2,100 research outputs found

    Supersonic laminar-flow control

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    Detailed, up to date systems studies of the application of laminar flow control (LFC) to various supersonic missions and/or vehicles, both civilian and military, are not yet available. However, various first order looks at the benefits are summarized. The bottom line is that laminar flow control may allow development of a viable second generation SST. This follows from a combination of reduced fuel, structure, and insulation weight permitting operation at higher altitudes, thereby lowering sonic boom along with improving performance. The long stage lengths associated with the emerging economic importance of the Pacific Basin are creating a serious and renewed requirement for such a vehicle. Supersonic LFC techniques are discussed

    Trading Inefficiencies in California's Electricity Markets

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    We study price convergence between the two major markets for wholesale electricity in California from their deregulation in April 1998 through November 2000, nearly the end of trading in one market. We would expect profit-maximizing traders to have eliminated persistent price differences between the markets. Institutional impediments and traders' incomplete understanding of the markets, however, could have delayed or prevented price convergence. We find that the two benchmark electricity prices in California -- the Power Exchange's day-ahead price and the Independent System Operator's real-time price -- differed substantially after the markets opened but then appeared to be converging by the beginning of 2000. Starting in May 2000, however, price levels and price differences increased dramatically. We consider several explanations for the significant price differences and conclude that rapidly changing market rules and market fundamentals, including one buyer's attempt to exercise a form of monopsony power, made it difficult for traders to take advantage of opportunities that ex post appear to have been profitable.

    Report of conference evaluation committee

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    A general classification is made of a number of approaches used for the prediction of turbulent shear flows. The sensitivity of these prediction methods to parameter values and initial data are discussed in terms of variable density, pressure fluctuation, gradient diffusion, low Reynolds number, and influence of geometry

    The supercuspidal representations of p-adic classical groups

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    Let G be a unitary, symplectic or special orthogonal group over a locally compact non-archimedean local field of odd residual characteristic. We construct many new supercuspidal representations of G, and Bushnell-Kutzko types for these representations. Moreover, we prove that every irreducible supercuspidal representation of G arises from our constructions.Comment: 55 pages -- minor changes from 1st version (mostly in sections 2.2, 4.2 and 6.2). To appear in Inventiones mathematicae, 2008 (DOI is not yet active as at 12 Nov 2007

    A compendium of NASA Aerobee sounding rocket launchings for 1966

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    Compendium of Aerobee sounding rocket launchings for 196

    Role of Computational Fluid Dynamics and Wind Tunnels in Aeronautics R and D

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    The purpose of this report is to investigate the status and future projections for the question of supplantation of wind tunnels by computation in design and to intuit the potential impact of computation approaches on wind-tunnel utilization all with an eye toward reducing the infrastructure cost at aeronautics R&D centers. Wind tunnels have been closing for myriad reasons, and such closings have reduced infrastructure costs. Further cost reductions are desired, and the work herein attempts to project which wind-tunnel capabilities can be replaced in the future and, if possible, the timing of such. If the possibility exists to project when a facility could be closed, then maintenance and other associated costs could be rescheduled accordingly (i.e., before the fact) to obtain an even greater infrastructure cost reduction

    Synthetic and Biomass Alternate Fueling in Aviation

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    While transportation fueling can accommodate a broad range of alternate fuels, aviation fueling needs are specific, such as the fuel not freezing at altitude or become too viscous to flow properly or of low bulk energy density that shortens range. The fuel must also be compatible with legacy aircraft, some of which are more than 50 years old. Worldwide, the aviation industry alone uses some 85-95 billion gallons of hydrocarbon-based fossil fuel each year, which is about 10% of the transportation industry. US civil aviation alone consumes nearly 14 billion gallons. The enormity of the problem becomes overwhelming, and the aviation industry is taking alternate fueling issues very seriously. Biofuels (algae, cyanobacteria, halophytes, weeds that use wastelands, wastewater and seatwater), when properly sourced, have the capacity to be drop-in fuel replacements for petroleum fuels. As such, biojet from such sources solves the aviation CO2 emissions issue without the downsides of 'conventional' biofuels, such as competing with food and fresh water resources. Of the many current fundamental problems, the major biofuel problem is cost. Both research and development and creative engineering are required to reduce these biofuels costs. Research is also ongoing in several 'improvement' areas including refining/processing and biologics with greater disease resistance, greater bio-oil productivity, reduced water/nutrient requirements, etc. The authors' current research is aimed at aiding industry efforts in several areas. They are considering different modeling approaches, growth media and refining approaches, different biologic feedstocks, methods of sequestering carbon in the processes, fuel certification for aviation use and, overall, ensuring that biofuels are feasible from all aspects - operability, capacity, carbon cycle and financial. The authors are also providing common discussion grounds/opportunities for the various parties, disciplines and concerned organization to share both issues and potential ways for moving forward, and overall, trying to educate those concerned about the innate limitations of 'conventional' biofuels and the solutions provided by non-traditional feedstocks that used waste lands/water or saline/salt water have an immense capacity potential

    Compliant Wall Surface Motion and its Effect on the Structure of a Turbulent Boundary Layer

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    The status of the continuing compliant wall drag reduction research at NASA-Langley Research Center is discussed. Preliminary surface motion calculations are reported along with compliant surface design concepts and their numerical models. A compliant drag reduction theory based on stabilizing the turbulent substructure is proposed and previous experiments have been examined relative to that theory. Results of recent low speed compliant surface experiments have been reported which include initial attempts to measure local compliant surface motion

    The development of grade related criteria in sixth form certificate drama

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    With the co-operation of a number of teachers throughout the country, this project developed, trialled and evaluated two parallel sets of grade related criteria for use in the assessment of Sixth Form Certificate Drama. The writing of the criteria occurred in 1990, while 1991 was devoted to trialling the statements drafted, and evaluating their usefulness as a form of achievement based assessment. A questionnaire sent to all 25 teachers who had taken part in the trial elicited substantial support for this method of assessing drama, although reservations were expressed about the wording of the draft sets. Grade related criteria were seen by teachers as a valid and valuable tool in assessment, having positive effects for teachers and students alike on the curriculum and classroom practice. They were considered to provide more precise and transparent evaluation than norm-referenced assessment, and there was emphatic support among project participants for their future development. The need for further training in the use of grade related criteria was commonly felt, and most participants in the project made gains in their professional development as a result of their involvement with it. The project recommends that a single set of grade related criteria be developed and trialled on a national level, with adequate support provided by (a) teacher relief for inservice teacher training, (b) the development of suitable moderation procedures, and (c) the writing of a comprehensive resource book
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