Low temperature premixed combustion within a small bore high speed direct injection (HSDI) optically accessible diesel engine using a retarded single injection

An optically accessible single-cylinder high speed direct-injection (HSDI) Diesel engine equipped with a Bosch common rail injection system was used to study low temperature Modulated Kinetics (MK) combustion with a retarded single main injection. High-speed liquid fuel Mie-scattering was employed to investigate the liquid distribution and evolution. By carefully setting up the optics, three-dimensional images of fuel spray were obtained from both the bottom of the piston and the side window. The NOx emissions were measured in the exhaust pipe. The influence of injection pressure and injection timing on liquid fuel evolution and combustion characteristics was studied under similar fuel quantities. Interesting spray development was seen from the side window images. Liquid impingement was found for all of the cases due to the small diameter of the piston bowl. The liquid fuel tip hits the bowl wall obliquely and spreads as a wall jet in the radial direction of the spray. Due to the bowl geometry, the fuel film moves back into the central part of the bowl, which enhances the air-fuel mixing process and prepares a more homogeneous air-fuel mixture. Stronger impingement was seen for high injection pressures. Injection timing had little effect on fuel impingement. No liquid fuel was seen before ignition, indicating premixed combustion for all the cases. High-speed combustion video was taken using the same frame rate. Ignition was seen to occur on or near the bowl wall in the vicinity of the spray tip, with the ignition delay being noticeably longer for lower injection pressure and later injection timing. The majority of the flame was confined to the bowl region throughout the combustion event. A more homogeneous and weaker flame was observed for higher injection pressures and later injection timing. The combustion structure also proves the mixing enhancement effect of the liquid fuel impingement. The results show that ultra-low sooting combustion is feasible in an HSDI diesel engine with a higher injection pressure, a higher EGR rate, or later injection timing, with little penalty on power output. It was also found that injection timing has more influence on HCCI-like combustion using a single main injection than the other two factors studied. Compared with the base cases, simultaneous reductions of soot and NOx were obtained by increasing EGR rate and retarding injection timing. By increasing injection pressure, NOx emissions were increased due to leaner and faster combustion with better air-fuel mixing. However, smoke emissions were significantly reduced with increased injection pressure.     

潮湿路面滑水现象及抗滑力模型

滑水及抗滑力的衰减是潮湿条件下影响道路及机场跑道交通安全的两个重要因素。模拟潮湿路面抗滑力是一个相对复杂的问题。笔者采用理论研究方法,提出了一个分析计算模型,用来模拟车轮滑移速度增加时,潮湿路面的滑水现象及抗滑力的衰减情况。该理论公式及三维有限元模型的理论基础是固体力学及流体动力学。通过NASA滑水速度方程,对模型计算的滑水速度进行分析验证。     

Ground travel mode choices of air arrivals at regional destinations: The significance of tourism attributes and destination contexts

The aim of this paper is to examine the air leisure arrivals’ ground travel mode choice in the context of their decision to disperse beyond the gateway. A stated choice experiment was designed to examine the dispersal and travel mode choice of leisure visitors arriving on air transport at Cairns. Results show that for a hypothetical public bus alternative, attributes such as ‘sightseeing opportunities’ and ‘driver quality’ were significant for trips made to less known destinations located south of Cairns, compared to destinations north of Cairns. Findings suggest that while travel mode attributes and trip characteristics are significant determinants of the mode choice of air leisure arrivals, the extent of their significance varied markedly across destinations. Although the data examined in this paper were collected in Cairns, this research should be of relevance to many regions interested in understanding the relationship between destination transport and dispersal of air arrivals.     

IP MULTICAST GROUP MANAGEMENT FOR BROADCAST LANS DISTRIBUTION

IntroductionThere are two traditional types of communica-tion in computer networks:unicastand broadcast.A unicast address (one to one) is designed to sendmessages to a single destination in a network.Abroadcast (one to all) address is used to send datato the entire network(all hosts) .Multicast(oneor many to many) can be viewed either as an inter-mediate case,or as a generalized mode encompass-ing both unicast and broadcast as special cases.Inmulticast mode,messages are sent to an arbitraryse…     

高速公路单点入口匝道RLRM控制方法

为缓解交通堵塞, 基于人工智能的强化学习理论, 提出了不完全信息下的强化学习单点入口匝道控制方法(RLRM)。基于6个仿真实例, 分别计算了平均速度、平均密度、流出交通量与旅行时间, 比较了无控制、定时控制与RLRM控制的控制效果。仿真结果表明: 在交通量较小的实例1中, 以旅行时间为评价指标, 定时控制与RLRM控制的交通阻塞缓解率分别为-6.25%、-9.38%, 几乎没有控制效果; 在交通量变大的实例3中, 以旅行时间为评价指标, 定时控制与RLRM控制的交通阻塞缓解率分别为-8.19%、3.51%, 匝道控制有一定效果, RLRM控制略优于定时控制; 在交通量最大的实例6中, 以平均速度、平均密度、流出交通量与旅行时间为评价指标, 定时控制的交通阻塞缓解率分别为8.20%、0.39%、18.97%与23.99%, RLRM控制的交通阻塞缓解率分别为18.18%、3.42%、30.65%与44.41%, RLRM控制明显优于定时控制。可见, 交通量越大, RLRM控制效果越明显。     

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研究印度城市道路上设置公交专用道后小汽车出行向公交转移的可能性. 借助新的混合交通流仿真模型测定设置公交专用道后公交服务水平改善状况. 基于陈述偏好入户调查的抽样数据,本文还引入其他影响出行方式转移的变量,标定出行方式选择二元Logit模型. 根据实际和预测数据,确定了公交服务水平改善条件下小汽车出行向公交转移的一系列主要影响因素. 基于两种方式出行时间差,绘制出行方式转换概率曲线,并为多变量宽值域条件下交通方式转移的预测提供一种易于操作的方法.     

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模糊控制器的应用于1977年首次在文献中提出,其中指出对于有简单绿灯延时控制的单车道交叉口,模糊控制器比车辆感应式控制器更具优势。此后,模糊控制器有了进一步发展,关于交通信号控制的模糊逻辑方法的研究也进一步深入,该方法被陆续应用于无转向车流的双车道交叉口、无限制的单车道交叉口、多交叉口、相位顺序和相位时长控制、拥挤交叉口和路网等等,尤其在高负荷和不均衡交通流条件下表现出优于传统交通信号控制方法的特性。模糊逻辑方法可以改善自适应交通信号控制,改变自适应控制器和TMS的整个决策过程,很大程度上改善未来的交通需求管理方法,然而这类交通信号控制和交通需求管理方法的实际应用并不多见。在诸如沙特阿拉伯这样的发展中国家,学者应根据本国的特有情况研究基于模糊逻辑的交通信号控制与TMS的发展潜力,从而减少拥挤导致的各种损失。     

Social inclusivity through public transportation: a strategic approach to improve quality of life in developing countries

Welfare services such as healthcare and education are commonly recognised as determinants of physical quality of life indices during the early phases of development in the third world. In order to benefit from these services, it is important that the general public have the mobility means to access welfare provision centres. However, very low vehicle ownership under the conditions of low per‐capita incomes and large shares of population living in deep rural areas prevent the masses from accessing such services, thereby retarding the process of social development, which is reflected in the very poor physical quality of life indices in low‐income countries. Public transportation could offer a viable and affordable solution to this apparent ambivalence. It could permit mobility for poor masses in spite of low per‐capita vehicle ownership enabled by the national income levels. The present research demonstrates this strategic niche through an econometric examination of the evolution of the physical quality of life indices such as maternal mortality, infant mortality and literacy as against the healthcare, education and affordable mobility proxies in post‐independent Sri Lanka. The country, which was then referred to as Ceylon, is often cited as a rare example of achieving social inclusion and reduced marginalisation and thereby a high social welfare standing, in spite of relatively poor per‐capita income levels. Copyright © 2015 John Wiley & Sons, Ltd.     

Co-operation and competition in international container transport: strategies for ports

This paper focuses on the response of port authorities to the changing market environment in which they operate. It documents the changes taking place in the relationships between port authorities and terminal management companies and considers the strategic issues faced by these groups and other port interests. In particular, it investigates the potential conflicts of interest for a port authority in matters related to the level of competition amongst terminals within a port and the amount of competition amongst ports.     

Attribute‐based perceptual mapping using discriminant analysis in a public sector passenger bus transport company: A case study

This study aims at evaluating the customer expectations in a public sector passenger transport company, a crucial sector in developing countries like India. A questionnaire containing 18 quality characteristics was administered to various customers of three bus depots of one division of a state road transport undertaking in South India. Attribute‐based perceptual mapping using discriminant analysis was done to position the three depots and to identify their strengths and weaknesses. The findings would help prioritize different parameters and also provide guidelines for managers to focus on and to improve. Copyright © 2012 John Wiley & Sons, Ltd.