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IBM Journal of Research and Development

Issue 4 • Date July 1989

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Displaying Results 1 - 8 of 8
  • Modeling and image processing for visualization of volcanic mapping

    Publication Year: 1989 , Page(s): 406 - 416
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1091 KB)  

    In countries such as Italy, Japan, and Mexico, where active volcanoes are located in highly populated areas, the problem of risk reduction is very important. Actual knowledge about volcanic behavior does not allow deterministic event prediction or the forecasting of eruptions. However, areas exposed to eruptions can be analyzed if eruption characteristics can be inferred or assumed. Models to simulate volcanic eruptions and identify hazardous areas have been developed by collaboration between the IBM Italy Pisa Scientific Center and the Earth Science Department of Pisa University (supported by the Italian National Group of Volcanology of the Italian National Research Council). The input to the models is the set of assumed eruption characteristics: the typology of the phenomenon (ash fall, pyroclastic flow, etc.), vent position, total eruptible mass, wind profile, etc. The output of the models shows volcanic product distribution at ground level. These models are reviewed and their use in hazard estimation (compared with the more traditional techniques currently in use) is outlined. Effective use of these models, by public administrators and planners in preparing plans for the evacuation of hazardous zones, requires the clear and effective display of model results. Techniques to display and visualize such data have been developed by the authors. In particular, a computer program has been implemented on the IBM 7350 Image Processing System to display model outputs, representing both volume (in two dimensions) and distribution of ejected material, and to superimpose the displays upon satellite images that show 3D oblique views of terrain. This form of presentation, realized for various sets of initial conditions and eruption times, represents a very effective visual tool for volcanic hazard zoning and evacuation planning. View full abstract»

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  • Natural quadrics: Projections and intersections

    Publication Year: 1989 , Page(s): 417 - 446
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2004 KB)  

    Geometrical modelers usually strive to support at least solids bounded by the results of Boolean operations on planes, spheres, cylinders, and cones, that is, the natural quadrics. Most often this set is treated as a subset of the set of quadric surfaces. Although the intersection of two quadrics is a mathematically tractable problem, in implementation it leads to complexity and stability problems. Even in the restriction to the natural quadrics these problems can persist. This paper presents a method which, by using the projections of natural quadrics onto planes and spheres, reduces the intersection of two natural quadrics to the calculation of the intersections of lines and circles on planes and spheres. In order to make the claims of the method easily verifiable and provide the tools necessary for implementation, explicit descriptions of the projections are also included. View full abstract»

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  • Femtosecond laser studies of the relaxation dynamics of semiconductors and large molecules

    Publication Year: 1989 , Page(s): 447 - 455
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (758 KB)  

    The use of femtosecond lasers and the related optical correlation spectroscopic technique for studying the relaxation dynamics of semiconductors and photoexcited molecules are reviewed. In particular, the results on the intraband relaxation of nonequilibrium carriers in GaAs and related compounds and quantum well structures are summarized. The optical correlation technique also led to the observation of quantum beats in the femtosecond time domain corresponding to the direct observation of molecular vibrations in the time domain. View full abstract»

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  • Effects of quasiperiodic (Penrose tile) symmetry on the eigenvalues and eigenfunctions of the wave equation

    Publication Year: 1989 , Page(s): 456 - 463
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    In addition to the basic crystalline and amorphous structures for solids, it is possible that solids may also form with a quasiperiodic, or Penrose tile, structure. A current problem in condensed-matter physics is to determine how this structure affects the various physical properties of a material. A fundamental question involves the consequences of quasiperiodic symmetry in the eigenvalue spectrum and eigenfunctions of a wave equation. While rigorous theorems have been derived for one-dimensional systems, there is currently no known “quasi-Bloch theorem” for two and three dimensions. To gain insight into this problem, an acoustic experiment has been used to study a two-dimensional wave system with a Penrose tile symmetry. The results show an eigenvalue spectrum containing bands and gaps with widths which are in the ratio of the Golden Mean, (√5 + 1)/2. View full abstract»

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  • Time series in M dimensions: The power spectrum

    Publication Year: 1989 , Page(s): 464 - 469
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (499 KB)  

    The approach presented here extends the modeling of M-dimensional (spatial) time series from the time domain into the frequency domain. The autocovariance function for an M-dimensional time series is transformed to obtain the power spectrum in M dimensions. The latter describes the variance within the series and can be used to identify dependencies and/or test the adequacy of a fitted model. An example is provided. View full abstract»

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  • Two-level coding for error control in magnetic disk storage products

    Publication Year: 1989 , Page(s): 470 - 484
    Cited by:  Papers (4)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1164 KB)  

    Error-control coding has played a significant role in the design and development of magnetic recording storage products. The trend toward higher densities and data rates presents continuing demands for an ability to operate at a lower signal-to-noise ratio and to tolerate an increased number of correctable errors. Heretofore, the magnetic disk storage products used coding schemes that provided correction of one burst of errors in a record of length ranging from a few bytes of data to a full track on the disk. In this paper, we present a new coding architecture that facilitates correction of multiple-burst errors in each record in a typical disk storage application. This architecture embodies a two-level coding scheme which offers high coding efficiency along with a fast decoding strategy that closely matches the requirements of on-line correction of multiple bursts of errors. The first level has a smaller block delay and provides very fast correction of most of the errors commonly encountered in an average disk file. The second level, on a larger block size, provides reserve capability for correcting additional errors which may be encountered in a device with symptoms of a weaker component or an oncoming failure. The new IBM 3380J and 3380K disk files use a two-level scheme that is designed around the coding structure of the extended Reed-Solomon code. This design and the related encoding and decoding methods and implementation are presented in detail. View full abstract»

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  • Recent publications by IBM authors

    Publication Year: 1989 , Page(s): 485 - 497
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1149 KB)  

    The information listed here is supplied by the Institute for Scientific Information and other outside sources. Reprints of the papers may be obtained by writing directly to the first author cited. Information on books may be obtained by writing the publisher. Papers and books are listed alphabetically by author. View full abstract»

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  • Recent IBM patents

    Publication Year: 1989 , Page(s): 498 - 500
    Save to Project icon | PDF file iconPDF (258 KB)  
    Freely Available from IEEE

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The IBM Journal of Research and Development is a peer-reviewed technical journal, published bimonthly, which features the work of authors in the science, technology and engineering of information systems.

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Editor-in-Chief
Clifford A. Pickover
IBM T. J. Watson Research Center