Control and dynamics of a flexible spacecraft during stationkeeping maneuvers

A case study of a spacecraft having flexible solar arrays is presented. A stationkeeping attitude control mode using both earth and rate gyro reference signals and a flexible vehicle dynamics modeling and implementation is discussed. The control system is designed to achieve both pointing accuracy and structural mode stability during stationkeeping maneuvers. Reduction of structural mode interactions over the entire mode duration is presented. The control mode using a discrete time observer structure is described to show the convergence of the spacecraft attitude transients during Delta-V thrusting maneuvers without preloading thrusting bias to the onboard control processor. The simulation performance using the three axis, body stabilized nonlinear dynamics is provided. The details of a five body dynamics model are discussed. The spacecraft is modeled as a central rigid body having cantilevered flexible antennas, a pair of flexible articulated solar arrays, and to gimballed momentum wheels. The vehicle is free to undergo unrestricted rotations and translations relative to inertial space. A direct implementation of the equations of motion is compared to an indirect implementation that uses a symbolic manipulation software to generate rigid body equations

Sled for Sampling Benthic Fish Larvae

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142040/1/naaq0118.pd

A Study of the Pollen and Pistils of Apples in Relation to the Germination of the Pollen

The failure of a fruit tree to develop a normal amount of fruit may be due to a number of causes as stated by Kraus in volume VI of the Journal of Heredity. However, unless a plant develops fruit parthenocarpically, the development of fruit depends primarily upon how the pollen and pistil function relative to each other. As Kraus points out, fertilization by no means insures the development of a fruit, for very commonly the fruit does not develop despite the fact that normal fertilization occurred, but, on the other hand, in the absence of fertilization, fruit seldom develops among apples

Heat Transfer and Pressure Drop in Concentric Annular Flows of Binary Inert Gas Mixtures

Studies of heat transfer and pressure drop of binary inert gas mixtures flowing through smooth concentric circular annuli, tubes with fully developed velocity profiles, and constant heating rate are described. There is a general lack of agreement among the constant property heat transfer correlations for such mixtures. No inert gas mixture data exist for annular channels. The intent of this study was to develop highly accurate and benchmarked pressure drop and heat transfer correlations that can be used to size heat exchangers and cores for direct gas Brayton nuclear power plants. The inside surface of the annular channel is heated while the outer surface of the channel is insulated. Annulus ratios range 0.5 < r* < 0.83. These smooth tube data may serve as a reference to the heat transfer and pressure drop performance in annuli, tubes, and channels having helixes or spacer ribs, or other surfaces

Exhibition catalogue — Imprints and Impressions: Milestones in Human Progress

Exhibition catalogue for Imprints and Impressions: Milestones in Human Progress — Highlights from the Rose Rare Book Collection. Includes an introduction by Kathleen M. Webb, dean of University Libraries; essays about the impact of the exhibition\u27s books on modern inquiry, the humanities, the sciences, and the social sciences; and photographs of the works in the exhibit.https://ecommons.udayton.edu/rosebk_supplemental/1000/thumbnail.jp

Measurement of Coherent Elastic Neutrino-Nucleus Scattering from reactor antineutrinos

The 96.4 day exposure of a 3 kg ultra-low noise germanium detector to the high flux of antineutrinos from a power nuclear reactor is described. A very strong preference ($p<1.2\times10^{-3}$) for the presence of a coherent elastic neutrino-nucleus scattering (CE$\nu$NS) component in the data is found, when compared to a background-only model. No such effect is visible in 25 days of operation during reactor outages. The best-fit CE$\nu$NS signal is in good agreement with expectations based on a recent characterization of germanium response to sub-keV nuclear recoils. Deviations of order 60\% from the Standard Model CE$\nu$NS prediction can be excluded using present data. Standing uncertainties in models of germanium quenching factor, neutrino energy spectrum, and background are examined.Comment: 6 pages, 5 figures. Data release and additional information in ancillary file