Dynamics of the normal–superconductor phase transition and the puzzle of the Meissner effect

The analysis of Pippard (1950) for the growth of the normal phase into the superconducting phase in the presence of a magnetic field H>H_c$H>H_c$ is applied in reverse to the case H<H_c$H<H_c$ (H_c=$H_c=$ critical magnetic field). We carry out the analysis both for a planar and a cylindrical geometry. As the superconducting phase grows into the normal phase, a supercurrent is generated at the superconductor–normal phase boundary that flows in direction opposite to the Faraday electric field resulting from the moving phase boundary. This supercurrent motion is in direction opposite to what is dictated by the Lorentz force on the current carriers, and in addition requires that mechanical momentum of opposite sign be transferred to the system as a whole to ensure momentum conservation. In the cylindrical geometry case, a macroscopic torque of unknown origin acts on the body as a whole as the magnetic field is expelled. We argue that the conventional BCS-London theory of superconductivity cannot explain these facts, and that as a consequence the Meissner effect remains unexplained within the conventional theory of superconductivity. We propose that the Meissner effect can only be understood by assuming that there is motion of charge in direction perpendicular to the normal–superconductor phase boundary and point out that the unconventional theory of hole superconductivity describes this physics.     

Flow characteristics in the downstream region of a conical diffuser

Using the Navier-Stokes equations in conjunction with the k-? model of turbulence, the characteristics of flow in the region downstream of a conical diffuser with 5° angle of inclination are calculated. Two representative stations 1D₂ and 10D₂ after the diffuser exit are selected for comparison against experimental results. The calculations indicate an underestimation of mean velocity and turbulence kinetic energy at the first station, while satisfactory agreement is obtained for the mean velocity at the second station. The use of a modified k-? model sensitive to adverse pressure conditions improves the predictions considerably. The effect of inlet properties and Reynolds number on the flow characteristics at the above stations is studied using various inlet profiles and a range of Reynolds numbers based on the inlet diameter from 50 000 to 280 000.     

基于分形博弈的动量和反转效应转换研究

动量和反转效应普遍存在于证券市场,且会相互转换,但两者间相互转换的特征却鲜有人知.在多数派和少数派博弈的基础上,首次引入分形市场理论对投资者决策特征进行描述,据此建立了分形博弈过程,以分析动量和反转效应转换的统计特征.研究结果表明:在三种博弈机制下,分形博弈机制下的仿真收益率序列的统计分形特征更为接近实际序列的对数收益率序列,且动量和反转效应的相互转换与真实情况也异常相似,这体现了采用分形博弈分析动量和反转效应转换的有效性,为投资者构建有效的动量或反转投资策略提供了决策参考.     

Interelectronic angle densities of atoms in momentum space

For the 102 atoms from He to Lr in their ground states, the Hartree–Fock interelectronic angle densities,¯A(¯₁₂), in momentum space are reported, where ¯₁₂ is the angle between the momentum vectorsp₁ and p₂ of two electrons. In the first three atoms, He–Be, ¯A(¯₁₂) is found to be uniform independent of ¯₁₂, while in the remaining 99 atoms,¯A(¯₁₂) is larger for a large ¯₁₂ than for a small ¯₁₂. Accordingly, the average interelectronic angles in momentum space are 90° precisely for the three atoms and greater than 90° for the 99 atoms.     

The dynamic properties of the two-level entangled atom in an optical field

The interaction of an optical field and one of the entangled atoms is analyzed in detail in this paper. Furthermore, the dynamic properties of the two-level entangled atom are manifested. The properties of the action are dependent on the initial state of the atom. After detecting the atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field influences the dynamic properties of the atom in the field.     

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利用静电探针阵列对HL-2A边缘等离子体径向和极向速度进行了测量,获得了最后闭合磁面附近湍流的雷诺协强〈(v)r(v)θ〉以及(v)r和(v)θ间相位差的剖面.实验表明,虽然(v)r、(v)θ的幅值对雷诺协强的大小会有影响,但雷诺协强的变化趋势主要取决于二者相位差的变化;另一方面,欧姆放电以及不同电子回旋加热功率L模放电条件下的实验结果显示,密度扰动引起的粒子输运所带来的极向动量输运的贡献与雷诺协强项对极向动量输运的贡献是可比的.这表明在分析湍流引起的动量输运时必须考虑粒子输运的贡献.     

从头计算研究超共轭效应对2-氯乙醇电子波函数的影响

运用从头算的B3LYP和MP2方法研究了2-氯乙醇分子五种构象的电子结构．在自然键轨道理论分析的基础上讨论了存在的分子内氢键和超共轭作用对构象稳定性的影响,结果说明后者是构象稳定性的主要因素．结合电子动量谱学研究了这种超共轭作用对最外价壳层轨道(HOMO)的电子波函数的影响,演示了动量空间HOMO波函数的不同．     

四种磁绝缘传输线的横向空间电荷流

根据电磁场基本理论及电子运动守恒方程,导出平板、圆柱、圆锥和圆盘这4种常用传输线的横向空间电荷流的数值模型和磁绝缘临界条件。通过数值模拟得到:传输线的电压越高,无磁场的横向空间电荷流越大,但是磁缘性能却越显著;若分别增大圆柱、圆锥的几何结构因子,既有助于减小它们的无磁场横向空间电荷流又有助于增强它们的磁绝缘性能;对于圆锥,若电极夹角较大,内电极的极角较小,则对减小无磁场空间电荷流和增强磁绝缘性也有一定好处。