Measurement and Analysis of Terminal Shock Oscillation and Buffet Forcing Functions on a Launch Vehicle Payload Fairing

The buffet loads on a launch vehicle payload shroud can be impacted by the unsteadiness associated with a terminal shock at high subsonic speeds. At these conditions, flow accelerates to supersonic speeds on the nose of the payload fairing and is terminated by a normal shock on the cylindrical section downstream of the nose cone/cylinder shoulder. The location of the terminal shock and associated separated boundary layer is affected by the freestream Mach number, Reynolds number, and the pitch/yaw of the launch vehicle. Furthermore, even when the freestream conditions and vehicle attitude are constant, this terminal shock oscillates on the surface of the vehicle. The time-varying surface pressure associated with the terminal shock results in unsteady aerodynamic loads that may interact with vehicle structural dynamic modes and the guidance and control of the vehicle. Buffet testing of a 3-percent scale rigid buffet model of a launch vehicle cargo configuration with a tangent-ogive payload shroud was conducted in 2012 and in 2016. Initial buffet forcing functions (BFFs) utilized a coarse pressure sensor distribution on the vehicle surface in which a single longitudinal station with eight sensors observed the terminal shock environment at Mach 0.90. An examination of these circumferential pressures reveal large impulse-like pressure fluctuations and an asymmetry in pressure when the vehicle is at a nonzeroangle of attack that result in high BFFs. Revisions to the shock integration region were made based on computational fluid dynamics and shadowgraph video of shock motion to better represent the BFFs and reduce the high loads resulting from this environment. To more clearly understand this terminal shock environment, a second wind tunnel test was conducted with a dense distribution of 256 sensors at the terminal shock location. These sensor arrays presents a unique opportunity to observe the unsteady terminal shock environment and to characterize the impact of various integration schemes on the BFFs. This paper presents a summary of the development of BFFs for this terminal shock and a detailed analyses of shock region pressure coefficients, coherence, BFFs, shock location time histories, and power spectral density to help guide development of BFFs for other launch vehicle test and analysis programs

Studies on the Reduction of Radon Plate-Out

The decay of common radioactive gases, such as radon, produces stable isotopes by a sequence of daughter particles with varied half-lives. These daughter particles are a significant source of gamma, neutron, and alpha particle backgrounds that can mimic desired signals in dark matter and neutrinoless double beta decay experiments. In the LUMINA Laboratory at Southern Methodist University (SMU), studies of radon plate-out onto copper samples are conducted using one of XIA's first five UltraLo 1800 alpha counters. We present results from investigations into various mitigation approaches. A custom-built copper holder (in either plastic or metal) has been designed and produced to maximize the copper's exposure to 220Rn. The 220Rn source is a collection of camping lantern mantles. We present the current status of control and experimental methods for addressing radon exposure levels.Comment: 4 pages, 1 figure, Conference Proceedings for Low Radioactivity Techniques 201

Letter to Carolyn Ahearn regarding AALL Nominations Committee, October 24, 1991

A letter from Maria Sekula and the AALL Nominations Committee to Carolyn Ahearn presenting the nominees for the 1992 AALL Executive Board

Novel Bayesian methodology for the analysis of single-cell RNA sequencing data.

With single-cell RNA sequencing (scRNA-seq) technology, researchers are able to gain a better understanding of health and disease through the analysis of gene expression data at the cellular-level; however, scRNA-seq data tend to have high proportions of zero values, increased cell-to-cell variability, and overdispersion due to abnormally large expression counts, which create new statistical problems that need to be addressed. This dissertation includes three research projects that propose Bayesian methodology suitable for scRNA-seq analysis. In the first project, a hurdle model for identifying differentially expressed genes across cell types in scRNA-seq data is presented. This model incorporates a correlated random effects structure based on an initial clustering of cells to capture the cell-to-cell variability within treatment groups but can easily be adapted to an independent random effect structure if needed. A sparse Bayesian factor model is introduced in the second project to uncover network structures associated with genes in scRNA-seq data. Latent factors impact the gene expression values for each cell and provide flexibility to account for the common features of scRNA-seq. The third project expands upon this latent factor model to allow for the comparison of networks across different treatment groups

Utilizing Computer Programming to Analyze Post-Tonal Music: A Segmentation and Contour Analysis of Twentieth-Century Music for Solo Flute

Two concepts will be synthesized in this dissertation: 1) the creation of accessible computer applications for melodic segmentation and contour reduction and 2) the application of segmentation and contour reduction to analyze twentieth-century post-tonal works for unaccompanied flute. Two analytical methodologies have been chosen: James Tenney and Larry Polanski\u27s Gestalt segmentation theory and Robert Schultz\u27s refinement of Robert Morris\u27s contour reduction algorithm. The investigation also utilizes Robert Schultz\u27s concept of diachronic-transformational analysis in conjunction with contour reduction. While both segmentation and contour reduction are invaluable analytical tools, they are meticulous and time-consuming processes. Computer implementation of these algorithmic procedures produces quick and accurate results while reducing analyst fatigue and human error. Microsoft Excel is used to complete melodic segmentation. Java programming language is used to create a contour reduction application. Each implementation greatly reduces the time needed to segment and analyze a melody. Computer programming is combined with pitch class set analysis to produce informed and expressive musical interpretations