汽车用爪极发电机新型控制系统

给出几种汽车用爪极发电机控制系统。首先给出双电压发电机系统电路图,并介绍其工作原理。在普通发电机三相绕组中间抽头,并增加可控桥就可以得到另一种新型汽车发电机系统,分别阐述高速和低速时工作原理。最后介绍未来汽车发电机电源系统发展趋势。     

一台220kV电容式电压互感器的故障分析

通过一台电容式电压互感器的故障分析，提出对电容式电压互感器的维护以及预防性试验的一些看法。     

星形接线并联补偿电容器的内部故障分析

电力电容器的故障分为内部故障和外部故障，本文以星形接线的三相电容器组为例。对电容器内部故障产生时电容器的相关电量加以分析。     

全电压关合试验中的控制策略及实现

对10kV架空绝缘线路的短路电流沿线分布和短路故障切除时间以及雷击闪络概率进行了计算和分析，提出了线路用防弧金具和放电箝位绝缘子的工频电弧试验条件：①工频电弧试验用的短路电流有效值和持续时间分为两挡：有效值取20kA，持续时间为0．1s和有效值取10kA，持续时间为0．5s。②工频电弧试验短路次数取5次比较合适。③绝缘导线和试品应按实际情况布置，水泥电杆高度大于2．0m等。     

一族新颖的ZCS-PWM变换器的研究

分析了一个新的零电流开关（ZCS）单元电路的特性。基于这个ZCS的单元电路，构建了一个新的ZCS的Boost电路，并对他们的工作机理进行了分析，而且在这个ZCS单元电路的基础上构建出更多的ZCS变换器。实验和仿真结果验证了理论分析。     

我国低压电器的现状及发展趋势

根据我国低压电器的发展状况,介绍了其主要产品的性能、特点；通过对比分析,指出了目前我国低压电器产品存在的主要问题；结合科学技术的发展,对我国低压电器及其主要产品的发展趋势作了较为详细地论述．     

基于Σ-Δ调制技术的TWACS通信信号特征提取

针对双向工频自动通信系统(TwoWayAutomaticCommunicationSystem———TWACS)通信信号时域检测方法特征量少和抗干扰能力差,而时频分析方法数据处理复杂,装置成本高,提出了基于Σ-Δ增量调制技术提取TWACS通信信号的新方法.该方法在电网信号的调制区域将Σ-Δ调制器输出的1位数据流信息进行累加,将前后两抽样值的差值进行量化编码来代表连续信号所包含的信息,即采用增量调制的方式对相邻两个电网波形的位流和求差值来判断通信信号的有无,同时推导了有效的时域检测算法.对实际电网的测试表明,这种方案能够提取强干扰下电网中的调制信号,扩展了TWACS通信系统的应用范围.     

Effect of heparin on high glucose induced proliferation and expression of matrix metalloproteinases in normal human mesangial cells

Background The pathogenesis of diabetic nephropathy (DN) is a complex pathophysiological process. Its precise mechanism is not fully known. In recent years it has been recognized that synthesis of various extracelluar matrix (ECM) components may increase, and that degradation of ECM may decrease in DN. It was reported heparin could inhibit mesangial cells proliferation in vitro. The main aim of this study is to explore whether heparin inhibits proliferation of mesangial cells grown in high glucose concentration and to measure the effect of heparin on matrix metalloproteinases (MMPs) expression in mesangial cells. Methods The medium contained either low glucose (5 mmol/L) or high glucose (25 mmol/L). The concentrations of heparin in the culture medium were 0, 25, 50, 100, 200 or 400 μg/mL. A metabolic (WST-1) assay was used to measure mesangial cell proliferation and Western blot analysis was used to measure MMPs expression of mesangial cells. Results Normal human mesangial cell (NHMC) proliferation was higher in high glucose (HG) medium than in low glucose (LG) medium. They showed a 1.93 fold expansion after 72 h in high glucose in contrast to a 1.63 fold expansion in low glucose. In the presence of heparin, mesangial cells proliferation was inhibited, which was more obvious at high glucose concentrations than at low glucose concentrations. In high glucose, with heparin concentration of 50, 100, 200 and 400 μg/mL, the mesangial cells showed a 0.61 fold, 0.52 fold, 0.52 fold and 0.41 fold reductions in cell number compared to cells grown without heparin. In low glucose, only concentrations of 200 μg/mL and 400 μg/mL showed reduction in cell number, namely 0.54 fold and 0.45 fold, when compared to cells grown without heparin. In Western blot analysis, MMP₁, MMP₂, MMP₃ and MMP₉ was expressed by mesangial cells expressed in both high and low glucose concentrations, which was more prominent in high glucose medium. Incubation of heparin further increased expression of MMP₁, MMP₂, MMP₃ and MMP₉. Conclusions This study suggests that glucose can accelerate mesangial cell proliferation while heparin can reduce proliferation, being more obvious at high glucose concentrations. Higher glucose concentrations led to increased MMP expression, which may take part in the regulation of mesangial matrix synthesis and degradation. Addition of heparin resulted in a corresponding increase in MMP expression, most notably at high glucose concentrations, indicating a potentially renoprotective role in DN. Foundation item: Project (30370663) supported by the National Natural Science Foundation of China     

Preparation, optical properties and cell staining of water soluble amine-terminated PAMAM G 2.0-Au nanocomposites

The solution chemical and optical characteristics of formation of amine-terminated polyamidoamine dendrimer G2.0(NH₂-PAMAM G2.0)-Au nanocomposites in the aqueous solution of NH₂-PAMAM G2.0 at various mole ratios of Au(III) to NH₂-PAMAM G2.0 were studied by both UV-visible spectrometry and fluorospectrometry. The NH₂-PAMAM G2.0-Au nanocomposites, with a type of structure in which one Au nanoparticle is surrounded by several NH₂-PAMAM G2.0 dendrimers, emit strong bluish violet fluorescence, and are uniform, water soluble and biocompatible as well as very stable in frozen conditions. The size of gold nanoparticles in the nanocomposites is about 2.5 nm and decreases with the increase of NH₂-PAMAM G2.0 concentration. The NH₂-PAMAM G2. 0 plays an important role in acting as host or micro-reactor for Au(III) before Au(III) reduction and acting as dispersant and stabilizer for gold nanoparticles after Au(III) reduction. Preliminary experiments of cells staining to human embryonic lung fibroblast cell lines show that the NH₂-PAMAM G2.0-Au nanocomposites can be used as optical imaging markers for bioanalyses and medical diagnoses.     

The Effects of Dense/Nanometer Hydroxyapatite on Proliferation and Osteogenetic Differentiation of Periodontal Ligament Cells

The objective of this study is to investigate possible effects of nanometer powder of hydroxyapatite on proliferation of periodontal ligament cells. With sol-gel method, the nanometer hydroxyapatite powder were fabricated. The primary periodontal ligcament cells were caltured on dense particle hydroxyapatite and nanometer particle hydroxyapatite. The effects on proliferation of periodontal ligament cell were examined in vitro with MTT （ methyl thiazolil tetracolium） test. The intercellalar effects were observed with scanning electron microscopy and energy dispersive X-ray analyzer. In addition, the influence of two materials on osteogenetic differentiation was determined with measurement of ALP （ alkaline phosphatase ） activity. It is concluded that nanometer hydroxyapatite can promote proliferation and osteogenetic differeraiation of periodontal ligament cells and it may become absorbable agent in osseous restoration.