用级数拟合求圆电流磁场解析解

采用将圆电流磁矢势表达式中一部分展成分数，使被积函数变成可积分的函数，用解析函数拟合积分的级数，代替无穷级数求和运算，得到可以计算圆电流在空间任保一点磁场的解析解，解决了计算非近轴区圆电流磁场问题。     

载流二次曲线磁场

在研究稳恒电流的磁场时,一般所碰到的是其电流分布为直线和圆,实际上载流线为二次曲线型也是一种典型的电流分布。在极坐标系下二次曲线具有统一的方程形式,采用新的分解方法求得空间磁场分布的统一表达式,并利用计算机数值方法描绘出二次曲线的空间磁场分布情况。     

圆电流在圆心附近的磁场

圆电流在圆心附近的磁场林敬与（北京航空航天大学数理系北京１０００８３）圆电流是电磁理论中的一个重要模型，它的磁场分布可以在许多有关的书籍中找到．通常求解磁场分布的解析式，总是先求出磁矢势人然后导出磁场Ｂ（或Ｈ）．一个半径为ａ、电流强度为Ｉ的圆电流，置...     

用毕－萨定律计算圆平行板电容器极板上电流的磁场

用毕－萨定律计算了分布在圆平行板电容器极板上电流的磁场,从而证实了：１）在似稳条件下磁场完全是由传导电流产生的,“位移电流”的磁场为零;２）极板电流在电路容器内部产生的磁场很大,它极大地的削弱了馈线电流的磁场,使得电容器内部的磁场很小．     

载流二次曲线焦点的磁场

在研究稳恒电流的磁场时,我们通常所碰到的是其电流分布为直线和圆,或者是二者的组合,很少接触到其它类型的电流分布.实际上载流线为二次曲线型也是一种典型的电流分布.当然要求出其在空间任意点的磁场分布,同求圆电流的任意点磁场分布一样,要牵涉到较深的数学知识.但是对其中的一些特殊点,如焦点的磁场,只要采取适当的方法,可以求得简单结果. 我们知道在直角坐标系下抛物线,椭圆,双曲线的标准方程分别为:其中p是抛物线焦点到准线的距离.a,b对于椭圆即为长、短半轴;对于双曲线即为实、虚半轴.现在我们以抛物线为例来研究真空中载流二次曲线…     

平面线电流的磁场

一、引言众所周知,关于平面线电流的磁场,通常用初等函数表示的有:1.直线电流外空间的任意点,2.圆电流轴线上的任意点,3.圆锥曲线电流的焦点.线电流的形状对场点的对称性越差的,其磁     

用毕—萨定律计算圆平行板电容器极板上电流的磁场

用毕－萨定律计算了分布在圆平行板电容器极板上电流的磁场，从而证实：１）在似稳定下磁场完全是由传导电流产生的，“位移电流”的磁场为零；２）极板电流在电路容器内部产生的磁场很大，它极大地削弱了馈线电流的磁场，使得电容器内部的磁场很小。     

圆形载流导线空间非近轴磁场分布解析解

在物理学实验研究及功能材料科研领域,分析感应电炉特性、电磁悬浮冶炼、区熔提纯熔点高、活性强、易与坩埚起反应的稀土材料的稳定性,圆形载流导线空间磁场的计算与分析有重要的实际意义.在电磁学及电动力学中讨论圆形载流导体产生的磁场时,通常只给出圆电流中心或轴线上的磁感强度[1,2].对非近轴磁场的计算相对繁难,需要借助圆电流轴外场涉及椭圆积分等较复杂的数学计算,难以得到较准确的解析解.     

用磁介质磁化理论的磁荷观点求解静磁场 兼谈无限大圆平面稳恒发散电流磁场求解的一种新方法

利用磁介质磁化理论的磁荷观点对一种静磁场非常方便而又简单地进行了求解,进而求出了该静磁场的磁化电流分布,在此基础上求出了一种特殊的磁化电流分布——无限大圆平面稳恒发散电流的磁场.还通过对以上这些问题的分析论述,指出了一种求解稳恒电流磁场的新方法途径.     

圆形电流磁场的级数解

给出了圆电流磁场的级数解，讨论了解的收敛性     

Calibration parameters for the probing tip of a magnetic force microscope in the field of a test current loop

The subject of discussion is calibration of the tip of a magnetic force microscope using the field of a ring-shaped current loop. To calculate the calibration parameters, the magnetic contribution from the extended tip of the probe in the field of the current loop to the rigidity of the cantilever is approximated by the contribution from a point magnetic dipole and magnetic “charge” in terms of the theoretical model adopted. Three simplified models of the conic tip (with a sharpened, blunted, and rounded top) are considered. The calculated dependences of the effective calibration parameters on the radius of the current loop are compared with experimental data. It is found that the model of a uniformly magnetized tip in the form of a blunted cone provides the best fit to the experiment. The calculation results may be helpful in simulating images obtained with a magnetic force microscope and numerically testing magnetic objects.     

Formation and dynamics of a virtual cathode in a tubular electron beam placed in a magnetic field

Mechanisms underlying the formation and dynamics of a virtual cathode (VC) in a tubular electron beam subjected to a magnetic field are studied using a numerical 2D model. Two qualitatively different competing types of space charge dynamics near the VC are discovered. Which of them predominates depends on the magnetic field strength. The beam current critical density at which a nonstationary VC forms in the system is also strongly dependent on the magnetic field. It is shown that the optimal strength of the magnetic field that minimizes the beam current critical density depends on the Brillouin magnetic field.     

计算圆电流磁场的一个方法

通过矢量积分变换计算圆电流的磁场分布.     

液态锂综合实验平台中液态锂流面与氩等离子体相互作用

介绍了由锂回路、直线等离子体装置及液态锂净化系统等组成的液态锂综合实验回路平台。研究了液态锂与高密度等离子体相互作用、液态锂与结构材料相容性、液态锂净化和液态锂回路热工水力学参数测量等问题。实验结果表明,流动液态锂的蒸发速率与放电电流、氩气流量及磁场强度呈正相关关系。由流动液态锂产生的锂蒸气在轴向分布不具规律性,在径向分布呈高斯分布。流动液态锂的蒸发速率随着实验时间的增长逐渐升高,并趋于稳定。磁场抑制了液态锂的流动性。在磁场和等离子体长时间的作用下,流动液态锂表面生成一层很薄的氧化锂。     

Analysis of the diamagnetic effect in multipole Galatea traps

The toroidal current emerging after the injection of a plasmoid through the magnetic shell of the Trimyx-3M (microwave) multipole trap is measured using the Rogowski loop. This current is due to diamagnetism of the plasma. The relation between the diamagnetic current and the maximal plasma pressure produced at the magnetic field separatrix is obtained. It is shown hence that magnetic measurements in a multi-pole trap for a known concentration make it possible to determine the plasma temperature in the trap and the energy confinement time.     

矢算变换在重矢积和重矢混合积积分中的应用

应用重矢积的矢算变换计算稳恒磁场中载流导线回路的磁力和导线回路定轴转动所产生的感应电动势。     

平面圆电流在远处任一点激发的磁场

文章用普通物理的方法计算了平面载流圆线圈在远处任意一点激发的磁场．     

Magneto-optical fiber sensor based on magnetic fluid

A novel magnetic field fiber sensor based on magnetic fluid is proposed. The sensor is configured as a Sagnac interferometer structure with a magnetic fluid film and a section of polarization maintaining fiber inserted into the fiber loop to produce a sinusoidal interference spectrum for measurement. The output interference spectrum is shifted as the change of the applied magnetic field strength with a sensitivity of 16.7 pm/Oe and a resolution of 0.60 Oe. The output optical power is varied with the change of the applied magnetic field strength with a sensitivity of 0.3998 dB/Oe.     

Observation of the external-ac-current-induced dc voltage proportional to the steady current in superconducting loops

A dc voltage induced by an external ac current was observed in a system of asymmetric aluminum loops at temperatures corresponding to 0.95–0.98 of the superconducting transition temperature. The voltage magnitude and sign change periodically in a magnetic field with a period corresponding to the magnetic flux quantum through the loop. The amplitude of these oscillations depends nonmonotonically on the amplitude of ac current and is almost independent of its frequency in the range from 100 Hz to 1 MHz. The observed phenomenon is interpreted as the result of displacing the loop into a dynamic resistive state by the external current, where the loop is “switched” back and forth between the closed superconducting state with a nonzero steady current and the nonclosed state with a nonzero resistance along the loop circle. It is shown that voltages are summed up in a system of loops connected in series. For systems with one, three, and twenty loops, the voltage reaches 10, 40, and 300 μ V, respectively.     

Spontaneous supercurrent induced by ferromagnetic pi junctions

We present magnetization measurements of mesoscopic superconducting niobium loops containing a ferromagnetic (PdNi) pi junction. The loops are prepared on top of the active area of a micro-Hall sensor based on high mobility GaAs/AlGaAs heterostructures. We observe asymmetric switching of the loop between different magnetization states when reversing the sweep direction of the magnetic field. This provides evidence for a spontaneous current induced by the intrinsic phase shift of the pi junction. In addition, the presence of the spontaneous current near zero applied field is directly revealed by an increase of the magnetic moment with decreasing temperature, which results in half integer flux quantization in the loop at low temperatures.