对运输业网络经济的探讨

运输业在基础设施和运输组织两个层次上都具有显著的网络经济特征,运输业的规模经济和范围经济均来自于其网络经济.建立了基本的运输网络经济分析模型,依据一体化特征对运输业进行了层次划分,对运输业不同产业层次的网络经济特征进行研究,提出相关运输经济管制政策取向的建议.     

Do you think that the home delivery is good for retailing?

Order placing and delivery always play a significant role in any business industry. Nowadays, most customers want useful products at their doorstep without visiting any retail store. In this current study, an advanced dual-channel supply chain model is constructed for a single product with two players. Customers can order online or offline from the retail store. In contrast, retailers use only offline mode to take the product from the manufacturer, and retailers charge a different amount for delivery. To optimize profit and satisfy the consumers, retailers only provide a free transportation service when customers order a certain quantity. If customers order less than the desired amount, a transportation charge will be applied to the customers. Contrary to the existing research, demand for the products varies with the selling price online and offline and is also affected by the free home delivery service. Manufacturers use a single-setup multi-delivery (SSMD) transportation strategy to enrich the system's profit. To make the study more applicable, all unit costs are considered fuzzy. Signed-distance defuzzification technique is adopted to defuzzify the fuzzy values. Finally, the total profit of the supply chain is optimized along with the optimized value of the decision-making variable through an uncertain optimization technique. Numerical experiments are carried out along with sensitivity analysis to show the applicability and optimality of this study. Though the crisp data set provided a 0.72% better result compared to the fuzzy data set, but fuzzy data set provided a more realistic result. Numerical results prove that the home delivery service provided 14.59% better profit. Finally, it can be stated that the home delivery policy with some charged amount based on ordered quantity is the best retailing strategy for the dual-channel supply chain.     

我国煤矿机电一体化技术的发展现状浅析

机电一体化技术在煤矿生产中起着举足轻重的作用。本文介绍了我国煤矿机电一体化技术的发展现状,分析了我国煤矿机电一体化技术所存在优势与劣势。对机电一体化发展有一定的指导意义。     

城市中心区的大学文化特色空间整体性研究——基于南京实证区的空间定量分析

我国近30年的快速城市化发展,使许多大城市的中心区面临着高强度开发带来的多重压力.尤其对于首批国家历史文化名城四大古都之一的南京,市中心具有近百年历史的高校传统风貌区,在周围不断耸立起的高层建筑挤压下,空间被逐步蚕食,严重削弱了城市的文化形象.基于这一背景,本文将南京市汉口路一线的南京大学等四所高校与周边社区所构成的区域,作为一种特殊的城市文化特色风貌区进行整体性研究;通过视觉界面分布、时间可这性、空间句法等空间定量及其可视化分析,结果表明:大学校园有力的承栽着周边社区居民的公共生活,是整个区域的景现、绿化、文化、体育与人流集聚中心,大学校园与周边社区一起形成了有机完整富有活力的历史文化特色区域,应该像历史街区一样进行立法保护.     

The influence of proximity to market on bean producer prices in Nicaragua

Transport costs are an important determinant of smallholder welfare in developing countries. In particular, transport costs influence the prices that smallholders receive for their produce. We propose a simple way of quantifying this influence. Taking the example of bean producers in Nicaragua, we employ a hedonic price model to estimate the effects of a smallholder's proximity to markets on the prices that he/she receives, while controlling for other factors such as the volume and quality of beans sold. We find that on average each additional minute of travel time reduces farm gate prices by 2.5 cents per quintal. Based on these results, the annual income from bean sales of the average smallholder in our sample would increase by between 24 and 110 USD if travel time to markets were reduced by 25%. Estimates of this nature can make an important contribution to cost–benefit assessments of infrastructure investments.     

区域经济发展视角下我国民航区域市场需求分析及发展政策研究

在现代社会中,民航运输业作为交通运输基础产业不仅是城市间物质、资源交换的载体,同时也是各地政府促进区域经济发展和转型升级的重要条件。本文首先基于对航空运输的网络产业特性的分析,揭示航空运输与区域经济的内在关系。其次从区域市场经济发展水平、运输能力等角度,构建民航区域市场需求的指标体系,利用多元统计分析方法和多年统计数据进行实证研究,并对我国各省市民航市场发展水平进行综合评价。根据民航发展的内在机理,提出政府发展和规划民航业的政策建议。     

Reliable design of an integrated supply chain with expedited shipments under disruption risks

This paper studied the design of a two-echelon supply chain where a set of suppliers serve a set of terminals that receive uncertain customer demands. In particular, we considered probabilistic transportation disruptions that may halt product supply from certain suppliers. We formulated this problem into an integer nonlinear program to determine the optimal system design that minimizes the expected total cost. A customized solution algorithm based on Lagrangian relaxation was developed to efficiently solve this model. Several numerical examples were conducted to test the proposed model and draw managerial insights into how the key parameters affect the optimal system design.     

Robust optimization for United States Department of Agriculture food aid bid allocations

The U.S. Department of Agriculture (USDA) currently uses a bidding system to determine carriers and suppliers that would partner in providing food aid annually in response to global emergencies and famine. We mimic the USDA approach via a robust optimization model featuring box and ellipsoid uncertainty frameworks to account for uncertainties in demand, supplier and carrier bid prices. Through a case study utilizing historical invoice data, we demonstrate our model applicability in improving ocean carrier and food supplier bid pricing strategy and similar supply chain network optimization problems. Through a validation algorithm we demonstrate the value of our robust models.     

Suburbanization and highways in Spain when the Romans and the Bourbons still shape its cities

We estimate the effects of highways on the suburbanization of Spanish cities. Based on Spain’s historical roads – the almost 2000 years old Roman roads and the 1760 Bourbon roads –, we rely on an instrumental variables (IV) strategy because of the endogeneity of highway provision. Our results show that, first, each highway emanating from central cities caused an 8–9% decline in central city population between 1960 and 2011. Second, each highway ray fostered a 20% population growth in the suburbs, in particular in suburban municipalities where ramps were located. Finally, we confirm the increasing role of highways on shaping urban form: each additional kilometer closer to the nearest highway ramp increased municipal density growth by an 8%.     

Truck and trailer scheduling in a real world,dynamic and heterogeneous context

We present a new variant of the Vehicle Routing Problem based on a real industrial scenario. This VRP is dynamic and heavily constrained and uses time-windows, a heterogeneous vehicle fleet and multiple types of job. A constructive solver is developed and tested using dynamic simulation of real-world data from a leading Scottish haulier. Our experiments establish the efficiency and reliability of the method for this problem. Additionally, a methodology for evaluating policy changes through simulation is presented, showing that our technique supports operations and management. We establish that fleet size can be reduced or more jobs handled by the company.