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At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Effects of prolonged weightlessness on the swimming pattern of fish aboard Skylab 3

Looping behavior of minnows aboard Skylab 3 is analyzed. Extensive looping patterns were observed at first look on the third day of weightlessness; thereafter, the frequency of the looping episodes diminished until complete adaptation on the twenty-first day, at which time the fish oriented themselves with their backs to the light. The swimming anomaly could be due to (1) absence of continuous bending of sense hairs to a certain extent by gravity, causing the fish to tilt forward in an attempt to increase leverage on the hairs - in the absence of all gravity, tilting is continued into looping (this hypothesis is supported by parabolic flight experiments with partial gravity, in which only tilting was seen); or (2) an attempt by the fish to create a gravitoinertial stimulus by 'centrifuging' its otoliths by looping.

Von Baumgarten, R. J.↗
NASA NTRS1976

Beam patterns of light-emitting diodes

IR-sensitive film, placed at various source-to-detector distances, records output beam pattern of LED. Information is then used to determine optimum position of detector surface for maximum radiation interception.

Thomas, E. F., Jr.↗
NASA NTRS1975

A method for the determination of potentially profitable service patterns for commuter air carriers

A methodology for estimating market conception was developed as a part of the short-haul air transportation program. It is based upon an analysis of actual documents which provide a record of known travel history. Applying this methodology a forecast was made of the demand for an air feeder service between Charlottesville, Virginia and Dulles International Airport. Local business travel vouchers and local travel agent records were selected to provide the documentation. The market was determined to be profitable for an 8-passenger Cessna 402B aircraft flying a 2-hour daily service pattern designed to mesh to the best extent possible with the connecting schedules at Dulles. The Charlottesville - Dulles air feeder service market conception forecast and its methodology are documented.

Ransone, R. K.↗
NASA NTRS1975

Air motion determination by tracking humidity patterns in isentropic layers

Determining air motions by tracking humidity patterns in isentropic layers was investigated. Upper-air rawinsonde data from the NSSL network and from the AVE-II pilot experiment were used to simulate temperature and humidity profile data that will eventually be available from geosynchronous satellites. Polynomial surfaces that move with time were fitted to the mixing-ratio values of the different isentropic layers. The velocity components of the polynomial surfaces are part of the coefficients that are determined in order to give an optimum fitting of the data. In the mid-troposphere, the derived humidity motions were in good agreement with the winds measured by rawinsondes so long as there were few or no clouds and the lapse rate was relatively stable. In the lower troposphere, the humidity motions were unreliable primarily because of nonadiabatic processes and unstable lapse rates. In the upper troposphere, the humidity amounts were too low to be measured with sufficient accuracy to give reliable results. However, it appears that humidity motions could be used to provide mid-tropospheric wind data over large regions of the globe.

Mancuso, R. L.↗
NASA NTRS1976

Evidence of the beam pattern concept of subsonic jet noise emission

The methods and results are described of an approach toward positively identifying the apparent location and strength of the sound source in a subsonic jet. The Green's function technique is applied to regenerate the three-dimensional distribution of the acoustic far field from measured data on a two-dimensional plane. The apparent sound-source location is also determined by using geometrical ray acoustics. The results revealed a number of features of the subsonic jet noise mechanisms; they show that the apparent sound source is highly localized within the jet flow and that the spontaneous noise emission from such a compact source volume is in the fashion of a narrow beam with random directions. These observable properties of the sound field offer the basis for a beam pattern concept of subsonic jet noise radiation. A powerful and accurate technique of aerodynamic noise measurement is verified. This technique is expected to have important applications in the development of jet noise reduction technology.

Pao, S. P.↗
NASA NTRS1976

Investigation of environmental change pattern in Japan: A study on change detection of land cover in Tokyo districts using multi-dates LANDSAT CCT

The author has identified the following significant results. The software program, which enables the geographically corrected LANDSAT digital data base, was developed. The data base could provide land use planners with land cover information and the environmental change pattern. Land cover was evaluated by the color representation for ratio of three primary components, water vegetation, and nonorganic matter. Software was also developed for the change detection within multidates LANDSAT MSS data.

Maruyasu, T.↗
NASA NTRS1975

Applications of matrix derivatives to optimization problems in statistical pattern recognition

A necessary condition for a real valued Frechet differentiable function of a vector variable have an extremum at a vector x sub 0 is that the Frechet derivative vanishes at x sub 0. A relationship between Frechet differentials and matrix derivatives was established that obtains a necessary condition on the matrix derivative at an extrema. These results are applied to various scalar functions of matrix variables which occur in statistical pattern recognition.

Morrell, J. S.↗
NASA NTRS1975

Some results on contractive mappings as related to pattern recognition

Several of the techniques used in pattern recognition are reformulated as the problem of determining fixed points of a function. If x sub 0 is a fixed point of f and if f is contractive at x sub 0, then, for any y belonging to a sufficiently small neighborhood of x sub 0 the orbit of y will converge to x sub 0. Several general results regarding contractive mappings are developed with emphasis on functions.

Brown, D. R.↗
NASA NTRS1974

Simulation techniques for estimating error in the classification of normal patterns

Methods of efficiently generating and classifying samples with specified multivariate normal distributions were discussed. Conservative confidence tables for sample sizes are given for selective sampling. Simulation results are compared with classified training data. Techniques for comparing error and separability measure for two normal patterns are investigated and used to display the relationship between the error and the Chernoff bound.

Whitsitt, S. J.↗
NASA NTRS1975

An algorithm for optimal single linear feature extraction from several Gaussian pattern classes

A computational algorithm is presented for the extraction of an optimal single linear feature from several Gaussian pattern classes. The algorithm minimizes the increase in the probability of misclassification in the transformed (feature) space. Numerical results on the application of this procedure to the remotely sensed data from the Purdue Cl flight line as well as LANDSAT data are presented. It was found that classification using the optimal single linear feature yielded a value for the probability of misclassification on the order of 30% less than that obtained by using the best single untransformed feature. Also, the optimal single linear feature gave performance results comparable to those obtained by using the two features which maximized the average divergence.

Starks, S. A.↗
NASA NTRS1976

Computation of scalar far-field patterns of large-aperture antennas

In computer programs used for evaluating the performance of high-gain antennas, efficient numerical methods for calculating the far-field patterns must be used since the majority of computer time and storage requirements may be attributed to this phase of the program. The numerical method most frequently used is the Fast Fourier Transform (FFT), which computes the far field as the Fourier transform of the field distribution in the antenna aperture. A new numerical method that in many applications is superior to the FFT in terms of reducing computer time and storage requirements is described.

Omalley, T. A.↗
NASA NTRS1976

Power conservation for reflector antennas with truncated feed patterns

Reflector-antenna calculations using idealised truncated feed patterns can lead to incorrect values of total secondary radiated power. It is demonstrated that this discrepancy is due to the presence of higher-order spherical modes incident on the reflector. When a proper spherical-wave expansion of the incident field is used, in conjunction with the physical-optics technique, to determine the scattered field, the total power of the scattered field will equal the power radiated by the feed.

Rush, W. V. T.↗
NASA NTRS1976

Wave patterns across the North Atlantic on September 28, 1974, from airborne radar imagery

Airborne coherent radar imagery taken during a cross-Atlantic flight was used to determine the two-dimensional wave pattern of waves on a path across the North Atlantic on September 28, 1974. The radar imagery was compared with ship reports and photographs taken during the part of the flight when no clouds were present. The wave images were related to the presence of two major storm areas in the North Atlantic just before flight time.

Elachi, C.↗
NASA NTRS1976

Radar imaging of ocean surface patterns

The paper presents some examples of imaging radar oceanographic observations and discusses physical phenomena on the surface that may cause the radar image. The different ocean scattering theories are briefly discussed, including the tangent plane model, the Bragg-Rice model, and the Rayleigh scattering model. All but one of the images presented were obtained with an L-band HH-polarized radar; they include deep-ocean swells, coastal swells, wave refractions, internal waves, ship wakes, abrupt transitions in open-ocean surface roughness, surface slicks, island wind shadowing, and currents. Analyses are shown to suggest that the primary source of the L-band imagery of ocean surface patterns is the variation of small-scale surface roughness and local tilt angle. It is also noted that surface irregularities behave as isotropic scatterers for a radar wavelength of 25 cm.

Brown, W. E., Jr.↗
NASA NTRS1976

Investigation of environmental change pattern in Japan

The author has identified the following significant results. A detailed land use classification for a large urban area of Tokyo was made using MSS digital data. It was found that residential, commercial, industrial, and wooded areas and grasslands can be successfully classified. A mesoscale vortex associated with large ocean current, Kuroshio, which is a rare phenomenon, was recognized visually through the analysis of MSS data. It was found that this vortex affects the effluent patterns of rivers. Lava flowing from Sakurajima Volcano was clearly classified for three major erruptions (1779, 1914, and 1946) using MSS data.

Maruyasu, T.↗
NASA NTRS1977

Investigation of environmental change pattern in Japan. Investigation of variations in the prominent oceanic current, Kuroshio

The author has identified the following significant results. Conspicuous results of composed color images were realized in the ground patterns, such as the fine meander of the Tenryu River. No significant difference was found between single band color image and multiband composed color image in the sea area. It was found that MSS was more advantageous for land than for sea; only band 4 shows dominant features in the sea.

Maruyasu, T.↗
NASA NTRS1975

System integration of pattern recognition, adaptive aided, upper limb prostheses

The requirements for successful integration of a computer aided control system for multi degree of freedom artificial arms are discussed. Specifications are established for a system which shares control between a human amputee and an automatic control subsystem. The approach integrates the following subsystems: (1) myoelectric pattern recognition, (2) adaptive computer aiding; (3) local reflex control; (4) prosthetic sensory feedback; and (5) externally energized arm with the functions of prehension, wrist rotation, elbow extension and flexion and humeral rotation.

Lyman, J.↗