15,019 research outputs found
An analysis of I/O efficient order-statistic-based techniques for noise power estimation in the HRMS sky survey's operational system
Noise power estimation in the High-Resolution Microwave Survey (HRMS) sky survey element is considered as an example of a constant false alarm rate (CFAR) signal detection problem. Order-statistic-based noise power estimators for CFAR detection are considered in terms of required estimator accuracy and estimator dynamic range. By limiting the dynamic range of the value to be estimated, the performance of an order-statistic estimator can be achieved by simpler techniques requiring only a single pass of the data. Simple threshold-and-count techniques are examined, and it is shown how several parallel threshold-and-count estimation devices can be used to expand the dynamic range to meet HRMS system requirements with minimal hardware complexity. An input/output (I/O) efficient limited-precision order-statistic estimator with wide but limited dynamic range is also examined
Applications of aerospace technology in the public sector
Current activities of the program to accelerate specific applications of space related technology in major public sector problem areas are summarized for the period 1 June 1971 through 30 November 1971. An overview of NASA technology, technology applications, and supporting activities are presented. Specific technology applications in biomedicine are reported including cancer detection, treatment and research; cardiovascular diseases, diagnosis, and treatment; medical instrumentation; kidney function disorders, treatment, and research; and rehabilitation medicine
The Transformation of Energy by Lucifer chacei (Crustacea, Decapoda)
A laboratory study of energy transformations by the pelagic decapod
crustacean Lucifer chacei was made. Three combined stages were cultured and
studied: the protozoea-zoea stages, the combined early and late schizopod stages,
and the combined adult stages. Growth rates, dry weight, ash content, and calorific
values were determined for each. Number of calories per hour ingested, assimilated,
and respired were also determined for each of the combined stages. An
energy flow diagram was constructed from the data.
Growth from egg to adult took slightly more than 3 weeks. Protozoea-zoea and
schizopod stages assimilated 10.1 percent and 10.4 percent of ingested Dunaliella
tertiolecta. Adults assimilated 7.7 percent of ingested Dunaliella tertiolecta and
approximately 22 percent of ingested Artemia salina nauplii. The data indicate that
a change from herbivorous larvae to omnivorous adults may have to occur in the
natural environment because the older stages cannot obtain enough energy for
growth from phytoplankton alone. When data for all stages were combined, gross
growth efficiency and net growth efficiency for Lucifer were approximately 10 percent
and 81 percent, respectively
Examination of Locus of Control, Health Locus of Control and Their Key Predictors in Urban vs. Rural Populations
The purpose of this study was to utilize a quantitative survey methodology, which explored the characteristicsof locus of control and health locus of control between a rural Tennessee population and an urban Tennessee population using scores from Rotter\u27s Internal-External Locus of Control Scale (LOC) and the Multidimensional Health Locus of Control Scale (HLOC). The results of this study help bridge the gap in the limited studies available that use LOC and HLOC to explore the differences between the two populations. Demographic information on the survey (age, gender, race, annual household income, size of household, level of education, spirituality) and the scores from the LOC and the HLOC were investigated to find the predictors of locus of control and health locus of control for the samples. A total of 156 people completed the voluntary survey, 79 reported rural residence and 77 reported urban residence. results showed a relationship between locus of control scores and health locus of control scores, r = -0.258, p \u3c 0.01. The rural group did not score significantly different than the urban group on helth locus of control. For the entire population, gender (p = .010) and spirituality (p = .006) were the only significant predictors of HLOC. For the rural participants, race (p = .004), income (p = .014), and level of education (p = .032) were significant predictors of HLOC. For the urban population gender was the only significant predictor of HLOC (p = .013). The rural population did not have any common predictors for locus of controland health locus of control. The urban population did have gender as a common predictor for locus of control and helath locus of control. The current study did not show the strong differences that were expected between these two populations. General LOC scores and HLOC scores were similar reguardless of geographic differences. However, through an analysis of possible factors that could contribute to LOC and HLOC scores this study gives insight into the specific needs of the different populations so that interventions may be taylored to the specific needs of the people
Technology applications
A summary of NASA Technology Utilization programs for the period of 1 December 1971 through 31 May 1972 is presented. An abbreviated description of the overall Technology Utilization Applications Program is provided as a background for the specific applications examples. Subjects discussed are in the broad headings of: (1) cancer, (2) cardiovascular disease, (2) medical instrumentation, (4) urinary system disorders, (5) rehabilitation medicine, (6) air and water pollution, (7) housing and urban construction, (8) fire safety, (9) law enforcement and criminalistics, (10) transportation, and (11) mine safety
Innovative Heuristics to Improve the Latent Dirichlet Allocation Methodology for Textual Analysis and a New Modernized Topic Modeling Approach
Natural Language Processing is a complex method of data mining the vast trove of documents created and made available every day. Topic modeling seeks to identify the topics within textual corpora with limited human input into the process to speed analysis. Current topic modeling techniques used in Natural Language Processing have limitations in the pre-processing steps. This dissertation studies topic modeling techniques, those limitations in the pre-processing, and introduces new algorithms to gain improvements from existing topic modeling techniques while being competitive with computational complexity. This research introduces four contributions to the field of Natural Language Processing and topic modeling. First, this research identifies a requirement for a more robust “stopwords” list and proposes a heuristic for creating a more robust list. Second, a new dimensionality-reduction technique is introduced that exploits the number of words within a document to infer importance to word choice. Third, an algorithm is developed to determine the number of topics within a corpus and demonstrated using a standard topic modeling data set. These techniques produce a higher quality result from the Latent Dirichlet Allocation topic modeling technique. Fourth, a novel heuristic utilizing Principal Component Analysis is introduced that is capable of determining the number of topics within a corpus that produces stable sets of topic words
Shaped Pupil Lyot Coronagraphs: High-Contrast Solutions for Restricted Focal Planes
Coronagraphs of the apodized pupil and shaped pupil varieties use the
Fraunhofer diffraction properties of amplitude masks to create regions of high
contrast in the vicinity of a target star. Here we present a hybrid coronagraph
architecture in which a binary, hard-edged shaped pupil mask replaces the gray,
smooth apodizer of the apodized pupil Lyot coronagraph (APLC). For any contrast
and bandwidth goal in this configuration, as long as the prescribed region of
contrast is restricted to a finite area in the image, a shaped pupil is the
apodizer with the highest transmission. We relate the starlight cancellation
mechanism to that of the conventional APLC. We introduce a new class of
solutions in which the amplitude profile of the Lyot stop, instead of being
fixed as a padded replica of the telescope aperture, is jointly optimized with
the apodizer. Finally, we describe shaped pupil Lyot coronagraph (SPLC) designs
for the baseline architecture of the Wide-Field Infrared Survey
Telescope-Astrophysics Focused Telescope Assets (WFIRST-AFTA) coronagraph.
These SPLCs help to enable two scientific objectives of the WFIRST-AFTA
mission: (1) broadband spectroscopy to characterize exoplanet atmospheres in
reflected starlight and (2) debris disk imaging.Comment: 41 pages, 15 figures; published in the JATIS special section on
WFIRST-AFTA coronagraph
Metallurgy and properties of plasma spray formed materials
Understanding the fundamental metallurgy of vacuum plasma spray formed materials is the key to enhancing and developing full material properties. Investigations have shown that the microstructure of plasma sprayed materials must evolve from a powder splat morphology to a recrystallized grain structure to assure high strength and ductility. A fully, or near fully, dense material that exhibits a powder splat morphology will perform as a brittle material compared to a recrystallized grain structure for the same amount of porosity. Metallurgy and material properties of nickel, iron, and copper base alloys will be presented and correlated to microstructure
Morning glory syndrome in children: association with endocrine and central-nervous-system anomalies
- …