Epistemic paradox and explicit modal logic
Year of Dissertation:
2010
The dissertation presents a unified treatment of what I refer to as the epistemic paradoxes (i.e. the Knower Paradox of Montague and Kaplan and Fitch's Paradox of Knowability) in the context of a quantified extension of Artemov's Logic of Proofs [LP]. The system adopted is a modified form of Fitting's Quantified Logic of Proofs [QLP] and contains not only so-called explicit modalities (i.e. statements of the form t:F with intended interpretation of "t denotes a proof of F") but also first-order quantifiers intended to range over proofs or informal justifications. This allows for a formalization of a justification-based notion of knowledge via statements of the form (exists x) x:F.
A SCALABLE AGENT-BASED SYSTEM FOR NETWORK FLOW RECONSTRUCTION WITH APPLICATIONS TO DETERMINING THE STRUCTURE AND DYNAMICS OF DISTRIBUTED DENIAL OF SERVICE ATTACKS
Year of Dissertation:
2010
In this thesis we describe a novel agent-based architecture for flow reconstruction, and demonstrate how it can be applied to obtain a description of the structure and dynamics of distributed denial of service (DDoS) attacks. We show that the system can operate in a decentralized manner, effectively providing a description of the structure and dynamics of traffic flows even with very modest levels of agent deployment. By providing structural information, the system facilitates the execution of DDoS mitigation strategies close to the actual sources of attack traffic.
Simplifying Network Testing: Techniques and Approaches Towards Automating and Simplifying the Testing Process
Author:
Constantinos Djouvas
Year of Dissertation:
2009
The dramatic increase of companies and consumers that heavily depend on networks mandates the creation of reliable network devices. Such reliability can be achieved by testing both the conformance of individual protocols of an implementation to their corresponding specifications and the interaction between different protocols. With the increase of computer power and the advances in network testing research, one would expect that efficient approaches for testing network implementations would be available. However, such approaches are not available due to reasons like the complexity of network protocols, the need for different protocols to interoperate, the limited information on implementation because of proprietary codes, and the potentially unbounded size of the network to be tested.
Multiscale Feature Extraction and Matching with Applications to 3D Face Recognition and 2D Shape Warping
Year of Dissertation:
2011
Shape matching is defined as the process of computing a dissimilarity measure between shapes. Partial 3D shape matching refers to a more difficult subproblem that deals with measuring the dissimilarity between partial regions of 3D objects. Despite a great deal of attention drawn to 3D shape matching in the fields of computer vision and computer graphics, partial shape matching applied to objects of arbitrary scale remains a difficult problem.
Automatic Readability Assessment
Year of Dissertation:
2010
We describe the development of an automatic tool to assess the readability of text documents. Our readability assessment tool predicts elementary school grade levels of texts with high accuracy. The tool is developed using supervised machine learning techniques on text corpora annotated with grade levels and other indicators of reading difficulty. Various independent variables or features are extracted from texts and used for automatic classification. We systematically explore different feature inventories and evaluate the grade-level prediction of the resulting classifiers. Our evaluation comprises well-known features at various linguistic levels from the existing literature, such as those based on language modeling, part-of-speech, syntactic parse trees, and shallow text properties, including classic readability formulas like the Flesch-Kincaid Grade Level formula. We focus in particular on discourse features, including three novel feature sets based on the density of entities, lexical chains, and coreferential inference, as well as features derived from entity grids. We evaluate and compare these different feature sets in terms of accuracy and mean squared error by cross-validation. Generalization to different corpora or domains is assessed in two ways. First, using two corpora of texts and their manually simplified versions, we evaluate how well our readability assessment tool can discriminate between original and simplified texts. Second, we measure the correlation between grade levels predicted by our tool, expert ratings of text difficulty, and estimated latent difficulty derived from experiments involving adult participants with mild intellectual disabilities. The applications of this work include selection of reading material tailored to varying proficiency levels, ranking of documents by reading difficulty, and automatic document summarization and text simplification.
SEARCHING FOR MOBILE DATA WITH A PRIORI STATISTICAL KNOWLEDGE OF THEIR WHEREABOUTS UNDER DELAY CONSTRAINTS
Year of Dissertation:
2011
One or more tokens are hidden into several boxes, and then the boxes are locked. The probabilities of each token being found in each box are known. All the probabilities are independent. A searcher is looking for one, some, or all of the tokens by unlocking boxes in a predetermined number of rounds. In each round, any subset of the boxes can be unlocked and the searcher collects all tokens in them. Each box is associated with a positive unlocking cost. The goal is to minimize the expected cost of unlocking boxes until the desired tokens are found.
Finsler Optimal Control Theory
Author:
Srikanth Gottipati
Year of Dissertation:
2009
This thesis is a contribution to solving problems of extracting optimal controls for complex systems. Its novelty consists of a detailed examination of Finsler geometry based control by connections as proposed by Kohn and Nerode and its relation to Pontryagin's maximum principle. The long term hope is that these methods will form the underpinning of the applications of control of hybrid systems.
MULTI-OBJECTIVE GENETIC PROGRAMMING FOR DATA VISUALIZATION AND CLASSIFICATION
Year of Dissertation:
2011
The process of knowledge discovery lies on a continuum ranging between the human driven (manual exploration) approaches to fully automatic data mining methods. As a hybrid approach, the emerging field of visual analytics aims to facilitate human-machine collaborative decision making by providing automated analysis of data via interactive visualizations. One area of interest in visual analytics is to develop data transformation methods that support visualization and analysis. In this thesis, we develop an evolutionary computing based multi-objective dimensionality reduction method for visual data classification. The algorithm is called Genetic Programming Projection Pursuit (G3P) where genetic programming is utilized in order to automatically create visualizations of higher dimensional labeled datasets which are assessed in terms of discriminative power and interpretability. We consider two forms of interpretability of the visualizations: clearly separated and compact class structures along with easily interpretable data transformation expressions relating the original data attributes to the visualization axes. The G3P algorithm incorporates a number of automated measures of interpretability that were found to be in alignment with human judgement through a user study we conducted.
Optimizing Resource Allocation Under Constraints
Year of Dissertation:
2010
The fundamental concept of resource allocation--assigning resources to tasks, and so on--gives rise to very broad families of problems, with instances in many domains, applications, disciplines. In the proposed thesis, we will study a series of assignment-oriented resource allocation problems modeling real-world situations, from the point of view of online and approximation algorithms. The complexities and character of these problems vary greatly. Separate from the problem definitions, we will also examine how the difficulty changes as we vary modalities such as online v. offline, distributed v. centralized, linear v. poly-time, thus mapping out a lattice of problem settings. For each problem and setting, we seek efficient algorithms of the appropriate kind (e.g., exact, approximation, competitive, distributed, ...). Three classes of problems examined in particular will be sensor-mission matching, battery charge scheduling, and geometric sensor coverage.
3D Map Building of Structured Indoor Environments with Heterogeneous Robots
Year of Dissertation:
2011
We explore a methodology to construct 3D maps of indoor environments using multiple heterogeneous robots. The robots acquire overlapping 3D range images at contiguous locations and fuse them together to form a complete range map. Our methodology involves three major steps in map construction: the first step is to estimate an initial pose between the multiple robots using a real-time camera pose estimation algorithm, the second step involves extracting polygon features from overlapping range images and the third step involves registration of the overlapping range images using extracted polygonal features. We evaluate the performance of several approaches to camera pose estimation, which is used to determine the initial estimate of pose between the multiple robots. We introduce a fast and robust segmentation algorithm, which extracts the polygonal features from the 3D range images. A polygon-based registration algorithm accurately fuses the overlapping range images. The algorithm further refines the initial pose estimate by minimizing the geometric distance between corresponding polygonal features extracted from overlapping range images. Our polygon-based registration combined with camera pose estimation executes in real-time and much faster compared to point-based scan registration techniques. We present experimental results obtained while building indoor maps and quantitative analysis of the algorithms used in map construction of indoor environments.