金属橡胶挤压油膜阻尼器阻尼性能分析

为了降低发动机转子高速旋转产生的振动，提高发动机的使用寿命，设计了一种端部安装金属橡胶环的新型挤压油膜阻尼器，并在π油膜假设条件下，利用斯托克斯方程和雷诺方程，给出了新型金属橡胶挤压油膜阻尼器的流量表达式以及非线性油膜力的近似表达式。通过传统短挤压油膜阻尼器和新型金属橡胶挤压油膜阻尼器的流量特性和油膜力特性的对比分析，表明新型金属橡胶挤压油膜阻尼器具有更好的阻尼性能和良好的节流特性。并通过试验证明了新型金属橡胶挤压油膜阻尼器具有更好的阻尼减振效果。     

铝锂合金——新一代轻型金属结构材料

在低比重铝合金基础上发展起来的铝锂合金的进展愈来愈快,在此期间首先为商业的需要,制造出了半成品,并投放市场。本文介绍了为首的三名制造者Alcan,Alcoa及Pechiney制造的合金,并说明了目前铝锂合金的研究和发展状况,同时试图谈谈未来发展概况。     

Laser Hardening of Metals

The first experiments on hardening metals by laserpeening induced residual compressive stress in the sur-face of metals for improving their resistance to cracking,stress corrosion and fatigue took place more than 30years ago. However, only today, with the development ofhigh-intensity pulse repetitive rate lasers, this methodstarts to compete to traditional peening, which use influ-ence of small metal balls.Laser peening uses pulses with high intensity 109￣1010 W/cm2 [1]. The laser energy abso…     

Hydrogeologic controls on episodic H2 release from precambrian fractured rocks--energy for deep subsurface life on earth and mars

Dissolved H(2) concentrations up to the mM range and H(2) levels up to 9-58% by volume in the free gas phase are reported for groundwaters at sites in the Precambrian shields of Canada and Finland. Along with previously reported dissolved H(2) concentrations up to 7.4 mM for groundwaters from the Witwatersrand Basin, South Africa, these findings indicate that deep Precambrian Shield fracture waters contain some of the highest levels of dissolved H(2) ever reported and represent a potentially important energy-rich environment for subsurface microbial life. The delta (2)H isotope signatures of H(2) gas from Canada, Finland, and South Africa are consistent with a range of H(2)-producing water-rock reactions, depending on the geologic setting, which include both serpentinization and radiolysis. In Canada and Finland, several of the sites are in Archean greenstone belts characterized by ultramafic rocks that have under-gone serpentinization and may be ancient analogues for serpentinite-hosted gases recently reported at the Lost City Hydrothermal Field and other hydrothermal seafloor deposits. The hydrogeologically isolated nature of these fracture-controlled groundwater systems provides a mechanism whereby the products of water-rock interaction accumulate over geologic timescales, which produces correlations between high H(2) levels, abiogenic hydrocarbon signatures, and the high salinities and highly altered delta (18)O and delta (2)H values of these groundwaters. A conceptual model is presented that demonstrates how periodic opening of fractures and resultant mixing control the distribution and supply of H(2) and support a microbial community of H(2)-utilizing sulfate reducers and methanogens.     

固体推进剂老化研究概述

老化研究的重要性是由于评定推进剂的安全期而引起的。本文评论的目的是介绍文献中对本课题有用的最新知识的全面情况,包括双基和复合固体推进剂。评论了以下几个课题:1)损坏准则 2)安全期的估价 3)弹道性能变化与分解特性 4)力学性能的变化 5)老化机理。     

毫米波雷达的原理与应用(二)

雷达距离方程和微波雷达一样,毫米波雷达的性能由基本的雷达距离方程、信标方程和干扰方程所决定,并能从这些方程预测出来。对微波雷达进行计算时,这些方程中的自由空间衰减项通常可以忽略;反之,对毫米波雷达说来,它也许是限制雷达性能的最重要的因素。     

Japanese telescience technology development for JEM and its utilization

Recognizing the importance of the telescience technology for the efficient and improved space environment utilization in JEM, we have undertaken telescience technology development since 1987. The purpose of this paper is to introduce the recent status of our telescience activity, the results of the testbed experiments in these years, and the new activities for the initial JEM operation and its future utilization.     

Blood volume regulating hormones response during two space related simulation protocols: four-week confinement and head-down bed-rest

The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriuretic factor), electrolytes and creatinine concentrations, and blood pressure were measured in two different four-week experimental protocols: respectively -6 degrees head-down bed-rest (5 subjects) and confinement (6 subjects). We observed a significant increase (P < 0.01 at D2 vs D-5) of systolic blood pressure during confinement and a different level of response for some hormones, especially for arginine vasopressin (300% increase during confinement instead of 50% during bed-rest). The renin-angiotensin-aldosterone system was enhanced during confinement and head-down bed-rest. In both conditions, we obtained a similar pattern of response for blood volume regulating hormones. During confinement, two main factors were inactivity and stress activation of the sympathetic nervous system. In the bed-rest study the response is principally due to the fluid shift and blood volume adaptation but it is not possible to exclude the role of inactivity and stress.     

一个包括气相和亚表面反应的过氯酸铵复合推进剂的点火模型

本文提出了 Ap 基复合推进剂点火的一个综合模型及其数值解。这一分析模拟位于滞止区的推进剂试样在快速加压条件下的点火过程。本模型的特点包括:a)考虑了 Ap 基复合推进剂点火的详细的化学动力学资料;b)推进剂几何形状是二维(轴对称)的;c)考虑了气相中压力迅速增加对点燃过程的影响。使用隐式有限差分格式求解瞬态二阶联立、非齐次、非线性偏微分控制方程组。数值解揭示在点火阶段顺序发生的一系列重要事件,包括:点火器气体流入接近样品表面的区域;压缩波到达处未燃成份的燃烧;向推进剂传热;氧化剂和燃烧剂的高温分解;气相反应导致点燃。这个模型正确地预测了实验观察到的现象:随着增压速率提高,点火延迟时间缩短。采用文中考虑的不同点火准则都得到和试验一样的趋势。     

宇航飞行器复合推进剂的发展

日本于1957年成功地发射了一枚小型探空火箭 K-3,这是日本第一枚复合固体推进剂火箭。从那时候以来,对复合固体推进剂进行了许多方面的研制。所研制的聚酯、聚硫、聚氨基甲酸酯以及聚丁二烯聚合物,均被广泛地作为探空火箭或卫星运载火箭的复合固体推进剂的粘合剂基体。日本研制的端羧基聚丁二烯(CTPB),在工艺性能、力学性能以及燃烧性能方面,均比其它聚合物好。这种聚合物(JSR·CTPB S-21)已经应用到日本典型的宇航飞行器中,例如 M-3 A、TT-500A、M-13等。另一方面 HTPB 最近作为一种新的优良的聚丁二烯粘合剂材料已引起人们极大的兴趣。它已用于目前正在研制的一些火箭发动机中。通过我们的共同努力,新的 HTPB 聚合物已经进入实用阶段。正在研制的高性能的远地点发动机(ABM)就使用这种 HTPB 推进剂。