Multi‐objective highway alignment optimization using a genetic algorithm

The available highway alignment optimization algorithms use the total cost as the objective function. This is a single objective optimization process. In this process, travel‐time, vehicle operation accident earthwork land acquisition and pavement construction costs are the basic components of the total cost. This single objective highway alignment optimization process has limited capability in handling the cost components separately. Moreover, this process cannot yield a set of alternative solutions from a single run. This paper presents a multi‐objective approach to overcome these shortcomings. Some of the cost components of highway alignments are conflicting in nature. Minimizing some of them will yield a straighter alignment; whereas, minimizing others would make the alignment circuitous. Therefore, the goal of the multiobjective optimization approach is to handle the trade‐off amongst the highway alignment design objectives and present a set of near optimal solutions. The highway alignment objectives, i.e., cost functions, are not continuous in nature. Hence, a special genetic algorithm based multi‐objective optimization algorithm is suggested The proposed methodology is demonstrated via a case study at the end.     

二甲醚均质充量压燃发动机燃烧特性试验研究

通过改造一台压缩比为16．5的2-135柴油机,在其上实现DME的HCCI燃烧方式。试验结果表明,DME HCCI发动机不但可以实现无烟燃烧,而且可以有效控制发动机NOx排放,使其接近0排放。在试验负荷范围内,CO排放随负荷增加而降低;HC的排放随负荷变化不大。     

Ground delay program planning under uncertainty in airport capacity

Abstract

This paper presents an algorithm for assigning flight departure delays under probabilistic airport capacity. The algorithm dynamically adapts to weather forecasts by revising, if necessary, departure delays. The proposed algorithm leverages state-of-the-art optimization techniques that have appeared in recent literature. As a case study, the algorithm is applied to assigning departure delays to flights scheduled to arrive at San Francisco International Airport in the presence of uncertainty in the fog clearance time. The cumulative distribution function of fog clearance time was estimated from historical data. Using daily weather forecasts to update the probabilities of fog clearance times resulted in improvement of the algorithm's performance. Experimental results also indicate that if the proposed algorithm is applied to assign ground delays to flights inbound at San Francisco International airport, overall delays could be reduced up to 25% compared to current level.     

质子交换膜燃料电池的效率分析

质子交换膜燃料电池(PEMFC)的效率受燃料电池设计和操作条件等多种因素的影响.文中建立了能够计算PEMFC效率的单电池稳态模型,模型预测的极化曲线与实验结果吻合良好.利用该模型研究了电池工作温度和工作压力对电池效率的影响.计算结果表明,在电池工作温度范围内,提高电池工作温度,有利于提高电池效率,高电流密度电池效率增幅要大;提高阴极和阳极工作压力均有利于电池效率提高,但阴极的工作压力增加对提高电池效率作用明显.     

非道路移动机械用柴油机排放法规与控制策略

本文介绍了美国、欧洲和中国的有关非道路用柴油机的排放法规情况,探讨了控制非道路用柴油机排气污染物的一些技术措施.     

EGR对二甲醚HCCI着火过程的数值模拟研究

从化学反应动力学的角度,应用单区燃烧模型和已建立的二甲醚（DME）化学反应机理,对DME均质充量压燃（HCCI）的着火过程进行了数值模拟,分析了不同EGR率对其着火过程的影响,并从热效应及化学效应两方面分析了内部热EGR对燃料着火过程的影响。研究结果表明：内部热EGR对DME的HCCI着火过程有着显著影响。     

压缩比与EGR对二甲醚的HCCI特性影响的模拟研究

应用单区燃烧模型和已建立的二甲醚氧化反应机理,对二甲醚的HCCI过程进行了模拟计算,研究了变压缩比和不同的冷却EGR率对二甲醚的HCCI特性的影响.结果表明:随着压缩比的升高,二甲醚的两阶段着火均有提前.且间隔减小,燃烧持续期缩短;冷却EGR率对二甲醚第一阶段着火时刻并无太大影响,第二阶段着火时刻随EGR率的增大逐渐延迟,缸内压力和温度均有所下降,燃烧持续期增大.     

CO2和H2对HCCI二甲醚发动机燃烧影响的数值模拟

模拟了燃用DME的HCC I发动机的燃烧过程,研究了进气添加剂CO2和H2对其着火时刻和指示功的影响。结果表明:CO2能延迟着火时刻,降低缸内压力和温度,从而扩大HCC I燃烧运行范围;H2也可推迟着火,并能有效提高发动机的指示功。为了既控制着火始点,又提高发动机指示功,提出进气中同时添加适量CO2和H2,并就此进行了计算。     

基于简易瞬态工况法的在用汽油车排放特性试验研究

以2009年捷达车1.6 L自然吸气汽油机为研究对象,搭建汽车尾气测试转鼓试验台架,安装自主研发的EGR系统和市售的三元催化器控制装置,结合GB 18285-2018《汽油车污染物排放限值及测量方法(双怠速法及简易工况法)》中简易瞬态工况法进行排放试验,综合评价了以上排放控制技术对在用轻型汽油车排放特性的影响.结果表明...