2,225 research outputs found
On acoustic propagation in three-dimensional rectangular ducts with flexible walls and porous linings
No full textThis is the post-print version of the Article. The official published version can be accessed from the links below - Copyright @ 2012 Acoustical Society of AmericaThe focus of this article is toward the development of hybrid analytic-numerical mode-matching methods for model problems involving three-dimensional ducts of rectangular cross-section and with flexible walls. Such methods require first closed form analytic expressions for the natural fluid-structure coupled waveforms that propagate in each duct section and second the corresponding orthogonality relations. It is demonstrated how recent theory [Lawrie, Proc. R. Soc. London, Ser. A 465, 2347–2367 (2009)] may be extended to a wide class of three-dimensional ducts, for example, those with a flexible wall and a porous lining (modeled as an equivalent fluid) or those with a flexible internal structure, such as a membrane (the “drum-like” silencer). Two equivalent expressions for the eigenmodes of a given duct can be formulated. For the ducts considered herein, the first ansatz is dependent on the eigenvalues/eigenfunctions appropriate for wave propagation in the corresponding two-dimensional flexible-walled duct, whereas the second takes the form of a Fourier series. The latter offers two advantages: no “root-finding” is involved and the method is appropriate for ducts in which the flexible wall is orthotropic. The first ansatz, however, provides important information about the orthogonality properties of the three-dimensional eigenmodes
Analytic mode-matching for acoustic scattering in three dimensional waveguides with flexible walls: Application to a triangular duct
No full textThis is the post-print version of the Article. The official published version can be accessed from the links below - Copyright @ 2012 ElsevierAn analytic mode-matching method suitable for the solution of problems involving scattering in three-dimensional waveguides with flexible walls is presented. Prerequisite to the development of such methods is knowledge of closed form analytic expressions for the natural fluid–structure coupled waveforms that propagate in each duct section and the corresponding orthogonality relations. In this article recent theory [J.B. Lawrie, Orthogonality relations for fluid–structural waves in a 3-D rectangular duct with flexible walls, Proc. R. Soc. A. 465 (2009) 2347–2367] is extended to construct the non-separable eigenfunctions for acoustic propagation in a three-dimensional rectangular duct with four flexible walls. For the special case in which the duct cross-section is square, the symmetrical nature of the eigenfunctions enables the eigenmodes for a right-angled, isosceles triangular duct with flexible hypotenuse to be deduced. The partial orthogonality relation together with other important properties of the triangular modes are discussed. A mode-matching solution to the scattering of a fluid–structure coupled wave at the junction of two identical semi-infinite ducts of triangular cross-section is demonstrated for two different sets of “junction” conditions
It's in the picture Kazuo Terakado, Scientific journalist
No full textKazuo Terakado is a leading scientific journalist in Japan. He has made a significant contribution to the popularization of science through his leadership in the epoch-making Newton Magazine. He is the author of numerous scientific books including Deep Space and Solar System Guidebook. On behalf of Document Design, Lawrie Hunter recently posed some document-related questions to Mr. Terakado.</jats:p
Sculptural model for the zodiac around the sundial, Libra and Scorpio
No full textPhotograph of a maquette (sculptural model) for the signs of the zodiac around the sundial on the south side of the Singing Tower. Depicts representations of the signs for Libra and Scorpio. The maquettes were created by Robert C. Wakeman, who was assistant to sculptor Lee Lawrie and oversaw the carvers onsite at Bok Tower Gardens. Photograph taken by A.L. Alexander of Lake Wales (Fla.). Maquettes are housed in the architectural archives at the University of Pennsylvania. Handwritten notes in pencil on front back back. Torn in two pieces down the center
Operator spectroscopy for 4D SCFTs with a=c
No full textWe study a rich set of four-dimensional superconformal field theories with both central charges identical: a=c. These are constructed via the diagonal N=2 or N=1 gauging of the flavor symmetry G of a collection of N=2 Argyres-Douglas theories of type Dp(G), with or without adjoint chiral multiplets, in 2106.12579 and 2111.12092. We compute superconformal indices of some theories where the rank of G is low, performing a refined test for unitarity, and further determine the relevant and marginal operator content in detail. We find that most of these theories flow to interacting superconformal field theories with a=c in the infrared. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.
An orthogonality condition for a class of problems with high order boundary conditions: Applications in sound/structure interaction
No full textThis is a pre-copy-editing, author-produced PDF of an article accepted for publication in The Quarterly Journal of Mechanics and Applied Mathematics following peer review. The definitive publisher-authenticated version: Lawrie, J.B. & Abrahams, I.D. (1999) “An orthogonality condition for a class of problems with high order boundary conditions; applications in sound/structure interaction.” Q. Jl. Mech. Appl. Math., 52(2), 161-181. is available online at: http://qjmam.oxfordjournals.org/cgi/content/abstract/52/2/161There are numerous interesting physical problems, in the fields of elasticity, acoustics and electromagnetism etc., involving the propagation of waves in ducts or pipes. Often the problems
consist of pipes or ducts with abrupt changes of material properties or geometry. For example, in car silencer design, where there is a sudden
change in cross-sectional area, or when the bounding wall is lagged. As the wavenumber spectrum in such problems is usually discrete, the wave-field is representable by a superposition of travelling or evanescent wave modes in each region of constant duct properties. The solution to the reflection or transmission of waves in ducts is therefore most frequently obtained by mode-matching across the interface
at the discontinuities in duct properties. This is easy to do if the eigenfunctions in each region form a complete orthogonal set of basis functions; therefore, orthogonality relations allow the eigenfunction coefficients to be
determined by solving a simple system of linear algebraic equations. The objective of this paper is to examine a class of problems in which the boundary conditions at the duct walls are not of
Dirichlet, Neumann or of impedance type, but involve second or higher derivatives of the dependent variable. Such wall conditions are found in models of fluid/structural
interaction, for example membrane or plate boundaries, and in electromagnetic wave propagation. In these models the eigenfunctions are not orthogonal, and also extra edge
conditions, imposed at the points of discontinuity, must be included when mode matching. This article presents a new orthogonality relation, involving eigenfunctions and their derivatives, for the general class of problems involving a scalar wave equation and
high-order boundary conditions. It also discusses the procedure for incorporating the necessary edge conditions. Via two specific examples from structural acoustics, both of which have exact solutions obtainable by other techniques, it is
shown that the orthogonality relation allows mode matching to follow through in the same manner as for simpler boundary conditions. That is, it yields coupled algebraic systems for the eigenfunction expansions which are easily solvable, and by which means more complicated cases, such as that illustrated in figure 1, are tractable
Landscape of 4d N=1 SCFTs with a = c
No full textWe study a landscape of four-dimensional N = 1 superconformal field theories (SCFTs) with identical central charges. These theories are obtained by renormalization group flows triggered by supersymmetrypreserving superpotential deformations of the N = 1 gauging of the flavor symmetry of a collection of N = 2 Dp(G) Argyres-Douglas SCFTs. In this work, we focus on the fixed points in the landscape of the SU(3) gauging of three copies of the D2(SU(3)) = H2 theory together with an adjoint-valued chiral multiplet. We catalog the network of a = c fixed points, and, along the way, we find a variety of dualities and instances of supersymmetry enhancement.
Better than Biggles: Michael Annesley’s ‘Lawrie Fenton’ spy thrillers.
No full textCaptain F.A.M. Webster, the athlete, athletics coach and author who lived from 1886 to 1949, wrote a series of fifteen spy thrillers under the pseudonym of Michael Annesley. His hero, Lawrie Fenton, is a lively and laid-back secret agent for the fictional Intelligence Branch of the (British) Foreign Office. The books were published between 1935 and 1950, and the series is important because of its European settings, analyses of contemporary politics, insights into contemporary points of view, and snapshots of events and places. Fenton was a new and exciting hero for his times. The paper establishes Webster’s unrecognized but important influence on the development of the spy thriller. The photographs are from the Webster family collection
Detection of single and resonant projectile fragments in C-12-induced reactions to the continuum
No full textDetector telescopes having a DeltaE-E configuration, consisting of either a Si surface barrier detector or a Si strip detector followed by a NaI(Tl) stopping detector, are described for measuring intermediate mass fragments in C-12-induced reactions to the continuum. These include the stable break-up fragments Be-7 and Be-9, as well as the resonant fragment Be-8. Energy calibration of the stopping detectors is based on a scintillation light-response model. Empirical approximating functions have been selected for inverting the theoretical functions relating light output to particle energy, in order to achieve calibration during rapid data sorting. The detector efficiency for resonant fragments is obtained by means of a Monte Carlo simulation. A dedicated eight-channel preamplifier module with good operational stability in vacuum, specifically designed for Si-strip detectors, is also described
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