introduction:  image  distortion  is  one  of  the  major  problems  of  magnetic  resonance  imaging  (mri) for use in 3dmri, velocity mri, fmri and radiotherapy treatment planning (rttp). it is  widely known that the most obvious effect of the inhomogenity of the magnetic fields and the  nonlinearity  of  the  gradient  is  the  geometric  distortion  of  mr  tomograms.  in  this  study,  the...

Previous studies have suggested that the accuracy of temperature measurements by surface-moored buoys may be affected by distortions of the near-surface temperature structure by the buoy hull on calm, sunny days. We obtained the first definite observational evidence that the temperature near the hull was not horizontally homogeneous at the same nominal depth. We observed large temperature diffe...

We present a framework for shape alignment that generalizes several existing methods for parametric registration. We assume that the shape is a closed genus zero surface. Our framework requires a diffeomorphic surface mapping to the 2-sphere which preserves rotation. The registration is based on maximizing spherical cross-correlation function of surface-intrinsic scalar attributes, weighted by ...

We present a novel approach to creating at maps of the brain. It is impossible to atten a curved surface in 3D space without metric and areal distortion; however, the Riemann Mapping Theorem implies that it is theoretically possible to preserve conformal (angular) information under attening. Our approach attempts to preserve the con-formal structure between the original cortical surface in 3-sp...

This article introduces a new method for surface parameterization for texture mapping. In the first step of the algorithm we compute a planar triangulation of the faceted surface, using an Angle Based Flattening (ABF) formulation. This provides a mapping function from a three-dimensional surface to the plane. The ABF formulation defines the flattening problem as a constrained minimization probl...

The use of attribute maps for 3D surfaces is an important issue in Geometric Modeling, Visualization and Simulation. Attribute maps describe various properties of a surface that are necessary in applications. In the case of visual properties, such as color, they are also called texture maps. Usually, the attribute representation exploits a parametrization g : U ⊂ R → R of a surface in order to ...

The projection on the base plane of a regular minimal surface S in R with isothermal parameters defines a complex-valued univalent harmonic function f = h(z) + g(z). The aim of this paper is to obtain the distortion inequalities for the Weierstrass-Enneper parameters of the minimal surface for the harmonic multivalent functions for which analytic part is an m-valent convex function. 2000 Mathem...

We prove that various subgroups of the mapping class group Mod(Σ) of a surface Σ are at least exponentially distorted. Examples include the Torelli group (answering a question of Hamenstädt), the “point-pushing” and surface braid subgroups, and the Lagrangian subgroup. Our techniques include a method to compute lower bounds on distortion via representation theory and an extension of Johnson the...