35,201 research outputs found

    Electromagnetic wave energy conversion research

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    Known electromagnetic wave absorbing structures found in nature were first studied for clues of how one might later design large area man-made radiant-electric converters. This led to the study of the electro-optics of insect dielectric antennae. Insights were achieved into how these antennae probably operate in the infrared 7-14um range. EWEC theoretical models and relevant cases were concisely formulated and justified for metal and dielectric absorber materials. Finding the electromagnetic field solutions to these models is a problem not yet solved. A rough estimate of losses in metal, solid dielectric, and hollow dielectric waveguides indicates future radiant-electric EWEC research should aim toward dielectric materials for maximum conversion efficiency. It was also found that the absorber bandwidth is a theoretical limitation on radiant-electric conversion efficiency. Ideally, the absorbers' wavelength would be centered on the irradiating spectrum and have the same bandwith as the irradiating wave. The EWEC concept appears to have a valid scientific basis, but considerable more research is needed before it is thoroughly understood, especially for the complex randomly polarized, wide band, phase incoherent spectrum of the sun. Specific recommended research areas are identified

    UAV as a Reliable Wingman: A Flight Demonstration

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    In this brief, we present the results from a flight experiment demonstrating two significant advances in software enabled control: optimization-based control using real-time trajectory generation and logical programming environments for formal analysis of control software. Our demonstration platform consisted of a human-piloted F-15 jet flying together with an autonomous T-33 jet. We describe the behavior of the system in two scenarios. In the first, nominal state communications were present and the autonomous aircraft maintained formation as the human pilot flew maneuvers. In the second, we imposed the loss of high-rate communications and demonstrated an autonomous safe “lost wingman” procedure to increase separation and reacquire contact. The flight demonstration included both a nominal formation flight component and an execution of the lost wingman scenario

    High temperature static strain gage alloy development program

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    The literature, applicable theory and finally an experimental program were used to identify new candidate alloy systems for use as the electrical resistance elements in static strain gages up to 1250K. The program goals were 50 hours of use in the environment of a test stand gas turbine engine with measurement accuracies equal to or better than 10 percent of full scale for strains up to + or - 2000 microstrain. As part of this effort, a computerized electrical resistance measurement system was constructed for use at temperatures between 300K and 1250K and heating and cooling rates of 250K/min and 10K/min. The two best alloys were an iron-chromium-aluminum alloy and a palladium base alloy. Although significant progress was made, it was concluded that a considerable additional effort would be needed to fully optimize and evaluate these candidate systems

    Analysis and application of digital spectral warping in analog and mixed-signal testing

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    Spectral warping is a digital signal processing transform which shifts the frequencies contained within a signal along the frequency axis. The Fourier transform coefficients of a warped signal correspond to frequency-domain 'samples' of the original signal which are unevenly spaced along the frequency axis. This property allows the technique to be efficiently used for DSP-based analog and mixed-signal testing. The analysis and application of spectral warping for test signal generation, response analysis, filter design, frequency response evaluation, etc. are discussed in this paper along with examples of the software and hardware implementation

    High temperature static strain gage development contract, tasks 1 and 2

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    Results are presented for the first two tasks to develop resistive strain gage systems for use up to 1250 K on blades and vanes in gas turbine engines under tests. The objective of these two tasks was to further improve and evaluate two static strain gage alloys identified as candidates in a previous program. Improved compositions were not found for either alloy. Further efforts on the Fe-11.9Al-10.6Cr weigth percent alloy were discontinued because of time dependent drift problems at 1250 K in air. When produced as a 6.5 micrometer thick sputtered film, the Pd-13Cr weight percent alloys is not sufficiently stable for this use in air at 1250 K and a protective overcoat system will need to be developed

    The forensic exploitation of fingermark chemistry: a review

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    There is evidence that the use of fingerprints for the identification of an individual, either for civil or criminal purposes, has been considered in some form for over 2000 years (Barnes, 2011). The comparison of a mark left by an individual at a crime scene with sets of reference prints taken under controlled conditions is a cornerstone of forensic investigation, first being proposed in 1880 (Faulds, 1880). Following the generation of classification systems for fingermark patterns (Galton, 1892) and filing systems enabling databases to be searched (Henry, 1901), fingerprint comparison and identification has been successfully employed for over 120 years. The fact that fingerprint patterns are ‘unique’ (to the best of scientific knowledge) and persistent throughout life makes them a powerful identification tool. Indeed, the term ‘fingerprint’ is widely used across many other branches of science to describe something that is characteristic and easily distinguished from (e.g.) spectra of other nominally similar substances. In criminal investigations the focus is on locating marks that may have been left by the suspect at the crime scene. These can be of three principal types; a positive mark where material is transferred from the fingertip to the surface, a negative mark where the fingertip removes material (e.g. dust) from the surface, or a ‘plastic’ mark where the fingertip leaves a permanent impression in a soft substance such as putty. The classification of a positive mark can be further divided into a ‘patent’ mark where the material transferred is readily visible to the eye (e.g. mud, ink), or a ‘latent’ mark where the material transferred cannot typically be readily seen by eye and needs further enhancement to be seen. The chemistry of the material transferred from the finger to the surface is important to the visualisation of the contact trace. This is because chemical substances present can be utilised by a range of processes that either convert a latent mark into one that is visible or assist in further enhancing the pre-existing detail in a patent mark. The chemical development of fingermarks was observed as early as the 1860s (Quinche & Margot, 2010) and was already being explored in a more focused way in the 1920s (Mitchell, 1920), with a range of chemical processes targeting different constituents being proposed for use. This review will focus on the material that is ultimately transferred from the fingertip to the surface to form a fingermark. It will consider how this highly complex chemistry can be utilised by a wide range of chemical reagents, and by advanced analytical techniques in combination with imaging capabilities, to reveal the fingermark ridge detail and additional information contained within it

    A simplified analysis of propulsion installation losses for computerized aircraft design

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    A simplified method is presented for computing the installation losses of aircraft gas turbine propulsion systems. The method has been programmed for use in computer aided conceptual aircraft design studies that cover a broad range of Mach numbers and altitudes. The items computed are: inlet size, pressure recovery, additive drag, subsonic spillage drag, bleed and bypass drags, auxiliary air systems drag, boundary-layer diverter drag, nozzle boattail drag, and the interference drag on the region adjacent to multiple nozzle installations. The methods for computing each of these installation effects are described and computer codes for the calculation of these effects are furnished. The results of these methods are compared with selected data for the F-5A and other aircraft. The computer program can be used with uninstalled engine performance information which is currently supplied by a cycle analysis program. The program, including comments, is about 600 FORTRAN statements long, and uses both theoretical and empirical techniques

    Economic Analysis of Incentives for Foreign Direct Investment in Beef Systems in Argentina and Uruguay

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    The European Union's (EU) ban of hormone-treated beef products in 1989 has virtually eliminated beef exports to the EU from countries where cattle are routinely implanted with growth hormones. This study examined whether or not foreign direct investment in beef systems in Argentina and Uruguay would provide a profitable method for investors who want to export beef to the EU. The results indicate that while investment in these systems is potentially profitable, government interventions designed to keep domestic beef prices low inject considerable risk into the investment decision.Investment in beef systems, South America, risk, cointegration, International Relations/Trade, Livestock Production/Industries,
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