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B.J. Carr J. McDowell H. Sato 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
We examine whether the IR background reported by Matsumoto (1983) could have been generated by stars or black holes in the pregalactic era, z=10100. 相似文献
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本文采用谐波平衡法,定量地解释了机翼颤振主动抑制风洞试验中出现的极限环现象。提出了比较精确的计及极限环基阶谐波与三阶谐波的分析计算方法。指出在采用液压舵机的情况下,伺服阀的不灵敏区是出现极限环现象的一个主要原因。 相似文献
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针对二冲程汽油发动机改用航空煤油后的爆震抑制和性能恢复进行了研究,利用GT-Power软件建立发动机的一维仿真模型并对煤油发动机的爆震进行了预测和优化。仿真结果表明:推迟点火时刻、远低于和远大于理论空燃比的混合气对爆震都有一定的抑制作用,试验结果验证了仿真结果的正确性。提出并采用协同推迟点火和增加喷油的控制策略进行试验研究。试验结果表明:在低转速大负荷工况下,爆震可被有效抑制,节气门全开时功率恢复在90%以上。发动机转速为5 500 r/min时,功率恢复能达到原机的95.7%。 相似文献
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随机二相码调相PD(脉冲多普勒)引信,是一种较为新颖的噪声调制引信体制。因距离旁瓣的存在会使该体制引信产生概率性的距离模糊,首先分析了其独特的距离旁瓣特性,然后分析了相关器组法进行距离旁瓣抑制的机理和性能,并提出了以限制码的最大游程加惯性积累电路来抑制的方法。分析表明,两者都能对距离旁瓣进行有效的抑制,而后者更适合于引信电路的特点。 相似文献
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M.N. Kouahla G. Moreels M. Faivre J. Clairemidi J.W. Meriwether G.A. Lehmacher E. Vidal O. Veliz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645 km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630 m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272 m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3 km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz = 83.5–88.0 km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3 × 10−4 and 5.4 × 10−4 J/m3, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude. 相似文献
89.
Shawqi Al Dallal 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Diffuse Galactic gamma-ray flux resulting from the evaporation of primordial black holes has been the subject of intensive research work during the last few decades. Theoretical work addressing this issue started in the 1970s whereas data started pouring in only in the 1990s. We discuss in this paper a model of the potential contribution to the Galactic gamma-ray flux of primordial black holes in binary systems and extend the argument to include stable gravitational bound states called Holeums. The model has a predictive power and can be tested by looking for gamma-ray excess in the vicinity of violent events occurring in the Galaxy such as supernova explosions. 相似文献
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