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Pablo Fajardo Sergio Barahona Angel Sanz-Andres 《Microgravity science and technology》2009,21(3):247-255
Some results of the analysis of the pictures taken along the performance of the Análisis de Propiedades Inerciales de Sólidos,
Analysis of the Inertia Properties of Solid Bodies (APIS) experiment carried out in the Cervantes mission on board ISS, are
presented. APIS was an educational experiment devoted to take advantage of the unique conditions of absence of relative gravity
forces of a space platform such as ISS, to show some of the characteristics of the free rotational motion of a solid body,
which are impossible to carry out on earth. This field of experimental research has application to aerospace engineering science
(e.g. attitude control of spacecrafts), to astrophysical sciences (e.g. state of rotation and tumbling motions of asteroids)
and to engineering education. To avoid the effect of the ambient atmosphere loads on the motion, the test body is placed inside
a sphere, which reduces the effect of the aerodynamic forces to just friction. The drastic reduction of the effect of the
surrounding air during the short duration of the experimental sequences allows us to compare the actual motion with the known
solutions for the solid body rotation in vacuum. In this paper, some selected, relevant sequences of the sphere enclosing
a body with a nominal cylindrical inertia tensor, put into rotation by the astronaut, are shown; the main problems to extract
the information concerning the characteristic parameters of the motion are outlined, and some of the results obtained concerning
the motion of the test probe are included, which show what seems to be a curious and unexpected solution of the Euler equations
for the solid body rotation in vacuum, without energy dissipation, when the angular momentum is almost perpendicular to the
axisymmetry axis. 相似文献
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成核剂TMC-328对可生物降解聚乳酸结晶性能的影响 总被引:2,自引:0,他引:2
用熔融法制备了含成核剂TMC-328质量分数分别为0、0.1%、0.2%、0.3%的聚乳酸(PLA)/TMC-328共混物,采用偏光显微镜(POM)、差示扫描量热仪(DSC)及扫描电子显微镜(SEM),研究了PLA共混物的结晶性能、热性能和内部形貌。结果表明,TMC-328对PLA结晶性能的影响体现在PLA的冷结晶过程上,并且最佳添加量为0.1%,相对应的冷结晶温度(Tcc)从126.14℃降到111.40℃,冷结晶焓(ΔHcc)从11.34J/g增加到23.49J/g,在100℃下完全结晶的时间为22min左右,SEM照片显示TMC-328的团聚现象随着含量的增加变得很明显。 相似文献
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万吨级多功能结构试验系统是中国建筑股份有限公司研制的重型结构试验设备,试验系统的综合功能和加载能力为世界同类设备之最。为减少试验系统对周边办公区域的影响,在设备的基座下面设置了隔振层。本文采用ANSYS瞬态动力学分析方法,针对试件断裂对万吨级多功能结构试验系统隔振层的冲击影响进行了分析,提取了试验系统基座底部边界角点的X、Y、Z方向位移和单个隔振器的Z方向受力时程曲线,对比分析了不同卸载时间对隔振响应的影响,并校核了隔振器的安全性,对模拟试件断裂的卸载时间提出了建议。针对不同隔振器数量布置的隔振层,计算了试件突然断裂时隔振效果的区别,提出了隔振器数量的建议。 相似文献
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The Influence of Carbon Nitride Nanosheets Doping on the Crystalline Formation of MIL‐88B(Fe) and the Photocatalytic Activities
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Zhen‐Dong Lei Yuan‐Cheng Xue Wen‐Qian Chen Lin Li Wen‐Hui Qiu Yong Zhang Liang Tang 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(35)
In this research, bulk graphitic carbon nitride (g‐C3N4) is exfoliated and transferred to the carbon nitride nanosheets (CNNSs), which are then coupled with MIL‐88B(Fe) to form the hybrid. From the results of the powder X‐ray diffraction, scanning electronic microscopy and thermogravimetric analysis, it is found that the doping of CNNSs on the surface of MIL‐88(Fe) could maintain the basic structure of MIL‐88B(Fe), and the smaller dimension of CNNSs might influence the crystallization process of metal‐organic frameworks (MOFs) compared to bulk g‐C3N4. Besides, the effects of the CNNSs incorporation on photocatalysis are also investigated. Through the photoluminescence spectra, electrochemical measurements, and photocatalytic experiments, the hybrid containing 6% CNNSs is certified to possess the highest catalytic activity to degrade methylene blue and reduce Cr(VI) under visible light. The improvement of the photocatalytic performance can be attributed to the matched energy level which favors the formation of the heterojunctions. Besides, it promotes the charge migration such that the contact between MOFs and CNNSs is more intimate, which can be inferred from the electronic microscopy images. Finally, a possible photocatalytic mechanism is put forward by the relative calculation and the employment of the scavengers to trap the active species. 相似文献