742 research outputs found
Signature extension preprocessing for LANDSAT MSS data
There are no author-identified significant results in this report
Signature extension using transformed cluster statistics and related techniques
There are no author-identified significant results in this report
Tidal Heating of Extra-Solar Planets
Extra-solar planets close to their host stars have likely undergone
significant tidal evolution since the time of their formation. Tides probably
dominated their orbital evolution once the dust and gas had cleared away, and
as the orbits evolved there was substantial tidal heating within the planets.
The tidal heating history of each planet may have contributed significantly to
the thermal budget that governed the planet's physical properties, including
its radius, which in many cases may be measured by observing transit events.
Typically, tidal heating increases as a planet moves inward toward its star and
then decreases as its orbit circularizes. Here we compute the plausible heating
histories for several planets with measured radii, using the same tidal
parameters for the star and planet that had been shown to reconcile the
eccentricity distribution of close-in planets with other extra-solar planets.
Several planets are discussed, including for example HD 209458 b, which may
have undergone substantial tidal heating during the past billion years, perhaps
enough to explain its large measured radius. Our models also show that GJ 876 d
may have experienced tremendous heating and is probably not a solid, rocky
planet. Theoretical models should include the role of tidal heating, which is
large, but time-varying.Comment: Accepted for publication to Ap
Changes in wave climate over the northwest European shelf seas during the last 12,000 years
Because of the depth attenuation of wave orbital velocity, wave-induced bed shear stress is much more sensitive to changes in total water depth than tidal-induced bed shear stress. The ratio between wave- and tidal-induced bed shear stress in many shelf sea regions has varied considerably over the recent geological past because of combined eustatic changes in sea level and isostatic adjustment. In order to capture the high-frequency nature of wind events, a two-dimensional spectral wave model is here applied at high temporal resolution to time slices from 12 ka BP to present using paleobathymetries of the NW European shelf seas. By contrasting paleowave climates and bed shear stress distributions with present-day conditions, the model results demonstrate that, in regions of the shelf seas that remained wet continuously over the last 12,000 years, annual root-mean-square (rms) and peak wave heights increased from 12 ka BP to present. This increase in wave height was accompanied by a large reduction in the annual rms wave- induced bed shear stress, primarily caused by a reduction in the magnitude of wave orbital velocity penetrating to the bed for increasing relative sea level. In regions of the shelf seas which remained wet over the last 12,000 years, the annual mean ratio of wave- to (M-2) tidal-induced bed shear stress decreased from 1 (at 12 ka BP) to its present-day value of 0.5. Therefore compared to present- day conditions, waves had a more important contribution to large-scale sediment transport processes in the Celtic Sea and the northwestern North Sea at 12 ka BP
Integrated optical directional coupler biosensor
We present measurements on biomolecular binding reactions, using a new type of integrated optical biosensor based on a planar directional coupler structure. The device is fabricated by Ag+-Na+ ion-exchange in glass and definition of the sensing region is achieved by use of transparent fluoropolymer isolation layers formed by thermal evaporation. The suitability of the sensor for application to the detection of environmental pollutants is considered
Integrated optics sensors for multi-sensing platforms
An overview is presented of research projects on optical sensing, in the Integrated Optical MicroSystems group of the MESA+ Institute for Nanotechnology at the University of Twente
Design and realisation of a MZI type polymer based high speed EO-modulator
We designed a 20 GHz Mach Zehnder interferometric EO-modulator based on a new developed polyesterimide. Measurements show a V/sub /spl pi// of 7.5 V, an insertion loss of 11 dB and an extinction ratio exceeding 20 dB for an interaction length of 2 cm
Small spacecraft power and thermal subsystems
This white paper provides a general guide to the conceptual design of satellite power and thermal control subsystems with special emphasis on the unique design aspects associated with small satellites. The operating principles of these technologies are explained and performance characteristics of current and projected components are provided. A tutorial is presented on the design process for both power and thermal subsystems, with emphasis on unique issues relevant to small satellites. The ability of existing technology to meet future performance requirements is discussed. Conclusions and observations are presented that stress cost-effective, high-performance design solutions
New insights on the relative sea level change during Holocene along the coasts of Tunisia and western Libya from archaeological and geomorphological markers
New data of sea level changes for the Mediterranean region along the coasts of northern Africa are
presented. Data are inferred from archaeological sites of Punic-Roman age located along the coast of
Tunisia, between Tunis and Jerba island and along the western coast of Libya, between Sabratha and
Leptis Magna. Data are based on precise measures of presently submerged archaeological markers that
are good indicators of past sea-level elevation. Nineteen selected archaeological sites were studied in
Tunisia and four in Libya, all aged between w2.0 and w1.5 ka BP. The functional elevations of significant
archaeological markers were measured with respect to the sea level at the time of measurements,
applying corrections for tide and atmospheric pressure values. The functional elevations of specific
architectural parts of the sites were interpreted, related to sea level at the time of their construction
providing data on the relative changes between land and sea. Observations were compared against sea
level change predictions derived from the glacio-hydro-isostatic model associated with the Last Glacial
cycle. The results indicate that local relative sea level change along the coast of Tunisia and Libya, has
increased 0.2 O 0.5 m since the last w2 ka. Besides minor vertical tectonic movements of the land, the
observed changes are produced by eustatic and glacio-hydro-isostatic variations acting in the Mediterranean
basin since the end of the last glacial maximum
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