悬挂式电磁分级机

SE系列7000悬挂式电磁分级机是由Eriez Magnetics设计,用来分离重载带式输送机或溜槽上的过程铁质。磁铁绕组工作中一直浸在油液之中,油箱可以防止空气进入以产生冷凝水蒸气损坏磁铁绕组,并可防止绕组因受潮而烧毁。为了在不增加尺寸的情况下使磁铁适用     

异步电动机空载电流过大原因分析及修理对策

文章分析了天津钢集团第二炼钢厂低压三相异步电动机因电流过大，运行中发热严重导致绕组烧毁故障的原因，并提出了相应的修理对策。     

发电机非同期并列案例分析

发电机非同期并列是发电机运行中严重的故障之一,它产生的冲击电流会对发电机、变压器及系统造成严重伤害,机组会发生强烈的振动,有可能使待并发电机绕组变形、绝缘崩裂,甚至将绕组烧毁。对不同发电机组的三起非同期并列事故进行了剖析,并针对不同事故提出了解决方案,为其他发电机组安全稳定运行提供了借鉴经验和警示,以避免类似事故的发生。     

Z4直流电机故障诊断

对济钢第一炼钢厂Z4－160－31（18．5kW)直流电机的故障原因进行总结,认为环境温度过高、通风效果不理想、火花严重造成片间短路击穿烧毁、电机内部绕组的散热能力影响电机寿命、电机的定额问题、焊接升高片时所用锡剂中的Sn、Pb含量影响焊剂的熔点等是造成直流电机现场烧毁的主要因素。     

发电机非同期并网事故分析及处理对策

介绍一起冶金企业发电机出口开关延时合闸,非同期造成发电机定子绕组烧毁的事故案例。详细分析了事故原因及处理方法,对事故进行了反思,阐述了执行电力行业规程规定的重要性,并由此延伸到行业标准,反事故措施的研究和灵活应用。供业内同行借鉴此事故教训,采取有效措施避免类似事故发生。     

大型高压电机智能监测与健康管理

本文阐述通过引进振动在线信号分析,绕组局放在线监测,两种技术结合,实现高压电机机械传动部件及绕组状态监测,这些数据分析评估,实现高压电机健康管理,降低电机运维成本,避免突发事故。     

变压器绕组变形测试技术应用分析与改进

针对变压器绕组变形测试技术判定准确率低的问题,应用质量分析及控制手段,重点针对被试体接地点的不同、测试相两接地线长短不一、原始数据资料缺乏及不可控未知因素、测试仪无法自校验等技术难点,通过使用自制双线夹固定式接地线,采用绕组电容量数据参考对比分析法,改进测试仪自检方法等一系列控制措施,将变压器绕组变形测试准确率由50%提高至95%。     

电梯与起重机用三相双速异步电动机的设计问题

本文介绍的电梯与起重机用笼型三相异步双速电动机，其特点是定子有两套绕组，每种极数下的转矩倍数与转差率各不相同。详细制定了空载和负载状态下，对磁路进行计算时的多极（ｐ≥６）绕组定子的漏磁通计算方法。推荐并研制成每极每相槽数为整数和分数的新三相绕组图。这些绕组图特别适用于定子有两套绕组的电动机。     

自饱和电抗器控制绕组的改造

从自饱和电抗器调压的原理分析着手，针对原电抗器控制绕组、位移绕组结构配置在设计及制造上的缺陷，阐述了电抗器控制、位移绕组由内外配置改为上下分层配置的理论及改造实践。     

热电厂电动机烧毁的原因及预防

１问题提出在对１９９８年３月～１２月的设备安全分析中,发现莱钢热电厂所属的１１５ｋＷ以上的鼠笼式三相异步电动机共发生烧毁事故７起,直接经济损失十几万元。事故影响了锅炉、风机、发电机的安全、可靠运行,从而对莱钢炼铁厂两座７５０ｍ３高炉的正常生产构成了一定的威胁。虽然每次都对烧毁的电机做了及时的抢修处理,迅速恢复生产,但是使电机不发生或少发生烧毁事故才是治本的方法。２原因分析针对这７起电动机烧毁事故进行了认真分析,现总结体会如下：２．１运行环境恶劣是造成电动机烧毁的主要原因长期以来,锅炉房内煤粉灰尘…     

开关磁阻电机调速系统在空压机、渣浆泵中的应用

高效节能电机与普通电机的功率等级及安装尺寸相同,所不同的是开关磁阻电机调速系统损耗低,效率高,缺相不烧电机。用高效节能电机是从根本上实现节能的最佳途径。     

K2500──2给水泵电机事故分析及其保护装置的改进

本文介绍了马钢公司热电厂 １# 给水泵电机因电源缺相严重烧坏电机转子的事故分析和教训，并改进和完善了大容量高压电机的继电保护装置。     

电动机加热装置的研制与应用

在经过现场试验、分析的基础上,焦家金矿研制并安装应用了电动机加热装置,该装置能够有效地解决高潮湿、多粉尘环境下的开启式交流电动机的加热除湿防潮、保证电动机绝缘、防止因受潮烧电动机的问题。     

Effects of drying methods and additives on structure and function of actin: mechanisms of dehydration-induced damage and its inhibition

Neurofilaments are essential for establishment and maintenance of axonal diameter of large myelinated axons, a property that determines the velocity of electrical signal conduction. One prominent model for how neurofilaments specify axonal growth is that the 660-amino acid, heavily phosphorylated tail domain of neurofilament heavy subunit (NF-H) is responsible for neurofilament-dependent structuring of axoplasm through intra-axonal crossbridging between adjacent neurofilaments or to other axonal structures. To test such a role, homologous recombination was used to generate NF-H-null mice. In peripheral motor and sensory axons, absence of NF-H does not significantly affect the number of neurofilaments or axonal elongation or targeting, but it does affect the efficiency of survival of motor and sensory axons. Loss of NF-H caused only a slight reduction in nearest neighbor spacing of neurofilaments and did not affect neurofilament distribution in either large- or small-diameter motor axons. Since postnatal growth of motor axon caliber continues largely unabated in the absence of NF-H, neither interactions mediated by NF-H nor the extensive phosphorylation of it within myelinated axonal segments are essential features of this growth.     

Practice schedules and the use of component skills in problem solving.

In motor and verbal learning, random practice schedules produce poorer acquisition performance but superior retention relative to blocked practice. We extend this contextual interference effect to the case of learning cognitive procedural skills to be used in problem solving. Subjects in three experiments practiced calculation with Boolean functions. After this acquisition phase, subjects solved problems requiring these procedures. Experiments 1 and 2 demonstrated superior transfer to problem solving for skills acquired under random schedules. In Experiment 3, subjects practiced component skills in a blocked schedule, with one of four tasks—same–different judgment, mental arithmetic, short-term memory, or long-term memory—intervening between trials. For same–different judgments and mental arithmetic, transfer performance was comparable to that found for random schedules in Experiments 1 and 2. This result suggests that the differences depend on processing rather than storage demands of intertrial activity. Implications for theories of problem solving and part–whole transfer are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

连轧中型平立转换轧机主传动创新与应用

介绍了宣钢型棒厂连轧中型生产线平立转换轧机主传动改造实践,将平立转换轧机主传动由共用一台电机的传动方式改为平/立减速机分别由电机驱动的独立传动方式,从而有效根除了原立轧机滑块磨损严重及频繁烧轴承的故障,实现型钢与圆钢的共线生产。     

Nerve damage in leprosy: an epidemiological and clinical study of 396 patients in west Nepal--Part 1. Definitions, methods and frequencies

A historic cohort study was performed to determine the prevalence and incidence rates of nerve function impairment (NFI) as demonstrated by sensory testing with a nylon monofilament and standard tests of motor function. The records of 396 new leprosy patients registering at Green Pastures Hospital, Pokhara, between January 1988 and January 1992 were analysed. The mean follow-up period was 21 months. In all, 36% (141/396) of patients had either sensory or motor function impairment at their initial examination. For each nerve the prevalence of sensory and motor impairment is reported separately. The posterior tibial nerve was the most frequently affected (sensory) nerve (21%). Sensory impairment of the ulnar nerve was found in 17% of the patients; 8.8% had sensory impairment of the median nerve. The overall incidence rate of motor function impairment was 7.5 (5.4-10) per 100 person years at risk (PYAR). Sensory impairment had a significantly higher rate of 13 (10-17)/100 PYAR (rate ratio (1.8 (1.2-2.7), p = 0.0076). Bl patients had a significantly higher incidence rate of nerve function impairment than BT patients (rate ratio 2.3 (1.4-3.7), p = 0.006). Altogether 152/396 (39%) of the patients required corticosteroid treatment for 'recent' or 'acquired' impairment, and 78 of the patients (20%) developed severe nerve function impairment during or after antileprosy treatment. Analysis of potential risk factors for nerve function impairment showed a significant association with the extent of clinical disease expressed as the number of body areas (out of 9) with primary or secondary signs of leprosy (rate ratio 5.0 (1.5-17), p = 0.0091). It was concluded that nerve function impairment is a serious problem, often occurring during or after multidrug therapy. The extent of clinical disease expressed as a count of body areas involved, or of skin or nerve lesions may identify patients who are at increased risk of nerve damage.     

Prolonged severe hemorrhagic shock and resuscitation in rats does not cause subtle brain damage

OBJECTIVE: Some patients who survived severe hemorrhagic shock (HS) seem to exhibit persistent subtle neurobehavioral deficits. This finding is of concern if limited hypotensive fluid resuscitation is applied in hypotensive victims with penetrating trauma. This study was designed to determine whether subtle brain damage would occur in rats after severe prolonged HS. We hypothesized that rats surviving HS with mean arterial pressure (MAP) controlled at 40 mm Hg for 60 minutes would recover with slight permanent brain damage in terms of cognitive function without morphologic loss of neurons and that rats surviving HS with MAP at 30 mm Hg for 45 minutes (60 minutes were not tolerated) would have grossly abnormal brain function and loss of neurons. METHODS: Under light nitrous oxide-halothane anesthesia, spontaneously breathing rats underwent MAP-controlled HS (HS phase I), volume resuscitation to normotension and invasive monitoring to 60 minutes (resuscitation phase II), and observation to 10 days with detailed assessment of cognitive function (observation phase III). Five conscious rats served as normal controls. Three treatment groups were compared: group 1, shams (11 of 12 rats survived to 10 days); group 2, HS at MAP 40 mm Hg for 60 minutes (10 of 17 rats survived); group 3, HS at 30 mm Hg for 45 minutes (10 of 14 rats survived). RESULTS: On post-HS day 10, all normal controls and all survivors of all three groups were functionally normal with overall performance category = 1 (normal) (overall performance category 1 = normal, 5 = death) and neurologic deficit scores < or = 7% (neurologic deficit scores 0-10% = normal, 100% = brain death). Post-HS beam balance, beam walking, and Morris water maze test results in HS groups 2 and 3 showed latencies not significantly different from those in shams and normal controls. Light microscopic scoring of five selectively vulnerable brain regions and other regions in five coronal sections revealed no ischemic (pyknotic, shrunken, eosinophilic) neurons in any of the survivors to 10 days. There was no statistical difference between normal controls, sham animals, and both HS groups in the number of normal neurons counted in the hippocampal CA-1 region in the 10-day survivors. All nonsurvivors died with intestinal necrosis. CONCLUSION: HS at MAP 40 mm Hg for 60 minutes or MAP 30 mm Hg for 45 minutes does not cause subtle functional or histologic brain damage in surviving rats. Controlling MAP at 30 mm Hg carries a risk of sudden cardiac arrest. These data suggest that limited fluid resuscitation, to maintain MAP at about 40 mm Hg, as recommended for victims of penetrating trauma with uncontrolled HS, is safe for the brain.     

Neurophysiologic evaluation of lower motor neuron damage in tetraplegia

We quantitatively investigated the extent of damage to motor neurons in tetraplegic subjects. Numbers of motor units in the patients were significantly lower for thenar, wrist extensor, and biceps brachii as compared to controls. Reduction in counts occurred even when M-response amplitudes were normal. Standard electromyography suggested a surprising frequency of lower motor neuron dysfunction below the level of injury. These results confirm previous reports and add data on motor units in the biceps brachii.     

简析电子热继电器在桥式起重机中的应用

文章介绍了一种由传感器和PLC组成的新型电子热继电器保护装置在桥式起重机中的应用。该保护装置对桥式起重机的三相异步电动机起到保护作用,具有过流、过热、断相等保护功能。性能可靠、稳定,可有效地对异步电动机进行保护,大大减少电动机在使用中的故障。