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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Component duration and relative response rates in multiple schedules.

Pigeons were trained on a multiple variable-interval 30-sec, variable interval 90-sec schedule with each component presented alternately for an equal duration. This duration of exposure was varied from 5 to 300 sec. The rate of response in the variable-interval 30-sec component relative to the rate of response in the variable-interval 90-sec component was studied. Results are plotted and discussed.

Todorov, J. C.↗
NASA NTRS1973

Self-imposed timeouts under increasing response requirements.

Three male White Carneaux pigeons were used in the investigation. None of the results obtained contradicts the interpretation of self-imposed timeouts as an escape response reinforced by the removal of unfavorable reinforcement conditions, although some details of the performances reflect either a weak control and/or operation of other controlling variables. Timeout key responding can be considered as one of several classes of behavior having a low probability of occurrence, all of which compete with the behavior maintained by positive reinforcement schedule.

Dardano, J. F.↗
NASA NTRS1974

FOD impact testing of composite fan blades

The results of impact tests on large, fiber composite fan blades for aircraft turbofan engine applications are discussed. Solid composite blades of two different sizes and designs were tested. Both graphite/epoxy and boron/epoxy were evaluated. In addition, a spar-shell blade design was tested that had a boron/epoxy shell bonded to a titanium spar. All blades were tested one at a time in a rotating arm rig to simulate engine operating conditions. Impacting media included small gravel, two inch diameter ice balls, gelatin and RTV foam-simulated birds, as well as starlings and pigeons. The results showed little difference in performance between the graphite and boron/epoxy blades. The results also indicate that composite blades may be able to tolerate ice ball and small bird impacts but need improvement to tolerate birds in the small duck and larger category.

Johns, R. H.↗
NASA NTRS1974

An atlas of volcanic ash

Volcanic ash samples collected from a variety of recent eruptions were studied, using petrography, chemical analyses, and scanning electron microscopy to characterize each ash type and to relate ash morphology to magma composition and eruption type. The ashes are best placed into two broad genetic categories: magnetic and hydrovolcanic (phreatomagmatic). Ashes from magmatic eruptions are formed when expanding gases in the magma form a froth that loses its coherence as it approaches the ground surface. During hydrovolcanic eruptions, the magma is chilled on contact with ground or surface waters, resulting in violent steam eruptions. Within these two genetic categories, ashes from different magma types can be characterized. The pigeon hole classification used here is for convenience; there are eruptions which are driven by both phreatic and magmatic gases.

Heiken, G.↗
NASA NTRS1973

Stimulus control in a two-choice discrimination procedure

Experimental investigation upon pigeons of the relation between performance during discriminative training and subsequently obtained stimulus control test results. The results obtained support the proposition that bias generated by training dependencies is a major determiner of stimulus control.

Galloway, W. D.↗
NASA NTRS1974

Response-produced timeouts under a progressive-ratio schedule with a punished reset option

An attempt is made to extend the generality of timeouts from positive reinforcement to more complex performances. Pigeons were provided with three continuously available options. Responses on one key resulted in food reinforcement under a progressive-ratio schedule, which requires a larger number of responses for successive reinforcements; responses on a second key, which were shocked, reset the progressive-ratio schedule to its first step; and responses on a third key produced a 3-min timeout. Some of these conditions have been studied previously (Dardano, 1968, 1973; Findley, 1958). Questions of general interest included the frequency and stability of response-produced timeouts, changes in the properties of the progressive-ratio performance resulting from the occurrence of timeouts, and the similarity of the relationships between timeouts and the reinforced behavior to relationships found under simpler conditions of reinforcement.

Dardano, J. F.↗
NASA NTRS1974

FOD impact testing of composite fan blades

The results of impact tests on large, fiber composite fan blades for aircraft turbofan engine applications are discussed. Solid composite blades of two different sizes and designs were tested. Both graphite/epoxy and boron/epoxy were evaluated. In addition, a spar-shell blade design was tested that had a boron/epoxy shell bonded to a titanium spar. All blades were tested one at a time in a rotating arm rig to simulate engine operating conditions. Impacting media included small gravel, two inch diameter ice balls, gelatin, and RTV foam-simulated birds, as well as starlings and pigeons. The results showed little difference in performance between the graphite and boron/epoxy blades. The results also indicate that composite blades may be able to tolerate ice ball and small bird impacts but need improvement to tolerate birds in the small duck and larger category.

Johns, R. H.↗
NASA NTRS1974

Impact testing on composite fan blades

The results of impact tests on large, fiber composite fan blades for aircraft turbofan engine applications are discussed. Solid composite blades of two different sizes and designs were tested. Both graphite/epoxy and boron/epoxy were evaluated. In addition, a spar-shell blade design was tested that had a boron/epoxy shell bonded to a titanium spar. All blades were tested one at a time in a rotating arm rig to simulate engine operating conditions. Impacting media included small gravel, two inch diameter ice balls, gelatin and RTV foam-simulated birds, as well as starlings and pigeons. The results showed little difference in performance between the graphite and boron/epoxy blades. The results also indicate that composite blades may be able to tolerate ice ball and small bird impacts but need improvement to tolerate birds in the small duck and larger category.

Johns, R. H.↗
NASA NTRS1981

Using Landsat MSS data with soils information to identify wetland habitats

A previous study showed that certain fresh water wetland vegetation types can be spectrally separated when a maximum likelihood classification procedure is applied to Landsat spectral data. However, wetland and upland types which have similar vegetative life forms (e.g., upland hardwoods and hardwood swamps) are often confused because of spectral similarity. Therefore, the current investigation attempts to differentiate similar wetland and upland types by combining Landsat multispectral scanner (MSS) data with soils information. The Pigeon River area in northern Indiana used in the earlier study was also employed in this investigation. A layered classification algorithm which combined soils and spectral data was used to generate a wetland classification. The results of the spectral/soils wetland classification are compared to the previous classification that had been based on spectral data alone. The results indicate wetland habitat mapping can be improved by combining soils and other ancillary data with Landsat spectral data.

Ernst, C. L.↗
NASA NTRS1981

Eye-head coordination during optokinetic stimulation in squirrel monkeys

Head and eye movements in the yaw plane were recorded during and after optokinetic stimulation in squirrel monkeys. 1) Phasic or tonic head deviations to the side of the ocular quick phase occurred in 94% of total recordings (n = 50) during the perstimulus period, and in 75% of recordings (n = 49) during the poststimulus period. Magnitude of mean head deviation was significantly different between perstimulus and poststimulus periods. 2) Head nystagmus associated with eye nystagmus was consistently observed in seven of nine squirrel monkeys during optokinetic stimulation. Squirrel monkeys are thereby less prone to display head nystagmus than either guinea pigs, pigeons or chickens. 3) Slow phase speeds of coupled head and eye nystagmus were subjected to statistical analysis. A highly significant negative correlation was found between slow phase head and eye speeds. The correlation coefficient was - 0.81 at 60 degrees / sec stimulus (n = 119) and -0.72 at 100 degrees / sec stimulus (n = 131). The gaze speed, calculated by summing the head and eye speeds, was 59.1 plus or minus 6.8 / sec at 60 degrees / sec and 92.2 plus or minus 11.4 at 100 degrees / sec stimulus. There was no significant difference between the gaze speed in a free head condition and the eye speed when the head was fixed.

Eye Movements↗
DOE OSTI2026

Laser–plasma amplification of an ultrabroadband laser pulse to 0.3 TW

Producing on-target laser intensities much greater than 10 23 W cm −2 with current laser technologies is a roadblock to accessing new regimes of physics such as strong-field quantum electrodynamics. Laser–plasma amplifiers show promise to realize these intensities by augmenting the final amplifier and compressor in traditional chirped-pulse-amplification architectures with a plasma-based amplification and compression stage that operates at a much higher damage threshold. Here we demonstrate amplification of an ultrabroadband (>60 nm) pulse in a laser–plasma Raman amplifier. We directly amplified seed intensities up to 3.7 × 10 15 W cm −2 and measured efficiencies up to 8.7%. Single-shot SPIDER measurements show a factor-of-2 reduction in the amplified pulse duration with final powers up to 0.3 TW, a 10× improvement over previous results. Final pulse durations of 64 fs are measured. Energy transfers greater than 220 mJ from the picosecond pump into the seed result in a 30× energy amplification of a 7.6 mJ seed. These results set the stage for a compact plasma afterburner based on Raman amplification that could extend the scientific capability of existing petawatt-class laser facilities to enable experiments at the intensity frontier.

Shaw, J. L. [Univ. of Rochester, NY (United States↗