Search results for "field"
showing 10 items of 15048 documents
Advances in microgeophysics for engineering and cultural heritage
2009
A large number of unconventional investigations have been implemented, tested, and validated in the field of microgeophysics, with the aim being to solve specific diagnostic and/or monitoring problems regarding civil engineering and cultural heritage studies. The investigations were carried out using different tomographic 2D and 3D approaches as well as different energy sources, namely sonic, ultrasonic and electromagnetic (radar) waves, electric potential fields, and infrared thermography. Many efforts have been made to modify instruments and procedures in order to improve the resolution of the surveys as well as to greatly reduce the time of the measurements without any loss of informatio…
Microwave response of bulk MgB2 samples of different granularity
2006
The microwave response of three high-density bulk MgB2 samples has been investigated in the linear and nonlinear regimes. The three samples, characterized by different mean size of grains, have been obtained by reactive infiltration of liquid Mg in powdered B preforms. The linear response has been studied by measuring the microwave surface impedance; the nonlinear response by detecting the power radiated by the sample at the second-harmonic frequency of the driving field. Our results suggest that bulk MgB2 prepared by the liquid Mg infiltration technique is particularly promising for manufacturing resonant cavities operating at microwave frequencies.
Differentiation among dairy products by combination of fast field cycling NMR relaxometry data and chemometrics
2021
A set of commercial milk and Sicilian cheeses was analysed by a combination of fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometry and chemometrics. The NMR dispersion (NMRD) curves were successfully analysed with a mathematical model applied on Parmigiano-Reggiano (PR) cheese. Regression parameters were led back to the molecular components of cheeses (water trapped in casein micelles, proteins and fats) and milk samples (water belonging to hydration shells around dispersed colloidal particles of different sizes and bulk water). The application of chemometric analysis on relaxometric data enabled differentiating milk from cheeses and revealing differences within the two sa…
A new approach to calibrate the thermal conditions in space charge measurements on HVDC mini-cables
2019
The PEA method is currently widespread used for space charge measurements in mini-cables in order to qualify the behavior of semicon-dielectric-semicon compound under electric and thermal stress. The main goal of this research is to quantitatively evaluate the relationship between the thermal boundary conditions applied to cables or mini-cables and the maximum local electric field due to the accumulated space charge. Hitherto, several research groups have obtained thermal gradients over the dielectric's radius heating the conductor by Joule effect due to an induced current. In this paper, a numerical approach is offered to calibrate the heat exchange boundary conditions to apply to a sample…
Localization of Multi-Class On-Road and Aerial Targets Using mmWave FMCW Radar
2021
mmWave radars play a vital role in autonomous systems, such as unmanned aerial vehicles (UAVs), unmanned surface vehicles (USVs), ground station control and monitoring systems. The challenging task when using mmWave radars is to estimate the accurate angle of arrival (AoA) of the targets, due to the limited number of receivers. In this paper, we present a novel AoA estimation technique, using mmWave FMCW radars operating in the frequency range 77–81 GHz by utilizing the mechanical rotation. Rotating the radar also increases the field of view in both azimuth and elevation. The proposed method estimates the AoA of the targets, using only a single transmitter and receiver. The measurements are…
Influence on the transient evoked otoacoustic emission by GSM 915 MHz electromagnetic fields: comparative analysis between control and exposed groups
2006
Vertical Line Array (VLA) Beam - Forming Algorithm with constant beam width.
2005
The algorithm proposed is a beam-forming algorithm. Many beam-steering and beam-forming algorithms exist and they are all based on the control of delay times between the signals driving the loudspeakers of the line array; this kind of control produces a variable beam-width depending on steering angle and frequency. In our case beam width doesn't depend on frequency and steering angle because a specific beam forming technique was applied by shading the amplitudes of signals for each element of the array according to the frequency applied. Furthermore a weighting function was utilized for spatial windowing. Spatial windowing allows reduction of secondary lobes without varying the directivity …
Functional Extrapolations to Tame Unbound Anions in Density-Functional Theory Calculations
2019
Standard flavors of density-functional theory (DFT) calculations are known to fail in describing anions, due to large self-interaction errors. The problem may be circumvented using localized basis sets of reduced size, leaving no variational flexibility for the extra electron to delocalize. Alternatively, a recent approach exploiting DFT evaluations of total energies on electronic densities optimized at the Hartree-Fock (HF) level has been reported, showing that the self-interaction-free HF densities are able to lead to an improved description of the additional electron, returning affinities in close agreement with the experiments. Nonetheless, such an approach can fail when the HF densitie…
Exploring Teachers' Motivation for Teaching and Professional Development in Ethiopia : Voices from the Field
2015
Teachers’ work, learning, and professional development are central to any effort aiming at improving schools. Consequently, teachers must consider themselves as a lifelong learner, engage in continuous professional learning and apply that learning to improve student learning and achievement. This article explores teachers’ motivation for teaching and professional development in secondary schools in Ethiopia. Data were collected via interviews and focus group discussions from 32 teachers. The analysis of the collected information revealed low salary and the absence of link between performance and reward as major motivational challenges for teachers. The identified motivational challenges wer…