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Orientadores: Edson Luiz Ursini, Paulo Sérgio Martins Pedro / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-24T15:16:37Z (GMT). No. of bitstreams: 1 Santos_VlademirFazio_M.pdf: 4330659 bytes, checksum: a576d09102c26740d57f44a9686c5b76 (MD5) Previous issue date: 2014 / Resumo: Iniciativas industriais para finalizar a produção de multi-commodities embaladas sem formar estoque requerem inovação tecnológica constante. Atuam sincronizadamente com o múltiplo carregamento simultâneo diretamente em caminhões. Para isso desenvolvemos um modelo de simulação por eventos discretos e apresentamos seu modelo analítico de tráfego validado com Redes de Filas de Jackson e pela Lei de Conservação de Little. Descrevemos os limites do intervalo de variação de tempos máximos e médios de permanência de multi-commodities em sistemas de tempo real para três servidores paralelos. Esse sistema opera com mudanças dinâmicas de diferentes políticas de escalonamento. Um resultado é a confirmação do compromisso entre tempos máximos e médios independentemente de intensidade de tráfego e de políticas de escalonamento a que o modelo seja submetido. Outro é a identificação de uma faixa de relativa estabilidade operacional fora de regiões críticas. Assim, contribuímos com os princípios de um método que pode ser adotado como apoio às decisões de planejamento em ambientes industriais complexos submetidos a filas em tempo real / Abstract: The industrial initiatives for the production finalization of packed multi-commodities without forming stock require constant technological innovation. They operate a synchronous process to simultaneous multi-loading straightly into trucks. Regarding to this we developed a discrete event simulation model and present its traffic analytical model validated with the theory of Jackson Queueing Networks and the Little's Conservation Law. We describe the limits for the range of multi-commodities throuput-times and maximum waiting time in real-time systems with three parallel servers. This system operates with dynamical changes of different scheduling policies. A reached result is the confirmation of the average and maximum times mutual commitment despite of traffic intensity and scheduling policies that the model is submitted to. Another is the identification of a range of relative operational stability out of critical regions. As a contribution we offer the principles of a method that can be used to planning decision support in complex industrial environments subject to real-time queues / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia

The aim of this thesis is to develop a tractable method for approximating the steady-state behavior of continuous-review base-stock controlled assembly systems with Poisson demand arrivals and manufacturing and assembly facilities modeled as Jackson networks. One class of systems studied is to produce a single type of finished product assembling a number of components and another class is to produce two types of finished products allowing component commonality. The performance measures evaluated are the expected backorders, fill rate and the stockout probability for finished product(s). A partially aggregated but exact model is approximated assuming that the state-dependent transition rates arising as a result of the partial aggregation are constant. This approximation leads to the derivation of a closed-form steady-state probability distribution, which is of product-form. Adequacy of the proposed model in approximating the steady-state performance measures is tested against simulation experiments over a large range of parameters and the approximation turns out to be quite accurate with absolute errors of 10% at most for fill rate and stockout probability, and of less than 1.37 (&amp / #8776 / 2) requests for expected backorders. A greedy heuristic which is proposed to be employed using approximate steady-state probabilities is devised to optimize base-stock levels while aiming at an overall service level for finished product(s).

Accounting for some the highest arrival rates and widest varieties of medical conditions in a hospital, the emergency department is highly dependent on efficient operations strategies in order to function effectively and provide qualitative health care. This is especially true for the emergency department of Karolinska University Hospital in Huddinge from which real patient data has been obtained. In attempting to improve service levels, current operational structures are evaluated and several different scenarios are simulated mathematically in this study. After validating the adequacy of modeling the emergency department as a Jackson Network, the network is simulated for various combinations of patient flow parameters enabling the study of the effects of resource allocation strategies. The results indicate that the current organization of, and resources available to, the emergency department leaves room for improvement in terms of service levels. Resource levels needed for specific target levels of service are found and the optimal allocations of resources is discussed. Additionally, a brief literature review of operations strategies and how simulation tools can serve as decision support systems for operations strategy managers is conducted. / Akutmottagningen är en av de avdelningar på ett sjukhus som utsätts för högst ankomstintensiteter och bredast variationer av besöksorsaker vilket orsakar höga krav på att utveckla effektiva verksamhetsstrategier för att upprätthålla en kvalitativ sjukvård. Akutmottagningen på Karolinska Universitetssjukhuset i Huddinge har studerats genom patientdata. För att försöka förbättra servicenivåer och förkorta väntetider för patienter utvärderas verksamhetens organisation och struktur. En matematisk modell av verksamhetens organisation konstrueras och valideras, varefter effekterna av olika resursallokeringar analyseras genom matematiska simuleringar. Resultaten visar på att akutvården som den är organiserad idag lämnar utrymme för förbättring och optimering av resursallokering. Genom matematiska simuleringar identifieras marginella resursers specifika servicenivåer och relativa förändringar i servicenivåer. Slutligen kompletteras den matematiska analysen med en kortare litteraturstudie. Här presenteras hur simuleringar kan utgöra beslutsstödsystem för att planera resursallokering och introducera lean-strategier i sjukvården.

Åre ski resort is the largest and most renowned ski resort in Sweden, offering excellent skiing opportunities, restaurants, and nightlife in a prime location. Meanwhile, it is often subject to heavy traffic during the peak season and has earned a bad reputation for struggling with long lift queues. To address the issue, this paper aimed at analyzing the current capacity of the ski resort with the purpose of identifying areas and cost-efficient measures for improvement. It was done by modeling the ski system as a Jackson Network based on queuing theory, with relevant parameters extracted from actual skier data provided by the operating company Skistar. Several models were constructed to capture varying skiing patterns throughout the day and under different weather conditions. The models suggested that the lift queues first start to form at the lifts VM 8:an, Sadelexpressen, and Bräckeliften when the number of skiers in the system ranges from 3,700 to 6,200. Recommendations were then proposed to Skistar on how to resolve the identified bottlenecks and increase the resort’s capacity to a range of 6,000 to 8,400 skiers. Lastly, the models estimated that the resort could / Åre är en av Sveriges mest populära skidorter, som med utmärkta kommunikationsmöjligheter erbjuder fantastisk skidåkning och ett brett utbud av restauranger och nöjesliv. Skidsystemet belastas samtidigt hårt under högsäsong och har ådragit sig ett rykte om att ofta vara drabbat av långa liftköer. Mot bakgrund av detta ämnade denna rapport att analysera skidsystemets kapacitet och identifiera förbättringsområden för att ta itu med problemet. Analysen grundade sig i en modellering av skidsystemet, utformat som ett Jacksonnätverk i enlighet med köteori. Skistar, som ansvarar för driften av skidsystemet, tillhandahöll data som låg till grund för framtagandet av nätverkets parametrar. Genom jämförelser mellan olika modeller kunde dagliga förändringar i åkmönster och variationer under olika väderförhållanden tas i beaktning i analysen. Modellerna indikerade att liftarna VM 8:an, Sadelexpressen och Bräckeliften först drabbas av köbildning, vilket sker då antalet skidåkare i systemet är mellan 3 700 och 6 200. De identifierade flaskhalsarna låg till grund för de rekommendationer som formulerades till Skistar och som innehöll kostnadseffektiva förslag på förändringar. Dessa skulle förbättra kapaciteten till en nivå mellan 6 000 och 8 400 skidåkare. Till sist estimerade modellerna systemets maximala kapacitet till 14 000 skidåkare, vilket endast uppnås vid ett optimalt nyttjande av samtliga liftar.

Um conjunto de modelos compostos de redes de filas em grades finitas servindo como ambientes aleatorios para um ou mais passeios aleatorios, que por sua vez podem afetar o comportamento das filas, e desenvolvido. Duas formas de interacao entre os passeios aleatorios sao consideradas. Para cada modelo, e provado que o processo Markoviano correspondente e recorrente positivo e reversivel. As equacoes de balanceamento detalhado sao analisadas para obter a forma funcional da medida invariante de cada modelo. Em todos os modelos analisados neste trabalho, a medida invariante em uma grade finita tem forma produto. Modelos de redes de filas como ambientes para multiplos passeios aleatorios sao estendidos a grades infinitas. Para cada modelo estendido, sao especificadas as condicoes para a existencia do processo estocastico na grade infinita. Alem disso, e provado que existe uma unica medida invariante na rede infinita cuja projecao em uma subgrade finita e dada pela medida correspondente de uma rede finita. Finalmente, e provado que essa medida invariante na rede infinita e reversivel. / A set of models composed of queueing networks serving as random environments for one or more random walks, which themselves can affect the behavior of the queues, is developed. Two forms of interaction between the random walkers are considered. For each model, it is proved that the corresponding Markov process is positive recurrent and reversible. The detailed balance equa- tions are analyzed to obtain the functional form of the invariant measure of each model. In all the models analyzed in the present work, the invariant measure on a finite lattice has product form. Models of queueing networks as environments for multiple random walks are extended to infinite lattices. For each model extended, the conditions for the existence of the stochastic process on the infinite lattice are specified. In addition, it is proved that there exists a unique invariant measure on the infinite network whose projection on a finite sublattice is given by the corresponding finite- network measure. Finally, it is proved that that invariant measure on the infinite lattice is reversible.

Um conjunto de modelos compostos de redes de filas em grades finitas servindo como ambientes aleatorios para um ou mais passeios aleatorios, que por sua vez podem afetar o comportamento das filas, e desenvolvido. Duas formas de interacao entre os passeios aleatorios sao consideradas. Para cada modelo, e provado que o processo Markoviano correspondente e recorrente positivo e reversivel. As equacoes de balanceamento detalhado sao analisadas para obter a forma funcional da medida invariante de cada modelo. Em todos os modelos analisados neste trabalho, a medida invariante em uma grade finita tem forma produto. Modelos de redes de filas como ambientes para multiplos passeios aleatorios sao estendidos a grades infinitas. Para cada modelo estendido, sao especificadas as condicoes para a existencia do processo estocastico na grade infinita. Alem disso, e provado que existe uma unica medida invariante na rede infinita cuja projecao em uma subgrade finita e dada pela medida correspondente de uma rede finita. Finalmente, e provado que essa medida invariante na rede infinita e reversivel. / A set of models composed of queueing networks serving as random environments for one or more random walks, which themselves can affect the behavior of the queues, is developed. Two forms of interaction between the random walkers are considered. For each model, it is proved that the corresponding Markov process is positive recurrent and reversible. The detailed balance equa- tions are analyzed to obtain the functional form of the invariant measure of each model. In all the models analyzed in the present work, the invariant measure on a finite lattice has product form. Models of queueing networks as environments for multiple random walks are extended to infinite lattices. For each model extended, the conditions for the existence of the stochastic process on the infinite lattice are specified. In addition, it is proved that there exists a unique invariant measure on the infinite network whose projection on a finite sublattice is given by the corresponding finite- network measure. Finally, it is proved that that invariant measure on the infinite lattice is reversible.