14,231 research outputs found
Geometric Morphology of Granular Materials
We present a new method to transform the spectral pixel information of a
micrograph into an affine geometric description, which allows us to analyze the
morphology of granular materials. We use spectral and pulse-coupled neural
network based segmentation techniques to generate blobs, and a newly developed
algorithm to extract dilated contours. A constrained Delaunay tesselation of
the contour points results in a triangular mesh. This mesh is the basic
ingredient of the Chodal Axis Transform, which provides a morphological
decomposition of shapes. Such decomposition allows for grain separation and the
efficient computation of the statistical features of granular materials.Comment: 6 pages, 9 figures. For more information visit
http://www.nis.lanl.gov/~bschlei/labvis/index.htm
Instability of Rotationally Tuned Dipolar Bose-Einstein Condensates
The possibility of effectively inverting the sign of the dipole-dipole
interaction, by fast rotation of the dipole polarization, is examined within a
harmonically trapped dipolar Bose-Einstein condensate. Our analysis is based on
the stationary states in the Thomas-Fermi limit, in the corotating frame, as
well as direct numerical simulations in the Thomas-Fermi regime, explicitly
accounting for the rotating polarization. The condensate is found to be
inherently unstable due to the dynamical instability of collective modes. This
ultimately prevents the realization of robust and long-lived rotationally tuned
states. Our findings have major implications for experimentally accessing this
regime.Comment: 9 pages with 5 figure
Application of Stainless Steels in Nuclear Technology
SINCE the advent of nuclear technology, stainless steel has found new applications not only because of its properties of superior corrosion resistance and strength,
but also because of its superior behaviour with respect
to ionizing radiation . As a result stainless steel is
the most important material of construction that finds
use both in the production of nuclear pure materials and
in the construction of nuclear reactors
Valence fuctuation and magnetic ordering in EuNi2(P1-xGex)2 single crystals
Unusual phases and phase transitions are seen at the magnetic-nonmagnetic
boundary in Ce, Eu and Yb-based compounds. EuNiP is a very unusual
valence fluctuating Eu system, because at low temperatures the Eu valence stays
close to 2.5 instead of approaching an integer value. Eu valence and thus the
magnetic property in this system can be tuned by Ge substitution in P site as
EuNiGe is known to exhibit antiferromagnetc (AFM) ordering of
divalent Eu moments with = 30 K. We have grown
EuNi(PGe) (0.0 0.5) single crystals and
studied their magnetic, thermodynamic and transport properties. Increasing Ge
doping to 0.4 results in a well-defined AFM ordered state with = 12
K for = 0.5. Moreover, the reduced value of magnetic entropy for = 0.5
at suggests the presence of valance fluctuation/ Kondo effect in this
compound. Interestingly, the specific heat exhibits an enhanced Sommerfeld
coefficient upon Ge doping. Subsequently, electronic structure calculations
lead to a non-integral valence in EuNiP but a stable divalent Eu
state in EuNiGe which is in good agreement with experimental results.Comment: 7 pages, 8 figure
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