Publications by authors named "Paul Von Allmen"

The effects of anionic site substitution on the electronic transport properties of YbMgSb As compounds were investigated using density functional theory (DFT) with on-site Coulomb interaction correction (PBE+U). By replacing the Sb atoms at the four symmetry sites in YbMgSb with As, we found that the electronic and thermoelectric properties of the compound can be altered substantially. For most of the cases, the thermoelectric properties improve compared to the base compound YbMgSb.

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Thermoelectric materials exhibit a voltage under an applied thermal gradient and are the heart of radioisotope thermoelectric generators (RTGs), which are the main power system for space missions such as I, II, and the Mars rover. However, materials currently in use enable only modest thermal-to-electrical conversion efficiencies near 6.5% at the system level, warranting the development of material systems with improved thermoelectric performance.

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Lidar is one of few remote sensing methods available to researchers to sense below the oceanic air-surface. We present polarimetric lidar measurements of turbulence in a laboratory generated turbulent flow. We found that the nearforward light depolarization characterized by the depolarization rate γ(z), varies with the turbulent flow parameter: χ(z)∊(z), where χ(z) and ∊(z) are the respective depth dependent, temperature variance, and turbulent kinetic energy dissipation rates.

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The thermoelectric properties from 300 - 1275 K of calcium-doped LaTe are reported. LaTe is a high temperature n-type thermoelectric material with a previously reported zT ~ 1.1 at 1273 K and x = 0.

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Heat transport and ice sublimation in comets are interrelated processes reflecting properties acquired at the time of formation and during subsequent evolution. The Microwave Instrument on the Rosetta Orbiter (MIRO) acquired maps of the subsurface temperature of comet 67P/Churyumov-Gerasimenko, at 1.6 mm and 0.

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The 'snowline' conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Models suggest that some of the icy bodies may have migrated into the asteroid belt. Recent observations indicate the presence of water ice on the surface of some asteroids, with sublimation a potential reason for the dust activity observed on others.

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We have developed manufacturable approaches for forming single, vertically aligned carbon nanotubes, where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 microm deep trenches. These wafer-scale approaches were enabled by using chemically amplified resists and high density, low pressure plasma etching techniques to form the 3D nanoscale architectures.

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We present the hydrogen sensing performance of individual Pd nanowires grown by electrodeposition into nanochannels of anodized aluminum oxide (AAO) templates investigated as a function of the nanowire diameter. Four-terminal devices based on individual Pd nanowires were found to successfully detect hydrogen gas (H(2)). Our experimental results show that the H(2) sensing sensitivity increases and the response time decreases with decreasing diameter of Pd nanowires with d = 400, 200, 80 and 20 nm, due to the high surface-to-volume ratio and short diffusion paths, respectively.

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