2,267 research outputs found
Quantum Transport Characteristics of Lateral pn-Junction of Single Layer TiS3
Using density functional theory and nonequilibrium Greens functions-based
methods we investigated the electronic and transport properties of monolayer
TiS3 pn-junction. We constructed a lateral pn-junction in monolayer TiS3 by
using Li and F adatoms. An applied bias voltage caused significant variability
in the electronic and transport properties of the TiS3 pn-junction. In
addition, spin dependent current-voltage characteristics of the constructed
TiS3 pn-junction were analyzed. Important device characteristics were found
such as negative differential resistance and rectifying diode behaviors for
spin-polarized currents in the TiS3 pn-junction. These prominent conduction
properties of TiS3 pn-junction offer remarkable opportunities for the design of
nanoelectronic devices based on a recently synthesized single-layered material
Ag and Au Atoms Intercalated in Bilayer Heterostructures of Transition Metal Dichalcogenides and Graphene
The diffusive motion of metal nanoparticles Au and Ag on monolayer and
between bilayer heterostructures of transition metal dichalcogenides and
graphene are investigated in the framework of density functional theory. We
found that the minimum energy barriers for diffusion and the possibility of
cluster formation depend strongly on both the type of nanoparticle and the type
of monolayers and bilayers. Moreover, the tendency to form clusters of Ag and
Au can be tuned by creating various bilayers. Tunability of the diffusion
characteristics of adatoms in van der Waals heterostructures holds promise for
controllable growth of nanostructures.Comment: accepted, APL Ma
Strange Particles and Neutron Stars - Experiments at Gsi
Experiments on strangeness production in nucleus-nucleus collisions at SIS
energies address fundamental aspects of modern nuclear physics: the
determination of the nuclear equation-of-state at high baryon densities and the
properties of hadrons in dense nuclear matter. Experimental data and
theoretical results will be reviewed. Future experiments at the FAIR
accelerator aim at the exploration of the QCD phase diagram at highest baryon
densities.Comment: %Invited talk given at the International Invited talk given at the
International Symposium on Heavy Ion Physics (ISHIP 2006) April 3-6 2006,
FIAS, Frankfurt, Germany Frankfurt, German
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Hydrologic Characterization of Ground Water Resources in South Central Hudspeth County, Texas
Regional and local hydrologic investigations have been conducted in Trans-Pecos Texas at the principal study area for a low-level radioactive waste repository. The area is approximately 40 mi (65 km) southeast of El Paso in the Hueco Bolson, a fault-bounded desert basin that developed in the late Tertiary. Groundwater in the principal study area is found in Hueco Bolson silts and sands at depths of 361 ft (110 m) and 478 ft (146 m), and at depths of 592 ft (180 m) in Cretaceous limestones. The unsaturated zone consists of approximately 50 ft (15 m) of alluvial silt, sand, and gravel underlain by 300 to 500 ft (91 to 152 m) of lacustrine and fluvial clay, silt, and fine sand. The scope of this investigation included (1) evaluating groundwater resources in the area, (2) determining groundwater flow paths and velocities, and (3) testing hydrologic hypotheses using groundwater flow models.
Development of groundwater resources in the vicinity of the principal study area is limited by two key factors: (1) costs of drilling and completing wells and of producing water at depths typically greater than 400 ft (122 m), and (2) the very low productivity of aquifers. Transmissivities of aquifers in bolson and Cretaceous strata, as revealed by 11 aquifer tests, range from approximately 0.19 to 290.0 ft²/d (0.018 to 26.9 m²/d); corresponding permeabilities range from 0.0015 to 2.82 ft/d (0.0005 to 0.861 m/d). A composite potentiometric surface based on water levels measured in all available wells and on the hydrologic interconnection of the Diablo Plateau aquifer, Hueco Bolson silt and sand aquifer, and Rio Grande alluvium aquifer indicates that groundwater is recharged on the Diablo Plateau and flows to the south and southwest toward the Rio Grande beneath the bolson pediment. The inferred distribution of permeability zones focuses flow from the eastern Diablo Plateau toward Cretaceous outcrops along the Campo Grande fault, creating an observed potentiometric high. The relatively low hydraulic heads near the principal study area are caused by preferential drainage along relatively permeable bolson deposits to the west and southwest toward the Rio Grande. Water chemistry data, particularly on tritium, carbon-14, and total dissolved solids, generally support the interpreted flow pattern; some discrepancies can be related to paleohydrologic effects associated with the incision of the Rio Grande during Quaternary time.Bureau of Economic Geolog
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Hydrologic Investigations of the Saturated Zone in South Central Hudspeth County, Texas
Hydrologic investigations are in progress in Trans-Pecos Texas at the proposed site of a low-level radioactive waste repository. The site is approximately 40 mi (65 km) southeast of El Paso in the Hueco Bolson, a fault-bounded desert basin that developed in the late Tertiary. Groundwater in the area of the proposed site is found at depths of 478 ft (146 m) and 592 ft (180 m) in bolson silt and sand and Cretaceous limestone, respectively. The unsaturated zone consists of approximately 50 ft (15 m) of alluvial silt, sand, and gravel underlain by 450 ft (137 m) of lacustrine and fluvial clay, silt, and fine sand.
High-priority tasks for characterizing the groundwater regime include (1) evaluating groundwater resources in the area, (2) determining groundwater flow paths and velocities, (3) testing hydrologic hypotheses using groundwater flow models, and (4) determining groundwater hydrochemistry. The objective of this report is to evaluate the groundwater resources and to discuss our current understanding of groundwater flow paths and velocities.
Groundwater resources in the vicinity of the site are limited by two key factors: (1) costs of drilling and completing wells and of producing water at depths greater than 400 ft (122 m) and (2) very low productivity of aquifers. Typical transmissivities of aquifers producing from bolson and Cretaceous strata, based on four tests, range from approximately 4.3 x 10^-2 ft²/day (4.0 x 10^-3 m²/day) to 2.9 x 10^2 ft²/day (2.7 x 10^1 m²/day). A composite potentiometric surface has been mapped on the basis of static water levels measured in all available wells. Regional groundwater flow is interpreted from the potentiometric surface to be generally south-southwest toward the Rio Grande.Bureau of Economic Geolog
AlN-based piezoelectric micropower generator for low ambient vibration energy harvesting
AbstractIn this paper a resonant micropower generator based on the transverse piezoelectric effect is presented. The generator consists of a large silicon mass attached to an polysilicon cantilever covered with an AlN thinfilm as piezoelectric material. To maximize the power density of the generator, a parametric study by means of analytical modeling and FEM simulation has been performed. Different optimized generators with resonance frequencies in the range from 100Hz up to 1kHz have been designed and fabricated, using dedicated MEMS technology processes. First unpackaged prototypes showed a quality factor of about 500 under atmospheric pressure and were able to generate an electrical output power of up to 1.9ÎĽW at an external acceleration of 1.6 m/s2
[FeFe]-Hydrogenases: recent developments and future perspectives
[FeFe]-Hydrogenases are the most efficient enzymes for catalytic hydrogen turnover. Their H2 production efficiency is hitherto unrivalled. However, functional details of the catalytic machinery and possible modes of application are discussed controversially. The incorporation of synthetically modified cofactors and utilization of semi-artificial enzymes only recently allowed us to shed light on key steps of the catalytic cycle. Herein, we summarize the essential findings regarding the redox chemistry of [FeFe]-hydrogenases and discuss their catalytic hydrogen turnover. We furthermore will give an outlook on potential research activities and exploit the utilization of synthetic cofactor mimics
Hadron Calorimeter (Projectile Spectator Detector—PSD) of NA61/SHINE experiment at CERN
The fixed target experiment NA61/SHINE at the CERN SPS aims to study the onset of deconfinement and search for the critical point of strongly interacting matter. A segmented hadron calorimeter, the Projectile Spectator Detector (PSD), is used in the NA61 experiment to determine the collision centrality and to reconstruct the event plane orientation in collisions of nuclei. The PSD precisely characterizes the event class for the analysis and provides the centrality selection at the trigger level The wide ranges of beam energies and sizes of the collision system require high dynamic range of the electronic readout. At the same time sensitivity to small signals is needed for the PSD calibration based on minimum ionizing particles. The PSD was also used for particle identification to distinguish electrons and positrons from pions in the 2017 data taking of reference measurements for Fermilab neutrino beam lines. The performance of the PSD for hadrons is discussed as well as a proposal to upgrade the PSD for the NA61 experimental program beyond 2020
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Characterization of Facies and Permeability Patterns in Carbonate Reservoirs Based on Outcrop Analogs
More than 13 billion barrels (Bbbl) of mobile oil and 17 Bbbl of residual oil will remain in the San Andres and Grayburg reservoir at abandonment under current development practices. Through the development and application of new recovery technology, a large part of this resource can be recovered. This report focuses on research for the development and testing of new techniques for improving recovery of this resource. Outcrop and subsurface geologic and engineering data are utilized to develop new methodologies through the integration of geologic observations and engineering data for improving numerical models that predict reservoir performance more accurately.
Extensive regional mapping of the 14-mile by 1,200-foot San Andres outcrop, located on the Algerita Escarpment, Guadalupe Mountains, New Mexico, demonstrates that the San Andres carbonate-ramp complex is composed of multiple depositional sequences that have significant basinward shifts in reservoir-quality facies tracts occurring across sequence boundaries. Detailed geologic and petrophysical mapping of three reservoir-quality facies tracts demonstrates that the fundamental scale of geologic description for reservoir characterization is the parasequence and its component rock-fabric-based facies. Descriptions of cores from the Seminole San Andres Unit illustrate that the parasequence is also the fundamental geologic scale for reservoir mapping in the subsurface.Bureau of Economic Geolog
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