Search results for "simulation"

Coupling BEM and VEM for the Analysis of Composite Materials with Damage

2021

Numerical tools which are able to predict and explain the initiation and propagation of damage at the microscopic level in heterogeneous materials are of high interest for the analysis and design of modern materials. In this contribution, we report the application of a recently developed numerical scheme based on the coupling between the Virtual Element Method (VEM) and the Boundary Element Method (BEM) within the framework of continuum damage mechanics (CDM) to analyze the progressive loss of material integrity in heterogeneous materials with complex microstructures. VEM is a novel numerical technique that, allowing the use of general polygonal mesh elements, assures conspicuous simplific…

Stress gradient versus strain gradient constitutive models within elasticity

2014

Abstract A stress gradient elasticity theory is developed which is based on the Eringen method to address nonlocal elasticity by means of differential equations. By suitable thermodynamics arguments (involving the free enthalpy instead of the free internal energy), the restrictions on the related constitutive equations are determined, which include the well-known Eringen stress gradient constitutive equations, as well as the associated (so far uncertain) boundary conditions. The proposed theory exhibits complementary characters with respect to the analogous strain gradient elasticity theory. The associated boundary-value problem is shown to admit a unique solution characterized by a Helling…

Special Splines of Exponential Type for the Solutions of Mass Transfer Problems in Multilayer Domains

2016

We consider averaging methods for solving the 3-D boundary-value problem of second order in multilayer domain. The special hyperbolic and exponential type splines, with middle integral values of piece-wise smooth function interpolation are considered. With the help of these splines the problems of mathematical physics in 3-D with piece-wise coefficients are reduced with respect to one coordinate to 2-D problems. This procedure also allows to reduce the 2-D problems to 1-D problems and the solution of the approximated problemsa can be obtained analytically. In the case of constant piece-wise coefficients we obtain the exact discrete approximation of a steady-state 1-D boundary-value problem.…

A COLLABORATIVE VIRTUAL REALITY ENVIRONMENT FOR NEUROSURGICAL PLANNING AND TRAINING

2007

OBJECTIVE We have developed a highly interactive virtual environment that enables collaborative examination of stereoscopic three-dimensional (3-D) medical imaging data for planning, discussing, or teaching neurosurgical approaches and strategies. MATERIALS AND METHODS The system consists of an interactive console with which the user manipulates 3-D data using hand-held and tracked devices within a 3-D virtual workspace and a stereoscopic projection system. The projection system displays the 3-D data on a large screen while the user is working with it. This setup allows users to interact intuitively with complex 3-D data while sharing this information with a larger audience. RESULTS We have…

Functional connectivity inference from fMRI data using multivariate information measures

2022

Abstract Shannon’s entropy or an extension of Shannon’s entropy can be used to quantify information transmission between or among variables. Mutual information is the pair-wise information that captures nonlinear relationships between variables. It is more robust than linear correlation methods. Beyond mutual information, two generalizations are defined for multivariate distributions: interaction information or co-information and total correlation or multi-mutual information. In comparison to mutual information, interaction information and total correlation are underutilized and poorly studied in applied neuroscience research. Quantifying information flow between brain regions is not explic…

Influence of the scalp thickness on the intracranial contribution to rheoencephalography

2004

In spite of the great efforts made by the scientific community, up to now there is no agreement about the rheoencephalography (REG) capability to reflect cerebral blood flow (CBF). Moreover, a standard procedure and the optimal electrode arrangement have not been established yet. In a previous study, we found, using a classical four-shell spherical model of the head and solving it by numerical methods that, theoretically, there could exist an electrode arrangement to register an REG II free of extracranial contribution. In this paper, we have studied the influence of scalp thickness on the intracranial contribution to REG II. The study has been performed by solving the head model, using in …

Evidence for long-lived, optically generated quenchers of excitons in single-walled carbon nanotubes.

2011

The nonlinear dependence of near-infrared photoluminescence (PL) emission on excitation intensity has been measured for individual nanotubes representing six different (n,m) species. Significant deviations from linearity are observed for intensities as low as ~100 W/cm(2), and an approximate inverse correlation is found between nonlinearity and PL action cross section (brightness). A model in which all PL nonlinearity arises from exciton-exciton annihilation is insufficient to account for the experimental data using realistic parameters. It is proposed that additional nonlinear quenching arises from photoinduced quenching states or species with longer lifetimes than emissive excitons. Evide…

Automotive Brushless Motor Powered by Fuel Cell

2014

The Role of Local Administrations in the Energy Retrofit of Public Buildings: a Case Study

2022

Recent regulations, and related incentives, concerning urban sustainability issued at European and national level place particular attention on improving the energy and environmental performance of buildings. In this sense, a particular focus has been placed on public buildings (offices, schools, hospitals, etc..), being these centers of gravitation of social life. Among the EU strategies on this matter is an initiative called Sustainable Energy and Climate Action Plan (SECAP), through which local administrators, based on the knowledge of their territory, are called to establish appropriate energy strategies and commit to achieving their targets within the timeframe set by the EU. The prese…

The European Standards for Energy Efficiency in Buildings: an analysis of the Evolution with Reference to a Case Study

2019

The improvement of the energy efficiency of building stocks represents an important contribution for the reduction of the energy consumption in the European Union (EU), along with the decrease of greenhouse gases emissions. In this aim both the public administrations and the technical experts need reliable calculation methodology to assess buildings’ energy performance. In this framework, despite the recent publication of the Standard EN ISO 52016, that deeply modifies the approach to the energy building simulation by introducing a new hourly dynamic calculation model, the current normative framework (EN ISO 13790) will maintain its validity until the incorporation of the new Standard in th…