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Numerical simulation and analysis of lithium plasma during low-pressure DC arc discharge

Plasma science and technology 2019年第4期21卷 16-21页

作者： Runhui WU Song CHAI Jiaqi LIU Shiyuan CONG Gang MENG National Key Laboratory of Science and Technology on Test Physics&Numerical Mathematics Beijing 100076People's Republic of China School of Physics Dalian University of TechnologyDalian 116024People's Republic of China

Alkali metal DC arc discharge has the characteristics of easy ionization,low power consumption,high plasma temperature and ionization degree,etc,which can be applied in aerospace vehicles in various *** this paper,we calculate the physical property parameters of lithium vapor,one of the major alkali metals,and analyze the discharge characteristics of lithium plasma with the magnetohydrodynamic(MHD)*** discharge effects between constant current and voltage sources are also *** is shown that the lithium plasma of DC arc discharge has relatively high temperature and current *** peak temperature can reach tens of thousands of K,and the current density reaches 6 x 107 A m *** the same rated power,the plasma parameters of the constant voltage source discharge are much higher than those of the constant current source discharge,which can be used as the preferred discharge mode for aerospace applications.

关键词： DC discharge lithium plasma numerical simulation low-pressure arc

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The Design of Large Arc-shape High-precision Walking Device in TV (thermal-vacuum) Conditions 3

The Design of Large Arc-shape High-precision Walking Device ...

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3rd International Conference on Design, Mechanical and Material Engineering, D2ME 2018

作者： Lian, Xue Hua, Nan Jiaqi, Liu Xin, Liu Gang, Meng National Key Laboratory of Science Technology on Test Physics and Numerical Mathematics China

The large-sized space environmental simulation test facility is mainly used for providing thermal radiation environment in high-vacuum, cold and dark space for satellites, spacecraft, lunar spacecraft to carry out whole satellite thermal vacuum test and for large equipment like antenna to carry out tests in TV conditions. Monitoring the spacecraft's surface optical image or temperature is a main task in space environment simulation test. In previous tests, optical image test mainly took place in a fixed position, so the measuring location and angle are limited. This paper focuses on large spherical space environmental simulation test facility, and designs a large arc-shape high-precision walking device in a space environment simulation test device. It introduces key technology in detail like structure design, thermal design, processes and manufacturing, etc. The test results show that this device can work steadily and reliably under simulation space environments, and the precision exceeds 0.5°. © 2018 The Authors, published by EDP sciences.

关键词： Design

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Automatic MHT Method Based on Target Characteristics Applied in the Small Space Targets 3

Automatic MHT Method Based on Target Characteristics Applied...

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3rd International Conference on Design, Mechanical and Material Engineering, D2ME 2018

作者： Zhao, Qian Niu, Zhenhong Xue, Lian Liu, Xin Li, Jianhua Li, Zhifeng National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics China

The Multi-Hypothesis Tracking (MHT) method is one of the most promising approaches to realize automatic tracking of small and dim targets in complex space scene. However, the number of hypotheses generated by this algorithm has an exponentially increasing relationship with the number of trajectories, measurement data, and the number of image frames. In the paper, the automatic detection and tracking method of judging the confidence coefficient of the trajectory obtained by the MHT which is based on the characteristics of dim targets, has been realized in the IRST system. The performance of this method is greatly improved. © 2018 The Authors, published by EDP sciences.

关键词： Target tracking

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Nonlinear control algorithm for smooth transition in large-angle attitude maneuver

Nonlinear control algorithm for smooth transition in large-a...

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2011 International Conference on Recent Advancements in Electrical, Electronics and Control Engineering, IConRAEeCE'11

作者： Du, Runle Liu, Jiaqi Wang, Yonghai Meng, Gang Mu, Chenyang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics China

ISBN: (纸本)9781457721472

Large-angle attitude maneuver is common during the mission of spacecrafts, such as aligning to star to calibrate navigation system. Published works on attitude tracking always focus on optimizing the time and fuel cost, neglecting the smoothness requirement and angular speed limitations. In this paper, a nonlinear control algorithm is prompted for smooth transition in large-angle attitude maneuver. A nonlinear filter is added to the attitude feedback control loop, to carry out angular speed control in large-angle maneuvers. Simulation results demonstrated the effectiveness and reliability of proposed approach. © 2011 IEEE.

关键词： Navigation systems

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An Absorptive/Transmissive Frequency Selective Surface with Wide Transmission Band and Low Insertion Loss

An Absorptive/Transmissive Frequency Selective Surface with ...

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2022 International Applied Computational Electromagnetics Society Symposium, ACES-China 2022

作者： Song, Hang Liu, Jiaqi Zhang, Shengjun National Key Laboratory of Science & Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781665452366

The Absorptive/transmissive Frequency Selective Surface (ATFSS) is a multi-layer composite periodic structure with out-of-band absorption and in-band transmission characteristics, usually composed of a lossy resistive sheet (RS) and a lossless bandpass FSS. In this paper, an equivalent circuit method based on transmission line theory was used to design the ATFSS with idea of higher frequencies for transmission and lower frequencies for absorption, as well as the impedance conditions for satisfying wave transmission and absorption. Furthermore, the S-parameters was fitted, which verifies the design concept. Finally, the simulation was performed with numerical method. It is shown from the simulation that the broadband absorption of the ATFSS ranges from 2.00 GHz to 6.29 GHz, and the broadband transmission ranges from 8.46 GHz to 11.32 GHz with an insertion loss of less than 1 dB. © 2022 IEEE.

关键词： Frequency selective surfaces

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A unified back-projection correction algorithm for squint SAR based on SPECAN processing

A unified back-projection correction algorithm for squint SA...

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2019 IEEE International Conference on Signal, Information and Data Processing, ICSIDP 2019

作者： Wang, Chao Sun, Heng Zhang, Xin-Yu Zhang, Ran National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781728123455

The missile-borne or airborne synthetic aperture radar (SAR) usually adopts the squint mode and subaperture to satisfy maneuvering and the real-time processing. A realtime imaging algorithm of squint SAR based on SPECAN processing is presented. It has high computational efficiency in low resolution. A unified back-projection algorithm is proposed to solve the problem of fan-shaped distortion and geometric distortion. Simulation results validate the effectiveness of the proposed method. © 2019 IEEE.

关键词： Computational efficiency

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Attitude maneuver path optimization for small scale spacescraft

Attitude maneuver path optimization for small scale spacescr...

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10th IEEE Jubilee International Symposium on Applied Machine Intelligence and Informatics, SAMI 2012

作者： Du, Runle Liu, Jiaqi Wang, Yonghai National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781457701979

During its flight, Spacecrafts need to maneuver its attitude across a number of predefined positions. The order to traverse these attitudes is a combinational optimization problem. In this article, fuel cost is estimated by analyzing the angular momentum change during attitude transitions. Based on this estimation, an optimization algorithm for both fuel-cost and maneuver-time oriented path planner is introduced. Simulation result demonstrated the effectiveness of proposed approach. © 2012 IEEE.

关键词： Attitude control

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Simulation and analysis of repeater deceptive jamming to SAR based on shift-frequency

Simulation and analysis of repeater deceptive jamming to SAR...

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2022 International Applied Computational Electromagnetics Society Symposium, ACES-China 2022

作者： Li, Daixuan Liu, Jiaqi Li, Jianhua Gao, Lu Zheng, Pei He, Zhonghang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781665452366

With the change of battlefield form, the pressure jamming requires the jammer to have large power, and the jamming efficiency is low, so the spoofing jamming comes into being. In this paper, the linear frequency modulation signal and fuzzy function are analyzed to verify the feasibility of using frequency shift forwarding to generate virtual images, and the two-dimensional frequency shift method is used to generate virtual images at specific locations to deceive local radar. © 2022 IEEE.

关键词： Synthetic aperture radar

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Online Tuning of Pre-trained Deep Neural Network for Guidance Against Non-cooperative Pursuer

Online Tuning of Pre-trained Deep Neural Network for Guidanc...

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2022 IEEE International Conference on Aerospace Electronics and Remote Sensing technology, ICARES 2022

作者： Du, Runle Shu, Yi Liu, Jiaqi Chen, Yang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (数字)9781665461917

ISBN: (纸本)9781665461917

In the astronautics, it is widely acknowledged as a hard problem that using neural network to handle the intelligent observation and guidance when dealing with non-cooperative pursuing vehicles. Due to the difficulty of obtaining training data set from non-cooperative vehicles, the inconsistency between training data and utilization data, application of neural network controller is by far very limited. In order to tackle this problem, an online tuning scheme of neural network is proposed in this paper aiming to boost the observation and counter action abilities against non-cooperative pursuer. In the proposed methodology, the deep neural network controller is pre-trained through dataset from generative network before deployment, and fine-tuned online through real time observations data set. In this way, the calculation pressure is alleviated for onboard computer and the contribution of real time observation data set is utilized more correctly, thus guaranteeing the efficiency and effectiveness of online tuning. Simulation results suggested that, both in the observation ability and counteractive guidance to avoid the pursuer, the proposed method all trumped traditional networks without online tuning, which resulting a higher chance to survive the pursuit. © 2022 IEEE.

关键词： Deep neural networks

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A Triple-layer Frequency Selective Surface with Flat Wide Passband 5

A Triple-layer Frequency Selective Surface with Flat Wide Pa...

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5th IEEE International Conference on Computational Electromagnetics, ICCEM 2019

作者： Cui, Yichun Zhang, Shengjun Wang, Mingliang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781538671115

In this paper, a novel triple-layer band-pass Frequency selective surface (FSS) with wide passband and low insertion loss is proposed. The proposed FSS is composed of three FSS layers and two dielectric substrates which are symmetric vertically. This structure realizes a three-order response and wide stop band with steep falling edge. Equivalent circuit analysis indicates that the three-order response is generated by resonance of FSS layers and coupling between layers, respectively. After optimization, the passband of proposed FSS ranges from 7.728GHz to 12.31GHz, whose fractional bandwidth reaches 44.5% with -0.044dB insertion loss. Meanwhile, this FSS has stable performance for TE polarization under oblique incidence. © 2019 IEEE.

关键词： Frequency selective surfaces

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