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。     

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。     

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。     

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.     

乳化沥青聚苯颗粒新型保温砂浆的研制

为降低成本以制备适用于乡村建筑节能的保温材料,对以廉价乳化沥青替代可再分乳胶粉制备保温砂浆的可行性进行了研究,并研究了乳化沥青聚苯颗粒保温砂浆的各项性能.结果表明,以乳化沥青部分或全部替代可再分散乳胶粉制备保温砂浆可行,且砂浆的干密度、体积稳定性和耐水性还有所改善.所研制的乳化沥青聚苯颗粒保温砂浆随着聚苯颗粒添加量的增大,干密度、抗压强度、压剪粘结强度和导热系数逐渐降低,线性收缩率和吸水率逐渐增大,而软化系数略有降低,除干密度和导热系数外各项性能均满足JG 158-2004标准对胶粉聚苯颗粒保温砂浆的要求.     

CO2/CH4/N2在沸石13X-APG上的吸附平衡

采用磁悬浮热天平测量了CO₂、CH₄与N₂在沸石13X-APG上的吸附等温线,温度为293、303、333和363 K,压力为0～500 kPa。对吸附平衡实验数据采用multi-site Langmuir模型和Sips模型进行拟合,均得到良好的拟合效果,非线性回归得到吸附热等模型参数,可为变压吸附工艺过程的开发提供基础热力学数据。将沸石13X-APG吸附分离性能与文献中报道的吸附材料(如沸石分子筛、活性炭、金属有机骨架材料和介孔硅分子筛)性能相比较。通过比较CO₂、CH₄与N₂吸附容量以及相对分离系数,探讨CO₂/CH₄(垃圾填埋气或者CO₂强化煤层甲烷回收气)体系、CO₂/N₂(燃煤电厂、水泥厂以及焦炭厂烟道气)体系以及CH₄/N₂(煤层气)体系吸附分离的高效材料,为未来二氧化碳吸附捕集和甲烷吸附回收提供基础数据。     

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.     

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.