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Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
Energy Quantity Estimation In Radiated Acoustic Fields, Eric B. Whiting
Energy Quantity Estimation In Radiated Acoustic Fields, Eric B. Whiting
Theses and Dissertations
Energy quantities, which are calculated from pressure and particle velocity, yield a great deal of information about acoustic fields. Errors in pressure or particle velocity estimation lead to bias errors the estimation of energy quantities. The bias errors arise from different probe configurations and processing methods. Two processing methods are examined: the traditional method and the recently developed Phase and Amplitude Gradient Estimation (PAGE) method. These two methods are compared to investigate how each estimates pressure and particle velocity and the subsequent bias errors in a plane wave, standing wave, and spherical spreading wave field. Analytical expressions are derived for …
Increasing The Computational Efficiency Of Combinatoric Searches, Wiley Spencer Morgan
Increasing The Computational Efficiency Of Combinatoric Searches, Wiley Spencer Morgan
Theses and Dissertations
A new algorithm for the enumeration of derivative superstructures of a crystal is presented. The algorithm will help increase the efficiency of computational material design methods such as cluster expansion by increasing the size and diversity of the types of systems that can be modeled. Modeling potential alloys requires the exploration of all possible configurations of atoms. Additionally, modeling the thermal properties of materials requires knowledge of the possible ways of displacing the atoms. One solution to finding all symmetrically unique configurations and displacements is to generate the complete list of possible configurations and remove those that are symmetrically equivalent. …
Emission From Black Holes And Supernovae In The Early Universe, Brandon Kerry Wiggins
Emission From Black Holes And Supernovae In The Early Universe, Brandon Kerry Wiggins
Theses and Dissertations
To constrain the era when the first galaxies and stars appeared upcoming instruments will rely on the brightest events in the universe: supernovae and brilliant emission from massive black holes. In this dissertation, we investigate the observability of certain types of supernovae of the very first stars (Population III stars) and find that while these events are sufficiently luminous to be observed with deep-sky instruments such as the James Webb Space Telescope (JWST), they may not observe these particular types of events in their lifetimes. We next explore the origins of massive black holes and introduce the direct collapse hypothesis …
Microfabrication With Smooth, Thin Cnt/Polymer Composite Sheets, Nathan Edward Boyer
Microfabrication With Smooth, Thin Cnt/Polymer Composite Sheets, Nathan Edward Boyer
Theses and Dissertations
Carbon nanotube (CNT)/polymer composite sheets can be extremely high strength and lightweight, which makes them attractive for fabrication of mechanical structures. This thesis demonstrates a method whereby smooth, thin CNT/polymer composite sheets can be fabricated and patterned on the microscale using a process of photolithography and plasma etching. CNT/polymer composites were made from CNTs grown using chemical vapor deposition using supported catalyst growth and floating catalyst growth. The composite sheets had a roughness of approximately 30nm and were about 61¼m or 261¼m depending on whether they were made from supported catalyst grown or floating catalyst grown CNTs. The composites were …
In Situ Magnetic Field Characterization With The Directional Hanle Effect, Jarom Silver Jackson
In Situ Magnetic Field Characterization With The Directional Hanle Effect, Jarom Silver Jackson
Theses and Dissertations
We present a novel method of in situ magnetic field mapping related to the Hanle effect. This method uses the change in spatial radiation pattern of scattered light, which we call a 'directional Hanle effect,' rather than the loss of polarization more commonly associated with the Hanle effect. It is particularly well suited for fields in a magneto-optical trap (MOT), requiring only the addition of a narrow slit and a camera to typical MOT components. The use of this method is demonstrated by measuring the gradient through, and location of, the zero-point of the field in our strontium MOT.
Improvements To The Two-Point In Situ Method For Measurement Of The Room Constant And Sound Power In Semi-Reverberant Rooms, Zachary R. Jensen
Improvements To The Two-Point In Situ Method For Measurement Of The Room Constant And Sound Power In Semi-Reverberant Rooms, Zachary R. Jensen
Theses and Dissertations
The two-point in situ method is a technique for measuring the room constant of a semi-reverberant room and the sound power of a source in that room simultaneously using two measurement positions. Using a reference directivity source, where the directivity factor along any given axis of the source has been measured, one is able to use the Hopkins-Stryker equation to measure both the room constant and the sound power level of another source rather simply. Using both numerical and experimental data, it was found that by using generalized energy density (GED) as a measurement quantity, the results were more accurate …
Development, Evaluation, And Validation Of A High-Resolution Directivity Measurement System For Played Musical Instruments, K Joshua Bodon
Development, Evaluation, And Validation Of A High-Resolution Directivity Measurement System For Played Musical Instruments, K Joshua Bodon
Theses and Dissertations
A high-resolution directivity measurement system at Brigham Young University has been renovated and upgraded. Acoustical treatments have been installed on the microphone array, professional-grade audio hardware and cabling have been utilized, and user-friendly MATLAB processing and plotting codes have been developed. The directivities of 16 played musical instruments and several loudspeakers have been measured by the system, processed, and plotted. Using loudspeakers as simulated musicians, a comprehensive analysis was completed to validate the system and understand its error bounds. A comparison and evaluation of repeated-capture to single-capture spherical systems was made to demonstrate the high level of detail provided by …