1,721,184 research outputs found
A study on the Influences of the Absorbing Boundary Conditions on the FDTD Modelling of Bioelectromagnetic Problems
No full textLille, Franc
Simulation of Cellular Phone Antennas by Using Inductive Lumped Elements in the 3D/FDTD Algorithm
No full textIn this paper a model of a cellular phone equipped with the whip antenna is presented. The model, developed with reference to the Finite-Difference Time-Domain method, is validated by comparing the H-field emitted from the phone with experimental data
Interaction between 3-T MRI systems and patients with an implanted pacemaker
No full textIn this paper, a transverse electro-magnetic
(TEM) coil operating at 128 MHz in a 3-T magnetic
resonance imaging system has been studied in terms of
the interaction with patients with or without an
implanted pacemaker. The pacemaker has been
simulated as a copper box with a catheter constituted by
an insulated copper wire with an uncapped tip and it has
been placed inside either box or anatomical models of
the thorax. Electromagnetic and thermal simulations
have been performed by using finite difference time
domain codes. The obtained results show that in the
absence of the pacemaker, and for a radiated power
producing in the box a whole body specific absorption
rate (SAR) of 1 W/kg, that is a typical value for MRI
examinations, the coil produces in the anatomical
models peak temperature values lower than the limits
issued by the International Electrotechnical
Commission (IEC). In the presence of the pacemaker,
temperature increments at the catheter tip in excess of
those issued by the IEC standard are obtained when the
MRI scanned area involves the pacemaker region. The
3-T coil produces lower SAR and temperature
increments with respect to a 64-MHz (1.5-T system)
birdcage antenna in patients with implanted pacemaker
A Method for Stability Analysis of Small-Signal Microwave Amplifiers
No full textThis paper presents a method for analyzing the stability of small-signal microwave amplifiers with any topology. This analysis is performed using the Nyquist criterion and allows detection of the so-called odd-mode instabilities. The method is easily applicable by using commercially available microwave CAD
Comparisons among EIT data collection techniques and reconstruction algorithms
No full textElectrical Impedance Tomography (EIT) is an imaging technique that aims to reconstruct the spatial electrical conductivity distribution in sections of the human body. In this paper, in order to solve the EIT forward and inverse problems, a finite difference approach to the solution of Maxwell’s equations and the Newton-Raphson algorithm have been employed, respectively. In particular, the inverse problem has been solved using the Tikhonov regularization with various choices of the regularization matrix. Moreover, different data collection methods have been tested on simulated measurements. The obtained results have been compared based on the average deviation of the estimated conductivity distribution with respect to the reference one. The reconstruction procedure has been validated through a comparison with the EIDORS open source software. The best image reconstruction has been obtained by using the neighboring data collection method with null regularization matrix, and using the truncated singular value decomposition to perform the matrix inversion. Moreover, the cross and opposite data collection methods showed better performance than the neighboring one in the presence of a random noise added to the measured signal, while the opposite method evidenced the best results with respect to electrode positioning uncertainties
SAR Distribution in the Human Head for People Using Wireless Communication Instruments in Closed Environments
No full textLille, Franc
Un modello accurato per lo studio dell'assorbimento di potenza indotto nella testa di un individuo esposto ad un telefono cellulare portatile
No full textUn modello teorico stocastico per lo studio cinetico dei canali proteinici di membrana esposti a campi elettromagnetici
No full textEvaluation of the SAR distribution in the human head for cellular phones used in a partially closed environment
No full textThe purpose of this paper is to calculate the specific absorption rate (SAR) distribution in a human head exposed to the electromagnetic field emitted from a handheld cellular phone operating in the 900 MHz range in a partially closed environment. The environment could be, for example, the interior of a car, a condition of exposure which is largely diffused nowadays. The presence of reflecting surfaces near the phone modifies the current distribution on, and the emitting properties of, the phone antenna. Therefore, the distribution of the absorbed power inside the head is different from that absorbed in the free space exposure condition. The finite-difference time-domain (FDTD) method has been used to evaluate the SAR in a realistic anatomically based model of the human head for different antenna-handset configurations and for different antenna-head distances. The environmental effects have been simulated through partially or totally reflecting walls located in various positions with reference to the phone. It is found that the presence of a horizontal reflecting wall over the head decreases the SAR values in the part of the head directly exposed to the phone antenna, while it increases the SAR values in the part not directly exposed. On the contrary, the presence of a vertical wall, located in proximity of the phone and parallel to it, raises the SAR values everywhere into the hea
A Stochastic Model for the analysis of Ionic Channels Gating under Electromagnetic Exposure
No full text- …
