青藏铁路开放边界块碎石类路基速度场和温度场特征非线性分析

针对青藏高原多风的特点及其气温和地质条件,在考虑全球变暖的条件下,研究青藏铁路开放块碎石夹层路基和开放块碎石护坡路基的速度场及其在未来50年的温度场变化特征。结果表明,在外界风的作用下,两种块碎石路基的道砟层和块碎石层内的对流换热方式以强迫对流为主;在年平均气温为-4.0℃,考虑未来50年青藏高原气温升高2.2℃条件下,这两种路基结构均能不同程度地抵消气候变暖和铁路建设所带来的负面影响,对其下部多年冻土起积极保护作用,但开放块碎石夹层路基的降温效果好于开放块碎石护坡路基,而且还发现在铁路运营50年后开放块碎石护坡路基内部将出现终年融化夹层,这一问题应引起设计与施工部门的重视,以采取相应的措施来维护这种冻土路基的多年稳定。     

国内外内燃机车、电力机车技术水平现状与差距(二)

为了实现铁路的跨越式发展,对于了解国内外铁路机车的技术水平现状与差距,是十分必要的。文章阐述了国内外内燃机车、电力机车的技术水平现状,以及与国外先进水平对比所存在的差距。     

国内外内燃机车、电力机车技术水平现状与差距(一)

为了实现铁路的跨越式发展,对于了解国内外铁路机车的技术水平现状与差距,是十分必要的。文章阐述了国内外内燃机车、电力机车的技术水平现状,以及与国外先进水平对比所存在的差距。     

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对城市、城市化以及城市发育作以简要概述，着重探讨了交通运输与城市发育两者的相互作用和影响。分别从四个方面进行阐述：区位论强调交通运输的重要作用，交通方式与城市发育的相互影响，交通网的完善与城市体系网络的相互影响，城市化的不同阶段对交通运输的影响。不同时期对城市交通运输的认识是不同的，交通的地位逐渐从被动向能动转化。随着城市化的发展，交通运输由稚嫩走向混乱，最后趋于成熟和完善。逐渐趋好的交通也会增加城市的吸引力，促进城市发育。总之，交通运输与城市发育两者相互作用互为影响。因此，解决城市交通问题有必要从城市的良好发育、合理的空间扩展上寻求答案。     

关于建立国际船舶和港口保安信息支持系统的若干建议

实施SOLAS公约第XI-2章及《国际船舶和港口保安规则》(ISPS),涉及到多方面的准备工作。其中,建立统一、完整的信息支持系统是最重要的工作内容之一。本文就该系统中的保安信息网络、海上保安信息系统的功能、构建方法提出了一些建议。     

Determinants of certified motorcycle helmet use among postal delivery riders at rural areas in Peninsular Malaysia

This study aims to identify the determinants of certified helmet use among postal delivery riders (PDRs) in rural areas of Peninsular Malaysia. A cross-sectional study was done among 269 PDRs from 50 postal distribution centres (DC) nationwide. Data collection was achieved through observation of the helmets and a questionnaire. The quality of the motorcycle helmets was determined by the presence of the certification label issued by the Standards and Industrial Research Institute of Malaysia (SIRIM). The response rate was 99.3%. The odds of full-shell helmets having the SIRIM label were 37.1 times more than that of the half-shell helmets. The odds of non-purchased helmets having the SIRIM label were 14.9 times more than that of the purchased helmets. The odds of expensive helmets having the SIRIM label were 4.4 times more than that for cheaper motorcycle helmets. The odds of helmets owned by riders without a previous crash history having the SIRIM label were 1.9 times more than helmets owned by riders with a crash history. Full-shell helmets with SIRIM standard certification, non-purchased helmets, helmet price of US$11.00 or more, and motorcycle riders without any previous crash history were determinants that contributed towards the use of a certified motorcycle helmet. Multiple logistic regression indicated that two variables significantly predicted the use of a certified motorcycle helmet among PDRs – helmet type and cost. An employer that provides the employees with full-shell motorcycle helmets with SIRIM standard certification label that costs at least US$11.00 and hiring motorcycle riders without any previous crash history gives a higher chance of compliance with standard certified motorcycle helmet usage.     

公路桥头跳车问题探讨

从路基沉降、施工方法和结构体系上分析了桥头跳车病害的原因 ,提出了减少病害的防治措施     

南京地铁运营物资管理中一些问题的思考

从地铁运营物资管理工作的组织体系入手,结合南京地铁运营物资管理的相关问题,提出了物资的分级管理、库存控制、预算体系的建立、供应方式等有关观点,以期达到创建南京地铁运营物资管理新模式的目的。     

Effects of sediment resuspension on organic matter processing in coastal environments: A simulation model

A model, constructed using STELLA™, was used to simulate changes in standing stocks and flows of organic matter resulting from sediment resuspension in shallow coastal environments. Previous studies suggested that resuspension may determine the sites and rates of organic matter mineralization in shallow environments (Hopkinson, 1985, 1987). Those studies predicted that resuspended organic material could exert an enhanced demand on dissolved oxygen. Our model results support this hypothesis. Total system metabolism receives increasing contributions from the water column as settling rate decreases. Water column respiration also increases relative to benthic respiration as the frequency and intensity of resuspension events increases. This is driven by higher specific degradation rates in the water column than in the benthic environment. Furthermore, overall respiration (benthic + pelagic) increases in response to resuspension.