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Articles 1 - 18 of 18
Full-Text Articles in Engineering
Semiflexible Oligomers Crystallize Via A Cooperative Phase Transition, Pierre Kawak, Dakota S. Banks, Douglas R. Tree
Semiflexible Oligomers Crystallize Via A Cooperative Phase Transition, Pierre Kawak, Dakota S. Banks, Douglas R. Tree
Faculty Publications
Semicrystalline polymers are ubiquitous, yet despite their fundamental and industrial importance, the theory of homogeneous nucleation from a melt remains a subject of debate. A key component of the controversy is that polymer crystallization is a non-equilibrium process, making it difficult to distinguish between effects that are purely kinetic and those that arise from the underlying thermodynamics. Due to computational cost constraints, simulations of polymer crystallization typically employ non-equilibrium molecular dynamics techniques with large degrees of undercooling that further exacerbate the coupling between thermodynamics and kinetics. In a departure from this approach, in this study, we isolate the near-equilibrium nucleation …
Large-Scale Reality Modeling Of A University Campus Using Combined Uav And Terrestrial Photogrammetry For Historical Preservation And Practical Use, Bryce Berrett, Cory Vernon, Haley Beckstrand, Madi Pollei, Kaleb Markert, Kevin Franke, John Hedengren
Large-Scale Reality Modeling Of A University Campus Using Combined Uav And Terrestrial Photogrammetry For Historical Preservation And Practical Use, Bryce Berrett, Cory Vernon, Haley Beckstrand, Madi Pollei, Kaleb Markert, Kevin Franke, John Hedengren
Faculty Publications
Unmanned aerial vehicles (UAV) enable detailed historical preservation of large-scale infrastructure and contribute to cultural heritage preservation, improved maintenance, public relations, and development planning. Aerial and terrestrial photo data coupled with high accuracy GPS create hyper-realistic mesh and texture models, high resolution point clouds, orthophotos, and digital elevation models (DEMs) that preserve a snapshot of history. A case study is presented of the development of a hyper-realistic 3D model that spans the complex 1.7 km2 area of the Brigham Young University campus in Provo, Utah, USA and includes over 75 significant structures. The model leverages photos obtained during the historic …
A High-Pressure Shear Testing Approach To Measure Flow Stresses Near A Friction Stir Welding Tool, David Prymak, Michael Miles, Tracy W. Nelson, Fredrick Michael
A High-Pressure Shear Testing Approach To Measure Flow Stresses Near A Friction Stir Welding Tool, David Prymak, Michael Miles, Tracy W. Nelson, Fredrick Michael
Faculty Publications
A new approach for measuring flow stresses near a spinning friction stir welding (FSW) tool is evaluated on AA 6061-T6 plate. The test consists of plunging a cylindrical tool with a flat face into the plate at different rotational speeds, using a variety of constant vertical loads. A viscosity-based model of the shear layer created under the tool is employed to estimate local flow stresses. The flow stresses measured by this approach exhibited an inverse relationship with temperature and a positive dependence on the pressure imposed by the spinning flat-faced tool. Compared to hot compression and hot torsion results, estimated …
Dynamic Simulation Of A Novel Nuclear Hybrid Energy System With Large-Scale Hydrogen Storage In An Underground Salt Cavern, An Ho, Kasra Mohammadi, Matthew Memmott, John Hedengren, Kody Powell
Dynamic Simulation Of A Novel Nuclear Hybrid Energy System With Large-Scale Hydrogen Storage In An Underground Salt Cavern, An Ho, Kasra Mohammadi, Matthew Memmott, John Hedengren, Kody Powell
Faculty Publications
In this study, a nuclear hybrid energy system (NHES) with large-scale hydrogen storage integrated with a gas turbine cycle is proposed as a flexible system for load following. The proposed system consists of a nuclear reactor, a steam Rankine cycle, a hydrogen electrolyzer, a storage system for hydrogen in an underground salt cavern, and a Brayton cycle that uses hydrogen as fuel to generate additional electricity to meet peak demand. A dynamic mathematical model is developed for each subsystem of the NHES. To evaluate the potential benefits of the system, a one-year study is conducted, using scaled grid demand data …
Electroanalytical Measurements Of Oxide Ions In Molten Cacl2 On W Electrode, Devin Rappleye, Chao Zhang, Art Nelson, Scott Simpson, Michael Simpson
Electroanalytical Measurements Of Oxide Ions In Molten Cacl2 On W Electrode, Devin Rappleye, Chao Zhang, Art Nelson, Scott Simpson, Michael Simpson
Faculty Publications
The electrochemical interaction of oxide ions with tungsten electrodes in molten calcium chloride (CaCl2) was analyzed by combining electroanalytical techniques with X-ray photoelectron spectroscopy. During a cyclic voltammetry (CV) scan, the oxide ions appear to interact with the tungsten working electrode via a multi-step oxidation and reduction process. The overall redox peaks behave reversibly up to 750 mV/s. This electrochemical process enables the oxide ion concentration to be correlated to CV oxidation peaks. The resulting correlation agrees well (8.8% difference) with back titration measurements and can be used to monitor oxide content in the salt in real-time during …
Vacuum Infusion Of Composites: Durability Of Hybrid Large Area Additive Tooling For Vacuum Infusion Of Composites, Nathan Northrup, Jason Weaver, Andy R. George
Vacuum Infusion Of Composites: Durability Of Hybrid Large Area Additive Tooling For Vacuum Infusion Of Composites, Nathan Northrup, Jason Weaver, Andy R. George
Faculty Publications
The durability of a hybrid large area additively manufactured fiberglass ABS mold for vacuum infusion of composites was evaluated. The validation was done by designing and fabricating a mold for a custom test artifact and analyzing the surface geometry over the course of multiple infusions until tool failure. After printing and machining, the mold required a sealer to maintain vacuum integrity. The mold was able to produce 10 parts successfully before the sealed tool surface began to tangibly roughen, resulting in increased difficulty of demolding and a rougher surface finish. After the 14th infusion, the part required destructive force to …
Merging Of Horizontally And Vertically Separated Small-Scale Buoyant Flames, Thomas H. Fletcher, Denver Haycock, Seth Tollefsen, David Lignell
Merging Of Horizontally And Vertically Separated Small-Scale Buoyant Flames, Thomas H. Fletcher, Denver Haycock, Seth Tollefsen, David Lignell
Faculty Publications
The purpose of this study was to investigate the merging behavior of small-scale buoyant flames that might be representative of flames from a leaf in a shrub. Zirconia felt pads soaked in n-heptane were suspended on thin rods and spaced both horizontally and vertically. Time-dependent video images from flames from two-pad and three-pad configurations were analyzed to determine merging probability, combined flame characteristics (height, area, and width), and changes in burn time. Correlations of these combined flame characteristics were developed based on horizontal and vertical spacing between the pads. Merging probability correlated with an exponential function that was quadratic in …
Production Of Pure Vanadium: Industry Review And Feasibility Study Of Electron Beam Melt Refining Of V–Al Alloys, Devin Rappleye, Rob Haun
Production Of Pure Vanadium: Industry Review And Feasibility Study Of Electron Beam Melt Refining Of V–Al Alloys, Devin Rappleye, Rob Haun
Faculty Publications
The vanadium industry has experienced significant change over the last two decades with the emergence of vanadium redox flow batteries for grid-level energy storage, the growing demand for high-strength steel, and the selection of vanadium as a critical material in multiple countries. This review presents the status of the vanadium industry examining production processes and detailing facilities. The available information for each producer is presented including vanadium products and capacity. The production of pure vanadium is identified as a potential vulnerability for some nations where vanadium metal is needed in small, yet strategic, applications and globally only two producers of …
Influencing Perceptions Of Stem Through The Best Stem Books List, Scott Bartholomew, Alexia Seymour
Influencing Perceptions Of Stem Through The Best Stem Books List, Scott Bartholomew, Alexia Seymour
Faculty Publications
One day, while discussing engineering and science as potential career options with a female student, we opened a search engine and typed in “engineer” and “scientist.” However, on the first pages of image results, only one female appeared for engineering and only a few females appeared for “scientist” (see Figure 1). This disparity was disturbing—if this student never saw another person like her filling careers in STEM fields, would she ever “picture herself” in those fields?
Application Of Compositional Data Analysis To Determine The Effects Of Heating Mode, Moisture Status And Plant Species On Pyrolysates, David R. Weise, Thomas H. Fletcher, Mohammad-Saeed Safdari, Elham Amini, Javier Palarea-Albaladejo
Application Of Compositional Data Analysis To Determine The Effects Of Heating Mode, Moisture Status And Plant Species On Pyrolysates, David R. Weise, Thomas H. Fletcher, Mohammad-Saeed Safdari, Elham Amini, Javier Palarea-Albaladejo
Faculty Publications
Pyrolysate gas mixtures are multivariate and relative in nature. Statistical techniques applied to these data generally ignore their relative nature. Published data for permanent gases (CO, CO2, H2, CH4) and tars produced by pyrolysing 15 wildland fuels were reanalysed using compositional data analysis techniques. Mass and mole fractions were compositionally equivalent. Plant species, moisture status and heating mode effects on compositional balances formed from subsets of pyrolysates were tested. Plant species affected the amount of phenol, primary and secondary/tertiary tars relative to permanent gases and relative amounts of single- and multi-ring compounds. Plant moisture status affected the amount of CO …
Reliable Mode Tracking In Gradient-Based Optimization Frameworks With Flutter Constraints, Taylor Mcdonnell, Andrew Ning
Reliable Mode Tracking In Gradient-Based Optimization Frameworks With Flutter Constraints, Taylor Mcdonnell, Andrew Ning
Faculty Publications
In order to construct mode-specific flutter constraints for use in gradient-based multidisciplinary design optimization frameworks, mode tracking must be used to associate the current iteration’s modes with the modes corresponding to each constraint function. Existing mode tracking methods, however, do not provide a method by which to ensure the accuracy of mode associations, making them unsuitable for use in situations where obtaining correct mode associations is critical. To remedy this issue, a new mode tracking method is presented which incorporates backtracking logic in order to maintain an arbitrarily high degree of confidence in mode correlations during gradient-based optimization and/or during …
Pyrolysis Kinetics Of Wildland Vegetation Using Model-Fitting Methods, Ellie Amini, Mohammad-Saeed Safdari, Nathan Johnson Brigham, David R. Weise, Thomas H. Fletcher
Pyrolysis Kinetics Of Wildland Vegetation Using Model-Fitting Methods, Ellie Amini, Mohammad-Saeed Safdari, Nathan Johnson Brigham, David R. Weise, Thomas H. Fletcher
Faculty Publications
Slow-heating pyrolysis experiments of 14 plant species native to forests in the southern United States were conducted in a TGA to find the kinetic parameters for slow pyrolysis of all live and air-dried plant samples. Kinetic coefficients were determined from the data using model-fitting methods, resulting in single kinetic parameters for the entire pyrolysis process which can be used by wildland fire modelers. The model forms explored here are a simple one-step model and single and multiple reaction distributed activation energy (DAE) models. The mass loss and derivative mass loss data were fitted simultaneously at heating rates of 10, 20, …
Using Blade Element Momentum Methods With Gradient-Based Design Optimization, Andrew Ning
Using Blade Element Momentum Methods With Gradient-Based Design Optimization, Andrew Ning
Faculty Publications
Blade element momentum methods are widely used for initial aerodynamic analysis of propellers and wind turbines. A wide variety of correction methods exist, but common to all variations, a pair of residuals are converged to ensure compatibility between the two theories. This paper shows how to rearrange the sequence of calculations reducing to a single residual. This yields the significant advantage that convergence can be guaranteed and to machine precision. Both of these considerations are particularly important for gradient- based optimization where a wide variety of atypical inputs may be explored, and where tight convergence is necessary for accurate derivative …
Nonlinear Trajectory Tracking Control For Winged Evtol Uavs, Jacob Willis, Randal W. Beard
Nonlinear Trajectory Tracking Control For Winged Evtol Uavs, Jacob Willis, Randal W. Beard
Faculty Publications
Current control methods for winged eVTOL UAVs consider the vehicle primarily as a fixed-wing aircraft with the addition of vertical thrust used only during takeoff and landing. These methods provide good long-range flight handling but fail to consider the full dynamics of the vehicle for tracking complex trajectories. We present a trajectory tracking controller for the full dynamics of a winged eVTOL UAV in hover, fixed-wing, and partially transitioned flight scenarios. We show that in low- to moderate-speed flight, trajectory tracking can be achieved using a variety of pitch angles. In these conditions, the pitch of the vehicle is a …
User Guide For Dust Modeling Using Cmaq 5.3.1 And Wrf 4.2.1, Zachary D. Lawless, Ariel S. Cable, Cameron B. Van Dyke, Bradley R. Adams
User Guide For Dust Modeling Using Cmaq 5.3.1 And Wrf 4.2.1, Zachary D. Lawless, Ariel S. Cable, Cameron B. Van Dyke, Bradley R. Adams
Faculty Publications
Researchers at Brigham Young University (BYU) have developed a software framework for modeling dust emission and transport using the Community Multiscale Air Quality (CMAQ) modeling system in conjunction with the Weather Research and Forecasting (WRF) model and other utility programs. This framework uses meteorological data, land use data, and soil properties to predict dust concentrations for a specified area. This User Guide describes the start-to-finish process required to install and utilize relevant software to calculate and visualize dust concentrations. Note that the examples and figures provided in the guide are specific to Utah in the western United States, where this …
Optimization Of Turbine Tilt In A Wind Farm, James Cutler, Andrew P.J. Stanley, Jared J. Thomas, Andrew Ning
Optimization Of Turbine Tilt In A Wind Farm, James Cutler, Andrew P.J. Stanley, Jared J. Thomas, Andrew Ning
Faculty Publications
Wind farm power production is significantly affected by upstream turbines creating wakes of slower wind speeds that overlap the rotor swept areas of downstream turbines. By optimizing the tilt angle of the turbines in a farm, wakes may be deflected away from downstream turbines, increasing the overall energy production. In this study, we optimized the tilt angle of turbines in a wind farm to maximize energy production. We used an analytic wake model modified for gradient-based optimization to consider wake deflection from tilt. We considered optimizing the tilt angle of each turbine assuming that it remained fixed for the lifetime …
Reducing Wind Farm Power Variance From Wind Direction Using Wind Farm Layout Optimization, Bertelsen Gagakuma, Andrew P.J. Stanley, Andrew Ning
Reducing Wind Farm Power Variance From Wind Direction Using Wind Farm Layout Optimization, Bertelsen Gagakuma, Andrew P.J. Stanley, Andrew Ning
Faculty Publications
This paper investigates reducing power variance caused by different wind directions by using wind farm layout optimization. The problem was formulated as a multi-objective optimization. The ε−constraint method was used to solve the bi-objective problem in a two-step optimization framework where two sequential optimizations were performed. The first was maximizing the mean wind farm power alone and the second was minimizing the power variance with a constraint on the mean power. The results show that the variance in power estimates can be greatly reduced, by as much as 30%, without sacrificing mean plant power for the different farm sizes and …
A Comparison Of Aerodynamic Models For Optimizing The Takeoff And Transition Of A Bi-Wing Tailsitter, Ryan Anderson, Jacob Willis, Jacob Johnson, Andrew Ning, Randal Beard
A Comparison Of Aerodynamic Models For Optimizing The Takeoff And Transition Of A Bi-Wing Tailsitter, Ryan Anderson, Jacob Willis, Jacob Johnson, Andrew Ning, Randal Beard
Faculty Publications
Electric vertical takeoff and landing (eVTOL) aircraft take advantage of distributed electric propulsion as well as aerodynamic lifting surfaces to take off vertically and perform long-duration flights. Complex aerodynamic interactions and a hard-to-predict transition maneuver from hover to wing-borne flight are one challenge in their development. To address this, we compare three different interaction models of varying fidelity for optimizing the transition trajectory of a biplane tailsitter. The first model accounts for simplified rotor-on-wing interactions using momentum theory, while the other two account for wing-on-wing interactions using a vortex lattice method and rotor-on-wing aerodynamic interactions using blade element momentum theory. …