Improving production systems with lean: a case study in a medium-sized manufacturer

Lean principles and tools have been increasingly employed in companies across several sectors, with numerous successful implementations both inside and outside production environments. In the case of Portuguese companies, few works have reported the application and corresponding results of lean, and even fewer focusing on small and medium sized companies. This work presents a case study of an implementation of several lean principles and tools in the production sector of a Portuguese medium-sized screw cap manufacturer. Visual management, A3 thinking, and single-minute exchange of die (SMED) were employed to identify and reduce inefficiencies and waste in the shop floor. The implementation of these principles and tools is detailed, showcasing the necessary adjustments for being correctly embedded in the company's culture. Qualitative and quantitative results are presented concerning the case study, where a continuous improvement culture was adhered to and a significant gain in productivity could be observed.publishe

Inventory models with reverse logistics for assets acquisition in a liquefied petroleum gas company

This paper addresses a case study regarding inventory models for acquiring liquefied petroleum gas (LPG) cylinders. This is an industrial challenge that was proposed at an European Study Group with Industry, by a Portuguese energy company, for which the LPG cylinder is the main asset of its LPG business. Due to the importance of this asset, an acquisition plan must be defined in order to determine the amount of LPG cylinders to acquire, and when to acquire them, in order to optimize the investment. As cylinders are returned and refilled, the reverse logistic flows of these assets must be considered. As the classical inventory models are not suitable for this case study, three new inventory models, which account for the return of LPG cylinders, are proposed in this work. The first proposed model considers deterministic constant demand and continuous returns of LPG cylinders, with discrete replenishment from the supplier. The second model is similar, but for the case when the returned cylinders cover for the demand. A third model is also proposed considering that both the demand and the returns are stochastic in nature and the replenishment from the supplier is discrete. The three models address different scenarios that the company is either currently facing or is expecting to occur in the near future.publishe

Apoio à decisão em problemas de localização distribuição: uma proposta

Mestrado em Gestão de OperaçõesA presente dissertação apresenta uma proposta de um sistema de apoio à decisão para problemas de localização-distribuição. Esta proposta é orientada essencialmente para decisores, tendo por esse motivo grandes preocupações ao nível da interface com o utilizador. Os problemas de localização e distribuição estão cada vez mais presentes no quotidiano das empresas e instituições, exigindo cada vez mais tomadas de decisão que, se forem mal fundamentadas, podem comprometer o seu futuro. Neste trabalho é feito um enquadramento deste tipo de problemas na logística, apresentando uma evolução histórica da sua percepção e abrangência para, com base nesse estudo, apresentar uma proposta de aproximação a um sistema de apoio à decisão. Em primeiro lugar é feita uma introdução aos sistemas logísticos e às questões relacionadas com a localização e com a distribuição. De seguida, é feita a interligação entre estas duas vertentes logísticas, apresentando os motivos para o seu estudo ser realizado de uma forma integrada. Com base nessa necessidade de um estudo integrado surge então uma revisão bibliográfica aos problemas de localização-distribuição e, mais especificamente, aos problemas de localização-distribuição com capacidade. Após a introdução e classificação dos problemas de localização-distribuição com capacidade é descrita a evolução histórica dos sistemas de apoio à decisão, apresentando-se também como se processa, tipicamente, uma tomada de decisão. Uma vez realizada a fundamentação de ambos os temas é descrita a metodologia adoptada para o desenvolvimento do sistema de apoio à decisão, sendo posteriormente apresentado o sistema desenvolvido e as suas funcionalidades principais. Dentro desta descrição é também apresentada a heurística utilizada no sistema de apoio à decisão, com a respectiva formulação matemática. Finalmente, é apresentada uma ilustração do sistema de apoio à decisão, recorrendo-se a um problema da literaturaThis thesis presents a proposal of a decision support system for locationrouting problems. This proposal is essentially oriented to decision-makers, hence having a considerable concern regarding the user interface. Location and routing problems are nowadays, more than ever, present in the quotidian of companies and institutions, increasingly demanding decisions that, if not correctly supported, may compromise their future. In this study an approach to this type of problems in logistics is presented, as well as its historical evolution and scope, in order to underpin the proposal of a decision support system in this area. First an introduction to logistic systems is made and the main issues concerning location and routing are briefly addressed. Subsequently, the associations between these two areas are tackled and the interest of their integrated study is clarified. This interest leads to a bibliographic review of location-routing problems in general and, more specifically, of capacitatedlocation routing problems. The historical evolution of decision support systems is addressed, as well as how the decision process is typically made. The methodology used to develop a prototype of the decision support system as well as its main functionality are presented. Moreover, the heuristics used to solve the location-routing problem, and their mathematical formulations, are also described. Finally, the application of the decision support system to a problem in the literature is shown

Problemas de localização-distribuição de serviços semiobnóxios: aproximações e apoio à decisão

Doutoramento em Gestão IndustrialA presente tese resulta de um trabalho de investigação cujo objectivo se centrou no problema de localização-distribuição (PLD) que pretende abordar, de forma integrada, duas actividades logísticas intimamente relacionadas: a localização de equipamentos e a distribuição de produtos. O PLD, nomeadamente a sua modelação matemática, tem sido estudado na literatura, dando origem a diversas aproximações que resultam de diferentes cenários reais. Importa portanto agrupar as diferentes variantes por forma a facilitar e potenciar a sua investigação. Após fazer uma revisão e propor uma taxonomia dos modelos de localização-distribuição, este trabalho foca-se na resolução de alguns modelos considerados como mais representativos. É feita assim a análise de dois dos PLDs mais básicos (os problema capacitados com procura nos nós e nos arcos), sendo apresentadas, para ambos, propostas de resolução. Posteriormente, é abordada a localização-distribuição de serviços semiobnóxios. Este tipo de serviços, ainda que seja necessário e indispensável para o público em geral, dada a sua natureza, exerce um efeito desagradável sobre as comunidades contíguas. Assim, aos critérios tipicamente utilizados na tomada de decisão sobre a localização destes serviços (habitualmente a minimização de custo) é necessário adicionar preocupações que reflectem a manutenção da qualidade de vida das regiões que sofrem o impacto do resultado da referida decisão. A abordagem da localização-distribuição de serviços semiobnóxios requer portanto uma análise multi-objectivo. Esta análise pode ser feita com recurso a dois métodos distintos: não interactivos e interactivos. Ambos são abordados nesta tese, com novas propostas, sendo o método interactivo proposto aplicável a outros problemas de programação inteira mista multi-objectivo. Por último, é desenvolvida uma ferramenta de apoio à decisão para os problemas abordados nesta tese, sendo apresentada a metodologia adoptada e as suas principais funcionalidades. A ferramenta desenvolvida tem grandes preocupações com a interface de utilizador, visto ser direccionada para decisores que tipicamente não têm conhecimentos sobre os modelos matemáticos subjacentes a este tipo de problemas.This thesis main objective is to address the location-routing problem (LRP) which intends to tackle, using an integrated approach, two highly related logistics activities: the location of facilities and the distribution of materials. The LRP, namely its mathematical formulation, has been studied in the literature, and several approaches have emerged, corresponding to different real-world scenarios. Therefore, it is important to identify and group the different LRP variants, in order to segment current research and foster future studies. After presenting a review and a taxonomy of location-routing models, the following research focuses on solving some of its variants. Thus, a study of two of the most basic LRPs (capacitated problems with demand either on the nodes or on the arcs) is performed, and new approaches are presented. Afterwards, the location-routing of semi-obnoxious facilities is addressed. These are facilities that, although providing useful and indispensible services, given their nature, bring about an undesirable effect to adjacent communities. Consequently, to the usual objectives when considering their location (cost minimization), new ones must be added that are able to reflect concerns regarding the quality of life of the communities impacted by the outcome of these decisions. The location-routing of semi-obnoxious facilities therefore requires to be analysed using multi-objective approaches, which can be of two types: noninteractive or interactive. Both are discussed and new methods proposed in this thesis; the proposed interactive method is suitable to other multi-objective mixed integer programming problems. Finally, a newly developed decision-support tool to address the LRP is presented (being the adopted methodology discussed, and its main functionalities shown). This tool has great concerns regarding the user interface, as it is directed at decision makers who typically don’t have specific knowledge of the underlying models of this type of problems

Challenges in the introduction of AGVS in production lines: Case studies in the automotive industry

Increasing customers´ requirements together with the current trend of digitization in the spirit of Industry 4.0 puts pressure on manufacturing companies to increase both the flexibility and the performance of their manufacturing and logistic processes. This work presents the challenges in the introduction of AGV (Automatically Guided Vehicles) technology in production lines through two case studies from two different countries, Portugal and the Czech Republic. Both companies are from the automotive industry. Case study research aims to explore and understand complex phenomena. The main purpose of this study is to investigate the limitations and necessary conditions that must be considered when implementing AGV technology for automating selected logistic processes. Based on the data collected through multiple observations, a three-phase methodology considering technological, organizational and safety aspects is proposed as the main output. The basic scheme also includes the proposal of some critical success factors and key performance indicators that should be monitored in order to evaluate the efficiency of implementing this technology in future projects.publishe

Application of lean manufacturing tools in the food and beverage industries

Recent years have shown an increasing use of lean manufacturing (LM) principles and tools in several industrial sectors. Already a well-established management philosophy, it has shown numerous successful applications even outside production environments. This work presents the application of some LM tools, and the corresponding shift in philosophy, in two Portuguese companies of the food and beverage industries. Main implementation issues are presented and discussed; followed by the results obtained from the application of LM tools in the production system of these companies. Significant gains are obtained in both companies and, more importantly, it instills a continuous improvement culture and increases production flexibility while reducing lead times

Monitoring goat milk quality during pasteurisation and ohmic treatment using UV-VIS-SWNIR spectroscopy

This study evaluates the effectiveness of UV-VIS-SWNIR spectroscopy of goat milk quality degradation during pasteurisation and ohmic heating, being performed on: i) raw goat milk; ii) non-processed milk but passing though pumps, pasteurizer and ohmic heater; and iii) processed milk by pasteurisation and ohmic heating. Spectra were collected by a transmittance probe for UV-VIS and UV-NIR wavelengths. The samples temperature was recorded (18.0 ± 2.0oC) and the probe was always checked for bubble formation or fat residues on lens/mirror system. The integration time was set to 25s and 4s for the collection of UV-VIS and VIS-NIR spectra respectively. Data analysis was performed on each product and for each spectral range independently. The spectra were normalized by its maximum intensity and the corrected for using a robust multiplicative scatter correction algorithm. A principal component analysis was performed to the pre-processed spectra. Results show that UV-VIS-SWNIR reflectance spectroscopy provides a quick and fast assessment of goat milk characteristics and thus it can be used as an indication of the overall product variability, allowing to develop monitoring and control models for both pasteurisation and ohmic heating of goat milk.Fundação para a Ciência e a Tecnologia (FCT)EDERPRIME progra

A Tool for Visually Exploring Multi-objective Mixed-Integer Optimization Models

Multi-objective optimization models have been increasingly used as optimal decisions are searched in settings considering several conflicting objectives. In these cases compromises must be made and often a large number of nondominated optimal solutions exist. From these solutions decisionmakers must find the preferred one. This is a difficult task both from a computational and cognitive point of views, as it requires several solutions to be obtained and compared. An interactive visualization tool for fully understanding the best trade-offs is therefore becoming increasingly important. This paper proposes visualization solutions, implemented in a tool, for aiding decision-makers in finding the preferred solution in multiobjective optimization problems

Impacts of climate change on the biogeography of three amnesic shellfish toxin producing diatom species

Harmful algal blooms (HABs) are considered one of the main risks for marine ecosystems and human health worldwide. Climate change is projected to induce significant changes in species geographic distribution, and, in this sense, it is paramount to accurately predict how it will affect toxin-producing microalgae. In this context, the present study was intended to project the potential biogeographical changes in habitat suitability and occurrence distribution of three key amnesic shellfish toxin (AST)-producing diatom species (i.e., Pseudo-nitzschia australis, P. seriata, and P. fraudulenta) under four different climate change scenarios (i.e., RCP-2.6, 4.5, 6.0, and 8.5) up to 2050 and 2100. For this purpose, we applied species distribution models (SDMs) using four abiotic predictors (i.e., sea surface temperature, salinity, current velocity, and bathymetry) in a MaxEnt framework. Overall, considerable contraction and potential extirpation were projected for all species at lower latitudes together with projected poleward expansions into higher latitudes, mainly in the northern hemisphere. The present study aims to contribute to the knowledge on the impacts of climate change on the biogeography of toxin-producing miinfo:eu-repo/semantics/publishedVersio

Projecting future climate change-mediated impacts in Three Paralytic Shellfish Toxins-Producing dinoflagellate species

Simple Summary Harmful algal blooms present a particular risk for marine ecosystems and human health alike. In this sense, it is important to accurately predict how toxin-producing microalgae could be affected by future climate change. The present study applied species distribution models (SDMs) to project the potential changes in the habitat suitability and distribution of three key paralytic shellfish toxin (PST)-producing dinoflagellate species (i.e., Alexandrium catenella, A. minutum, and Gymnodinium catenatum), up to 2040/50 and 2090/2100, across four different greenhouse gas emission scenarios, and using four abiotic predictors (i.e., sea surface temperature, salinity, current velocity, and bathymetry). In general, considerable contractions were observed for all three species in the lower latitudes of their distribution, together with projected expansions into higher latitudes, particularly in the Northern Hemisphere. This study aims to entice further research on the future biogeographical impacts of climate change in toxin-producing microalgae species while, at the same time, helping to advise the correct environmental management of coastal habitats and ecosystems. Toxin-producing microalgae present a significant environmental risk for ecosystems and human societies when they reach concentrations that affect other aquatic organisms or human health. Harmful algal blooms (HAB) have been linked to mass wildlife die-offs and human food poisoning episodes, and climate change has the potential to alter the frequency, magnitude, and geographical extent of such events. Thus, a framework of species distribution models (SDMs), employing MaxEnt modeling, was used to project changes in habitat suitability and distribution of three key paralytic shellfish toxin (PST)-producing dinoflagellate species (i.e., Alexandrium catenella, A. minutum, and Gymnodinium catenatum), up to 2050 and 2100, across four representative concentration pathway scenarios (RCP-2.6, 4.5, 6.0, and 8.5; CMIP5). Despite slightly different responses at the regional level, the global habitat suitability has decreased for all the species, leading to an overall contraction in their tropical and sub-tropical ranges, while considerable expansions are projected in higher latitudes, particularly in the Northern Hemisphere, suggesting poleward distributional shifts. Such trends were exacerbated with increasing RCP severity. Yet, further research is required, with a greater assemblage of environmental predictors and improved occurrence datasets, to gain a more holistic understanding of the potential impacts of climate change on PST-producing species.info:eu-repo/semantics/publishedVersio