Search NASA⌕ Search

SEARCH · Search NASA

Results for “Unity”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Analysis of the interaction of a weak normal shock wave with a turbulent boundary layer

The method of matched asymptotic expansions is used to analyze the interaction of a normal shock wave with an unseparated turbulent boundary layer on a flat surface at transonic speeds. The theory leads to a three-layer description of the interaction in the double limit of Reynolds number approaching infinity and Mach number approaching unity. The interaction involves an outer, inviscid rotational layer, a constant shear-stress wall layer, and a blending region between them. The pressure distribution is obtained from a numerical solution of the outer-layer equations by a mixed-flow relaxation procedure. An analytic solution for the skin friction is determined from the inner-layer equations. The significance of the mathematical model is discussed with reference to existing experimental data.

Melnik, R. E.↗
NASA NTRS1974

Albedos and densities of the inner satellites of Saturn

Broad-band radiometry at 20 microns is presented for Rhea and Dione; the measured flux densities, together with visual photometry, indicate that both satellites have geometric albedos near 0.6 and that their radii are, respectively, 800 plus or minus 125 and 575 plus or minus 100 km. The density of Dione is 1.4 plus or minus 0.6 g per cu cm; for Tethys, Enceladus, and Mimas, whose densities have not been measured, a 'photometric density' is defined from the available data, and it is shown that their densities are probably near unity. These satellites must therefore all be composed primarily of ices.

Morrison, D.↗
NASA NTRS1974

Infrared radiometry of the rings of Saturn

Broad-band radiometry with a spatial resolution of 5 sec is presented for Saturn and its rings. The brightness temperature of the B ring is 96 plus or minus 3 K at 20 microns and 91 plus or minus 3 K at 11 microns. These values constrain the bolometric Bond albedo of the ring particles to be less than 0.6, thus requiring a phase integral of less than unity. From differences in the thermal emission of the ansae, it is suggested that the leading side of the particles has higher albedo than the trailing side. A measured drop in temperature of the B ring following eclipse of 2 plus or minus 0.5 K is consistent with radii for the ring particles of 2 cm or larger.

Morrison, D.↗
NASA NTRS1974

Physics of compact nonthermal sources. II Determination of physical parameters

A set of restrictions upon the magnetic field and visible angular size of a canonical nonthermal source (one whose emission is incoherent electron synchrotron) has been obtained in another paper. The degree of electron anisotropy and magnetic field disordering were left as free parameters. In the present paper these restrictions are applied to the variable compact radio sources 3C 84, 3C 120, 3C 273, 3C 279, 3C 454.3, CTA 102, 3C 446, PKS 2134 + 004, VRO 42.22.01, and OJ 287. The theoretically derived angular sizes for these sources are in reasonable agreement with published VLBI sizes, provided that the characteristic pitch angles are not extremely small. The magnetic field strengths determined from the degree of circular polarization are generally compatible with field strengths derived from the self-absorption and synchrotron self-Compton conditions, again provided that the pitch angles are not too small. It is argued that the self-absorption optical depth cannot be much less than unity near the low-frequency turnovers; otherwise, serious discrepancies with observation result.

Jones, T. W.↗
NASA NTRS1974

Granulometric characteristics of lunar surface material from the Sea of Fertility

The particle size distributions in the 1-1000 micrometer range along the length of the core of lunar surface material returned by Luna 16 were recorded by electrical impulse as well as sieve methods. The measurements are represented in the form of cumulative functions of the logarithm of size versus the logarithm of particle number, and also as the logarithm of size versus particle mass on a probability scale. The former functions at all depths consist of the super-positioning of two straight lines with slopes from 2.10 to 4.05. The second functions are near linear, which together with the closeness of the calculated asymmetries of the distribution to zero and the nearness of the calculated excess of the distributions to unity indicate the closeness of the recorded distributions to the logarithmically normal law. This agrees with the assumption that regolith particles were formed in a process of intensive mechanical grinding.

Stakheyev, Y. I.↗
NASA NTRS1974

Nonlinear equations of motion for the elastic bending and torsion of twisted nonuniform rotor blades

The equations of motion are developed by two complementary methods, Hamilton's principle and the Newtonian method. The resulting equations are valid to second order for long, straight, slender, homogeneous, isotropic beams undergoing moderate displacements. The ordering scheme is based on the restriction that squares of the bending slopes, the torsion deformation, and the chord/radius and thickness/radius ratios are negligible with respect to unity. All remaining nonlinear terms are retained. The equations are valid for beams with mass centroid axis and area centroid (tension) axis offsets from the elastic axis, nonuniform mass and stiffness section properties, variable pretwist, and a small precone angle. The strain-displacement relations are developed from an exact transformation between the deformed and undeformed coordinate systems. These nonlinear relations form an important contribution to the final equations. Several nonlinear structural and inertial terms in the final equations are identified that can substantially influence the aeroelastic stability and response of hingeless helicopter rotor blades.

Hodges, D. H.↗
NASA NTRS1973

Evaluation of black and white microfilm system

Microfilms and processes suitable for microscopying black-and-white films from the Earth Resources Aircraft Program were selected. A further purpose was to chose duplication materials which are suitable for multiple generation copies for economical dissemination to satisfy index and reference purposes. The basic requirements are that the gamma of the negative film and the overall system gamma of the multistage duplication process should be near unity, and that there should be sufficient resolution to reproduce the major salient image features of the original 9 1/2-inch format film.

Gooding, R. A.↗
NASA NTRS1974

Physics of sub-micron cosmic dust particles

Laboratory tests with simulated micrometeoroids to measure the heat transfer coefficient are discussed. Equations for ablation path length for electrically accelerated micrometeoroids entering a gas target are developed which yield guidelines for the laboratory measurement of the heat transfer coefficient. Test results are presented for lanthanum hexaboride (LaB sub 6) microparticles in air, argon, and oxygen targets. The tests indicate the heat transfer coefficient has a value of approximately 0.9 at 30 km/sec, and that it increases to approximately unity at 50 km/sec and above. Test results extend to over 100 km/sec. Results are also given for two types of small particle detectors. A solid state capacitor type detector was tested from 0.61 km/sec to 50 km/sec. An impact ionization type detector was tested from 1.0 to 150 km/sec using LaB sub 6 microparticles.

Roy, N. L.↗
NASA NTRS1974

Cybernetic prosthesis

Design and development of a prosthetic device fitted to an above elbow amputee is reported that derives control information from the human to modulate power to an actuator to drive the substitute limb. In turn, the artificial limb generates sensory information feedback to the human nervous system and brain. This synergetic unity feeds efferent or motor control information from the human to the machine, and the machine responds, delivering afferent or sensory information back to the man.

Mann, R. W.↗
NASA NTRS1975

Insulated electrocardiographic electrodes

An integrated system is disclosed including an insulated electrode and an impedance transformer which can be assembled in a small plastic housing and used for the acquisition of electrocardiographic data. The electrode may be employed without a paste electrolyte and may be attached to the body for extended usage without producing skin reaction. The electrode comprises a thin layer of suitable nontoxic dielectric material preferably deposited by radio frequency sputtering onto a conductive substrate. The impedance transformer preferably comprises an operational amplifier having an FET input stage connected in the unity gain configuration which provides a very low lower cut-off frequency, a high input impedance with a very small input bias current, a low output impedance, and a high signal-to-noise ratio.

David, R. M.↗
NASA NTRS1975

Hypersonic research engine project. Phase 2: Preliminary report on the performance of the HRE/AIM at Mach 6

Test results of the Aerothermodynamic Integration Model are presented. A program was initiated to develop a hydrogen-fueled research-oriented scramjet for operation between Mach 3 and 8. The primary objectives were to investigate the internal aerothermodynamic characteristics of the engine, to provide realistic design parameters for future hypersonic engine development as well as to evaluate the ground test facility and testing techniques. The engine was tested at the NASA hypersonic tunnel facility with synthetic air at Mach 5, 6, and 7. The hydrogen fuel was heated up to 1500 R prior to injection to simulate a regeneratively cooled system. The engine and component performance at Mach 6 is reported. Inlet performance compared very well both with theory and with subscale model tests. Combustor efficiencies up to 95 percent were attained at an equivalence ratio of unity. Nozzle performance was lower than expected. The overall engine performance was computed using two different methods. The performance was also compared with test data from other sources.

Sun, Y. H.↗
NASA NTRS1975

Side cracked plated subject to combined direct and bending forces

The opening mode stress intensity factor and the associated crack mouth displacement are comprehensively treated using planar boundary collocation results supplemented by end point values from the literature. Data are expressed in terms of dimensionless coefficients of convenient form which are each functions of two dimensionless parameters, the relative crack length, and a load combination parameter which uniquely characterizes all possible combinations of tension or compression with bending or counterbending. Accurate interpolation expressions are provided which cover the entire ranges of both parameters. Application is limited to specimens with ratios of effective half-height to width not less than unity.

Srawley, J. E.↗
NASA NTRS1975

An investigation of turbulent transport in the extreme lower atmosphere

A model in which the Lagrangian autocorrelation is expressed by a domain integral over a set of usual Eulerian autocorrelations acquired concurrently at all points within a turbulence box is proposed along with a method for ascertaining the statistical stationarity of turbulent velocity by creating an equivalent ensemble to investigate the flow in the extreme lower atmosphere. Simultaneous measurements of turbulent velocity on a turbulence line along the wake axis were carried out utilizing a longitudinal array of five hot-wire anemometers remotely operated. The stationarity test revealed that the turbulent velocity is approximated as a realization of a weakly self-stationary random process. Based on the Lagrangian autocorrelation it is found that: (1) large diffusion time predominated; (2) ratios of Lagrangian to Eulerian time and spatial scales were smaller than unity; and, (3) short and long diffusion time scales and diffusion spatial scales were constrained within their Eulerian counterparts.

Koper, C. A., Jr.↗
NASA NTRS1974

The small-scale, quasi-periodic, disk component of solar radio radiation

Interferometric observations of the sun at wavelengths of 3.7 and 11 cm show that small-scale, quasi-periodic radio emission is coming from the sun. The periods occur in a band of periods with a midband frequency of 3.75 mHz and a bandwidth of 2.5 mHz. The peak-to-peak fluctuations in brightness temperature, lie between 4,000 and 500,000 K. The radio emission is less than about 10% linearly or circularly polarized; the angular size of the emitting regions is of the order of 10 seconds. The radio emission originates at the base of the chromosphere-corona transition region at approximately 2200 km above the level at which the optical depth at 5000 A is unity.

Lang, K. R.↗
NASA NTRS1974

O/1 D/ production in ozone photolysis near 3100 A

Relative quantum yields of O(1 D) production in ozone photolysis from 2750 to 3340 A have been determined in the gas phase at -40 C. The O(1 D) was monitored by means of its reaction with isobutane to form isobutyl alcohol. The light source was a high pressure mercury lamp combined with a monochromator, with a bandwidth of 16 A. The results show a constant O(1 D) production below 3000 A, which is taken as unity on the basis of previous work. There is a very sharp fall-off in O(1 D) production which is centered at 3080 A. At 3130 A, O(1 D) production is not greater than 0.1.

Lin, C.-L.↗
NASA NTRS1974

Solar prominences in the extreme ultraviolet as observed from the Apollo Telescope Mount

Observations of quiescent solar prominences with the Harvard College Observatory spectrometer aboard Skylab show that prominence material is optically thick in the Lyman alpha line and the Lyman continuum. The color temperature of the Lyman continuum has a mean of 6600 K and an upward gradient toward the top of the prominence. The departure coefficient of the ground state of hydrogen is found to be of the order of unity, as expected from theory. The optical depth of the C III sheath region is determined directly from the observation of the limb through the prominence and is used to infer the mean electron density and the temperature gradient of the sheath. The result implies that the sheath density is about 0.4, and the temperature gradient about 1.4 times the respective value in the C III transition zone of the quiet sun. The C III triplet-singlet ratio for the prominence is found to give a density compatible, within the uncertainty of the atomic parameters, with the density obtained from the optical depth.

Schmahl, E. J.↗
NASA NTRS1974

Nature of the Venus clouds as derived from their polarization

The linear polarization of sunlight reflected by Venus is analyzed by comparing observations with extensive multiple scattering computations. The analysis establishes that Venus is veiled by a cloud or haze layer of particles which have a narrow size distribution with a mean radius of about 1 micron. The refractive index of the particles is 1.44 at 0.55 micron wavelength with a small normal dispersion, the refractive index decreasing from the ultraviolet toward the infrared. The particles exist at a high level in the atmosphere, with the optical thickness unity occurring where the pressure is about 50 mb. The particle properties deduced from the polarization eliminate all but one of the cloud compositions which have been proposed for Venus. A concentrated solution of sulfuric acid provides good agreement with the polarization data.

Hansen, J. E.↗
NASA NTRS1975

The origin of infrared emission from the nucleus of NGC 1068

Recent infrared observational results for the nucleus of the Seyfert galaxy NGC 1068 are reviewed and analyzed in terms consistent with information available at other wavelengths. It is concluded that the infrared and optical data imply that more than 85 percent of the infrared emission at 10 microns is radiation from dust grains in the nucleus. Observed reddening of spectral lines implies geometrical optical depths at visual wavelengths of about 7-15 if the nuclear dust cloud is approximately spherically symmetric. The dust grains emitting the infrared radiation could be silicates with a 10-micron optical depth near unity, but this identification is not uniquely established. The grains are heated radiatively by an underlying source or sources of radiation also responsible for ionizing the emission-line-producing gas. The underlying source could be nonthermal, or it could be a hot plasma. Physical constraints on each of these models are derived.

Jones, T. W.↗