Search results for "current"
showing 10 items of 2224 documents
Simple and scalable electrochemical synthesis of 2,1-benzisoxazoles and quinoline N-oxides.
2019
Cathodic reduction of the nitro moiety and subsequent intramolecular cyclization affords different substituted 2,1-benzisoxazoles and quinoline N-oxides. This methodology allows the synthesis of two different types of heterocycles from common simple starting materials, using electrons as a sole reagent for this transformation. The electrolysis can be conducted in a very simple undivided electrolysis cell under constant current conditions. This permits working on a larger scale compared to other electrochemical methodologies and represents a significant advantage.
Intracranial measurement of current densities induced by transcranial magnetic stimulation in the human brain
2003
Transcranial magnetic stimulation (TMS) is a non-invasive technique that uses the principle of electromagnetic induction to generate currents in the brain via pulsed magnetic fields. The magnitude of such induced currents is unknown. In this study we measured the TMS induced current densities in a patient with implanted depth electrodes for epilepsy monitoring. A maximum current density of 12 microA/cm2 was recorded at a depth of 1 cm from scalp surface with the optimum stimulation orientation used in the experiment and an intensity of 7% of the maximal stimulator output. During TMS we recorded relative current variations under different stimulating coil orientations and at different points…
Winding loss analysis and optimization of an AC inductor for a galvanically isolated PV inverter
2012
This paper describes simple treatments for fringing fields of air gaps in the core and bypass fluxes in the winding window area of an existing high frequency AC inductor used by a commercial developer of PV inverters. For this purpose, Maxwell (ANSOFT) electromagnetic software package is used for winding eddy current loss analysis. It is displayed that air gaps cause high flux strength and, therefore, induce significantly high eddy currents to the surrounded windings. Proximity effect also causes non uniform current density in the winding. Altogether, the inductor is affected by fringing fields, and proximity effect produces a very high AC resistance, consequently resulting in undesirable h…
Nonadiabatic dynamics in strongly driven diffusive Josephson junctions
2019
By measuring the Josephson emission of a diffusive Superconductor-Normal metal-Superconductor (SNS) junction at a finite temperature we reveal a non-trivial sensitivity of the supercurrent to microwave irradiation. We demonstrate that the harmonic content of the current-phase relation is modified due to the energy redistribution of quasiparticles in the normal wire induced by the electromagnetic field. The distortion originates from the phase-dependent out-of-equilibrium distribution function which is strongly affected by the ac-response of the spectral supercurrent. For phases close to $\pi$, transitions accross the Andreev gap are dynamically favored leading to a supercurrent reduction. T…
Electrolyte Flow and Temperature Calculations in Finite Cylinder Caused by Alternating Current
2006
The distribution of electromagnetic fields, forces and source term of temperature induced by an alternating axially-symmetric system of electric current in a cylinder of a finite length with 6 electrodes has been investigated and calculated in [2, 1].
Ultra-nonlocality in density functional theory for photo-emission spectroscopy.
2014
We derive an exact expression for the photo-current of photo-emission spectroscopy using time-dependent current density functional theory (TDCDFT). This expression is given as an integral over the Kohn-Sham spectral function renormalized by effective potentials that depend on the exchange-correlation kernel of current density functional theory. We analyze in detail the physical content of this expression by making a connection between the density-functional expression and the diagrammatic expansion of the photo-current within many-body perturbation theory. We further demonstrate that the density functional expression does not provide us with information on the kinetic energy distribution of…
Quantum superpositions of clockwise and counterclockwise supercurrent states in the dynamics of a rf-SQUID exposed to a quantized electromagnetic fie…
2002
The dynamical behavior of a superconducting quantum interference device (a rf-SQUID) irradiated by a single mode quantized electromagnetic field is theoretically investigated. Treating the SQUID as a flux qubit, we analyze the dynamics of the combined system within the low lying energy Hilbert subspace both in the asymmetric and in the symmetric SQUID potential configurations. We show that the temporal evolution of the system is dominated by an oscillatory behavior characterized by more than one, generally speaking, incommensurable Rabi frequencies whose expressions are explicitly given. We find that the external parameters may fixed in such a way to realize a control on the dynamical repla…
Comparative Determinations of Magnetic Induction in AC and DC Circuits
2019
The influence of the electromagnetic field on the human body, although still heavily studied, can have long-term negative effects. The static electromagnetic field is generated by a continuous current source and has a current flow characteristic conventionally set + from -. The variable electromagnetic field is produced by the alternating current and has the ability to change its direction over time with a frequency of 50 or 60 Hz. It is considered that the non-hazardous limit value for the magnetic field (according to Federal Office for Radiation Security in Germany) is 100 microT for 50 Hz and 83 microT for 60 Hz. For the electric field, the exposure limit value is 5kV/m. Electromagnetic …
Concepciones alternativas y dificultades de aprendizaje en electrostática : selección de cuestiones elaboradas para su detección y tratamiento
2021
The work we are presenting here tries to summarise the contributions made by research on the ideas and difficulties of students within the field of Electrostatics. These researches reveal that the concepts introduced in this domain, such as electric field and potential, are necessary prerequisites so as to acquire a scientific vision of electromagnetic phenomena. Thus, taking into account the importance of the concepts involved for a scientific vision of the circuits of continuous current and, in general, of the electromagnetic theory, we think it is important for teachers to have a first idea on which are the most problematic conceptions or at least, those that have been studied most.
Gigahertz Single-Electron Pumping Mediated by Parasitic States
2018
In quantum metrology, semiconductor single-electron pumps are used to generate accurate electric currents with the ultimate goal of implementing the emerging quantum standard of the ampere. Pumps based on electrostatically defined tunable quantum dots (QDs) have thus far shown the most promising performance in combining fast and accurate charge transfer. However, at frequencies exceeding approximately 1 GHz, the accuracy typically decreases. Recently, hybrid pumps based on QDs coupled to trap states have led to increased transfer rates due to tighter electrostatic confinement. Here, we operate a hybrid electron pump in silicon obtained by coupling a QD to multiple parasitic states, and achi…