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Articles 1 - 30 of 394
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Multifunctional Nanocomposites For High Damping Performance, Lee Algozzini
Multifunctional Nanocomposites For High Damping Performance, Lee Algozzini
Electronic Theses and Dissertations
Composite structures for aerospace and wind turbine applications are subjected to high acoustic and vibrational loading and exhibit very high amplitude displacements and thus premature failure. Materials with high damping or absorbing properties are crucially important to extend the life of structures. Traditional damping treatments are based on the combinations of viscoelastic, elastomeric, magnetic, and piezoelectric materials. In this work, the use of carbon nanofibers (CNFs) in the form of interconnected self-supportive paper as reinforcement can significantly improve damping performance. The interfacial friction is the primary source of energy dissipation in CNF paper based nanocomposites. The approach entailed making CNF …
Thermo-Mechanical Characterization Of High-Temperature Shape Memory Ni-Ti-Pd Wires, Matthew Fox
Thermo-Mechanical Characterization Of High-Temperature Shape Memory Ni-Ti-Pd Wires, Matthew Fox
Electronic Theses and Dissertations
Actuator applications of shape memory alloys have typically been limited by their phase transformation temperatures to around 100 degrees C. However, recently with a focus on aerospace and turbomachinery applications there have been successful efforts to increase the phase transformation temperatures. Several of these alloy development efforts have involved ternary and quaternary elemental additions (e.g., Pt, Pd, etc.) to binary NiTi alloys. Experimentally assessing the effects of varying composition and thermo-mechanical processing parameters can be cost intensive, especially when expensive, high-purity elemental additions are involved. Thus, in order to save on development costs there is value in establishing a methodology …
Magnetically Deflectable Mems Actuators For Optical Sensing Applications, Matthew Montgomery
Magnetically Deflectable Mems Actuators For Optical Sensing Applications, Matthew Montgomery
Electronic Theses and Dissertations
In this work, new small deflection magnetic actuators have been proposed, designed, and tested for applications in Surface Enhanced Raman Scattering optical sensors. Despite the fact that SERS sensors have been shown to increase Raman over ten orders of magnitude for molecular detection, several technological challenges have prevented the design of practical sensors, such as making SERS sensors that can efficiently detect a wide variety of molecules. Since the optimum signal-to-noise in SERS occurs at different excitation wavelengths for different molecules, individual metal nanostructures need to be designed and fabricated for each independent chemical species. One possible solution to this …
Consumer Perspectives Of Health During Prenatal Care In The Usa And Iceland: An Exploratory Study, Claudia Wiseman
Consumer Perspectives Of Health During Prenatal Care In The Usa And Iceland: An Exploratory Study, Claudia Wiseman
Electronic Theses and Dissertations
Purpose: Prenatal care (PNC) is the healthcare service most often provided to women of childbearing age throughout the world. Poorly understood and defined, based on culture, and expensive for any healthcare system, PNC remains a target for change and improvement. The purpose of this cross-national qualitative research study using narrative inquiry methods was to explore consumer perspectives of individual health and routine PNC in the USA and Iceland. Methods: A purposive sampling technique was used to identify study participants (n = 32) from the United States (n = 16) and Iceland (n = 16). Data were collected via a semi …
Femtosecond Laser Written Volumetric Diffractive Optical Elements And Their Applications, Jiyeon Choi
Femtosecond Laser Written Volumetric Diffractive Optical Elements And Their Applications, Jiyeon Choi
Electronic Theses and Dissertations
Since the first demonstration of femtosecond laser written waveguides in 1996, femtosecond laser direct writing (FLDW) has been providing a versatile means to fabricate embedded 3-D microstructures in transparent materials. The key mechanisms are nonlinear absorption processes that occur when a laser beam is tightly focused into a material and the intensity of the focused beam reaches the range creating enough free electrons to induce structural modification. One of the most useful features that can be exploited in fabricating photonic structures is the refractive index change which results from the localized energy deposition. The laser processing system for FLDW can …
Beliefs Of Graduate Students About Unstructured Computer Use In Face-To-Face Classes With Internet Access And Its Influence On Student Recall, Gregory Johnson
Beliefs Of Graduate Students About Unstructured Computer Use In Face-To-Face Classes With Internet Access And Its Influence On Student Recall, Gregory Johnson
Electronic Theses and Dissertations
The use of computers equipped with Internet access by students during face-toface (F2F) class sessions is perceived as academically beneficial by a growing number of students and faculty members in universities across the United States. Nevertheless, some researchers suggest unstructured computer use detached from the immediate class content may negatively influence student participation, increase distraction levels, minimize recall of recently presented information, and decrease student engagement. This study investigates graduate students’ beliefs about computer use with Internet access during graduate face-to-face lecture classes in which computer use is neither mandated nor integrated in the class and the effect of such …
Contextualizing Observational Data For Modeling Human Performance, Viet Trinh
Contextualizing Observational Data For Modeling Human Performance, Viet Trinh
Electronic Theses and Dissertations
This research focuses on the ability to contextualize observed human behaviors in efforts to automate the process of tactical human performance modeling through learning from observations. This effort to contextualize human behavior is aimed at minimizing the role and involvement of the knowledge engineers required in building intelligent Context-based Reasoning (CxBR) agents. More specifically, the goal is to automatically discover the context in which a human actor is situated when performing a mission to facilitate the learning of such CxBR models. This research is derived from the contextualization problem left behind in Fernlund's research on using the Genetic Context Learner …
Visual Inspection Of Railroad Tracks, Pavel Babenko
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 …
Detecting Malicious Software By Dynamicexecution, Jianyong Dai
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 …
The Impact Of Social Capital On Youth Substance Use, Ali Unlu
The Impact Of Social Capital On Youth Substance Use, Ali Unlu
Electronic Theses and Dissertations
Substance use, such as alcohol, cigarette, and marijuana, is a threat to the health and well-being of the youth, their families, and society as well. Government supports and implements several programs to protect youth from substance use. The aim of this study is to evaluate the impact of social capital on youth behavior and to suggest evidence-based policy interventions. Social capital refers to individual embeddedness in web of social relations and their behaviors guided by social structure. Therefore, adolescents' social interactions with their peers, parents, and community were investigated. The substance use was measured by the usage of cigarettes, alcohol, …
An Architecture For High-Performance Privacy-Preserving And Distributed Data Mining, James Secretan
An Architecture For High-Performance Privacy-Preserving And Distributed Data Mining, James Secretan
Electronic Theses and Dissertations
This dissertation discusses the development of an architecture and associated techniques to support Privacy Preserving and Distributed Data Mining. The field of Distributed Data Mining (DDM) attempts to solve the challenges inherent in coordinating data mining tasks with databases that are geographically distributed, through the application of parallel algorithms and grid computing concepts. The closely related field of Privacy Preserving Data Mining (PPDM) adds the dimension of privacy to the problem, trying to find ways that organizations can collaborate to mine their databases collectively, while at the same time preserving the privacy of their records. Developing data mining algorithms for …
An Examination Of Central Asian Geopolitics Through The Expected Utility Model: The New Great Game, Corey Stutte
An Examination Of Central Asian Geopolitics Through The Expected Utility Model: The New Great Game, Corey Stutte
Electronic Theses and Dissertations
The New Great Game is a geopolitical competition between regional stakeholders over energy resources in Central Asia. The author seeks to use the expected utility voting model based on Black's median voter theorem for forecasting the New Great Game in Central Asia. To judge the external validity of the voting model, the author uses data from the Correlates of War project data set, to formulate three distinct models based only on the numbers in 1992 and 1993. Capabilities and alliance data were used to develop balance of power positions and compare the outcome of 100 simulations to the actual outcome …
Alliances In Graphs: Parameterized Algorithms And On Partitioning Series-Parallel Graphs, Rosa Enciso
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 …
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 …
Concept Learning By Example Decomposition, Sameer Joshi
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 …
Connectionless Approach: A Localized Scheme To Mobile Ad Hoc Networks, Yao Ho
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 …
Modeling Scenes And Human Activities In Videos, Arslan Basharat
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 …
Learning Techniques For Information Retrieval And Mining In High-Dimensional Databases, Hao Cheng
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. …
Efficient Techniques For Relevance Feedback Processing In Content-Based Image Retrieval, Danzhou Liu
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, …
Geometric Invariance In The Analysis Of Human Motion In Video Data, Yuping Shen
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 …
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 …
Validation Of Quickscat Radiometer (Qrad) Microwave Brightness Temperture Measurments, Rafik Hanna
Validation Of Quickscat Radiometer (Qrad) Microwave Brightness Temperture Measurments, Rafik Hanna
Electronic Theses and Dissertations
After the launch of NASA's SeaWinds scatterometer in 1999, a radiometer function was implemented in the Science Ground Data Processing Systems to allow the measurement of the earth's microwave brightness temperature. This dissertation presents results of a comprehensive validation to assess the quality of QRad brightness temperature measurements using near-simultaneous ocean Tb comparisons between the SeaWinds on QuikSCAT (QRad) and WindSat polarimetric radiometer on Coriolis. WindSat was selected because it is a well calibrated radiometer that has many suitable collocations with QuikSCAT; and it has a 10.7 GHz channel, which is close to QRad frequency of 13.4 GHz. Brightness temperature …
Embedded Magnetics For Power System On Chip (Psoc), Jian Lu
Embedded Magnetics For Power System On Chip (Psoc), Jian Lu
Electronic Theses and Dissertations
A novel concept of on-chip bondwire inductors and transformers with ferrite epoxy glob coating is proposed, offering a cost effective approach to realize power systems on chip (PSoC) or System-in-Package (PSiP). The concept has been investigated both experimentally and with finite element modeling. Improvement in total inductance is demonstrated for multi-turn bondwire inductors over single bondwire inductors. The inductance and Q factor can be further boosted with coupled multi-turn inductor concept. Transformer parameters including self- and mutual inductance, and coupling factors are extracted from both modeled and measured S-parameters. More importantly, the bondwire magnetic components can be easily integrated into …
Learning Semantic Features For Visual Recognition, Jingen Liu
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 …
Study Of Gate Oxide Breakdown And Hot Electron Effect On Cmos Circuit Performances, Jun Ma
Study Of Gate Oxide Breakdown And Hot Electron Effect On Cmos Circuit Performances, Jun Ma
Electronic Theses and Dissertations
In the modern semiconductor world, there is a significant scaling of the transistor dimensions--The transistor gate length and the gate oxide thickness drop down to only several nanometers. Today the semiconductor industry is already dominated by submicron devices and other material devices for the high transistor density and performance enhancement. In this case, the semiconductor reliability issues are the most important thing for commercialization. The major reliability issues caused by voltage are hot carrier effects (HCs) and gate oxide breakdown (BD) effects. These issues are recently more important to industry, due to the small size and high lateral field in …
Phase Shaping In The Infrared By Planar Quasi-Periodic Surfaces Comprised Of Sub-Wavelength Elements, James Ginn
Phase Shaping In The Infrared By Planar Quasi-Periodic Surfaces Comprised Of Sub-Wavelength Elements, James Ginn
Electronic Theses and Dissertations
Reflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time--at frequencies as high as 194 THz. Relevant aspects of computational electromagnetic modeling are explored, to yield design procedures optimized for these high frequencies. Modeling is also utilized to demonstrate the phase response of a generalized …
Unsupervised Building Detection From Irregularly Spaced Lidar And Aerial Imagery, Nicholas Shorter
Unsupervised Building Detection From Irregularly Spaced Lidar And Aerial Imagery, Nicholas Shorter
Electronic Theses and Dissertations
As more data sources containing 3-D information are becoming available, an increased interest in 3-D imaging has emerged. Among these is the 3-D reconstruction of buildings and other man-made structures. A necessary preprocessing step is the detection and isolation of individual buildings that subsequently can be reconstructed in 3-D using various methodologies. Applications for both building detection and reconstruction have commercial use for urban planning, network planning for mobile communication (cell phone tower placement), spatial analysis of air pollution and noise nuisances, microclimate investigations, geographical information systems, security services and change detection from areas affected by natural disasters. Building detection …
Unified Large And Small Signal State-Space Based Modeling And Symbolic Simulation For Pwm Converters, Ehab Shoubaki
Unified Large And Small Signal State-Space Based Modeling And Symbolic Simulation For Pwm Converters, Ehab Shoubaki
Electronic Theses and Dissertations
In this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulation, this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic …
Physical Properties Of Wave Scattering By Chiral Periodic Structure, Xiaomin Yang
Physical Properties Of Wave Scattering By Chiral Periodic Structure, Xiaomin Yang
Electronic Theses and Dissertations
Attention has been focused on electromagnetic chirality and its potential applications to microwave, millimeter wave and optical wave devices. In this work, wave propagation through a chiral periodic structure with arbitrary shape is investigated. Although perturbation theory and coupled-mode theory have been used to analyze chiral periodic structure, those are approximate methods and can only be used for low frequency applications. In this work, the rigorous mode-matching method is used to solve the problem. Staircase approximation is introduced to change the curved structure to a multilayer structure. The field solutions in the uniform air regions and unbounded air-chiral periodic array …
Control Of Nonh=Holonomic Systems, Hongliang Yuan
Control Of Nonh=Holonomic Systems, Hongliang Yuan
Electronic Theses and Dissertations
Many real-world electrical and mechanical systems have velocity-dependent constraints in their dynamic models. For example, car-like robots, unmanned aerial vehicles, autonomous underwater vehicles and hopping robots, etc. Most of these systems can be transformed into a chained form, which is considered as a canonical form of these nonholonomic systems. Hence, study of chained systems ensure their wide applicability. This thesis studied the problem of continuous feed-back control of the chained systems while pursuing inverse optimality and exponential convergence rates, as well as the feed-back stabilization problem under input saturation constraints. These studies are based on global singularity-free state transformations and …