The geostationary orbit and satellite communications: concepts older than commonly supposed

The first proposal for a radio-equipped, man-made satellite in geostationary orbit is customarily attributed to author Arthur Charles Clarke (1917-), however, he makes no claim to having originated the geostationary orbit. Clarke's now classic article, in the October 1945 issue of Wireless World described a system of worldwide broadcasting via three satellites in geostationary orbit. In the article, Clarke listed seven references, including two to previous significant works by Willy Ley (Rockets, first published in 1944) and Hermann Noordung (The Problems of Space Travel, published in 1929). Both these works make reference to the geostationary orbit but as Clarke (see IEEE Spectrum, vol. 31, no.3, p. 4 et seq., Mar. 1994) points out the concept predates these works. It goes back at least to the works of Konstantin Eduardovich Tsiolkovsky (1857-1935), a Russian scientist now regarded as the father of space research. His book, ("Dreams of Earth and Sky"), published in 1895, was the first by a scientist on the subject.     

The Earth's Magnetosphere Response to Solar Wind Events according to the INTERBALL Project Data

The results of studying the interaction of two types of the solar wind (magnetic clouds and solar wind of extremely low density) with the Earth's magnetosphere are discussed. This study is based of the INTERBALL space project measurements and on the other ground-based and space observations. For moderate variations of the solar wind and interplanetary magnetic field (IMF) parameters, the response of the magnetosphere is similar to its response to similar changes in the absence of magnetic clouds and depends on a previous history of IMF variations. Extremely large density variations on the interplanetary shocks, and on leading and trailing edges of the clouds result in a strong deformation of the magnetosphere, in large-scale motion of the geomagnetic tail, and in the development of magnetic substorms and storms. The important consequences of these processes are: (1) the observation of regions of the magnetosphere and its boundaries at great distances from the average location; (2) density and temperature variations in the outer regions of the magnetosphere; (3) multiple crossings of geomagnetic tail boundaries by a satellite; and (4) bursty fluxes of electrons and ions in the magnetotail, auroral region, and the polar cap. Several polar activations and substorms can develop during a single magnetic cloud arrival; a greater number of these events are accompanied, as a rule, by the development of a stronger magnetic storm. A gradual, but very strong, decrease of the solar wind density on May 10–12, 1999, did not cause noticeable change of geomagnetic indices, though it resulted in considerable expansion of the magnetosphere.     

System identification of dynamic closed-loop control of total peripheral resistance by arterial and cardiopulmonary baroreceptors.

Prolonged exposure to microgravity in space flight missions (days) impairs the mechanisms responsible for defense of arterial blood pressure (ABP) and cardiac output (CO) against orthostatic stress in the post-flight period. The mechanisms responsible for the observed orthostatic intolerance are not yet completely understood. Additionally, effective counter measures to attenuate this pathophysiological response are not available. The aim of this study was to investigate the ability of our proposed system identification method to predict closed-loop dynamic changes in TPR induced by changes in mean arterial pressure (MAP) and right atrial pressure (RAP). For this purpose we designed and employed a novel experimental animal model for the examination of arterial and cardiopulmonary baroreceptors in the dynamic closed-loop control of total peripheral resistance (TPR), and applied system identification to the analysis of beat-to-beat fluctuations in the measured signals. Grant numbers: NAG5-4989.     

Population dynamics of transgenic microorganisms in the different microecosystem conditions.

The role of key environmental factors in adaptation of spore-forming and non-spore-forming transgenic microorganisms (TM) have been studied in model ecosystems. Model TM Escherichia coli Z905 (bearing plasmid genes of bacterial luminescence Ap (r) Lux+) has been found to have a higher adaptation potential than TM Bacillus subtilis 2335/105 (bearing genes of human alpha 2-interferon Km (r) Inf+), planned for employment as a living vaccine under varying environmental conditions. Effects of abiotic factors on migration of natural and recombinant plasmids between microorganisms under model ecosystem conditions has been estimated. The transgenic microorganisms with low copy number survived better under introduction conditions in the microcosms studied. This trend has been shown to be independent of the microcosm type and its complexity. Grant numbers: 99-04-96017, 25, 00-07-9011.     

Energy storage at 77 K in multilayer ceramic capacitors

A ceramic material having a large dielectric constant at 77 K, ε=8000-12000, has been developed for capacitive energy storage at this temperature. A large matrix of multilayer ceramic capacitors were fabricated using conventional tape-casting methods to optimize the dielectric breakdown strength at 77 K, and measured energy storage values on these capacitors range up to 6 J/cm³ at 77 K. An unfused bank of these capacitors was voltage-cycled 10⁵ times at 77 K without failure, and the heating effects during cycling were immeasurably small (i.e., nitrogen boiloff was monitored). An electrocaloric effect on discharge (ΔT~1 K) contributes to the thermal stability. Measurements of the frequency dependence of the dielectric properties of the ceramic at 77 K indicate a fundamental limit of about 8 μs for the switching repetition rate. Improved capacitor-manufacturing methods are discussed which can increase the energy density to the 20-30 J/cm³ range     

快速成型技术（RP技术）对产品开发的影响

快速成型技术是目前工业领域内一门崭新的技术，为产品开发过程开辟了一个截然不同的新思路。本文首先介绍RP技术的发展及常用的几种RP处理系统；通过RP技术生成的试件原型在开发过程中的作用，说明RP技术对产品开发的影响；文章最后提出RP技术应用的前提条件。     

“自由伊拉克作战”检讨报告——轮式车与无人载具

虽然“自由伊拉克作战”（Operation Iraqi Freedom）已经告一段落，但是美军在伊拉克所面对的问题却是有增无减，其中又以伊拉克反美武装所实施的攻击为甚，虽然美军、联军和伊拉克过渡政府的保安部队坐拥15万兵力，但是却无法避免伊拉克反美武装对美军接二连三攻击所造成的有生力量伤亡，截至2005年2月18日为止，美军总计有1462名官士兵阵亡（含军方雇员），10968人负伤，换言之，美军在2003年5月15日结束“自由伊拉克作战”之后，在作战行动中阵亡的官兵仅仅只有109名，但是在战后因为伊拉克伊拉克反美武装攻击而阵亡的官士兵却已经堂堂突破1000大关，足足是作战阵亡人数的10倍，更不用提上万名的负伤者。[编者按]     

田捷砚凌空飞撷西部大地之美

应该感谢摄影家田捷砚数年数以百次不知倦怠的艰辛西部航拍之旅，以及他在某种高度上忘我创作的数以万张的精彩图片，让我们心驰神往的境界变成可观可感的实际图像。[编按]     

双向进气结构脉管制冷机直流形成机理

在脉管制冷机中,由双向进气结构诱发的直流流动,不仅会增加冷端换热器的负载,降低制冷机性能,而且还是引起制冷温度不稳定的重要原因。如何有效地抑制直流流动已成为脉管制冷机能否大规模应用的关键。而对直流形成机理进行全面、深入的研究是发展简单、有效直流抑制手段的前提。针对该研究热点,本文开展了双向进气结构脉管制冷机直流形成机理研究,基于流体网络理论,考察工质物性对直流的影响和作用机理,进一步揭示了直流的形成本质。     

Identification of a 2D turbulent wind spectrum

Turbulent wind spectrum models usually involve nonrational terms. For such models the development of a Markovian time simulator relies on a rational approximation obtained by the way of an identification stage. This paper presents a general method to manage this identification stage, that provides us with a family of stable rational approximations which is proved to converge towards the true model as the dimension increases. We first give an exact but infinite dimensional state space representation of the spectrum. It is based on the use of a diffusive equation. For bi-dimensional (2D) signals it also uses decoupling by spatial Fourier transformation. Then the discretization of this exact model leads easily to stable finite dimensional approximations over a prescribed frequency range. This approach is applied to the identification of a theoretical 2D turbulent wind spectrum, and of a 1D turbulent wind spectrum estimated from in flight recorded data.