77 research outputs found
On the relation between the Feynman paradox and Aharonov-Bohm effects
The magnetic Aharonov-Bohm (A-B) effect occurs when a point charge interacts
with a line of magnetic flux, while its dual, the Aharonov-Casher (A-C) effect,
occurs when a magnetic moment interacts with a line of charge. For the two
interacting parts of these physical systems, the equations of motion are
discussed in this paper. The generally accepted claim is that both parts of
these systems do not accelerate, while Boyer has claimed that both parts of
these systems do accelerate. Using the Euler-Lagrange equations we predict that
in the case of unconstrained motion only one part of each system accelerates,
while momentum remains conserved. This prediction requires a time dependent
electromagnetic momentum. For our analysis of unconstrained motion the A-B
effects are then examples of the Feynman paradox. In the case of constrained
motion, the Euler-Lagrange equations give no forces in agreement with the
generally accepted analysis. The quantum mechanical A-B and A-C phase shifts
are independent of the treatment of constraint. Nevertheless, experimental
testing of the above ideas and further understanding of A-B effects which is
central to both quantum mechanics and electromagnetism may be possible.Comment: 21 pages, 5 figures, recently submitted to New Journal of Physic
Flexible n-i-p thin film silicon solar cells on polyimide foils with textured ZnO:Ga back reflector
In thin film silicon solar cells on opaque substrates in n-i-p deposition sequence where the textured transparent conductive oxide (TCO) layer serves as a back reflector, one can independently optimize the morphology of the TCO layer without compromise on transparency and conductivity of this layer and further adjust the electro-optical properties of the back contact by using additional layers on top of the textured TCO. In the present work, we use this strategy to obtain textured back reflectors for solar cells in n-i-p deposition sequence on non-transparent flexible plastic foils. Gallium doped ZnO (ZnO:Ga) films were deposited on polyimide substrates by DC magnetron sputtering at a temperature of 200 °C. A wet-chemical etching step was performed by dipping the ZnO:Ga covered foil into a diluted HCl solution. The textured ZnO:Ga is then coated with a highly reflective Ag/ZnO double layer. On this back reflector, we develop thin film silicon solar cells with a microcrystalline silicon absorber layer. The current density for the cell with the textured ZnO:Ga layer is ~ 23 mA/cm2, 4 mA/cm2 higher than the one without such layer, and a maximum efficiency of 7.5% is obtained for a 1 cm2 cell.Fundação para a Ciência e a Tecnologia (FCT
Enhanced Algorithms for Multi-Site Scheduling
This paper discusses two approaches to enhance multi-site scheduling for grid environments. First the potential improvements of multi-site scheduling by applying constraints for the job fragmentation are presented. Subsequently, an adaptive multi-site scheduling algorithm is pointed out and evaluated. The adaptive multi-site scheduling uses a simple decision rule whether to use or not to use multi-site scheduling
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