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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Subbarrier absorption in a stationary superlattice

The calculation of the interband absorption coefficient was carried out in the classical case, when the frequency of light was assumed to bind two miniband subbarrier states of different bands. The influence of two dimensional Mott excitons on this absorption was studied and a comparison was made with the experiment. All of these considerations were done taking into account the photon wave vector (the phase spatial heterogeneity). The basic traits of the energy spectra of superlattice semiconductors, their kinetic and optical properties, and possible means of electromagnetic wave intensification were examined. By the density matrix method, a theory of electrical and electromagnetic properties of superlattices was suggested.

Arutyunyan, G. M.↗
NASA NTRS1984

ECUT: Energy Conversion and Utilization Technologies program - Biocatalysis research activity

The activities of the Biocatalysis Research Activity are organized into the Biocatalysis and Molecular Modeling work elements and a supporting planning and analysis function. In the Biocatalysis work element, progress is made in developing a method for stabilizing genetically engineered traits in microorganisms, refining a technique for monitoring cells that are genetically engineered, and identifying strains of fungi for highly efficient preprocessing of biomass for optimizing the efficiency of bioreactors. In the Molecular Modeling work element, a preliminary model of the behavior of enzymes is developed. A preliminary investigation of the potential for synthesizing enzymes for use in electrochemical processes is completed. Contact with industry and universities is made to define key biocatalysis technical issues and to broaden the range of potential participants in the activity. Analyses are conducted to identify and evaluate potential concepts for future research funding.

Wilcox, R.↗
NASA NTRS1984

Image-plane processing of visual information

Shannon's theory of information is used to optimize the optical design of sensor-array imaging systems which use neighborhood image-plane signal processing for enhancing edges and compressing dynamic range during image formation. The resultant edge-enhancement, or band-pass-filter, response is found to be very similar to that of human vision. Comparisons of traits in human vision with results from information theory suggest that: (1) Image-plane processing, like preprocessing in human vision, can improve visual information acquisition for pattern recognition when resolving power, sensitivity, and dynamic range are constrained. Improvements include reduced sensitivity to changes in lighter levels, reduced signal dynamic range, reduced data transmission and processing, and reduced aliasing and photosensor noise degradation. (2) Information content can be an appropriate figure of merit for optimizing the optical design of imaging systems when visual information is acquired for pattern recognition. The design trade-offs involve spatial response, sensitivity, and sampling interval.

Huck, F. O.↗
NASA NTRS1983

The disposition of DNA in Prochloron (Prochlorophyta)

The discovery of both chlorophyll a and b in the prokaryote Prochloron Lewin, a trait otherwise unique to eukaryotic photosynthetic organisms, has stimulated speculation on the possible endosymbiont origins of the plastids of eukaryotic cells. The arrangement of DNA in Prochloron was therefore dyed in situ with the fluorochrome dye DAPI and compared with the plastid DNA of various eukaryote cells. The DNA of Prochloron is found to be clearly different in arrangement and locale from that of blue-green algae. In the great size of its nucleoids and their apparently high DNA content, Prochloron also differs from the plastids of any eukaryotes, with the possible exception of dinoflagellates. Prochloron remains an evolutionary puzzle.

Coleman, A. W.↗
NASA NTRS1984

Classification Systems for Individual Differences in Multiple-task Performance and Subjective Estimates of Workload

Human factors practitioners often are concerned with mental workload in multiple-task situations. Investigations of these situations have demonstrated repeatedly that individuals differ in their subjective estimates of workload. These differences may be attributed in part to individual differences in definitions of workload. However, after allowing for differences in the definition of workload, there are still unexplained individual differences in workload ratings. The relation between individual differences in multiple-task performance, subjective estimates of workload, information processing abilities, and the Type A personality trait were examined.

Damos, D. L.↗
NASA NTRS1985

Chemolithotrophy and physiology of bacterial nutrient limitation

An overview of the physiology of chemolithotrophic bacteria, particularly the thiobacilli, was presented. In these bacteria unique physiological traits are expressed during nutrient limited growth. Different physiological types of chemolithotrophs, pathways of sulfur oxidation, and electron transport in the thiobacilli, problems encountered by chemolithotrophs in the generation of reducing power, and some explanations of the phenomenon of obligate chemolithotrophy were considered. Mixotrophy in the thiobacilli has been studied extensively both under nutrient excess and limitation. In nature, bacteria usually grow under nutrient limitation. Yet the bulk of our knowledge of microbial metabolic function is derived from bacteria grown in laboratory batch cultures containing a great abundance of nutrients. Microbial behavior in these two types of environments can be very different, indicating the need for basing an understanding of microbial ecology on studies that rely on cultivation of microorganisms under nutrient limitation. Nutrient limited bacteria differ in several ways from those growing in large quantities of nutrients. They have different surface structures and make a much fuller use of their metabolic potential, especially by the synthesis of unique pathways of catabolic enzymes.

Matin, A.↗
NASA NTRS1984

Cockpit management attitudes

Distinctions are drawn between personality traits and attitudes. The stability of the personality and the malleability of attitudes are stressed. These concepts are related to pilot performance, especially in the areas of crew coordination and cockpit resource management. Airline pilots were administered a Cockpit Management Attitudes questionnaire; empirical data from that survey are reported and implications of the data for training in crew coordination are discussed.

Helmreich, R. L.↗
NASA NTRS1985

'Meatball searching' - The adversarial approach to online information retrieval

It is proposed that the different styles of online searching can be described as either formal (highly precise) or informal with the needs of the client dictating which is most applicable at a particular moment. The background and personality of the searcher also come into play. Particular attention is focused on meatball searching which is a form of online searching characterized by deliberate vagueness. It requires generally comprehensive searches, often on unusual topics and with tight deadlines. It is most likely to occur in search centers serving many different disciplines and levels of client information sophistication. Various information needs are outlined as well as the laws of meatball searching and the adversarial approach. Traits and characteristics important to sucessful searching include: (1) concept analysis, (2) flexibility of thinking, (3) ability to think in synonyms and (4) anticipation of variant word forms and spellings.

Jack, R. F.↗
NASA NTRS1986

Stratified processes to analyze SSME parts and subsystems using Weibull methodology

Due to the various parts found in a Space Shuttle Main Engine (SSME), analyzation of every part is not feasible or needed. Based on previous mathematical modeling experience of high velocity cryogenic equipment, the environmental traits of location of the part, temperature range, fluid velocity, pressure range, and elevation variation of fluid flow as being significant factors were determined. Six parts categories were developed. The part categories are: (1) fuel turbomachinery, (2) oxidizer, (3) combustion devices, (4) valves, (5) ducts, and (6) lines. Due to a suspicion that superficial failure modes exist, six status codes were developed. The codes are: (1) part is in service presently, (2) part is out-of-service due to its own failure, (3) part is out-of-service due to engine (or some other part failure), (4) part is out-of-service because it's retired/obsolete (time related), (5) never fired-scrapped due to own problem or part is store, and (6) part is out-of-service for repair. It was suggested that to properly model failure behavior of SSME parts that: (1) significant factors contributing to failure must be examined, (2) relatively precision based on real life data must be examined, and (3) alternative definitions of failure must be initialized by the engineers.

Gray, Lou Allen Bell↗
NASA NTRS1987

Extremely Luminous Far-infrared Sources (ELFS)

The Infrared Astronomical Satellite (IRAS) survey uncovered a class of Extremely Luminous Far Infrared Sources (ELFS), exhibiting luminosities up to and occasionally exceeding 10 to the 12th power L sub 0. Arguments are presented to show that sources with luminosities L equal to or greater than 3 x 10 to the 10th power L sub 0 may represent gas rich galaxies in collision. The more conventional explanation of these sources as sites of extremely active star formation fails to explain the observed low optical luminosities of ELFS as well as their high infrared excess. In contrast, a collisional model heats gas to a temperature of approx. 10 to the 6th power K where cooling takes place in the extreme ultraviolet. The UV is absorbed by dust and converted into far infrared radiation (FIR) without generation of appreciable optical luminosity. Gas recombination as it cools generates a Lyman alpha photon only once for every two extreme ultraviolet approx. 50eV photons emitted by the 10 to the 6th power gas. That accounts for the high infrared excess. Finally, the model also is able to explain the observed luminosity distribution of ELFS as well as many other traits.

Harwit, Martin↗
NASA NTRS1983

Software development predictors, error analysis, reliability models and software metric analysis

The use of dynamic characteristics as predictors for software development was studied. It was found that there are some significant factors that could be useful as predictors. From a study on software errors and complexity, it was shown that meaningful results can be obtained which allow insight into software traits and the environment in which it is developed. Reliability models were studied. The research included the field of program testing because the validity of some reliability models depends on the answers to some unanswered questions about testing. In studying software metrics, data collected from seven software engineering laboratory (FORTRAN) projects were examined and three effort reporting accuracy checks were applied to demonstrate the need to validate a data base. Results are discussed.

Basili, Victor↗
NASA NTRS1986

Implications of the inferred compositions of asteroids for their collisional evolution

The inferred compositions of mainbelt asteroids set constraints on the nature and degree of collisional evolution of the asteroids. The existence of a basaltic crust on 4 Vesta seems to require that there has been very little collisional evolution since the presumably ancient solidification of its crust, which is consistent with most recent models of collisional evolution. But interpretations of the compositions of M- and S-type asteroids as collisionally stripped cores of differentiated parent bodies argue for much more extensive collisions. A major problem is presented by the extreme rarity of olivine-rich asteroids and olivine meteorites. Studies of the compositions of members of dynamical families suggest that most supposed families are either not real, or at least are not genetically related fragments of a cosmochemically reasonable precursor body. The mutual incompatibilities among various 'accepted' traits of the asteroids deserve further study in order to develop a self-consistent scenario for the chemical and physical evolution of the asteroids.

Chapman, C. R.↗
NASA NTRS1987

Photometric geodesy of main-belt asteroids. I - Lightcurves of 26 large, rapid rotators

A 'photometric geodesy' program is selected on the basis of light-curve data from five years' observations of large, rapidly rotating asteroids, where the observing protocol was designed to obtain precise, absolute photometry at a wide variety of orbital longitudes and phase angles. A total of 257 complete or partial light-curves are obtained for 26 asteroids; the data set will allow the future determination of pole positions and shapes, as well as to constrain the geophysical traits of these bodies.

Weidenschilling, S. J.↗
NASA NTRS1987

Planform effects on the supersonic aerodynamics of multibody configurations

An experimental and theoretical investigation of the effect of planform on the supersonic aerodynamics of low-fineness-ratio multibody configurations was conducted. Longitudinal and lateral-directional aerodynamic and flow visualization data were obtained on three multibody configurations. The data indicated that planform has a small effect on the zero lift drag of a multibody configuration. The longitudinal data obtained at lifting conditions showed a sensitivity to planform shape. Lateral-directional data obtained for all configurations did not uncover any unusual stability traits for this class of configuration. A comparison study was also made between the planform effects observed on single-body and multibody configurations. Results from this study indicate that the multibody concept appears to offer a mechanism for employing a low-sweep wing with no significant increase in zero-lift drag but still retaining high-performance characteristics at high-lift conditions. Evaluation of the linear-theory prediction methods revealed a general inability of the methods to predict the characteristics of low-fineness-ratio geometries.

Mcmillin, Naomi↗
NASA NTRS1982

Pilot selection and training

Personality and situational factors relevant to individual and group performance in highly demanding environments, such as those faced by astronauts or by jet transport crew, are discussed. It is emphasized that although technical competence and proficiency in pilot selection are prerequisites for safety, operating a modern jet transport is a group endeavor that requires the effective coordination of the entire crew. A self-report test battery for measuring positive and negative personality traits of pilot candidates, termed the Personal Characteristics Inventory, is described.

Helmreich, Robert L.↗
NASA NTRS1985

The role of psychologists in future spaceflight

The need for psychologists to have a more active role in planning space missions is discussed. It is suggested that it would be beneficial if psychologists conducted research aimed at optimizing the organization, composition, and performance of crews; participated in the selection and training of crews; and monitored the actual performance and adjustment of crews during missions. The areas which require further research and the types of research strategies to be implemented are described. The desirable traits for future space personnel and the role of psychologists in mission control are examined.

Helmreich, Robert L.↗
NASA NTRS1983

Beyond face validity - A comment on Nicholls, Licht, and Pearl

In their discussion of the Bem Sex Role Inventory (BSRI; Bem, 1974) and the Personal Attributes Questionnaire (PAQ; Spence and Helmrich, 1978), Nicholls, et al. (1982) blur two issues. The first concerns the legitimacy of equating the clusters of gender-related personality traits tapped by these instruments with the global constructs of masculinity and feminity. The second concerns item similarity between the PAQ and BSRI M scales and measures of self-esteem and the question of whether the several instruments measure the same or separable constructs. Decisions about each of these issues involve complex considerations that do not directly involve face validity.

Spence, Janet T.↗
NASA NTRS1988

Planetary astronomy

The goal is to use a variety of observational techniques and instruments to reduce, interpret, and synthesize groundbased astronomical data concerning the comets, asteroids, and other small bodies of the solar system in order to study the compositions, physical characteristics, population properties, and evolution of these bodies. This year's research has involved five distinct efforts. Chapman has studied asteroids, with emphasis on synthesizing groundbased databases to determine surface mineralogies and population characteristics; many new results on astronomy, size-distributions, and asteroid family traits have been obtained.

Chapman, Clark R.↗