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71.
矩形变截面梁横向振动自振频率的传递函数渐近解法 总被引:1,自引:0,他引:1
分析具有固定宽度而高度成线性分布的楔形梁。引入状态变量将模形梁的自由振动控制方程及边界方程写成状态空间形式。定义小参数,并利用摄动方法,得到常系数微分方程,从而得到问题的摄动解。最后给出了一些数值算例,验证了方法的可行性。 相似文献
72.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(4):1210-1224
This work develops an autonomous trajectory planning algorithm for 6-DOF asteroid landing. The trajectory planning problem is formulated as a nonconvex time-optimal optimization problem with two-phase free final time, while the cost is regularized by augmenting a fuel consumption penalty. The nonconvex optimization problem is solved in successive solution method, and successive convexification is used to convert the original nonconvex problem into a sequence of convex subproblems, where each subproblem is obtained by linearizing the nonconvex dynamics and state constraints and using the velocity increment to give a convex expression of the fuel consumption penalty in cost function. Specifically, in the linearization, we divide the flight time interval into two parts and normalize each part using a time dilation coefficient to solve the problem that both the final times for the two flight phases are unknown, so that the original free final time problem turns to a fixed-time problem by minimizing the sum of the two time dilation coefficients and fuel consumption penalty. Besides, trust regions and virtual control are used to increase robustness of the algorithm. A convergence analysis is presented which indicates the successive solution will recover the local optimality of the original problem. Then the validity of the proposed algorithm and effects of different factors on flight time and fuel consumption are examined by simulations of landing on an irregular asteroid. 相似文献
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研究了一种新型高微重力水平气球舱内试验平台的动力特性,考虑了稀薄气体的影响,建立了落舱及平台的动力学方程,通过数值计算获得了平台微重力水平与落舱控制精度、平台与落舱的分离时刻、真空舱内真空度的关系。 相似文献
75.
This paper presents a gaskinetic study on high-speed, highly rarefied jets expanding into a vacuum from a cluster of planar or annular exits. Based on the corresponding exact expressions for a planar or annular jet, it is convenient to derive the combined multiple jet flowfield solutions of density and velocity components. For the combined temperature and pressure solutions, extra attention is needed. Several direct simulation Monte Carlo simulation results are provided to validate these analytical solutions. The analytical and numerical solutions are essentially identical for these high Knudsen number jet flows. 相似文献
76.
本文报道利用红外热象仪 AGA780系统测量金属铝、铜和非金属石膏的平板及圆柱表面温度的准确度实验研究的结果。给出了表面形状不影响温度测量的“自由极角”范围,并且对影响测量准确性的其他因素也进行了讨论。 相似文献
77.
I. Kitiashvili A. Gusev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,42(8):1391-1397
PSR B1828-11 has long-term, highly periodic and correlated variations in pulse shape and a slow-down rate with period variations of approximately 1000, 500 and 250 days [Stairs, I.H., Lyne, A.G., Shemar, S.L. Evidence for free precession in a pulsar. Nature 406, 484–486, 2000]. There are three potential explanations of pulses time-of-arrival from a pulsar. These are related to the interior of the neutron star, planetary bodies, free precession and nutation. We use the Hamiltonian canonical method of Getino (1995) for analyzing the dynamically symmetric pulsar PSR B1828-11, consisting of a rigid crust, elliptical liquid outer core and solid inner core. Using the theory of differential rotation of a pulsar, we investigate the dependence on Chandler wobble period, inner core wobble, retrograde free core nutation and prograde free inner core nutation from ellipticity of the inner crystal core, outer liquid core and total pulsar. 相似文献
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自由软件运动的兴起,带给导航系统一个全新的设计模式,即根据所设计的导航系统定制实时内核,将应用层的设计和内核层的设计融合在一起。文章将自由软件应用到导航系统设计中,提出了基于自由软件的导航系统设计方法,并给出了基于自由软件uC/OS的GPS/INS组合导航系统的实现,经实验验证,本系统具有良好的性能。 相似文献