Analytical expression for distant retrograde orbits around a small natural satellite

An analytical expression for distant retrograde orbits (DROs) is obtained in this study. Owing to the fact that a planar DRO is a closed orbit and can be expressed as an approximately elliptical orbit, respective geometries and periods of DROs are analytically calculated. A switching point, where various properties of planar DROs change abruptly with an increase in the orbital radius, is determined. The Mars–Deimos system is taken as a case study in this work. The proposed method can be applied to cases where the Hill’s approximation of the restricted three-body problem is valid. Numerical calculations are performed to validate the proposed method.     

特征结构配置法在输出反馈控制器设计中的应用

现代控制理论中的特征结构配置法(Eigenstructure Assignment),揭示了线性定常系统状态反馈控制规律的设计能力,并向设计者提供了充分的设计自由度。本文介绍了一种利用特征结构配置法进行输出反馈控制器设计的算法。当n阶r个输入m个输出的线性定常系统满足关系r+m>n时,运用该算法可以获得配置任意希望闭环特征值集合的线性输出反馈控制规律,并具有一定的特征结构配置自由度;对于不满足r+m>n的系统,利用积分器增广可以获得比Luenbetger状态估计器阶数低的动态输出反馈控制器,以实现闭环特征值任意配置。该算法容易用数字计算机编程实现。     

变容量限制多阶段存储问题及其求解算法

本文给出了求变容量限制多阶段存储问题的最优存储方案的一个数值算法，证明了它的理论依据，并举例说明了算法的应用。该算法具有概念清楚、步骤明确、收敛性好、易于编程实现等优点，在存贮管理中有推广应用价值。     

裂缝区域优化随机扩展航路规划方法

针对密集障碍代价空间中存在的局部裂缝区域,基于采样的路径规划方法随机生成的节点无法进行有效扩展,形成可行路径的概率极低的问题,采用电势原理建立环境威胁模型,提出局部区域启发模式转换机制及节点一步检测方法.采用路径代价改进Transition-based RRT算法的节点选择机制,实现节点扩展的双启发.仿真结果表明,该算法能够有效地解决上述问题,其算法性能和路径生成优于同类算法.     

非线性递推最小模型误差估计

基于最优控制理论和两点边值问题的不变式嵌入法，提出了模型不确定性非线性性系统递推最小模型误差估计，并推导了估计算法。仿真例说明，该方法是模型不确定性非线性系统状态递推估计的有效方法。     

我国国有企业法人治理结构存在的问题及对策

完善国有企业法人治理结构是国有企业公司制改革的关键，本文阐述了公司法人治理结构的含义和基本构成，分析了我国国有企业法人治理结构存在的问题，并针对存在的问题提出了相应的对策和建议。     

Bayesian approach to retrieval of vertical ozone profile from radiometry data

A technique for retrieving vertical distributions (profiles) of atmospheric gas constituents from data of passive remote sensing of the atmosphere is proposed. The goal of the technique based on the statistical (Bayesian) approach to solution of inverse problems is construction of probability distribution for a sought quantity throughout the interval of the studied heights. It is assumed that initial data contain measurement noise, and a priori information about properties of the profile is used. It is proposed to approximate the sought profile by a function in the form of an artificial neural network. This approximation allows optimal inclusion of a priori information into retrieval procedure, thus ensuring the most effective regularization of the problem. Efficiency of the proposed technique is demonstrated on an example of retrieval of vertical ozone profile from data of ground-based sounding of the atmosphere in the millimeter wavelength range. Results of profile retrieval from model data and from spectra of radiation temperature of the atmosphere measured in the Apatity (67° N, 33° E) in the winter of 2002–2003 are presented.     

目标天体极轨道卫星的轨道寿命

星际探测器轨道的特征与探测目的密切相关，对目标天体两级地区进行探测显然采用的是极轨道（或接近极轨道）。对于这类卫星（或称轨道器），如果轨道半长径较大，则会因第三体报骚动国导致轨道偏心率增大，使其近星距减小到等于目标天体的赤道半径而落到该天体上，结束其运动寿命，即使目标天体不存在大气（如月球等）亦会如此。     

我国不同类型卓越工程师人才培养的思考

通过剖析我国卓越工程人才培养过程中存在的问题,提出从高校自身、校企结合、政府扶持等多方面改善工程人才培养过程,在注重理论的基础上关注实验、实践的重要作用,将不同类型的工程师培养标准融入高校工程人才培养之中,加强校企结合,高校和企业共同设计培养目标,制定培养方案,共同实施培养过程。     

Properties of transit trajectory in the restricted three and four-body problem

In the restricted three-body problem if the Jacobi constant is just below the value corresponding to Lagrangian point only a little neck exists around the equilibrium point and capture trajectories are indicated as low-energy. Capture properties depend on the dynamics around these critical points and qualitative results can be obtained using linearized systems. In this paper, to study transit trajectory properties in the restricted three and four-body problem, the Earth–Moon–Sun–Satellite system is considered as example and studied using different models. In the circular restricted three-body problem (Earth–Moon–Satellite), transit, non transit and asymptotic trajectories, are easily identified by using the principal reference frame. Dynamics around Lagrangian point are then studied introducing the Moon eccentricity into the elliptical restricted three-body model. A preferential region for transit orbit is individuated and studied as a function of eigenvalue properties. To introduce the Sun effect, the bi-circular four-body model is considered and dynamics around Lagrangian points studied as a function of angular distance between Earth–Sun and Earth–Moon line. Finally, results obtained in the elliptical three-body model and bi-circular four-body model, are compared with numerical simulations using real Sun–Moon–Earth ephemeris.