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Early time electron-positron correlation in vacuum pair-production in an external field is investigated. The entangled electron and positron wave functions are obtained analytically in the configuration and momentum spaces. It is shown that, relative to that of the one-dimensional theory, two- and three-dimensional calculations yield enhanced spatial correlation and broadened momentum spectra. In fact, at early times the electron and positron almost coincide spatially. The correlation also depends on the direction of the applied field. For the spatial correlation, the transverse correlation is stronger than the longitudinal correlation. 相似文献
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Introduction N,N'-Bis[N-(2,2,2-trinitroethyl)-N-nitro]ethyenedi- amine (BTNEDA) is a typical nitramine compound, which is structurally shown in Figure 1. The crystal density is 1.87 gcm-3. The detonation velocity corresponding to r=1.842 gcm-3 is about 8970 ms-1.1 Therefore, BTNEDA is used as high explosive. Its thermogram has been reported.2 In this paper, its kinetic parameters of the exothermic decomposition reaction are described. This is quite useful in the evaluation of its ther… 相似文献
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The thermal behavior and kinetic parameters of the exothermic decomposition reaction of N-methyl-N-nitro-2,2,2-trinitroethanamine in a temperature-programmed mode have been investigated by means of differential scanning calorimetry (DSC).The kinetic equation of the exothermic decomposition process of the compound is proposed. The values of the apparent activation energy (Ea), pre-exponential factor (A), entropy of activation (ΔS^≠ ), enthalpy of activation (ΔH^≠ ), and free energy of activation (ΔG^≠ ) of this reaction and the critical temperature of thermal explosion of the compound are reported. Information is obtained on the mechanism of the initial stage of the thermal decomposition of the compound. 相似文献
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本文依据线弹性力学原理,用复变函数法求得在拉伸载荷下有限宽平板斜裂纹问题的K_Ⅰ和K_Ⅱ,并采用最大剪应变判据((d~2ε_θ)/(dθ~2)<0及(ε_θ)max与K_R相应),求得裂纹扩展角及当量Ⅰ型应力强度因子K_((?)q),再用能量准则求得失稳时的临界应力及裂纹容限.用此方法对几种初始角的几何斜裂纹有限宽平板的剩余强度作了计算,计算结果与有关文献中的数据和试验值相比,开裂角、临界应力及裂纹容限的误差均满足工程要求(2~7%).为进行二维薄壁结构的损伤容限设计,本文提供了剩余强度分析的工程方法及计算程序. 相似文献
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唐琐同学由一道关于抛物线的题,联想到椭圆和双曲线的相应问题,这种学习方法值得提倡.文中的性质不一定是新的,但唐琐同学经过研究把它发现出来是值得赞许的. 相似文献
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