851 research outputs found
Forest inventory attribute estimation using airborne laser scanning, aerial stereoimagery, radargrammetry and interferometry - Finnish experiences of the 3D techniques
Three-dimensional (3D) remote sensing has enabled detailed mapping of terrain and vegetation heights. Consequently, forest
inventory attributes are estimated more and more using point clouds and normalized surface models. In practical applications,
mainly airborne laser scanning (ALS) has been used in forest resource mapping. The current status is that ALS-based forest
inventories are widespread, and the popularity of ALS has also raised interest toward alternative 3D techniques, including airborne
and spaceborne techniques. Point clouds can be generated using photogrammetry, radargrammetry and interferometry. Airborne
stereo imagery can be used in deriving photogrammetric point clouds, as very-high-resolution synthetic aperture radar (SAR) data
are used in radargrammetry and interferometry. ALS is capable of mapping both the terrain and tree heights in mixed forest
conditions, which is an advantage over aerial images or SAR data. However, in many jurisdictions, a detailed ALS-based digital
terrain model is already available, and that enables linking photogrammetric or SAR-derived heights to heights above the ground.
In other words, in forest conditions, the height of single trees, height of the canopy and/or density of the canopy can be measured
and used in estimation of forest inventory attributes. In this paper, first we review experiences of the use of digital stereo imagery
and spaceborne SAR in estimation of forest inventory attributes in Finland, and we compare techniques to ALS. In addition, we
aim to present new implications based on our experiences
Local behavior of p-harmonic Green's functions in metric spaces
We describe the behavior of p-harmonic Green's functions near a singularity
in metric measure spaces equipped with a doubling measure and supporting a
Poincar\'e inequality
System size dependence of nuclear modification and azimuthal anisotropy of jet quenching
We investigate the system size dependence of jet-quenching by analyzing
transverse momentum spectra of neutral pions in Au+Au and Cu+Cu collisions at
=200 GeV for different centralities. The fast partons
are assumed to lose energy by radiating gluons as they traverse the plasma and
undergo multiple collisions. The energy loss per collision, , is
taken as proportional to (where is the energy of the parton),
proportional to , or a constant depending on whether the formation
time of the gluon is less than the mean path, greater than the mean free path
but less than the path length, or greater than the path length of the partons,
respectively. NLO pQCD is used to evaluate pion production by modifying the
fragmentation function to account for the energy loss. We reproduce the nuclear
modification factor by treating as the only free
parameter, depending on the centrality and the mechanism of energy loss. These
values are seen to explain the nuclear modification of prompt photons, caused
by the energy lost by final state quarks before they fragment into photons.
These also reproduce the azimuthal asymmetry of transverse momentum
distribution for pions within a factor of two and for prompt photons in a fair
agreement with experimental data.Comment: 26 pages, 17 figures. One more figure added. Discussion expanded.
Typographical corrections done, several references added. To appear in
Journal of Physics
The H\"older-Poincar\'e Duality for -cohomology
We prove the following version of Poincare duality for reduced
-cohomology: For any , the -cohomology of a
Riemannian manifold is in duality with the interior 1/p+1/p'=11/q+1/q'=1$.Comment: 21 page
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