534 research outputs found
Wind-Tunnel Investigation of a 1/60-Scale Model of the Republic MX-1554 Airplane at a Mach Number of 2.85
Using multiple criteria decision analysis (MCDA) to assist in estimating residential housing values
Considerable literature exists regarding the complexity of the residential real estate appraisal process and the methods employed to determine initial listing prices as estimates of intrinsic market prices. Deviations in residential real estate intrinsic values occur due to a multiplicity of attributes and explanatory factors requiring consideration. We conduct a panel study using a Multiple Criteria Decision Analysis (MCDA) based framework that utilizes the skills and knowledge of a panel of residential real estate professionals (i.e. appraisers and realtors). We demonstrate how cognitive mapping and the Measuring Attractiveness by a Categorical Based Evaluation Technique (MACBETH) may assist in estimating appropriate offer/sale prices and strengthening current valuation approaches such as using comparables and/or hedonic modeling. The managerial implications of our MCDA-based framework and some avenues for future research are also presented.info:eu-repo/semantics/publishedVersio
Effect of Tail Surfaces on the Base Drag of a Body of Revolution at Mach Numbers of 1.5 and 2.0
Wind-tunnel tests were performed at Mach numbers of 1.5 and 2.0 to investigate the influence of tail surfaces on the base drag of a body of revolution without boattailing and having a turbulent boundary layer. The tail surfaces were of rectangular plan form of aspect ratio 2.33 and has symmetrical, circular-arc airfoil section. The results of the investigation showed that the addition of these tail surfaces with the trailing edges at or near the body base incurred a large increase in the base-drag coefficient. For a cruciform tail having a 10-percent-thick airfoil section, this increase was about 70 percent at a Mach number of 1.5 and 35 percent at a Mach number of 2.0. As the trailing edge of the tail was moved forward or rearward of the base by about one tail-chord length, the base-drag increment was reduced to nearly zero. The increments in base-drag coefficient due to the presence of 10-percent-thick tail surfaces were generally twice those for 5-percent-thick surfaces. The base-drag increments due to the presence of a cruciform tail were less than twice those for a plane tail. An estimate of the change in base pressure due to the tail surfaces was made, based on a simple superposition of the airfoil-pressure field onto the base-pressure field behind the body. A comparison of the results with the experimental values indicated that in most cases the trend in the variation of the base-drag increment with changes in tail position could be predicted by this approximate method but that the quantitative agreement at most tail locations was poor
Measurements in Flight of the Lateral-Control Characteristics of an Airplane Equipped with Full-Span Zap Flaps and Simple Circular-Arc-Type Ailerons
Flight tests were conducted on the OS2U-2 seaplane with simple circular-arc-type ailerons directly connected to the actuating torque tube. Two aileron test installations were made, differing only in the inclination of the projecting surface with the wing's upper surface. The lateral-control characteristics of the airplane were determined from data obtained in stalls and rudder-fixed aileron rolls. The revised ailerons were deficient in maximum rolling effectiveness, but were capable of controlling the rolling tendencies of the airplane near the stall
Wind-tunnel Investigation of the Vortex Wake and Downwash Field Behind Triangular Wings and Wing-body Combinations at Supersonic Speeds
MULTIPLE-SOURCE SCHLIEREN SYSTEM (TRANSONIC WIND TUNNEL)
A flow visualization system was developed for the Sandia Corporation 12 x 12-inch transonic blowdown wind tunnel. -The arrangement comprises a multiple- source schlieren system with sharp focusing properties to keep the perforated plexiglas side walls out of focus. The detailed mechanical design of the schlieren system is not completed. However, a bench-type setup representative of the final system has been made at the wind tunnel. The system is shown and each component is discussed briefly. (auth
Survey Simulations of a New Near-Earth Asteroid Detection System
We have carried out simulations to predict the performance of a new
space-based telescopic survey operating at thermal infrared wavelengths that
seeks to discover and characterize a large fraction of the potentially
hazardous near-Earth asteroid (NEA) population. Two potential architectures for
the survey were considered: one located at the Earth-Sun L1 Lagrange point, and
one in a Venus-trailing orbit. A sample cadence was formulated and tested,
allowing for the self-follow-up necessary for objects discovered in the daytime
sky on Earth. Synthetic populations of NEAs with sizes >=140 m in effective
spherical diameter were simulated using recent determinations of their physical
and orbital properties. Estimates of the instrumental sensitivity, integration
times, and slew speeds were included for both architectures assuming the
properties of new large-format 10 um detector arrays capable of operating at
~35 K. Our simulation included the creation of a preliminary version of a
moving object processing pipeline suitable for operating on the trial cadence.
We tested this pipeline on a simulated sky populated with astrophysical sources
such as stars and galaxies extrapolated from Spitzer and WISE data, the catalog
of known minor planets (including Main Belt asteroids, comets, Jovian Trojans,
etc.), and the synthetic NEA model. Trial orbits were computed for simulated
position-time pairs extracted from the synthetic surveys to verify that the
tested cadence would result in orbits suitable for recovering objects at a
later time. Our results indicate that the Earth-Sun L1 and Venus-trailing
surveys achieve similar levels of integral completeness for potentially
hazardous asteroids larger than 140 m; placing the telescope in an interior
orbit does not yield an improvement in discovery rates. This work serves as a
necessary first step for the detailed planning of a next-generation NEA survey.Comment: AJ accepted; corrected typ
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