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Articles 1801 - 1830 of 4566

Full-Text Articles in Engineering

Multifunctional, Multimaterial Particle Fabrication Via An In-Fiber Fluid Instability, Joshua Kaufman Jan 2014

Multifunctional, Multimaterial Particle Fabrication Via An In-Fiber Fluid Instability, Joshua Kaufman

Electronic Theses and Dissertations

Spherical micro- and nano-particles have found widespread use in many various applications from paint to cosmetics to medicine. Due to the multiplicity of desired particle material(s), structure, size range, and functionality, many approaches exist for generating such particles. Bottom-up methods such as chemical synthesis have a high yield and work with a wide range of materials; however, these processes typically lead to large polydispersity and cannot produce structured particles. Top-down approaches such as microfluidics overcome the polydispersity issue and may produce a few different structures in particles, but at lower rates and only at the micro-scale. A method that can …

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Quantifying Ultra-High Performance Concrete Flexural System Mechanical Response, Yulin Xiao Jan 2014

Quantifying Ultra-High Performance Concrete Flexural System Mechanical Response, Yulin Xiao

Electronic Theses and Dissertations

The research and application of Ultra-high Performance Concrete (UHPC) has been developed significantly within the last 1-2 decades. Due to the specific property of high strength capacity, it is potential to be used in bridge deck system without shear reinforcement so that it provides even lighter self-weight of the deck. However, one of the shear component, dowel action, has not been adequately investigated in the past. In this dissertation, a particular test was designed and carried out to fully investigate the dowel action response, especially its contribution to shear resistance. In addition, research on serviceability and fatigue behaviors were expanded …

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Functional Scaffolding For Musical Composition: A New Approach In Computer-Assisted Music Composition, Amy K. Hoover Jan 2014

Functional Scaffolding For Musical Composition: A New Approach In Computer-Assisted Music Composition, Amy K. Hoover

Electronic Theses and Dissertations

While it is important for systems intended to enhance musical creativity to define and explore musical ideas conceived by individual users, many limit musical freedom by focusing on maintaining musical structure, thereby impeding the user's freedom to explore his or her individual style. This dissertation presents a comprehensive body of work that introduces a new musical representation that allows users to explore a space of musical rules that are created from their own melodies. This representation, called functional scaffolding for musical composition (FSMC), exploits a simple yet powerful property of multipart compositions: The pattern of notes and rhythms in different …

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Development Of Full Surface Transient Thermochromic Liquid Crystal Technique For Internal Cooling Channels, Lucky Tran Jan 2014

Development Of Full Surface Transient Thermochromic Liquid Crystal Technique For Internal Cooling Channels, Lucky Tran

Electronic Theses and Dissertations

Proper design of high performance industrial heat transfer equipment relies on accurate knowledge and prediction of the thermal boundary conditions. In order to enhance the overall gas turbine efficiency, advancements in cooling technology for gas turbines and related applications are continuously investigated to increase the turbine inlet temperature without compromising the durability of the materials used. For detailed design, local distributions are needed in addition to bulk quantities. Detailed local distributions require advanced experimental techniques whereas they are readily available using numerical tools. Numerical predictions using a computational fluid dynamics approach with popular turbulence models are benchmarked against a semi-empirical …

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A Framework For Workforce Management An Agent Based Simulation Approach, Mario Marin Jan 2014

A Framework For Workforce Management An Agent Based Simulation Approach, Mario Marin

Electronic Theses and Dissertations

In today's advanced technology world, enterprises are in a constant state of competition. As the intensity of competition increases the need to continuously improve organizational performance has never been greater. Managers at all levels must be on a constant quest for finding ways to maximize their enterprises' strategic resources. Enterprises can develop sustained competitiveness only if their activities create value in unique ways. There should be an emphasis to transfer this competitiveness to the resources it has on hand and the resources it can develop to be used in this environment. The significance of human capital is even greater now, …

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Synthesis, Processing And Characterization Of Polymer Derived Ceramic Nanocomposite Coating Reinforced With Carbon Nanotube Preforms, Hongjiang Yang Jan 2014

Synthesis, Processing And Characterization Of Polymer Derived Ceramic Nanocomposite Coating Reinforced With Carbon Nanotube Preforms, Hongjiang Yang

Electronic Theses and Dissertations

Ceramics have a number of applications as coating material due to their high hardness, wear and corrosion resistance, and the ability to withstand high temperatures. Critical to the success of these materials is the effective heat transfer through a material to allow for heat diffusion or effective cooling, which is often limited by the low thermal conductivity of many ceramic materials. To meet the challenge of improving the thermal conductivity of ceramics without lowering their performance envelope, carbon nanotubes were selected to improve the mechanical properties and thermal dispersion ability due to its excellent mechanical properties and high thermal conductivity …

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Decentralized Power Management In Microgrids, Amit Bhattacharjee Jan 2014

Decentralized Power Management In Microgrids, Amit Bhattacharjee

Electronic Theses and Dissertations

A large number of power sources, operational in a microgrid, optimum power sharing and accordingly controlling the power sources along with scheduling loads are the biggest challenges in modern power system. In the era of smart grid, the solution is certainly not simple paralleling. Hence it is required to develop a control scheme that delivers the overall power requirements while also adhering to the power limitations of each source. As the penetration of distributed generators increase and are diversifi ed, the choice of decentralized control becomes preferable. In this work, a decentralized control framework is conceived. The primary approach is …

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Synthetic Generators For Simulating Social Networks, Awrad Mohammed Ali Jan 2014

Synthetic Generators For Simulating Social Networks, Awrad Mohammed Ali

Electronic Theses and Dissertations

An application area of increasing importance is creating agent-based simulations to model human societies. One component of developing these simulations is the ability to generate realistic human social networks. Online social networking websites, such as Facebook, Google+, and Twitter, have increased in popularity in the last decade. Despite the increase in online social networking tools and the importance of studying human behavior in these networks, collecting data directly from these networks is not always feasible due to privacy concerns. Previous work in this area has primarily been limited to 1) network generators that aim to duplicate a small subset of …

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Processing And Characterization Of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics, Sarah Cox Jan 2014

Processing And Characterization Of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics, Sarah Cox

Electronic Theses and Dissertations

The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures …

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Non-Oxide Porous Ceramics From Polymer Precursor, Xueping Yang Jan 2014

Non-Oxide Porous Ceramics From Polymer Precursor, Xueping Yang

Electronic Theses and Dissertations

Non-oxide porous ceramics exhibit many unique and superior properties, such as better high-temperature stability, improved chemical inertness/corrosive resistance, as well as wide band-gap semiconducting behavior, which lead to numerous potential applications in catalysis, high temperature electronic and photonic devices, and micro-electromechanical systems. Currently, most mesoporous non-oxide ceramics (e.g. SiC) are formed by two-step templating methods, which are hard to adjust the pore sizes, and require a harmful etching step or a high temperature treatment to remove the templates. In this dissertation, we report a novel technique for synthesizing hierarchically mesoporous non-oxide SiC ceramic from a block copolymer precursor. The copolymer …

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Photonic Filtering For Applications In Microwave Generation And Metrology, Marcus Bagnell Jan 2014

Photonic Filtering For Applications In Microwave Generation And Metrology, Marcus Bagnell

Electronic Theses and Dissertations

This work uses the photonic filtering properties of Fabry-Perot etalons to show improvements in the electrical signals created upon photodetection of the optical signal. First, a method of delay measurement is described which uses multi-heterodyne detection to find correlations in white light signals at 20 km of delay to sub millimeter resolution. By filtering incoming white light with a Fabry-Perot etalon, the pseudo periodic signal is suitable for measurement by combining and photodetecting it with an optical frequency comb. In this way, optical data from a large bandwidth can be downconverted and sampled on low frequency electronics. Second, a high …

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A Program Manager's Dilemma: Measuring The Effect On Performance Of Different Visual Modalities In Mixed Reality Aerial Door Gunnery, Jonathan Stevens Jan 2014

A Program Manager's Dilemma: Measuring The Effect On Performance Of Different Visual Modalities In Mixed Reality Aerial Door Gunnery, Jonathan Stevens

Electronic Theses and Dissertations

The United States Army continues to develop new and effective ways to use simulation for training. One example is the Non-Rated Crew Member Manned Module (NCM3), a simulator designed to train helicopter crewmembers in critical, high risk tasks such as crew coordination, flight, aerial gunnery, hoist and sling load related tasks. The goal of this study was to evaluate visual modalities' effect on performance in mixed reality aerial door gunnery. There is a strong belief in the United States Army that the greater the degree of immersion in a virtual simulation, the more effective that simulation is. However, little scientific …

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Parity-Time And Supersymmetry In Optics, Mohammad Ali Miri Jan 2014

Parity-Time And Supersymmetry In Optics, Mohammad Ali Miri

Electronic Theses and Dissertations

Symmetry plays a crucial role in exploring the laws of nature. By exploiting some of the underlying analogies between the mathematical formalism of quantum mechanics and that of electrodynamics, in this dissertation we show that optics can provide a fertile ground for studying, observing, and utilizing some of the peculiar symmetries that are currently out of reach in other areas of physics. In particular, in this work, we investigate two important classes of symmetries, parity-time symmetry (PT) and supersymmetry (SUSY), within the context of classical optics. The presence of PT symmetry can lead to entirely real spectra in non-Hermitian systems. …

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Context-Aware Mobile Augmented Reality Visualization In Construction Engineering Education, Arezoo Shirazi Jan 2014

Context-Aware Mobile Augmented Reality Visualization In Construction Engineering Education, Arezoo Shirazi

Electronic Theses and Dissertations

Recent studies suggest that the number of students pursuing science, technology, engineering, and mathematics (STEM) degrees has been generally decreasing. An extensive body of research cites the lack of motivation and engagement in the learning process as a major underlying reason of this decline. It has been discussed that if properly implemented, instructional technology can enhance student engagement and the quality of learning. Therefore, the main goal of this research is to implement and assess effectiveness of augmented reality (AR)-based pedagogical tools on student learning. For this purpose, two sets of experiments were designed and implemented in two different construction …

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Conae Microwave Radiometer (Mwr) Counts To Brightness Temperature Algorithm, Zoubair Ghazi Jan 2014

Conae Microwave Radiometer (Mwr) Counts To Brightness Temperature Algorithm, Zoubair Ghazi

Electronic Theses and Dissertations

This dissertation concerns the development of the MicroWave Radiometer (MWR) brightness temperature (Tb) algorithm and the associated algorithm validation using on-orbit MWR Tb measurements. This research is sponsored by the NASA Earth Sciences Aquarius Mission, a joint international science mission, between NASA and the Argentine Space Agency (Comision Nacional de Actividades Espaciales, CONAE). The MWR is a CONAE developed passive microwave instrument operating at 23.8 GHz (K-band) H-pol and 36.5 GHz (Ka-band) H- and V-pol designed to complement the Aquarius L-band radiometer/scatterometer, which is the prime sensor for measuring sea surface salinity (SSS). MWR measures the Earth's brightness temperature and …

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High Resolution Time-Resolved Imaging System In The Vacuum Ultraviolet Region, Yuseong Jang Jan 2014

High Resolution Time-Resolved Imaging System In The Vacuum Ultraviolet Region, Yuseong Jang

Electronic Theses and Dissertations

High-power debris-free vacuum ultraviolet (VUV) light sources have applications in several scientific and engineering areas, such as high volume manufacturing lithography and inspection tools in the semiconductor industry, as well as other applications in material processing and photochemistry. For the past decades, the semiconductor industry has been driven by what is called "Moore's Law". The entire semiconductor industry relies on this rule, which requires chip makers to pack transistors more tightly with every new generation of chips, shrinking the size of transistors. The ability to solve roadmap challenges is, at least partly, proportional to our ability to measure them. The …

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Practical Implementations Of The Active Set Method For Support Vector Machine Training With Semi-Definite Kernels, Christopher Sentelle Jan 2014

Practical Implementations Of The Active Set Method For Support Vector Machine Training With Semi-Definite Kernels, Christopher Sentelle

Electronic Theses and Dissertations

The Support Vector Machine (SVM) is a popular binary classification model due to its superior generalization performance, relative ease-of-use, and applicability of kernel methods. SVM training entails solving an associated quadratic programming (QP) that presents significant challenges in terms of speed and memory constraints for very large datasets; therefore, research on numerical optimization techniques tailored to SVM training is vast. Slow training times are especially of concern when one considers that re-training is often necessary at several values of the models regularization parameter, C, as well as associated kernel parameters. The active set method is suitable for solving SVM problem …

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Complementary Layered Learning, Sean Mondesire Jan 2014

Complementary Layered Learning, Sean Mondesire

Electronic Theses and Dissertations

Layered learning is a machine learning paradigm used to develop autonomous robotic-based agents by decomposing a complex task into simpler subtasks and learns each sequentially. Although the paradigm continues to have success in multiple domains, performance can be unexpectedly unsatisfactory. Using Boolean-logic problems and autonomous agent navigation, we show poor performance is due to the learner forgetting how to perform earlier learned subtasks too quickly (favoring plasticity) or having difficulty learning new things (favoring stability). We demonstrate that this imbalance can hinder learning so that task performance is no better than that of a suboptimal learning technique, monolithic learning, which …

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Improved Internet Security Protocols Using Cryptographic One-Way Hash Chains, Amerah Alabrah Jan 2014

Improved Internet Security Protocols Using Cryptographic One-Way Hash Chains, Amerah Alabrah

Electronic Theses and Dissertations

In this dissertation, new approaches that utilize the one-way cryptographic hash functions in designing improved network security protocols are investigated. The proposed approaches are designed to be scalable and easy to implement in modern technology. The first contribution explores session cookies with emphasis on the threat of session hijacking attacks resulting from session cookie theft or sniffing. In the proposed scheme, these cookies are replaced by easily computed authentication credentials using Lamport's well-known one-time passwords. The basic idea in this scheme revolves around utilizing sparse caching units, where authentication credentials pertaining to cookies are stored and fetched once needed, thereby, …

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Transparent Oxide Semiconductor Gate Based Mosfets For Sensor Applications, Ashwin Kumar Saikumar Jan 2014

Transparent Oxide Semiconductor Gate Based Mosfets For Sensor Applications, Ashwin Kumar Saikumar

Electronic Theses and Dissertations

Starting from small scale laboratories to the highly sophisticated industrial facilities, monitoring and control forms the most integral part. In order to perform this continuous monitoring we require an interface, that would operate between the system and its processing conditions and in turn which facilitates us to act accordingly. This interface is called as a sensor. There are various types of sensors available which have wide range of functionality in various different fields. The use of transparent conducting oxide (TCO) in the field of sensor applications has increased and has been the subject of extensive research. Good electrical properties, good …

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Semiconductor Laser Based On Thermoelectrophotonics, Xiaohang Liu Jan 2014

Semiconductor Laser Based On Thermoelectrophotonics, Xiaohang Liu

Electronic Theses and Dissertations

This dissertation presents to our knowledge the first demonstration of a quantum well (QW) laser monolithically integrated with internal optical pump based on a light emitting diode (LED). The LED with high efficiency is operated in a thermoelectrophotonic (TEP) regime for which it can absorb both its own emitted light and heat. The LED optical pump can reduce internal optical loss in the QW laser, and enables monolithically integrated TEP heat pumps to the semiconductor laser. The design, growth and fabrication processes of the laser chip are discussed, and its experimental data is presented. In order to further increase the …

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Multimaterial Fibers In Photonics And Nanotechnology, Guangming Tao Jan 2014

Multimaterial Fibers In Photonics And Nanotechnology, Guangming Tao

Electronic Theses and Dissertations

Recent progress in combing multiple materials with distinct optical, electronic, and thermomechanical properties monolithically in a kilometer-long fiber drawn from a preform offers unique multifunctionality at a low cost. A wide range of unique in-fiber devices have been developed in fiber form-factor using this strategy. Here, I summary my recent results in this nascent field of 'multimaterial fibers'. I will focus on my achievements in producing robust infrared optical fibers and in appropriating optical fiber production technology for applications in nanofabrication. The development of optical components suitable for the infrared (IR) is crucial for applications in this spectral range to …

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Laser Filamentation - Beyond Self-Focusing And Plasma Defocusing, Khan Lim Jan 2014

Laser Filamentation - Beyond Self-Focusing And Plasma Defocusing, Khan Lim

Electronic Theses and Dissertations

Laser filamentation is a highly complex and dynamic nonlinear process that is sensitive to many physical parameters. The basic properties that define a filament consist of (i) a narrow, high intensity core that persists for distances much greater than the Rayleigh distance, (ii) a low density plasma channel existing within the filament core, and (iii) a supercontinuum generated over the course of filamentation. However, there remain many questions pertaining to how these basic properties are affected by changes in the conditions in which the filaments are formed; that is the premise of the work presented in this dissertation. To examine …

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Distribution Of Laser Induced Heating In Multi-Component Chalcogenide Glass And Its Associated Effects, Laura Sisken Jan 2014

Distribution Of Laser Induced Heating In Multi-Component Chalcogenide Glass And Its Associated Effects, Laura Sisken

Electronic Theses and Dissertations

Chalcogenide glasses are well known to have good transparency into the infrared spectrum. These glasses though tend to have low thresholds as compared to oxide glasses for photo-induced changes and thermally-induced changes. Material modification such as photo-induced darkening, bleaching, refractive index change, densification or expansion, ablation of crystallization have been demonstrated, and are typically induced by a thermal furnace-based heat treatment, an optical source such as a laser, or a combination of photo-thermal interactions. Solely employing laser-based heating has an advantage over a furnace, since one has the potential to be able to spatially modify the materials properties with much …

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Highly-Sensitive Stoichiometric Analysis Of Yag Ceramics Using Laser-Induced Breakdown Spectroscopy (Libs), Jahromi, Ali Kazemi Jan 2014

Highly-Sensitive Stoichiometric Analysis Of Yag Ceramics Using Laser-Induced Breakdown Spectroscopy (Libs), Jahromi, Ali Kazemi

Electronic Theses and Dissertations

Transparent ceramics are an important class of optical materials with applications in high-strength windows, radiation detectors and high-power lasers. Despite the many successful developments of the past decades, their challenging fabrication still needs to be perfected to achieve a better consistency in optical quality. In particular, ternary phase materials such as Yttrium Aluminum Garnet (YAG, Y3Al5O12), a long standing high-power laser host, require a precise control of stoichiometry, often beyond the precision of current analytical techniques, in order to reduce scattering losses and the presence of deleterious point defects. This work explores the potential of Laser-Induced Breakdown Spectroscopy (LIBS) for …

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Broad Bandwidth, All-Fiber, Thulium-Doped Photonic Crystal Fiber Amplifier For Potential Use In Scaling Ultrashort Pulse Peak Powers, Alex Sincore Jan 2014

Broad Bandwidth, All-Fiber, Thulium-Doped Photonic Crystal Fiber Amplifier For Potential Use In Scaling Ultrashort Pulse Peak Powers, Alex Sincore

Electronic Theses and Dissertations

Fiber based ultrashort pulse laser sources are desirable for many applications; however generating high peak powers in fiber lasers is primarily limited by the onset of nonlinear effects such as self-phase modulation, stimulated Raman scattering, and self-focusing. Increasing the fiber core diameter mitigates the onset of these nonlinear effects, but also allows unwanted higher-order transverse spatial modes to propagate. Both large core diameters and single-mode propagation can be simultaneously attained using photonic crystal fibers. Thulium-doped fiber lasers are attractive for high peak power ultrashort pulse systems. They offer a broad gain bandwidth, capable of amplifying sub-100 femtosecond pulses. The longer …

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Techniques For Characterization Of Third Order Optical Nonlinearities, Manuel Ferdinandus Jan 2014

Techniques For Characterization Of Third Order Optical Nonlinearities, Manuel Ferdinandus

Electronic Theses and Dissertations

This dissertation describes the development of novel techniques for characterization of nonlinear properties of materials. The dissertation is divided into two parts, a background and theory section and a technique development section. In the background and theory section we explain the origins of the nonlinear optical response of materials across many different spatial and temporal scales. The mechanisms that we are most interested in are the electronic nuclear and reorientational responses, which occur on the range of sub-femtosecond to several picoseconds. The electronic mechanism is due to the electrons of a material experiencing a non-parabolic potential well due a strong …

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Multimaterial Fibers And Tapers A Platform For Nonlinear Photonics And Nanotechnology, Soroush Shabahang Jan 2014

Multimaterial Fibers And Tapers A Platform For Nonlinear Photonics And Nanotechnology, Soroush Shabahang

Electronic Theses and Dissertations

The development of optical sources and components suitable for the mid-infrared is crucial for applications in this spectral range to reach the maturity level of their counterparts in the visible and near-infrared spectral regimes. The recent commercialization of quantum cascade lasers is leading to further interest in this spectral range. Wideband mid-infrared coherent sources, such as supercontinuum generation, have yet to be fully developed. A mid-infrared supercontinuum source would allow for unique applications in spectroscopy and sensing. Over the last decade, it has been shown that high-index confinement in highly nonlinear fibers pumped with high-peak-power pulses is an excellent approach …

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Development Of Traffic Safety Zones And Integrating Macroscopic And Microscopic Safety Data Analytics For Novel Hot Zone Identification, Jaeyoung Lee Jan 2014

Development Of Traffic Safety Zones And Integrating Macroscopic And Microscopic Safety Data Analytics For Novel Hot Zone Identification, Jaeyoung Lee

Electronic Theses and Dissertations

Traffic safety has been considered one of the most important issues in the transportation field. With consistent efforts of transportation engineers, Federal, State and local government officials, both fatalities and fatality rates from road traffic crashes in the United States have steadily declined from 2006 to 2011.Nevertheless, fatalities from traffic crashes slightly increased in 2012 (NHTSA, 2013). We lost 33,561 lives from road traffic crashes in the year 2012, and the road traffic crashes are still one of the leading causes of deaths, according to the Centers for Disease Control and Prevention (CDC). In recent years, efforts to incorporate traffic …

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Climate And Landscape Controls On Seasonal Water Balance At The Watershed Scale, Xi Chen Jan 2014

Climate And Landscape Controls On Seasonal Water Balance At The Watershed Scale, Xi Chen

Electronic Theses and Dissertations

The main goal of this dissertation is to develop a seasonal water balance model for evaporation, runoff and water storage change based on observations from a large number of watersheds, and further to obtain a comprehensive understanding on the dominant physical controls on intra-annual water balance. Meanwhile, the method for estimating evaporation and water storage based on recession analysis is improved by quantifying the seasonal pattern of the partial contributing area and contributing storage to base flow during low flow seasons. A new method for quantifying seasonality is developed in this research. The difference between precipitation and soil water storage …

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