Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Localization”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Intermediate-velocity gas in the local interstellar medium

Scans of interstellar ultraviolet absorption lines of N I, N II, and Si III for 17 stars are combined with previously published data for 30 stars. The extremal velocities at which detectable absorption occurs are tabulated, and it is shown that these are correlated for the three species. The data suggest that intermediate-velocity gas (20 to 60 km/s), best known from Na I and Ca II absorption, contains both neutral and ionized hydrogen. Features characteristic of intermediate-velocity isothermal shocks (greater than 60 km/s) are conspicuously rare. The intermediate-velocity gas may be in the form of clouds containing both H I and H II regions or of radiative shocks propagating in the interstellar medium; in the latter case the gas should be detectable in H-alpha emission.

Cowie, L. L.↗
NASA NTRS1978

The localized origin of equatorial F region irregularity patches

An intensive study of nighttime irregularities of electron density in the equatorial ionosphere was performed in October 1976 by making 50-MHz radar backscatter measurements at Jicamarca, Peru, and scintillation measurements of 249-MHz transmissions from Les 9 at two ground stations (Ancon and Huancayo, both in Peru) as well as by aircraft flying in the vicinity of the stations. The 137-MHz scintillations from the orbiting Wideband satellite were also recorded at Huancayo. The results of such measurements made on October 16-17, 1976, are discussed in this report. We find that on this particular night a large-scale irregularity patch evolved first in the west, as was detected by the radar at Jicamarca, and drifted eastward to cause successive onsets of scintillation activity on propagation paths from Ancon and Huancayo. The observations indicate the east-west dimension of the large-scale structure to be 400 km drifting eastward at a speed of approximately 100 m/s, having a lifetime of several hours, and containing a hierarchy of irregularity scale sizes in the range of kilometers to meters causing both scintillations at 249 MHz and radar backscatter at 50 MHz.

Aarons, J.↗
NASA NTRS1977

A multiscale numerical study into the cascade of kinetic energy leading to severe local storms

The cascade of kinetic energy from macro- through mesoscales is studied on the basis of a nested grid system used to solve a set of nonlinear differential equations. The kinetic energy cascade and the concentration of vorticity through the hydrodynamic spectrum provide a means for predicting the location and intensity of severe weather from large-scale data sets. A mechanism described by the surface pressure tendency equation proves to be important in explaining how initial middle-tropospheric mass-momentum imbalances alter the low-level pressure field.

Paine, D. A.↗
NASA NTRS1975

The effect of local magnetic fields on the lunar photoelectron layer while the moon is in the plasma sheet

Data from the Charged Particle Lunar Environment Experiment (CPLEE), at the Apollo 14 site, are used to investigate the interactive properties of the plasma sheet and the lunar photoelectron layer. It is shown that the predictions of the Guernsey-Fu model are compatible with SIDE but not CPLEE observations. The apparent contradiction is resolved by fitting the remanent magnetic field to that of a dipole buried about 1.1 km beneath the surface. In this case a charge separation layer must form above the instrument due to the different rigidities of plasma sheet electrons and protons. The qualitative properties of the charge separation layer needed to reconcile CPLEE and SIDE observations are presented.

Burke, W. J.↗
NASA NTRS1978

A method for localizing wing flow separation at stall to alleviate spin entry tendencies

A wing leading-edge modification has been developed, applicable at present to single-engine light aircraft, which produces stabilizing vortices at stall and beyond. These vortices have the effect of fixing the stall pattern of the wing such that the various portions of the wing upper surface stall nearly symmetrically. The lift coefficient produced is essentially constant to very high angles of attack above the stall angle of the unmodified wing. It is hypothesized that these characteristics will help prevent inadvertent spin entry after a stall. Results are presented from recent large-scale wind-tunnel tests of a complete light aircraft, both with and without the modification.

Feistel, T. W.↗
NASA NTRS1978

Optical detection of local interstellar particles during an out-of-ecliptic mission

A proposed NASA/ESA 'out of ecliptic' mission for placing limits on the brightness of the interstellar (IS) relative to the interplanetary (IP) component of zodiacal light is discussed. The brightness integral used to estimate the monochromatic is introduced, and it is explained that, although the interstellar contribution is below the limit of detectability for earth-based measurements, sunwards viewing from a spacecraft located at a distance of 1 AU would be able to detect the IS component. The color difference between the IS and IP components is considered in an analysis of the upper limit of IS component detectability.

Greenberg, J. M.↗
NASA NTRS1979

Time-dependent local density measurements in unsteady flows

A laser-induced fluorescence technique for measuring the relative time-dependent density fluctuations in unsteady or turbulent flows is demonstrated. Using a 1.5-W continuous-wave Kr(+) laser, measurements have been obtained in 0.1-mm-diameter by 1-mm-long sampling volumes in a Mach 3 flow of N2 seeded with biacetyl vapor. A signal amplitude resolution of 2% was achieved for a detection frequency bandwidth of 10 kHz. The measurement uncertainty was found to be dominated by noise behaving as photon statistical noise. The practical limits of signal-to-noise ratios have been characterized for a wide range of detection frequency bandwidths that encompasses those of interest in supersonic turbulence measurements.

Mckenzie, R. L.↗
NASA NTRS1979

An assessment of local risk

A status report is presented on the assessment of the risk at Washington National Airport and the surrounding Washington, D.C. area associated with commercial operations of aircraft with graphite fiber composite in their structures. The presentation is outlined as follows: (1) overall strategy; (2) need for individual airport results; (3) airport-metro area model - submodels, method, assumptions and data; and (4) preliminary results for National Airport - D.C. area.

Pocinki, L. S.↗
NASA NTRS1979

Interference effects of aircraft components on the local blade angle of attack of a wing-mounted propeller

The aerodynamic interference effects on a propeller operating in the presence of different wing-body-nacelle combinations was studied. The unsteady blade angle of attack variation with azimuth angle by varying the pitch and yaw of the nacelle was minimized. Results indicate for the particular configuration of interest the minimum blade angle of attack variation occurred with the nacelle pitched downward 4.5 deg and yawed inward 3.0 deg.

Mendoza, J. P.↗
NASA NTRS1979

Operator performance and localized muscle fatigue in a simulated space vehicle control task

Fourier transforms in a special purpose computer were utilized to obtain power spectral density functions from electromyograms of the biceps brachii, triceps brachii, brachioradialis, flexor carpi ulnaris, brachialis, and pronator teres in eight subjects performing isometric tracking tasks in two directions utilizing a prototype spacecraft rotational hand controller. Analysis of these spectra in general purpose computers aided in defining muscles involved in performing the task, and yielded a derived measure potentially useful in predicting task termination. The triceps was the only muscle to show significant differences in all possible tests for simple effects in both tasks and, overall, was the most consistently involved of the six muscles. The total power monitored for triceps, biceps, and brachialis dropped to minimal levels across all subjects earlier than for other muscles. However, smaller variances existed for the biceps, brachioradialis, brachialis, and flexor carpi ulnaris muscles and could provide longer predictive times due to smaller standard deviations for a greater population range.

Lewis, J. L., Jr.↗
NASA NTRS1979

Summary of the NASA/MSFC FY-79 Severe Storm and Local Weather research review

Significant acomplishments, current focus of work, plans for FY-80, and recommendations for new research are outlined for 36 research projects proposed for technical monitoring by the Atmospheric Sciences Division at Marshall Space Flight Center. Topics of the investigations, which were reviewed at a two-day meeting, relate to cloud physics, atmospheric electricity, and mesoscale/storm dynamics.

Source record↗
NASA NTRS1978

Measuring software development characteristics in the local environment

In a brief evaluation of software-related considerations, it is found that suitable approaches for software development depend to a large degree on the characteristics of the particular project involved. An analysis is conducted of development problems in an environment in which ground support software is produced for spacecraft control. The amount of work involved is in the range from 6 to 10 man-years. Attention is given to a general project summary, a programmer/analyst survey, a component summary, a component status report, a resource summary, a change report, a computer program run analysis, aspects of data collection on a smaller scale, progress forecasting, problems of overhead, and error analysis.

Basili, V. R.↗
NASA NTRS1979

Effects of aeration on formation and localization of the acetyl coenzyme A synthetases of Saccharomyces cerevisiae

Previous studies on the yeast Saccharomyces cerevisiae have shown that two different forms of the enzyme acetyl coenzyme A synthetase (ACS) are present, depending on the conditions under which the cells are grown. The paper evaluates the usefulness of a method designed to assay both synthetases simultaneously in yeast homogenates. The data presented confirm the possibility of simultaneous detection and estimation of the amount of both ACSs of S. cerevisiae in crude homogenates of this strain, making possible the study of physiological factors involved in the formation of these isoenzymes. One important factor for specifying which of the two enzymes is found in these yeast cells is the presence or absence of oxygen in their environment. Aeration not only affects the ratio of the two ACSs but also appears to affect the cellular distribution of these enzymes. Most of the data presented suggest the possibility that the nonaerobic ACS may serve as a precursor to the aerobic form.

Klein, H. P.↗
NASA NTRS1979

Changes in apparent body orientation and sensory localization induced by vibration of postural muscles - Vibratory myesthetic illusions

Human experiments are carried out which support the observation of Goodwin (1973) and Goodwin et al. (1972) that vibration of skeletal muscles can elicit illusory limb motion. These experiments extend the class of possible myesthetic illusions by showing that vibration of the appropriate muscles can produce illusory body motion in nearly any desired direction. Such illusory changes in posture occur only when visual information about body orientation is absent; these changes in apparent posture are sometimes accompanied by a slow-phase nystagmus that compensates for the direction of apparent body motion. During illusory body motion a stationary target light that is fixated will appear to move with the body at the same apparent velocity. However, this pattern of apparent body motion and conjoint visual - defined as propriogyral illusion - is suppressed if the subject is in a fully illuminated environment providing cues about true body orientation. Persuasive evidence is thus provided for the contribution of both muscle afferent and touch-pressure information to the supraspinal mechanisms that determine apparent orientation on the basis of ongoing patterns of interoceptive and exteroceptive activity.

Lackner, J. R.↗
NASA NTRS1979

Time-dependent local density measurements in unsteady flows

A laser-induced fluorescence technique for measuring the relative time-dependent density fluctuations in unsteady or turbulent flows is demonstrated. Using a 1.5-W continuous-wave Kr(+) laser, measurements have been obtained in 0.1-mm diameter by 1-mm-long sampling volumes in a Mach 3 flow of N2 seeded with biacetyl vapor. A signal amplitude resolution of 2% was achieved for a detection frequency bandwidth of 10 kHz. The measurement uncertainty was found to be dominated by noise behaving as photon statistical noise. The practical limits of signal-to-noise ratios have been characterized for a wide range of detection frequency bandwidths that encompasses those of interest in supersonic turbulence measurements.

Mckenzie, R. L.↗
NASA NTRS1979

Optimal local control of flexible structures

The steady state solution of the linear quadratic optimal control problem with the constraint that only partial state information is available for feedback is derived. This development results in a systematic and computationally efficient approach for reducing the complexity of the control law for high order systems. Numerical examples and performance evaluation of (1) a simple fourth order system, and (2) a free-free flexible beam, are included.

Schaechter, D. B.↗