Damping characterization in large structures

This research project has as its main goal the development of methods for selecting the damping characteristics of components of a large structure or multibody system, in such a way as to produce some desired system damping characteristics. The main need for such an analytical device is in the simulation of the dynamics of multibody systems consisting, at least partially, of flexible components. The reason for this need is that all existing simulation codes for multibody systems require component-by-component characterization of complex systems, whereas requirements (including damping) often appear at the overall system level. The main goal was met in large part by the development of a method that will in fact synthesize component damping matrices from a given system damping matrix. The restrictions to the method are that the desired system damping matrix must be diagonal (which is almost always the case) and that interbody connections must be by simple hinges. In addition to the technical outcome, this project contributed positively to the educational and research infrastructure of Tuskegee University - a Historically Black Institution

Auxin regulates SCFTIR1-dependent degradation of AUX/IAA proteins

The plant hormone auxin is central in many aspects of plant development. Previous studies have implicated the ubiquitin-ligase SCFTIR1 and the AUX/IAA proteins in auxin response. Dominant mutations in several AUX/IAA genes confer pleiotropic auxin-related phenotypes, whereas recessive mutations affecting the function of SCFTIR1 decrease auxin response. Here we show that SCFTIR1 is required for AUX/IAA degradation. We demonstrate that SCFTIR1 interacts with AXR2/IAA7 and AXR3/IAA17, and that domain II of these proteins is necessary and sufficient for this interaction. Further, auxin stimulates binding of SCFTIR1 to the AUX/IAA proteins, and their degradation. Because domain II is conserved in nearly all AUX/IAA proteins in Arabidopsis, we propose that auxin promotes the degradation of this large family of transcriptional regulators, leading to diverse downstream effects

Assessment of Axial Wave Number and Mean Flow Uncertainty on Acoustic Liner Impedance Education

A key parameter in designing and assessing advanced broadband acoustic liners to achieve the current and future noise reduction goals is the acoustic impedance presented by the liner. This parameter, intrinsic to a specific liner configuration, is dependent on sound pressure level and grazing flow velocity. Current impedance eduction approaches have, in general, provided excellent results and continue to be employed throughout the acoustic liner community. However, some recent applications have indicated a possible dependence of the educed impedance on the direction of incident waves relative to the mean flow. The purpose of the current study is to investigate this unexpected behavior for various impedance eduction methods based on the Pridmore-Brown and convected Helmholtz equations. Specifically, the effects of flow profile and axial wavenumber uncertainties on educed impedances for upstream and downstream sources are investigated. The uniform flow results demonstrate the importance of setting a correct Mach number value in obtaining consistent educed impedances for upstream and downstream sources. In fact, the consistency of results over the two source locations was greatly improved by a slight modification of the uniform flow Mach number. In addition, uncertainty in educed axial wavenumber was also illustrated to correlate well with differences in the educed impedances, even with modified uniform flow Mach number. Finally, while less straightforward than in the uniform flow case, it appears that modification of the mean flow profile may also improve consistency of results for upstream and downstream results when shear flow is included

Hubble-Lema\^itre fragmentation and the path to equilibrium of merger-driven cluster formation

This paper discusses a new method to generate self-coherent initial conditions for young substructured stellar cluster. The expansion of a uniform system allows stellar sub-structures (clumps) to grow from fragmentation modes by adiabatic cooling. We treat the system mass elements as stars, chosen according to a Salpeter mass function, and the time-evolution is performed with a collisional N-body integrator. This procedure allows to create a fully-coherent relation between the clumps' spatial distribution and the underlying velocity field. The cooling is driven by the gravitational field, as in a cosmological Hubble-Lema\^itre flow. The fragmented configuration has a `fractal'-like geometry but with a self-grown velocity field and mass profile. We compare the characteristics of the stellar population in clumps with that obtained from hydrodynamical simulations and find a remarkable correspondence between the two in terms of the stellar content and the degree of spatial mass-segregation. In the fragmented configuration, the IMF power index is ~0.3 lower in clumps in comparison to the field stellar population, in agreement with observations in the Milky Way. We follow in time the dynamical evolution of fully fragmented and sub-virial configurations, and find a soft collapse, leading rapidly to equilibrium (timescale of 1 Myr for a ~ 10^4 Msun system). The low-concentration equilibrium implies that the dynamical evolution including massive stars is less likely to induce direct collisions and the formation of exotic objects. Low-mass stars already ejected from merging clumps are depleted in the end-result stellar clusters, which harbour a top-heavy stellar mass function.Comment: 22 pages, accepted for publication in MNRA

Estelle Angier Summer Vol. A-2 Travel Journal

August 3rd-7th, 1941 summer travel journal of Estelle Angier (Class of 1914). Accounts her travel between Wheaton, Illinois and Hollins University. Photos include guests of the 1941 Class Agents\u27 Houseparty and campus buildings.https://digitalcommons.hollins.edu/scrapbooks/1002/thumbnail.jp

Estelle Angier Summer Vol. I Travel Journal

May 15th-20, 1942 summer travel journal of Estelle Angier (Class of 1914). Accounts of her travels back to Hollins University for the Centennial of Hollins College, celebrated between May 17th-19th, 1942. Includes calendar of events, snapshots of her travel to the campus, and of participants attending the events.https://digitalcommons.hollins.edu/scrapbooks/1003/thumbnail.jp

Estelle Angier Summer Vol. II Travel Journal

May 18th-20th, 1942 summer travel journal of Estelle Angier (Class of 1914). Accounts the last couple of days of the Centennial of Hollins College. Includes photos of surrounding areas of Roanoke, attendees of the Centennial, and friends.https://digitalcommons.hollins.edu/scrapbooks/1004/thumbnail.jp

Estelle Angier Summer Vol. A-1 Travel Journal

July 31st-August 7th, 1941 summer travel journal of Estelle Angier (Class of 1914). Writings include accounts of traveling in between Wheaton, Illinois and Hollins University. Various newspaper clippings as well as a detailed account of a Class Agent Houseparty that took place from August 1-4th can be found.https://digitalcommons.hollins.edu/scrapbooks/1001/thumbnail.jp

Estelle Angier Photography Scrapbook

1910-1912 Photography Scrapbook of M. Estelle Angier (Class of 1914). Photos range from landscape shots of campus, to pictures of traditions such as Tinker Day and the May Day celebration. Photos also include snapshots of Hollins students, faculty and staff, as well as some snapshots of Angier\u27s travels during the years.https://digitalcommons.hollins.edu/scrapbooks/1000/thumbnail.jp