Simultaneous lotsizing and scheduling - extensions and solution approaches

The present thesis focuses on simultaneous lotsizing and scheduling. A comprehensive review of the literature is presented in which the historical development of the subject and the current research gaps are, based on a classification scheme, described. Additionally, a review focusing on so-called secondary resources (e.g., setup operators or raw materials), which are considered alongside the primary production resource, is provided. The insights on different types of secondary resources help to develop a new model formulation generalizing and extending the currently used approaches, which are specific to certain settings. Some illustrative examples demonstrate the functional principle and flexibility of this new formulation which can thus be used in a wide range of applications. Finally, a new heuristic to solve large-scaled simultaneous lotsizing and scheduling problems is presented. The heuristic creates a modified multi-line master problem by aggregating products into groups. The resulting problem is less complex and its solution can be used to define single-line sub problems. These sub problems are solved by heuristics present in the literature and the results are then combined to form a solution to the original problem. Numerical tests show the applicability of the aforementioned approach to solve problems of practical relevance.Die vorliegende Ausarbeitung betrachtet das Thema der simultanen Losgrößen- und Reihenfolgeplanung tiefergehend. Ein ausführlicher Literaturüberblick zeigt unter Zuhilfenahme eines Klassifizierungsschemas den Entwicklungsverlauf und aktuelle Forschungslücken in diesem Bereich auf. Weiterhin wird ein auf zusätzliche Ressourcen (sogenannte secondary resources) fokussierter Literaturüberblick erstellt. Diese Ressourcen (z.B. Personal zur Umrüstung oder Rohmaterial) werden zusätzlich zu der primären Produktionsressource benötigt. Die Erkenntnisse zu den verschiedenen Typen von zusätzlichen Ressourcen werden verwendet, um ein generelles Modell zu entwickeln, welches die bisherigen, auf bestimmte Anwendungsfälle spezialisierten, Formulierungen abbildet und erweitert. Testläufe mit Beispielszenarien demonstrieren die Funktionalität und die Flexibilität der neuen Modellformulierung welche für einen Vielzahl von Anwendungsfällen verwendet werden kann. Abschließend wird eine neue Heuristik zum Lösen von simultanen Losgrößen- und Reihenfolgeplanungsproblemen praxisrelevanter Größen vorgestellt. Innerhalb der Heuristik wird durch Produktaggregation ein modifiziertes Mehrlinien-Masterproblem generiert. Das resultierende Problem ist weniger komplex und die dafür gefundene Lösung kann zum Erstellen von Einlinien-Teilproblemen verwendet werden. Diese Teilprobleme werden mit aus der Literatur bekannten Heuristiken gelöst. Die Ergebnisse werden zu einer Lösung für das ursprüngliche Problem zusammengefasst. Numerische Tests belegen die Tauglichkeit des Verfahrens zum Lösen von praxisrelevanten Problemen

Proposta de modelo matemático para a produção e teste de funcionalidade em ambiente de máquinas

Orientadora : Profª. Neida Maria Patias VolpiTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia e Ciências Exatas, Programa de Pós-Graduação em Métodos Numéricos em Engenharia-Programação Matemática. Defesa: Curitiba, 10/04/2017Inclui referências : f. 104-109Resumo: Este trabalho está baseado nos estudos de modelos matemáticos para problemas de dimensionamento e sequenciamento de lotes existentes na literatura. Com base nesses trabalhos foi proposto um modelo matemático envolvendo um ambiente produtivo com máquinas distintas em paralelo em um setor de uma indústria que sincroniza dois estágios do ambiente operacional, ou seja, a produção e o teste de funcionalidade com estoque intermediário. O primeiro estágio consiste num ambiente onde ocorre a produção de itens em várias máquinas paralelas distintas. O segundo é formado por fornos de teste nos quais são simuladas situações climáticas adversas de modo a testar o funcionamento dos itens fabricados.É proposto um modelo matemático para auxílio no processo de gestão das ordens de produção, de modo a determinar em quais máquinas bem como em que ordem os itens serão produzidos no primeiro estágio, de modo a reduzir custos de produção neste estágio, bem como atender ao melhor aproveitamento possível dos fornos de teste, evitando a operação destes contendo espaços ociosos e controlando os estoques intermediários. É importante fazer um sincronismo na linha de produção durante o planejamento da produção, para evitar excessos de estoques e paradas de máquinas, reduzindo assim custos desnecessários. Devido à busca pela minimização de custos, torna-se necessário sempre que possível, utilizar ao máximo a capacidade dos fornos, buscando atender às demandas previstas para o horizonte de planejamento. Para validação do modelo, propõe-se uma aplicação com dados genéricos obtidos de uma empresa fabricante de inversores, o qual é resolvido com uso do software CPLEX e as heurísticas Relax-and-Fix e Fix-and-Optimize. Nos testes realizados a heurística Relax-and-Fix teve um desempenho melhor em cenários onde a quantidade de subproblemas foi maior. O modelo pode ser aplicado em outros ambientes industriais com características similares, como por exemplo, no processo de montagem de um computador ou de um refrigerador, entre outros. Palavras-chaves: Dimensionamento e Sequenciamento de Lotes. Estoques Intermediários. Teste de Funcionalidade.Abstract: This work is based on the studies of mathematical models for problems of dimensioning and sequencing of lots existing in the literature. Based on these works, a mathematical model involving a productive environment with distinct machines in parallel was proposed in a sector of an industry that synchronizes two stages of the operational environment, that is, the production and the test of functionality with intermediate stock. The first stage consists of an environment where the production of items occurs in several different parallel machines. The second is formed by test furnaces in which adverse weather conditions are simulated in order to test the operation of the manufactured items. A mathematical model is proposed to aid in the process of the management of the production orders, in order to determine in which machines as well as in which order the items will be produced in the first stage, in order to reduce production costs at this stage, as well as to take care of the best possible use of the test furnaces, avoiding the operation of these containing idle spaces and controlling the intermediate stocks. It is important to synchronize the production line during production planning to avoid overstocking and downtime, thus reducing unnecessary costs. Due to the search for cost minimization, it is necessary, whenever possible, to make maximum use of the furnace capacity, in order to meet the demands for the planning horizon. To validate the model, it is proposed an application with generic data obtained from an inverter manufacturer, which is solved using the CPLEX software and the Relax-and-Fix and Fix-and-Optimize heuristics. In the tests performed the Relax-and-Fix heuristic performed better in scenarios where the number of subproblems was greater. The model can be applied in other industrial environments with similar characteristics, for example, in the process of assembling a computer or a refrigerator, among others. Key-words: Lot Sizing and Scheduling. Intermediate Stocks. Functionality Test

OTIMIZAÇÃO DO PROCESSO PRODUTIVO NUMA INDÚSTRIA DE VINHOS: REDUÇÃO DE DESPERDÍCIOS

A otimização dos processos produtivos torna-se cada vez mais necessária nos dias de hoje, uma vez que permite a maximização dos recursos e das matérias-primas bem como a redução de desperdícios. O desperdício pode estar associado a custos, tempo, resíduos e mão-de-obra. Assim, o presente trabalho teve como principal objetivo a otimização do processo produtivo de uma indústria de vinhos, através da redução dos diversos desperdícios. Começou-se por observar as linhas de produção em funcionamento para a realização de um levantamento de situações não conformes, motivos de paragens e, ainda, motivos de quebra que levam a desperdícios de materiais de embalagem e a um aumento dos resíduos gerados. Os principais resultados indicaram que as linhas com maiores tempos de paragem foram as linhas 3 e 6 e que os materiais de embalagem com maior propensão para quebra e, portanto, desperdício foram o vidro, as cápsulas PVC e as caixas. Quer para os tempos de paragem, quer para as quebras, o principal motivo é a avaria de equipamentos, pelo que uma das sugestões de melhoria passou pela revisão do plano de manutenções preventivas já existente, ponderando tornar as mesmas mais regulares. Sugeriu-se também a tentativa de aproveitamento de mate-riais que atualmente são rejeitados, ainda que possam ser reaproveitados sem comprometer a qualidade do produto acabado. Foram ainda apresentadas outras medidas de redução do desperdício e elaborados posters para sensibilização dos colaboradores, no âmbito da sustentabilidade e da necessidade de um correto encaminhamento de resíduos.The optimization of production processes becomes more and more necessary nowa-days, as it allows resources and raw materials to be maximized and waste to be reduced. Waste can be associated to costs, time, industrial waste, or labour. Thus, this work had as its main objective the optimization of the production process of a wine industry, through the reduction of various wastes. It started by observing the production lines in operation, to carry out a survey of non-compliant situations, reasons for stoppages and reasons for breakages that lead to waste of packaging materials and an increase in waste generated. The main results indicated that the lines with the longest downtimes were lines 3 and 6, and that the packaging materials most prone to breakage, and therefore waste, were glass, PVC capsules and boxes. Both for stoppage times and breakages, the main reason is equipment breakdown, so that one of the suggestions for improvement was the review of the preventive maintenance plan already existing, considering making them more regular. It was also suggested the use of materials that are currently being rejected, although they can be reused without com-promising the quality of the finished product. Other measures to reduce waste were also presented and posters were produced to raise awareness among employees about sustainability and the need for correct waste disposal

Factors Influencing Customer Satisfaction towards E-shopping in Malaysia

Online shopping or e-shopping has changed the world of business and quite a few people have decided to work with these features. What their primary concerns precisely and the responses from the globalisation are the competency of incorporation while doing their businesses. E-shopping has also increased substantially in Malaysia in recent years. The rapid increase in the e-commerce industry in Malaysia has created the demand to emphasize on how to increase customer satisfaction while operating in the e-retailing environment. It is very important that customers are satisfied with the website, or else, they would not return. Therefore, a crucial fact to look into is that companies must ensure that their customers are satisfied with their purchases that are really essential from the ecommerce’s point of view. With is in mind, this study aimed at investigating customer satisfaction towards e-shopping in Malaysia. A total of 400 questionnaires were distributed among students randomly selected from various public and private universities located within Klang valley area. Total 369 questionnaires were returned, out of which 341 questionnaires were found usable for further analysis. Finally, SEM was employed to test the hypotheses. This study found that customer satisfaction towards e-shopping in Malaysia is to a great extent influenced by ease of use, trust, design of the website, online security and e-service quality. Finally, recommendations and future study direction is provided. Keywords: E-shopping, Customer satisfaction, Trust, Online security, E-service quality, Malaysia

Malaysian bilateral trade relations and economic growth

This paper examines the structure and trends of Malaysian bilateral exports and imports and then investigates whether these bilateral exports and imports have caused Malaysian economic growth. Although the structure of Malaysia’s trade has changed quite significantly over the last three decades, the direction of Malaysia’s trade remains generally the same. Broadly, ASEAN, the EU, East Asia, the US and Japan continue to be the Malaysia’s major trading partners. The Granger causality tests have shown that it is the bilateral imports that have caused economic growth in Malaysia rather than the bilateral exports

Exchange rate misalignments in ASEAN-5 countries

The purpose of this paper is to estimate the exchange rate misalignments for Indonesia, Malaysia, Philippines, Singapore and Thailand before the currency crisis. By employing the sticky-price monetary exchange rate model in the environment of vector error-correction, the results indicate that the Indonesia rupiah, Malaysian ringgit, Philippines peso and Singapore dollar were overvalued before the currency crisis while Thai baht was undervalued on the eve of the crisis. However, they suffered modest misalignment. Therefore, little evidence of exchange misalignment is found to exist in 1997:2. In particular, Indonesia rupiah, Malaysia ringgit, Philippines peso and Singapore dollar were only overvalued about 1 to 4 percent against US dollar while the Thai baht was only 2 percent undervalued against US dollar

Aeronautical engineering: A cumulative index to a continuing bibliography

This bibliography is a cumulative index to the abstracts contained in NASA SP-7037 (197) through NASA SP-7037 (208) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, foreign technology, contract, report number, and accession number indexes