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Digital filtering of oscillations intrinsic to transmission line modeling based on lumped parameters

Da Costa, Eduardo Coelho Marques; Kurokawa, Sérgio; Shinoda, Ailton Akira; Pissolato, José
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 908-915
Português
Relevância na Pesquisa
36.7%
A correction procedure based on digital signal processing theory is proposed to smooth the numeric oscillations in electromagnetic transient simulation results from transmission line modeling based on an equivalent representation by lumped parameters. The proposed improvement to this well-known line representation is carried out with an Finite Impulse Response (FIR) digital filter used to exclude the high-frequency components associated with the spurious numeric oscillations. To prove the efficacy of this correction method, a well-established frequency-dependent line representation using state equations is modeled with an FIR filter included in the model. The results obtained from the state-space model with and without the FIR filtering are compared with the results simulated by a line model based on distributed parameters and inverse transforms. Finally, the line model integrated with the FIR filtering is also tested and validated based on simulations that include nonlinear and time-variable elements. © 2012 Elsevier Ltd. All rights reserved.

Filtragem de sistemas discretos com parametros sujeitos a saltos markovianos; Filtering of discrete-time Markov jump linear systems Markov jump linear systems

Andre Ricardo Fioravanti
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/10/2007 Português
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Esta dissertação tem par principal objetivo o estudo do problema de projeto de filtros H2 e Hoo de sistemas lineares discretos com parâmetros sujeitos a saltos markovianos. Inicialmente, sob a hipótese de que o parâmetro da cadeia de Markov é mensurável, fornecemos a caracterização de todos os filtros tais que o erro de estimação é limitado por uma norma, produzindo a solução completa do problema de projeto dependente do modo da cadeia. Baseado neste resultado, consideramos o projeto do filtro robusto capaz de lidar com incertezas paramétricas. Em seguida, propomos um procedimento de projeto de filtros sem o conhecimento da cadeia. Todos os problemas de filtragem são expressos em termos de desigualdades matriciais lineares. Os resultados teóricos são ilustrados através de uma aplicação prática que consiste na comunicação de dados através de um canal markoviano.; This thesis addresses the H2 and Hoo filtering design problem of discrete-time Markov jump linear systems. First, under the assumption that the Markov parameter is measurable, we provide the characterization of all filters such that the estimation errar remains bounded by a given narm leveI, yielding the complete solution of the mode-dependent filtering design problem. Based on this result...

Symbiotic filtering for spam email detection

Lopes, Clotilde; Cortez, Paulo; Sousa, Pedro; Rocha, Miguel; Rio, Miguel
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /08/2011 Português
Relevância na Pesquisa
36.83%
This paper presents a novel spam filtering technique called Symbiotic Filtering (SF) that aggregates distinct local filters from several users to improve the overall perfor- mance of spam detection. SF is an hybrid approach combining some features from both Collaborative (CF) and Content-Based Filtering (CBF). It allows for the use of social networks to personalize and tailor the set of filters that serve as input to the filtering. A comparison is performed against the commonly used Naive Bayes CBF algorithm. Several experiments were held with the well-known Enron data, under both fixed and incremental symbiotic groups. We show that our system is competitive in performance and is robust against both dictionary and focused con- tamination attacks. Moreover, it can be implemented and deployed with few effort and low communication costs, while assuring privacy.; Fundação para a Ciência e a Tecnologia (FCT) - bolsa PTDC/EIA/64541/2006

Multi-user frequency pre-filtering technique for MIMO SFBC MC-CDMA systems

Silva, Adão; Silva, Elídio; Gameiro, Atílio
Fonte: IEEE Publicador: IEEE
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
36.75%
This paper deals with downlink space-frequency block coding (SFBC) with a multi-user pre-filtering technique for MIMO MC-CDMA systems. We consider the use of an antenna array at both the base station (BS) and the user terminal (UT). The space-frequency block codes allow that the spatial diversity be efficiently exploited and the linear multi-user frequency pre-filtering technique modulates the transmitted signal to eliminate the effects of multiple access interference (MAI) and channel distortions at the user terminals. The aim of this technique is to transfer the most computational complexity from UT to the BS, keeping the first one at very low complexity. The performance of the proposed scheme is evaluated, considering typical pedestrian scenario and both uncoded data and channel turbo coding based on UMTS specifications. © 2008 IEEE.; FCT - FFT-XXI (POSI/CPS/4670/2007); PHOTON(PTDC/EEA-TEL/72890/06)

Combining space frequency coding with a pre-filtering technique for TDD downlink MC-CDMA systems in a beyond 3G context

Silva, Adão; Gameiro, Atílio
Fonte: Institution of Engineering and Technology Publicador: Institution of Engineering and Technology
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
36.75%
This paper deals with downlink space-frequency block coding with a joint pre-filtering and spreading technique for time division duplex MC-CDMA. We consider the use of antenna arrays at the base station (BS) and a single antenna at the mobile terminal (MT). The space-frequency block codes allow that the spatial diversity be efficiently exploited and the linear multi-user pre-filtering technique allows to format the transmitted signals so that the multiple access interference and channel distortions at mobile terminals are completely removed, keeping the MT at low complexity. Simulations results are carried out in scenarios with both perfect and imperfect channel estimates and using the channel turbo code specified for current UMTS system, to demonstrate the effectiveness of the proposed SFBC with a linear multi-user pre-filtering approach.; European project IST-2001-507039 4MORE; FCT - POSI/CPS/46701/2002

SFBC with pre-filtering technique for DL TDD MC-CDMA systems in high data rate context

Silva, Adão; Gameiro, Atílio
Fonte: IEEE Publicador: IEEE
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
36.7%
This paper deals with downlink space-frequency block coding with a pre-filtering technique for time division duplex MC-CDMA. We consider the use of antenna arrays at the base station (BS) and a single antenna at the mobile terminal (MT). The space-frequency block codes allow that the spatial diversity be efficiently exploited and the linear multi-user pre-filtering technique allows to format the transmitted signals so that the multiple access interference (MAI) and channel distortions at mobile terminals are completely removed. The aim of this technique is to transfer the most computational complexity from MT to the BS, keeping the first one at very low complexity. Simulations results are carried out in high data rate scenarios with the channel turbo code specified for the current UMTS system, to demonstrate the effectiveness of the proposed multi-user pre-filtering algorithm with SFBC. © 2005 IEEE.; IST-2001-507039 4MORE; FCT - POSI/CPS/46701/2002

Assessment of the performance of eight filtering algorithms by using full-waveform LiDAR data of unmanaged eucalypt forest

Gonçalves, G.; Gomes Pereira, L.
Fonte: FeLis/ University of Freiburg Publicador: FeLis/ University of Freiburg
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
36.75%
In this study the strengths and weaknesses of eight filtering algorithms are evaluated by using the mean, standard deviation and RMSE metrics. Seven of these algorithms are implemented in the freeware software ALDPAT (Airborne LiDAR Data Processing and Analysis Tools) and the eighth, known as the Axelsson filter, in the commercial software Terrascan. The referred metrics are calculated by using DTM of topographic surfaces with quite different morphologies and vegetation covers. Forty-three of these surfaces, on circular plots of 400 m2 each, are covered by brushwood and unmanaged eucalypt forest with different stand characteristics. The mean tree density is around 1600 trees per hectare. The reference DTM for assessing the DTM produced by filtering full-waveform LiDAR data using the eight filtering algorithms are created with the help of a total station and geodetic GNSS receivers. The results show that the Axelsson and the so-called Polynomial Two Surface Fitting filters give the best results in terms of RMSE. Nonetheless, the results also show that all the tested filters are suitable for the filtering of full-waveform LiDAR data used in forestry related work, and collected over areas with great amount and high brushwood, chaotic eucalypt tree distribution and high tree density. The results obtained for a forest area with such characteristics – among which it should be mentioned a RMSE of 15 cm - are quite surprising.

Recomendação de música: comparação entre collaborative filtering e context filtering

Canhoto, Vicente
Fonte: Instituto Universitário de Lisboa Publicador: Instituto Universitário de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2013 Português
Relevância na Pesquisa
36.88%
Mestrado em Gestão de Sistemas de Informação; A massificação de serviços de música online democratizou o acesso a milhões de músicas. No entanto, é impossível para os utilizadores ouvirem e conhecerem todas essas músicas. De modo a auxiliar na sugestão sobre o que ouvir num dado momento, foram desenvolvidos sistemas que recomendam músicas ao utilizador. A técnica de Collaborative Filtering gera recomendações com base nas músicas ouvidas por utilizadores com gostos semelhantes. Apesar de apresentar um bom desempenho, vários investigadores propuseram melhoramentos aos mesmos. Um dos mais referidos é a utilização de informação contextual sobre o utilizador. A relação entre a utilização desta informação em sistemas de recomendação e o aumento da satisfação dos utilizadores foi provada por diversos investigadores. O trabalho desenvolvido nesta dissertação focou-se na comparação entre um algoritmo de recomendação por Collaborative Filtering tradicional e outro baseado em determinados elementos do contexto. Para isso foi proposto e implementado um sistema de recomendação online que integra estas duas abordagens, apoiado numa revisão da literatura. Por fim, este sistema foi utilizado numa experiência de campo online em que qualquer utilizador pôde fazer pedidos de recomendação. Estes pedidos foram servidos alternadamente por cada um dos algoritmos de recomendação...

Analysis of the efficiency of a cloth cyclone: the effect of the permeability of the filtering medium

Rodrigues,M.V.; Arouca,F.O.; Barrozo,M.A.S.; Damasceno,J.J.R.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2003 Português
Relevância na Pesquisa
36.75%
The cloth cyclone is a solid-gas separation device that consists of a Lapple cyclone whose conical section has been replaced by a conical filtering wall. The present research was undertaken with the aim of examining the influence of a conical filtering section made of three different materials on the performance of a Lapple design cyclone. The overall efficiency and pressure drops of the cloth cyclone and a conventional one were compared. The effect of the filtering medium on the behavior of the cyclone was also evaluated using an equation that correlates the cut size diameter with the operational conditions, the properties of the gas-solid system and the resistance of the filtering medium. The experimental results demonstrated that the overall efficiency of the conventional cyclone was similar to that of the proposed device, with the latter displaying a reduction in pressure drop. Consequently, energy costs are lowered when cloth cyclones are used.

An Autoregressive Conditional Filtering Process to remove Intraday Seasonal Volatility and its Application to Testing the Noisy Rational Expectations Model

Cho, Jang Hyung
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
Relevância na Pesquisa
36.75%
We develop a new autoregressive conditional process to capture both the changes and the persistency of the intraday seasonal (U-shape) pattern of volatility in essay 1. Unlike other procedures, this approach allows for the intraday volatility pattern to change over time without the filtering process injecting a spurious pattern of noise into the filtered series. We show that prior deterministic filtering procedures are special cases of the autoregressive conditional filtering process presented here. Lagrange multiplier tests prove that the stochastic seasonal variance component is statistically significant. Specification tests using the correlogram and cross-spectral analyses prove the reliability of the autoregressive conditional filtering process. In essay 2 we develop a new methodology to decompose return variance in order to examine the informativeness embedded in the return series. The variance is decomposed into the information arrival component and the noise factor component. This decomposition methodology differs from previous studies in that both the informational variance and the noise variance are time-varying. Furthermore, the covariance of the informational component and the noisy component is no longer restricted to be zero. The resultant measure of price informativeness is defined as the informational variance divided by the total variance of the returns. The noisy rational expectations model predicts that uninformed traders react to price changes more than informed traders...

Robust H∞ filtering for 2-D systems with intermittent measurements; Robust H-infinity filtering for 2-D systems with intermittent measurements

Liu, X.; Gao, H.; Shi, P.
Fonte: SP Birkhäuser Verlag Boston Publicador: SP Birkhäuser Verlag Boston
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
Relevância na Pesquisa
36.75%
This paper is concerned with the problem of robust H ∞ filtering for uncertain two-dimensional (2-D) systems with intermittent measurements. The parameter uncertainty is assumed to be of polytopic type, and the measurements transmission is assumed to be imperfect, which is modeled by a stochastic variable satisfying the Bernoulli random binary distribution. Our attention is focused on the design of an H ∞ filter such that the filtering error system is stochastically stable and preserves a guaranteed H ∞ performance. This problem is solved in the parameter-dependent framework, which is much less conservative than the quadratic approach. By introducing some slack matrix variables, the coupling between the positive definite matrices and the system matrices is eliminated, which greatly facilitates the filter design procedure. The corresponding results are established in terms of linear matrix inequalities, which can be easily tested by using standard numerical software. An example is provided to show the effectiveness of the proposed approach.; Xiuming Liu, Huijun Gao, Peng Shi

H-Infinity filtering of 2-D systems with packet losses; H-Infinity filtering of 2-D systems with packet losses

Liu, X.; Gao, H.; Shi, P.; Wang, Y.
Fonte: IEEE; China Publicador: IEEE; China
Tipo: Conference paper
Publicado em //2008 Português
Relevância na Pesquisa
36.75%
This paper is concerned with the problem of robust Hinfin filtering for uncertain 2-D systems with intermittent measurements. The parameter uncertainty is assumed to be of polytopic type, and the measurements transmission is assumed to be imperfect, which is modelled by a stochastic variable. Our attention is focused on the design of an Hinfin filter such that the filtering error system is stochastically stable and preserves a guaranteed Hinfin performance. This problem is solved in the parameter-dependent framework and the corresponding results are established in terms of LMIs. An example is provided to show the effectiveness of the proposed approach.; Liu Xiuming, Gao Huijun, Shi Peng, Wang Yuandao

Incorporating filtering techniques in a fuzzy linguistic multi-agent model for information gathering on the web

Herrera, Francisco; Herrera-Viedma, E.; Mart??nez, L.; Herrera, J.C.; L??pez Herrera, Antonio Gabriel
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
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In (Computing with Words, Wiley, New York, 2001, p. 251; Soft Comput. 6 (2002) 320; Fuzzy Logic and The Internet, Physica-Verlag, Springer, Wurzburg, Berlin, 2003) we presented diferent fuzzy linguistic multi-agent models for helping users in their information gathering processes on the Web. In this paper we describe a new fuzzy linguistic multi-agent model that incorporates two information filtering techniques in its structure: a content-based filtering agent and a collaborative filtering agent. Both elements are introduced to increase the information filtering possibilities of multi-agent system on the Web and, in such a way, to improve its retrieval issues.

Sinogram bow-tie filtering in FBP PET reconstruction

Abella, Mónica; Vaquero, Juan José; Soto-Montenegro, M. L.; Lage, E.; Desco, Manuel
Fonte: American Association of Physicists in Medicine Publicador: American Association of Physicists in Medicine
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article Formato: application/pdf
Publicado em /05/2009 Português
Relevância na Pesquisa
36.9%
Low-pass filtering of sinograms in the radial direction is the most common practice to limit noise amplification in filtered back projection FBP reconstruction of positron emission tomography studies. Other filtering strategies have been proposed to prevent the loss in resolution due to low-pass radial filters, although results have been diverse. Using the well-known properties of the Fourier transform of a sinogram, the authors defined a binary mask that matches the expected shape of the support region in the Fourier domain of the sinogram “bow tie”. This mask was smoothed by a convolution with a ten-point Gaussian kernel which not only avoids ringing but also introduces a pre-emphasis at low frequencies. A new filtering scheme for FBP is proposed, comprising this smoothed bow-tie filter combined with a standard radial filter and an axial filter. The authors compared the performance of the bow-tie filtering scheme with that of other previously reported methods: Standard radial filtering, angular filtering, and stackgram-domain filtering. All the quantitative data in the comparisons refer to a baseline reconstruction using a ramp filter only. When using the smallest size of the Gaussian kernel in the stackgram domain, the authors achieved a noise reduction of 33% at the cost of degrading radial and tangential resolutions 14.5% and 16%...

A Multi-level Approach to Intelligent Information Filtering: Model, System, and Evaluation

Mostafa, J.; Mukhopahyay, S.; Lam, W.; Palakal, M.
Fonte: Rob Kling Center for Social Informatics Publicador: Rob Kling Center for Social Informatics
Tipo: Trabalho em Andamento Formato: 10176 bytes; 4056 bytes; image/jpeg; text/html
Português
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36.75%
To conduct efficient information filtering, uncertanties occurring at multiple levels must be managed. Uncertainties can occur due to changing document space as well as stochasticity and non-stationarity of the user. In this paper, a filtering model is proposed that decomposes the overall task into subsystem functionalities and highlights the need for multiple adaptation techniques to cope with uncertainties. A filtering system, named SIFTER, has been implemented based on the model, using established techniques in information retrieval and artificial intelligence. These techniques include document representation using vector-space model, document classification by unsupervised learning, and user modeling by reinforcement learning. The system can filter information based on content and user's specific interests. The user's interest is automatically learned with only limited user intervention in the form of optional relevance feedbacks for documents. We also describe extensive experimental studies conducted with SIFTER to filter computer and information science documents collected from the Internet and commercial database services. The experimental results demonstrate that the system performs very well in filtering documents in a realistic problem setting.; Indiana University

Prediction and Filtering of Stationary Processes: Yaglom’s Method and Minimax Filtering

Mascher, Philipp
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
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36.83%
The aim of this work is to give a basic introduction to the theory of stationary stochastic processes, particularly to the somewhat specialized problem of prediction and filtering of such processes. Kolmogorov was the first to make a contribution to its solution using involved mathematical theory. In the years following the publication of Wiener’s famous book, the theory gained considerable popularity from the applied sciences, particularly radio engineering. In this work, we shall present Yaglom’s method to solving the problems considered in Wiener’s book. This alternative approach is entirely based on rather basic facts from Hilbert space theory and the theory of complex variables. As it turns out, the theory of filtering of stationary processes heavily relies on spectral properties of the processes. In particular, Yaglom’s approach assumes complete knowledge of the spectral densities. In this work, however, we shall not be concerned with the problem of estimating such quantities based on a finite sample. Instead, in order to account for uncertainty as frequently encountered in practice, we shall discuss the problem of minimax filtering which has emerged from the practical need of allowing for incomplete knowledge about spectral properties.

Performance analysis and design of filtering hydrocyclones

Vieira,L. G. M.; Barbosa,E. A.; Damasceno,J. J. R.; Barrozo,M. A. S.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2005 Português
Relevância na Pesquisa
36.86%
The filtering hydrocyclone is a solid-liquid separation device patented by the Chemical Engineering Department at the Federal University of Uberlândia, which consists of a hydrocyclone whose conical section was replaced by a conical filtering wall. The objective of this work is to compare the performances of the filtering hydrocyclones designed by Bradley and by Rietema. The experimental results obtained with the filtering hydrocyclones under the same operational conditions as those used with the conventional device allow the conclusion that performance of the Bradley and Rietema types is significantly influenced by the filtering medium. Rietema's filtering hydrocyclones had a lower volumetric feed flowrate than the conventional device and Bradley's filtering hydrocyclones showed increases in this same variable. In both designs, overall efficiency was influenced by the underflow-to-throughput ratio.

Computer enhancement of real world photographic images using homomorphic and linear filtering

Sampat, Nitin
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.75%
Digital Image Processing techniques have become increasingly popular in the last few years. Conventional silver halide photography continues to be used by the large amateur market, but not without "imperfect" images. There is almost always a need for enhancement or subsequent improvement after the photograph is made. This study dealt with computer image enhancement of such "imperfect" photographs using homomorphic (non-linear) and linear frequency-domain digital filtering (on a VAX-11/785) and a comparison in effectiveness was determined, using a subjective criteria for image quality. It was found that, in general, linear filtering is to be the preferred method of choice when implementing image enhancement on amateur type photographs. Differences in "image quality improvement" by the two techniques was minimal, when the image was subjected to histogram equalization after processing. Homomorphic filtering requires substantial post processing without which it is a potential failure. Linear filtering was both computationally less demanding and subjectively more pleasing.

Spatial filtering of a projection printer, using partially coherent light

Vlahakes, Leon
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.75%
This investigation applied the technique of spatial filtering to a projection printer utilizing partially coherent illumination. The affect of filtering on image quality parameters such as resolution, edge gradient and MTF were determined for a black and white film. Edge gradient analysis was used to derive MTF data from sampled edges. A source diameter of 3 mm and spatial filter diameters of .6, 2.2, and 3.0 mm were used. Spatial filtering was seen to have a drastic affect on edge gradient and MTF. Increasing the filter diameter resulted in a decrease of cutoff frequency of the system. Spatial filtering had the affect of boosting low frequency modulation by up to 30 percent. Subjectively, however, changes could not be detected, indicating that the alterations made to the system are not significant to be detected visually. Resolution was found to fluctuate only 15 percent between the application of each filter. Despite gross changes in other imaging characteristics, resolution remained nearly unchanged, indicating that resolution is a poor discriptor of image quality.

Risk Sensitive Filtering with Poisson Process Observations

Malcolm, W Paul; James, Matthew; Elliott, Robert J
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Português
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36.8%
In this paper we consider risk sensitive filtering for Poisson process observations. Risk sensitive filtering is a type of robust filtering which offers performance benefits in the presence of uncertainties. We derive a risk sensitive filter for a stochastic system where the signal variable had dynamics described by a diffusion equation and determines the rate function for an observation process. The filtering equations are stochastic integral equations. Computer simulations are presented to demonstrate the performance gain for the risk sensitive filter compared with the risk neutral filter.