高原环境下喷孔夹角对某增压柴油机性能影响的数值模拟与分析

基于ECFM-3Z燃烧模型建立适应高原环境柴油机缸内工作过程模型,在平原试验验证的基础上,对喷油器喷孔夹角为147°、150°、153°、156°四种情况进行数值模拟,分析了喷孔夹角对海拔4550m下缸内燃烧过程的影响。研究结果表明,喷孔夹角增大后,缸内压力和温度上升,功率得到一定恢复,柴油机的排放随之上升。综合考虑柴油机的动力性和排放,海拔4550m下将喷孔夹角从150°(平原原机值)增加到153°比较合理。     

M15甲醇汽油与93^#汽油的发动机性能参数

甲醇作为一种代用燃料,可以与汽油混合使用,人们对使用低比例甲醇燃料发动机的性能十分关注。文章对加入M15甲醇汽油和加入93#汽油的发动机分别经过300 h台架强化试验,测试发动机功率、扭矩及油耗率。强化后,2种燃料的动力性能相近,但M15甲醇汽油的燃料消耗量比汽油高出9%。在汽油发动机中,直接使用M15甲醇汽油,除发动机燃料经济性变差外其他基本无变化。     

Bus Rapid Transit implementation in Beijing: An evaluation of performance and impacts

Bus Rapid Transit (BRT) systems are undergoing rapid development in many countries due to the unique characteristics of this form of mass transit. In China, BRT schemes are being adopted as a key strategy for relieving traffic problems. As a case-study, this paper examines the performance and impacts of BRT in Beijing, the first full-featured BRT system in China. It considers in turn the role of ITS technology in influencing the operational efficiency, technical performance and cost issues associated with BRT. Particular attention is given to the consequent impacts of BRT on travel behaviour change, traffic environment and property development. While some challenges remain, the early performance of BRT suggests that it is one of the key measures for promoting sustainable mobility.     

Factoring a real value of cargo in port investment and funding decisions

Ports are marine gateways to economic activities. Ports’ ability to perform services depends on their facilities, harbor conditions, and other factors. Generally, ports have control over their facilities but must compete for funding to improve them. As for waterways, in the U.S., a Harbor Maintenance Trust Fund was established to fund dredging, which levies a 0.125% cargo value tax on most shippers using U.S. coastal and Great Lakes harbors. Yet, commonly, a gross tonnage metric is used to allocate the fund’s resources, resulting in under-maintenance of some harbors. This, reportedly, deters additional port funding and hinders valuable commerce. Supplemental economic metrics, such as value of commerce or cargo, can improve port financing decisions, but such data is not readily available. Container ports collect cargo value data in nominal terms, but bulk ports do not. When making economic decisions, however, real values must be used. Further, when allocating resources, decision-makers must be able to assess ports over time and relative to each other. Conforming to these criteria, this paper develops three port financing indicators based on a real value of cargo and illustrates their calculations using the U.S. Port of Duluth-Superior as a case study.     

一种可被生物降解的复合材料开发

现有淀粉基PP材料制作的一次性食品包装用容器耐候性和抗冻性较差,气温低于-10℃时易脆化开裂,且卫生指标有若干项严重超标,长期使用可能会对人体有害。为有效解决淀粉基PP材料的诸多缺点,提出一种聚乙烯、淀粉与无机填料相互结合的复合材料体系。采用高速搅拌混合、挤出造粒的工艺制备了该复合材料,经过万能试验机测试了力学性能,发现其大多数力学性能和耐热指标达到或超过了淀粉基PP材料,且在一定范围内微调配方,对该材料的综合性能影响比较小,其最高值与最低值误差不超过15％;又采用定量溶剂浸泡实验测试了其卫生指标,证实该材料已达到国家标准,长期使用对人体无害;并且对该材料做了户外耐候性、抗冷冻、耐化学腐蚀性测试,发现其外观无明显变化,力学性能也无明显下降。     

基于模糊综合评价的农村公路建设项目绩效评价研究

文章根据农村公路的特点和绩效评价要求,建立了农村公路建设项目绩效评价指标体系,并以HW农村公路建设项目为实例,采用模糊综合法对该农村公路建设项目管理绩效进行了评价,其结果可为农村公路建设项目投资与管理提供参考依据。     

桥面铺装沥青混合料的技术性能与标准研究

运用有限元软件ANSYS分别建立水泥混凝土桥沥青混凝土铺装层结构和沥青混凝土路面结构的三维实体模型,通过桥面铺装层结构与路面面层结构的应力状态对比研究发现：桥面铺装层结构的最大拉拔力σmax和最大剪应力τmax分别高于路面面层结构的56.1%和45.5%。同时,通过添加剂对沥青混合料性能提升的研究,综合考虑现有的施工技术及工程经验,提出桥面铺装沥青混合料技术指标与标准。     

沥青路面裂缝修补材料技术性能对比研究

通过室内性能试验对5种裂缝修补材料的高温稳定性、低温抗裂性、抗异物嵌入性、耐腐蚀性、抗老化性、抗剪强度与抗拉强度等技术性能进行了对比研究;同时通过野外实体工程对其实际应用效果进行了验证。室内外研究发现：裂缝修补专用材料的各项技术性能均非常理想,修补效果优良,适用于要求较高的高等级沥青路面裂缝修补;加热施工类材料的各种性能虽不及专用材料,但也处于较理想的水平,适用于低等级沥青路面裂缝修补;常温施工类材料的各种性能与修补效果均较差,仅在紧急抢修、低温或雨后、裂缝潮湿等不利条件下可以使用。     

重心位置对水翼复合小水线面双体船阻力性能的影响

本文采用Star-CCM+计算软件来研究重心位置对水翼复合小水线面双体船阻力性能的影响。以静排水量为1000t的水翼复合小水线面双体船为研究对象,研究不同速度下重心位置对于船体阻力性能的影响,对提高复合船型的阻力性能有重要意义。     

浅谈路面结构的组成、使用性能以及设计内容

从解析路面结构的组成入手,介绍了路面的结构和使用性能,对道路工程设计人员加深对路面结构的理解、做好路面结构设计工作具有重要意义.