利用RTDS测试输电线路行波故障定位装置

针对输电线路行波故障定位装置的测试问题,利用ＲＴＤＳ仿真一个小型的５００ｋＶ环网,在其线路上设备各种特征故障,来测试输电线路行波故障定位装置的性能,并结合高精度测量仪分析其误差,在分析误差的基础上,结合ＲＴＤＳ的计算步长和Ｄ／Ａ转换时间等,总结出一种提高ＲＴＤＳ波形精度的补偿算法,输入补偿算法后的数据,获得了较理想的仿真结果。模拟试验表明,用ＲＴＤＳ对该装置进行试验是一种较好的方法。     

简析共产主义水库水源地水环境形势与保护对策

通过对共产主义水库水源地周边生态环境现状及污染源的实地调查,结合对水库及上游来水的水质监测结果分析,得出影响共产主义水库水环境的主要因素为面源污染,包括水产养殖废水、农药化肥、生活污水、生活垃圾以及畜禽粪便等污染源。针对污染源的形成的原因,提出了拆除土坝禁止投料养殖、建造污水处理工程和生活垃圾收集站以及开展水生态修复等系列保护对策,以达到改善和稳定共产主义水库水质,保证其满足各项水功能的要求。     

应力波因子技术中一些问题的回顾和展望

首先就正在发展中的应力波因子技术的起源和思想进行了回顾,然后就该技术的早期工作进行了系统的归纳和评价,最后就该技术应用和理论研究的现状进行了评论并指出了将来应解决的问题。     

微系统封装热问题探讨

电子机械系统微型化就是把不同功能的各种元器件封装到紧密空间, 目的在于分析有关封装设计负载下降的方案. 采用计算机程序配置发生器生成系统的热传递路径的几何构造和平面基板上热分布作为样本的方法,把这些构造的温度解决方案压缩进入快速估计公式中,使封装设计能够自由地进行相关的热传递分析. 通过涉及到几何学方面复杂的传热路径的系统热传递分析,快速完成每个设计改变. 结果表明系统微型化热设计,就是系统构造和整个向周围环境热损耗之间的耦合,就是热通过自然对流和辐射,从系统外壳上的一个区域向周围扩散. 最后得出结论,外壳材料热传导性跨越的参数领域,以及系统的性能长度为系统级热传递领域,对系统的构造敏感.性能长度对塑料封装系统而言约为1cm,对陶瓷及合金封装约为3~10cm,在铜或铝金属包层系统为10~40 cm.     

Acid- and base-catalyzed hydrolyses of aliphatic polycarbonates and polyesters

Poly(propylene carbonate) (PPC) was synthesized by the zinc glutarate catalyzed copolymerization of carbon dioxide and propylene oxide (PO). Hydrolytic degradability of the PPC polymer was examined in tetrahydrofuran solutions containing 10 wt.% acidic or basic aqueous solutions of varying pH using viscometry and GPC analysis. Further, the hydrolysis behaviors of all PPC solutions were compared with those of poly(com/scidirimg/entities/25b.gif" alt="var epsilon" title="var epsilon" border="0">-caprolactone) (PCL) and poly(d,l-lactic acid) (PLA). All polymers studied show higher degradability in strong basic conditions than in strong acidic conditions, but very low degradability in moderate acidic, basic and neutral conditions. Moreover, PPC is degraded less in strong acidic conditions than the polyesters, while in strong basic conditions, the polycarbonate is more easily degraded. The difference in degradabilities of these polymers in acidic conditions is associated with the different nucleophilicities of their carbonyl oxygen atoms, while in basic conditions the differences are associated with the different electrophilicities of the corresponding carbonyl carbon atoms. With regard to the hydrolysis results and the structural and chemical nature of the polymer backbones, degradation mechanisms are proposed for the acid- and base-catalyzed hydrolyses of PPC, PCL and PLA.     

A novel route to α,ω-telechelic poly(-caprolactone) diols, precursors of biodegradable polyurethanes, using catalysis by decamolybdate anion

A new convenient route for the synthesis of poly(com/scidirimg/entities/25b.gif" alt="var epsilon" title="var epsilon" border="0">-caprolactone) (PCL) with α,ω-telechelic diols' end-groups is presented. Synthesis of α,ω-telechelic PCL diols (HOPCLOH) was achieved by ring-opening polymerization (ROP) of com/scidirimg/entities/25b.gif" alt="var epsilon" title="var epsilon" border="0">-caprolactone (CL) catalyzed with ammonium decamolybdate (NH₄)₈[Mo₁₀O₃₄] and using diethylene glycol (DEG) as initiator. Obtained HOPCLOH was characterized by ¹H and ¹³C NMR, FT-IR, GPC and MALDI-TOF. Comparative studies demonstrate that ammonium decamolybdate (NH₄)₈[Mo₁₀O₃₄] is better catalyst than Sn-octanoate (SnOct₂) toward CL polymerization in presence of DEG, under the conditions tested. A biodegradable poly(ester-urethane-urea) derivative was efficiently prepared from synthesized HOPCLOH. Obtained polymer shows minor differences with respect to the properties recorded for a poly(ester-urethane-urea) obtained from commercial HOPCLOH.     

Electrochemically reduced titanocene dichloride as a catalyst of reductive dehalogenation of organic halides

We have studied a reaction between the reduced form of titanocene dichloride (Cp₂TiCl₂) and a group of organic halides: benzyl derivatives (4-Xcom/sd/entities/sbnd" class="glyphImg">C₆H₄CH₂Cl, X = H, NO₂, CH₃; 4-Xcom/sd/entities/sbnd" class="glyphImg">C₆H₄CH₂Br, X = H, NO₂, PhC(O); 4-Xcom/sd/entities/sbnd" class="glyphImg">C₆H₄CH₂SCN, X = H, NO₂) as well as three aryl halides (4-NO₂C₆H₄Hal, Hal = Cl, Br; 4-CH₃O-C₆H₄Cl). It has been shown that the electrochemical reduction of Cp₂TiCl₂ in the presence of these benzyl halides leads to a catalytic cycle resulting in the reductive dehalogenation of these organic substrates to yield mostly corresponding toluene derivatives as the main product. No dehalogenation has been observed for aryl derivatives. Based on electrochemical data and digital simulation, possible schemes of the catalytic process have been outlined. For non-substituted benzyl halides halogen atom abstraction is a key step. For the reaction of nitrobenzyl halides the complexation of Ti(III) species with the nitro group takes place, with the electron transfer from Ti(III) to this group (owing to its highest coefficient in LUMO of the nitro benzyl halide) followed by an intramolecular dissociative electron redistribution in the course of the heterolytic Ccom/sd/entities/sbnd" class="glyphImg">Hal bond cleavage.The results for reduced titanocene dichloride centers immobilized inside a polymer film showed that the catalytic reductive dehalogenation of the p-nitrobenzyl chloride does occur but with a low efficiency because of the partial deactivation of the film due to the blocking of the electron charge transport between the electrode and catalytic centers.     

Selection of NF membrane to improve quality of chemically treated surface water

The requirement for higher quality drinking water necessitates the application of more efficient water treatment techniques. Nanofiltration is one promising option for enhanced water treatment, for example, in enhanced organic matter removal. The characteristics of different nanofiltration membranes vary remarkably, and the selection of a membrane has to be made according to the requirements of an application. In this study six nanofiltration membranes (NF70, NF255, NTR-7450, NTR-7410, Desal-5 and TFC-S) were evaluated in improving the quality of chemically pre-treated surface water in a pilot-scale process. The results indicate that the membrane with high organics removal and slightly reduced ion removal characteristics (NF255) performed best in terms of product water quality as well as membrane productivity and fouling. The most permeable membrane (NTR-7410) suffered intensive fouling and insufficient product water quality. An interesting finding was that the permeates of all the tested membranes possessed a significant potential for microbial growth, despite the low nutrient contents.     

北京报觉寺小区25号商住楼清水混凝土施工

着重介绍清水混凝土施工对模板工程的技术要求和具体做法及混凝土的浇筑振捣方法。     

磨齿机在机检测机构几何误差链建模与补偿

由于几何误差的影响,现有研究主要考虑末端机构或关键运动轴几何误差补偿,尚缺逐次补偿运动轴几何误差.为了避免形成在机检测机构几何误差链而产生误差累积效应,有效提升在机检测精度.根据自主研发卧式磨齿机在机检测原理,基于多刚体系统运动学和齐次坐标变换理论,建立在机检测机构几何误差链模型.逐次识别并补偿几何误差链中运动轴几何误...