Search results for "Geometry"
showing 10 items of 4487 documents
Vortex dynamics in rotating counterflow and plane Couette and Poiseuille turbulence in superfluid Helium
2008
An equation previously proposed to describe the evolution of vortex line density in rotating counterflow turbulent tangles in superfluid helium is generalized to incorporate nonvanishing barycentric velocity and velocity gradients. Our generalization is compared with an analogous approach proposed by Lipniacki, and with experimental results by Swanson et al. in rotating counterflow, and it is used to evaluate the vortex density in plane Couette and Poiseuille flows of superfluid helium.
Weighted Hardy Spaces of Quasiconformal Mappings
2019
We establish a weighted version of the $H^p$-theory of quasiconformal mappings.
Generalized wave propagation problems and discrete exterior calculus
2018
We introduce a general class of second-order boundary value problems unifying application areas such as acoustics, electromagnetism, elastodynamics, quantum mechanics, and so on, into a single framework. This also enables us to solve wave propagation problems very efficiently with a single software system. The solution method precisely follows the conservation laws in finite-dimensional systems, whereas the constitutive relations are imposed approximately. We employ discrete exterior calculus for the spatial discretization, use natural crystal structures for three-dimensional meshing, and derive a “discrete Hodge” adapted to harmonic wave. The numerical experiments indicate that the cumulat…
Topological canal foliations
2019
Regular canal surfaces of $\mathbb{R}^3$ or $\mathbb{S}^3$ admit foliations by circles: the characteristic circles of the envelope. In order to build a foliation of $\mathbb{S}^3$ with leaves being canal surfaces, one has to relax the condition “canal” a little (“weak canal condition”) in order to accept isolated umbilics. Here, we define a topological condition which generalizes this “weak canal” condition imposed on leaves, and classify the foliations of compact orientable 3-manifolds we can obtain this way.
Influence of brand image of a sports event on the recommendation of its participants
2020
The aim of this research is to test the psychometric properties and relationships of a model where, from brand congruence of a sport event, trust and commitment to it can be generated, influencing future behavior of participants and resulting in a higher recommendation also called Word of Mouth (hereinafter WOM). A quantitative approach has been carried out by means of a validated questionnaire with Likert-type responses, and data were analyzed with the EQS 6.4 software. The findings indicated that the model is adequate, and also confirm that from congruence, we can explain, at a theoretical level, 45% of trust, and in the same way, from the congruence and trust, we can explain 67% of the c…
Introduction to Mathematical Logic, Edition 2021
2021
Textbook for students in mathematical logic. First order languages. Axioms of constructive and classical logic. Proving formulas in propositional and predicate logic. Glivenko's theorem and constructive embedding. Axiom independence. Interpretations, models and completeness theorems. Normal forms. Tableaux and resolution methods. Herbrand's theorem. Sections 1, 2, 3 represent an extended translation of the corresponding chapters of the book: V. Detlovs, Elements of Mathematical Logic, Riga, University of Latvia, 1964, 252 pp. (in Latvian).
Sur la réductibilité des graphes de contraintes géométriques
2017
La modélisation géométrique par contraintes dont les applications intéressent des communautés issues de divers domaines tels l'ingénierie mécanique, la conception assistée par ordinateur, le calcul symbolique ou la chimie moléculaire est maintenant intégré dans les outils standards de modélisation. Dans cette discipline une forme géométrique est spécifiée par les relations que doivent vérifier les composants de cette forme au lieu de spécifier explicitement ces composants. Le but de la résolution est de déduire la forme répondant à toutes ces contraintes. Diverses méthodes ont été proposées pour résoudre ce problème. Nous nous intéresserons spécifiquement aux méthodes dites graphiques ou ba…
Formation, Structural Characterization, and Calculated NMR Chemical Shifts of Selenium-Nitrogen Compounds from SeCl4 and ArNHLi (Ar = supermesityl, m…
2004
Supermesityl selenium diimide [Se{N(C6H2tBu3-2, 4, 6)}2; Se{N(mes*)}2] can be prepared in a good yield from the reaction of SeCl4 and (mes*)NHLi. The molecule adopts an unprecedented anti, anti-conformation, as deduced by DFT calculations at PBE0/TZVP level of theory and supported by 77Se NMR spectroscopy and a crystal structure determination. An analogous reaction involving (C6H2Me3-2, 4, 6)NHLi [(mes)NHLi] unexpectedly lead to the reduction of selenium and afforded the selenium diamide Se{NH(mes)}2 that was characterized by X-ray crystallography and 77Se NMR spectroscopy. The Se-N bonds of 1.847(3) and 1.852(3) A show normal single bond lengths. The <NSeN bond angle of 109.9(1)° also indi…
Who Can See My Stuff? : Online Self-Disclosure and Gender Differences on Facebook
2018
This study investigates the gendered privacy practices and concerns on Facebook, by leaning on the idea of privacy management as a form of digital labour. We analyse if young Facebook users are more concerned about the privacy against other users than against Facebook as a company or against third-party partners. We also analyse if privacy concerns and visibility rules are differentiated by gender. Using a structured online survey, we collected responses from a sample of 813 Italian university students (aged 18-34). Our results show that the respondents have just slightly more privacy concerns against other users than against Facebook, and much less against third-party partners. Unlike a ma…
Closure to "Assessing stage-discharge relationships for circular overflow structure" by M. Bijankhan and V. ferro
2018
The paper is a closure to a previous article.