Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Brigham Young University

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 3781 - 3810 of 4850

Full-Text Articles in Engineering

Aerobatic Maneuvering Of Miniature Air Vehicles Using Attitude Trajectories, James K. Hall, Timothy W. Mclain Aug 2008

Aerobatic Maneuvering Of Miniature Air Vehicles Using Attitude Trajectories, James K. Hall, Timothy W. Mclain

Faculty Publications

We develop aerobatic maneuvering for miniature air vehicles (MAVs) using time-parameterized attitude trajectory generation and an associated attitude tracking control law. We develop two methodologies, polynomial or trigonometric, for creating smooth functions that specify pitch and roll angle trajectories. For both approaches, the functions are constrained by the maneuver boundary conditions for aircraft position and velocity. We develop a feedback control law to regulate aircraft orientation throughout the maneuvers. The performance of our trajectory generation algorithm and our attitude tracking control law is demonstrated through simulated and actual flight tests of aerobatic maneuvers.

Go to article

Fish Passage At Udot Culverts: Prioritization And Assessment, Aaron Evens Beavers Jul 2008

Fish Passage At Udot Culverts: Prioritization And Assessment, Aaron Evens Beavers

Theses and Dissertations

State Departments of Transportation are becoming more involved in providing Aquatic Organism Passage (AOP) at road-stream crossings. Department of Transportation (DOT) emphasis on AOP has been driven largely in response to endangered species listings, other agencies' initiatives, and the desire to restore ecosystem connectivity to watercourses. UDOT is currently responsible for approximately 47,000 culverts, but AOP is currently addressed only on an as-needed basis. Currently UDOT has no prioritization or assessment strategy procedure for AOP at UDOT road-stream crossings. Historical fish passage strategies have focused on federally listed adult anadromous salmon and trout. These are generally very large fish whose …

Go to article

The Development Of A Computational Model Of Thrombosis In Hemodialysis Catheters, Daniel J. Lattin Jul 2008

The Development Of A Computational Model Of Thrombosis In Hemodialysis Catheters, Daniel J. Lattin

Theses and Dissertations

Thromboembolism (TE) significantly limits the usefulness and safety of blood-contacting devices such as hemodialysis catheters. Computer simulation of TE can provide understanding of the process and can facilitate the design of more effective devices. Previous work conducted at BYU successfully modeled TE in a simple, two-dimensional flow cell design by adding quantitative TE code to a commercial computational fluid dynamics (CFD) package, Fluent. This two-dimensional model predicted thrombus initiation and growth and adjusted flow to accommodate thrombus geometries, but was limited by computational power and unsophisticated meshing techniques. To build upon this work, and take advantage of BYU's new supercomputing …

Go to article

Localized Coarsening Of Conforming All-Hexahedral Meshes, Adam C. Woodbury Jul 2008

Localized Coarsening Of Conforming All-Hexahedral Meshes, Adam C. Woodbury

Theses and Dissertations

Finite element mesh adaptation methods can be used to improve the efficiency and accuracy of solutions to computational modeling problems. For many finite element modeling applications, a conforming all-hexahedral mesh is preferred. When adapting a hexahedral mesh, localized modifications that preserve topologic conformity are often desired. Effective hexahedral refinement methods that satisfy these criteria have recently become available. However, due to hexahedral mesh topology constraints, little progress has been made in the area of hexahedral coarsening. This thesis presents a new method to locally coarsen conforming all-hexahedral meshes. The method works on both structured and unstructured meshes and is not …

Go to article

Three-Dimensional Direct Numerical Simulation Of Soot Formation And Transport In A Temporally Evolving Nonpremixed Ethylene Jet Flame, David O. Lignell, Jacqueline H. Chen, Philip J. Smith Jul 2008

Three-Dimensional Direct Numerical Simulation Of Soot Formation And Transport In A Temporally Evolving Nonpremixed Ethylene Jet Flame, David O. Lignell, Jacqueline H. Chen, Philip J. Smith

Faculty Publications

Three-dimensional direct numerical simulation of soot formation with complex chemistry is presented. The simulation consists of a temporally evolving, planar, nonpremixed ethylene jet flame with a validated, 19-species reduced mechanism. A four-step, three-moment, semiempirical soot model is employed. Previous two-dimensional decaying turbulence simulations have shown the importance of multidimensional flame dynamical effects on soot concentration [D.O. Lignell, J.H. Chen, P.J. Smith, T. Lu, C.K. Law, Combust. Flame 151 (1–2) (2007) 2–28]. It was shown that flame curvature strongly impacts the diffusive motion of the flame relative to soot (which is essentially convected with the flow), resulting in soot being differentially …

Go to article

Quantitative Uncertainty Of Chemical Plume Transport In Low Wind Speeds Using Measured Field Data And Stochastic Modeling, Veronica Elaine Wannberg Jul 2008

Quantitative Uncertainty Of Chemical Plume Transport In Low Wind Speeds Using Measured Field Data And Stochastic Modeling, Veronica Elaine Wannberg

Theses and Dissertations

Low wind speed conditions should be studied because these conditions can present risk, particularly for areas immediately surrounding the release point, where high concentrations can occur and not dissipate. The following research attempts to clarify the processes governing both the general and low wind speed cases by determining the accuracy and uncertainty of standard prediction methods for contaminant plume transport in low wind speed plume modeling. Multiple techniques were utilized to incorporate field measured data, previously gathered for a different purpose, to generate parameter distributions and ground-truth data that could be used in stochastic models for chemical plume prediction. These …

Go to article

Ability Of Adv Measurements To Detect Turbulence Differences Between Angular And Rounded Gravel Beds Of Intermediate - Roughness Scale, Benjamin B. Haws Jul 2008

Ability Of Adv Measurements To Detect Turbulence Differences Between Angular And Rounded Gravel Beds Of Intermediate - Roughness Scale, Benjamin B. Haws

Theses and Dissertations

A set of laboratory experiments was carried out to distinguish flow characteristics(bed origin, shear velocity, turbulence intensity, turbulent kinetic energy) between beds of differing gravel angularity. Ten vertical profiles of velocity measurements were taken from angular and rounded fixed gravel beds with a 16 MHz micro acoustic Doppler velocimeter (ADV) sampling at 50 Hz. Both gravel beds had a bottom slope of 0.2% and were in the intermediate - roughness scale. Shear velocities were calculated using three common methods: St Venant, Reynolds stress, and Clauser. The Reynolds stress method resulted in the closest visual match to turbulence distributions proposed by …

Go to article

Planning Continuous Curvature Paths Using Constructive Polylines, Joshua H. Henrie Jul 2008

Planning Continuous Curvature Paths Using Constructive Polylines, Joshua H. Henrie

Theses and Dissertations

Previous methods for planning clothoid based continuous curvature paths aim at minimizing path length. However, minimal length paths are not always smooth, natural, and drivable. A method of generating clothoid-based trajectories is discussed using constructive polylines. The goal of the motion planner is to create a path for a large car-like vehicle in human driving environments. Thus, the trajectories generated by the motion planner must be smooth, drivable, and natural such that the vehicle can follow the planned path on human roadways. Several examples are shown of trajectories developed for a DARPA Urban Challenge vehicle and a method of testing …

Go to article

A Gis-Based Strategy For Managing Levee Simulation Data, Jeffrey R. Handy Jul 2008

A Gis-Based Strategy For Managing Levee Simulation Data, Jeffrey R. Handy

Theses and Dissertations

Understanding and improving the state of the nation's levees has become a national priority following the devastating events surrounding Hurricanes Katrina and Rita. Federal legislation passed in 2007 created a new national Committee on Levee Safety and spurred the development of the National Levee Database, a central repository of information relating to the location and state of levees across the United States (Water Resources Development Act, 2007). One of the major goals in developing such a database is to improve the safety of America's levees. The National Levee Database, however, does not include features for storing seepage and slope stability …

Go to article

Nineteen-Element Phased-Array Feed Development And Analysis On Effects Of Focal Plane Offset And Beam Steering On Sensitivity, Jacob S. Waldron Jul 2008

Nineteen-Element Phased-Array Feed Development And Analysis On Effects Of Focal Plane Offset And Beam Steering On Sensitivity, Jacob S. Waldron

Theses and Dissertations

Presented herein is the design and construction process in the expansion of BYU's seven-element experimental platform to a nineteen-element platform for phased array feed experiments. The nineteen-element system was deployed at the National Radio Astronomy Observatory (NRAO) in Green Bank West Virginia for use on the Green Bank 20-Meter Telescope. Numerical simulations were performed to determine how sensitivity was affected by electronic beam steering and offset of the phased array feed (PAF) relative to the focal plane of the reflector. These simulated results were then compared to experimental data.

Go to article

Compact Trench-Based Silicon-On-Insulator Rib Waveguide 90-Degree And 105-Degree Bend And Splitter Design, Jiguo Song Jul 2008

Compact Trench-Based Silicon-On-Insulator Rib Waveguide 90-Degree And 105-Degree Bend And Splitter Design, Jiguo Song

Theses and Dissertations

This thesis presents a theoretical and numerical investigation of silicon-on-insulator trench based passive optical components, bend and splitter, respectively. Compact 90 degree and 105 degree bend and splitter are designed with high index-contrast rib waveguide at wavelength 1550nm and serve as building blocks of splitting network in micro-cantilever biosensing application. The main characteristic of trench based bend and splitter structures is their miniature size and their low radiation loss due to the strong light confinement in high index-contrast systems. Thus large scale, high density optical integrated splitting network becomes possible with the associated advantages of compactness. With FDTD simulation, we …

Go to article

Evaluating Shallow-Flow Rock Structures As Scour Countermeasures At Bridges, Benjamin P. Dahle Jul 2008

Evaluating Shallow-Flow Rock Structures As Scour Countermeasures At Bridges, Benjamin P. Dahle

Theses and Dissertations

The Utah Department of Transportation commissioned a study to determine whether or not shallow-flow rock structures could reliably be used at bridge abutments in place of riprap. Research was conducted in a two-phase effort beginning with numerical modeling and ending with field verification of model findings. As part of phase one, two finite element meshes were created in Surface-water Modeling Software (SMS) and analyzed with FESWMS-2DH. Second, field studies were conducted and a preliminary database was developed to track field studies conducted on 98 shallow-flow rock structures in Utah. Data organization in ArcGIS® and Microsoft Access® is presented followed by …

Go to article

Effects Of Moisture On Combustion Of Live Wildland Forest Fuels, Brent M. Pickett Jul 2008

Effects Of Moisture On Combustion Of Live Wildland Forest Fuels, Brent M. Pickett

Theses and Dissertations

Current operational wildland fire models are based on numerous correlations from experiments performed on dry (dead) fuel beds. However, experience has shown distinct differences in burning behaviors between dry and moist (live) fuels. To better understand these fundamental differences, an experiment was designed to use a flat-flame burner to simulate a moving fire front which heated and ignited a stationary, individual fuel sample. Samples included various U.S. species from the California chaparral, the intermountain west, and the southeastern regions. Temperature, mass, and video images were recorded throughout each experimental run from which numerous data values were obtained such as time …

Go to article

Vapor-Liquid Equilibrium Of Polymer Solutions During Thermal Decomposition Of Rigid Foams, Nathan H. King Jul 2008

Vapor-Liquid Equilibrium Of Polymer Solutions During Thermal Decomposition Of Rigid Foams, Nathan H. King

Theses and Dissertations

Removable Epoxy Foam (REF) and other rigid foams experience severe changes in structure and properties when exposed to high heat. As thermal energy breaks network bonds in the foam many species are formed, including large polymer-like network fragments and smaller solvent-like molecules. During this process a liquid phase may form. The vapor-liquid equilibrium (VLE) behavior of the polymer solutions formed during initial decomposition can be highly non-ideal. In this research VLE behavior of high-temperature polymer solutions was studied and a procedure was developed for predicting that behavior during decomposition of rigid foams. A high-temperature VLE facility was built and validated, …

Go to article

Freeze-Thaw Durability Of Pervious Concrete, Carson B. Demille Jul 2008

Freeze-Thaw Durability Of Pervious Concrete, Carson B. Demille

Theses and Dissertations

Although the use of pervious concrete is expanding, only a limited number of scholarly papers have been published on the resistance of pervious concrete to deterioration under frost action. Based on this need for additional research on the durability of pervious concrete in cold regions, the objective of this research was to evaluate the resistance of pervious concrete to degradation during freeze-thaw cycling under different soil clogging and water saturation conditions. The laboratory research associated with this project involved three primary measures of pervious concrete performance, including freeze-thaw durability, compressive strength, and permeability. Testing associated with freeze-thaw durability involved two …

Go to article

Microkinetic Model Of Fischer-Tropsch Synthesis On Iron Catalysts, Uchenna Prince Paul Jul 2008

Microkinetic Model Of Fischer-Tropsch Synthesis On Iron Catalysts, Uchenna Prince Paul

Theses and Dissertations

Fischer-Tropsch synthesis (FTS), developed in the early 1900's, is defined as the catalytic conversion of H2 and CO to hydrocarbons and oxygenates with the production of H2O and CO2. Accurate microkinetic modeling can in principle provide insights into catalyst design and the role of promoters. This work focused on gaining an understanding of the chemistry of the kinetically relevant steps in FTS on Fe catalyst and developing a microkinetic model that describes FTS reaction kinetics. Stable Al2O3-supported/promoted (20% Fe, 1% K, 1% Pt) and unsupported Fe (99% Fe, 1% Al2O3) catalysts were prepared and characterized. Transient experiments including temperature programmed …

Go to article

Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen Jul 2008

Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen

Theses and Dissertations

Image quality metrics for several inverse scattering methods and algorithms are presented. Analytical estimates and numerical simulations provide a basis for poor image quality diagnostics. The limitations and noise behavior of reconstructed images are explored analytically and empirically using a contrast ratio. Theoretical contrast ratio estimates using the canonical PEC circular cylinder are derived. Empirical studies are conducted to confirm theoretical estimates and to provide examples of image quality vs SNR for more complex scatterer profiles. Regularized sampling is shown to be more noise sensitive than tomographic reconstructive methods.

Go to article

Optically Powered Logic Transistor, Hanho Cho Jul 2008

Optically Powered Logic Transistor, Hanho Cho

Theses and Dissertations

This thesis presents the modeling and fabrication of a new solid-state device meant to be used for digital logic circuits. Most current logic circuits are based on MOSFETs. The new logic device uses some of the same operating principles, but also relies on optical illumination to provide input power. In order to obtain the desired current-voltage behavior of the new device, the Silvaco (Atlas) device simulation was used to give some insight into the correct doping levels in the semiconductor and device geometries. Prototypes were fabricated on p-type silicon wafers using CMOS fabrication processes including oxide growth, photolithography, precise plasma …

Go to article

Predicting The Longevity Of Dvdr Media By Periodic Analysis Of Parity, Jitter, And Ecc Performance Parameters, Daniel Patrick Wells Jul 2008

Predicting The Longevity Of Dvdr Media By Periodic Analysis Of Parity, Jitter, And Ecc Performance Parameters, Daniel Patrick Wells

Theses and Dissertations

For the last ten years, DVD-R media have played an important role in the storage of large amounts of digital data throughout the world. During this time it was assumed that the DVD-R was as long-lasting and stable as its predecessor, the CD-R. Several reports have surfaced over the last few years questioning the DVD-R's ability to maintain many of its claims regarding archival quality life spans. These reports have shown a wide range of longevity between the different brands. While some DVD-Rs may last a while, others may result in an early and unexpected failure. Compounding this problem is …

Go to article

Modeling Phase Transitions Of Nanoemulsion For Ultrasonic Gene Delivery, Ghaleb A. Husseini, William G. Pitt, Ram Singh Jul 2008

Modeling Phase Transitions Of Nanoemulsion For Ultrasonic Gene Delivery, Ghaleb A. Husseini, William G. Pitt, Ram Singh

Faculty Publications

A computer model was written that simulates the transformation of a nanoemulsion droplet to a gas bubble by the application of ultrasound. Experimentally such a technique could be used to enhance non-viral gene transfection beyond the boundary of the endothelial lining of the circulatory system, particularly in tumors exhibiting enhanced permeation and retention of nanoparticles.

Go to article

Analog Feedback Control Of An Active Sound Transmission Control Module, Jason Derek Sagers Jul 2008

Analog Feedback Control Of An Active Sound Transmission Control Module, Jason Derek Sagers

Theses and Dissertations

This thesis provides analytical and experimental proof-of-concept for a new feedback-controlled sound transmission control module for use in an active segmented partition (ASP) array. The objective of such a module is to provide high transmission loss down to low audible frequencies while minimizing the overall mass of the module. This objective is accomplished in the new module by using actively controlled panels in conjunction with analog feedback controllers. The new module also overcomes two limitations that exist in current ASP modules: the inability to control broadband random-noise and the lack of bidirectional control through the module. Overcoming these limitations represents …

Go to article

Multi-Physics Modeling And Calibration For Self-Sensing Of Thermomechanical In-Plane Microactuators, Kendall B. Teichert Jul 2008

Multi-Physics Modeling And Calibration For Self-Sensing Of Thermomechanical In-Plane Microactuators, Kendall B. Teichert

Theses and Dissertations

As technology advances and engineering capabilities improve, more research has focused on microscopic possibilities. Microelectromechanical systems (MEMS) is one area that has received much attention recently. Within MEMS much research has focused on sensing and actuation. This thesis presents work on a particular actuator of interest, the thermomechanical in-plane microactuator (TIM). Recent work has shown the possibility of a novel approach of sensing mechanical outputs of the TIM without ancillary sensors. This sensing approach exploits the piezoresistive property of silicon. However, to implement this approach a full model of the TIM would need to be obtained to describe the physics …

Go to article

Mode I Fracture Toughness Testing Of Friction Stir Processed Hsla-65, Jeffery D. Horschel Jul 2008

Mode I Fracture Toughness Testing Of Friction Stir Processed Hsla-65, Jeffery D. Horschel

Theses and Dissertations

In order to investigate the viability of friction stir welding for use in Naval construction, mode one elastic-plastic fracture toughness of friction stir processed HSLA-65 was determined using current ASTM 1820 and BS 7448 standards. Double-sided welds were used to achieve 12.7 mm thick samples. A constant feed rate of 100 mm/min was used for all welds. To explore the effect of weld parameters on toughness, welds were produced using two rotational speeds: 340 RPM and 490 RPM. The weld centerline, advancing side hardened region (ASHR), and TMAZ/HAZ regions were sampled, in addition to un-welded parent material. All elastic-plastic fracture …

Go to article

A Compliant Threshold Acceleration Sensor Integrated With Radio Frequency Identifiable Tags, Benjamin L. Todd Jul 2008

A Compliant Threshold Acceleration Sensor Integrated With Radio Frequency Identifiable Tags, Benjamin L. Todd

Theses and Dissertations

Fully compliant bistable mechanisms have been proposed to be used as threshold accelerometers. The advantages to using these devices are that they require no external power to operate and maintain their sensing state. Using this characteristic the devices can be integrated with passive radio frequency identification tags (RFID). This allows for the sensing package to lay dormant with no maintenance needed until the sensor is read by the RFID reader. This thesis presents a successfully fabricated and integrated threshold accelerometer with a passive RFID tag. This in turn has been successfully read with an RFID reader and shown to act …

Go to article

Characterization Of A Phased Array Feed Model, David A. Jones Jul 2008

Characterization Of A Phased Array Feed Model, David A. Jones

Theses and Dissertations

Creating accurate software based models of phased array feeds (PAFs) is one of many steps to successfully integrating PAFs with current and future radio telescopes, which is a goal of many groups around the globe. This thesis characterizes the latest models of a 19 element hexagonal PAF of dipoles used by the BYU radio astronomy research group and presents comparisons of these models with experimental data obtained using a prototype array. Experiments were performed at the NRAO site in Green Bank, West Virginia, and utilized the outdoor antenna test range and 20 meter radio telescope. Accurate modeling of the PAF …

Go to article

Development And Evaluation Of A Sub-Grid Combustion Model For A Landscape Scale 3-D Wildland Fire Simulator, Michael M. Clark Jul 2008

Development And Evaluation Of A Sub-Grid Combustion Model For A Landscape Scale 3-D Wildland Fire Simulator, Michael M. Clark

Theses and Dissertations

A mixture-fraction-based thermodynamic equilibrium approach for modeling gas-phase combustion was adapted and used in FIRETEC, a wildfire computational fluid dynamics model. The motivation behind this work was the desire to incorporate the features of complex chemistry calculations from the thermodynamic equilibrium model into FIRETEC without significantly increasing the computational burden of the program. In order to implement the mixture-fraction-based thermodynamic equilibrium approach, a sub-grid pocket model was developed to simulate the local mixture fraction of sub-grid flame sheets. Numerical simulations of wildfires were performed using FIRETEC with the new sub-grid, mixture-fraction-based pocket model to model gas-phase combustion. The thermodynamic equilibrium …

Go to article

A Satisficing Approach To Aircraft Conflict Resolution, Wynn C. Stirling, James K. Archibald, Nicholas A. Jepsen, Richard L. Frost, Jared C. Hill Jul 2008

A Satisficing Approach To Aircraft Conflict Resolution, Wynn C. Stirling, James K. Archibald, Nicholas A. Jepsen, Richard L. Frost, Jared C. Hill

Faculty Publications

Future generations of air traffic management systems may give appropriately equipped aircraft the freedom to change flight paths in real time. This would require a conflict avoidance and resolution scheme that is both decentralized and cooperative. We describe a multiagent solution to aircraft conflict resolution based on satisficing game theory. A key feature of the theory is that satisficing decision makers form their preferences by taking into consideration the preferences of others, unlike conventional game theory that models agents that maximize self-interest metrics. This makes possible situational altruism, a sophisticated form of unselfish behavior in which the preferences of another …

Go to article

Development Of A Particle Flow Test For Rotational Molding, Russell B. Whatcott Jun 2008

Development Of A Particle Flow Test For Rotational Molding, Russell B. Whatcott

Theses and Dissertations

One of the current testing method (the Dry Flow test) to qualify resin for use in production in the rotomolding process has been shown to have many flaws in both equipment and procedure. Research was done here to investigate a possible alternative that could eliminate some of these testing deficiencies. By reducing equipment and operator errors, the testing of materials becomes more valuable of an exercise. The Angular Flow test developed in this research can increase repeatability. By coming to understand the rotational molding process better, an evaluation that can give more valid information was devised.

Go to article

The Study Of Superintendent Training And Its Effects On Homebuilding Cycle Time, John Wesley Burk Jun 2008

The Study Of Superintendent Training And Its Effects On Homebuilding Cycle Time, John Wesley Burk

Theses and Dissertations

This study was conducted to determine how much time would be saved in the homebuilding cycle when field superintendents received training. The study took place during the 2007 calendar year with a production homebuilder in southern Nevada. New technologies and techniques were introduced during weekly training meetings that were held at both the corporate office and construction job sites. A scheduling tool was introduced along with new procedures and policies. The superintendents were required to report daily on the tasks that had been completed. This gave the superintendent and upper management the ability to follow the home throughout the building …

Go to article

Modeling Of Electronic And Ionic Transport Resistances Within Lithium-Ion Battery Cathodes, David E. Stephenson Jun 2008

Modeling Of Electronic And Ionic Transport Resistances Within Lithium-Ion Battery Cathodes, David E. Stephenson

Theses and Dissertations

In this work, a mathematical model is reported and validated, which describes the performance of porous electrodes under low and high rates of discharge. This porous battery model can be used to provide researchers a better physical understanding relative to prior models of how cell morphology and materials affect performance due to improved accounting of how effective resistance change with morphology and materials. The increased understanding of cell resistances will enable improved design of cells for high-power applications, such as hybrid and plug-in-hybrid electric vehicles. It was found electronic and liquid-phase ionic transport resistances are strongly coupled to particle conductivity, …

Go to article

First Prev Next Last