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排序方式: 共有253条查询结果,搜索用时 15 毫秒
221.
Johannes B Salnitski VP Korsun VG Kaleri AJ Kirsch K Schewtschenko OI Fischer F Dudukin AV Gunga HC 《Acta Astronautica》1998,42(1-8):215-218
A complex psychophysiological test battery (ECG, blood pressure, SCL, finger temperature e.t.c.) was applied on two subjects in space. It could be shown that the subjects react under space conditions differently than on earth. The data received could be classified into four types of regulation. The subjects changed this type of regulation during the flight and returned to their former pattern after the flight. 相似文献
222.
DFVLR已在VFW614轻型喷气运输机基础上研制出了一架叫做ATTAS(Advanced Tech-nologies Testing Aircraft System)的新的空中飞行模拟器。该系统将于1988年底投入使用。本文简述了ATTAS系统,包括飞机改装,仪器设备及地面ATTAS模拟设备,以及最近的一些飞行试验结果。 相似文献
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利用有限元法分析了一个用废塑料做成的蜂窝状刚性(道)路面(CRP)设施,从中得出了标准公路当量单轴荷载(ESAL)下产生的应力。通过参数分析研究了该铺筑面的不同板块、基层、底基层、土基的厚度和弹性性能以及两种不同的胎压。本文将分析出的应力与相同荷载条件下实体(硬)板(solid salb)的应力作了比较。尽管蜂窝状刚性道(路)面的应力高于实体板的压力,但最大应力仍在铺筑刚性道面所容许使用的范围之内。基于荷载抗力和疲劳标准,这种蜂窝状刚性道(路)面能够明显地节省铺筑料、能源和费用,其值可达25%;并能使废物得到充分利用。这种CRP铺筑技术也适用于铺筑停车场、人行道、护坡、渠道衬砌、地面上的地板及类似铺面设施。 相似文献
226.
Cockell CS Voytek MA Gronstal AL Finster K Kirshtein JD Howard K Reitner J Gohn GS Sanford WE Horton JW Kallmeyer J Kelly L Powars DS 《Astrobiology》2012,12(3):231-246
Although a large fraction of the world's biomass resides in the subsurface, there has been no study of the effects of catastrophic disturbance on the deep biosphere and the rate of its subsequent recovery. We carried out an investigation of the microbiology of a 1.76 km drill core obtained from the ~35 million-year-old Chesapeake Bay impact structure, USA, with robust contamination control. Microbial enumerations displayed a logarithmic downward decline, but the different gradient, when compared to previously studied sites, and the scatter of the data are consistent with a microbiota influenced by the geological disturbances caused by the impact. Microbial abundance is low in buried crater-fill, ocean-resurge, and avalanche deposits despite the presence of redox couples for growth. Coupled with the low hydraulic conductivity, the data suggest the microbial community has not yet recovered from the impact ~35 million years ago. Microbial enumerations, molecular analysis of microbial enrichment cultures, and geochemical analysis showed recolonization of a deep region of impact-fractured rock that was heated to above the upper temperature limit for life at the time of impact. These results show how, by fracturing subsurface rocks, impacts can extend the depth of the biosphere. This phenomenon would have provided deep refugia for life on the more heavily bombarded early Earth, and it shows that the deeply fractured regions of impact craters are promising targets to study the past and present habitability of Mars. 相似文献
227.
一次性运载火箭的重新使用,将成为发展低成本空间运输系统的关键一步。先前的研究以及航天飞机固体火箭助推器的经验表明,运载火箭构件的回收和再用在经济上是有利的。由于认识到这个事实,NASA/MSFC与先锋航空航天公司签订了称作高级运载火箭先进回收系统(ARS)的第一阶段研究合同。本文论述了研究期间所完成的工作和由此而得到的结论。 先锋公司首先研究了这样一种方法,用它可以在预定点完整回收各种运载火箭硬件,供整修后再用。然后集中精力研究一个回收系统以用于近期很可能用得上的项目,即推进和电子设备舱(P/AM)的回收。 这次研究在如下方面是成功的: ·满意地达到了所有的研究目标; ·按照规定的时间,呈报了所有资料文本; ·对第二阶段试验所用的P/AM回收系统进行了设计,该系统具有成本低,重量轻、性能好,具有定点着陆潜力和使用灵活的优点。 相似文献
228.
Thermoluminescent (TL) detectors were used for dosimetric investigations on the outer surface as well as inside Soviet spacecrafts of the "Cosmos" series. At the outer surface, ultrathin TL detectors, based on CaF2-PTFE and LiF, were arranged in special stacks and exposed to unshielded cosmic radiation. The strong decrease of dose within a few mg/cm2 demonstrates that weakly penetrating radiation is dominating in the radiation field under investigation. On the basis of glow curve analysis of LiF thermoluminescent detectors it could be shown, that the high doses are caused by electrons. 相似文献
229.
作者对最新设计的具有方形硅膜片的 CMOS 集成硅压力传感器的特性进行了理论的和实验的分析。结果表明:传感器的非线性是由硅膜片的大幅度偏折(deflecti-on)和压阻元件的非线性压阻特性所引起的。文章还指出了将非线性减至最小程度时传感器的最佳结构形式。对所制得的压力传感器的非线性作了测量,其值与数学分析值十分吻合。 相似文献
230.
Pettis CR Drake M Witten ML Truitt J Braun E Lindberg K McNeil G Hall JN 《Acta Astronautica》2002,50(6):393-398
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. 相似文献