Load Reduction Using Rapidly Deployed Trailing-Edge Flaps

This thesis details investigations into the aerodynamic properties of a small, rapidlyactuated, actively controlled trailing-edge ap and the potential of such a device to alleviate the unsteady loading experienced by wind turbine blades due to atmospheric turbulence and the atmospheric boundary layer, although such a device would have potential applications in other elds such as rotorcraft. The main goals of this work were to investigate whether aerodynamic loadings could in fact be alleviated by the use of a small trailing-edge ap using only measurements of the unsteady lift on the wing as a control input and to assess such a device's capacity to reject atmospheric disturbances with both numerical and experimental work, carried out in the Aeronautics Department at Imperial College London. The numerical work covered in the thesis comprises the results of linear and nonlinear aerodynamic and control simulations (e.g. PID, LQG controllers) and the results of computational uid dynamics (CFD) simulations using the commercial package FLUENT. The thesis also lays out the results obtained from testing an experimental prototype in the Hydrodynamics Laboratory in the Aeronautics Department. This prototype successfully rejected intentionally introduced ow disturbances from the vortex street of a square block upstream of the wing and the application of control provided a very signi cant reduction in the unsteady loading experienced by the wing. The ndings show the potential of this method of load control for the rejection of unsteady aerodynamic loading by the sole use of measurements of the wing loading and this has been demonstrated both theoretically and experimentally. The work is closed with a conclusion and suggestions for future research proposals

The Potential Applications of Optical Dating to the Sandy Uplands of East Texas and Northwest Louisiana

The fine, sandy soils of East Texas and Northwest Louisiana have been the source of archaeological debate for some time. This discourse concerns the mode of burial of cultural material in the easily eroded soils and the mechanics of recent (Holocene) landform evolution. Because these deposits are typically well-drained, organic matter does not preserve well, thus hindering the dating of the geomorphic events that figure prominently in their development and the prehistoric occupations which lie buried throughout uplands of this region. A relatively new dating technique, optical dating, has much to offer this region and the archaeological community as it measures the period of time that has elapsed since sand grains were last exposed to sunlight. Hence, it directly dates the time of sediment transportation and deposition. This method is therefore applicable to a number of archaeological and geomorphic processes which may not be dated by traditional methods, owing to the lack of organic matter suitable for radiocarbon dating. In geomorphic contexts, optical dating may be preferred over radiocarbon as it directly dates the time of sedimentation rather than the age of organic matter in features such as buried soils that may be significantly different from the geomorphic event which fossilized the soil

Evidence for A Parsec-scale Jet from The Galactic Center Black Hole: Interaction with Local Gas

Despite strong physical reasons that they should exist and decades of search, jets from the Galactic Center Black Hole, Sgr A*, have not yet been convincingly detected. Based on high-resolution Very Large Array images and ultra-deep imaging-spectroscopic data produced by the Chandra X-ray Observatory, we report new evidence for the existence of a parsec-scale jet from Sgr A*, by associating a linear feature G359.944-0.052, previously identified in X-ray images of the Galactic Center, with a radio shock front on the Eastern Arm of the Sgr A West HII region. We show that the shock front can be explained in terms of the impact of a jet having a sharp momentum peak along the Galaxy's rotation axis, whereas G359.944-0.052, a quasi-steady feature with a power-law spectrum, can be understood as synchrotron radiation from shock-induced ultrarelativistic electrons cooling in a finite post-shock region downstream along the jet path. Several interesting implications of the jet properties are discussed.Comment: 33 pages, 7 figures; Accepted for publication in The Astrophysical Journa

True Lies: Canossa as Myth

This essay is a response to Paul Horwitz, “Freedom of the Church without Romance,” published as part of a symposium on “The Freedom of the Church.” The essay endorses Horwitz’s central thesis that advocates of a contemporary “freedom of the Church” have overlooked historical complexities in marking the 11th-century investiture conflict between Henry IV and Pope Gregory VII, often simply referred to “Canossa” after the small Emilian village where Henry sought absolution from Gregory, as the birth of that freedom. The essay goes beyond Horwitz to argue that the historical account of “Canossa” presupposed by freedom-of-the-Church advocates is literally false. “Canossa,” instead, is a myth. More salient, nonmythical analogies for a “freedom of the Church” exist in U.S. constitutional history: genuine state sovereignty and dual-sovereignty federalism from the 19th century, and state dignity and native American domestic dependency from the contemporary era. These more historically accessible analogies all suggest that any “freedom of the Church” in U.S. constitutional doctrine is greatly diminished from the robust freedom argued for by those who invoke “Canossa” as that freedom’s defining moment. But even the mythical “Canossa” remains important. Myths are stories that a society tells about itself, stories that preserve and clarify its deepest values and commitments. Like the “myth of Magna Carta” that has exerted so much influence on English and American constitutional law, “Canossa” emphasizes the dangers to liberty from a government that sees no bounds on its jurisdiction and authority. Though historically false, “Canossa” might be mythically true

Public Life and Hostility to Religion

Many who value the contributions of religion to American life have contended that American public life is hostile to religion. They perceive many of the Supreme Court\u27s Religion Clause opinions as hostile to religion, and circulate anecdotes about the antireligious hostility of public life. Studies also suggest that some of the principle actors in American public life systematically marginalize religious viewpoints relative to secular ones. Nevertheless, others are baffled by the suggestion that public life discriminates against religion. These people note that religion is deeply (if controversially) involved in much of contemporary American politics, and dismiss anecdotes about such hostility as isolated instances of departure from a rule of religious accommodation in public life. This Essay seeks to demonstrate in a more precise way how American public life is hostile to religion. Like so much else, the hostility of public life to religion can be traced to one of the conceptual foundations of liberal political theory: the distinction between the public and the private. The Essay begins with a sketch of this distinction in American liberal thought, noting that the public is generally privileged over the private. The Essay argues that, because knowledge is associated with public life and belief with private life, both the distinction between knowledge and belief and the predominance of the former over the latter are assumed rather than demonstrated. It illustrates this thesis with an analysis of two Supreme Court decisions, Aguillard v. Edwards, a creation science decision, and Employment Division v. Smith, a decision about religious exemptions. The Essay closes with some observations about the significance of recognizing that American public life is hostile to belief

Indeterminacy and the Establishment Clause

Part of Symposium: Establishment and Fairnes

Narrative Pluralism and the Doctrine Incoherence in Hosanna-Tabor

In Hosanna-Tabor Church and School v. EEOC, the Supreme Court recognized for the first time that the Religion Clauses require a “ministerial exception” to federal antidiscrimination laws, holding that religious congregations have a broad and categorical immunity against government interference in ministerial employment decisions.Hosanna-Tabor is filled with ironies. The case is as much about unjustified discrimination and administrative inconsistency as religious liberty. The Court’s endorsement of the exception as a feature of church autonomy overlooks that churches subvert autonomy as often as they protect it. The exception described by the Court is so broad, absolute, and inflexible that it is likely to be carved up with exceptions and limitations. And finally, the Court goes to this trouble to protect a conception and practice of religion that are quickly passing from the scene