600MW发电机组出口PT故障分析及解决方案

600 MW发电机组是我国目前电力系统的主力发电机组,对电力系统的稳定可靠运行有非常直接的影响。但在600 MW发电机组的实际运行中,出口PT一次设备常常发生故障,对发电机组的正常运行产生了不良影响。掌握出口PT故障排查与解决方法对提高600 MW发电机组运行安全性有非常重要的意义,现结合元宝山电厂600 MW发电机组出口PT故障实例,对故障原因进行深入分析,并简要探讨故障排查与解决方案。     

地铁车辆LCU系统及故障解决方案

福州地铁既有列车的控制电路采用传统的继电器控制方式,其故障率高且运维难度大,新线项目已引入LCU系统。文章主要阐述福州地铁车辆LCU系统的基本结构,关键控制电路采用“二乘二取二”的冗余配置,非关键电路采用“热备双冗余”的方式,有效提升了列车控制电路的整体可靠性;针对LCU系统在应用过程中的输入不一致、ETH板离线、输出自检异常等故障,提出相应解决方案,在优化故障诊断策略和编码电路后,故障未再发生,进一步降低了LCU系统故障率,使地铁车辆处于安全、稳定的运行工况中。     

水系统中红锈现象的产生和整体解决方案

从红锈的危害入手,探讨了红锈产生的原因,并通过提高前期设计建造的工程质量、中期合理的运行管理、定期系统酸洗钝化维护处理等方法,阐述了红锈的整体解决方案,以降低红锈的产生几率及其所带来的质量风险。     

浅谈通风管道和水系统管道的故障及检修

本文结合个人施工经验,分析通风管道和水系统管道出现故障的原因,介绍了相应的检修方法。     

基于 Petri 网和图像识别方法的故障预防系统研究及实施

以国家ＣＩＭＳ工程技术研究中心制造系统为对象，设计并实施了一个制造系统故障预防系统。文中首先提出了制造系统的谓词／变迁网模型，以此为基础设计了基于Ｐｅｔｒｉ网可达性树分析方法和图像识别方法的制造系统故障预防系统，并给出了系统的总体结构图和相应的模块结构图。该故障预防系统已完成实施，在提高制造系统运行的安全性和可靠性方面，发挥了重要作用。     

The effect of 1.5 T and 3 T magnetic resonance imaging on microleakage of amalgam restorations

The aim of this article is to compare the effects of 1.5 T and 3 T MRI on microleakage of amalgam restorations. A total of 90 extracted molar teeth were used in this study. Amalgam was used to restore standard Class V preparations (5 × 3 × 2 mm). Following the restoration, the teeth were divided into three groups according to magnetic resonance imaging (MRI) protocol (Group I: Control, Group II: 1.5 T MRI, and Group III: 3 T MRI). A total of 6,000 thermal cycles at 5°C–55°C were applied on all samples. Microleakage values were measured in millimeters using the ImageJ program. Microleakage values were higher in the gingival region compared to the occlusal region in all groups and the differences were statistically significant (p < .05). Microleakage values were not statistically different among the groups in the occlusal region (p > .05), while there were statistically significant differences among the groups with respect to microleakage values in the gingival region (p < .01). The highest mean microleakage amount in the gingival region was measured in Group III (1.192 ± 0.941 mm). This was followed by Group II (0.519 ± 0.813 mm) and Group I (0.347 ± 0.726 mm), respectively. Within the limitations of this in vitro study, we observed that higher microleakage values in amalgam restored teeth in which were exposed to MRI procedure. We also found that the teeth exposed to the stronger magnetic field showed higher microleakage amount.     

Broadband electron spin resonance at 4-40 GHz and magnetic fields up to 10 T

A broadband electron spin resonance spectrometer is described which operates at frequencies between 4 and 40 GHz and can be used in superconducting magnets. A tunable cylindrical cavity is connected to a vector network analyzer via coaxial cables, and the radiation is fed into the cavity by a coupling loop. No field modulation is employed. Resonance frequencies below 14 GHz are obtained by inserting dielectrics with different permittivities into the cavity. The setup allows for measurements with the microwave magnetic field either parallel or perpendicular to the external field.