10kV压变高压侧熔丝熔断原因及抑制措施

针对10kV中性点不接地系统的特点,介绍运行中的电磁式电压互感器高压侧熔丝熔断,详细分析了产生故障的原因,分析表明系统在单相接地时或接地故障消失后都可能会产生过电流,系统装设消弧线圈或采用零序电压互感器接线方式都能较好地抑制此过电流。     

聚合物熔体挤出流动中的弹性行为

研究了聚合物熔体挤出过程中出口压力降ΔＰｅｘｉｔ与剪切应力τｗ和挤出胀大比Ｂ三者之间的关系。提出了描述这一关系的方程：ΔＰｅｘｉｔ＝τｗ（Ｂ＾４－１）＾０５／３。初步验证，用该方程计算的ΔＰｅｘｉｔ值与文献提供的毛细管挤出实测值有较好的一致性。     

丙烯腈-丙烯酸甲酯共聚物的合成、结构与性能

采用水相沉淀法制备了含有0~30 m o l%丙烯酸甲酯(M A)的丙烯腈(AN)-丙烯酸甲酯共聚物,采用红外光谱(FT-IR)、差热分析(DSC)、X射线衍射(XRD)、核磁共振(NM R)等方法对聚合产物进行了分析。聚合产物的组成比与投料比相近,随M A比例的增加,分解温度升高,玻璃化转变温度(Tg)降低。含M A 30m o l%的共聚物的分解温度为338.8℃,而熔融温度仅为188.8℃,由于第二单体M A的加入,使得共聚物的熔点降低至分解温度之前,这为改性聚丙烯腈的无增塑熔融纺丝提供了可能性。     

基于新型相位幅值控制的三相PWM整流器双向工作状态分析

介绍了一种三相PWM双向变流器的新型间接电流控制系统。采用变流器前端电压与交流电源电压的滞后角度(?) 作为输入变量的新型相位幅值控制方法,并在闭环系统中将 PI调节器输出作为滞后角(?)。重点分析了单位功率因数下 PWM变流器整流和逆变双向工作原理、调制比mr和滞后角(?)的关系并给出了关系曲线。分析了保证系统稳定工作参量(?)变化范围和约束条件和负载扰动时系统调节过程,得出了系统稳定工作条件。新型相位幅值控制简单且容易实现, 通过仿真和实验验证了该系统可双向工作且能实现单位功率因数。     

Oxidation kinetics and high temperature in-situ observation of the oxidation behaviour of NbSi_2 at 1023 K

Pest oxidation has been known for a long time in refractory transition-metal disilicides such as NbSi2 and MoSi2[1―4]. However, the origin of pesting reaction of these materials is still under debate. Although the pesting phenomenon in NbSi2 has been reported in several works[5―7], a direct study of the mechanism is scarce at the moment. Compared to NbSi2, pesting in MoSi2 has received relatively extensive attention. Mckamey et al.[8] showed fragmentation near 773K occurred easily in as…     

成型加工对熔融插层制备聚合物/粘土纳米复合物的影响

对近年来关于熔融插层法制备聚合物/粘土纳米复合物(PCN)过程中成型加工影响作用的研究进展进行了综述。介绍了不同加工设备对制备PCN的不同影响,并指出双螺杆挤出机是进行熔融混合的最合适的加工设备。概述了停留时间、螺杆结构等加工条件和不同成型工艺对制备PCN的不同作用。并对今后的研究提出了展望。     

从低品位钼精矿中提取钼的新工艺新方法

改进传统处理低品位钼精矿工艺路线，采用简单的设备，低成本，高收率，提取低品位钼精矿中钼，生产制备出晶体工业一级钼酸钠，环保指标达到国家标准。     

Electrochemical impedance spectra of V_2O_5 xerogel films with intercalation of lithium ion

1INTRODUCTION Vanadiumpentoxidexerogel(VXG)filmshavereceivedsignificantattentionduringthelasttwo decadesduetotheirbroadindustrialapplicationsespeciallyinopticalswitchingdevices[1,2],electro chromicdevices[3]andreversiblecathodesforlithi umrechargeablebatteries.ThecommonmethodsofpreparingVXGfilmsareconventionaltech niques,includingpulsedlaserdeposition[4],sput tering[5]andvacuum deposition[6].However,suchmethodsalwaysinvolveconditionsofhightemper atureandvacuum,whichrequirecomplicated…     

Determination of the Composition of the Surface Layer of Binary Metal Alloys

We have analyzed the effect of various parameters (surface tensions of the components, molar volumes of the components and the solution, compression and depression in alloy formation, activity coefficients of the components in the melt) on the shape of the surface tension isotherm as a function of the surface layer composition. We compare the analysis results with experimental data. We propose a method for estimating the composition of the surface layer based on a model assuming an additive variation in the surface tension of the solution as a function of the composition of the surface layer. We have calculated the concentration of the surface-active component in the surface layer of melts in the systems Ge - Sn, Ge - Pb, and Ge - Bi.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 60–67, January–February, 2005.     

船用核动力SGTR事故安全分析

本文论述了船用核动力装置蒸汽发生器传热管断裂事故（SGTR）安全分析的重要性。并以陆奥号核动力商船为例，运用事件树分析技术，对SGTR事故进行了安全分析。得出了事故后可能导致堆芯熔化的事故序列，确定了堆芯熔化数学模型，并进行了定量化分析。最后根据对支配性事故序列和各题头事件重要度的分析，提出了降低SGTR事故导致堆芯熔化发生概率应采取的相应措施。