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很久以来,人们对光就进行了各种各样的研究。光的本性到底是什么,这个问题长久以来困扰了很多有智之士。光的波动说笛卡儿(R.Descartes,1596~1650)就光的本性问题,在1637年提出两种假说。一种假说认为,光是类似于微粒的一种物质;另一种假说认为光是一种以“以太”为媒质的压力。虽然笛卡儿更强调媒介对光的影响和作用,但他的这两种假说为17世纪的微粒说和波动说的争论埋下了伏笔。17世纪中期,意大利的格里马第(F.Grimaldi,1618~1663)首先注意到衍射现象,这是光的波动理论的萌芽。 相似文献
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Sankar Hajra 《中国物理 B》2014,(4):147-156
Relativists have exposed various precessions and developed ingenious experiments to verify those phenomena with extreme precisions. The Gravity Probe B mission was designed to study the precessions of the gyroscopes rotating round the Earth in a nearly circular near-Earth polar orbit to demonstrate the geodetic effect and the Lense-Thirring effect as predicted by the general relativity theory. In this paper, we show in a very simple and novel analysis that the precession of the perihelion of Mercury, the Thomas precession, and the precession data (on the de Sitter and Lense-Thirring precessions) collected from the Gravity Probe B mission could easily be explained from classical physics, too. 相似文献
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A new technique of residual-type a posteriori error analysis is developed for the lowest- order Raviart-Thomas mixed finite element discretizations of convection-diffusion-reaction equations in two- or three-dimension. Both centered mixed scheme and upwind-weighted mixed scheme are considered. The a posteriori error estimators, derived for the stress variable error plus scalar displacement error in L_2-norm, can be directly computed with the solutions of the mixed schemes without any additional cost, and are proven to be reliable. Local efficiency dependent on local variations in coefficients is obtained without any saturation assumption, and holds from the cases where convection or reaction is not present to convection- or reaction-dominated problems. The main tools of the analysis are the postprocessed approximation of scalar displacement, abstract error estimates, and the property of modified Oswald interpolation. Numerical experiments are carried out to support our theoretical results and to show the competitive behavior of the proposed posteriori error estimates. 相似文献
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托马斯--杨是一位多才多艺的学者, 在光学、声学、流体动力学、医学、材料力学、
考古学、语言学、保险学等众多领域做出了突出贡献, 但由于种种原因使他在力学方面的贡
献未曾得到学术界的足够重视. 杨在力学方面的研究涉及到材料力学、血液流动力学、能量、
冲击动力学、表面浸润力学、工程结构分析等方面. 他是一位纯粹的自然哲学家, 同时他能
够将理论与实验和工程实际相结合, 实现了后辈力学家所提倡的``技术科学'的理念. 相似文献
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相对论中的托马斯旋进,国内献论述较少。托马斯旋进实际上是由维格纳转动引起,本对维格纳转动进行讨论,并由此得出托马斯旋进。 相似文献
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Femtosecond laser-induced dissociation and Coulomb explosion of polyatomic molecule C_2H_6 were systematically investigated using a time-of-flight mass spectrometer and a chirped pulse amplifier laser. With the laser intensity varying from 2.4×10^{15}W/cm^{2} to 1.2×10^{16}W/cm^2, strong molecular ions C_2H_n^+ (n=0-6) and atomic ions C^{m+} (m=1-3) signals were observed. The double-peak structure of atomic ions indicated the occurrence of Coulomb explosion. Compared with the nearly isotropic distribution of C^{+}, highly charged ions C^{m+} (m=2-3) exhibited a sharply anisotropic angular distribution, which was attributed to the geometric alignment. 相似文献