Search results for "problems"
showing 10 items of 620 documents
Partial data inverse problems for Maxwell equations via Carleman estimates
2015
In this article we consider an inverse boundary value problem for the time-harmonic Maxwell equations. We show that the electromagnetic material parameters are determined by boundary measurements where part of the boundary data is measured on a possibly very small set. This is an extension of earlier scalar results of Bukhgeim-Uhlmann and Kenig-Sj\"ostrand-Uhlmann to the Maxwell system. The main contribution is to show that the Carleman estimate approach to scalar partial data inverse problems introduced in those works can be carried over to the Maxwell system.
On the semiclassical limit of the defocusing Davey-Stewartson II equation
2018
Inverse scattering is the most powerful tool in theory of integrable systems. Starting in the late sixties resounding great progress was made in (1+1) dimensional problems with many break-through results as on soliton interactions. Naturally the attention in recent years turns towards higher dimensional problems as the Davey-Stewartson equations, an integrable generalisation of the (1+1)-dimensionalcubic nonlinear Schrödinger equation. The defocusing Davey-Stewartson II equation, in its semi-classical limit has been shown in numerical experiments to exhibit behavior that qualitatively resembles that of its one-dimensional reduction, namely the generation of a dispersive shock wave: smooth i…
Advanced techniques for solving groundwater and surface water problems in the context of inverse methods and climate change.
2021
[ES] El tema de la investigación se centra en técnicas avanzadas para manejar problemas de aguas subterráneas y superficiales relacionados con métodos inversos y cambio climático. Los filtros de Kalman, con especial atención en Ensemble Smoother with Multiple Data Assimilation (ES-MDA), se analizan y mejoran para la solución de diferentes tipos de problemas inversos. En particular, la principal novedad es la aplicación de estos métodos para la identificación de series temporales. La primera parte de la tesis, luego de la descripción del método, presenta el desarrollo de un software escrito en Python para la aplicación de la metodología propuesta. El software cuenta con un flujo de trabajo f…
Characterizations of {K,s+1}-Potent Matrices and Applications
2012
Recently, situations where a matrix coincides with some of its powers have been studied. This kind of matrices is related to the generalized inverse matrices. On the other hand, it is possible to introduce another class of matrices that involve an involutory matrix, generalizing the well-known idempotent matrix, widely useful in many applications. In this paper, we introduce a new kind of matrices called {K,s+1}-potent, as an extension of the aforementioned ones. First, different properties of {K,s+1}-potent matrices have been developed. Later, the main result developed in this paper is the characterization of this kind of matrices from a spectral point of view, in terms of powers of the ma…
Learning, regularization and ill-posed inverse problems
2005
Many works have shown that strong connections relate learning from examples to regularization techniques for ill-posed inverse problems. Nevertheless by now there was no formal evidence neither that learning from examples could be seen as an inverse problem nor that theoretical results in learning theory could be independently derived using tools from regularization theory. In this paper we provide a positive answer to both questions. Indeed, considering the square loss, we translate the learning problem in the language of regularization theory and show that consistency results and optimal regularization parameter choice can be derived by the discretization of the corresponding inverse prob…
Learning from examples as an inverse problem
2005
Many works related learning from examples to regularization techniques for inverse problems, emphasizing the strong algorithmic and conceptual analogy of certain learning algorithms with regularization algorithms. In particular it is well known that regularization schemes such as Tikhonov regularization can be effectively used in the context of learning and are closely related to algorithms such as support vector machines. Nevertheless the connection with inverse problem was considered only for the discrete (finite sample) problem and the probabilistic aspects of learning from examples were not taken into account. In this paper we provide a natural extension of such analysis to the continuo…
Numerical modelling of electromagnetic sources by integral formulation
2012
Analysis of electromagnetic (EM) transients can be carried out by employing a eld approach in frequency domain, based on an appropriate integral equation. This approach is a powerful method for the analysis of EM antennas and scatterers. Recent work by the authors in modeling electromagnetic scattering in frequency domain are summarized. Thin-wire electric eld integral equation has been handled and possible application in obtaining sources localization information are discussed. Moments method (MoM) is used and time domain analysis is also carried out by discrete Fourier transform. Di erent approaches have been considered by using direct MoM formulation. Simulation results obtained both via…
Linearized Calderón problem and exponentially accurate quasimodes for analytic manifolds
2022
In this article we study the linearized anisotropic Calderon problem on a compact Riemannian manifold with boundary. This problem amounts to showing that products of pairs of harmonic functions of the manifold form a complete set. We assume that the manifold is transversally anisotropic and that the transversal manifold is real analytic and satisfies a geometric condition related to the geometry of pairs of intersecting geodesics. In this case, we solve the linearized anisotropic Calderon problem. The geometric condition does not involve the injectivity of the geodesic X-ray transform. Crucial ingredients in the proof of our result are the construction of Gaussian beam quasimodes on the tra…
History, Processing and Quality Enhancement of Traditional Egyptian Kariesh Cheese: A Review
2013
Kariesh is a soft acid cheese made from skimmed cow's milk, buffalo milk or buttermilk from sour cream; apparently it is made only on farmsteads. It is considered to be one of the most important traditional Egyptian dairy products, commonly made in the Egyptian countryside, especially in small villages, as low-income people such as farmers use Kariesh cheese in their diet owing to its high protein content, low fat and price. Therefore, nowadays, Kariesh cheese is a promising food in the avoidance of health problems associated with fat, particularly for old people. The aim of this article is to provide a wide range of information on Egyptian Kariesh cheese starting with a brief description o…
Virtual Enterprise Simulation Game as an Environment for Collaborative Creativity and Learning
2021
AbstractWhen employees become accustomed to everyday working habits it can prevent them from generating creative ideas. This familiarity takes the forms of mainly collaborating with familiar colleagues, playing roles that develop over years, and solving encountered problems with proven strategies. This chapter considers how a virtual enterprise simulation game (RealGame) can potentially foster digital creativity and collaborative learning. The game simulates a situation where team members take responsibility for managing a virtual manufacturing company and its supply chain. Theoretically, we consider RealGame a facilitating environment for people to collaborate by offering a safe environmen…