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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Robust manufacturing system design using petri nets and bayesian methods

Sharda, Bikram 10 October 2008 (has links)
Manufacturing system design decisions are costly and involve significant investment in terms of allocation of resources. These decisions are complex, due to uncertainties related to uncontrollable factors such as processing times and part demands. Designers often need to find a robust manufacturing system design that meets certain objectives under these uncertainties. Failure to find a robust design can lead to expensive consequences in terms of lost sales and high production costs. In order to find a robust design configuration, designers need accurate methods to model various uncertainties and efficient ways to search for feasible configurations. The dissertation work uses a multi-objective Genetic Algorithm (GA) and Petri net based modeling framework for a robust manufacturing system design. The Petri nets are coupled with Bayesian Model Averaging (BMA) to capture uncertainties associated with uncontrollable factors. BMA provides a unified framework to capture model, parameter and stochastic uncertainties associated with representation of various manufacturing activities. The BMA based approach overcomes limitations associated with uncertainty representation using classical methods presented in literature. Petri net based modeling is used to capture interactions among various subsystems, operation precedence and to identify bottleneck or conflicting situations. When coupled with Bayesian methods, Petri nets provide accurate assessment of manufacturing system dynamics and performance in presence of uncertainties. A multi-objective Genetic Algorithm (GA) is used to search manufacturing system designs, allowing designers to consider multiple objectives. The dissertation work provides algorithms for integrating Bayesian methods with Petri nets. Two manufacturing system design examples are presented to demonstrate the proposed approach. The results obtained using Bayesian methods are compared with classical methods and the effect of choosing different types of priors is evaluated. In summary, the dissertation provides a new, integrated Petri net based modeling framework coupled with BMA based approach for modeling and performance analysis of manufacturing system designs. The dissertation work allows designers to obtain accurate performance estimates of design configurations by considering model, parameter and stochastic uncertainties associated with representation of uncontrollable factors. Multi-objective GA coupled with Petri nets provide a flexible and time saving approach for searching and evaluating alternative manufacturing system designs.
42

Audio browsing of automaton-based hypertext

Ustun, Selen 30 September 2004 (has links)
With the wide-spread adoption of hypermedia systems and the World Wide Web (WWW) in particular, these systems have evolved from simple systems with only textual content to those that incorporate a large content base, which consists of a wide variety of document types. Also, with the increase in the number of users, there has grown a need for these systems to be accessible to a wider range of users. Consequently, the growth of the systems along with the number and variety of users require new presentation and navigation mechanisms for a wider audience. One of the new presentation methods is the audio-only presentation of hypertext content and this research proposes a novel solution to this problem for complex and dynamic systems. The hypothesis is that the proposed Audio Browser is an efficient tool for presenting hypertext in audio format, which will prove to be useful for several applications including browsers for visually-impaired and remote users. The Audio Browser provides audio-only browsing of contents in a Petri-based hypertext system called Context-Aware Trellis (caT). It uses a combination of synthesized speech and pre-recorded speech to allow its user to listen to contents of documents, follow links, and get information about the navigation process. It also has mechanisms for navigating within documents in order to allow users to view contents more quickly.
43

Augmenting Petri Nets to Model Health-Care Protocols

Whittaker, Sarah-Jane 28 September 2011 (has links)
An outbreak of an infectious illness can have a devastating impact on a population. Once confirmed, local health care organizations will attempt to reduce the spread of the disease by adopting a set of pre-defined guidelines. Modelling such a system presents a number of unique challenges: timing and probability constraints must be captured, scaling must be seamless and methods for analysis must be robust and efficient. To satisfy these requirements, an augmented form of Petri net known as a choice-point net is introduced in this thesis. In this data structure, timing is associated with event-based transitions that may fire multiple times to simulate the same event occurring several times in parallel. Events may result in several possible outcomes, or choices, each of which is given a probability of occurrence. A choice-point net may be scaled without requiring structural changes to the model and may be analyzed by unravelling it into a finite-state automaton representing (perhaps portions of) its behaviour. By translating questions about the protocol into the mathematical language of the net, recursive algorithms may then be employed to provide health-care professionals with answers to their questions. To demonstrate the expressiveness of choice-point nets, an actual, in-use protocol to control respiratory infection outbreaks in long-term care homes is modelled. Three similar abridged scenarios set in a small long-term care home are also modelled, analyzed and compared. / Thesis (Ph.D, Computing) -- Queen's University, 2011-09-27 21:23:16.13
44

Semi-formal verifcation of analog mixed signal systems using multi-domain modeling languages

Ramirez, Ricardo, active 2013 18 December 2013 (has links)
The verification of analog designs has been a challenging task for a few years now. Several approaches have been taken to tackle the main problem related to the complexity that such task presents to design and verification teams. The methodology presented in this document is based on the experiences and research work carried out by the Concordia University's Hardware Verification and the U. of Texas' IC systems design groups. The representation of complex systems where different interactions either mechanical or electrical take place requires an intricate set of mathematical descriptions which greatly vary according to the system under test. As a simple and very relevant example one can look at the integration of RF-MEMS as active elements in System-On-Chip architectures. In order to tackle such heterogeneous interaction for a consistent model, the use of stochastic hybrid models is described and implemented for very simple examples using high level modeling tools for a succinct and precise description. / text
45

Formal data flow diagrams (FDFD): a petri-netbased requirements specification language

Pong, Lih, 龐立 January 1985 (has links)
published_or_final_version / Computer Science / Master / Master of Philosophy
46

Model aware execution of composite web services

Zurowska, Karolina 15 August 2008
In the Service Oriented Architecture (SOA) services are computational elements that are published, discovered, consumed and aggregated across platform and organizational borders. The most commonly used technology to achieve SOA are Web Services (WSs). This is due to standardization process (WSDL, SOAP, UDDI standards) and a wide range of available infrastructure and tools. A very interesting aspect of WSs is their composeability. WSs can be easily aggregated into complex workflows, called Composite Web Services (CWSs). These compositions of services enable further reuse and in this way new, even more complex, systems are built.<p>Although there are many languages to specify or implement workflows, in the service-oriented systems BPEL (Business Process Execution Language) is widely accepted. With this language WSs are orchestrated and then executed with specialized engines (like ActiveBPEL). While being very popular, BPEL has certain limitations in monitoring and optimizing executions of CWSs. It is very hard with this language to adapt CWSs to changes in the performance of used WSs, and also to select the optimal way to execute a CWS. <p>To overcome the limitations of BPEL, I present a model-aware approach to execute CWSs. To achieve the model awareness the Coloured Petri Nets (CPN) formalism is considered as the basis of the execution of CWSs. This is different than other works in using formal methods in CWSs, which are restricted to purposes like verification or checking of correctness. Here the formal and unambiguous notation of the CPN is used to model, analyze, execute and monitor CWSs. Furthermore this approach to execute CWSs, which is based on the CPN formalism, is implemented in the model-aware middleware. It is also demonstrated how the middleware improves the performance and reliability of CWSs.
47

Model aware execution of composite web services

Zurowska, Karolina 15 August 2008 (has links)
In the Service Oriented Architecture (SOA) services are computational elements that are published, discovered, consumed and aggregated across platform and organizational borders. The most commonly used technology to achieve SOA are Web Services (WSs). This is due to standardization process (WSDL, SOAP, UDDI standards) and a wide range of available infrastructure and tools. A very interesting aspect of WSs is their composeability. WSs can be easily aggregated into complex workflows, called Composite Web Services (CWSs). These compositions of services enable further reuse and in this way new, even more complex, systems are built.<p>Although there are many languages to specify or implement workflows, in the service-oriented systems BPEL (Business Process Execution Language) is widely accepted. With this language WSs are orchestrated and then executed with specialized engines (like ActiveBPEL). While being very popular, BPEL has certain limitations in monitoring and optimizing executions of CWSs. It is very hard with this language to adapt CWSs to changes in the performance of used WSs, and also to select the optimal way to execute a CWS. <p>To overcome the limitations of BPEL, I present a model-aware approach to execute CWSs. To achieve the model awareness the Coloured Petri Nets (CPN) formalism is considered as the basis of the execution of CWSs. This is different than other works in using formal methods in CWSs, which are restricted to purposes like verification or checking of correctness. Here the formal and unambiguous notation of the CPN is used to model, analyze, execute and monitor CWSs. Furthermore this approach to execute CWSs, which is based on the CPN formalism, is implemented in the model-aware middleware. It is also demonstrated how the middleware improves the performance and reliability of CWSs.
48

Structural analysis and control of resource allocation systems using petri nets

Park, Jonghun 12 1900 (has links)
No description available.
49

[en] LANBRET-DMS - VOICE AND DATA INTEGRATED MESSAGE SYSTEM FOR LOCAL AREA NETWORK ENVIRONMENT / [pt] LANBRETA-DMS - UM SISTEMA INTEGRADO DE VOZ E DADOS PARA TROCA DE MENSAGENS EM UM AMBIENTE DE REDE LOCAL DE COMPUTADORES

NELSON RAMOS RIBEIRO 08 August 2007 (has links)
[pt] Este trabalho visa apresentar a integração de várias mídias de informação, como voz, texto, imagem e gráficos em um ambiente de troca de mensagens como a melhor resposta às solicitações de evolução de sistemas de troca de informação. Assim, será apresentado do LANBRETA-DMS (LAN-Based real Time Áudio-Data Message System), com ênfase na especificação de seus serviços, descrevendo-se a sintaxe do protocolo empregado e sua semântica, sendo esta última apresentada sob a forma de uma pseudo-linguagem de programação e sob a forma de redes de Petri. Uma implementação do LANBRETA-DMS, realizada nos laboratórios da PUC-RJ será também apresentada, seguindo- se proposições para extensões futuras. / [en] This work presents the integration of information media such as voice, text, imge and graphics in a message Exchange environment as the best answer to evolution of information Exchange systems. LANBRETA-DMS (LAN-Based Real Time Audio-Data Messege System) will be presented, with enphasis on the specification of its services, the protocol sintax used and its semantics, the latter being presented in a pseudo- programming language and in Petri Networks. An implementation of LANBRETA-DMS, made at PUC-RJ, will alos be introced, with some proposais for future extrensions following.
50

Testing concurrent systems through event structures / Test de systèmes concurrents à l'aide de structures d'événements

Ponce de León, Hernan 07 November 2014 (has links)
Les systèmes logiciels complexes sont omniprésents dans notre vie quotidienne. De ce fait, un dysfonctionnement peut occasionner aussi bien une simple gêne qu'un danger mettant en péril des vies humaines. Le test est l'une des techniques les plus répandues (en particulier dans l'industrie) pour détecter les erreurs d'un système. Lorsque le cahier des charges d'un système est décrit par une spécification formelle, le test de conformité est utilisé pour garantir un certain niveau de confiance dans la correction d'une implémentation de ce système - dans ce cadre, la relation de conformité formalise la notion de correction. Cette thèse se focalise sur le test de conformité pour les systèmes concurrents. Le test de conformité pour les systèmes concurrents utilise principalement des modèles qui interprètent la concurrence par des entrelacements. Néanmoins, cette approche souffre du problème de l'explosion de l'espace d'états et elle n'offre pas la possibilité de tester certaines propriétés de la spécification telle que l'indépendance entre actions. Pour ces raisons, nous utilisons une sémantique d'ordres partiels pour la concurrence. De plus, nous proposons une nouvelle sémantique qui permet à certaines actions concurrentes d'être entrelacées et en force d'autres à être implémentées indépendamment. Nous proposons une généralisation de la relation de conformité ioco où les spécifications sont des réseaux de Petri et leur sémantique d'ordres partiels est donnée par leur dépliage. Cette relation de conformité permet de préserver l'indépendance, dans l'implémentation, des actions spécifiées comme concurrentes. Nous présentons un cadre de test complet pour cette relation. Nous définissons la notion de cas de test globaux gérant la concurrence, réduisant ainsi non seulement la taille des cas de test mais aussi celle de la suite de tests. Nous montrons comment les cas de test globaux peuvent être construits à partir du dépliage de la spécification en s'appuyant sur une traduction SAT, et nous réduisons le problème de la sélection de tests à la sélection d'un préfixe fini de ce dépliage : nous définissons différents critères de sélection à partir de la notion d'événement limite (cut-off event). Enfin, en supposant que chaque processus d'un système distribué possède une horloge locale, nous montrons que la conformité globale peut être testée dans une architecture de test distribuée en utilisant seulement des testeurs locaux ne communiquant pas entre eux. / Complex systems are everywhere and are part of our daily life. As a consequence, their failures can range from being inconvenient to being life-threatening. Testing is one of the most widely accepted techniques (especially in industry) to detect errors in a system. When the requirements of the system are described by a formal specification, conformance testing is used to guarantee a certain degree of confidence in the correctness of an implementation- in this setting a conformance relation formalizes the notion of correctness. This thesis focuses on conformance testing for concurrent systems. Conformance testing for concurrent system has mainly focused on models that interpret concurrency by interleavings. This approach does not only suf- fer from the state space explosion problem, but also lacks the ability to test properties of the specification such as independence between actions. For such reasons, we focus not only on partial order semantics for concurrency, but also propose a new semantics that allows to interleave some actions while forcing others to be implemented as independent. We propose a generalization of the ioco conformance relation, based on Petri nets specifications and their partial order semantics given by their unfoldings, preserving thus independence of actions from the specification. A complete testing framework for this conformance relation is presented. We introduce the notion of global test cases which handle concurrency, reducing not only the size of the test case, but also the number of tests in the test suite. We show how global test cases can be constructed from the unfolding of the specification based on a SAT encoding and we reduce the test selection problem to select a finite prefix of such unfolding: different testing criteria are defined based on the notion of cut-off events. Finally, we show that assuming each process of a distributed system has a local clock, global conformance can be tested in a distributed testing architecture using only local testers without any communication.

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