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Collazo, Rodrigo A. "The dynamic chain event graph." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/91075/.
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The Chain Event Graph (CEG) is a type of tree-based graphical model that accommodates all discrete Bayesian Networks as a particular subclass. It has already been successfully used to capture context-specific conditional independence structures of highly asymmetric processes in a way easily appreciated by domain experts. Being built from a tree, a CEG has a huge number of free parameters that makes the class extremely expressive but also very large. Exploring the enormous CEG model space then makes it necessary to design bespoke algorithms for this purpose. All Bayesian algorithms for CEG model selection in the literature are based on the Dirichlet characterisation of a family of CEGs spanned by a single event tree. Here I generalise this framework for a CEG model space spanned by a collection of different event trees. A new concept called hyper-stage is also introduced and provides us with a framework to design more efficient algorithms. These improvements are nevertheless insufficient to scale up the model search for more challenging applications. In other contexts, recent analyses of Bayes Factor model selection using conjugate priors have suggested that the use of such prior settings tends to choose models that are not sufficiently parsimonious. To sidestep this phenomenon, non-local priors (NLPs) have been successfully developed. These priors enable the fast identification of the simpler model when it really does drive the data generation process. In this thesis, I define three new families of NLPs designed to be applied specifically to discrete processes defined through trees. In doing this, I develop a framework for a CEG model search which appears to be both robust and computationally efficient. Finally, I define a Dynamic Chain Event Graph (DCEG). I develop object-recursive methods to fully analyse a particularly useful and feasibly implementable new subclass of these models called the N Time-Slice DCEG (NT-DCEG). By exploiting its close links with the Dynamic Bayesian Network I show how the NT-DCEG can be used to depict various structural and Granger causal hypotheses about a studied process. I also show how to construct from the topology of this graph intrinsic random variables which exhibit context-specific independences that can then be checked by domain experts. Throughout the thesis my methods are illustrated using examples of multivariate processes describing inmate radicalisation in a prison, and survey data concerning childhood hospitalisation and booking a tourist train.
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Thwaites, Peter. "Chain event graphs : theory and application." Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/49194/.
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This thesis is concerned with the Graphical model known as the Chain Event Graph (CEG) [1][60][61], and develops the theory that appears in the currently published papers on this work. Results derived are analogous to those produced for Bayesian Networks (BNs), and I show that for asymmetric problems the CEG is generally superior to the BN both as a representation of the problem and as an analytical tool. The CEG is designed to embody the conditional independence structure of problems whose state spaces are asymmetric and do not admit a natural Product Space structure. In this they differ from BNs and other structures with variable-based topologies. Chapter 1 details researchers' attempts to adapt BNs to model such problems, and outlines the advantages CEGs have over these adaptations. Chapter 2 describes the construction of CEGs. In chapter 3I create a semantic structure for the reading of CEGs, and derive results expressible in the form of context-specific conditional independence statements, that allow us to delve much more deeply into the independence structure of a problem than we can do with BNs. In chapter 4I develop algorithms for the updating of a CEG following observation of an event, analogous to the Local Message Passing algorithms used with BNs. These are more efficient than the BN-based algorithms when used with asymmetric problems. Chapter 5 develops the theory of Causal manipulation of CEGs, and introduces the singular manipulation, a class of interventions containing the set of interventions possible with BNs. I produce Back Door and Front Door Theorems analogous to those of Pearl [42], but more flexible as they allow asymmetric manipulations of asymmetric problems. The ideas and results of chapters 2 to 5 are summarised in chapter 6.
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Freeman, Guy. "Learning and predicting with chain event graphs." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/4529/.
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Graphical models provide a very promising avenue for making sense of large, complex datasets. The most popular graphical models in use at the moment are Bayesian networks (BNs). This thesis shows, however, they are not always ideal factorisations of a system. Instead, I advocate for the use of a relatively new graphical model, the chain event graph (CEG), that is based on event trees. Event trees directly represent graphically the event space of a system. Chain event graphs reduce their potentially huge dimensionality by taking into account identical probability distributions on some of the event tree’s subtrees, with the added benefits of showing the conditional independence relationships of the system — one of the advantages of the Bayesian network representation that event trees lack — and implementation of causal hypotheses that is just as easy, and arguably more natural, than is the case with Bayesian networks, with a larger domain of implementation using purely graphical means. The trade-off for this greater expressive power, however, is that model specification and selection are much more difficult to undertake with the larger set of possible models for a given set of variables. My thesis is the first exposition of how to learn CEGs. I demonstrate that not only is conjugate (and hence quick) learning of CEGs possible, but I characterise priors that imply conjugate updating based on very reasonable assumptions that also have direct Bayesian network analogues. By re-casting CEGs as partition models, I show how established partition learning algorithms can be adapted for the task of learning CEGs. I then develop a robust yet flexible prediction machine based on CEGs for any discrete multivariate time series — the dynamic CEG model — which combines the power of CEGs, multi-process and steady modelling, lattice theory and Occam’s razor. This is also an exact method that produces reliable predictions without requiring much a priori modelling. I then demonstrate how easily causal analysis can be implemented with this model class that can express a wide variety of causal hypotheses. I end with an application of these techniques to real educational data, drawing inferences that would not have been possible simply using BNs.
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Albors, Marques Laura, and Jagathishvar Jayakumar. "Discrete Event Simulation for Aftermarket Supply Chain." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280678.
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The planning of an Aftermarket Supply Chain is a very complex task. This is due to an unpredictable demand which is driven by the need for maintenance and repair. This drive translates to a high variety of lead times, a large number of stock-keeping units (SKUs) and the capacity to deliver spare parts during its full lifecycle. With all these complexities in place, optimizing and parametrizing the planning process is a difficult and time-consuming task. Moreover, the current optimization tool focuses only on one node (each warehouse individually) of the whole Supply Chain, without considering the information such as inventory levels of the other nodes. Hence, the Supply Chain is not completely connected, making it difficult to get a better understanding of the system performance to identify cost draining areas. This leads to capital being tied up in the upper stream of the Supply Chain and later adding unnecessary costs like high inventory costs, rush freight costs, return or scrapping cost. In this study, Discrete Event Simulation (DES) is explored as an additional optimization tool that could analyse and improve the performance of the whole Supply Chain. To do that, the functioning of a node is modelled by replicating the logics behind the flow of material, which includes analysing some manual workflows which are currently present. In Addition, all the information needed from the orders, order lines and parts are mapped. The later part of the study aims to connect all the nodes to form a whole overview of the Supply Chain and further perform optimizations globally. As an outcome, Multi-Echelon Inventory Optimization has been performed on the whole Supply Chain after connecting all the nodes and thus getting an overview. Furthermore, the impact of different parameters has been studied on the whole model to understand the sensitivity of parameters such as variations in lead time and demand. Finally, different what-if scenarios such as COVID and problems with delay in suppliers were studied, which could help understand the impact of unforeseen situations.Planeringen av en eftermarknadskedja är en mycket komplex uppgift. Detta beror på en oförutsägbar efterfrågan som drivs av behovet av underhåll och reparation. Enheten översätter till många olika ledtider, ett stort antal lagerhållningsenheter (SKU) och kapacitet att leverera reservdelar under hela dess livscykel. Med alla dessa komplexiteter på plats är optimering och parametrering av planeringsprocessen en svår och tidskrävande uppgift. Dessutom fokuserar det nuvarande optimeringsverktyget bara på en nod (varje lager separat) i hela leveranskedjan utan att beakta informationen som lagernivåerna för de andra noderna. Därför är försörjningskedjan inte helt ansluten, vilket gör det svårt att få en bättre förståelse för systemets prestanda för att identifiera kostnadsavtappningsområden. Detta leder till att kapital binds i den övre strömmen i försörjningskedjan och senare lägger till onödiga kostnader som höga lagerkostnader, snabba fraktkostnader, retur- eller skrotningskostnader. I denna studie undersöks Discrete Event Simulation (DES) som ett ytterligare optimeringsverktyg som kan analysera och förbättra prestanda för hela försörjningskedjan. För att göra det modelleras en nods funktion genom att replikera logiken bakom materialflödet, vilket inkluderar analys av några manuella arbetsflöden som för närvarande finns. Dessutom kartläggs all information som behövs från beställningar, orderrader och delar. Den senare delen av studien syftar till att ansluta alla noder för att bilda en hel översikt över försörjningskedjan och ytterligare utföra optimeringar globalt. Som ett resultat har Multi-Echelon Lageroptimering utförts i hela försörjningskedjan efter att alla noder har anslutits och därmed fått en översikt. Dessutom har effekterna av olika parametrar studerats på hela modellen för att förstå känsligheten hos parametrar som variationer i ledtid och efterfrågan. Slutligen studerades olika tänkbara scenarier som COVID och problem med förseningar hos leverantörer, vilket kan hjälpa till att förstå effekterna av oförutsedda situationer.
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Suzuki, Yuya. "Rare-event Simulation with Markov Chain Monte Carlo." Thesis, KTH, Matematisk statistik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-138950.
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In this thesis, we consider random sums with heavy-tailed increments. By the term random sum, we mean a sum of random variables where the number of summands is also random. Our interest is to analyse the tail behaviour of random sums and to construct an efficient method to calculate quantiles. For the sake of efficiency, we simulate rare-events (tail-events) using a Markov chain Monte Carlo (MCMC) method. The asymptotic behaviour of sum and the maximum of heavy-tailed random sums is identical. Therefore we compare random sum and maximum value for various distributions, to investigate from which point one can use the asymptotic approximation. Furthermore, we propose a new method to estimate quantiles and the estimator is shown to be efficient.
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Gudmundsson, Thorbjörn. "Rare-event simulation with Markov chain Monte Carlo." Doctoral thesis, KTH, Matematisk statistik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157522.
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Stochastic simulation is a popular method for computing probabilities or expecta- tions where analytical answers are difficult to derive. It is well known that standard methods of simulation are inefficient for computing rare-event probabilities and there- fore more advanced methods are needed to those problems. This thesis presents a new method based on Markov chain Monte Carlo (MCMC) algorithm to effectively compute the probability of a rare event. The conditional distri- bution of the underlying process given that the rare event occurs has the probability of the rare event as its normalising constant. Using the MCMC methodology a Markov chain is simulated, with that conditional distribution as its invariant distribution, and information about the normalising constant is extracted from its trajectory. In the first two papers of the thesis, the algorithm is described in full generality and applied to four problems of computing rare-event probability in the context of heavy- tailed distributions. The assumption of heavy-tails allows us to propose distributions which approximate the conditional distribution conditioned on the rare event. The first problem considers a random walk Y1 + · · · + Yn exceeding a high threshold, where the increments Y are independent and identically distributed and heavy-tailed. The second problem is an extension of the first one to a heavy-tailed random sum Y1+···+YN exceeding a high threshold,where the number of increments N is random and independent of Y1 , Y2 , . . .. The third problem considers the solution Xm to a stochastic recurrence equation, Xm = AmXm−1 + Bm, exceeding a high threshold, where the innovations B are independent and identically distributed and heavy-tailed and the multipliers A satisfy a moment condition. The fourth problem is closely related to the third and considers the ruin probability for an insurance company with risky investments. In last two papers of this thesis, the algorithm is extended to the context of light- tailed distributions and applied to four problems. The light-tail assumption ensures the existence of a large deviation principle or Laplace principle, which in turn allows us to propose distributions which approximate the conditional distribution conditioned on the rare event. The first problem considers a random walk Y1 + · · · + Yn exceeding a high threshold, where the increments Y are independent and identically distributed and light-tailed. The second problem considers a discrete-time Markov chains and the computation of general expectation, of its sample path, related to rare-events. The third problem extends the the discrete-time setting to Markov chains in continuous- time. The fourth problem is closely related to the third and considers a birth-and-death process with spatial intensities and the computation of first passage probabilities. An unbiased estimator of the reciprocal probability for each corresponding prob- lem is constructed with efficient rare-event properties. The algorithms are illustrated numerically and compared to existing importance sampling algorithms.QC 20141216
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Fantozzi, Esmè 1968. "A strategic approach to supply chain event management." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/28565.
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Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2003.Includes bibliographical references (p. 35).
This thesis project explores the possibility to apply project management techniques, specifically critical path method, and PERT, to supply chain event management. The idea behind the project is to create a framework for putting supply chain events into a broader supply chain context and assessing their criticality. Such a framework can then be utilized as a starting point for supply chain event management software applications. The problem has been approached from a "micro" point of view, with the analysis and PERT modeling of a single order fulfillment process, and from a "macro" point of view, with the analysis and a very simple model of the inventory itself. Finally, there are important factors that can drive the development and adoption of such systems in the future, including a higher level of supply chain informatization, removal of inter-and intra-company communication barriers, and better software integration technologies to effectively link all the element of the supply chain network.
by Esmè Fantozzi.
M.Eng.in Logistics
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Wiedenbruch, Alexander [Verfasser]. "A Modeling Language for Supply Chain Event Management / Alexander Wiedenbruch." München : Verlag Dr. Hut, 2014. http://d-nb.info/1047994801/34.
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Barclay, Lorna M. "Modelling and reasoning with chain event graphs in health studies." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/63223/.
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The Chain Event Graph (CEG) is a new class of graphical model, first introduced in Smith and Anderson [2008], which is derived from a probability tree by merging vertices whose associated conditional probabilities are the same. It is proving to be a useful framework for modelling asymmetric problems and further generalises the Bayesian Network (BN), by allowing for context-specific dependence structures between the variables of the problem. This thesis provides a first demonstration of the value of using the CEG in real-world applications and the new techniques developed here are motivated by problems that arise from two health studies; the Christchurch Health and Development Study (CHDS) and the UK Cerebral Palsy (UKCP) Cohort Study. A direct comparison of the BN and CEG on the CHDS demonstrates that the CEG can lead to significantly higher scoring models than the BN and further that it enables additional conclusions to be drawn on the health study directly from the topology of its graph. An extension of the CEG, the Ordinal CEG, is developed in this thesis, which further enhances the graphical representation of the CEGs for studies with a binary outcome. Motivated by the UKCP this thesis further investigates how missing data structures can be explicitly represented by a CEG and how its graph can consequently provide a precise understanding of the influence of missingness. Finally, a dynamic version of the CEG is developed and it is demonstrated how this new class of models generalises the Dynamic BN and is further closely linked to (semi-) Markov processes. The expressiveness of this model is illustrated through a fictional example.
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Mendling, Jan, and Gustaf Neumann. "Yet Another Event-driven Process Chain - Modelling Workflow Patterns with yEPCs." Gesellschaft für Informatik e.V, 2005. http://epub.wu.ac.at/6018/1/Mendling_etal_2005_EMISA_Yet%2DAnother%2DEvent%2Ddriven.pdf.
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The 20 workflow patterns proposed by van der Aalst et al. provide a comprehensive benchmark for comparing process modelling languages. In this article, we discuss workflow pattern support of Event-Driven Process Chains (EPCs). Building on this analysis, we propose three extensions to EPCs in order to provide for workflow pattern support. These are the introduction of the so-called empty connector; inclusion of multiple instantiation concepts; and a cancellation construct. As both the latter are inspired by YAWL, we refer to this new class of EPCs as Yet Another Event-driven Process Chain (yEPC). Furthermore, we sketch how a transformation to YAWL can be used to specify the semantics of yEPCs.
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Amundson, Joseph S. "Modeling of Biorefinery Supply Chain Economic Performance with Discrete Event Simulation." UKnowledge, 2013. http://uknowledge.uky.edu/ms_etds/6.
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As competition for fossil fuels accelerates, alternative sources of chemicals, fuels, and energy production become more appealing to researchers and the layman. Among the candidates to fill this growing niche is lignocellulosic biomass. Many researchers have examined supply chain design and optimization for biofuel and bioenergy production throughout the years. However, these models often fail to capture the variability and uncertainty inherent to the biomass supply chain. Multiple factors with high degrees of stochasticity can have major impacts on the performance of a biorefinery: weather, biomass quality, feedstock availability, and market demand for products are just a few. To begin to address this issue, a discrete event simulation model has been developed to examine the economic performance of a region specific, multifeedstock biorefinery supply chain. Probability distributions developed for product demand and feedstock supply begin to address the random nature of the supply chain. Model development is discussed in the context of a multidisciplinary framework for biorefinery supply chain design. A case study, sensitivity analysis, and scenario analysis, are utilized to examine the capabilities of the model.
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Pavlou, Soultana. "An information systems framework for event management in supply chain operations." Thesis, City University London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434582.
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Hunewald, Christian. "Supply Chain Event Management : Anforderungen und Potentiale am Beispiel der Automobilindustrie /." Wiesbaden : Deutscher Universitäts-Verlag, 2005. http://www.gbv.de/dms/zbw/484947206.pdf.
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Gudmundsson, Thorbjörn. "Markov chain Monte Carlo for rare-event simulation in heavy-tailed settings." Licentiate thesis, KTH, Matematisk statistik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-134624.
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Saad, Nordin. "Modelling, simulation, and analysis of supply chain systems using discrete-event simulation." Thesis, University of Sheffield, 2003. http://etheses.whiterose.ac.uk/14771/.
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Many approaches have been developed which support the construction of detailed supply chain models useful for analysis and simulation. However, most of these approaches lack the ability to model the supply chain in a single model, and usually produce solutions that lead to conflicting strategies between the companies. Simulation using a discrete-event simulation (DES) is an effective tool for the dynamically changing supply chain variables, thus allowing the system to be modelled more realistically. Considering the complexities of the supply chain system and the interrelations between its various systems, the task of developing such a model is challenging. The aim of this thesis is to develop a simulation model of a fast moving consumer goods (FMCG) supply chain with a DES tool. This model would be utilised as a decision-support system (DSS) for the investigation of the effectiveness of several inventory policies towards effective coordination and control of production inventory system, in various situations. This thesis discusses fundamental issues in the development of a simulation model for a supply chain using the DES tool, ARENA. A modelling procedure for the development of a supply chain simulation model is presented. The overall structure of the model is constructed by incorporating the well documented concept of modelling materials flowing downstream with an approach of modelling orders flowing upstream (modelling of feedback information). The model has an easily adaptable structure where rules (inventory policies) and model variables can be modified. The flexibility in the model's structure allows devising appropriate experimental designs, for several tests to be performed to imitate some realistic situations or scenarios (including the presence of disturbances). A new control theory oriented inventory policy, called the pseudo PID, is proposed. Detailed evaluations of five inventory policies for a production-inventory control under dynamic and stochastic conditions is presented. The findings demonstrate the ability of the approach to provide a wealth of potential solutions to the decision-maker, and confirm the qualitative behaviour of a supply chain in response to the different policies.
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Lodha, Rakesh. "An Event-Trigger-Rule based supply-chain management system over the Internet." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001163.
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Ceccolin, Sofia <1997>. "THE IMPACT OF DIGITALIZATION IN THE TRANSITION TOWARDS AN INTEGRATED SUPPLY CHAIN A Supply Chain Event Management Case Study." Master's Degree Thesis, Università Ca' Foscari Venezia, 2021. http://hdl.handle.net/10579/20375.
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During the last few decades, the change in the world’s economic environment has led to a transformation of supply chain activities and logistics operations. The growing globalization, the increase of destructive events (such as the current global health crisis), and the drive towards digital innovation dictated by the Fourth Industrial Revolution require companies to make an organizational change regarding both internal and external activities. We are witnessing a radical transition from competition between individual companies to competition between industrial supply chains. There is a shift from the traditional supply chain, characterized by the linearity of operations, to a more integrated supply chain model, where information flows in more than one direction at once. This thesis aims to study how the supply chain can fully experience the benefits brought about by integration mainly thanks to the support provided by the enabling technologies of Industry 4.0. The primary goals of the research are understanding which are the pressures towards the integration and digitalization of supply chain activities, evaluating the advantages and challenges, and studying how a supply chain can be integrated through digitalization. To support the thesis, a case study on Supply Chain Event Management carried out by the author is reported.
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Tröger, Ralph. "Supply Chain Event Management – Bedarf, Systemarchitektur und Nutzen aus Perspektive fokaler Unternehmen der Modeindustrie." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-155014.
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Supply Chain Event Management (SCEM) bezeichnet eine Teildisziplin des Supply Chain Management und ist für Unternehmen ein Ansatzpunkt, durch frühzeitige Reaktion auf kritische Ausnahmeereignisse in der Wertschöpfungskette Logistikleistung und -kosten zu optimieren.
Durch Rahmenbedingungen wie bspw. globale Logistikstrukturen, eine hohe Artikelvielfalt und volatile Geschäftsbeziehungen zählt die Modeindustrie zu den Branchen, die für kritische Störereignisse besonders anfällig ist. In diesem Sinne untersucht die vorliegende Dissertation nach einer Beleuchtung der wesentlichen Grundlagen zunächst, inwiefern es in der Modeindustrie tatsächlich einen Bedarf an SCEM-Systemen gibt.
Anknüpfend daran zeigt sie nach einer Darstellung bisheriger SCEM-Architekturkonzepte Gestaltungsmöglichkeiten für eine Systemarchitektur auf, die auf den Designprinzipien der Serviceorientierung beruht. In diesem Rahmen erfolgt u. a. auch die Identifikation SCEM-relevanter Business Services. Die Vorzüge einer serviceorientierten Gestaltung werden detailliert anhand der EPCIS (EPC Information Services)-Spezifikation illustriert.
Abgerundet wird die Arbeit durch eine Betrachtung der Nutzenpotenziale von SCEM-Systemen. Nach einer Darstellung von Ansätzen, welche zur Nutzenbestimmung infrage kommen, wird der Nutzen anhand eines Praxisbeispiels aufgezeigt und fließt zusammen mit den Ergebnissen einer Literaturrecherche in eine Konsolidierung von SCEM-Nutzeffekten. Hierbei wird auch beleuchtet, welche zusätzlichen Vorteile sich für Unternehmen durch eine serviceorientierte Architekturgestaltung bieten.
In der Schlussbetrachtung werden die wesentlichen Erkenntnisse der Arbeit zusammengefasst und in einem Ausblick sowohl beleuchtet, welche Relevanz die Ergebnisse der Arbeit für die Bewältigung künftiger Herausforderungen innehaben als auch welche Anknüpfungspunkte sich für anschließende Forschungsarbeiten ergeben.
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Ahmadi, Mansour. "The application of system dynamics and discrete event simulation in supply chain management of Swedish manufacturing industries." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-16150.
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Increasing competition from traditional and emerging channels has placed new emphasis on rapid innovation and continuous differentiation in every aspect of supply chain, from earliest production stage to the final distribution steps. To bridge the gap between brilliant ideas and successful business initiatives, leading companies implement engineering simulation particularly in logistics and supply chain management (LSCM). Discrete event simulation (DES) and system dynamics (SD) are two modeling approaches widely used in this field. However there are not much done researches about the applications of these simulation approaches in supply chain context of Swedish Manufacturing Industries (SMI). This study explores the application of DES and SD in LSCM of SMI by looking at the nature and level of issues modeled. Journal papers and master theses that use these modeling approaches to study supply chains, published between 1990 and 2012 are reviewed. A total of 39 articles are analyzed to identify the frequency with which the two simulation approaches are used as modeling tools in LSCM of SMI. Our findings suggest that DES has been used more frequently to model supply chains in SMI. The results also show that not all the LSCM issues have been addressed evenly and generally tactical/operational issues have been modeled more frequently. The results of this study inform the existing literature about the use of DES and SD in LSCM of SMI.
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Regali, Christopher Ralph [Verfasser], and Horst [Akademischer Betreuer] Fischer. "Exclusive event generation for the COMPASS-II experiment at CERN and improvements for the Monte-Carlo chain." Freiburg : Universität, 2016. http://d-nb.info/1122831862/34.
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Batista, Janaina Siegler Marques. "Supply chain turbulence: the impact of a mid-range event in multi-tier, multi-dimension supply chains." reponame:Repositório Institucional do FGV, 2015. http://hdl.handle.net/10438/13937.
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Nota: A autora agradece à Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) pela concessão de bolsa de estudos para o desenvolvimento deste projeto de pesquisa.Submitted by Janaina Siegler (janaina.siegler@gmail.com) on 2015-08-18T00:46:34Z No. of bitstreams: 1 Jana Tese 10 ficha catalog.pdf: 5941307 bytes, checksum: 72743b682d62fd8c625ec73724627d90 (MD5)
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This dissertation aims at understanding complex multi-tier, multi-dimension supply chains, investigating why and how an event in a focal firm affects members of its own and other supply chains. To fulfill this goal, two approaches were used, a theoretical and an empirical approach. For the theoretical study, we developed a novel way to look at dissemination of the impact of an event over a supply chain through metaphorical transfer. We built upon the physics of stone skipping, analyzing the correspondence between elements from physics and supply chains at the levels of ontology, analogy, and identity. The main contributions of the theoretical study were the development of six propositions and a model of dissemination of the impact of an event over a supply chain. Second, we applied the propositions using a set of qualitative data collected in the cosmetics industry in Brazil. We conducted 131 semi-structured in-depth interviews and 22 site visits, in addition to observation and analysis of documents. The multiple case studies were based on six complex, multi-tier, multi-dimension supply chains encompassing up to seven tiers each. Within and cross-case analysis were conducted. The results of the empirical study are presented in two parts. First, we analyzed the six supply chains in detail and identified six mid-range events that had impacts beyond the source firm. Second, we tested the propositions from the theoretical part of this study and their application to the identified mid-range events. Our results indicated that, differently from the current literature, supply chains are not linear. In multi-tier, multi-dimension supply chains, the same firm can play different roles according to the supply chain it is part of different times. Thus, supply chains are better portrayed as a set of interlocking networks. Our findings also support viewing a supply chain as a chain of individual relationships. Several elements impact the dissemination of the impact of an event over a supply chain. Among them, power of the source firm and the personal social influence of the individuals in the source firm play a significant role. In addition, because individuals make decisions and implement events, it is important to consider that personal heuristics, biases, and locus of control will be manifested by the individuals in all contexts, both internal (focal firm), and external (supply chin links), and that those human irrationalities will impact the perception of the event and influence the continuity and extent of its impact in the supply chain. Our findings also support the notion that the impact of an event is disseminated over a supply chain through its members’ weak ties.
Esta tese objetivou compreender cadeias de suprimento multi niveis e multi dimensionais, investigando como e porque um evento em uma empresa focal afeta membros de sua propria cadeia de suprimentos e outras cadeias. Para atender este objetivo, duas abordagens foram utilizadas: uma teórica e uma empírica. Para o estudo teórico, desenvolvemos uma nova forma de olhar a disseminação do impacto de um evento na cadeia de suprimentos utilizando transferência metafórica. Nos baseamos na física de pedras que saltam na água, analisando a correspondência dentre os elementos da física e das cadeias de suprimentos nos niveis de ontologia, analogia e identidade. A principal contribuição do estudo teórico reside no desenvolvimento de seis proposições e um modelo para a disseminação do impacto de um evento na cadeia de suprimentos. Em seguida, nós aplicamos tais proposições numa base de dados coletada no setor de cosméticos no Brasil. Foram conduzidas 131 entrevistas em profundidade e 22 visitas à fábricas e unidades de negócio por todo o país. Complementarmente também foram conduzidas observações e análise de documentos secundários. Estudos de casos múltiplos individuais e comparativos foram desenvolvidos baseados em seis cadeias de suprimentos complexas, multi-niveis e multi-dimensionais, que englobaram de cinco a sete niveis cada uma. Os resultados foram apresentados em duas partes. No primeiro, anlisamos as seis cadeias de suprimentos em detalhes e identificamos seis eventos de médio porte que tiveram impactos em suas cadeias de suprimentos além da empresa focal onde foi iniciado. Em seguida, aplicamos as proposições do estudo teórico nos eventos de médio porte identificados. Nosso resultados indicaram que, diferentemente da literatura, cadeias de suprimentos não são lineares. Em condicões reais, a mesma empresa pode representar diferentes papéis de acordo com a cadeia de suprimento que ela é parte em diferentes momentos. Assim, cadeias de suprimentos são melhor representadas como um conjunto de redes interligadas. Nossos achados também suportam a visão de cadeias de suprimentos como uma rede de relações individuais. Vários diferentes elementos influenciam na disseminação do impacto de um evento em uma cadeia de suprimentos, dentre eles, o poder da empresa e a habilidade de influência social dos indivíduos que fazem parte daquela empresa têm papel relevante. Também é importante considerar que irracionalidades pessoais como heurísitcas, vieses, e locus de controle serão manifestados por indivíduos em todos os contextos, interno (empresa focal) e externo (cadeia de suprimentos), e que tais irracionalidades impactam a percepção do evento, a continuidade e extensão de seus impactos na cadeia de suprimentos. Nossos achados ainda suportam a noção de que o impacto de um evento é disseminado na cadeia de suprimentos por meio dos laços fracos construídos pelos membros das organizações.
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Timóteo, Júlio Esteves Dantas. "Supply chain management na indústria de festivais de música : o caso "Paredes de Coura"." Master's thesis, Instituto Superior de Economia e Gestão, 2018. http://hdl.handle.net/10400.5/17502.
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Mestrado em MarketingA indústria dos festivais de música tem crescido exponencialmente em Portugal. Considerando o sucesso deste tipo de eventos e o elevado número de relacionamentos empresariais que exigem, torna-se importante entender de que forma práticas aplicadas de gestão poderão explicar esse fenómeno. Assim, o objetivo desta dissertação passa por entender de que forma funcionam esses relacionamentos na organização de um evento de larga escala nesta indústria, para compreender se existe filosofia de cadeia de aprovisionamento, até que ponto é implementada e se é feito voluntária ou espontaneamente. Para a recolha de dados primários foi realizado um estudo qualitativo, em forma de case study, com amostragem não probabilística por julgamento, composta por três profissionais diretamente ligados à cadeia de produção de um grande evento nacional desta indústria, a quem foram realizadas entrevistas semiestruturadas. Através do estudo empírico, concluiu-se que não existe supply chain management na produção do evento, ou abertura para tal pela organização. Percebeu-se que esta assume um papel de líder na rede, promovendo o prolongamento dos relacionamentos no tempo e, pontualmente, colaborações sistémicas. Notou-se que a interdependência é encarada negativamente pela organização e apenas existe assinalavelmente no relacionamento com o main sponsor, sendo todos os outros vistos como parcerias facilmente substituíveis. Foi também descoberto que os processos interorganizacionais e interfuncionais são maioritariamente espontâneos e não uma solução estratégica. As vantagens competitivas do evento são tidas pela organização como um produto conjunto de todos os parceiros, embora um aumento do customer value seja apenas considerado proveniente do engenho próprio da produtora.
The music festival industry has been growing exponentially in Portugal. Given the success of these events and the high number of business relationships which they demand, it becomes important to understand how applied management practices can explain the phenomena. Accordingly, the purpose of this thesis is to understand how these relationships work in the production of a large-scale event in this industry, with the aim of understanding if there?s a supply chain philosophy, how it is implemented and if it is done voluntarily or spontaneously. With the objective of collecting primary data a case study was carried out, employing a non-probabilistic sample composed by three intervenients within the chain of production of one successful and long-running event, with whom semi-structured interviews were conducted. Through the empirical study, it was concluded that there is no supply chain management in the production of the studied event, nor openness by the organization for such. The latter assumes a role of leadership in the network, promoting long-term relationships and, occasionally, systemic collaborations. It could be noted that interdependence is regarded negatively by the organization and is only noticeable in the relationship with the main sponsor, all other partnerships are seen as easily replaceable. It was also found that, if existent, interorganizational and interfunctional processes are mostly spontaneous and not a strategic solution. The competitive advantages of the event are considered by the producer as a joint product of all partners, although the increase of the customer value is revendicated as solely their own.
info:eu-repo/semantics/publishedVersion
23
Guyon, Tristan. "Non-reversible Markov-chain Monte Carlo algorithms : beyond translational flows and applications to the simulation of dimer systems." Electronic Thesis or Diss., Université Clermont Auvergne (2021-...), 2024. http://www.theses.fr/2024UCFA0089.
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Les algorithmes Event-chain Monte Carlo sont une classe de méthodes Monte Carlo par chaînes de Markov non réversibles, qui brisent la symétrie par renversement du temps au cœur du cadre réversible et versatile de l'algorithme de Metropolis-Hastings. Dans les systèmes de particules, les méthodes Event-chain reviennent à bouger une particule à la fois selon un certain flot déterministe, jusqu'à un événement donné par un processus de Poisson inhomogène, où la particule active est changée. Ces méthodes peuvent être caractérisée comme des Processus de Markov Déterministes par Morceaux, et si le flot déterministe constitue un degré de liberté de l'algorithme, peu de méthodes d'échantillonnage non réversibles et non translationnelles existent dans la littérature. Ce manuscrit présente deux contributions. La contribution principale est une étude détaillée des symétries nécessaires et suffisantes qui apparaissent en Event-chain Monte Carlo. Une classe de flots uniforme-idéaux est explorée, pour guider l'élaboration de méthodes non réversibles en pratique. Des flots de rotation explicites sont construits pour les systèmes de sphères et de dimères, et étudiés numériquement pour les sphères dures et les dimères durs. La seconde contribution est un travail en cours, et concerne la parallélisation des méthodes Event-chain Monte Carlo. Un cadre pour la décomposition de domaines dans les Processus de Markov Déterministes par Morceaux est ébauché, et une méthode de parallélisation pour les dimères est présentéeEvent-chain Monte Carlo is a class of non-reversible Markov-chain Monte Carlo algorithms, breaking free from the time-reversal symmetry at the heart of the all-purpose, reversible Metropolis-Hastings framework. In particle systems, Event-chain schemes amount to moving one particle at a time along a certain deterministic flow, until an event given by an inhomogeneous Poisson process, where the moving particle is changed. These methods can be characterized as generating Piecewise-deterministic Markov Processes, and while the deterministic flow is a degree of freedom of the algorithm, few instances of non-translational, non-reversible samples are available in the literature. This manuscript presents two contributions. The main contribution is a detailed study of the necessary and sufficient conditions appearing in Event-chain Monte Carlo. A class of uniform-ideal flows is explored, to guide the design of non-reversible sampling algorithms in practice. Explicit rotational flows are constructed following this method for sphere and dimer systems, and studied at the numerical level for hard spheres and hard dimers. The second contribution is still ongoing work, and deals with the parallelization of Event-chain Monte Carlo. A framework for domain decomposition in Piecewise-deterministic Markov Processes is sketched, and a dimer parallelization scheme is presented
24
Tipi, Nicoleta-Steluta. "Evaluation of on-line scheduling and heuristic control for production and supply chain systems using discrete event simulation." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340133.
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Yegul, Mert. "Simulation Analysis Of The Blood Supply Chain And A Case Study." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608870/index.pdf.
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Efficient management of blood throughout the countries is of great economic importance, in addition to its major impact on the success of medical operations. This study is concerned with the analysis of policies for managing a unique blood
supply chain network, which is defined in the new Blood and Blood Products Law of the Republic of Turkey. The main objective of the study is to obtain a better understanding of the system, and to find improved policies to be able to manage it efficiently. A discrete event simulation model is developed to analyze the blood supply chain of a pilot region in Turkey. Effects of different management policies on
the supply chain performance are analyzed. Important improvements are achieved in terms of the selected performance measures such as outdate, mismatch and shortage rates of the region. Our proposed model can be used by both national health authorities and the Turkish Red Crescent Society as a decision support tool to analyze other regions and to examine alternative policies.
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Sadeghi, Azadeh. "Global Supply Chain Inventory Management and Production Planning Strategies." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1509528764663001.
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Venkateswaran, Jayendran. "PRODUCTION AND DISTRIBUTION PLANNING FOR DYNAMIC SUPPLY CHAINS USING MULTI-RESOLUTION HYBRID MODELS." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1185%5F1%5Fm.pdf&type=application/pdf.
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Smith, Christopher Rand. "The Programmatic Generation of Discrete-Event Simulation Models from Production Tracking Data." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5829.
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Discrete-event simulation can be a useful tool in analyzing complex system dynamics in various industries. However, it is difficult for entry-level users of discrete-event simulation software to both collect the appropriate data to create a model and to actually generate the base-case simulation model. These difficulties decrease the usefulness of simulation software and limit its application in areas in which it could be potentially useful. This research proposes and evaluates a data collection and analysis methodology that would allow for the programmatic generation of simulation models using production tracking data. It uses data collected from a GPS device that follows products as they move through a system. The data is then analyzed by identifying accelerations in movement as the products travel and then using those accelerations to determine discrete events of the system. The data is also used to identify flow paths, pseudo-capacities, and to characterize the discrete events. Using the results of this analysis, it is possible to then generate a base-case discrete event simulation. The research finds that discrete event simulations can be programmatically generated within certain limitations. It was found that, within these limitations, the data collection and analysis method could be used to build and characterize a representative simulation model. A test scenario found that a model could be generated with 2.1% error on the average total throughput time of a product in the system, and less than 8% error on the average throughput time of a product through any particular process in the system. The research also found that the time to build a model under the proposed method is likely significantly less, as it took an experienced simulation modeler .4% of the time to build a simple model based off a real-world scenario programmatically than it did to build the model manually.
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Sherwell, Cabello Pablo. "Three essays concerning economic analysis associated with the supply chain." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1715.
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Han, Taehee. "The Radio Frequency Identification enabled logistics process for supply chain event management from China to the United States via Hong Kong." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33318.
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Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2005.Includes bibliographical references (leaves 65-66).
This thesis reviews the current logistics processes and issues for container shipments in the supply chain. In particular, the problems associated with container shipments from China to the US, via the Hong Kong Port, includes low end-to-end visibility, security concerns, low product- handling productivity, and unmanageable unexpected events. Research was conducted using results from both interviews and surveys to collect information about the current process. This thesis also proposes the use of RFID-enabled logistics to improve the current processes and discusses the impact and value of the RFID-enabled processes. The research results show that through RFID technology, collaborators in the supply chain can improve product-handling productivity, supply chain visibility, and product security. Furthermore, the RFID application for supply chain management can increase the use of direct shipment and cross-docking, which result in considerable cost savings to both a manufacturer and a retailer.
by Taehee Han.
M.Eng.in Logistics
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Xu, Liou. "A MARKOV TRANSITION MODEL TO DEMENTIA WITH DEATH AS A COMPETING EVENT." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/42.
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The research on multi-state Markov transition model is motivated by the nature of the longitudinal data from the Nun Study (Snowdon, 1997), and similar information on the BRAiNS cohort (Salazar, 2004). Our goal is to develop a flexible methodology for handling the categorical longitudinal responses and competing risks time-to-event that characterizes the features of the data for research on dementia. To do so, we treat the survival from death as a continuous variable rather than defining death as a competing absorbing state to dementia. We assume that within each subject the survival component and the Markov process are linked by a shared latent random effect, and moreover, these two pieces are conditionally independent given the random effect and their corresponding predictor variables. The problem of the dependence among observations made on the same subject (repeated measurements) is addressed by assuming a first order Markovian dependence structure.
A closed-form expression for the individual and thus overall conditional marginal likelihood function is derived, which we can evaluate numerically to produce the maximum likelihood estimates for the unknown parameters. This method can be implemented using standard statistical software such as SAS Proc Nlmixed©. We present the results of simulation studies designed to show how the model’s ability to accurately estimate the parameters can be affected by the distributional form of the survival term.
Then we focus on addressing the problem by accommodating the residual life time of the subject’s confounding in the nonhomogeneous chain. The convergence status of the chain is examined and the formulation of the absorption statistics is derived. We propose using the Delta method to estimate the variance terms for construction of confidence intervals. The results are illustrated with applications to the Nun Study data in details.
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Tröger, Ralph [Verfasser], Rainer [Akademischer Betreuer] Alt, Rainer [Gutachter] Alt, and Wolfgang [Gutachter] Stölzle. "Supply Chain Event Management – Bedarf, Systemarchitektur und Nutzen aus Perspektive fokaler Unternehmen der Modeindustrie / Ralph Tröger ; Gutachter: Rainer Alt, Wolfgang Stölzle ; Betreuer: Rainer Alt." Leipzig : Universitätsbibliothek Leipzig, 2014. http://d-nb.info/1239421575/34.
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Tröger, Ralph, and Rainer Alt. "Design Options for Supply Chain Visibility Services – Learnings from Three EPCIS Implementations." Springer, 2017. https://ul.qucosa.de/id/qucosa%3A32385.
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Supply chains in many industries are experiencing an ever-growing complexity. They involve many actors and, similar to intra-organizational processes, visibility is an important enabler for managing supply chains in an inter-organizational setting. It is the backbone of advanced sup-ply chain (event) management solutions, which serve to detect critical incidents in time and to determine alternative actions. Due to the numerous parties involved, distributed supply chains call for a modular system architecture that aims at re-using visibility data from standardized sources. Following the wide variety of supply chain configurations in many industries there are also many options to design such services. This paper sheds light on these aspects by conduct-ing a case study on EPCIS, a global service specification for capturing and sharing visibility data. Based on three implementations, it shows the main design options for a supply chain vis-ibility service, generic operator models as well as major potentials.:1. Introduction and motivation
2. Research questions and methodology
3. Literature analysis
4. EPCIS case study
4.1. Deutsche Post DHL
4.2. ThyssenKrupp
4.3. GS1 Germany
5. Discussion and findinds
5.1.Design options
5.2. Operator models
5.3. Potentials
6. Conclusions
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Nickel, Thomas, and Jan Schliebener. "Assessing supply chain resilience within the automotive industry in the event of a pandemic : A multiple case study of the COVID-19 disruption in the Scandinavian and German automotive industry." Thesis, Jönköping University, IHH, Företagsekonomi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-53154.
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Background: The automotive industry experiences significant challenges such as electric mobility, autonomous cars, smart factories, and ridesharing. Above that, the COVID-19 pandemic did not only affect the global health care system but also caused a disruption that challenged the automotive manufacturing sector and its supply chains. Purpose: The automotive industry was investigated to assess the supply chain resilience during the COVID-19 disruption. Therefore, the supply chain performance along the disruption stages was determined. Also, the usage and value of supply chain resilience measures were explored to characterise the current state of supply chain resilience in the industry. Method: A multiple case study and purposeful sampling were used to gather empirical data. Semi-structured interviews with 21 automotive experts from the Scandinavian and German automotive industry were conducted. A content analysis approach was applied to analyse the primary data. The investigation was supported by a systematic literature review prior to the study and additional company reports as secondary data. Conclusion: The level of supply chain resilience within the automotive industry can be assessed as high. A quick recovery and a corresponding rebound of the production volume can be identified, even though the findings indicate that the COVID-19 disruption also caused a bullwhip effect. To compensate for this effect, agility measures, increased collaboration and information sharing, and risk management were used. Other supply chain resilience measures like technological innovations or sustainability were only used to a limited extent.
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Janius, Camilla, and Sahel Mir. "Using discrete event simulation : Improving efficiency and eliminating nonvalue added work." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35065.
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Process improvement is one of the challenging tasks within manufacturing companies. This study has been focused on analysing a packaging station by using a discrete event simulation tool. Packaging is an important part of the production and logistics process, but it is seldom considered when analysing non-value added activities. Discrete event simulation has been used in the analysis of non-value added activities in production systems, but noted by the low number of articles related to the usage of discrete event simulation within packaging, there exists a limited understanding of discrete event simulation use in this area. The authors divided the scope of the research into the following research questions, which are presented below: RQ1: How can discrete event simulation be used as a tool to identify time wastes and create efficiency in a packaging station? RQ2: What method is suitable when creating a simulation project? These questions were to be answered by performing a literature review and a case study in ABB AB Control Products Vasteras, mentioned as ABB in later in the thesis, where the packaging station were in need of improvements. The results from theoretical and empirical finding were analysed, they highlight the importance of packaging and its impact on logistics and supply chain management performance. By creating discrete event simulation models for both current and future stage, the authors were able to provide analysed improvements of the packaging station. The result of the models illustrated by implementing the improvements it could generate in less pressure on the operators as well as an approximated improvement of 125% more packed product. The improvements of the model involve a better material handling and a more optimized packaging station in order to create a more efficient workstation. The conclusion of the study is that the company should develop the product simultaneously as the production, were every activity and process should be included. They should also consider what impacts the development has on the entire supply chain. This could be a way to eliminate non-value activities from the start. Discrete event simulation is a tool that could be of help when visualizing the process and it allows the developers to see the impact of a change or improvement on the other processes.
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Bolatli, Yurtseven. "Utility Analysis And Computer Simulation Of Rfid Technologies In The Supply Chain Applications Of Production Systems." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611261/index.pdf.
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In this thesis, the feasibility of deploying RFID technologies in the case of &ldquolowvolume high-value&rdquo
products is considered by focusing on the production processes of a real company. First, the processes of the company are examined and associated problems are determined. Accordingly, a simulation of the current situation is constructed by using the discrete event simulation technique, in order to obtain an accurate model. In addition to modeling the current situation, this simulation model provides a flexible platform to analyze different scenarios and their effects on the company production. Next, various scenarios including RFID technology deployment are examined, and their results are compared with respect to profitanalysis which takes into consideration the changes in the production, work in process (WIP) inventory, stockouts, transportation and initial investment. Finally, the analysis of the results and conclusions are given in order to provide guidance for companies with &ldquo
low-volume high-value&rdquo
product portfolios.
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Aslan, Ercan. "A Cots-software Requirements Elicitation Method From Business Process Models." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/260208/index.pdf.
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In this thesis, COTS-software requirements elicitation, which is an input for RFP in software intensive automation system&rsquos acquisition, is examined. Business Process Models are used for COTS-software requirements elicitation. A new method, namely CREB, is developed to meet the requirements of COTS-software. A software intensive system acquisition of a military organization is used to validate the method.
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Gow, Rachel. "An investigation into long-chain polyunsaturated essential fatty acids, event related potential assessments of brain function and behavioural measures in children and adolescents with and without attention deficit hyperactivity disorder." Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/an-investigation-into-longchain-polyunsaturated-essential-fatty-acids-event-related-potential-assessments-of-brain-function-and-behavioural-measures-in-children-and-adolescents-with-and-without-attention-deficit-hyperactivity-disorder(48284ca7-2c07-48a3-b025-0b5911ddaeb1).html.
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This PhD research project investigated differences in long-chain polyunsaturated fatty acids (LC-PUFA) between male adolescents with and without ADHD, and the relationship between these and performance and event related potential (ERP) assessments of brain function and clinical behavioural measures. ERPs were also investigated in a randomised, double-blind, placebo-controlled clinical trial of 12 weeks PUFA supplementation in ADHD. Comparison of LC-PUFA measures between two groups of ADHD showed no differences in the first group, but in the second group, omega-3/6 indices were lower in ADHD compared to controls. No relationships were observed between LC-PUFA and clinical behaviour measures except between specific omega-3 indices which were inversely related to callous and unemotional traits in the ADHD group only, suggesting a specific relationship with socio-emotional behaviour. Despite performance differences there were no ERP differences between ADHD and controls during the sustained attention task and specific P3 reduction in ADHD for the Go process of the Go/NoGo task. The performance was correlated with LC-PUFA in controls only. Associations were observed between reduced P3 and LC-PUFA in both groups, possibly suggesting enhanced neuronal efficiency. For the emotion processing task, patients showed reduced N2 and N4 amplitudes relative to controls. Omega-3 was associated with more normal N4 function in ADHD for happy faces. The 12 week supplementation trial demonstrated only enhanced P2 to happy faces in the active group relative to placebo at follow up. Overall, the findings demonstrate reduced PUFA blood levels in some groups of ADHD children but limited and very specific associations between fatty acids, clinical measures and brain function in ADHD.
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Wei, Shaoceng. "MULTI-STATE MODELS FOR INTERVAL CENSORED DATA WITH COMPETING RISK." UKnowledge, 2015. http://uknowledge.uky.edu/statistics_etds/10.
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Multi-state models are often used to evaluate the effect of death as a competing event to the development of dementia in a longitudinal study of the cognitive status of elderly subjects. In this dissertation, both multi-state Markov model and semi-Markov model are used to characterize the flow of subjects from intact cognition to dementia with mild cognitive impairment and global impairment as intervening transient, cognitive states and death as a competing risk.
Firstly, a multi-state Markov model with three transient states: intact cognition, mild cognitive impairment (M.C.I.) and global impairment (G.I.) and one absorbing state: dementia is used to model the cognitive panel data. A Weibull model and a Cox proportional hazards (Cox PH) model are used to fit the time to death based on age at entry and the APOE4 status. A shared random effect correlates this survival time with the transition model.
Secondly, we further apply a Semi-Markov process in which we assume that the wait- ing times are Weibull distributed except for transitions from the baseline state, which are exponentially distributed and we assume no additional changes in cognition occur between two assessments. We implement a quasi-Monte Carlo (QMC) method to calculate the higher order integration needed for the likelihood based estimation.
At the end of this dissertation we extend a non-parametric “local EM algorithm” to obtain a smooth estimator of the cause-specific hazard function (CSH) in the presence of competing risk.
All the proposed methods are justified by simulation studies and applications to the Nun Study data, a longitudinal study of late life cognition in a cohort of 461 subjects.
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Mosunich, Marissa Anne. "A Simulation Model for Decision Support in Business Continuity Planning." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1610.
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Enterprises with a global supply network are at risk of lost revenue as a result of disruptive disasters at supplier locations. Various strategies exist for addressing this risk, and a variety of types of research has been done regarding the identification, assessment and response to the risk of disruption in a supply chain network.
This thesis establishes a decision model to support Business Continuity Planning at the first-tier supplier level. The decision model incorporates discrete-event simulation of supply chain networks (through Simio software), Monte Carlo simulation, and risk index optimization. After modeling disruption vulnerability in a supply chain network, costs of implementing all combinations of Business Continuity Plans are ranked and then tested in discrete-event simulation for further insight into inventory levels, unmet customer demand, production loss and related costs.
A case study demonstrates the implementation of the decision support process and tests a historical set of data from a large manufacturing company. Discrete-event simulation modeling of loss is confirmed to be accurate. The relevance of the model concept is upheld and recommendations for future work are made.
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Novotný, Tomáš. "Analýza a návrh workflow vybraných procesů podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2010. http://www.nusl.cz/ntk/nusl-222606.
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The master’s thesis is concerning the field of process management and workflow in company 2Tom s.r.o. Theoretical part of the thesis presents actual trends of management and methods of increasing process effectiveness, the thesis analyses actual state of the company and presents proposals for implementation and usage of workflow oriented on the key processes of the company.
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Gibelati, Elizângela de Jesus. "Aplicação da simulação a eventos discretos no apoio à definição do estoque de segurança em operações de serviços com demanda estocástica." Universidade Nove de Julho, 2015. http://bibliotecatede.uninove.br/handle/tede/1618.
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The discrete event simulation is one of the most used techniques in operational research area. It is a support decision technique, in which the search for problem solving is done by analyzing a computer model that describes the behavior of the system under study. Applications of this technique are found in several areas and have very significant results, especially for manufacturing and logistics industry. This paper presents the construction of a simulation discrete event model in the computer system Arena® to analyze a part of the supply chain of a service company, aiming to help define the minimum stock level of material in a distribution center. The adopted simulation approach considers the material as the main entity, and it represents the volume of stock in the links in the chain as lines on the template simulation modules, which simplifies the modeling and gives a uniqueness of character to the proposal. As a result, you can determine the best inventory security levels of in different stochastic demand scenarios with high variability, considering pre-established service levels and uncertainty in delivering the material.
A simulação a eventos discretos é uma das técnicas mais utilizadas na área de pesquisa operacional. Trata-se de uma técnica de apoio à decisão, em que a busca pela solução de um problema é feita pela análise de um modelo computacional que descreve o comportamento do sistema em estudo. Aplicações dessa técnica são encontradas em diversas áreas e apresentam resultados muito significativos, com destaque para a manufatura e logística na indústria. Este trabalho apresenta a construção de um modelo de simulação a eventos discretos, no sistema computacional Arena®, para analisar uma parte da cadeia de suprimentos de uma empresa de serviços, visando auxiliar na definição do nível de estoque mínimo de material em um centro de distribuição. A abordagem de simulação adotada considera o material como entidade principal, e representa o volume de estoque nos elos da cadeia como filas nos módulos do modelo, o que permite simplificar a modelagem e confere um caráter de originalidade à proposta. Como resultado, é possível determinar os melhores níveis de estoque de segurança em diferentes cenários de demanda estocástica com alta variabilidade, considerando níveis de atendimento preestabelecidos e incertezas na entrega do material.
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Manno, Gabriele Antonino. "Reliability modelling of complez systems: an adaptive transition system approach to match accuracy and efficiency." Doctoral thesis, Università di Catania, 2012. http://hdl.handle.net/10761/1039.
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In questa tesi è introdotto un linguaggio di modellizzazione per la valutazione di misure di affidabilità di sistemi complessi.
Adaptive Transition Systems (ATS) è un linguaggio di modellizzazione basato su macchine di stato interdipendenti dotate di variabili che sono inputs e outputs di un set di funzoni di comunicazione che permettono l'adattamento delle prprietà legate alle transizioni delle macchine di stato rispetto all'evoluzione del sistema. Le funzioni di comunicazione sono il mezzo per modellizzare le dipendenze tra le parti del sistema.
Gli algoritmi per la risoluzione simulativa ed analitica del modello ATS sono definiti. Un applicazione per la risoluzione di alberi di guasto dinamici con componenti riparabili è anche riportata.
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Kano, Célia Hanako. "Modelagem e análise das cadeias de suprimentos globais e resilientes baseadas em rede de Petri." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-16062016-144200/.
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Em um cenário de aumento de competitividade, crescente expectativa por inovações do produto e necessidade de atender diferentes perfis de consumidores, o conceito de gerenciamento de cadeias de suprimentos globais (GSCM) surge como uma estratégia para coordenar mais eficazmente as atividades dispersas geograficamente dos sistemas produtivos. Na adoção do GSCM, as organizações devem lidar com rupturas que impactam no gerenciamento das suas atividades, tais como a interrupção de vias de transporte, pane no fornecimento de energia, desastres naturais e até ataques terroristas. Nesse contexto, o trabalho introduz um procedimento sistematizado para modelagem das cadeias de suprimentos visto como um sistema a eventos discretos e sua análise por simulação das atividades do GSCM baseada em técnicas formais como a rede de Petri (PN) e o Production Flow Schema (PFS). Um exemplo é também apresentado para ilustrar e comprovar as vantagens do método proposto na análise do GSCM.In a context of increasing competition, rising of expectations for product innovations and need to satisfy different consumer needs, the concept of global supply chain management (GSCM) emerges as a strategy to more efficiently coordinate the geographically dispersed activities of production systems. Adopting GSCM, organizations have to deal with external disruptions that impact management activities, such as transport interruption, power supply failure, natural disasters and terrorist attacks. In this way, a systematized procedure for modeling supply chains as a discrete event system and simulation analysis of GSCM activities based on formal techniques, such as Petri net (PN) and Production Flow Schema (PFS) is introduced. An example is also presented to illustrate and confirm the advantages of the proposed method for GSCM analysis.
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CARLI, FEDERICO. "Stratified Staged Trees: Modelling, Software and Applications." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1057653.
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The thesis is focused on Probabilistic Graphical Models (PGMs), which are a rich framework for encoding probability distributions over complex domains. In particular, joint multivariate distributions over large numbers of random variables that interact with each other can be investigated through PGMs and conditional independence statements can be succinctly represented with graphical representations. These representations sit at the intersection of statistics and computer science, relying on concepts mainly from probability theory, graph algorithms and machine learning. They are applied in a wide variety of fields, such as medical diagnosis, image understanding, speech recognition, natural language processing, and many more.
Over the years theory and methodology have developed and been extended in a multitude of directions. In particular, in this thesis different aspects of new classes of PGMs called Staged Trees and Chain Event Graphs (CEGs) are studied. In some sense, Staged Trees are a generalization of Bayesian Networks (BNs). Indeed, BNs provide a transparent graphical tool to define a complex process in terms of conditional independent structures. Despite their strengths in allowing for the reduction in the dimensionality of joint probability distributions of the statistical model and in providing a transparent framework for causal inference, BNs are not optimal GMs in all situations. The biggest problems with their usage mainly occur when the event space is not a simple product of the sample spaces of the random variables of interest, and when conditional independence statements are true only under certain values of variables. This happens when there are context-specific conditional independence structures.
Some extensions to the BN framework have been proposed to handle these issues: context-specific BNs, Bayesian Multinets, or Similarity Networks citep{geiger1996knowledge}. These adopt a hypothesis variable to encode the context-specific statements over a particular set of random variables. For each value taken by the hypothesis variable the graphical modeller has to construct a particular BN model called local network. The collection of these local networks constitute a Bayesian Multinet, Probabilistic Decision Graphs, among others. It has been showed that Chain Event Graph (CEG) models encompass all discrete BN models and its discrete variants described above as a special subclass and they are also richer than Probabilistic Decision Graphs whose semantics is actually somewhat distinct.
Unlike most of its competitors, CEGs can capture all (also context-specific) conditional independences in a unique graph, obtained by a coalescence over the vertices of an appropriately constructed probability tree, called Staged Tree.
CEGs have been developed for categorical variables and have been used for cohort studies, causal analysis and case-control studies. The user’s toolbox to efficiently and effectively perform uncertainty reasoning with
CEGs further includes methods for inference and probability propagation, the exploration of equivalence classes and robustness studies.
The main contributions of this thesis to the literature on Staged Trees are related to Stratified Staged Trees with a keen eye of application. Few observations are made on non-Stratified Staged Trees in the last part of the thesis. A core output of the thesis is an R software package which efficiently implements a host of functions for learning and estimating Staged Trees from data, relying on likelihood principles. Also structural learning algorithms based on distance or divergence between pair of categorical probability distributions and based on the clusterization of probability distributions in a fixed number of stages for each stratum of the tree are developed. Also a new class of Directed Acyclic Graph has been introduced, named Asymmetric-labeled DAG (ALDAG), which gives a BN representation of a given Staged Tree. The ALDAG is a minimal DAG such that the statistical model embedded in the Staged Tree is contained in the one associated to the ALDAG. This is possible thanks to the use of colored edges, so that each color indicates a different type of conditional dependence: total, context-specific, partial or local.
Staged Trees are also adopted in this thesis as a statistical tool for classification purpose. Staged Tree Classifiers are introduced, which exhibit comparable predictive results based on accuracy with respect to algorithms from state of the art of machine learning such as neural networks and random forests. At last, algorithms to obtain an ordering of variables for the construction of the Staged Tree are designed.
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Brunát, Tomáš. "Optimalizace podnikového procesu a návrh implementace ve společnosti APS HOLDING SE." Master's thesis, Vysoká škola ekonomická v Praze, 2015. http://www.nusl.cz/ntk/nusl-201682.
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The thesis is mainly driven by the modelling of business processes focusing on process optimization namely processes related to Investment Banking. The main goal of the thesis is driven by the EPC process modelling for optimization the key Investment process in a particular company APS HOLDING SE. The theoretical part contains processes descriptions optimizations and process modelling standards. The practical part is devoted to design and optimize of the process related to Debt Assets Investment Banking under the EPC modelling standards. Each part of the Investment process is described below the model. Reader can feel more comfortable by using the glossary of terms attached in appendix. Focus on higher efficiency of the Investment management process will be the key goal for the company management in 2016.
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Sarac, Aysegul. "Modélisation et aide à la décision pour l'introduction des technologies RFID dans les chaînes logistiques." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2010. http://tel.archives-ouvertes.fr/tel-00541012.
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Les technologies RFID présentent des avantages non négligeables en comparaison aux technologies d'identification actuelles. Cependant, l'intégration de ces technologies dans les chaînes logistiques implique souvent des coûts élevés. Ainsi, les entreprises doivent conduire des analyses poussées pour évaluer l'impact des RFID sur le fonctionnement et l'économie des chaînes logistiques et décider de l'intégration ou non de ces technologies.Dans cette thèse nous nous concentrons sur la modélisation et l'analyse de l'introduction des technologies RFID dans les chaînes logistiques. Nous présentons d'abord une information générale sur les technologies RFID. Nous analysons ensuite la littérature sur l'intégration des RFID dans les chaînes logistiques en focalisant sur les défis et les avantages liés à l'intégration de ces technologies. Nous développons deux approches (analytique et par simulation) afin d'évaluer les impacts qualitatifs et quantitatifs des technologies RFID sur le fonctionnement et le profit des chaînes logistiques. Nous développons aussi une analyse du retour sur investissement (ROI), pour comparer les revenus obtenus à l'aide des technologies RFID avec les coûts associés à leur intégration. D'autre part, nous nous intéressons à l'amélioration des avantages de RFID dans les chaînes logistiques. Nous comparons les impacts de l'intégration de différentes RFID dans les chaînes logistiques par un remplacement simple des technologies d'identification actuelles et par la réorganisation des chaînes logistiques utilisant les nouvelles possibilités des technologies RFID. Les résultats obtenus dans ce travail mettent en évidence des perspectives intéressantes pour des études futures. L'originalité de cette étude est que nous comparons les impacts de plusieurs technologies RFID en les intégrant aux systèmes actuels et en reconstruisant des chaînes logistique grâce aux possibilités offertes par des technologies RFID. Notre modèle de simulation à événements discrets peut être utilisé comme un outil d'aide à la décision pour les sociétés qui visent à intégrer des technologies RFID.L'originalité de cette étude est que nous comparons les impacts de plusieurs technologies RFID en les intégrant aux systèmes actuels et en reconstruisant des chaînes logistique par les possibilités offertes par des technologies RFID. Notre simulation peut être utilisée comme un outil d'aide à la décision pour les sociétés qui considèrent l'intégration de technologies RFID.
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Ursino, Giovanni. "Essays in theory of the firm and indivisual decision making experiments." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7404.
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Esta tesis se compone de dos partes separadas y sin relación entre ellas. El primer capítulo, coautorado con el Profesor Greg Barron, es un experimento en toma de decisiones individuales. Este capítulo se construye a partir de una literatura creciente, que enfatiza el siguiente punto: cuando aprendemos las probabilidades y los resultados de una lotería a través de la experiencia en vez de la descripción visual del problema -un prospecto- entonces tomamos decisiones como si estuviéramos devaluando eventos poco probables. Esto contrasta con el fenómeno bien conocido de que las probabilidades pequeñas suelen sobrevaluarse cuando se toman decisiones a partir de prospectos. Nuestro trabajo contribuye a la literatura dando fuerza al punto mencionado frente a algunas críticas. En particular, nosotros encontramos que la devaluación sobrevive la eliminación de un problema de muestreo que afectaba trabajos anteriores y está correcto en el nuestro. Encontramos tambi´en que hay devaluación de probabilidades pequeñas vii en toma de decisiones al mismo tiempo que sobrevaluación en juicio sobre las mismas probabilidades. Este útimo resultado no puede ser explicado. El segundo capítulo introduce una nueva teoría de integración vertical a partir del hecho de que aumentar el poder contractual de una empresa es citado muy a menudo como una razón para integrarse verticalmente con los proveedores. En mi modelo las empresas se integran para ganar poder contractual hacia proveedores no integrados en la cadena productiva. El coste de la integración es una pérdida de flexibilidad a la hora de escoger los proveedores más apropiados para un particular producto final. Muestro como las empresas que tienen inversiones más específicas en el proceso productivo tienen un ayor incentivo a integrarse. La teoría presentada permite explicar numerosos hechos estilizados como el efecto del desarrollo financiero sobre la estructura vertical de las empresas, la evolución que se observa de inversión extranjera directa a outsourcing en el comercio internacional, la conexi´on entre ciclo de vida del producto y la estructura vertical, etc.This thesis is composed of two separate, unrelated chapters. Chapter I, coauthored with Greg Barron, is an experiment in individual decision making. It builds on a small and growing literature which makes the following point: whenever we learn the odds and outcomes of a binary choice problem through experience rather than from a visual description -a prospect- then we take decisions as if we were underweighting rare events. This is in contrast to the well known phenomenon of overweighting rare events in prospect based decisions. Our work contributes to the literature by strengthening this finding in the face of earlier criticism. In particular we find that the underweighting is robust to the elimination of sampling bias which affected previous studies and is absent from ours. We also find that underweighting in choice happens at the same time as overweighting in probability judgment. This remains unexplained. Chapter II introduces a new theory of vertical integration building on the fact that improving a company's bargaining position is often cited as a chief motivation to vertically integrate with suppliers. In my model firms integrate to gain bargaining power against other suppliers in the production process. The cost of integration is a loss of flexibility in choosing the most suitable suppliers for a particular final product. I show that the firms who make the most specific investments in the production process have the greatest incentive to integrate. The theory provides novel insights to the understanding of numerous stylized facts such as the effect of financial development on the vertical structure of firms, the observed pattern from FDI to outsourcing in international trade, the connection between product cycle and vertical structure, etc.
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Miclo, Romain. "Challenging the "Demand Driven MRP" Promises : a Discrete Event Simulation Approach." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2016. http://www.theses.fr/2016EMAC0016/document.
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Les principaux enjeux des supply chain d’aujourd’hui concernent l’adaptation à des environnements instables. Demand Driven Material Requirements Planning (DDMRP) est une méthode récente et prometteuse de gestion des flux qui a été conçue pour faire face aux problématiques actuelles. Le travail de recherche réalisé détaille et positionne DDMRP par rapport aux autres méthodes connues de pilotage de flux. Le but de ce travail est de challenger les principales promesses de DDMRP. Pour cela, un plan d’expériences a été réalisé sur un cas d’étude pour évaluer le comportement de MRP II, Kanban et DDMRP face à différentes sources de variabilité. Le dimensionnement des buffers DDMRP est un sujet majeur pour la méthode. Il a été traité sur un cas d’étude avec un travail d’optimisation. Toutes les contributions ont été expérimentées avec l’implémentation de DDMRP sur un cas réel. La thèse permet ainsi de valider certains atouts de DDMRP, tels que l’adaptation du système à différentes formes de variabilités, mais elle permet également de souligner des perspectives majeures de recherche sur ce sujetThe main Supply Chain current issues concern the adaptation to unstable environments. Demand Driven Material Requirements Planning (DDMRP) is a recent and promising material management method that is designed to tackle these current issues. The research work details and classifies DDMRP compared to the other material management methods known. The goal of this work is to challenge the main DDMRP promises. This is why a design of experiments was realised on a case study in order to assess MRP II, Kanban and DDMRP behaviours with different variability sources. The DDMRP buffer sizing is a major issue. It was dealt with an optimisation work on a case study. All the contributions were experimented with a DDMRP implementation on a real case. The research work enables several DDMRP advantages to be validated, such as the system adjustment to different variability sources, however this work also allows research perspectives to be underlined
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Couto, Carla Renata. "Viroses respitarórias após vacinação contra influenza em profissionais de saúde (Projeto Tira-teima)." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/5/5134/tde-27052010-161855/.
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INTRODUÇÃO: A adesão à vacinação contra influenza é historicamente baixa entre profissionais da área da saúde (PAS) (2 a 36%). A ocorrência de sintomas respiratórios após vacinação é freqüentemente interpretada como falha vacinal. No Hospital das Clínicas da FMUSP, um estudo preliminar mostrou que as principais razões para não adesão são a percepção da ineficácia da vacina e o medo de reações adversas. OBJETIVOS: Identificar a incidência de eventos adversos pós-vacinação e identificar os vírus respiratórios (VR) responsáveis por eventuais episódios de infecção de via aérea superior (IVAS) que ocorram entre indivíduos vacinados. MÉTODOS: Foi seguida uma coorte de 398 PAS vacinados objetivando verificar a ocorrência de eventos adversos até 48 h após a vacinação. Durante 4 meses, 337 PAS foram seguidos 2 vezes por semana para avaliar a ocorrência de sintomas respiratórios. Lavados nasais foram coletados na presença de sintomas para pesquisa de VR. A técnica de imunofluorescência direta foi usada para diagnosticar vírus sincicial respiratório, influenza A e B, adenovírus e parainfluenza. PCR foi utilizada para detectar picornavírus e coronavírus e PCR em tempo real para diagnosticar metapneumovírus. Para assegurar melhor sensibilidade, influenza A e B foi também detectado pela PCR em tempo real e adenovírus pela PCR. RESULTADOS: Eventos adversos foram relatados por 30% dos PAS, predominando cefaléia (15,1%), mialgia (14,3%) e mal estar (13,6%). Nenhum evento adverso grave foi observado. Cento e vinte e um PAS (35,9%) desenvolveram sintoma respiratório durante o seguimento e lavado nasal foi colhido em 93 dos 192 episódios apresentados. Vírus influenza A foi detectado em 5 dos 93 episódios (5,3%) e outros vírus respiratórios em 26 (27,9%). No restante dos 61 episódios (65,6%) nenhum vírus foi encontrado. A densidade de incidência de infecção pelo vírus influenza foi de 4,3 episódios por 100 pacientes-mês enquanto que a densidade de infecção por outros vírus respiratórios foi de 10,8 episódios por pacientes-mês. CONCLUSÃO: Vacina da influenza é segura. O medo de eventos adversos grave parece injustificado, bem como, a percepção da ineficácia da vacina. O presente estudo evidencia que IVAS após vacinação é predominantemente causada por outros vírus respiratórios (28%) e não pelo vírus influenza (5%)INTRODUCTION: Compliance with influenza vaccination has been historically poor among health care workers (HCW), ranging from 2 to 36% world around. The occurrence of respiratory symptoms following influenza vaccination is frequently taken as vaccine failure which reinforces vaccine disbelief. A preliminary study conducted at Hospital das Clínicas, University of São Paulo School of Medical Sciences, showed that the main reasons for non-compliance with influenza vaccination were the perception of vaccine inefficacy and fear of adverse events. OBJECTIVES: To determine the incidence of adverse events after seasonal influenza vaccination and identify other respiratory viruses causing upper respiratory infections in vaccinated HCWs. METHODS: A cohort of 398 vaccinated HCWs was prospectively surveyed for the occurrence of any adverse event in the first 48h after vaccination. A subset of the original cohort (337 HCWs) was followed up during four months, twice a week, for the detection of respiratory symptoms. Nasal washes were taken if respiratory symptoms occurred. Direct immunofluorescent assay (DFA) was performed for the detection of respiratory syncytial virus (RSV), influenza (INF) A and B, parainfluenza (PIV) 1, 2 and 3, and adenovirus (ADV). PCR was performed for the detection of human rhinoviruses (HRV), ADV and coronaviruses (hCoV); and real time PCR for the detection of human metapneumovirus (hMPV). To assure greatest sensitivity of influenza diagnosis, real time PCR was added to the diagnostic tools of influenza viruses. RESULTS: Adverse events were reported by 30% of the HCWs, being headache and myalgia reported by 50% and 47% of the participants, respectively. No severe adverse event was observed. One hundred and twenty-one HCWs (35.9%) developed 192 episodes of respiratory symptoms during follow-up and nasal washes were taken in 93 of them. Influenza A virus was detected in five of the 93 episodes (5.3%) and other respiratory viruses in 26 (27.9%). In the remaining 61 episodes (65.6%) no respiratory virus was identified. The incidence density of influenza was 4.3 episodes per 100 HCW-month, while the incidence density of other respiratory viruses was 10.8 episodes per HCW-month. CONCLUSIONS: Influenza vaccine is safe. The fear of adverse events as well as the perception of vaccine inefficacy seems to be unjustified in this population. The present study showed that the occurrence of upper respiratory infection during the four months following seasonal influenza vaccination of HCWs is generally caused by other respiratory viruses (28%) and not by influenza viruses (5%)