载人登月软着陆制动段最优制导方法(英文)

提出一种解决软着陆制动段燃料最优制导以及闭环控制的方案.首先使用庞氏极大值原理将制动段燃料最优问题转化为一个初值问题,并使用遗传算法搜索求解;其次为了解决最优制导的闭环控制问题,将最优弹道作为标称弹道,使用RCS系统对轨道面内两个方向误差量进行解耦,分别使用极限环控制.仿真表明,所规划出的燃料最优弹道比阿波罗方案能节约159.7 kg的燃料,而闭环控制系统可以将初始1 000 m的位置误差和5 m/s的速度误差收敛到接近段入口误差要求以内,在闭环控制过程中,燃料消耗不大于87.75 kg,总体燃料消耗节约至少71.95 kg.     

军用飞机综合效能/费用评估方法

军用飞机的效能与费用是两个相互制约的因素,对两者进行科学合理的综合评估,对于军用飞机的发展和使用有着很重要的意义。在分析综合效能/费用的基本评估指标基础上,提出了在军用飞机全寿命周期综合效能/费用评估指标,重点对作战使用阶段的最佳效能/费用进行评估分析,最后给出结论。     

Statistical equivalency and optimality of simple step‐stress accelerated test plans for the exponential distribution

Accelerated life testing (ALT) is commonly used to obtain reliability information about a product in a timely manner. Several stress loading designs have been proposed and recent research interests have emerged concerning the development of equivalent ALT plans. Step‐stress ALT (SSALT) is one of the most commonly used stress loadings because it usually shortens the test duration and reduces the number of required test units. This article considers two fundamental questions when designing a SSALT and provides formal proofs in answer to each. Namely: (1) can a simple SSALT be designed so that it is equivalent to other stress loading designs? (2) when optimizing a multilevel SSALT, does it degenerate to a simple SSALT plan? The answers to both queries, under certain reasonable model assumptions, are shown to be a qualified YES. In addition, we provide an argument to support the rationale of a common practice in designing a SSALT, that is, setting the higher stress level as high as possible in a SSALT plan. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

自润滑关节轴承磨损寿命模型

自润滑关节轴承寿命的计算和预测对于提高装备的运行安全性具有重大的意义。针对自润滑关节轴承磨损寿命计算和预测的需求,本文从自润滑关节轴承的磨损机理出发,依据材料摩擦磨损理论,采用组合磨损计算方法分别建立了自润滑推力关节轴承和向心关节轴承的磨损寿命模型。该模型综合考虑了影响自润滑关节轴承寿命的磨损机理、结构特点、工作特性以及零部件功能要求等因素,特别是将结构参数和功能要求显式的在模型中表示,可直接反映结构变化和功能要求对自润滑关节轴承磨损寿命的影响。计算实例和分析结果表明：相对目前使用的自润滑关节轴承经验计算公式,本文模型计算结果准确,理论依据更充分,对于特殊结构和功能的特种自润滑关节轴承适用性更好。     

Change as a cost driver in defence procurement

This paper discusses change transactions that occur in connection with the procurement of defence systems. The bases for the reasoning are the ideas of Miller and Vollman (1985 Miller JG Vollman TE (1985) The hidden factory – cutting the explosive growth of overhead costs requires mastery of more than just what happens on the shop floor Harvard Business Review Sept–Oct 142 150  [Google Scholar]) and Eppinger (2001 Eppinger DE (2001) Innovation at the speed of information Harvard Business Review January 149 158  [Google Scholar]). These researchers argue that unplanned flows of information lead to change transactions, causing significant overhead costs. According to this paper, change transactions in defence procurement could be caused by (a) the changes in technology taking place during the long lifetime of a defence system and (b) the structure and contents of the agreements between the defence agent (the procurer) and the defence industry (the supplier).     

THE NUCLEAR THRESHOLD STATES

“Nuclear threshold states”—those that have chosen nuclear restraint despite having significant nuclear capabilities—seem like the perfect partners for the reinvigorated drive toward global nuclear disarmament. Having chosen nuclear restraint, threshold states may embrace disarmament as a way to guarantee the viability of their choice (which may be impossible in a proliferating world). Supporting disarmament efforts affirms their restraint, both self-congratulating and self-fulfilling. Additionally, the commitment to their non-nuclear status springs at least in part from a moral stance against nuclear weapons that lends itself to energetic support of global disarmament. However, threshold states also offer significant challenges to the movement for nuclear weapons elimination, in particular in relation to acquisition of enrichment and reprocessing facilities. This article analyzes both the challenges and opportunities posed by threshold states by examining the cases of Brazil and Japan.     

论高中《政治生活》实施探究性学习的一般模式

探究性学习的实质是要求教师转变教育观念,在教学中充分调动学生学习的主动性和积极性,激发学生学习的主人翁意识,真正使学生成为学习的主人。因此高中政治课的课堂教学应该充分渗透探究性学习的精神,同时教师又应在这一宗旨的指导下,根据教材的内容和特点的不同采用不同的模式,选用不同的方法,这样才能达到构建高效课堂的目的。     

化学键合胶凝材料抗硫酸盐侵蚀性能

采用浸-烘循环的方法模拟干湿循环交替环境进行新型化学键合胶凝材料抗硫酸盐加速侵蚀试验.侵蚀溶液为质量浓度为5％的硫酸钠溶液,一组试验采用全浸-烘循环,另一组试验采用半浸-烘循环.在经受30×N(N=1,2,3,4,5)次循环后,测定试件的强度耐蚀系数和质量损失率,以此评价化学键合胶凝材料抗硫酸盐侵蚀性能.试验结果表明:半浸-烘循环的侵蚀比全浸-烘循环的侵蚀严重;在经受150次侵蚀循环后,试件外观无严重破损,质量不减反增,强度也不降低,说明化学键合胶凝材料具有优良的抗硫酸盐侵蚀性能.     

Maintenance scheduling for modular systems: Modeling and algorithms

We study new models of scheduled maintenance management for modular systems, consisting of multiple components with respective cycle limits. The cycle limit of each component specifies the time interval in which this component must be repaired or replaced. The goal is to compute a feasible maintenance schedule that minimizes the cost associated with component maintenance. Applications of these models arise in Air Force aircraft maintenance as well as in other arenas with required preventive maintenance. The typical cost structures that arise in practical settings are submodular, which make the resulting models computationally challenging. We develop two efficient and operationally tenable approximation algorithms. We prove constant factor worst‐case guarantees for both algorithms, and present computational experiments showing that these algorithms perform within a few percent of optimality on operationally relevant instances. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 472–488, 2014     

The single and multi‐item transshipment problem with fixed transshipment costs

This article deals with supply chain systems in which lateral transshipments are allowed. For a system with two retailers facing stochastic demand, we relax the assumption of negligible fixed transshipment costs, thus, extending existing results for the single‐item case and introducing a new model with multiple items. The goal is to determine optimal transshipment and replenishment policies, such that the total centralized expected profit of both retailers is maximized. For the single‐item problem with fixed transshipment costs, we develop optimality conditions, analyze the expected profit function, and identify the optimal solution. We extend our analysis to multiple items with joint fixed transshipment costs, a problem that has not been investigated previously in the literature, and show how the optimality conditions may be extended for any number of items. Due to the complexity involved in solving these conditions, we suggest a simple heuristic based on the single‐item results. Finally, we conduct a numerical study that provides managerial insights on the solutions obtained in various settings and demonstrates that the suggested heuristic performs very well. © 2014 Wiley Periodicals, Inc. Naval Research Logistics, 61: 637–664, 2014