National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical

Beijing, China

National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical

Beijing, China
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Wang H.-Y.,Beihang University | Qin T.-M.,Beihang University | Liu J.-Q.,China Aerospace Science and Technology Corporation | Liu J.-Q.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

To improve the preprocessing speed of star map and reduce the resource consumption of embedded system of star tracker, a parallel pipeline real-time preprocessing algorithm is presented. The two characteristics, the mean and the noise standard deviation of the background gray of a star map, are firstly obtained dynamically by the means that the intervene of the star image itself to the background is removed in advance. The criterion on whether or not the following noise filtering is needed is established, then the extraction threshold value is assigned according to the level of background noise, so that the centroiding accuracy is guaranteed. In the processing algorithm, as low as two lines of pixel data are buffered, and only 100 shift registers are used to record the connected domain label, by which the problems of resources wasting and connected domain overflow are solved. The simulating results show that the necessary data of the selected bright stars could be immediately accessed in a delay time as short as 10us after the pipeline processing of a 496×496 star map in 50Mb/s is finished, and the needed memory and registers resource total less than 80kb. To verify the accuracy performance of the algorithm proposed, different levels of background noise are added to the processed ideal star map, and the statistic centroiding error is smaller than 1/23 pixel under the condition that the signal to noise ratio is greater than 1. The parallel pipeline algorithm of real time star map preprocessing helps to increase the data output speed and the anti-dynamic performance of star tracker. © 2017 SPIE.


Wu R.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Liu H.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Liu J.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Chang Q.,Beihang University
Beijing Hangkong Hangtian Daxue Xuebao/Journal of Beijing University of Aeronautics and Astronautics | Year: 2013

A vehicle flying in the atmosphere at transonic velocity creates plasma sheath, and the communication signal is defiladed or its energy is attenuated by the plasma sheath, thus the communication system is discontinued between the vehicle and the signal station. The phase changed and the energy absorbed of the communication signal in plasma sheath which is made by the shock tube was studied, and the experiment of different plasma parameter was finished. Two measuring systems were built, one is the signals generator and data sampler, and its modulation is quaternary phase shift keying (QPSK), and its carrier frequency is 7.5 GHz; the other is the E8362B test system. The contrastive results of the signal phase changed and the signal energy attenuated at the plasma and no plasma were obtained. The experimental results show that not only is affected the communication by the plasma sheath absorbing, but also the phase changed of QPSK signals is achieved, the signals demodulated/decoded are badly aberrant, and the Pe of communication system is increased, and the receiver is unable to offer the original information sent by transmitter.


Li X.,Beijing Institute of Technology | Hu C.,Beijing Institute of Technology | Zeng D.,Beijing Institute of Technology | Long T.,Beijing Institute of Technology | Liu X.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical
IEEE National Radar Conference - Proceedings | Year: 2011

In the ground-based FSR, the strong ground reflected signal seriously cancel the useful signal, as a result the estimation methods of the target images in current SISAR imaging technology are no longer applicable. The height difference of the target can't be estimated from the amplitude of complex profile function (CPF). In this paper, firstly, the multipath interference on the forward scatter (FS) signal model and imaging results of the moving target are analyzed by the two ray path model. Then, the estimation methods of the target profile image under multipath interference condition are presented. As a result, the accurate target images that cannot be achieved by using the current imaging algorithm can be extracted using the modified imaging algorithm. Finally, the effectiveness of the estimation methods is validated by the simulations. © 2011 IEEE.


Chao Z.,Soochow University of China | Yan Z.C.,Soochow University of China | Cheng H.,Beijing Institute of Technology | Rong L.X.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical
IET Conference Publications | Year: 2013

The Doppler shift, azimuth and elevation angles estimation is the precondition of target tracking and SISAR imaging in forward scatter radar (FSR). With the utilization of a spacetime processing (STP) algorithm, the Doppler shift and azimuth angle or elevation angle can be jointly estimated. The impacts of the observation interval and multipath interference on parameters estimation accuracy are analyzed. The quasioptimal observation interval is given after considering the contradiction between the frequency resolution and dynamic error. The correctness of these analyses is verified by quantitative simulation results.


Zhang C.-F.,Beijing Institute of Technology | Liu C.-J.,Beijing Institute of Technology | Hu C.,Beijing Institute of Technology | Liu X.-R.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical
IET Conference Publications | Year: 2013

The research of statistical properties and simulation methods of radar clutter have vital importance to the design, simulation and development of radar systems. Based on the analysis of some experimental data of forward scattering radar (FSR) clutter, it was found that under low wind speed and narrow dynamic range, the amplitude of FSR clutter was subject to K distribution; while under high wind speed or wide dynamic range, it was subject to lognormal distribution; the clutter power spectrum was subject to the fourth-order all-pole model. With the above statistical analysis, the forward scatter coherent clutter was simulated using a method combining zero-memory nonlinear transformation with spherically invariant random process. The statistical characteristics of the simulated clutter were identical to those of the measured clutter, which verified the validity of this method.


Xu S.-L.,Hefei University of Technology | Liu Y.-G.,Hefei University of Technology | Wang D.-R.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Tan Z.-H.,Hefei University of Technology | Zheng H.,Hefei University of Technology
Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics | Year: 2013

Based on one-stage light gas gun, series of experiments including oblique planar impact with inclination angles of 0~15° and impact velocity ranging from 68 to 201 m/s were carried out to investigate the responses of alumina microvoid ceramics with high porosity subjected to impact loading. Experimental results show that since the diameter of microvoid in sample is smaller than 5 μm, the process of sample compression is gradually and evenly developed, and there is no porous collapse observed. The dynamic shear behaviors are similar to those of brittle materials. Based on the Hoek-Brown criteria and Cap-model, the dynamic model for the failure surface and the double yield surfaces of porous brittle materials was built. Based on the experimental data of compression and shear combined impact loading, the preliminary analyses were carried out and the results show the applicability of the model.


Tian Y.,Xidian University | Ai X.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Han Y.,Xidian University | Liu X.,Science and Technology on Space Physics Laboratory
Physics of Plasmas | Year: 2014

In this paper, we investigate the propagation of terahertz (THz) electromagnetic wave in an anisotropic magnetized plasma by JE convolution-finite difference time domain method. The anisotropic characteristic of the plasma, which leads to right-hand circularly polarized (RCP) and right-hand circularly polarized (LCP) waves, has been taken into account. The interaction between electromagnetic waves and magnetized plasma is illustrated by reflection and transmission coefficients for both RCP and LCP THz waves. The effects of both the magnetized plasma thickness and the external magnetized field are analyzed and numerical results demonstrate that the two factors could influence the THz wave greatly. It is worthy to note that besides the reflection and transmission coefficients in the frequency domain, the waveform of the electric field in the time domain varying with thicknesses and external magnetic fields for different polarized direction has been studied. © 2014 AIP Publishing LLC.


Yu Z.-F.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Yu Z.-F.,China Aerodynamics Research And Development Center | Liu J.-Q.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Ren A.-M.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | And 3 more authors.
Yuhang Xuebao/Journal of Astronautics | Year: 2011

The communication blackout, caused by plasma sheath around a hypersonic vehicle flying in atmosphere is a problem to aerospace vehicles. A magneto window will be formed when a static magnetic field is applied to plasma sheath, and it can be used to reduce the attenuation of right circularly polarized wave in the sheath. The best way to build the magnetic window is by use of superconductive devices. However, there are some problems such as heavy weight and complex structure in use for superconductive devices to generate a magneto window. In this paper, an integrated concept, i. e. magneto window antenna, is proposed. A circular polarized GPS antenna is designed according to this concept. The antenna patch was made of copper and the ground plate is made of rare earth magnet NdFeB. The magnet will work as a part of antenna and be used to produce a strong magnetic field for magneto window as well. Radiation pattern and magnetic field intensity surrounding the antenna are analyzed by numerical simulation. It is shown that the attenuation of right circularly polarized wave through plasma sheath is reduced obviously.


Zhang D.,Northwestern Polytechnical University | Gao Z.,Northwestern Polytechnical University | Huang L.,Northwestern Polytechnical University | Wang M.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical
Chinese Journal of Aeronautics | Year: 2011

Constructing metamodel with global high-fidelity in design space is significant in engineering design. In this paper, a double-stage metamodel (DSM) which integrates advantages of both interpolation metamodel and regression metamodel is constructed. It takes regression model as the first stage to fit overall distribution of the original model, and then interpolation model of regression model approximation error is used as the second stage to improve accuracy. Under the same conditions and with the same samples, DSM expresses higher fidelity and represents physical characteristics of original model better. Besides, in order to validate DSM characteristics, three examples including Ackley function, airfoil aerodynamic analysis and wing aerodynamic analysis are investigated. In the end, airfoil and wing aerodynamic design optimizations using genetic algorithm are presented to verify the engineering applicability of DSM. © 2011 Elsevier Ltd. All rights reserved.


Tian Y.,Xidian University | Ai X.,National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical | Han Y.,Xidian University | Guo L.,Xidian University
Physics of Plasmas | Year: 2015

In this paper, the interaction between terahertz electromagnetic wave and a non-uniform magnetized plasma slab is investigated. Different from most of the published literatures, the plasma employed in this work is inhomogeneous in both collision frequency and electron density. Profiles are introduced to describe the non-uniformity of the plasma slab. At the same time, magnetic field is applied to the background of the plasma slab. It came out with an interesting phenomenon that there would be a valley in the absorption band as the plasma's electromagnetic characteristic is affected by the magnetic field. In addition, the valley located just near the middle of the absorption peak. The cause of the valley's appearance is inferred in this paper. And the influences of the variables, such as magnetic field strength, electron density, and collision frequency, are discussed in detail. The objective of this work is also pointed out, such as the applications in flight communication, stealth, emissivity, plasma diagnose, and other areas of plasma. © 2015 AIP Publishing LLC.

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