5,939 research outputs found
Joule heating generated by spin current through Josephson junctions
We theoretically study the spin-polarized current flowing through a Josephson
junction (JJ) in a spin injection device. When the spin-polarized current is
injected from a ferromagnet (FM) in a superconductor (SC), the charge current
is carried by the superconducting condensate (Cooper pairs), while the spin-up
and spin-down currents flow in the equal magnitude but in the opposite
direction in SC, because of no quasiparticle charge current in SC. This
indicates that not only the Josephson current but also the spin current flow
across JJ at zero bias voltage, thereby generating Joule heating by the spin
current. The result provides a new method for detecting the spin current by
measuring Joule heating at JJ.Comment: 3 pages, 2 figure
Global symmetries and 't Hooft anomalies in brane tilings
We investigate the relation between gauge theories and brane configurations
described by brane tilings. We identify U(1)_B (baryonic), U(1)_M (mesonic),
and U(1)_R global symmetries in gauge theories with gauge symmetries in the
brane configurations. We also show that U(1)_MU(1)_B^2 and U(1)_RU(1)_B^2 't
Hooft anomalies are reproduced as gauge transformations of the classical brane
action.Comment: 41 pages, 6 figure
Development of single-cell protectors for sealed silver-zinc cells
Three design approaches to cell-level protection were developed, fabricated, and tested. These systems are referred to as the single-cell protector (SCP), multiplexed-cell protector(MCP). To evaluate the systems 18-cell battery packs without cell level control were subjected to cycle life test. A total of five batteries were subjected to simulate synchronous orbit cycling at 40% depth of discharge at 22C. Batteries without cell-level protection failed between 345 and 255 cycles. Cell failure in the cell level protected batteries occurred between 412 and 540. It was determined that the cell-level monitoring and protection is necessary to attain the long cycle life of a AgZn battery. The best method of providing control and protection of the AgZn cells depends on the specific application and capability of the user
Enhancement of the Gilbert damping constant due to spin pumping in noncollinear ferromagnet/nonmagnet/ferromagnet trilayer systems
We analyzed the enhancement of the Gilbert damping constant due to spin
pumping in non-collinear ferromagnet / non-magnet / ferromagnet trilayer
systems. We show that the Gilbert damping constant depends both on the
precession angle of the magnetization of the free layer and on the direction of
the magntization of the fixed layer. We find the condition to be satisfied to
realize strong enhancement of the Gilbert damping constant.Comment: 4 pages, 3 figures, to be published in Phys. Rev.
Development of single cell protectors for sealed silver-zinc cells, phase 1
A single cell protector (SCP) assembly capable of protecting a single silver-zinc (Ag Zn) battery cell was designed, fabricated, and tested. The SCP provides cell-level protection against overcharge and overdischarge by a bypass circuit. The bypass circuit consists of a magnetic-latching relay that is controlled by the high and low-voltage limit comparators. Although designed specifically for secondary Ag-Zn cells, the SCP is flexible enough to be adapted to other rechargeable cells. Eighteen SCPs were used in life testing of an 18-cell battery. The cells were sealed Ag-Zn system with inorganic separators. For comparison, another 18-cell battery was subjected to identical life test conditions, but with battery-level protection rather than cell-level. An alternative approach to the SCP design in the form of a microprocessor-based system was conceptually designed. The comparison of SCP and microprocessor approaches is also presented and a preferred approach for Ag-Zn battery protection is discussed
Performance of Wood Products as Media for Culture of Anthuriums
A study was conducted on Anthurium andraeanum Andre cv. Kozohara Red testing wood bark, wood chips, redwood bark, and bagasse media with fertilizer levels of 100, 200, and 400lb N-P205 -K20/A/year. Media ranking from best to poorest for flower production, flower stem length, and flower size were wood bark > wood chips > bagasse = redwood bark. Flower production and flower size increased linearly with increase in fertilizer rate. Flower stem length was not affected by fertilizer rate. Fertilizer response was similar on all media
Ricci-flat deformation of orbifolds and localized tachyonic modes
We study Ricci-flat deformations of orbifolds in type II theory. We obtain a
simple formula for mass corrections to the twisted modes due to the
deformations, and apply it to originally tachyonic and massless states in
several examples. In the case of supersymmetric orbifolds, we find that
tachyonic states appear when the deformation breaks all the supersymmetries. We
also study nonsupersymmetric orbifolds C^2/Z_{2N(2N+1)}, which is T-dual to N
type 0 NS5-branes. For N>=2, we compute mass corrections for states, which have
string scale tachyonic masses. We find that the corrected masses coincide to
ones obtained by solving the wave equation for the tachyon field in the smeared
type 0 NS5-brane background geometry. For N=1, we show that the unstable mode
representing the bubble creation is the unique tachyonic mode.Comment: 20 pages, minor collection
Kondo effect in quantum dots coupled to ferromagnetic leads
We study the Kondo effect in a quantum dot which is coupled to ferromagnetic
leads and analyse its properties as a function of the spin polarization of the
leads. Based on a scaling approach we predict that for parallel alignment of
the magnetizations in the leads the strong-coupling limit of the Kondo effect
is reached at a finite value of the magnetic field. Using an equation-of-motion
technique we study nonlinear transport through the dot. For parallel alignment
the zero-bias anomaly may be split even in the absence of an external magnetic
field. For antiparallel spin alignment and symmetric coupling, the peak is
split only in the presence of a magnetic field, but shows a characteristic
asymmetry in amplitude and position.Comment: 5 pages, 2 figure
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