Maria Sameiro Carvalho

New mixed integer-programming model for the pickup-and-delivery problem with transshipment

In recent years, many important real-world applications are studied as “rich” vehicle routing problems that are variants and generalizations of the well-known vehicle routing problem. In this paper we address the pickup-and-delivery version of this problem and consider further generalization by allowing transshipment in the network. Moreover, we allow heterogenous vehicles and flexible fleet size. We describe mixed integer-programming formulations for the problem with and without time windows for services. The number of constraints and variables in the models are bounded by polynomial size of the problem. We discuss several problem variants that are either captured by our models or can be easily captured through simple modifications. Computational work gave promising results and confirms that transshipment in network can indeed enhance optimization.

An extensive structural model of supply chain quality management and firm performance

Purpose – The purpose of this paper is to explore the concept of supply chain quality management (SCQM) and to propose a research model that considers the impact of SCQM practices on firm performance. Design/methodology/approach – Based on a comprehensive literature review, SCQM most relevant practices were analyzed and selected. These practices were categorized into four dimensions: upstream (supplier assessment, supplier quality management (QM)), downstream sides of a supply chain (customer focus), internal process (product/service design, process management and logistics) and support practices (top management support, human resource management, information and supply chain integration). The measurement instrument of firm performance was also developed, including three aspects: operational performance, customer satisfaction and financial performance. Findings – An innovative conceptual framework that provides a comprehensive picture covering core dimensions of SCQM and various aspects of firm performanc...

A warehouse design decision model — Case study

Todaypsilas competitive and volatile market requires flexibility, quality and efficiency from the logistics operations. In this context, warehouses are an important link of the logistic chain and warehouse management plays an important role over customerpsilas service. Throughout this work we analyze a mathematical model aiming to support warehouse management decisions. A case study is used for that purpose and the model jointly identifies product allocation to the functional areas in the warehouse, as well as the size of each area. This case study also evaluates the performance of the model when real data is used. Model is solved using LINGO 9.0 mixed-integer commercial solver, and potential savings achieved using the proposed technique are discussed.

Managing construction supply chain

Construction industry involves several players in a same project. Defining and coordinating such players and their activities is a very complex task. Hence, an information system capable of aggregate and display the relevant information, in the right time, is an extraordinary tool to help the construction site managers. There is a diversity of software available in the market that is very powerful in many specialised areas, but lacks the supply chain management overview. An integrated web portal to assist the managers in their daily tasks and simultaneously effectively control the entirely construction project is a partial result of a research project in a Portuguese construction company. This paper intends to show the main developments and preliminary conclusions in the implementation of this web portal to assist the logistics of construction projects.

An Integrated Simulation and Business Intelligence Framework for Designing and Planning Demand Responsive Transport Systems

Transportation planners, analysts and decision-makers usually make use of simulation tools in order to accurately predict the performance of new practices and policies before their implementation. Additionally, most of them, recently introduced new auxiliary Business Intelligence decision support tools in order to transform their available huge amount of real operating data into timely and accurate information for their decisions. However, although both of those types of automated decision support are valuable, very few attempts were already made by researchers to integrate them into a unified tool.

Design of wood biomass supply chains

The purpose of this paper is to propose a mathematical programming approach to minimize the total cost in a biomass supply chain. A company that collects material from forests, transforms it into chipped product, stores and delivers it to its customers is considered. For tackling all the aspects of the supply chain management, a mixed integer programming model that supports tactical and operational decisions was developed and optimized using a general purpose solver. The model was implemented in C++ and several computational tests have been performed.

Implementation of Multiple Criteria Decision Analysis Approaches in the Supplier Selection Process: A Case Study

Supplier evaluation and selection is recognized as a multiple criteria problem. Having considerable economic impact and influencing a competitive position of a buyer, supplier selection has been modelled by different multiple criteria decision analysis approaches. This case study focuses on the reported “relevance gap” between theoretical approaches to the supplier selection problem and practice. The research was conducted in a textile group, addressing a typical buying situation of a main raw material. The decision process was structured with weighted score, AHP and goal programming models. Three models elaborated have led to the very similar output, recognized as realistic and consistent by the decision makers. Acquired skills of multiple criteria decision analysis were considered as beneficial for supplier selection decisions.

Warehouse design and planning: a mathematical programming approach

The dynamic nature of todays competitive markets compels organizations to an incessant reassessment in an effort to respond to continuous challenges. Therefore, warehouses as an important link in most supply chains, must be continually re-evaluated to ensure that they are consistent with both markets demands and managements strategies. A number of warehouse decision support models have been proposed in the literature but considerable difficulties in applying these models still remain, due to the large amount of information to be processed and to the large number of possible alternatives. In this paper we discuss a mathematical programming model aiming to support some warehouse management and inventory decisions. In particular a large mixed-integer nonlinear programming model (MINLP) is presented to capture the trade-offs among the different inventory and warehouse costs in order to achieve global optimal design satisfying throughput requirements.

Urban logistics: A systematic literature review

City Logistics aims to reduce the nuisances associated to freight transportation in urban areas while supporting the economic and social development of the cities. Sustainable freight transport today are on the political, social and technological agenda of many actors operating in urban contexts. The purpose of this paper is to present a systematic literature review (SLR) that aims to consolidate the knowledge on urban logistics by reviewing the developments of the last 17 years in the field of Freight Transport research and innovation. The majority of articles focused on issues like commodity flows and economic modelling aspects, but there has been relatively little research reported on issues like collaboration among stakeholders, usage of Intelligent Transportation Systems (ITS) and E-commerce. Finally, based on the findings from the literature review, future research directions are proposed in an attempt to stimulate further studies on emerging trends and innovative strategies in the broad area of urban logistics.

Integer Programming Model for Ship Loading Management

Industries only survive in the modern business world if they are prepared to improve processes whenever it is necessary. Therefore, companies need to adapt and/or modify processes to improve the level of service and reduce needless costs. In this article the logistics problem of planning a ship load operation of a Portuguese cement company is addressed. The objective is to determine the best way to transport the bagged cement from the warehouse to a ship reducing costs and optimizing forklifts operations. A mathematical programming model is proposed showing this methodology as a powerful tool to provide effective support to a more intelligent decision process.