无油润滑压缩机活塞环的研究进展

为实现压缩机的无油润滑，需采用无润滑活塞环。无润滑活塞环由自润滑材料制造。本文分析了常用自润滑材料，如填充聚四氟乙烯、填充聚酰亚胺等的性能及工程应用，并报道了金属材料、复合型填充聚四氟乙烯、CFRP等新材料。介绍了整体开口活塞环及无背压活塞环的结构、特点、应用及设计计算。对活塞环结构型式的研究进展，如T型环、压力平衡环、超短迷宫式无托环整体无背压活塞环、一槽双环等作了介绍，并展望了无润滑活塞环的研究前景。     

高炉无钟炉顶设备布料偏析现象

高炉布料制度能够调节煤气流,控制高炉顺行,在高炉生产中发挥重要作用。基于离散元方法对焦炭在高炉炉顶设备内的偏析行为进行模拟研究,主要针对串罐式无钟炉顶设备和并罐式无钟炉顶设备,并对其料罐和料面的模拟结果进行讨论。模拟结果表明:由于渗透作用,焦炭颗粒在料罐内会发生偏析,串罐和并罐罐体结构不同,其偏析现象亦不同;焦炭颗粒运动到溜槽时,由于溜槽的旋转,料流轨迹会发生变化、焦炭在下降过程中存在一定距离的偏移;并罐式布料器由于料罐重心与高炉中心线不重合,焦炭在料面上的质量偏析现象比串罐式严重。在无钟式炉顶布料器布料过程中,炉料的偏析现象直接影响煤气流在高炉内部的分布,当大颗粒集中在炉喉中心时,中心透气性好,中心煤气流得到发展。反之,中心煤气流受到抑制,边缘煤气流得到发展。     

Still more about the comprehension of "less."

32 3-4 yr old children were asked to indicate "Which one has less?" in 4 different contexts. Results indicate that performance was the same in all contexts indicating that "more" is acquired before "less" and that those children who do not know "less" treat it as a synonym of "more." Differing results of previous studies cannot be attributed to the type of materials to which the comparative judgments are applied. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The determination of phosphate availability for some less conventional phosphate fertilisers

More than in the case of the other major fertiliser elements the performance of phosphorus in fertilisers in dependent on the state of chemical combination of the element. As distinct from typical American practice where fully acidulated fertilisers are emphasised, some other countries have moved in part to production of materials of less than full acidulation where some reliance is placed on the reactivity of the original phosphate rock. Solutions of various aliphatic acids and their salts have been used as tests for the availability of phosphorus in fully acidulated fertilisers and, to a degree, for phosphate rocks themselves. Less than fully acidulated products are at present assessed in the same way as fully acidulated materials, but in this and other evaluations problems and anomalies arise which are discussed within the framework of a number of fertiliser systems. Analytical data are adduced which illustrate the effects of some extraneous cations on the results achieved which conflict with some previous opinions. Research towards a fuller understanding of the subject is suggested.     

Dependence of urban air pollutants on meteorology

Dependence of air pollutants on meteorology is presented with the aim of understanding the governing processes pollutants phase interaction. Intensive measurements of particulate matter (PM10) and gaseous materials (e.g., CO, NO2, SO2, and O3) are carried out regularly in 2002 at 14 measurement sites distributed over the whole territory of Great Cairo by the Egyptian Environmental Affairs Agency to assess the characteristics of air pollutants. The discussions in this work are based upon measurements performed at Abbassiya site as a case study. The nature of the contributing sources has been investigated and some attempts have been made to indicate the role played by neighboring regions in determining the air quality at the site mentioned. The results hint that, wind direction was found to have an influence not only on pollutant concentrations but also on the correlation between pollutants. As expected, the pollutants associated with traffic were at highest ambient concentration levels when wind speed was low. At higher wind speeds, dust and sand from the surrounding desert was entrained by the wind, thus contributing to ambient particulate matter levels. We also found that, the highest average concentration for NO2 and O3 occurred at humidity相似文献   

非萘系减水剂和复合超细粉对高性能混凝土渗透性的影响

使用非萘系高效减水剂和复合超细粉体配制的高性能混凝土具有较好的流动性、抗压强度和抗渗性。混凝土的扩展度达22 cm以上,在2小时内坍落度损失少于3 cm,可以满足远距离运输,混凝土28d的抗压强度达60MPa以上。测定的C l-扩散系数及通过的电量说明了使用非萘系减水剂和复合超细粉体配制的混凝土具有较好的耐久性能。     

Impact in Scotland of UK and EC Sewage Legislation

The EC Directive (91/271/EEC) concerning urban waste water treatment has far-reaching financial and technological implications for local authorities in Scotland which are responsible for sewerage. Increased capital consent limits and additional financial assistance from central government are essential if the requirements of the legislation are to be met.
Although the Directive is welcomed in general terms, the sections of the legislation dealing with the identification of sensitive waters and the provision of primary treatment for coastal discharges to less sensitive waters are of limited environmental significance in Scotland.
The elimination of sewage sludge disposal at sea will create severe difficulties for Scottish authorities as a high percentage of sewage sludge is currently disposed of at sea. Each of the main alternative disposal options presents environmental, financial and technical problems and, in the case of incineration, the certainty of widespread unpopularity with the public.     

关于余值变率折旧策略的深入研究

余值变率法属加速型折旧策略 .深入分析了余值变率法的实质 ,指出了目前国内使用不普遍的原因 ,给出了该法与双倍余额递减法的联系与区别 ,提出了处理残余价值的思路和方法 ,并通过示例加以说明 .     

降低破碎产品粒度提高磨矿生产效率

为解决云锡老厂锡矿所属选矿厂普遍存在的入磨矿石粒度过大的突出问题,通过加强技术管理,完善破碎流程,采用先进破碎设备,取得了提高磨矿效率、节能降耗的明显效果,充分体现了细碎入磨(多碎少磨)技术路线的正确性。     

JB4732-95 免除疲劳分析条款中有关问题的探讨

经实例分析 ,对JB4 732— 95标准中有关的问题进行了探讨。