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R. LEVY Development Laboratories, Inc. Needham, Massachusetts

DIGITALCOMPUTERPROCESSCONTROL, by Cecil L. Smith. 289 pages, 6x 9 in. Intext Educational Publishers, Scranton, Pa., 1972. Price $12.95 (approx. $4.90). The basic objective of this book is to present techniques by which digital computers can be used to generate a larger economic return from a process than can be obtained by using conventional control instrumentation. Unfortunately, the book falls short of this objective. The author presents instead a survey of hardware and software used in the process computer configuration, the design techniques us’mg z-tr&sforms,~identif%&ion, feedforwardfeedback control systems, adaptive control, and a rather cursory treatment of ontimal control. In fact. the chanter on optimal control has a negative effect on the reader since it makes dynamic programming appear too restrictive to be of I

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any practical value and, in the use of Pontryagin’s maximum principle, it overestimates the difficulty of solving the twopoint boundary value problem for nonlinear systems. The chapter on identification barely serves as an introduction since it does not take into account the effects of correlated noise which cannot be neglected for many physical processes, and limits the discussion to processes with one input and one output. But the author brings the reader into the realm of physical systems by examining the control of a distillation column and a chemical reactor. He also considers the practical aspects of choosing the sampling time although the optimum sampling time is not the sampling time corresponding to the point where the cost of decrease in loop performance equals the cost of computing effort. The lack of precision in the deflnit,ion and in the use of fundamental terms (such as physical model vs mathematical model, factor vs term, algorithm, functional, and A) coupled with minor errors in various equations (e.g. Eqs. 3-17, 6-19, 620, 621, 7-22, 7-23, 9-26 and 9-27) and the occasional omission of a period over a symbol (to denote differentiation with respect to time) will probably make the book difficult to read for one not familiar with the field. But since the book is intended for graduate instruction, these are of minor consequence as compared to its overall shortcomings in not providing sufficient depth for evaluating the real possibilities of digital computer control. Department

REIN Luus of Chemical Engineering University of Toronto Toronto, Ontario, Canada

ATOMIC AND MOLECULAR RADIATION r(,___:_.-_-1 _~~_~~.672 PHYSICS, by I cr. fi bnrls~“pn”r”u oases. diaeran is, 6 x 9 in. Wiley 1 ionographs in Chemical Physics (eds. John B. Birks and Sean P. McGlynn). New York, John Wiley & Sons, 1971. Price, $29.00 (approx. fll.50). 1.

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Intended for the postgraduate student and research worker in the field, Christophorou states that the book “deals with

Journalof

The

Franklin Institute

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