Thermal resistance in satellite mounting plates due to conductive heat transfer

The thermal resistance due to conductive heat transfer between two heat generating boxes mounted symmetrically on a thin mounting plate, one side of which is subjected to a constant heat flux and the opposite side is convectively cooled, is considered. The other two sides are maintained at constant temperature. A numerical solution for the temperature field is obtained and the heat transfer between the boxes is found by integrating between the critical heat flow lines. Various nondimensional parameters are identified and their influence on the thermal resistance is studied.     

一种新型混合网络演化模型

提出了一种新的局域网络混合演化模型,该模型中新结点与网络中已有结点的连接数成对数增长,并且在连接方式上区别于BA网络中的优先连接,采用优先连接与随机连接相结合的连接方式,即以概率l-p随机连接,以概率p依照BA网络进行优先连接.对新闻模型进行仿真和理论分析,发现新型混合网络具备局域网络的更多特性,更加接近现实网络.     

Electrostatic Noise Spectrum at the Electron Cyclotron Frequency and Electromagnetic Emission in the Inhomogeneous Plasma of the Topside Ionosphere

Measurements of the wave emission of the topside ionosphere made onboard the APEX satellite using the electric component of the wave field in the 0.1–10 MHz frequency band are presented. At middle latitudes a wave intensity decrease was observed in the broad-band spectrum of the electrostatic noise at the electron cyclotron frequency. It is shown that a break in the spectrum of electrostatic modes at the electron cyclotron frequency (the absence of the plasma eigen-frequencies) may be a cause of the observed effect. The increase of the intensity at the electron cyclotron frequency in the ionospheric trough and at latitudes above the trough region as compared to middle latitudes may be explained by the capture by plasma irregularities of the electromagnetic emission of the auroral electron fluxes.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 201–208.Original Russian Text Copyright © 2005 by Izhovkina, Prutensky, Pulinets, Kiraga, Klos, Rothkael.     

Skylab experiment M-092: results of the first manned mission

Blood pressure at 30-sec intervals, heart rate, and percentage increase in leg volume continuously were recorded during a 25-min protocol in the M092 Inflight Lower Body Negative Pressure (LBNP) experiment carried out in the first manned Skylab mission. These data were collected during six tests on each crewman over a 5-month preflight period. The protocol consisted of a 5-min resting control period, 1 min at -8, 1 min at -16, 3 min at -30, 5 min at -40, and 5 min at -50 mm Hg LBNP. A 5-min recovery period followed. Inflight tests were performed at approximately 3-day intervals through the 28-day mission. Individual variations in cardiovascular responses to LBNP during the preflight period continued to be demonstrated in the inflight tests. Measurements of the calf indicated that a large volume of fluid was shifted out of the legs early in the flight and that a slower decrease in leg volume, presumably due to loss of muscle tissue, continued throughout the flight. Resting heart rates tended to be low early in the flight and to increase slightly as the flight progressed. Resting blood pressure varied but usually was characterized by slightly elevated systolic blood pressure, lower diastolic pressure, and higher pulse pressures than during preflight examinations. During LBNP inflight a much greater increase in leg volume occurred than in preflight tests. Large increases occurred even at the smallest levels of negative pressure, suggesting that the veins of the legs were relatively empty at the beginning of the LBNP. The greater volume of blood pooled in the legs was associated with greater increases of heart rate and diastolic pressure and larger falls of systolic and pulse pressure than seen in preflight tests. The LBNP protocol represented a greater stress inflight, and on three occasions it was necessary to stop the test early because of impending syncopal reactions. LBNP responses inflight appeared to predict the degree of postflight orthostatic intolerance. Postflight responses to LBNP during the first 48 hours were characterized by marked elevations of heart rate and instability of blood pressure. In addition, systolic and diastolic pressures were typically elevated considerably both at rest and also during stress. The time required for cardiovascular responses to return to preflight levels was much slower than in the case of Apollo crewmen.     

Soviet proposals on the militarization of space

The USSR has submitted several proposals to the United Nations in recent years which are aimed at avoiding the militarization of outer space. This article examines three of the proposals and evaluates them in the context of existing treaties, to see whether or not they could resolve the political and legal problems which might arise. The reactions of the United Nations General Assembly and individual nations are also considered. The author concludes that several questions regarding the military aspects of space activity are left unresolved by the Soviet proposals.     

Changes in organ perfusion and weight ratios in post-simulated microgravity recovery

Head-down tilt models have been used as ground-based simulations of microgravity. Our previous animal research has demonstrated that there are significant changes in fluid distribution within 2 h after placement in a 45 degrees head-down tilt (45HDT) position and these changes in fluid distribution were still present after 14 days of 45HDT. Consequently, we investigated changes in fluid distribution during recovery from 16 days of 45HDT. Changes in radioactive tracer distribution and organ/body weight ratio were examined in rats randomly assigned to a 45HDT or prone control group. The 45HDT rats were suspended for 16 days and then allowed to recover at the prone position 0, 77, 101, or 125 h post-suspension. Animals were injected with technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, MW=492 amu, physical half-life of 6.02 h) and then killed 30 min post-injection. Lungs, heart, liver, spleen, kidneys, and brain were harvested, weighed, and measured for radioactive counts. Statistical analyses included two-way analysis of variance (ANOVA) that compared 45HDT versus controls at the four experimental time points. The organ weight divided by the body weight ratio for the brain, heart, kidneys and liver in the 45HDT rats was significantly different than the control rats, regardless of time (treatment). There was no difference between the different time points (time). The average 99mTcDTPA count divided by the organ weight ratio values for the heart, liver, and spleen were significantly higher in the 45HDT group than the control group. The average counts for the heart and spleen were significantly higher at 77, 101, and 125 h than at time zero. We conclude that the major organs have different recovery patterns after 45HDT for 16 days in the rat.     

Choroidal responses in microgravity. (SLS-1, SLS-2 and hindlimb-suspension experiments)

Fluid and electrolyte shifts occuring during human spaceflight have been reported and investigated at the level of blood, cardio-vascular and renal responses. Very few data were available concerning the cerebral fluid and electrolyte adaptation to microgravity, even in animal models. It is the reason why we developed several studies focused on the effects of spaceflight (SLS-1 and SLS-2 programs, carried on NASA STS 40 and 56 missions, which were 9- and 14-day flights, respectively), on structural and functional features of choroid plexuses, organs which secrete 70–90 % of cerebrospinal fluid (CSF) and which are involved in brain homeostasis. Rats flown aboard space shuttles were sacrificed either in space (SLS-2 experiment, on flight day 13) or 4–8 hours after landing (SLS-1 and SLS-2 experiments). Quantitative autoradiography performed by microdensitometry and image analysis, showed that lateral and third ventricle choroid plexuses from rats flown for SLS-1 experiment demonstrated an increased number (about x 2) of binding sites to natriuretic peptides (which are known to be involved in mechanisms regulating CSF production). Using electron microscopy and immunocytochemistry, we studied the cellular response of choroid plexuses, which produce cerebrospinal fluid (CSF) in brain lateral, third and fourth ventricles. We demonstrated that spaceflight (SLS-2 experiment, inflight samples) induces changes in the choroidal cell structure (apical microvilli, kinocilia organization, vesicle accumulation) and protein distribution or expression (carbonic anhydrase II, water channels,…). These observations suggested a loss of choroidal cell polarity and a decrease in CSF secretion. Hindlimb-suspended rats displayed similar choroidal changes. All together, these results support the hypothesis of a modified CSF production in rats during long-term (9, 13 or 14 days) adaptations to microgravity.     

基于小波分解与分形内插相结合的地形数据压缩方法

地形匹配制导中需要使用大量的地形数据，因此有效的地形数据压缩技术是非常重要的。传统的地形数据压缩方法主要采用线性内插的方法，但这对于地形起伏较大的山区地形失真太大，不能满足高精度导航的要求。本文基于小波分解与分形内插相结合的方法，提出了一种新的地形数据压缩方法，它具有压缩比高，保真性好，解码快的特点，特别适合山区地形数据的压缩。     

The effect of small vibrations on Marangoni convection and the free surface of a liquid bridge

The effects of small vibrations on Marangoni convection were investigated experimentally using a liquid bridge of 5 cSt silicone oil with a disk diameter of 7.0 mm, and an aspect ratio close to 0.5. Experiments were performed to determine the critical temperature difference data for no vibration case and with small vibrations applied. The experimental results have shown that the effect of small vibrations on the onset of oscillatory flow is small since the critical temperature difference data for different aspect ratios were not affected by the vibrations. To clarify the surface oscillation phenomena induced by external vibrations, a 3-D numerical simulation model was also developed using a level set algorithm to predict the surface oscillations of isothermal silicone oil bridges. By subjecting the liquid bridge to small vibrations, the surface oscillation characteristics were predicted numerically, and the numerical results compared well with the predictions of an analytical model proposed previously. Furthermore, the effect of small vibrations on the surface vibration amplitude of the liquid bridge is also discussed.