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Multitemporal Spaceborne Polarimetric SAR Data for Urban Land Cover MappingNiu, Xin January 2012 (has links)
Urban land cover mapping represents one of the most important remote sensing applications in the context of rapid global urbanization. In recent years, high resolution spaceborne Polarimetric Synthetic Aperture Radar (PolSAR) has been increasingly used for urban land cover/land-use mapping, since more information could be obtained in multiple polarizations and the collection of such data is less influenced by solar illumination and weather conditions. The overall objective of this research is to develop effective methods to extract accurate and detailed urban land cover information from spaceborne PolSAR data. Six RADARSAT-2 fine-beam polarimetric SAR and three RADARSAT-2 ultra-fine beam SAR images were used. These data were acquired from June to September 2008 over the north urban-rural fringe of the Greater Toronto Area, Canada. The major landuse/land-cover classes in this area include high-density residential areas, low-density residential areas, industrial and commercial areas, construction sites, roads, streets, parks, golf courses, forests, pasture, water and two types of agricultural crops. In this research, various polarimetric SAR parameters were evaluated for urban land cover mapping. They include the parameters from Pauli, Freeman and Cloude-Pottier decompositions, coherency matrix, intensities of each polarization and their logarithms. Both object-based and pixel-based classification approaches were investigated. Through an object-based Support Vector Machine (SVM) and a rule-based approach, efficiencies of various PolSAR features and the multitemporal data combinations were evaluated. For the pixel-based approach, a contextual Stochastic Expectation-Maximization (SEM) algorithm was proposed. With an adaptive Markov Random Field (MRF) and a modified Multiscale Pappas Adaptive Clustering (MPAC), contextual information was explored to improve the mapping results. To take full advantages of alternative PolSAR distribution models, a rule-based model selection approach was put forward in comparison with a dictionary-based approach. Moreover, the capability of multitemporal fine-beam PolSAR data was compared with multitemporal ultra-fine beam C-HH SAR data. Texture analysis and a rule-based approach which explores the object features and the spatial relationships were applied for further improvement. Using the proposed approaches, detailed urban land-cover classes and finer urban structures could be mapped with high accuracy in contrast to most of the previous studies which have only focused on the extraction of urban extent or the mapping of very few urban classes. It is also one of the first comparisons of various PolSAR parameters for detailed urban mapping using an object-based approach. Unlike other multitemporal studies, the significance of complementary information from both ascending and descending SAR data and the temporal relationships in the data were the focus in the multitemporal analysis. Further, the proposed novel contextual analyses could effectively improve the pixel-based classification accuracy and present homogenous results with preserved shape details avoiding over-averaging. The proposed contextual SEM algorithm, which is one of the first to combine the adaptive MRF and the modified MPAC, was able to mitigate the degenerative problem in the traditional EM algorithms with fast convergence speed when dealing with many classes. This contextual SEM outperformed the contextual SVM in certain situations with regard to both accuracy and computation time. By using such a contextual algorithm, the common PolSAR data distribution models namely Wishart, G0p, Kp and KummerU were compared for detailed urban mapping in terms of both mapping accuracy and time efficiency. In the comparisons, G0p, Kp and KummerU demonstrated better performances with higher overall accuracies than Wishart. Nevertheless, the advantages of Wishart and the other models could also be effectively integrated by the proposed rule-based adaptive model selection, while limited improvement could be observed by the dictionary-based selection, which has been applied in previous studies. The use of polarimetric SAR data for identifying various urban classes was then compared with the ultra-fine-beam C-HH SAR data. The grey level co-occurrence matrix textures generated from the ultra-fine-beam C-HH SAR data were found to be more efficient than the corresponding PolSAR textures for identifying urban areas from rural areas. An object-based and pixel-based fusion approach that uses ultra-fine-beam C-HH SAR texture data with PolSAR data was developed. In contrast to many other fusion approaches that have explored pixel-based classification results to improve object-based classifications, the proposed rule-based fusion approach using the object features and contextual information was able to extract several low backscatter classes such as roads, streets and parks with reasonable accuracy. / <p>QC 20121112</p>
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Interplay of Disorder and Transverse-Field Induced Quantum Fluctuations in the LiHo_xY_{1-x}F_4 Ising Magnetic MaterialTabei, Seyed Mohiaddeen Ali January 2008 (has links)
The LiHo_xY_{1-x}F_4 magnetic material in a transverse magnetic
field B_x perpendicular to the Ising spin direction has long been used
to study tunable quantum phase transitions in pure and random disordered systems.
We first present analytical and numerical evidences for the validity of an effective spin-1/2
approach to the description of a general dipolar spin
glass model with strong uniaxial Ising anisotropy and subject to weak
B_x.
We relate this toy model to the LiHo_xY_{1-x}F_4 transverse field Ising material.
We show that an effective spin-1/2
model is able to capture both the qualitative and quantitative aspects of the
physics at small B_x.
After confirming the validity of the effective spin-1/2 approach, we show that the field-induced magnetization along the
x direction,
combined with the local random dilution-induced
destruction of crystalline mirror symmetries
generates, via the predominant dipolar interactions between Ho^{3+} ions,
random fields along the Ising z direction.
This identifies LiHo_xY_{1-x}F_4 in B_x as a new
random field Ising system.
We show that the random fields explain the smearing
of the nonlinear susceptibility at the spin glass transition
with increasing B_x.
In this thesis, we also investigate the phase diagram of non-diluted LiHoF_4 in the presence of B_x, by performing
Monte-Carlo simulations. A previous quantum Monte Carlo (QMC) simulation found that even for small B_x where quantum fluctuations are small, close to the classical critical
point, there is a discrepancy between experiment and the QMC results. We revisit this problem, focusing on
weak B_x close to the classical T_c, using an alternative approach. For small B_x, by applying a so-called cumulant
expansion, the quantum fluctuations around the classical T_c are taken into account perturbatively. We derived an effective
perturbative classical Hamiltonian, on which MC simulations are performed. With this method we
investigate different proposed sources of uncertainty which can affect the numerical results.
We fully reproduce the previous QMC results at small B_x. Unfortunately, we find that
none of the modifications to the microscopic Hamiltonian that we explore are able to provide a B_x-T phase diagram compatible with the experiments in the small
semi-classical B_x regime.
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Interplay of Disorder and Transverse-Field Induced Quantum Fluctuations in the LiHo_xY_{1-x}F_4 Ising Magnetic MaterialTabei, Seyed Mohiaddeen Ali January 2008 (has links)
The LiHo_xY_{1-x}F_4 magnetic material in a transverse magnetic
field B_x perpendicular to the Ising spin direction has long been used
to study tunable quantum phase transitions in pure and random disordered systems.
We first present analytical and numerical evidences for the validity of an effective spin-1/2
approach to the description of a general dipolar spin
glass model with strong uniaxial Ising anisotropy and subject to weak
B_x.
We relate this toy model to the LiHo_xY_{1-x}F_4 transverse field Ising material.
We show that an effective spin-1/2
model is able to capture both the qualitative and quantitative aspects of the
physics at small B_x.
After confirming the validity of the effective spin-1/2 approach, we show that the field-induced magnetization along the
x direction,
combined with the local random dilution-induced
destruction of crystalline mirror symmetries
generates, via the predominant dipolar interactions between Ho^{3+} ions,
random fields along the Ising z direction.
This identifies LiHo_xY_{1-x}F_4 in B_x as a new
random field Ising system.
We show that the random fields explain the smearing
of the nonlinear susceptibility at the spin glass transition
with increasing B_x.
In this thesis, we also investigate the phase diagram of non-diluted LiHoF_4 in the presence of B_x, by performing
Monte-Carlo simulations. A previous quantum Monte Carlo (QMC) simulation found that even for small B_x where quantum fluctuations are small, close to the classical critical
point, there is a discrepancy between experiment and the QMC results. We revisit this problem, focusing on
weak B_x close to the classical T_c, using an alternative approach. For small B_x, by applying a so-called cumulant
expansion, the quantum fluctuations around the classical T_c are taken into account perturbatively. We derived an effective
perturbative classical Hamiltonian, on which MC simulations are performed. With this method we
investigate different proposed sources of uncertainty which can affect the numerical results.
We fully reproduce the previous QMC results at small B_x. Unfortunately, we find that
none of the modifications to the microscopic Hamiltonian that we explore are able to provide a B_x-T phase diagram compatible with the experiments in the small
semi-classical B_x regime.
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A New Look Into Image Classification: Bootstrap ApproachOchilov, Shuhratchon January 2012 (has links)
Scene classification is performed on countless remote sensing images in support of operational activities. Automating this process is preferable since manual pixel-level classification is not feasible for large scenes. However, developing such an algorithmic solution is a challenging task due to both scene complexities and sensor limitations. The objective is to develop efficient and accurate unsupervised methods for classification (i.e., assigning each pixel to an appropriate generic class) and for labeling (i.e., properly assigning true labels to each class). Unique from traditional approaches, the proposed bootstrap approach achieves classification and labeling without training data. Here, the full image is partitioned into subimages and the true classes found in each subimage are provided by the user. After these steps, the rest of the process is automatic. Each subimage is individually classified into regions and then using the joint information from all subimages and regions the optimal configuration of labels is found based on an objective function based on a Markov random field (MRF) model. The bootstrap approach has been successfully demonstrated with SAR sea-ice and lake ice images which represent challenging scenes used operationally for ship navigation, climate study, and ice fraction estimation. Accuracy assessment is based on evaluation conducted by third party experts. The bootstrap method is also demonstrated using synthetic and natural images. The impact of this technique is a repeatable and accurate methodology that generates classified maps faster than the standard methodology.
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On Parametric and Nonparametric Methods for Dependent DataBandyopadhyay, Soutir 2010 August 1900 (has links)
In recent years, there has been a surge of research interest in the analysis of time series
and spatial data. While on one hand more and more sophisticated models are being
developed, on the other hand the resulting theory and estimation process has become
more and more involved. This dissertation addresses the development of statistical
inference procedures for data exhibiting dependencies of varied form and structure.
In the first work, we consider estimation of the mean squared prediction error
(MSPE) of the best linear predictor of (possibly) nonlinear functions of finitely many
future observations in a stationary time series. We develop a resampling methodology
for estimating the MSPE when the unknown parameters in the best linear predictor
are estimated. Further, we propose a bias corrected MSPE estimator based on the
bootstrap and establish its second order accuracy. Finite sample properties of the
method are investigated through a simulation study.
The next work considers nonparametric inference on spatial data. In this work
the asymptotic distribution of the Discrete Fourier Transformation (DFT) of spatial
data under pure and mixed increasing domain spatial asymptotic structures are
studied under both deterministic and stochastic spatial sampling designs. The deterministic
design is specified by a scaled version of the integer lattice in IRd while
the data-sites under the stochastic spatial design are generated by a sequence of independent
random vectors, with a possibly nonuniform density. A detailed account
of the asymptotic joint distribution of the DFTs of the spatial data is given which, among other things, highlights the effects of the geometry of the sampling region and
the spatial sampling density on the limit distribution. Further, it is shown that in
both deterministic and stochastic design cases, for "asymptotically distant" frequencies,
the DFTs are asymptotically independent, but this property may be destroyed if
the frequencies are "asymptotically close". Some important implications of the main
results are also given.
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Multi-view Video Coding Via Dense Depth FieldOzkalayci, Burak Oguz 01 September 2006 (has links) (PDF)
Emerging 3-D applications and 3-D display technologies raise
some transmission problems of the next-generation multimedia data.
Multi-view Video Coding (MVC) is one of the challenging topics in
this area, that is on its road for standardization via ISO MPEG. In
this thesis, a 3-D geometry-based MVC approach is proposed and
analyzed in terms of its compression performance. For this purpose,
the overall study is partitioned into three preceding parts. The
first step is dense depth estimation of a view from a fully
calibrated multi-view set. The calibration information and
smoothness assumptions are utilized for determining dense
correspondences via a Markov Random Field (MRF) model, which is
solved by Belief Propagation (BP) method. In the second part, the
estimated dense depth maps are utilized for generating (predicting)
arbitrary (other camera) views of a scene, that is known as novel
view generation. A 3-D warping algorithm, which is followed by an
occlusion-compatible hole-filling process, is implemented for this
aim. In order to suppress the occlusion artifacts, an intermediate
novel view generation method, which fuses two novel views generated
from different source views, is developed. Finally, for the last
part, dense depth estimation and intermediate novel view generation
tools are utilized in the proposed H.264-based MVC scheme for the
removal of the spatial redundancies between different views. The
performance of the proposed approach is compared against the
simulcast coding and a recent MVC proposal, which is expected to be
the standard recommendation for MPEG in the near future. These
results show that the geometric approaches in MVC can still be
utilized, especially in certain 3-D applications, in addition to
conventional temporal motion compensation techniques, although the
rate-distortion performances of geometry-free approaches are quite
superior.
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A Fusion Model For Enhancement of Range Images / EnglishHua, Xiaoben, Yang, Yuxia January 2012 (has links)
In this thesis, we would like to present a new way to enhance the “depth map” image which is called as the fusion of depth images. The goal of our thesis is to try to enhance the “depth images” through a fusion of different classification methods. For that, we will use three similar but different methodologies, the Graph-Cut, Super-Pixel and Principal Component Analysis algorithms to solve the enhancement and output of our result. After that, we will compare the effect of the enhancement of our result with the original depth images. This result indicates the effectiveness of our methodology. / Room 401, No.56, Lane 21, Yin Gao Road, Shanghai, China
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Stochastic Modelling and Analysis for Bridges under Spatially Varying Ground MotionsZhang, Deyi January 2013 (has links)
Earthquake is undoubtedly one of the greatest natural disasters that can induce serious structural damage and huge losses of properties and lives. The resulting destructive consequences not only have made structural seismic analysis and design much more important but have impelled the necessity of more realistic representation of ground motions, such as inclusion of ground motion spatial variations in earthquake modelling and seismic analysis and design of structures.
Recorded seismic ground motions exhibit spatial variations in their amplitudes and phases, and the spatial variabilities have an important effect on the responses of structures extended in space, such as long span bridges. Because of the multi-parametric nature and the complexity of the problems, the development of specific design provisions on spatial variabilities of ground motions in modern seismic
codes has been impeded. Eurocode 8 is currently the only seismic standard worldwide that gives a set of detailed guidelines to explicitly tackle spatial variabilities of ground motions in bridge design, providing both a simplified design scheme and an analytical approach. However, there is gap between the code-specified provisions in Eurocode 8 and the realistic representation of spatially varying ground motions (SVGM) and the corresponding stochastic vibration analysis (SVA) approaches. This study is devoted to bridge this gap on modelling of SVGM and development of SVA approaches for structures extended in space under SVGM.
A complete and realistic SVGM representation approach is developed by accounting for the incoherence effect, wave-passage effect, site-response effect, ground motion nonstationarity, tridirectionality, and spectra-compatibility. This effort brings together
various aspects regarding rational seismic scenarios determination, comprehensive methods of accounting for varying site effects, conditional modelling of SVGM nonstationarity, and code-specified ground motion spectra-compatibility.
A comprehensive, systematic, and efficient SVA methodology is derived for long span structures under tridirectional nonstationary SVGM. An absolute-response-oriented scheme of pseudo-excitation method and an improved high precision direct
integration method are proposed to reduce the enormous computational effort of conventional nonstationary SVA. A scheme accounting for tridirectional varying site-response effect is incorporated in the nonstationary SVA scheme systematically.
The proposed highly efficient and accurate SVA approach is implemented and verified in a general finite element analysis platform to make it readily applicable in SVA of complex structures. Based on the proposed SVA approach, parametric studies
of two practical long span bridges under SVGM are conducted.
To account for spatial randomness and variability of soil properties in soil-structure interaction analysis of structures under SVGM, a meshfree-Galerkin approach is proposed within the Karhunen-Loeve expansion scheme for representation of spatial soil properties modelled as a random field. The meshfree shape functions are proposed as a set of basis functions in the Galerkin scheme to solve integral equation of Karhunen-Loeve expansion, with a proposed optimization scheme in treating the compatibility between the target and analytical covariance models. The accuracy and validity of the meshfree-Galerkin scheme are assessed and demonstrated by representation of covariance models for various homogeneous and nonhomogeneous spatial fields.
The developed modelling approaches of SVGM and the derived analytical SVA approaches can be applied to provide more refined solutions for quantitatively assessing code-specified design provisions and developing new design provisions. The proposed meshfree-Galerkin approach can be used to account for spatial randomness and variability of soil properties in soil-structure interaction analysis.
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A New Look Into Image Classification: Bootstrap ApproachOchilov, Shuhratchon January 2012 (has links)
Scene classification is performed on countless remote sensing images in support of operational activities. Automating this process is preferable since manual pixel-level classification is not feasible for large scenes. However, developing such an algorithmic solution is a challenging task due to both scene complexities and sensor limitations. The objective is to develop efficient and accurate unsupervised methods for classification (i.e., assigning each pixel to an appropriate generic class) and for labeling (i.e., properly assigning true labels to each class). Unique from traditional approaches, the proposed bootstrap approach achieves classification and labeling without training data. Here, the full image is partitioned into subimages and the true classes found in each subimage are provided by the user. After these steps, the rest of the process is automatic. Each subimage is individually classified into regions and then using the joint information from all subimages and regions the optimal configuration of labels is found based on an objective function based on a Markov random field (MRF) model. The bootstrap approach has been successfully demonstrated with SAR sea-ice and lake ice images which represent challenging scenes used operationally for ship navigation, climate study, and ice fraction estimation. Accuracy assessment is based on evaluation conducted by third party experts. The bootstrap method is also demonstrated using synthetic and natural images. The impact of this technique is a repeatable and accurate methodology that generates classified maps faster than the standard methodology.
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Phase transitions and multifractal properties of random field Ising modelsNowotny, Thomas 28 November 2004 (has links) (PDF)
In dieser Arbeit werden Zufallsfeld-Ising-Modelle mit einem eingefrorenen dichotomen symmetrischen Zufallsfeld für den eindimensionalen Fall und das Bethe-Gitter untersucht. Dabei wird die kanonische Zustandssumme zu der eines einzelnen Spins in einem effektiven Feld umformuliert. Im ersten Teil der Arbeit werden das mulktifraktale Spektrum dieses effektiven Feldes untersucht, Übergänge im Spektrum erklärt und Ungleichungen zwischen lokalen und globalen Dimensionsbegriffen bewiesen, die eine weitgehend vollständige Charakterisierung des multifraktalen Spektrums durch eine Reihe von Schranken erlauben. Ein weiterer Teil der Arbeit beschäftigt sich mit einer ähnlichen Charakterisierung des Maßes der lokalen Magnetisierung, das aus dem Maß des effektiven Feldes durch Faltung hervorgeht. In diesem Zusammenhang wird die Faltung von Multifraktalen in einem allgemeineren Rahmen behandelt und Zusammenhänge zwischen den multifraktalen Eigenschaften der Faltung und denen der gefalteten Maße bewiesen. Im dritten Teil der Dissertation wird der Phasenübergang von Ferro- zu Paramagnetismus im Modell auf dem Bethe Gitter untersucht. Neben verbesserten exakten Schranken für die Eindeutigkeit des paramagnetischen Zustands werden im wesentlichen drei Kriterien für die tatsächliche Lage des Übergangs angegeben und numerisch ausgewertet. Die multifraktalen Eigenschaften des effektiven Felds im Modell auf dem Bethe-Gitter schließlich erweisen sich als trivial, da die interessanten Dimensionen nicht existieren. / In this work random field Ising models with quenched dichotomous symmetric random field are considered for the one-dimensional case and on the Bethe lattice. To this end the canonical partition function is reformulated to the partition function of one spin in an effective field. In the first part of the work the multifractal spectrum of this effective field is investigated, transitions in the spectrum are explained and inequalities between local and global generalized fractal dimensions are proven which allow to characterize the multifractal spectrum bei various bounds. A further part of the work is dedicated to the characterization of the measure of the local magnetization which is obtained by convolution of the measure of the effective field with itself. In this context the convolution of multifractals is investigated in a more general setup and relations between the multifractal properties of the convolution and the multifractal properties of the convoluted measures are proven. The phase transition from ferro- to paramagnetismus for the model on the Bethe lattice is investigated in the third part of the thesis. Apart from improved exact bounds for the uniqueness of the paramagnetic state essentially three criteria for the transition are developped and numerically evaluated to determine the transition line. The multifractal properties of the effective field for the model on the Bethe lattice finally turn out to be trivial because the interesting dimensions do not exist.
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