313 research outputs found
Study of optical techniques for the Ames unitary wind tunnel: Digital image processing, part 6
A survey of digital image processing techniques and processing systems for aerodynamic images has been conducted. These images covered many types of flows and were generated by many types of flow diagnostics. These include laser vapor screens, infrared cameras, laser holographic interferometry, Schlieren, and luminescent paints. Some general digital image processing systems, imaging networks, optical sensors, and image computing chips were briefly reviewed. Possible digital imaging network systems for the Ames Unitary Wind Tunnel were explored
Study of optical techniques for the Ames unitary wind tunnels. Part 4: Model deformation
A survey of systems capable of model deformation measurements was conducted. The survey included stereo-cameras, scanners, and digitizers. Moire, holographic, and heterodyne interferometry techniques were also looked at. Stereo-cameras with passive or active targets are currently being deployed for model deformation measurements at NASA Ames and LaRC, Boeing, and ONERA. Scanners and digitizers are widely used in robotics, motion analysis, medicine, etc., and some of the scanner and digitizers can meet the model deformation requirements. Commercial stereo-cameras, scanners, and digitizers are being improved in accuracy, reliability, and ease of operation. A number of new systems are coming onto the market
Change detection in SAR time-series based on the coefficient of variation
This paper discusses change detection in SAR time-series. Firstly, several
statistical properties of the coefficient of variation highlight its pertinence
for change detection. Then several criteria are proposed. The coefficient of
variation is suggested to detect any kind of change.
Then other criteria based on ratios of coefficients of variations are
proposed to detect long events such as construction test sites, or point-event
such as vehicles.
These detection methods are evaluated first on theoretical statistical
simulations to determine the scenarios where they can deliver the best results.
Then detection performance is assessed on real data for different types of
scenes and sensors (Sentinel-1, UAVSAR). In particular, a quantitative
evaluation is performed with a comparison of our solutions with
state-of-the-art methods
Study of optical techniques for the Ames unitary wind tunnel, part 7
A summary of optical techniques for the Ames Unitary Plan wind tunnels are discussed. Six optical techniques were studied: Schlieren, light sheet and laser vapor screen, angle of attack, model deformation, infrared imagery, and digital image processing. The study includes surveys and reviews of wind tunnel optical techniques, some conceptual designs, and recommendations for use of optical methods in the Ames Unitary Plan wind tunnels. Particular emphasis was placed on searching for systems developed for wind tunnel use and on commercial systems which could be readily adapted for wind tunnels. This final report is to summarize the major results and recommendations
Additional illustrations of NL-SAR method for resolution-preserving (Pol)(In)SAR denoising
This document provides additional information and results of the method NL-SAR described in our paper: "NL-SAR: a unified Non-Local framework for resolution-preserving (Pol)(In)SAR denoising" submitted to IEEE Trans. on Geoscience and Remote Sensing [Deledalle et al., 2013]. NL-SAR is a fully automatic method for speckle reduction that handles amplitude, polarimetric and/or interferometric SAR data. It can process single look and multi-look images. The source code of the method is freely available at: http://www.math.u-bordeaux1.fr/cdeledal/nlsar.php
Aeronautical engineering: A continuing bibliography with indexes (supplement 262)
This bibliography lists 474 reports, articles, and other documents introduced into the NASA scientific and technical information system in Jan. 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics
Study of optical techniques for the Ames unitary wind tunnel. Part 5: Infrared imagery
A survey of infrared thermography for aerodynamics was made. Particular attention was paid to boundary layer transition detection. IR thermography flow visualization of 2-D and 3-D separation was surveyed. Heat transfer measurements and surface temperature measurements were also covered. Comparisons of several commercial IR cameras were made. The use of a recently purchased IR camera in the Ames Unitary Plan Wind Tunnels was studied. Optical access for these facilities and the methods to scan typical models was investigated
Investigating Cepheid Carinae's Cycle-to-cycle Variations via Contemporaneous Velocimetry and Interferometry
Baade-Wesselink-type (BW) techniques enable geometric distance measurements
of Cepheid variable stars in the Galaxy and the Magellanic clouds. The leading
uncertainties involved concern projection factors required to translate
observed radial velocities (RVs) to pulsational velocities and recently
discovered modulated variability. We carried out an unprecedented observational
campaign involving long-baseline interferometry (VLTI/PIONIER) and spectroscopy
(Euler/Coralie) to search for modulated variability in the long-period (P
35.5 d) Cepheid Carinae. We determine highly precise angular diameters
from squared visibilities and investigate possible differences between two
consecutive maximal diameters, . We characterize the
modulated variability along the line-of-sight using 360 high-precision RVs.
Here we report tentative evidence for modulated angular variability and confirm
cycle-to-cycle differences of Carinae's RV variability. Two successive
maxima yield = 13.1 0.7 (stat.) {\mu}as for
uniform disk models and 22.5 1.4 (stat.) {\mu}as (4% of the total angular
variation) for limb-darkened models. By comparing new RVs with 2014 RVs we show
modulation to vary in strength. Barring confirmation, our results suggest the
optical continuum (traced by interferometry) to be differently affected by
modulation than gas motions (traced by spectroscopy). This implies a previously
unknown time-dependence of projection factors, which can vary by 5% between
consecutive cycles of expansion and contraction. Additional interferometric
data are required to confirm modulated angular diameter variations. By
understanding the origin of modulated variability and monitoring its long-term
behavior, we aim to improve the accuracy of BW distances and further the
understanding of stellar pulsations.Comment: Accepted for publication in MNRAS. 19 pages, 13 figures, 10 table
Aeronautical Engineering, a continuing bibliography with indexes
This bibliography lists 352 reports, articles and other documents introduced into the NASA scientific and technical information system in November 1983
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