Bus driver rostering by hybrid methods based on column generation

Tese de doutoramento, Informática (Engenharia Informática), Universidade de Lisboa, Faculdade de Ciências, 2018Rostering problems arise in a diversity of areas where, according to the business and labor rules, distinct variants of the problem are obtained with different constraints and objectives considered. The diversity of existing rostering problems, allied with their complexity, justifies the activity of the research community addressing them. The current research on rostering problems is mainly devoted to achieving near-optimal solutions since, most of the times, the time needed to obtain optimal solutions is very high. In this thesis, a Bus Driver Rostering Problem is addressed, to which an integer programming model is adapted from the literature, and a new decomposition model with three distinct subproblems representations is proposed. The main objective of this research is to develop and evaluate a new approach to obtain solutions to the problem in study. The new approach follows the concept of search based on column generation, which consists in using the column generation method to solve problems represented by decomposition models and, after, applying metaheuristics to search for the best combination of subproblem solutions that, when combined, result in a feasible integer solution to the complete problem. Besides the new decomposition models proposed for the Bus Driver Rostering Problem, this thesis proposes the extension of the concept of search by column generation to allow using population-based metaheuristics and presents the implementation of the first metaheuristic using populations, based on the extension, which is an evolutionary algorithm. There are two additional contributions of this thesis. The first is an heuristic allowing to obtain solutions for the subproblems in an individual or aggregated way and the second is a repair operator which can be used by the metaheuristics to repair infeasible solutions and, eventually, generate missing subproblem solutions needed. The thesis includes the description and results from an extensive set of computational tests. Multiple configurations of the column generation with three decomposition models are tested to assess the best configuration to use in the generation of the search space for the metaheuristic. Additional tests compare distinct single-solution metaheuristics and our basic evolutionary algorithm in the search for integer solutions in the search space obtained by the column generation. A final set of tests compares the results of our final algorithm (with the best column generation configuration and the evolutionary algorithm using the repair operator) and the solutions obtained by solving the problem represented by the integer programming model with a commercial solver.Programa de Apoio à Formação Avançada de Docentes do Ensino Superior Politécnico (PROTEC), SFRH/PROTEC/67405/201

Ontologies for context-aware applications

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Robotic Process Automation: Estudo de Caso da Aplicação a um Processo de Negócio

Trabalho apresentado em V International Forum on Management, 19-20 fevereiro 2021, Setúbal, PortugalNa atual economia global e dinâmica a adoção de tecnologias de (RPA) tem-se revelado uma mais-valia para as empresas na automatização de alguns dos seus processos de negócio. Os estudos realizados nesta área apresentam um conjunto de benefícios obtidos com a implementação desta solução, nomeadamente aumento da produtividade e velocidade de execução, redução de custos, redução de erros, melhoria na qualidade do serviço, etc. A presente investigação teve como objetivos analisar o impacto no desempenho dos processos de negócio, do departamento de de uma empresa, com a implementação de uma solução de RPA; comparar o desempenho do processo em análise antes e depois da implementação de RPA e avaliar os ganhos em termos de desempenho dos indicadores de tempo de execução dos processos, número de erros e discutir os impactos dessa alteração nos custos operacionais da atividade. Os resultados demonstram os benefícios alcançados com a implementação, tendo sido identificados um aumento da velocidade de execução do processo, inexistência de pedidos em atraso, um incremento significativo na taxa de precisão, uma redução acentuada dos custos operacionais e oportunidades de redução e realocação de recursos humanos afetos à execução do processo em análise.In the current global and dynamic economy, the adoption of Robotic Process Automation (RPA) technologies has proven to be an asset for companies in automating some of their business processes. The research in this area shows a set of benefits obtained from implementing this solution, namely increased productivity and speed of execution, cost reduction, error reduction, improvement of quality service delivered, etc. The present investigation aimed to analyse the impact on the performance of business processes, of a company's back-office department, with the implementation of a RPA solution; compare the performance of the process before and after the implementation of RPA and evaluate the gains in terms of performance of the process execution time indicators and number of errors and discuss the impacts of this change on the operational costs of the activity. The results show the benefits achieved with the implementation, having identified an increase in the speed of execution of the process, the absence of back orders, a significant increase in the accuracy rate, a reduction of operational costs and opportunities to a reduction and reallocation of human resources related to the execution of the process.info:eu-repo/semantics/publishedVersio

Extração de conhecimento através de Data Mining: obtenção de regras de associação num dataset público

Trabalho apresentado em XXX Jornadas Luso-Espanholas de Gestão Científica, 5-8 fevereiro 2020, Bragança, PortugalEste artigo apresenta um trabalho de investigação que consistiu na Análise de Carrinhos de Compras (Market Basket Analysis) através da aplicação de técnicas de data mining a um conjunto de dados de dimensão significativa. Pretende-se encontrar conjuntos de itens habitualmente comprados em conjunto e daí gerar Regras de Associação, as quais podem ser valiosas para campanhas promocionais ou sistemas de recomendação. Foi adotada a metodologia de investigação CRISP, especialmente vocacionada para data mining, e são descritas as diversas fases da mesma, com foco na análise exploratória dos dados (para os conhecer), a preparação dos dados para aplicação e configuração do algoritmo Apriori e o estudo do comportamento do modelo obtido, aumento e diminuição do número de Regras de Associação geradas, de acordo com a variação dos parâmetros e dos dados utilizados.This paper presents a research that consisted of a Market Basket Analysis through the application of data mining techniques to a large dataset. The aim is to find sets of items commonly purchased together and then generate Association Rules, which can be valuable for promotional campaigns or recommendation systems. The CRISP research methodology was adopted, which is especially designed for data mining research. Its various phases are described, focusing on the exploratory data analysis (to understand better the data), the preparation of data for application and configuration of the Apriori algorithm and the assessment of the model behaviour, measured by the increase and decrease of the number of generated Association Rules, according to the variation of the parameters and the selected dataN/

Análise comparativa entre os resultados de simulação dos impactos da integração de geração distribuída na rede elétrica empregrando-se os softwares Anarede e OpenDSS

Trabalho de Conclusão Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2019.O crescimento do uso de geração distribuída fotovoltaica (GDFV) nas modalidades de minigeração e microgeração gera a necessidade de analisar os impactos desses sistemas na rede elétrica de distribuição. O programa Anarede é o software mais utilizado no setor elétrico brasileiro para análises de fluxo de potência e se mostra uma ferramenta útil nas análises de geração distribuída, mas não é o único programa capaz de realizar essas análises. Este trabalho pretende comparar a performance do programa OpenDSS e do programa Anarede, listando as vantagens e desvantagens de cada programa. Para tanto, esse trabalho busca recriar o modelo de Medeiros, C. V. P., que simula a conexão de uma GD que insere até 5 MW de potência em um alimentador da CEB, e comparar os resultados dos dois softwares. Cada programa apresenta vantagens e desvantagens, e apesar do Anarede ser mais amplamente utilizado, o OpenDSS apresenta potencial para ser usado em diversas análises de sistemas elétricos de potência

Optimizing high-volume ultrasonic melt degassing using synchronized kinematic translation

Ultrasonic vibration is a physical processing technique that has been gathering support as an environmentally friendly approach to degas light alloy melts. Since metallic sonotrodes promote melt inclusions due to erosion, ceramic sonotrodes have also been shown as a viable solution for ultrasonic melt degassing in industrial scales. This study shows that resonant ceramic sonotrodes are characterized by a complex low-amplitude radial eigen mode, while particle image velocimetry reveals that their efficiency depends on the angular direction. An approach based on synchronized kinematic translation was designed to optimize the degassing efficiency in ultrasonic approaches, assuring its angle with higher cavitation is always facing the center of the crucible. Results show that this approach can reach lower degassing thresholds (Hmin ¼ 0.13 ml/100 g Al) at higher degassing rates, relatively to both Argon inflation (Hmin ¼ 0.22 ml/100 g Al) and static Ultrasound (Hmin ¼ 0.18 ml/100 g Al) methods. An enhanced grain refinement further supports the hypothesis that promoting a synchronized kinematic translation enhances the ultra sonic degassing efficiency. Considering these results, this approach is suggested as a reliable route to implement efficient ultrasonic degassing techniques in industrial light alloy melt treatment.This work was supported by PTDC/EMEEME/30967/2017 and NORTE-0145-FEDER-030967, co-financed by the European Regional Development Fund (ERDF), through the Operational Programme for Competitiveness and Internationalization (COMPETE 2020), under Portugal 2020, and by the Fundação para a Ciencia e a Tecnologia e FCT I.P. national funds. Also, this work was supported by Portuguese FCT, under the reference project UIDB/04436/2020 and Stimulus of Scientific Employment Application CEECIND/03991/2017