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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. Source


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. Source


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. Source


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. Source


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. Source

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