38,561 research outputs found
Review of the Synergies Between Computational Modeling and Experimental Characterization of Materials Across Length Scales
With the increasing interplay between experimental and computational
approaches at multiple length scales, new research directions are emerging in
materials science and computational mechanics. Such cooperative interactions
find many applications in the development, characterization and design of
complex material systems. This manuscript provides a broad and comprehensive
overview of recent trends where predictive modeling capabilities are developed
in conjunction with experiments and advanced characterization to gain a greater
insight into structure-properties relationships and study various physical
phenomena and mechanisms. The focus of this review is on the intersections of
multiscale materials experiments and modeling relevant to the materials
mechanics community. After a general discussion on the perspective from various
communities, the article focuses on the latest experimental and theoretical
opportunities. Emphasis is given to the role of experiments in multiscale
models, including insights into how computations can be used as discovery tools
for materials engineering, rather than to "simply" support experimental work.
This is illustrated by examples from several application areas on structural
materials. This manuscript ends with a discussion on some problems and open
scientific questions that are being explored in order to advance this
relatively new field of research.Comment: 25 pages, 11 figures, review article accepted for publication in J.
Mater. Sc
Improving the scalability of parallel N-body applications with an event driven constraint based execution model
The scalability and efficiency of graph applications are significantly
constrained by conventional systems and their supporting programming models.
Technology trends like multicore, manycore, and heterogeneous system
architectures are introducing further challenges and possibilities for emerging
application domains such as graph applications. This paper explores the space
of effective parallel execution of ephemeral graphs that are dynamically
generated using the Barnes-Hut algorithm to exemplify dynamic workloads. The
workloads are expressed using the semantics of an Exascale computing execution
model called ParalleX. For comparison, results using conventional execution
model semantics are also presented. We find improved load balancing during
runtime and automatic parallelism discovery improving efficiency using the
advanced semantics for Exascale computing.Comment: 11 figure
The chemistry of fluorine-bearing molecules in diffuse and dense interstellar gas clouds
We present a theoretical investigation of the chemistry of fluorine-bearing
molecules in diffuse and dense interstellar gas clouds. The chemistry of
interstellar fluorine is qualitatively different from that of any other
element, because - unlike the neutral atoms of any other element found in
diffuse or dense molecular clouds - atomic fluorine undergoes an exothermic
reaction with molecular hydrogen. Over a wide range of conditions attained
within interstellar gas clouds, the product of that reaction - hydrogen
fluoride - is predicted to be the dominant gas-phase reservoir of interstellar
fluorine nuclei. Our model predicts HF column densities ~ 1.E+13 cm-2 in dark
clouds and column densities as large as 1.E-11 cm-2 in diffuse interstellar gas
clouds with total visual extinctions as small as 0.1 mag. Such diffuse clouds
will be detectable by means of absorption line spectroscopy of the J = 1 - 0
transition at 243.2 micron using the Stratospheric Observatory for Infrared
Astronomy (SOFIA) and the Herschel Space Observatory (HSO). The CF+ ion is
predicted to be the second most abundant fluorine-bearing molecule, with
typical column densities a factor ~ 100 below those of HF; with its lowest two
rotational transitions in the millimeter-wave spectral region, CF+ may be
detectable from ground-based observatories. HF absorption in quasar spectra is
a potential probe of molecular gas at high redshift, providing a possible
bridge between the UV/optical observations capable of probing H2 in low column
density systems and the radio/millimeter-wavelength observations that probe
intervening molecular clouds of high extinction and large molecular fraction;
at redshifts beyond ~ 0.3, HF is potentially detectable from ground-based
submillimeter observatories in several atmospheric transmission windows.Comment: 34 pages, including 11 figures (10 color), accepted for publication
in Ap
Recommended from our members
ToScA North America (6 – 8 June 2017, The University of Texas, Austin, TX) Program
ToScA North America will address key areas of science,
including Multi-modal Imaging, Geosciences, Forensics, Increasing Contrast,
Educational Outreach, Data, Materials Science and Medical and Biological
Science.University of Texas High-Resolution X-ray CT Facility (UTCT);
Jackson School of Geosciences, The University of Texas at Austin;
Natural History Museum (London);
Royal Microscopical Society (Oxford, UK)Geological Science
Wayne E. Sabbe Arkansas Soil Fertility Studies 2017
Rapid technological changes in crop management and production require that the research efforts be presented in an expeditious manner. The contributions of soil fertility and fertilizers are major production factors in all Arkansas crops. The studies described within will allow producers to compare their practices with the university’s research efforts. Additionally, soil-test data and fertilizer sales are presented to allow comparisons among years, crops, and other areas within Arkansas
Grain Growth-Controlled Giant Permittivity in Soft Chemistry CaCu3Ti4O12 Ceramics
We report a dielectric constant of up to 5.4105 at room temperature and 1 kHz for CaCu3Ti4O12 (CCTO) ceramics,
derived from multiphase powders (coprecipitation products),
made by a ‘‘chimie douce’’ (coprecipitation) method, and then sintered in air. The sintered products are pure-phase CCTO ceramics. The high dielectric constant is achieved by tuning the size of grains and the thickness of grain boundaries. The grain growth is controlled by varying the concentration of excess CuO in the initial powder (calcined coprecipitation products) between 1 and 3.1 wt%. The dielectric constant of pure CCTO ceramics increases with the initial CuO concentration, reaching its maximum at 2.4 wt% of CuO. A further increase of excess CuO in powders results in a permittivity decrease, accompanied by the formation of CuO as a separate phase in the sintered products. The unusual grain growth behavior is attributed to a eutectic
reaction between CuO and TiO2 present in the initial powder
Meiobenthos of the discovery Bay Lagoon, Jamaica, with an emphasis on nematodes.
PhDSediment granulometry, microphytobenthos and meiobenthos were investigated
at five habitats (white and grey sands, backreef border, shallow and deep
thalassinid ghost shrimp mounds) within the western lagoon at Discovery Bay,
Jamaica. Habitats were ordinated into discrete stations based on sediment
granulometry. Microphytobenthic chlorophyll-a ranged between 9.5- and 151.7
mg m-2 and was consistently highest at the grey sand habitat over three sampling
occasions, but did not differ between the remaining habitats. It is suggested that
the high microphytobenthic biomass in grey sands was related to upwelling of
nutrient rich water from the nearby main bay, and the release and excretion of
nutrients from sediments and burrowing heart urchins, respectively. Meiofauna
abundance ranged from 284- to 5344 individuals 10 cm-2 and showed spatial
differences depending on taxon. Of 22 higher taxa recorded, nematodes
dominated followed by copepods, together accounting for ~80 % of all
individuals. Both taxa were most abundant in grey sands, suggesting a response,
either directly or indirectly, to the high microphyte biomass. Significant withinhabitat
spatial variability in both meio- and microphytobenthos was found,
causes of which are discussed. Nematode feeding groups varied between
habitats. Fine white sands and both thalassinid mound habitats were dominated
by non-selective deposit feeders. Slender and plump nematode morphotypes
were found, yet the plump morphotype was largely absent from coarse sands
subjected to high wave swash at the backreef border habitat. Here, nematode
lengths were significantly higher than at other habitats. Nematode biomass
spectra differed significantly between habitats, with a shift in peak biomass
values towards larger size classes in the disturbed sediments. It is suggested that
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longer and larger nematodes represent an adaptation to sediment disturbance,
helping to prevent being displaced from the benthos by hydrodynamic forces and
bioturbation
Comprehensive Review of Opinion Summarization
The abundance of opinions on the web has kindled the study of opinion summarization over the last few years. People have introduced various techniques and paradigms to solving this special task. This survey attempts to systematically investigate the different techniques and approaches used in opinion summarization. We provide a multi-perspective classification of the approaches used and highlight some of the key weaknesses of these approaches. This survey also covers evaluation techniques and data sets used in studying the opinion summarization problem. Finally, we provide insights into some of the challenges that are left to be addressed as this will help set the trend for future research in this area.unpublishednot peer reviewe
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