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101.
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1992年夏,随着极紫外探测卫星(EUVE)一起发射了一台单频GPS接收机。EUVE卫星轨道低,并在星体上直接安装了二个天线,可用来研究误差源,以及未来卫星可达到的定轨精度。利用GDPSY—OASLSⅡ软件处理了几段GPS教据。从EUVE来的数据和从全球GPS接机网来的数据相结合,消除了SA的影响。研究了几种消除单频数据中电离层延时误差以及利用简化动力学法求解轨道的方法。通过内符合检验并与哥达德航天中心产生的GTDS轨道解作比对,鉴定了GPS测轨精度。利用GPS的测轨精密度和准确度在一米量级。 相似文献
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Blum V Andriske M Kreuzberg K Paassen U Schreibman MP Voeste D 《Acta Astronautica》1998,42(1-8):25-35
Based on the construction principle of the Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) two novel combined animal-plant production systems were developed in laboratory scale the first of which is dedicated to mid-term operation in closed state up to two years. In principle both consist of the "classic" C.E.B.A.S. subcomponents: animal tank (Zoological Component), plant cultivators (Botanical Component), ammonia converting bacteria filter (Microbial Component) and data acquisition/control unit (Electronical Component). The innovative approach in the first system is the utilization of minimally three aquatic plant cultivators for different species. In this one the animal tank has a volume of about 160 liters and is constructed as an "endless-way system" surrounding a central unit containing the heat exchanger and the bacteria filter with volumes of about 1.5 liters each. A suspension plant cultivator (1 liter) for the edible duckweed Wolffia arrhiza is externally connected. The second plant cultivator is a meandric microalgal bioreactor for filamentous green algae. The third plant growth facility is a chamber with about 2.5 liters volume for cultivation of the "traditional" C.E.B.A.S. plant species, the rootless buoyant Ceratophyllum demersum. Both latter units are illuminated with 9 W fluorescent lamps. In the current experiment the animal tank contains the live-bearing teleost fish Xiphophorus helleri and the small pulmonate water snail Biomphalaria glabrata because their physiological adaptation to the closed system conditions is well known from many previous C.E.B.A.S. experiments. The water temperature is maintained at 25 degrees C and the oxygen level is regulated between 4 and 7 mg/l by switching on and off the plant cultivator illuminations according to a suitable pattern thus utilizing solely the oxygen produced by photosynthesis. The animals and the microorganisms of filter and biofilm provide the plants with a sufficient amount of carbon dioxide. Oxygen concentration, pH value, temperature and redox potential are on-line recorded. Ion concentrations and numbers of living germs in the system water are determined twice monthly in the laboratory from samples taken from a special "sample removal module"; the sample volume is automatically replaced from an reservoir container. A rotatory pump produces a water flow of about 38 l/min. For a similar smaller test system with approx. 10 l volume developed from the C.E.B.A.S.-MINI-MODULE a novel indirect solar energy supply is tested which has a buffer capacity to maintain the system for 7 days in darkness under central European climate conditions also in winter. It contains only a single plant cultivator which is operated with Wollfia arrhiza. This lemnacean plant is able to produce large amounts of plant biomass in a short time by vegetative reproduction via daughter fronds. This easy-to-handle apparatus is dedicated to be operative more than 4 month. The experimental animals and microorganisms are the same as in the large system. The paper provides detailed information on the system construction principles and the biological, physical and chemical data of the initial phase of the test runs of both systems with the main focus on the large one. 相似文献
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The long-term bed-rest was organized by ESA and CNES, in order to simulate the physiological effects of weightlessness: eight volunteers had to stay 42 days in bed, in a head down tilt position (-6 degrees). There were two subjects in a room, they could not be alone and it was difficult for them to have their own personal space and intimacy. In these circumstances, as in outer space, interpersonal relationships were of prime importance. This situation enabled us, through systematic observation, to analyze the evolution of the relational behavior in dyads, and to quote some social indicators of adaptation. Results show significant withdrawal, and the time spent alone was marked by the emergence, during the experiment, of specific preferential activities. Behavioral contagion was observed in each dyad (people engaged in the same activities at the same time), except in the one case of abandon. Moreover, the highest rates of inactivity and withdrawal were noted in this case. Verbal indicators were useful to comment these results and showed that, for all the dyads, one of the two subjects always played a regulating role by expressing a very positive perception of the situation. These results emphasize the importance of psycho-sociological factors in isolation and confinement. Thus, it appears that different modalities of interpersonal relationships, and not only verbal interactions, play a significant role in adaptation to stress situations. 相似文献
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通常情况下,常规船用捷联惯性导航系统在运动中约需4小时实现初始对准与标定。本文提出了一种有效的快速初始对准与标定方法,应用此方法的船用捷联惯性导航系统有三个光纤陀螺与三个常规加速度主。 相似文献
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Gaidos E Deschenes B Dundon L Fagan K Menviel-Hessler L Moskovitz N Workman M 《Astrobiology》2005,5(2):100-126
We review recent work that directly or indirectly addresses the habitability of terrestrial (rocky) planets like the Earth. Habitability has been traditionally defined in terms of an orbital semimajor axis within a range known as the habitable zone, but it is also well known that the habitability of Earth is due to many other astrophysical, geological, and geochemical factors. We focus this review on (1) recent refinements to habitable zone calculations; (2) the formation and orbital stability of terrestrial planets; (3) the tempo and mode of geologic activity (e.g., plate tectonics) on terrestrial planets; (4) the delivery of water to terrestrial planets in the habitable zone; and (5) the acquisition and loss of terrestrial planet carbon and nitrogen, elements that constitute important atmospheric gases responsible for habitable conditions on Earth's surface as well as being the building blocks of the biosphere itself. Finally, we consider recent work on evidence for the earliest habitable environments and the appearance of life itself on our planet. Such evidence provides us with an important, if nominal, calibration point for our search for other habitable worlds. 相似文献