两类电场和两类磁场

通常意义上的电流激发磁场和变化的电场激发磁场,本质上都是运动电荷产生磁场。变化的感生电场激发的磁场则属另一类磁场,这样界定两类磁场才比较妥当。     

非对称勾形磁场的三维优化设计与实现

根据坩埚内熔体对流的类型和分布区域,分析控制对流对勾形(cusp)磁场磁感应强度和磁场位形分布的要求,提出了磁场优化设计目标。采用有限元三维(3D)建模法对cusp磁场进行了建模,利用所建立的模型对比了对称结构和非对称结构对磁场位形分布的影响,分析了在非对称cusp磁场线圈横向层数一定的情况下磁场纵向层数、屏蔽体厚度、上下线圈间距对磁感应强度、磁场位形、磁场功率的影响,优化了磁场结构;根据优化的结构参数制造了磁场并进行了实验测试,结果表明非对称cusp磁场的位形分布与设计结果一致,从而验证了3D优化建模方法的有效性。     

格子Boltzmann方法模拟磁场作用下的融化传热过程

采用格子Boltzmann方法对磁场作用下方腔内相变材料的融化传热及液相流体流动过程进行数值模拟,重点分析磁场倾角对融化相变传热过程的影响,为实现相变传热的主动控制技术提供参考.研究表明磁场可以控制融化相变传热过程,当磁场倾角大于180°时,磁场加速度方向指向热壁面方向,磁场强化换热,热壁面平均Nu_h数增加,融化速率加快;当磁场倾角小于90°、磁场加速度方向指向冷壁面侧时,磁场弱化换热,热壁面平均Nu_h数下降,融化速率降低;磁场倾角为231°时,磁场强化传热效果最佳.     

永磁体作用下电阻点焊熔核中的电磁场分布规律

采用数值模拟方法研究了外加永磁体磁场作用下,电阻点焊熔核内的外部磁场、感应磁场及复合磁场强度及其磁场力的分布规律,并对熔化金属的流体流动模式进行了定性分析.结果表明,在外加磁场作用下,点焊熔核内的复合磁场分布以感应磁场为主导,从熔核中心至边缘逐渐增强,其径向磁感应强度分量随着永磁体工作距离增加而逐渐减小.熔核内同时存在由感应磁场生成的位于电极轴对称平面内的磁场力,以及由外加磁场引起的垂直于该平面的磁场力.在该正交磁场力的作用下,熔核内的熔化金属在电极轴对称平面及垂直于该平面的圆周方向同时进行高速流动,并呈现出沿熔核直径方向向外冲击的趋势.     

带电粒子在喇叭形磁场中的运动分析

将带电粒子在非均匀磁场中的运动看成是在均匀磁场中的回旋。进而描述磁场的非均匀性,具体的分析了仅有散度项、曲率项、梯度项不等于零的磁场。介绍一种常见的喇叭形非均匀磁场,讨论了带电粒子在喇叭形磁场中的螺旋轨道半径、纵向速度分量以及运动的角度与磁场的关系和磁约束原理。目的是加深带电粒子在非均匀磁场中运动的理解。     

舰船平面磁场的边界矢量积分延拓方法

根据矢量格林恒等式,得到了大平面边界上各点磁场的矢量积分关系,进而找到了大平面内测量磁场和未知磁场的积分关系,通过边界剖分离散化形成线性方程组,求解得到未知磁场,达到磁场延拓的目的.延拓得到的大平面磁场能够提高远场磁场的计算精度.实验算例证明了该延拓方法的有效性,表明利用该方法能够较准确地由小范围测量磁场延拓得到大平面...     

基于条件生成对抗网络的涡流磁场深度换算

为提高舰船磁隐身能力,对舰船涡流磁场的深度换算进行研究,以满足消磁勤务的要求.首先,采用COMSOL仿真软件,使用有限元法进行铜板涡流磁场建模,通过外加磁场的改变模拟产生的两个深度涡流磁场,建立涡流磁场数据库;然后,在此基础上使用条件生成对抗神经网络(CGAN)对涡流磁场数据进行训练和学习,建立不同深度的涡流磁场推算模型.得到的模型对涡流磁场的推算准确度较高,训练结果较好,对实际的涡流磁场研究有指导意义.     

考虑螺距时有限长超导螺线管电流磁场的分布

应用数值模拟方法 ,分析了疏松型超导螺线管电流轴线外的磁场与螺距、长宽比、管内位置的变化关系 .计算结果表明 ,当螺距较大时 ,其磁场分布与密绕螺线管电流的磁场 (均匀磁场 )分布相差很大 ,磁场在空间各个方向都有分量 ,螺距越大 ,长宽比越小 ,垂直于轴线方向的磁场分量越大 ;但当螺距较小 ,长宽比较大或距螺线管中心较近处 ,磁场几乎与密绕螺线管电流产生的磁场相当 ,可用密绕螺线管电流轴线上磁场的简单公式来近似     

密绕椭圆截面螺线管轴线上的磁场

应用数值模拟方法,求解密绕椭圆截面螺线管轴线上的磁场,并分析了磁场与长短轴、管内轴线上位置的关系.计算结果表明,其磁场分布与密绕圆截面螺线管电流的磁场分布相差很大,磁场在空间各个方向都有分量,长宽比越小,垂直于轴线方向的磁场分量越大;长宽比较大或距螺线管中心较近处,磁场几乎与密绕圆截面螺线管电流产生的磁场相当,可用密绕圆截面螺线管电流轴线上磁场的简单公式来近似.     

矩形平面直流磁控溅射装置工作区域磁场分析

通过分析磁场对磁控溅射过程的影响,总结出了矩形平面直流磁控溅射装置工作区域磁场的设计原则,并给出了两种磁体结构.采用有限元方法对一套装置的磁场进行了计算,磁场计算结果与测量值吻合较好.基于上述分析计算,研究了磁场分布对靶材刻蚀形貌的影响,并进一步提出了具体的磁场改进措施.采用分流条垫补方法可以改进磁场分布,如果磁场水平分量呈马鞍形分布,靶材的利用率可以提高,采用磁极斜面结构对磁场分布的改进意义不大.另外,错开磁体间安装接缝和对永磁体精确充磁能够有效提高工作区域磁场分布的均匀性.     

各向异性Ginzburg-Landau超导模型整体极小元的注记

研究当磁场$h_{ex}$小于第一临界磁场$H_{C_{1}}$时,各向异性Ginzburg-Landau超导模型整体极小元的存在性了;找到了存在无涡漩的整体极小元;当$H_{c_{1}}h_{ex}H_{c_{2}}$时,证明了涡漩的密度等于外加磁场.     

Ginzburg-Landau涡漩的运动与曲率流(I)：2维问题

本文讨论与超导相关的各向导性Ginzburg-Landau涡漩的动力学规律。证明了在2维情形,涡漩的运动服从一个常微分方程组。     

色味连锁夸克物质中非阿贝尔涡旋磁效应的新进展

最近的研究表明强磁场对强相互作用物质,特别是稠密夸克物质的色味连锁相,会产生非常重要的影响.稠密夸克物质提供诸如涡旋,畴壁,单极子,扭结,布胶(boojum)等各种拓扑孤立子,因此可以预期强磁场也应该会影响这些孤立子.在这篇小综述中,介绍了在色味连锁夸克物质磁场效应研究的最新进展, 特别是特定条件下最基础的类弦拓扑激发非阿贝尔涡旋.在金兹堡-朗道框架下研究了它们的相关性质(如轮廓函数和张力能)以及磁场依赖性.     

The existence of global solution and their weak limit of generalized Ginzburg-Landau equations in two dimensions

By the uniform a priori estimate of solution about parameters, we prove the existence of global solution and inviscid limit to a generalized Ginzburg-Landau equations in two dimensions. We also prove that the solution to the Ginzburg-Landau equations converges to the weak solution to the derivative nonlinear Schrödinger equations.     

On the Cauchy problem of generalized complex Ginzburg-Landau equation in three dimensions

The generlized complex Ginzburg-Landau equation (CGL) under periodic boundary condition is studied. The existence of global solution for this equation is established under appropriate assumption on a nonlinear σ, which rigorously establishes the foundation for further investigation of this type of model.     

Mesoscopic superconductor as a ballistic quantum switch.

Several key experiments have revealed a rich variety of vortex structures in mesoscopic superconductors in which only a few quanta of magnetic flux are trapped: these structures are polygon-like vortex 'molecules' and multi-quanta giant vortices. Ginzburg-Landau calculations confirmed second-order phase transitions between the giant vortex states and stable molecule-like configurations. Here we study theoretically the electronic structure and the related phase-coherent transport properties of such mesoscopic superconductor systems. The quasiparticle excitations in the vortices form coherent quantum-mechanical states that offer the possibility of controlling the phase-coherent transport through the sample by changing the number of trapped flux quanta and their configuration. The sample conductance measured in the direction of the applied magnetic field is determined by the transparency of multi-vortex configurations, which form a set of quantum channels. The transmission coefficient for each channel is controlled by multiple Andreev reflections within the vortex cores and at the sample edge. These interference phenomena result in a stepwise behaviour of the conductance as a function of the applied magnetic field, and we propose to exploit this effect to realize a vortex-based quantum switch where the magnetic field plays the role of the gate voltage.     

非线性耦合Ginzburg-Landau方程组的整体吸引子

为研究系数与时间有关的一维非线性耦合Ginzburg-Landau方程组在周期边界条件下整体吸引子的存在性,采用经典的Galerkin逼近方法,得到了方程组在周期边界条件下整体解的存在性及唯一性,再利用能量方法,证明了整体吸引子的存在性.     

Global existence theory for the two-dimensional derivative Ginzburg-Landau equation

The generalized derivative Ginzburg-Landau equation in two spatial dimensions is discussed. The existence and uniqueness of global solution arc obtained by Galerkin method and bya priori estimates on the solution inH ¹-norm andH ²-norm.     

带时滞复金兹堡-朗道方程常数平衡解的渐近性态

讨论了具有时滞的复金兹堡-朗道方程的渐进性态.当参数满足一定的条件时,得到了复金兹堡-朗道方程具有第一边界条件时零解的线性和非线性稳定性及不稳定性;当参数和时滞满足一定的条件时,得到了复金兹堡-朗道方程具有第二边界条件时常数平衡解的线性化方程的渐进性态.     

Prediction of a global climate change on Jupiter

Jupiter's atmosphere, as observed in the 1979 Voyager space craft images, is characterized by 12 zonal jet streams and about 80 vortices, the largest of which are the Great Red Spot and three White Ovals that had formed in the 1930s. The Great Red Spot has been observed continuously since 1665 and, given the dynamical similarities between the Great Red Spot and the White Ovals, the disappearance of two White Ovals in 1997-2000 was unexpected. Their longevity and sudden demise has been explained however, by the trapping of anticyclonic vortices in the troughs of Rossby waves, forcing them to merge. Here I propose that the disappearance of the White Ovals was not an isolated event, but part of a recurring climate cycle which will cause most of Jupiter's vortices to disappear within the next decade. In my numerical simulations, the loss of the vortices results in a global temperature change of about 10 K, which destabilizes the atmosphere and thereby leads to the formation of new vortices. After formation, the large vortices are eroded by turbulence over a time of approximately 60 years--consistent with observations of the White Ovals-until they disappear and the cycle begins again.