101,350 research outputs found
The National Superficial Deposit Thickness Model. (Version 5)
The Superficial Deposits Thickness Model (SDTM) is a raster-based dataset designed to demonstrate the variation in thickness of Quaternary-age superficial deposits across Great Britain. Quaternary deposits (all unconsolidated material deposited in the last 2.6 million years) are of particular importance to environmental scientists and consultants concerned with our landscape, environment and habitats. The BGS has been generating national models of the thickness of Quaternary-age deposits since 2001, and this latest version of the model is based upon DiGMapGB-50 Version 5 geological mapping and borehole records registered with BGS before August 2008
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Optimal Policy Derivation for Transmission Duty-Cycle Constrained LPWAN
Low-power wide-area network (LPWAN) technologies enable Internet of Things (IoT) devices to efficiently and robustly communicate over long distances, thus making them especially suited for industrial environments. However, the stringent regulations on the usage of certain industrial, scientific, and medical bands in many countries in which LPWAN operate limit the amount of time IoT motes can occupy the shared bands. This is particularly challenging in industrial scenarios, where not being able to report some detected events might result in the failure of critical assets. To alleviate this, and by mathematically modeling LPWAN-based IoT motes, we have derived optimal transmission policies that maximize the number of reported events (prioritized by their importance) while still complying with current regulations. The proposed solution has been customized for two widely known LPWAN technologies: 1) LoRa and 2) Sigfox. Analytical results reveal that our solution is feasible and performs remarkably close to the theoretical limit for a wide range of network activity patterns
Thin-thick coexistence behavior of 8CB liquid crystalline films on silicon
The wetting behavior of thin films of 4'-n-octyl-4-cyanobiphenyl (8CB) on Si
is investigated via optical and x-ray reflectivity measurement. An experimental
phase diagram is obtained showing a broad thick-thin coexistence region
spanning the bulk isotropic-to-nematic () and the nematic-to-smectic-A
() temperatures. For Si surfaces with coverages between 47 and
nm, reentrant wetting behavior is observed twice as we increase the
temperature, with separate coexistence behaviors near and .
For coverages less than 47 nm, however, the two coexistence behaviors merge
into a single coexistence region. The observed thin-thick coexistence near the
second-order NA transition is not anticipated by any previous theory or
experiment. Nevertheless, the behavior of the thin and thick phases within the
coexistence regions is consistent with this being an equilibrium phenomenon.Comment: 4 pages, 3 figure
Numerical Study of a Lyapunov Functional for the Complex Ginzburg-Landau Equation
We numerically study in the one-dimensional case the validity of the
functional calculated by Graham and coworkers as a Lyapunov potential for the
Complex Ginzburg-Landau equation. In non-chaotic regions of parameter space the
functional decreases monotonically in time towards the plane wave attractors,
as expected for a Lyapunov functional, provided that no phase singularities are
encountered. In the phase turbulence region the potential relaxes towards a
value characteristic of the phase turbulent attractor, and the dynamics there
approximately preserves a constant value. There are however very small but
systematic deviations from the theoretical predictions, that increase when
going deeper in the phase turbulence region. In more disordered chaotic regimes
characterized by the presence of phase singularities the functional is
ill-defined and then not a correct Lyapunov potential.Comment: 20 pages,LaTeX, Postcript version with figures included available at
http://formentor.uib.es/~montagne/textos/nep
The use of Planetary Nebulae precursors in the study of Diffuse Interstellar Bands
We present the first results of a systematic search for Diffuse Interstellar
Bands in a carefully selected sample of post-AGB stars observed with high
resolution optical spectroscopy. These stars are shown to be ideal targets to
study this old, intriguing astrophysical problem. Our results suggest that the
carrier(s) of these bands may not be present in the circumstellar environments
of these evolved stars. The implications of the results obtained on the
identification of the still unknown carrier(s) are discussed.Comment: 4 pages, 2 figures, proceedings of the conference 'Planetary Nebulae
as Astrophysical Tools', held in Gdansk, Poland (June 28 - July 2, 2005
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