Optimal route decision with a geometric ground-airborne hybrid model under weather uncertainty

Adverse weather is the dominant cause of delays in the National Airspace System (NAS). Since the future weather condition is only predictable with a certain degree of accuracy, managing traffic in the weather-affected airspace is a challenging task. In this paper, we propose a geometric model to generate an optimal combination of ground delay and route choice to hedge against weather risk. The geometric recourse model (GRM) is a strategic Probabilistic Air Traffic Management (PATM) model that generates optimal route choice, incorporating route hedging and en-route recourse to respond to weather change: hedged routes are routes other than the nominal or the detour one, and recourse occurs when the weather restricted airspace becomes flyable and aircraft are re-routed to fly direct to the destination. Among several variations of the GRM, we focus on the hybrid Dual Recourse Model (DRM), which allows ground delay as well as route hedging and recourses, when the weather clearance time follows a uniform distribution. The formulation of the hybrid DRM involves two decision variables - ground delay and route choice - and four parameters: storm location, storm size, maximum storm duration time, and ground-airborne cost ratio. The objective function has two components: expected total ground delay cost and expected total airborne cost. We propose a solution algorithm that guarantees to find the global optimum of the hybrid-DRM. Based on the numerical analysis, we find that ground-holding is effective only when combined with the nominal route. Otherwise, it is optimal to fly on the route determined by the DRM without ground delay. We also find the formula of the threshold ground-airborne cost ratio, which we call the Critical Cost Ratio (CCR), that determines the efficacy of ground delay: the higher the CCR, the more effective the strategies involving ground delay. We conclude that both ground delay and route hedging should be considered together to produce the best ATM decisions.     

中国城市空气污染收敛性研究--以二氧化硫为例的实证分析

SO2作为一种常规污染物在1990年代初就受到中国政府的重点管控。文章利用2002-2012年我国113个城市的人均SO2排放量面板数据探讨了我国人均SO2排放量变化的内在规律,使用静态和动态面板数据的回归方法检验了市级人均SO2排放量的收敛性,并分析了人均SO2收敛速度的影响因素。实证结果显示：在全国范围及东、中、西部三大区域内,城市人均SO2排放量存在着绝对与相对收敛;在影响收敛速度的各因素中,人均收入的提高可以加快人均SO2排放的收敛速度,而人口密度的增加则会降低人均SO2排放量的收敛速度。     

人口集聚、空气污染与经济可持续发展

探究人口集聚、空气污染与经济可持续发展的关系是关乎国家经济高质量发展的关键性议题。选取 266 个中国地级以上城市作为研究基点,精研人口、环境同经济之间的关系,结果表明：人口集聚对经济可持续发展影响具有空间溢出效应,人口集聚与经济可持续发展之间存在非线性关系;空气污染与经济可持续发展二者之间存在非线性关系,且具有空间溢出效应;人口集聚对经济可持续发展的影响存在空气污染的中介效应。研究逻辑框架表明,人口集聚、空气污染与经济可持续发展者之间的关系存在“人口集聚—空气污染—经济可持续发展”的解释机制。最终得出结论：人口集聚导致城市拥挤城市耗能和排放增加加重了空气污染从而对经济可持续发展形成一定的制约。空气污染的存在削弱了人口集聚对经济可持续发展的促进作用,因此,要更加注意短期内人口快速集聚对经济可持续发展形成的制约,警惕人口过度集聚对空气污染的影响及由此对经济可持续发展带来的负面影响。升擢城市“温度”、拓展城市“宽度”、增益城市“浓度”、聚焦城市“密度”,引导人口在区域范围内合理适度集聚,形成人口集聚合理布局,以技术创新发展方式转变和生产率提升减轻人口集聚对空气污染的负面影响从而降低由于空气污染造成的对经济可持续发展的制约,推动经济可持续绿色发展。     

要想富，先修路？——不同交通运输发展在贫困地区经济发展效应的差异

基于中国11个集中连片贫困地区所涉及的87个地级市的动态面板数据,利用系统广义矩估计法克服内生性问题,可对不同交通运输方式在贫困地区的经济发展效应进行实证研究。研究发现,交通运输发展对贫困地区经济发展总体上起到了正向的促进作用,但不同交通运输方式在不同地区存在明显的差异。公路运输的发展在西南贫困地区和中部贫困地区的促进效果比在西北地区好。航空运输对中部贫困地区和西北贫困地区的经济发展同样起着显著的促进作用。普通铁路则因为在贫困地区的发展优势不明显,对经济发展的促进作用没有很好地发挥出来。     

新型室内空气污染物——SVOC危害与研究进展

当今社会,室内空气质量受到越来越多的关注。研究表明,室内空气污染中除了大家熟知的甲醛、挥发性有机化合物,还有一种半挥发性有机化合物(SVOC)。目前,我国室内SVOC污染研究还处于起步阶段,相关研究还比较少。本文主要对现阶段室内SVOC污染状况及其健康风险评价内容进行梳理、分析与总结,推动室内SVOC相关研究发展,以完善我国室内空气污染物检测体系,提升室内环境安全水平。     

Measuring imported case risk of COVID-19 from inbound international flights --- A case study on China

With COVID-19 spreading around the world, many countries are exposed to the imported case risk from inbound international flights. Several governments issued restrictions on inbound flights to mitigate such risk. But with the pandemic controlled in many countries, some decide to reopen the economy by relaxing the international air travel bans. As the virus has still been prevailing in many regions, this relaxation raises the alarm to import overseas cases and results in the revival of local pandemic. This study proposes a risk index to measure one country's imported case risk from inbound international flights. The index combines both daily dynamic international air connectivity data and the updated global COVID-19 data. It can measure the risk at the country, province and even specific route level. The proposed index was applied to China, which is the first country to experience and control COVID-19 pandemic while later becoming exposed to high imported case risk after the epidemic centers switched to Europe and the US afterward. The calculated risk indexes for each Chinese province or region show both spatial and temporal patterns from January to April 2020. It is found that China's strict restriction on inbound flights since March 26 was very effective to cut the imported case risk by half than doing nothing. But the overall index level kept rising because of the deteriorating pandemic conditions around the world. Hong Kong and Taiwan are the regions facing the highest imported case risk due to their superior international air connectivity and looser restriction on inbound flights. Shandong Province had the highest risk in February and early March due to its well-developed air connectivity with South Korea and Japan when the pandemic peaked in these two countries. Since mid-March, the imported case risk from Europe and the US dramatically increased. Last, we discuss policy implications for the relevant stakeholders to use our index to dynamically adjust the international air travel restrictions. This risk index can also be applied to other contexts and countries to relax restrictions on particular low-risk routes while still restricting the high-risk ones. This would balance the essential air travels need and the requirement to minimize the imported case risk.     

基于流畅度的空中交通流量管理分析

中国的空中交通流量管理业务由民用航空管理局空中交通管理局运行管理中心负责。当全国空中交通流量超过容量即临界值、预计管制员工作量过大时,运行管理中心对空中交通实行管制和限制,以防止流量超过容量的现象,但运行管理中心对全国流量进行管理控制的过程呈现出诸多不便。为此,对空中交通管制员在处理实际交通时的行为进行测量和分析,同时记录实际空中交通流量,并计算空中交通流畅度,最终确定交通流畅度和管制员工作负荷之间的关系。由此可见,在空中交通流量管理中,可以使用交通流畅废来为空中交通流量管理单位提供决策支持。     

全货运航空公司单分配严格枢纽航线网络优化设计

针对全货运航空公司,研究其货运航线网络的构建问题。基于单分配严格枢纽航线网络,对传统模型进行改进。以各航线上货物的委托运输成本和自有机队的运输成本,取代传统的单位运输成本和折扣因子,考虑枢纽点的中转成本和载运率对路径选择的影响。结合航空货运夜航的特征考虑各机队夜间可用时间的限制,以总成本最小为目标,构建数学模型,采用LINGO优化软件求解,验证模型的有效性,为全货运航空公司构建货运航线网络提供参考。     

废旧家用空调器的回收及关键技术研究

家用空调器等废旧家电的回收再利用，对全球的可持续发展具有重要意义，已经受到国内外的高度重视。介绍了一般废旧家用电器的回收过程、回收方法，并对废旧家用空调器的回收过程做了具体介绍，最后提出了家用空调器等废旧家电的回收再利用过程中的关键技术。     

汽车节能和排放环保的现状与发展趋势

文章介绍了由于计算机精确控制的、采用多气阀、高压直喷、稀薄燃烧等新技术的汽车发动机正在普及,现代电子控制装置在发动机上已全面应用,由此带来了油耗降低、排放污染下降显著的效果,并指出新型清洁能源车辆逐步走向实用,其相应的社会配套设施将形成一系列大有可为的全新行业。