171 research outputs found
OBJECT-BASED CLASSIFICATION OF EARTHQUAKE DAMAGE FROM HIGH-RESOLUTION OPTICAL IMAGERY USING MACHINE LEARNING
Object-based approaches to the segmentation and supervised classification of remotely-sensed images yield more promising results compared to traditional pixel-based approaches. However, the development of an object-based approach presents challenges in terms of algorithm selection and parameter tuning. Subjective methods and trial and error are often used, but time consuming and yield less than optimal results. Objective methods are warranted, especially for rapid deployment in time sensitive applications such as earthquake induced damage assessment.
Our research takes a systematic approach to evaluating object-based image segmentation and machine learning algorithms for the classification of earthquake damage in remotely-sensed imagery using Trimble’s eCognition software. We tested a variety of algorithms and parameters on post-event aerial imagery of the 2011 earthquake in Christchurch, New Zealand. Parameters and methods are adjusted and results compared against manually selected test cases representing different classifications used. In doing so, we can evaluate the effectiveness of the segmentation and classification of buildings, earthquake damage, vegetation, vehicles and paved areas, and compare different levels of multi-step image segmentations. Specific methods and parameters explored include classification hierarchies, object selection strategies, and multilevel segmentation strategies.
This systematic approach to object-based image classification is used to develop a classifier that is then compared against current pixel-based classification methods for post-event imagery of earthquake damage. Our results show a measurable improvement against established pixel-based methods as well as object-based methods for classifying earthquake damage in high resolution, post-event imagery
Characterization of dimensional changes of cement pastes and mortars in fresh state applying an interferometric technique
The effect produced by the incorporation of additives in Portland cement based materials over dimensional changes occurring during the setting process was evaluated employing a fiber optic Fizeau interferometric sensor. The sensor system employed a broadband light source (SLED) centered at 1550 nm, whose spectral emission was modulated by the interferometer formed between the material surface and the end of the optical fiber used to illuminate the sample. An optical spectrum analyzer was used to monitor the variation of the modulated spectrum, while the mentioned process took place. The expansion or contraction experienced by materials with different compositions was observed and quantified. Results obtained point out the accuracy and the potential of the technique.Fil: Mesa Yandy, Angelica Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigaciones Opticas (i); Argentina. Universidad Nacional de La Plata. Facultad de Ingenieria; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Duchowicz, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigaciones Opticas (i); Argentina. Universidad Austral. Facultad de Ingeniería; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Russo, Nelida Araceli. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigaciones Opticas (i); Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Zerbino, Raul Luis. Universidad Nacional de La Plata. Facultad de Ingenieria; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentin
PACOMAR 91/92 - Fahrtbericht SONNE 76 [SO76], 20. Dezember 1991 bis 25. Januar 1992
Das PACOMAR Projekt (PAcific COntinental MARgins) ist ein gemeinsames
Vorhaben von deutschen und costaricanischen Forschungseinrichtungen.
Es wird hauptsächlich unterstützt vom Bundesministerium für
Forschung und Technologie (BMFT) in Form von Zuwendungen an das
GEOMAR-Forschungszentrum für marine Geowissenschaften, an das
Geologisch-Paläontologische Institut (GPI) der Christian-Aibrechts-Universität
zu Kiel sowie an die Bundesanstalt für Geowissenschaften
und Rohstoffe (BGR) in Hannover. Auf Seiten Costa Ricas wird das
Projekt durch Kooperation mit der costaricanischen
Elektrizitätsgesellschaft (ICE), dem Geologischen Institut an der
Universität Costa Rica und der costaricanischen Erdölgesellschaft
(RECOPE) unterstützt.
Dieses Vorhaben befaßt sich mit der Untersuchung von katastrophalen
Naturereignissen, wie Erdbeben oder durch sie erzeugte Flutwellen
(Tsunamis), und grundlegenden vulkanischen Prozessen. In diesem
Fahrtbericht sind die ersten Ergebnisse der Forschungsfahrt S0-76 mit
dem F/S Sonne vom 20. Dezember 1991 bis zum 25. Januar 1992 zusammengefaßt.
Diese Ergebnisse sowie anschließende Laboruntersuchungen
und Auswertungen an Land bilden die Grundlage für die Pla-nungen
und Vorbereitungen einer zweiten Fahrt mit dem gleichen Forschungsschiff,
S0-81, im August und September 1992
Equation of state and initial temperature of quark gluon plasma at RHIC
In gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) a
perfect fluid of quarks, sometimes called the strongly interacting quark gluon
plasma (sQGP) is created for an extremely short time. The time evolution of
this fluid can be described by hydrodynamical models. After expansion and
cooling, the freeze-out happens and hadrons are created. Their distribution
reveals information about the final state of the fluid. To investigate the time
evolution one needs to analyze penetrating probes, such as direct photon
observables. Transverse momentum distributions of low energy direct photons
were mesured in 2010 by PHENIX, while azimuthal asymmetry in 2011. These
measurements can be compared to hydrodynamics to determine the equation of
state and the initial temperature of sQGP. In this paper we analyze an 1+3
dimensional solution of relativistic hydrodynamics. We calculate momentum
distribution, azimuthal asymmetry and momentum correlations of direct photons.
Based on earlier fits to hadronic spectra, we compare photon calculations to
measurements to determine the equation of state and the initial temperature of
sQGP. We find that the initial temperature in the center of the fireball is
507+-12 MeV, while for the sound speed we get a speed of sound of 0.36+-0.02.
We also estimate a systematic error of these results. We find that the measured
azimuthal asymmetry is also not incompatible with this model, and predict a
photon source that is significantly larger in the out direction than in the
side direction.Comment: 12 pages, 4 figures. This work was supported by the OTKA grant
NK-73143 and NK-101438 and M. Csanad's Bolyai scholarshi
Quantum geometry of 2d gravity coupled to unitary matter
We show that there exists a divergent correlation length in 2d quantum
gravity for the matter fields close to the critical point provided one uses the
invariant geodesic distance as the measure of distance. The corresponding
reparameterization invariant two-point functions satisfy all scaling relations
known from the ordinary theory of critical phenomena and the KPZ exponents are
determined by the power-like fall off of these two-point functions. The only
difference compared to flat space is the appearance of a dynamically generated
fractal dimension d_h in the scaling relations. We analyze numerically the
fractal properties of space-time for Ising and three-states Potts model coupled
to 2d dimensional quantum gravity using finite size scaling as well as small
distance scaling of invariant correlation functions. Our data are consistent
with d_h=4, but we cannot rule out completely the conjecture d_H =
-2\alpha_1/\alpha_{-1}, where \alpha_{-n} is the gravitational dressing
exponent of a spin-less primary field of conformal weight (n+1,n+1). We compute
the moments and the loop-length distribution function and show that the
fractal properties associated with these observables are identical, with good
accuracy, to the pure gravity case.Comment: LaTeX2e, 38 pages, 13 figures, 32 eps files, added one referenc
The quantum space-time of c=-2 gravity
We study the fractal structure of space-time of two-dimensional quantum
gravity coupled to c=-2 conformal matter by means of computer simulations. We
find that the intrinsic Hausdorff dimension d_H = 3.58 +/- 0.04. This result
supports the conjecture d_H = -2 \alpha_1/\alpha_{-1}, where \alpha_n is the
gravitational dressing exponent of a spinless primary field of conformal weight
(n+1,n+1), and it disfavours the alternative prediction d_H = 2/|\gamma|. On
the other hand ~ r^{2n} for n>1 with good accuracy, i.e. the boundary
length l has an anomalous dimension relative to the area of the surface.Comment: 46 pages, 16 figures, 32 eps files, using psfig.sty and epsf.st
Inclusive and Diffractive Structure Functions at Small x
In the semiclassical approach, inclusive and diffractive quark and gluon
distributions are expressed in terms of correlation functions of Wilson loops.
Each Wilson loop integrates the colour field strength in the area between the
trajectories of two fast partons penetrating the proton. We introduce a
specific model for averaging over the relevant colour field configurations.
Within this model, all parton distributions at some low scale Q_0^2 are given
in terms of three parameters. Inclusive and diffractive structure functions at
higher values of Q^2 are determined in a leading-order QCD analysis. In both
cases, the evolution is driven by a large gluon distribution. A satisfactory
description of the structure functions F_2(x,Q^2) and F_2^D(3)(xi,beta,Q^2) is
obtained. The observed rise of F_2^D(3) with xi is parametrized by a
non-perturbative logarithmic energy dependence, compatible with unitarity. In
our analysis, the observed rise of F_2 at small x is largely due to the same
effect.Comment: 26 pages LaTeX, 8 figures included, uses psfi
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