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Wang J.,Wuhan Naval University of Engineering | Wang J.,Jiuquan Satellite Launching Center | Chen L.,Wuhan Naval University of Engineering | Ge Y.,Wuhan Naval University of Engineering | Sun F.,Wuhan Naval University of Engineering
International Journal of Sustainable Energy | Year: 2014

An endoreversible closed modified simple Brayton cycle model with isothermal heat addition coupled to variable-temperature heat reservoirs is established using finite-time thermodynamics. Analytical expressions of dimensionless power output, thermal efficiency, dimensionless entropy generation rate and dimensionless ecological function are derived. Influences of cycle thermodynamic parameters on ecological performance and optimal compressor pressure ratio, optimal power output, optimal cycle thermal efficiency and optimal entropy generation rate corresponding to maximum ecological function are obtained and compared with those corresponding to maximum power output. The results show that cycle thermal efficiency improvement and entropy generation rate reduction are obtained at the expense of higher compressor pressure ratio and a little sacrifice of power output at maximum ecological function. The compromises between power output and entropy generation rate and between power output and cycle thermal efficiency, respectively, are achieved. © 2013 Taylor & Francis. Source

Zhang Y.,Beijing Institute of Technology | Wang X.,Beijing Space Information Relay Transmission Technology Center | Qi W.,Jiuquan Satellite Launching Center
Jiefangjun Ligong Daxue Xuebao/Journal of PLA University of Science and Technology (Natural Science Edition) | Year: 2015

To solve the problems such as small target size, low signal to noise ratio(SNR), serious interference of background and clutter, a star map enhancement method was presented based on background and clutter suppression. The model of star background image enhancement was established and multi-structure elements adopted in the morphology filter to suppress the star background and clutter. The plateaus histogram image equalization algorithm was also adopted in the weighed average of multiple morphology filters to improve the further image resolution. With this standing, the image enhancement effects were simulated, and SNR and background suppression factor of enhanced image calculated. The results show that the star background and clutter can be suppressed to a great extent, that the contrast ratio of image is improved remarkably, and that in the image the target is eabier to be tracked down and detected. ©, 2015, University of Science and Technology. All right reserved. Source

Hu Z.-H.,National University of Defense Technology | Hu Z.-H.,Jiuquan Satellite Launching Center | Zhu J.-B.,National University of Defense Technology | He F.,National University of Defense Technology | Liang D.-N.,National University of Defense Technology
Dianzi Yu Xinxi Xuebao/Journal of Electronics and Information Technology | Year: 2012

The performance of Direction-Of-Arrival (DOA) estimation of classical algorithms may degrade substantially in the presence of mutual coupling. In this paper, a blind source separation based algorithm is proposed for DOA estimation using uniform linear array. Firstly, the generalized array manifold matrix is estimated using blind source separation techniques; Then, based on the property that the mutual coupling matrix of uniform linear array can be modeled by a symmetric Toeplitz matrix, DOA estimation problem is transformed into multiple separable nonlinear least squares problems, and DOAs can be obtained by multiple one-dimensional peak searching. The proposed algorithm does not need multidimensional peak searching or multidimensional iteration, and imposes weaker constraints on the number of non-zero coefficients in the mutual coupling matrix. Besides, the proposed algorithm is applicable even if the number of non-zero coefficients in the mutual coupling matrix is unknown. Simulation results demonstrate the effectiveness of the proposed algorithm. Source

Ma S.-N.,Academy of Armored force Engineering | Suo X.-B.,Jiuquan Satellite Launching Center | Qiu J.,Academy of Armored force Engineering | Zhu H.-Y.,Academy of Armored force Engineering
Hangkong Cailiao Xuebao/Journal of Aeronautical Materials | Year: 2012

Al 2O 3 coatings embedded with SiO 2 nanoparticles were produced on 7A52 aluminum alloy by adding SiO 2 nanoparticles into the electrolyte. The effect of n-SiO 2 on the growth kinetics of the micro-arc oxidized coating under the two modes of constant voltage and constant current was investigated. The results show that nano-SiO 2 increased the growth rate of micro-arc oxidized coating and the current efficiency. Nano-SiO 2 is formed impurity energy level and narrowed band gap, so that impurity discharge is existed during the breakdown process and promoted the micro-arc oxidation process of electrical breakdown, resulting in the improvement of the growth efficiency of micro-arc oxidized coating. Source

Li T.,Jiuquan Satellite Launching Center
Journal of Mechanical Design, Transactions of the ASME | Year: 2012

The spherical gear is a gear-driven mechanism with two degrees of freedom (DOF), which can transfer spatial motion. The spherical gear pairs have two types of basic assembly structures including an ideal mechanism and a gimbal mechanism, and whose kinematic characteristics are analyzed. The 2-DOF gearing principle of conjugate tooth surfaces of the spherical gear pair is introduced first. Then, the relative slide between two tooth surfaces in the mesh is analyzed. Finally, the equations of the meshing coned surface and the conjugate surface are established based on the meshing models of the spherical gear pairs. Furthermore, the sliding ratios of the tooth surfaces of the spherical gear pairs are obtained when they mesh in different meshing conditions based on two-parameter movement analysis. The computational results show that the sliding ratios of the spherical gear teeth are related to the angle velocity ratio in the ideal mechanism and they are not only related with angle velocity ratio but also related with the assembly axes in the gimbal mechanism, which are useful in theory for further studying the wear of the spherical gear. © 2012 American Society of Mechanical Engineers. Source

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