Página 1 dos resultados de 1759 itens digitais encontrados em 0.014 segundos

A simple ESR identification methodology for electrolytic capacitors condition monitoring

Leite, V.; Teixeira, H.; Cardoso, A.J. Marques; Araújo, R.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36%
Electrolytic capacitors are usually used in power electronic systems for smoothing, energy storage or filtering. They have the best overall performance for these objectives being a critical element in the design of these systems, in several applications, with different requirements. But, unfortunately, in most cases, they are the most life-limiting device. The expected life of electrolytic capacitors depends on their internal temperature and is determined by the ratio of the electrolyte solution evaporation used in their fabrication. The deterioration caused by this evaporation is reflected in electrical parameters, mainly the equivalent series resistance (ESR). As the volume of the electrolyte decreases, ESR increases and capacitance decreases. Additionally, the increase in ESR has a positive feedback effect since it leads the temperature to increase and this in turn leads to further evaporation of the electrolyte leading to the ESR increase and so forth. This paper presents a simple ESR identification methodology for electrolytic capacitors condition monitoring in view of preventive maintenance to signal the need of maintenance and or replacement. The identification methodology is based on a simple continuous-time model and some recursive prediction error methods...

Generating a lexicon of errors in Portuguese to support an error identification system for Spanish native learners

Torres, Lianet Sepúlveda; Duran, Magali Sanches; Aluisio, Sandra Maria
Fonte: European Language Resources Association - ERLA; Reykjavik Publicador: European Language Resources Association - ERLA; Reykjavik
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
45.95%
Portuguese is a less resourced language in what concerns foreign language learning. Aiming to inform a module of a system designed to support scientific written production of Spanish native speakers learning Portuguese, we developed an approach to automatically generate a lexicon of wrong words, reproducing language transfer errors made by such foreign learners. Each item of the artificially generated lexicon contains, besides the wrong word, the respective Spanish and Portuguese correct words. The wrong word is used to identify the interlanguage error and the correct Spanish and Portuguese forms are used to generate the suggestions. Keeping control of the correct word forms, we can provide correction or, at least, useful suggestions for the learners. We propose to combine two automatic procedures to obtain the error correction: i) a similarity measure and ii) a translation algorithm based on aligned parallel corpus. The similarity-based method achieved a precision of 52%, where as the alignment-based method achieved a precision of 90%. In this paper we focus only on interlanguage errors involving suffixes that have different forms in both languages. The approach, however, is very promising to tackle other types of errors, such as gender errors.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A posteriori error estimations for the generalized finite element method and modified versions; Estimativas de erro a-posteriori para o método dos elementos finitos generalizados e versões modificadas

Lins, Rafael Marques
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/08/2015 EN
Relevância na Pesquisa
35.99%
This thesis investigates two a posteriori error estimators, based on gradient recovery, aiming to fill the gap of the error estimations for the Generalized FEM (GFEM) and, mainly, its modified versions called Corrected XFEM (C-XFEM) and Stable GFEM (SGFEM). In order to reach this purpose, firstly, brief reviews regarding the GFEM and its modified versions are presented, where the main advantages attributed to each numerical method are highlighted. Then, some important concepts related to the error study are presented. Furthermore, some contributions involving a posteriori error estimations for the GFEM are shortly described. Afterwards, the two error estimators hereby proposed are addressed focusing on linear elastic fracture mechanics problems. The first estimator was originally proposed for the C-XFEM and is hereby extended to the SGFEM framework. The second one is based on a splitting of the recovered stress field into two distinct parts: singular and smooth. The singular part is computed with the help of the J integral, whereas the smooth one is calculated from a combination between the Superconvergent Patch Recovery (SPR) and Singular Value Decomposition (SVD) techniques. Finally, various numerical examples are selected to assess the robustness of the error estimators considering different enrichment types...

Fusion of fingerprint recognition methods for robust human identification

Falguera, Fernanda Pereira Sartori; Marana, Aparecido Nilceu; Falguera, Juan Rogelio
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 413-420
ENG
Relevância na Pesquisa
36.01%
Biometrics is one of the biggest tendencies in human identification. The fingerprint is the most widely used biometric. However considering the automatic fingerprint recognition a completely solved problem is a common mistake. The most popular and extensively used methods, the minutiae-based, do not perform well on poor-quality images and when just a small area of overlap between the template and the query images exists. The use of multibiometrics is considered one of the keys to overcome the weakness and improve the accuracy of biometrics systems. This paper presents the fusion of a minutiae-based and a ridge-based fingerprint recognition method at rank, decision and score level. The fusion techniques implemented leaded to a reduction of the Equal Error Rate by 31.78% (from 4.09% to 2.79%) and a decreasing of 6 positions in the rank to reach a Correct Retrieval (from rank 8 to 2) when assessed in the FVC2002-DB1A database. © 2008 IEEE.

Modelos de Volterra : identificação não paramétrica e robusta utilizando funções ortonormais de Kautz e generalizadas; Volterra models : nonparametric and robust identification using Kautz and generalized orthonormal functions

Márcio Feliciano Braga
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/06/2011 PT
Relevância na Pesquisa
36.01%
Enfoca-se a modelagem de sistemas não-lineares usando modelos de Volterra com bases de funções ortonormais (Orthonormal Basis Functions - OBF) distintas para cada direção do kernel. Os modelos de Volterra constituem uma classe de modelos polinomiais não-recursivos, modelos sem realimentação da saída. Tais modelos são parametrizados por funções multidimensionais, chamadas kernels de Volterra, e representam uma generalização do bem conhecido modelo de resposta ao impulso (FIR) para a descrição de sistemas não-lineares. Como os modelos de Volterra não possuem realimentação do sinal de saída, um número elevado de parâmetros é necessário para representar os kernels de Volterra, especialmente quando o comportamento não-linear do sistema depende fortemente do sinal de saída. No entanto, é possível contornar esta desvantagem por descrever cada kernel por meio de uma expansão em bases de funções ortonormais (OBF). Resultando num modelo que, em geral, possui um número menor de termos para representar o sistema. O modelo resultante, conhecido como modelo OBF-Volterra, pode ser truncado em um número menor de termos se as funções da base forem projetadas adequadamente. O problema reside na questão de como selecionar os polos livres que completamente parametrizam estas funções de forma a reduzir o número de termos a serem utilizados em cada base. Uma abordagem já utilizada envolve a otimização numérica das bases de funções ortonormais usadas para a aproximação de sistemas dinâmicos. Esta estratégia é baseada no cálculo de expressões analíticas para os gradientes da saída dos filtros ortonormais com relação aos polos da base. Estes gradientes fornecem direções de busca exatas para otimizar uma dada base ortonormal. As direções de busca...

Identificação inversa de sistemas dinâmicos não-lineares com parâmetros dependentes do deslocamento; Inverse identification for non-linear dynamic systems with displacement dependent parameters

Maurício Roselli Sica
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/07/2011 PT
Relevância na Pesquisa
36%
As simulações físicas em laboratórios da indústria automotiva são realizadas utilizando informações colhidas de veículos que são submetidos a ciclos de testes em rotas urbanas. Medir as respostas em pontos específicos durante uma rota de teste, não significa conhecer as excitações a que o veículo esta sendo submetido, visto que este normalmente é composto por sistemas mecânicos não lineares. O objetivo deste trabalho é desenvolver um algoritmo que possibilite através dos dados de resposta medidos em campo, conhecer as excitações de entrada, contribuindo para a reprodução da rota de teste. A metodologia utilizada está baseada na obtenção de funções de resposta em freqüência, de modelos lineares simples e no desenvolvimento de sinais de entrada, capazes de reproduzir as mesmas respostas medidas nas rotas nos sistemas não lineares. O algoritmo desenvolvido foi avaliado com simulações em sistemas lineares e não lineares de um, dois e quatro graus de liberdade. Através dos sinais de resposta medidos em um sistema e, utilizando sinal de identificação tipo Schroeder, foi possível estimar as forças de excitação, com um erro menor do que 1,0% para sistemas de dois graus de liberdade lineares e não lineares. No caso de sistemas com quatro graus de liberdade este valor foi menor do que 1...

Identification and Analysis of Error Types in High-Throughput Genotyping

Ewen, Kelly R.; Bahlo, Melanie; Treloar, Susan A.; Levinson, Douglas F.; Mowry, Bryan; Barlow, John W.; Foote, Simon J.
Fonte: The American Society of Human Genetics Publicador: The American Society of Human Genetics
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.15%
Although it is clear that errors in genotyping data can lead to severe errors in linkage analysis, there is as yet no consensus strategy for identification of genotyping errors. Strategies include comparison of duplicate samples, independent calling of alleles, and Mendelian-inheritance–error checking. This study aimed to develop a better understanding of error types associated with microsatellite genotyping, as a first step toward development of a rational error-detection strategy. Two microsatellite marker sets (a commercial genomewide set and a custom-designed fine-resolution mapping set) were used to generate 118,420 and 22,500 initial genotypes and 10,088 and 8,328 duplicates, respectively. Mendelian-inheritance errors were identified by PedManager software, and concordance was determined for the duplicate samples. Concordance checking identifies only human errors, whereas Mendelian-inheritance–error checking is capable of detection of additional errors, such as mutations and null alleles. Neither strategy is able to detect all errors. Inheritance checking of the commercial marker data identified that the results contained 0.13% human errors and 0.12% other errors (0.25% total error), whereas concordance checking found 0.16% human errors. Similarly...

Carriage Error Identification Based on Cross-Correlation Analysis and Wavelet Transformation

Mu, Donghui; Chen, Dongju; Fan, Jinwei; Wang, Xiaofeng; Zhang, Feihu
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 12/07/2012 EN
Relevância na Pesquisa
35.99%
This paper proposes a novel method for identifying carriage errors. A general mathematical model of a guideway system is developed, based on the multi-body system method. Based on the proposed model, most error sources in the guideway system can be measured. The flatness of a workpiece measured by the PGI1240 profilometer is represented by a wavelet. Cross-correlation analysis performed to identify the error source of the carriage. The error model is developed based on experimental results on the low frequency components of the signals. With the use of wavelets, the identification precision of test signals is very high.

Ein Modell zur Kalkulation von Fehlerkosten für das medizinische Risikomanagement; A model for calculating error costs in medical risk management

Marquardt, Klaus
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
46.18%
Im klinischen Alltag ist ein gewisser Prozentsatz der Behandlungsfälle von unerwünschten Ereignissen bzw. Fehlern betroffen. Die Identifikation von (potentiellen) Fehlern ist ein wesentlicher Bestandteil des Risikomanagements. Durch die anschließende Bewertung der (potentiellen) Fehler sollen Maßnahmen zur Risikoreduktion effektiv eingesetzt werden. In der vorliegenden Arbeit wird zunächst die Prävalenz unerwünschter Ereignisse dargestellt. Anschließend wird ein Modell zur Berechnung der Fehlerkosten entworfen, welches die Bewertung von Risiken ermöglichen soll. Mittels Auswertung von Studien und Literaturrecherchen wurde die Prävalenz unerwünschter medizinischer Ereignisse bestimmt und Methoden der Fehleridentifikation evaluiert. Mit der Methode der Erwartungswertberechnung als Basis wurde ein Modell zur Fehlerkostenberechnung entworfen und anschließend auf die Untergruppe der Medikationsfehler angewendet. Die betrachteten Studien wiesen für unerwünschte Ereignisse eine durchschnittliche Prävalenz von 11,3% auf. Ein Klinikaufenthalt verlängerte sich hierdurch um durchschnittlich 7,4 Tage. Praktikable Methoden der Fehleridentifikation sind das Beschwerdemanagement, Fehlermeldesysteme, die retrospektive Fallanalyse und die verschiedenen Arten der Prozessanalyse. Die entwickelte Fehlerkostenberechnung verarbeitet die möglichen unterschiedlichen Verläufe von Fehlern...

A Model for Run-time Measurement of Input and Round-off Error

Meng, Nicholas Jie
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
35.98%
For scientists, the accuracy of their results is a constant concern. As the programs they write to support their research grow in complexity, there is a greater need to understand what causes the inaccuracies in their outputs, and how they can be mitigated. This problem is difficult because the inaccuracies in the outputs come from a variety of sources in both the scientific and computing domains. Furthermore, as most programs lack a testing oracle, there is no simple way to validate the results. We define a model for the analysis of error propagation in software. Its novel combination of interval arithmetic and automatic differentiation allows for the error accumulated in an output to be measurable at runtime, attributable to individual inputs and functions, and identifiable as either input error, round-off error, or error from a different source. This allows for the identification of the subset of inputs and functions that are most responsible for the error seen in an output and how it can be best mitigated. We demonstrate the effectiveness of our model by analyzing a small case study from the field of nuclear engineering, where we are able to attribute the contribution of over 99% of the error to 3 functions out of 15, and identify the causes for the observed error.; Thesis (Master...

Identification of the Servomechanism used for micro-displacement

BOGDAN, Ioana-Corina; ABBA, Gabriel
Fonte: IEEE Publicador: IEEE
EN
Relevância na Pesquisa
35.97%
Friction causes important errors in the control of small servomechanism and should be determined with precision in order to increase the system performance. This paper describes the method to identify the model parameters of a small linear drive with ball-screw. Two kinds of friction models will be applied for the servomechanism looking to rise its micropositioning abilities. The first one includes the static, viscous and Stribeck friction with hysteresis, and the second one uses the Lugre model. The results will be compared taking into account the criterion error, the accuracy and the normalized mean-square-error of the identified mechanical parameters. The coefficients of the models are identified by a recursive identification method using data acquisition and special filtering technics. The least square identification method is used in this paper in order to establish the motor parameters used as initial condition of the recursive estimation method. Computer simulations and experimental results demonstrate the efficiency of the proposed model.

An information geometric approach to ML estimation with incomplete data: Application to semiblind MIMO channel identification

Zia, A.; Reilly, J.P.; Manton, Jonathan; shirani, S.
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.97%
In this paper, we cast the stochastic maximum-likelihood estimation of parameters with incomplete data in an information geometric framework. In this vein, we develop the information geometric identification (IGID) algorithm. The algorithm consists of ite

Robustness Analysis Tools for an Uncertainty Set Obtained by Prediction Error Identification

Bombois, Xavier; Gevers, Michel; Scorletti, Gérard; Anderson, Brian
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.01%
This paper presents a robust stability and performance analysis for an uncertainty set delivered by classical prediction error identification. This nonstandard uncertainty set, which is a set of parametrized transfer functions with a parameter vector in a

Combined Deterministic-Stochastic Identification with Application to Control of Wave Energy Harvesting Systems

Li, Quan
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
36.13%

This thesis proposes an integrated procedure for identifying the nominal models of the deterministic part and the stochastic part of a system, as well as their model error bounds in different uncertainty structures (e.g. $\mathcal{H}_2$-norm and $\mathcal{H}_{\infty}$-norm) based on the measurement data. In particular, the deterministic part of a system is firstly identified by closed-loop instrumental variable method in which a known external signal sequence uncorrelated with the system noises is injected in the control input for the identifiability of the system in closed loop. By exploiting the second-order statistics of the noise-driven output components, the stochastic part of a system is identified by the improved subspace approach in which a new and straightforward linear-matrix-inequality-based optimization is proposed to obtain a valid model even under insufficient measurement data.

To derive an explicit model error bound on the identification model, we investigate a complete asymptotic analysis for identification of the stochastic part of the system. We first derive the asymptotically normal distributions of the empirical sample covariance and block-Hankel matrix of the outputs. Thanks to these asymptotic distributions and the perturbation analysis of singular value decomposition and discrete algebraic Riccati equation...

Closed-loop output error identification of nonlinear plants using Kernel representations

De Bruyne, Franky; Anderson, Brian; Landau, I
Fonte: Casual Productions Publicador: Casual Productions
Tipo: Conference paper
Relevância na Pesquisa
56.13%
In this paper, we extend the family of algorithms presented in [3,4] for the identification of continuous time nonlinear plants operating in closed-loop. The main novelty is that the identification of unstable plants is covered in its generality.

Model Validation for Control and Controller Validation in a Prediction error Identification Framework - Part II: illustrations

Covers, Michel; Bombois, Xavier; Codrons, Bonoit; Scorletti, Gérard; Anderson, Brian
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.14%
The results on model validation for control and controller validation in a prediction error identification framework are illustrated. The results are illustrated with two realistic identification and control design applications. The first is the control of a flexible mechanical system with a tracking objective and the second is the control of a ferrosilicon production process with a disturbance rejection objective.

Quantification of frequency domain error bounds with guaranteed confidence level in prediction error identification

Bombois, Xavier; Anderson, Brian; Gevers, Michel
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.19%
This paper considers prediction error identification of linearly parametrized models in the situation where the system is in the model set. For such situation it is easy to construct a confidence ellipsoid in parameter space in which the true parameter lies with an a priori fixed probability level, α. Surprisingly perhaps, the construction of a corresponding uncertainty set in the frequency domain, to which the true system belongs with probability α, is still an open problem. We show in this paper how to construct such frequency domain uncertainty set with a probability level of at least α.

Model Validation for Control and Controller Validation in a Prediction error Identification Framework - Part I

Gevers, Michel; Bombois, Xavier; Codrons, Bonoit; Scorletti, Gérard; Anderson, Brian
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.15%
We propose a model validation procedure that consists of a prediction error identification experiment with a full order model. It delivers a parametric uncertainty ellipsoid and a corresponding set of parameterized transfer functions, which we call prediction error (PE) uncertainty set. Such uncertainty set differs from the classical uncertainty descriptions used in robust control analysis and design. We develop a robust control analysis theory for such uncertainty sets, which covers two distinct aspects: (1) Controller validation. We present necessary and sufficient conditions for a specific controller to stabilize - or to achieve a given level of performance with - all systems in such PE uncertainty set. (2) Model validation for robust control. We present a measure for the size of such PE uncertainty set that is directly connected to the size of a set controllers that stabilize all systems in the model uncertainty set. This allows us to establish that one uncertainty set is better tuned for robust control design than another, leading to control-oriented validation objectives.

Closed-loop Identification with an Unstable or Nonminimum Phase Controller

Codrons, Bonoit; Anderson, Brian; Gevers, Michel
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46%
In many practical cases, the identification of a system is done in closed loop with some controller. In this paper, we show that the internal stability of the resulting model, in closed loop with the same controller, is not always guaranteed if this controller is unstable and/or nonminimum phase, and that the classical closed-loop prediction-error identification methods present different properties regarding this stability issue. With some of these methods, closed-loop instability of the identified model is actually guaranteed. This is a serious drawback if this model is to be used for the design of a new controller. We give guidelines to avoid the emergence of this instability problem; these guidelines concern both the experiment design and the choice of the identification method.

Internal State Identification for Black Box Systems

Medel Juárez,José de Jesús; Zagaceta Álvarez,María Teresa
Fonte: Centro de Investigación en computación, IPN Publicador: Centro de Investigación en computación, IPN
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
46.11%
In digital filter theory, the identification process describes internal dynamic states based on a reference system, commonly known as a black box. The identification process as a function of: a) transition function, b) identified delayed states, c) gain function which depends on convergence correlation error, and d) an innovation process based on the error described by the differences between the output reference system and the identification result. Unfortunately, in the black box concept, the exponential transition function considers the unknown internal parameters. This means that the identification process does not operate correctly because its transition function has no access to the internal dynamic gain. An approximation for solving this problem includes the estimation in the identification technique. This paper presents an estimation for a "single input single output" (SISO) system with stationary properties applied to internal state identification.