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JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 1986年第1期79卷 91-99页

作者： BIRDSALL, TG METZGER, K Communications and Signal Processing Laboratory Electrical Engineering and Computer Science Department The University of Michigan Ann Arbor Michigan 48109

Factor inverse matched filtering (FIMF) and factor inverse filtering (FIF) are signal processing techniques used to obtain desired signal responses. Both are especially useful procedures for ‘‘pulse‐compression’’ processing and channel measurements. The theory is developed for a simple channel and known noise power spectral density so that comparison may be made with matched filtering. Expressions for the pulse‐compression energy gain, nonflatness loss NFL, and total performance are derived. The NFL is useful in selecting the best among practical pulse‐compression modulations, and with FIMF and FIF, has been used extensively since 1974 by the authors and their co‐workers in underwater acoustic propagation measurements and ocean acoustictomography.

关键词： Acoustic tomography Acoustical measurements Ocean acoustics Signal processing Tomography

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DIFFERENTIAL AND INTEGRAL METHODS FOR MULTIDIMENSIONAL INVERSE SCATTERING PROBLEMS

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JOURNAL OF MATHEMATICAL PHYSICS 1986年第10期27卷 2584-2591页

作者： YAGLE, AE Communications and Signal Processing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor Michigan 48109

A layer stripping procedure for solving three‐dimensional Schr?dinger equationinverse scattering problems is developed. This procedure operates by recursively reconstructing the Radon transform of the potential from the jump in the Radon transform of the scattered field at the wave front. This reconstructed potential is then used to propagate the wave front and scattered field differentially further into the support of the potential. The connections between this differential procedure and integral equation procedures are then illustrated by the derivations of two well known exact integral equation procedures using the Radon transform and a generalized Radon transform. These procedures, as well as the layer stripping procedure, are then reduced to the familiar Born approximation result for this problem by neglecting multiple scattering events. This illustrates the central role of the Radon transform in both exact and approximate inversion procedures.

关键词： Integral transforms Integral equations Acoustic wave front reconstruction Inverse scattering Differential equations

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FIR Anisotropic filters for image enhancement

FIR Anisotropic filters for image enhancement

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International Conference on Acoustics, Speech, and Signal processing (ICASSP)

作者： V. Algazi Signal and Image Processing Laboratory Department Electrical and Computer Engineering University of California Davis USA

This paper describes a technique for the enhancement of images by FIR filters which compensates for the decreased response of human vision at high spatial frequencies. Because many images contain mainly horizontal and vertical features, and because vision is less acute along diagonals, it is possible to design anisotropic enhancement filters which do not increase greatly the background noise. The anisotropic design methodology also incorporates other results on filter design based on human vision which have recently been reported by the author and coworkers.

关键词： Finite impulse response filter Anisotropic filters Image enhancement Humans Nonlinear filters Frequency response Additive noise Image processing Anisotropic magnetoresistance Visual perception

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Improved pitch detection algorithm for noisy speech

Improved pitch detection algorithm for noisy speech

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International Conference on Acoustics, Speech, and Signal processing (ICASSP)

作者： Sanguoon Chung V. Algazi Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

We propose a new, robust pitch detection algorithm for speech degraded by additive noise. Our algorithm exploits the high correlation between adjacent pitch periods that does not exist for the segment as a whole and performs well in the vicinity of voiced/unvoiced regions where the local SNR is low. The algorithm works as follows. We first determine an estimate of the pitch period near the short time peak energy where the local SNR is highest. We then adaptively estimate the local pitch period from the peak towards the transition region by using pitch synchronous cross-correlation with an updated waveform. The performance of this new algorithm is compared to the SIFT and CEPSTRUM algorithms.

关键词： Detection algorithms Speech enhancement Cepstrum Acoustic noise Working environment noise Detectors Cepstral analysis Algorithm design and analysis Time measurement Speech synthesis

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LEARNING CHARACTERISTICS OF STOCHASTIC-GRADIENT-DESCENT ALGORITHMS - A GENERAL STUDY, ANALYSIS, AND CRITIQUE

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SIGNAL processing 1984年第2期6卷 113-133页

作者： GARDNER, WA Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis 95616 USA

A comprehensive analysis of the mean-square learning characteristics of stochastic-descent algorithms is presented. The approach is based on the commonly exploited simplifying assumption of stationary independent training vectors. Characteristics analyzed include stability, steady-state misadjustment, initial rate of convergence, optimum step size, and steady-state autocovariance and spectral characteristics of the weight-vector. Effects on these characteristics due to degree of randomness of stochastic gradient, particular data distribution, and data corruption are isolated and analyzed. An objective of the work is to keep the number of simplifying assumptions and approximations to a minimum. Comparison of results with previous more approximate analyses are made. Lernkurven von stochastischen Gradienten Algorithmen werden untersucht. Die vereinfachende Annahme von stationären, unabhängigen Trainingsvektoren wird benutzt. Charakteristiken die untersucht werden beinhalten Stabilität, ‘steady state’ Fehlanpassung, Start Konvergenz, optimaler Schritt sowie ‘steady state’ Autokovarianz und spektrale Charakteristik des Gewichtsvektors. Die Effekten auf diese Charakteristiken von dem Zufälligkeitsgrad des stichastischen Gradienten, besonderer Daten Verteilung und Daten Verderbung werden isoliert und analysiert. Ein Zielpunkt dieser Arbeit ist es die Anzahl vereinfachenden Annahmen und Approximationen auf ein minimum zu beschränken. Vergleiche mit Resultaten die von approximativeren Analysen stammen werden gezogen. Une analyse d'ensemble des caractéristiques de convergence de l'erreur quadratique moyenne dans les algorithmes utilisant la décroissance du gradient stochastique est presentée. Cette approche est basée sur l'hypothése simplificatrice classique de stationnarité et indépendance des vecteurs de test. Les caractéristiques analysées comprennent la stabilité, l'écart d'état stable, la vitesse initiale de convergence, le pas optimum d'incrémentation, et l'autocovarian

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SEGMENTATION OF A HIGH-RESOLUTION URBAN SCENE USING TEXTURE OPERATORS

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computer VISION GRAPHICS AND IMAGE processing 1984年第3期25卷 273-310页

作者： CONNERS, RW TRIVEDI, MM HARLOW, CA Remote Sensing and Image Processing Laboratory Department of Electrical and Computer Engineering Louisiana State University Baton Rouge Louisiana 70803

A study aimed at segmenting a high-resolution black and white image of Sunnyvale, California, is described. In this study regions were classified as belonging to any one of nine classes: residential, commercial/industrial, mobile home, water, dry land, runway/taxiway, aircraft parking, multilane highway, and vehicle parking. The classes were selected so that they directly relate to the Defense Mapping Agency's Mapping, Charting and Geodesy tangible features. To attack the problem a statistical segmentation procedure was devised. The primitive operators used to drive the segmentation are texture measures derived from cooccurrence matrices. The segmentation procedure considers three kinds of regions at each level of the segmentation: uniform, boundary, and unspecified. At every level the procedure differentiates uniform regions from boundary and unspecified regions. In the assigns a class label to the uniform regions. The boundary and unspecified regions are split to form higher level regions. The methodologies involved are mathematically developed as a series of hypothesis tests. While only a one-level segmentation was performed studies are described which show the capabilities of each of these hypothesis tests. In particular an 83% correct classification was obtained in testing the labeling procedure. These studies indicate that the proposed procedure should be useful for land use classifications as well as other problems.

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A PIPELINED RECURSIVE RESIDUE NUMBER SYSTEM DIGITAL-FILTER

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS 1984年第4期31卷 415-417页

作者： SODERSTRAND, MA SINHA, B Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA IBM Corporation Boca Raton FL USA University of California Davis CA USA

The well-known advantages of pipelining as applied to Finite Impulse Response (FIR) Residue Number System (RNS) arithmetic digital filters is extended to the important area of Infinite Impulse Response (IIR) digital filters through a new technique based on augmentation of the IIR transfer function. Through this technique, pipelined IIR filters based on RNS Read-Only-Memory (ROM) table look-up techniques can be designed which offer throughput rates equal to the table look-up time of the ROM's. This high-speed realization can be achieved even though the recursive filter algorithm requires multiple delays in realizing the output of the filter. For the example of a typical second-order IIR filter, the pipelined structure represents a five-fold increase in speed over standard techniques. Higher order realizations will yield proportionately higher speed improvements. Although the new technique does increase somewhat the hardware complexity of the filter, the increase in speed will often justify the additional hardware. The paper discusses the basic technique, stability considerations, and hardware realizations.

关键词： Digital filters IIR filters Finite impulse response filter Hardware Read only memory Pipeline processing Digital arithmetic Transfer functions Throughput Delay

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Identification of unique objects in high resolution aerial images

Identification of unique objects in high resolution aerial i...

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Applications of Artificial Intelligence I 1984

作者： Trivedi, Mohan M. Harlow, Charles A. Remote Sensing and Image Processing Laboratory Department of Electrical and Computer Engineering Louisiana State University Baton RougeLA70803 United States

Accurate and reliable detection of unique objects is an important component of an image understanding system. The objects are considered to have a unique pattern and should be recognized based upon their own characteristics. An object detection approach applicable to the high resolution aerial images is developed in the paper. The methodologies incorporate features such as minimal sensitivity to the backgrounds on which objects may appear, ability to detect objects appearing in arbitrary orientations, and use of a unified set of operators to analyze various levels of details. Specifically the gray level cooccurrence matrix is used to provide the early vision operators. Results of several experiments show the promise for the prpposed methods. © 1984 SPIE. All rights reserved.

关键词： Object detection

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Application of a simple hearing model to the design of audio filters

Application of a simple hearing model to the design of audio...

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International Conference on Acoustics, Speech, and Signal processing (ICASSP)

作者： M. Ready V. Algazi Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

Filtering audio signals with filters designed exclusively from frequency domain specifications may result in an audible distortion in the vicinity of sharp amplitude transitions. This paper considers the application of known psychoacoustical properties to the design of digital audio filters which minimizes this distortion while approximating some ideal frequency domain characteristics. Psychoacoustic properties and a simple model for hearing are reviewed. A weighted least squares design criteria based on the model and frequency domain specifications is given. Examples of FIR and IIR filters are given and compared to classical frequency domain filters.

关键词： Auditory system Finite impulse response filter Frequency domain analysis Psychoacoustic models IIR filters Psychology Filtering Signal design Distortion Digital filters

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Radon transform theory for random fields and optimum image reconstruction from noisy projections

Radon transform theory for random fields and optimum image r...

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International Conference on Acoustics, Speech, and Signal processing (ICASSP)

作者： A. Jain S. Ansari Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

In this paper we present some new results on Radon transform theory for stationary random fields. In particular we present a new projection theorem which gives the relation between the power spectrum density of one dimensional projections of a stationary random field and its two dimensional power spectrum density. This result yields the optimum mean square reconstruction filter from noisy projections and is useful in other problems such as multidimensional spectral estimation from one dimensional projections, noise analysis in computed tomography, etc. Example are given to demonstrate the usefulness of these results.

关键词： Image reconstruction Filters Frequency response Computed tomography Fourier transforms Convolution Stochastic processes Signal processing Image processing Laboratories

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