1,676 research outputs found

    Undergraduate Catalog of Studies, 2023-2024

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    Graduate Catalog of Studies, 2023-2024

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    Undergraduate Catalog of Studies, 2023-2024

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    Computational Modelling of the Plasma in the Charge Exchange Thruster

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    The Charge Exchange Thruster (CXT) is a novel plasma thruster that produces thrust via energetic neutrals leaving the device. This is done by accelerating ions with an electrostatic potential inside of a so-called hollow cathode device: some of these ions then undergo charge exchange and leave the thruster as energetic neutrals whilst others contribute to the formation of an electrical discharge inside the thruster. In this thesis a new 2D-3V particle-in-cell-Monte Carlo (PIC-MCC) simulation code is developed and tested with the purpose of modelling the plasma inside the CXT. This code includes multiple chemical processes involving hydrogen ions, atoms, and molecular species, an external circuit simulation, probabilistic reflections from boundaries, and the generation of secondary electrons, all of which are found to be vital in the plasma initiation and development. The new PIC-MCC code is benchmarked successfully against the theoretical plasma sheath width as well as experimental Paschen curves for a parallel plate discharge, being found to reproduce these results well. Similarly, by modelling hollow cathode discharge systems it is found that the code can reproduce two effects specific to hollow cathode devices, a higher plasma density inside the cathode than outside, as well as beams of energetic neutrals. The code was able to reproduce the experimental results of the original CXT paper reasonably well but suffered from numerical instabilities that prevented the simulation from modelling the discharge in a steady state. It was found that simulating the thruster in a lower pressure discharge mode did not produce as much thrust but was able to reach a steady state and was numerically stable over timescales of tens of microseconds. Future work on investigating the cause of the numerical instabilities at high pressures, as well as a more complex model for the background gas dynamics in the thruster are recommended

    Graduate Catalog of Studies, 2023-2024

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    AI: Limits and Prospects of Artificial Intelligence

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    The emergence of artificial intelligence has triggered enthusiasm and promise of boundless opportunities as much as uncertainty about its limits. The contributions to this volume explore the limits of AI, describe the necessary conditions for its functionality, reveal its attendant technical and social problems, and present some existing and potential solutions. At the same time, the contributors highlight the societal and attending economic hopes and fears, utopias and dystopias that are associated with the current and future development of artificial intelligence

    Undergraduate Catalog of Studies, 2022-2023

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    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Simulating substrate binding sites in the S. aureus Type II NADH Dehydrogenase

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    "Type II NADH Oxidoreductase (NDH-2) from Staphylococcus aureus was established as a therapeutic target against the virulency of this bacterium and an alternative to treat Complex I-derived diseases. To accurately model interactions of NDH-2 with its substrates such as menaquinones and NADH, Coarse-Grain (CG) simulations were employed. "N/
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