38,781 research outputs found

    Design study of special purpose systems for the lunar surface

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    Design of special purpose systems for lunar surface operation

    Does Accessibility Planning address what matters? A review of current practice and practitioner perspectives

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    'Accessibility' has become commonplace in transport planning and as such there is a plethora of interpretations of what accessibility means, what constitutes a good measure of accessibility, and how this might be applied in practice. This paper presents an overview of approaches to measuring accessibility and presents a case study of Accessibility Planning in England — one approach to formalising the concept of accessibility. Results of semi-structured interviews with local authority officers are discussed to establish whether current approaches, allow their desired outcomes to be met. This approach demonstrates where there might be gaps between measured or modelled accessibility and the perceptions of the individuals. Findings suggest that while the process is deemed useful in raising the profile of accessibility issues, measures of accessibility do not necessarily easily translate into quantifying benefits of those improvements that are perceived by practitioners to improve accessibility and reduce transport disadvantage

    Performance of Agronomic Crop Varieties in Alaska 1978 –2002

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    There is no such thing as the perfect variety for Alaska. Some varieties are adapted to a wide range of climatic and geographic locations, while others are more specific in their adaptation. The change in elevation of a few hundred feet or a move of a few miles can have a considerable effect on the performance of any variety. Also, cultural practices such as tillage, fertilizer rates, planting date, seeding rate, pest control, and a multitude of other factors can also influence crop yields. This is especially noticeable in northern environments such as Alaska. For example, date-of-planting studies done by F.J. Wooding (1973) and C.W. Knight (1989) found that any date after the middle of May for planting an agronomic crop can result in delayed maturity, low yields, and low quality grain, even for the best adapted varieties for Alaska

    Heavy Vehicle Performance During Recovery From Forced-Flow Urban Freeway Conditions Due To Incidents, Work Zones and Recurring Congestion

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    Information contained in the Highway Capacity Manual on the influence heavy vehicles have on freeway traffic operations has been based on few field data collection efforts and relied mostly on traffic simulation efforts. In the 2010 Manual heavy vehicle impact is evaluated based on “passenger car equivalent” values for buses, recreational vehicles and trucks. These values were calibrated for relatively uncongested freeway conditions (levels of service A through C) since inadequate field data on heavy vehicle behavior under congested conditions were available. A number of field data collection efforts, that were not included in deriving the passenger car equivalent values used in the Highway Capacity Manual, indicated that heavy vehicle impacts on traffic operations may increase as freeway congestion levels increase and freeways operate under unstable flow conditions. The goal of the present effort was to collect and analyze field data with an emphasis on heavy vehicle behavior under lower speeds and derive passenger car equivalent values under such conditions

    Hybrid vehicle assessment. Phase 1: Petroleum savings analysis

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    The results of a comprehensive analysis of near term electric hybrid vehicles are presented, with emphasis on their potential to save significant amounts of petroleum on a national scale in the 1990s. Performance requirements and expected annual usage patterns of these vehicles are first modeled. The projected U.S. fleet composition is estimated, and conceptual hybrid vehicle designs are conceived and analyzed for petroleum use when driven in the expected annual patterns. These petroleum consumption estimates are then compared to similar estimates for projected 1990 conventional vehicles having the same performance and driven in the same patterns. Results are presented in the form of three utility functions and comparisons of sevral conceptual designs are made. The Hybrid Vehicle (HV) design and assessment techniques are discussed and a general method is explained for selecting the optimum energy management strategy for any vehicle mission battery combination. Conclusions and recommendations are presented, and development recommendations are identified

    Technology transfer: Transportation

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    Standard Research Institute (SRI) has operated a NASA-sponsored team for four years. The SRI Team is concentrating on solving problems in the public transportation area and on developing methods for decreasing the time gap between the development and the marketing of new technology and for aiding the movement of knowledge across industrial, disciplinary, and regional boundaries. The SRI TAT has developed a methodology that includes adaptive engineering of the aerospace technology and commercialization when a market is indicated. The SRI Team has handled highway problems on a regional rather than a state basis, because many states in similar climatic or geologic regions have similar problems. Program exposure has been increased to encompass almost all of the fifty states

    Achieving Very High PV Penetration

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    This article argues that optimally deployed intermittency solutions could affordably transform solar power generation into the firm power delivery system modern economies require, thereby enabling very high solar penetration and the displacement conventional power generation. The optimal deployment of these high‐penetration enabling solutions imply the existence of a healthy power grid, and therefore imply a central role for utilities and grid operators. This article also argues that a value‐based electricity compensation mechanism, recognizing the multifaceted, penetration‐dependent value and cost of solar energy, and capable of shaping consumption patterns to optimally match resource and demand, would be an effective vehicle to enable high solar penetration and deliver affordable firm power generation

    Noncontacting device to indicate deflection of turbopump internal rotating parts

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    Phase 2 (development) which was concluded for the ultrasonic Doppler device and the light-pipe-reflectance device is reported. An ultrasonic Doppler breadboard system was assembled which accurately measured runout in the J-2 LOX pump impeller during operation. The transducer was mounted on the outside of the pump volute using a C-clamp. Vibration was measured by conducting the ultrasonic wave through the volute housing and through the fluid in the volute to the impeller surface. The impeller vibration was also measured accurately using the light-pipe probe mounted in an elastomeric-gland fitting in the pump case. A special epoxy resin developed for cryogenic applications was forced into the end of the fiber-optic probe to retain the fibers. Subsequently, the probe suffered no damage after simultaneous exposure to 2150 psi and 77 F. Preliminary flash X-radiographs were taken of the turbine wheel and the shaft-bearing-seal assembly, using a 2-megavolt X-ray unit. Reasonable resolution and contrast was obtained. A fast-neutron detector was fabricated and sensitivity was measured. The results demonstrated that the technique is feasible for integrated-time measurements requiring, perhaps, 240 revolutions to obtain sufficient exposure at 35,000 rpm. The experimental verification plans are included
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