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NASA Technical Reports Server (NTRS) (656,648 recursos)
The NTRS is a valuable resource for students, educators, researchers, and the public for access to NASA's current and historical technical literature since it was first released in 1994. NTRS provides access to approximately 500K aerospace related citations, 90K full-text online documents, and 111K images and videos. NTRS numbers continues to grow over time as new scientific and technical information (STI) is created or funded by NASA. The type of information found in NTRS include: conference papers, images, journal articles, photos, meeting papers, movies, patents, research reports, and technical videos.

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Mostrando recursos 1 - 20 de 3,021

1. International VLBI Service for Geodesy and Astrometry 2012 Annual Report - Behrend, Dirk; Baver, Karen D.; Armstrong, Kyla L.
This volume of reports is the 2012 Annual Report of the International VLBI Service for Geodesy and Astrometry (IVS). The individual reports were contributed by VLBI groups in the international geodetic and astrometric community who constitute the permanent components of IVS. The IVS 2012 Annual Report documents the work of the IVS components for the calendar year 2012, our fourteenth year of existence. The reports describe changes, activities, and progress ofthe IVS. Many thanks to all IVS components who contributed to this Annual Report. With the exception of the first section and parts of the last section (described below), the...

2. Chemical Enrichment and Physical Conditions in IZw18* - Hubeny, I.; Heap, S.; Lebouteiller, V.; Kunth, D.
Low-metallicity star-forming dwarf galaxies are prime targets to understand the chemical enrichment of the interstellar medium. The H I region contains the bulk of the mass in blue compact dwarfs, and it provides important constraints on the dispersal and mixing of heavy elements released by successive star-formation episodes. The metallicity of the H I region is also a critical parameter to investigate the future star-formation history, as metals provide most of the gas cooling that will facilitate and sustain star formation. Aims. Our primary objective is to study the enrichment of the H I region and the interplay between star-formation...

3. Analysis of Supergranule Sizes and Velocities Using Solar Dynamics Observatory (SDO)/Helioseismic Magnetic Imager (HMI) and Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) Dopplergrams - Williams, Peter E.; Beck, J. G.; Pesnell, William D.; Lee, S.
Co-temporal Doppler images from Solar and Heliospheric Observatory (SOHO)/ Michelson Doppler Imager (MDI) and Solar Dynamics Observatory (SDO)/Helioseismic Magnetic Imager (HMI) have been analyzed to extract quantitative information about global properties of the spatial and temporal characteristics of solar supergranulation. Preliminary comparisons show that supergranules appear to be smaller and have stronger horizontal velocity flows within HMI data than was measured with MDI. There appears to be no difference in their evolutionary timescales. Supergranule sizes and velocities were analyzed over a ten-day time period at a 15-minute cadence. While the averages of the time-series retain the aforementioned differences, fluctuations of...

4. Structural Benchmark Creep Testing for Microcast MarM-247 Advanced Stirling Convertor E2 Heater Head Test Article SN18 - Krause, David L.; Brewer, Ethan J.; Pawlik, Ralph
This report provides test methodology details and qualitative results for the first structural benchmark creep test of an Advanced Stirling Convertor (ASC) heater head of ASC-E2 design heritage. The test article was recovered from a flight-like Microcast MarM-247 heater head specimen previously used in helium permeability testing. The test article was utilized for benchmark creep test rig preparation, wall thickness and diametral laser scan hardware metrological developments, and induction heater custom coil experiments. In addition, a benchmark creep test was performed, terminated after one week when through-thickness cracks propagated at thermocouple weld locations. Following this, it was used to develop...

5. Contact Thermocouple Methodology and Evaluation for Temperature Measurement in the Laboratory - Pawlik, Ralph J.; Krause, David L.; Brewer, Ethan J.
Laboratory testing of advanced aerospace components very often requires highly accurate temperature measurement and control devices, as well as methods to precisely analyze and predict the performance of such components. Analysis of test articles depends on accurate measurements of temperature across the specimen. Where possible, this task is accomplished using many thermocouples welded directly to the test specimen, which can produce results with great precision. However, it is known that thermocouple spot welds can initiate deleterious cracks in some materials, prohibiting the use of welded thermocouples. Such is the case for the nickel-based superalloy MarM-247, which is used in the...

6. Rapid Assessment of Contrast Sensitivity with Mobile Touch-screens - Mulligan, Jeffrey B.
The availability of low-cost high-quality touch-screen displays in modern mobile devices has created opportunities for new approaches to routine visual measurements. Here we describe a novel method in which subjects use a finger swipe to indicate the transition from visible to invisible on a grating which is swept in both contrast and frequency. Because a single image can be swiped in about a second, it is practical to use a series of images to zoom in on particular ranges of contrast or frequency, both to increase the accuracy of the measurements and to obtain an estimate of the reliability of...

7. Prospective Safety Analysis and the Complex Aviation System - Smith, Brian E.
Fatal accident rates in commercial passenger aviation are at historic lows yet have plateaued and are not showing evidence of further safety advances. Modern aircraft accidents reflect both historic causal factors and new unexpected "Black Swan" events. The ever-increasing complexity of the aviation system, along with its associated technology and organizational relationships, provides fertile ground for fresh problems. It is important to take a proactive approach to aviation safety by working to identify novel causation mechanisms for future aviation accidents before they happen. Progress has been made in using of historic data to identify the telltale signals preceding aviation accidents...

8. One-carbon (bio ?) Geochemistry in Subsurface Waters of the Serpentinizing Coast Range Ophiolite - Mccollom, Tom; Hoehler, Tori M.; Schrenk, Matt; Cardace, Dawn
Serpentinization - the aqueous alteration of ultramafic rocks - typically imparts a highly reducing and alkaline character to the reacting fluids. In turn, these can influence the speciation and potential for metabolism of one-carbon compounds in the system. We examined the aqueous geochemistry and assessed the biological potential of one-carbon compounds in the subsurface of the McLaughlin Natural Reserve (Coast Range Ophiolite, California, USA). Fluids from wells sunk at depths of 25-90 meters have pH values ranging from 9.7 to 11.5 and dissolved inorganic carbon (DIC concentrations) generally below 60 micromolar. Methane is present at concentrations up to 1.3 millimolar...

9. Web Based Prognostics and 24/7 Monitoring - Strautkalns, Miryam; Robinson, Peter
We created a general framework for analysts to store and view data in a way that removes the boundaries created by operating systems, programming languages, and proximity. With the advent of HTML5 and CSS3 with JavaScript the distribution of information is limited to only those who lack a browser. We created a framework based on the methodology: one server, one web based application. Additional benefits are increased opportunities for collaboration. Today the idea of a group in a single room is antiquated. Groups will communicate and collaborate with others from other universities, organizations, as well as other continents across times...

10. NextGen Operations in a Simulated NY Area Airspace - Brasil, Connie; Yoo, Hyo-Sang; Cabrall, Chris; Rein-Weston, Daphne; Lin, Cindy; Parke, Bonny; Omar, Faisal; Buckley, Nathan; Lee, Paul; Homola, Jeff; Smith, Nancy M.; Chevalley, Eric; Morey, Susan
A human-in-the-loop simulation conducted in the Airspace Operations Laboratory (AOL) at NASA Ames Research Center explored the feasibility of a Next Generation Air Transportation System (NextGen) solution to address airspace and airport capacity limitations in and around the New York metropolitan area. A week-long study explored the feasibility of a new Optimal Profile Descent (OPD) arrival into the airspace as well as a novel application of a Terminal Area Precision Scheduling and Spacing (TAPSS) enhancement to the Traffic Management Advisor (TMA) arrival scheduling tool to coordinate high volume arrival traffic to intersecting runways. In the simulation, four en route sector...

11. Precision Departure Release Capability (PDRC) Overview and Results: NASA to FAA Research Transition - Engelland, Shawn; Davis, Tom.
NASA researchers developed the Precision Departure Release Capability (PDRC) concept to improve the tactical departure scheduling process. The PDRC system is comprised of: 1) a surface automation system that computes ready time predictions and departure runway assignments, 2) an en route scheduling automation tool that uses this information to estimate ascent trajectories to the merge point and computes release times and, 3) an interface that provides two-way communication between the two systems. To minimize technology transfer issues and facilitate its adoption by TMCs and Frontline Managers (FLM), NASA developed the PDRC prototype using the Surface Decision Support System (SDSS) for...

12. Helioseismology of a Realistic Magnetoconvective Sunspot Simulation - Duvall, T. L., Jr.; Braun, D. C.; Rempel, M.; Birch, A. C.
We compare helioseismic travel-time shifts measured from a realistic magnetoconvective sunspot simulation using both helioseismic holography and time-distance helioseismology, and measured from real sunspots observed with the Helioseismic and Magnetic Imager instrument on board the Solar Dynamics Observatory and the Michelson Doppler Imager instrument on board the Solar and Heliospheric Observatory. We find remarkable similarities in the travel-time shifts measured between the methodologies applied and between the simulated and real sunspots. Forward modeling of the travel-time shifts using either Born or ray approximation kernels and the sound-speed perturbations present in the simulation indicates major disagreements with the measured travel-time shifts....

13. The Chandra Delta Ori Large Project: Occultation Measurements of the Shocked Gas tn the Nearest Eclipsing O-Star Binary - Hole, Tabetha; Hoffman, Jennifer; Maiz-Apellaniz, Jesus; Rauw, Gregor; Iping, Rosina; Nichols, Joy; Leutenegger, Maurice; Walborn, Nolan; Pollock, Andrew; Waldron, Wayne; Naze, Yael; Owocki, Stan; Moffat, Anthony; Richardson, Noel; Lomax, Jamie; Gull, Ted; Hamann, W. -R.; Hole, Tabetha; Evans, Nancy; Ignace, Rico; Russell, Chris; Corcoran, Michael F.; Hamaguchi, Kenji; Gayley, Ken; Oskinova, Lida
Delta Ori is the nearest massive, single-lined eclipsing binary (O9.5 II + B0.5III). As such it serves as a fundamental calibrator of the mass-radius-luminosity relation in the upper HR diagram. It is also the only eclipsing O-type binary system which is bright enough to be observable with the CHANDRA gratings in a reasonable exposure. Studies of resolved X-ray line complexes provide tracers of wind mass loss rate and clumpiness; occultation by the X-ray dark companion of the line emitting region can provide direct spatial information on the location of the X-ray emitting gas produced by shocks embedded in the wind...

14. A New Population of High-z, Dusty Lyman-alpha Emitters and Blobs Discovered by WISE: Feedback Caught in the Act? - Lonsdale, Carol; Blain, Andrew; Petty, Sara; Jarrett, Tom; Eisenhardt, Peter; Wu, Jingwen; Farrah, Duncan; Borys, Colin J. K.; Stanford. Spencer A.; Wright, Edward L.; Bridge, Carrie R.; Griffith, Roger, L.; Benford, Dominic; Stern, Daniel; Tsai, Chao-Wei
By combining data from the NASA Wide-field Infrared Survey Explorer (WISE) mission with optical spectroscopy from the W. M. Keck telescope, we discover a mid-IR color criterion that yields a 78% success rate in identifying rare, typically radio-quiet, 1.6 approx. < z approx. < 4.6 dusty Ly-alpha emitters (LAEs). Of these, at least 37% have emission extended on scales of 30-100 kpc and are considered Ly-alpha "blobs" (LABs). The objects have a surface density of only approx.. 0.1 deg(exp -2), making them rare enough that they have been largely missed in deep, small area surveys. We measured spectroscopic redshifts for...

15. Optical Properties of Iron Silicates in the Infrared to Millimeter as a Function of Wavelength and Temperature - Rinhart, S. A.; Kinzer, R. E.; Nuth, J. A.; Silverberg, R. F.; Cataldo, G.; Richey, C. R.; Benford, D. J.; Wollack, E. J.
The Optical Properties of Astronomical Silicates with Infrared Techniques program utilizes multiple instruments to provide spectral data over a wide range of temperatures and wavelengths. Experimental methods include Vector Network Analyzer and Fourier transform spectroscopy transmission, and reflection/scattering measurements. From this data, we can determine the optical parameters for the index of refraction, n, and the absorption coefficient, k. The analysis of the laboratory transmittance data for each sample type is based upon different mathematical models, which are applied to each data set according to their degree of coherence. Presented here are results from iron silicate dust grain analogs, in...

16. Scientific Objectives for UV-Visible Astrophysics Investigations: A Summary of Responses by the Community (2012) - Perez, Mario R.; Scowen, Paul A.; Bedford, Dominic J.; Neff, Susan G.
Following several recommendations presented by the Astrophysics Decadal Survey 2010 centered around the need to define "a future ultraviolet-optical space capability," on 2012 May 25, NASA issued a Request for Information (RFI) seeking persuasive ultraviolet (UV) and visible wavelength astrophysics science investigations. The goal was to develop a cohesive and compelling set of science objectives that motivate and support the development of the next generation of ultraviolet/visible space astrophysics missions. Responses were due on 10 August 2012 when 34 submissions were received addressing a number of potential science drivers. A UV/visible Mission RFI Workshop was held on 2012 September 20...

17. A Comparison between High-Energy Radiation Background Models and SPENVIS Trapped-Particle Radiation Models - Krizmanic, John F.
We have been assessing the effects of background radiation in low-Earth orbit for the next generation of X-ray and Cosmic-ray experiments, in particular for International Space Station orbit. Outside the areas of high fluxes of trapped radiation, we have been using parameterizations developed by the Fermi team to quantify the high-energy induced background. For the low-energy background, we have been using the AE8 and AP8 SPENVIS models to determine the orbit fractions where the fluxes of trapped particles are too high to allow for useful operation of the experiment. One area we are investigating is how the fluxes of SPENVIS...

18. Kepler Observations of V447 Lyr: an Eclipsing U Gem Cataclysmic Variable - Cannizzo, John K.; Ramsay, Gavin; Howell, Steve B.; Still, Martin; Wood, Matt A.; Smale, Alan; Barclay, Thomas
We present the results of an analysis of Kepler data covering 1.5 yr of the dwarf nova V447 Lyr. We detect eclipses of the accretion disc by the mass donating secondary star every 3.74 h which is the binary orbital period. V447 Lyr is therefore the first dwarf nova in the Kepler field to show eclipses.We also detect five long outbursts and six short outbursts showing V447 Lyr is a U Gem-type dwarf nova. We show that the orbital phase of the mid-eclipse occurs earlier during outbursts compared to quiescence and that the width of the eclipse is greater during...

19. Variability and Trends of Aerosol Properties over Kanpur, Northern India using AERONET Data (2001-10) - Gautam, Ritesh; Tripathi, S. N.; Kosmopoulos, P. G.; Kaskaoutis, Dimitris G.; Singh, Ramesh.P.; Sharma, Manish
Natural and anthropogenic aerosols over northern India play an important role in influencing the regional radiation budget, causing climate implications to the overall hydrological cycle of South Asia. In the context of regional climate change and air quality, we discuss aerosol loading variability and trends at Kanpur AERONET station located in the central part of the Indo-Gangetic plains (IGP), during the last decade (2001-10). Ground-based radiometric measurements show an overall increase in column-integrated aerosol optical depth (AOD) on a yearly basis. This upward trend is mainly due to a sustained increase in the seasonal/monthly averaged AOD during the winter (Dec-Feb)...

20. The Influence of Mineralogy on Recovering Organic Acids from Mars Analogue Materials Using the One-Pot Derivatization Experiment on the Sample Analysis at Mars(SAM) Instrument Suite - Eigenbrode, J. L.; Stalport, Fabien; Coll, P.; Dworkin, J. P.; Glavin, Daniel P.; Buch, A.; Bish, D.; Blake, D.; McAdam, A.; Szopa, C.; Mahaffy, P. R.
The search for complex organic molecules on Mars, including important biomolecules such as amino acids and carboxylic acids, will require a chemical extraction and a derivatization step to transform these organic compounds into species that are sufficiently volatile to be detected by gas chromatography mass spectrometry (GCMS). We have developed a ''one-pot'' extraction and chemical derivatization protocol using N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) and dimethylformamide (DMF) for the Sample Analysis at Mars (SAM) experiment instrument suite on NASA's the Mars Science Laboratory (MSL) mission. The temperature and duration of the derivatization reaction, pre-concentration of chemical derivatives, and gas chromatographic separation parameters have...

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