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Ferdinando Chiacchio - One of the best experts on this subject based on the ideXlab platform.
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shyftoo an object oriented monte carlo simulation library for the modeling of stochastic hybrid fault Tree Automaton
Expert Systems With Applications, 2020Co-Authors: Ferdinando Chiacchio, Jose Ignacio Aizpurua, Lucio Compagno, Diego DursoAbstract:Abstract Dependability assessment is a crucial activity to ensure the correct operation of complex systems. The output of dependability assessment activities include the quantification of reliability, availability, maintenance and safety related metrics. These metrics can assist in the identification of the system weak points or in the conception of mitigation strategies to increase the system dependability level. The development of advanced computer-aided methodologies to support dependability assessment activities is essential to automate and reduce the efforts implied by this process and similarly, the development of accurate dependability assessment methods is very important to increase the quality of the results. In this context, it is possible to identify different contributions that improve the dependability assessment through general-purpose modeling methodologies. However, existing solutions are ad-hoc applications specified with low-level stochastic formalisms and this complicates their adoption in the industry. Accordingly, this paper presents Stochastic Hybrid Fault Tree Automaton (SHyFTA) based simulation algorithm that allows the accurate dependability analysis of repairable multi-state systems. SHyFTA integrates the stochastic and deterministic operation of the system under study as well as their interactions. The algorithm is formalized through an object-oriented software architecture, which is developed as a software library for the modeling and simulation of repairable SHyFTA models. Following the proposed architecture, a Matlab® implementation of this library, SHyFTOO, has been developed and validated with a thorough test campaign. In order to provide a guideline to the end-users and show the potential of the SHyFTOO library, the case study of a feed-water pumping system is implemented in detail and it is used to evaluate different preventive maintenance policies. The SHyFTOO library can open the way to further investigations that address the interactions between the failure behavior and the functional operation of a system and their combined effect on system dependability.
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dynamic performance evaluation of photovoltaic power plant by stochastic hybrid fault Tree Automaton model
Energies, 2018Co-Authors: Ferdinando Chiacchio, Jose Ignacio Aizpurua, Diego Durso, Fabio Famoso, S Brusca, Luca CedolaAbstract:The contribution of renewable energies to the reduction of the impact of fossil fuels sources and especially energy supply in remote areas has occupied a role more and more important during last decades. The estimation of renewable power plants performances by means of deterministic models is usually limited by the innate variability of the energy resources. The accuracy of energy production forecasting results may be inadequate. An accurate feasibility analysis requires taking into account the randomness of the primary resource operations and the effect of component failures in the energy production process. This paper treats a novel approach to the estimation of energy production in a real photovoltaic power plant by means of dynamic reliability analysis based on Stochastic Hybrid Fault Tree Automaton (SHyFTA). The comparison between real data, deterministic model and SHyFTA model confirm how the latter better estimate energy production than deterministic model.
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shyfta a stochastic hybrid fault Tree Automaton for the modelling and simulation of dynamic reliability problems
Expert Systems With Applications, 2016Co-Authors: Ferdinando Chiacchio, Lucio Compagno, Diego Durso, Marzio Pennisi, Francesco Pappalardo, Gabriele MannoAbstract:Discussion about the state of the art of expert systems and reliability assessment.Formalisation of the Stochastic Hybrid Fault Tree Automaton modelling technique.Conception of Hybrid Basic Events.Experimental Comparison of DFT and SHyFTA model for an industrial case study.Implementation of the SHyFTA in Simulink using MatCarloRE library. Reliability assessment of industrial processes is traditionally performed with RAMS techniques. Such techniques are static in nature because they are unable to consider the multi-state operational and failure nature of systems and the dynamic variations of the environment in which they operate.Stochastic Hybrid Automaton appears to overcome this weakness coupling a deterministic and a stochastic process and integrating the features of a dynamic system with the concepts of dynamic reliability.At the state of the art, no attempts to enhance a formal RAMS technique with dynamic reliability has been tried, nor a computer-aided tool that plays as expert system has been coded yet.The aim of this paper is to fill this gap with a simulation formalism and a modelling tool able to combine the Dynamic Fault Tree technique and the Stochastic Hybrid Automaton within the Simulink environment. To this aim the MatCarloRE toolbox was adapted to interact with a Simulink dynamic system. The resulting assembly represents an important step ahead for the delivering of a user-friendly computer-aided tool for the dynamic reliability.
Hans Zantema - One of the best experts on this subject based on the ideXlab platform.
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on Tree automata that certify termination of left linear term rewriting systems
Information & Computation, 2007Co-Authors: Alfons Geser, Dieter Hofbauer, Johannes Waldmann, Hans ZantemaAbstract:We present a new method for automatically proving termination of left-linear term rewriting systems on a given regular language of terms. It is a generalization of the match bound method for string rewriting. To prove that a term rewriting system terminates we first construct an enriched system over a new signature that simulates the original derivations. The enriched system is an infinite system over an infinite signature, but it is locally terminating: every restriction of the enriched system to a finite signature is terminating. We then construct iteratively a finite Tree Automaton that accepts the enriched given regular language and is closed under rewriting modulo the enriched system. If this procedure stops, then the enriched system is compact: every enriched derivation involves only a finite signature. Therefore, the original system terminates. We present two methods to construct the enrichment: roof heights for left-linear systems, and match heights for linear systems. For linear systems, the method is strengthened further by a forward closure construction. Using these methods, we give examples for automated termination proofs that cannot be obtained by standard methods.
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on Tree automata that certify termination of left linear term rewriting systems
Rewriting Techniques and Applications, 2005Co-Authors: Alfons Geser, Dieter Hofbauer, Johannes Waldmann, Hans ZantemaAbstract:We present a new method for proving termination of term rewriting systems automatically. It is a generalization of the match bound method for string rewriting. To prove that a term rewriting system terminates on a given regular language of terms, we first construct an enriched system over a new signature that simulates the original derivations. The enriched system is an infinite system over an infinite signature, but it is locally terminating: every restriction of the enriched system to a finite signature is terminating. We then construct iteratively a finite Tree Automaton that accepts the enriched given regular language and is closed under rewriting modulo the enriched system. If this procedure stops, then the enriched system is compact: every enriched derivation involves only a finite signature. Therefore, the original system terminates. We present three methods to construct the enrichment: top heights, roof heights, and match heights. Top and roof heights work for left-linear systems, while match heights give a powerful method for linear systems. For linear systems, the method is strengthened further by a forward closure construction. Using these methods, we give examples for automated termination proofs that cannot be obtained by standard methods.
Diego Durso - One of the best experts on this subject based on the ideXlab platform.
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shyftoo an object oriented monte carlo simulation library for the modeling of stochastic hybrid fault Tree Automaton
Expert Systems With Applications, 2020Co-Authors: Ferdinando Chiacchio, Jose Ignacio Aizpurua, Lucio Compagno, Diego DursoAbstract:Abstract Dependability assessment is a crucial activity to ensure the correct operation of complex systems. The output of dependability assessment activities include the quantification of reliability, availability, maintenance and safety related metrics. These metrics can assist in the identification of the system weak points or in the conception of mitigation strategies to increase the system dependability level. The development of advanced computer-aided methodologies to support dependability assessment activities is essential to automate and reduce the efforts implied by this process and similarly, the development of accurate dependability assessment methods is very important to increase the quality of the results. In this context, it is possible to identify different contributions that improve the dependability assessment through general-purpose modeling methodologies. However, existing solutions are ad-hoc applications specified with low-level stochastic formalisms and this complicates their adoption in the industry. Accordingly, this paper presents Stochastic Hybrid Fault Tree Automaton (SHyFTA) based simulation algorithm that allows the accurate dependability analysis of repairable multi-state systems. SHyFTA integrates the stochastic and deterministic operation of the system under study as well as their interactions. The algorithm is formalized through an object-oriented software architecture, which is developed as a software library for the modeling and simulation of repairable SHyFTA models. Following the proposed architecture, a Matlab® implementation of this library, SHyFTOO, has been developed and validated with a thorough test campaign. In order to provide a guideline to the end-users and show the potential of the SHyFTOO library, the case study of a feed-water pumping system is implemented in detail and it is used to evaluate different preventive maintenance policies. The SHyFTOO library can open the way to further investigations that address the interactions between the failure behavior and the functional operation of a system and their combined effect on system dependability.
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dynamic performance evaluation of photovoltaic power plant by stochastic hybrid fault Tree Automaton model
Energies, 2018Co-Authors: Ferdinando Chiacchio, Jose Ignacio Aizpurua, Diego Durso, Fabio Famoso, S Brusca, Luca CedolaAbstract:The contribution of renewable energies to the reduction of the impact of fossil fuels sources and especially energy supply in remote areas has occupied a role more and more important during last decades. The estimation of renewable power plants performances by means of deterministic models is usually limited by the innate variability of the energy resources. The accuracy of energy production forecasting results may be inadequate. An accurate feasibility analysis requires taking into account the randomness of the primary resource operations and the effect of component failures in the energy production process. This paper treats a novel approach to the estimation of energy production in a real photovoltaic power plant by means of dynamic reliability analysis based on Stochastic Hybrid Fault Tree Automaton (SHyFTA). The comparison between real data, deterministic model and SHyFTA model confirm how the latter better estimate energy production than deterministic model.
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shyfta a stochastic hybrid fault Tree Automaton for the modelling and simulation of dynamic reliability problems
Expert Systems With Applications, 2016Co-Authors: Ferdinando Chiacchio, Lucio Compagno, Diego Durso, Marzio Pennisi, Francesco Pappalardo, Gabriele MannoAbstract:Discussion about the state of the art of expert systems and reliability assessment.Formalisation of the Stochastic Hybrid Fault Tree Automaton modelling technique.Conception of Hybrid Basic Events.Experimental Comparison of DFT and SHyFTA model for an industrial case study.Implementation of the SHyFTA in Simulink using MatCarloRE library. Reliability assessment of industrial processes is traditionally performed with RAMS techniques. Such techniques are static in nature because they are unable to consider the multi-state operational and failure nature of systems and the dynamic variations of the environment in which they operate.Stochastic Hybrid Automaton appears to overcome this weakness coupling a deterministic and a stochastic process and integrating the features of a dynamic system with the concepts of dynamic reliability.At the state of the art, no attempts to enhance a formal RAMS technique with dynamic reliability has been tried, nor a computer-aided tool that plays as expert system has been coded yet.The aim of this paper is to fill this gap with a simulation formalism and a modelling tool able to combine the Dynamic Fault Tree technique and the Stochastic Hybrid Automaton within the Simulink environment. To this aim the MatCarloRE toolbox was adapted to interact with a Simulink dynamic system. The resulting assembly represents an important step ahead for the delivering of a user-friendly computer-aided tool for the dynamic reliability.
Rafael Penaloza - One of the best experts on this subject based on the ideXlab platform.
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automata based axiom pinpointing
Journal of Automated Reasoning, 2010Co-Authors: Franz Baader, Rafael PenalozaAbstract:Axiom pinpointing has been introduced in description logics (DL) to help the user understand the reasons why consequences hold by computing minimal subsets of the knowledge base that have the consequence in question (MinA). Most of the pinpointing algorithms described in the DL literature are obtained as extensions of tableau-based reasoning algorithms for computing consequences from DL knowledge bases. In this paper, we show that automata-based algorithms for reasoning in DLs and other logics can also be extended to pinpointing algorithms. The idea is that the Tree Automaton constructed by the automata-based approach can be transformed into a weighted Tree Automaton whose so-called behaviour yields a pinpointing formula, i.e., a monotone Boolean formula whose minimal valuations correspond to the MinAs. We also develop an approach for computing the behaviour of a given weighted Tree Automaton. We use the DL $\mathcal{SI}$ as well as Linear Temporal Logic (LTL) to illustrate our new pinpointing approach.
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automata based axiom pinpointing
International Joint Conference on Automated Reasoning, 2008Co-Authors: Franz Baader, Rafael PenalozaAbstract:Axiom pinpointing has been introduced in description logics (DL) to help the user understand the reasons why consequences hold by computing minimal subsets of the knowledge base that have the consequence in question (MinA). Most of the pinpointing algorithms described in the DL literature are obtained as extensions of tableau-based reasoning algorithms for computing consequences from DL knowledge bases. In this paper, we show that automata-based algorithms for reasoning in DLs can also be extended to pinpointing algorithms. The idea is that the Tree Automaton constructed by the automata-based approach can be transformed into a weighted Tree Automaton whose so-called behaviour yields a pinpointing formula, i.e., a monotone Boolean formula whose minimal valuations correspond to the MinAs. We also develop an approach for computing the behaviour of a given weighted Tree Automaton.
Alfons Geser - One of the best experts on this subject based on the ideXlab platform.
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on Tree automata that certify termination of left linear term rewriting systems
Information & Computation, 2007Co-Authors: Alfons Geser, Dieter Hofbauer, Johannes Waldmann, Hans ZantemaAbstract:We present a new method for automatically proving termination of left-linear term rewriting systems on a given regular language of terms. It is a generalization of the match bound method for string rewriting. To prove that a term rewriting system terminates we first construct an enriched system over a new signature that simulates the original derivations. The enriched system is an infinite system over an infinite signature, but it is locally terminating: every restriction of the enriched system to a finite signature is terminating. We then construct iteratively a finite Tree Automaton that accepts the enriched given regular language and is closed under rewriting modulo the enriched system. If this procedure stops, then the enriched system is compact: every enriched derivation involves only a finite signature. Therefore, the original system terminates. We present two methods to construct the enrichment: roof heights for left-linear systems, and match heights for linear systems. For linear systems, the method is strengthened further by a forward closure construction. Using these methods, we give examples for automated termination proofs that cannot be obtained by standard methods.
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on Tree automata that certify termination of left linear term rewriting systems
Rewriting Techniques and Applications, 2005Co-Authors: Alfons Geser, Dieter Hofbauer, Johannes Waldmann, Hans ZantemaAbstract:We present a new method for proving termination of term rewriting systems automatically. It is a generalization of the match bound method for string rewriting. To prove that a term rewriting system terminates on a given regular language of terms, we first construct an enriched system over a new signature that simulates the original derivations. The enriched system is an infinite system over an infinite signature, but it is locally terminating: every restriction of the enriched system to a finite signature is terminating. We then construct iteratively a finite Tree Automaton that accepts the enriched given regular language and is closed under rewriting modulo the enriched system. If this procedure stops, then the enriched system is compact: every enriched derivation involves only a finite signature. Therefore, the original system terminates. We present three methods to construct the enrichment: top heights, roof heights, and match heights. Top and roof heights work for left-linear systems, while match heights give a powerful method for linear systems. For linear systems, the method is strengthened further by a forward closure construction. Using these methods, we give examples for automated termination proofs that cannot be obtained by standard methods.
