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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Metallicities of Emission-Line Galaxies from HST ACS PEARS and HST WFC3 ERS Grism Spectroscopy at 0.6 is less than z is less than 2.4

Galaxies selected on the basis of their emission line strength. show low metallicities, regardless of their redshifts. We conclude this from a sample of faint galaxies at redshifts between 0.6 < z < 2.4, selected by their prominent emission lines in low resolution grism spectra in the optiCa.i with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) and in the near-infrared using Wide-Field Camera 3 (WFC3). Using a sample of 11 emission line galaxies (ELGs) at 0.6 < z < 2.4 with luminosities of -22 approx < MB approx -19 which have [OII], H-Beta, and [OIII] line flux measurements from the combination of two grism spectral surveys, we use the R23 method to derive the gas-phase oxygen abundances: 7.5 <12+log(0/H)<8.5. The galaxy stellar masses are derived using Bayesian based Markov Chain Monte Carlo (pi MC(exp 2)) fitting of their Spectral Energy Distribution (SED), and span the mass range 8.1 < log(M(stellar)/M(solar)) < 10.1. These galaxies show a mass-metal1icity (M-L) and Luminosity-Metallicity (LZ) relation, which is offset by -<J.6 dex in meta1licity at given absolute magnitude and stellar mass relative to the local SDSS galaxies, as well as continuum selected DEEP2 samples at similar redshifts. The emission-line selected galaxies most resemble the local "green peas" galaxies and Lyman-alpha galaxies at z approx = 0.3 and z approx = 2.3 in the M-Z and L-Z relations and their morphologies. The G - M(sub 20) morphology analysis shows that 10 out of 11 show disturbed morphology, even as the star-forming regions are compact. These galaxies may be intrinsically metal poor, being at early stages of formation, or the low metallicities may be due to gas infall and accretion due to mergers.

Xia, Lifang↗
NASA NTRS2015

Contractors Road Heavy Equipment Area SWMU 055 Corrective Measures Implementation Progress Report Kennedy Space Center, Florida

This Corrective Measures Implementation (CMI) Progress Report documents: (i) activities conducted as part of supplemental assessment activities completed from June 2009 through November 2014; (ii) Engineering Evaluation (EE) Advanced Data Packages (ADPs); and (iii) recommendations for future activities related to corrective measures at the Site. Applicable meeting minutes are provided as Appendix A. The following EE ADPs for CRHE are included with this CMI Progress Report: center dot Supplemental Site Characterization ADP (Step 1 EE) (Appendix B) center dot Site Characterization ADP (Step 1 EE) for Hot Spot 1 (HS1) (Appendix C) center dot Remedial Alternatives Evaluation (Step 2 EE) ADP for HS1 (Appendix D) center dot Interim Measures Work Plan (Step 3 EE) ADP for HS1 (Appendix E) center dot Site Characterization ADP (Step 1 EE) ADP for Hot Spot 2 (HS2), High Concentration Plume (HCP), and Low Concentration Plume (LCP) (Appendix F) A summary of direct-push technology (DPT) and groundwater monitoring well sampling results are provided in Appendices G and H, respectively. The Interim Land Use Control Implementation Plan (LUCIP) is provided as Appendix I. Monitoring well completion reports, other applicable field forms, survey data, and analytical laboratory reports are provided as Appendices J through M, respectively, in the electronic copy of this document. Selected Site photographs are provided in Appendix N. The interim groundwater monitoring plan and document revision log are included as Appendices O and P, respectively. KSC Electronic Data Deliverable (KEDD) files are provided on the attached compact disk.

Johnson, Jill W.↗
NASA NTRS2001

Characteristics of the Variable Star P Cygni Determined from Cluster Membership

Empirical information on the luminosity, reddening, age, and mass of the variable B2 Oe supergiant P Cygni is derived from its assumed membership in the sparse anonymous cluster on which it is projected, as well as its association with the spatially adjacent cluster IC 4996, which forms a double cluster with the P Cyg cluster. Evidence for the high luminosity of P Cyg is confirmed by its derived absolute magnitude of M(sub V)= -8.46 +/- 0.03, which translates to log (L/L(sun)) = 5.54 +/- 0.02 for an effective temperature consistent with the star's derived space reddening (E(sub B-V) = 0.53 +/- 0.02). More surprising is an age for the associated clusters of 6 (+/- 1.5) x 10(exp 6) years, corresponding to a turnoff point mass of 25.1 (+/- 5.5) M(sun). By inference, P Cygni, as a post main-sequence object, should have a mass of no more than approximately 23-35 M(sun).

Turner, David G.↗
NASA NTRS1991

The SERENDIP 2 SETI project: Current status

Over the past 30 years, interest in extraterrestrial intelligence has progressed from philosophical discussion to rigorous scientific endeavors attempting to make contact. Since it is impossible to assess the probability of success and the amount of telescope time needed for detection, Search for Extraterrestrial Intelligence (SETI) Projects are plagued with the problem of attaining the large amounts of time needed on the world's precious few large radio telescopes. To circumvent this problem, the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP) instrument operates autonomously in a piggyback mode utilizing whatever observing plan is chosen by the primary observer. In this way, large quantities of high-quality data can be collected in a cost-effective and unobtrusive manner. During normal operations, SERENDIP logs statistically significant events for further offline analysis. Due to the large number of terrestrial and near-space transmitters on earth, a major element of the SERENDIP project involves identifying and rejecting spurious signals from these sources. Another major element of the SERENDIP Project (as well as most other SETI efforts) is detecting extraterrestrial intelligence (ETI) signals. Events selected as candidate ETI signals are studied further in a targeted search program which utilizes between 24 to 48 hours of dedicated telescope time each year.

Bowyer, C. S.↗
NASA NTRS1991

A systems approach to solder joint fatigue in spacecraft electronic packaging

Differential expansion induced fatigue resulting from temperature cycling is a leading cause of solder joint failures in spacecraft. Achieving high reliability flight hardware requires that each element of the fatigue issue be addressed carefully. This includes defining the complete thermal-cycle environment to be experienced by the hardware, developing electronic packaging concepts that are consistent with the defined environments, and validating the completed designs with a thorough qualification and acceptance test program. This paper describes a useful systems approach to solder fatigue based principally on the fundamental log-strain versus log-cycles-to-failure behavior of fatigue. This fundamental behavior has been useful to integrate diverse ground test and flight operational thermal-cycle environments into a unified electronics design approach. Each element of the approach reflects both the mechanism physics that control solder fatigue, as well as the practical realities of the hardware build, test, delivery, and application cycle.

Ross, R. G., Jr.↗
NASA NTRS1985

Development and testing of tip devices for horizontal axis wind turbines

A theoretical and field experimental program has been carried out to investigate the use of tip devices on horizontal axis wind turbine rotors. The objective was to improve performance by the reduction of tip losses. While power output can always be increased by a simple radial tip extension, such a modification also results in an increased gale load both because of the extra projected area and longer moment arm. Tip devices have the potential to increase power output without such a structural penalty. A vortex lattice computer model was used to optimize three basic tip configuration types for a 25 kW stall limited commercial wind turbine. The types were a change in tip planform, and a single-element and double-element nonplanar tip extension (winglets). A complete data acquisition system was developed which recorded three wind speed components, ambient pressure, temperature, and turbine output. The system operated unattended and could perform real-time processing of the data, displaying the measured power curve as data accumulated in either a bin sort mode or polynomial curve fit. Approximately 270 hr of perormance data were collected over a three-month period. The sampling interval was 2.4 sec; thrus over 400,000 raw data points were logged. Results for each of the three new tip devices, compared with the original tip, showed a small decrease (of the order of 1 kW) in power output over the measured range of wind speeds from cut-in at about 4 m/s to over 20 m/s, well into the stall limiting region. Changes in orientation and angle-of-attack of the winglets were not made. For aircraft wing tip devices, favorable tip shapes have been reported and it is likely that the tip devices tested in this program did not improve rotor performance because they were not optimally adjusted.

Gyatt, G. W.↗
NASA NTRS1973

The log-periodic array at the Clark Lake Radio Observatory

A log-periodic array, 3 km in length, is operating at Clark Lake Radio Observatory. It makes one-dimensional sweeps of the solar brightness distribution in the frequency range 20 to 65 MHz once per sec. The phasing of the array and the receiving system are described, as well as how the dynamic spectra are analyzed for the positions of solar radio sources. Simultaneous measurements at many frequencies enable the observer to remove the effects of ionospheric refraction and to obtain fundamental positions to an accuracy of about one arc min at decametric wavelengths. Fundamental positions are given for Cassiopeia A.

Erickson, W. C.↗
NASA NTRS1994

An optical region elemental abundance analysis of the chemically peculiar HgMn star chi Lupi

The optical spectrum of the chemically peculiar HgMn type binary star chi Lupi has been analyzed to determine atmospheric parameters and elemental abundances. Echelle spectra were obtained with the 3.9 m Anglo-Australian telescope to exploit the extreme shape-lined nature of the spectrum. This study was undertaken in support of ultraviolet analyses currently underway that utilize echell spectra obtained with the Hubble Space Telescope. For the B9.5 V primary star we obtain T(sub eff) = 10650 K, log g = 3.9, and xi = 0 km/s, while for the A2 V secondary, T(sub eff) = 9200 K, log g = 4.0, and xi = 2 km/s. Most of the elemental abundances are typical of HgMn stars with similar T(sub eff) showing an overall iron-peak elemental abundance distribution that is basically solar in nature with enhancement of the light elements Si, P, and S, as well as all detected elements heavier than the iron group. Abundances for several elements have been determined for the first time in this star, including several of the rare-earths. The secondary star spectrum shows Am star characteristics. We also discuss the relative merits of the equivalent width and synthetic spectrum techniques in determining the elemental abundences, concluding that the synthetic spectrum technique is necessary for obtaining abundances with the utmost accuracy.

Wahlgren, Glenn M.↗
NASA NTRS2004

Accelerated Electrons in the LLBL as Observed by Interball on February 15, 1996

We analyze electron observations in the low latitude boundary layer (LLBL) with the Interball Tail satellite under a southward-duskward magnetosheath magnetic field. It is well known that the LLBL is characterized by bi-directional electron velocity distributions, which leads to an enhancement of the electron temperature. It is also well known that the electron temperature within the LLBL increases with a decrease of the LLBL number density. We found that the parallel electron velocity distribution changes self-consistently with varying number density. Namely, the shape of the parallel velocity distribution does not change in a log-log scale indicating that electron parallel velocities increase proportionately as the number density decreases. This suggests a possible role for the Fermi acceleration mechanism. We also discuss the LLBL topology that is provided by electron velocity distributions.

Vaisberg, O. L.↗
NASA NTRS1994

The dynamics and structure of the S0 galaxy NGC 7332

Spectroscopic and photometric observations of the edge-on S0 galaxy NGC 7332 are presented. The spectra show the galaxy to possess a rapidly counter-rotating extended gas disk as detected from both (O III) 5007 A and H alpha emission. Multiple slit orientations at a variety of position angles clearly show the decoupling of the angular momenta between the stellar and gaseous components. The gas is distributed asymmetrically and displays noncircular motions indicating that it has not reached equilibrium. These observations are strong evidence in support of an accretion process having occurred in NGC 7332. Broad R and B band CCD images show the boxy isophotes that NGC 7332 has long been known to possess while offset spectra taken parallel to the major and minor axes display the cylindrical rotation common to galaxies with box-shaped bulges. The bulge of NGC 7332 is well described by an r(exp 1/4)-law on both the major and minor axes while the outer disk is exponential. The B-R color of the disk is uniform; the only indication of a trend to blue colors is a Delta(B-R(sub c))/Delta log r= -0.04 +/- 0.01 gradient seen perpendicular to the bulge and disk. There exists a 10 sec long region of nearly constant surface brightness along the major axis between the bulge and disk components. Not likely due to absorbing material, the relation of this feature to the already complicated structure of the galaxy is considered.

Fisher, David↗
NASA NTRS2014

Monitoring with Data Automata

We present a form of automaton, referred to as data automata, suited for monitoring sequences of data-carrying events, for example emitted by an executing software system. This form of automata allows states to be parameterized with data, forming named records, which are stored in an efficiently indexed data structure, a form of database. This very explicit approach differs from other automaton-based monitoring approaches. Data automata are also characterized by allowing transition conditions to refer to other parameterized states, and by allowing transitions sequences. The presented automaton concept is inspired by rule-based systems, especially the Rete algorithm, which is one of the well-established algorithms for executing rule-based systems. We present an optimized external DSL for data automata, as well as a comparable unoptimized internal DSL (API) in the Scala programming language, in order to compare the two solutions. An evaluation compares these two solutions to several other monitoring systems.

log analysis↗
NASA NTRS2019

UH-60A Airloads Flight Test Program: Data Counter 9017

Aeromechanics Branch interns at Ames Research Center have been directly contributing to the data quality analysis and reporting of the UH-60A Airloads Flight Test Program for many years. In chronological order (together with the semester and year): Caroline Edwards (Summer 2011); Joni DeGuzman and Carson Turner (Fall 2011); Eric Fritz (Spring 2012); Connor Beierle (Fall 2012); Christopher Olinger (Spring and Summer 2013); Needa Lin, Anatole Levkoff, Maxwell Loebig, Jose Orejel, Megan Prout, and Albert Sue (Summer 2014); Jared Archey (Fall 2014); Alexander Crone (Summer 2015); Jeffrey Diament, Austin Djang, and Jessica Swan (Summer 2016); Makenzie Allen (Summer 2017); Colin Lauzon (Fall 2017); Eric Gilkey (Spring 2018); and Nicholas Masso (Summer 2019). These interns have spent their internships reviewing flight logs, extracting the data out of TRENDS, formatting the data into spreadsheets, writing code to automate the process, and plotting results. Without their efforts, much of the work would be unfinished. The authors appreciate the achievements of the UH-60A Airloads Working Group during its 20-year lifetime, as well the contributions of Randy Peterson, Tom Norman, and William Warmbrodt to the data processing and assistance with the report preparation. Lastly, this report is dedicated to William Bousman for his efforts preceding, during, and subsequent to the UH-60A Airloads Flight Test Program.

Kufeld, Robert M.↗
NASA NTRS2011

Analysis of Noise Exposure Measurements Made Onboard the International Space Station

The International Space Station (ISS) is a unique workplace environment for U.S. astronauts and Russian cosmonauts to conduct research and live for a period of six months or more. Noise has been an enduring environmental physical hazard that has been a challenge for the U.S. space program since before the Apollo era. Noise exposure in ISS poses significant risks to the crewmembers, such as; hearing loss (temporary or permanent), possible disruptions of crew sleep, interference with speech intelligibility and communication, possible interference with crew task performance, and possible reduction in alarm audibility. Acoustic measurements are made aboard ISS and compared to requirements in order to assess the acoustic environment to which the crewmembers are exposed. The purpose of this paper is to describe in detail the noise exposure monitoring program as well as an assessment of the acoustic dosimeter data collected to date. The hardware currently being used for monitoring the noise exposure onboard ISS will be discussed. Acoustic data onboard ISS has been collected since the beginning of ISS (Increment 1, November 2000). Noise exposure data analysis will include acoustic dosimetry logged data from crew-worn during work and sleep periods and also fixed-location measurements from Increment 1 to present day. Noise exposure levels (8-, 16- and 24-hr), LEQ, will also be provided and discussed in this paper. Discussions related to hearing protection will also be included. Future directions and recommendations for the noise exposure monitoring program will be highlighted. This acoustic data is used to ensure a safe and healthy working and living environment for the crewmembers aboard the ISS.

Limardo, Jose G.↗
NASA NTRS2011

Analysis of Noise Exposure Measurements Acquired Onboard the International Space Station

The International Space Station (ISS) is a unique workplace environment for U.S. astronauts and Russian cosmonauts to conduct research and live for a period of six months or more. Noise has been an enduring environmental physical hazard that has been a challenge for the U.S. space program since before the Apollo era. Noise exposure in ISS poses significant risks to the crewmembers, such as; hearing loss (temporary or permanent), possible disruptions of crew sleep, interference with speech intelligibility and communication, possible interference with crew task performance, and possible reduction in alarm audibility. Acoustic measurements were made onboard ISS and compared to requirements in order to assess the acoustic environment to which the crewmembers are exposed. The purpose of this paper is to describe in detail the noise exposure monitoring program as well as an assessment of the acoustic dosimeter data collected to date. The hardware currently being used for monitoring the noise exposure onboard ISS will be discussed. Acoustic data onboard ISS has been collected since the beginning of ISS (Increment 1, November 2001). Noise exposure data analysis will include acoustic dosimetry logged data from crew-worn dosimeters during work and sleep periods and also fixed-location measurements from Increment 1 to present day. Noise exposure levels (8-, 16- and 24-hr), LEQ, will also be provided and discussed in this paper. Future directions and recommendations for the noise exposure monitoring program will be highlighted. This acoustic data is used to ensure a safe and healthy working and living environment for the crewmembers onboard the ISS.

Limardo, Jose G.↗
NASA NTRS2011

Fermi/GBM Observations of SGRJ0501 + 4516 Bursts

We present our temporal and spectral analyses of 29 bursts from SGRJ0501+4516, detected with the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray Space Telescope during the 13 days of the source activation in 2008 (August 22 to September 3). We find that the T(sub 90) durations of the bursts can be fit with a log-normal distribution with a mean value of approx. 123 ms. We also estimate for the first time event durations of Soft Gamma Repeater (SGR) bursts in photon space (i.e., using their deconvolved spectra) and find that these are very similar to the T(sub 90)s estimated in count space (following a log-normal distribution with a mean value of approx. 124 ms). We fit the time-integrated spectra for each burst and the time-resolved spectra of the five brightest bursts with several models. We find that a single power law with an exponential cutoff model fits all 29 bursts well, while 18 of the events can also be fit with two black body functions. We expand on the physical interpretation of these two models and we compare their parameters and discuss their evolution. We show that the time-integrated and time-resolved spectra reveal that E(sub peak) decreases with energy flux (and fluence) to a minimum of approx. 30 keV at F = 8.7 x 10(exp -6)erg/sq cm/s, increasing steadily afterwards. Two more sources exhibit a similar trend: SGRs J1550 - 5418 and 1806 - 20. The isotropic luminosity, L(sub iso), corresponding to these flux values is roughly similar for all sources (0.4 - l.5 x 10(exp 40) erg/s.

Lin, Lin↗
NASA NTRS1995

A multiparametric analysis of the Einstein sample of early-type galaxies. 2: Galaxy formation history and properties of the interstellar medium

We have conducted bivariate and multivariate statistical analysis of data measuring the integrated luminosity, shape, and potential depth of the Einstein sample of early-type galaxies (presented by Fabbiano et al. 1992). We find significant correlations between the X-ray properties and the axial ratios (a/b) of our sample, such that the roundest systems tend to have the highest L(sub x) and L(sub x)/L(sub B). The most radio-loud objects are also the roundest. We confirm the assertion of Bender et al. (1989) that galaxies with high L(sub x) are boxy (have negative a(sub 4)). Both a/b and a(sub 4) are correlated with L(sub B), but not with IRAS 12 um and 100 um luminosities. There are strong correlations between L(sub x), Mg(sub 2), and sigma(sub nu) in the sense that those systems with the deepest potential wells have the highest L(sub x) and Mg(sub 2). Thus the depth of the potential well appears to govern both the ability to reatin an ISM at the present epoch and to retain the enriched ejecta of early star formation bursts. Both L(sub x)/L(sub B) and L(sub 6) (the 6 cm radio luminosity) show threshold effects with sigma(sub nu) exhibiting sharp increases at log sigma(sub nu) approximately = 2.2. Finally, there is clearly an interrelationship between the various stellar and structural parameters: The scatter in the bivariate relationships between the shape parameters (a/b and a(sub 4)) and the depth parameter sigma(sub nu) is a function of abundance in the sense that, for a given a(sub 4) or a/b, the systems with the highest sigma(sub nu) also have the highest Mg(sub 2). Furthermore, for a constant sigma(sun nu), disky galaxies tend to have higher Mg(sub 2) than boxy ones. Alternatively, for a given abundance, boxy ellipticals tend to be more massive than disky ellipticals. One possibility is that early-type galaxies of a given mass, originating from mergers (boxy ellipticals), have lower abundances than 'primordial' (disky) early-type galaxies. Another is that disky inner isophotes are due not to primordial dissipation collapse, but to either the self-gravitating inner disks of captured spirals or the dissipational collapse of new disk structures from the premerger ISM. The high measured nuclear Mg(sub 2) values would thus be due to enrichment from secondary bursts of star formation triggered by the merging event.

Eskridge, Paul B.↗
NASA NTRS2018

Calculating the Modal Mineralogy of Aubrite Meteorites Using X-Ray Computed Tomography

The aubrites are a group of differentiated meteorites that formed in extremely reducing conditions, with oxygen fugacities (ƒO2) ranging from ~2 to ~6 log units below the Iron-Wüstite buffer. At these extreme conditions, elements that are lithophile (silica-loving) on Earth can behave as chalcophiles (sulfur-loving) or siderophiles (metal-loving), and FeO-poor silicates and exotic sulfides can form. Elemental partitioning among minerals at these conditions are still not well understood, thus studying aubrites could help better constrain elemental behavior. Only 30 aubrites exist; however, they display various textures, which can be difficult to identify in small samples. Identifying composite clasts can help in understanding the igneous history of the aubrite parent bodies. In order to distinguish different minerals and textures in larger samples, we use X-ray computed tomography (XCT), which is a useful, non-destructive analysis that can produce a 3D representation of a meteorite's textures, structures, and modal mineralogy. This study investigates the Norton County aubrite using XCT. Norton County is a fragmental impact breccia aubrite, and was an observed fall with a main mass of 1.1 tons. This large amount of material offers an opportunity to investigate a great volume of reduced, aubritic sample and study a more diverse variety of clasts. Here we report XCT results of two samples of Norton County (NC 15417) in order to constrain the 3D modal mineralogy of silicates, sulfides, and metals, and to identify unique clasts within the matrix.

Wilbur, Zoe↗
NASA NTRS1995

Pressure correlations at a fluid/structure interface

The structure of pressure-pressure correlations at the interface of an incompressible steady-state turbulent flow with a rigid boundary was investigated. For the sake of completeness, the absolute value of the correlation between two random varying functions is herein defined as a number greater than or equal to zero and less than or equal to unity which is a measure of that fraction of one of the functions that 'follows' the second function (or vice versa). It was found that the soughtafter correlations can be determined by consideration of the high Re Navier-Stokes equation, but that the complexity of boundary layer turbulence, in particular the inhomogeneity perpendicular to the boundary and the anisotropy due to convective flow gradients, makes the structure of said correlations extremely difficult to assess. One of the earlier researchers in this field described the quantity under present consideration as 'a quantity which is beyond assessment.' Nonetheless, it was found that under some rather simplifying assumptions the determination of the required structure necessitates the formulation of the related structure of second order two-point correlations of turbulent velocity gradients, as well as third order two-point correlations of velocity gradients. The presence of these latter gradients is due to the nonlinearity in the turbulence ('turbulence self-interaction'). Both of these correlations are scaled, although not similarly, by factors dependent upon the magnitude of the convective flow, which can be modeled using a log law approximation. Fourth order correlations, although present, can be ignored, since they constitute 'higher order terms.' In a slightly more complex situation, it was found that convective flow gradients also have to be incorporated. At the moment, no definitive algebraic information peculiar to pressure-pressure correlations is available in the most highly idealized cases.

Trevino, George↗