寻找“暗物质”

当天体物理学家理查·艾利斯将哈勃望远镜对准40亿光年之外的AC114星系群时,发现了一个特异现象:星系群中心有两个相互映衬的天体影像.艾利斯认为,实在的天体仅有一个,另一个只是该实在天体的虚像.AC114星系群强大的引力起到了凸透镜的作用,将遥远星系发出的射线捕获.使之弯曲折射.由此造成了上述现象.     

跟踪与数据中继卫星系统的性能

一、引言 自60年代初,NASA就组建和操作一个为近地轨道卫星服务的跟踪和数据获取网。TDRSS是一个新测控网,为目前和直到2000年的预期卫星任务服务。该网利用了已经验证的空间和地面系统有关技术构成一个全新的测控站,只是其前端设备置于地球同步轨道上。尽量采用了自动化技术,使系统设置到数据采集以及整个跟踪期间的通信几乎都不需要人操作。     

数字滤波器的一般原理和靶场现用滤波器的述评

本文阐述了靶场司令委员会成员靶场广泛采用的几种数字滤波器，介绍了这些滤波器的基本原理，以及用于某些数据处理的滤波器设计技术。     

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.