Costs of air pollutants from shipping: a meta-regression analysis

ABSTRACT

This study estimated the external cost of air pollution from shipping by means of a meta-regression analysis, which has not been made before. Three pollutants, which were included in most of the primary studies, were considered: nitrogen oxides (NO_x), sulphur dioxides (SO₂) and particulate matters with a diameter of max 2.5 micrometres (PM_2.5). All primary studies included damages of health and a majority added impacts on agriculture and estimated the cost of air pollutants by transferring cost estimates from studies on costs of air emissions from transports in Europe. Different regression models and estimators were used and robust results were found of statistically significant emission elasticities of below one, i.e. total external costs increase by less than 1% when emissions increase by 1%. There was a small variation between the pollutants, with the highest elasticity for PM_2.5 and lowest for NO_x. Calculations of the marginal external cost of the pollutants showed the same pattern, with this cost being approximately six times higher for PM_2.5 than for the other pollutants. Common to all pollutants was that the marginal external cost decreases when emission increases. Another robust result was a significant increase in the cost of studies published in journals compared with other publication outlets. These findings point out some caution when transferring constant external unit cost of air pollutant from shipping, which is much applied in the literature, and the cost functions estimated in this study could thus provide a complementary transfer mechanism.     

浅谈车用电动空压机在新能源汽车上的应用

文章以车用电动空压机为研究内容,对其使用环境进行分析,同时对其在新能源车辆上控制策略做了分析,最后对其管路布局做分析,望对各大主机后续空压机管路布局有所借鉴。     

不确定条件下机场群系统均衡配流模型研究

为探索客流在机场群的分布规律，以整个航空出行链为视角，综合考虑空中交通、地面交通和旅客出行选择偏好，构建机场群系统均衡配流模型.以路径时间、机场停留时间、出行票价和旅客类型为主要参考属性，提出机场群系统旅客出行成本模型.由于路径时间与流量相关且存在不确定性，基于预算超出时间对路径时间的均值与方差进行统一度量.综合路径时间、出行票价、机场停留时间与旅客类型，基于Logit模型建立旅客对航空出行路径的选择模型，将机场群系统的客流均衡条件转换为变分不等式.基于投影收缩算法对变分不等式求解，从而得出客流在机场群间的均衡分布状态.算例结果表明，机场群系统均衡配流模型有效建立了客流分布状态，调整路径时间、机场服务水平、票价等因素均可促进客流在机场群间的均衡分布.     

有轨电车氢燃料电池系统通风散热方法研究

为解决有轨电车氢燃料电池系统的散热问题,文章提出一种新型车载氢燃料电池系统通风散热方法,分析了该方法的散热原理和控制策略,并对通风散热结构进行了详细介绍。该车载氢燃料电池系统通风散热方法提高了系统散热效率,降低了散热风机能耗。     

基于数据驱动的机场水泥混凝土道面性能退化预测

针对机场道面性能退化过程的精确预测问题，本文采用数据驱动的机场道面预测性维护方法，通过指示变量将两种数据集进行联合分析，考虑机场道面性能退化过程受飞行交通量和道面面层厚度的影响，以机场道面性能状况指数衰变的非线性函数为期望函数，建立一种机场道面性能退化双参数预测模型；根据模型的参数估计结果，采用边际效应分析结合预测性能曲线图示，对不同飞行交通量水平和不同道面厚度等级的道面性能退化过程预测进行分析。结果表明，采用数据驱动和非线性混合效应方法，搭载联合估计技术，能较为显著地提高机场道面性能退化预测的精度和效果。     

Optimal bus fleet management strategy for emissions reduction

Transportation is a major cause for environmental degradation via exhaust emissions. For many transit-oriented metropolitan areas, bus trips often constitute a sizeable mode share. Managing the bus fleet, in particular updating buses to comply with the newer emissions standards, therefore, can have a substantial impact on transportation-induced air quality. This paper presents the approach of remaining life additional benefit–cost (RLABC) analysis for maximising the total net benefit by either early-retiring or retrofitting the current bus fleet within their lifespans. By referring to the net benefits for different bus types estimated by RLABC analysis, the most beneficial management scheme for the current bus fleet can be identified. Optimal bus fleet management (BFM) models based on the RLABC analysis for the operator and the government are developed. Then a government subsidy plan is produced to achieve win–win solutions, which will offer efficient and flexible management schemes. To illustrate the approach, the largest bus company in Hong Kong, which carries more than 23% of the total trips in Hong Kong, is taken as a case study example. Instead of adopting a fixed retirement plan, such as replacing buses at the age of 17 as is currently practised, the proposed method develops an optimal BFM scheme that progressively phases out buses or retrofits them. This study produces promising results to demonstrate the large benefit of this approach for optimal bus fleet management.     

密闭空间空气净化用滤材检测设备设计研究

随着机动车辆的普及,人们呆在密闭空间即驾乘室以及室内的时间会逐渐拉长,如何有效的控制密闭空间的PM2.5浓度值值得我们去探讨和研究。通过对密闭空间空气净化原理的分析,采用激光粒子计数方法,设计了密闭空间空气净化检验流程及相配套的检测设备,将密闭空间(含室内及驾乘室)大气中的PM2.5含量控制在标准要求的浓度值以内。     

船舶舱室置换通风系统的数值模拟和优化

船上有些空间大、人员集中、船体结构复杂的舱室,传统送风方式难以满足需求,给空气环境设计带来很大挑战。文章采用计算流体力学方法研究置换通风系统在船舶舱室中的应用,通过建立物理和数值计算模型,在设计初始阶段对其进行气流组织、热舒适性等方面的模拟分析和优化应用研究;针对某实船舱室的置换通风系统原始方案和优化方案进行对比分析,结果表明置换通风系统具有流动分层和垂直温度梯度的特点。相比原始方案,优化方案使舱室内温度、风速和热舒适性指标等得到优化,有效降低了吹风感,保证人体周围的空气品质,热舒适性指标也符合标准要求。对船舶置换通风系统的应用研究具有借鉴意义。     

自升式风电平台冲桩系统设计与研究

冲桩系统是自升式风电平台关键的辅助系统。该文介绍了自升式风电平台冲桩系统,列举了目前常见的几种冲桩系统配置方案,对各种方案进行了对比,并通过冲桩系统在实际平台上的第一手应用数据,得出了在特定海床土质情况下,高压水冲桩系统具有较好冲桩效果的结论。结论对最新一代自升式风电平台冲桩系统的设计有着重要的指导意义,对今后自升式风电平台冲桩系统的设计也提供了思路。     

某平台机舱进排风口气流组织的CFD模拟

某自升式平台的机舱进、排风口位置比较接近,机舱排出的热气受大气风影响可能返回进风口,进而提高进风温度,成为一个设计隐患。文章应用CFD技术,通过模拟一定的大气环境条件下进排风口处的气流组织,找出最不利工况,并提出切实可行的改进建议。