818 research outputs found
Investigating prescriptions for artificial resistivity in smoothed particle magnetohydrodynamics
In numerical simulations, artificial terms are applied to the evolution
equations for stability. To prove their validity, these terms are thoroughly
tested in test problems where the results are well known. However, they are
seldom tested in production-quality simulations at high resolution where they
interact with a plethora of physical and numerical algorithms. We test three
artificial resistivities in both the Orszag-Tang vortex and in a star formation
simulation. From the Orszag-Tang vortex, the Price et. al. (2017) artificial
resistivity is the least dissipative thus captures the density and magnetic
features; in the star formation algorithm, each artificial resistivity
algorithm interacts differently with the sink particle to produce various
results, including gas bubbles, dense discs, and migrating sink particles. The
star formation simulations suggest that it is important to rely upon physical
resistivity rather than artificial resistivity for convergence.Comment: 8 pages, 7 figures. Proceedings of the "12th international SPHERIC
workshop", Ourense, Spain, 13-15 June 201
Windfall Wealth and Shale Development in Appalachian Ohio: Preliminary Results
The response by agriculture/natural resources and community development Extension educators to shale development in Ohio has been proactive. There is a need, however, to understand the impact that shale development is having broadly on families and communities and specifically as it relates to lease payments and the perceptions and realities of resource windfalls or sudden wealth. This article presents the preliminary results of a qualitative study. In the course of data analysis, themes emerged around the topics of money, family and community life, and land. A discussion of the role of Extension professionals is provided
Drop entrainment from the surface of oil mist filters: mechanisms, kinetics, and drop spectra
Oil entrainment from coalescence filters has been characterized by different techniques. Drop spectra and entrainment rates were measured by a combination of techniques from 1 mm over long periods of time. Dominant entrainment mechanism(s) are identified on the basis of comparisons of entrainment rates measured in different regions of the filter surface with rates of air bubble formation, measurements of oil film thickness, as well as visual observations. Experiments are supported by force estimates to entrain oil into the gas flow
Thermal stabilization of metal matrix nanocomposites by nanocarbon reinforcements
Metal matrix composites reinforced by nanocarbon materials, such as carbon nanotubes or nanodiamonds, are very promising materials for a large number of functional and structural applications. Carbon
nanotubes and nanodiamonds-reinforced metal matrix nanocomposites with different concentrations of
the carbon phase were processed by high-pressure torsion deformation and the evolving nanostructures
were thoroughly analyzed by electron microscopy. Particular emphasis is placed on the thermal stability
of the nanocarbon reinforced metal matrix composites, which is less influenced by the amount of added
nanocarbon reinforcements than by the nanocarbon reinforcement type and its distribution in the metal
matrix
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Tungsten fibre-reinforced composites for advanced plasma facing components
AbstractThe European Fusion Roadmap foresees water cooled plasma facing components in a first DEMO design in order to provide enough margin for the cooling capacity and to only moderately extrapolate the technology which was developed and tested for ITER. In order to make best use of the water cooling concept copper (Cu) and copper-chromium-zirconium alloy (CuCrZr) are envisaged as heat sink whereas as armour tungsten (W) based materials will be used. Combining both materials in a high heat flux component asks for an increase of their operational range towards higher temperature in case of Cu/CuCrZr and lower temperatures for W. A remedy for both issues- brittleness of W and degrading strength of CuCrZr- could be the use of W fibres (Wf) in W and Cu based composites. Fibre preforms could be manufactured with industrially viable textile techniques. Flat textiles with a combination of 150/70 µm W wires have been chosen for layered deposition of tungsten-fibre reinforced tungsten (Wf/W) samples and tubular multi-layered braidings with W wire thickness of 50 µm were produced as a preform for tungsten-fibre reinforced copper (Wf /Cu) tubes. Cu melt infiltration was performed together with an industrial partner resulting in sample tubes without any blowholes. Property estimation by mean field homogenisation predicts strongly enhanced strength of the Wf/CuCrZr composite compared to its pure CuCrZr counterpart. Wf /W composites show very high toughness and damage tolerance even at room temperature. Cyclic load tests reveal that the extrinsic toughening mechanisms counteracting the crack growth are active and stable. FEM simulations of the Wf/W composite suggest that the influence of fibre debonding, which is an integral part of the toughening mechanisms, and reduced thermal conductivity of the fibre due to the necessary interlayers do not strongly influence the thermal properties of future components
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