论人造地球卫星运行的规律性

由于在我们周围的自然界出现了苏联所发射的人造天体,自然很多人都会产生这样的问题:这些天体是怎样发射的?它们为什么能飞? 这里不打算极其确切地说明考虑到地球的非球状体及地球大气阻力的情况下,一切作用于卫星的力,仅试图对于有关卫星利用多级火箭来加速并绕地球运行所遵循的规律     

Chronic orthostatic and antiorthostatic restraint induce neuroendocrine, immune and neurophysiologial disorders in rats

The tail-cast suspension rat model has been developed in ground laboratories interested in space physiology for extensive study of mechanisms causing the pathophysiological syndrome associated with space flights. We used individually-caged male rats to explore the effects of acute and chronic (7d) orthostatic restraint (OR) and head-down anti-orthostatic restraint (AOR) on a series of physiological variables. The acute restraint study showed that (1) the installation of the OR device induced an acute reaction for 2 days, with a substantial rise in ACTH (x2) and CORT (x6), and that (2) the head-down tilt from OR to AOR induced (i) within 10 min and lasting 60 min a 2-fold rise in the intra-cerebro-ventricular pressure (Picv) monitored with an icv telemetric recording system, which receded to normal between 60 and 120 min; and (ii) within 30 min a short-lived 4-fold rise in plasma ACTH and CORT levels. Chronic OR induced (1) the suppression of the diurnal ACTH/CORT rhythm, with increased mean levels, especially for ACTH, (2) a degraded circadian locomotor activity rhythm manifested by a significant reduction in the spectral power of the 24h periodicity and a concomitant emergence of shorter (ultradian) periodicities, (3) an associated, but less pronounced alteration of the diurnal rhythm in body temperature; and (4) a marked increase in baseline plasma levels of IL-1β and an increased reactivity in cytokine release following an E. coli endotoxin (LPS) challenge. AOR induced (1) a similar obliteration of the circadian ACTH/CORT rhythm, (2) the loss of close correlation between ACTH and CORT, (3) a generalized increase in baseline plasma IL-1β levels and (4) more extensive degradation of the arcadian periodicity for both locomotor activity and, to a lesser extent, body temperature, replaced by dominant spectral powers for ultradian periodicities (3 to 10h). In conclusion, both experimental paradigms — but AOR more than OR — caused a blockade of the arcadian rhythmicity of major physiological variables, the loss of normal correlations between ACTH and CORT, and inflammatory-immune hyperreactivity. These pathophysiological disorders may all be parts of a complex chronic stress syndrome.     

Natural killer cells after ALTAIR mission

Reduced in vitro NK cytotoxic activity have routinely been observed after both prolonged and short-term space flights. This study investigated the effects of space flight on NK cell functions, NK cell counts and the production of IL-2 and TNF by lymphocytes of French-Russian crew members. In the French cosmonaut, after 21 days space flight, the cytotoxic activity of NK cells, the capacity the NK cells to bind and lyse the individual target cells and the percentage of NK cells were decreased. In this cosmonaut a twofold reduction TNF production in cultures of lymphocytes stimulated with PMA and with the mixture of PHA and PMA was observed on the first day after landing. However, the activity of the production of TNF in 48-hour PHA-cultures of lymphocytes was unchanged and the biological activity of IL-2 was not reduced. The immunological examination did not detecte any substantial deviations from the norm in both russian cosmonauts after 197 days space flight. Various explanations for decreased cytotoxicity in cosmonauts after space flight can be proposed, and these include the defective function of NK cells and reduced numbers of circulating effector cells.     

Recent results of the joint ESA-DARA/IBMP experiments Biokosmos "Seeds"

Comparison of experimental data obtained from short (SDEF) and long duration exposure flights (LDEF) have recently led to results which will be significant for longer and/or repeated sojourn of man in space. Under orbital conditions biological stress and damage are induced in test subjects by cosmic radiation, especially the high energetic, densely ionizing component of heavy ions. Plant seeds were successful model systems for a biotest in studying the physiological damages and mutagenic effect caused by ionizing cosmic radiation in particular stem cells. Dosimetrically, the subdivision into charge- and Let-groups reveals the contribution of the intermediate group (LET = 350-1000 MeV/cm) due to the medium heavy ions (Z = 6-10). Their relative contribution increases with the lower inclination of the orbit of LDEF-1; on the other hand, the total fluence becomes higher with longer duration of the flight. The observed endpoints of the biological radiation damage hint at a correlation with particle dose rate rather than with the dose; additionally, data on shielding effects inside and outside the space craft and its exposure were gained from the different SDEF- and LDEF-missions.     

飞行模拟摄象装置中解决景深问题的新方法

在飞行模拟目视系统中,象是由闭路电视的光学探头由地景模型摄取的,对横过整个象区的模型表面成象,特别是当探头入瞳非常接近模型时的成象是一个重要的问题。当我们试图改善闭路电视摄象机的鉴别率和减小地景模型的比例时,这个问题就更加大了,使得在探头光学系统内部移动和倾斜透镜的普通技术对某些重要的探头系统不足以解决问题。对于大范围的物体共轭距离,探头系统光学象差的校正是一个密切相关的问题。对于标准的电视系统和激光电视系统中的这些问题都作了评论。叙述了一种新型的倾斜透镜系统。     

飞行模拟的虚象显示

利用简单的未经校正的塑料透镜给出飞行模拟器中飞行景象的虚象。虚象显示给模拟器驾驶员以真实的印象,因为象似乎离开模拟器一个实在的距离。好多飞行员在飞行模拟器中作了着陆和起飞试验,以客观地评价虚象显示。这种显示包括斯密特彩色投影器,后投影屏和一个大直径长焦距的平凸塑料透镜。还评述了另一种利用一个彩色电视监视器和两个平凸塑料透镜的虚象显示,但没有正式飞行员的评论。对各种透镜参数进行了研究以决定它们对飞行景象的影响。结论是:在某些条件下,简单的透镜是可以使用的,以利用斯密特投影系统或电视监视器得到有用的飞行景象的虚象模拟。     

GE90的飞行试验验证了其使用性

GE公司已经完成了推力为377千牛的GE90发动机的使用性和系统验证飞行试验,证明这种发动机可以由波音公司开始进行获准180分钟ETOPS的飞行试验.GE90的飞行试验是在1993年12月到今年3月17日分两个阶段进行的.试验时此发动机装在GE公司的波音747空中试车台2号位上.这是一架曾经由泛美航空公司用过的波音747-100飞机,已经过大量改装.     

非地球同步轨道的应用潜力

最近的一项研究详细论述了在通信业务高峰期,利用非地球同步轨道卫星通信系统所具有的巨大优势。     

Invariant and energy analysis of an axially retracting beam

The mechanism of a retracting cantilevered beam has been investigated by the invariant and energy-based analysis. The time-varying parameter partial differential equation governing the transverse vibrations of a beam with retracting motion is derived based on the momentum theorem. The assumed-mode method is used to truncate the governing partial differential equation into a set of ordinary differential equations (ODEs) with time-dependent coefficients. It is found that if the order of truncation is not less than the order of the initial conditions, the assumed-mode method can yield accurate results. The energy transfers among assumed modes are discussed during retrac-tion. The total energy varying with time has been investigated by numerical and analytical methods, and the results have good agreement with each other. For the transverse vibrations of the axially retracting beam, the adiabatic invariant is derived by both the averaging method and the Bessel function method.     

用航空遥感器对海岸带海洋水色的分析

本文介绍了一种利用航空遥感器分析海岸带海洋水色的方法,这种方法已应用于亚得利亚海北部试验区,在不同高度上所获得的多光谱数据中。从海洋水色辐射计(工作谱段与海岸带彩色扫描仪相同)和六通道辐射计(工作在叶绿素自然荧光的光谱区域)所获得的数据,已用水色遥感辐射过程的模型,对大气和海面的影响进行了修正。遥感得到的水辐射光谱以及叶绿素和沉积物浓度经大气和海面影响修正之后的数据,证实了这种方法对悬浮或溶解于海水中的物质具有定量分析的能力。