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141.
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
142.
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
147.
Single track and single layer formation in selective laser melting of niobium solid solution alloy 总被引:1,自引:2,他引:1
Selective laser melting (SLM) was employed to fabricate Nb-37Ti-13Cr-2Al-1Si (at%) alloy, using pre-alloyed powders prepared by plasma rotating electrode processing (PREP). A series of single tracks and single layers under different processing parameters was manufactured to evaluate the processing feasibility by SLM, including laser power, scanning speed, and hatch distance. Results showed that continuous single tracks could be fabricated using proper laser powers and scanning velocities. Both the width of a single track and its penetration depth into a substrate increased with an increase of the linear laser beam energy density (LED), i.e., an increase of the laser power and a decrease of the scanning speed. Nb, Ti, Si, Cr, and Al elements distributed heterogeneously over the melt pool in the form of swirl-like patterns. An excess of the hatch distance was not able to interconnect neighboring tracks. Under improper processing parameters, a balling phenomenon occurred, but could be eliminated with an increased LED. This work testified the SLM-processing feasibility of Nb-based alloy and promoted the application of SLM to the manufacture of niobium-based alloys. 相似文献
148.
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