Use Of Current Injection Research Articles

Combining an obstacle and electrically driven vortices to enhance heat transfer in a quasi-two-dimensional MHD duct flow

The design of vortex promoters in a heated-wall duct is often limited by the considerations of practicality, especially in complex systems such as fusion blankets. The present study investigates the use of current injection to invoke a street of vortices in quasi-two-dimensional high transverse magnetic field magnetohydrodynamic duct flows to enhance instability behind a cylinder. The intent is to generate intensive flow vorticity parallel to a magnetic field downstream of a field-aligned cylinder. Electric current enters the flow through an electrode embedded in one of the Hartmann walls, radiates outward, imparting a rotational forcing around the electrode due to the Lorentz force. The quasi-two-dimensional nature of these flows then promotes a vortical rotation across the interior of the duct with axis aligned to the magnetic field. The hot and cold walls are parallel to the magnetic field. Electric current amplitude and pulse width, excitation frequency and electrode position are systematically varied to explore their influences on the convective heat transport phenomenon. This investigation builds on a recommendation from previous work of Bühler (J. Fluid Mech., vol. 326, 1996, pp. 125–150) dedicated to understanding of the flow stability in a similar configuration. This study provides supportive evidence for the use of current injection as an alternative to the conventional mechanically actuated turbuliser, with heat transfer almost doubled for negligible additional pumping power requirements.

Separation of bulk and contact interface degradation in thin film silicon solar cells

The use of current injection and light exposure is shown to distinguish the impact of degradation in the contact, and intrinsic regions of a-Si:H solar cells, respectively. The drop in the maximum power conversion capability of the cell after light exposure is a consequence of an increase of dangling bonds in the intrinsic layer of the cell due to the Staebler-Wronksi effect. This has a detrimental effect on short circuit current, open circuit voltage, and fill factor. On the other hand, injected current increases the open circuit voltage and greatly reduces the fill factor without affecting the short circuit current, which is attributed to an increase of defects in the p-layer. A clear distinction from both degradation mechanisms is observed from evolution of the ideality factor m of the main junction, and the ideality factor n of the ZnO/a-Si:H(p) interface. A back-to-back diode model of a solar cell that considers the effect of non-ideal contacts, where a high value of n represents an increased tunneling transport at the contact interface, can effectively address the separation of damage in the two regions.

Analysis of Mechanisms of Spiking in Normally ‘Non-Spiking’ Motoneurone Somata in Crayfish

ABSTRACT The soma membrane of the abdominal giant motor neurone (MoG) of the crayfish was studied by use of current injection and by measurements of total and local membrane current under voltage-clamp. Depolarization of the soma from the recorded resting potential (about −70 mV) did not produce a regenerative potential. Sodium and calcium currents were observed under voltage-clamp. It was shown that the sodium spike cannot develop at the usual resting potential since sodium channels are already partially inactivated; the spike can appear after the removal of inactivation by a hyperpolarizing prepulse. It was also shown that an early outward current prevents the Ca2+ regenerative potential; the potential can appear after inactivation of this outward current by a depolarizing prepulse.