Search results for " Geometry."
showing 10 items of 2189 documents
New shape from Shading methods
1993
Shape from Shading is perhaps the most difficult topic to deal with in Artificial Vision: several researchers have faced it using different approaches. The most part of these methods are based on the Horn algorithm so they require very heavy regularity assumptions about the perceived objects' shape and are computationally expensive.
Multifractal models and their formal properties in urban geography
2019
International audience; Fractal analysis for exploring the spatial organization of settlement patterns is used since a coupleof years. On the one hand, scaling behavior turned out to be a suitable approach for characterizingsuch patterns, but town sections, issued from different periods of urban history or corresponding toparticular planning concepts show different types of scaling behavior what aided classifying urbanpatterns. However, on the scale of agglomerations these different scaling behaviors are mixed. Thatincites asking whether multifractal approaches could be of interest when considering urban patternsor settlement systems, as local properties like different degrees of concentrat…
Solution for the fragment-size distribution in a crack-branching model of fragmentation
2007
It is well established that rapidly propagating cracks in brittle material are unstable such that they generate side branches. It is also known that cracks are attracted by free surfaces, which means that they attract each other. This information is used here to formulate a generic model of fragmentation in which the small-size part of the fragment-size distribution results from merged crack branches in the damage zones along the paths of the propagating cracks. This model is solved under rather general assumptions for the fragment-size distribution. The model leads to a generic distribution S(-gamma) exp(-S/S(0)) for fragment sizes S, where gamma = 2d-1/d with d the Euclidean dimension, an…
Analysis of Geometrical Relationships and Friction Losses in Small-Diameter Lay-Flat Polyethylene Pipes
2016
[EN] The use of lay-flat polyethylene pipes to irrigate horticultural crops has been receiving widespread attention in the last decade, due to the significant improvements in their hydraulic performance, their potentially high application efficiency, and their limited installation costs. However, even if hydraulic design procedures for conventional microirrigation systems are fairly well established, there is still the need to know how different pipe-wall thicknesses of lay-flat pipes can affect the pipe geometry under different operating pressures as well as the related consequences on friction losses. This paper, after comparing two different procedures (caliper and photographic) to asses…
Prediction of phase evolutions during friction stir welding of Ti-grade 5 T-joints using finite element modeling
2022
Friction Stir Welding (FSW) is a solid-state welding technology pioneered by The Welding Institute (TWI) in 1991. Originally used to weld aluminum alloys, it is now effectively utilized to weld high-resistance materials as well. The ultimate mechanical characteristics of the joints are inextricably linked to the microstructural evolutions that occur during the process in terms of phase change. It is then crucial, in order to carry out an effective process engineering, to predict the final material microstructure determined by the thermal history that occurred during the process itself. In the paper, a 3D Finite Element Method (FEM) model for the FSW of T-joints is proposed, based on a therm…
Albanese Maps and Fundamental Groups of Varieties With Many Rational Points Over Function Fields
2020
We investigate properties of the Albanese map and the fundamental group of a complex projective variety with many rational points over some function field, and prove that every linear quotient of the fundamental group of such a variety is virtually abelian, as well as that its Albanese map is surjective, has connected fibres, and has no multiple fibres in codimension one.
Optimization Under Fuzzy Max-t-Norm Relation Constraints
2019
Fuzzy relation equations and inequalities play an important role in many tools of fuzzy modelling and have been extensively studied. In many practical applications they are used as constraints in optimization. Algorithms for specific objective functions have been proposed by many authors. In this paper we introduce a method to convert a system of fuzzy relation constraints with max-t-norm composition to a linear constraint system by adding integer variables. A numerical example is provided to illustrate the proposed method.
Reduced reference 3D mesh quality assessment based on statistical models
2015
International audience; During their geometry processing and transmission 3D meshes are subject to various visual processing operations like compression, watermarking, remeshing, noise addition and so forth. In this context it is indispensable to evaluate the quality of the distorted mesh, we talk here about the mesh visual quality (MVQ) assessment. Several works have tried to evaluate the MVQ using simple geometric measures, However this metrics do not correlate well with the subjective score since they fail to reflect the perceived quality. In this paper we propose a new objective metric to evaluate the visual quality between a mesh with a perfect quality called reference mesh and its dis…
Gauss maps on canal hypersurfaces of generic curves in R4
2021
Abstract We analyze the generic behavior of the Gauss map in a special case provided by the canal 3-manifolds of curves generically immersed in R 4 and obtain geometrical characterizations for its singularities. We also study the geometrical properties of their corresponding parabolic surfaces, considered as surfaces immersed in R 4 .
Quantitative lower bounds to the Euclidean and the Gaussian Cheeger constants
2020
We provide a quantitative lower bound to the Cheeger constant of a set $\Omega$ in both the Euclidean and the Gaussian settings in terms of suitable asymmetry indexes. We provide examples which show that these quantitative estimates are sharp.