偏置○形圈轴封的弹性流体动力润滑效应

本文针对一种新型轴封的润滑机理和工作性能进行了基本理论研究。光学干涉法已成功地用于研究镜面橡胶密封件的液膜剖面。业已发现,在广泛的工况范围内,存在着弹性流体动力润滑效应。对偏置密封件的其他性能参数的研究证明:其有效应用范围界于填料密封和机械密封之间     

Adaptive environmental control for optimal results during plant microgravity experiments

The SVET Space Greenhouse (SG)--the first and the only automated plant growth facility onboard the MIR Space Station in the period 1990-2000 was developed on a Russian-Bulgarian Project in the 80s. The aim was to study plant growth under microgravity in order to include plants as a link of future Biological Life Support Systems for the long-term manned space missions. An American developed Gas Exchange Measurement System (GEMS) was added to the existing SVET SG equipment in 1995 to monitor more environmental and physiological parameters. A lot of long-duration plant flight experiments were carried out in the SVET+GEMS. They led to significant results in the Fundamental Gravitational Biology field--second-generation wheat seeds were produced in the conditions of microgravity. The new International Space Station (ISS) will provide a perfect opportunity for conducting full life cycle plant experiments in microgravity, including measurement of more vital plant parameters, during the next 15-20 years. Nowadays plant growth facilities for scientific research based on the SVET SG functional principles are developed for the ISS by different countries (Russia, USA, Italy, Japan, etc.). A new Concept for an advanced SVET-3 Space Greenhouse for the ISS, based on the Bulgarian experience and "know-how" is described. The absolute and differential plant chamber air parameters and some plant physiological parameters are measured and processed in real time. Using the transpiration and photosynthesis measurement data the Control Unit evaluates the plant status and performs adaptive environmental control in order to provide the most favorable conditions for plant growth at every stage of plant development in experiments. A conceptual block-diagram of the SVET-3 SG is presented.     

Metabolic changes in the animals subjected to space flight

The activity of the enzymes involved in aminoacid metabolism (tyrosine aminotransferase, TAT, tryptophan pyrrolase TP, serine dehydratase, SD) with rapid response to glucocorticoids and enzymes requiring for activity increase repeated administration of corticosterone (alanine aminotransferase, ALT, aspartate aminotransferase, AST) in liver, the changes of lipolysis in adipose tissue and the plasma corticosterone levels were studied in rats subjected to space flight (F), in animals from synchron model experiments (SM, simulated conditions of space flight in laboratory) and in intact controls (C). The increase of plasma corticosterone concentration and of the activity of rapidly (TAT, TP, SD) and slowly activating enzymes (ALT, AST) was found in F group 6-10 hr after space flight (18.5 days on biosatellite COSMOS 1129). This suggested the presence of acute-stress (associated primarily with the landing) and chronic stress induced hypercorticosteronemia during the flight. After the short 6-day period of recovery the plasma corticosterone concentrations and the activities of liver enzymes returned to control levels. The exposition of animals to repeated immobilization stress showed higher response of corticosterone levels in flight rats as compared to intact controls. No changes in basal lipolysis were observed in flight rats in comparison to intact controls, however the stimulation of lipolysis by norepinephrine was lower in animals from F and SM groups. This lower response of lipolytic processes to norepinephrine was found in flight animals also after six days period of recovery. These results showed that there are important changes in the regulation of lipolytic processes in adipose tissue of rats after space flight and in the conditions of model experiments.     

Respective effects of hindlimb suspension, confinement and spaceflight on myotendinous junction ultrastructure

This study compares the effects of 14-day confinement and spaceflight with the respective effects of 8, 18 and 29-day hindlimb suspension on rat soleus and plantaris MTJ ultrastructure. Independently of the experimental situation, greater morphological changes were observed in the soleus as compared to the plantaris MTJ. 18 days of suspension and 14 days of confinement resulted in ultrastructural modifications of the digit-like processes in the soleus MTJ. Additional changes were observed in the myofibrils, microtendon and tendon after 29 days of suspension and 4 days of spaceflight. These results emphasize the influence of the intensity and duration of the muscle loading on the MTJ ultrastructure.     

纤维缠绕壳体材料的粘弹性蠕变性能

在各种载荷条件下测量了用于固体火箭发动机壳体的 S-901玻璃纤维/环氧树脂复合材料的粘弹蠕变特性。试样从纤维缠绕发动机壳体的前封头,纤维缠绕角为±20°和±70°的区域内切取。在不同的拉伸应力和四点梁弯曲应力水平的条件下对试样进行测试。通过几次蠕变——恢复周期来确定材料的蠕变特性。为了测定材料在较低的应力水平下的滞后现象也用四点梁弯曲试验进行了等位移速率试验。发现材料的特性在许多方面类似于从前在等同条件下试验的气压釜固化的平板试样的特性。蠕变特性随时间的变化服从如下幂定律:D=D_0+D_1f~n式中:D 为蠕变柔量(磅/英寸~2~(-1))D_0为初始弹性蠕变柔量。D_1和 n 确定了材料的粘弹响应特性。在线性粘弹性范围,n=0.19。这与环氧树脂本身得出的数据完全一致。在较高应力水平下,由于复合材料内部产生的微裂纹而使 n 值增加。在第一次和第二次加载循环之间,蠕变——恢复特性出现最大差值,而在随后的加载条件下 n 值稍许降低。     

通过一台发动机点火试验获得推进剂的燃速特性—一种分析方法

本文提出了表征固体推进剂燃速的一种分析方法。它不同于传统的燃速处理方法,用一台发动机点火即可表征推进剂在一定压力范围下的燃速。该方法将修改的弹道试验发动机和一个计算机分析程序包结合起来完成这一任务。本文详细地叙述了所采用的发动机,其药柱通道为锥形,以产生非等面燃烧压力——时间曲线。此外,讨论了计算机分析程序包。这一分析程序包采用一个内弹道模型,用优化方法确定燃速规律。这一分析方法已由一整套理论研究所证实,并提出了这些研究的某些结果。此外,本方法对复合和双基两种推进剂都进行了试验验证。这些试验结果表明,由单个试验发动机点火试验处理的燃速数据和常规方法处理的数据符合较好。本文也给出了这些研究的某些结果。     

Effects of HZE particle on the nigrostriatal dopaminergic system in a future Mars mission

Because of long duration travel outside the Earth's magnetic field, the effect of iron-rich high charge and energy (HZE) particles in Galactic Cosmic Rays on human body is the major concern in radiation protection. Recently attention has been directed to effects on the central nervous system in addition to mutagenic effects. In particular, a reduction in striatal dopamine content on nigrostriatal dopaminergic system has been reported by investigators using accelerated iron ions in ground-based mammalian studies. In addition, studies of the pathophysiology of Parkinson's disease demonstrated that excess iron cause a reduction in the dopamine content in the substantia nigra. This suggests an intriguing possibility to explain the selective detrimental effects of HZE particles on the dopaminergic system. Should these particles have biochemical effects, possible options for countermeasures are: (1) nutritional prevention, (2) medication, and (3) surgical placement of a stimulator electrode at a specific anatomic site in the basal ganglia.     

特殊套装的可变面积比可延伸出口锥的设计特性和现状

本文论述一种新的 EEC 方案,本方案不受其它“传统的”EEC 方案的限制,它具有某些特有的设计优点。盖板折叠 EEC(SLEEC)由烧蚀材料或者碳碳材料做成的许多块内外盖板组成。这些盖板重叠特殊,并且紧密套装在喷管固定出口锥的周围,从而使收藏体积大为缩小。作动系统由同步的轴向和径向传动装置组成,这种传动装置当反作用力引起轴向和环向载荷时同时提供延伸和径向扩展。因此锥越来越大而得到展开,使锥成为一个膨胀面确实可变的装置,在火箭发动机的加速级允许最佳高度补偿。对 SLEEC 的不同应用所获得的性能作了对比研究。     

固体推进剂空隙含量的体积模量测定

本研究采用体积压缩系数测量来确定固体推进剂中因气体逸出而导致的内部空隙含量(空隙区)的变化。而且测定了复合改性双基(CMDB)、交联双基(XLDB)和硝酸酯增塑聚醚(NEPE)三种推进剂体内空隙形成的速率。发现在400mm立方体内空隙含量和体积压缩系数,同用X—射线的检查结果具有良好的一致性。在这三种推进剂中,采用70和80℃下的高温贮存来加速空隙的形成。其中CMDB推进剂显示出最高的空隙形成速率。最后,探讨了断裂力学在空隙形成研究中应用的最新进展。