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Articles 1231 - 1260 of 4566

Full-Text Articles in Engineering

Academic Blade Geometries For Baseline Comparisons Of Forced Vibration Response Predictions, James Little Jan 2017

Academic Blade Geometries For Baseline Comparisons Of Forced Vibration Response Predictions, James Little

Electronic Theses and Dissertations

Predicting the damping associated with underplatform dampers remains a challenge in turbomachinery blade and friction damper design. Turbomachinery blade forced response analysis methods usually rely on nonlinear codes and reduced order models to predict vibration characteristics of blades. Two academic blade geometries coupled with underplatform dampers are presented here for comparison of these model reduction and forced response simulation techniques. The two blades are representative of free-standing turbine blades and exhibit qualitatively similar behavior as highly-complex industrial blades. This thesis fully describes the proposed academic blade geometries and models; it further analyzes and predicts the blades forced response characteristics using …

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Hydrologic Controls On The Natural Drainage Networks Extracted From High-Resolution Topographic Data, Milad Hooshyar Jan 2017

Hydrologic Controls On The Natural Drainage Networks Extracted From High-Resolution Topographic Data, Milad Hooshyar

Electronic Theses and Dissertations

Drainage networks are important geomorphologic and hydrologic features which significantly control runoff generation. Drainage networks are composed of unchannelized valleys and channels. At valley heads, flow changes from unconfined sheet flow on the hillslope to confined flow in valley. Localized confined flow dominates in valleys as a result of convergent topography with positive curvature. Channels initiate at some distance down from the valley head, and the transition from unchannelized valley to channel is referred to as the channel head. Channel heads occur at a point where fluvial transport dominates over diffusive transport. From the hydrologic perspective, channels are categorized as …

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Study Of Surface Passivation Behavior Of Crystalline Silicon Solar Cells, Haider Ali Jan 2017

Study Of Surface Passivation Behavior Of Crystalline Silicon Solar Cells, Haider Ali

Electronic Theses and Dissertations

To achieve efficiencies approaching the theoretical limit of 29.4% for industrially manufactured solar cells based on crystalline silicon, it is essential to have very low surface recombination velocities at both the front and rear surfaces of the silicon substrate. Typically, the substrate surfaces feature contacted and uncontacted regions, and recombination should be limited for both to maximize the energy conversion efficiency. Uncontacted silicon surfaces are often passivated by the deposition of silicon nitride (SiNx) or an aluminum oxide film with SiNx as capping layer (Al2O3/SiNx stack). Further, proper surface preparation and cleaning of Si wafers prior to deposition also plays …

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Hydro-Thermo-Mechanical Behavior Of Concrete At Elevated Temperatures, Manar Al Fadul Jan 2017

Hydro-Thermo-Mechanical Behavior Of Concrete At Elevated Temperatures, Manar Al Fadul

Electronic Theses and Dissertations

In the light of recent tragic events, such as, natural disasters, arson and terrorism, studying the thermo mechanical behavior of concrete at elevated temperatures has become of special concern. In addition, the fact that concrete has been widely used as a structural material in many critical applications, such as high rise buildings, pressure vessels, and nuclear plants, enhances the potential risk of exposing concrete to high temperatures. Accordingly, the potential damage to large-scale structures during the course of the fire, besides the possible loss of human life, emphasizes the necessity to better understand the thermo-structural behavior and failure mechanism of …

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Site Specific Sinkhole Risk Assessment In Central Florida Using Cone Penetrometer Testing, Ryan Shamet Jan 2017

Site Specific Sinkhole Risk Assessment In Central Florida Using Cone Penetrometer Testing, Ryan Shamet

Electronic Theses and Dissertations

As Florida's population is expanding and greater fluctuations in groundwater levels are being recorded, Central Florida has been experiencing a higher frequency of sinkhole occurrences than ever before in recorded history. Sinkholes in Central Florida are formed by a combination of bedrock weathering and overburden soil erosion due to the groundwater recharge and are a part of Florida's past and future geology. The initial stage of a sinkhole is referred to as soil raveling and is the most effective time to perform soil improvement measures, such as grouting, to mitigate further expansion of a subterranean void. Subsurface exploration tests, commonly …

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Interaction Between Carbon Nanotubes And Metals (Al, Cu) And The Effects On Resultant Properties Of The Hybrid Materials, Jingyin Jiang Jan 2017

Interaction Between Carbon Nanotubes And Metals (Al, Cu) And The Effects On Resultant Properties Of The Hybrid Materials, Jingyin Jiang

Electronic Theses and Dissertations

Due to the exceptional strength, stiffness and excellent electrical and thermal properties, carbon nanotubes (CNTs) have been regarded as promising candidates for advanced nanoelectronics and multifunctional nanocomposites. In this dissertation, the interaction of CNTs with metals have been investigated and the resultant electrical conduction have been analyzed, aiming to develop innovative avenues to best utilize CNTs' potential. In order to do so, quantum mechanics calculations have been carried out to study that how to obtain greater electrical conduction by doping metals (Cu, Al) which tailor the electronic structure of three different types of metal-CNT interactions, : 1) encapsulation of atoms …

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A Study On The Plasticity And Fracture Behaviors Of Inconel 718 Under Multiaxial Stress And Extremely Low Cycle Fatigue Loadings, Mohammed Algarni Jan 2017

A Study On The Plasticity And Fracture Behaviors Of Inconel 718 Under Multiaxial Stress And Extremely Low Cycle Fatigue Loadings, Mohammed Algarni

Electronic Theses and Dissertations

Engineering materials and structures are usually subjected to multiaxial stress states loading due to geometrical effects, residual stresses, or multi-directional loading. Ductile fracture and Extremely Low Cycle Fatigue (ELCF), less than 100 cycles to fail, are two common and co-exist failure modes in many engineering structures. However, the linkage between these two failure modes under multi-axial loading conditions has never been systematically studied. This research summarizes an extensive work of experimental and numerical studies of ductile fracture and ELCF under different stress states for nickel-base superalloy material "IN718" under room temperature. Specially designed specimens and tests were used to achieve …

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Pedestrian Safety Analysis Through Effective Exposure Measures And Examination Of Injury Severity, Md Imran Shah Jan 2017

Pedestrian Safety Analysis Through Effective Exposure Measures And Examination Of Injury Severity, Md Imran Shah

Electronic Theses and Dissertations

Pedestrians are considered the most vulnerable road users who are directly exposed to traffic crashes. In 2014, there were 4,884 pedestrians killed and 65,000 injured in the United States. Pedestrian safety is a growing concern in the development of sustainable transportation system. But often it is found that safety analysis suffers from lack of accurate pedestrian trip information. In such cases, determining effective exposure measures is the most appropriate safety analysis approach. Also it is very important to clearly understand the relationship between pedestrian injury severity and the factors contributing to higher injury severity. Accurate safety analysis can play a …

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Water And Energy Costs Of Landfilled Food Waste, Tonmoy Sarker Jan 2017

Water And Energy Costs Of Landfilled Food Waste, Tonmoy Sarker

Electronic Theses and Dissertations

Energy and water are consumed or contaminated during both the production and disposal of wasted food. To date, evaluations of water and energy resources associated with food waste have considered only resources used in food production. To allow for the full characterization of food waste within a Food Energy Water (FEW) nexus framework, this study addresses a fundamental knowledge gap related to the energy and water impacts of food waste after disposal. Fluxes of water and energy related to disposal of wasted food in landfills within the state of Florida were characterized. It is estimated that each metric ton (Mg) …

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Multi-Transit Echo Suppression For Passive Wireless Surface Acoustic Wave Sensors Using 3rd Harmonic Unidirectional Transducers And Walsh-Hadamard-Like Reflectors, Luis Manuel Rodriguez Cordoves Jan 2017

Multi-Transit Echo Suppression For Passive Wireless Surface Acoustic Wave Sensors Using 3rd Harmonic Unidirectional Transducers And Walsh-Hadamard-Like Reflectors, Luis Manuel Rodriguez Cordoves

Electronic Theses and Dissertations

A passive wireless surface acoustic wave sensor of a delay-line type is composed of an antenna, a transducer that converts the EM signal into a surface acoustic wave, and a set of acoustic reflectors that reflect the incoming signal back out through the antenna. A cavity forms between the transducer and the reflectors, trapping energy and causing multiple unwanted echoes. The work in this dissertation aims to reduce the unwanted echoes so that only the main transit signal is left--the signal of interest with sensor information. The contributions of this dissertation include reflective delay-line device response in the form of …

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Hymod Matlab Code, Mohammadhossein Alipour Jan 2017

Hymod Matlab Code, Mohammadhossein Alipour

Streamflow Prediction under Extreme Data-scarcity

No abstract provided.

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The Effect Of Morphology On Reflectance In Silicon Nanowires Grown By Electroless Etching, Victor Velez Jan 2017

The Effect Of Morphology On Reflectance In Silicon Nanowires Grown By Electroless Etching, Victor Velez

Electronic Theses and Dissertations

The strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and stable metal is used these days as a precursor to react with silicon and then form the nanowires. Its adequate selection of solution concentration for a …

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Prototype Development In General Purpose Representation And Association Machine Using Communication Theory, Huihui Li Jan 2017

Prototype Development In General Purpose Representation And Association Machine Using Communication Theory, Huihui Li

Electronic Theses and Dissertations

Biological system study has been an intense research area in neuroscience and cognitive science for decades of years. Biological human brain is created as an intelligent system that integrates various types of sensor information and processes them intelligently. Neurons, as activated brain cells help the brain to make instant and rough decisions. From the 1950s, researchers start attempting to understand the strategies the biological system employs, then eventually translate them into machine-based algorithms. Modern computers have been developed to meet our need to handle computational tasks which our brains are not capable of performing with precision and speed. While in …

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Spray-Deposited Titanium-Oxide Films For Infrared Optics, Photonics, And Solar Cell Applications., Sarmad Alhasan Jan 2017

Spray-Deposited Titanium-Oxide Films For Infrared Optics, Photonics, And Solar Cell Applications., Sarmad Alhasan

Electronic Theses and Dissertations

Self-assembled TiO2 foam-like films, were grown by the water based Streaming Process for Electrodeless Electrochemical Deposition (SPEED). The morphology of the ∼1 µm thick films consists of a tangled ropy structure with individual strands of ∼ 200 nm diameter and open pores of 0.1 to 3 micron dimensions. Such films are advantageous for proposed perovskite solar cell comprising CH3NH3PbI3 absorber with additional inorganic films as contact and conduction layers, all deposited by SPEED. Lateral film resistivity is in the range 20 - 200 kΩ-cm, increasing with growth temperature, while sheet resistance is in the range 2 − 20 × 108 …

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Investigating And Modeling The Impacts Of Illegal U-Turn Violations At Medials Located On Florida's Limited Access Highways, Omar Al-Sahili Jan 2017

Investigating And Modeling The Impacts Of Illegal U-Turn Violations At Medials Located On Florida's Limited Access Highways, Omar Al-Sahili

Electronic Theses and Dissertations

Illegal U-turn violations are considered part of the Wrong-Way Driving (WWD) maneuvers that could result in head-on crashes and severe injuries, which are often severe because of the high speed of the approaching traffic and limited time to avoid such crash. Therefore, reviewing this type of violation and understanding the contributing factors that may lead drivers to commit such illegal maneuver would help officials foresee and consequently minimize the potential risks that could lead to WWD crashes. The purpose of this thesis is to investigate the illegal U-turn maneuvers on limited access facilities and find the significant contributing factors that …

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Analysis Of Pedestrian Safety Using Micro-Simulation And Driving Simulator, Jiawei Wu Jan 2017

Analysis Of Pedestrian Safety Using Micro-Simulation And Driving Simulator, Jiawei Wu

Electronic Theses and Dissertations

In recent years, traffic agencies have begun to place emphasis on the importance of pedestrian safety. In the United States, nearly 70,000 pedestrians were reported injured in 2015. Although the number only account for 3% of all the people injured in traffic crashes, the number of pedestrian fatalities is still around 15% of total traffic fatalities. Furthermore, the state of Florida has consistently ranked as one of the worst states in terms of pedestrian crashes, injuries and fatalities. Therefore, it is befitting to focus on the pedestrian safety. This dissertation mainly focused on pedestrian safety at both midblock crossings and …

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An Emissive Antenna Correction For The Tropical Rainfall Measuring Mission Microwave Imager (Tmi), Faisal Alquaied Jan 2017

An Emissive Antenna Correction For The Tropical Rainfall Measuring Mission Microwave Imager (Tmi), Faisal Alquaied

Electronic Theses and Dissertations

This dissertation deals with the radiometric calibration of a satellite microwave radiometer known as the TRMM Microwave Imager (TMI), which operated on NASA’s Tropical Rainfall Measuring Mission (TRMM). This multi-frequency, conical-scanning, passive microwave, remote sensor measures the earth’s blackbody emissions (brightness temperature, Tb) from a low earth orbit and covers the tropics (±35° latitude). The original scientific objective for TRMM’s 3-year mission was to measure the statistics of rainfall in the tropics. However, the mission was quite successful, and TRMM was extended for greater than 17 years to provide a long-term satellite rain measurements, which has contributed significantly to the …

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A Multiagent Q-Learning-Based Restoration Algorithm For Resilient Distribution System Operation, Jungseok Hong Jan 2017

A Multiagent Q-Learning-Based Restoration Algorithm For Resilient Distribution System Operation, Jungseok Hong

Electronic Theses and Dissertations

Natural disasters, human errors, and technical issues have caused disastrous blackouts to power systems and resulted in enormous economic losses. Moreover, distributed energy resources have been integrated into distribution systems, which bring extra uncertainty and challenges to system restoration. Therefore, the restoration of power distribution systems requires more efficient and effective methods to provide resilient operation. In the literature, using Q-learning and multiagent system (MAS) to restore power systems has the limitation in real system application, without considering power system operation constraints. In order to adapt to system condition changes quickly, a restoration algorithm using Q-learning and MAS, together with …

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Continuous Oscillation: Vibrational Effects And Acceptable Frequency Ranges Of Small Bore Piping In Field Applications, Marie Kasprzyk Jan 2017

Continuous Oscillation: Vibrational Effects And Acceptable Frequency Ranges Of Small Bore Piping In Field Applications, Marie Kasprzyk

Electronic Theses and Dissertations

In turbomachinery, a common failure mode is cracking of welds at the equipment and piping connection point. Each incidence of these cracks causes a forced shutdown to perform repairs that cost millions of dollars. This type of failure is predominately seen in small bore piping, which has a nominal diameter of 2 inches and smaller. This thesis addresses the failure prediction analysis of small bore piping, specifically in turbomachinery applications. Performing failure analysis to predict the potential cracking of welds will allow for replacement of the piping during a planned shutdown which in the long term saves money due to …

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Statistical Analysis Of Multi-Row Film Cooling Flowfields, Craig Fernandes Jan 2017

Statistical Analysis Of Multi-Row Film Cooling Flowfields, Craig Fernandes

Electronic Theses and Dissertations

A huge part of modern day power generation research and development strives to achieve higher thermal efficiencies and specific work outputs for both gas turbine Brayton and combined cycles. Advances in cooling technologies, both internal to turbine blades and external, provide the easiest way to accomplish this by raising the turbine inlet temperature far beyond the super-alloy's allowable temperature. Discrete film cooling injection, an external cooling technique, ensures a cool blanket of compressed air protects the blade surface from the harsh mainstream gas. To optimize the coverage and effectiveness of the film, a thorough understanding of the behavior and flow …

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Dynamic Job-Shop Scheduling Program (Djsp) Analysis For Preventive Military Helicopter Maintenance System (Pms), Kyungjin Park Jan 2017

Dynamic Job-Shop Scheduling Program (Djsp) Analysis For Preventive Military Helicopter Maintenance System (Pms), Kyungjin Park

Electronic Theses and Dissertations

Republic of Korea Army(ROKA) has been founding new attack helicopter troops since last year by adopting US main attack helicopter, AH-64E Apache, and peripheral system like pilots and mechanics training systems and their organization. The AH-64E Apache is a major attack helicopter of the US Army and all of its systems are verified in terms of the effectiveness in real operations for several decades. However, ROKA still needs their own version of systems including tactics, template, and maintenance which are suitable for Korean terrain, climate, personnel, and so on. At least ROKA needs to have a chance to verify that …

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Printable Carbon Nanotube Based Multifunctional Nanocomposites For Strain Sensing And Self-Heating, Xin Wang Jan 2017

Printable Carbon Nanotube Based Multifunctional Nanocomposites For Strain Sensing And Self-Heating, Xin Wang

Electronic Theses and Dissertations

The unique properties of carbon nanotubes (CNTs) represent a potential for developing a piezo-resistive strain sensor and a resistive heating sheet with a smart structure. Conventional fabrication techniques of CNT based nanocomposites such as molding, casting or spray coating lack the ability to control the geometry and properties of fabricated composites. In order to meet the various requirements of strain sensing or self-heating applications, nanocomposites with complex geometry and controllable properties are in high demand. Digital printing technique is able to fabricate CNT films with precisely controlled geometry with the help of computer aided design, and their properties could also …

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Development And Implementation Of A Streamlined Process For The Creation And Mechanization Of Negative Poisson's Ratio Meso-Scale Patterns, Matthew Shuler Jan 2017

Development And Implementation Of A Streamlined Process For The Creation And Mechanization Of Negative Poisson's Ratio Meso-Scale Patterns, Matthew Shuler

Electronic Theses and Dissertations

This thesis focuses on the development a streamlined process used to create novel meso-scale pattern used to induce negative Poisson's ratio (NPR) behavior at the bulk scale. This process includes, the development, optimization, and implementation of a candidate pattern. Currently, the majority of NPR structures are too porous to be utilized in conventional applications. For others, manufacturing methods have yet to realize the meso-scale pattern. Consequently, new NPR meta-materials must be developed in order to confer transformative thermomechanical responses to structures where transverse expansion is more desirable than contraction. For example, materials at high temperature. Additionally, patterns that take into …

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Tensile-Compressive Asymmetry And Anisotropy Of Fused Deposition Modeling Pla Under Monotonic Conditions, Casey Perkowski Jan 2017

Tensile-Compressive Asymmetry And Anisotropy Of Fused Deposition Modeling Pla Under Monotonic Conditions, Casey Perkowski

Electronic Theses and Dissertations

Additive Manufacturing (AM) continues to gain popularity for its ability to produce complexly-shaped final use components that are impractical to manufacture by traditional methods; however, additive manufactured parts contain complex mesostructures that result in directionally-dependent mechanical properties that have yet to be fully characterized. This effort demonstrates a framework of experimental and analytical methods needed to characterize the uniaxial monotonic behavior of fused deposition modeling PLA using tensile and compressive experiments on specimens printed at various orientations. Based on experimental results, the asymmetry and anisotropy of the tensile and compressive response was analyzed for a candidate material. Specimens from different …

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Online Neuro-Adaptive Learning For Power System Dynamic State Estimation, Rahul Birari Jan 2017

Online Neuro-Adaptive Learning For Power System Dynamic State Estimation, Rahul Birari

Electronic Theses and Dissertations

With the increased penetration of renewable generation in the smart grid , it is crucial to have knowledge of rapid changes of system states. The information of real-time electro-mechanical dynamic states of generators are essential to ensuring reliability and detecting instability of the grid. The conventional SCADA based Dynamic State Estimation (DSE) was limited by the slow sampling rates (2-4 Hz). With the advent of PMU based synchro-phasor technology in tandem with Wide Area Monitoring System (WAMS), it has become possible to avail rapid real-time measurements at the network nodes. These measurements can be exploited for better estimates of system …

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Energy-Aware Data Movement In Non-Volatile Memory Hierarchies, Navid Khoshavi Najafabadi Jan 2017

Energy-Aware Data Movement In Non-Volatile Memory Hierarchies, Navid Khoshavi Najafabadi

Electronic Theses and Dissertations

While technology scaling enables increased density for memory cells, the intrinsic high leakage power of conventional CMOS technology and the demand for reduced energy consumption inspires the use of emerging technology alternatives such as eDRAM and Non-Volatile Memory (NVM) including STT-MRAM, PCM, and RRAM. The utilization of emerging technology in Last Level Cache (LLC) designs which occupies a signifcant fraction of total die area in Chip Multi Processors (CMPs) introduces new dimensions of vulnerability, energy consumption, and performance delivery. To be specific, a part of this research focuses on eDRAM Bit Upset Vulnerability Factor (BUVF) to assess vulnerable portion of …

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Modeling Of Flow Generated Sound In A Constricted Duct At Low Mach Number Flow, Peshala Thibbotuwawa Gamage Jan 2017

Modeling Of Flow Generated Sound In A Constricted Duct At Low Mach Number Flow, Peshala Thibbotuwawa Gamage

Electronic Theses and Dissertations

Modelling flow and acoustics in a constricted duct at low Mach numbers is important for investigating many physiological phenomena such as phonation, generation of arterial murmurs, and pulmonary conditions involving airway obstruction. The objective of this study is to validate computational fluid dynamics (CFD) and computational aero-acoustics (CAA) simulations in a constricted tube at low Mach numbers. Different turbulence models were employed to simulate the flow field. Models included Reynolds Average Navier-Stokes (RANS), Detached eddy simulation (DES) and Large eddy simulation (LES). The models were validated by comparing study results with laser doppler anemometry (LDA) velocity measurements. The comparison showed …

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Multi-Axial Thermomechanical Characterization Of Shape Memory Alloys For Improved Stability, Douglas Nicholson Jan 2017

Multi-Axial Thermomechanical Characterization Of Shape Memory Alloys For Improved Stability, Douglas Nicholson

Electronic Theses and Dissertations

Shape recovery in shape memory alloys (SMAs) occurs against external stress by means of a reversible thermoelastic solid state phase transformation typically between so-called austenite, martensite and R-phases. The ability to do work enables their use as high-force actuators in automotive and aerospace applications while superelastic NiTi is of interest in biomedical devices such as stents. Both R-phase and martensite can detwin, reorient and undergo a thermal or stress induced transformation. For these reasons, it is difficult from ordinary macroscopic measurements to decouple elastic and inelastic contributions (from their respective phases) from the overall deformation. In situ neutron diffraction is …

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Coupling Infrastructure Resilience And Flood Risk Assessment For A Coastal Urban Watershed, Justin Joyce Jan 2017

Coupling Infrastructure Resilience And Flood Risk Assessment For A Coastal Urban Watershed, Justin Joyce

Electronic Theses and Dissertations

This thesis sheds light on coupling potential flood risk and drainage infrastructure resilience of low-lying areas of a coastal urban watershed to flood hazards and subsequent multi-scale impacts of those hazards via detailed modeling frameworks. Physically based models along with statistical models are employed to highlight the complexity for characterizing flood risk while evaluating such risk under various levels of adaptive capacity from traditional flood management techniques to low impact development (LID), as a first step to conduct resilience assessment. Findings indicate that the coupling flood risk and infrastructure resilience is achievable by the careful formulation of flood risk associated …

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Local Transient Characterization Of Thermofluid Heat Transfer Coefficient At Solid-Liquid Nano-Interfaces, Mehrdad Mehrvand Jan 2017

Local Transient Characterization Of Thermofluid Heat Transfer Coefficient At Solid-Liquid Nano-Interfaces, Mehrdad Mehrvand

Electronic Theses and Dissertations

The demands for increasingly smaller, more capable, and higher power density technologies in microelectronics, energy, or aerospace systems have heightened the need for new methods to manage and characterize extreme heat fluxes (EHF). Microscale liquid cooling techniques are viewed as a promising solution for removing heat from high heat flux (HHF) systems. However, there have been challenges in physical understanding and predicting local thermal transport at the interface of micro and nanoscale structures/devices due to ballistic effects and complex coupling of mass, momentum, and energy transport at the solid-liquid-vapor interfaces over multiple time and length scales. Moreover, it's challenging to …

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