No 203 Research Institute
No 203 Research Institute
Li S.,Northwestern Polytechnical University |
Ma J.,No 203 Research Institute
Proceedings - 2016 9th International Congress on Image and Signal Processing, BioMedical Engineering and Informatics, CISP-BMEI 2016 | Year: 2016
Because the contrast of the image for guiding the high-speed infrared air-to-air missile is low, its signal to noise ratio is poor and the target and its background gray-scale coupling is strong, the paper analyzes the reasons why the threshold value segmentation method and the fuzzy C-means clustering method have the over-segmentation and under-segmentation in segmenting the above type of image. Hence we propose the kernel fuzzy clustering segmentation algorithm based on histogram and spatial constraint, which utilizes the global first-moment histogram of the infrared image to restrict the number of clusters and the clustering center, improves the spatial correlation function that fully manifests the correlations among pixels inside a neighbor domain and reconstructs the membership degree matrix and the clustering central function, thus segmenting the infrared image with the kernel fuzzy clustering algorithm. The results on the experiments on a sequential infrared image show preliminarily that, compared with the traditional threshold value segmentation algorithm, the fuzzy C-means segmentation algorithm and the kernel fuzzy clustering algorithm, the improved algorithm proposed in the paper can reduce entropy segmentation by about 60% on average and increase the correlation degrees among clusters by around 10%, thus enhancing to a certain extent the efficiency and precision for segmenting the fuzzy image whose target gray-scale and background gray-scale are strongly coupled. © 2016 IEEE.
Huang P.,Northwestern Polytechnical University |
Zhao Y.,Northwestern Polytechnical University |
Zhang F.,Northwestern Polytechnical University |
Ma J.,No 203 Research Institute |
And 3 more authors.
Aerospace Science and Technology | Year: 2017
The Hub-Spoke Tethered Formation System (HS-TFS) is now a hot issue in many space applications, such as multi-point measurements, providing flexible frame for solar sail and other membrane or net structures. To achieve the valuable advantages, such as reduction of fuel consumption, promotion of the formation stability, the HS-TFS is usually in the rotating state. In addition, it is necessary to change the length of the tethers to obtain a variable coverage of the entire plane of the rotating HS-TFS in some applications, that is, the deployment and retraction problems of the rotating HS-TFS. However, the rotating motion will increase the complexity of the deployment and retraction of the rotating HS-TFS. In this paper, the deployment and retraction of a rotating HS-TFS is investigated. Firstly, a mathematical model is derived to describe the dynamics of the rotating HS-TFS. Then, the Gauss pseudospectral method is employed to solve the optimal deployment and retraction problems of the rotating HS-TFS. Finally, numerical simulations for deployment and retraction of the rotating HS-TFS are performed. Numerical simulation results reveal that it is necessary to apply active control on the deployment and retraction phases of the rotating HS-TFS, and after employing the optimal control (Gauss pseudospectral method), the HS-TFS can reach the desired configuration. © 2017 Elsevier Masson SAS
Yang Z.-Z.,No 203 Research Institute |
Liu Y.-H.,Chang'an University |
Zhao S.-L.,Shaanxi Institute of Geological Survey
Northwestern Geology | Year: 2013
According to the systematic investigation of the cross-sections in the boundary areas of Shaanxi, Henan and Hubei provinces, a new division of Nanhua-Cambrian is made on the previously measured sections in the area. It is suggested that the Liantuo formation of Nanhua era should exist in the district. The upper Cambrian should be restored as a formation name, and Shiwenzi formation should no longer represent both Wugongya formation in upper Cambrian and Shuihetian formation in lower Ordovician, due to the fact that the Shiwengzi formation in Zhashui area is merely magnesian carbonate deposits without fossils, located above the carbonaceous and silicious slate. According to the collected fossils and relics, the Cambrian can be clearly divided into lower, middle and upper (including Furongian) parts. The lithofacies palaeogeography features of each formation are systematically described, and provide significant foundation for regional strata division and provincial comparison.
Cao Q.,Northwestern Polytechnical University |
Feng X.,Northwestern Polytechnical University |
Li J.,Northwestern Polytechnical University |
Dong T.,No 203 Research Institute
Advanced Materials Research | Year: 2012
According to the performance detecting requirements in development and manufacture of solid rocket motor, a test platform had been set up based on flexible test fixture, a measurement & control platform had been built using virtual instrument technology, a set of solid rocket motor ground test performance detecting software including parameter calibration module, data measurement module and data processing module had been developed based on the LabVIEW7.1, and the solid rocket motor performance detecting system was constructed. The application results through testing normative solid rocket motor show that: the system could actualize parameter calibration expediently, experimental data collection and processing rapidly, even reach the measurement precision by 0.3% that required in project and could monitor the working process of solid rocket motor simultaneously, which satisfies high-precision requirement of motor performance detecting. © (2012) Trans Tech Publications, Switzerland.
Liu C.,No 203 Research Institute |
Lu Z.,Northwestern Polytechnical University |
Luo Z.,No 203 Research Institute |
Zhang M.,Northwestern Polytechnical University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2011
Three available robust reliability indexes include the robust reliability index based on interval analysis, the robust reliability index based on expansion function, and the robust reliability index based on infinite norm. The characteristics of these indexes are discussed in detail, and the advantage and disadvantage of them are demonstrated. To solve the existing problem, a general robust reliability index is set up, which may be applied to linear system and nonlinear system including various uncertainty convexes. In process of solving the proposed index, the multiple size parameters of many various uncertainty convexes are transform into the single size of a general uncertainty convex which includes all of the basic variables, then the lower limit of the single size, which makes the general convex overlap with failure set, is taken as the robust reliability index η. The proposed index shows the safety degree of linear system and nonlinear system definitely in the current conditions. η<1 shows that the system failure is possible in the current uncertainty condition of basic variables. η>1 shows that the system failure is impossible in the current uncertainty condition of basic variables, and that the system is in critical condition of safety and possible failure when the size parameter of the current uncertainty convex is multiplied by η. And the solving of the robust reliability index η is transformed into an optimization problem, which can be solved by the simulated method. Finally, the results of illustrations show the rationality and wide applicability of the presented method. © 2011 Journal of Mechanical Engineering.
Dong H.,Xi'an Technological University |
Ma C.,No 203 Research Institute |
Fang Z.,Xi'an Technological University |
Zhao X.,Xi'an Technological University
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics | Year: 2015
Based on the error and the actual tooth surface modification, a dynamic mechanics model of dual power split transmission system is established. The concentration of quality standard is used to establish the bend-torsion coupling dynamics differential equation of the system, and the equation is solved to get the frequency domain and time domain responses of the system. The results show that: through a combination of the real tooth surface fitting and the loaded tooth contact analysis (LTCA) technology, the more accurate mechanical properties of gear in different working conditions and tooth surface conditions can be gotten; the gear tooth modification can reduce the transmission error, improve the tooth surface contact, and significantly reduce the dynamic load fluctuation of the system. ©, 2015, Nanjing University of Aeronautics an Astronautics. All right reserved.