Closed-circuit television welding- electrode guidance system

Closed-circuit TV camera is mounted parallel to electrode and moves along with it. Camera is scanned along seam so seam is viewed parallel with scan lines on TV monitor. Two fiber optics illuminators are attached to guidance system; they illuminate seam for TV camera

(3+1) Massive Dirac Fermions with Ultracold Atoms in Optical Lattices

We propose the experimental realization of (3+1) relativistic Dirac fermions using ultracold atoms in a rotating optical lattice or, alternatively, in a synthetic magnetic field. This approach has the advantage to give mass to the Dirac fermions by coupling the ultracold atoms to a Bragg pulse. A dimensional crossover from (3+1) to (2+1) Dirac fermions can be obtained by varying the anisotropy of the lattice. We also discuss under which conditions the interatomic potentials give rise to relativistically invariant interactions among the Dirac fermions

Smoothed Particle Hydrodynamics simulations of expanding HII regions. I. Numerical methods and tests

We describe a new algorithm for including the dynamical effects of ionizing radiation in SPH simulations, and we present several examples of how the algorithm can be applied to problems in star formation. We use the HEALPix software to tessellate the sky and to solve the equation of ionization equilibrium along a ray towards each of the resulting tesserae. We exploit the hierarchical nature of HEALPix to make the algorithm adaptive, so that fine angular resolution is invoked only where it is needed, and the computational cost is kept low. We present simulations of (i) the spherically symmetric expansion of an HII region inside a uniform-density, non--self-gravitating cloud; (ii) the spherically symmetric expansion of an HII region inside a uniform-density, self-gravitating cloud; (iii) the expansion of an off-centre HII region inside a uniform-density, non--self-gravitating cloud, resulting in rocket acceleration and dispersal of the cloud; and (iv) radiatively driven compression and ablation of a core overrun by an HII region. The new algorithm provides the means to explore and evaluate the role of ionizing radiation in regulating the efficiency and statistics of star formation.Comment: 12 pages, 16 figures, simulation movies available at http://galaxy.ig.cas.cz/~richard/HIIregion

Upper ocean manifestations of a reducing meridional overturning circulation

Most climate models predict a slowing down of the Atlantic Meridional Overturning Circulation during the 21st century. Using a 100year climate change integration of a high resolution coupled climate model, we show that a 5.3Sv reduction in the deep southward transport in the subtropical North Atlantic is balanced solely by a weakening of the northward surface western boundary current, and not by an increase in the southward transport integrated across the interior ocean away from the western boundary. This is consistent with Sverdrup balance holding to a good approximation outside of the western boundary region on decadal time scales, and may help to spatially constrain past and future change in the overturning circulation. The subtropical gyre weakens by 3.4Sv over the same period due to a weakened wind stress curl. These changes combine to give a net 8.7Sv reduction in upper western boundary transport. © 2012. American Geophysical Union. All Rights Reserved

Back-propagation of accuracy

In this paper we solve the problem: how to determine maximal allowable errors, possible for signals and parameters of each element of a network proceeding from the condition that the vector of output signals of the network should be calculated with given accuracy? "Back-propagation of accuracy" is developed to solve this problem. The calculation of allowable errors for each element of network by back-propagation of accuracy is surprisingly similar to a back-propagation of error, because it is the backward signals motion, but at the same time it is very different because the new rules of signals transformation in the passing back through the elements are different. The method allows us to formulate the requirements to the accuracy of calculations and to the realization of technical devices, if the requirements to the accuracy of output signals of the network are known.Comment: 4 pages, 5 figures, The talk given on ICNN97 (The 1997 IEEE International Conference on Neural Networks, Houston, USA

The Oceanic Variability Spectrum and Transport Trends

Oceanic meridional transports evaluated over the width of the Pacific Ocean from altimetric observations become incoherent surprisingly rapidly with meridional separation. Even with 15 years of data, surface slopes show no significant coherence beyond 5◦ of latitude separation at any frequency. An analysis of the frequency/zonal-wavenumber spectral density shows a broad continuum of motions at all time and space scales, with a significant excess of energy along a “non-dispersive” line extending between the simple barotropic and first baroclinic mode Rossby waves. It is speculated that much of that excess energy lies with coupled barotropic and first mode Rossby waves. The statistical significance of apparent oceanic transport trends depends upon the existence of a reliable frequency/wavenumber spectrum and for which only a few observational elements now exist.Jet Propulsion Laboratory (U.S.).United States. National Aeronautics and Space Administration (Jason-1 program)National Oceanographic Partnership Program (U.S.

Friction force on slow charges moving over supported graphene

We provide a theoretical model that describes the dielectric coupling of a 2D layer of graphene, represented by a polarization function in the Random Phase Approximation, and a semi-infinite 3D substrate, represented by a surface response function in a non-local formulation. We concentrate on the role of the dynamic response of the substrate for low-frequency excitations of the combined graphene-substrate system, which give rise to the stopping force on slowly moving charges above graphene. A comparison of the dielectric loss function with experimental HREELS data for graphene on a SiC substrate is used to estimate the damping rate in graphene and to reveal the importance of phonon excitations in an insulating substrate. A signature of the hybridization between graphene's pi plasmon and the substrate's phonon is found in the stopping force. A friction coefficient that is calculated for slow charges moving above graphene on a metallic substrate shows an interplay between the low-energy single-particle excitations in both systems.Comment: 13 pages, 5 figures, submitted to Nanotechnology for a special issue related to the NGC 2009 conference (http://asdn.net/ngc2009/index.shtml

An Optical Implementation of Adaptive Resonance Utilizing Phase Conjugation

A novel adaptive resonance theory (ART) device has been conceived that is fully optical in the input-output processing path. This device is based on holographic information processing in a phase-conjugating crystal. This sets up an associative pattern retrieval in a resonating loop utilizing angle-multiplexed reference beams for pattern classification. A reset mechanism is used to reject any given beam, allowing an ART search strategy. The design is similar to that of an existing nonlearning optical associative memory, but is does allow learning and makes use of information the other device discards. This new device is expected to offer higher information storage density that alternative ART implementation

An Optical Adaptive Resonance Neural Network Utilizing Phase Conjugation

An adaptive resonance (ART) device has been conceived that is fully optical in the input-output processing path. It is based on holographic information processing in a phase-conjugating crystal. This sets up an associative pattern retrieval in a resonating loop utilizing angle-multiplexed reference beams for pattern classification. A reset mechanism is used to reject any given beam, allowing an ART search strategy. The design is similar to an existing nonlearning optical associative memory, but it does allow learning and makes use of information the other device discards. This device is expected to offer higher information storage density than alternative ART implementations