392 research outputs found
An investigation of the principles of Athenian architecture; or, The results of a recent survey conducted chiefly with reference to the optical refinements exhibited in the construction of the ancient buildings at Athens
No full textArchitectural detail, the Propylaea of the Acropolis, Athens [colour plate 23]; Penrose, Francis Cranmer, 1817-1903 An investigation of the principles of Athenian architecture; or, The results of a recent survey conducted chiefly with reference to the optical refinements exhibited in the construction of the ancient buildings at Athens. New and enl. ed. London, Macmillan, 1888. Physical descrip: xii, 128 p. 48 plates. Source: University of Toronto Libraries; http://main.library.utoronto.ca/ (accessed 1/12/2008
Material Deformations of Penrose Tiling
No full textThe heart of this work is exploring Penrose tiling. Penrose tilings are ways tocompletely cover an infi nite plane with perfectly fi tting shapes, in a pattern that neverrepeats – they have moments of local symmetry, where it may look like they are regular andordered, but on a larger scale, this order is always disrupted. We use a technique thatchanges the shape of the tiles while keeping the underlying pattern to create a rich,generative space for artistic explorationGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Arts & CraftsHuman Information Communication Desig
The Funk transform as a Penrose transform
No full textThe Funk transform is the integral transform from the space of smooth even functions on the unit sphere S²[subset or is implied by][open face R]³ to itself defined by integration over great circles. One can regard this transform as a limit in a certain sense of the Penrose transform from [open face C][open face P]₂ to [open face C][open face P]*ast;₂. We exploit this viewpoint by developing a new proof of the bijectivity of the Funk transform which proceeds by considering the cohomology of a certain involutive (or formally integrable) structure on an intermediate space. This is the simplest example of what we hope will prove to be a general method of obtaining results in real integral geometry by means of complex holomorphic methods derived from the Penrose transform.By Toby N. Bailey Michael G. Eastwood, A. Rod Gover, and Lionel J. Maso
Penrose Demosaicking
No full textThe Penrose pixel layout, an aperiodic pixel layout in rhombus Penrose tiling, has been shown to substantially outperform the existing square pixel layout in super-resolution. However, it was tested only on grayscale images. To study its performance on color images, we have to reconstruct regular color images from Penrose raw images, i. e., images with only one color component at each Penrose pixel, resulting in the problem of demosaicking from Penrose pixels. Penrose demosaicking is more difficult than regular demosaicking, because none of the color components of the reconstructed regular color images are available. Therefore, most of the traditional demosaicking methods do not apply. We develop a sparse representation-based method for Penrose demosaicking. Extensive experiments show that Penrose pixel layout outperforms regular pixel layouts in terms of both perceptual evaluation and S-CIELAB. The Penrose pixel layout is unique among all irregular layouts because it is uniformly three-colorable and it has only two pixel shapes, thick and thin rhombi, making its manufacturing relatively easy.973 Program of China [2015CB352502]; National Natural Science Foundation of China (NNSFC) [61272341, 61231002]; Cooperative Medianet Innovation Center; Microsoft Research Asia Collaborative Research Program; NNSFC [61033013]; Ph.D. Programs Foundation of Ministry of Education of China [20120009110006]; Program for Changjiang Scholars and Innovative Research Team in University [IRT201206]; Beijing Committee of Science and Technology of China [Z131110002813118]; Japanese Ministry of Education, Culture, Sports, Science and Technology through the Support Program for the Strategic Research Foundation at Private UniversitiesSCI(E)[email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Penrose and the Indifferent Crowd
No full textToday Lionel Penrose is recognised as the co-author of one of the two leading indices of power in voting legislatures – a field of study that game theory in general, and cooperative game theory in particular, has been reclaiming from sociology and political science since the 1950s. The main claim of this paper is that Penrose developed his index so as to tackle questions that go vastly beyond the narrow domain of voting; namely, acute social issues during the Cold War such as the outburst and propagation of panics, the ideological susceptibility of populations, the escalation of military conflict and the successful installation of authoritarian regimes. Furthermore, by revisiting the history of the Penrose power index, the paper re-evaluates some of its key underlying assumptions: assumptions that have been heavily – and unfairly, as the paper argues – criticised over the last decade
Penrose high-dynamic-range imaging
No full textHigh-dynamic-range (HDR) imaging is becoming increasingly popular and widespread. The most common multishot HDR approach, based on multiple low-dynamic-range images captured with different exposures, has difficulties in handling camera and object movements. The spatially varying exposures (SVE) technology provides a solution to overcome this limitation by obtaining multiple exposures of the scene in only one shot but suffers from a loss in spatial resolution of the captured image. While aperiodic assignment of exposures has been shown to be advantageous during reconstruction in alleviating resolution loss, almost all the existing imaging sensors use the square pixel layout, which is a periodic tiling of square pixels. We propose the Penrose pixel layout, using pixels in aperiodic rhombus Penrose tiling, for HDR imaging. With the SVE technology, Penrose pixel layout has both exposure and pixel aperiodicities. To investigate its performance, we have to reconstruct HDR images in square pixel layout from Penrose raw images with SVE. Since the two pixel layouts are different, the traditional HDR reconstruction methods are not applicable. We develop a reconstruction method for Penrose pixel layout using a Gaussian mixture model for regularization. Both quantitative and qualitative results show the superiority of Penrose pixel layout over square pixel layout. (C) 2016 SPIE and IS&TFundamental Research Funds for the Central Universities [K16JB00080]; 973 Program of China [2015CB352502]; National Natural Science Foundation of China (NSFC) [61272341, 61231002]; Microsoft Research Asia Collaborative Research Program; NSFC [61370129]; PhD Programs Foundation of Ministry of Education of China [20120009110006]SCI(E)[email protected]
Fashion, faith, and fantasy in the new physics of the Universe
No full textWhat can fashionable ideas, blind faith, or pure fantasy possibly have to do with the scientific quest to understand the universe? Surely, theoretical physicists are immune to mere trends, dogmatic beliefs, or flights of fancy? In fact, acclaimed physicist and bestselling author Roger Penrose argues that researchers working at the extreme frontiers of physics are just as susceptible to these forces as anyone else. In this provocative book, he argues that fashion, faith, and fantasy, while sometimes productive and even essential in physics, may be leading today's researchers astray in three of the field's most important areas--string theory, quantum mechanics, and cosmology. Arguing that string theory has veered away from physical reality by positing six extra hidden dimensions, Penrose cautions that the fashionable nature of a theory can cloud our judgments of its plausibility. In the case of quantum mechanics, its stunning success in explaining the atomic universe has led to an uncritical faith that it must also apply to reasonably massive objects, and Penrose responds by suggesting possible changes in quantum theory. Turning to cosmology, he argues that most of the current fantastical ideas about the origins of the universe cannot be true, but that an even wilder reality may lie behind them. Finally, Penrose describes how fashion, faith, and fantasy have ironically also shaped his own work, from twistor theory, a possible alternative to string theory that is beginning to acquire a fashionable status, to "conformal cyclic cosmology," an idea so fantastic that it could be called "conformal crazy cosmology." The result is an important critique of some of the most significant developments in physics today from one of its most eminent figures
On the isoperimetric Riemannian Penrose inequality
Get PDFWe prove that the Riemannian Penrose inequality holds for asymptotically flat 3-manifolds with nonnegative scalar curvature and connected horizon boundary, provided the optimal decay assumptions are met, which result in the (Formula presented.) mass being a well-defined geometric invariant. Our proof builds on a novel interplay between the Hawking mass and a potential-theoretic version of it, recently introduced by Agostiniani, Oronzio, and the third named author. As a consequence, we establish the equality between (Formula presented.) mass and Huisken's isoperimetric mass under the above sharp assumptions. Moreover, we establish a Riemannian Penrose inequality in terms of the isoperimetric mass on any 3-manifold with nonnegative scalar curvature, connected horizon boundary, and which supports a well-posed notion of weak inverse mean curvature flow (IMCF). In particular, such isoperimetric Riemannian Penrose inequality does not require the asymptotic flatness of the manifold. The argument is based on a new asymptotic comparison result involving Huisken's isoperimetric mass and the Hawking mass
On the Isoperimetric Riemannian Penrose Inequality
Get PDFWe prove that the Riemannian Penrose Inequality holds for Asymptotically Flat -manifolds with nonnegative scalar curvature and connected horizon boundary, provided the optimal decay assumptions are met, which result in the mass being a well-defined geometric invariant. Our proof builds on a novel interplay between the Hawking mass and a potential-theoretic version of it, recently introduced by Agostiniani, Oronzio and the third named author. As a consequence, we establish the equality between mass and Huisken\u27s Isoperimetric mass under the above sharp assumptions. Moreover, we establish a Riemannian Penrose Inequality in terms of the Isoperimetric mass on any -manifold with nonnegative scalar curvature, connected horizon boundary, and which supports a well-posed notion of weak Inverse Mean Curvature Flow. In particular, such Isoperimetric Riemannian Penrose Inequality does not require the asymptotic flatness of the manifold. The argument is based on a new asymptotic comparison result involving Huisken\u27s Isoperimetric mass and the Hawking mass
Photonic band gap effect and localization in two-dimensional Penrose lattice
No full textDate of Conference: 6-11 May 2001Conference Name: Conference on Lasers and Electro-Optics, CLEO 2001A study of photonic bandgap effect and localization in two-dimensional Penrose lattice was performed. Penrose quasicrystals consisted of dielectric rods and defect characteristics of various inequivalent sites of the crystal were investigated. It was observed that the defect characteristics of quasi periodic photonic crystals were different from the periodic case. Localization properties of the defect modes in quasicrystals depended on the position of the removed rod and different defect frequencies could be obtained by removal of rods from various positions
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