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STABILITY T H E O R Y A N D ITS A P P L I C A T I O N S TO S T R U C T U R A L MECHANICS 1974, Clive L. Dym. Leyden, The Netherlands: Noordhofflnternational Publishing Co. viii + 191 pp.; price s

This is No. 3 in a series of monographs on the mechanics ofelastic stability edited by H. H. E. Leipholz. The author, C. L. Dym, is a staff member of the famous company of Bolt Beranek and Newman Inc., and the material has been taught by him as graduate courses at two universities.

The author's guiding precept is that structural stability should be taught from a dynamical rather than a statical point of view. He soon becomes involved therefore with concepts of Lyapunov stability, and the first three chapters are devoted to the necessary mathematical background ofstability of equilibrium for discrete systems described by ordinary differential equations.

Stability concepts for continuous systems described by partial differential equations are introduced in chapter four, through the example of stability of a column and its Euler buckling load. The chapter ends with some theorems on stability in the L2 norm due to W. T. Koiter.

Non-linear elasticity is introduced in chapter 5 and includes consideration of large deflec- tions of columns, the yon Kfirm~in theory of plates and deflection of arches. Chapter 6 discusses the buckling and post-buckling behaviour of pinned-end columns and introduces the effect of imperfections. Chapter 7 extends the analysis to rectangular plates under com- pressive and shear loads and circular plates under radial compression and chapter 8 to circular arches under constant directional pressure or "dead" pressure.

Chapter 9 is a collection of applications of Lyapunov functionals taken from current literature on aeroelasticity and fluid mechanics, especially papers by R. H. Plaut.

The book contains much interesting material and has copious references, but chapters 6-8 seem curiously disjointed from the other parts, since after a big build up in chapters 1-4 Lyapunov functionals do not appear again until chapter 9. There are signs of hasty work in preparing the text--figures slightly incorrectly drawn, references mixed up and there are a few misprints. The author also uses some curious verbs, "envision", "intuit" and "posit", for example.

One important point which does not emerge from the book is that stability conditions deduced from linearized partial differential equations are not necessarily valid when non- linear terms are taken into account, a worrying feature that does not arise for ordinary differential equations. Consider, for example, the partial differential equation

a,,-,,(l g-i = - ax! ]

and a "small" saw-tooth perturbation for which lau/Oxl > 1. This book can be recommended to those teaching, studying or researching in the structural

stability field. It also will be ofsome interest to those concerned with the theory ofdistributed parameter control systems.

P. C. PARKS

ACOUSTICS AND VIBRATION PROGRESS, VOLUME I 1974, edited by R. W. B. Stephens and H. G. LeventhaII. London : Chapman and Hall. x + 243 pp.; price s

This book necessarily spans many disciplines and this makes the reading doubly difficult yet doubly rewarding. It is the first of a series which aim to provide readers with more than just a fleeting contact with subjects which, while being within the general field of acoustics and vibration, are not their own.

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The subjects covered are Traffic Noise, Acoustic Emission, Chemical Aspects of Ultra- sonics, Vibration and Noise Transmission in Building Structures and Underwater Ambient Noise. An essential part of such articles should be a general introduction which, while some knowledge of acoustics and vibrations may be assumed, should introduce the reader to the more particular aspects of the subject. This is a difficult thing to do but nevertheless should be given a lot of effort both on the part of the article writers and the editors. Unfortunately, this has not been done in all cases. The editors do not appear to have "edited" at all. Thus we are presented with a variety of styles from excellent to very poor and a variety of article lengths. The choice of subjects for a first volume can be criticized: some of the topics are very much on the fringes of vibrations and acoustics (chemical aspects of ultrasonics and underwater ambient noise particularly). They are thus less likely to attract the reader to a second volume. Perhaps it would have been better not to have stuck strictly to technical matters but to have been a little more ambitious and included a subjective, legal or sociological chapter.

Fortunately, the first article is the best so that one becomes well-disposed towards the book at a first reading. This is by Dr M. E. Delany on "Traffic Noise". The article is beautifully written and packed full of us6ful information for anyone who might have only temporary contact with the subject, such as engineers or planners. It is a complete statement of the present state of knowledge and above all else it makes enjoyable reading. The book is worth buying for this article alone.

However, the same cannot be said of the next article on "Acoustic Emission" (AE). The subject is a very interesting one and it is worth struggling through the article. AE is the study of sounds emitted by deformation processes in materials. It has led particularly to defect location techniques. In the article a clear account of AE is lacking and the historical perspective is glossed over in half a sentence. The author obviously is much more interested in the measurement of AE (as opposed to the sound sources) and the editors have allowed the article to be unbalanced in this direction. The editors also have failed to weed out the extensive and unexplained jargon in the article and there is even a section headed "Technical Aspects" for no apparent reason. On top of all this the author has been unwise enough to slip in some original work (incomprehensible to the general reader) in what essentially should be a review type article. No serious attempt is made at assessing the commercial aspects of the technique though it is obviously already in use in high-cost engineering structures. It is difficult to imagine, as suggested, how such a high-cost technique possibly could be of economical use in the timber industry.

The next article on chemical aspects of ultrasonics is interesting for the wide range of aspects offered. However, a sound knowledge of Chemical Physics (or should it be Physical Chemistry) is necessary even for a rudimentary understanding of the article. Therefore, on this occasion, all that may be said is that the article is too long (over one-third of the book and 244 references); it should be a book by itself. Experts on the subject may well find this article very satisfying (though that is hardly the point).

On the other hand, the fourth article by H. M. Nelson on Vibration and Noise Transmission in Building Structures is perhaps too short. At a first reading there appeared to be an unusual pun on the first page where " . . . the shear magnitude of the (normal mode) formula t ion . . . " is mentioned but it is probably a spelling mistake! The reviewer's first introduction to this subject was Cremer's classic D.S.I.R. report written at the end of the last war (reference [23] in the article). Since then the subject has come far and recently the statistical energy method has been applied to the subject with far-reaching results and considerable further promise for the future. Nelson covers the subject well, i fa little academically, but seems to have confined his account in an unnecessarily short number of pages. Rather more space could have been devoted to practical experimental researches such as those made at the Building Research

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Establishment. The account shows well that a considerable amount of further work is required in this field in order to bring theoretical results to practical use. On the whole this is a well-written and informative chapter.

The last chapter is concerned with Underwater Ambient Noise by E. M. and T. Arase. This is a very interesting article and, like Chapter l, is well sprinkled with easily compre- hensible graphical information. There is a particularly interesting section on sources of underwater noise with a touch of mystery in the form of a 20 t tz pulsing noise source which travels at 2-4 knots and which is thought to derive from some part of the finback whale. The section also mentions rain noise and leads one to wonder whether rain noise has been studied in the context of buildings. A section on hydrophones and measurement methods and problems would have been a useful addition. Although this is perhaps a fringe subject of limited interest it makes very interesting reading and is thought-provoking--which is perhaps what a book like this should primarily be for.

It is too much to expect such a book to be uniformly exciting and a different reviewer might have a very different view of what suited his taste. The present reviewer has found it quite sufficiently interesting to recommend to you at a cost of s and he looks forward to the forthcoming volumes.

A. J. PRETLOVE