4,144 research outputs found
Nondestructive assessment of penetration of electron-beam welds
Empirical method correlates penetration of an electron-beam weld with external measurements of the weld. Empirical polygon accurately confirms full-penetration welds while a second, larger polygon provides for penetration of welds near the tip
Anomalous organic magnetoresistance from competing carrier-spin-dependent interactions with localized electronic and nuclear spins
We describe a new regime for low-field magnetoresistance in organic
semiconductors, in which the spin-relaxing effects of localized nuclear spins
and electronic spins interfere. The regime is studied by the controlled
addition of localized electronic spins to a material that exhibits substantial
room-temperature magnetoresistance (\%). Although initially the
magnetoresistance is suppressed by the doping, at intermediate doping there is
a regime where the magnetoresistance is insensitive to the doping level. For
much greater doping concentrations the magnetoresistance is fully suppressed.
The behavior is described within a theoretical model describing the effect of
carrier spin dynamics on the current
Isogrid design handbook
Handbook has been published which presents information needed for design of isogrid triangular integral-stiffened structures. It develops equations, methods, and graphs to handle wide variety of loadings, materials, and geometry. Handbook is divided into seven sections. Handbook may be used by marine and civil engineers and by students and designers without access to computers
Dynamical control of electron spin coherence in a quantum dot
We investigate the performance of dynamical decoupling methods at suppressing
electron spin decoherence from a low-temperature nuclear spin reservoir in a
quantum dot. The controlled dynamics is studied through exact numerical
simulation, with emphasis on realistic pulse delays and long-time limit. Our
results show that optimal performance for this system is attained by a periodic
protocol exploiting concatenated design, with control rates substantially
slower than expected from the upper spectral cutoff of the bath. For a known
initial electron spin state, coherence can saturate at long times, signaling
the creation of a stable ``spin-locked'' decoherence-free subspace. Analytical
insight on saturation is obtained for a simple echo protocol, in good agreement
with numerical results.Comment: 4 pages, 4 figures with 3 of them in colo
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