3,750 research outputs found
Catching the Right Wave: Evaluating Wave Energy Resources and Potential Compatibility with Existing Marine and Coastal Uses
Many hope that ocean waves will be a source for clean, safe, reliable and affordable energy, yet wave energy conversion facilities may affect marine ecosystems through a variety of mechanisms, including competition with other human uses. We developed a decision-support tool to assist siting wave energy facilities, which allows the user to balance the need for profitability of the facilities with the need to minimize conflicts with other ocean uses. Our wave energy model quantifies harvestable wave energy and evaluates the net present value (NPV) of a wave energy facility based on a capital investment analysis. The model has a flexible framework and can be easily applied to wave energy projects at local, regional, and global scales. We applied the model and compatibility analysis on the west coast of Vancouver Island, British Columbia, Canada to provide information for ongoing marine spatial planning, including potential wave energy projects. In particular, we conducted a spatial overlap analysis with a variety of existing uses and ecological characteristics, and a quantitative compatibility analysis with commercial fisheries data. We found that wave power and harvestable wave energy gradually increase offshore as wave conditions intensify. However, areas with high economic potential for wave energy facilities were closer to cable landing points because of the cost of bringing energy ashore and thus in nearshore areas that support a number of different human uses. We show that the maximum combined economic benefit from wave energy and other uses is likely to be realized if wave energy facilities are sited in areas that maximize wave energy NPV and minimize conflict with existing ocean uses. Our tools will help decision-makers explore alternative locations for wave energy facilities by mapping expected wave energy NPV and helping to identify sites that provide maximal returns yet avoid spatial competition with existing ocean uses
Trace ideals for Fourier integral operators with non-smooth symbols II
We consider Fourier integral operators with symbols in modulation spaces and
non-smooth phase functions whose second orders of derivatives belong to certain
types of modulation space. We establish continuity and Schatten-von Neumann
properties of such operators when acting on modulation spaces.Comment: 25 page
Thirty-fold: Extreme gravitational lensing of a quiescent galaxy at
We report the discovery of eMACSJ1341-QG-1, a quiescent galaxy at
located behind the massive galaxy cluster eMACSJ1341.92442 (). The
system was identified as a gravitationally lensed triple image in Hubble Space
Telescope images obtained as part of a snapshot survey of the most X-ray
luminous galaxy clusters at and spectroscopically confirmed in
ground-based follow-up observations with the ESO/X-Shooter spectrograph. From
the constraints provided by the triple image, we derive a first, crude model of
the mass distribution of the cluster lens, which predicts a gravitational
amplification of a factor of 30 for the primary image and a factor of
6 for the remaining two images of the source, making eMACSJ1341-QG-1 by
far the most strongly amplified quiescent galaxy discovered to date. Our
discovery underlines the power of SNAPshot observations of massive, X-ray
selected galaxy clusters for lensing-assisted studies of faint background
populations
The size-star formation relation of massive galaxies at 1.5<z<2.5
We study the relation between size and star formation activity in a complete
sample of 225 massive (M > 5 x 10^10 Msun) galaxies at 1.5<z<2.5, selected from
the FIREWORKS UV-IR catalog of the CDFS. Based on stellar population synthesis
model fits to the observed restframe UV-NIR SEDs, and independent MIPS 24
micron observations, 65% of galaxies are actively forming stars, while 35% are
quiescent. Using sizes derived from 2D surface brightness profile fits to high
resolution (FWHM_{PSF}~0.45 arcsec) groundbased ISAAC data, we confirm and
improve the significance of the relation between star formation activity and
compactness found in previous studies, using a large, complete mass-limited
sample. At z~2, massive quiescent galaxies are significantly smaller than
massive star forming galaxies, and a median factor of 0.34+/-0.02 smaller than
galaxies of similar mass in the local universe. 13% of the quiescent galaxies
are unresolved in the ISAAC data, corresponding to sizes <1 kpc, more than 5
times smaller than galaxies of similar mass locally. The quiescent galaxies
span a Kormendy relation which, compared to the relation for local early types,
is shifted to smaller sizes and brighter surface brightnesses and is
incompatible with passive evolution. The progenitors of the quiescent galaxies,
were likely dominated by highly concentrated, intense nuclear star bursts at
z~3-4, in contrast to star forming galaxies at z~2 which are extended and
dominated by distributed star formation.Comment: 6 pages, 4 figures, accepted for publication in Ap
Distant red galaxies in the Hubble Ultra Deep Field
We take advantage of the Hubble Ultra Deep Field (UDF) data to study the
restframe optical and ultra violet (UV) morphologies of the novel population of
Distant Red Galaxies (DRGs). Six galaxies with J-Ks > 2.3 are found to Ks=21.5,
five of which have photometric redshifts z_phot > 2, corresponding to a surface
density of 0.9/arcmin^2. The surface brightness distributions of the z_phot > 2
galaxies are better represented by exponential disks than R^{1/4}-laws. Two of
the z_phot > 2 galaxies are extended, while three have compact morphologies.
The restframe optical morphology of the z_phot > 2 galaxies is quite different
from the restframe UV morphology: all the galaxies have red central components
which dominate in the NICMOS H_{160}-band images, and distinct off-center blue
features which show up in (and often dominate) the ACS images. The mean
measured effective radius of the z_phot > 2 galaxies is =1.9+/-1.4 kpc,
similar (within the errors) to the mean size of LBGs at similar redshifts. All
the DRGs are resolved in the ACS images, while four are resolved in the NICMOS
images. Two of the z_phot > 2 galaxies are bright X-ray sources and hence host
AGN. The diverse restframe optical and UV morphological properties of DRGs
derived here suggest that they have complex stellar populations, consisting of
both evolved populations that dominate the mass and the restframe optical
light, and younger populations, which show up as patches of star formation in
the restframe UV light; in many ways resembling the properties of normal local
galaxies. This interpretation is supported by fits to the broadband SEDs, which
for all five z_phot > 2 are best represented by models with extended star
formation histories and substantial amounts of dust.Comment: Accepted for publication in APJ
Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor
The upgrade of the cold neutron triple-axis spectrometer FLEXX is described.
We discuss the characterisation of the gains from the new primary spectrometer,
including a larger guide and double focussing monochromator, and present
measurements of the energy and momentum resolution and of the neutron flux of
the instrument. We found an order of magnitude gain in intensity (at the cost
of coarser momentum resolution), and that the incoherent elastic energy widths
are measurably narrower than before the upgrade. The much improved count rate
should allow the use of smaller single crystals samples and thus enable the
upgraded FLEXX spectrometer to continue making leading edge measurements.Comment: 8 pages, 7 figures, 5 table
Changes of variables in modulation and Wiener amalgam spaces
In this paper various properties of global and local changes of variables as well as properties of canonical transforms are investigated on modulation and Wiener amalgam spaces. We establish several relations among localisations of such spaces and, as a consequence, we obtain several versions of local and global Beurling–Helson type theorems. We also establish a number of positive results such as local boundedness of canonical transforms on modulation spaces, properties of homogeneous changes of variables, and local continuity of Fourier integral operators on equation image. Finally, counterparts of these results are discussed for spaces on the torus
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