Anna Maria Coves Moreno

Performance evaluation of hybrid-CLP vs. GA: non-permutation flowshop with constrained resequencing buffers

This paper is located in the area of mixed model non-permutation flowshop production lines where jobs of more than one model are being processed on the same production line in an arbitrary sequence. Nevertheless, the majority of publications in this area are limited to solutions which determine the job sequence before the jobs enters the line and maintains it without interchanging jobs until the end of the production line, which is known as permutation flowshop. The present work considers a non-permutation flowshop. Resequencing is permitted where stations have access to intermediate or centralised resequencing buffers. The access to the buffers is restricted by the number of available buffer places and the physical size of the products. The primary objective is the minimisation of the make span, but also setup-cost and setup-time is contemplated. A hybrid approach, using constraint logic programming (CLP), is presented and compared to a genetic algorithm (GA). These solution methods are conceptually different and recommendations for their applicability are presented.

Semi-dynamic Demand in a Non-permutation Flowshop with Constrained Resequencing Buffers

This work presents the performance comparison of two conceptually different approaches for a mixed model non-permutation flowshop production line. The demand is a semi-dynamic demand with a fixed job sequence for the first station. Resequencing is permitted where stations have access to intermediate or centralized resequencing buffers. The access to the buffers is restricted by the number of available buffer places and the physical size of the products. An exact approach, using Constraint Logic Programming (CLP), and a heuristic approach, a Genetic Algorithm (GA), were applied.

Performance study of a genetic algorithm for sequencing in mixed model non-permutation flowshops using constrained buffers

This paper presents the performance study of a Genetic Algorithm applied to a mixed model non-permutation flowshop production line. Resequencing is permitted where stations have access to intermittent or centralized resequencing buffers. The access to the buffers is restricted by the number of available buffer places and the physical size of the products. Characteristics such as the difference between the intermittent and the centralized case, the number of buffer places and the distribution of the buffer places are analyzed. Improvements that come with the introduction of constrained resequencing buffers are highlighted.

Analysis of the Criteria Used by Organizations in Supplier Selection

In order to analyse the criteria used by organizations in their selection of suppliers and to compare them with those provided by the literature, a survey has been designed with which a field study has been carried out. The article shows some the most relevant conclusions of the field study, after a statistical analysis (descriptive and principal components) of the responses. In this work the methodology used for the creation of the survey is also detailed.

The reduction of CO2 emission into the supply network design: A review of current trends in mathematical models

The problem of global warming is attracting increasing attention in the academic and industrial world. Today a major portion of the population is aware that greenhouse gases (GHGs) are the main contributors to climate change. This article reviews current trends in CO2 emission reductions in supply network design. This article focuses on mathematical models employed in supply network design that include environmental characteristics. Facility location and technology selection are important factors in supply design, and may determine the possible environmental damage and economic impact of a supply network. The CO2 market appears as an interesting alternative for managing emissions using CO2 credits. In the area of production, emphasis is placed on reducing emissions through efficient energy use and in the transport area through freight transport consolidation, and more efficient vehicle utilization.