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21.
月尘运动是月球探测器软着陆过程中不可或缺的重要环节,针对发动机羽流作用下月尘运动真实感不强和月尘颗粒运动模型过于简单的问题,提出了一种逼真的实时月尘运动仿真方法.通过计算流体动力学(CFD, Computational Fluid Dynamics)和二次谢别德插值(Quadratic Shepard)方法,分析和计算单个月尘颗粒的运动学模型,得到一定初始条件下粒子运动的二维轨迹曲线;通过分析粒子的数量、初始位置、初始速度、生命周期等参数对粒子运动学的影响和变化规律,抽象出月尘系统的粒子集;建立基于月尘粒子集的月尘运动模型.实验结果显示:该运动模型逼真的模拟了发动机羽流作用下月尘腾起、飞溅、弥漫、消散等运动过程,视觉真实感和实时性能良好,对研究真空环境中的月尘运动及月球软着陆等相关领域具有一定的参考意义.目前该方法已应用于北航虚拟现实国家重点实验室月球软着陆仿真系统. 相似文献
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信道估计是无线通信系统的关键技术之一。文章提出一种基于压缩感知(Compressed Sensing)的信道估计方法,这种方法通过分析信道时延和多普勒域的稀疏度,可以有效降低导频的数量,从而提高系统的频谱利用率。通过与最小均方(Least Square,LS)信道估计方法的对比,可以明显看到导频数量的降低。 相似文献
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王海燕%张敏%王海峰%张永生%彭桂荣 《宇航材料工艺》2008,38(5)
进行了改性羰基铁粉-氯磺化聚乙烯(CSM)吸波涂层的臭氧环境暴露试验,并利用SEM、XRD、IR、DSC和TG等方法研究了臭氧对其表面结构和性能的影响。结果表明,臭氧造成CSM表层分解,部分羰基铁粉脱落,但未影响改性羰基铁粉的相组成,对涂层吸波性能的影响不显著。 相似文献
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J. Pavlů I. RichterováZ. Němeček J. Šafránková 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The space plasma environment usually contains charged dust grains. The grain charge is an important parameter determining its migration through the space, coagulation, formation of dust clouds and so on. The knowledge of its charge is thus one of the basic information we want to know. There are several emission processes leading to both positive and negative charges, among others photoemission, all kinds of secondary emissions, field emissions, etc. The present study is focused on a laboratory simulation of emissions caused by impacts by energetic ions. Our experiment is based on the Paul trap which gives us an opportunity to catch a single dust grain for several days inside the vacuum vessel and exposed it by electron/ion beams. This experimental approach allows us to separate an individual charging process. We have chosen spherically shaped gold grains and discussed the processes leading to the limitation of the grain charge. We suggested that the implantation of charging ions leads to deformations of the grain surface. The deformations enhance the local electric field strength that becomes sufficient for the field ionization. 相似文献
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Alain Abergel Laurent Verstraete Christine Joblin René Laureijs Marc-Antoine Miville-Deschênes 《Space Science Reviews》2005,119(1-4):247-271
Infrared spectroscopy and photometry with ISO covering most of the emission range of the interstellar medium has led to important
progress in the understanding of the physics and chemistry of the gas, the nature and evolution of the dust grains and also
the coupling between the gas and the grains. We review here the ISO results on the cool and low-excitation regions of the
interstellar medium, where T
gas≲ 500 K, n
H∼ 100–105 cm−3 and the electron density is a few 10−4.
JEL codes: D24, L60, 047
Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries:
France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA. 相似文献
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The ISO-SWS instrument offering a large wavelength coverage and a resolution well adapted to the solid phase has changed our
knowledge of the physical-chemical properties of ices in space. The discovery of many new ice features was reported and the
comparison with dedicated laboratory experiments allowed the determination of more accurate abundances of major ice components.
The presence of CO2 ice has recently been confirmed with the SWS (Short Wavelength Spectrometer) as a dominant ice component of interstellar
grain mantles. The bending mode of CO2 ice shows a particular triple-peak structure which provides first evidence for extensive ice segregation in the line-of-sight
toward massive protostars. A comparison of interstellar and cometary ices using recent ISO data and ground-based measurements
has revealed important similarities but also indicated that comets contain, beside pristine interstellar material, admixtures
of processed material. The investigation of molecules in interstellar clouds is essential to reveal the link between dust
in the interstellar medium and in the Solar System.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献