Search results for "equation"
showing 10 items of 4219 documents
Monotonicity and enclosure methods for the p-Laplace equation
2018
We show that the convex hull of a monotone perturbation of a homogeneous background conductivity in the $p$-conductivity equation is determined by knowledge of the nonlinear Dirichlet-Neumann operator. We give two independent proofs, one of which is based on the monotonicity method and the other on the enclosure method. Our results are constructive and require no jump or smoothness properties on the conductivity perturbation or its support.
A constructive theory of shape
2021
We formulate a theory of shape valid for objects of arbitrary dimension whose contours are path connected. We apply this theory to the design and modeling of viable trajectories of complex dynamical systems. Infinite families of qualitatively similar shapes are constructed giving as input a finite ordered set of characteristic points (landmarks) and the value of a continuous parameter $\kappa \in (0,\infty)$. We prove that all shapes belonging to the same family are located within the convex hull of the landmarks. The theory is constructive in the sense that it provides a systematic means to build a mathematical model for any shape taken from the physical world. We illustrate this with a va…
Enclosure method for the p-Laplace equation
2014
We study the enclosure method for the p-Calder\'on problem, which is a nonlinear generalization of the inverse conductivity problem due to Calder\'on that involves the p-Laplace equation. The method allows one to reconstruct the convex hull of an inclusion in the nonlinear model by using exponentially growing solutions introduced by Wolff. We justify this method for the penetrable obstacle case, where the inclusion is modelled as a jump in the conductivity. The result is based on a monotonicity inequality and the properties of the Wolff solutions.
Convexities and optimal transport problems on the Wiener space
2013
The aim of this PhD is to study the optimal transportation theory in some abstract Wiener space. You can find the results in four main parts and they are aboutThe convexity of the relative entropy. We will extend the well known results in finite dimension to the Wiener space, endowed with the uniform norm. To be precise the relative entropy is (at least weakly) geodesically 1-convex in the sense of the optimal transportation in the Wiener space.The measures with logarithmic concave density. The first important result consists in showing that the Harnack inequality holds for the semi-group induced by such a measure in the Wiener space. The second one provides us a finite dimensional and dime…
A parametric analysis of the transient behavior of lightning protection systems
2005
The paper have the purpose of investigate the influence of different parameters to enable better understanding of the transient performance of complex lightning protection systems (LPS). Lightning discharges constitute the major source of atmospheric or natural noise that can interfere with electric and electronic installations. The electromagnetic characterisation of the LPS environment plays a fundamental role in order to prevent unwanted coupling phenomena that may generate abnormal signals, electric stresses dangerous for the insulation of electric components, disruptive discharges and danger to persons. The model, developed by the authors, is based on a field-approach: the numerical so…
Innovation in services through learning in a joint venture
2011
Innovation determines a firm's competitiveness and survival and a joint venture is a fast and effective way to acquire the missing knowledge that partners require to innovate, but ‘knowing how to cooperate’ can be a determining factor in achieving the successful transfer of knowledge. Employing a sample of 81 service-sector firms and using a structural equation modeling methodology, we found a positive and direct impact between the cooperative learning process and partners' commitment to innovation.
Coping and Life Satisfaction in Colombian Older Adults
2021
Background. Effective coping strategies facilitate older adults’ optimal adaptation and contribute to their well-being. Problem-focused strategies are associated with active styles and enhance well-being. This study analyzes the role of coping strategies in Colombian older adults’ subjective well-being (SWB) using structural equation modelling. Additionally, Confirmatory Factor Analyses of the Life Satisfaction Scale and Coping Strategies Questionnaires are performed. Method. A cross-sectional study is conducted with 455 Colombian older adults, ranging from 65 to 92 years old. Results. The results show that problem-focused coping has a positive effect on SWB, whereas emotion-focused coping …
Predicting Well-Being Among the Elderly: The Role of Coping Strategies
2020
Objectives: This study aims to give a wider view on the role of coping strategies on elderly’s well-being, by means of literature-based competitive structural equation models (SEM). Methods: 857 older adults were surveyed with Ryff’s scales of Psychological Well-being and the Coping Strategies Questionnaire. Competitive full SEMs were tested. Results: The best fitting model was the one in which the religious coping dimension was removed, leaving the remaining dimensions defined by problem- and emotion-focused coping, which explained both psychological and subjective well-being factors (χ2(46)=165.910, p<.001; CFI=.906; GFI=.957; RMSEA=.058 [.048, .067]). Discussion: Results pointed the rele…
Different drinking motives, different adverse consequences? Evidence among adolescents from 10 European countries
2017
INTRODUCTION AND AIM: This study, which builds on previous research demonstrating that drinking motives are associated with adverse consequences, investigates the associations between drinking motives and non-alcohol-attributed adverse consequences and disentangles alcohol-related and direct effects. DESIGN AND METHOD: On the basis of a sample of 22 841 alcohol-using 13- to 16-year-olds (50.6% female) from Belgium, Denmark, Estonia, Finland, Ireland, Portugal, Scotland, Slovakia, Switzerland and Wales, structural equation models were used to estimate direct and indirect effects. Additionally, differences across countries were tested in a multigroup analysis. RESULTS: The indirect effect (vi…
Individual, co-active and collective coping and organizational stress: A longitudinal study
2019
This study aims to identify the association between changes in three types of problem-focused coping (individual, organizational co-active and collective) and the change in the appraisal of different facets of employees' stress and the organizational stress climate. These relationships are tested by means of Bayesian Multilevel Structural Equation Modeling and a two-wave panel design. The sample is composed of 525 teachers in 100 schools. Stress experiences and coping behaviors are assessed during the first and third terms of the academic year. The results show that an increase in the use of individual problem-focused coping has little to no effect on the decrease in individual stress appra…