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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Digital processing of mesoscale analysis and space sensor data

The mesoscale analysis and space sensor (MASS) data management and analysis system on the research computer system is presented. The MASS data base management and analysis system was implemented on the research computer system which provides a wide range of capabilities for processing and displaying large volumes of conventional and satellite derived meteorological data. The research computer system consists of three primary computers (HP-1000F, Harris/6, and Perkin-Elmer 3250), each of which performs a specific function according to its unique capabilities. The overall tasks performed concerning the software, data base management and display capabilities of the research computer system in terms of providing a very effective interactive research tool for the digital processing of mesoscale analysis and space sensor data is described.

Hickey, J. S.↗
NASA NTRS1984

The Sensitivity of Solar Eigenfrequencies to the Treatment of the Equation of State

The principal uncertainties in the equation of state involve the treatment of pressure ionization, the Debye-Huckel coulomb corrections, and the treatment of many-particle interaction effects. It is found that, for the lowest degree modes (l between 0 and 3), the terms and procedures used in the equation of state which deal with these uncertainties introduce changes in the frequencies which are less than 4 micro Hz. Recently, Shibahashi, Noels and Gabriel (1983) published solar eigenfrequencies using a theory with an equation of state improved with respect to the theory used earlier by Shibahashi and Osaki (1981). Their comparison between the two sets of results suggested that uncertainties in the frequencies as large as 10 micro Hz could be caused by the equation of state. It is felt that since the entire effect of the uncertain terms is only 4 micro Hz and since the uncertainties are only a fraction of each term, the 10 micro Hz changes found by Shibahashi et al must be a consequence of differences between the earlier and later calculations in areas other than the equation of state.

Ulrich, R. K.↗
NASA NTRS1985

Ultrahigh energy gamma rays: Carriers of cosmological information

Observational data being the basis of contemporary cosmological models are not numerous: Hubble law of redshift for galaxies, element abundances, and observation of cosmic microwave background radiation (MBR). The significance of MBR discovery predicted in the Big-Band model is particularly stressed. Radio astronomical measurements give an information on MBR only near the Earth. Experimental confirmation of evolution of MBR, i.e., its probing in remote epochs, might obviously present a direct verification of the hypothesis of hot expanding Universe. The carriers of similar cosmological information should be particles which, firstly, effectively interact with MBR, and secondly, make it possible to identify unambiguously the epoch of interaction. A possibility to verify a number of cosmological hypotheses by searching the cutoffs in spectra of ultrahigh energy gamma-rays (UHEGR) from extragalactic sources is discussed.

Aharonian, F. A.↗
NASA NTRS1984

Unsolved problems in planetary ring dynamics

Voyager photographic data are used for microscopic and macroscopic analyses of the dynamics of the Saturn rings. Attention is given to particle collisions, local velocity dispersion, the particle size distribution, mechanisms governing the ring structure and interactive effects with Saturn satellite orbits. The mechanical properties and collision dynamics of the particles are discussed, along with models for perturbed and unperturbed disks. The forces involved and true scale of particle erosion are considered, as are instabilities in the rings, satellite torques, resonances, and the time scale for the evolution of the satellite orbits. Finally, the possibility that angular momentum exchanges are occurring between individual rings and satellite orbits is examined.

Borderies, N.↗
NASA NTRS1986

Fatigue-Crack-Growth Structural Analysis

Elastic and plastic deformations calculated under variety of loading conditions. Prediction of fatigue-crack-growth lives made with FatigueCrack-Growth Structural Analysis (FASTRAN) computer program. As cyclic loads are applied to initial crack configuration, FASTRAN predicts crack length and other parameters until complete break occurs. Loads are tensile or compressive and of variable or constant amplitude. FASTRAN incorporates linear-elastic fracture mechanics with modifications of load-interaction effects caused by crack closure. FASTRAN considered research tool, because of lengthy calculation times. FASTRAN written in FORTRAN IV for batch execution.

Newman, J. C., Jr.↗
NASA NTRS1985

An improved viscid/inviscid interaction procedure for transonic flow over airfoils

A new interacting boundary layer approach for computing the viscous transonic flow over airfoils is described. The theory includes a complete treatment of viscous interaction effects induced by the wake and accounts for normal pressure gradient effects across the boundary layer near trailing edges. The method is based on systematic expansions of the full Reynolds equation of turbulent flow in the limit of Reynolds numbers, Reynolds infinity. Procedures are developed for incorporating the local trailing edge solution into the numerical solution of the coupled full potential and integral boundary layer equations. Although the theory is strictly applicable to airfoils with cusped or nearly cusped trailing edges and to turbulent boundary layers that remain fully attached to the airfoil surface, the method was successfully applied to more general airfoils and to flows with small separation zones. Comparisons of theoretical solutions with wind tunnel data indicate the present method can accurately predict the section characteristics of airfoils including the absolute levels of drag.

Melnik, R. E.↗
NASA NTRS1985

Influence of load interactions on crack growth as related to state of stress and crack closure

Fatigue crack propagation (FCP) after an application of a low-high loading sequence was investigated as a function of specimen thickness and crack closure. No load interaction effects were detected for specimens in a predominant plane strain state. However, for the plane stress specimens, initially high FCP rates after transition to a higher stress intensity range were observed. The difference in observed behavior was explained by examining the effect of the resulting closure stress intensity values on the effective stress intensity range.

Telesman, J.↗
NASA NTRS1986

van der Waals force between positronium and hydrogenic atoms Finite-mass corrections

The Feshbach projection-operator formalism is used to derive the asymptotic effective interaction potential between two atoms. Beyond the usual van der Waals potential, falling like x exp -6, three x exp -8 terms are also obtained: an attractive dipole-quadrupole term (absent in the positronium-positronium case because of symmetry), a repulsive energy-dependent term, and a repulsive mass-dependent but energy-independent one. This last term was not obtained by Manson and Ritchie (1985) using an independent method.

Au, C. K.↗
NASA NTRS1986

Vibration of a large space beam under gravity effect

The structural characteristics of a large simply supported beam subjected to gravity are described. The nonlinear governing equations for both the static and the dynamic response are derived and solved analytically. The results show the feasibility of verifying the on-orbit dynamic characteristics of a large space beam by utilizing ground test data of such a structure. It is noted that the gravity effect interacts mostly with the first vibration mode. It was also found that the system of a large space beam subjected to its own weight is a hardening system. The differential equation for the asymmetric mode is a Duffing type equation. However, the governing equation for the symmetric mode has an additional quadratic term. It is this term that causes the maximum vibration amplitudes at different phases to be non-identical.

Shih, C.-F.↗
NASA NTRS1986

IUE observations of V Sagittae

Observations of the nova-like variable V Sge are discussed, and the ground-based light curve is analyzed, compensating for the component interaction effect. Low-dispersion IUE spectra indicate that interstellar reddening is smaller than suggested from visible-band observations. The UV and visible continuum are modeled by a He-rich model and by a simple accretion disk, and the UV spectrum emission lines are used to determine ionization temperatures and a lower N(e) limit. The present data are consistent with the picture of the companion to the He star being embedded in an accretion disk, with the disk being large (of dimension comparable to that of the embedding Roche lobe as a result of vigorous mass transfer) at the time of the ground-based data, and with the disk having been diminished to a radius of the order of 200 times of the neutron star, at the time of the IUE spectra.

Koch, R. H.↗
NASA NTRS1987

Integrated Analysis Capability Program

Integrated Analysis Capability (IAC) software system provides highly effective, interactive analysis tool for integrated design of large structures. Developed to serve as interface for programs from fields of structures, thermodynamics, controls, and system dynamics with executive system and data base to yield highly-efficient multidisciplinary system. Written in FORTRAN 77.

Frisch, Harold P.↗
NASA NTRS1986

The effect of Cr, Co, Al, Mo and Ta on a series of cast Ni-base superalloys on the stability of an aluminide coating during cyclic oxidation in Mach 0.3 burner rig

The influence of varying the content of Co, Cr, Mo, Ta, and Al in a series of cast Ni-based gamma/gamma'superalloys on the behavior of aluminide coatings was studied in burner rig cyclic oxidation tests at 1100 C. The alloys had nominally fixed levels of Ti, W, Cb, Zr, C, and B. The alloy compositions were based on a full 2(sup 5)-fractional statistical design supplemented by 10 star point alloys and a center point alloy. This full central composite design of 43 alloys plus two additional alloys with extreme Al levels allowed a complete second degree estimating equation to be derived from the 5-compositional variables. The weight change/time data for the coated samples fitted well to the paralinear oxidation model and enabled a modified oxidation attack parameter, K'(sub a) to be derived to rank the alloys and log K' (sub a ) to be used as the dependent variable in the estimating equation to determine the oxidation resistance of the coating as a function of the underlying alloy content. The most protective aluminide coatings are associated with the highest possible base ally contents of CR and Al and at a 4 percent Ta level. The Mo and Co effects interact but at fixed levels of 0, 5, or 10% Co. A 4% Mo level is optimum.

Zaplatynsky, I.↗
NASA NTRS1986

Development of a ROT22 - DATAMAP interface

This report (Contract NAS2-10331- Mod 10), outlines the development and validation of an interface between the three-dimensional transonic analysis program ROT22 and the Data from Aeromechanics Test and Analytics-Management and Analysis Package (DATAMAP). After development of the interface, the validation is carried out as follows. First, the DATAMAP program is used to analyze a portion of the Tip Aerodynamics and Acoustics Test (TAAT) data. Specifically, records 2872 and 2873 are analyzed at an azimuth of 90 deg, and record 2806 is analyzed at 60 deg. Trim conditions for these flight conditions are then calculated using the Bell performance prediction program ARAM45. Equivalent shaft, pitch, and twist angles are calculated from ARAM45 results and used as input to the ROT22 program. The interface uses the ROT22 results and creates DATAMAP information files from which the surface pressure contours and sectional pressure coefficients are plotted. Twist angles input to ROT22 program are then iteratively modified in the tip region until the computed pressure coefficients closely match the measurements. In all cases studied, the location of the shock is well predicted. However, the negative pressure coefficients were underpredicted. This could be accounted for by blade vortex interaction effects.

Shenoy, K. R.↗
NASA NTRS1987

Fatigue damage interaction behavior of PWA 1480

The fatigue damage interaction behavior of PWA 1480 single crystal alloy has been experimentally established for the two-level loading case in which a block of low-cycle fatigue loading is followed by high-cycle fatigue loading to failure. A relative life ratio N1/N2 (where N1 and N2 are the low- and high-cycle fatigue baseline lives, respectively) of approximately 0.002 was explored to assess the interaction behavior. The experimental results thus far show evidence of a loading order interaction effect to a similar degree of detriment as has been observed in polycrystalline materials. Current generation single crystal alloys in general, and PWA 1480 in particular, contain pores; indeed, it was observed in all cases that specimen failure initiated from pores connected with or immediately below the surface. Detailed fractographic and metallographic studies are currently being made to assess the nature of the porosity in terms of its effect on fatigue life.

Mcgaw, Michael A.↗
NASA NTRS1987

Transonic flow visualization using holographic interferometry

An account is made of some of the applications of holographic interferometry to the visualization of transonic flows. In the case of the compressor shock visualization, the method is used regularly and has moved from being a research department invention to a design test tool. With the implementation of automatic processing and simple digitization systems, holographic vibrational analysis has also moved into routine nondestructive testing. The code verification interferograms were instructive, but the main turbomachinery interest is now in 3 dimensional flows. A major data interpretation effort will be required to compute tomographically the 3 dimensional flow around the leading or the trailing edges of a rotating blade row. The bolt on approach shows the potential application to current unsteady flows of interest. In particular that of the rotor passing and vortex interaction effects is experienced by the new generation of unducted fans. The turbocharger tests presents a new area for the application of holography.

Bryanston-Cross, Peter J.↗
NASA NTRS1987

Stigmatically focusing partial pressure analyzer with dual chamber ion source

The partial pressure analyzer developed has a high absolute sensitivity and high resolution. Interaction effects, as they occur in conventional partial pressure analyzers between the heating filament for the emission of electrons and the residual gas, are suppressed by removing the heating filament from the measurement area. The electron beam is generated in an auxiliary vacuum compartment, and passes subsequently through an aperture into the ionization compartment. The probability is small, therefore, that the presence of substances produced at the heating filament by chemical reactions and thermal decompositions will have disturbing effects. The high sensitivity and resolution of the instrument are obtained with the aid of an electron path configuration of unconventional characteristics.

Rasskopf, Klaus F.↗
NASA NTRS1986

On the atomic roughness of solid-vapor interfaces - Significance of many-body interactions

Published experimental data on the atomic roughness of solid-vapor interfaces (SVIs) are compiled in a table and compared with the predictions of theoretical models based on the Bragg-Williams approximation (e.g., Jackson, 1958). Significant discrepancies are observed, and a new model employing site-dependent bond strengths based on many-body-interaction effects is developed and demonstrated. Predictions for Cu, Pb, and Zn are presented in extensive tables and graphs and characterized in detail: good agreement with experimental observations of anisotropic melting is obtained.

Chen, Jenn-Shing↗
NASA NTRS1987

Oscillator strengths for S I, S II, and S III

A series of calculations for atomic data of various sulfur and oxygen ions is examined. Recent observations of the Io plasma torus obtained with the Voyager UV Spectrometer, the IUE satellite short wavelength spectrograph, and the rocket-borne faint object telescope are discussed. The calculation of oscillator strengths for S II, the P I sequence, S I, and S III in terms of configuration interaction effects is described. The derivation of orbital wave functions is considered. The use of the close coupling method to estimate collision strengths is studied. The accuracy of these calculations depends on: (1) the number of states used in the close coupling expansion; (2) resonance contributions to the thermally averaged collision strength; and (3) the quality of the target state wave functions. Tables of the derived oscillator strengths are presented.

Ho, Y. K.↗