4,886 research outputs found
Infinitary Combinatory Reduction Systems: Normalising Reduction Strategies
We study normalising reduction strategies for infinitary Combinatory
Reduction Systems (iCRSs). We prove that all fair, outermost-fair, and
needed-fair strategies are normalising for orthogonal, fully-extended iCRSs.
These facts properly generalise a number of results on normalising strategies
in first-order infinitary rewriting and provide the first examples of
normalising strategies for infinitary lambda calculus
Conceptual design of a lunar base thermal control system
Space station and alternate thermal control technologies were evaluated for lunar base applications. The space station technologies consisted of single-phase, pumped water loops for sensible and latent heat removal from the cabin internal environment and two-phase ammonia loops for the transportation and rejection of these heat loads to the external environment. Alternate technologies were identified for those areas where space station technologies proved to be incompatible with the lunar environment. Areas were also identified where lunar resources could enhance the thermal control system. The internal acquisition subsystem essentially remained the same, while modifications were needed for the transport and rejection subsystems because of the extreme temperature variations on the lunar surface. The alternate technologies examined to accommodate the high daytime temperatures incorporated lunar surface insulating blankets, heat pump system, shading, and lunar soil. Other heat management techniques, such as louvers, were examined to prevent the radiators from freezing. The impact of the geographic location of the lunar base and the orientation of the radiators was also examined. A baseline design was generated that included weight, power, and volume estimates
Distinguishing fractional and white noise in one and two dimensions
We discuss the link between uncorrelated noise and Hurst exponent for one and
two-dimensional interfaces. We show that long range correlations cannot be
observed using one-dimensional cuts through two-dimensional self-affine
surfaces whose height distributions are characterized by a Hurst exponent lower
than -1/2. In this domain, fractional and white noise are not distinguishable.
A method analysing the correlations in two dimensions is necessary. For Hurst
exponents larger than -1/2, a crossover regime leads to a systematic over
estimate of the Hurst exponent.Comment: 3 pages RevTeX, 4 Postscript figure
Substrate influence on the plasmonic response of clusters of spherical nanoparticles
The plasmonic response of nanoparticles is exploited in many subfields of
science and engineering to enhance optical signals associated with probes of
nanoscale and subnanoscale entities. We develop a numerical algorithm based on
previous theoretical work that addresses the influence of a substrate on the
plasmonic response of collections of nanoparticles of spherical shape. Our
method is a real space approach within the quasi-static limit that can be
applied to a wide range of structures. We illustrate the role of the substrate
through numerical calculations that explore single nanospheres and nanosphere
dimers fabricated from either a Drude model metal or from silver on dielectric
substrates, and from dielectric spheres on silver substrates.Comment: 12 pages, 13 figure
Synchronization Model for Stock Market Asymmetry
The waiting time needed for a stock market index to undergo a given
percentage change in its value is found to have an up-down asymmetry, which,
surprisingly, is not observed for the individual stocks composing that index.
To explain this, we introduce a market model consisting of randomly fluctuating
stocks that occasionally synchronize their short term draw-downs. These
synchronous events are parameterized by a ``fear factor'', that reflects the
occurrence of dramatic external events which affect the financial market.Comment: 4 pages, 4 figure
The Importance of Suspension Stability for the Hot-wire Measurements of Thermal Conductivity of Colloidal Suspensions.
The development of advanced heat transfer fluids with enhanced thermal conductivity is essential to improve the effective heat transfer behavior of conventional coolants. Thermal conductivity enhancement has been reported for colloidal suspensions formulated with different nanoparticles. Reliable thermal conductivity measurement requires that the suspension is stable against sedimentation during the measurement since particle sedimentation may effect the experimental results. The present study proposes a criterion to ensure that thermal conductivity data is independent of the particle sedimentation. A measuring device based on the transient hot-wire method is designed to allow vertical and horizontal thermal conductivity data collection. Our investigation shows that the thermal conductivity measurements in the horizontal and vertical configurations are almost identical when the colloidal suspension is stable while they differ for unstable systems
Low-loss photonic crystal fibers for transmission systems and their dispersion properties
We report on a single-mode photonic crystal fiber with attenuation and
effective area at 1550 nm of 0.48 dB/km and 130 square-micron, respectively.
This is, to our knowledge, the lowest loss reported for a PCF not made from VAD
prepared silica and at the same time the largest effective area for a low-loss
(< 1 dB/km) PCF. We briefly discuss the future applications of PCFs for data
transmission and show for the first time, both numerically and experimentally,
how the group velocity dispersion is related to the mode field diameterComment: 5 pages including 3 figures + 1 table. Accepted for Opt. Expres
Photonic crystal fiber with a hybrid honeycomb cladding
We consider an air-silica honeycomb lattice and demonstrate a new approach to
the formation of a core defect. Typically, a high or low-index core is formed
by adding a high-index region or an additional air-hole (or other low-index
material) to the lattice, but here we discuss how a core defect can be formed
by manipulating the cladding region rather than the core region itself.
Germanium-doping of the honeycomb lattice has recently been suggested for the
formation of a photonic band-gap guiding silica-core and here we experimentally
demonstrate how an index-guiding silica-core can be formed by fluorine-doping
of the honeycomb lattice.Comment: 5 pages including 3 figures. Accepted for Optics Expres
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