Dissertations / Theses on the topic 'Stochastic Time Petri Nets'
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Wiley, Richard Paul. "Performance analysis of Stochastic Timed Petri Nets." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15002.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaves 305-310.
by Richard Paul Wiley.
Sc.D.
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Tabacchi, Peter J. "Analysis of engineer C2 as modeled by stochastic, timed attributed Petri Nets." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA238339.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, September 1990.Thesis Advisor(s): Caldwell, William J. ; Read, Robert R. Second Reader: Whitaker, Lyn R. "September 1990." Description based on title screen as viewed on December 21, 2009. DTIC Identifier(s): Command And Control Systems, Timed Petri Nets, Attributed Petri Nets, Land Warfare, Thesis. Author(s) subject terms: Land Warfare, Military Planning, Military Science, Petri Nets, Command and Control, Combat Engineers. Includes bibliographical references (p. 80). Also available in print.
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Ďuriš, Anton. "Simulace distribuovaných systémů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442811.
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This thesis is focused on distributed systems modeling using Petri nets. Distributed systems are increasingly being implemented in applications and computing systems, where their task is to ensure sufficient performance and stability for a large number of its users. When modeling a distributed systems, stochastic behavior of Petri nets is important, which will provide more realistic simulations. Therefore, this thesis focuses mainly on timed Petri nets. The theoretical part of this thesis summarizes distributed systems, their properties, types and available architectures, as well as Petri nets, their representation, types and the principle of an operation. In the practical part, two models were implemented, namely a horizontally scaled web application divided into several services with a distributed database and a large grid computing system, more precisely the BOINC platform with the Folding@home project. Both models were implemented using the PetNetSim library of Python. The goal of this thesis is to perform simulations on the created models for different scenarios of their behavior.
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Rau, de Almeida Callou Gustavo. "Energy consumption and execution time estimation of embedded system applications." Universidade Federal de Pernambuco, 2009. https://repositorio.ufpe.br/handle/123456789/1877.
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Previous issue date: 2009Nos últimos anos, a redução do consumo de energia das aplicações dos sistemas embarcados tem recebido uma grande atenção da comunidade científica, visto que, como o tempo de resposta e o baixo consumo de energia são requisitos conflitantes, esses estudos tornam-se altamente necessários. Nesse contexto, é proposta uma metodologia aplicada nas fases iniciais de projeto para dar suporte às decisões relativas ao consumo de energia e ao desempenho das aplicações desses dispositivos embarcados. Al´em disso, esse trabalho propõe modelos temporizados de eventos discretos que são avaliados através de uma metodologia de simulção estocástica com o objetivo de representar diferentes cenários dos sistemas com facilidade. Dessa forma, para cada cenário ´e preciso decidir o n´umero máximo de simulações e o tamanho de cada rodada da simulação, onde ambos os fatores podem impactar no desempenho para se obter tais estimativas. Essa metodologia considera também, um modelo intermediário que representa a descrição do comportamento do sistema e, é através desse modelo que cenários são analisados. Esse modelo intermediário ´e baseado em redes de Petri coloridas temporizadas que permitem não somente a anáise do software, mas também fornece suporte a um conjunto de métodos bem estabelecidos para verificações de propriedades. É nesse contexto que o software, ALUPAS, responsável por estimar o consumo de energia e o tempo de execução dos sistemas embarcados é apresentado. Por fim, um caso de estudo real, assim como tamb´em, exemplos customizados são apresentados com a finalidade de mostrar a aplicabilidade desse trabalho, onde usuários não especializados não precisam interagir diretamente com o formalismo de redes de Petri.
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Li, Yao Carleton University Dissertation Engineering Electrical. "Solution techniques for stochastic petri nets." Ottawa, 1992.
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Lucic, Diana. "On exact equilibrium distributions of stochastic Petri nets /." Title page, contents and summary only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phl937.pdf.
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Coleman, James L. "Stochastic Petri Nets with product form equilibrium distributions /." Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phc6922.pdf.
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Stojic, Ivan <1982>. "Algorithms for stationary analysis of stochastic Petri nets." Doctoral thesis, Università Ca' Foscari Venezia, 2016. http://hdl.handle.net/10579/10300.
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Stochastic Petri nets (SPN) are a Markovian formalism for qualitative and quantitative analysis of discrete event dynamic systems. Among other uses, they have been used extensively in performance evaluation of telecommunication systems, computer systems and networks. Analysis of an SPN model usually requires stationary analysis of a continuous-time Markov chain (CTMC) underlying the SPN, whose state space for many practical models is too large to be analysed by direct methods. This serious drawback is shared with many other modelling formalisms and is usually referred to as state space explosion. Usually simulation can be employed to analyse such models. An alternative is to restrict the SPN formalism to product-form SPNs, a class of nets whose unnormalised stationary probability distribution can be obtained in closed form, making stationary analysis much simpler. In this thesis we present algorithms for stationary analysis of SPN models based on efficient encoding of state spaces and transition functions by multi-way decision diagrams, an efficient data structure. After a short introduction to SPNs and their stationary analysis, we start with simulation of SPNs and present an algorithm for perfect simulation in SPNs that can be used to directly obtain samples from the stationary distribution. After this, we turn to simulation of product-form SPNs and present simulation stopping criteria that exploit the product-form property. Finally, we present an algorithm for fast computation of normalizing constant, needed for the normalisation of stationary probabilities in the analysis of product-form models.
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Bowden, Fred D. J. "The modelling and analysis of command and control decision processes using extended time petri nets." Title page, table of contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phb784.pdf.
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Bibliography: leaves 177-191. This thesis uses a new type of extended time Petri net to model and analyse command and control decision processes. A comprehensive review of existing time Petri net structures is given. This concludes with the introduction of time Petri net structure that incorporates the most commonly used time structures. This extended time Petri net structure is then used in the definition of the basic modelling blocks required to model command and control decision processes. This basic modelling block forms the basis of the direct analysis techniques that are introduced in the thesis.
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Kumari, Jaya. "Asset Management of Railway Tracks Using Stochastic Petri Nets." Thesis, Luleå tekniska universitet, Drift, underhåll och akustik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75631.
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Railways are one of the most important transport systems. It is crucial to have a rail network that is safe, reliable and available. Asset Management for railways involves the optimization of the maintenance activities based on asset condition, life cycle cost and availability of equipment. Irregularities in the track cause the wear of rail resulting in passenger discomfort, speed restrictions and line closures. The track is inspected for these irregularities and corrected using a tamping vehicle. The degradation behavior of the track can be modelled to predict the future degradation. This prediction forms the basis of the maintenance planning based on the expected track condition. A petri net model can be used to simulate the track degradation, inspection and maintenance process over a period of 20 years, and the outputs of the model are used for LCC analysis. Further, the cost is optimized with the safety risk to suggest maintenance threshold levels and Inspection Interval. The proposed methodology will assist the maintenance decision system for Asset Management of Railway track, which is strategic and cost effective. This methodology is demonstrated using a case study of a Line 414 in Sweden, by modelling the track behavior with Standard Deviation of Longitudinal Level. It can be further expanded and adapted for maintenance planning for similar assets within railways.
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Rugina, Ana-Elena. "Dependability modeling and evaluation – From AADL to stochastic Petri nets." Phd thesis, Toulouse, INPT, 2007. http://oatao.univ-toulouse.fr/7649/1/rugina.pdf.
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Performing dependability evaluation along with other analyses at architectural level allows both predicting the effects of architectural decisions on the dependability of a system and making tradeoffs. Thus, both industry and academia focus on defining model driven engineering (MDE) approaches and on integrating several analyses in the development process. AADL (Architecture Analysis and Design Language) has proved to be efficient for architectural modeling and is considered by industry in the context presented above. Our contribution is a modeling framework allowing the generation of dependability-oriented analytical models from AADL models, to facilitate the evaluation of dependability measures, such as reliability or availability. We propose an iterative approach for system dependability modeling using AADL. In this context, we also provide a set of reusable modeling patterns for fault tolerant architectures. The AADL dependability model is transformed into a GSPN (Generalized Stochastic Petri Net) by applying model transformation rules. We have implemented an automatic model transformation tool. The resulting GSPN can be processed by existing tools to obtain dependability measures. The modeling approach is illustrated on a subsystem of the French Air trafic Control System.
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Li, Man. "Colored generalized Stochastic Petri Nets for integrated systems protocol modelling." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5138.
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Alexin, Johann [Verfasser]. "Ageing notions in the analysis of stochastic Petri nets / Johann Alexin." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1041805403/34.
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Davies, Ian. "Symbolic techniques for the performance analysis of generalised stochastic petri nets." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/6389.
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Includes abstract Thesis (M.Sc. (Computer Science))-- University of Cape Town, 2001.Includes bibliographical references.
Binary Decision Diagrams (BDDs) have been successfully used in sequential circuit theory, VLSI, and model checking. They form a highly memory efficient canonical representation of a Boolean function. In this dissertation, following on the success of BDDs in other fields, we investiage the applicability of symbolic techniques in the performance analysis of timed transition systems, particularly those of Generalised Stochastic Petri Nets (GSPNs). We make use of symbolic methods, where states are represented implicitly rather than explicitly, primarily to conserve memory during the state space exploration process - a necessary step in the performance analysis pipeline. We have investigated the use of BDDs in two different ways. The first, our own novel technique, allows the user to effectively place an upper bound on the amount of memory to use during state space exploration. The second makes use of transition to find the successor states at each level of the state graph. Both of these techniques rely on a novel and efficient GSPN to BDD encoding function that we have derived.
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Cavalcante, Sergio Vanderlei. "A hardware-software co-design system for embedded real-time applications." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360339.
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Buchholz, Peter, and Igor V. Tarasyuk. "A Class of Stochastic Petri Nets with Step Semantics and Related Equivalence Notions." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-100383.
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This paper presents a class of Stochastic Petri Nets with concurrent transition firings. It is assumed that transitions occur in steps and that for every step each enabled transition decides probabilistically whether it wants to participate in the step or not. Among the transitions which what to participate in a step, a maximal number is chosen to perform the firing step. The observable behavior is defined and equivalence relations are introduced. The equivalence relations extend the well-known trace and bisimulation equivalences for systems with step semantics to Stochastik Petri Nets with concurrent transition firing. It is shown that the equivalence notions form a lattice of interrelations.
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Inkpen, Christopher John. "The application of Petri-nets and stochastic processes to knowledge based project planning." Thesis, University of Brighton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305771.
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Buchholz, Peter, and Igor V. Tarasyuk. "A Class of Stochastic Petri Nets with Step Semantics and Related Equivalence Notions." Technische Universität Dresden, 2000. https://tud.qucosa.de/id/qucosa%3A26298.
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This paper presents a class of Stochastic Petri Nets with concurrent transition firings. It is assumed that transitions occur in steps and that for every step each enabled transition decides probabilistically whether it wants to participate in the step or not. Among the transitions which what to participate in a step, a maximal number is chosen to perform the firing step. The observable behavior is defined and equivalence relations are introduced. The equivalence relations extend the well-known trace and bisimulation equivalences for systems with step semantics to Stochastik Petri Nets with concurrent transition firing. It is shown that the equivalence notions form a lattice of interrelations.
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Kabutz, Heinz Max. "Analytical performance evaluation of concurrent communicating systems using SLD and stochastic Petri nets." Doctoral thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/13524.
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Bibliography: leaves 113-117.In this thesis, the performance analysis of SDL with a new type of stochastic Petri net is described. This new net is called SDL-net. The Concurrent Communicating System is described, and the need for qualitative and quantitative analysis of such systems is motivated. Formal methods are demonstrated which can be used to represent such Concurrent Communicating Systems. The Specification and Description Language (SDL) is shown in the context of Concurrent Communicating Systems and the software development cycle is described for SDL systems. Correctness and performance of SDL are discussed and it is shown how the semantics of time for performance can be introduced into SDL by adding external information, by extending the SDL syntax or by using compiler directives. In this thesis only external information is added.
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Jones, Robert Linzey III. "Simulation and numerical solution of stochastic Petri nets with discrete and continuous timing." W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539623410.
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We introduce a novel stochastic Petri net formalism where discrete and continuous phase-type firing delays can appear in the same model. By capturing deterministic and generally random behavior in discrete or continuous time, as appropriate, the formalism affords higher modeling fidelity and efficiencies to use in practice. We formally specify the underlying stochastic process as a general state space Markov chain and show that it is regenerative, thus amenable to renewal theory techniques to obtain steady-state solutions. We present two steady-state analysis methods depending on the class of problem: one using exact numerical techniques, the other using simulation. Although regenerative structures that ease steady-state analysis exist in general, a noteworthy problem class arises when discrete-time transitions are synchronized. In this case, the underlying process is semi-regenerative and we can employ Markov renewal theory to formulate exact and efficient numerical solutions for the stationary distribution. We propose a solution method that shows promise in terms of time and space efficiency. Also noteworthy are the computational tradeoffs when analyzing the "embedded" versus the "subordinate" Markov chains that are hidden within the original process. In the absence of simplifying assumptions, we propose an efficient regenerative simulation method that identifies hidden regenerative structures within continuous state spaces. The new formalism and solution methods are demonstrated with two applications.
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Jiffry, Mustafa Abdulrahman. "Petri nets approach for the analysis of MASCOT interprocess communications." Thesis, King's College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324637.
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Rogge-Solti, Andreas, Laura Vana, and Jan Mendling. "Time Series Petri Net Models - Enrichment and Prediction." CEUR Workshop Proceedings, 2015. http://epub.wu.ac.at/5394/1/paper8.pdf.
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Operational support as an area of process mining aims to predict the
temporal performance of individual cases and the overall business process. Although
seasonal effects, delays and performance trends are well-known to exist
for business processes, there is up until now no prediction model available that
explicitly captures this. In this paper, we introduce time series Petri net models.
These models integrate the control flow perspective of Petri nets with time series
prediction. Our evaluation on the basis of our prototypical implementation demonstrates
the merits of this model in terms of better accuracy in the presence of time
series effects.
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Barate', A. "Application of Petri Nets to the Real-Time Interaction with Music Structures." Doctoral thesis, Università degli Studi di Milano, 2009. http://hdl.handle.net/2434/56013.
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Li, Man. "Applying decomposition and aggregation theory to the analysis of stochastic Petri nets and queueing networks." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7893.
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In this thesis, a class of Stochastic Petri Nets, called Local Balance Stochastic Petri Nets, and a class of queuing networks, called product form queueing networks are investigated. The parametric analysis of Stochastic Petri Nets in general is also studied. The major analysis tool used in this thesis is the Simon and Ando's Decomposition and Aggregation theory. Local Balance Stochastic Petri Nets have the property that their equilibrium state probability distributions have product form solutions. In this thesis, we extend the boundary of the Local Balance Stochastic Petri Nets, propose a systematic test procedure, as well as a C language program to identify this class of Stochastic Petri Nets, and prove that the Stochastic Petri Nets that have passed the test have product form solutions. Simon and Ando's Decomposition and Aggregation theory is then applied to the analysis of Local Balance Stochastic Petri Nets. A Decomposition by Subnet method is proposed. The analysis of a Local Balance Stochastic Petri Net is decomposed into the analysis of subnets. The results are combined to obtain the analysis for the original system. Through the Decomposition by Subnet method, a Norton's theorem for Local Balance Stochastic Petri Nets is developed. By decomposing according to a particular subnet, an aggregated net is constructed. This is that subnet with marking dependent firing rates. We show that the aggregated net may concisely and exactly represent the original Stochastic Petri Net. One of the applications of the Norton's theorem is to facilitate parametric analysis of Local Balance Stochastic Petri Nets. When a Stochastic Petri Net is not a Local Balance Stochastic Petri Net, the concept of "Ideal Aggregate" is used to develop efficient parametric analysis of it. By following a systematic way of constructing the infinitesimal matrix, the transition rate of interest is confined into a small diagonal submatrix. According to the algorithm, every time that particular rate takes a new value, only a Markov Chain of the order of the small diagonal submatrix needs to be analyzed. As a result, computational time requirements are greatly reduced. For the product form queueing networks, we first improve the efficiency of the Distribution Analysis by Chain (DAC) algorithm. We show that the calculation of marginal queue length distribution and throughput in each recursion may be avoided. As a result, computational time requirements are reduced. In addition, the improved algorithm has the benefits with regard to reducing possible numerical errors. Simon and Ando's Decomposition and Aggregation theory is used to develop an Independent Decomposition and Aggregation method for the analysis of product form queueing methods. The queueing network is first transformed into a network with nodes of Infinite Server types. That network is then decomposed independently chain by chain. Through the Independent Decomposition and Aggregation method, an algorithm called Adaptive Convolution By Chain (ACCAL) is derived. It is efficient in dealing with networks that have many chains and a few nodes. Compared with other algorithms, ACCAL has a smaller number of operations. In addition, ACCAL first converts the network into an equivalent one that may be analysed more efficiently. There are three independent parts in the algorithm that may be executed in parallel on a multiprocessor system to further improve the efficiency. The adaptive nature of the parallel processing characteristic distinguish ACCAL from other algorithms. (Abstract shortened by UMI.)
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Xia, Fei. "Supporting the MASCOT method with Petri net techniques for real-time systems development." Thesis, King's College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325515.
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Soltani-Moghaddam, Alireza. "Network simulator design with extended object model and generalized stochastic petri-net /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9999317.
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Clark, Ian George. "A unified approach to the study of asynchronous communication mechanisms in real-time systems." Thesis, King's College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326237.
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Rohr, Christian [Verfasser], Monika [Gutachter] Heiner, Wolfgang [Gutachter] Marwan, and David [Gutachter] Gilbert. "Simulative analysis of coloured extended stochastic Petri nets / Christian Rohr ; Gutachter: Monika Heiner, Wolfgang Marwan, David Gilbert." Cottbus : BTU Cottbus - Senftenberg, 2017. http://d-nb.info/1127580922/34.
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Schwarick, Martin [Verfasser], Monika [Akademischer Betreuer] Heiner, Susanna [Akademischer Betreuer] Donatelli, and Peter [Akademischer Betreuer] Kemper. "Symbolic on-the-fly analysis of stochastic Petri nets / Martin Schwarick ; Monika Heiner, Susanna Donatelli, Peter Kemper." Cottbus : BTU Cottbus - Senftenberg, 2014. http://d-nb.info/111428291X/34.
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Shi, Lihua. "Uniting formal and structured methods for the development of reliable software." Thesis, Manchester Metropolitan University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388141.
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Rogge-Solti, Andreas, Ronny S. Mans, der Aalst Wil M. P. van, and Mathias Weske. "Repairing event logs using stochastic process models." Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6679/.
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Companies strive to improve their business processes in order to remain competitive. Process mining aims to infer meaningful insights from process-related data and attracted the attention of practitioners, tool-vendors, and researchers in recent years. Traditionally, event logs are assumed to describe the as-is situation. But this is not necessarily the case in environments where logging may be compromised due to manual logging. For example, hospital staff may need to manually enter information regarding the patient’s treatment. As a result, events or timestamps may be missing or incorrect.
In this paper, we make use of process knowledge captured in process models, and provide a method to repair missing events in the logs. This way, we facilitate analysis of incomplete logs. We realize the repair by combining stochastic Petri nets, alignments, and Bayesian networks. We evaluate the results using both synthetic data and real event data from a Dutch hospital.Unternehmen optimieren ihre Geschäftsprozesse laufend um im kompetitiven Umfeld zu bestehen. Das Ziel von Process Mining ist es, bedeutende Erkenntnisse aus prozessrelevanten Daten zu extrahieren. In den letzten Jahren sorgte Process Mining bei Experten, Werkzeugherstellern und Forschern zunehmend für Aufsehen. Traditionell wird dabei angenommen, dass Ereignisprotokolle die tatsächliche Ist-Situation widerspiegeln. Dies ist jedoch nicht unbedingt der Fall, wenn prozessrelevante Ereignisse manuell erfasst werden. Ein Beispiel hierfür findet sich im Krankenhaus, in dem das Personal Behandlungen meist manuell dokumentiert. Vergessene oder fehlerhafte Einträge in Ereignisprotokollen sind in solchen Fällen nicht auszuschließen. In diesem technischen Bericht wird eine Methode vorgestellt, die das Wissen aus Prozessmodellen und historischen Daten nutzt um fehlende Einträge in Ereignisprotokollen zu reparieren. Somit wird die Analyse unvollständiger Ereignisprotokolle erleichtert. Die Reparatur erfolgt mit einer Kombination aus stochastischen Petri Netzen, Alignments und Bayes'schen Netzen. Die Ergebnisse werden mit synthetischen Daten und echten Daten eines holländischen Krankenhauses evaluiert.
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Cortés, Luis Alejandro. "A Petri Net based Modeling and Verification Technique for Real-Time Embedded Systems." Licentiate thesis, Linköping University, Linköping University, ESLAB - Embedded Systems Laboratory, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5751.
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Embedded systems are used in a wide spectrum of applications ranging from home appliances and mobile devices to medical equipment and vehicle controllers. They are typically characterized by their real-time behavior and many of them must fulfill strict requirements on reliability and correctness.
In this thesis, we concentrate on aspects related to modeling and formal verification of realtime embedded systems.
First, we define a formal model of computation for real-time embedded systems based on Petri nets. Our model can capture important features of such systems and allows their representations at different levels of granularity. Our modeling formalism has a welldefined semantics so that it supports a precise representation of the system, the use of formal methods to verify its correctness, and the automation of different tasks along the design process.
Second, we propose an approach to the problem of formal verification of real-time embedded systems represented in our modeling formalism. We make use of model checking to prove whether certain properties, expressed as temporal logic formulas, hold with respect to the system model. We introduce a systematic procedure to translate our model into timed automata so that it is possible to use available model checking ools. Various examples, including a realistic industrial case, demonstrate the feasibility of our approach on practical applications.
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Marsal, Gaëlle. "Evaluation of time performances of ethernet-based automation systems by simulation of high-level Petri nets." Cachan, Ecole normale supérieure, 2006. http://tel.archives-ouvertes.fr/tel-00162228.
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Nous évaluons dans cette thèse deux performances temporelles des architectures d’automatisation distribuées sur Ethernet commuté et utilisant un modèle de coopération client/serveur : Le temps de réponse entre une occurrence d’un événement d’entrée et l’occurrence de l’événement de sortie correspondant ; Le temps de cycle réeseau pour la scrutation par un contrôleur de l’ensemble de ses modules d’entrées / sorties déportées. La conjonction de trois mécanismes de consommation de temps rend ces deux performances variables et difficiles à déterminer de manière analytique. Par conséquent, la méthode proposée se base sur la simulation d’un modèle en réseau de Petri temporisé et coloré du comportement dynamique de l’architecture complète. Les résultats obtenus sur six architectures test permettent de : Montrer que les architectures multi-contrôleurs utilisant le modèle de coopération client / serveur donnent des temps de cycle réseau plus rapide que celles basées sur les modèles maître / esclave et producteur / consommateur ; Quantifier l’influence du réseau et des mécanismes de consommation du tempsIn this work, two time performances of switched Ethernet automation systems that use a client/server cooperation model are evaluated : The response time from an occurrence of an input event to the occurrence of the corresponding output event ; The network cycle time for the scanning by a controller of the whole set of its remote inputs / outputs modules. The conjunction of three time consumption mechanisms makes both time performances variable and difficult to compute in an analytic fashion. Thus, the proposed method is based on simulation of a timed and coloured Petri net model of the dynamic behaviour of the whole automation architecture. The results which have been obtained on six benchmark architectures enabled us : To show that multi-controllers architectures using a client/server cooperation model provide faster network cycle times than those based on master/slave and producer/consumer models ; To quantify the influence of the time consumption mechanisms on these performances
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Cândido, Renato Markele Ferreira 1988. "Filtros de partículas aplicados a sistemas max plus." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259747.
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Orientador: Rafael Santos MendesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: A principal contribuição desta dissertação é a proposta de algoritmos de filtragem por partículas em sistemas a eventos discretos nos quais predominam os problemas de sincronização. Esta classe de sistemas pode ser descrita por meio de equações lineares em uma álgebra não convencional usualmente conhecida como álgebra Max Plus. Os Filtros de Partículas são algoritmos Bayesianos sub-ótimos que realizam uma amostragem sequencial de Monte Carlo para construir uma aproximação discreta da densidade de probabilidade dos estados baseada em um conjunto de partículas com pesos associados. É apresentada uma revisão de sistemas a eventos discretos, de filtragem não linear e de filtros de partículas de um modo geral. Após apresentar esta base teórica, são propostos dois algoritmos de filtros de partículas aplicados a sistemas Max Plus. Em seguida algumas simulações foram apresentadas e os resultados apresentados mostraram a eficiência dos filtros desenvolvidos
Abstract: This thesis proposes, as its main contribution, particle filtering algorithms for discrete event systems in which synchronization phenomena are prevalent. This class of systems can be described by linear equation systems in a nonconventional algebra commonly known as Max Plus algebra. Particles Filters are suboptimal Bayesian algorithms that perform a sequential Monte Carlo sampling to construct a discrete approximation of the probability density of states based on a set of particles with associated weights. It is presented a review of discrete event systems, nonlinear filtering and particle filters. After presenting this theoretical background, two particle filtering algorithms applied to Max Plus systems are proposed. Finally some simulation results are presented, confirming the accuracy of the designed filters
Mestrado
Automação
Mestre em Engenharia Elétrica
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Thumu, Prashanth. "TIME CONDITION SYSTEMS." UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_theses/374.
Full textAbstract:
The current thesis considers the issue of state estimation of condition systems, a form of petri net with signal inputs and outputs. In previous research the problem of unobservability due to progress confusion was identified, in the presence of which state estimation is not possible. Here we introduce the notion of Time Condition Systems", a class of condition systems that uses timing information from condition models to overcome state estimation problem caused by progress confusion. To make use of the timing information in the plant model, a procedure called Exploded Time Plant" is synthesized. This procedure makes the plant model an observable model. It is proved that this procedure does not alter the structural and temporal behavior of the plant model and the plant maintains its integrity. The time plant(s) and the corresponding Exploded time plant(s) are subsequently used to develop observer(s) and controller(s) for Time condition models.
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Bhat, Aniket Anant. "Stochastic Petri Net Models of Service Availability in a PBNM System for Mobile Ad Hoc Networks." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/10000.
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Policy based network management is a promising approach for provisioning and management of quality of service in mobile ad hoc networks. In this thesis, we focus on performance evaluation of this approach in context of the amount of service received by certain nodes called policy execution points (PEPs) or policy clients from certain specialized nodes called the policy decision points (PDPs) or policy servers. We develop analytical models for the study of the system behavior under two scenarios; a simple Markovian scenario where we assume that the random variables associated with system processes follow an exponential distribution and a more complex non-Markovian scenario where we model the system processes according to general distribution functions as observed through simulation. We illustrate that the simplified Markovian model provides a reasonable indication of the trend of the service availability seen by policy clients and highlight the need for an exact analysis of the system without relying on Poisson assumptions for system processes. In the case of the more exact non-Markovian analysis, we show that our model gives a close approximation to the values obtained via empirical methods. Stochastic Petri Nets are used as performance evaluation tools in development and analysis of these system models.Master of Science
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Djafri, Hilal. "Numerical and statistical approaches for model checking of stochastic processes." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-00751927.
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We propose in this thesis several contributions related to the quantitative verification of systems. This discipline aims to evaluate functional and performance properties of a system. Such a verification requires two ingredients: a formal model to represent the system and a temporal logic to express the desired property. Then the evaluation is done with a statistical or numerical method. The spatial complexity of numerical methods which is proportional to the size of the state space of the model makes them impractical when the state space is very large. The method of stochastic comparison with censored Markov chains is one of the methods that reduces memory requirements by restricting the analysis to a subset of the states of the original Markov chain. In this thesis we provide new bounds that depend on the available information about the chain. We introduce a new quantitative temporal logic named Hybrid Automata Stochastic Logic (HASL), for the verification of discrete event stochastic processes (DESP). HASL employs Linear Hybrid Automata (LHA) to select prefixes of relevant execution paths of a DESP. LHA allows rather elaborate information to be collected on-the-fly during path selection, providing the user with a powerful mean to express sophisticated measures. In essence HASL provides a unifying verification framework where temporal reasoning is naturally blended with elaborate reward-based analysis. We have also developed COSMOS, a tool that implements statistical verification of HASL formulas over stochastic Petri nets. Flexible manufacturing systems (FMS) have often been modelized by Petri nets. However the modeler should have a good knowledge of this formalism. In order to facilitate such a modeling we propose a methodology of compositional modeling that is application oriented and does not require any knowledge of Petri nets by the modeler.
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Marsal, Gaelle [Verfasser]. "Evaluation of time performances of Ethernet-based Automation Systems by simulation of High-level Petri Nets / Gaelle Marsal." Aachen : Shaker, 2007. http://d-nb.info/1166512339/34.
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Habib, Zadeh Esmaeil. "Modelling and Quantitative Analysis of Performance vs Security Trade-offs in Computer Networks: An investigation into the modelling and discrete-event simulation analysis of performance vs security trade-offs in computer networks, based on combined metrics and stochastic activity networks (SANs)." Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/17412.
Full textAbstract:
Performance modelling and evaluation has long been considered of paramount
importance to computer networks from design through development, tuning and
upgrading. These networks, however, have evolved significantly since their first introduction
a few decades ago. The Ubiquitous Web in particular with fast-emerging
unprecedented services has become an integral part of everyday life. However, this
all is coming at the cost of substantially increased security risks. Hence cybercrime is
now a pervasive threat for today’s internet-dependent societies. Given the frequency
and variety of attacks as well as the threat of new, more sophisticated and destructive
future attacks, security has become more prevalent and mounting concern in
the design and management of computer networks. Therefore equally important if
not more so is security.
Unfortunately, there is no one-size-fits-all solution to security challenges. One security
defence system can only help to battle against a certain class of security threats. For overall security, a holistic approach including both reactive and proactive
security measures is commonly suggested. As such, network security may have
to combine multiple layers of defence at the edge and in the network and in its
constituent individual nodes.
Performance and security, however, are inextricably intertwined as security measures
require considerable amounts of computational resources to execute. Moreover, in
the absence of appropriate security measures, frequent security failures are likely
to occur, which may catastrophically affect network performance, not to mention
serious data breaches among many other security related risks.
In this thesis, we study optimisation problems for the trade-offs between performance
and security as they exist between performance and dependability. While
performance metrics are widely studied and well-established, those of security are
rarely defined in a strict mathematical sense. We therefore aim to conceptualise and
formulate security by analogy with dependability so that, like performance, it can
be modelled and quantified.
Having employed a stochastic modelling formalism, we propose a new model for a
single node of a generic computer network that is subject to various security threats.
We believe this nodal model captures both performance and security aspects of a
computer node more realistically, in particular the intertwinements between them.
We adopt a simulation-based modelling approach in order to identify, on the basis
of combined metrics, optimal trade-offs between performance and security and facilitate
more sophisticated trade-off optimisation studies in the field.
We realise that system parameters can be found that optimise these abstract combined
metrics, while they are optimal neither for performance nor for security individually.
Based on the proposed simulation modelling framework, credible numerical
experiments are carried out, indicating the scope for further work extensions for a
systematic performance vs security tuning of computer networks.
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Kriščiūnas, Darius. "Gyvenamojo namo šildymo ir vėdinimo sistemos kompiuterinio valdymo modelio sudarymas ir tyrimas naudojant Petri tinklą." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050522_223544-30240.
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Presently information systems are increasingly penetrating to our daily life. Recently it is relevant to integrate the newest technologies. In that way traditional system becomes “smart” who are more economical, optimal, and self-sufficient. The biggest problem is to make a model of “smart” system. There were analyzed modeling methods, heating and cooling control systems in this job. Mathematical model for heating and cooling controller using timed Petri nets was presented. According to analyzed problems it was made verification with Matlab during experimental phase. There was made comparison evaluation of mathematical model made with timed Petri nets and fuzzy logic.
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Antunes, Dante Carlos. "Modelagem temporal de sistemas : uma abordagem fundamentada em redes de petri." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1997. http://hdl.handle.net/10183/21112.
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Neste trabalho e proposta a abordagem TempER-Tr, uma técnica de modelagem conceitual, fundamentada em rede de Petri, que integra a especificação das propriedades dinâmicas de um sistema a um modelo de dados temporal do tipo entidade relacionamento. Um modelo ou esquema conceitual descreve as propriedades identificadas de um sistema a ser desenvolvido. Estas propriedades podem ser classificadas em propriedades estáticas e propriedades dinâmicas As propriedades estáticas descrevem os estados que o sistema pode alcançar, enquanto que as propriedades dinâmicas descrevem as transições entre estes estados. A modelagem conceitual das propriedades estáticas é normalmente conhecida como modelagem de dados. A modelagem das propriedades dinâmicas é denominada de modelagem funcional ou comportamental. Mais especificamente, o modelo TempER-Tr é uma extensão de um trabalho anterior, conhecido como ER-Tr. No modelo ER-Tr, para descrever as propriedades estáticas de um sistema utiliza-se o modelo entidade-relacionamento convencional. No modelo TempER-Tr passa-se a adotar um modelo entidade-relacionamento temporal. Aliado a isto, uma nova linguagem de anotação, baseada em SQL, com mais poder de expressão é proposta. O modelo entidade-relacionamento convencional não possui dispositivos de modelagem capazes de especificar restrições que envolvam a associação dos objetos com o tempo, exigindo que isto se faca ao nível da modelagem das propriedades dinâmicas. Em um modelo entidade-relacionamento convencional, os conjuntos de entidades e relacionamentos apresentam apenas duas dimensões: a primeira refere-se as instâncias (linhas) e a segunda aos atributos (colunas). Em uma abordagem entidade relacionamento temporal, uma nova dimensão e acrescentada: o eixo temporal, possibilitando que as restrições temporais decorrentes da associação entre os objetos possam ser especificadas ao nível do modelo estático. Um requisito importante a ser preenchido por um modelo de dados temporal é permitir que em um mesmo diagrama seja possível associar objetos (entidades, relacionamentos ou atributos) temporalizados com objetos não temporalizados. lsto porque em sistemas de informação alguns dados precisam ser explicitamente referenciados ao tempo e outros não, ou porque não mudam com o tempo, ou porque é irrelevante ao usuário saber quando os fatos ocorreram. O modelo de dados temporal proposto neste trabalho, denominado TempER, pressupõe que todas as entidades, sejam elas temporalizadas ou não temporalizadas, apresentam uma "existência", ou seja, uma validade temporal. No caso das entidades temporalizadas esta existência é um subconjunto de pontos do eixo temporal. Em virtude disto são chamadas de entidades transitórias. Em relação as entidades não temporalizadas, e assumido que "existem sempre", ou seja, a sua validade temporal é constante, implícita e igual a todo o eixo temporal. Por isto são denominadas entidades perenes. Tanto as entidades transitórias quanto as entidades perenes, são focalizadas pelo modelo TempER através de duas perspectivas: uma intemporal e outra temporal. Através da perspectiva intemporal as entidades apresentam duas dimensões, semelhança do que ocorre em um modelo entidade-relacionamento convencional. Através da perspectiva temporal as entidades apresentam três dimensões, as duas convencionais e mais o tempo. Enquanto que o modelo de dados temporal descreve as propriedades estáticas de um sistema, o modelo comportamental, a outra face da abordagem TempER-Tr, focaliza as transações executadas no interior do sistema, em resposta a eventos que ocorrem no ambiente externo. Estas transações, quando efetivadas, provocam mudanças de estados no sistema. Entretanto, para estarem habilitadas a ocorrer, é necessário que um determinado conjunto de restrições dinâmicas sejam atendidas, o que se configura em um comportamento análogo ao de uma rede de Petri. O modelo TempER-Tr é completamente mapeável, inclusive o modelo de dados temporal, para a rede CEM, um tipo de rede de Petri de alto nível. Isto permite que a sua semântica seja formalmente especificada e possibilita o aproveitamento das características das redes de Petri.This dissertation presents TempER-Tr approach. TempER-Tr is a conceptual modeling technique based on Petri nets that integrates the specification of the dynamic properties of system to a temporal entity-relationship data model. A model or conceptual schema describes the identified properties of a system. These properties can be classified into static and dynamic properties. The static properties describe the states that the system can reach, while the dynamic properties describe the transitions between the states. The conceptual modeling of the static properties is usually known as data modeling, while behavioral or functional modeling deals with dynamic properties. The TempER-Tr model is an extension of a model known as ER-Tr. In the ER-Tr model, the conventional entity-relationship model is used to describe the static properties of a system. In the TempER-Tr model, it is adopted a kind of temporal entityrelationship model. In addition, a new notation language is proposed, based on SQL, with more expression power. The conventional entity-relationship model doesn't provide tools to specify constraints that involve the association of objects with the time dimension, requiring that this have to be done at the dynamic properties modeling level. At the conventional entityrelationship model the entities and relationships sets present just two dimensions: the first one is related to the instance (lines) and the second to the attributes (columns). At a temporal entity-relationship approach, a new dimension is added: the time line. This way, the temporal constraints can be specified at the level of the static diagrams. An important requirement to be supplied by any temporal data model is the possibility to relate, into the same diagram, time-varying objects with time-invarying objects. This is due to the fact that in information systems some data need to be explicitly related to time and others don't, either because they don't change with time, or because users don't need to know when the facts occurred. • The temporal data model proposed in this work, nominated TempER, presupposes that all entities, being them time-varying or time-invarying, have an "existence", or a temporal validity. At the time-varying entities, named transitory entities, this existence is a subset of points from the time line. In time-invarying entities, named perennial entities, it is assumed that they "always exist", i.e., their temporal validity is constant, implicit, and equal to all points of the time line. Transitory entities, as much as perennial entities, are focused by the TempER model through two perspectives: a temporal perspective and a non-temporal perspective. Through the non-temporal perspective the entities present two dimensions - lines and columns - similar to a conventional entity-relationship model. Through the temporal perspective the entities present three dimensions: the two conventional dimensions and, in addition, the time dimension. While the temporal data model describes the static properties of a system, the behavioral model in the TempER-Tr approach focus the transactions that are executed by the system, in response to the events that occur at the external environment. A certain set of dynamic constraints must be attended so that transactions are enable to occur. This configures a behavior similar to a Petri net. The TempER-Tr model is completely mappeable, inclusive the temporal data model, to the CEM net, a kind of high level Petri net. This way, the semantic of TempER-Tr model is formally specified. In addition, the utilization of the characteristics of Petri nets is possible.
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Sousa, João Carlos Tanganho de. "Parallel run-time for CO-OPN." Master's thesis, Faculdade de Ciências e Tecnologia, 2009. http://hdl.handle.net/10362/8101.
Full textAbstract:
Dissertação para obtenção do Grau de Mestre em
Engenharia InformáticaDomain Specific Modeling (DSM) is a methodology to provide programs or system’s specification at higher level of abstraction, making use of domain concepts instead of low level programming details. To support this approach, we need to have enough expressive power in terms of those domain concepts, which means that we need to develop new languages , usually termed Domain Specific Languages (DSLs). An approach to execute specifications developed using DSLs goes by applying a model transformation technique to produce a specification in another language. These transformation techniques are applied sucessively until the specification reaches a language with an implemented run-time. The language named Concurrent Object-Oriented Petri Nets (CO-OPN) is being used successfully as a target language for such model transformation techniques. CO-OPN is an object-oriented formal language for specifying concurrent systems, that separates coordination from computational tasks. CO-OPN offers mechanisms to define the system structure and behavior, and like DSLs, relieves the developer from stipulate how that structure and behavior are attained by the underlying system. The currently available code generator for CO-OPN only produces sequential code, despite of this language potential of expressing specifications rich in concurrent behavior. The generated sequential code can be executed either in a Sequential Run-Time or in the step simulator, which is part of CO-OPN Builder IDE. The generation of sequential code turns out to be an adversity to CO-OPN application since concurrent specifications cannot be executed in parallel and therefore this languages potential is not fully exploited. This dissertation aims at filling this CO-OPN’s execution gap, through the development of a Parallel Run-Time. The new Run-Time is achieved through the adaptation of the sequential code generator and actual execution support mechanisms. In this manner, all concurrent specifications that target CO-OPN benefit from thread safe code, ready for execution in parallel and distributed environments, relieving the developer from delving into parallel programming details.By guaranteeing a safe execution environment, CO-OPN becomes an alternative to the way parallel software is nowadays developed.
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Valenzuela, Vega Rene Cristian. "Compact reliability and maintenance modeling of complex repairable systems." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51850.
Full textAbstract:
Maintenance models are critical for evaluation of the alternative maintenance
policies for modern engineering systems. A poorly selected policy can result in excessive
life-cycle costs as well as unnecessary risks for catastrophic failures of the system. Economic dependence refers to the difference between the cost of combining the maintenance of a number of components and the cost of performing the same maintenance actions individually. Maintenance that takes advantage of this difference is often called opportunistic.
Large number of components and economic inter-dependence are two pervasive characteristics of modern engineering systems that make the modeling of their maintenance processes particularly challenging. Simulation is able to handle both of these characteristics computationally, but the complexity, especially from the model verification perspective, becomes overwhelming as the number of components increases. This research introduces a new procedure for maintenance models of multi-unit repairable systems with economic dependence among its components and under opportunistic maintenance policies. The procedure is based on the stochastic Petri net with aging tokens modeling framework and it makes use of a component-level model approach to overcome the state explosion of the model combined with a novel order-reduction scheme that effectively combines the impact of other components into a single distribution. The justification for
the used scheme is provided, the accuracy is assessed, and applications for the systems of realistic complexity are considered.
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TAVARES, Eduardo Antônio Guimarães. "Software Synthesis for Energy-Constrained Hard Real-Time Embedded Systems." Universidade Federal de Pernambuco, 2009. https://repositorio.ufpe.br/handle/123456789/1403.
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Previous issue date: 2009A grande expansão do mercado de dispositivos digitais tem forçado empresas desenvolvedoras de sistemas embarcados em lidar com diversos desafios para prover sistemas complexos nesse nicho de mercado. Um dos desafios prominentes está relacionado ao consumo de energia, principalmente, devido aos seguintes fatores: (i) mobilidade; (ii) problemas ambientais; e (iii) o custo da energia. Como consequência, consideráveis esforços de pesquisa têm sido dedicados para a criação de técnicas voltadas para aumentar a economia de energia. Na última década, diversas técnicas foram desenvolvidas para reduzir o consumo de energia em sistemas embarcados. Muitos métodos lidam com gerenciamento dinâmico de energia (DPM), como, por exemplo, dynamic voltage scaling (DVS), cooperativamente com sistemas operacionais especializados, a fim de controlar o consumo de energia durante a execução do sistema. Entretanto, apesar da disponibilidade de muitos métodos de redução de consumo de energia, diversas questões estão em aberto, principalmente, no contexto de sistemas de tempo real crítico. Este trabalho propõe um método de síntese de software, o qual leva em consideração relação entre tarefas, overheads, restrições temporais e de energia. O método é composto por diversas atividades, as quais incluem: (i) medição; (ii) especificação; (iii) modelagem formal; (vi) escalonamento; e (v) geração de código. O método também é centrado no formalismo redes de Petri, o qual define uma base para geração precisa de escalas em tempo de projeto, adotando DVS para reduzir o consumo de energia. A partir de uma escala viável, um código customizado é gerado satisfazendo as restrições especificadas, e, dessa forma, garantindo previsibilidade em tempo de execução. Para lidar com a natureza estática das escalas geradas em tempo de projeto, um escalonador simples em tempo de execução é também proposto para melhorar o consumo de energia durante a execução do sistema. Diversos experimentos foram conduzidos, os quais demonstram a viabilidade da abordagem proposta para satisfazer restrições críticas de tempo e energia. Adicionalmente, um conjunto integrado de ferramentas foram desenvolvidas para automatizar algumas atividades do método de síntese de software proposto
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Mohan, Sridhar. "Deadlock avoidance in mixed capacity flexible manufacturing systems." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000428.
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Miskeen, Guzlan M. A. "Performance and Security Trade-offs in High-Speed Networks. An investigation into the performance and security modelling and evaluation of high-speed networks based on the quantitative analysis and experimentation of queueing networks and generalised stochastic Petri nets." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6362.
Full textAbstract:
Most used security mechanisms in high-speed networks have been adopted without adequate quantification of their impact on performance degradation. Appropriate quantitative network models may be employed for the evaluation and prediction of ¿optimal¿ performance vs. security trade-offs. Several quantitative models introduced in the literature are based on queueing networks (QNs) and generalised stochastic Petri nets (GSPNs). However, these models do not take into consideration Performance Engineering Principles (PEPs) and the adverse impact of traffic burstiness and security protocols on performance.
The contributions of this thesis are based on the development of an effective quantitative methodology for the analysis of arbitrary QN models and GSPNs through discrete-event simulation (DES) and extended applications into performance vs. security trade-offs involving infrastructure and infrastructure-less high-speed networks under bursty traffic conditions. Specifically, investigations are carried out focusing, for illustration purposes, on high-speed network routers subject to Access Control List (ACL) and also Robotic Ad Hoc Networks (RANETs) with Wired Equivalent Privacy (WEP) and Selective Security (SS) protocols, respectively. The Generalised Exponential (GE) distribution is used to model inter-arrival and service times at each node in order to capture the traffic burstiness of the network and predict pessimistic ¿upper bounds¿ of network performance.
In the context of a router with ACL mechanism representing an infrastructure network node, performance degradation is caused due to high-speed incoming traffic in conjunction with ACL security computations making the router a bottleneck in the network. To quantify and predict the trade-off of this degradation, the proposed quantitative methodology employs a suitable QN model consisting of two queues connected in a tandem configuration. These queues have single or quad-core CPUs with multiple-classes and correspond to a security processing node and a transmission forwarding node. First-Come-First-Served (FCFS) and Head-of-the-Line (HoL) are the adopted service disciplines together with Complete Buffer Sharing (CBS) and Partial Buffer Sharing (PBS) buffer management schemes. The mean response time and packet loss probability at each queue are employed as typical performance metrics. Numerical experiments are carried out, based on DES, in order to establish a balanced trade-off between security and performance towards the design and development of efficient router architectures under bursty traffic conditions.
The proposed methodology is also applied into the evaluation of performance vs. security trade-offs of robotic ad hoc networks (RANETs) with mobility subject to Wired Equivalent Privacy (WEP) and Selective Security (SS) protocols. WEP protocol is engaged to provide confidentiality and integrity to exchanged data amongst robotic nodes of a RANET and thus, to prevent data capturing by unauthorised users. WEP security mechanisms in RANETs, as infrastructure-less networks, are performed at each individual robotic node subject to traffic burstiness as well as nodal mobility. In this context, the proposed quantitative methodology is extended to incorporate an open QN model of a RANET with Gated queues (G-Queues), arbitrary topology and multiple classes of data packets with FCFS and HoL disciplines under bursty arrival traffic flows characterised by an Interrupted Compound Poisson Process (ICPP). SS is included in the Gated-QN (G-QN) model in order to establish an ¿optimal¿ performance vs. security trade-off. For this purpose, PEPs, such as the provision of multiple classes with HoL priorities and the availability of dual CPUs, are complemented by the inclusion of robot¿s mobility, enabling realistic decisions in mitigating the performance of mobile robotic nodes in the presence of security. The mean marginal end-to-end delay was adopted as the performance metric that gives indication on the security improvement.
The proposed quantitative methodology is further enhanced by formulating an advanced hybrid framework for capturing ¿optimal¿ performance vs. security trade-offs for each node of a RANET by taking more explicitly into consideration security control and battery life. Specifically, each robotic node is represented by a hybrid Gated GSPN (G-GSPN) and a QN model. In this context, the G-GSPN incorporates bursty multiple class traffic flows, nodal mobility, security processing and control whilst the QN model has, generally, an arbitrary configuration with finite capacity channel queues reflecting ¿intra¿-robot (component-to-component) communication and ¿inter¿-robot transmissions. Two theoretical case studies from the literature are adapted to illustrate the utility of the QN towards modelling ¿intra¿ and ¿inter¿ robot communications. Extensions of the combined performance and security metrics (CPSMs) proposed in the literature are suggested to facilitate investigating and optimising RANET¿s performance vs. security trade-offs.
This framework has a promising potential modelling more meaningfully and explicitly the behaviour of security processing and control mechanisms as well as capturing the robot¿s heterogeneity (in terms of the robot architecture and application/task context) in the near future (c.f. [1]. Moreover, this framework should enable testing robot¿s configurations during design and development stages of RANETs as well as modifying and tuning existing configurations of RANETs towards enhanced ¿optimal¿ performance and security trade-offs.Ministry of Higher Education in Libya and the Libyan Cultural Attaché bureau in London
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Miskeen, Guzlan Mohamed Alzaroug. "Performance and security trade-offs in high-speed networks : an investigation into the performance and security modelling and evaluation of high-speed networks based on the quantitative analysis and experimentation of queueing networks and generalised stochastic Petri nets." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6362.
Full textAbstract:
Most used security mechanisms in high-speed networks have been adopted without adequate quantification of their impact on performance degradation. Appropriate quantitative network models may be employed for the evaluation and prediction of 'optimal' performance vs. security trade-offs. Several quantitative models introduced in the literature are based on queueing networks (QNs) and generalised stochastic Petri nets (GSPNs). However, these models do not take into consideration Performance Engineering Principles (PEPs) and the adverse impact of traffic burstiness and security protocols on performance. The contributions of this thesis are based on the development of an effective quantitative methodology for the analysis of arbitrary QN models and GSPNs through discrete-event simulation (DES) and extended applications into performance vs. security trade-offs involving infrastructure and infrastructure-less high-speed networks under bursty traffic conditions. Specifically, investigations are carried out focusing, for illustration purposes, on high-speed network routers subject to Access Control List (ACL) and also Robotic Ad Hoc Networks (RANETs) with Wired Equivalent Privacy (WEP) and Selective Security (SS) protocols, respectively. The Generalised Exponential (GE) distribution is used to model inter-arrival and service times at each node in order to capture the traffic burstiness of the network and predict pessimistic 'upper bounds' of network performance. In the context of a router with ACL mechanism representing an infrastructure network node, performance degradation is caused due to high-speed incoming traffic in conjunction with ACL security computations making the router a bottleneck in the network. To quantify and predict the trade-off of this degradation, the proposed quantitative methodology employs a suitable QN model consisting of two queues connected in a tandem configuration. These queues have single or quad-core CPUs with multiple-classes and correspond to a security processing node and a transmission forwarding node. First-Come-First-Served (FCFS) and Head-of-the-Line (HoL) are the adopted service disciplines together with Complete Buffer Sharing (CBS) and Partial Buffer Sharing (PBS) buffer management schemes. The mean response time and packet loss probability at each queue are employed as typical performance metrics. Numerical experiments are carried out, based on DES, in order to establish a balanced trade-off between security and performance towards the design and development of efficient router architectures under bursty traffic conditions. The proposed methodology is also applied into the evaluation of performance vs. security trade-offs of robotic ad hoc networks (RANETs) with mobility subject to Wired Equivalent Privacy (WEP) and Selective Security (SS) protocols. WEP protocol is engaged to provide confidentiality and integrity to exchanged data amongst robotic nodes of a RANET and thus, to prevent data capturing by unauthorised users. WEP security mechanisms in RANETs, as infrastructure-less networks, are performed at each individual robotic node subject to traffic burstiness as well as nodal mobility. In this context, the proposed quantitative methodology is extended to incorporate an open QN model of a RANET with Gated queues (G-Queues), arbitrary topology and multiple classes of data packets with FCFS and HoL disciplines under bursty arrival traffic flows characterised by an Interrupted Compound Poisson Process (ICPP). SS is included in the Gated-QN (G-QN) model in order to establish an 'optimal' performance vs. security trade-off. For this purpose, PEPs, such as the provision of multiple classes with HoL priorities and the availability of dual CPUs, are complemented by the inclusion of robot's mobility, enabling realistic decisions in mitigating the performance of mobile robotic nodes in the presence of security. The mean marginal end-to-end delay was adopted as the performance metric that gives indication on the security improvement. The proposed quantitative methodology is further enhanced by formulating an advanced hybrid framework for capturing 'optimal' performance vs. security trade-offs for each node of a RANET by taking more explicitly into consideration security control and battery life. Specifically, each robotic node is represented by a hybrid Gated GSPN (G-GSPN) and a QN model. In this context, the G-GSPN incorporates bursty multiple class traffic flows, nodal mobility, security processing and control whilst the QN model has, generally, an arbitrary configuration with finite capacity channel queues reflecting 'intra'-robot (component-to-component) communication and 'inter'-robot transmissions. Two theoretical case studies from the literature are adapted to illustrate the utility of the QN towards modelling 'intra' and 'inter' robot communications. Extensions of the combined performance and security metrics (CPSMs) proposed in the literature are suggested to facilitate investigating and optimising RANET's performance vs. security trade-offs. This framework has a promising potential modelling more meaningfully and explicitly the behaviour of security processing and control mechanisms as well as capturing the robot's heterogeneity (in terms of the robot architecture and application/task context) in the near future (c.f. [1]. Moreover, this framework should enable testing robot's configurations during design and development stages of RANETs as well as modifying and tuning existing configurations of RANETs towards enhanced 'optimal' performance and security trade-offs.
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Ramos, Andre Gustavo. "Análise de disponibilidade de um sistema de tratamento de gás em instalações \"offshore\" utilizando redes de Petri estocásticas." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-13072018-134254/.
Full textAbstract:
Numa unidade offshore de produção de petróleo, o gás produzido é tratado para atingir as especificações requeridas e permitir sua utilização em diferentes demandas como gás combustível, gas lift, exportação de gás ou injeção de gás. No Brasil, a Agência Nacional do Petróleo regula a produção de óleo e gás, limita a queima de gás e controla a movimentação e utilização de gás de acordo com as estimativas informadas pelo operador. Falhas no sistema de tratamento de gás levam à queima e podem causar parada de produção. A confiabilidade e disponibilidade do sistema de tratamento de gás é uma preocupação relevante. Entender as relações e influências dos vários subsistemas e equipamentos do sistema nessas medidas de desempenho pode levar a melhorias nas estratégias de manutenção que podem minimizar perdas na produção de óleo e de gás. Dentre os vários métodos de análise de confiabilidade, as redes de Petri estocásticas se destacam quando comparadas às ferramentas tradicionais como diagrama de blocos ou árvore de falhas devido a sua habilidade em modelar aspectos como dependências funcionais, lógicas e sequências. Nesse trabalho foram construídos quatro modelos utilizando redes de Petri estocásticas para analisar a disponibilidade do sistema de tratamento de gás. A facilidade de construção modelo A sugere sua utilização em etapas preliminares de projeto para validar o arranjo inicial, as quantidades de equipamentos e as configurações de redundância. O modelo B pode ser utilizado para identificar os subsistemas e equipamentos que mais contribuem para as falhas do sistema e para realizar previsões quanto aos modos de operação do sistema e índice de aproveitamento de gás. A análise de sensibilidade dos resultados de disponibilidade quanto aos dados de falha utilizados mostrou que a variação do tempo médio para reparo tem maior influência. Por meio do modelo C verificou-se que uma plataforma operando num conjunto e sujeita a restrições de importação e exportação de gás tem maior indisponibilidade e maior probabilidade de falha do que uma plataforma operando isolada. O modelo D permite concluir que a inclusão de um modo de falha ao modelo não implica em variação significativa dos resultados de confiabilidade e que nos resultados de disponibilidade a variação passa a ser significativa quando adotam-se pequenos valores de tempo médio entre falhas e grandes valores de tempo médio para reparo. A construção das redes de Petri estocásticas para o sistema completo exige uma compreensão detalhada do funcionamento do sistema em análise o que também pode ser destacado como uma vantagem das redes de Petri estocásticas, contribuindo para aquisição de conhecimento acerca do sistema e dando segurança quanto a fidelidade do modelo criado.In an offshore oil production facility, produced gas is treated to meet the necessary specifications to allow its use in different demands, as gas fuel, as exportation gas and as injection gas. In Brazil, the National Petroleum Agency regulates oil and gas production, establishing and gas flaring limits, the utilization and distribution of gas according to the operator\'s estimations. Failures in the gas treatment system eventually can cause oil production interruptions to avoid attaining the gas flaring limits. Reliability and availability of the gas treatment system is a major concern. Understanding the relationships and influences of the various gas treatment subsystems and equipment on these performance measures may lead to design or maintenance strategies improvements that could ultimately minimize oil and gas losses in the facility. Among several modelling methods stochastic Petri nets stands out comparing to traditional reliability tools like reliability block diagrams or fault tree analysis due to its ability to model aspects such as functional dependencies, logics and sequences. In this work, four models were built using stochastic Petri nets to assess the availability of a gas treatment system. The model A is easy to build and may be used in preliminary design stages to validate the initial arrangement, equipment and redundancies. The model B may be used to identify subsystems and equipment that most contribute to system failures and to predict operation modes and efficiency in the gas utilization. The sensibility analysis of reliability data has shown a predominant influence of the mean time to repair. Using model C, it could be noticed that a platform operating in a group submitted to injection and exportation gas limits has a greater unavailability and probability of failure than an isolated operating platform. Model D allow one to conclude that including a failure mode in the model does not imply in significant variation in the reliability results and that the variation is only significant in availability when using small mean time to failure values and large mean time to repair values. The stochastic Petri nets construction for the complete system requires an accurate comprehension about the system operation what could also be mentioned as an advantage of the stochastic Petri nets.
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Foyo, Pedro Manuel González Del. "Verificação formal de sistemas discretos distribuídos." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-11082010-164641/.
Full textAbstract:
O presente trabalho trata da verificação e design de sistemas complexos, especificamente da verificação de sistemas de tempo real concorrentes e distribuídos. Propõe-se uma técnica enumerativa para a verificação formal de modelos que permite determinar a validade de propriedades quantitativas, além das qualitativas. A técnica proposta separa a construção do espaço de estados dos algoritmos de rotulação das fórmulas temporais, o que possibilita a diminuição da complexidade do processo de verificação, tornando-o viável para aplicações práticas. A técnica proposta foi inicialmente aplicada sobre modelos de redes de Petri temporizadas e depois em uma rede unificada chamada GHENeSys para aproveitar as características de abstração, hierarquia e de elementos de interação chamados pseudo-boxes. A definição da rede GHENeSys foi modificada para permitir a modelagem de sistemas onde os requisitos temporais devem ser expressos através de atrasos e prazos como e o caso dos sistemas de tempo real. A rede suporta ainda mecanismos de refinamento tanto para os elementos ativos quanto os passivos. A demonstração da manutenção de propriedades como invariantes, vivacidade, limitação assim como da validade de fórmulas lógicas no processo de refinamento constitui um aspecto fundamental no projeto de sistemas complexos, e foi portanto revista em detalhes para a rede GHENeSys. Alguns exemplos práticos são apresentados para avaliar o desempenho dos algoritmos e um estudo de caso finaliza a apresentação, onde se pode contrastar os algoritmos propostos com os implementados na ferramenta UPPAAL.This work deals with the process of design and verification of complex systems, mainly real time, concurrent and distributed systems. An enumerative technique is proposed for model-checking which is capable of determining both quantitative and qualitative properties. The proposed technique detach the algorithm for labeling the formula being checked from the state space construction, allowing a better result in the verification process. This model-checking approach shows itself valuable in practical applications. This approach was first applied to systems modeled by Time Petri Nets and further extended to a unified net called GHENeSys, which includes abstraction and hierarchy concepts as well as elements for data and control interchange, called pseudo-boxes. The GHENeSys definition was modified in order to deal with systems in which temporal requirements can be expressed through delays and deadlines as in the real-time systems. The GHENeSys environment supports a refinement technique applied to both passive and active elements. Net properties like invariants, liveness, boundedness and also the validity of temporal formulas was proved to be maintained through the refinement process if some conditions are satisfied. Such characteristics are useful to deal with complex systems design. Some experiments based on well known academic articles were used to avaliate the performance of the algorithms and a case study is presented in order to compare obtained results with those obtained using the UPPAAL tool.
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Kecir, Abd-El-Karim. "Performance evaluation of urban rail traffic management techniques." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S026/document.
Full textAbstract:
Le trafic ferroviaire urbain est quotidiennement sujet à des perturbations qui le dévient de son comportement nominal. Afin de minimiser l'impact de ces perturbations, les opérateurs ferroviaires usent de diverses techniques. Nonobstant leur efficacité, les performances de ces techniques ne sont généralement pas bien étudiées ni sont-elles optimales, car élaborées empiriquement. C'est dans ce cadre-ci que vient cet ouvrage fournir des solutions qui permettent d'évaluer ces techniques de régulation et d'en comparer les performances dans des contextes variés. L’approche proposée se base sur des variantes de réseaux de Petri comme modèles et sur la méthode de Monte-Carlo pour en simuler l’exécution. Cette combinaison a donné naissance à SIMSTORS, un outil de simulation pour les systèmes ferroviaires urbains, et plus généralement, pour les systèmes stochastiques régulés. Additionnellement, nous nous intéressons dans cette thèse à la problématique de la réalisabilité des tables horaires qui pilotent le trafic ferroviaire. Ces tables décrivent le comportement temporel désiré des systèmes pour lesquels elles sont conçues. Or, la construction de ces tables ne garantit pas toujours sa réalisabilité, notamment dans un contexte stochastique. Ainsi, nous proposons ici une méthode permettant de vérifier si une table horaire est bien réalisable avec une probabilité strictement positiveUrban rail traffic is subject to numerous disrupting events that drift it from its nominal behavior. In order to minimize the impact of these disturbances, rail operators rely on a set of techniques. Despite their efficiency, performances of theses techniques are rarely well studied, nor are they of proven optimality; a direct consequence of them being empirically built. It is in this particular context that comes our work to provide solutions that allow for the evaluation of such techniques and for the comparison of their relative performances in various scenarios. The proposed approach is based on variants of Petri nets as models, and on the Monte-Carlo method for the simulation of their execution. This combination has led to the development of SIMSTORS, a tool for the simulation of urban rail systems, and more generally, stochastic systems under dynamic rescheduling. Additionally, this thesis addresses the question of timetable realizability; that is whether or not a given timetable is indeed realizable by a system for which it was built. Indeed, a timetable is meant to drive the behavior of a system but there is no guarantee as to its realizability. We therefore propose a method for the verification of the realizability of timetables with a strictly positive probability