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Chen L.,Beijing Institute of Electronic System Engineering | Zhang L.,Beijing Institute of Electronic System Engineering | Zhang L.,Science and Technology on Special System Simulation Laboratory | Guo M.,Beijing Institute of Electronic System Engineering
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

When high-speed flight vehicles fly in the atmosphere, they can generate serious aero-optical effect. The optical window temperature rises sharply because of aerodynamic heating. It will form radiation interference that can lead infrared detectors to producing non-uniform radiation backgrounds, decreasing system SNR and detection range. Besides, there exits temperature difference due to uneven heating. Under the thermo-optical and elastic-optical effects, optical windows change into inhomogeneous mediums which influence the ray propagation. In this paper, a model of thermal radiation effect was built by a finite element analysis method. Firstly, the optical window was divided into uniform grids. Then, radiation distribution on the focal planes at different angles of the window's normal line and optical axis was obtained by tracing light rays of each grid. Finally, simulation results indicate that radiation distribution reflects the two directions-the length and width-of temperature distribution, and the change of angle causes the center of radiation distribution to shift to one direction of the image surface under the same window temperature. © 2015 SPIE. Source


Guo K.,Beijing Institute of Technology | Zhang Y.,Beijing Institute of Technology | Sheng X.,Beijing Institute of Technology | Shen R.,Science and Technology on Special System Simulation Laboratory | Jin C.,Science and Technology on Special System Simulation Laboratory
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2012

Nowadays the existing approach to extract various micro Doppler characteristics from backscattered signals by multi-targets usually employ blind source separation technique based on independent component analysis. However, this approach has a great limitation in real application. First, micro Doppler characteristics to be separated must be statistically independent; second, independent component analysis method is generally limited to the conditions of exact determined or over determined equations. Under the radar scene with multiple targets, the number of radar signal receivers is commonly less than the number of targets, as well as the micro Doppler characteristics may not satisfy the independent condition, which makes micro Doppler characteristics extraction more difficult. In order to solve these problems, an approach based on underdetermined blind source separation method is pro-posed in this paper. The approach not only work well for the situation that the number of received radar signals is less than that of targets, but also has fewer limitations in the micro Doppler characteristic to be separated. The simulation presented in this paper validates the proposed extraction approach. Copyright ©2012 by Editorial Department of Chinese Journal of Radio Science. Source


Guo K.-Y.,Beijing Institute of Technology | Sheng X.-Q.,Beijing Institute of Technology | Shen R.-H.,Science and Technology on Special System Simulation Laboratory | Jing C.-J.,Science and Technology on Special System Simulation Laboratory
IET Radar, Sonar and Navigation | Year: 2013

The micro-motion characteristics of radar target are useful features for target recognition. Extended targets (as opposed to point target) have various scattering centres, such as the familiar point, localised and distributed scattering centres, as well as the rarely discussed but often encountered migratory scattering centres. The migratory scattering phenomenon of smooth surface is particularly concerned in this study. The motion information recoded in radar signals are actually that of migratory scattering centres rather than the real motions of the rigid target. Therefore the misleading motion information will bring unpredictable error to the radar application of target discrimination or recognition. To tackle this problem, the influence of migratory scattering phenomena of extended targets on micro-motion characteristics contained in radar signal is analysed in detail. Some meaningful conclusions are reached. The backscattered signals of extended targets are computed by the well-validated fullwave numerical method, hybrid finite element-boundary integral-multilevel fast multipole algorithm. The numerical results agree well with the analytical conclusions given in this study. © The Institution of Engineering and Technology 2013. Source


An N.,Beihang University | Wang R.,Beihang University | Luan Z.,Beihang University | Qian D.,Beihang University | And 2 more authors.
Proceedings - 2015 IEEE 17th International Conference on High Performance Computing and Communications, 2015 IEEE 7th International Symposium on Cyberspace Safety and Security and 2015 IEEE 12th International Conference on Embedded Software and Systems, HPCC-CSS-ICESS 2015 | Year: 2015

Mobile crowdsourcing with smartphones is a novel paradigm that collects distributed data efficiently. Millions ofcrowdsourcing tasks should be assigned and performed every day. In order to give good service quality for mobile sensing applications, a practical assignment approach is indispensable for a task platform to select appropriate users. This paper considers heterogeneous task assignment problem in the mobile sensing network that cannot label users. We consider the following scenario: a requester posts a set of tasks onto the platform, the platform selects a subset of proper smartphones to complete the different kinds of tasks under a budget constraint, all users inthese transactions are strategic for maximizing their individual utility. The assignment approach should be designed to fight against strategic behaviors of smartphone users. We address this problem by introducing a novel mechanism for mobile sensing assignment based on the multi-armed bandit problem. Moreover, we present an adaptive algorithm to assign users according to the properties of task and which task they are good at. Finally, we evaluate the performance of our mechanism based on a real dataset, and the results demonstrate that proposed algorithm achieves better in high-quality assignment. © 2015 IEEE. Source


An J.,Xian Jiaotong University | An J.,A+ Network | Gui X.,Xian Jiaotong University | Gui X.,A+ Network | And 2 more authors.
Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University | Year: 2011

An awareness algorithm to discover service nodes is proposed to deal with the problem of data-awareness and data-transmit in both time and space in mobility-aware of Internet of Things (IoT), which is caused by nodes mobility and random. The algorithm bases on social relations cognition, and quantizes the social relation of all nodes by introducing interconnection factor and distance factor. Then, cohesive subgroups and a node-mobile probability table are constructed to predict the trace of mobile nodes. Finally, awareness service nodes in the objective regions are determined through trust-transference and probability tree calculation. Simulation experiments show that the proposed method effectively reduces both the shortest distance among mobile nodes and the network average distance, improves the way of date acquisition and increases the quality of awareness service in IoT. Source

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