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Completely conservative and oscillationless semi-Lagrangian schemes for advection transportation

JOURNAL OF computational PHYSICS 2001年第2期170卷 498-522页

作者： Xiao, F Yabe, T Tokyo Inst Technol Dept Energy Sci Midori Ku Yokohama Kanagawa 2268502 Japan Tokyo Inst Technol Dept Mech Engn & Sci Meguro Ku Tokyo 1528552 Japan SEAVANS N Frontier Res Syst Global Change Minato Ku Tokyo 1056791 Japan

In this paper, we present a new type of semi-Lagrangian scheme for advection transportation equation. The interpolation function is based on a cubic polynomial and is constructed under the constraints of conservation of cell-integrated average and the slope modification. The cell-integrated average is defined via the spatial integration of the interpolation function over a single grid cell and is advanced using a flux form. Nonoscillatory interpolation is constructed by choosing proper approximation to the cell-center values of the first derivative of the interpolation function. which appears to be a free parameter in the present formulation. The resulting scheme is exactly conservative regarding the cell average of the advected quantity and does not produce any spurious oscillation. Oscillationless solutions to linear transportation problems were obtained. Incorporated with an entropy-enforcing numerical nux, the presented schemes can accurately compute shocks and sonic rarefaction waves when applied to nonlinear problems. (C) 2001 Academic Press.

关键词： atmospheric modeling computational algorithm semi-Lagrangian scheme linear and nonlinear transportation equations mass conservation shock wave

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An optimal design of multiattribute control charts for processes subject to a multiplicity of assignable causes

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APPLIED MATHEMATICS AND COMPUTATION 2000年第2-3期114卷 187-203页

作者： Jolayemi, JK Univ Zululand Dept Math & Stat ZA-3886 Kwa Dlangezwa KwaZulu Natal South Africa

We have developed a model for the optimal design of multiattribute control charts (MACCs) for processes subject to multiple assignable causes. The development of the model is based on the J approximation (J.K. Jolayemi, Comput. Stat. Data Anal., 18, 1994, pp 403-417;J.K. Jolayemi and J.N. Berrettoni, Appl. Math. Comput. 32 (1) (1989) pp. 1-16) and on the modification and extension of Gibra's model for the design of attribute control charts (I.N. Gibra, J. Quality Technol. 13 (2) (1981) pp. 93-99). A computational procedure for optimizing the model is presented. Some numerical examples are given to illustrate the model and the computational procedure. The examples show that the MACC and its design parameters are very sensitive to changes in the values of the input parameters. The model does not require any approximation by the "matching" process (see I.N. Gibra, J. Quality Technol. 13 (2) (1981) pp. 93-99 for an example of the matching process), as an exact solution to it is very easy to obtain. The justifications for applying the J approximation (JA) are illustrated by numerical examples. The numerical examples show that JA is very accurate in determining sample sizes. The examples also show that unlike when used to compute convolution probability values, JA is indifferent to the differences in the values of the proportion defectives when applied for determining sample sizes - whatever the magnitudes of the differences. (C) 2000 Elsevier Science Inc. All rights reserved.

关键词： convolution approximation binomial variables design parameters computational algorithm

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A model for the statistical design of multivariate control charts with multiple control regions

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APPLIED MATHEMATICS AND COMPUTATION 2000年第1期109卷 73-91页

作者： Jolayemi, JK Univ Zululand Dept Math Sci ZA-3886 Kwa Dlangezwa South Africa

This paper develops a statistical model for the design of multivariate control charts with multiple control regions (MCCMCR). The model produces the sample size and values of the control limits needed for the operations of MCCMCR. It allows the consumers and the producers to specify desired values for the risks and power functions that have the greatest effects on the efficiency of the chart. Numerical examples are given to illustrate the model and to study the properties of MCCMCR. (C) 2000 Elsevier Science Inc. All rights reserved.

关键词： multivariate control charts sample size control-limit constants assignable causes computational algorithm

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A method for dynamic response analysis of time-variant discrete systems

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COMPUTERS & STRUCTURES 2000年第4期76卷 545-550页

作者： Kucharski, T Gdansk Tech Univ Dept Mech Engn PL-80952 Gdansk Poland

A method is proposed for analysing the transient response of structures when variation with respect to time of the stiffness and damping coefficients are taken into account. The state-variable technique is employed to formulate the dynamic equilibrium equation for the time-variant system. Excitation is represented as a series of impulses. It allows introduction of virtual initial conditions which are equivalent to the impulse excitations in the state space equations. The effective method for evaluation of a state transition matrix is used. Numerical tests of an illustrative example demonstrate the validity and effectiveness of the approach suggested in this paper. The method has great advantages when the behaviour of the semi-active system is calculated and the optimal control of the systems is simulated. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： method for dynamic analysis computational algorithm computer simulation semi-active control system semi-active suspension

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Constructing exactly conservative scheme in a non-conservative form

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COMPUTER PHYSICS COMMUNICATIONS 2000年第3期126卷 232-243页

作者： Tanaka, R Nakamura, T Yabe, T Tokyo Inst Technol Dept Energy Sci Midori Ku Yokohama Kanagawa 2268502 Japan

A non-conservative scheme that guarantees exact mass conservation is proposed, Although it is in a non-conservative form, the mass of each cell is employed as an additional variable that is advanced in a conservative form. Some numerical tests are carried out to demonstrate the mass conservation and the accurate calculation of the speed of a shock wave even without the viscosity term. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： CIP computational algorithm mass conservation semi-Lagrangian

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An exponential queue with competition for service

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EUROPEAN JOURNAL OF OPERATIONAL RESEARCH 2000年第3期126卷 587-602页

作者： Brill, PH Hlynka, M Univ Windsor Dept Math & Stat Windsor ON N9B 3P4 Canada Univ Windsor Dept Management Sci Windsor ON N9B 3P4 Canada

We consider an M/M/c queue, where a single 'special' customer C-p arrives. If C-p must wait, then either C-p will eventually start service at some completion epoch with probability p, or C-p will 'float' into service at the end of a busy period. The model is interpreted as C-p competing for service against the regular customers. We study the waiting time of C-p. We analyze the effect of C-p on the waiting times of the regular customers. Examples and applications are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： queueing M/M/c ballot theorem Laplace-Stieltjes transform computational algorithm

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A computational model for suspended large rigid bodies in 3D unsteady viscous flows

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JOURNAL OF computational PHYSICS 1999年第2期155卷 348-379页

作者： Xiao, F RIKEN Inst Phys & Chem Res Sci Computat Lab Wako Saitama 3510198 Japan

A 3D numerical model for computing large rigid objects suspended in fluid flow has been developed. Rather than calculating the surface pressure upon the solid body, we evaluate the net force and torque based on a volume force formulation. The total effective force is obtained by summing up the forces at the Eulerian grids occupied by the rigid body. The effects of the moving bodies are coupled to the fluid flow by imposing the velocity field of the bodies to the fluid. A Poisson equation is used to compute the pressure over the whole domain. The objects are identified by color functions and calculated by the PPM scheme and a tangent function transformation which scales the transition region of the computed interface to a compact thickness. The model is then implemented on a parallel computer of distributed memory and validated with Stokes and low Reynolds number hows. (C) 1999 Academic Press.

关键词： computational algorithm fluid dynamics large suspended objects multiphase flows low Reynolds number parallel computing

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A novel algorithm for computing autocorrelation of randomly sampled sequences

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CIRCUITS SYSTEMS AND SIGNAL PROCESSING 1999年第6期18卷 525-537页

作者： Lo, KC Hong Kong Polytech Univ Dept Elect & Informat Engn Kowloon Peoples R China

Random sampling is one of the methods used to achieve sub-Nyquist sampling. This paper proposes a novel algorithm to evaluate the circular autocorrelation of a randomly sampled sequence, from which its power density spectrum can be obtained. With uniform, sampling, the size of each lag (the step size) for computing an autocorrelation of a sequence is the same as the sampling period. When random sampling is adopted, the step size should be chosen such that the highest-frequency component of interest contained in a sequence can be accommodated. To find overlaps between a time sequence and its shifted version, an appropriate window is opened in one of the time sequences. To speed up the process, a marker is set to limit the range of searching for overlaps. The proposed method of estimating the power spectrum via autocorrelation is comparable in terms of accuracy and signal-to-noise ratio (SNR) to the conventional point rule. The techniques introduced can also apply to other operations for randomly sampled sequences.

关键词： random sampling digital signal processing spectral estimation computational algorithm

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Numerical computation of a damped slewing beam with tip mass

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COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING 1999年第4期15卷 249-261页

作者： Chen, GR Chen, ZY Xu, YS Univ Houston Dept Elect & Comp Engn Houston TX 77204 USA Zhongshan Univ Dept Comp Sci Guangzhou Peoples R China N Dakota State Univ Dept Math Fargo ND 58105 USA

This paper describes an analytical model for a beam system, based on a modified Timoshenko theory, where the beam is pinned to a hub driven by an actuator at one end and is subject to a heavy load at the other end. A new efficient computational algorithm is then proposed for solving the higher-order non-canonical partial differential equation model, which is developed based on the generalized difference method. This allows a suitable selection of different trial and test spaces, so as to improve the computational efficiency while preserving the high convergence rate of the standard finite element method. With the trial space of cubic Hermite finite elements and the test space of piecewise linear functions, the computational scheme reduces to a semi-discretized or even fully discretized computational algorithm. A numerical simulation result is included to visualize the theoretical modelling and computational results. Copyright (C) 1999 John Wiley & Sons, Ltd.

关键词： computational algorithm damped slewing beam higher-order non-linear PDE finite element method

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Development of a flow solver using the adaptive Cartesian mesh algorithm for wind environment assessment

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JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS 1999年第1-3期81卷 377-389页

作者： Ogawa, T Shimizu Corp Inst Technol Koto Ku Tokyo 135 Japan

A new flow solver is developed for wind environment assessment in which a very complex flow held over a number of buildings should be taken into account. The adaptive Cartesian mesh algorithm is used so as to automatically generate meshes for complicated flow geometry. In this approach, a flow field is decomposed into a number of cubic cells and a cell is recursively divided into eight children cells where curvature of flow geometry or gradient of flow variables are large. The numerical scheme is based on the artificial compressibility method and the finite volume method is used for discretization, The cells are organized with the tree data structure and the numerical algorithm for the tree data structure is described. computational results are presented and the efficiency of the algorithm is discussed, (C) 1999 Elsevier Science Ltd. All rights reserved.

关键词： numerical simulation computational algorithm tree data structure

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