经颅磁刺激线圈结构设计分析综述

为了优化磁刺激线圈设计,解决磁场聚焦性不足的问题,并为以后经颅磁刺激(TMS)线圈结构的进一步改进提供设计依据,将经颅磁刺激技术更好的应用到临床治疗和科学研究中,在深入查阅研究相关文献的基础上,介绍了现有的几种典型线圈结构,并对经颅磁刺激中使用的不同线圈以及其在空间中产生的电场和磁场的强度和分布进行了分析、对比,研究了不同线圈结构的聚焦性和应用场合。研究结果表明:现有的改进型线圈结构虽然都具有自身的优点,并且在聚焦性或刺激深度方面大大超越了传统线圈,但结构过于复杂,能耗过高,实用性不足,在需要精确刺激靶点区域的情况下仍然不能提供令人满意的空间分辨率,因此经颅磁刺激线圈结构的进一步优化设计仍然具有很大的提升空间。     

用于工业三维点测量的接触式光学探针

为了快速、准确地获得大尺寸工业产品或带有深槽孔工件的关键点三维坐标,本文基于工业近景摄影测量理论、立体视觉技术等,研究并实现了两种工业便携式、接触式光学探针测量系统。研究了测量系统涉及的探针设计、探针标定以及三维点解算等关键技术,设计了点阵式和手持相机式两种适用于不同工业场合的工业探针。针对点阵式探针的测量,提出了一种用于解算探针坐标系与世界坐标系相对关系的点云匹配方法。此外,采用拟合虚拟球的方法准确标定了两种探针的内部参数。最后,通过对比标准球与三坐标测量机的测量结果,得到系统的测量精度可达0.1 mm/m。该精度满足一般大、中型工件的三维点测量精度标准。     

Technique for the measurement of the amplitude and phase velocity of a slow space charge wave on a relativistic electron beam

A technique is described for the measurement of the axial electric field of a slow space charge wave. The measurement employs a double probe arranged to give an output proportional to the rate of change of magnetic flux linking the probe loop. This output may be related to the electric field of the wave. Two such probes used in an interferometer arrangement allow for the measurement of the phase velocity of the wave.     

Simple cell for the measurement of the radio frequency electrical properties of earth materials

The design of a simple cell for determining the radio frequency electrical properties of earth materials is described. Basically, the cell consists of a coaxial sample holder fitted with electric and magnetic field probes. When excited as a section of transmission line the induced probe voltages are related in a straightforward manner to the electrical properties of the sample. The device is intended for use with a vector voltmeter which permits the direct and simultaneous measurement of the relative amplitudes and phases of these probe voltages. The cell permits the accurate and rapid determination of the conductivity and dielectric constant of earth materials over the frequency range 1 MHz-1 GHz, without the tedious and time consuming procedures associated with the bridge and slotted line techniques commonly used in this frequency range.     

GMR array uniform eddy current probe for defect detection in conductive specimens

The usage of eddy current probes (ECP) with a single magnetic field sensor represents a common solution for defect detection in conductive specimens but it is a time consuming procedure that requires huge amount of scanning steps when large surface specimens are to be inspected. In order to speed-up the nondestructive testing procedure, eddy current probes including a single excitation coil and an array of sensing coils present a good solution. The solution investigated in this paper replaces the sensing coils for giant magneto-resistors (GMRs), due to their high sensitivity and frequency broadband response. Thus, the ECP excitation coil can be driven at lower frequencies than the traditional ones allowing defects to be detected in thicker structures.In this work an optimized uniform eddy current probe architecture including two planar excitation coils, a rectangular magnetic field biasing coil and a GMR magnetometer sensor array is presented. An ac current is applied to the planar spiral rectangular coil of the probe, while a set of GMR magnetometer sensors detects the induced magnetic field in the specimens under test. The rectangular coil provides the DC uniform magnetic field, assuring appropriate biasing of the GMR magnetometers of the probe, setting-up the functioning point on the linear region and at the same branch of the GMR static characteristics. The differences on the images obtained for the same specimen for each GMR are reduced if all sensors are biased on the same working point. Elements of the automated measurement system used to inspect the plate under test using the proposed eddy current probe, including a validation procedure based on a 2D template matching algorithm and the corresponding experimental results are included in the paper.     

Nuclear magnetic resonance apparatus for pulsed high magnetic fields

A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T.     

Technique for designing and evaluating probe caps used in optical topography of infants using a real head model based on three dimensional magnetic resonance images

We have developed an effective technique for aiding the design and evaluating the performance of the probe caps used to perform optical topography (OT) on infants. To design and evaluate a probe cap, it is necessary to determine the measurement positions for conducting OT on the brain surface of subjects. One technique for determining these positions on the brain surface is to find their three-dimensional (3D) coordinates using a 3D magnetic space digitizer, which consists of a 3D magnetic source and a 3D magnetic sensor. The problem with this technique is that it takes a long time to determine all the measurement points on the subject's head and it is difficult to use with infants. It is a particular problem with infants who cannot support their own heads. Therefore, we have developed a real model of an infant subject's head based on 3D magnetic resonance (MR) images. The model is made from an optical-curable resin using 3D computer-aided-format coordinate data taken from 3D MR image-format coordinate data. We have determined the measurement positions on the surface of the model corresponding to a scalp using a 3D magnetic space digitizer and displayed the positions on a 3D MR image of the infant's brain. Using this technique, we then determined the actual 72 measurement positions located over the entire brain surface area for use with our new whole-head probe cap for neonates and infants. This method is useful for evaluating the performance of and designing probe caps.     

一种磁流变液性能测试用的凹字型磁路结构设计与研究

剪切屈服应力是反映磁流变液流变特性的主要参数之一,稳定可控的磁场直接影响磁流变液剪切屈服应力的测量精度,因此磁场设计是否合理对磁流变液的流变性能测试具有重要的影响。针对外置式线圈产生的磁场强度较低且存在漏磁现象、对称式线圈中磁流变液装载不便导致测量过程持续性差等问题,设计了一种凹字型磁路,通过调整线圈位置来改变磁场结构,使磁力线垂直穿过磁流变液流动方向,同时可拆卸的组合式磁路设计在保证磁场强度需要的前提下实现了磁流变液的连续性测量。此外,还分析了不同电流下的磁场强度分布规律,并基于优化的磁路开展了磁流变液剪切屈服应力等力学性能参数的测试。与主流标准测试仪器相比,具有凹字型磁路结构的磁流变液测试系统所测得的剪切屈服应力平均相对偏差值约为10%,重复误差在6.34%以内,说明该磁路结构是磁流变测试中磁场装置设计的一种可行方法。     

基于DSP的永磁同步电动机矢量控制系统

为了实现对永磁同步电动机的最优控制,设计了一种基于TMS320F2812的永磁同步电动机矢量控制系统。该系统选用TMS320F2812数字信号处理器（DSP）芯片为主控制器;根据磁场定向控制器的控制原理,实现了电机的位置、速度和电流三闭环矢量控制策略;给出了基于磁场定向控制原理而设计的控制器的硬件组成结构及软件设计流程;最后,完成了系统仿真。仿真结果表明：该控制方案合理可行。     

新型两用表面形貌测量仪的研究与开发

开发了一种大量程、高分辨率、非接触式与接触式测量两用的新型表面形貌测量仪器。仪器本体为非接触测量轮廓仪,通过插入接触式测头实现接触测量。非接触式测头采用傅科法自动聚焦原理,接触式测量采用微恒力电感测量原理,它们共用一个音圈电机,各自跟踪电气零位,实现大量程、高分辨率的位移测量。文中还介绍了仪器采用的共运动基面二维工作台。     

Estimating effects from trapped magnetic fluxes in superconducting magnetic levitation measurement

Superconducting magnetic levitation measurement is one of the most promising approaches to define mass standard based on the fundamental physical constants. However, the present system has unknown factors causing error larger than 50 ppm. We examined the effects of magnetic fluxes trapped in the superconducting coil and the superconducting floating body. When fluxes were trapped in either coil or floating body, their effects were able to be cancelled by reversing polarities of current and magnetic field, as had been believed. However, fluxes trapped in both coil and body induced an attractive force between them and caused error. In order to reduce the fluxes, the coil and the floating body should be cooled in low magnetic field in magnetic and electromagnetic shields.     

Comparative evaluation of coil and hall probes in hole detection and thickness measurement on aluminum plates using eddy current testing

The design, test, and comparison of one coil probe and one Hall probe using eddy current testing in the field of non-destructive evaluation is presented. Real tests were performed using alumi- num plates. This research concludes that (1) both probes provided broadband frequency responses up to 1000 KHz, which are wide enough for the most common applications; (2) the coil probe provided higher signal to noise ratio (SNR) than the Hall probe; (3) both probes detected the four holes success- fully and provided enough sensitivity to classify them by diameter; and (4) the coil probe provided higher accuracy than the Hall probe when measuring thickness lower than 1 mm, and lower accuracy when measuring thickness higher than 1.5 mm.     

感应式磁声成像脉冲磁场的测量方法

阐述了利用电磁感应法测量脉冲磁场的磁感应强度,首先测量放置在标准的已知正弦波磁场里的探测线圈的线圈常数,再用这种已知线圈常数的探测线圈进行脉冲磁场的测量。介绍了微型磁场探测线圈的绕制和固定方法,设计了脉冲磁场的实际测量装置,给出了线圈平面的调整方法,利用该装置实际测量了感应式磁声成像系统中的脉冲磁场,并对测量结果进行了误差分析。     

高温电涡流传感器感应探头的优化设计

为解决电涡流传感器探头在高温(600℃)环境中测量失效的问题,设计了一种感应探头结构,主要由低温共烧陶瓷基底和Ag线圈组成.首先分析涡流检测的原理和普通探头在高温下失效的原因,根据要求选择低温共烧陶瓷作为基底材料,为在一定区域内提高电感值将线圈设计为多层立体螺旋结构.通过电磁仿真和机械—热仿真确定线圈的形状、材料等,结...     

Note: design of a novel rotating magnetic field device

A novel device to produce a rotating magnetic field was designed, constructed, and tested. The system consists of a Helmholtz coil pair which is mechanically coupled to a dc electric motor whose angular velocity is controlled. The coil pair generates a uniform magnetic field; the whole system is rotated maintaining the coils energized using brushes. The magnetic field strength is uniform (≈5.8 mT) for a workspace of about 100 mm along the rotation axis. The system remains free of undesirable high amplitude mechanical vibrations for rotation frequencies below 10 Hz. We verified the performance of the apparatus by conducting experiments with magnetic swimmers.     

电磁MEMS磁珠操控微线圈三维磁场数值计算与模拟

磁珠具有偶联容量高、比表面积大、易于操控等特点,基于磁珠技术的电磁MEMS可实现磁珠液滴非接触式操控,其微线圈三维磁场分析是磁珠操控优化设计的基础.对静态液体磁珠操控进行了理论分析,确定了影响磁珠操控的主要因素,并应用毕奥-萨伐尔定律和积分方程法,对关键部件微线圈的三维微磁场分布特性进行了分析.运用成熟的商业有限元分析工具Ansys建模分析微线圈三维静态磁场,所得结果与数值计算方法进行了比较,表明所用方法对于磁珠微系统三维恒定磁场的分析是可行的.     

Mapping the magnetic field vector in a fountain clock

We show how the mapping of the magnetic field vector components can be achieved in a fountain clock by measuring the Larmor transition frequency in atoms that are used as a spatial probe. We control two vector components of the magnetic field and apply audio frequency magnetic pulses to localize and measure the field vector through Zeeman spectroscopy.     

Magnetically insulated baffled probe for real-time monitoring of equilibrium and fluctuating values of space potentials, electron and ion temperatures, and densities

By restricting the electron-collection area of a cold Langmuir probe compared to the ion-collection area, the probe floating potential can become equal to the space potential, and thus conveniently monitored, rather than to a value shifted from the space potential by an electron-temperature-dependent offset, i.e., the case with an equal-collection-area probe. This design goal is achieved by combining an ambient magnetic field in the plasma with baffles, or shields, on the probe, resulting in species-selective magnetic insulation of the probe collection area. This permits the elimination of electron current to the probe by further adjustment of magnetic insulation which results in an ion-temperature-dependent offset when the probe is electrically floating. Subtracting the floating potential of two magnetically insulated baffled probes, each with a different degree of magnetic insulation, enables the electron or ion temperature to be measured in real time.     

Structure optimization for magnetic equipment of permanent magnet retarder

The main purpose of this research is to perform a magnetic analysis on the magnetic equipment of permanent magnet retarder (PMR) and optimize the structure of magnetic equipment with the commercial FEM software ANSYS and its design optimization module. The FEM model is built as an axisymmetric model according to the characteristics of the structure of magnetic equipment. Using this model, the magnetic field distribution and magnetic force are calculated by ANSYS. The mathematical model of structure optimization is also built. The design variables are structural parameters including the dimensions of permanent magnets and magnetic yoke, and the objective function is the magnetic force. The unconstrained optimization model takes the maximum value of magnetic force as the objective. A first-order optimization method is used to determine the optimum design of this problem. The optimization process works entirely with the ANSYS parametric design language (APDL). The design tools are used to understand design space and the behavior of the dependent variables. It is shown that designing a structure with the ANSYS optimization module and its design tools is an effective means to improve the structure.     

一阶数控球形反馈磁张量梯度仪动态特性研究

磁通门张量探头在非零的地磁场环境下存在稳定性差、非线性误差大等不足。为克服此类缺陷,需采用磁补偿技术使磁通门工作在零磁场环境。以提高磁通门张量探头的探测精度为目的,采用球形线圈及对应的驱动模块作为磁补偿装置,利用一阶数字控制系统的方法建立磁补偿装置的数学模型,并对其进行参数优化实现最优控制。实验结果显示,当带有球形反馈线圈磁通门张量探头的稳态误差在52.56 nT之内时,系统的带宽将扩展至4.75 Hz,该结果能够同时满足磁张量梯度仪的探测精度及带宽要求,提高了其在航空地球物理探测中的应用价值。