View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector MATHEMATICAL MODELLING An Ihternational Journal Editors Xavier J.R. Avula Ervin Y. Rodin Department of Engineering Mechanics Department of Systems Science and University of Missouri-Rolla Mathematics Rolla, Missouri 65401, USA Box 1040, Washington University St. Louis, Missouri 63130, USA Editorial Board Publishing, Subscription and Advertising Offices: Rutherford Aris Simon A. Levin Pergamon Press, Inc., Fairview Park, University of Minnesota Cornell University Elmsford, NY 10523, USA; and Pergamon H.T. Banks William F. Lucas Press Ltd., Headington Hill Hall, Oxford Brown University Cornell University OX3 OBW, England. Richard Bellman N. Metropolis Published Bimonthly. (ISSN 0270-0255) University of Southern California Los Alamos Scientific Laboratory, Annualsubscription rate( 1982) $115.00; New Mexico Edward .I. Beltrami Two-year rate (1982/83) $218.50; State University of New York at E.W. Montroll Special individual rate for those whose Stony Brook University of Rochester, New York institution subscribes at the regular rate (1982) $45.00; Personal rate for Raymond Bisplinghoff J.C.J. Nihoul Tyco Laboratories, New Jersey University de Liege, Belgium members of AMS/MAA, SIAI\I1, IAMM, and SES (1982) $30.00. Prices Martin Braun Hans Oestreicher include surface postage and insurance; Queens College, New York Aerospace Medical Research air mail subscriptions extra. Laboratory, Ohio Roger W. Brockett Microform Subscriptions: Simultaneous Harvard University Edward C. Posner California Institute of Technology subscriptions on microfiche and micro- Colin W. Clark film are available from Pergamon Press University of British Columbia Ilya Prigogine and/or its division, Microforms Interna- Brussels, Belgium G.B. Dantzig tional Marketing Company, Fairview Stanford University C.R. Rao Park, Elmsford, New York 10523, USA; University of Pittsburgh and Headington Hill Hall, Oxford OX3 John U. Farley OBW, England. Columbia University Fred S. Roberts Rutgers University Copyright 0 1982 Pergamon Press Ltd. R. Glowinski Laboratorie de Recherche en Robert Rosen If is a condition of publicationthat manuscripts sub- Informatique et Automatique, Dalhousie University, Canada mitted to this journal have not been published and Le Chesnay, France will DOI be simultaneously submitted or published Gian-Carlo Rota elsewhere. By submltring a manuscript, the authors Massachusetts Institute of Technology H.S. Green agree that the copyright for their article is transfer- University of Adelaide, South Australia red to the publisher if and when the article is ac- Thomas L. Saaty ceoted for publication. The copyright covers rheex- Frank Harary University of Pittsburgh cl&&e rights to reproduce and distribute the arucie. University of Michigan mcluding reprints. photographic reproductions. Stephen Smale microform or any other reproducfmns of simdar J.N.R. Jeffers University of California nature and translarions. No part of this publication Institute of Terrestrial Ecology, may be reproduced. stored in a retrieval system or Jerome Spanier transmitted in any form or by any means. electromc. England Claremont Graduate School, California electrostatic, magn&c tape. mechanical. photo- Mark Kac copying, recordingorotherwise. without permission Lynn Arthur Steen in wnting from the copyright holder. Rockefeller University, New York St. Olaf College, Minnesota Rudolf E. Kalman U.S. Copyright Law applicable 10 users in the USA: Samuel C.C. Ting The Article Fee Code on the first page of an art~le in Swiss Federal Institute of Technology, Massachusetts Institute of Technology this journal indicates the copyrighrbwner’s consent Zurich and University of Florida that in the U.S.A. copies may be made for personal Stanislaw M. Ulam or internal use provided the stated fee for copymg Herbert Keller University of Colorado bevond rhar Dermitted bv Section 107W 108 of the California Institute of Technology United States Copyright Law is paid. The aQQrOQri- H. van Gierke ate remittance should be forwarded with a copy of Murray S. Klamkin Yell0 w Springs, Ohio the first page of the article to the Copyrtght Clear- University of Alberta, Canada ance Cenrei Inc.. 21 Congress Street, Salem, MA Lotfi Zadeh 01970. If a code does nor appear copies of the article M.D. Kruskal University of California, Berkeley may be madewithout charge. pro&led permnsion IS Princeton University obtained from the publisher. The copyright owner’s O.C. Zienkiewicz consent does not extend to copying for general distri- Roger E. Levien University of Wales bution, for promotion, for creating new works or International Instituie of Applied for resale. Specific wntten permission must be ob- System Analysis, Laxenburg, Austria Hans-Jurgen Zimmerman tamed from the publisher for such copymg. In case Rheinisch- Westfalische Technische of doubt please contacr your new% Pergamon Hochschule Aachen, FR Germany offtce. .