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Title
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Some contributions to dimensionality reduction
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Creator
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Tong, Wei
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Date
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2010
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Collection
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Electronic Theses & Dissertations
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Description
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Dimensionality reduction is a long standing challenging problem in the fields of statistical learning, pattern recognition and computer vision. Numerous algorithms have been proposed and studied in the past decades. In this dissertation we address several challenging problems emerged in recent studies of dimensionality reduction. We first explore the dimensionality reduction method for semi-supervised classification via the idea of mixed label propagation in which we attempt to find the best...
Show moreDimensionality reduction is a long standing challenging problem in the fields of statistical learning, pattern recognition and computer vision. Numerous algorithms have been proposed and studied in the past decades. In this dissertation we address several challenging problems emerged in recent studies of dimensionality reduction. We first explore the dimensionality reduction method for semi-supervised classification via the idea of mixed label propagation in which we attempt to find the best one dimensional embedding of the data in which data points in different classes can be well separated and the class labels are obtained by simply thresholding the one dimensional representation. In the next, we explore the dimensionality reduction methods for non-vector data representations. We first look into the problem in which a datum is represented by a matrix. We give a convex formulation to the problem of dimensionality reduction for matrices and developed an efficient approximating algorithm to solve the associated semi-definite programming problem. In the last, we studied the problem ofdimensionality reduction with even more challenging data representation, i.e., each datum is described as a different numberof unordered vectors. We convert the problem into the functional data dimensionality reduction and study it in the context of large scale image retrieval.
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Title
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Synthesizing realistic animated human motion using multiple natural spaces
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Creator
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Ferrydiansyah, Reza
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Date
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2011
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Collection
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Electronic Theses & Dissertations
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Description
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When animating virtual human, it is important that the movements created are realistic as well as meet various constraint. One way to create motion, given a starting pose, is to first find an ending pose that meets the various constraints. This is followed by calculating the motion needed from the starting space to the ending space. Traditional inverse kinematics method are able to find poses that meets certain constraints, however these poses are not always natural. Linear interpolation...
Show moreWhen animating virtual human, it is important that the movements created are realistic as well as meet various constraint. One way to create motion, given a starting pose, is to first find an ending pose that meets the various constraints. This is followed by calculating the motion needed from the starting space to the ending space. Traditional inverse kinematics method are able to find poses that meets certain constraints, however these poses are not always natural. Linear interpolation between starting pose and ending pose can be used to create motion. Once again however, the interpolation method does not always create motion that is natural. This thesis proposes the creation of natural space. The natural space is a hyper-dimensional space in which every point in this space describes a natural pose. Motion can be created by traversing over the points in this space. The natural space is created by reducing the dimensionality of motion capture data using Principal Component Analysis (PCA). Points in the reduced space retain the characteristic of the original data. Multiple natural spaces are created on different segment of the human skeleton.This thesis describes a method to generate new constrained natural poses that is natural. The poses synthesized are more natural than traditional inverse kinematics, and single space PCA. Motion is created through a space consisting of pose configurations and angular speed. A method to generate realistic looking motion based on this space is given in this thesis.
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Title
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Network reachability : quantification, verification, troubleshooting, and optimization
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Creator
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Khakpour, Amir Reza
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Date
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2012
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Collection
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Electronic Theses & Dissertations
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Description
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Quantifying, verifying, troubleshooting, and optimizing the network reachability is essential for network management and network security monitoring as well as various aspects of network auditing, maintenance, and design. Although attempts to model network reachability have been made, feasible solutions for computing, maintaining and optimally designing network reachability have remained unknown. Network reachability control is very critical because, on one hand, reachability errors can cause...
Show moreQuantifying, verifying, troubleshooting, and optimizing the network reachability is essential for network management and network security monitoring as well as various aspects of network auditing, maintenance, and design. Although attempts to model network reachability have been made, feasible solutions for computing, maintaining and optimally designing network reachability have remained unknown. Network reachability control is very critical because, on one hand, reachability errors can cause network security breaches or service outages, leading to millions of dollars of revenue loss for an enterprise network. On the other hand, network operators suffer from lack of tools that thoroughly examine network access control configurations and audit them to avoid such errors. Besides, finding reachability errors is by no means easy. The access control rules, by which network reachability is restricted, are often very complex and manually troubleshooting them is extremely difficult. Hence, having a tool that finds the reachability errors and fix them automatically can be very useful. Furthermore, flawed network reachability design and deployment can degrade the network performance significantly. Thus, it is crucial to have a tool that designs the network configurations such that they have the least performance impact on the enterprise network.In this dissertation, we first present a network reachability model that considers connectionless and connection-oriented transport protocols, stateless and stateful routers/firewalls, static and dynamic NAT, PAT, IP tunneling, etc. We then propose a suite of algorithms for quantifying reachability based on network configurations (mainly access control lists (ACLs)) as well as solutions for querying network reachability. We further extend our algorithms and data structures for detecting reachability errors, pinpointing faulty access control lists, and fixing them automatically and efficiently. Finally, we propose algorithms to place rules on network devices optimally so that they satisfy the networks central access policies. To this end, we define correctness and performance criteria for rule placement and in turn propose cost-based algorithms with adjustable parameters (for the network operators) to place rules such that the correctness and performance criteria are satisfied.We implemented the algorithms in our network reachability tool called Quarnet and conducted experiments on a university network. Experimental results show that the offline computation of reachability matrices takes a few hours and the online processing of a reachability query takes 75 milliseconds on average. We also examine our reachability error detection and correction algorithms on a few real-life networks to examine their performance and ensure that Quarnet is efficient enough to be practically useful. The results indicate that we can find reachability errors in order of minutes and fix them in order of seconds depending on the size of network and number of ACLs. Finally, we added the rule placement suite of algorithms to Quarnet, which can design a network ACL in based on the network central policies in order of tens of minutes for an enterprise network. We compare it with Purdue ACL placement, the state-of-the-art access policy design technique, and explain its pros and cons.
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