Showing papers on "Computation published in 1969"

On The Subject Of A Flood Propagation Computation Method (Musklngum Method)

Abstract: (1969). On The Subject Of A Flood Propagation Computation Method (Musklngum Method) Journal of Hydraulic Research: Vol. 7, No. 2, pp. 205-230.

Real-Time Computation by n-Dimensional Iterative Arrays of Finite-State Machines

Abstract: An n-dimensional iterative array of finite-state machines is formally introduced as a real-time tape acceptor. The computational characteristics of iterative arrays are illuminated by establishing several results concerning the sets of tapes that they recognize. Intercommunication between machines in an array is characterized by specifying a stencil for the array. The computing capability of the array is preserved even if its stencil is reduced to a simple form in which machines communicate only with their nearest neighbors. An increase of computing speed by a constant factor k is defined by encoding k-length blocks of the input tapes, which reduces the lengths of the tapes by 1/k; the time available for computation is correspondingly reduced since the computation must be real time. The computation speed of iterative arrays can be increased by any constant factor k. Two examples of one-dimensional arrays are provided. The first accepts the set of palindromes; the second accepts the set of all tapes of the form ττ (for any tape τ). The latter set of tapes is not a context-free language; therefore, the sets of tapes accepted by iterative arrays are not all contained in the class of context-free languages. Conversely, the class of context-free languages is not contained in the class of sets of tapes accepted by iterative arrays. The sets of tapes accepted by iterative arrays are closed under the operations: union, intersection, and complement; therefore, they form a Boolean algebra. They are not closed under the reflection or concatenation-product operations.

A graph model for parallel computations

Abstract: This report presents a computational model called program graphs which makes possible a precise description of parallel computations of arbitrary complexity on non-structured data. In the model, the computation steps are represented by the nodes of a directed graph whose links represent the elements of storage and transmission of data and/or control information. The activation of computation represented by a node depends only on the control information residing in each of the links incident into and out of the node. At any given time any number of nodes may be active, and there are no assumptions in the model regarding either the length of time required to perform the computation represented by a node or the length of time required to transmit data or control information from one node to another. Data dependent decisions are incorporated in the model in a novel way which makes a sharp distinction between the local sequencing requirements arising form the data dependency of the computation steps and the global sequencing requirements determined by the logical structure for the algorithm.

Computation of Laplacian potentials by an equivalent-source method

Abstract: An algorithm for the computation of the solution to Laplace's equation in a 2-dimensional region is given in terms of equivalent sources on the boundary. The region may be of an arbitrary shape, and the boundary conditions may be an arbitrary combination of Dirichlet, Neumann and impedance types. The solution is obtained by a moment method, using either a step approximation to the source, or a piecewise-linear approximation. Point matching is used for testing the boundary conditions. Computer programs are available for the general problem, and some electromagnetic-field applications are discussed.

On arithmetic expressions and trees

Abstract: A description is given of how a tree representing the evaluation of an arithmetic expression can be drawn in such a way that the number of accumulators needed for the computation can be represented in a straightforward manner. This representation reduces the choice of the best order of computation to a specific problem under the theory of graphs. An algorithm to solve this problem is presented.

Modular computer sharing system with intercomputer communication control apparatus

Abstract: A bank of interchangeable computers are provided, each of which is a memory/processor pair, the computers being respectively assigned to process terminal jobs as they arrive from a remote terminal One of the computers serves as the master or control processor and supervises the collection and distribution of messages from and to the remote terminal, a disk drive suitably being provided for each connected terminal A cross point switching network permits any of the disk drives to be connected to any computer of the bank, under the control of the control computer Thus, while each active terminal is operatively related to a dedicated disk drive each terminal user may share the control computer with many other terminal users in a simple manner The ratio of users to computers is dependent on the size and power of the computers which are employed and the computation requirement of the particular combination of users

The measurement of infrared spectra with digitally recording spectrophotometers

Abstract: INTRODUCTION Before proceeding to our main topic, I want first to discuss the impact of the electronic computer on molecular spectroscopy. This is not intended to suggest that the use of a computer is an innovation in spectroscopic research. Many in this audience have employed electronic computers for several years to aid in the evaluation of molecular force fields, to calculate normal coordinates of the vibrations of polyatomic molecules, and to compute molecular energy levels by quantum mechanical methods. Until recently, however, the necessary computing facilities could be found only in a few specially equipped laboratories. In the two years that have passed since the Copenhagen Congress we have witnessed an explosive expansion in the availability of large electronic computers so that it is fast becoming the accepted practice to have extensive computation facilities as part of the standard services of the spectroscopy laboratory. Molecular spectroscopists use electronic computers in three distinct ways: (i) For data acquisition (ii) For data storage and retrieval (iii) For data analysis and interpretation arid it is convenient to consider these separately.

A Two-Sets-of-Eigenvalues Approach to the Computer Analysis of Linear Systems

Abstract: This paper is concerned with techniques for the determination of all the critical frequencies (i.e., all the poles and zeros) of the transfer function of a linear time-invariant singleinput single-output system. Unlike methods involving the computation of polynomial coefficients, the techniques presented find the transfer zeros as the eigenvalues of a matrix obtained from the state and output equations of the system. A computational assessment is given with illustrative examples. In particular, the computation of actual bounds on the critical frequencies is discussed, and the application of these techniques to frequency analysis of networks is considered. Preliminary computer test results have confirmed that they require significantly less computation time and admit the possibility of detailed roundoff error analysis.

Computation of synthetic spectra for a semi- infinite atmosphere

Abstract: Absorption spectra computation for model planetary atmosphere using Neumann series for solving semiinfinite radiative transfer equation

Optimization of control systems with discontinuities and terminal constraints

Abstract: The "successive sweep method," a Newton-Raphson algorithm in function space, based upon [1]-[3], is applied to the computation of optimal solutions to control problems which are characterized by terminal constraints and discontinuities in the control functions. The computational technique of using piecewise constant gains is introduced for the successive sweep method in order to reduce computer storage. Two examples are considered. The first example concerns the three-dimensional attitude control of an orbiting vehicle. The second example is the two-dimensional transfer of a low thrust vehicle in a gravitational field.

Pattern recognition apparatus

Abstract: Described is apparatus, employing a mathematical transform involving addition and differencing only, for recognizing patterns or characters which can be distorted or misaligned with respect to optical-sensing means without any sacrifice in the accuracy of the device. When executed on a digital computer, the mathematical transform utilized in accordance with the invention needs only a fraction of the computation time needed for transforms utilized by prior art devices. At the same time, it is better able to cope with certain distortions that are characteristic of hand-printed letters and digits such as inclination, small rotation and the like.

An investigation of the utility of computer simulation to predict ship structural response in waves

Abstract: Methods of computer simulation of ship structural response in waves are described, with emphasis given to the slowly varying bending moments due to waves and to slamming responses. Analog, digital, and hybrid computer systems are analyzed, and results obtained by use of the most efficient computational procedures for each type of structural response. The vertical and lateral bending moments due to waves are determined by use of a digital computer, and sample computations illustrated for determin- ing frequency domain outputs. Time history outputs of vertical bending moments due to nonlinear slamming are obtained using a modal model of the ship structural dynamic representation, together with time histories of the wave-induced vertical bending moment due to the same wave system. The capabilities of various computer systems to obtain the required responses, the form of the mathematical model appropriate for computational means, and the time requirements for carrying out the operations are also presented. The rapid assessment of spectral responses and their related statistical properties by means of digital computation, together with time history responses at rates faster than real time, provides a useful tool for determin- ing many aspects of ship structural response characteris- tics by means of computer simulation.

Three-dimensional seismic depth computation using space-sampled velocity logs

Abstract: Due to the large amount of velocity information provided through adequate signal processing of multicoverage seismic data, approaches for depth computation presuming the velocity to be described by some simple analytic function may no longer be considered adequate. Three approaches to depth computation, are applied to cases of arbitrarily complicated velocity distributions. When we use these approaches, accuracy may be increased to any desired degree or to any degree which seems reasonable with respect to the velocity information available.

Generalized Multi-Step Methods with an Application to Orbit Computation

Abstract: Generalized predictor-corrector algorithms are developed based on non-polynomial functions. The special case of two-body elliptic motion is examined, suitable function sets are established, and numerical results described.

Computation of sub–optimal linear controls for non–linear stochastic systems†

Abstract: A successive approximation technique based on statistical linearization is developed which permits the design of sub–optimal linear controls for non–linear time–invariant processes perturbed by Gaussian random disturbances. The application of the technique to a chemical process example is given, and the validity of the results is confirmed by simulation.

Functional Analysis for Computers

Abstract: In order to take further advantage of the high speed of computers it is of interest to consider the possibility of mechanizing some parts of functional analysis. An approach based on computations with interval valued functions is discussed.

Flowgraph analysis of linear systems using remote time-shared computation

Abstract: Loops and paths in Mason signal flow graph of linear systems using algorithm with remote time shared digital computation

A branch and bound method for optimal fault finding

Abstract: : The problem is that of optimally testing a coherent system to learn some characteristic of it, for example, whether it is operating or not. A branch and bound and a dynamic programming solution are given, as well as a comparison of computer computation times for both. Several specific models with analytical solutions are also presented.

Use of space-charge approximation as trial solution in the computation of potential distributions in semiconductor devices

Abstract: It is shown that the use of the space-charge approximation as a trial solution in the computation of potential distributions in semiconductor devices leads to considerable gains in computer time.