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131.
Thermal springs in evaporitic environments provide a unique biological laboratory in which to study natural selection and evolutionary diversification. These isolated systems may be an analogue for conditions in early Earth or Mars history. One modern example of such a system can be found in the Chihuahuan Desert of north-central Mexico. The Cuatro Cienegas basin hosts a series of thermal springs that form a complex of aquatic ecosystems under a range of environmental conditions. Using landmark-based morphometric techniques, we have quantified an unusually high level of morphological variability in the endemic gastropod Mexipyrgus from Cuatro Cienegas. The differentiation is seen both within and between hydrological systems. Our results suggest that this type of environmental system is capable of producing and maintaining a high level of morphological diversity on small spatial scales, and thus should be a target for future astrobiological research. 相似文献
132.
By the end of 2006,China had launched 24 recoverable satellites(FSW)in total.Among them,23 were launched successfully,of which all but one were successfully recovered.Recoverable satellites launched by China are listed in Table 1. 相似文献
133.
Extraterrestrial infrastructure is key to the development of a space economy. Means for accelerating transition from today's isolated projects to a broad-based economy are considered. A large system integration approach is proposed. The beginnings of an economic simulation model are presented, along with examples of how interactions and coordination bring down costs. A global organization focused on space infrastructure and economic expansion is proposed to plan, coordinate, fund and implement infrastructure construction. This entity also opens a way to raise low-cost capital and solve the legal and public policy issues of access to extraterrestrial resources. 相似文献
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Investigations into sensing characteristics of circular thin-plate electrostatic sensors for gas path monitoring 总被引:1,自引:0,他引:1
Circular thin-plate electrostatic sensors are promising in gas path monitoring due to their advantages of non-intrusiveness and easy installation. The spatial sensitivity and filtering effect are two important performance parameters. In this paper, an analytically mathematical model of induced charge on a circular thin-plate electrode is first derived. Then the spatial sensitivity and filtering effect of the circular electrostatic sensor are investigated by numerical calculations. Finally,experimental studies are performed to testify the theoretical results. Both theoretical and experimental results demonstrate that circular thin-plate electrostatic sensors act as a low-pass filter in the spatial frequency domain, and both the spatial filtering effect and the temporal frequency response characteristics depend strongly on the spatial position and velocity of the charged particle. These conclusions can provide guidelines for the optimal design of circular thin-plate electrostatic sensors. 相似文献
138.
论文针对如今招生趋势良好的高校艺术类专业的学生当中存在的一些问题进行了分析和探讨,从树立正确的人生观和价值观、学会感恩以及培养各方面素质全面发展的人才这三个方面入手,建设性地提出了相关的引导学生改进所存在问题的方法和策略. 相似文献
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波音系列飞机一定时间后,飞机尾部结构出现疲劳裂纹,需用涡轮检测法进行损伤检查。 相似文献