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相对论性粒子螺旋度守恒与能量-动量张量的对称性无关 总被引:1,自引:1,他引:1
在相对论性量子体系中轨道角动量和自旋不能分别守恒,无论能量-动量张量算符是否对称,守恒的只是总角动量。 相似文献
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上海游泳馆大跨度屋盖采用变高度空间网架结构.由于该网架体型特殊,边界条件较复杂,除采用SPS-402程序在TQ-16机上计算外,又采用国际上普遍承认的SAP5结构分析通用程序在ACOS-300机上复算、校核.最后与模型试验结果比较表明,SAP5程序的计算获得了理想的效果.本文简要地介绍SAP5程序在计算中的有关情况. 相似文献
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An investigation on the average number v of prompt neutrons emitted per thermal neutron induced fission of U235 has been made with the Fermi gas statistical model. Weizsacker-Fermi semi-empirical mass equation has been used in calculating the neutron binding energies of the fission fragments. Using Stern's value for the mass of U235, the total excitation energy Ee of the fission fragments has been estimated to be of the order of 10 to 20 Mev for different hypotheses regarding the primary fission products. The results of calculation (given in the third table) show that only the hypothesis of equal radioactive chain lengths together with the assumption (A) that the excitation energy Ee is shared by the two fragments in proportion to their masses yields values of v exceeding 2. The latter assumption is not in accord with the experimental finding of Fraser that the light fragment group emits on the average 30% more neutrons than does the heavy. However, a shift of mass of U235 towards larger values or of kinetic energy of fission fragments towards lower values so that 5 Mev more excitation energy is available would make v considerably larger than 2 even with the assumption (B) that the excitation energy is shared by the two fragments in inverse proportion to their masses, thus making possible conformity with Fraser's discovery. Even then, in no case has the value of v thus calculated exceeded 3 (as shown in the fourth table), which may then be taken as a theoretical upper bound for the value of ν for thermal neutron induced fission of U235. The results of this investigation are thus seen to be in harmony with the recently announced experimental value 2.5 ±0.1 for ν. 相似文献
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1976年秋,文化大革命结束,理科大批判组撤销.1975至1985年我被选为上海市物理学会理事长;其后被选为其名誉理事长.由于逐渐对外开放,我受命多次接待科学界上层外宾(包括杨振宁、李政道),并在市内主持其学术报告.在担任上海市物理学会理事长期间,我积极支持组织“近代物理讨论班”,主持一系列关于粒子理论的讲座,后来不少活跃在粒子物理领域的研究人员就是听了这些讲座产生兴趣的.1978年我应《自然杂志》要求撰写了《蓬勃发展的现代物理学》长篇文章,在其5月创刊号发表.1978年底我还应上海科学技术出版社的要求,撰写了《高能粒子物理学漫谈》一书,1979年11月出版. 相似文献
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用0.2%硫酸锌糖浆和葡萄糖酸锌合剂治疗缺锌患儿46例,观察治疗前后发中元素含量的改变,服药后发锌含量明显增加,铁、铜、铅含量明显减少,钙含量无变化,说明元素间存在拮抗作用,提示给患儿补锌要谨慎,必须严格掌握适应症、剂量、疗程、方法等。千万不能把锌剂当做营养药给儿童长期服用,以免导致体内元素平衡失调,造成不良后果。 相似文献
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国内外主要围岩分类换算原则和方法 总被引:1,自引:0,他引:1
本文阐述围岩分类的意义,分类换算的提出、基础、原则、方法和工程实例。为便于工程应用,将换算对照结果,经综合分析以换算对照汇总表形式给出。 相似文献