Carina Pimentel

Comparing Dantzig-Wolfe decompositions and branch-and-price algorithms for the multi-item capacitated lot sizing problem

In this article, we consider the multi-item capacitated lot sizing problem with setup times. Starting from an original mixed integer programming model, we apply the standard Dantzig–Wolfe decomposition (DWD) in two different ways: defining the subproblems by items and defining the subproblems by periods. A third decomposition is developed in which the subproblems of both types are integrated in the same model. The linear relaxation of this last approach, which we denote as multiple DWD, provides lower bounds (equal to or) better than the bounds obtained by the other decompositions, which in turn, provide lower bounds (equal to or) better than the ones given by the original model. For solving the three decomposition models, we implemented three branch-and-price algorithms. We describe their main aspects and report on their computational results in instances from the literature.

Exact and heuristic approaches for lot splitting and scheduling on identical parallel machines

In this paper, we address a lot splitting and scheduling problem existent in a textile factory. The factory we study produces a set of products that are made of, or assembled from, a list of components. During production, each component can be split into one or several lots of different sizes and each lot will be produced independently on one of a group of identical parallel machines. We formulate the problem into a mixed integer programming model and develop a heuristic method to solve the model. The heuristic method is based on a network flow model with the objective to minimise the weighted sum of the total tardiness of products and the deviations occurred during production of each product. The deviation of a product is measured by the deviation of product completion time (the last component lot completion time) and completion time of the rest of components lots for the same product. We present computational results and performance measures of the network flow heuristic for a set of randomly generated instances based on real world data.

Lean Manufacturing Tools

This chapter is focused on the more visible part of JIT, providing a detailed description of a set of basic lean manufacturing tools for a successful JIT implementation. The Lean tools explored in this chapter are: 5S, Standardized Work, SMED—Single Minute Exchange of Die, and Kanban System. The chapter is enriched with a case study used to explain the application of the Lean manufacturing tools in practice. Many examples of practical applications and some worksheets are incorporated to help managers in the implementation issues. In general, for each tool a detailed description of the tool and of its elements is presented. Next, the requirements for its implementation are elaborated. Afterwards, the implementation issues are explained, followed by a demonstration of the practical application of the tool in a case study company and an exposition of the results achieved.

A Mathematical Model for the Container Stowage and Ship Routing Problem

The main goal of this paper is to present a mathematical model for a fleet of containerships with no pre-defined routes, considering demands and delivery deadlines and overstowing prevention. The objective is to minimize the total distribution cost in the contest of the short sea shipping. The short sea shipping is a very complex problem that belongs to the class of routing problems, more precisely, to the Capacitated Vehicle Routing Problem with deadlines and loading constraints. In this problem two major decisions must be made: which ports should be visited by each vessel and the related visit sequence, and where to load the containers in vessels in order to prevent overstowing. A mixed integer programming model for the problem is presented and solved. This mathematical formulation intends to contribute to a better management of small fleets of containerships in order to reduce transportation time and delivering costs.

A Fast Heuristic for a Lot Splitting and Scheduling Problem of a Textile Industry

Abstract In this paper we address a lot splitting and scheduling problem of a Textile factory that produces garment pieces. Each garment piece is made of a set of components that are produced on the knitting section of the company. The problem consists of finding a weekly production plan for the knitting section, establishing the quantities to produce of each component (organized in one or several lots), and where and when (starting/completion times) to produce them. The main contribution of this work is the development of a constructive heuristic that generates automated knitting scheduling plans. The heuristic produces solutions very fast for a set of randomly generated instances based on real world data.

Final Considerations Regarding the Just-in-Time Framework

This chapter proposes a framework to serve as a roadmap for Just in time (JIT) implementation in plants, grounded on the practical experience acquired during the implementation of a JIT plant and considering the difficulties and suggestions that emerged during the implementation process. An outlook of the JIT implementation is also included in this chapter. The chapter concludes with some final remarks and recommendations for a smooth introduction and long-lasting JIT operation in an organization.

Lean Manufacturing and Kaizen

This chapter answers the questions: What is lean manufacturing? What is Kaizen? This chapter covers a brief description of lean manufacturing foundations, its main principles and wastes, and also the benefits companies can reach with the implementation of lean manufacturing best practices, grounded on several surveys reported in literature to analyse the impact of lean manufacturing on performance. The chapter also describes the Kaizen philosophy reflecting the concern with a continuous improvement culture, where strategic areas of generic continuous improvement behaviours are enhanced. The kaizen philosophy is also presented as an innovation driver. Moreover, the main characteristics of kaizen, the kaizen events, the requirements for continuous improvement success and a set of behavioural routines critical for long-term success with continuous improvement and development over time are offered too.

Assessing Entrepreneurial Profiles: A Study of Transversal Competence Gaps in Four European Countries

The need to develop entrepreneurial competences in young professionals has been a key priority in the agendas of policy makers and industry leaders for some time. This chapter offers several contributions to address this issue, drawing on the results of an in-depth study addressing the meaning, and the requirements, for entrepreneurial competences across four European contexts (Cyprus, Lithuania, Poland and Portugal). Building on the literature as well as on exploratory data from interviews with employers and young graduates, the chapter starts by identifying and characterizing ten transversal entrepreneurial competences that were identified at the forefront of requirements for economic and social development, as determinants for job creation, employability, social emancipation and personal fulfilment in labour contexts. Using this competence framework, a scale for the assessment of entrepreneurial competences has been developed and empirically validated. The chapter then presents the results of the application of the scale in the four countries addressed in the study. This investigation addressed a sample of 449 young professionals and 88 employers, and offers insights on two perspectives: (1) the competence profile of young professionals, from different educational backgrounds, and across distinct European contexts; (2) the entrepreneurial competence requirements reported by the employers of leading industries. These two perspectives are matched in order to infer the importance of the gap between the requirements of employers and the offer from the graduates. The chapter therefore offers a timely contribution for the understanding of the span of psychological and behavioural characteristics, along with management and technical knowledge and skills that need to be at the forefront of education and training, and aligned with societal development goals.

Introduction to Lean and Just-in-Time Manufacturing

Lean manufacturing is widely used by industries mainly to mitigate and eliminate all kinds of waste and to improve productivity as a way of enhancing the competitiveness of organizations. A positive correlation between lean implementation and business performance has been highlighted in numerous researches.

Internal Logistics System Selection with Total Cost of Ownership Analysis

In this paper a methodology was followed in order to support the decision-making of one industrial unit regarding its internal logistics system. The addressed factory was facing issues with their internal logistics approach. Some alternatives were pointed out and a proper total cost of ownership (TCO) analysis was developed. This analysis was taken in order to demonstrate the more cost-effective solution for the internal logistics system. This tool is more and more valued by the companies, due to their willing to reduce the costs that are associated with the way of doing business. Despite the proposal of the best choice for the internal logistics system of the enterprise, this study also intends to present some conclusions about the match between the nature of the industrial unit and the logistics systems that best fit the requirements of those.