Time-Domain Measurement of Voltage Induction by Transient EM Fields

An efficient measurement technique for studying the effect of transient electromagnetic fields under controlled conditions has been described. Broad-band TEM fields with a rise-time of a few nanoseconds were generated using a stripline method. Theoretical results are obtained and experimental measurements which confirm these results are described. The work will form the basis for a study of the susceptibility of digital integrated circuits and their interconnections to transient electromagnetic fields.     

An Inverter-Fed Induction Motor Diagnostic Tool Based on Time-Domain Current Analysis

In this paper, a novel virtual-instrument-based monitoring and diagnosis technique that permits the identification of rotor faults in small inverter-fed induction motors is presented and discussed. Since it allows the continuous monitoring of the machine, it is a useful tool for the implementation of advanced maintenance strategies. Through a proper experimental setup, the performance, repeatability, and portability of the proposed algorithm have been evaluated.     

基于物理的布料模拟研究综述

目的 在图形硬件计算性能不断提高,物理仿真动画技术蓬勃发展的背景下,对基于物理的布料模拟技术中的主流方法进行总结和归纳,指出未来发展趋势,为相关技术与应用研究提供参考.方法 通过文献收集和整理,从布料物理模型、物理模拟算法、碰撞处理算法和高分辨率加速算法等方面入手,对基于物理的布料模拟相关研究成果进行综述,分析现有方法的本质、优缺点和内在联系,基于分析归纳预测其未来发展趋势和所面临的挑战.结论 总结归纳了布料物理模拟算法的研究进展,研究围绕隐式时间积分无约束优化问题展开的共同点,以及GPU并行加速和多重网格方法对于高分辨率布料实时模拟的贡献,指明了布料物理模拟的发展趋势是模拟动画真实感与模拟算法高效性会得到不断提高,其面临的挑战是随着硬件性能的发展进一步提高模拟精度,以及在有限计算性能下需要更好地平衡模拟精度和效率的问题.     

基于时域加权的单位脉冲响应模型的非叠代算法

提出了一种基于时域加权的新的非叠代优化算法,用于重构经过采样示波器测量的阶跃信号、脉冲信号等。该算法构造了一个期望误差函数,由于这个期望误差函数与真实误差很接近,因此构造了新的价值函数,并使用时域加权来优化不同的波形,在减小时域振铃时有效的控制噪声放大。与误差能量,归一化方法相比,该算法经过仿真实验表明了其可行性和有效性。     

A Model for the Forward Problem in Magnetic Induction Tomography Using Boundary Integral Equations

We propose a new formulation for the forward problem in magnetic induction tomography (MIT). We formulate the problem in terms of interior and exterior boundary integral equations (BIEs), subject to appropriate boundary conditions. We then transform a standard exterior BIE involving the magnetic vector potential to a BIE involving the electric fields. This transformation eliminates two boundary conditions involving the magnetic vector potential and its normal derivative. This greatly reduces the computational complexity of the model. Here, we compare numerical solutions of the model to analytical solutions.      

浅谈磁感应强度和磁场强度

本文由磁场的存在和特斯拉计的检定引出了磁感应强度和磁场强度两个概念,分析了其区别和联系,并由此得出了该二者的正确用法.     

Determining Basic Characteristics of Magnetic Induction Measures

Basic characteristics are determined for Helmholtz coils with particular nonoptimal dimensions. It is shown that such a coil can be used as part of a tester for instruments of V&E-METR type.     

Simulation of the Magnetic Induction Vector of a Magnetic Core to be Used in FFC NMR Relaxometry

This paper is a contribution for the assessment and comparison of magnet properties based on magnetic field characteristics particularly concerning the magnetic induction uniformity in the air gaps. For this aim, a solver was developed and implemented to determine the magnetic field of a magnetic core to be used in Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry. The electromagnetic field computation is based on a 2D finite-element method (FEM) using both the scalar and the vector potential formulation. Results for the magnetic field lines and the magnetic induction vector in the air gap are presented. The target magnetic induction is 0.2 T, which is a typical requirement of the FFC NMR technique, which can be achieved with a magnetic core based on permanent magnets or coils. In addition, this application requires high magnetic induction uniformity. To achieve this goal, a solution including superconducting pieces is analyzed. Results are compared with a different FEM program.     

The Development of a Narrow-Band Time-Domain Reflectometer

The capability of accurately determining the value of impedance discontinuities in transmission line systems is obtained by replacing the dc pulse with a gated RF source in a conventional time-domain reflectometer (TDR) system. Such a system allows complex impedance measurements to be made upon elements in a system that are physically inaccessible. Due to the sensitivity available in TDR systems, low orders of magnitude of return losses are easily detectable and measurable. In systems where multiple impedance discontinuities exist, each individual discontinuity may be isolated and hence analyzed separately. The modifications to a conventional TDR system are described in this paper. A method of using the modified narrow-band TDR system to measure complex impedance is presented. This method is complementary to that used by the Hewlett-Packard model 1580A narrow-band TDR and offers the avantages of both phase information and lower modulation frequency.     

A General Model for Investigating the Effects of the Frequency Converter on the Magnetic Iron Losses of a Squirrel-Cage Induction Motor

We present a comprehensive analysis of iron losses in an inverter-fed induction motor. We performed experimental and numerical investigations to assess the additional losses produced by a pulsewidth modulated (PWM) supply compared to a sinusoidal supply. We developed an iron-loss model, called the hybrid model, and incorporated it into a two-dimensional (2-D) finite-element method (FEM) to investigate the losses. The model predicts the $Bhbox{-}H$ loops and the ensuing iron losses. We also used a traditional iron-loss model based on the statistical theory for the sake of comparison. We solved the nonlinear dynamic equations of the FEM by the fixed-point method and the Crank-Nicolson time-stepping scheme. We found the hybrid model to be fairly accurate in reproducing the iron losses obtained experimentally on a squirrel-cage induction motor operated under several different conditions. The numerical analysis also provided interesting results regarding the role of the PWM supply in characterizing the behavior and distribution of iron losses in the geometry of the motor.      

Determining Geomagnetic Field Induction Against a Background of Magnetic Interference from a Mobile Object

Determining the geomagnetic field induction is considered against a background of magnetic interference from a moving object, in which the angular position of the object is measured along with the projections of the magnetic induction vectors by means of three-component magnetometric sensors.     

基于单片机磁感分布的测试

介绍磁感分布的原理与设计,详细地介绍了利用单片机进行磁感分布测试的软、硬件的设计过程.     

Saturation Magnetic Induction Prediction for Amorphous Magnetic Alloys by Using Support Vector Regression

This paper illustrates an application of support vector regression (SVR) approach in forecasting the saturation magnetic induction (B _s ) of amorphous magnetic alloys. SVR was trained and tested with an experimental data set comprised of five input variables, comprising the average number of valence electrons of amorphous magnetic alloys, mixed entropy, ratio of radii, difference of electron density, and difference of work function. The prediction performance of SVR was compared with that of artificial neural networks’ (ANN) model. The results demonstrate that the prediction ability of SVR is superior to that of ANN. This investigation indicates that SVR-based modeling is a practically useful tool in prediction of the saturation magnetic induction of amorphous alloys. This study provides a novel methodology to foresee the saturation magnetic induction in sintering/development of novel amorphous magnetic alloys possessing high saturation magnetic induction.     

纳米磁热复温玻璃化低温保存大鼠肾脏的研究

纳米磁热复温有望解决器官玻璃化低温保存复温的难题。本文测试了氧化铁纳米颗粒在VS55低温保护剂溶液中的胶体稳定性及磁热性能。结果表明,纳米颗粒VS55溶液分散体系即使在玻璃化冷冻磁热复温后,仍在较长时间内保持胶体稳定,且磁热性能随交变磁场电流、纳米颗粒浓度的增加而提升。磁共振成像结果显示通过灌注能够基本实现纳米颗粒在大鼠肾脏组织中的均匀分布与完全洗脱。肾脏总体结构在玻璃化冷冻磁热复温后保持完整,但磁共振成像显示其内部血管网络可能受到一定程度的损伤。研究结果说明,通过进一步提升磁场强度或纳米颗粒的磁热性能,优化灌注加载流程,有望实现更加快速均匀的复温,从而在不久的将来解决器官玻璃化保存的复温难题。     

Measurement of the Sensitivity Function in a Time-Domain Atomic Interferometer

We present here an analysis of the sensitivity of a time-domain atomic interferometer to the phase noise of the lasers used to manipulate the atomic wave packets. The sensitivity function is calculated in the case of a three-pulse Mach-Zehnder interferometer, which is the configuration of the two inertial sensors we are building at the Laboratoire National de Metrologie et d'Essais-Systeme de References Temps-Espace. We successfully compare this calculation to experimental measurements. The sensitivity of the interferometer is limited by the phase noise of the lasers as well as by residual vibrations. We evaluate the performance that could be obtained with state-of-the-art quartz oscillators, as well as the impact of the residual phase noise of the phase-locked loop. Requirements on the level of vibrations are derived from the same formalism.