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- Aria, S., et al.
(författare)
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GLINT Gravitational-wave laser INterferometry triangle
- 2017
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 44:2, s. 181-208
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Tidskriftsartikel (refereegranskat)abstract
- When the universe was roughly one billion years old, supermassive black holes (10(3)-10(6) solar masses) already existed. The occurrence of supermassive black holes on such short time scales are poorly understood in terms of their physical or evolutionary processes. Our current understanding is limited by the lack of observational data due the limits of electromagnetic radiation. Gravitational waves as predicted by the theory of general relativity have provided us with the means to probe deeper into the history of the universe. During the ESA Alpach Summer School of 2015, a group of science and engineering students devised GLINT (Gravitational-wave Laser INterferometry Triangle), a space mission concept capable of measuring gravitational waves emitted by black holes that have formed at the early periods after the big bang. Morespecifically at redshifts of 15
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| 5. |
- Svelander, Frida, 1989
(författare)
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Robust intersection of hexahedral meshes and triangle meshes with applications in finite volume methods
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The topic of this thesis is the intersection of a structured hexahedral grid and one or more triangle meshes. The interest in the problem has arisen in connection with a finite volume method for simulation of conjugated heat transfer. In the particular finite volume method, axis-aligned hexahedra are used for the discretization of the simulation domain, and solids are represented by triangle meshes. The heat equation is discretized over the hexahedral cells. Special treatment is needed in the cells that are intersected by the surface of the solid. In these cells, the solid temperature is found after discretization of the heat equation over the solid part of the cell. To implement the above, it is of great importance to find the geometry of the cut cells. Of particular interest is the solid volume fraction of a cell, and the solid area fraction of the cell faces. The solid volume fraction is defined as the fraction of the hexahedral cell that is intersected by the solid. Similarly, the solid area fraction is defined for each cell face as the fraction of the face that is intersected by the solid. Two algorithms for calculation of the solid volume fraction and the solid area fractions are presented. One algorithm is exact, and the other is approximate. The algorithms are extended to handle double surfaces, which is a common mesh degeneracy in engineering applications. A double surface is two layers of coplanar triangles, formed when the triangles are put on top of each other. The handling of double surfaces is an extension of similar algorithms, which only handle non degenerate triangle meshes. This work is a step towards an algorithm that can be used with such meshes without preprocessing through a repair algorithm. A mesh repair method could be adopted, if available, but that is not always desirable since the existing repair algorithms could fail in removing the degeneracies without introducing unwanted side effects. This motivates the need for an algorithm that handles degenerate triangle meshes. The algorithms are validated against a geometry from an industrial application, which includes a double surface. It is concluded that the exact algorithm is independent of cell size, while the approximate algorithm is second order accurate for the test case that has been studied. It is further concluded that the methods handle the major problems with double surfaces. Finally, it is described how the algorithms are used in a finite volume framework for simulation of conjugated heat transfer.
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| 7. |
- Sintorn, Erik, 1980, et al.
(författare)
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Per-Triangle Shadow Volumes Using a View-Sample Cluster Hierarchy
- 2014
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Ingår i: Proceedings of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games (I3D 2014). - New York, NY, USA : ACM.
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Konferensbidrag (refereegranskat)abstract
- Rendering pixel-accurate shadows in scenes lit by a point lightsource in real time is still a challenging problem. For scenes of moderate complexity, algorithms based on Shadow Volumes are by far the most efficient in most cases, but traditionally, these algorithms struggle with views where the volumes generate a very high depth complexity. Recently, a method was suggested that alleviates this problem by testing each individual triangle shadow volume against a hierarchical depth map, allowing volumes that are in front of, or behind, the rendered view samples to be efficiently culled. In this paper, we show that this algorithm can be greatly improved by building a full 3D acceleration structure over the view samples and testing per-triangle shadow volumes against that. We show that our algorithm can elegantly maintain high frame-rates even for views with very high-frequency depth-buffers where previous algorithms perform poorly. Our algorithm also performs better than previous work in general, making it, to the best of our knowledge, the fastest pixel-accurate shadow algorithm to date. It can be used with any arbitrary polygon soup as input, with no restrictions on geometry or required pre-processing, and trivially supports transparent and textured shadow-casters.
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| 8. |
- Friberg, Jöran, 1934, et al.
(författare)
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Goetze’s Compendium from Old Babylonian Shaduppûm and Two Catalog Texts from Old Babylonian Susa
- 2016
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Ingår i: Sources and Studies in the History of Mathematics and Physical Sciences. - Cham : Springer International Publishing. ; , s. 391-419
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The three tablets IM 52916 (in the present chapter, Sec. 10.1), and IM 52685 + IM 52304 (in Sec. 10.2) were published and correctly interpreted by Goetze in Sumer 7 (1951). Goetze called them together “a mathematical compendium from Tell Harmal”. The three tablets are very poorly preserved.
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| 9. |
- Friberg, Jöran, 1934
(författare)
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Old Babylonian Hand Tablets with Geometric Exercises
- 2007
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Ingår i: Sources and Studies in the History of Mathematics and Physical Sciences. - New York, NY : Springer New York. ; , s. 189-229
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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