一种电网电压过零点精确锁相方法的研究

针对电网电压过零锁相时存在的零点漂移和相位延迟问题,提出了一种电网电压过零点精确锁相的方法。通过软件PQ滤波去除ADC采样结果中的零点漂移;通过人为设定一个过零点锁相提前量,可提前预见到电网电压的过零点;然后通过软件自适应补偿算法,实现电网电压过零点的精确检测。详细阐述了该方法的原理和计算过程,在无整流器自充电电压暂变补偿装置上的实验结果证实了所提方法的正确性。     

10kV手车式开关柜防误闭锁装置的标准化验收

为标准化、流程化验收开关柜防误闭锁装置,避免凭经验验收可能导致的随意、遗漏甚至错误等问题,以ABB公司10 kV ZS1型手车式开关柜为例,通过分析其闭锁逻辑和验收方法,建议闭锁验收采用两阶段验收法,并提出一种基于编制开关柜闭锁标准验收卡的验收方案。研究表明,ZS1型开关柜内采用机械和电气闭锁,柜间采用电气闭锁,其防误闭锁装置较为完善、可靠;闭锁验收应满足验收全面、操作量少、验收标准化、不强行用力和操作逻辑清晰的要求。     

机架锁紧方式对三辊连轧管机轧制精度的影响分析

介绍了侧向换辊式三辊连轧管机中两种常用的机架锁紧方式(上下锁紧和斜向锁紧),分析了两种锁紧方式对轧辊定位精度的影响及对轧辊轴向力的承受能力等。分析认为:上下锁紧方式对于三辊连轧管机轧辊定位精度的提高具有积极效果;斜向锁紧方式虽然降低了轧辊的定位精度,但是能承受更大的轧辊轴向力,轧制机架定位更加稳定,是一种更为可靠的机架锁紧方式。     

一种新型级进模具结构设计和工作过程分析

通过对导轨锁定器零件的级进模设计的介绍,阐述了一种新型级进模具结构设计及工作的全过程。具体从制件的冲压工艺出发,进而设计排样方案,确定模具结构,论述了模具的设计过程及冲裁模具结构和运作原理。介绍了该种模具关键部位的结构设计,浮动抬料块、杠杆结构、抽芯式弯曲结构、斜楔驱动滑动式弯曲成形机构。实践证明,此种模具结构设计新颖、模具后期维修快捷,生产操作方便,效率高,冲制的产品质量精度高。     

201厌氧胶锁固扭矩影响因素的研究

通过分析配胶、烘干时间、温度等因素对锁固扭矩的影响,解决神龙飞轮螺栓残余扭矩不合格问题。重新编写了涂胶作业指导书,针对各种影响因素做出改进,保证了神龙201胶涂胶件静态松脱扭矩合格,产品顺利供货。     

软件锁相及其在电工测量仪表中的应用

本介绍软件锁相的特点、设计技巧及其在电工测量仪表中的应用 。     

C beam elements based on the Refined Zigzag Theory for multilayered composite and sandwich laminates

The paper deals with the development and computational assessment of three- and two-node beam finite elements based on the Refined Zigzag Theory (RZT) for the analysis of multilayered composite and sandwich beams. RZT is a recently proposed structural theory that accounts for the stretching, bending, and transverse shear deformations, and which provides substantial improvements over previously developed zigzag and higher-order theories. This new theory is analytically rigorous, variationally consistent, and computationally attractive. The theory is not affected by anomalies of most previous zigzag and higher-order theories, such as the vanishing of transverse shear stress and force at clamped boundaries. In contrast to Timoshenko theory, RZT does not employ shear correction factors to yield accurate results. From the computational mechanics perspective RZT requires C⁰-continuous shape functions and thus enables the development of efficient displacement-type finite elements. The focus of this paper is to explore several low-order beam finite elements that offer the best compromise between computational efficiency and accuracy. The initial attention is on the choice of shape functions that do not admit shear locking effects in slender beams. For this purpose, anisoparametric (aka interdependent) interpolations are adapted to approximate the four independent kinematic variables that are necessary to model the planar beam deformations. To achieve simple two-node elements, several types of constraint conditions are examined and corresponding deflection shape-functions are derived. It is recognized that the constraint condition requiring a constant variation of the transverse shear force gives rise to a remarkably accurate two-node beam element. The proposed elements and their predictive capabilities are assessed using several elastostatic example problems, where simply supported and cantilevered beams are analyzed over a range of lamination sequences, heterogeneous material properties, and slenderness ratios.     

车辆换档控制系统逻辑分析

该文介绍了车辆换档控制系统的逻辑表达式及逻辑分析的一般方法,并采用该方法对某种车辆换档控制系统进行分析,证明该控制系统完全满足设计要求.     

超短激光脉冲技术及其研究进展

首先阐述超短激光脉冲发展的几个历史阶段及其特点．并介绍了飞秒激光器的类型及飞秒脉冲的产生、放大与测量，最后介绍了飞秒激光技术的相关学科。     

Six years of experience with nightly home hemodialysis access

Background: Lynchburg Nephrology Dialysis Incorporated started its nightly home hemodialysis (NHHD) program in September 1997. Purpose: The purpose of this study was to evaluate episodes of exit‐site infections, catheter sepsis, and safety and longevity of accesses for patients doing NHHD. Method: If internal jugular (IJ) catheter was chosen, the patient was started on 2 mg coumadin per day when catheter was placed. If catheter malfunctioned, it was blocked with a thrombolytic agent and coumadin was adjusted to meet a goal international normalized ratio (INR) of 1.5 to 2.25. If the problem persisted, the catheter was exchanged. For catheters, a threaded lock cannula (BD InterLink device, BD) was used to prevent air emboli and infections and a locking device was used to prevent disconnects. If arteriovenous (AV) fistula was used, four buttonholes were established using 16‐gauge needles. If AV graft was used, patients were taught the rope ladder cannulation technique using 16‐gauge needles. Results: As of September 1, 2003, 45 patients have completed training and have performed 27,063 treatments at home. Total catheter time at home was 930 months. Total AV fistula and AV graft times at home were 190 and 20 months, respectively. Upon completion of training, 34 patients were using tunneled IJ catheters, 10 were using AV fistulas, and 1 was using an AV graft. The IJ catheter exit‐site and sepsis infection rates were 0.35 and 0.52 episodes per 1000 patient‐days, respectively. Mean catheter life was 8.5 months with the longest being 66.7 months and the shortest being 0.2 months. The AV fistula and graft exit‐site and sepsis infection rates were 0.16 and 0 episodes per 1000 patient‐days, respectively. Catheter complications included one episode of disconnect due to patient's failure to use the locking device, one episode of central stenosis, and one episode of intracranial hemorrhage, due to prolonged INR, with resolution of symptoms. Conclusion: Data support the fact that tunneled IJ catheters, AV fistulas, and AV grafts are effective and safe permanent accesses for patients on NHHD.