An inventory-based simulation model for annual-to-daily temporal freight assignment

In the aggregate freight demand modeling literature, temporal assignment (annual to daily flows) is often oversimplified or neglected altogether. Unlike passenger flows, freight flows over the course of a year are not uniform and can vary significantly as the result of trade-offs between inventory and transportation cost management. We introduce the first temporal assignment model that explicitly considers these trade-offs for aggregate freight forecasting. A two-stage model is proposed that first decomposes aggregate annual zonal flows to firm group annual flows using a supply chain network model, which are then temporally assigned by simulating purchase order transactions throughout supply chains. Lot sizes are estimated with an Economic Order Quantity (EOQ) model and calibrated with monthly inventory data. The result is an aggregate-disaggregate-aggregate model that fits into aggregate freight forecasting models but makes use of more disaggregate logistical data. The model is illustrated with a simple replicable example, followed by a case study conducted with California statewide data to break out the distributed zonal flows into average daily volumes for network assignment. Calibration results using 2007 IMPLAN data showed a median percentage difference of simulated annual flows from FAF³ data of 2.38%, and a median percentage difference of simulated inventories from IMPLAN data of 4.85%, which suggests an excellent fit. Empirical validation results showed the model outperforms fixed factor approaches in mean value accuracy by 15–31%.     

Modeling downstream petroleum supply chain: The importance of multi-mode transportation to strategic planning

This paper proposes a deterministic mixed integer linear programming (MILP) model for downstream petroleum supply chain (PSC) network to determine the optimal distribution center (DC) locations, capacities, transportation modes, and transfer volumes. The model minimizes multi-echelon multi-product cost along the refineries, distribution centers, transportation modes and demand nodes. The relationship between strategic planning and multimodal transportation is further elucidated. A case study was considered with real data from the U.S. petroleum industry and transportation networks within Geographic Information System (GIS). A scenario analysis is also conducted to demonstrate the impact of key parameters on PSC decisions and total cost.     

Dynamic electric power supply chains and transportation networks: An evolutionary variational inequality formulation

In this paper, we develop a static electric power supply chain network equilibrium model with known demands and establish the equivalence between the model and a transportation network equilibrium model with fixed demands over an appropriately constructed supernetwork. This equivalence yields a new interpretation of electric power supply chain network equilibria in path flows. We then exploit this equivalence to propose a dynamic electric power supply chain network model in which the demand varies over time using an evolutionary variational inequality formulation. Finally, we demonstrate how numerical dynamic electric power supply chain network problems can be solved utilizing recently obtained theoretical results in the unification of evolutionary variational inequalities and projected dynamical systems.     

The geography of maritime networks: A critical review

Despite early cartographical and graph-theoretical analyses of maritime flows in the 1940s and 1960s, it is only from the 2000s onwards that maritime network analysis had grown apace, backed by newly available shipping data, increased computational power, and renewed conceptual frameworks to study networks in general. The evolution of maritime network analysis, in geography and other sciences, is marked by a wide diversity of methods and themes, which we classify into three main parts. We first present studies looking at maritime flows in an abstract space, focusing on operational, statistical, or managerial aspects where navigation, graph structure, and firms' strategies are the key concerns. Second, we review researches where maritime flows and networks are markers and vectors of wider geo-economic structures and dynamics, such as regional inequalities and areas of dominance. Lastly, maritime networks have also been considered as integral parts of territories and wider chained systems, such as urban networks, regional networks, and coupled networks. We conclude that network analysis and maritime transport still share many uncovered areas and discuss potential research pathways for future works.     

Disruption-driven supply chain (re)-planning and performance impact assessment with consideration of pro-active and recovery policies

In this study, an approach to re-planning the multi-stage supply chain (SC) subject to disruptions is developed. We analyze seven proactive SC structures, compute recovery policies to re-direct material flows in the case of two disruption scenarios, and assess the performance impact for both service level and costs with the help of a SC (re)planning model containing elements of system dynamics and linear programming. In the result, an explicit connection of performance impact assessment and SC plan reconfiguration issues with consideration of the duration of disruptions and the costs of recovery has been achieved.     

Design and planning for green global supply chains under periodic review replenishment policies

We quantify the impact of jointly optimizing strategic network design and tactical inventory planning on the cost and CO₂ emissions of multi-echelon logistics networks. The obtained insights indicate that longer optimized replenishment cycles reduce a node’s transportation cost and CO₂ emissions but increase its inventory costs. Moreover, under a fixed replenishment cycle, a node’s service level increases when supplied by a satellite warehouse. Finally: (i) the costs of implementing optimal green network design decisions could be misleading if inventory planning is neglected, (ii) greening of supply chains could become expensive, (iii) current legislative CO₂ ton prices hardly influence logistics networks.     

A multi-level spatial-temporal model for freight movement: The case of manufactured goods flows on the U.S. highway networks

The spatial production, attraction, and movement of manufactured goods are vital to the economy of a region and country. The U.S. department of transportation also mandates to incorporate continuing and efficient freight movement and infrastructure into statewide and local long range planning. Studies on supply, demand, and transport of manufactured goods by firm, industry, mode, or commodity are vast in the logistics and supply chain literature. However, relatively sparse research is available on aggregated movement or freight on national, state, or local transportation networks. Better understanding and modeling freight movement on highway networks to facilitate local transportation, land use, economic development, and comprehensive planning is at the heart of freight research. Therefore, the major endeavors and novel contributions of this research include a conceptual framework proposed for freight movement research, a multi-level spatial-temporal freight model based upon the social optimum assignment for optimal “from”, “to”, “within”, and “through” freight flows of manufactured goods on the U.S. highway networks, and a set of performance measures designed to reveal states in terms of their competitive advantages in production, attraction, self-sufficiency, or cross-road. The freight flows were first visualized and highlighted by state at the U.S. level, then by county at the state level for Oklahoma, and finally by traffic analysis zone for the Tulsa metropolitan area. The spatial split of freight flows was accomplished through using freight, network, and demographic-economic databases at state, county, and zone scales.     

Scheduling commercial vehicle queues at a Canada-US border crossing

Using the context of queue operations at a major Canada-US commercial border crossing for truck-borne trade flows, we report on a computer simulation study to predict the likely impacts of smoothing those flows. We quantify the operational and resource efficiencies of smoothing for trans-border trucking companies and their trans-border supply chain partners as well as for government authorities with regulatory jurisdiction at border crossings. Our study’s major conclusion is that smoothing can achieve queue performance levels that, in the absence of smoothing, would require significant investment in truck processing capacity at border crossings.     

A multilevel spatial interaction model of transit flows incorporating spatial and network autocorrelation

While it is well known that ignoring spatial dependence often results in misspecification of models, travel demand models almost never account for this phenomenon. The aim of this paper is to empirically demonstrate the importance of accounting for potential spatial dependence between observations in the specification of spatial interaction models. As a case study, we analyze travel flows on the public transport system in an urban region in the Netherlands. We develop five distinct spatial interaction models (SIMs) of increasing complexity, each encompassing a lower and upper level model. At the lower level, the attractiveness of neighborhoods for boarding and alighting is modeled based on spatial and transit supply characteristics. At the upper level, spatial interactions among zones are modeled taking into account competing origins, competing destinations as well as network characteristics. We systematically compare more traditional SIM formulations with a SIM that explicitly accounts for spatial and network autocorrelation. The results show a substantial difference between the former models and the latter, in terms of the estimated total marginal impacts of the different variables and the pattern of the error terms. The results of our study underscore that the failure to incorporate autocorrelation effects in travel models is likely to influence model outcomes, which in turn may have profound implications for the very design of public transport networks in cities and regions.     

城市轨道交通牵引供电制式的比较与选择

牵引供电制式的选择对于轨道交通来说意义重大,介绍城市轨道交通供电系统组成．说明DC1500V与DC750V的不同特点,分析接触轨与接触网的不同。通过技术特点的比较．得出DC1500V架空接触网方式是最优方式,也将是轨道交通供电系统的发展方向的结论。     

A supply chain-transport supernetwork equilibrium model with the behaviour of freight carriers

This paper presents a supernetwork equilibrium model integrating supply chain networks with a transport network, namely, a supply chain-transport supernetwork equilibrium model. The model takes into account the behaviour of freight carriers and transport network users to endogenously determine the transport costs generated in the supply chain networks. The interaction between transport network and supply chain networks can also be examined. Results of the numerical tests reveal that the improvement of transport network could enhance the efficiency of supply chain networks. The paper makes contributions to modelling of supply chain networks as well as to that of transport networks.     

Supply chain integration,landside operations and port accessibility in metropolitan Chicago

Seaports have traditionally been the focus of maritime logistics supply chains. Changing production patterns demanding greater end to end visibility by customers and accessibility to key inland population centers assume greater importance in the organization and design of transport resources and cargo flows. While synchronization of all aspects of the supply chain has become an operational necessity for firms, it is often held hostage to the efficiency of hinterland networks who must respond to a large group of stakeholders with sporadic coordination. This is particularly true when looking at the central US city and region of Chicago, a critical intermodal exchange point for truck, air and river barge traffic domestic and global, as well as a major central distribution location. This paper analyzes supply chain integration (SCI) efforts in the metropolitan Chicago region and considers efforts by public and private actors to collaborate for region-wide SCI improvements. Pareto analysis suggests that concentrated freight corridors exist, influencing freight planning for regional transportation networks more directly than diffused regional freight movements. If the corridor service becomes less responsive or congested the corridor will move to different end nodes within the broad region. Regional planning must thus address national, regional, and local moves. Private/public sector infrastructure firms should address functional cooperation on SCI by focusing on corridors as well as local improvements.     

Analysis of traffic congestion costs in a competitive supply chain

We study a competitive facility location problem with identical suppliers competing in multiple markets subject to distribution network congestion. We first analyze the solution of a symmetric competitive location game and discuss the firms’ facility location and equilibrium market supply decisions. Then, we utilize the model to provide analytical characterization of the effects of traffic congestion costs on equilibrium distribution flows. These analytical results permit qualitative characterization of how changes in congestion levels and costs affect equilibrium location and distribution decisions. The results of extensive numerical studies serve to further illustrate the effects of traffic congestion costs on location, market supply quantity, and distribution decisions.     

Increasing the resilience of air traffic networks using a network graph theory approach

Air traffic networks are essential to today’s global society. They are the fastest means of transporting physical goods and people and are a major contributor to the globalisation of the world’s economy. This increasing reliance requires these networks to have high resilience; however, previous events show that they can be susceptible to natural hazards. We assess two strategies to improve the resilience of air traffic networks and show an adaptive reconfiguration strategy is superior to a permanent re-routing solution. We find that, if traffic networks have fixed air routes, the geographical location of airports leaves them vulnerable to spatial hazard.     

Gravitational force exerted by Brazilian tourist destinations on foreign air travelers

This article analyses the context of international tourist flows by air and tourism in Brazil, by applying the principles of the gravity model. The study includes 13 Brazilian international airports that served 108 origin-destination pairs, which accounted for 80.14% of the total tourist flows by air in 2012. In the statistical analysis applied, the dependent variable Ft is the tourist flow between the country of origin and the Brazilian state of destination. To approximate an explanatory equation, we formulated a linear function that was able to support, in 31.7% of the cases, the dependence of the international tourist flows with the variables considered in the linear regression performed. The conclusion is that the assumptions considered in this study only partially explain the gravitational force exerted by Brazilian tourist destinations, so there is a need to refine the model by including other variables that can influence the flows by air of international tourists.     

More than medical tourism: lessons from Indonesia and Malaysia on South–South intra-regional medical travel

While scholars increasingly acknowledge that most contemporary international medical travel comprises South–South flows, these have gone curiously unexamined. Rather, policy, scholarly and media attention focuses predominantly on North–South flows of ‘medical tourists’. However, this focus diverts attention from the actual and potential impacts of South–South intra-regional medical travel flows on both their source and receiving contexts. As such, we present findings from a study examining South–South intra-regional medical travellers' motivations, preparations and practices to better understand the social, economic and political situations that condition them and their effects on the destinations that receive them. Our study of Indonesian medical travellers pursuing health care in Malaysia draws on 35 semi-structured interviews with Indonesian patients, their companions, medical staff and agents in both countries. From this, we suggest that South–South medical travellers' diverse socio-economic conditions shape decision-making and spending behaviour relative to treatment, accommodation and transport choices as well as length of stay. We identify ways in which informal economies and social care networks sustain the formal medical travel industry. Finally, we observe how medical travel increasingly serves as a means through which chronic and everyday health needs are met through temporary, visa-free intra-regional movement.     

Designing the distribution network in a supply chain

This paper describes a framework for designing the distribution network in a supply chain. Various factors influencing the choice of distribution network are described. We then discuss different choices of distribution networks and their relative strengths and weaknesses. The paper concludes by identifying distribution networks that are best suited for a variety of customer and product characteristics.     

A supply chain network design model for biomass co-firing in coal-fired power plants

We propose a framework for designing the supply chain network for biomass co-firing in coal-fired power plants. This framework is inspired by existing practices with products with similar physical characteristics to biomass. We present a hub-and-spoke supply chain network design model for long-haul delivery of biomass. This model is a mixed integer linear program solved using benders decomposition algorithm. Numerical analysis indicates that 100 million tons of biomass are located within 75 miles from a coal plant and could be delivered at $8.53/dry-ton; 60 million tons of biomass are located beyond 75 miles and could be delivered at $36/dry-ton.     

Strategic design and operational management optimization of a multi stage physical distribution system

Design and management of logistic networks is one of the most critical issues in supply chain management. However, the literature does not contain any effective models, methods, and applications that simultaneously support management decisions in the strategic design of the distribution system, in the operational planning and organization of vehicles, and in container trips organization adopting different modes of transportation. The aim of this paper is to illustrate an original framework for the design and optimization of a multi echelon and multi level production/distribution system that combines mixed-integer linear programming modeling with cluster analysis, heuristic algorithms, and optimal transportation rules. A significant case study is illustrated revealing the effectiveness of the approach and tools proposed.     

On the design of closed-loop networks for product life cycle management: Economic,environmental and geography considerations

The management of the product life cycle needs industrial synergies along large-scale networks to collect, recycle, reuse, and recover the end-of-life products. This paper provides a tool to assess the enabling economic, environmental, and transport geography conditions to design sustainable closed-loop networks for the management of a generic product along its life-cycle. The proposed tool is built through a mixed-integer linear programming (MILP) model for the strategic design of a multi-echelon closed-loop network. The product life cycle is handled via a cascade through seven stages, including raw material suppliers, manufacturing plants, distribution centers, retailers, collection nodes for waste and by-products, recycling centers, and landfills.The model minimizes a cost-based and a carbon-based function to determine the optimal geographic location of the nodes of the network and the allocation of transport flows. The model is applied to a case study inspired by the furniture industry over the Italian geography and a multi-scenario analysis is illustrated. The resulting considerations on the economic, environmental performances of the network couple with the transport geography to provide guidelines for designer, logistics planners and regional geographers toward a circular economy scenario.