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Search Results: 1 - 10 of 55883 matches for " Paul van Tilburg "
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Reactive Turing Machines
Jos C. M. Baeten,Bas Luttik,Paul van Tilburg
Computer Science , 2011,
Abstract: We propose reactive Turing machines (RTMs), extending classical Turing machines with a process-theoretical notion of interaction, and use it to define a notion of executable transition system. We show that every computable transition system with a bounded branching degree is simulated modulo divergence-preserving branching bisimilarity by an RTM, and that every effective transition system is simulated modulo the variant of branching bisimilarity that does not require divergence preservation. We conclude from these results that the parallel composition of (communicating) RTMs can be simulated by a single RTM. We prove that there exist universal RTMs modulo branching bisimilarity, but these essentially employ divergence to be able to simulate an RTM of arbitrary branching degree. We also prove that modulo divergence-preserving branching bisimilarity there are RTMs that are universal up to their own branching degree. Finally, we establish a correspondence between executability and finite definability in a simple process calculus.
Expressiveness modulo Bisimilarity of Regular Expressions with Parallel Composition (Extended Abstract)
Jos C. M. Baeten,Bas Luttik,Tim Muller,Paul van Tilburg
Electronic Proceedings in Theoretical Computer Science , 2010, DOI: 10.4204/eptcs.41.1
Abstract: The languages accepted by finite automata are precisely the languages denoted by regular expressions. In contrast, finite automata may exhibit behaviours that cannot be described by regular expressions up to bisimilarity. In this paper, we consider extensions of the theory of regular expressions with various forms of parallel composition and study the effect on expressiveness. First we prove that adding pure interleaving to the theory of regular expressions strictly increases its expressiveness up to bisimilarity. Then, we prove that replacing the operation for pure interleaving by ACP-style parallel composition gives a further increase in expressiveness. Finally, we prove that the theory of regular expressions with ACP-style parallel composition and encapsulation is expressive enough to express all finite automata up to bisimilarity. Our results extend the expressiveness results obtained by Bergstra, Bethke and Ponse for process algebras with (the binary variant of) Kleene's star operation.
Expressiveness modulo Bisimilarity of Regular Expressions with Parallel Composition (Extended Abstract)
Jos C. M. Baeten,Bas Luttik,Tim Muller,Paul van Tilburg
Computer Science , 2010, DOI: 10.1017/S0960129514000309
Abstract: The languages accepted by finite automata are precisely the languages denoted by regular expressions. In contrast, finite automata may exhibit behaviours that cannot be described by regular expressions up to bisimilarity. In this paper, we consider extensions of the theory of regular expressions with various forms of parallel composition and study the effect on expressiveness. First we prove that adding pure interleaving to the theory of regular expressions strictly increases its expressiveness up to bisimilarity. Then, we prove that replacing the operation for pure interleaving by ACP-style parallel composition gives a further increase in expressiveness. Finally, we prove that the theory of regular expressions with ACP-style parallel composition and encapsulation is expressive enough to express all finite automata up to bisimilarity. Our results extend the expressiveness results obtained by Bergstra, Bethke and Ponse for process algebras with (the binary variant of) Kleene's star operation.
Een heilzame vergissing. Het urine- en fecali nprobleem van Grieken tot Gouwenaars
Cornelis van Tilburg
Studium : Tijdschrift voor Wetenschaps- en Universiteits-Geschiedenis , 2012,
Abstract: Nowadays, faeces and urine are considered as noxious and unhealthy. In ancient times, however, urine and excrements were seen as undangerous and even useful; urine for textile production and excrements for agriculture. The Romans constructed sewers like the Cloaca Maxima, in the first place to remove (rain)water and drainage. Only later, toilets were connected to these sewers to remove the smell of urine and excrements. The idea that sewers were constructed with the specific aim of removing urine and excrements is therefore no longer valid, but the memory of this function of the (Roman) sewers was maintained in the Middle Ages. From the Renaissance onwards, city planners developed their ‘ideal cities’. In these cities, there was no place for the dirty smell of urine and excrements, so subterranean sewers had to be constructed. Yet such ideas proved difficult to implement in the Dutch context. The Dutch engineer Simon Stevin realised that the situation described by the ancient and Renaissance sources did not offer a solution for the problems in Dutch cities, with standing water in canals and without natural drainage. Moreover, in this period there was not yet an awareness of the relation between the presence and smell of urine and excrements, on the one hand, and hygiene and public health on the other. Awareness of this relation came not earlier than the 18th century. The German physician Johann Peter Frank argued in favour of diminishing the bad smell by means of filling up canals; the city physician Willem Frederik Büchner was confronted with the extremely unhealthy situation in the typical Dutch city of Gouda. But their political influence was small. Only at the end of the 19th century, the construction of sewers began in Dutch cities, thus – improving health conditions.
G. Hekma, Goed verkeerd. Een geschiedenis van homoseksuele mannen en lesbische vrouwen in Nederland
M. van Tilburg
BMGN : Low Countries Historical Review , 1992,
Abstract:
H. Peeters, L. Dresen-Coenders, T. Brandenbarg, Vijf eeuwen gezinsleven. Liefde, huwelijk en opvoeding in Nederland
M. van Tilburg
BMGN : Low Countries Historical Review , 1991,
Abstract:
G. Hekma, H. Roodenburg, Soete minne en helsche boosheit. Seksuele voorstellingen in Nederland, 1300-1850
M. van Tilburg
BMGN : Low Countries Historical Review , 1990,
Abstract:
Ageing societies and the welfare state: where the inter-generational contract is not breached
Kathrin Komp,Theo van Tilburg
International Journal of Ageing and Later Life , 2010,
Abstract:
Maximizing Boosted Top Identification by Minimizing N-subjettiness
Jesse Thaler,Ken Van Tilburg
Physics , 2011, DOI: 10.1007/JHEP02(2012)093
Abstract: N-subjettiness is a jet shape designed to identify boosted hadronic objects such as top quarks. Given N subjet axes within a jet, N-subjettiness sums the angular distances of jet constituents to their nearest subjet axis. Here, we generalize and improve on N-subjettiness by minimizing over all possible subjet directions, using a new variant of the k-means clustering algorithm. On boosted top benchmark samples from the BOOST2010 workshop, we demonstrate that a simple cut on the 3-subjettiness to 2-subjettiness ratio yields 20% (50%) tagging efficiency for a 0.23% (4.1%) fake rate, making N-subjettiness a highly effective boosted top tagger. N-subjettiness can be modified by adjusting an angular weighting exponent, and we find that the jet broadening measure is preferred for boosted top searches. We also explore multivariate techniques, and show that additional improvements are possible using a modified Fisher discriminant. Finally, we briefly mention how our minimization procedure can be extended to the entire event, allowing the event shape N-jettiness to act as a fixed N cone jet algorithm.
Identifying Boosted Objects with N-subjettiness
Jesse Thaler,Ken Van Tilburg
Physics , 2010, DOI: 10.1007/JHEP03(2011)015
Abstract: We introduce a new jet shape -- N-subjettiness -- designed to identify boosted hadronically-decaying objects like electroweak bosons and top quarks. Combined with a jet invariant mass cut, N-subjettiness is an effective discriminating variable for tagging boosted objects and rejecting the background of QCD jets with large invariant mass. In efficiency studies of boosted W bosons and top quarks, we find tagging efficiencies of 30% are achievable with fake rates of 1%. We also consider the discovery potential for new heavy resonances that decay to pairs of boosted objects, and find significant improvements are possible using N-subjettiness. In this way, N-subjettiness combines the advantages of jet shapes with the discriminating power seen in previous jet substructure algorithms.
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