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Results for “NOISE ELIMINATION”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1967

Electrocardiogram preprocessing unit.

Analog circuit for presenting fixed pulse output corresponding to each cardiac cycle of given electrocardiogram and highly unresponsive to noise interference

ELECTROCARDIOGRAM↗
NASA NTRS1972

Baysian recursive image estimation.

Discussion of a statistical procedure for treatment of noise-affected images to recover unaffected images by recursive processing with noise background elimination. The feasibility of the application of a recursive linear Kalman filtering technique to image processing is demonstrated. The procedure is applicable to images which are characterized statistically by mean and correlation functions. A time invariant dynamic model is proposed to provide stationary statistics for the scanner output.

Nahi, N. E.↗
NASA NTRS1978

Sea level data and techniques for detecting vertical crustal movements

An attempt is made to survey problems, requirements, and the outlook for the future in the study of sea level time series so as to determine the relative movement of land and sea levels. The basic aim is to eliminate from the record the contributions from whatever marine dynamic phenomena respond to treatment, allowing the secular element to be identified with optimum clarity. Nevertheless the concept of sea level perturbation varies according to regional experience. The recent work of the Permanent Service for Mean Sea Level helps to eliminate geodetic noise from the series and makes it possible, perhaps, to treat the global mean sea level data bank so as to define eustatic changes in ocean volume which, in the present context, may be regarded as the final goal, allowing the identification of vertical crustal motion itself.

Lennon, G. W.↗
NASA NTRS1983

Evaluation of radiometric and geometric characteristics of LANDSAT-D imaging system

With vegetation masked and noise sources eliminated or minimized, different carbonate facies could be discriminated in a south Florida scene. Laboratory spectra of grab samples indicate that a 20% change in depth of the carbonate absorption band was detected despite the effects of atmospheric absorption. Both bright and dark hydrothermally altered volcanic rocks can be discriminated from their unaltered equivalents. A previously unrecognized altered area was identified on the basis of the TM images. The ability to map desert varnish in semi-arid terrains has economic significance as it defines areas that are less susceptible desert erosional process and suitable for construction development.

Salisbury, J. W.↗
NASA NTRS1983

Technology evaluation of man-rated acceleration test equipment for vestibular research

The considerations for eliminating acceleration noise cues in horizontal, linear, cyclic-motion sleds intended for both ground and shuttle-flight applications are addressed. the principal concerns are the acceleration transients associated with change in direction-of-motion for the carriage. The study presents a design limit for acceleration cues or transients based upon published measurements for thresholds of human perception to linear cyclic motion. The sources and levels for motion transients are presented based upon measurements obtained from existing sled systems. The approaches to a noise-free system recommends the use of air bearings for the carriage support and moving-coil linear induction motors operating at low frequency as the drive system. Metal belts running on air bearing pulleys provide an alternate approach to the driving system. The appendix presents a discussion of alternate testing techniques intended to provide preliminary type data by means of pendulums, linear motion devices and commercial air bearing tables.

Taback, I.↗
NASA NTRS1987

Sound radiation from single and annular stream nozzles, with modal decomposition of in-duct acoustic power

An experimental program was carried out to study the acoustic characteristics of single and annular stream duct-nozzle systems at various flow conditions by using a refined acoustic impulse technique. In this technique, signal synthesis and signal averaging processes are incorporated to generate a desired impulsive signal from acoustic driver(s) and to eliminate background noise (flow noise) from in-duct and far field signals, respectively. The contribution of higher order modes to incident reflected and transmitted acoustic powers is accounted for by using a modal decomposition process. The annular stream terminations were tested statically at various annular stream flow velocities with no inner stream flow. The results derived from the experiments include in-duct acoustic powers, termination reflection coefficients, transmission coefficients, far field power, and acoustic dissipation.

Salikuddin, M.↗
NASA NTRS1989

Estimation of the two-dimensional ocean current shear field with a synthetic aperture radar

A double inverse method to convert SAR data to estimates of current shear was developed theoretically. Problems of applying the technique to real SAR data were examined. The first step of the inversion process involved elimination of noise in the (x-vector, k-vector) wave spectra deduced from SAR images. The second step, estimation of current shear, required the existence of well defined swell and a favorable single of interaction between swell and ocean current. Application of the method in the Antarctic circumpolar current encountered sea conditions that both satisfied and violated these requirements. Where the wave-current geometry was favorable, realistic surface current velocity fields were obtained, suggesting the presence of a substantial mesoscale eddy. Another attempt to apply the method in the Gulf Stream produced wave spectral estimates that showed no clear peak and hence produced no current estimates.

Barnett, Tim P.↗
NASA NTRS1992

Ionospheric gravity wave measurements with the USU dynasonde

A method for the measurement of ionospheric Gravity Wave (GW) using the USU Dynasonde is outlined. This method consists of a series of individual procedures, which includes functions for data acquisition, adaptive scaling, polarization discrimination, interpolation and extrapolation, digital filtering, windowing, spectrum analysis, GW detection, and graphics display. Concepts of system theory are applied to treat the ionosphere as a system. An adaptive ionogram scaling method was developed for automatically extracting ionogram echo traces from noisy raw sounding data. The method uses the well known Least Mean Square (LMS) algorithm to form a stochastic optimal estimate of the echo trace which is then used to control a moving window. The window tracks the echo trace, simultaneously eliminating the noise and interference. Experimental results show that the proposed method functions as designed. Case studies which extract GW from ionosonde measurements were carried out using the techniques described. Geophysically significant events were detected and the resultant processed results are illustrated graphically. This method was also developed for real time implementation in mind.

Berkey, Frank T.↗