低乙烯含量抗冲聚丙烯的结构表征

采用二甲苯为溶剂，将不同乙烯含量（５％￣１５％质量）的抗冲聚丙烯用特定程序进行分级，将各样品分为室温下可溶于甲苯和不可溶于甲苯的两部分。使用＾１３Ｃ－ＮＭＲ方法和ＦＴ－ＩＲ方法对各组分进行表征，明确了乙烯链段在聚丙烯链上的分布，并在此基础上提出了产生这种链结构的聚合工艺的特点。     

Dynamic elastic-plastic buckling phenomena in a rod due to axial impact

Dynamic elastic-plastic buckling phenomena which might develop in a rod from an axial impact loading are studied in order to identify the conditions for quasi-static behaviour. A discrete model for dynamic elastic-plastic buckling, which retains the axial and the lateral inertia forces, is proposed, and the relationship between the model parameters and the characteristics of an actual structure is given. Examples of different external loadings and boundary conditions are considered in order to clarify the influence of elastic-plastic axial wave propagation on the buckling process. The critical time for the initiation of buckling is obtained and the post-buckling behaviour of the model is analysed. Particular attention is paid to the role of the striking mass on the characteristics of the buckling process and on the development of the buckling shape. The numerical study reveals that the inertia of the striking mass affects considerably the development of the buckling shape causing different patterns of axial strain distributions at the initiation of buckling. The comparisons which are made between the model predictions and some previously published experimental data show that the buckling process is governed by the impact velocity as well as by the external loading history provided by the experimental technique.     

实证分析:上市公司资本结构的影响因素

在国内外相关研究的基础上，利用我国资本市场的公开数据，对上市公司资本结构的影响因素进行实证研究，得出了若干重要结论。     

A study of impact toughness of Fe-Cr-X damping alloys

A study was carried out on the impact toughness of Fe- Cr- Х damping alloys. Two measures proved to be effective in improving impact toughness. One was to lower carbon plus nitrogen content to an ultra- low level. This method is suitable for single- phase ferrite alloy. The other is to use dual- phase damping alloys. The presence of martensite in Fe- Cr- Х alloys can enhance impact toughness remarkably, but lower damping capacity drastically. This shows the importance of achieving balance between mechanical prop-erties and damping capacity by properly controlling martensite volume fraction in dual- phase alloys.     

Experimental evaluation of the strength distribution of E-glass fibres at high strain rates

A bimodal Weibull distribution function was applied to analyse the strength distribution of glass fibre bundles under tensile impact. The simulation was performed using a one-dimensional damage constitutive model. The results show that there were two concurrent flaw populations in the fracture process. The regression analysis using the bimodal Weibull distribution function was in good agreement with experiment.     

全球气候变暖对水资源的影响

全球气候变暖加剧了干旱、洪涝、台风等自然灾害的发生，是目前各国政府和社会公众普遍关注的热点问题。根据有关资料对气候变暖研究进展情况作相关介绍，可供参考。     

残留奥氏体对1500MPa级新型低碳Mn-Si-Cr系合金钢冲击韧度的影响

15 0 0MPa级无碳化物贝氏体 马氏体复相钢的第一类回火脆性开始温度高于 36 0℃。实验表明 ,这并非由于贝氏体 马氏体复相韧化 ,而是与无碳化物贝氏体中的膜状残留奥氏体有关。无碳化物贝氏体中机械稳定性较高的残留奥氏体可能是导致无碳化物贝氏体 马氏体复相钢第一类回火脆性开始温度升高的直接原因。     

泥岩压实动态分析法定量评价石油初次运移

在分析影响油气初次运移主要因素的基础上，剖析应用泥岩压实静态分析方法研究油气初次运移的局限性，提出应用泥岩压实动态分析方法定量评价油气初次运移的观点，并建立了相应的地质模型、数学模型和模拟流程。以栓辽盆地乾长凹陷为例，对主要烃源层青山口组进行压实动态分析，并估算其油气初次运移量，计算结果与其它多种方法计算结果以及前人计算结果十分接近。     

云南省水环境状况及问题分析

根据2000年云南省主要河流水质监测评价结果，全省评价河段总长9280km中，水质为Ⅰ－Ⅲ类的河长占76．3％，总体上，云南省内各大水系水质良好，但水污染总体上正在加重，从1985－2000年，Ⅰ类河长年均减少2．3％，V类河长年均增长0．6％，废污水直接排入江河是引起污染的重要原因。水环境问题已成为社会经济可持续发展的关键问题，要切实加强水资源的保护，科学地开发利用水土资源，为了有效地改善水环境的质量，污染控制应从源头开始并采取综合治理措施。