用四个开路/短路器校准多端口反射计

本文介绍一种采用四个已知反射系数的反射标准来校准任意的实际多端口反射计的简化方法。文中表明,这四个标准反射系数的模值可以使之都等于1。计算机模拟证明,反射系数的相位分布,在很宽范同内,对理想的和非理想的五端口和六端口反射计,不会出现奇异性(Singularity)。列出了对一种实际的简单六端口的一组校准结果,以表明这种校准过程;利用这些已校准的网络参数得出了某些测量结果,并与美国国家标准局(NBS)所测得的数值进行了比较。计算机模拟结果和实际的结果值表明,在多端口校准过程中可能碰到的那些数值上的奇异性不是多端口的固有特性,而是与数学处理有关。     

壁压法低速风洞洞壁干扰修正

 对于低速风洞中大模型、大迎角以及一般具有分离流的情况,本文采用壁压测量用影响函数法计算了洞壁干扰,并进行了实验验证.计算与实验表明,本文的计算是可靠的提供的曲线数据可供实际使用。     

未来攻击机机械系统综合控制

文章对未来攻击机通用系统实现数字化控制和监测进行说明，使用这一系统的目的在于：1）减小重量和减少与常规系统相关的发动机起 功率因子，2）减小飞行员工作负荷；3）提高维护性。4）提高生存性。5）降低用户费用，本文通过对与通用系统连接的分布式处理器和数据终端的研究来阐述系统设计的各种方法，目前，研究表明两个目标已实现，而且效果明显，例如：在双发攻击机上，能使100kg重量减小大约50％；飞行员工作负荷可以减小1／4。     

Early renal changes in 45 degrees HDT rats

Background: Both microgravity and simulated microgravity models, such as the 45HDT (45 degrees head-down tilt), cause a redistribution of body fluids indicating a possible adaptive process to the microgravity stressor. Understanding the physiological processes that occur in microgravity is a first step to developing countermeasures to stop its harmful effects, i.e., (edema, motion sickness) during long-term space flights. Hypothesis: Because of the kidneys' functional role in the regulation of fluid volume in the body, it plays a key role in the body's adaptation to microgravity. Methods: Rats were injected intramuscularly with a radioactive tracer and then lightly anesthetized in order to facilitate their placement in the 45HDT position. They were then placed in the 45HDT position using a specially designed ramp (45HDT group) or prone position (control group) for an experimental time period of 1 h. During this period, the 99mTc-DTPA (technetium-labeled diethylenepentaacetate, MW=492 amu, physical half-life of 6.02 h) radioactive tracer clearance rate was determined by measuring gamma counts per minute. The kidneys were then fixed and sectioned for electron microscopy. A point counting method was used to quantitate intracellular spaces of the kidney proximal tubules. Results: 45HDT animals show a significantly (p=0.0001) increased area in the interstitial space of the proximal tubules. Conclusions: There are significant changes in the kidneys during a 1 h exposure to a simulated microgravity environment that consist primarily of anatomical alterations in the kidney proximal tubules. The kidneys also appear to respond differently to the initial periods of head-down tilt.     

使用连续流动法测量高氯酸铵表面积

1、引言为了予测复合固体推进剂的弹道性能,必须要知道推进剂中各组份的粒度或表面积。在塑料型推进剂的制造过程中固体粒子会发生机械破碎,尽管如此,仍发现高氯酸铵的初始表面积与推进剂的弹道性能有关。爆炸物研制公司(ERDE)测量高氯酸铵表面积的作法是采用以空气渗透法为基础的菲希尔(Fisher)筛分机。由于塑料型推进剂中使用的高氯酸铵的比表面积范围通常为1000～9000cm~2/cm~3(0.051～0.46m~2/g),因此,菲希尔法完全能满足这一要求。为了生产较高燃速的推进剂,爆炸物研制公司最近研究的推进剂配方中含有更细的高氯酸铵(9000～10000cm~2/cm~3)。在端羧基聚丁二烯和端羟基聚丁二烯两种橡胶型推进剂中,即     

室内火箭试车台的理论和试验评定

用于固体火箭发动机静态试车的一种新的室内试验设施最近在荷兰全国应用科学研究中心的Prins Maurits实验室建成。本文介绍了试车的概况,气体动力学特性,强度和减声特性,以及验证试验的结果。     

含硝酸酯增塑剂的固体推进剂的脆化研究

本文介绍硝酸酯增塑的聚醚聚氨酯推进剂在低温贮存中,解决失去应变能力(脆化)问题的研究结果。这种高度增塑的推进剂在低温下短期贮存,几乎完全失去了应变能力。研究这种脆化的原因表明,交联密度以及粘合剂配方是起作用的因素。湿度曾被考虑是因素之一,但实验证明并非如此。实验表明增塑剂结晶是脆变的主要原因但不一定与增塑剂的凝固点有关。重新测定某些增塑剂的凝固点是研究工作的一部份。放入增塑剂晶体增加了推进剂脆变速度。单独采用丁三醇三硝酸酯(BTTN)或是混合增塑剂可以解决这个问题。采用混合增塑剂可以得到最好的低温性能。     

中巴地球资源卫星在巴西的应用

重点介绍了当前巴西以用户为导向的中巴地球资源卫星(CBERS-1)数据在森林采伐监测、土地利用规划、影像制图和科学应用等方面的应用项目，对今后利用中巴地球资源卫星开展国家项目发表了一些看法。     

A Canadian high-energy neutron spectrometry system for measurements in space

Bubble Technology Industries Inc. (BTI), with the support of the Canadian Space Agency, has finished the construction of the Canadian High-Energy Neutron Spectrometry System (CHENSS). This spectrometer is intended to measure the high energy neutron spectrum (approximately 1-100 MeV) encountered in spacecraft in low earth orbit. CHENSS is designed to fly aboard a US space shuttle and its scientific results should facilitate the prediction of neutron dose to astronauts in space from readings of different types of radiation dosimeters that are being used in various missions.     

ELITE-S2: the multifactorial movement analysis facility for the International Space Station

Experimental observations of adaptation processes of the motor control system to altered gravity conditions can provide useful elements to the investigations on the mechanisms underlying motor control of human subject. The microgravity environment obtained on orbital flights represents a unique experimental condition for the monitoring of motor adaptation. The research in motor control exploits the changes caused by microgravity on the overall sensorimotor process, due to the impairment of the sensory systems whose function depends upon the presence of the gravity vector. Motor control in microgravity has been investigated during parabolic flights and short-term space missions, in particular for analysis of movement-posture co-ordination when equilibrium is no longer a constraint. Analysis of long-term adaptation would also be very interesting, calling for long-term body motion observations during the process of complete motor adaptation to the weightlessness environment. ELITE-S2 is an innovative facility for quantitative human movement analysis in weightless conditions onboard the International Space Station (ISS). ELITE-S2 is being developed by the Italian Space Agency, ASI is to be delivering the flight models to NASA to be included in an expressed rack in US Lab Module in February 2004. First mission is currently planned for summer 2004 (increment 10 ULF 2 ISS).