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In order to clarify the validity of the theory of nuclearβ-transition a new formulation is given. The nuclear properties are contained in form factors, arising from a decomposition of the matrix element of the V-A operator for nuclear states. The connection of these form factors with nuclear physics matrix elements is tabulated. The total transition amplitude can be written as an integral over these form factors folded with off-shell amplitudes for elastic and inelastic electron scattering on nuclei.  相似文献   

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Elastic “hard” fibers may be prepared from a number of semicrystalline polymers, notably polypropylene, poly-3-methylbutene-1, and polyoxymethylene. These materials show typically a high degree of length recovery from large extensions, a marked, more-or-less recoverable reduction of apparent density on stretching, and the generation of very large amounts of accessible volume and surface area on stretching. Wide- and low-angle X-ray and electron-microscopic observations indicate that the morphological basis for these properties lies in an array of closely packed lamellae of which the normals lie predominantly parallel to the fiber extrusion direction. It is the tilting and splaying apart of the lamellar network which creates the internal volume and surface area on stretching. The long-range elasticity is believed to be distinctly nonrubberlike, as reflected in an insensitivity of mechanical properties to low temperatures, and to arise from bending of the lamellae. This unusual class of materials provides a significant link between macroscopic properties and a particular morphological structure.  相似文献   

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乔夫雷·殷格拉姆·泰勒(Geoffrey In-gram Taylor)爵士是本世纪物理学大师之一.他一直从事研究流体力学和固体力学及其在航空学、化学工程、气象学、机械工程、金属物理学和海洋学方面的应用.他的研究方式与众不同,他能透彻地认识自己所考虑到的问题的本质.他常常能设计一些简单但是很实用的实验仪器,并用这些仪器检验和证实他的理论概念.泰勒生于1886年3月7日,在最近召开的庆祝他百岁诞辰的大会(1986年3月24日—28日)上,有人提出了他的工作风格对当代研究工作者是否仍然适用和有价值的问题. 泰勒很喜欢自己独立从事工作,尽量不求助于他…  相似文献   

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<正>These two volumes can really be recommended to anyone interested in vibro-acoustics or the field of sound and vibration.The two volumes include 16 chapters and some 890 pages.The work is the result of cooperation between the Key Laboratory of Acoustics,The Chinese Academy of Sciences and The Royal Institute of Technology,KTH.The topic describes how structures are excited,energy flows from an excitation point to a sound radiating surface,and  相似文献   

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significance of non-linear acoustics in aerial sound isdiscussed.In this instalment,basic theory and effects of high-intensitysound are reviewed,interesting points are stressed and further investiga-tions are suggested.  相似文献   

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