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Publicações

Publicações por SYSTEM

2014

HOPS - Hamming-Oriented Partition Search production planning in the spinning industry

Autores
Camargo, VCB; Toledo, FMB; Almada Lobo, B;

Publicação
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
In this paper, we investigate a two-stage lot-sizing and scheduling problem in a spinning industry. A new hybrid method called HOPS (Hamming-Oriented Partition Search), which is a branch-and-bound based procedure that incorporates a fix-and-optimize improvement method is proposed to solve the problem. An innovative partition choice for the fix-and-optimize is developed. The computational tests with generated instances based on real data show that HOPS is a good alternative for solving mixed integer problems with recognized partitions such as the lot-sizing and scheduling problem.

2014

Models for capacitated lot-sizing problem with backlogging, setup carryover and crossover

Autores
Belo Filho, MAF; Toledo, FMB; Almada Lobo, B;

Publicação
JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY

Abstract
Setup operations are significant in some production environments. It is mandatory that their production plans consider some features, as setup state conservation across periods through setup carryover and crossover. The modelling of setup crossover allows more flexible decisions and is essential for problems with long setup times. This paper proposes two models for the capacitated lot-sizing problem with backlogging and setup carryover and crossover. The first is in line with other models from the literature, whereas the second considers a disaggregated setup variable, which tracks the starting and completion times of the setup operation. This innovative approach permits a more compact formulation. Computational results show that the proposed models have outperformed other state-of-the-art formulation.

2014

Influence of consumer purchasing behaviour on the production planning of perishable food

Autores
Amorim, P; Costa, AM; Almada Lobo, B;

Publicação
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

A rich vehicle routing problem dealing with perishable food: a case study

Autores
Amorim, P; Parragh, SN; Sperandio, F; Almada Lobo, B;

Publicação
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.

2014

An Optimization based on Simulation Approach to the Patient Admission Scheduling Problem: Diagnostic Imaging Department Case Study

Autores
Granja, C; Almada Lobo, B; Janela, F; Seabra, J; Mendes, A;

Publicação
JOURNAL OF DIGITAL IMAGING

Abstract
The growing influx of patients in healthcare providers is the result of an aging population and emerging self-consciousness about health. In order to guarantee the welfare of all the healthcare stakeholders, it is mandatory to implement methodologies that optimize the healthcare providers' efficiency while increasing patient throughput and reducing patient's total waiting time. This paper presents a case study of a conventional radiology workflow analysis in a Portuguese healthcare provider. Modeling tools were applied to define the existing workflow. Re-engineered workflows were analyzed using the developed simulation tool. The integration of modeling and simulation tools allowed the identification of system bottlenecks. The new workflow of an imaging department entails a reduction of 41 % of the total completion time.

2014

The project risk management process, a preliminary study

Autores
Rodrigues da Silva, LH; Crispim, JA;

Publicação
CENTERIS 2014 - CONFERENCE ON ENTERPRISE INFORMATION SYSTEMS / PROJMAN 2014 - INTERNATIONAL CONFERENCE ON PROJECT MANAGEMENT / HCIST 2014 - INTERNATIONAL CONFERENCE ON HEALTH AND SOCIAL CARE INFORMATION SYSTEMS AND TECHNOLOGIES

Abstract
A process of risk management in projects is a rational chain of practices by which decision-agents plan and execute actions and control the results in order to keep the implementation of the project under certain conditions (time, cost and quality parameters' set). With the purpose of providing guidelines for the selection of the best practices taking into account the organizational maturity and project complexity, a theoretical framework to classify and associate those practices to each phase of the project life cycle and to each project risk management process is proposed. Future research efforts will be directed towards refining the framework and testing it in multiple case studies. (C) 2014 The Authors. Published by Elsevier Ltd.

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