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Yang X.,Tsinghua University | Yang X.,PLA Second Artillery Engineering University | Lu F.,Equipment Research Institute of the Second Artillery | Guo J.,Tsinghua University | And 2 more authors.
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2011

Single observation passive locating systems are widely used in the military and in navigation, aerospace and geophysics systems because they have a long response distance, can be easily hidden and are easily deployed. Howerve, current passive locating methods can not easily deal with uncertainties and asymmetry. Thus, a fuzzy passive location system was developed with a fuzzy single observation passive location algorithm. The algorithm is based on information for the phase-difference, the phase-difference rate of change and the Doppler frequency rate of change, with a fuzzy extended Kalman filter to locate and track the object. The algorithm can handle not only fuzzy uncertainties but also Gaussian systems. Simulations demonstrate that this approach is quite accurate.

Yu A.-X.,National University of Defense Technology | Wang Q.-S.,Equipment Research Institute of the Second Artillery | Meng Z.-Y.,Unit 63889 of PLA | Dong Z.,National University of Defense Technology
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2016

For the conventional prominent scatterers method, InSAR performance is over evaluated because of the higher coherence of the scatterers. An improved InSAR performance evaluation method is proposed based on virtual prominent scatterers (VPS). The VPS are some ordinary scatterers distributed around the prominent scatterers and treated as statistical samples. The pixel position of the VPS can be precisely estimated with the accurate relative geolocation because of the high signal to clutter ratio of the prominent scatterers. And the absolute/relative interferometric phase and height precisions can be more accurately calculated. Experiment results based on spaceborne InSAR signal simulation show the validation of the VPS-based method. © 2016, Science Press. All right reserved.

Lu Y.,Beihang University | Lu Y.,Equipment Research Institute of the Second Artillery | Wang F.,China Aerospace Science and Technology Corporation | Deng B.,China Aerospace Science and Technology Corporation
Jiefangjun Ligong Daxue Xuebao/Journal of PLA University of Science and Technology (Natural Science Edition) | Year: 2013

The special nature of Web application makes testing challenging. A clear test model was established to help guide the test, to form a test case for the next step and to lay the foundation for the implementation of the test. Based on the analysis of Web application, a combination of testing modeling approach was proposed, the approach from three aspects, object, navigation behavior and system architecture. Then the method to modeling and to generate test cases was introduced. The object model extends the relational structure, navigation behavior model takes account of the behavior of the browser, and the system structure is reflected from both control flow and data flow. The approach can fully consider the characteristics of Web application, intuitively reflect the relationships between Web applications, and effectively guide the testing.

Zhang M.-Z.,Equipment Research Institute of the Second Artillery | Mou J.-H.,Equipment Research Institute of the Second Artillery | Liu Y.,Equipment Research Institute of the Second Artillery | Peng X.-J.,Equipment Research Institute of the Second Artillery | Wang B.-X.,Tsinghua University
Guangxue Jingmi Gongcheng/Optics and Precision Engineering | Year: 2012

To reduce the effect of large number of invalid data in fringe patterns on calculation results in the measurement of high dynamic flows using interferometry or Moiré deflectometry, an effective phase extraction method was proposed based on the wavelet transform using complex Morlet wavelet. Through choosing proper parameters for the wavelet, the maximum modulus of the wavelet transform of a pattern was proportional to its modulation factor, then it was used as a weighting factor of a phase unwrapping algorithm based on weighted least squares to guarantee reliable phase unwrapping. In the process of wavelet ridge routing, a simple algorithm based on curve fitting was proposed to substantially reduce the routing time and the precision deterioration due to image noise. In simulation experiment, the relative error between calculated phase and actual phase is less than 0.01%. In internal wave measurement experiment, the method is used to analyze the fringe patterns, and the density gradient measurement precision has reached 5×10 -6 g/cm 4. It shows that the method can reduce the effect of invalid data on analysis precision effectively and can obtain reliable unwrapped phases.

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