2014
Authors
Amorim, P; Costa, AM; Almada Lobo, B;
Publication
OR SPECTRUM
Abstract
This paper addresses the impact of consumer purchasing behaviour on the production planning of perishable food products for companies operating in the fast moving consumer goods using direct store delivery. The research presented here builds on previous marketing studies related to the effects of expiry dates in order to derive mathematical formulae, which express the age dependent demand for different categories of perishable products. These demand expressions take into account both customer willingness to pay and product quality risk. The paper presents deterministic and stochastic production planning models, which incorporate the customer's eagerness to pick up the fresher products available. Results indicate that model approximations neglecting the fact that customers pick up the fresher products or considering that all products have the same product quality risk have a reduced impact on profit losses. On the other hand, not considering the decreasing customer willingness to pay has an important impact both on the profit losses and on the amount of spoiled products.
2014
Authors
Amorim, P; Parragh, SN; Sperandio, F; Almada Lobo, B;
Publication
TOP
Abstract
This paper presents a successful application of operations research techniques in guiding the decision making process to achieve a superior operational efficiency in core activities. We focus on a rich vehicle routing problem faced by a Portuguese food distribution company on a daily basis. This problem can be described as a heterogeneous fleet site dependent vehicle routing problem with multiple time windows. We use the adaptative large neighbourhood search framework, which has proven to be effective to solve a variety of different vehicle routing problems. Our plans are compared against those of the company and the impact that the proposed decision support tool may have in terms of cost savings is shown. The algorithm converges quickly giving the planner considerably more time to focus on value-added tasks, rather than manually correct the routing schedule. Moreover, contrarily to the necessary adaptation time of the planner, the tool is quite flexible in following market changes, such as the introduction of new customers or new products.
2021
Authors
Saputro, TE; Figueira, G; Almada Lobo, B;
Publication
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
Abstract
In the current global market, managing supply is not a straightforward process and it becomes even more complex as uncertainty and disruptions occur. In order to mitigate their impact, the selection of suppliers of strategic items should have a more holistic view of the operations in the supply chain. We propose an integrated model for supplier selection, considering inventory management and inbound transportation. We approach this problem, incorporating stochastic demand and suppliers' imperfect quality. Imperfect quality triggers additional costs, including external failure and holding costs. Supply disruptions also affect the suppliers' lead time, resulting in delivery delays. We develop a methodology to address this challenge with simulation-optimisation. A genetic algorithm determines supplier selection decisions, while inventory decisions are computed analytically. Discrete-event simulation is used to evaluate the overall performance, as well as to update the lead time dynamically, according to the disruptions. Finally, sensitivity analysis providing managerial insights reveals that criteria in supplier selection should be given a different priority depending on the characteristics of the items, and the effectiveness of disruption mitigation strategies depends on the disruption characteristics.
2023
Authors
Saputro, TE; Figueira, G; Almada-Lobo, B;
Publication
EXPERT SYSTEMS WITH APPLICATIONS
Abstract
Supplier selection for strategic items requires a comprehensive framework dealing with qualitative and quantitative aspects of a company's competitive priorities and supply risk, decision scope, and uncertainty. In order to address these aspects, this study aims to tackle supplier selection for strategic items with a multi-sourcing, taking into account multi-criteria, incorporating uncertainty of decision-makers judgment and supplier-buyer parameters, and integrating with inventory management which the past studies have not addressed well. We develop a novel two-phase solution approach based on integrated multi-criteria decision -making (MCDM) and multi-objective simulation-optimization (S-O). First, MCDM methods, including fuzzy AHP and interval TOPSIS, are applied to calculate suppliers' scores, incorporating uncertain decision makers' judgment. S-O then combines the (quantitative) cost-related criteria and considers supply disruptions and uncertain supplier-buyer parameters. By running this approach on data generated based on previous studies, we evaluate the impact of the decision maker's and the objective's weight, which are considered important in supplier selection.
2023
Authors
Rodrigues, LF; Dos Santos, MO; Almada-Lobo, B;
Publication
COMPUTERS & INDUSTRIAL ENGINEERING
Abstract
This article addresses the Production Routing Problem (PRP), which consists of determining, in an integrated way, production and inventory planning, and vehicle routing to minimize the costs involved. In the problem, a plant is responsible for producing several types of products to meet the known demand of a set of customers using a homogeneous fleet of vehicles over the planning horizon. In the literature, evolutionary approaches have not been explored in depth for the PRP, specifically for the problem with multiple products. Thus, this work mitigates this gap, presenting a novel Memetic Algorithm and testing its effectiveness on randomly generated sets of instances, comparing the results obtained with a commercial optimization solver. In our solution approach, several classic operators from the literature were implemented. Furthermore, we propose four novel genetic operators. In addition, we evaluated the proposed method's performance in classical instances of literature considering a single item. The computational experiments were carried out to assess the impact of the numerous parameter combinations involving the metaheuristic, and, from statistical analyses, we evidence the proposed technique's robustness. Computational experiments showed that our proposed method outperforms the commercial solver Gurobi in determining feasibly high-quality solutions, mainly on large instances for the PRP with multiple items.
2006
Authors
Estima, M; Mendes, D; Almada Lobo, B; Magalhaes, B;
Publication
SEFI 2006 - 34th Annual Conference: Engineering Education and Active Students
Abstract
Several discussions concerning the improvement of engineering students' learning process take place. The use of Active Learning tools is grabbing the attention of the pedagogical community as an answer to the recent education process requirements for the new century. A debut-mother project named PESC (To Project, To Undertake, To Know How to Achieve) aimed to fulfil these needs by involving students in a hands-on experience. Within this framework, the development of an industrial engineering and management game (IMAGE) was conducted. PESC initiative shows some similarities with CDIO (Conceiving-Designing-Implementing-Operating). However, the authors consider that this framework needs to be improved addressing other important attributes such as the capacity of identifying, evaluating and formulating problems beforehand. The argument is that PESC fulfils these requirements, based on the creation of multidisciplinary working teams under the students' leadership. Work organization and control were vital to the accomplishment of the proposed task. The project key success factors were the establishment of a direct communication and of ambitious assignments that would challenge the whole group. Moreover, detailed task scheduling, weekly meetings and weekly progress reports were implemented by the leaders. These steps induced team work, dynamism, competition and responsibility on the students, enabling the fulfilment of the ambitious deadlines.
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