The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Jan Philipp Wächter - One of the best experts on this subject based on the ideXlab platform.
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On the structure theory of partial Automaton semigroups
Semigroup Forum, 2020Co-Authors: Daniele D’angeli, Emanuele Rodaro, Jan Philipp WächterAbstract:We study Automaton structures, i.e., groups, monoids and semigroups generated by an Automaton, which, in this context, means a deterministic finite-state letter-to-letter transducer. Instead of considering only complete automata, we specifically investigate semigroups generated by partial automata. First, we show that the class of semigroups generated by partial automata coincides with the class of semigroups generated by complete automata if and only if the latter class is closed under removing a previously adjoined zero, which is an open problem in (complete) Automaton semigroup theory stated by Cain. Then, we show that no semidirect product (and, thus, also no direct product) of an arbitrary semigroup with a (non-trivial) subsemigroup of the free monogenic semigroup is an Automaton semigroup. Finally, we concentrate on inverse semigroups generated by invertible but partial automata, which we call Automaton-inverse semigroups, and show that any inverse Automaton semigroup can be generated by such an Automaton (showing that Automaton-inverse semigroups and inverse Automaton semigroups coincide).
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On the Complexity of the Word Problem for Automaton Semigroups and Automaton Groups
Advances in Applied Mathematics, 2017Co-Authors: Daniele D'angeli, Emanuele Rodaro, Jan Philipp WächterAbstract:In this paper, we study the word problem for Automaton semigroups and Automaton groups from a complexity point of view. As an intermediate concept between Automaton semigroups and Automaton groups, we introduce Automaton-inverse semigroups, which are generated by partial, yet invertible automata. We show that there is an Automaton-inverse semigroup and, thus, an Automaton semigroup with a PSPACE-complete word problem. We also show that there is an Automaton group for which the word problem with a single rational constraint is PSPACE-complete. Additionally, we provide simpler constructions for the uniform word problems of these classes. For the uniform word problem for Automaton groups (without rational constraints), we show NL-hardness. Finally, we investigate a question asked by Cain about a better upper bound for the length of a word on which two distinct elements of an Automaton semigroup must act differently.
Sylvain Lombardy - One of the best experts on this subject based on the ideXlab platform.
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The universal Automaton
2008Co-Authors: Sylvain Lombardy, Jacques SakarovitchAbstract:This paper is a survey on the universal Automaton, which is an Automaton canonically associated with every language. In the last forty years, many objects have been defined or studied, that are indeed closely related to the universal Automaton. We first show that every Automaton that accepts a given language has a morphic image which is a subAutomaton of the universal Automaton of this language. This property justifies the name "universal" that we have coined for this Automaton. The universal Automaton of a regular language is finite and can be effectively computed in the syntactic monoid or, more efficiently, from the minimal Automaton of the language. We describe the construction that leads to tight bounds on the size of the universal Automaton. Another outcome of the effective construction of the universal Automaton is the computation of a minimal NFA accepting a given language, or approximations of such a minimal NFA. From another point of view, the universal Automaton of a language is based on the factorisations of this language, and is thus involved in the problems of factorisations and approximations of languages. Last, but not least, we show how the universal Automaton gives an elegant solution to the star height problem for some classes of languages (pure-group or reversible languages).
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Logic and Automata - The universal Automaton.
2008Co-Authors: Sylvain Lombardy, Jacques SakarovitchAbstract:This paper is a survey on the universal Automaton, which is an Automaton canonically associated with every language. In the last forty years, many objects have been defined or studied, that are indeed closely related to the universal Automaton. We first show that every Automaton that accepts a given language has a morphic image which is a subAutomaton of the universal Automaton of this language. This property justifies the name “universal” that we have coined for this Automaton. The universal Automaton of a regular language is finite and can be effectively computed in the syntactic monoid or, more efficiently, from the minimal Automaton of the language. We describe the construction that leads to tight bounds on the size of the universal Automaton. Another outcome of the effective construction of the universal Automaton is the computation of a minimal NFA accepting a given language, or approximations of such a minimal NFA. From another point of view, the universal Automaton of a language is based on the factorisations of this language, and is thus involved in the problems of factorisations and approximations of languages. Last, but not least, we show how the universal Automaton gives an elegant solution to the star height problem for some classes of languages (pure-group or reversible languages). With every language is canonically associated an Automaton, called the universal Automaton of the language, which is finite whenever the language is regular. It is large, it is complex, it is complicated to compute, but it contains, hopefully, many interesting informations on the language. In the last forty years, it has been described a number of times, more or less explicitly,
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On the construction of reversible automata for reversible languages
2002Co-Authors: Sylvain LombardyAbstract:Reversible languages occur in many different domains. Although the decision for the membership of reversible languages was solved in 1992 by Pin, an effective construction of a reversible Automaton for a reversible language was still unknown. We give in this paper a method to compute a reversible Automaton from the minimal Automaton of a reversible language. With this intention, we use the universal Automaton of the language that can be obtained from the minimal Automaton and that contains an equivalent Automaton which is quasi-reversible. This quasi-reversible Automaton has nearly the same properties as a reversible one and can easily be turnes into a reversible Automaton.
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ICALP - On the Construction of Reversible Automata for Reversible Languages
Automata Languages and Programming, 2002Co-Authors: Sylvain LombardyAbstract:Reversible languages occur in many different domains. Although the decision for the membership of reversible languages was solved in 1992 by Pin, an effective construction of a reversible Automaton for a reversible language was still unknown. We give in this paper a method to compute a reversible Automaton from the minimal Automaton of a reversible language. With this intention, we use the universal Automaton of the language that can be obtained from the minimal Automaton and that contains an equivalent Automaton which is quasi-reversible. This quasi-reversible Automaton has nearly the same properties as a reversible one and can easily be turned into a reversible Automaton.
D H Stjohn - One of the best experts on this subject based on the ideXlab platform.
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investigation into the effect of nucleation parameters on grain formation during solidification using a cellular Automaton finite control volume method
Journal of Materials Research, 2008Co-Authors: Xiangdong Yao, Matthew S Dargusch, A K Dahle, C J Davidson, D H StjohnAbstract:A cellular automation (CA) model has successfully been used to model the development of microstructure of an aluminum alloy during solidification to produce detailed structure maps for the solidified alloys. More recently, the application of CA models to practical castings/solidification conditions has attracted increasing research interest. However, the determination of the calculation parameters of any model associated with nucleation is difficult. Accordingly, this work investigates the detailed effect of the six parameters of nucleation on microstructure formation and morphology as well as the grain size by cellular Automaton-finite control volume method (CAFVM). The nucleation parameters can be determined or estimated by comparing the calculated and experimental results, which enables a more practical prediction of the microstructure (morphology and grain size).
Péter Barkóczy - One of the best experts on this subject based on the ideXlab platform.
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Scaling Cellular Automaton Simulations of Short-Range Diffusion Processes
Materials Science Forum, 2012Co-Authors: Szilvia Gyöngyösi, Péter BarkóczyAbstract:By applying the cellular Automaton method the short-range diffusion processes in metals can be efficiently simulated. Several examples for the two-and three dimensional modeling of recrystallization and grain-coarsening are know at the literature. In some previous works, results have been performed concerning the two-dimensional, stochastic Automatons of grain-coarsening, recrystallization and allotropic transformation. In order to use these simulations also in technological processes, it is necessary to scale the results reached by the simulation. The primary aspect of adapting the Automaton in technological processes is the quick-operating simulation. The aim is to develop a most simplified, scalable cellular Automaton by which scaling can be efficiently performed.
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Simulation of Phase Transformations Driven by Short Range Diffusion by Cellular Automaton
Materials Science Forum, 2010Co-Authors: Szilvia Gyöngyösi, Anita Tóth, Péter BarkóczyAbstract:The same property of the phase transformations driven by short range diffusion (recrystallization, allotropic transformation, grain coarsening) is that the movements of the grain or the phase boundaries take place by atomic jumps through the boundaries. The probability (frequency) of these jumps depends on only on the energy state of the closenear neighborhood of the atoms. In the operation of cellular automata Consequently, only the closenear neighborhood of the cells is taken into account in the operation of the cellular Automaton. This similarity makes applicable the cellular Automaton applicable to simulate the aforementioned phase transformation processes. A condition (rule) of the movement of grain and phase boundaries is introduced, which makes it possible to simulate all the all mentioned phase transformation by the same Automatona.
Manuela Veloso - One of the best experts on this subject based on the ideXlab platform.
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Event-based automated refereeing for robot soccer
Autonomous Robots, 2017Co-Authors: Danny Zhu, Manuela VelosoAbstract:The RoboCup Small Size League (SSL) is a robot soccer game with robots that play on a customized field with overhead cameras. The majority of the research effort to date has been on the performance of the autonomous teams in aspects of motion planning and team strategy. However, another critical component of a robot game is the referee. In current SSL games, refereeing is done by humans, who use a “referee box” that passes their calls to the robots. In this work, we contribute an automated referee (autoref) for SSL games, towards enabling games to proceed with little or no human supervision. The goal is to move closer to the eventual full automation of complete games with real robots. The technical challenges include the clear definition of the rules of the game in terms of features to be extracted from the visual perception, temporal sequencing, and corresponding calls and game management. We provide a description of a game of SSL as it is relevant to an autoref, by categorizing the rules of the game and presenting the structure of a game as a hybrid Automaton. We then describe the complete autoref using a modular event-based architecture, following up on the Automaton as a guideline, to keep track of the state of a game and issue referee commands accordingly. We present the results of using our autoref to referee games on real robots, as well as a comparison of the events detected by the autoref to the calls made by a human referee during the real SSL games at RoboCup 2014.
