Publications related to Spherical geometry

Well-posedness Issues For the Half-Wave Maps Equation With Hyperbolic And Spherical Targets

This thesis is a study of the global well-posedness of the Cauchy problems for half-wave maps from the Minkowski space of dimension n+1 to the 2-dimensional sphere and the hyperbolic plane. The work is mainly based on the results from Krieger-Sire 17' in ...

EPFL2023

On the Maximum Power Density of Implanted Antennas within Simplified Body Phantoms

Anja Skrivervik, Mingxiang Gao, Zvonimir Sipus

With the application requirements of wireless technology in implantable bioelectronics, knowledge of the fundamental limits for implanted antennas becomes critical. In this work, we investigated the variation of maximum power density within simplified body ...

IEEE2022

Realizing doubles: a conjugation zoo

Jérôme Scherer

Conjugation spaces are topological spaces equipped with an involution such that their fixed points have the same mod 2 cohomology (as a graded vector space, a ring and even an unstable algebra) but with all degrees divided by two, generalizing the classica ...

CAMBRIDGE UNIV PRESS2021

Building a Casimir metrology platform with a commercial MEMS sensor

Matthias Imboden

The Casimir Effect is a physical manifestation of quantum fluctuations of the electromagnetic vacuum. When two metal plates are placed close together, typically much less than a micron, the long wavelength modes between them are frozen out, giving rise to ...

Springer2019

A Weak Form Implementation of Nonlinear Axisymmetric Shell Equations With Examples

Pedro Miguel Nunes Pereira de Almeida Reis, Matteo Pezzulla

We present a weak form implementation of the nonlinear axisymmetric shell equations. This implementation is suitable to study the nonlinear deformations of axisymmetric shells, with the capability of considering a general mid-surface shape, non-homogeneous ...

2019

Spherical Clustering of Users Navigating 360° Content

Pascal Frossard, Francesca De Simone, Laura Toni

In Virtual Reality (VR) applications, understanding how users explore the omnidirectional content is important to optimize content creation, to develop user-centric services, or even to detect disorders in medical applications. Clustering users based on th ...

IEEE2019

Specification of aspherical surfaces used as refractive elements in micro-optical systems

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

The optical performance of refractive plano-convex microlenses is mainly related to the quality of their (a)spherical surface. An efficient tolerancing of this surface is a key step towards the manufacturing of high quality microlenses. However, we demonst ...

SPIE-INT SOC OPTICAL ENGINEERING2019

Geometry Aware Convolutional Filters for Omnidirectional Images Representation

Pascal Frossard, Renata Khasanova

Due to their wide field of view, omnidirectional cameras are frequently used by autonomous vehicles, drones and robots for navigation and other computer vision tasks. The images captured by such cameras, are often analyzed and classified with techniques de ...

2019

Graph-Based Detection of Seams In 360-Degree Images

Pascal Frossard, Francesca De Simone, Sohyeong Kim, Roberto Gerson De Albuquerque Azevedo

In this paper, we propose an algorithm to detect a specific kind of distortions, referred to as seams, which commonly occur when a 360-degree image is represented in planar domain by projecting the sphere to a polyhedron, e.g, via the Cube Map (CM) project ...

2019

Rayleigh-Taylor instability under a spherical substrate

Gioele Mariano Nicolò Balestra, François Gallaire, David Minh-Phuc Nguyen

We investigate the Rayleigh-Taylor instability of a thin viscous film coating the inside of a spherical substrate. The aim of this work is to find and characterize the instability pattern in this spherical geometry. In contrast to the Rayleigh-Taylor insta ...

2018

Rate Distortion Optimized Graph Partitioning for Omnidirectional Image Coding

Pascal Frossard, Francesca De Simone, Thomas Maugey, Mira Rizkallah

Omnidirectional images are spherical signals captured by cameras with 360-degree field of view. In order to be compressed using existing encoders, these signals are mapped to planar domain. A commonly used planar representation is the equirectangular one, ...

IEEE COMPUTER SOC2018

Improved calibration of vertical scanning optical profilometers for spherical profiles measurements

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

A new method for calibrating optical scanning profilometers is presented. Especially adapted to spherical and aspherical profile measurements, it shows an increase of accuracy bigger than one order of magnitude for radius of curvature measurements. Calibra ...

2018

Deformable block based motion estimation in omnidirectional image sequences

Pascal Frossard, Francesca De Simone

This paper presents an extension of block-based motion estimation for omnidirectional videos, based on a camera and translational object motion model that accounts for the spherical geometry of the imaging system. We use this model to design a new algorith ...

2017

Effect of geometry modifications on the engulfment in micromixers: Numerical simulations and stability analysis

Andrea Fani, Lorenzo Siconolfi

The effect of geometry variations on the engulfment regime in micromixers is investigated. The engulfment regime is a steady flow regime resulting from a symmetry-breaking pitchfork bifurcation as the Reynolds number (based on the hydraulic diameter and bu ...

Elsevier2016

An advanced methodology for the mix design optimization of hot mix asphalt

André-Gilles Dumont, Sara Bressi, Manfred Partl

The bitumen quantity to add to asphalt mixtures depends on the surfaces of aggregates and filler to be coated. The formulas currently available in the literature have limitations such as considering all the fillers with the same specific surface or the agg ...

Elsevier Sci Ltd2016

3D galaxy clustering with future wide-field surveys: Advantages of a spherical Fourier-Bessel analysis

Anaïs Marie Rassat

Context. Upcoming spectroscopic galaxy surveys are extremely promising to help in addressing the major challenges of cosmology, in particular in understanding the nature of the dark universe. The strength of these surveys, naturally described in spherical ...

EDP Sciences2015

Reconfigurable Forward Homography Estimation System for Real-Time Applications

Yusuf Leblebici, Vladan Popovic

Image processing and computer vision algorithms extensively use projections, such as homography, as one of the processing steps. Systems for homography calculation usually observe homography as an inverse problem and provide an exact solution. However, the ...

2014

Light confinement effect of non-spherical nanoscale solid immersion lenses

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim, Gaël David Osowiecki, David Nguyen

We report on the light confinement effect observed in non-ideally shaped (i.e., non-spherical) nanoscale solid immersion lenses (SILs). To investigate this effect, nanostructures of various shapes are fabricated by electron-beam lithography. When completel ...

Spie-Int Soc Optical Engineering2013

Real-time Implementation of Gaussian Image Blending in a Spherical Light Field Camera

Alexandre Schmid, Yusuf Leblebici, Vladan Popovic, Hossein Afshari

Panoptic is a custom spherical light field camera used as a polydioptric system where imagers are distributed over a spherical geometry, each having its own vision of the surrounding and a distinct focal plane. The spherical light field camera records ligh ...

Ieee2013

Image Blending in a High Frame Rate FPGA-based Multi-Camera System

Alexandre Schmid, Yusuf Leblebici, Vladan Popovic, Hossein Afshari, Abdulkadir Akin, Kerem Seyid, Ömer Cogal

Panoptic is a custom spherical light field camera used as a polydioptric system where imagers are distributed over a hemispherical surface, each having its own vision of the surroundings and a distinct focal plane. The spherical light field camera records ...

2013