Search results for "Geometry"
showing 10 items of 4487 documents
Influences of surface processes on fold growth during 3-D detachment folding
2014
In order to understand the interactions between surface processes and multilayer folding systems, we here present fully coupled three-dimensional numerical simulations. The mechanical model represents a sedimentary cover with internal weak layers, detached over a much weaker basal layer representing salt or evaporites. Applying compression in one direction results in a series of three-dimensional buckle folds, of which the topographic expression consists of anticlines and synclines. This topography is modified through time by mass redistribution, which is achieved by a combination of fluvial and hillslope erosion, as well as deposition, and which can in return influence the subsequent defor…
Geometric and morphologic evolution of normal fault planes and traces from 2D to 4D data
2003
Abstract The detailed 3D geometry of normal fault planes is described and analysed using datasets from outcrop studies (2D), seismic surveys (3D) and analogue models (4D). Different geometric configurations of simple isolated normal faults are studied by reference to processes of normal fault propagation. When a normal fault propagates without interacting with other fault zones, the entire border of the principal plane displays characteristic connected secondary structures. These secondary structures cause bifurcations of the principal fault terminations. The along-strike terminations of the principal plane display typical bifurcation configurations (‘ear geometry‘). The orientation of the …
Influence of pre-existing fabrics on fault kinematics and rift geometry of interacting segments: Analogue models based on the Albertine Rift (Uganda)…
2011
This study aims at showing how far pre-existing crustal weaknesses left behind by Proterozoic mobile belts, that pass around cratonic Archean shields (Tanzania Craton to the southeast and Congo Craton to the northwest), control the geometry of the Albertine Rift. Focus is laid on the development of the Lake Albert and Lake Edward/George sub-segments and between them the greatly uplifted Rwenzori Mountains, a horst block located within the rift and whose highest peak rises to >5000 m above mean sea level. In particular we study how the southward propagating Lake Albert sub-segment to the north interacts with the northward propagating Lake Edward/George sub-segment south of it, and how this i…
Flow-induced vegetation uprooting in a meandering bend : experimental investigation
2022
Abstract Vegetation uprooting is a complex process which depends on many interrelated factors. In this paper, attention is focused on the flow-induced uprooting in river bends, where the flow characteristics vary as effected by the channel's curvature and its continuous changing in the downstream direction. Results are presented by an experimental work done in a high-amplitude meandering flume with mature herbaceous vegetation on the bed. In the first part of the paper, the variation along the bend of the geometrical (length, thickness, and radical architecture) and the mechanical (resistance force) characteristics of the roots are analyzed. In the second part of the paper, the transition f…
Freshwater discharge and sediment dispersal — Control on growth, ecological structure and geometry of Late Miocene shallow-water coral ecosystems (ea…
2007
Abstract Insolation-driven oceanographic changes are well documented in the Mediterranean deep-sea record and reflect episodes of high precipitation and/or freshwater discharge. In the shallow-water record, however, changes in relative sea-level and sea surface temperature are usually regarded as prime controls on Miocene coral reefs, whereas pulses of freshwater influx represent a hitherto unrecognized factor influencing their growth, ecological structure and geometry. On the island of Crete (NW Messara Basin, Greece) early Tortonian coral biostromes occur associated with deltas along the basin margin and rimming islands formed by large uplifted tectonic blocks. In turbid delta environment…
A boundary condition for arbitrary shaped inlets in lattice-Boltzmann simulations
2009
We introduce a mass-flux-based inlet boundary condition for the lattice-Boltzmann method. The proposed boundary condition requires minimal amount of boundary data, it produces a steady-state velocity field which is accurate close to the inlet even for arbitrary inlet geometries, and yet it is simple to implement. We demonstrate its capability for both simple and complex inlet geometries by numerical experiments. For simple inlet geometries, we show that the boundary condition provides very accurate inlet velocities when Re less than or similar to 1. Even with moderate Reynolds number, the inlet velocities are accurate for practical purposes. Furthermore, the potential of our boundary condit…
From Dupin cyclides to scaled cyclides
2003
Dupin cyclides are algebraic surfaces introduced for the first time in 1822 by the French mathematician Pierre-Charles Dupin. They have a low algebraic degree and have been proposed as a solution to a variety of geometric modeling problems. The circular curvature line’s property facilitates the construction of the cyclide (or the portion of a cyclide) that blends two circular quadric primitives. In this context of blending, the only drawback of cyclides is that they are not suitable for the blending of elliptic quadric primitives. This problem requires the use of non circular curvature blending surfaces. In this paper, we present another formulation of cyclides: Scaled cyclides. A scaled cy…
Temari Balls, Spheres, SphereHarmonic: From Japanese Folkcraft to Music
2022
Temari balls are traditional Japanese toys and artworks. The variety of their geometries and tessellations can be investigated formally and computationally with the means of combinatorics. As a further step, we also propose a musical application of the core idea of Temari balls. In fact, inspired by the classical idea of music of spheres and by the CubeHarmonic, a musical application of the Rubik’s cube, we present the concept of a new musical instrument, the SphereHarmonic. The mathematical (and musical) description of Temari balls lies in the wide background of interactions between art and combinatorics. Concerning the methods, we present the tools of permutations and tessellations we ado…
THE GEOMETRY THROUGH THE BODY: DOING, ACTING, THINKING
2016
The geometry has been for more than two millennia one of the most important fields of knowledge of mathematics, identifying with it for a long time. In education, the relationship between the geometry and the physical world has always been considered one of the main elements for the acquisition of specific skills and competences. In the teaching-learning processes the thinking and the interconnection between doing, acting, thinking is therefore crucial. Teaching through the body may prove effective for teaching mathematics which, very often, is hard to be learned because of difficulties that the child encounters in assimilating mathematical symbolism and, after, applying it to real life and…
On Augmented Reality for the Learning of 3D-Geometric Contents: A Preliminary Exploratory Study with 6-Grade Primary Students
2019
Nowadays, Augmented Reality (AR) is one of the emerging technologies with a greater impact in the Education field. Research has proved that AR-based activities improve the teaching and learning processes. Also, the use of this type of technology in classroom facilitates the understanding of contents from different areas as Arts, Mathematics or Science. In this work we propose an AR-based instruction in order to explore the benefits in a 6th-grade Primary course related to 3D-geometry shapes. This first experiment, designed from an exploratory approach, will shed light on new study variables to perform new implementations whose conclusions become more consistent. The results obtained allow u…