65,799 research outputs found
Effects of nanoscale spatial inhomogeneity in strongly correlated systems
We calculate ground-state energies and density distributions of Hubbard
superlattices characterized by periodic modulations of the on-site interaction
and the on-site potential. Both density-matrix renormalization group and
density-functional methods are employed and compared. We find that small
variations in the on-site potential can simulate, cancel, or even
overcompensate effects due to much larger variations in the on-site interaction
. Our findings highlight the importance of nanoscale spatial inhomogeneity
in strongly correlated systems, and call for reexamination of model
calculations assuming spatial homogeneity.Comment: 5 pages, 1 table, 4 figures, to appear in PR
Investigation of the agricultural resources in Sri Lanka
The author has identified the following significant results. Several in-house capabilities were developed. The facilities to prepare color composites of excellent quality were developed, using bulk B/W 70 mm transparencies or 1:1,000,000 positive transparencies. These color composites were studied through optical devices on light tables. A zoom transfer scope was also added, enabling direct transfer of LANDSAT composite data on to base maps
Using mixed methods for analysing culture : The Cultural Capital and Social Exclusion project
This paper discusses the use of material generated in a mixed method investigation into cultural tastes and practices, conducted in Britain from 2003 to 2006, which employed a survey, focus groups and household interviews. The study analysed the patterning of cultural life across a number of fields, enhancing the empirical and methodological template provided by Bourdieuâs Distinction. Here we discuss criticisms of Bourdieu emerging from subsequent studies of class, culture and taste, outline the arguments related to the use of mixed methods and present illustrative results from the analysis of these different types of data. We discuss how the combination of quantitative and qualitative methods informed our analysis of cultural life in contemporary Britain. No single method was able to shed light on all aspects of our inquiry, lending support to the view that mixing methods is the most productive strategy for the investigation of complex social phenomena
Symbolic Sequences and Tsallis Entropy
We address this work to investigate symbolic sequences with long-range
correlations by using computational simulation. We analyze sequences with two,
three and four symbols that could be repeated times, with the probability
distribution . For these sequences, we verified that
the usual entropy increases more slowly when the symbols are correlated and the
Tsallis entropy exhibits, for a suitable choice of , a linear behavior. We
also study the chain as a random walk-like process and observe a nonusual
diffusive behavior depending on the values of the parameter .Comment: Published in the Brazilian Journal of Physic
Some new class of Chaplygin Wormholes
Some new class of Chaplygin wormholes are investigated in the framework of a
Chaplygin gas with equation of state , . Since
empty spacetime () does not follow Chaplygin gas, so the
interior Chaplygin wormhole solutions will never asymptotically flat. For this
reason, we have to match our interior wormhole solution with an exterior vacuum
solution i.e. Schwarzschild solution at some junction interface, say .
We also discuss the total amount of matter characterized by Chaplygin gas that
supplies fuel to construct a wormhole.Comment: 14 pages, 12 figures, Accepted for publication in Mod.Phys.Lett.
Household water security through stored rainwater and consumer acceptability: a case study of the Anuradhapura District
Rainwater harvesting has increased in popularity in Sri Lanka over the past two decades due to the number of water supply projects funded by the government and non-governmental organizations (NGOs). The stored rainwater can provide accessible, reliable, timely and adequate supplies of water to households but there are uncertainties as to safety, in terms of water quality, and consumer acceptability. A study was, therefore, conducted in the Anuradhapura District, in the dry zone, to assess consumer acceptability of stored rainwater for household purposes and to conduct rainwater quality tests in a laboratory. The majority of households in Anuradhapura meet their drinking water requirements from protected wells (59.6 %). Prior to the project, people greatly preferred open wells as a source of domestic water, followed by tubewells, because they believed that water in open wells is of good quality and drinkable. However, stored rainwater has become the priority source now, especially through roof rainwater harvesting (RRWH), which is used during the dry periods. The study revealed that more than 85 % of households use stored rainwater for drinking although some have concerns over the quality and only drink it after boiling. The easy accessibility of water and the assurance by the project team that it is of good quality are the main reasons that people are willing to drink it. The acceptability of stored rainwater for consumption was very high in water-scarce areas and with the increasing distance to the nearest and alternative sources of good-quality water. Of those who felt that they had adequate water, 84 % of the sample households found it adequate in the wet season but only 21 % in the dry season. Water quality analysis revealed that the chemical and physical quality of stored rainwater is within the acceptable range with respect to Sri Lankan Standards, SLS: 614, for potable water quality (SLIS 1983). Other domestic water sources exceeded standards for electrical conductivity, total alkalinity, hardness, ammonium nitrogen, fluorides and total iron. However, stored rainwater was of lower biological quality than other domestic water sources.Length: pp.87-97Domestic waterWater securityWater harvestingWater qualityRural areasCase studies
Tunable photonic band gaps with coherently driven atoms in optical lattices
Optical lattice loaded with cold atoms can exhibit a tunable photonic band
gap for a weak probe field under the conditions of electromagnetically induced
transparency. This system possesses a number of advantageous properties,
including reduced relaxation of Raman coherence and the associated probe
absorption, and simultaneous enhancement of the index modulation and the
resulting reflectivity of the medium. This flexible system has a potential to
serve as a testbed of various designs for the linear and nonlinear photonic
band gap materials at a very low light level and can be employed for realizing
deterministic entanglement between weak quantum fields
Activation Energy of Metastable Amorphous Ge2Sb2Te5 from Room Temperature to Melt
Resistivity of metastable amorphous Ge2Sb2Te5 (GST) measured at device level
show an exponential decline with temperature matching with the steady-state
thin-film resistivity measured at 858 K (melting temperature). This suggests
that the free carrier activation mechanisms form a continuum in a large
temperature scale (300 K - 858 K) and the metastable amorphous phase can be
treated as a super-cooled liquid. The effective activation energy calculated
using the resistivity versus temperature data follow a parabolic behavior, with
a room temperature value of 333 meV, peaking to ~377 meV at ~465 K and reaching
zero at ~930 K, using a reference activation energy of 111 meV (3kBT/2) at
melt. Amorphous GST is expected to behave as a p-type semiconductor at Tmelt ~
858 K and transitions from the semiconducting-liquid phase to the
metallic-liquid phase at ~ 930 K at equilibrium. The simultaneous Seebeck (S)
and resistivity versus temperature measurements of amorphous-fcc mixed-phase
GST thin-films show linear S-T trends that meet S = 0 at 0 K, consistent with
degenerate semiconductors, and the dS/dT and room temperature activation energy
show a linear correlation. The single-crystal fcc is calculated to have dS/dT =
0.153 {\mu}V/K for an activation energy of zero and a Fermi level 0.16 eV below
the valance band edge.Comment: 5 pages, 5 figure
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