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Search Results: 1 - 10 of 54063 matches for " David Carter "
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Improving Language Models by Clustering Training Sentences
David Carter
Computer Science , 1994,
Abstract: Many of the kinds of language model used in speech understanding suffer from imperfect modeling of intra-sentential contextual influences. I argue that this problem can be addressed by clustering the sentences in a training corpus automatically into subcorpora on the criterion of entropy reduction, and calculating separate language model parameters for each cluster. This kind of clustering offers a way to represent important contextual effects and can therefore significantly improve the performance of a model. It also offers a reasonably automatic means to gather evidence on whether a more complex, context-sensitive model using the same general kind of linguistic information is likely to reward the effort that would be required to develop it: if clustering improves the performance of a model, this proves the existence of further context dependencies, not exploited by the unclustered model. As evidence for these claims, I present results showing that clustering improves some models but not others for the ATIS domain. These results are consistent with other findings for such models, suggesting that the existence or otherwise of an improvement brought about by clustering is indeed a good pointer to whether it is worth developing further the unclustered model.
Rapid Development of Morphological Descriptions for Full Language Processing Systems
David Carter
Computer Science , 1995,
Abstract: I describe a compiler and development environment for feature-augmented two-level morphology rules integrated into a full NLP system. The compiler is optimized for a class of languages including many or most European ones, and for rapid development and debugging of descriptions of new languages. The key design decision is to compose morphophonological and morphosyntactic information, but not the lexicon, when compiling the description. This results in typical compilation times of about a minute, and has allowed a reasonably full, feature-based description of French inflectional morphology to be developed in about a month by a linguist new to the system.
The TreeBanker: a Tool for Supervised Training of Parsed Corpora
David Carter
Computer Science , 1997,
Abstract: I describe the TreeBanker, a graphical tool for the supervised training involved in domain customization of the disambiguation component of a speech- or language-understanding system. The TreeBanker presents a user, who need not be a system expert, with a range of properties that distinguish competing analyses for an utterance and that are relatively easy to judge. This allows training on a corpus to be completed in far less time, and with far less expertise, than would be needed if analyses were inspected directly: it becomes possible for a corpus of about 20,000 sentences of the complexity of those in the ATIS corpus to be judged in around three weeks of work by a linguistically aware non-expert.
Vertebrate gene finding from multiple-species alignments using a two-level strategy
David Carter, Richard Durbin
Genome Biology , 2006, DOI: 10.1186/gb-2006-7-s1-s6
Abstract: We describe DOGFISH, a vertebrate gene finder consisting of a cleanly separated site classifier and structure predictor. The classifier scores potential splice sites and other features, using sequence alignments between multiple vertebrate species, while the structure predictor hypothesizes coding transcripts by combining these scores using a simple model of gene structure. This also identifies and assigns confidence scores to possible additional exons. Performance is assessed on the ENCODE regions. We predict transcripts and exons across the whole human genome, and identify over 10,000 high confidence new coding exons not in the Ensembl gene set.We present a practical multiple species gene prediction method. Accuracy improves as additional species, up to at least eight, are introduced. The novel predictions of the whole-genome scan should support efficient experimental verification.Gene finding can usefully be viewed as a two-level task. At the lower or local level there is a classification task: one of assigning probability estimates to potential features such as splice sites and coding start and stop sites on the basis of sequence information associated with each potential feature. At the higher or global level, on the other hand, we have a structure-building task: finding the most probable way(s) to combine potential features into exons, transcripts and genes. Classification and structure building are very different tasks, and although a gene finder can be based on a single formalism, such as hidden Markov models (HMMs) [1,2], there is no reason to assume that the same technique will be optimal for both tasks. Although HMMs seem to offer a good basis for structure building, they impose independence assumptions that are not particularly well suited to feature classification; formalisms such as neural networks [3,4], maximum entropy modeling [5], Bayesian networks [6-8], support vector machines [9-11] and relevance vector machines (RVMs) [12-14] provide alternativ
Kalb-Ramond coupled vortex fibration model for relativistic superfluid dynamics
Brandon Carter,David Langlois
Physics , 1996, DOI: 10.1016/0550-3213(95)00425-R
Abstract: The macroscopic dynamics of a rotating superfluid deviates from that of a simple perfect fluid due to the effect of vorticity quantisation, which gives rise to a substructure of cosmic string type line defects that results in a local anisotropy whereby the effective average pressure in the direction of the vortex lines is reduced below its value in lateral directions. Whereas previous descriptions of this effect have been restricted to a non-relativistic framework that is adequate for the treatment of liquid helium in a laboratory context, the present work provides a fully relativistic description of the kind required for application to rotating neutron star models. To start with, the general category of vortex fibration models needed for this purpose is set up on the basis of a Kalb-Ramond type variational principle. The appropriate specification of the particular model to be chosen within this category will ultimately be governed by the conclusions of microscopic investigations that have not yet been completed, but the results available so far suggest that a uniquely simple kind of model with an elegant dilatonic formulation should be tentatively adopted as a provisional choice so long as there is no indication that a more complicated alternative is needed.
Explicit Relativistic Vortex Solutions for Cool Two-Constituent Superfluid Dynamics
Brandon Carter,David Langlois
Physics , 1995, DOI: 10.1103/PhysRevD.52.4640
Abstract: We give a class of explicit solutions for the stationary and cylindrically symmetric vortex configurations for a ``cool'' two-component superfluid (i.e. superfluid with an ideal gas of phonons). Each solution is characterized only by a set of (true) constants of integration. We then compute the effective asymptotic contribution of the vortex to the stress energy tensor by comparison with a uniform reference state without vortex.
The Equation of State for Cool Relativistic Two-Constituent Superfluid Dynamics
Brandon Carter,David Langlois
Physics , 1995, DOI: 10.1103/PhysRevD.51.5855
Abstract: The natural relativistic generalisation of Landau's two constituent superfluid theory can be formulated in terms of a Lagrangian $L$ that is given as a function of the entropy current 4-vector $s^\rho$ and the gradient $\nabla\varphi$ of the superfluid phase scalar. It is shown that in the ``cool" regime, for which the entropy is attributable just to phonons (not rotons), the Lagrangian function $L(\vec s, \nabla\varphi)$ is given by an expression of the form $L=P-3\psi$ where $P$ represents the pressure as a function just of $\nabla\varphi$ in the (isotropic) cold limit. The entropy current dependent contribution $\psi$ represents the generalised pressure of the (non-isotropic) phonon gas, which is obtained as the negative of the corresponding grand potential energy per unit volume, whose explicit form has a simple algebraic dependence on the sound or ``phonon" speed $c_P$ that is determined by the cold pressure function $P$.
Relativistic models for Superconducting-Superfluid Mixtures
Brandon Carter,David Langlois
Physics , 1998, DOI: 10.1016/S0550-3213(98)00430-1
Abstract: The material below the crust of a neutron star is understood to be describable in terms of three principal independently moving constituents, identifiable as neutrons, protons, and electrons, of which the first two are believed to form mutually coupled bosonic condensates. The large scale comportment of such a system will be that of a positively charged superconducting superfluid in a negatively charged ``normal'' fluid background. As a contribution to the development of the theory of such a system, the present work shows how, subject to neglect of dissipative effects, it is possible to set up an elegant category of simplified but fully relativistic three-constituent superconducting superfluid models whose purpose is to provide realistic approximations for cases in which a strictly conservative treatment is sufficient. A "mesoscopic" model, describing the fluid between the vortices, is constructed, as well as a "macroscopic" model taking into account the average effect of quantised vortices.
Tusnady's inequality revisited
Andrew Carter,David Pollard
Mathematics , 2005, DOI: 10.1214/009053604000000733
Abstract: Tusnady's inequality is the key ingredient in the KMT/Hungarian coupling of the empirical distribution function with a Brownian bridge. We present an elementary proof of a result that sharpens the Tusnady inequality, modulo constants. Our method uses the beta integral representation of Binomial tails, simple Taylor expansion and some novel bounds for the ratios of normal tail probabilities.
The Speech-Language Interface in the Spoken Language Translator
David Carter,Manny Rayner
Computer Science , 1994,
Abstract: The Spoken Language Translator is a prototype for practically useful systems capable of translating continuous spoken language within restricted domains. The prototype system translates air travel (ATIS) queries from spoken English to spoken Swedish and to French. It is constructed, with as few modifications as possible, from existing pieces of speech and language processing software. The speech recognizer and language understander are connected by a fairly conventional pipelined N-best interface. This paper focuses on the ways in which the language processor makes intelligent use of the sentence hypotheses delivered by the recognizer. These ways include (1) producing modified hypotheses to reflect the possible presence of repairs in the uttered word sequence; (2) fast parsing with a version of the grammar automatically specialized to the more frequent constructions in the training corpus; and (3) allowing syntactic and semantic factors to interact with acoustic ones in the choice of a meaning structure for translation, so that the acoustically preferred hypothesis is not always selected even if it is within linguistic coverage.
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