四辊轧机压下电磁离合器失效原因分析及调整

本文对四辊轧机压下电磁离合器的性能和失效原因进行了详细分析，成功地应用模具法对该离合器进行了调整，保证了离合器的可靠运行。     

电控永磁离合器在起重机起升机构上的应用

起重机起升同步机构的电磁离合器在工作状态时需要长时间通电,导致设备能耗高而且线圈容易发热烧坏、失磁,最终使同步工作的设备失去传递力矩而发生事故.为了克服电磁离合器的缺陷,对此进行了技术改造,改进后的方案将传统电磁线圈改为电控永磁体.由于当起重机起升机构双钩同步运行时,电控永磁离合器处于非工作状态;起升机构单钩运行时处于短时上作,所以具有安全、节能的特点,克服了电磁离合器的缺点,避免了起升机构相关事故的发生,特别适合机械设备主、从传动的同步、单步模式切换.     

1780热轧粗轧电动压下控制原理分析

介绍了1780热轧粗轧电动压下传动的控制原理和电磁离合器的控制原理及其速度的设定,并对离合器控制中存在的问题采取了改正措施,实际运行结果表明,达到了较为满意的效果。     

CA6510车床片式电磁离合器剖析

分析CA6150车床片式电磁离合器的结构、原理、掌握检修维护该类离合器的程序，要领，扩大知识面。     

800公斤·米液压离合器

一、前言 大连钢厂制造的精锻机于1981年投入试生产,这台精锻机夹头的63公斤·米干式电磁离合器,国内未生产,乃用湿式电磁离合器代替。由于机械结构上受到限制,无法给湿式电磁离合器润滑,在使用中承受不了锻钢的冲击震动,经常失灵甚至损坏,造成抱不住钢,产生偏扭使锻件扭麻花,倒棱这道工序不能进行,为精锻机配套的步进炉也不能用,曾迫使我们不得不改变生产工艺,改由蒸汽锤为精锻机开坯,将方坯开成圆坯交给精锻机,严重影响精锻机的生产。     

2800mm热粗轧机压下离合器改造

中铝西南铝业(集团)有限责任公司的2800 mm热粗轧机两侧压下装置原来采用电磁摩擦离合器连接,在联动调整辊缝时,离合器经常打滑,导致辊缝跑偏.改用气动牙嵌式离合器后,没有再出现跑偏现象.这种改造效果良好,不仅提高了产品质量,还取得了良好的经济效益.     

WJL微机自动控制功率调节器在电弧炉上的应用

中小型电弧炉电极升降调节器已历经三相异步电动机手动调节、电机——放大机、可控硅——直流电机、可控硅——电磁转差离合器、可控硅——力矩电机等型式,就其性能及使用情况而言,后三种调节器较为先进,因而应用较普遍。我厂5吨电弧炉原用可控硅——电磁转差离合器,其下降是以横臂偏重为动力,以加速度下降,因而系统超词较大;电磁转差离合器线圈的时间常数较大,响应较慢;从维护角度上看,离合器铝质电枢易受热变形,影响电极升降。另外,测速环节一旦损坏,会引起系统失控,电极超速下坠,折断电极,损坏蜗轮箱。1989年4月引进了由西安冶金设备总厂生产的 WJL 型微机自动功     

涟钢60t电炉电极升降调节系统测试分析

采用计算机数据测试系统对涟钢进口６０ｔ电弧炉电极升降调节系统进行了测试，得到了电流、电压感应叠加信号及电磁滑差离合器转速数据，经分析后可得到电极升降调节系统的有关性能参数。     

交流调速方式驱动技术的综合比较

本文简述了交流感应电动机速度控制的各种方式,如变极变换方式、定子电压控制方式、定子频率控制方式、电磁离合器控制方式和双频控制方式等,并对各种调速方式的性能特点,根据不同控制对象和工艺要求,用列表方法进行了综合比较。     

济钢中板厂2#矫直机压下系统改造

济钢中板厂2#矫直机压下系统由于蜗杆热处理不良及蜗杆与压下减速机输出轴不同心等原因,引起蜗杆断裂,并因电磁离合器打滑引起辊缝横向漂移造成钢板矫直瓢曲、矫废等问题。为此,将蜗杆与压下减速机输出轴间的连接改为半齿半刚型联轴器,改变蜗杆材质但保持硬度不变,去除电磁离合器,横向辊缝调整做周期性微调等,消除了设备隐患和产品质量问题。     

Improved Explicit Method for Structural Dynamics

An explicit method, which simultaneously has the most promising advantages of the explicit and implicit methods, is presented. It is shown that numerical properties of the proposed explicit method are exactly the same as those of the constant average acceleration method for linear elastic systems. However, for nonlinear systems, it has unconditional stability for an instantaneous stiffness softening system and conditional stability for an instantaneous stiffness hardening system. This conditional stability property is much better than that of the Newmark explicit method. Hence, the proposed explicit method is possible to have the most important property of unconditional stability for an implicit method. On the other hand, this method can be implemented as simply as an explicit method, and hence, possesses the most important property of explicit implementation for an explicit method. Apparently, the integration of these two most important properties of explicit and implicit methods will allow the proposed explicit method to be competitive with other integration methods for structural dynamics.     

Eigensolution Method for Structures with Multiple or Close Eigenvalues

A solution method that can calculate the eigenproblem for large structures with multiple or close natural frequencies is presented. The method is formulated by the accelerated Newton-Raphson method for the transformed problem. The method can calculate the natural frequencies and mode shapes without any of the numerical instability that may be encountered in the inverse iteration process with a shift of the well-known methods, such as the subspace iteration method or the determinant search method, which have been widely used for solving an eigenproblem. The efficiency of the method is verified by comparing convergence and solution times for numerical examples with those of the subspace iteration method and the determinant search method.     

纯铝中硅铁铜镓钛的光度法快速测定

提出了用一份制备液同是测定纯铝中硅，铁，铜，镓钛的新方法。用氧化钠溶解试样，盐酸酸化，然后用硅钼蓝光度法测定硅，邻二氮杂菲光度法测定铁，双环己酮草酰二腙光度法测定铜，丁基罗丹明Ｂ光度法测定镓，二安替比啉甲烷光度法测定钛，利用该方法分析铝标样，其结果与标准值合合，该方法简便，快速，准确。     

Comparison of three methods for determining aflatoxins in melon seeds

The suitability of 3 methods for determining aflatoxins in melon seeds was examined. The first 2 are the Contaminants Branch (CB) method and the Best Foods (BF) method, both official methods for determining aflatoxins in peanuts and peanut products. The third method, the modified CB method-Rapid Modification of the Cottonseed (CB-RCS-Mod) method, devised in this work, was derived by combining steps from the CB method and the Rapid Modification of the Cottonseed method. The CB method was superior to the other 2 methods for quantitation of aflatoxins. It gave better recoveries and cleaner extracts that exhibit less fluorescent interference for thin-layer chromatography (TLC) than the BF method. Also, its solvent efficiency was better than that of the CB-RCS-Mod method. With the CB method, recoveries from spiked samples were 85.0% for aflatoxin B1 and 90.0% for aflatoxin B2. Recoveries of G aflatoxins were more variable, averaging 90.0% for aflatoxin G1 and 72.5% for aflatoxin G2. Total aflatoxin recovery was 86.5% for the CB method. At a low aflatoxin contamination level (8 micrograms B1/kg sample), aflatoxin B1 was detectable by the CB method but not by the BF method. Detection of aflatoxins in BF method sample extracts by TLC was not improved by the use of chloroform-acetone-water (88 + 12 + 1), benzene-ethanol-water, or ether-methanol-water (96 + 3 + 1) in place of the standard chloroform-acetone (88 + 12) developer. Use of ether-methanol-water (96 + 3 + 1) for detecting aflatoxins by TLC in the CB method extracts increased interference compared with the standard chloroform-acetone (88 + 12) developer.     

Colony size can be used to determine the MIC of fluconazole for pathogenic yeasts

This report describes a new statistical method for estimating the MIC of fluconazole for yeasts pathogenic to humans. This method is based on comparison of the colony sizes on solid media containing different concentrations of fluconazole. By this method, the MICs of fluconazole for 10 yeast strains were comparable to results obtained by the standard method recommended by the National Committee for Clinical Laboratory Standards. This method is simple to perform and easy to interpret. The turnaround time is faster than other methods. The method should be applicable to the determination MICs of other antifungal drugs for yeasts.     

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In order to improve the accuracy of calculation for erosion of lining of blast furnace hearth and shorten the calculation time, quasi- 3D dimensional method was used for calculation of erosion for shaft section of lining of blast furnace hearth. The calculation used the correction item of circumferential heat transfer to replace circumferential heat transfer and gave the treatment method for correction item of circumferential heat transfer. The erosion model for axial section of lining of hearth was established by using ANSYS software. The successive approximation method was adopted to modify the boundary of erosion, then the steady- state calculation was done. The calculation steps of quasi three dimensional method was described. The difference between the models established by 2D method and quasi- 3D method was analyzed by actual example. The simulation results show that quasi- three- dimensional method has a smaller amount of calculation but higher accuracy than two- dimensional method, which verifies that quasi- three- dimensional method is suitable to analysis of erosion.     

How should nuclear cardiologists prepare for the next 5 to 10 years?

We developed a simple and easy nonsurgical percutaneous method for autografting parathyroid tissue into the forearm muscles. This method was applied to 30 patients suffering from secondary hyperparathyroidism who were then refractory to medical treatment. The operative results were then compared with 16 patients who underwent treatment using Wells' method. The graft "take," judged by a significant intact parathyroid hormone (PTH) ratio (> 1.5) between grafted and nongrafted arm vein blood, was 82% for the percutaneous method group and 75% for the Wells' method group, respectively. The percentage of recurrent hyperparathyroidism necessitating a subtotal removal of the autograft was equal in the two groups. No complications were noted for either method. Wells' method can thus be replaced by this simple and easy nonoperative method.     

渗碳层厚度及碳含量的表征方法

为了衡量渗碳工艺是否合适,需要对渗碳层的厚度及碳含量进行准确测定。实验探索了一种能够快速准确地表征渗碳层厚度及碳含量的方法,并以18CrNiMo7-6钢为例进行了相关测定。首先,利用化学法验证了电子探针法测定渗碳层的准确性。其次,对比了电子探针法与硬度法的结果,两种方法测定渗碳层厚度的结果一致,电子探针法同时给出了不同渗碳层厚度与碳含量的变化曲线。再次,利用金相法观察了渗碳层及基体的微观组织,由于渗碳层厚度超过了金相法的测定范围,无法做出结果对比。综上所述,电子探针法既可以测定渗碳层的厚度,也可同时得到相应厚度渗碳层的碳含量,是准确表征渗碳层的有效方法,可以作为衡量渗碳工艺是否合适的依据。     

Simplified Method for Calculating Lateral Distribution Factors for Live Load Shear

The simplified equal distribution factor (EDF) method for live load shear presented in this study originates from Henry’s method, a method that has been used in Tennessee for nearly forty years. Henry’s method allows for equal distribution of live load effects in all beams. This study focused on a careful examination and modification of Henry’s method by comparing shear distribution factors obtained from Henry’s method with those from finite element analysis and other code-specified methods for actual bridges. Twenty-four Tennessee bridges with six different types of superstructures were used in the study. The effects of structural parameters on the shear distribution factors were also studied. Modification factors to Henry’s method were proposed based on the comparison study. The proposed modification factors include structure type factors that are applied to different types of superstructures and a skew correction factor that is used to account for the effects of skew angle for skewed bridges. With proper modifications, the simplified EDF method can produce very reasonable and reliable distribution factors for live load shear.     

Evaluation of therapeutic effect using enhanced MRI in lung cancer: evaluation of methods in terms of necrosis

To evaluate therapeutic effect in terms of necrosis or cavity, enhanced MRI was performed in 40 lung cancer patients treated by conservative therapy. We provided the reduction ratio of the viable tumor as calculated by a volume method and a cross-sectional method. In the volume method, the volume of necrosis was subtracted from the volume of the tumor, and in the cross-sectional method, the product of the longest diameter and widest perpendicular diameter of necrosis was subtracted from the product of the longest diameter and widest perpendicular diameter of the tumor. We then examined whether we could substitute the cross-sectional method for the volume method. The reduction ratios of viable tumor calculated by the two methods were in good correlation. The limits of agreement of each method and their repeatability coefficients were considered small enough for clinical use. Therefore, we concluded that the cross-sectional method could be used in place of the volume method for clinical purposes. In evaluating therapeutic effect in terms of necrosis when using contrast-enhanced MR imaging, the reduction ratio of the viable tumor determined by the cross-sectional method can be substituted for that determined by the volume method.