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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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1 Citations
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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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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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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Wang, Jing; Zeng, Jinyan
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3 Citations
The symmetry and m partialwave analysis for twodimensional (2D) Coulombscattering is investigated. As a function of energyE, the m partialwave scattering amplitudef_{m}(θ) is analytically continuated to the, negativeE (complexk) plane, and it is found that the bound state energy eigenvalues (E<0) are just located at the poles off_{m}(θ) on the positive imaginaryk axis as is expected. In addition, as a function of m,f_{m}(θ) is analytically continuated to the complex m plane, the bound state energy eigenvalues are just located at the poles off_{m}(θ) on the positive real m axis.
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Chen, Yonghu; Liu, Bo; Shi, Chaoshu; Tao, Ye; Ju, Xin
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The emission and excitation spectra of Gd_{2}SiO_{5}∶Eu^{3+} were investigated using the VUV beam line of the Beijing Synchrotron Radiation Facility (BSRF). The experimental results were discussed in the frame of visible quantum cutting process involved in Gd^{3+}−Eu^{3+} system. Upon direct excitation into the^{6}G_{J} states of Gd^{3+}, two visible photon emissions from Eu^{3+} were observed. Cursory evaluation proved that Gd_{2}SiO_{5}∶Eu^{3+} is an efficient visible quantum cutter.
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