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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Tensile strength of composite sheets with unidirectional stringers and crack-like damage: A brief report

The residual strength of composite sheets with bonded composite stringers loaded in tension was determined. The results are summarized. About 50 graphite/epoxy composite panels with crack-like slots were monotonically loaded in tension to failure. Both sheet layup and stringer configuration were varied. The composite panels have considerable damage tolerance. The stringers arrested cracks that ran from the crack-like slots, and the residual strengths were considerably greater than those of unstiffened composite sheets. A stress-intensity factor analysis was developed to predict the failing strains of the stiffened panels. Using the analysis, a single design curve was produced for composite sheets with bonded stringers of any configuration.

Poe, C. C., Jr.↗
NASA NTRS1985

Impact of Thematic Mapper Sensor Characteristics on Classification Accuracy

A fixed effect, three factor (two levels per factor) analysis of variance was used to quantitatively assess the significance of the improved spectral, spatial and radiometric resolution capabilities of the LANDSAT-4 thematic mapper sensor relative to the familiar MSS sensor. TM data acquired over the Washington, D.C. area were progressively degraded in spectral, spatial and radiometric characteristics to simulate the MSS, and classification accuracies were derived in a consistent manner for all eight treatments in the ANOVA design. Statistical testing of the significance of differences in classification accuracies between treatments indicated that the increased number of spectral bands and the improved quantization capabilities afforded by the TM sensor design would lead to significant improvements in classification accuracies attainable relative to MSS. In contrast, however, the improved spatial resolution provided by the TM sensor did not enhance classification accuracy. This latter result was felt to be more a function of the type of classification algorithms available.

Williams, D. L.↗
NASA NTRS1985

H-chondrites - Trace element clues to their origin

RNAA is used to determine the abundances of 20 trace elements in four H4, two H3, two H5, and two H6 chondrites from the British Museum, as a contribution to a multiple-method study of these objects. The results are presented in tables and graphs and analyzed in terms of the inhomogeneity of the parent bodies and the depletion of volatiles in the higher petrologic types. Features observed include siderophile depletion in H3 chondrites; systematic variation of siderophile abundance pattern with petrologic type; volatile depletion as a primary feature; mineralogy consistent with accretion at 420-500 K; and the factor-analysis groupings siderophiles (Os, Re, Ir, Ni, Pd, Au, and Ge), volatiles (Ag, Br, In, Cd, Bi, and Tl), and alkalis (Rb and Cs).

Morgan, J. W.↗
NASA NTRS1986

Aircrew coordination and decisionmaking: Peer ratings of video tapes made during a full mission simulation

Six professionally active, retired captains rated the coordination and decisionmaking performances of sixteen aircrews while viewing videotapes of a simulated commercial air transport operation. The scenario featured a required diversion and a probable minimum fuel situation. Seven point Likert-type scales were used in rating variables on the basis of a model of crew coordination and decisionmaking. The variables were based on concepts of, for example, decision difficulty, efficiency, and outcome quality; and leader-subordin ate concepts such as person and task-oriented leader behavior, and competency motivation of subordinate crewmembers. Five-front-end variables of the model were in turn dependent variables for a hierarchical regression procedure. The variance in safety performance was explained 46%, by decision efficiency, command reversal, and decision quality. The variance of decision quality, an alternative substantive dependent variable to safety performance, was explained 60% by decision efficiency and the captain's quality of within-crew communications. The variance of decision efficiency, crew coordination, and command reversal were in turn explained 78%, 80%, and 60% by small numbers of preceding independent variables. A principle component, varimax factor analysis supported the model structure suggested by regression analyses.

Murphy, M. R.↗
NASA NTRS1985

Growth and differentiation of mammalian embryonic tissues exposed to hypergravity in vivo and in vitro

Decreased cartilage areas in embryonic limbs developing under excess g in vitro, is reported, as well as delayed skeletal development in embryos and fetuses exposed to excess g in utero. 12.5-day mouse limb buds were cultured at 2.6 g, and fixed at two days and six days of culture. In vivo experiments used alizarin-stained 18-day fetuses exposed to 2.3 g. In all studies, cartilage areas were determined using a digitized tablet. Form factor analysis determined that the main effect of in vitro centrifugation was a reduction in length of the limb elements, probably due to the precocious chondrogenesis seen in the upper regions of centrifuged limbs. Similar reductions in length of ossified areas was seen in the in utero studies.

Duke, J.↗
NASA NTRS1986

Selective factors in sun-weather research

Research on the correlations between solar wind/IMF disturbances and subsequent winter troposphere vorticity changes (denoted SV) are reviewed to investigate sun-weather relationships. Uncertainties in the research attempting to link short-term solar variations and associated changes in the lower atmosphere are discussed, and it is noted that such analyses have generally not addressed either the choice of parameters or the selective factors involved in the physical relationships existing between parameters. It is suggested that the identification of a viable mechanism scenario would require a detailed multiparameter selective factor analysis, extending to the investigation of the atmospheric data as well as the solar wind/IMF parameters.

Taylor, H. A., Jr.↗
NASA NTRS1987

Making it without losing it: Type A, achievement motivation, and scientific attainment revisited

In a study by Matthews et al. (1980), responses by academic psychologists to the Jenkins Activity Survey for Health Prediction, a measure of the Type A construct, were found to be significantly, positively correlated with two measures of attainment, citations by others to published work and number of publications. In the present study, JAS responses from the Matthews et al. sample were subjected to a factor analysis with oblique rotation and two new subscales were developed on the basis of this analysis. The first, Achievement Strivings (AS) was found to be significantly correlated with both the publication and citation measures. The second scale, Impatience and Irritability (I/I), was uncorrelated with the achievement criteria. Data from other samples indicate that I/I is related to a number of health symptoms. The results suggest that the current formulation of the Type A construct may contain two components, one associated with positive achievement and the other with poor health.

Helmreich, Robert L.↗
NASA NTRS1987

Mixing levels, the Apennine Front soil component, and compositional trends in the Apollo 15 soils

New compositional data (by INAA) for 29 samples of Apollo 15 soil fractions are presented along with data for six depth intervals of the bottom half of the double drive tube at station 2 on the Apennine Front. The compositional trends in the Apollo 15 soils are discussed in terms of four techniques used to determine the important components of the regolith: graphical techniques, factor analysis, chemical analysis of individual soil particles, and mixing models. The concept of 'mixing levels' is introduced, which states that a sample of lunar regolith can be considered as a mixture on several different compositional levels (I, igneous rock types; II, local rock types; III, soils), and it is shown that most attempts at modeling lunar soils as mixtures have been directed at level II. It is argued that only four components are required to account for the variation in concentrations of lithophile elements in the Apollo 15 samples: mare basalt, KREEP basalt, green glass, and Apennine front soil (best represented by the station 2 samples).

Korotev, Randy L.↗
NASA NTRS1988

Human workload in aviation

The application of human-factors analysis techniques to the evaluation of aircraft-crew workloads is discussed in an introductory overview. Consideration is given to the importance of workload for safety, crew size, automation, and certification; the definition and measurement of workload, physical vs mental workloads, subjective ratings, secondary tasks, biocybernetic measures, and attention and workload. Recent studies of pilot and ATC workloads are reviewed, and typical data are presented in graphs. Future trends are discussed, and it is predicted that increased cockpit automation will eventually require new methods to maintain operator attention rather than reduce workload.

Kantowitz, Barry H.↗
NASA NTRS1989

Small scale patches of suspended matter and phytoplankton in the Elbe River estuary, German Bight and tidal flats

Landsat 5 TM measurements are found suitable for study of small scale features in coastal waters; three independent factors, namely suspended matter concentration, atmospheric scattering, and sea-surface temperature, were extracted from all seven TM channels on the basis of factor analysis. The distribution of suspended matter in near-surface water layer and sea surface temperature is observable with a spatial resolution of at least 120 x 120 sq m. The high correlation between water depth and suspended matter distribution established by ship-gathered data supports the presently hypothesized control by bottom topography and wind-modified tidal currents of eddy and front formation.

Doerffer, R.↗
NASA NTRS1989

Flight Set 360T004 (STS-30) Insulation Component, Interim Release, Volume 3

The insulation component of the Redesigned Solid Rocket Motor (RSRM) is discussed. The results of all visual evaluations and a thermal safety factor analysis are given. The data contained here supersedes the interim release and the insulation data presented in the Clearfield 10 day report. The objective is to document the postflight condition of the internal and external insulation of nozzle to case joints, the case field joints, the igniter to case joints, and the acreage insulation which made up RSRM-4A and RSRM-4B.

Passman, James A.↗
NASA NTRS1990

Flight set 360L007 (STS-33) insulation component. Volume 3: Final release

Volume 3 of this postfire report deals with the insulation component of the RSRM. The report is released twice for each flight set. The interim release contract date is on or before 60 days after the last field joint or nozzle to case joint is disassembled at KSC and contain the results of the KSC visual evaluation. The data contained in Volume 3 interim release supersedes the insulation data presented in the KSC 10 day report. The final release contract data is on or before 60 days after the last factory joint is disassembled at the Clearfield H-7 facility and contains the results of all visual evaluations and a thermal safety factor analysis. The data contained in the Volume 3 final release supersedes the interim release and the insulation data presented in the Clearfield 10 day report.

Hicken, Steve↗
NASA NTRS1990

Simple explicit upwind schemes for solving compressible flows

Several upwind numerical methods for solving the compressible inviscid and viscous flow equations are discussed. Due to their explicit nature, the schemes are very simple and easy to apply to solutions on multi-block structured grids. Their favorable high frequence damping results in good rates of convergence when combined with multigrid procedures. The schemes are optimized using a simple stability and damping factor analysis. Results for three-dimensional test cases are shown and discussed. Attention is payed to the relative efficiencies of these schemes.

Von Lavante, E.↗
NASA NTRS1990

Acousto-ultrasonics

The theoretical development, methodology, and potential applications of acousto-ultrasonic nondestructive testing are set forth in an overview to assess the effectiveness of the technique. Stochastic wave propagation is utilized to isolate and describe defects in fiber-reinforced composites, particularly emphasizing the integrated effects of diffuse populations of subcritical flaws. The generation and nature of acousto-ultrasonic signals are described in detail, and stress-wave factor analysis of the signals is discussed. Applications of acousto-ultrasonics are listed including the prediction of failure sites, assessing fatique and impact damage, calculating ultimate tensile strength, and determining interlaminar bond strength. The method can identify subtle but important variations in fiber-reinforced composites, and development of the related instrumentation technology is emphasized.

Vary, Alex↗
NASA NTRS1990

Experimentation in machine discovery

KEKADA, a system that is capable of carrying out a complex series of experiments on problems from the history of science, is described. The system incorporates a set of experimentation strategies that were extracted from the traces of the scientists' behavior. It focuses on surprises to constrain its search, and uses its strategies to generate hypotheses and to carry out experiments. Some strategies are domain independent, whereas others incorporate knowledge of a specific domain. The domain independent strategies include magnification, determining scope, divide and conquer, factor analysis, and relating different anomalous phenomena. KEKADA represents an experiment as a set of independent and dependent entities, with apparatus variables and a goal. It represents a theory either as a sequence of processes or as abstract hypotheses. KEKADA's response is described to a particular problem in biochemistry. On this and other problems, the system is capable of carrying out a complex series of experiments to refine domain theories. Analysis of the system and its behavior on a number of different problems has established its generality, but it has also revealed the reasons why the system would not be a good experimental scientist.

Kulkarni, Deepak↗
NASA NTRS1991

Hand controller study of force and control mode

The objectives are to compare and evaluate the utility and effectiveness of various input control devices, e.g., hand controllers, with respect to the relative importance of force and operation control mode (rate or position) for Space Station Freedom (SSF) related tasks. The topics are presented in viewgraph form and include the: Intelligent Research Systems Lab (ISRL) experimental design; Telerobotic Systems Research Laboratory (TSRL) final experimental design; and factor analysis summary of results.

A Terry Morris↗
NASA NTRS1992

Effects of temperature-dependent molecular absorption coefficients on the thermal infrared remote sensing of the earth surface

The effect of temperature-dependent molecular absorption coefficients on thermal infrared spectral signatures measured from satellite sensors is investigated by comparing results from the atmospheric transmission and radiance codes LOWTRAN and MODTRAN and the accurate multiple scattering radiative transfer model ATRAD for different atmospheric profiles. The sensors considered include the operational NOAA AVHRR and two research instruments planned for NASA's Earth Observing System (EOS): MODIS-N (Moderate Resolution Imaging Spectrometer-Nadir-Mode) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). The difference in band transmittance is as large as 6 percent for some thermal bands within atmospheric windows and more than 30 percent near the edges of these atmospheric windows. The effect of temperature-dependent molecular absorption coefficients on satellite measurements of sea-surface temperature can exceed 0.6 K. Quantitative comparison and factor analysis indicate that more accurate measurements of molecular absorption coefficients and better radiative transfer simulation methods are needed to achieve SST accuracy of 0.3 K, as required for global numerical models of climate, and to develop land-surface temperature algorithms at the 1-K accuracy level.

Wan, Zhengming↗
NASA NTRS1995

Thermal barrier coatings for aircraft engines: History and directions

Thin thermal barrier coatings for protecting aircraft turbine section airfoils are examined. The discussion focuses on those advances that led first to their use for component life extension and more recently as an integral part of airfoil design. It is noted that development has been driven by laboratory rig and furnace testing corroborated by engine testing and engine field experience. The technology has also been supported by performance modeling to demonstrate benefits and life modeling for mission analysis. Factors which have led to the selection of the current state-of-the-art plasma sprayed and physical vapor deposited zirconia-yttria/MCrAlY TBC's is emphasized in addition to observations fundamentally related to their behavior. Current directions in research into thermal barrier coatings and recent progress at NASA is also noted.

Miller, R. A.↗