Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 62 for “"Tetrahedra"”.
-
Tetrahedra and Their Nets: Mathematical and Pedagogical Implications
… there may be as many 30 different (incongruent) tetrahedra with the six lengths. Although tetrahedra have been studied in many cultures (Greece, India, China, etc.) Over thousands of years, there are surprisingly many simple questions about them that still have not been answered. This thesis …
-
Librational displacements of silicate tetrahedra in response to temperature and pressure
… it has been concluded that the SiO₄ silicate tetrahedra in crystals behave as rigid bodies. This conclusion is based on analyses of the atomic displacement factors of Si and O atoms obtained from single crystal diffraction experiments wherein the amplitudes of atomic vibrations are ascribed to …
-
Parallel Delaunay Refinement and Space -Time Meshing
… of three-dimensional domains with acute tetrahedra are useful in mesh generation. We give several constructions for tiling space with acute tetrahedra.
-
Sliver -Free Three Dimensional Delaunay Mesh Generation
… the circumsphere of the tetrahedron. Among the tetrahedra created by inserting this new point there could be tetrahedra with large radius-edge ratios, or slivers, or both. However, the new point is incident to every new tetrahedron. We first eliminate tetrahedra with large radius-edge ratios. We …
-
Compact representations for fast nonrigid registration of medical images
… to represent such regions compactly using tetrahedra. Unlike voxel-based representations, tetrahedra can accurately describe the expected smooth surfaces of medical objects. Furthermore, the interior of such objects can be represented using a small number of tetrahedra. Rather than …
-
Structural variations of feldspars at high pressure and high temperature
… mechanism involves tilting of the AlO4 and SiO4 tetrahedra. Similarly, high-temperature single-crystal X-ray diffraction data collected from an ordered An26 plagioclase and powder X-ray diffraction collected on a suite of Na-rich plagioclases that were refined using the Rietveld method indicate …
-
Modeling the properties of silicates
… displacement parameters (ADPs) obtained for TO₄ tetrahedra (T = Si, Al) suggest rigid TO bonds are more common in non-framework than in framework silicates. Correlated motion is found among the ADPs that is consistent with TLS rigid body motion. For these data, the translational motion is …
-
Exploring kinetics and thermodynamics in fast-ion conductors and hydrogen-storage materials using ab-initio molecular dynamics
… bonds, the ... H hydrogen bonds, and the SO4 tetrahedra in promoting proton conduction. A high reversal rate limits the apparent success rate of the otherwise rapid chemical-bond dynamics, which are dominated by the Grotthuss mechanism of proton transfer. Rapid angular hops in concert with …
-
Interactive Visualization of Large Higher-Order Tetrahedral Data
… render volumes on the order of 20 million tetrahedra with cubic-order polynomial solution data at interactive rates. Our methods are not limited to higher-order tetrahedral data, they can be generalized to other non-linear or linear volumetric data sets as sell.
-
Veering Triangulations: Theory and Experiment
… as a union of isometrically embedded hyperbolic tetrahedra. In the second part, we prove that veering triangulations are in fact generically non-geometric.
-
New Developments in the Crystal Chemistry of Selected Borophosphates and Phosphates
… rings of alternating borate and phosphate tetrahedra (a loop–branched hexamer with B : P = 1 : 2). The anionic partial structure of CsSc[B2P3O11(OH)3] represents the new type of oligomer containing boron in three– and four– fold coordination (B : P = 2 : 3). This is also the first time that …
-
Phosphor(V)-nitride durch Hochdruck-Hochtemperatur-Synthese
… network structure of corner-sharing PN4 tetrahedra with Na + ions in the channels. According to the formula ¥ 3 [(P [4] 4 N 5 [2] N 2 [3] ) - ] N [2] - and N [3] -bridges exist in a molar ratio 5 : 2. KP4N7 (Pnma, a = 1222.72(2), b = 984.25(2), c = 466.24(1) pm, Z = 4, Rp = 0.0865, wRp = …
-
Finite element comparison for a geologically motivated benchmark
… do not significantly improve the performance of tetrahedra for the models tested, but could be accurate enough to model curved problem geometries. Comparisons for other models, such as a thrust fault, can be made using a twodimensional simplification of the three-dimensional problem. If …
-
Phase equilibria in the LiF-AlF₃-Na₃AlF₆-Al₂O₃ system
… The quaternary system contains 7 compatibility tetrahedra at 500°C.
-
Energy transfer and waveguide studies of Eu3+ and Tb3+ doped 2 SiO2-TiO2 glass prepared via the sol-gel route
… the next step involves condensation, where Si-OH tetrahedra linkages occur and eventually result in an SiO 2 network. The third step involves solvent evaporation to eliminate residual organics and hydroxyl groups within the pores of the gel. This thesis reports on the luminescence properties of Eu …
-
A structural investigation of the mercury-sulphur interaction
… mercury atom is generally found to be distorted tetrahedra or octahedra, with a very strong tendency to retain the linear character of the R - Hg - S angle. The electronegativity of sulphur is found to be the most influential parameter in determining the coordination geonetry of the mercury atom. …
-
A simplex cut-cell adaptive method for high-order discretizations of the compressible Navier-Stokes equations
… the background mesh consists of triangles or tetrahedra that can be stretched in arbitrary directions to efficiently resolve boundary-layer and wake features.
-
Finite Element Modeling Driven by Health Care and Aerospace Applications
… lattice-based discretizations of well-shaped tetrahedra or mixed elements (i.e., tetrahedra, pentahedra and hexahedra). This method operates directly on segmented images, thus skipping a surface reconstruction that is required by traditional Computer-Aided Design (CAD)-based meshing techniques …
Page 1 of 4