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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Flow and temperature fields following injection of a jet normal to a cross stream

The interaction of a jet entering into a freestream normal to the main flow direction has been studied with particular attention directed to visualization of the large-scale flow interactions and to measurement of the film-cooling performance. Large eddies are apparent downstream of the entering jet even at moderate blowing rate (defined as the ratio of the mass velocity of the jet to the mass velocity of the freestream). At higher blowing rate, there is only intermittent contact between the mass from the jet and the downstream wall. The film cooling downstream from a single normal jet yields a lower centerline effectiveness compared to an inclined jet through a greater lateral spreading. The greater spreading provides a more uniform effectiveness across the span of the downstream wall, in particular at large blowing rate.

Goldstein, R. J.↗
NASA NTRS1979

A theory of stationary long waves. III - Quasi-normal modes in a singular waveguide

The present paper deals with the fundamental issue of whether one can treat waves as normal modes when critical surface, where the phase speed of the wave matches the zonal wind speed, are present. In particular the question of whether a Rossby critical level (such as the zero-wind line for stationary waves) is absorbing or reflecting is raised and subsequently addressed. It is found that the critical level is never totally absorbing; Rossby waves are partially reflected even if the critical layer is dominated by dissipative processes. The relevance of nonlinearity in planetary-scale Rossby wave critical layers is also discussed and it is found to be the dominant mechanism. With the relative magnitudes of nonlinearity versus viscosity relevant to the earth's atmosphere it is found that the steady-state critical level should be almost perfectly reflecting to incident Rossby waves. Consequently, normal-mode solutions can be found; the quantization condition for these waves is also derived.

Tung, K. K.↗
NASA NTRS1979

Radiographic Comparison of Human Lung Shape During Normal Gravity and Weightlessness

Chest radiographs in five seated normal volunteers at 1 G and 0 G were made with a view toward comparing human lung shape during normal gravity and weightlessness. Lung shape was assessed by measuring lung heights and widths in upper, middle and lower lung regions. No significant differences were found between any of the 1-G and 0-G measurements, although there was a slight tendency for the lung to become shorter and wider at 0 G. The evidence that gravity causes regional differences in ventilation by direct action on the lung is consistent with the theoretical analysis of West and Matthews (1972).

Michels, D. B.↗
NASA NTRS1980

Bivariate normal, conditional and rectangular probabilities: A computer program with applications

Some results for the bivariate normal distribution analysis are presented. Computer programs for conditional normal probabilities, marginal probabilities, as well as joint probabilities for rectangular regions are given: routines for computing fractile points and distribution functions are also presented. Some examples from a closed circuit television experiment are included.

Swaroop, R.↗
NASA NTRS1980

Normal and shear impact of layered composite with a crack - Dynamic stress intensification

The dynamic response of a layered composite under normal and shear impact is analyzed by assuming that the composite contains an initial flaw in the matrix material. One of the objectives was to develop an analytical method for determining dynamic stress solutions which should lead to a numerical method which utilizes Fourier transform for the space variable and Laplace transform for the time variable. The time-dependent angle loading is separated into two parts: a symmetric and a skew-symmetric with reference to the crack plane. By superposition, the transient boundary conditions consist of applying normal and shear tractions to a crack embedded in a layered composite; one phase of the composite could represent the fiber while the other could be the matrix. Mathematically, these conditions reduce the problem to a system of dual integral equations solved in the transform plane for the transform of the dynamic stress-intensity factor.

Sih, G. C.↗
NASA NTRS1980

Characterization of renal response to prolonged immersion in normal man

?jDuring the initial phase of space flight, there is a translocation of fluid from the lower parts of the body to the central vascular compartment with a resultant natriuresis, diuresis, and weight loss. Because water immersion is regarded as an appropriate model for studying the redistribution of fluid that occurs in weightlessness, an immersion study of relatively prolonged duration was carried out in order to characterize the temporal profile of the renal adaptation to central hypervolemia. Twelve normal male subjects underwent an immersion study of 8-h duration in the sodium-replete state. Immersion resulted in marked natriuresis and diuresis which were sustained throughout the immersion period. The failure of that natriuresis and diuresis of immersion to abate or cease despite marked extracellular fluid volume contraction as evidenced by a mean weight loss of -2.2 + or - 0.3 kg suggests that central blood volume was not restored to normal and that some degree of central hypervolemia probably persisted.

Epstein, M.↗
NASA NTRS1980

On the existence, uniqueness, and asymptotic normality of a consistent solution of the likelihood equations for nonidentically distributed observations: Applications to missing data problems

A general theorem is given which establishes the existence and uniqueness of a consistent solution of the likelihood equations given a sequence of independent random vectors whose distributions are not identical but have the same parameter set. In addition, it is shown that the consistent solution is a MLE and that it is asymptotically normal and efficient. Two applications are discussed: one in which independent observations of a normal random vector have missing components, and the other in which the parameters in a mixture from an exponential family are estimated using independent homogeneous sample blocks of different sizes.

Peters, C.↗
NASA NTRS1981

Combustion of solid carbon rods in zero and normal gravity

In order to investigate the mechanism of carbon combustion and to assess the importance of gravitational induced convection on the process, zero and normal gravity experiments were conducted in which spectroscopic carbon rods were resistance ignitied and burned in dry oxygen environments. In the zero-gravity drop tower tests, a blue flame surrounded the rod, showing that a gas phase reaction in which carbon monoxide was oxidized to carbon dioxide was taking place. The ratio of flame diameter to rod diameter was obtained as a function of time. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter. In the normal gravity tests, direct mass spectrometric sampling was used to measure gas phase concentrations. The gas sampling probe was positioned near the circumference of a horizontally mounted 0.615 cm diameter carbon rod, either at the top or at angles of 45 deg to 90 deg from the top, and yielded concentration profiles of CO2, CO, and O2 as a function of distance from the surface. The mechanism controlling the combustion process was found to change from chemical process control at the 90 deg and 45 deg probe positions to mass transfer control at the 0 deg probe position at the top of the rod. Under the experimental conditions used, carbon combustion was characterized by two surface reactions, 2C + O2 yields 2CO and CO2 + C yields 2CO, and a gas phase reaction, 2CO + O2 yields 2CO2.

Spuckler, C. M.↗
NASA NTRS1981

Principal normal curvature of surfaces

Certain principal normal curvatures of differential geometry were developed for use in curvature matrices associated with the asymptotic solution of electromagnetic diffraction problems. The effort is directed toward microwave antenna simulations and high speed digital computer analysis of radiometric instruments used to obtain soil moisture, sea state, salinity and temperature data. It is shown that the methods used to develop the principal normal curvatures for paraboloid, hyperboloid, ellipsoid, sphere, and cone can be applied to other radiometer geometries such as the parabolic torus, even though the surface parameterizations are different. It is concluded that deployable offset geometries, distorted by rotational forces and solar loads may be analyzed by similar means given a suitable surface description.

Schmidt, R. F.↗
NASA NTRS1981

Ubiquitous isotopic anomalies in Ti from normal Allende inclusions

A novel technique for the high-precision isotopic analysis of titanium was applied to three terrestrial rocks and coarse- and fine-grained Allende inclusions. Repeated analyses of the three terrestrial rocks gave excellent agreement with a Ti metal standard. All seven Allende inclusions were previously determined to contain isotopically normal Nd and/or Sm, indicating that none belongs to a small group of peculiar intrusions. The discovery of widespread Ti isotopic anomalies in normal Allende inclusions establishes Ti as the first non-noble gas element studied since oxygen to show such isotopic heterogeneity. A survey of nucleosynthetic origins of Ti isotopes suggests that the dominant Ti-50 excesses in these inclusions are due to the relative enrichment of isotopes synthesized during hydrostatic burning in, or near, the core of a massive star.

Niemeyer, S.↗
NASA NTRS1981

Rossby normal modes in nonuniform background configurations. I Simple fields. II - Equinox and solstice conditions

An investigation is conducted regarding the influence of mean field variations on the realization of planetary normal modes, taking into account the mode response and structure in the presence of simple background nonuniformities. It is found that mean field variations have the combined effect of depressing, shifting, and broadening the characteristic response of Rossby normal modes. While nonuniformities in both the mean wind and temperature fields contribute to the reduction in peak response, the former are primarily responsible for translation and spectral broadening. An investigation is conducted to determine which modes may be realized in actual atmospheric configurations and which may be identified. For both the equinox and solstice configurations, response peaks corresponding to all of the first four modes of wavenumbers 1, 2, and 3 are readily visible above the noise.

Salby, M. L.↗
NASA NTRS1982

Imaging performance of a normal incidence soft X-ray telescope

Measurements are presented of the imaging performance of a normal incidence spherical soft X-ray mirror at BK-alpha (67.6 A). The reflector was a 124-layer coating consisting of alternating Re-W alloy and C layers with a protective C overcoat 34 A thick deposited on a Zerodur substrate. Measurements made at an angle of 1.5 deg off axis with the prototype of the Einstein Observatory high resolution imager reveal the resolution of the mirror to be about 1 arcsec FWHM, with 50% of the reflected power within the detector field of 512 arcsec contained within a diameter of 5 arcsec. The data demonstrate the practicality and potential good performance of normal-incidence soft X-ray optics, and show that the scattering performances of such devices may be as good or better than the best grazing incidence devices.

Henry, J. P.↗
NASA NTRS1982

Utilization of normal mode initial conditions for detecting errors in the dynamics part of primitive equation global models

When a global atmospheric basic state has constant angular velocity and its temperature varies with altitude only, there exist normal mode solutions to the linearized global primitive equations. The use of these normal modes, which have known behavior in time, is superior to the use of the Rossby-Haurwitz wave as initial conditions for detecting errors in the dynamics part of primitive equation global models. With these initial conditions, integration through only one time step is sufficient to detect many formulation and coding errors. Other tests are still required for detecting problems of nonlinear instability and conservation of integral properties, however.

Chao, W. C.↗
NASA NTRS1981

Studies of planning behavior of aircraft pilots in normal, abnormal, and emergency situations

A methodology for the study of human planning behavior in complex dynamic systems is presented and applied to the study of aircraft pilot behavior in normal, abnormal and emergency situations. The method measures the depth of planning, that is the level of detail employed with respect to a specific task, according to responses to a verbal questionnaire, and compares planning depth with variables relating to time, task criticality and the probability of increased task difficulty. In two series of experiments, depth of planning was measured on a five- or ten-point scale during various phases of flight in a HFB-320 simulator under normal flight conditions, abnormal scenarios involving temporary runway closure due to snow removal or temporary CAT-III conditions due to a dense fog, and emergency scenarios involving engine shut-down or hydraulic pressure loss. Results reveal a dichotomy between event-driven and time-driven planning, different effects of automation in abnormal and emergency scenarios and a low correlation between depth of planning and workload or flight performance.

Johannsen, G.↗
NASA NTRS1982

Tangential blowing for control of strong normal shock - Boundary layer interactions on inlet ramps

The use of tangential blowing from a row of holes in an aft facing step is found to provide good control of the ramp boundary layer, normal shock interaction on a fixed geometry inlet over a wide range of inlet mass flow ratios. Ramp Mach numbers of 1.36 and 1.96 are investigated. The blowing geometry is found to have a significant effect on system performance at the highest Mach number. The use of high-temperature air in the blowing system, however, has only a slight effect on performance. The required blowing rates are significantly high for the most severe test conditions. In addition, the required blowing coefficient is found to be proportional to the normal shock pressure rise.

Schwendemann, M. F.↗
NASA NTRS1982

Stationary state model for normal metal tunnel junction phenomena

A model applicable to normal metal tunnel junctions is presented. This model, referred to herein as the stationary state model, is an extension of the extended basis function theory of Kleinman and Duke (1972). Under the assumption that elastic tunneling is the dominant transport mechanism under static bias, the theory has been extended to include the case where there is an ac component of bias potential, and the fluctuation spectrum has been derived. In this approach structure eigenstates are used as the basis, allowing observables to be evaluated without recourse to the perturbation theory inherent in the transfer Hamiltonian model. Comparison is made to the appropriate results of the first order transfer Hamiltonian model, and it is found that there is close but not always exact agreement to lowest order in the tunneling exponential. The stationary state model should be accurate with large barrier transmission, as it includes all orders of the tunneling exponential. The model as presented here should be applicable to normal metal tunnel junctions, where elastic tunneling is the dominant transport mechanism (under static bias), up to infrared excitation frequencies.

Whiteley, S. R.↗
NASA NTRS1982

Water Raman normalization of airborne laser fluorosensor measurements - A computer model study

The technique for normalizing airborne lidar measurements of chlorophyll fluoresence by the water Raman scattering signal is investigated for laser-excitation wavelengths of 480 and 532 nm using a semianalytic Monte Carlo methodology (SALMON). The signal-integration depth for chlorophyll fluorescence Z(90,F), is found to be insensitive to excitation wavelength and ranges from a maximum of 4.5 m in clearest waters to less than 1 m at a chlorophyll concentration of 20 microgram/liter. For excitation at 532 nm, the signal-integration depth for Raman scattering, Z(90,R), is comparable to Z(90,F). For excitation at 480 nm, Z(90,R) is four times as large as Z(90,F) in clearest waters but nearly equivalent at chlorophyll concentrations greater than 2-3 microgram/liter. Absolute signal levels are stronger with excitation at 480 nm than with excitation at 532 nm, but this advantage must be weighed against potential ambiguities resulting from different integration depths for the fluorescence and Raman scattering signals in clearer waters. To the precision of the simulations, Raman normalization produces effectively linear response to chlorophyll concentration for both excitation wavelengths.

Poole, L. R.↗