## Search

Now showing items 1-10 of 12

#### Recognition and matching in the presence of deformation and lighting change

(2008-11-21)

Natural images of objects and scenes show a fascinating amount of
variability due to different factors like lighting and viewpoint change,
occlusion, articulation and non-rigid deformation. There are certain cases
like recognition of specular objects and images with arbitrary deformations
where existing techniques do not perform well. For image deformation, we
propose a method for faster keypoint matching with histogram descriptors and a
completely deformation invariant representation. We also propose a method for
improving specular object recognition.
Histograms are a powerful statistical representation for keypoint matching
and content based image retrieval. The <EM>earth mover's distance</EM> (EMD) is an
important perceptually meaningful metric for comparing histograms, but it
suffers from high (O(n<SUP>3</SUP> log n)) computational complexity. We
propose a novel

**linear time**algorithm for approximating EMD with the weighted L<SUB>1</SUB> norm of the wavelet transform of the difference histogram. We prove that the resulting wavelet EMD metric is equivalent to EMD. We experimentally show that wavelet EMD is a good approximation to EMD, has similar performance, but requires much less computation. We also give a fast algorithm for the best partial EMD match between two histograms. Images of non-planar object can undergo a large non-linear deformation due to a viewpoint change. Complex deformations occur in images of non-rigid objects, for example, in medical image sequences. We propose using the <EM>contour tree</EM> as a novel framework invariant to arbitrary deformations for representing and comparing images. It represents all the deformation invariant information in an image. Lighting changes greatly affect the appearance of <EM>specular</EM> objects and make recognition difficult much more than for Lambertian objects. In model based recognition of specular objects, an important constraint is that the estimated lighting should be non-negative everywhere. We propose a new method to enforce this constraint and explore its usefulness in specular object recognition, using the spherical harmonic representation of lighting. The new method is faster as well as more accurate than previous methods. Experiments on both synthetic and real data indicate that the constraint can improve recognition of specular objects by better separating the correct and incorrect models....#### Algorithms for Solving Linear and Polynomial Systems of Equations over Finite Fields with Applications to Cryptanalysis

(2007-06-07)

This dissertation contains algorithms for solving linear and polynomial systems
of equations over GF(2). The objective is to provide fast and exact tools for algebraic
cryptanalysis and other applications. Accordingly, it ...

#### Gradient Flow Based Matrix Joint Diagonalization for Independent Componenet Analysis

(2004-05-06)

In this thesis, employing the theory of matrix Lie groups, we develop gradient based flows for the problem of Simultaneous or Joint Diagonalization (JD) of a set of symmetric matrices. This problem has applications in many ...

#### The Virtual Filament Model

(2006-08-04)

In the present work, a framework is proposed for studying autonomous agents which interact locally yet effect a globally coherent behavior. This problem of locally induced organization is ubiquitous in decentralized ...

#### NONLINEAR SPIN DYNAMICS AND ULTRA-FAST PRECESSIONAL SWITCHING

(2005-04-20)

This thesis is intended to provide a theoretical analysis of magnetization dynamics in nanometer scale structures over picosecond time scales. This research has been motivated by promising technological applications in the ...

#### The ADI-FDTD Method for High Accuracy Electrophysics Applications

(2006-11-24)

The Finite-Difference Time-Domain (FDTD) is a dependable method to simulate a wide range of problems from acoustics, to electromagnetics, and to photonics, amongst others. The execution time of an FDTD simulation is inversely ...

#### Entropy-Based Moment Closures in Semiconductor Models

(2006-04-27)

We investigate aspects of entropy-based moment closures which are used to simplify kinetic models of particle systems. Closures of this type use variational principles to formally generate balance laws for velocity moments ...

#### Multicasting in All-Optical WDM Networks

(2008-09-26)

n this dissertation, we study the problem of (i) routing and wavelength assignment, and (ii) traffic grooming for multicast traffic in Wavelength Division Multiplexing (WDM) based all-optical networks.
We focus on the ...

#### Network Tomography

(2006-08-24)

While conventional tomography is associated to the Radon transform in Euclidean spaces, electrical impedance tomography, or EIT, is associated to the Radon transform in the hyperbolic plane. In this dissertation, we discuss ...

#### Robust Network Trust Establishment for Collaborative Applications and Protocols

(2007-05-07)

In networks without centralized control (e.g. ad-hoc or peer-to-peer networks) the users cannot always be assumed to follow the protocol that they are supposed to. They will cooperate in the operation of the network to the ...