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Collective diffusion in carbon nanotubes: Crossover between one dimension and three dimensions
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Using non-equilibrium molecular dynamics and Monte Carlo methods, we study the collective diffusion of helium in carbon nanotubes. The results show that the collective diffusion coefficient(CDC) increases with the dimension of the channel. The collective diffusion coefficient has a linear relationship with the temperature and the concentration. There exist a ballistic transport in short carbon nanotubes and a diffusive transport in long carbon nanotubes. Fick's law has an invalid region in the nanoscale channel. 相似文献
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从理论上研究了一个上臂与下臂各嵌有一个量子点的三终端三臂量子环中的自旋极化的电子输运性质.考虑了两个量子点中的库仑互作用并假设在某一个环臂中存在Rashba自旋轨道耦合作用.利用非平衡态格林函数方法,发现不需要借助任何磁场与磁性物质Rashba自旋轨道耦合作用导致的量子干涉效应就可以从器件中驱动出一个自旋流.适当调节外加偏压、Rashba自旋轨道耦合作用强度以及量子点能级等系统参数时器件中甚至还可以产生完全自旋极化电流或纯自旋流.另外,还讨论了系统参数对自旋流大小、符号、自旋极化度以及峰值的影响. 相似文献
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The electron transport through a Rashba ring with a magnetic flux and driven by a temperature difference is investigated. It is found that the spin interference effect induced by the Rashba spin-orbit interaction and by the magnetic flux can break the balance between the spin-up and spin-down component currents in the thermally driven charge current and thus result in a spin current. The analytical derivation and numerical calculations reveal that the magnitude, sign, peaks and spin-polarization of the generated spin current can be readily modulated by the system parameters. In particular, with some choices of the parameters, the spin polarization of the generated spin current can reach 100%, that is, a fully spin-polarized thermospin current can be produced. These results may help the use of the spin-dependent Seebeck effect to generate and manipulate a spin current. 相似文献
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作为孕育新闻的第一级土壤,市直部门、县(区)部门、乡镇党委政府等基层单位,应该运用好新闻媒体平台,做好新闻宣传工作,更好地展示成果、鼓舞士气、凝聚人心。文章结合实际,围绕做好基层新闻宣传工作的意义和内容,工作中存在的问题,以及如何创新基层新闻宣传工作展开论述,以期对做好基层新闻宣传工作有一定的指导作用。 相似文献
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