7,359 research outputs found
Radiant Emission Characteristics of Diffuse Conical Cavities
Radiant-energy emission of diffuse conical cavitie
Thermal Radiation Absorption in Rectangular-Groove Cavities
Thermal radiation absorption in rectangular-groove cavitie
Absorption and Emission Characteristics of Diffuse Spherical Enclosures
The thermal radiation characteristics of spherical cavities are of practical interest in connection with the absorption of radiant energy for both space-vehicle and terrestrial applications. Also, spherical cavities are of potential use as sources of black-body energy. The purpose of this brief paper is to determine both the absorption and emission characteristics of spherical cavities which are diffuse reflectors and emitters
Generation of surface plasmons by electron beam excitation
We report on the first demonstration of excitation of propagating surface plasmon polaritons (SPPs) by injection of a beam of free electrons on an unstructured metal interface, providing a highly localized and intense source of plasmon waves. The plasmons were detected by a grating-assisted decoupling into light at a set of distances from the excitation point. This technique allows the high-resolution mapping of plasmon and photon emission from metal nanostructures
Random trees with superexponential branching weights
We study rooted planar random trees with a probability distribution which is
proportional to a product of weight factors associated to the vertices of
the tree and depending only on their individual degrees . We focus on the
case when grows faster than exponentially with . In this case the
measures on trees of finite size converge weakly as tends to infinity
to a measure which is concentrated on a single tree with one vertex of infinite
degree. For explicit weight factors of the form with
we obtain more refined results about the approach to the infinite
volume limit.Comment: 19 page
Five-Torsion in the Homology of the Matching Complex on 14 Vertices
J. L. Andersen proved that there is 5-torsion in the bottom nonvanishing
homology group of the simplicial complex of graphs of degree at most two on
seven vertices. We use this result to demonstrate that there is 5-torsion also
in the bottom nonvanishing homology group of the matching complex on
14 vertices. Combining our observation with results due to Bouc and to
Shareshian and Wachs, we conclude that the case is exceptional; for all
other , the torsion subgroup of the bottom nonvanishing homology group has
exponent three or is zero. The possibility remains that there is other torsion
than 3-torsion in higher-degree homology groups of when and .Comment: 11 page
Inertial forces and the foundations of optical geometry
Assuming a general timelike congruence of worldlines as a reference frame, we
derive a covariant general formalism of inertial forces in General Relativity.
Inspired by the works of Abramowicz et. al. (see e.g. Abramowicz and Lasota,
Class. Quantum Grav. 14 (1997) A23), we also study conformal rescalings of
spacetime and investigate how these affect the inertial force formalism. While
many ways of describing spatial curvature of a trajectory has been discussed in
papers prior to this, one particular prescription (which differs from the
standard projected curvature when the reference is shearing) appears novel. For
the particular case of a hypersurface-forming congruence, using a suitable
rescaling of spacetime, we show that a geodesic photon is always following a
line that is spatially straight with respect to the new curvature measure. This
fact is intimately connected to Fermat's principle, and allows for a certain
generalization of the optical geometry as will be further pursued in a
companion paper (Jonsson and Westman, Class. Quantum Grav. 23 (2006) 61). For
the particular case when the shear-tensor vanishes, we present the inertial
force equation in three-dimensional form (using the bold face vector notation),
and note how similar it is to its Newtonian counterpart. From the spatial
curvature measures that we introduce, we derive corresponding covariant
differentiations of a vector defined along a spacetime trajectory. This allows
us to connect the formalism of this paper to that of Jantzen et. al. (see e.g.
Bini et. al., Int. J. Mod. Phys. D 6 (1997) 143).Comment: 42 pages, 7 figure
Hydrogen transport in superionic system Rb3H(SeO4)2: a revised cooperative migration mechanism
We performed density functional studies of electronic properties and
mechanisms of hydrogen transport in Rb3H(SeO4)2 crystal which represents
technologically promising class M3H(XO4)2 of proton conductors (M=Rb,Cs, NH4;
X=S,Se). The electronic structure calculations show a decisive role of lattice
dynamics in the process of proton migration. In the obtained revised mechanism
of proton transport, the strong displacements of the vertex oxygens play a key
role in the establishing the continuous hydrogen transport and in the achieving
low activation energies of proton conduction which is in contrast to the
standard two-stage Grotthuss mechanism of proton transport. Consequently, any
realistic model description of proton transport should inevitably involve the
interactions with the sublattice of the XO4 groups.Comment: 11 pages, 11 figures, to appear in Physical Review
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