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Sample records for core helium flash

  1. Hydrodynamic simulations of the core helium flash

    CERN Document Server

    Mocak, M; Weiss, A; Kifonidis, K; 10.1017/S1743921308022813

    2009-01-01

    We describe and discuss hydrodynamic simulations of the core helium flash using an initial model of a 1.25 M_sol star with a metallicity of 0.02 near at its peak. Past research concerned with the dynamics of the core helium flash is inconclusive. Its results range from a confirmation of the standard picture, where the star remains in hydrostatic equilibrium during the flash (Deupree 1996), to a disruption or a significant mass loss of the star (Edwards 1969; Cole & Deupree 1980). However, the most recent multidimensional hydrodynamic study (Dearborn 2006) suggests a quiescent behavior of the core helium flash and seems to rule out an explosive scenario. Here we present partial results of a new comprehensive study of the core helium flash, which seem to confirm this qualitative behavior and give a better insight into operation of the convection zone powered by helium burning during the flash. The hydrodynamic evolution is followed on a computational grid in spherical coordinates using our new version of th...

  2. The core helium flash revisited III. From Pop I to Pop III stars

    CERN Document Server

    Mocak, Miroslav; Mueller, Ewald; Kifonidis, Konstantinos

    2010-01-01

    Degenerate ignition of helium in low-mass stars at the end of the red giant branch phase leads to dynamic convection in their helium cores. One-dimensional (1D) stellar modeling of this intrinsically multi-dimensional dynamic event is likely to be inadequate. Previous hydrodynamic simulations imply that the single convection zone in the helium core of metal-rich Pop I stars grows during the flash on a dynamic timescale. This may lead to hydrogen injection into the core, and a double convection zone structure as known from one-dimensional core helium flash simulations of low-mass Pop III stars. We perform hydrodynamic simulations of the core helium flash in two and three dimensions to better constrain the nature of these events. To this end we study the hydrodynamics of convection within the helium cores of a 1.25 \\Msun metal-rich Pop I star (Z=0.02), and a 0.85 \\Msun metal-free Pop III star (Z=0) near the peak of the flash. These models possess single and double convection zones, respectively. We use 1D stell...

  3. The core helium flash revisited: I. One and two-dimensional hydrodynamic simulations

    CERN Document Server

    Mocak, M; Weiss, A; Kifonidis, K

    2008-01-01

    We investigate the hydrodynamics of the core helium flash near its peak. Past research concerned with the dynamics of this event is inconclusive. However, the most recent multidimensional hydrodynamic studies suggest a quiescent behavior and seem to rule out an explosive scenario. Previous work indicated, that depending on initial conditions, employed turbulence models, grid resolution, and dimensionality of the simulation, the core helium flash leads either to the disruption of a low-mass star or to a quiescent quasi-hydrostatic evolution. We try to clarify this issue by simulating the evolution with advanced numerical methods and detailed microphysics. Assuming spherical or axial symmetry, we simulate the evolution of the helium core of a $1.25 M_{\\odot}$ star with a metallicity Z=0.02 during the core helium flash at its peak with a grid-based hydrodynamics code. We find that the core helium flash neither rips the star apart, nor that it significantly alters its structure, as convection plays a crucial role...

  4. The core helium flash revisited. II. Two and three-dimensional hydrodynamic simulations

    Science.gov (United States)

    Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K.

    2009-07-01

    Context: We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations. Aims: In a previous study we found that the temporal evolution and the properties of the convection inferred from two-dimensional hydrodynamic studies are similar to those predicted by quasi-hydrostatic stellar evolutionary calculations. However, as vorticity is conserved in axisymmetric flows, two-dimensional simulations of convection are characterized by incorrect dominant spatial scales and exaggerated velocities. Here, we present three-dimensional simulations that eliminate the restrictions and flaws of two-dimensional models and that provide a geometrically unbiased insight into the hydrodynamics of the core helium flash. In particular, we study whether the assumptions and predictions of stellar evolutionary calculations based on the mixing-length theory can be confirmed by hydrodynamic simulations. Methods: We used a multidimensional Eulerian hydrodynamics code based on state-of-the-art numerical techniques to simulate the evolution of the helium core of a 1.25 M⊙ Pop I star. Results: Our three-dimensional hydrodynamic simulations of the evolution of a star during the peak of the core helium flash do not show any explosive behavior. The convective flow patterns developing in the three-dimensional models are structurally different from those of the corresponding two-dimensional models, and the typical convective velocities are lower than those found in their two-dimensional counterparts. Three-dimensional models also tend to agree more closely with the predictions of mixing length theory. Our hydrodynamic simulations show the turbulent entrainment that leads to a growth of the convection zone on a dynamic time scale. In contrast to mixing length theory, the outer part of the convection zone is characterized by a subadiabatic temperature gradient.

  5. The core helium flash revisited. III. From Population I to Population III stars

    Science.gov (United States)

    Mocák, M.; Campbell, S. W.; Müller, E.; Kifonidis, K.

    2010-09-01

    Context. Degenerate ignition of helium in low-mass stars at the end of the red giant branch phase leads to dynamic convection in their helium cores. One-dimensional (1D) stellar modeling of this intrinsically multi-dimensional dynamic event is likely to be inadequate. Previous hydrodynamic simulations imply that the single convection zone in the helium core of metal-rich Pop I stars grows during the flash on a dynamic timescale. This may lead to hydrogen injection into the core and to a double convection zone structure as known from one-dimensional core helium flash simulations of low-mass Pop III stars. Aims: We perform hydrodynamic simulations of the core helium flash in two and three dimensions to better constrain the nature of these events. To this end we study the hydrodynamics of convection within the helium cores of a 1.25 M_⊙ metal-rich Pop I star (Z = 0.02), and, for the first time, a 0.85 M_⊙ metal-free Pop III star (Z = 0) near the peak of the flash. These models possess single and double convection zones, respectively. Methods: We use 1D stellar models of the core helium flash computed with state-of-the-art stellar evolution codes as initial models for our multidimensional hydrodynamic study, and simulate the evolution of these models with the Riemann solver based hydrodynamics code Herakles, which integrates the Euler equations coupled with source terms corresponding to gravity and nuclear burning. Results: The hydrodynamic simulation of the Pop I model involving a single convection zone covers 27 h of stellar evolution, while the hydrodynamic simulations of a double convection zone, in the Pop III model, span 1.8 h of stellar life. We find differences between the predictions of mixing length theory and our hydrodynamic simulations. The simulation of the single convection zone in the Pop I model shows a strong growth of the size of the convection zone due to turbulent entrainment. We therefore predict that for the Pop I model a hydrogen injection

  6. The core helium flash revisited: II. Two and three-dimensional hydrodynamic simulations

    CERN Document Server

    Mocak, M; Weiss, A; Kifonidis, K

    2008-01-01

    We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations. We use a multidimensional Eulerian hydrodynamics code based on state-of-the-art numerical techniques to simulate the evolution of the helium core of a $1.25 M_{\\odot}$ Pop I star. Our three-dimensional hydrodynamic simulations of the evolution of a star during the peak of the core helium flash do not show any explosive behavior. The convective flow patterns developing in the three-dimensional models are structurally different from those of the corresponding two-dimensional models, and the typical convective velocities are smaller than those found in their two-dimensional counterparts. Three-dimensional models also tend to agree better with the predictions of mixing length theory. Our hydrodynamic simulations show the presence of turbulent entrainment that results in a growth of the convection zone on a dynamic time scale. Contrary to mixing length theory,...

  7. Helium in Earth's early core

    Science.gov (United States)

    Bouhifd, M. A.; Jephcoat, Andrew P.; Heber, Veronika S.; Kelley, Simon P.

    2013-11-01

    The observed escape of the primordial helium isotope, 3He, from the Earth's interior indicates that primordial helium survived the energetic process of planetary accretion and has been trapped within the Earth to the present day. Two distinct reservoirs in the Earth's interior have been invoked to account for variations in the 3He/4He ratio observed at the surface in ocean basalts: a conventional depleted mantle source and a deep, still enigmatic, source that must have been isolated from processing throughout Earth history. The Earth's iron-based core has not been considered a potential helium source because partitioning of helium into metal liquid has been assumed to be negligible. Here we determine helium partitioning in experiments between molten silicates and iron-rich metal liquids at conditions up to 16GPa and 3,000K. Analyses of the samples by ultraviolet laser ablation mass spectrometry yield metal-silicate helium partition coefficients that range between 4.7×10-3 and 1.7×10-2 and suggest that significant quantities of helium may reside in the core. Based on estimated concentrations of primordial helium, we conclude that the early core could have incorporated enough helium to supply deep-rooted plumes enriched in 3He throughout the age of the Earth.

  8. Helium shells and faint emission lines from slitless flash spectra.

    Science.gov (United States)

    Bazin, Cyril; Koutchmy, Serge

    2013-05-01

    At the time of the two last solar total eclipses of August 1st, 2008 in Siberia and July 11th, 2010 in French Polynesia, high frame rate CCD flash spectra were obtained. These eclipses occurred in quiet Sun period and after. The slitless flash spectra show two helium shells, in the weak Paschen α 4686 Å line of the ionized helium HeII and in the neutral helium HeI line at 4713 Å. The extensions of these helium shells are typically 3 Mm. In prominences, the extension of the interface with the corona is much more extended. The observations and analysis of these lines can properly be done only in eclipse conditions, when the intensity threshold reaches the coronal level, and the parasitic scattered light is virtually zero. Under the layers of 1 Mm above the limb, many faint low FIP lines were also seen in emission. These emission lines are superposed on the continuum containing absorption lines. The solar limb can be defined using the weak continuum appearing between the emission lines at the time of the second and third contact. The variations of the singly ionized iron line, the HeI and HeII lines and the continuum intensity are analyzed. The intensity ratio of ionized to neutral helium is studied for evaluating the ionization rate in low layers up to 2 Mm and also around a prominence.

  9. Helium shells and faint emission lines from slitless flash spectra

    Directory of Open Access Journals (Sweden)

    Cyril Bazin

    2013-05-01

    Full Text Available At the time of the two last solar total eclipses of August 1st, 2008 in Siberia and July 11th, 2010 in French Polynesia, high frame rate CCD flash spectra were obtained. These eclipses occurred in quiet Sun period and after. The slitless flash spectra show two helium shells, in the weak Paschen α 4686 Å line of the ionized helium HeII and in the neutral helium HeI line at 4713 Å. The extensions of these helium shells are typically 3 Mm. In prominences, the extension of the interface with the corona is much more extended. The observations and analysis of these lines can properly be done only in eclipse conditions, when the intensity threshold reaches the coronal level, and the parasitic scattered light is virtually zero. Under the layers of 1 Mm above the limb, many faint low FIP lines were also seen in emission. These emission lines are superposed on the continuum containing absorption lines. The solar limb can be defined using the weak continuum appearing between the emission lines at the time of the second and third contact. The variations of the singly ionized iron line, the HeI and HeII lines and the continuum intensity are analyzed. The intensity ratio of ionized to neutral helium is studied for evaluating the ionization rate in low layers up to 2 Mm and also around a prominence.

  10. On the helium flash in low-mass Population III Red Giant stars

    CERN Document Server

    Schlattl, H; Salaris, M; Weiss, A

    2001-01-01

    We investigate the evolution of initially metal-free, low-mass Red Giant stars through the He core flash at the tip of the Red Giant Branch. The low entropy barrier between the helium- and hydrogen-rich layers enables a penetration of the helium flash driven convective zone into the inner tail of the extinguishing H-burning shell. As a consequence, protons are mixed into high-temperature regions triggering a H-burning runaway. The subsequent dredge-up of matter processed by He and H burning enriches the stellar surface with large amounts of helium, carbon and nitrogen. Extending previous results by Hollowell et al. (1990) and Fujimoto et al. (2000), who claimed that the H-burning runaway is an intrinsic property of extremely metal-poor low-mass stars, we found that its occurrence depends on additional parameters like the initial composition and the treatment of various physical processes. We perform some comparisons between predicted surface chemical abundances and observational measurements for extremely met...

  11. A New Estimation of Mass Accumulation Efficiency in Helium Shell Flashes toward Type Ia Supernova Explosions

    CERN Document Server

    Kato, M

    1999-01-01

    We have calculated the mass accumulation efficiency during helium shell flashes to examine whether or not a carbon-oxygen white dwarf (C+O WD) grows up to the Chandrasekhar mass limit to ignite a Type Ia supernova explosion. It has been frequently argued that luminous super-soft X-ray sources and symbiotic stars are progenitors of SNe Ia. In such systems, a C+O WD accretes hydrogen-rich matter from a companion and burns hydrogen steadily on its surface. The WD develops a helium layer underneath the hydrogen-rich envelope and undergoes periodic helium shell flashes. Using OPAL opacity, we have reanalyzed a full cycle of helium shell flashes on a 1.3 M_ødot C+O WD and confirmed that the helium envelope of the WD expands to blow a strong wind. A part of the accumulated matter is lost by the wind. The mass accumulation efficiency is estimated as \\eta_{He} = -0.175 (\\log accretion rate \\dot M is in units of M_ødot yr^{-1}. In relatively high mass accretion rates as expected in recent SN Ia progenitor models, the...

  12. Diffusion and the occurrence of hydrogen shell flashes in helium white dwarf stars

    CERN Document Server

    Althaus, L G; Benvenuto, O G

    2000-01-01

    We investigate the effects of element diffusion on the structure and evolution of low-mass helium white dwarfs (WD). Attention is focused on the occurrence of hydrogen shell flashes induced by diffusion processes during cooling phases. Initial models from 0.406 to 0.161 solar masses are constructed by applying mass loss rates at different stages of the RGB evolution of a solar model. The multicomponent flow equations describing gravitational settling, and chemical and thermal diffusion are solved and the diffusion calculations are coupled to an evolutionary code. In addition, the same sequences are computed but neglecting diffusion. We find that element diffusion strongly affects the structure and cooling history of helium WD. In particular, diffusion induces the occurrence of hydrogen shell flashes in models with masses ranging from 0.18 to 0.41 solar masses, which is in sharp contrast from the situation when diffusion is neglected. In connection with the further evolution, these diffusion-induced flashes le...

  13. OLD PUZZLE, NEW INSIGHTS: A LITHIUM-RICH GIANT QUIETLY BURNING HELIUM IN ITS CORE

    Energy Technology Data Exchange (ETDEWEB)

    Aguirre, V. Silva; Christensen-Dalsgaard, J.; Jessen-Hansen, J. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Ruchti, G. R. [Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-221 00 Lund (Sweden); Hekker, S. [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Cassisi, S. [INAF-Astronomical Observatory of Teramo, Via M. Maggini sn, I-64100 Teramo (Italy); Datta, A. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721302 (India); Jendreieck, A. [Max-Planck-Institut für Astrophysics, Karl Schwarzschild Strasse 1, D-85748 Garching (Germany); Mazumdar, A. [Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088 (India); Mosser, B. [LESIA Observatoire de Paris, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, F-92195 Meudon Cedex (France); Stello, D. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Beck, P. G.; De Ridder, J. [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2014-03-20

    About 1% of giant stars have been shown to have large surface Li abundances, which is unexpected according to standard stellar evolution models. Several scenarios for lithium production have been proposed, but it is still unclear why these Li-rich giants exist. A missing piece in this puzzle is the knowledge of the exact stage of evolution of these stars. Using low- and-high-resolution spectroscopic observations, we have undertaken a survey of lithium-rich giants in the Kepler field. In this Letter, we report the finding of the first confirmed Li-rich core-helium-burning giant, as revealed by asteroseismic analysis. The evolutionary timescales constrained by its mass suggest that Li production most likely took place through non-canonical mixing at the RGB tip, possibly during the helium flash.

  14. Old puzzle, new insights: a lithium rich giant quietly burning helium in its core

    CERN Document Server

    Aguirre, V Silva; Hekker, S; Cassisi, S; Christensen-Dalsgaard, J; Datta, A; Jendreieck, A; Jessen-Hansen, J; Mazumdar, A; Mosser, B; Stello, D; Beck, P G; de Ridder, J

    2014-01-01

    About 1% of giant stars have been shown to have large surface Li abundances, which is unexpected according to standard stellar evolution models. Several scenarios for lithium production have been proposed, but it is still unclear why these Li-rich giants exist. A missing piece in this puzzle is the knowledge of the exact stage of evolution of these stars. Using low-and-high-resolution spectroscopic observations, we have undertaken a survey of lithium-rich giants in the Kepler field. In this letter, we report the finding of the first confirmed Li-rich core-helium-burning giant, as revealed by asteroseismic analysis. The evolutionary timescales constrained by its mass suggest that Li-production most likely took place through non-canonical mixing at the RGB-tip, possibly during the helium flash.

  15. Radioactive core ions of microclusters, ``snowballs`` in superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, N. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Shimoda, T. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Fujita, Y. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Miyatake, H. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Mizoi, Y. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Kobayashi, H. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Sasaki, M. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Shirakura, T. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Itahashi, T. [Research Center for Nuclear Physics, Osaka Univ., Ibaraki (Japan); Mitsuoka, S. [Research Center for Nuclear Physics, Osaka Univ., Ibaraki (Japan); Matsukawa, T. [Naruto Univ. of Education, Tokushima (Japan); Ikeda, N. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics; Morinobu, S. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics; Hinde, D.J. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences; Asahi, K. [Tokyo Inst. of Tech. (Japan). Dept. of Physics; Ueno, H. [Tokyo Inst. of Tech. (Japan). Dept. of Physics; Izumi, H. [Tokyo Inst. of Tech. (Japan). Dept. of Physics

    1996-12-01

    Short-lived beta-ray emitters, {sup 12}B, sustaining nuclear spin polarization were introduced into superfluid helium. The nuclear polarization of {sup 12}B was observed via measurement of beta-ray asymmetry. It was found that the nuclear polarization was preserved throughout the lifetime of {sup 12}B (20.3 ms). This suggests that the ``snowball``, an aggregation of helium atoms produced around an alien ion, constitutes a suitable milieu for freezing-out the nuclear spin of the core ion and that most likely the solidification takes place at the interior of the aggregation. (orig.).

  16. THE CIRCUMSTELLAR ENVIRONMENT OF R CORONAE BOREALIS: WHITE DWARF MERGER OR FINAL-HELIUM-SHELL FLASH?

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, Geoffrey C.; Andrews, J. E. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Sugerman, Ben E. K. [Department of Physics and Astronomy, Goucher College, 1021 Dulaney Valley Rd., Baltimore, MD 21204 (United States); Adam Stanford, S. [IGPP, Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Whitney, B. A. [Space Science Institute, 4750 Walnut St. Suite 205, Boulder, CO 80301 (United States); Honor, J.; Babler, B. [Department of Astronomy, 475 North Charter St., University of Wisconsin, Madison, WI 53706 (United States); Barlow, M. J. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Gordon, K. D.; Bond, Howard E.; Matsuura, M. [STScI, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Geballe, T. R. [Gemini Observatory, 670 N. A' ohoku Place, Hilo, HI 96720 (United States); De Marco, O. [Department of Physics, Macquarie University, Sydney, NSW 2109 (Australia); Lawson, W. A. [School of PEMS, University of New South Wales, ADFA, P.O. Box 7916, Canberra, ACT 2610 (Australia); Sibthorpe, B. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Olofsson, G. [Department of Astronomy, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, SE-10691 Stockholm (Sweden); Polehampton, E. [Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom); Gomez, H. L.; Hargrave, P. C. [School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff, Wales CF24 3YB (United Kingdom); Ivison, R. J., E-mail: gclayton@phys.lsu.edu, E-mail: jandrews@phys.lsu.edu, E-mail: ben.sugerman@goucher.edu, E-mail: stanford@physics.ucdavis.edu, E-mail: bwhitney@spacescience.org, E-mail: jhonor@astro.wisc.edu, E-mail: brian@astro.wisc.edu, E-mail: mjb@star.ucl.ac.uk [UK Astronomy Technology Centre, ROE, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); and others

    2011-12-10

    In 2007, R Coronae Borealis (R CrB) went into a historically deep and long decline. In this state, the dust acts like a natural coronagraph at visible wavelengths, allowing faint nebulosity around the star to be seen. Imaging has been obtained from 0.5 to 500 {mu}m with Gemini/GMOS, Hubble Space Telescope/WFPC2, Spitzer/MIPS, and Herschel/SPIRE. Several of the structures around R CrB are cometary globules caused by wind from the star streaming past dense blobs. The estimated dust mass of the knots is consistent with their being responsible for the R CrB declines if they form along the line of sight to the star. In addition, there is a large diffuse shell extending up to 4 pc away from the star containing cool 25 K dust that is detected all the way out to 500 {mu}m. The spectral energy distribution of R CrB can be well fitted by a 150 AU disk surrounded by a very large diffuse envelope which corresponds to the size of the observed nebulosity. The total masses of the disk and envelope are 10{sup -4} and 2 M{sub Sun }, respectively, assuming a gas-to-dust ratio of 100. The evidence pointing toward a white dwarf merger or a final-helium-shell flash origin for R CrB is contradictory. The shell and the cometary knots are consistent with a fossil planetary nebula. Along with the fact that R CrB shows significant lithium in its atmosphere, this supports the final-helium-shell flash. However, the relatively high inferred mass of R CrB and its high fluorine abundance support a white dwarf merger.

  17. Evolution and colours of helium-core white dwarf stars the case of low metallicity progenitors

    CERN Document Server

    Serenelli, A M; Rohrmann, R D; Benvenuto, O G

    2002-01-01

    The present work is designed to explore the evolution of helium-core white dwarf (HeWD) stars for the case of metallicities much lower than the solar one (Z=0.001 and Z=0.0002). Evolution is followed in a self-consistent way with the predictions of detalied and new non-grey atmospheres, time-dependent element diffusion and the history of the white dwarf progenitor. Reliable initial models for low mass HeWDs are obtained by applying mass loss rates to a 1msun stellar model. The loss of angular momentum caused by gravitational wave emission and magnetic stellar wind braking are considered. Model atmospheres, based on a detailed treatment of the microphysics entering the WD atmosphere enable us to provide accurate colours and magnitudes at both early and advanced evolutionary stages. We find that most of our evolutionary sequences experience several episodes of hydrogen thermonuclear flashes. In particular, the lower the metallicity, the larger the minimum stellar mass for the occurrence fo flashes induced by CN...

  18. Helium-filled soap bubbles for vortex core velocimetry

    Science.gov (United States)

    Caridi, Giuseppe Carlo Alp; Sciacchitano, Andrea; Scarano, Fulvio

    2017-09-01

    Velocity measurements within the core of high-swirl vortices are often hampered by heavier-than-air particle tracers being centrifuged outside the vortex core region. The use of neutrally buoyant and lighter-than-air tracers is investigated to aim at homogeneous tracers concentration in air flow experiments dealing with high-swirl vortices using particle image velocimetry. Helium-filled soap bubbles (HFSB) of sub-millimeter diameter are employed as flow tracers. Their density is controlled varying the relative amount of helium and soap solution composing the bubbles. The dynamics of HFSB and micro-size droplets is modeled within a Lamb-Oseen vortex to retrieve the order of magnitude of the tracers slip velocity. A positive radial drift for heavier-than-air tracers leads to an empty vortex core. In contrast, the concentration at the vortex axis is expected to increase for lighter than air tracers. Experiments are conducted on a sharp-edged slender delta wing at 20° incidence. At chosen chord-based Reynolds numbers of 2 × 105 and 6 × 105, a stable laminar vortex is formed above the delta wing. Laser sheet visualization is used to inspect the spatial concentration of tracers. A comparison is made between micron-sized fog droplets and HFSB tracers in the nearly neutrally buoyant condition. Stereo-PIV measurements with fog droplets return a systematically underestimated axial velocity distribution within the vortex core due to drop-out of image cross-correlation signal. The nearly neutrally buoyant HFSB tracers appear to maintain a homogeneous spatial concentration and yield cross-correlation signal up to the vortex axis. The resulting velocity measurements are in good agreement with literature data.

  19. Helium transport in the core and stochastic edge layer in LHD

    Science.gov (United States)

    Ida, K.; Yoshinuma, M.; Goto, M.; Schmitz, O.; Dai, S.; Bader, A.; Kobayashi, M.; Kawamura, G.; Moon, C.; Nakamura, Y.; The LHD Experiment Group

    2016-07-01

    Radial profiles of the density ratio of helium to hydrogen ions are measured using charge exchange spectroscopy with a two-wavelength spectrometer in the large helical device. Helium transport at the last closed flux surface (LCFS) and stochastic magnetic field layer outside the LCFS as well as in the core plasma is studied for a wide range of helium fractions, i.e. from hydrogen-dominated plasmas up to helium-dominated plasmas. The helium density profile becomes more peaked and inward convection velocity increases in the hydrogen-dominant plasma, while it becomes flat or hollow and the convection velocity is in the outward direction in the helium-dominant plasmas. The density gradient of helium at the LCFS is twice that of hydrogen and becomes steeper as the hydrogen becomes more dominant.

  20. Improved synthetic spectra of helium-core white dwarf stars

    CERN Document Server

    Rohrmann, R D; Althaus, L G; Benvenuto, O G

    2002-01-01

    We examine the emergent fluxes from helium-core white dwarfs following their evolution from the end of pre-white dwarf stages down to advanced cooling stages. For this purpose, we include a detailed treatment of the physics of the atmosphere, particularly an improved representation of the state of the gas by taking into account non-ideal effects according to the so-called occupation probability formalism. The present calculations also incorporate hydrogen line opacity from Lyman, Balmer and Paschen series, pseudo-continuum absorptions and new updated induced-dipole absorption from H$_2$-H$_2$, H$_2$-He and H-He pairs. We find that the non-ideal effects and line absorption alter the appearance of the stellar spectrum and have a significant influence upon the photometric colours in the UBVRI-JHKL system. This occurs specially for hot models $T_{\\rm eff}\\ga 8000$ due to line and pseudo-continuum opacities, and for cool models $T_{\\rm eff}\\la 4000$ where the perturbation of atoms and molecules by neighbour partic...

  1. Carbon Shell or Core Ignitions in White Dwarfs Accreting from Helium Stars

    CERN Document Server

    Brooks, Jared; Schwab, Josiah; Paxton, Bill

    2016-01-01

    White dwarfs accreting from helium stars can stably burn at the accreted rate and avoid the challenge of mass loss associated with unstable Helium burning that is a concern for many Type Ia supernovae scenarios. We study binaries with helium stars of mass $1.25 M_\\odot\\le M_{\\rm{He}} \\le 1.8 M_\\odot$, which have lost their hydrogen rich envelopes in an earlier common envelope event and now orbit with periods ($P_{\\rm orb}$) of several hours with non-rotating $0.84$ and $1.0 M_\\odot$ C/O WDs. The helium stars fill their Roche lobes (RLs) after exhaustion of central helium and donate helium on their thermal timescales (${\\sim}10^5$yr). As shown by others, these mass transfer rates coincide with the steady helium burning range for WDs, and grow the WD core up to near the Chandrasekhar mass ($M_{\\rm Ch}$) and a core carbon ignition. We show here, however, that many of these scenarios lead to an ignition of hot carbon ashes near the outer edge of the WD and an inward going carbon flame that does not cause an explo...

  2. Evolution and nucleosynthesis of extremely metal-poor and metal-free low- and intermediate-mass stars II. s-process nucleosynthesis during the core He flash

    CERN Document Server

    Campbell, Simon W; Karakas, Amanda I

    2010-01-01

    Models of primordial and hyper-metal-poor stars with masses similar to the Sun experience an ingestion of protons into the hot core during the core helium flash phase at the end of their red giant branch evolution. This produces a concurrent secondary flash powered by hydrogen burning that gives rise to further nucleosynthesis in the core. We perform post-process nucleosynthesis calculations on a one-dimensional stellar evolution calculation of a star of 1 solar mass and metallicity [Fe/H] = -6.5 that suffers a proton ingestion episode. Our network includes 320 nuclear species and 2,366 reactions and treats mixing and burning simultaneously. The mixing and burning of protons into the hot convective core leads to the production of 13C, which then burns via the 13C(alpha,n)16O reaction releasing a large number of free neutrons. During the first two years of neutron production the neutron poison 14N abundance is low, allowing the prodigious production of heavy elements such as strontium, barium, and lead via slo...

  3. Helium Isotopic Ratios of Core Samples from IODP Exp. 319 (NanTroSEIZE Stage 2)

    Science.gov (United States)

    Horiguchi, K.; Matsuda, J.; Wiersberg, T.; Shimo, Y.; Tamura, H.; Kumagai, H.; Suzuki, K.; Saito, S.; Kinoshita, M.; Araki, E.; Byrne, T.; McNeill, L. C.; Saffer, D.; Takahashi, K.; Eguchi, N. O.; Toczko, S.

    2009-12-01

    IODP Exp.319 of Nankai Trough Seismogenic Zone Drilling Program Stage 2 started at May 2009. Various advanced technologies including first riser-based scientific ocean drilling were carried out at this cruise. The Hole C0009A (Site C0009/ Hole A) recovered cutting and partly core samples from 703.9-1604 mbsf by riser-drilling. The core samples were collected between the depth of 1510.5 and 1593.9 mbsf. Here we report preliminary helium isotopic ratios of these cores. We collected three types of samples for our study: (1) gas of cores, (2) whole round cores (100 cc) and (3) small whole round cores (10 cc). The gas samples were taken immediately after the core recovery. The gas samples were collected from each core section by using a syringe, and it was transferred to the glass bottle using the water displacement method. The glass bottle was made by Pyrex glass with vacuum valve at each end. We collected two sizes of whole round core samples (100 cc and 10 cc) The 100 cc cores were collected from the bottom and top sections of coring. The 10 cc cores were taken from the other sections. The outer parts of these samples were carefully removed to avoid contaminations from drilling fluid. After the removal of contamination, we immediately stored the 100 cc samples into vacuum container and 10 cc samples into plastic bag under a dry condition, respectively. The gas samples were measured for helium isotopic ratios. The noble gas measurement was carried out at Osaka University by using VG5400 mass spectrometer. We measured helium isotopic ratio and 4He/20Ne ratio. The latter is useful for making correction of the air contamination. The obtained result of helium isotopic ratios shows that the radiogenic helium is prominent in all samples. In addition, the helium isotope ratios show a trend that the ratio at shallower part is slightly higher than that at deeper part. It is conceivable that this trend is due to the larger radiogenic ingrowths at the deeper part. However, the

  4. Is the semi-regular variable RU Vulpeculae undergoing a helium-shell flash?

    CERN Document Server

    Uttenthaler, S; Templeton, M

    2015-01-01

    The semi-regular variable star RU Vulpeculae (RU Vul) is being observed visually since 1935. Its pulsation period and amplitude are declining since $\\sim1954$. A leading hypothesis to explain the period decrease in asymptotic giant branch (AGB) stars such as RU Vul is an ongoing flash of the He-burning shell, also called a thermal pulse (TP), inside the star. In this paper, we present a CCD photometric light curve of RU Vul, derive its fundamental parameters, and test if the TP hypothesis can describe the observed period decline. We use CCD photometry to determine the present-day pulsation period and amplitude in three photometric bands, and high-resolution optical spectroscopy to derive the fundamental parameters. The period evolution of RU Vul is compared to predictions by evolutionary models of the AGB phase. We find that RU Vul is a metal-poor star with a metallicity $[{\\rm M}/{\\rm H}]=-1.59\\pm0.05$ and an effective surface temperature of $T_{\\rm eff}=3634\\pm20$ K. The low metallicity of RU Vul and its ki...

  5. Is the semi-regular variable RU Vulpeculae undergoing a helium-shell flash?

    Science.gov (United States)

    Uttenthaler, S.; Greimel, R.; Templeton, M.

    2016-03-01

    The semi-regular variable star RU Vulpeculae (RU Vul) is being observed visually since 1935. Its pulsation period and amplitude are declining since ˜ 1954. A leading hypothesis to explain the period decrease in asymptotic giant branch (AGB) stars such as RU Vul is an ongoing flash of the He-burning shell, also called a thermal pulse (TP), inside the star. In this paper, we present a CCD photometric light curve of RU Vul, derive its fundamental parameters, and test if the TP hypothesis can describe the observed period decline. We use CCD photometry to determine the present-day pulsation period and amplitude in three photometric bands, and high-resolution optical spectroscopy to derive the fundamental parameters. The period evolution of RU Vul is compared to predictions by evolutionary models of the AGB phase. We find that RU Vul is a metal-poor star with a metallicity [M/H]=-1.59±0.05 and an effective surface temperature of T_eff=3634±20 K. The low metallicity of RU Vul and its kinematics indicate that it is an old, low-mass member of the thick disc or the halo population. The present day pulsation period determined from our photometry is ˜ 108 d, the semi-amplitude in the V-band is 0.39±0.03 mag. The observed period decline is found to be well matched by an evolutionary AGB model with stellar parameters comparable to those of RU Vul. We conclude that the TP hypothesis is in good agreement with the observed period evolution of RU Vul. Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  6. Stripped Red Giants - Helium Core White Dwarf Progenitors and their sdB Siblings

    Science.gov (United States)

    Heber, U.

    2017-03-01

    Some gaps in the mosaic of binary star evolution have recently been filled by the discoveries of helium-core white dwarf progenitors (often called extremely low mass (ELM) white dwarfs) as stripped cores of first-giant branch objects. Two varieties can be distinguished. One class is made up by SB1 binaries, companions being white dwarfs as well. Another class, the so-called EL CVn stars, are composite spectrum binaries, with A-Type companions. Pulsating stars are found among both classes. A riddle is posed by the apparently single objects. There is a one-to-one correspondence of the phenomena found for these new classes of star to those observed for sdB stars. In fact, standard evolutionary scenarios explain the origin of sdB stars as red giants that have been stripped close to the tip of first red giant branch. A subgroup of subluminous B stars can also be identified as stripped helium-cores of red giants. They form an extension of the ELM sequence to higher temperatures. Hence low mass white dwarfs of helium cores and sdB stars in binaries are close relatives in terms of stellar evolution.

  7. Neutron capture nucleosynthesis during core helium burning in massive stars

    Energy Technology Data Exchange (ETDEWEB)

    Prantzos, N.; Arnould, M.; Arcoragi, J.P.

    1987-04-01

    Neutron-capture nucleosynthesis during core He burning in massive (ZAMS mass = 50-100 solar mass) mass-losing stars, which are identified with Wolf-Rayet stars, is studied in the framework of recent stellar models based on the Roxburgh criterion for convection and on the latest nuclear data available. The nucleosynthesis is followed with the aid of a full nuclear reaction network incorporating up-to-date Maxwellian-averaged neutron-capture cross sections and new density- and temperature-dependent beta-decay rates. Numerical techniques are developed in order to integrate efficiently the set of coupled differential equations of the network. The resulting stellar core and surface abundances are presented, as well as the composition of the stellar winds ejected during the WC phase. Consideration is given to the implications of these results for the composition of OB associations and of the solar system, for the isotopic anomalies in meteorites and in the galactic cosmic rays, as well as for nuclear gamma-ray line astronomy. 114 references.

  8. The ages and colours of cool helium-core white dwarf stars

    CERN Document Server

    Serenelli, A M; Rohrmann, R D; Benvenuto, O G

    2001-01-01

    The purpose of this work is to explore the evolution of helium-core white dwarf stars in a self-consistent way with the predictions of detailed non-gray model atmospheres and element diffusion. To this end, we consider helium-core white dwarf models with stellar masses of 0.406, 0.360, 0.327, 0.292, 0.242, 0.196 and 0.169 solar masses and follow their evolution from the end of mass loss episodes during their pre-white dwarf evolution down to very low surface luminosities. We find that when the effective temperature decreases below 4000K, the emergent spectrum of these stars becomes bluer within time-scales of astrophysical interest. In particular, we analyse the evolution of our models in the colour-colour and colour-magnitude diagrams and we find that helium-core white dwarfs with masses ranging from approx. 0.18 to 0.3 solar masses can reach the turn-off in their colours and become blue again within cooling times much less than 15 Gyr and then remain brighter than M_V approx. 16.5. In view of these results,...

  9. Lithium Inventory of 2 Solar Mass Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism

    Science.gov (United States)

    Carlberg, Joleen K.; Cunha, Katia; Smith, Verne V.

    2016-01-01

    The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 solar mass experience a shortlived phase of Li-richness at the onset of core He-burning. Many of these stars have low C-12/C-13, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 solar mass. We find six Li-rich stars (A(Li) greater than or equal to 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low C-12/C-13. Such low C-12/C-13, seen in many field Li-rich stars, should persist even after lithium has returned to normal low levels. Thus, if Li synthesis during the He flash occurs, it is a rare, but potentially long-lived occurrence rather than a short-lived phase for all stars. We estimate a conservative upper limit of the fraction of stars going through a Li-rich phase to be less than 47%, based on stars that have low C-12/C-13 for their observed A(Li).

  10. Lithium Inventory of 2 M ⊙ Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism

    Science.gov (United States)

    Carlberg, Joleen K.; Cunha, Katia; Smith, Verne V.

    2016-08-01

    The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 M ⊙ experience a short-lived phase of Li-richness at the onset of core He-burning. Many of these stars have low 12C/13C, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 M ⊙. We find six Li-rich stars (A(Li) ≥ 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low 12C/13C. Such low 12C/13C, seen in many field Li-rich stars, should persist even after lithium has returned to normal low levels. Thus, if Li synthesis during the He flash occurs, it is a rare, but potentially long-lived occurrence rather than a short-lived phase for all stars. We estimate a conservative upper limit of the fraction of stars going through a Li-rich phase to be \\lt 47 % , based on stars that have low 12C/13C for their observed A(Li).

  11. Suppression of superconductivity in thin Nb nanowires fabricated in the vortex cores of superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, Eugene B., E-mail: Gordon.eb@gmail.com [Institute of Problems of Chemical Physics RAS, Semenov Avenue 1, 142432 Chernogolovka, Moscow Region (Russian Federation); Bezryadin, Alexey V. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61874 (United States); Karabulin, Alexander V. [Institute of Problems of Chemical Physics RAS, Semenov Avenue 1, 142432 Chernogolovka, Moscow Region (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe Highway 31, 115409 Moscow (Russian Federation); Matyushenko, Vladimir I. [The Branch of Talrose Institute for Energy Problems of Chemical Physics RAS, Semenov Avenue 1/10, 142432 Chernogolovka, Moscow Region (Russian Federation); Khodos, Igor I. [Institute of Microelectronics Technology and High Purity Materials RAS, Institutskaya Street 6, 142432 Chernogolovka, Moscow Region (Russian Federation)

    2015-09-15

    Highlights: • Laser ablation in superfluid helium allows producing thin nanowires of any metal. • Nb nanowires, about 4 nm in diameter, form in the cores of superfluid vortices. • Our oxide-free Nb nanowires exhibit a quantum superconductor-to-insulator transition. • The insulating behavior in Nb wires is explained in terms of quantum phase slips. • Such nanowires can be used in superconducting phase-slip qubits and transistors. - Abstract: Nanowires of niobium, platinum and indium–lead In{sub 88}Pb{sub 12} alloy with diameters of 4.2, 3.6 and 8 nm, respectively, were grown in quantized vortices of superfluid helium, and the dependences of their resistance on temperature have been studied. Through a detailed comparison of these dependences we present evidence that superconducting niobium wires allow a high rate of quantum phase slip. This phase slippage leads to a phase transition to an insulating state at T → 0.

  12. Stripped red giants - Helium core white dwarf progenitors and their sdB siblings

    CERN Document Server

    Heber, Ulrich

    2016-01-01

    Some gaps in the mosaic of binary star evolution have recently been filled by the discoveries of helium-core white dwarf progenitors (often called extremely low mass (ELM) white dwarfs) as stripped cores of first-giant branch objects. Two varieties can be distinguished. One class is made up by SB1 binaries, companions being white dwarfs as well, another class, the so-called EL CVn stars, are composite spectrum binaries, with A-Type companions. Pulsating stars are found among both classes. A riddle is posed by the apparently single objects. There is a one-to-one correspondence of the phenomena found for these new classes of star to those observed for sdB stars. In fact, standard evolutionary scenarios explain the origin of sdB stars as red giants that have been stripped close to the tip of first red giant branch. A subgroup of subluminous B stars can also be identified as stripped helium-cores of red giants. They form an extension of the ELM sequence to higher temperatures. Hence low mass white dwarfs of heliu...

  13. Exploring the helium core of the delta Scuti star CoRoT 102749568 with asteroseismology

    CERN Document Server

    Chen, Xinghao; Lin, Guifang; Chen, Yanhui; Guo, Junjun

    2016-01-01

    Based on regularities in rotational splittings, we seek possible multiplets for the observed frequencies of CoRoT 102749568. Twenty-one sets of multiplets are identified, including four sets of multiplets with $l=1$, nine sets of multiplets with $l=2$, and eight sets of multiplets with $l=3$. In particular, there are three complete triplets ($f_{10}$, $f_{12}$, $f_{14}$), ($f_{31}$, $f_{34}$, $f_{35}$), and ($f_{41}$, $f_{43}$, $f_{44}$). The rotational period of CoRoT 102749568 is estimated to be $1.34^{+0.04}_{-0.05}$ days. When doing model fittings, three $l=1$ modes ($f_{12}$, $f_{34}$, and $f_{43}$) and the radial first overtone $f_{13}$ are used. Our results shows that the three nonradial modes ($f_{12}$, $f_{34}$, and $f_{43}$) are mixed modes, which mainly provide constraints on the helium core. The radial first overtone $f_{13}$ mainly provides constraint on the stellar envelope. Hence the size of the helium core of CoRoT 102749568 is determined to be $M_{\\rm He}$ = 0.148 $\\pm$ 0.003 $M_{\\odot}$ and ...

  14. Extreme ultraviolet fluorescence spectroscopy of pure and core-shell rare gas clusters at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Schroedter, Lasse

    2013-08-15

    The interaction of rare gas clusters with short-wavelength radiation of free-electron lasers (FELs) has been studied extensively over the last decade by means of electron and ion time-of-flight spectroscopy. This thesis describes the design and construction of a fluorescence spectrometer for the extreme ultraviolet (XUV) spectral range and discusses the cluster experiments performed at FLASH, the Free-electron LAser in Hamburg. Fluorescence of xenon and of argon clusters was studied, both in dependence on the FEL pulse intensity and on the cluster size. The FEL wavelength was set to the giant 4d-resonance of xenon at 13.5 nm and the FEL pulse intensity reached peak values of 2.7.10{sup 15} W/cm{sup 2}. For xenon clusters, charge states of at least 11+ were identified. For argon, charge states up to 7+ were detected. The cluster-size dependent study revealed a decrease of the fluorescence yield per atom with increasing cluster size. This decrease is explained with the help of a geometric model. It assumes that virtually the entire fluorescence yield stems from shells of ions on the cluster surface, whereas ions in the cluster core predominantly recombine non-radiatively with electrons. However, the detailed analysis of fluorescence spectra from clusters consisting of a core of Xe atoms and a surrounding shell of argon atoms shows that, in fact, a small fraction of the fluorescence signal comes from Xe ions in the cluster core. Interestingly, these ions are as highly charged as the ions in the shells of a pure Xe cluster. This result goes beyond the current understanding of charge and energy transfer processes in these systems and points toward the observation of ultrafast charging dynamics in a time window where mass spectrometry is inherently blind. (orig.)

  15. Evaluation of the cryogenic helium recovery process from natural gas based on flash separation by advanced exergy cost method - Linde modified process

    Science.gov (United States)

    Ansarinasab, Hojat; Mehrpooya, Mehdi; Parivazh, Mohammad Mehdi

    2017-10-01

    In this paper, exergy cost analysis method is used to evaluate a new cryogenic Helium recovery process from natural gas based on flash separation. Also advanced exergoeconomic analysis was made to determine the amount of avoidable exergy destruction cost of the process component. This proposed process can extract Helium from a feed gas stream with better efficiency than other existing processes. The results indicate that according to the avoidable endogenous exergy destruction cost C-4 (287.2/hr), C-5 (257.3/hr) and C-6 (181.6/hr) compressors should be modified first, respectively. According to the endogenous investment and exergy destruction cost, the interactions between the process components are not strong. In compressors, a high proportion of the cost of exergy destruction is avoidable while in these components, investment costs are unavoidable. In heat exchangers and air coolers, a high proportion of the exergy destruction cost is unavoidable while in these components, investment costs are avoidable. Finally, three different strategies are suggested to improve performance of each component, and the sensitivity of exergoeconomic factor and cost of exergy destruction to operating variables of the process are studied.

  16. The treatment of mixing in core helium burning models: I. Implications for asteroseismology

    CERN Document Server

    Constantino, Thomas; Christensen-Dalsgaard, Joergen; Lattanzio, John C; Stello, Dennis

    2015-01-01

    The detection of mixed oscillation modes offers a unique insight into the internal structure of core helium burning (CHeB) stars. The stellar structure during CHeB is very uncertain because the growth of the convective core, and/or the development of a semiconvection zone, is critically dependent on the treatment of convective boundaries. In this study we calculate a suite of stellar structure models and their non-radial pulsations to investigate why the predicted asymptotic g-mode $\\ell = 1$ period spacing $\\Delta\\Pi_1$ is systematically lower than is inferred from Kepler field stars. We find that only models with large convective cores, such as those calculated with our newly proposed "maximal-overshoot" scheme, can match the average $\\Delta\\Pi_1$ reported. However, we also find another possible solution that is related to the method used to determine $\\Delta\\Pi_1$: mode trapping can raise the observationally inferred $\\Delta\\Pi_1$ well above its true value. Even after accounting for these two proposed reso...

  17. The treatment of mixing in core helium burning models - II. Constraints from cluster star counts

    Science.gov (United States)

    Constantino, Thomas; Campbell, Simon W.; Lattanzio, John C.; van Duijneveldt, Adam

    2016-03-01

    The treatment of convective boundaries during core helium burning is a fundamental problem in stellar evolution calculations. In the first paper of this series, we showed that new asteroseismic observations of these stars imply they have either very large convective cores or semiconvection/partially mixed zones that trap g modes. We probe this mixing by inferring the relative lifetimes of asymptotic giant branch (AGB) and horizontal branch (HB) from R2, the observed ratio of these stars in recent HST photometry of 48 Galactic globular clusters. Our new determinations of R2 are more self-consistent than those of previous studies and our overall calculation of R2 = 0.117 ± 0.005 is the most statistically robust now available. We also establish that the luminosity difference between the HB and the AGB clump is Δ log {L}_HB^AGB = 0.455 ± 0.012. Our results accord with earlier findings that standard models predict a lower R2 than is observed. We demonstrate that the dominant sources of uncertainty in models are the prescription for mixing and the stochastic effects that can result from its numerical treatment. The luminosity probability density functions that we derive from observations feature a sharp peak near the AGB clump. This constitutes a strong new argument against core breathing pulses, which broaden the predicted width of the peak. We conclude that the two mixing schemes that can match the asteroseismology are capable of matching globular cluster observations, but only if (i) core breathing pulses are avoided in models with a semiconvection/partially mixed zone, or (ii) that models with large convective cores have a particular depth of mixing beneath the Schwarzschild boundary during subsequent early-AGB `gravonuclear' convection.

  18. The treatment of mixing in core helium burning models -- II. Constraints from cluster star counts

    CERN Document Server

    Constantino, Thomas; Lattanzio, John C; van Duijneveldt, Adam

    2015-01-01

    The treatment of convective boundaries during core helium burning is a fundamental problem in stellar evolution calculations. In Paper~I we showed that new asteroseismic observations of these stars imply they have either very large convective cores or semiconvection/partially mixed zones that trap g-modes. We probe this mixing by inferring the relative lifetimes of asymptotic giant branch (AGB) and horizontal branch (HB) from $R_2$, the observed ratio of these stars in recent HST photometry of 48 Galactic globular clusters. Our new determinations of $R_2$ are more self-consistent than those of previous studies and our overall calculation of $R_2 = 0.117 \\pm 0.005$ is the most statistically robust now available. We also establish that the luminosity difference between the HB and the AGB clump is $\\Delta \\log{L}_\\text{HB}^\\text{AGB} = 0.455 \\pm 0.012$. Our results accord with earlier findings that standard models predict a lower $R_2$ than is observed. We demonstrate that the dominant sources of uncertainty in ...

  19. Two candidate brown dwarf companions around core helium-burning stars

    CERN Document Server

    Schaffenroth, V; Nagel, K; Geier, S; Koen, C; Heber, U; Edelmann, H

    2014-01-01

    Hot subdwarf stars of spectral type B (sdBs) are evolved, core helium-burning objects. The formation of those objects is puzzling, because the progenitor star has to lose almost its entire hydrogen envelope in the red-giant phase. Binary interactions have been invoked, but single sdBs exist as well. We report the discovery of two close hot subdwarf binaries with small radial velocity amplitudes. Follow-up photometry revealed reflection effects originating from cool irradiated companions, but no eclipses. The lower mass limits for the companions of CPD-64$^{\\circ}$481 ($0.048\\,M_{\\rm \\odot}$) and PHL\\,457 ($0.027\\,M_{\\rm \\odot}$) are significantly below the stellar mass limit. Hence they could be brown dwarfs unless the inclination is unfavourable. Two very similar systems have already been reported. The probability that none of them is a brown dwarf is very small, 0.02%. Hence we provide further evidence that substellar companions with masses that low are able to eject a common envelope and form an sdB star. ...

  20. Helium-Core White Dwarfs in the Globular Cluster NGC 6397

    CERN Document Server

    Strickler, R R; Anderson, J; Cohn, H N; Lugger, P M; Serenelli, A M

    2009-01-01

    We present results of a study of the central regions of NGC 6397 using Hubble Space Telescope's Advanced Camera for Surveys, focusing on a group of 24 faint blue stars that form a sequence parallel to, but brighter than, the more populated sequence of carbon-oxygen white dwarfs (CO WDs). Using F625W, F435W, and F658N filters with the Wide Field Channel we show that these stars, 18 of which are newly discovered, have magnitudes and colors consistent with those of helium-core white dwarfs (He WDs) with masses ~ 0.2-0.3 Msun. Their H-alpha--R625 colors indicate that they have strong H-alpha absorption lines, which distinguishes them from cataclysmic variables in the cluster. The radial distribution of the He WDs is significantly more concentrated to the cluster center than that of either the CO WDs or the turnoff stars and most closely resembles that of the cluster's blue stragglers. Binary companions are required to explain the implied dynamical masses. We show that the companions cannot be main-sequence stars ...

  1. Lithium Inventory of 2 $M_\\odot$ Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism

    CERN Document Server

    Carlberg, Joleen K; Smith, Verne V

    2016-01-01

    The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 $M_\\odot$ experience a short-lived phase of Li-richness at the onset of core He-burning. Many of these stars have low 12C/13C, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 $M_\\odot$. We find six Li-rich stars (A(Li) > 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low 12C/13C. Such low 12C/13C, seen in ma...

  2. Code dependencies of pre-supernova evolution and nucleosynthesis in massive stars: Evolution to the end of core helium burning

    CERN Document Server

    Jones, Samuel; Pignatari, Marco; Heger, Alexander; Georgy, Cyril; Nishimura, Nobuya; Fryer, Chris; Herwig, Falk

    2014-01-01

    Massive stars are key sources of radiative, kinetic, and chemical feedback in the universe. Grids of massive star models computed by different groups each using their own codes, input physics choices and numerical approximations, however, lead to inconsistent results for the same stars. We use three of these 1D codes---GENEC, KEPLER and MESA---to compute non-rotating stellar models of $15~\\mathrm{M}_\\odot$, $20~\\mathrm{M}_\\odot$, and $25~\\mathrm{M}_\\odot$ and compare their nucleosynthesis. We follow the evolution from the main sequence until the end of core helium burning. The GENEC and KEPLER models hold physics assumptions used in large grids of published models. The MESA code was set up to use convective core overshooting such that the CO core masses are consistent with those obtained by GENEC. For all models, full nucleosynthesis is computed using the NuGrid post-processing tool MPPNP. We find that the surface abundances predicted by the models are in reasonable agreement. In the helium core, the standard...

  3. Reconstructing a flash flood record from the late Holocene in sediment cores from the Gulf of Aqaba-Eilat (Red Sea)

    Science.gov (United States)

    Kalman, Akos; Katz, Timor; Mathalon, Alysse; Hill, Paul; Goodman, Beverly

    2017-04-01

    Episodic rainfall over the hyperarid desert may cause flash floods in ephemeral rivers surrounding the Gulf of Aqaba-Eilat. These floods constitute an essential factor in the region's ecology but may also damage infrastructure and risk lives. Some floods reach the head of the Gulf of Aqaba and their sediments deposit on the shelf where they play an important role in structuring the ecosystem, such as limiting the distribution of coral reefs. Much of these sediments are later transported further offshore to the deep basin. To date, there is no continuous record of flash floods that may provide a long term perspective of the frequency and magnitude of flash floods in this region and their shifts over time; anticipation of future risks caused by local flash floods (or prolonged droughts) is therefore largely speculative. This ongoing study aims to reconstruct to the best possible resolution a late Holocene flood record in the GOA and trends therein. The methodology includes chemical and physical characterization of the flood deposits and to recognize them in the microstratigraphy (1 cm intervals) of dated cores from the shallow and deep seafloor. Our results show that characteristics of suspended flood sediment, e.g. grain size distribution and elemental composition are distinguishable and recognizable in the stratigraphy of the cores. Flood sediment concentration changes are clearly detectable in 20-40 cm push cores and a 312 cm long pneumatic core from the shelf (at 13 m depth in front of the floods' drainage outlet) as well as in a 80 cm long core from 450 m depth. Flood sediment stratigraphy in a 312 cm long pneumatic core shows recurring fluctuations, but also three more long term environmental shifts that require further explanation. These promising results will be complemented with micropaleontological analysis of the cores as well as additional dating to reconstruct a long term record of floods and related climatic conditions in the area of the GOA making it

  4. Demonstration of the self-magnetic-pinch diode as an X-ray source for flash core-punch radiography.

    Energy Technology Data Exchange (ETDEWEB)

    Cordova, Steve Ray; Rovang, Dean Curtis; Portillo, Salvador; Oliver, Bryan Velten; Bruner, Nichelle Lee (Voss Scientific, Albuquerque, NM); Ziska, Derek Raymond (K-Tech Corporation, Albuquerque, NM)

    2007-10-01

    Minimization of the radiographic spot size and maximization of the radiation dose is a continuing long-range goal for development of electron beam driven X-ray radiography sources. In collaboration with members of the Atomic Weapons Establishment(AWE), Aldermaston UK, the Advanced Radiographic Technologies Dept. 1645 is conducting research on the development of X-ray sources for flash core-punch radiography. The Hydrodynamics Dept. at AWE has defined a near term radiographic source requirement for scaled core-punch experiments to be 250 rads{at}m with a 2.75 mm source spot-size. As part of this collaborative effort, Dept. 1645 is investigating the potential of the Self-Magnetic-Pinched (SMP) diode as a source for core-punch radiography. Recent experiments conducted on the RITS-6 accelerator [1,2] demonstrated the potential of the SMP diode by meeting and exceeding the near term radiographic requirements established by AWE. During the demonstration experiments, RITS-6 was configured with a low-impedance (40 {Omega}) Magnetically Insulated Transmission Line (MITL), which provided a 75-ns, 180-kA, 7.5-MeV forward going electrical pulse to the diode. The use of a low-impedance MITL enabled greater power coupling to the SMP diode and thus allowed for increased radiation output. In addition to reconfiguring the driver (accelerator), geometric changes to the diode were also performed which allowed for an increase in dose production without sacrificing the time integrated spot characteristics. The combination of changes to both the pulsed power driver and the diode significantly increased the source x-ray intensity.

  5. Biodistribution and fate of core-labeled (125)I polymeric nanocarriers prepared by Flash NanoPrecipitation (FNP).

    Science.gov (United States)

    Tang, Christina; Edelstein, Jasmine; Mikitsh, John L; Xiao, Edward; Hemphill, Aaron H; Pagels, Robert; Chacko, Ann-Marie; Prud'homme, Robert

    2016-04-14

    Non-invasive medical imaging techniques such as positron emission tomography (PET) imaging are powerful platforms to track the fate of radiolabeled materials for diagnostic or drug delivery applications. Polymer-based nanocarriers tagged with non-standard PET radionuclides with relatively long half-lives (e.g. (64)Cu: t1/2 = 12.7 h, (76)Br: t1/2 = 16.2h, (89)Zr: t1/2 = 3.3 d, (124)I: t1/2 = 4.2 d) may greatly expand applications of nanomedicines in molecular imaging and therapy. However, radiolabeling strategies that ensure stable in vivo association of the radiolabel with the nanocarrier remain a significant challenge. In this study, we covalently attach radioiodine to the core of pre-fabricated nanocarriers. First, we encapsulated polyvinyl phenol within a poly(ethylene glycol) coating using Flash NanoPrecipitation (FNP) to produce stable 75 nm and 120 nm nanocarriers. Following FNP, we radiolabeled the encapsulated polyvinyl phenol with (125)I via electrophilic aromatic substitution in high radiochemical yields (> 90%). Biodistribution studies reveal low radioactivity in the thyroid, indicating minimal leaching of the radiolabel in vivo. Further, PEGylated [(125)I]PVPh nanocarriers exhibited relatively long circulation half-lives (t1/2 α = 2.9 h, t1/2 β = 34.9 h) and gradual reticuloendothelial clearance, with 31% of injected dose in blood retained at 24 h post-injection.

  6. Professional Flash Lite Mobile Development

    CERN Document Server

    Anderson, J G

    2010-01-01

    Discover how to create Flash Lite mobile apps from the ground up. Adobe Flash is an ideal choice for developing rich interactive content for "Flash-enabled" mobile devices; and with this book, you'll learn how to create unique applications with Flash Lite. Through a series of code samples and extensive example applications, you'll explore the core concepts, key features, and best practices of the Flash Lite player. Coverage reveals various ways to develop Flash mobile content, create applications with a cross-platform programming framework based on the Model, View and Controller conc

  7. Physics Flash December 2016

    Energy Technology Data Exchange (ETDEWEB)

    Kippen, Karen Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). ADEPS Communications

    2016-12-01

    This is the December 2016 issue of Physics Flash, the newsletter of the Physics Division of Los Alamos National Laboratory (LANL). In this issue, the following topics are covered: Novel liquid helium technique to aid highly sensitive search for a neutron electrical dipole moment; Silverleaf: Prototype Red Sage experiments performed at Q-site; John L. Kline named 2016 APS Fellow; Physics students in the news; First Entropy Engine quantum random number generator hits the market; and celebrating service.

  8. Evolution and colors of helium-core white dwarf stars with high-metallicity progenitors

    CERN Document Server

    Althaus, L G; Romero, A D; Rohrmann, R D; Córsico, A H; García-Berro, E; Bertolami, M M Miller

    2009-01-01

    Motivated by the recent detection of single and binary He-core white dwarfs in metal-rich clusters, we present a full set of evolutionary calculations and colors appropriate for the study of such white dwarfs. The paper is also aimed at investigating whether stable hydrogen burning may constitute a main source of energy for massive He-core white dwarfs resulting from high-metallicity progenitors. White dwarf sequences are derived by taking into account the evolutionary history of progenitor stars with supersolar metallicities. We also incorporate a self-consistent, time-dependent treatment of gravitational settling and chemical diffusion, as well as of the residual nuclear burning. We find that the influence of residual nuclear burning during the late stages of white dwarf evolution is strongly dependent on the occurrence of chemical diffusion at the base of the hydrogen-rich envelope. When no diffusion is considered, residual hydrogen burning strongly influences the advanced stages of white dwarf cooling, in...

  9. Neutrino-Induced Nucleosynthesis in Helium Shells of Early Core-Collapse Supernovae

    Directory of Open Access Journals (Sweden)

    Banerjee Projjwal

    2016-01-01

    Full Text Available We summarize our studies on neutrino-driven nucleosynthesis in He shells of early core-collapse supernovae with metallicities of Z ≲ 10−3 Z⊙. We find that for progenitors of ∼ 11–15 M⊙, the neutrons released by 4He(ν¯ee, e+n3H in He shells can be captured to produce nuclei with mass numbers up to A ∼ 200. This mechanism is sensitive to neutrino emission spectra and flavor oscillations. In addition, we find two new primary mechanisms for neutrino-induced production of 9Be in He shells. The first mechanism produces 9Be via 7Li(n,γ8Li(n,γ9Li(e− ν¯ee9Be and relies on a low explosion energy for its survival. The second mechanism operates in progenitors of ∼ 8 M⊙, where 9Be can be produced directly via 7Li(3H, n09Be during the rapid expansion of the shocked Heshell material. The light nuclei 7Li and 3H involved in these mechanisms are produced by neutrino interactions with 4He. We discuss the implications of neutrino-induced nucleosynthesis in He shells for interpreting the elemental abundances in metal-poor stars.

  10. New Observational Evidence of Flash Mixing on the White Dwarf Cooling Curve

    CERN Document Server

    Brown, Thomas M; Sweigart, Allen V; Cracraft, Misty; Hubeny, Ivan; Landsman, Wayne B

    2012-01-01

    Blue hook stars are a class of subluminous extreme horizontal branch stars that were discovered in UV images of the massive globular clusters omega Cen and NGC 2808. These stars occupy a region of the HR diagram that is unexplained by canonical stellar evolution theory. Using new theoretical evolutionary and atmospheric models, we have shown that the blue hook stars are very likely the progeny of stars that undergo extensive internal mixing during a late helium-core flash on the white dwarf cooling curve. This "flash mixing" produces hotter-than-normal EHB stars with atmospheres significantly enhanced in helium and carbon. The larger bolometric correction, combined with the decrease in hydrogen opacity, makes these stars appear subluminous in the optical and UV. Flash mixing is more likely to occur in stars born with a high helium abundance, due to their lower mass at the main sequence turnoff. For this reason, the phenomenon is more common in those massive globular clusters that show evidence for secondary p...

  11. Infrared transmission at the 3.39 micron helium-neon laser wavelength in liquid-core quartz fibers

    Science.gov (United States)

    Majumdar, A. K.; Hinkley, E. D.; Menzies, R. T.

    1979-01-01

    Infrared transmission at the 3.39 micron helium-neon laser wavelength has been measured in a tetrachloroethylene-filled fused-quartz fiber. The loss measurements were taken for three different settings of laser light intensity using a series of neutral density filters. The average value of transmission loss at this wavelength was found to be 56 dB/km.

  12. Liquid helium

    CERN Document Server

    Atkins, K R

    1959-01-01

    Originally published in 1959 as part of the Cambridge Monographs on Physics series, this book addresses liquid helium from the dual perspectives of statistical mechanics and hydrodynamics. Atkins looks at both Helium Three and Helium Four, as well as the properties of a combination of the two isotopes. This book will be of value to anyone with an interest in the history of science and the study of one of the universe's most fundamental elements.

  13. Helium cryogenics

    CERN Document Server

    Van Sciver, Steven W

    2012-01-01

    Twenty five years have elapsed since the original publication of Helium Cryogenics. During this time, a considerable amount of research and development involving helium fluids has been carried out culminating in several large-scale projects. Furthermore, the field has matured through these efforts so that there is now a broad engineering base to assist the development of future projects. Helium Cryogenics, 2nd edition brings these advances in helium cryogenics together in an updated form. As in the original edition, the author's approach is to survey the field of cryogenics with emphasis on helium fluids. This approach is more specialized and fundamental than that contained in other cryogenics books, which treat the associated range of cryogenic fluids. As a result, the level of treatment is more advanced and assumes a certain knowledge of fundamental engineering and physics principles, including some quantum mechanics. The goal throughout the work is to bridge the gap between the physics and engineering aspe...

  14. Primary proton and helium spectra at energy range from 50 TeV to 1015 eV observed with the new Tibet AS core detector array

    Directory of Open Access Journals (Sweden)

    Huang Jing

    2013-06-01

    Full Text Available A new EAS hybrid experiment has been designed by constructing a YAC (Yangbajing Air shower Core detector array inside the existing Tibet-III air shower array. The first step of YAC, called “YAC-I” has been successfully carried out in 2009–2010 together with Tibet-III air-shower array. YAC-II has also been operated from 2011. Preliminary results of YAC-I and performance of YAC-II are presented in this paper. The primary proton and helium spectra at energy range from50 TeV to 1015 eV derived from YAC-I data based on QGSJET2 and SIBYLL2.1 are reported. The obtained P+He spectrum is smoothly connected with directobservation data below 100 TeV and also with our previously reported results at higher energies within statistical error s. Based on these results and the sharp kneeof all-particle energy spectrum observed by our experiment, the possible origin of the sharp knee is discussed. See the published papers.

  15. Helium release during shale deformation: Experimental validation

    Science.gov (United States)

    Bauer, Stephen J.; Gardner, W. Payton; Heath, Jason E.

    2016-07-01

    This work describes initial experimental results of helium tracer release monitoring during deformation of shale. Naturally occurring radiogenic 4He is present in high concentration in most shales. During rock deformation, accumulated helium could be released as fractures are created and new transport pathways are created. We present the results of an experimental study in which confined reservoir shale samples, cored parallel and perpendicular to bedding, which were initially saturated with helium to simulate reservoir conditions, are subjected to triaxial compressive deformation. During the deformation experiment, differential stress, axial, and radial strains are systematically tracked. Release of helium is dynamically measured using a helium mass spectrometer leak detector. Helium released during deformation is observable at the laboratory scale and the release is tightly coupled to the shale deformation. These first measurements of dynamic helium release from rocks undergoing deformation show that helium provides information on the evolution of microstructure as a function of changes in stress and strain.

  16. Antiprotonic helium

    CERN Multimedia

    Eades, John

    2005-01-01

    An exotic atom in w hich an electron and an antiproton orbit a helium nucleus could reveal if there are any differences between matter and antimatter. The author describes this unusual mirror on the antiworld (5 pages)

  17. Foundation Flash Catalyst

    CERN Document Server

    Goralski, Greg

    2010-01-01

    This book offers an introduction to Flash Catalyst for designers with intermediate to advanced skills. It discusses where Catalyst sits within the production process and how it communicates with other programs. It covers all of the features of the Flash Catalyst workspace, teaching you how to create designs from scratch, how to build application designs and add functionality, and how to master the Catalyst/Flex workflow. * Introduces Flash Catalyst * Focuses on production process * Covers the interrelation between Flash Catalyst and Photoshop/Illustrator/Flex/Flash What you'll learn Starting f

  18. Thermal fluid dynamic behavior of coolant helium gas in a typical reactor VHTGR channel of prismatic core; Comportamento termofluidodinamico do gas refrigerante helio em um canal topico de reator VHTGR de nucleo prismatico

    Energy Technology Data Exchange (ETDEWEB)

    Belo, Allan Cavalcante

    2016-08-01

    The current studies about the thermal fluid dynamic behavior of the VHTGR core reactors of 4{sup th} generation are commonly developed in 3-D analysis in CFD (computational fluid dynamics), which often requires considerable time and complex mathematical calculations for carrying out these analysis. The purpose of this project is to achieve thermal fluid dynamic analysis of flow of gas helium refrigerant in a typical channel of VHTGR prismatic core reactor evaluating magnitudes of interest such as temperature, pressure and fluid velocity and temperature distribution in the wall of the coolant channel from the development of a computer code in MATLAB considering the flow on one-dimensional channel, thereby significantly reducing the processing time of calculations. The model uses three different references to the physical properties of helium: expressions given by the KTA (German committee of nuclear safety standards), the computational tool REFPROP and a set of constant values for the entire channel. With the use of these three references it is possible to simulate the flow treating the gas both compressible and incompressible. The results showed very close values for the interest quantities and revealed that there are no significant differences in the use of different references used in the project. Another important conclusion to be observed is the independence of helium in the gas compressibility effects on thermal fluid dynamic behavior. The study also indicated that the gas undergoes no severe effects due to high temperature variations in the channel, since this goes in the channel at 914 K and exits at approximately 1263 K, which shows the excellent use of helium as a refrigerant fluid in reactor channels VHTGR. The comparison of results obtained in this work with others in the literature served to confirm the effectiveness of the one-dimensional consideration of method of gas flow in the coolant channel to replace the models made in 3-D for the pressure range

  19. NAND flash memory technologies

    CERN Document Server

    Aritome, Seiichi

    2016-01-01

    This book discusses basic and advanced NAND flash memory technologies, including the principle of NAND flash, memory cell technologies, multi-bits cell technologies, scaling challenges of memory cell, reliability, and 3-dimensional cell as the future technology. Chapter 1 describes the background and early history of NAND flash. The basic device structures and operations are described in Chapter 2. Next, the author discusses the memory cell technologies focused on scaling in Chapter 3, and introduces the advanced operations for multi-level cells in Chapter 4. The physical limitations for scaling are examined in Chapter 5, and Chapter 6 describes the reliability of NAND flash memory. Chapter 7 examines 3-dimensional (3D) NAND flash memory cells and discusses the pros and cons in structure, process, operations, scalability, and performance. In Chapter 8, challenges of 3D NAND flash memory are dis ussed. Finally, in Chapter 9, the author summarizes and describes the prospect of technologies and market for the fu...

  20. Optical Flashes Preceding GRBs

    CERN Document Server

    Paczynski, B

    2001-01-01

    Only one optical flash associated with a gamma-ray burst has been detected so far by ROTSE. There are also upper limits obtained by several groups for several bursts. Recent model calculations indicate a possibility that optical flash may precede the GRB. Such flashes are undetectable in the currently popular observing mode, with optical instruments responding to GRB triggers. There is a need to develop all sky optical monitoring system capable of recognizing flashes in real time, and more powerful instruments that could respond robotically to optical triggers and carry out follow up observations.

  1. Pro Android Flash

    CERN Document Server

    Chin, Stephen; Campesato, Oswald

    2011-01-01

    Did you know you can take your Flash skills beyond the browser, allowing you to make apps for Android, iOS and the BlackBerry Tablet OS? Build dynamic apps today starting with the easy-to-use Android smartphones and tablets. Then, take your app to other platforms without writing native code. Pro Android Flash is the definitive guide to building Flash and other rich Internet applications (RIAs) on the Android platform. It covers the most popular RIA frameworks for Android developers - Flash and Flex - and shows how to build rich, immersive user experiences on both Android smartphones and tablet

  2. CORE

    DEFF Research Database (Denmark)

    Krigslund, Jeppe; Hansen, Jonas; Hundebøll, Martin

    2013-01-01

    different flows. Instead of maintaining these approaches separate, we propose a protocol (CORE) that brings together these coding mechanisms. Our protocol uses random linear network coding (RLNC) for intra- session coding but allows nodes in the network to setup inter- session coding regions where flows...... intersect. Routes for unicast sessions are agnostic to other sessions and setup beforehand, CORE will then discover and exploit intersecting routes. Our approach allows the inter-session regions to leverage RLNC to compensate for losses or failures in the overhearing or transmitting process. Thus, we...... increase the benefits of XORing by exploiting the underlying RLNC structure of individual flows. This goes beyond providing additional reliability to each individual session and beyond exploiting coding opportunistically. Our numerical results show that CORE outperforms both forwarding and COPE...

  3. CORE

    DEFF Research Database (Denmark)

    Krigslund, Jeppe; Hansen, Jonas; Hundebøll, Martin

    2013-01-01

    different flows. Instead of maintaining these approaches separate, we propose a protocol (CORE) that brings together these coding mechanisms. Our protocol uses random linear network coding (RLNC) for intra- session coding but allows nodes in the network to setup inter- session coding regions where flows...... intersect. Routes for unicast sessions are agnostic to other sessions and setup beforehand, CORE will then discover and exploit intersecting routes. Our approach allows the inter-session regions to leverage RLNC to compensate for losses or failures in the overhearing or transmitting process. Thus, we...... increase the benefits of XORing by exploiting the underlying RLNC structure of individual flows. This goes beyond providing additional reliability to each individual session and beyond exploiting coding opportunistically. Our numerical results show that CORE outperforms both forwarding and COPE...

  4. Flash-Type Discrimination

    Science.gov (United States)

    Koshak, William J.

    2010-01-01

    This viewgraph presentation describes the significant progress made in the flash-type discrimination algorithm development. The contents include: 1) Highlights of Progress for GLM-R3 Flash-Type discrimination Algorithm Development; 2) Maximum Group Area (MGA) Data; 3) Retrieval Errors from Simulations; and 4) Preliminary Global-scale Retrieval.

  5. Understanding Green Flashes

    Science.gov (United States)

    Young, Andrew T.

    1998-05-01

    Most astronomers learn about green flashes from either Minnaert's old book (Dover, 1954) or O'Connell's ``The Green Flash....'' Both have defects. Minnaert's account mostly represents what was known in the 1920s; it repeats Mulder's 3-fold classification, which omits Joule's second type of flash --- the one most commonly seen from mountain observatories. O'Connell searched only the astronomical literature, missing Dietze's crucially important paper (Z.f.Met. 9, 169 (1955)) showing that the ``textbook'' mechanism cannot produce flashes visible to the naked eye. He also erred in thinking that distortions of the setting Sun arise in the upper atmosphere (they are due to the marine boundary layer), and copied an error from Feenstra Kuiper's thesis that misidentified a common mirage-like phenomenon as Wegener's ``blank strip'' (Young et al., Appl. Opt. 36, 2689 (1997).) Most phenomena shown in O'Connell's book are caused by inversion layers below eye level, not above as in Wegener's phenomenon. The two commonest forms of green flash are associated with the inferior mirage and the mock mirage, corresponding to Fisher's Type A and Type B sunsets, respectively. Superrefraction, advocated by Wood and by Rayleigh as the cause of large flashes, actually suppress them: the airmass is proportional to the refraction (by Laplace's extinction theorem), so no green is transmitted when refraction is much larger than average. Although there is a physical green flash that can be photographed, the colors seen at sunset are strongly modified by bleaching of the L cones. Most ``green'' sunset flashes are actually yellow. Writers should stop representing Jules Verne's ``ancient legend'' as fact, as it was invented by Verne as a plot device for his novel ``Le Rayon Vert.'' Green-flash photos and simulations will be shown. This material is based upon work supported by the NSF under Award No. ATM-9714357.

  6. Floods and Flash Flooding

    Science.gov (United States)

    Floods and flash flooding Now is the time to determine your area’s flood risk. If you are not sure whether you ... If you are in a floodplain, consider buying flood insurance. Do not drive around barricades. If your ...

  7. Charged Condensate and Helium Dwarf Stars

    CERN Document Server

    Gabadadze, Gregory

    2008-01-01

    White dwarf stars composed of carbon, oxygen or heavier elements are expected to crystallize as they cool down below certain temperatures. Yet, simple arguments suggest that the helium white dwarf cores may not solidify, mostly because of zero-point oscillations of the helium ions that would dissolve the crystalline structure. We argue that the interior of the helium dwarfs may instead form a macroscopic quantum state in which the charged helium-4 nuclei are in a Bose-Einstein condensate, while the relativistic electrons form a neutralizing degenerate Fermi liquid. We discuss the electric charge screening, and the spectrum of this substance, showing that the bosonic long-wavelength fluctuations exhibit a mass gap. Hence, there is a suppression at low temperatures of the boson contribution to the specific heat -- the latter being dominated by the specific heat of the electrons near the Fermi surface. This state of matter may have observational signatures.

  8. Professional Flash Mobile Development Creating Android and iPhone Applications

    CERN Document Server

    Wagner, Richard

    2010-01-01

    Professional Flash Mobile Development: Creating Android and iPhone ApplicationsEverything Flash developers need to know to create native Android and iPhone appsThis Wrox guide shows Flash developers how to create native applications for Android and iPhone mobile devices using Flash. Packed with practical examples, it shows how to build a variety of apps and integrate them with core mobile services such as Accelerometer, GPS, Photo Library,and more.Offers Flash developers the tools to create apps for the Android and iPhone mobile devicesSho

  9. Foundation Flash Cartoon Animation

    CERN Document Server

    Jones, Tim; Rosson, Allan S

    2008-01-01

    One of Flash s most common uses is still animation for cartoons, games, advertising etc, and this book takes a fresh look at the topic, breaking it down pre-production, production, and post production, and looking at each section in detail, and covering topics such as storyboarding, character libraries and camera mechanics like no Flash book has before. The book is written by members of the Emmy award winning ANIMAX team, who have created work for clients such as Disney, AOL, Fox, WWE, ESPN, and Sesame workshop. This book is an opportunity for them to share their secrets, and is written to sui

  10. Cooling with Superfluid Helium

    CERN Document Server

    Lebrun, P

    2014-01-01

    The technical properties of helium II (‘superfluid’ helium) are presented in view of its applications to the cooling of superconducting devices, particularly in particle accelerators. Cooling schemes are discussed in terms of heat transfer performance and limitations. Large-capacity refrigeration techniques below 2 K are reviewed, with regard to thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation. Keywords: superfluid helium, cryogenics

  11. Learning Flash CS4 Professional

    CERN Document Server

    Shupe, Rich

    2009-01-01

    Learning Flash CS4 Professional offers beginners and intermediate Flash developers a unique introduction to the latest version of Adobe's powerful multimedia application. This easy-to-read book is loaded with full-color examples and hands-on tasks to help you master Flash CS4's new motion editor, integrated 3D system, and character control using the new inverse kinematics bones animation system. No previous Flash experience is necessary.

  12. Flash Builder and Flash Catalyst The New Workflow

    CERN Document Server

    Peeters, Steven

    2010-01-01

    The Flash Platform is changing. Flash Builder and Flash Catalyst have brought a new separation of design and coding to web development that enables a much more efficient and streamlined workflow. For designers and developers used to the close confines of Flash, this is a hugely liberating but at first alien concept. This book teaches you the new workflow for the Flash platform. It gives an overview of the technologies involved and provides you with real-world project examples and best-practice guidelines to get from design to implementation with the tools at hand. * Includes many examples* Foc

  13. Jaan Toomik Flash Artis

    Index Scriptorium Estoniae

    1999-01-01

    1999. a. mai-juuni 'Flash Artis' on ajakirja Eesti korrespondendi Ando Keskküla artikkel Jaan Toomikust. Jaan Toomik on kutsutud esinema Londoni The Photographers' Gallery grupinäitusele, tema videot 'Father and Son' näidatakse Londonis avataval näitusel 'Near and Elsewhere' 11.-24. juunini

  14. Inessa Josing Flash Artis

    Index Scriptorium Estoniae

    1999-01-01

    'Flash Art'i' 1998. a. nov.-dets. numbris Rosa Martínezi artiklis suvisest Manifesta II näitusest Luxembourg'is on positiivselt mainitud ka Inessa Josingut. Illustratsiooniks toodud seitsmest fotost ühel on I. Josingu aknakujundus 'What Must I Do to be Saved?'

  15. Inessa Josing Flash Artis

    Index Scriptorium Estoniae

    1999-01-01

    'Flash Art'i' 1998. a. nov.-dets. numbris Rosa Martínezi artiklis suvisest Manifesta II näitusest Luxembourg'is on positiivselt mainitud ka Inessa Josingut. Illustratsiooniks toodud seitsmest fotost ühel on I. Josingu aknakujundus 'What Must I Do to be Saved?'

  16. Jaan Toomik Flash Artis

    Index Scriptorium Estoniae

    1999-01-01

    1999. a. mai-juuni 'Flash Artis' on ajakirja Eesti korrespondendi Ando Keskküla artikkel Jaan Toomikust. Jaan Toomik on kutsutud esinema Londoni The Photographers' Gallery grupinäitusele, tema videot 'Father and Son' näidatakse Londonis avataval näitusel 'Near and Elsewhere' 11.-24. juunini

  17. Helium the disappearing element

    CERN Document Server

    Sears, Wheeler M

    2015-01-01

    The subject of the book is helium, the element, and its use in myriad applications including MRI machines, particle accelerators, space telescopes, and of course balloons and blimps. It was at the birth of our Universe, or the Big Bang, where the majority of cosmic helium was created; and stellar helium production continues. Although helium is the second most abundant element in the Universe, it is actually quite rare here on Earth and only exists because of radioactive elements deep within the Earth. This book includes a detailed history of the discovery of helium, of the commercial industry built around it, how the helium we actually encounter is produced within the Earth, and the state of the helium industry today. The gas that most people associate with birthday party balloons is running out. “Who cares?” you might ask. Well, without helium, MRI machines could not function, rockets could not go into space, particle accelerators such as those used by CERN could not operate, fiber optic cables would not...

  18. Numerical Experiments for Nuclear Flashes toward Superbursts in an Accreting Neutron Star

    Directory of Open Access Journals (Sweden)

    Masa-aki Hashimoto

    2014-01-01

    Full Text Available We show that the superburst would be originated from thermonuclear burning ignited by accumulated fuels in the deep layers compared to normal X-ray bursts. Two cases are investigated for models related to superbursts by following thermal evolution of a realistic neutron star: helium flash and carbon flash accompanied with many normal bursts. For a helium flash, the burst shows the long duration when the accretion rate is low compared with the observation. The flash could become a superburst if the burning develops to the deflagration and/or detonation. For a carbon flash accompanied with many normal bursts, after successive 2786 normal bursts during 1.81 × 109 s, the temperature reaches the deflagration temperature. This is due to the produced carbon which amount reaches to ≈0.1 in the mass fraction. The flash will develop to dynamical phenomena of the deflagration and/or detonation, which may lead to a superburst.

  19. The Essential Guide to 3D in Flash

    CERN Document Server

    Olsson, Ronald A

    2010-01-01

    If you are an ActionScript developer or designer and you would like to work with 3D in Flash, this book is for you. You will learn the core Flash 3D concepts, using the open source Away3D engine as a primary tool. Once you have mastered these skills, you will be able to realize the possibilities that the available Flash 3D engines, languages, and technologies have to offer you with Flash and 3D.* Describes 3D concepts in theory and their implementation using Away3D* Dives right in to show readers how to quickly create an interactive, animated 3D scene, and builds on that experience throughout

  20. Document Flash Thermography

    OpenAIRE

    Larsen, Cory; Baker, Doran

    2011-01-01

    This paper presents an extension of flash thermography techniques to the analysis of documents. Motivation for this research is to develop the ability to reveal covered writings in archaeological artifacts such as the Codex Selden or Egyptian Cartonnage. An emphasis is placed on evaluating several common existing signal processing techniques for their effectiveness in enhancing subsurface writings found within a set of test documents. These processing techniques include: contrast stretching, ...

  1. The lightning flash

    CERN Document Server

    Cooray, Vernon

    2014-01-01

    With contributions from today's leading lightning engineers and researchers, this updated 2nd edition of Vernon Cooray's classic text, The Lightning Flash provides the reader with an essential introduction to lightning and its impact on electrical and electronic equipment. Providing the reader with a thorough background into almost every aspect of lightning and its impact on electrical and electronic equipment, this new edition is updated throughout and features eight new chapters that bring the science up to date.

  2. Flash Lidar Data Processing

    Science.gov (United States)

    Bergkoetter, M. D.; Ruppert, L.; Weimer, C. S.; Ramond, T.; Lefsky, M. A.; Burke, I. C.; Hu, Y.

    2009-12-01

    Late last year, a prototype Flash LIDAR instrument flew on a series of airborne tests to demonstrate its potential for improved vegetation measurements. The prototype is a precursor to the Electronically Steerable Flash LIDAR (ESFL) currently under development at Ball Aerospace and Technology Corp. with funding from the NASA Earth Science Technology Office. ESFL may soon significantly expand our ability to measure vegetation and forests and better understand the extent of their role in global climate change and the carbon cycle - all critical science questions relating to the upcoming NASA DESDynI and ESA BIOMASS missions. In order to more efficiently exploit data returned from the experimental Flash Lidar system and plan for data exploitation from future flights, Ball funded a graduate student project (through the Ball Summer Intern Program, summer 2009) to develop and implement algorithms for post-processing of the 3-Dimensional Flash Lidar data. This effort included developing autonomous algorithms to resample the data to a uniform rectangular grid, geolocation of the data, and visual display of large swaths of data. The resampling, geolocation, surface hit detection, and aggregation of frame data are implemented with new MATLAB code, and the efficient visual display is achieved with free commercial viewing software. These efforts directly support additional tests flights planned as early as October 2009, including possible flights over Niwot Ridge, CO, for which there is ICESat data, and a sea-level coastal area in California to test the effect of higher altitude (above ground level) on the divergence of the beams and the beam spot sizes.

  3. Physics Flash August 2016

    Energy Technology Data Exchange (ETDEWEB)

    Kippen, Karen Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-25

    Physics Flash is the newsletter for the Physics Division at Los Alamos National Laboratory. This newsletter is for August 2016. The following topics are covered: "Accomplishments in the Trident Laser Facility", "David Meyerhofer elected as chair-elect APS Nominating Committee", "HAWC searches for gamma rays from dark matter", "Proton Radiography Facility commissions electromagnetic magnifier", and "Cosmic ray muon computed tomography of spent nuclear fuel in dry storage casks."

  4. Flash pryolysis of biomass with reactive and nonreactive gases

    Science.gov (United States)

    Sundaram, M. S.; Steinberg, M.; Fallon, P. T.

    1982-10-01

    Studies were done on the flash pyrolysis of Douglas Fir wood in the presence of reactive and nonreactive gases including hydrogen, methane, and helium. Pyrolysis and gasification of the wood particles was done in one step, without catalysts. Almost complete (98%) gasification of the carbon in Douglas fir wood was achieved at 10000C and 500-psi hydrogen pressure. The reaction products were methane, ethane, ethylene, carbon monoxide, BTX, and water. Flash hydropyrolysis produced a large yield of hydrocarbon gases (up to 78% C) comprising methane and ethane. High yields of ethylene (up to 21% C) and BTX (up to 12% C) were obtained via methane pyrolysis of fir wood; a free radical mechanism is proposed to explain the enhanced yield of ethylene in a methane atmosphere.

  5. Advances in Helium Cryogenics

    Science.gov (United States)

    Sciver, S. W. Van

    This review provides a survey of major advances that have occurred in recent years in the area of helium cryogenics. Helium-temperature cryogenics is the enabling technology for a substantial and growing number of low-temperature systems from superconducting magnets to space-based experimental facilities. In recent years there have been many advances in the technology of low-temperature helium, driven mostly by new applications. However, to keep the review from being too broad, this presentation focuses mainly on three of the most significant advances. These are: (1) the development of large-scale recuperative refrigeration systems mainly for superconducting magnet applications in accelerators and other research facilities; (2) the use of stored superfluid helium (He II) as a coolant for spacebased astrophysics experiments; and (3) the application of regenerative cryocoolers operating at liquid helium temperatures primarily for cooling superconducting devices. In each case, the reader should observe that critical technologies were developed to facilitate these applications. In addition to these three primary advances, other significant helium cryogenic technologies are briefly reviewed at the end of this chapter, along with some vision for future developments in these areas.

  6. Flash Point Performance Evaluation

    Science.gov (United States)

    2014-03-01

    7094 Grabner D3828B Seta Flash CL12-3453 42.5 43.8 43.8 47.7 44.3 47.3 42.0 42.5 43.8 43.8 47.7 45.3 47.2 42.0 CL12-3475 58.5 61.7 58.7 59.7 61.3...division of Petroleum Analyzers Company (PAC) Houston, TX 14. Herzog is division of PAC 15. Stanhope- Seta , London, UK 16. Grabner Instruments is a

  7. Methods of flash sintering

    Energy Technology Data Exchange (ETDEWEB)

    Raj, Rishi; Cologna, Marco; Francis, John S.

    2016-05-10

    This disclosure provides methods of flash sintering and compositions created by these methods. Methods for sintering multilayered bodies are provided in which a sintered body is produced in less than one minute. In one aspect, each layer is of a different composition, and may be constituted wholly from a ceramic or from a combination of ceramic and metallic particles. When the body includes a layer of an anode composition, a layer of an electrolyte composition and a layer of a cathode composition, the sintered body can be used to produce a solid oxide fuel cell.

  8. Flash floods in the Tatra Mountain streams: frequency and triggers.

    Science.gov (United States)

    Ballesteros-Cánovas, J A; Czajka, B; Janecka, K; Lempa, M; Kaczka, R J; Stoffel, M

    2015-04-01

    Flash floods represent a frequently recurring natural phenomenon in the Tatra Mountains. On the northern slopes of the mountain chain, located in Poland, ongoing and expected future changes in climate are thought to further increase the adverse impacts of flash floods. Despite the repeat occurrence of major floods in the densely populated foothills of the Polish Tatras, the headwaters have been characterized by a surprising lack of data, such that any analysis of process variability or hydrometeorological triggers has been largely hampered so far. In this study, dendrogeomorphic techniques have been employed in four poorly-gauged torrential streams of the northern slope of the Tatra Mountains to reconstruct temporal and spatial patterns of past events. Using more than 1100 increment cores of trees injured by past flash floods, we reconstruct 47 events covering the last 148 years and discuss synoptic situations leading to the triggering of flash floods with the existing meteorological and flow gauge data. Tree-ring analyses have allowed highlighting the seasonality of events, providing new insights about potential hydrometeorological triggers as well as a differentiating flash flood activity between catchments. Results of this study could be useful to design future strategies to deal with flash flood risks at the foothills of the Polish Tatras and in the Vistula River catchment.

  9. State of the Art Report for a Bearing for VHTR Helium Circulator

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Seon; Song, Kee Nam; Kim, Yong Wan; Lee, Won Jae

    2008-10-15

    A helium circulator in a VHTR(Very High Temperature gas-cooled Reactor) plays a core role which translates thermal energy at high temperature from a nuclear core to a steam generator. Helium as a operating coolant circulates a primary circuit in high temperature and high pressure state, and controls thermal output of a nuclear core by controlling flow rate. A helium circulator is the only rotating machinery in a VHTR, and its reliability should be guaranteed for reliable operation of a reactor and stable production of hydrogen. Generally a main helium circulator is installed on the top of a steam generator vessel, and helium is circulated only by a main helium circulator in a normal operation state. An auxiliary or shutdown circulator is installed at the bottom of a reactor vessel, and it is an auxiliary circulator for shutting down a reactor in case of refueling or accelerating cooling down in case of fast cooling. Since a rotating shaft of a helium circulator is supported by bearings, bearings are the important machine elements which determines reliability of a helium circulator and a nuclear reactor. Various types of support bearings have been developed and applied for circulator bearings since 1960s, and it is still developing for developing VHTRs. So it is necessary to review and analyze the current technical state of helium circulator support bearings to develop bearings for Koran developing VHTR helium circulator.

  10. Geomorphological factors of flash floods

    Science.gov (United States)

    Kuznetsova, Yulia

    2016-04-01

    Growing anthropogenic load, rise of extreme meteorological events frequency and total precipitation depth often lead to increasing danger of catastrophic fluvial processes worldwide. Flash floods are one of the most dangerous and less understood types of them. Difficulties of their study are mainly related to short duration of single events, remoteness and hard access to origin areas. Most detailed researches of flash floods focus on hydrological parameters of the flow itself and its meteorological factors. At the same time, importance of the basin geological and geomorphological structure for flash floods generation and the role they play in global sediment redistribution is yet poorly understood. However, understanding and quantitative assessment of these features is a real basis for a complete concept of factors, characteristics and dynamics of flash floods. This work is a review of published data on flash floods, and focuses on the geomorphological factors of the phenomenon. We consider both individual roles and interactions between different geomorphological features (the whole basin parameters, characteristics of the single slopes and valley bottom). Special attention is paid to critical values of certain factors. This approach also highlights the gaps or less studied factors of flash floods. Finally, all data is organized into a complex diagram that may be used for flash floods modeling. This also may help to reach a new level of flash flood predictions and risk assessment.

  11. Flashing LEDs for Microalgal Production.

    Science.gov (United States)

    Schulze, Peter S C; Guerra, Rui; Pereira, Hugo; Schüler, Lisa M; Varela, João C S

    2017-08-30

    Flashing lights are next-generation tools to mitigate light attenuation and increase the photosynthetic efficiency of microalgal cultivation systems illuminated by light-emitting diodes (LEDs). Optimal flashing light conditions depend on the reaction kinetics and properties of the linear electron transfer chain, energy dissipation, and storage mechanisms of a phototroph. In particular, extremely short and intense light flashes potentially mitigate light attenuation in photobioreactors without impairing photosynthesis. Intelligently controlling flashing light units and selecting electronic components can maximize light emission and energy efficiency. We discuss the biological, physical, and technical properties of flashing lights for algal production. We combine recent findings about photosynthetic pathways, self-shading in photobioreactors, and developments in solid-state technology towards the biotechnological application of LEDs to microalgal production. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Cosmic Ray Helium Hardening

    CERN Document Server

    Ohira, Yutaka

    2010-01-01

    Recent observations by CREAM, ATIC-2 and PAMELA experiments suggest that (1) the spectrum of cosmic ray (CR) helium is harder than that of CR proton below the knee $10^15 eV$ and (2) all CR spectra become hard at $\\gtrsim 10^{11} eV/n$. We propose a new picture that higher energy CRs are generated in more helium-rich region to explain the hardening (1) without introducing different sources for CR helium. The helium to proton ratio at $\\sim 100$ TeV exceeds the Big Bang abundance $Y=0.25$ by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in the chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium when escaping from the supernova remnant (SNR) shock. We provide a simple analytical spectrum that also fits well the hardening (2) because of the decreasing Mach number in the hot superbubble with $\\sim 10^6$ K. Our model predicts hard and con...

  13. Step & flash imprint lithography

    Directory of Open Access Journals (Sweden)

    Douglas J. Resnick

    2005-02-01

    Full Text Available The escalating cost of next generation lithography (NGL is driven in part by the need for complex sources and optics. The cost for a single NGL tool could soon exceed $50 million, a prohibitive amount for many companies. As a result, several research groups are looking at alternative, low-cost methods for printing sub-100 nm features. Many of these methods are limited in their ability to do precise overlay. In 1999, Willson and Sreenivasan developed step and flash imprint lithography (S-FIL™. The use of a quartz template opens up the potential for optical alignment of the wafer and template. This paper reviews several key aspects of the S-FIL process, including template, tool, ultraviolet (UV-curable monomer, and pattern transfer. Two applications are also presented: contact holes and surface acoustic wave (SAW filters.

  14. Nuclear fusion and carbon flashes on neutron stars

    Science.gov (United States)

    Taam, R. E.; Picklum, R. E.

    1978-01-01

    This paper reports on detailed calculations of the thermal evolution of the carbon-burning shells in the envelopes of accreting neutron stars for mass-accretion rates of 1 hundred-billionth to 2 billionths of a solar mass per yr and neutron-star masses of 0.56 and 1.41 solar masses. The work of Hansen and Van Horn (1975) is extended to higher densities, and a more detailed treatment of nuclear processing in the hydrogen- and helium-burning regions is included. Results of steady-state calculations are presented, and results of time-dependent computations are examined for accretion rates of 3 ten-billionths and 1 billionth of solar mass per yr. It is found that two evolutionary sequences lead to carbon flashes and that the carbon abundance at the base of the helium shell is a strong function of accretion rate. Upper limits are placed on the accretion rates at which carbon flashes will be important.

  15. Broken symmetry makes helium

    CERN Multimedia

    Gray, P L

    2003-01-01

    "The subatomic pion particle breaks the charge symmetry rule that governs both fusion and decay. In experiments performed at the Indiana University Cyclotron Laboratory, physicists forced heavy hydrogen (1 proton + 1 neutron) to fuse into helium in a controlled, measurable environment" (1 paragraph).

  16. Flash sintering of ceramic materials

    OpenAIRE

    Dancer, C. E. J.

    2016-01-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sint...

  17. The effect of primordial hydrogen/helium fractionation on the solar neutrino flux

    Science.gov (United States)

    Wheeler, J. C.; Cameron, A. G. W.

    1975-01-01

    If hydrogen and helium are immiscible below some critical temperature, gravitational separation could occur in the proto-sun, resulting in a nearly pure helium core and a nearly pure hydrogen shell. We have constructed solar models according to this scenario and find the neutrino flux reduced to 1.5-3 SNU.

  18. Education in Helium Refrigeration

    Science.gov (United States)

    Gistau Baguer, G. M.

    2004-06-01

    On the one hand, at the end of the time I was active in helium refrigeration, I noticed that cryogenics was stepping into places where it was not yet used. For example, a conventional accelerator, operating at room temperature, was to be upgraded to reach higher particle energy. On the other hand, I was a little bit worried to let what I had so passionately learned during these years to be lost. Retirement made time available, and I came gradually to the idea to teach about what was my basic job. I thought also about other kinds of people who could be interested in such lessons: operators of refrigerators or liquefiers who, often by lack of time, did not get a proper introduction to their job when they started, young engineers who begin to work in cryogenics… and so on. Consequently, I have assembled a series of lessons about helium refrigeration. As the audiences have different levels of knowledge in the field of cryogenics, I looked for a way of teaching that is acceptable for all of them. The course is split into theory of heat exchangers, refrigeration cycles, technology and operation of main components, process control, and helium purity.

  19. Semiclassical calculation of ionisation rate for Rydberg helium atoms in an electric field

    Institute of Scientific and Technical Information of China (English)

    Wang De-Hua

    2011-01-01

    The ionisation of Rydberg helium atoms in an electric field above the classical ionisation threshold has been examined using the semiclassical method, with particular emphasis on discussing the influence of the core scattering on the escape dynamics of electrons. The results show that the Rydberg helium atoms ionise by emitting a train of electron pulses. Unlike the case of the ionisation of Rydberg hydrogen atom in parallel electric and magnetic fields,where the pulses of the electron are caused by the external magnetic field, the pulse trains for Rydberg helium atoms are created through core scattering. Each peak in the ionisation rate corresponds to the contribution of one core-scattered combination trajectory. This fact further illustrates that the ionic core scattering leads to the chaotic property of the Rydberg helium atom in external fields. Our studies provide a simple explanation for the escape dynamics in the ionisation of nonhydrogenic atoms in external fields.

  20. Flash Professional CS5 Digital Classroom

    CERN Document Server

    Gerantabee, Fred

    2011-01-01

    Learn Flash in a flash with this full-color book and video training package! Adobe Flash is used by designers, game programmers, and hobbyists to create interactive Web sites, digital experiences, and mobile content. The latest release of Flash promises exciting new capabilities and this book-and-video training package makes learning the new features of Flash less intimidating. Fifteen self-paced lessons encourage you to discover essential skills and explore new aspects of Flash. The tutorials featured in the videos are each approximately five minutes long and supplement the concepts and topic

  1. Helium anion formation inside helium droplets

    Science.gov (United States)

    Maalouf, Elias Jabbour Al; Reitshammer, Julia; Ribar, Anita; Scheier, Paul; Denifl, Stephan

    2016-07-01

    The formation of He∗- is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗- inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15-70 nA) a quadratic dependence of the He∗- ion yield on the electron current is observed. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  2. Liquid uranium alloy-helium fission reactor

    Science.gov (United States)

    Minkov, V.

    1984-06-13

    This invention describes a nuclear fission reactor which has a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200 to 1800/sup 0/C range, and even higher to 2500/sup 0/C.

  3. Atomistic simulation of helium bubble nucleation in palladium

    Energy Technology Data Exchange (ETDEWEB)

    Wang Liang [Department of Applied Physics, Hunan University, Changsha 410082 (China); Hu, Wangyu [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: wangyuhu2001cn@yahoo.com.cn; Xiao Shifang [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: sfxiao@yahoo.com.cn; Yang Jianyu [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China); Deng Huiqiu [Department of Applied Physics, Hunan University, Changsha 410082 (China)

    2009-09-15

    A palladium crystal has been constructed with 11808 atoms. 55 helium atoms occupied the octahedral position of palladium crystal are introduced and retained in a spherical region. Molecular dynamic simulations are performed in a constant temperature and constant volume ensemble (NVT) with temperature controlled by Nose-Hoover thermostat. The interactions between palladium atoms are described with modified analytic embedded atom method (MAEAM), the interactions between palladium atom and helium atom are in the form of Morse potential, and the interactions between helium atoms are in the form of L-J potential function. With the analysis of the radial distribution function (RDF) and microstructure, it reveals that some of helium atoms form a series of clusters with different size, and the nucleation core is random at low temperature, and which is the embryo of helium bubble. Increasing temperature can accelerate the process of bubble nucleation, and the clusters will aggregate and coalesce into a bigger one in which there are no palladium atoms, and it is considered as a helium bubble.

  4. Flashing light in microalgae biotechnology.

    Science.gov (United States)

    Abu-Ghosh, Said; Fixler, Dror; Dubinsky, Zvy; Iluz, David

    2016-03-01

    Flashing light can enhance photosynthesis and improve the quality and quantity of microalgal biomass, as it can increase the products of interest by magnitudes. Therefore, the integration of flashing light effect into microalgal cultivation systems should be considered. However, microalgae require a balanced mix of the light/dark cycle for higher growth rates, and respond to light intensity differently according to the pigments acquired or lost during the growth. This review highlights recently published results on flashing light effect on microalgae and its applications in biotechnology, as well as the recently developed bioreactors designed to fulfill this effect. It also discusses how this knowledge can be applied in selecting the optimal light frequencies and intensities with specific technical properties for increasing biomass production and/or the yield of the chemicals of interest by microalgae belonging to different genera.

  5. Flash sintering of ceramic materials

    Science.gov (United States)

    Dancer, C. E. J.

    2016-10-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity. Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique non-etheless holds great potential for exceptional control of the ceramic sintering process.

  6. Flash Builder building user interaction

    CERN Document Server

    Rocchi, Cesare

    2010-01-01

    Develop a working understanding of events and components, and containers and states so you can build and deploy RIAs in Flex. Work through a demo implementation of a login panel that employs feedback from the server side, to hone your understanding. Use the validators and the debugger to inspect your code execution. Building User Interaction is the second of five articles that will be compiled in the book, Data Visualization with Flash Builder: Designing RIA and AIR Applications with Remote Data Sources. Each full-color article illustrates specific aspects of Flash Builder data visualization

  7. Quick Guide to Flash Catalyst

    CERN Document Server

    Elmansy, Rafiq

    2011-01-01

    How do you transform user interface designs created in Photoshop or Illustrator into interactive web pages? It's easier than you think. This guide shows you how to use Adobe Flash Catalyst to create interactive UIs and website wireframes for Rich Internet Applications-without writing a single line of code. Ideal for web designers, this book introduces Flash Catalyst basics with detailed step-by-step instructions and screenshots that illustrate every part of the process. You'll learn hands-on how to turn your static design or artwork into working user interfaces that can be implemented in Fla

  8. Flash Builder charting and multimedia

    CERN Document Server

    Rocchi, Cesare

    2010-01-01

    Charting and multimedia are two vital tools for data-driven applications. Learn about the main components of the chart library included in Flash Builder, and see how to build and customize widely used charts. Turning your attention to the multimedia capabilities of the Flex framework, you will review the multimedia components built into the Flex library, and learn how to use ActionScript to manipulate video and audio files. Charting and Multimedia is the third of five articles that will be compiled in the book, Data Visualization with Flash Builder: Designing RIA and AIR Applications with Rem

  9. Effects of a New Triple-alpha Reaction on X-ray Bursts of a Helium Accreting Neutron Star

    CERN Document Server

    Matsuo, Y; Noda, T; Saruwatari, M; Ono, M; Hashimoto, M; Fujimoto, M

    2011-01-01

    The effects of a new triple-$\\alpha$ reaction rate (OKK rate) on the helium flash of a helium accreting neutron star in a binary system have been investigated. Since the ignition points determine the properties of a thermonuclear flash of type I X-ray bursts, we examine the cases of different accretion rates, $dM/dt (\\dot{M})$, of helium from $3\\times10^{-10} M_{\\odot} \\rm yr^{-1}$ to $3\\times10^{-8} M_{\\odot} \\rm yr^{-1}$, which could cover the observed accretion rates. We find that for the cases of low accretion rates, nuclear burnings are ignited at the helium layers of rather low densities. As a consequence, helium deflagration would be triggered for all cases of lower accretion rate than $\\dot{M}\\simeq 3\\times10^{-8} M_{\\odot} \\rm yr^{-1}$. We find that OKK rate could be barely consistent with the available observations of the X-ray bursts on the helium accreting neutron star. However this coincidence is found to depend on the properties of crustal heating and the neutron star model.We suggest that OKK r...

  10. 3D Flash LIDAR Space Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc. (ASC) is a small business that has developed 3D Flash LIDAR systems for space and terrestrial applications. 3D Flash LIDAR is...

  11. High Efficiency Regenerative Helium Compressor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Helium plays several critical rolls in spacecraft propulsion. High pressure helium is commonly used to pressurize propellant fuel tanks. Helium cryocoolers can be...

  12. Cavitation in liquid helium

    Energy Technology Data Exchange (ETDEWEB)

    Finch, R. D.; Kagiwada, R.; Barmatz, M.; Rudnick, I.

    1963-11-15

    Ultrasonic cavitation was induced in liquid helium over the temperature range 1.2 to 2.3 deg K, using a pair of identical transducers. The transducers were calibrated using a reciprocity technique and the cavitation threshold was determined at 90 kc/s. It was found that this threshold has a sharp peak at the lambda point, but is, at all temperatures quite low, with an approximate range of 0.001 to 0.01 atm. The significance of the results is discussed. (auth)

  13. Flash CS4: The Missing Manual

    CERN Document Server

    Grover, Chris

    2008-01-01

    Unlock the power of Flash and bring gorgeous animations to life onscreen. Flash CS4: The Missing Manual includes a complete primer on animation, a guided tour of the program's tools and capabilities, lots of new illustrations, and more details on working with video. Beginners will learn to use the software in no time, and experienced Flash designers will improve their skills.

  14. Evaluation of Flash Bainite in 4130 Steel

    Science.gov (United States)

    2011-07-01

    Technical Report ARWSB-TR-11011 Evaluation of Flash Bainite in 4130 Steel G. Vigilante M. Hespos S. Bartolucci...4. TITLE AND SUBTITLE Evaluation of Flash Bainite in 4130 Steel 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...STATEMENT 13. SUPPLEMENTARY NOTES 14. ABSTRACT ARDEC independently evaluated a Flash Bainite process developed by Gary Cola, Jr., Sirius Protection

  15. Jaan Toomik ajakirjas Flash Art

    Index Scriptorium Estoniae

    1999-01-01

    Kunstiajakirja "Flash Art" maikuu numbris Ando Keskküla artikkel, mis annab ülevaate J. Toomiku loomingust ja peatub pikemalt tema olulisematel töödel. 10. juunist J. Toomiku isiknäitus Londoni fotograafide galeriis. Eksponeeritud video "Uisutaja"

  16. Ingmar Muusikuse foto Flash Artis

    Index Scriptorium Estoniae

    1999-01-01

    Flash Arti 1999. a. oktoobrinumbris virtuaalse näituse rubriigis Ando Keskküla artikkel radikaalsemast eesti kunstist ja kunstielust postsotsialistlikul ajastul. Illustratsiooniks Liina Siibi fotokompositsioonid, Ingmar Muusikuse foto Raoul Kurvitza, Ene-Liis Semperi ja Kiwa Eesti Panga performance'ist

  17. Ingmar Muusikuse foto Flash Artis

    Index Scriptorium Estoniae

    1999-01-01

    Flash Arti 1999. a. oktoobrinumbris virtuaalse näituse rubriigis Ando Keskküla artikkel radikaalsemast eesti kunstist ja kunstielust postsotsialistlikul ajastul. Illustratsiooniks Liina Siibi fotokompositsioonid, Ingmar Muusikuse foto Raoul Kurvitza, Ene-Liis Semperi ja Kiwa Eesti Panga performance'ist

  18. Jaan Toomik ajakirjas Flash Art

    Index Scriptorium Estoniae

    1999-01-01

    Kunstiajakirja "Flash Art" maikuu numbris Ando Keskküla artikkel, mis annab ülevaate J. Toomiku loomingust ja peatub pikemalt tema olulisematel töödel. 10. juunist J. Toomiku isiknäitus Londoni fotograafide galeriis. Eksponeeritud video "Uisutaja"

  19. Regimes Of Helium Burning

    CERN Document Server

    Timmes, F X

    2000-01-01

    The burning regimes encountered by laminar deflagrations and ZND detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts which start with a thermonuclear runaway on the surface of a neutron star, and the thin shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial directions encounter a transition from the distributed regime to the flamlet regime at a density of 10^8 g cm^{-3}. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than 10^6 g cm^{-3}. Self-sustained laminar deflagrations travelling in the radial direction cannot exist below this density. Similarily, the planar ZND detonation width becomes larger than the pressure scale height at 10^7 g cm^{-3}, suggesting that a steady-state, self-sustained detonations cannot come into exista...

  20. Helium diffusion in carbonates

    Science.gov (United States)

    Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion

  1. Helium in near Earth orbit

    CERN Document Server

    Alcaraz, J; Ambrosi, G; Anderhub, H; Ao, L; Arefev, A; Azzarello, P; Babucci, E; Baldini, L; Basile, M; Barancourt, D; Barão, F; Barbier, G; Barreira, G; Battiston, R; Becker, R; Becker, U; Bellagamba, L; Béné, P; Berdugo, J; Berges, P; Bertucci, B; Biland, A; Bizzaglia, S; Blasko, S; Bölla, G; Boschini, M; Bourquin, Maurice; Brocco, L; Bruni, G; Buénerd, M; Burger, J D; Burger, W J; Cai, X D; Camps, C; Cannarsa, P; Capell, M; Casadei, D; Casaus, J; Castellini, G; Cecchi, C; Chang, Y H; Chen, H F; Chen, H S; Chen, Z G; Chernoplekov, N A; Tzi Hong Chiueh; Chuang, Y L; Cindolo, F; Commichau, V; Contin, A; Cristinziani, M; Da Cunha, J P; Dai, T S; Deus, J D; Dinu, N; Djambazov, L; D'Antone, I; Dong, Z R; Emonet, P; Engelberg, J; Eppling, F J; Eronen, T; Esposito, G; Extermann, Pierre; Favier, Jean; Fiandrini, E; Fisher, P H; Flügge, G; Fouque, N; Galaktionov, Yu; Gervasi, M; Giusti, P; Grandi, D; Grimm, O; Gu, W Q; Hangarter, K; Hasan, A; Hermel, V; Hofer, H; Huang, M A; Hungerford, W; Ionica, M; Ionica, R; Jongmanns, M; Karlamaa, K; Karpinski, W; Kenney, G; Kenny, J; Kim, W; Klimentov, A; Kossakowski, R; Koutsenko, V F; Kräber, M H; Laborie, G; Laitinen, T; Lamanna, G; Laurenti, G; Lebedev, A; Lee, S C; Levi, G; Levchenko, P M; Liu, C L; Liu Hong Tao; Lopes, I; Lu, G; Lü, Y S; Lübelsmeyer, K; Luckey, D; Lustermann, W; Maña, C; Margotti, A; Mayet, F; McNeil, R R; Meillon, B; Menichelli, M; Mihul, A; Mourão, A M; Mujunen, A; Palmonari, F; Papi, A; Park, I H; Pauluzzi, M; Pauss, Felicitas; Perrin, E; Pesci, A; Pevsner, A; Pimenta, M; Plyaskin, V; Pozhidaev, V; Pohl, M; Postolache, V; Produit, N; Rancoita, P G; Rapin, D; Raupach, F; Ren, D; Ren, Z; Ribordy, M; Richeux, J P; Riihonen, E; Ritakari, J; Röser, U; Roissin, C; Sagdeev, R; Sartorelli, G; Schultz von Dratzig, A; Schwering, G; Scolieri, G; Seo, E S; Shoutko, V; Shoumilov, E; Siedling, R; Son, D; Song, T; Steuer, M; Sun, G S; Suter, H; Tang, X W; Ting, Samuel C C; Ting, S M; Tornikoski, M; Torsti, J; Trümper, J E; Ulbricht, J; Urpo, S; Usoskin, I; Valtonen, E; Van den Hirtz, J; Velcea, F; Velikhov, E P; Verlaat, B; Vetlitskii, I; Vezzu, F; Vialle, J P; Viertel, Gert M; Vitè, Davide F; Von Gunten, H P; Waldmeier-Wicki, S; Wallraff, W; Wang, B C; Wang, J Z; Wang, Y H; Wiik, K; Williams, C; Wu, S X; Xia, P C; Yan, J L; Yan Lu Guang; Yang, C G; Yang, M; Ye Shu Wei; Yeh, P; Xu, Z Z; Zhang, H Y; Zhang, Z P; Zhao, D X; Zhu, G Y; Zhu, W Z; Zhuang, H L; Zichichi, A; Zimmermann, B; Zuccon, P

    2000-01-01

    The helium spectrum from 0.1 to 100 GeV/nucleon was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380 km. Above the geomagnetic cutoff the spectrum is parameterized by a power law. Below the geomagnetic cutoff a second helium spectrum was observed. In the second helium spectra over the energy range 0.1 to 1.2 GeV/nucleon the flux was measured to be (6.3+or-0.9)*10/sup -3/ (m/sup 2/ sec sr)/sup -1/ and more than ninety percent of the helium was determined to be /sup 3/He (at the 90% CL). Tracing helium from the second spectrum shows that about half of the /sup 3/He travel for an extended period of time in the geomagnetic field and that they originate from restricted geographic regions similar to protons and positrons. (22 refs).

  2. Observers can reliably identify illusory flashes in the illusory flash paradigm.

    Science.gov (United States)

    van Erp, Jan B F; Philippi, Tom G; Werkhoven, Peter

    2013-04-01

    In the illusory flash paradigm, a single flash may be experienced as two flashes when accompanied by two beeps or taps, and two flashes may be experienced as a single flash when accompanied by one beep or tap. The classic paradigm restricts responses to '1' and '2' (2-AFC), ignoring possible qualitative differences between real and illusory flashes and implicitly assuming that illusory flashes are indistinguishable from real flashes. We added a third response category 'different from that of either 1 or 2 flashes' (3-AFC). Eight naïve and 6 experienced observers responded to 160 real and 160 illusory flash trials. Experienced observers were exposed to 1,200 trials before the experiment but without receiving feedback on their performance. The third response category was used for only 4 % of the real flash trials and for 44 % of the illusory flash trials. Experienced observers did so more often (78 %) than naïve observers (18 %). This shows that observers can reliably identify illusory flashes and indicates that mere exposure to illusory flash trials (without feedback) is enough to detect and classify potential qualitative differences between real and illusory flashes.

  3. On multiphase negative flash for ideal solutions

    DEFF Research Database (Denmark)

    Yan, Wei; Stenby, Erling Halfdan

    2012-01-01

    coefficients. It is shown that this inner loop, named here as multiphase negative flash for ideal solutions, can be solved either by Michelsen's algorithm for multiphase normal flash, or by its variation which uses F−1 phase amounts as independent variables. In either case, the resulting algorithm is actually...... simpler than the corresponding normal flash algorithm. Unlike normal flash, multiphase negative flash for ideal solutions can diverge if the feasible domain for phase amounts is not closed. This can be judged readily during the iteration process. The algorithm can also be extended to the partial negative...

  4. Foundation Flash CS4 for Designers

    CERN Document Server

    Green, Tom

    2008-01-01

    In this book, you'll learn:* How to create effective animations using the new Motion Editor and animation tools * How to use the new 3D features to animate objects in 3D space * Best-practice tips and techniques from some of the top Flash practitioners on the planet * How to create captioned video and full-screen video, and deploy HD video using Flash * Techniques for using the Flash UI components as well as XML documents to create stunning,interactive presentations If you're a Flash designer looking for a solid overview of Flash CS4, this book is for you. Through the use of solid and practica

  5. uFlip: Understanding Flash IO Patterns

    DEFF Research Database (Denmark)

    Bouganim, Luc; Jonsson, Bjørn; Bonnet, Philippe

    2009-01-01

    want to establish what kind of IOs should be favored (or avoided) when designing algorithms and architectures for flash-based systems. In this paper, we focus on flash IO patterns, that capture relevant distribution of IOs in time and space, and our goal is to quantify their performance. We define u......FLIP, a benchmark for measuring the response time of flash IO patterns. We also present a benchmarking methodology which takes into account the particular characteristics of flash devices. Finally, we present the results obtained by measuring eleven flash devices, and derive a set of design hints that should drive...

  6. Effects of helium on titanium films and the helium diffusion

    Institute of Scientific and Technical Information of China (English)

    SONG YingMin; LUO ShunZhong; LONG XingGui; AN Zhu; LIU Ning; PANG HongChao; WU XingChun; YANG BenFu; ZHENG SiXiao

    2008-01-01

    Using direct current-magnetron sputtering, Helium-trapped Ti films with a He/Ar mixture was studied. The relative helium content, helium depth profiles for the Ti films and crystallization capacity were analyzed by Enhanced Proton Backscattering Spectrometry (EPBS) and X-ray diffraction (XRD). It was found that helium diffusion enhanced as more helium trapping into Ti films, and the He holding ratios were 95.9%, 94.9%, 93.9%, 82.8% when the Ti films with the He/Ti of concentrations of 9.7 at.Q, 19.5 at.Q, 19.7 at.Q, 48.3 at.% were measured again 4 months later, respectively. The diffraction peaks be-came weak and wider, the peak of (002) plane was shifted to smaller diffraction angles and the relevant interplanar spacing d(hkl) increased gradually as more helium trapping into Ti films. The main peak was made trending to the (101) plane by both higher deposition temperature and more helium trapping.

  7. Kinematics of Subluminous O and B Stars by Surface Helium Abundance

    Science.gov (United States)

    Martin, P.; Jeffery, C. S.; Naslim, N.; Woolf, V. M.

    2016-12-01

    The majority of hot subdwarf stars are low-mass core-helium-burning stars. Their atmospheres are generally helium deficient; however a minority have extremely helium-rich surfaces. An additional fraction have an intermediate surface-helium abundance, occasionally accompanied by peculiar abundances of other elements. We have identified a sample of 88 hot subdwarfs including 38 helium-deficient, 27 intermediate-helium and 23 extreme-helium stars for which radial-velocity and proper-motion measurements, together with distances, allow a calculation of Galactic space velocities. We have investigated the kinematics of these three groups to determine whether they belong to similar or different Galactic populations. The majority of helium-deficient subdwarfs in our sample show a kinematic distribution similar to that of thick disk stars. Helium-rich sdBs show a more diverse kinematic distribution. Although the majority are probably disk stars, a minority show a much higher velocity dispersion consistent with membership of a Galactic halo population. Several of the halo subdwarfs are members of the class of "heavy-metal" subdwarfs discovered by Naslim et al. (2011, 2013).

  8. From Sulfide Flash Smelting to a Novel Flash Ironmaking Technology

    Science.gov (United States)

    Sohn, Hong Yong

    A novel flash ironmaking technology is under development at the University of Utah under the support of U.S. Department of Energy (DOE) and American Iron and Steel Institute (AISI). The history of the development from the conception of the idea to the current status will be discussed. The flash ironmaking process produces iron directly from fine iron ore concentrates without requiring cokemaking and pelletization/sintering, which will enable the technology to significantly reduce energy consumption and carbon dioxide emissions compared with blast furnace ironmaking. Unlike other gas-based ironmaking processes, this technology will not suffer from the problems of solid sticking and fusion. Current work is focused on the method of supplying the energy required to maintain the necessary temperature, as an intermediate step to determine the scalability for larger, industrial-scale pilot trials.

  9. Spurious dispersion effects at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Prat, Eduard

    2009-07-15

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  10. Alkali-helium snowball complexes formed on helium nanodroplets.

    Science.gov (United States)

    Müller, S; Mudrich, M; Stienkemeier, F

    2009-07-28

    We systematically investigate the formation and stability of snowballs formed by femtosecond photoionization of small alkali clusters bound to helium nanodroplets. For all studied alkali species Ak = (Na,K,Rb,Cs) we observe the formation of snowballs Ak(+)He(N) when multiply doping the droplets. Fragmentation of clusters Ak(N) upon ionization appears to enhance snowball formation. In the case of Na and Cs we also detect snowballs Ak(2) (+)He(N) formed around Ak dimer ions. While the snowball progression for Na and K is limited to less than 11 helium atoms, the heavier atoms Rb and Cs feature wide distributions at least up to Ak(+)He(41). Characteristic steps in the mass spectra of Cs-doped helium droplets are found at positions consistent with predictions on the closure of the first shell of helium atoms around the Ak(+) ion based on variational Monte Carlo simulations.

  11. Electronic properties of physisorbed helium

    Energy Technology Data Exchange (ETDEWEB)

    Kossler, Sarah

    2011-09-22

    This thesis deals with electronic excitations of helium physisorbed on metal substrates. It is studied to what extent the electronic properties change compared to the gas phase due to the increased helium density and the proximity of the metal. Furthermore, the influence of different substrate materials is investigated systematically. To this end, up to two helium layers were adsorbed onto Ru (001), Pt (111), Cu (111), and Ag (111) surfaces in a custom-made cryostat. These samples were studied spectroscopically using synchrotron radiation and a time-of-flight detector. The experimental results were then analyzed in comparison with extensive theoretical model calculations.

  12. Transferring superfluid helium in space

    Science.gov (United States)

    Kittel, Peter

    1986-01-01

    A simple thermodynamic model of a transfer system for resupplying liquid helium in space is presented, with application to NASA projects including the Space Infrared Telescope Facility, the Large Deployable Reflector, and the Hubble Space Telescope. The relations between different thermodynamic regimes that can be expected in the transfer line are used to study the relative efficiencies of various possible transfer techniques. Low heat leak into the transfer line, particularly at point sources such as the coupling, is necesssary for efficient transfer of liquid helium, and proper selection of supply tank temperature is important during helium resupply.

  13. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof

  14. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof

  15. Resistor monitors transfer of liquid helium

    Science.gov (United States)

    Hesketh, W. D.

    1966-01-01

    Large resistance change of a carbon resistor at the liquid helium temperature distinguishes between the transfer of liquid helium and gaseous helium into a closed Dewar. The resistor should be physically as small as possible to reduce the heat load to the helium.

  16. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures

  17. Multi-stage flash degaser

    Science.gov (United States)

    Rapier, Pascal M.

    1982-01-01

    A multi-stage flash degaser (18) is incorporated in an energy conversion system (10) having a direct-contact, binary-fluid heat exchanger to remove essentially all of the noncondensable gases from geothermal brine ahead of the direct-contact binary-fluid heat exchanger (22) in order that the heat exchanger (22) and a turbine (48) and condenser (32) of the system (10) can operate at optimal efficiency.

  18. Lightning Flash Initiation Locations in Four Storms over Land and Ocean

    Science.gov (United States)

    Stolzenburg, Maribeth; Karunarathna, Nadeeka; Marshall, Thomas; Karunarathne, Sumedhe

    2017-04-01

    This study examines initiation locations of intracloud (IC) and cloud-to-ground (CG) lightning in four storms that occurred near Kennedy Space Center, Florida, on one day. One unicellular and two multicellular thunderstorms occurred over land, and one multicellular storm was 30 km offshore. The storm over ocean was visible on radar 47-51 minutes before its first flash (of 17 total); first radar echoes in the storms over land were just 23, 12, and 16 minutes prior to their first flashes (of 34, 16, and 9 total). Initiation points of 66 flashes were identified using the first initial breakdown (IB) pulse location from electric field change measurements or a VHF source coincident with the first IB pulse; the other ten flashes occurred without enough data to similarly locate the initiation. Most of the IC initiations were above the echo core and above 7.5 km altitude, while nearly all the CG initiations were beside or atop the core and below 6.8 km. The off-shore storm had similar lightning duration, IC:CG ratio, and initiation altitudes as the storms over land, but it took that storm much longer to get from first radar echo to first flash and from first flash to first CG. In both regions, early and mature stage flash initiation locations were tightly clustered in small horizontal areas covering just 10-30% of the entire radar reflectivity areas in these small storms. In this presentation, we focus on comparison of temporal trends in the flash initiation altitudes among the storms and the radar reflectivity structure near the initiation locations.

  19. Trajectory Codes for Flash Memory

    CERN Document Server

    Anxiao,; Langberg, Michael; Schwartz, Moshe; Bruck, Jehoshua

    2010-01-01

    Flash memory is well-known for its inherent asymmetry: the flash-cell charge levels are easy to increase but are hard to decrease. In a general rewriting model, the stored data changes its value with certain patterns. The patterns of data updates are determined by the data structure and the application, and are independent of the constraints imposed by the storage medium. Thus, an appropriate coding scheme is needed so that the data changes can be updated and stored efficiently under the storage-medium's constraints. In this paper, we define the general rewriting problem using a graph model. It extends many known rewriting models such as floating codes, WOM codes, buffer codes, etc. We present a new rewriting scheme for flash memories, called the trajectory code, for rewriting the stored data as many times as possible without block erasures. We prove that the trajectory code is asymptotically optimal in a wide range of scenarios. We also present randomized rewriting codes optimized for expected performance (g...

  20. FLASH2: Operation, beamlines, and photon diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Plönjes, Elke, E-mail: elke.ploenjes@desy.de; Faatz, Bart; Kuhlmann, Marion; Treusch, Rolf [Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg (Germany)

    2016-07-27

    FLASH2, a major extension of the soft X-ray free-electron laser FLASH at DESY, turns FLASH into a multi-user FEL facility. A new undulator line is located in a separate accelerator tunnel and driven additionally by the FLASH linear accelerator. First lasing of FLASH2 was achieved in August 2014 with simultaneous user operation at FLASH1. The new FLASH2 experimental hall offers space for up to six experimental end stations, some of which will be installed permanently. The wide wavelength range spans from 4-60 nm and 0.8 nm in the 5{sup th} harmonic and in the future deep into the water window in the fundamental. While this is of high interest to users, it is challenging from the beamline instrumentation point of view. Online diagnostics - which are mostly pulse resolved - for beam intensity, position, wavelength, wave front, and pulse length have been to a large extent developed at FLASH(1) and have now been optimized for FLASH2. Pump-probe facilities for XUV-XUV, XUV optical and XUV-THz experiments will complete the FLASH2 user facility.

  1. Radiation damage in gallium-stabilized δ-plutonium with helium bubbles

    Science.gov (United States)

    Wu, FengChao; Wang, Pei; Liu, XiaoYi; Wu, HengAn

    2017-02-01

    To understand the role of helium on self-irradiation effects in δ-plutonium, microstructure evolutions due to α-decay events near pre-existing helium bubbles in gallium-stabilized δ-plutonium are investigated using molecular dynamics simulations. Bubble promoting effect plays a dominating role in point defects production, resulting in increasing number of point defects. When lightweight helium atoms act as media, energy transfer discrepancy and altered spatial morphology of point defects induced by mass effect are revealed. The evolution of stacking faults surrounding the disordered core is studied and their binding effect on the propagation of point defects are presented. The cascade-induced bubble coalescence, resolution and re-nucleation driven by internal pressure are obtained in the investigation on helium behaviors. The intrinsic tendency in our simulated self-irradiation with helium bubbles is significant for understanding the underlying mechanism of aging in plutonium and its alloys.

  2. Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars

    NARCIS (Netherlands)

    Bedding, T.R.; Mosser, B.; Huber, D.; Montalbán, J.; Beck, P.; Christensen-Dalsgaard, J.; Elsworth, Y.P.; García, R.A.; Miglio, A.; Stello, D.; White, T.R.; de Ridder, J.; Hekker, S.; Aerts, C.; Barban, C.; Belkacem, K.; Broomhall, A.M.; Brown, T.M.; Buzasi, D.L.; Carrier, F.; Chaplin, W.J.; Di Mauro, M.P.; Dupret, M.-A.; Frandsen, S.; Gilliland, R.L.; Goupil, M.J.; Jenkins, J.M.; Kallinger, T.; Kawaler, S.; Kjeldsen, H.; Mathur, S.; Noels, A.; Silva Aguirre, V.; Ventura, P.

    2011-01-01

    Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties

  3. Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars

    DEFF Research Database (Denmark)

    Bedding, Timothy R.; Mosser, Benoit; Huber, Daniel;

    2011-01-01

    Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertaint...

  4. Flash Sintering of Alumina-based Ceramics

    OpenAIRE

    Biesuz, Mattia

    2017-01-01

    Flash sintering is an electrical field-assisted consolidation technology and represents a very novel technique for producing ceramic materials, which allows to decrease sensibly both processing temperature and time. Starting from 2010, when flash sintering was discovered, different ceramic materials with a wide range of electrical properties have been successfully densified. Up to date, the research on flash sintering has been mainly focused on ionic and electronic conductors and on semicondu...

  5. ITER helium ash accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Hogan, J.T.; Hillis, D.L.; Galambos, J.; Uckan, N.A. (Oak Ridge National Lab., TN (USA)); Dippel, K.H.; Finken, K.H. (Forschungszentrum Juelich GmbH (Germany, F.R.). Inst. fuer Plasmaphysik); Hulse, R.A.; Budny, R.V. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

    1990-01-01

    Many studies have shown the importance of the ratio {upsilon}{sub He}/{upsilon}{sub E} in determining the level of He ash accumulation in future reactor systems. Results of the first tokamak He removal experiments have been analysed, and a first estimate of the ratio {upsilon}{sub He}/{upsilon}{sub E} to be expected for future reactor systems has been made. The experiments were carried out for neutral beam heated plasmas in the TEXTOR tokamak, at KFA/Julich. Helium was injected both as a short puff and continuously, and subsequently extracted with the Advanced Limiter Test-II pump limiter. The rate at which the He density decays has been determined with absolutely calibrated charge exchange spectroscopy, and compared with theoretical models, using the Multiple Impurity Species Transport (MIST) code. An analysis of energy confinement has been made with PPPL TRANSP code, to distinguish beam from thermal confinement, especially for low density cases. The ALT-II pump limiter system is found to exhaust the He with maximum exhaust efficiency (8 pumps) of {approximately}8%. We find 1<{upsilon}{sub He}/{upsilon}{sub E}<3.3 for the database of cases analysed to date. Analysis with the ITER TETRA systems code shows that these values would be adequate to achieve the required He concentration with the present ITER divertor He extraction system.

  6. Search Engine Optimization for Flash Best Practices for Using Flash on the Web

    CERN Document Server

    Perkins, Todd

    2009-01-01

    Search Engine Optimization for Flash dispels the myth that Flash-based websites won't show up in a web search by demonstrating exactly what you can do to make your site fully searchable -- no matter how much Flash it contains. You'll learn best practices for using HTML, CSS and JavaScript, as well as SWFObject, for building sites with Flash that will stand tall in search rankings.

  7. Adobe Flash Professional CS6 digital classroom

    CERN Document Server

    Team, AGI Creative

    2012-01-01

    Full-color book and video package teaches you Flash in a flash! If you want to design and maintain dynamic websites with Adobe Flash, this full-color book-and-video training package from expert instructors is the perfect place to start. Fifteen self-paced, step-by-step lessons are accompanied by video tutorials, and this powerful combination helps you master the basics, acquire essential skills, and learn what's new. Making all aspects of Flash less intimidating, this superb training tool covers topics such as using layers to build animation sequences, creating interactive web

  8. Flash CS5 The Missing Manual

    CERN Document Server

    Grover, Chris

    2010-01-01

    Once you know how to use Flash, you can create everything from simple animations to high-end desktop applications, but it's a complex tool that can be difficult to master on your own-unless you have this Missing Manual. This book will help you learn all you need to know about Flash CS5 to create animations that bring your ideas to life. Learn animation basics. Find everything you need to know to get started with FlashMaster the Flash tools. Learn the animation and effects toolset, with clear explanations and hands-on examplesUse 3D effects. Rotate and put objects in motion in three dimensions

  9. Summary of results from the TEXTOR helium self-pumping experiment

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, J.N.; Krauss, A. [Argonne National Lab., IL (United States); Nygren, R.E.; Doyle, B.L. [Sandia National Labs., Albuquerque, NM (United States); Dippel, K.H.; Finken, K.H. [Association Euratom-Kernforschungsanlage Juelich (Germany). Inst. fuer Plasmaphysik

    1992-03-01

    Helium removal experiments were conducted in TEXTOR with a small helium self-pumping module located in a modified ALT-I limiter head. The module contained two heated nickel alloy trapping plates, a nickel deposition filament array, a Langmuir probe, flux probe, and thermocouples. The experiment examined plasma helium removal via trapping of helium ions in the deposited nickel surfaces. Such helium removal was successfully observed, with about 10% of the helium He/D plasma being removed in a {approximately}1 s period. The module was found to be compatible with overall tokamak operation with essentially no sputtered nickel entering the core plasma. The temperature rise on the ion-exposed inner trapping plate, during a plasma shot, is consistent with a nickel a local sheath potential of {approximately}3 kT{sub e}. Post-tokamak test examination of the trapping plates shows helium atom concentrations in the deposited nickel consistent with the observed helium removal, and shows very small D concentrations.

  10. Optical spectroscopy and current detection during warm-up and destruction of impurity-helium condensates

    Science.gov (United States)

    Krushinskaya, I. N.; Boltnev, R. E.; Bykhalo, I. B.; Pelmenev, A. A.; Khmelenko, V. V.; Lee, D. M.

    2015-06-01

    New experimental results on detection of optical spectra and ion currents during destruction of impurity-helium condensates (IHCs) have been obtained. It is shown that emission during IHC sample destruction is accompanied by current pulses, pressure peaks and temperature changes. The molecular bands of excimer molecules XeO* are assigned to molecules stabilized in films of molecular nitrogen covering the heavier cores of impurity clusters which form impurity-helium condensates.

  11. GeckoFTL: Scalable Flash Translation Techniques For Very Large Flash Devices

    DEFF Research Database (Denmark)

    Dayan, Niv; Bonnet, Philippe; Idreos, Stratos

    2016-01-01

    The volume of metadata needed by a flash translation layer (FTL) is proportional to the storage capacity of a flash device. Ideally, this metadata should reside in the device's integrated RAM to enable fast access. However, as flash devices scale to terabytes, the necessary volume of metadata...

  12. OPTIMIZING THE USE OF AN SPI FLASH PROM IN MICROBLAZE-BASED EMBEDDED SYSTEMS

    Directory of Open Access Journals (Sweden)

    Ahmed Hanafi

    2013-11-01

    Full Text Available This paper aims to simplify FPGA designs that incorporate Embedded Software Systems using a soft core Processor. It describes a simple solution to reduce the need of multiple non-volatile memory devices by using one SPI (Serial Peripheral Interface Flash PROM for FPGA configuration data, software code (Processor applications, and miscellaneous user data. We have thus developed a design based on a MicroBlaze soft processor implemented on a Xilinx Spartan-6 FPGA SP605 Evaluation Kit. The hardware architecture with SPI flash was designed using the Xilinx Platform Studio (XPS and the software applications, including the bootloader, was developed with Xilinx Software Development Kit (SDK. ISE Design Tools prepared by Xilinx Company, is employed to create the files used to program flash memory which are SREC (S-record file associated with software code, Hexadecimal file for user data, and bootloader file to configure the FPGA and allows software applications stored in flash memory to be executed when the system is powered on. Reading access to the SPI Flash memory is simplified by the use of Xilinx In-System Flash (ISF library.

  13. Helium removal and transport studies in TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Hillis, D.L.; Hogan, J.T.; Horton, L.D.; Isler, R.C.; Klepper, C.C.; Mioduszewski, P.K. (Oak Ridge National Lab., TN (USA)); Finken, K.H.; Dippel, K.H.; Pospieszczyk, A.; Rusbueldt, D.; Euringer, H. (Association Euratom-Kernforschungsanlage Juelich (Germany, F.R.). Inst. fuer Plasmaphysik); Wolf, G.H.; Moyer, R.A.; Conn, R.W.; Gray, D.S. (California Univ., Los Angeles, CA (USA). Inst. of Plasma and Fusion Re

    1990-01-01

    Experiments demonstrating direct control of the He{sup 2+} density in a tokamak plasma have been performed in the TEXTOR tokamak with the Advanced Limiter Test-II pump limiter. Helium is injected in a short gas puff from the outside of the plasma, is observed to reach the plasma core, and then is readily from the plasma. Active He pumping is found to be a valuable technique for discriminating the actual He confinement time from {tau}*{sub He}, which is strongly dependent on recycling. Active charge-exchange spectroscopy is used to study the exhaust and transport of He{sup 2+} within the plasma, and the density evolution is modeled with the diffusive/convective transport code, MIST. 8 refs., 3 figs.

  14. Rh-flash acquisition card

    CERN Document Server

    Bourrion, O

    2003-01-01

    The rh-flash card main purpose is to convert and store the image of the analog data present at input into an output buffer, namely in a given timing window besides a stop signal (like a digital oscilloscope). It is conceived in VME format 1U wide with an additional connector. Novelty of this card is its ability to sample at a high frequency, due to flash coders, and this at a high repetition rate. To do that the card allows the storage of the data considered 'useful' and that is done by storing only the data exceeding a certain threshold. This can be useful for instance for viewing peaks in a spectrum, and obtaining their relative location. The goal is to stock and process the data sampled before and after the arrival of a stop signal (what entails a storage depth). A threshold is defined and any peak exceeding its level will really be stored in the output buffer which is readable through the VME bus. The peak values will be stored as well as m preceding and n subsequent values (both programmable). Obviously,...

  15. Flash Expansion Threshold in Whirligig Swarms.

    Directory of Open Access Journals (Sweden)

    William L Romey

    Full Text Available In the selfish herd hypothesis, prey animals move toward each other to avoid the likelihood of being selected by a predator. However, many grouped animals move away from each other the moment before a predator attacks. Very little is known about this phenomenon, called flash expansion, such as whether it is triggered by one individual or a threshold and how information is transferred between group members. We performed a controlled experiment with whirligig beetles in which the ratio of sighted to unsighted individuals was systematically varied and emergent flash expansion was measured. Specifically, we examined: the percentage of individuals in a group that startled, the resulting group area, and the longevity of the flash expansion. We found that one or two sighted beetles in a group of 24 was not enough to cause a flash expansion after a predator stimulus, but four sighted beetles usually initiated a flash expansion. Also, the more beetles that were sighted the larger the resulting group area and the longer duration of the flash expansion. We conclude that flash expansion is best described as a threshold event whose adaptive value is to prevent energetically costly false alarms while quickly mobilizing an emergent predator avoidance response. This is one of the first controlled experiments of flash expansion, an important emergent property that has applications to understanding collective motion in swarms, schools, flocks, and human crowds. Also, our study is a convincing demonstration of social contagion, how the actions of one individual can pass through a group.

  16. On Coding Efficiency for Flash Memories

    CERN Document Server

    Ma, Xudong

    2012-01-01

    Recently, flash memories have become a competitive solution for mass storage. The flash memories have rather different properties compared with the rotary hard drives. That is, the writing of flash memories is constrained, and flash memories can endure only limited numbers of erases. Therefore, the design goals for the flash memory systems are quite different from these for other memory systems. In this paper, we consider the problem of coding efficiency. We define the "coding-efficiency" as the amount of information that one flash memory cell can be used to record per cost. Because each flash memory cell can endure a roughly fixed number of erases, the cost of data recording can be well-defined. We define "payload" as the amount of information that one flash memory cell can represent at a particular moment. By using information-theoretic arguments, we prove a coding theorem for achievable coding rates. We prove an upper and lower bound for coding efficiency. We show in this paper that there exists a fundamen...

  17. Bed system performance in helium circulation mode

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yean Jin; Jung, Kwang Jin; Ahn, Do Hee; Chung, Hong Suk [UST, Daejeon (Korea, Republic of); Kang, Hee Suk [KAERI, Daejeon (Korea, Republic of); Yun, Sei Hun [NFRI, Deajeon (Korea, Republic of)

    2016-05-15

    As a part of the International Thermonuclear Experimental Reactor (ITER) Project, We have conducted an experiment for storing hydrogen to depleted uranium and zirconium cobalt. The helium blanket effect has been observed in experiments using metal hydrides. The collapse of the hydrogen isotopes are accompanied by the decay heat and helium-3. Helium-3 dramatically reduces the hydrogen isotope storage capacity by surrounding the metal. This phenomenon is called a helium blanket effect. In addition the authors are working on the recovery and removal techniques of helium-3. In this paper, we discuss the equipment used to test the helium blanket effect and the results of a helium circulation experiment. The helium-3 produced surrounds the storage material surface and thus disturbs the reaction of the storage material and the hydrogen isotope. Even if the amount of helium-3 is small, the storage capacity of the SDS bed significantly drops. This phenomenon is the helium blanket effect. To resolve this phenomenon, a circulating loop was introduced. Using a circulating system, helium can be separated from the storage material. We made a helium loop that includes a ZrCo bed. Then using a metal bellows pump, we tested the helium circulation.

  18. Non-sequential double ionization of helium-like atom

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, author investigated the effect of the Coulomb potential of the core of atomic helium on the rescattering processes. Through the calculation author concluded that the Coulomb potential effect may not play an important role in causing the discrepancy between the experimental data and theoretical results of Kuchievs model, and the NS ionization is dependent on the frequency of the laser field. Furthermore, it is concluded that the strength of the laser field and the charge number of the core affect the frequency regime corresponding to the peak value of the NS ionization rate.

  19. Heat wave flash droughts in decline

    Science.gov (United States)

    Mo, Kingtse C.; Lettenmaier, Dennis P.

    2015-04-01

    Flash drought is a term that was popularized during rapidly evolving droughts in the Central U.S. in 2012 that were associated with heat waves. We posit that there are two kinds of flash droughts, and we will focus on heat wave flash droughts, of which the 2012 events were typical. We find, based on an analysis of temperature observations and model-reconstructed soil moisture (SM) and evapotranspiration from 1916 to 2013, that heat wave flash droughts in the conterminous U.S. (CONUS) are most likely to occur over the Midwest and the Pacific Northwest during the growing season. We also find that the number of such events across the CONUS has been decreasing over the last century but rebounded after 2011. The long-term downward trends appear to be associated with generally increasing trends in SM resulting from increasing trends in precipitation over the areas where heat wave flash droughts are most likely to occur.

  20. Rogue mantle helium and neon.

    Science.gov (United States)

    Albarède, Francis

    2008-02-15

    The canonical model of helium isotope geochemistry describes the lower mantle as undegassed, but this view conflicts with evidence of recycled material in the source of ocean island basalts. Because mantle helium is efficiently extracted by magmatic activity, it cannot remain in fertile mantle rocks for long periods of time. Here, I suggest that helium with high 3He/4He ratios, as well as neon rich in the solar component, diffused early in Earth's history from low-melting-point primordial material into residual refractory "reservoir" rocks, such as dunites. The difference in 3He/4He ratios of ocean-island and mid-ocean ridge basalts and the preservation of solar neon are ascribed to the reservoir rocks being stretched and tapped to different extents during melting.

  1. Pierre Gorce working on a helium pump.

    CERN Multimedia

    1975-01-01

    This type of pump was designed by Mario Morpurgo, to circulate liquid helium in superconducting magnets wound with hollow conductors. M. Morpurgo, Design and construction of a pump for liquid helium, CRYIOGENICS, February 1977, p. 91

  2. The cosmic production of Helium

    CERN Document Server

    Jiménez, R; MacDonald, J; Gibson, B K; Jimenez, Raul; Flynn, Chris; Donald, James Mac; Gibson, Brad K.

    2003-01-01

    We estimate the cosmic production rate of helium relative to metals ($\\Delta Y/\\Delta Z$) using K dwarf stars in the Hipparcos catalog with accurate spectroscopic metallicities. The best fitting value is $\\Delta Y/\\Delta Z=2.1 \\pm 0.4$ at the 68% confidence level. Our derived value agrees with determinations from HII regions and with theoretical predictions from stellar yields with standard assumptions for the initial mass function. The amount of helium in stars determines how long they live and therefore how fast they will enrich the insterstellar medium with fresh material.

  3. Negative ions in liquid helium

    Science.gov (United States)

    Khrapak, A. G.; Schmidt, W. F.

    2011-05-01

    The structure of negative ions in liquid 4He is analyzed. The possibility of cluster or bubble formation around impurity ions of both signs is discussed. It is shown that in superfluid helium, bubbles form around negative alkaline earth metal ions and clusters form around halogen ions. The nature of "fast" and "exotic" negative ions is also discussed. It is assumed that "fast" ions are negative ions of helium excimer molecules localized inside bubbles. "Exotic" ions are stable negative impurity ions, which are always present in small amounts in gas discharge plasmas. Bubbles or clusters with radii smaller the radius of electron bubbles develop around these ions.

  4. Statistical Evolution of the Lightning Flash

    Science.gov (United States)

    Zoghzoghy, F. G.; Cohen, M.; Said, R.; Inan, U. S.

    2012-12-01

    Natural lightning is one of the most fascinating and powerful electrical processes on Earth. To date, the physics behind this natural phenomenon are not fully understood, due primarily to the difficulty of obtaining measurements inside thunderstorms and to the wide range of timescales involved (from nanoseconds to seconds). Our aim is to use accurate lightning geo-location data from the National Lightning Detection Network (NLDN) to study statistical patterns in lightning, taking advantage of the fact that millions of lightning flashes occur around the globe every day. We present two sets of results, one involving the patterns of flashes in a storm, and a second involving the patterns of strokes in a flash. These patterns can provide a surrogate measure of the timescales and the spatial extents of the underlying physical processes. First, we study the timescales of charge buildup inside thunderstorms. We find that, following a lightning flash, the probability of another neighboring flash decreases and takes tens of seconds to recover. We find that this suppression effect is a function of flash type, stroke peak current, cloud-to-ground (CG) stroke multiplicity, and other lightning and geographical parameters. We find that the probabilities of subsequent flashes are more suppressed following oceanic lightning, or following flashes with higher peak currents and/or higher multiplicities (for CG flashes). Second, we use NLDN data to study the evolution of the strokes within a CG flash. A CG flash typically includes multiple return strokes, which can occur in the same channel or in multiple channels within a few kilometers. We cluster NLDN stroke data into flashes and produce the probability density function of subsequent strokes as a function of distance and time-delays relative to the previous stroke. Using this technique, we investigate processes which occur during the CG lightning flash with nanosecond to millisecond timescales. For instance, our results suggest

  5. Flash Learning Games Wow Students and Instructors: Moving Toward An Academic Gaming Portal

    Directory of Open Access Journals (Sweden)

    Dan H Lim

    2003-02-01

    Full Text Available This paper describes and discusses the rationale, background, design, and implementation of Flash learning games. The paper explains why Macromedia Flash has been selected as the authoring tool in the development of highly interactive learning games for online learning. The background evolutionary process of developing the learning games points out why it has been a daunting task to create compelling learning games that impact learning. Designing learning game objects that allow other educators to customize game content is the core of this paper. The author envisions this academic gaming project will evolve into an academic gaming portal, developed in conjunction with other major institutional partners.

  6. Terrestrial gamma-ray flashes

    Energy Technology Data Exchange (ETDEWEB)

    Marisaldi, Martino, E-mail: marisaldi@iasfbo.inaf.it [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Fuschino, Fabio; Labanti, Claudio [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Tavani, Marco [INAF-IASF Roma, Via Fosso del Cavaliere 100, I-00133 Roma (Italy); Argan, Andrea [INAF, Viale del Parco Mellini 84, 00136 Roma (Italy); Del Monte, Ettore [INAF-IASF Roma, Via Fosso del Cavaliere 100, I-00133 Roma (Italy); Longo, Francesco; Barbiellini, Guido [Dipartimento di Fisica Università di Trieste and INFN Trieste, via A. Valerio 2, I-34127 Trieste (Italy); Giuliani, Andrea [INAF-IASF Milano, Via Bassini 15, I-20133 Milano (Italy); Trois, Alessio [INAF Osservatorio Astronomico di Cagliari, loc. Poggio dei Pini, strada 54, I-09012 Capoterra (Italy); Bulgarelli, Andrea; Gianotti, Fulvio; Trifoglio, Massimo [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy)

    2013-08-21

    Lightning and thunderstorm systems in general have been recently recognized as powerful particle accelerators, capable of producing electrons, positrons, gamma-rays and neutrons with energies as high as several tens of MeV. In fact, these natural systems turn out to be the highest energy and most efficient natural particle accelerators on Earth. Terrestrial Gamma-ray Flashes (TGFs) are millisecond long, very intense bursts of gamma-rays and are one of the most intriguing manifestation of these natural accelerators. Only three currently operative missions are capable of detecting TGFs from space: the RHESSI, Fermi and AGILE satellites. In this paper we review the characteristics of TGFs, including energy spectrum, timing structure, beam geometry and correlation with lightning, and the basic principles of the associated production models. Then we focus on the recent AGILE discoveries concerning the high energy extension of the TGF spectrum up to 100 MeV, which is difficult to reconcile with current theoretical models.

  7. [Nikola Tesla: flashes of inspiration].

    Science.gov (United States)

    Villarejo-Galende, Albero; Herrero-San Martín, Alejandro

    2013-01-16

    Nikola Tesla (1856-1943) was one of the greatest inventors in history and a key player in the revolution that led to the large-scale use of electricity. He also made important contributions to such diverse fields as x-rays, remote control, radio, the theory of consciousness or electromagnetism. In his honour, the international unit of magnetic induction was named after him. Yet, his fame is scarce in comparison with that of other inventors of the time, such as Edison, with whom he had several heated arguments. He was a rather odd, reserved person who lived for his inventions, the ideas for which came to him in moments of inspiration. In his autobiography he relates these flashes with a number of neuropsychiatric manifestations, which can be seen to include migraine auras, synaesthesiae, obsessions and compulsions.

  8. Helium in atmospheres of binary stars

    Energy Technology Data Exchange (ETDEWEB)

    Leushin, V.V. (Rostovskij-na-Donu Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Fiziki)

    The helium abundances were obtained for 25 bright components of binary stars by model atmosphere analysis. The helium abundance for binary stars that lie on the main sequence are larger in the average than in single normal stars. The stars on the Hertzsppung - russel diagram lie at a larger distance from the zero age line than those with normal helium abundance.

  9. Radiometry of flashing LED sources

    Science.gov (United States)

    Gregory, Don A.; Medley, Stephanie; Roberts, Adam

    2008-08-01

    A laboratory based technique has been devised for measuring the illumination characteristics of flashing light emitting diode (LED) sources. The difference between the photopic measurement of a continuous source and a flashing source is that some analytic method must be incorporated into the measurement to account for the response of the eye. Ohno et al have devised an analytic expression for the impulse response of the eye, which closely matches existing forms used for finding effective intensity1. These other forms are the Blondel-Rey equation, the Form Factor method, and the Allard method.4,5,6 Ohno's research suggests a modified Allard method, but offers no procedure for actually making the measurement. In this research, the modified Allard1 method approach has been updated using standard laboratory equipment such as a silicon detector in conjunction with a digital multi-meter and Labview® software to make this measurement. Labview® allows exact computation of the modified Allard method. However, an approximation scheme for the conversion from radiometric units to photopic units must be adopted. The LED spectral form is approximately a Gaussian line shape with full width at half maximum of about 15 to 30nm. The Gaussian curve makes converting from radiometric to photopic units difficult. To simplify, the technique presented here estimates the spectral form of the LEDs to be a Dirac delta function situated at the peak wavelength. This allows the conversion from watts to lumens to be a simple application of the luminous efficiency curve.2 For LEDs with a full width half maximum of 20nm, this scheme is found to be accurate to +/- 5%.

  10. Helium resources of Mare Tranquillitatis

    Science.gov (United States)

    Cameron, Eugene N.

    Wisconsin Center for Space Automation and Robotics, Univ. of Wisc., Madison, Wisc. Mare Tranquillitatis, about 300000 sq km in area, is currently the most promising lunar source of He-3 for fueling fusion power plants on Earth. About 60 pct. of the mare regolith consists of particles 100 microns or less in diameter. Helium and other gases derived from the solar wind are concentrated in the fine size fractions. Studies of very small craters indicate that the average regolith exceeds 3 m in areas away from larger craters and other mare features not amenable to mining. There is no evidence of decrease of helium content of regolith and depth. Helium is known to be enriched in regoliths that are high in TiO2 content. Remote sensing indicates that about 90 pct. of Mare Tranquillitatis is covered by regolith ranging from about 6 to +7.5 pct. TiO2; inferred He contents range from 20 to at least 45 wppm total helium (7 to 18 wppb He-3). Detailed studies of craters and inferred ejecta halos displayed on high resolution photographs of the Apollo 11 and Ranger 8 areas suggest that as much as 50 pct. of the mare regolith may be physically minable, on average, with appropriate mining equipment. Assuming that the average thickness of regolith is 3 m, and that 50 pct. of the mare area is minable, the He-3 content of minable regolith containing 20 to 45 wppm total He is estimated at about 94,000 tonnes.

  11. Machine Learning Predictions of Flash Floods

    Science.gov (United States)

    Clark, R. A., III; Flamig, Z.; Gourley, J. J.; Hong, Y.

    2016-12-01

    This study concerns the development, assessment, and use of machine learning (ML) algorithms to automatically generate predictions of flash floods around the world from numerical weather prediction (NWP) output. Using an archive of NWP outputs from the Global Forecast System (GFS) model and a historical archive of reports of flash floods across the U.S. and Europe, we developed a set of ML models that output forecasts of the probability of a flash flood given a certain set of atmospheric conditions. Using these ML models, real-time global flash flood predictions from NWP data have been generated in research mode since February 2016. These ML models provide information about which atmospheric variables are most important in the flash flood prediction process. The raw ML predictions can be calibrated against historical events to generate reliable flash flood probabilities. The automatic system was tested in a research-to-operations testbed enviroment with National Weather Service forecasters. The ML models are quite successful at incorporating large amounts of information in a computationally-efficient manner and and result in reasonably skillful predictions. The system is largely successful at identifying flash floods resulting from synoptically-forced events, but struggles with isolated flash floods that arise as a result of weather systems largely unresolvable by the coarse resolution of a global NWP system. The results from this collection of studies suggest that automatic probabilistic predictions of flash floods are a plausible way forward in operational forecasting, but that future research could focus upon applying these methods to finer-scale NWP guidance, to NWP ensembles, and to forecast lead times beyond 24 hours.

  12. Flash memory in embedded Java programs

    DEFF Research Database (Denmark)

    Korsholm, Stephan Erbs

    2011-01-01

    This paper introduces a Java execution environment with the capability for storing constant heap data in Flash, thus saving valuable RAM. The extension is motivated by the structure of three industrial applications which demonstrate the need for storing constant data in Flash on small embedded...... devices. The paper introduces the concept of host initialization of constant data to prepare a Flash image of constant data that can be kept outside the heap during runtime. The concept is implemented in an interpreter based Java execution environment....

  13. Simplicity works for superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bowley, Roger [University of Nottingham, Nottingham (United Kingdom)

    2000-02-01

    The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

  14. Precision spectroscopy of the helium atom

    Institute of Scientific and Technical Information of China (English)

    Shui-ming HU; Zheng-Tian LU; Zong-Chao YAN

    2009-01-01

    Persistent efforts in both theory and experiment have yielded increasingly precise understanding of the helium atom. Because of its simplicity, the helium atom has long been a testing ground for relativistic and quantum electrodynamic effects in few-body atomic systems theoretically and experimentally.Comparison between theory and experiment of the helium spectroscopy in ls2p3pJ can potentially extract a very precise value of the fine structure constant a. The helium atom can also be used to explore exotic nuclear structures. In this paper, we provide a brief review of the recent advances in precision calculations and measurements of the helium atom.

  15. Influence of operation parameters on flash smelting furnace based on CFD

    Institute of Scientific and Technical Information of China (English)

    Xinfeng Li; Shiheng Peng; Xiangli Han; Chi Mei; Tianyuan Xiao

    2004-01-01

    The influence of three important operation parameters in Jinlong flash smelting furnace, including the distributing blast speed, the oxygen enrichment rate of process air and the ratio of central oxygen to overall oxygen (Oc/Oo), has been investigated using a virtual simulation system on copper flash smelting furnace. The core of this virtual simulation system is a numerical simulation of CFD (computational fluid dynamics), and this system incorporates coupling momentum transport, heat transport, mass transport,reaction kinetics between gas and particles and chemical reactions between gas and gas. A set of numerical predicted data were obtained. The CFD simulation shows that there is a sensitive zone of the distributing blast speed, and the dust content ascends when the speed exceeds 180 m-s-1. Increasing the oxygen concentration of processing air benefits the efficient production of the flash smelting furnace.

  16. HeREF-2003: Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 Cost per participant: 500.- CHF Language: Bilingual English...

  17. HeREF-2003 : Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. • Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 • Cost per participant: 500.- CHF ...

  18. The flash-lag effect and the flash-drag effect in the same display.

    Science.gov (United States)

    Murai, Yuki; Murakami, Ikuya

    2016-09-01

    Visual motion distorts the perceived position of a stimulus. In the flash-drag effect (FDE), the perceived position of a flash appears to be shifted in the direction of nearby motion. In the flash-lag effect (FLE), a flash adjacent to a moving stimulus appears to lag behind. The FLE has been explained by several models, including the differential latency hypothesis, that a moving stimulus has a shorter processing latency than a flash does. The FDE even occurs when the flash is presented earlier than the moving stimulus, and it has been discussed whether this temporal property can be explained by the differential latency model. In the present study, we simultaneously quantified the FDE and FLE using the random jump technique (Murakami, 2001b) and compared their temporal properties. While the positional offset between a randomly jumping stimulus and a flashed stimulus determined the FLE, a drifting grating appeared next to the flash at various stimulus-onset asynchronies to induce the FDE. The grating presented up to 200 ms after the flash onset induced the FDE, whose temporal tuning was explained by a simple convolution model incorporating stochastic fluctuations of differential latency estimated from the FLE data and a transient-sustained temporal profile of motion signals. Thus, a common temporal mechanism to compute the stimulus position in reference to surrounding stimuli governs both the FDE and the FLE.

  19. Flash Point: Evaluation, Experimentation and Estimation

    Science.gov (United States)

    Rowley, J. R.; Freeman, D. K.; Rowley, R. L.; Oscarson, J. L.; Giles, N. F.; Wilding, W. V.

    2010-05-01

    The flash point is an important indicator of the flammability of a chemical. For safety purposes, many data compilations report the lowest value and not the most likely. This practice, combined with improper documentation and poor data storage methods, has resulted in compilations filled with fire-hazard data that are inconsistent with related properties and between members of homologous chemical series. In this study, the flash points reported in the DIPPR® 801 database and more than 1,400 other literature values were critically reviewed based on measurement method, inter-property relations, and trends in chemical series. New measurements for seven compounds illustrate the differences between experimental flash points and data commonly found in fire-hazard compilations. With a critically reviewed set of experimental data, published predictive methods for the flash point were evaluated for accuracy.

  20. 3D Flash LIDAR Space Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc (ASC) is a small business, which has developed a compact, eye-safe 3D Flash LIDARTM Camera (FLC) well suited for real-time...

  1. Hot Flashes amd Night Sweats (PDQ)

    Science.gov (United States)

    ... Other Funding Find NCI funding for small business innovation, technology transfer, and contracts Training Cancer Training at ... remedies for hot flashes. These include dong quai , milk thistle , red clover , licorice root extract , and chaste ...

  2. Method for programming a flash memory

    Science.gov (United States)

    Brosky, Alexander R.; Locke, William N.; Maher, Conrado M.

    2016-08-23

    A method of programming a flash memory is described. The method includes partitioning a flash memory into a first group having a first level of write-protection, a second group having a second level of write-protection, and a third group having a third level of write-protection. The write-protection of the second and third groups is disabled using an installation adapter. The third group is programmed using a Software Installation Device.

  3. Interaction of Helium Rydberg State Molecules with Dense Helium.

    Science.gov (United States)

    Bonifaci, Nelly; Li, Zhiling; Eloranta, Jussi; Fiedler, Steven L

    2016-11-17

    The interaction potentials of the He2(*) excimer, in the a(3)Σu, b(3)Πg, c(3)Σg, and d(3)Σu electronic states with a ground state helium atom are presented. The symmetry of the interaction potentials closely follows the excimer Rydberg electron density with pronounced short-range minima appearing along the nodal planes of the Rydberg orbital. In such cases, a combination of the electrostatic short-range attraction combined with Pauli repulsion leads to the appearance of unusual long-range maxima in the potentials. Bosonic density functional calculations show that the (3)d state excimer resides in a localized solvation bubble in dense helium at 4.5 K, with radii varying from 12.7 Å at 0.1 MPa to 10.8 Å at 2.4 MPa. The calculated (3)d → (3)b pressure-induced fluorescence band shifts are in good agreement with experimental results determined by application of corona discharge. The magnitude of the spectral shifts indicate that the observed He2(*) molecules emit from dense helium whereas the corresponding fluorescence signal from the discharge zone appears quenched. This implies that fluorescence spectroscopy involving this electronic transition can only be used to probe the state of the surrounding medium rather than the discharge zone itself.

  4. The free-electron laser FLASH

    Institute of Scientific and Technical Information of China (English)

    Siegfried Schreiber; Bart Faatz

    2015-01-01

    FLASH at DESY, Hamburg, Germany is the first free-electron laser(FEL) operating in the extreme ultraviolet(EUV)and soft x-ray wavelength range. FLASH is a user facility providing femtosecond short pulses with an unprecedented peak and average brilliance, opening new scientific opportunities in many disciplines. The first call for user experiments has been launched in 2005. The FLASH linear accelerator is based on TESLA superconducting technology, providing several thousands of photon pulses per second to user experiments. Probing femtosecond-scale dynamics in atomic and molecular reactions using, for instance, a combination of x-ray and optical pulses in a pump and probe arrangement,as well as single-shot diffraction imaging of biological objects and molecules, are typical experiments performed at the facility. We give an overview of the FLASH facility, and describe the basic principles of the accelerator. Recently,FLASH has been extended by a second undulator beamline(FLASH2) operated in parallel to the first beamline, extending the capacity of the facility by a factor of two.

  5. Hydrogen in hot subdwarfs formed by double helium white dwarf mergers

    CERN Document Server

    Hall, Philip D

    2016-01-01

    Isolated hot subdwarfs might be formed by the merging of two helium-core white dwarfs. Before merging, helium-core white dwarfs have hydrogen-rich envelopes and some of this hydrogen may survive the merger. We calculate the mass of hydrogen that is present at the start of such mergers and, with the assumption that hydrogen is mixed throughout the disrupted white dwarf in the merger process, estimate how much can survive. We find a hydrogen mass of up to about $2 \\times 10^{-3}\\,\\mathrm{M}_{\\odot}$ in merger remnants. We make model merger remnants that include the hydrogen mass appropriate to their total mass and compare their atmospheric parameters with a sample of apparently isolated hot subdwarfs, hydrogen-rich sdBs. The majority of these stars can be explained as the remnants of double helium white dwarf mergers.

  6. Confined helium on Lagrange meshes

    CERN Document Server

    Baye, Daniel

    2015-01-01

    The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.

  7. Helium atom scattering from surfaces

    CERN Document Server

    1992-01-01

    High resolution helium atom scattering can be applied to study a number of interesting properties of solid surfaces with great sensitivity and accuracy. This book treats in detail experimental and theoretical aspects ofthis method as well as all current applications in surface science. The individual chapters - all written by experts in the field - are devoted to the investigation of surface structure, defect shapes and concentrations, the interaction potential, collective and localized surface vibrations at low energies, phase transitions and surface diffusion. Over the past decade helium atom scattering has gained widespread recognitionwithin the surface science community. Points in its favour are comprehensiveunderstanding of the scattering theory and the availability of well-tested approximation to the rigorous theory. This book will be invaluable to surface scientists wishing to make an informed judgement on the actual and potential capabilities of this technique and its results.

  8. Experimental studies of antiprotonic helium

    CERN Document Server

    Widmann, E

    1998-01-01

    This talk describes the experimental studies of metastable antiprotonic helium "atomcules" pHe/sup +/ (a neutral exotic atom consisting of a helium nucleus, an antiproton and an electron) performed at CERN-LEAR, and future plans for experiments at the forthcoming Antiproton Decelerator (AD) at CERN. Laser spectroscopy experiments are reviewed which led to the observation of a total of 13 resonant transitions of the antiproton in both p/sup 4/He/sup +/ and p/sup 3/He/sup +/, and revealed a hyperfine splitting in one transition. A level of precision has been reached where the most accurate 3-body calculations need to include QED effects like the Lamb-shift to come close to the experimental results. (52 refs).

  9. Rapidly pulsed helium droplet source

    Energy Technology Data Exchange (ETDEWEB)

    Pentlehner, Dominik; Riechers, Ricarda; Dick, Bernhard; Slenczka, Alkwin [Institute for Physical and Theoretical Chemistry, University of Regensburg, 93053 Regensburg (Germany); Even, Uzi; Lavie, Nachum; Brown, Raviv; Luria, Kfir [Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv (Israel)

    2009-04-15

    A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 10{sup 4} and 10{sup 6} helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.

  10. Elusive structure of helium trimers

    CERN Document Server

    Stipanović, Petar; Boronat, Jordi

    2016-01-01

    Over the years many He-He interaction potentials have been developed, some very sophisticated, including various corrections beyond Born-Oppenheimer approximation. Most of them were used to predict properties of helium dimers and trimers, examples of exotic quantum states, whose experimental study proved to be very challenging. Recently, detailed structural properties of helium trimers were measured for the first time, allowing a comparison with theoretical predictions and possibly enabling the evaluation of different interaction potentials. The comparisons already made included adjusting the maxima of both theoretical and experimental correlation functions to one, so the overall agreement between theory and experiment appeared satisfactory. However, no attempt was made to evaluate the quality of the interaction potentials used in the calculations. In this work, we calculate the experimentally measured correlation functions using both new and old potentials, compare them with experimental data and rank the po...

  11. Particle detection using superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.

    1991-01-01

    We have observed 5 MeV {alpha} particles stopped in volumes-up to two liters of liquid helium at 70 mK. A fraction of the kinetic energy of an {alpha} particle is converted to elementary excitations (rotons and phonons), which progagate ballistically in isotopically pure {sup 4}He below 0.1 K. Most of these excitations have sufficient energy to evaporate helium atoms on hitting a free surface. The evaporated helium atoms can be detected calorimetrically when adsorbed on a thin silicon wafer ({approximately}1.7 g, 35 cm{sup 2}) suspended above the liquid. Temperature changes of the silicon are measured with a NTD germanium bolometer. For the geometry studied the observed temperature change of the silicon resulting from an {alpha} event in the liquid is approximately 5% of the temperature rise from an {alpha} hitting the silicon directly. The implications of these measurements will be discussed as they relate to the possible construction of a large scale detector of solar neutrinos.

  12. Particle detection using superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.

    1991-12-31

    We have observed 5 MeV {alpha} particles stopped in volumes-up to two liters of liquid helium at 70 mK. A fraction of the kinetic energy of an {alpha} particle is converted to elementary excitations (rotons and phonons), which progagate ballistically in isotopically pure {sup 4}He below 0.1 K. Most of these excitations have sufficient energy to evaporate helium atoms on hitting a free surface. The evaporated helium atoms can be detected calorimetrically when adsorbed on a thin silicon wafer ({approximately}1.7 g, 35 cm{sup 2}) suspended above the liquid. Temperature changes of the silicon are measured with a NTD germanium bolometer. For the geometry studied the observed temperature change of the silicon resulting from an {alpha} event in the liquid is approximately 5% of the temperature rise from an {alpha} hitting the silicon directly. The implications of these measurements will be discussed as they relate to the possible construction of a large scale detector of solar neutrinos.

  13. Development of Helium-Mass-Spectrometry-Permeameter for the Measurement of Permeability of Near-Impermeable Rock

    Science.gov (United States)

    Lee, Moo Y.; Bauer, Stephen J.

    2016-12-01

    A helium leakage detection system was modified to measure gas permeability on extracted cores of nearly impermeable rock. The Helium-Mass-Spectrometry-Permeameter (HMSP) is duplicating the classic Darcy's experiment with a constant pressure differential and steady-state flow through a sample using helium gas. Under triaxial stress condition, the newly developed HMSP can measure hydraulic permeability of rocks and geomaterials down to the nanoDarcy scale (10-21 m2). The extension of measuring the lower end of the permeability scale may help answer important questions regarding the permeability of rock at great depth where fractures may close completely under high lithostatic stress.

  14. Optical and electron spin resonance studies of xenon-nitrogen-helium condensates containing nitrogen and oxygen atoms.

    Science.gov (United States)

    Boltnev, Roman E; Bykhalo, Igor B; Krushinskaya, Irina N; Pelmenev, Alexander A; Khmelenko, Vladimir V; Mao, Shun; Meraki, Adil; Wilde, Scott C; McColgan, Patrick T; Lee, David M

    2015-03-19

    We present the first observations of excimer XeO* molecules in molecular nitrogen films surrounding xenon cores of nanoclusters. Multishell nanoclusters form upon the fast cooling of a helium jet containing small admixtures of nitrogen and xenon by cold helium vapor (T = 1.5 K). Such nanoclusters injected into superfluid helium aggregate into porous impurity-helium condensates. Passage of helium gas with admixtures through a radio frequency discharge allows the storage of high densities of radicals stabilized in impurity-helium condensates. Intense recombination of the radicals occurs during destruction of such condensates and generates excited species observable because of optical emission. Rich spectra of xenon-oxygen complexes have been detected upon destruction of xenon-nitrogen-helium condensates. A xenon environment quenches metastable N((2)D) atoms but has a much weaker effect on the luminescence of N((2)P) atoms. Electron spin resonance spectra of N((4)S) atoms trapped in xenon-nitrogen-helium condensates have been studied. High local concentrations of nitrogen atoms (up to 10(21) cm(-3)) stabilized in xenon-nitrogen nanoclusters have been revealed.

  15. Improving the flash flood frequency analysis applying dendrogeomorphological evidences

    Science.gov (United States)

    Ruiz-Villanueva, V.; Ballesteros, J. A.; Bodoque, J. M.; Stoffel, M.; Bollschweiler, M.; Díez-Herrero, A.

    2009-09-01

    Flash floods are one of the natural hazards that cause major damages worldwide. Especially in Mediterranean areas they provoke high economic losses every year. In mountain areas with high stream gradients, floods events are characterized by extremely high flow and debris transport rates. Flash flood analysis in mountain areas presents specific scientific challenges. On one hand, there is a lack of information on precipitation and discharge due to a lack of spatially well distributed gauge stations with long records. On the other hand, gauge stations may not record correctly during extreme events when they are damaged or the discharge exceeds the recordable level. In this case, no systematic data allows improvement of the understanding of the spatial and temporal occurrence of the process. Since historic documentation is normally scarce or even completely missing in mountain areas, tree-ring analysis can provide an alternative approach. Flash floods may influence trees in different ways: (1) tilting of the stem through the unilateral pressure of the flowing mass or individual boulders; (2) root exposure through erosion of the banks; (3) injuries and scars caused by boulders and wood transported in the flow; (4) decapitation of the stem and resulting candelabra growth through the severe impact of boulders; (5) stem burial through deposition of material. The trees react to these disturbances with specific growth changes such as abrupt change of the yearly increment and anatomical changes like reaction wood or callus tissue. In this study, we sampled 90 cross sections and 265 increment cores of trees heavily affected by past flash floods in order to date past events and to reconstruct recurrence intervals in two torrent channels located in the Spanish Central System. The first study site is located along the Pelayo River, a torrent in natural conditions. Based on the external disturbances of trees and their geomorphological position, 114 Pinus pinaster (Ait

  16. Investigations of levitated helium drops

    Science.gov (United States)

    Whitaker, Dwight Lawrence

    1999-11-01

    We report on the development of two systems capable of levitating drops of liquid helium. Helium drops of ˜20 mum have been levitated with the radiation pressure from two counter-propagating Nd:YAG laser beams. Drops are produced with a submerged piezoelectric transducer, and could be held for up to three minutes in our optical trap. Calculations show that Brillouin and Raman scattering of the laser light in the liquid helium produces a negligible rate of evaporation of the drop. Evaporation caused by the enhanced vapor pressure of the curved drop surfaces appears to be a significant effect limiting the drop lifetimes. Helium drops as large as 2 cm in diameter have been suspended in the earth's gravitational field with a magnetic field. A commercial superconducting solenoid provides the necessary field, field-gradient product required to levitate the drops. Drops are cooled to 0.5 K with a helium-3 refrigerator, and can be held in the trap indefinitely. We have found that when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. This effect is a result of the evaporation of liquid from between the two drops, and is found to occur only for normal fluid drops. We can induce shape oscillations in charged, levitated drops with an applied ac electric field. We have measured the resonance frequencies and damping rates for the l = 2 mode of oscillation as function of temperature. We have also developed a theory to describe the small amplitude shape oscillations of a He II drop surrounded by its saturated vapor. In our theory, we have considered two sets of boundary conditions---one where the drop does not evaporate and another in which the liquid and vapor are in thermodynamic equilibrium. We have found that both solutions give a frequency that agrees well with experiment, but that the data for the damping rate agree better with the solution without evaporation.

  17. FPGA Flash Memory High Speed Data Acquisition

    Science.gov (United States)

    Gonzalez, April

    2013-01-01

    The purpose of this research is to design and implement a VHDL ONFI Controller module for a Modular Instrumentation System. The goal of the Modular Instrumentation System will be to have a low power device that will store data and send the data at a low speed to a processor. The benefit of such a system will give an advantage over other purchased binary IP due to the capability of allowing NASA to re-use and modify the memory controller module. To accomplish the performance criteria of a low power system, an in house auxiliary board (Flash/ADC board), FPGA development kit, debug board, and modular instrumentation board will be jointly used for the data acquisition. The Flash/ADC board contains four, 1 MSPS, input channel signals and an Open NAND Flash memory module with an analog to digital converter. The ADC, data bits, and control line signals from the board are sent to an Microsemi/Actel FPGA development kit for VHDL programming of the flash memory WRITE, READ, READ STATUS, ERASE, and RESET operation waveforms using Libero software. The debug board will be used for verification of the analog input signal and be able to communicate via serial interface with the module instrumentation. The scope of the new controller module was to find and develop an ONFI controller with the debug board layout designed and completed for manufacture. Successful flash memory operation waveform test routines were completed, simulated, and tested to work on the FPGA board. Through connection of the Flash/ADC board with the FPGA, it was found that the device specifications were not being meet with Vdd reaching half of its voltage. Further testing showed that it was the manufactured Flash/ADC board that contained a misalignment with the ONFI memory module traces. The errors proved to be too great to fix in the time limit set for the project.

  18. Single Particle Difraction at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Bogan, M.; Boutet, S.; Starodub, Dmitri; Decorwin-Martin, Philippe; /SLAC; Chapman, H.; Bajt, S.; Schulz, J.; /DESY; Hajdu, Janos; Seibert, M.M.; Iwan, Bianca; Timneanu, Nicusor; /Uppsala U.; Marchesini, Stefano; /LBL, Berkeley; Barty, Anton; Benner, W.Henry; Frank, Matthias; Hau-Riege, Stefan P.; Woods, Bruce; /LLNL, Livermore; Rohner, Urs; /Tofwerk AG, Thun

    2010-06-11

    Single-pulse coherent diffraction patterns have been collected from randomly injected single particles with a soft X-ray free-electron laser (FEL). The intense focused FEL pulse gives a high-resolution low-noise coherent diffraction pattern of the object before that object turns into a plasma and explodes. A diffraction pattern of a single particle will only be recorded when the particle arrival into the FEL interaction region coincides with FEL pulse arrival and detector integration. The properties of the experimental apparatus coinciding with these three events set the data acquisition rate. For our single particle FLASH diffraction imaging experiments: (1) an aerodynamic lens stack prepared a particle beam that consisted of particles moving at 150-200 m/s positioned randomly in space and time, (2) the 10 fs long FEL pulses were delivered at a fixed rate, and (3) the detector was set to integrate and readout once every two seconds. The effect of these experimental parameters on the rate of data acquisition using randomly injected particles will be discussed. Overall, the ultrashort FEL pulses do not set the limit of the data acquisition, more important is the effective interaction time of the particle crossing the FEL focus, the pulse sequence structure and the detector readout rate. Example diffraction patterns of randomly injected ellipsoidal iron oxide nanoparticles in different orientations are presented. This is the first single particle diffraction data set of identical particles in different orientations collected on a shot-to-shot basis. This data set will be used to test algorithms for recovering 3D structure from single particle diffraction.

  19. Karst flash floods: an example from the Dinaric karst (Croatia

    Directory of Open Access Journals (Sweden)

    O. Bonacci

    2006-01-01

    Full Text Available Flash floods constitute one of the deadliest and costliest natural disasters worldwide. This paper explains the karst flash flood phenomenon, which represents a special kind of flash flood. As the majority of flash floods karst flash floods are caused by intensive short-term precipitation in an area whose surface rarely exceeds a few square kilometres. The characteristics of all flash floods are their short duration, small areal extent, high flood peaks and rapid flows, and heavy loss of life and property. Karst flash floods have specific characteristics due to special conditions for water circulation, which exist in karst terrains. During karst flash floods a sudden rise of groundwater levels occurs, which causes the appearance of numerous, unexpected, abundant and temporary karst springs. This paper presents in detail an example of a karst flash flood in the Marina bay (Dinaric karst region of Croatia, which occurred in December 2004.

  20. Charging dynamics of dopants in helium nanoplasmas

    DEFF Research Database (Denmark)

    Heidenreich, Andreas; Grüner, Barbara; Schomas, Dominik

    2017-01-01

    We present a combined experimental and theoretical study of the charging dynamics of helium nanodroplets doped with atoms of different species and irradiated by intense near-infrared laser pulses (≤1015 W cm−2). In particular, we elucidate the interplay of dopant ionization inducing the ignition...... of a helium nanoplasma, and the charging of the dopant atoms driven by the ionized helium host. Most efficient nanoplasma ignition and charging is found when doping helium droplets with xenon atoms, in which case high charge states of both helium (He2+) and of xenon (Xe21+) are detected. In contrast, only low...... charge states of helium and dopants are measured when doping with potassium and calcium atoms. Classical molecular dynamics simulations which include focal averaging generally reproduce the experimental results and provide detailed insights into the correlated charging dynamics of guest and host clusters....

  1. Critical Landau velocity in helium nanodroplets.

    Science.gov (United States)

    Brauer, Nils B; Smolarek, Szymon; Loginov, Evgeniy; Mateo, David; Hernando, Alberto; Pi, Marti; Barranco, Manuel; Buma, Wybren J; Drabbels, Marcel

    2013-10-11

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitations of the helium atoms in the liquid. In the present work we determine to what extent this concept can still be applied to nanometer-scale, finite size helium systems. To this end, atoms and molecules embedded in helium nanodroplets of various sizes are accelerated out of the droplets by means of optical excitation, and the speed distributions of the ejected particles are determined. The measurements reveal the existence of a critical velocity in these systems, even for nanodroplets consisting of only a thousand helium atoms. Accompanying theoretical simulations based on a time-dependent density functional description of the helium confirm and further elucidate this experimental finding.

  2. A Comparative Study of Reduced-Variables-Based Flash and Conventional Flash

    DEFF Research Database (Denmark)

    Yan, Wei; Stenby, Erling Halfdan; Michelsen, Michael Locht

    2013-01-01

    the advantages of the reduced-variables methods in their recent paper. A fair comparison between the reduced-variables-based flash and the conventional flash is not straightforward because it is difficult to formulate the former as unconstrained minimization problems, and the flash calculation time is also...... related to the implementation quality. With the recent formulations by Nichita and Graciaa (2011), it is possible to code the reduced-variables methods without extensive modifications of Michelsen's conventional flash algorithm. A minimization-based reduced-variables algorithm was coded and compared...... with the conventional minimization-based flash. A test with the use of the SPE 3 example (Kenyon and Behie 1987) showed that the best reduction in time was less than 20% for the extreme situation of 25 components and just one row/column with nonzero BIPs. A better performance can be achieved by a simpler implementation...

  3. AM Canum Venaticorum Progenitors with Helium Star Donors and the resultant Explosions

    CERN Document Server

    Brooks, Jared; Marchant, Pablo; Paxton, Bill

    2015-01-01

    We explore the outcome of mass transfer via Roche lobe overflow (RLOF) of $M_{\\rm He}\\lesssim0.51 M_\\odot$ pure helium burning stars in close binaries with white dwarfs (WDs). The evolution is driven by the loss of angular momentum through gravitational wave radiation (GWR), and both stars are modeled using Modules for Experiments in Stellar Astrophysics (MESA). The donors have masses of $M_{\\rm He}=0.35, 0.4, \\&\\ 0.51M_\\odot$ and accrete onto WDs of mass $M_{\\rm WD}$ from $0.6M_\\odot$ to $1.26M_\\odot$. The initial orbital periods ($P_{\\rm{orb}}$) span 20 to 80 minutes. For all cases, the accretion rate onto the WD is below the stable helium burning range, leading to accumulation of helium followed by unstable ignition. The mass of the convective core in the donors is small enough so that the WD accretes enough helium-rich matter to undergo a thermonuclear runaway in the helium shell before any carbon-oxygen enriched matter is transferred. The mass of the accumulated helium shell depends on $M_{\\rm WD}$ a...

  4. Behaviour of helium after implantation in molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Viaud, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France)], E-mail: viaud@dircad.cea.fr; Maillard, S.; Carlot, G.; Valot, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France); Gilabert, E. [Chimie Nucleaire Analytique and Bio-environnementale (CNAB), Gradignan (France); Sauvage, T. [CEMHTI-CNRS, Orleans (France); Peaucelle, C.; Moncoffre, N. [Institut de Physique Nucleaire de Lyon (IPNL), Lyon (France)

    2009-03-31

    This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature.

  5. General review of flashing jet studies.

    Science.gov (United States)

    Polanco, Geanette; Holdø, Arne Erik; Munday, George

    2010-01-15

    The major concern on the management of superheated liquids, in industrial environments, is the large potential hazards involved in cases of any accidental release. There is a possibility that a violent phase change could take place inside the fluid released generating a flashing jet. This violent phase change might produce catastrophic consequences, such as explosions, fires or toxic exposure, in the installations and in the surroundings. The knowledge and understanding of the mechanisms involved in those releases become an important issue in the prevention of these consequences and the minimization of their impact. This work presents a comprehensive review of information about flashing processes. The review begins with a description of the single phase jet followed by a description of the two-phase flashing jet. The concepts and implications of the thermodynamic and mechanical effects on the behaviour of the jets are considered at the beginning of the review. Following the review is devoted to the classification of the different study approaches used to understand flashing processes in the past, highlighting various critical parameters on the behaviour and the hazard consequences of flashing jets. The review also contains an extensive compilation of experimental, theoretical and numerical data relating to these phenomena, which includes information on the distinct characteristics of the jet, since type of jet, velocity distribution, expansion angle and mass phase change all require individual estimation.

  6. General review of flashing jet studies

    Energy Technology Data Exchange (ETDEWEB)

    Polanco, Geanette, E-mail: gpolanco@usb.ve [Simon Bolivar University, Caracas (Venezuela, Bolivarian Republic of); Holdo, Arne Erik, E-mail: Erik.Holdo@coventry.ac.uk [Narvik University College, Narvik (Norway); Munday, George, E-mail: G.Munday@isaaconsult.co.uk [Coventry University, Coventry (United Kingdom)

    2010-01-15

    The major concern on the management of superheated liquids, in industrial environments, is the large potential hazards involved in cases of any accidental release. There is a possibility that a violent phase change could take place inside the fluid released generating a flashing jet. This violent phase change might produce catastrophic consequences, such as explosions, fires or toxic exposure, in the installations and in the surroundings. The knowledge and understanding of the mechanisms involved in those releases become an important issue in the prevention of these consequences and the minimization of their impact. This work presents a comprehensive review of information about flashing processes. The review begins with a description of the single phase jet followed by a description of the two-phase flashing jet. The concepts and implications of the thermodynamic and mechanical effects on the behaviour of the jets are considered at the beginning of the review. Following the review is devoted to the classification of the different study approaches used to understand flashing processes in the past, highlighting various critical parameters on the behaviour and the hazard consequences of flashing jets. The review also contains an extensive compilation of experimental, theoretical and numerical data relating to these phenomena, which includes information on the distinct characteristics of the jet, since type of jet, velocity distribution, expansion angle and mass phase change all require individual estimation.

  7. Lightning flash multiplicity in eastern Mediterranean thunderstorms

    Science.gov (United States)

    Yair, Y.; Shalev, S.; Erlich, Z.; Agrachov, A.; Katz, E.; Saaroni, H.; Price, C.; Ziv, B.

    2014-02-01

    Cloud-to-ground lightning flashes usually consist of one or several strokes coming in very short temporal succession and close spatial proximity. A commonly used method for converting stroke data into flashes is using the National Lightning Detection Network (NLDN) thresholds of maximum temporal separation of 0.5 s and maximum lateral distance of 10 km radius between successive strokes. In the present study, we tested a location-based algorithm with several spatial and temporal ranges, and analyzed stroke data obtained by the Israel Lightning Location System (ILLS) during one year (1.8.2009-31.7.2010). We computed the multiplicity, the percentage of single stroke flashes and the geographical distribution of average multiplicity values for thunderstorms in the Eastern Mediterranean region. Results show that for the NLDN thresholds, the percentage of single stroke flashes in Israel was 37% and the average multiplicity was 1.7. We reanalyzed the data with a spatial range that equals twice the ILLS location error and shorter times. For the new thresholds of maximum distance of 2.5 km and maximum allowed temporal separation of 0.2 s we find that the mean multiplicity of negative CGs is lowered to 1.4 and find a percentage of 58% of single stroke flashes. A unique severe storm from 30 October 2009 is analyzed and compared with the annual average of 2009/2010, showing that large deviations from the mean values can occur in specific events.

  8. The Past and Future of Detached Double White Dwarfs with Helium Donors

    CERN Document Server

    Macias, Phillip J; Ramirez-Ruiz, Enrico

    2015-01-01

    We present a method for modeling the evolution of detached double white dwarf (DWD) binaries hosting helium donors from the end of the common envelope (CE) phase to the onset of Roche Lobe overflow (RLOF). This is achieved by combining detailed stellar evolution calculations of extremely low mass (ELM) helium WDs possessing hydrogen envelopes with the the orbital shrinking of the binary driven by gravitational radiation. We show that the consideration of hydrogen fusion in these systems is crucial, as a significant fraction ($\\approx$50%) of future donors are expected to still be burning when mass transfer commences. We apply our method to two detached eclipsing DWD systems, SDSS J0651+2844 and NLTT-11748, in order to demonstrate the effect that carbon-nitrogen-oxygen (CNO) flashes have on constraining the evolutionary history of such systems. We find that when CNO flashes are absent on the low mass WD ($M_{2}$ < $0.18 M_{\\odot}$), such as in NLTT-11748, we are able to self consistently solve for the donor...

  9. Effect of wall thickness and helium cooling channels on duct magnetohydrodynamic flows

    Energy Technology Data Exchange (ETDEWEB)

    He, Qingyun; Feng, Jingchao; Chen, Hongli, E-mail: hlchen1@ustc.edu.cn

    2016-02-15

    Highlights: • MHD flows in ducts of different wall thickness compared with wall uniform. • Study of velocity, pressure distribution in ducts MHD flows with single pass of helium cooling channels. • Comparison of three types of dual helium cooling channels and acquisition of an option for minimum pressure drop. • A single short duct MHD flow in blanket without FCI has been simulated for pressure gradient analysis. - Abstract: The concept of dual coolant liquid metal (LM) blanket has been proposed in different countries to demonstrate the technical feasibility of DEMO reactor. In the system, helium gas and PbLi eutectic, separated by structure grid, are used to cool main structure materials and to be self-cooled, respectively. The non-uniform wall thickness of structure materials gives rise to wall non-homogeneous conductance ratio. It will lead to electric current distribution changes, resulting in significant changes in the velocity distribution and pressure drop of magnetohydrodynamic (MHD) flows. In order to investigate the effect of helium channels on MHD flows, different methods of numerical simulations cases are carried out including the cases of different wall thicknesses, single pass of helium cooling channels, and three types of dual helium cooling channels. The results showed that helium tubes are able to affect the velocity distribution in the boundary layer by forming wave sharp which transfers from Hartmann boundary layer to the core area. In addition, the potential profile and pressure drop in the cases have been compared to these in the case of walls without cooling channel, and the pressure gradient of a simplified single short duct MHD flow in blanket shows small waver along the central axis in the helium channel position.

  10. Reduced Comparator Flash ADC for ECG Applications

    Directory of Open Access Journals (Sweden)

    Saravanan. V. A

    2013-03-01

    Full Text Available A CMOS based low power 4-bit Flash Analog to Digital Converter (ADC design with reduced number of comparators than the conventional Flash Analog to Digital Converter and multiplexer based architecture is proposed. For improving the conversion rate, both the analog and digital parts of the ADC are fully modified and the architecture uses only 4 comparators instead of 15 as used in conventional flash ADC, thus saving considerable amount of power. The proposed 4-bit ADC is designed and simulated in TANNER tools with 1.2 V supply voltage using TSpice simulation. The proposed design consumes low power of 2.15mW and operates at a faster rate hence it is suitable for ECG applications.

  11. Mental models of flash floods and landslides.

    Science.gov (United States)

    Wagner, Klaus

    2007-06-01

    Perceptions of flash floods and landslides were analyzed in four communities of the Bavarian Alps using the mental model approach. Thirty-eight qualitative interviews, two telephone surveys with 600 respondents, and two onsite interviews (74/95 respondents) were conducted. Mental models concerning flash floods are much better developed than those for landslides because the key physical processes for flash floods are easier for the general public to recognize and understand. Mental models are influenced by the local conditions. People who have a better knowledge about the hazards are those who use many different sources to inform themselves, express fear about natural hazards, or have previous experience with hazards. Conclusions for how to improve information for the general public are discussed.

  12. Helium stratification in HD 145792: a new Helium strong star

    CERN Document Server

    Catanzaro, G

    2007-01-01

    In this paper we report on the real nature of the star HD 145792, classified as He weak in {\\it ``The General Catalogue of Ap and Am stars''}. By means of FEROS@ESO1.52m high resolution spectroscopic data, we refined the atmospheric parameters of the star, obtaining: T$_{\\rm eff}$ = 14400 $\\pm$ 400 K, $\\log g$ = 4.06 $\\pm$ 0.08 and $\\xi$ = 0 $^{+0.6}$ km s$^{-1}$. These values resulted always lower than those derived by different authors with pure photometric approaches. Using our values we undertook an abundance analysis with the aim to derive, for the first time, the chemical pattern of the star's atmosphere. For metals a pure LTE synthesis (ATLAS9 and SYNTHE) has been used, while for helium a hybrid approach has been preferred (ATLAS9 and SYNSPEC). The principal result of our study is that HD 145792 belongs to He strong class contrary to the previous classification. Moreover, helium seems to be vertically stratified in the atmosphere, decreasing toward deepest layers. For what that concerns metals abundanc...

  13. Helium transfer line installation details.

    CERN Multimedia

    G. Perinic

    2007-01-01

    A particularity of the 32 m long four in one helium transfer line in between the cold box in USC55 and the cavern UX5 is the fact that the transfer line passes through a hole in the crane rail support beam. In order to ensure the alignment of the suspension rail in the interconnecting tunnel with the hole in the rail support as well as the connection points at both ends required precise measurements of the given geometries as well as the installation of a temporary target for the verification of the theoretical predictions.

  14. Helium II level measurement techniques

    Science.gov (United States)

    Celik, D.; Hilton, D. K.; Zhang, T.; Van Sciver, S. W.

    2001-05-01

    In this paper, a survey of cryogenic liquid level measurement techniques applicable to superfluid helium (He II) is given. The survey includes both continuous and discrete measurement techniques. A number of different probes and controlling circuits for this purpose have been described in the literature. They fall into one of the following categories: capacitive liquid level gauges, superconducting wire liquid level gauges, thermodynamic (heat transfer-based) liquid level gauges, resistive gauges, ultrasound and transmission line-based level detectors. The present paper reviews these techniques and their suitability for He II service. In addition to these methods, techniques for measuring the total liquid volume and mass gauging are also discussed.

  15. Centrally active nonhormonal hot flash therapies.

    Science.gov (United States)

    Loprinzi, Charles L; Stearns, Vered; Barton, Debra

    2005-12-19

    Given the problems associated with hormonal therapy, and the prominent problem of hot flashes in menopausal women, there is a need for nonhormonal agents to alleviate hot flashes. Several compounds that appear to act on the central nervous system have been investigated. Potential mechanisms for their effects on hot flashes have been described. Bellergal (no longer available on the US market, where it was known as Bellergal-S), a combination preparation sedative that consists of low-dose phenobarbital, ergotamine tartrate, and levorotatory alkaloids of belladonna, is an old agent that was popular approximately 20 years ago; however, there is limited suggestion of efficacy for this agent. Clonidine, an older antihypertensive drug, is another centrally active agent that has been studied. Randomized trials have demonstrated that it clearly works for reducing hot flashes, but the magnitude of efficacy is somewhat limited. Toxicity from this agent limits its utility in the clinic. Methyldopa is another centrally active agent that has been studied but to a more limited degree. It appears to have minimal efficacy and too much toxicity to make it clinically useful. Anecdotal observations from a number of sources suggested that newer antidepressants can alleviate hot flashes. This led to pilot trials of venlafaxine and paroxetine, with results suggesting benefit from both drugs. Subsequently, randomized, placebo-controlled, double-blind clinical trials of venlafaxine, paroxetine, and fluoxetine were conducted. All 3 of these clinical trials demonstrated statistically significant reductions in hot flashes with these newer antidepressants compared with placebo. Pilot trials of citalopram and mirtazapine, 2 other newer antidepressants, have also suggested efficacy. Toxicity evaluations have suggested that these agents are, again, well tolerated by the majority of patients. A recent trial, however, was unable to demonstrate any benefit for fluoxetine or citalopram over a placebo

  16. Foundation Flash CS5 for Designers

    CERN Document Server

    Green, T

    2010-01-01

    Flash is one of the most engaging, innovative, and versatile technologies available - allowing the creation of anything from animated banners and simple cartoons to Rich Internet Applications, interactive videos, and dynamic user interfaces for web sites, kiosks, devices, or DVDs. The possibilities are endless, and now it just got better. Flash CS5 boasts a host of new features, including better support for mobile devices, a whole new animation engine enabling full manipulation of tweens and paths, custom easing, improved inverse kinematics, a revamped timeline, built-in 3D, and much more. Thi

  17. Cancer treatment: dealing with hot flashes and night sweats

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000826.htm Cancer treatment: dealing with hot flashes and night sweats To ... this page, please enable JavaScript. Certain types of cancer treatments can cause hot flashes and night sweats. Hot ...

  18. Flash3D EDL Sensor Technology Advancement Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Scientific Concepts Inc. (ASC) is a small business, which has developed a number of 3D flash LADAR systems. Flash Ladar sensors are 3D video systems that...

  19. 3D Flash LIDAR EDL Resolution Improvement Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc. (ASC) is a small business that has developed 3D Flash LIDAR systems for space and terrestrial applications. 3D Flash LIDAR is...

  20. Sunset science. III. Visual adaptation and green flashes.

    Science.gov (United States)

    Young, A T

    2000-12-01

    Photographs of green flashes do not preclude a role for physiological effects in these phenomena. While green flashes are certainly not after-images, there is compelling evidence that adaptation in the visual system strongly affects the perceived color of most sunset green flashes. Furthermore, the retinal image of the setting Sun is usually bright enough to bleach most of the red-sensitive photopigment in a few seconds, making the yellow stage of a sunset flash appear green. Even in air so hazy that no green light reaches the eye, a yellow flash may occur and appear green. Many, but not all, visual observations of sunset green flashes are of this yellow flash. The yellow portion of sunset green flashes helps explain their reported durations, which exceed those expected for the appearance of green light alone.

  1. The Research of PID Control in a Large Scale Helium Refrigerator

    Science.gov (United States)

    Pan, W.; Wu, J. H.; Li, L. F.; Liu, H. M.; Li, Q.

    2015-12-01

    In the development of a helium refrigerator, the control of load temperature stability is an important requirement. We usually use multistage control strategies to achieve the precise control of it. Each level has its strict control logic. PID controllers are the core control module in the process. Therefore, a research of its principle and parameters’ setting occupies an important position in the development work. This paper detailed describes the PID control principle used in a large scale helium refrigerator of 10kW@20K, as well as several improvements on PID parameters’ setting, by using simulations and experiments in combination. The temperature is eventually controlled more precise.

  2. Measurements of the production and transport of helium ash on the TFTR Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Synakowski, E.J.; Bell, R.E.; Budny, R.V. [and others

    1995-03-01

    Helium ash production and transport have been measured in TFTR deuterium-tritium plasmas using charge-exchange recombination spectroscopy. The helium ash confinement time, including recycling effects, is 6--10 times the energy confinement time and is compatible with sustained ignition in a reactor. The ash confinement time is dominated by edge pumping rates rather than core transport. The measured evolution of the local thermal ash density agrees with modeling, indicating that alpha particle slowing-down calculations used in the modeling are reasonable.

  3. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van Veldhoven, E.; Chen, P.; Sidorkin, V; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2009-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  4. Radioactive ions and atoms in superfluid helium

    NARCIS (Netherlands)

    Dendooven, P.G.; Purushothaman, S.; Gloos, K.; Aysto, J.; Takahashi, N.; Huang, W.; Harissopulos, S; Demetriou, P; Julin, R

    2006-01-01

    We are investigating the use of superfluid helium as a medium to handle and manipulate radioactive ions and atoms. Preliminary results on the extraction of positive ions from superfluid helium at temperatures close to 1 K are described. Increasing the electric field up to 1.2 kV/cm did not improve t

  5. Organ protection by the noble gas helium

    NARCIS (Netherlands)

    Smit, K.F.

    2017-01-01

    The aims of this thesis were to investigate whether helium induces preconditioning in humans, and to elucidate the mechanisms behind this possible protection. First, we collected data regarding organ protective effects of noble gases in general, and of helium in particular (chapters 1-3). In chapter

  6. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van veldhoven, E.; Chen, P.; Sidorkin, V.; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2010-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  7. LOX Tank Helium Removal for Propellant Scavenging

    Science.gov (United States)

    Chato, David J.

    2009-01-01

    System studies have shown a significant advantage to reusing the hydrogen and oxygen left in these tanks after landing on the Moon in fuel cells to generate power and water for surface systems. However in the current lander concepts, the helium used to pressurize the oxygen tank can substantially degrade fuel cell power and water output by covering the reacting surface with inert gas. This presentation documents an experimental investigation of methods to remove the helium pressurant while minimizing the amount of the oxygen lost. This investigation demonstrated that significant quantities of Helium (greater than 90% mole fraction) remain in the tank after draining. Although a single vent cycle reduced the helium quantity, large amounts of helium remained. Cyclic venting appeared to be more effective. Three vent cycles were sufficient to reduce the helium to small (less than 0.2%) quantities. Two vent cycles may be sufficient since once the tank has been brought up to pressure after the second vent cycle the helium concentration has been reduced to the less than 0.2% level. The re-pressurization process seemed to contribute to diluting helium. This is as expected since in order to raise the pressure liquid oxygen must be evaporated. Estimated liquid oxygen loss is on the order of 82 pounds (assuming the third vent cycle is not required).

  8. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van veldhoven, E.; Chen, P.; Sidorkin, V.; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2010-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  9. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van Veldhoven, E.; Chen, P.; Sidorkin, V; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2009-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  10. Paramagnetic Attraction of Impurity-Helium Solids

    Science.gov (United States)

    Bernard, E. P.; Boltnev, R. E.; Khmelenko, V. V.; Lee, D. M.

    2003-01-01

    Impurity-helium solids are formed when a mixture of impurity and helium gases enters a volume of superfluid helium. Typical choices of impurity gas are hydrogen deuteride, deuterium, nitrogen, neon and argon, or a mixture of these. These solids consist of individual impurity atoms and molecules as well as clusters of impurity atoms and molecules covered with layers of solidified helium. The clusters have an imperfect crystalline structure and diameters ranging up to 90 angstroms, depending somewhat on the choice of impurity. Immediately following formation the clusters aggregate into loosely connected porous solids that are submerged in and completely permeated by the liquid helium. Im-He solids are extremely effective at stabilizing high concentrations of free radicals, which can be introduced by applying a high power RF dis- charge to the impurity gas mixture just before it strikes the super fluid helium. Average concentrations of 10(exp 19) nitrogen atoms/cc and 5 x 10(exp 18) deuterium atoms/cc can be achieved this way. It shows a typical sample formed from a mixture of atomic and molecular hydrogen and deuterium. It shows typical sample formed from atomic and molecular nitrogen. Much of the stability of Im-He solids is attributed to their very large surface area to volume ratio and their permeation by super fluid helium. Heat resulting from a chance meeting and recombination of free radicals is quickly dissipated by the super fluid helium instead of thermally promoting the diffusion of other nearby free radicals.

  11. Helium abundances and the helium isotope anomaly of sdB stars

    CERN Document Server

    Geier, S; Edelmann, H; Morales-Rueda, L; Kilkenny, D; O'Donoghue, D; Marsh, T R; Copperwheat, C

    2011-01-01

    Helium abundances and atmospheric parameters have been determined from high resolution spectra for a new sample of 46 bright hot subdwarf B (sdB) stars. The helium abundances have been measured with high accuracy. We confirm the correlation of helium abundance with temperature and the existence of two distinct sequences in helium abundance found previously. We focused on isotopic shifts of helium lines and found helium-3 to be strongly enriched in 8 of our programme stars. Most of these stars cluster in a small temperature range between 27000 K and 31000 K very similar to the known helium-3-rich main sequence B stars, which cluster at somewhat lower temperatures. This phenomenon is most probably related to diffusion processes in the atmosphere, but poses a challenge to diffusion models.

  12. Elusive structure of helium trimers

    Science.gov (United States)

    Stipanović, Petar; Vranješ Markić, Leandra; Boronat, Jordi

    2016-09-01

    Over the years many He-He interaction potentials have been developed, some very sophisticated, including various corrections beyond the Born-Oppenheimer approximation. Most of them were used to predict properties of helium dimers and trimers, examples of exotic quantum states, whose experimental study proved to be very challenging. Recently, detailed structural properties of helium trimers were measured for the first time, allowing a comparison with theoretical predictions and possibly enabling the evaluation of different interaction potentials. The comparisons already made included adjusting the maxima of both theoretical and experimental correlation functions to one, so the overall agreement between theory and experiment appeared satisfactory. However, no attempt was made to evaluate the quality of the interaction potentials used in the calculations. In this work, we calculate the experimentally measured correlation functions using both new and old potentials, compare them with experimental data and rank the potentials. We use diffusion Monte Carlo simulations at T = 0, which give within statistical noise exact results of the ground state properties. All models predict both trimers 4He3 and 4He{}2{}3He to be in a quantum halo state.

  13. Mainostoimiston Flash-tuotantoprosessin kehittäminen

    OpenAIRE

    Heinonen, Toni

    2012-01-01

    Tämän opinnäytetyön tarkoituksena oli kehittää mainostoimiston Flash-tuotantoprosessia. Mainostoimiston Flash-tuotanto on pääosin display-mainonnan eli bannereiden sekä Flashmainoskampanjasivustojen luontia. Lisäksi tarkoituksena oli tutkia mahdollisuutta soveltaa ohjelmistokehityksessä toimiviksi havaittujen ketterien prosessimallien soveltamista mainostoimiston Flash-tuotantoprosessiin. Työ aloitettiin kuvaamalla mainostoimiston nykyinen Flash-tuotantoprosessi tarkoitukseen ...

  14. Ultrafast-Contactless Flash Sintering using Plasma Electrodes

    OpenAIRE

    Theo Saunders; Salvatore Grasso; Reece, Michael J.

    2016-01-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 ...

  15. Photochemistry inside superfluid helium nano droplets

    Energy Technology Data Exchange (ETDEWEB)

    Slenczka, Alkwin; Vdovin, Alexander; Dick, Bernhard [Inst. fuer Physikalische und Theoretische Chemie, Univ. Regensburg (Germany)

    2007-07-01

    Superfluid helium nano droplets serve as the most gentle cyrogenic matrix for creating isolated and cold molecules. High resolution electronic spectroscopy is sensitive for the investigation of the very weak perturbation of the helium droplet on the embedded molecule. Fluorescence excitation spectra, dispersed emission spectra and pump--probe-spectra show details of the salvation of molecules in helium droplets which were attributed to relaxation processes of the first solvation layer around the dopant. Photochemistry such as ESIPT, tautomerization by proton transfer and charge transfer are highly sensitive on intermolecular perturbations. We have studies such processes in superfluid helium droplets. The comparison with the respective gas phase experiments and quantum chemical calculations reveals further details on the photochemistry as well as on the perturbation by the superfluid helium droplet.

  16. Permeability of Hollow Microspherical Membranes to Helium

    Science.gov (United States)

    Zinoviev, V. N.; Kazanin, I. V.; Pak, A. Yu.; Vereshchagin, A. S.; Lebiga, V. A.; Fomin, V. M.

    2016-01-01

    This work is devoted to the study of the sorption characteristics of various hollow microspherical membranes to reveal particles most suitable for application in the membrane-sorption technologies of helium extraction from a natural gas. The permeability of the investigated sorbents to helium and their impermeability to air and methane are shown experimentally. The sorption-desorption dependences of the studied sorbents have been obtained, from which the parameters of their specific permeability to helium are calculated. It has been established that the physicochemical modification of the original particles exerts a great influence on the coefficient of the permeability of a sorbent to helium. Specially treated cenospheres have displayed high efficiency as membranes for selective extraction of helium.

  17. Gemini helium closed cycle cooling system

    Science.gov (United States)

    Lazo, Manuel; Galvez, Ramon; Rogers, Rolando; Solis, Hernan; Tapia, Eduardo; Maltes, Diego; Collins, Paul; White, John; Cavedoni, Chas; Yamasaki, Chris; Sheehan, Michael P.; Walls, Brian

    2008-07-01

    The Gemini Observatory presents the Helium Closed Cycle Cooling System that provides cooling capacity at cryogenic temperatures for instruments and detectors. It is implemented by running three independent helium closed cycle cooling circuits with several banks of compressors in parallel to continuously supply high purity helium gas to cryocoolers located about 100-120 meters apart. This poster describes how the system has been implemented, the required helium pressures and gas flow to reach cryogenic temperature, the performance it has achieved, the helium compressors and cryocoolers in use and the level of vibration the cryocoolers produce in the telescope environment. The poster also describes the new technology for cryocoolers that Gemini is considering in the development of new instruments.

  18. Formation of the helium EUV resonance lines

    CERN Document Server

    Golding, Thomas Peter; Carlsson, Mats

    2016-01-01

    Context: While classical models successfully reproduce intensities of many transition region lines, they predict helium EUV line intensities roughly an order of magnitude lower than the observed value. Aims: To determine the relevant formation mechanism(s) of the helium EUV resonance lines, capable of explaining the high intensities under quiet sun conditions. Methods: We synthesise and study the emergent spectra from a 3D radiation-magnetohydrodynamics simulation model. The effects of coronal illumination and non-equilibrium ionisation of hydrogen and helium are included self-consistently in the numerical simulation. Results: Radiative transfer calculations result in helium EUV line intensities that are an order of magnitude larger than the intensities calculated under the classical assumptions. The enhanced intensity of He I 584 is primarily caused by He II recombination cascades. The enhanced intensity of He II 304 and He II 256 is caused primarily by non-equilibrium helium ionisation. Conclusion: The anal...

  19. Global helium particle balance in LHD

    Energy Technology Data Exchange (ETDEWEB)

    Motojima, G., E-mail: motojima.gen@lhd.nifs.ac.jp [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Masuzaki, S.; Tokitani, M.; Kasahara, H.; Yoshimura, Y.; Kobayashi, M.; Sakamoto, R.; Morisaki, T.; Miyazawa, J.; Akiyama, T. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Ohno, N. [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan); Mutoh, T.; Yamada, H. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

    2015-08-15

    Global helium particle balance in long-pulse discharges is analyzed for the first time in the Large Helical Device (LHD) with the plasma-facing components of the first wall and the divertor tiles composed of stainless steel and carbon, respectively. During the 2-min discharge sustained by ion cyclotron resonance heating (ICRH) and electron cyclotron heating (ECH), helium is observed to be highly retained in the wall (regarded as both the first wall and the divertor tiles). Almost all (about 96%) puffed helium particles (1.3 × 10{sup 22} He) are absorbed in the wall near the end of the discharge. Even though a dynamic retention is eliminated, 56% is still absorbed. The analysis is also applied to longer pulse discharges over 40 min by ICRH and ECH, indicating that the helium wall retention is dynamically changed in time. At the initial phase of the discharge, a mechanism for adsorbing helium other than dynamical retention is invoked.

  20. Lightning flash sizes relative to storm structure and turbulence during the Kinematic Texture and Lightning Experiment

    Science.gov (United States)

    Bruning, E. C.; Salinas, V.; Berkseth, S.; Chmielewski, V.; Brothers, M.

    2016-12-01

    Ongoing work as part of the Kinematic Texture and Lightning Experiment at Texas Tech University has quantified the lightning flash size, rate, and energy alongside the turbulent structure of thunderclouds. 2016 was the final year of observations, which fielded two high-resolution mobile Ka-band radars and mobile environmental soundings. Lightning measurements were made by a VHF Lightning Mapping Array. In order to enhance the detection of the smallest lightning discharges in the turbulent portions of the thundercloud, a rapidly-deployable mobile Lightning Mapping Array (LMA) station augmented a traditional fixed LMA. This capability of targeting particular storm complexes with LMA measurements will be described, and the improved detection capability quantified. The complete set of field measurements from 2014-16 sampled numerous individual cells and storm complexes, ranging in intensity from multicellular convection to supercells and mesoscale convective systems. Flash measurements coincident with radar observations included deep, highly turbulent convective cores and extensive anvil regions. Comparison of flash characteristics across these storm morphologies will be shown, with a focus on the dynamical organization of storms and the turbulent kinematics that drive differences in lightning flash sizes and rates.

  1. Thermal hydraulic analysis of the annular flow helium heater design

    Science.gov (United States)

    Chen, N. C.; Sanders, J. P.

    1982-05-01

    Core support performance test (CSPT) by use of an existing facility, components flow test loop (CFTL), as part of the high temperature gas cooled reactor (HTGR) application program were conducted. A major objective of the CSPT is to study accelerated corrosion of the core graphite support structure in helium at reactor conditions. Concentration of impurities will be adjusted so that a 6 month test represents the 30 year reactor life. Thermal hydraulic and structural integrity of the graphite specimen, will be studied at high pressure of 7.24 MPa (1050 psi) and high temperature of 1000 deg C in a test vessel. To achieve the required high temperature at the test section, a heater bundle has to be specially designed and properly manufactured. Performance characteristics of the heater which were determined from an analysis based on this design are presented.

  2. Mathematical modeling of the flash converting process

    Energy Technology Data Exchange (ETDEWEB)

    Sohn, H.Y.; Perez-Tello, M.; Riihilahti, K.M. [Utah Univ., Salt Lake City, UT (United States)

    1996-12-31

    An axisymmetric mathematical model for the Kennecott-Outokumpu flash converting process for converting solid copper matte to copper is presented. The model is an adaptation of the comprehensive mathematical model formerly developed at the University of Utah for the flash smelting of copper concentrates. The model incorporates the transport of momentum, heat, mass, and reaction kinetics between gas and particles in a particle-laden turbulent gas jet. The standard k-{epsilon} model is used to describe gas-phase turbulence in an Eulerian framework. The particle-phase is treated from a Lagrangian viewpoint which is coupled to the gas-phase via the source terms in the Eulerian gas-phase governing equations. Matte particles were represented as Cu{sub 2}S yFeS, and assumed to undergo homogeneous oxidation to Cu{sub 2}O, Fe{sub 3}O{sub 4}, and SO{sub 2}. A reaction kinetics mechanism involving both external mass transfer of oxygen gas to the particle surface and diffusion of oxygen through the porous oxide layer is proposed to estimate the particle oxidation rate Predictions of the mathematical model were compared with the experimental data collected in a bench-scale flash converting facility. Good agreement between the model predictions and the measurements was obtained. The model was used to study the effect of different gas-injection configurations on the overall fluid dynamics in a commercial size flash converting shaft. (author)

  3. In Situ Flash Pyrolysis of Straw

    DEFF Research Database (Denmark)

    Bech, Niels

    In-Situ Flash Pyrolysis of Straw Ph.D. dissertation by Niels Bech Submitted: April 2007. Supervisors: Professor Kim Dam-Johansen, Associate Professor Peter Arendt Jensen Erfaringerne med forbrænding af halm opnået gennem et årti har vist, at en proces der kan koncentrere energien på marken, fjerne...

  4. High-fidelity flash lidar model development

    Science.gov (United States)

    Hines, Glenn D.; Pierrottet, Diego F.; Amzajerdian, Farzin

    2014-06-01

    NASA's Autonomous Landing and Hazard Avoidance Technologies (ALHAT) project is currently developing the critical technologies to safely and precisely navigate and land crew, cargo and robotic spacecraft vehicles on and around planetary bodies. One key element of this project is a high-fidelity Flash Lidar sensor that can generate three-dimensional (3-D) images of the planetary surface. These images are processed with hazard detection and avoidance and hazard relative navigation algorithms, and then are subsequently used by the Guidance, Navigation and Control subsystem to generate an optimal navigation solution. A complex, high-fidelity model of the Flash Lidar was developed in order to evaluate the performance of the sensor and its interaction with the interfacing ALHAT components on vehicles with different configurations and under different flight trajectories. The model contains a parameterized, general approach to Flash Lidar detection and reflects physical attributes such as range and electronic noise sources, and laser pulse temporal and spatial profiles. It also provides the realistic interaction of the laser pulse with terrain features that include varying albedo, boulders, craters slopes and shadows. This paper gives a description of the Flash Lidar model and presents results from the Lidar operating under different scenarios.

  5. Flash-Aware Page Replacement Algorithm

    Directory of Open Access Journals (Sweden)

    Guangxia Xu

    2014-01-01

    Full Text Available Due to the limited main memory resource of consumer electronics equipped with NAND flash memory as storage device, an efficient page replacement algorithm called FAPRA is proposed for NAND flash memory in the light of its inherent characteristics. FAPRA introduces an efficient victim page selection scheme taking into account the benefit-to-cost ratio for evicting each victim page candidate and the combined recency and frequency value, as well as the erase count of the block to which each page belongs. Since the dirty victim page often contains clean data that exist in both the main memory and the NAND flash memory based storage device, FAPRA only writes the dirty data within the victim page back to the NAND flash memory based storage device in order to reduce the redundant write operations. We conduct a series of trace-driven simulations and experimental results show that our proposed FAPRA algorithm outperforms the state-of-the-art algorithms in terms of page hit ratio, the number of write operations, runtime, and the degree of wear leveling.

  6. RELATIONSHIP BETWEEN FLASH POINTS OF SOME BINARY ...

    African Journals Online (AJOL)

    B. S. Chandravanshi

    and BS-150 in the formulation of engine oils, the recent mineral oils were chosen for study. On the other .... blend. Upon analysis of the data due to Figure 1 (b) it can be shown that the flash point of every. SN-150: .... complex compositions.

  7. Exotic helium molecules; Molecules exotiques d'helium

    Energy Technology Data Exchange (ETDEWEB)

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  8. On Helium-Dominated Stellar Evolution: The Mysterious Role of the O(He)-Type Stars

    Science.gov (United States)

    Reindl, N.; Rauch, T.; Werner, K.; Kruk, J. W.; Todt, H.

    2014-01-01

    Context. About a quarter of all post-asymptotic giant branch (AGB) stars are hydrogen-deficient. Stellar evolutionary models explain the carbon-dominated H-deficient stars by a (very) late thermal pulse scenario where the hydrogen-rich envelope is mixed with the helium-rich intershell layer. Depending on the particular time at which the final flash occurs, the entire hydrogen envelope may be burned. In contrast, helium-dominated post-AGB stars and their evolution are not yet understood. Aims. A small group of very hot, helium-dominated stars is formed by O(He)-type stars. A precise analysis of their photospheric abundances will establish constraints to their evolution. Methods. We performed a detailed spectral analysis of ultraviolet and optical spectra of four O(He) stars by means of state-of-the-art non-LTE model-atmosphere techniques. Results. We determined effective temperatures, surface gravities, and the abundances of H, He, C, N, O, F, Ne, Si, P, S, Ar, and Fe. By deriving upper limits for the mass-loss rates of the O(He) stars, we found that they do not exhibit enhanced mass-loss. The comparison with evolutionary models shows that the status of the O(He) stars remains uncertain. Their abundances match predictions of a double helium white dwarf (WD) merger scenario, suggesting that they might be the progeny of the compact and of the luminous helium-rich sdO-type stars. The existence of planetary nebulae that do not show helium enrichment around every other O(He) star precludes a merger origin for these stars. These stars must have formed in a different way, for instance via enhanced mass-loss during their post-AGB evolution or a merger within a common-envelope (CE) of a CO-WD and a red giant or AGB star. Conclusions. A helium-dominated stellar evolutionary sequence exists that may be fed by different types of mergers or CE scenarios. It appears likely that all these pass through the O(He) phase just before they become WDs.

  9. Initial electric field changes of lightning flashes in two thunderstorms

    Science.gov (United States)

    Chapman, Ryan; Marshall, Thomas; Karunarathne, Sumedhe; Stolzenburg, Maribeth

    2017-04-01

    The beginning of all 75 lightning flashes in two small thunderstorms was investigated using an array of electric field change (E-change) meters and an array of VHF sensors with the goal of determining if an initial E-change (IEC) preceded the initial breakdown (IB) pulses in each flash. IECs were found at the beginning of all 62 flashes in Storm 1 and all 13 flashes in Storm 2. Hence, it is concluded that an IEC is a fundamental part of most or all lightning initiations and that an IEC is needed prior to the first IB pulse in a flash. IEC durations averaged 0.23 ms for cloud-to-ground (CG) flashes (range 0.08-0.54 ms) and averaged 2.7 ms for normal intracloud (IC) flashes (range 0.04-9.8 ms). IEC point dipole moments averaged 26 C m for CG flashes (range 4-86 C m) and averaged -140 C m for normal IC flashes (range -8 to -650 C m). IEC current moments averaged 120 kA m for CG flashes (range 41-410 kA m) and averaged -91 kA m for normal IC flashes (range -2 to -630 kA m). E-change data support the suggestion that weak narrow bipolar event type events initiate some lightning flashes, but 41 of the 75 flashes had no detectable initiating pulse > 0.04 V m-1 range normalized to 100 km. Two flashes had two IECs; the second IEC of each flash initiated a new lightning channel that propagated in a new direction and at a higher altitude than the original development after the first IEC.

  10. Electric response in superfluid helium

    Science.gov (United States)

    Chagovets, Tymofiy V.

    2016-05-01

    We report an experimental investigation of the electric response of superfluid helium that arises in the presence of a second sound standing wave. It was found that the signal of the electric response is observed in a narrow range of second sound excitation power. The linear dependence of the signal amplitude has been derived at low excitation power, however, above some critical power, the amplitude of the signal is considerably decreased. It was established that the rapid change of the electric response is not associated with a turbulent regime generated by the second sound wave. A model of the appearance of the electric response as a result of the oscillation of electron bubbles in the normal fluid velocity field in the second sound wave is presented. Possible explanation for the decrease of the electric response are presented.

  11. From the tunneling dimer to the onset of microsolvation: Infrared spectroscopy of allyl radical water aggregates in helium nanodroplets

    Science.gov (United States)

    Leicht, Daniel; Kaufmann, Matin; Pal, Nitish; Schwaab, Gerhard; Havenith, Martina

    2017-03-01

    The infrared spectrum of allyl:water clusters embedded in helium nanodroplets was recorded. Allyl radicals were produced by flash vacuum pyrolysis and trapped in helium droplets. Deuterated water was added to the doped droplets, and the infrared spectrum of the radical water aggregates was recorded in the frequency range 2570-2820 cm-1. Several absorption bands are observed and assigned to 1:1 and 1:2 allyl:D2O clusters, based on pressure dependent measurements and accompanying quantum chemical calculations. The analysis of the 1:1 cluster spectrum revealed a tunneling splitting as well as a combination band. For the 1:2 cluster, we observe a water dimer-like motif that is bound by one π-hydrogen bond to the allyl radical.

  12. In Beam Tests of Implanted Helium Targets

    CERN Document Server

    McDonald, J E; Ahmed, M W; Blackston, M A; Delbar, T; Gai, M; Kading, T J; Parpottas, Y; Perdue, B A; Prior, R M; Rubin, D A; Spraker, M C; Yeomans, J D; Weissman, L; Weller, H R; Delbar, Th.; Conn, LNS/U; Duke, TUNL/

    2006-01-01

    Targets consisting of 3,4He implanted into thin aluminum foils (approximately 100, 200 or 600 ug/cm^2) were prepared using intense (a few uA) helium beams at low energy (approximately 20, 40 or 100 keV). Uniformity of the implantation was achieved by a beam raster across a 12 mm diameter tantalum collimator at the rates of 0.1 Hz in the vertical direction and 1 Hz in the horizontal direction. Helium implantation into the very thin (approximately 80-100 ug/cm^2) aluminum foils failed to produce useful targets (with only approximately 10% of the helium retained) due to an under estimation of the range by the code SRIM. The range of low energy helium in aluminum predicted by Northcliffe and Shilling and the NIST online tabulation are observed on the other hand to over estimate the range of low energy helium ions in aluminum. An attempt to increase the amount of helium by implanting a second deeper layer was also carried out, but it did not significantly increase the helium content beyond the blistering limit (ap...

  13. Enhancement of helium exhaust by resonant magnetic perturbation fields at LHD and TEXTOR

    Science.gov (United States)

    Schmitz, O.; Ida, K.; Kobayashi, M.; Bader, A.; Brezinsek, S.; Evans, T. E.; Funaba, H.; Goto, M.; Mitarai, O.; Morisaki, T.; Motojima, G.; Nakamura, Y.; Narushima, Y.; Nicolai, D.; Samm, U.; Tanaka, H.; Yamada, H.; Yoshinuma, M.; Xu, Y.; TEXTOR, the; LHD Experiment Groups

    2016-10-01

    The ability to exhaust helium as the fusion born plasma impurity is a critical requirement for burning plasmas. We demonstrate in this paper that resonant magnetic perturbation (RMP) fields can be used to actively manipulate helium exhaust characteristics. We present results from puff/pump studies at TEXTOR as example for a tokamak with a pumped limiter and from the Large Helical Device (LHD) with the closed helical divertor as example for a heliotron/stellarator device. For LHD, the effective helium confinement time τ p,\\text{He}\\ast is a factor of 7-8 higher in the low and high density regimes explored when compared to TEXTOR discharges. This is attributed to ion root impurity transport which is one particular impurity transport regime assessed experimentally at LHD and which facilitates helium penetration to the plasma core. However, when an edge magnetic island is induced by externally applied RMP fields, τ p,\\text{He}\\ast is decreased by up to 30% and hence τ p,\\text{He}\\ast values closer to those of TEXTOR can be established. The combination of TEXTOR and LHD results suggest that a magnetic island induced by the RMP field in the plasma source region is an important ingredient for improving helium exhaust. The reduction in τ p,\\text{He}\\ast seen is caused by a combination of improved helium exhaust due to an enhanced coupling to the pumping systems, increased outward transport and a reduced fueling efficiency for the helium injected and recycling from the wall elements.

  14. Matter Flashed at Ultra Speed

    Science.gov (United States)

    2007-06-01

    "REM observations of GRB060418 and GRB060607A: the onset of the afterglow and the initial fireball Lorentz factor determination", by E. Molinari, S. D. Vergani, D. Malesani, S. Covino, et al. The paper is available at http://dx.doi.org/10.1051/0004-6361:20077388 (A&A, 469, L13-L16, 2007). The REM team is formed by G. Chincarini, E. Molinari, F.M. Zerbi, L.A. Antonelli, S. Covino, P. Conconi, L. Nicastro, E. Palazzi, M. Stefanon, V. Testa, G. Tosti, F. Vitali, A. Monfardini, F. D'Alessio, P. D'Avanzo, D. Fugazza, G. Malaspina, S. Piranomonte, S.D. Vergani, P.A. Ward, S. Campana, P. Goldoni, D. Guetta, D. Malesani, N. Masetti, E.J.A. Meurs, L. Norci, E. Pian, A. Fernandez-Soto, L. Stella, G. Tagliaferri, G. Ihle, L. Gonzalez, A. Pizarro, P. Sinclair, and J. Valenzuela. Notes Gamma-ray bursts (GRBs) are short flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous quantity of energy in this short time making them the most powerful events since the Big Bang. They come in two different flavours, long and short ones. Over the past few years, international efforts have convincingly shown that long gamma-ray bursts are linked with the ultimate explosion of massive stars (hypernovae; see e.g. ESO PR 16/03) while the short ones most likely originate from the violent collision of neutron stars and/or black holes (see e.g. ESO PR 26/05 and 32/05). Irrespective of the original source of the GRB energy, the injection of so much energy into a confined volume will cause a fireball to form. Gamma-ray photons have nearly a million times more energy than the 'visual' photons the eye can see. Strictly speaking, the Lorentz factor is the ratio between the total and rest-mass energy of the fireball. REM (Rapid Eye Mount) is a small (60 cm mirror diameter) rapid reaction automatic telescope dedicated to monitor the prompt afterglow of Gamma Ray Burst events. It is located at the ESO La Silla Observatory in Chile. For more information, see

  15. Next High Performance and Low Power Flash Memory Package Structure

    Institute of Scientific and Technical Information of China (English)

    Jung-Hoon Lee

    2007-01-01

    In general, SAND flash memory has advantages in low power consumption, storage capacity, and fast erase/write performance in contrast to NOR flash. But, main drawback of the SAND flash memory is the slow access time for random read operations. Therefore, we proposed the new SAND flash memory package for overcoming this major drawback. We present a high performance and low power SAND flash memory system with a dual cache memory. The proposed SAND flash package consists of two parts, i.e., an SAND flash memory module, and a dual cache module. The new SAND flash memory system can achieve dramatically higher performance and lower power consumption compared with any conventional NAND-type flash memory module. Our results show that the proposed system can reduce about 78% of write operations into the flash memory cell and about 70% of read operations from the flash memory cell by using only additional 3KB cache space. This value represents high potential to achieve low power consumption and high performance gain.

  16. Experiments and numerical analysis of a control method for natural circulation through helium gas injection

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Tetsuaki, E-mail: ttakeda@yamanashi.ac.jp; Hatori, Hirofumi; Funatani, Shumpei

    2016-09-15

    This study investigated a control method for natural circulation of air by helium gas injection. A depressurization accident is a design-basis accident of a very high temperature reactor. When a primary pipe rupture accident occurs, air is expected to enter the reactor pressure vessel from the breach. Thus, in-core graphite structures are oxidized. In order to predict and analyze the phenomena of air ingress during a depressurization accident, numerical analysis was carried out using a one-dimensional (1D) analysis code and three-dimensional computational fluid dynamics (3D CFD). An experiment was carried out regarding natural circulation using a circular pipe consisting of a reverse U-shaped channel. The channel consisted of two vertical heated and cooled pipes. The temperature difference between the vertical pipes was maintained at 40–80 K, and a small amount of helium gas was injected into the channel. The injected volume of helium was about 3.1–12.5% of the total channel volume. After injecting helium gas, each component gas moved through molecular diffusion and very weak natural circulation. After approximately 1180 s, ordinary natural circulation of air was suddenly produced. The numerical results of the 3D CFD code were in good agreement with the experimental results. The numerical results also showed that the natural circulation of air can be controlled by helium gas injection.

  17. Evolution of dopant-induced helium nanoplasmas

    CERN Document Server

    Krishnan, S R; Fechner, L; Sharma, V; Kremer, M; Fischer, B; Camus, N; Pfeifer, T; Jha, J; Krishnamurthy, M; Schroeter, C -D; Ullrich, J; Stienkemeier, F; Moshammer, R; Fennel, Th; Mudrich, M

    2012-01-01

    Two-component nanoplasmas generated by strong-field ionization of doped helium nanodroplets are studied in a pump-probe experiment using few-cycle laser pulses in combination with molecular dynamics simulations. High yields of helium ions and a pronounced, droplet size-dependent resonance structure in the pump-probe transients reveal the evolution of the dopant-induced helium nanoplasma. The pump-probe dynamics is interpreted in terms of strong inner ionization by the pump pulse and resonant heating by the probe pulse which controls the final charge states detected via the frustration of electron-ion recombination.

  18. Particle detection by evaporation from superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.H. (Department of Physics, Brown University, Providence, Rhode Island 02912 (United States))

    1992-04-20

    We report the first experiments in which 5-MeV alpha particles are detected via evaporation from a bath of superfluid helium. The {alpha} excites phonons and rotons in the liquid helium, and these excitations are sufficiently energetic to evaporate helium atoms when they reach the free surface of the liquid. The approximate overall efficiency of this process has been determined, and we compare this with expectations. We have also been able to detect evaporation induced by a flux of {gamma}'s from a {sup 137}Cs source.

  19. A Temporal Locality-Aware Page-Mapped Flash Translation Layer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Youngjae [ORNL; Gupta, Aayush [IBM Corporation, Almaden Research Center; Urgaonkar, Bhuvan [Pennsylvania State University

    2013-01-01

    The poor performance of random writes has been a cause of major concern which needs to be addressed to better utilize the potential of flash in enterprise-scale environments. We examine one of the important causes of this poor performance: the design of the flash translation layer (FTL) which performs the virtual-to-physical address translations and hides the erase-before-write characteristics of flash. We propose a complete paradigm shift in the design of the core FTL engine from the existing techniques with our Demand-Based Flash Translation Layer (DFTL) which selectively caches page- level address mappings. Our experimental evaluation using FlashSim with realistic enterprise-scale workloads endorses the utility of DFTL in enterprise-scale storage systems by demonstrating: 1) improved performance, 2) reduced garbage collection overhead and 3) better overload behavior compared with hybrid FTL schemes which are the most popular implementation methods. For example, a predominantly random-write dominant I/O trace from an OLTP application running at a large financial institution shows a 78% improvement in average response time (due to a 3-fold reduction in operations of the garbage collector), compared with the hybrid FTL scheme. Even for the well-known read-dominant TPC-H benchmark, for which DFTL introduces additional overheads, we improve system response time by 56%. Moreover, interestingly, when write-back cache on DFTL-based SSD is enabled, DFTL even outperforms the page-based FTL scheme, improving their response time by 72% in Financial trace.

  20. Far-UV Spectroscopy of Two Extremely Hot, Helium-Rich White Dwarfs

    Science.gov (United States)

    Werner, K.; Rauch, T.; Kruk, J. W.

    2017-01-01

    A large proportion of hot post-asymptotic giant branch stars and white dwarfs (WDs) are hydrogen-deficient. Two distinct evolutionary sequences have been identified. One of them comprises stars of spectral type [WC] and PG1159, and it originates from a late helium-shell flash, creating helium-rich stellar atmospheres with significant admixtures of carbon (up to about 50, mass fraction). The other sequence comprises stars of spectral type O(He) and luminous subdwarf O stars which possibly are descendants of RCrB stars and extreme helium stars. Their carbon abundances are significantly lower (of the order of 1 or less) and it is thought that they originate from binary-star evolution (through merger or common-envelope evolution). Here we investigate two of the three hottest known helium-rich (DO) WDs (PG 1034+001 and PG 0038+199). They are the only ones for which spectra were recorded with the Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope, allowing a comprehensive ultraviolet spectral analysis. We find effective temperatures of T(eff) =115000 +/- 5000 K and 125000 +/- 5000 K, respectively, and a surface gravity of log g = 7 +/-0.5. In both stars, nitrogen is strongly oversolar while C and O are significantly subsolar. For all other assessed metals (Ne, Si, P, S, Ar, Fe, and Ni) we find abundances close to solar. We conclude that these WDs are immediate descendants of O(He) stars and, hence, result from close-binary evolution.

  1. Calculated Regenerator Performance at 4 K with HELIUM-4 and HELIUM-3

    Science.gov (United States)

    Radebaugh, Ray; Huang, Yonghua; O'Gallagher, Agnes; Gary, John

    2008-03-01

    The helium-4 working fluid in regenerative cryocoolers operating with the cold end near 4 K deviates considerably from an ideal gas. As a result, losses in the regenerator, given by the time-averaged enthalpy flux, are increased and are strong functions of the operating pressure and temperature. Helium-3, with its lower boiling point, behaves somewhat closer to an ideal gas in this low temperature range and can reduce the losses in 4 K regenerators. An analytical model is used to find the fluid properties that strongly influence the regenerator losses as well as the gross refrigeration power. The thermodynamic and transport properties of helium-3 were incorporated into the latest NIST regenerator numerical model, known as REGEN3.3, which was used to model regenerator performance with either helium-4 or helium-3. With this model we show how the use of helium-3 in place of helium-4 can improve the performance of 4 K regenerative cryocoolers. The effects of operating pressure, warm-end temperature, and frequency on regenerators with helium-4 and helium-3 are investigated and compared. The results are used to find optimum operating conditions. The frequency range investigated varies from 1 Hz to 30 Hz, with particular emphasis on higher frequencies.

  2. Using GHz Flash ADCs at STACEE

    Science.gov (United States)

    Zweerink, Jeffrey

    2002-04-01

    The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) detects 50-500 GeV gamma rays by sampling the Cherenkov light wavefront generated as the gamma rays interact with the atmosphere. Using steerable heliostat mirrors and stationary secondary optics at the National Solar Thermal Test Facility in New Mexico, the Cherenkov light is recorded using fast electronics with good timing. One significant improvement of the full 64 channel STACEE detector over earlier prototypes is the addition of GHz flash ADCs on each channel. We are developing analysis techniques to extract timing and other pulse information from the flash ADCs in order to 1.) discriminate against the abundant cosmic ray background, and 2.) understand how well the shower direction and energy can be reconstructed. We describe the techniques and present results from data taken during the 2001-2002 observing season.

  3. Electrical Safety and Arc Flash Protections

    Energy Technology Data Exchange (ETDEWEB)

    R. Camp

    2008-03-04

    Over the past four years, the Electrical Safety Program at PPPL has evolved in addressing changing regulatory requirements and lessons learned from accident events, particularly in regards to arc flash hazards and implementing NFPA 70E requirements. This presentation will discuss PPPL's approaches to the areas of electrical hazards evaluation, both shock and arc flash; engineered solutions for hazards mitigation such as remote racking of medium voltage breakers, operational changes for hazards avoidance, targeted personnel training and hazard appropriate personal protective equipment. Practical solutions for nominal voltage identification and zero voltage checks for lockout/tagout will also be covered. Finally, we will review the value of a comprehensive electrical drawing program, employee attitudes expressed as a personal safety work ethic, integrated safety management, and sustained management support for continuous safety improvement.

  4. Direct flash steam geothermal power plant assessment

    Science.gov (United States)

    Alt, T. E.

    1982-01-01

    The objective was to analyze the capacity and availability factors of an operating direct flash geothermal power plant. System and component specifications, operating procedures, maintenance history, malfunctions, and outage rate are discussed. The plant studied was the 75 MW(e) geothermal power plant at Cerro Prieto, Mexico, for the years 1973 to 1979. To describe and assess the plant, the project staff reviewed documents, visited the plant, and met with staff of the operating utility. The high reliability and availability of the plant was documented and actions responsible for the good performance were identified and reported. The results are useful as guidance to US utilities considering use of hot water geothermal resources for power generation through a direct flash conversion cycle.

  5. ASACUSA Anti-protonic Helium_Final

    CERN Multimedia

    CERN Audiovisual Production Service; CERN AD; Paola Catapano; Julien Ordan, Arzur Catel; Paola Catapano; ASACUSA COLLABORATION

    2016-01-01

    Latest precision measurement of the mass of the proton and the anti proton though the production of antiprotonic helium by the ASACUSA experiment at CERN's antimatter factory, with a beam from the Antiproton Decelerator

  6. Charging dynamics of dopants in helium nanoplasmas

    OpenAIRE

    Heidenreich, Andreas; Grüner, Barbara; Schomas, Dominik; Stienkemeier, Frank; Krishnan, Siva Rama; Mudrich, Marcel

    2016-01-01

    We present a combined experimental and theoretical study of the charging dynamics of helium nanodroplets doped with atoms of different species and irradiated by intense near-infrared (NIR) laser pulses (

  7. Helium-Hydrogen Recovery System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Immense quantities of expensive liquefied helium are required at Stennis and Kennedy Space Centers for pre-cooling rocket engine propellant systems prior to filling...

  8. Primary helium heater for propellant pressurization systems

    Science.gov (United States)

    Reichmuth, D. M.; Nguyen, T. V.; Pieper, J. L.

    1991-01-01

    The primary helium heater is a unique design that provides direct heating of pressurant gas for large pressure fed propulsion systems. It has been conceptually designed to supply a heated (800-1000 R) pressurization gas to both a liquid oxygen and an RP-1 propellant tank. This pressurization gas is generated within the heater by mixing super critical helium (40-300 R and 3000-1600 psi) with an appropriate amount of combustion products from a 4:1 throttling stoichiometric LO2/LH2 combustor. This simple, low cost and reliable mixer utilizes the large quantity of helium to provide stoichiometric combustor cooling, extend the throttling limits and enhance the combustion stability margin. Preliminary combustion, thermal, and CFD analyses confirm that this low-pressure-drop direct helium heater can provide the constant-temperature pressurant suitable for tank pressurization of both fuel and oxidizer tanks of large pressure fed vehicles.

  9. Helium liquefier cycles with saturated vapor compression

    Science.gov (United States)

    Minta, M.; Smith, J. L., Jr.

    The three refrigeration stages of the conventional helium liquefaction cycle are related to liquid nitrogen precooling, the use of expansion engines, and a J-T expansion. For an operation of helium refrigerators at temperatures below 4.2 K reduced pressure levels are required. Such an operation makes it necessary to enhance the compressor size and the heat exchanger surface area. In the case of 1.8 K refrigerators, practical cycles with three pressure levels are employed. It is pointed out that the saturated-vapor-compression (SVC) helium cycle provides an alternative solution to these problems. The present investigation is concerned with the design study of a SVC helium liquifier operating at elevated pressures. The study was conducted to demonstrate the potential of the SVC cycle on the basis of a direct comparison with a conventional cycle using the same precooling expanders and a supercritical wet expander instead of a J-T valve.

  10. How to give a science flash talk

    DEFF Research Database (Denmark)

    Veldhuis, Djuke

    2015-01-01

    Whether you are applying for funding, telling a family member about your research or engaging the public, your success will depend on how well you communicate. Persuading people that your research should be prioritised and funded relies on being a solid negotiator and developing political nous; b......; but these skills are also rooted in communication. One way to do this is by challenging yourself to summarise your research in a short, sharp, three-minute elevator pitch, or ‘flash talk’....

  11. Flash CS3 The Missing Manual

    CERN Document Server

    Grover, Chris

    2008-01-01

    Flash CS3, the latest version of the premier tool for creating web animations and interactive web sites, can be intimidating to learn. This entertaining reference tutorial provides a reader-friendly animation primer and a guided tour of all the program's tools and capabilities. Beginners will learn to use the software in no time, and experienced users will quickly take their skills to the next level.

  12. Mechanisms of Flash Sintering in Cubic Zirconia

    OpenAIRE

    Downs, John Axel

    2013-01-01

    The recently discovered flash sintering technique has shown that the application of a sufficiently large dc electric field (E-field) to a ceramic during sintering can cause sintering at temperatures several hundred degrees below conventional temperatures with sintering rates that allow for sintering in seconds rather than hours. This technique has already been demonstrated in wide range of ceramic materials including ionic conductors, electronic conductors, semi-conductors and insulators. Th...

  13. Advances in flash flood monitoring using UAVs

    Science.gov (United States)

    Perks, Matthew; Russell, Andrew; Large, Andrew

    2016-04-01

    UAVs have the potential to capture information about the earth's surface in dangerous and previously inaccessible locations. Through image acquisition of flash flood events and subsequent object-based analysis, highly dynamic and oft-immeasurable hydraulic phenomenon may be quantified at previously unattainable spatial and temporal resolutions. The potential for this approach to provide valuable information about the hydraulic conditions present during dynamic, high-energy flash floods has until now not been explored. In this paper we adopt a novel approach, utilising the Kande-Lucas-Tomasi (KLT) algorithm to track features present on the water surface which are related to the free-surface velocity. Following the successful tracking of features, a method analogous to the vector correction method has enabled accurate geometric rectification of velocity vectors. Uncertainties associated with the rectification process induced by unsteady camera movements are subsequently explored. Geo-registration errors are relatively stable and occur as a result of persistent residual distortion effects following image correction. The apparent ground movement of immobile control points between measurement intervals ranges from 0.05 - 0.13m. The application of this approach to assess the hydraulic conditions present in Alyth Burn, Scotland during a 1:200 year flash flood resulted in the generation of an average 4.2 measurements/m2 at a rate of 508 measurements/s. Analysis of these vectors provide a rare insight into the complexity of channel-overbank interactions during flash floods. The uncertainty attached to the calculated velocities is relatively low with a spatial average across the area of ± 0.15m/s. Little difference is observed in the uncertainty attached to out-of-bank velocities (± 0.15m/s), and within-channel velocities (± 0.16m/s), illustrating the consistency of the approach.

  14. Membuat Game Kuis Menggunakan Macromedia Flash 8

    OpenAIRE

    Lumban Gaol, Cindi N

    2016-01-01

    In the final project , the author makes an application quiz games . This application is a medium of learning that helps students to study for a quiz pep contained in this application relate to the lessons in school . Methods and design a quiz game designed by using software Macromedia Flash 8 as the programming language , script editor program , and is also used to design this application . This study was made aiming to broaden how to create a quiz game simple one. Word Keys : Mac...

  15. Magnesia-Chrome Refractories for Flash Furnace

    Institute of Scientific and Technical Information of China (English)

    LI Yong; CHEN Kaixian; LU Xinghua; LIU Jianlong; SUN Jialin; HONG Yanruo

    2002-01-01

    The rapid development of our country's heavy nonferrous metallurgical technology and the revolution in new type of heavynon-ferrous metallurgical furnace have imposed more critical demand on the refractory materials ,i. e. high quality and long service life. This paper presents the domestic status of the refractories for flash furnace , briefly describes the wear of the refractory used , and it is considered that the domestic in refractories for flashfurnace can be surely realized.

  16. Helium behaviour in implanted boron carbide

    Directory of Open Access Journals (Sweden)

    Motte Vianney

    2015-01-01

    Full Text Available When boron carbide is used as a neutron absorber in nuclear power plants, large quantities of helium are produced. To simulate the gas behaviour, helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 °C in order to observe the influence of temperature and duration of annealing. The determination of the helium diffusion coefficient was carried out using the 3He(d,p4He nuclear reaction (NRA method. From the evolution of the width of implanted 3He helium profiles (fluence 1 × 1015/cm2, 3 MeV corresponding to a maximum helium concentration of about 1020/cm3 as a function of annealing temperatures, an Arrhenius diagram was plotted and an apparent diffusion coefficient was deduced (Ea = 0.52 ± 0.11 eV/atom. The dynamic of helium clusters was observed by transmission electron microscopy (TEM of samples implanted with 1.5 × 1016/cm2, 2.8 to 3 MeV 4He ions, leading to an implanted slab about 1 μm wide with a maximum helium concentration of about 1021/cm3. After annealing at 900 °C and 1100 °C, small (5–20 nm flat oriented bubbles appeared in the grain, then at the grain boundaries. At 1500 °C, due to long-range diffusion, intra-granular bubbles were no longer observed; helium segregates at the grain boundaries, either as bubbles or inducing grain boundaries opening.

  17. Multiple Population Theory: Extreme helium population problem

    OpenAIRE

    Yi, Sukyoung K.

    2009-01-01

    The spreads in chemical abundances inferred by recent precision observations suggest that some or possibly all globular clusters can no longer be considered as simple stellar populations. The most striking case is omega Cen in the sense that its bluest main-sequence despite its high metallicity demands an extreme helium abundance of Y > 0.4. I focus on this issue of "the extreme helium population problem" in this review.

  18. Cosmogenic helium in a terrestrial igneous rock

    Science.gov (United States)

    Kurz, M. D.

    1986-01-01

    New helium isotopic measurements on samples from the Kula formation of Haleakala volcano of Hawaii are presented that are best explained by an in situ cosmogenic origin for a significant fraction of the He-3. Results from crushing and stepwise heating experiments, and consideration of the exposure age of the sample at the surface and the cosmic ray fluxes strongly support this hypothesis. Although crustal cosmogenic helium has been proposed previously, this represents its first unambiguous identification in a terrestrial sample.

  19. Effects of helium impurities on superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Selle, J.E.

    1977-07-01

    A review of the literature on the effects of helium impurities on superalloys at elevated temperatures was undertaken. The actual effects of these impurities vary depending on the alloy, composition of the gas atmosphere, and temperature. In general, exposure in helium produces significant but not catastrophic changes in the structure and properties of the alloys. The effects of these treatments on the structure, creep, fatigue, and mechanical properties of the various alloys are reviewed and discussed. Suggestions for future work are presented.

  20. Helium Reionization in From New Sightlines

    Science.gov (United States)

    Syphers, David

    2017-01-01

    A very small number of sightlines to z~3 quasars have been studied in detail to show the progress of helium reionization. Although studying the same sightlines with each new UV spectrograph lead to a better understanding of them, the sightline variance is very strong during this patchy and extended process. We discuss detailed R>10,000 COS data from new sightlines, and what they reveal about the progress and end of helium reionization.

  1. A Comparative Study of Reduced Variables Based Flash and Conventional Flash

    DEFF Research Database (Denmark)

    Michelsen, Michael Locht; Yan, Wei; Stenby, Erling Halfdan

    Speeding up flash calculation is a central issue in compositional reservoir simulations since phase equilibrium calculation is the most time-consuming part in those simulations. The reduced variables methods, or the reduction methods, reformulate the original phase equilibrium problem with a smal......Speeding up flash calculation is a central issue in compositional reservoir simulations since phase equilibrium calculation is the most time-consuming part in those simulations. The reduced variables methods, or the reduction methods, reformulate the original phase equilibrium problem....... Most of the studies in the last decade suggest that the reduced variables methods are much more efficient than the conventional flash method. However, Haugen and Beckner questioned the advantages of the reduced variables methods in their recent paper (SPE 141399). A fair comparison between the reduced...... variables based flash and the conventional flash is not straightforward since the former is difficult to be formulated as unconstrained minimization and involves more complicated composition derivatives. With the recent formulations by Nichita and Graciaa (2010), it is possible to code the reduced variables...

  2. Extreme flash floods in Barcelona County

    Directory of Open Access Journals (Sweden)

    A. Barrera

    2005-01-01

    Full Text Available In this paper the catastrophic and extraordinary floods occurring in Barcelona County (Catalonia, NE Spain are studied, in order to characterise the temporal evolution of extreme flash floods in that area and their main features. These events usually cause economical losses and major problems for undertaking daily activity in Barcelona city. This kind of floods is a very common feature in the North-east of Spain and they are recorded every year in some point of Catalonia. This contribution also shows the frequency of those events, within the framework of all the floods that have occurred in Barcelona since the 14th century, but also describes the flooded area, urban evolution, impacts and the weather conditions for any of most severe events. The evolution of flood occurrence shows the existence of oscillations in the earlier and later modern age periods that can be attributed to climatic variability, evolution of the perception threshold and changes in vulnerability. A great increase of vulnerability can be assumed for the period 1850-1900. The analysis of the time evolution for the Barcelona rainfall series (1854-2000 shows that no trend exists, although, due to the changes in urban planning, flash-floods impact has changed over this time. The number of catastrophic flash floods has diminished, although the extraordinary ones have increased.

  3. A revaluation of helium/dpa ratios for fast reactor and thermal reactor data in fission-fusion correlations

    Energy Technology Data Exchange (ETDEWEB)

    Garner, F.A.; Greenwood, L.R. [Pacific Northwest National Lab., Richland, WA (United States); Oliver, B.M.

    1996-10-01

    For many years it has been accepted that significant differences exist in the helium/dpa ratios produced in fast reactors and various proposed fusion energy devices. In general, the differences arise from the much larger rate of (n,{alpha}) threshold reactions occurring in fusion devices, reactions which occur for energies {ge} 6 MeV. It now appears, however, that for nickel-containing alloys in fast reactors the difference may not have been as large as was originally anticipated. In stainless steels that have a very long incubation period for swelling, for instance, the average helium concentration over the duration of the transient regime have been demonstrated in an earlier paper to be much larger in the FFTF out-of-core regions than first calculated. The helium/dpa ratios in some experiments conducted near the core edge or just outside of the FFTF core actually increase strongly throughout the irradiation, as {sup 59}Ni slowly forms by transmutation of {sup 58}Ni. This highly exothermic {sup 59}Ni(n,{alpha}) reaction occurs in all fast reactors, but is stronger in the softer spectra of oxide-fueled cores such as FFTF and weaker in the harder spectra of metal-fueled cores such as EBR-II. The formation of {sup 59}Ni also increases strongly in out-of-core unfueled regions where the reactor spectra softens with distance from the core.

  4. Proteomics Core

    Data.gov (United States)

    Federal Laboratory Consortium — Proteomics Core is the central resource for mass spectrometry based proteomics within the NHLBI. The Core staff help collaborators design proteomics experiments in a...

  5. Proteomics Core

    Data.gov (United States)

    Federal Laboratory Consortium — Proteomics Core is the central resource for mass spectrometry based proteomics within the NHLBI. The Core staff help collaborators design proteomics experiments in...

  6. Pyridine Aggregation in Helium Nanodroplets

    Science.gov (United States)

    Nieto, Pablo; Poerschke, Torsten; Habig, Daniel; Schwaab, Gerhard; Havenith, Martina

    2012-06-01

    Pyridine crystals show the unusual property of isotopic polymorphism. Experimentally it has been observed that deuterated pyridine crystals exist in two phases while non-deuterated pyridine does not show a phase transition. Therefore, although isotopic substitution is the smallest possible modification of a molecule it greatly affects the stability of pyridine crystals. A possible experimental approach in order to understand this striking effect might be the study of pyridine aggregation for small clusters. By embedding the clusters in helium nanodroplets the aggregates can be stabilized and studied by means of Infrared Depletion Spectroscopy. Pyridine oligomers were investigated in the C-H asymmetric vibration region (2980-3100 cm-1) using this experimental technique. The number of molecules for the clusters responsibles for each band were determined by means of pick-up curves as well as mass sensitive depletion spectra. Furthermore, the intensity dependence of the different bands on applying a dc electric field was studied. The assignment of the different structures for pyridine clusters on the basis of these measurements were also carried out. S. Crawford et al., Angew. Chem. Int. Ed., 48, 755 (2009).

  7. Photoionization rates for helium: update

    CERN Document Server

    Sokół, Justyna M

    2014-01-01

    The NIS He gas has been observed at a few AU to the Sun almost from the beginning of the space age. To model its flow an estimate of the loss rates due to ionization by solar extreme-ultraviolet (EUV) flux is needed. The EUV irradiance has been measured directly from mid 1990-ties, but with high temporal and spectral resolution only from 2002. Beforehand only EUV proxies are available. A new method of reconstruction of the Carrington rotation averaged photoionization rates for neutral interstellar helium (NIS He) in the ecliptic at 1 AU to the Sun before 2002 is presented. We investigate the relation between the solar rotation averaged time series of the ionization rates for NIS He at 1 AU derived from TIMED measurements of EUV irradiance and the solar 10.7 cm flux (F10.7) only. We perform a weighted iterative fit of a nonlinear model to data split into sectors. The obtained formula allows to reconstruct the solar rotation averages of photoionization rates for He between ~1947 and 2002 with an uncertainty ran...

  8. Helium and Neon in Comets

    Science.gov (United States)

    Jewitt, David

    1996-01-01

    Two comets were observed with EUVE in late 1994. Both comet Mueller and comet Borrelly are short-period comets having well established orbital elements and accurate ephemerides. Spectra of 40 ksec were taken of each. No evidence for emission lines from either Helium or Neon was detected. We calculated limits on the production rates of these atoms (relative to solar) assuming a standard isotropic outflow model, with a gas streaming speed of 1 km/s. The 3-sigma (99.7% confidence) limits (1/100,000 for He, 0.8 for Ne) are based on a conservative estimate of the noise in the EUVE spectra. They are also weakly dependent on the precise pointing and tracking of the EUVE field of view relative to the comet during the integrations. These limits are consistent with ice formation temperatures T greater than or equal to 30 K, as judged from the gas trapping experiments of Bar-Nun. For comparison, the solar abundances of these elements are He/O = 110, Ne/O = 1/16. Neither limit was as constraining as we had initially hoped, mainly because comets Mueller and Borrelly were intrinsically less active than anticipated.

  9. Stopping power of 1.0-3.0 MeV helium in Mylar, Makrofol and Kapton foils

    CERN Document Server

    Chekirine, M

    1999-01-01

    The stopping powers of 1.0-3.0 MeV of helium ( sup 4 He) in Makrofol KG, Mylar and Kapton were measured. The results were compared with scanty experimental data in the literature and with values predicted by both Bragg's rule and cores-and-bonds model. These values agree with each other within the uncertainties; maximum deviations are <5%.

  10. Neoclassical flows in deuterium-helium plasma density pedestals

    CERN Document Server

    Buller, Stefan; Newton, Sarah; Omotani, John

    2016-01-01

    In tokamak transport barriers, the radial scale of profile variations can be comparable to a typical ion orbit width, which makes the coupling of the distribution function across flux surfaces important in the collisional dynamics. We use the radially global steady-state neoclassical {\\delta}f code Perfect to calculate poloidal and toroidal flows, and radial fluxes, in the pedestal. In particular, we have studied the changes in these quantities as the plasma composition is changed from a deuterium bulk species with a helium impurity to a helium bulk with a deuterium impurity, under specific profile similarity assumptions. The poloidally resolved radial fluxes are not divergence-free in isolation in the presence of sharp radial profile variations, which leads to the appearance of poloidal return-flows. These flows exhibit a complex radial-poloidal structure that extends several orbit widths into the core and is sensitive to abrupt radial changes in the ion temperature gradient. We find that a sizable neoclassi...

  11. Flash memories economic principles of performance, cost and reliability optimization

    CERN Document Server

    Richter, Detlev

    2014-01-01

    The subject of this book is to introduce a model-based quantitative performance indicator methodology applicable for performance, cost and reliability optimization of non-volatile memories. The complex example of flash memories is used to introduce and apply the methodology. It has been developed by the author based on an industrial 2-bit to 4-bit per cell flash development project. For the first time, design and cost aspects of 3D integration of flash memory are treated in this book. Cell, array, performance and reliability effects of flash memories are introduced and analyzed. Key performance parameters are derived to handle the flash complexity. A performance and array memory model is developed and a set of performance indicators characterizing architecture, cost and durability is defined.   Flash memories are selected to apply the Performance Indicator Methodology to quantify design and technology innovation. A graphical representation based on trend lines is introduced to support a requirement based pr...

  12. Modeling on Flash Flood Disaster Induced by Bed Load

    Institute of Scientific and Technical Information of China (English)

    CAO Shuyou; LIU Xingnian; HUANG Er; YANG Keiun

    2008-01-01

    Flash floods result from a complex interaction among hydro-meteorological, hydrologi-cal, and hydraulic processes across various spatial and temporal scales. Sichuan Province suffers flash floods frequently owing to mountain weather and topography. A flash flood and gravel bed load transport are two key relative problems in mountain river engineering. Bed materials are often encountered in alternate scouring and deposition in mountain fluvial processes during a flash flood.In this circumstance, CRS-1 bed load numerical model jointly with scale physical model is em-ployed to predict water level and gravel bed scour and deposition for design of flood control dykes and flash flood disaster mitigation. A case study on the mechanism of a flash flood disaster in-duced by bed load transport for a hydropower station in Sichuan Province is conducted. Finally,suggestions to protect the hydropower station are proposed.

  13. Onset conditions for flash sintering of UO2

    Science.gov (United States)

    Raftery, Alicia M.; Pereira da Silva, João Gustavo; Byler, Darrin D.; Andersson, David A.; Uberuaga, Blas P.; Stanek, Christopher R.; McClellan, Kenneth J.

    2017-09-01

    In this work, flash sintering was demonstrated on stoichiometric and non-stoichiometric uranium dioxide pellets at temperatures ranging from room temperature (26 °C) up to 600 °C . The onset conditions for flash sintering were determined for three stoichiometries (UO2.00, UO2.08, and UO2.16) and analyzed against an established thermal runaway model. The presence of excess oxygen was found to enhance the flash sintering onset behavior of uranium dioxide, lowering the field required to flash and shortening the time required for a flash to occur. The results from this study highlight the effect of stoichiometry on the flash sintering behavior of uranium dioxide and will serve as the foundation for future studies on this material.

  14. Effect of dislocations on helium retention in deformed pure iron

    Science.gov (United States)

    Gong, Y. H.; Cao, X. Z.; Jin, S. X.; Lu, E. Y.; Hu, Y. C.; Zhu, T.; Kuang, P.; Xu, Q.; Wang, B. Y.

    2016-12-01

    The effects of dislocations created by deformation on helium retention in pure iron, including the helium atoms diffusion along the dislocation line and desorption from dislocation trapping sites, were investigated. The dislocation defect was introduced in specimens by cold-rolling, and then 5 keV helium ions were implanted into the deformed specimens. Slow positron beam technology and thermal desorption spectroscopy were used to investigate the evolution of dislocation defects and the desorption behavior of helium atoms under influence of dislocation. The behaviors of S-E, W-E and S-W plots indicate clearly that lots of helium atoms remain in the deformed specimen and helium atoms combining with dislocation change the distribution of electron density. The helium desorption plot indicates that dislocation accelerates helium desorption at 293 K-600 K and facilitates helium dissociation from HenVm (n/m = 1.8) cluster.

  15. Operational flash flood forecasting platform based on grid technology

    Science.gov (United States)

    Thierion, V.; Ayral, P.-A.; Angelini, V.; Sauvagnargues-Lesage, S.; Nativi, S.; Payrastre, O.

    2009-04-01

    effort in term of grid technology development. This paper presents an operational flash flood forecasting platform which have been developed in the framework of CYCLOPS European project providing one of virtual organizations of EGEE project. This platform has been designed to enable multi-simulations processes to ease forecasting operations of several supervised watersheds on Grand Delta (SPC-GD) territory. Grid technology infrastructure, in providing multiple remote computing elements enables the processing of multiple rainfall scenarios, derived to the original meteorological forecasting transmitted by Meteo-France, and their respective hydrological simulations. First results show that from one forecasting scenario, this new presented approach can permit simulations of more than 200 different scenarios to support forecasters in their aforesaid mission and appears as an efficient hydrological decision-making tool. Although, this system seems operational, model validity has to be confirmed. So, further researches are necessary to improve models core to be more efficient in term of hydrological aspects. Finally, this platform could be an efficient tool for developing others modelling aspects as calibration or data assimilation in real time processing.

  16. Nucleosynthesis in helium-enriched asymptotic giant branch models: Implications for Heavy Element Enrichment in Omega Centauri

    CERN Document Server

    Karakas, Amanda I; Nataf, David M

    2014-01-01

    We investigate the effect of helium enrichment on the evolution and nucleosynthesis of low-mass asymptotic giant branch (AGB) stars of 1.7Msun and 2.36Msun with a metallicity of Z=0.0006 ([Fe/H] = -1.4). We calculate evolutionary sequences with the primordial helium abundance (Y = 0.24) and with helium-enriched compositions (Y = 0.30, 0.35, 0.40). For comparison we calculate models of the same mass but at a lower metallicity Z=0.0003 ([Fe/H] = -1.8) with Y=0.24. Post-processing nucleosynthesis calculations are performed on each of the evolutionary sequences to determine the production of elements from hydrogen through to bismuth. Elemental surface abundance predictions and stellar yields are presented for each model. The models with enriched helium have shorter main sequence and AGB lifetimes, and enter the AGB with a more massive hydrogen exhausted core than the primordial helium model. The main consequences are 1) low-mass AGB models with enhanced helium will evolve more than twice as fast, giving them the ...

  17. Multi-channel analyzer controlled by applet and flash

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Both java applet and flash were applied to emulate virtual panel of multi-channel pulse height analyzer (MCA), and Microsoft IE browser was used to control MCA through internet to measure the γ-ray energy spectrum of 137Cs. It Was shown that most of the work completed by applet can be done by flash too, and with flash, more beautiful panel of the remote controlled instruments can be easily designed.

  18. Multi—channel analyzer controlled by applet and flash

    Institute of Scientific and Technical Information of China (English)

    HUANGWen-Da

    2002-01-01

    Both java applet and flash were applied to emulate virtual panel of multi-channel pulse height analyzer(MCA),and Microsoft IE browser was used to control MCA through internet to measure the γ-ray energy spectrum of 137Cs.It was shown that most of the work completed by applet can be done by flash too,and with flash,more beautiful panel of the remote controlled instruments can be easily designed.

  19. Solid helium, a superfluid?; L'helium solide, un superfluide?

    Energy Technology Data Exchange (ETDEWEB)

    Balibar, S. [Centre National de la Recherche Scientifique (CNRS), Lab. de Physique Statistique de l' Ecole Normale Superieure, 75 - Paris (France)

    2007-06-15

    At very low temperature, liquid helium becomes superfluid, meaning that it can flow practically without any friction. But what about solid helium? A recent experiment carried out at the Ecole Normale Superieure of Paris (France) has given amazing results: in some conditions some matter can flow through helium without friction. This article makes a synthesis of the experiments carried out on solid helium since the end of the 1960's and which have tried to explain this 'super-solidity' effect. The recent results indicate that the super-solidity of solid helium is linked to its disorder and probably localized at the grain joints, but is not a fundamental property of its crystalline state. (J.S.)

  20. On the occurrence and detectability of Bose-Einstein condensation in helium white dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, O.G.; Vito, M.A. De, E-mail: obenvenu@fcaglp.unlp.edu.ar, E-mail: adevito@fcaglp.unlp.edu.ar [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, B1900FWA, La Plata (Argentina); Instituto de Astrofísica de La Plata, IALP, CCT-CONICET-UNLP (Argentina)

    2011-02-01

    It has been recently proposed that helium white dwarfs may provide promising conditions for the occurrence of the Bose-Einstein condensation. The argument supporting this expectation is that in some conditions attained in the core of these objects, the typical De Broglie wavelength associated with helium nuclei is of the order of the mean distance between neighboring nuclei. In these conditions the system should depart from classical behavior showing quantum effects. As helium nuclei are bosons, they are expected to condense. In order to explore the possibility of detecting the Bose-Einstein condensation in the evolution of helium white dwarfs we have computed a set of models for a variety of stellar masses and values of the condensation temperature. We do not perform a detailed treatment of the condensation process but mimic it by suppressing the nuclei contribution to the equation of state by applying an adequate function. As the cooling of white dwarfs depends on average properties of the whole stellar interior, this procedure should be suitable for exploring the departure of the cooling process from that predicted by the standard treatment. We find that the Bose-Einstein condensation has noticeable, but not dramatic effects on the cooling process only for the most massive white dwarfs compatible with a helium dominated interior ( ≈ 0.50M{sub s}un) and very low luminosities (say, Log(L/L{sub s}un) < −4.0). These facts lead us to conclude that it seems extremely difficult to find observable signals of the Bose-Einstein condensation. Recently, it has been suggested that the population of helium white dwarfs detected in the globular cluster NGC 6397 is a good candidate for detecting signals of the Bose-Einstein condensation. We find that these stars have masses too low and are too bright to have an already condensed interior.

  1. Full Scale Thermo-hydraulic Simulation of a Helium-Helium Printed Circuit Heat Exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Injun; Hong, Sungyull; Bai, Cheolho; Shim, Jaesool [Yeungnam Univ., Gyeongsan (Korea, Republic of); Kim, Chansoo; Hong, Sungdeok; Kim, Minhwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    In this paper, the thermo-hydraulic full scale simulation is performed to study the temperature distributions, thermal stress, pressure drop and outlet temperature in a Helium-Helium printed circuit heat exchanger (PCHE) in a VHTR simulate helium loop. The entire PCHE is composed of 40 stacks of rectangular shaped micro-channels for helium gas [type A] (inlet temperature, 400 .deg. C) and 40 stacks of semi-ellipse shaped micro-channels for helium [type B] (inlet temperature, 300 .deg. C). The experimental result is compared to that of computer simulation, COMSOL multi-physics software. The Helium-Helium PCHE is considered a prototype of the newly developed PCHE by Korea Atomic Energy Research Institute (KAERI). The full scale thermo-hydraulic simulation was successfully performed to obtain temperature distribution, pressure drop and thermal stress in 40 sets of flow channel stacks in a helium-helium printed circuit heat exchanger in a VHTR simulate helium loop. We obtained a quite similar temperature distribution with the 3D measured infrared temperature distribution. To our knowledge, this is the first full scale numerical study on the PCHE, which considers all microchannels, that the convection effect on the outside surfaces of the PCHE is applied. The very high-temperature reactor (VHTR) or high-temperature gas-cooled reactor(HTGR) is a fourth-generation nuclear power reactor that uses the ceramic coated fuel, TRISO, in which the fission gas does not leak even at temperatures higher than 1600 .deg. C. The VHTR necessarily requires an intermediate loop composed of a hot gas duct (HGD), an intermediate heat exchanger (IHX) and a process heat exchanger (PHE). The IHX is one of the important components of VHTR system because the IHX transfers the 950 .deg. C of high temperature massive heat to a hydrogen production plant or power conversion unit at high system pressure.

  2. The echo-enabled harmonic generation options for FLASH II

    CERN Document Server

    Deng, Haixiao; Faatz, Bart

    2011-01-01

    FLASH II is an upgrade to the existing free electron laser (FEL) FLASH. The echo-enabled harmonic generation (EEHG) scheme is proposed to be a potential seeding option of FLASH II. In this paper, the possibility of EEHG operation of FLASH II is investigated for the first time. With a combination of existing numerical codes, i.e. a laser-beam interaction code in an undulator (LBICU), a beam tracking code in a chicane (ELEGANT) and an universal FEL simulating code (GENESIS), the effects of beam energy chirp and coherent synchrotron radiation (CSR) on EEHG operation are studied as well. In addition, several interesting issues concerning EEHG simulation are discussed.

  3. Flash CS5.5 The Missing Manual

    CERN Document Server

    Grover, Chris

    2011-01-01

    You can build everything from simple animations to full-fledged iOS and Android apps with Flash CS5.5, but learning this complex program can be difficult-unless you have this fully updated, bestselling guide. Learn how to create gorgeous Flash effects even if you have no programming experience. With Flash CS5.5: The Missing Manual, you'll move from the basics to power-user tools with ease. Learn animation basics. Discover how to turn simple ideas into stunning animations.Master Flash's tools. Learn the animation and effects tools with clear explanations and hands-on examples.Use 3D effects. R

  4. Thermal Performance of the XRS Helium Insert

    Science.gov (United States)

    Breon, Susan R.; DiPirro, Michael J.; Tuttle, James G.; Shirron, Peter J.; Warner, Brent A.; Boyle, Robert F.; Canavan, Edgar R.

    1999-01-01

    The X-Ray Spectrometer (XRS) is an instrument on the Japanese Astro-E satellite, scheduled for launch early in the year 2000. The XRS Helium Insert comprises a superfluid helium cryostat, an Adiabatic Demagnetization Refrigerator (ADR), and the XRS calorimeters with their cold electronics. The calorimeters are capable of detecting X-rays over the energy range 0.1 to 10 keV with a resolution of 12 eV. The Helium Insert completed its performance and verification testing at Goddard in January 1999. It was shipped to Japan, where it has been integrated with the neon dewar built by Sumitomo Heavy Industries. The Helium Insert was given a challenging lifetime requirement of 2.0 years with a goal of 2.5 years. Based on the results of the thermal performance tests, the predicted on-orbit lifetime is 2.6 years with a margin of 30%. This is the result of both higher efficiency in the ADR cycle and the low temperature top-off, more than compensating for an increase in the parasitic heat load. This paper presents a summary of the key design features and the results of the thermal testing of the XRS Helium Insert.

  5. Helium release from radioisotope heat sources

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, D.E.; Early, J.W.; Starzynski, J.S.; Land, C.C.

    1984-05-01

    Diffusion of helium in /sup 238/PuO/sub 2/ fuel was characterized as a function of the heating rate and the fuel microstructure. The samples were thermally ramped in an induction furnace and the helium release rates measured with an automated mass spectrometer. The diffusion constants and activation energies were obtained from the data using a simple diffusion model. The release rates of helium were correlated with the fuel microstructure by metallographic examination of fuel samples. The release mechanism consists of four regimes, which are dependent upon the temperature. Initially, the release is controlled by movement of point defects combined with trapping along grain boundaries. This regime is followed by a process dominated by formation and growth of helium bubbles along grain boundaries. The third regime involves volume diffusion controlled by movement of oxygen vacancies. Finally, the release at the highest temperatures follows the diffusion rate of intragranular bubbles. The tendency for helium to be trapped within the grain boundaries diminishes with small grain sizes, slow thermal pulses, and older fuel.

  6. Optical and Electron Spin Resonance Studies of Destruction of Porous Structures Formed by Nitrogen-Rare Gas Nanoclusters in Bulk Superfluid Helium

    Science.gov (United States)

    McColgan, Patrick T.; Meraki, Adil; Boltnev, Roman E.; Lee, David M.; Khmelenko, Vladimir V.

    2016-11-01

    We studied optical and electron spin resonance spectra during destruction of porous structures formed by nitrogen-rare gas (RG) nanoclusters in bulk superfluid helium containing high concentrations of stabilized nitrogen atoms. Samples were created by injecting products of a radio frequency discharge of nitrogen-rare gas-helium gas mixtures into bulk superfluid helium. These samples have a high energy density allowing the study of energy release in chemical processes inside of nanocluster aggregates. The rare gases used in the studies were neon, argon, and krypton. We also studied the effects of changing the relative concentrations between nitrogen and rare gas on thermoluminescence spectra during destruction of the samples. At the beginning of the destructions, α -group of nitrogen atoms, Vegard-Kaplan bands of N_2 molecules, and β -group of O atoms were observed. The final destruction of the samples were characterized by a series bright flashes. Spectra obtained during these flashes contain M- and β -bands of NO molecules, the intensities of which depend on the concentration of molecular nitrogen in the gas mixture as well as the type of rare gas present in the gas mixture.

  7. Laser Flash Photolysis Studies on Gallic Acid

    Institute of Scientific and Technical Information of China (English)

    ZHU Hong-Ping; ZHAO Hong-Wei; ZHANG Zhao-Xia; WANG Wen-Feng; YAO Si-De

    2006-01-01

    The transient species of gallic acid (GA) have been studied by 266 nm nanosecond laser flash photolysis in aqueous solution and acetonitrile. The intermediate with absorption at 320 nm was identified as excited triplet state (3GA*), the decay rates of which were obtained in aqueous solution and acetonitrile respectively. Energy transfer from 3GA* to β-carotene was observed and the energy transfer rate constant kent was determined to be 2.2 × 109 mol-1·L·s-1. GA underwent photoionization during photolysis and the quantum yield of photoionization was determined to be 0.12 at room temperature with KI as a reference.

  8. Animación con Flash

    OpenAIRE

    Agelet Ordobàs, Ferran; Villar Posada, Feliciano

    2009-01-01

    Flash es una aplicación informática producida por la empresa de software norteamericana Macromedia, que se utiliza principalmente para la generación de páginas web animadas e interactivas. Este programa se está convirtiendo en un estándar para la creación de contenidos animados y altamente interactivos para ser distribuidos en la Red. Este tutorial pretende recorrer el camino necesario para llegar a conocer las posibilidades de la aplicación sin experiencia previa. El usuario interesado tiene...

  9. 3D flash lidar imager onboard UAV

    Science.gov (United States)

    Zhou, Guoqing; Liu, Yilong; Yang, Jiazhi; Zhang, Rongting; Su, Chengjie; Shi, Yujun; Zhou, Xiang

    2014-11-01

    A new generation of flash LiDAR sensor called GLidar-I is presented in this paper. The GLidar-I has been being developed by Guilin University of Technology in cooperating with the Guilin Institute of Optical Communications. The GLidar-I consists of control and process system, transmitting system and receiving system. Each of components has been designed and implemented. The test, experiments and validation for each component have been conducted. The experimental results demonstrate that the researched and developed GLiDAR-I can effectively measure the distance about 13 m at the accuracy level about 11cm in lab.

  10. Influence of Pressure in Flash Sintering Technique

    Science.gov (United States)

    Pcheliakov, D. A.; Yurlova, M. S.; Grigoryev, E. G.; Olevsky, E. A.

    An innovative pressure-assisted flash-sintering technique has been developed to investigate the effect of pressure applied on microstructure and the sintering behavior of titanium dioxide. There are numerous applications for titanium dioxide in ceramics including microeletronics, glass ceramics, refractive materials, structural ceramics and titanium-containing ceramic materials and chemical intermediates. The traditional sintering of titanium dioxide usually requires several hours at over 1200 °C. The conducted research indicates that titanium dioxide can be sintered to full density in only a few seconds at 800-1000 °C, when subjected to a DC electrical field at a certain temperature moment.

  11. Flash ADC data processing with correlation coefficients

    Energy Technology Data Exchange (ETDEWEB)

    Blyth, D.; Gibson, M.; Mcfarland, D.; Comfort, J.R., E-mail: Joseph.Comfort@asu.edu

    2014-02-21

    The large growth of flash ADC techniques for processing signals, especially in applications of streaming data, raises issues such as data flow through an acquisition system, long-term storage, and greater complexity in data analysis. In addition, experiments that push the limits of sensitivity need to distinguish legitimate signals from noise. The use of correlation coefficients is examined to address these issues. They are found to be quite successful well into the noise region. The methods can also be extended to Field Programmable Gate Array modules for compressing the data flow and greatly enhancing the event rate capabilities.

  12. Helium Burning Reaction Rate Uncertainties and Consequences for Supernovae

    Science.gov (United States)

    Tur, C.; Heger, A.; Austin, S. M.

    2007-10-01

    The triple alpha and ^12C(,)^16O reaction rates determine the carbon to oxygen ratio at the completion of core helium burning in stars, which, in turn, influences the later stellar burning stages. We explored the dependence of massive star evolution and nucleosynthesis yields on the experimental uncertainties in the triple alpha rate (10 to 12%) and the ^12C(,)^16O rate (25 to 35%) using full stellar models followed to core collapse and including supernova explosion. The production factors of medium-weight elements obtained by using the Lodders (2003) solar abundances for the initial star composition, rather than the abundances of Anders & Grevesse (1989), provide a less stringent constraint on the ^12C(,)^16O rate. Variations within the current uncertainties in both reaction rates, however, induce significant changes in the central carbon abundance at core carbon ignition and in the mass of the supernova remnant. An experiment is being carried out by an NSCL/WMU collaboration to improve the accuracy of the triple alpha reaction rate.

  13. A GPU accelerated Barnes-Hut tree code for FLASH4

    Science.gov (United States)

    Lukat, Gunther; Banerjee, Robi

    2016-05-01

    We present a GPU accelerated CUDA-C implementation of the Barnes Hut (BH) tree code for calculating the gravitational potential on octree adaptive meshes. The tree code algorithm is implemented within the FLASH4 adaptive mesh refinement (AMR) code framework and therefore fully MPI parallel. We describe the algorithm and present test results that demonstrate its accuracy and performance in comparison to the algorithms available in the current FLASH4 version. We use a MacLaurin spheroid to test the accuracy of our new implementation and use spherical, collapsing cloud cores with effective AMR to carry out performance tests also in comparison with previous gravity solvers. Depending on the setup and the GPU/CPU ratio, we find a speedup for the gravity unit of at least a factor of 3 and up to 60 in comparison to the gravity solvers implemented in the FLASH4 code. We find an overall speedup factor for full simulations of at least factor 1.6 up to a factor of 10.

  14. A GPU accelerated Barnes-Hut Tree Code for FLASH4

    CERN Document Server

    Lukat, Gunther

    2016-01-01

    We present a GPU accelerated CUDA-C implementation of the Barnes Hut (BH) tree code for calculating the gravita- tional potential on octree adaptive meshes. The tree code algorithm is implemented within the FLASH4 adaptive mesh refinement (AMR) code framework and therefore fully MPI parallel. We describe the algorithm and present test results that demonstrate its accuracy and performance in comparison to the algorithms available in the current FLASH4 version. We use a MacLaurin spheroid to test the accuracy of our new implementation and use spherical, collapsing cloud cores with effective AMR to carry out performance tests also in comparison with previous gravity solvers. Depending on the setup and the GPU/CPU ratio, we find a speedup for the gravity unit of at least a factor of 3 and up to 60 in comparison to the gravity solvers implemented in the FLASH4 code. We find an overall speedup factor for full simulations of at least factor 1.6 up to a factor of 10

  15. The attentional modulation of the flash-lag effect

    Directory of Open Access Journals (Sweden)

    M.V.C. Baldo

    2002-08-01

    Full Text Available If a dot is flashed in perfect alignment with a pair of dots rotating around the visual fixation point, most observers perceive the rotating dots as being ahead of the flashing dot (flash-lag effect. This perceptual effect has been interpreted to result from the perceptual extrapolation of the moving dots, the differential visual latencies between flashing and moving stimuli, as well as the modulation of attentional mechanisms. Here we attempted to uncouple the attentional effects brought about by the spatial predictability of the flashing dot from the sensory effects dependent on its visual eccentricity. The stimulus was a pair of dots rotating clockwise around the fixation point. Another dot was flashed at either the upper right or the lower left of the visual field according to three separate blocked situations: fixed, alternate and random positions. Twenty-four participants had to judge, in all three situations, the location of the rotating dots in relation to the imaginary line connecting the flashing dot and the fixation point at the moment the dot was flashed. The flash-lag effect was observed in all three situations, and a clear influence of the spatial predictability of the flashing dot on the magnitude of the perceptual phenomenon was revealed, independently of sensory effects related to the eccentricity of the stimulus in the visual field. These findings are consistent with our proposal that, in addition to sensory factors, the attentional set modulates the magnitude of the differential latencies that give rise to the flash-lag phenomenon.

  16. Feasibility of lunar Helium-3 mining

    Science.gov (United States)

    Kleinschneider, Andreas; Van Overstraeten, Dmitry; Van der Reijnst, Roy; Van Hoorn, Niels; Lamers, Marvin; Hubert, Laurent; Dijk, Bert; Blangé, Joey; Hogeveen, Joel; De Boer, Lennaert; Noomen, Ron

    With fossil fuels running out and global energy demand increasing, the need for alternative energy sources is apparent. Nuclear fusion using Helium-3 may be a solution. Helium-3 is a rare isotope on Earth, but it is abundant on the Moon. Throughout the space community lunar Helium-3 is often cited as a major reason to return to the Moon. Despite the potential of lunar Helium-3 mining, little research has been conducted on a full end-to-end mission. This abstract presents the results of a feasibility study conducted by students from Delft University of Technology. The goal of the study was to assess whether a continuous end-to-end mission to mine Helium-3 on the Moon and return it to Earth is a viable option for the future energy market. The set requirements for the representative end-to-end mission were to provide 10% of the global energy demand in the year 2040. The mission elements have been selected with multiple trade-offs among both conservative and novel concepts. A mission architecture with multiple decoupled elements for each transportation segment (LEO, transfer, lunar surface) was found to be the best option. It was found that the most critical element is the lunar mining operation itself. To supply 10% of the global energy demand in 2040, 200 tons of Helium-3 would be required per year. The resulting regolith mining rate would be 630 tons per second, based on an optimistic concentration of 20 ppb Helium-3 in lunar regolith. Between 1,700 to 2,000 Helium-3 mining vehicles would be required, if using University of Wisconsin’s Mark III miner. The required heating power, if mining both day and night, would add up to 39 GW. The resulting power system mass for the lunar operations would be in the order of 60,000 to 200,000 tons. A fleet of three lunar ascent/descent vehicles and 22 continuous-thrust vehicles for orbit transfer would be required. The costs of the mission elements have been spread out over expected lifetimes. The resulting profits from Helium

  17. Primary neutral helium in the heliosphere

    CERN Document Server

    Mueller, Hans-Reinhard

    2012-01-01

    Two years of neutral measurements by IBEX-Lo have yielded several direct observations of interstellar neutral helium and oxygen during preferred viewing seasons. Besides the interstellar signal, there are indications of the presence of secondary neutral helium and oxygen created in the heliosphere. Detailed modeling of these particle species is necessary to connect the measured fluxes to the pristine local interstellar medium while accounting for loss and production of neutral particles during their path through the heliosphere. In this contribution, global heliosphere models are coupled to analytic calculations of neutral trajectories to obtain detailed estimates of the neutral distribution function of primary interstellar helium atoms in the heliosphere, in particular in the inner heliosphere.

  18. The muonic helium lamb shift experiment

    Energy Technology Data Exchange (ETDEWEB)

    Goetzfried, Johannes; Krauth, Julian [Max-Planck-Institute of Quantum Optics, Garching (Germany); Collaboration: CREMA collaboration

    2014-07-01

    Because of its high sensitivity on finite size effects of the nucleus, the measurement of the Lamb shift in exotic atoms has been on the wish-list of atomic and nuclear physics for a long time. Our previous experiment allowed to determine the proton radius with an order of magnitude higher precision compared to spectroscopic measurements of ordinary hydrogen. The successor experiment in muonic helium is currently performed at the Paul-Scherrer-Institute in Switzerland. Using a low energy muon beam line muons are stopped within low pressure helium gas, where exotic atoms are created. Here we measure the 2S-2P transition frequency of muonic helium illuminated by a pulsed TiSa-laser system pumped with a newly developed Yb-YAG thin disk laser. This measurement will ultimately improve the values of the charge radii of {sup 3}He{sup +} and {sup 4}He{sup +} by an order of magnitude.

  19. Helium corona-assisted air discharge

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Nan; Gao Lei; Ji Ailing; Cao Zexian [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-10-15

    Operation of atmospheric discharge of electronegative gases including air at low voltages yet without consuming any inert gas will enormously promote the application of non-thermal plasmas. By taking advantage of the low onset voltage for helium corona, air discharge was successfully launched at much reduced voltages with a needle-plate system partly contained in a helium-filled glass bulb--for a needle-plate distance of 12 mm, 1.0 kV suffices. Ultraviolet emission from helium corona facilitates the discharging of air, and the discharge current manifests distinct features such as relatively broad Trichel pulses in both half periods. This design allows safe and economic implementation of atmospheric discharge of electronegative gases, which will find a broad palette of applications in surface modification, plasma medicine and gas treatment, etc.

  20. Superfluid helium-4 in one dimensional channel

    Science.gov (United States)

    Kim, Duk Y.; Banavar, Samhita; Chan, Moses H. W.; Hayes, John; Sazio, Pier

    2013-03-01

    Superfluidity, as superconductivity, cannot exist in a strict one-dimensional system. However, the experiments employing porous media showed that superfluid helium can flow through the pores of nanometer size. Here we report a study of the flow of liquid helium through a single hollow glass fiber of 4 cm in length with an open id of 150 nm between 1.6 and 2.3 K. We found the superfluid transition temperature was suppressed in the hollow cylinder and that there is no flow above the transition. Critical velocity at temperature below the transition temperature was determined. Our results bear some similarity to that found by Savard et. al. studying the flow of helium through a nanohole in a silicon nitrite membrane. Experimental study at Penn State is supported by NSF Grants No. DMR 1103159.

  1. Catching proteins in liquid helium droplets

    CERN Document Server

    Kupser, Peter; Meijer, Gerard; von Helden, Gert

    2010-01-01

    An experimental approach is presented that allows for the incorporation of large mass/charge selected ions in liquid helium droplets. It is demonstrated that droplets can be efficiently doped with a mass/charge selected amino acid as well as with the much bigger m$\\approx$12 000 amu protein Cytochrome C in selected charge states. The sizes of the ion-doped droplets are determined via electrostatic deflection. Under the experimental conditions employed, the observed droplet sizes are very large and range, dependent on the incorporated ion, from 10$^{10}$ helium atoms for protonated Phenylalanine to 10$^{12}$ helium atoms for Cytochrome C. As a possible explanation, a simple model based on the size- and internal energy-dependence of the pickup efficiency is given.

  2. The formation of a helium white dwarf in a close binary system with diffusion

    Science.gov (United States)

    Benvenuto, O. G.; De Vito, M. A.

    2004-07-01

    We study the evolution of a system composed of a 1.4-Msolar neutron star and a normal, solar composition star of 2 Msolar in orbit with a period of 1 d. Calculations were performed employing the binary HYDRO code presented by Benvenuto & De Vito that handle the mass transfer rate in a fully implicit way. We then included the main standard physical ingredients together with the diffusion processes and a proper outer boundary condition. We have assumed fully non-conservative mass transfer episodes. In order to study the interplay of mass loss episodes and diffusion we considered evolutionary sequences with and without diffusion in which all Roche lobe overflows (RLOFs) produce mass transfer. Another two sequences in which thermonuclearly driven RLOFs were not allowed to drive mass transfer have been computed with and without diffusion. As far as we are aware, this study represents the first binary evolution calculations in which diffusion is considered. The system produces a helium white dwarf of ~0.21 Msolar in an orbit with a period of ~4.3 d for the four cases. We find that mass transfer episodes induced by hydrogen thermonuclear flashes drive a tiny amount of mass transfer. As diffusion produces stronger flashes, the amount of hydrogen-rich matter transferred is slightly higher than in the models without diffusion. We find that diffusion is the main agent in determining the evolutionary time-scale of low-mass white dwarfs even in the presence of mass transfer episodes.

  3. Synthesis of nanoparticles in helium droplets—A characterization comparing mass-spectra and electron microscopy data

    Energy Technology Data Exchange (ETDEWEB)

    Thaler, Philipp; Volk, Alexander; Lackner, Florian; Steurer, Johannes; Schnedlitz, Martin; Ernst, Wolfgang E., E-mail: wolfgang.ernst@tugraz.at [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz (Austria); Knez, Daniel; Haberfehlner, Georg [Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, TU Graz, Steyrergasse 17, A-8010 Graz (Austria)

    2015-10-07

    Micrometer sized helium droplets provide an extraordinary environment for the growth of nanoparticles. The method promises great potential for the preparation of core-shell particles as well as one-dimensional nanostructures, which agglomerate along quantum vortices, without involving solvents, ligands, or additives. Using a new apparatus, which enables us to record mass spectra of heavy dopant clusters (>10{sup 4} amu) and to produce samples for transmission electron microscopy simultaneously, we synthesize bare and bimetallic nanoparticles consisting of various materials (Au, Ni, Cr, and Ag). We present a systematical study of the growth process of clusters and nanoparticles inside the helium droplets, which can be described with a simple theoretical model.

  4. Scaling of triple differential cross-sections for asymmetric (, 2) process on helium isoelectronic ions by fast electrons

    Indian Academy of Sciences (India)

    M K Srivastava

    2005-01-01

    A simple scaling law is obtained for asymmetric (, 2) process on helium isoelectronic ions by fast electrons. It is based on treating the targets as having one active electron moving in the effective Coulomb field of the atomic core with an effective charge ' = − 5/8. This effective charge is also used in the description of the scattered and ejected electrons. The model has been tested against other available (, 2) results on helium in asymmetric geometry. The scaling law is found to work reasonably well for fast incident electrons and becomes increasingly accurate as target increases.

  5. Adsorption of Helium Atoms on Two-Dimensional Substrates

    Science.gov (United States)

    Burganova, Regina; Lysogorskiy, Yury; Nedopekin, Oleg; Tayurskii, Dmitrii

    2016-01-01

    The study of the adsorption phenomenon of helium began many decades ago with the discovery of graphite as a homogeneous substrate for the investigation of physically adsorbed monolayer films. In particular, helium monoatomic layers on graphite were found to exhibit a very rich phase diagram. In the present work we have investigated the adsorption phenomenon of helium atoms on graphene and silicene substrates by means of density functional theory with Born-Oppenheimer approximation. Helium-substrate and helium-helium interactions were considered from first principles. Vibrational properties of adsorbed monolayers have been used to explore the stability of the system. This approach reproduces results describing the stability of a helium monolayer on graphene calculated by quantum Monte Carlo (QMC) simulations for low and high coverage cases. However, for the moderate coverage value there is a discrepancy with QMC results due to the lack of helium zero point motion.

  6. A helium liquefier using three 4 k pulse tube cryocoolers

    Science.gov (United States)

    Wang, Chao; Oviedo, Abner

    2012-06-01

    We have developed a helium liquefier which can be used for recondensing/reliquefying helium vapor in a helium cryostat or liquefying helium gas in a storage dewar. The helium liquefier employs three 4 K pulse tube cryocoolers, Cryomech model PT415. Each PT415 has remote motor/rotary valve assembly to minimize vibration, providing ≥ 1.5W at 4.2K. The liquefier can liquefy room temperature helium gas with a liquefaction rate of 62 Liter/day. When installing it in the cryostat, it can recondense and reliquefy helium vapor with a rate of 78 L/day. The liquefier will be installed in a gravitational wave detector in Brazil to recondense/reliquefy the helium boil off from the cryostat.

  7. Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

    Institute of Scientific and Technical Information of China (English)

    SUN Tie-Ying; LONG Xing-Gui; WANG Jun; HOU Qing; WU Zhong-Cheng; PENG Shu-Ming; LUO Shun-Zhong

    2008-01-01

    Molecular dynamics simulations are performed to investigate the behaviour of helium atoms in titanium at a temperature of 300 K.The nucleation and growth of helium bubble has been simulated up to 50 helium atoms.The approach to simulate the bubble growth is to add helium atoms one by one to the bubble and let the system evolve.The titanium cohesion is based on the tight binding scheme derived from the embedded atom method,and the helium-titanium interaction is characterized by fitted potential in the form of a Lennard-Jones function.The pressure in small helium bubbles is approximately calculated.The simulation results show that the pressure will decrease with the increasing bubble size,while increase with the increasing helium atoms.An analytic function about the quantitative relationship of the pressure with the bubble size and number of helium atoms is also fitted.

  8. Adsorption of Helium Atoms on Two-Dimensional Substrates

    Science.gov (United States)

    Burganova, Regina; Lysogorskiy, Yury; Nedopekin, Oleg; Tayurskii, Dmitrii

    2016-12-01

    The study of the adsorption phenomenon of helium began many decades ago with the discovery of graphite as a homogeneous substrate for the investigation of physically adsorbed monolayer films. In particular, helium monoatomic layers on graphite were found to exhibit a very rich phase diagram. In the present work we have investigated the adsorption phenomenon of helium atoms on graphene and silicene substrates by means of density functional theory with Born-Oppenheimer approximation. Helium-substrate and helium-helium interactions were considered from first principles. Vibrational properties of adsorbed monolayers have been used to explore the stability of the system. This approach reproduces results describing the stability of a helium monolayer on graphene calculated by quantum Monte Carlo (QMC) simulations for low and high coverage cases. However, for the moderate coverage value there is a discrepancy with QMC results due to the lack of helium zero point motion.

  9. Flash Vacuum Pyrolysis - Techniques and Reactions.

    Science.gov (United States)

    Wentrup, Curt

    2017-07-04

    While pyrolysis reactions have been performed since ancient times and been crucial for the invention of several technologies, the methodology now commonly known as flash vacuum pyrolysis, FVP (or flash vacuum thermolysis, FVT) had its early beginnings in the 1940s and1950s, mainly through mass spectrometric detection of pyrolytically formed free radicals. In the 1960s many organic chemists started performing FVP experiments with the purpose of isolating new and interesting compounds and understanding pyrolysis processes. Meanwhile, many different types of apparatus and techniques have been developed, and it is the purpose of this review to present the most important methods as well as a survey of typical reactions and observations that can be achieved with the various techniques. This includes preparative FVP, chemical trapping reactions, matrix isolation and low temperature spectroscopy of reactive intermediates and unstable molecules, the use of online mass, photoelectron, microwave and millimeterwave spectroscopies, gas-phase laser pyrolysis, pulsed pyrolysis with supersonic jet expansion, very low pressure pyrolysis for kinetic investigations, solution-spray and falling-solid FVP for involatile compounds, and pyrolysis over solid supports and reagents. Moreover, the combination of FVP with matrix isolation and photochemistry is a powerful tool for investigations of reaction mechanism. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Flash pyrolysis fuel oil: BIO-POK

    Energy Technology Data Exchange (ETDEWEB)

    Gust, S. [Neste Oy, Porvoo (Finland)

    1995-12-31

    Flash pyrolysis oil from Ensyn Tech., Canada and Union Fenosa, Spain was combusted with simple pressure atomisation equipment commonly used with light fuel oils in intermediate size (0.1-1 MW) boilers. With a number of modifications to the combustion system, carbon monoxide (CO) and nitrous oxide (NO{sub x}) could be reduced to acceptable levels: CO < 30 ppm and NO{sub x} < 140 ppm. Particulate emissions which were initially very high (Bacharach 4-5) were reduced (Bach. 2-3) by system changes but are still higher than from light fuel oil (Bach. <1). The modifications to the combustion system were: acid resistant progressive cavity pump, higher oil preheat temperature and higher oil pressure than for light fuel oils, refractory section between burner and boiler warmed up to at least 800 deg C. In addition, it was necessary to store pyrolysis oil samples under inert conditions to prevent oxidation and to rinse nozzles with alcohol after shutdown to prevent coking. The complexity and cost of these system modifications are considered to be too great for current grades of flash pyrolysis oil to be sold as a light fuel oil replacement. Improvements to fuel quality will be necessary. The main improvements are lowering of viscosity and improving of stability

  11. Honeywell optical investigations on FLASH program

    Science.gov (United States)

    O'Rourke, Ken; Peterson, Eric; Yount, Larry

    1995-05-01

    The increasing performance and reduction of life cycle cost requirements placed on commercial and military transport aircraft are resulting in more complex, highly integrated aircraft control and management systems. The use of fiber optic data transmission media can make significant contributions in achieving these performance and cost goals. The Honeywell portion of Task 2A on the Fly-by-Light Advanced System Hardware (FLASH) program is evaluating a Primary Flight Control System (PFCS) using pilot and copilot inputs from Active Hand Controllers (AHC) which are optically linked to the primary flight Control Computers (PFCC). Customer involvement is an important element of the Task 2A activity. Establishing customer requirements and perspectives on productization of systems developed under FLASH are key to future product success. The Honeywell elements of the PFCS demonstrator provide a command path that is optically interfaced from crew inputs to commands of distributed, smart actuation subsystems commands. Optical communication architectures are implemented using several protocols including the new AS-1773A 20 Mbps data bus standard. The interconnecting fiber optic cable plant is provided by our Task 1A teammate McDonnell Douglas Aerospace (West). Fiber optic cable plant fabrication uses processed, tools and materials reflecting necessary advances in manufacturing required to make fly-by-light avionics systems marketable.

  12. Nanocrystalline magnetic materials obtained by flash annealing

    Directory of Open Access Journals (Sweden)

    R.K. Murakami

    1999-04-01

    Full Text Available The aim of the present work was to produce enhanced-remanence nanocrystalline magnetic material by crystallizing amorphous or partially amorphous Pr4.5Fe77B18.5 alloys by the flash annealing process, also known as the dc-Joule heating process, and to determine the optimal conditions for obtaining good magnetic coupling between the magnetic phases present in this material. Ribbons of Pr4.5Fe77B18.5 were produced by melt spinning and then annealed for 10-30 s at temperatures 500 - 640 °C by passing current through the sample to develop the enhanced-remanence nanocrystalline magnetic material. These materials were studied by X-ray diffraction, differential thermal analysis and magnetic measurements. Coercivity increases of up to 15% were systematically observed in relation to furnace-annealed material. Two different samples were carefully examined: (i a sample annealed at 600 °C which showed the highest coercive field Hc and remanence ratio Mr/Ms and (ii a sample annealed at 520 °C which showed phase separation in the second quadrant demagnetization curve. Our results are in agreement with other studies which show that flash annealing improves the magnetic properties of some amorphous ferromagnetic ribbons.

  13. Flash Infrared Thermography Contrast Data Analysis Technique

    Science.gov (United States)

    Koshti, Ajay

    2014-01-01

    This paper provides information on an IR Contrast technique that involves extracting normalized contrast versus time evolutions from the flash thermography inspection infrared video data. The analysis calculates thermal measurement features from the contrast evolution. In addition, simulation of the contrast evolution is achieved through calibration on measured contrast evolutions from many flat-bottom holes in the subject material. The measurement features and the contrast simulation are used to evaluate flash thermography data in order to characterize delamination-like anomalies. The thermal measurement features relate to the anomaly characteristics. The contrast evolution simulation is matched to the measured contrast evolution over an anomaly to provide an assessment of the anomaly depth and width which correspond to the depth and diameter of the equivalent flat-bottom hole (EFBH) similar to that used as input to the simulation. A similar analysis, in terms of diameter and depth of an equivalent uniform gap (EUG) providing a best match with the measured contrast evolution, is also provided. An edge detection technique called the half-max is used to measure width and length of the anomaly. Results of the half-max width and the EFBH/EUG diameter are compared to evaluate the anomaly. The information provided here is geared towards explaining the IR Contrast technique. Results from a limited amount of validation data on reinforced carbon-carbon (RCC) hardware are included in this paper.

  14. On the stability of cationic complexes of neon with helium--solving an experimental discrepancy.

    Science.gov (United States)

    Bartl, Peter; Denifl, Stephan; Scheier, Paul; Echt, Olof

    2013-10-21

    Helium nanodroplets are doped with neon and ionized by electrons. The size-dependence of the ion abundance of HenNex(+), identified in high-resolution mass spectra, is deduced for complexes containing up to seven neon atoms and dozens of helium atoms. Particularly stable ions are inferred from anomalies in the abundance distributions. Two pronounced anomalies at n = 11 and 13 in the HenNe(+) series confirm drift-tube data reported by Kojima et al. [T. M. Kojima et al., Z. Phys. D, 1992, 22, 645]. The discrepancy with previously published spectra of neon-doped helium droplets, which did not reveal any abundance anomalies [T. Ruchti et al., J. Chem. Phys., 1998, 109, 10679-10687; C. A. Brindle et al., J. Chem. Phys., 2005, 123, 064312], is most likely due to limited mass resolution, which precluded unambiguous analysis of contributions from different ions with identical nominal mass. However, calculated dissociation energies of HenNe(+) reported so far do not correlate with the present data, possibly because of challenges in correctly treating the linear, asymmetric [He-Ne-He](+) ionic core in HenNe(+). Anomalies identified in the distributions of HenNex(+) for x > 1, including prominent ones at He12Ne2(+) and He14Ne2(+), may help to better understand solvation of Ne(+) and Nex(+) in helium.

  15. On the occurrence and detectability of Bose-Einstein condensation in helium white dwarfs

    CERN Document Server

    Benvenuto, O G

    2011-01-01

    It has been recently proposed that helium white dwarfs may provide promising conditions for the occurrence of the Bose-Einstein condensation. The argument supporting this expectation is that in some conditions attained in the core of these objects, the typical De Broglie wavelength associated with helium nuclei is of the order of the mean distance between neighboring nuclei. In these conditions the system should depart from classical behavior showing quantum effects. As helium nuclei are bosons, they are expected to condense. In order to explore the possibility of detecting the Bose-Einstein condensation in the evolution of helium white dwarfs we have computed a set of models for a variety of stellar masses and values of the condensation temperature. We do not perform a detailed treatment of the condensation process but mimic it by suppressing the nuclei contribution to the equation of state by applying an adequate function. As the cooling of white dwarfs depends on average properties of the whole stellar int...

  16. Optical absorption properties of electron bubbles and experiments on monitoring individual electron bubbles in liquid helium

    Science.gov (United States)

    Guo, Wei

    When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms, which is referred to as an electron bubble. It represents a fine example of a quantum-mechanical particle confined in a potential well. In this dissertation, we describe our studies on bubble properties, especially the optical absorption properties of ground state electron bubbles and experiments on imaging individual electron bubbles in liquid helium. We studied the effect of zero-point and thermal fluctuations on the shape of ground state electron bubbles in liquid helium. The results are used to determine the line shape for the 1S to 1P optical transition. The calculated line shape is in very good agreement with the experimental measurements of Grimes and Adams. For 1S to 2P transition, the obtained transition line width agrees well with the measured data of Zipfel over a range of pressure up to 15 bars. Fluctuations in the bubble shape also make other "unallowed" transitions possible. The transition cross-sections from the 1S state to the 1D and 2D states are calculated with magnitude approximately two orders smaller than that of the 1S to 1P and 2P transitions. In our electron bubble imaging experiments, a planar ultrasonic transducer was used to generate strong sound wave pulse in liquid helium. The sound pulse passed through the liquid so as to produce a transient negative pressure over a large volume (˜ 1 cm3). An electron bubble that was passed by the sound pulse exploded for a fraction of a microsecond and grew to have a radius of around 10 microns. While the bubble had this large size it was illuminated with a flash lamp and its position was recorded. In this way, we can determine its position. Through the application of a series of sound pulses, we can then take images along the track of individual electrons. The motion of individual electron bubbles has been successfully monitored. Interesting bubble tracks that may relate to electrons

  17. Intramolecular quantum chaos in doped helium nanodroplets

    Science.gov (United States)

    Polyakova, E.; Stolyarov, D.; Zhang, X.; Kresin, V. V.; Wittig, C.

    2003-07-01

    A mass spectrometric depletion spectrum (17 700-18 300 cm -1) is reported for NO 2 in superfluid (0.37 K) helium nanodroplets. Gas phase NO 2 is believed to be vibronically chaotic at these energies. Transitions are broadened and blue-shifted relative to their gas phase counterparts. The spectrum is fitted reasonably well by setting all of the widths and shifts equal to 7 cm -1. Modest dispersions (i.e., 90% lie within 2 cm -1 of the central values) are consistent with quantum chaos in NO 2. Relaxation is dominated by interactions of NO 2 with its non-superfluid helium nearest neighbors.

  18. O(^3 p) Doped Helium Droplets

    Science.gov (United States)

    Brice, Joseph T.; Douberly, Gary E.

    2017-06-01

    Atomic oxygen (^3 P) is generated via thermolysis in a commerical thermal gas cracker (Mantis Ltd. MGC-75). Complexes with HCN were investigated to qualitatively assess the doping efficiency of O(^3 P) into a helium droplet. Theoretical calculations of a linear O \\cdot\\cdot\\cdot HCN (^3 Σ) complex at the CCSD(T)/aug-cc-pVTZ level are consistent with the rotational constants extracted from the rotational substructure in the experimental spectra, and with dipole moments approximated from Stark spectra. The thermal source will be used to study reactions between O(^3 P) and hydrocarbons in helium droplets, and preliminary data on this topic will be presented.

  19. Trace Detection of Metastable Helium Molecules in Superfluid Helium by Laser-Induced Fluorescence

    CERN Document Server

    McKinsey, D N; Nikkel, J A; Rellergert, W

    2005-01-01

    We describe an approach to detecting ionizing radiation that combines the special properties of superfluid helium with the sensitivity of quantum optics techniques. Ionization in liquid helium results in the copious production of metastable helium molecules, which can be detected by laser-induced fluorescence. Each molecule can be probed many times using a cycling transition, resulting in the detection of individual molecules with high signal to noise. This technique could be used to detect neutrinos, weakly interacting massive particles, and ultracold neutrons, and to image superfluid flow in liquid He-4.

  20. Variational calculations of coupling of an incident helium atom to a slab of superfluid helium four

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C.E.; Halley, J.W.; Hoon, S. [and others

    1995-04-01

    In previous work on the interaction of single helium atoms with a slab of superfluid helium the authors found a large amplitude, dependent on the condensate fraction, for transmission with re-emission of a helium atom at the other side of the slab. Here they report a variational formulation of the problem which permits a time dependent calculation and which does not require any perturbation expansion. The variational principle involves a minimization of the expectation value of the square of the difference H-E. They will present preliminary results of a variational Monte Carlo calculation using a simple variational form for the wave function.

  1. Simulating High Lightning Flash Rates at Upper Levels in Strong and Severe Thunderstorms

    Science.gov (United States)

    Mansell, E.

    2015-12-01

    Lightning mapping systems have detected high lightning flash rates at the top of convective cores above the environmental -30°C level, particularly in severe storms. Previous 3-D model simulations have reproduced similarly high flash rates using bulk (one or two moment) microphysics, but the details of the charge separation were not closely examined. Recent work has raised questions as to whether the charging processes have been adequately simulated, both in terms of grid resolution and microphysical processes. New simulations of a severe supercell storm with Takahashi spectral bin microphysics and 4x better grid resolution (250m horizontal and 125 vertical spacing) are better able to capture the steep vertical temperature gradients (on the order of 8°C per km) and the process of freezing of larger liquid particles. The results suggest that high charge separation rates can occur as larger drops freeze homogeneously while smaller droplets remain liquid. This process far outstrips other small ice particle production processes like vapor nucleation or ice multiplication. This intense and vertically narrow charging zone then leads to sufficiently fast electric field growth that favors smaller flashes. These results form the hypothesis that high rates of spatially small lightning flashes result from a high density charging current in a relatively small volume, such that initiation electric field thresholds are met quickly before larger net charge regions have time to form. Results will also be presented for bulk microphysics with an updated droplet freezing scheme that emulates the freezing of droplets based on diameter and ambient temperature. An important consideration in both schemes is how to handle newly-freezing droplets in the calculation of riming rate (or cloud water content) in the charge separation rate equations.

  2. Initial Electric Field Changes of Lightning Flashes in Two Thunderstorms

    Science.gov (United States)

    Marshall, T. C.; Stolzenburg, M.; Karunarathne, S.; Chapman, R.

    2015-12-01

    In a study of lightning initiation, Marshall et al. [2014, JGR Atmospheres] found that an initial electric field change (IEC) occurred before the initial breakdown (IB) pulses in 18 cloud-to-ground (CG) flashes and in 18 intracloud (IC) flashes. Because the IECs were small in amplitude and slowly developing (i.e., primarily electrostatic events), they were only detected by sensors within the reversal distance of each flash. In this presentation we report on a search for IECs in two small Florida thunderstorms that occurred close to several E-change sensors. One storm had 57 flashes; the other had only 13 flashes. The key result is that 69 of the 70 flashes began with detectable IECs. For the one flash without a detectable IEC, the closest sensor was at the reversal distance, presumably masking the IEC. Three of the flashes analyzed seemed to begin twice, in the sense that they had two sets of IB pulses; each beginning was preceded by an IEC.

  3. Algorithms for Lunar Flash Video Search, Measurement, and Archiving

    Science.gov (United States)

    Swift, Wesley; Suggs, Robert; Cooke, Bill

    2007-01-01

    Lunar meteoroid impact flashes provide a method to estimate the flux of the large meteoroid flux and thus their hazard to spacecraft. Although meteoroid impacts on the Moon have been detected using video methods for over a decade, the difficulty of manually searching hours of video for the rare, extremely brief impact flashes has discouraged the technique's systematic implementation. A prototype has been developed for the purpose of automatically searching lunar video records for impact flashes, eliminating false detections, editing the returned possible flashes, Z and archiving and documenting the results. The theory and organization of the program is discussed with emphasis on the filtering out of several classes of false detections and retaining the brief portions of the raw video necessary for in depth analysis of the flashes detected. Several utilities for measurement, analysis, and location of the flashes on the moon included in the program are demonstrated. Application of the program to a year's worth of lunar observations is discussed along with examples of impact flashes as well as several classes of false impact flashes.

  4. Assessment of Vulnerability to Extreme Flash Floods in Design Storms

    Directory of Open Access Journals (Sweden)

    Hyun Il Choi

    2011-07-01

    Full Text Available There has been an increase in the occurrence of sudden local flooding of great volume and short duration caused by heavy or excessive rainfall intensity over a small area, which presents the greatest potential danger threat to the natural environment, human life, public health and property, etc. Such flash floods have rapid runoff and debris flow that rises quickly with little or no advance warning to prevent flood damage. This study develops a flash flood index through the average of the same scale relative severity factors quantifying characteristics of hydrographs generated from a rainfall-runoff model for the long-term observed rainfall data in a small ungauged study basin, and presents regression equations between rainfall characteristics and the flash flood index. The aim of this study is to develop flash flood index-duration-frequency relation curves by combining the rainfall intensity-duration-frequency relation and the flash flood index from probability rainfall data in order to evaluate vulnerability to extreme flash floods in design storms. This study is an initial effort to quantify the flash flood severity of design storms for both existing and planned flood control facilities to cope with residual flood risks due to extreme flash floods that have ocurred frequently in recent years.

  5. Sunshine Trading: Flashes of Trading Intent at the NASDAQ

    NARCIS (Netherlands)

    J.A. Skjeltorp (Johannes); E. Sojli (Elvira); W.W. Tham (Wing Wah)

    2012-01-01

    textabstractWe use the introduction and the subsequent removal of the flash order facility (an actionable indication of interest, IOI) from the NASDAQ as a natural experiment to investigate the impact of voluntary disclosure of trading intent on market quality. We find that flash orders significantl

  6. Assessment of vulnerability to extreme flash floods in design storms.

    Science.gov (United States)

    Kim, Eung Seok; Choi, Hyun Il

    2011-07-01

    There has been an increase in the occurrence of sudden local flooding of great volume and short duration caused by heavy or excessive rainfall intensity over a small area, which presents the greatest potential danger threat to the natural environment, human life, public health and property, etc. Such flash floods have rapid runoff and debris flow that rises quickly with little or no advance warning to prevent flood damage. This study develops a flash flood index through the average of the same scale relative severity factors quantifying characteristics of hydrographs generated from a rainfall-runoff model for the long-term observed rainfall data in a small ungauged study basin, and presents regression equations between rainfall characteristics and the flash flood index. The aim of this study is to develop flash flood index-duration-frequency relation curves by combining the rainfall intensity-duration-frequency relation and the flash flood index from probability rainfall data in order to evaluate vulnerability to extreme flash floods in design storms. This study is an initial effort to quantify the flash flood severity of design storms for both existing and planned flood control facilities to cope with residual flood risks due to extreme flash floods that have ocurred frequently in recent years.

  7. Microstructure of wood charcoal prepared by flash heating

    NARCIS (Netherlands)

    Kurosaki, F; Ishimaru, K; Hata, T; Bronsveld, P; Kobayashi, E; Imamura, Y

    2003-01-01

    Carbonized wood prepared by flash heating at 800 degreesC for I h shows a different microstructure and surface chemical structure than char formed after slow heating at 4 degreesC/min to 800 degreesC for I h. Flash heating produces pores that are surrounded by aggregates of carbon structures 25 to 1

  8. Flash ionisation signature in coherent cyclotron emission from Brown Dwarfs

    CERN Document Server

    Vorgul, Irena

    2016-01-01

    Brown dwarfs form mineral clouds in their atmospheres, where charged particles can produce large-scale discharges in form of lightning resulting in a substantial sudden increase of local ionisation. Brown dwarfs are observed to emit cyclotron radio emission. We show that signatures of strong transient atmospheric ionisation events (flash ionisation) can be imprinted on a pre-existing radiation. Detection of such flash ionisation events will open investigations into the ionisation state and atmospheric dynamics. Such ionisation events can also result from explosion shock waves, bursts or eruptions. We present an analytical model that describes the modulation of a pre-existing electromagnetic radiation by a time-dependent (flash) conductivity that is characteristic for flash ionisation events like lightning. Our conductivity model reproduces the conductivity function derived from observations of Terrestrial Gamma Ray Flashes, and is applicable to astrophysical objects with strong temporal variations in the loca...

  9. Lightning Mapping Array flash detection performance with variable receiver thresholds

    Science.gov (United States)

    Chmielewski, Vanna C.; Bruning, Eric C.

    2016-07-01

    This study characterizes Lightning Mapping Array performance for networks that participated in the Deep Convective Clouds and Chemistry field program using new Monte Carlo and curvature matrix model simulations. These open-source simulation tools are readily adapted to real-time operations or detailed studies of performance. Each simulation accounted for receiver threshold and location, as well as a reference distribution of source powers and flash sizes based on thunderstorm observations and the mechanics of station triggering. Source and flash detection efficiency were combined with solution bias and variability to predict flash area distortion at long ranges. Location errors and detection efficiency were highly dependent on the station configuration and thresholds, especially at longer ranges, such that performance varied more than expected across different networks and with azimuth within networks. Error characteristics matched prior studies, which led to an increase in flash distortion with range. Predicted flash detection efficiency exceeded 95% within 100 km of all networks.

  10. Ice cores

    DEFF Research Database (Denmark)

    Svensson, Anders

    2014-01-01

    Ice cores from Antarctica, from Greenland, and from a number of smaller glaciers around the world yield a wealth of information on past climates and environments. Ice cores offer unique records on past temperatures, atmospheric composition (including greenhouse gases), volcanism, solar activity......, dustiness, and biomass burning, among others. In Antarctica, ice cores extend back more than 800,000 years before present (Jouzel et al. 2007), whereas. Greenland ice cores cover the last 130,000 years...

  11. Ice cores

    DEFF Research Database (Denmark)

    Svensson, Anders

    2014-01-01

    Ice cores from Antarctica, from Greenland, and from a number of smaller glaciers around the world yield a wealth of information on past climates and environments. Ice cores offer unique records on past temperatures, atmospheric composition (including greenhouse gases), volcanism, solar activity......, dustiness, and biomass burning, among others. In Antarctica, ice cores extend back more than 800,000 years before present (Jouzel et al. 2007), whereas. Greenland ice cores cover the last 130,000 years...

  12. Features of positive ground flashes observed in Kathmandu Nepal

    Science.gov (United States)

    Adhikari, Pitri Bhakta; Sharma, Shriram; Baral, Kedarnath

    2016-07-01

    Lightning vertical electric fields pertinent to the subtropical thunderstorms occurring over the rugged terrain have been measured and recorded at a hilly station Kathmandu, Nepal. In the present work, waveforms of the positive ground flashes have been selected from all the records and were analyzed. To the best of our knowledge, this is the first time that fine structure of electric field signature pertinent to the positive return stroke; have been analyzed and presented from Nepal. One hundred and thirty three (133) of the total of four hundred twenty-five (425) flashes were selected from seven thunderstorm days and analyzed. Of the data recorded for seven days, 133 flashes (31.3%) were positive flashes and 276 flashes (64.9%) were cloud flashes. Majority of the positive ground flashes were found to be single stroke ones, whereas, the average number of strokes per flash is found to be 1.1 with a maximum value of 4. Majority of the positive ground flashes were found either lacking the initial breakdown process and the leader stage or these processes could not be detected. The return strokes are found to be succeeded by large in cloud activity in the continuing current portion of the flash. The average zero-crossing time of the positive return strokes was found to be 60.45 μs with a range of 447.81 μs and the average rise time was found to be 9.44 μs with a range of 42.56 μs.

  13. Mechanisms of cutaneous vasodilation during the postmenopausal hot flash

    Science.gov (United States)

    Low, David A.; Hubing, Kimberley A.; Del Coso, Juan; Crandall, Craig G.

    2010-01-01

    Objective Menopausal hot flashes can seriously disrupt the lives of symptomatic women. The physiological mechanisms of the hot flash efferent responses, particularly in the cutaneous circulation, are not completely understood. The aim of this study was to examine the mechanisms of increases in skin blood flow during the postmenopausal hot flash in symptomatic women. Methods Healthy postmenopausal women rested in a temperature controlled laboratory while responses prior to and during hot flashes were recorded for three unique protocols. Protocols 1 and 2: Women were locally pretreated with an intradermal injection of botulinum toxin A (BTX; blocks the release of neurotransmitters from sympathetic cholinergic nerves) in the forearm (protocol 1) and in the glabellar region (protocol 2). Protocol 3: Skin sympathetic nerve activity from the peroneal nerve was recorded, along with skin blood flow and sweating within the region innervated by that neural signal. Skin blood flow was indexed using laser-Doppler flowmetry at BTX-treated and adjacent untreated control sites. The onset of a hot flash was objectively identified as a transient and pronounced elevation of sternal sweat rate. Results The elevation in forearm (protocol 1) and glabellar skin blood flow (protocol 2) during hot flashes were attenuated at BTX sites relative to adjacent untreated sites (P<0.05 for both protocols). In protocol 3, skin sympathetic nerve activity significantly increased during hot flashes and returned to pre-flash levels following the hot flashes. Conclusion Elevations in skin blood flow during the postmenopausal hot flash are neurally mediated primarily through BTX sensitive nerves; presumably sympathetic cholinergic. PMID:21107299

  14. Electron transfer kinetics in purified reaction centers from the green sulfur bacterium Chlorobium tepidum studied by multiple-flash excitation.

    Science.gov (United States)

    Kusumoto, N; Sétif, P; Brettel, K; Seo, D; Sakurai, H

    1999-09-14

    Reaction center preparations from the green sulfur bacterium Chlorobium tepidum, which contain monoheme cytochrome c, were studied by flash-absorption spectroscopy in the near-UV, visible, and near-infrared regions. The decay kinetics of the photooxidized primary donor P840(+), together with the amount of photooxidized cytochrome c, were analyzed along a series of four flashes spaced by 1 ms: 95% of the P840(+) was reduced by cytochrome c with a t(1/2) of approximately 65 micros after the first flash, 80% with a t(1/2) of approximately 100 micros after the second flash, and 23% with a t(1/2) of approximately 100 micros after the third flash; after the fourth flash, almost no cytochrome c oxidation occurred. The observed rates, the establishment of redox equilibrium after each flash, and the total amount of photooxidizable cytochrome c are consistent with the presence of two equivalent cytochrome c molecules per photooxidizable P840. The data are well fitted assuming a standard free energy change DeltaG degrees of -53 meV for electron transfer from one cytochrome c to P840(+), DeltaG degrees being independent of the oxidation state of the other cytochrome c. These observations support a model with two monoheme cytochromes c which are symmetrically arranged around the reaction center core. From the ratio of menaquinone-7 to the bacteriochlorophyll pigment absorbing at 663 nm, it was estimated that our preparations contain 0.6-1.2 menaquinone-7 molecules per reaction center. However, no transient signal due to menaquinone could be observed between 360 and 450 nm in the time window from 10 ns to 4 micros. No recombination reaction between the primary partners P840(+) and A(0)(-) could be detected under normal conditions. Such a recombination was observed (t(1/2) approximately 19 ns) under highly reducing conditions or after accumulation of three electrons on the acceptor side during a series of flashes, showing that the secondary acceptors can stabilize three electrons

  15. Looking for Similarities Between Lowland (Flash) Floods

    Science.gov (United States)

    Brauer, C.; Teuling, R.; Torfs, P.; Hobbelt, L.; Jansen, F.; Melsen, L.; Uijlenhoet, R.

    2012-12-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events. Over an area of 740 km2 more than 120 mm of rainfall were observed in 24 h. We investigated the unprecedented flash flood triggered by this exceptionally heavy rainfall event (return period > 1000 years) in the 6.5 km2 Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study improved our understanding of the dynamics of such lowland flash floods (Brauer et al., 2011). These observations, however, only show how our experimental catchment behaved and the results cannot be extrapolated directly to different floods in other (neighboring) lowland catchments. Therefore, it is necessary to use the information collected in one well-monitored catchment in combination with data from other, less well monitored catchments to find common signatures which could describe the runoff response during a lowland flood as a function of catchment characteristics. Because of the large spatial extent of the rainfall event in August 2010, many brooks and rivers in the Netherlands and Germany flooded. With data from several catchments we investigated the influence of rainfall and catchment characteristics (such as slope, size and land use) on the reaction of discharge to rainfall. We also investigated the runoff response in these catchments during previous floods by analyzing the relation between storage and discharge and the recession curve. In addition to the flood in August 2010, two other floods occurred in The Netherlands in recently. The three floods occurred in different parts of the country, after different types of rainfall events and with different initial conditions. We selected several catchments during each flood to compare their response and find out if these cases are fundamentally different or that they were produced by the same underlying processes and can be treated in a

  16. Interatomic Coulombic decay in helium nanodroplets

    DEFF Research Database (Denmark)

    Shcherbinin, Mykola; Laforge, Aaron; Sharma, Vandana

    2017-01-01

    Interatomic Coulombic decay (ICD) is induced in helium nanodroplets by photoexciting the n=2 excited state of He+ using XUV synchrotron radiation. By recording multiple-coincidence electron and ion images we find that ICD occurs in various locations at the droplet surface, inside the surface region...

  17. Photoassociation of cold metastable helium atoms

    NARCIS (Netherlands)

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to tr

  18. Messer to provide helium for LHC

    CERN Document Server

    2008-01-01

    Over the course of the next few years, industrial gas specialist The Messer Group, through its Swiss subsidiary Messer Schweiz AG, is to provide a 160,000kg supply of helium to the European Organisation for Nuclear Research (CERN) for the operation of the world's largest particle accelerator.

  19. Messer to provide helium for LHC project

    CERN Multimedia

    2008-01-01

    Over the course of the next few years, industrial gas specialist The Messer Group, through its Swiss subsidiary Messer Schweiz AG, is to provide a 160,000kg supply of helium to the European Organisation for Nuclear Research (CERN) for the operation of the world's largest particle accelerator.

  20. Thermalization of magnetically trapped metastable helium

    CERN Document Server

    Browaeys, A; Sirjean, O; Poupard, J; Nowak, S; Boiron, D; Westbrook, C I; Aspect, Alain

    2001-01-01

    We have observed thermalization by elastic collisions of magnetically trapped metastable helium atoms. Our method directly samples the reconstruction of a thermal energy distribution after the application of an RF knife. The relaxation time of our sample towards equilibrium gives an elastic collision rate constant close to the unitarity limit.

  1. Critical Landau Velocity in Helium Nanodroplets

    NARCIS (Netherlands)

    N.B. Brauer; S. Smolarek; E. Loginov; D. Mateo; A. Hernando; M. Pi; M. Barranco; W.J. Buma; M. Drabbels

    2013-01-01

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitatio

  2. Helium and Sulfur Hexafluoride in Musical Instruments

    Science.gov (United States)

    Forinash, Kyle; Dixon, Cory L.

    2014-01-01

    The effects of inhaled helium on the human voice were investigated in a recent article in "The Physics Teacher." As mentioned in that article, demonstrations of the effect are a popular classroom activity. If the number of YouTube videos is any indication, the effects of sulfur hexafluoride on the human voice are equally popular.…

  3. Photoassociation of cold metastable helium atoms

    NARCIS (Netherlands)

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to

  4. Photoassociation of cold metastable helium atoms

    NARCIS (Netherlands)

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to tr

  5. Development of a helium cryostat for laser spectroscopy of atoms with unstable nuclei in superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, Kei, E-mail: kimamura@riken.jp [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Furukawa, Takeshi [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Wakui, Takashi [Cyclotron and Radioisotope Center, Tohoku University, 6-3 Aoba, Aramaki, Aoba, Sendai, Miyagi 980-8578 (Japan); Yang, Xiaofei [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); School of Physics, Peking University, Chengfu Road, Haidian District, Beijing 100871 (China); Yamaguchi, Yasuhiro [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Tetsuka, Hiroki [Department of Physics, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501 (Japan); Mitsuya, Yosuke [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Tsutsui, Yoshiki [Department of Physics, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501 (Japan); Fujita, Tomomi [Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Ebara, Yuta; Hayasaka, Miki [Department of Physics, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501 (Japan); Arai, Shino; Muramoto, Sosuke [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Ichikawa, Yuichi [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Department of Physics, Tokyo Instutute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551 (Japan); Ishibashi, Yoko [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Department of Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); and others

    2013-12-15

    We are developing a new nuclear laser spectroscopic technique for the study of nuclear structure that can be applied to short-lived low-yield atoms with unstable nuclei. The method utilizes superfluid helium (He II) as a trapping medium for high-energy ion beams. A liquid helium cryostat with optical windows is a key apparatus for this type of experiment. We describe the design and the performance of the cryostat which is developed for the present project.

  6. Femtosecond spectroscopy on alkali-doped helium nanodroplets; Femtosekundenspektroskopie an alkalidotierten Helium-Nanotroepfchen

    Energy Technology Data Exchange (ETDEWEB)

    Claas, P.

    2006-01-15

    In the present thesis first studies on the short-time dynamics in alkali dimers and microclusters, which were bound on the surface of superfluid helium droplets, were presented. The experiments comprehended pump-probe measurements on the fs scale on the vibration dynamics on the dimers and on the fragmentation dynamics on the clusters. Generally by the studies it was shown that such extremely short slopes can also be observed on helium droplets by means of the femtosecond spectroscopy.

  7. The thermonuclear-flash model for X-ray burst sources - A new tool for observing neutron stars

    Science.gov (United States)

    Joss, P. C.

    1979-01-01

    The helium-flash model for X-ray burst sources, in which matter is presumed to accrete onto the surface of a neutron star, is discussed. Attention is given to the accretion process, nuclear burning, X-ray emission, and the energy released by convection as well as by radiative diffusion near the surface. The rise times of observed bursts, their spectral evolution, and the properties of the spectrally soft X-ray transients are considered. Problems in interpreting the continuum spectra are discussed, along with problems in the detection and measurement of line features in the spectra. Also considered are the ratio of time-averaged persistent luminosity to time-averaged burst luminosity, peak burst luminosities, and the possibility of detecting binary membership for burst sources.

  8. 浅析OpenFlashChart的使用%Brief Introduction Usage of Open Flash Chart

    Institute of Scientific and Technical Information of China (English)

    周伟伟; 童敏娟

    2012-01-01

    Open Flash Chart是基于Web网络应用图表技术,用简单方便配置提供出绚丽动画效果,并且图表类型丰富多彩、数据文件结构清晰而明了.通过Open Flash Chart可以生成线图、饼状图、柱状图、雷达图、区域图以及组合图表等.设定颜色、字体、背景等CSS样式,为用户提供了大量可选择的数据图表显示方式.

  9. Helium accreting CO white dwarfs with rotation: helium novae instead of double detonation

    CERN Document Server

    Yoon, S C

    2004-01-01

    We present evolutionary models of helium accreting carbon-oxygen white dwarfs in which we include the effects of the spin-up of the accreting star induced by angular momentum accretion, rotationally induced chemical mixing and rotational energy dissipation. Initial masses of 0.6 Msun and 0.8 Msun and constant accretion rates of a few times 10^{-8} Msun/yr of helium rich matter have been considered, which is typical for the sub-Chandrasekhar mass progenitor scenario for Type Ia supernovae. It is found that the helium envelope in an accreting white dwarf is heated efficiently by friction in the differentially rotating spun-up layers. As a result, helium ignites much earlier and under much less degenerate conditions compared to the corresponding non-rotating case. Consequently, a helium detonation may be avoided, which questions the sub-Chandrasekhar mass progenitor scenario for Type Ia supernovae. We discuss implications of our results for the evolution of helium star plus white dwarf binary systems as possible...

  10. Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets

    Energy Technology Data Exchange (ETDEWEB)

    Pentlehner, D.; Slenczka, A., E-mail: alkwin.slenczka@chemie.uni-regensburg.de [Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93040 Regensburg (Germany)

    2015-01-07

    Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (Δν > 100 cm{sup −1}) diffuse signals. Despite the large number of example spectra in the literature, a quantitative understanding of the helium induced fine structure of the zero phonon line and the phonon wing is missing. Our approach is a systematic investigation of related molecular compounds, which may help to shed light on this key feature of microsolvation in superfluid helium droplets. This paper is part of a comparative study of the helium induced fine structure observed in electronic spectra of anthracene derivatives with particular emphasis on a spectrally sharp multiplet splitting at the electronic origin. In addition to previously discussed species, 9-cyanoanthracene and 9-chloroanthracene will be presented in this study for the first time.

  11. Article coated with flash bonded superhydrophobic particles

    Science.gov (United States)

    Simpson, John T [Clinton, TN; Blue, Craig A [Knoxville, TN; Kiggans, Jr., James O [Oak Ridge, TN

    2010-07-13

    A method of making article having a superhydrophobic surface includes: providing a solid body defining at least one surface; applying to the surface a plurality of diatomaceous earth particles and/or particles characterized by particle sizes ranging from at least 100 nm to about 10 .mu.m, the particles being further characterized by a plurality of nanopores, wherein at least some of the nanopores provide flow through porosity, the particles being further characterized by a plurality of spaced apart nanostructured features that include a contiguous, protrusive material; flash bonding the particles to the surface so that the particles are adherently bonded to the surface; and applying a hydrophobic coating layer to the surface and the particles so that the hydrophobic coating layer conforms to the nanostructured features.

  12. Flash photolysis-shock tube studies

    Energy Technology Data Exchange (ETDEWEB)

    Michael, J.V. [Argonne National Laboratory, IL (United States)

    1993-12-01

    Even though this project in the past has concentrated on the measurement of thermal bimolecular reactions of atomic species with stable molecules by the flash or laser photolysis-shock tube (FP- or LP-ST) method using atomic resonance absorption spectrometry (ARAS) as the diagnostic technique, during the past year the authors have concentrated on studies of the thermal decompositions of selected chlorocarbon molecules. These studies are necessary if the degradation of chlorine containing organic molecules by incineration are to be understood at the molecular level. Clearly, destruction of these molecules will not only involve abstraction reactions, when possible, but also thermal decomposition followed by secondary reactions of the initially formed atoms and radicals. Studies on the thermal decomposition of CH{sub 3}Cl are complete, and the curve-of-growth for Cl-atom atomic resonance absorption has been determined. The new thermal decomposition studies are similar to those already reported for CH{sub 3}Cl.

  13. Evaluation of helium cooling for fusion divertors

    Energy Technology Data Exchange (ETDEWEB)

    Baxi, C.B.

    1993-09-01

    The divertors of future fusion reactors will have a power throughput of several hundred MW. The peak heat flux on the diverter surface is estimated to be 5 to 15 MW/m{sup 2} at an average heat flux of 2 MW/m{sup 2}. The divertors have a requirement of both minimum temperature (100{degrees}C) and maximum temperature. The minimum temperature is dictated by the requirement to reduce the absorption of plasma, and the maximum temperature is determined by the thermo-mechanical properties of the plasma facing materials. Coolants that have been considered for fusion reactors are water, liquid metals and helium. Helium cooling has been shown to be very attractive from safety and other considerations. Helium is chemically and neutronically inert and is suitable for power conversion. The challenges associated with helium cooling are: (1) Manifold sizes; (2) Pumping power; and (3) Leak prevention. In this paper the first two of the above design issues are addressed. A variety of heat transfer enhancement techniques are considered to demonstrate that the manifold sizes and the pumping power can be reduced to acceptable levels. A helium-cooled diverter module was designed and fabricated by GA for steady-state heat flux of 10 MW/m{sup 2}. This module was recently tested at Sandia National Laboratories. At an inlet pressure of 4 MPa, the module was tested at a steady-state heat flux of 10 MW/m{sup 2}. The pumping power required was less than 1% of the power removed. These results verified the design prediction.

  14. Limits to Determining the Core of Jupiter

    Science.gov (United States)

    Stevenson, David J.

    2016-10-01

    Simple, approximate models based on perturbations of the n=1 polytrope are used to identify some general properties of models for nearly-isentropic Jupiter-like planets where the total heavy element mass fraction is small. In these models, it is found that the radius is remarkably insensitive to the distribution of heavy elements and is effectively a measure of total heavy element enrichment (sum of core and envelope). The gravity harmonic J2 and the normalized moment of inertia α=I/MR2 are almost entirely determined by the density structure outside the core, and this depends on the reduced core mass, defined to be the actual core mass minus the mass of hydrogen and helium that would occupy that region in the absence of the core. The actual core mass or its radius or composition cannot be well determined, even when there is perfect knowledge of the equation of state, thermal state and envelope enrichment by heavy elements. The central concentration of heavy elements is approximately determined, even when the actual core is more massive and contaminated with hydrogen and helium by mixing or erosion (double diffusive convection). At fixed J2, the dependence of α on core structure is very small, and only exceeds the likely detection limit ~0.1-0.2% for very extended cores. Even though these results are obtained for a simple model, it is argued that they are semi-quantitatively applicable to realistic models. A perturbation scheme is presented for testing this systematically and for assessing the consequences of perturbations to the equation of state, compositional profile and temperature structure for the trade-off between reduced core mass and envelope enrichment.

  15. Long-lasting but Dim Brethren of Cosmic Flashes

    Science.gov (United States)

    2006-08-01

    astronomers with a large data set to document this new class of events. The group led by Elena Pian indeed confirmed that the event was tied to a supernova called SN 2006aj a few days later. Remarkable details about the chemical composition of the star debris continue to be analysed. The newly discovered supernova is dimmer than hypernovae associated with normal long gamma-ray bursts by about a factor of two, but it is still a factor of 2-3 more luminous than regular core-collapse supernovae. All together, these facts point to a substantial diversity between supernovae associated with GRBs and supernovae associated with X-ray flashes. This diversity may be related to the masses of the exploding stars. Whereas gamma-ray bursts probably mark the birth of a black hole, X-ray flashes appear to signal the type of star explosion that leaves behind a neutron star. Based on the VLT data, a team led by Paolo Mazzali of the Max Planck Institute for Astrophysics in Garching, Germany, postulate that the 18 February event might have led to a highly magnetic type of neutron star called a magnetar. Mazzali and his team find indeed that the star that exploded had an initial mass of 'only' 20 times the mass of the Sun. This is smaller, by about a factor two at least, than those estimated for the typical GRB-supernovae. "The properties of GRB 060218 suggest the existence of a population of events less luminous than 'classical' GRBs, but possibly much more numerous", said Mazzali. "Indeed, these events may be the most abundant form of X- or gamma-ray bursts in the Universe, but instrumental limits allow us to detect them only locally." The astronomers find that the number of such events could be about 100 times more numerous than typical gamma-ray bursts.

  16. A new French flash flood warning service

    Directory of Open Access Journals (Sweden)

    de Saint-Aubin Céline

    2016-01-01

    Full Text Available The French State services in charge of flood forecasting supervise about 22,000 km among the 120,000 km of the French rivers within a warning procedure called Vigilance Crues (http://www.vigicrues.gouv.fr. Some recent dramatic flood events on small watershed not covered by Vigilance Crues highlight the need for a new warning procedure to anticipate violent flash floods that regularly affect rapid river-basins. Thus the concept emerged of an automatic warning service specifically dedicated to local crisis managers. This service will be less elaborated than Vigilance Crues, probably with false alarms and missed events sometimes, but it will deliver a first information. The generation of the warning is based on a simple rainfall-runoff hydrological model developed by Irstea on all French rivers, fed with radar-gauge rainfall grids provided by Meteo-France. Every fifteen minutes, the hydrological model estimates the discharges on the rivers eligible to the service and determine if certain thresholds corresponding to a high or very high flood are likely to be exceeded. The last step of the real-time system is to determine which municipalities are concerned with flood risk and send them an automatic warning by voice call, optionally by sms or email. A specific web interface is available for users to monitor the evolution of the flood risk on maps that are updated every 15 minutes. This new flash flood warning service will be operational early 2017 as a free service for about 8,000 French municipalities.

  17. Carbon nanotube-templated polyaniline nanofibers: synthesis, flash welding and ultrafiltration membranes

    Science.gov (United States)

    Liao, Yaozu; Yu, Deng-Guang; Wang, Xia; Chain, Wei; Li, Xin-Gui; Hoek, Eric M. V.; Kaner, Richard B.

    2013-04-01

    Electro-active switchable ultrafiltration membranes are of great interest due to the possibility of external control over permeability, selectivity, anti-fouling and cleaning. Here, we report on hybrid single-walled carbon nanotube (SWCNT)-polyaniline (PANi) nanofibers synthesized by in situ polymerization of aniline in the presence of oxidized SWCNTs. The composite nanofibers exhibit unique morphology of core-shell (SWCNT-PANi) structures with average total diameters of 60 nm with 10 to 30 nm thick PANi coatings. The composite nanofibers are easily dispersed in polar aprotic solvents and cast into asymmetric membranes via a nonsolvent induced phase separation. The hybrid SWCNT-PANi membranes are electrically conductive at neutral pH and exhibit ultrafiltration-like permeability and selectivity when filtering aqueous suspensions of 6 nm diameter bovine serum albumin and 48 nm diameter silica particles. A novel flash welding technique is utilized to tune the morphology, porosity, conductivity, permeability and nanoparticle rejection of the SWCNT-PANi composite ultrafiltration membranes. Upon flash welding, both conductivity and pure water permeability of the membranes improves by nearly a factor of 10, while maintaining silica nanoparticle rejection levels above 90%. Flash welding of SWCNT-PANi composite membranes holds promise for formation of electrochemically tunable membranes.Electro-active switchable ultrafiltration membranes are of great interest due to the possibility of external control over permeability, selectivity, anti-fouling and cleaning. Here, we report on hybrid single-walled carbon nanotube (SWCNT)-polyaniline (PANi) nanofibers synthesized by in situ polymerization of aniline in the presence of oxidized SWCNTs. The composite nanofibers exhibit unique morphology of core-shell (SWCNT-PANi) structures with average total diameters of 60 nm with 10 to 30 nm thick PANi coatings. The composite nanofibers are easily dispersed in polar aprotic solvents and

  18. Storage Coding for Wear Leveling in Flash Memories

    CERN Document Server

    Anxiao,; Mateescu, Robert; Yaakobi, Eitan; Bruck, Jehoshua; Siegel, Paul H; Vardy, Alexander; Wolf, Jack K

    2009-01-01

    Flash memory is a non-volatile computer memory comprised of blocks of cells, wherein each cell is implemented as either NAND or NOR floating gate. NAND flash is currently the most widely used type of flash memory. In a NAND flash memory, every block of cells consists of numerous pages; rewriting even a single page requires the whole block to be erased and reprogrammed. Block erasures determine both the longevity and the efficiency of a flash memory. Therefore, when data in a NAND flash memory are reorganized, minimizing the total number of block erasures required to achieve the desired data movement is an important goal. This leads to the flash data movement problem studied in this paper. We show that coding can significantly reduce the number of block erasures required for data movement, and present several optimal or nearly optimal data-movement algorithms based upon ideas from coding theory and combinatorics. In particular, we show that the sorting-based (non-coding) schemes require at least O(nlogn) erasu...

  19. Simulated CONUS Flash Flood Climatologies from Distributed Hydrologic Models

    Science.gov (United States)

    Flamig, Z.; Gourley, J. J.; Vergara, H. J.; Kirstetter, P. E.; Hong, Y.

    2016-12-01

    This study will describe a CONUS flash flood climatology created over the period from 2002 through 2011. The MRMS reanalysis precipitation dataset was used as forcing into the Ensemble Framework For Flash Flood Forecasting (EF5). This high resolution 1-sq km 5-minute dataset is ideal for simulating flash floods with a distributed hydrologic model. EF5 features multiple water balance components including SAC-SMA, CREST, and a hydrophobic model all coupled with kinematic wave routing. The EF5/SAC-SMA and EF5/CREST water balance schemes were used for the creation of dual flash flood climatologies based on the differing water balance principles. For the period from 2002 through 2011 the daily maximum streamflow, unit streamflow, and time of peak streamflow was stored along with the minimum soil moisture. These variables are used to describe the states of the soils right before a flash flood event and the peak streamflow that was simulated during the flash flood event. The results will be shown, compared and contrasted. The resulting model simulations will be verified on basins less than 1,000-sq km with USGS gauges to ensure the distributed hydrologic models are reliable. The results will also be compared spatially to Storm Data flash flood event observations to judge the degree of agreement between the simulated climatologies and observations.

  20. Molecular dynamics study of helium bubble pressure in titanium

    Institute of Scientific and Technical Information of China (English)

    Zhang Bao-Ling; Wang Jun; Hou Qing

    2011-01-01

    In this paper, the pressure state of the helium bubble in titanium is simulated by a molecular dynamics (MD) method. First, the possible helium/vacancy ratio is determined according to therelation between the bubble pressure and helium/vacancy ratio; then the dependences of the helium bubble pressure on the bubble radius at different temperatures are studied. It is shown that the product of the bubble pressure and the radius is approximately a constant, a result justifying the pressure-radius relation predicted by thermodynamics-based theory for gas bubble. Furthermore, a state equation of the helium bubble is established based on the MD calculations. Comparison between the results obtained by the state equation and corresponding experimental data shows that the state equation can describe reasonably the state of helium bubble and thus could be used for Monte Carlo simulations of the evolution of helium bubble in metals.

  1. OGLE-2013-SN-079: A LONELY SUPERNOVA CONSISTENT WITH A HELIUM SHELL DETONATION

    Energy Technology Data Exchange (ETDEWEB)

    Inserra, C.; Sim, S. A.; Smartt, S. J.; Nicholl, M.; Jerkstrand, A.; Chen, T.-W. [Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Wyrzykowski, L. [University of Warsaw, Astronomical Observatory, Al. Ujazdowskie 400-478 Warszawa (Poland); Fraser, M.; Blagorodnova, N.; Campbell, H. [Institute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA Cambridge (United Kingdom); Shen, K. J. [Department of Astronomy and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States); Gal-Yam, A. [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); Howell, D. A.; Valenti, S. [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102 Goleta, CA 93117 (United States); Maguire, K. [European Southern Observatory for Astronomical Research in the Southern Hemisphere (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching b. Munchen (Germany); Mazzali, P.; Bersier, D. [Astrophysics Research Institute, Liverpool John Moores University, Liverpool (United Kingdom); Taubenberger, S.; Benitez-Herrera, S. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany); Elias-Rosa, N., E-mail: c.inserra@qub.ac.uk [INAF - Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); and others

    2015-01-20

    We present observational data for a peculiar supernova discovered by the OGLE-IV survey and followed by the Public ESO Spectroscopic Survey for Transient Objects. The inferred redshift of z = 0.07 implies an absolute magnitude in the rest-frame I-band of M{sub I} ∼ –17.6 mag. This places it in the luminosity range between normal Type Ia SNe and novae. Optical and near infrared spectroscopy reveal mostly Ti and Ca lines, and an unusually red color arising from strong depression of flux at rest wavelengths <5000 Å. To date, this is the only reported SN showing Ti-dominated spectra. The data are broadly consistent with existing models for the pure detonation of a helium shell around a low-mass CO white dwarf and ''double-detonation'' models that include a secondary detonation of a CO core following a primary detonation in an overlying helium shell.

  2. Unusual behavior in magnesium-copper cluster matter produced by helium droplet mediated deposition

    Energy Technology Data Exchange (ETDEWEB)

    Emery, S. B., E-mail: samuel.emery@navy.mil; Little, B. K. [University of Dayton Research Institute, 300 College Park, Dayton, Ohio 45469 (United States); Air Force Research Laboratory, Munitions Directorate, 2306 Perimeter Rd., Eglin AFB, Florida 32542 (United States); Xin, Y. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States); Ridge, C. J.; Lindsay, C. M. [Air Force Research Laboratory, Munitions Directorate, 2306 Perimeter Rd., Eglin AFB, Florida 32542 (United States); Buszek, R. J. [ERC Inc., Edwards AFB, California 93524 (United States); Boatz, J. A. [Air Force Research Laboratory, Aerospace System Directorate, Edwards AFB, California 93524 (United States); Boyle, J. M. [Naval Surface Warfare Center Indian Head Explosive Ordnance Technology Division, Indian Head, Maryland 20640 (United States)

    2015-02-28

    We demonstrate the ability to produce core-shell nanoclusters of materials that typically undergo intermetallic reactions using helium droplet mediated deposition. Composite structures of magnesium and copper were produced by sequential condensation of metal vapors inside the 0.4 K helium droplet baths and then gently deposited onto a substrate for analysis. Upon deposition, the individual clusters, with diameters ∼5 nm, form a cluster material which was subsequently characterized using scanning and transmission electron microscopies. Results of this analysis reveal the following about the deposited cluster material: it is in the un-alloyed chemical state, it maintains a stable core-shell 5 nm structure at sub-monolayer quantities, and it aggregates into unreacted structures of ∼75 nm during further deposition. Surprisingly, high angle annular dark field scanning transmission electron microscopy images revealed that the copper appears to displace the magnesium at the core of the composite cluster despite magnesium being the initially condensed species within the droplet. This phenomenon was studied further using preliminary density functional theory which revealed that copper atoms, when added sequentially to magnesium clusters, penetrate into the magnesium cores.

  3. Flash ionization signature in coherent cyclotron emission from brown dwarfs

    Science.gov (United States)

    Vorgul, I.; Helling, Ch.

    2016-05-01

    Brown dwarfs (BDs) form mineral clouds in their atmospheres, where charged particles can produce large-scale discharges in the form of lightning resulting in substantial sudden increase of local ionization. BDs are observed to emit cyclotron radio emission. We show that signatures of strong transient atmospheric ionization events (flash ionization) can be imprinted on a pre-existing radiation. Detection of such flash ionization events will open investigations into the ionization state and atmospheric dynamics. Such events can also result from explosion shock waves, material outbursts or (volcanic) eruptions. We present an analytical model that describes the modulation of a pre-existing electromagnetic radiation by a time-dependent (flash) conductivity that is characteristic for flash ionization events like lightning. Our conductivity model reproduces the conductivity function derived from observations of terrestrial gamma-ray flashes, and is applicable to astrophysical objects with strong temporal variations in the local ionization, as in planetary atmospheres and protoplanetary discs. We show that the field responds with a characteristic flash-shaped pulse to a conductivity flash of intermediate intensity. More powerful ionization events result in smaller variations of the initial radiation, or in its damping. We show that the characteristic damping of the response field for high-power initial radiation carries information about the ionization flash magnitude and duration. The duration of the pulse amplification or the damping is consistently shorter for larger conductivity variations and can be used to evaluate the intensity of the flash ionization. Our work suggests that cyclotron emission could be probe signals for electrification processes inside BD atmosphere.

  4. Weak positive cloud-to-ground flashes in Northeastern Colorado

    Science.gov (United States)

    Lopez, Raul E.; Maier, Michael W.; Garcia-Miguel, Juan A.; Holle, Ronald L.

    1991-01-01

    The frequency distributions of the peak magnetic field associated with the first detected return stroke of positive and negative cloud-to-ground (CG) flashes were studied using lightning data from northeastern Colorado. These data were obtained during 1985 with a medium-to-high gain network of three direction finders (DF's). The median signal strength of positive flashes was almost two times that of the negatives for flashes within 300 km of the DF's, which have an inherent detection-threshold bias that tends to discriminate against weak signals. This bias increases with range, and affects the detection of positive and negative flashes in different ways, because of the differing character of their distributions. Positive flashes appear to have a large percentage of signals clustered around very weak values that are lost to the medium-to-high gain Colorado Detection System very quickly with increasing range. The resulting median for positive signals could thus appear to be much larger than the median for negative signals, which are more clustered around intermediate values. When only flashes very close to the DF's are considered, however, the two distributions have almost identical medians. The large percentage of weak positive signals detected close to the DF's has not been explored previously. They have been suggested to come from intracloud discharges and thus are improperly classified as CG flashes. Evidence in hand, points to their being real positive, albeit weak CG flashes. Whether or not they are real positive ground flashes, it is important to be aware of their presence in data from magnetic DF networks.

  5. Study on control method of natural circulation by injection of helium gas

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Tetsuaki, E-mail: ttakeda@yamanashi.ac.jp; Nomura, Masashi; Yanagawa, Naoto; Funatani, Shumpei

    2014-05-01

    This study is to investigate a control method of natural circulation of air by injection of helium gas. A depressurization accident is one of the design-basis accidents of a very high temperature reactor (VHTR). When the primary pipe rupture accident occurs in the VHTR, air is expected to enter into the reactor pressure vessel from the breach and oxidize in-core graphite structures. Finally, it seems to be probable that the natural circulation flow of air in the reactor pressure vessel produce continuously. In order to predict or analyze the air ingress phenomena during the depressurization accident of the VHTR, therefore, it is important to develop the method for prevention of air ingress during the accident. The experiment has been carried out regarding natural circulation using a circular tube consisting of a reverse U-shaped type. The vertical channel consists of the one side heated tube and the other side cooled tube. The experimental procedure is as follows. Firstly, the apparatus is filled with air and one vertical tube is heated. Then, natural circulation of air will be produced in the channel. After the steady state is established, a very small amount of helium gas injects from the top of the channel. The velocity, temperature of gas, and temperature of the tube wall are measured during the experiment. The analysis also has been carried out regarding natural circulation. The results were obtained as follows. The temperature difference between the vertical pipes was 50–130 K, and a small amount of helium gas injected to the channel. The volume of injected helium gas is about 3.5–10% of the total volume of the channel. When the temperature difference between the vertical tubes was kept at 52 K, the velocity of natural circulation flow became about 0.12 m/s. During a steady state, a small amount of helium gas injected into the channel. Then, the flow velocity of natural circulation suddenly decreased. The volume of injected helium gas is about 3% of the

  6. Gamma ray flashes add to mystery of upper atmosphere

    Science.gov (United States)

    Atmospheric electricity research has come a long way since Benjamin Franklin's kite-flying days. But what researchers have been learning lately about above-thunderstorm electricity has wrought a whole new era of mysteries.For a start, last summer a Colorado meteorologist sparked interest in a terrestrial phenomenon that the community first observed more than 100 years ago: optical flashes that occur above thunderstorms—at least 30 km above Earth. Walter Lyons with the Ft. Collins-based Mission Research Corporation, demonstrated that such flashes are not anomalies, as conventional scientific wisdom had held. He filmed hundreds of flashes during a 2-week period.

  7. FLASH is an essential component of Cajal bodies.

    Science.gov (United States)

    Barcaroli, D; Dinsdale, D; Neale, M H; Bongiorno-Borbone, L; Ranalli, M; Munarriz, E; Sayan, A E; McWilliam, J M; Smith, T M; Fava, E; Knight, R A; Melino, G; De Laurenzi, V

    2006-10-03

    Cajal bodies are small nuclear organelles with a number of nuclear functions. Here we show that FLICE-associated huge protein (FLASH), originally described as a component of the apoptosis signaling pathway, is mainly localized in Cajal bodies and is essential for their structure. Reduction in FLASH expression by short hairpin RNA results in disruption of the normal architecture of the Cajal body and relocalization of its components. Because the function of FLASH in the apoptosis receptor signaling pathway has been strongly questioned, we have now identified a clear function for this protein.

  8. FLASH-OFDM-通信业的新宠

    Institute of Scientific and Technical Information of China (English)

    李勇民

    2008-01-01

    OFDM技术是宽带无线接(BWA)领域内的一种重要技术,本文从介绍OFDM原理入手,突出了它抗干扰能力强、频谱利用率高等特点,而FLASH-OFDM则是OFDM技术中的一种.之后进一步介绍了FLASH-OFDM技术的协议模型,对物理层、MAC/路层和网络层进行了详细的介绍,从而得到了FLASH-OFDM技术的优越性.

  9. Development and Dissemination of a Nationwide Helium Database for a National Assessment of Helium Resources.

    Science.gov (United States)

    Brennan, S. T.; East, J. A., II; Garrity, C. P.

    2015-12-01

    In 2013, Congress passed the Helium Stewardship Act requiring the U.S. Geological Survey (USGS) to undertake a national helium gas resource assessment to determine the nation's helium resources. An important initial component necessary to complete this assessment was the development of a comprehensive database of Helium (He) concentrations from petroleum exploration wells. Because Helium is often used as the carrier gas for compositional analyses for commercial and exploratory oil and gas wells, this limits the available helium concentration data. A literature search in peer-reviewed publications, state geologic survey databases, USGS energy geochemical databases, and the Bureau of Land Management databases provided approximately 16,000 data points from wells that had measurable He concentrations in the gas composition analyses. The data from these wells includes, date of sample collection, American Petroleum Institute well number, formation name, field name, depth of sample collection, and location. The gas compositional analyses, some performed as far back as 1934, do not all have the same level of precision and accuracy, therefore the date of the analysis is critical to the assessment as it indicates the relative amount of uncertainty in the analytical results. Non-proprietary data was used to create a GIS based interactive web interface that allows users to visualize, inspect, interact, and download our most current He data. The user can click on individual locations to see the available data at that location, as well as zoom in and out on a data density map. Concentrations on the map range from .04 mol% (lowest concentration of economic value) to 12% (highest naturally occurring values). This visual interface will allow users to develop a rapid appreciation of the areas with the highest potential for high helium concentrations within oil and gas fields.

  10. Heavy rainfall induced flash flood management

    Science.gov (United States)

    Weiler, Markus; Steinbrich, Andreas; Stölzle, Michael; Leistert, Hannes

    2016-04-01

    Heavy rain induced flash floods are still a serious hazard. In context of climate change even a rise of threat potential of flash flood must be suspected. To improve prediction of endangered areas hydraulic models was developed in the past that implement topography information in heigh resolution, gathered by laser scan applications. To run such models it is crucial to estimate the runoff input spatial distributed. However, this information is usually derived with relatively simple models lacking the process rigour that is required for prediction in engaged basins. Though available rain runoff models are able to model runoff response integral for measured catchments they do not indicate the spatial distribution of processes. Moreover they are commonly calibrated to measured runoff data and not applicable in other environments. Since runoff generation is commonly not measured, a calibration on it is hardly possible. In this study, we present a new approach for quantification of runoff generation in height spatial and temporal resolution. A suited model needs to work without calibration in every given environment under any given conditions. It is possible to develop such a model by combining spatial distributed input data of land surface properties (e.g. soil, geology, land use, …) with worldwide findings of runoff generation research. We developed such a model for the state of Baden-Württemberg, what has an extensive pool of spatial data. E.g. a digital elevation model of 1*1m² resolution, degree of sealing of the earth surface in 1*1m² resolution, soil properties (1:50.000) and geology (1:200.000). Within the state of Baden-Württemberg different regions are situated, with distinct environmental characteristics concerning as well climate, soil properties, land use, topography and geology. The model was tested and validated by modelling 36 observed flood events in 13 mesoscale catchments representing the different regions of Baden-Württemberg as well as by

  11. Helium-cooling in fusion power plants

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.P.C.; Baxi, C.B.; Hamilton, C.J.; Schleicher, R.W.; Streckert, H.

    1994-11-01

    This paper reviews different helium-cooled first wall and blanket designs; and compares the selection of structural materials. The authors found that the solid breeder, SiC-composite material option generates the lowest amount of induced radioactivity and afterheat and has the highest temperature capability. When combined with the direct cycle gas turbine system, it has the potential to be the most economical fusion system and can compete with advanced fission reactors. When compared to martensitic steel and V-alloy, SiC-composite is the least developed of these three structural materials, a focused development effort will be needed. Fundamental research has begun in addressing the issues of optimized composite materials, irradiation effects, leak tightness and low activation braze materials. Development of helium-cooled high heat flux components and further development of the direct cycle gas turbine system will also be needed.

  12. Survivor from asphyxiation due to helium inhalation

    Directory of Open Access Journals (Sweden)

    Massimiliano Etteri

    2016-06-01

    Full Text Available In this rare case report we describe a 27- year-old white man survived to suicide by asphyxiation using the so-called suicide bag (or exit bag filled with helium supplied through a plastic tube. He had no previous psychiatric or organic illnesses. At the time of presentation to our Emergency Department he was awake and reported severe dyspnea with a clinical pattern of acute respiratory failure. Imaging studies showed pulmonary edema and the patient was treated with non-invasive ventilation in Intensive Care Unit. After 15 days the patient was discharged from hospital in optimal conditions. These rare cases of survivor might suggest the possible causes of death from inhaling helium.

  13. Robust Flash 3D-FPA Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc. (ASC) is a small business, which has developed a compact, eye-safe 3D Flash LIDARTM Camera (FLC) well suited for real-time...

  14. Flash3D EDL Sensor Technology Advancement Project

    Data.gov (United States)

    National Aeronautics and Space Administration — 3D Flash LIDAR is ideal for determining real-time spacecraft trajectory, speed, orientation, and range to the planet surface, as well as evaluating potential hazards...

  15. Flash 3D Rendezvous and Docking Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — 3D Flash Ladar is a breakthrough technology for many emerging and existing 3D vision areas, and sensor improvements will have an impact on nearly all these fields....

  16. Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Space Micro proposes to build a radiation hardened by design (RHBD) flash memory, using a modified version of our RH-eDRAM Memory Controller to solve all the single...

  17. Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light

    NARCIS (Netherlands)

    Vejrazka, C.; Janssen, M.G.J.; Streefland, M.; Wijffels, R.H.

    2011-01-01

    Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing-induced flashing light regimes. In this study, photosynthetic efficienc

  18. Quantitative observation of light flash sensations experiment MA-106

    Science.gov (United States)

    Budinger, T. F.; Tobias, C. A.; Schopper, E.; Schott, J. U.; Huesman, R. H.; Upham, F. T.; Wieskamp, T. F.; Kucala, J. M.; Goulding, F. S.; Landis, D. A.

    1976-01-01

    Light flashes caused by the interaction of cosmic particles with the visual apparatus have been observed by astronauts on all space missions since Apollo 11. This Apollo Soyuz Test Project experiment compared measurements of the observer's visual sensitivity with measurements of the ambient radiation environment and with the frequency and character of the flashes observed. The data obtained reveal a latitude dependence of the frequency of observed flashes. This distribution of flashes is correlated with the distribution of cosmic particles with stopping power greater than 15 keV/ micrometers in the eye. The interaction of dark adaptation, specific ionization, and range of particles in the retina as factors in the visualization of particle passage is discussed.

  19. Flash Cracking Reactor for Waste Plastic Processing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to design, model, build, and test a novel flash cracking reactor to convert plastic waste, and potentially other unconventional hydrocarbon feedstocks,...

  20. Impact of rainfall spatial variability on Flash Flood Forecasting

    Science.gov (United States)

    Douinot, Audrey; Roux, Hélène; Garambois, Pierre-André; Larnier, Kevin

    2014-05-01

    According to the United States National Hazard Statistics database, flooding and flash flooding have caused the largest number of deaths of any weather-related phenomenon over the last 30 years (Flash Flood Guidance Improvement Team, 2003). Like the storms that cause them, flash floods are very variable and non-linear phenomena in time and space, with the result that understanding and anticipating flash flood genesis is far from straightforward. In the U.S., the Flash Flood Guidance (FFG) estimates the average number of inches of rainfall for given durations required to produce flash flooding in the indicated county. In Europe, flash flood often occurred on small catchments (approximately 100 km2) and it has been shown that the spatial variability of rainfall has a great impact on the catchment response (Le Lay and Saulnier, 2007). Therefore, in this study, based on the Flash flood Guidance method, rainfall spatial variability information is introduced in the threshold estimation. As for FFG, the threshold is the number of millimeters of rainfall required to produce a discharge higher than the discharge corresponding to the first level (yellow) warning of the French flood warning service (SCHAPI: Service Central d'Hydrométéorologie et d'Appui à la Prévision des Inondations). The indexes δ1 and δ2 of Zoccatelli et al. (2010), based on the spatial moments of catchment rainfall, are used to characterize the rainfall spatial distribution. Rainfall spatial variability impacts on warning threshold and on hydrological processes are then studied. The spatially distributed hydrological model MARINE (Roux et al., 2011), dedicated to flash flood prediction is forced with synthetic rainfall patterns of different spatial distributions. This allows the determination of a warning threshold diagram: knowing the spatial distribution of the rainfall forecast and therefore the 2 indexes δ1 and δ2, the threshold value is read on the diagram. A warning threshold diagram is

  1. Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light

    NARCIS (Netherlands)

    Vejrazka, C.; Janssen, M.G.J.; Streefland, M.; Wijffels, R.H.

    2011-01-01

    Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing-induced flashing light regimes. In this study, photosynthetic

  2. Distributed query processing in flash-based sensor networks

    Institute of Scientific and Technical Information of China (English)

    Jianliang XU; Xueyan TANG; Wang-Chien LEE

    2008-01-01

    Wireless sensor networks are used in a large array of applications to capture,collect,and analyze physical environmental data.Many existing sensor systems instruct sensor nodes to report their measurements to central repositories outside the network,which is expensive in energy cost.Recent technological advances in flash memory have given rise to the development of storagecentric sensor networks,where sensor nodes are equipped with high-capacity flash memory storage such that sensor data can b.e stored and managed inside the network to reduce expensive communication.This novel architecture calls for new data management techniques to fully exploit distributed in-network data storage.This paper describes some of our research on distributed query processing in such flash-based sensor networks.Of particular interests are the issues that arise in the design of storage management and indexing structures combining sensor system workload and read/write/erase characteristics of flash memory.

  3. 3D Flash LIDAR EDL Resolution Improvement Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc. (ASC) is a small business, which has developed a compact, eye-safe 3D Flash LIDARTM Camera (FLC) well suited for real-time...

  4. 3D Flash LIDAR Real-Time Embedded Processing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — 3D Flash LIDAR (3DFL) is ideal for determining real-time spacecraft trajectory, speed and orientation to the planet surface, as well as evaluating potential hazards...

  5. Interim report on flash floods, Area 5 - Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    French, R.H.

    1980-09-01

    Examination of the presently available data indicates that consideration must be given to the possibility of flash floods when siting waste management facilities in Area 5 of the Nevada Test Site. 6 figures, 7 tables.

  6. Percepciones sobre seguridad ciudadana en Lima. Encuesta Flash

    OpenAIRE

    Zavaleta Martínez Vargas, Alfonso; Chávez, Virgilio; Tapia, Luis; Vertiz, Rosa

    2016-01-01

    La investigación presenta un aporte relacionado con "consumo de drogas cocaínicas, alcohol y violencia". Resultados de la encuesta flash "Seguridad Ciudadana" realizada por CEDRO en diciembre de 2015.

  7. 3D Flash LIDAR Real-Time Embedded Processing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Scientific Concepts, Inc. (ASC) is a small business, which has developed a compact, eye-safe 3D Flash LIDARTM Camera (FLC) well suited for real-time...

  8. Dynamic simulation of flash drums using rigorous physical property calculations

    Directory of Open Access Journals (Sweden)

    F. M. Gonçalves

    2007-06-01

    Full Text Available The dynamics of flash drums is simulated using a formulation adequate for phase modeling with equations of state (EOS. The energy and mass balances are written as differential equations for the internal energy and the number of moles of each species. The algebraic equations of the model, solved at each time step, are those of a flash with specified internal energy, volume and mole numbers (UVN flash. A new aspect of our dynamic simulations is the use of direct iterations in phase volumes (instead of pressure for solving the algebraic equations. It was also found that an iterative procedure previously suggested in the literature for UVN flashes becomes unreliable close to phase boundaries and a new alternative is proposed. Another unusual aspect of this work is that the model expressions, including the physical properties and their analytical derivatives, were quickly implemented using computer algebra.

  9. Transformer core

    NARCIS (Netherlands)

    Mehendale, A.; Hagedoorn, Wouter; Lötters, Joost Conrad

    2010-01-01

    A transformer core includes a stack of a plurality of planar core plates of a magnetically permeable material, which plates each consist of a first and a second sub-part that together enclose at least one opening. The sub-parts can be fitted together via contact faces that are located on either side

  10. Transformer core

    NARCIS (Netherlands)

    Mehendale, A.; Hagedoorn, Wouter; Lötters, Joost Conrad

    2008-01-01

    A transformer core includes a stack of a plurality of planar core plates of a magnetically permeable material, which plates each consist of a first and a second sub-part that together enclose at least one opening. The sub-parts can be fitted together via contact faces that are located on either side

  11. Laser-Induced Breakdown in Liquid Helium

    Science.gov (United States)

    Sirisky, S.; Yang, Y.; Wei, W.; Maris, H. J.

    2017-10-01

    We report on experiments in which focused laser light is used to induce optical breakdown in liquid helium-4. The threshold intensity has been measured over the temperature range from 1.1 to 2.8 K with light of wavelength 1064 nm. In addition to the measurement of the threshold, we have performed experiments to study how the breakdown from one pulse modifies the probability that a subsequent pulse will result in breakdown.

  12. Correlation of Helium Solubility in Liquid Nitrogen

    Science.gov (United States)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2012-01-01

    A correlation has been developed for the equilibrium mole fraction of soluble gaseous helium in liquid nitrogen as a function of temperature and pressure. Experimental solubility data was compiled and provided by National Institute of Standards and Technology (NIST). Data from six sources was used to develop a correlation within the range of 0.5 to 9.9 MPa and 72.0 to 119.6 K. The relative standard deviation of the correlation is 6.9 percent.

  13. Flash-flood impacts cause changes in wood anatomy of Alnus glutinosa, Fraxinus angustifolia and Quercus pyrenaica.

    Science.gov (United States)

    Ballesteros, J A; Stoffel, M; Bollschweiler, M; Bodoque, J M; Díez-Herrero, A

    2010-06-01

    Flash floods may influence the development of trees growing on channel bars and floodplains. In this study, we analyze and quantify anatomical reactions to wounding in diffuse-porous (Alnus glutinosa L.) and ring-porous (Fraxinus angustifolia Vahl. and Quercus pyrenaica Willd.) trees in a Mediterranean environment. A total of 54 cross-sections and wedges were collected from trees that had been injured by past flash floods. From each of the samples, micro-sections were prepared at a tangential distance of 1.5 cm from the injury to determine wounding-related changes in radial width, tangential width and lumen of earlywood vessels, and fibers and parenchyma cells (FPC). In diffuse-porous A. glutinosa, the lumen area of vessels shows a significant (non-parametric test, P-value <0.05) decrease by almost 39% after wounding. For ring-porous F. angustifolia and Q. pyrenaica, significant decreases in vessel lumen area are observed as well by 59 and 42%, respectively. Radial width of vessels was generally more sensitive to the decrease than tangential width, but statistically significant values were only observed in F. angustifolia. Changes in the dimensions of earlywood FPC largely differed between species. While in ring-porous F. angustifolia and Q. pyrenaica the lumen of FPC dropped by 22 and 34% after wounding, we observed an increase in FPC lumen area in diffuse-porous A. glutinosa of approximately 35%. Our data clearly show that A. glutinosa represents a valuable species for flash-flood research in vulnerable Mediterranean environments. For this species, it will be possible in the future to gather information on past flash floods with non-destructive sampling based on increment cores. In ring-porous F. angustifolia and Q. pyrenaica, flash floods leave less drastic, yet still recognizable, signatures of flash-flood activity through significant changes in vessel lumen area. In contrast, the use of changes in FPC dimensions appears less feasible for the determination of

  14. Laser Spectroscopy of Antiprotonic Helium Atoms

    CERN Multimedia

    2002-01-01

    %PS205 %title\\\\ \\\\Following the discovery of metastable antiprotonic helium atoms ($\\overline{p}He^{+} $) at KEK in 1991, systematic studies of their properties were made at LEAR from 1991 to 1996. In the first two years the lifetime of $\\overline{p}He^{+}$ in liquid and gaseous helium at various temperatures and pressures was measured and the effect of foreign gases on the lifetime of these atoms was investigated. Effects were also discovered which gave the antiproton a 14\\% longer lifetime in $^4$He than in $^3$He, and resulted in important differences in the shape of the annihilation time spectra in the two isotopes.\\\\ \\\\Since 1993 laser spectroscopy of the metastable $\\overline{p}He^{+}$ atoms became the main focus of PS205. Transitions were stimulated between metastable and non-metastable states of the $\\overline{p}He^{+}$ atom by firing a pulsed dye laser beam into the helium target every time an identified metastable atom was present (Figure 1). If the laser frequency matched the transition energy, the...

  15. Modeling Flash Floods in Small Ungaged Watersheds using Embedded GIS

    OpenAIRE

    Knocke, Ethan William

    2006-01-01

    Effective prediction of localized flash flood regions for an approaching rainfall event requires an in-depth knowledge of the land surface and stream characteristics of the forecast area. Flash Flood Guidance (FFG) is currently formulated once or twice a day at the county level by River Forecast Centers (RFC) in the U.S. using modeling systems that contain coarse, generalized land and stream characteristics and hydrologic runoff techniques that often are not calibrated for the forecast regio...

  16. Tutorial Pengenalan Adobe Photoshop Menggunakan Adobe Flash CS3

    OpenAIRE

    Mayoka, Rio

    2011-01-01

    Kajian ini bertujuan untuk membangun sebuah aplikasi yang dapat menjadi alat bantu dalam pembelajaran Adobe Photoshop, dimana terdapat beberapa materi pengenalan dasar Adobe Photoshop. Aplikasi ini suatu gagasan dengan membuat tutorial beranimasi yang interatif. Aplikasi ini dibuat dengan menggunakan Adobe Flash CS3 dan dapat dijalankan dengan Flash player. Aplikasi ini dapat membantu para penggunanya dalam memahami pengenalan Adobe Photoshop, terutama pengenalan tool pada Adob...

  17. Neural Coding of Green Flash in Retinal Bipolar Pathways

    OpenAIRE

    Caiping Hu

    2012-01-01

    What visual information do the graded potentials among retinal bipolar pathways actually transmit from photoreceptors to ganglion cells? The answer does not exist. Even the graded electric signals have not been understood completely. Here, this paper tries to analyze the encoding mechanisms of graded signals among the parallel bipolar pathways in response to brief green flash. The typical ON, OFF and ON-OFF bipolar cells simultaneously abstracted vectors from green flash stimulus with sine-li...

  18. Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

    OpenAIRE

    Eugene A. Olevsky; Stephen M. Rolfing; Maximenko, Andrey L.

    2016-01-01

    A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the f...

  19. Coherence measurements and coherent diffractive imaging at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Vartanyants, I A; Mancuso, A P; Singer, A; Yefanov, O M; Gulden, J, E-mail: ivan.vartaniants@desy.d [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg (Germany)

    2010-10-14

    We present an overview of recent experiments performed at the free-electron laser (FEL) FLASH at DESY in Hamburg. Experiments were focused on coherence measurements and coherent x-ray diffractive imaging (CXDI) of periodic and non-periodic biological samples. Young's double slit experiment was performed at FLASH to measure its coherence properties at a fundamental wavelength of 13.7 nm. Additionally, a uniformly redundant array was used to measure the coherence properties of the third harmonic (2.7 nm) of an 8 nm fundamental wavelength at FLASH. Coherent imaging of a two-dimensional (2D) finite crystal structure using a single pulse train of FLASH radiation was demonstrated. We show that the structure is reconstructed to the detector-limited resolution of 220 nm, given an adequate signal to noise ratio. We have also employed CXDI in a non-destructive regime to compare the images of a biological sample using single, femtosecond pulses of FLASH radiation. We have verified that images reconstructed using CXDI are similar for statistically different FEL pulses. We have also demonstrated Fourier transform holography of the same biological sample and present diffraction data measured at the third harmonic of FLASH, reaching into the water window.

  20. Establishment of the NIST flashing-light photometric unit

    Science.gov (United States)

    Ohno, Yoshihiro; Zong, Yuqin

    1997-09-01

    There is a need for accurate measurement of flashing lights for the proper maintenance of aircraft anticollision lights. A large variation in the measured intensities of anticollision lights has been a problem, and thus, NIST has undertaken the task to establish flashing-light photometric standards to provide calibration services in this area. A flashing-light photometric unit [lux second, (lx (DOT) s)] has been realized based on the NIST detector-based candela, using four standard photometers equipped with current integrators. Two different approaches have been taken to calibrate these standard photometers: one based on electrical calibration of the current integrator, and the other based on electronic pulsing of a steady-state photometric standard. The units realized using these two independent methods agreed to within 0.2%. The relative expanded uncertainty (k equals 2) of the standard photometers, in the measurement of the white xenon flash, is estimated to be 0.6%. The standard photometers are characterized for temporal response, linearity, and spectral responsivity, to be used for measurement of xenon flash sources of various waveforms and colors. Calibration services have been established at NIST for flashing-light photometers with white and red anticollision lights.

  1. Flash light sintering of nickel nanoparticles for printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sung-Hyeon [School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kim, Hak-Sung, E-mail: kima@hanyang.ac.kr [School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Institute of Nano Science and Technology, Hanyang University, Seoul 133-79 (Korea, Republic of)

    2014-01-01

    In this paper, a sintering process for nickel nanoparticles using flash light irradiation was investigated for multilayer ceramic capacitors, magnetic devices and printed electronics. The existence of a small amount of 10 nm size nanoparticles in the ink significantly improved the flash light absorption and induced the melting and sintering of the nanoparticles. Due to this phenomenon, uniform diameter nickel nanoparticles (50 nm) could not be sintered, while the nickel nanoparticles with varying diameters (5–500 nm) were sintered by flash light irradiation. In order to acquire high electrical conductivity in the sintered nickel nanoparticles, several flash light sintering parameters such as light energy and pulsed light patterns were optimized. Also, the nickel nano-ink was optimized by changing the weight fractions of organic binder in the ink. - Highlights: • Nickel nanoparticle was sintered by flash light irradiation technique. • The existence of 10 nm size nanoparticles improved the flash light absorption. • The melting temperature of the 10 nm size nanoparticles is significantly decreased. • The only nickel nanoparticles with varying diameters (5–500 nm) were sintered. • Several sintering parameters were optimized for conductivity of nickel nanoparticle.

  2. Production of bio-oil with flash pyrolysis; Biooeljyn tuotanto flash-pyrolyysillae ja sen poltto

    Energy Technology Data Exchange (ETDEWEB)

    Nyroenen, T. [Vapo Oy, Jyvaeskylae (Finland)

    1997-12-01

    The target of the R and D work is to study the production of bio-oils using Flash-pyrolysis technology and utilisation of the bio-oil in oil-fuelled boilers. The PDU-unit was installed at VTT Energy in Otaniemi in April 1996. The first test were carried out in June. In the whole project Vapo Oy is responsible for: acquiring the 20 kg/h PDU-device for development; follow up of the engine tests; the investment of 5 MW demonstration plant; to carry on the boiler and engine tests with Finnish bio-oils. (orig.)

  3. Flash lidar performance testing: configuration and results

    Science.gov (United States)

    Poberezhskiy, Ilya; Johnson, Andrew; Chang, Daniel; Ek, Eric; Natzic, David; Spiers, Gary; Penniman, Steve; Short, Brad

    2012-06-01

    Future planetary and lunar landers can benefit from a hazard detection (HD) system that employs a lidar to create a highresolution 3D terrain map in the vicinity of the landing site and an onboard computer to process the lidar data and identify the safest landing site within the surveyed area. A divert maneuver would then be executed to land in this safe site. An HD system enables landing in regions with a relatively high hazard abundance that would otherwise be considered unacceptably risky, but are of high interest to the scientific community. A key component of a HD system is a lidar with the ability to generate a 3D terrain image with the required range precision in the prescribed time and fits within the project resource constraints. In this paper, we present the results obtained during performance testing of a prototype "GoldenEye" 3D flash lidar developed by ASC, Inc. The testing was performed at JPL with the lidar and the targets separated by 200 m. The analysis of the lidar performance obtained for different target types and albedos, pulse energies, and fields of view is presented and compared to key HD lidar requirements identified for the Mars 2018 lander.

  4. Studying white dwarf merger remnants with FLASH

    Science.gov (United States)

    Jenks, Malia

    2017-01-01

    There is still uncertainty as to the progenitor systems of type Ia supernova (SN Ia). Both single and double degenerate systems have been suggested as progenitors. In a double degenerate system a merger between the two white dwarfs, with total mass at or exceeding the Chandrasekhar mass, leads to the supernova. If the explosion occurs during the merging process it is a violent merger. If an explosion doesn't occur while the stars merge the system becomes a white dwarf of unstable mass. For mergers of this type with differing starting masses it has been shown that during the viscous evolution carbon burning starts far from the center and stably converts the star to oxygen and neon. In this case the star will eventually collapse to a neutron star and not produce an SN Ia. The case of similar mass mergers has been much less explored. Using the results of a smooth particle hydrodynamic merger we simulate the viscous evolution of models of different mass ratios with FLASH. These simulations test if a similar mass merger can lead to an SN Ia, and begin to probe where the transition from similar to dissimilar mass occurs.

  5. Flash pyrolysis fuel oil: bio-pok

    Energy Technology Data Exchange (ETDEWEB)

    Gust, S. [Neste Oy, Porvoo (Finland)

    1997-12-01

    Samples of flash pyrolysis liquid produced by Union Fenosa, Spain from pine and straw and samples produced by Ensyn of Canada from mixed hardwoods were combusted with simple pressure atomization equipment commonly used with light fuel oils in intermediate size (0.1-1 MW) boilers. With a number of modifications to the combustion system, carbon monoxide (CO) and nitrous oxide (NO{sub x}) could be reduced to acceptable levels: CO < 30 ppm and NO{sub x} < 140 ppm. Particulate emissions which were initially very high (Bacharach 4-5) were reduced (Bach. 2-3) by system improvements but are still higher than from light fuel oil (Bach. <1). The modifications to the combustion system were: refractory section between burner and boiler, acid resistant progressive cavity pump, higher liquid preheat temperature and higher pressure than for light fuel oils. The main problems with pyrolysis liquids concerns their instability or reactivity. At temperatures above 100 deg C they begin to coke, their viscosity increases during storage and oxygen from air causes skin formation. This requires that special handling procedures are developed for fuel storage, delivery and combustion systems. (orig.)

  6. Development of gas cooled reactors and experimental setup of high temperature helium loop for in-pile operation

    Energy Technology Data Exchange (ETDEWEB)

    Miletić, Marija, E-mail: marija_miletic@live.com [Czech Technical University in Prague, Prague (Czech Republic); Fukač, Rostislav, E-mail: fuk@cvrez.cz [Research Centre Rez Ltd., Rez (Czech Republic); Pioro, Igor, E-mail: Igor.Pioro@uoit.ca [University of Ontario Institute of Technology, Oshawa (Canada); Dragunov, Alexey, E-mail: Alexey.Dragunov@uoit.ca [University of Ontario Institute of Technology, Oshawa (Canada)

    2014-09-15

    Highlights: • Gas as a coolant in Gen-IV reactors, history and development. • Main physical parameters comparison of gas coolants: carbon dioxide, helium, hydrogen with water. • Forced convection in turbulent pipe flow. • Gas cooled fast reactor concept comparisons to very high temperature reactor concept. • High temperature helium loop: concept, development, mechanism, design and constraints. - Abstract: Rapidly increasing energy and electricity demands, global concerns over the climate changes and strong dependence on foreign fossil fuel supplies are powerfully influencing greater use of nuclear power. In order to establish the viability of next-generation reactor concepts to meet tomorrow's needs for clean and reliable energy production the fundamental research and development issues need to be addressed for the Generation-IV nuclear-energy systems. Generation-IV reactor concepts are being developed to use more advanced materials, coolants and higher burn-ups fuels, while keeping a nuclear reactor safe and reliable. One of the six Generation-IV concepts is a very high temperature reactor (VHTR). The VHTR concept uses a graphite-moderated core with a once-through uranium fuel cycle, using high temperature helium as the coolant. Because helium is naturally inert and single-phase, the helium-cooled reactor can operate at much higher temperatures, leading to higher efficiency. Current VHTR concepts will use fuels such as uranium dioxide, uranium carbide, or uranium oxycarbide. Since some of these fuels are new in nuclear industry and due to their unknown properties and behavior within VHTR conditions it is very important to address these issues by investigate their characteristics within conditions close to those in VHTRs. This research can be performed in a research reactor with in-pile helium loop designed and constructed in Research Center Rez Ltd. One of the topics analyzed in this article are also physical characteristic and benefits of gas

  7. Shift and broadening of resonance lines of antiprotonic helium atoms in solid helium

    CERN Document Server

    Adamczak, Andrzej

    2014-01-01

    We have estimated the shift and broadening of the resonance lines in the spectrum of antiprotonic helium atoms $\\bar{p}\\mathrm{He}^{+}$ implanted in solid helium $^4$He. The application of the response function for crystalline helium has enabled determination of the contributions from the collective degrees of freedom to the shift and broadening. It occurs that the broadening due to the collective motion is negligible compared to the natural line width. The available pair-correlation functions for crystalline $^4$He have been applied for estimating the resonance-line shift due to collisions of $\\bar{p}\\mathrm{He}^{+}$ atom with the surrounding $^4$He atoms. The dependence of the line shift, which has been calculated in the quasistatic limit, on the solid-$^4$He density is nonlinear.

  8. Multipurpose closed-cycle cryocooler for liquefying hydrogen, helium-4 or helium-3

    Science.gov (United States)

    Winter, Calvin

    1990-08-01

    A cryogenic refrigerator utilizing helium-4 gas in closed-cycle Gifford-McMahon and Joule-Thomson cooling loops was built and achieves continuous operating temperatures of 2.8R. The object cooled is a thin walled (0.1mm) seamless electroformed nickel target sample cell with a volume of 160m1. Room temperature hydrogen, helium-4 or helium-3 gas, supplied at a pressure slightly above atmospheric, is liquefied by the cryocooler and fills the cell. Unusual features include: horizontal operation; a long narrow extension on the vacuum shroud (900mm long, 76mm diameter) and special valves to select an operating temperature appropriate to the sample gas and maximize the cooling power available at that temperature.

  9. THERMAL UNIFORMITY OF LIQUID HELIUM IN ELECTRON BUBBLE CHAMBER.

    Energy Technology Data Exchange (ETDEWEB)

    WANG,L.; JIA,L.

    2002-07-22

    A CRYOGENIC RESEARCH APPARATUS TO MEASURE THE MOVEMENT OF ELECTRONS UNDER A HIGH ELECTRIC FIELD IN A LIQUID HELIUM BATH WAS DESIGNED AND BUILT AT THE BROOKHAVEN NATIONAL LABORATORY AND THE NEVIS LABORATORY OF COLUMBIA UNIVERSITY. THE LIQUID HELIUM CHAMBER IS A DOUBLE WALLED CYLINDRICAL CONTAINER EQUIPPED WITH 5 OPTICS WINDOWS AND 10 HIGH VOLTAGE CABLES. TO SHIELD THE LIQUID HELIUM CHAMBER AGAINST THE EXTERNAL HEAT LOADS AND TO PROVIDE THE THERMAL UNIFORMITY IN THE LIQUID HELIUM CHAMBER, THE DOUBLE WALLED JACKET WAS COOLED BY A PUMPED HELIUM BATH. THE HELIUM CHAMBER WAS BUILT INTO A COMMERICAL LN2 / LHE CRYOSTAT. THIS PAPER PRESENTS THE DESIGN AND THE NUMERICAL SIMULATION ANALYSIS ON THERMAL UNIFORMITY OF THE ELECTRON BUBBLE CHAMBER.

  10. Helium liquefaction with a 4 K pulse tube cryocooler

    Science.gov (United States)

    Wang, Chao

    2001-07-01

    Helium liquefaction with a two-stage 4 K pulse tube cryocooler is introduced in this paper. The helium liquefier has a feature of precooling helium gas to be liquefied by using inefficiency of the second stage regenerator in the pulse tube cryocooler. This process reduces enthalpy of the incoming helium gas when entering the condenser and significantly increases the condensation rate. Numerical analysis predicts the precooling heat load on the second stage regenerator, decreases the PTC second stage cooling capacity by only 11% of the heat actually absorbed into the regenerator. A prototype pulse tube helium liquefier was built, which has two precooling heat exchangers on the first stage cold head and the second stage regenerator. It continuously liquefies helium with a rate of 4.8 l/day under normal pressure while consumes 4.6 kW power input.

  11. Diffusion behaviors of helium atoms at two Pd grain boundaries

    Institute of Scientific and Technical Information of China (English)

    XIA Ji-xing; HU Wang-yu; YANG Jian-yu; AO Bing-yun

    2006-01-01

    The diffusion behaviors of helium atoms at two symmetric grain boundaries (Σ5{210} and Σ3 {112}) of Pd were investigated using molecular dynamics simulations through an analytical embedded-atom method(MAEAM) model. The simulations demonstrate that the interstitial helium atoms are easily trapped at the grain boundaries and precipitated into clusters. Due to the closed-shell electronic configurations of both helium and palladium,Pd grain boundaries yield strong capability of retaining helium atoms. By calculating the mean square displacements(MSD) of an interstitial helium atom at the grain boundaries,the diffusion coefficients were determined,and the linear fits to Arrhenius relation. The diffusion activation energies of interstitial helium atom at these two Pd grain boundaries were also evaluated.

  12. Capacity enhancement of indigenous expansion engine based helium liquefier

    Science.gov (United States)

    Doohan, R. S.; Kush, P. K.; Maheshwari, G.

    2017-02-01

    Development of technology and understanding for large capacity helium refrigeration and liquefaction at helium temperature is indispensable for coming-up projects. A new version of helium liquefier designed and built to provide approximately 35 liters of liquid helium per hour. The refrigeration capacity of this reciprocating type expansion engine machine has been increased from its predecessor version with continuous improvement and deficiency debugging. The helium liquefier has been built using components by local industries including cryogenic Aluminum plate fin heat exchangers. Two compressors with nearly identical capacity have been deployed for the operation of system. Together they consume about 110 kW of electric power. The system employs liquid Nitrogen precooling to enhance liquid Helium yield. This paper describes details of the cryogenic expander design improvements, reconfiguration of heat exchangers, performance simulation and their experimental validation.

  13. A faint type of supernova from a white dwarf with a helium-rich companion.

    Science.gov (United States)

    Perets, H B; Gal-Yam, A; Mazzali, P A; Arnett, D; Kagan, D; Filippenko, A V; Li, W; Arcavi, I; Cenko, S B; Fox, D B; Leonard, D C; Moon, D-S; Sand, D J; Soderberg, A M; Anderson, J P; James, P A; Foley, R J; Ganeshalingam, M; Ofek, E O; Bildsten, L; Nelemans, G; Shen, K J; Weinberg, N N; Metzger, B D; Piro, A L; Quataert, E; Kiewe, M; Poznanski, D

    2010-05-20

    Supernovae are thought to arise from two different physical processes. The cores of massive, short-lived stars undergo gravitational core collapse and typically eject a few solar masses during their explosion. These are thought to appear as type Ib/c and type II supernovae, and are associated with young stellar populations. In contrast, the thermonuclear detonation of a carbon-oxygen white dwarf, whose mass approaches the Chandrasekhar limit, is thought to produce type Ia supernovae. Such supernovae are observed in both young and old stellar environments. Here we report a faint type Ib supernova, SN 2005E, in the halo of the nearby isolated galaxy, NGC 1032. The 'old' environment near the supernova location, and the very low derived ejected mass ( approximately 0.3 solar masses), argue strongly against a core-collapse origin. Spectroscopic observations and analysis reveal high ejecta velocities, dominated by helium-burning products, probably excluding this as a subluminous or a regular type Ia supernova. We conclude that it arises from a low-mass, old progenitor, likely to have been a helium-accreting white dwarf in a binary. The ejecta contain more calcium than observed in other types of supernovae and probably large amounts of radioactive (44)Ti.

  14. Design of the Helium Purifier for IHEP-ADS Helium Purification System

    CERN Document Server

    Jianqin, Zhang; Zhuo, Zhang; Rui, Ge

    2015-01-01

    Helium Purification System is an important sub-system in the Accelerator Driven Subcritical System of the Institute of High Energy Physics(IHEP ADS). The purifier is designed to work at the temperature of 77K. The purifier will work in a flow rate of 5g/s at 20MPa in continuous operation of 12 hours. The oil and moisture are removed by coalescing filters and a dryer, while nitrogen and oxygen are condensed by a phase separator and then adsorbed in several activated carbon adsorption cylinders. After purification, the purified helium has an impurity content of less than 5ppm.

  15. Existence of liquid helium above melting curve pressures

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, A.L.; Brewer, D.F.; Naji, T.; Haynes, S. (Sussex Univ., Brighton (UK). Dept. of Physics); Reppy, J.D. (Cornell Univ., Ithaca, NY (USA))

    Data are presented on the specific heat of helium confined at a high externally applied pressure within the 60 A pores of vycor glass. The specific heat shows that the helium within the pores remains in the liquid state down to temperatures well below 1 K. On the other hand the helium outside the vycor behaves normally, changing phase from solid to liquid as it warms.

  16. "Know What to Do If You Encounter a Flash Flood": Mental Models Analysis for Improving Flash Flood Risk Communication and Public Decision Making.

    Science.gov (United States)

    Lazrus, Heather; Morss, Rebecca E; Demuth, Julie L; Lazo, Jeffrey K; Bostrom, Ann

    2016-02-01

    Understanding how people view flash flood risks can help improve risk communication, ultimately improving outcomes. This article analyzes data from 26 mental models interviews about flash floods with members of the public in Boulder, Colorado, to understand their perspectives on flash flood risks and mitigation. The analysis includes a comparison between public and professional perspectives by referencing a companion mental models study of Boulder-area professionals. A mental models approach can help to diagnose what people already know about flash flood risks and responses, as well as any critical gaps in their knowledge that might be addressed through improved risk communication. A few public interviewees mentioned most of the key concepts discussed by professionals as important for flash flood warning decision making. However, most interviewees exhibited some incomplete understandings and misconceptions about aspects of flash flood development and exposure, effects, or mitigation that may lead to ineffective warning decisions when a flash flood threatens. These include important misunderstandings about the rapid evolution of flash floods, the speed of water in flash floods, the locations and times that pose the greatest flash flood risk in Boulder, the value of situational awareness and environmental cues, and the most appropriate responses when a flash flood threatens. The findings point to recommendations for ways to improve risk communication, over the long term and when an event threatens, to help people quickly recognize and understand threats, obtain needed information, and make informed decisions in complex, rapidly evolving extreme weather events such as flash floods.

  17. Scaled-energy spectroscopy of helium \\|M\\|=1 Rydberg atoms in a static electric field

    Science.gov (United States)

    Kips, Annemieke; Vassen, Wim; Hogervorst, Wim; Dando, Paul A.

    1998-10-01

    We present scaled-energy spectra on helium Rydberg atoms in a static electric field. \\|M\\|=1 states were studied in excitation from the 2 1S0 metastable state. Spectra were recorded for ɛ=-2.940(4), ɛ=-2.350(4), both below the saddle point, and ɛ=-1.760(4), above the saddle point. Closed-orbit theory was applied to interpret the spectra. A recent extension to closed-orbit theory, incorporating core effects, was used. This significantly improved agreement between experiment and theory.

  18. Helium vs. Proton Induced Displacement Damage in Electronic Materials

    Science.gov (United States)

    Ringo, Sawnese; Barghouty, A. F.

    2010-01-01

    In this project, the specific effects of displacement damage due to the passage of protons and helium nuclei on some typical electronic materials will be evaluated and contrasted. As the electronic material absorbs the energetic proton and helium momentum, degradation of performance occurs, eventually leading to overall failure. Helium nuclei traveling at the same speed as protons are expected to impart more to the material displacement damage; due to the larger mass, and thus momentum, of helium nuclei compared to protons. Damage due to displacement of atoms in their crystalline structure can change the physical properties and hence performance of the electronic materials.

  19. Asteroseismic estimate of helium abundance of 16 Cyg A, B

    Directory of Open Access Journals (Sweden)

    Verma Kuldeep

    2015-01-01

    Full Text Available The helium ionization zone in a star leaves a characteristic signature on its oscillation frequencies, which can be used to estimate the helium content in the envelope of the star. We use the oscillation frequencies of 16 Cyg A and B, obtained using 2.5 years of Kepler data, to estimate the envelope helium abundance of these stars. We find the envelope helium abundance to lie in the range 0.231–0.251 for 16 Cyg A and 0.218–0.266 for 16 Cyg B.

  20. Ice Cores

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Records of past temperature, precipitation, atmospheric trace gases, and other aspects of climate and environment derived from ice cores drilled on glaciers and ice...

  1. Core BPEL

    DEFF Research Database (Denmark)

    Hallwyl, Tim; Højsgaard, Espen

    extensions. Combined with the fact that the language definition does not provide a formal semantics, it is an arduous task to work formally with the language (e.g. to give an implementation). In this paper we identify a core subset of the language, called Core BPEL, which has fewer and simpler constructs......, does not allow omissions, and does not contain ignorable elements. We do so by identifying syntactic sugar, including default values, and ignorable elements in WS-BPEL. The analysis results in a translation from the full language to the core subset. Thus, we reduce the effort needed for working...... formally with WS-BPEL, as one, without loss of generality, need only consider the much simpler Core BPEL. This report may also be viewed as an addendum to the WS-BPEL standard specification, which clarifies the WS-BPEL syntax and presents the essential elements of the language in a more concise way...

  2. Core BPEL

    DEFF Research Database (Denmark)

    Hallwyl, Tim; Højsgaard, Espen

    extensions. Combined with the fact that the language definition does not provide a formal semantics, it is an arduous task to work formally with the language (e.g. to give an implementation). In this paper we identify a core subset of the language, called Core BPEL, which has fewer and simpler constructs......, does not allow omissions, and does not contain ignorable elements. We do so by identifying syntactic sugar, including default values, and ignorable elements in WS-BPEL. The analysis results in a translation from the full language to the core subset. Thus, we reduce the effort needed for working...... formally with WS-BPEL, as one, without loss of generality, need only consider the much simpler Core BPEL. This report may also be viewed as an addendum to the WS-BPEL standard specification, which clarifies the WS-BPEL syntax and presents the essential elements of the language in a more concise way...

  3. Core benefits

    National Research Council Canada - National Science Library

    Keith, Brian W

    2010-01-01

    This SPEC Kit explores the core employment benefits of retirement, and life, health, and other insurance -benefits that are typically decided by the parent institution and often have significant governmental regulation...

  4. Spectroscopic Orbital Elements for the Helium-Rich Subdwarf Binary PG1544+488

    CERN Document Server

    Şener, H Tuğça

    2014-01-01

    PG1544+488 is an exceptional short-period spectroscopic binary containing two subdwarf B stars. It is also exceptional because the surfaces of both components are extremely helium-rich. We present a new analysis of spectroscopy of PG1544+488 obtained with the William Herschel Telescope. We obtain improved orbital parameters and atmospheric parameters for each component. The orbital period $P=0.496\\pm0.002$\\,d, dynamical mass ratio $M_{\\rm B}/M_{\\rm A}=0.911\\pm0.015$, and spectroscopic radius ratio $R_{\\rm B}/R_{\\rm A}=0.939\\pm0.004$ indicate a binary consisting of nearly identical twins. The data are insufficient to distinguish any difference in surface composition between the components, which are slightly metal-poor (1/3 solar) and carbon-rich (0.3% by number). The latter indicates that the hotter component, at least, has ignited helium. The best theoretical model for the origin of PG1544+488 is by the ejection of a common envelope from a binary system in which both components are giants with helium cores o...

  5. Characteristics of capacitively coupled RF helium/neon discharges in a hollow fiber

    Science.gov (United States)

    Duan, Lian; Wang, Xinbing; Zuo, Duluo

    2016-11-01

    Capacitively coupled radio-frequency microplasmas are produced in hollow fibers with an inner diameter of hundreds of micrometers powered by an 80-MHz power supply. Considering the narrow space of the hollow core, optical emission spectrometry is used to obtain the spatially resolved characteristics of the microplasmas. The rotational temperature, excitation temperature, and electron density of microplasmas are determined based on the second positive band of nitrogen, the atomic spectra of bulk neutral particles of plasmas, and the Hβ line of the hydrogen Balmer series, respectively. In our experiments, the rotational temperature, excitation temperature, and electron density of typical inert gases helium and neon are in the ranges of 300-500 K, 7000-9500 K, and 1013 cm-3, respectively. The results obtained with different external parameters of power and pressure show that the light emission intensity increases with power and pressure. The distributions of the rotational temperature, excitation temperature, and electron density of the microplasmas are almost constant over the gap between the electrodes. These distributions are mostly insensitive to the change of power and pressure in single-component plasmas. The characteristics of mixed plasmas are also investigated. The plasma with a larger helium content possesses higher excitation temperature and lower rotational temperature and electron density than those of the plasma with a lower helium content.

  6. Post-event analysis and flash flood hydrology in Slovakia

    Directory of Open Access Journals (Sweden)

    Hlavčová Kamila

    2016-12-01

    Full Text Available This work examines the main features of the flash flood regime in Central Europe as revealed by an analysis of flash floods that have occurred in Slovakia. The work is organized into the following two parts: The first part focuses on estimating the rainfall-runoff relationships for 3 major flash flood events, which were among the most severe events since 1998 and caused a loss of lives and a large amount of damage. The selected flash floods occurred on the 20th of July, 1998, in the Malá Svinka and Dubovický Creek basins; the 24th of July, 2001, at Štrbský Creek; and the 19th of June, 2004, at Turniansky Creek. The analysis aims to assess the flash flood peaks and rainfall-runoff properties by combining post-flood surveys and the application of hydrological and hydraulic post-event analyses. Next, a spatially-distributed hydrological model based on the availability of the raster information of the landscape’s topography, soil and vegetation properties, and rainfall data was used to simulate the runoff. The results from the application of the distributed hydrological model were used to analyse the consistency of the surveyed peak discharges with respect to the estimated rainfall properties and drainage basins. In the second part these data were combined with observations from flash flood events which were observed during the last 100 years and are focused on an analysis of the relationship between the flood peaks and the catchment area. The envelope curve was shown to exhibit a more pronounced decrease with the catchment size with respect to other flash flood relationships found in the Mediterranean region. The differences between the two relationships mainly reflect changes in the coverage of the storm sizes and hydrological characteristics between the two regions.

  7. Atmospheric Rivers, Floods, and Flash Floods in California

    Science.gov (United States)

    Skelly, Klint T.

    Atmospheric Rivers (ARs) are long (>2000 km), narrow (<1000 km) corridors of enhanced vertically integrated water vapor (IWV) and enhanced IWV transport (IVT). The landfall of ARs along the U.S. West Coast have been linked to extreme precipitation and flooding/flash flooding in regions of complex topography. The objective of this study is to investigate the relationship between a 10 water-year (2005-2014) climatology of floods, flash floods, and landfalling ARs. The ARs in this study are defined using IVT following the Rutz et al. (2013) methodology, whereas floods and flash floods are identified by the National Centers for Environmental Information (NCEI) Storm Events Database. The results of this study indicate that landfalling ARs are present on a majority of days that there are floods in northern California. Landfalling ARs are predominantly present on a majority of days that there are flash flood reports during the cold-season (November-March); however, the North American monsoon is present on days that there are flash flood reports during the warm-season (April-October). Two exemplary case studies are provided to illustrate the hydrologic impact of landfalling ARs. The first case study illustrated a flood event that occurred in associated with three landfalling ARs that produced 800 mm in regions over the Russian River watershed in northern California and the second case study illustrated a flash flood event that occurred in association with a landfalling AR that produced ˜225 mm of precipitation in regions over the Santa Ynez xii watershed in which produced a flash flood over the southern portions of Santa Barbara County in southern California.

  8. Modelling of chalcopyrite oxidation reactions in the Outokumpu flash smelting process

    Energy Technology Data Exchange (ETDEWEB)

    Ahokainen, T.; Jokilaakso, A. [Helsinki Univ. of Technology, Otaniemi (Finland)

    1996-12-31

    A mathematical model for simulating oxidation reactions of chalcopyrite particles together with momentum, heat and mass transfer between particle and gas phase in a flash smelting furnace reaction shaft is presented. In simulation, the equations governing the gas flow are solved numerically with a commercial fluid flow package, Phoenics. The particle phase is introduced into the gas flow by a Particle Source In Cell (PSIC) - technique, where a number of discrete particles is tracked in a gas flow and the relevant source terms for momentum, mass, and heat transfer are added to the gas phase equations. The gas phase equations used are elliptic in nature and the fluid turbulence is described by the (k-{epsilon}) -model. Thermal gas phase radiation is simulated with a six-flux radiation model. The chemical reactions of concentrate particles are assumed to happen at two sharp interfaces, and a shrinking core model is applied to describe the mass transfer of chemical species through the reaction product layer. In a molten state, the oxygen consumption is controlled by a film penetration concept. The reacting concentrate particles are a mixture of chalcopyrite and silica. Also a certain amount of pure inert silica is fed to the process as flux. In the simulations the calculation domain includes the concentrate burner and a cylindrical reaction shaft of an industrial scale flash smelting furnace. Some examples about the simulations carried out by the combustion model are presented. (author)

  9. A simple flash sintering setup under applied mechanical stress and controlled atmosphere.

    Science.gov (United States)

    Caliman, L B; Bichaud, E; Soudant, P; Gouvea, D; Steil, M C

    2015-01-01

    Most flash sintering experimental set-ups use dog bone-shaped specimen and DC current, which results in heterogeneously distributed densification and grain growth throughout the sample. This is the reason why only the sample's core characteristics after flash are taken into account. On the other hand, some recent procedures suggest the use of cylindrical pellets, which have some advantages compared to the traditional mode as the use of easily conformed samples and its final uniformity. Our new experimental set-up offers the possibility of atmosphere control and pressure application. Also the electrodes material change can be easily made when necessary. Shrinkage measurements and impedance spectroscopy are realized in situ and experimental parameters, as oven heating for example, can be varied to control microstructure changes. •Sample can be entirely recovered at the end of the experiment and can be analyzed throughout its entire extension, including regions in contact with the electrodes that may present some differences from pellets inner part.•The use of AC current enables the study of different frequencies effects.•Experimental set-up can be adapted to different kinds of electrolytes (samples), easily changing electrode's material and atmosphere.

  10. Flash Mixing on the White Dwarf Cooling Curve: Spectroscopic Confirmation in NGC 2808

    CERN Document Server

    Brown, Thomas M; Sweigart, Allen V; Cracraft, Misty; Hubeny, Ivan; Landsman, Wayne B

    2012-01-01

    [Abridged] We present new HST FUV spectroscopy of 24 hot evolved stars in NGC2808, a massive globular cluster with a large population of "blue-hook" (BHk) stars. The BHk stars are found in UV color-magnitude diagrams of the most massive globular clusters, where they fall at luminosities immediately below the hot end of the horizontal branch (HB), in a region of the HR diagram unexplained by canonical stellar evolution theory. Using new evolutionary and atmospheric models, we have shown that these subluminous HB stars are very likely the progeny of stars that undergo extensive internal mixing during a late He-core flash on the white dwarf cooling curve. This flash mixing leads to hotter temperatures and an enormous enhancement of the surface He and C; these hotter temperatures, together with the decrease in H opacity shortward of the Lyman limit, make the BHk stars brighter in the EUV while appearing subluminous in the UV and optical. Our FUV spectroscopy demonstrates that, relative to normal HB stars at the s...

  11. Helium-3 and Helium-4 acceleration by high power laser pulses for hadron therapy

    CERN Document Server

    Bulanov, S S; Schroeder, C B; Leemans, W P; Bulanov, S V; Margarone, D; Korn, G; Haberer, T

    2015-01-01

    The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions. This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes this species an interesting candidate for the laser driven ion source. Two mechanisms (Magnetic Vortex Acceleration and hole-boring Radiation Pressure Acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the ...

  12. Helium-3 and helium-4 acceleration by high power laser pulses for hadron therapy

    Directory of Open Access Journals (Sweden)

    S. S. Bulanov

    2015-06-01

    Full Text Available The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions (heavier than protons. This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes this species an interesting candidate for the laser driven ion source. Two mechanisms (magnetic vortex acceleration and hole-boring radiation pressure acceleration of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He^{3} ions, having almost the same penetration depth as He^{4} with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.

  13. Lamb shift in muonic helium ion

    CERN Document Server

    Martynenko, A P

    2006-01-01

    The Lamb shift (2P_{1/2}-2S_{1/2}) in the muonic helium ion (mu ^4_2He)^+ is calculated with the account of contributions of orders alpha^3, alpha^4, alpha^5 and alpha^6. Special attention is given to corrections of the electron vacuum polarization, the nuclear structure and recoil effects. The obtained numerical value of the Lamb shift 1381.716 meV can be considered as a reliable estimate for the comparison with experimental data.

  14. Heat capacity of helium in cylindrical environments

    Science.gov (United States)

    Gatica, S. M.; Hernández, E. S.; Szybisz, L.

    2003-10-01

    We perform a systematic investigation of the structure, elementary, and phonon excitations of quantum fluid 4He adsorbed in the interior of carbon nanotubes. We show that the helium fluid inside the cylinder behaves exactly as in planar films on a graphite substrate, presenting the same kind of layering transition. This tendency is confirmed by the behavior of a single 3He impurity diluted into adsorbed 4He. We also present a simple description of the lowest excitation modes of the adsorbed fluid and compute the low-temperature contribution of the phonon spectrum to the specific heat, which displays the dimensionality characteristics reported in previous works.

  15. Fano Resonances observed in Helium Nanodroplets

    CERN Document Server

    LaForge, A C; Jabbari, G; Gokhberg, K; Kryzhevoi, N V; Krishnan, S R; Hess, M; O'Kee?e, P; Ciavardini, A; Prince, K C; Richter, R; Moshammer, R; Cederbaum, L S; Pfeifer, T; Stienkemeier, F; Mudrich, M

    2015-01-01

    Doubly-excited Rydberg states of helium (He) nanodroplets have been studied using synchrotron radiation. We observed Fano resonances related to the atomic N = 2,0 series as a function of droplet size. Although similar qualitatively to their atomic counterparts, the resonance lines are broader and exhibit a shift in energy which increases for the higher excited states. Furthermore, additional resonances are observed which are not seen in atomic systems. We discuss these features in terms of delocalized atomic states perturbed by the surrounding He atoms and compare to singly excited droplets.

  16. Variable helium diffusion characteristics in fluorite

    Science.gov (United States)

    Wolff, R.; Dunkl, I.; Kempe, U.; Stockli, D.; Wiedenbeck, M.; von Eynatten, H.

    2016-09-01

    Precise analysis of the diffusion characteristics of helium in fluorite is crucial for establishing the new fluorite (U-Th-Sm)/He thermochronometer (FHe), which potentially provides a powerful tool for dating ore deposits unsuitable for the application of conventional geochronometers. Incremental helium outgassing experiments performed on fluorites derived from a spectrum of geological environments suggest a thermally activated volume diffusion mechanism. The diffusion behaviour is highly variable and the parameters range between log D0/a2 = 0.30 ± 0.27-7.27 ± 0.46 s-1 and Ea = 96 ± 3.5-182 ± 3.8 kJ/mol. Despite the fact that the CaF2 content of natural fluorites in most cases exceeds 99 weight percent, the closure temperature (Tc) of the fluorite (U-Th-Sm)/He thermochronometer as calculated from these diffusion parameters varies between 46 ± 14 °C and 169 ± 9 °C, considering a 125 μm fragment size. Here we establish that minor substitutions of calcium by rare earth elements and yttrium (REE + Y) and related charge compensation by sodium, fluorine, oxygen and/or vacancies in the fluorite crystal lattice have a significant impact on the diffusivity of helium in the mineral. With increasing REE + Y concentrations F vacancies are reduced and key diffusion pathways are narrowed. Consequently, a higher closure temperature is to be expected. An empirical case study confirms this variability: two fluorite samples from the same deposit (Horni Krupka, Czech Republic) with ca. 170 °C and ca. 43 °C Tc yield highly different (U-Th-Sm)/He ages of 290 ± 10 Ma and 79 ± 10 Ma, respectively. Accordingly, the fluorite sample with the high Tc could have quantitatively retained helium since the formation of the fluorite-bearing ores in the Permian, despite subsequent Mesozoic burial and associated regional hydrothermal heating. In contrast, the fluorite with the low Tc yields a Late Cretaceous age close to the apatite fission track (AFT) and apatite (U-Th)/He ages (AHe

  17. Influence of Helium in Gravitational Instabilities

    Science.gov (United States)

    Corona-Galindo, M. G.; Cardona, O.; Klapp, J.

    1990-11-01

    RESUMEN. Hemos analizado los modos hid rod inamicos de un modelo de fluido de dos componentes (hidr6geno y helio), y hemos obtenido la condici6n de inestabilidad para masas mayores que 1.39 veces la bien conocida masa dejeans. ABSTRACT, We have analysed the hydrodynamical modes of a two component fluid model (hydrogen and helium), and we have obtained the instability condition for masses greater than 1.39 times the well-known Jeans mass. K words: COSMOLOGY - GRAVITATION - INSTABILITIES

  18. Central Flash Analysis of the 29 June 2015 Occultation

    Science.gov (United States)

    Person, Michael J.; Bosh, A. S.; Sickafoose, A. A.; Zuluaga, C. A.; Levine, S. E.; Pasachoff, J. M.; Babcock, B. A.; Dunham, E. W.; McLean, I.; Wolf, J.; Abe, F.; Becklin, E.; Bida, T. A.; Bright, L. P.; Brothers, T. C.; Christie, G.; Collins, P. L.; Durst, R. F.; Gilmore, A. C.; Hamilton, R.; Harris, H. C.; Johnson, C.; Kilmartin, P. M.; Kosiarek, M. R.; Leppik, K.; Logsdon, S. E.; Lucas, R.; Mathers, S.; Morley, C. J. K.; Natusch, T.; Nelson, P.; Ngan, H.; Pfueller, E.; Roeser, H.-P.; Sallum, S.; Savage, M.; Seeger, C. H.; Siu, H.; Stockdale, C.; Suzuki, D.; Thanathibodee, T.; Tilleman, T.; Tristram, P. J.; Van Cleeve, J.; Varughese, C.; Weisenbach, L. W.; Widen, E.; Wiedemann, M.

    2015-11-01

    After an extensive prediction effort, the 29 June 2015 occultation by Pluto was observed from both airborne (Stratospheric Observatory for Infrared Astronomy - SOFIA) and numerous ground-based telescopes (Bosh et al. - this meeting). Real-time prediction updates allowed placement of the SOFIA telescope with its four detectors deep within the central-flash region of the atmospheric occultation. Fortuitously, the Mount John University Observatory (Lake Tekapo, New Zealand) was also within the central-flash region (Pasachoff et al. - this meeting). This happenstance resulted in multiple central-flash detections in several colors from each facility allowing direct comparison of different areas of the central-flash evolute.Here we examine and discuss the central-flash signatures from the highest signal-to-noise light curves from each facility. The relative orientations and asymmetries in the central flashes allow us to use them to tightly constrain the lower atmospheric ellipticity and orientation of likely winds with respect to Pluto’s figure. The ratio of the two separate central flashes is also a strong constraint on the geometric solution for the full occultation data set, and the absolute height of the central flashes with respect to those expected for a clear isothermal atmosphere places constraints on haze densities and thermal gradients in Pluto’s lower atmosphere. We can also compare the central-flash signatures in several colors (similar to Sickafoose et. al - this meeting) to establish bounds on haze-particle sizes in the lower atmosphere.SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NAS2-97001, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. Support for this work was provided, in part, by NASA grants SSO NNX15AJ82G (Lowell Observatory), PA NNX10AB27G (MIT), and PA NNX12AJ29G (Williams College), as well as the National Research Foundation of

  19. Multi-Level Bitmap Indexes for Flash Memory Storage

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Kesheng; Madduri, Kamesh; Canon, Shane

    2010-07-23

    Due to their low access latency, high read speed, and power-efficient operation, flash memory storage devices are rapidly emerging as an attractive alternative to traditional magnetic storage devices. However, tests show that the most efficient indexing methods are not able to take advantage of the flash memory storage devices. In this paper, we present a set of multi-level bitmap indexes that can effectively take advantage of flash storage devices. These indexing methods use coarsely binned indexes to answer queries approximately, and then use finely binned indexes to refine the answers. Our new methods read significantly lower volumes of data at the expense of an increased disk access count, thus taking full advantage of the improved read speed and low access latency of flash devices. To demonstrate the advantage of these new indexes, we measure their performance on a number of storage systems using a standard data warehousing benchmark called the Set Query Benchmark. We observe that multi-level strategies on flash drives are up to 3 times faster than traditional indexing strategies on magnetic disk drives.

  20. An Evaluation of Flash Cells Used in Critical Applications

    Science.gov (United States)

    Katz, Richard B.; Flowers, David; Bergevin, Keith

    2016-01-01

    Due to the common use of Flash technology in many commercial and industrial Programmable Logic Devices (PLDs) such as FPGAs and mixed-signal microcontrollers, flash technology is being utilized in fuzed munition applications. This presents a long-term reliability issue for both DoD and NASA safety- and mission-critical applications. A thorough understanding of the data retention failure modes and statistics associated with Flash data retention is of vital concern to the fuze safety community. A key retention parameter for a flash cell is the threshold voltage (VTH), which is an indirect indicator of the amount of charge stored on the cells floating gate. Initial test results based on a study of charge loss in flash cells in an FPGA device is presented. Statistical data taken from a small sample set indicates quantifiable charge loss for devices stored at both room temperature and 150 C. Initial evaluation of the distribution of threshold voltage in a large sample set (800 devices) is presented. The magnitude of charge loss from exposure to electrostatic discharge and electromagnetic fields is measured and presented. Simulated data (and measured data as available) resultant from harsh-environment testing (neutron, heavy ion, EMP) is presented.

  1. Venlafaxine and desvenlafaxine in the management of menopausal hot flashes

    Directory of Open Access Journals (Sweden)

    Johnson ED

    2011-09-01

    Full Text Available Vasomotor flushes are common complaints of women during and after menopause, affecting about 75 percent of this population. Estrogen therapy is the most effective treatment for hot flashes. However, there are a significant number of women who have contraindications or choose not to use estrogen due to potential risks such as breast cancer and thromboembolic disorders. These women need alternative options. The selective norepinephrine reuptake inhibitors, venlafaxine and desvenlafaxine, have shown efficacy in alleviating hot flashes.Objective: The purpose of this review is to assess the efficacy and tolerability of these two agents for treatment of hot flashes in healthy postmenopausal women.Methods: A literature search of the MEDLINE and Ovid databases from inception to June 2011 was conducted. Randomized controlled trials, published in English, with human participants were included. Studies included postmenopausal women, and trials with breast cancer only populations were excluded.Results: Venlafaxine reduced hot flashes by 37 to 61 percent and desvenlafaxine by 55 to 69 percent. Both agents were well tolerated. The most common adverse effects were headache, dry mouth, nausea, insomnia, somnolence, and dizziness.Conclusion: Based on the evidence, venlafaxine and desvenlafaxine are both viable options for reducing the frequency and severity of hot flashes.

  2. Multi-Level Bitmap Indexes for Flash Memory Storage

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Kesheng; Madduri, Kamesh; Canon, Shane

    2010-07-23

    Due to their low access latency, high read speed, and power-efficient operation, flash memory storage devices are rapidly emerging as an attractive alternative to traditional magnetic storage devices. However, tests show that the most efficient indexing methods are not able to take advantage of the flash memory storage devices. In this paper, we present a set of multi-level bitmap indexes that can effectively take advantage of flash storage devices. These indexing methods use coarsely binned indexes to answer queries approximately, and then use finely binned indexes to refine the answers. Our new methods read significantly lower volumes of data at the expense of an increased disk access count, thus taking full advantage of the improved read speed and low access latency of flash devices. To demonstrate the advantage of these new indexes, we measure their performance on a number of storage systems using a standard data warehousing benchmark called the Set Query Benchmark. We observe that multi-level strategies on flash drives are up to 3 times faster than traditional indexing strategies on magnetic disk drives.

  3. X-ray flashes in ROSAT PSPC data

    Energy Technology Data Exchange (ETDEWEB)

    Sun, X.; Li, H.; Fenimore, E.E. [Los Alamos National Lab., NM (United States); Wang, Q.D. [Northwestern Univ., Evanston, IL (United States)

    1998-12-01

    The authors find 24 short (200--2,500s) X-ray flashes from all the ROSAT Position Sensitive Proportional Counter (PSPC) observations above galactic latitude 30 degrees ({approximately} 9.6 Msec) and some observations toward low latitudes ({approximately} 2.4 Msec). The brightest flash is quite extraordinary. Its flux rises from nondetection by a factor of > 200 in less than 100 sec. Its spectrum can be fitted either by a thermal plasma model with kT {ge} 2.4 keV, or by a single power-law with the photon number index of {approx} {minus}1.7. Photon statistics are not sufficient to obtain spectra for other flashes. The flash event fields can vary from optically crowded regions to blank fields. Although eight flashes are found from observations from nearby galaxies, and three of them are within the optical extent of their corresponding galaxies, they could not statistically establish that there are two different populations between nearby galaxies and control fields.

  4. Flash on disk for low-power multimedia computing

    Science.gov (United States)

    Singleton, Leo; Nathuji, Ripal; Schwan, Karsten

    2007-01-01

    Mobile multimedia computers require large amounts of data storage, yet must consume low power in order to prolong battery life. Solid-state storage offers low power consumption, but its capacity is an order of magnitude smaller than the hard disks needed for high-resolution photos and digital video. In order to create a device with the space of a hard drive, yet the low power consumption of solid-state storage, hardware manufacturers have proposed using flash memory as a write buffer on mobile systems. This paper evaluates the power savings of such an approach and also considers other possible flash allocation algorithms, using both hardware- and software-level flash management. Its contributions also include a set of typical multimedia-rich workloads for mobile systems and power models based upon current disk and flash technology. Based on these workloads, we demonstrate an average power savings of 267 mW (53% of disk power) using hardware-only approaches. Next, we propose another algorithm, termed Energy-efficient Virtual Storage using Application-Level Framing (EVS-ALF), which uses both hardware and software for power management. By collecting information from the applications and using this metadata to perform intelligent flash allocation and prefetching, EVS-ALF achieves an average power savings of 307 mW (61%), another 8% improvement over hardware-only techniques.

  5. Environmental Effects on Data Retention in Flash Cells

    Science.gov (United States)

    Katz, Rich; Flowers, David; Bergevin, Keith

    2017-01-01

    Flash technology is being utilized in fuzed munition applications and, based on the development of digital logic devices in the commercial world, usage of flash technology will increase. Antifuse technology, prevalent in non-volatile field programmable gate arrays (FPGAs), will eventually be phased out as new devices have not been developed for approximately a decade. The reliance on flash technology presents a long-term reliability issue for both DoD and NASA safety- and mission-critical applications. A thorough understanding of the data retention failure modes and statistics associated with Flash data retention is of vital concern to the fuze safety community. A key retention parameter for a flash cell is the threshold voltage (VTH), which is an indirect indicator of the amount of charge stored on the cells floating gate. This paper will present the results of our on-going tests: long-term storage at 150 C for a small population of devices, neutron radiation exposure, electrostatic discharge (ESD) testing, and the trends of large populations (over 300 devices for each condition) exposed to three difference temperatures: 25 C, 125 C, and 150 C.

  6. Venlafaxine and desvenlafaxine in the management of menopausal hot flashes

    Science.gov (United States)

    Johnson, Emily D; Carroll, Dana G

    Vasomotor flushes are common complaints of women during and after menopause, affecting about 75 percent of this population. Estrogen therapy is the most effective treatment for hot flashes. However, there are a significant number of women who have contraindications or choose not to use estrogen due to potential risks such as breast cancer and thromboembolic disorders. These women need alternative options. The selective norepinephrine reuptake inhibitors, venlafaxine and desvenlafaxine, have shown efficacy in alleviating hot flashes. Objective The purpose of this review is to assess the efficacy and tolerability of these two agents for treatment of hot flashes in healthy postmenopausal women. Methods A literature search of the MEDLINE and Ovid databases from inception to June 2011 was conducted. Randomized controlled trials, published in English, with human participants were included. Studies included postmenopausal women, and trials with breast cancer only populations were excluded. Results Venlafaxine reduced hot flashes by 37 to 61 percent and desvenlafaxine by 55 to 69 percent. Both agents were well tolerated. The most common adverse effects were headache, dry mouth, nausea, insomnia, somnolence, and dizziness. Conclusions Based on the evidence, venlafaxine and desvenlafaxine are both viable options for reducing the frequency and severity of hot flashes. PMID:24367464

  7. Theoretical investigation of flash vaporisation in a screw expander

    Science.gov (United States)

    Vasuthevan, Hanushan; Brümmer, Andreas

    2017-08-01

    In the present study flash vaporisation of liquid injection in a twin screw expander for a Trilateral Flash Cycle (TFC) is examined theoretically. The TFC process comprises a pressure increase in the working fluid, followed by heating the liquid close to boiling point. The hot liquid is injected into the working chamber of a screw expander. During this process the pressure of the liquid drops below the saturation pressure, while the temperature of the liquid remains virtually constant. Hence the liquid is superheated and in a metastable state. The liquid jet seeks to achieve a stable state in thermodynamic equilibrium and is therefore partially vaporised. This effect is referred to as flash vaporisation. Accordingly, a two-phase mixture, consisting of vapour and liquid, exists in the working chamber. Thermodynamic simulations were carried out using water as the working fluid for representative screw expander geometry. The simulations presented are performed from two different aspects during the filling process of a screw expander. The first case is the vaporisation of the injected liquid in a state of thermodynamic equilibrium, whereby the two-phase mixture is treated entirely as a compressible and homogeneous gas. The second case considers flashing efficiency. It describes the quantity of flashed vapour and consists of a liquid and vapour domain. Both models are compared and analysed with respect to the operational behaviour of a screw expander.

  8. Desorption of deuterium from beryllium codeposits using flash heating

    Science.gov (United States)

    Yu, J. H.; Baldwin, M. J.; Doerner, R. P.; Pitts, R. A.; Smirnov, R. D.; Xu, H. W.

    2013-07-01

    As a result of safety concerns, limits will be placed on the allowable tritium inventory retained inside the ITER vacuum vessel. The primary motivation for the present work is to test the proposed method of removing tritium from main chamber codeposits using radiative heat flashing from controlled ITER plasma shutdowns. Detritiation of Be codeposits is studied in the PISCES-B facility using flash-heating by a 10 ms laser with up to 2 MJ/m2 of absorbed energy density. Three types of codeposits are flash-heated with layer thickness ranging from 0.1 to 1.2 μm. Less than 25% of the D in the Be layer escapes at ITER-relevant flash energy densities and with peak surface temperature up to ˜900 °C. Repetitive flashing with peak surface temperature of 400-500 °C results in an increased population of higher energy trap sites, implying that transient heating which causes appropriate surface temperature excursion redistributes D among codeposit trap sites.

  9. Design of NAND FLASH File System Based on Loss of Balance Algorithm

    Directory of Open Access Journals (Sweden)

    Jinwu Ju

    2011-02-01

    Full Text Available NAND FLASH is a commonly large capacity memory, which used in embedded systems .It often used to store the operating system kernel and file system. NAND FLASH memory has a limited number of block erase feature. Built file system in NAND FLASH, loss of balance method should be adopted. A balanced system of block erase operation, can extend the life of NAND FLASH and improve overall system reliability. The paper analyzes the characteristics of NAND FLASH work .presents a loss of balance algorithm which used in NAND FLASH memory , and given out the implementation of the algorithm design method.

  10. The Essential Guide to Flash CS4 with ActionScript

    CERN Document Server

    Milbourne, P

    2009-01-01

    For any professional designer or developer working in the world of web technologies or multimedia, Flash is the must-have application, and knowing how to use it effectively is vital. Add in ActionScript 3.0, and Flash becomes an even more powerful tool for the development of high-performance web applications. The Essential Guide to Flash CS4 with ActionScript introduces and explores the possibilities available to you through using Flash CS4. You will learn the aspects basics of Flash's working environment and, using a step-by-step approach, work through the features of Flash and ActionScript n

  11. Formation and evolution of a 0.242 Msun helium white dwarf in presence of element diffusion

    CERN Document Server

    Althaus, L G; Benvenuto, O G; Althaus, Leandro; Serenelli, Aldo; Benvenuto, Omar

    2000-01-01

    A 0.242 Msun object that finally becomes a helium white dwarf is evolved from Roche lobe detachment down to very low luminosities. In doing so, we employ our stellar code to which we have added a set of routines that compute the effects due to gravitational settling, and chemical and thermal diffusion. Initial model is constructed by abstracting mass to a 1 Msun red giant branch model up to the moment at which the model begins to evolve bluewards. We find that element diffusion introduces noticeable changes in the internal structure of the star. In particular, models undergo three thermonuclear flashes instead of one flash as we found with the standard treatment. This fact has a large impact on the total mass fraction of hydrogen left in the star at entering the final cooling track. As a result, at late stages of evolution models with diffusion are characterized by a much smaller nuclear energy release, and they evolve significantly faster compared to those found with the standard treatment. We find that mode...

  12. Core analyses for selected samples from the Culebra Dolomite at the Waste Isolation Pilot Plant site

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, V.A.; Saulnier, G.J. Jr. (INTERA, Inc., Austin, TX (USA))

    1990-11-01

    Two groups of core samples from the Culebra Dolomite Member of the Rustler Formation at and near the Waste Isolation Pilot Plant were analyzed to provide estimates of hydrologic parameters for use in flow-and-transport modeling. Whole-core and core-plug samples were analyzed by helium porosimetry, resaturation and porosimetry, mercury-intrusion porosimetry, electrical-resistivity techniques, and gas-permeability methods. 33 refs., 25 figs., 10 tabs.

  13. Core analyses for selected samples from the Culebra Dolomite at the Waste Isolation Pilot Plant site

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, V.A.; Saulnier, G.J. Jr. (INTERA, Inc., Austin, TX (USA))

    1990-11-01

    Two groups of core samples from the Culebra Dolomite Member of the Rustler Formation at and near the Waste Isolation Pilot Plant were analyzed to provide estimates of hydrologic parameters for use in flow-and-transport modeling. Whole-core and core-plug samples were analyzed by helium porosimetry, resaturation and porosimetry, mercury-intrusion porosimetry, electrical-resistivity techniques, and gas-permeability methods. 33 refs., 25 figs., 10 tabs.

  14. Modular, Microprocessor-Controlled Flash Lighting System

    Science.gov (United States)

    Kiefer, Dwayne; Gray, Elizabeth; Skupinski, Robert; Stachowicz, Arthur; Birchenough, William

    2006-01-01

    A microprocessor-controlled lighting system generates brief, precisely timed, high-intensity flashes of light for scientific imaging at frame rates up to about 1 kHz. The system includes an array of light-emitting diodes (LEDs) that are driven in synchronism with an externally generated timing signal (for example, a timing signal generated by a video camera). The light output can be varied in peak intensity, pulse duration, pulse delay, and pulse rate, all depending on the timing signal and associated externally generated control signals. The array of LEDs comprises as many as 16 LED panels that can be attached together. Each LED panel is a module consisting of a rectangular subarray of 10 by 20 LEDs of advanced design on a printed-circuit board in a mounting frame with a power/control connector. The LED panels are controlled by an LED control module that contains an AC-to-DC power supply, a control board, and 8 LED-panel driver boards. In prior LED panels, the LEDs are packaged at less than maximum areal densities in bulky metal housings that reduce effective active areas. In contrast, in the present LED panels, the LEDs are packed at maximum areal density so as to afford 100-percent active area and so that when panels are joined side by side to form the array, there are no visible seams between them and the proportion of active area is still 100 percent. Each panel produces an illuminance of .5 x 10( exp 4) lux at a distance of 5.8 in. (approx.1.6 cm). The LEDs are driven according to a pulse-width-modulation control scheme that makes it safe to drive the LEDs beyond their rated steady-state currents in order to generate additional light during short periods. The drive current and the pulse-width modulation for each LED panel can be controlled independently of those of the other 15 panels. The maximum allowable duration of each pulse of drive current is a function of the amount of overdrive, the total time to be spent in overdrive operation, and the limitations

  15. Helium isotopic compositions in fluid inclusions of the Gangxi fault belt in the Huanghua Depression, Bohai Bay Basin

    Institute of Scientific and Technical Information of China (English)

    DING Weiwei; DAI Jinxing; YANG Chiyin; TAO Shizhen; HOU Lu

    2005-01-01

    The authors obtained 30 core samples from 15 wells in Gangxi fault belt, Huanghua Depression. Using a VG5400 mass spectrometer, the helium isotopic compositions in fluid inclusion of these samples were analysed. Interpretation of results suggests a significant amount of mantle-derived helium in the inclusions, which were likely trapped during Neocene. Mantle-derived helium have mostly accumulated in the intersections of the NWW trending Xuzhuangzi and NE trending Gangxi faults, and decreased away from the intersections. This pattern implied a close relationship to the local tectonic setting. Gangxi fault belt experienced intensive neo-tectonic activities in the Cenozoic. Widespread faulted-depressions and strong volcanic eruptions manifested its tectonic status of extensional stress field. Mantle uplift caused the movement of magma that carried mantle-derived gas, and the deep-rooted tension faults provided the passages for the gases to shallow crust levels. High-content abiogenic CO2 pools occurred in the study area, hence, using the helium isotopic compositions is of great significance to the exploration of abiogenic natural gases.

  16. Effects of helium pre-implantation on the microstructure and mechanical properties of irradiated 316 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Toloczko, M.B.; Tedeski, G.R.; Lucas, G.E.; Odette, G.R. [Univ. of California, Santa Barbara, CA (United States). Dept. of Chemical and Nuclear Engineering; Stoller, R.E. [Oak Ridge National Lab., TN (United States); Hamilton, M.L. [Pacific Northwest Lab., Richland, WA (United States)

    1994-11-01

    Transmission electron microscopy (TEM) specimens of a First Core heat of 316 stainless steel, in both the solution annealed and 20% cold worked condition, were irradiated to 46 dpa at 420 C, to 49 dpa at 520 C, and to 34 dpa at 600 C in FFTF/MOTA. Prior to irradiation, about half of the specimens were pre-implanted with approximately 100 appm of helium, and of these, several of the solution annealed and pre-implanted specimens were aged at 800 C for 2 hr. Post-irradiation density measurements showed little difference in density between the unimplanted alloys and their helium implanted counterparts. Microstructural observations on specimens irradiated at 420 C and 520 C showed relatively minor differences in defect distributions between the unimplanted and the helium implanted materials; in all cases the defect sizes and number densities were consistent with data in the literature. Where possible, irradiation hardening of the alloys was experimentally evaluated by microhardness and shear punch; experimentally obtained values were compared to values calculated using a computer model based on barrier hardening and the microstructural data. All methods indicated relatively small effects of helium implantation, and both measured and calculated values were in agreement with the range of values reported in the literature.

  17. Deposition, milling, and etching with a focused helium ion beam

    NARCIS (Netherlands)

    Alkemade, P.F.A.; Veldhoven, E. van

    2012-01-01

    The recent successful development of the helium ion microscope has produced both a new type of microscopy and a new tool for nanoscale manufacturing. This chapter reviews the first explorations in this new field in nanofabrication. The studies that utilize the Orion helium ion microscope to grow or

  18. Laser-Induced Rotation of Iodine Molecules in Helium Nanodroplets

    DEFF Research Database (Denmark)

    Shepperson, Benjamin; Sondergaard, Anders A.; Christiansen, Lars

    2017-01-01

    Rotation of molecules embedded in helium nanodroplets is explored by a combination of fs laser-induced alignment experiments and angulon quasiparticle theory. We demonstrate that at low fluence of the fs alignment pulse, the molecule and its solvation shell can be set into coherent collective...... its helium shell. Our results open novel opportunities for studying nonequilibrium solute-solvent dynamics and quantum thermalization....

  19. Helium on Venus - Implications for uranium and thorium

    Science.gov (United States)

    Prather, M. J.; Mcelroy, M. B.

    1983-01-01

    Helium is removed at an average rate of 10 to the 6th atoms per square centimeter per second from Venus's atmosphere by the solar wind following ionization above the plasmapause. The surface source of helium-4 on Venus is similar to that on earth, suggesting comparable abundances of crustal uranium and thorium.

  20. Thermal Desorption of Helium Implanted in Tungsten at RT

    Institute of Scientific and Technical Information of China (English)

    ZHANGFu; XUZengyu; LIUXiang; CHENJiming; XUYing; N.Yoshida; H.Iwakiri

    2002-01-01

    Tungsten is envisaged as one of the main candidate materials for divertor plate of ITER and future fusion reactors. Due to D-T reaction, PFMs would suffer helium irradiation from plasma additional to the high heat loads. Helium retention and thermal desorption behavior are largely concerned.

  1. Deposition, milling, and etching with a focused helium ion beam

    NARCIS (Netherlands)

    Alkemade, P.F.A.; Veldhoven, E. van

    2012-01-01

    The recent successful development of the helium ion microscope has produced both a new type of microscopy and a new tool for nanoscale manufacturing. This chapter reviews the first explorations in this new field in nanofabrication. The studies that utilize the Orion helium ion microscope to grow or

  2. Turnkey Helium Purification and Liquefaction Plant for DARWIN, Australia

    Science.gov (United States)

    Lindemann, U.; Boeck, S.; Blum, L.; Kurtcuoglu, K.

    2010-04-01

    The Linde Group, through its Australian subsidiary BOC Limited, has signed an agreement with Darwin LNG Pty Ltd for the supply of feed-gas to Linde's new helium refining and liquefaction facility in Darwin, Australia. Linde Kryotechnik AG, located in Switzerland, has carried out the engineering and fabrication of the equipment for the turn key helium plant. The raw feed gas flow of 20'730 Nm3/h contains up to of 3 mol% helium. The purification process of the feed gas consists of partial condensation of nitrogen in two stages, cryogenic adsorption and finally catalytic oxidation of hydrogen followed by a dryer system. Downstream of the purification the refined helium is liquefied using a modified Bryton process and stored in a 30'000 gal LHe tank. For further distribution and export of the liquid helium there are two stations available for filling of truck trailers and containers. The liquid nitrogen, required for refrigeration capacity to the nitrogen removal stages in the purification process as well as for the pre-cooling of the pure helium in the liquefaction process, is generated on site during the feed gas purification process. The optimized process provides low power consumption, maximum helium recovery and a minimum helium loss.

  3. The Orsay polarized electron source from a flowing helium afterglow

    Science.gov (United States)

    Arianer, J.; Brissaud, I.; Essabaa, S.; Humblot, H.; Zerhouni, W.

    1993-12-01

    A polarized electron source was designed at Orsay. We have chosen to adapt the flowing helium afterglow source working at Rice University because it provides a very high polarization. We have investigated a new way for the optical pumping of the helium metastables. An 85% electron polarization was reached.

  4. Neutrons on a surface of liquid helium

    Science.gov (United States)

    Grigoriev, P. D.; Zimmer, O.; Grigoriev, A. D.; Ziman, T.

    2016-08-01

    We investigate the possibility of ultracold neutron (UCN) storage in quantum states defined by the combined potentials of the Earth's gravity and the neutron optical repulsion by a horizontal surface of liquid helium. We analyze the stability of the lowest quantum state, which is most susceptible to perturbations due to surface excitations, against scattering by helium atoms in the vapor and by excitations of the liquid, comprised of ripplons, phonons, and surfons. This is an unusual scattering problem since the kinetic energy of the neutron parallel to the surface may be much greater than the binding energies perpendicular. The total scattering time of these UCNs at 0.7 K is found to exceed 1 h, and rapidly increases with decreasing temperature. Such low scattering rates should enable high-precision measurements of the sequence of discrete energy levels, thus providing improved tests of short-range gravity. The system might also be useful for neutron β -decay experiments. We also sketch new experimental propositions for level population and trapping of ultracold neutrons above a flat horizontal mirror.

  5. Neutrons on a surface of liquid helium

    CERN Document Server

    Grigoriev, P D; Ziman, T; Grigoriev, A D

    2015-01-01

    We investigate the possibility of ultracold neutron (UCN) storage in quantum states defined by the combined potentials of the Earth's gravity and the neutron optical repulsion by a horizontal surface of liquid helium. We analyse the stability of the lowest quantum state, which is most susceptible to perturbations due to surface excitations, against scattering by helium atoms in the vapor and by excitations of the liquid, comprised of ripplons, phonons and surfons. This is an unusual scattering problem since the kinetic energy of the neutron parallel to the surface may be much greater than the binding energies perpendicular. The total scattering time constant of these UCNs at 0.7 K is found to exceed one hour, and rapidly increasing with decreasing temperature. Such low scattering rates should enable high-precision measurements of the scheme of discrete energy levels, thus providing improved access to short-range gravity. The system might also be useful for neutron beta-decay experiments. We also sketch new ex...

  6. Mining for helium: Site selection and evaluation

    Science.gov (United States)

    Cameron, Eugene N.

    1988-09-01

    Part of the University of Wisconsin study of the feasibility of recovering He-3 from the moon is selection and evaluation of potential mining sites. Selection and evaluation are based primarily on salient findings by investigators: (1) Regoliths from areas underlain by highland materials contain less than 20 wppm He; (2) Regoliths of certain maria or parts of maria also contain less than 20 wppm He, but mare regoliths at the Apollo 11 and 17 sites contain 25 to 49 wppm He; (3) The helium content of a regolith is a function of its composition; and (4) Helium is concentrated in the -50 micron size fractions of regoliths. In site selection, the concern is with the compositions of lunar regoliths, in particular with their titanium contents. It is widely accepted that compositions of mare regoliths are controlled by the nature of the underlying basalts from which the regoliths are largely derived. The distribution and extent of the three groups of basalts and the regoliths derived from them are the first basis for site selection and evaluation. Other considerations are briefly discussed.

  7. Submersion of potassium clusters in helium nanodroplets

    Science.gov (United States)

    An der Lan, Lukas; Bartl, Peter; Leidlmair, Christian; Schöbel, Harald; Denifl, Stephan; Märk, Tilmann D.; Ellis, Andrew M.; Scheier, Paul

    2012-03-01

    Small alkali clusters do not submerge in liquid helium nanodroplets but instead survive predominantly in high spin states that reside on the surface of the nanodroplet. However, a recent theoretical prediction by Stark and Kresin [Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.81.085401 81, 085401 (2010)], based on a classical description of the energetics of bubble formation for a fully submerged alkali cluster, suggests that the alkali clusters can submerge on energetic grounds when they exceed a critical size. Following recent work on sodium clusters, where ion yield data from electron impact mass spectrometry was used to obtain the first experimental evidence for alkali cluster submersion, we report here on similar experiments for potassium clusters. Evidence is presented for full cluster submersion at n>80 for Kn clusters, which is in good agreement with the recent theoretical prediction. In an additional observation, we report “magic number” sizes for both Kn+ and Kn2+ ions derived from helium droplets, which are found to be consistent with the jellium model.

  8. Muon transfer from deuterium to helium

    CERN Document Server

    Augsburger, M A; Breunlich, W H; Cargnelli, M; Chatellard, D; Egger, J P; Gartner, B; Hartmann, F J; Huot, O; Jacot-Guillarmod, R; Kammel, P; King, R; Knowles, P; Kosak, A; Lauss, B; Marton, J; Mühlbauer, M; Mulhauser, F; Petitjean, C; Prymas, W; Schaller, L A; Schellenberg, L; Schneuwly, H; Tresch, S; Von Egidy, T; Zmeskal, J

    2003-01-01

    We report on an experiment at the Paul Scherrer Institute, Villigen, Switzerland measuring x rays from muon transfer from deuterium to helium. Both the ground state transfer via the exotic dmu3,4He* molecules and the excited state transfer from mud* were measured. The use of CCD detectors allowed x rays from 1.5 keV to 11 keV to be detected with sufficient energy resolution to separate the transitions to different final states in both deuterium and helium. The x-ray peaks of the dmu3He* and dmu4He* molecules were measured with good statistics. For the D2+3He mixture, the peak has its maximum at E_dmu3He = 6768 +- 12 eV with FWHM Gamma_dmu3He = 863 +- 10 eV. Furthermore the radiative branching ratio was found to be kappa_dmu3He = 0.301 +- 0.061. For the D_2+4He mixture, the maximum of the peak lies at E_dmu4He = 6831 +- 8 eV and the FWHM is Gamma_dmu4He = 856 +- 10 eV. The radiative branching ratio is kappa_dmu4He = 0.636 +- 0.097. The excited state transfer is limited by the probability to reach the deuterium...

  9. Diagnostics of a High Pressure Helium Microplasma

    Science.gov (United States)

    Wang, Qiang; Koleva, Ivanka; Economou, Demetre; Donnelly, Vincent

    2004-09-01

    Gas and plasma diagnostics were performed in a slot-type DC microplasma (200 microns gap) discharge at high pressures. The gas temperature in a helium discharge was estimated by adding small quantities of nitrogen (excimer. At 250 Torr pressure and 200 mA/cm2 current density, the gas temperature was Tg = 350 +/- 25 K. The measured gas temperature was almost independent (to within experimental uncertainty) of pressure (in the range of 150 Torr - 600 Torr), and current density (in the range of 100 mA/cm2 - 400 mA/cm2). These measurements were consistent with a simple heat transfer model. Spatially resolved measurements of electron temperature were also performed using trace rare gas optical emission actinometry (TRG-OES). These measurements are greatly complicated by collisional quenching at the high operating pressures. Electron density and electron temperature profiles was deduced by comparing emission intensities from the Paschen 2px (x = 1-10) manifold of Ne, Ar, Kr and Xe trace gases. Results suggested that the electron temperature peaks in the cathode sheath region, while the plasma density peaks away from the cathode sheath. A self-consistent fluid model of a DC helium microdischarge was in agreement with the experimental data. The model was used to study the dependence of discharge characteristics on operating conditions (pressure, gap spacing, current density, etc.).

  10. High-precision spectroscopy of antiprotonic helium

    CERN Document Server

    Widmann, E

    2001-01-01

    We present first results of laser and microwave spectroscopy experiments of antiprotonic helium performed at the new Antiproton Decelerator (AD) at CERN. Extending a series of previous measurements done at the Low Energy Antiproton Ring (LEAR) of CERN, several laser- induced transitions of the antiproton in the exotic three-body system He/sup 2+/-e/sup -/-p could be determined with a precision down to 1.3*10/sup -7/. This constitutes an improvement of a factor 3 over previous measurements, and allows to test accurate three-body calculations of this system that include QED corrections. The observed agreement on the same level can be used to infer CPT limits on the antiproton charge and mass. Furthermore, a first indication of a resonance signal of a two-laser microwave triple experiment to measure the hyperfine splitting of antiprotonic helium could been observed. Such a measurement has the potential to determine the antiproton magnetic moment to a higher precision that it is known today. (19 refs).

  11. Model of UV flashes due to gigantic blue jets

    Energy Technology Data Exchange (ETDEWEB)

    Milikh, G M [University of Maryland, College Park, MD, 20742 (United States); Shneider, M N [Princeton University, Princeton, NJ (United States)], E-mail: milikh@astro.umd.edu, E-mail: shneyder@princeton.edu

    2008-12-07

    Analysis of UV flashes observed by the UV detector on board the 'Tatiana' microsatellite suggests, based on their location, pulse width and energy of the source of the photons, that the flashes were generated by gigantic blue jets (GBJs). Presented in this paper is a numerical model of UV flashes due to a bunch of long streamers which form a leader, a prong such as that observed in a GBJ. Using a previously developed model of upward propagation of a long streamer in the exponential atmosphere the paper describes temporal evolution of the UV flux generated by a bunch of long streamers, in the given spectral range 300-400 nm used by the UV detector on board 'Tatiana'. The model is in agreement with the observations.0.

  12. Post-irradiation flashes and continuous emission from solid deuterium

    Energy Technology Data Exchange (ETDEWEB)

    Forrest, J.A.; Brooks, R.L. [Guelph-Waterloo Program for Graduate Work in Physics, University of Guelph, Guelph, Ontario, N1G2W1 (CANADA)

    1997-01-01

    Optical emission from proton-beam-irradiated solid deuterium near 800 nm has been studied after termination of the proton beam. The continuous red emission shows a residual intensity that persists over 30 min from termination of the beam. Optical flashes can also be thermally triggered over 10 min after termination of irradiation. Such triggered flashes are shown to quench the infrared absorption of Stark-shifted charge-induced features. Ultraviolet photons can stimulate this red emission after termination of irradiation with no measurable decrease in intensity for 40 min. The cause of this continuous emission and optical flashes is discussed in the light of these results. {copyright} {ital 1997} {ital The American Physical Society}

  13. DERIVING FLASH FLOODS IN THE CASE OF SIMULATED PRECIPITATIONS

    Directory of Open Access Journals (Sweden)

    GYŐRI MARIA-MIHAELA

    2013-01-01

    Full Text Available Deriving flash floods in the case of simulated precipitations. The present study sets to determine the historical flash-floods on the Petriș watershed making use of the implemented mathematical models in a Hydrological Modeling System. In order to simulate the 1%, 2% and 10% exceedance probability flash-floods, the Intensity-Frequency-Duration (IDF curves have been built on the basis of 22 years of precipitation records (1988-2009. They serve as input data together with the hydrological parameters identified by the means of a Geographic Information Systems. The results, computed mainly on the basis of the Soil Conservation Service (SCS method, consist of hyetographs and hydrographs at the outlet of the main watershed, as well as to that of the ungauged tributaries of the Petriș River.

  14. X-ray Flashes from Off-axis Nonuniform Jets

    Institute of Scientific and Technical Information of China (English)

    Zhi-Ping Jin; Da-Ming Wei

    2004-01-01

    It has been widely believed that the outflows in gamma-ray bursts are jetted and some jets may have structures like ∈(θ) ∝θ-κ. We check the possibility that X-ray flashes come from such jets. Both qualitative and quantitative analyses have shown that this model can reproduce most of the observational features of both X-ray flashes and gamma-ray bursts. Using the usual parameters of gamma-ray bursts, we have carried out numerical calculations for both uniform and nonuniform jets, of their fluxes, spectra and peak energies. It seems that nonuniform jets are more appropriate to these observational properties than uniform jets. We have also shown that in our model the observational ratio of gamma-ray bursts to X-ray flashes is about a few units.

  15. Storage Management Strategy of Flash-Based Platform

    Institute of Scientific and Technical Information of China (English)

    WANG Taiyong; ZHAO Li; HU Shiguang; WANG Tao

    2009-01-01

    Storage management strategy can be expressed by a file system. Commercial file system for embedded application is generally complicated and resource wasted. In this paper, a specified file system adapted to embedded system with flash-based memory is developed. To guarantee the average usage of flash storage sectors, the strategy of wear leveling and adaptive damage management is introduced, in which a dynamic storage space management mode and the strategy of first in first out (FIFO) are adopted. Moreover, the strategy of redundancy design and fast-calculation and tracing is also adopted to extend the life of kernel sector, which can guarantee the reliable ser-vice of system booting. The practical application in an embedded CNC (computerized numerical control) platform proves that the file system has effective performance. Furthermore, the flash file system can be transplanted to dif-ferent embedded platforms by changing a few bottom hardware parameters with universality.

  16. A simple experiment that demonstrates the ``green flash''

    Science.gov (United States)

    Courtial, Johannes

    2012-11-01

    The green flash occurs when, under certain atmospheric conditions, the top segment of the low sun is visibly green. It is surrounded—in at least a few minds—by an air of mystery. I describe a simple experiment that demonstrates different aspects of the green flash. The experiment uses an odd-shaped, water-filled, fish tank to simulate the refractive properties of the atmosphere; milk powder added to the water mimicks the atmosphere's scattering properties. A circular white-light source is viewed through the fish tank and the combination of refraction and scattering makes one end of the light source look green. The setup also allows experimentation with mirage effects, thereby drawing attention to their often neglected contribution to the green flash.

  17. Shock Compression of Liquid Helium to 56 GPa (560) Kbar

    Science.gov (United States)

    Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Trainor, R. J.; Governo, G. K.; Ross, M.; Young, D. A.

    1985-01-01

    Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

  18. Shock compression of liquid helium to 56 GPa (560 kbar)

    Science.gov (United States)

    Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Governo, G. K.; Ross, M.; Young, D. A.; Trainor, R. J.

    1984-01-01

    Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation of the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

  19. Localized helium excitations in 4He_N-benzene clusters

    CERN Document Server

    Huang, P; Huang, Patrick

    2003-01-01

    We compute ground and excited state properties of small helium clusters 4He_N containing a single benzene impurity molecule. Ground-state structures and energies are obtained for N=1,2,3,14 from importance-sampled, rigid-body diffusion Monte Carlo (DMC). Excited state energies due to helium vibrational motion near the molecule surface are evaluated using the projection operator, imaginary time spectral evolution (POITSE) method. We find excitation energies of up to ~23 K above the ground state. These states all possess vibrational character of helium atoms in a highly anisotropic potential due to the aromatic molecule, and can be categorized in terms of localized and collective vibrational modes. These results appear to provide precursors for a transition from localized to collective helium excitations at molecular nanosubstrates of increasing size. We discuss the implications of these results for analysis of anomalous spectral features in recent spectroscopic studies of large aromatic molecules in helium clu...

  20. FlashCam: A fully digital camera for CTA telescopes

    CERN Document Server

    Pühlhofer, G; Biland, A; Florin, D; Föhr, C; Gadola, A; Hermann, G; Kalkuhl, C; Kasperek, J; Kihm, T; Koziol, J; Manalaysay, A; Marszalek, A; Rajda, P J; Schanz, T; Steiner, S; Straumann, U; Tenzer, C; Vogler, P; Vollhardt, A; Weitzel, Q; Winiarski, K; Zietara, K

    2012-01-01

    The future Cherenkov Telescope Array (CTA) will consist of several tens of telescopes of different mirror sizes. CTA will provide next generation sensitivity to very high energy photons from few tens of GeV to >100 TeV. Several focal plane instrumentation options are currently being evaluated inside the CTA consortium. In this paper, the current status of the FlashCam prototyping project is described. FlashCam is based on a fully digital camera readout concept and features a clean separation between photon detector plane and signal digitization/triggering electronics.