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排序方式: 共有10000条查询结果,搜索用时 390 毫秒
561.
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A. L. Broadfoot B. R. Sandel D. E. Shemansky S. K. Atreya T. M. Donahue H. W. Moos J. L. Bertaux J. E. Blamont J. M. Ajello D. F. Strobel J. C. McConnell A. Dalgarno R. Goody M. B. McElroy Y. L. Yung 《Space Science Reviews》1977,21(2):183-205
The Voyager Ultraviolet Spectrometer (UVS) is an objective grating spectrometer covering the wavelength range of 500–1700 Å with 10 Å resolution. Its primary goal is the determination of the composition and structure of the atmospheres of Jupiter, Saturn, Uranus and several of their satellites. The capability for two very different observational modes have been combined in a single instrument. Observations in the airglow mode measure radiation from the atmosphere due to resonant scattering of the solar flux or energetic particle bombardment, and the occultation mode provides measurements of the atmospheric extinction of solar or stellar radiation as the spacecraft enters the shadow zone behind the target. In addition to the primary goal of the solar system atmospheric measurements, the UVS is expected to make valuable contributions to stellar astronomy at wavelengths below 1000 Å. 相似文献
563.
Defending a Moving Target Against Missile or Torpedo Attack 总被引:4,自引:0,他引:4
Problems involving kinematics of a counterweapon intercepting an attacking missile are well known. However, when the attacker's target, the counterweapon's launch platform, is moving, the problem generally becomes amenable only to trajectory simulation. Such may be the case in defense against torpedo attack against a ship and other situations involving the use of antimissile missiles. This paper derives the kinematic relations among the three bodies (missile, target, and counterweapon) in closed form under the asymptotic approximation of constant-bearing trajectories (collision courses). It is shown that the defending target, even if moving, can still determine the optimum course for its counterweapon when range and speed of the attacking vehicle are unknown. A simple relation is derived for the ratio between the attacker-target range (and time to impact) at counterweapon launch and the range at interception of the attacker by the counterweapon. Normalized curves are presented for some representative cases of defense by a counterweapon of known speed against a torpedo or missile attack on a moving target. The equations are shown to reduce to the familiar form for a stationary target. 相似文献
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吴爱萍%邹贵生%张红军%王国庆%谢美蓉 《宇航材料工艺》2001,31(6):58-62
研究了Ti-24Al-17Nb合金的激光焊接及其接头的力学性能.研究结果表明,连续激光氦气双面保护可以获得保护效果可靠、无缺陷、成型良好的焊接接头.焊接热输入增大不利于接头的纵向弯曲塑性,而接头的横向拉伸强度与母材基本相同,塑性可以接近母材的塑性,达到14%~17%. 相似文献
567.
A survey of current knowledge about Jupiter, Saturn, Uranus, Neptune, Pluto, and their satellites is presented. The best available
numerical values are given for physical parameters, including orbital and body properties, atmospheric composition and structure,
and photometric parameters. The more acceptable current theories of these bodies are outlined with thorough referencing offering
access to the details. The survey attempts to cover the literature through May 1, 1972.
Prepared Under Contract No. NAS7-100 National Aeronautics and Space Administration. 相似文献
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为了获得涡流阀参数对发动机推力调节性能的影响规律,针对涡流阀的加注方式以及几何结构,利用建立的基于涡流阀方案的固体火箭发动机推力可调实验系统开展了实验研究。通过实验结果的分析,得到了加注环孔径、涡流室高度和直径以及中心进气面积的不同对涡流阀调节性能的影响规律。结果表明:适当降低涡流室的高度、较大的中心进气面积、较大的涡流室直径有利于提高涡流阀的调节性能。因此,可以通过对涡流阀结构的优化设计来提高发动机的推力调节性能。 相似文献