A multi-path routing-inventory problem for a closed-loop supply chain considering the heterogeneous fleet of vehicles

In this paper, the inventory-routing problem is studied for a closed-loop supply chain. This closed-loop supply chain considers suppliers, manufacturers, whole-sellers, and disposal centers. To formulate this problem, a mixed integer linear programming model is proposed. This mathematical model minimizes the total costs of the supply chain, including the fixed and variable costs of vehicles, and holding inventory costs of final products and scraps. The proposed model considers the road roughness degree, multi-path setting and the heterogeneous fleet of vehicles, which increases its flexibility and the quality of solutions. Then, two symmetry-breaking constraints are proposed to reduce the complexity of the mathematical model. In order to evaluate the integrity of the proposed model, 20 instances of different sizes are randomly generated and solved. Finally, a comprehensive sensitivity analysis is conducted with respect to five key features of the problem, such as the impact of the symmetry-breaking constraints on the CPU time, multi-path setting, fixed cost of vehicles, heterogeneous fleet of vehicles, and lost sales. The results indicate that the consideration of multi-path setting and the heterogeneous fleet of vehicles improves the quality of solutions significantly.     

石油企业如何深入推进车队HSE标准化建设

标准化管理不仅是企业发展的内在需求也是企业适应市场的客观需要。本文基于石油企业车队现有的管理基础,探讨车队HSE标准化建设经验,通过着力抓好"基础管理-驾驶员管理-车辆管理-运行控制-应急管理"5个方面,深入推进车队标准化建设,建立交通运输风险防控长效机制。从实践情况来看,提升了企业交通安全管理水平,对企业的长远发展具有重大的现实意义。     

基于机会约束规划的航班应急调度问题研究

为应对民航突发情况,保障民航运行安全,提出应急调度这一概念。阐述常规情况下航班调度基本模型,分析其在应急情况下的弊端。引入机会约束,构建应对突发状况的应急调度模型。研究兼顾航空公司成本、航班运行安全及旅客随机需求的机型分配问题(FAP)模型和机组排班问题(CSP)模型。比较混合智能算法、隐枚举法、等价转化法的优缺点及适用度。根据案例数据,使用Matlab软件编程,并采用随机模拟与粒子群(PSO)算法相结合的智能算法对模型求解。结果表明,机会约束规划模型在考虑随机因素的情况下,比基本模型更符合实际动态环境。     

基于模糊灰色关联的航空公司机队可靠性指标的优选

机队是航空公司运输能力的关键,机队可靠性是航空公司安全保障的重要环节之一。鉴于影响航空公司机队可靠性指标具有多模糊性和随机性等灰色系统特征,结合模糊灰色关联特性,建立了机队可靠性指标模糊灰色关联分析优选模型。同时为了提高关联度分辨力和满足关联分析更符合实际,对分辨系数取值做了合理的判定。以航空公司机队可靠性统计数据为例,计算得出机队可靠性指标与可靠性等级的关联度和关联序,确定影响机队可靠性指标主要相关因素,找出了机队可靠性最佳优先控制指标。该研究为确定机队可靠性优先控制指标的选取提供了一种较为科学的定量化依据,有助于掌握机队可靠性规律提供支持,对于提高航空公司机队可靠性管理水平具有现实的意义。     

Threats of illegal,unregulated, and unreported fishing to biodiversity and food security in the Republic of the Congo

Illegal, unregulated, and unreported (IUU) fishing poses a major threat to effective management of marine resources, affecting biodiversity and communities dependent on these coastal resources. Spatiotemporal patterns of industrial fisheries in developing countries are often poorly understood, and global efforts to describe spatial patterns of fishing vessel activity are currently based on automatic identification system (AIS) data. However, AIS is often not a legal requirement on fishing vessels, likely resulting in underestimates of the scale and distribution of legal and illegal fishing activity, which could have significant ramifications for targeted enforcement efforts and the management of fisheries resources. To help address this knowledge gap, we analyzed 3 years of vessel monitoring system (VMS) data in partnership with the national fisheries department in the Republic of the Congo to describe the behavior of national and distant-water industrial fleets operating in these waters. We found that the spatial footprint of the industrial fisheries fleet encompassed over one-quarter of the Exclusive Economic Zone. On average, 73% of fishing activity took place on the continental shelf (waters shallower than 200 m). Our findings highlight that VMS is not acting as a deterrent or being effectively used as a proactive management tool. As much as 33% (13% on average) of fishing effort occurred in prohibited areas set aside to protect biodiversity, including artisanal fisheries resources, and the distant-water fleet responsible for as much as 84% of this illegal activity. Given the growth in industrial and distant-water fleets across the region, as well as low levels of management and enforcement, these findings highlight that there is an urgent need for the global community to help strengthen regional and national capacity to analyze national scale data sets if efforts to combat IUU fishing are to be effective.     

Application and Quality Assessment of an Instantaneous Vehicle Emission Model at Fleet Level

A developed instantaneous emission model is applied to predict emission factors for small vehicle fleets for quality assessment. Extensive vehicle measurements of pre-Euro-1 gasoline, Euro-3 gasoline, and Euro-2 diesel vehicles are available. The data were used to develop individual vehicle emission models for each car. The prediction quality for each vehicle category was determined by averaging the results obtained from the individual vehicle models. The results show that the prediction quality is improved in comparison with the individual vehicles, even with a small number of vehicles in a specific category. This indicates that the errors in the individual models are mainly random and that prediction quality, when applied to fleets of cars, is exceptionally high.     

济南市机动车保有现状及其污染排放控制措施

近年来，济南市机动车保有量增长较快，本文主要研究济南市机动车的保有现状、发展趋势和机动车污染排放分布状况，在机动车污染控制方面提出了应对措施，包括：发展清洁汽车、优先发展大型公交、严格控制机动车污染排放、严格执行机动车报废制度、实施机动车环保分类标志管理等。     

中国机动车污染物排放因子及其修正方法研究

中国机动车污染物排放已成为影响空气质量的重要源。机动车污染的研究中,排放因子的确定是关键。根据机动车使用状况,车用燃料硫含量和行驶状况,运用MOBILE6．2的方法和原理确定了中国各类型机动车HC、CO、NOx的综合排放因子。小型汽油客车国0阶段CO、HC、NOx的综合排放因子分别为34．29g／km、3．45g／km和0．856g／km;国Ⅰ阶段CO、HC、NOx的综合排放因子分别为2．80g／km、0．25g/km和0．40g／km;国Ⅱ阶段CO、HC、NOx的综合排放因子分别为1．39g／km、0．16g／km和0．09g／km。