2,843 research outputs found
Silicate luminescence and remote compositional mapping
Silicate luminescence and remote compositional mappin
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Capitalizing On Diversity: Interpersonal Congruence In Small Work Groups
We examine interpersonal congruence, the degree to which group members see others in the group as others see themselves, as a moderator of the relationship between diversity and group effectiveness. A longitudinal study of 83 work groups revealed that diversity tended to improve creative task performance in groups with high interpersonal congruence, whereas diversity undermined the performance of groups with low interpersonal congruence. This interaction effect also emerged on measures of social integration, group identification, and relationship conflict. By eliciting self-verifying appraisals, members of some groups achieved enough interpersonal congruence during their first ten minutes of interaction to benefit their group outcomes four months later. In contrast to theories of social categorization, the interpersonal congruence approach suggests that group members can achieve harmonious and effective work processes by expressing rather than suppressing the characteristics that make them unique.Managemen
Spectral representation of the effective dielectric constant of graded composites
We generalize the Bergman-Milton spectral representation, originally derived
for a two-component composite, to extract the spectral density function for the
effective dielectric constant of a graded composite. This work has been
motivated by a recent study of the optical absorption spectrum of a graded
metallic film [Applied Physics Letters, 85, 94 (2004)] in which a broad
surface-plasmon absorption band has been shown to be responsible for enhanced
nonlinear optical response as well as an attractive figure of merit. It turns
out that, unlike in the case of homogeneous constituent components, the
characteristic function of a graded composite is a continuous function because
of the continuous variation of the dielectric function within the constituent
components. Analytic generalization to three dimensional graded composites is
discussed, and numerical calculations of multilayered composites are given as a
simple application.Comment: Physical Review E, submitted for publication
Twenty-first semiannual report to Congress, 1 January - 30 June 1969
Manned space flights, satellite observations, space sciences, and air traffic control - NASA report to Congress for 1 Jan. to 30 June 196
Electromagnetic semitransparent -function plate: Casimir interaction energy between parallel infinitesimally thin plates
We derive boundary conditions for electromagnetic fields on a
-function plate. The optical properties of such a plate are shown to
necessarily be anisotropic in that they only depend on the transverse
properties of the plate. We unambiguously obtain the boundary conditions for a
perfectly conducting -function plate in the limit of infinite
dielectric response. We show that a material does not "optically vanish" in the
thin-plate limit. The thin-plate limit of a plasma slab of thickness with
plasma frequency reduces to a -function plate
for frequencies () satisfying . We show that the Casimir interaction energy between two parallel perfectly
conducting -function plates is the same as that for parallel perfectly
conducting slabs. Similarly, we show that the interaction energy between an
atom and a perfect electrically conducting -function plate is the usual
Casimir-Polder energy, which is verified by considering the thin-plate limit of
dielectric slabs. The "thick" and "thin" boundary conditions considered by
Bordag are found to be identical in the sense that they lead to the same
electromagnetic fields.Comment: 21 pages, 7 figures, references adde
Realizability of metamaterials with prescribed electric permittivity and magnetic permeability tensors
We show that any pair of real symmetric tensors \BGve and \BGm can be
realized as the effective electric permittivity and effective magnetic
permeability of a metamaterial at a given fixed frequency. The construction
starts with two extremely low loss metamaterials, with arbitrarily small
microstructure, whose existence is ensured by the work of Bouchitt{\'e} and
Bourel and Bouchitt\'e and Schweizer, one having at the given frequency a
permittivity tensor with exactly one negative eigenvalue, and a positive
permeability tensor, and the other having a positive permittivity tensor, and a
permeability tensor having exactly one negative eigenvalue. To achieve the
desired effective properties these materials are laminated together in a
hierarchical multiple rank laminate structure, with widely separated length
scales, and varying directions of lamination, but with the largest length scale
still much shorter than the wavelengths and attenuation lengths in the
macroscopic effective medium.Comment: 12 pages, no figure
Electromagnetic field fluctuations near a dielectric-vacuum boundary and surface divergences in the ideal conductor limit
We consider the electric and magnetic field fluctuations in the vacuum state
in the region external to a half-space filled with a homogeneous
non-dissipative dielectric. We discuss an appropriate limit to an ideal metal
and concentrate our interest on the renormalized field fluctuations, or
equivalently to renormalized electric and magnetic energy densities, in the
proximity of the dielectric-vacuum interface. We show that surface divergences
of field fluctuations arise at the interface in an appropriate ideal conductor
limit, and that our limiting procedure allows to discuss in detail their
structure. Field fluctuations close to the surface can be investigated through
the retarded Casimir-Polder interaction with an appropriate polarizable body.Comment: 6 pages, 2 figure
The quantum metrology triangle and the re-definition of the SI ampere and kilogram; Analysis of a reduced set of observational equations
We have developed a set of seven observational equations that include all of
the physics necessary to relate the most important of the fundamental constants
to the definitions of the SI kilogram and ampere. We have used these to
determine the influence of alternative definitions being considered for the SI
kilogram and ampere on the uncertainty of three of the fundamental constants
(h, e and mu). We have also reviewed the experimental evidence for the
exactness of the quantum metrology triangle resulting from experiments
combining the quantum Hall effect, the Josephson effects and single-electron
tunnelling.Comment: 16 pages, 3 figures & 5 table
Casimir effect for the scalar field under Robin boundary conditions: A functional integral approach
In this work we show how to define the action of a scalar field in a such a
way that Robin boundary condition is implemented dynamically, i.e., as a
consequence of the stationary action principle. We discuss the quantization of
that system via functional integration. Using this formalism, we derive an
expression for the Casimir energy of a massless scalar field under Robin
boundary conditions on a pair of parallel plates, characterized by constants
and . Some special cases are discussed; in particular, we show that
for some values of and the Casimir energy as a function of the
distance between the plates presents a minimum. We also discuss the
renormalization at one-loop order of the two-point Green function in the
theory submitted to Robin boundary condition on a plate.Comment: 16 pages, 2 figures. Version 2: contains a new section on the
renormalization of the two-point Green function in the presence of a flat
boundary. Accepted for publication in J. Phys.
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