9,845 research outputs found
Entanglement Concentration Using Quantum Statistics
We propose an entanglement concentration scheme which uses only the effects
of quantum statistics of indistinguishable particles. This establishes the fact
that useful quantum information processing can be accomplished by quantum
statistics alone. Due to the basis independence of statistical effects, our
protocol requires less knowledge of the initial state than most entanglement
concentration schemes. Moreover, no explicit controlled operation is required
at any stage.Comment: 2 figure
Lower bounds on the dilation of plane spanners
(I) We exhibit a set of 23 points in the plane that has dilation at least
, improving the previously best lower bound of for the
worst-case dilation of plane spanners.
(II) For every integer , there exists an -element point set
such that the degree 3 dilation of denoted by in the domain of plane geometric spanners. In the
same domain, we show that for every integer , there exists a an
-element point set such that the degree 4 dilation of denoted by
The
previous best lower bound of holds for any degree.
(III) For every integer , there exists an -element point set
such that the stretch factor of the greedy triangulation of is at least
.Comment: Revised definitions in the introduction; 23 pages, 15 figures; 2
table
A New Interpretation of the Anomalous Magnetic and Optical Behaviour of Copper Acetate Monohydrate
Numerical Investigation of the Influence of Span-wise Force Variation in Circular Cylinders Undergoing Vortex Induced Vibrations at High Reynolds Number
The focus of this research is on the development
of a new approach for simulating vortex induced vibrations on
marine risers at high Reynolds numbers. This method considers
the span-wise variation of the lift and drag forces, and determines
the moment acting on the cylinder. The predicted motion then
consists of a rotational component to accompany the traditional
cross-stream and stream-wise translations normally associated
with vortex induced vibrations. This was accomplished by describing
the motion of the cylinder using a set of springs and
dampers. A moment acting on the cylinder causes the springs on
one end to compress, and stretch on the other, thus rotating the
cylinder.
A Large Eddy Simulation (LES) computational fluid dynamics
code running on 16 3Ghz processors was used to calculate the
unsteady flow and at each time step the hydrodynamic forces
acting on the cylinder were calculated in a separate routine based
on the pressure distribution around the cylinder. This information
was then used to solve two second-order ordinary differential
equations, which gave the velocity and displacement of the
cylinder in cross-flow and rotational planes. This information was
transferred back to the code where the cylinder was displaced
and another cycle of calculations was started.
The simulated results showed that the correlation length was
higher for a cylinder subject to pure translation compared to a
cylinder free to translate and rotate in the cross-stream direction.
This has implications for current numerical and experimental
techniques since it has been traditionally assumed that the
flow around a circular cylinder becomes two-dimensional during
vortex induced vibrations. Consequently, empirical,numerical
and experimental models have generally only considered cross
stream and/or stream-wise translation. The extent to which the
experimental apparatus or harmonic model may have influenced
the behavior of the riser by eliminating span-wise amplitude
variation is important information that should be considered for
future riser designs
Lattice-mismatch-induced granularity in CoPt-NbN and NbN-CoPt superconductor-ferromagnet heterostructures: Effect of strain
The effect of strain due to lattice mismatch and of ferromagnetic (FM)
exchange field on superconductivity (SC) in NbN-CoPt bilayers is investigated.
Two different bilayer systems with reversed deposition sequence are grown on
MgO (001) single crystals. While robust superconductivity with high critical
temperature (T_c ~ 15.3 K) and narrow transition width DelT_c ~ 0.4 K) is seen
in two types of CoPt-NbN/MgO heterostructures where the magnetic anisotropy of
CoPt is in-plane in one case and out-of-plane in the other, the NbN-CoPt/MgO
system shows markedly suppressed SC response. The reduced SC order parameter of
this system, which manifests itself in Tc, temperature dependence of critical
current density J_c (T), and angular (Phi) variation of flux-flow resistivity
Rho_f is shown to be a signature of the structure of NbN film and not a result
of the exchange field of CoPt. The Rho_f (H,T,Phi) data further suggest that
the domain walls in the CoPt film are of the Neel type and hence do not cause
any flux in the superconducting layer. A small, but distinct increase in the
low-field critical current of the CoPt-NbN couple is seen when the magnetic
layer has perpendicular anisotropy.Comment: 9 figure
Probabilistic creep life assessment of austenitic stainless steel
Experimental investigations on the creep behaviour of engineering materials are frequently conducted for the purposes of design, development and service life prediction. However, tests on a single specimen yield a definite value for each material parameter. But when a number of specimens are tested, the parameter values randomly fluctuate from specimen to specimen. The scatter observed in creep deformation and failure data is of considerable technological importance because it greatly complicates the task of making accurate deformation and lifetime estimates for high temperature components. Repeat data on austenitic stainless steel provided a unique opportunity to identify stochastic creep properties and to use this information to build a probabilistic creep damage assessment for this alloy
Seasonal landings of oil sardine, Sardinella longiceps at Rameswaram, Pamban and Mandapam areas
Unusual and unprecedented landings of oil sardine, Sardinella langiceps were noticed at Rameswaram and Pamban during January and February 1992. The estimated catch of oil sardine at Rameswaram for January- February 1992 was 4,561 t. The pair trawlers contributed 4,244 t and fish trawlers 317 t. The C/E varied from 1.5 to 8 t. At Pamban the pair trawling during the period realised 741 t
Spin dynamics of a one-dimensional spin-1/2 fully anisotropic Ising-like antiferromagnet in a transverse magnetic field
We consider the one-dimensional Ising-like fully anisotropic S=1/2 Heisenberg
antiferromagnetic Hamiltonian and study the dynamics of domain wall excitations
in the presence of transverse magnetic field . We obtain dynamical spin
correlation functions along the magnetic field and
perpendicular to it . It is shown that the line shapes of
and are purely symmetric at the
zone-boundary. It is observed in for that the
spectral weight moves toward low energy side with the increase of . This
model is applicable to study the spin dynamics of CsCoCl in the presence of
weak interchain interactions.Comment: 19 pages, LaTeX, 12 eps figure
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