860 research outputs found
L'espace social, lecture géographique des sociétés
No full text@incollection{OL-TURBOUTF-2005, author = {Loew-Turbout, F.}, title = {L'espace social, lecture géographique des sociétés}, pages = {217-234}, year = {2005}, publisher = {Armand Colin} }International audienc
Orbit design for future SpaceChip swarm missions in a planetary atmosphere
No full textThe effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag
Oregon statewide status and trends report
No full textReport -- Appendix A. Black Rock Desert-Humboldt -- Appendix B. Columbia River -- Appendix C. Deschutes -- Appendix D. Goose Lake -- Appendix E. Grande Ronde -- Appendix F. John Day -- Appendix G. Klamath -- Appendix H. Malheur -- Appendix I. Mid Coast -- Appendix J. Middle-Columbia-Hood -- Appendix K. North Coast-Lower Columbia -- Appendix L. Oregon Closed Basins -- Appendix M. Owyhee -- Appendix N. Powder-Burnt -- Appendix O. Rogue -- Appendix P. Sandy -- Appendix Q. Snake River -- Appendix R. South Coast -- Appendix S. Umatilla-Walla Walla-Willow -- Appendix T. Umpqua -- Appendix U. Willamette.prepared by: Colin Donald and Ryan Michie.Title from PDF cover (viewed on November 4, 2022).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographical references.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Oregon statewide status and trends report
No full textChapter 1-3. Introduction and Methods -- Chapter 4-5. Results and Citations -- Appendix A. Black Rock Desert-Humboldt -- Appendix B. Columbia River -- Appendix C. Deschutes -- Appendix D. Goose Lake -- Appendix E. Grande Ronde -- Appendix F. John Day -- Appendix G. Klamath -- Appendix H. Malheur -- Appendix I. Mid Coast -- Appendix J. Middle-Columbia-Hood -- Appendix K. North Coast-Lower Columbia -- Appendix L. Oregon Closed Basins -- Appendix M. Owyhee -- Appendix N. Powder-Burnt -- Appendix O. Rogue -- Appendix P. Sandy -- Appendix Q. Snake River -- Appendix R. South Coast -- Appendix S. Umatilla-Walla Walla-Willow -- Appendix T. Umpqua -- Appendix U. Willamette.prepared by: Colin Donald, Yuan Grund, and Ryan Michie.Title from PDF cover (viewed on October 27, 2020).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographical references.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Oregon statewide status and trends report
No full textReport -- Appendix A. Black Rock Desert-Humboldt -- Appendix B. Columbia River -- Appendix C. Deschutes -- Appendix D. Goose Lake -- Appendix E. Grande Ronde -- Appendix F. John Day -- Appendix G. Klamath -- Appendix H. Malheur -- Appendix I. Mid Coast -- Appendix J. Middle-Columbia-Hood -- Appendix K. North Coast-Lower Columbia -- Appendix L. Oregon Closed Basins -- Appendix M. Black Owyhee -- Appendix N. Powder-Burnt -- Appendix O. Rogue -- Appendix P. Sandy -- Appendix Q. Snake River -- Appendix R. South Coast -- Appendix S. Umatilla-Walla Walla-Willow -- Appendix T. Umpqua -- Appendix U. Willamette.prepared by: Colin Donald, Ryan Michie, and Yuan Grund.Title from PDF cover (viewed on March 20, 2020).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographical references.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Integration of the Multi-Functional Information Distribution System F-15 Fighter Data Link into the F-15C Eagle
No full textThe Multi-Functional Information Distribution System (MIDS) provides improved information distribution, position location, and identification capability for the forces of the U.S. Air Force, U.S. Army, U.S. Navy, U.S. Marine Corps, United Kingdom, France, and the North Atlantic treaty Organization (NATO). The system is currently implemented through the use of a variety of terminals and tailored interface configurations designed to meet the needs of specific users. This paper describes the MIDS Fighter Data Link as it is implemented in the F-15 fighter aircraft. It describes system architecture, F-15 aircraft integration, and system testing. The paper explains the effectiveness of the system by presenting the information management challenge involved in accomplishing the F-15\u27s mission of gaining and maintaining air superiority, and outlining the awesome capability of the Fighter Data Link to meet this challenge. Finally, the paper proposes an application of the MIDS Fighter Data Link System to the challenges of commercial aircraft separation and control in a congested environment. The paper is written from the author\u27s perspective as a user and tester of the Fighter Data Link System. The author was first introduced to the system in 1994 when he performed an assessment of the system\u27s utility as an operational F-15C fighter pilot participating in a special project at Mountain Home Air Force Base. Since that time, the author completed test pilot training and is currently involved in both developmental and operational test of the production version of the system. Recent testing has included both ground and flight test of system integration, as well as assessment of technical performance and operational effectiveness
Simulating the acoustic response of cavities to improve microphone array measurements in closed test section wind tunnels
No full textCavities placed along wind tunnel walls can attenuate the turbulent boundary layer (TBL) fluctuations as they propagate into the cavity. Placing microphones within the cavities can thus improve the signal-to-noise ratio of acoustic data. However, standing waves form within these cavities distorting the acoustic measurements. This work uses a finite element (FE) solver to evaluate how cavity geometry (depth, diameter, and wall angle) and wall material (hard-walled and melamine foam) affect the amplitude and eigenfrequency of standing waves when excited by an incident acoustic plane wave. Good agreement between predicted and measured acoustic transfer functions is shown. Compared to cylindrical cavities, countersunk and conical cavities improve the overall response, i.e., reducing the quality factor quantifying the resonance and damping characteristics. Stainless steel coverings also reduce the quality factor. A finding is that the shape of the external foam holder rather than the cavity shape drives the standing wave characteristics for the melamine foam cavities. The optimization problem of minimizing the acoustic response while also attenuating the TBL is thus decoupled by using the melamine foam. Consequently, these considerations can be addressed independently by optimizing the outer cavity shape for acoustics and the melamine foam insert for TBL attenuation. Aircraft Noise and Climate EffectsWind Energ
THE RYDBERG STATES OF ACETYLENE: FOCUS ON THE 1260 TO 1370 {\AA} REGION OF THE ABSORPTION SPECTRUM
No full text(1) P. G. WILKINSON, J. Molec. Spectrosc., 2, 387-404 (1958). (2) R. COLIN, M. HERMAN and I. KOPP, 21st International Astrophysical Symposium, Liege 1977, ed. Univ. Liege (in Press)Author Institution:The absorption spectrum of the acetylene molecule in the region of 1260 {\AA} to 1370 {\AA} is reinvestigated with and isotopes and studied for the first time with the isotopes. As for and , first studied by Wilkinson (1), three trans-bending hot-band progressions are identified in the spectrum. They confirm the existence of three electronic states ( and ) in this region. An extra cis-bending hot-band progression belonging to the transition is identified in the spectrum. The very dense upper state progressions are reinvestigated and some modifications of the previous analysis (1) are suggested. These results and those obtained from the analysis of the entire Rydberg region of the acetylene isotopic species (20 allow to discuss the Rydberg-valence character, the symmetry and the molecular geometry of these electronic states and to modify some of the previous conclusions (1)
The amoebic growth of project costs
No full textIn the public arena, we often hear about projects that have suffered massive cost overruns. Often they are related to large public construction projects such as airports, bridges, or public buildings. Large overruns also exist in private industry. However, often these do not appear in the newspapers, so the public is not as aware of them. Of course, not all projects go badly wrong, but quite a few do, and frequently we find ourselves uncertain of the causes for such overruns. In this paper, industrial projects that overrun and overrun in a surprising manner are considered. In other words, the paper considers those many projects where the extent of the overrun is well beyond what might ever have been anticipated, even though what was going wrong within the projects was, for the most part, understood.The basis for the content of the paper (that is, the structure and lessons), are drawn from a postmortem analysis of many large projects as part of claims analysis, particularly "delay and disruption" claims for projects whose total expenditure appeared, at first look, inexplicable or surprising. The aim of the paper is to contribute to an understanding of how projects go badly wrong, when they do, and in particular to draw some lessons from this exploration that are likely to help all managers. The reasons for cost escalation are not just the responsibility of project managers.<br/
Improving Acoustic Measurements with Cavities in Closed Test Section Wind Tunnels
No full textAerodynamic noise produced by aircraft, wind turbines, and other objects subjected to airflow contribute to environmental noise pollution, which adversely affects human and animal health. Consequently, governments impose restrictions on aircraft and wind turbine noise levels. These restrictions can have an economic impact by limiting aircraft traffic and reducing wind turbine energy production. Accordingly, improving the design of aerodynamic surfaces to reduce their noise levels benefits health while enabling improved operational efficiency. Therefore, aeroacoustic research focuses on identifying and understanding the physical mechanisms behind aerodynamic noise to improve noise mitigation technologies. This research relies on acoustic wind tunnel measurements to validate simulations, theories, and design improvements. Closed test section wind tunnels are widely used for aerodynamic testing but are less suitable for acoustic measurements because microphones must be installed in the wall. This location subjects the microphones to pressure fluctuations from the turbulent boundary layer (TBL), which contaminates acoustic measurements and reduces the signal-to-noise ratio (SNR). The impact of the TBL can be mitigated by recessing microphones within cavities and covering them with an acoustically transparent material. Modifying existing wind tunnel walls by installing cavity--mounted microphones is a straightforward and cost-effective improvement that enables combined aerodynamic and acoustic measurement campaigns. The cavity geometry, i.e., depth, aperture size, wall angle, and presence of a covering determines the amount of TBL attenuation and consequently the improvement to SNR. While several studies have shown empirically that these parameters have an effect, few studies focus on identifying the physical mechanisms that explain the relationship between geometry and the reduction in TBL pressure fluctuations at the microphone. Thus, this thesis aims to identify these physical mechanisms through experiments and different modeling approaches to better explain the relationship between cavity geometry, the amount of TBL attenuation, and the subsequent impact on the measured acoustic signal.Experimental data were collected to develop an empirical model to quantify how varying cavity geometry affects the measured pressure spectra. Moreover, experiments were also performed to validate simulation results and to quantify the SNR improvement when applying a beamforming algorithm to microphone array data. The modeling and simulation efforts focus on explaining the trends and phenomena identified in the experimental data. Initially, a physical model was developed that assumed acoustic propagation into an axisymmetric cavity with a constant cross-section. This model decomposes a pressure field, resulting from a TBL, into circular duct modes and was used to evaluate the relationship between cavity geometry and the propagation of these acoustic modes into the cavity. This model was followed up with a finite element method (FEM) simulation to study the influence of different cavity geometric parameters and wall materials on the acoustic response of the cavity when subjected to an acoustic wave. The FEM simulation showed that the cavity's acoustic response is determined by the presence of standing waves in the form of acoustic depth modes. This simulation showed that cavities with angled walls have depth modes with lower amplitude waves and thus distort the acoustic signal less. Furthermore, it is shown that the acoustic responses of cavities formed out of sound-absorbing foam are driven by the shape of the foam holder and not the cavity shapes within the foam. Thus, the holder can be optimized to minimize the acoustic response, while the cavity itself can be optimized to reduce the influence of the TBL. Building upon these simulations, a Lattice Boltzmann based computational fluid dynamics (CFD) method was used to simulate the pressure and flow fields within three uncovered cavities and covered cavities resulting from the presence of a turbulent boundary layer. The CFD simulations confirmed a significant finding of the physical model, that the amount of TBL attenuation increases as the cavity aperture size increases relative to the TBL streamwise coherence length. This is due to the resulting modal decomposition of the pressure field above larger cavities having more energy distributed across higher-order modes than for smaller cavities. These higher-order modes decay exponentially into the cavity, resulting in increased attenuation of the TBL. Smaller cavities have most of their energy in their first mode, which does not decay with increasing cavity depth. Furthermore, these simulations showed that the pressure field within covered cavities is primarily acoustic and can be decomposed into acoustic circular duct modes. Since the propagation of TBL pressure fluctuations into covered cavities is primarily acoustic, the shape of future cavities can be efficiently optimized using FEM simulations. Finally, beamforming used with cavities improved the acoustic measurement SNR. Analysis shows that the improvements due to beamforming are independent of those attributed to the cavity geometry. Thus, combining the two approaches improves the SNR of acoustic measurements in closed test section wind tunnels.Aircraft Noise and Climate Effect
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