with the growth of dimension. Although CKF can effectively improve the shortcomings, the discarded error is proportional to the state dimension, which may be large in high dimensional state. In view of the above problems, this paper presents an orthogonal cubature Kalman filter (OCKF) algorithm. This algorithm reduces the sampling error by introducing special orthogonal matrix to change the method of cubature sampling based on CKF. It eliminates the dimension impact on the sampling error. In the absence of additional computation, it effectively improves the tracking precision. Simulation results show that, based on the TDOA and FDOA, compared with the EKF and CKF algorithms, OCKF algorithm can improve the tracking performance significantly.
Complex background model and foreground detection based on random aggregation
Authors: Bi Guo-Ling  , Xu Zhi-Jun  , Chen Tao  , Wang Jian-Li  , Zhang Yan-Kun  ,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   University of Chinese Academy of Science, Beijing 100049, China;,   QiMing Information Technology CO., LTD, Changchun 130033, China
Published: December 2020

In order to build a robust background model and improve the accuracy of the foreground object detection, we give a comprehensive consideration on the same location pixels of the relevance of time and the correlation of space with its adjacent pixels; and based on the classic ViBe of random algorithm ideas, a kind of complex background model and foreground detection method is proposed. Using the first n series of images to initialize the background model with the sample consistency principle, we can avoid the appearance of the “Ghost” phenomenon; and get the difference between each pixel and its multiple sample value in the background model, and then compute the sum and the average. The average shows the dynamic degree of the background point which is the corresponding pixel background of dynamic feedback information. We get the adaptive clustering threshold and adaptive updating threshold with the dynamic feedback to make random clusters realize the adaptability to dynamic background and combine the global disturbance threshold with the local pixel level judgment threshold to implement the immunity of illumination with slow changes, fast changes or sudden changes, so that we can segment the prospect target accurately. By selecting neighborhood pixels to update the neighborhood background randomly in terms of spatial information dissemination mechanism, a good detection effect is obtained in the case of camera shake. Through multiple sets of test data, experimental results show that this algorithm can significantly improve the adaptability and robustness of the background model such as dynamic backgrounds, illumination changes, and camera shake. The algorithm can well apply to the occasion of moving targets in infrared image detection, and expand its application range. Without any image preprocessing and morphological post-processing, the original detection accuracy of foreground is superior to other algorithms.
Theoretical study on spectroscopic properties and predissociation mechanisms of the electronic states of carbon monofluoride
Authors: Xing Wei  , Liu Hui  , Shi De-Heng  , Sun Jin-Feng  , Zhu Zun-Lü  , Lü Shu-Xia  ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China;,   College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The potential energy curves of twenty-five Ω states generated from the eleven Λ-S states (X2Π, a4Σ-, A2Σ+, B2Δ, 14Π, 12Σ-, 24Π, 14Δ, 14Σ+, 22Σ- and 24Σ-) of the carbon monofluoride are calculated using the internally contracted multireference configuration interaction approach with the Davidson modification (icMRCI+Q) in the correlation-consistent aug-cc-pV5Z and aug-cc-pV6Z basis sets, for the first time so far as we know. The spin-orbit coupling, core-valence correlation, and relativistic corrections are taken into account, and all the potential energy curves are extrapolated to the complete basis set limit by separately extrapolating the Hartree-Fock and correlation energies scheme. Based on the calculated potential energy curves, the spectroscopic parameters of the bound and quasibound Λ-S and Ω states are obtained, and a very good agreement with experiment is achieved. It demonstrates that the spectroscopic parameters of A2Σ+(1st well), 24Π Λ-S and the eleven Ω states reported here for the first time can be expected to be reliably predicted results. The 24Π quasibound state caused by avoiding crossings are found, and the important electronic configurations of the bound and quasibound Λ-S states near the equilibrium positions Re are given. Various crossings in curves of Λ-S states are revealed, and with the help of our computed spin-orbit coupling matrix elements, the predissociation mechanisms of the a4Σ- and B2Δ states are analyzed. Dissociation relationships and dissociation channels of the twenty-five Ω states also are given. The transition properties of the A2Σ+-X2Π transitions are finally predicted, and our computed Franck-Condon factors and radiative lifetimes match the available experimental results very well.
Properties of ground state and spectrum of CdSe in different external electric fields
Authors: Wu Yong-Gang  , Li Shi-Xiong  , Hao Jin-Xin  , Xu Mei  , Sun Guang-Yu  , Linghu Rong-Feng  ,   School of Physics and Electronic Science, Guizhou Normal College, Guiyang 550018, China;,   School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, China
Published: December 2020

Density functional theoretical (B3PW91) method with LANL2 DZ basis sets has been used to study the equilibrium structure, total energy, the highest occupied molecular orbital (HOMO) energy level, the lowest unoccupied molecular orbital(LUMO) energy level, energy gap, dipole moment, atomic charge distribution, infrared intensities of CdSe ground state molecule etc. in different intense electric fields. The excitation energy, wavelengths and oscillator strengths in ground state and the first nine different excited states are investigated by the time-dependent density functional (B3PW91) method in external electric fields. Results show that the excitation wavelength is in agreement with the experimental result and the excitation energy is close to the experimental data. With the increase of the external field, the bond length, electric dipole moment, infrared intensities are observed to decrease first, and increase afterwards. But the HOMO energy, LUMO energy, energy gap are seen to decrease. And the total energy and harmonic frequency are found to increase first, and then decrease. In addition, the external electric fields have significant effects on the excitation energy, wavelength and oscillator strengths of CdSe molecule.
Structure and potential energy function of PuNO molecules
Authors: Hao Dan-Hui  , Kong Fan-Jie  , Jiang Gang  ,   Xi’an University of Architecture and Technology, Hua Qing College, Xi’an 710043, China;,   Department of Basic Courses of Yancheng Institute of Technology, Yancheng 224051, China;,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
Published: December 2020

Density functional (B3LPY) method has been utilized to optimize the possible structures of PuN, PuO, NO and PuNO molecules using the contracted valence basis set (LANL2 DZ) for Pu atom, and the AUG-cc-pVTZ basis set for N and O atoms. It is shown that the ground state of the PuNO molecules has Cv (Pu-N-O) symmetry and the ground electronic state is 6-. The equilibrium nuclear distances for Pu-N and N-O bonds in the PuNO molecules are RPuN=0.22951 nm and RNO=0.12257 nm, and the dissociation energy is De=8.10537 eV. Furthermore, the other two metastable states of the PuNO molecules are also obtained, and the electronic states of the two configurations are 6- and A with Cv (Pu-O-N) and Cs (O-Pu-N) symmetry, respectively. Then the Murrell-Sorbie potential energy functions of the PuN, PuO and NO molecules have been simulated and the analytical potential energy function of the PuNO molecules has been derived using the many-body expansion theory. The contours of the potential energy functions reproduce exactly the most stable equilibrium structures, the two metastable state structures as well as the dissociation energy of the PuNO molecules. The molecular static reaction pathway, based on the potential energy function, is also discussed.
Temperature dependence of air- and N2-broadening coefficients in the v3 band of 13CH4
Authors: Ma Hong-Liang  , Su Ming-Guo  , Liu An-Wen  , Aurore Vicet  , Chen Wei-Dong  , Cao Zhen-Song  , Wang Gui-Shi  , Liu Qiang  , Gao Xiao-Ming  , Rao Rui-Zhong  ,   Key Laboratory of Atmospheric Composition and Optical Radiation, Anhui Institute of Optics & Fine Mechanics, Chinese Academy Sciences, Hefei 230031, China;,   Hefei National Laboratoryfor Physical Sciences at the Micro-scale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China;,   Université Montpellier 2, Campus St Priest; IES Institut d’Electronique et des Systémes, 860 rue de St Priest. 34095 Montpellier cedex 5, France;,   Laboratoire de Physicochimie de l’Atmosphe’re, Universite’ du Littoral Côte d’Opale, 189A, Av. Maurice Schumann, 59140 Dunkerque, France;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

By using a mid-infrared tunable diode laser and a home-made cooling cell, the N2- and air-broadening coefficients of 13CH4 have been measured at room and low temperatures around 3.38 μm. Four transitions are studied for the 13CH4 diluted with nitrogen and air at temperatures 296, 252, 213, and 173 K. Measurements at low temperatures allow the determination of the temperature dependent parameter of the collisional broadening coefficients. The line parameters are obtained by fitting the experimental profile to the Voigt line shape. The N2- and air-broadening coefficients increase with the drop of the temperature. The collisional broadening coefficients of N2 are always larger than those of air at the same temperature. These data support the remote sensing of the Earth and outer planet atmospheres. According to our knowledge, the line parameters are reported experimentally for the first time.
Investigation of Compton profiles of NO and C2H2
Authors: Ma Yong-Peng  , Zhao Xiao-Li  , Liu Ya-Wei  , Xu Long-Quan  , Kang Xu  , Yang Ke  , Yan Shuai  , Zhu Lin-Fan  ,   Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China;,   Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
Published: December 2020

The Compton profiles of nitric oxide and acetylene molecules have been determined at an incident photon energy of 20 keV. Compton profile measurements are carried out with the beamline BL15U1 at the Shanghai Synchrotron Radiation Facility (SSRF). A dedicated gas cell is used, in which diffuse scattering is effectively suppressed. By considering that the statistical accuracy of 0.2% at pz ≈ 0 is achieved, the Compton profiles of NO and C2H2 determined in this paper can serve as the experimental benchmark data. Furthermore, the density functional theory (DFT) and HF calculation for different basis sets are used to calculate the Compton profiles of nitric oxide and acetylene. It is found that the DFT calculations with the diffuse basis sets are closer to the experimental results, indicating that the electronic density distribution of nitric oxide is more diffuse. For acetylene, the HF calculation is of better agreement with the experimental result. To better understand Compton profiles, we have compared them with distributions of electron density by theoretical calculation. There are clear correspondences between them: diffuse distribution is related to the localized profile and complex structure in electron density distribution, which also shows a subtle structure in profile. The present Compton profiles of nitric oxide and acetylene molecules achieved by synchrotron radiation are the most accurate up to now, as far as we know.
Design and study of the elliptically cylindrical transparent concentrator based on transformation optics
Authors: Wang Hui-Bo  , Luo Xiao-Yang  , Dong Jian-Feng  ,   The Faculty of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211, China
Published: December 2020

The design of a novel elliptically cylindrical transparent concentrator with functions of both electromagnetic transparency and electromagnetic concentration is put forward based on the form invariance of Maxwell’s equations in different coordinate transformation and transformation optics theory, and through the design of material constitutive parameters (permittivity and permeability) to guide the electromagnetic wave propagation. The electromagnetic wave transparent body does not prevent the transmission of electromagnetic waves that can interact in the cloak. An electromagnetic wave concentrator is an electromagnetic device that controls the electromagnetic waves to focus on an area or at a point to realize the electromagnetic wave energy concentration according to the requirement when the electromagnetic waves are incident on the device. In this paper, the expressions of the relative permittivity and permeability tensors in every layer of the electromagnetic device are derived by compression transformation and extension transformation. Then full-wave simulations for the electromagnetic device are performed by using finite-element software. The distributions of z-component of the magnetic field for the electromagnetic waves incident from different directions are obtained. Simulation results confirm the validity of the design method and the constitutive parameter tensors. Finally, effect of electromagnetic loss on the performance of the device is also discussed. To a certain extent, the function of the device will be weakened when the electromagnetic loss increases gradually. The design method proposed in this paper provides a new approach that can be used to design other novel electromagnetic devices.
High speed bidirectional dual-channel chaos secure communication based on semiconductor ring lasers
Authors: Wang Shun-Tian  , Wu Zheng-Mao  , Wu Jia-Gui  , Zhou Li  , Xia Guang-Qiong  ,   School of Physical Science and Technology, Southwest University, Chongqing 400715, China
Published: December 2020

Chaos is a fascinating phenomenon of nonlinear dynamical systems, and optical chaos communication has been one of potential frontier techniques to implement secure transmission of information. In this paper a novel high-speed bidirectional dual-channel chaos secure communication system is proposed based on semiconductor ring lasers (SRLs). In this system, the time delay signatures in chaotic output of clockwise (CW) and counterclockwise (CCW) patterns from a driving SRL (D-SRL) are firstly suppressed by using the double optical cross-feedback frame. Then, the chaotic output of D-SRL is injected into two response SRLs (R-SRLs) to drive the corresponding CW and CCW patterns of R-SRLs that are synchronized and bandwidth enhanced simultaneously. Thus, a bidirectional dual-channel chaos communication could be built based on chaotic synchronization of the two R-SRLs. We theoretically investigated the chaotic characteristics of a D-SRL under double optical cross-feedback and the chaotic synchronization features between R-SRL1 and R-SRL2 under different driving conditions. Results show that the time delay signatures of CW and CCW patterns of D-SRL could be effectively hidden under proper feedback conditions. The bandwidths of CW and CCW patterns of the D-SRL could be enhanced significantly. Furthermore, high-quality isochronous synchronization between R-SRL1 and R-SRL2 can be realized by choosing appropriate injection strength and detuning frequency in D-SRL and R-SRLs. Finally, the communication performances of bidirectional dual-channel chaos secure communication based on this proposed system are preliminarily examined and discussed, and the simulated results demonstrate that for 10 Gbit/s message, the Q factor of decoded message could be maintained above 6 after 10 kilometers distance transmission.
Optimization of microsphere’s DQ product based on resonant micro-optical gyro
Authors: Liu Jian-Hua  , Tang Jun  , Shang Cheng-Long  , Zhang Wei  , Bi Yu  , Zhai Chen-Ting  , Guo Ze-Bin  , Wang Ming-Huan  , Guo Hao  , Qian Kun  , Liu Jun  , Xue Chen-Yang  ,   Key Laboratory of Instrumentation Science and Dynamic Measurement, Ministry of Education; Science and Technology on Electronic Test & Measurement Laboratory, North University of China, Taiyuan 030051, China
Published: December 2020

Based on the development of high sensitivity, low cost, high integration and miniaturization demand of the resonant micro-optical gyro(R-MOG), and in order to achieve a resonant micro-optical-mechano-electrical integrative gyro having high sensitivity, a microsphere optical resonator key sensitive element for producting a cavity with high quality value (Q value) and large diameter in the field of integrated optical micro resonator is proposed, for making a resonant micro optical gyro. Microsphere optical resonator is made by means of water-hydrogen flame melting, and the SiO2 microspherical cavity is formed under the natural cooling and contraction surface tension. Microsphere optical resonator with its diameter D ranging from 300 μm to 2200 μm is fabricated by melting method with hydrogen flame as a heat source through controlling the hydrogen flame’s area by regulating the flow of hydrogen gas. The resonator serves as the key unit of the resonant optical gyro sensitive parts, its Q value and diameter D have direct effect on the performance of the resonant angular velocity sensor. Affect parameters on the performance of the microsphere optical resonator with different diameters is tested and processed to obtain the result. The corresponding relationship among Q value, DQ product, resonant micro-optical gyro’s sensitivity and microspherical cavity diameter D is analyzed, and the reason for them is given. With the increase of microspherical cavity diameter D, the Q value and DQ product reduce after rising first, while the gyro sensitivity goes to rise and fall. Based on the microsphere optical resonator DQ product optimization research, the resonant micro-optical gyro’s key sensitive unit with best parameters is obtained. When the microspherical cavity diameter D varies from 600 to 200 μm, the gyro sensitivity can meet the condition that δΩ D is 1260 μm, the Q value of microsphere optical resonator is 7.18×107 and the corresponding optimal limited sensitivity of the resonant micro-optical gyro is almost 10°/h, and this result adequately meets the requirement of business level gyro applications. This work can serve as an experimental foundation in the research of new type resonant micro optical gyro at chip level, high accuracy and low cost, and will also provide a technical reference for further study of high integrated and high precision resonant micro optical gyro.
Effective medium theory of two-dimensional photonic crystal for transverse electric mode beyond the long-wavelength limit
Authors: Geng Tao  , Wang Yan  , Wang Xin  , Dong Xiang-Mei  ,   Shanghai Key Lab of Modern Optical System, Engineering Research Center of Optical Instrument and System, Ministry of Education, University of Shanghai for Science and Technology, Shanghai 200093, China
Published: December 2020

An effective medium theory of two-dimensional photonic crystal for TE mode beyond the long-wavelength limit has been established based on the Mie scattering theory. Först, the proposed theory has been used to study the negative-refractive-index photonic crystals for TE mode. This theory can be used to calculate the effective indices and the effective impedance, and to predict the position of the band gap. Results agree well with the band structures, especially when the equifrequency surface contours are almost circular. Then the proposed theory is used to study the zero-refractive-index photonic crystals for TE mode. It can be seen a triply-degenerate point at Γ point, forming a Dirac cone in the band structures. It has been called an “accidental-degeneracy-induced Dirac point”, where the effective index is zero and the effective impedance is 1. Results calculated using the proposed theory agree well with the band structures. This means that the theory can be used well beyond the long-wavelength limit. Furthermore, the additional impedance information, which cannot be obtained by band structures, can be derived from the proposed theory.
Experimental study on a low switching energy and high-linearity all-optical sampler based on terahertz optical asymmetric demultiplexer
Authors: Jiang Lei  , Li Pu  , Zhang Jian-Zhong  , Sun Yuan-Yuan  , Hu Bing  , Wang Yun-Cai  ,   Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China;,   Institute of Optoelectronic Engineering, College of Physics & Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

We demonstrate experimentally a low switching energy and high-linearity all-optical sampler based on terahertz optical asymmetric demultiplexer (TOAD) composed of a nonlinear semiconductor optical amplifier (SOA) with a multiple quantum well structure. Effects of the sampling pulse power and asymmetric offset of SOA on the shape, width and amplitude of sampling windows are analyzed in detail respectively. It is found that the sampling pulse power has no effect on both the shape and the width of sampling windows, but has a significant effect on the window amplitude. Meanwhile there exists an optimal power which maximizes the sampled output and determines the switching energy of TOAD. The asymmetric offset of SOA from the center position in the loop determines the width of sampling windows and has great influences on both the shape and the amplitude of the sampling window. The sampling windows with different widths have approximately the same rise edge due to the fast response of SOA for the sampling pulse. However, the normalized amplitude of sampling windows firstly increases sharply with the increase of the asymmetry, then gradually flattens out, and tends to be stable in the end. In addition, the switching energy and linearity of TOAD are studied. The switching energy is as low as 25 fJ, and the linearity is as high as 0.99. Moreover, at different window widths, the switching energy of TOAD remains the same and the sampling windows have a very good linearity. However, the sensitivity of a TOAD sampler with different width is different: the wider the sampling window, the higher the sensitivity and the larger the corresponding dynamic range.
Mechanism for local resonant acoustic metamaterial
Authors: Liu Jiao  , Hou Zhi-Lin  , Fu Xiu-Jun  ,   Department of Physics, South China University of Physics, Guangzhou 510640, China
Published: December 2020

Taking the flexural wave propagating in elastic thin plate as an example, we investigate the mechanism for gap opening in the resonator-based acoustic metamaterials. Results show that the band gap in such a kind of structure depends not only on the abrupt phase change of the wave when it is scattered by the resonators, but also on the retarded phase of wave when it is propagating in host. This means that the dispersion of wave in the structure can be adjusted either by the scattering or by the propagating phase. Based on this understanding, we show that the defect state at subwavelength scale (obtained either by changing locally the resonating property of the resonator or by changing locally the distance between the resonators) can be understood simply by the band gap condition. We show further in this paper that, because the dispersion of the metamaterial can be adjusted by the propagating phase, the structures with negative band at a subwavelength scale can also be achieved by arranging the resonators into a compound lattice.
Sparse channel estimation and pilot optimization for underwater acoustic orthogonal frequency division multiple access uplink communications
Authors: Ma Lu  , Liu Song-Zuo  , Qiao Gang  ,   Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China;,   College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Considering that the conventional channel interpolation method with sparse and irregular spaced pilots will lead to an error floor in underwater acoustic (UWA) orthogonal frequency division multiple access (OFDMA) uplink communications, a method for sparse channel estimation and pilot optimization is proposed in this paper. A compressed sensing (CS) algorithm is utilized for sparse channel impulse response estimation, which performs well in sparse and irregular spaced pilots and significantly decreases the channel estimation error. Besides, the pilots’ pattern and power joint optimization algorithm based on the random search technique is proposed for the minimum mutual coherence criterion in CS theory, which further improves the performance of CS estimation algorithm. During each iteration step, we randomly pick a pilots’ pattern from the subcarrier index set and a pilots’ power subset from the available power set. Then we perform this step iteratively within a certain searching time. Finally, the local optimal solution of the objective function for minimizing mutual coherence is considered as the feasible pilots’ pattern and power. Simulation results show that the convergence performance of the pilots’ pattern and power joint optimization algorithm is much better than that of the pilots’ pattern optimization algorithm. Furthermore, the channel estimation error of the proposed method is much lower than that of conventional least-squares channel estimator based on linear interpolation, CS channel estimator without pilot optimization, and CS channel estimator merely with pilots’ pattern optimization in channels of different multipath delay spreads. Finally, performance of the proposed method is demonstrated in the UWA uplink OFDMA systems with interleaved and generalized carrier assignment schemes respectively in the two-user case in a pool experiment. Experimental results show that the proposed method decreases dramatically the bit error rate in both carrier assignment schemes, and simultaneous reception for two users is achieved when signal noise ratio is larger than 10 dB.
Flow-induced noise calculations for vector hydrophones in towed arrays
Authors: Shi Sheng-Guo  , Yu Shu-Hua  , Shi Jie  , A Gen-Mao  ,   Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China;,   College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China;,   Hangzhou Applied Acoustics Research Institute, Hangzhou 310012, China
Published: December 2020

The purpose of this study is to develop an integrated analytical method of flow-induced noise for vector hydrophones in towed arrays and discuss the parameters that influence flow-induced noise character. Based on Carpenter turbulent boundary layer pressure fluctuation model for slender cylinder, the power spectra and cross power spectra of acoustic pressure and particle velocity of flow-induced noise, are deduced by utilizing the wavenumber-frequency spectral analysis. It is shown that the flow-induced noise is determined by the towed speed, the size of both vector hydrophones and elastomer tube, the material parameters of elastomer tube and so on. In addition, the condition that cylindrical vector hydrophones are distributed non-axially in elastomer tube is also taken into account. Considering the influence of the axis-off distance on acoustic pressure, axial particle velocity and radial particle velocity, a set of numerical results show that the influence of the axis-off distance on the high-frequency component of the acoustic pressure and axial particle velocity is greater than that on the low-frequency component. The radial particle velocity is influenced by the axis-off distance within the full frequency range. The impact of the axis-off distance on the particle velocity is far greater than that on acoustic pressure.
Mechanical response study of glass-rubber particle mixtures
Authors: Chen Qiong  , Wang Qing-Hua  , Zhao Chuang  , Zhang Qi  , Hou Mei-Ying  ,   Key Laboratory of Soft Matter Physics, Beijing National Laboratory for Condense Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;,   Department of Physics, Beijing Institute of Technology, Beijing 100081, China;,   Science School, Guizhou University, Guiyang 550025, China
Published: December 2020

Mechanical response of mixtures composed of glass and rubber particles are investigated in direct shear experiments in laboratory and by means of discrete element method simulations. The mixtures are prepared with different contents of rubber fractions. It is found that, with increasing rubber particles, volume phase transition occurs from dilatancy to reduction, and the elastic properties of the mixtures are improved. Experimental results show that, as the rubber particles (up to 30% in volume) are added, the value of the shear stress falls, and the volume phase transition occurs, but the critical states are the same. The shear stress is independent of shear rates, however, it grows with the normal force. We have obtained the consistent results in the simulation. Furthermore, statistical analysis of the simulation results shows that the average coordination number is raised with the increase of rubber particles. Volume phase transition occurs at low rubber fraction when the normal force is large. It is very important to keep in mind that the average coordination number is always between 5.6 and 5.9 at the phase transition points even under different normal forces. When the rubber fraction is less than 30%, the residual shear strength is nearly the same as in the system of glass beads. However, the residual shear strength decreases when the rubber particles increase to the fraction larger than 30%. Meanwhile, the residual shear strength increases with the normal pressure.
Analysis of evolution mechanism of traffic energy dissipation by considering driver’s forecast effect
Authors: Sun Di-Hua  , Kang Yi-Rong  , Li Hua-Min  ,   Key Laboratory of Dependable Service Computing in Cyber Physical Society, Ministry of Education, Chongqing 400044, China;,   College of Automation, Chongqing University, Chongqing 400044, China
Published: December 2020

Starting from the full velocity difference model, an extended car-following model is proposed by considering the influence that in real traffic the driver’s forecast has an effect on car-following behavior of traffic flow. The mechanism how the stability and energy dissipation of traffic flow are in fluenced by the driver’s forecast effect is revealed by the application of the proposed new model. The linear stability condition of the new model is derived theoretically through linear stability theory. The phase diagram of linear stability condition is divided into two regions by each stability curve: the stable and unstable regions. And the corresponding stable region will be enlarged with the increase of driver’s forecast time, hence the traffic condition will be improved through considering driver’s forecast effect. By numerical simulation method, the space-time evolution relation between the velocity and headway of vehicles in car-following queue is investigated systematically under the influence of driver’s forecast. In the same time, the evolution mechanisms of the overall average energy dissipation of traffic flow and individual vehicle energy consumption with the addition of small disturbance are discussed explicitly under a periodic condition, and it is discovered that the overall average energy consumption in traffic flow and the energy dissipation of individual vehicle is accompanied by a complex critical phase transition process. Good agreement between the numerical simulation and the theoretical analysis show that by considering of driver’s forecast effect, not only the stability of traffic flow is enhanced obviously, but the energy consumption is reduced remarkably as we expect. Furthermore, it is verified that both the overall average energy consumption of the considered traffic flow and the energy consumption of an individual vehicle are reduced gradually along with the increase of driver’s forecast time. On the other hand, numerical simulation results verify that the shortcoming of negative speed appearing in the full velocity difference model with low reaction coefficient can be effectively avoided by increasing the driver’s forecast time in the improved model, which means that the dynamic characteristics of traffic flow can be described more precisely by the proposed model.
Lattice Boltzmann simulation of dissolution and precipitation in porous media
Authors: Zhang Ting  , Shi Bao-Chang  , Chai Zhen-Hua  ,   College of Sciences, Wuhan University of Science and Technology, Wuhan 430081, China;,   School of Mathematics and Statistics, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

In this paper, we simulate numerically the dissolution and precipitation in porous media by using the lattice Boltzmann method (LBM). The fluid flow in porous media is simulated by using a multiple-relaxation-time (MRT) LBM, while a D2Q9 lattice BGK model is used for reactive solute transport. Frst, the code of LBM is tested by simulating the diffusion and reaction at a boundary in an open rectangular domain, and comparing the results with the analytic solution. Then, the effects of the Reynolds number (Re), the Schmidt number (Sc) and the Damkohler number (Da) on the variations of the geometry of the porous media and the concentration field are carefully studied. It can be found that for the dissolution (precipitation), as Re is increased, the porosity of the porous media will be increased (decreased), and the average concentration will be decreased (increased). Besides, at low Damkohler numbers or Schmidt numbers, the dissolution and precipitation will be reaction-controlled and are highly uniform. However, as Da or Sc is high, the dissolution and precipitation will be diffution-controlled, and mainly occur in the upstream and large pore space.
Direct solution method of efficient large-scale parallel computation for 3D turbulent Rayleigh-Bénard convection
Authors: Zhang Yi-Zhao  , Bao Yun  ,   Department of Mechanics, Sun Yet-Sen University, Guangzhou 510275, China
Published: December 2020

Research of turbulence Rayleigh-Bénard convection with high Ra number is a hot topic in physics research in the world. DNS simulation is one of the important means to study the subject. The computing work is hard to achieve when the calculation size is increased and the grid number is bigger. Numerical simulation for high Ra turbulent convection faces some major challenges. So the direct (non iterative) solution method of efficient large-scale parallel computation for the 3D turbulent convection is created in this paper. Main difficulties are the parallel computing technology for the pressure Poisson equation. The mass efficient parallel approximate solution with the block tridiagonal equations of OpenMP and MPI used simultaneously after decoupling pressure Poisson equation using FFT is presented. Through the validation of the efficiency of this method in parallel computing, the new method for direct solution of parallel computing have good parallel efficiency and computational time. Results of thermal convection in 3D narrow cavity show that the convection characteristics calculated by using the new method is reasonable. The direct solution method for efficient large-scale parallel computation of 3D turbulent convection created in this paper also is likely to be a breakthrough in computing technology about efficient large-scale parallel computing incompressible NS equations in some special cases.
Evaporation enhancement effect of TiO2 nanoparticles on silicone oil in electrorheological fluid suspension
Authors: Wang De  , Shen Rong  , Liu Can-Can  , Wei Shi-Qiang  , Lu Kun-Quan  ,   National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230019, China;,   Laboratory of Soft Matter and Biological Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Electrorheological (ER) fluids are suspensions which consist of dielectric particles and insulation fluid. The ER fluids can change from liquid-like to solid-like state under the applied electric field. For traditional ER fluids, the maximum yield/shear stress is only several kPa and the size of dielectric particles is generally of micron. Since 2003, a series of new type ER fluids have been discovered, of which the yield/shear stress is as high as several hundred kPa. Such a type of ER fluid is called giant ER fluid or polar molecule-dominated ER fluid (PM-ER fluid), in which the size of dispersed particles is of nanoscale. Dimethyl silicone oil is the most commonly used dispersing agent in ER fluids, because of its stable physical and chemical behaviors. There is no obvious evaporation in traditional ER fluids when it is mixed with micron grade particles. However, when it is mixed with nanoparticles to prepare giant ER fluids, the silicone oil volatilizes easily in atmosphere. If time is long enough, the silicone oil in ER suspension can even be evaporated completely. In this paper, the existence of TiO2 nanoparticles in ER suspensions enhances the volatilization phenomenon has been studied through experiment. Analysis shows that the nanoparticles caused convex nanoscale curved surfaces on the gas-solid interface makes the vapor pressure increase greatly at the silicone oil surface, and leads to the enhancement of its volatilization. Influence of particle concentration, environmental temperature and viscosity of silicone oil on the evaporation enhancement effect is also studied and analysed systematically. Results show that the increase of the fraction of nanoparticles, viscosity of silicone oil as well as the temperature would promote the effect of evaporation enhancement of silicone oil in the suspensions.
Phonon stability and magnetism of -Fe4N crystalline state alloys at high pressure
Authors: Cheng Tai-Min  , Sun Teng  , Zhang Long-Yan  , Zhang Xin-Xin  , Zhu Lin  , Li Lin  ,   Department of Mathematics and Physics, Shenyang University of Chemical Technology, Shenyang 110142, China;,   College of Science, Northeastern University, Shenyang 110004, China
Published: December 2020

By using projection augmented plane wave method (PAW) and based on the density functional theory, the stability of lattice dynamics and the magnetism of ordered crystalline alloy -Fe4N are studied at high external pressures. In comparison with the phonon spectrum of -Fe4N without considering the spin-polarization, it is found that the ground-state lattice dynamics stability of the ferromagnetic phase -Fe4N is induced by the spontaneous magnetization at pressures below 1 GPa. The phonon spectra at point (0.37, 0.37, 0) in line , points X and M become softening at pressures between 1.03 and 31.5 GPa. The pressure-induced effect and the spontaneous magnetization effect on the atoms reach a stable equilibrium state at the pressures between 31.5 and 60.8 GPa, which result in the phonon spectrum stability. As the pressure exceeds 61.3 GPa, the system becomes more instable dynamically with the increase of the external pressure. The softening at point M of the acoustic phonon is treated by the soft-mode phase theory at 10 GPa, and a new dynamic stability high-pressure phase with a space group of P2/m is found. This new phase is thermodynamically stable and possesses the same magnetic moments as that of -Fe4N at pressures below 1 GPa. The enthalpy value of the phase P2/m is less than that of phase at the pressures between 2.9 and 19 GPa, therefore its ground-state structure is more stable. As the pressure exceeds 20 GPa, both phases possess almost the same magnetic moments.
Study on equation of state based on Thomas-Fermi-Kirzhnits model
Authors: Wang Kun  , Shi Zong-Qian  , Shi Yuan-Jie  , Wu Jian  , Jia Shen-Li  , Qiu Ai-Ci  ,   Xi’an Jiaotong University, State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an 710049, China
Published: December 2020

A wide-range semi-empirical equation of state is constructed for numerical simulation of high-energy density experiments, such as, wire-array Z-pinch etc. The equation of state consists of zero-temperature free energy term, and thermal contributions of electron and ion. Thomas-Fermi model, which was firstly put forward by Thomas and Fermi, is initially developed to study the electron distribution of multi-electron atoms. Since its advent, this model has been widely used in solid-state physics, atomic physics, astrophysics and equation of state computations. It is a particularly important model to describe the behavior of matter under extreme conditions of high temperature and high density. This model provides reasonably accurate results that are validated experimentally for some thermodynamic quantities, such as the pressure. However, the Thomas-Fermi model yields a pressure of a few GPa under normal density even at very low temperature, and the pressure is always positive, indicating an obvious limitation of this model. Kirzhnits has evaluated the influence of quantum effect and exchange effect on temperature-dependent Thomas-Fermi model and their contributions to the Thomas-Fermi equation of state. Basically, the Thomas-Fermi model with its quantum and exchange corrections which is called Thomas-Fermi-Kirzhnits model, can be applied to calculate the thermal contribution of electrons to the thermodynamic functions, which can lower the pressure given from the Thomas-Fermi model. The zero-temperature free energy term in the semi-empirical equation of state is described by a polynomial expression. The coefficients of the polynomial expression is calculated by using zero-temperature Thomas-Fermi-Kirzhnits model and the relation between thermodynamic quantities. A quasi-harmonic model is adopted to describe the behavior of ions. It is originally applied to calculate the contribution of ions in the condensed state. However, the quasi-harmonic model is close to an ideal equation of state in the high-temperature and low-density region. This model makes the description of the behavior of ions in the phase transition from the solid state to plasma state be approximated. Thomas-Fermi-Kirzhnits model is adopted to calculate the thermal contribution of electrons. The semi-empirical equation of state has the advantages of less calculation and clear physical concepts. Experimental data of isothermal compression at 300 K is fruitful and accurate. They can be used to verify the results of the semi-empirical equation of state. An isothermal compression curve is calculated by the present work and compared with experimental data. The pressures over a wide-range of temperature and density are derived and compared with corresponding data of SESAME database. The trajectory of the electrical explosion of aluminum is demonstrated from solid state to ideal plasma state.
Thermodynamic properties of one-dimensional Gaudin-Yang model at finite temperature
Authors: Zhang Tian-Bao  , Yu Xuan-Ping  , Chen A-Hai  ,   Department of Physics, Zhejiang Normal University, Jinhua 321004, China;,   Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
Published: December 2020

The one-dimensional system interacting via a delta-function interparticle interaction is a very important one in cold atomic systems and has fundamental importance in many-body physics. In one dimension, due to the geometric confinement induced quantum correlations and quantum fluctuations, there may exist a number of unusual phenomena, such as spin-charge separation, effective fermionization and quantum criticality. This paper studies the basic properties of a uniform one-dimensional Gaudin-Yang model for fermions by solving the thermodynamic Bethe-ansatz equations by a numerical method. Numerically, we use the many-variable Newton’s method to solve the coupled equations. We analyze the physical properties, including density, interaction, temperature and entropy at a given temperature and a given interaction, separately. We know that a lot of researches are limited to zero temperature. However, we cannot reach the absolute zero temperature in the real cold atomic experiment. So it is important to deal with the finite temperature problems. We study the density and entropy as a function of the chemical potential, temperature and interaction and, then give the phase diagrams, respectively. We found that there is a quantum critical zone in the phase diagram of entropy, including the high temperature zone with thermal fluctuations and the Luttinger liquid zone with quantum fluctuations. For a given temperature and low chemical potential, the thermal fluctuations are the main factor in the entropy. With the increase of chemical potential, the system enters the quantum critical zone where the competitive effect between the thermal fluctuations and the quantum fluctuations exists. When the chemical potential is large enough, the quantum fluctuations become the main factor in the system’s entropy, and we get the Luttinger liquid phase. Our results can be further used in the finite temperature density-functional theory and to analyze the collective phenomena at a finite temperature.