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Articles 4051 - 4080 of 4850
Full-Text Articles in Engineering
Agglomeration Of Bed Particles In Low-Temperature Black Liquor Gasification, Mark A. Woodruff
Agglomeration Of Bed Particles In Low-Temperature Black Liquor Gasification, Mark A. Woodruff
Theses and Dissertations
The increasing concern for emissions and pollutants from power generation plants has increased the desire for and the study of biomass fuels. Biomass combustion produces less carbon monoxide as well as other greenhouse gases. Black liquor is a byproduct from the Kraft process in making paper. Black liquor can be gasified and used as a fuel in recovery boilers and fluidized bed steam reformers. Recovery boilers have a low efficiency and are used today because of their reliability. Steam reformers have a much higher efficiency but they are a relatively new science and are not as reliable. One of the …
Potential Energy Surfaces For Small Alcohol Dimers I: Methanol And Ethanol, Richard L. Rowley, Tapani A. Pakkanen, Christopher M. Tracy
Potential Energy Surfaces For Small Alcohol Dimers I: Methanol And Ethanol, Richard L. Rowley, Tapani A. Pakkanen, Christopher M. Tracy
Faculty Publications
Potential energy landscapes for homogeneous dimers of methanol and ethanol were calculated using counterpoise (CP) corrected energies at the MP2/6-311+G(2df,2pd) level. The landscapes were sampled at approximately 15 dimer separation distances for different relative monomer geometries, or routes, given in terms of a relative monomer yaw, pitch, and roll and the spherical angles between the monomer centers (taken as the C atom attached to the O). The 19 different routes studied for methanol and the 22 routes examined for ethanol include 607 CP corrected energies. Both landscapes can be adequately represented by site-site, pairwise-additive models, suitable for use in molecular …
Modeling Arsenic Partitioning In Coal-Fired Power Plants, Constance L. Senior, David O. Lignell, Adel F. Sarofim, Arun Mehta
Modeling Arsenic Partitioning In Coal-Fired Power Plants, Constance L. Senior, David O. Lignell, Adel F. Sarofim, Arun Mehta
Faculty Publications
Vapor-phase arsenic in coal combustion flue gas causes deactivation of the catalysts used in selective catalytic reduction (SCR) systems for NOx control. A one-dimensional model has been developed to predict the behavior of arsenic in the postcombustion region of a coal-fired boiler as a function of gas residence time. The purpose of the model is to calculate the partitioning of arsenic between the vapor phase from volatilization and arsenic on the ash particles due to surface reaction and/or condensation at temperatures characteristic of SCR systems. The model accounts for heterogeneous condensation of arsenic on the fly ash, as well …
Optical Emission Study Of Nonthermal Plasma Confirms Reaction Mechanisms Involving Neutral Rather Than Charged Species, Morris D. Argyle, Gui-Bing Zhao, Maciej Radosz
Optical Emission Study Of Nonthermal Plasma Confirms Reaction Mechanisms Involving Neutral Rather Than Charged Species, Morris D. Argyle, Gui-Bing Zhao, Maciej Radosz
Faculty Publications
Charge transfer reactions are commonly used to explain NOX conversion in nonthermal plasma. An analysis of optical emission spectra induced by pulsed corona discharge in NOX-containing argon suggests that, in fact, the contribution of charge transfer reactions to NOX conversion in nonthermal plasma is negligible. During electrical discharge in such gas mixtures, NO(B), an electronic excited state of NO formed due to the dissociative recombination reactions of NO2+ and N2O+ and the optical emission of NO(B) could be a proof that cations are responsible for NOX conversion. However, the optical emission of NO(B) is not observed, leading to the conclusion …
Design And Realization Of A Single Stage Sigma-Delta Adc With Low Oversampling Ratio, Yongjie Cheng
Design And Realization Of A Single Stage Sigma-Delta Adc With Low Oversampling Ratio, Yongjie Cheng
Theses and Dissertations
Due to the rapid growth of the communication market, a large amount of research is in process toward a high speed and high resolution sigma-delta A/D converter. This dissertation focuses on the design of a single-stage sigma-delta A/D converter with very low oversampling ratio for the wireless application. An architecture for a multibit single-stage delta-sigma A/D converter with two-step quantization is proposed. Both the MSB and LSB signals produced by the two-step quantization are fed back simultaneously to all integrator stages, making it suitable for low oversampling ratios. The two-step ADC avoids the problem that the complexity of an internal …
Performance Of Algebraic Multigrid For Parallelized Finite Element Dns/Les Solvers, Gregory James Larson
Performance Of Algebraic Multigrid For Parallelized Finite Element Dns/Les Solvers, Gregory James Larson
Theses and Dissertations
The implementation of a hybrid spectral/finite-element discretization on the unsteady, incompressible, Navier-Stokes equations with a semi-implicit time-stepping method, an explicit treatment of the advective terms, and an implicit treatment of the pressure and viscous terms leads to an algorithm capable of calculating 3D flows over complex 2D geometries. This also results in multiple Fourier mode linear systems which must be solved at every timestep, which naturally leads to two parallelization approaches: Fourier space partitioning, where each processor individually and simultaneously solves a linear system, and physical space partitioning, where all processors collectively solve each linear system, sequentially advancing through Fourier …
Numerical Simulation Of Plasma-Based Actuator Vortex Control Of A Turbulent Cylinder Wake, Nathan Keith Mcmullin
Numerical Simulation Of Plasma-Based Actuator Vortex Control Of A Turbulent Cylinder Wake, Nathan Keith Mcmullin
Theses and Dissertations
A numerical study has been performed to investigate the mechanics of the turbulent wake of a circular cylinder that is controlled by a plasma actuator. The numerical investigation implements a straightforward moving wall boundary condition to model the actuator's effects on the flow. Validations of the moving wall for this simulation are set forth with the understanding that the moving wall can model the plasma actuator bulk flow effects at a distance downstream and not in a region near or on the plasma actuator. The moving wall boundary condition is then applied to a circular cylinder at a Reynolds number …
Obstacle Avoidance For Small Unmanned Air Vehicles, Brandon R. Call
Obstacle Avoidance For Small Unmanned Air Vehicles, Brandon R. Call
Theses and Dissertations
Small UAVs are used for low altitude surveillance flights where unknown obstacles can be encountered. These UAVs can be given the capability to navigate in uncertain environments if obstacles are identified. This research presents an obstacle avoidance system for small UAVs. First, a mission waypoint path is created that avoids all known obstacles using a genetic algorithm. Then, while the UAV is in flight, obstacles are detected using a forward looking, onboard camera. Image features are found using the Harris Corner Detector and tracked through multiple video frames which provides three dimensional localization of the features. A sparse three dimensional …
Low-Frequency Ultrasound Increases Outer Membrane Permeability Of Pseudomonas Aeruginosa, Christopher M. Runyan, John C. Carmen, Benjamin L. Beckstead, Jared L. Nelson, Richard A. Robison, William G. Pitt
Low-Frequency Ultrasound Increases Outer Membrane Permeability Of Pseudomonas Aeruginosa, Christopher M. Runyan, John C. Carmen, Benjamin L. Beckstead, Jared L. Nelson, Richard A. Robison, William G. Pitt
Faculty Publications
Low-frequency ultrasound has been investigated as an adjuvant to antimicrobial therapy, targeted at both planktonic and biofilm (sessile) organisms. Our previous work showed that ultrasound (US) effectively enhances the bactericidal activity of certain antibiotics against planktonic cultures (Pitt et al., 1994; Rediske et al., 1999) and in vitro biofilms (Johnson et al., 1998; Qian et al., 1999) and in vivo biofilms (Carmen et al., 2004b, 2005; Rediske et al., 2000) of gram-positive and gram-negative bacteria. Ultrasound was shown to increase the transport of antibiotics through biofilms (Carmen et al., 2004a) which could account for some (or all) of the enhanced …
Design And Fabrication Of Rotationally Tristable Compliant Mechanisms, Tyler M. Pendleton
Design And Fabrication Of Rotationally Tristable Compliant Mechanisms, Tyler M. Pendleton
Theses and Dissertations
The purpose of this research is to develop the tools necessary to create tristable compliant mechanisms; the work presents the creation of models and concepts for design and a demonstration of the feasibility of the designs through the fabrication of tristable compliant mechanism prototypes on the macro scale. Prior methods to achieve tristable mechanisms rely on detents, friction, or power input; disadvantages to these methods include a high number of parts, the necessity for lubrication, and wear. A compliant tristable mechanism accomplishes tristability through strain energy storage. These mechanisms would be preferable because of increased performance and cost savings due …
Automatic, Unstructured Mesh Generation For 2d Shelf Based Tidal Models, Cameron L. Mcdonald
Automatic, Unstructured Mesh Generation For 2d Shelf Based Tidal Models, Cameron L. Mcdonald
Theses and Dissertations
Numeric models use a collection of triangular facets called elements connected over a domain in what is referred to as a mesh or unstructured grid as the computational basis for calculations. The density of elements in a mesh affects the numeric stability of a model when performing computations. Furthermore, these meshes can be difficult and time consuming to create. This thesis describes an automated process of creating meshes which utilizes local truncation analysis to generate a spatially varied size function. An advancing frontal mesh generation algorithm uses this function to optimize node placement and density. Further analysis to better understand …
Design Of Piezoresistive Mems Force And Displacement Sensors, Tyler Lane Waterfall
Design Of Piezoresistive Mems Force And Displacement Sensors, Tyler Lane Waterfall
Theses and Dissertations
MEMS (MicroElectroMechanical Systems) sensors are used in acceleration, flow, pressure and force sensing applications on the micro and macro levels. Much research has focused on improving sensor precision, range, reliability, and ease of manufacture and operation. One exciting possibility for improving the capability of micro sensors lies in exploiting the piezoresistive properties of silicon, the material of choice in many MEMS fabrication processes. Piezoresistivity—the change of electrical resistance due to an applied strain—is a valuable material property of silicon due to its potential for high signal output and on-chip and feedback-control possibilities. However, successful design of piezoresistive micro sensors requires …
Melt Detection In Antarctic Ice Shelves Using Scatterometers And Microwave Radiometers, David G. Long, Lucas B. Kunz
Melt Detection In Antarctic Ice Shelves Using Scatterometers And Microwave Radiometers, David G. Long, Lucas B. Kunz
Faculty Publications
Ku-band dual-polarization radar backscatter measurements from the SeaWinds-on-QuikSCAT scatterometer are used to determine periods of surface freeze and melt in the Antarctic ice shelves. The normalized horizontal-polarization radar backscatter (sigmao) and backscatter polarization ratio are used in maximum-likelihood estimation of the ice state. This method is used to infer the daily ice-surface conditions for 25 study locations located on the Ronne, Ross, Larsen, Amery, Shackleton, and other ice shelves. The temporal and spatial variations of the radar response are observed for various neighborhood sizes surrounding each given location during the study period. Criteria for determining the dates of melt onset …
Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard
Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard
Faculty Publications
Despite the tremendous potential demonstrated by miniature aerial vehicles (MAV) in numerous applications, they are currently limited to operations in open air space, far away from obstacles and terrain. To broaden the range of applications for MAVs, methods to enable operation in environments of increased complexity must be developed. In this article, we presented two strategies for obstacle and terrain avoidance that provide a means for avoiding obstacles in the flight path and for staying centered in a winding corridor.
Comparison Of Microcantilever Hg Sensing Behavior With Thermal Higher Order Modes For As-Deposited Sputtered And Thermally Evaporated Au Films, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam
Comparison Of Microcantilever Hg Sensing Behavior With Thermal Higher Order Modes For As-Deposited Sputtered And Thermally Evaporated Au Films, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam
Faculty Publications
As-deposited sputtered and thermally evaporated Au films are studied for Hg sensing with rectangular Si microcantilevers. Microcantilever deflection and frequency shifts in the first four thermally induced flexural modes are measured for each type of Au film as a function of Hg exposure. All thermally induced higher order modes show shifts in their frequencies for Hg exposures when the Au is sputter deposited whereas typically only the third and fourth order modes show frequency shifts when the Au is thermally evaporated. A technique is employed in order to vary Au coverage along a microcantilever surface. The shifts in the thermal …
Experimental And Modeling Investigations Of Biomass Particle Combustion, Hong Lu
Experimental And Modeling Investigations Of Biomass Particle Combustion, Hong Lu
Theses and Dissertations
This investigation provides a comprehensive analysis of entrained-flow biomass combustion processes. Experimental and theoretical investigations indicate how particle shape and size influence biomass combustion rates. Experimental samples include flake-like, cylinder-like, and equant (nearly spherical) shapes with similar particle masses and volumes but different surface areas. Samples of small (less than 500 µm) particles were passed through a laboratory entrained-flow reactor in a nitrogen/air atmosphere and a maximum reactor wall temperature of 1600 K, while large samples were reacted in suspension in a single particle furnace operated at similar conditions as the entrained-flow reactor. A separately developed computer and image analysis …
Recovering Grain Boundary Inclination Parameters Through Oblique Double-Sectioning, Eric Richards Homer
Recovering Grain Boundary Inclination Parameters Through Oblique Double-Sectioning, Eric Richards Homer
Theses and Dissertations
A method for the retrieval of grain boundary inclination parameters of the grain boundary character distribution by oblique double-sectioning is proposed. The method, which is similar to the recovery of the orientation distributions from sets of incomplete pole-figures, is described along with a framework for implementation. The method directly measures grain boundary inclinations in a manner similar to serial sectioning while statistically sampling the microstructure comparably to stereological methods. Computer simulations of the method were used to confirm the mathematical framework. Additional simulations, where the grain boundary normal distributions were recovered by both oblique double-sectioning and stereological methods, showed that …
Systematic Design Process For Slanted Graing Couplers,, Gregory P. Nordin, J. Jiang, B. Wang
Systematic Design Process For Slanted Graing Couplers,, Gregory P. Nordin, J. Jiang, B. Wang
Faculty Publications
We have developed a systematic design process for recently proposed slanted grating couplers (SGCs) that operates in the strong coupling regime. Based on rigorous analysis of SGC properties, this design process utilizes the k-vector diagram and a rigorous grating leaky-mode solver to intentionally enforce the phase-match and Bragg conditions. We demonstrate that the resultant SGC designs have performance similar to those obtained by parallel micro-genetic algorithm (µGA) optimization with the twodimensional finite-difference time-domain (2D FDTD) method. Only two 2D FDTD simulations are necessary in the later stages of our systematic design process. Therefore the time saving is tremendous compared to …
Analysis Of The Sediment Transport Capabilities Of Feswms Fst2dh, Mark K. Ipson
Analysis Of The Sediment Transport Capabilities Of Feswms Fst2dh, Mark K. Ipson
Theses and Dissertations
Many numeric models simulate the transport of sediment within rivers and streams. Engineers use such models to monitor the overall condition of a river or stream and to analyze the impact that the aggradation and degradation of sediment has on the stability of bridge piers and other features within a stretch of a river or stream. A model developed by the Federal Highway Administration, FST2DH, was recently modified to include the simulation of sediment movement within a channel. The tools for modeling sediment movement with FST2DH remain unproven. This thesis examines the sediment capabilities of FST2DH. It evaluates the sediment …
Methane Conversion In Pulsed Corona Discharge Reactors, Morris D. Argyle, Gui-Bing Zhao, Sanil John, Ji-Jun Zhang, Linna Wang, Suresh S. Muknahallipatna, Jerry C. Hamann, John F. Ackerman, Ovid A. Plumb
Methane Conversion In Pulsed Corona Discharge Reactors, Morris D. Argyle, Gui-Bing Zhao, Sanil John, Ji-Jun Zhang, Linna Wang, Suresh S. Muknahallipatna, Jerry C. Hamann, John F. Ackerman, Ovid A. Plumb
Faculty Publications
This work reports the effect of capacitance, cathode material, gas flow rate and specific energy input on methane conversion, energy efficiency and product selectivity in a co-axial cylinder pulsed corona discharge reactor. Ethan and acetylene appear to be formed from dimerization of CH3 radicals and CH radicals, respectively, while ethylene is formed mainly from the dehydrogenation of ethane. At a given power input, low capacitance with high pulse frequency results in higher methane conversion and energy efficiency than operation at high capacitance with low pulse frequency. Platinum coated stainless steel cathodes slightly enhance methane conversion relative to stainless steel cathodes, …
Adaptive Control Of Micro Air Vehicles, Joshua Stephen Matthews
Adaptive Control Of Micro Air Vehicles, Joshua Stephen Matthews
Theses and Dissertations
Although PID controllers work well on Miniature Air Vehicles (MAVs), they require tuning for each MAV. Also, they quickly lose performance in the presence of actuator failures or changes in the MAV dynamics. Adaptive control algorithms that self tune to each MAV and compensate for changes in the MAV during flight are explored. However, because the autopilots on MAVs are small, many of the adaptive control algorithms like those that employ least squares estimation may take too much code space, memory, and/or computing power. In this thesis we develop several Lyapunov-based model reference adaptive control (MRAC) schemes that are both …
Improved State Estimation For Miniature Air Vehicles, Andrew Mark Eldredge
Improved State Estimation For Miniature Air Vehicles, Andrew Mark Eldredge
Theses and Dissertations
Research in Unmanned Air Vehicles (UAV's) continues to push the limitations of size and weight. As technical advances have made UAV's smaller and less expensive, they have become more flexible and extensive in their roles. To continue using smaller and less expensive components while retaining and even enhancing performance requires more sophisticated processing of sensor data in order for the UAV to accurately determine its state and thereby allow the use of feedback in controlling the aircraft automatically. This work presents a three-stage state-estimation scheme for the class of UAV's know as Miniature Air Vehicles (MAV's). The first stage estimates …
Cross-Layer Issues In Mac Protocol Design For Mimo Ad Hoc Networks, Michael A. Jensen, A. Lee Swindlehurst, Michele Zorzi, James R. Zeidler, Adam L. Anderson, Bhaskar Rao, John Proakis, Srikanth Krishnamurthy
Cross-Layer Issues In Mac Protocol Design For Mimo Ad Hoc Networks, Michael A. Jensen, A. Lee Swindlehurst, Michele Zorzi, James R. Zeidler, Adam L. Anderson, Bhaskar Rao, John Proakis, Srikanth Krishnamurthy
Faculty Publications
In this article, we discuss research and design issues that arise in the development of networking protocols for an ad hoc network where nodes are equipped with multiple antenna elements and have the ability to perform signal processing operations as required by adaptive beamforming, interference cancellation, and space-time coding.
Preliminary Modeling, Control, And Trajectory Design For Miniature Autonomous Tailsitters, Nathan B. Knoebel, Stephen R. Osborne, Deryl Snyder, Timothy W. Mclain, Randal W. Beard, Andrew Mark Eldredge
Preliminary Modeling, Control, And Trajectory Design For Miniature Autonomous Tailsitters, Nathan B. Knoebel, Stephen R. Osborne, Deryl Snyder, Timothy W. Mclain, Randal W. Beard, Andrew Mark Eldredge
Faculty Publications
A tailsitter UAV has unique advantages over typical fixed wing aircraft or hovercraft. This paper highlights topics of interest in our preliminary research in developing a tailsitter UAV. An aerodynamic model and quaternion-based attitude and position control scheme is presented for controlling a tailsitter through hover maneuvers, with simulation results. Desired trajectories are also developed through feedback linearization of the dynamic equations, intended for quaternion-based attitude control. Finally, a hardware platform is proposed.
Modeling And Validation Of Tension-Element Based Mechanisms For Golf Ball-Club Impact, Aaron Robison
Modeling And Validation Of Tension-Element Based Mechanisms For Golf Ball-Club Impact, Aaron Robison
Theses and Dissertations
Previous work has systematically and numerically demonstrated feasibility and performance benefits of the tension-element concept in golf club heads; however, higher fidelity models needed to be created and validated for this concept. There is a need for more accurate models for this concept to further investigate its performance benefits. Performance is measured in terms of impact efficiency of the ball and head and is referred to as coefficient of restitution (COR). COR is affected by the dynamic effective face stiffness and mass properties of the club. This thesis creates and validates high-fidelity, non-linear, dynamic finite element models for the tension-element …
Video Stabilization And Target Localization Using Feature Tracking With Video From Small Uavs, David Linn Johansen
Video Stabilization And Target Localization Using Feature Tracking With Video From Small Uavs, David Linn Johansen
Theses and Dissertations
Unmanned Aerial Vehicles (UAVs) equipped with lightweight, inexpensive cameras have grown in popularity by enabling new uses of UAV technology. However, the video retrieved from small UAVs is often unwatchable due to high frequency jitter. Beginning with an investigation of previous stabilization work, this thesis discusses the challenges of stabilizing UAV based video. It then presents a software based computer vision framework and discusses its use to develop a real-time stabilization solution. A novel approach of estimating intended video motion is then presented. Next, the thesis proceeds to extend previous target localization work by allowing the operator to easily identify …
Determining The Value Of A Master's Degree In Construction Management, Benjamin K. Davis
Determining The Value Of A Master's Degree In Construction Management, Benjamin K. Davis
Theses and Dissertations
The purpose of this study is to determine the value of a master's degree in construction management in southern Idaho. A telephone and Internet survey was employed to determine the value that members of the construction industry in southern Idaho place on construction management (CM) degrees, both graduate and undergraduate. The survey included 27 self-described general contractors who are members of The Associated General Contractors of America (AGC) in regions 3 and 4 in the state of Idaho. Regions three and four include Twin Falls, Idaho Falls, Pocatello, Ketchum, Burley and surrounding communities. Following the compilation of surveys, it was …
Melt Detection And Estimation In Greenland Using Tandem Quikscat And Seawinds Scatterometers, Brandon R. Hicks
Melt Detection And Estimation In Greenland Using Tandem Quikscat And Seawinds Scatterometers, Brandon R. Hicks
Theses and Dissertations
Ku-band dual-polarization radar backscatter measurements from the SeaWinds on QuikScat (QuikScat) and SeaWinds on ADEOS-2 (SeaWinds) scatterometers are used to classify the melt state and estimate melt severity in Greenland. Backscatter measurements are organized into high temporal and high spatial resolution images created using the Scatterometer Image Reconstruction (SIR) algorithm and a new temporal data segmentation technique. Melt detection is performed using a layered electromagnetic model combined with a Markov chain model. The new melt detection method allows classification of the snow-pack into three states: melt, refreeze, and frozen. Melt severity and refreeze severity indexes are also developed. The melt …
Modeling The Mechanical Effects Of Liquid Mediated Adhesion Between The Human Vocal Folds, Gifford Zach Decker
Modeling The Mechanical Effects Of Liquid Mediated Adhesion Between The Human Vocal Folds, Gifford Zach Decker
Theses and Dissertations
The vocal folds are a complex self-oscillating biological system. In the current research, an equation was developed to model viscous adhesion forces that occur when the collision of the vocal folds results in the formation of a liquid bridge. The adhesion equation was validated using experimental data, and simplified to a one-dimensional approximation with an included correction factor that adjusted the predicted pressure in situations where the one-dimensional approximation was invalid. A non-oscillating vocal fold model with a modeled liquid bridge was used to study stress resulting from viscous adhesion. The vertical normal stress magnitude ranged from about 80 to …
Comparing Time And Accuracy Of Building Information Modeling To On-Screen Takeoff For A Quantity Takeoff Of A Conceptual Estimate, Morgan A. Alder
Comparing Time And Accuracy Of Building Information Modeling To On-Screen Takeoff For A Quantity Takeoff Of A Conceptual Estimate, Morgan A. Alder
Theses and Dissertations
Estimating is a critical aspect of every construction project. The most tedious component of an estimate is the quantity takeoff. Different tools are available to improve an estimator's productivity for a quantity takeoff. Faster quantity takeoffs enable estimator to bid more jobs. This study analyzed the time and accuracy of performing quantity takeoffs when using building information modeling (BIM) through a comparison study using Revit (BIM software) and On-Center's OST. In preparation for the study the researcher conducted a pilot study. Participants of the study were asked to perform a quantity takeoff using both Revit and OST. Their resulting data …