浅析提高煤质的意义及主要途径

针对商品煤质量在激烈的煤炭市场竞争中所处的重要地位，结合实际分析了提高煤质不仅关系到国民经济全局，影响着人们生活环境，还左右着煤炭企业自身的存在和可持续发展等问题。并立足现有的设施装备和科技水平，提出了提高煤质的基本途径。     

化学外加剂对砂浆流变性能的影响

研究了水胶比、聚羧酸减水剂(PCE)分子结构、高吸水性树脂(SAP)及阴离子型黏度调节剂(VMA)对砂浆流变性能的影响。结果表明:提升水胶比能降低砂浆的屈服应力和塑性黏度并提高其流动度保持能力。PCE的掺入可显著降低砂浆的屈服应力且PCE侧链的空间位阻作用是一个主要原因。侧链抑制PCE在水泥颗粒表面的吸附。增加PCE侧链长度对水泥浆初始流变性影响较小。SAP通过降低砂浆中自由水含量来提高其屈服应力和塑性黏度,其作用机理与降低水胶比的作用相似。VMA在低掺量下通过桥接作用提高砂浆的屈服应力,但对塑性黏度影响不大;高掺量下,VMA的桥接作用减弱却能大幅提高液相的黏度,因而对砂浆屈服应力的提升作用减弱而大幅提高其塑性黏度。     

降低传统法电解阴极铜贴标率

本文介绍了复杂原料下,市场对传统法电解阴极铜外观做出了进一步要求：阴极铜的贴标率需控制在6.24%左右。通过对复杂阳极进行分类管理和攻关,同时优化设备功能、提升电解精细管理,不仅降低了复杂阳极造成的阴极铜贴标率上升的问题,也提升了阴极铜质量。     

Rheological behaviors of fresh cement pastes with polycarboxylate superplasticizer

The rheologicalbehaviors of fresh cement paste with polycarboxylate superplasticizer were systematically investigated.Influentialfactors including superplasticizer to cement ratio(Sp/C),water to cement ratio(w/c),temperature,and time were discussed.Fresh cement pastes with Sp/Cs in the range of 0 to 2.0% and varied W/Cs from 0.25 to 0.5 were prepared and tested at 0,20 and 40 °C,respectively.Flowability and rheologicaltests on cement pastes were conducted to characterize the development of the rheologicalbehavior of fresh cement pastes over time.The exprimentalresults indicate that the initialflowability and flowability retention over shelf time increase with the growth in superplasticizer dosage due to the plasticizing effect and retardation effect of superplasticizer.Higher temperature usually leads to a sharper drop in initialflowability and flowability retention.However,for the cement paste with high Sp/C or w/c,the flowability is slightly affected by temperature.Yield stress and plastic viscosity show similar variation trends to the flowability under the abovementioned influentialfactors at low Sp/C.In the case of high Sp/C,yield stress and plastic viscosity start to decline over shelf time and the decreasing rate descends at elevated temperature.Moreover,two equations to roughly predict yield stress and plastic viscosity of the fresh cement pastes incorporating Sp/C,w/c,temperature and time are developed on the basis of the existing models,in which experimentalconstants can be extracted from a database created by the rheologicaltest results.     

美国军用通信市场

据美国 Frost-Sullivan 公司的一篇报告中透露,美国1983年的军用通信市场为59亿美元,到1988年财政年度将增加到90亿美元。六年的市场总值为469亿美元,其中增长最快的是采购费用,1983年为25亿美元,占军用通信市场总值的43％,到1988年,预计达50亿美元,增长一倍,占总的军用通信市场的56％。这就意味着,将增添现有设备的种类,改进现有设备和购买更多的备件。其中最大的单项工程是 Tri-Tac,预计占采购经费的四分之一。     

移动通信中的隧道中继系统

一、前言十多年来,世界各国先后开始了移动通信网的研究和开发。在日本、美国和西欧,150MHz频段、450MHz频段或800MHz频段的移动通信网相继问世。在国内,近年来也加紧了400MHz频段的自动电话网的研制,并正对800MHz频段通信网的可实现性进行着有益的探讨。在一些工业发达的国家和地区,这类通信网已应用于公共汽车、航海、救灾、矿山、军事等场合,其应用范围正日益扩大。在国内,随着技术的不断发展,这种通信网也将获得越来越多的应用。     

移动无线电业务需要更多的频谱

无线电与电子设备协会欧洲会议主席呼吁增加移动无线电业务的使用频率。他认为,无线频谱中的1000MHz频段应划分给移动无线电使用。他在一次马可尼基金费赞助的会议上问道:“我们为什么不能在世界范围内同意一项民远目标——把30～1000MHz的频谱只供移动无线电应用?”他还主张,固定通信业务应当让给有线或光纤通信,或者使用与移动无线通信频率无关的频率,这样可以保证移动无线电的优点能充分发挥。这位主席认为,这样做也许要花二十多年的时间。     

Sincgars-V系列电台的设计特点

美国国防部选中ITT公司的Sincgars—V系列电台作为美军新一代战术通信电台,ITT公司认为该产品中选的原因主要是:(1)具有适合现代战场通信所需的电子反对抗能力;(2)具备美军三军联合战术通信系统要求的系统配套能力;     

聚羧酸减水剂的研究进展

聚羧酸减水剂进一步发展,已经不仅仅是学术界的科学研究问题,也不仅仅是工程界的工程应用和经验性总结的问题,而是需要学术界和工程界共同提出问题、并从理论上解释其机理,最后从减水剂的分子设计合成、生产制备、工程应用提出普适性的解决措施,才能为聚羧酸减水剂的进一步发展打开一道大门.     

Mechanical properties of silica aerogels prepared from a mixture of TEOS and organo-alkoxysilanes of type R1SiX3

Silica aerogels were prepared from a mixture of tetraethylorthosilicate and organo- alkoxysilanes. The effects of organo-alkoxysilanes on the mechanical properties of the silica aerogels were studied. The flexibility of silica aerogels was significantly improved by incorporation of organo-alkoxysilanes. When MTES and TEOS were combined as precursors of silica areogels, with the increased amount of MTES, the apparent elastic modulus and apparent compressive strength monotonously rose. At the same organo- alkoxysilanes to TEOS ratio, the size of alkyl groups of the organo-alkoxysilanes had little effect on the mechanical properties. In series of MTES and TEOS, the lowest elastic modulus of silica skeleton and the highest compressive strength of silica skeleton were observed at MTES to TEOS ratio of around 50：50. At a certain organo-alkoxysilanes to TEOS ratio, the elastic modulus of silica skeleton increased and the compressive strength of silica skeleton decreased with the size increase of the alkvl grouns.