147 research outputs found
A multi-sphere particle numerical model for non-invasive investigations of neuronal human brain activity
In this paper, a multi-sphere particle method is built-up in order to estimate the solution of the Poisson's equation with Neumann boundary conditions describing the neuronal human brain
activity. The partial differential equations governing the relationships
between neural current sources and the data produced by neuroimaging
technique, are able to compute the scalp potential and magnetic field
distributions generated by the neural activity. A numerical approach is proposed with current dipoles as current sources and going on in the
computation by avoiding the mesh construction. The current dipoles
are into an homogeneous spherical domain modeling the head and the
computational approach is extended to multilayered con¯guration with
different conductivities. A good agreement of the numerical results is
shown and, for the first time compared with the analytical ones
ANALISI DEL POSSIBILE IMPIEGO DI CAVI HVDC PER LO SMART STORAGE
L’idea alla base dell’attività di ricerca è quella di investigarela possibilità di utilizzare l’energia che,durante il normale servizio,è immagazzinata nei cavi dei sistemi di trasmissione ad alta tensione in corrente continua (HVDC), quando si verifichino scenari tecnico-economici favorevoli tali da giustificare,o per necessità o per scelta, la messa fuori servizio dei cavi stessi
An advanced variant of an interpolatory graphical display algorithm
In this paper an advanced interpolatory graphical display algorithm based on cardinal B-spline functions is provided. It is well-known that B-spline functions are a flexible tool to design various scale rapresentations of a signal. The proposed method allows to display without recursion a function at any desiderable resolution so that only initial data and opportune vectors weight are involved. In this way the structure of the algorithm is independent across the scale and a computational efficiency is reached. In this paper mono and bi-dimensional vectors weight generated by means of centered cubic cardinal B-spline functions have been supplied
A Meshfree Solver for the MEG Forward Problem
Noninvasive estimation of brain activity via magnetoencephalography (MEG) involves an inverse problem whose solution requires an accurate and fast forward solver. To this end, we propose the Method of Fundamental Solutions (MFS) as a meshfree alternative to the Boundary Element Method (BEM). The solution of the MEG forward problem is obtained, via the Method of Particular
Solutions (MPS), by numerically solving a boundary value problem for the electric scalar potential, derived from the quasi-stationary approximation of Maxwell’s equations. The magnetic field is then computed by the Biot-Savart law. Numerical experiments have been carried out in a realistic single-shell head geometry. The proposed solver is compared with a state-of-the-art BEM solver. A good agreement and a reduced computational load show the attractiveness of the meshfree approach
Viscoelasticity: an electrical point of view
Time dependent hereditary properties of complex materials are well described by power-laws with real order exponent. This experimental observation and analogous electrical experiments, yield a description of these properties by using fractional-order operators. In this paper, elasto-viscous and viscoelastic behaviors of fractional order hereditary materials are firstly described by using fractional mathematical operators,
based on recent work of some of the authors. Then, electrical analogous models are introduced. Viscoelastic models have elastic and viscous components which can be obtained by combining springs and dashpots: these models can be equivalently viewed
as electrical circuits, where the spring and dashpot are analogous to the capacitance and resistance, respectively. The proposed
models are validated by using modal analysis. The use of electrical analogous in viscoelasticity can better reveal the real behavior of fractional hereditary materials
Design and Performance Evaluation of a High Power-Density EMI Filter for PWM Inverter-Fed Induction-Motor Drives
This paper presents the design of an electromagnetic interference (EMI) filter for a low-voltage high-current induction-motor drives supplied by dc power grids. In order to effectively design the EMI filter, a suitable common-mode/differential-mode (CM/DM) separation technique has been used. Due to the high operating currents, the software-based separation technique using time-domain measurements has been applied. The proposed technique allows the CM and DM sections of the EMI filter to be properly selected in a more economical way, i.e., without the need of a dedicated hardware or costly radio frequency (RF) instrumentation. The design has been done according to a power-density criterion. The effectiveness of the proposed CM/DM separation technique and the EMI filter features/performance has been assessed by experimental tests, carried out with an 1.1-kW pulsewidth modulation (PWM) inverter-fed induction-motor drive, supplied by a 48-V dc power grid
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