共查询到18条相似文献,搜索用时 405 毫秒
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目前利用激光来冷却和囚禁中性原子的技术已取得激动人心的进展。通过使用廉价的二极管激光器和蒸汽室收集器,有效地降低了囚禁原子的复杂性和高成本,在零点几μK温度下,可得到1011个原子/cm3的原子密度。本文介绍了有关激光冷却与囚禁技术,讨论了其现实应用:频率标准一基本物理性质研究。 相似文献
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介绍上海天文台25 m射电望远镜首次单天线脉冲星观测。2010年4月23日,使用上海天文台位于佘山观测基地的25 m射电望远镜对脉冲星J0332+5434在L波段进行了观测,此次观测使用VLBI终端进行数据采集记录,通过对观测数据进行非相干消色散和周期折叠,成功获得目标源的平均轮廓。此次观测的成功,表明该天线具备开展单天线脉冲星观测的条件,并为上海天文台建设中的65 m天线的天文观测提供了参考,为将来自主研发脉冲星终端进行了技术储备。 相似文献
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为了获得稳定、可靠的卫星电视时间比对数据,成功研制了以秒信号提取器为主要部件的新一代卫星电视时间解调器。介绍了秒脉冲信号提取器的设计原理,详细阐述了钳位电路、采样保持电路和数字延迟电路的设计思路。对采用新的解调器和采用旧的解调器的卫星电视秒信号监测系统所得到的比对数据进行了分析,结果表明新的电视时间解码器的性能得到明显提高。 相似文献
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Rao Chang-hui Jiang Wen-han Ling Ning Jacques M. Beckers 《Chinese Astronomy and Astrophysics》2001,25(4):225-445
The contrast of the solar surface granulation detected in the focal plane of the observing system as well as its relations with the aperture of the observing system, the coherent length of atmospheric turbulence and the sensitivity of the detecting system are analyzed. The results of numerical calculation of the granulation contrast as functions of aperture, coherent length of atmospheric turbulence and sensitivity of the detecting system are presented. Results of a related observation are also given. 相似文献
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Pavel Voráček 《Astrophysics and Space Science》1985,116(1):197-206
Mach's principle is formulated in two different ways, heuristic and mathematical. Known problems of the principle are listed and two of them, the problem of its validity in the case the Universe is open and the boundary condition problem, are analyzed separately. Moreover, the history of the cosmic potential is outlined and a short modification of Horák's deduction of the potential is presented together with a discussion on the conditions of the solution. The conclusions are drawn that the Universe is closed and that Mach's principle is compatible with the general theory of relativity, provided that the Big Bang did not start from a singularity but from finite volume and density. In the last section it is shown that Rosen's bimetric theory is compatible with our picture of the Universe. 相似文献
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The problem of optimizing the interplanetary trajectories of a spacecraft (SC) with a solar electric propulsion system (SEPS) is examined. The problem of investigating the permissible power minimum of the solar electric propulsion power plant required for a successful flight is studied. Permissible ranges of thrust and exhaust velocity are analyzed for the given range of flight time and final mass of the spacecraft. The optimization is performed according to Portnyagin’s maximum principle, and the continuation method is used for reducing the boundary problem of maximal principle to the Cauchy problem and to study the solution/ parameters dependence. Such a combination results in the robust algorithm that reduces the problem of trajectory optimization to the numerical integration of differential equations by the continuation method. 相似文献
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We searched for a sidereal modulation in the rate of neutrinos produced by the NuMI beam and observed by the MINOS far detector. The detection of such harmonic signals could be a signature of neutrino–antineutrino mixing due to Lorentz and CPT violation as described by the Standard-Model Extension framework. We found no evidence for these sidereal signals and we placed limits on the coefficients in this theory describing the effect. This is the first report of limits on these neutrino–antineutrino mixing coefficients. 相似文献