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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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Recursive estimation of radar or radio astronomy target parameters, considering functional dependence of covariance function of received signals
Human subjects making comparisons of duration of two tones in forced choice situation for signal with same or different intensities
Optimum mean square linear interpolation for random sampling, discussing periodic and Poisson sampling
Error free recovery of signals from irregularly spaced samples in terms of completeness of sets of nonharmonic exponentials
Mechanical antenna beam switching device detects weak signals over atmospheric and equipment noise sources in microwave antennas. It periodically nutates the paraboloidal subdish in a Cassegrainian reflector system.
Lasers for wideband planetary communication, describing heterodyne receiver and transmitter designs
Influence on hits and false alarms of response and signal events on preceding trial
Asymptotic relative efficiency of mixed statistical threshold tests with Gaussian samples
Ultrasonic pulse velocity and attenuation measurement in presence of noise, using coherent detection and signal averaging
Detecting pulse signals in insulation systems from application of alternating voltage
Lateralization and detection of signals under antiphasic noise masking measured at various SNR levels
Maximum likelihood receiver /MLR/ to detect pulsed signal propagated through turbulent medium, assuming optical propagation over long path in atmosphere
Technology developed for signal and data processing was applied to diagnostic techniques in the area of phonocardiography (pcg), the graphic recording of the sounds of the heart generated by the functioning of the aortic and ventricular valves. The relatively broad bandwidth of the PCG signal (20 to 2000 Hz) was reduced to less than 100 Hz by the use of a heart sound envelope. The process involves full-wave rectification of the PCG signal, envelope detection of the rectified wave, and low pass filtering of the resultant envelope.
The probability is analyzed that intelligent civilizations capable of interstellar communication exist in the galaxy. Drake's (1960) equation for the prevalence of communicative civilization is used in the calculations, and attempts are made to place limits on the search range that must be covered to contact other civilizations, the longevity of the communicative phase of such civilizations, and the possible number of two-way exchanges between civilizations in contact with each other. The minimum estimates indicate that some 100,000 civilizations probably coexist within several tens of astronomical units of each other and that some 1,000,000 probably coexist within 10 light years of each other. Attempts to detect coherent signals characteristic of intelligent life are briefly noted, including Projects Ozma and Cyclops as well as some Soviet attempts. Recently proposed American and Soviet programs for interstellar communication are outlined.
In new tracking loop, separate phase detection algorithm is incorporated for acquisition; programmed acquisition-to-track sequence includes automatic bandwidth switching. Additionally, system has very effective phase detection signal-to-noise ratio and can operate at any rate by changing master clock frequency. All system parameters remain constant.
The focus here is on sensory adaptation, or progressively more appropriate attention, as repeated observations yield more information about a signal with an uncertain parameter. The signal was a brief sinusoid; its uncertain parameter was frequency. Detection performance is predicted from data on a signal of known and constant frequency, as a function of the number of frequencies the uncertain signal could assume. A comparison condition presented a signal that varied in a manner not permitting adaptation. Models derived from signal detection theory describe the ideal observation processes for the three signal conditions, and supply quantitative predictions of relative performances. The models are generally supported by the data.
The Imperial College hard X-ray detector which is used to make spectral measurements in the 26 keV to 1.2 MeV energy range on celestial X-ray sources from the Ariel-5 satellite is described. Details are given of the design, calibration and in-orbit performance of the detector. A modulation process is used to detect weak signals against a background and we give details of the spectrum unfolding techniques used to convert the measured spectra into corrected incident spectra.
Modified optoacoustic gas detector identifies gases by measuring pressure-induced voltage charge in electric signals. Can detect water vapor, atmospheric fluorocarbons, or certain nitrous or nitric compounds that indicate presence of explosives.