1,797 research outputs found
Exotic Smooth Structures on Small 4-Manifolds
Let M be either CP^2#3CP^2bar or 3CP^2#5CP^2bar. We construct the first
example of a simply-connected symplectic 4-manifold that is homeomorphic but
not diffeomorphic to M.Comment: 11 page
Exotic smooth structures on 4-manifolds with zero signature
For every integer , we construct infinite families of mutually
nondiffeomorphic irreducible smooth structures on the topological -manifolds
and (2k-1)(\CP#\CPb), the connected sums of
copies of and \CP#\CPb.Comment: 6 page
Identification of image attributes that are most affected with changes in displayed image size
This paper describes an investigation of changes in image appearance when images are viewed at different image sizes on a high-end LCD device. Two digital image capturing devices of different overall image quality were used for recording identical natural scenes with a variety of pictorial contents. From each capturing device, a total of sixty four captured scenes, including architecture, nature, portraits, still and moving objects and artworks under various illumination conditions and recorded noise level were selected. The test set included some images where camera shake was purposefully introduced. An achromatic version of the image set that contained only lightness information was obtained by processing the captured images in CIELAB space. Rank order experiments were carried out to determine which image attribute(s) were most affected when the displayed image size was altered. These evaluations were carried out for both chromatic and achromatic versions of the stimuli. For the achromatic stimuli, attributes such as contrast, brightness, sharpness and noisiness were rank-ordered by the observers in terms of the degree of change. The same attributes, as well as hue and colourfulness, were investigated for the chromatic versions of the stimuli. Results showed that sharpness and contrast were the two most affected attributes with changes in displayed image size. The ranking of the remaining attributes varied with image content and illumination conditions. Further, experiments were carried out to link original scene content to the attributes that changed mostly with changes in image size
Social behaviour of pigs
Improper social behavior development brings problems in later social life. Several time points are known to be crucial for the development and in other words, susceptible to interruptions during those time points. In conventional pigs, those time points could be categorized to three interaction periods, the period for piglet-sow interaction (suckling), between littermates interaction (before weaning), social interaction with other littermates (after weaning).
In this research, 4 cages (51 pigs) of pigs were observed for figuring out circadian rhythm and social behavior pattern. In group observation, the circadian rhythm of conventional pigs was established as a pair of active hours in early morning and early evening. Over three recordings of three different time points of day 10, 14 and 24, the behavior status ‘active’ increased with their physical developmental status and this is suggesting increase in potential social behaviors. In individual observation, the environmental change induced by maternal separation and mixing of other littermates resulted change in specific social behavioral pattern. Additional second individual observation also showed changed social behavioral pattern.
The results in this research could suggest the needs for proper social behavioral development according to the critical time points and social environmental changes so that prevent existing behavioral problems and improve the welfare of conventional farm pigs
First-principles study of (BiScO3){1-x}-(PbTiO3){x} piezoelectric alloys
We report a first-principles study of a class of (BiScO3)_{1-x}-(PbTiO3)_x
(BS-PT) alloys recently proposed by Eitel et al. as promising materials for
piezoelectric actuator applications. We show that (i) BS-PT displays very large
structural distortions and polarizations at the morphotropic phase boundary
(MPB) (we obtain a c/a of ~1.05-1.08 and P_tet of ~1.1 C/m^2); (ii) the
ferroelectric and piezoelectric properties of BS-PT are dominated by the onset
of hybridization between Bi/Pb-6p and O-2p orbitals, a mechanism that is
enhanced upon substitution of Pb by Bi; and (iii) the piezoelectric responses
of BS-PT and Pb(Zr_{1-x}Ti_x)O3 (PZT) at the MPB are comparable, at least as
far as the computed values of the piezoelectric coefficient d_15 are concerned.
While our results are generally consistent with experiment, they also suggest
that certain intrinsic properties of BS-PT may be even better than has been
indicated by experiments to date. We also discuss results for PZT that
demonstrate the prominent role played by Pb displacements in its piezoelectric
properties.Comment: 6 pages, with 3 postscript figures embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/ji_bi/index.htm
Novel Synthesis and High Pressure Behavior of Na0.3CoO2 x 1.3 H2O and Related Phases
We have prepared powder samples of NaxCoO2 x yH2O using a new synthesis
route. Superconductivity was observed in Na0.3CoO2 x 1.3H2O between 4 and 5K as
indicated by the magnetic susceptibility. The bulk compressibilities of
Na0.3CoO2 x 1.3H2O, Na0.3CoO2 x 0.6H2O and Na0.3CoO2 were determined using a
diamond anvil cell and synchrotron powder diffraction. Chemical changes
occurring under pressure when using different pressure transmitting media are
discussed and further transport measurements are advocated.Comment: 7 pages, 4 figures, PRrapid submitte
Ab initio study of ferroelectric domain walls in PbTiO3
We have investigated the atomistic structure of the 180-degree and 90-degree
domain boundaries in the ferroelectric perovskite compound PbTiO3 using a
first-principles ultrasoft-pseudopotential approach. For each case we have
computed the position, thickness and creation energy of the domain walls, and
an estimate of the barrier height for their motion has been obtained. We find
both kinds of domain walls to be very narrow with a similar width of the order
of one to two lattice constants. The energy of the 90-dergree domain wall is
calculated to be 35 mJ/m^2, about a factor of four lower than the energy of its
180-degree counterpart, and only a miniscule barrier for its motion is found.
As a surprising feature we detected a small offset of 0.15-0.2 eV in the
electrostatic potential across the 90-degree domain wall.Comment: 12 pages, with 9 postscript figures embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/bm_dw/index.htm
Lognormal Properties of SGR 1806-20 and Implications for Other SGR Sources
The time interval between successive bursts from SGR 1806-20 and the
intensity of these bursts are both consistent with lognormal distributions.
Monte Carlo simulations of lognormal burst models with a range of distribution
parameters have been investigated. The main conclusions are that while most
sources like SGR 1806-20 should be detected in a time interval of 25 years,
sources with means about 100 times longer have a probability of about 5\% of
being detected in the same interval. A new breed of experiments that operate
for long periods are required to search for sources with mean recurrence
intervals much longer than SGR 1806-20.Comment: 4 pages, latex with seperate file containing 2 uuencoded, gzip'ed,
tarred, .eps figures. Replaced with file that does not use kluwer.sty to
allow automatic postscript generation. To appear in proceedings of ESLAB 2
Anomalous enhancement of tetragonality in PbTiO3 induced by negative pressure
Using a first-principles approach based on density-functional theory, we find
that a large tetragonal strain can be induced in PbTiO3 by application of a
negative hydrostatic pressure. The structural parameters and the dielectric and
dynamical properties are found to change abruptly near a crossover pressure,
displaying a ``kinky'' behavior suggestive of proximity to a phase transition.
Analogous calculations for BaTiO3 show that the same effect is also present
there, but at much higher negative pressure. We investigate this unexpected
behavior of PbTiO3 and discuss an interpretation involving a phenomenological
description in terms of a reduced set of relevant degrees of freedom.Comment: 9 pages, with 9 postscript figures embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/st_pbti/index.htm
Fluctuation-Induced Interactions between Rods on a Membrane
We consider the interaction between two rods embedded in a fluctuating
surface. The modification of fluctuations by the rods leads to an attractive
long-range interaction between them. We consider fluctuations governed by
either surface tension (films) or bending rigidity (membranes). In both cases
the interaction falls off with the separation of the rods as . The
orientational part of the interaction is proportional to in the former case, and to in the latter, where and
are angles between the rods and the line joining them. These
interactions are somewhat reminiscent of dipolar forces and will tend to align
collections of such rods into chains.Comment: REVTEX, 14 pages, with 2 Postscript figure
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