7,830 research outputs found

    Presentism and eternalism

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    Effect of blade planform variation on the forward-flight performance of small-scale rotors

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    An investigation was conducted in the Glenn L. Martin Wind Tunnel to determine the effect of blade planform variation on the forward-flight performance of four small-scale rotors. The rotors were 5.417 ft in diameter and differed only in blade planform geometry. The four planforms were: (1) rectangular; (2) 3:1 linear taper starting at 94 percent radius; (3) 3:1 linear taper starting at 75 percent radius; and (4) 3:1 linear taper starting at 50 percent radius. Each planform had a thrust-weighted solidity of 0.098. The investigation included forward-flight simulation at advance ratios from 0.14 to 0.43 for a range of rotor lift and drag coefficients. Among the four rotors, the rectangular rotor required the highest torque for the entire range of rotor drag coefficients attained at advanced ratios greater than 0.14 for rotor lift coefficients C sub L from 0.004 to 0.007. Among the rotors with tapered blades and for C sub L = 0.004 to 0.007, either the 75 percent tapered rotor or the 50 percent tapered rotor required the least amount of torque for the full range of rotor drag coefficients attained at each advance ratio. The performance of the 94 percent tapered rotor was generally between that of the rectangular rotor and the 75 and 50 percent tapered rotors at each advance ratio for this range of rotor lift coefficients

    Monitoring of Potential N Losses from Dairy and Organic Farming Systems

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    End of Project ReportThe project was carried out at Johnstown Castle and was concerned with monitoring potential nitrogen (N) leaching losses from organic and dairy farming systems. Some plots were cut for silage in year one; only grazed plots were used in year two. There were low input manure N plots in the organic system with low and high input fertiliser N plots in the dairy system. Soil samples, in 15 cm intervals from the surface to 90cm deep, were taken in triplicate from one plot of each treatment on three successive days per month from October to March in year 1 and from September to March in year 2. Extraction of nitrate-N (NO3-N) and ammonium-N (NH4- N) was carried out on un-bulked soil cores by taking a 20 g sub-sample and using 100 ml 2 molar KCl. A 20 g sub-sample of each day`s bulked replicates was dried at 105 degrees C overnight for moisture determination. The concentrations of NO3-N and NH4-N in the extracts were determined on an automatic analyser and the results were converted to kg per ha using the following bulk densities for the soil layers: 0-15, 15-30, 30-60, 60-90, 1.3, 1.4, 1.6, 1.75 g per cm3, respectively. In year 1 the results showed no significant difference between treatments in the level of NO3-N, NH4-N and total mineral N in the soil layers and total amounts to 90 cm. On four of the six dates, November, December, January, early-March, the level of total mineral N was lowest in the low N treatment. Among treatments, NH4-N was lowest in the low N treatment on four dates, November, December, January, early-March while NO3-N was also lowest on four dates, November, December, early-March and late-March. At the November, December, January and early-March sampling, the organic farm NH4-N data to 90 cm was highest which was reflected in the total mineral N results to 90 cm for November, December and early-March. In year 2 the results showed no significant difference between treatments in the level of NO3- N, NH4-N and total mineral N in the soil layers and total amounts to 90 cm. In September, October, November, December and February, total mineral N to 90 cm was highest in the high N treatment. This was a reflection of high NO3-N levels in that treatment for those sampling dates. Among treatments, total mineral N to 90 cm was lowest in the organic farm samples in September, October, November, December and February. This result reflected, among treatments, lowest NH4-N levels in September, October, November, December, February and lowest NO3- N levels in November and December. Estimates of the amounts of applied N leached, averaged over the two years of the experiment, were 22% for the Low N treatment and 12% for the High N treatment. An equation, developed from studies carried out in County Cork (Richards, 1999), gave predictions of N available for leaching in November from the N treatments in year 2 which were in very good agreement at low N and within 23% of those actually recorded at high N. Assessment of available N leaching models led to the conclusion that the relatively simple UK `N Cycle` model was most adaptable to Irish conditions since other European and US models require input parameters not readily available including those for soil texture, soil hydrology and soil organic matter.European Union Structural Funding (EAGGF

    Two-boxing is irrational

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    Philosophers debate whether one-boxing or two-boxing is the rational act in a Newcomb situation. I shall argue that one-boxing is the only rational choice. This is so because there is no intelligible aim by reference to which you can justify the choice of two-boxing over one-boxing once you have come to think that you will two-box (whereas there is such an aim by reference to which you can justify one-boxing). The only aim by which the agent in the Newcomb situation can justify his two-boxing is the subjunctively described aim of ‘getting more than I would if I were to one-box’. But such a subjunctively described aim can justify an action only if it can be seen as generating, in conjunction with the agent’s beliefs, an indicatively describable aim which justifies the action. In the case of the Newcomb agent the aim of 'getting more than I would if I were to one-box’ cannot be seen in this way

    Overcoming Barriers to Efficiency

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    The article discusses factors that hinder the installation of high-performance heating, ventilation and air conditioning (HVAC) equipment in commercial and residential buildings in the United States. For owner-occupied buildings, the utility and capital expenses are ultimately included in one corporate budget. Thus, decision processes become a justification of any additional expense for higher performing equipment relative to the expected returns via lower energy costs. In an existing building, business management principles determine the evaluation process. Certain economic factors apply regardless of building ownership. For example, a cost is associated with the information gathering process for new technology or obtaining information relevant to current resource use. This is primarily a direct expense in the form of employee salaries or consultant fees. INSET: Sustainable HVAC for Modular Classrooms

    The Nature and Frequency of the Gas Outbursts in Comet 67P/Churyumov-Gerasimenko observed by the Alice Far-ultraviolet Spectrograph on Rosetta

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    Alice is a far-ultraviolet imaging spectrograph onboard Rosetta that, amongst multiple objectives, is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/Churyumov-Gerasimenko. The initial observations, made following orbit insertion in August 2014, showed emissions of atomic hydrogen and oxygen spatially localized close to the nucleus and attributed to photoelectron impact dissociation of H2O vapor. Weaker emissions from atomic carbon were subsequently detected and also attributed to electron impact dissociation, of CO2, the relative H I and C I line intensities reflecting the variation of CO2 to H2O column abundance along the line-of-sight through the coma. Beginning in mid-April 2015, Alice sporadically observed a number of outbursts above the sunward limb characterized by sudden increases in the atomic emissions, particularly the semi-forbidden O I 1356 multiplet, over a period of 10-30 minutes, without a corresponding enhancement in long wavelength solar reflected light characteristic of dust production. A large increase in the brightness ratio O I 1356/O I 1304 suggests O2 as the principal source of the additional gas. These outbursts do not correlate with any of the visible images of outbursts taken with either OSIRIS or the navigation camera. Beginning in June 2015 the nature of the Alice spectrum changed considerably with CO Fourth Positive band emission observed continuously, varying with pointing but otherwise fairly constant in time. However, CO does not appear to be a major driver of any of the observed outbursts.Comment: 6 pages, 4 figures, accepted for publication in the Astrophysical Journal Letter

    Numerical Simulations of Various Rotor Designs in Hover and Forward Flight

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    This paper presents numerical simulations of different rotor designs using high-fidelity CFD methods. Firstly, hover results are presented for the PSP rotor blade. The impact of a transitional turbulence model on the blade performance was examined and good correlation with test data was obtained. A grid sensitivity study indicated an influence on the transition location predictions, however, the effect on the integrated loads was not significant. The surface pressure distributions and sectional loads were also examined. The PSP rotor was also simulated in forward flight and blade surface pressure was compared with wind tunnel data. The predictions were found to follow data obtained from pressure transducers

    Cancer prevention by targeting angiogenesis

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    Healthy individuals can harbour microscopic tumours and dysplastic foci in different organs in an undetectable and asymptomatic state for many years. These lesions do not progress in the absence of angiogenesis or inflammation. Targeting both processes before clinical manifestation can prevent tumour growth and progression. Angioprevention is a chemoprevention approach that interrupts the formation of new blood vessels when tumour cell foci are in an indolent state. Many efficacious chemopreventive drugs function by preventing angiogenesis in the tumour microenvironment. Blocking the vascularization of incipient tumours should maintain a dormancy state such that neoplasia or cancer exist without disease. The current limitations of antiangiogenic cancer therapy may well be related to the use of antiangiogenic agents too late in the disease course. In this Review, we suggest mechanisms and strategies for using antiangiogenesis agents in a safe, preventive clinical angioprevention setting, proposing different levels of clinical angioprevention according to risk, and indicate potential drugs to be employed at these levels. Finally, angioprevention may go well beyond cancer in the prevention of a range of chronic disorders where angiogenesis is crucial, including different forms of inflammatory or autoimmune diseases, ocular disorders, and neurodegeneration

    Development and application of an acceptance testing model

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    The process of acceptance testing large software systems for NASA has been analyzed, and an empirical planning model of the process constructed. This model gives managers accurate predictions of the staffing needed, the productivity of a test team, and the rate at which the system will pass. Applying the model to a new system shows a high level of agreement between the model and actual performance. The model also gives managers an objective measure of process improvement
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