Search results for " engineering"
showing 10 items of 38291 documents
2021
Atomic layer deposition (ALD) technology has unlocked new ways of manipulating the growth of inorganic materials. The fine control at the atomic level allowed by ALD technology creates the perfect conditions for the inclusion of new cationic or anionic elements of the already-known materials. Consequently, novel material characteristics may arise with new functions for applications. This is especially relevant for inorganic luminescent materials where slight changes in the vicinity of the luminescent centers may originate new emission properties. Here, we studied the luminescent properties of CaS:Eu by introducing europium with oxygen ions by ALD, resulting in a novel CaS:EuO thin film. We …
A Simple Approach for Determination of Numerical Values of Ferrite Nonlinear Susceptibilities
2020
This article presents a straightforward approach for determination of numerical values of nonlinear susceptibilities of soft magnetic ferrites. It is shown that numerical values of susceptibilities can be calculated from the measured amplitudes of harmonics in the output voltage of ferrite core transformer. For this purpose, useful expressions for the susceptibilities are derived and as example, numerical values of the largest nonlinear susceptibilities those of the third and fifth orders are calculated. Additionally, errors of the measured susceptibilities also are determined. Based on the expressions obtained, the analysis of phase shifts between components of flux density on different fr…
On asymmetric periodic solutions in relay feedback systems
2021
Abstract Asymmetric self-excited periodic motions or periodic solutions which are produced by relay feedback systems that have symmetric characteristics are studied in the paper. Two different mechanisms of producing an asymmetric oscillation by a system with symmetric properties are noted and analyzed by the locus of a perturbed relay system (LPRS) method. Bifurcation between the ability to excite symmetric and asymmetric oscillation with variation of system parameters is analyzed. An algorithm of finding asymmetric solutions is proposed.
The Acoustic Wave Behavior Within the PEA Cell for Space Charge Measurement
2018
In order to evaluate the acoustic wave behavior within the Pulsed Electro Acoustic (PEA) cell, a simulation model has been developed in this work. The model, implemented in Matlab environment, is based on the analogy between acoustic and electrical quantities. Therefore, it was possible to model the PEA cell as cascade connected lossy transmission lines. The model has been validated theoretically by making a comparison with a simulation result found in literature. The experimental validation has also been made by using the PEA cell of the LEPRE high voltage lab. In addition, four graphs have been realized. Two of them can be used to establish in easy and fast way to obtain the minimum groun…
Dynamics of quantum discord of two coupled spin-1/2’s subjected to time-dependent magnetic fields
2019
Abstract We describe the dynamics of quantum discord of two interacting spin-1/2’s subjected to controllable time-dependent magnetic fields. The exact time evolution of discord is given for various input mixed states consisting of classical mixtures of two Bell states. The quantum discord manifests a complex oscillatory behaviour in time and is compared with that of quantum entanglement, measured by concurrence. The interplay of the action of the time-dependent magnetic fields and the spin-coupling mechanism in the occurrence and evolution of quantum correlations is examined in detail.
The ${JV}$ -Characteristic of Intermediate Band Solar Cells With Overlapping Absorption Coefficients
2017
An analytic expression for the $\textit {JV}$ -characteristic of intermediate band (IB) solar cells with overlapping absorption coefficients is derived. The characteristic contains six voltage-independent parameters that are calculated from material properties, cell properties, and external conditions. Combined with exponential functions containing the cell voltage, these describe the full $\textit {JV}$ -characteristic. Expressions are also derived for the short-circuit current and open-circuit voltage. The model represents a major simplification compared with the existing model for this type of devices. The simplicity will facilitate the understanding of the operation of such cells. Furth…
High-frequency EPR study on Cu4Cu- and Co4Co-metallacrown complexes
2019
Abstract High-frequency/high-field electron paramagnetic resonance studies on two homonuclear 12-MC-4 metallacrown complexes Cu4Cu and Co4Co are presented. For Cu4Cu, our data imply axial-type g-anisotropy with g x = 2.03 ± 0.01 , g y = 2.04 ± 0.01 , and g z = 2.23 ± 0.01 , yielding g = 2.10 ± 0.02 . No significant zero field splitting (ZFS) of the ground state mode is observed. In Co4Co, we find a m S = ± 3 / 2 ground state with g = 2.66 . The data suggest large anisotropy D of negative sign.
Numerical values of MnZn ferrite nonlinear susceptibilities in a lossless approximation
2017
On the basis of expressions for nonlinear magnetic susceptibilities of soft ferrites obtained earlier the analysis of phase shifts between components of flux density on different frequencies and the magnetic field strength is carried out. Only the largest nonlinear susceptibilities those of third and fifth order are considered. It is shown that in the frequency range where losses are small and can be neglected the susceptibility of third order is negative but that of fifth order is positive. These statements allow explaining the shape of output voltage of toroidal transformer with soft ferrite core induced by strong harmonic field strength in the input. Numerical values of nonlinear suscept…
An Analytic Approach to the Modeling of Multijunction Solar Cells
2020
Analytic expressions for the $JV$ -characteristics of three types of multijunction configurations are derived. From these, expressions for the short-circuit current, open-circuit voltage, and voltage at the maximum power point are found for multiterminal devices, and for series-connected tandem stacks. For voltage-matched devices, expressions for the optimal ratio of the number of bottom cells to the number of top cells are established. Luminescent coupling is incorporated throughout the article. It should be highlighted that the maximum power point of a series-connected tandem stack is described, with good accuracy for all interesting band gap combinations, by a single analytic expression.…
A Planar Generator for a Wave Energy Converter
2019
This article presents a permanent magnet planar translational generator which is able to exploit multiple modes of sea wave energy extraction. Linear electrical generators have recently been studied for the exploitation of sea wave energy, but, to the best of our knowledge, no synchronous planar translational generator has been proposed. In this article, to maximize the energy extraction, we have considered all the potential modes of motion due to wave excitation and included them within the mathematical model of the proposed system. The principle of operation of the generator can be summarized as follows: the moving part (translator) of the generator is driven from the sea waves and induce…