Search results for "shape"
showing 10 items of 585 documents
Deformation
2020
In the continuous model of a solid object, which is ideally considered composed of such material points that each one of them is surrounded by a dense neighbourhood fully occupied by other points, the deformation is a variation carried out by a transformation, which does not preserve isometry. Deformations differ from displacements caused by rigid motions. For a closed boundary curve in the three-dimensional space, Plateau wondered what surfaces would minimize the potential surface energy. Deformation was held to underlie the evolution of biological forms, described by the “Cartesian transformations”, or the interpolation function of landmarks covariation over a thin-plate spline, the perce…
Form constancy
2020
Form constancy denotes the appearance of the invariant shape of objects in the environment, notwithstanding the variability due to changes of the viewpoint, caused by subjects movement, to objects displacement, to illumination, lightness, color, and texture whose variation can affect the internal and external boundaries of the surfaces that fall in the simultaneous or successive views of solid objects. In early psychology of perception, shape invariance was called form constancy to highlight the perceptual ability to derive something constant from the changing forms of the multiple views of objects. Shape is an attribute of 2D surfaces and 3D objects, which are invariant across the transfor…
Shape
2020
In geometry, shape is the object of theorems associated to a class of transformations. It corresponds to the invariant properties of regions, figures, solids, which are not altered by transformations. The concept of shape implies the concepts of space, upon which transformations are acted, and metric, if distance is preserved, or a measurement function. The invariant properties of shape are fundamental to perception too. However, the classes of transformations build a hierarchy along which shape is more and more abstract from the Euclidean to the topological group, and accordingly, a greater number of perceptual properties are being lost. The science of perception addresses also the questio…
FDA dimension reduction techniques and components separation in Fourier-transform infrared spectroscopy
2020
FTIR spectroscopy is a measurement technique used to obtain an infrared spectrum of absorption of a solid (or a liquid or a gas), for the characterization of specific chemical components of materials. When repeated measures are taken on samples of materials, the result is a collection of spectra representing a set of samples from continous functions (signals) defined in the domain of the frequencies. An unifying approach to the study of a collection of FTIR spectra is proposed to deal with the presence of random shifts in the peaks, the identification of representative spectra and finally the characterization of the observed differences: in the functional data framework, the performance of …
Segmentation automatique et analyse de forme d'hippocampes humains dans l'étude de la maladie d'Alzheimer
2011
The aim of this thesis is to investigate the shape change in hippocampus due to the atrophy in Alzheimer’s disease (AD). To this end, specific algorithms and methodologies were developed to segment the hippocampus from structural magnetic resonance (MR) images and model variations in its shape. We use a multi-atlas based segmentation propagation approach for the segmentation of hippocampus which has been shown to obtain accurate parcellation of brain structures. We developed a supervised method to build a population specific atlas database, by propagating the parcellations from a smaller generic atlas database. Well segmented images are inspected and added to the set of atlases, such that t…
Inverse procedural modeling of 3D models for virtual worlds
2016
This course presents a collection of state-of-the-art approaches for modeling and editing of 3D models for virtual worlds, simulations, and entertainment, in addition to real-world applications. The first contribution of this course is a coherent review of inverse procedural modeling (IPM) (i.e., proceduralization of provided 3D content). We describe different formulations of the problem as well as solutions based on those formulations. We show that although the IPM framework seems under-constrained, the state-of-the-art solutions actually use simple analogies to convert the problem into a set of fundamental computer science problems, which are then solved by corresponding algorithms or opt…
On the Methods for Optimal Shape Design
1990
A short survey of the numerical methods for solving optimal shape design problems is given.
Hydrodynamic Analysis of Floating Docks With Alternative Geometries for Floating Wind Turbine Installation
2021
Abstract Installation of spar floating wind turbine offshore is a challenging task. Usually, the spar platform is upended first, and mating of the tower assembly with the spar platform is assisted by a crane vessel. Due to motions of the spar platforms and of the crane vessel, such an operation often takes place in shielded areas with relatively small wave heights and wind speed. The floating dock concept has been recently proposed to expand the weather window for installing spar floating wind turbines. The idea is to use a cylindrical dock to shield the spar platform from wave excitations. However, because of the trapped internal fluid, the cylindrical geometry is subjected to piston mode …
Automatic differentiation of melanoma from dysplastic nevi.
2015
International audience; Malignant melanoma causes the majority of deaths related to skin cancer. Nevertheless, it is the most treatable one, depending on its early diagnosis. The early prognosis is a challenging task for both clinicians and dermatologist, due to the characteristic similarities of melanoma with other skin lesions such as dysplastic nevi. In the past decades, several computerized lesion analysis algorithms have been proposed by the research community for detection of melanoma. These algorithms mostly focus on differentiating melanoma from benign lesions and few have considered the case of melanoma against dysplastic nevi. In this paper, we consider the most challenging task a…