By Topic

Proceedings of the IEEE

Issue 10 • Date Oct 1993

Filter Results

Displaying Results 1 - 9 of 9
  • Thelma Estrin, biomedical engineer: a pioneer of applied computing

    Publication Year: 1993 , Page(s): 1370 - 1382
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1252 KB)  

    An account is given of the career of Thelma Estrin. Estrin entered engineering because of the urgent need for workers in the defense industries during World War II. After earning a Ph.D degree in electrical engineering in 1951, she worked in medical electronics (mainly electroencephalography) and on the design and construction of a digital computer (the WEIZAC). In 1960 she began a long association with UCLA's Brain Research Institute, where she organized and directed the Data Processing Laboratory. Estrin pioneered in the application of computers to biomedical research-especially in the areas of data acquisition and graphic display-and health-care delivery. In addition, she has done much to increase the number of women in engineering, both by direct efforts to assist others and by providing a role model View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Signal compression based on models of human perception

    Publication Year: 1993 , Page(s): 1385 - 1422
    Cited by:  Papers (285)  |  Patents (46)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3468 KB)  

    The notion of perceptual coding, which is based on the concept of distortion masking by the signal being compressed, is developed. Progress in this field as a result of advances in classical coding theory, modeling of human perception, and digital signal processing, is described. It is proposed that fundamental limits in the science can be expressed by the semiquantitative concepts of perceptual entropy and the perceptual distortion-rate function, and current compression technology is examined in that framework. Problems and future research directions are summarized View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fractals in the twist-and-flip circuit

    Publication Year: 1993 , Page(s): 1466 - 1491
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2124 KB)  

    The twist-and-flip circuit contains only three circuit elements: two linear capacitors connected across the ports of a gyrator characterized by a nonlinear gyration conductance function g( v1, v2). When driven by a square-wave voltage source of amplitude a and frequency ω, the resulting circuit is described by a system of two nonautonomous state equations. For almost any choice of nonlinear g (v1, v2)>0, and over a very wide region of the a-ω parameter plane, the twist-and-flip circuit is imbued with the full repertoire of complicated chaotic dynamics typical of those predicted by the classic KAM theorem from Hamiltonian dynamics. The significance of the twist-and-flip circuit is that its associated nonautonomous state equations have an explicit Poincare map, called the twist-and-flip map, thereby making it possible to analyze and understand the intricate dynamics of the system, including its many fractal manifestations. The focus is on the many fractals associated with the twist-and-flip circuit View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wavelet-based representations for the 1/f family of fractal processes

    Publication Year: 1993 , Page(s): 1428 - 1450
    Cited by:  Papers (103)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1784 KB)  

    It is demonstrated that 1/f fractal processes are, in a broad sense, optimally represented in terms of orthonormal wavelet bases. Specifically, via a useful frequency-domain characterization for 1/f processes, the wavelet expansion's role as a Karhunen-Loeve-type expansion for 1/f processes is developed. As an illustration of potential, it is shown that wavelet-based representations naturally lead to highly efficient solutions to some fundamental detection and estimation problems involving 1/f processes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrasonic characterization of fractal models

    Publication Year: 1993 , Page(s): 1523 - 1533
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    Ultrasonic scattering in inhomogeneous fluid media is examined. Of particular interest are those media having a compressibility that varies on a continuum of spatial scales. It is shown that the internal features of such media can be extracted by an analysis of the forward scattered field. The angular distribution of scattered pressure intensity is found to vary with frequency and compressibility contrast. The scattered field data can be rendered stationary to such variations by an application of a similarity transformation. Examples are given for cases where the spatial variation in the compressibility of the media obeys either a power law or exponential correlation function. When these similarity transformations are applied, an estimate of the characteristic radius of the scatterers and the fractal dimension of the medium can be directly obtained View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Overview of electrical processes in fractal geometry: from electrodynamic relaxation to superconductivity

    Publication Year: 1993 , Page(s): 1500 - 1510
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    The consequences of the parameterization of the fractal set on the electrodynamics of this set are analyzed. The relevance of scaling properties to electrochemical, dielectric, and magnetic relaxations is considered with a special emphasis on the use of noninteger derivative operators in electromagnetism and superconductivity. In electromagnetism, the above analysis includes a brief overview of the main results already obtained, focusing especially on the introduction of dissipative terms in the equation of propagation and on the generalized form of the uncertainty principle in fractal media. The new Laplacian and d'Alembertian operators are evoked as well as the scale relativity on which this new analysis is founded. For superconductivity, the analysis introduces a geometrical interpretation founded on frustration acting not only on topology but on the metric of the space-time in a particular type of fractal geometry. Although this point of view may appear as a breakthrough in the theory of superconductors, the model offers some relations with the theory of fractional statistics and the theory of Anyons View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A fractal analysis of interconnection complexity

    Publication Year: 1993 , Page(s): 1492 - 1499
    Cited by:  Papers (10)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    The emergent, collective properties of computer interconnections are shown to be characterized by a noninteger dimension Di , which is, in general, different from the system's Euclidean dimension. This dimension characterizes the properties of a fractal support, or substrate, on which interconnections are placed to provide communication throughout the system. The interconnection support also acts as a host for a multifractal spectrum of interconnection distribution processes which characterize the change in connectivity in moving from the backplane to the transistor level. The properties of fractal systems are investigated by attempting to minimize their total wire length using a simulated annealing algorithm. Systems whose interconnection dimension is approximately equal to their Euclidean dimension are shown to possess minimum wire length arrangements. These results are then interpreted in terms of a geometrical temperature T i=1/Di. This analysis indicates that the system passes through a phase transition at Ti≈1/2 and that attainable system temperatures are bounded by 1/3⩽Ti⩽1. The consequences for simulated annealing are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fractal image coding: a review

    Publication Year: 1993 , Page(s): 1451 - 1465
    Cited by:  Papers (148)  |  Patents (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1140 KB)  

    An approach to image coding based on a fractal theory of iterated contractive transformations defined piecewise is described. The main characteristics of this approach are that it relies on the assumption that image redundancy can be efficiently captured and exploited through piecewise self-transformability on a block-wise basis, and it approximates an original image by a fractal image, obtained from a finite number of iterations of an image transformation called a fractal code. This approach is referred to as fractal block coding. The general coding-decoding system is based on the construction, for an image to be encoded, of a fractal code-a contractive image transformation for which the original image is an approximate fixed point-which, when applied iteratively on any initial image of the decoder, produces a sequence of images which converges to a fractal approximation of the original. The design of a system for the encoding of monochrome digital images at rates below 1 b/pixel is described. Ideas and extensions from the work of other researchers are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fractional Brownian motion models for synthetic aperture radar imagery scene segmentation

    Publication Year: 1993 , Page(s): 1511 - 1522
    Cited by:  Papers (38)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    The application of fractal random process models and their related scaling parameters as features in the analysis and segmentation of clutter in high-resolution, polarimetric synthetic aperture radar (SAR) imagery is demonstrated. Specifically, the fractal dimension of natural clutter sources, such as grass and trees, is computed and used as a texture feature for a Bayesian classifier. The SAR shadows are segmented in a separate manner using the original backscatter power as a discriminant. The proposed segmentation process yields a three-class segmentation map for the scenes considered in this study (with three clutter types: shadows, trees, and grass). The difficulty of computing texture metrics in high-speckle SAR imagery is addressed. In particular, a two-step preprocessing approach consisting of polarimetric minimum speckle filtering followed by noncoherent spatial averaging is used. The relevance of the resulting segmentation maps to constant-false-alarm-rate (CFAR) radar target detection techniques is discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

The most highly-cited general interest journal in electrical engineering and computer science, the Proceedings is the best way to stay informed on an exemplary range of topics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
H. Joel Trussell
North Carolina State University