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IBM Journal of Research and Development

Issue 2 • Date March 1973

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Displaying Results 1 - 11 of 11
  • Empirically Derived Micromodels for Sequences of Page Exceptions

    Page(s): 86 - 100
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    Based on a statistical analysis of actual computer program address traces, some results are presented of a study aimed at deriving empirically valid stochastic models for program reference patterns in a computer system operating under demand paging. For the address traces examined, a semi-Markov model for the (univariate) point process of page exceptions is formulated and found to be an adequate characterization of the data. View full abstract»

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  • Bounds for Weight Balanced Trees

    Page(s): 101 - 105
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (369 KB)  

    It has been shown that the cost W of a weight balanced binary tree satisfies the inequalities, H ≤ W ≤ H + 3, where H is the entropy of the set of the leaves. For a class of “smooth” distributions the inequalities, H ≤ W ≤ H + 2, are derived.<p>These results imply that for sets with large entropy the search times provided by such trees cannot be substantially shortened when binary decisions are being used. View full abstract»

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  • Optimum Storage Allocation for a File with Open Addressing

    Page(s): 106 - 114
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    File organizations utilizing key-to-address transformation and open addressing are studied. A simulation method and a Markov model, which were used for evaluation, are presented. The cost of retrieval as a function of storage space and accesses is also formulated. The minimum of the combined costs for different operational conditions is determined. View full abstract»

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  • Quasimaximum Likelihood Estimators for Two-parameter Gamma Distributions

    Page(s): 115 - 124
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (642 KB)  

    The Gamma probability distribution is defined by the density function [βαγ(α)]−1 exp (−x/β). This paper presents new estimators for the parameters α−1 and β. Required calculations are simple, primarily involving the inner product of certain elementary statistics and their logarithms. Both of the new estimators are shown to be unbiased. The variance formulas for each and their covariance formula are derived—counterparts of these for the method of moments (MM) and the method of maximum likelihood (ML) not being known except in the asymptotic form. Curve-fitting results from samples of size 50 are provided. They support the proposition that the new quasimaximum likelihood estimators (QML) are at least as effective as MM and ML estimators. Illustrative estimation based on samples of size 5 also is presented for comparison; the results highlight relative smaller variances for the ML estimators. The same Monte Carlo results signal a possibility that significant negative bias occurs with both the MM and ML techniques if small samples are used. View full abstract»

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  • Theory of MNOS Memory Device Behavior

    Page(s): 125 - 134
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (575 KB)  

    This paper extends the direct-tunneling theory of MNOS memory device behavior to account for traps that are distributed both spatially and energetically. It shows that the Pulver and Dorda model is a special case of the Ross and Wallmark model, which is itself a restricted version of the more general theory proposed here. A general equation for the total charge transfer is derived, for monoenergetic and for energetically uniform trap distributions, for high fields as well as low fields. The theory predicts the time dependence of the total charge transfer to be initially linear, then roughly logarithmic, and finally to reach saturation. There is no essential difference in the results whether the trap distribution is monoenergetic or energetically uniform. The operational dependence on characteristic parameters is investigated and found to be greatest for changes in the extent of spatial distribution of traps. The switching time varies inversely with trap density and tunnelling probability, and exponentially with the oxide thickness. View full abstract»

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  • Axioms and Theorems for a Theory of Arrays

    Page(s): 135 - 175
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1292 KB)  

    Array theory combines APL with set theory, transfinite arithmetic, and operationally transformed functions to produce an axiomatic theory in which the theorems hold for all arrays having any finite number of axes of arbitrary countable ordinal lengths. The items of an array are again arrays. The treatment of ordinal numbers and letters is similar to Quine's treatment of individuals in set theory. The theory is developed first as a theory of lists. This paper relates the theory to the eight axioms of Zermelo–Fraenkel set theory, describes the structure of arrays, interprets empty arrays in terms of vector spaces, presents a system of axioms for certain properties of operations related to the APL function of reshaping, deduces a few hundred theorems and corollaries, develops an algebra for determining the behavior of operations applied to empty arrays, begins the axiomatic development of a replacement operator, and provides an informal account of unions. Cartesian products, Cartesian arrays, and outer, positional, separation, and reduction transforms. View full abstract»

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  • Automatic Equalizers having Minimum Adjustment Time

    Page(s): 176 - 179
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (323 KB)  

    Two new types of automatic equalizers for telephone lines are discussed. The modular configurations shown are designed for minimum adjustment time and are ready to receive data as soon as the response of the unequalized line has been measured. Two forms of such equalizers are compared with respect to upper bounds on the residual distortion. View full abstract»

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  • Recent Papers by IBM Authors

    Page(s): 180 - 184
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Reprints of the papers listed here can usually be obtained by writing directly to the authors. The authors' IBM divisions are identified as follows: ASDD is the Advanced Systems Development Division: DPD, Data Processing Division: FED, Field Engineering Division; FSD, Federal Systems Division; GPD General Products Division; GSD, General Systems Division: OPD, Ofice Products Division: RES, Research Division; SDD, System Development Division; SPD, System Products Division: and WTC, World Trude Corporation. Papers are listed alphabetically by nume of journal. View full abstract»

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  • Recent IBM Patents

    Page(s): 185 - 187
    Save to Project icon | PDF file iconPDF (285 KB)  
    Freely Available from IEEE
  • Authors

    Page(s): 188 - 189
    Save to Project icon | PDF file iconPDF (230 KB)  
    Freely Available from IEEE
  • Contents of previous issues

    Page(s): 190 - 193
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    Freely Available from IEEE

Aims & Scope

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.

Full Aims & Scope

Meet Our Editors

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