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  • Astronomy  (272)
  • Aircraft Propulsion and Power
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2002-12-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 2002 Dec 20;298(5602):2297-303.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12493876" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Astronomical Phenomena ; Astronomy ; Biological Evolution ; Cosmic Radiation ; Elementary Particles ; Genome ; Hominidae ; Humans ; Ion Channels/physiology ; Lasers ; Light ; Microwaves ; Motion Pictures as Topic ; Optics and Photonics ; Retinal Ganglion Cells/physiology ; Rod Opsins/physiology ; *Science ; Sequence Analysis, DNA ; Temperature ; Tomography/methods
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2002-12-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 2002 Dec 20;298(5602):2299.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12493878" target="_blank"〉PubMed〈/a〉
    Keywords: Astronomical Phenomena ; Astronomy ; Diagnostic Imaging ; Embryo, Mammalian/cytology ; Genetics, Medical ; Haplotypes ; Humans ; Optics and Photonics ; Proteomics ; *Science ; Stem Cells
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2002-12-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 2002 Dec 20;298(5602):2298.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12493877" target="_blank"〉PubMed〈/a〉
    Keywords: Astronomical Phenomena ; Astronomy ; Biological Evolution ; Budgets ; Climate ; Elementary Particles ; Extraterrestrial Environment ; Ice ; Science/economics/*trends
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2004-12-03
    Description: The objectives of this report was to develop a methodology to predict the time-dependent reliability (probability of failure) of brittle material components subjected to transient thermomechanical loading, taking into account the change in material response with time. This methodology for computing the transient reliability in ceramic components subjected to fluctuation thermomechanical loading was developed, assuming SCG (Slow Crack Growth) as the delayed mode of failure. It takes into account the effect of varying Weibull modulus and materials with time. It was also coded into a beta version of NASA's CARES/Life code, and an example demonstrating its viability was presented.
    Keywords: Aircraft Propulsion and Power
    Type: Fifth Annual Workshop on the Application of Probabilistic Methods for Gas Turbine Engines; 555-586; NASA/CP-2002-211682
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  • 5
    Publication Date: 2004-12-03
    Description: 'NASA is preparing to launch the Next Generation Space Telescope (NGST). This telescope will be larger than the Hubble Space Telescope, be launched on an Atlas missile rather than the Space Shuttle, have a segmented primary mirror, and be placed in a higher orbit. All these differences pose significant challenges.' This effort addresses the challenge of implementing an algorithm for aligning the segments of the primary mirror during the initial deployment that was designed by Philip Olivier and members of SOMTC (Space Optics Manufacturing Technology Center). The implementation was to be performed on the SIBOA (Systematic Image Based Optical Alignment) test bed. Unfortunately, hardware/software aspect concerning SIBOA and an extended time period for algorithm development prevented testing before the end of the study period. Properties of the digital camera were studied and understood, resulting in the current ability of selecting optimal settings regarding saturation. The study was successful in manually capturing several images of two stacked segments with various relative phases. These images can be used to calibrate the algorithm for future implementation. Currently the system is ready for testing.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XLII-1 - XLII-5; NASA/CR-2002-211840
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  • 6
    Publication Date: 2004-12-03
    Description: At the end of World War II Duane Deming, an internationally known economist enunciated what later came to be called "Total Quality Management" (TQM). The basic thrust of this economic theory called for companies and governments to identify their customers and to do whatever was necessary to meet their demands and to keep them satisfied. It also called for companies to compete internally. That is, they were to build products that competed with their own so that they were always improving. Unfortunately most U.S. corporations failed to heed this advice. Consequently, the Japanese who actively sought Deming's advice and instituted it in their corporate planning, built an economy that outstripped that of the U.S. for the next three to four decades. Only after U.S. corporations reorganized and fashioned joint ventures which incorporated the tenets of TQM with their Japanese competitors did they start to catch up. Other institutions such as the U.S. government and its agencies and schools face the same problem. While the power of the U.S. government is in no danger of being usurped, its agencies and schools face real problems which can be traced back to not heeding Deming's advice. For example, the public schools are facing real pressure from private schools and home school families because they are not meeting the needs of the general public, Likewise, NASA and other government agencies find themselves shortchanged in funding because they have failed to convince the general public that their missions are important. In an attempt to convince the general public that its science mission is both interesting and important, in 1998 the Science Directorate at NASA's Marshall Space Flight Center (MSFC) instituted a new outreach effort using the interact to reach the general public as well as the students. They have called it 'Science@NASA'.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XXIX-1 - XXIX-5; NASA/CR-2002-211840
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  • 7
    Publication Date: 2004-12-03
    Description: NASA is preparing to launch the Next Generation Space Telescope (NGST). This telescope will be larger than the Hubble Space Telescope, be launched on an Atlas missile rather than the Space Shuttle, have a segmented primary mirror, and be placed in a higher orbit. All these differences pose significant challenges. This effort addresses the challenge of aligning the segments of the primary mirror during the initial deployment. The segments need to piston values aligned to within one tenth of a wavelength. The present study considers using a neuro-fuzzy model of the Fraunhofer diffraction theory. The intention of the current study was to experimentally verify the algorithm derived earlier. The experimental study was to be performed on the SIBOA (Systematic Image Based Optical Alignment) test bed. Unfortunately the hardware/software for SIBOA was not ready by the end of the study period. We did succeed in capturing several images of two stacked segments with various relative phases. These images can be used to calibrate the algorithm for future implementation. This effort is a continuation of prior work. The basic effort involves developing a closed loop control algorithm to phase a segmented mirror test bed (SIBOA). The control algorithm is based on a neuro-fuzzy model of SIBOA and incorporates nonlinear observers built from observer banks. This effort involves implementing the algorithm on the SIBOA test bed.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XXXVIII-1 - XXXVIII-5; NASA/CR-2002-211840
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  • 8
    Publication Date: 2004-12-03
    Description: Traditionally, study of the plasmasphere has involved terrestrial observation of local characteristics. Global modeling of the plasmasphere in such an observation regime made use of an ensemble of (sparse) local measurements. Recently, sensors aboard the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite (in particular, the EUV (Extreme Ultra Violet) Imager) have created the potential for truly global study of the plasmasphere. IMAGE was launched in spring of 2000 in an orbit with apogee altitude 7.2 RE(Earth radii) and perigee altitude 1000 km. IMAGE's EUV sensor allows an external view of the distribution of cold plasma in the plasmasphere to be acquired. EUV is designed to image light emission at 30.4 nanometers, which is the emission wavelength of the He+ ion in the presence of solar radiation. He+ makes up approximately 15-20% of the plasma in the plasmasphere, thus imaging of He+ enables determination of plasma distribution. The EUV instrument provides a 90 deg by 84 deg field of view which is imaged as an equally spaced 150x140 pixel array on a spherical imaging surface. The EUV produces an image approximately every 10 minutes when the sensor is operating. Since EUV images contain line-of-sight integrations of plasma distributions, they do not directly express equatorial plane density (which would enable comparison of observed plasma distributions with predictions from models). Furthermore, the plasma density at any point in three-space is not known. The goal of our work was development of a technique that can enable plasma density to be determined throughout three-space. Our approach to creation of a three-space representation of the plasma distribution involves disintegrating the EUV lines of sight to form a volumetric map of plasma densities.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XXXVI-1 - XXXVI-5; NASA/CR-2002-211840
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  • 9
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    In:  CASI
    Publication Date: 2009-05-17
    Description: The Far Ultraviolet Spectroscopic Explorer (FUSE) is studying a wide range of astronomical problems in the 905-1187 Angstrom wavelength region through the use of high resolution spectroscopy. The FUSE bandpass forms a nearly optimal complement to the spectral coverage provided by the Hubble Space Telescope (HST), which extends down to approximately 1170 Angstroms. The photoionization threshold of atomic hydrogen (911 Angstroms) sets a natural short-wavelength limit for the FUV. FUSE was launched in June 1999 from Cape Canaveral, Florida, on a Delta II rocket into a 768 km circular orbit. Scientific observations started later that year. This spectral region is extremely rich in spectral diagnostics of astrophysical gases over a wide range of temperatures (100 K to over 10 million K). Important strong spectral lines in this wavelength range include those of neutral hydrogen, deuterium, nitrogen, oxygen, and argon (H I, D I, N I, O I, and Ar I), molecular hydrogen (H2), five-times ionized oxygen (O VI), and several ionization states of sulfur (S III - S VI). These elements are essential for understanding the origin and evolution of the chemical elements, the formation of stars and our Solar System, and the structure of galaxies, including our Milky Way. FUSE is one of NASA's Explorer missions and a cooperative project of NASA and the space agencies of Canada and France. These missions are smaller, more scientifically focused missions than the larger observatories, like Hubble and Chandra. FUSE was designed, built and operated for NASA by the Department of Physics and Astronomy at Johns Hopkins University. Hundreds of astronomers world-wide are using FUSE for a wide range of scientific research. Some of the important scientific discoveries from the first two years of the mission are described.
    Keywords: Astronomy
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  • 10
    Publication Date: 2004-10-05
    Description: The bright variable star theta(sup 2) Tau was monitored with the star camera on the Wide-Field Infrared Explorer satellite. Twelve independent frequencies were detected down to the 0.5 mmag amplitude level. Their reality was investigated by searching for them using two different algorithms and by some internal checks: both procedures strengthened our confidence in the results. All the frequencies are in the range 10.8-14.6 cd(exp -1). The histogram of the frequency spacings shows that 81% are below 1.8 d; rotation may thus play a role in the mode excitation. The fundamental radial mode is not observed, although it is expected to occur in a region where the noise level is very low (55 mu mag). The rms residual is about two times lower than that usually obtained from successful groundbased multisite campaigns. The comparison of the results of previous campaigns with the new ones establishes the amplitude variability of some modes.
    Keywords: Astronomy
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  • 11
    Publication Date: 2011-08-23
    Description: This paper presents performance results for pulse detonation engines taking into account the effects of dissociation and recombination. The amount of sensible heat recovered through recombination in the PDE chamber and exhaust process was found to be significant. These results have an impact on the specific thrust, impulse and fuel consumption of the PDE.
    Keywords: Aircraft Propulsion and Power
    Type: 26th JANNAF Airbreathing Propulsion Subcommittee Meeting; Volume 1; 337-349; CPIA-Publ-713-Vol-1
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  • 12
    Publication Date: 2011-08-23
    Description: The 89 s X-ray pulsar XTE J1906+09 was discovered during Rossi X-Ray Timing Explorer (RXTE) observations of SGR 1900+14 in 1996. Because of monitoring campaigns of SGR 1900+14, XTE J1906+09 was also monitored regularly in 1996 September, 1998 May-June, 1998 August-1999 July, and 2000 March-2001 January. A search for pulsations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August-September. Pulsed flux upper limits for the rest of the observations show that XTE J1906+09 is a transient X-ray pulsar and likely has a Be star companion. The RXTE all-sky monitor did not reveal XTE J1906+09. Pulse-timing analysis of the second outburst discovered a sinusoidal signature in the pulse frequencies that is likely produced by an orbital periastron passage. Fits to pulse phases using an orbital model and quadratic phase model have chi(exp 2) minima at orbital periods of 26-30 days for fixed mass functions of 5, 10, 15, and 20 solar masses. The pulse shape showed energy- and intensity-dependent variations. Pulse-phase spectroscopy quantified the energy-dependent variations. The phase-averaged spectrum used the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the Galactic ridge and was well fitted by an absorbed power law with a high-energy cutoff with column density N(sub H) = 6 +/- 1 x 10(exp 22)/sq cm, a photon index of 1.01 +/- 0.08, cutoff energy E(sub cut) = 11 +/- 1 keV, and e-folding energy E(sub fold) = 19 +/- 4 keV. Estimated 2-10 keV peak fluxes, corrected for contributions from the Galactic ridge and SGR 1900+14, are 6 x l0(exp -12) and 1.1 x 10(exp -10) ergs/sq cm/s for the 1996 and 1998 outbursts, respectively. XTE J1906+09 may be part of an unusual class of Be/X-ray binaries that do not lie on the general spin period versus orbital period correlation with the majority of Be/X-ray binaries.
    Keywords: Astronomy
    Type: The Astrophysical Journal; Volume 565; 1150-1160
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  • 13
    Publication Date: 2011-08-23
    Description: We map the average line-of-sight velocities of the X-ray-emitting mass in the supernova remnant Cassiopeia A using measurements of the centroid of the Si-Healpha blend with the Advanced CCD Imaging Spectrometer on the Chandra X-Ray Observatory. This 4 inch scale map confirms the broad trends noted in previous studies, namely, that the line-of-sight velocity scale is roughly 2000-3000 kilometers per second with relatively more blueshifted material in the southeastern region of the remnant than in the northwest; new details are that the northwestern region consists of two arcs, with the southernmost one representing the most redshifted X-ray-emitting material in Cas A. These results are consistent with contemporaneous results from XMM-Newton. The X-ray patterns resemble the complex velocity patterns measured at optical wavelengths for much denser ejecta, and they support the growing body of evidence that the explosion and subsequent evolution of Cas A were highly asymmetrical.
    Keywords: Astronomy
    Type: The American Astrophysical Society; Volume 560; L175-L179
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  • 14
    Publication Date: 2011-08-23
    Description: We investigate the effect of pulsar polar cap (PC) heating produced by positrons returning from the upper pair formation front. Our calculations are based on a self-consistent treatment of the pair dynamics and the effect of electric field screening by the returning positrons. We calculate the resultant X-ray luminosities and discuss the dependence of the PC heating efficiencies on pulsar parameters, such as characteristic spin-down age, spin period, and surface magnetic field strength. In this study we concentrate on the regime where the pairs are produced in a magnetic field by curvature photons emitted by accelerating electrons. Our theoretical results are not in conflict with the available observational x-ray data and suggest that the effect of PC heating should significantly contribute to the thermal x-ray fluxes from middle-aged and old pulsars. The implications for current and future x-ray observations of pulsars are briefly outlined.
    Keywords: Astronomy
    Type: The Astrophysical Journal; Volume 556; 987-1001
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  • 15
    Publication Date: 2011-08-23
    Description: We present a 2-10 keV ASCA (Advanced Satellite for Cosmology and Astrophysics) observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux equal to approximately 5 x 10(exp -12) ergs cm(exp -2) s(exp -1). We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations.
    Keywords: Astronomy
    Type: Astrophysical Journal; Volume 528; L21-L23
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  • 16
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    In:  Other Sources
    Publication Date: 2011-08-23
    Description: With the observation of low-energy radiation coming from the site of gamma-ray bursts in the hours to weeks after the initial gamma ray burst, it appears that astronomers have discovered a cosmological imprint made by the burster on its surroundings. This paper discusses the phenomenon of postburst emission in Burst and Transient Source Experiment (BATSE) gamma-ray bursts at energies usually associated with prompt emission. After summing up the background-subtracted signals from hundreds of bursts, it is found that tails out to hundreds of seconds after the trigger could be a common feature of events of a duration greater than 2 seconds, and perhaps of the shorter bursts at a lower and shorter-lived level. The tail component may be softer and seems independent of the duration (within the long-GRB sample) and brightness of the prompt burst emission. Some individual bursts have visible tails at gamma-ray energies, and the spectrum in a few cases differs from that of the prompt emission. For one of these bursts, GRB 991216, afterglow at lower energies was detected, which raised the possibility of seeing afterglow observations over large energy ranges using the next generation of GRB detectors in addition to sensitive space- or ground-based telescopes.
    Keywords: Astronomy
    Type: The Astrophysical Journal; Volume 567; 1028-1036
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  • 17
    Publication Date: 2013-08-31
    Description: In 1939, W. Weibull developed what is now commonly known as the "Weibull Distribution Function" primarily to determine the cumulative strength distribution of small sample sizes of elemental fracture specimens. In 1947, G. Lundberg and A. Palmgren, using the Weibull Distribution Function developed a probabilistic lifing protocol for ball and roller bearings. In 1987, E. V. Zaretsky using the Weibull Distribution Function modified the Lundberg and Palmgren approach to life prediction. His method incorporates the results of coupon fatigue testing to compute the life of elemental stress volumes of a complex machine element to predict system life and reliability. This paper examines the Zaretsky method to determine the probabilistic life and reliability of a model gas turbine disk using experimental data from coupon specimens. The predicted results are compared to experimental disk endurance data.
    Keywords: Aircraft Propulsion and Power
    Type: Fifth Annual Workshop on the Application of Probabilistic Methods for Gas Turbine Engines; 603-625; NASA/CP-2002-211682
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  • 18
    Publication Date: 2013-08-29
    Description: This paper presents an overview of the Hubble Space Telescope (HST) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Cryo Cooler (MCC) system, a description of the micro-vibration characterization testing performed, and a discussion of the simulated performance. The NCC is a reverse Brayton cycle system that employs micro turbo-machinery to provide cooling to the NICMOS instrument. Extensive testing was conducted to quantify the expected on-orbit disturbances caused by the micro turbo-machinery and provide input to a flexible-body dynamic simulation to demonstrate compliance with the HST 7 milli-arcsecond root mean square jitter requirement.
    Keywords: Astronomy
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  • 19
    Publication Date: 2013-08-29
    Description: We describe the problem of scheduling observations for an airborne observatory. The problem is more complex than traditional scheduling problems in that it incorporates complex constraints relating the feasibility of an astronomical observation to the position and time of a mobile observatory, as well as traditional temporal constraints and optimization criteria. We describe the problem, its proposed solution and the empirical validation of that solution.
    Keywords: Astronomy
    Type: 13th International Conference on Artificial Intelligence and Planning and Scheduling; United States
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  • 20
    Publication Date: 2013-08-29
    Description: We present Chandra CCD images of Tycho's supernova remnant that delineate its outer shock, seen as a thin, smooth rim along the straight northeastern edge and most of the circular western half. The images also show that the Si and S ejecta are highly clumpy, and have reached the forward shock at numerous locations. Most of the X-ray spectra that we examine along the rim show line emission from Si and S, which in some cases must come from ejecta; the continuum is well represented by either thermal or nonthermal models. In the case that the continuum is assumed to be thermal, the temperatures at the rim are all similar at about 2 keV, and the ionization ages are very low because of the overall weakness of the line emission. Assuming shock velocities inferred from radio and X-ray expansion measurements, these temperatures are substantially below those expected for equilibration of the electron and ion temperatures; electron to mean temperature ratios of approximately less than 0.1 - 0.2 indicate at most modest collisionless heating of the electrons at the shock. The nonthermal contribution to these spectra may be important, however, and may account for as many as half of the counts in the 4-6 keV energy range, based on an extrapolation of the hard X-ray spectrum above 10 keV.
    Keywords: Astronomy
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  • 21
    Publication Date: 2013-08-29
    Description: We present results from a Chandra observation of the NGC 346 star formation region, which contains numerous massive stars, and is related to N66, the largest H(II) region of the SMC (Small Magellanic Cloud). In this first paper, we will focus on the characteristics of the main objects of the field. The NGC 346 cluster itself shows only relatively faint X-ray emission (with L((sub X)(sup unabs)) is approximately 1.5 x 10(exp 34) erg s(exp -1), tightly correlated with the core of the cluster. In the field also lies HD 5980, a LBV (Luminous Blue Variable) star in a binary (or triple system) that is detected for the first time at X-ray energies. The star is X-ray bright, with an unabsorbed luminosity of L((sub X)(sup unabs)) is approximately 1.7 x 10(exp 34) erg s(exp -1), but needs to be monitored further to investigate its X-ray variability over a complete orbital cycle. The high X-ray luminosity may be associated either with colliding winds in the binary system or with the 1994 eruption. HD 5980 is surrounded by a region of diffuse X-ray emission, which may be a superimposed supernova remnant.
    Keywords: Astronomy
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  • 22
    Publication Date: 2013-08-29
    Description: The International Focusing Optics Collaboration for micron Crab Sensitivity (InFOC micronS) balloon-borne hard x-ray incorporates graded multilayer technology to obtain significant effective area at energies previously inaccessible to x-ray optics. The telescope mirror consists of 2040 segmented thin aluminum foils coated with replicated Pt/C multilayers. A sample of these foils was scanned using a pencil-beam reflectometer to determine, multilayer quality. The results of the reflectometer measurements demonstrate our capability to produce large quantity of foils while maintaining high-quality multilayers with a mean Nevot-Croce interface roughness of 0.5nm. We characterize the performance of the complete InFOC micronS telescope with a pencil beam raster scan to determine the effective area and encircled energy function of the telescope. The effective area of the complete telescope is 78, 42 and 22 square centimeters at 20 30 and 40 keV. respectively. The measured encircled energy fraction of the mirror has a half-power diameter of 2.0 plus or minus 0.5 arcmin (90% confidence). The mirror successfully obtained an image of the accreting black hole Cygnus X-1 during a balloon flight in July, 2001. The successful completion and flight test of this telescope demonstrates that graded-multilayer telescopes can be manufactured with high reliability for future x-ray telescope missions such as Constellation-X.
    Keywords: Astronomy
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  • 23
    Publication Date: 2013-08-31
    Description: In an era of shrinking development budgets and resources, where there is also an emphasis on reducing the product development cycle, the role of system assessment, performed in the early stages of an engine development program, becomes very critical to the successful development of new aeropropulsion systems. A reliable system assessment not only helps to identify the best propulsion system concept among several candidates, it can also identify which technologies are worth pursuing. This is particularly important for advanced aeropropulsion technology development programs, which require an enormous amount of resources. In the current practice of deterministic, or point-design, approaches, the uncertainties of design variables are either unaccounted for or accounted for by safety factors. This could often result in an assessment with unknown and unquantifiable reliability. Consequently, it would fail to provide additional insight into the risks associated with the new technologies, which are often needed by decision makers to determine the feasibility and return-on-investment of a new aircraft engine. In this work, an alternative approach based on the probabilistic method was described for a comprehensive assessment of an aeropropulsion system. The statistical approach quantifies the design uncertainties inherent in a new aeropropulsion system and their influences on engine performance. Because of this, it enhances the reliability of a system assessment. A technical assessment of a wave-rotor-enhanced gas turbine engine was performed to demonstrate the methodology. The assessment used probability distributions to account for the uncertainties that occur in component efficiencies and flows and in mechanical design variables. The approach taken in this effort was to integrate the thermodynamic cycle analysis embedded in the computer code NEPP (NASA Engine Performance Program) and the engine weight analysis embedded in the computer code WATE (Weight Analysis of Turbine Engines) with the fast probability integration technique (FPI). FPI was developed by Southwest Research Institute under contract with the NASA Glenn Research Center. The results were plotted in the form of cumulative distribution functions and sensitivity analyses and were compared with results from the traditional deterministic approach. The comparison showed that the probabilistic approach provides a more realistic and systematic way to assess an aeropropulsion system. The current work addressed the application of the probabilistic approach to assess specific fuel consumption, engine thrust, and weight. Similarly, the approach can be used to assess other aspects of aeropropulsion system performance, such as cost, acoustic noise, and emissions. Additional information is included in the original extended abstract.
    Keywords: Aircraft Propulsion and Power
    Type: Fifth Annual Workshop on the Application of Probabilistic Methods for Gas Turbine Engines; 139-164; NASA/CP-2002-211682
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  • 24
    Publication Date: 2011-08-23
    Description: Aircraft fan and compressor blade leading edges suffer from atmospheric particulate erosion that reduces aerodynamic performance. Recontouring the blade leading edge region can restore blade performance. This process typically results in blades of varying chord length. The question therefore arises as to whether performance of refurbished fans and compressors could be further improved if blades of varying chord length are installed into the disk in a certain order. To investigate this issue the aerodynamic performance of a transonic compressor rotor operating with blades of varying chord length was measured in back-to-back compressor test rig entries. One half of the rotor blades were the full nominal chord length while the remaining half of the blades were cut back at the leading edge to 95% of chord length and recontoured. The rotor aerodynamic performance was measured at 100, 80, and 60% of design speed for three blade installation configurations: nominal-chord blades in half of the disk and short-chord blades in half of the disk; four alternating quadrants of nominal-chord and short-chord blades; nominal-chord and short-chord blades alternating around the disk. No significant difference in performance was found between configurations, indicating that blade chord variation is not important to aerodynamic performance above the stall chord limit if leading edges have the same shape. The stall chord limit for most civil aviation turbofan engines is between 94-96% of nominal (new) blade chord.
    Keywords: Aircraft Propulsion and Power
    Type: Journal of Turbomachinery; Volume 24; 351-357
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  • 25
    Publication Date: 2011-08-23
    Description: This paper presents progress on the development of a generic component level model of a turbofan engine simulation, with a digital controller, in an advanced graphical simulation environment. The goal of this effort is to develop and demonstrate a flexible simulation platform for future research in propulsion system control and diagnostic technology. A FORTRAN-based model of a modem, high performance, military-type turbofan engine is being used to validate the platform development. The implementation process required the development of various innovative procedures, which are discussed in the paper. Open-loop and closed-loop comparisons are made between the two simulations. Future enhancements that are to be made to the modular engine simulation are summarized.
    Keywords: Aircraft Propulsion and Power
    Type: 26th JANNAF Airbreathing Propulsion Subcommittee Meeting; Volume 1; 249-257; CPIA-Publ-713-Vol-1
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  • 26
    Publication Date: 2011-08-23
    Description: The Chandra X-Ray Observatory (CXO) was launched on 1999 July 23 by the Columbia Space Shuttle. The first X-rays focused by the telescope were seen on 1999 August 12 after the satellite systems were activated. Beginning with the first observation, it was clear that the telescope was not damaged by the launch environment and was operating as planned. After the early surprise due to the discovery that the telescope concentrated CCD-damaging low-energy protons far more efficiently than had been expected, the observatory is performing optimally and is returning excellent scientific data. Together with other space observatories, especially XMM-Newton, it is obvious that we have entered a new era of discovery in high-energy astrophysics.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific; Volume 114; 1-24
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  • 27
    Publication Date: 2013-08-29
    Description: Although a number of missions to perform asteroseismology from orbit are planned, such as the French COROT (currently scheduled for launch in 2004), the Canadian MOST (2002), and the Danish MONS (2003), none has yet been successfully flown. However, from May 1999 through September 2000, the PI of this proposal initiated a program using the star camera on board the WIRE spacecraft to perform high-precision photometry of solar-like and giant stars. This program relied on the on-board star camera, which consists of a 50mm f/1.75 telescope feeding a 512(sup 2) SITe CCD, which can be read out at rates as high as 10 Hz. The high cadence of observations available with this star camera is made possible by software that locates the 5 brightest stars in the field and reads only an 8x8 pixel box around one selected image. An additional mode of operation, available since November 1999, makes count rate data available on all five stellar images, with a consequent loss of read rate (to 2 Hz for 5 stars). Stellar images are defocused (to allow for more accurate image centroiding), but the entire stellar image lies within the 64-pixel box. we note that in many ways, this instrument is similar to the French instrument EVRIS, which was intended to perform asteroseismology with a 90 mm telescope, but which unfortunately flew as part of the failed Russian MARS 96 spacecraft.
    Keywords: Astronomy
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  • 28
    Publication Date: 2013-08-29
    Description: The Chandra X-Ray Observatory (originally called the Advanced X-Ray Astrophysics Facility - AXAF) is the X-Ray component of NASA's "Great Observatory" Program. Chandra is a NASA facility that provides scientific data to the international astronomical community in response to scientific proposals for its use. The Observatory is the product of the efforts of many organizations in the United States and Europe. The Great Observatories also include the Hubble Space Telescope for space-based observations of astronomical objects primarily in the visible portion of the electromagnetic spectrum, the now defunct Compton Gamma- Ray Observatory that was designed to observe gamma-ray emission from astronomical objects, and the soon-to-be-launched Space Infrared Telescope Facility (SIRTF). The Chandra X-Ray Observatory (hereafter CXO) is sensitive to X-rays in the energy range from below 0.1 to above 10.0 keV corresponding to wavelengths from 12 to 0.12 nanometers. The relationship among the various parts of the electromagnetic spectrum, sorted by characteristic temperature and the corresponding wavelength, is illustrated. The German physicist Wilhelm Roentgen discovered what he thought was a new form of radiation in 1895. He called it X-radiation to summarize its properties. The radiation had the ability to pass through many materials that easily absorb visible light and to free electrons from atoms. We now know that X-rays are nothing more than light (electromagnetic radiation) but at high energies. Light has been given many names: radio waves, microwaves, infrared, visible, ultraviolet, X-ray and gamma radiation are all different forms. Radio waves are composed of low energy particles of light (photons). Optical photons - the only photons perceived by the human eye - are a million times more energetic than the typical radio photon, whereas the energies of X-ray photons range from hundreds to thousands of times higher than that of optical photons. Very low temperature systems (hundreds of degrees below zero Celsius) produce low energy radio and microwave photons, whereas cool bodies like our own (about 30 degrees Celsius) produce infrared radiation. Very high temperatures (millions of degrees Celsius) are one way of producing X-rays.
    Keywords: Astronomy
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  • 29
    Publication Date: 2013-08-29
    Description: Two methods are commonly used to control the secondary/separated flows (and associated losses) in supersonic turbines: endwall contouring and airfoil stacking. In the current investigation the flow path between the first-stage vanes and rotors, and the stacking of the first-stage vanes were varied in an effort to improve turbine performance. The geometric variations have been studied by performing a series of unsteady three-dimensional numerical simulations for the two-stage turbine.
    Keywords: Aircraft Propulsion and Power
    Type: 2002 AIAA Aerospace Sciences Meeting; Unknown
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  • 30
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society 199th Meeting; Washington, DC; United States
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  • 31
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  • 32
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Space Place: a column for amature astronomy club members
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  • 33
    Publication Date: 2018-06-08
    Description: Interferometric observations in the atmospheric windows of the near infrared (1 to 4 microns) can be efficiently used to probe the chemical composition of Miras atmosphere and provide direct measurements of extended gas layers around these stars. This is illustrated by recent Miras observations carried out with the FLUOR instrument of the IOTA interferometer (Mennesson et al. 2002, and Perrin et al. proceedings of this conference) and with the PTI test-bed (Thompson 2002, Thompson et al. 2002). These visibility measurements show evidence for continuum emission from very extended ( 2-3 stellar radii) semi-transparent gaseous atmospheric layers, and large apparent diameter changes with pulsation phase. Interestingly these observations are consistent with the extended molecular gas layers (H20, CO ...) already inferred around some of these objects from IS0 and high resolution ground-based FTS infrared spectra.
    Keywords: Astronomy
    Type: Mass-Losing Pulsating Stars and Their Circumstellar Matter; Sendai; Japan
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  • 34
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Space place column for amateur astronomy club partner newsletters
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  • 35
    Publication Date: 2018-06-08
    Description: We present angular size measurements of 22 oxygen-rich Mira variable stars.
    Keywords: Astronomy
    Type: Astronomical Journal
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  • 36
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: X-ray Surveys, in the Light of New Observatories; Satander; Spain
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  • 37
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Hubble's Science Legacy: Future Optical-UV Astronomy from Space Workshop; Chicago, IL; United States
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  • 38
    Publication Date: 2018-06-11
    Description: We report results of ground-based 10 mu m photometry of main-sequence stars with warm circumstellar dust.
    Keywords: Astronomy
    Type: Symposium on Debris Disks and Planet Formation; Tucson, AZ; United States
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  • 39
    Publication Date: 2018-06-05
    Description: The NASA Glenn Research Center is working with the aeronautics industry to develop highly fuel-efficient and environmentally friendly gas turbine combustor technology. This effort includes testing new hardware designs at conditions that simulate the high-temperature, high-pressure environment expected in the next-generation of high-performance engines. Glenn has the only facilities in which such tests can be performed. One aspect of these tests is the use of nonintrusive optical and laser diagnostics to measure combustion species concentration, fuel/air ratio, fuel drop size, and velocity, and to visualize the fuel injector spray pattern and some combustion species distributions. These data not only help designers to determine the efficacy of specific designs, but provide a database for computer modelers and enhance our understanding of the many processes that take place within a combustor. Until recently, we lacked one critical capability, the ability to measure temperature. This article summarizes our latest developments in that area. Recently, we demonstrated the first-ever use of spontaneous Raman scattering to measure combustion temperatures within the Advanced Subsonics Combustion Rig (ASCR) sector rig. We also established the highest rig pressure ever achieved for a continuous-flow combustor facility, 54.4 bar. The ASCR facility can provide operating pressures from 1 to 60 bar (60 atm). This photograph shows the Raman system setup next to the ASCR rig. The test was performed using a NASA-concept fuel injector and Jet-A fuel over a range of air inlet temperatures, pressures, and fuel/air ratios.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 40
    Publication Date: 2018-06-02
    Description: System Power Analysis for Capability Evaluation (SPACE) is a computer model of the International Space Station's (ISS) Electric Power System (EPS) developed at the NASA Glenn Research Center. This uniquely integrated, detailed model can predict EPS capability, assess EPS performance during a given mission with a specified load demand, conduct what-if studies, and support on-orbit anomaly resolution.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 41
    Publication Date: 2018-06-02
    Description: As part of the NASA Aviation Safety Program, a unique model-based diagnostics method that employs neural networks and genetic algorithms for aircraft engine performance diagnostics has been developed and demonstrated at the NASA Glenn Research Center against a nonlinear gas turbine engine model. Neural networks are applied to estimate the internal health condition of the engine, and genetic algorithms are used for sensor fault detection, isolation, and quantification. This hybrid architecture combines the excellent nonlinear estimation capabilities of neural networks with the capability to rank the likelihood of various faults given a specific sensor suite signature. The method requires a significantly smaller data training set than a neural network approach alone does, and it performs the combined engine health monitoring objectives of performance diagnostics and sensor fault detection and isolation in the presence of nominal and degraded engine health conditions.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 42
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Brown Dwarfs - International Astronomical Union Symposisum; Waikoloa, HI; United States
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  • 43
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Brown Dwarfs International Astronomical Union (IAU) Symposium; Kona, HI; United States
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  • 44
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Stellar Rotation/ International Astronomical Union (IAU) Symposium No. 215; Cancun; Mexico
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  • 45
    Publication Date: 2018-06-08
    Description: We examine the early angular momentum history of stars in young clusters. We reported based on 197 photometric periods in the Orion Flanking Fields and 83 photometric periods in the NGC 2264, that PMS stars apparently do not conserve stellar angular momentum as they evolve down their connective tracks, but instead evolve at nearly constant angular velocity.
    Keywords: Astronomy
    Type: AAS 200th Meeting; Albuquerque, NM; United States
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  • 46
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: AS 05: Astronomy with Large Telescopes: Interferometery for Optical Astronomy II; Waikoloa, HI; United States
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  • 47
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Astronomical Telescopes and Instrumentation; Waikoloa, HI; United States
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  • 48
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    Publication Date: 2018-06-08
    Description: Communicating the world of infrared astronomy to the public is the main vocation of the Education and Public Outreach Office of the SIRTF Science Center; but certainly not its only goal. In the past few years we have created a wide variety of educational products that explains the infrared as well as the multi-wavelength universe.
    Keywords: Astronomy
    Type: International Astronomical Union Symposium 213: Bioastronomy 2002: Life Among the Stars; Australia
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  • 49
    Publication Date: 2018-06-08
    Description: We report on the characterization of bolometers fabricated at the Jet Propulsion Laboratory for the High Frequency Instrument (HFI) of the joint ESA/NASA Herschel/Planck mission to be launched in 2007.
    Keywords: Astronomy
    Type: International Society for Optical Engineering (SPIE) Astronomical Telescopes and Instrumentation; Waikoloa, HI; United States|Proceedings of the SPIE Astronomical Telescopes and Instrumentation
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  • 50
    Publication Date: 2018-06-08
    Description: The High Frequency Instrument on the NASA/ESA Planck Surveyor, scheduled for launch in 2007, will map the entire sky in 6 frequency bands ranging from 100 GHz to 857 GHz to probe Cosmic Microwave Background (CMB) anisotropy and polarization with angular resolution ranging from 9' to 5'. The HFI focal plane will contain 48 silicon nitride micromesh bolometers operating from a 100 mK heat sink. Four detectors in each of the 6 bands will detect unpolarized radiation. An additional 4 pairs of detectors will provide sensitivity to linear polarization of emission at 143, 217 and 353 GHz. We report on the development and characterization of these detectors before delivery to the European HFI consortium.
    Keywords: Astronomy
    Type: Proceedings of SPIE, Millimeter and Submillimeter Detectors for Astronomy|SPIE, Millimeter and Submillimeter Detectors for Astronomy; Waikoloa, HI; United States
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  • 51
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Astronomical Union (IAU) Symposium 213 Bioastronomy 2002: Life Among the Stars; Hamilton Island; Australia
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  • 52
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: EuroWinter School Observing with the Very Large Telescope Interferometer; Les Houches; France
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  • 53
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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  • 54
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    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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  • 55
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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  • 56
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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  • 57
    Publication Date: 2018-06-08
    Description: The radio astronomy community has begun work on a radio telescpe with a square kilometer of connecting area- the Square Kilometer Array (SKA).
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; New Orleans, LA; United States
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  • 58
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th American Astronomical Society Meeting; Washington, DC; United States
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  • 59
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society; Washington, DC; United States
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  • 60
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 76th UCL Astronomy Colloquium; Windsor; United Kingdom
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  • 61
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 200th Meeting of the American Astronomical Society; Albuquerque, NM; United States
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  • 62
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Fred Gillett Symposium on Debris Disks and Planet Formation; Tucson, AZ; United States
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  • 63
    Publication Date: 2018-06-08
    Description: This paper summarizes two very different strategies envisioned for calibrating the systematic field dependent biases present in the Space Interferometry Mission (SIM) instrument. The Internal Calibration strategy is based on pre-launch measurements combined with a set of on orbit measurements generated by a source internal to the instrument. The External Calibration strategy uses stars as an external source for generating the calibration function. Both approaches demand a significant amount of innovation given that SIM's calibration strategy requires a post-calibration error of 100picometers over a 15 degree field of regard while the uncalibrated instrument introduces 10's-100's of nanometers of error. The calibration strategies are discussed in the context of the Wide Angle Astrometric mode of the instrument, although variations on the Internal Calibration Strategy may be used for doing Narrow Angle Astrometry.
    Keywords: Astronomy
    Type: Astronomical Telescopes and Instrumentation Conference; Waikoloa, HI; United States
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  • 64
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Astronomical Telescopes and Instrumentation; Waikoloa, HI; United States
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  • 65
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    Keywords: Astronomy
    Type: International Astronomical Union Symposium 213: Bioastronomy 2002: Life Among the Stars; Australia
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  • 66
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: X-Ray Binaries in the Chandra and XMM-Newton Era; Boston, MA; United States
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  • 67
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Astronomical Union Symposium #215: Stellar Rotation; Cancun; Mexico
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  • 68
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Galactic Center Workshop 2002; Kona, HI; United States
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  • 69
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences 34th Meeting of the American Astronomical Society; Birmingham, AL; United States
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  • 70
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Winds, Bubbles and Explosions; Patzcuaro, Michoacan; Mexico
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  • 71
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Astronomical Union (IAU) Symposium No. 215, Stellar Rotation; Cancun; Mexico
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  • 72
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    Publication Date: 2018-06-08
    Description: The Space Interferometry Mission (SIM) is fundamentally a one-dimensional instrument with a 15-degree field-of-regard. Mission objectives require a global reference grid of thousands of well-understood stars with positions known to 4 microarcseconds which will be used to establish the instrument baseline vector during scientific observations. This accuracy will be achieved by frequently observing a set of stars throughout the mission and performing a global fit of the observations to determine position, proper motion and parallax for each star. Each star will be observed approximately 200 times with about 6.5 stars per single instrument field on the sky. We describe the nature of the reference grid, the candidate objects, and the results of simulations demonstrating grid performance, including estimates of the grid robustness when including effects such as instrument drift and possible contamination of the grid star sample by undetected binaries.
    Keywords: Astronomy
    Type: International Society for Optical Engineering (SPIE) Astronomical Telescopes and Instrumentation Conference; Waikoloa, HI; United States
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  • 73
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    Publication Date: 2018-06-08
    Description: Here we discuss the molecular gas environments of the Wolf-Rayet star WR18, which has as associated optical ring nebula NGC3199.
    Keywords: Astronomy
    Type: A Massive Star Odyssey; Lanarote, Canary Islands; Spain
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  • 74
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Bioastronomy 2002: Life Among the Stars; Hamilton Island; Australia
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  • 75
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Astronomical Union Symposium #210: Modeling of Stellar Atmospheres; Uppsala; Sweden
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  • 76
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Astronomical Union Symposium #210: Modeling of Stellar Atmospheres; Uppsala; Sweden
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  • 77
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: A Festschrift for R. F. Garrison on his 66th Birthday; Tucson, AZ; United States
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  • 78
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th American Astronomical Society Meeting; Washington, DC; United States
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  • 79
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society 199th Meeting; Washington, DC; United States
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  • 80
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society 199th Meeting; Washington, DC; United States
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  • 81
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society 199th Meeting; Washington, DC; United States
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  • 82
    Publication Date: 2018-06-08
    Description: With SIM, we will break the microlensing degeneracy, and allow detailed interpretation of individual microlensing events. We will thus develop a detailed census of the dark and luminous stellar population of the Galaxy.
    Keywords: Astronomy
    Type: 199th American Astronomical Society Meeting; Washington, DC; United States
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  • 83
    Publication Date: 2018-06-06
    Description: The Center for Star Formation Studies, a consortium of scientists from the Space Science Division at Ames and the Astronomy Departments of the University of California at Berkeley and Santa Cruz, conducts a coordinated program of theoretical research on star and planet formation. Under the directorship of D. Hollenbach (Ames), the Center supports postdoctoral fellows, senior visitors, and students; meets regularly at Ames to exchange ideas and to present informal seminars on current research; hosts visits of outside scientists; and conducts a week-long workshop on selected aspects of star and planet formation each summer.
    Keywords: Astronomy
    Type: Ames Research Center Research and Technology 2000; 118-119; NASA/TM-2001-210935
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  • 84
    Publication Date: 2018-06-05
    Description: The Numerical Propulsion System Simulation (NPSS) is a full propulsion system simulation tool used by aerospace engineers to predict and analyze the aerothermodynamic behavior of commercial jet aircraft, military applications, and space transportation. The NPSS framework was developed to support aerospace, but other applications are already leveraging the initial capabilities, such as aviation safety, ground-based power, and alternative energy conversion devices such as fuel cells. By using the framework and developing the necessary components, future applications that NPSS could support include nuclear power, water treatment, biomedicine, chemical processing, and marine propulsion. NPSS will dramatically reduce the time, effort, and expense necessary to design and test jet engines. It accomplishes that by generating sophisticated computer simulations of an aerospace object or system, thus enabling engineers to "test" various design options without having to conduct costly, time-consuming real-life tests. The ultimate goal of NPSS is to create a numerical "test cell" that enables engineers to create complete engine simulations overnight on cost-effective computing platforms. Using NPSS, engine designers will be able to analyze different parts of the engine simultaneously, perform different types of analysis simultaneously (e.g., aerodynamic and structural), and perform analysis in a more efficient and less costly manner. NPSS will cut the development time of a new engine in half, from 10 years to 5 years. And NPSS will have a similar effect on the cost of development: new jet engines will cost about a billion dollars to develop rather than two billion. NPSS is also being applied to the development of space transportation technologies, and it is expected that similar efficiencies and cost savings will result. Advancements of NPSS in fiscal year 2001 included enhancing the NPSS Developer's Kit to easily integrate external components of varying fidelities, providing the initial Visual-Based Syntax (VBS) capability, and developing additional capabilities to support space transportation. NPSS was supported under NASA's High Performance Computing and Communications Program. Through the NASA/Industry Cooperative Effort agreement, NASA Glenn and its industry and Government partners are developing NPSS. The NPSS team consists of propulsion experts and software engineers from GE Aircraft Engines, Pratt & Whitney, The Boeing Company, Honeywell, Rolls-Royce Corporation, Williams International, Teledyne Continental Motors, Arnold Engineering Development Center, Wright Patterson Air Force Base, and the NASA Glenn Research Center. Glenn is leading the way in developing NPSS--a method for solving complex design problems that's faster, better, and cheaper.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 85
    Publication Date: 2018-06-05
    Description: The Oil-Free Turbomachinery team at the NASA Glenn Research Center has unlocked one of the mysteries surrounding foil air bearing performance. Foil air bearings are self-acting hydrodynamic bearings that use ambient air, or any fluid, as their lubricant. In operation, the motion of the shaft's surface drags fluid into the bearing by viscous action, creating a pressurized lubricant film. This lubricating film separates the stationary foil bearing surface from the moving shaft and supports load. Foil bearings have been around for decades and are widely employed in the air cycle machines used for cabin pressurization and cooling aboard commercial jetliners. The Oil-Free Turbomachinery team is fostering the maturation of this technology for integration into advanced Oil-Free aircraft engines. Elimination of the engine oil system can significantly reduce weight and cost and could enable revolutionary new engine designs. Foil bearings, however, have complex elastic support structures (spring packs) that make the prediction of bearing performance, such as load capacity, difficult if not impossible. Researchers at Glenn recently found a link between foil bearing design and load capacity performance. The results have led to a simple rule-of-thumb that relates a bearing's size, speed, and design to its load capacity. Early simple designs (Generation I) had simple elastic (spring) support elements, and performance was limited. More advanced bearings (Generation III) with elastic supports, in which the stiffness is varied locally to optimize gas film pressures, exhibit load capacities that are more than double those of the best previous designs. This is shown graphically in the figure. These more advanced bearings have enabled industry to introduce commercial Oil-Free gas-turbine-based electrical generators and are allowing the aeropropulsion industry to incorporate the technology into aircraft engines. The rule-of-thumb enables engine and bearing designers to easily size and select bearing technology for a new application and determine the level of complexity required in the bearings. This new understanding enables industry to assess the feasibility of new engine designs and provides critical guidance toward the future development of Oil-Free turbomachinery propulsion systems.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 86
    Publication Date: 2018-06-06
    Description: The reported infrared (IR) emission spectra from 1999 Leonid fireballs show a 3.4 micron C-H emission band and unidentified bands at longer wavelengths. Upon atmospheric entry, the Leonid meteorites were flash-heated to temperatures around 2400K, which would destroy any organics on the surface of the meteorite grains. We propose that the nu(sub )CH emission band in the Leonid emission spectra arises from matrix-embedded C(sub n)-H-O entities that are protected from instant pyrolysis. Our model is based on IR absorption nu(sub )CH bands, which we observed in laboratory-grown MgO and natural olivine single crystals, where they arise from C(sub n)-H-O units imbedded in the mineral matrix, indicative of aliphatic -CH2- and -CH3 organics. Instead of being pyrolyzed, the C(sub n)-H-O entities in the Leonid trails become vibrationally excited to higher levels n = 1, 2, 3 etc. During de-excitation they emit at 3.4 microns, due to the (0 =〉 1) transition, and at longer wavelengths, due to hot bands. As a first step toward verifying this hypothesis we measured the C-H vibrational manifold of hexane (C6H14). The calculated positions of the (2 =〉 l ) , (3 =〉 2), and possibly (4 =〉 3) hot bands agree with the Leonid emission bands at 3.5, 3.8 and 4.l microns.
    Keywords: Astronomy
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 245-248; NASA/CP-2002-211863
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  • 87
    Publication Date: 2018-06-06
    Description: Recent measurements of the cosmic ray (CR) antiproton flux have been shown to challenge existing CR propagation models. It was shown that the reacceleration models designed to match secondary to primary nuclei ratio (e.g., Boron/Carbon) produce too few antiprotons, while the traditional non-reacceleration models can reproduce the antiproton flux but fall short of explaining the low-energy decrease in the secondary to primary nuclei ratio. Matching both the secondary to primary nuclei ratio and antiproton flux requires artificial breaks in the diffusion coefficient and the primary injection spectrum suggesting the need for other approaches. In the present paper we discuss one possibility to overcome these difficulties. Using the measured antiproton flux to fix the diffusion coefficient, we show that the spectra of primary nuclei as measured in the heliosphere may contain a fresh local unprocessed component at low energies, thus decreasing the measured secondary to primary nuclei ratio. A model reproducing antiprotons, B/C ratio, and abundances up to Ni is presented.
    Keywords: Astronomy
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  • 88
    Publication Date: 2018-06-06
    Description: This paper reports the analysis of two Chandra X-ray observations of the young magnetic B star rho Ophiuchus S1. X-ray emission from the star was detected in both observations. The average flux is almost the same in both, but during each observation the flux shows significant time variations by a factor of two on timescales of 20-40 ksec. Each spectrum can be fit by either an absorbed power law model with a photon index of approx. -3 or a thin-thermal plasma model with a temperature of approx. 2 keV and an extremely low metal abundance (approx. less than 0.1 solar). The spectrum of the first observation has an apparent line feature at about 6.8 keV, which likely corresponds to highly ionized iron K alpha. In contrast, the spectrum of the second observation shows an anomalous edge absorption component at E approx. 1 keV. The continuum emission and log (L(sub X)/L(sub bol)) approx. -6 are similar to those of young intermediate-mass stars (Herbig Ae/Be stars) although the presence of the magnetic field inferred from the detection of non-thermal radio emission has drawn an analogy between rho Ophiuchus S1 and magnetic chemically peculiar (MCP) stars. If the X-ray emission is thermal, the highest plasma temperature observed is too high to be explained by the conventional theories of magnetic stars, and favors some kind of magnetic dynamo activity, while if the emission is nonthermal, it might be related to mass infall. The 6.8 keV line and 4 keV edge features are marginal but they give important information near the stellar body if they are real. Their physical interpretation is discussed.
    Keywords: Astronomy
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  • 89
    Publication Date: 2018-06-06
    Description: We present results of analyses of Chandra HETG soft X-ray spectra (Lambda = 1.5-25 A) of seven cataclysmic variables. We find that these spectra divide unambiguously into two distinct types. Spectra of the first type, consisting of EX Hya, V603 Aql, U Gem, and SS Cyg, are remarkably well fit by a simple cooling flow model, which assumes only steady-state isobaric radiative cooling. This model has only two free parameters, the maximum temperature, kT(sub max), which provides a rough measurement of the depth of the potential well, and the overall normalization, which provides a highly precise measurement of the total accretion rate. Spectra of the second type, consisting of V1223 Sgr, A Psc, and GK Per, are grossly inconsistent with a simple cooling flow model. They instead exhibit a hard continuum, and, in addition, show strong H-like and He-like ion emission but little Fe L-shell emission, which is consistent with expectations for line emission from a photoionized plasma. Using a simple photoionization model, we argue that the observed line emission for these sources can be driven entirely by the hard continuum. The physical significance of these two distinct types of X-ray spectra is also explored.
    Keywords: Astronomy
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  • 90
    Publication Date: 2018-06-06
    Description: Accretion onto compact objects in X-ray binaries (black hole, neutron star (NS), white dwarf) is characterized by non-uniform flow density profiles. Such an effect of heterogeneity in presence of gravitational forces and pressure gradients exhibits Rayleigh-Taylor gravity waves (RTGW). They should be seen as quasiperiodic wave oscillations (QPO) of the accretion flow in the transition (boundary) layer between the Keplerian disk and the central object. In this paper the author shows that the main QPO frequency, which is very close to the Keplerian frequency, is split into separate frequencies (hybrid and low branch) under the influence of the gravitational forces in the rotational frame of reference. The RTGWs must be present and the related QPOs should be detected in any system where the gravity, buoyancy and Coriolis force effects cannot be excluded (even in the Earth and solar environments). The observed low and high QPO frequencies are an intrinsic signature of the RTGW. The author elaborates the conditions for the density profile when the RTGW oscillations are stable. A comparison of the inferred QPO frequencies with QPO observations is presented. The author finds that hectohertz frequencies detected from NS binaries can be identified as the RTGW low branch frequencies. The author also predicts that an observer can see the double NS spin frequency during the NS long (super) burst events when the pressure gradients and buoyant forces are suppressed. The Coriolis force is the only force which acts in the rotational frame of reference and its presence causes perfect coherent pulsations with a frequency twice of the NS spin. The QPO observations of neutron binaries have established that the high QPO frequencies do not go beyond of the certain upper limit. The author explains this observational effect as a result of the density profile inversions. Also the author demonstrates that a particular problem of the gravity waves in the rotational frame of reference in the approximation of very small pressure gradients is reduced to the problem of the classical oscillator in the rotational frame of reference which was previously introduced and applied for the interpretation of kHZ QPO observation by Osherovich & Titarchuk.
    Keywords: Astronomy
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  • 91
    Publication Date: 2018-06-05
    Description: The development of design optimization technology for turbomachinery has been initiated using the multiobjective evolutionary algorithm under NASA's Intelligent Synthesis Environment and Revolutionary Aeropropulsion Concepts programs. As an alternative to the traditional gradient-based methods, evolutionary algorithms (EA's) are emergent design-optimization algorithms modeled after the mechanisms found in natural evolution. EA's search from multiple points, instead of moving from a single point. In addition, they require no derivatives or gradients of the objective function, leading to robustness and simplicity in coupling any evaluation codes. Parallel efficiency also becomes very high by using a simple master-slave concept for function evaluations, since such evaluations often consume the most CPU time, such as computational fluid dynamics. Application of EA's to multiobjective design problems is also straightforward because EA's maintain a population of design candidates in parallel. Because of these advantages, EA's are a unique and attractive approach to real-world design optimization problems.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 92
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences - American Astronomical Society 34th Annual Meeting; Birmingham, AL; United States
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  • 93
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences 34th Meeting of the American Astronomical Society; Birmingham, AL; United States
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  • 94
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 200th Meeting of the American Astronomical Society; Albuquerque, NM; United States
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  • 95
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Society for Optical Engineering (SPIE) Astronomical Telescope and Instrumentation; Waikoloa, HI; United States
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  • 96
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Second Workshop on New Concepts for Far-IR Submillimeter Space Astronomy; College Park, MD; United States
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  • 97
    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Symposium on Astronomical Telescopes and Instrumentation; Waikoloa, HI; United States
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  • 98
    Publication Date: 2018-06-08
    Description: We present and analyze infrared spectra of the supergiant VR 5-7, in the Quintuplet cluster 30 pc from the Galactic center. Within the uncertainties, the [C/H],[N/H], and [O/H] abundances in this star are equal of Ori, a star which exhibits mixing of CNO processed elements, but distinct from the abundance patterns in IRS 7.
    Keywords: Astronomy
    Type: Galactic Center Workshop 2002; Kona, HI; United States
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  • 99
    Publication Date: 2018-06-08
    Description: A new architecture for all-sky browsing of astronomical datasets has been designed and implemented in the form of a graphical frontend to the yourSky custom mosaicking engine.
    Keywords: Astronomy
    Type: Astronomical Data Analysis Software and Systems XII; Baltimore, MD; United States
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  • 100
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Astronomical Data Analysis Software and Systems (ADASS) XXI; Baltimore, MD; United States
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