A Splitting Algorithm for Medical Image Denoising

In this work we consider a stable algorithm for integrating a mathematical model based on mean curvature motion equation proposed in (Alvarez, Lions, Morel 1992) for image denoising. The scheme is constructed using a finite difference space discretisation and semi-implicit time discretisation and is considered with a splitting algorithm that can be implemented in parallel. We apply this algorithm to the problem of denoising optical coherence tomograms from the human retina while preserving image features

Convergence of an Explicit Iterative Leap-frog Discontinuous Galerkin Method for Time-domain Maxwell's Equations in Anisotropic Materials

We propose an explicit iterative leap-frog discontinuous Galerkin method for time-domain Maxwell's equations in anisotropic materials and derive its convergence properties. The a priori error estimates are illustrated by numerical means in some experiments. Motivated by a real application which encompasses modeling electromagnetic wave's propagation through the eye's structures, we simulate our model in a 2D domain aiming to represent a simple example of light scattering in the outer nuclear layer of the retina.Comment: 14 pages, 6 figure

Stability of finite difference schemes for complex diffusion processes

In this paper we present a rigorous proof for the stability of a class of finite difference schemes applied to nonlinear complex diffusion equations. Complex diffusion is a common and broadly used denoising procedure in image processing. To illustrate the theoretical results we present some numerical examples based on an explicit scheme applied to a nonlinear equation in the context of image denoising.FCT PTDC/SAU-ENB/111139/200

A hybrid numerical method for a two-dimensional second order hyperbolic equation

Second order hyperbolic differential equations have been used to model many problems that appear related to heat conduction, mass diffusion and fluid dynamics. In this work a numerical method is presented to solve a two dimensional second order hyperbolic equation with convection terms. A hybrid numerical method is considered which consists of applying the Laplace transform in time and a finite volume discretization in space, where the shape functions associated with the finite volume method are chosen as the combination of hyperbolic functions. We present some numerical tests to show the efficiency of the numerical method

Digital media artefacts: hybrid praxis

The special issue on Digital Media Artefacts, “Hybrid Praxis”, is a post-congress collective reflection about technology, science, and art. The invited authors participated in ARTeFACTo 2020 or ARTECH 2021; two key congresses were exploring state-of-the-art digital media arts. These encounters gather experiences from the academic world, practitioner world, and hybrid praxis, with art practice-based research as the common thread. If we reflect on contemporary technology, science, and art, we can see that technology is pushing more profound changes in sciences and arts than the other way around. Just take your eyes off the screen, look around you, and compare your daily life to what it was twenty or even ten years ago. Digital technology has profoundly changed your everyday life, relationships, possibilities, and how you express, explore, research, share, and do. We could therefore look exclusively into the digital domain to frame the relationship between the elements of this triad as it now stands.info:eu-repo/semantics/publishedVersio

Accessing Wireless Sensor Networks Via Dynamically Reconfigurable Interaction Models

The Wireless Sensor Networks (WSNs) technology is already perceived as fundamental for science across many domains, since it provides a low cost solution for environment monitoring. WSNs representation via the service concept and its inclusion in Web environments, e.g. through Web services, supports particularly their open/standard access and integration. Although such Web enabled WSNs simplify data access, network parameterization and aggregation, the existing interaction models and run-time adaptation mechanisms available to clients are still scarce. Nevertheless, applications increasingly demand richer and more flexible accesses besides the traditional client/server. For instance, applications may require a streaming model in order to avoid sequential data requests, or the asynchronous notification of subscribed data through the publish/subscriber. Moreover, the possibility to automatically switch between such models at runtime allows applications to define flexible context-based data acquisition. To this extent, this paper discusses the relevance of the session and pattern abstractions on the design of a middleware prototype providing richer and dynamically reconfigurable interaction models to Web enabled WSNs

Numerical solution for a non-Fickian diffusion in a periodic potential

Numerical solutions of a non-Fickian diffusion equation belonging to a hyperbolic type are presented in one space dimension. The Brownian particle modelled by this diffusion equation is subjected to a symmetric periodic potential whose spatial shape can be varied by a single parameter. We consider a numerical method which consists of applying Laplace transform in time; we then obtain an elliptic diffusion equation which is discretized using a finite difference method. We analyze some aspects of the convergence of the method. Numerical results for particle density, flux and mean-square-displacement (covering both inertial and diffusive regimes) are presented

Improved adaptive complex diffusion despeckling filter

Despeckling optical coherence tomograms from the human retina is a fundamental step to a better diagnosis or as a preprocessing stage for retinal layer segmentation. Both of these applications are particularly important in monitoring the progression of retinal disorders. In this study we propose a new formulation for a well-known nonlinear complex diffusion filter. A regularization factor is now made to be dependent on data, and the process itself is now an adaptive one. Experimental results making use of synthetic data show the good performance of the proposed formulation by achieving better quantitative results and increasing computation speed.Fundação para a Ciência e TecnologiaFEDERPrograma COMPET

Accessing wireless sensor networks via dynamically reconfigurable interaction models

The Wireless Sensor Networks (WSNs) technology is already perceived as fundamental for science across many domains, since it provides a low cost solution for environment monitoring. WSNs representation via the service concept and its inclusion in Web environments, e.g. through Web services, supports particularly their open/standard access and integration. Although such Web enabled WSNs simplify data access, network parameterization and aggregation, the existing interaction models and run-time adaptation mechanisms available to clients are still scarce. Nevertheless, applications increasingly demand richer and more flexible accesses besides the traditional client/server. For instance, applications may require a streaming model in order to avoid sequential data requests, or the asynchronous notification of subscribed data through the publish/subscriber. Moreover, the possibility to automatically switch between such models at runtime allows applications to define flexible context-based data acquisition. To this extent, this paper discusses the relevance of the session and pattern abstractions on the design of a middleware prototype providing richer and dynamically reconfigurable interaction models to Web enabled WSNs.publishersversionpublishe