冷轧机组卷取系统的缺陷分析及优化改造

莱钢1500mm冷轧机组卷取机由于卷筒中楔形块的设计不合理,导致设备故障率较高。将原来的铜质楔形块改成42CrMo,改造楔形块结构及润滑油路,增设轧机卷筒冷却装置,改造轧机挤于辊,改造后设备运行状况良好,生产作业率提高了10％。     

一起隔离开关支柱绝缘子断裂的原因分析及防范措施

高压隔离开关是电力系统中重要的开关电气设备，由于隔离开关结构相对简单、缺陷易于处理，因此隔离开关的日常管理和维护不太受人重视。但是近年来，隔离开关的支柱绝缘子发生的故障率呈上升趋势。重点探讨了隔离开关支柱绝缘子故障的预防措施。     

钢丝绳用楔形接头的选择及应用

在采用钢丝绳连接或传动的设备中，楔形接头固定钢丝绳端部是继绳夹固定外，应用最多的固定方式，其结构简单，安装方便，性能可靠。一般起重机钢丝绳一端固定在卷筒上，另一端通常采用楔形接头固定在起重机小车架或者吊钩滑轮组上。针对楔形接头在起重机械行业的应用情况进行分析讨论，提出如何正确选用钢丝绳楔形接头，如果标准楔形接头无法满足使用要求时，采用非标楔形接头应注意哪些事项。总结了楔形接头在安装使用过程中存在的一些不合理或者不规范的情况，易造成钢丝绳断丝、断股、楔形接头损坏等情况出现。在选用楔形接头时，尤其是连接重要用途钢丝绳时，在满足安装方式、强度等条件的情况下，要注意钢丝绳在楔形接头内的安装方式，按照楔形接头的工作原理，钢丝绳应正确引入楔形接头内，保证钢丝绳、楔形接头等相关件的受力方向和有效接触形式，避免错误的安装方式导致相关件的过早疲劳破坏或失效，造成设备的故障或者存在安全隐患。     

35kV隔离开关分合闸故障分析及处理

介绍了德兴铜矿变电站35k V隔离开关故障,并对故障情况进行分析,寻找解决隔离开关分合闸故障率高的问题,从变电站发生的各种分合闸故障找出最主要的影响因素,并对此因素进行攻关,在变电站实施攻关措施,并在各变电站加于应用,有效地解决了变电站35k V隔离开关分合闸故障次数多的问题,预防和杜绝不能正常分合闸跳闸现象,降低变电站故障次数,保障了变电站安全稳定运行。     

MR M型有载分接开关连续调档故障分析与处理

变压器有载分接开关在电力系统、工业生产中使用广泛,随之而来的故障率会不断增加。通过马钢LF炉有载分接开关的远程连续调档故障,从有载分接开关的原理出发,简单说明有载分接开关和ED机构的工作原理,进而详细分析MR公司M型有载分接开关及远程连续调档故障的查找和处理方法。     

原料区露天皮带拉绳开关改造

烧结厂原料区露天皮带拉绳开关在使用过程中经常出现故障,且故障查找时间长。通过对露天皮带拉绳开关进行改造,降低了拉绳开关故障率,减少了维修人员工作量,降低了材料消耗。     

HCDSPZ-9000kVA/35kV单相电炉变压器的改造

文章介绍了单相电炉变压器的性能及调压原理,采用CM型正反调开关进行27个档位调节;8字形绕组主串变结构满足二次恒压差变化;以及该变压器的故障现象,原因分析和改造措施.     

变压器油色谱分析及故障判断

特征气体组分、成分超标分析和比值判断法等色谱分析技术可判断变压器故障类型及故障点温度,运用这种有效的技术手段成功地诊断出某110kV变电站#1主变有载分接开关C相极性开关烧蚀的故障.     

变坟器有载开关故障原因浅析与预防

近几年来，因电业部门采取分时计价政策，我玫衽分时供电，帮此，变压器有载开关操作过度频繁，引起故障增多，故障的程度加重。本文论述了相起有载开关故障的主要原因和提出了预防措施。     

铸轧机辊缝调整装置的结构优化

辊缝调节装置是铝连续铸轧机的关键部件之一。本文对核心零件楔形块的两种不同结构形式进行受力分析和比较，从加工制造的角度优化了楔形块的结构，从而使该装置的加工工艺性更为合理。     

Verification of the omni wedge technique

The optimal field shape achieved using a multileaf collimator (MLC) often requires collimator rotation to minimize the adverse effects of the scalloped dose distribution the leaf steps produce. However, treatment machines are designed to deliver wedged fields parallel or perpendicular to the direction of the leaves. An analysis of cases from our clinic showed that for 25% of the wedged fields used to treat brain and lung tumors, the wedge direction and optimal MLC orientation differed by 20 degrees or more. The recently published omni wedge technique provides the capability of producing a wedged field with orientation independent of the orientation of the collimator. This paper presents a comparison of the three-dimensional (3D) dose distributions of the omni wedged field with distributions of wedged fields produced using both the universal and dynamic wedge techniques. All measurements were performed using film dosimetry techniques. The omni wedge generated fields closely matched the conventional wedged fields. Throughout 95% of the irradiated volume (excluding the penubra), the dose distribution of the omni wedged field ranged from +5.5 to -3.5 +/- 1.5% of that of the conventionally wedged fields. Calculation of the omni wedged field is as accurate as conventional wedged field calculation when using a 3D treatment planning systems. For two-dimensional treatment planning systems, where one must assume that the omni wedged field is identical to a conventional field, the calculated field and the delivered field differs by a small amount.     

Validity of universal wedge equation over the range of 60Cobalt to 25 MV photon beam energies

PURPOSE: Evaluating the validity of the universal wedge equation over the range of 60Cobalt (60CO) to 25 MV photon beam energies. METHODS AND MATERIALS: The universal wedge equation relates the beam weight of the wedged field to the effective wedge angle produced by combining the wedged field to the nonwedged field and is expressed as tan (theta) = B tan (theta w), where B is the normalized weight imposed on the wedged field, theta w is the maximum wedge angle of the wedge filter, and theta is the effective wedge angle. The isodose distributions from 60Co to 25 MV photon beam energies were used. For each photon energy, the isodose distributions of wedged and nonwedged fields were combined in different proportions. The effective wedge angle was determined from each resultant isodose distribution. RESULTS: The relationship between the weight of wedged field and the effective wedge angle was found to be nonlinear for wedge filters with maximum wedge angle greater than 30 degrees. The universal wedge equation predicts the effective wedge angle to within 2 degrees compared to the measured value.     

Contrast-medium-induced ventricular fibrillation: arrhythmogenic mechanisms and the role of antiarrhythmic drugs in dogs

RATIONALE AND OBJECTIVES: Small electrolyte additions to a nonionic contrast medium reduce the risk of ventricular fibrillation (VF) during wedged catheter injection of a contrast medium. The current study was designed to further investigate contrast-medium-induced VF by studying the effect of pretreatment with different antiarrhythmic drugs. METHODS: During a simulated wedged catheter situation, iohexol was injected into the anterior descending branch of the left coronary artery in five open-chest, anesthetized dogs pretreated with lidocaine, propranolol, amiodarone, almokalant, or verapamil. RESULTS: Wedging the catheter for 60 sec did not induce VF. However, all 15 wedged catheter injections with iohexol induced VF within 28 sec (19 +/- 1 [mean +/- standard error of the mean]) despite pretreatment with antiarrhythmic drugs. Prior to VF, conduction was slowed and monophasic action potential duration lengthened in the contrast-medium-perfused myocardium, although no significant changes occurred in the control area. CONCLUSION: The combination of catheter wedging and long-lasting contrast medium injection has a high risk of causing VF. Although adding a small amount of electrolytes to nonionic contrast media can reduce the risk of VF, antiarrhythmic drug therapy may not have a protective effect.     

The influence of cardiac frequency on the hemodynamic consequences of mitral stenosis (author's transl)

In eleven patients with isolated mitral stenosis and regular sinus rhythm a right cardiac catheterization was performed and the wedged pulmonary capillary pressure recorded at rest and during electrical pacing of the right atrium at successive frequencies of 100, 120, 140, and, occasionally, 160 and 180 beats/min, while cardiac output was estimated by the Fick's principle. In all cases a significant elevation of pulmonary capillary pressure with a simultaneous reduction in cardiac output was obtained. The rise of wedged pulmonary pressure was proportional to the increment in cardiac frequency and related also to the calculated area of the mitral valve. The influence of active atrial contraction upon pulmonary pressure and cardiac output is discussed and comparisons with other studies are made. Emphasis is made on the value of atrial pacing as a diagnostic method in mitral stenosis, especially in cases in whom classical effort manoeuvres can not be applied or are insufficient to rise cardiac frequency.     

A successful surgical repair of congenital mitral stenosis due to commissural papillary muscle fusion]

A case of congenital mitral stenosis, patent ductus arteriosus, pulmonary hypertension was reported. At one year of age, the patient underwent surgical division of PDA because of persistent left heart failure. She went well after the operation. At seven year of age, she was readmitted to our hospital for easy fatigability. The cardiac catheterization revealed remarkably elevated pulmonary arterial pressure and pulmonary capillary wedged pressure. She underwent a surgical intervention for the mitral stenosis at eight year of age. At operation, the mitral valve exhibited the characteristics of type IIc according to Carpentier's classification: thickened and dysplastic leaflet, extremely short chordae tendanae fused with papillary muscles, obliteration of interchordal space and hypertrophic two papillary muscles. We replaced the valve with 23 mm Carbomedicus prosthetic valve because it seemed to be difficult to repair the native valve satisfactorily without residual stenosis or insufficiency. Her postoperative course was uneventful and the pulmonary arterial pressure and pulmonary capillary wedged pressure decreased remarkably one year after the operation.     

热轧带钢半无头轧制动态变规格过程张力设定

在常规连轧张力公式和冷连轧动态变规格张力公式的基础上,分析了热轧带钢半无头轧制工艺动态变规格过程张力设定值变化规律的要求,合理确定了张力设定变更点,并给出热轧带钢半无头轧制工艺动态变规格过程楔形区张应力的设定计算公式。     

A three-dimensional algorithm for optimizing beam weights and wedge filters

An essential step towards optimizing and automating radiation therapy treatment planning is to develop an effective algorithm to find the optimal beam weights and wedge filters for a given set of beam directions and modalities. This problem is solved by introducing a variable transformation based on the universal and omni wedge principles. Instead of directly optimizing an objective function with respect to wedge angles and orientations, each field is first decomposed into a superposition of an open field and two orthogonal wedged fields. This transforms the problem of finding J beam weights, wedge angles, and orientations to that of optimizing a system with 3J beam weights (J open beams and 2J nominal wedged beams), where J is the total number of incident beam directions. An iterative algorithm based on a method originally developed for image reconstruction is used to find the 3J beam weights. The technique is applied to a few clinical cases. Treatment plans are improved compared to those obtained through the conventional manual trial and error planning process. In addition, planning time and effort are greatly reduced.     

Dosimetry of wedged fields with asymmetric collimation

Shaping of wedged fields with asymmetric collimators (independent jaws) produces dosimetric effects which need to be taken into account when calculating isodose distributions and accelerator monitor units. These effects were studied using ion chamber dosimetry in a water phantom. Wedged fields of 30 degrees to 60 degrees wedge angles were shaped by an asymmetric collimator. A system of dose calculation was developed to take into account the changes in dose in the open portion of the field. The formalism utilizes regular symmetric field parameters (e.g., Sc, Sp, and TPR). Calculated point doses and profiles agreed well with the measured data.     

Additivity of the effects of retention interval and context change on latent inhibition: Toward resolution of the context forgetting paradox.

Three experiments with rats examined retention interval and context switch effects factorially in the latent inhibition paradigm. In Experiment 1, a 28-day retention interval abolished a context switch effect on latent inhibition. In Experiment 2, re-exposure to the contexts before conditioning re-established the context switch effect at the 28-day interval. In this case, the retention interval and context switch effects were additive: Latent inhibition was weakest when the retention interval and context switch were combined. Experiment 3 replicated the context switch effect at the 28-day interval. The results suggest that context switch and retention interval effects may be based on the same process. Context switch effects may weaken over time because physical contexts are embedded in superordinate temporal contexts; animals fail to retrieve physical context when the temporal context changes. This view helps resolve a paradox that has been noted for contextual change theories of forgetting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Graffiti: some clinical observations

Hepatic angiosarcoma, recently discovered in a large series of vinyl chloride workers, demonstrates characteristic angiographic and radionuclide changes. Tumors exhibiting central hypovascularity with puddling are usually surrounded by a peripheral stain. A negative peripheral defect is demonstrated on hepatic scan. Healing hepatic infarction secondary to wedged hepatic venography creates a false-positive lesion on angiography similar to angiosarcoma. Splenomegaly and systemic venous hypertension develop in a number of these patients.