9,823 research outputs found
Surface Electromagnetic Waves Thermally Excited: Radiative Heat Transfer, Coherence Properties and Casimir Forces Revisited in the Near Field
We review in this article the influence of surface waves on the thermally
excited electromagnetic field. We study in particular the field emitted at
subwalength distances of material surfaces. After reviewing the main properties
of surface waves, we introduce the fluctuation-dissipation theorem that allows
to model the fluctuating electromagnetic fields. We then analyse the
contribution of these waves in a variety of phenomena. They give a leading
contribution to the density of electromagnetic states, they produce both
temporal coherence and spatial coherence in the near field of planar thermal
sources. They can be used to modify radiative properties of surfaces and to
design partially spatially coherent sources. Finally, we discuss the role of
surface waves in the radiative heat transfer and the theory of dispersion
forces at the subwavelength scale.Comment: Redig\'{e} \`{a} la fin de l'ann\'{e}e 2004. Accept\'{e} dans Surface
Science Report
Fluctuational Electrodynamics in Atomic and Macroscopic Systems: van der Waals Interactions and Radiative Heat Transfer
We present an approach to describing fluctuational electrodynamic (FED)
interactions, particularly van der Waals (vdW) interactions as well as
radiative heat transfer (RHT), between material bodies of vastly different
length scales, allowing for going between atomistic and continuum treatments of
the response of each of these bodies as desired. Any local continuum
description of electromagnetic (EM) response is compatible with our approach,
while atomistic descriptions in our approach are based on effective electronic
and nuclear oscillator degrees of freedom, encapsulating dissipation,
short-range electronic correlations, and collective nuclear vibrations
(phonons). While our previous works using this approach have focused on
presenting novel results, this work focuses on the derivations underlying these
methods. First, we show how the distinction between "atomic" and "macroscopic"
bodies is ultimately somewhat arbitrary, as formulas for vdW free energies and
RHT look very similar regardless of how the distinction is drawn. Next, we
demonstrate that the atomistic description of material response in our approach
yields EM interaction matrix elements which are expressed in terms of
analytical formulas for compact bodies or semianalytical formulas based on
Ewald summation for periodic media; we use this to compute vdW interaction free
energies as well as RHT powers among small biological molecules in the presence
of a metallic plate as well as between parallel graphene sheets in vacuum,
showing strong deviations from conventional macroscopic theories due to the
confluence of geometry, phonons, and EM retardation effects. Finally, we
propose formulas for efficient computation of FED interactions among material
bodies in which those that are treated atomistically as well as those treated
through continuum methods may have arbitrary shapes, extending previous
surface-integral techniques.Comment: 25 pages, 5 figures, 2 appendice
Radiation Effects on Flow Characteristics in Combustion Chambers
A JANNAF sponsored workshop was held to discuss the importance and role of radiative heat transfer in rocket combustion chambers. The potential impact of radiative transfer on hardware design, reliability, and performance was discussed. The current state of radiative transfer prediction capability in CFD modeling was reviewed and concluded to be substantially lacking in both the physical models used and the radiative property data available. There is a clear need to begin to establish a data base for making radiation calculations in rocket combustion chambers. A natural starting point for this effort would be the NASA thermochemical equilibrium code (CEC)
Localized States and Resultant Band Bending in Graphene Antidot Superlattices
We fabricated dye sensitized graphene antidot superlattices with the purpose
of elucidating the role of the localized edge state density. The fluorescence
from deposited dye molecules was found to strongly quench as a function of
increasing antidot filling fraction, whereas it was enhanced in unpatterned but
electrically back-gated samples. This contrasting behavior is strongly
indicative of a built-in lateral electric field that accounts for fluorescence
quenching as well as p-type doping. These findings are of great interest for
light-harvesting applications that require field separation of electron-hole
pairs.Comment: NanoLetters, 201
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