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201.
通过对有源低通滤波器,频率/电压转换器AD650及其变容二极管的特性分析,提出由信号频率来自调节有源低通滤波器截止频率的新设计方案,并对其可行性进行了分析和研究。 相似文献
202.
Florence Durret Gastão B. Lima Neto 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
We have analyzed XMM-Newton archive data for five clusters of galaxies (redshifts 0.223–0.313) covering a wide range of dynamical states, from relaxed objects to clusters undergoing several mergers. We present here temperature maps of the X-ray gas together with a preliminary interpretation of the formation history of these clusters. 相似文献
203.
郑晓辉郭腾飞余圣晖 《民用飞机设计与研究》2014,(3):15-20
前缘缝翼、襟翼活动面及其支承结构的疲劳试验是民用飞机取证前要开展的一项重要工作。在试验中采用主动驱动和随动加载方法加载,不仅能缩小试验规模,同时可提高试验精度。国内某型机采用此技术成功进行了前缘缝翼、襟翼及其悬挂结构的疲劳试验。从试验件及其支承设计、系统构成和载荷与运行三方面,介绍了一种适用于大中型固定翼飞机前缘缝翼和襟翼的疲劳试验技术。 相似文献
204.
We briefly review some questions of extragalactic astrophysics and cosmology that would most benefit from future missions outside the Earth's atmosphere in the IR and submillimeter. These include the formation and early evolution phases in galaxies and the probably related question of quasar formation; the observation of Active Galactic Nuclei embedded in thick dusty structures (torii) and its impact on the still debated unified model of AGN activity; the observability of radiation processes occurring at very highz through background measurements; the investigation of the large scale structure and velocity field in the distant universe; and studies of the interstellar medium in galaxies. Some more emphasis is given on the galaxy formation problem, because we believe that IR-mm sensitive observations will be crucial to its final solution. 相似文献
205.
206.
主动控制式对接机构对接预捕获阶段的仿真 总被引:2,自引:0,他引:2
介绍了主动控制式对接机构对接的基本操作过程,并以具有六个作动阻尼器的主动接制式对接机构为例,对对接预捕获阶段作了详细的研究。 该阶段两对接飞行器的运动方程,给出了作动/阻尼器为满足捕获条件所需达到的长度的计算方法,设计了控制回路,在此基础上作了数值仿真。仿真结果表明,建立的数学模型是正确的,设计的控制系统控制效果良好。 相似文献
207.
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209.
N. Visvanathan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
Multiaperture photometry in V (5500Å), r (6738Å) and IV (10500Å) of 52 spirals in nearby clusters Virgo, Fornax and Grus and farther clusters Cancer, Zw 74-23 and Peg I in the redshift range up to 6000 Km s−1 was combined with HI width to derive three independant distances for each galaxy in these clusters.The plot between the mean distance of each cluster and its redshift, indicates the Hubble ratios of distant clusters Cancer, Zw 74-23 and Peg I are about 77 Km s−1 Mpc−1. Further, the Hubble ratios of distant clusters vary only from 76.3 to 78.9 Km s−1 Mpc−1 while those of nearby clusters Virgo, Fornax and Grus vary through a large range of 58.5 to 83.5 Km s−1 Mpc−1. We interpret these data by postulating a systematic motion toward Virgo for the Local Group.The best value for the global Hubble constant from farther and nearby clusters is derived as 74.3± 4 Km s−1 Mpc−1 and an average value of 289±60 Km s−1 for the infall velocity of the Local Group toward Virgo is also derived. 相似文献
210.
Nicholas E. White 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2632-2636
The X-ray evolution of the luminosity of normal galaxies is primarily driven by the evolution of their X-ray binary populations. The imprints left by a cosmological evolution of the star formation rate (SFR) will cause the average X-ray luminosity of galaxies to appear higher in the redshift range 1–3. As reported by White and Ghosh [ApJ, 504 (1998) L31] the profile of X-ray luminosity with redshift can both serve as a diagnostic probe of the SFR profile and constrain evolutionary models for X-ray binaries. In order to observe the high redshift (z>3) universe in the X-ray band, it is necessary to avoid confusion from foreground field galaxies. We report on the predictions of these models of the X-ray flux expected from galaxies and the implications for the telescope parameters of future deep universe X-ray observatories. 相似文献