Página 1 dos resultados de 17 itens digitais encontrados em 0.016 segundos

## A boot-strap estimator for joint flux and parameters online identification for vector controlled induction motor drives

Leite, V.; Araújo, R.; Freitas, D.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
Português
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This paper presents a new approach for joint rotor flux and electrical parameters on-line identification in vector controlled high-performance induction motor drives based on a boot-strap estimator that uses a reduced order extended Kalman filter for rotor flux components and rotor parameters estimation and a recursive prediction error method for stator parameters estimation. Within the prediction error method some approaches are used and compared that affect both the adaptation gain and the direction in which the updates of stator parameters are made. The induction motor model structures are described in the rotor reference frame in order to reduce the computational effort by using a higher sampling time interval.

## A new online identification methodology for flux and parameters estimation of vector controlled induction motors

Leite, V.; Araújo, R.; Freitas, D.
Tipo: Conferência ou Objeto de Conferência
Português
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A new online identification methodology for estimation of the rotor flux components and the main electrical parameters of vector controlled induction motors is presented in this paper. The induction motor model is referred to the rotor reference frame for estimation of rotor flux and rotor parameters, and referred to the stator reference frame to estimate stator parameters. The stator parameters estimation is achieved by a prediction error method based on a model structure described by a linear regression that is independent of rotor speed and rotor parameters. The rotor flux components and rotor parameters are estimated by a reduced order extended Kalman filter, using a 4th-order state-space model structure where the state equation is described by matrices that are diagonal and independent of rotor speed as well as stator parameters. Both methods work in a boot-strap manner.

## Morphology and phylogenetic relationships of a remarkable new genus and two new species of Neotropical freshwater stingrays from the Amazon basin (Chondrichthyes: Potamotrygonidae)

CARVALHO, Marcelo R. De; LOVEJOY, Nathan R.
Fonte: MAGNOLIA PRESS Publicador: MAGNOLIA PRESS
Tipo: Artigo de Revista Científica
Português
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The morphology and phylogenetic relationships of a new genus and two new species of Neotropical freshwater stingrays, family Potamotrygonidae, are investigated and described in detail. The new genus, Heliotrygon, n. gen., and its two new species, Heliotrygon gomesi, n. sp. (type-species) and Heliotrygon rosai, n. sp., are compared to all genera and species of potamotrygonids, based on revisions in progress. Some of the derived features of Heliotrygon include its unique disc proportions (disc highly circular, convex anteriorly at snout region, its width and length very similar), extreme subdivision of suborbital canal (forming a complex honeycomb-like pattern anterolaterally on disc), stout and triangular pelvic girdle, extremely reduced caudal sting, basibranchial copula with very slender and acute anterior extension, and precerebral and frontoparietal fontanellae of about equal width, tapering very little posteriorly. Both new species can be distinguished by their unique color patterns: Heliotrygon gomesi is uniform gray to light tan or brownish dorsally, without distinct patterns, whereas Heliotrygon rosai is characterized by numerous white to creamy-white vermiculate markings over a light brown, tan or gray background color. Additional proportional characters that may further distinguish both species are also discussed. Morphological descriptions are provided for dermal denticles...

## Cloning of Giardia lamblia heat shock protein HSP70 homologs: implications regarding origin of eukaryotic cells and of endoplasmic reticulum.

Gupta, R S; Aitken, K; Falah, M; Singh, B
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The genes for two different 70-kDa heat shock protein (HSP70) homologs have been cloned and sequenced from the protozoan Giardia lamblia. On the basis of their sequence features, one of these genes corresponds to the cytoplasmic form of HSP70. The second gene, on the basis of its characteristic N-terminal hydrophobic signal sequence and C-terminal endoplasmic reticulum (ER) retention sequence (Lys-Asp-Glu-Leu), is the equivalent of ER-resident GRP78 or the Bip family of proteins. Phylogenetic trees based on HSP70 sequences show that G. lamblia homologs show the deepest divergence among eukaryotic species. The identification of a GRP78 or Bip homolog in G. lamblia strongly suggests the existence of ER in this ancient eukaryote. Detailed phylogenetic analyses of HSP70 sequences by boot-strap neighbor-joining and maximum-parsimony methods show that the cytoplasmic and ER homologs form distinct subfamilies that evolved from a common eukaryotic ancestor by gene duplication that occurred very early in the evolution of eukaryotic cells. It is postulated that because of the essential "molecular chaperone" function of these proteins in translocation of other proteins across membranes, duplication of their genes accompanied the evolution of ER or nucleus in the eukaryotic cell ancestor. The presence in all eukaryotic cytoplasmic HSP70 homologs (including the cognate...

## Markov, fractal, diffusion, and related models of ion channel gating. A comparison with experimental data from two ion channels.

Sansom, M S; Ball, F G; Kerry, C J; McGee, R; Ramsey, R L; Usherwood, P N
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The gating kinetics of single-ion channels are generally modeled in terms of Markov processes with relatively small numbers of channel states. More recently, fractal (Liebovitch et al. 1987. Math. Biosci. 84:37-68) and diffusion (Millhauser et al. 1988. Proc. Natl. Acad. Sci. USA. 85:1502-1507) models of channel gating have been proposed. These models propose the existence of many similar conformational substrates of the channel protein, all of which contribute to the observed gating kinetics. It is important to determine whether or not Markov models provide the most accurate description of channel kinetics if progress is to be made in understanding the molecular events of channel gating. In this study six alternative classes of gating model are tested against experimental single-channel data. The single-channel data employed are from (a) delayed rectifier K+ channels of NG 108-15 cells and (b) locust muscle glutamate receptor channels. The models tested are (a) Markov, (b) fractal, (c) one-dimensional diffusion, (d) three-dimensional diffusion, (e) stretched exponential, and (f) expo-exponential. The models are compared by fitting the predicted distributions of channel open and closed times to those observed experimentally. The models are ranked in order of goodness-of-fit using a boot-strap resampling procedure. The results suggest that Markov models provide a markedly better description of the observed open and closed time distributions for both types of channel. This provides justification for the continued use of Markov models to explore channel gating mechanisms.

## Molecular and Morphological Characterization and Biological Control Capabilities of a Pasteuria ssp. Parasitizing Rotylenchulus reniformis, the Reniform Nematode

Schmidt, Liesbeth M.; Hewlett, Thomas E.; Green, April; Simmons, Lee J.; Kelley, Karen; Doroh, Mark; Stetina, Salliana R.
Fonte: The Society of Nematologists Publicador: The Society of Nematologists
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Rotylenchulus reniformis is one of 10 described species of reniform nematodes and is considered the most economically significant pest within the genus, parasitizing a variety of important agricultural crops. Rotylenchulus reniformis collected from cotton fields in the Southeastern US were observed to have the nematode parasitic bacterium Pasteuria attached to their cuticles. Challenge with a Pasteuria-specific monoclonal antibody in live immuno-fluorescent assay (IFA) confirmed the discovery of Pasteuria infecting R. reniformis. Scanning and transmission electron microscopy were employed to observe endospore ultrastructure and sporogenesis within the host. Pasteuria were observed to infect and complete their life-cycle in juvenile, male and female R. reniformis. Molecular analysis using Pasteuria species-specific and degenerate primers for 16s rRNA and spoII, and subsequent phylogenetic assessment, placed the Pasteuria associated with R. reniformis in a distinct clade within established assemblages for the Pasteuria infecting phytopathogenic nematodes. A global phylogenetic assessment of Pasteuria 16s rDNA using the Neighbor-Joining method resulted in a clear branch with 100% boot-strap support that effectively partitioned the Pasteuria infecting phytopathogenic nematodes from the Pasteuria associated with bacterivorous nematodes. Phylogenetic analysis of the R. reniformis Pasteuria and Pasteuria spp. parasitizing a number of economically important plant parasitic nematodes revealed that Pasteuria with different host specificities are closely related and likely constitute biotypes of the same species. This suggests host preference...

## Modeling and structural analysis of cellulases using Clostridium thermocellum as template

Kumar, Nathan Vinod; Rani, Mary Esther; Gunaseeli, Rathinasamy; Kannan, Narayanan Dhiraviam; Sridhar, Jayavel
Fonte: Biomedical Informatics Publicador: Biomedical Informatics
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Cellulase is one of the most widely distributed enzymes with wide application. They are involved in conversion of biomass into simpler sugars. Cellulase of Trichoderma longibrachiatum, a known cellulolytic fungus was compared with Clostridium thermocellum [AAA23226.1] cellulase. Blastp was performed with AAA23226.1 as query sequence to obtain nine similar sequences from NCBI protein data bank. The physicochemical properties of cellulase were analyzed using ExPASy’s ProtParam tool namely ProtParam, SOPMA and GOR IV. Homology modeling was done using SWISS MODEL and checked quality by RMSD values using VMD1.9.1. Active sites of each model were predicted using automated active site prediction server of SCFBio. Study revealed instability of cellulase of two eukaryotic strains namely Trichoderma longibrachiatum [CAA43059.1] and Melanocarpus albomyces [CAD56665.1]. The negative GRAVY score value of cellulases ensured better interaction and activity in aqueous phase. It was found that molecular weight (M. Wt) ranges between 25-127.56 kDa. Iso-electric point (pI) of cellulases was found to be acidic in nature. GOR IV and SOPMA were used to predict secondary structure of cellulase, which showed that random coil, was dominated. Neighbor joining tree with C. thermocellum [AAA23226.1] cellulase as root showed that cellulases of Thermoaerobacter subterraneus [ZP_07835928] and C. thermocellum [CAA4305.1] were more similar to eukaryotic cellulases supported by least boot strap values. Pseudoalteromonas haloplanktis cellulase was found to be the ideal model supported by least RMSD score among the predicted structures. Trichoderma longibrachiatum cellulase was found to be the best compared to other cellulases...

## Inference for modulated stationary processes

Zhao, Zhibiao; Li, Xiaoye
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We study statistical inferences for a class of modulated stationary processes with time-dependent variances. Due to non-stationarity and the large number of unknown parameters, existing methods for stationary or locally stationary time series are not applicable. Based on a self-normalization technique, we address several inference problems, including self-normalized central limit theorem, self-normalized cumulative sum test for the change-point problem, long-run variance estimation through blockwise self-normalization, and self-normalization-based wild boot-strap. Monte Carlo simulation studies show that the proposed self-normalization-based methods outperform stationarity-based alternatives. We demonstrate the proposed methodology using two real data sets: annual mean precipitation rates in Seoul during 1771–2000, and quarterly U.S. Gross National Product growth rates during 1947–2002.

## Avaliação de testes estatísticos em dados de Q-PCR.

CARVALHO, F. M.; BARIONI JUNIOR, W.; NAKATA, L. C.; REGITANO, L. C. de A.
Tipo: Resumo em anais de congresso (ALICE) Formato: p. 410
Português
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## Finite-Sample Diagnostics for Multivariate Regressions with Applications to Linear Asset Pricing Models

DUFOUR, Jean-Marie; KHALAF, Lynda; BEAULIEU, Marie-Claude
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica Formato: 219916 bytes; application/pdf
Português
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In this paper, we propose several finite-sample specification tests for multivariate linear regressions (MLR) with applications to asset pricing models. We focus on departures from the assumption of i.i.d. errors assumption, at univariate and multivariate levels, with Gaussian and non-Gaussian (including Student t) errors. The univariate tests studied extend existing exact procedures by allowing for unspecified parameters in the error distributions (e.g., the degrees of freedom in the case of the Student t distribution). The multivariate tests are based on properly standardized multivariate residuals to ensure invariance to MLR coefficients and error covariances. We consider tests for serial correlation, tests for multivariate GARCH and sign-type tests against general dependencies and asymmetries. The procedures proposed provide exact versions of those applied in Shanken (1990) which consist in combining univariate specification tests. Specifically, we combine tests across equations using the MC test procedure to avoid Bonferroni-type bounds. Since non-Gaussian based tests are not pivotal, we apply the “maximized MC” (MMC) test method [Dufour (2002)], where the MC p-value for the tested hypothesis (which depends on nuisance parameters) is maximized (with respect to these nuisance parameters) to control the test’s significance level. The tests proposed are applied to an asset pricing model with observable risk-free rates...

## Bound-State Instability of the Chiral Luttinger Liquid in One-Dimension

Ho, A. F.; Coleman, P.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We have developed a new boot-strap method for solving a class of interacting one-dimensional chiral fermions. The conventional model for interacting right-moving electrons with spin has an SO(4) symmetry, and can be written as four interacting Majorana fermions, each with the same velocity. We have found a method for solving some cases when the velocities of these Majorana fermions are no longer equal. We demonstrate in some detail the remarkable result that corrections to the non skeleton self-energy identically vanish for these models, and this enables us to solve them exactly. For the cases where the model can be solved by bosonization, our method can be explicitly checked. However, we are also able to solve some new cases where the excitation spectrum differs qualitatively from a Luttinger liquid. Of particular interest, is the so-called SO(3) model, where a triplet of Majorana fermions moving at one velocity, interact with a single Majorana fermion moving at another velocity. We show using our method, that a sharp bound (or anti-bound) state splits off from the original Luttinger liquid continuum, cutting off the X-ray singularity to form a broad incoherent excitation with a lifetime that grows linearly with frequency.; Comment: 12 pages...

## Breakdown of the Chiral Luttinger Liquid in One-Dimension

Ho, A. F.; Coleman, P.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.902676%
We have developed a fermionic boot-strap method to solve a class of chiral one dimensional fermion model which cannot be tackled by bosonization. Using this scheme, we show that Luttinger liquid behavior in a gas of four interacting chiral Majorana fermions is highly sensitive to the velocity degeneracy. Upon changing the velocity of a one chiral fermion, a sharp bound (or anti-bound) state splits off from the original Luttinger liquid continuum, cutting off the X-ray singularity to form a broad incoherent excitation with a lifetime that grows linearly with frequency.; Comment: 13 pages, 7 figs

## Evolving Modular Genetic Regulatory Networks with a Recursive, Top-Down Approach

Garcia-Bernardo, Javier; Eppstein, Margaret J.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Being able to design genetic regulatory networks (GRNs) to achieve a desired cellular function is one of the main goals of synthetic biology. However, determining minimal GRNs that produce desired time-series behaviors is non-trivial. In this paper, we propose a 'top-down' approach to evolving small GRNs and then use these to recursively boot-strap the identification of larger, more complex, modular GRNs. We start with relatively dense GRNs and then use differential evolution (DE) to evolve interaction coefficients. When the target dynamical behavior is found embedded in a dense GRN, we narrow the focus of the search and begin aggressively pruning out excess interactions at the end of each generation. We first show that the method can quickly rediscover known small GRNs for a toggle switch and an oscillatory circuit. Next we include these GRNs as non-evolvable subnetworks in the subsequent evolution of more complex, modular GRNs. Successful solutions found in canonical DE where we truncated small interactions to zero, with or without an interaction penalty term, invariably contained many excess interactions. In contrast, by incorporating aggressive pruning and the penalty term, the DE was able to find minimal or nearly minimal GRNs in all test problems.

## Impact of accretion on the statistics of neutron star masses

Cheng, Z.; Taani, A.; Zhao, Y. H.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We have collected the parameter of 38 neutron stars (NSs) in binary systems with spin periods and measured masses. By adopting the Boot-strap method, we reproduced the procedure of mass calculated for each system separately, to determine the truly mass distribution of the NS that obtained from observation. We also applied the Monte-Carlo simulation and introduce the characteristic spin period 20 ms, in order to distinguish between millisecond pulsars (MSPs) and less recycled pulsars. The mass distributions of MSPs and the less recycled pulsars could be fitted by a Gaussian function as $\rm 1.45\pm0.42 M_{\odot}$ and $\rm 1.31\pm0.17 M_{\odot} (\rm with ~ 1\sigma)$ respectively. As such, the MSP masses are heavier than those in less recycled systems by factor of $\rm \sim 0.13M_{\odot}$, since the accretion effect during the recycling process.; Comment: 2 pages, 2 figures

## Global solutions of coupled Klein-Gordon equations with different velocities in four space-time dimensions

Ma, Yue
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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In this article one will discuss the system of coupled nonlinear Klein-Gordon equations with different velocities and different masses. The nonlinearity considered is a general quadratic nonlinearity without any restriction. The method is a classical boot-strap argument combined with a serious of techniques including conformal energy estimate, global sobolev's lemma and Hardy type inequalities.; Comment: This paper has been withdrawn by the author due to a crucial sign error in energy estimate

## Pion resonances

Zachariasen, Fredrik; Zemach, Charles
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf