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 $1.4308$, improving the previously best lower bound of $1.4161$ for the worst-case dilation of plane spanners. (II) For every integer $n\geq13$, there exists an $n$-element point set $S$ such that the degree 3 dilation of $S$ denoted by $\delta_0(S,3) \text{ equals } 1+\sqrt{3}=2.7321\ldots$ in the domain of plane geometric spanners. In the same domain, we show that for every integer $n\geq6$, there exists a an $n$-element point set $S$ such that the degree 4 dilation of $S$ denoted by $\delta_0(S,4) \text{ equals } 1 + \sqrt{(5-\sqrt{5})/2}=2.1755\ldots$ The previous best lower bound of $1.4161$ holds for any degree. (III) For every integer $n\geq6$, there exists an $n$-element point set $S$ such that the stretch factor of the greedy triangulation of $S$ is at least $2.0268$.Comment: Revised definitions in the introduction; 23 pages, 15 figures; 2 table

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 $h_x$. We obtain dynamical spin correlation functions along the magnetic field $S^{xx}(q,\omega)$ and perpendicular to it $S^{yy}(q,\omega)$. It is shown that the line shapes of $S^{xx}(q,\omega)$ and $S^{yy}(q,\omega)$ are purely symmetric at the zone-boundary. It is observed in $S^{yy}(q,\omega)$ for $\pi/2<q<\pi$ that the spectral weight moves toward low energy side with the increase of $h_x$. This model is applicable to study the spin dynamics of CsCoCl$_3$ in the presence of weak interchain interactions.Comment: 19 pages, LaTeX, 12 eps figure