1,721,057 research outputs found
A Wavelet Based Neural Network Procedure for the Field Reconstruction of NMR Main Magnet
No full textA novel procedure to identify and correct the field inhomogeneities in Nuclear Magnetic Resonance (NMR) devices is proposed. Instead of local field measurements, the procedure makes only use of the information supplied by the standard output (absorption spectrum) of the device to determine the correction field to be supplied to the magnet. The reconstruction of the actual field map starting from the spectrum is carried out by means of a Neural Network (NN) approach. The inputs of NN are, in turn, the moments of the spectrum or a pattern of features extracted by a wavelet pre-processor. The accuracy achieved in correcting the field is acceptable and the computational burden of the operation phases appears to be smaller with respect to other methods. The nature and shape of the wavelets are particularly suitable for treating the asborption spectra signal. The procedure promises to be a possible alternative tool to the frequently needed routine calibrations of the magnetic field in Nuclear Magnetic Resonance devices
Analysis of Absence Seizure Generation using EEG Spatial-temporal Regularity Measures
Full text linkEpileptic seizures are generated and evolve through an underlying anomaly of synchronization in the
activity of groups of neuronal populations. The related dynamic scenario of state transitions is revealed
by detecting changes in the dynamical properties of Electroencephalography (EEG) signals. The recruit-
ment procedure ending with the crisis can be analyzed by means of a spatial-temporal plot from which
to extract suitable descriptors that are able to monitor and quantify the evolving synchronization level
from the EEG tracings. In this paper, a spatial-temporal analysis of EEG synchronization based on the
concept of Permutation Entropy (PE) is proposed. The performance of PE are tested on a database of 24
patients affected by absence (generalized) seizures. The results achieved are compared to the dynamical
behavior of the EEG of 40 healthy subjects. Being PE a feature which is dependent on two-parameters,
an extensive study of the sensitivity of the performance of PE with respect to the parameters’ setting
was carried out on scalp EEG. Once the optimal PE configuration was determined, its ability to detect
the different brain states was evaluated. One relevant result of the study is that, in contrast to the widely
accepted interpretation of the transition to absence seizure as an abrupt change, within the limits of the
analyzed database, the “jump” transition to the epileptic status is heralded well before the seizure on-
set. Indeed, ever since the interictal stages, the frontal-temporal scalp areas appear constantly associated
to PE levels that are higher compared to the remaining electrodes, whereas the parieto-occipital areas
appear associated to lower-PE values. The EEG of healthy subjects does not show any similar dynamic
behavior nor exhibits any recurrent portrait in PE topography
Gap Estimation with Neural Network Models Iter Task on Diagnostics Design and R&D
No full textReport CREATE/ITER/DIAG/2001/1 (N 55 LR 1 01-05-07 W 0.1
Performance Improvement in Eddy Current Testing via Phase Information
No full textin Electromagnetic Nondestructive Evaluation (II), R. Albanese et al. (Eds.), IOS Pres
Experimental infrared measurements for hydrocarbon pollutant determination in subterranean waters
Full text linkSubterranean waters are often polluted by industrial and anthropic effluents that are drained in subsoil. To prevent and control pollution, legislations of different developed countries require an online monitoring measurement, especially for detecting organic solvents (chlorinated and unchlorinated ones). Online measurements include both real-time and no real-time measurements. In general, it is difficult to implement real-time measurements in stricto sensu for online acquisitions on aqueous effluents since they need to be processed by a modeling. This research presents an experimental measurement system based on infrared (IR) spectroscopy for aqueous effluents containing hydrocarbons and capable of displaying excellent values of pollutant concentrations even in instable conditions; the system is able to detect pollutants either in laminar or turbulent flow. The results show the possibility of avoiding the use of “Pitot tube” that is employed to create a stagnation point in order to convert kinetic energy into potential one. This conversion allows the transformation of a turbulent flow in a laminar flow making easy measurement of pollutants included in an aqueous effluent. Obviously, “Pitot tube” is also used for other fluid effluents. The obtained results have been compared with those produced by means of sophisticated IR instrumentation for laboratory applications.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
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