7,568 research outputs found
Influence of optimized leading-edge deflection and geometric anhedral on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration
An investigation conducted in the Langley 7 by 10 foot tunnel to determine the influence of an optimized leading-edge deflection on the low speed aerodynamic performance of a configuration with a low aspect ratio, highly swept wing. The sensitivity of the lateral stability derivative to geometric anhedral was also studied. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to spanwise variation of unwash, the resulting optimized leading edge was a smooth, continuously warped surface for which the deflection varied from 16 deg at the side of body to 50 deg at the wing tip. For the particular configuration studied, levels of leading-edge suction on the order of 90 percent were achieved. The results of tests conducted to determine the sensitivity of the lateral stability derivative to geometric anhedral indicate values which are in reasonable agreement with estimates provided by simple vortex-lattice theories
Leading-edge deflection optimization for a highly swept arrow wing configuration
Tests were also conducted to determine the sensitivity of the lateral stability derivative C sub l sub beta to geometric anhedral. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to the spanwise variation of upwash, the resulting optimized leading edge was a smooth, continuously warped surface. For the particular configuration studied, levels of leading edge suction on the order of 90 percent were achieved with the smooth, continuously warped leading edge contour. The results of tests conducted to determine the sensitivity of C sub l sub beta to geometric anhedral indicate values of delta C sub l sub beta/delta T which are in reasonable agreement with estimates provided by simple vortex lattice theories
Experimental study of wing leading-edge devices for improved maneuver performance of a supercritical maneuvering fighter configuration
Wind tunnel tests were conducted to examine the use of wing leading-edge devices for improved subsonic and transonic maneuver performance. These devices were tested on a fighter configuration which utilized supercritical-wing technology. The configuration had a leading-edge sweep of 45 deg and an aspect ratio of 3.28. The tests were conducted at Mach numbers of 0.60 and 0.85 with angles of attack from -0.5 deg to 22 deg. At both Mach numbers, sharp leading-edge flaps produced vortices which greatly altered the flow pattern on the wing and resulted in substantial reductions in drag at high lift. Underwing or pylon-type vortex generators also reduced drag at high lift. The vortex generators worked better at a Mach number of 0.60. The vortex generators gave the best overall results with zero toe-in angle and when mounted on either the outboard part of the wing or at both an outboard location and halfway out the semispan. Both the flaps and the vortex generators had a minor effect on the pitching moment. Fluorescent minitufts were found to be useful for flow visualization at transonic maneuver conditions
Critical Thinking Assessment: The Link Between Critical Thinking and Student Application in the Basic Course
The intent of this study is to evaluate existing literature on the concept, teaching and assessment of critical thinking. To reach this goal, critical thinking will be examined in terms of its multiple definitions, and its relationship to higher order thinking, critical teaching, and assessment.
In response to the need for a more generative and creative way of assessing critical thinking, the authors offer an activity assigned in the basic course (artifacts) as a viable tool for allowing students to take an active role in learning to think critically. The artifacts are then analyzed to determine if they serve as an authentic form of critical thinking assessment
Overview of the Langley subsonic research effort on SCR configuration
Recent advances achieved in the subsonic aerodynamics of low aspect ratio, highly swept wing designs are summarized. The most significant of these advances was the development of leading edge deflection concepts which effectively reduce leading edge flow separation. The improved flow attachment results in substantial improvements in low speed performance, significant delay of longitudinal pitch up, increased trailing edge flap effectiveness, and increased lateral control capability. Various additional theoretical and/or experimental studies are considered which, in conjunction with the leading edge deflection studies, form the basis for future subsonic research effort
Matroids and Quantum Secret Sharing Schemes
A secret sharing scheme is a cryptographic protocol to distribute a secret
state in an encoded form among a group of players such that only authorized
subsets of the players can reconstruct the secret. Classically, efficient
secret sharing schemes have been shown to be induced by matroids. Furthermore,
access structures of such schemes can be characterized by an excluded minor
relation. No such relations are known for quantum secret sharing schemes. In
this paper we take the first steps toward a matroidal characterization of
quantum secret sharing schemes. In addition to providing a new perspective on
quantum secret sharing schemes, this characterization has important benefits.
While previous work has shown how to construct quantum secret sharing schemes
for general access structures, these schemes are not claimed to be efficient.
In this context the present results prove to be useful; they enable us to
construct efficient quantum secret sharing schemes for many general access
structures. More precisely, we show that an identically self-dual matroid that
is representable over a finite field induces a pure state quantum secret
sharing scheme with information rate one
Inferring the CO2 Abundance in Comet 45P/Honda-Mrkos-Pajdu\v{s}\'akov\'a from [O I] Observations: Implications for the Source of Icy Grains in Cometary Comae
The study of cometary composition is important for understanding our solar
system's early evolutionary processes. Carbon dioxide (CO2) is a common
hypervolatile in comets that can drive activity but is more difficult to study
than other hypervolatiles due to severe telluric absorption. CO2 can only be
directly observed from space-borne assets. Therefore, a proxy is needed to
measure CO2 abundances in comets using ground-based observations. The flux
ratio of the [O I] 5577 A line to the sum of the [O I] 6300 A and [O I] 6364 A
lines (hereafter referred to as the [O I] line ratio) has, with some success,
been used in the past as such a proxy. We present an [O I] line ratio analysis
of comet 45P/Honda-Mrkos-Pajdu\v{s}\'akov\'a (HMP), using data obtained with
the Tull Coud\'e Spectrograph on the 2.7-meter Harlan J. Smith telescope at
McDonald Observatory, taken from UT February 21-23, 2017 when the comet was at
heliocentric distances of 1.12-1.15 AU. HMP is a hyperactive Jupiter family
comet (JFC). Icy grains driven out by CO2 sublimation have been proposed as a
driver of hyperactivity, but the CO2 abundance of HMP has not been measured.
From our [O I] line ratio measurements, we find a CO2/H2O ratio for HMP of 22.9
+/- 1.4%. We compare the CO2/H2O ratios to the active fractions of the nine
comets (including HMP) in the literature that have data for both values. We
find no correlation. These findings imply that CO2 sublimation driving out icy
grains is not the only factor influencing active fractions for cometary nuclei.Comment: 17 pages, 8 figures. To be published in The Planetary Science Journa
Maximizing the relationship of yield to site-specific management zones with object-oriented segmentation of hyperspectral images
Quick and low cost delineation of site-specific management zones (SSMZ) would improve applications of precision agriculture. In this study, a new method for delineating SSMZ using object-oriented segmentation of airborne imagery was demonstrated. Three remote sensing domains—spectral, spatial, and temporal- are exploited to improve the SSMZ relationship to yield. Common vegetation indices (VI), and first and second derivatives ([Formula: see text], [Formula: see text]) from twelve airborne hyperspectral images of a cotton field for one season [Formula: see text] were used as input layers for object-oriented segmentation. The optimal combination of VI, SSMZ size and crop phenological stage were used as input variables for SSMZ delineation, determined by maximizing the correlation to segmented yield monitor maps. Combining narrow band vegetation indices and object-oriented segmentation provided higher correlation between VI and yield at SSMZ scale than that at pixel scale by reducing multi-resource data noise. VI performance varied during the cotton growing season, providing better SSMZ delineation at the beginning and middle of the season (days after planting (DAP) 66–143).The optimal scale determined for SSMZ delineation was approximately 240 polygons for the study field, but the method also provided flexibility enabling the setting of practical scales for a given field. For a defined scale, the optimal single phenological stage for the study field was near July 11 (DAP 87) early in the growing season. SSMZs determined from multispectral VIs at a single stage were also satisfactory; compared to hyperspectral indices, temporal resolution of multi-spectral data seems more important for SSMZ delineation
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