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Full-Text Articles in Computer Sciences

Research In High Performance And Low Power Computer Systems For Data-Intensive Environment, Pengju Shang Jan 2011

Research In High Performance And Low Power Computer Systems For Data-Intensive Environment, Pengju Shang

Electronic Theses and Dissertations

According to the data affinity, DAFA re-organizes data to maximize the parallelism of the affinitive data, and also subjective to the overall load balance. This enables DAFA to realize the maximum number of map tasks with data-locality. Besides the system performance, power consumption is another important concern of current computer systems. In the U.S. alone, the energy used by servers which could be saved comes to 3.17 million tons of carbon dioxide, or 580,678 cars {Kar09}. However, the goals of high performance and low energy consumption are at odds with each other. An ideal power management strategy should be able …


Virtual Router Approach For Wireless Ad Hoc Networks, Ai Hua Ho Jan 2011

Virtual Router Approach For Wireless Ad Hoc Networks, Ai Hua Ho

Electronic Theses and Dissertations

Wireless networks have become increasingly popular in recent years. There are two variations of mobile wireless networks: infrastructure mobile networks and infrastructureless mobile networks. The latter are also known as mobile ad hoc network (MANET). MANETs have no fixed routers. Instead, mobile nodes function as relay nodes or routers, which discover and maintain communication connections between source nodes and destination nodes for various data transmission sessions. In other words, an MANET is a self-organizing multi-hop wireless network in which all nodes within a given geographical area participate in the routing and data forwarding process. Such networks are scalable and self-healing. …


A Robust Wireless Mesh Access Environment For Mobile Video Users, Fei Xie Jan 2010

A Robust Wireless Mesh Access Environment For Mobile Video Users, Fei Xie

Electronic Theses and Dissertations

The rapid advances in networking technology have enabled large-scale deployments of online video streaming services in today's Internet. In particular, wireless Internet access technology has been one of the most transforming and empowering technologies in recent years. We have witnessed a dramatic increase in the number of mobile users who access online video services through wireless access networks, such as wireless mesh networks and 3G cellular networks. Unlike in wired environment, using a dedicated stream for each video service request is very expensive for wireless networks. This simple strategy also has limited scalability when popular content is demanded by a …


Markerless Tracking Using Polar Correlation Of Camera Optical Flow, Prince Gupta Jan 2010

Markerless Tracking Using Polar Correlation Of Camera Optical Flow, Prince Gupta

Electronic Theses and Dissertations

We present a novel, real-time, markerless vision-based tracking system, employing a rigid orthogonal configuration of two pairs of opposing cameras. Our system uses optical flow over sparse features to overcome the limitation of vision-based systems that require markers or a pre-loaded model of the physical environment. We show how opposing cameras enable cancellation of common components of optical flow leading to an efficient tracking algorithm that captures five degrees of freedom including direction of translation and angular velocity. Experiments comparing our device with an electromagnetic tracker show that its average tracking accuracy is 80% over 185 frames, and it is …


Architectural Support For Improving Computer Security, Jingfei Kong Jan 2010

Architectural Support For Improving Computer Security, Jingfei Kong

Electronic Theses and Dissertations

Computer security and privacy are becoming extremely important nowadays. The task of protecting computer systems from malicious attacks and potential subsequent catastrophic losses is, however, challenged by the ever increasing complexity and size of modern hardware and software design. We propose several methods to improve computer security and privacy from architectural point of view. They provide strong protection as well as performance efficiency. In our first approach, we propose a new dynamic information flow method to protect systems from popular software attacks such as buffer overflow and format string attacks. In our second approach, we propose to deploy encryption schemes …


Real-Time Cinematic Design Of Visual Aspects In Computer-Generated Images, Juraj Obert Jan 2010

Real-Time Cinematic Design Of Visual Aspects In Computer-Generated Images, Juraj Obert

Electronic Theses and Dissertations

Creation of visually-pleasing images has always been one of the main goals of computer graphics. Two important components are necessary to achieve this goal --- artists who design visual aspects of an image (such as materials or lighting) and sophisticated algorithms that render the image. Traditionally, rendering has been of greater interest to researchers, while the design part has always been deemed as secondary. This has led to many inefficiencies, as artists, in order to create a stunning image, are often forced to resort to the traditional, creativity-baring, pipelines consisting of repeated rendering and parameter tweaking. Our work shifts the …


A New Framework For Qos Provisioning In Wireless Lans Using The P-Persistent Mac Protocol, Kiran Babu Anna Jan 2010

A New Framework For Qos Provisioning In Wireless Lans Using The P-Persistent Mac Protocol, Kiran Babu Anna

Electronic Theses and Dissertations

The support of multimedia traffic over IEEE 802.11 wireless local area networks (WLANs) has recently received considerable attention. This dissertation has proposed a new framework that provides efficient channel access, service differentiation and statistical QoS guarantees in the enhanced distributed channel access (EDCA) protocol of IEEE 802.11e. In the first part of the dissertation, the new framework to provide QoS support in IEEE 802.11e is presented. The framework uses three independent components, namely, a core MAC layer, a scheduler, and an admission control. The core MAC layer concentrates on the channel access mechanism to improve the overall system efficiency. The …


Spatio-Temporal Maximum Average Correlation Height Templates In Action Recognition And Video Summarization, Mikel Rodriguez Jan 2010

Spatio-Temporal Maximum Average Correlation Height Templates In Action Recognition And Video Summarization, Mikel Rodriguez

Electronic Theses and Dissertations

Action recognition represents one of the most difficult problems in computer vision given that it embodies the combination of several uncertain attributes, such as the subtle variability associated with individual human behavior and the challenges that come with viewpoint variations, scale changes and different temporal extents. Nevertheless, action recognition solutions are critical in a great number of domains, such video surveillance, assisted living environments, video search, interfaces, and virtual reality. In this dissertation, we investigate template-based action recognition algorithms that can incorporate the information contained in a set of training examples, and we explore how these algorithms perform in action …


A Fpga-Based Architecture For Led Backlight Driving, Zhaoshi Zheng Jan 2010

A Fpga-Based Architecture For Led Backlight Driving, Zhaoshi Zheng

Electronic Theses and Dissertations

In recent years, Light-emitting Diodes (LEDs) have become a promising candidate for backlighting Liquid Crystal Displays [1] (LCDs). Compared with traditional Cold Cathode Fluorescent Lamps (CCFLs) technology, LEDs offer not only better visual quality, but also improved power efficiency. However, to fully utilized LEDs' capability requires dynamic independent control of individual LEDs, which remains as a challenging topic. A FPGA-based hardware system for LED backlight control is proposed in this work. We successfully achieve dynamic adjustment of any individual LED's intensity in each of the three color channels (Red, Green and Blue), in response to a real time incoming video …


Alliances In Graphs: Parameterized Algorithms And On Partitioning Series-Parallel Graphs, Rosa Enciso Jan 2009

Alliances In Graphs: Parameterized Algorithms And On Partitioning Series-Parallel Graphs, Rosa Enciso

Electronic Theses and Dissertations

Alliances are used to denote agreements between members of a group with similar interests. Alliances can occur between nations, biological sequences, business cartels, and other entities. The notion of alliances in graphs was first introduced by Kristiansen, Hedetniemi, and Hedetniemi in . A defensive alliance in a graph G = (V, E) is a non empty set S ⊆ V where, for all x ∈ S, |N[x] ∩ S| ≥ |N[x] − S|. Consequently, every vertex that is a member of a defensive alliance has at least as many vertices defending it as there are vertices attacking it. Alliances can …


On The Application Of Locality To Network Intrusion Detection: Working-Set Analysis Of Real And Synthetic Network Server Traffic, Robert Lee Jan 2009

On The Application Of Locality To Network Intrusion Detection: Working-Set Analysis Of Real And Synthetic Network Server Traffic, Robert Lee

Electronic Theses and Dissertations

Keeping computer networks safe from attack requires ever-increasing vigilance. Our work on applying locality to network intrusion detection is presented in this dissertation. Network servers that allow connections from both the internal network and the Internet are vulnerable to attack from all sides. Analysis of the behavior of incoming connections for properties of locality can be used to create a normal profile for such network servers. Intrusions can then be detected due to their abnormal behavior. Data was collected from a typical network server both under normal conditions and under specific attacks. Experiments show that connections to the server do …


Search And Delivery Techniques In Peer-To-Peer Networks, Tai Do Jan 2009

Search And Delivery Techniques In Peer-To-Peer Networks, Tai Do

Electronic Theses and Dissertations

The presence of millions of interconnected personal computing devices has given rise to a new class of decentralized networking applications, which are loosely labeled as peer-to-peer (P2P) applications. These P2P applications leverage resources such as processing cycles, storage, content, and network bandwidth available to the user devices, which are also known as peers. A number of current systems - SETI@home, Napster, BitTorrent, and Pastry - are examples of these emerging P2P systems. To fully realize the potential of the peer-to-peer technology, there is a need to define and provide a set of core competencies, serving as the basic services upon …


Connectionless Approach: A Localized Scheme To Mobile Ad Hoc Networks, Yao Ho Jan 2009

Connectionless Approach: A Localized Scheme To Mobile Ad Hoc Networks, Yao Ho

Electronic Theses and Dissertations

According to a Gartner Group (www.gartner.com) report in September 2008, the worldwide telecommunications market is on pace to reach $2 trillion in 2008. Gartner predicts that by 2012, the ratio of mobile to fixed connections will exceed 4-to-1. The North American mobile data market grew to 141.1 million connections in 2007, with a compound annual growth rate of 41.7 percent. It is believed that a large portion will be ad hoc and multi-hop connections, which will open many opportunities for Mobile Ad hoc NETwork (MANET) applications and Wireless Mesh Network (WMN) applications. A MANET is a self-organizing multi-hop wireless network …


Learning Techniques For Information Retrieval And Mining In High-Dimensional Databases, Hao Cheng Jan 2009

Learning Techniques For Information Retrieval And Mining In High-Dimensional Databases, Hao Cheng

Electronic Theses and Dissertations

The main focus of my research is to design effective learning techniques for information retrieval and mining in high-dimensional databases. There are two main aspects in the retrieval and mining research: accuracy and efficiency. The accuracy problem is how to return results which can better match the ground truth, and the efficiency problem is how to evaluate users' requests and execute learning algorithms as fast as possible. However, these problems are non-trivial because of the complexity of the high-level semantic concepts, the heterogeneous natures of the feature space, the high dimensionality of data representations and the size of the databases. …


Scheduling And Resource Management For Complex Systems: From Large-Scale Distributed Systems To Very Large Sensor Networks, Chen Yu Jan 2009

Scheduling And Resource Management For Complex Systems: From Large-Scale Distributed Systems To Very Large Sensor Networks, Chen Yu

Electronic Theses and Dissertations

In this dissertation, we focus on multiple levels of optimized resource management techniques. We first consider a classic resource management problem, namely the scheduling of data-intensive applications. We define the Divisible Load Scheduling (DLS) problem, outline the system model based on the assumption that data staging and all communication with the sites can be done in parallel, and introduce a set of optimal divisible load scheduling algorithms and the related fault-tolerant coordination algorithm. The DLS algorithms introduced in this dissertation exploit parallel communication, consider realistic scenarios regarding the time when heterogeneous computing systems are available, and generate optimal schedules. Performance …


Automatic Graphics And Game Content Generation Through Evolutionary Computation, Erin Hastings Jan 2009

Automatic Graphics And Game Content Generation Through Evolutionary Computation, Erin Hastings

Electronic Theses and Dissertations

Simulation and game content includes the levels, models, textures, items, and other objects encountered and possessed by players during the game. In most modern video games and simulation software, the set of content shipped with the product is static and unchanging, or at best, randomized within a narrow set of parameters. However, ideally, if game content could be constantly and automatically renewed, players would remain engaged longer in the evolving stream of content. This dissertation introduces three novel technologies that together realize this ambition. (1) The first, NEAT Particles, is an evolutionary method to enable users to quickly and easily …


Detecting Malicious Software By Dynamicexecution, Jianyong Dai Jan 2009

Detecting Malicious Software By Dynamicexecution, Jianyong Dai

Electronic Theses and Dissertations

Traditional way to detect malicious software is based on signature matching. However, signature matching only detects known malicious software. In order to detect unknown malicious software, it is necessary to analyze the software for its impact on the system when the software is executed. In one approach, the software code can be statically analyzed for any malicious patterns. Another approach is to execute the program and determine the nature of the program dynamically. Since the execution of malicious code may have negative impact on the system, the code must be executed in a controlled environment. For that purpose, we have …


Attacks On Difficult Instances Of Graph Isomorphism: Sequential And Parallel Algorithms, Greg Tener Jan 2009

Attacks On Difficult Instances Of Graph Isomorphism: Sequential And Parallel Algorithms, Greg Tener

Electronic Theses and Dissertations

The graph isomorphism problem has received a great deal of attention on both theoretical and practical fronts. However, a polynomial algorithm for the problem has yet to be found. Even so, the best of the existing algorithms perform well in practice; so well that it is challenging to find hard instances for them. The most efficient algorithms, for determining if a pair of graphs are isomorphic, are based on the individualization-refinement paradigm, pioneered by Brendan McKay in 1981 with his algorithm nauty. Nauty and various improved descendants of nauty, such as bliss and saucy, solve the graph isomorphism problem by …


Concept Learning By Example Decomposition, Sameer Joshi Jan 2009

Concept Learning By Example Decomposition, Sameer Joshi

Electronic Theses and Dissertations

For efficient understanding and prediction in natural systems, even in artificially closed ones, we usually need to consider a number of factors that may combine in simple or complex ways. Additionally, many modern scientific disciplines face increasingly large datasets from which to extract knowledge (for example, genomics). Thus to learn all but the most trivial regularities in the natural world, we rely on different ways of simplifying the learning problem. One simplifying technique that is highly pervasive in nature is to break down a large learning problem into smaller ones; to learn the smaller, more manageable problems; and then to …


Visual Inspection Of Railroad Tracks, Pavel Babenko Jan 2009

Visual Inspection Of Railroad Tracks, Pavel Babenko

Electronic Theses and Dissertations

In this dissertation, we have developed computer vision methods for measurement of rail gauge, and reliable identification and localization of structural defects in railroad tracks. The rail gauge is the distance between the innermost sides of the two parallel steel rails. We have developed two methods for evaluation of rail gauge. These methods were designed for different hardware setups: the first method works with two pairs of unaligned video cameras while the second method works with depth maps generated by paired laser range scanners. We have also developed a method for detection of rail defects such as damaged or missed …


Design And Analysis Of Effective Routing And Channel Scheduling For Wavelength Division Multiplexing Optical Networks, Xingbo Gao Jan 2009

Design And Analysis Of Effective Routing And Channel Scheduling For Wavelength Division Multiplexing Optical Networks, Xingbo Gao

Electronic Theses and Dissertations

Optical networking, employing wavelength division multiplexing (WDM), is seen as the technology of the future for the Internet. This dissertation investigates several important problems affecting optical circuit switching (OCS) and optical burst switching (OBS) networks. Novel algorithms and new approaches to improve the performance of these networks through effective routing and channel scheduling are presented. Extensive simulations and analytical modeling have both been used to evaluate the effectiveness of the proposed algorithms in achieving lower blocking probability, better fairness as well as faster switching. The simulation tests were performed over a variety of optical network topologies including the ring and …


Modeling Scenes And Human Activities In Videos, Arslan Basharat Jan 2009

Modeling Scenes And Human Activities In Videos, Arslan Basharat

Electronic Theses and Dissertations

In this dissertation, we address the problem of understanding human activities in videos by developing a two-pronged approach: coarse level modeling of scene activities and fine level modeling of individual activities. At the coarse level, where the resolution of the video is low, we rely on person tracks. At the fine level, richer features are available to identify different parts of the human body, therefore we rely on the body joint tracks. There are three main goals of this dissertation: (1) identify unusual activities at the coarse level, (2) recognize different activities at the fine level, and (3) predict the …


Geometric Invariance In The Analysis Of Human Motion In Video Data, Yuping Shen Jan 2009

Geometric Invariance In The Analysis Of Human Motion In Video Data, Yuping Shen

Electronic Theses and Dissertations

Human motion analysis is one of the major problems in computer vision research. It deals with the study of the motion of human body in video data from different aspects, ranging from the tracking of body parts and reconstruction of 3D human body configuration, to higher level of interpretation of human action and activities in image sequences. When human motion is observed through video camera, it is perspectively distorted and may appear totally different from different viewpoints. Therefore it is highly challenging to establish correct relationships between human motions across video sequences with different camera settings. In this work, we …


Vectorpad: A Tool For Visualizing Vector Operations, Jared Bott Jan 2009

Vectorpad: A Tool For Visualizing Vector Operations, Jared Bott

Electronic Theses and Dissertations

Visualization of three-dimensional vector operations can be very helpful in understanding vector mathematics. However, creating these visualizations using traditional WIMP interfaces can be a troublesome exercise. In this thesis, we present VectorPad, a pen-based application for three-dimensional vector mathematics visualization. VectorPad allows users to define vectors and perform mathematical operations upon them through the recognition of handwritten mathematics. The VectorPad user interface consists of a sketching area, where the user can write vector definitions and other mathematics, and a 3D graph for visualization. After recognition, vectors are visualized dynamically on the graph, which can be manipulated by the user. A …


Efficient Techniques For Relevance Feedback Processing In Content-Based Image Retrieval, Danzhou Liu Jan 2009

Efficient Techniques For Relevance Feedback Processing In Content-Based Image Retrieval, Danzhou Liu

Electronic Theses and Dissertations

In content-based image retrieval (CBIR) systems, there are two general types of search: target search and category search. Unlike queries in traditional database systems, users in most cases cannot specify an ideal query to retrieve the desired results for either target search or category search in multimedia database systems, and have to rely on iterative feedback to refine their query. Efficient evaluation of such iterative queries can be a challenge, especially when the multimedia database contains a large number of entries, and the search needs many iterations, and when the underlying distance measure is computationally expensive. The overall processing costs, …


Learning Semantic Features For Visual Recognition, Jingen Liu Jan 2009

Learning Semantic Features For Visual Recognition, Jingen Liu

Electronic Theses and Dissertations

Visual recognition (e.g., object, scene and action recognition) is an active area of research in computer vision due to its increasing number of real-world applications such as video (image) indexing and search, intelligent surveillance, human-machine interaction, robot navigation, etc. Effective modeling of the objects, scenes and actions is critical for visual recognition. Recently, bag of visual words (BoVW) representation, in which the image patches or video cuboids are quantized into visual words (i.e., mid-level features) based on their appearance similarity using clustering, has been widely and successfully explored. The advantages of this representation are: no explicit detection of objects or …


Realnav: Exploring Natural User Interfaces For Locomotion In Video Games, Brian Williamson Jan 2009

Realnav: Exploring Natural User Interfaces For Locomotion In Video Games, Brian Williamson

Electronic Theses and Dissertations

We present an exploration into realistic locomotion interfaces in video games using spatially convenient input hardware. In particular, we use Nintendo Wii Remotes to create natural mappings between user actions and their representation in a video game. Targeting American Football video games, we used the role of the quarterback as an exemplar since the game player needs to maneuver effectively in a small area, run down the field, and perform evasive gestures such as spinning, jumping, or the "juke". In our study, we developed three locomotion techniques. The first technique used a single Wii Remote, placed anywhere on the user's …


New Computational Approaches For Multiple Rna Alignment And Rna Search, Daniel Deblasio Jan 2009

New Computational Approaches For Multiple Rna Alignment And Rna Search, Daniel Deblasio

Electronic Theses and Dissertations

In this thesis we explore the the theory and history behind RNA alignment. Normal sequence alignments as studied by computer scientists can be completed in O(n2) time in the naive case. The process involves taking two input sequences and finding the list of edits that can transform one sequence into the other. This process is applied to biology in many forms, such as the creation of multiple alignments and the search of genomic sequences. When you take into account the RNA sequence structure the problem becomes even harder. Multiple RNA structure alignment is particularly challenging because covarying mutations make sequence …


Detecting Curved Objects Against Cluttered Backgrounds, Jan Prokaj Jan 2008

Detecting Curved Objects Against Cluttered Backgrounds, Jan Prokaj

Electronic Theses and Dissertations

Detecting curved objects against cluttered backgrounds is a hard problem in computer vision. We present new low-level and mid-level features to function in these environments. The low-level features are fast to compute, because they employ an integral image approach, which makes them especially useful in real-time applications. The mid-level features are built from low-level features, and are optimized for curved object detection. The usefulness of these features is tested by designing an object detection algorithm using these features. Object detection is accomplished by transforming the mid-level features into weak classifiers, which then produce a strong classifier using AdaBoost. The resulting …


Multi-View Approaches To Tracking, 3d Reconstruction And Object Class Detection, Saad Khan Jan 2008

Multi-View Approaches To Tracking, 3d Reconstruction And Object Class Detection, Saad Khan

Electronic Theses and Dissertations

Multi-camera systems are becoming ubiquitous and have found application in a variety of domains including surveillance, immersive visualization, sports entertainment and movie special effects amongst others. From a computer vision perspective, the challenging task is how to most efficiently fuse information from multiple views in the absence of detailed calibration information and a minimum of human intervention. This thesis presents a new approach to fuse foreground likelihood information from multiple views onto a reference view without explicit processing in 3D space, thereby circumventing the need for complete calibration. Our approach uses a homographic occupancy constraint (HOC), which states that if …