似稳磁场激发的涡旋电场

根据Ｍａｘｗｅｌｌ电磁场理论建立似稳磁场激发电场满足的方程,给出该方程在无界空间的解,并论证似稳磁场的涡旋电场等于多极电砀的叠加。     

纳米带中涡旋畴壁在磁场驱动下的振荡行为

利用微磁学模拟软件(OOMMF),对坡莫合金纳米带中涡旋畴壁在略高于Walker极限的磁场驱动下的动力学行为进行模拟,分析外磁场强度、纳米带尺寸及自旋极化电流对畴壁振荡频率的影响。结果表明,纳米带中涡旋畴壁的振荡频率随外磁场强度的增大而增加,随着纳米带宽度的增加呈先增加后减小再增大最后基本保持不变的趋势;外加与磁场方向相反的平衡电流,虽然不改变畴壁振荡频率随外磁场强度和纳米带宽度的变化规律,但能起到减小畴壁振荡频率的作用,且平衡电流随外磁场强度和纳米带宽度的变化趋势与畴壁振荡频率基本相反,而其随着阻尼系数的增大而线性增加。     

层状超导体磁通格子固相熔化的温度效应

发展了层状超导体中3D磁通线模型,用动力学模拟方法数值研究了磁通格子的有序-无序熔化相变.在无序强度温度相图中,发现从有序的布拉格玻璃相到无序的磁通玻璃相之间的固-固相变线在中等温度区域有一个突起,与最近实验上得到的"反向熔化"现象一致.这一反向熔化行为起因于磁通之间相互作用的异常温度效应.     

起偏器参量对磁场传感器光偏振态的影响

为了研究磁场传感器中出射光偏振态,用Poincaré球法分析了磁场传感器起偏角对光偏振态的影响.结果表明:Faraday材料中线双折射率的存在,使线偏振光演进为椭圆偏振光.无论外加磁场及Faraday材料线双折射率如何变化,当起偏角为45°时,出射偏振光始终为左旋椭圆偏振光;当起偏角为135°时,出射偏振光始终为右旋椭圆偏振光.其结果对偏振型磁场传感器的信号检测设计有一定的参考价值.     

一个涡旋与变形场的相互作用指数

为了分析涡旋在变形场中的短期强度、移动路径和速度的变化,提出了一个涡旋与变形场的相互作用指数VDI(interaction index of vortex and deformation field),采用基于Lanczos窗口函数的数字滤波合成分析方法,分析了2001年8月5、6日造成上海特大暴雨的热带低压(TD)过...     

强激光场中涡旋电子的动力学过程

研究了携带固有轨道角动量的强涡旋电子在强激光中的动力学过程.利用相对论拉莫进动方程和自旋进动方程(T-BMT)方程,研究了涡旋电子的内禀轨道角动量和自旋角动量在啁啾激光场中的演化规律.由于啁啾激光脉冲的不对称性,初始静止的涡旋电子在啁啾脉冲的作用下获得了MeV的加速,并实现了自旋和固有轨道角动量的纵向旋转.因此,通过调控啁啾激光的啁啾参数可以获得具有任意角动量方向的相对论涡旋电子.此外,在FoldyWouthuysen表象中,强涡旋电子的运动受到类Stern-Gerlach力的显著影响,从而偏离散射平面.这一现象揭示了轨道角动量和电磁场的相互作用及其与电子动量之间的内在关联,并为控制相对论电子的运动提供了一种全新的手段.     

Quantum magnetic excitations from stripes in copper oxide superconductors

In the copper oxide parent compounds of the high-transition-temperature superconductors the valence electrons are localized--one per copper site--by strong intra-atomic Coulomb repulsion. A symptom of this localization is antiferromagnetism, where the spins of localized electrons alternate between up and down. Superconductivity appears when mobile 'holes' are doped into this insulating state, and it coexists with antiferromagnetic fluctuations. In one approach to describing the coexistence, the holes are believed to self-organize into 'stripes' that alternate with antiferromagnetic (insulating) regions within copper oxide planes, which would necessitate an unconventional mechanism of superconductivity. There is an apparent problem with this picture, however: measurements of magnetic excitations in superconducting YBa2Cu3O6+x near optimum doping are incompatible with the naive expectations for a material with stripes. Here we report neutron scattering measurements on stripe-ordered La1.875Ba0.125CuO4. We show that the measured excitations are, surprisingly, quite similar to those in YBa2Cu3O6+x (refs 9, 10) (that is, the predicted spectrum of magnetic excitations is wrong). We find instead that the observed spectrum can be understood within a stripe model by taking account of quantum excitations. Our results support the concept that stripe correlations are essential to high-transition-temperature superconductivity.     

A one-dimensional chain state of vortex matter.

Magnetic flux penetrates isotropic type II superconductors in flux-quantized vortices, which arrange themselves into a lattice structure that is independent of the direction of the applied field. In extremely anisotropic high-transition-temperature (high-Tc) superconductors, a lattice of stacks of circular 'pancake' vortices forms when a magnetic field is applied perpendicular to the copper oxide layers, while an orthogonal elongated lattice of elliptical Josephson vortices forms when the applied field is parallel to the layers. Here we report that when a tilted magnetic field is applied to single crystals of Bi2Sr2CaCu2O8+delta, these lattices can interact to form a new state of vortex matter in which all stacks of pancake vortices intersect the Josephson vortices. The sublattice of Josephson vortices can therefore be used to manipulate the sublattice of pancake vortices. This result explains the suppression of irreversible magnetization by in-plane fields as seen in Bi2Sr2CaCu2O8+delta crystals, a hitherto mysterious observation. The ability to manipulate sublattices could be important for flux-logic devices, where a 'bit' might be represented by a pancake vortex stack, and the problem of vortex positioning is overcome through sublattice interactions. This also enables the development of flux transducers and amplifiers, considerably broadening the scope for applications of anisotropic high-Tc superconductors.     

A multi-component Fermi surface in the vortex state of an underdoped high-Tc superconductor

To understand the origin of superconductivity, it is crucial to ascertain the nature and origin of the primary carriers available to participate in pairing. Recent quantum oscillation experiments on high-transition-temperature (high-T(c)) copper oxide superconductors have revealed the existence of a Fermi surface akin to that in normal metals, comprising fermionic carriers that undergo orbital quantization. The unexpectedly small size of the observed carrier pocket, however, leaves open a variety of possibilities for the existence or form of any underlying magnetic order, and its relation to d-wave superconductivity. Here we report experiments on quantum oscillations in the magnetization (the de Haas-van Alphen effect) in superconducting YBa(2)Cu(3)O(6.51) that reveal more than one carrier pocket. In particular, we find evidence for the existence of a much larger pocket of heavier mass carriers playing a thermodynamically dominant role in this hole-doped superconductor. Importantly, characteristics of the multiple pockets within this more complete Fermi surface impose constraints on the wavevector of any underlying order and the location of the carriers in momentum space. These constraints enable us to construct a possible density-wave model with spiral or related modulated magnetic order, consistent with experimental observations.     

基于磁定位技术的冲击侵彻尺度的测量

在小天体的探测任务中，探测器需要应对小行星表面特殊的风化层地貌环境。而人们目前对于风化层与探测器间的多尺度、强非线性的复杂动力学行为认知尚不充分，且对于撞击侵彻参数的测量缺乏合适的方法。为了掌握着陆过程中探测器的侵彻尺度关系，提出了一种实验室环境下基于磁偶极子模型的撞击动力学测量系统，通过迭代标定和GA-LM最优化算法提高了定位精度。将其应用于斜坡的撞击实验中，测量了撞击过程中撞击物2个方向的侵彻深度数据。结果表明：通过迭代标定算法和GA-LM算法平均提高了三轴31%的定位精度，使得最终的单轴定位误差小于3 mm；撞击斜坡过程中存在Y方向垂直穿透和Z方向横向滑动两种侵彻过程。Y方向的垂直穿透与下落高度符合1/3的幂律关系，而Z方向的滑动位移的标度规律并不稳定，原因是存在颗粒层崩塌的影响，并使得该位移与下落高度呈现非线性增加特征。     

The calculation of ground state energies of double-electron systems in an uniform magnetic field below 109 G

Energies for the ground states of double-electron systems in a uniform magnetic fieldB≤10⁹ G are calculated by using the modified Slater basis and configuration interaction method, and the result for energy in zero magnetic field is comparable with those obtained by different methods. Supported by the Opening Foundation of Wuhan Institute of Physics, Chinese Academy of Science Wu Liangkai: born in 1970, Graduate student     

永磁非金属液体电磁泵磁场数值分析

将电磁泵体求解场域按二维平面场处理,考虑了外磁场对永磁体的磁化效应,用有限元法对永磁非金属液体电磁泵的磁场进行了数值分析,得到了该电磁泵气隙中的磁密曲线以及载流海水在气隙中流动所受到的电磁力.实验证明该数值分析的结果是准确的,这些数据为永磁非金属液体电磁泵的设计和应用提供了可靠依据,同时也说明了可用永磁体代替价格昂贵的超导磁体应用于非金属液体电磁泵的磁极设计.图7,参7.     

驻涡燃烧室内涡系分布研究

为清晰了解驻涡燃烧室内流场的涡系分布,对中心驻体为67%燃烧室当量宽度的驻涡燃烧室流场,在驻涡腔无喷射和有喷射两种状况下分别进行冷态数值模拟,详细研究流场内旋涡分布情况.结果表明:流道前部存在4个影响很小、沿流动方向运动、分布于驻体与端壁角区的螺旋状旋涡;流道后部存在1个由2个旋涡构成、面积较大的回流区;流道中部的驻涡区旋涡情况复杂,在驻涡腔无喷射情况下,主流与驻涡区之间悬挂驻留2个稳定的驻涡,驻涡腔内存在不稳定且数目不确定的旋涡;当驻涡腔前驻体有喷射存在时,驻涡腔内形成4个均匀且稳定的旋涡.     

磁传感器在航海上的应用

针对磁传感器技术发展中存在的问题,论述了霍尔罗经、磁通门罗经、磁阻罗经和巨磁电阻罗经的基本原理、工作特点及其在航海上的应用.并基于巨磁电阻传感器工作原理,结合微处理机技术,研制了可在船上应用的巨磁电阻罗经,在航海上有广阔的应用前景.     

旋风分离器排气管内气相流场的数值模拟

采用雷诺应力模型对直切式旋风分离器内气相流动的三维流场进行数值模拟,分析了排气管内的气相流场特点及排气管直径对气相流场的影响.结果表明:排气管内气流旋转强度较高,轴向速度呈强剪切流特征,并且存在回流区,这些都是造成能量损失的重要原因;减小排气管直径可以抑制短路流量,使旋风分离器整个空间内的切向速度增大,有利于颗粒分离,但同时压降增大.     

随时间演化的磁场中电子性质的研究

电子在随时间演化的磁场中的运动,其相位的变化是众所周知的.在此运用二能级系统幺正演化算符的方法,求解几种较为典型特例的严格解,分析其相位的变化.通过含时Schrodinger方程解得动力学相位,就可以得到A-A相,再与Berry相位进行比较.     

利用FEMLAB模拟微电磁石的磁场区域

利用FEMLAB软件模拟出在2D和3D的情况下微电磁石的电磁感应对磁场强度的影响.因为在3D界面下不能完全将实际模型重建,采用缩小实体的方法,将缩小后的模型在2D环境下模拟,可以显示出与大空间范围构造相似的仿真结果.3D仿真结果显示的大体结构及空间范围的情况与2D仿真结果大致相同,且3D仿真结果的误差在正常情况下至少为10%,因此3D与2D仿真环境下的磁体结构是可以比较的.     

磁荷的多极辐射场强和能流密度

在Dirac磁单极存在的情况下,考虑保持Maxwell方程双矢势下的电磁对偶性。利用有磁荷存在的d′Alembert方程推迟解,求出了带磁荷粒子的电磁辐射的表达式。最后得到磁多极辐射表达式。     

外磁场下自旋系统的平移算子

利用Y（SL（2））的自旋－1／2实现，给出在外磁场情况下两自旋耦合系统的Berry拓扑相因子态之间与核磁共振态之间新的平移算子，它们超出原有李代数的范围，描述了在任意时刻量子态之间新的跃迁。     

四态叠加多模叠加态光场中广义磁场的N次方H压缩

构造了由多模偶相干态与多模虚偶相干态线性叠加组成的一种新型四态叠加多模叠加态光场Ψ(4)e,Ⅲ〉q中广e,Ⅲ〉q,利用多模压缩态理论,研究了态Ψ(4)义磁场分量的等幂次N次方H压缩特性.结果表明,当腔模总数q与压缩次数N的乘积qN=4m(m=1,2,3,…)时,态Ψ(4)e,Ⅲ〉q的广义磁场分量可恒处于等幂次N H最小测不准态;当qN=4m′ 2(m′=0,1,2,3,…)时,若态间的初始相位差(θ1-θ2)、各模初始相位和∑qR2j分别满足一定取值φj及各模平均光子数之和∑qj=1j=1条件,态Ψ(4)e,Ⅲ〉q的广义磁场分量可呈现周期性等幂次N次方H压缩效应.