空间站通信和跟踪系统

本文将对空间站通信和跟踪系统的现有要求、结构和设计思想进行全面描述,着重阐述那些需要用新方法才能构成高成本—效率飞行系统的领域。其中包括空对空线路、确定自由飞行器相对位置的差分全球定位系统、多目标雷达、数据包/等时信号处理和激光对接系统。另外,本文还将概述预先研制、试验和分析的重要性。     

装备研制中的并行工程方法

对装备开发中所采用的两种不同的组织形式进行了分析对比,介绍了"并行工程"的基本概念,并从管理角度出发论述了利用并行工程方法进行装备开发的几个关键过程.     

Eutectic phases in ice facilitate nonenzymatic nucleic acid synthesis

Polymeric compounds similar to oligonucleotides are relevant to the origin of life and particularly to the concept of an RNA world. Although short oligomers of RNA can be synthesized nonenzymatically under laboratory conditions by second-order reactions in concentrated solutions, there is no consensus on how these polymers could have been synthesized de novo on the early Earth from dilute solutions of monomers. To address this question in the context of an RNA world, we have explored ice eutectic phases as a reaction medium. When an aqueous solution freezes, the solutes become concentrated in the spaces between the ice crystals. The increased concentration offsets the effect of the lower temperature and accelerates the reaction. Here we show that in the presence of metal ions in dilute solutions, frozen samples of phosphoimidazolide-activated uridine react within days at -18 degrees C to form oligouridylates up to 11 bases long. Product yields typically exceed 90%, and approximately 30% of the oligomers include one or more 3'-5' linkages. These conditions facilitate not only the notoriously difficult oligouridylate synthesis, but also the oligomerization of activated cytidylate, adenylate, and guanylate. To our knowledge, this represents the first report to indicate that ice matrices on the early Earth may have accelerated certain prebiotic polymerization reactions.     

公众演示表明远现技术大有希望

上星期,坐在温暖舒适的美国航空航天博物馆控制站内的操作手,与数千公里以外水下机器人进行电气连接,通过广角镜头观看了南极冰层下面的水下生命,并且自引导观看了冰土边沿。该演示透露了一种将来用于遥控机器人探索遥远世界表面的技术。 目前,随着高速数据网,交互性电视和计算机软、硬件的发展,已能操作远距离的地面远控车辆,反映未来机器人星际探测的希望。该技术称为远现(telepresence),人类借助它能探测各种遥远和危险的环境。     

Challenges of assuring crew safety in space shuttle missions with international cargoes

The top priority in America's manned space flight program is the assurance of crew and vehicle safety. This priority gained greater focus during and after the Space Shuttle return-to-flight mission (STS-26). One of the interesting challenges has been to assure crew safety and adequate protection of the Space Shuttle, as a national resource, from increasingly diverse cargoes and operations. The control of hazards associated with the deployment of complex payloads and cargoes has involved many international participants. These challenges are examined in some detail along with examples of how crew safety has evolved in the manned space program and how the international partners have addressed various scenarios involving control and mitigation of potential hazards to crew and vehicle safety.     

航天轴承摩擦力矩的最大熵概率分布与bootstraP推断

滚动轴承摩擦力矩具有不确定的波动和趋势变化,属于概率分布与趋势规律都未知的乏信息系统。这是一个重要问题,它阻碍了对轴承摩擦力矩的小样本分析与总体把握。为了解决这个问题,根据最大熵原理,从小样本入手建立航天轴承摩擦力矩的概率密度函数。以此为基础,在讨论了摩擦力矩的时域特征与概率分布特征后,用bootstrap对摩擦力矩总体的分布参数进行统计推断。试验研究表明,推断结果和试验结果之间的误差很小,满足工程要求。因此,用小样本可以描述航天轴承摩擦力矩总体的统计特征。     

Force and power characteristics of a resistive exercise device for use in space

We have developed a non-gravity dependent mechanical device, which provides resistance during coupled concentric and eccentric muscle actions, through the inertia of a spinning fly-wheel (Fly-Wheel Ergometry; FWE). Our research shows that lower-limb FWE exercise can produce forces and thus muscular stress comparable to what is typical of advanced resistance training using free weights. FWE also offers greater training stimuli during eccentric relative to concentric muscle actions, as evidenced by force and electromyographic (EMG) measurements. Muscle use of specific muscle groups, as assessed by the exercise-induced contrast shift of magnetic resonance images, is similar during lower-limb FWE and the barbell squat. Unlike free-weight exercise, FWE allows for maximal voluntary effort in each repetition of an exercise bout. Likewise, FWE exercise, not unassisted free-weight exercise, produces eccentric "overload". Collectively, the inherent features of this resistive exercise device and the results of the physiological evaluations we have performed, suggest that resistance exercise using FWE could be used as an effective exercise counter-measure in space. The flywheel principle can be employed to any exercise configuration and designed into a compact device allowing for exercises stressing those muscles and bone structures, which are thought to be most affected by long-duration spaceflight.     

平尾均值在武器装备科学技术奖成果评定中的应用

分析、比较了样本均值、截尾均值、平尾均值在统计学意义下的特性和差别,阐述了在武器装备科学技术奖成果评定中,以平尾均值替代样本均值的必要性和意义。