Dynamics and equilibria of ecological predator-prey networks as nature’s supply chains

In this paper, we develop a dynamic network model of ecological food webs and prove that the set of stationary points of the projected dynamical system coincides with the set of solutions of a variational inequality governing the equilibrium of predator-prey networks. We also establish the equivalence between the ecological models and supply chain network equilibrium models and highlight the connections to spatial price equilibrium problems. We propose an algorithmic scheme, provide convergence results, and apply it to a food web drawn from a fisheries application.This paper is a contribution to the interdisciplinary supply chain network literature.     

The origins,development and future directions of data envelopment analysis approach in transportation systems

Over the last two decades, application of Data envelopment analysis (DEA) in transportation problems have gained considerable research attention. This paper presents a literature review and classification of the applications of DEA in transportation systems (TSs). First by classifying 40 papers from 2007 to 2018, the origins of DEA in transportation problems have been reviewed. Then the development and an overall view of DEA applications in TSs have been presented. We have classified the applications of DEA into six different contexts. In each context, published papers have deeply been analyzed. Content of analysis includes “Number of published papers during the time”, “target journals”, “countries”, “keyword frequency”, “most cited papers”, “map of most co-cited publications”. More important, we reported the “inputs and outputs variables” used in each paper. Further “a review of the selected papers” and “gaps/future research directions” have been given within each cluster. The results show that DEA is one of the most useful approach in evaluating TSs for policy makers. On the other hand, DEA can help the decision makers in transportation especially regarding environmental factors, sustainable development and eco-design. Finally, we proposed subjects for future researches including guidance for new studies in the field of DEA applications in TSs.     

A method to assess the eco-efficiency of a public bus transportation service

Brazilian Public Bus Transportation Service transports over 34.4 million passengers daily using approximately 107,000 urban buses. This service costs millions of dollars annually to the municipality and emits several pollutants to the atmosphere. Therefore, this paper proposes a method to assess the eco-efficiency of a Public Bus Transportation Service. The proposed method was tested in a medium-sized urban region in Brazil. Different scenarios representing changes in the vehicles engines and fuels were tested and analyzed. Six eco-efficiency indicators regarding emissions and fuel consumption were proposed to assess which mix of engines and fuels would bring the greatest eco-efficiency. The results were compared to targets based on Brazilian regulation and showed that the renewal of the fleet is necessary to meet the environmental targets, while also achieving fuel costs reduction.     

GAME THEORY AND PORT ECONOMICS: A SURVEY OF RECENT RESEARCH

The last decade has seen a significant upsurge of studies seeking to examine the impacts of port agents’ strategic decisions. The outcome has been a wide range of results and conclusions. The aim of this work is to provide a review of this recent research in the port industry that uses strategic interaction approaches from industrial organization and game theory. The paper concentrates on five topics: ownership, relationship between ports and their hinterlands, port authorities and port operators’ relations, capacity investment decisions, and port specialization. We present the objectives, methodologies and results of the papers reviewed, with special emphasis on how models are developed. The results are not always consistent between the works analyzed. On the one hand, this could be due to the complexity of the port industry and the high number of agents that intervene. Researchers need to simplify reality to build their models by imposing restrictive assumptions. On the other hand, results could be very sensitive to the techniques used or to the differences on the port environment of the countries of study. However, some conclusions can be extracted and they present a good starting point to develop more sophisticated models. Finally, we also propose avenues for future research.     

Is transportation improving urbanization in China?

This study applies the rolling-window causality test to analyze the interaction between transportation infrastructure and urbanization in China. Our results obviously support search-matching theory in that transportation infrastructure exerts positive effects on urbanization in sub-sample periods. Urbanization does not Granger cause transportation infrastructure development except for the 1977–1980 period, when urbanization exerted negative effects on transportation infrastructure. The transportation structure is inadequate, and rational allocation of transportation resources is needed to improve the level of urbanization. This means that transportation improves urbanization due to government investment and regional integration. Development of transportation infrastructure has been rapid, which improved urbanization during the Great Cultural Revolution period. Urbanization urgently needs to keep up with the development of traffic infrastructure construction by adding to traffic investment. Transportation infrastructure requires whole planning, a unified layout, and rational adjustment of the transportation structure.     

Optimizing a bi-objective inventory model of a three-echelon supply chain using a tuned hybrid bat algorithm

This paper presents a bi-objective VMI problem in a single manufacturer-single vendor multi-retailer (SM-SV-MR) supply chain, which a redundancy allocation problem is incorporated. In the hybridized problem, a manufacturer produces a single item using several machines that work in series, and stores it in a warehouse to replenish one vendor who delivers it to several retailers using the shortest possible route. A novel meta-heuristic, called hybrid bat algorithm (HBA), with calibrated parameters is utilized to find a near-optimum solution. To show the efficiency of HBA, the results are compared to the ones using the traditional BA and a genetic algorithm.     

西部开发重点区域交通基础设施评价--以南贵昆经济区为例

交通基础设施作为社会先行资本,能够为一个区域的发展提供强有力的物质基础,国家西部开发的战略把交通基础设施的建设摆在极其重要的位置上.以西部开发的一个重点区域--南贵昆经济区为例,研究该区域的交通基础设施的建设现状及存在的问题,并结合西部开发的战略要求,探索适合该区域的交通基础设施发展方向.     

粮食仓库仓顶输送设备选型分析

粮食仓库仓顶入仓工艺及设备的选择,应根据项目不同的功能,分析投资和使用成本,来合理选用仓顶多点卸料的形式,满足业主的特殊要求。基于此,主要针对粮食筒仓的仓顶输送设备选型进行分析。     

An empirical study on coalition formation and cost/savings allocation

Interest has been raised by the recent identification of potential savings through collaborative planning in logistics operations. Even though substantial savings can be realized, two key questions exist: (i) how should potential savings be divided among a group of collaborating companies and (ii) among potential collaborating companies, how should collaborating group(s) be formed? These two questions are studied in a specific context: among potential collaborating companies; a subset, denoted the leading companies, performs collaborative planning on behalf of the others and together, they initiate formation of a collaborating group. We use the concept of a business model to detail such context. Based on the literature on network formation where potential savings are modelled by a cooperative game, four business models are explored in four different subsets of leading companies. We propose a network model as a method to determine the stable collaborating group in each computation. A case study including eight forest companies is described and analyzed. Results show that very different solution characteristics can be achieved depending on the business model selected.     

房价水平、交通成本与产业区位分布关系再考量

中心城市房价水平或地租水平的提高具有客观性。房价水平和交通成本变动对制造业区位分布影响较大,而对于生产性服务业的影响并不显著。占用土地面积较大的制造业向外转移不仅有可能抵消房价上涨的压力,而且为具有更高附加值的生产性服务业的发展创造条件。房价水平上涨和交通成本提高加快中心城市制造业的扩散以及生产性服务业的集聚,客观上促使城市间由专业化分工向功能分工结构转变,推动中心城市实现产业升级,有利于形成合理的区域分工格局。