Search results for "FREQUENCY"
showing 10 items of 2158 documents
The effects of monetary policy on income and wealth inequality in the U.S. Exploring different channels
2020
We assess the effects of monetary policy shocks on income and wealth inequality through direct inequality measures and by analyzing several transmission channels explored in recent literature. Furthermore, we analyze two additional channels: the Housing and the Fiscal channels. The methodology adopted is a Bayesian proxy SVAR using a high-frequency identification based on the external instruments approach. Our own policy shocks are constructed for this purpose. The results show that an expansionary monetary policy shock does not have a significant effect on income inequality due to the existence of opposite channels, whereas it increases wealth inequality mainly through the portfolio channe…
Optimising the efficiency of olive harvesting considering operator safety
2019
Mechanical-assisted harvesting of olives, which is carried out using hand-held harvesting units that detach the drupes through vibration supplied by electric motor or combustion engines, is a widespread method used in southern Italy. Such machines are able to harvest more than 80% of the overall quantity of olives available per tree in 5–10 min, but their performance is influenced by several factors related to the mechanical characteristics of the device and to the features of the trees. Here the problem of optimising harvesting efficiency whilst minimising the health risks to the operators is investigated, with the aim of demonstrating that it is possible to determine an optimum harvesting…
CNN based Gearbox Fault Diagnosis and Interpretation of Learning Features
2021
Machine learning based fault diagnosis schemes have been intensively proposed to deal with faults diagnosis of rotating machineries such as gearboxes, bearings, and electric motors. However, most of the machine learning algorithms used in fault diagnosis are pattern recognition tools, which can classify given data into two or more classes. The underlined physical phenomena in fault diagnosis are not directly interpretable in machine learning schemes, thus it is usually called black/gray box models. In this study, convolutional neural networks (CNN) machine learning algorithm is proposed to classify gearbox faults, and the learning features of the CNN filters are visualized to understand the…
Detection of Ventricular Fibrillation Using the Image from Time-Frequency Representation and Combined Classifiers without Feature Extraction
2018
Due the fact that the required therapy to treat Ventricular Fibrillation (V F) is aggressive (electric shock), the lack of a proper detection and recovering therapy could cause serious injuries to the patient or trigger a ventricular fibrillation, or even death. This work describes the development of an automatic diagnostic system for the detection of the occurrence of V F in real time by means of the time-frequency representation (T F R) image of the ECG. The main novelties are the use of the T F R image as input for a classification process, as well as the use of combined classifiers. The feature extraction stage is eliminated and, together with the use of specialized binary classifiers, …
An Advanced Numerical Model in Solving Thin-Wire Integral Equations by Using Semi-Orthogonal Compactly Supported Spline Wavelets
2003
Abstract—In this paper, the semi-orthogonal compactly sup- ported spline wavelets are used as basis functions for the efficient solution of the thin-wire electric field integral equation (EFIE) in frequency domain. The method of moments (MoM) is used via the Galerkin procedure. Conventional MoM directly applied to the EFIE, leads to dense matrix which often becomes computation- ally intractable when large-scale problems are approached. To overcome these difficulties, wavelets can be used as a basis set so obtaining the generation of a sparse matrix; this is due to the local supports and the vanishing moments properties of the wavelets. In the paper, this technique is applied to analyze elec…
Experimental investigation of low-frequency pulsed Lorentz force influence on the motion of Galinstan melt
2016
Abstract The paper presents the results of the numerical and physical experiments, aimed at assessing the influence of pulsed force of electromagnetic field on the melt motion and the fluid velocities. The experiment was performed on the eutectic alloy Galinstan in the cylindrical volume, where an ultrasonic Doppler velocimeter was employed for velocity measurements under conditions of pulsed and steady EM field application. A numerical simulation of the melt flow, forced by the steady EM force, involved a 2D axisymmetric model. The k-e turbulence model was used to obtain the information about the melt velocities. The verification of the numerical model was carried out for the steady case. …
No effects of pulsed radio frequency electromagnetic fields on melatonin, cortisol, and selected markers of the immune system in man.
2001
There is growing public concern that radio frequency electromagnetic fields may have adverse biological effects. In the present study eight healthy male students were tested to see whether or not radio frequency electromagnetic fields as used in modern digital wireless telecommunication (GSM standard) have noticeable effects on salivary melatonin, cortisol, neopterin, and immunoglobulin A (sIgA) levels during and several hours after exposure. In a specifically designed, shielded experimental chamber, the circularly polarized electromagnetic field applied was transmitted by an antenna positioned 10 cm behind the head of upright sitting test persons. The carrier frequency of 900 MHz was pulse…
A numerical study of the Schumann resonances in Mars with the FDTD method
2007
[1] Natural electromagnetic waves generated near the surface by electrostatic discharges in dust storms (dust devils) or by geological activity could be trapped in the resonant cavity formed by the surface and lower ionosphere of Mars, as it occurs on Earth giving rise to Schumann resonances. The finite difference time-domain technique (FDTD) is applied to model the atmosphere of Mars in order to determine Schumann resonant frequencies, and natural electromagnetic fields at the extremely low frequency range (ELF). A numerical tool is provided to analyze the electrical conductivity profile of the Martian atmosphere, with the aim of obtaining Schumann resonance frequencies and their dependenc…
A Novel Technique for Deembeding the Unloaded Resonance Frequency from Measurements of Microwave Cavities
2006
[EN] A novel technique to extract the influence of coupling networks on the resonant frequency of cavities in one-port measurements is presented. The determination of the unloaded resonant frequency is performed directly from measurements without either the need to obtain the electromagnetic fields in the resonator or to deembed the delay of transmission lines from the measuring equipment to the resonator. The importance of the Foster's form on the modeling of the frequency detuning of the resonators is also discussed and a criterion for the choice of the appropriate Foster's form is suggested. The procedure is validated with simulations and experimental measurements of manufactured cavities
Efficient Low-Frequency Modal Analysis of Anechoic Chamber
2007
An efficient method to analyze the electromagnetic field inside rectangular anechoic and semianechoic chambers from 30 to 100 MHz is shown. A modal expansion is employed to develop the homogeneous and the inhomogeneous field. This is combined with circuital techniques to compute the effect of the layers of ferrite and dielectrics in the walls of the chamber. Several numerical results of the Free Space Transmission Loss (FSTL) of an anechoic chamber and the Normalized Site Attenuation (NSA) of a semianechoic chamber are provided.