Browsing by Author "Nowak, Robert David"
Now showing items 146 of 46

Adaptive Wavelet Transforms via Lifting
Claypoole, Roger L.; Baraniuk, Richard G.; Nowak, Robert David (19980501)This paper develops two new adaptive wavelet transforms based on the lifting scheme. The lifting construction exploits a spatialdomain, predictionerror interpretation of the wavelet transform and provides a powerful ... 
Adaptive Wavelet Transforms via Lifting
Claypoole, Roger L.; Baraniuk, Richard G.; Nowak, Robert David (19990115)This paper develops new algorithms for adapted multiscale analysis and signal adaptive wavelet transforms. We construct our adaptive transforms with the <i>lifting scheme</i>, which decomposes the wavelet transform into ... 
Adaptive Wavelet Transforms via Lifting
Claypoole, Roger L.; Baraniuk, Richard G.; Nowak, Robert David (19990501)This paper develops new algorithms for adapted multiscale analysis and signal adaptive wavelet transforms. We construct our adaptive transforms with the <i>lifting scheme</i>, which decomposes the wavelet transform into ... 
Adaptive Weighted Highpass Filters Using Multiscale Analysis
Nowak, Robert David; Baraniuk, Richard G. (19980701)In this paper, we propose a general framework for studying a class of weighted highpass filters. Our framework, based on a multiscale signal decomposition, allows us to study a wide class of filters and to assess the ... 
A Bayesian Multiscale Approach to Joint Image Restoration and Edge Detection
Wan, Yi; Nowak, Robert David (19990720)This paper presents a novel waveletbased method for simultaneous image restoration and edge detection. The Bayesian framework developed here is general enough to treat a wide class of linear inverse problems involving ... 
Coding Theoretic Approach to Image Segmentation
Ndili, Unoma; Nowak, Robert David; Figueiredo, Mario (20011020)In this paper, using a coding theoretic approach, we implement Rissanen's concept of minimum description length (MDL) for segmenting an image into piecewise homogeneous regions. Our image model is a Gaussian random field ... 
CORT: Classification Or Regression Trees
Scott, Clayton; Willett, Rebecca; Nowak, Robert David (20030420)In this paper we challenge three of the underlying principles of CART, a well know approach to the construction of classification and regression trees. Our primary concern is with the penalization strategy employed to prune ... 
CORT: Classification Or Regression Trees
Scott, Clayton; Willett, Rebecca; Nowak, Robert David (20030620)In this paper we challenge three of the underlying principles of CART, a well know approach to the construction of classification and regression trees. Our primary concern is with the penalization strategy employed to prune ... 
Distributed Image Compression for Sensor Networks using Correspondence Analysis and SuperResolution
Wagner, Raymond; Nowak, Robert David; Baraniuk, Richard G. (20030901)We outline a distributed coding technique for images captured from sensors with overlapping fields of view in a sensor network. First, images from correlated views are roughly registered (relative to a sensor of primary ... 
Efficient Methods for Identification of Volterra Filters
Nowak, Robert David; Van Veen, Barry D. (19960201)A major drawback of the truncated Volterra series or "Volterra filter" for system identification is the large number of parameters required by the standard filter structure. The corresponding estimation problem requires ... 
Generalized likelihood ratio detection for fMRI using complex data
Nan, F.Y.; Nowak, Robert David (19990420)The majority of fMRI studies obtain functional information using statistical tests based on the magnitude image reconstructions. Recently, a complex correlation (CC) test was proposed based on teh complex image data in ... 
Hidden Markov Models for Waveletbased Signal Processing
Crouse, Matthew; Baraniuk, Richard G.; Nowak, Robert David (19961101)Current waveletbased statistical signal and image processing techniques such as shrinkage and filtering treat the wavelet coefficients as though they were statistically independent. This assumption is unrealistic; considering ... 
Hierarchical WaveletBased Image Model for Pattern Analysis and Synthesis
Scott, Clayton; Nowak, Robert David (20000720)Despite their success in other areas of statistical signal processing, current waveletbased image models are inadequate for modeling patterns in images, due to the presence of unknown transformations (e.g., translation, ... 
Image Restoration Using the EM Algorithm and WaveletBased Complexity Regularization
Figueiredo, Mario; Nowak, Robert David (20020520)This paper introduces an <i>expectationmaximization</i> (EM) algorithm for image restoration (deconvolution) based on a penalized likelihood formulated in the wavelet domain. Regularization is achieved by promoting a ... 
Lifting Construction of NonLinear Wavelet Transforms
Claypoole, Roger L.; Baraniuk, Richard G.; Nowak, Robert David (19981001)This paper analyzes nonlinear wavelet transforms using the lifting construction. The lifting construction exploits a spatialdomain, predictionerror interpretation of the wavelet transform and provides a powerful framework ... 
Low Rank Estimation of Higher Order Statistics
Nowak, Robert David; Van Veen, Barry D. (19951201)Low rank estimators for higher order statistics are considered in this paper. Rank reduction methods offer a general principle for trading estimator bias for reduced estimator variance. The biasvariance tradeoff is analyzed ... 
Modelbased Inverse Halftoning with WaveletVaguelette Deconvolution
Neelamani, Ramesh; Nowak, Robert David; Baraniuk, Richard G. (20000901)In this paper, we demonstrate based on the linear model of Kite that inverse halftoning is equivalent to the wellstudied problem of deconvolution in the presence of colored noise. We propose the use of the simple and ... 
Multiresolution Nonparametric Intensity and Density Estimation
Willett, Rebecca; Nowak, Robert David (20020520)This paper introduces a new multiscale method for nonparametric piecewise polynomial intensity and density estimation of point processes. Fast, piecewise polynomial, maximum penalized likelihood methods for intensity and ... 
A Multiscale Bayesian Framework for Linear Inverse Problems and Its Application to Image Restoration
Wan, Yi; Nowak, Robert David (20010120)In this paper we develop a waveletbased statistical method for solving linear inverse problems. The Bayesian framework developed here is general enough to treat a wide class of linear inverse problems involving (white ... 
Multiscale Density Estimation
Willett, Rebecca; Nowak, Robert David (20030820)The nonparametric density estimation method proposed in this paper is computationally fast, capable of detecting density discontinuities and singularities at a very high resolution, spatially adaptive, and offers near ... 
Multiscale Likelihood Analysis and Complexity Penalized Estimation
Kolaczyk, Eric D.; Nowak, Robert David (20010820)We describe here a framework for a certain class of multiscale likelihood factorization wherein, in analogy to a wavlet decomposition of an LÂ² function, a given likelihood function has an alternative representation as a ... 
Multiscale Likelihood Analysis and Image Reconstruction
Willett, Rebecca; Nowak, Robert David (20030820)The nonparametric multiscale polynomial and platelet methods presented here are powerful new tools for signal and image denoising and reconstruction. Unlike traditional waveletbased multiscale methods, these methods are ... 
Multiscale modeling and estimation of Poisson processes with application to photonlimited imaging
Timmerman, Klaus; Nowak, Robert David (19990420)Many important problems in engineering and science are wellmodeled by Poisson processes. In many applications it is of great interest to accurately estimate the intensities underlying observed Poisson data. In particular, ... 
Network Loss Inference Using Unicast EndtoEnd Measurement
Coates, Mark J.; Nowak, Robert David (20000920)The fundamental objective of this work is to determine the extent to which unicast, endtoend network measurement is capable of determining internal network losses. The major contributions of this paper are twofold: we ... 
New Bayesian Model Averaging Framework for WaveletBased Signal Processing
Wan, Yi; Nowak, Robert David (20000620)This paper develops a new signal modeling framework using Bayesian model averaging formulation and the redundant or translationinvariant wavelet transform. The aim of this framework is to provide a paradigm general enough ... 
Optimally Weighted Highpass Filters using Multiscale Analysis
Nowak, Robert David; Baraniuk, Richard G. (19960401)An obvious approach to image enhancement is to sharpen bright regions of an image more than darker regions. One very simple method to accomplish this is to weight the amount of highpass filtering proportional to the local ... 
Platelets for Multiscale Analysis in Medical Imaging
Willett, Rebecca; Nowak, Robert David (20020420)This paper describes the development and use of multiscale, plateletbased image reconstruction algorithms in medical imaging. Such algorithms are effective because platelets approximate images in certain (piecewise) ... 
Platelets for Multiscale Analysis in PhotonLimited Imaging
Willett, Rebecca; Nowak, Robert David (20020920)This paper proposes a new multiscale image decomposition based on platelets. Platelets are localized functions at various scales, locations, and orientations that produce piecewise linear image approximations. For smoothness ... 
Platelets: A Multiscale Approach for Recovering Edges and Surfaces in PhotonLimited Medical Imaging
Willett, Rebecca; Nowak, Robert David (20011020)This paper proposes a new multiscale image decomposition based on platelets. Platelets are localized functions at various scales, locations, and orientations that produce piecewise linear image approximations. Platelets ... 
QuasiCircular Rotation Invariance in Image Denoising
Wan, Yi; Nowak, Robert David (19991020)This paper studies a new method for waveletbased image denoising which is translation invariant (TI) <b>and</b> rotation invariant (RI). These invariances are crucial in image denoising and, more generally, may play ... 
Signal Estimation using WaveletMarkov Models
Crouse, Matthew; Baraniuk, Richard G.; Nowak, Robert David (19970401)Current waveletbased statistical signal and image processing techniques such as shrinkage and filtering treat the wavelet coefficients as though they were statistically independent. This assumption is unrealistic; considering ... 
A Statistical Multiscale Framework for Poisson Inverse Problems
Nowak, Robert David; Kolaczyk, Eric D. (20000820)This paper describes a statistical modeling and analysis method for linear inverse problems involving Poisson data based on a novel multiscale framework. The framework itself is founded upon a multiscale analysis associated ... 
TEMPLAR: A WaveletBased Framework for Pattern Learning and Analysis
Scott, Clayton; Nowak, Robert David (20010420)Despite the success of wavelet decompositions in other areas of statistical signal and image processing, current waveletbased image models are inadequate for modeling patterns in images, due to the presence of unknown ... 
Template Learning from Atomic Representations: A WaveletBased Approach to Pattern Analysis
Scott, Clayton; Nowak, Robert David (20010420)Despite the success of wavelet decompositions in other areas of statistical signal and image processing, current waveletbased image models are inadequate for modeling patterns in images, due to the presence of unknown ... 
Tensor Product Basis Approximations for Volterra Filters
Nowak, Robert David; Van Veen, Barry D. (19960201)This paper studies approximations for a class of nonlinear filters known as Volterra filters. Although the Volterra filter provides a relatively simple and general representation for nonlinear filtering, often it is highly ... 
Volterra Filter Identification Using Penalized Least Squares
Nowak, Robert David (19960520)Volterra filters have been applied to many nonlinear system identification problems. However, obtaining good filter estimates from short and/or noisy data records is a difficult task. We propose a penalized least squares ... 
Wavelet Based Statistical Signal Processing using Hidden Markov Models
Crouse, Matthew; Nowak, Robert David; Baraniuk, Richard G. (19980401)Waveletbased statistical signal processing techniques such as denoising and detection typically model the wavelet coefficients as independent or jointly Gaussian. These models are unrealistic for many realworld signals. ... 
Wavelet Domain Filtering for Nuclear Medicine Imaging
Nowak, Robert David; Baraniuk, Richard G. (19961101)The authors propose a new filtering/estimation method for nuclear medicine imaging. The statistical method of crossvalidation is used to design optimal wavelet domain filters for improved image estimation. The quality of ... 
WaveletBased Denoising Using Hidden Markov Models
Borran, Mohammad Jaber; Nowak, Robert David (20010520)Hidden Markov models have been used in a wide variety of waveletbased statistical signal processing applications. Typically, Gaussian mixture distributions are used to model the wavelet coefficients and the correlation ... 
Waveletbased Rician noise removal for magnetic resonance imaging
Nowak, Robert David (19991020)It is wellknown that the noise in magnetic resonance magnitude images obeys a Rician distribution. Unlike additive Gaussian noise, Rician noise is signaldependent and consequently spearating signal from noise is a ... 
A WaveletBased Statistical Model for Image Restoration
Wan, Yi; Nowak, Robert David (20011020)In this paper we develop a waveletbased statistical method for solving the image restoration problem. In this approach, a signal prior is set up by modeling the image wavelet coefficients as independent Gaussian mixture ... 
WaveletBased Transformations for Nonlinear Signal Processing
Nowak, Robert David; Baraniuk, Richard G. (19970401)Nonlinearities are often encountered in the analysis and processing of realworld signals. This paper develops new transformations for nonlinear signal processing. The theory of tensor norms is employed to show that wavelets ... 
WaveletBased Transformations for Nonlinear Signal Processing
Nowak, Robert David; Baraniuk, Richard G. (19990701)Nonlinearities are often encountered in the analysis and processing of realworld signals. In this paper, we introduce two new structures for nonlinear signal processing. The new structures simplify the analysis, design, ... 
WaveletBased Transformations for Nonlinear Signal Processing
Nowak, Robert David; Baraniuk, Richard G. (20010701)Nonlinearities are often encountered in the analysis and processing of realworld signals. We introduce two new structures for nonlinear signal processing. The new structures simplify the analysis, design, and implementation ... 
WaveletDomain Filtering for Photon Imaging Systems
Nowak, Robert David; Baraniuk, Richard G. (19990501)Many imaging systems rely on photon detection as the basis of image formation. One of the major sources of error in these systems is Poisson noise due to the quantum nature of the photon detection process. Unlike additive ... 
WInHD: Waveletbased Inverse Halftoning via Deconvolution
Neelamani, Ramesh; Nowak, Robert David; Baraniuk, Richard G. (20021020)We propose the <i>Waveletbased Inverse Halftoning via Deconvolution</i> (WInHD) algorithm to perform inverse halftoning of errordiffused halftones. WInHD is motivated by our realization that inverse halftoning can be ...