807 research outputs found
Strong Pinning Enhancement in MgB2 Using Very Small Dy2O3 Additions
0.5 to 5.0 wt.% Dy2O3 was in-situ reacted with Mg + B to form pinned MgB2.
While Tc remained largely unchanged, Jc was strongly enhanced. The best sample
(only 0.5 wt.% Dy2O3) had a Jc of 6.5 x 10^5 A/cm^2 at 6K, 1T and 3.5 x 10^5
A/cm^2 at 20K, 1T, around a factor of 4 higher compared to the pure sample, and
equivalent to hot-pressed or nano-Si added MgB2 at below 1T. Even distributions
of nano-scale precipitates of DyB4 and MgO were observed within the grains. The
room temperature resistivity decreased with Dy2O3 indicative of improved grain
connectivity.Comment: 13 pages, 4 figures and 1 tabl
Raising Bi-O bands above the Fermi energy level of hole-doped BiSrCaCuO and other cuprate superconductors
The Fermi surface (FS) of BiSrCaCuO
(Bi2212) predicted by band theory displays Bi-related pockets around the
point, which have never been observed experimentally. We show that
when the effects of hole doping either by substituting Pb for Bi or by adding
excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi
energy () and the resulting first-principles FS is in remarkable accord
with measurements. With decreasing hole-doping the Bi-O bands drop below
and the system self-dopes below a critical hole concentration. Computations on
other Bi- as well as Tl- and Hg-based compounds indicate that lifting of the
cation-derived band with hole doping is a general property of the electronic
structures of the cuprates.Comment: 4 pages, 4 figures; PRL (2006, in press
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Introducing creativity techniques and software apps to the care of people with dementia
This poster reports research to introduce creative problem solving techniques and software to the care for people with dementia in residential homes
Improved Current Densities in MgB2 By Liquid-Assisted Sintering
Polycrystalline MgB2 samples with GaN additions were prepared by reaction of
Mg, B, and GaN powders. The presence of Ga leads to a low melting eutectic
phase which allowed liquid phase sintering and produces plate-like grains. For
low-level GaN additions (5% at. % or less), the critical transition
temperature, Tc, remained unchanged and in 1T magnetic field, the critical
current density, Jc was enhanced by a factor of 2 and 10, for temperatures of
\~5K and 20K, respectively. The values obtained are approaching those of hot
isostatically pressed samples.Comment: 12 pages, 1 table, 4 figures, accepted in Applied Physics Letter
Evaluating coefficient of performance and rate of moisture loss of some biomass humidifiers materials with a developed simple direct stand-alone evaporative cooling system for farmers
© 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)The purpose of this study was to investigate the feasibility of deploying direct evaporative cooler with Jute fiber, palm fruit mesocarp fiber and wooden charcoal as humidifier in Nigeria. High cost of imported evaporative coolers and humidifiers can discourage farmers and limited adoption of evaporative cooling technology. For this purpose an experimental direct evaporative cooling test rig was developed and assembled in south western Nigeria with biomass humidifier. The evaluation parameters were the humidifying efficiency, the rate of moisture loss, coefficient of performance and sensible heat ratio. The humidifier presented average cooling efficiency of 55.9 to 78.62 %, average rate of moisture loss of 1.37 × 10 -3 to 2.61 × 10 -3 kg/s, average COP of 8.48 to 23.42 (EER of 11 to 78) and average sensible heat ratio of 1.28 × 10 -4 to 4.06 × 10 -4 for the air velocity of 3.0 to 4.5 m/s. The obtain performance can be better in a dryer month or nearly impossible in a very wet month as the humidifying efficiency of direct evaporative coolers are found to diminish at high humidity. To avoid casting doubt on the effectiveness of direct evaporative cooler by farmers, it should only serve as stop gap preservation equipment and deployed during the favorable weather condition especially during the winter when the air is dry. These can be identified from the metrological charts of the chosen location.Peer reviewe
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Ferroelectric/multiferroic self-assembled vertically aligned nanocomposites: Current and future status
Thin-Film Trilayer Manganate Junctions
Spin-dependent conductance across a manganate-barrier-manganate junction has
recently been demonstrated. The junction is a LaSrMnO%
-SrTiO-La SrMnO trilayer device supporting
current-perpendicular transport. Large magnetoresistance of up to a factor of
five change was observed in these junctions at 4.2K in a relatively low field
of the order of 100 Oe. Temperature and bias dependent studies revealed a
complex junction interface structure whose materials physics has yet to be
understood.Comment: 20 pages, 14 figures. To appear in Phil. Trans. R. Soc. Lond. A
vol.356 (1998
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Lithium outdiffusion in LiTi<inf>2</inf>O<inf>4</inf> thin films grown by pulsed laser deposition
We report surface chemical cation composition analysis of high quality superconducting LiTiO thin films, grown epitaxially on MgAlO (111) substrates by pulsed laser deposition. The superconducting transition temperature of the films was ~13.8 K.
Surface chemical composition is crucial for the formation of a good metal/insulator interface for integrating LiTiO into full-oxide spin-filtering devices in order to minimize the formation of structural defects and increase the spin polarisation efficiency. In consideration of this, we report a detailed angle resolved x-ray photoelectron spectroscopy analysis. Results show Li segregation at the surface of LiTiO films. We attribute this process due to outdiffusion of Li toward the outermost LiTiO layers.The research leading to these results has received funding from the European Union Seventh Framework Programme ([FP7/2007–2013] [FP7/2007–2011]) under Grant agreement 316657 (SpinIcur), the European Research Council AdG (291442 “Superspin”), European Research Council AdG (247276 “NOVOX”) and the EPSRC (Equipment Account Grant EP/K035282/1).This is the final version of the article. It first appeared from Elsevier via https://doi.org/10.1016/j.jcrysgro.2016.09.01
Normal state properties of high angle grain boundaries in (Y,Ca)Ba2Cu3O7-delta
By lithographically fabricating an optimised Wheatstone bridge geometry, we
have been able to make accurate measurements of the resistance of grain
boundaries in Y1-xCaxBa2Cu3O7-d between the superconducting transition
temperature, Tc, and room temperature. Below Tc the normal state properties
were assessed by applying sufficiently high currents. The behaviour of the
grain boundary resistance versus temperature and of the conductance versus
voltage are discussed in the framework charge transport through a tunnel
barrier. The influence of misorientation angle, oxygen content, and calcium
doping on the normal state properties is related to changes of the height and
shape of the grain boundary potential barrier.Comment: 17 pages, 1 table, 5 figures, submitted to PR
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