Search results for "Conductor"
showing 10 items of 1270 documents
A mathematical simulation of high temperature induction heating of electroconductive solids
2007
The mathematical model of non-stationary coupled electromagnetic and thermal processes in polarizable and magnetizable axisymmetric electroconductive solids subjected to electromagnetic field generated by external currents is proposed. The processes parameters are connected through heat sources and temperature dependence of material characteristics. The problem is solved by finite element method. The process of induction heating of a finite steel cylinder is considered.
Interaction-induced spin polarization in quantum dots.
2010
The electronic states of lateral many electron quantum dots in high magnetic fields are analyzed in terms of energy and spin. In a regime with two Landau levels in the dot, several Coulomb blockade peaks are measured. A zig-zag pattern is found as it is known from the Fock-Darwin spectrum. However, only data from Landau level 0 show the typical spin-induced bimodality, whereas features from Landau level 1 cannot be explained with the Fock-Darwin picture. Instead, by including the interaction effects within spin-density-functional theory a good agreement between experiment and theory is obtained. The absence of bimodality on Landau level 1 is found to be due to strong spin polarization.
Microstructure of Ag2BI4(B = Ag, Cd) superionics studied by SEM, impedance spectroscopy and fractal dimension analysis
2008
Two silver ion conducting solid electrolytes, Ag2HgI4 and Ag2CdI4, representing a wide class of AgI-based halogenide superionics have been the subjects of study by means of electrical impedance spectroscopy, SEM, porosity measurements and fractal dimension analysis. Even though both materials have been obtained by the same method under strictly identical conditions they were found to exhibit certain differences at the microstructural level. Thus, by the direct measurements of porosity and density it was found that the grain boundaries are better developed in silver mercuric iodide. On the assumption that pore geometry in the materials under study displays fractal character it was shown that…
Internal photoemission in solar blind AlGaN Schottky barrier photodiodes
2005
We have analyzed the photoresponse of solar blind AlGaN Schottky barrier photodiodes below the alloy band gap energy, in the 3.5-4.5 eV range, and we show that it is dominated by internal photoemission. The n-type Schottky barrier height is shown to increase linearly with the band gap energy of the AlGaN alloy. The amplitude of the internal photoemission signal is about 20 times smaller than the value given by the Fowler theory based on a free electron model. We explain this result by taking into account the interband transitions and the ballistic transport of photoexcited electrons in the metal. This low value of internal photoemission allows us to achieve a spectral rejection ratio betwee…
How does graphene enhance the photoelectric conversion efficiency of dye sensitized solar cells? An insight from a theoretical perspective
2019
The main goal of this work is to clearly answer the question from a theoretical perspective: how does graphene enhance the photoelectric conversion efficiency in the semiconducting layer of a dye sensitized solar cell? Several arrangements of the graphene layer between the dye molecule and the TiO2 (101) surface are carefully studied and discussed. The dynamic interfacial electron propagations are simulated with consideration of the underlying nuclear motion effect. Theoretical investigation shows that graphene can speed up the electron injection from the dye molecules to the semiconductor layer, only when the graphene sheet is bonded to the TiO2 surface via C–Ti bonds. The excited electron…
Characterization of clamp-on current transformers under nonsinusoidal conditions
2009
This paper reports the performance of clamp-on current transformers under nonsinusoidal conditions. A set of experimental measurements helped to determine the ratio and the phase errors under two conditions: 1) sinusoidal excitation with frequencies from 45 to 1000 Hz and 2) nonsinusoidal excitation using the fundamental frequency and one harmonic, with adjusted phase shift. It was found that ratio and phase errors are affected by the phase angle between the harmonic and the fundamental and the harmonic amplitude. The effects of conductor location in the current transformer's window and of the air-gap width were also investigated. It was concluded that harmonic phase and ratio errors measur…
Eddy current imaging with an atomic radio-frequency magnetometer
2016
We use a radio-frequency $^{85}$Rb alkali-vapor cell magnetometer based on a paraffin-coated cell with long spin-coherence time and a small, low-inductance driving coil to create highly resolved conductivity maps of different objects. We resolve sub-mm features in conductive objects, we characterize the frequency response of our technique, and by operating at frequencies up to 250 kHz we are able to discriminate between differently conductive materials based on the induced response. The method is suited to cover a wide range of driving frequencies and can potentially be used for detecting non-metallic objects with low DC conductivity.
Electrical ammeter based on spin-valve sensor.
2012
The present work shows an electrical ammeter for laboratory purpose based on a magnetoresistive (MR) spin-valve (SV) sensor. The proposed ammeter measures a 10 A maximum current and offers a maximum frequency response between 150 and 800 kHz depending on the electronics whole gain. These features are due to the use of a new generation MR-SV current sensor and a conditioning electronics that compensates in frequency and temperature the sensor response. With little adjustments in the electronics and changing the position of the sensor with respect to current carrying conductor, the designed instrument is able to measure higher current levels. The work shows the proposed ammeter with its diffe…
Efficient microwave-assisted synthesis of PCBM methanofullerenes (C60 and C70)
2015
PCBM is a fullerene derivative (phenyl-C61-butyric acid methyl ester) considered to be one of the best n-type organic semiconductors and plays a relevant role in organic photovoltaic solar cells. Much effort has been devoted to the optimization of the synthesis of PCBM derivatives. In this paper, PC61BM and PC71BM fullerene mono-adducts but also PCBM-like derivatives are successfully prepared by a one- step cyclopropanation reaction under microwave irradiation. The products are collected in good yields in short time, during which isomerization of the open [5,6] to the closed [6,6] form takes place in situ. In addition, with the use of two cycles of irradiation, a series of mixtures of bis-a…
Multiexciton complex from extrinsic centers in AlGaAs epilayers on Ge and Si substrates
2013
The multiexciton properties of extrinsic centers from AlGaAs layers on Ge and Si substrates are addressed. The two photon cascade is found both in steady state and in time resolved experiments. Polarization analysis of the photoluminescence provides clearcut attribution to neutral biexciton complexes. Our findings demonstrate the prospect of exploiting extrinsic centers for generating entangled photon pairs on a Si based device. © 2013 AIP Publishing LLC.