40,812 research outputs found
Effective control of the error in a direct measurement of core-loss power
Accuracy of a direct measurement of core-loss power is severely limited in many applications by the extra phase shift between the measured voltage and current. An analysis of the error is for the first time performed, which not only unfolds the hidden physical nature behind it, but also reveals a simple and effective method to control the sensitivity and hence the error. This method can also be used to satisfy a prescribed tolerance. Extensive measurements on a TDK PC40 core yield results which support the analysis
A practical approach for magnetic core-loss characterization
A practical approach for magnetic core-loss characterization up to a few megahertz is presented. An error analysis is for the first time performed, revealing that corrections are needed to compensate for errors introduced by the extra phase shift inherent in a measurement setup, and by shunt parasitic capacitance associated with an inductive device under test. A simple technique is then proposed to control the error so as to satisfy prescribed tolerances. Extensive measurements done on a TDK PC40 core yield results which support the analysis. Several sample cores are then characterized at a few megahertz
A ballistic pn junction in suspended graphene with split bottom gates
We have developed a process to fabricate suspended graphene devices with
local bottom gates, and tested it by realizing electrostatically controlled pn
junctions on a suspended graphene mono-layer nearly 2 micrometers long.
Measurements as a function of gate voltage, magnetic field, bias, and
temperature exhibit characteristic Fabry-Perot oscillations in the cavities
formed by the pn junction and each of the contacts, with transport occurring in
the ballistic regime. Our results demonstrate the possibility to achieve a high
degree of control on the local electronic properties of ultra-clean suspended
graphene layers, a key aspect for the realization of new graphene
nanostructures.Comment: 10 pages, 4 figure
Algebraic approach to the Hulthen potential
In this paper the energy eigenvalues and the corresponding eigenfunctions are
calculated for Hulthen potential. Then we obtain the ladder operators and show
that these operators satisfy SU(2) commutation relation.Comment: 8 Pages, 1 Tabl
Kondo correlation and spin-flip scattering in spin-dependent transport through a quantum dot coupled to ferromagnetic leads
We investigate the linear and nonlinear dc transport through an interacting
quantum dot connected to two ferromagnetic electrodes around Kondo regime with
spin-flip scattering in the dot. Using a slave-boson mean field approach for
the Anderson Hamiltonian having finite on-site Coulomb repulsion, we find that
a spin-flip scattering always depresses the Kondo correlation at arbitrary
polarization strength in both parallel and antiparallel alignment of the lead
magnetization and that it effectively reinforces the tunneling related
conductance in the antiparallel configuration. For systems deep in the Kondo
regime, the zero-bias single Kondo peak in the differential conductance is
split into two peaks by the intradot spin-flip scattering; while for systems
somewhat further from the Kondo center, the spin-flip process in the dot may
turn the zero-bias anomaly into a three-peak structure.Comment: 4 pages, 2 figure
Mesoscopic Kondo effect of a quantum dot embedded in an Aharonov-Bohm ring with intradot spin-flip scattering
We study the Kondo effect in a quantum dot embedded in a mesoscopic ring
taking into account intradot spin-flip scattering . Based on the finite-
slave-boson mean-field approach, we find that the Kondo peak in the density of
states is split into two peaks by this coherent spin-flip transition, which is
responsible for some interesting features of the Kondo-assisted persistent
current circulating the ring: (1) strong suppression and crossover to a sine
function form with increasing ; (2) appearance of a "hump" in the
-dependent behavior for odd parity. -induced reverse of the persistent
current direction is also observed for odd parity.Comment: 7 pages,6 figures, to be published by Europhys. Let
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