31,808 research outputs found
Investigation of Partial Discharge in Solid Dielectric under DC Voltage
A partial discharge, or PD, is defined as an electrical discharge that is localized within only a part of the insulation between two separated conductors. Recent research on PD mainly focuses on the study of PD characteristics under AC voltage. Compared with DC, PD under AC is more serious and can be easily detected in terms of PD number. As the results of these concentrated research, the understanding of PD under AC condition has been significantly improved and features extracted from PD measurements have been used to diagnose the insulation condition of many power apparatus. Recently, rapid development in HVDC transmission and power grids connection, and widely applied DC cable and gas-insulated switchgear because of their benefit in long distance usage lead to an increasing concern about PD under DC. However, available study for the condition is little and related research is therefore necessary and essential for understanding the lifetime and reliability of apparatus. <br/
Coupled ion - nanomechanical systems
We study ions in a nanotrap, where the electrodes are nanomechanical
resonantors. The ions play the role of a quantum optical system which acts as a
probe and control, and allows entanglement with or between nanomechanical
resonators.Comment: 4 pages, 2 figures, submitted for publicatio
Evidence for massive bulk Dirac Fermions in PbSnSe from Nernst and thermopower experiments
The lead chalcogenides (Pb,Sn)Te and (Pb,Sn)Se are the first examples of
topological crystalline insulators (TCI) predicted \cite{Fu,Hsieh} (and
confirmed \cite{Hasan,Story,Takahashi}) to display topological surface Dirac
states (SDS) that are protected by mirror symmetry. A starting premise
\cite{Hsieh} is that the SDS arise from bulk states describable as massive
Dirac states \cite{Wallis,Svane}, but this assumption is untested. Here we show
that the thermoelectric response of the bulk states display features specific
to the Dirac spectrum. We show that, in the quantum limit, the lowest Landau
Level (LL) is singly spin-degenerate, whereas higher levels are doubly
degenerate. The abrupt change in spin degeneracy leads to a large step-decrease
in the thermopower . In the lowest LL, displays a striking
linear increase vs. magnetic field. In addition, the Nernst signal undergoes an
anomalous sign change when the bulk gap inverts at 180 K.Comment: 16 pages, 8 figure
Exceptional del Pezzo hypersurfaces
We compute global log canonical thresholds of a large class of quasismooth
well-formed del Pezzo weighted hypersurfaces in
. As a corollary we obtain the existence
of orbifold K\"ahler--Einstein metrics on many of them, and classify
exceptional and weakly exceptional quasismooth well-formed del Pezzo weighted
hypersurfaces in .Comment: 149 pages, one reference adde
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