Wyniki wyszukiwania - BazTech

1

Factors Influencing Essential Hypertension and Cardiovascular Disease Modeled and Analyzed using Stochastic Petri Nets

Formanowicz D., Rybarczyk A., Formanowicz P.

Fundamenta Informaticae

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2018

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Vol. 160, nr 1/2

143--165

EN

Essential hypertension is the world’s most prevalent cardiovascular disorder, however, its etiology remains poorly understood, making it difficult to study. The evidence suggests that inflammation can lead to the development of hypertension and that oxidative stress and endothelial dysfunction are involved in the inflammatory cascade. In this work, to investigate the influence of these factors on the essential hypertension development, a stochastic Petri net model has been built and then analyzed. To obtain appropriate initial marking and kinetic rate constants for the model, a simple heuristic has been developed. The application of this variant of Petri nets allowed for taking into account some important dependencies present in the modeled system what would be impossible in the case of qualitative models. This has enabled for an in-depth analysis of the studied phenomenon and a validation of biological conclusions previously obtained on the basis of a qualitative model.

2

Discrete-Time Leap Method for Stochastic Simulation

Rohr C.

Fundamenta Informaticae

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2018

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Vol. 160, nr 1/2

181--198

EN

We present an approach to improve the efficiency of stochastic simulation for large and dense biochemical reaction networks. We use stochastic Petri nets as modelling framework, but the proposed simulation approach is not limited to Petri net representations. The underlying continuous-time Markov chain (CTMC) is converted to an equivalent discrete-time Markov chain (DTMC); this itself gains no efficiency. We improve the efficiency via discrete-time leaps, even though this results in an approximate method. The discrete-time leaps are done by applying the maximum firing rule; this reduces drastically the number of steps. The presented algorithm is implemented in our modelling and simulation tool Snoopy, as well as in our advanced analysis and model checking tool MARCIE. We demonstrate the approach on models of different sizes and complexities.

3

Intermittent fault’s parameter framework and stochastic petri net based formalization model

Shen Q., Qiu J., Liu G., Lv K.

Eksploatacja i Niezawodność

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2016

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Vol. 18, no. 2

210--217

EN

The intermittent fault widely exists in many products and brings high safety risk and maintenance cost. At present there are some different opinions on the notion of intermittent fault and there is no comprehensive parameter framework for fully describing intermittent fault. Also the formalization model which can mathematically describe intermittent fault hasn’t been constructed. In this paper, the conception of intermittent fault is discussed. A new definition of intermittent fault is put forward. Then the intermittent fault’s parameter framework is presented. After that, the Stochastic Petri Net (SPN) based formalization model for intermittent fault is constructed. Finally an application of the SPN formalization model is shown. The parameters for intermittent fault are computed based on the proposed model and a case study is presented. The result shows the validity of the model. The model could assist the further research such as intermittent fault diagnosis and prognostic of remaining life.

PL

Niezdatność przejściowa charakteryzuje wiele produktów i pociąga za sobą wysokie zagrożenie bezpieczeństwa oraz wysokie koszty eksploatacji. Obecnie istnieje wiele poglądów na temat pojęcia niezdatności przejściowej; nie stworzono jednak kompleksowego modelu parametrycznego pozwalającego w pełni opisać zjawisko niezdatności przejściowej. Nie skonstuowano także modelu formalnego, za pomocą którego można by opisać niezdatność przejściową w kategoriach matematycznych. W pracy omówiono koncepcję niezdatności przejściowej. Zaproponowano nową definicję tego pojęcia a następnie przedstawiono model parametryczny niezdatności przejściowej. Skonstruowano także model formalny niezdatności przejściowej oparty na stochastycznej sieci Petriego (SPN). Wreszcie, pokazano zastosowanie formalizacji SPN. Na podstawie zaproponowanego modelu obliczono parametry dla niezdatności przejściowej. Przedstawiono także studium przypadku. Otrzymane wyniki potwierdzają wiarygodność modelu. Opracowany model może być pomocny w dalszych badaniach dotyczących problemów, takich jak diagnozowanie niezdatności przejściowej czy prognozowanie pozostałego okresu użytkowania produktu.

4

Stochastic Petri Box Calculus with Discrete Time

Tarasyuk I.V.

Fundamenta Informaticae

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2007

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Vol. 76, nr 1-2

189-218

EN

In the last decades, a number of stochastic enrichments of process algebras was constructed to allow one for specification of stochastic processes within the well-developed framework of algebraic calculi. In [], a continuous time stochastic extension of finite Petri box calculus (PBC) was proposed called sPBC. The algebra sPBC has interleaving semantics due to the properties of continuous time distributions. At the same time, PBC has step semantics, and it could be natural to propose its concurrent stochastic enrichment. We construct a discrete time stochastic extension dtsPBC of finite PBC. A step operational semantics is defined in terms of labeled transition systems based on action and inaction rules. A denotational semantics is defined in terms of a subclass of labeled discrete time stochastic Petri nets (LDTSPNs) called discrete time stochastic Petri boxes (dts-boxes). A consistency of both semantics is demonstrated. In addition, we define a variety of probabilistic equivalences that allow one to identify stochastic processes with similar behaviour which are differentiated by too strict notion of the semantic equivalence. The interrelations of all the introduced equivalences are investigated.

5

Distributed simulation of stochastic Petri nets

Koniewski R.

Przegląd Elektrotechniczny

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2005

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R. 81, nr 6

19-21

EN

Petri nets are otten used to simulate different types of systems. The simplest way on accelerate this process is threading, but creation of proper algorithm is not easy. The biggest problem is to synchronize all the threads in optimal way. This article presents an algorithm which does not require global synchronization, during whole simulation process.

PL

Sieci Petriego często używane są do symulacji systemów różnego typu. Najprostszą metodą przyspieszenia tego procesu jest jego rozproszenie, ale stworzenie odpowiedniego algorytmu nie jest proste. Największym problemem jest synchronizacja wszystkich wątków w optymalny sposób. Przedstawiony artykuł prezentuje algorytm, który nie wymaga globalnej synchronizacji, podczas całego procesu symulacyjnego.