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Southeastern Symposium on System Theory

作者： J.K. Richstein D.J. Fouts R.J. Pieper T.-C. Poon Department of Electrical and Computer Engineering Naval Postgraduate School Monterrey CA USA Optical Image Processing Laboratory Bradley Department of Electrical Engineering Virginia Polytechnic Institute and State University Blacksburg VA USA

Histogram generation, a standard image processing operation, is a record of the intensity distribution in the image. A prototype of an optical-electronic histogram generator has been designed and tested for 1D objects using wirewrapped MSI TTL components (Richstein et al. 1993). The overall system design is such that the electronic signal obtained from the optically scanned two-dimensional semi-opaque image is processed and displayed within a period of one cycle of the scanning process. The authors report a VLSI design to be used in a two-dimensional real-time histogram generation scheme.< >

关键词： Very large scale integration CMOS integrated circuits Histograms Optical recording image generation image processing Prototypes Optical devices Optical design Testing

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Maximum likelihood parameter estimation for non-Gaussian prior signal models

Maximum likelihood parameter estimation for non-Gaussian pri...

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IEEE International Conference on image processing

作者： R.R. Schultz R.L. Stevenson A. Lumsdaine Laboratory for Image and Signal Analysis Electrical Engineering University of Notre Dame Notre Dame IN USA Department of Computer Science and Engineering University of Notre Dame Notre Dame IN USA

For signals containing discontinuities, the usual assumptions of Gauss-Markov distributed signal sources do not hold. To preserve edges, non-Gaussian prior models have been developed for use in Bayesian restoration. These models are generally dependent upon two parameters, one controlling the size of reconstructed discontinuities, and the other controlling data smoothing. The authors propose a maximum likelihood technique for automatically estimating these parameters, resulting in the optimization of an expression dependent upon the prior model partition function. An exact expression is derived for the 1D signal model partition function, while an approximation is proposed for the 2D image model partition function. Parameters estimated from degraded signals result in high quality restorations.< >

关键词： Maximum likelihood estimation Parameter estimation image restoration signal restoration Automatic control Size control Gaussian distribution Bayesian methods image reconstruction Smoothing methods

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Real-time frame-to-frame automatic contour detection on echocardiograms

Real-time frame-to-frame automatic contour detection on echo...

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computers in Cardiology (CinC)

作者： J.G. Bosch G. van Burken S.S. Schukking R. Wolff A.J. van de Goor J.H.C. Reiber Laboratory for Clinical and Experimental Image Processing Department of Diagnostic Radiology University Hospital Leiden Netherlands Department of Computer Architecture Faculty of Electrical Engineering Delft University of Technnology Netherlands

A PC-based system for real-time left ventricular endocardial contour detection on echocardiographic images has been developed in our laboratories. The system consists of an IBM-compatible PC equipped with a commercially available frame grabber and the special-purpose Minimum Cost Contour Detector (MCCD) board developed for this project. The MCCD board uses 1 or 2 Intel i960 processors and receives digital images (512*512*8 bit) from the frame grabber over a digital video bar in real time. The contour detection algorithm is based on dynamic programming. Detected contours and other results are transferred to the host via the AT-bus. processing time is short enough for real-time performance in a practical situation. Area of contours and regional areas in 8 segments are calculated in real time and displayed in graphs on the host system. The MCCD board is fully programmable and may be used for similar real-time contour detection applications, e.g. for X-ray angiography and intravascular ultrasound.< >

关键词： Real time systems Laboratories Costs Digital images Detection algorithms Dynamic programming X-ray detection X-ray detectors Angiography Ultrasonic imaging

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Design of limit-cycle-free recursive transfer functions for fixed-point direct form implementation

Design of limit-cycle-free recursive transfer functions for ...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： T.I. Laakso M. Lang T. Saramaki Nokia Research Center Helsinki Finland Electrical and Computer Engineering Department Rice University TX USA Signal Processing Laboratory Tampere University of Technology Tampere Finland

An approach for the design of limit-cycle-free digital fixed-point filters is proposed. By constraining the transfer function already in the design phase, it is guaranteed that the filter will be free from limit cycles and overflow oscillations in the direct form implementation. The design strategy also guarantees low roundoff noise. The proposed approach is illustrated with design examples. The examples show that typically a 50-100% increase in the filter order (as compared to standard elliptic design) is needed for the limit-cycle-free implementation of a lowpass filter with the direct form (DF) structure. Since the DF structure is very efficient to implement in signal processors, the proposed filters are very attractive for such environment, whereas dedicated filter structures (wave digital, state-space, etc.) easily result in a 3 to 4-fold implementation complexity.< >

关键词： Transfer functions Limit-cycles Electronic mail Digital filters Stability criteria Algorithm design and analysis Design engineering Laboratories Elliptic design signal processing

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Bayesian techniques for equalization of rapidly fading frequency selective channels

Bayesian techniques for equalization of rapidly fading frequ...

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IEEE Conference on Vehicular Technology (VTC)

作者： Gen-Kwo Lee M.P. Fitz S.B. Gelfand Vides Signal Processing Department Computer & Communication Research Laboratory Industrial Technology and Research Institute Hsinchu Taiwan School of Electrical Engineering Purdue University West Lafayette IN USA

This paper applies the Bayesian conditional decision feedback estimator (BCDFE) to rapidly fading frequency selective channels. The BCDFE is a model-based deconvolution algorithm which jointly estimates the transmitted data and channel parameters. The BCDFE applies joint symbol-by-symbol MAP demodulation and channel estimation to equalize channels, and consequently provides robust performance in rapidly fading channels. We provide a brief derivation of the BCDFE and characterize the performance on the land mobile radio channel. We assess the BCDFE's principle design characteristics and the resulting performance in both transient and steady-state operation. The effects of delay spread, Doppler spread, and co-channel interference on the BEP performance are also presented. The BCDFE demonstrates many of the desirable characteristics of an equalizer for mobile radio.< >

关键词： Bayesian methods Fading Frequency estimation Land mobile radio Feedback Deconvolution Demodulation Channel estimation Robustness Steady-state

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On the methodology for comparing learning algorithms: a case

On the methodology for comparing learning algorithms: a case

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Australian and New Zealand Conference on Intelligent Information Systems

作者： A. Bradley B. Lovell M. Ray G. Hawson Department of Electrical and Computer Engineering University of Queensland Brisbane Australia Cooperative Research Centre for Sensor Signal and Information Processing Australia Haemostatis Research Laboratory The Prince Charles Hospital Queensland Health Brisbane Australia

We explore several issues relevant to the benchmarking and comparison of machine learning algorithms. We illustrate those issues with a case study using the decision tree induction algorithms C4.5 (J. Quinlan, 1993) and multiscale classification (MSC) (A.P. Bradley and B.C. Lovell, 1994), multilayer perceptrons (MLP) and multivariable regression (MVR). Then for a "real world" problem we compare estimates of the true error rates for each classifier, first on a single train and test partition, and then using cross validated subsampling techniques. The relevance of the /spl chi//sup 2/ test is then discussed in relation to comparing the classifier accuracies. The paper concludes by evaluating the performance of these four fundamentally different approaches to the solution of this regression problem.< >

关键词： computer aided software engineering Decision trees Classification tree analysis Hospitals Machine learning algorithms Multilayer perceptrons Error analysis Blood Australia signal processing

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USING ANGULAR-DISPERSION OF GRADIENT DIRECTION FOR DETECTING EDGE RIBBONS

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1993年第7期15卷 682-696页

作者： GREGSON, PH Computer Vision image Processing Laboratory Department of Electrical Engineering Technical University of Nova Scotia Halifax NS Canada

Selection of suitable thresholds for edgel detection is frequently problematical due to the conflicting requirements of minimizing the number of false edgels detected while simultaneously minimizing the number of valid edgels missed. To minimize detection errors, detection thresholds should be based on the image signal to noise ratio (SNR), with the added benefit of maximizing the useful dynamic range of the imaging system. Edges in the scene generally project to smooth continuous curves nearly everywhere in the image. This results in low angular deviation of the intensity gradients in small neighborhoods straddling edges. Angular deviation is shown to be a measure of SNR. A theoretical analysis of angular deviation arising due to i.i.d. N(0, sigma2) random noise is presented. Angular deviation thresholds for neighborhood sizes from 3 x 3 to 11 x 11 are determined both from this analysis and numerical examples. The proposed gradient angular dispersion detection algorithm detects edge elements by comparing the measured angular deviation with values computed for the minimum acceptable SNR. Low values of deviation violate the ''no edge'' hypothesis. The algorithm is shown to make good use of the limited dynamic range of the imaging system. The sensitivity and selectivity of the strategy are both shown to be high.

关键词： ADAPTIVE THRESHOLDING ANGULAR DISPERSION EDGE DETECTION GRADIENT DIRECTION signal-TO-NOISE RATIO

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ON THE HYSTERESIS AND ROBUSTNESS OF HOPFIELD NEURAL NETWORKS

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-ANALOG AND DIGITAL signal processing 1993年第11期40卷 745-748页

作者： SCHONFELD, D Signal and Image Research Laboratory Department of Electrical Engineering and Computer Science University of Illinois Chicago Chicago IL USA

The effect of noise degradation on the Hopfield neural network is studied. The notion of a hysteresis network is defined. A noisy Hopfield neural network is subsequently proven to be a hysteresis network. The effect of the hysteresis phenomenon on the robustness of the Hopfield neural network to noise degradation is then investigated. An optimal Hopfield neural network is defined as the Hopfield neural network which minimizes an upper-bound on the probability of error. The minimal robustness indicator of a Hopfield neural network is defined. The upper bound on the probability of error of a noisy Hopfield neural network is derived in terms of the minimal robustness indicator. We finally prove that an optimal Hopfield neural network is obtained when the minimal robustness indicator is maximized.

关键词： Hysteresis Hopfield neural networks Neural networks Noise robustness Upper bound Thermal degradation Integrated circuit noise Psychology Humans Digital signal processing

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A new adaptive image contrast enhancement method

A new adaptive image contrast enhancement method

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image and Video processing 1993

作者： Yu, Tian-Hu Mitra, S.K. Department of Electrical and Computer Engineering Signal and Image Processing Laboratory University of California Santa BarbaraCA93106 United States

In direct methods of contrast enhancement, a contrast measure is first defined, which is then modified by a mapping function to generate the pixel value of the enhanced image. Various mapping functions such as the square root function, the exponential function, etc., have been introduced for the contrast measure modification. However, these functions do not produce satisfactory contrast enhancement results and are usually sensitive to noise and digitization effects. In addition, they are computationally complex from the point of view of implementation. In this paper, we propose a simple polynomial mapping function for the contrast measure modification. The polynomial function is easy to implement on digital computers and provides very satisfactary contrast enhancement. We also introduce an adaptive clipping technique to control the dynamic range of the output image. © 1993 SPIE. All rights reserved.

关键词： Exponential functions

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Histogram-shape preserving algorithm for image enhancement

Histogram-shape preserving algorithm for image enhancement

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： T.-H. Yu S.K. Mitra Department of Electrical and Computer Engineering Signal and Image Processing Laboratory University of California Santa Barbara CA USA

A new direct contrast enhancement algorithm is proposed. It can be used to enhance the contrast of an image without increasing the dynamic range of the pixel values. A distinctive property of the proposed method is that it yields results matching the characteristic of the human visual system. The histogram of the enhanced image has almost the same shape as that of the original image.< >

关键词： image enhancement Dynamic range Pixel Histograms Shape Humans Visual system Displays Computational complexity signal processing

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