1,290 research outputs found
Photon localization barrier can be overcome
In contradistinction to a widespread belief that the spatial localization of
photons is restricted by a power-law falloff of the photon energy density,
I.Bialynicki-Birula [Phys. Rev. Lett. 80, 5247 (1998)] has proved that any
stronger -- up to an almost exponential -- falloff is allowed. We are showing
that for certain specifically designed cylindrical one-photon states the
localization is even better in lateral directions. If the photon state is built
from the so-called focus wave mode, the falloff in the waist cross-section
plane turns out to be quadratically exponential (Gaussian) and such strong
localization persists in the course of propagation.Comment: Short communication -- 4 pages, 2 figure
MHD oxidant intermediate temperature ceramic heater study
The use of three types of directly fired ceramic heaters for preheating oxygen enriched air to an intermediate temperature of 1144K was investigated. The three types of ceramic heaters are: (1) a fixed bed, periodic flow ceramic brick regenerative heater; (2) a ceramic pebble regenerative heater. The heater design, performance and operating characteristics under conditions in which the particulate matter is not solidified are evaluated. A comparison and overall evaluation of the three types of ceramic heaters and temperature range determination at which the particulate matter in the MHD exhaust gas is estimated to be a dry powder are presented
Dynamics of Macrosystems; Proceedings of a Workshop, September 3-7, 1984
There is an increasing awareness of the important and persuasive role that instability and random, chaotic motion play in the dynamics of macrosystems. Further research in the field should aim at providing useful tools, and therefore the motivation should come from important questions arising in specific macrosystems. Such systems include biochemical networks, genetic mechanisms, biological communities, neutral networks, cognitive processes and economic structures. This list may seem heterogeneous, but there are similarities between evolution in the different fields. It is not surprising that mathematical methods devised in one field can also be used to describe the dynamics of another.
IIASA is attempting to make progress in this direction. With this aim in view this workshop was held at Laxenburg over the period 3-7 September 1984. These Proceedings cover a broad canvas, ranging from specific biological and economic problems to general aspects of dynamical systems and evolutionary theory
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Active Device Fabrication Using Fiber Encapsulation Additive Manufacturing
Fiber Encapsulation Additive Manufacturing (FEAM) is a novel solid freeform
fabrication process in which a fiber and a matrix are co-deposited simultaneously within a single
printer along straight and curved 2-D and 3-D paths. Using a FEAM approach in which the fiber
is a metal wire and the matrix is a thermoplastic polymer, simple electromechanical devices such
as voice coils, inductive sensors, and membrane switches have been successfully produced. This
paper will present an overview of the FEAM process, describe several fabricated devices, and
discuss recent developments in controllably stopping and starting the wire, and in creating
electrical junctions between individual wires, which together enable much more complex devices
to be made.Mechanical Engineerin
Modularity and Optimality in Social Choice
Marengo and the second author have developed in the last years a geometric
model of social choice when this takes place among bundles of interdependent
elements, showing that by bundling and unbundling the same set of constituent
elements an authority has the power of determining the social outcome. In this
paper we will tie the model above to tournament theory, solving some of the
mathematical problems arising in their work and opening new questions which are
interesting not only from a mathematical and a social choice point of view, but
also from an economic and a genetic one. In particular, we will introduce the
notion of u-local optima and we will study it from both a theoretical and a
numerical/probabilistic point of view; we will also describe an algorithm that
computes the universal basin of attraction of a social outcome in O(M^3 logM)
time (where M is the number of social outcomes).Comment: 42 pages, 4 figures, 8 tables, 1 algorithm
Pulsed light beams in vacuum with superluminal and negative group velocities
Gouy's phase of transversally limited pulses can create a strong anomalous
dispersion in vacuum leading to highly superluminal and negative group
velocities. As a consequence, a focusing pulse can diverge beyond the focus
before converging into it. A simple experiment is proposed.Comment: 4 pages, 5 figure
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