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Results for “Comparative visualization”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Visual Acuity Using Head-fixed Displays During Passive Self and Surround Motion

The ability to read head-fixed displays on various motion platforms requires the suppression of vestibulo-ocular reflexes. This study examined dynamic visual acuity while viewing a head-fixed display during different self and surround rotation conditions. Twelve healthy subjects were asked to report the orientation of Landolt C optotypes presented on a micro-display fixed to a rotating chair at 50 cm distance. Acuity thresholds were determined by the lowest size at which the subjects correctly identified 3 of 5 optotype orientations at peak velocity. Visual acuity was compared across four different conditions, each tested at 0.05 and 0.4 Hz (peak amplitude of 57 deg/s). The four conditions included: subject rotated in semi-darkness (i.e., limited to background illumination of the display), subject stationary while visual scene rotated, subject rotated around a stationary visual background, and both subject and visual scene rotated together. Visual acuity performance was greatest when the subject rotated around a stationary visual background; i.e., when both vestibular and visual inputs provided concordant information about the motion. Visual acuity performance was most reduced when the subject and visual scene rotated together; i.e., when the visual scene provided discordant information about the motion. Ranges of 4-5 logMAR step sizes across the conditions indicated the acuity task was sufficient to discriminate visual performance levels. The background visual scene can influence the ability to read head-fixed displays during passive motion disturbances. Dynamic visual acuity using head-fixed displays can provide an operationally relevant screening tool for visual performance during exposure to novel acceleration environments.

Wood, Scott J.↗
NASA NTRS1998

Analysis of Ceramic Color by Special Reflectance

Radiometric and visual techniques are compared as quantitative methods for determining pottery color. An analysis of fifty-two prehistoric sherds selected at random from a multicomponent site indicates that there is an increase in the accuracy and efficiency in determining color using a spectroradiometer over subjective visual observations. Further, radiometric data can be transformed to CIE chromacity coordinates and Munsell color from spectral reflectance curves and analysed directly to access quantitative accuracy.

Giardino, Marco↗
NASA NTRS1987

High resolution thermal infrared mapping of Martian channels

Viking Infrared Thermal Mapper (IRTM) high resolution (2 to 5 km) data were compiled and compared to Viking Visual Imaging Subsystem (VIS) data and available 1:5M geologic maps for several Martian channels including Dao, Harmakhis, Mangala, Shalbatana, and Simud Valles in an effort to determine the surface characteristics and the processes active during and after the formation of these channels. Results show a dominance of aeolian processes active in and around the channels. These processes have left materials thick enough to mask any genuine channel deposits. Results also indicate that very comparable Martian channels and their surrounding terrain are blanketed by deposits which are homogeneous in their thermal inertia values. However, optimum IRTM data does not cover the entire Martian surface and because local deposits of high thermal inertia material may not be large enough in areal extent or may be in an unfavorable location on the planet, a high resolution data track may not always occur over these deposits. Therefore, aeolian processes may be even more active than the IRTM data tracts can always show.

Craddock, R. A.↗
NASA NTRS1997

Superimposition, symbology, visual attention, and the head-up display

In two experiments we examined a number of related factors postulated to influence head-up display (HUD) performance. We addressed the benefit of reduced scanning and the cost of increasing the number of elements in the visual field by comparing a superimposed HUD with an identical display in a head-down position in varying visibility conditions. We explored the extent to which the characteristics of HUD symbology support a division of attention by contrasting conformal symbology (which links elements of the display image to elements of the far domain) with traditional instrument landing system (ILS) symbology. Together the two experiments provide strong evidence that minimizing scanning between flight instruments and the far domain contributes substantially to the observed HUD performance advantage. Experiment 1 provides little evidence for a performance cost attributable to visual clutter. In Experiment 2 the pattern of differences in lateral tracking error between conformal and traditional ILS symbology supports the hypothesis that, to the extent that the symbology forms an object with the far domain, attention may be divided between the superimposed image and its counterpart in the far domain.

Attention↗
NASA NTRS1999

Summary of Work for Joint Research Interchanges with DARWIN Integrated Product Team 1998

The intent of Stanford University's SciVis group is to develop technologies that enabled comparative analysis and visualization techniques for simulated and experimental flow fields. These techniques would then be made available under the Joint Research Interchange for potential injection into the DARWIN Workspace Environment (DWE). In the past, we have focused on techniques that exploited feature based comparisons such as shock and vortex extractions. Our current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching and vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will briefly (1) describe current technologies in the area of comparison techniques, (2) will describe the theory of our new method and finally (3) summarize a few of the results.

Hesselink, Lambertus↗
NASA NTRS1999

Summary of Work for Joint Research Interchanges with DARWIN Integrated Product Team

The intent of Stanford University's SciVis group is to develop technologies that enabled comparative analysis and visualization techniques for simulated and experimental flow fields. These techniques would then be made available un- der the Joint Research Interchange for potential injection into the DARWIN Workspace Environment (DWE). In the past, we have focused on techniques that exploited feature based comparisons such as shock and vortex extractions. Our current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching an@ vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will briefly (1) describe current technologies in the area of comparison techniques, (2) will describe the theory of our new method and finally (3) summarize a few of the results.

Hesselink, Lambertus↗
NASA NTRS1975

Quantitative density visualization in a transonic rotor

The flow in a two foot diameter transonic rotor has been visualized using a fluorescent gas, 2, 3 butanedione, as a tracer. The technique allows the three dimensional flow to be imaged as a set of distinct planes. Quantitative static density maps can be obtained after correcting the images for distortion and nonlinearities introduced by the illumination and imaging systems. The visualized flow is compared to data taken simultaneously by high frequency pressure transducers near the rotor entrance and exit planes.

Epstein, A. H.↗
NASA NTRS1979

Experimental and theoretical investigations concerning a frequency filter behavior of the human retina regarding electric pulse currents

Investigation involving patients with injuries in the visual nervous system are discussed. This led to the identification of the epithelial ganglion of the retina as a frequency filter. Threshold curves of the injured visual organs were compared with threshold curves obtained with a control group as a basis for identification. A model which considers the epithelial ganglion as a homogeneous cell layer in which adjacent neurons interact is discussed. It is shown the behavior of the cells against alternating exciting currents can be explained.

Meier-Koll, A.↗
NASA NTRS1980

First Scientific Working Group Meeting of Airborne Doppler Lidar Wind Velocity Measurement Program, appendix J

Three projects are suggested which could be done using the Doppler lidar. The first is a cooperative effort at BAO, the purpose of which is to check out instrumentation and contribute to boundary layer investigations at BAO. The second concerns unintended weather modification. Its purpose is to detect mechanisms by which regions of industry and urbanization modify weather. The cirrus cloud study proposes to characterize cirrus clouds by their lidar signal and to compare lidar and visually observed characteristics.

Koenig, L. R.↗
NASA NTRS1981

Three-dimensional separated flows past ground vehicles

The separated flow past a thick body is calculated using a theoretical model based on a discrete wake-vortex representation. Rehbach's unsteady inviscid scheme (1977) was used in the three-dimensional analysis. The obstacle is represented by singularities, and the wake is modeled by vortex particles emitted at the separation line. Calculated results for an axisymmetric body are compared with flow visualization results.

Chometon, F.↗
NASA NTRS1981

Preliminary report on IUE spectra of the Crab Nebula

The Crab Nebula is marginally observable with the IUE. Observations of the optically brightest filamentary regions, made with IUE in August 1979, show the C IV lambda 1549, He II lambda 1640, and C III lambda 1909 emission lines. The intensities of these lines were compared with the visual wavelength data. It appears that carbon is not overabundant in the Crab; carbon/oxygen is approximately normal and oxygen is slightly scarcer than normal as a fraction of the total mass.

Davidson, K.↗
NASA NTRS1983

ANS ultraviolet observations of dwarf Cepheids

Ultraviolet observations of three dwarf Cepheids (VZ Cnc, SX Phe, and AI Vel) are presented. The UV light curves are consistent with those in the visual region. When compared to standard stars, all three dwarf Cepheids exhibit flux deficiencies at the shortest observed wavelengths. The most extreme deficiencies appear for SX Phe; these may be related to the other properties previously noted for this star, including low metallicity, high space motion, and low luminosity.

Sturch, C. R.↗
NASA NTRS1984

Dilution jets in accelerated cross flows

Results of flow visualization experiments and measurements of the temperature field produced by a single jet and a row of dilution jets issued into a reverse flow combustor are presented. The flow in such combustors is typified by transverse and longitudinal acceleration during the passage through its bending section. The flow visualization experiments are designed to examine the separate effects of longitudinal and transverse acceleration on the jet trajectory and spreading rate. A model describing a dense single jet in a lighter accelerating cross flow is developed. The model is based on integral conservation equations, including the pressure terms appropriate to accelerating flows. It uses a modified entrainment correlation obtained from previous experiments of a jet in a cross stream. The flow visualization results are compared with the model calculations in terms of trajectories and spreading rates. Each experiment is typified by a set of three parameters: momentum ratio, density ratio and the densimetric Froude number.

Lipshitz, A.↗
NASA NTRS1983

Infrared properties of extragalactic H II complexes

Infrared observations of relatively isolated giant H II complexes in the LMC and the spiral arms of M33 and M101 are discussed, and complexes which extend over several kiloparsecs near the galactic centers are examined. The 30 Doradus nebula is emphasized, showing the variation of the 50-100 micron color temperature with position in that object. Ten-micron scans through the nucleus of NGC 1097 are compared to a visual photograph, showing the enhanced infrared emission which occurs at the nucleus and at the ring of H II regions about 1 kpc from the nucleus.

Telesco, C. M.↗
NASA NTRS1985

Flow visualization in the Space Shuttle's main engine

The analysis and design of the Space Shuttle's main engine (SSME) power head involved extended finite difference computations conducted on a supercomputer. Certain problems arise, however, in connection with such a computer, and it is pointed out that the massive output from such analyses can actually inhibit insight into physical behavior. It is, therefore, also important to develop effective techniques for computer-user data transfer which match the computer's computational speed. In order to satisfy such requirements, powerful engineering workstations and three-dimensional color computer graphics codes were employed in the computational fluid dynamics (CFD) analyses of the Shuttle's engine. Consequently, the complex physical characteristics of the SSME's hot-gas manifold could be quickly visualized, interpreted, and compared with alternative designs.

Belie, G.↗
NASA NTRS1987

A comparative review of optical surface contamination assessment techniques

This paper will review the relative sensitivities and practicalities of the common surface analytical methods that are used to detect and identify unwelcome adsorbants on optical surfaces. The compared methods include visual inspection, simple reflectometry and transmissiometry, ellipsometry, infrared absorption and attenuated total reflectance spectroscopy (ATR), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and mass accretion determined by quartz crystal microbalance (QCM). The discussion is biased toward those methods that apply optical thin film analytical techniques to spacecraft optical contamination problems. Examples are cited from both ground based and in-orbit experiments.

Heaney, James B.↗