4,108 research outputs found

    Gaps, rings, and spirals in scattered light: Discs observed around Herbig Ae/Be and T-Tauri stars

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    Planetary systems have their origins in protoplanetary discs, which are thin, rotating struc- tures of dust and gas encircling protostellar objects. The processes governing the formation of protoplanets are expected to influence the structure of these discs. The resulting structures around other stars can now be observed in scattered light, using instruments such as the Gemini Planet Imager (GPI) with techniques including Extreme Adaptive Optics and Polarimetric Differential Imaging. The observations presented in this thesis were obtained with GPI for Gemini-LIGHTS, a survey aiming to categorise the structures seen around a representative sample of Herbig Ae/Be and T-Tauri objects. Early Gemini-LIGHTS data showed irregular structures that eluded simple classifications. I present a detailed analysis of five of these objects, which include new detections of four objects and an improved-quality image of a fifth, FU Ori, which revealed a previously-unknown shadow. I discuss these objects in the context of age and misaligned discs. I present observations of the Herbig B[e] star HD 45677, which has had a highly-contested evolutionary status for decades. I created a Monte Carlo Radiative Transfer (MCRT) model of HD 45677 that was consistent with three data sets: a small-scale inner wall; a large-scale envelope with bipolar cavity; and ultraviolet to far-infrared photometry. This analysis strongly supports the classification of HD 45677 as a pre-main-sequence object. Finally, the transition disc around HD 34700 showed the highest number of spiral arms ever observed, each of which was unexpectedly loosely-wound. I developed a method to quantitatively characterise the spiral winding properties. I found that there are at least eight arms, each with pitch angle >30â—¦, and that hyperbolic spirals fit the most-constrained structure best but cannot describe the whole system. These findings are incompatible with current spiral formation theories, and so provide a starting point for follow-up observations and modelling.Science and Technology Facilities Counci

    Apollo communications system. Task E-59B - MSFTP-2 bit synchronizer performance analysis

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    Mathematical model for predicting performance degradation of MSFTP-2 bit synchronizer used in MSF

    Clarence A. Laws to James H. Meredith (Undated)

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    https://egrove.olemiss.edu/mercorr_pro/1835/thumbnail.jp

    Developing A Sustainable AoL Framework Using Supply Chain Principles

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    Many accreditation agencies have adopted Assurance of Learning (AoL)-based paradigms for assessing educational institutions. Colleges/universities transitioning to an Assurance of Learning (AoL) system encounter common challenges while implementing new standards. In this research, the authors develop a stakeholder driven AoL framework which addresses common transitional issues while maintaining the Southern Association of Colleges and Schools (SACS) and Association to Advance Collegiate Schools of Business (AACSB) accreditation standards. The model incorporates supply chain practices by best in class (BIC) companies to optimize overall assessment efforts. The model decreases the number of redundant processes, improves collaboration throughout the university, and promotes a more comprehensive curriculum. After the model implementation, the authors examine mission statements and tenure, promotion and reappointment documents to gain insight about how to sustain accreditation

    Letter from James Laws & Samuel A. Latta to James B. Finley

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    Due to the cholera epidemic in Cincinnati, many members of the Ohio Conference are wary of attending the 1833 Annual Conference planned for Cincinnati. Xenia has been proposed as an alternative location. Laws and Latta write to confirm that folks in Xenia would be happy to host the conference. They ask for Finley\u27s assistance to get the move approved. Abstract Number - 142https://digitalcommons.owu.edu/finley-letters/1140/thumbnail.jp
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