11,197 research outputs found
Flux jumps, Second Magnetization Peak anomaly and the Peak Effect phenomenon in single crystals of and
We present magnetization measurements in single crystals of the tetragonal
compound, which exhibit the phenomenon of peak effect as well as
the second magnetization peak anomaly for H 0.5T (H c). At the lower
field (50mT H 200mT), we have observed the presence of flux jumps,
which seem to relate to a structural change in the local symmetry of the flux
line lattice (a first order re-orientation transition across a local field in
some parts of the sample, in the range of 100mT to 150mT). These flux jumps are
also observed in a single crystal of for H c in the field
region from 2 mT to 25 mT, which are compatible with the occurrence of a
re-orientation transition at a lower field in a cleaner crystal of this
compound, as compared to those of . Vortex phase diagrams drawn for
H c in and show that the ordered elastic glass
phase spans a larger part of (H, T) space in the former as compared to latter,
thereby, reaffirming the difference in the relative purity of the two samples.Comment: 11 pages, 14 figure
Vortex Phase Diagram of weakly pinned YBaCuO for H c
Vortex phase diagram in a weakly pinned crystal of YBCO for H c
is reviewed in the light of a recent elucidation of the process of `inverse
melting' in a Bismuth cuprate system and the imaging of an interface between
the ordered and the disordered regions across the peak effect in 2H-NbSe.
In the given YBCO crystal, a clear distinction can be made between the second
magnetization peak (SMP) and the peak effect (PE) between 65 K and 75 K. The
field region between the peak fields of the SMP (H) and the onset
fields of the PE (H)is not only continuously connected to the Bragg
glass phase at lower fields but it is also sandwiched between the higher
temperature vortex liquid phase and the lower temperature vortex glass phase.
Thus, an ordered vortex state between H and H can get
transformed to the (disordered) vortex liquid state on heating as well as to
the (disordered) vortex glass state on cooling, a situation analogous to the
thermal melting and the inverse melting phenomenon seen in a Bismuth cuprate.Comment: Presented in IWCC-200
Hydrogen absorption properties of amorphous (Ni0.6Nb0.4−yTay)100−xZrx membranes
Ni based amorphous materials have great potential as hydrogen purification membranes. In the present work
the melt spun (Ni0.6Nb0.4−yTay)100−xZrx with y=0, 0.1 and x=20, 30 was studied. The result of X-ray diffraction
spectra of the ribbons showed an amorphous nature of the alloys. Heating these ribbons below T < 400 °C, even
in a hydrogen atmosphere (1−10 bar), the amorphous structure was retained. The crystallization process was
characterized by differential thermal analysis and the activation energy of such process was obtained. The
hydrogen absorption properties of the samples in their amorphous state were studied by the volumetric method,
and the results showed that the addition of Ta did not significantly influence the absorption properties, a clear
change of the hydrogen solubility was observed with the variation of the Zr content. The values of the
hydrogenation enthalpy changed from ~37 kJ/mol for x=30 to ~9 kJ/mol for x=20. The analysis of the
volumetric data provides the indications about the hydrogen occupation sites during hydrogenation, suggesting
that at the beginning of the absorption process the deepest energy levels are occupied, while only shallower
energy levels are available at higher hydrogen content, with the available interstitial sites forming a continuum
of energy levels
A momentum-conserving, consistent, Volume-of-Fluid method for incompressible flow on staggered grids
The computation of flows with large density contrasts is notoriously
difficult. To alleviate the difficulty we consider a consistent mass and
momentum-conserving discretization of the Navier-Stokes equation.
Incompressible flow with capillary forces is modelled and the discretization is
performed on a staggered grid of Marker and Cell type. The Volume-of-Fluid
method is used to track the interface and a Height-Function method is used to
compute surface tension. The advection of the volume fraction is performed
using either the Lagrangian-Explicit / CIAM (Calcul d'Interface Affine par
Morceaux) method or the Weymouth and Yue (WY) Eulerian-Implicit method. The WY
method conserves fluid mass to machine accuracy provided incompressiblity is
satisfied which leads to a method that is both momentum and mass-conserving. To
improve the stability of these methods momentum fluxes are advected in a manner
"consistent" with the volume-fraction fluxes, that is a discontinuity of the
momentum is advected at the same speed as a discontinuity of the density. To
find the density on the staggered cells on which the velocity is centered, an
auxiliary reconstruction of the density is performed. The method is tested for
a droplet without surface tension in uniform flow, for a droplet suddenly
accelerated in a carrying gas at rest at very large density ratio without
viscosity or surface tension, for the Kelvin-Helmholtz instability, for a
falling raindrop and for an atomizing flow in air-water conditions
Patient reactions to a web-based cardiovascular risk calculator in type 2 diabetes: a qualitative study in primary care.
Use of risk calculators for specific diseases is increasing, with an underlying assumption that they promote risk reduction as users become better informed and motivated to take preventive action. Empirical data to support this are, however, sparse and contradictory
Fission widths of hot nuclei from Langevin dynamics
Fission dynamics of excited nuclei is studied in the framework of Langevin
equation. The one body wall-and-window friction is used as the dissipative
force in the Langevin equation. In addition to the usual wall formula friction,
the chaos weighted wall formula developed earlier to account for
nonintegrability of single-particle motion within the nuclear volume is also
considered here. The fission rate calculated with the chaos weighted wall
formula is found to be faster by about a factor of two than that obtained with
the usual wall friction. The systematic dependence of fission width on
temperature and spin of the fissioning nucleus is investigated and a simple
parametric form of fission width is obtained.Comment: RevTex, 12 pages including 9 Postscript figure
Seed Production of \u3cem\u3eBrachiaria ruziziensis\u3c/em\u3e in India--Seed Collection Methods and Feed Opportunities
Brachiaria ruziziensis is an important fodder crop suitable for high rainfall areas and soils with low nutrient supply. Though the area under B. ruziziensis cultivation in India is not properly documented, it is widely grown in Kerala (Stür et al. 1996) and in parts of Karnataka and Goa. By virtue of its shade tolerance and adaptability, B. ruziziensis have wide scope for adoption in other parts of India. In India, Brachiaria is mainly planted through root slips as availability of good quality filled seeds is very less. It is known that the proportion of filled to unfilled seeds depends on method of harvest and seed collection method (Hare et al., 2007). Appropriate method of harvest depends on growth habit, synchrony of crop development, standing seeds, fallen seeds, availability of labour and on previous experience. Hence a study was conducted for first time in India to standardise harvesting and seed collection method in B.ruziziensis
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