1,825 research outputs found

    Cathode Ray Tube Display with Cancellation of Electric Field Emissions

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    A cathode ray tube display having reduced electric field emissions comprising a cathode ray tube 100, an element 200 for detecting modulations in the final anode voltage of the CRT, the signal not being directly dependent on the deflection driving means 115. A matching network 205 provides phase and gain correction to the signal from element 200, amplification means 210 receives the signal from network 205 and an emission means 215 radiates a cancelling electric field dependent on the modulations detected by said element 200

    Specifying Self-configurable Component-based Systems with FracToy

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    International audienceOne of the key research challenges in autonomic computing is to define rigorous mathematical models for specifying, analyzing, and verifying high-level self-* policies. This paper presents the FracToy formal methodology to specify self-configurable component-based systems, and particularly both their component-based architectural description and their self-configuration policies. This rigorous methodology is based on the first-order relational logic, and is implemented with the Alloy formal specication language. The paper presents the dierent steps of the FracToy methodology and illustrates them on a self-configurable component-based example

    The Casimir Problem of Spherical Dielectrics: Quantum Statistical and Field Theoretical Approaches

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    The Casimir free energy for a system of two dielectric concentric nonmagnetic spherical bodies is calculated with use of a quantum statistical mechanical method, at arbitrary temperature. By means of this rather novel method, which turns out to be quite powerful (we have shown this to be true in other situations also), we consider first an explicit evaluation of the free energy for the static case, corresponding to zero Matsubara frequency (n=0n=0). Thereafter, the time-dependent case is examined. For comparison we consider the calculation of the free energy with use of the more commonly known field theoretical method, assuming for simplicity metallic boundary surfaces.Comment: 31 pages, LaTeX, one new reference; version to appear in Phys. Rev.

    Physical properties of a nickel-base alloy prepared by isostatic pressing and sintering of the powdered metal *

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    The physical and mechanical properties of samples of a nickel-base alloy fabricated by powder metallurgy were determined. The particle sizes of the powders used to make the samples varied from –80/+ 200 mesh to –325 mesh. The compaction pressure varied from 138 to 414 MN/m 2 and the sintering temperature varied from 1150 to 1250°C. The shrinkage during processing, the porosity, tensile strength, yield strength, elongation, and elastic modulus were used to characterize the samples. The strength of the samples generally increased with decreasing particle size of the powder and increasing compaction pressure and sintering temperatures. The porosity and strength, therefore, could be varied over a wide range by controlling the various parameters. The properties of the samples prepared by powder metallurgy were compared with those of the cast alloy and compact bone. Conditions can be selected that will yield equivalent or better properties by powder metallurgy than by casting.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74945/1/j.1365-2842.1976.tb00939.x.pd

    Minimal Riesz energy on the sphere for axis-supported external fields

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    We investigate the minimal Riesz s-energy problem for positive measures on the d-dimensional unit sphere S^d in the presence of an external field induced by a point charge, and more generally by a line charge. The model interaction is that of Riesz potentials |x-y|^(-s) with d-2 <= s < d. For a given axis-supported external field, the support and the density of the corresponding extremal measure on S^d is determined. The special case s = d-2 yields interesting phenomena, which we investigate in detail. A weak* asymptotic analysis is provided as s goes to (d-2)^+.Comment: 42 pages, 2 figure

    A real Lorentz-FitzGerald contraction

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    Many condensed matter systems are such that their collective excitations at low energies can be described by fields satisfying equations of motion formally indistinguishable from those of relativistic field theory. The finite speed of propagation of the disturbances in the effective fields (in the simplest models, the speed of sound) plays here the role of the speed of light in fundamental physics. However, these apparently relativistic fields are immersed in an external Newtonian world (the condensed matter system itself and the laboratory can be considered Newtonian, since all the velocities involved are much smaller than the velocity of light) which provides a privileged coordinate system and therefore seems to destroy the possibility of having a perfectly defined relativistic emergent world. In this essay we ask ourselves the following question: In a homogeneous condensed matter medium, is there a way for internal observers, dealing exclusively with the low-energy collective phenomena, to detect their state of uniform motion with respect to the medium? By proposing a thought experiment based on the construction of a Michelson-Morley interferometer made of quasi-particles, we show that a real Lorentz-FitzGerald contraction takes place, so that internal observers are unable to find out anything about their `absolute ' state of motion. Therefore, we also show that an effective but perfectly defined relativistic world can emerge in a fishbowl world situated inside a Newtonian (laboratory) system. This leads us to reflect on the various levels of description in physics, in particular regarding the quest towards a theory of quantum gravity.Comment: 6 pages, no figures. Minor changes reflect published versio

    DD-dimensions Dirac fermions BEC-BCS cross-over thermodynamics

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    An effective Proca Lagrangian action is used to address the vector condensation Lorentz violation effects on the equation of state of the strongly interacting fermions system. The interior quantum fluctuation effects are incorporated as an external field approximation indirectly through a fictive generalized Thomson Problem counterterm background. The general analytical formulas for the dd-dimensions thermodynamics are given near the unitary limit region. In the non-relativistic limit for d=3d=3, the universal dimensionless coefficient ξ=4/9\xi ={4}/{9} and energy gap Δ/ϵf=5/18\Delta/\epsilon_f ={5}/{18} are reasonably consistent with the existed theoretical and experimental results. In the unitary limit for d=2d=2 and T=0, the universal coefficient can even approach the extreme occasion ξ=0\xi=0 corresponding to the infinite effective fermion mass m=m^*=\infty which can be mapped to the strongly coupled two-dimensions electrons and is quite similar to the three-dimensions Bose-Einstein Condensation of ideal boson gas. Instead, for d=1d=1, the universal coefficient ξ\xi is negative, implying the non-existence of phase transition from superfluidity to normal state. The solutions manifest the quantum Ising universal class characteristic of the strongly coupled unitary fermions gas.Comment: Improved versio

    Pattern Stability and Trijunction Motion in Eutectic Solidification

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    We demonstrate by both experiments and phase-field simulations that lamellar eutectic growth can be stable for a wide range of spacings below the point of minimum undercooling at low velocity, contrary to what is predicted by existing stability analyses. This overstabilization can be explained by relaxing Cahn's assumption that lamellae grow locally normal to the eutectic interface.Comment: 4 pages, 5 eps figure

    Background Thermal Contributions in Testing the Unruh Effect

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    We consider inertial and accelerated Unruh-DeWitt detectors moving in a background thermal bath and calculate their excitation rates. It is shown that for fast moving detectors such a thermal bath does not affect substantially the excitation probability. Our results are discussed in connection with a possible proposal of testing the Unruh effect in high energy particle accelerators.Comment: 13 pages, (REVTEX 3.0), 3 figures available upon reques
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