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Shen, Yunwen; Liu, Mengjun; Dong, Haijun
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In some mechanical nonlinear systems, the transient motion will be undergoing a very long process and the attractorbasin boundaries are so complicated that some difficulties occur in analyzing the system global behavior. To solve this problem a mixed cell mapping method based on the point mapping and the principle of simple celll mapping is developed. The algorithm of the mixed cell mapping is studied. A dynamic model of a gear pair is established with the backlash, damping, transmission error and the timevarying stiffness taken into consideration. The global behaviors of this system are analyzed. The coexistence of the system attractors and the respective attractorbasin of each attractor with different parameters are obtained, thus laying a theoretical basis for improvement of the dynamic behaviors of gear system.
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Ma, Jianbo; Xu, Jin; Cao, Zhibin
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In this paper a method of autonomous orbit determination using star sensor is studied. By building relatively consummate dynamical models which simulate attitude motion of satellite and observation from satellite to background stars, the simulant computation of this method is executed, and it is shown that the method of autonomous orbit determination is feasible. Academic and calculation analyses have been done for the relation between the direction of star sensor with respect to statellitebody coordinate system and the accuracy of autonomous orbit determination.
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Zhang, Dongming; Luo, Jisheng; Zhou, Heng
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Based on the theoretical model for a single coherent structure in the wall region of a turbulent boundary layer, we studied the interaction of two coherent structures by direct numerical simulation in order to explain the mechanism for the formation of lowspeed streaks.
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Huang, Jianguo; Han, Jianwei
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A key point in SEE (Single Event Effect) simulation experiment is how to calculate the equivalent LET (Linear Energy Transfer) for laser pulse. In this paper, the calculation method considering the influences of nonlinear absorption in semiconductor, reflection and refraction on device surface and other factors is presented. Simultaneously an instance of calculation is provided, with the result in good agreement with the SEU (Single Event Upset) threshold measured by heavy ions.
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Liu, Chun; Zhang, Laibin; Wang, Zhaohui
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Condition monitoring and life prediction of the vehicle engine is an important and urgent problem during the vehicle development process. The vibration signals that are closely associated with the engine running condition and its development trend are complex and nonlinear. The chaos theory is used to treat the nonlinear dynamical system recently. A novel chaos method in conjunction with SVD (singular value decomposition) denoising skill are used to predict the vibration time series. Two types of time series and their prediction errors are provided to illustrate the practical utility of the method.
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Li, Yanchun; Sun, Liling; Cao, Limin; Zhao, Jianhua; Wang, Haiyan; Nan, Yun; Gao, Zhenshan; Wang, Wenkui
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Bulk single crystals βFeSi_{2}, as a new photoelectric and thermoelectric material, has been successfully grown using chemical vapor transport technique by using iodine as transport agent in a sealed ampoule. The effects of crystal growth condition on quality and morphologies of the single crystals were studied. Both needlelike and grainlike single crystals were gained. By changing substrate temperature, tetrahedral high quality αFeSi_{2} single crystals were also obtained.
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Chen, Zhenpeng; Zhang, Rui; Sun, Yeying; Liu, Tingjin
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The error propagation features with Rmatrix model fitting^{7}Li,^{11}B and^{17}O systems have been researched systematically. Some laws of error propagation have been revealed, an experience formula for describing standard error propagation has been established, and the most possible error range for evaluated standard cross section of^{6}Li (n, α),^{10}B (n, α) and^{10}B (n, α_{1}) has been determined.
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Hu, Jingfu; Li, Xin; Yang, Fumin; Chen, Wanzhen; Zhang, Zhongping
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The effective area of spaceborne laser retroreflector directly influences the intensity of the return signals for satellite laser ranging. The configuration of the retroreflector array determines the effective area. The formula for the effective area of the spaceborne retroreflector array with different inclination angles at arbitrary celestial zone was deduced in this paper. As an example, the calculation result about effective area for the retroreflector array of the ShenzhouIV orbital module was given.
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Lin, Liu; Xin, Wang
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While approaching the target body, the deepspace probe is orbiting hyperbolically before the maneuver. We discuss the variation of perturbed hyperbolic orbit using the method similar to that used in elliptic orbit. Ephemeris calculating and orbit control will benefit from the given analytical solution.
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Feng, Gan; Zhu, Jianjun; Shen, Xiaoming; Zhang, Baoshun; Zhao, Degang; Wang, Yutian; Yang, Hui; Liang, Junwu
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In this paper we propose a new method for measuring the thickness of the GaN epilayer, by using the ratio of the integrated intensity of the GaN epilayer Xray diffraction peaks to that of the sapphire substrate ones. This ratio shows a linear dependence on the GaN epilayer thickness up to 2 μm. The new method is more accurate and convenient than those of using the relationship between the integrated intensity of GaN epilayer diffraction peaks and the GaN thickness. Besides, it can eliminate the absorption effect of the GaN epilayer.
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