计算机电源高效率DC/DC变换器分析

归纳和总结了3种计算机电源Dc/Dc变换器,并对其进行效率分析。重点介绍了高效率的有源箝位正激变换器和LLC谐振变换器。指出有源箝住正激变换器和LLC谐振变换器可大幅提高计算机电源效率。     

MTS TestStar疲劳试验机上预制钢轨轨腰水平疲劳裂纹的研究

介绍了在MTS TestStar四立柱疲劳试验机上疲劳预制钢轨实物轨腰水平裂纹的研究。对应具体的轨型,设计并加工了用于疲劳预制钢轨轨腰水平裂纹的夹具。改变夹具工作部分的形状并去除与轨腰对应的夹具部分,可用于疲劳预制对应轨型的轨腰裂纹。试验采用位移控制方式。     

一种实现经济型数控车床自动钻孔的夹具

经济型数控车床约占数控机床总量的25％。由于其结构及其经济性,尾座没有自动进给功能,零件需钻孔时,按常规的做法,仍然是和在普通车床上一样在尾座上安装钻头,通过转动尾座手轮进行钻孔。批量生产中,操作者的劳动强度增大,生产效率较低,而且孔的深度尺寸精度也不高。鉴于此,本文特设计了一套能实现经济式数控车床自动钻孔的夹具,以进一步完善经济型数控车床的自动化功能,既保证了产品的质量又较好地捍高了牛产妁率。     

压板式夹具加工磨削刀具深孔的方法

该文介绍在磨削刀具深孔时所采用压板式夹具的加工方法,其磨削效率高,既能提高磨削刀具深孔基准的精度,降低废品率,又可节约辅助工时,延长夹具的使用寿命。     

电子秤护线盘零件车铣加工工艺探析

在分析护线盘零件结构特征的基础上,设计了其加工的工艺方案,提出了后续工序加工中防薄壁变形的工艺问题,设计了弹性内胀夹紧以及引线槽侧立铣削加工的简易夹具,并就其设计制作的要点进行了分析说明,有效地保证了实际加工的需要。     

基于ADAMS的杠杆夹紧器的仿真与分析

基于ADAMS虚拟样机仿真软件平台,对拟设计的一种钢厂用杠杆夹紧器进行了建模仿真及运动学和动力学分析,得到了杠杆夹紧器工作下的运动曲线及夹紧力曲线,并比较了有阻尼和无阻尼情况下的夹紧力及连杆的速度、加速度,为夹紧器的进一步优化设计提供了参考。     

铸钢索夹节点在弦支穹顶结构中的应用

铸钢节点作为一种新型的节点形式正越来越多地应用于空间钢结构中.常见的铸钢节点形式有铸钢球节点、铸钢相贯节点及铸钢支座节点.结合武汉体育馆弦支穹顶钢屋盖工程,介绍了另一种铸钢节点--铸钢索夹节点,并对该类铸钢节点的设计、有限元计算与分析进行了探讨,以期给类似工程设计提供参考.     

细胞膜离子通道及其检测技术的研究进展

作对细胞膜离子通道的特性、种类及其电压门控钠、钾离子通道的分子结构与功能，以及离子通道在新药开发中的意义和离子通道检测技术的研究新进展进行综述和讨论。并着重介绍了检测细胞膜离子通道功能的新技术--膜片钳技术及其与逆转录多聚酶链式反应技术(RT-PCR)结合在生命学科中的应用。     

Mechanism of action of two insect toxins huwentoxin-III and hainantoxin-VI on voltage-gated sodium channels

Selenocosmia huwena and Selenocosmia hainana are two tarantula species found in southern China. Their venoms contain abundant peptide toxins. Two new neurotoxic peptides, huwentoxin-III (HWTX-III) and hainantoxin-VI (HNTX-VI), were obtained from the venom using ion-exchange chromatography and reverse-phase high performance liquid chromatography (RP-HPLC). The mechanism of action of HWTX-III and HNTX-VI on insect neuronal voltage-gated sodium channels (VGSCs) was studied via whole-cell patch clamp techniques. In a fashion similar to δ-atracotoxins, HNTX-VI can induce a slowdown of current inactivation of the VGSC and reduction in the peak of Na⁺ current in cockroach dorsal unpaired median (DUM) neurons. Meanwhile, 10 μmol/L HNTX-IV caused a positive shift of steady-state inactivation of sodium channel. HWTX-III inhibited VGSCs on DUM neurons (concentration of toxin at half-maximal inhibition (IC₅₀)≈1.106 μmol/L) in a way much similar to tetrodotoxin (TTX). HWTX-III had no effect on the kinetics of activation and inactivation. The shift in the steady-state inactivation curve was distinct from other depressant spider toxins. The diverse effect and the mechanism of action of the two insect toxins illustrate the diverse biological activities of spider toxins and provide a fresh theoretical foundation to design and develop novel insecticides.     

Single-stage active clamp power factor correction AC/DC converter

A simple single-stage AC/DC converter circuit with active clamp is presented. The operation theory and state are analyzed. The experimental results show that the voltage across main switch can be clamped to a certain value,and zero voltage switching (ZVS) can be achieved. The voltage stress and switching loss are both decreased. In range of the whole load,power factors can be always more than 97%,and the highest efficiency can reach 88%.