磁共振多通道射频接收线圈性能评估

磁共振成像技术追求高信噪比和快速扫描。与单通道线圈相比,多通道线圈具有高信噪比、高分辨率和成像速度快的特点。为服务于射频线圈设计和制作,开发了基于磁共振k空间数据的多通道射频线圈性能评估软件。此软件可以准确方便地计算多通道线圈噪声耦合矩阵和信噪比。     

小浪底与西霞院水电站水轮机调速器的异同及特点分析

水轮机调速器是水电站重要的自动化设备,其质量的好坏直接影响到电能品质和水电站安全及经济运行.文章主要从小浪底和西霞院及西沟水电站调速器的选用来分析其各自调速器的异同及特点.     

计算机硬件系统常见故障的分析处理

归纳总结了计算机用户在日常工作、生活中可能碰到的多种代表性的电脑软硬件故障和问题及解决方法。各种故障问题类型和故障排除思维习惯来编排,具体包括开关机故障、死机故障、显示故障、声音故障、存储设备故障、CPU故障、内存故障、主板故障。在碰到电脑故障时,能快速判断和解决一些有规律可循的常见故障,以及如何维护电脑、如何避免电脑故障。     

开卷机钢卷直径计算优化算法在带钢纵剪生产线中的应用

在带钢纵剪生产线的电气控制系统中,开卷机的钢卷卷径（以下简称卷径）是一个重要的检测参数,其检测和计算的准确性对系统的控制精度影响很大。本文介绍了一种适用于纵剪生产线开卷卷径的测量与计算方法,并且简要说明了如何通过西门子S7-400PLC来实现。经过实际的生产运行证明,该方法可以提高开卷机的实际卷径精度,增强测控系统的稳定性和可靠性。     

小型钨丝电热原子吸收光谱仪的电源

随着对分析仪器的小型化、便携式需求的提高,钨丝电热原子吸收光谱仪在便携式分析仪器方面显示了很大的潜力.为进一步满足现场分析的需要,以单片机为芯片,为小型钨丝电热原子吸收光谱仪的空心阴极灯和钨丝电热原子化器设计稳定的一体化恒流电源;并编写PC机的控制软件,以USB或RS232方式与电源通信,方便控制空心阴极灯和钨丝电热原子化器电流,以及原子吸收过程.以此电路设计的小型钨丝电热原子吸收光谱仪对镉、铅、金和银的标准溶液测试结果为:检出限分别为(0.1,6.0,5.0,0.6)μg/L,相对标准偏差分别为8.2%,5.3%,6.0%和7.2%.测试结果表明:电源很稳定,达到了文献报道的钨丝电热原子吸收光谱的分析性能.     

基于Rogowski线圈的工频大电流测试仪的设计

介绍Rogowski线圈的原理,描述工频大电流测试仪系统的各部分硬件电路设计,以及实现系统功能的软件设计。介绍了产品的使用情况。     

基于模型预测控制的配电网单相接地故障有源消弧

针对配电网非有效接地系统长期存在单相接地故障消弧的难题,现多采用附加有源补偿和消弧线圈相结合的方案对接地故障电弧进行抑制,而有源补偿系统的控制策略的性能直接决定了消弧的性能,本文设计了一种基于预测控制的有源消弧的实现方案,分析了采用注入电流方式的有源消弧的原理,采用三级联多电平H桥的有源补偿的拓扑,优选了代价函数,设计了基于预测控制的有源电流消弧闭环控制系统方案。该方案较PI控制策略的有源电流消弧闭环控制系统具有无需进行参数整定,即能实现对多次谐波电流的精确追踪,能进一步实现对接地电流的有效补偿。仿真分析以及实验验证均表明：本文所提的方案能够更加有效的抑制接地故障电流,满足不同场景下可靠消弧的要求     

非晶合金配电变压器铁心截面优化设计

本文在参考传统立体卷硅钢变压器截面设计的基础上,分析立体卷铁心柱的截面特点,推导出截面设计公式。考虑非晶合金硬度高、脆性大的特点,本文给出两种适合非晶带材加工的约束条件,提出对应于两种约束条件的设计方案,即理论最大截面设计与实用经济截面设计,为非晶合金配电变压器的设计提供参考。     

Calibration of a multi-mobile coil magnetic manipulation system utilizing a control-oriented magnetic model

In this paper, we address the calibration of a family of magnetic manipulation systems composed of several coils that are moved around by serial robot manipulators. We show in this paper that the calibration of the whole system ultimately results in calibrating the manipulator and coil separately up to an unknown rigid transformation. For calibration of the coil, we propose to use a model that has not been used so far in the literature; a control-oriented model which is sufficiently accurate and computes the magnetic field in real time. A protocol for calibrating the magnetic manipulation system using the Nelder–Mead algorithm to estimate the model parameters is presented. Calibration was performed through simulations and validated experimentally on a physical system. It was observed that the root mean square error was reduced by 37% after calibration of the physical system, indicating an improvement in accurately estimating the magnetic model.     

Breathhold imaging of the upper abdomen using a circular polarized-array coil: comparison with standard body coil imaging

Current studies emphasize the use of array coils to decrease noise and increase the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). We applied Tl-weighted and T2-weighted standard nonbreathhold spin echo (SE) sequences and Tl-weighted FLASH, TurboFLASH, T2-weighted spin-echo time (TSE), and heavily T2-weighted half Fourier acquisition single-shot TSE (HASTE) sequences during breathhold for abdominal imaging in 15 normal volunteers. The breathhold scans were performed using both a standard coil and a circular polarized array coil. We analyzed the signal intensity (SI), SNR, and CNR of abdominal organs in all sequences. SNRs increased in all cases by an overall factor of 3 due to an 8% increase in overall Sis and a 50% decrease in noise when applying the array coil. Although the array-coil FLASH sequence performed at least as well as the respective SE sequence, the SNRs of the array-coil TurboFLASH, TSE breathhold, and HASTE sequences were generally lower. We conclude that array-coil imaging significantly improves fast imaging of the abdomen.