世界标准日祝词

就最广泛的意义来讲,运输意味着把各种人员、技术和组织团体相互联结起来的一个错综复杂的网络。请设想一下,为了乘小汽车、长途汽车或火车以及飞机来加速商务活动或每家每户歼出度假的旅行,为了把     

GENERATION AND APPLICATION OF UNSTRUCTURED ADAPTIVE MESHES WITH MOVING BOUNDARIES

INTRODUCTIONMany engineering applications require thenumerical prediction of strongly unsteady flowsinteracting with moving bodies.A case in pointis that the detailed calculation of sphere motionsin an unsteady field induced by blast waves is akey issue to determine the drag force exerting up-on the sphere by the surrounding gas and,inturn,to reveal the mechanism of unsteady effectson the drag coefficient.To cope with such pro-blems,one should simulate unsteady flows withmoving boundary co…     

Skill maintenance in extended spaceflight: a human factors analysis of space and analogue work environments

This paper discusses the implications of increasing mission lengths of manned spaceflight for the design of future space systems from a human factors point of view. It is argued that the increase in mission duration has brought about a number of new problems, which have not been sufficiently addressed in space research. Therefore, a review of analogue work environments is carried out to make up for the paucity of space research found in the area of human performance in long-duration spaceflight. This resulted in an evaluation of seven analogue environments concerning their similarity to space with industrial process control and nuclear submarines coming out as the closest match on the technical dimension. Finally, some recommendations are given from the lessons learned in spaceflight, simulation studies and appropriate analogue environments.     

Psychological considerations of man in space: problems & solutions

With concrete plans for long duration flight taking form a new impetus is lent to preparing man for this hostile and unnatural environment. Cramped conditions, isolation from family and loved ones, work stress, fear, and incompatibility with fellow crew, are but a few of the problems suffered by astronauts and cosmonauts during their long missions in orbit about the earth.

Although criteria for selection of crew is one aspect of attacking the problem, it has not solved it Notwithstanding good selection, team combination, and counselling before flight, problems have still occurred with unwanted consequences. Incompatibility of team members, far from being the exception, has been frequent. This has been detrímental both physiologically and psychologically for the individual as well as for the operational success and safety of the missions.

Because problems will inevitably occur in future long duration missions, especially when they are of international and multi-cultural nature, the importance of dealing with them is underlined. This paper takes a different approach towards ameliorating these problems, namely that of psychological group training before a mission.     

Effects of microgravity on the binding of acetylsalicylic acid by Rhizobium leguminosarum bv. trifolii

Bacteroids can be induced in vitro by treating growing Rhizobium leguminosarum bv. trifolii with succinic acid or succinic acid structural analogs like acetysalicylic acid. Quantitating bacteroid induction by measuring acetylsalicylic binding under normal (1 g) conditions showed two forms of binding to occur. In one form of binding cells immediately bound comparatively high levels of acetylsalicylic acid, but the binding was quickly reversed. The second form of binding increased with time by first order kinetics and reached saturation in 40 s. Similar experiments performed in the microgravity environment aboard the NASA 930 aircraft showed only one form of binding and total acetylsalicyclic acid bound was 32% higher than at 1 g.     

Project Phoenix and beyond. Pesek Lecture

Although there are no federally funded projects at this time, SETI (the search for extraterrestrial intelligence) is a vigorous exploratory science. There are currently eight observational programs on telescopes around the world, of which the Phoenix Project is the most comprehensive. Most of these projects are rooted in the conclusions of the pioneering studies of the early 1970's that are summarized in the Cyclops Report. Technology has experienced an exponential growth over the past two and a half decades. It is reasonable to reassess the Cyclops conclusions as SETI enters the next century. Listening for radio signals is still the preferred method of searching, however new technologies are making searches at other wavelengths possible and are modifying the ways in which the radio searches can and should be conducted. It may be economically feasible to undertake the construction of very large telescopes that can simultaneously provide multiple beams on the sky for use by SETI and the radioastronomy community.     

MX导弹第一级发动机

MX导弹第一级发动机在系统论证阶段后,现在正进入研制阶段。其设计原则是选择能使性能、成本和进度三者之间得到平衡的技术。由于MX导弹第一级发动机是为弹道导弹研制的迄今最大的固体动力装置,因而其设计具有普遍意义。     

导弹性能和喷管/可延伸扩散段(EEC)设计变量之间的参数关系

1 引言在战略导弹系统容积受到限制的约束下,设计具有最高性能的发动机装入有效的外壳中,而同时又能满足系统设计和操纵的所有要求,包括载荷、重量和射程的要求,这个问题是很重要的。对导弹性能有很大影响的一个关键设计参数是发动机喷管的膨胀比。在容积有限的条件下,为了要做到大的喷管膨胀比,现实的设计方法是应用可延伸扩散段(EEC)~#。本     

复合固体推进剂浇入发动机时的流变学

浇铸时未固化的复合固体推进剂的流动特性是十分重要的,因为它直接关系到发动机装药的完整性。增加推进剂的固体含量,可以提高能量特性,却导致药浆的流动性变坏。固体含量高的推进剂呈现非牛顿假塑性流动特性,即表观粘度依赖于剪切应力,以及随着未固化推进剂存放时间的增长,假塑性也增加。本文介绍了在 NASA 主办下进行浇铸研究的一些情况。对浇铸过程中剪切应力的三个明显不同区域和每一区域中推进剂的流动特性,进行了讨论。叙述了推进剂组分和工艺条件的变化对表观粘度的影响和浇铸过程中形成药柱缺陷的有关流变性能的实验结果。     

机载阵列雷达抑制运动杂波的学习算法

一种称为自适应空时处理器(STP)的线性滤波器是一种相对比较新的方法，它使机载阵列天线雷达目标检测概率达到最大。理论上，全自适应STP可以实时获得最优解(一种维恩滤波器)。但是，实际上全自适应STP也存在一些问题。首先，线性滤波器的加权数可能非常大。其次，单一加权矢量的计算复杂度大约为O(MN)^3。再次，STP为线性滤波器但却工作在非线性不稳定的环境中。这些问题导致采用空时处理器传统技术的实时、最佳处理是现行计算技术内所不及的。为使运动杂波对目标检测的影响最小，本文探讨了人工神经网络和几种学习算法的可应用性。人工神经网络是一种自适应、并行、分布式处理系统，可以实时完成复杂计算。学习算法的机理是为了存储新的信息或变更信息，人工神经网络中的长期存储器要不断更新而又不被破坏。由于学习算法既能在系统的使用期内保留信息又能变更信息，所以对雷达系统的计算要求降到了最低，同时还能适应环境的变化。