1,721,009 research outputs found
Review of Symmetry: The Ordering Principle
No full textSymmetry: The Ordering Principle by architect David Wade is more discursive, and less mathematical. While there is a nod to classifications of symmetries it soon becomes clear that the author is more interested in patterns than in symmetry per se, and many of the objects under discussion, such as strange attractors and vortex streets, are not truly symmetrical. The somewhat ineffable concept of ’Li’ is introduced (though not defined, to my satisfaction at least) – the subject of another book by this author in the same series
Review of The Golden Section: Nature's Greatest Secret
No full textProfessor Olsen repeats all the popular fallacies about the golden ratio so ably demolished by Markowsky [1] (in fairness, Polster manages one too) and adds a few of his own.That ’only’ should manage to offend the devout as much as the secular. The prose lives up to the series title, and while the pages might be in sepia there’s an unmistakeable whiff of green ink here.<br/
Aeroacoustic carousel
No full textClosed-Circuit wind tunnels in which air is driven by fans
are widely used for aerodynamic testing. For aeroacoustic
tests, in which the radiated sound field must be measured in the
presence of flow, they have two major problems: the fan makes
them noisy, and the hard walls make them reverberant. The ideal aeroacoustic test facility would be quiet and anechoic. It is difficult to satisfy these requirements in a standard wind tunnel because anechoic and noise-muffling treatments tend to increase flow resistance so that the fan has to work harder resulting in more noise. In this Note a novel alternative that will eliminate the fan and allow as much anechoic treatment as desired will be proposed
Wavefield decomposition
No full textThis book aims to give a thorough grounding in the mathematical tools necessary for research in acoustics. Twelve authors, all highly-respected researchers in the field of acoustics, provide a comprehensive introduction to mathematical analysis and its applications in acoustics, through material developed for a summer school in mathematics for acoustics researchers funded by the UK Engineering and Physical Sciences Research Council.
Mathematical Methods, Wave Motion, Aeroacoustics and Signal Processing are covered in fourteen chapters by authors including Keith Attenborough (Hull), John Chapman (Keele), Trevor Cox (Salford), Chris Linton and Maureen McIver (Loughborough), and Nigel Peake (Cambridge). There are worked examples, exercises and suggestions for further reading where appropriate. This book is suitable for advanced undergraduate and graduate courses in acoustics and will form an important reference source for researchers in the field. Contents: Mathematical Methods:
Vector Calculus (J W Elliott)
Functions of a Complex Variable (J W Elliott)
Integral Transforms (J W Elliott)
Asymptotic Expansion of Integrals (R H Self)
Wave Motion:
The Wiener–Hopf Technique (M C M Wright)
Waveguides (M McIver & C M Linton)
Wavefield Decomposition (M C M Wright)
Acoustics of Rigid–Porous Materials (K Attenborough & O Umnova)
Aeroacoustics:
Generalised Functions in Aeroacoustics (N Peake)
Monopoles, Dipoles, and Quadrupoles (C J Chapman)
Corrugated Pipe Flow (J W Elliott)
Signal Processing:
Digital Filters (P J Duncan)
Measurement of Linear Time-Invariant Systems (T J Cox & P Darlington)
Numerical Optimisation (T J Cox & P Darlington)
Readership: Graduate students, advanced undergraduate students, researchers in mechanical engineering and mathematical physics
Review of Q.E.D.: Beauty in Mathematical Proof
No full textQ.E.D.: Beauty in Mathematical Proof by Monash University Mathematics Professor Burkard Polster. As might be expected, the emphasis is on visually oriented proofs and constructions, which are admirably illustrated, but induction and regrouping get a look-in as well. Of course a partial proof is no proof at all, but excessive rigour is the enemy of terse exposition. Polster resolves this problem neatly by including an appendix that looks at how careless proofs can fail
Hybrid analytical/numerical method for mode scattering in azimuthally non-uniform duct liners
No full textSound-absorbing liners for ducts are often made in several azimuthal sections with acoustically hard strips, known as splices, between them. These can alter the liner's performance by causing scattering between mode orders, usually to the detriment of overall attenuation. Three-dimensional finite element methods, often involving specialised codes, have previously been used to predict the performance of such spliced liners. Here, an alternative approach is presented which uses a readily available two-dimensional finite element solver to find the modes of the spliced liner and then matches them to the analytical modes of the hard duct. The results are compared with three-dimensional finite element calculations to verify their accuracy. The method as described is for ducts with no flow, but can be extended to flow ducts if necessary
Comments on 'Theory of acoustic eigenmodes in parabolic cylindrical enclosures' by Willatzen, M. and Lew Yan Voon, L.C.
No full textA short history of bad acoustics
No full textEvery branch of science attracts its share of cranks and pseudoscientists, and acoustics has been no exception. A brief survey of those who touched on acoustics is given with quotations from the more interesting or egregious examples. A contrast is drawn between the nineteenth century contrarian's quarrel with particular theories and the modern new age wholesale rejection of theory. This world-view is traced back to the later scientific writings of Goethe. Examples of pseudoscience applied to biomedical acoustics, architectural acoustics, and audio reproduction are given
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