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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Nonparametric algorithms for the search of signals

Two algorithms for the search of signals in noise are constructed. Two independent measurable properties of a discreet time-dependent stochastic process F are described. The functions A sub K and B sub K fully satisfy conditions for the application of a test based on Spearman's rank correlation coefficient. A statistic to which the one-sided signal test can be applied is constructed under sufficiently natural assumptions about the noise process. The constructed statistics are simplified. Processing results from calculations of statistics constructed for concrete processes are presented.

Myshenkova, T. S.↗
NASA NTRS1980

The annoyance caused by noise around airports

A comprehensive study of noise around selected airports in France was performed. By use of questionnaires, the degree of annoyance caused by aircraft noise was determined. Three approaches used in the study were: (1) analytical study on the influence of noise on sleep; (2) sociological study on the satisfaction of occupants of buildings which conform to laws which are supposed to guarantee sufficient comfort; and (3) statistical study of correlations between external noises and psychological and pathological disturbances in residences.

JOSSE↗
NASA NTRS1984

Investigation of several aspects of LANDSAT-4 data quality

The Thematic Mapper scene of Sacramento, CA acquired during the TDRSS test was received in TIPS format. Quadrants for both scenes were tested for band-to-band registration using reimplemented block correlation techniques. Summary statistics for band-to-band registrations of TM band combinations for Quadrant 4 of the NE Arkansas scene in TIPS format are tabulated as well as those for Quadrant 1 of the Sacramento scene. The system MTF analysis for the San Francisco scene is completed. The thermal band did not have sufficient contrast for the targets used and was not analyzed.

Wrigley, R. C.↗
NASA NTRS1984

Statistical structure of convective periods derived from satellite ground based data

The documentation of characteristics of Vertical Atmospheric Soundings (VAS) through the use of statistical structure and correlation functions is presented. A measure of random error is also provided. Rawinsonde data from various periods is analyzed. Structure and correlation functions are used to compare VAS retrievals obtained using a physical algorithm with those from a regression technique. Results from both procedures are evaluated against those from a mesoscale network of rawinsonde stations. The parameters documented include temperature, mixing ratio, geopotential height, thickness, and precipitable water. Calculation are performed at several layers in the lower and upper troposphere.

Meyer, P. J.↗
NASA NTRS1988

An investigation of the relationship between sub-Saharan rainfall and global sea surface temperatures

The relationship between SST and rainfall index anomalies over sub-Saharan Africa for the 1970-1984 period is investigated. Results of an empirical orthogonal function analysis indicate that the most dominant eigenmode, EOF1, is characterized by warming over the central eastern Pacific, cooling over the eastern midlatitude Pacific, and warming over the entire Atlantic and Indian ocean basins. EOF1 is found to have statistically signifiant monthly correlations for the Sahel and Soudan regions, with the warm El Nino-like phases of SST EOF1 corresponding to drought conditions. These results suggest that the large-scale SST anomalies may be responsible for a large component of the observed vacillation of sub-Saharan rainfall.

Semazzi, F. H. M.↗
NASA NTRS1989

Oscillations in D-region absorption at periods of one to two months

One to two month oscillations in D-region absorption are found in seven years of daily f-min data from low latitude stations at Singapore (1N, 104E) and Rarotonga (21S, 160W). Coherency (cross-spectral) analyses reveal that solar flux variations account for much of the f-min variance at these periods. Over the range of periods from 10 to 200 days, statistically significant linear correlation is found between the f-min time series and contemporaneous 10.7 cm solar flux mearurements at periods of 16 to 19 days, the 26 to 29 day solar rotation band, and a broad band covering 43 to 80 day periods.

Stanford, J. L.↗
NASA NTRS1989

Oscillations in D-region absorption at periods of one to two months

One to two month oscillations in D-region absorption are found in seven years of daily f-min data from low latitude stations at Singapore (1 deg N, 104 deg E) and Rarotonga (21 deg S, 160 deg W). Coherency (cross-spectral) analyses reveal that solar flux variations account for much of the f-min variance at these periods. Over the range of periods from 10 to 200 days, statistically significant linear correlation is found between the f-min time series and contemporaneous 10.7 cm solar flux measurements at periods of 16-19 days, the 26-29 day solar rotation band, and a broad band covering 43-80 day periods.

Stanford, J. L.↗
NASA NTRS1990

Responses of women to orthostatic and exercise stresses

The results are presented from a special physiological study of women at the Johnson Space Center in 1976 to 1977. Its purpose was to establish a large (98 subjects) database from normal working women. The data sets are medical historical, clinical, anthropometric, and stress response statistics useful for establishing medical criteria for selecting women astronauts. Stressors were lower body negative pressure and static standing (both orthostatic) and treadmill exercise (ergometric). Data shown are original individual values with analyses and subsets, and statistical summaries and correlations relating to human responses to microgravity. Similarities appear between the characteristics of women in this study and those of women astronauts currently flying in Shuttle crews.

Hoffler, G. W.↗
NASA NTRS1991

Sensor data validation and reconstruction. Phase 1: System architecture study

The sensor validation and data reconstruction task reviewed relevant literature and selected applicable validation and reconstruction techniques for further study; analyzed the selected techniques and emphasized those which could be used for both validation and reconstruction; analyzed Space Shuttle Main Engine (SSME) hot fire test data to determine statistical and physical relationships between various parameters; developed statistical and empirical correlations between parameters to perform validation and reconstruction tasks, using a computer aided engineering (CAE) package; and conceptually designed an expert system based knowledge fusion tool, which allows the user to relate diverse types of information when validating sensor data. The host hardware for the system is intended to be a Sun SPARCstation, but could be any RISC workstation with a UNIX operating system and a windowing/graphics system such as Motif or Dataviews. The information fusion tool is intended to be developed using the NEXPERT Object expert system shell, and the C programming language.

Source record↗
NASA NTRS1991

Line-shape asymmetry of water vapor absorption lines in the 720-nm wavelength region

Spectral line-shape analyses were performed for water vapor lines broadened by argon, oxygen, and xenon in the 720-nm wavelength region. A line-shape asymmetry was observed, which is attributed to statistical dependence or correlation between velocity- and state-changing collisions. The generalized (asymmetric) Galatry profile, which results from the soft-collision profile and includes correlation between velocity- and state-changing collisions, was fitted to the observed line shapes and was found to compare favorably with the observed data. The most prominent asymmetries were observed with xenon as the buffer gas.

Grossmann, Benoist E.↗
NASA NTRS1997

Computer Supported Indexing: A History and Evaluation of NASA's MAI System

Computer supported indexing systems may be categorized in several ways. One classification scheme refers to them as statistical, syntactic, semantic or knowledge-based. While a system may emphasize one of these aspects, most systems actually combine two or more of these mechanisms to maximize system efficiency. Statistical systems can be based on counts of words or word stems, statistical association, and correlation techniques that assign weights to word locations or provide lexical disambiguation, calculations regarding the likelihood of word co-occurrences, clustering of word stems and transformations, or any other computational method used to identify pertinent terms. If words are counted, the ones of median frequency become candidate index terms. Syntactical systems stress grammar and identify parts of speech. Concepts found in designated grammatical combinations, such as noun phrases, generate the suggested terms. Semantic systems are concerned with the context sensitivity of words in text. The primary goal of this type of indexing is to identify without regard to syntax the subject matter and the context-bearing words in the text being indexed. Knowledge-based systems provide a conceptual network that goes past thesaurus or equivalent relationships to knowing (e.g., in the National Library of Medicine (NLM) system) that because the tibia is part of the leg, a document relating to injuries to the tibia should he indexed to LEG INJURIES, not the broader MeSH term INJURIES, or knowing that the term FEMALE should automatically be added when the term PREGNANCY is assigned, and also that the indexer should be prompted to add either HUMAN or ANIMAL. Another way of categorizing indexing systems is to identify them as producing either assigned- or derived-term indexes.

Silvester, June P.↗
NASA NTRS2000

South American Summer Monsoon of 1997/1998 and 1998/1999

It is well known that during El Nino years severe drought occurs in the area of Amazon and northeastern Brazil. According to the linear model result the reduced latent heating over the Amazon may lead to a weaker than normal upper tropospheric Bolivian high. As a result, some studies have suggested a weaker South American summer monsoon (SASM) during El Nino years. Using re-analysis. Zhou and Lau data found a statistically significant positive correlation between the tropical eastern Pacific sea surface temperature (SST) and the strength of low-level jet (LLJ) along the eastern foothills of the tropical-subtropical Andes. Douglas also showed a strong LLJ at Santa Cruz, Bolivia during a special pilot balloon observation period in 1997/98 El Nino austral summer. Since this LLJ is an integral part of the monsoon system in the summertime, these results indicated that SASM could be stronger than normal in El Nino years. To clarify this issue, we conducted an investigation on SASM anomaly in the recent ENSO event of 1997/98 El Nino and 1998/99 La Nina In the following we first give a brief review on SASM and the interannual variability of summer rainfall over South America. Then, the impact of 1997-99 ENSO on the South American regional thermal structure and its dynamical consequences to SASM will be discussed.

Lau, William K.-M.↗
NASA NTRS2001

Response to Comment on "Does the Earth Have an Adaptive Infrared Iris?"

In his comment on Lindzen et al., Harrison found that the amount of high-level clouds, A, and the sea-surface temperature beneath clouds, T, averaged over a large oceanic domain in the western Pacific have secular linear trends of opposite signs over a period of 20 months. He found that when the linear trends are subtracted from the data, the correlation between the residual A and T is much reduced. His estimates of the confidence levels for the correlation indicate, moreover, that this correlation is not statistically significant. The domain-averaged A and, to a lesser degree, T, have distinct intra-seasonal and seasonal variations. These variations are influenced by the large-scale wind and temperature distributions and by the seasonal variation of insolation. To separate the local effect from the effect of slowly changing large-scale conditions, rather than subtracting 20-month linear trends from the series, which has the potential to spuriously extrapolate intra-seasonal and seasonal variations to even longer time scales, we subtracted 30-day running means of A and T from each time series; in effect, the data were high-pass filtered. The number of points (days), N, is reduced by this process from the original value of 510 to 480.

Bell, Thomas L.↗
NASA NTRS2001

The Impact of Organization Culture on Satisfaction of Engineers in Technology

In today's technological workplace with the shortage of qualified knowledge workers, the factors that lead to job satisfaction have increasing importance. Several past studies have indicated that knowledge worker job satisfaction increases when Herzberg motivators are present. Other research has indicated that job satisfaction improves as the degree of organic organizational culture increases. After examining the factors that led to knowledge worker job satisfaction, the current study was undertaken. Knowledge workers in varying organizational cultures were surveyed in an effort to determine if there is a relationship between the degree of knowledge worker job satisfaction and the measure of organic organization culture. Two survey instruments, the Organizational Cultural Assessment (OCA) developed by Riegle, and the Minnesota Satisfaction Questionnaire (MSQ), were utilized. The OCA delineates degree of organic culture present whereas the MSQ measures job satisfaction. Results of both surveys were statistically analyzed to determine if knowledge workers experience higher satisfaction levels in organic organizational cultures. Once data was analyzed and the hypothesis proven, this could lead companies to move toward an organic culture with emphasis on motivators in an effort to make their organizational culture more conducive to higher employee retention. Through understanding the factors that lead to increased job satisfaction, corporate resources could more efficiently utilized. A total of eight high technology workplaces were surveyed. Five of the eight workplaces yielded statistically significant positive correlation between a positive organizational culture and increased job satisfaction. These initial results indicate the connection between culture and job satisfaction. The relationship will be further analyzed through future surveys of numerous high technology workplaces.

Westbrook, Jerry W.↗
NASA NTRS2004

What the Long-Term Sunspot Record Tells Us About Space Climate

Direct observations of sunspots span the nearly 400 years since the time of Galileo. Dedicated observing programs at several observatories over the last 150 years have provided detailed information not only on the number of sunspots but on their sizes and positions as well. The data acquired by those original observers, and by those who have more recently brought those observations to light, provide important clues about the nature of the solar cycle and its contribution to space climate. The period of the cycle, the equator-ward drift of the active latitudes, the asymmetry between the rise to maximum and the fill to minimum, shifting asymmetries between northern and southern hemisphere activity, the tilt of active regions, and the increasing amplitude of the cycles since the Maunder Minimum are all well established. Other, less well established characteristics such as multi-cycle and short-term periodicities, often depend upon the method of data analysis. The strong correlation between sunspot statistics and other measures of solar activity, coupled with the length of the sunspot record, make these observations extremely valuable for characterizing and understanding space climate.

Hathaway, D. H.↗
NASA NTRS2012

Human Thermal Model Evaluation Using the JSC Human Thermal Database

Human thermal modeling has considerable long term utility to human space flight. Such models provide a tool to predict crew survivability in support of vehicle design and to evaluate crew response in untested space environments. It is to the benefit of any such model not only to collect relevant experimental data to correlate it against, but also to maintain an experimental standard or benchmark for future development in a readily and rapidly searchable and software accessible format. The Human thermal database project is intended to do just so; to collect relevant data from literature and experimentation and to store the data in a database structure for immediate and future use as a benchmark to judge human thermal models against, in identifying model strengths and weakness, to support model development and improve correlation, and to statistically quantify a model s predictive quality. The human thermal database developed at the Johnson Space Center (JSC) is intended to evaluate a set of widely used human thermal models. This set includes the Wissler human thermal model, a model that has been widely used to predict the human thermoregulatory response to a variety of cold and hot environments. These models are statistically compared to the current database, which contains experiments of human subjects primarily in air from a literature survey ranging between 1953 and 2004 and from a suited experiment recently performed by the authors, for a quantitative study of relative strength and predictive quality of the models.

Bue, Grant↗
NASA NTRS2012

Estimating the Length of the North Atlantic Basin Hurricane Season

For the interval 1945-2011, the length of the hurricane season in the North Atlantic basin averages about 130 +/- 42 days (the +/-1 standard deviation interval), having a range of 47 to 235 days. Runs-testing reveals that the annual length of season varies nonrandomly at the 5% level of significance. In particular, its trend, as described using 10-yr moving averages, generally has been upward since about 1979, increasing from about 113 to 157 days (in 2003). Based on annual values, one finds a highly statistically important inverse correlation at the 0.1% level of significance between the length of season and the occurrence of the first storm day of the season. For the 2012 hurricane season, based on the reported first storm day of May 19, 2012 (i.e., DOY = 140), the inferred preferential regression predicts that the length of the current season likely will be about 173 +/- 23 days, suggesting that it will end about November 8 +/- 23 days, with only about a 5% chance that it will end either before about September 23, 2012 or after about December 24, 2012.

Wilson, Robert M.↗
NASA NTRS2013

Effects of Microstructural Variability on Thermo-Mechanical Properties of a Woven Ceramic Matrix Composite

The objectives of this paper include identifying important architectural parameters that describe the SiC/SiC five-harness satin weave composite and characterizing the statistical distributions and correlations of those parameters from photomicrographs of various cross sections. In addition, realistic artificial cross sections of a 2D representative volume element (RVE) are generated reflecting the variability found in the photomicrographs, which are used to determine the effects of architectural variability on the thermo-mechanical properties. Lastly, preliminary information is obtained on the sensitivity of thermo-mechanical properties to architectural variations. Finite element analysis is used in combination with a response surface and it is shown that the present method is effective in determining the effects of architectural variability on thermo-mechanical properties.

Goldsmith, Marlana B.↗