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- Reed, R. A., et al.
(författare)
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Anthology of the Development of Radiation Transport Tools as Applied to Single Event Effects
- 2013
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 60:3, s. 1876-1911
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Tidskriftsartikel (refereegranskat)abstract
- This anthology contains contributions from eleven different groups, each developing and/or applying Monte Carlo-based radiation transport tools to simulate a variety of effects that result from energy transferred to a semiconductor material by a single particle event. The topics span from basic mechanisms for single-particle induced failures to applied tasks like developing websites to predict on-orbit single event failure rates using Monte Carlo radiation transport tools.
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| 3. |
- Tomac, Maximilian, et al.
(författare)
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Comparing & benchmarking engineering methods on the prediction of X-31 aerodynamics
- 2010
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Ingår i: 28th AIAA Applied Aerodynamics Conference. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781617389269 ; , s. 2010-4694-
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Konferensbidrag (refereegranskat)abstract
- NATO RTO-AVT-161 is an assessment of Stability and Control Prediction Methods for NATO Air and Sea Vehicles. Though the assessment includes the use of advanced CFD methods, a number of useful engineering methods are available for fast and economic estimates of the aerodynamic characteristics of complex flight vehicles. The objective of this paper is to investigate the use of three specific engineering methods on the X-31 fighter configuration for which CFD, wind tunnel, and flight test data are available for comparison and evaluation purposes. The emphasis is on static longitudinal stability aspects up to high angles of attack; however, selected asymmetric and unsteady effects are considered. Results from the engineering methods are in good agreement with experiment and CFD for angles of attack up to 15 degrees for most cases and higher angles for some cases. Results for pitching moment are in good agreement with CFD, but many of the nonlinear characteristics of the airplane are not predicted by the engineering methods. The quality of the longitudinal stability results is discussed in terms of the prediction of the center of pressure on the vehicle. The results provide improved understanding of the continued usefulness of engineering methods as an analysis tool during the design phase and into the flight test diagnostic phase of a new aircraft.
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| 4. |
- Tomac, Maximillian, et al.
(författare)
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Engineering methods applied to an unmanned combat air vehicle configuration
- 2012
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Ingår i: Journal of Aircraft. - 0021-8669 .- 1533-3868. ; 49:6, s. 1610-1618
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Tidskriftsartikel (refereegranskat)abstract
- Engineering methods provide fast and economic predictions of the aerodynamic characteristics of complex flight vehicles. This paper investigates the application of three specific engineering methods to a unmanned combat air vehicle (UCAV) configuration, termed the Stability and Control Configuration (SACCON), that is still under investigation and that is the subject of an intensive computational and experimental study by the NATO Research and Technology Organization task group AVT-161 for better understanding of its stability and control characteristics. Computational fluid dynamics (CFD) data are computed for theSACCONat wind-tunnel conditions and are compared and evaluated against the measured values, especially in terms of their implications for low-speed longitudinal flight characteristics. Because of their reduced-order modeling compared with Reynolds-averaged Navier-Stokes CFD, predictions by the engineering methods are restricted to the flight-condition range governed by linear flow physics, which, for the SACCON in low speed is 0 α 10 deg. Despite the limited range in angle of attack, it was discovered that, due to the large sweep angle of theSACCONwing and its tip section of zero taper ratio, peak suction levels at the tip were so high that the boundary layer separated there instead. This viscous effect caused a discrepancy between the predicted and measured values of the pitching moment. The remedy taken was to increase the washout for theSACCONwing by modifying its twist and camber, and predictions made for this shape confirmed that linear flow physics prevailed then and that the static stability margin was increased. Furthermore, a series of predictions were made at high speed to establish the drag-divergence Mach numberMdd. The investigations carried out here demonstrate the continued usefulness of engineering methods not only as an analysis tool during the initial aircraft design phase but also as a design tool to improve the shape definition of the vehicle to achieve better performance.
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| 8. |
- Karpa, Daniel S., et al.
(författare)
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Confronting and resolving competing values behind conservation objectives
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:35, s. 11132-11137
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Tidskriftsartikel (refereegranskat)abstract
- Diverse motivations for preserving nature both inspire and hinder its conservation. Optimal conservation strategies may differ radically depending on the objective. For example, creating nature reserves may prevent extinctions through protecting severely threatened species, whereas incentivizing farmland hedgerows may benefit people through bolstering pest-eating or pollinating species. Win-win interventions that satisfy multiple objectives are alluring, but can also be elusive. To achieve better outcomes, we developed and implemented a practical typology of nature conservation framed around seven common conservation objectives. Using an intensively studied bird assemblage in southern Costa Rica as a case study, we applied the typology in the context of biodiversity's most pervasive threat: habitat conversion. We found that rural habitats in a varied tropical landscape, comprising small farms, villages, forest fragments, and forest reserves, provided biodiversity-driven processes that benefit people, such as pollination, seed dispersal, and pest consumption. However, species valued for their rarity, endemism, and evolutionary distinctness declined in farmland. Conserving tropical forest on farmland increased species that international tourists value, but not species discussed in Costa Rican newspapers. Despite these observed trade-offs, our analyses also revealed promising synergies. For example, we found that maintaining forest cover surrounding farms in our study region would likely enhance most conservation objectives at minimal expense to others. Overall, our typology provides a framework for resolving the competing objectives of modern conservation.
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| 9. |
- Mendenhall, M.R., et al.
(författare)
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Comparing and benchmarking engineering methods for the prediction of X-31 aerodynamics
- 2012
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638 .- 1626-3219. ; 20:1, s. 12-20
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Tidskriftsartikel (refereegranskat)abstract
- A number of useful engineering methods are available for fast and economic estimates of the aerodynamic characteristics of complex flight vehicles. This article investigates the application of three specific engineering methods to the X-31 fighter configuration, and CFD, wind tunnel, and flight test data are used for comparison and evaluation purposes. The emphasis is on static longitudinal stability aspects up to high angles of attack; however, selected asymmetric and unsteady effects are considered. Results from the engineering methods are in good agreement with experiment and CFD for angles of attack up to 15° for most cases and higher angles for some cases. Results for pitching moment are in good agreement with CFD, but many of the nonlinear characteristics of the airplane are not predicted by the engineering methods. The quality of the longitudinal stability results is discussed in terms of the prediction of the center of pressure on the vehicle. The results provide improved understanding of the continued usefulness of engineering methods as an analysis tool during the design phase and into the flight test diagnostic phase of a new aircraft.
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