3,021 research outputs found

    Adhesives for Aerospace

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    The industry is hereby challenged to integrate adhesive technology with the total structure requirements in light of today's drive into automation/mechanization. The state of the art of adhesive technology is fairly well meeting the needs of the structural designers, the processing engineer, and the inspector, each on an individual basis. The total integration of these needs into the factory of the future is the next collective hurdle to be achieved. Improved processing parameters to fit the needs of automation/mechanization will necessitate some changes in the adhesive forms, formulations, and chemistries. Adhesives have, for the most part, kept up with the needs of the aerospace industry, normally leading the rest of the industry in developments. The wants of the aerospace industry still present a challenge to encompass all elements, achieving a totally integrated joined and sealed structural system. Better toughness with hot-wet strength improvements is desired. Lower cure temperatures, longer out times, and improved corrosion inhibition are desired

    Design, analysis, and fabrication of the technology integration box beam

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    Numerous design concepts, materials, and manufacturing methods were investigated analytically and empirically for the covers and spars of a transport wing box. This information was applied to the design, analysis, and fabrication of a full-scale section of a transport wing box. A blade-stiffened design was selected for the upper and lower covers of the box. These covers have been constructed using three styles of AS4/974 prepreg fabrics. The front and rear T-stiffened channel spars were filament wound using AS4/1806 towpreg. Covers, ribs, and spars were assembled using mechanical fasteners. When they are completed later this year, the tests on the technology integration box beam will demonstrate the structural integrity of an advanced composite wing design which is 25 percent lighter than the metal baseline

    Home Bias, Transactions Costs, and Prospects for the Euro: A More Detailed Analysis

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    This paper brings together the literature on determination of home bias in equity holdings and the portfolio balance model of exchange rates to consider whether the dollar might be affected by a change in transactions costs that alters international portfolio allocations. Our empirical findings lend support to the view that transactions costs have a significant influence on US portfolio holdings, even after accounting for float market share. In addition, new survey evidence on the equity holdings of European firms indicates home bias for European investors, and points to a reduction in the magnitude of this home bias since 1997.portfolio choice, equity flows, exchange rates

    Home bias, transactions costs, and prospects for the Euro: A more detailed analysis

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    This paper brings together the literature on determination of home bias in equity holdings and the portfolio balance model of exchange rates to consider whether the dollar might be affected by a change in transactions costs that alters international portfolio allocations. The empirical findings lend support to the view that transactions costs have a significant influence on US portfolio holdings, even after accounting for float market share. In addition, new survey evidence on the equity holdings of European firms indicates home bias for European investors, and points to a reduction in the magnitude of this home bias since 1997. --portfolio choice,equity flows,exchange rates

    Home Bias, Transaction Costs, and Prospects for the Euro: A More Detailed Analysis

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    This paper brings together the literature on determination of home bias in equity holdings and the portfolio balance model of exchange rates to consider whether the dollar might be affected by a change in transactions costs that alters international portfolio allocations. Our empirical findings lend support to the view that transactions costs have a significant influence on US portfolio holdings, even after accounting for float market share. In addition, new survey evidence on the equity holdings of European firms indicates home bias for European investors, and points to a reduction in the magnitude of this home bias since 1997.Home bias, Transactions costs, Euro, EMU, Europe, exchange rates, portfolio

    Manufacturing development of pultruded composite panels

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    The weight savings potential, of graphite-epoxy composites for secondary and medium primary aircraft structures, was demonstrated. One of the greatest challenges facing the aircraft industry is to reduce the acquisition costs for composite structures to a level below that of metal structures. The pultrusion process, wherein reinforcing fibers, after being passed through a resin bath are drawn through a die to form and cure the desired cross-section, is an automated low cost manufacturing process for composite structures. The Lockheed Aeronautical Systems Company (LASC) Composites Development Center designed, characterizated materials for, fabricated and tested a stiffened cover concept compatible with the continuous pultrusion process. The procedures used and the results obtained are presented

    Development of the technology for the fabrication of reliable laminar from control panels

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    Materials were assessed and fabrication techniques were developed for use in the manufacture of wing surface materials compatible with the application of both aluminum alloys and nonmetallic composites. The concepts investigated included perforations and slots in the metallic test panels and microporosity and perforations in the composite test panels. Perforations were produced in the metallic test panels by the electron beam process and slots were developed by controlled gaps between the metal sheets. Microporosity was produced in the composite test panels by the resin bleed process, and perforations were produced by the fugitive fiber technique. Each of these concepts was fabricated into test panels, and air flow tests were conducted on the panels

    Long-range electron transfer in structurally engineered pentaammineruthenium (histidine-62) cytochrome c

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    In many biological processes, long-range electron transfer (ET) plays a key role. When the three-dimensional structures of proteins are accurately known, use of modified proteins and protein-protein complexes provides an experimental approach to study ET rates between two metal centers. For Ru(His)- modified proteins, the introduction of histidine residues at any desired surface location by site-directed mutagenesis opens the way for systematic investigations of ET pathways
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