Página 1 dos resultados de 399 itens digitais encontrados em 0.070 segundos

## Estimação de estado em sistemas elétricos de potência: composição de erros de medidas; State estimation in power systems: measurement error composition

Piereti, Saulo Augusto Ribeiro
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
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Bretas et al. (2009) prova matematicamente, e através da interpretação geométrica, que o erro de medida se divide em componentes detectáveis e não-detectáveis. Demonstra ainda que as metodologias até então utilizadas, para o processamento de Erros Grosseiros (EGs), consideram apenas a componente detectável do erro. Assim, dependendo da amplitude das componentes do erro, essas metodologias podem falhar. Face ao exposto, neste trabalho é proposto uma nova metodologia para processar as medidas portadoras de EGs. Essa proposição será obtida decompondo o erro da medida em duas componentes: a primeira, é ortogonal ao espaço da imagem da matriz jacobiana cuja amplitude é igual ao resíduo da medida, a outra, pertence ao espaço da imagem da matriz jacobiana e que, por conseguinte, não contribui para o resíduo da medida. A relação entre a norma dessas componentes, aqui denominado Índice de Inovação (II), prevê uma nova informação, isto é, informação não contida nas outras medidas. Usando o II, calcula-se um valor limiar (TV) para cada medida, esse limiar será utilizado para inferir se a medida é ou não suspeita de possuir EG. Em seguida, com as medidas suspeitas em mãos, desenvolve-se um índice de filtragem (FI) que será utilizado para identificar qual daquelas medidas tem maior probabilidade de possuir EG. Os sistemas de 14 e 30 barras do IEEE...

## Controle e filtragem para sistemas lineares discretos incertos sujeitos a saltos Markovianos; Control and filtering for uncertain discrete-time Markovian jump linear systems

Cerri, João Paulo
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
Relevância na Pesquisa
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## A comparison between single site modeling and multiple site modeling approaches using Kalman filtering

Monteiro, Magda; Costa, Marco
Fonte: AIP Publishing Publicador: AIP Publishing
Tipo: Conferência ou Objeto de Conferência
Português
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This work presents a comparative study between two approaches to calibrate radar rainfall in real time. The weather radar provides continuous measurements in real-time which have errors of either meteorological or instrumental nature. Locally, gauge measurements have a greater performance than radar measurements that can be used to improve radar estimates. One way of doing that is via a state space representation associated to the Kalman filter algorithm. In the single- site modeling approach we use the linear calibration model applied in [1] and [3] while the multivariate state-space model proposed in [6] is used in the multiple site approach. This work aims to discuss and compare these two different state space formulations based on the same data set.

## Spectral Rate Theory for Two-State Kinetics

Prinz, Jan-Hendrik; Chodera, John D.; Noé, Frank
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Classical rate theories often fail in cases where the observable(s) or order parameter(s) used is a poor reaction coordinate or the observed signal is deteriorated by noise, such that no clear separation between reactants and products is possible. Here, we present a general spectral two-state rate theory for ergodic dynamical systems in thermal equilibrium that explicitly takes into account how the system is observed. The theory allows the systematic estimation errors made by standard rate theories to be understood and quantified. We also elucidate the connection of spectral rate theory with the popular Markov state modeling approach for molecular simulation studies. An optimal rate estimator is formulated that gives robust and unbiased results even for poor reaction coordinates and can be applied to both computer simulations and single-molecule experiments. No definition of a dividing surface is required. Another result of the theory is a model-free definition of the reaction coordinate quality. The reaction coordinate quality can be bounded from below by the directly computable observation quality, thus providing a measure allowing the reaction coordinate quality to be optimized by tuning the experimental setup. Additionally, the respective partial probability distributions can be obtained for the reactant and product states along the observed order parameter...

## A hidden Markov approach to the forward premium puzzle

Elliott, R.; Han, B.
Fonte: World Scientific Publishing Co Pte Ltd Publicador: World Scientific Publishing Co Pte Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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A Hidden Markov Chain (HMC) is applied to study the forward premium puzzle. The weekly quotient of the interest rate differential divided by the log exchange rate change is modeled as a Hidden Markov process. Compared with existing standard approaches, the Hidden Markov approach allows a detailed analysis of the puzzle on a day-to-day basis while taking into full account the presence of noise in the observations. Two and three state models are investigated. A three-state HMC model performs better than two-state models. Application of the three-state model reveals that the above quotient is mostly zero, and hence leads to the rejection of the uncovered interest rate parity hypothesis.; Robert J. Elliott; Bing Han

## Multiple Priors and Asset Pricing

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The asset pricing implications of a statistical model consistent with multiple priors, or beliefs about return distributions, are developed. It is shown that quite generally equilibrium differences in mean returns across priors are to be explained in terms of perceived risk differences between these priors. Advances in filtering theory are employed on time series data to filter all the multiple state conditional components of risks and rewards. It is then observed that excess return differentials across priors are broadly consistent with required risk compensations under these priors, though the sharp hypothesis of zero intercept and unit slope is rejected. The filtered results also deliver numerous other interesting statistics. Here we focus on the construction of long horizon return distributions from data on daily returns using a Markov chain approach to incorporate stochasticity in elementary risk characterizations like volatility, skewness and kurtosis.; Dilip B. Madan and Robert J. Elliott

## Two-phase layered learning recommendation via category structure

Ji, K.; Shen, H.; Tian, H.; Wu, Y.; Wu, J.
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Conference paper
Relevância na Pesquisa
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Context and social network information have been introduced to improve recommendation systems. However, most existing work still models users’ rating for every item directly. This approach has two disadvantages: high cost for handling large amount of items and unable to handle the dynamic update of items. Generally, items are classified into many categories. Items in the same category have similar/relevant content, and hence may attract users of the same interest. These characteristics determine that we can utilize the item’s content similarity to overcome the difficultiess of large amount and dynamic update of items. In this paper, aiming at fusing the category structure, we propose a novel two-phase layered learning recommendation framework, which is matrix factorization approach and can be seen as a greedy layer-wise training: first learn user’s average rating to every category, and then, based on this, learn more accurate estimates of user’s rating for individual item with content and social relation ensembled. Based on two kinds of classifications, we design two layered gradient algorithms in our framework. Systematic experiments on real data demonstrate that our algorithms outperform other state-of-the-art methods, especially for recommending new items.; Ke Ji...

## Filtragem robusta recursiva para sistemas lineares a tempo discreto com parâmetros sujeitos a saltos Markovianos; Recursive robust filtering for discrete-time Markovian jump linear systems

Jesus, Gildson Queiroz de
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
Relevância na Pesquisa
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Este trabalho trata de filtragem robusta para sistemas lineares sujeitos a saltos Markovianos discretos no tempo. Serão desenvolvidas estimativas preditoras e filtradas baseadas em algoritmos recursivos que são úteis para aplicações em tempo real. Serão desenvolvidas duas classes de filtros robustos, uma baseada em uma estratégia do tipo H \'INFINITO\' e a outra baseada no método dos mínimos quadrados regularizados robustos. Além disso, serão desenvolvidos filtros na forma de informação e seus respectivos algoritmos array para estimar esse tipo de sistema. Neste trabalho assume-se que os parâmetros de saltos do sistema Markoviano não são acessíveis.; This work deals with the problem of robust state estimation for discrete-time uncertain linear systems subject to Markovian jumps. Predicted and filtered estimates are developed based on recursive algorithms which are useful in on-line applications. We develop two classes of filters, the first one is based on a H \'INFINITO\' approach and the second one is based on a robust regularized leastsquare method. Moreover, we develop information filter and their respective array algorithms to estimate this kind of system. We assume that the jump parameters of the Markovian system are not acessible.

## Stability of Kalman filtering with Markovian packet losses

Huang , Minyi; Dey, Subhrakanti
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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We consider Kalman filtering in a network with packet losses, and use a two state Markov chain to describe the normal operating condition of packet delivery and transmission failure. Based on the sojourn time of each visit to the failure or successful pac

## Kalman Filtering with Markovian Packet Losses and Stability Criteria

Huang , Minyi; Dey, Subhrakanti
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Português
Relevância na Pesquisa
37.063252%
We consider Kalman filtering in a network with packet losses, and use a two state Markov chain to describe the normal operating condition of packet delivery and transmission failure. We analyze the behavior of the estimation error covariance matrix and in

## Two-Time-Scale Approximation for Wonham Filters

Zhang, Qing; Yin, George; Moore, John
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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This paper is concerned with approximation of Wonham filters. A focal point is that the underlying hidden Markov chain has a large state space. To reduce computational complexity, a two-time-scale approach is developed. Under time scale separation, the st

## Solving single molecules: filtering noisy discrete data made of photons and other type of observables

Flomenbom, Ophir
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.16139%
In numerous systems in biophysics and related fields, scientists measure (with very smart methods) individual molecules (e.g. biopolymers (proteins, DNA, RNA, etc), nano - crystals, ion channels), aiming at finding a model from the data. But the noise is not solved accurately in not so few cases and this may lead to misleading models. Here, we solve the noise. We consider two state photon trajectories from any on off kinetic scheme (KS): the process emitting photons with a rate {\gamma}on when it is in the on state, and emitting with a rate {\gamma}off when it is in the off state. We develop a filter that removes the noise resulting in clean data also in cases where binning fails. The filter is a numerical algorithm with various new statistical treatments. It is based on a new general likelihood function developed here, with observable dependent form. The filter can solve the noise, in the detectable region of the rate space: that is, we also find a region where the data is "too" noisy. Consistency tests will find the region's type from the data. If the data is ruled "too noisy", binning obviously fails, and one should apply simpler methods on the raw data and realizing that the extracted information is partial. We show that not applying the filter while cleaning results in erroneous rates. This filter (with minor adjustments) can solve the noise in any discrete state trajectories...

## Spectral rate theory for projected two-state kinetics

Prinz, Jan-Hendrik; Chodera, John D.; Noe, Frank
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.182754%
Classical rate theories often fail in cases where the observable(s) or order parameter(s) used are poor reaction coordinates or the observed signal is deteriorated by noise, such that no clear separation between reactants and products is possible. Here, we present a general spectral two-state rate theory for ergodic dynamical systems in thermal equilibrium that explicitly takes into account how the system is observed. The theory allows the systematic estimation errors made by standard rate theories to be understood and quantified. We also elucidate the connection of spectral rate theory with the popular Markov state modeling (MSM) approach for molecular simulation studies. An optimal rate estimator is formulated that gives robust and unbiased results even for poor reaction coordinates and can be applied to both computer simulations and single-molecule experiments. No definition of a dividing surface is required. Another result of the theory is a model-free definition of the reaction coordinate quality (RCQ). The RCQ can be bounded from below by the directly computable observation quality (OQ), thus providing a measure allowing the RCQ to be optimized by tuning the experimental setup. Additionally, the respective partial probability distributions can be obtained for the reactant and product states along the observed order parameter...

## Two-state filtering for joint state-parameter estimation

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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This paper presents an approach for simultaneous estimation of the state and unknown parameters in a sequential data assimilation framework. The state augmentation technique, in which the state vector is augmented by the model parameters, has been investigated in many previous studies and some success with this technique has been reported in the case where model parameters are additive. However, many geophysical or climate models contains non-additive parameters such as those arising from physical parametrization of sub-grid scale processes, in which case the state augmentation technique may become ineffective since its inference about parameters from partially observed states based on the cross covariance between states and parameters is inadequate if states and parameters are not linearly correlated. In this paper, we propose a two-stages filtering technique that runs particle filtering (PF) to estimate parameters while updating the state estimate using Ensemble Kalman filter (ENKF; these two "sub-filters" interact. The applicability of the proposed method is demonstrated using the Lorenz-96 system, where the forcing is parameterized and the amplitude and phase of the forcing are to be estimated jointly with the states. The proposed method is shown to be capable of estimating these model parameters with a high accuracy as well as reducing uncertainty while the state augmentation technique fails.

## Kalman Filtering over Gilbert-Elliott Channels: Stability Conditions and the Critical Curve

Wu, Junfeng; Shi, Guodong; Anderson, Brian D. O.; Johansson, Karl Henrik
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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This paper investigates the stability of Kalman filtering over Gilbert-Elliott channels where random packet drop follows a time-homogeneous two-state Markov chain whose state transition is determined by a pair of failure and recovery rates. First of all, we establish a relaxed condition guaranteeing peak-covariance stability described by an inequality in terms of the spectral radius of the system matrix and transition probabilities of the Markov chain. We further show that that condition can be interpreted using a linear matrix inequality feasibility problem. Next, we prove that the peak-covariance stability implies mean-square stability, if the system matrix has no defective eigenvalues on the unit circle. This connection between the two stability notions holds for any random packet drop process. We prove that there exists a critical curve in the failure-recovery rate plane, below which the Kalman filter is mean-square stable and no longer mean-square stable above, via a coupling method in stochastic processes. Finally, a lower bound for this critical failure rate is obtained making use of the relationship we establish between the two stability criteria, based on an approximate relaxation of the system matrix.

## Optimal unambiguous filtering of a quantum state: An instance in mixed state discrimination

Bergou, Janos; Herzog, Ulrike; Hillery, Mark
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Deterministic discrimination of nonorthogonal states is forbidden by quantum measurement theory. However, if we do not want to succeed all the time, i.e. allow for inconclusive outcomes to occur, then unambiguous discrimination becomes possible with a certain probability of success. A variant of the problem is set discrimination: the states are grouped in sets and we want to determine to which particular set a given pure input state belongs. We consider here the simplest case, termed quantum state filtering, when the $N$ given non-orthogonal states, $\{|\psi_{1} >,..., |\psi_{N} > \}$, are divided into two sets and the first set consists of one state only while the second consists of all of the remaining states. We present the derivation of the optimal measurement strategy, in terms of a generalized measurement (POVM), to distinguish $|\psi_1>$ from the set $\{|\psi_2 >,...,|\psi_N > \}$ and the corresponding optimal success and failure probabilities. The results, but not the complete derivation, were presented previously [\prl {\bf 90}, 257901 (2003)] as the emphasis there was on appplication of the results to novel probabilistic quantum algorithms. We also show that the problem is equivalent to the discrimination of a pure state and an arbitrary mixed state.; Comment: 8 pages

## Quantum-state filtering applied to the discrimination of Boolean functions

Bergou, Janos A.; Hillery, Mark
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Quantum state filtering is a variant of the unambiguous state discrimination problem: the states are grouped in sets and we want to determine to which particular set a given input state belongs.The simplest case, when the N given states are divided into two subsets and the first set consists of one state only while the second consists of all of the remaining states, is termed quantum state filtering. We derived previously the optimal strategy for the case of N non-orthogonal states, {|\psi_{1} >, ..., |\psi_{N} >}, for distinguishing |\psi_1 > from the set {|\psi_2 >, ..., |\psi_N >} and the corresponding optimal success and failure probabilities. In a previous paper [PRL 90, 257901 (2003)], we sketched an appplication of the results to probabilistic quantum algorithms. Here we fill in the gaps and give the complete derivation of the probabilstic quantum algorithm that can optimally distinguish between two classes of Boolean functions, that of the balanced functions and that of the biased functions. The algorithm is probabilistic, it fails sometimes but when it does it lets us know that it did. Our approach can be considered as a generalization of the Deutsch-Jozsa algorithm that was developed for the discrimination of balanced and constant Boolean functions.; Comment: 8 pages

## Filtering of matter wave vibrational states via spatial adiabatic passage

Loiko, Yu.; Ahufinger, V.; Corbalán, R.; Birkl, G.; Mompart, J.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We discuss the filtering of the vibrational states of a cold atom in an optical trap, by chaining this trap with two empty ones and controlling adiabatically the tunneling. Matter wave filtering is performed by selectively transferring the population of the highest populated vibrational state to the most distant trap while the population of the rest of the states remains in the initial trap. Analytical conditions for two-state filtering are derived and then applied to an arbitrary number of populated bound states. Realistic numerical simulations close to state-of-the-art experimental arrangements are performed by modeling the triple well with time dependent P\"oschl-Teller potentials. In addition to filtering of vibrational states, we discuss applications for quantum tomography of the initial population distribution and engineering of atomic Fock states that, eventually, could be used for tunneling assisted evaporative cooling.; Comment: 7 pages, 6 figures

## Filtering of matter-wave vibrational states via spatial adiabatic passage

Loiko, Yury; Ahufinger, Verònica; Corbalán, R.; Birkl, Gerhard; Mompart Penina, Jordi
Tipo: Artigo de Revista Científica Formato: application/pdf