Massless and quantized modes of kinks in the phase space of superconducting gaps

We investigated quantized modes of kinks in the phase space of superconducting gaps in a superconductor with multiple gaps. The kink is described by the sine-Gordon model in a two-gap superconductor and by the double sine-Gordon model in a three-gap superconductor. A fractional-flux vortex exists at the edge of the kink, and a fractional-flux vortex will be stable in a three-gap superconductor with time-reversal symmetry breaking. The kink and fractional-flux vortex exhibit massless modes as a sliding motion. We show further that there are one zero-energy mode (massless mode) and quantized excitation modes in kinks, which are characteristic features of multi-gap superconductors. The equation of quantized modes for the double sine-Gordon model is solved numerically. The correction to the ground-state energy is calculated based on the renormalization theory.     

Evolution of three-dimensional coherent structures in compressible axisymmetric jet

A high order difference scheme is used to simulate the spatially developing compressible axisymmetric jet. The results show that the Kelvin-Helmholtz instability appears first when the jet loses its stability, and then with development of jet the increase in nonlinear effects leads to the secondary instability and the formation of the streamwise vortices. The evolution of the three-dimensional coherent structure is presented. The computed results verify that in axisymmetric jet the secondary instability and formation of the streamwise vortices are the important physical mechanism of enhancing the flow mixing and transition occurring.     

Quasi-particle excitations around a pair of half-quantum vortices in p- wave superconductors

Triplet superconductors such as Sr₂RuO₄ and Na_xCoO₂⋅yH₂O are now found to be p-wave (p_x ± ip_y) or f-wave ((p_x ± ip_y) cos cp_z) superconductors. It was phenomenologically suggested that in these p-wave or f-wave superconductors, a pair of half-quantum vortices (HQVs) becomes stable. Using the Bogoliubov-de Gennes equation, previously we have analyzed quasi-particle excitations around an HQV at one end of a d-soliton for simplicity. In next study, we will investigate the stability of the pair of HQV’s, which are connected by the d-soliton. For this purpose, we have developed a new numerical method to solve the Bogoliubov-de Gennes equation for two vortices state, using Mathieu functions.     

隔离板对流向振荡圆柱尾流旋涡脱落的抑制

用隔离板对直径为D, 沿流向振荡的圆柱后涡脱落进行抑制. 隔离板放于圆柱尾流中心线上,控制参数包括隔离板长度L/D以及隔离板前缘到柱体振荡中心的距离G/D. 实验的雷诺数范围Re=V_∞D/v=1.01×10⁴～1.69×10⁴,柱体折减振频范围f_eD/V_∞=0～0.03, 柱体振幅固定为A/D=0.2. 风洞烟线显示和热线测量结果表明:当 G/D位于一个有效区域内时,可有效抑制振荡柱体尾流的旋涡脱落. 该有效区的大小随着隔离板板长的增大而增大, 随着Re数和圆柱振荡频率的增大而减小.     

Reynolds数对大攻角细长旋成体绕流滚转角效应影响的数值研究

使用低耗散的Roe格式,数值模拟了Reynolds数(Re)对大攻角细长旋成体绕流滚转角效应的影响.模型头部加了几何小扰动块以引发流场的不对称.在较大的Re数(Re=10 5)下,本文的计算结果与实验是相符的,此时细长体的滚转会导致双稳态、双周期现象,即侧向力随滚转角呈现类似方波形式的双周期变化,方波中侧向力基本保持不变的状态对应于流场的正则态,且两个正则态的侧向力方向相反,方波中侧向力基本保持不变的状态对应于流场的正则态,且两个正则态的侧向力方向相反;而在较小的Re数(Re=4 000)下,如果扰动足够大,细长体的滚转将导致不同的双稳态现象,此时两个正则态的侧向力方向相同,而在较小扰动下双稳态现象不再出现;Re数更小时(Re=1 000),即使在较大的扰动下,双稳态现象也不再出现,侧向力随滚动角仍是连续变化的.本文的计算结果表明,Re数越小,流场对头部扰动的感受性越弱.     

60°三角翼前缘涡破裂及其控制实验研究

本文应用流动显示技术对矢量差动喷流情况下60°三角翼前缘涡破裂特性进行了实验研究,结果表明:矢量差动喷流可以有效地控制前缘涡的破裂位置,且整个流场主要受喷流速度大的喷流的影响,该侧前缘涡的破裂位置随喷流速度的增大向下游发展,而另一侧前缘涡的破裂则提前发生;另外,在喷流速度差一定的情况下,喷流速度越小,对前缘涡的控制作用越明显.     

高温超导体磁通动力学和混合态相图(Ⅰ)

文章简要介绍了高温超导体磁通动力学和混合态物理在过去十余年的发展.高温超导体由于其自身的一些特点,使得它与常规超导体相比较拥有极其丰富的相图,磁通动力学也表现出了非常丰富的研究内容,很多新的概念被提出,新的现象被观察到.比如说涡旋玻璃态,集体钉扎和蠕动,磁通格子的一级和二级熔化相变,布拉格玻璃,峰值效应,二维涡旋饼态,Josephson 磁通运动等等,均是在高温超导体发现之后提出来的新的概念或新发现的现象.有些研究结果目前尚无定论,如关于涡旋玻璃态存在与否的争论至今仍然在进行,但是这些研究内容无疑会大大促进超导物理的发展.高温超导体磁通动力学纷繁复杂的研究内容可以归结为三个相互关联的数字：Ginzburg数(Tc/H2cεζ3)2/2,量子电阻Qu=(e2/)(ρn/εζ),和临界电流的比值jc/j0,这里ζ是相干长度,Hc是热力学临界磁场,ε是有效质量的各向异性度,ρn是正常态电阻率,jc是零温临界电流,j0是拆对临界电流.对于高温超导体前两个数值（Ginzburg数和量子电阻）很大,而临界电流比值较小,因此导致有强的热涨落和量子涨落,以及很强的磁通运动行为（对应小的实测临界电流）.磁通动力学的研究从更深层次影响超导体的临界电流问题和强电应用的发展,最后简要地介绍了这方面的情况     

第三讲 非线性原子光学

随着玻色-爱因斯坦凝聚（BEC）的实现及其非线性效应研究的快速发展,原子光学的一门新兴分支学科——“非线性原子光学”已初步形成,并取得了一系列重大的实验进展.文章重点介绍了非线性原子光学的研究内容、实验结果及其最新进展,主要包括原子孤子、原子物质波中的四波混频、光速减慢与负群速现象、超流及涡流（vortex）、Josephson效应和物质波的相位相干放大等.     

非正则光涡旋通过倾斜透镜的动态传输

基于广义惠更斯-菲涅尔衍射积分公式,研究了寄居于高斯光束背景下含有相位拓扑荷（拓扑电荷）     

气液两相涡街稳定性的研究

通过气液两相涡街试验研究和理论分析,首次得出了当有稳定的气液两相涡街发生时,气液两相涡街结构参数的取值及变化规律