8,132 research outputs found

    Designs and Technology Requirements for Civil Heavy Lift Rotorcraft

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    The NASA Heavy Lift Rotorcraft Systems Investigation examined in depth several rotorcraft configurations for large civil transport, designed to meet the technology goals of the NASA Vehicle Systems Program. The investigation identified the Large Civil Tiltrotor as the configuration with the best potential to meet the technology goals. The design presented was economically competitive, with the potential for substantial impact on the air transportation system. The keys to achieving a competitive aircraft were low drag airframe and low disk loading rotors; structural weight reduction, for both airframe and rotors; drive system weight reduction; improved engine efficiency; low maintenance design; and manufacturing cost comparable to fixed-wing aircraft. Risk reduction plans were developed to provide the strategic direction to support a heavy-lift rotorcraft development. The following high risk areas were identified for heavy lift rotorcraft: high torque, light weight drive system; high performance, structurally efficient rotor/wing system; low noise aircraft; and super-integrated vehicle management system

    Breeding Birds of Arctic Bay, Baffin Island, N.W.T., with Notes on the Biogeographic Significance of the Avifauna

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    The known avifauna of the Arctic Bay area consists of 38 species, of which 22 are probable or proven breeders and 3 are permanent residents. Arctic Bay appears to be in a transition area between characteristic high arctic and low arctic forms. Eurasian or Greenlandic forms include breeding Ringed Plover and 'Greenland' Hoary Redpoll; and transient Wheatear, Red Knot and Ruddy Turnstone. The absence of several sea-associated species as breeders or even transients may be attributed to the normal late ice break-up in Admiralty Inlet

    The Dovekie, Alle alle, as a Spring Migrant in Eastern Lancaster Sound and Western Baffin Bay

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    The distribution and numbers of dovekies during spring migration were studied by aerial surveys of eastern Lancaster Sound (1976, 1978, 1979) and western Baffin Bay (1978, 1979). Dovekies that nest in northwest Greenland migrated north through the study area during May. Extrapolations of recorded densities indicate that a peak of ~14 million dovekies may have been present in eastern Lancaster Sound and northwest Baffin Bay in mid-May 1978: fewer were present in May 1979, although the migration was more protracted and total numbers migrating through these areas may have been similar. Dovekies preferred offshore pack ice habitats with moderate to heavy ice cover. Possible reasons for the highly variable distributions in the three years are discussed.Key words: dovekie, Alle alle, spring migration, Lancaster Sound, Baffin Bay, aerial survey

    NASA Heavy Lift Rotorcraft Systems Investigation

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    The NASA Heavy Lift Rotorcraft Systems Investigation examined in depth several rotorcraft configurations for large civil transport, designed to meet the technology goals of the NASA Vehicle Systems Program. The investigation identified the Large Civil Tiltrotor as the configuration with the best potential to meet the technology goals. The design presented was economically competitive, with the potential for substantial impact on the air transportation system. The keys to achieving a competitive aircraft were low drag airframe and low disk loading rotors; structural weight reduction, for both airframe and rotors; drive system weight reduction; improved engine efficiency; low maintenance design; and manufacturing cost comparable to fixed-wing aircraft. Risk reduction plans were developed to provide the strategic direction to support a heavy-lift rotorcraft development. The following high risk areas were identified for heavy lift rotorcraft: high torque, light weight drive system; high performance, structurally efficient rotor/wing system; low noise aircraft; and super-integrated vehicle management system

    The New Economics of Livestock Production Management

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    The importance of heterogeneity of animal attributes in livestock production is assessed. Preliminary results indicate that variance and skew measures of attributes may be becoming more important over time.livestock economics, herd management, livestock marketing, Livestock Production/Industries, Marketing,

    Survey of Diseases in Wild Turkeys in Arkansas

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    Nineteen dead wild turkeys were necropsied and 573 live wild turkeys were physically examined for pathological agents in Arkansas between 1992 and 1997 to determine the proximate role disease may play in declining wild populations in Arkansas. Necropsy of the dead wild turkeys identified avian pox and histomoniasis as the most common diseases (16% and 11% of necropsies, respectively). Avian pox was recorded from three major physiographic regions in the state (Ozark Highlands, Ouachita Mountains, Gulf Coastal Plain). One hen died of non-accidental crop impaction, the fifth occurrence observed in the southeastern United States. Another hen died after developing severe, focal necrotic dermatitis caused by a Penicillium sp. fungus, the first occurrence observed in wild turkeys. All live wild turkeys appeared free of gross signs of disease. We found diseases in wild turkeys in Arkansas are not uncommon and are more diverse than previously reported. Continued monitoring of disease in wild turkeys is therefore encouraged
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