冲击电流计线圈运动状态的理论及数值计算研究

简要介绍了冲击电流计的实验原理,探究了冲击电流计中偏转线圈在磁场中的三种运动状态,利用数理方法和物理知识推导出冲击电流计中线圈偏转角度随时间变化的数学表达式,并数值计算给出了三种运动状态中偏转角随时间变化曲线图。对深入了解和掌握冲击电流计的具体工作原理及特性具有重要理论指导意义。     

电流计外临界电阻的测定

一、引言测定电流计的外临界电阻的常用方法是:通过改变外电路电阻R_o的值,使电流计活动部分由周期性运动(欠阻尼运动状态)逐渐变成非周期性运动(T→∞),此时的R_o即为外临界电阻R_c,而相应的运动状态称为临界阻尼运动状态,此方法是由实验者观察电流计指示部分的运动状态经判断得出R_c,这种观察往往由于电流计在接近临界阻尼运动状态时,外电阻的值即使变化范围较大,运动状态并无明显差别而不易判断,因而由此得到的R_c值可信程度较低,本文所介绍的测量方法克服了上述方法的弊端,还是在原有的实验仪器上进行测量,但在整个测量过程中让电流计始终处于较易观     

对观察灵敏电流计三种运动状态方法的建议

对观察灵敏电流计三种运动状态方法的建议杨德甫，孙新义（延安大学物理系７１６０００）观察灵敏电流计的三种运动状态（欠阻尼、临界阻尼、过阻尼）并确定外临界电阻值是灵敏电流计特性研究的实验中主要内容之一．在目前所使用的教材’“中所采取的方法是单刀双掷开关转...     

用数字式冲击电流计测高电阻

介绍了数字式冲击电流计测量高值电阻的原理和方法，对两种冲击电流计的测量进行了比较，阐述了数字式冲击电流计的优点。     

测定电流计外临界电阻的一种方法

电流计线圈的运动状态，与外电路电阻R的值有关，当改变R的值，逐渐由大调小时，线圈可由欠阻尼运动状态变化到临界阻尼运动状态及过阻尼运动状态。若线因处于临界阻尼运动状态，则对应的外电路电阻R便是外临界电阻RC．在实验中，往往是调节电阻R值的大小，通过观察电流计指示部分的运动状态来判定外临界电阻R。这种方法简便易行，物理思想明确，常被采用．但是，由于带有主观判断的局限性，R。值的可信程度不高．为了客观地测定凡值，本文将根据电流计线自运动的特点，导出确定凡值的解析函数式．按照该式，在实验中需要调节外电路电阻…     

用冲击法测量直螺线管磁场误差来源的分析

用冲击电流计测量长直螺线管在轴线上磁感强度的分布,是个很重要的实验,通过这个实验可以掌握冲击电流计的使用方法,还可加深对圆形电流磁场理论的理解。一、冲击电流计的使用条件 1.冲击电流计必须在远离外磁场源的地方使用,特别注意应防止电流计测量回路     

冲击电流计标尺非圆弧产生误差的计算

计算了用冲击电流计测量磁场时冲击电流计标尺非圆弧所产生误差的大小。     

浅谈冲击电流计阻尼度的选择

浅谈冲击电流计阻尼度的选择席存蒸，王澜涛（石家庄铁道学院０５００４３）冲击电流计与灵敏电流计不同，利用冲击电流计测量时读取的是第一次最大偏转量ｄ。，此量以及从零点偏转到此量所需时间ｔ；均与回路的阻尼度有关，即冲击电流计的灵敏度以及它为测量者提供的读数...     

冲击法测定直螺线管磁场的误差分析

冲击电流计是测量在极短时间内电路中通过的电量的高灵敏度仪器，可用来测磁场、电容、电感等.本文结合用冲击法测定螺线管磁场的实际教学经验，对实验中出现的一些误差及对测量的影响进行了较详细的分析，并试图对冲击电流计的正确、合理使用进行探讨.一、测量原理及线路冲击法测量磁场是根据电磁感应定律，利用被测直螺线管中磁通量变化时，包围在这个磁通回路的探测线圈感应出电动势为基础，由串联在探测回路中的冲击电流计准确地测出流过回路的瞬时电量，借以计算磁场.磁场测定的实验线路如图1所示，BG为电流计，N1和N2分别是被测螺管…     

冲击电流计测高阻实验中放电与计时同步装置的设计

用电子秒表和双刀双掷闸刀结合设计出冲击电流计测高阻实验中的计时与放电同步装置，大大减小了测量误差，且操作更加方便。     

The rf coil as a sensitive motion detector for magnetic resonance imaging

A new sensor principle for detection of patient movement in magnetic resonance imaging has been successfully applied for the reduction of motion artifacts. It uses a device that is already present in every MRI system, namely the rf coil. Patient movement within the coil causes changes in the rf impedance match of the coil, which can be measured as variations in the reflected rf power. The principle used for the detection of respiratory and cardiac motion is described, and experimental results measured with several coil arrangements are given. Images are presented which were acquired with respiratory gating derived from the rf body coil of a 2 Tesla whole body MRI system.     

校正磁场和cos/sin线圈的设计

 介绍了控制束心corkscrew运动的原理,给出了用cos/sin线圈产生校正磁场方法并比较两种设计的结果。指出用较严格设计的cos/sin线圈能更有效地调节校正磁场。     

Structure of a collapsed polymer chain with stickers: a single- or multiflower?

Using an amphiphilic copolymer with evenly spaced hydrophobic styrene segments (stickers), poly(N-isopropylacrylamide-s-styrene), we recently confirmed a long-standing prediction that such a copolymer chain in a solvent selectively poor for the stickers could self-fold from a random coil to a single-flowerlike core-shell nanostructure. Moreover, we found that the self-folding involves the movement of the sticks to the center and the transition from the random coil to the collapsed globule passes through a proposed ordered coil state.     

用洛伦兹磁场力挑战狭义相对论首文的论点简

实验论证表明：基于欧式空间的伽利略相对运动,①当磁铁静止而线圈运动时,其感应电流是经典洛伦兹磁力F1的作用结果;②当线圈静止而磁铁运动时,其感应电流是广义洛伦兹磁力F2的作用结果。这就否定了狭义相对论的论点,也质疑了麦克斯韦电动力学。     

大面积NBI 射频离子源电气参数设计分析

为探究射频离子源驱动器线圈电气参数对射频放电的影响,主要进行了射频离子源等离子体激发的物理分析,并计算了射频电源的频率选择与线圈放电电流、线圈匝间电压以及放电气压之间的关系,设计了射频离子源驱动器的主要参数。研制的射频离子源驱动器装置,成功获得氢等离子体射频放电。实验结果和理论计算结果符合很好。     

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为探究射频离子源驱动器线圈电气参数对射频放电的影响,主要进行了射频离子源等离子体激发的物理分析,并计算了射频电源的频率选择与线圈放电电流、线圈匝间电压以及放电气压之间的关系,设计了射频离子源驱动器的主要参数。研制的射频离子源驱动器装置,成功获得氢等离子体射频放电。实验结果和理论计算结果符合很好。     

Levitation in the field of a nonsuperconducting coil with magnetic flux stabilization

A method providing the “frozen flux” conditions in a nonsuperconducting coil is suggested and demonstrated with a model. The feasibility of permanent magnet stable levitation in the field of the coil with magnetic flux stabilization and mean current control is shown. The method allows researchers to exploit permanent magnet-superconducting body interaction in physical devices, for example, to reproduce, using nonsuperconducting coils, the frozen magnetic flux conditions required for the stable levitation of the magnet over a superconducting body.     

An integrated head immobilization system and high-performance RF coil for fMRI of visual paradigms at 1.5 T.

A flexible quadrature radiofrequency coil that maximizes the signal-to-noise ratio over the field of view of the human brain has been integrated into a head immobilization and visor system for fMRI at 1.5 T. Head motion is reduced by the visor that incorporates a head clamp and a simple visual sighting system that provides feedback on head position. This system is demonstrated in serial images by correction of deliberate head motions. The sensitivity at the cortical surface of fMRI using blood oxygenation level dependent contrast is increased significantly above that of the commercial rigid volume RF coil under the same acquisition conditions. This improved performance is demonstrated using visual activation and eye movement paradigms.     

霍尔效应推力器放电双稳态机理研究

实验发现霍尔效应推力器在自励磁模式下具有两个稳定的放电工作点,且运 行过程中在这两个工作点上往复跳变,很大程度上影响了推力器通道内等离子体的放 电物理过程及其综合性能.本文结合推力器放电磁安特性曲线与励磁电流曲线的相互关 系,给出了推力器放电双稳态特性形成的物理机理．在此基础上提出了通过改变励磁电 流曲线斜率,使推力器稳定工作于单放电工作点的方法,结合一维动态流体模型给予了物 理解释,并通过实验加以验证.     

5T有源屏蔽式超导磁体结构设计

介绍了为兰州Penning离子阱项目专门设计的5T有源屏蔽式超导磁体。 为达到物理设计要求的场均匀度, 超导磁体有3层共计6个线包组成。 同时为了确保线圈绕制的定位精度和在强磁场下的稳定性, 绕制骨架采用三筒体结构, 模拟计算表明线圈的绝缘和固定结构能够达到强磁场下的电气和机械性能要求。 对5T有源屏蔽式超导磁体结构设计材料选择以及线圈的绕制工艺进行了详细的论述。 A 5T actively shielded superconducting magnet was designed for Lanzhou Penning Trap project. In order to achieve homogeneity of physical requirements, superconducting magnet was made up of six coils, which were wound on framework of three layers. Meanwhile, three framework structure can ensure the precision of coil winding and the mechanical stability under intense magnetic field. The results of simulation show that the insulation and fixed structure of the coil can satisfy the electrical and mechanical requirements under intense magnetic field. At last, properties of the used materials and coil fabrication have been presented.