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24th European Navigation Conference, ENC 2016

作者： Run-Le, Du Jia-Qi, Liu Zhi-Feng, Li Zhen-Hong, Niu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781479989157

Recognition of guidance law on non-cooperative vehicle is drawing research interest among the literature, while insufficient accuracy of modeling and measurement makes it a hard problem. In this paper, a Frequency Divided Adaptive Kalman Filter is proposed to implement guidance law recognition. In FD-AKF, a Low Pass Filter is applied to extract the noise directly from state vector and measurement vector, and estimate the co-variance matrices of observation noise and prediction noise online. Without intertwined iterating equation of prediction noise and observation noise, FD-AKF decouples the estimation on prediction noise and observation noise, and thus avoids the risk of bias and divergence. Simulation results show that, FD-AKF improves robustness of guidance recognition significantly over Kalman Filter and Sage-Husa. © 2016 IEEE.

关键词： Forecasting

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Study of RF structure and Beam Wave Interaction system for a W-band Sheet Beam EIK

Study of RF structure and Beam Wave Interaction system for a...

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2017 International Conference on Radar Systems, Radar 2017

作者： Chen, Shuyuan Liu, Jiaqi Gao, Lu Bai, Jinliang Jiang, Zhiye Xu, Feng Qin, Peng Liu, Hongyan Liu, Xin Li, Hu Gao, Jingpeng National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781785615153

Sheet beam Extended Interaction Klystron (EIK) is an attractive Millimeter Waves (MMW) amplifier because of its high gain per unit length and compact configuration, which can be used in radar transmission system. In this paper, RF structure and beam wave interaction system of W band sheet beam EIK has been designed. A new and effective method of designing and studying the beam wave interaction system is presented in this *** whole tube consists of one single-gap cavity, six tri-gaps cavities and one five-gaps cavity. By optimizing the position of cavities, the output power can achieve 30 kW and high gain of 50 dB, which is calculated by three dimensional particle in cell (3D-PIC)*** provides a powerful basis for the subsequent study of sheet beam EIK. © 2017 Institution of Engineering and technology. All rights reserved.

关键词： Millimeter waves

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Study of RF structure for W band sheet beam EIK

Study of RF structure for W band sheet beam EIK

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IET International Radar Conference 2015

作者： Chen, Shuyuan Jiang, Zhiye Liu, Jiaqi Gao, Lu Bai, Jingliang Liu, Hongyan Meng, Gang Xu, Feng Li, Hu Liu, Chengguo Zhu, Guangsheng National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781849199940

Microwave tubes are vacuum electron devices used for the generation and amplification of radio frequencies in the microwave frequency range. Klystron is a kind of microwave tubes which is used in radar. A sheet-beam Extended Interaction Klystron (SBEIK) is an attractive MMW amplifier because of its high gain per unit length and compact configuration. The RF structure is an important part of the whole tube, which is used for beam wave interaction. In this paper, two kinds of barbell cavity has been studied. The difference between the separating multi-gap barbell resonant cavity and the strong coupling multi-gap barbell cavity has been discussed. RF parameters have been calculated by 3D simulations.

关键词： Microwaves

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Effects of reflection distance on Richtmyer–Meshkov instability in the reshock process: A discrete Boltzmann study

arXiv

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arXiv 2025年

作者： Lai, Huilin Lin, Chuandong Li, Demei Yang, Tao Gan, Yanbiao Lian, Lingyan Xu, Aiguo Fujian Normal University Fuzhou350117 China Sino-French Institute of Nuclear Engineering and Technology Sun Yat-sen University Zhuhai519082 China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Energy and Power Engineering Tsinghua University Beijing100084 China Hebei Key Laboratory of Trans-Media Aerial Underwater Vehicle School of Liberal Arts and Sciences North China Institute of Aerospace Engineering Langfang065000 China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P. O. Box 8009-26 Beijing100088 China National Key Laboratory of Shock Wave and Detonation Physics Mianyang621999 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China State Key Laboratory of Explosion Science and Safety Protection Beijing Institute of Technology Beijing100081 China

The Richtmyer–Meshkov (RM) instability occurs when a perturbed interface between two fluids undergoes impulsive acceleration due to a shock wave. In this paper, a numerical investigation of the RM instability during the reshock process is conducted using the two-component discrete Boltzmann method. The influence of reflection distance on the RM instability, including both hydrodynamic and thermodynamic non-equilibrium effects, is explored in detail. The interaction time between the reflected shock wave and the material interface varies with different reflection distances. Larger reflection distances lead to a longer evolution time of the material interface before reshock, resulting in more complex effects on the interface deformation, the mixing extent of the fluid system, and non-equilibrium behaviors after reshock. Additionally, while the reflection distance has a minimal impact on mixing entropy before the secondary impact, a significant difference emerges after the secondary impact. This suggests that the secondary impact enhances the evolution of the RM instability. Furthermore, non-equilibrium behaviors or quantities exhibit complex dynamics due to the influence of the transmitted shock wave, transverse waves, rarefaction waves, material interfaces, and dissipation/diffusion processes. Copyright © 2025, The Authors. All rights reserved.

关键词： Shock waves

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Supersonic flow kinetics: Mesoscale structures, thermodynamic nonequilibrium effects and entropy production mechanisms

arXiv

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arXiv 2025年

作者： Gan, Yanbiao Zhuang, Zhaowen Yang, Bin Xu, Aiguo Zhang, Dejia Chen, Feng Song, Jiahui Wu, Yanhong Hebei Key Laboratory of Trans-Media Aerial Underwater Vehicle North China Institute of Aerospace Engineering Langfang065000 China School of Energy and Safety Engineering Tianjin Chengjian University Tianjin300384 China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P. O. Box 8009-26 Beijing100088 China National Key Laboratory of Shock Wave and Detonation Physics Mianyang621999 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing100081 China School of Physical Science and Technology Guangxi University Nanning530004 China School of Aeronautics Shan Dong Jiaotong University Jinan250357 China School of Aerospace Engineering Beijing Institute of Technology Beijing100081 China

Supersonic flow is a typical nonlinear, nonequilibrium, multiscale, and complex phenomenon. Compared to scenarios described by Navier-Stokes (NS) theory, mesoscale behavior in supersonic flow exhibits greater discreteness and a higher degree of nonequilibrium. Meanwhile, the entropy production mechanism, which involves compression efficiency and the ability to perform external work, is a significant focus in supersonic flow fields. As the degree of discrete/nonequilibrium effects increases, the study of entropy production based on NS theory may need reevaluation and appropriate revision. To address these issues, this paper develops and applies the discrete Boltzmann modeling and analysis method/model (DBM), based on kinetic and mean-field theories, to simulate, and analyze these phenomena. The study provides the following results: A Burnett-level DBM suitable for supersonic flow is constructed based on the Shakhov-BGK model. Higher-order analytical expressions for typical thermodynamic nonequilibrium effects are derived, providing a constitutive basis for improving traditional macroscopic hydrodynamics modeling. Criteria for evaluating the validity of DBM are established by comparing numerical and analytical solutions of nonequilibrium effects. The multiscale DBM is used to investigate discrete/nonequilibrium characteristics and entropy production mechanisms in shock regular reflection. The findings include: (a) Compared to the NS-level DBM, the Burnett-level DBM offers more accurate representations of viscous stress and heat flux, i.e., more precise dissipative mechanisms, ensures non-negativity of entropy production in accordance with the second law of thermodynamics, and exhibits better numerical stability. (b) Near the interfaces of incident and reflected shock waves, strong nonequilibrium driving forces lead to prominent nonequilibrium effects. By monitoring the timing and location of peak nonequilibrium quantities, the evolution characteristics of incident and

关键词： Supersonic flow

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Experimental Studies of Low-Pressure Plasma Jet by Means of Langmuir Probes and Emission Spectra

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Plasma science and technology 2009年第3期11卷 307-313页

作者：刘磊曹金祥牛田野王亮孟刚刘鑫袁雷邬润辉张生俊任爱民 Key Laboratory of Basic Plasma Physics Chinese Academy of Sciencesand Department of Modern PhysicsUniversity of Science and Technology of China China Academy of Space Technology Test Physics & Numerical Mathematics Laboratory

An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.

关键词： plasma jet spatial distribution probe array emission spectrum

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The fundamental localization phases in quasiperiodic systems: A unified framework and exact results

arXiv

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arXiv 2025年

作者： Zhou, Xin-Chi Yao, Bing-Chen Wang, Yongjian Wang, Yucheng Wei, Yudong Zhou, Qi Liu, Xiong-Jun International Center for Quantum Materials School of Physics Peking University Beijing100871 China Hefei National Laboratory Hefei230088 China School of Mathematics and Statistics Nanjing University of Science and Technology Nanjing210094 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China International Quantum Academy Shenzhen518048 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Chern Institute of Mathematics and LPMC Nankai University Tianjin300071 China

The disordered quantum systems host three types of quantum states, the extended, localized, and critical, which bring up various distinct fundamental phases, including the pure phases and coexisting ones with mobility edges. The quantum phases involving critical states are of particular importance, but are less understood compared with the other ones, and the different phases have been separately studied in different quasiperiodic models. Here we propose a unified framework based on a spinful quasiperiodic system which unifies the realizations of all the fundamental Anderson phases, with the exact and universal results being obtained for these distinct phases. Through the duality transformation and renormalization group method, we show that the pure phases are obtained when the (emergent) chiral symmetry preserves in the proposed spin-1/2 quasiperiodic model, which provides a criterion for the emergence of the pure phases or the coexisting ones with mobility edges. Further, we uncover a new universal mechanism for the critical states that the emergence of such states is protected by the generalized incommensurate matrix element zeros in the spinful quasiperiodic model, as a novel generalization of the quasiperiodic hopping zeros in the spinless systems. We also show with the Avila’s global theory the criteria of exact solvability for the present unified quasiperiodic system, with which we identify several new quasiperiodic models derived from the spinful system hosting exactly solvable Anderson phases. In particular, we reach a single model that hosts all the seven fundamental phases of Anderson localization. Finally, an experimental scheme is proposed to realize these models using quasiperiodic optical Raman lattices. This study establishes a unified theoretical framework which enables an in-depth exploration of the broad classes of all fundamental localization phases in quasiperiodic systems, and offers key insights for constructing their exactly solvable models w

关键词： numerical models

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Research on dual-polarisation printed dipole antenna for spherical near-field measurements

Research on dual-polarisation printed dipole antenna for sph...

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IET International Radar Conference 2018, IRC 2018

作者： Zheng, Pei Liu, JiaQi Wang, ShangYue Zhang, Ran Fan, Hu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

Here a dual-polarisation printed dipole antenna for spherical near-field measurements is proposed. The printed dipole employs double-layered structure to obtain low cross-polarisation and uses irregular patch to get wide bandwidth. Two such dipoles are cross arranged to form a dual-polarisation dipole antenna. Simulated results show that the bandwidth is over 72% when VSWR is less than 3, the cross-polarisation ratio is better than 30 dB, the port isolation between two dipoles is better than −26 dB, while good radiation performance is also obtained. All the results above prove that the crossed arrangement structure will not affect the performance of the printed dipole, and the strength of mutual coupling between probes can be neglected. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Dipole antennas

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Research on near-field focusing algorithm of reconfigurable reflect-array

Research on near-field focusing algorithm of reconfigurable ...

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IET International Radar Conference 2018, IRC 2018

作者： Liu, Hong Yan Zheng, Pei Wang, Chao Guo, Lei Zhang, Xin Yu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

In this study, the near-field beam focusing algorithm of reconfigurable reflect array for security imaging application is proposed. The proposed near-field focusing algorithm is based on classic array method, which is usually adopted for far-field pattern calculation. In order to satisfy the near-field imaging application, the imaging distance is added to array method, and the improved formula can calculate the shifting phase of every array element precisely. In addition, due to discrete phase characteristic of reconfigurable reflect array, a phase choice method based on trigonometric function is used in authors' design. Based on the proposed algorithm, the shifting phase of every element is calculated and obtained the simulated beam focusing patterns. Meanwhile, the calculated shifting phase is written to whole array by field-programmable gate array, the near-field beam scanning patterns is measured and the measured results are in good agreement with the simulated ones. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Field programmable gate arrays (FPGA)

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Dispersive FDTD scheme with conformal technology for analyzing electromagnetic scattering of inhomogeneous plasma array

Dispersive FDTD scheme with conformal technology for analyzi...

引用

IET International Radar Conference 2015

作者： Ai, Xia Liu, Shendong Zhang, Shengjun Wang, Mingliang Liu, Jiaqi Meng, Gang Zhou, Hongchao National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical China

ISBN: (纸本)9781849199940

In this paper, a dispersive conformal FDTD method have been proposed to accurate model the interface between two adjacent dispersive mediums. The method is based on the technology of area average between two adjacent dispersive interfaces, which is different from existing dispersive conformal FDTD schemes which involve with the interface between free space and dispersive medium. numerical results show the proposed method would enhance the accurate level compared to the staircasing FDTD scheme involved in the inhomogeneous plasma.

关键词： numerical methods

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