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Articles 31 - 60 of 184
Full-Text Articles in Engineering
Ultrafast Laser Material Processing For Photonic Applications, Mark Ramme
Ultrafast Laser Material Processing For Photonic Applications, Mark Ramme
Electronic Theses and Dissertations
Femtosecond Laser Direct Writing (FLDW) is a viable technique for producing photonic devices in bulk materials. This novel manufacturing technique is versatile due to its full 3D fabrication capability. Typically, the only requirement for this process is that the base material must be transparent to the laser wavelength. The modification process itself is based on non-linear energy absorption of laser light within the focal volume of the incident beam. This thesis addresses the feasibility of this technique for introducing photonic structures into novel dielectric materials. Additionally, this work provides a deeper understanding of the lightmatter interaction mechanism occurring at high …
Ytterbium-Doped Fiber-Seeded Thin-Disk Master Oscillator Power Amplifier Laser System, Christina Willis-Ott
Ytterbium-Doped Fiber-Seeded Thin-Disk Master Oscillator Power Amplifier Laser System, Christina Willis-Ott
Electronic Theses and Dissertations
Lasers which operate at both high average power and energy are in demand for a wide range of applications such as materials processing, directed energy and EUV generation. Presented in this dissertation is a high-power 1 μm ytterbium-based hybrid laser system with temporally tailored pulse shaping capability and up to 62 mJ pulses, with the expectation the system can scale to higher pulse energies. This hybrid system consists of a low power fiber seed and pre-amplifier, and a solid state thin-disk regenerative amplifier. This system has been designed to generate high power temporally tailored pulses on the nanosecond time scale. …
High Energy, High Average Power, Picosecond Laser Systems To Drive Few-Cycle Opcpa, Andreas Vaupel
High Energy, High Average Power, Picosecond Laser Systems To Drive Few-Cycle Opcpa, Andreas Vaupel
Electronic Theses and Dissertations
The invention of chirped-pulse amplification (CPA) in 1985 led to a tremendous increase in obtainable laser pulse peak intensities. Since then, several table-top, Ti:sapphire-based CPA systems exceeding the 100 TW-level with more than 10 W average power have been developed and several systems are now commercially available. Over the last decade, the complementary technology of optical parametric chirped-pulse amplification (OPCPA) has improved in its performance to a competitive level. OPCPA allows direct amplification of an almost-octave spanning bandwidth supporting few-cycle pulse durations at center wavelengths ranging from the visible to the mid-IR. The current record in peak power from a …
Pulsed Tm-Fiber Laser For Mid-Ir Generation, Pankaj Kadwani
Pulsed Tm-Fiber Laser For Mid-Ir Generation, Pankaj Kadwani
Electronic Theses and Dissertations
The thulium fiber laser has gained interest due to its long emission wavelength, large bandwidth (~1.8 – 2.1 µm), high efficiencies (~60 %), and high output power levels both in cw as well as pulsed regimes. Applications like remote sensing, machining, medical tissue ablation, and mid-infrared generation benefit from high peak power thulium laser sources. Pulsed thulium fiber laser systems are advancing rapidly towards higher peak power levels and are becoming the preferred sources for these applications. This dissertation work describes the development of novel nanosecond pulsed thulium fiber laser systems with record high peak power levels targeting mid-infrared generation. …
Load Estimation For Electric Power Distribution Networks, Chiebuka Eyisi
Load Estimation For Electric Power Distribution Networks, Chiebuka Eyisi
Electronic Theses and Dissertations
In electric power distribution systems, the major determinant in electricity supply strategy is the quantity of demand. Customers need to be accurately represented using updated nodal load information as a requirement for efficient control and operation of the distribution network. In Distribution Load Estimation (DLE), two major categories of data are utilized: historical data and direct real-time measured data. In this thesis, a comprehensive survey on the state-of-the-art methods for estimating loads in distribution networks is presented. Then, a novel method for representing historical data in the form of Representative Load Curves (RLCs) for use in realtime DLE is also …
Fast-Response Liquid Crystals For Photonic And Display Applications, Jie Sun
Fast-Response Liquid Crystals For Photonic And Display Applications, Jie Sun
Electronic Theses and Dissertations
Liquid crystal devices are attractive for many applications such as information displays, spatial light modulators and adaptive optics, because their optical properties are electrically tunable. However, response time of liquid crystal devices is a serious concern for many applications especially for those who require large phase modulation (≥2π). This is because a thick LC layer is usually needed to achieve a large phase shift while the response time of a nematic LC is highly determined by the cell gap.
An Exploration Of Unmanned Aerial Vehicle Direct Manipulation Through 3d Spatial Interaction, Kevin Pfeil
An Exploration Of Unmanned Aerial Vehicle Direct Manipulation Through 3d Spatial Interaction, Kevin Pfeil
Electronic Theses and Dissertations
We present an exploration that surveys the strengths and weaknesses of various 3D spatial interaction techniques, in the context of directly manipulating an Unmanned Aerial Vehicle (UAV). Particularly, a study of touch- and device- free interfaces in this domain is provided. 3D spatial interaction can be achieved using hand-held motion control devices such as the Nintendo Wiimote, but computer vision systems offer a different and perhaps more natural method. In general, 3D user interfaces (3DUI) enable a user to interact with a system on a more robust and potentially more meaningful scale. We discuss the design and development of various …
Investigation On Electrical Properties Of Rf Sputtered Deposited Bcn Thin Films, Adithya Prakash
Investigation On Electrical Properties Of Rf Sputtered Deposited Bcn Thin Films, Adithya Prakash
Electronic Theses and Dissertations
The ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated circuit (ULSI) devices. In order to reduce the time delay, it is necessary to introduce a wiring metal with low resistivity and …
Life Long Learning In Sparse Learning Environments, John Reeder
Life Long Learning In Sparse Learning Environments, John Reeder
Electronic Theses and Dissertations
Life long learning is a machine learning technique that deals with learning sequential tasks over time. It seeks to transfer knowledge from previous learning tasks to new learning tasks in order to increase generalization performance and learning speed. Real-time learning environments in which many agents are participating may provide learning opportunities but they are spread out in time and space outside of the geographical scope of a single learning agent. This research seeks to provide an algorithm and framework for life long learning among a network of agents in a sparse real-time learning environment. This work will utilize the robust …
Simulation-Based Cognitive Workload Modeling And Evaluation Of Adaptive Automation Invoking And Revoking Strategies, Christina Rusnock
Simulation-Based Cognitive Workload Modeling And Evaluation Of Adaptive Automation Invoking And Revoking Strategies, Christina Rusnock
Electronic Theses and Dissertations
In human-computer systems, such as supervisory control systems, large volumes of incoming and complex information can degrade overall system performance. Strategically integrating automation to offload tasks from the operator has been shown to increase not only human performance but also operator efficiency and safety. However, increased automation allows for increased task complexity, which can lead to high cognitive workload and degradation of situational awareness. Adaptive automation is one potential solution to resolve these issues, while maintaining the benefits of traditional automation. Adaptive automation occurs dynamically, with the quantity of automated tasks changing in real-time to meet performance or workload goals. …
Development Of Polymer Derived Sialcn Ceramic And Its Applications For High-Temperature Sensors, Gang Shao
Development Of Polymer Derived Sialcn Ceramic And Its Applications For High-Temperature Sensors, Gang Shao
Electronic Theses and Dissertations
Polymer-derived ceramic (PDC) is the name for a class of materials synthesized by thermal decomposition of polymeric precursors which excellent thermomechanical properties, such as high thermal stability, high oxidation/corrosion resistance and high temperature multifunctionalities. Direct polymer-to-ceramic processing routes of PDCs allow easier fabrication into various components/devices with complex shapes/structures. Due to these unique properties, PDCs are considered as promising candidates for making high-temperature sensors for harsh environment applications, including high temperatures, high stress, corrosive species and/or radiation. The SiAlCN ceramics were synthesized using the liquid precursor of polysilazane (HTT1800) and aluminum-sec-tri-butoxide (ASB) as starting materials and dicumyl peroxide (DP) as …
Wavelength Scale Resonant Structures For Integrated Photonic Applications, Matthew Weed
Wavelength Scale Resonant Structures For Integrated Photonic Applications, Matthew Weed
Electronic Theses and Dissertations
An approach to integrated frequency-comb filtering is presented, building from a background in photonic crystal cavity design and fabrication. Previous work in the development of quantum information processing devices through integrated photonic crystals consists of photonic band gap engineering and methods of on-chip photon transfer. This work leads directly to research into coupled-resonator optical waveguides which stands as a basis for the primary line of investigation. These coupled cavity systems offer the designer slow light propagation which increases photon lifetime, reduces size limitations toward on-chip integration, and offers enhanced light-matter interaction. A unique resonant structure explained by various numerical models …
Active Learning With Unreliable Annotations, Liyue Zhao
Active Learning With Unreliable Annotations, Liyue Zhao
Electronic Theses and Dissertations
With the proliferation of social media, gathering data has became cheaper and easier than before. However, this data can not be used for supervised machine learning without labels. Asking experts to annotate sufficient data for training is both expensive and time-consuming. Current techniques provide two solutions to reducing the cost and providing sufficient labels: crowdsourcing and active learning. Crowdsourcing, which outsources tasks to a distributed group of people, can be used to provide a large quantity of labels but controlling the quality of labels is hard. Active learning, which requires experts to annotate a subset of the most informative or …
Study Of Transport Phenomena In Carbon-Based Materials, Walid Aboelsoud
Study Of Transport Phenomena In Carbon-Based Materials, Walid Aboelsoud
Electronic Theses and Dissertations
In air-cooled heat exchangers, air-side thermal resistance is usually the largest compared to conduction and liquid-side thermal resistances. Thus, reducing the air-side thermal resistance with fin-like structures can greatly improve overall cooling performance. The performance of these structures is usually characterized by the rate of heat which can be transferred and the pumping power required. One promising solution is to use a high-thermal-conductivity material with a large surface per unit volume such as carbon foam. This study presents a method of utilizing V-shape corrugated carbon foam. The air-side heat transfer coefficient and the pressure drop across the foam have been …
Distributed Extremum Seeking And Cooperative Control For Mobile Cooperative Communication Systems, Said Alabri
Distributed Extremum Seeking And Cooperative Control For Mobile Cooperative Communication Systems, Said Alabri
Electronic Theses and Dissertations
In this thesis, a distributed extremum seeking and cooperative control algorithm is designed for mobile agents to disperse themselves optimally in maintaining communication quality and maximizing their coverage. The networked mobile agents locally form a virtual multiple-input multipleoutput (MIMO) communication system, and they cooperatively communicate among them by using the decode and forward cooperative communication technique. The outage probability is used as the measure of communication quality, and it can be estimated real-time. A general performance index balancing outage probability and spatial dispersion is chosen for the overall system. The extremum seeking control approach is used to estimate and optimize …
The Impact Of Growth Conditions On Cubic Znmgo Ultraviolet Sensors, Ryan Boutwell
The Impact Of Growth Conditions On Cubic Znmgo Ultraviolet Sensors, Ryan Boutwell
Electronic Theses and Dissertations
Cubic Zn1-xMgxO (c-Zn1-xMgxO) thin films have opened the deep ultraviolet (DUV) spectrum to exploration by oxide optoelectronic devices. These extraordinary films are readily wet-etch-able, have inversion symmetric lattices, and are made of common and safe constituents. They also host a number of new exciting experimental and theoretical challenges. Here, the relation between growth conditions of the c-Zn1-xMgxO film and performance of fabricated ultraviolet (UV) sensors is investigated. Plasma-Enhanced Molecular Beam Epitaxy was used to grow Zn1-xMgxO thin films and formation conditions were explored by varying the growth temperature, Mg source flux, oxygen flow rate, and radio-frequency (RF) power coupled into …
Generation And Printing Of Strictly Monodisperse Droplets, Hongxu Duan
Generation And Printing Of Strictly Monodisperse Droplets, Hongxu Duan
Electronic Theses and Dissertations
Highly monodisperse droplets are attracting great attention both in many research areas, such as aerosol science, combustion, and Nano-manufacturing. This thesis invents a novel aerosol generator: “Periodic Electro Hydro-dynamic Chopper” termed as “PEHD chopper”, and develops a new method to directly print micro-patterns with monodisperse droplets. The principle of the PEHD chopper is to use the fringe electric field of a capacitor to introduce controlled perturbation on a liquid jet. We first derived the governing equations for a circular inviscid liquid jet under transverse electric fields. The electric fields were obtained through numerical simulation. Then we used a high speed …
A Linear Multiplexed Electrospray Thin Film Deposition System, Brandon Lojewski
A Linear Multiplexed Electrospray Thin Film Deposition System, Brandon Lojewski
Electronic Theses and Dissertations
Liquid spray is essential to industries requiring processes such as spray coating, spray drying, spray pyrolysis, or spray cooling. This thesis reports the design, fabrication, and characterization of a thin film deposition system which utilizes a linear multiplexed electrospray (LINES) atomizer. First, a thorough review of the advantages and limitations of prior multiplexed electrospray systems leads to discussion of the design rationale for this work. Next, the line of charge model was extended to prescribe the operating conditions for the experiments and to estimate the spray profile. The spray profile was then simulated using a Lagrangian model and solved using …
Experimental And Numerical Investigations On Bond Durability Of Cfrp Strengthened Concrete Members Subjected To Environmental Exposure, Haider Al-Jelawy
Experimental And Numerical Investigations On Bond Durability Of Cfrp Strengthened Concrete Members Subjected To Environmental Exposure, Haider Al-Jelawy
Electronic Theses and Dissertations
Fiber reinforced polymer (FRP) composites have become an attractive alternative to conventional methods for external-strengthening of civil infrastructure, particularly as applied to flexural strengthening of reinforced concrete (RC) members. However, durability of the bond between FRP composite and concrete has shown degradation under some aggressive environments. Although numerous studies have been conducted on concrete members strengthened with FRP composites, most of those studies have focused on the degradation of FRP material itself, relatively few on bond behavior under repeated mechanical and environmental loading. This thesis investigates bond durability under accelerated environmental conditioning of two FRP systems commonly employed in civil …
A Posteriori And Interactive Approaches For Decision-Making With Multiple Stochastic Objectives, Ahmed Bakhsh
A Posteriori And Interactive Approaches For Decision-Making With Multiple Stochastic Objectives, Ahmed Bakhsh
Electronic Theses and Dissertations
Computer simulation is a popular method that is often used as a decision support tool in industry to estimate the performance of systems too complex for analytical solutions. It is a tool that assists decision-makers to improve organizational performance and achieve performance objectives in which simulated conditions can be randomly varied so that critical situations can be investigated without real-world risk. Due to the stochastic nature of many of the input process variables in simulation models, the output from the simulation model experiments are random. Thus, experimental runs of computer simulations yield only estimates of the values of performance objectives, …
Evaluating The Use Of Recycled Concrete Aggregate In French Drain Applications, Zachary Behring
Evaluating The Use Of Recycled Concrete Aggregate In French Drain Applications, Zachary Behring
Electronic Theses and Dissertations
Recycled concrete aggregate (RCA) is often used as a replacement of virgin aggregate in road foundations (base course), embankments, hot-mix asphalt, and Portland cement concrete. However, the use of RCA in exfiltration drainage systems, such as French drains, is currently prohibited in many states of the U.S. The French drain system collects water runoff from the road pavement and transfers to slotted pipes underground and then filters through coarse aggregate and geotextile. The primary concerns with using RCA as a drainage media are the fines content and the precipitation of calcium carbonate to cause a reducing in filter fabric permittivity. …
A Framework For Measuring The Value-Added Of Knowledge Processes With Analysis Of Process Interactions And Dynamics, Jose Cintron
A Framework For Measuring The Value-Added Of Knowledge Processes With Analysis Of Process Interactions And Dynamics, Jose Cintron
Electronic Theses and Dissertations
The most known and widely used methods use cash flows and tangible assets to measure the impact of investments in the organization’s outputs. But in the last decade many newer organizations whose outputs are heavily dependent on information technology utilize knowledge as their main asset. These organizations’ market values lie on the knowledge of its employees and their technological capabilities. In the current technology-based business landscape the value added by assets utilized for generation of outputs cannot be appropriately measured and managed without considering the role that intangible assets and knowledge play in executing processes. The analysis of processes for …
Silicon Photonic Devices For Optical Delay Lines And Mid Infrared Applications, Saeed Khan
Silicon Photonic Devices For Optical Delay Lines And Mid Infrared Applications, Saeed Khan
Electronic Theses and Dissertations
Silicon photonics has been a rapidly growing subfield of integrated optics and optoelectronic in the last decade and is currently considered a mature technology. The main thrust behind the growth is its compatibility with the mature and low-cost microelectronic integrated circuits fabrication process. In recent years, several active and passive photonic devices and circuits have been demonstrated on silicon. Optical delay lines are among important silicon photonic devices, which are essential for a variety of photonic system applications including optical beam-forming for controlling phased-array antennas, optical communication and networking systems and optical coherence tomography. In this thesis, several types of …
Differential Games For Multi-Agent Systems Under Distributed Information, Wei Lin
Differential Games For Multi-Agent Systems Under Distributed Information, Wei Lin
Electronic Theses and Dissertations
In this dissertation, we consider differential games for multi-agent systems under distributed information where every agent is only able to acquire information about the others according to a directed information graph of local communication/sensor networks. Such games arise naturally from many applications including mobile robot coordination, power system optimization, multiplayer pursuit-evasion games, etc. Since the admissible strategy of each agent has to conform to the information graph constraint, the conventional game strategy design approaches based upon Riccati equation(s) are not applicable because all the agents are required to have the information of the entire system. Accordingly, the game strategy design …
Strategic Improvement: A Systems Approach Using The Balanced Scorecard Methodology To Increase Federally Financed Research At The University Of Central Florida, Joseph Walters
Electronic Theses and Dissertations
The University of Central Florida has many successful measures to reflect on as it celebrates its 50th year in 2013. It is the university with the 2nd largest student population in the U. S. and its overall ranking in the U.S. News & World Report has improved 4 years in a row. However, with respect to research, the federally funded research and development for the University of Central Florida (UCF) has remained flat. In addition, when compared to other schools, its portion of those federal research dollars is small. This thesis lays the groundwork for developing a model for improving …
Modeling And Simulation Of All-Electric Aircraft Power Generation And Actuation, David Woodburn
Modeling And Simulation Of All-Electric Aircraft Power Generation And Actuation, David Woodburn
Electronic Theses and Dissertations
Modern aircraft, military and commercial, rely extensively on hydraulic systems. However, there is great interest in the avionics community to replace hydraulic systems with electric systems. There are physical challenges to replacing hydraulic actuators with electromechanical actuators (EMAs), especially for flight control surface actuation. These include dynamic heat generation and power management. Simulation is seen as a powerful tool in making the transition to all-electric aircraft by predicting the dynamic heat generated and the power flow in the EMA. Chapter 2 of this dissertation describes the nonlinear, lumped-element, integrated modeling of a permanent magnet (PM) motor used in an EMA. …
A Real-Time Crane Service Scheduling Decision Support System (Css-Dss) For Construction Tower Cranes, Amir Tork
A Real-Time Crane Service Scheduling Decision Support System (Css-Dss) For Construction Tower Cranes, Amir Tork
Electronic Theses and Dissertations
The success of construction projects depends on proper use of construction equipment and machinery to a great extent. Thus, appropriate planning and control of the activities that rely on construction equipment could have significant effects on improving the efficiency of project operations. Cranes are the largest and most conspicuous construction equipment, widely used in typical construction sites. They play a major role in relocation of materials in horizontal and vertical directions on construction sites. Given the nature of activities relying on construction cranes in various stages of a project, cranes normally have control over the critical path of the project …
A Hybrid Constitutive Model For Creep, Fatigue, And Creep-Fatigue Damage, Calvin Stewart
A Hybrid Constitutive Model For Creep, Fatigue, And Creep-Fatigue Damage, Calvin Stewart
Electronic Theses and Dissertations
In the combustion zone of industrial- and aero- gas turbines, thermomechanical fatigue (TMF) is the dominant damage mechanism. Thermomechanical fatigue is a coupling of independent creep, fatigue, and oxidation damage mechanisms that interact and accelerate microstructural degradation. A mixture of intergranular cracking due to creep, transgranular cracking due to fatigue, and surface embrittlement due to oxidation is often observed in gas turbine components removed from service. The current maintenance scheme for gas turbines is to remove components from service when any criteria (elongation, stress-rupture, crack length, etc.) exceed the designed maximum allowable. Experimental, theoretical, and numerical analyses are performed to …
Barium Based Halide Scintillator Ceramics For Gamma Ray Detection, William Shoulders
Barium Based Halide Scintillator Ceramics For Gamma Ray Detection, William Shoulders
Electronic Theses and Dissertations
As our understanding of ceramic processing methods for the purpose of fabricating polycrystalline optical materials has increased over the past few decades, the race is on to bring ceramic technology to markets where single crystalline materials have traditionally been used. One such market is scintillators. This Master’s thesis focuses specifically on a class of materials attractive for use as gamma-ray scintillators. These barium based halides can potentially be utilized in applications ranging from ionizing radiation detection in the field to high-energy physics experimentation. Barium bromide iodide and barium chloride single crystals have already showed high light yield, fast scintillation decay, …
Growth And Characterization Of Zno Based Semiconductor Materials And Devices, Ming Wei
Growth And Characterization Of Zno Based Semiconductor Materials And Devices, Ming Wei
Electronic Theses and Dissertations
Wide band gap semiconductors such as MgxZn1-xO represent an excellent choice for making optical photodetectors and emitters operating in the UV spectral region. High crystal and optical quality MgxZn1-xO thin films were grown epitaxially on c-plane sapphire substrates by plasma-assisted Molecular Beam Epitaxy. ZnO thin films with high crystalline quality, low defect and dislocation densities, and sub-nanometer surface roughness were achieved by applying a low temperature nucleation layer. The critical growth conditions were discussed to obtain a high quality film: the sequence of Zn and O sources for initial growth of nucleation layer, growth temperatures for both ZnO nucleation and …