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911.
Gong-Bo Wang · Yun-He Meng · Wei Zheng · Guo-Jian Tang College of Aerospace Material Engineering National University of Defense Technology Changsha China 《Acta Mechanica Sinica》2011,27(5):809-816
Sun synchronous orbit and frozen orbit formed due to J 2 perturbation have very strict constraints on orbital parameters,which have restricted the application a lot.In this paper,several control strategies were illustrated to realize Sun synchronous frozen orbit with arbitrary orbital elements using continuous low-thrust.Firstly,according to mean element method,the averaged rate of change of the orbital elements,originating from disturbing constant accelerations over one orbital period,was derived from Gauss’ variation of parameters equations.Then,we proposed that binormal acceleration could be used to realize Sun synchronous orbit,and radial or transverse acceleration could be adopted to eliminate the rotation of the argument of the perigee.Finally,amending methods on the control strategies mentioned above were presented to eliminate the residual secular growth.Simulation results showed that the control strategies illustrated in this paper could realize Sun synchronous frozen orbit with arbitrary orbital elements,and can save much more energy than the schemes presented in previous studies,and have no side effect on other orbital parameters’ secular motion. 相似文献
912.
Steady thermocapillary-buoyant convection in a shallow annular pool. Part 1: Single layer fluid 总被引:1,自引:0,他引:1
You-Rong Li · Shuang-Cheng Wang · Chuan-Mei Wu College of Power Engineering Chongqing University Chongqing China Key Laboratory of Low-grade Energy Utilization Technologies Systems Ministry of Education China 《Acta Mechanica Sinica》2011,27(3):360-370
This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios,which is defined as the ratio of the layer thickness to the gap width. The flow domain is divided into the core region away from the cylinder walls and two end regions near each cylinder wall. Asymptotic solutions are obtained in the core region by solving the core and end flows separately and then joining them through matched asymptotic expansions. For the system of silicon melt,the asymptotic solutions are compared with the results of numerical simulations. It is found that the two kinds of solutions have a good agreement in the core region for a small aspect ratio. With the increase of aspect ratio,the applicability of the present asymptotic solutions decreases gradually. 相似文献
913.
Yan-Song Li · Zeng-He Xu · Wen-Jie Feng Institute of Engineering Mechanics Northeastern University Shenyang China Department of Engineering Mechanics Shijiazhuang Tiedao University Shijiazhuang China 《Acta Mechanica Sinica》2011,27(3):371-381
A penny-shaped interfacial crack between dissimilar magnetoelectroelastic layers subjected to magnetoelectromechanical loads is investigated,where the magnetoelectrically impermeable crack surface condition is adopted. By using Hankel transform technique,the mixed boundary value problem is firstly reduced to a system of singular integral equations,which are further reduced to a system of algebraic equations. The field intensity factors and energy release rate are finally derived. Numerical results elucidate the eects of crack configuration,electric and/or magnetic loads,and material parameters of the magnetoelectroelastic layers on crack propagation and growth. This work should be useful for the design of magnetoelectroelastic composite structures. 相似文献
914.
Approximate and numerical analysis of nonlinear forced vibration of axially moving viscoelastic beams 总被引:1,自引:0,他引:1
Hu Ding · Li-Qun Chen Shanghai Institute of Applied Mathematics Mechanics Shanghai University Shanghai China Department of Mechanics Shanghai China 《Acta Mechanica Sinica》2011,27(3):426-437
Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially uniform and temporally harmonic. The transverse motion of axially moving beams is governed by a nonlinear partial-differential equation and a nonlinear integro-partial-differential equation. The material time derivative is used in the viscoelastic constitutive relation. The method of multiple scales is applied to the governing equations to investigate primary resonances under general boundary conditions. It is demonstrated that the mode uninvolved in the resonance has no effect on the steady-state response. Numerical examples are presented to demonstrate the effects of the boundary constraint stiffness on the amplitude and the stability of the steady-state response. The results derived for two governing equations are qualitatively the same,but quantitatively different. The differential quadrature schemes are developed to verify those results via the method of multiple scales. 相似文献
915.
Powell dynamic identification of displacement parameters of indeterminate thin-walled curve box based on FCSE theory 总被引:1,自引:0,他引:1
Jian Zhang · Chu-Wei Zhou · Jia-Shou Zhuo College of Aerospace Engineering Nanjing University of Aeronautics Astronautics Nanjing China College of Mechanics Material Hohai University Nanjing China 《Acta Mechanica Sinica》2011,27(3):452-460
The FCSE controlling equation of pinned thinwalled curve box was derived and the indeterminate problem of continuous thin-walled curve box with diaphragm was solved based on flexibility theory. With Bayesian statistical theory,dynamic Bayesian error function of displacement parameters of indeterminate curve box was founded. The corresponding formulas of dynamic Bayesian expectation and variance were deduced. Combined with one-dimensional Fibonacci automatic search scheme of optimal step size,the Powell optimization theory was utilized to research the stochastic identification of displacement parameters of indeterminate thin-walled curve box. Then the identification steps were presented in detail and the corresponding calculation procedure was compiled. Through some classic examples,it is obtained that stochastic performances of systematic parameters and systematic responses are simultaneously deliberated in dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step size is solved by adopting Fibonacci search method. And the Powell identification of displacement parameters of indeterminate thin-walled curve box has satisfied numerical stability and convergence,which demonstrates that the presented method and the compiled procedure are correct and reliable.During parameters’ iterative processes,the Powell theory is irrelevant with the calculation of finite curve strip element(FCSE) partial differentiation,which proves high computation effciency of the studied method. 相似文献
916.
917.
就变截面的半无限圆柱体,当横向边界值为0时,研究半线性抛物线型方程的初边值问题解的空间衰减.对其解的一个L2p横截面量,导出的2阶微分不等式表明,空间衰减呈D(exp{-z2/[4(t+t0)]}).同时导出了引起增长或衰减的1阶微分不等式.在爆破空间中得到增长情况下的上界,当衰减情况时,根据已知的数据,得到总能量的上界. 相似文献
918.
919.
研究由一个可靠机器,一个不可靠机器与一个无穷容量的缓冲库构成的系统主算子在左半复平面中的特征值,证明对一切θ∈(0,1),(2(λη_1μη_2)~(1/2)-λη_1-μη_2)θ都是该主算子的几何重数为1的一个特征值. 相似文献
920.
运用Hille-Yosida定理,Phillips定理与Fattorini定理证明第二种服务可选的M/G/1排队模型存在唯一的概率瞬态解. 相似文献