WorldWideScience

Sample records for wind mass-loss rate

  1. THE TRANSITION MASS-LOSS RATE: CALIBRATING THE ROLE OF LINE-DRIVEN WINDS IN MASSIVE STAR EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Vink, Jorick S.; Graefener, Goetz, E-mail: jsv@arm.ac.uk [Armagh Observatory, College Hill, BT61 9DG Armagh (United Kingdom)

    2012-06-01

    A debate has arisen regarding the importance of stationary versus eruptive mass loss for massive star evolution. The reason is that stellar winds have been found to be clumped, which results in the reduction of unclumped empirical mass-loss rates. Most stellar evolution models employ theoretical mass-loss rates which are already reduced by a moderate factor of {approx_equal}2-3 compared to non-corrected empirical rates. A key question is whether these reduced rates are of the correct order of magnitude, or if they should be reduced even further, which would mean that the alternative of eruptive mass loss becomes necessary. Here we introduce the transition mass-loss rate M-dot{sub trans} between O and Wolf-Rayet stars. Its novelty is that it is model independent. All that is required is postulating the spectroscopic transition point in a given data set, and determining the stellar luminosity, which is far less model dependent than the mass-loss rate. The transition mass-loss rate is subsequently used to calibrate stellar wind strength by its application to the Of/WNh stars in the Arches cluster. Good agreement is found with two alternative modeling/theoretical results, suggesting that the rates provided by current theoretical models are of the right order of magnitude in the {approx}50 M{sub Sun} mass range. Our results do not confirm the specific need for eruptive mass loss as luminous blue variables, and current stellar evolution modeling for Galactic massive stars seems sound. Mass loss through alternative mechanisms might still become necessary at lower masses, and/or metallicities, and the quantification of alternative mass loss is desirable.

  2. THE TRANSITION MASS-LOSS RATE: CALIBRATING THE ROLE OF LINE-DRIVEN WINDS IN MASSIVE STAR EVOLUTION

    International Nuclear Information System (INIS)

    Vink, Jorick S.; Gräfener, Götz

    2012-01-01

    A debate has arisen regarding the importance of stationary versus eruptive mass loss for massive star evolution. The reason is that stellar winds have been found to be clumped, which results in the reduction of unclumped empirical mass-loss rates. Most stellar evolution models employ theoretical mass-loss rates which are already reduced by a moderate factor of ≅2-3 compared to non-corrected empirical rates. A key question is whether these reduced rates are of the correct order of magnitude, or if they should be reduced even further, which would mean that the alternative of eruptive mass loss becomes necessary. Here we introduce the transition mass-loss rate M-dot trans between O and Wolf-Rayet stars. Its novelty is that it is model independent. All that is required is postulating the spectroscopic transition point in a given data set, and determining the stellar luminosity, which is far less model dependent than the mass-loss rate. The transition mass-loss rate is subsequently used to calibrate stellar wind strength by its application to the Of/WNh stars in the Arches cluster. Good agreement is found with two alternative modeling/theoretical results, suggesting that the rates provided by current theoretical models are of the right order of magnitude in the ∼50 M ☉ mass range. Our results do not confirm the specific need for eruptive mass loss as luminous blue variables, and current stellar evolution modeling for Galactic massive stars seems sound. Mass loss through alternative mechanisms might still become necessary at lower masses, and/or metallicities, and the quantification of alternative mass loss is desirable.

  3. Effect of rotational mixing and metallicity on the hot star wind mass-loss rates

    Czech Academy of Sciences Publication Activity Database

    Krtička, J.; Kubát, Jiří

    2014-01-01

    Roč. 567, July (2014), A63/1-A63/7 ISSN 0004-6361 R&D Projects: GA ČR GA13-10589S Grant - others:GA MŠk(CZ) LM2010005 Institutional support: RVO:67985815 Keywords : stars: winds * outflows * stars: mass-loss Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  4. Mass-loss rates of cool stars

    Science.gov (United States)

    Katrien Els Decin, Leen

    2015-08-01

    Over much of the initial mass function, stars lose a significant fraction of their mass through a stellar wind during the late stages of their evolution when being a (super)giant star. As of today, we can not yet predict the mass-loss rate during the (super)giant phase for a given star with specific stellar parameters from first principles. This uncertainty directly impacts the accuracy of current stellar evolution and population synthesis models that predict the enrichment of the interstellar medium by these stellar winds. Efforts to establish the link between the initial physical and chemical conditions at stellar birth and the mass-loss rate during the (super)giant phase have proceeded on two separate tracks: (1) more detailed studies of the chemical and morpho-kinematical structure of the stellar winds of (super)giant stars in our own Milky Way by virtue of the proximity, and (2) large scale and statistical studies of a (large) sample of stars in other galaxies (such as the LMC and SMC) and globular clusters eliminating the uncertainty on the distance estimate and providing insight into the dependence of the mass-loss rate on the metallicity. In this review, I will present recent results of both tracks, will show how recent measurements confirm (some) theoretical predictions, but also how results from the first track admonish of common misconceptions inherent in the often more simplified analysis used to analyse the large samples from track 2.

  5. ESCAPING PARTICLE FLUXES IN THE ATMOSPHERES OF CLOSE-IN EXOPLANETS. II. REDUCED MASS-LOSS RATES AND ANISOTROPIC WINDS

    International Nuclear Information System (INIS)

    Guo, J. H.

    2013-01-01

    In Paper I, we presented a one-dimensional hydrodynamic model for the winds of close-in exoplanets. However, close-in exoplanets are tidally locked and irradiated only on the day sides by their host stars. This requires two-dimensional hydrodynamic models with self-consistent radiative transfer calculations. In this paper, for the tidal-locking (two-dimensional radiative transfer) and non-tidal-locking cases (one-dimensional radiative transfer), we constructed a multi-fluid two-dimensional hydrodynamic model with detailed radiative transfer to depict the escape of particles. We found that the tidal forces (the sum of tidal gravity of the star and centrifugal force due to the planetary rotation) supply significant accelerations and result in anisotropic winds. An important effect of the tidal forces is that it severely depresses the outflow of particles near the polar regions where the density and the radial velocity are a factor of a few (ten) smaller than those of the low-latitude regions. As a consequence, most particles escape the surface of the planet from the regions of low latitude. Comparing the tidal-locking and non-tidal-locking cases, we found that their optical depths are very different so that the flows also emerge with a different pattern. In the case of non-tidal locking, the radial velocities at the base of the wind are higher than the meridional velocities. However, in the case of tidal locking, the meridional velocities dominate the flow at the base of the wind, and they can effectively transfer mass and energy from the day sides to the night sides. Further, we also found that the differences of the winds show a middle extent at large radii. This means that the structure of the wind at the base can be changed by the two-dimensional radiative transfer due to large optical depths, but the extent is reduced with an increase in radius. Because the escape is depressed in the polar regions, the mass-loss rate predicted by the non-tidal-locking model, in

  6. Comoving frame models of hot star winds II. Reduction of O star wind mass-loss rates in global models

    Czech Academy of Sciences Publication Activity Database

    Krtička, J.; Kubát, Jiří

    2017-01-01

    Roč. 606, October (2017), A31/1-A31/12 E-ISSN 1432-0746 R&D Projects: GA ČR GA13-10589S Institutional support: RVO:67985815 Keywords : stars * winds * outflows Subject RIV: BN - Astronomy , Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.014, year: 2016

  7. O Star Wind Mass-Loss Rates and Shock Physics from X-ray Line Profiles in Archival XMM RGS Data

    Science.gov (United States)

    Cohen, David

    O stars are characterized by their dense, supersonic stellar winds. These winds are the site of X-ray emission from shock-heated plasma. By analyzing high-resolution X-ray spectra of these O stars, we can learn about the wind-shock heating and X-ray production mechanism. But in addition, the X-rays can also be used to measure the mass-loss rate of the stellar wind, which is a key observational quantity whose value affects stellar evolution and energy, momentum, and mass input to the Galactic interstellar medium. We make this X-ray based mass-loss measurement by analyzing the profile shapes of the X-ray emission lines observed at high resolution with the Chandra and XMM-Newton grating spectrometers. One advantage of our method is that it is insensitive to small-scale clumping that affects density-squared diagnostics. We are applying this analysis technique to O stars in the Chandra archive, and are finding mass-loss rates lower than those traditionally assumed for these O stars, and in line with more recent independent determinations that do account for clumping. By extending this analysis to the XMM RGS data archive, we will make significant contributions to the understanding of both X-ray production in O stars and to addressing the issue of the actual mass-loss rates of O stars. The XMM RGS data archive provides several extensions and advantages over the smaller Chandra HETGS archive: (1) there are roughly twice as many O and early B stars in the XMM archive; (2) the longer wavelength response of the RGS provides access to diagnostically important lines of nitrogen and carbon; (3) the very long, multiple exposures of zeta Pup provide the opportunity to study this canonical O supergiant's X-ray spectrum in unprecedented detail, including looking at the time variability of X-ray line profiles. Our research team has developed a sophisticated empirical line profile model as well as a computational infrastructure for fitting the model to high-resolution X-ray spectra

  8. Mass Loss Rates of Fasting Polar Bears.

    Science.gov (United States)

    Pilfold, Nicholas W; Hedman, Daryll; Stirling, Ian; Derocher, Andrew E; Lunn, Nicholas J; Richardson, Evan

    2016-01-01

    Polar bears (Ursus maritimus) have adapted to an annual cyclic regime of feeding and fasting, which is extreme in seasonal sea ice regions of the Arctic. As a consequence of climate change, sea ice breakup has become earlier and the duration of the open-water period through which polar bears must rely on fat reserves has increased. To date, there is limited empirical data with which to evaluate the potential energetic capacity of polar bears to withstand longer fasts. We measured the incoming and outgoing mass of inactive polar bears (n = 142) that were temporarily detained by Manitoba Conservation and Water Stewardship during the open-water period near the town of Churchill, Manitoba, Canada, in 2009-2014. Polar bears were given access to water but not food and held for a median length of 17 d. Median mass loss rates were 1.0 kg/d, while median mass-specific loss rates were 0.5%/d, similar to other species with high adiposity and prolonged fasting capacities. Mass loss by unfed captive adult males was identical to that lost by free-ranging individuals, suggesting that terrestrial feeding contributes little to offset mass loss. The inferred metabolic rate was comparable to a basal mammalian rate, suggesting that while on land, polar bears can maintain a depressed metabolic rate to conserve energy. Finally, we estimated time to starvation for subadults and adult males for the on-land period. Results suggest that at 180 d of fasting, 56%-63% of subadults and 18%-24% of adult males in this study would die of starvation. Results corroborate previous assessments on the limits of polar bear capacity to withstand lengthening ice-free seasons and emphasize the greater sensitivity of subadults to changes in sea ice phenology.

  9. Mass loss rates of OB stars derived from infrared observations

    International Nuclear Information System (INIS)

    Tanzi, E.G.; Tarenghi, M.; Panagia, N.

    1981-01-01

    In this paper the authors report briefly on a study of the mass loss of early type stars in the infrared. Up to now near infrared (1.25 - 4.8 μ) broad band photometry of 70 southern OB stars of various luminosity class has been secured. Program stars have been selected, among those bright enough in the infrared to give a suitable photometric accuracy, in order to cover a wide range of spectral types. 37 stars are found to exhibit emission in excess over a blackbody photospheric continuum, which is interpreted in terms of gas ejected in the form of an accelerated wind. By means of model calculations the corresponding mass loss rates are derived. The obtained values compare well with those determined independently by various authors for stars in common. Their data show that mass loss rates increase with luminosity and are a decreasing function of surface gravity. (Auth.)

  10. A Self-consistent Model for a Full Cycle of Recurrent Novae—Wind Mass-loss Rate and X-Ray Luminosity

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Mariko [Department of Astronomy, Keio University, Hiyoshi, Yokohama 223-8521 (Japan); Saio, Hideyuki [Astronomical Institute, Graduate School of Science, Tohoku University, Sendai, 980-8578 (Japan); Hachisu, Izumi, E-mail: mariko.kato@hc.st.keio.ac.jp [Department of Earth Science and Astronomy, College of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan)

    2017-04-01

    An unexpectedly slow evolution in the pre-optical-maximum phase was suggested in the very short recurrence period of nova M31N 2008-12a. To obtain reasonable nova light curves we have improved our calculation method by consistently combining optically thick wind solutions of hydrogen-rich envelopes with white dwarf (WD) structures calculated by a Henyey-type evolution code. The wind mass-loss rate is properly determined with high accuracy. We have calculated light curve models for 1.2 M {sub ⊙} and 1.38 M {sub ⊙} WDs with mass accretion rates corresponding to recurrence periods of 10 yr and 1 yr, respectively. The outburst lasts 590/29 days, in which the pre-optical-maximum phase is 82/16 days, for 1.2/1.38 M {sub ⊙}, respectively. Optically thick winds start at the end of the X-ray flash and cease at the beginning of the supersoft X-ray phase. We also present supersoft X-ray light curves including a prompt X-ray flash and later supersoft X-ray phase.

  11. Mass loss rates in the Hertzsprung-Russell diagram

    International Nuclear Information System (INIS)

    Jager, C. de; Nieuwenhuijzen, H.; Hucht, K.A. van der

    1988-01-01

    From the literature we collected values for the rate of mass loss for 271 stars, nearly all of population I, and of spectral types 0 through M. Rates of stellar mass loss determined according to six different methods were compared and appear to yield the same result per star within the limits of errors; this is true regardless of the star's position in the HR-diagram. Thus average rates of mass loss were determined, and weights were allocated to the M-determinations for each star. In addition we studied some groups of other stars: fast rotators (22 Be-type stars), and chemically evolved stars (31 Wolf-Rayet stars; 11 C- and 4 S-type stars and 15 nuclei of planetary nebulae). The chemically evolved stars have rates of mass loss which are larger than those of ''normal'' stars occupying the same positions in the Hertzprung-Russel diagram, by factors: 160 for Wolf-Rayet stars; 11 for C-type stars, and by estimated factors of 10 3 to 10 4 for the nuclei of planetary nebulae

  12. Fast Winds and Mass Loss from Metal-Poor Field Giants

    Science.gov (United States)

    Dupree, A. K.; Smith, Graeme H.; Strader, Jay

    2009-11-01

    Echelle spectra of the infrared He I λ10830 line were obtained with NIRSPEC on the Keck 2 telescope for 41 metal-deficient field giant stars including those on the red giant branch (RGB), asymptotic giant branch (AGB), and red horizontal branch (RHB). The presence of this He I line is ubiquitous in stars with T effgsim 4500 K and MV fainter than -1.5, and reveals the dynamics of the atmosphere. The line strength increases with effective temperature for T effgsim 5300 K in RHB stars. In AGB and RGB stars, the line strength increases with luminosity. Fast outflows (gsim 60 km s-1) are detected from the majority of the stars and about 40% of the outflows have sufficient speed as to allow escape of material from the star as well as from a globular cluster. Outflow speeds and line strengths do not depend on metallicity for our sample ([Fe/H]= -0.7 to -3.0), suggesting the driving mechanism for these winds derives from magnetic and/or hydrodynamic processes. Gas outflows are present in every luminous giant, but are not detected in all stars of lower luminosity indicating possible variability. Mass loss rates ranging from ~3 × 10-10 to ~6 × 10-8 M sun yr-1 estimated from the Sobolev approximation for line formation represent values with evolutionary significance for red giants and RHB stars. We estimate that 0.2 M sun will be lost on the RGB, and the torque of this wind can account for observations of slowly rotating RHB stars in the field. About 0.1-0.2 M sun will be lost on the RHB itself. This first empirical determination of mass loss on the RHB may contribute to the appearance of extended horizontal branches in globular clusters. The spectra appear to resolve the problem of missing intracluster material in globular clusters. Opportunities exist for "wind smothering" of dwarf stars by winds from the evolved population, possibly leading to surface pollution in regions of high stellar density. Data presented herein were obtained at the W. M. Keck Observatory, which

  13. Rate of Mass Loss Across the Instability Threshold for Thwaites Glacier Determines Rate of Mass Loss for Entire Basin

    Science.gov (United States)

    Waibel, M. S.; Hulbe, C. L.; Jackson, C. S.; Martin, D. F.

    2018-01-01

    Rapid change now underway on Thwaites Glacier (TG) raises concern that a threshold for unstoppable grounding line retreat has been or is about to be crossed. We use a high-resolution ice sheet model to examine the mechanics of TG self-sustained retreat by nudging the grounding line just past the point of instability. We find that by modifying surface slope in the region of the grounding line, the rate of the forcing dictates the rate of retreat, even after the external forcing is removed. Grounding line retreats that begin faster proceed more rapidly because the shorter time interval for the grounding line to erode into the grounded ice sheet means relatively thicker ice and larger driving stress upstream of the boundary. Retreat is sensitive to short-duration re-advances associated with reduced external forcing where the bathymetry allows regrounding, even when an instability is invoked.

  14. The Influence of Coronal Mass Ejections on the Mass-loss Rates of Hot-Jupiters

    Energy Technology Data Exchange (ETDEWEB)

    Cherenkov, A.; Bisikalo, D. [Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya St. 119017, Moscow (Russian Federation); Fossati, L.; Möstl, C., E-mail: bisikalo@inasan.ru [Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz (Austria)

    2017-09-01

    Hot-Jupiters are subject to extreme radiation and plasma flows coming from their host stars. Past ultraviolet Hubble Space Telescope observations, supported by hydrodynamic models, confirmed that these factors lead to the formation of an extended envelope, part of which lies beyond the Roche lobe. We use gas-dynamic simulations to study the impact of time variations in the parameters of the stellar wind, namely that of coronal mass ejections (CMEs), on the envelope of the typical hot-Jupiter HD 209458b. We consider three CMEs characterized by different velocities and densities, taking their parameters from typical CMEs observed for the Sun. The perturbations in the ram-pressure of the stellar wind during the passage of each CME tear off most of the envelope that is located beyond the Roche lobe. This leads to a substantial increase of the mass-loss rates during the interaction with the CME. We find that the mass lost by the planet during the whole crossing of a CME is of ≈10{sup 15} g, regardless of the CME taken into consideration. We also find that over the course of 1 Gyr, the mass lost by the planet because of CME impacts is comparable to that lost because of high-energy stellar irradiation.

  15. Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

    Energy Technology Data Exchange (ETDEWEB)

    Cranmer, Steven R. [Department of Astrophysical and Planetary Sciences, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309 (United States)

    2017-05-10

    Coronal mass ejections (CMEs) are eruptive events that cause a solar-type star to shed mass and magnetic flux. CMEs tend to occur together with flares, radio storms, and bursts of energetic particles. On the Sun, CME-related mass loss is roughly an order of magnitude less intense than that of the background solar wind. However, on other types of stars, CMEs have been proposed to carry away much more mass and energy than the time-steady wind. Earlier papers have used observed correlations between solar CMEs and flare energies, in combination with stellar flare observations, to estimate stellar CME rates. This paper sidesteps flares and attempts to calibrate a more fundamental correlation between surface-averaged magnetic fluxes and CME properties. For the Sun, there exists a power-law relationship between the magnetic filling factor and the CME kinetic energy flux, and it is generalized for use on other stars. An example prediction of the time evolution of wind/CME mass-loss rates for a solar-mass star is given. A key result is that for ages younger than about 1 Gyr (i.e., activity levels only slightly higher than the present-day Sun), the CME mass loss exceeds that of the time-steady wind. At younger ages, CMEs carry 10–100 times more mass than the wind, and such high rates may be powerful enough to dispel circumstellar disks and affect the habitability of nearby planets. The cumulative CME mass lost by the young Sun may have been as much as 1% of a solar mass.

  16. Mass loss from Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Willis, A.J.

    1982-01-01

    Recent results relating to the stellar winds and mass loss rates of the WR stars are reviewed, emphasising new data and their interpretation acquired at UV, IR and Radio wavelengths. The subject is discussed under the headings: physical and chemical properties of WR stars (effective temperatures and radiative luminosities; masses; chemical abundances); velocity, ionisation and excitation structure of WR winds; mass loss rates of WR stars; mass loss properties of WR stars in the LMC; comparisons with theoretical models of mass loss; ring nebulae around WR stars; conclusions. (author)

  17. Comparison of the Heat Release Rate from the Mass Loss Calorimeter to the Cone Calorimeter for Wood-based Materials

    Science.gov (United States)

    Laura E. Hasburgh; Robert H. White; Mark A. Dietenberger; Charles R. Boardman

    2015-01-01

    There is a growing demand for material properties to be used as inputs in fi re behavior models designed to address building fire safety. This comparative study evaluates using the mass loss calorimeter as an alternative to the cone calorimeter for obtaining heat release rates of wood-based materials. For this study, a modified mass loss calorimeter utilized an...

  18. The circumstellar shells and mass loss rates of four M supergiants

    International Nuclear Information System (INIS)

    Bernat, A.P.

    1977-01-01

    A reanalysis of the physical structure of the circumstellar gas shells of four bright M supergiants, Betelgeuse, Antares, α Herculis, and μ Cephei, has been undertaken. The observational data include old Hale Observatories plates, recent McDonald Struve telescope plates, and McDonald 2.7 m photoelectric scans. These data are analyzed in the full expanding spherical geometry formulation of the radiative transfer equation.The results of the present analysis indicate that column densities in the gas shells must be revised downward compared with the previous plane-parallel results. However, the physical extents of the shells are considerably larger than previously assumed. These extents are inferred through ionization modeling, Weymann's Ca II technique, and direct observation. Also inferred are schematic wavelength-dependent chromospheric color temperatures. These results lead to much larger mass loss rates (in the range 6.7 x 10 -7 to 4.2 x 10 -4 M/sub sun/ yr -2 ) than previously inferred. The influence of these large rates of mass loss on the evolution of both stars and the Galaxy is briefly discussed

  19. Luminosities and mass-loss rates of Local Group AGB stars and red supergiants

    Science.gov (United States)

    Groenewegen, M. A. T.; Sloan, G. C.

    2018-01-01

    Context. Mass loss is one of the fundamental properties of asymptotic giant branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking. Aims: We aim to investigate mass loss and luminosity in a large sample of evolved stars in several Local Group galaxies with a variety of metalliticies and star-formation histories: the Small and Large Magellanic Cloud, and the Fornax, Carina, and Sculptor dwarf spheroidal galaxies (dSphs). Methods: Dust radiative transfer models are presented for 225 carbon stars and 171 oxygen-rich evolved stars in several Local Group galaxies for which spectra from the Infrared Spectrograph on Spitzer are available. The spectra are complemented with available optical and infrared photometry to construct spectral energy distributions. A minimization procedure was used to determine luminosity and mass-loss rate (MLR). Pulsation periods were derived for a large fraction of the sample based on a re-analysis of existing data. Results: New deep K-band photometry from the VMC survey and multi-epoch data from IRAC (at 4.5 μm) and AllWISE and NEOWISE have allowed us to derive pulsation periods longer than 1000 days for some of the most heavily obscured and reddened objects. We derive (dust) MLRs and luminosities for the entire sample. The estimated MLRs can differ significantly from estimates for the same objects in the literature due to differences in adopted optical constants (up to factors of several) and details in the radiative transfer modelling. Updated parameters for the super-AGB candidate MSX SMC 055 (IRAS 00483-7347) are presented. Its current mass is estimated to be 8.5 ± 1.6 M⊙, suggesting an initial mass well above 8 M⊙ in agreement with estimates based on its large Rubidium abundance. Using synthetic photometry, we present and discuss colour-colour and

  20. THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. VI. LUMINOSITIES AND MASS-LOSS RATES ON POPULATION SCALES

    International Nuclear Information System (INIS)

    Riebel, D.; Meixner, M.; Srinivasan, S.; Sargent, B.

    2012-01-01

    We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to ∼30,000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionary parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 2.1 × 10 –5 M ☉ yr –1 , equivalent to a total mass injection rate (including the gas) into the ISM of ∼6 × 10 –3 M ☉ yr –1 . Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K s band as a function of J – K s color, BC K s = -0.40(J-K s ) 2 + 1.83(J-K s ) + 1.29. We determine several IR color proxies for the dust mass-loss rate (M-dot d ) from C-rich AGB stars, such as log M-dot d = (-18.90/((K s -[8.0])+3.37) - 5.93. We find that a larger fraction of AGB stars exhibiting the 'long-secondary period' phenomenon are more O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.

  1. A Conceptual Analysis of Mass Loss and Frequency Redistribution in Wolf-Rayet Winds

    OpenAIRE

    Onifer, A. J.; Gayley, K. G.

    2007-01-01

    To better understand Wolf-Rayet stars as progenitors of gamma-ray bursts, an understanding of the effect metallicity has on Wolf-Rayet mass loss is needed. Using simple analytic models, we study the Mdot - Z relation of a WN star and compare the results to similar models. We find that Mdot roughly follows a power law in Z with index 0.88 from -2.5 < log Z/Z_sun < -1 and appears to flatten by log Z/Z_sun ~ -0.5.

  2. Mass loss from pre-main-sequence accretion disks. I - The accelerating wind of FU Orionis

    Science.gov (United States)

    Calvet, Nuria; Hartmann, Lee; Kenyon, Scott J.

    1993-01-01

    We present evidence that the wind of the pre-main-sequence object FU Orionis arises from the surface of the luminous accretion disk. A disk wind model calculated assuming radiative equilibrium explains the differential behavior of the observed asymmetric absorption-line profiles. The model predicts that strong lines should be asymmetric and blueshifted, while weak lines should be symmetric and double-peaked due to disk rotation, in agreement with observations. We propose that many blueshifted 'shell' absorption features are not produced in a true shell of material, but rather form in a differentially expanding wind that is rapidly rotating. The inference of rapid rotation supports the proposal that pre-main-sequence disk winds are rotationally driven.

  3. Main sequence mass loss

    International Nuclear Information System (INIS)

    Brunish, W.M.; Guzik, J.A.; Willson, L.A.; Bowen, G.

    1987-01-01

    It has been hypothesized that variable stars may experience mass loss, driven, at least in part, by oscillations. The class of stars we are discussing here are the δ Scuti variables. These are variable stars with masses between about 1.2 and 2.25 M/sub θ/, lying on or very near the main sequence. According to this theory, high rotation rates enhance the rate of mass loss, so main sequence stars born in this mass range would have a range of mass loss rates, depending on their initial rotation velocity and the amplitude of the oscillations. The stars would evolve rapidly down the main sequence until (at about 1.25 M/sub θ/) a surface convection zone began to form. The presence of this convective region would slow the rotation, perhaps allowing magnetic braking to occur, and thus sharply reduce the mass loss rate. 7 refs

  4. Effect of mass loss by stellar wind on the chemical enrichment of the galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Chiosi, C [Padua Univ. (Italy). Istituto di Astronomia

    1979-01-01

    The rate of production of heavy elements is rediscussed using the models of Arnett (1978) for late stage nucleosynthesis in massive stars, the M(M,) relationship of Chiosi et al. (1978b) for losing mass models in the core H and He-Burning phases, and the stellar birth rate of Miller and Scalo (1978). Contrary to that found by Wheeler et al (1978), we do not encounter the difficulty of heavy element overproduction. The explosive nucleosynthesis from massive stars is still compatible with the observed abundance distribution of the solar system, and a stellar birth rate decreasing over the history of the galactic disk.

  5. The effect of mass loss by stellar wind on the chemical enrichment of the galaxy

    International Nuclear Information System (INIS)

    Chiosi, C.

    1979-01-01

    The rate of production of heavy elements is rediscussed using the models of Arnett (1978) for late stage nucleosynthesis in massive stars, the M(M,) relationship of Chiosi et al. (1978b) for losing mass models in the core H and He-Burning phases, and the stellar birth rate of Miller and Scalo (1978). Contrary to that found by Wheeler et al (1978), we do not encounter the difficulty of heavy element overproduction. The explosive nucleosynthesis from massive stars is still compatible with the observed abundance distribution of the solar system, and a stellar birth rate decreasing over the history of the galactic disk. (orig.)

  6. Photometric and polarimetric variability and mass-loss rate of the massive binary Wolf-Rayet star HDE 311884 (WN6 + 05: V)

    International Nuclear Information System (INIS)

    Moffat, A.F.J.; Drissen, L.; Robert, C.; Lamontagne, R.; Coziol, R.

    1990-01-01

    Photometric and polarimetric monitoring of the Wolf-Rayet (W-R) + O-type binary system HDE 311884 = WR 47 over many orbital cycles shows the clear effects of phase-dependent electron scattering of O-star light as the orbiting O companion shines through varying column density of W-R stellar wind material. In contrast to this wind-type eclipse, the stars themselves do not quite eclipse. Both photometry and polarimetry give a consistent estimate of the mass-loss rate of the W-R component: at about 0.00003 solar mass/yr. The orbital inclination, i = 70 deg, along with the previously published velocity orbit, yields high masses: M(WN6) = 48 solar masses and M(O5:V) = 57 solar masses. 33 refs

  7. A new analysis of the momentum and mass-loss rates of stellar jets

    International Nuclear Information System (INIS)

    Raga, A.C.

    1991-01-01

    A very important question in the theory of bipolar outflows from young stars is posed by the still not understood relation between molecular outflows and optical outflows (i.e., stellar jets and Herbig-Haro objects). In some past studies, estimates of mass and momentum rates associated with these outflows indicated that stellar jets have approximately 2 orders of magnitude smaller values for these parameters than the molecular outflows associated with the same sources. However, a reanalysis of observations of stellar jets in the light of new theoretical jet models yields values of mass and momentum rates comparable to the ones of molecular outflows. From this result it can be tentatively speculated that stellar jets (or Herbig-Haro objects) and molecular outflows might be different manifestations of basically the same flow. 21 refs

  8. Evolutionary effects of mass loss in low-mass stars

    International Nuclear Information System (INIS)

    Renzini, A.

    1981-01-01

    The effects of mass loss on the evolution of low-mass stars (actual mass smaller than 1.4 solar masses) are reviewed. The case of globular cluster stars is discussed in some detail, and it is shown that evolutionary theory sets quite precise limits to the mass-loss rate in population II red giants. The effects of mass loss on the final evolutionary stages of stars producing white dwarfs is also discussed. In particular, the interaction of the wind from the hot central star with the surrounding planetary nebula is considered. Finally, the problem of the origin of hydrogen-deficient stars is briefly discussed. (Auth.)

  9. Mass loss from S stars

    International Nuclear Information System (INIS)

    Jura, M.

    1988-01-01

    The mass-loss process in S stars is studied using 65 S stars from the listing of Wing and Yorka (1977). The role of pulsations in the mass-loss process is examined. It is detected that stars with larger mass-loss rates have a greater amplitude of pulsations. The dust-to-gas ratio for the S stars is estimated as 0.002 and the average mass-loss rate is about 6 x 10 to the -8th solar masses/yr. Some of the properties of the S stars, such as scale height, surface density, and lifetime, are measured. It is determined that scale height is 200 pc; the total duration of the S star phase is greater than or equal to 30,000 yr; and the stars inject 3 x 10 to the -6th solar masses/sq kpc yr into the interstellar medium. 46 references

  10. Stringent limits on the ionized mass loss from A and F dwarfs

    International Nuclear Information System (INIS)

    Brown, A.; Veale, A.; Judge, P.; Bookbinder, J.A.; Hubeny, I.

    1990-01-01

    Following the suggestion of Willson et al. (1987) that A- and F-type main-sequence stars might undergo significant mass loss due to pulsationally driven winds, upper limits to the ionized mass loss from A and F dwarfs have been obtained using VLA observations. These stringent upper limits show that the level of ionized mass loss would have at most only a small effect on stellar evolution. Radiative-equilibrium atmospheric and wind models for early A dwarfs indicate that it is highly likely that a wind flowing from such stars would be significantly ionized. In addition, late A and early F dwarfs exhibit chromospheric emission indicative of significant nonradiative heating. The present mass-loss limits are thus representative of the total mass-loss rates for these stars. It is concluded that A and F dwarfs are not losing sufficient mass to cause A dwarfs to evolve into G dwarfs. 24 refs

  11. A drop in the pond: the effect of rapid mass-loss on the dynamics and interaction rate of collisionless particles

    Science.gov (United States)

    Penoyre, Zephyr; Haiman, Zoltán

    2018-01-01

    In symmetric gravitating systems experiencing rapid mass-loss, particle orbits change almost instantaneously, which can lead to the development of a sharply contoured density profile, including singular caustics for collisionless systems. This framework can be used to model a variety of dynamical systems, such as accretion discs following a massive black hole merger and dwarf galaxies following violent early star formation feedback. Particle interactions in the high-density peaks seem a promising source of observable signatures of these mass-loss events (i.e. a possible EM counterpart for black hole mergers or strong gamma-ray emission from dark matter annihilation around young galaxies), because the interaction rate depends on the square of the density. We study post-mass-loss density profiles, both analytic and numerical, in idealized cases and present arguments and methods to extend to any general system. An analytic derivation is presented for particles on Keplerian orbits responding to a drop in the central mass. We argue that this case, with initially circular orbits, gives the most sharply contoured profile possible. We find that despite the presence of a set of singular caustics, the total particle interaction rate is reduced compared to the unperturbed system; this is a result of the overall expansion of the system dominating over the steep caustics. Finally, we argue that this result holds more generally, and the loss of central mass decreases the particle interaction rate in any physical system.

  12. Observations of mass loss from OB and Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Barlow, M.J.

    1982-01-01

    In this review, three observationally accessible parameters of the winds of OB and Wolf-Rayet stars are discussed: (1) Terminal velocities, (2) Velocity laws, (3) Mass loss rates. In addition, some discussion of the ionisation structure of the winds is included. In general, only the most recent results for OB stars are mentioned. (Auth.)

  13. Mass loss from Eta Carinae

    International Nuclear Information System (INIS)

    Andriesse, C.D.; Viotti, R.

    1979-01-01

    This high luminosity (5x10 6 solar luminosity) star since 1840 is losing mass at the rate of 7.5x10 -2 solar masses per year. The large mass loss could be the result of vibrational instabilities produced in the CNO hydrogen burning phase of a very massive (160 solar masses) star. The presence of high excitation lines in the ultraviolet spectrum of Eta Car suggests the idea of a hot zone excited by dissipation of the supersonic turbulent flow. (Auth.)

  14. PULSATION-TRIGGERED MASS LOSS FROM AGB STARS: THE 60 DAY CRITICAL PERIOD

    International Nuclear Information System (INIS)

    McDonald, I.; Zijlstra, A. A.

    2016-01-01

    Low- and intermediate-mass stars eject much of their mass during the late, red giant branch (RGB) phase of evolution. The physics of their strong stellar winds is still poorly understood. In the standard model, stellar pulsations extend the atmosphere, allowing a wind to be driven through radiation pressure on condensing dust particles. Here, we investigate the onset of the wind, using nearby RGB stars drawn from the Hipparcos catalog. We find a sharp onset of dust production when the star first reaches a pulsation period of 60 days. This approximately coincides with the point where the star transitions to the first overtone pulsation mode. Models of the spectral energy distributions show stellar mass-loss rate suddenly increasing at this point, by a factor of ∼10 over the existing (chromospherically driven) wind. The dust emission is strongly correlated with both pulsation period and amplitude, indicating stellar pulsation is the main trigger for the strong mass loss, and determines the mass-loss rate. Dust emission does not strongly correlate with stellar luminosity, indicating radiation pressure on dust has little effect on the mass-loss rate. RGB stars do not normally appear to produce dust, whereas dust production by asymptotic giant branch stars appears commonplace, and is probably ubiquitous above the RGB-tip luminosity. We conclude that the strong wind begins with a step change in mass-loss rate and is triggered by stellar pulsations. A second rapid mass-loss-rate enhancement is suggested when the star transitions to the fundamental pulsation mode at a period of ∼300 days.

  15. Mass loss by stars on the asymptotic giant branch

    International Nuclear Information System (INIS)

    Frantsman, Yu.L.

    1986-01-01

    The theoretical populations of white dwarfs and carbon stars were generated for Salpeter initial mass function and constant stellar birth rate history. The effect of very strong mass loss on the mass distribution of white dwarfs and luminosity distribution of carbon stars is discussed and the results are compared with observations. This comparison suggested that a signioficant mass loss by stars on the asymptotic giant branch occurs besides stellar wind and planetary nebulae ejection. Thus it is possible to explain the absence of carbon stars with Msub(bol) 1.0 Msub(sun). The luminosity of asymptotic giant branch stars in the globular clusters of the Magellanic Clouds appears to be a very good indicator of the age

  16. Massive stars evolution with mass-loss. 20-100 M(sun) models

    Energy Technology Data Exchange (ETDEWEB)

    Chiosi, C; Sreenivasan, S R [Calgary Univ., Alberta (Canada). Dept. of Physics; Nasi, E [Padua Univ. (Italy). Istituto di Astronomia

    1978-02-01

    The evolution of stars with initial masses 20, 30, 40, 60, 80, 100 M(sun) and Population I chemical composition (X = 0.700, Z = 0.02) is calculated, taking into account mass-loss due to stellar winds, from the main sequence up to the early stages of central He-burning. This study incorporates mass-loss rates predicted by the theory of Castor et al. (1975) for the early type phases and a novel way of treating mass-loss rates due to acoustic energy flux driven winds in the later stages analogous to the work of Fusi-Pecci and Renzini (1975a). The results are presented in terms of evolutionary tracks, isochrones, loci of constant mass-loss rates and loci of constant mass in the HR diagram. The effects of mass-loss on the internal structure of the models as well as on the occurrence of semiconvection are also investigated. A detailed comparison of the theoretical predictions and observational results is made and possible implications for O, Of, Wolf-Rayet stars and red supergiants are brought out.

  17. Mass loss from the K dwarf in V471 Tauri

    International Nuclear Information System (INIS)

    Mullan, D.J.; Bruhweiler, F.; Sion, E.M.

    1988-01-01

    Spectra of MgII h and k have been obtained for V471 Tau at phases zero (K dwarf in front) and 0.5 (white dwarf in front). At phase zero, strong blueshifted absorption is present, suggestive of a wind from the K dwarf with terminal velocity 600-700 km/sec and mass loss rate at least three orders of magnitude greater than solar. Discrete blue-shifted absorption features occur at velocities of about 200 and 500 km/sec. At phase 0.5, the blueshifted absorption is much weaker, although still detectable

  18. Evidence for Pulsation-Driven Mass Loss from δ Cephei

    Science.gov (United States)

    Marengo, M.; Evans, N. R.; Matthews, L. D.; Bono, G.; Barmby, P.; Welch, D. L.; Romaniello, M.; Su, K. Y. L.; Fazio, G. G.; Huelsman, D.

    We found the first direct evidence that the Cepheid class namesake, δ Cephei, is currently losing mass. These observations are based on data obtained with the Spitzer Space Telescope in the infrared, and with the Very Large Array in the radio. We found that δ Cephei is associated with a vast circumstellar structure, reminiscent of a bow shock. This structure is created as the wind from the star interacts with the local interstellar medium. We measure an outflow velocity of ≈ 35. 5 km s- 1 and a mass loss rate of ≈ 10- 7-10- 6 M ⊙ year- 1. The very low dust content of the outflow suggests that the wind is possibly pulsation-driven, rather than dust-driven as common for other classes of evolved stars.

  19. Mass loss and cepheid pulsation

    International Nuclear Information System (INIS)

    Davis, C.G. Jr.

    1977-01-01

    Two purposes are served: to discuss the latest improvements in nonlinear pulsation theory indicating the ability to resolve features such as the ''Christy bump'' on the light curves and to show from the results of a bump model and recent observations that mass loss is one of the possible explanations for the mass discrepancy problem between evolutionary and pulsation theories. Recent observations by Sanford and Gow of Los Alamos and Bernat (McDonald Observatory) show that extensive mass loss has occurred in the evolution of the M supergiant α Orionis

  20. Effect of mass loss on the chemical yields from massive stars

    Energy Technology Data Exchange (ETDEWEB)

    Chiosi, C; Caimmi, R [Padua Univ. (Italy). Istituto di Astronomia

    1979-01-01

    Recent results on the calculation of the chemical yields from massive stars, are rediscussed by taking into account the occurrence of mass loss by stellar wind during the core H- and He-burning phases. The new yields are found to be compatible with the observed distribution of chemical abundances in the solar system, except for He. The net enrichment of several elements over the galaxy's lifetime is found to be consistent with the current estimate of the star formation rate, if we adopt a two phase process of galaxy formation (halodisk). The relative He to heavy element enrichment rate ..delta..Y/..delta..Z turns out to agree with the observational value when mass loss by stellar wind is taken into account.

  1. Mass loss on the Asymptotic Giant Branch

    OpenAIRE

    Zijlstra, Albert

    2006-01-01

    Mass loss on the Asymptotic Giant Branch provides the origin of planetary nebulae. This paper reviews several relevant aspects of AGB evolution: pulsation properties, mass loss formalisms and time variable mass loss, evidence for asymmetries on the AGB, binarity, ISM interaction, and mass loss at low metallicity. There is growing evidence that mass loss on the AGB is already asymmetric, but with spherically symmetric velocity fields. The origin of the rings may be in pulsational instabilities...

  2. DUST PRODUCTION AND MASS LOSS IN THE GALACTIC GLOBULAR CLUSTER 47 TUCANAE

    International Nuclear Information System (INIS)

    McDonald, I.; Zijlstra, A. A.; Boyer, M. L.; Van Loon, J. Th.

    2011-01-01

    Dust production among post-main-sequence stars is investigated in the Galactic globular cluster 47 Tucanae (NGC 104) based on infrared photometry and spectroscopy. We identify metallic iron grains as the probable dominant opacity source in these winds. Typical evolutionary timescales of asymptotic giant branch stars suggest the mass-loss rates we report are too high. We suggest that this is because the iron grains are small or elongated and/or that iron condenses more efficiently than at solar metallicity. Comparison to other works suggests metallic iron is observed to be more prevalent toward lower metallicities. The reasons for this are explored, but remain unclear. Meanwhile, the luminosity at which dusty mass loss begins is largely invariant with metallicity, but its presence correlates strongly with long-period variability. This suggests that the winds of low-mass stars have a significant driver that is not radiation pressure, but may be acoustic driving by pulsations.

  3. The coupling between pulsation and mass loss in massive stars

    OpenAIRE

    Townsend, Rich

    2007-01-01

    To what extent can pulsational instabilities resolve the mass-loss problem of massive stars? How important is pulsation in structuring and modulating the winds of these stars? What role does pulsation play in redistributing angular momentum in massive stars? Although I cannot offer answers to these questions, I hope at the very least to explain how they come to be asked.

  4. Effect of mass loss on the. beta. Cephei instability strip

    Energy Technology Data Exchange (ETDEWEB)

    Chiosi, C [Padua Univ. (Italy). Ist. di Astronomia

    1980-07-01

    In this paper we aim to suggest on a speculative basis that the existence of mass loss by stellar wind in massive stars (M > 10 Msub(sun)) may affect the properties of the ..beta.. Cephei instability strip, and remove some of the difficulties encountered in the interpretation of their pulsation.

  5. Mass loss from interacting close binary systems

    Science.gov (United States)

    Plavec, M. J.

    1981-01-01

    The three well-defined classes of evolved binary systems that show evidence of present and/or past mass loss are the cataclysmic variables, the Algols, and Wolf-Rayet stars. It is thought that the transformation of supergiant binary systems into the very short-period cataclysmic variables must have been a complex process. The new evidence that has recently been obtained from the far ultraviolet spectra that a certain subclass of the Algols (the Serpentids) are undergoing fairly rapid evolution is discussed. It is thought probable that the remarkable mass outflow observed in them is connected with a strong wind powered by accretion. The origin of the circumbinary clouds or flat disks that probably surround many strongly interacting binaries is not clear. Attention is also given to binary systems with hot white dwarf or subdwarf components, such as the symbiotic objects and the BQ stars; it is noted that in them both components may be prone to an enhanced stellar wind.

  6. Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars

    Science.gov (United States)

    Šurlan, B.; Hamann, W.-R.; Aret, A.; Kubát, J.; Oskinova, L. M.; Torres, A. F.

    2013-11-01

    Context. Recent studies of O-type stars have demonstrated that discrepant mass-loss rates are obtained when different diagnostic methods are employed. Fitting the unsaturated UV resonance lines (e.g., P v) gives drastically lower values than obtained from the Hα emission. Wind inhomogeneity (so-called "clumping") may be the main cause of this discrepancy. Aims: In a previous paper, we presented 3D Monte-Carlo calculations for the formation of scattering lines in a clumped stellar wind. In the present paper we select five O-type supergiants (from O4 to O7) and test whether the reported discrepancies can be resolved this way. Methods: In the first step, the analyses started with simulating the observed spectra with Potsdam Wolf-Rayet (PoWR) non-LTE model atmospheres. The mass-loss rates are adjusted to fit to the observed Hα emission lines best. For the unsaturated UV resonance lines (i.e., P v) we then applied our 3D Monte-Carlo code, which can account for wind clumps of any optical depths ("macroclumping"), a non-void interclump medium, and a velocity dispersion inside the clumps. The ionization stratifications and underlying photospheric spectra were adopted from the PoWR models. The properties of the wind clumps were constrained by fitting the observed resonance line profiles. Results: Our results show that with the mass-loss rates that fit Hα (and other Balmer and He ii lines), the UV resonance lines (especially the unsaturated doublet of P v) can also be reproduced with no problem when macroclumping is taken into account. There is no need to artificially reduce the mass-loss rates or to assume a subsolar phosphorus abundance or an extremely high clumping factor, unlike what was claimed by other authors. These consistent mass-loss rates are lower by a factor of 1.3 to 2.6, compared to the mass-loss rate recipe from Vink et al. Conclusions: Macroclumping resolves the previously reported discrepancy between Hα and P v mass-loss diagnostics. Based on

  7. Mass loss in early stages of stellar evolution

    International Nuclear Information System (INIS)

    Dearborn, D.S.P.; Kozlowski, M.; Schramm, D.

    1976-01-01

    It is known that stars lose mass between their birth on the main sequence and their death as white dwarfs, or as neutron stars or black holes for more massive stars. Solar wind considerations indicate that not all of the mass loss occurs in a 'last gasp' to form a planetary nebula. Mass loss has be observed in O-B stars and in red giants, but the mass loss observed in these stages do not appear sufficient to account for all the loss required for stars to become white dwarfs. The problem is at what stages and in what manner the excess mass is lost. Suggestions have tended to favour He flashes for stars with M < 2.25 M. and possibly double shell instability flashes for stars in the range from 2.25 M. to 8 M. Although is is possible that significant mass is lost during these stages, there appears to be no quantitative support for this suggestion, and in particular none for the He flash. It is shown here that there is increasing evidence for substantial mass loss during the immediate post main sequence stages when the star is moving from the main sequence to the giant branch. Mass loss at these early stages of evolution may have implications on the subsequent evolution of the star and the amount of nuclearly processed material that is ejected into the interstellar-medium. The behaviour of Arcturus is discussed in these connections. (U.K.)

  8. Constraining the Mass Loss Geometry of Beta Lyrae

    Directory of Open Access Journals (Sweden)

    Jamie R. Lomax

    2012-03-01

    Full Text Available Massive binary stars lose mass by two mechanisms: jet-driven mass loss during periods of active mass transfer and by wind-driven mass loss. Beta Lyrae is an eclipsing, semi-detached binary whose state of active mass transfer provides a unique opportunity to study how the evolution of binary systems is affected by jet-driven mass loss. Roche lobe overflow from the primary star feeds the thick accretion disk which almost completely obscures the mass-gaining star. A hot spot predicted to be on the edge of the accretion disk may be the source of beta Lyrae’s bipolar outflows. I present results from spectropolarimetric data taken with the University of Wisconsin’s Half-Wave Spectropolarimeter and the Flower and Cook Observatory’s photoelastic modulating polarimeter instrument which have implications for our current understanding of the system’s disk geometry. Using broadband polarimetric analysis, I derive new information about the structure of the disk and the presence and location of a hot spot. These results place constraints on the geometrical distribution of material in beta Lyrae and can help quantify the amount of mass lost from massive interacting binary systems during phases of mass transfer and jet-driven mass loss.

  9. Evidence for mass loss at moderate to high velocity in Be stars

    International Nuclear Information System (INIS)

    Snow, T.P. Jr.; Marlborough, J.M.

    1976-01-01

    Ultraviolet spectra of intermediate resolution have been obtained with Copernicus of 12 objects classified as Be or shell stars, and 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si iv doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km s -1 . Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotation effects reduce the effective gravity near the equator. The mass loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be 10 -10 --10 -9 M/sub sun/ yr -1 . The data are suggestive that the extended atmospheres associated with Be star phenomena may be formed by mass ejection

  10. Evidence for mass loss at moderate to high velocity in Be stars

    Science.gov (United States)

    Snow, T. P., Jr.; Marlborough, J. M.

    1976-01-01

    Ultraviolet spectra of intermediate resolution have been obtained with Copernicus for 12 objects classified as Be or shell stars and for 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km/s. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered, there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotational effects reduce the effective gravity near the equator. The mass-loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be one billionth or one ten-billionth of a solar mass per year. The data suggest that the extended atmospheres associated with Be-star phenomena may be formed by mass ejection.

  11. Low-mass stars with mass loss and low-luminosity carbon star formation

    International Nuclear Information System (INIS)

    Boothroyd, A.I.

    1987-01-01

    The effects of large carbon enrichments in static stellar envelopes were investigated, using new Los Alamos opacities (including low-temperature carbon and molecular opacities) and including carbon ionizations. To search for the production of low-mass,low-luminosity carbon stars, detailed stellar evolutionary computations were carried out for a grid of low-mass stars of two different metallicities. The stars were evolved from the main sequence through all intermediate stages and through helium-shell flashes on the asymptotic giant branch. The effects of the latest nuclear reaction rates, the new Los Alamos opacities, Reimers-type wind mass loss, and detailed treatment of convection and semi-convection were investigated. Two low-luminosity carbon stars were achieved, in excellent agreement with observations. Conditions favoring dredge-up (and thus carbon-star production) include a reasonably large convective mixing length, low metallicity, relatively large envelope mass, and high flash strength. Mass loss was of major importance, tending to oppose dredge-up; the total mass-loss amounts inferred from observations suffice to prevent formation of high-mass, high-luminosity carbon stars

  12. The evolution of massive stars with mass loss: the H- and the He-burning phases

    International Nuclear Information System (INIS)

    Chieffi, Alessandro; Limongi, Marco

    2010-01-01

    The evolution of a massive star to its final fate is strongly modified by the efficient mass loss episodes it experiences during its lifetime. In the following, we will briefly summarize how the H- and the He- burning phases depend on the adopted mass loss rate.

  13. Annoyance rating of wind turbine noise

    International Nuclear Information System (INIS)

    Iredale, R.

    1993-01-01

    Annoyance rating is important, but more important still is agreement on techniques for formulating minimal complaint criteria for design and specification purposes thus integrating noise control into the plant at the outset. A minimal complaint design criteria is suggested that finds its origin in the logic and techniques used successfully over many years for a wide range of power plant and other installations. The criterion is based on the masking of the wind turbine noise by the wind generated background noise. Satisfactory use of the criterion depends on the specification of inaudibility for the tones generated by the mechanical plant. Wind turbines generate more drive train noise than is realized and this contains many tones which tend to characterize the noise. Reduction of drive train noise would not only reduce the overall noise level but also give it a more acceptable character providing a margin against complaint in unusual circumstances of propagation. This requires very careful design of noise and vibration control in individual components. Vibration isolation between the support structures and the nacelle also requires careful attention. (UK)

  14. First stars. II. Evolution with mass loss

    Czech Academy of Sciences Publication Activity Database

    Bahena, David; Hadrava, Petr

    2012-01-01

    Roč. 337, č. 2 (2012), s. 651-663 ISSN 0004-640X R&D Projects: GA MŠk(CZ) LC506; GA ČR GA202/09/0772 Institutional research plan: CEZ:AV0Z10030501 Keywords : first stars * evolution * mass loss Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.064, year: 2012

  15. Episodic mass loss from the hydrogen-deficient central star of the planetary nebula Longmore 4

    Energy Technology Data Exchange (ETDEWEB)

    Bond, Howard E., E-mail: heb11@psu.edu [Current address: Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA. (United States)

    2014-09-01

    A spectacular transient mass-loss episode from the extremely hot, hydrogen-deficient central star of the planetary nebula (PN) Longmore 4 (Lo 4) was discovered in 1992 by Werner et al. During that event, the star temporarily changed from its normal PG 1159 spectrum to that of an emission-line low-luminosity early-type Wolf-Rayet [WCE] star. After a few days, Lo 4 reverted to its normal, predominantly absorption-line PG 1159 type. To determine whether such events recur, and if so how often, I monitored the optical spectrum of Lo 4 from early 2003 to early 2012. Out of 81 spectra taken at random dates, 4 of them revealed mass-loss outbursts similar to that seen in 1992. This indicates that the episodes recur approximately every 100 days (if the recurrence rate has been approximately constant and the duration of a typical episode is ∼5 days), and that the star is in a high-mass-loss state about 5% of the time. Since the enhanced stellar wind is hydrogen-deficient, it arises from the photosphere and is unlikely to be related to phenomena such as a binary or planetary companion or infalling dust. I speculate on plausible mechanisms for these unique outbursts, including the possibility that they are related to the non-radial GW Vir-type pulsations exhibited by Lo 4. The central star of the PN NGC 246 has stellar parameters similar to those of Lo 4, and it is also a GW Vir-type pulsator with similar pulsation periods. I obtained 167 spectra of NGC 246 between 2003 and 2011, but no mass ejections were found.

  16. Increasing mass loss from Greenland's Mittivakkat Gletscher

    DEFF Research Database (Denmark)

    Hasholt, Bent; Mernild, S.H.; Knudsen, N.T.

    2011-01-01

    Warming in the Arctic during the past several decades has caused glaciers to thin and retreat, and recent mass loss from the Greenland Ice Sheet is well documented. Local glaciers peripheral to the ice sheet are also retreating, but few mass-balance observations are available to quantify that ret...... a local phenomenon, but are indicative of glacier changes in the broader region. Mass-balance observations for the MG therefore provide unique documentation of the general retreat of Southeast Greenland's local glaciers under ongoing climate warming....

  17. Annoyance rating of wind turbine noise

    International Nuclear Information System (INIS)

    Iredale, R.A.

    1992-01-01

    This paper proposes a simple criterion for noise limitation of wind turbines: 'The La A50 from a Wind Farm should not exceeding the L A50 of the wind generated background plus 5dB at any place of potential complaint'. This criterion is then examined and developed in the light of experience to date with turbine noise complaint and procedures. (author)

  18. Mass loss of stars on the asymptotic giant branch. Mechanisms, models and measurements

    Science.gov (United States)

    Höfner, Susanne; Olofsson, Hans

    2018-01-01

    As low- and intermediate-mass stars reach the asymptotic giant branch (AGB), they have developed into intriguing and complex objects that are major players in the cosmic gas/dust cycle. At this stage, their appearance and evolution are strongly affected by a range of dynamical processes. Large-scale convective flows bring newly-formed chemical elements to the stellar surface and, together with pulsations, they trigger shock waves in the extended stellar atmosphere. There, massive outflows of gas and dust have their origin, which enrich the interstellar medium and, eventually, lead to a transformation of the cool luminous giants into white dwarfs. Dust grains forming in the upper atmospheric layers play a critical role in the wind acceleration process, by scattering and absorbing stellar photons and transferring their outward-directed momentum to the surrounding gas through collisions. Recent progress in high-angular-resolution instrumentation, from the visual to the radio regime, is leading to valuable new insights into the complex dynamical atmospheres of AGB stars and their wind-forming regions. Observations are revealing asymmetries and inhomogeneities in the photospheric and dust-forming layers which vary on time-scales of months, as well as more long-lived large-scale structures in the circumstellar envelopes. High-angular-resolution observations indicate at what distances from the stars dust condensation occurs, and they give information on the chemical composition and sizes of dust grains in the close vicinity of cool giants. These are essential constraints for building realistic models of wind acceleration and developing a predictive theory of mass loss for AGB stars, which is a crucial ingredient of stellar and galactic chemical evolution models. At present, it is still not fully possible to model all these phenomena from first principles, and to predict the mass-loss rate based on fundamental stellar parameters only. However, much progress has been made

  19. Evolution of a 30 solar mass star: the interplay of nuclear burning and mass loss

    International Nuclear Information System (INIS)

    Falk, H.J.; Mitalas, R.

    1981-01-01

    Evolutionary tracks for a 30 solar mass star with various mass loss rates (MLR) were evolved to core He exhaustion. The 'overluminosity' of mass losing (ML) stars is explained in terms of the well known mass-luminosity (M-L) law. A critical ZAMS MLR above which mass loss leads to evolution to fainter luminosities is derived. Two tracks showed reversals in their direction of evolution across the HR diagram. These have been shown to be a consequence of mass loss dominating over the effects of the shell source. An analytic criterion for this condition has been derived. (Auth.)

  20. ALMA observations of anisotropic dust mass loss in the inner circumstellar environment of the red supergiant VY Canis Majoris

    Science.gov (United States)

    O'Gorman, E.; Vlemmings, W.; Richards, A. M. S.; Baudry, A.; De Beck, E.; Decin, L.; Harper, G. M.; Humphreys, E. M.; Kervella, P.; Khouri, T.; Muller, S.

    2015-01-01

    The processes leading to dust formation and the subsequent role it plays in driving mass loss in cool evolved stars is an area of intense study. Here we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These data enable us to study the dust in its inner circumstellar environment at a spatial resolution of 129 mas at 321 GHz and 59 mas at 658 GHz, thus allowing us to trace dust on spatial scales down to 11 R⋆ (71 AU). Two prominent dust components are detected and resolved. The brightest dust component, C, is located 334 mas (61 R⋆) southeast of the star and has a dust mass of at least 2.5 × 10-4 M⊙. It has a dust emissivity spectral index of β = -0.1 at its peak, implying that it is optically thick at these frequencies with a cool core of Td ≲ 100 K. Interestingly, not a single molecule in the ALMA data has emission close to the peak of this massive dust clump. The other main dust component, VY, is located at the position of the star and contains a total dust mass of 4.0 × 10-5 M⊙. It also contains a weaker dust feature extending over 60 R⋆ to the north with the total component having a typical dust emissivity spectral index of β = 0.7. We find that at least 17% of the dust mass around VY CMa is located in clumps ejected within a more quiescent roughly spherical stellar wind, with a quiescent dust mass loss rate of 5 × 10-6 M⊙yr-1. The anisotropic morphology of the dust indicates a continuous, directed mass loss over a few decades, suggesting that this mass loss cannot be driven by large convection cells alone. Appendices are available in electronic form at http://www.aanda.org

  1. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  2. Long-lasting X-ray emission from type IIb supernova 2011dh and mass-loss history of the yellow supergiant progenitor

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, Keiichi [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Katsuda, Satoru [RIKEN (The Institute of Physical and Chemical Research) Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Bamba, Aya [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258 (Japan); Terada, Yukikatsu [Graduate School of Science and Engineering, Saitama University, Shimo-Okubo 255, Sakura, Saitama 338-8570 (Japan); Fukazawa, Yasushi, E-mail: keiichi.maeda@kusastro.kyoto-u.ac.jp [Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

    2014-04-20

    Type IIb supernova (SN) 2011dh, with conclusive detection of an unprecedented yellow supergiant (YSG) progenitor, provides an excellent opportunity to deepen our understanding on the massive star evolution in the final centuries toward the SN explosion. In this paper, we report on detection and analyses of thermal X-ray emission from SN IIb 2011dh at ∼500 days after the explosion on Chandra archival data, providing a solidly derived mass-loss rate of a YSG progenitor for the first time. We find that the circumstellar media should be dense, more than that expected from a Wolf-Rayet (W-R) star by one order of magnitude. The emission is powered by a reverse shock penetrating into an outer envelope, fully consistent with the YSG progenitor but not with a W-R progenitor. The density distribution at the outermost ejecta is much steeper than that expected from a compact W-R star, and this finding must be taken into account in modeling the early UV/optical emission from SNe IIb. The derived mass-loss rate is ∼3 × 10{sup –6} M {sub ☉} yr{sup –1} for the mass-loss velocity of ∼20 km s{sup –1} in the final ∼1300 yr before the explosion. The derived mass-loss properties are largely consistent with the standard wind mass-loss expected for a giant star. This is not sufficient to be a main driver to expel nearly all the hydrogen envelope. Therefore, the binary interaction, with a huge mass transfer having taken place at ≳ 1300 yr before the explosion, is a likely scenario to produce the YSG progenitor.

  3. Clouds enhance Greenland ice sheet mass loss

    Science.gov (United States)

    Van Tricht, Kristof; Gorodetskaya, Irina V.; L'Ecuyer, Tristan; Lenaerts, Jan T. M.; Lhermitte, Stef; Noel, Brice; Turner, David D.; van den Broeke, Michiel R.; van Lipzig, Nicole P. M.

    2015-04-01

    Clouds have a profound influence on both the Arctic and global climate, while they still represent one of the key uncertainties in climate models, limiting the fidelity of future climate projections. The potentially important role of thin liquid-containing clouds over Greenland in enhancing ice sheet melt has recently gained interest, yet current research is spatially and temporally limited, focusing on particular events, and their large scale impact on the surface mass balance remains unknown. We used a combination of satellite remote sensing (CloudSat - CALIPSO), ground-based observations and climate model (RACMO) data to show that liquid-containing clouds warm the Greenland ice sheet 94% of the time. High surface reflectivity (albedo) for shortwave radiation reduces the cloud shortwave cooling effect on the absorbed fluxes, while not influencing the absorption of longwave radiation. Cloud warming over the ice sheet therefore dominates year-round. Only when albedo values drop below ~0.6 in the coastal areas during summer, the cooling effect starts to overcome the warming effect. The year-round excess of energy due to the presence of liquid-containing clouds has an extensive influence on the mass balance of the ice sheet. Simulations using the SNOWPACK snow model showed not only a strong influence of these liquid-containing clouds on melt increase, but also on the increased sublimation mass loss. Simulations with the Community Earth System Climate Model for the end of the 21st century (2080-2099) show that Greenland clouds contain more liquid water path and less ice water path. This implies that cloud radiative forcing will be further enhanced in the future. Our results therefore urge the need for improving cloud microphysics in climate models, to improve future projections of ice sheet mass balance and global sea level rise.

  4. Wind Turbine Contingency Control Through Generator De-Rating

    Science.gov (United States)

    Frost, Susan; Goebel, Kai; Balas, Mark

    2013-01-01

    Maximizing turbine up-time and reducing maintenance costs are key technology drivers for wind turbine operators. Components within wind turbines are subject to considerable stresses due to unpredictable environmental conditions resulting from rapidly changing local dynamics. In that context, systems health management has the aim to assess the state-of-health of components within a wind turbine, to estimate remaining life, and to aid in autonomous decision-making to minimize damage to the turbine. Advanced contingency control is one way to enable autonomous decision-making by providing the mechanism to enable safe and efficient turbine operation. The work reported herein explores the integration of condition monitoring of wind turbines with contingency control to balance the trade-offs between maintaining system health and energy capture. The contingency control involves de-rating the generator operating point to achieve reduced loads on the wind turbine. Results are demonstrated using a high fidelity simulator of a utility-scale wind turbine.

  5. Effects of mass loss on the evolution of massive stars. I. Main-sequence evolution

    International Nuclear Information System (INIS)

    Dearborn, D.S.P.; Blake, J.B.; Hainebach, K.L.; Schramm, D.N.

    1978-01-01

    The effect of mass loss on the evolution and surface composition of massive stars during main-sequence evolution are examined. While some details of the evolutionary track depend on the formula used for the mass loss, the results appear most sensitive to the total mass removed during the main-sequence lifetime. It was found that low mass-loss rates have very little effect on the evolution of a star; the track is slightly subluminous, but the lifetime is almost unaffected. High rates of mass loss lead to a hot, high-luminosity stellar model with a helium core surrounded by a hydrogen-deficient (Xapprox.0.1) envelope. The main-sequence lifetime is extended by a factor of 2--3. These models may be identified with Wolf-Rayet stars. Between these mass-loss extremes are intermediate models which appear as OBN stars on the main sequence. The mass-loss rates required for significant observable effects range from 8 x 10 -7 to 10 -5 M/sub sun/ yr -1 , depending on the initial stellar mass. It is found that observationally consistent mass-loss rates for stars with M> or =30 M/sub sun/ may be sufficiently high that these stars lose mass on a time scale more rapidly than their main-sequence core evolution time. This result implies that the helium cores resulting from the main-sequence evolution of these massive stars may all be very similar to that of a star of Mapprox.30 M/sub sun/ regardless of the zero-age mass

  6. Mass loss from OH/IR stars - Models for the infrared emission of circumstellar dust shells

    Science.gov (United States)

    Justtanont, K.; Tielens, A. G. G. M.

    1992-01-01

    The IR emission of a sample of 24 OH/IR stars is modeled, and the properties of circumstellar dust and mass-loss rate of the central star are derived. It is shown that for some sources the observations of the far-IR emission is well fitted with a lambda exp -1 law, while some have a steeper index of 1.5. For a few sources, the presence of circumstellar ice grains is inferred from detailed studies of the observed 10-micron feature. Dust mass-loss rates are determined from detailed studies for all the stars in this sample. They range from 6.0 x 10 exp -10 solar mass/yr for an optically visible Mira to 2.2 x 10 exp -6 solar mass/yr for a heavily obscured OH/IR star. These dust mass-loss rates are compared to those calculated from IRAS photometry using 12-, 25-, and 60-micron fluxes. The dust mass-loss rates are also compared to gas mass-loss rates determined from OH and CO observations. For stars with tenuous shells, a dust-to-gas ratio of 0.001 is obtained.

  7. The theory of radiation driven stellar winds and the Wolf-Rayet phenomenon

    International Nuclear Information System (INIS)

    Abbott, D.C.

    1982-01-01

    The author considers the question of whether the mass loss observed from Wolf-Rayet stars can be explained by a version of wind theory which is scaled to the conditions found in the envelopes of Wolf-Rayet stars. He discusses the following topics: - The calculated radiation pressure in OB stars, and its dependence on temperature, density, and chemical composition. - A comparison between predicted and observed mass loss rates and terminal velocities for OB stars. - The applicability of the standard radiation driven wind models to Wolf-Rayet stars. - Speculations on how Wolf-Rayet stars achieve their enormous mass loss rates within the context of the radiation pressure mechanism. (Auth.)

  8. DUST PRODUCTION AND MASS LOSS IN THE GALACTIC GLOBULAR CLUSTER NGC 362

    International Nuclear Information System (INIS)

    Boyer, Martha L.; Gordon, Karl D.; Meixner, Margaret; Sewilo, Marta; Shiao, Bernie; Whitney, Barbara; McDonald, Iain; Van Loon, Jacco Th.; Oliveira, Joana M.; Babler, Brian; Bracker, Steve; Meade, Marilyn; Block, Miwa; Engelbracht, Charles; Misselt, Karl; Hora, Joe; Indebetouw, Remy

    2009-01-01

    We investigate dust production and stellar mass loss in the Galactic globular cluster NGC 362. Due to its close proximity to the Small Magellanic Cloud (SMC), NGC 362 was imaged with the Infrared Array Camera and Multiband Imaging Photometer cameras onboard the Spitzer Space Telescope as part of the Surveying the Agents of Galaxy Evolution (SAGE-SMC) Spitzer Legacy program. We detect several cluster members near the tip of the red giant branch (RGB) that exhibit infrared excesses indicative of circumstellar dust and find that dust is not present in measurable quantities in stars below the tip of the RGB. We modeled the spectral energy distribution (SED) of the stars with the strongest IR excess and find a total cluster dust mass-loss rate of 3.0 +2.0 -1.2 x 10 -9 M sun yr -1 , corresponding to a gas mass-loss rate of 8.6 +5.6 -3.4 x 10 -6 M sun yr -1 , assuming [Fe/H] =-1.16. This mass loss is in addition to any dustless mass loss that is certainly occurring within the cluster. The two most extreme stars, variables V2 and V16, contribute up to 45% of the total cluster dust-traced mass loss. The SEDs of the more moderate stars indicate the presence of silicate dust, as expected for low-mass, low-metallicity stars. Surprisingly, the SED shapes of the stars with the strongest mass-loss rates appear to require the presence of amorphous carbon dust, possibly in combination with silicate dust, despite their oxygen-rich nature. These results corroborate our previous findings in ω Centauri.

  9. Greenland Ice Sheet Mass Loss from GRACE Monthly Models

    DEFF Research Database (Denmark)

    Sørensen, Louise Sandberg; Forsberg, René

    2010-01-01

    The Greenland ice sheet is currently experiencing a net mass loss. There are however large discrepancies between the published qualitative mass loss estimates, based on different data sets and methods. There are even large differences between the results based on the same data sources, as is the ...

  10. Effects of main-sequence mass loss on stellar and galactic chemical evolution

    International Nuclear Information System (INIS)

    Guzik, J.A.

    1988-01-01

    L.A. Willson, G.H. Bowen and C. Struck-Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10 -9 M mass of sun/yr, diminishing over several times 10 8 years. The author attempts to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M 0 , and mass-loss rates decreasing exponentially over 2-3 x 10 8 years. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 M mass of sun and mass loss timescales 0.2 to 2.0 Gry. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M mass of sun and a metallicity-dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus-remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main sequence to the present

  11. Effect of mass loss on the driving of g-modes in B supergiant stars

    Energy Technology Data Exchange (ETDEWEB)

    Godart, Melanie; Noels, Arlette [Institut d' Astrophysique et de Geophysique, Liege (Belgium); Dupret, Marc-Antoine [Observatoire de Paris-Meudon, LESIA (France)], E-mail: Helanie.Godart@ulg.ac.be, E-mail: Arlette.Noels@ulg.ac.be, E-mail: ma.dupret@obspm.fr

    2008-10-15

    MOST has detected p and g-modes in the B supergiant star HD163899. Saio et al. (2006) have explained the driving of g-modes in a post main sequence star by the presence of a convective shell which prevents some modes from entering the damping radiative core. We show that this scenario depends on the evolution of the star, with or without mass loss. If the mass loss rate is high enough, the convective shell disappears and all the g-modes are stable.

  12. Effect of mass loss on the driving of g-modes in B supergiant stars

    International Nuclear Information System (INIS)

    Godart, Melanie; Noels, Arlette; Dupret, Marc-Antoine

    2008-01-01

    MOST has detected p and g-modes in the B supergiant star HD163899. Saio et al. (2006) have explained the driving of g-modes in a post main sequence star by the presence of a convective shell which prevents some modes from entering the damping radiative core. We show that this scenario depends on the evolution of the star, with or without mass loss. If the mass loss rate is high enough, the convective shell disappears and all the g-modes are stable.

  13. HRR Upgrade to mass loss calorimeter and modified Schlyter test for FR Wood

    Science.gov (United States)

    Mark A. Dietenberger; Charles R. Boardman

    2013-01-01

    Enhanced Heat Release Rate (HRR) methodology has been extended to the Mass Loss Calorimeter (MLC) and the Modified Schlyter flame spread test to evaluate fire retardant effectiveness used on wood based materials. Modifications to MLC include installation of thermopile on the chimney walls to correct systematic errors to the sensible HRR calculations to account for...

  14. Thermal radio emission from the winds of single stars

    International Nuclear Information System (INIS)

    Abbott, D.C.

    1985-01-01

    Observations of thermal emission at radio wavelengths provides a powerful diagnostic of the rate of mass loss and temperature of the winds of early-type stars. Some winds are also strong sources of nonthermal emission. Case studies of known thermal and nonthermal sources provide empirical criteria for classifying the observed radio radiation. Mass loss rates are derived for 37 OB and Wolf-Rayet stars considered definite or probable thermal wind sources by these criteria. The rate of mass loss is strongly linked to stellar luminosity in OB stars and probably linked to stellar mass in Wolf-Rayet stars, with no measurable correlation with any other stellar property. A few late-type giants and supergiants also have detectable thermal emission, which arises from extended, accelerating, partially-ionized chromospheres. (orig.)

  15. CONNECTING FLARES AND TRANSIENT MASS-LOSS EVENTS IN MAGNETICALLY ACTIVE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Osten, Rachel A. [Space Telescope Science Institute 3700 San Martin Drive, Baltimore, MD 21218 (United States); Wolk, Scott J., E-mail: osten@stsci.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States)

    2015-08-10

    We explore the ramification of associating the energetics of extreme magnetic reconnection events with transient mass-loss in a stellar analogy with solar eruptive events. We establish energy partitions relative to the total bolometric radiated flare energy for different observed components of stellar flares and show that there is rough agreement for these values with solar flares. We apply an equipartition between the bolometric radiated flare energy and kinetic energy in an accompanying mass ejection, seen in solar eruptive events and expected from reconnection. This allows an integrated flare rate in a particular waveband to be used to estimate the amount of associated transient mass-loss. This approach is supported by a good correspondence between observational flare signatures on high flaring rate stars and the Sun, which suggests a common physical origin. If the frequent and extreme flares that young solar-like stars and low-mass stars experience are accompanied by transient mass-loss in the form of coronal mass ejections, then the cumulative effect of this mass-loss could be large. We find that for young solar-like stars and active M dwarfs, the total mass lost due to transient magnetic eruptions could have significant impacts on disk evolution, and thus planet formation, and also exoplanet habitability.

  16. Three-dimensional hydrodynamical models of wind and outburst-related accretion in symbiotic systems

    Science.gov (United States)

    de Val-Borro, M.; Karovska, M.; Sasselov, D. D.; Stone, J. M.

    2017-07-01

    Gravitationally focused wind accretion in binary systems consisting of an evolved star with a gaseous envelope and a compact accreting companion is a possible mechanism to explain mass transfer in symbiotic binaries. We study the mass accretion around the secondary caused by the strong wind from the primary late-type component using global three-dimensional hydrodynamic numerical simulations during quiescence and outburst stages. In particular, the dependence of the mass accretion rate on the mass-loss rate, wind parameters and phases of wind outburst development is considered. For a typical wind from an asymptotic giant branch star with a mass-loss rate of 10-6 M⊙ yr-1 and wind speeds of 20-50 km s-1, the mass transfer through a focused wind results in efficient infall on to the secondary. Accretion rates on to the secondary of 5-20 per cent of the mass-loss from the primary are obtained during quiescence and outburst periods where the wind velocity and mass-loss rates are varied, about 20-50 per cent larger than in the standard Bondi-Hoyle-Lyttleton approximation. This mechanism could be an important method for explaining observed accretion luminosities and periodic modulations in the accretion rates for a broad range of interacting binary systems.

  17. Core-powered mass-loss and the radius distribution of small exoplanets

    Science.gov (United States)

    Ginzburg, Sivan; Schlichting, Hilke E.; Sari, Re'em

    2018-05-01

    Recent observations identify a valley in the radius distribution of small exoplanets, with planets in the range 1.5-2.0 R⊕ significantly less common than somewhat smaller or larger planets. This valley may suggest a bimodal population of rocky planets that are either engulfed by massive gas envelopes that significantly enlarge their radius, or do not have detectable atmospheres at all. One explanation of such a bimodal distribution is atmospheric erosion by high-energy stellar photons. We investigate an alternative mechanism: the luminosity of the cooling rocky core, which can completely erode light envelopes while preserving heavy ones, produces a deficit of intermediate sized planets. We evolve planetary populations that are derived from observations using a simple analytical prescription, accounting self-consistently for envelope accretion, cooling and mass-loss, and demonstrate that core-powered mass-loss naturally reproduces the observed radius distribution, regardless of the high-energy incident flux. Observations of planets around different stellar types may distinguish between photoevaporation, which is powered by the high-energy tail of the stellar radiation, and core-powered mass-loss, which depends on the bolometric flux through the planet's equilibrium temperature that sets both its cooling and mass-loss rates.

  18. Mass loss by stars at the stage of the asymptotic giant branch

    International Nuclear Information System (INIS)

    Frantsman, Y.L.

    1986-01-01

    For a given initial stellar mass function, star formation function, and initial chemical composition, distributions have been constructed for stars of the asymptotic giant branch by luminosity, and for white dwarfs by mass, by calculating the approximate evolution of a large number of stars. Variants are calculated with different assumptions about the mass loss in the asymptotic branch. Theory can be reconciled with observation only if it is assumed that at this stage there is also a still large mass loss in addition to the stellar wind and the ejection of a planetary nebula shell. This provides the explanation for the absence in the Magellanic clouds of carbon stars with M /sub bol/ 1.0M /sub ./. The degenerate carbon-oxygen nuclei of stars evolving along the asymptotic giant branch cannot attain the Chandrasekhar limit on account of the great mass loss by the stars. The luminosity of stars of the asymptotic giant branch in the globular clusters of the Magellanic Clouds is a good indicator of the age of the clusters

  19. Effects of Main-Sequence Mass Loss on Stellar and Galactic Chemical Evolution.

    Science.gov (United States)

    Guzik, Joyce Ann

    1988-06-01

    L. A. Willson, G. H. Bowen and C. Struck -Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10^{-9}M o/yr, diminishing over several times 10^8 years. We attempted to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M o, and mass-loss rates decreasing exponentially over 2-3 times 10^8 years. Compared to a constant -mass model, these models require a reduced initial ^4He abundance, have deeper envelope convection zones and higher ^8B neutrino fluxes. Early processing of present surface layers at higher interior temperatures increases the surface ^3He abundance, destroys Li, Be and B, and decreases the surface C/N ratio following first dredge-up. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 Mo and mass loss timescales 0.2 to 2.0 Gyr. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M o and a metallicity -dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus -remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main

  20. The Cepheid mass discrepancy and pulsation-driven mass loss

    NARCIS (Netherlands)

    Neilson, H.R.; Cantiello, M.; Langer, N.

    2011-01-01

    Context. A longstanding challenge for understanding classical Cepheids is the Cepheid mass discrepancy, where theoretical mass estimates using stellar evolution and stellar pulsation calculations have been found to differ by approximately 10−20%. Aims. We study the role of pulsation-driven mass loss

  1. Fire spread in chaparral: comparison of data with flame-mass loss relationships

    Science.gov (United States)

    David R. Weise; Thomas H. Fletcher; Shankar Mahalingam; Xiangyang Zhou; Lulu Sun

    2017-01-01

    The relationships between flame length, mass loss rate, and the Froude number have become well-established for many different fuels over the past 60 years. Chaparral, a mixture of shrub plants from the Mediterranean climate zone of southwestern North America, represents a fuel type—living plants—that has seldom been included in the development of these relationships....

  2. Constraining the Stellar Mass Function in the Galactic Center via Mass Loss from Stellar Collisions

    Directory of Open Access Journals (Sweden)

    Douglas Rubin

    2011-01-01

    Full Text Available The dense concentration of stars and high-velocity dispersions in the Galactic center imply that stellar collisions frequently occur. Stellar collisions could therefore result in significant mass loss rates. We calculate the amount of stellar mass lost due to indirect and direct stellar collisions and find its dependence on the present-day mass function of stars. We find that the total mass loss rate in the Galactic center due to stellar collisions is sensitive to the present-day mass function adopted. We use the observed diffuse X-ray luminosity in the Galactic center to preclude any present-day mass functions that result in mass loss rates >10-5M⨀yr−1 in the vicinity of ~1″. For present-day mass functions of the form, dN/dM∝M-α, we constrain the present-day mass function to have a minimum stellar mass ≲7M⨀ and a power-law slope ≳1.25. We also use this result to constrain the initial mass function in the Galactic center by considering different star formation scenarios.

  3. Initial mass function and global rates of mass, momentum, and energy input to the interstellar medium via stellar winds

    International Nuclear Information System (INIS)

    Van Buren, D.

    1985-01-01

    Using the Michigan HD catalog volumes I--III, the all-sky sample of O stars of Garmany, Conti, and Chiosi, Lucke's map of the distribution of obscuring material within 2 kpc, and an amalgam of recent stellar evolution calculations, the number of stars formed kpc -2 yr -1 [log (M/M/sub sun/)] -1 (IMF) is psi = 5.4 x 10 -4 (M/M/sub sun/)/sup -1.03/. A calibration of mass-loss rates with stellar parameters based on published data yields m = 2.0 x 10 -13 (L/L/sub sun/)/sup 1.25/M/sub sun/ yr -1 . Energy injection into the ISM by winds and supernovae balances mechanical energy dissipation via cloud-cloud collisions. For stars M>5 M/sub sun/ there is near balance between the rate at which mass is turned into stars and the rate at which it is lost from them, implying small remnant masses

  4. Massive stars with mass loss: Evolution, nucleosynthesis, and astrophysical implications

    International Nuclear Information System (INIS)

    Prantzos, N.

    1986-06-01

    Evolution and nucleosynthesis of mass loss WR stars is studied, particularly evolution of stars with initial mass between 50 and 100 solar masses, during combustion of H and He. A semi-empirical mass loss formalism, the Roxburgh criterion for convection, and nuclear data are used. Composition of the stellar surface and ejecta (and ejecta contribution to cosmic ray composition) are derived. The contribution of these stars to s elements in our solar system is shown. Their production of 26 Al is compared to the quantity in the galaxy. Gamma ray emission at 1.8 MeV from the decay of this radionuclide is estimated in galactic longitude. The stars evolve as 0 and 0f stars during H combustion and spend 20% of their He combustion period as WN stars and 80% as WC-W0. Evolution always occurs in the blue part of the HR diagram, and satisfies observational constraints on its upper part [fr

  5. Mass loss of the Greenland Ice Sheet since the Little Ice Age, implications on sea level

    DEFF Research Database (Denmark)

    Kjeldsen, K. K.; Bjork, A. A.; Khan, Shfaqat Abbas

    The impact of mass loss from the Greenland Ice Sheet (GrIS) on 20th Century sea level rise (SLR) has long been subject to intense discussions. While globally distributed tide gauges suggest a global mean SLR of 15-20 cm, quantifying the separate components is of great concern - in particular...... for modeling sea level projections into the 21st Century. Estimates of the past GrIS contribution to SLR have been derived using a number of different approaches, e.g. surface mass balance (SMB) calculations combined with estimates of ice discharge found by in correlating SMB anomalies and calving rates. Here......-2010, NASA's Ice, Cloud, and land Elevation Satellite (ICESat) from 2003-2009, and NASA's Land, Vegetation, and Ice Sensor (LVIS) from 2010, to estimate mass loss throughout the 20th and early 21st Century. We present mass balance estimates of the GrIS since retreat commence from the maximum extent...

  6. Spread of ice mass loss into northwest Greenland observed by GRACE and GPS

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Wahr, John; Bevis, Michael

    2010-01-01

    Global Positioning System (GPS) measurements from three long-term sites on bedrock adjacent to the ice sheet. The GRACE results provide a direct measure of mass loss averaged over scales of a few hundred km. The GPS data are used to monitor crustal uplift caused by ice mass loss close to the sites....... The GRACE results can be used to predict crustal uplift, which can be compared with the GPS data. In addition to showing that the northwest ice sheet margin is now losing mass, the uplift results from both the GPS measurements and the GRACE predictions show rapid acceleration in southeast Greenland in late...... 2003, followed by a moderate deceleration in 2006. Because that latter deceleration is weak, southeast Greenland still appears to be losing ice mass at a much higher rate than it was prior to fall 2003. In a more general sense, the analysis described here demonstrates that GPS uplift measurements can...

  7. The Colorado Ultraviolet Transit Experiment (CUTE): Observing Mass Loss on Short-Period Exoplanets

    Science.gov (United States)

    Egan, Arika; Fleming, Brian; France, Kevin

    2018-06-01

    The Colorado Ultraviolet Transit Experiment (CUTE) is an NUV spectrograph packaged into a 6U CubeSat, designed to characterize the interaction between exoplanetary atmospheres and their host stars. CUTE will conduct a transit spectroscopy survey, gathering data over multiple transits on more than 12 short-period exoplanets with a range of masses and radii. The instrument will characterize the spectral properties of the transit light curves to atomic and molecular absorption features predicted to exist in the upper atmospheres of these planets, including Mg I, Mg II, Fe II, and OH. The shape and evolution of these spectral light curves will be used to quantify mass loss rates, the stellar drives of that mass loss, and the possible existence of exoplanetary magnetic fiends. This poster presents the science motivation for CUTE, planned observation and data analysis methods, and expected results.

  8. Effects of main-sequence mass loss on the turnoff ages of globular clusters

    International Nuclear Information System (INIS)

    Guzik, J.A.

    1989-01-01

    Willson, Bowen, and Struck-Marcell have proposed that globular cluster main-sequence turnoff ages can be reconciled with the lower ages of the Galaxy and universe deduced from other methods by incorporating an epoch of early main-sequence mass-loss by stars of spectral types A through early-F. The proposed mass loss is pulsation-driven, and facilitated by rapid rotation. This paper presents stellar evolution calculations of Pop. II (Z = 0.001) mass-losing stars of initial mass 0.8 to 1.6 M circle dot , with exponentially-decreasing mass loss rates of e-folding times 0.5 to 2.0 Gyr, evolving to a final mass of 0.7 M circle dot . The calculations indicate that a globular cluster with apparent turnoff age 18 Gyr could have an actual age as low as ∼12 Gyr. Observational implications that may help to verify the hypothesis, e.g. low C/N abundance ratios among red giants following first dredge-up, blue stragglers, red giant deficiencies, and signatures in cluster mass/luminosity functions, are also discussed.25 refs., 4 figs., 3 tabs

  9. Convection and mass loss through the chromosphere of Betelgeuse

    Science.gov (United States)

    Ridgway, Stephen

    2011-10-01

    Betelgeuse is well suited for detailed study of the mass loss process in a massive red supergiant. We have engaged in a multi-scale, multi-color study to trace the ejected material from the photosphere to the interstellar medium, and understand its chemical evolution {formation of molecules and dust}. Infrared interferometry already gave us a detailed image of the photosphere, compatible with large convective cells. Adaptive optics spectro-imaging {1.0-2.2 microns} allowed us to detect the presence of the CN molecule and mass loss plume structures up to at least 6 R*. At larger distances, we observed silicate-rich dust in thermal IR {8-20 microns}. From the surface to 100 R*, we therefore have a continuous coverage with multicolor imagery. The chromosphere lies at a key location, between the photosphere and the molecular envelope. As shown by STIS spatially resolved spectroscopy {Lobel & Dupree 2001}, it contains rising and falling gases. Such structure is supported by our 3D modeling of the convection. In order to probe the dynamics of the envelope and its relation to photospheric spots and mass loss plumes, we propose to obtain UV imaging with STIS at 3 epochs to complement our coordinated ground-based effort as well as the earlier HST UV snapshots. We will use this imagery to correlate structures at different radii and temperatures, and to explore the time-scales of evolution. With the support of our 3D models, this information will answer specific questions including deciding between convective and polar explanations for bright spots and plumes. Our infrared imaging observations will be repeated contemporaneously with the requested HST/STIS images.

  10. Rate of rotation measurement using back-EMFS associated with windings of a brushless DC motor

    Science.gov (United States)

    Howard, David E. (Inventor)

    2000-01-01

    A system and method are provided for measuring rate of rotation. A brushless DC motor is rotated and produces a back electromagnetic force (emf) on each winding thereof. Each winding's back-emf is integrated and multiplied by the back-emf associated with an adjacent winding. The multiplied outputs associated with each winding are combined to produce a directionally sensitive DC output proportional only to the rate of rotation of the motor's shaft.

  11. Delta progradation in Greenland driven by increasing glacial mass loss

    DEFF Research Database (Denmark)

    Bendixen, Mette; Iversen, Lars Lonsmann; Bjork, Anders Anker

    2017-01-01

    imagery. We find that delta progradation was driven by high freshwater runoff from the Greenland Ice Sheet coinciding with periods of open water. Progradation was controlled by the local initial environmental conditions (that is, accumulated air temperatures above 0 degrees C per year, freshwater runoff...... of erosion and accretion along the large deltas of the main rivers in the Arctic5-7. Our results improve the understanding of Arctic coastal evolution in a changing climate, and reveal the impacts on coastal areas of increasing ice mass loss and the associated freshwater runoff and lengthening of open-water...

  12. The fluctuation theory of the stellar mass loss

    International Nuclear Information System (INIS)

    Andriesse, C.D.

    1981-01-01

    The idea that fluctuations in the mass flow are as significant as the very existence of the flow has led to the development of a fluctuation theory of the stellar mass loss. A general theory for fluctuations in non-equilibrium systems - and such are stellar atmospheres - was developed long ago. In developing the general theory to a specific stellar theory, however, the arguments have not come up in their logical order. The present sketch of this theory improves on that order and is offered as a framework for further study. (Auth.)

  13. Spatial pattern of mass loss processes across the Greenland Ice Sheet from the Little Ice Age to 2010

    DEFF Research Database (Denmark)

    Kjaer, K. H.; Korsgaard, N. J.; Kjeldsen, K. K.

    The Greenland Ice Sheet loses mass through surface meltwater runoff and discharge from marine terminating outlet glaciers. The spatial variability and magnitude of these processes have been studied and described in detail for the past decades. Here, we combine the mass loss between the LIA to 2010...... these components are variable between the different sectors of the GrIS, e.g. in the southeast sector of the GrIS we find substantial mass loss, possibly driven by high precipitation rates but also the presence of a large number of marine terminating glaciers. Furthermore many areas currently undergoing changes...

  14. Sharply increased mass loss from glaciers and ice caps in the Canadian Arctic Archipelago.

    Science.gov (United States)

    Gardner, Alex S; Moholdt, Geir; Wouters, Bert; Wolken, Gabriel J; Burgess, David O; Sharp, Martin J; Cogley, J Graham; Braun, Carsten; Labine, Claude

    2011-05-19

    Mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond. The Canadian Arctic Archipelago, located off the northwestern shore of Greenland, contains one-third of the global volume of land ice outside the ice sheets, but its contribution to sea-level change remains largely unknown. Here we show that the Canadian Arctic Archipelago has recently lost 61 ± 7 gigatonnes per year (Gt yr(-1)) of ice, contributing 0.17 ± 0.02 mm yr(-1) to sea-level rise. Our estimates are of regional mass changes for the ice caps and glaciers of the Canadian Arctic Archipelago referring to the years 2004 to 2009 and are based on three independent approaches: surface mass-budget modelling plus an estimate of ice discharge (SMB+D), repeat satellite laser altimetry (ICESat) and repeat satellite gravimetry (GRACE). All three approaches show consistent and large mass-loss estimates. Between the periods 2004-2006 and 2007-2009, the rate of mass loss sharply increased from 31 ± 8 Gt yr(-1) to 92 ± 12 Gt yr(-1) in direct response to warmer summer temperatures, to which rates of ice loss are highly sensitive (64 ± 14 Gt yr(-1) per 1 K increase). The duration of the study is too short to establish a long-term trend, but for 2007-2009, the increase in the rate of mass loss makes the Canadian Arctic Archipelago the single largest contributor to eustatic sea-level rise outside Greenland and Antarctica.

  15. Development and Validation of a Rating Scale for Wind Jazz Improvisation Performance

    Science.gov (United States)

    Smith, Derek T.

    2009-01-01

    The purpose of this study was to construct and validate a rating scale for collegiate wind jazz improvisation performance. The 14-item Wind Jazz Improvisation Evaluation Scale (WJIES) was constructed and refined through a facet-rational approach to scale development. Five wind jazz students and one professional jazz educator were asked to record…

  16. Controls on mass loss and nitrogen dynamics of oak leaf litter along an urban-rural land-use gradient

    Science.gov (United States)

    Richard V. Pouyat; Margaret M. Carreiro

    2003-01-01

    Using reciprocal leaf litter transplants, we investigated the effects of contrasting environments (urban vs. rural) and intraspecific variations in oak leaf litter quality on mass loss rates and nitrogen (N) dynamics along an urban-rural gradient in the New York City metropolitan area. Differences in earthworm abundances and temperature had previously been documented...

  17. MASS LOSS IN PRE-MAIN-SEQUENCE STARS VIA CORONAL MASS EJECTIONS AND IMPLICATIONS FOR ANGULAR MOMENTUM LOSS

    Energy Technology Data Exchange (ETDEWEB)

    Aarnio, Alicia N. [Astronomy Department, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Matt, Sean P. [Laboratoire AIM Paris-Saclay, CEA/Irfu Universite Paris-Diderot CNRS/INSU, F-91191 Gif-sur-Yvette (France); Stassun, Keivan G., E-mail: aarnio@umich.edu [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States)

    2012-11-20

    We develop an empirical model to estimate mass-loss rates via coronal mass ejections (CMEs) for solar-type pre-main-sequence (PMS) stars. Our method estimates the CME mass-loss rate from the observed energies of PMS X-ray flares, using our empirically determined relationship between solar X-ray flare energy and CME mass: log (M {sub CME}[g]) = 0.63 Multiplication-Sign log (E {sub flare}[erg]) - 2.57. Using masses determined for the largest flaring magnetic structures observed on PMS stars, we suggest that this solar-calibrated relationship may hold over 10 orders of magnitude in flare energy and 7 orders of magnitude in CME mass. The total CME mass-loss rate we calculate for typical solar-type PMS stars is in the range 10{sup -12}-10{sup -9} M {sub Sun} yr{sup -1}. We then use these CME mass-loss rate estimates to infer the attendant angular momentum loss leading up to the main sequence. Assuming that the CME outflow rate for a typical {approx}1 M {sub Sun} T Tauri star is <10{sup -10} M {sub Sun} yr{sup -1}, the resulting spin-down torque is too small during the first {approx}1 Myr to counteract the stellar spin-up due to contraction and accretion. However, if the CME mass-loss rate is {approx}> 10{sup -10} M {sub Sun} yr{sup -1}, as permitted by our calculations, then the CME spin-down torque may influence the stellar spin evolution after an age of a few Myr.

  18. Mass loss and asymmetries in the lines of Iota Coronae Borealis

    International Nuclear Information System (INIS)

    Kapp, A.H.

    1976-01-01

    Recent observations by Smith and Parsons of the Hg--Mn star iota CrB have revealed slight asymmetries in the absorption lines. While these asymmetries are near the limits of detection at the resolution used, their appearance in several lines indicates that they are real. Proposed explanations of this phenomenon are not completely satisfactory. In this Letter it will be shown that the asymmetries are consistent with an accelerating radial flow of material in the photosphere of this star. The velocity needed to reproduce the observed asymmetry corresponds to a mass loss rate of roughly 10 -7 M/sub solar mass/ yr -1

  19. Radio Photosphere and Mass-Loss Envelope of VY Canis Majoris

    Science.gov (United States)

    Lipscy, S. J.; Jura, M.; Reid, M. J.

    2005-06-01

    We have used the VLA to detect emission from the supergiant VY CMa at radio wavelengths and have constructed 3000-4500 K isothermal outer atmospheres constrained by the data. These models produce a radio photosphere at 1.5-2 R*. An extrapolation of the model can account for the observed total mass-loss rate of the star. We also present mid-infrared imaging of the supergiant which suggests that warm dust is extended in the same direction as the near-infrared reflection nebula around VY CMa. The origin of the asymmetries in the outflow remains an unsolved problem.

  20. Evolutionary calculations for planetary nebula nuclei with continuing mass loss and realistic starting conditions

    International Nuclear Information System (INIS)

    Faulkner, D.J.; Wood, P.R.

    1984-01-01

    Evolutionary calculations for nuclei of planetary nebulae are described. They were made using assumptions regarding mass of the NPN, phase in the He shell flash cycle at which the NPN leaves the AGB, and time variation of the mass loss rate. Comparison of the evolutionary tracks with the observational Harman-Seaton sequence indicates that some recently published NPN luminosities may be too low by a factor of three. Comparison of the calculated timescales with the observed properties of NPN and of white dwarfs provides marginal evidence for the PN ejection being initiated by the helium shell flash itself

  1. The Roles of Tidal Evolution and Evaporative Mass Loss in the Origin of CoRoT-7 b

    Science.gov (United States)

    Jackson, Brian; Miller, Neil; Barnes, Rory; Raymond, Sean N.; Fortney, Jonathan J.; Greenberg, Richard

    2010-01-01

    CoRoT-7 b is the first confirmed rocky exoplanet, but, with an orbital semimajor axis of 0.0172 au, its origins may be unlike any rocky planet in our Solar System. In this study, we consider the roles of tidal evolution and evaporative mass loss in CoRoT-7 b's history, which together have modified the planet's mass and orbit. If CoRoT-7 b has always been a rocky body, evaporation may have driven off almost half its original mass, but the mass loss may depend sensitively on the extent of tidal decay of its orbit. As tides caused CoRoT-7 b's orbit to decay, they brought the planet closer to its host star, thereby enhancing the mass loss rate. Such a large mass loss also suggests the possibility that CoRoT-7 b began as a gas giant planet and had its original atmosphere completely evaporated. In this case, we find that CoRoT-7 b's original mass probably did not exceed 200 Earth masses (about two-third of a Jupiter mass). Tides raised on the host star by the planet may have significantly reduced the orbital semimajor axis, perhaps causing the planet to migrate through mean-motion resonances with the other planet in the system, CoRoT-7 c. The coupling between tidal evolution and mass loss may be important not only for CoRoT-7 b but also for other close-in exoplanets, and future studies of mass loss and orbital evolution may provide insight into the origin and fate of close-in planets, both rocky and gaseous.

  2. Pulsation, Mass Loss and the Upper Mass Limit

    Science.gov (United States)

    Klapp, J.; Corona-Galindo, M. G.

    1990-11-01

    RESUMEN. La existencia de estrellas con masas en exceso de 100 M0 ha sido cuestionada por mucho tiempo. Lfmites superiores para la masa de 100 M0 han sido obtenidos de teorfas de pulsaci6n y formaci6n estelar. En este trabajo nosotros primero investigamos la estabilidad radial de estrellas masivas utilizando la aproximaci6n clasica cuasiadiabatica de Ledoux, la aproximaci6n cuasiadiabatica de Castor y un calculo completamente no-adiabatico. Hemos encontrado que los tres metodos de calculo dan resultados similares siempre y cuando una pequefia regi6n de las capas externas de la estrella sea despreciada para la aproximaci6n clasica. La masa crftica para estabilidad de estrellas masivas ha sido encontrada en acuerdo a trabajos anteriores. Explicamos Ia discrepancia entre este y trabajos anteriores por uno de los autores. Discunmos calculos no-lineales y perdida de masa con respecto a) lfmite superior de masa. The existence of stars with masses in excess of 100 M0 has been questioned for a very long time. Upper mass limits of 100 Me have been obtained from pulsation and star formation theories. In this work we first investigate the radial stability of massive stars using the classical Ledoux's quasiadiabatic approximation. the Castor quasiadiabatic approximation and a fully nonadiabatic calculation. We have found that the three methods of calculation give similar results provided that a small region in outer layers of the star be neglected for the classical approximation. The critical mass for stability of massive stars is found to be in agreement with previous work. We explain the reason for the discrepancy between this and previous work by one of the authors. We discuss non-linear calculations and mass loss with regard to the upper mass limit. Key words: STARS-MASS FUNCTION - STARS-MASS LOSS - STARS-PULSATION

  3. Modeling of Camembert-type cheese mass loss in a ripening chamber: main biological and physical phenomena.

    Science.gov (United States)

    Hélias, A; Mirade, P-S; Corrieu, G

    2007-11-01

    A model of the mass loss of Camembert-type cheese was established with data obtained from 2 experimental ripening trials carried out in 2 pilot ripening chambers. During these experiments, a cheese was continuously weighed and the relative humidity, temperature, oxygen, and carbon dioxide concentrations in the ripening chamber were recorded online. The aim was to establish a simple but accurate model that would predict cheese mass changes according to available online measurements. The main hypotheses were that 1) the cheese water activity was constant during ripening, 2) the respiratory activity of the microflora played a major role by inducing heat production, combined with important water evaporation, 3) the temperature gradient existing inside the cheese was negligible, and the limiting phenomenon was the convective transfer. The water activity and the specific heat of the cheeses were assessed by offline measurements. The others parameters in the model were obtained from the literature. This dynamic model was built with 2 state variables: the cheese mass and the surface temperature of the cheese. In this way, only the heat transfer coefficient had to be fitted, and it was strongly determined by the airflow characteristics close to the cheeses. Model efficiency was illustrated by comparing the estimated and measured mass and the mass loss rate for the 2 studied runs; the relative errors were less than 1.9 and 3.2% for the mass loss and the mass loss rate, respectively. The dynamic effects of special events, such as room defrosting or changes in chamber relative humidity, were well described by the model, especially in terms of kinetics (mass loss rates).

  4. Dynamics of Line-Driven Winds from Disks in Cataclysmic Variables. I. Solution Topology and Wind Geometry

    OpenAIRE

    Feldmeier, Achim; Shlosman, Isaac

    1999-01-01

    We analyze the dynamics of 2-D stationary, line-driven winds from accretion disks in cataclysmic variable stars. The driving force is that of line radiation pressure, in the formalism developed by Castor, Abbott & Klein for O stars. Our main assumption is that wind helical streamlines lie on straight cones. We find that the Euler equation for the disk wind has two eigenvalues, the mass loss rate and the flow tilt angle with the disk. Both are calculated self-consistently. The wind is characte...

  5. Continuum emission from classical nova winds

    International Nuclear Information System (INIS)

    Harkness, R.P.

    1983-01-01

    The emergent continuum of a slow classical nova during outburst is considered in the quasi-steady optically thick, transonic wind model. Models are presented for various steady mass loss rates and are related to the evolution of slow novae during decline and early post-maximum. The continuum emission is found to depart radically from a blackbody spectrum and to exhibit features common to highly extended stellar atmospheres. (author)

  6. Asymptotically simple spacetimes and mass loss due to gravitational waves

    Science.gov (United States)

    Saw, Vee-Liem

    The cosmological constant Λ used to be a freedom in Einstein’s theory of general relativity (GR), where one had a proclivity to set it to zero purely for convenience. The signs of Λ or Λ being zero would describe universes with different properties. For instance, the conformal structure of spacetime directly depends on Λ: null infinity ℐ is a spacelike, null, or timelike hypersurface, if Λ > 0, Λ = 0, or Λ 0 in Einstein’s theory of GR. A quantity that depends on the conformal structure of spacetime, especially on the nature of ℐ, is the Bondi mass which in turn dictates the mass loss of an isolated gravitating system due to energy carried away by gravitational waves. This problem of extending the Bondi mass to a universe with Λ > 0 has spawned intense research activity over the past several years. Some aspects include a closer inspection on the conformal properties, working with linearization, attempts using a Hamiltonian formulation based on “linearized” asymptotic symmetries, as well as obtaining the general asymptotic solutions of de Sitter-like spacetimes. We consolidate on the progress thus far from the various approaches that have been undertaken, as well as discuss the current open problems and possible directions in this area.

  7. Global-scale hydrological response to future glacier mass loss

    Science.gov (United States)

    Huss, Matthias; Hock, Regine

    2018-01-01

    Worldwide glacier retreat and associated future runoff changes raise major concerns over the sustainability of global water resources1-4, but global-scale assessments of glacier decline and the resulting hydrological consequences are scarce5,6. Here we compute global glacier runoff changes for 56 large-scale glacierized drainage basins to 2100 and analyse the glacial impact on streamflow. In roughly half of the investigated basins, the modelled annual glacier runoff continues to rise until a maximum (`peak water') is reached, beyond which runoff steadily declines. In the remaining basins, this tipping point has already been passed. Peak water occurs later in basins with larger glaciers and higher ice-cover fractions. Typically, future glacier runoff increases in early summer but decreases in late summer. Although most of the 56 basins have less than 2% ice coverage, by 2100 one-third of them might experience runoff decreases greater than 10% due to glacier mass loss in at least one month of the melt season, with the largest reductions in central Asia and the Andes. We conclude that, even in large-scale basins with minimal ice-cover fraction, the downstream hydrological effects of continued glacier wastage can be substantial, but the magnitudes vary greatly among basins and throughout the melt season.

  8. Mass loss from red giants - A simple evolutionary model for NGC 7027

    Science.gov (United States)

    Jura, M.

    1984-01-01

    NGC 7027 is a young planetary nebula with the remnants of a red giant circumstellar envelope surrounding the central, ionized region. By comparing the outer molecular envelope with the inner ionized material, it is argued that the mass loss rate has decreased by at least a factor of 3, and more probably by about a factor of 10, during the past 1000 years. From this result, it is argued that the luminosity of the central star has also decreased substantially during the same time, consistent with models for the rapid evolution of stars just after they evolve off the asymptotic giant branch. In this picture, the distance to NGC 7027 is less than 1300 pc. NGC 7027 was the last (and best) example of a star where apparently the momentum in the outflowing mass /M(dot)v/ is considerably greater than the momentum in the radiation field (L/c). With the above description of this object, the evidence is now strong that quite often the mass lost from late-type giants is ultimately driven to infinity by radiation pressure on grains. If M(dot)v is as large as L/c for asymptotic branch stars, then it is expected that the total amount of mass lost during this stage of evolution is of the same magnitude as the initial mass of the star, and therefore this mass loss can profoundly affect the star's ultimate fate.

  9. Surface Mass Balance Contributions to Acceleration of Antarctic Ice Mass Loss during 2003- 2013

    Science.gov (United States)

    Seo, K. W.; Wilson, C. R.; Scambos, T. A.; Kim, B. M.; Waliser, D. E.; Tian, B.; Kim, B.; Eom, J.

    2015-12-01

    Recent observations from satellite gravimetry (the GRACE mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6±7.2 GTon/yr2. Of this total, we find that the surface mass balance component is -8.2±2.0 GTon/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8±5.8 GTon/yr2. Correcting for this yields an ice discharge acceleration of -15.1±6.5 GTon/yr2.

  10. The Effect of Wind Velocity on the Cooling Rate of Water

    OpenAIRE

    Shrey Aryan

    2016-01-01

    The effect of wind velocity on the cooling rate of water was investigated by blowing air horizontally over the surface of water contained in a plastic water-bottle cap. The time taken for the temperature to fall to the average of the surrounding and initial temperatures was recorded at different values of wind velocity. It was observed that on increasing the wind velocity, the time taken to achieve average temperature not only decreased but also remained the same after a certain point.

  11. Analysis of the wind data and estimation of the resultant air concentration rates

    International Nuclear Information System (INIS)

    Hu, Shze Jer; Katagiri, Hiroshi; Kobayashi, Hideo

    1988-09-01

    Statistical analyses and comparisons of the meteorological wind data obtained by the propeller and supersonic anemometers for the year of 1987 in the Japan Atomic Energy Research Institute, Tokai, were performed. For wind speeds less than 1 m/s, the propeller readings are generally 0.5 m/s less than those of the supersonic readings. The resultant average air concentration and ground level γ exposure rates due to the radioactive releases for the normal operation of a nuclear plant are over-estimated when calculated using the propeller wind data. As supersonic anemometer can give accurate wind speed to as low as 0.01 m/s, it should be used to measure the low wind speed. The difference in the average air concentrations and γ exposure rates calculated using the two different sets of wind data, is due to the influence of low wind speeds at calm. If the number at calm is large, actual low wind speeds and wind directions should be used in the statistical analysis of atmospheric dispersion to give a more accurate and realistic estimation of the air concentrations and γ exposure rates due to the normal operation of a nuclear plant. (author). 4 refs, 3 figs, 9 tabs

  12. Soil erosion rates caused by wind and saltating sand stresses in a wind tunnel

    International Nuclear Information System (INIS)

    Ligotke, M.W.

    1993-02-01

    Wind erosion tests were performed in a wind tunnel in support of the development of long-term protective barriers to cap stabilized waste sites at the Hanford Site. Controlled wind and saltating sand erosive stresses were applied to physical models of barrier surface layers to simulate worst-case eolian erosive stresses. The goal of these tests was to provide information useful to the design and evaluation of the surface layer composition of an arid-region waste site barrier concept that incorporates a deep fine-soil reservoir. A surface layer composition is needed that will form an armor resistant to eolian erosion during periods of extreme dry climatic conditions, especially when such conditions result in the elimination or reduction of vegetation by water deprivation or wildfire. Because of the life span required of Hanford waste barriers, it is important that additional work follow these wind tunnel studies. A modeling effort is planned to aid the interpretation of test results with respect to the suitability of pea gravel to protect the finite-soil reservoir during long periods of climatic stress. It is additionally recommended that wind tunnel tests be continued and field data be obtained at prototype or actual barrier sites. Results wig contribute to barrier design efforts and provide confidence in the design of long-term waste site caps for and regions

  13. ANISOTROPIC WINDS FROM CLOSE-IN EXTRASOLAR PLANETS

    International Nuclear Information System (INIS)

    Stone, James M.; Proga, Daniel

    2009-01-01

    We present two-dimensional hydrodynamic models of thermally driven winds from highly irradiated, close-in extrasolar planets. We adopt a very simple treatment of the radiative heating processes at the base of the wind, and instead focus on the differences between the properties of outflows in multidimensions in comparison to spherically symmetric models computed with the same methods. For hot (T ∼> 2 x 10 4 K) or highly ionized gas, we find that strong (supersonic) polar flows are formed above the planet surface which produce weak shocks and outflow on the night side. In comparison to a spherically symmetric wind with the same parameters, the sonic surface on the day side is much closer to the planet surface in multidimensions, and the total mass-loss rate is reduced by almost a factor of 4. We also compute the steady-state structure of interacting planetary and stellar winds. Both winds end in a termination shock, with a parabolic contact discontinuity which is draped over the planet separating the two shocked winds. The planetary wind termination shock and the sonic surface in the wind are well separated, so that the mass-loss rate from the planet is essentially unaffected. However, the confinement of the planetary wind to the small volume bounded by the contact discontinuity greatly enhances the column density close to the planet, which might be important for the interpretation of observations of absorption lines formed by gas surrounding transiting planets.

  14. A Mass Loss Penetration Model to Investigate the Dynamic Response of a Projectile Penetrating Concrete considering Mass Abrasion

    Directory of Open Access Journals (Sweden)

    NianSong Zhang

    2015-01-01

    Full Text Available A study on the dynamic response of a projectile penetrating concrete is conducted. The evolutional process of projectile mass loss and the effect of mass loss on penetration resistance are investigated using theoretical methods. A projectile penetration model considering projectile mass loss is established in three stages, namely, cratering phase, mass loss penetration phase, and remainder rigid projectile penetration phase.

  15. Photometry of SN 2002ic and implications for the progenitor mass-loss history

    International Nuclear Information System (INIS)

    Wood-Vasey, W.M.; Wang, L.; Aldering, G.

    2004-01-01

    We present new pre-maximum and late-time optical photometry of the Type Ia/IIn supernova 2002ic. These observations are combined with the published V-band magnitudes of Hamuy et al. (2003) and the VLT spectrophotometry of Wang et al. (2004) to construct the most extensive light curve to date of this unusual supernova. The observed flux at late time is significantly higher relative to the flux at maximum than that of any other observed Type Ia supernova and continues to fade very slowly a year after explosion. Our analysis of the light curve suggests that a non-Type Ia supernova component becomes prominent ∼20 days after explosion. Modeling of the non-Type Ia supernova component as heating from the shock interaction of the supernova ejecta with pre-existing circumstellar material suggests the presence of a ∼1.7 x 1015 cm gap or trough between the progenitor system and the surrounding circumstellar material. This gap could be due to significantly lower mass-loss ∼15 (nu omega /10 km/s) -1 years prior to explosion or evacuation of the circumstellar material by a low-density fast wind. The latter is consistent with observed properties of proto-planetary nebulae and with models of white-dwarf + asymptotic giant branch star progenitor systems with the asymptotic giant branch star in the proto-planetary nebula phase

  16. Acceleration of the GrIS mass loss as observed by GRACE

    DEFF Research Database (Denmark)

    Svendsen, Peter Limkilde; Andersen, Ole Baltazar; Nielsen, Allan Aasbjerg

    2012-01-01

    The mass loss of the Greenland Ice Sheet (GrIS) has previously been analysed in a variety of ways, including altimetry, gravimetry and mass budget calculations, establishing a continuing decrease in the ice mass, with a number of studies finding acceleration in the mass loss. Here, we examine...

  17. Evolution of thermally pulsing asymptotic giant branch stars. IV. Constraining mass loss and lifetimes of low mass, low metallicity AGB stars

    Energy Technology Data Exchange (ETDEWEB)

    Rosenfield, Philip; Dalcanton, Julianne J.; Weisz, Daniel; Williams, Benjamin F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Marigo, Paola [Department of Physics and Astronomy G. Galilei, University of Padova, Vicolo dell' Osservatorio 3, I-35122 Padova (Italy); Girardi, Léo; Gullieuszik, Marco [Osservatorio Astronomico di Padova—INAF, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Bressan, Alessandro [Astrophysics Sector, SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Dolphin, Andrew [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Aringer, Bernhard [Department of Astrophysics, University of Vienna, Turkenschanzstraße 17, A-1180 Wien (Austria)

    2014-07-20

    The evolution and lifetimes of thermally pulsating asymptotic giant branch (TP-AGB) stars suffer from significant uncertainties. In this work, we analyze the numbers and luminosity functions of TP-AGB stars in six quiescent, low metallicity ([Fe/H] ≲ –0.86) galaxies taken from the ACS Nearby Galaxy Survey Treasury sample, using Hubble Space Telescope (HST) photometry in both optical and near-infrared filters. The galaxies contain over 1000 TP-AGB stars (at least 60 per field). We compare the observed TP-AGB luminosity functions and relative numbers of TP-AGB and red giant branch (RGB) stars, N{sub TP-AGB}/N{sub RGB}, to models generated from different suites of TP-AGB evolutionary tracks after adopting star formation histories derived from the HST deep optical observations. We test various mass-loss prescriptions that differ in their treatments of mass loss before the onset of dust-driven winds (pre-dust). These comparisons confirm that pre-dust mass loss is important, since models that neglect pre-dust mass loss fail to explain the observed N{sub TP-AGB}/N{sub RGB} ratio or the luminosity functions. In contrast, models with more efficient pre-dust mass loss produce results consistent with observations. We find that for [Fe/H] ≲ –0.86, lower mass TP-AGB stars (M ≲ 1 M{sub ☉}) must have lifetimes of ∼0.5 Myr and higher masses (M ≲ 3 M{sub ☉}) must have lifetimes ≲ 1.2 Myr. In addition, assuming our best-fitting mass-loss prescription, we show that the third dredge-up has no significant effect on TP-AGB lifetimes in this mass and metallicity range.

  18. [Contribution of soil fauna to the mass loss of Betula albosinensis leaf litter at early decomposition stage of subalpine forest litter in western Sichuan].

    Science.gov (United States)

    Xia, Lei; Wu, Fu-Zhong; Yang, Wan-Qin; Tan, Bo

    2012-02-01

    In order to quantify the contribution of soil fauna to the decomposition of birch (Betula albosinensis) leaf litter in subalpine forests in western Sichuan of Southwest China during freeze-thaw season, a field experiment with different mesh sizes (0.02, 0.125, 1 and 3 mm) of litterbags was conducted in a representative birch-fir (Abies faxoniana) forest to investigate the mass loss rate of the birch leaf litter from 26 October, 2010 to 18 April, 2011, and the contributions of micro-, meso- and macro-fauna to the decomposition of the leaf litter. Over the freeze-thaw season, 11.8%, 13.2%, 15.4% and 19.5% of the mass loss were detected in the litterbags with 0.02, 0. 125, 1 and 3 mm mesh sizes, respectively. The total contribution of soil fauna to the litter decomposition accounted for 39.5% of the mass loss, and the taxa and individual relative density of the soil fauna in the litterbags had the similar variation trend with that of the mass loss rate. The contribution rate of soil fauna to the leaf litter mass loss showed the order of micro- soil fauna played an important role in the litter decomposition in subalpine forests of western Sichuan during freeze-thaw season.

  19. RECONSTRUCTING THE SOLAR WIND FROM ITS EARLY HISTORY TO CURRENT EPOCH

    Energy Technology Data Exchange (ETDEWEB)

    Airapetian, Vladimir S.; Usmanov, Arcadi V., E-mail: vladimir.airapetian@nasa.gov, E-mail: avusmanov@gmail.com [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

    2016-02-01

    Stellar winds from active solar-type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass-loss rates cannot be directly derived from observations. We employed a three-dimensional magnetohydrodynamic Alfvén wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass-loss rate, terminal velocity, and wind temperature at 0.7, 2, and 4.65 Gyr. Our model treats the wind thermal electrons, protons, and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electron temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfvén wave amplitude, and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constrains. Our model results show that the velocity of the paleo solar wind was twice as fast, ∼50 times denser and 2 times hotter at 1 AU in the Sun's early history at 0.7 Gyr. The theoretical calculations of mass-loss rate appear to be in agreement with the empirically derived values for stars of various ages. These results can provide realistic constraints for wind dynamic pressures on magnetospheres of (exo)planets around the young Sun and other active stars, which is crucial in realistic assessment of the Joule heating of their ionospheres and corresponding effects of atmospheric erosion.

  20. RECONSTRUCTING THE SOLAR WIND FROM ITS EARLY HISTORY TO CURRENT EPOCH

    International Nuclear Information System (INIS)

    Airapetian, Vladimir S.; Usmanov, Arcadi V.

    2016-01-01

    Stellar winds from active solar-type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass-loss rates cannot be directly derived from observations. We employed a three-dimensional magnetohydrodynamic Alfvén wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass-loss rate, terminal velocity, and wind temperature at 0.7, 2, and 4.65 Gyr. Our model treats the wind thermal electrons, protons, and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electron temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfvén wave amplitude, and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constrains. Our model results show that the velocity of the paleo solar wind was twice as fast, ∼50 times denser and 2 times hotter at 1 AU in the Sun's early history at 0.7 Gyr. The theoretical calculations of mass-loss rate appear to be in agreement with the empirically derived values for stars of various ages. These results can provide realistic constraints for wind dynamic pressures on magnetospheres of (exo)planets around the young Sun and other active stars, which is crucial in realistic assessment of the Joule heating of their ionospheres and corresponding effects of atmospheric erosion

  1. Predicting Ionization Rates from SEP and Solar Wind Proton Precipitation into the Martian Atmosphere

    Science.gov (United States)

    Jolitz, R.; Dong, C.; Lee, C. O.; Curry, S.; Lillis, R. J.; Brain, D.; Halekas, J. S.; Larson, D. E.; Bougher, S. W.; Jakosky, B. M.

    2017-12-01

    Precipitating energetic particles ionize planetary atmospheres and increase total electron content. At Mars, the solar wind and solar energetic particles (SEPs) can precipitate directly into the atmosphere because solar wind protons can charge exchange to become neutrals and pass through the magnetosheath, while SEPs are sufficiently energetic to cross the magnetosheath unchanged. In this study we will present predicted ionization rates and resulting electron densities produced by solar wind and SEP proton ionization during nominal solar activity and a CME shock front impact event on May 16 2016. We will use the Atmospheric Scattering of Protons and Energetic Neutrals (ASPEN) model to compare ionization by SEP and solar wind protons currently measured by the SWIA (Solar Wind Ion Analyzer) and SEP instruments aboard the MAVEN spacecraft. Results will help to quantify how the ionosphere responds to extreme solar events during solar minimum.

  2. Constraints on continental crustal mass loss via chemical weathering using lithium and its isotopes

    Science.gov (United States)

    Rudnick, R. L.; Liu, X. M.

    2012-04-01

    The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" that is the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems point to the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 1×10^10 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

  3. Compton-heated winds and coronae above accretion disks. II. Instability and oscillations

    International Nuclear Information System (INIS)

    Shields, G.A.; Mckee, C.F.; Lin, D.N.C.; Begelman, M.C.; California Univ., Berkeley; California Univ., Santa Cruz; Colorado Univ., Boulder)

    1986-01-01

    The stability and evolution of windy accretion disks is investigated in detail. The basic disk evolution equations are briefly recapitulated, and an idealized analytic treatment of the wind and viscosity is used to show that steady disk flow is indeed unstable for sufficiently large ratio of the mass loss rate in the wind to the central accretion rate. Numerical solutions for a more realistic and appropriate expression for the mass loss rate and the standard ad hoc alpha model prescription for the viscosity are presented. The application of these results to real systems with Compton-heated winds is discussed, and a general formula for the oscillation period is given. The prediction is compared with observed periodic behavior of Galactic X-ray sources and AGNs. 17 references

  4. The kinetic of mass loss of grades A and B of melted TNT by isothermal and non-isothermal gravimetric methods

    Directory of Open Access Journals (Sweden)

    Hamid Reza Pouretedal

    2018-04-01

    Full Text Available The kinetic and activation energy of mass loss of two grades of melted TNT explosive, grade A and grade B, with freezing points of 80.57 and 78.15 °C, respectively, were studied by isothermal and non-isothermal gravimetric methods. In isothermal method, the mass loss of samples in containers of glass and aluminum was followed in temperatures of 80, 90 and 100 °C. The kinetic of the mass loss of the samples in the aluminum container was higher than the kinetic of it in the glass container that can be related to the effects of heat transfer and catalytic of aluminum metal. Also, the presence of impurities in grade B was due to increasing of kinetic of mass loss of it versus grade A. The non-isothermal curves were obtained in range of 30–330 °C at heating rates of 10, 15 and 20 °C⋅min−1. The TG/DTG data were used for determination of activation energy (Ea of mass loss of TNT samples upon degradation by using Ozawa, Kissinger, Ozawa-Flynn-Wall (OFW and Kissinger-Akahira-Sunose (KAS methods as model free methods. The activation energies of grades of A and B of TNT was obtained 99–120 and 66–70 kJ mol−1, respectively. The lower values of activation energy of the degradation reaction of grade B confirm the effect of impurities in the kinetics of mass loss of this grade. Keywords: TNT, Isothermal, Non-isothermal, Kinetic, Mass loss

  5. The formation of molecules in protostellar winds

    International Nuclear Information System (INIS)

    Glassgold, A.E.; Mamon, G.A.; Huggins, P.J.

    1991-01-01

    The production and destruction processes for molecules in very fast protostellar winds are analyzed and modeled with a one-dimensional chemical kinetics code. Radial density and temperature distributions suggested by protostellar theory are explored as are a range of mass-loss rates. The efficiency of in situ formation of heavy molecules is found to be high if the wind temperature falls sufficiently rapidly, as indicated by theory. The degree of molecular conversion is a strong function of the mass-loss rate and of density gradients associated with the acceleration and collimation of the wind. Even in cases where essentially all of the heavy atoms are processed into molecules, a significant fraction of atomic hydrogen remains so that hghly molecular, protostellar winds are able to emit the 21-cm line. Although CO has a substantial abundance in most models relevant to very young protostars, high abundances of other molecules such as SiO and H2O signify more complete association characteristic of winds containing regions of very high density. Although the models apply only to regions close to the protostar, they are in qualitative accord with recent observations at much larger distances of both atomic and molecular emission from extremely high-velocity flow. 57 refs

  6. The Effect of Wind Velocity on the Cooling Rate of Water

    Directory of Open Access Journals (Sweden)

    Shrey Aryan

    2016-01-01

    Full Text Available The effect of wind velocity on the cooling rate of water was investigated by blowing air horizontally over the surface of water contained in a plastic water-bottle cap. The time taken for the temperature to fall to the average of the surrounding and initial temperatures was recorded at different values of wind velocity. It was observed that on increasing the wind velocity, the time taken to achieve average temperature not only decreased but also remained the same after a certain point.

  7. Large dust grains in the wind of VY Canis Majoris

    OpenAIRE

    Scicluna, P.; Siebenmorgen, R.; Wesson, R.; Blommaert, J. A. D. L; Kasper, M.; Voshchinnikov, N. V.; Wolf, S.

    2015-01-01

    Massive stars live short lives, losing large amounts of mass through their stellar wind. Their mass is a key factor determining how and when they explode as supernovae, enriching the interstellar medium with heavy elements and dust. During the red supergiant phase, mass-loss rates increase prodigiously, but the driving mechanism has proven elusive. Here we present high-contrast optical polarimetric-imaging observations of the extreme red supergiant VY Canis Majoris and its clumpy, dusty, mass...

  8. Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles - I. Theoretical model - Mass-loss history unravelled in VYCMa

    NARCIS (Netherlands)

    Decin, L.; Hony, S.; de Koter, A.; Justtanont, K.; Tielens, A. G. G. M.; Waters, L. B. F. M.

    Context. Mass loss plays a dominant role in the evolution of low mass stars while they are on the Asymptotic Giant Branch (AGB). The gas and dust ejected during this phase are a major source in the mass budget of the interstellar medium. Recent studies have pointed towards the importance of

  9. Evolution of Mass Functions of Coeval Stars through Wind Mass Loss and Binary Interactions

    NARCIS (Netherlands)

    Schneider, F.R.N.; Izzard, R.G.; Langer, N.; de Mink, S.E.

    2015-01-01

    Accurate determinations of stellar mass functions and ages of stellar populations are crucial to much of astrophysics. We analyze the evolution of stellar mass functions of coeval main-sequence stars, including all relevant aspects of single and binary star evolution. We show that the slope of the

  10. Mass Loss and Nutrient Release through Leaching in Tectona ...

    African Journals Online (AJOL)

    Tectona grandis and Theobroma cacao are common plantation tree crops planted to replace natural forest in Nigeria because of their faster growth rate and economic values. The changes in land use have marked effects on the soil nutrients and organic matter stock, thereby affecting physical, chemical properties and soil ...

  11. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013

    OpenAIRE

    Seo, Ki-Weon; Wilson, Clark R.; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E.; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-01-01

    Abstract Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE?derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by ...

  12. Mass loss due to gravitational waves with Λ > 0

    Science.gov (United States)

    Saw, Vee-Liem

    2017-07-01

    The theoretical basis for the energy carried away by gravitational waves that an isolated gravitating system emits was first formulated by Hermann Bondi during the ’60s. Recent findings from the observation of distant supernovae revealed that the rate of expansion of our universe is accelerating, which may be well explained by sticking a positive cosmological constant into the Einstein field equations for general relativity. By solving the Newman-Penrose equations (which are equivalent to the Einstein field equations), we generalize this notion of Bondi mass-energy and thereby provide a firm theoretical description of how an isolated gravitating system loses energy as it radiates gravitational waves, in a universe that expands at an accelerated rate. This is in line with the observational front of LIGO’s first announcement in February 2016 that gravitational waves from the merger of a binary black hole system have been detected.

  13. Mass loss due to gravitational waves with $\\Lambda>0$

    OpenAIRE

    Saw, Vee-Liem

    2017-01-01

    The theoretical basis for the energy carried away by gravitational waves that an isolated gravitating system emits was first formulated by Hermann Bondi during the 1960s. Recent findings from looking at distant supernovae revealed that the rate of expansion of our universe is accelerating, which may be well-explained by sticking in a positive cosmological constant into the Einstein field equations for general relativity. By solving the Newman-Penrose equations (which are equivalent to the Ein...

  14. Evaluation of total energy-rate feedback for glidescope tracking in wind shear

    Science.gov (United States)

    Belcastro, C. M.; Ostroff, A. J.

    1986-01-01

    Low-altitude wind shear is recognized as an infrequent but significant hazard to all aircraft during take-off and landing. A total energy-rate sensor, which is potentially applicable to this problem, has been developed for measuring specific total energy-rate of an airplane with respect to the air mass. This paper presents control system designs, with and without energy-rate feedback, for the approach to landing of a transport airplane through severe wind shear and gusts to evaluate application of this sensor. A system model is developed which incorporates wind shear dynamics equations with the airplance equations of motion, thus allowing the control systems to be analyzed under various wind shears. The control systems are designed using optimal output feedback and are analyzed using frequency domain control theory techniques. Control system performance is evaluated using a complete nonlinear simulation of the airplane and a severe wind shear and gust data package. The analysis and simulation results indicate very similar stability and performance characteristics for the two designs. An implementation technique for distributing the velocity gains between airspeed and ground speed in the simulation is also presented, and this technique is shown to improve the performance characteristics of both designs.

  15. Increased protein intake reduces lean body mass loss during weight loss in athletes.

    Science.gov (United States)

    Mettler, Samuel; Mitchell, Nigel; Tipton, Kevin D

    2010-02-01

    To examine the influence of dietary protein on lean body mass loss and performance during short-term hypoenergetic weight loss in athletes. In a parallel design, 20 young healthy resistance-trained athletes were examined for energy expenditure for 1 wk and fed a mixed diet (15% protein, 100% energy) in the second week followed by a hypoenergetic diet (60% of the habitual energy intake), containing either 15% (approximately 1.0 g x kg(-1)) protein (control group, n = 10; CP) or 35% (approximately 2.3 g x kg(-1)) protein (high-protein group, n = 10; HP) for 2 wk. Subjects continued their habitual training throughout the study. Total, lean body, and fat mass, performance (squat jump, maximal isometric leg extension, one-repetition maximum (1RM) bench press, muscle endurance bench press, and 30-s Wingate test) and fasting blood samples (glucose, nonesterified fatty acids (NEFA), glycerol, urea, cortisol, free testosterone, free Insulin-like growth factor-1 (IGF-1), and growth hormone), and psychologic measures were examined at the end of each of the 4 wk. Total (-3.0 +/- 0.4 and -1.5 +/- 0.3 kg for the CP and HP, respectively, P = 0.036) and lean body mass loss (-1.6 +/- 0.3 and -0.3 +/- 0.3 kg, P = 0.006) were significantly larger in the CP compared with those in the HP. Fat loss, performance, and most blood parameters were not influenced by the diet. Urea was higher in HP, and NEFA and urea showed a group x time interaction. Fatigue ratings and "worse than normal" scores on the Daily Analysis of Life Demands for Athletes were higher in HP. These results indicate that approximately 2.3 g x kg(-1) or approximately 35% protein was significantly superior to approximately 1.0 g x kg(-1) or approximately 15% energy protein for maintenance of lean body mass in young healthy athletes during short-term hypoenergetic weight loss.

  16. 77 FR 57082 - Prairie Rose Wind, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2012-09-17

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-2542-000] Prairie Rose Wind, LLC; Supplemental Notice That Initial Market- Based Rate Filing Includes Request for Blanket... Rose Wind, LLC's application for market-based rate authority, with an accompanying rate schedule...

  17. 76 FR 72697 - Heritage Garden Wind Farm I, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2011-11-25

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-421-000] Heritage Garden Wind Farm I, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... Heritage Garden Wind Farm I, LLC's application for market-based rate authority, with an accompanying rate...

  18. 78 FR 26771 - Mesa Wind Power Corporation; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2013-05-08

    ... Wind Power Corporation's application for market-based rate authority, with an accompanying rate... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER13-1346-000] Mesa Wind Power Corporation; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for...

  19. 77 FR 62510 - Niagara Wind Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2012-10-15

    ... Wind Power, LLC's application for market-based rate authority, with an accompanying rate schedule... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER13-17-000] Niagara Wind Power, LLC; Supplemental Notice That Initial Market- Based Rate Filing Includes Request for Blanket...

  20. 76 FR 41238 - Post Rock Wind Power Project, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2011-07-13

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-3959-000] Post Rock Wind Power Project, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... Rock Wind Power Project, LLC's application for market-based rate authority, with an accompanying rate...

  1. 76 FR 6614 - Elk Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request...

    Science.gov (United States)

    2011-02-07

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-2765-000] Elk Wind Energy, LLC; Supplemental Notice That Initial Market- Based Rate Filing Includes Request for Blanket... proceeding of Elk Wind Energy, LLC's application for market-based rate authority, with an accompanying rate...

  2. 77 FR 21555 - Flat Ridge 2 Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2012-04-10

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-1400-000] Flat Ridge 2 Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... Wind Energy LLC's application for market-based rate authority, with an accompanying rate tariff, noting...

  3. 77 FR 47625 - Laurel Hill Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2012-08-09

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-2313-000] Laurel Hill Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request For... Laurel Hill Wind Energy, LLC's application for market-based rate authority, with an accompanying rate...

  4. 78 FR 62300 - Prairie Breeze Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2013-10-15

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER14-25-000] Prairie Breeze Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... Breeze Wind Energy LLC's application for market-based rate authority, with an accompanying rate schedule...

  5. 77 FR 106 - California Ridge Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2012-01-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-645-000] California Ridge Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... California Ridge Wind Energy LLC's application for market-based rate authority, with an accompanying rate...

  6. 77 FR 41400 - Mehoopany Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2012-07-13

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-2200-000] Mehoopany Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... Wind Energy LLC's application for market-based rate authority, with an accompanying rate tariff, noting...

  7. 75 FR 18202 - Vantage Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2010-04-09

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-956-000] Vantage Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... of Vantage Wind Energy, LLC's application for market-based rate authority, with an accompanying rate...

  8. Prevalence of skeletal muscle mass loss and its association with swallowing function after cardiovascular surgery.

    Science.gov (United States)

    Wakabayashi, Hidetaka; Takahashi, Rimiko; Watanabe, Naoko; Oritsu, Hideyuki; Shimizu, Yoshitaka

    2017-06-01

    The aim of this study was to assess the prevalence of skeletal muscle mass loss and its association with swallowing function in patients with dysphagia after cardiovascular surgery. A retrospective cohort study was performed in 65 consecutive patients with dysphagia after cardiovascular surgery who were prescribed speech therapy. Skeletal muscle index (SMI) was calculated as total psoas muscle area assessed via abdominal computed tomography divided by height squared. Cutoff values were 6.36 cm 2 /m 2 for men and 3.92 cm 2 /m 2 for women. The Food Intake Level Scale (FILS) was used to assess the swallowing function. Univariate and ordered logistic regression analyses were applied to examine the associations between skeletal muscle mass loss and dysphagia. The study included 50 men and 15 women (mean age 73 ± 8 y). The mean SMI was 4.72 ± 1.37 cm 2 /m 2 in men and 3.33 ± 1.42 cm 2 /m 2 in women. Skeletal muscle mass loss was found in 53 (82%) patients. Twelve had tracheostomy cannula. Thirteen were non-oral feeding (FILS levels 1-3), 5 were oral food intake and alternative nutrition (levels 4-6), and 47 were oral food intake alone (levels 7-9) at discharge. The FILS at discharge was significantly lower in patients with skeletal muscle mass loss. Ordered logistic regression analysis of swallowing function showed that skeletal muscle mass loss and tracheostomy cannula were associated independently with the FILS at discharge. The prevalence of skeletal muscle mass loss is very high, and skeletal muscle mass loss is associated with swallowing function. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Plant litter functional diversity effects on litter mass loss depend on the macro-detritivore community.

    Science.gov (United States)

    Patoine, Guillaume; Thakur, Madhav P; Friese, Julia; Nock, Charles; Hönig, Lydia; Haase, Josephine; Scherer-Lorenzen, Michael; Eisenhauer, Nico

    2017-11-01

    A better understanding of the mechanisms driving litter diversity effects on decomposition is needed to predict how biodiversity losses affect this crucial ecosystem process. In a microcosm study, we investigated the effects of litter functional diversity and two major groups of soil macro-detritivores on the mass loss of tree leaf litter mixtures. Furthermore, we tested the effects of litter trait community means and dissimilarity on litter mass loss for seven traits relevant to decomposition. We expected macro-detritivore effects on litter mass loss to be most pronounced in litter mixtures of high functional diversity. We used 24 leaf mixtures differing in functional diversity, which were composed of litter from four species from a pool of 16 common European tree species. Earthworms, isopods, or a combination of both were added to each litter combination for two months. Litter mass loss was significantly higher in the presence of earthworms than in that of isopods, whereas no synergistic effects of macro-detritivore mixtures were found. The effect of functional diversity of the litter material was highest in the presence of both macro-detritivore groups, supporting the notion that litter diversity effects are most pronounced in the presence of different detritivore species. Species-specific litter mass loss was explained by nutrient content, secondary compound concentration, and structural components. Moreover, dissimilarity in N concentrations increased litter mass loss, probably because detritivores having access to nutritionally diverse food sources. Furthermore, strong competition between the two macro-detritivores for soil surface litter resulted in a decrease of survival of both macro-detritivores. These results show that the effects of litter functional diversity on decomposition are contingent upon the macro-detritivore community and composition. We conclude that the temporal dynamics of litter trait diversity effects and their interaction with

  10. Microwave Remote Sensing of Ocean Surface Wind Speed and Rain Rates over Tropical Storms

    Science.gov (United States)

    Swift, C. T.; Dehority, D. C.; Black, P. G.; Chien, J. Z.

    1984-01-01

    The value of using narrowly spaced frequencies within a microwave band to measure wind speeds and rain rates over tropical storms with radiometers is reviewed. The technique focuses on results obtained in the overflights of Hurricane Allen during 5 and 8 of August, 1980.

  11. Hurricane Imaging Radiometer Wind Speed and Rain Rate Retrievals during the 2010 GRIP Flight Experiment

    Science.gov (United States)

    Sahawneh, Saleem; Farrar, Spencer; Johnson, James; Jones, W. Linwood; Roberts, Jason; Biswas, Sayak; Cecil, Daniel

    2014-01-01

    Microwave remote sensing observations of hurricanes, from NOAA and USAF hurricane surveillance aircraft, provide vital data for hurricane research and operations, for forecasting the intensity and track of tropical storms. The current operational standard for hurricane wind speed and rain rate measurements is the Stepped Frequency Microwave Radiometer (SFMR), which is a nadir viewing passive microwave airborne remote sensor. The Hurricane Imaging Radiometer, HIRAD, will extend the nadir viewing SFMR capability to provide wide swath images of wind speed and rain rate, while flying on a high altitude aircraft. HIRAD was first flown in the Genesis and Rapid Intensification Processes, GRIP, NASA hurricane field experiment in 2010. This paper reports on geophysical retrieval results and provides hurricane images from GRIP flights. An overview of the HIRAD instrument and the radiative transfer theory based, wind speed/rain rate retrieval algorithm is included. Results are presented for hurricane wind speed and rain rate for Earl and Karl, with comparison to collocated SFMR retrievals and WP3D Fuselage Radar images for validation purposes.

  12. Can mountain glacier melting explains the GRACE-observed mass loss in the southeast Tibetan Plateau: From a climate perspective?

    Science.gov (United States)

    Song, Chunqiao; Ke, Linghong; Huang, Bo; Richards, Keith S.

    2015-01-01

    The southeast Tibetan Plateau (SETP) includes the majority of monsoonal temperate glaciers in High Mountain Asia (HMA), which is an important source of water for the upper reaches of several large Asian river systems. Climatic change and variability has substantial impacts on cryosphere and hydrological processes in the SETP. The Gravity Recovery and Climate Experiment (GRACE) gravimetry observations between 2003 and 2009 suggest that there was an average mass loss rate of - 5.99 ± 2.78 Gigatonnes (Gt)/yr in this region. Meanwhile, the hydrological data by model calculations from the GLDAS/Noah and CPC are used to estimate terrestrial water storage (TWS) changes with a slight negative trend of about - 0.3 Gt/yr. The recent studies (Kääb et al., 2012; Gardner et al., 2013) reported the thinning rates of mountain glaciers in HMA based on the satellite laser altimetry, and an approximate estimation of the glacier mass budget in the SETP was 4.69 ± 2.03 Gt/yr during 2003-2009. This estimate accounted for a large proportion ( 78.3%) of the difference between the GRACE TWS and model-calculated TWS changes. To better understand the cause of sharp mass loss existing in the SETP, the correlations between key climatic variables (precipitation and temperature) and the GRACE TWS changes are examined at different timescales between 2003 and 2011. The results show that precipitation is the leading factors of abrupt, seasonal and multi-year undulating signals of GRACE TWS anomaly time series, but with weak correlations with the inter-annual trend and annual mass budget of GRACE TWS. In contrast, the annual mean temperature is tightly associated with the annual net mass budget (r = 0.81, p < 0.01), which indirectly suggests that the GRACE-observed mass loss in the SETP may be highly related to glacial processes.

  13. Decreasing cloud cover drives the recent mass loss on the Greenland Ice Sheet.

    Science.gov (United States)

    Hofer, Stefan; Tedstone, Andrew J; Fettweis, Xavier; Bamber, Jonathan L

    2017-06-01

    The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased ice discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation.

  14. Accelerated ice-sheet mass loss in Antarctica from 18-year satellite laser ranging measurements

    Directory of Open Access Journals (Sweden)

    Shuanggen Jin

    2016-02-01

    Full Text Available Accurate estimate of the ice-sheet mass balance in Antarctic is very difficult due to complex ice sheet condition and sparse in situ measurements. In this paper, the low-degree gravity field coefficients of up to degree and order 5 derived from Satellite Laser Ranging (SLR measurements are used to determine the ice mass variations in Antarctica for the period 1993–2011. Results show that the ice mass is losing with -36±13 Gt/y in Antarctica, -42±11 Gt/y in the West Antarctica and 6±10 Gt/y in the East Antarctica from 1993 to 2011. The ice mass variations from the SLR 5×5 have a good agreement with the GRACE 5×5, GRACE 5×5 (1&2 and GRACE (60×60 for the entire continent since 2003, but degree 5 from SLR is not sufficient to quantify ice losses in West and East Antarctica, respectively. The rate of ice loss in Antarctica is -28±17 Gt/y for 1993-2002 and -55±17 Gt/y for 2003-2011, indicating significant accelerated ice mass losses since 2003. Furthermore, the results from SLR are comparable with GRACE measurements.

  15. Deviation from goal pace, body temperature and body mass loss as predictors of road race performance.

    Science.gov (United States)

    Adams, William M; Hosokawa, Yuri; Belval, Luke N; Huggins, Robert A; Stearns, Rebecca L; Casa, Douglas J

    2017-03-01

    The purpose of this study was to examine the relationship between pacing, gastrointestinal temperature (T GI ), and percent body mass loss (%BML) on relative race performance during a warm weather 11.3km road race. Observational study of a sample of active runners competing in the 2014 Falmouth Road Race. Participants ingested a T GI pill and donned a GPS enabled watch with heart rate monitoring capabilities prior to the start of the race. Percent off predicted pace (% OFF ) was calculated for seven segments of the race. Separate linear regression analyses were used to assess the relationship between pace, T ​GI , and %BML on relative race performance. One-way ANOVA was used to analyse post race T GI (≥40°C vs 0.05). There was a trend in a slower pace (p=0.055) and greater % OFF (p=0.056) in runners finishing the race with a T GI >40°C. Overall, finish time was influenced by greater variations in pace during the first two miles of the race. In addition, runners who minimized fluid losses and had lower T GI were associated with meeting self-predicted goals. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  16. Ring current energy injection rate and solar wind-magnetosphere energy coupling

    International Nuclear Information System (INIS)

    Lee, L.C.; Kan, J.R.; Akasofu, S.-I.

    1982-01-01

    The purpose of this paper is to (i) formulate the ring current injection rate Usub(R) in terms of phisub(CT) (cross-tail potential drop) by assuming that the ring current formation is a direct consequence of an enhanced convection, (ii) examine the relationship between the injection rate Usub(R) and the power transferred from the solar wind to the magnetosphere and (iii) demonstrate that an enhanced convection indeed leads to the formation of the ring current. (author)

  17. Offshore wind energy storage concept for cost-of-rated-power savings

    International Nuclear Information System (INIS)

    Qin, Chao; Saunders, Gordon; Loth, Eric

    2017-01-01

    Highlights: •Investigated CAES + HPT system concept for offshore wind energy; •Validated cost model for offshore wind farm including CAPEX and OPEX items; •Quantified cost-of-rated-power savings associated with CAES + HPT concept; •Estimated savings of 21.6% with CAES + HPT for a sample $2.92 billion project. -- Abstract: The size and number of off-shore wind turbines over the next decade is expected to rapidly increase due to the high wind energy potential and the ability of such farms to provide utility-scale energy. In this future, inexpensive and efficient on-site wind energy storage can be critical to address short-time (hourly) mismatches between wind supply and energy demand. This study investigates a compressed air energy storage (CAES) and hydraulic power transmission (HPT) system concept. To assess cost impact, the NREL Cost and Scaling Model was modified to improve accuracy and robustness for offshore wind farms with large turbines. Special attention was paid to the support structure, installation, electrical interface and connections, land leasing, and operations and maintenance cost items as well as specific increased/reduced costs reductions associated with CAES + HPT systems. This cost model was validated and applied to a sample $2.92 billion project Virginia Offshore case It was found that adaption of CAES + HPT can lead to a substantial savings of 21.6% of this 20-year lifetime cost by dramatically reducing capital and operating cost of the generator and power transmission components. However, there are several additional variables that can impact the off-shore energy policy and planning for this new CAES + HPT concept. Furthermore, these cost-savings are only first-order estimates based on linear mass-cost relationships, and thus detailed engineering and economic analysis are recommended.

  18. Numerical analysis of Eucalyptus grandis × E. urophylla heat-treatment: A dynamically detecting method of mass loss during the process

    Science.gov (United States)

    Zhao, Zijian; Ma, Qing; Mu, Jun; Yi, Songlin; He, Zhengbin

    Eucalyptus particles, lamellas and boards were applied to explore a simply-implemented method with neglected heat and mass transfer to inspect the mass loss during the heat-treatment course. The results revealed that the mass loss of a certain period was theoretically the definite integration of loss rate to time in this period, and a monitoring model for mass loss speed was developed with the particles and validated with the lamellas and boards. The loss rate was correlated to the temperature and temperature-evolving speed in the model which was composed of three functions during different temperature-evolving period. The sample mass loss was calculated in the MATLAB for the lamellas and boards and the model was validated and adjusted based on the difference between the computed results and the practically measured loss values. The error ranges of the new models were -16.30% to 18.35% for wood lamellas and -9.86% to 6.80% for wood boards. This method made it possible to acquire the instantaneous loss value through continuously detecting the wood temperature evolution. This idea could provide a reference for the Eucalyptus heat-treatment to detect the treating course and control the final material characteristics.

  19. Energy Cascade Rate in Compressible Fast and Slow Solar Wind Turbulence

    International Nuclear Information System (INIS)

    Hadid, L. Z.; Sahraoui, F.; Galtier, S.

    2017-01-01

    Estimation of the energy cascade rate in the inertial range of solar wind turbulence has been done so far mostly within incompressible magnetohydrodynamics (MHD) theory. Here, we go beyond that approximation to include plasma compressibility using a reduced form of a recently derived exact law for compressible, isothermal MHD turbulence. Using in situ data from the THEMIS / ARTEMIS spacecraft in the fast and slow solar wind, we investigate in detail the role of the compressible fluctuations in modifying the energy cascade rate with respect to the prediction of the incompressible MHD model. In particular, we found that the energy cascade rate (1) is amplified particularly in the slow solar wind; (2) exhibits weaker fluctuations in spatial scales, which leads to a broader inertial range than the previous reported ones; (3) has a power-law scaling with the turbulent Mach number; (4) has a lower level of spatial anisotropy. Other features of solar wind turbulence are discussed along with their comparison with previous studies that used incompressible or heuristic (nonexact) compressible MHD models.

  20. Energy Cascade Rate in Compressible Fast and Slow Solar Wind Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Hadid, L. Z.; Sahraoui, F.; Galtier, S., E-mail: lina.hadid@lpp.polytechnique.fr [LPP, CNRS, Ecole Polytechnique, UPMC Univ Paris 06, Univ. Paris-Sud, Observatoire de Paris, Université Paris-Saclay, Sorbonne Universités, PSL Research University, F-91128 Palaiseau (France)

    2017-03-20

    Estimation of the energy cascade rate in the inertial range of solar wind turbulence has been done so far mostly within incompressible magnetohydrodynamics (MHD) theory. Here, we go beyond that approximation to include plasma compressibility using a reduced form of a recently derived exact law for compressible, isothermal MHD turbulence. Using in situ data from the THEMIS / ARTEMIS spacecraft in the fast and slow solar wind, we investigate in detail the role of the compressible fluctuations in modifying the energy cascade rate with respect to the prediction of the incompressible MHD model. In particular, we found that the energy cascade rate (1) is amplified particularly in the slow solar wind; (2) exhibits weaker fluctuations in spatial scales, which leads to a broader inertial range than the previous reported ones; (3) has a power-law scaling with the turbulent Mach number; (4) has a lower level of spatial anisotropy. Other features of solar wind turbulence are discussed along with their comparison with previous studies that used incompressible or heuristic (nonexact) compressible MHD models.

  1. The effect of wind on the rate of heat loss from avian cup-shaped nests.

    Science.gov (United States)

    Heenan, Caragh B; Seymour, Roger S

    2012-01-01

    Forced convection can significantly influence the heat loss from birds and their offspring but effects may be reduced by using sheltered micro-sites such as cavities or constructing nests. The structural and thermal properties of the nests of two species, the spiny-cheeked honeyeater (Acanthagenys rufogularis) and yellow-throated miner (Manorina flavigula), were measured in relation to three wind speeds. Nest dimensions differ between the two species, despite the similar body mass of the incubating adults, however nest conductance is comparable. As wind speed increases, so does the rate of heat loss from the nests of both species, and further still during incubation recesses. The significance of forced convection through the nest is a near-doubling in heat production required by the parent, even when incubating at relatively low wind speeds. This provides confirmation that selecting a sheltered nest site is important for avian reproductive success.

  2. The effect of wind on the rate of heat loss from avian cup-shaped nests.

    Directory of Open Access Journals (Sweden)

    Caragh B Heenan

    Full Text Available Forced convection can significantly influence the heat loss from birds and their offspring but effects may be reduced by using sheltered micro-sites such as cavities or constructing nests. The structural and thermal properties of the nests of two species, the spiny-cheeked honeyeater (Acanthagenys rufogularis and yellow-throated miner (Manorina flavigula, were measured in relation to three wind speeds. Nest dimensions differ between the two species, despite the similar body mass of the incubating adults, however nest conductance is comparable. As wind speed increases, so does the rate of heat loss from the nests of both species, and further still during incubation recesses. The significance of forced convection through the nest is a near-doubling in heat production required by the parent, even when incubating at relatively low wind speeds. This provides confirmation that selecting a sheltered nest site is important for avian reproductive success.

  3. Comparing avian and bat fatality rate estimates among North American wind energy projects

    Energy Technology Data Exchange (ETDEWEB)

    Smallwood, Shawn

    2011-07-01

    Full text: Wind energy development has expanded rapidly, and so have concerns over bird and bat impacts caused by wind turbines. To assess and compare impacts due to collisions, investigators use a common metric, fatalities/MW/year, but estimates of fatality rates have come from various wind turbine models, tower heights, environments, fatality search methods, and analytical methods. To improve comparability and asses large-scale impacts, I applied a common set of assumptions and methods to data in fatality monitoring reports to estimate fatality rates of birds and bats at 71 wind projects across North America (52 outside the Altamont Pass Wind Resource Area, APWRA). The data were from wind turbines of 27 sizes (range 0.04-3.00 MW) and 28 tower heights (range 18.5-90 m), and searched at 40 periodic intervals (range 1-90 days) and out to 20 distances from turbines (range 30-126 m). Estimates spanned the years 1982 to 2010, and involved 1-1,345 turbines per unique combination of project, turbine size, tower height, and search methodology. I adjusted fatality rates for search detection rates averaged from 425 detection trials, and for scavenger removal rates based on 413 removal trials. I also adjusted fatality rates for turbine tower height and maximum search radius, based on logistic functions fit to cumulative counts of carcasses that were detected at 1-m distance intervals from the turbine. For each tower height, I estimated the distance at which cumulative carcass counts reached an asymptote, and for each project I calculated the proportion of fatalities likely not found due to the maximum search radius being short of the model-predicted distance asymptote. I used the same estimator in all cases. I estimated mean fatalities/MW/year among North American wind projects at 12.6 bats (80% CI: 8.1-17.1) and 11.1 birds (80% CI: 9.5-12.7), including 1.6 raptors (80% CI: 1.3-2.0), and excluding the Altamont Pass I estimated fatality rates at 17.2 bats (80% CI: 9

  4. Operational and Strategic Implementation of Dynamic Line Rating for Optimized Wind Energy Generation Integration

    International Nuclear Information System (INIS)

    Gentle, Jake Paul

    2016-01-01

    One primary goal of rendering today's transmission grid 'smarter' is to optimize and better manage its power transfer capacity in real time. Power transfer capacity is affected by three main elements: stability, voltage limits, and thermal ratings. All three are critical, but thermal ratings represent the greatest opportunity to quickly, reliably and economically utilize the grid's true capacity. With the 'Smarter Grid', new solutions have been sought to give operators a better grasp on real time conditions, allowing them to manage and extend the usefulness of existing transmission infrastructure in a safe and reliable manner. The objective of the INL Wind Program is to provide industry a Dynamic Line Rating (DLR) solution that is state of the art as measured by cost, accuracy and dependability, to enable human operators to make informed decisions and take appropriate actions without human or system overloading and impacting the reliability of the grid. In addition to mitigating transmission line congestion to better integrate wind, DLR also offers the opportunity to improve the grid with optimized utilization of transmission lines to relieve congestion in general. As wind-generated energy has become a bigger part of the nation's energy portfolio, researchers have learned that wind not only turns turbine blades to generate electricity, but can cool transmission lines and increase transfer capabilities significantly, sometimes up to 60 percent. INL's DLR development supports EERE and The Wind Energy Technology Office's goals by informing system planners and grid operators of available transmission capacity, beyond typical Static Line Ratings (SLR). SLRs are based on a fixed set of conservative environmental conditions to establish a limit on the amount of current lines can safely carry without overheating. Using commercially available weather monitors mounted on industry informed custom brackets developed by INL in combination with Computational Fluid Dynamics (CFD

  5. High-Resolution, Long-Slit Spectroscopy of VY Canis Majoris: The Evidence for Localized High Mass Loss Events

    Science.gov (United States)

    Humphreys, Roberta M.; Davidson, Kris; Ruch, Gerald; Wallerstein, George

    2005-01-01

    High spatial and spectral resolution spectroscopy of the OH/IR supergiant VY CMa and its circumstellar ejecta reveals evidence for high mass loss events from localized regions on the star occurring over the past 1000 yr. The reflected absorption lines and the extremely strong K I emission lines show a complex pattern of velocities in the ejecta. We show that the large, dusty northwest arc, expanding at ~50 km s-1 with respect to the embedded star, is kinematically distinct from the surrounding nebulosity and was ejected about 400 yr ago. Other large, more filamentary loops were probably expelled as much as 800-1000 yr ago, whereas knots and small arcs close to the star resulted from more recent events 100-200 yr ago. The more diffuse, uniformly distributed gas and dust is surprisingly stationary, with little or no velocity relative to the star. This is not what we would expect for the circumstellar material from an evolved red supergiant with a long history of mass loss. We therefore suggest that the high mass loss rate for VY CMa is a measure of the mass carried out by these specific ejections accompanied by streams or flows of gas through low-density regions in the dust envelope. VY CMa may thus be our most extreme example of stellar activity, but our results also bring into question the evolutionary state of this famous star. In a separate appendix, we discuss the origin of the very strong K I and other rare emission lines in its spectrum.

  6. Relaxing the Small Particle Approximation for Dust-grain opacities in Carbon-star Wind Models

    OpenAIRE

    Mattsson, Lars; Höfner, Susanne

    2010-01-01

    We have computed wind models with time-dependent dust formation and grain-size dependent opacities, where (1) the problem is simplified by assuming a fixed dust-grain size, and where (2) the radiation pressure efficiency is approximated using grain sizes based on various means of the actual grain size distribution. It is shown that in critical cases, the effect of grain sizes can be significant. For well-developed winds, however, the effects on the mass-loss rate and the wind speed are small.

  7. 75 FR 27339 - Blackstone Wind Farm II, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2010-05-14

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-1184-000] Blackstone Wind Farm II, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... proceeding of Blackstone Wind Farm, LLCs application for market-based rate authority, with an accompanying...

  8. 75 FR 76727 - Evergreen Wind Power III, LLC; Supplemental Notice that Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2010-12-09

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-2201-000] Evergreen Wind Power III, LLC; Supplemental Notice that Initial Market-Based Rate Filing Includes Request for... proceeding of Evergreen Wind Power III, LLC's application for market-based rate authority, with an...

  9. 75 FR 18201 - Juniper Canyon Wind Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2010-04-09

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-975-000] Juniper Canyon Wind Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... of Juniper Canyon Wind Power, LLC's application for market-based rate authority, with an accompanying...

  10. 75 FR 52321 - Dry Lake Wind Power II LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2010-08-25

    ... proceeding, of Dry Lake Wind Power II LLC application for market-based rate authority, with an accompanying... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-1720-000] Dry Lake Wind Power II LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket...

  11. 75 FR 42745 - Hardscrabble Wind Power LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2010-07-22

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-1725-000] Hardscrabble Wind Power LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... of Hardscrabble Wind Power LLC's application for market-based rate authority, with an accompanying...

  12. 75 FR 68352 - Salmon Falls Wind Park, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2010-11-05

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-1893-000] Salmon Falls Wind Park, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket... proceeding of Salmon Falls Wind Park, LLC's application for market-based rate authority, with an accompanying...

  13. 75 FR 42744 - Synergics Roth Rock Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2010-07-22

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-1637-000] Synergics Roth Rock Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request...-referenced proceeding of Synergics Roth Rock Wind Energy, LLC's application for market-based rate authority...

  14. 75 FR 42743 - Synergics Roth Rock North Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate...

    Science.gov (United States)

    2010-07-22

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-1673-000] Synergics Roth Rock North Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...-referenced proceeding of Synergics Roth Rock North Wind Energy, LLC's application for market- based rate...

  15. 75 FR 57016 - Top of the World Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2010-09-17

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-2522-000] Top of the World Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for...-referenced proceeding of Top of the World Wind Energy, LLC's application for market-based rate authority...

  16. 76 FR 69720 - NaturEner Rim Rock Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2011-11-09

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [ Docket No. ER12-295-000] NaturEner Rim Rock Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... NaturEner Rim Rock Wind Energy, LLC's application for market-based rate authority, with an accompanying...

  17. 75 FR 71425 - North Wind Turbines, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2010-11-23

    ... proceeding, of North Wind Turbines, LLC's application for market-based rate authority, with an accompanying... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-2108-000] North Wind Turbines, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket...

  18. 75 FR 74039 - FPL Energy Montezuma Wind, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2010-11-30

    ... proceeding, of FPL Energy Montezuma Wind, LLC's application for market-based rate authority, with an... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-2160-000] FPL Energy Montezuma Wind, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket...

  19. 76 FR 61687 - NextEra Energy Montezuma II Wind, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2011-10-05

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-4677-000] NextEra Energy Montezuma II Wind, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request... of NextEra Energy Montezuma II Wind, LLC's application for market-based rate authority, with an...

  20. Colliding winds: Interaction regions with strong heat conduction

    International Nuclear Information System (INIS)

    Imamura, J.N.; Chevalier, R.A.

    1984-01-01

    The interaction of fast stellar wind with a slower wind from previous mass loss gives rise to a region of hot, shocked gas. We obtain self-similar solutions for the interaction region under the assumptions of constant mass loss rate and wind velocity for the two winds, conversion of energy in the shock region, and either isothermal electrons and adiabatic ions or isothermal electrons ad ions in the shocked region. The isothermal assumption is intended to show the effects of strog heat conduction. The solutions have no heat conduction through the shock waves and assume that the electron and ion temperatures are equilibriated in the shock waves. The one-temperature isothermal solutions have nearly constant density through the shocked region, while the two-temperature solutions are intermediate between the one-temperature adiabatic and isothermal solutions. In the two-temperature solutions, the ion temperature goes to zero at the point where the gas comoves with the shocked region and the density peaks at this point. The solution may qualitatively describe the effects of heat conduction on interaction regions in the solar wind. It will be important to determine whether the assumption of no thermal waves outside the shocked region applies to shock waves in the solar wind

  1. Wind Tunnel Experiments to Study Chaparral Crown Fires.

    Science.gov (United States)

    Cobian-Iñiguez, Jeanette; Aminfar, AmirHessam; Chong, Joey; Burke, Gloria; Zuniga, Albertina; Weise, David R; Princevac, Marko

    2017-11-14

    The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low velocity fire wind tunnel where two distinct layers of fuel were constructed to represent surface and crown fuels in chaparral. Chamise, a common chaparral shrub, comprised the live crown layer. The dead fuel surface layer was constructed with excelsior (shredded wood). We developed a methodology to measure mass loss, temperature, and flame height for both fuel layers. Thermocouples placed in each layer estimated temperature. A video camera captured the visible flame. Post-processing of digital imagery yielded flame characteristics including height and flame tilt. A custom crown mass loss instrument developed in-house measured the evolution of the mass of the crown layer during the burn. Mass loss and temperature trends obtained using the technique matched theory and other empirical studies. In this study, we present detailed experimental procedures and information about the instrumentation used. The representative results for the fuel mass loss rate and temperature filed within the fuel bed are also included and discussed.

  2. Mass loss and chemical structures of wheat and maize straws in response to ultraviolet-B radiation and soil contact

    Science.gov (United States)

    Zhou, Guixiang; Zhang, Jiabao; Mao, Jingdong; Zhang, Congzhi; Chen, Lin; Xin, Xiuli; Zhao, Bingzi

    2015-01-01

    The role of photodegradation, an abiotic process, has been largely overlooked during straw decomposition in mesic ecosystems. We investigated the mass loss and chemical structures of straw decomposition in response to elevated UV-B radiation with or without soil contact over a 12-month litterbag experiment. Wheat and maize straw samples with and without soil contact were exposed to three radiation levels: a no-sunlight control, ambient solar UV-B, and artificially elevated UV-B radiation. A block control with soil contact was not included. Compared with the no-sunlight control, UV-B radiation increased the mass loss by 14–19% and the ambient radiation by 9–16% for wheat and maize straws without soil contact after 12 months. Elevated UV-B exposure decreased the decomposition rates of both wheat and maize straws when in contact with soil. Light exposure resulted in decreased O-alkyl carbons and increased alkyl carbons for both the wheat and maize straws compared with no-sunlight control. The difference in soil contact may influence the contribution of photodegradation to the overall straw decomposition process. These results indicate that we must take into account the effects of photodegradation when explaining the mechanisms of straw decomposition in mesic ecosystems. PMID:26423726

  3. Mass loss and chemical structures of wheat and maize straws in response to ultraviolet-B radiation and soil contact.

    Science.gov (United States)

    Zhou, Guixiang; Zhang, Jiabao; Mao, Jingdong; Zhang, Congzhi; Chen, Lin; Xin, Xiuli; Zhao, Bingzi

    2015-10-01

    The role of photodegradation, an abiotic process, has been largely overlooked during straw decomposition in mesic ecosystems. We investigated the mass loss and chemical structures of straw decomposition in response to elevated UV-B radiation with or without soil contact over a 12-month litterbag experiment. Wheat and maize straw samples with and without soil contact were exposed to three radiation levels: a no-sunlight control, ambient solar UV-B, and artificially elevated UV-B radiation. A block control with soil contact was not included. Compared with the no-sunlight control, UV-B radiation increased the mass loss by 14-19% and the ambient radiation by 9-16% for wheat and maize straws without soil contact after 12 months. Elevated UV-B exposure decreased the decomposition rates of both wheat and maize straws when in contact with soil. Light exposure resulted in decreased O-alkyl carbons and increased alkyl carbons for both the wheat and maize straws compared with no-sunlight control. The difference in soil contact may influence the contribution of photodegradation to the overall straw decomposition process. These results indicate that we must take into account the effects of photodegradation when explaining the mechanisms of straw decomposition in mesic ecosystems.

  4. Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System

    Science.gov (United States)

    Fossati, L.; Koskinen, T.; France, K.; Cubillos, P. E.; Haswell, C. A.; Lanza, A. F.; Pillitteri, I.

    2018-03-01

    WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (extinction (E(B-V) ≈ 0.01 mag) and then the interstellar medium (ISM) column density for a number of ions, concluding that ISM absorption is not the origin of the anomaly. We measure the flux of the four stellar emission features detected in the COS spectrum (C II, C III, C IV, Si IV). Comparing the C II/C IV flux ratio measured for WASP-18 with that derived from spectra of nearby stars with known age, we see that the far-UV spectrum of WASP-18 resembles that of old (>5 Gyr), inactive stars, in stark contrast with its young age. We conclude that WASP-18 has an intrinsically low activity level, possibly caused by star–planet tidal interaction, as suggested by previous studies. Re-scaling the solar irradiance reference spectrum to match the flux of the Si IV line, yields an XUV integrated flux at the planet orbit of 10.2 erg s‑1 cm‑2. We employ the rescaled XUV solar fluxes to models of the planetary upper atmosphere, deriving an extremely low thermal mass-loss rate of 10‑20 M J Gyr‑1. For such high-mass planets, thermal escape is not energy limited, but driven by Jeans escape. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from MAST at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13859. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 092.D-0587.

  5. Wireless AE Event and Environmental Monitoring for Wind Turbine Blades at Low Sampling Rates

    Science.gov (United States)

    Bouzid, Omar M.; Tian, Gui Y.; Cumanan, K.; Neasham, J.

    Integration of acoustic wireless technology in structural health monitoring (SHM) applications introduces new challenges due to requirements of high sampling rates, additional communication bandwidth, memory space, and power resources. In order to circumvent these challenges, this chapter proposes a novel solution through building a wireless SHM technique in conjunction with acoustic emission (AE) with field deployment on the structure of a wind turbine. This solution requires a low sampling rate which is lower than the Nyquist rate. In addition, features extracted from aliased AE signals instead of reconstructing the original signals on-board the wireless nodes are exploited to monitor AE events, such as wind, rain, strong hail, and bird strike in different environmental conditions in conjunction with artificial AE sources. Time feature extraction algorithm, in addition to the principal component analysis (PCA) method, is used to extract and classify the relevant information, which in turn is used to classify or recognise a testing condition that is represented by the response signals. This proposed novel technique yields a significant data reduction during the monitoring process of wind turbine blades.

  6. Equation of Motion of an Interstellar Bussard Ramjet with Radiation and Mass Losses

    Science.gov (United States)

    Semay, Claude; Silvestre-Brac, Bernard

    2008-01-01

    An interstellar Bussard ramjet is a spaceship using the protons of the interstellar medium in a fusion engine to produce thrust. In recent papers, it was shown that the relativistic equation of motion of an ideal ramjet and that of a ramjet with radiation loss are analytical. When a mass loss appears, the limit speed of the ramjet is more strongly…

  7. SYNTHETIC AGB EVOLUTION .3. THE INFLUENCE OF DIFFERENT MASS-LOSS LAWS

    NARCIS (Netherlands)

    GROENEWEGEN, MAT; DEJONG, T

    In Paper I of this series we presented a model to calculate in a synthetic way the evolution of thermal-pulsing AGB stars. The model was applied to the LMC and values were derived for the minimum core mass for third dredge-up and the dredge-up efficiency. In Paper I mass loss on the AGB was

  8. Mid-Pleistocene climate transition drives net mass loss from rapidly uplifting St. Elias mountains, Alaska

    Digital Repository Service at National Institute of Oceanography (India)

    Gulick, S.P.S.; Jaeger, J.M.; Mix, A.C.; Asahi, H.; Bahlburg, H.; Belanger, C.L.; Berbel, G.B.B.; Childress, L.; Cowan, E.; Drab, L.; Forwick, M.; Fukumura, A.; Ge, S.; Gupta, S.M.; Kioka, A.; Konno, S.; LeVay, L.J.; Marz, C.; Matsuzaki, K.M.; McClymont, E.L.; Moy, C.; Muller, J.; Nakamura, A.; Ojima, T.; Ribeiro, F.R.; Ridgway, K.D.; Romero, O.E.; Slagle, A.L.; Stoner, J.S.; St-Onge, G.; Suto, I.; Walczak, M.D.; Worthington, L.L.; Bailey, I.; Enkelmann, E.; Reece, R.; Swartz, J.M.

    the onset of quasi-periodic (~100-ky) glacial cycles in the mid-Pleistocene climate transition (1.2–0.7 Ma). Since then, erosion and transport of material out of the orogen has outpaced tectonic influx by 50–80%. Such a rapid net mass loss explains apparent...

  9. Accelerated mass loss from Greenland ice sheet : Links to atmospheric circulation in the North Atlantic

    NARCIS (Netherlands)

    Seo, Ki-Weon; Waliser, Duane E.; Lee, Choon-Ki; Tian, Baijun; Scambos, Ted; Kim, Baek-Min; van Angelen, Jan H.; van den Broeke, Michiel R.

    Understanding the mechanisms that drive the mass imbalance of the Greenland ice sheet (GrIS) is critical to the accurate projection of its contribution to future sea level rise. Greenland's ice mass loss has been accelerating recently. Using satellite Earth-gravity and regional climate model data,

  10. AGB mass-loss variations: What can we learn from (sub)millimetre observations?

    NARCIS (Netherlands)

    Dehaes, S.; Groenewegen, M.A.T.; Decin, L.; Hony, S.; Raskin, G.; Blommaert, J.A.D.L.

    2008-01-01

    It is generally acknowledged that the mass loss of Asymptotic Giant Branch (AGB) stars undergoes variations on different time scales. We address here the question of the influence of these variations on the spectral energy distribution (SED) of these sources. We therefore constructed models for the

  11. Isotopes of carbon, nitrogen and oxygen as probes of nucleosynthesis, stellar mass losses and galactic evolution

    International Nuclear Information System (INIS)

    Audouze, J.; Lequeux, J.; Vigroux, L.

    1975-01-01

    Evidences for a 12 C/ 13 C ratio different in the interstellar medium and in the solar system (40 instead of 89) and for a large N/O ratio in the centers of galaxies are reviewed and are explained by an enrichment of the interstellar medium in 13 C and N by mass loss of stars of various masses [fr

  12. Mass loss of evolved massive stars: the circumstellar environment at high angular resolution

    International Nuclear Information System (INIS)

    Montarges, Miguel

    2014-01-01

    Mass loss of evolved stars is still largely mysterious, despite its importance as the main evolution engine for the chemical composition of the interstellar medium. For red supergiants (RSG), the triggering of the outflow and the mechanism of dust condensation remain unknown. Concerning red giant stars, we still do not know how their mass loss is able to form a bipolar planetary nebula. During my PhD thesis, I observed evolved stars with high angular resolution techniques. They allowed us to study the surface and the close environment of these stars, from where mass loss originates. With near-infrared interferometric observations, I characterized the water vapor and carbon monoxide envelope of the nearby RSG Betelgeuse. I also monitored a hot spot on its surface and analyzed the structure of its convection, as well as that of Antares (another very nearby supergiant) thanks to radiative hydrodynamical simulations. Diffraction-limited imaging techniques (near-infrared adaptive optics, ultraviolet space telescope) allowed me to observe the evolution of inhomogeneities in the circumstellar envelope of Betelgeuse and to discover a circumstellar disk around L2 Puppis, an asymptotic giant branch star. These multi-scale and multi-wavelength observations obtained at several epochs allowed us to monitor the evolution of the structures and to derive information on the dynamics of the stellar environment. With a wider stellar sample expected in the next few years, this observing program will allow a better understanding of the mass loss of evolved stars. (author)

  13. The Secret Lives of Cepheids: Evolution, Mass-Loss, and Ultraviolet Emission of the Long-period Classical Cepheid

    Science.gov (United States)

    Neilson, Hilding R.; Engle, Scott G.; Guinan, Edward F.; Bisol, Alexandra C.; Butterworth, Neil

    2016-06-01

    The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive (M ≥ 8 M ⊙) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change. The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the rate of period change. We compare our new rate of period change with stellar evolution models to measure the properties of l Car, but find models and observations are, at best, marginally consistent. The results imply that l Car does not have significantly enhanced mass-loss rates like that measured for δ Cephei. We find that the mass of l Car is about 8-10 M ⊙. We present Hubble Space Telescope Cosmic Origins Spectrograph observations that also differ from measurements for δ Cep and β Dor. These measurements further add to the challenge of understanding the physics of Cepheids, but do hint at the possible relation between enhanced mass-loss and ultraviolet emission, perhaps both due to the strength of shocks propagating in the atmospheres of Cepheids. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13019. This work is also based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA), associated with program #060374.

  14. 77 FR 28594 - Bethel Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2012-05-15

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-1739-000] Bethel Wind Energy LLC; Supplemental Notice That Initial Market- Based Rate Filing Includes Request for Blanket Section 204 Authorization This is a supplemental notice in the above-referenced proceeding of Bethel Wind...

  15. 77 FR 28593 - Rippey Wind Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2012-05-15

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER12-1740-000] Rippey Wind Energy LLC; Supplemental Notice That Initial Market- Based Rate Filing Includes Request for Blanket Section 204 Authorization This is a supplemental notice in the above-referenced proceeding of Rippey Wind...

  16. The spatial variable glacier mass loss over the southeast Tibet Plateau and the climate cause analyses

    Science.gov (United States)

    Ke, L.; Ding, X.; Song, C.; Sheng, Y.

    2016-12-01

    Temperate glaciers can be highly sensitive to global climate change due to relatively humid and warm local climate. Numerous temperate glaciers are distributed in the southeastern Tibet Plateau (SETP) and their changes are still poorly represented. Based on a latest glacier inventory and ICESat altimetry measurements, we examine the spatial heterogeneity of glacier change in the SETP (including the central and eastern Nyainqêntanglha ranges) and further analyze its relation with climate change by using station-based and gridded meteorological data. Our results show that SETP glaciers experienced drastic surface lowering at about -0.84±0.26 m a-1 on average over 2003-2008. Debris-covered ice thinned at an average rate of -1.13±0.32 m a-1, in comparison with -0.92±0.17 m a-1 over the debris-free ice areas. The thinning rate is the strongest in the southeastern sub-region (up to -1.24 m a-1 ) and moderate ( -0.45 m a-1 ) in the central and northwestern parts, which is in general agreement with the pattern of surface mass changes based on the GRACE gravimetry observation. Long-term climate data at weather stations show that, in comparison with the period of 1992-2002, mean temperature increased by 0.46 °C - 0.59 °C in the recent decade (2003-2013); while the change of summer precipitation exhibited remarkably spatial variability, following a southeast-northwest contrasting pattern (decreasing by over 10% in the southeast, to stable level in the central region, and increment up to 10% in the northwest). This spatially variable precipitation change is consistent with results from CN05 grid data and ERA re-analysis data, and agrees well with the spatial pattern of glacier surface elevation changes. The results suggest that overall negative glacier mass balances in SETP are governed by temperature rising, while the different precipitation change could contribute to inconsistent glacier thinning rates. The spatial pattern of precipitation decrease and mass loss might

  17. Operational and Strategic Implementation of Dynamic Line Rating for Optimized Wind Energy Generation Integration

    Energy Technology Data Exchange (ETDEWEB)

    Gentle, Jake Paul [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-12-01

    One primary goal of rendering today’s transmission grid “smarter” is to optimize and better manage its power transfer capacity in real time. Power transfer capacity is affected by three main elements: stability, voltage limits, and thermal ratings. All three are critical, but thermal ratings represent the greatest opportunity to quickly, reliably and economically utilize the grid’s true capacity. With the “Smarter Grid”, new solutions have been sought to give operators a better grasp on real time conditions, allowing them to manage and extend the usefulness of existing transmission infrastructure in a safe and reliable manner. The objective of the INL Wind Program is to provide industry a Dynamic Line Rating (DLR) solution that is state of the art as measured by cost, accuracy and dependability, to enable human operators to make informed decisions and take appropriate actions without human or system overloading and impacting the reliability of the grid. In addition to mitigating transmission line congestion to better integrate wind, DLR also offers the opportunity to improve the grid with optimized utilization of transmission lines to relieve congestion in general. As wind-generated energy has become a bigger part of the nation’s energy portfolio, researchers have learned that wind not only turns turbine blades to generate electricity, but can cool transmission lines and increase transfer capabilities significantly, sometimes up to 60 percent. INL’s DLR development supports EERE and The Wind Energy Technology Office’s goals by informing system planners and grid operators of available transmission capacity, beyond typical Static Line Ratings (SLR). SLRs are based on a fixed set of conservative environmental conditions to establish a limit on the amount of current lines can safely carry without overheating. Using commercially available weather monitors mounted on industry informed custom brackets developed by INL in combination with Computational

  18. Type IIP supernova light curves affected by the acceleration of red supergiant winds

    Science.gov (United States)

    Moriya, Takashi J.; Förster, Francisco; Yoon, Sung-Chul; Gräfener, Götz; Blinnikov, Sergei I.

    2018-05-01

    We introduce the first synthetic light-curve model set of Type IIP supernovae exploded within circumstellar media in which the acceleration of the red supergiant winds is taken into account. Because wind acceleration makes the wind velocities near the progenitors low, the density of the immediate vicinity of the red supergiant supernova progenitors can be higher than that extrapolated by using a constant terminal wind velocity. Therefore, even if the mass-loss rate of the progenitor is relatively low, it can have a dense circumstellar medium at the immediate stellar vicinity and the early light curves of Type IIP supernovae are significantly affected by it. We adopt a simple β velocity law to formulate the wind acceleration. We provide bolometric and multicolour light curves of Type IIP supernovae exploding within such accelerated winds from the combinations of three progenitors, 12-16 M⊙; five β, 1-5; seven mass-loss rates, 10-5-10-2 M⊙ yr-1; and four explosion energies, (0.5-2) × 1051 erg. All the light-curve models are available at https://goo.gl/o5phYb. When the circumstellar density is sufficiently high, our models do not show a classical shock breakout as a consequence of the interaction with the dense and optically thick circumstellar media. Instead, they show a delayed `wind breakout', substantially affecting early light curves of Type IIP supernovae. We find that the mass-loss rates of the progenitors need to be 10-3-10-2 M⊙ yr-1 to explain typical rise times of 5-10 d in Type IIP supernovae assuming a dense circumstellar radius of 1015 cm.

  19. Numerical Simulations of Wind Accretion in Symbiotic Binaries

    Science.gov (United States)

    de Val-Borro, M.; Karovska, M.; Sasselov, D.

    2009-08-01

    About half of the binary systems are close enough to each other for mass to be exchanged between them at some point in their evolution, yet the accretion mechanism in wind accreting binaries is not well understood. We study the dynamical effects of gravitational focusing by a binary companion on winds from late-type stars. In particular, we investigate the mass transfer and formation of accretion disks around the secondary in detached systems consisting of an asymptotic giant branch (AGB) mass-losing star and an accreting companion. The presence of mass outflows is studied as a function of mass-loss rate, wind temperature, and binary orbital parameters. A two-dimensional hydrodynamical model is used to study the stability of mass transfer in wind accreting symbiotic binary systems. In our simulations we use an adiabatic equation of state and a modified version of the isothermal approximation, where the temperature depends on the distance from the mass losing star and its companion. The code uses a block-structured adaptive mesh refinement method that allows us to have high resolution at the position of the secondary and resolve the formation of bow shocks and accretion disks. We explore the accretion flow between the components and formation of accretion disks for a range of orbital separations and wind parameters. Our results show the formation of stream flow between the stars and accretion disks of various sizes for certain orbital configurations. For a typical slow and massive wind from an AGB star the flow pattern is similar to a Roche lobe overflow with accretion rates of 10% of the mass loss from the primary. Stable disks with exponentially decreasing density profiles and masses of the order 10-4 solar masses are formed when wind acceleration occurs at several stellar radii. The disks are geometrically thin with eccentric streamlines and close to Keplerian velocity profiles. The formation of tidal streams and accretion disks is found to be weakly dependent on

  20. NUMERICAL SIMULATIONS OF WIND ACCRETION IN SYMBIOTIC BINARIES

    International Nuclear Information System (INIS)

    De Val-Borro, M.; Karovska, M.; Sasselov, D.

    2009-01-01

    About half of the binary systems are close enough to each other for mass to be exchanged between them at some point in their evolution, yet the accretion mechanism in wind accreting binaries is not well understood. We study the dynamical effects of gravitational focusing by a binary companion on winds from late-type stars. In particular, we investigate the mass transfer and formation of accretion disks around the secondary in detached systems consisting of an asymptotic giant branch (AGB) mass-losing star and an accreting companion. The presence of mass outflows is studied as a function of mass-loss rate, wind temperature, and binary orbital parameters. A two-dimensional hydrodynamical model is used to study the stability of mass transfer in wind accreting symbiotic binary systems. In our simulations we use an adiabatic equation of state and a modified version of the isothermal approximation, where the temperature depends on the distance from the mass losing star and its companion. The code uses a block-structured adaptive mesh refinement method that allows us to have high resolution at the position of the secondary and resolve the formation of bow shocks and accretion disks. We explore the accretion flow between the components and formation of accretion disks for a range of orbital separations and wind parameters. Our results show the formation of stream flow between the stars and accretion disks of various sizes for certain orbital configurations. For a typical slow and massive wind from an AGB star the flow pattern is similar to a Roche lobe overflow with accretion rates of 10% of the mass loss from the primary. Stable disks with exponentially decreasing density profiles and masses of the order 10 -4 solar masses are formed when wind acceleration occurs at several stellar radii. The disks are geometrically thin with eccentric streamlines and close to Keplerian velocity profiles. The formation of tidal streams and accretion disks is found to be weakly dependent

  1. Computational Modelling of the Structural Integrity following Mass-Loss in Polymeric Charred Cellular Solids

    OpenAIRE

    J. P. M. Whitty; J. Francis; J. Howe; B. Henderson

    2014-01-01

    A novel computational technique is presented for embedding mass-loss due to burning into the ANSYS finite element modelling code. The approaches employ a range of computational modelling methods in order to provide more complete theoretical treatment of thermoelasticity absent from the literature for over six decades. Techniques are employed to evaluate structural integrity (namely, elastic moduli, Poisson’s ratios, and compressive brittle strength) of honeycomb systems known to approximate t...

  2. Model atmospheres with periodic shocks. [pulsations and mass loss in variable stars

    Science.gov (United States)

    Bowen, G. H.

    1989-01-01

    The pulsation of a long-period variable star generates shock waves which dramatically affect the structure of the star's atmosphere and produce conditions that lead to rapid mass loss. Numerical modeling of atmospheres with periodic shocks is being pursued to study the processes involved and the evolutionary consequences for the stars. It is characteristic of these complex dynamical systems that most effects result from the interaction of various time-dependent processes.

  3. Investigation of Electron Beam Induced Mass Loss of Embedding Media in the Low Voltage STEM

    Czech Academy of Sciences Publication Activity Database

    Novotná, V.; Hrubanová, Kamila; Nebesářová, J.; Krzyžánek, Vladislav

    2014-01-01

    Roč. 20, S3 (2014), s. 1270-1271 ISSN 1431-9276 R&D Projects: GA MŠk EE.2.3.20.0103; GA MŠk(CZ) LO1212; GA ČR(CZ) GA14-20012S; GA TA ČR TE01020118 Institutional support: RVO:68081731 Keywords : mass loss * mass -thickness measurement * low voltage STEM Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.877, year: 2014

  4. Antarctic Mass Loss from GRACE from Space- and Time-Resolved Modeling with Slepian Functions

    Science.gov (United States)

    Simons, F. J.; Harig, C.

    2013-12-01

    The melting of polar ice sheets is a major contributor to global sea-level rise. Antarctica is of particular interest since most of the mass loss has occurred in West Antarctica, however updated glacial isostatic adjustment (GIA) models and recent mass gains in East Antarctica have reduced the continent-wide integrated decadal trend of mass loss. Here we present a spatially and temporally resolved estimation of the Antarctic ice mass change using Slepian localization functions. With a Slepian basis specifically for Antarctica, the basis functions maximize their energy on the continent and we can project the geopotential fields into a sparse set of orthogonal coefficients. By fitting polynomial functions to the limited basis coefficients we maximize signal-to-noise levels and need not perform smoothing or destriping filters common to other approaches. In addition we determine an empirical noise covariance matrix from the GRACE data to estimate the uncertainty of mass estimation. When applied to large ice sheets, as in our own recent Greenland work, this technique is able to resolve both the overall continental integrated mass trend, as well as the spatial distribution of the mass changes over time. Using CSR-RL05 GRACE data between Jan. 2003 and Jan 2013, we estimate the regional accelerations in mass change for several sub-regions and examine how the spatial pattern of mass has changed. The Amundsen Sea coast of West Antarctica has experienced a large acceleration in mass loss (-26 Gt/yr^2). While mass loss is concentrated near Pine Island and Thwaites glaciers, it has also increased along the coast further towards the Ross ice shelf.

  5. Ultraviolet spectroscopy of the blue supergiant SBW1: the remarkably weak wind of a SN 1987A analogue

    Science.gov (United States)

    Smith, Nathan; Groh, Jose H.; France, Kevin; McCray, Richard

    2017-06-01

    The Galactic blue supergiant SBW1 with its circumstellar ring nebula represents the best known analogue of the progenitor of SN 1987A. High-resolution imaging has shown Hα and infrared structures arising in an ionized flow that partly fills the ring's interior. To constrain the influence of the stellar wind on this structure, we obtained an ultraviolet (UV) spectrum of the central star of SBW1 with the Hubble Space Telescope Cosmic Origins Spectrograph. The UV spectrum shows none of the typical wind signatures, indicating a very low mass-loss rate. Radiative transfer models suggest an extremely low rate below 10-10 M⊙ yr-1, although we find that cooling time-scales probably become comparable to (or longer than) the flow time below 10-8 M⊙ yr-1. We therefore adopt this latter value as a conservative upper limit. For the central star, the model yields Teff = 21 000 ± 1000 K, log(geff) = 3.0, L ≃ 5 × 104 L⊙, and roughly Solar composition except for enhanced N abundance. SBW1's very low mass-loss rate may hinder the wind's ability to shape its nebula and to shed angular momentum. The spin-down time-scale for magnetic breaking is more than 500 times longer than the age of the ring. This, combined with the star's slow rotation rate, constrains merger scenarios to form ring nebulae. The mass-loss rate is at least 10 times lower than expected from mass-loss recipes, without any account of clumping. The physical explanation for why SBW1's wind is so weak presents an interesting mystery.

  6. THE EFFECT OF MASS LOSS ON THE TIDAL EVOLUTION OF EXTRASOLAR PLANET

    International Nuclear Information System (INIS)

    Guo, J. H.

    2010-01-01

    By combining mass loss and tidal evolution of close-in planets, we present a qualitative study on their tidal migrations. We incorporate mass loss in tidal evolution for planets with different masses and find that mass loss could interfere with tidal evolution. In an upper limit case (β = 3), a significant portion of mass may be evaporated in a long evolution timescale. Evidence of greater modification of the planets with an initial separation of about 0.1 AU than those with a = 0.15 AU can be found in this model. With the assumption of a large initial eccentricity, the planets with initial mass ≤1 M J and initial distance of about 0.1 AU could not survive. With the supposition of β = 1.1, we find that the loss process has an effect on the planets with low mass at a ∼ 0.05 AU. In both cases, the effect of evaporation on massive planets can be neglected. Also, heating efficiency and initial eccentricity have significant influence on tidal evolution. We find that even low heating efficiency and initial eccentricity have a significant effect on tidal evolution. Our analysis shows that evaporation on planets with different initial masses can accelerate (decelerate) the tidal evolution due to the increase (decrease) in tide of the planet (star). Consequently, the effect of evaporation cannot be neglected in evolutionary calculations of close-in planets. The physical parameters of HD 209458b can be fitted by our model.

  7. Explaining individual variation in patterns of mass loss in breeding birds

    Directory of Open Access Journals (Sweden)

    Cuthill Innes C

    2006-05-01

    Full Text Available Abstract Background Studies of birds have a disproportionate representation in the literature on life-history evolution, because of the (apparent ease with which the costs and benefits can be quantified and manipulated. During reproduction, birds frequently show a highly conserved pattern of mass change and changes in mass loss during breeding have been widely considered to be a valid short-term measure of the costs of reproduction. Experimental manipulations of the breeding attempts of birds usually argue that the presence of a response shows that a cost of reproduction exists, but there is little consensus as to how the size of these costs can be measured. Results We model this mass loss by considering how a parent can maximise its lifetime reproductive success, using a theoretical framework that is particularly suited to modelling parental care in altricial birds. If lifetime reproductive success is taken to be the sum of a parent's current and future reproductive success, we show that the exact forms of these components will influence the optimal amount of mass a parent should lose. In particular, we demonstrate that the shape of the relationship between parental investment and chick survival will lead to differing degrees of investment between parents of different initial qualities: parents with initially high levels of energy reserves could conceivably invested a lesser, similar or greater amount of resources than parents with initially low reserves, and these initially 'heavy' parents could potentially end up being lighter than the initially 'lighter' individuals. Conclusion We argue that it is difficult to make predictions about the dependence of a parent's final mass on its initial mass, and therefore mass loss should only be used as a short-term measure of the costs of reproduction with caution. The model demonstrates that we require a better understanding of the relationship between mass loss and both current and future reproductive

  8. Wind accretion and formation of disk structures in symbiotic binary systems

    Science.gov (United States)

    de Val-Borro, M.; Karovska, M.; Sasselov, D. D.; Stone, J. M.

    2015-05-01

    We investigate gravitationally focused wind accretion in binary systems consisting of an evolved star with a gaseous envelope and a compact accreting companion. We study the mass accretion and formation of an accretion disk around the secondary caused by the strong wind from the primary late-type component using global 2D and 3D hydrodynamic numerical simulations. In particular, the dependence of the mass accretion rate on the mass loss rate, wind temperature and orbital parameters of the system is considered. For a typical slow and massive wind from an evolved star the mass transfer through a focused wind results in rapid infall onto the secondary. A stream flow is created between the stars with accretion rates of a 2--10% percent of the mass loss from the primary. This mechanism could be an important method for explaining periodic modulations in the accretion rates for a broad range of interacting binary systems and fueling of a large population of X-ray binary systems. We test the plausibility of these accretion flows indicated by the simulations by comparing with observations of the symbiotic variable system CH Cyg.

  9. A Study of Hypergiant Mass Loss in the Near-To-Mid Infrared: VY CMa, IRC +10420, mu Cep and rho Cas

    Science.gov (United States)

    Shenoy, Dinesh Prabhakar

    2016-01-01

    Stars of initial mass greater than 9 M_sun become red supergiants (RSGs), a short-lived stage during which they experience mass-loss that strongly influences their post-RSG evolution and end state. The highest luminosity RSGs, referred to here as hypergiants, experience episodic mass-loss whose mechanism remains poorly understood and motivates observations to help constrain it. This thesis studies mass loss from hypergiant stars with near-to-mid infrared imaging over a range of angular scales. The recent mass-loss history of the extreme red supergiant VY Canis Majoris and the warm hypergiant star IRC +10420 are studied at the sub-arcsecond scale with adaptive optics imaging and imaging polarimetry from 1 - 5 micron using LMIRCam on the Large Binocular Telescope (LBT) and MMT-Pol at the MMT Observatory. The nebular features of VY CMa are found to be highly polarized at 1.3 and 3.1 micron, with optically thick scattering required to reproduce the observed surface brightness. The flux of VY CMa's peculiar ``Southwest Clump'' is demonstrated to be due almost entirely to optically thick scattering, with little thermal emission, and with a lower limit mass of 5E-03 M_sun in this single feature. The imaging polarimetry of IRC +10420 at 2.2 micron resolves nebular emission with intrinsic polarization of 30%, with a high surface brightness indicating optically thick scattering largely in the plane of the sky. Using the polarimetry to constrain the scattered light emission, it is shown that the nebula's the emission is mostly thermal with a color temperature well above that for typical astrophysical dust. To probe further into hypergiants' history of mass-loss, mid-IR imaging with MMT/ MIRAC and SOFIA/FORCAST is used to study VY CMa, IRC +10420 and two additional hypergiants: the RSG mu Cep and the warm hypergiant rho Cas. Using DUSTY 1-D radiative transfer models, mu Cep's mass-loss rate is found to have declined by about a factor of 5 over a 13,000 history, ranging from 5E

  10. Collecting the Missing Piece of the Puzzle: The Wind Temperatures of Arcturus (K2 III) and Aldeberan (K5 III)

    Science.gov (United States)

    Harper, Graham

    2017-08-01

    Unravelling the poorly understood processes that drive mass loss from red giant stars requires that we empirically constrain the intimately coupled momentum and energy balance. Hubble high spectral resolution observations of wind scattered line profiles, from neutral and singly ionized species, have provided measures of wind acceleration, turbulence, terminal speeds, and mass-loss rates. These wind properties inform us about the force-momentum balance, however, the spectra have not yielded measures of the much needed wind temperatures, which constrain the energy balance.We proposed to remedy this omission with STIS E140H observations of the Si III 1206 Ang. resonance emission line for two of the best studied red giants: Arcturus (alpha Boo: K2 III) and Aldebaran (alpha Tau: K5 III), both of which have detailed semi-empirical wind velocity models. The relative optical depths of wind scattered absorption in Si III 1206 Ang., O I 1303 Ang. triplet., C II 1335 Ang., and existing Mg II h & k and Fe II profiles give the wind temperatures through the thermally controlled ionization balance. The new temperature constraints will be used to test existing semi-empirical models by comparision with multi-frequency JVLA radio fluxes, and also to constrain the flux-tube geometry and wave energy spectrum of magnetic wave-driven winds.

  11. Metallic Winds in Dwarf Galaxies

    International Nuclear Information System (INIS)

    Robles-Valdez, F.; Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A.

    2017-01-01

    We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters, which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N -Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time, a non-nuclear starburst produces a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.

  12. Effects of geometric non-linearity on energy release rates in a realistic wind turbine blade cross section

    DEFF Research Database (Denmark)

    Eder, Martin Alexander; Bitsche, Robert; Belloni, Federico

    2015-01-01

    Most wind turbine rotor blades comprise several adhesively connected sub-components typically made from glass fibre reinforced polymer composite materials. It is a well-known fact that wind turbine blades are prone to fail in their adhesive joints. However, owing to the complexity...... of their structural behaviour, little is known about the root causes of adhesive joint failure. This paper investigates the effects of geometrical non-linearity on energy release rates (ERRs) of transversely oriented cracks present in the adhesive joints of a wind turbine rotor blade. Utilising a computationally...

  13. Elastic uplift in southeast Greenland due to rapid ice mass loss

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Van dam, Tonie; Hamilton, Gordon S.

    2007-01-01

    The rapid unloading of ice from the southeastern sector of the Greenland ice sheet between 2001 and 2006 caused an elastic uplift of 35 mm at a GPS site in Kulusuk. Most of the uplift results from ice dynamic-induced volume losses on two nearby outlet glaciers. Volume loss from Helheim Glacier...... between 62N and 66N. Citation: Khan, S. A., J. Wahr, L. A. Stearns, G. S. Hamilton, T. van Dam, K. M. Larson, and O. Francis (2007), Elastic uplift in southeast Greenland due to rapid ice mass loss....

  14. Time-dependent mass loss from hot stars with and without radiative driving

    International Nuclear Information System (INIS)

    Castor, J.I.; Owocki, S.P.; Rybicki, G.B.

    1988-01-01

    A numerical hydrodynamics code is used to investigate two aspects of the winds of hot stars. The first is the question of the instability of the massive radiatively-driven wind of an O star that is caused by the line shape mechanism: modulation of the radiation force by velocity fluctuations. The evolution of this instability is studied in a model O star wind, and is found, /ital modulo/ some numerical uncertainty, to lead to wave structures that are compatible with observations of wind instabilities. The other area of investigation is of main-sequence B star winds. Attempts were made to simulate a radiatively-driven and a pulsation-driven wind in a B star, but in each case the wind turned out to be very weak. It is argued that the pulsation-driven wind model is not likely to apply to B stars. 28 refs., 11 figs

  15. A Closer Earth and the Faint Young Sun Paradox: Modification of the Laws of Gravitation or Sun/Earth Mass Losses?

    Directory of Open Access Journals (Sweden)

    Lorenzo Iorio

    2013-10-01

    Full Text Available Given a solar luminosity LAr = 0.75L0 at the beginning of the Archean 3.8 Ga ago, where L0 is the present-day one, if the heliocentric distance, r, of the Earth was rAr = 0.956r0, the solar irradiance would have been as large as IAr = 0.82I0. It would have allowed for a liquid ocean on the terrestrial surface, which, otherwise, would have been frozen, contrary to the empirical evidence. By further assuming that some physical mechanism subsequently displaced the Earth towards its current distance in such a way that the irradiance stayed substantially constant over the entire Archean from 3.8 to 2.5 Ga ago, a relative recession per year as large as r˙/r ≈3.4 × 10−11 a−1 would have been required. Although such a figure is roughly of the same order of magnitude of the value of the Hubble parameter 3.8 Ga ago HAr = 1.192H0 = 8.2 × 10−11 a−1, standard general relativity rules out cosmological explanations for the hypothesized Earth’s recession rate. Instead, a class of modified theories of gravitation with nonminimal coupling between the matter and the metric naturally predicts a secular variation of the relative distance of a localized two-body system, thus yielding a potentially viable candidate to explain the putative recession of the Earth’s orbit. Another competing mechanism of classical origin that could, in principle, allow for the desired effect is the mass loss, which either the Sun or the Earth itself may have experienced during the Archean. On the one hand, this implies that our planet should have lost 2% of its present mass in the form of eroded/evaporated hydrosphere. On the other hand, it is widely believed that the Sun could have lost mass at an enhanced rate, due to a stronger solar wind in the past for not more than ≈ 0.2–0.3 Ga.

  16. Response Load Extrapolation for Wind Turbines during Operation Based on Average Conditional Exceedance Rates

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Naess, Arvid; Saha, Nilanjan

    2011-01-01

    to cases where the Gumbel distribution is the appropriate asymptotic extreme value distribution. However, two extra parameters are introduced by which a more general and flexible class of extreme value distributions is obtained with the Gumbel distribution as a subclass. The general method is implemented...... within a hierarchical model where the variables that influence the loading are divided into ergodic variables and time-invariant non-ergodic variables. The presented method for statistical response load extrapolation was compared with the existing methods based on peak extrapolation for the blade out......The paper explores a recently developed method for statistical response load (load effect) extrapolation for application to extreme response of wind turbines during operation. The extrapolation method is based on average conditional exceedance rates and is in the present implementation restricted...

  17. Improving the Penetration of Wind Power with Dynamic Thermal Rating System, Static VAR Compensator and Multi-Objective Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Jiashen Teh

    2018-04-01

    Full Text Available The integration of renewable energy sources, especially wind energy, has been on the rise throughout power systems worldwide. Due to this relatively new introduction, the integration of wind energy is often not optimized. Moreover, owing to the technical constraints and transmission congestions of the power network, most of the wind energy has to be curtailed. Due to various factors that influence the connectivity of wind energy, this paper proposes a well-organized posterior multi-objective (MO optimization algorithm for maximizing the connections of wind energy. In this regard, the dynamic thermal rating (DTR system and the static VAR compensator (SVC have been identified as effective tools for improving the loadability of the network. The propose MO algorithm in this paper aims to minimize: (1 wind energy curtailment, (2 operation cost of the network considering all investments and operations, also known as the total social cost, and (3 SVC operation cost. The proposed MO problem was solved using the non-dominated sorting genetic algorithm (NSGA II and it was tested on the modified IEEE reliability test system (IEEE-RTS. The results demonstrate the applicability of the proposed algorithm in aiding power system enhancement planning for integrating wind energy.

  18. Wind dependence on the flow rate in a natural draught cooling tower

    International Nuclear Information System (INIS)

    Baer, E.; Ernst, G.; Wurz, D.

    1981-01-01

    The efficiency of a natural draught cooling tower depends, among other things, on the effect of the wind on the flow in the tower stack. Determinations were made on a natural draught wet cooling tower 100 metres high, for the purpose of studying this effects. As characteristic quantity, a typical height was determined, the values of which were worked out from the results of the measurements. The efficiency of the stack is affected the most in the case of average wind velocities (when the velocity of the wind is about equal to the mean velocity of the plume). This effect diminishes when the velocity of the wind increases. In the case of average wind velocities, the direction of the wind has an effect, owing to the neighbouring buildings; for slightly greater wind velocities, no effect could be found [fr

  19. Chlorine loss and mass loss from polyvinylchloride and polyvinylidenchloride under the electron beam

    International Nuclear Information System (INIS)

    Lindberg, K.A.H.; Bertilsson, H.E.

    1985-01-01

    The loss of chlorine during the irradiation of PVC and PVDC in the electron microscope has been measured by the decay of the X-ray chlorine Kα signal. A number of factors affecting the measured beam damage curves have been considered and the experimental errors reduced to +- 10%. The results show that the chlorine decay curves can be best described by the sum of two exponentials, corresponding to the two different chlorine decay processes, these being: the dehydrochlorination of the polymer molecules and the dehydrochlorination of the polyene structure formed by the beam damage. The higher initial chlorine content of PVDC compared to PVC will result in a larger amount of chlorine atoms reacting with the polyene structure, which is more stable in the electron beam than the undamaged polymer. The chlorine loss, measured by X-ray analysis, has been compared to the mass loss, measured by energy loss analysis, and also with the volume changes of isolated spherical PVC particles. It has been concluded that the mass loss is almost entirely due to chlorine loss and that the residual structure has a density similar to the undamaged PVC. (author)

  20. Mass loss, levitation, accretion, and the sharp-lined features in hot white dwarfs

    International Nuclear Information System (INIS)

    Bruhweiler, F.C.; Kondo, Y.

    1983-01-01

    We have studied eight white dwarfs, seven DA and one He-rich types, observed at a high resolution (lambda/Δlambdaroughly-equal10 4 ) with the International Ultraviolet Explorer (IUE). Of the seven DA white dwarfs, three show spectral signatures of ionized heavy elements, such as Si II, SI III, C IV, Si IV, and N V, arising in the immediate environment of these stars. The shortward-shifted lines in two (G191--B2B and 2111+49) of the three DA types showing metallic lines are tentatively interpreted as an indication of mass loss from these stars. The He-rich white dwarf shows the features due to C cV and He II, which also arise in the immediate environment of that star. Although the statistical sample presented here is limited, we tentatively suggest a temperature and effective gravity range (T/sub eff/> or approx. =20,000 K and log (g) < or approx. =8.0) in DA white dwarfs within which metallic lines are present either in the photosphere or in the halo of the stars. We examine the physical processes relevant to the appearance of such metallic lines. We tentatively propose that radiative levitation can explain the appearance of the observed lines in the hot DA white dwarfs, although the role of radiation forces in mass loss is not clear

  1. Atmospheric mass-loss of extrasolar planets orbiting magnetically active host stars

    Science.gov (United States)

    Lalitha, Sairam; Schmitt, J. H. M. M.; Dash, Spandan

    2018-06-01

    Magnetic stellar activity of exoplanet hosts can lead to the production of large amounts of high-energy emission, which irradiates extrasolar planets, located in the immediate vicinity of such stars. This radiation is absorbed in the planets' upper atmospheres, which consequently heat up and evaporate, possibly leading to an irradiation-induced mass-loss. We present a study of the high-energy emission in the four magnetically active planet-bearing host stars, Kepler-63, Kepler-210, WASP-19, and HAT-P-11, based on new XMM-Newton observations. We find that the X-ray luminosities of these stars are rather high with orders of magnitude above the level of the active Sun. The total XUV irradiation of these planets is expected to be stronger than that of well-studied hot Jupiters. Using the estimated XUV luminosities as the energy input to the planetary atmospheres, we obtain upper limits for the total mass- loss in these hot Jupiters.

  2. Limited influence of climate change mitigation on short-term glacier mass loss

    Science.gov (United States)

    Marzeion, Ben; Kaser, Georg; Maussion, Fabien; Champollion, Nicolas

    2018-04-01

    Glacier mass loss is a key contributor to sea-level change1,2, slope instability in high-mountain regions3,4 and the changing seasonality and volume of river flow5-7. Understanding the causes, mechanisms and time scales of glacier change is therefore paramount to identifying successful strategies for mitigation and adaptation. Here, we use temperature and precipitation fields from the Coupled Model Intercomparison Project Phase 5 output to force a glacier evolution model, quantifying mass responses to future climatic change. We find that contemporary glacier mass is in disequilibrium with the current climate, and 36 ± 8% mass loss is already committed in response to past greenhouse gas emissions. Consequently, mitigating future emissions will have only very limited influence on glacier mass change in the twenty-first century. No significant differences between 1.5 and 2 K warming scenarios are detectable in the sea-level contribution of glaciers accumulated within the twenty-first century. In the long-term, however, mitigation will exert strong control, suggesting that ambitious measures are necessary for the long-term preservation of glaciers.

  3. Relationship between oxidative stress and muscle mass loss in early postmenopause: an exploratory study.

    Science.gov (United States)

    Zacarías-Flores, Mariano; Sánchez-Rodríguez, Martha A; García-Anaya, Oswaldo Daniel; Correa-Muñoz, Elsa; Mendoza-Núñez, Víctor Manuel

    2018-04-09

    Endocrine changes due to menopause have been associated to oxidative stress and muscle mass loss. The study objective was to determine the relationship between both variables in early postmenopause. An exploratory, cross-sectional study was conducted in 107 pre- and postmenopausal women (aged 40-57 years). Levels of serum lipid peroxides and uric acid and enzymes superoxide dismutase and glutathione peroxidase, as well as total plasma antioxidant capacity were measured as oxidative stress markers. Muscle mass using bioelectrical impedance and muscle strength using dynamometry were also measured. Muscle mass, skeletal muscle index, fat-free mass, and body mass index were calculated. More than 90% of participants were diagnosed with overweight or obesity. Postmenopausal women had lower values of muscle mass and strength markers, with a negative correlation between lipid peroxide level and skeletal muscle index (r= -0.326, p<.05), and a positive correlation between uric acid and skeletal muscle index (r=0.295, p<.05). A multivariate model including oxidative stress markers, age, and waist circumference showed lipid peroxide level to be the main contributor to explain the decrease in skeletal muscle mass in postmenopause, since for every 0.1μmol/l increase in lipid peroxide level, skeletal muscle index decreases by 3.03 units. Our findings suggest an association between increased oxidative stress and muscle mass loss in early postmenopause. Copyright © 2018 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.

  4. The Contribution of Stellar Winds to Cosmic Ray Production

    Science.gov (United States)

    Seo, Jeongbhin; Kang, Hyesung; Ryu, Dongsu

    2018-04-01

    Massive stars blow powerful stellar winds throughout their evolutionary stages from the main sequence to Wolf-Rayet phases. The wind mechanical energy of a massive star deposited to the interstellar medium can be comparable to the explosion energy of a core-collapse supernova that detonates at the end of its life In this study, we estimate the kinetic energy deposition by massive stars in our Galaxy by considering the integrated Galactic initial mass function and modeling the stellar wind luminosity. The mass loss rate and terminal velocity of stellar winds during the main sequence, red supergiant, and Wolf-Rayet stages are estimated by adopting theoretical calculations and observational data published in the literature. We find that the total stellar wind luminosity by all massive stars in the Galaxy is about Lw ≈ 1.1×1041 ergs, which is about 1/4 of the power of supernova explosions, LSN ≈ 4.8×1041 ergs. If we assume that ˜1-1% of the wind luminosity could be converted to Galactic cosmic rays (GCRs) through collisonless shocks such as termination shocks in stellar bubbles and superbubbles, colliding-wind shocks in binaries, and bow-shocks of massive runaway stars, stellar winds are expected to make a significant contribution to GCR production, though lower than that of supernova remnants.

  5. How much can Greenland melt? An upper bound on mass loss from the Greenland Ice Sheet through surface melting

    Science.gov (United States)

    Liu, X.; Bassis, J. N.

    2015-12-01

    With observations showing accelerated mass loss from the Greenland Ice Sheet due to surface melt, the Greenland Ice Sheet is becoming one of the most significant contributors to sea level rise. The contribution of the Greenland Ice Sheet o sea level rise is likely to accelerate in the coming decade and centuries as atmospheric temperatures continue to rise, potentially triggering ever larger surface melt rates. However, at present considerable uncertainty remains in projecting the contribution to sea level of the Greenland Ice Sheet both due to uncertainty in atmospheric forcing and the ice sheet response to climate forcing. Here we seek an upper bound on the contribution of surface melt from the Greenland to sea level rise in the coming century using a surface energy balance model coupled to an englacial model. We use IPCC Representative Concentration Pathways (RCP8.5, RCP6, RCP4.5, RCP2.6) climate scenarios from an ensemble of global climate models in our simulations to project the maximum rate of ice volume loss and related sea-level rise associated with surface melting. To estimate the upper bound, we assume the Greenland Ice Sheet is perpetually covered in thick clouds, which maximize longwave radiation to the ice sheet. We further assume that deposition of black carbon darkens the ice substantially turning it nearly black, substantially reducing its albedo. Although assuming that all melt water not stored in the snow/firn is instantaneously transported off the ice sheet increases mass loss in the short term, refreezing of retained water warms the ice and may lead to more melt in the long term. Hence we examine both assumptions and use the scenario that leads to the most surface melt by 2100. Preliminary models results suggest that under the most aggressive climate forcing, surface melt from the Greenland Ice Sheet contributes ~1 m to sea level by the year 2100. This is a significant contribution and ignores dynamic effects. We also examined a lower bound

  6. The assessment and rating of noise from wind farms. Final report

    International Nuclear Information System (INIS)

    1996-09-01

    The findings of a Working Group on Wind Turbine Noise in the United Kingdom are presented. The broad topics covered are: the philosophy and practice of noise emission control; description of noise emission from wind turbines; a review of current practice and guidance; a survey of public reaction to noise from wind farms; recommendations on noise limits; noise monitoring; the planning obligation. In deriving suggested noise limits, a reasonable degree of protection to wind farm neighbours has been sought which will not place unreasonable restrictions and undue added costs and administrative burdens on wind farm developers or local authorities. Examples of practice in the control of noise emissions at wind farms in the United Kingdom and the USA are assembled in an Appendix. (29 figures; 13 tables; 32 references) (UK)

  7. Objective and subjective rating of tonal noise radiated from UK wind farms: Pt. 2

    International Nuclear Information System (INIS)

    1996-01-01

    This final report provides data on the assessment of tonal noise radiation from wind turbines in the United Kingdom. Both objective and subjective assessments of the noise pollution from various wind farms are incorporated in the study. Previous subjective tests are verified here using a larger subject and sample size compared to the initial study. The study also aims to produce an objective automatic tonal assessment procedure which identifies tones and broad band masking noise in wind farm radiated noise spectra. (UK)

  8. SEARCHING FOR COOL DUST IN THE MID-TO-FAR INFRARED: THE MASS-LOSS HISTORIES OF THE HYPERGIANTS μ Cep, VY CMa, IRC+10420, AND ρ Cas

    Energy Technology Data Exchange (ETDEWEB)

    Shenoy, Dinesh; Humphreys, Roberta M.; Jones, Terry J.; Gehrz, Robert D. [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455 (United States); Marengo, Massimo [Department of Physics, Iowa State University, Ames, IA 50011 (United States); Helton, L. Andrew [USRA-SOFIA Science Center, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Hoffmann, William F.; Skemer, Andrew J.; Hinz, Philip M., E-mail: shenoy@astro.umn.edu [Department of Astronomy/Steward Observatory, University of Arizona, 933N. Cherry Avenue, Tucson, AZ 85721 (United States)

    2016-03-15

    We present mid- and far-IR imaging of four famous hypergiant stars: the red supergiants μ Cep and VY CMa, and the warm hypergiants IRC +10420 and ρ Cas. Our 11–37 μm SOFIA/FORCAST imaging probes cool dust not detected in visual and near-IR imaging studies. Adaptive optics 8–12 μm imaging of μ Cep and IRC +10420 with MMT/MIRAC reveals extended envelopes that are the likely sources of these stars’ strong silicate emission features. We find μ Cep’s mass-loss rate to have declined by about a factor of five over a 13,000 year history, ranging from 5 × 10{sup −6} down to ∼1× 10{sup −6} M{sub ⊙} yr{sup −1}. The morphology of VY CMa indicates a cooler dust component coincident with the highly asymmetric reflection nebulae seen in the visual and near-IR. The lack of cold dust at greater distances around VY CMa indicates that its mass-loss history is limited to the last ∼1200 years, with an average rate of 6 × 10{sup −4} M{sub ⊙} yr{sup −1}. We find two distinct periods in the mass-loss history of IRC +10420 with a high rate of 2 × 10{sup −3} M{sub ⊙} yr{sup −1} until approximately 2000 years ago, followed by an order of magnitude decrease in the recent past. We interpret this change as evidence of its evolution beyond the RSG stage. Our new infrared photometry of ρ Cas is consistent with emission from the expanding dust shell ejected in its 1946 eruption, with no evidence of newer dust formation from its more recent events.

  9. Equation of motion of an interstellar Bussard ramjet with radiation and mass losses

    International Nuclear Information System (INIS)

    Semay, Claude; Silvestre-Brac, Bernard

    2008-01-01

    An interstellar Bussard ramjet is a spaceship using the protons of the interstellar medium in a fusion engine to produce thrust. In recent papers, it was shown that the relativistic equation of motion of an ideal ramjet and that of a ramjet with radiation loss are analytical. When a mass loss appears, the limit speed of the ramjet is more strongly reduced. However, the parametric equations in terms of the ramjet's speed for the position of the ramjet in the inertial frame of the interstellar medium, the time in this frame and the proper time indicated by the clocks on board the spaceship can still be obtained in an analytical form. The non-relativistic motion and the motion near the limit speed are studied

  10. Equation of motion of an interstellar Bussard ramjet with radiation and mass losses

    Energy Technology Data Exchange (ETDEWEB)

    Semay, Claude [Groupe de Physique Nucleaire Theorique, Universite de Mons-Hainaut, Academie universitaire Wallonie-Bruxelles, Place du Parc 20, B-7000 Mons (Belgium); Silvestre-Brac, Bernard [LPSC, Universite Joseph Fourier, Grenoble 1, CNRS/IN2P3, Institut Polytechnique de Grenoble, Avenue des Martyrs 53, F-38026 Grenoble-Cedex (France)], E-mail: claude.semay@umh.ac.be, E-mail: silvestre@lpsc.in2p3.fr

    2008-11-15

    An interstellar Bussard ramjet is a spaceship using the protons of the interstellar medium in a fusion engine to produce thrust. In recent papers, it was shown that the relativistic equation of motion of an ideal ramjet and that of a ramjet with radiation loss are analytical. When a mass loss appears, the limit speed of the ramjet is more strongly reduced. However, the parametric equations in terms of the ramjet's speed for the position of the ramjet in the inertial frame of the interstellar medium, the time in this frame and the proper time indicated by the clocks on board the spaceship can still be obtained in an analytical form. The non-relativistic motion and the motion near the limit speed are studied.

  11. 3D Radiative Transfer in Eta Carinae: Application of the SimpleX Algorithm to 3D SPH Simulations of Binary Colliding Winds

    Science.gov (United States)

    Clementel, N.; Madura, T. I.; Kruip, C. J. H.; Icke, V.; Gull, T. R.

    2014-01-01

    Eta Carinae is an ideal astrophysical laboratory for studying massive binary interactions and evolution, and stellar wind-wind collisions. Recent three-dimensional (3D) simulations set the stage for understanding the highly complex 3D flows in Eta Car. Observations of different broad high- and low-ionization forbidden emission lines provide an excellent tool to constrain the orientation of the system, the primary's mass-loss rate, and the ionizing flux of the hot secondary. In this work we present the first steps towards generating synthetic observations to compare with available and future HST/STIS data. We present initial results from full 3D radiative transfer simulations of the interacting winds in Eta Car. We use the SimpleX algorithm to post-process the output from 3D SPH simulations and obtain the ionization fractions of hydrogen and helium assuming three different mass-loss rates for the primary star. The resultant ionization maps of both species constrain the regions where the observed forbidden emission lines can form. Including collisional ionization is necessary to achieve a better description of the ionization states, especially in the areas shielded from the secondary's radiation. We find that reducing the primary's mass-loss rate increases the volume of ionized gas, creating larger areas where the forbidden emission lines can form. We conclude that post processing 3D SPH data with SimpleX is a viable tool to create ionization maps for Eta Car.

  12. Soil erosion rates from mixed soil and gravel surfaces in a wind tunnel: A preliminary report

    International Nuclear Information System (INIS)

    Ligotke, M.W.

    1988-12-01

    Tests of wind erosion were performed in a controlled-environment wind tunnel to support the development of natural-material protective barriers for long-term isolation of radioactive waste. Barrier performance standards currently being developed for internal and external barrier performance are expected to mandate a surface layer that is resistant to wind erosion. The purpose of this study was to initiate a series of tests to determine suitable soil and gravel mixtures for such a barrier and to test worst-case surface layer conditions under the influence of high wind speeds. Six mixed soil and gravel surfaces were prepared, weathered to represent natural wind-blown desert areas, and subjected to controlled wind erosion forces in a wind tunnel. The applied erosive forces, including surface shear forces, were characterized to provide a means of relating wind tunnel results with actual field conditions. Soil particle losses from the surfaces caused by suspension, saltation, and surface creep were monitored by aerosol sample probes and mass balance measurements. 23 refs., 22 figs., 3 tabs

  13. Objective and subjective rating of tonal noise radiated from UK wind farms

    International Nuclear Information System (INIS)

    1996-01-01

    The radiation of noise to the environment is currently a major issue with regard to U.K. wind farm developments. The reason for this concern is not that wind turbines are unduly noisy, but rather because wind farms are often located in rural areas where background noise levels can fall very low. The fact that background noise levels fall so low in these areas means that the permissible noise radiation from wind farms must also be kept similarly low if nuisance to local residents is to be avoided. However, ensuring that the overall noise level of the wind farm does not exceed the pre-existing background noise level by more than a set amount is not the whole story. Noise radiated from wind turbines can exhibit characteristics that set it apart from the natural background noises typically found in quiet rural areas, where ''natural'' background noises might include the sound of the wind blowing through trees, or the sound of running water. One of the acoustic characteristics that can be attributed to some wind turbines is the radiation of tonal noise from mechanical plant located in the nacelles. It is well accepted that tonal components in otherwise broad band, or ''characterless'', noise, can increase the subjective perception of that noise. Account for increased annoyance due to tones is found in both of the British Standards which relate to environmental noise; BS4142 and BS7445. (UK)

  14. Aspects regarding the Calculation of the Dielectric Loss Angle Tangent between the Windings of a Rated 40 MVA Transformer

    Directory of Open Access Journals (Sweden)

    Cristinel Popescu

    2015-09-01

    Full Text Available The paper aims to identify how to determine the dielectric loss angle tangent of the electric transformers from the transformer stations. Autors of the paper managed a case study on the dielectric established between high respectively medium voltage windings of an electrical rated 40 MVA transformer.

  15. Variation in body mass dynamics among sites in Black Brant Branta bernicla nigricans supports adaptivity of mass loss during moult

    Science.gov (United States)

    Fondell, Thomas F.; Flint, Paul L.; Schmutz, Joel A.; Schamber, Jason L.; Nicolai, Christopher A.

    2013-01-01

    Birds employ varying strategies to accommodate the energetic demands of moult, one important example being changes in body mass. To understand better their physiological and ecological significance, we tested three hypotheses concerning body mass dynamics during moult. We studied Black Brant in 2006 and 2007 moulting at three sites in Alaska which varied in food availability, breeding status and whether geese undertook a moult migration. First we predicted that if mass loss during moult were simply the result of inadequate food resources then mass loss would be highest where food was least available. Secondly, we predicted that if mass loss during moult were adaptive, allowing birds to reduce activity during moult, then birds would gain mass prior to moult where feeding conditions allowed and mass loss would be positively related to mass at moult initiation. Thirdly, we predicted that if mass loss during moult were adaptive, allowing birds to regain flight sooner, then across sites and groups, mass at the end of the flightless period would converge on a theoretical optimum, i.e. the mass that permits the earliest possible return to flight. Mass loss was greatest where food was most available and thus our results did not support the prediction that mass loss resulted from inadequate food availability. Mass at moult initiation was positively related to both food availability and mass loss. In addition, among sites and years, variation in mass was high at moult initiation but greatly reduced at the end of the flightless period, appearing to converge. Thus, our results supported multiple predictions that mass loss during moult was adaptive and that the optimal moulting strategy was to gain mass prior to the flightless period, then through behavioural modifications use these body reserves to reduce activity and in so doing also reduce wing loading. Geese that undertook a moult migration initiated moult at the highest mass, indicating that they were more than able to

  16. Mass-loss evolution of close-in exoplanets: Evaporation of hot Jupiters and the effect on population

    International Nuclear Information System (INIS)

    Kurokawa, H.; Nakamoto, T.

    2014-01-01

    During their evolution, short-period exoplanets may lose envelope mass through atmospheric escape owing to intense X-ray and extreme ultraviolet (XUV) radiation from their host stars. Roche-lobe overflow induced by orbital evolution or intense atmospheric escape can also contribute to mass loss. To study the effects of mass loss on inner planet populations, we calculate the evolution of hot Jupiters considering mass loss of their envelopes and thermal contraction. Mass loss is assumed to occur through XUV-driven atmospheric escape and the following Roche-lobe overflow. The runaway effect of mass loss results in a dichotomy of populations: hot Jupiters that retain their envelopes and super Earths whose envelopes are completely lost. Evolution primarily depends on the core masses of planets and only slightly on migration history. In hot Jupiters with small cores (≅ 10 Earth masses), runaway atmospheric escape followed by Roche-lobe overflow may create sub-Jupiter deserts, as observed in both mass and radius distributions of planetary populations. Comparing our results with formation scenarios and observed exoplanets populations, we propose that populations of closely orbiting exoplanets are formed by capturing planets at/inside the inner edges of protoplanetary disks and subsequent evaporation of sub-Jupiters.

  17. Mass-loss evolution of close-in exoplanets: Evaporation of hot Jupiters and the effect on population

    Energy Technology Data Exchange (ETDEWEB)

    Kurokawa, H. [Department of Physics, Nagoya Univsersity, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan); Nakamoto, T., E-mail: kurokawa@nagoya-u.jp [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2014-03-01

    During their evolution, short-period exoplanets may lose envelope mass through atmospheric escape owing to intense X-ray and extreme ultraviolet (XUV) radiation from their host stars. Roche-lobe overflow induced by orbital evolution or intense atmospheric escape can also contribute to mass loss. To study the effects of mass loss on inner planet populations, we calculate the evolution of hot Jupiters considering mass loss of their envelopes and thermal contraction. Mass loss is assumed to occur through XUV-driven atmospheric escape and the following Roche-lobe overflow. The runaway effect of mass loss results in a dichotomy of populations: hot Jupiters that retain their envelopes and super Earths whose envelopes are completely lost. Evolution primarily depends on the core masses of planets and only slightly on migration history. In hot Jupiters with small cores (≅ 10 Earth masses), runaway atmospheric escape followed by Roche-lobe overflow may create sub-Jupiter deserts, as observed in both mass and radius distributions of planetary populations. Comparing our results with formation scenarios and observed exoplanets populations, we propose that populations of closely orbiting exoplanets are formed by capturing planets at/inside the inner edges of protoplanetary disks and subsequent evaporation of sub-Jupiters.

  18. Interactions between exoplanets and the winds of young stars

    Directory of Open Access Journals (Sweden)

    Vidotto A. A.

    2014-01-01

    Full Text Available The topology of the magnetic field of young stars is important not only for the investigation of magnetospheric accretion, but also responsible in shaping the large-scale structure of stellar winds, which are crucial for regulating the rotation evolution of stars. Because winds of young stars are believed to have enhanced mass-loss rates compared to those of cool, main-sequence stars, the interaction of winds with newborn exoplanets might affect the early evolution of planetary systems. This interaction can also give rise to observational signatures which could be used as a way to detect young planets, while simultaneously probing for the presence of their still elusive magnetic fields. Here, we investigate the interaction between winds of young stars and hypothetical planets. For that, we model the stellar winds by means of 3D numerical magnetohydrodynamic simulations. Although these models adopt simplified topologies of the stellar magnetic field (dipolar fields that are misaligned with the rotation axis of the star, we show that asymmetric field topologies can lead to an enhancement of the stellar wind power, resulting not only in an enhancement of angular momentum losses, but also intensifying and rotationally modulating the wind interactions with exoplanets.

  19. Compensating effect of minor portal hypertension on the muscle mass loss-related poor prognosis in cirrhosis.

    Science.gov (United States)

    Maruyama, Hitoshi; Kobayashi, Kazufumi; Kiyono, Soichiro; Ogasawara, Sadahisa; Suzuki, Eichiro; Ooka, Yoshihiko; Chiba, Tetsuhiro; Yamaguchi, Tadashi

    2017-01-01

    Background: To examine the influence of the severity of portal hemodynamic abnormality on the prognosis of cirrhosis with respect to the muscle mass loss (MML). Methods: The study involved a subgroup analysis in 98 cirrhosis patients (63.5 ± 11.8 years) who prospectively underwent both Doppler ultrasound and hepatic venous catheterization. The prognostic influence of MML diagnosed by computed tomography using the L3 skeletal muscle index was evaluated (median observation period, 32.7 months). Results: The cumulative survival rate showed difference between patients with MML (n = 34; 82.2%/1year, 41.2%/3years and 36.1%/5years) and those without (n = 64; 92.1%/1year, 74.9%/3years and 69.4%/5years; P = 0.005). When divided with respect to the portal velocity, the survival rate showed differences between patients with and without MML in the cohort 12 mmHg. However, in the cohort with HVPG ≤ 12 mmHg, survival rate showed no difference between patients with MML (n=10; 100%/1year, 61.9%/3years and 61.9%/5years) and those without (n=19; 93.8%/1year, 71.2%/3years and 59.4%/5years; p = 0.493) Conclusion: Lower HVPG has a compensating effect on the MML-induced poor prognosis of cirrhosis. Care should be taken in the evaluation of the influence of MML in consideration of the severity of portal hypertension.

  20. Variability of sea ice deformation rates in the Arctic and their relationship with basin-scale wind forcing

    Directory of Open Access Journals (Sweden)

    A. Herman

    2012-12-01

    Full Text Available The temporal variability of the moments of probability distribution functions (pdfs of total sea ice deformation rates in the Arctic is analyzed in the context of the basin-scale wind forcing acting on the ice. The pdfs are estimated for 594 satellite-derived sea ice deformation maps from 11 winter seasons between 1996/1997 and 2007/2008, provided by the RADARSAT Geophysical Processor System. The temporal scale analyzed equals 3 days. The moments of the pdfs, calculated for a range of spatial scales (12.5–900 km, have two dominating components of variability: a seasonal cycle, with deformation rates decreasing throughout winter towards a minimum in March; and a short-term, synoptic variability, strongly correlated with the area-averaged magnitude of the wind stress over the Arctic, estimated based on the NCEP-DOE Reanalysis-2 data (correlation coefficient of 0.71 for the mean deformation rate. Due to scaling properties of the moments, logarithms of higher moments are strongly correlated with the wind stress as well. Exceptions are observed only at small spatial scales, as a result of extreme deformation events, not directly associated with large-scale wind forcing. By repeating the analysis within regions of different sizes and locations, we show that the wind–ice deformation correlation is largest at the basin scale and decreases with decreasing size of the area of study. Finally, we suggest that a positive trend in seasonally averaged correlation between sea ice deformation rates and the wind forcing, present in the analyzed data, may be related to an observed decrease in the multi-year ice area in the Arctic, indicating possibly even stronger correlations in the future.

  1. Rating Requirements of the UPQC to Integrate the FSIG Type Wind Generation to the Grid

    OpenAIRE

    Jayanti, N.; Basu, Malabika; Conlon, Michael; Gaughan, Kevin

    2009-01-01

    The ability of wind generation to remain connected to the grid in the event of system faults and dynamic reactive power compensation are two aspects of grid integration, which have received particular attention. The wind driven, fixed-speed induction generator (FSIG) on its own fails to fulfil these requirements of grid integration. The application of a unified power quality conditioner (UPQC) to overcome the grid integration problems of the FSIG is investigated. The role of the UPQC in enhan...

  2. Galactic chemical evolution with main-sequence mass loss and the distribution of F and G dwarfs

    International Nuclear Information System (INIS)

    Guzik, J.A.; Struck-Marcell, C.

    1988-01-01

    Simple closed galactic chemical-evolution models incorporating early main-sequence stellar mass loss have been developed for disk ages of 5, 10, and 15 Gyr. Relative to models without stellar mass loss, the models are shown to produce a 30-60 percent increase in the present mass ratio of dwarfs to dwarfs plus remnants, and a 200-250 percent increase in the total mass of late F dwarfs remaining on the main sequence at the current disk age. For present disk ages 5 and 10 Gyr, the total mass of mid-F dwarfs remaining on the main sequence is also shown to increase by 90-120 percent. It is concluded that models with main-sequence mass loss have a slightly reduced gas metallicity and slightly increased gas fraction midway through the evolution. 30 references

  3. FUNDAMENTAL PARAMETERS, INTEGRATED RED GIANT BRANCH MASS LOSS, AND DUST PRODUCTION IN THE GALACTIC GLOBULAR CLUSTER 47 TUCANAE

    International Nuclear Information System (INIS)

    McDonald, I.; Zijlstra, A. A.; Boyer, M. L.; Gordon, K.; Meixner, M.; Sewilo, M.; Shiao, B.; Whitney, B.; Van Loon, J. Th.; Hora, J. L.; Robitaille, T.; Babler, B.; Meade, M.; Block, M.; Misselt, K.

    2011-01-01

    Fundamental parameters and time evolution of mass loss are investigated for post-main-sequence stars in the Galactic globular cluster 47 Tucanae (NGC 104). This is accomplished by fitting spectral energy distributions (SEDs) to existing optical and infrared photometry and spectroscopy, to produce a true Hertzsprung-Russell diagram. We confirm the cluster's distance as d = 4611 +213 -200 pc and age as 12 ± 1 Gyr. Horizontal branch models appear to confirm that no more red giant branch mass loss occurs in 47 Tuc than in the more metal-poor ω Centauri, though difficulties arise due to inconsistencies between the models. Using our SEDs, we identify those stars that exhibit infrared excess, finding excess only among the brightest giants: dusty mass loss begins at a luminosity of ∼1000 L sun , becoming ubiquitous above L = 2000 L sun . Recent claims of dust production around lower-luminosity giants cannot be reproduced, despite using the same archival Spitzer imagery.

  4. VizieR Online Data Catalog: Adiabatic mass loss in binary stars. II. (Ge+, 2015)

    Science.gov (United States)

    Ge, H.; Webbink, R. F.; Chen, X.; Han, Z.

    2016-02-01

    In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z=0.02) of mass 0.10M⊙-100M⊙ from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. For intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio qad (throughout this paper, we follow the convention of defining the binary mass ratio as q{equiv}Mdonor/Maccretor) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, qad plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with qad declining with decreasing mass, and asymptotically approaching qad=2/3, appropriate to a classical isentropic n=3/2 polytrope. Our calculated qad values agree well with the behavior of time-dependent models by Chen & Han (2003MNRAS.341..662C) of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as systems that must be stable against rapid mass

  5. Tidal heating and mass loss in neutron star binaries - Implications for gamma-ray burst models

    Science.gov (United States)

    Meszaros, P.; Rees, M. J.

    1992-01-01

    A neutron star in a close binary orbit around another neutron star (or stellar-mass black hole) spirals inward owing to gravitational radiation. We discuss the effects of tidal dissipation during this process. Tidal energy dissipated in the neutron star's core escapes mainly as neutrinos, but heating of the crust, and outward diffusion of photons, blows off the outer layers of the star. This photon-driven mass loss precedes the final coalescence. The presence of this eject material impedes the escape of gamma-rays created via neutrino interactions. If an e(+) - e(-) fireball, created in the late stages of coalescence, were loaded with (or surrounded by) material with the mean column density of the ejecta, it could not be an efficient source of gamma-rays. Models for cosmologically distant gamma-rays burst that involve neutron stars must therefore be anisotropic, so that the fireball expands preferentially in directions where the column density of previously blown-off material is far below the spherically averaged value which we have calculated. Some possible 'scenarios' along these lines are briefly discussed.

  6. Transient Mass-loss Analysis of Solar Observations Using Stellar Methods

    Energy Technology Data Exchange (ETDEWEB)

    Crosley, M. K.; Norman, C. [Johns Hopkins University, Department of Physics and Astronomy, 3400 N. Charles Street, Baltimore, MD 21218 (United States); Osten, R. A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2017-08-10

    Low-frequency dynamic spectra of radio bursts from nearby stars offer the best chance to directly detect the stellar signature of transient mass loss on low-mass stars. Crosley et al. (2016) proposes a multi-wavelength methodology to determine coronal mass ejection (CME) parameters, such as speed, mass, and kinetic energy. We test the validity and accuracy of the results derived from the methodology by using Geostationary Operational Environmental Satellite X-ray observations and Bruny Island Radio Spectrometer radio observations. These are analogous observations to those that would be found in the stellar studies. Derived results from these observations are compared to direct white light measurements of the Large Angle and Spectrometric Coronagraph. We find that, when a pre-event temperature can be determined, the accuracy of CME speeds are within a few hundred km s{sup −1}, and are reliable when specific criteria has been met. CME mass and kinetic energies are only useful in determining the approximate order of magnitude measurements when considering the large errors associated to them. These results will be directly applicable to the interpretation of any detected stellar events and the derivation of stellar CME properties.

  7. Exploring the effect of East Antarctic ice mass loss on GIA-induced horizontal bedrock motions

    Science.gov (United States)

    Konfal, S. A.; Whitehouse, P. L.; Hermans, T.; van der Wal, W.; Wilson, T. J.; Bevis, M. G.; Kendrick, E. C.; Dalziel, I.; Smalley, R., Jr.

    2017-12-01

    Ice history inputs used in Antarctic models of GIA include major centers of ice mass loss in West Antarctica. In the Transantarctic Mountains (TAM) region spanning the boundary between East and West Antarctica, horizontal crustal motions derived from GPS observations from the Antarctic Network (ANET) component of the Polar Earth Observing Network (POLENET) are towards these West Antarctic ice mass centers, opposite to the pattern of radial crustal motion expected in an unloading scenario. We investigate alternative ice history and earth structure inputs to GIA models in an attempt to reproduce observed crustal motions in the region. The W12 ice history model is altered to create scenarios including ice unloading in the Wilkes Subglacial Basin based on available glaciological records. These altered ice history models, along with the unmodified W12 ice history model, are coupled with 60 radially varying (1D) earth model combinations, including approximations of optimal earth profiles identified in published GIA models. The resulting model-predicted motions utilizing both the modified and unmodified ice history models fit ANET GPS-derived crustal motions in the northern TAM region for a suite of earth model combinations. Further south, where the influence of simulated Wilkes unloading is weakest and West Antarctic unloading is strongest, observed and predicted motions do not agree. The influence of simulated Wilkes ice unloading coupled with laterally heterogeneous earth models is also investigated. The resulting model-predicted motions do not differ significantly between the original W12 and W12 with simulated Wilkes unloading ice histories.

  8. Modelling historical and recent mass loss of McCall Glacier, Alaska, USA

    Directory of Open Access Journals (Sweden)

    C. Delcourt

    2008-03-01

    Full Text Available Volume loss of valley glaciers is now considered to be a significant contribution to sea level rise. Understanding and identifying the processes involved in accelerated mass loss are necessary to determine their impact on the global system. Here we present results from a series of model experiments with a higher-order thermomechanically coupled flowline model (Pattyn, 2002. Boundary conditions to the model are parameterizations of surface mass balance, geothermal heating, observed surface and 10 m ice depth temperatures. The time-dependent experiments aim at simulating the glacier retreat from its LIA expansion to present according to different scenarios and model parameters. Model output was validated against measurements of ice velocity, ice surface elevation and terminus position at different stages. Results demonstrate that a key factor in determining the glacier retreat history is the importance of internal accumulation (>50% in the total mass balance. The persistence of a basal temperate zone characteristic for this polythermal glacier depends largely on its contribution. Accelerated glacier retreat since the early nineties seems directly related to the increase in ELA and the sudden reduction in AAR due to the fact that a large lower elevation cirque – previously an important accumulation area – became part of the ablation zone.

  9. Sustained mass loss of the northeast Greenland ice sheet triggered by regional warming

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Kjaer, Kurt H.; Bevis, Michael

    2014-01-01

    The Greenland ice sheet has been one of the largest contributors to global sea-level rise over the past 20 years, accounting for 0.5 mm yr(-1) of a total of 3.2 mm yr(-1). A significant portion of this contribution is associated with the speed-up of an increased number of glaciers in southeast...... and northwest Greenland. Here, we show that the northeast Greenland ice stream, which extends more than 600 km into the interior of the ice sheet, is now undergoing sustained dynamic thinning, linked to regional warming, after more than a quarter of a century of stability. This sector of the Greenland ice sheet...... is of particular interest, because the drainage basin area covers 16% of the ice sheet (twice that of Jakobshavn Isbrae) and numerical model predictions suggest no significant mass loss for this sector, leading to an under-estimation of future global sea-level rise. The geometry of the bedrock and monotonic trend...

  10. Wind energy development: Methods to assess bird and bat fatality rates post-construction

    Science.gov (United States)

    Huso, Manuela; Dalthorp, Daniel; Miller, T J; Bruns, Dawn

    2016-01-01

    Monitoring fatalities at wind energy facilities after they have been constructed can provide valuable information regarding impacts of wind power development on wildlife. The objective of this monitoring is to estimate abundance of a super-population of carcasses that entered the area within a designated period of time. By definition, the population is not closed and carcasses can enter as they are killed through collision with turbines, and leave as they are removed by scavengers or decompose to a point where they are not recognizable. In addition, the population is not inherently mobile, but can only change location through some external force. A focus on number of animal carcasses comprising the super-population, combined with peculiar traits that resist classic assumptions, distinguish fatality estimation at wind-power facilities from more classic abundance estimates that can be addressed through mark-recapture techniques or other well-known abundance estimators. We review the available methods to estimate the super-population of carcasses at wind power facilities. We discuss the role of these estimates in determining appropriate levels of minimization and mitigation of impacts to individual species of concern. We discuss the potential to extrapolate these measurements to reflect the cumulative effect of the industry on individual species. Finally, we suggest avenues of research needed to strengthen our understanding of the effect wind power development has, and might have in the future, on wildlife on this continent and worldwide.

  11. MAGNETIC NESTED-WIND SCENARIOS FOR BIPOLAR OUTFLOWS: PREPLANETARY AND YSO NEBULAR SHAPING

    International Nuclear Information System (INIS)

    Dennis, Timothy J.; Frank, Adam; Blackman, Eric G.; DeMarco, Orsola; Balick, Bruce; Mitran, Sorin

    2009-01-01

    We present results of a series of magnetohydrodynamic (MHD) and hydrodynamic (HD) 2.5 dimensional simulations of the morphology of outflows driven by nested wide-angle winds, i.e., winds that emanate from a central star as well as from an orbiting accretion disk. While our results are broadly relevant to nested-wind systems, we have tuned the parameters of the simulations to touch on issues in both young stellar objects and planetary nebula (PN) studies. In particular, our studies connect to open issues in the early evolution of PNs. We find that nested MHD winds exhibit marked morphological differences from the single MHD wind case along both dimensions of the flow. Nested HD winds, on the other hand, give rise mainly to geometric distortions of an outflow that is topologically similar to the flow arising from a single stellar HD wind. Our MHD results are insensitive to changes in ambient temperature between ionized and un-ionized circumstellar environments. The results are sensitive to the relative mass-loss rates and the relative speeds of the stellar and disk winds. We also present synthetic emission maps of both nested MHD and HD simulations. We find that nested MHD winds show knots of emission appearing on-axis that do not appear in the HD case.

  12. Changes in mass loss and chemistry of AG-80 epoxy resin after 160 keV proton irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Gao Yu [Space Materials and Environment Engineering Lab, Harbin Institute of Technology, Harbin, 150001 (China)]. E-mail: czq04@yahoo.com.cn; Sun Mingren [College of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001 (China); Yang Dezhuang [Space Materials and Environment Engineering Lab, Harbin Institute of Technology, Harbin, 150001 (China); He Shiyu [Space Materials and Environment Engineering Lab, Harbin Institute of Technology, Harbin, 150001 (China); Wang Jinhe [Precision Engineering Research Institute, Harbin Institute of Technology, Harbin, 150001 (China); Xiao Jingdong [Space Materials and Environment Engineering Lab, Harbin Institute of Technology, Harbin, 150001 (China); Li Zhijun [39th Institute, China Electronic Science and Technology Groups Inc., Xi-an 710065 (China)

    2005-06-01

    The AG-80 resin is a new type of thermosetting matrix for advanced carbon/epoxy composites. Mass loss effect and the related outgassing are major concerns for its application in space. The changes in mass loss, outgassing and chemical structure under 160 keV proton exposure were investigated for the AG-80 epoxy resin. The variation in chemistry was characterized by X-ray photoelectron spectroscopy. Experimental results show that with increasing the proton fluence, the surface colour of specimens is getting darker. Mass loss ratios ascend remarkably until the fluence of approximately 5.5 x 10{sup 15} cm{sup -2}, and then tend to leveling off. The surface roughness of specimens exhibits an increasing trend followed by decreasing as a function of proton fluence. Under the exposure, the C-C, C-H, C-N and C-O bonds are broken, a variety of molecule ions with smaller molecule weight are formed, and carbon is enriched in the surface layer of specimens. The changes in mass loss and surface roughness of the AG-80 epoxy resin could be attributed to the formation of the molecule ions and the enrichment of carbon content in the surface layer due to proton radiation.

  13. ALMA observations of anisotropic dust mass loss in the inner circumstellar environment of the red supergiant VY Canis Majoris

    NARCIS (Netherlands)

    O'Gorman, E.; Vlemmings, W.; Richards, A.M.S.; Baudry, A.; De Beck, E.; Decin, L.; Harper, G.M.; Humphreys, E.M.; Kervella, P.; Khouri, T.; Muller, S.

    2015-01-01

    The processes leading to dust formation and the subsequent role it plays in driving mass loss in cool evolved stars is an area of intense study. Here we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These

  14. A Post-Harvest Prediction Mass Loss Model for Tomato Fruit Using A Numerical Methodology Centered on Approximation Error Minimization

    Directory of Open Access Journals (Sweden)

    Francisco Javier Bucio

    2017-10-01

    Full Text Available Due to its nutritional and economic value, the tomato is considered one of the main vegetables in terms of production and consumption in the world. For this reason, an important case study is the fruit maturation parametrized by its mass loss in this study. This process develops in the fruit mainly after harvest. Since that parameter affects the economic value of the crop, the scientific community has been progressively approaching the issue. However, there is no a state-of-the-art practical model allowing the prediction of the tomato fruit mass loss yet. This study proposes a prediction model for tomato mass loss in a continuous and definite time-frame using regression methods. The model is based on a combination of adjustment methods such as least squares polynomial regression leading to error estimation, and cross validation techniques. Experimental results from a 50 fruit of tomato sample studied over a 54 days period were compared to results from the model using a second-order polynomial approach found to provide optimal data fit with a resulting efficiency of ~97%. The model also allows the design of precise logistic strategies centered on post-harvest tomato mass loss prediction usable by producers, distributors, and consumers.

  15. Mass loss and flammability of insulation materials used in sandwich panels during the pre-flashover phase of fire

    NARCIS (Netherlands)

    Giunta d'Albani, A.W.; de Kluiver, L.L.; de Korte, A.C.J.; van Herpen, R.; Weewer, R.; Brouwers, H.J.H.

    2017-01-01

    Nowadays, buildings contain more and more synthetic insulation materials in order to meet the increasing energy-performance demands. These synthetic insulation materials have a different response to fire. In this study, the mass loss and flammability limits of different sandwich panels and their

  16. Stellar and wind parameters of massive stars from spectral analysis

    Science.gov (United States)

    Araya, Ignacio; Curé, Michel

    2017-11-01

    The only way to deduce information from stars is to decode the radiation it emits in an appropriate way. Spectroscopy can solve this and derive many properties of stars. In this work we seek to derive simultaneously the stellar and wind characteristics of a wide range of massive stars. Our stellar properties encompass the effective temperature, the surface gravity, the stellar radius, the micro-turbulence velocity, the rotational velocity and the Si abundance. For wind properties we consider the mass-loss rate, the terminal velocity and the line-force parameters α, k and δ (from the line-driven wind theory). To model the data we use the radiative transport code Fastwind considering the newest hydrodynamical solutions derived with Hydwind code, which needs stellar and line-force parameters to obtain a wind solution. A grid of spectral models of massive stars is created and together with the observed spectra their physical properties are determined through spectral line fittings. These fittings provide an estimation about the line-force parameters, whose theoretical calculations are extremely complex. Furthermore, we expect to confirm that the hydrodynamical solutions obtained with a value of δ slightly larger than ~ 0.25, called δ-slow solutions, describe quite reliable the radiation line-driven winds of A and late B supergiant stars and at the same time explain disagreements between observational data and theoretical models for the Wind-Momentum Luminosity Relationship (WLR).

  17. The Impact of Atmospheric Modeling Errors on GRACE Estimates of Mass Loss in Greenland and Antarctica

    Science.gov (United States)

    Hardy, Ryan A.; Nerem, R. Steven; Wiese, David N.

    2017-12-01

    Systematic errors in Gravity Recovery and Climate Experiment (GRACE) monthly mass estimates over the Greenland and Antarctic ice sheets can originate from low-frequency biases in the European Centre for Medium-Range Weather Forecasts (ECMWF) Operational Analysis model, the atmospheric component of the Atmospheric and Ocean Dealising Level-1B (AOD1B) product used to forward model atmospheric and ocean gravity signals in GRACE processing. These biases are revealed in differences in surface pressure between the ECMWF Operational Analysis model, state-of-the-art reanalyses, and in situ surface pressure measurements. While some of these errors are attributable to well-understood discrete model changes and have published corrections, we examine errors these corrections do not address. We compare multiple models and in situ data in Antarctica and Greenland to determine which models have the most skill relative to monthly averages of the dealiasing model. We also evaluate linear combinations of these models and synthetic pressure fields generated from direct interpolation of pressure observations. These models consistently reveal drifts in the dealiasing model that cause the acceleration of Antarctica's mass loss between April 2002 and August 2016 to be underestimated by approximately 4 Gt yr-2. We find similar results after attempting to solve the inverse problem, recovering pressure biases directly from the GRACE Jet Propulsion Laboratory RL05.1 M mascon solutions. Over Greenland, we find a 2 Gt yr-1 bias in mass trend. While our analysis focuses on errors in Release 05 of AOD1B, we also evaluate the new AOD1B RL06 product. We find that this new product mitigates some of the aforementioned biases.

  18. Greenland Ice Sheet Surface Temperature, Melt, and Mass Loss: 2000-2006

    Science.gov (United States)

    Hall, Dorothy K.; Williams, Richard S., Jr.; Luthcke, Scott B.; DiGirolamo, Nocolo

    2007-01-01

    Extensive melt on the Greenland Ice Sheet has been documented by a variety of ground and satellite measurements in recent years. If the well-documented warming continues in the Arctic, melting of the Greenland Ice Sheet will likely accelerate, contributing to sea-level rise. Modeling studies indicate that an annual or summer temperature rise of 1 C on the ice sheet will increase melt by 20-50% therefore, surface temperature is one of the most important ice-sheet parameters to study for analysis of changes in the mass balance of the ice-sheet. The Greenland Ice Sheet contains enough water to produce a rise in eustatic sea level of up to 7.0 m if the ice were to melt completely. However, even small changes (centimeters) in sea level would cause important economic and societal consequences in the world's major coastal cities thus it is extremely important to monitor changes in the ice-sheet surface temperature and to ultimately quantify these changes in terms of amount of sea-level rise. We have compiled a high-resolution, daily time series of surface temperature of the Greenland Ice Sheet, using the I-km resolution, clear-sky land-surface temperature (LST) standard product from the Moderate-Resolution Imaging Spectroradiometer (MODIS), from 2000 - 2006. We also use Gravity Recovery and Climate Experiment (GRACE) data, averaged over 10-day periods, to measure change in mass of the ice sheet as it melt and snow accumulates. Surface temperature can be used to determine frequency of surface melt, timing of the start and the end of the melt season, and duration of melt. In conjunction with GRACE data, it can also be used to analyze timing of ice-sheet mass loss and gain.

  19. Rate bounded linear parameter varying control of a wind turbine in full load operation

    DEFF Research Database (Denmark)

    Østergaard, Kasper Zinck; Stoustrup, Jakob; Brath, Per

    2008-01-01

    This paper considers the control of wind turbines using an LPV design technique. The controller design is done by a combination of a method that uses elimination of controller variables and a method using a congruent transformation followed by a change of variables. An investigation is performed ...

  20. The Role of the North Atlantic Oscillation (NAO) on Recent Greenland Surface Mass Loss and Mass Partitioning

    Science.gov (United States)

    Tedesco, M.; Alexander, P.; Porter, D. F.; Fettweis, X.; Luthcke, S. B.; Mote, T. L.; Rennermalm, A.; Hanna, E.

    2017-12-01

    Despite recent changes in Greenland surface mass losses and atmospheric circulation over the Arctic, little attention has been given to the potential role of large-scale atmospheric processes on the spatial and temporal variability of mass loss and partitioning of the GrIS mass loss. Using a combination of satellite gravimetry measurements, outputs of the MAR regional climate model and reanalysis data, we show that changes in atmospheric patterns since 2013 over the North Atlantic region of the Arctic (NAA) modulate total mass loss trends over Greenland together with the spatial and temporal distribution of mass loss partitioning. For example, during the 2002 - 2012 period, melting persistently increased, especially along the west coast, as a consequence of increased insulation and negative NAO conditions characterizing that period. Starting in 2013, runoff along the west coast decreased while snowfall increased substantially, when NAO turned to a more neutral/positive state. Modeled surface mass balance terms since 1950 indicate that part of the GRACE-period, specifically the period between 2002 and 2012, was exceptional in terms of snowfall over the east and northeast regions. During that period snowfall trend decreased to almost 0 Gt/yr from a long-term increasing trend, which presumed again in 2013. To identify the potential impact of atmospheric patterns on mass balance and its partitioning, we studied the spatial and temporal correlations between NAO and snowfall/runoff. Our results indicate that the correlation between summer snowfall and NAO is not stable during the 1950 - 2015 period. We further looked at changes in patterns of circulation using self organizing maps (SOMs) to identify the atmospheric patterns characterizing snowfall during different periods. We discuss potential implications for past changes and future GCM and RCM simulations.

  1. Estimation of the variations of ventilation rate and indoor radon concentration using the observed wind velocity and indoor-outdoor temperature difference

    International Nuclear Information System (INIS)

    Nagano, Katsuhiro; Inose, Yuichi; Kojima, Hiroshi

    2006-01-01

    The indoor radon concentration in the building depends on the ventilation rate. Measurement results of indoor-outdoor pressure difference showed the ventilation rate correlated closely with the indoor-outdoor pressure difference. The observation results showed that one of factor of indoor-outdoor pressure difference was the wind velocity. When the wind velocity is small, the ventilation rate is affected by the indoor-outdoor temperature difference and the effect depends on the wind velocity. The temporal variation of indoor radon concentration was predicted by the time depending indoor radon balance model and the ventilation rate estimated from the wind velocity and the indoor-outdoor temperature difference. The temporal variations of predicted radon concentration gave good agreement with the experimental values. The measurement method, indoor radon concentration and ventilation rate, factors of temporal variation of ventilation rate, and prediction of indoor radon concentration are reported. (S.Y.)

  2. A 7-day high protein hypocaloric diet promotes cellular metabolic adaptations and attenuates lean mass loss in healthy males

    Directory of Open Access Journals (Sweden)

    Matthew Furber

    2017-08-01

    Full Text Available Mitochondrial quantity and density are associated with increased oxidative metabolism. It has been demonstrated that a hypocaloric high fat/low carbohydrate (HF/LC diet can up-regulate transcriptional markers of mitochondrial biogenesis; this was yet to be explored in vivo subsequent to a high protein/low carbohydrate (HP/LC diet. Thus the aims of the study were to explore such diets on transcriptional markers or mitochondrial biogenesis, body composition and resting metabolic rate (RMR. Forty-five healthy male participants were randomly assigned one of four intervention diets: eucaloric high protein low carbohydrate (PRO-EM, hypocaloric high protein low carbohydrate (PRO-ER, eucaloric high carbohydrate (CHO-EM or hypocaloric high carbohydrate (CHO-ER. The macronutrient ratio of the high protein diet and high carbohydrate diets was 40:30:30% and 10:60:30% (PRO:CHO:FAT respectively. Energy intake for the hypocaloric diets were calculated to match resting metabolic rate. Participants visited the laboratory on 3 occasions each separated by 7 days. On each visit body composition, resting metabolic rate and a muscle biopsy from the vastus lateralis was collected. Prior to visit 1 and 2 habitual diet was consumed which was used as a control, between visit 2 and 3 the intervention diet was consumed continuously for 7-days. No group × time effect was observed, however in the PRO-ER group a significant increase in AMPK, PGC-1α, SIRT1 and SIRT3 mRNA expression was observed post diet intervention groups (p < 0.05. No change was observed in any of the transcriptional markers in the other 3 groups. Despite ∼30% reduction in calorie intake no difference in lean mass (LM loss was observed between the PRO-ER and CHO-EM groups. The results from this study suggest that a 7-day a high protein low carbohydrate hypocaloric diet increased AMPK, SIRT1 and PGC-1 α mRNA expression at rest, and also suggest that increased dietary protein may attenuate LM mass

  3. MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel.

    Science.gov (United States)

    Jiang, Naibo; Webster, Matthew; Lempert, Walter R; Miller, Joseph D; Meyer, Terrence R; Ivey, Christopher B; Danehy, Paul M

    2011-02-01

    Nitric oxide planar laser-induced fluorescence (NO PLIF) imaging at repetition rates as high as 1 MHz is demonstrated in the NASA Langley 31 in. Mach 10 hypersonic wind tunnel. Approximately 200 time-correlated image sequences of between 10 and 20 individual frames were obtained over eight days of wind tunnel testing spanning two entries in March and September of 2009. The image sequences presented were obtained from the boundary layer of a 20° flat plate model, in which transition was induced using a variety of different shaped protuberances, including a cylinder and a triangle. The high-speed image sequences captured a variety of laminar and transitional flow phenomena, ranging from mostly laminar flow, typically at a lower Reynolds number and/or in the near wall region of the model, to highly transitional flow in which the temporal evolution and progression of characteristic streak instabilities and/or corkscrew-shaped vortices could be clearly identified.

  4. New Solutions to Line-Driven Winds of Hot Massive Stars

    Science.gov (United States)

    Gormaz-Matamala, Alex C.; Curé, Michel; Cidale, Lydia; Venero, Roberto

    2017-11-01

    In the frame of radiation driven wind theory (Castor et al.1975), we present self-consistent hydrodynamical solutions to the line-force parameters (k, α, δ) under LTE conditions. Hydrodynamic models are provided by HydWind (Curé 2004). We evaluate these results with those ones previously found in literature, focusing in different regions of the optical depth to be used to perform the calculations. The values for mass-loss rate and terminal velocity obtained from our calculations are also presented. We also examine the line-force parameters for the case when large changes in ionization throughout the wind occurs (δ-slow solutions, Curé et al.2011).

  5. A new class of galactic discrete gamma ray sources: Chaotic winds of massive stars

    Science.gov (United States)

    Chen, Wan; White, Richard L.

    1992-01-01

    We propose a new class of galactic discrete gamma-ray sources, the chaotic, high mass-loss-rate winds from luminous early-type stars. Early-type stellar winds are highly unstable due to intrinsic line-driven instabilities, and so are permeated by numerous strong shocks. These shocks can accelerate a small fraction of thermal electrons and ions to relativistic energies via the first-order Fermi mechanism. A power-law-like photon spectrum extending from keV to above 10 MeV energies is produced by inverse Compton scattering of the extremely abundant stellar UV photons by the relativistic electrons. In addition, a typical pi(sup 0)-decay gamma-ray spectrum is generated by proton-ion interactions in the densest part of the winds.

  6. ACUTE EFFECTS OF SELF-SELECTED REGIMEN OF RAPID BODY MASS LOSS IN COMBAT SPORTS ATHLETES

    Directory of Open Access Journals (Sweden)

    Jaan Ereline

    2008-06-01

    Full Text Available The purpose of the study was to assess the acute effects of the self-selected regimen of rapid body mass loss (RBML on muscle performance and metabolic response to exercise in combat sports athletes. Seventeen male athletes (20.8 ± 1.0 years; mean ± SD reduced their body mass by 5.1 ± 1.1% within 3 days. The RBML was achieved by a gradual reduction of energy and fluid intake and mild sauna procedures. A battery of tests was performed before (Test 1 and immediately after (Test 2 RBML. The test battery included the measurement of the peak torque of knee extensors for three different speeds, assessment of total work (Wtot performed during a 3-min intermittent intensity knee extension exercise and measurements of blood metabolites (ammonia, lactate, glucose and urea. Absolute peak torque was lower in Test 2 compared with Test 1 at angular velocities of 1.57 rad·s-1 (218.6 ± 40.9 vs. 234.4 ± 42.2 N·m; p = 0.013 and 3.14 rad·s-1 (100.3 ± 27.8 vs. 111.7 ± 26.2 N·m; p = 0.008. The peak torque in relation to body mass remained unchanged for any speed. Absolute Wtot was lower in Test 2 compared with Test 1 (6359 ± 2326 vs. 7452 ± 3080 J; p = 0.003 as well as Wtot in relation to body mass (89.1 ± 29.9 vs. 98.6 ± 36.4 J·kg-1; p = 0.034, respectively. As a result of RBML, plasma urea concentration increased from 4.9 to 5.9 mmol·l-1 (p = 0.003. The concentration of ammonia in a post-test sample in Test 2 tended to be higher in comparison with Test 1 (80.9 ± 29.1 vs. 67.6 ± 26.5 mmol·l-1; p = 0.082. The plasma lactate and glucose responses to exercise were similar in Test 1 and Test 2. We conclude that the self-selected regimen of RBML impairs muscle performance in 3-min intermittent intensity exercise and induces an increase in blood urea concentration in experienced male combat sports athletes

  7. Extratropical Influence of Sea Surface Temperature and Wind on Water Recycling Rate Over Oceans and Coastal Lands

    Science.gov (United States)

    Hu, Hua; Liu, W. Timothy

    1999-01-01

    Water vapor and precipitation are two important parameters confining the hydrological cycle in the atmosphere and over the ocean surface. In the extratropical areas, due to variations of midlatitude storm tracks and subtropical jetstreams, water vapor and precipitation have large variability. Recently, a concept of water recycling rate defined previously by Chahine et al. (GEWEX NEWS, August, 1997) has drawn increasing attention. The recycling rate of moisture is calculated as the ratio of precipitation to total precipitable water (its inverse is the water residence time). In this paper, using multi-sensor spacebased measurements we will study the role of sea surface temperature and ocean surface wind in determining the water recycling rate over oceans and coastal lands. Response of water recycling rate in midlatitudes to the El Nino event will also be discussed. Sea surface temperature data are derived from satellite observations from the Advanced Very High Resolution Radiometer (AVHRR) blended with in situ measurements, available for the period 1982-1998. Global sea surface wind observations are obtained from spaceborne scatterometers aboard on the European Remote-Sensing Satellite (ERS1 and 2), available for the period 1991-1998. Global total precipitable water provided by the NASA Water Vapor Project (NVAP) is available for the period 1988-1995. Global monthly mean precipitation provided by the Global Precipitation Climatology Project (GPCP) is available for the period 1987-1998.

  8. The origin of ultrafast outflows in AGN: Monte Carlo simulations of the wind in PDS 456

    Science.gov (United States)

    Hagino, Kouichi; Odaka, Hirokazu; Done, Chris; Gandhi, Poshak; Watanabe, Shin; Sako, Masao; Takahashi, Tadayuki

    2015-01-01

    Ultrafast outflows (UFOs) are seen in many AGN, giving a possible mode for AGN feedback on to the host galaxy. However, the mechanism(s) for the launch and acceleration of these outflows are currently unknown, with UV line driving apparently strongly disfavoured as the material along the line of sight is so highly ionized that it has no UV transitions. We revisit this issue using the Suzaku X-ray data from PDS 456, an AGN with the most powerful UFO seen in the local Universe. We explore conditions in the wind by developing a new 3D Monte Carlo code for radiation transport. The code only handles highly ionized ions, but the data show the ionization state of the wind is high enough that this is appropriate, and this restriction makes it fast enough to explore parameter space. We reproduce the results of earlier work, confirming that the mass-loss rate in the wind is around 30 per cent of the inferred inflow rate through the outer disc. We show for the first time that UV line driving is likely to be a major contribution to the wind acceleration. The mass-loss rate in the wind matches that predicted from a purely line driven system, and this UV absorption can take place out of the line of sight. Continuum driving should also play a role as the source is close to Eddington. This predicts that the most extreme outflows will be produced from the highest mass accretion rate flows on to high-mass black holes, as observed.

  9. Contributions of natural and anthropogenic radiative forcing to mass loss of Northern Hemisphere mountain glaciers and quantifying their uncertainties.

    Science.gov (United States)

    Hirabayashi, Yukiko; Nakano, Kazunari; Zhang, Yong; Watanabe, Satoshi; Tanoue, Masahiro; Kanae, Shinjiro

    2016-07-20

    Observational evidence indicates that a number of glaciers have lost mass in the past. Given that glaciers are highly impacted by the surrounding climate, human-influenced global warming may be partly responsible for mass loss. However, previous research studies have been limited to analyzing the past several decades, and it remains unclear whether past glacier mass losses are within the range of natural internal climate variability. Here, we apply an optimal fingerprinting technique to observed and reconstructed mass losses as well as multi-model general circulation model (GCM) simulations of mountain glacier mass to detect and attribute past glacier mass changes. An 8,800-year control simulation of glaciers enabled us to evaluate detectability. The results indicate that human-induced increases in greenhouse gases have contributed to the decreased area-weighted average masses of 85 analyzed glaciers. The effect was larger than the mass increase caused by natural forcing, although the contributions of natural and anthropogenic forcing to decreases in mass varied at the local scale. We also showed that the detection of anthropogenic or natural influences could not be fully attributed when natural internal climate variability was taken into account.

  10. Contributions of natural and anthropogenic radiative forcing to mass loss of Northern Hemisphere mountain glaciers and quantifying their uncertainties

    Science.gov (United States)

    Hirabayashi, Yukiko; Nakano, Kazunari; Zhang, Yong; Watanabe, Satoshi; Tanoue, Masahiro; Kanae, Shinjiro

    2016-07-01

    Observational evidence indicates that a number of glaciers have lost mass in the past. Given that glaciers are highly impacted by the surrounding climate, human-influenced global warming may be partly responsible for mass loss. However, previous research studies have been limited to analyzing the past several decades, and it remains unclear whether past glacier mass losses are within the range of natural internal climate variability. Here, we apply an optimal fingerprinting technique to observed and reconstructed mass losses as well as multi-model general circulation model (GCM) simulations of mountain glacier mass to detect and attribute past glacier mass changes. An 8,800-year control simulation of glaciers enabled us to evaluate detectability. The results indicate that human-induced increases in greenhouse gases have contributed to the decreased area-weighted average masses of 85 analyzed glaciers. The effect was larger than the mass increase caused by natural forcing, although the contributions of natural and anthropogenic forcing to decreases in mass varied at the local scale. We also showed that the detection of anthropogenic or natural influences could not be fully attributed when natural internal climate variability was taken into account.

  11. Time-dependent Occurrence Rate of Electromagnetic Cyclotron Waves in the Solar Wind: Evidence for the Effect of Alpha Particles?

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, G. Q.; Feng, H. Q. [Institute of Space Physics, Luoyang Normal University, Luoyang (China); Wu, D. J. [Purple Mountain Observatory, CAS, Nanjing (China); Chu, Y. H. [Institute of Space Science, National Central University, Chungli, Taiwan (China); Huang, J. [CAS Key Laboratory of Solar Activity, National Astronomical Observatories, Beijing (China)

    2017-09-20

    Previous studies revealed that electromagnetic cyclotron waves (ECWs) near the proton cyclotron frequency exist widely in the solar wind, and the majority of ECWs are left-handed (LH) polarized waves. Using the magnetic field data from the STEREO mission, this Letter carries out a survey of ECWs over a long period of 7 years and calculates the occurrence rates of ECWs with different polarization senses. Results show that the occurrence rate is nearly a constant for the ECWs with right-handed polarization, but it varies significantly for the ECWs with LH polarization. Further investigation of plasma conditions reveals that the LH ECWs take place preferentially in a plasma characterized by higher temperature, lower density, and larger velocity. Some considerable correlations between the occurrence rate of LH ECWs and the properties of ambient plasmas are discussed. The present research may provide evidence for the effect of alpha particles on the generation of ECWs.

  12. ALMA Compact Array observations of the Fried Egg nebula: Evidence for large-scale asymmetric mass-loss from the yellow hypergiant IRAS 17163-3907.

    Science.gov (United States)

    Wallström, S H J; Lagadec, E; Muller, S; Black, J H; Cox, N L J; Galván-Madrid, R; Justtanont, K; Longmore, S; Olofsson, H; Oudmaijer, R D; Quintana-Lacaci, G; Szczerba, R; Vlemmings, W; van Winckel, H; Zijlstra, A

    2017-01-10

    Yellow hypergiants are rare and represent a fast evolutionary stage of massive evolved stars. That evolutionary phase is characterised by a very intense mass loss, the understanding of which is still very limited. Here we report ALMA Compact Array observations of a 50″-mosaic toward the Fried Egg nebula, around one of the few Galactic yellow hypergiants IRAS 17163-3907. The emission from the 12 CO J=2-1 line, H30 α recombination line, and continuum is imaged at a resolution of ~8″, revealing the morphology of the molecular environment around the star. The continuum emission is unresolved and peaks at the position of the star. The radio recombination line H30 α shows unresolved emission at the star, with an approximately gaussian spectrum centered on a velocity of 21±3 km s -1 with a width of 57±6 km s -1 . In contrast, the CO 2-1 emission is complex and decomposes into several components beyond the contamination from interstellar gas in the line of sight. The CO spectrum toward the star is a broad plateau, centered at the systemic velocity of +18 km s -1 and with an expansion velocity of 100±10 km s -1 . Assuming isotropic and constant mass-loss, we estimate a mass-loss rate of 8±1.5 ×10 -5 M ⊙ yr -1 . At a radius of 25″ from the star, we detect CO emission associated with the dust ring previously imaged by Herschel . The kinematics of this ring, however, is not consistent with an expanding shell, but show a velocity gradient of v sys ±20 km s -1 . In addition, we find a puzzling bright feature radially connecting the star to the CO ring, at a velocity of +40 km s -1 relative to the star. This spur feature may trace a unidirectional ejection event from the star. Our ACA observations reveal the complex morphology around IRAS 17163 and illustrate the breakthroughs that ALMA will bring to the field of massive stellar evolution.

  13. Conceptual design of a fixed-pitch wind turbine generator system rated at 400 kilowatts

    Science.gov (United States)

    Pintz, A.; Kasuba, R.; Spring, J.

    1984-01-01

    The design and cost aspects of a fixed pitch, 400 kW Wind Turbine Generator (WTG) concept are presented. Improvements in reliability and cost reductions were achieved with fixed pitch operation and by incorporating recent advances in WTG technology. The specifications for this WTG concept were as follows: (1) A fixed pitch, continuous wooden rotor was to be provided by the Gougeon Bros. Co. (2) An 8 leg hyperboloid tower that showed promise as a low cost structure was to be used. (3) Only commercially available components and parts that could be easily fabricated were to be considered. (4) Design features deemed desirable based on recent NASA research efforts were to be incorporated. Detailed costs and weight estimates were prepared for the second machine and a wind farm of 12 WTG's. The calculated cost of energy for the fixed pitch, twelve unit windfarm is 11.5 cents/kW hr not including the cost of land and access roads. The study shows feasibility of fixed pitch, intermediate power WTG operation.

  14. ON THE LAUNCHING AND STRUCTURE OF RADIATIVELY DRIVEN WINDS IN WOLF–RAYET STARS

    Energy Technology Data Exchange (ETDEWEB)

    Ro, Stephen; Matzner, Christopher D., E-mail: ro@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)

    2016-04-20

    Hydrostatic models of Wolf–Rayet (WR) stars typically contain low-density outer envelopes that inflate the stellar radii by a factor of several and are capped by a denser shell of gas. Inflated envelopes and density inversions are hallmarks of envelopes that become super-Eddington as they cross the iron-group opacity peak, but these features disappear when mass loss is sufficiently rapid. We re-examine the structures of steady, spherically symmetric wind solutions that cross a sonic point at high optical depth, identifying the physical mechanism through which the outflow affects the stellar structure, and provide an improved analytical estimate for the critical mass-loss rate above which extended structures are erased. Weak-flow solutions below this limit resemble hydrostatic stars even in supersonic zones; however, we infer that these fail to successfully launch optically thick winds. WR envelopes will therefore likely correspond to the strong, compact solutions. We also find that wind solutions with negligible gas pressure are stably stratified at and below the sonic point. This implies that convection is not the source of variability in WR stars, as has been suggested; however, acoustic instabilities provide an alternative explanation. Our solutions are limited to high optical depths by our neglect of Doppler enhancements to the opacity, and do not account for acoustic instabilities at high Eddington factors; yet, they do provide useful insights into WR stellar structures.

  15. New Mass-Conserving Bedrock Topography for Pine Island Glacier Impacts Simulated Decadal Rates of Mass Loss

    Science.gov (United States)

    Nias, I. J.; Cornford, S. L.; Payne, A. J.

    2018-04-01

    High-resolution ice flow modeling requires bedrock elevation and ice thickness data, consistent with one another and with modeled physics. Previous studies have shown that gridded ice thickness products that rely on standard interpolation techniques (such as Bedmap2) can be inconsistent with the conservation of mass, given observed velocity, surface elevation change, and surface mass balance, for example, near the grounding line of Pine Island Glacier, West Antarctica. Using the BISICLES ice flow model, we compare results of simulations using both Bedmap2 bedrock and thickness data, and a new interpolation method that respects mass conservation. We find that simulations using the new geometry result in higher sea level contribution than Bedmap2 and reveal decadal-scale trends in the ice stream dynamics. We test the impact of several sliding laws and find that it is at least as important to accurately represent the bedrock and initial ice thickness as the choice of sliding law.

  16. Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

    Science.gov (United States)

    Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem

    2012-01-01

    Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

  17. Role of protein and amino acids in promoting lean mass accretion with resistance exercise and attenuating lean mass loss during energy deficit in humans.

    Science.gov (United States)

    Churchward-Venne, Tyler A; Murphy, Caoileann H; Longland, Thomas M; Phillips, Stuart M

    2013-08-01

    Amino acids are major nutrient regulators of muscle protein turnover. After protein ingestion, hyperaminoacidemia stimulates increased rates of skeletal muscle protein synthesis, suppresses muscle protein breakdown, and promotes net muscle protein accretion for several hours. These acute observations form the basis for strategized protein intake to promote lean mass accretion, or prevent lean mass loss over the long term. However, factors such as protein dose, protein source, and timing of intake are important in mediating the anabolic effects of amino acids on skeletal muscle and must be considered within the context of evaluating the reported efficacy of long-term studies investigating protein supplementation as part of a dietary strategy to promote lean mass accretion and/or prevent lean mass loss. Current research suggests that dietary protein supplementation can augment resistance exercise-mediated gains in skeletal muscle mass and strength and can preserve skeletal muscle mass during periods of diet-induced energy restriction. Perhaps less appreciated, protein supplementation can augment resistance training-mediated gains in skeletal muscle mass even in individuals habitually consuming 'adequate' (i.e., >0.8 g kg⁻¹ day⁻¹) protein. Additionally, overfeeding energy with moderate to high-protein intake (15-25 % protein or 1.8-3.0 g kg⁻¹ day⁻¹) is associated with lean, but not fat mass accretion, when compared to overfeeding energy with low protein intake (5 % protein or ~0.68 g kg⁻¹ day⁻¹). Amino acids represent primary nutrient regulators of skeletal muscle anabolism, capable of enhancing lean mass accretion with resistance exercise and attenuating the loss of lean mass during periods of energy deficit, although factors such as protein dose, protein source, and timing of intake are likely important in mediating these effects.

  18. Contributions of solar-wind induced potential sputtering to the lunar surface erosion rate and it's exosphere

    Science.gov (United States)

    Alnussirat, S. T.; Barghouty, A. F.; Edmunson, J. E.; Sabra, M. S.; Rickman, D. L.

    2018-04-01

    Sputtering of lunar regolith by solar-wind protons and heavy ions with kinetic energies of about 1 keV/amu is an important erosive process that affects the lunar surface and exosphere. It plays an important role in changing the chemical composition and thickness of the surface layer, and in introducing material into the exosphere. Kinetic sputtering is well modeled and understood, but understanding of mechanisms of potential sputtering has lagged behind. In this study we differentiate the contributions of potential sputtering from the standard (kinetic) sputtering in changing the chemical composition and erosion rate of the lunar surface. Also we study the contribution of potential sputtering in developing the lunar exosphere. Our results show that potential sputtering enhances the total characteristic sputtering erosion rate by about 44%, and reduces sputtering time scales by the same amount. Potential sputtering also introduces more material into the lunar exosphere.

  19. Aeroelastic impact of above-rated wave-induced structural motions on the near-wake stability of a floating offshore wind turbine rotor

    Science.gov (United States)

    Rodriguez, Steven; Jaworski, Justin

    2017-11-01

    The impact of above-rated wave-induced motions on the stability of floating offshore wind turbine near-wakes is studied numerically. The rotor near-wake is generated using a lifting-line free vortex wake method, which is strongly coupled to a finite element solver for kinematically nonlinear blade deformations. A synthetic time series of relatively high-amplitude/high-frequency representative of above-rated conditions of the NREL 5MW referece wind turbine is imposed on the rotor structure. To evaluate the impact of these above-rated conditions, a linear stability analysis is first performed on the near wake generated by a fixed-tower wind turbine configuration at above-rated inflow conditions. The platform motion is then introduced via synthetic time series, and a stability analysis is performed on the wake generated by the floating offshore wind turbine at the same above-rated inflow conditions. The stability trends (disturbance modes versus the divergence rate of vortex structures) of the two analyses are compared to identify the impact that above-rated wave-induced structural motions have on the stability of the floating offshore wind turbine wake.

  20. The solar wind in time: a change in the behaviour of older winds?

    Science.gov (United States)

    O'Fionnagáin, D.; Vidotto, A. A.

    2018-05-01

    In this paper, we model the wind of solar analogues at different ages to investigate the evolution of the solar wind. Recently, it has been suggested that winds of solar type stars might undergo a change in properties at old ages, whereby stars older than the Sun would be less efficient in carrying away angular momentum than what was traditionally believed. Adding to this, recent observations suggest that old solar-type stars show a break in coronal properties, with a steeper decay in X-ray luminosities and temperatures at older ages. We use these X-ray observations to constrain the thermal acceleration of winds of solar analogues. Our sample is based on the stars from the `Sun in Time' project with ages between 120 and 7000 Myr. The break in X-ray properties leads to a break in wind mass-loss rates (\\dot{M}) at roughly 2 Gyr, with \\dot{M} (t 2 Gyr) ∝ t-3.9. This steep decay in \\dot{M} at older ages could be the reason why older stars are less efficient at carrying away angular momentum, which would explain the anomalously rapid rotation observed in older stars. We also show that none of the stars in our sample would have winds dense enough to produce thermal emission above 1-2 GHz, explaining why their radio emissions have not yet been detected. Combining our models with dynamo evolution models for the magnetic field of the Earth, we find that, at early ages (≈100 Myr), our Earth had a magnetosphere that was three or more times smaller than its current size.

  1. Mass loss from OB supergiants in x-ray binary systems

    International Nuclear Information System (INIS)

    Alme, M.L.; Wilson, J.R.

    1975-01-01

    A study of the atmospheres of OB supergiants in x-ray binary systems indicates that when the stellar surface is close enough to the saddle in the gravitational potential to provide a mass transfer rate adequate to power a compact x-ray source, large-amplitude variations in the rate of mass flow occur. 9 references

  2. Volcanic eruptions on Io - Implications for surface evolution and mass loss

    Science.gov (United States)

    Johnson, T. V.; Soderblom, L. A.

    1982-01-01

    Active volcanism on Io results in a continual resurfacing of the satellite. Analysis of required burial rates to erase impact craters, the mass production in the observed plumes, and the energy requirements for the volcanic activity suggest resurfacing rates of 0.001 to 10 cm/yr in recent geologic time. If this rate is typical of the last 4.5 Gyr, then extensive recycling of the upper crust and mantle must have occurred. The currently estimated loss rate of S, O, and Na from Io into the magnetosphere corresponds to only a small fraction of the resurfacing rate and should not have resulted in either extensive erosion or total depletion of any of the escaping species.

  3. Directionality Effects of Aligned Wind and Wave Loads on a Y-Shape Semi-Submersible Floating Wind Turbine under Rated Operational Conditions

    Directory of Open Access Journals (Sweden)

    Shengtao Zhou

    2017-12-01

    Full Text Available The Y-shape (triangular semi-submersible foundation has been adopted by most of the built full-scale floating wind turbines, such as Windfloat, Fukushima Mirai and Shimpuu. Considering the non-fully-symmetrical shape and met-ocean condition, the foundation laying angle relative to wind/wave directions will not only influence the downtime and power efficiency of the floating turbine, but also the strength and fatigue safety of the whole structure. However, the dynamic responses induced by various aligned wind and wave load directions have scarcely been investigated comparatively before. In our study, the directionality effects are investigated by means of combined wind and wave tests and coupled multi-body simulations. By comparing the measured data in three load directions, it is found that the differences of platform motions are mainly derived from the wave loads and larger pitch motion can always be observed in one of the directions. To make certain the mechanism underlying the observed phenomena, a coupled multi-body dynamic model of the floating wind turbine is established and validated. The numerical results demonstrate that the second-order hydrodynamic forces contribute greatly to the directionality distinctions for surge and pitch, and the first-order hydrodynamic forces determine the variations of tower base bending moments and nacelle accelerations. These findings indicate the directionality effects should be predetermined comprehensively before installation at sea, which is important for the operation and maintenance of the Y-shape floating wind turbines.

  4. The extraordinary mass-loss bubble G2.4 + 1.4 and its central star

    International Nuclear Information System (INIS)

    Dopita, M.A.; Mcgregor, P.J.; Rawlings, S.J.; Lozinskaia, T.A.

    1990-01-01

    Data are presented on the WR 102 star and the surrounding nebula (G2.4 + 1.4). It is shown that WR 102 and the nebula are associated, the nebula being a mass-loss bubble powered by the central star. From a photoionization analysis of the surrounding nebula, the star was determined to have the following parameters: log T(ion) = 5.20 + or - 0.05; log (R/solar R) = about 0.05; and log (L/solar L) = 5.85 + or - 0.20. 42 refs

  5. Effect of control activity on blade fatigue damage rate for a small horizontal axis wind turbine

    Energy Technology Data Exchange (ETDEWEB)

    Riddle, A F; Freris, L L; Graham, J M.R. [Imperial College, London (United Kingdom)

    1996-09-01

    An experiment into the effect of control activity on blade fatigue damage rate for a 5 kW, two bladed, teetered HAWT has been performed. It has been shown that control activity influences the distribution of strain in the blade but that in a high rotor speed, high cycle fatigue regime this has little influence on damage rate. The experiment was conducted on a small test turbine by implementing variable speed stall, pitch and yaw control strategies and measuring blade flapwise strain response at root and midspan locations. A full description of the investigation is provided. (au)

  6. Short-term variability and mass loss in Be stars. III. BRITE and SMEI satellite photometry of 28 Cygni

    Science.gov (United States)

    Baade, D.; Pigulski, A.; Rivinius, Th.; Carciofi, A. C.; Panoglou, D.; Ghoreyshi, M. R.; Handler, G.; Kuschnig, R.; Moffat, A. F. J.; Pablo, H.; Popowicz, A.; Wade, G. A.; Weiss, W. W.; Zwintz, K.

    2018-03-01

    Context. Be stars are important reference laboratories for the investigation of viscous Keplerian discs. In some cases, the disc feeder mechanism involves a combination of non-radial pulsation (NRP) modes. Aims: We seek to understand whether high-cadence photometry can shed further light on the role of NRP modes in facilitating rotation-supported mass loss. Methods: The BRITE-Constellation of nanosatellites obtained mmag photometry of 28 Cygni for 11 months in 2014-2016. We added observations with the Solar Mass Ejection Imager (SMEI) in 2003-2010 and 118 Hα line profiles, half of which were from 2016. Results: For decades, 28 Cyg has exhibited four large-amplitude frequencies: two closely spaced frequencies of spectroscopically confirmed g modes near 1.5 c/d, one slightly lower exophotospheric (Štefl) frequency, and at 0.05 c/d the difference (Δ) frequency between the two g modes. This top-level framework is indistinguishable from η Cen (Paper I), which is also very similar in spectral type, rotation rate, and viewing angle. The circumstellar (Štefl) frequency alone does not seem to be affected by the Δ frequency. The amplitude of the Δ frequency undergoes large variations; around maximum the amount of near-circumstellar matter is increased and the amplitude of the Štefl frequency grows by a factor of a few. During such brightenings dozens of transient spikes appear in the frequency spectrum; these spikes are concentrated into three groups. Only 11 frequencies were common to all years of BRITE observations. Conclusions: Be stars seem to be controlled by several coupled clocks, most of which are not very regular on timescales of weeks to months but function for decades. The combination of g modes to the slow Δ variability and/or the atmospheric response to it appears significantly non-linear. As in η Cen, the Δ variability seems to be mainly responsible for the modulation of the star-to-disc mass transfer in 28 Cyg. A hierarchical set of Δ frequencies

  7. Metal-enhanced galactic winds. I

    International Nuclear Information System (INIS)

    Vader, J.P.

    1986-01-01

    Supernova-driven gas loss during the early evolution of elliptical galaxies is considered as a possible explanation for the correlations among the observed chemical and structural properties of these systems. Mass loss from systems with a chemically homogeneous interstellar medium does not work. It is pointed out that supernova-driven winds are in fact metal-enhanced with respect to the star-forming gas because the metal production of any supernova that drives the wind is directly flushed out of the galaxy. The fraction of the total metal production lost in the wind is thus at least as large as the fraction epsilon(z) of supernovae that power the wind, independent of the total mass loss. As a corollary, the yield of heavy elements that are recycled in the galaxy is reduced by a factor 1 - epsilon(z). Metal-enhanced galactic winds, which can carry away a large fraction of the metal production in spite of a moderate total mass loss, offer a promising explanation for the low metallicities of dwarf elliptical galaxies. 62 references

  8. Large dust grains in the wind of VY Canis Majoris

    Science.gov (United States)

    Scicluna, P.; Siebenmorgen, R.; Wesson, R.; Blommaert, J. A. D. L.; Kasper, M.; Voshchinnikov, N. V.; Wolf, S.

    2015-12-01

    Massive stars live short lives, losing large amounts of mass through their stellar wind. Their mass is a key factor determining how and when they explode as supernovae, enriching the interstellar medium with heavy elements and dust. During the red supergiant phase, mass-loss rates increase prodigiously, but the driving mechanism has proven elusive. Here we present high-contrast optical polarimetric-imaging observations of the extreme red supergiant VY Canis Majoris and its clumpy, dusty, mass-loss envelope, using the new extreme-adaptive-optics instrument SPHERE at the VLT. These observations allow us to make the first direct and unambiguous detection of submicron dust grains in the ejecta; we derive an average grain radius ~0.5 μm, 50 times larger than in the diffuse ISM, large enough to receive significant radiation pressure by photon scattering. We find evidence for varying grain sizes throughout the ejecta, highlighting the dynamical nature of the envelope. Grains with 0.5 μm sizes are likely to reach a safe distance from the eventual explosion of VY Canis Majoris; hence it may inject upwards of 10-2 M⊙ of dust into the ISM. Based on observations made with European Southern Observatory (ESO) telescopes at the La Silla Paranal Observatory under program 60.A-9368(A).Appendix A is available in electronic form at http://www.aanda.org

  9. THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. II. DUST PROPERTIES FOR OXYGEN-RICH ASYMPTOTIC GIANT BRANCH STARS

    International Nuclear Information System (INIS)

    Sargent, Benjamin A.; Meixner, M.; Gordon, Karl D.; Srinivasan, S.; Kemper, F.; Woods, Paul M.; Tielens, A. G. G. M.; Speck, A. K.; Matsuura, M.; Bernard, J.-Ph.; Hony, S.; Indebetouw, R.; Marengo, M.; Sloan, G. C.

    2010-01-01

    900 K and 430 K, respectively, and with optical depths at 10 μm through the shells of 0.095 and 0.012, respectively. The models compute the dust mass-loss rates for the two stars to be 2.0 x 10 -9 M sun yr -1 and 2.3 x 10 -9 M sun yr -1 , respectively. When a dust-to-gas mass ratio of 0.002 is assumed for SSTSAGE052206 and HV 5715, the dust mass-loss rates imply total mass-loss rates of 1.0 x 10 -6 M sun yr -1 and 1.2 x 10 -6 M sun yr -1 , respectively. These properties of the dust shells and stars, as inferred from our models of the two stars, are found to be consistent with properties observed or assumed by detailed studies of other O-rich AGB stars in the LMC and elsewhere.

  10. A Method for Increasing the Operating Limit Capacity of Wind Farms Using Battery Energy Storage Systems with Rate of Change of Frequency

    Directory of Open Access Journals (Sweden)

    Dae-Hee Son

    2018-03-01

    Full Text Available In this paper, the appropriate rated power of battery energy storage system (BESS and the operating limit capacity of wind farms are determined considering power system stability, and novel output control methods of BESS and wind turbines are proposed. The rated power of BESS is determined by correlation with the kinetic energy that can be released from wind turbines and synchronous generators when a disturbance occurs in the power system. After the appropriate rated power of BESS is determined, a novel control scheme for quickly responding to disturbances should be applied to BESS. It is important to compensate the insufficient power difference between demand and supply more quickly after a disturbance, and for this purpose, BESS output is controlled using the rate of change of frequency (ROCOF. Generally, BESS output is controlled by the frequency droop control (FDC, however if ROCOF falls below the threshold, BESS output increases sharply. Under this control for BESS, the power system’s stability can be improved and the operating limit capacity of wind farms can be increased. The operating limit capacity is determined as the smaller of technical limit and dynamic limit capacity. The technical limit capacity is calculated by the difference between the maximum power of the generators connected to the power system and the magnitude of loads, and the dynamic limit capacity is determined by considering dynamic stability of a power system frequency when the wind turbines drop out from a power system. Output of the dynamic model developed for wind turbine is based on the operating limit capacity and is controlled by blade pitch angle. To validate the effectiveness of the proposed control method, different case studies are conducted, with simulations for BESS and wind turbine using Power System Simulation for Engineering (PSS/E.

  11. Weaving the history of the solar wind with magnetic field lines

    Science.gov (United States)

    Alvarado Gomez, Julian

    2017-08-01

    Despite its fundamental role for the evolution of the solar system, our observational knowledge of the wind properties of the young Sun comes from a single stellar observation. This unexpected fact for a field such as astrophysics arises from the difficulty of detecting Sun-like stellar winds. Their detection relies on the appearance of an astrospheric signature (from the stellar wind-ISM interaction region), visible only with the aid of high-resolution HST Lyman-alpha spectra. However, observations and modelling of the present day Sun have revealed that magnetic fields constitute the main driver of the solar wind, providing guidance on how such winds would look like back in time. In this context we propose observations of four young Sun-like stars in order to detect their astrospheres and characterise their stellar winds. For all these objects we have recovered surface magnetic field maps using the technique of Zeeman Doppler Imaging, and developed detailed wind models based on these observed field distributions. Even a single detection would represent a major step forward for our understanding of the history of the solar wind, and the outflows in more active stars. Mass loss rate estimates from HST will be confronted with predictions from realistic models of the corona/stellar wind. In one of our objects the comparison would allow us to quantify the wind variability induced by the magnetic cycle of a star, other than the Sun, for the first time. Three of our targets are planet hosts, thus the HST spectra would also provide key information on the high-energy environment of these systems, guaranteeing their legacy value for the growing field of exoplanet characterisation.

  12. Wind energy.

    Science.gov (United States)

    Leithead, W E

    2007-04-15

    From its rebirth in the early 1980s, the rate of development of wind energy has been dramatic. Today, other than hydropower, it is the most important of the renewable sources of power. The UK Government and the EU Commission have adopted targets for renewable energy generation of 10 and 12% of consumption, respectively. Much of this, by necessity, must be met by wind energy. The US Department of Energy has set a goal of 6% of electricity supply from wind energy by 2020. For this potential to be fully realized, several aspects, related to public acceptance, and technical issues, related to the expected increase in penetration on the electricity network and the current drive towards larger wind turbines, need to be resolved. Nevertheless, these challenges will be met and wind energy will, very likely, become increasingly important over the next two decades. An overview of the technology is presented.

  13. SN 2008D: A WOLF-RAYET EXPLOSION THROUGH A THICK WIND

    International Nuclear Information System (INIS)

    Svirski, Gilad; Nakar, Ehud

    2014-01-01

    Supernova (SN) 2008D/XRT 080109 is considered to be the only direct detection of a shock breakout from a regular SN to date. While a breakout interpretation was favored by several papers, inconsistencies remain between the observations and current SN shock breakout theory. Most notably, the duration of the luminous X-ray pulse is considerably longer than expected for a spherical breakout through the surface of a type Ibc SN progenitor, and the X-ray radiation features, mainly its flat spectrum and its luminosity evolution, are enigmatic. We apply a recently developed theoretical model for the observed radiation from a Wolf-Rayet SN exploding through a thick wind and show that it naturally explains all of the observed features of SN 2008D X-ray emission, including the energetics, the spectrum, and the detailed luminosity evolution. We find that the inferred progenitor and SN parameters are typical for an exploding Wolf-Rayet. A comparison of the wind density found at the breakout radius and the density at much larger radii, as inferred by late radio observations, suggests an enhanced mass-loss rate taking effect about 10 days prior to the SN explosion. This finding joins accumulating evidence for a possible late phase in the stellar evolution of massive stars, involving vigorous mass loss a short time before the SN explosion

  14. SN 2008D: A WOLF-RAYET EXPLOSION THROUGH A THICK WIND

    Energy Technology Data Exchange (ETDEWEB)

    Svirski, Gilad; Nakar, Ehud [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

    2014-06-10

    Supernova (SN) 2008D/XRT 080109 is considered to be the only direct detection of a shock breakout from a regular SN to date. While a breakout interpretation was favored by several papers, inconsistencies remain between the observations and current SN shock breakout theory. Most notably, the duration of the luminous X-ray pulse is considerably longer than expected for a spherical breakout through the surface of a type Ibc SN progenitor, and the X-ray radiation features, mainly its flat spectrum and its luminosity evolution, are enigmatic. We apply a recently developed theoretical model for the observed radiation from a Wolf-Rayet SN exploding through a thick wind and show that it naturally explains all of the observed features of SN 2008D X-ray emission, including the energetics, the spectrum, and the detailed luminosity evolution. We find that the inferred progenitor and SN parameters are typical for an exploding Wolf-Rayet. A comparison of the wind density found at the breakout radius and the density at much larger radii, as inferred by late radio observations, suggests an enhanced mass-loss rate taking effect about 10 days prior to the SN explosion. This finding joins accumulating evidence for a possible late phase in the stellar evolution of massive stars, involving vigorous mass loss a short time before the SN explosion.

  15. RW Aur A FROM THE X-WIND POINT OF VIEW: GENERAL FEATURES

    International Nuclear Information System (INIS)

    Liu, Chun-Fan; Shang, Hsien

    2012-01-01

    In this paper, the RW Aur A microjet is studied from the point of view of X-wind models. The archived Hubble Space Telescope/STIS spectra of the optical forbidden lines [O I], [S II], and [N II] from RW Aur A, taken in Cycle 8 with seven parallel slits along the jet axis, spaced at 0.''07 apart, were analyzed. Images, position-velocity diagrams, and line ratios among the species were constructed, and compared with synthetic observations generated by selected solutions of the X-wind. Prominent features arising in a steady-state X-wind could be identified within the convolved images and position-velocity diagrams, including FWHM and high-velocity peaks on both of the redshifted and blueshifted jets. The well-known asymmetric velocity profiles of the opposite jets were built into the selected models. We discuss model selections within the existing uncertainties of the stellar parameters and inclination angle of the system. In this framework, the mass-loss rates that were inferred to be decreasing along the jet axis in the literature are the results of slowly decreasing excitation conditions and electron density profiles. Despite the apparent asymmetry in the terminal velocities, line intensities and mass-loss rates, the average linear momenta from the opposite sides of the jet are actually balanced. These previously hard-to-explain features of the asymmetric RW Aur A jet system can now be interpreted in a different but self-consistent manner within the X-wind framework.

  16. RW Aur A FROM THE X-WIND POINT OF VIEW: GENERAL FEATURES

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chun-Fan [Graduate Institute of Astrophysics, National Taiwan University, Taipei 10617, Taiwan (China); Shang, Hsien, E-mail: shang@asiaa.sinica.edu.tw [Theoretical Institute for Advanced Research in Astrophysics (TIARA), Academia Sinica, P.O. Box 23-141, Taipei 10641, Taiwan (China)

    2012-12-20

    In this paper, the RW Aur A microjet is studied from the point of view of X-wind models. The archived Hubble Space Telescope/STIS spectra of the optical forbidden lines [O I], [S II], and [N II] from RW Aur A, taken in Cycle 8 with seven parallel slits along the jet axis, spaced at 0.''07 apart, were analyzed. Images, position-velocity diagrams, and line ratios among the species were constructed, and compared with synthetic observations generated by selected solutions of the X-wind. Prominent features arising in a steady-state X-wind could be identified within the convolved images and position-velocity diagrams, including FWHM and high-velocity peaks on both of the redshifted and blueshifted jets. The well-known asymmetric velocity profiles of the opposite jets were built into the selected models. We discuss model selections within the existing uncertainties of the stellar parameters and inclination angle of the system. In this framework, the mass-loss rates that were inferred to be decreasing along the jet axis in the literature are the results of slowly decreasing excitation conditions and electron density profiles. Despite the apparent asymmetry in the terminal velocities, line intensities and mass-loss rates, the average linear momenta from the opposite sides of the jet are actually balanced. These previously hard-to-explain features of the asymmetric RW Aur A jet system can now be interpreted in a different but self-consistent manner within the X-wind framework.

  17. Understanding the Role of Wind in Reducing the Surface Mass Balance Estimates over East Antarctica

    Science.gov (United States)

    Das, I.; Scambos, T. A.; Koenig, L.; Creyts, T. T.; Bell, R. E.; van den Broeke, M. R.; Lenaerts, J.; Paden, J. D.

    2014-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. An improved estimate of surface mass balance must include the significant role near-surface wind plays in the sublimation and redistribution of snow across Antarctica. We have developed an empirical model based on airborne radar and lidar observations, and modeled surface mass balance and wind fields to produce a continent-wide prediction of wind-scour zones over Antarctica. These zones have zero to negative surface mass balance, are located over locally steep ice sheet areas (>0.002) and controlled by bedrock topography. The near-surface winds accelerate over these zones, eroding and sublimating the surface snow. This scouring results in numerous localized regions (≤ 200 km2) with reduced surface accumulation. Each year, tens of gigatons of snow on the Antarctic ice sheet are ablated by persistent near-surface katabatic winds over these wind-scour zones. Large uncertainties remain in the surface mass balance estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss through sublimation or redistribution over the wind-scour zones. In this study, we integrate Operation IceBridge's snow radar over the Recovery Ice Stream with a series of ice core dielectric and depth-density profiles for improved surface mass balance estimates that reflect the mass loss over the wind-scour zones. Accurate surface mass balance estimates from snow radars require spatially variable depth-density profiles. Using an ensemble of firn cores, MODIS-derived surface snow grain size, modeled accumulation rates and surface temperatures from RACMO2, we assemble spatially variable depth-density profiles and use our mapping of snow density variations to estimate layer mass and net accumulation rates from snow radar layer data. Our study improves the quantification of

  18. A model on CME/Flare initiation: Loss of Equilibrium caused by mass loss of quiescent prominences

    Science.gov (United States)

    Miley, George; Chon Nam, Sok; Kim, Mun Song; Kim, Jik Su

    2015-08-01

    Coronal Mass Ejections (CMEs) model should give an answer to enough energy storage for giant bulk plasma into interplanetary space to escape against the sun’s gravitation and its explosive eruption. Advocates of ‘Mass Loading’ model (e.g. Low, B. 1996, SP, 167, 217) suggested a simple mechanism of CME initiation, the loss of mass from a prominence anchoring magnetic flux rope, but they did not associate the mass loss with the loss of equilibrium. The catastrophic loss of equilibrium model is considered as to be a prospective CME/Flare model to explain sudden eruption of magnetic flux systems. Isenberg, P. A., et al (1993, ApJ, 417, 368)developed ideal magnetohydrodynamic theory of the magnetic flux rope to show occurrence of catastrophic loss of equilibrium according to increasing magnetic flux transported into corona.We begin with extending their study including gravity on prominence’s material to obtain equilibrium curves in case of given mass parameters, which are the strengths of the gravitational force compared with the characteristic magnetic force. Furthermore, we study quasi-static evolution of the system including massive prominence flux rope and current sheet below it to obtain equilibrium curves of prominence’s height according to decreasing mass parameter in a properly fixed magnetic environment. The curves show equilibrium loss behaviors to imply that mass loss result in equilibrium loss. Released fractions of magnetic energy are greater than corresponding zero-mass case. This eruption mechanism is expected to be able to apply to the eruptions of quiescent prominences, which is located in relatively weak magnetic environment with 105 km of scale length and 10G of photospheric magnetic field.

  19. Time-Course of Muscle Mass Loss, Damage, and Proteolysis in Gastrocnemius following Unloading and Reloading: Implications in Chronic Diseases

    Science.gov (United States)

    Chacon-Cabrera, Alba; Lund-Palau, Helena; Gea, Joaquim; Barreiro, Esther

    2016-01-01

    Background Disuse muscle atrophy is a major comorbidity in patients with chronic diseases including cancer. We sought to explore the kinetics of molecular mechanisms shown to be involved in muscle mass loss throughout time in a mouse model of disuse muscle atrophy and recovery following immobilization. Methods Body and muscle weights, grip strength, muscle phenotype (fiber type composition and morphometry and muscle structural alterations), proteolysis, contractile proteins, systemic troponin I, and mitochondrial content were assessed in gastrocnemius of mice exposed to periods (1, 2, 3, 7, 15 and 30 days) of non-invasive hindlimb immobilization (plastic splint, I cohorts) and in those exposed to reloading for different time-points (1, 3, 7, 15, and 30 days, R cohorts) following a seven-day period of immobilization. Groups of control animals were also used. Results Compared to non-exposed controls, muscle weight, limb strength, slow- and fast-twitch cross-sectional areas, mtDNA/nDNA, and myosin content were decreased in mice of I cohorts, whereas tyrosine release, ubiquitin-proteasome activity, muscle injury and systemic troponin I levels were increased. Gastrocnemius reloading following splint removal improved muscle mass loss, strength, fiber atrophy, injury, myosin content, and mtDNA/nDNA, while reducing ubiquitin-proteasome activity and proteolysis. Conclusions A consistent program of molecular and cellular events leading to reduced gastrocnemius muscle mass and mitochondrial content and reduced strength, enhanced proteolysis, and injury, was seen in this non-invasive mouse model of disuse muscle atrophy. Unloading of the muscle following removal of the splint significantly improved the alterations seen during unloading, characterized by a specific kinetic profile of molecular events involved in muscle regeneration. These findings have implications in patients with chronic diseases including cancer in whom physical activity may be severely compromised. PMID

  20. Turbulence Dissipation Rates in the Planetary Boundary Layer from Wind Profiling Radars and Mesoscale Numerical Weather Prediction Models during WFIP2

    Science.gov (United States)

    Bianco, L.; McCaffrey, K.; Wilczak, J. M.; Olson, J. B.; Kenyon, J.

    2016-12-01

    When forecasting winds at a wind plant for energy production, the turbulence parameterizations in the forecast models are crucial for understanding wind plant performance. Recent research shows that the turbulence (eddy) dissipation rate in planetary boundary layer (PBL) parameterization schemes introduces significant uncertainty in the Weather Research and Forecasting (WRF) model. Thus, developing the capability to measure dissipation rates in the PBL will allow for identification of weaknesses in, and improvements to the parameterizations. During a preliminary field study at the Boulder Atmospheric Observatory in spring 2015, a 915-MHz wind profiling radar (WPR) measured dissipation rates concurrently with sonic anemometers mounted on a 300-meter tower. WPR set-up parameters (e.g., spectral resolution), post-processing techniques (e.g., filtering for non-atmospheric signals), and spectral averaging were optimized to capture the most accurate Doppler spectra for measuring spectral widths for use in the computation of the eddy dissipation rates. These encouraging results lead to the implementation of the observing strategy on a 915-MHz WPR in Wasco, OR, operating as part of the Wind Forecasting Improvement Project 2 (WFIP2). These observations are compared to dissipation rates calculated from the High-Resolution Rapid Refresh model, a WRF-based mesoscale numerical weather prediction model run for WFIP2 at 3000 m horizontal grid spacing and with a nest, which has 750-meter horizontal grid spacing, in the complex terrain region of the Columbia River Gorge. The observed profiles of dissipation rates are used to evaluate the PBL parameterization schemes used in the HRRR model, which are based on the modeled turbulent kinetic energy and a tunable length scale.

  1. What can we learn from the self-attraction and loading fingerprints about pre-GRACE mass-loss acceleration from Greenland and Antarctica?

    Science.gov (United States)

    Davis, J. L.; Vinogradova, N. T.

    2017-12-01

    Tide-gauge records from the North Atlantic reveal significant acceleration in sea level starting in the late 20th century. We have analyzed the tide-gauge data using a model in which the accelerations are assumed to be zero prior to 1990. The estimated accelerations range from -1 to +3 m cy-2 and exhibit a systematic spatial variability. Davis and Vinogradova [2017] demonstrated that to model this variability in sea-level acceleration requires contributions from several distinct physical processes: accelerated mass loss from the Greenland and Antarctic Ice Sheets and acceleration associated with ocean circulation and heat uptake. Atmospheric pressure also contributes to the observed changes in sea level, at a much smaller amplitude. Because we are focusing on sea-level accelerations (i.e., sea-level rate changes), the contribution from Glacial Isostatic Adjustment (GIA) is negligible. Modeling of observed sea-level acceleration is achieved using external constraints for the important physical processes. Using GRACE results, we can calculate the sea-level "fingerprints" for Greenland and Antarctica associated with mass loading and gravitational perturbations. For the North Atlantic, Greenland induces a significant spatial variation in sea-level change—dominated by the solid-Earth response to the mass loss—whereas Antarctica contributes a spatially constant acceleration. The observations prefer a scaling of the solid-Earth/gravitational response, and we present the implications of this result for ice-mass changes prior to the onset of GRACE observations (2002-3).

  2. Structure and evolution of the drainage system of a Himalayan debris-covered glacier, and its relationship with patterns of mass loss

    Science.gov (United States)

    Benn, Douglas I.; Thompson, Sarah; Gulley, Jason; Mertes, Jordan; Luckman, Adrian; Nicholson, Lindsey

    2017-09-01

    We provide the first synoptic view of the drainage system of a Himalayan debris-covered glacier and its evolution through time, based on speleological exploration and satellite image analysis of Ngozumpa Glacier, Nepal. The drainage system has several linked components: (1) a seasonal subglacial drainage system below the upper ablation zone; (2) supraglacial channels, allowing efficient meltwater transport across parts of the upper ablation zone; (3) sub-marginal channels, allowing long-distance transport of meltwater; (4) perched ponds, which intermittently store meltwater prior to evacuation via the englacial drainage system; (5) englacial cut-and-closure conduits, which may undergo repeated cycles of abandonment and reactivation; and (6) a "base-level" lake system (Spillway Lake) dammed behind the terminal moraine. The distribution and relative importance of these elements has evolved through time, in response to sustained negative mass balance. The area occupied by perched ponds has expanded upglacier at the expense of supraglacial channels, and Spillway Lake has grown as more of the glacier surface ablates to base level. Subsurface processes play a governing role in creating, maintaining, and shutting down exposures of ice at the glacier surface, with a major impact on spatial patterns and rates of surface mass loss. Comparison of our results with observations on other glaciers indicate that englacial drainage systems play a key role in the response of debris-covered glaciers to sustained periods of negative mass balance.

  3. Wind Turbine Driving a PM Synchronous Generator Using Novel Recurrent Chebyshev Neural Network Control with the Ideal Learning Rate

    Directory of Open Access Journals (Sweden)

    Chih-Hong Lin

    2016-06-01

    Full Text Available A permanent magnet (PM synchronous generator system driven by wind turbine (WT, connected with smart grid via AC-DC converter and DC-AC converter, are controlled by the novel recurrent Chebyshev neural network (NN and amended particle swarm optimization (PSO to regulate output power and output voltage in two power converters in this study. Because a PM synchronous generator system driven by WT is an unknown non-linear and time-varying dynamic system, the on-line training novel recurrent Chebyshev NN control system is developed to regulate DC voltage of the AC-DC converter and AC voltage of the DC-AC converter connected with smart grid. Furthermore, the variable learning rate of the novel recurrent Chebyshev NN is regulated according to discrete-type Lyapunov function for improving the control performance and enhancing convergent speed. Finally, some experimental results are shown to verify the effectiveness of the proposed control method for a WT driving a PM synchronous generator system in smart grid.

  4. Wind power

    Energy Technology Data Exchange (ETDEWEB)

    1979-01-01

    This publication describes some of the technical, economic, safety and institutional considerations involved in the selection, installation and evaluation of a wind generation system. This information is presented, where possible, in practical, non-technical terms. The first four sections provide background information, theory, and general knowledge, while the remaining six sections are of a more specific nature to assist the prospective owner of a wind generator in his calculations and selections. Meteorological information is provided relating to the wind regime in Nova Scotia. The section on cost analysis discusses some of the factors and considerations which must be examined in order to provide a logical comparison between the alternatives of electricity produced from other sources. The final two sections are brief summaries of the regulations and hazards pertaining to the use of wind generators. The cost of wind-generated electricity is high compared to present Nova Scotia Power Corporation rates, even on Sable Island, Nova Scotia's highest wind area. However, it may be observed that Sable Island is one of the areas of Nova Scotia which is not presently supplied through the power grid and, particularly if there was a significant increase in the price of diesel oil, wind-generated electricity may well be the most economical alternative in that area. Generally speaking, however, where a consumer can purchase electricity at the normal domestic rate, wind generators are not economical, and they will not become economical unless there is a great reduction in their cost, an great increase in electricity rates, or both. Includes glossary. 23 figs., 11 tabs.

  5. Benefits of Group Living Include Increased Feeding Efficiency and Lower Mass Loss during Desiccation in the Social and Inbreeding Spider Stegodyphus dumicola

    Science.gov (United States)

    Vanthournout, Bram; Greve, Michelle; Bruun, Anne; Bechsgaard, Jesper; Overgaard, Johannes; Bilde, Trine

    2016-01-01

    Group living carries a price: it inherently entails increased competition for resources and reproduction, and may also be associated with mating among relatives, which carries costs of inbreeding. Nonetheless, group living and sociality is found in many animals, and understanding the direct and indirect benefits of cooperation that override the inherent costs remains a challenge in evolutionary ecology. Individuals in groups may benefit from more efficient management of energy or water reserves, for example in the form of reduced water or heat loss from groups of animals huddling, or through reduced energy demands afforded by shared participation in tasks. We investigated the putative benefits of group living in the permanently social spider Stegodyphus dumicola by comparing the effect of group size on standard metabolic rate, lipid/protein content as a body condition measure, feeding efficiency, per capita web investment, and weight/water loss and survival during desiccation. Because energetic expenditure is temperature sensitive, some assays were performed under varying temperature conditions. We found that feeding efficiency increased with group size, and the rate of weight loss was higher in solitary individuals than in animals in groups of various sizes during desiccation. Interestingly, this was not translated into differences in survival or in standard metabolic rate. We did not detect any group size effects for other parameters, and group size effects did not co-vary with experimental temperature in a predictive manner. Both feeding efficiency and mass loss during desiccation are relevant ecological factors as the former results in lowered predator exposure time, and the latter benefits social spiders which occupy arid, hot environments. PMID:26869936

  6. Benefits of group living include increased feeding efficiency and lower mass loss during desiccation in the social and inbreeding spider Stegodyphus dumicola.

    Directory of Open Access Journals (Sweden)

    Bram eVanthournout

    2016-02-01

    Full Text Available Group living carries a price: it inherently entails increased competition for resources and reproduction, and may also be associated with mating among relatives, which carries costs of inbreeding. Nonetheless, group living and sociality is found in many animals, and understanding the direct and indirect benefits of cooperation that override the inherent costs remains a challenge in evolutionary ecology. Individuals in groups may benefit from more efficient management of energy or water reserves, for example in the form of reduced water or heat loss from groups of animals huddling, or through reduced energy demands afforded by shared participation in tasks. We investigated the putative benefits of group living in the permanently social spider Stegodyphus dumicola by comparing the effect of group size on standard metabolic rate, lipid/protein content as a body condition measure, feeding efficiency, per capita web investment and weight/water loss and survival during desiccation. Because energetic expenditure is temperature sensitive, some assays were performed under varying temperature conditions. We found that feeding efficiency increased with group size, and the rate of weight loss was higher in solitary individuals than in animals in groups of various sizes during desiccation. Interestingly, this was not translated into differences in survival or in standard metabolic rate. We did not detect any group size effects for other parameters, and group size effects did not co-vary with experimental temperature in a predictive manner. Both feeding efficiency and mass loss during desiccation are relevant ecological factors as the former results in lowered predator exposure time, and the latter benefits social spiders which occupy arid, hot environments.

  7. ζ Oph and the weak-wind problem

    Science.gov (United States)

    Gvaramadze, V. V.; Langer, N.; Mackey, J.

    2012-11-01

    Mass-loss rate, ?, is one of the key parameters affecting evolution and observational manifestations of massive stars and their impact on the ambient medium. Despite its importance, there is a factor of ˜100 discrepancy between empirical and theoretical ? of late-type O dwarfs, the so-called weak-wind problem. In this Letter, we propose a simple novel method to constrain ? of runaway massive stars through observation of their bow shocks and Strömgren spheres, which might be of decisive importance for resolving the weak-wind problem. Using this method, we found that ? of the well-known runaway O9.5 V star ζ Oph is more than an order of magnitude higher than that derived from ultraviolet (UV) line fitting and is by a factor of 6-7 lower than those based on the theoretical recipe by Vink et al. and the Hα line. The discrepancy between ? derived by our method and that based on UV lines would be even more severe if the stellar wind is clumpy. At the same time, our estimate of ? agrees with that predicted by the moving reversing layer theory by Lucy.

  8. Atomic Physics of Shocked Plasma in Winds of Massive Stars

    Science.gov (United States)

    Leutenegger, Maurice A.; Cohen, David H.; Owocki, Stanley P.

    2012-01-01

    High resolution diffraction grating spectra of X-ray emission from massive stars obtained with Chandra and XMM-Newton have revolutionized our understanding of their powerful, radiation-driven winds. Emission line shapes and line ratios provide diagnostics on a number of key wind parameters. Modeling of resolved emission line velocity profiles allows us to derive independent constraints on stellar mass-loss rates, leading to downward revisions of a factor of a few from previous measurements. Line ratios in He-like ions strongly constrain the spatial distribution of Xray emitting plasma, confirming the expectations of radiation hydrodynamic simulations that X-ray emission begins moderately close to the stellar surface and extends throughout the wind. Some outstanding questions remain, including the possibility of large optical depths in resonance lines, which is hinted at by differences in line shapes of resonance and intercombination lines from the same ion. Resonance scattering leads to nontrivial radiative transfer effects, and modeling it allows us to place constraints on shock size, density, and velocity structure

  9. Magnetic confinement, Alfven wave reflection, and the origins of X-ray and mass-loss 'dividing lines' for late-type giants and supergiants

    Science.gov (United States)

    Rosner, R.; An, C.-H.; Musielak, Z. E.; Moore, R. L.; Suess, S. T.

    1991-01-01

    A simple qualitative model for the origin of the coronal and mass-loss dividing lines separating late-type giants and supergiants with and without hot, X-ray-emitting corona, and with and without significant mass loss is discussed. The basic physical effects considered are the necessity of magnetic confinement for hot coronal material on the surface of such stars and the large reflection efficiency for Alfven waves in cool exponential atmospheres. The model assumes that the magnetic field geometry of these stars changes across the observed 'dividing lines' from being mostly closed on the high effective temperature side to being mostly open on the low effective temperature side.

  10. The Colorado Ultraviolet Transit Experiment (CUTE): a dedicated cubesat mission for the study of exoplanetary mass loss and magnetic fields

    Science.gov (United States)

    Fleming, Brian T.; France, Kevin; Nell, Nicholas; Kohnert, Richard; Pool, Kelsey; Egan, Arika; Fossati, Luca; Koskinen, Tommi; Vidotto, Aline A.; Hoadley, Keri; Desert, Jean-Michel; Beasley, Matthew; Petit, Pascal

    2017-08-01

    The Colorado Ultraviolet Transit Experiment (CUTE) is a near-UV (2550 - 3300 Å) 6U cubesat mission designed to monitor transiting hot Jupiters to quantify their atmospheric mass loss and magnetic fields. CUTE will probe both atomic (Mg and Fe) and molecular (OH) lines for evidence of enhanced transit absorption, and to search for evidence of early ingress due to bow shocks ahead of the planet's orbital motion. As a dedicated mission, CUTE will observe > 60 spectroscopic transits of hot Jupiters over a nominal seven month mission. This represents the equivalent of > 700 orbits of the only other instrument capable of these measurements, the Hubble Space Telescope. CUTE efficiently utilizes the available cubesat volume by means of an innovative optical design to achieve a projected effective area of ˜ 22 cm2 , low instrumental background, and a spectral resolving power of R ˜ 3000 over the entire science bandpass. These performance characteristics enable CUTE to discern a transit depth of motivation and expected results, and an overview of the projected fabrication, calibration and launch timeline.

  11. Colorado Ultraviolet Transit Experiment: a dedicated CubeSat mission to study exoplanetary mass loss and magnetic fields

    Science.gov (United States)

    Fleming, Brian T.; France, Kevin; Nell, Nicholas; Kohnert, Richard; Pool, Kelsey; Egan, Arika; Fossati, Luca; Koskinen, Tommi; Vidotto, Aline A.; Hoadley, Keri; Desert, Jean-Michel; Beasley, Matthew; Petit, Pascal M.

    2018-01-01

    The Colorado Ultraviolet Transit Experiment (CUTE) is a near-UV (2550 to 3300 Å) 6U CubeSat mission designed to monitor transiting hot Jupiters to quantify their atmospheric mass loss and magnetic fields. CUTE will probe both atomic (Mg and Fe) and molecular (OH) lines for evidence of enhanced transit absorption, and to search for evidence of early ingress due to bow shocks ahead of the planet's orbital motion. As a dedicated mission, CUTE will observe ≳100 spectroscopic transits of hot Jupiters over a nominal 7-month mission. This represents the equivalent of >700 orbits of the only other instrument capable of these measurements, the Hubble Space Telescope. CUTE efficiently utilizes the available CubeSat volume by means of an innovative optical design to achieve a projected effective area of ˜28 cm2, low instrumental background, and a spectral resolving power of R˜3000 over the primary science bandpass. These performance characteristics enable CUTE to discern transit depths between 0.1% and 1% in individual spectral absorption lines. We present the CUTE optical and mechanical design, a summary of the science motivation and expected results, and an overview of the projected fabrication, calibration, and launch timeline.

  12. Hurricane Imaging Radiometer (HIRAD) Observations of Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate During NASA's GRIP and HS3 Campaigns

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2012-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain spatial resolution of approximately 2 km, out to roughly 30 km each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. The physical retrieval technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  13. MASS LOSS AND NITROGEN DYNAMICS DURING THE DECOMPOSITION OF A N-LABELED N2-FIXING EPOPHYTIC LICHEN, LOBARIA OREGANA (TUCK.) MULL. ARG.

    Science.gov (United States)

    We studied mass loss and nitrogen dynamics during fall and spring initiated decomposition of an N2-fixing epiphytic lichen, Lobaria oregana (Tuck.) Mull. Arg. using 15N. We developed a method of labeling lichens with 15N that involved spraying lichen material with a nutrient sol...

  14. Mass loss and nutrient concentrations of buried wood as a function of organic matter removal, soil compaction, and vegetation control in a regenerating oak-pine forest

    Science.gov (United States)

    Felix Ponder; John M. Kabrick; Mary Beth Adams; Deborah S. Page-Dumroese; Marty F. Jurgensen

    2017-01-01

    Mass loss and nutrient concentrations of northern red oak (Quercus rubra) and white oak (Q. alba) wood stakes were measured 30 months after their burial in the upper 10 cm of soil in a regenerating forest after harvesting and soil disturbance. Disturbance treatments were two levels of organic matter (OM) removal (only...

  15. Vapour pressures of selected organic compounds down to 1 mPa, using mass-loss Knudsen effusion method

    International Nuclear Information System (INIS)

    Fonseca, José M.S.; Gushterov, Nikola; Dohrn, Ralf

    2014-01-01

    Graphical abstract: - Highlights: • A recently described mass-loss Knudsen apparatus was used for measurements of vapour pressures down to around 1 mPa. • Complementary calorimetric studies were performed in a Calvet-type calorimeter. • New vapour pressures are given for benzoic acid and benzanthrone, in ranges in which no consistent data existed. • Vapour pressures for solid n-octadecane are presented, correcting existing values from literature. - Abstract: A recently developed Knudsen effusion apparatus was improved and used for measurements of vapour pressures of selected organic compounds. Calorimetric studies were conducted using a Calvet-type calorimeter, complementing the information obtained for the vapour pressures and facilitating the modelling and analysis of the data. Vapour pressures of benzoic acid, a reference substance, were determined at temperatures between 269 K and 317 K, corresponding to a pressure range from 2 mPa to 1 Pa, extending the range of results available in the literature to lower pressures. Benzanthrone was studied between temperatures 360 K and 410 K (5 mPa–1 Pa) in order to test the apparatus at higher temperatures. Values presented in the literature for the vapour pressure of solid n-octadecane, one of the most promising compounds to be used as “phase change material” for textile applications, were found inconsistent with the triple point of the substance. Sublimation pressures were measured for this compound between T = 286 K and 298 K (2–20 mPa) allowing the correction of the existing values. Finally, vapour pressures of diphenyl carbonate, a compound of high industrial relevance for its use in the production of polycarbonates, were determined from T = 302 K to 332 K (0.02–1 Pa)

  16. Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

    Science.gov (United States)

    Martínez-Núñez, Silvia; Kretschmar, Peter; Bozzo, Enrico; Oskinova, Lidia M.; Puls, Joachim; Sidoli, Lara; Sundqvist, Jon Olof; Blay, Pere; Falanga, Maurizio; Fürst, Felix; Gímenez-García, Angel; Kreykenbohm, Ingo; Kühnel, Matthias; Sander, Andreas; Torrejón, José Miguel; Wilms, Jörn

    2017-10-01

    Massive stars, at least ˜10 times more massive than the Sun, have two key properties that make them the main drivers of evolution of star clusters, galaxies, and the Universe as a whole. On the one hand, the outer layers of massive stars are so hot that they produce most of the ionizing ultraviolet radiation of galaxies; in fact, the first massive stars helped to re-ionize the Universe after its Dark Ages. Another important property of massive stars are the strong stellar winds and outflows they produce. This mass loss, and finally the explosion of a massive star as a supernova or a gamma-ray burst, provide a significant input of mechanical and radiative energy into the interstellar space. These two properties together make massive stars one of the most important cosmic engines: they trigger the star formation and enrich the interstellar medium with heavy elements, that ultimately leads to formation of Earth-like rocky planets and the development of complex life. The study of massive star winds is thus a truly multidisciplinary field and has a wide impact on different areas of astronomy. In recent years observational and theoretical evidences have been growing that these winds are not smooth and homogeneous as previously assumed, but rather populated by dense "clumps". The presence of these structures dramatically affects the mass loss rates derived from the study of stellar winds. Clump properties in isolated stars are nowadays inferred mostly through indirect methods (i.e., spectroscopic observations of line profiles in various wavelength regimes, and their analysis based on tailored, inhomogeneous wind models). The limited characterization of the clump physical properties (mass, size) obtained so far have led to large uncertainties in the mass loss rates from massive stars. Such uncertainties limit our understanding of the role of massive star winds in galactic and cosmic evolution. Supergiant high mass X-ray binaries (SgXBs) are among the brightest X

  17. Stellar feedback in galaxies and the origin of galaxy-scale winds

    Science.gov (United States)

    Hopkins, Philip F.; Quataert, Eliot; Murray, Norman

    2012-04-01

    Feedback from massive stars is believed to play a critical role in driving galactic super-winds that enrich the intergalactic medium and shape the galaxy mass function, mass-metallicity relation and other global galaxy properties. In previous papers, we have introduced new numerical methods for implementing stellar feedback on sub-giant molecular cloud (sub-GMC) through galactic scales in numerical simulations of galaxies; the key physical processes include radiation pressure in the ultraviolet through infrared, supernovae (Type I and Type II), stellar winds ('fast' O star through 'slow' asymptotic giant branch winds), and H II photoionization. Here, we show that these feedback mechanisms drive galactic winds with outflow rates as high as ˜10-20 times the galaxy star formation rate. The mass-loading efficiency (wind mass-loss rate divided by the star formation rate) scales roughly as ? (where Vc is the galaxy circular velocity), consistent with simple momentum-conservation expectations. We use our suite of simulations to study the relative contribution of each feedback mechanism to the generation of galactic winds in a range of galaxy models, from Small Magellanic Cloud like dwarfs and Milky Way (MW) analogues to z˜ 2 clumpy discs. In massive, gas-rich systems (local starbursts and high-z galaxies), radiation pressure dominates the wind generation. By contrast, for MW-like spirals and dwarf galaxies the gas densities are much lower and sources of shock-heated gas such as supernovae and stellar winds dominate the production of large-scale outflows. In all of our models, however, the winds have a complex multiphase structure that depends on the interaction between multiple feedback mechanisms operating on different spatial scales and time-scales: any single feedback mechanism fails to reproduce the winds observed. We use our simulations to provide fitting functions to the wind mass loading and velocities as a function of galaxy properties, for use in cosmological

  18. HOW THERMAL EVOLUTION AND MASS-LOSS SCULPT POPULATIONS OF SUPER-EARTHS AND SUB-NEPTUNES: APPLICATION TO THE KEPLER-11 SYSTEM AND BEYOND

    International Nuclear Information System (INIS)

    Lopez, Eric D.; Miller, Neil; Fortney, Jonathan J.

    2012-01-01

    We use models of thermal evolution and extreme ultraviolet (XUV) driven mass loss to explore the composition and history of low-mass, low-density transiting planets. We investigate the Kepler-11 system in detail and provide estimates of both the current and past planetary compositions. We find that an H/He envelope on Kepler-11b is highly vulnerable to mass loss. By comparing to formation models, we show that in situ formation of the system is extremely difficult. Instead we propose that it is a water-rich system of sub-Neptunes that migrated from beyond the snow line. For the broader population of observed planets, we show that there is a threshold in bulk planet density and incident flux above which no low-mass transiting planets have been observed. We suggest that this threshold is due to the instability of H/He envelopes to XUV-driven mass loss. Importantly, we find that this mass-loss threshold is well reproduced by our thermal evolution/contraction models that incorporate a standard mass-loss prescription. Treating the planets' contraction history is essential because the planets have significantly larger radii during the early era of high XUV fluxes. Over time low-mass planets with H/He envelopes can be transformed into water-dominated worlds with steam envelopes or rocky super-Earths. Finally, we use this threshold to provide likely minimum masses and radial-velocity amplitudes for the general population of Kepler candidates. Likewise, we use this threshold to provide constraints on the maximum radii of low-mass planets found by radial-velocity surveys.

  19. Winds of AGB stars: does size matter?

    International Nuclear Information System (INIS)

    Hoefner, S

    2008-01-01

    Asymptotic giant branch (AGB) stars are showing clear signs of significant mass loss through cool stellar winds. These outflows are attributed to the combined effects of pulsation-induced shocks and radiation pressure on dust grains formed in the outer atmospheric layers. This paper gives an overview of the current status of radiation-hydrodynamical modelling of these processes, and presents a toy model that allows analysis of certain features of detailed models, such as the influence of grain size dependent opacities and basic differences in winds of C- and M-type AGB stars.

  20. Wind energy

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    This chapter discusses the role wind energy may have in the energy future of the US. The topics discussed in the chapter include historical aspects of wind energy use, the wind energy resource, wind energy technology including intermediate-size and small wind turbines and intermittency of wind power, public attitudes toward wind power, and environmental, siting and land use issues

  1. A combined HST and XMM-Newton campaign for the magnetic O9.7 V star HD 54879. Constraining the weak-wind problem of massive stars

    Science.gov (United States)

    Shenar, T.; Oskinova, L. M.; Järvinen, S. P.; Luckas, P.; Hainich, R.; Todt, H.; Hubrig, S.; Sander, A. A. C.; Ilyin, I.; Hamann, W.-R.

    2017-10-01

    Context. HD 54879 (O9.7 V) is one of a dozen O-stars for which an organized atmospheric magnetic field has been detected. Despite their importance, little is known about the winds and evolution of magnetized massive stars. Aims: To gain insights into the interplay between atmospheres, winds, and magnetic fields of massive stars, we acquired UV and X-ray data of HD 54879 using the Hubble Space Telescope and the XMM-Newton satellite. In addition, 35 optical amateur spectra were secured to study the variability of HD 54879. Methods: A multiwavelength (X-ray to optical) spectral analysis is performed using the Potsdam Wolf-Rayet (PoWR) model atmosphere code and the xspec software. Results: The photospheric parameters (T∗ = 30.5 kK, log g = 4.0 [cm s-2], log L = 4.45 [L⊙]) are typical for an O9.7 V star. The microturbulent, macroturbulent, and projected rotational velocities are lower than previously suggested (ξph,vmac,vsini ≤ 4 km s-1). An initial mass of 16 M⊙ and an age of 5 Myr are inferred from evolutionary tracks. We derive a mean X-ray emitting temperature of log TX = 6.7 [K] and an X-ray luminosity of LX = 1 × 1032 erg s-1. Short- and long-scale variability is seen in the Hα line, but only a very long period of P ≈ 5 yr could be estimated. Assessing the circumstellar density of HD 54879 using UV spectra, we can roughly estimate the mass-loss rate HD 54879 would have in the absence of a magnetic field as log ṀB = 0 ≈ -9.0 [M⊙ yr-1]. The magnetic field traps the stellar wind up to the Alfvén radius rA ≳ 12 R∗, implying that its true mass-loss rate is log Ṁ ≲ -10.2 [M⊙ yr-1]. Hence, density enhancements around magnetic stars can be exploited to estimate mass-loss rates of non-magnetic stars of similar spectral types, essential for resolving the weak wind problem. Conclusions: Our study confirms that strongly magnetized stars lose little or no mass, and supplies important constraints on the weak-wind problem of massive main sequence

  2. The effect of buffer-layer on the steady-state energy release rate of a tunneling crack in a wind turbine blade joint

    DEFF Research Database (Denmark)

    Jørgensen, Jeppe Bjørn; Sørensen, Bent F.; Kildegaard, Casper

    2018-01-01

    propagation of tunneling cracks. However, for wind turbine blade relevant material combinations it is found more effective to reduce the thickness of the adhesive layer since the stiffness mismatch between the existing laminate and the adhesive is already high. The effect of material orthotropy was found......The effect of a buffer-layer on the steady-state energy release rate of a tunneling crack in the adhesive layer of a wind turbine blade joint, loaded in tension, is investigated using a parametric 2D tri-material finite element model. The idea of embedding a buffer-layer in-between the adhesive...... and the basis glass fiber laminate to improve the existing joint design is novel, but the implications hereof need to be addressed.The results show that it is advantageous to embed a buffer-layer near the adhesive with controllable thickness-and stiffness properties in order to improve the joint design against...

  3. Wind Generators

    Science.gov (United States)

    1989-01-01

    When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.

  4. Wind accretion in the massive X-ray binary 4U 2206+54: abnormally slow wind and a moderately eccentric orbit

    Science.gov (United States)

    Ribó, M.; Negueruela, I.; Blay, P.; Torrejón, J. M.; Reig, P.

    2006-04-01

    Massive X-ray binaries are usually classified by the properties of the donor star in classical, supergiant and Be X-ray binaries, the main difference being the mass transfer mechanism between the two components. The massive X-ray binary 4U 2206+54 does not fit in any of these groups, and deserves a detailed study to understand how the transfer of matter and the accretion on to the compact object take place. To this end we study an IUE spectrum of the donor and obtain a wind terminal velocity (v_∞) of ~350 km s-1, which is abnormally slow for its spectral type. We also analyse here more than 9 years of available RXTE/ASM data. We study the long-term X-ray variability of the source and find it to be similar to that observed in the wind-fed supergiant system Vela X-1, reinforcing the idea that 4U 2206+54 is also a wind-fed system. We find a quasi-period decreasing from ~270 to ~130 d, noticed in previous works but never studied in detail. We discuss possible scenarios for its origin and conclude that long-term quasi-periodic variations in the mass-loss rate of the primary are probably driving such variability in the measured X-ray flux. We obtain an improved orbital period of P_orb=9.5591±0.0007 d with maximum X-ray flux at MJD 51856.6±0.1. Our study of the orbital X-ray variability in the context of wind accretion suggests a moderate eccentricity around 0.15 for this binary system. Moreover, the low value of v_∞ solves the long-standing problem of the relatively high X-ray luminosity for the unevolved nature of the donor, BD +53°2790, which is probably an O9.5 V star. We note that changes in v_∞ and/or the mass-loss rate of the primary alone cannot explain the different patterns displayed by the orbital X-ray variability. We finally emphasize that 4U 2206+54, together with LS 5039, could be part of a new population of wind-fed HMXBs with main sequence donors, the natural progenitors of supergiant X-ray binaries.

  5. Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars

    Czech Academy of Sciences Publication Activity Database

    Šurlan, Brankica; Hamann, W.-R.; Aret, A.; Kubát, Jiří; Oskinova, L.M.; Torres, A.F.

    2013-01-01

    Roč. 559, November (2013), A130/1-A130/17 ISSN 0004-6361 R&D Projects: GA ČR(CZ) GAP209/11/1198; GA MŠk 7AMB12AR021 Grant - others: NASA (US) NNX09AF08G Institutional support: RVO:67985815 Keywords : stars * winds * outflows Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.479, year: 2013

  6. The contribution to future flood risk in the Severn Estuary from extreme sea level rise due to ice sheet mass loss

    Science.gov (United States)

    Quinn, N.; Bates, P. D.; Siddall, M.

    2013-12-01

    The rate at which sea levels will rise in the coming century is of great interest to decision makers tasked with developing mitigation policies to cope with the risk of coastal inundation. Accurate estimates of future sea levels are vital in the provision of effective policy. Recent reports from UK Climate Impacts Programme (UKCIP) suggest that mean sea levels in the UK may rise by as much as 80 cm by 2100; however, a great deal of uncertainty surrounds model predictions, particularly the contribution from ice sheets responding to climatic warming. For this reason, the application of semi-empirical modelling approaches for sea level rise predictions has increased of late, the results from which suggest that the rate of sea level rise may be greater than previously thought, exceeding 1 m by 2100. Furthermore, studies in the Red Sea indicate that rapid sea level rise beyond 1m per century has occurred in the past. In light of such research, the latest UKCIP assessment has included a H++ scenario for sea level rise in the UK of up to 1.9 m which is defined as improbable but, crucially, physically plausible. The significance of such low-probability sea level rise scenarios upon the estimation of future flood risk is assessed using the Somerset levels (UK) as a case study. A simple asymmetric probability distribution is constructed to include sea level rise scenarios of up to 1.9 m by 2100 which are added to a current 1:200 year event water level to force a two-dimensional hydrodynamic model of coastal inundation. From the resulting ensemble predictions an estimation of risk by 2100 is established. The results indicate that although the likelihood of extreme sea level rise due to rapid ice sheet mass loss is low, the resulting hazard can be large, resulting in a significant (27%) increase to the projected annual risk. Furthermore, current defence construction guidelines for the coming century in the UK are expected to account for 95% of the sea level rise distribution

  7. Radiatively driven relativistic spherical winds under relativistic radiative transfer

    Science.gov (United States)

    Fukue, J.

    2018-05-01

    We numerically investigate radiatively driven relativistic spherical winds from the central luminous object with mass M and luminosity L* under Newtonian gravity, special relativity, and relativistic radiative transfer. We solve both the relativistic radiative transfer equation and the relativistic hydrodynamical equations for spherically symmetric flows under the double-iteration processes, to obtain the intensity and velocity fields simultaneously. We found that the momentum-driven winds with scattering are quickly accelerated near the central object to reach the terminal speed. The results of numerical solutions are roughly fitted by a relation of \\dot{m}=0.7(Γ _*-1)\\tau _* β _* β _out^{-2.6}, where \\dot{m} is the mass-loss rate normalized by the critical one, Γ* the central luminosity normalized by the critical one, τ* the typical optical depth, β* the initial flow speed at the central core of radius R*, and βout the terminal speed normalized by the speed of light. This relation is close to the non-relativistic analytical solution, \\dot{m} = 2(Γ _*-1)\\tau _* β _* β _out^{-2}, which can be re-expressed as β _out^2/2 = (Γ _*-1)GM/c^2 R_*. That is, the present solution with small optical depth is similar to that of the radiatively driven free outflow. Furthermore, we found that the normalized luminosity (Eddington parameter) must be larger than unity for the relativistic spherical wind to blow off with intermediate or small optical depth, i.e. Γ _* ≳ \\sqrt{(1+β _out)^3/(1-β _out)}. We briefly investigate and discuss an isothermal wind.

  8. Diurnal and seasonal variability of TKE dissipation rate in the ABL over a tropical station using UHF wind profiler

    CSIR Research Space (South Africa)

    Kalapureddy, MCR

    2007-04-01

    Full Text Available . The turbulent variance is related to e by the following equation given by White et al. (1999). � ¼ s3turbð4p=AÞ3=2J�3=2, (1) 0 and p=2 for both spherical coordinates j and f. J has to be solved numerically with an estimate of the mean wind speed provided...National Physical Laboratory, New Delhi, India fFrontier Observational Research System for Global Change, Yokohama, Japan Received 10 March 2006; received in revised form 30 October 2006; accepted 30 October 2006 Available online 16 January 2007 Abstract...

  9. Monte Carlo simulations of the detailed iron absorption line profiles from thermal winds in X-ray binaries

    Science.gov (United States)

    Tomaru, Ryota; Done, Chris; Odaka, Hirokazu; Watanabe, Shin; Takahashi, Tadayuki

    2018-05-01

    Blueshifted absorption lines from highly ionized iron are seen in some high inclination X-ray binary systems, indicating the presence of an equatorial disc wind. This launch mechanism is under debate, but thermal driving should be ubiquitous. X-ray irradiation from the central source heats disc surface, forming a wind from the outer disc where the local escape velocity is lower than the sound speed. The mass-loss rate from each part of the disc is determined by the luminosity and spectral shape of the central source. We use these together with an assumed density and velocity structure of the wind to predict the column density and ionization state, then combine this with a Monte Carlo radiation transfer to predict the detailed shape of the absorption (and emission) line profiles. We test this on the persistent wind seen in the bright neutron star binary GX 13+1, with luminosity L/LEdd ˜ 0.5. We approximately include the effect of radiation pressure because of high luminosity, and compute line features. We compare these to the highest resolution data, the Chandra third-order grating spectra, which we show here for the first time. This is the first physical model for the wind in this system, and it succeeds in reproducing many of the features seen in the data, showing that the wind in GX13+1 is most likely a thermal-radiation driven wind. This approach, combined with better streamline structures derived from full radiation hydrodynamic simulations, will allow future calorimeter data to explore the detail wind structure.

  10. The effect of wind shielding and pen position on the average daily weight gain and feed conversion rate of grower/finisher pigs

    DEFF Research Database (Denmark)

    Jensen, Dan B.; Toft, Nils; Cornou, Cécile

    2014-01-01

    of the effects of wind shielding, linear mixed models were fitted to describe the average daily weight gain and feed conversion rate of 1271 groups (14 individuals per group) of purebred Duroc, Yorkshire and Danish Landrace boars, as a function of shielding (yes/no), insert season (winter, spring, summer, autumn...... groups placed in the 1st and 4th pen (p=0.0001). A similar effect was not seen on smaller pigs. Pen placement appears to have no effect on feed conversion rate.No interaction effects between shielding and distance to the corridor could be demonstrated. Furthermore, in models including both factors......). The effect could not be tested for Yorkshire and Danish Landrace due to lack of data on these breeds. For groups of pigs above the average start weight, a clear tendency of higher growth rates at greater distances from the central corridor was observed, with the most significant differences being between...

  11. Wind: new wind markets

    International Nuclear Information System (INIS)

    Cameron, A.

    2005-01-01

    The June 2005 edition of 'Wind Force 12' suggests that wind could generate 12% of global electricity requirements by 2020. But what moves a potential market into an emerging one? Geographical factors include a good wind resource, plenty of open space and the ability to get the generated electricity to end-users. A country's political framework is equally important, with fixed price systems, renewable quota systems and political will all playing a part. Some potential wind markets around the world are thought to have the conditions necessary to become key players in the wind industry. The emerging markets in countries such as Australia, Brazil, Canada, France, Japan and the Philippines are highlighted as examples

  12. THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. IV. CONSTRUCTION AND VALIDATION OF A GRID OF MODELS FOR OXYGEN-RICH AGB STARS, RED SUPERGIANTS, AND EXTREME AGB STARS

    International Nuclear Information System (INIS)

    Sargent, Benjamin A.; Meixner, M.; Srinivasan, S.

    2011-01-01

    To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the 'Grid of Red supergiant and Asymptotic giant branch star ModelS' (GRAMS). This model grid explores four parameters-stellar effective temperature from 2100 K to 4700 K; luminosity from 10 3 to 10 6 L sun ; dust shell inner radii of 3, 7, 11, and 15 R star ; and 10.0 μm optical depth from 10 -4 to 26. From an initial grid of ∼1200 2Dust models, we create a larger grid of ∼69,000 models by scaling to cover the luminosity range required by the data. These models are available online to the public. The matching in color-magnitude diagrams and color-color diagrams to observed O-rich asymptotic giant branch (AGB) and red supergiant (RSG) candidate stars from the SAGE and SAGE-Spec LMC samples and a small sample of OH/IR stars is generally very good. The extreme AGB star candidates from SAGE are more consistent with carbon-rich (C-rich) than O-rich dust composition. Our model grid suggests lower limits to the mid-infrared colors of the dustiest AGB stars for which the chemistry could be O-rich. Finally, the fitting of GRAMS models to spectral energy distributions of sources fit by other studies provides additional verification of our grid and anticipates future, more expansive efforts.

  13. Wind Farms: Modeling and Control

    DEFF Research Database (Denmark)

    Soleimanzadeh, Maryam

    2012-01-01

    is minimized. The controller is practically feasible. Yet, the results on load reduction in this approach are not very significant. In the second strategy, the wind farm control problem has been divided into below rated and above rated wind speed conditions. In the above rated wind speed pitch angle and power....... Distributed controller design commences with formulating the problem, where a structured matrix approach has been put in to practice. Afterwards, an H2 control problem is implemented to obtain the controller dynamics for a wind farm such that the structural loads on wind turbines are minimized.......The primary purpose of this work is to develop control algorithms for wind farms to optimize the power production and augment the lifetime of wind turbines in wind farms. In this regard, a dynamical model for wind farms was required to be the basis of the controller design. In the first stage...

  14. Green Bank Telescope Detection of HI Clouds in the Fermi Bubble Wind

    Science.gov (United States)

    Lockman, Felix; Di Teodoro, Enrico M.; McClure-Griffiths, Naomi M.

    2018-01-01

    We used the Robert C. Byrd Green Bank Telescope to map HI 21cm emission in two large regions around the Galactic Center in a search for HI clouds that might be entrained in the nuclear wind that created the Fermi bubbles. In a ~160 square degree region at |b|>4 deg. and |long|<10 deg we detect 106 HI clouds that have large non-circular velocities consistent with their acceleration by the nuclear wind. Rapidly moving clouds are found as far as 1.5 kpc from the center; there are no detectable asymmetries in the cloud populations above and below the Galactic Center. The cloud kinematics is modeled as a population with an outflow velocity of 330 km/s that fills a cone with an opening angle ~140 degrees. The total mass in the clouds is ~10^6 solar masses and we estimate cloud lifetimes to be between 2 and 8 Myr, implying a cold gas mass-loss rate of about 0.1 solar masses per year into the nuclear wind.The Green Bank Telescope is a facility of the National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.

  15. THE MASS LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD: EMPIRICAL RELATIONS FOR EXCESS EMISSION AT 8 AND 24 μm

    International Nuclear Information System (INIS)

    Srinivasan, Sundar; Meixner, Margaret; Leitherer, Claus; Vijh, Uma; Gordon, Karl D.; Sewilo, Marta; Volk, Kevin; Blum, Robert D.; Harris, Jason; Babler, Brian L.; Bracker, Steve; Meade, Marilyn; Block, Miwa; Engelbracht, Charles W.; For, Bi-Qing; Misselt, Karl A.; Cohen, Martin; Hora, Joseph L.; Indebetouw, Remy; Markwick-Kemper, Francisca

    2009-01-01

    We present empirical relations describing excess emission from evolved stars in the Large Magellanic Cloud (LMC) using data from the Spitzer Space Telescope Surveying the Agents of a Galaxy's Evolution (SAGE) survey which includes the Infrared Array Camera (IRAC) 3.6, 4.5, 5.8, and 8.0 μm and Multiband Imaging Photometer (MIPS) 24, 70, and 160 μm bands. We combine the SAGE data with the Two Micron All Sky Survey (2MASS; J, H, and K s ) and the optical Magellanic Cloud Photometric Survey (MCPS; U, B, V, and I) point source catalogs in order to create complete spectral energy distributions (SEDs) of the asymptotic giant branch (AGB) star candidates in the LMC. AGB star outflows are among the main producers of dust in a galaxy, and this mass loss results in an excess in the fluxes observed in the 8 and 24 μm bands. The aim of this work is to investigate the mass loss return by AGB stars to the interstellar medium of the LMC by studying the dependence of the infrared excess flux on the total luminosity. We identify oxygen-rich, carbon-rich, and extreme AGB star populations in our sample based on their 2MASS and IRAC colors. The SEDs of oxygen- and carbon-rich AGB stars are compared with appropriate stellar photosphere models to obtain the excess flux in all the IRAC bands and the MIPS 24 μm band. Extreme AGB stars are dominated by circumstellar emission at 8 and 24 μm; thus we approximate their excesses with the flux observed in these bands. We find about 16,000 O-rich, 6300 C-rich, and 1000 extreme sources with reliable 8 μm excesses, and about 4500 O-rich, 5300 C-rich, and 960 extreme sources with reliable 24 μm excesses. The excesses are in the range 0.1 mJy to 5 Jy. The 8 and 24 μm excesses for all three types of AGB candidates show a general increasing trend with luminosity. The color temperature of the circumstellar dust derived from the ratio of the 8 and 24 μm excesses decreases with an increase in excess, while the 24 μm optical depth increases with

  16. Nonspherical Radiation Driven Wind Models Applied to Be Stars

    Science.gov (United States)

    Arauxo, F. X.

    1990-11-01

    ABSTRACT. In this work we present a model for the structure of a radiatively driven wind in the meridional plane of a hot star. Rotation effects and simulation of viscous forces were included in the motion equations. The line radiation force is considered with the inclusion of the finite disk correction in self-consistent computations which also contain gravity darkening as well as distortion of the star by rotation. An application to a typical BlV star leads to mass-flux ratios between equator and pole of the order of 10 and mass loss rates in the range 5.l0 to Mo/yr. Our envelope models are flattened towards the equator and the wind terminal velocities in that region are rather high (1000 Km/s). However, in the region near the star the equatorial velocity field is dominated by rotation. RESUMEN. Se presenta un modelo de la estructura de un viento empujado radiativamente en el plano meridional de una estrella caliente. Se incluyeron en las ecuaciones de movimiento los efectos de rotaci6n y la simulaci6n de fuerzas viscosas. Se consider6 la fuerza de las lineas de radiaci6n incluyendo la correcci6n de disco finito en calculos autoconsistentes los cuales incluyen oscurecimiento gravitacional asi como distorsi6n de la estrella por rotaci6n. La aplicaci6n a una estrella tipica BlV lleva a cocientes de flujo de masa entre el ecuador y el polo del orden de 10 de perdida de masa en el intervalo 5.l0 a 10 Mo/ano. Nuestros modelos de envolvente estan achatados hacia el ecuador y las velocidads terminales del viento en esa regi6n son bastante altas (1000 Km/s). Sin embargo, en la regi6n cercana a la estrella el campo de velocidad ecuatorial esta dominado por la rotaci6n. Key words: STARS-BE -- STARS-WINDS

  17. Joint release rate estimation and measurement-by-measurement model correction for atmospheric radionuclide emission in nuclear accidents: An application to wind tunnel experiments.

    Science.gov (United States)

    Li, Xinpeng; Li, Hong; Liu, Yun; Xiong, Wei; Fang, Sheng

    2018-03-05

    The release rate of atmospheric radionuclide emissions is a critical factor in the emergency response to nuclear accidents. However, there are unavoidable biases in radionuclide transport models, leading to inaccurate estimates. In this study, a method that simultaneously corrects these biases and estimates the release rate is developed. Our approach provides a more complete measurement-by-measurement correction of the biases with a coefficient matrix that considers both deterministic and stochastic deviations. This matrix and the release rate are jointly solved by the alternating minimization algorithm. The proposed method is generic because it does not rely on specific features of transport models or scenarios. It is validated against wind tunnel experiments that simulate accidental releases in a heterogonous and densely built nuclear power plant site. The sensitivities to the position, number, and quality of measurements and extendibility of the method are also investigated. The results demonstrate that this method effectively corrects the model biases, and therefore outperforms Tikhonov's method in both release rate estimation and model prediction. The proposed approach is robust to uncertainties and extendible with various center estimators, thus providing a flexible framework for robust source inversion in real accidents, even if large uncertainties exist in multiple factors. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Wind Energy

    International Nuclear Information System (INIS)

    Rodriguez D, J.M.

    1998-01-01

    The general theory of the wind energy conversion systems is presented. The availability of the wind resource in Colombia and the ranges of the speed of the wind in those which is possible economically to use the wind turbines are described. It is continued with a description of the principal technological characteristics of the wind turbines and are split into wind power and wind-powered pumps; and its use in large quantities grouped in wind farms or in autonomous systems. Finally, its costs and its environmental impact are presented

  19. 2KJ/S 1KV, 25HZ PRR capacitor charging power supply with twin phase shifted primary windings to achieve high charge transfer rate and stability

    International Nuclear Information System (INIS)

    Kelkar, Y.; Singh, Y.P.; Thakurta, A.C.

    2013-01-01

    The capacitor charging power supply (CCPS) was developed to charge bank of 150uF energy storage capacitor (15uf , 10 nos in parallel) upto 1kV in 35 ms exhibiting a peak charging power of 2 kJ/s at a repetition rate of 25 pps. A CCPS observes a large change in load variations at the output. Initially the capacitor will act as a short circuit so the topology must be such that it should withstand short circuit condition repetitively. The High Voltage capacitor charging power supply consist of two identical full bridge resonant converters feeding to two primary windings of a transformer with rectified secondary connected to capacitor load. Topology selection is based on the fact that the series resonant converter with switching frequency f s , below 50% of the resonant frequency f r (f s ≤ 0.5 f r ) act as a current source. (author)

  20. Factors which modulate the rates of skeletal muscle mass loss in non-small cell lung cancer patients: a pilot study.

    Science.gov (United States)

    Atlan, Philippe; Bayar, Mohamed Amine; Lanoy, Emilie; Besse, Benjamin; Planchard, David; Ramon, Jordy; Raynard, Bruno; Antoun, Sami

    2017-11-01

    Advanced non-small cell lung cancer (NSCLC) is associated with weight loss which may reflect skeletal muscle mass (SMM) and/or total adipose tissue (TAT) depletion. This study aimed to describe changes in body composition (BC) parameters and to identify the factors unrelated to the tumor which modulate them. SMM, TAT, and the proportion of SMM to SMM + TAT were assessed with computed tomography. Estimates of each BC parameter at follow-up initiation and across time were derived from a mixed linear model of repeated measurements with a random intercept and a random slope. The same models were used to assess the independent effect of gender, age, body mass index (BMI), and initial values on changes in each BC parameter. Sixty-four patients with stage III or IV NSCLC were reviewed. The mean ± SD decreases in body weight and SMM were respectively 59 ± 3 g/week (P SMM to SMM + TAT, estimated at 37 ± 2% at baseline. SMM loss was influenced by initial BMI (P SMM values (P = 0.0002): the higher the initial BMI or SMM values, the greater the loss observed. Weight loss was greater when the initial weight was heavier (P SMM wasting in NSCLC is lower when initial SMM and BMI values are low. These exploratory findings after our attempt to better understand the intrinsic factors associated with muscle mass depletion need to be confirmed in larger studies.

  1. An Exploratory Study on a High-Energy Flux (HEF) Calorimeter to Characterize Flammability of Advanced Engineered Polymers: Phase 1 - Ignition and Mass Loss Rate

    National Research Council Canada - National Science Library

    Tewarson, A

    1999-01-01

    This report describes a newly designed high-energy flux (HEF) calorimeter for the flammability evaluation of high fire resistant plastics exposed to high heat flux typical of combat field scenarios and large-scale fires...

  2. Asteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819

    DEFF Research Database (Denmark)

    Miglio, A.; Brogaard, Karsten Frank; Stello, D.

    2012-01-01

    Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G–K giants in open clusters with Kepler, we can now directly determine stellar masses...... for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar...... masses were determined by combining the available seismic parameters νmax and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between...

  3. The evaluation of tissue mass loss in the incision line of prostate with benign hyperplasia performed using holmium laser and cutting electrode.

    Science.gov (United States)

    Szewczyk, Mariusz; Jesionek-Kupnicka, Dorota; Lipiński, Marek Ireneusz; Lipinski, Piotr; Różański, Waldemar

    2014-01-01

    The aim of this study is to compare the changes in the incision line of prostatic adenoma using a monopolar cutting electrode and holmium laser, as well as the assessment of associated tissue mass and volume loss of benign prostatic hyperplasia (BPH). The material used in this study consisted of 74 preparations of prostatic adenoma obtained via open retropubic adenomectomy, with an average volume of 120.7 ml. The material obtained cut in vitro before fixation in formaldehyde. One lobe was cut using holmium laser, the other using a monopolar cutting electrode. After the incision was made, tissue mass and volume loss were evaluated. Thermocoagulation changes in the incision line were examinedunder light microscope. In the case of the holmium laser incision, the average tissue mass loss was 1.73 g, tissue volume loss 3.57 ml and the depth of thermocoagulation was 1.17 mm. When the monopolar cutting electrode was used average tissue mass loss was 0.807 g, tissue volume loss 2.48 ml and the depth of thermocoagulation was 0.19 mm. Where holmium laser was used, it was observed that the layer of tissue with thermocoagulation changes was deeper than in the case of the monopolar cutting electrode. Moreover, it was noticed that holmium laser caused bigger tissue mass and volume loss than the cutting electrode.

  4. High-velocity winds from a dwarf nova during outburst

    Science.gov (United States)

    Cordova, F. A.; Mason, K. O.

    1982-01-01

    An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km/s, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with relatively high luminosities (more than about 10 solar luminosities) and low inclination angles with respect to the observer's line of sight. The mass loss rate for cataclysmic variables is of order 10 to the -11th solar mass per yr; this is from 0.01 to 0.001 of the mass accretion rate onto the compact star in the binary. The mass loss may occur by a mechanism similar to that invoked for early-type stars, i.e., radiation absorbed in the lines accelerates the accreting gas to the high velocities observed.

  5. Could wind replace nuclear?

    International Nuclear Information System (INIS)

    2017-01-01

    This article aims at assessing the situation produced by a total replacement of nuclear energy by wind energy, while facing consumption demand at any moment, notably in December. The authors indicate the evolution of the French energy mix during December 2016, and the evolution of the rate between wind energy production and the sum of nuclear and wind energy production during the same month, and then give briefly some elements regarding necessary investments in wind energy to wholly replace nuclear energy. According to them, such a replacement would be ruinous

  6. Radiation-driven winds in x-ray binaries

    International Nuclear Information System (INIS)

    Friend, D.B.; Castor, J.I.

    1982-01-01

    We discuss the properties of a radiation-driven stellar wind in an X-ray binary system. The Castor, Abbott, Klein line-driven wind model is used, but the effects of the compact companion (gravity and continuum radiation pressure) and the centrifugal force due to orbital motion are included. These forces destroy the spherical symmetry of the wind and can make the mass loss and accretion strong functions of the size of the primary relative to its critical potential lobe. We in most systems the wind alone could power the X-ray emission. It also appears that, in the evolution of these systems, there would be a continuous transition from wind accretion to critical potential lobe overflow. The model is also used to make a prediction about the nature of a suspected binary system which is not known to be an X-ray emitter

  7. Water vapor concentration dependence and temperature dependence of Li mass loss from Li{sub 2}TiO{sub 3} with excess Li and Li{sub 4}SiO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Shimozori, Motoki [Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1, Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Katayama, Kazunari, E-mail: kadzu@nucl.kyushu-u.ac.jp [Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1, Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Hoshino, Tsuyoshi [Breeding Functional Materials Development Group, Department of Blanket Systems Research, Rokkasho Fusion Institute, Sector of Fusion Research and Development, Japan Atomic Energy Agency, 2-166 Obuch, Omotedate, Rokkasho-mura, Kamikita-gun, Aomori 039-3212 (Japan); Ushida, Hiroki; Yamamoto, Ryotaro; Fukada, Satoshi [Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1, Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan)

    2015-10-15

    Highlights: • Li mass loss from Li{sub 2.11}TiO{sub 3} increased proportionally to water vapor pressure. • Li mass loss from Li{sub 2.11}TiO{sub 3} at 600 °C was significantly smaller than expected. • Differences of Li mass loss behavior from Li{sub 2.11}TiO{sub 3} and Li{sub 4}SiO{sub 4} were shown. - Abstract: In this study, weight reduction of Li{sub 2}TiO{sub 3} with excess Li and Li{sub 4}SiO{sub 4} at elevated temperatures under hydrogen atmosphere or water vapor atmosphere was investigated. The Li mass loss for the Li{sub 2}TiO{sub 3} at 900 °C was 0.4 wt% under 1000 Pa H{sub 2} atmosphere and 1.5 wt% under 50 Pa H{sub 2}O atmosphere. The Li mass loss for the Li{sub 2}TiO{sub 3} increased proportionally to the water vapor pressure in the range from 50 to 200 Pa at 900 °C and increased with increasing temperature from 700 to 900 °C although Li mass loss at 600 °C was significantly smaller than expected. It was found that water vapor concentration dependence and temperature dependence of Li mass loss for the Li{sub 2}TiO{sub 3} and the Li{sub 4}SiO{sub 4} used in this work were quite different. Water vapor is released from the ceramic breeder materials into the purge gas due to desorption of adsorbed water and water formation reaction. The released water vapor possibly promotes Li mass loss with the formation of LiOH on the surface.

  8. Axially symmetric two-body problem in general relativity. III. Bondi mass loss and the failure of the quadrupole formula

    International Nuclear Information System (INIS)

    Cooperstock, F.I.; Hobill, D.W.

    1979-01-01

    Suggested difficulties and criticism regarding earlier work is addressed. It is demonstrated that the rate of gravitational energy loss from the authors' model free-fall system employing the widely accepted Bondi method agrees precisely with the results described in prior works. Origins of the breakdown of the quadrupole formalism for free fall, previously indicated, are now delineated in detail. The role of source structure in the energy loss rate re-emerges, bringing into question much of the earlier work of others. The iterative technique with flat-space wave operators is justified. A new approach to quasiperiodic systems such as binary stars is described. Ideally modeled upon the actual birth of such systems, it evolves from an initially stationary configuration, again avoiding the problems and ambiguities regarding incoming radiation

  9. Greenland Ice Sheet Mass Balance: Distribution of Increased Mass Loss with Climate Warming; 2003-07 Versus 1992-2002

    Science.gov (United States)

    Zwally, H. Jay; Li, Jun; Benner, Anita C.; Beckley, Matthew; Cornejo, Helen G.; DiMarzio, John; Giovinetto, Mario B.; Neumann, Thomas A.; Robbins, John; Saba, Jack L.; hide

    2011-01-01

    We derive mass changes of the Greenland ice sheet (GIS) for 2003-07 from ICESat laser altimetry and compare them with results for 1992-2002 from ERS radar and airborne laser altimetry. The GIS continued to grow inland and thin at the margins during 2003 07, but surface melting and accelerated flow significantly increased the marginal thinning compared with the 1990s. The net balance changed from a small loss of 7 plus or minus 3 Gt a 1(sup -1) in the 1990s to 171 plus or minus 4 Gt a (sup -1) for 2003-07, contributing 0.5 mm a(sup -1) to recent global sea-level rise. We divide the derived mass changes into two components: (1) from changes in melting and ice dynamics and (2) from changes in precipitation and accumulation rate. We use our firn compaction model to calculate the elevation changes driven by changes in both temperature and accumulation rate and to calculate the appropriate density to convert the accumulation-driven changes to mass changes. Increased losses from melting and ice dynamics (17-206 Gt a(sup-1) are over seven times larger than increased gains from precipitation (10 35 Gt a(sup-1) during a warming period of approximately 2 K (10 a)(sup -1) over the GIS. Above 2000m elevation, the rate of gain decreased from 44 to 28 Gt a(sup-1), while below 2000m the rate of loss increased from 51 to 198 Gt a(sup-1). Enhanced thinning below the equilibrium line on outlet glaciers indicates that increased melting has a significant impact on outlet glaciers, as well as accelerating ice flow. Increased thinning at higher elevations appears to be induced by dynamic coupling to thinning at the margins on decadal timescales.

  10. A 7-day high protein hypocaloric diet promotes cellular metabolic adaptations and attenuates lean mass loss in healthy males

    OpenAIRE

    Matthew Furber; Ana Anton-Solanas; Emma Koppe; Charlotte Ashby; Michael Roberts; Justin Roberts

    2017-01-01

    Mitochondrial quantity and density are associated with increased oxidative metabolism. It has been demonstrated that a hypocaloric high fat/low carbohydrate (HF/LC) diet can up-regulate transcriptional markers of mitochondrial biogenesis; this was yet to be explored in vivo subsequent to a high protein/low carbohydrate (HP/LC) diet. Thus the aims of the study were to explore such diets on transcriptional markers or mitochondrial biogenesis, body composition and resting metabolic rate (RMR). F...

  11. SEA-LEVEL RISE. Sea-level rise due to polar ice-sheet mass loss during past warm periods.

    Science.gov (United States)

    Dutton, A; Carlson, A E; Long, A J; Milne, G A; Clark, P U; DeConto, R; Horton, B P; Rahmstorf, S; Raymo, M E

    2015-07-10

    Interdisciplinary studies of geologic archives have ushered in a new era of deciphering magnitudes, rates, and sources of sea-level rise from polar ice-sheet loss during past warm periods. Accounting for glacial isostatic processes helps to reconcile spatial variability in peak sea level during marine isotope stages 5e and 11, when the global mean reached 6 to 9 meters and 6 to 13 meters higher than present, respectively. Dynamic topography introduces large uncertainties on longer time scales, precluding robust sea-level estimates for intervals such as the Pliocene. Present climate is warming to a level associated with significant polar ice-sheet loss in the past. Here, we outline advances and challenges involved in constraining ice-sheet sensitivity to climate change with use of paleo-sea level records. Copyright © 2015, American Association for the Advancement of Science.

  12. LIGHT CURVES OF CORE-COLLAPSE SUPERNOVAE WITH SUBSTANTIAL MASS LOSS USING THE NEW OPEN-SOURCE SUPERNOVA EXPLOSION CODE (SNEC)

    International Nuclear Information System (INIS)

    Morozova, Viktoriya; Renzo, Mathieu; Ott, Christian D.; Clausen, Drew; Couch, Sean M.; Ellis, Justin; Roberts, Luke F.; Piro, Anthony L.

    2015-01-01

    We present the SuperNova Explosion Code (SNEC), an open-source Lagrangian code for the hydrodynamics and equilibrium-diffusion radiation transport in the expanding envelopes of supernovae. Given a model of a progenitor star, an explosion energy, and an amount and distribution of radioactive nickel, SNEC generates the bolometric light curve, as well as the light curves in different broad bands assuming blackbody emission. As a first application of SNEC, we consider the explosions of a grid of 15 M ⊙ (at zero-age main sequence, ZAMS) stars whose hydrogen envelopes are stripped to different extents and at different points in their evolution. The resulting light curves exhibit plateaus with durations of ∼20–100 days if ≳1.5–2 M ⊙ of hydrogen-rich material is left and no plateau if less hydrogen-rich material is left. If these shorter plateau lengths are not seen for SNe IIP in nature, it suggests that, at least for ZAMS masses ≲20 M ⊙ , hydrogen mass loss occurs as an all or nothing process. This perhaps points to the important role binary interactions play in generating the observed mass-stripped supernovae (i.e., Type Ib/c events). These light curves are also unlike what is typically seen for SNe IIL, arguing that simply varying the amount of mass loss cannot explain these events. The most stripped models begin to show double-peaked light curves similar to what is often seen for SNe IIb, confirming previous work that these supernovae can come from progenitors that have a small amount of hydrogen and a radius of ∼500 R ⊙

  13. LIGHT CURVES OF CORE-COLLAPSE SUPERNOVAE WITH SUBSTANTIAL MASS LOSS USING THE NEW OPEN-SOURCE SUPERNOVA EXPLOSION CODE (SNEC)

    Energy Technology Data Exchange (ETDEWEB)

    Morozova, Viktoriya; Renzo, Mathieu; Ott, Christian D.; Clausen, Drew; Couch, Sean M.; Ellis, Justin; Roberts, Luke F. [TAPIR, Walter Burke Institute for Theoretical Physics, MC 350-17, California Institute of Technology, Pasadena, CA 91125 (United States); Piro, Anthony L., E-mail: morozvs@tapir.caltech.edu [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2015-11-20

    We present the SuperNova Explosion Code (SNEC), an open-source Lagrangian code for the hydrodynamics and equilibrium-diffusion radiation transport in the expanding envelopes of supernovae. Given a model of a progenitor star, an explosion energy, and an amount and distribution of radioactive nickel, SNEC generates the bolometric light curve, as well as the light curves in different broad bands assuming blackbody emission. As a first application of SNEC, we consider the explosions of a grid of 15 M{sub ⊙} (at zero-age main sequence, ZAMS) stars whose hydrogen envelopes are stripped to different extents and at different points in their evolution. The resulting light curves exhibit plateaus with durations of ∼20–100 days if ≳1.5–2 M{sub ⊙} of hydrogen-rich material is left and no plateau if less hydrogen-rich material is left. If these shorter plateau lengths are not seen for SNe IIP in nature, it suggests that, at least for ZAMS masses ≲20 M{sub ⊙}, hydrogen mass loss occurs as an all or nothing process. This perhaps points to the important role binary interactions play in generating the observed mass-stripped supernovae (i.e., Type Ib/c events). These light curves are also unlike what is typically seen for SNe IIL, arguing that simply varying the amount of mass loss cannot explain these events. The most stripped models begin to show double-peaked light curves similar to what is often seen for SNe IIb, confirming previous work that these supernovae can come from progenitors that have a small amount of hydrogen and a radius of ∼500 R{sub ⊙}.

  14. A Comparison between Physics-based and Polytropic MHD Models for Stellar Coronae and Stellar Winds of Solar Analogs

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, O. [Lowell Center for Space Science and Technology, University of Massachusetts, Lowell, MA 01854 (United States)

    2017-02-01

    The development of the Zeeman–Doppler Imaging (ZDI) technique has provided synoptic observations of surface magnetic fields of low-mass stars. This led the stellar astrophysics community to adopt modeling techniques that have been used in solar physics using solar magnetograms. However, many of these techniques have been neglected by the solar community due to their failure to reproduce solar observations. Nevertheless, some of these techniques are still used to simulate the coronae and winds of solar analogs. Here we present a comparative study between two MHD models for the solar corona and solar wind. The first type of model is a polytropic wind model, and the second is the physics-based AWSOM model. We show that while the AWSOM model consistently reproduces many solar observations, the polytropic model fails to reproduce many of them, and in the cases where it does, its solutions are unphysical. Our recommendation is that polytropic models, which are used to estimate mass-loss rates and other parameters of solar analogs, must first be calibrated with solar observations. Alternatively, these models can be calibrated with models that capture more detailed physics of the solar corona (such as the AWSOM model) and that can reproduce solar observations in a consistent manner. Without such a calibration, the results of the polytropic models cannot be validated, but they can be wrongly used by others.

  15. Galactic winds and the hubble sequence

    International Nuclear Information System (INIS)

    Bregman, J.N.

    1978-01-01

    The conditions for maintenance of supernova-driven galactic winds have been investigated to assess their role in the morphology of disk-bulge galaxies. A fluid mechanical model with gas and stars which includes galactic rotation has been used to investigate several classes of winds. It is found that many galaxies, once their initial gas is depleted, can maintain a wind throughout the entire galaxy, a conditon most easily satisfied by systems with a small bulge-to-disk ratio. If the ratio of supernova heating to total mass loss falls below a critical value that depends on galaxy type and mass, only a partial wind exterior to a critical surface can exist, with infall occurring at interior points. Galaxies in which only the bulge was depleted of gas may support a bulge wind that does not interact with the colder and denser gas in the disk.These results indicate that if SO galaxies are a transition class between elliptical and spiral galaxies, it is probably because early galactic winds, which may initially deplete a galaxy of gas, are more prevalent in SO than in spiral galaxies. However, if SO's form a parallel sequence with spirals, the initial gas-depletion mechanism must be independent of bulge-to-disk ratio. These results are not strongly influenced by altering the galactic mass model, including electron conduction in the flow equations, or adding massive halos

  16. Wind energy

    International Nuclear Information System (INIS)

    Kotevski, Darko

    2003-01-01

    Wind is not only free, it is inexhaustible. Wind energy has come a very long way since the prototypes of just 20 years ago. today's wind turbines are state-of-the-art technology - modular and quick to install anywhere where there is sufficient wind potential to provide secure, centralised or distributed generation. It is a global phenomenon, the world's fastest growing energy sector, a clean and effective modern technology that completely avoids pollution and thus reducing the 'green house' effect. (Original)

  17. Response of small glaciers to climate change: runoff from glaciers of the Wind River range, Wyoming

    Science.gov (United States)

    Bliss, A. K.; Stamper, B.

    2017-12-01

    Runoff from glaciers affects downstream ecosystems by influencing the quantity, seasonality, and chemistry of the water. We describe the present state of glaciers in the Wind River range, Wyoming and consider how these glaciers will change in the future. Wind River glaciers have been losing mass in recent decades, as seen with geodetic techniques and by examining glacier morphology. Interestingly, the 2016/7 winter featured one of the largest snowfalls on record. Our primary focus is the Dinwoody Glacier ( 3 km^2, 3300-4000 m above sea level). We present data collected in mid-August 2017 including glacier ablation rates, snow line elevations, and streamflow. We compare measured glacier mass loss to streamflow at the glacier terminus and at a USGS stream gauge farther downstream. Using a hydrological model, we explore the fate of glacial runoff as it moves into downstream ecosystems and through ranchlands important to local people. The techniques used here can be applied to similar small-glacier systems in other parts of the world.

  18. Wind Structure and Wind Loading

    DEFF Research Database (Denmark)

    Brorsen, Michael

    The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...

  19. Wind tipping point

    International Nuclear Information System (INIS)

    Wood, E.

    2006-01-01

    In this article the author looks at how in five years wind energy has rapidly evolved into a mainstream industry. The United States has begun to look at wind differently - from a macroeconomic perspective.'This country is going to become increasingly committed to renewable energy, and it's not about altruism', said Alan Waxman, managing director of Goldman Sachs and Co., a financial giant that has invested $1 billion in the resource. Wind is seen not just as an environmentally benign alternative, but also as a means to solve some large problems plaguing the energy business and ultimately the United States as a whole. The last year brought record-breaking electricity rate increases, in some cases doubling consumer costs, and escalating the flight of large enterprises out of high-cost energy regions - or out of business altogether. The rate hikes were caused by hurricanes that hit the southern states and disrupted natural gas and oil operations. Adding wind power to the grid is increasingly seen as a way to limit the price shock caused by such events. Wind power reduces reliance on gas and oil-fired generation and, in particular, creates a hedge against spikes in natural gas, a fuel that increasingly sets the marginal price. Large energy users, too, are becoming aware of wind's hedging benefits. The author looks at the cost issues and how the future of wind energy in the country can be sustained as a reliable alternative fuel

  20. Chronologically scheduled snacking with high-protein products within the habitual diet in type-2 diabetes patients leads to a fat mass loss: a longitudinal study

    Directory of Open Access Journals (Sweden)

    Martínez J Alfredo

    2011-07-01

    Full Text Available Abstract Background Obesity is the most relevant overnutrition disease worldwide and is associated to different metabolic disorders such as insulin resistance and type-2 diabetes. Low glycemic load foods and diets and moderately high protein intake have been shown to reduce body weight and fat mass, exerting also beneficial effects on LDL-cholesterol, triglyceride concentrations, postprandial glucose curve and HDL-cholesterol levels. The present study aimed at studying the potential functionality of a series of low glycemic index products with moderately high protein content, as possible coadjuvants in the control of type-2 diabetes and weight management following a chronologically planned snacking offer (morning and afternoon. Methods The current trial followed a single group, sequential, longitudinal design, with two consecutive periods of 4 weeks each. A total of 17 volunteers participated in the study. The first period was a free living period, with volunteers' habitual ad libitum dietary pattern, while the second period was a free-living period with structured meal replacements at breakfast, morning snack and afternoon snack, which were exchanged by specific products with moderately high protein content and controlled low glycemic index, following a scheduled temporal consumption. Blood extractions were performed at the beginning and at the end of each period (free-living and intervention. Parameters analysed were: fasting glucose, insulin, glycosylated hemoglobin, total-, HDL- and LDL-cholesterol, triglyceride, C - reactive protein and Homocysteine concentrations. Postprandial glucose and insulin were also measured. Anthropometrical parameters were monitored each 2 weeks during the whole study. Results A modest but significant (p = 0.002 reduction on body weight (1 kg was observed during the intervention period, mainly due to the fat mass loss (0.8 kg, p = 0.02. This weight reduction was observed without apparently associated changes in

  1. Balanced conditions or slight mass gain of glaciers in the Lahaul and Spiti region (northern India, Himalaya during the nineties preceded recent mass loss

    Directory of Open Access Journals (Sweden)

    C. Vincent

    2013-04-01

    Full Text Available The volume change of the Chhota Shigri Glacier (India, 32° 20 N, 77° 30' E between 1988 and 2010 has been determined using in situ geodetic measurements. This glacier has experienced only a slight mass loss between 1988 and 2010 (−3.8 ± 2.0 m w.e. (water equivalent corresponding to −0.17 ± 0.09 m w.e. yr−1. Using satellite digital elevation models (DEM differencing and field measurements, we measure a negative mass balance (MB between 1999 and 2010 (−4.8 ± 1.8 m w.e. corresponding to −0.44 ± 0.16 m w.e. yr−1. Thus, we deduce a slightly positive or near-zero MB between 1988 and 1999 (+1.0 ± 2.7 m w.e. corresponding to +0.09 ± 0.24 m w.e. yr−1. Furthermore, satellite DEM differencing reveals that the MB of the Chhota Shigri Glacier (−0.39 ± 0.15 m w.e. yr−1 has been only slightly less negative than the MB of a 2110 km2 glaciarized area in the Lahaul and Spiti region (−0.44 ± 0.09 m w.e. yr−1 during 1999−2011. Hence, we conclude that the ice wastage is probably moderate in this region over the last 22 yr, with near equilibrium conditions during the nineties, and an ice mass loss after. The turning point from balanced to negative mass budget is not known but lies probably in the late nineties and at the latest in 1999. This positive or near-zero MB for Chhota Shigri Glacier (and probably for the surrounding glaciers of the Lahaul and Spiti region during at least part of the 1990s contrasts with a recent compilation of MB data in the Himalayan range that indicated ice wastage since 1975. However, in agreement with this compilation, we confirm more negative balances since the beginning of the 21st century.

  2. Stellar Evolution in NGC 6791: Mass Loss on the Red Giant Branch and the Formation of Low-Mass White Dwarfs

    Science.gov (United States)

    Kalirai, Jasonjot S.; Bergeron, P.; Hansen, Brad M. S.; Kelson, Daniel D.; Reitzel, David B.; Rich, R. Michael; Richer, Harvey B.

    2007-12-01

    We present the first detailed study of the properties (temperatures, gravities, and masses) of the NGC 6791 white dwarf population. This unique stellar system is both one of the oldest (8 Gyr) and most metal-rich ([Fe/H]~+0.4) open clusters in our Galaxy and has a color-magnitude diagram (CMD) that exhibits both a red giant clump and a much hotter extreme horizontal branch. Fitting the Balmer lines of the white dwarfs in the cluster using Keck/LRIS spectra suggests that most of these stars are undermassive, =0.43+/-0.06 Msolar, and therefore could not have formed from canonical stellar evolution involving the helium flash at the tip of the red giant branch. We show that at least 40% of NGC 6791's evolved stars must have lost enough mass on the red giant branch to avoid the flash and therefore did not convert helium into carbon-oxygen in their core. Such increased mass loss in the evolution of the progenitors of these stars is consistent with the presence of the extreme horizontal branch in the CMD. This unique stellar evolutionary channel also naturally explains the recent finding of a very young age (2.4 Gyr) for NGC 6791 from white dwarf cooling theory; helium-core white dwarfs in this cluster will cool ~3 times slower than carbon-oxygen-core stars, and therefore the corrected white dwarf cooling age is in fact >~7 Gyr, consistent with the well-measured main-sequence turnoff age. These results provide direct empirical evidence that mass loss is much more efficient in high-metallicity environments and therefore may be critical in interpreting the ultraviolet upturn in elliptical galaxies. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based on observations obtained at the

  3. Wind power

    International Nuclear Information System (INIS)

    Gipe, P.

    2007-01-01

    This book is a translation of the edition published in the USA under the title of ''wind power: renewable energy for home, farm and business''. In the wake of mass blackouts and energy crises, wind power remains a largely untapped resource of renewable energy. It is a booming worldwide industry whose technology, under the collective wing of aficionados like author Paul Gipe, is coming of age. Wind Power guides us through the emergent, sometimes daunting discourse on wind technology, giving frank explanations of how to use wind technology wisely and sound advice on how to avoid common mistakes. Since the mid-1970's, Paul Gipe has played a part in nearly every aspect of wind energy development from installing small turbines to promoting wind energy worldwide. As an American proponent of renewable energy, Gipe has earned the acclaim and respect of European energy specialists for years, but his arguments have often fallen on deaf ears at home. Today, the topic of wind power is cropping up everywhere from the beaches of Cape Cod to the Oregon-Washington border, and one wind turbine is capable of producing enough electricity per year to run 200 average American households. Now, Paul Gipe is back to shed light on this increasingly important energy source with a revised edition of Wind Power. Over the course of his career, Paul Gipe has been a proponent, participant, observer, and critic of the wind industry. His experience with wind has given rise to two previous books on the subject, Wind Energy Basics and Wind Power for Home and Business, which have sold over 50,000 copies. Wind Power for Home and Business has become a staple for both homeowners and professionals interested in the subject, and now, with energy prices soaring, interest in wind power is hitting an all-time high. With chapters on output and economics, Wind Power discloses how much you can expect from each method of wind technology, both in terms of energy and financial savings. The book updated models

  4. Wind Turbine Generator System Acoustic Noise Test Report for the Gaia Wind 11-kW Wind Turbine

    Energy Technology Data Exchange (ETDEWEB)

    Huskey, A.

    2011-11-01

    This report details the acoustic noise test conducted on the Gaia-Wind 11-kW wind turbine at the National Wind Technology Center. The test turbine is a two- bladed, downwind wind turbine with a rated power of 11 kW. The test turbine was tested in accordance with the International Electrotechnical Commission standard, IEC 61400-11 Ed 2.1 2006-11 Wind Turbine Generator Systems -- Part 11 Acoustic Noise Measurement Techniques.

  5. The origin of carbon revisited: winds of carbon-stars

    International Nuclear Information System (INIS)

    Mattsson, L

    2008-01-01

    Chemical evolution models, differing in the nucleosynthesis prescriptions (yields) for carbon, nitrogen and oxygen, have been computed for the Milky Way and Andromeda (NGC 224). All models fit the observed O/H gradients well and reproduce the main characteristics of the gas distributions, but they are also designed to do so. The N/O gradient for NGC 224 cannot be reproduced without ad hoc modifications to the yields and a similar result is obtained for the Milky Way N/O gradient, although in the latter case the slopes of the gradients obtained with unmodified yields are consistent with the observed gradient. For the C/O gradients (obtained from B stars) the results are inconclusive. The C/Fe, N/Fe, O/Fe versus Fe/H, as well as C/O versus O/H trends predicted by the models for the solar neighbourhood were compared with stellar abundances from the literature. For O/Fe versus Fe/H, all models fit the data, but for C/Fe, N/Fe versus Fe/H and C/O versus O/H, only modified sets of yields provide good fits. Since in the best-fit model, the yields were modified such that carbon should be primarily produced in low-mass stars, it is quite possible that in every environment where the peak of star formation happened a few Gyr back in time, the winds of carbon stars are responsible for most of the carbon enrichment, although models with a significant contribution from high-mass stars cannot be ruled out. In the solar neighbourhood, almost two-thirds of the carbon in the interstellar medium may come from carbon stars. Finally, the challenges met by stellar evolution and nucleosynthesis modelling due to this 'carbon star hypothesis' for the origin of carbon are discussed. It is suggested that a mass-loss prescription where the mass-loss rate depends on the carbon excess may act as a self-regulating mechanism for how much carbon a carbon star can deliver to the interstellar medium.

  6. Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method

    Directory of Open Access Journals (Sweden)

    Xingjun Lv

    2011-11-01

    Full Text Available In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.

  7. Brillouin corrosion expansion sensors for steel reinforced concrete structures using a fiber optic coil winding method.

    Science.gov (United States)

    Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

    2011-01-01

    In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.

  8. Meteorological Controls on Wind Turbine Wakes

    DEFF Research Database (Denmark)

    Barthelmie, Rebecca J.; Hansen, Kurt Schaldemose; Pryor, S.C.

    2013-01-01

    , modeling, and predicting this complex and interdependent system is therefore critical to understanding and modeling wind farm power losses due to wakes, and to optimizing wind farm layout. This paper quantifies the impact of these variables on the power loss due to wakes using data from the large offshore......The primary control on the magnitude of the power losses induced by wind turbine wakes in large wind farms is the hub-height wind speed via its link to the turbine thrust coefficient. Hence, at low to moderate wind speeds (between cut-in and rated turbine wind speeds) when the thrust coefficient...

  9. Assessing high wind energy penetration

    DEFF Research Database (Denmark)

    Tande, J.O.

    1995-01-01

    In order to convincingly promote installing wind power capacity as a substantial part of the energy supply system, a set of careful analyses must be undertaken. This paper applies a case study concentrated on assessing the cost/benefit of high wind energy penetration. The case study considers...... expanding the grid connected wind power capacity in Praia, the capital of Cape Verde. The currently installed 1 MW of wind power is estimated to supply close to 10% of the electric energy consumption in 1996. Increasing the wind energy penetration to a higher level is considered viable as the project...... with the existing wind power, supply over 30% of the electric consumption in 1996. Applying the recommended practices for estimating the cost of wind energy, the life-cycle cost of this 2.4 MW investment is estimated at a 7% discount rate and a 20 year lifetime to 0.26 DKK/kW h....

  10. Hydrodynamic effects of nuclear active galaxy winds on host galaxies

    International Nuclear Information System (INIS)

    Schiano, A.V.R.

    1984-01-01

    In order to test the hypothesized existence of a powerful, thermal wind in active galactic nuclei, the hydrodynamic effects of such a wind on a model galactic interstellar medium (ISM) are investigated. The properties of several model ISMs are derived from observations of the Milky Way's ISM and those of nearby spiral and elliptical galaxies. The propagation of the wind into the low density gas component of the ISM is studied using the Kompaneets approximation of a strong explosion in an exponential atmosphere. Flattened gas distributions are shown to experience blow-out of wind gas along the symmetry axis. Next, the interaction of dense, interstellar clouds with the wind is investigated. The stability and mass loss of clouds in the wind are studied and it is proposed that clouds survive the encounter with the wind over large timescales. It is proposed that the narrow emission line regions (NELR) of active galaxies are the result of the interaction of active nuclei photons and a thermal wind on large, interstellar clouds

  11. Integrative Analyses of miRNA-mRNA Interactions Reveal let-7b, miR-128 and MAPK Pathway Involvement in Muscle Mass Loss in Sex-Linked Dwarf Chickens

    Science.gov (United States)

    Luo, Wen; Lin, Shumao; Li, Guihuan; Nie, Qinghua; Zhang, Xiquan

    2016-01-01

    The sex-linked dwarf (SLD) chicken is an ideal model system for understanding growth hormone (GH)-action and growth hormone receptor (GHR) function because of its recessive mutation in the GHR gene. Skeletal muscle mass is reduced in the SLD chicken with a smaller muscle fiber diameter. Our previous study has presented the mRNA and miRNA expression profiles of the SLD chicken and normal chicken between embryo day 14 and seven weeks of age. However, the molecular mechanism of GHR-deficient induced muscle mass loss is still unclear, and the key molecules and pathways underlying the GHR-deficient induced muscle mass loss also remain to be illustrated. Here, by functional network analysis of the differentially expressed miRNAs and mRNAs between the SLD and normal chickens, we revealed that let-7b, miR-128 and the MAPK pathway might play key roles in the GHR-deficient induced muscle mass loss, and that the reduced cell division and growth are potential cellular processes during the SLD chicken skeletal muscle development. Additionally, we also found some genes and miRNAs involved in chicken skeletal muscle development, through the MAPK, PI3K-Akt, Wnt and Insulin signaling pathways. This study provides new insights into the molecular mechanism underlying muscle mass loss in the SLD chickens, and some regulatory networks that are crucial for chicken skeletal muscle development. PMID:26927061

  12. Wind/Hybrid Electricity Applications

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, Lori [Iowa Department of Natural Resources, Des Moines, IA (United States)

    2001-03-01

    Wind energy is widely recognized as the most efficient and cost effective form of new renewable energy available in the Midwest. New utility-scale wind farms (arrays of large turbines in high wind areas producing sufficient energy to serve thousands of homes) rival the cost of building new conventional forms of combustion energy plants, gas, diesel and coal power plants. Wind energy is not subject to the inflationary cost of fossil fuels. Wind energy can also be very attractive to residential and commercial electric customers in high wind areas who would like to be more self-sufficient for their energy needs. And wind energy is friendly to the environment at a time when there is increasing concern about pollution and climate change. However, wind energy is an intermittent source of power. Most wind turbines start producing small amounts of electricity at about 8-10 mph (4 meters per second) of wind speed. The turbine does not reach its rated output until the wind reaches about 26-28 mph (12 m/s). So what do you do for power when the output of the wind turbine is not sufficient to meet the demand for energy? This paper will discuss wind hybrid technology options that mix wind with other power sources and storage devices to help solve this problem. This will be done on a variety of scales on the impact of wind energy on the utility system as a whole, and on the commercial and small-scale residential applications. The average cost and cost-benefit of each application along with references to manufacturers will be given. Emerging technologies that promise to shape the future of renewable energy will be explored as well.

  13. Formulation and evaluation of the use of edible coatings based on gellan chunks of fresh pineapple cut to minimize deterioration of quality attributes and mass loss

    International Nuclear Information System (INIS)

    Saborio Marin, Laura

    2014-01-01

    The result of the use of edible coatings on special based of gellan in various formulations applied on pieces of fresh cut pineapple is evaluated to reduce the degradation of the quality characteristics and mass loss, as a plan to increase the usefulness. The effect of storage time of the fruit before processing (TAP), the application of vacuum pressure and concentration has been studied of the active components (gellan (0,50-1,00%), oil (0,00 -0,20%), glycerol and sorbitol (1,5-2,5%), CaCl 2 (1.0-10,0%)) of the forming solutions of coating. Several parameters are evaluated: the loss of juice, weight and composition of O 2 and CO 2 in the headspace, content of soluble solids (SS), titratable acidity (TA) color, darkening and appearance of pineapple chunks. The effect of forming solutions is measured on the adhesion, uniformity, coverage and determination of the water vapor resistance (RVA) coating and the presence of molds and yeasts during refrigerated storage at 5 degrees Celsius and 80% relative humidity. Another finding was that the loss of juice of the pieces uncoated increased (p≤0,05) as the increase TAP of 1 to 3 weeks, still higher than those of the coated pieces (0,50-0,75% gellan ), which have been minimal, while weight loss has decreased. The application of a vacuum pressure of 0,08 MPa before coating the pieces has favored the juice loss after the first two weeks of storage and reduced weight loss of uncoated pieces along the storage. The formulation comprised of 0,75% gellan, 1,5% glycerol, 0,10% oil and 1,0% of CaCl 2 has been which allows further reduction of juice loss and weight of pineapple chunks stored at 5 degrees Celsius and 80% RH [es

  14. Comparison of WindTrax and flux-gradient technique in determining PM10 emission rates from a beef cattle feedlot

    Science.gov (United States)

    Several emission estimation methods can be used to determine emission fluxes from ground-level area sources, including open-lot beef cattle feedlots. This research determined PM10 emission fluxes from a commercial cattle feedlot in Kansas using WindTrax, a backward Lagrangian stochastic-based atmosp...

  15. VisibleWind: wind profile measurements at low altitude

    Science.gov (United States)

    Wilkerson, Tom; Bradford, Bill; Marchant, Alan; Apedaile, Tom; Wright, Cordell

    2009-09-01

    VisibleWindTM is developing an inexpensive rapid response system, for accurately characterizing wind shear and small scale wind phenomena in the boundary layer and for prospecting suitable locations for wind power turbines. The ValidWind system can also collect reliable "ground truth" for other remote wind sensors. The system employs small (0.25 m dia.) lightweight balloons and a tracker consisting of an Impulse 200 XL laser rangefinder coupled to a PC for automated data recording. Experiments on balloon trajectories demonstrate that the laser detection of range (+/- 0.5 m), together with measured azimuth and altitude, is an inexpensive, convenient, and capable alternative to other wind tracking methods. The maximum detection range has been increased to 2200 meters using micro-corner-cube retroreflector tape on balloons. Low power LEDs enable nighttime tracking. To avoid large balloon gyrations about the mean trajectory, we use balloons having low ascent rates and subcritical Reynolds numbers. Trajectory points are typically recorded every 4 - 7 seconds. Atmospheric features observed under conditions of inversions or "light and variable winds" include abrupt onsets of shear at altitudes of 100-250 m, velocity changes of order 1-3 m/s within layers of 10-20 m thickness, and veering of the wind direction by 180 degrees or more as altitude increases from 300 to 500 m. We have previously reported comparisons of balloon-based wind profiles with the output of a co-located sodar. Even with the Impulse rangefinder, our system still requires a "man in the loop" to track the balloon. A future system enhancement will automate balloon tracking, so that laser returns are obtained automatically at 1 Hz. While balloon measurements of large-scale, high altitude wind profiles are well known, this novel measurement system provides high-resolution, real-time characterization of the fluctuating local wind fields at the bottom of the boundary layer where wind power turbines and other

  16. Stellar winds and coronae of low-mass Population II/III stars

    Science.gov (United States)

    Suzuki, Takeru K.

    2018-06-01

    We investigated stellar winds from zero-/low-metallicity low-mass stars by magnetohydrodynamical simulations for stellar winds driven by Alfvén waves from stars with mass M = (0.6-0.8) M⊙ and metallicity Z = (0-1) Z⊙, where M⊙ and Z⊙ are the solar mass and metallicity, respectively. Alfvénic waves, which are excited by the surface convection, travel upward from the photosphere and heat up the corona by their dissipation. For lower Z, denser gas can be heated up to the coronal temperature because of the inefficient radiation cooling. The coronal density of Population II/III stars with Z ≤ 0.01 Z⊙ is one to two orders of magnitude larger than that of a solar-metallicity star with the same mass, and as a result, the mass loss rate, \\dot{M}, is 4.5-20 times larger. This indicates that metal accretion on low-mass Pop. III stars is negligible. The soft X-ray flux of the Pop. II/III stars is also expected to be ˜1-30 times larger than that of a solar-metallicity counterpart owing to the larger coronal density, even though the radiation cooling efficiency is smaller. A larger fraction of the input Alfvénic wave energy is transmitted to the corona in low-Z stars because they avoid severe reflection owing to the smaller density difference between the photosphere and the corona. Therefore, a larger fraction is converted to the thermal energy of the corona and the kinetic energy of the stellar wind. From this energetics argument, we finally derived a scaling of \\dot{M} as \\dot{M}∝ L R_{\\star }^{11/9} M_{\\star }^{-10/9} T_eff^{11/2}[\\max (Z/Z_{⊙},0.01)]^{-1/5}, where L, R⋆, and Teff are the stellar luminosity, radius, and effective temperature, respectively.

  17. Stellar winds and coronae of low-mass Population II/III stars

    Science.gov (United States)

    Suzuki, Takeru K.

    2018-04-01

    We investigated stellar winds from zero-/low-metallicity low-mass stars by magnetohydrodynamical simulations for stellar winds driven by Alfvén waves from stars with mass M = (0.6-0.8) M⊙ and metallicity Z = (0-1) Z⊙, where M⊙ and Z⊙ are the solar mass and metallicity, respectively. Alfvénic waves, which are excited by the surface convection, travel upward from the photosphere and heat up the corona by their dissipation. For lower Z, denser gas can be heated up to the coronal temperature because of the inefficient radiation cooling. The coronal density of Population II/III stars with Z ≤ 0.01 Z⊙ is one to two orders of magnitude larger than that of a solar-metallicity star with the same mass, and as a result, the mass loss rate, \\dot{M}, is 4.5-20 times larger. This indicates that metal accretion on low-mass Pop. III stars is negligible. The soft X-ray flux of the Pop. II/III stars is also expected to be ˜1-30 times larger than that of a solar-metallicity counterpart owing to the larger coronal density, even though the radiation cooling efficiency is smaller. A larger fraction of the input Alfvénic wave energy is transmitted to the corona in low-Z stars because they avoid severe reflection owing to the smaller density difference between the photosphere and the corona. Therefore, a larger fraction is converted to the thermal energy of the corona and the kinetic energy of the stellar wind. From this energetics argument, we finally derived a scaling of \\dot{M} as \\dot{M}∝ L R_{\\star }^{11/9} M_{\\star }^{-10/9} T_eff^{11/2}[\\max (Z/Z_{⊙},0.01)]^{-1/5}, where L, R⋆, and Teff are the stellar luminosity, radius, and effective temperature, respectively.

  18. Persistent X-Ray Emission from ASASSN-15lh: Massive Ejecta and Pre-SLSN Dense Wind?

    Science.gov (United States)

    Huang, Yan; Li, Zhuo

    2018-06-01

    The persistent soft X-ray emission from the location of the most luminous supernova (SN) so far, ASASSN-15lh (or SN 2015L), with L∼ {10}42 {erg} {{{s}}}-1, is puzzling. We show that it can be explained by radiation from electrons accelerated by the SN shock inverse-Compton scattering the intense UV photons. The non-detection in radio requires strong free–free absorption in the dense medium. In these interpretations, the circumstellar medium is derived to be a wind (n ∝ R ‑2) with mass-loss rate of \\dot{{M}}≳ 3× {10}-3{{M}}ȯ ({{v}}{{w}}/{10}3 {{k}}{{m}} {{{s}}}-1) {{{y}}{{r}}}-1, and the initial velocity of the bulk SN ejecta is ≲ 0.02c. These constraints imply a massive ejecta mass of ≳ 60({E}0/2× {10}52 {erg}){M}ȯ in ASASSN-15lh, and a strong wind ejected by the progenitor star within ∼ 8{({v}{{w}}/{10}3{km}{{{s}}}-1)}-1 yr before explosion.

  19. Commercial wind power

    International Nuclear Information System (INIS)

    Braun, G.W.; Smith, D.R.

    1992-01-01

    In 1990 the 23,000 wind turbines in the world connected to utility grids were rated at a total of 2200 MW and produced 3,353,000,000 kWh of electricity. This represents the residential use of a city with population of 1,000,000 at US energy use rates, or 2,000,000 at European rates. Denmark produced about 2% of its electricity from the wind, while California and Hawaii produced about 1% of theirs. California wind farms produced 76% of the world total, and Pacific Gas and Electric Company (PG and E) received nearly half of this. In addition to these grid-connected turbines, more than 50,000 smaller turbines (averaging about 100 watts each) supplied electricity to remote areas, such as Mongolia. Such non-grid-connected turbines can be components of hybrid generation systems when combined with energy storage and/or complementary power sources. However, the emphasis of this paper is on utility-connected wind turbines. Wind also supplies mechanical energy, such as for water pumping

  20. Wind energy power plants (wind farms) review and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Newbold, K B; McKeary, M [McMaster Univ., Hamilton, ON (Canada). McMaster Inst. of Environment and Health

    2010-07-01

    Global wind power capacity has increased by an average cumulative rate of over 30 percent over the past 10 years. Although wind energy emits no air pollutants and facilities can often share spaces with other activities, public opposition to wind power development is an ongoing cause of concern. Development at the local level in Ontario has been met with fierce opposition on the basis of health concerns, aesthetic values, potential environmental impacts, and economic risks. This report was prepared for the Town of Wasaga Beach, and examined some of the controversy surrounding wind power developments through a review of evidence found in the scientific literature. The impacts of wind power developments related to noise, shadow flicker, avian mortality, bats, and real estate values were evaluated. The study included details of interviews conducted with individuals from Ontario localities where wind farms were located. 77 refs., 1 tab., 1 fig., 2 appendices.

  1. Grid Integration of Offshore Wind | Wind | NREL

    Science.gov (United States)

    Grid Integration of Offshore Wind Grid Integration of Offshore Wind Much can be learned from the existing land-based integration research for handling the variability and uncertainty of the wind resource Arklow Bank offshore wind park consists of seven GE Wind 3.6-MW wind turbines. Integration and

  2. European wind turbine catalogue

    International Nuclear Information System (INIS)

    1994-01-01

    The THERMIE European Community programme is designed to promote the greater use of European technology and this catalogue contributes to the fulfillment of this aim by dissemination of information on 50 wind turbines from 30 manufacturers. These turbines are produced in Europe and are commercially available. The manufacturers presented produce and sell grid-connected turbines which have been officially approved in countries where this approval is acquired, however some of the wind turbines included in the catalogue have not been regarded as fully commercially available at the time of going to print. The entries, which are illustrated by colour photographs, give company profiles, concept descriptions, measured power curves, prices, and information on design and dimension, safety systems, stage of development, special characteristics, annual energy production, and noise pollution. Lists are given of wind turbine manufacturers and agents and of consultants and developers in the wind energy sector. Exchange rates used in the conversion of the prices of wind turbines are also given. Information can be found on the OPET network (organizations recognised by the European Commission as an Organization for the Promotion of Energy Technologies (OPET)). An article describes the development of the wind power industry during the last 10-15 years and another article on certification aims to give an overview of the most well-known and acknowledged type approvals currently issued in Europe. (AB)

  3. Wind Energy

    Energy Technology Data Exchange (ETDEWEB)

    Beurskens, H.J.M. [SET Analysis, Kievitlaan 26, 1742 AD Schagen (Netherlands); Brand, A.J. [Energy research Centre of the Netherlands ECN, Unit Wind Energy, P.O. Box 1, 1755 ZG Petten (Netherlands)

    2013-02-15

    Over the years, wind energy has become a major source of renewable energy worldwide. The present chapter addresses the wind resource, which is available for exploitation for large-scale electricity production, and its specific physical properties. Furthermore, the technical options available to convert the energy of the air flow into mechanical energy and electricity are described. Specific problems of large-scale integration of wind energy into the grid as well as the present and future market developments are described in this chapter. Finally, environmental aspects are discussed briefly.

  4. EDITORIAL: Wind energy

    Science.gov (United States)

    Mann, Jakob; Nørkær Sørensen, Jens; Morthorst, Poul-Erik

    2008-01-01

    Wind energy is rapidly growing. In 2006 the installed generating capacity in the world increased by 25%, a growth rate which has more or less been sustained during the last decade. And there is no reason to believe that this growth will slow significantly in the coming years. For example, the United Kingdom's goal for installed wind turbines by 2020 is 33 GW up from 2 GW in 2006, an average annual growth rate of 22% over that period. More than half of all turbines are installed in Europe, but United States, India and lately China are also rapidly growing markets. The cradle of modern wind energy was set by innovative blacksmiths in rural Denmark. Now the wind provides more than 20% of the electrical power in Denmark, the industry has professionalized and has close ties with public research at universities. This focus issue is concerned with research in wind energy. The main purposes of research in wind energy are to: decrease the cost of power generated by the wind; increase the reliability and predictability of the energy source; investigate and reduce the adverse environmental impact of massive deployment of wind turbines; build research based educations for wind energy engineers. This focus issue contains contributions from several fields of research. Decreased costs cover a very wide range of activities from aerodynamics of the wind turbine blades, optimal site selection for the turbines, optimization of the electrical grid and power market for a fluctuating source, more efficient electrical generators and gears, and new materials and production techniques for turbine manufacturing. The United Kingdom recently started the construction of the London Array, a 1 GW off-shore wind farm east of London consisting of several hundred turbines. To design such a farm optimally it is necessary to understand the chaotic and very turbulent flow downwind from a turbine, which decreases the power production and increases the mechanical loads on other nearby turbines. Also

  5. Coastal Ohio Wind Project

    Energy Technology Data Exchange (ETDEWEB)

    Gorsevski, Peter [Bowling Green State Univ., OH (United States); Afjeh, Abdollah [Univ. of Toledo, OH (United States); Jamali, Mohsin [Univ. of Toledo, OH (United States); Bingman, Verner [Bowling Green State Univ., OH (United States)

    2014-04-04

    to collect additional monitoring parameters such as passage rates, flight paths, flight directions, and flight altitudes of nocturnal migrating species. Our work focused on the design and development of custom built marine radar that used t-bar and parabolic dish antennas. The marine radar used in the project was Furuno (XANK250) which was coupled with a XIR3000B digitizing card from Russell Technologies for collection of the radar data. The radar data was processed by open source radR processing software using different computational techniques and methods. Additional data from thermal IR imaging cameras were collected to detect heat emitted from objects and provide information on movements of birds and bats, data which we used for different animal flight behavior analysis. Lastly, the data from the acoustic recorders were used to provide the number of bird calls for assessing patterns and peak passage rates during migration. The development of the geospatial database included collection of different data sources that are used to support offshore wind turbine development. Many different data sets were collected and organized using initial version of web-based repository software tools that can accommodate distribution of rectified pertinent data sets such as the lake depth, lake bottom engineering parameters, extent of ice, navigation pathways, wind speed, important bird habitats, fish efforts and other layers that are relevant for supporting robust offshore wind turbine developments. Additional geospatial products developed during the project included few different prototypes for offshore wind farm suitability which can involve different stakeholders and participants for solving complex planning problems and building consensus. Some of the prototypes include spatial decision support system (SDSS) for collaborative decision making, a web-based Participatory Geographic Information System (PGIS) framework for evaluating importance of different decision alternatives

  6. World Wind

    Data.gov (United States)

    National Aeronautics and Space Administration — World Wind allows any user to zoom from satellite altitude into any place on Earth, leveraging high resolution LandSat imagery and SRTM elevation data to experience...

  7. Wind power

    International Nuclear Information System (INIS)

    2009-01-01

    At the end of 2008,the European wind power capacity had risen to 65,247 MW which is a 15,1% increase on 2007. The financial crisis does not appear to have any real consequences of the wind power sector's activity in 2008. At the end of 2008 the European Union accommodated 53,9% of the world's wind power capacity. The top ten countries in terms of installed wind capacities are: 1) Usa with 25,388 MW, 2) Germany with 23,903 MW, 3) Spain with 16,740 MW, 4) China with 12,200 MW, 5) India with 9,645 MW, 6) Italy with 3,736 MW, 7) France with 3,542 MW, 8) U.K. with 3,406 MW, 9) Denmark with 3,166 MW and 10) Portugal with 2,862 MW. (A.C.)

  8. WindPACT Reference Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Dykes, Katherine L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rinker, Jennifer [Former National Renewable Energy Laboratory (NREL) employee

    2018-04-02

    To fully understand how loads and turbine cost scale with turbine size, it is necessary to have identical turbine models that have been scaled to different rated powers. The report presents the WindPACT baseline models, which are a series of four baseline models that were designed to facilitate investigations into the scalings of loads and turbine cost with size. The models have four different rated powers (750 kW, 1.5 MW, 3.0 MW, and 5.0 MW), and each model was designed to its specified rated power using the same design methodology. The models were originally implemented in FAST_AD, the predecessor to NREL's open-source wind turbine simulator FAST, but have yet to be implemented in FAST. This report contains the specifications for all four WindPACT baseline models - including structural, aerodynamic, and control specifications - along with the inherent assumptions and equations that were used to calculate the model parameters. It is hoped that these baseline models will serve as extremely useful resources for investigations into the scalings of costs, loads, or optimization routines.

  9. The Local ISM and its Interaction with the Winds of Nearby Late-type Stars

    Science.gov (United States)

    Wood, Brian E.; Linsky, Jeffrey L.

    1998-01-01

    the collision is supersonic and that there should therefore be a bow shock outside the heliopause in the upwind direction. Finally, we estimate stellar wind pressures (P sub wind) from the measured hydrogen-wall column densities. These estimates represent the first empirical measurements of wind properties for late-type main-sequence stars. The wind pressures appear to be correlated with stellar X-ray surface fluxes, F(x), in a manner consistent with the relation P(wind) varies as F(x)(exp -1/2), a relation that is also consistent with the variations of P(sub wind) and F(sub x) observed during the solar activity cycle. If this relation can in fact be generalized to solar-like stars, as is suggested by our data, then it is possible to estimate stellar wind properties simply by measuring stellar X-rays. One implication of this is that stellar wind pressures and mass-loss rates are then predicted to increase with time, since F(sub x) is known to decrease with stellar age.

  10. Wake flow characteristics at high wind speed

    DEFF Research Database (Denmark)

    Aagaard Madsen, Helge; Larsen, Torben J.; Larsen, Gunner Chr.

    2016-01-01

    Wake flow characteristic at high wind speeds is the main subject of this paper. Although the wake losses decrease at high wind speeds it has been found in a recent study that for multiple wake inflow the increase in loading due to wake effects are substantial even at wind speeds well above rated ...

  11. Birth to death analysis of the energy payback ratio and CO2 gas emission rates from coal, fission, wind, and DT-fusion electrical power plants

    International Nuclear Information System (INIS)

    White, Scott W.; Kulcinski, Gerald L.

    2000-01-01

    The amount of electrical energy produced over the lifetime of coal, LWR fission, UP fusion, and wind power plants is compared to the total amount of energy required to procure the fuel, build, operate, and decommission the power plants. The energy payback ratio varies from a low of 11 for coal plants to a high of 27 for DT-fusion plants. The magnitude of the energy investment and the source of the various energy inputs determine the CO 2 emission factor. This number varies from a low of 9 to a high of 974 tonnes of CO 2 per GW e h for DT-fusion and coal plants, respectively

  12. Conditional prediction intervals of wind power generation

    DEFF Research Database (Denmark)

    Pinson, Pierre; Kariniotakis, Georges

    2010-01-01

    A generic method for the providing of prediction intervals of wind power generation is described. Prediction intervals complement the more common wind power point forecasts, by giving a range of potential outcomes for a given probability, their so-called nominal coverage rate. Ideally they inform...... on the characteristics of prediction errors for providing conditional interval forecasts. By simultaneously generating prediction intervals with various nominal coverage rates, one obtains full predictive distributions of wind generation. Adapted resampling is applied here to the case of an onshore Danish wind farm...... to the case of a large number of wind farms in Europe and Australia among others is finally discussed....

  13. Using wind tunnels to predict bird mortality in wind farms: the case of griffon vultures.

    Science.gov (United States)

    de Lucas, Manuela; Ferrer, Miguel; Janss, Guyonne F E

    2012-01-01

    Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topography and wind flows in relation to flight paths of griffon vultures, using a scaled model of the wind farm area in an aerodynamic wind tunnel, and test the difference between the observed flight paths of griffon vultures and the predominant wind flows. Different wind currents for each wind direction in the aerodynamic model were observed. Simulations of wind flows in a wind tunnel were compared with observed flight paths of griffon vultures. No statistical differences were detected between the observed flight trajectories of griffon vultures and the wind passages observed in our wind tunnel model. A significant correlation was found between dead vultures predicted proportion of vultures crossing those cells according to the aerodynamic model. Griffon vulture flight routes matched the predominant wind flows in the area (i.e. they followed the routes where less flight effort was needed). We suggest using these kinds of simulations to predict flight paths over complex terrains can inform the location of wind turbines and thereby reduce soaring bird mortality.

  14. Using wind tunnels to predict bird mortality in wind farms: the case of griffon vultures.

    Directory of Open Access Journals (Sweden)

    Manuela de Lucas

    Full Text Available BACKGROUND: Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. METHODOLOGY/PRINCIPAL FINDINGS: As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topography and wind flows in relation to flight paths of griffon vultures, using a scaled model of the wind farm area in an aerodynamic wind tunnel, and test the difference between the observed flight paths of griffon vultures and the predominant wind flows. Different wind currents for each wind direction in the aerodynamic model were observed. Simulations of wind flows in a wind tunnel were compared with observed flight paths of griffon vultures. No statistical differences were detected between the observed flight trajectories of griffon vultures and the wind passages observed in our wind tunnel model. A significant correlation was found between dead vultures predicted proportion of vultures crossing those cells according to the aerodynamic model. CONCLUSIONS: Griffon vulture flight routes matched the predominant wind flows in the area (i.e. they followed the routes where less flight effort was needed. We suggest using these kinds of simulations to predict flight paths over complex terrains can inform the location of wind turbines and thereby reduce soaring bird mortality.

  15. Assessing high wind energy penetration

    International Nuclear Information System (INIS)

    Tande, J.O.

    1995-01-01

    In order to convincingly promote installing wind power capacity as a substantial part of the energy supply system, a set of careful analyses must be undertaken. This paper applies a case study concentrated on assessing the cost/benefit of high wind energy penetration. The case study considers expanding the grid connected wind power capacity in Praia, the capital of Cape Verde. The currently installed 1 MW of wind power is estimated to supply close to 10% of the electric energy consumption in 1996. Increasing the wind energy penetration to a higher level is considered viable as the project settings are close to ideal, including a very capable national utility company, Electra, a conventional power supply system based on imported heavy fuel and gas oil, and favourable wind conditions with an estimated annual average of 9.3 m/s at the hub height of the wind turbines. With the applied case study assumptions, simulations with WINSYS over the lifetime of the assessed wind power investment show that investments up to 4.2 MW are economically viable. The economic optimum is found at 2.4 MW reaching an internal rate of return of almost 8% p.a. This 2.4 MW of wind power would, together with the existing wind power, supply over 30% of the electric consumption in 1996. Applying the recommended practices for estimating the cost of wind energy, the life-cycle cost of this 2.4 MW investment is estimated at a 7% discount rate and a 20 year lifetime to 0.26 DKK/kW h. (Author)

  16. Wind turbine

    Science.gov (United States)

    Cheney, Jr., Marvin C.

    1982-01-01

    A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

  17. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Science.gov (United States)

    2013-05-20

    ...-005, QF07-55-005, QF07-56-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains...

  18. Remote Sensing Wind and Wind Shear System.

    Science.gov (United States)

    Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.

  19. DOUBLE COMPACT OBJECTS. I. THE SIGNIFICANCE OF THE COMMON ENVELOPE ON MERGER RATES

    International Nuclear Information System (INIS)

    Dominik, Michal; Belczynski, Krzysztof; Bulik, Tomasz; Fryer, Christopher; Holz, Daniel E.; Berti, Emanuele; Mandel, Ilya; O'Shaughnessy, Richard

    2012-01-01

    The last decade of observational and theoretical developments in stellar and binary evolution provides an opportunity to incorporate major improvements to the predictions from population synthesis models. We compute the Galactic merger rates for NS-NS, BH-NS, and BH-BH mergers with the StarTrack code. The most important revisions include updated wind mass-loss rates (allowing for stellar-mass black holes up to 80 M ☉ ), a realistic treatment of the common envelope phase (a process that can affect merger rates by 2-3 orders of magnitude), and a qualitatively new neutron star/black hole mass distribution (consistent with the observed m ass gap ) . Our findings include the following. (1) The binding energy of the envelope plays a pivotal role in determining whether a binary merges within a Hubble time. (2) Our description of natal kicks from supernovae plays an important role, especially for the formation of BH-BH systems. (3) The masses of BH-BH systems can be substantially increased in the case of low metallicities or weak winds. (4) Certain combinations of parameters underpredict the Galactic NS-NS merger rate and can be ruled out. (5) Models incorporating delayed supernovae do not agree with the observed NS/BH 'mass gap', in accordance with our previous work. This is the first in a series of three papers. The second paper will study the merger rates of double compact objects as a function of redshift, star formation rate, and metallicity. In the third paper, we will present the detection rates for gravitational-wave observatories, using up-to-date signal waveforms and sensitivity curves.

  20. Wind energy

    International Nuclear Information System (INIS)

    Portilla S, L.A.

    1995-01-01

    The wind energy or eolic energy is a consequence of solar energy, the one which is absorbed by the atmosphere and is transformed into energy of movement of large bulks of air. In this process the atmosphere acts as the filter to the solar radiation and demotes the ultraviolet beams that result fatal to life in the Earth. The ionosphere is the most external cap and this is ionized by means of absorption process of ultraviolet radiation arising to the Sun. The atmosphere also acts as a trap to the infrared radiation, it that results from the continual process of energetic degradation. In this way, the interaction between Earth - Atmospheres, is behaved as a great greenhouse, maintaining the constant temperatures, including in the dark nights. Processes as the natural convection (that occur by the thermodynamic phenomenon), equatorial calmness, trade winds and against trade winds and global distribution of the air currents are described. The other hand, techniques as the transformation of the wind into energy and its parameters also are shown

  1. Wind power

    International Nuclear Information System (INIS)

    2006-06-01

    This road-map proposes by the Group Total aims to inform the public on the wind power. It presents the principles, the technology takes off, its applications and technology focus, the global market trends and the outlooks and Total commitments in the domain. (A.L.B.)

  2. Wind Energy Japan

    Energy Technology Data Exchange (ETDEWEB)

    Komatsubara, Kazuyo [Embassy of the Kingdom of the Netherlands, Tokyo (Japan)

    2012-06-15

    An overview is given of wind energy in Japan: Background; Wind Energy in Japan; Japanese Wind Energy Industry; Government Supports; Useful Links; Major Japanese Companies; Profiles of Major Japanese Companies; Major Wind Energy Projects in Japan.

  3. Wind energy systems

    Science.gov (United States)

    Stewart, H. J.

    1978-01-01

    A discussion on wind energy systems involved with the DOE wind energy program is presented. Some of the problems associated with wind energy systems are discussed. The cost, efficiency, and structural design of wind energy systems are analyzed.

  4. Meteorological aspects of siting large wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Hiester, T.R.; Pennell, W.T.

    1981-01-01

    This report, which focuses on the meteorological aspects of siting large wind turbines (turbines with a rated output exceeding 100 kW), has four main goals. The first is to outline the elements of a siting strategy that will identify the most favorable wind energy sites in a region and that will provide sufficient wind data to make responsible economic evaluations of the site wind resource possible. The second is to critique and summarize siting techniques that were studied in the Department of Energy (DOE) Wind Energy Program. The third goal is to educate utility technical personnel, engineering consultants, and meteorological consultants (who may have not yet undertaken wind energy consulting) on meteorological phenomena relevant to wind turbine siting in order to enhance dialogues between these groups. The fourth goal is to minimize the chances of failure of early siting programs due to insufficient understanding of wind behavior.

  5. Is the dissociation of coronene in stellar winds a source of molecular hydrogen? application to the HD 44179 nebula

    Science.gov (United States)

    Champeaux, J.-P.; Moretto-Capelle, P.; Cafarelli, P.; Deville, C.; Sence, M.; Casta, R.

    2014-06-01

    The physical interactions of polycyclic aromatic hydrocarbons (PAHs) with stellar particular radiation are key to understanding the life cycle of PAHs, their abundance and their role in the complex astrochemistry of the interstellar medium. In this context, we present experimental results on the ionization/fragmentation of isolated coronene by a 100-keV proton, reproducing interactions between stellar winds and PAH molecules in the star's environment. In particular, we show, without ambiguity, that such ionization/fragmentation induces intense dehydrogenation processes for which the loss of even numbers of hydrogen atoms and the detection of CH_2+ cations as a possible H2 precursor strongly suggest the formation of H2 neutral molecules along a scenario revealed by a quantum chemical calculation. We have evaluated the H2 emission cross-section from the coronene/proton interaction at 100 and 1.6 keV to be 2.97 × 10-16 and 3.3 × 10-16 cm2, respectively. A qualitative discussion on the formation rate of H2 in the HD 44179 Red Rectangle (RR) nebula leads to the conclusion that such processes could be very efficient, especially inside planetary nebulae rich in PAH molecules interacting with high proton mass-loss rate stars (such as post-asymptotic giant branch stars) or high velocity jets produced by an accretion disc.

  6. Mastering the power of wind

    International Nuclear Information System (INIS)

    Stiegel, J.

    1999-01-01

    In this paper the author deals with environmental aspects use of fossil fuels for the energy production. As a way for our planet to get back to a normal and ecologically balanced system the fossil fuels reduction and their replacement by renewable racecourses is recommended. Energetic potential of flowing sun, wind and tidal waves as power resources is discussed. The natural ecological resources are best utilised in the United States where the installed wind power output is 1600 MW. With 360 MW installed output in 1991 the Denmark took lead among European countries in utilising the wind power. The most dynamic power plant development among the European Union countries was recorded in Germany, where the installed power output of the wind power plants is 632 MW, i.e. i.e. 11.5 times higher compared to 55 MW in 1991. The economy of wind power in Germany and in Slovakia is compared. In Slovakia with annual 200 000 kWh power generation annually and the present kWh purchase price guarantee the rate of return of 10 million slovak crowns investment into a wind power plant project is in 100 years. Although the first wind power plants have already been built in the Zahorie, Kremnicke Bane, and Secovce regions, the wind exploitation status in Slovakia is still limping. According to professionals, the wind conditions in Slovakia are not ideal, but sufficient for a supplementary wind power plant system, that can be quite motivating especially for villages. Mount Chopok or mount Krizna are ideal sites to erect the three-blade tower with respect to wind speed. And also the anticipated Kremnicke vrchy site is worth considering. (author)

  7. Suppressing star formation in quiescent galaxies with supermassive black hole winds.

    Science.gov (United States)

    Cheung, Edmond; Bundy, Kevin; Cappellari, Michele; Peirani, Sébastien; Rujopakarn, Wiphu; Westfall, Kyle; Yan, Renbin; Bershady, Matthew; Greene, Jenny E; Heckman, Timothy M; Drory, Niv; Law, David R; Masters, Karen L; Thomas, Daniel; Wake, David A; Weijmans, Anne-Marie; Rubin, Kate; Belfiore, Francesco; Vulcani, Benedetta; Chen, Yan-mei; Zhang, Kai; Gelfand, Joseph D; Bizyaev, Dmitry; Roman-Lopes, A; Schneider, Donald P

    2016-05-26

    Quiescent galaxies with little or no ongoing star formation dominate the population of galaxies with masses above 2 × 10(10) times that of the Sun; the number of quiescent galaxies has increased by a factor of about 25 over the past ten billion years (refs 1-4). Once star formation has been shut down, perhaps during the quasar phase of rapid accretion onto a supermassive black hole, an unknown mechanism must remove or heat the gas that is subsequently accreted from either stellar mass loss or mergers and that would otherwise cool to form stars. Energy output from a black hole accreting at a low rate has been proposed, but observational evidence for this in the form of expanding hot gas shells is indirect and limited to radio galaxies at the centres of clusters, which are too rare to explain the vast majority of the quiescent population. Here we report bisymmetric emission features co-aligned with strong ionized-gas velocity gradients from which we infer the presence of centrally driven winds in typical quiescent galaxies that host low-luminosity active nuclei. These galaxies are surprisingly common, accounting for as much as ten per cent of the quiescent population with masses around 2 × 10(10) times that of the Sun. In a prototypical example, we calculate that the energy input from the galaxy's low-level active supermassive black hole is capable of driving the observed wind, which contains sufficient mechanical energy to heat ambient, cooler gas (also detected) and thereby suppress star formation.

  8. Stellar Winds and Dust Avalanches in the AU Mic Debris Disk

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Eugene; Fung, Jeffrey, E-mail: echiang@astro.berkeley.edu, E-mail: jeffrey.fung@berkeley.edu [Department of Astronomy, University of California at Berkeley, Campbell Hall, Berkeley, CA 94720-3411 (United States)

    2017-10-10

    We explain the fast-moving, ripple-like features in the edge-on debris disk orbiting the young M dwarf AU Mic. The bright features are clouds of submicron dust repelled by the host star’s wind. The clouds are produced by avalanches: radial outflows of dust that gain exponentially more mass as they shatter background disk particles in collisional chain reactions. The avalanches are triggered from a region a few au across—the “avalanche zone”—located on AU Mic’s primary “birth” ring at a true distance of ∼35 au from the star but at a projected distance more than a factor of 10 smaller: the avalanche zone sits directly along the line of sight to the star, on the side of the ring nearest Earth, launching clouds that disk rotation sends wholly to the southeast, as observed. The avalanche zone marks where the primary ring intersects a secondary ring of debris left by the catastrophic disruption of a progenitor up to Varuna in size, less than tens of thousands of years ago. Only where the rings intersect are particle collisions sufficiently violent to spawn the submicron dust needed to seed the avalanches. We show that this picture works quantitatively, reproducing the masses, sizes, and velocities of the observed escaping clouds. The Lorentz force exerted by the wind’s magnetic field, whose polarity reverses periodically according to the stellar magnetic cycle, promises to explain the observed vertical undulations. The timescale between avalanches, about 10 yr, might be set by time variability of the wind mass loss rate or, more speculatively, by some self-regulating limit cycle.

  9. Spiral field inhibition of thermal conduction in two-fluid solar wind models

    International Nuclear Information System (INIS)

    Nerney, S.; Barnes, A.

    1978-01-01

    The two-fluid solar wind equations, including inhibition of heat conduction by the spiral magnetic field, have been solved for steady radial flow, and the results are compared with those of our previous study of two-fluid models with straight interplanetary field lines. The main effects of the spiral field conduction cutoff are to bottle up electron heat inside 1 AU and to produce adiabatic electron (an proton) temperature profiles at large heliocentric distances. Otherwise, the spiral field models are nearly identical with straight field models with the same temperatures and velocity at 1 AU, except for models associated with very low coronal base densities (n 0 approx.10 6 cm -3 at 1R/sub s/). Low base density spiral models give a nearly isothermal electron temperature profile over 50--100 AU together with high velocities and temperatures at 1 AU. In general, high-velocity models do not agree well with observed high-velocity streams: lower-velocity states can be represented reasonably well at 1 AU, but only for very high proton temperatures (T/sub p/approx.2T/sub e/) at the coronal base. For spherically symmetric base conditions the straight field and spiral field models can be regarded, in lowest order, as approximations to the polar and equatorial three-dimensional flows, respectively. This viewpoint suggests a pole to equator electron temperature gradient in the region 1-10 AU, which would be associated with a meridional velocity of approx.0.5-1.0 km/s, diverging away from the equatorial plane. The formalism developed in this paper shows rather stringent limits to the mass loss rate for conductively driven winds and, in particular, illustrates that putative T Tauri outflows could not be conductively driven

  10. Wind around the world

    International Nuclear Information System (INIS)

    Rackstraw, K.

    1998-01-01

    A combination of cost reductions and progressive policies in key markets kept the world wind market percolating in 1997 with a record 1510 MW of new wind capacity installed, representing annual sales of more than $1.5 billion. This new record surpasses last year''s total by 24 percent, about the average annual rate of growth for the last three years. Worldwide utility-scale wind installations at the end of 1997 totaled 7763 MW. Most activity occurred in Europe, which accounted for over 75 percent of 1997 installations. Germany was again the world''s leading single market, this time by quite a large margin, accounting for more than one-third of the annual total by itself at 532 MW in 1997. The end of 1997 also marked the time at which Germany officially passed the US as the largest total single market with over 2079 MW in total installations versus about 1805 MW for the US, although the US had actually lost the lead by mid-year. Spain is the new addition to the top echelon of world wind markets, installing 215 MW in 1997 that more than doubles their total installed capacity over the previous year and ranks them number three in the world for the year. Denmark''s 1997 total of 300 MW is also a record, although this estimate could go up as the official count is finalized. India, the second largest wind market in 1995 and 1996, slipped several notches because of a variety of factors, including a change in government and a slowdown in the economy. The US wind market continues to stagnate as it has for the last several years, largely because of the uncertainty surrounding restructuring of US electric utilities. The US market is poised for a big comeback in 1998, however

  11. 2014 Wind Technologies Market Report

    Energy Technology Data Exchange (ETDEWEB)

    Wiser, R; Bolinger, M.

    2015-08-01

    According to the 2014 Wind Technologies Market Report, total installed wind power capacity in the United States grew at a rate of eight percent in 2014, bringing the United States total installed capacity to nearly 66 gigawatts (GW), which ranks second in the world and meets 4.9 percent of U.S. end-use electricity demand in an average year. In total, 4,854 MW of new wind energy capacity were installed in the United States in 2014. The 2014 Wind Technologies Market Report also finds that wind energy prices are at an all-time low and are competitive with wholesale power prices and traditional power sources across many areas of the United States. Additionally, a new trend identified by the 2014 Wind Technologies Market Report shows utility-scale turbines with larger rotors designed for lower wind speeds have been increasingly deployed across the country in 2014. The findings also suggest that the success of the U.S. wind industry has had a ripple effect on the American economy, supporting 73,000 jobs related to development, siting, manufacturing, transportation, and other industries.

  12. Wind Loads on Structures

    DEFF Research Database (Denmark)

    Dyrbye, Claes; Hansen, Svend Ole

    Wind loads have to be taken into account when designing civil engineering structures. The wind load on structures can be systematised by means of the wind load chain: wind climate (global), terrain (wind at low height), aerodynamic response (wind load to pressure), mechanical response (wind...... pressure to structural response) and design criteria. Starting with an introduction of the wind load chain, the book moves on to meteorological considerations, atmospheric boundary layer, static wind load, dynamic wind load and scaling laws used in wind-tunnel tests. The dynamic wind load covers vibrations...... induced by wind turbulence, vortex shedding, flutter and galloping. The book gives a comprehensive treatment of wind effects on structures and it will be useful for consulting engineers designing wind-sensitive structures. It will also be valuable for students of civil engineering as textbook...

  13. Transmission Line Ampacity Improvements of AltaLink Wind Plant Overhead Tie-Lines Using Weather-Based Dynamic Line Rating

    Energy Technology Data Exchange (ETDEWEB)

    Bhattarai, Bishnu P.; Gentle, Jake P.; Hill, Porter; McJunkin, Tim; Myers, Kurt S.; Abbound, Alex; Renwick, Rodger; Hengst, David

    2017-07-01

    Abstract—Overhead transmission lines (TLs) are conventionally given seasonal ratings based on conservative environmental assumptions. Such an approach often results in underutilization of the line ampacity as the worst conditions prevail only for a short period over a year/season. We presents dynamic line rating (DLR) as an enabling smart grid technology that adaptively computes ratings of TLs based on local weather conditions to utilize additional headroom of existing lines. In particular, general line ampacity state solver utilizes measured weather data for computing the real-time thermal rating of the TLs. The performance of the presented method is demonstrated from a field study of DLR technology implementation on four TL segments at AltaLink, Canada. The performance is evaluated and quantified by comparing the existing static and proposed dynamic line ratings, and the potential benefits of DLR for enhanced transmission assets utilization. For the given line segments, the proposed DLR results in real-time ratings above the seasonal static ratings for most of the time; up to 95.1% of the time, with a mean increase of 72% over static rating.

  14. Winding up the molecular clock in the genus Carabus (Coleoptera: Carabidae: assessment of methodological decisions on rate and node age estimation

    Directory of Open Access Journals (Sweden)

    Andújar Carmelo

    2012-03-01

    Full Text Available Abstract Background Rates of molecular evolution are known to vary across taxa and among genes, and this requires rate calibration for each specific dataset based on external information. Calibration is sensitive to evolutionary model parameters, partitioning schemes and clock model. However, the way in which these and other analytical aspects affect both the rates and the resulting clade ages from calibrated phylogenies are not yet well understood. To investigate these aspects we have conducted calibration analyses for the genus Carabus (Coleoptera, Carabidae on five mitochondrial and four nuclear DNA fragments with 7888 nt total length, testing different clock models and partitioning schemes to select the most suitable using Bayes Factors comparisons. Results We used these data to investigate the effect of ambiguous character and outgroup inclusion on both the rates of molecular evolution and the TMRCA of Carabus. We found considerable variation in rates of molecular evolution depending on the fragment studied (ranging from 5.02% in cob to 0.26% divergence/My in LSU-A, but also on analytical conditions. Alternative choices of clock model, partitioning scheme, treatment of ambiguous characters, and outgroup inclusion resulted in rate increments ranging from 28% (HUWE1 to 1000% (LSU-B and ITS2 and increments in the TMRCA of Carabus ranging from 8.4% (cox1-A to 540% (ITS2. Results support an origin of the genus Carabus during the Oligocene in the Eurasian continent followed by a Miocene differentiation that originated all main extant lineages. Conclusions The combination of several genes is proposed as the best strategy to minimise both the idiosyncratic behaviors of individual markers and the effect of analytical aspects in rate and age estimations. Our results highlight the importance of estimating rates of molecular evolution for each specific dataset, selecting for optimal clock and partitioning models as well as other methodological issues

  15. Stellar winds in binary X-ray systems

    Science.gov (United States)

    Macgregor, K. B.; Vitello, P. A. J.

    1982-01-01

    It is thought that accretion from a strong stellar wind by a compact object may be responsible for the X-ray emission from binary systems containing a massive early-type primary. To investigate the effect of X-ray heating and ionization on the mass transfer process in systems of this type, an idealized model is constructed for the flow of a radiation-driven wind in the presence of an X-ray source of specified luminosity, L sub x. It is noted that for low values of L sub x, X-ray photoionization gives rise to additional ions having spectral lines with wavelengths situated near the peak of the primary continuum flux distribution. As a consequence, the radiation force acting on the gas increases in relation to its value in the absence of X-rays, and the wind is accelerated to higher velocities. As L sub x is increased, the degree of ionization of the wind increases, and the magnitude of the radiation force is diminished in comparison with the case in which L sub x = 0. This reduction leads at first to a decrease in the wind velocity and ultimately (for L sub x sufficiently large) to the termination of radiatively driven mass loss.

  16. Using Wind Tunnels to Predict Bird Mortality in Wind Farms: The Case of Griffon Vultures

    OpenAIRE

    de Lucas, Manuela; Ferrer, Miguel; Janss, Guyonne F. E.

    2012-01-01

    Background: Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. Methodology/Principal Findings: As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topo...

  17. Wind conditions for wind turbine design

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B.

    1999-04-01

    Delegates from Europe and USA attended the meeting and discussed general aspects of wind conditions for wind turbine design. The subjects and the presented papers covered a very broad range of aspects of wind conditions and related influence on the wind turbine. (EHS)

  18. Turbine Control Strategies for Wind Farm Power Optimization

    DEFF Research Database (Denmark)

    Mirzaei, Mahmood; Göçmen Bozkurt, Tuhfe; Giebel, Gregor

    2015-01-01

    In recent decades there has been increasing interest in green energies, of which wind energy is the most important one. In order to improve the competitiveness of the wind power plants, there are ongoing researches to decrease cost per energy unit and increase the efficiency of wind turbines...... and wind farms. One way of achieving these goals is to optimize the power generated by a wind farm. One optimization method is to choose appropriate operating points for the individual wind turbines in the farm. We have made three models of a wind farm based on three difference control strategies...... the generated power by changing the power reference of the individual wind turbines. We use the optimization setup to compare power production of the wind farm models. This paper shows that for the most frequent wind velocities (below and around the rated values), the generated powers of the wind farms...

  19. Management of moderate wind energy coastal resources

    International Nuclear Information System (INIS)

    Karamanis, D.

    2011-01-01

    Research highlights: → Life cycle analysis reveals the viability of moderate wind fields utilization. → Wind turbine is the greenest electricity generator at a touristic site. → Wind parks should be collective applications of small hotel-apartments owners. -- Abstract: The feasibility of wind energy utilization at moderate wind fields was investigated for a typical touristic coastal site in Western Greece. Initially, the wind speed and direction as well as its availability, duration and diurnal variation were assessed. For an analysis period of eight years, the mean wind speed at ten meters was determined as 3.8 m s -1 with a small variation in monthly average wind speeds between 3.0 (January) and 4.4 m s -1 (October). The mean wind power density was less than 200 W m -2 at 10 m indicating the limiting suitability of the site for the usual renewable energy applications. However, life cycle analysis for wind turbine generators with lower cut-in, cut-out, and rated speeds revealed that the energy yield ratio can reach a value of six for a service life of 20 years while the energy pay-back period can be 3 years with 33 kt CO 2 -e of avoided greenhouse emissions. Therefore, the recent technological turbine improvements make wind power viable even at moderate wind fields. Moreover, the study of electricity supply of typical small hotel-apartments in the region of Western Greece indicated that the installation of 300 wind turbine generators in these moderate wind fields would cover the total consumption during the open touristic period with profits during the rest of the year. According to these results, wind turbine generators are the 'greenest' way of generating electricity in touristic coastal sites, even of moderate wind speeds.

  20. Close binary evolution. II. Impact of tides, wind magnetic braking, and internal angular momentum transport

    Science.gov (United States)

    Song, H. F.; Meynet, G.; Maeder, A.; Ekström, S.; Eggenberger, P.; Georgy, C.; Qin, Y.; Fragos, T.; Soerensen, M.; Barblan, F.; Wade, G. A.

    2018-01-01

    Context. Massive stars with solar metallicity lose important amounts of rotational angular momentum through their winds. When a magnetic field is present at the surface of a star, efficient angular momentum losses can still be achieved even when the mass-loss rate is very modest, at lower metallicities, or for lower-initial-mass stars. In a close binary system, the effect of wind magnetic braking also interacts with the influence of tides, resulting in a complex evolution of rotation. Aims: We study the interactions between the process of wind magnetic braking and tides in close binary systems. Methods: We discuss the evolution of a 10 M⊙ star in a close binary system with a 7 M⊙ companion using the Geneva stellar evolution code. The initial orbital period is 1.2 days. The 10 M⊙ star has a surface magnetic field of 1 kG. Various initial rotations are considered. We use two different approaches for the internal angular momentum transport. In one of them, angular momentum is transported by shear and meridional currents. In the other, a strong internal magnetic field imposes nearly perfect solid-body rotation. The evolution of the primary is computed until the first mass-transfer episode occurs. The cases of different values for the magnetic fields and for various orbital periods and mass ratios are briefly discussed. Results: We show that, independently of the initial rotation rate of the primary and the efficiency of the internal angular momentum transport, the surface rotation of the primary will converge, in a time that is short with respect to the main-sequence lifetime, towards a slowly evolving velocity that is different from the synchronization velocity. This "equilibrium angular velocity" is always inferior to the angular orbital velocity. In a given close binary system at this equilibrium stage, the difference between the spin and the orbital angular velocities becomes larger when the mass losses and/or the surface magnetic field increase. The

  1. On the Fatigue Analysis of Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, Herbert J.

    1999-06-01

    Modern wind turbines are fatigue critical machines that are typically used to produce electrical power from the wind. Operational experiences with these large rotating machines indicated that their components (primarily blades and blade joints) were failing at unexpectedly high rates, which led the wind turbine community to develop fatigue analysis capabilities for wind turbines. Our ability to analyze the fatigue behavior of wind turbine components has matured to the point that the prediction of service lifetime is becoming an essential part of the design process. In this review paper, I summarize the technology and describe the ''best practices'' for the fatigue analysis of a wind turbine component. The paper focuses on U.S. technology, but cites European references that provide important insights into the fatigue analysis of wind turbines.

  2. Wind Power Meteorology

    DEFF Research Database (Denmark)

    Lundtang Petersen, Erik; Mortensen, Niels Gylling; Landberg, Lars

    Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind...... resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed......: wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed...

  3. Wind Energy Basics | NREL

    Science.gov (United States)

    Wind Energy Basics Wind Energy Basics We have been harnessing the wind's energy for hundreds of grinding grain. Today, the windmill's modern equivalent-a wind turbine can use the wind's energy to most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and

  4. Prospecting for Wind

    Science.gov (United States)

    Swapp, Andy; Schreuders, Paul; Reeve, Edward

    2011-01-01

    Many people use wind to help meet their needs. Over the years, people have been able to harness or capture the wind in many different ways. More recently, people have seen the rebirth of electricity-generating wind turbines. Thus, the age-old argument about technology being either good or bad can also be applied to the wind. The wind can be a…

  5. Careers in Wind Energy

    Science.gov (United States)

    Liming, Drew; Hamilton, James

    2011-01-01

    As a common form of renewable energy, wind power is generating more than just electricity. It is increasingly generating jobs for workers in many different occupations. Many workers are employed on wind farms: areas where groups of wind turbines produce electricity from wind power. Wind farms are frequently located in the midwestern, western, and…

  6. Reliability & availability of wind turbine electrical & electronic components

    NARCIS (Netherlands)

    Tavner, P.; Faulstich, S.; Hahn, B.; Bussel, van G.J.W.

    2010-01-01

    Recent analysis of European onshore wind turbine reliability data has shown that whilst wind turbine mechanical subassemblies tend to have relatively low failure rates but long downtimes, electrical and electronic subassemblies have relatively high failure rates and short downtimes. For onshore wind

  7. Wind Spires as an Alternative Energy Source

    Energy Technology Data Exchange (ETDEWEB)

    Majid Rashidi, Ph.D., P.E.

    2012-10-30

    This report discloses the design and development of an innovative wind tower system having an axisymmetric wind deflecting structure with a plurality of symmetrically mounted rooftop size wind turbines near the axisymmetric structure. The purpose of the wind deflecting structure is to increase the ambient wind speed that in turn results in an overall increase in the power capacity of the wind turbines. Two working prototypes were constructed and installed in the summer of 2009 and 2012 respectively. The system installed in the Summer of 2009 has a cylindrical wind deflecting structure, while the tower installed in 2012 has a spiral-shape wind deflecting structure. Each tower has 4 turbines, each rated at 1.65 KW Name-Plate-Rating. Before fabricating the full-size prototypes, computational fluid dynamic (CFD) analyses and scaled-down table-top models were used to predict the performance of the full-scale models. The performance results obtained from the full-size prototypes validated the results obtained from the computational models and those of the scaled-down models. The second prototype (spiral configuration) showed at a wind speed of 11 miles per hour (4.9 m/s) the power output of the system could reach 1,288 watt, when a typical turbine installation, with no wind deflecting structure, could produce only 200 watt by the same turbines at the same wind speed. At a wind speed of 18 miles per hour (8 m/sec), the spiral prototype produces 6,143 watt, while the power generated by the same turbines would be 1,412 watt in the absence of a wind deflecting structure under the same wind speed. Four US patents were allowed, and are in print, as the results of this project (US 7,540,706, US 7,679,209, US 7,845,904, and US 8,002,516).

  8. Effects of Yaw Error on Wind Turbine Running Characteristics Based on the Equivalent Wind Speed Model

    Directory of Open Access Journals (Sweden)

    Shuting Wan

    2015-06-01

    Full Text Available Natural wind is stochastic, being characterized by its speed and direction which change randomly and frequently. Because of the certain lag in control systems and the yaw body itself, wind turbines cannot be accurately aligned toward the wind direction when the wind speed and wind direction change frequently. Thus, wind turbines often suffer from a series of engineering issues during operation, including frequent yaw, vibration overruns and downtime. This paper aims to study the effects of yaw error on wind turbine running characteristics at different wind speeds and control stages by establishing a wind turbine model, yaw error model and the equivalent wind speed model that includes the wind shear and tower shadow effects. Formulas for the relevant effect coefficients Tc, Sc and Pc were derived. The simulation results indicate that the effects of the aerodynamic torque, rotor speed and power output due to yaw error at different running stages are different and that the effect rules for each coefficient are not identical when the yaw error varies. These results may provide theoretical support for optimizing the yaw control strategies for each stage to increase the running stability of wind turbines and the utilization rate of wind energy.

  9. Applications of wind turbines in Canada

    Energy Technology Data Exchange (ETDEWEB)

    South, P; Rangi, R S; Templin, R J

    1977-01-01

    There are differing views as to the role of wind energy in the overall requirements. While some people tend to ignore it there are others who think that wind could be a major source of energy. In this paper an effort has been made to determine the wind power potential and also the amount that is economically usable. From the existing wind data a map showing the distribution of wind power density has been prepared. This map shows that the maritime provinces and the west coast of Hudson Bay have high wind power potential. These figures show that the wind power potential is of the same order as the installed electrical generating capacity in Canada (58 x 10/sup 6/kW in 1974). However, in order to determine how much of this power is usable the economics of adding wind energy to an existing system must be considered. A computer program has been developed at NRC to analyze the coupling of wind turbines with mixed power systems. Using this program and making certain assumptions about the cost of WECS and fuel the maximum amount of usable wind energy has been calculated. It is shown that if an installed capacity of 420 megawatts of wind power was added to the existing diesel capacity it would result in a savings of 60,000,000 gallons of fuel oil per year. On the other hand it is shown that if the existing installed hydro electric capacity of 37,000 megawatts (1976) was increased to 60,000 megawatts without increasing the average water flow rate, an installed capacity of 60,000 megawatts of wind power could be added to the system. This would result in an average of 14,000 megawatts from the wind. Using projected manufacturing costs for vertical axis wind turbines, the average cost of wind energy could be in the range of 1.4 cents/kwh to 3.6 cents/kwh.

  10. The Wind Energy Potential of Kurdistan, Iran

    Science.gov (United States)

    Arefi, Farzad; Moshtagh, Jamal; Moradi, Mohammad

    2014-01-01

    In the current work by using statistical methods and available software, the wind energy assessment of prone regions for installation of wind turbines in, Qorveh, has been investigated. Information was obtained from weather stations of Baneh, Bijar, Zarina, Saqez, Sanandaj, Qorveh, and Marivan. The monthly average and maximum of wind speed were investigated between the years 2000–2010 and the related curves were drawn. The Golobad curve (direction and percentage of dominant wind and calm wind as monthly rate) between the years 1997–2000 was analyzed and drawn with plot software. The ten-minute speed (at 10, 30, and 60 m height) and direction (at 37.5 and 10 m height) wind data were collected from weather stations of Iranian new energy organization. The wind speed distribution during one year was evaluated by using Weibull probability density function (two-parametrical), and the Weibull curve histograms were drawn by MATLAB software. According to the average wind speed of stations and technical specifications of the types of turbines, the suitable wind turbine for the station was selected. Finally, the Divandareh and Qorveh sites with favorable potential were considered for installation of wind turbines and construction of wind farms. PMID:27355042

  11. Wind energy program overview

    International Nuclear Information System (INIS)

    1992-02-01

    This overview emphasizes the amount of electric power that could be provided by wind power rather than traditional fossil fuels. New wind power markets, advances in technology, technology transfer, and wind resources are some topics covered in this publication

  12. Cost optimization of wind turbines for large-scale offshore wind farms

    International Nuclear Information System (INIS)

    Fuglsang, P.; Thomsen, K.

    1998-02-01

    This report contains a preliminary investigation of site specific design of off-shore wind turbines for a large off-shore wind farm project at Roedsand that is currently being proposed by ELKRAFT/SEAS. The results were found using a design tool for wind turbines that involve numerical optimization and aeroelastic calculations of response. The wind climate was modeled in detail and a cost function was used to estimate costs from manufacture and installation. Cost of energy is higher for off-shore installations. A comparison of an off-shore wind farm site with a typical stand alone on-shore site showed an increase of the annual production of 28% due to the difference in wind climate. Extreme loads and blade fatigue loads were nearly identical, however,fatigue loads on other main components increased significantly. Optimizations were carried out to find the optimum overall off-shore wind turbine design. A wind turbine for the off-shore wind farm should be different compared with a stand-alone on-shore wind turbine. The overall design changed were increased swept area and rated power combined with reduced rotor speed and tower height. Cost was reduced by 12% for the final 5D/14D off-shore wind turbine from 0.306 DKr/kWh to 0.270 DKr/kWh. These figures include capital costs from manufacture and installation but not on-going costs from maintenance. These results make off-shore wind farms more competitive and comparable to the reference on-shore stand-alone wind turbine. A corresponding reduction of cost of energy could not be found for the stand alone on-shore wind turbine. Furthermore the fatigue loads on wind turbines in on-shore wind farms will increase and cost of energy will increase in favor of off-shore wind farms. (au) EFP-95; EU-JOULE-3; 21 tabs., 7 ills., 8 refs

  13. Energy costs form European wind farms

    Energy Technology Data Exchange (ETDEWEB)

    Milborrow, D [Windpower Monthly, Knebel (Denmark)

    1996-12-31

    Energy generation costs from European wind farms span a very wide range. Reasons for these variations, include differences in capital and operating costs, wind speeds and differing legislative and regulatory frameworks. This article compares costs, wind speeds and discount rates for British and German windfarms and sets these alongside data from elsewhere in the European Union. In this way it is possible to determine the reasons for differences in energy generation costs. (author)

  14. Energy costs form European wind farms

    Energy Technology Data Exchange (ETDEWEB)

    Milborrow, D. [Windpower Monthly, Knebel (Denmark)

    1995-12-31

    Energy generation costs from European wind farms span a very wide range. Reasons for these variations, include differences in capital and operating costs, wind speeds and differing legislative and regulatory frameworks. This article compares costs, wind speeds and discount rates for British and German windfarms and sets these alongside data from elsewhere in the European Union. In this way it is possible to determine the reasons for differences in energy generation costs. (author)

  15. Solar winds along curved magnetic field lines

    OpenAIRE

    Li, Bo; Xia, Li-Dong; Chen, Yao

    2011-01-01

    Both remote-sensing measurements using the interplanetary scintillation (IPS) technique and in situ measurements by the Ulysses spacecraft show a bimodal structure for the solar wind at solar minimum conditions. At present what makes the fast wind fast and the slow wind slow still remains to be answered. While a robust empirical correlation exists between the coronal expansion rate $f_c$ of the flow tubes and the speeds $v$ measured in situ, further data analysis suggests that $v$ depends on ...

  16. Energy costs form European wind farms

    International Nuclear Information System (INIS)

    Milborrow, D.

    1995-01-01

    Energy generation costs from European wind farms span a very wide range. Reasons for these variations, include differences in capital and operating costs, wind speeds and differing legislative and regulatory frameworks. This article compares costs, wind speeds and discount rates for British and German windfarms and sets these alongside data from elsewhere in the European Union. In this way it is possible to determine the reasons for differences in energy generation costs. (author)

  17. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    OpenAIRE

    Ju Feng; Wen Zhong Shen

    2015-01-01

    Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data a...

  18. Wind speed and direction shears with associated vertical motion during strong surface winds

    Science.gov (United States)

    Alexander, M. B.; Camp, D. W.

    1984-01-01

    Strong surface winds recorded at the NASA 150-Meter Ground Winds Tower facility at Kennedy Space Center, Florida, are analyzed to present occurrences representative of wind shear and vertical motion known to be hazardous to the ascent and descent of conventional aircraft and the Space Shuttle. Graphical (percentage frequency distributions) and mathematical (maximum, mean, standard deviation) descriptions of wind speed and direction shears and associated updrafts and downdrafts are included as functions of six vertical layers and one horizontal distance for twenty 5-second intervals of parameters sampled simultaneously at the rate of ten per second during a period of high surface winds.

  19. Wind farm project economics : value of wind

    Energy Technology Data Exchange (ETDEWEB)

    Bills-Everett, T. [Mainstream Renewable Power, Toronto, ON (Canada)

    2010-07-01

    This PowerPoint presentation discussed methods of increasing the value of wind power projects. Appropriate turbine selection and layout is needed to ensure that wind resources are fully developed. Construction costs have a significant impact on project costs. The world turbine price index has not significantly fluctuated since 2006. Operating costs, and the value of wind power projects, are linked with OPEX fluctuations. Wind power projects can significantly reduce greenhouse gas (GHG) emissions. An increase in wind power capacity will reduce the overall cost of energy produced from wind power. Countries can use wind power as part of a renewable energy portfolio designed to reduce risks related to diminishing petroleum supplies. Wind power will help to ensure a global transition to renewable energy use. tabs., figs.

  20. Wind turbines, is it just wind?

    International Nuclear Information System (INIS)

    Boiteux, M.

    2012-01-01

    The author first outlines that wind energy is not only random, but almost absent in extreme situations when it would be needed (for example and notably, very cold weather without wind). He suggests the association of a gas turbine to each wind turbine, so that the gas turbine will replace non operating wind turbines. He notices that wind turbines are not proximity energy as they were said to be, and that profitability in fact requires tens of grouped giant wind turbines. He also outlines the high cost of construction of grids for the connection of these wind turbines. Thus, he states that wind energy is far from being profitable in the present conditions of electricity tariffs in France

  1. Wind of opportunity

    International Nuclear Information System (INIS)

    Jamieson, Peter

    1999-01-01

    This article traces the move towards the offshore exploitation of wind energy in Europe, and presents information on existing offshore wind energy projects and proposed wind turbine prototypes for offshore operation. The building of the first major offshore wind project at Vindeby, the use of rock socketed monopile foundations for pile drilling and erection of the wind turbines from a mobile jack-up barge, the costs of wind turbines, the fatigue loads on the support structures due to the wind loading, and the offshore wind market in the UK and Europe are discussed. (UK)

  2. Advanced structural wind engineering

    CERN Document Server

    Kareem, Ahsan

    2013-01-01

    This book serves as a textbook for advanced courses as it introduces state-of-the-art information and the latest research results on diverse problems in the structural wind engineering field. The topics include wind climates, design wind speed estimation, bluff body aerodynamics and applications, wind-induced building responses, wind, gust factor approach, wind loads on components and cladding, debris impacts, wind loading codes and standards, computational tools and computational fluid dynamics techniques, habitability to building vibrations, damping in buildings, and suppression of wind-induced vibrations. Graduate students and expert engineers will find the book especially interesting and relevant to their research and work.

  3. The evolution of low-mass close binary systems. IV. 0.80 M/sub sun/+0.40 M/sub sun/: Catastrophic mass loss

    International Nuclear Information System (INIS)

    Webbink, R.F.

    1977-01-01

    The evolution of both components of a 0.80 M/sub sun/+0.40 M/sub sun/ binary with initial separation 1.60 R/sub sun/ is presented. This system reaches mass transfer during core hydrogen burning in the primary. The primary has such a deep convective envelope that mass transfer proceeds on a dynamical time scale. Mass exchange is followed through the first 6.25 x 10 -3 M/sub sun/, by which time the transfer rate has reached 8.33 x 10 -4 M/sub sun/ yr -1 .It is shown that mass transfer on a dynamical time scale leads to supercritical accretion by the secondary component, and hence is presumably accompanied by extensive mass and angular momentum losses. Stability against such rapid mass transfer may impose severe limitations on the masses and mass ratios of cataclysmic variables

  4. Wind influence on a coastal buoyant outflow

    Science.gov (United States)

    Whitney, Michael M.; Garvine, Richard W.

    2005-03-01

    This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ Wind events, however, overwhelm the buoyancy-driven flow (∣Ws∣ > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

  5. Modeling the influence of potassium content and heating rate on biomass pyrolysis

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Surup, Gerrit; Shapiro, Alexander

    2017-01-01

    This study presents a combined kinetic and particle model that describes the effect of potassium and heating rate during the fast pyrolysis of woody and herbaceous biomass. The model calculates the mass loss rate, over a wide range of operating conditions relevant to suspension firing...

  6. China Wind Power Outlook 2010

    International Nuclear Information System (INIS)

    Junfeng, Li; Pengfei, Shi; Hu, Gao

    2010-10-01

    China's wind power can reach 230 GW of installed capacity by 2020, which is equal to 13 times the current capacity of the Three Gorges Dam; its annual electricity output of 464.9 TWh could replace 200 coal fire power plants. In 2009, China led the world in newly installed wind-energy devices, reaching a capacity of 13.8 GW (10,129 turbines) - a rate of one new turbine every hour. In terms of overall capacity, China ranks second, at 25.8 GW. The report projects that by 2020, China's total wind power capacity will reach at least 150GW, possibly up to 230GW, which, if realized, could cut 410 million tons of CO2 emission, or 150 million tons of coal consumption. Compared to multinationals, many Chinese companies are young and lack a strong basis for research and development. Despite a renewable energy policy requiring grid companies to purchase all electricity from wind farms, access to wind power for the grid is frequently lagging behind an unstable, out-dated grid infrastructure. There is also the problem of a lack of incentives and penalties for grid companies, and slow progress in more wind energy technologies.

  7. China Wind Power Outlook 2010

    Energy Technology Data Exchange (ETDEWEB)

    Junfeng, Li; Pengfei, Shi; Hu, Gao [Chinese Renewable Energy Industries Association CREIA, Beijing (China)

    2010-10-15

    China's wind power can reach 230 GW of installed capacity by 2020, which is equal to 13 times the current capacity of the Three Gorges Dam; its annual electricity output of 464.9 TWh could replace 200 coal fire power plants. In 2009, China led the world in newly installed wind-energy devices, reaching a capacity of 13.8 GW (10,129 turbines) - a rate of one new turbine every hour. In terms of overall capacity, China ranks second, at 25.8 GW. The report projects that by 2020, China's total wind power capacity will reach at least 150GW, possibly up to 230GW, which, if realized, could cut 410 million tons of CO2 emission, or 150 million tons of coal consumption. Compared to multinationals, many Chinese companies are young and lack a strong basis for research and development. Despite a renewable energy policy requiring grid companies to purchase all electricity from wind farms, access to wind power for the grid is frequently lagging behind an unstable, out-dated grid infrastructure. There is also the problem of a lack of incentives and penalties for grid companies, and slow progress in more wind energy technologies.

  8. Power Transformer Application for Wind Plant Substations

    Energy Technology Data Exchange (ETDEWEB)

    Behnke, M. R. [IEEE PES Wind Plant Collector System Design Working Group; Bloethe, W.G. [IEEE PES Wind Plant Collector System Design Working Group; Bradt, M. [IEEE PES Wind Plant Collector System Design Working Group; Brooks, C. [IEEE PES Wind Plant Collector System Design Working Group; Camm, E H [IEEE PES Wind Plant Collector System Design Working Group; Dilling, W. [IEEE PES Wind Plant Collector System Design Working Group; Goltz, B. [IEEE PES Wind Plant Collector System Design Working Group; Li, J. [IEEE PES Wind Plant Collector System Design Working Group; Niemira, J. [IEEE PES Wind Plant Collector System Design Working Group; Nuckles, K. [IEEE PES Wind Plant Collector System Design Working Group; Patino, J. [IEEE PES Wind Plant Collector System Design Working Group; Reza, M [IEEE PES Wind Plant Collector System Design Working Group; Richardson, B. [IEEE PES Wind Plant Collector System Design Working Group; Samaan, N. [IEEE PES Wind Plant Collector System Design Working Group; Schoene, Jens [IEEE PES Wind Plant Collector System Design Working Group; Smith, Travis M [ORNL; Snyder, Isabelle B [ORNL; Starke, Michael R [ORNL; Walling, R. [IEEE PES Wind Plant Collector System Design Working Group; Zahalka, G. [IEEE PES Wind Plant Collector System Design Working Group

    2010-01-01

    Wind power plants use power transformers to step plant output from the medium voltage of the collector system to the HV or EHV transmission system voltage. This paper discusses the application of these transformers with regard to the selection of winding configuration, MVA rating, impedance, loss evaluation, on-load tapchanger requirements, and redundancy.

  9. Field test of a lidar wind profiler

    NARCIS (Netherlands)

    Kunz, G.J.

    1996-01-01

    Wind speeds and wind directions are measured remotely using an incoherent backscatter lidar system operating at a wavelength of 1.06 mm with a maximum repetition rate of 13 Hz. The principle of the measurements is based on following detectable atmospheric structures, which are transported by the

  10. Wind Development on Tribal Lands

    Energy Technology Data Exchange (ETDEWEB)

    Ken Haukaas; Dale Osborn; Belvin Pete

    2008-01-18

    Background: The Rosebud Sioux Tribe (RST) is located in south central South Dakota near the Nebraska border. The nearest community of size is Valentine, Nebraska. The RST is a recipient of several Department of Energy grants, written by Distributed Generation Systems, Inc. (Disgen), for the purposes of assessing the feasibility of its wind resource and subsequently to fund the development of the project. Disgen, as the contracting entity to the RST for this project, has completed all the pre-construction activities, with the exception of the power purchase agreement and interconnection agreement, to commence financing and construction of the project. The focus of this financing is to maximize the economic benefits to the RST while achieving commercially reasonable rates of return and fees for the other parties involved. Each of the development activities required and its status is discussed below. Land Resource: The Owl Feather War Bonnet 30 MW Wind Project is located on RST Tribal Trust Land of approximately 680 acres adjacent to the community of St. Francis, South Dakota. The RST Tribal Council has voted on several occasions for the development of this land for wind energy purposes, as has the District of St. Francis. Actual footprint of wind farm will be approx. 50 acres. Wind Resource Assessment: The wind data has been collected from the site since May 1, 2001 and continues to be collected and analyzed. The latest projections indicate a net capacity factor of 42% at a hub height of 80 meters. The data has been collected utilizing an NRG 9300 Data logger System with instrumentation installed at 30, 40 and 65 meters on an existing KINI radio tower. The long-term annual average wind speed at 65-meters above ground level is 18.2 mph (8.1 mps) and 18.7 mph (8.4 mps) at 80-meters agl. The wind resource is excellent and supports project financing.

  11. Sensitivity analysis of floating offshore wind farms

    International Nuclear Information System (INIS)

    Castro-Santos, Laura; Diaz-Casas, Vicente

    2015-01-01

    Highlights: • Develop a sensitivity analysis of a floating offshore wind farm. • Influence on the life-cycle costs involved in a floating offshore wind farm. • Influence on IRR, NPV, pay-back period, LCOE and cost of power. • Important variables: distance, wind resource, electric tariff, etc. • It helps to investors to take decisions in the future. - Abstract: The future of offshore wind energy will be in deep waters. In this context, the main objective of the present paper is to develop a sensitivity analysis of a floating offshore wind farm. It will show how much the output variables can vary when the input variables are changing. For this purpose two different scenarios will be taken into account: the life-cycle costs involved in a floating offshore wind farm (cost of conception and definition, cost of design and development, cost of manufacturing, cost of installation, cost of exploitation and cost of dismantling) and the most important economic indexes in terms of economic feasibility of a floating offshore wind farm (internal rate of return, net present value, discounted pay-back period, levelized cost of energy and cost of power). Results indicate that the most important variables in economic terms are the number of wind turbines and the distance from farm to shore in the costs’ scenario, and the wind scale parameter and the electric tariff for the economic indexes. This study will help investors to take into account these variables in the development of floating offshore wind farms in the future

  12. Solutions to raptor-wind farm interactions

    Energy Technology Data Exchange (ETDEWEB)

    Madders, M.; Walker, D.G. [CRE Energy Ltd., Scottish Power, Glasgow (United Kingdom)

    2000-07-01

    Wind energy developments in the uplands have the potential to adversely impact upon a number of raptor species by lowering survival and reproductive rates. In many cases, wind farms are proposed in areas where raptors are already under pressure from existing land uses, notably sheep grazing and forestry. This paper summarises the approach used to assess the impact of a 30MW wind farm on a pair of golden eagles in the Kintyre peninsula, Scotland. We outline the method being used to manage habitats for the benefit of the eagles and their prey. By adopting management practices that are both wide-scale and long-term, we aim to reduce the impact to the wind farm to levels considered acceptable by the conservation agencies, and improve breeding productivity of the eagles using the wind farm. The implications of this innovative approach for future raptor--wind farm interactions are discussed. (Author)

  13. Wind gust models derived from field data

    Science.gov (United States)

    Gawronski, W.

    1995-01-01

    Wind data measured during a field experiment were used to verify the analytical model of wind gusts. Good coincidence was observed; the only discrepancy occurred for the azimuth error in the front and back winds, where the simulated errors were smaller than the measured ones. This happened because of the assumption of the spatial coherence of the wind gust model, which generated a symmetric antenna load and, in consequence, a low azimuth servo error. This result indicates a need for upgrading the wind gust model to a spatially incoherent one that will reflect the real gusts in a more accurate manner. In order to design a controller with wind disturbance rejection properties, the wind disturbance should be known at the input to the antenna rate loop model. The second task, therefore, consists of developing a digital filter that simulates the wind gusts at the antenna rate input. This filter matches the spectrum of the measured servo errors. In this scenario, the wind gusts are generated by introducing white noise to the filter input.

  14. Assessment of wind power generation along the coast of Ghana

    Energy Technology Data Exchange (ETDEWEB)

    Adaramola, Muyiwa S., E-mail: muyiwa.adaramola@umb.no [Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, Ås (Norway); Agelin-Chaab, Martin [Department of Automotive, Mechanical and Manufacturing Engineering, University of Ontario Institute of Technology, Oshawa, ON (Canada); Paul, Samuel S. [REHAU Industries, Winnipeg, Manitoba (Canada)

    2014-01-15

    Highlights: • The wind energy and its economic viability along the coastal region of Ghana are examined. • Wind resource along the coastal region of Ghana fall into Class 2 or less wind resource. • Wind turbine with rated speed from 9 to 11 m/s is suggested for wind power development. • The unit cost of wind generated electricity is found be between 0.0732 GH¢/kW h and 0.2905 GH¢/kW h. - Abstract: This study examined the wind energy potential and the economic viability of using wind turbine for electricity generation in selected locations along the coastal region of Ghana. The two-parameter Weibull probability density function was employed to analyze the wind speed data obtained from the Ghana Energy Commission. The energy output and unit cost of electricity generated from medium size commercial wind turbine models with rated powers ranging from 50 kW to 250 kW were determined. It was found that the wind resource along the coastal region of Ghana can be classified into Class 2 or less wind resource which indicate that this resource in this area is marginally suitable for large scale wind energy development or suitable for small scale applications and be useful as part of hybrid energy system. It was further observed that wind turbine with designed cut-in wind speed of less than 3 m/s and moderate rated wind speed between 9 and 11 m/s is more suitable for wind energy development along the coastal region of Ghana. Based on the selected wind turbine and assumptions used in this study, it was estimated that the unit cost of electricity varied between 0.0695 GH¢/kW h and 0.2817 GH¢/kW h.

  15. Assessment of wind power generation along the coast of Ghana

    International Nuclear Information System (INIS)

    Adaramola, Muyiwa S.; Agelin-Chaab, Martin; Paul, Samuel S.

    2014-01-01

    Highlights: • The wind energy and its economic viability along the coastal region of Ghana are examined. • Wind resource along the coastal region of Ghana fall into Class 2 or less wind resource. • Wind turbine with rated speed from 9 to 11 m/s is suggested for wind power development. • The unit cost of wind generated electricity is found be between 0.0732 GH¢/kW h and 0.2905 GH¢/kW h. - Abstract: This study examined the wind energy potential and the economic viability of using wind turbine for electricity generation in selected locations along the coastal region of Ghana. The two-parameter Weibull probability density function was employed to analyze the wind speed data obtained from the Ghana Energy Commission. The energy output and unit cost of electricity generated from medium size commercial wind turbine models with rated powers ranging from 50 kW to 250 kW were determined. It was found that the wind resource along the coastal region of Ghana can be classified into Class 2 or less wind resource which indicate that this resource in this area is marginally suitable for large scale wind energy development or suitable for small scale applications and be useful as part of hybrid energy system. It was further observed that wind turbine with designed cut-in wind speed of less than 3 m/s and moderate rated wind speed between 9 and 11 m/s is more suitable for wind energy development along the coastal region of Ghana. Based on the selected wind turbine and assumptions used in this study, it was estimated that the unit cost of electricity varied between 0.0695 GH¢/kW h and 0.2817 GH¢/kW h

  16. Wind engineering in Africa

    NARCIS (Netherlands)

    Wisse, J.A.; Stigter, C.J.

    2007-01-01

    The International Association for Wind Engineering (IAWE) has very few contacts in Africa, the second-largest continent. This paper reviews important wind-related African issues. They all require data on wind climate, which are very sparse in Africa. Wind engineering in Africa can assist in

  17. Turbulent wind at the equatorial segment of an operating Darrieus wind turbine blade

    Science.gov (United States)

    Connell, J. R.; Morris, V. R.

    1989-09-01

    Six turbulent wind time series, measured at equally spaced equator-height locations on a circle 3 m outside a 34-m Darrieus rotor, are analyzed to approximate the wind fluctuations experienced by the rotor. The flatwise lower root-bending stress of one blade was concurrently recorded. The wind data are analyzed in three ways: wind components that are radial and tangential to the rotation of a blade were rotationally sampled; induction and wake effects of the rotor were estimated from the six Eulerian time series; and turbulence spectra of both the measured wind and the modeled wind from the PNL theory of rotationally sampled turbulence. The wind and the rotor response are related by computing the spectral response function of the flatwise lower root-bending stress. Two bands of resonant response that surround the first and second flatwise modal frequencies shift with the rotor rotation rate.

  18. Closed and open magnetic fields in stellar winds

    Science.gov (United States)

    Mullan, D. J.; Steinolfson, R. S.

    1983-01-01

    A numerical study of the interaction between a thermal wind and a global dipole field in the sun and in a giant star is reported. In order for closed field lines to persist near the equator (where a helmet-streamer-like configuration appears), the coronal temperature must be less than a critical value Tc, which scales as M/R. This condition is found to be equivalent to the following: for a static helmet streamer to persist, the sonic point above the helmet must not approach closer to the star than 2.2-2.6 stellar radii. Implications for rapid mass loss and X-ray emission from cool giants are pointed out. The results strengthen the case for identifying empirical dividing lines in the H-R diagram with a magnetic topology transition locus (MTTL). Support for the MTTL concept is also provided by considerations of the breakdown of magnetostatic equilibrium.

  19. Determining the impact of wind on system costs via the temporal patterns of load and wind generation

    International Nuclear Information System (INIS)

    Davis, Clay D.; Gotham, Douglas J.; Preckel, Paul V.; Liu, Andrew L.

    2013-01-01

    Ambitious targets have been set for expanding electricity generation from renewable sources, including wind. Expanding wind power impacts needs for other electricity generating resources. As states plan for increasing levels of wind generation in their portfolio of generation resources it is important to consider how this intermittent resource impacts the need for other generation resources. A case study for Indiana estimates the value of wind capacity and demonstrates how to optimize its level and the levels of other generation resources. Changes are driven by temporal patterns of wind power output and load. System wide impacts are calculated for energy, capacity, and costs under multiple wind expansion scenarios which highlight the geographic characteristics of a systems portfolio of wind generation. The impacts of carbon prices, as proposed in the Bingaman Bill, are considered. Finally, calculations showing the effect increasing levels of wind generation will have on end use Indiana retail rates are included. - Highlights: • We estimate the value of wind capacity. • We determine wind generation's impact on the optimal mix of non-wind generation. • Optimal levels of wind and non-wind generation are determined. • We consider the impact of a carbon price on the optimal mix of resources. • The impact of additional wind capacity on Indiana residential rates is calculated

  20. Wind power plant

    Energy Technology Data Exchange (ETDEWEB)

    Caneghem, A.E. von

    1975-07-24

    The invention applies to a wind power plant in which the wind is used to drive windmills. The plant consists basically of a vertical tube with a lateral wind entrance opening with windmill on its lower end. On its upper end, the tube carries a nozzle-like top which increases the wind entering the tube by pressure decrease. The wind is thus made suitable for higher outputs. The invention is illustrated by constructional examples.

  1. Wind energy analysis system

    OpenAIRE

    2014-01-01

    M.Ing. (Electrical & Electronic Engineering) One of the most important steps to be taken before a site is to be selected for the extraction of wind energy is the analysis of the energy within the wind on that particular site. No wind energy analysis system exists for the measurement and analysis of wind power. This dissertation documents the design and development of a Wind Energy Analysis System (WEAS). Using a micro-controller based design in conjunction with sensors, WEAS measure, calcu...

  2. Wind power. [electricity generation

    Science.gov (United States)

    Savino, J. M.

    1975-01-01

    A historical background on windmill use, the nature of wind, wind conversion system technology and requirements, the economics of wind power and comparisons with alternative systems, data needs, technology development needs, and an implementation plan for wind energy are presented. Considerable progress took place during the 1950's. Most of the modern windmills feature a wind turbine electricity generator located directly at the top of their rotor towers.

  3. Wind farms production: Control and prediction

    Science.gov (United States)

    El-Fouly, Tarek Hussein Mostafa

    and the time delay of the incident wind speed of the different turbines on the farm, and to simulate the fluctuation in the generated power more accurately and more closer to real-time operation. Recently, wind farms with considerable output power ratings have been installed. Their integrating into the utility grid will substantially affect the electricity markets. This thesis investigates the possible impact of wind power variability, wind farm control strategy, wind energy penetration level, wind farm location, and wind power prediction accuracy on the total generation costs and close to real time electricity market prices. These issues are addressed by developing a single auction market model for determining the real-time electricity market prices.

  4. Local ownership, smart energy systems and better wind power economy

    DEFF Research Database (Denmark)

    Hvelplund, Frede; Möller, Bernd; Sperling, Karl

    2013-01-01

    is never sold at a lower price than the most expensive heat alternative. The other is to lower the average costs of wind power by building more onshore wind power capacity, and proportionally less offshore wind power. This is facilitated by local and regional majority ownership models that increase...... the acceptance rate of onshore wind. The economy of wind power is thus improved by both increasing its value and reducing its costs.......Increasing wind power shares enhances the need to integrate wind power into the energy system and to improve its economy. In this study we propose two ways of achieving this end. One is to increase the value of wind power by integrating the heat and power markets, and thus ensures that wind power...

  5. Blowing in the Milky Way Wind: Neutral Hydrogen Clouds Tracing the Galactic Nuclear Outflow

    Science.gov (United States)

    Di Teodoro, Enrico M.; McClure-Griffiths, N. M.; Lockman, Felix J.; Denbo, Sara R.; Endsley, Ryan; Ford, H. Alyson; Harrington, Kevin

    2018-03-01

    We present the results of a new sensitive survey of neutral hydrogen above and below the Galactic Center with the Green Bank Telescope. The observations extend up to Galactic latitude | b| resolution of 9.‧5 and an average rms brightness temperature noise of 40 mK in a 1 {km} {{{s}}}-1 channel. The survey reveals the existence of a population of anomalous high-velocity clouds extending up to heights of about 1.5 kpc from the Galactic plane and showing no signature of Galactic rotation. These clouds have local standard of rest velocities | {V}LSR}| ≲ 360 {km} {{{s}}}-1, and assuming a Galactic Center origin, they have sizes of a few tens of parsec and neutral hydrogen masses spanning 10{--}{10}5 {M}ȯ . Accounting for selection effects, the cloud population is symmetric in longitude, latitude, and V LSR. We model the cloud kinematics in terms of an outflow expanding from the Galactic Center and find the population consistent with being material moving with radial velocity {V}{{w}}≃ 330 {km} {{{s}}}-1 distributed throughout a bicone with opening angle α > 140^\\circ . This simple model implies an outflow luminosity {L}{{w}}> 3× {10}40 erg s‑1 over the past 10 Myr, consistent with star formation feedback in the inner region of the Milky Way, with a cold gas mass-loss rate ≲ 0.1 {{M}ȯ {yr}}-1. These clouds may represent the cold gas component accelerated in the nuclear wind driven by our Galaxy, although some of the derived properties challenge current theoretical models of the entrainment process.

  6. Wind Resource Assessment and Requested Wind Turbine Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Ken [Municipal Civil Corporation, Gas City, IN (United States); Wolar, John [Municipal Civil Corporation, Gas City, IN (United States)

    2012-10-22

    Alternate Energy Solutions, Inc. (“AESWR”) was engaged by the Town of Brookston (“Brookston”) to assemble, erect and maintain one 60 m XHD meteorological tower manufactured by NRG Systems, Inc.; for monitoring, recording and evaluating collected wind data. It is the opinion of AESWR staff that study results support the development of a wind turbine project at the Bol Family Farm provided: a) additional land is leased for the project; b) project construction costs are controlled; and c) a prudent power purchase agreement is negotiated with a power take-off entity. We believe that a project having an aggregate nameplate rating sized from 6.0 MW to 20 MW would be appropriate for this location. We recommend 100-125 acres of land per installed MW be used as a general rule for acquiring wind energy land lease agreements, total land lease holdings to be acquired would then approach 750 acres to 2,500 acres.

  7. Highly reliable wind-rolling triboelectric nanogenerator operating in a wide wind speed range

    Science.gov (United States)

    Yong, Hyungseok; Chung, Jihoon; Choi, Dukhyun; Jung, Daewoong; Cho, Minhaeng; Lee, Sangmin

    2016-01-01

    Triboelectric nanogenerators are aspiring energy harvesting methods that generate electricity from the triboelectric effect and electrostatic induction. This study demonstrates the harvesting of wind energy by a wind-rolling triboelectric nanogenerator (WR-TENG). The WR-TENG generates electricity from wind as a lightweight dielectric sphere rotates along the vortex whistle substrate. Increasing the kinetic energy of a dielectric converted from the wind energy is a key factor in fabricating an efficient WR-TENG. Computation fluid dynamics (CFD) analysis is introduced to estimate the precise movements of wind flow and to create a vortex flow by adjusting the parameters of the vortex whistle shape to optimize the design parameters to increase the kinetic energy conversion rate. WR-TENG can be utilized as both a self-powered wind velocity sensor and a wind energy harvester. A single unit of WR-TENG produces open-circuit voltage of 11.2 V and closed-circuit current of 1.86 μA. Additionally, findings reveal that the electrical power is enhanced through multiple electrode patterns in a single device and by increasing the number of dielectric spheres inside WR-TENG. The wind-rolling TENG is a novel approach for a sustainable wind-driven TENG that is sensitive and reliable to wind flows to harvest wasted wind energy in the near future. PMID:27653976

  8. Stator winding service life analysis of wet winding motor RCP

    International Nuclear Information System (INIS)

    Yeoh Eingyee; Li Linsen; Wang Ziguan; Shen Feng

    2017-01-01

    The reactor coolant pump type RUV of KSB is specially designed for the Westinghouse AP1000 reactor. It is hermetically sealed, wet winding motor pump. This wet winding motor concept has higher efficiency as compared to a canned motor since there are no eddy current losses, but this makes the stator cable insulator face the challenge of degradation by γ-irradiation in coolant. Radiation dose at the RUV is evaluated in interest from the material degradation point of view and the service life of stator winding in RUV is preliminarily analyzed. The values obtained are less than the dose rate and the dose which change the mechanical properties of the insulator material. According to the preliminary analysis, it can be concluded that the degradation of cable insulator of stator winding by γ-irradiation in coolant is negligible for the 60 years' service life of reactor coolant pump. This result also ensures crosslinked polyethylene used as cable insulator of stator winding is reliable in reactor coolant pump. (author)

  9. Extreme wind estimate for Hornsea wind farm

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo

    The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...... strength is taken as 0.1. The shear exponents at several heights were calculated from the measurements. The values at 100 m are less than the limit given by IEC standard for all sectors. The 50-year winds have been calculated from various global reanalysis and analysis products as well as mesoscale models...

  10. Climatic wind tunnel for wind engineering tasks

    Czech Academy of Sciences Publication Activity Database

    Kuznetsov, Sergeii; Pospíšil, Stanislav; Král, Radomil

    2015-01-01

    Roč. 112, 2-B (2015), s. 303-316 ISSN 1897-628X R&D Projects: GA ČR(CZ) GA14-12892S Keywords : climatic tunnel * wind tunnel * atmospheric boundary layer * flow resistance * wind tunnel contraction Subject RIV: JM - Building Engineering https://suw.biblos.pk.edu.pl/resources/i5/i6/i6/i7/i6/r56676/KuznetsovS_ClimaticWind.pdf

  11. Modelling of environmental and climatic problems: Wind and water erosion

    International Nuclear Information System (INIS)

    Aslan, Z.

    2004-01-01

    Magnitude of wind and water erosion mainly depend on wind velocity, rainfall rate, slope and soil characteristics. The main purpose of this lecture is to define the role of small, meso and large scale phenomena (local and synoptic fluctuations) on water and wind erosion. These lecture notes present some results on wind speed simulation and seasonal fluctuations of water deficit for the selected station in different erosion risque and transition regions of Turkey. (author)

  12. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  13. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling; Said Said, Usama; Badger, Jake

    2006-01-01

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  14. The potentialities of the wind driven engines with Magnus effect

    International Nuclear Information System (INIS)

    Bychkov, N.M.; Gorelov, V.P.; Gorelov, S.V.; Kachanov, A.N.

    1999-01-01

    Possibilities of wind engine realizing of Magnus effect like of untraditional kind energy source is shown in the article. In this engine instead of traditional propellers the rotatable cylinders are installed. According interaction of the cylinders with wind the Magnus force arises. Magnus force exceeds propellers rise force in 5-10 times and maintain very large turning moment of wind wheel and most effective operation of engine, especially at low wind rates. Advantage of the engine consists in that it switch on under wind rate 1 m/c, when for propeller one requires 4-5 m/c

  15. Wind tunnel simulation of Martian sand storms

    Science.gov (United States)

    Greeley, R.

    1980-01-01

    The physics and geological relationships of particles driven by the wind under near Martian conditions were examined in the Martian Surface Wind Tunnel. Emphasis was placed on aeolian activity as a planetary process. Threshold speeds, rates of erosion, trajectories of windblown particles, and flow fields over various landforms were among the factors considered. Results of experiments on particles thresholds, rates of erosion, and the effects of electrostatics on particles in the aeolian environment are presented.

  16. Numerical simulations of flow fields through conventionally controlled wind turbines and wind farms

    International Nuclear Information System (INIS)

    Yilmaz, Ali Emre; Meyers, Johan

    2014-01-01

    In the current study, an Actuator-Line Model (ALM) is implemented in our in-house pseudo-spectral LES solver SP-WIND, including a turbine controller. Below rated wind speed, turbines are controlled by a standard-torque-controller aiming at maximum power extraction from the wind. Above rated wind speed, the extracted power is limited by a blade pitch controller which is based on a proportional-integral type control algorithm. This model is used to perform a series of single turbine and wind farm simulations using the NREL 5MW turbine. First of all, we focus on below-rated wind speed, and investigate the effect of the farm layout on the controller calibration curves. These calibration curves are expressed in terms of nondimensional torque and rotational speed, using the mean turbine-disk velocity as reference. We show that this normalization leads to calibration curves that are independent of wind speed, but the calibration curves do depend on the farm layout, in particular for tightly spaced farms. Compared to turbines in a lone-standing set-up, turbines in a farm experience a different wind distribution over the rotor due to the farm boundary-layer interaction. We demonstrate this for fully developed wind-farm boundary layers with aligned turbine arrangements at different spacings (5D, 7D, 9D). Further we also compare calibration curves obtained from full farm simulations with calibration curves that can be obtained at a much lower cost using a minimal flow unit

  17. 75 FR 23263 - Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC...

    Science.gov (United States)

    2010-05-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL10-62-000] Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC; Alta Wind VI, LLC; Alta Wind VII, LLC; Alta Wind VIII, LLC; Alta Windpower Development, LLC; TGP Development Company, LLC...

  18. 77 FR 29633 - Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC...

    Science.gov (United States)

    2012-05-18

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-68-000] Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC, Alta Wind XIII, LLC, Alta Wind XIV, LLC, Alta Wind XV, LLC, Alta Windpower Development, LLC, TGP Development Company, LLC...

  19. Economic feasibility of developing wind turbines in Aligoodarz, Iran

    International Nuclear Information System (INIS)

    Mohammadi, Kasra; Mostafaeipour, Ali

    2013-01-01

    Highlights: • Three hourly long term measured wind speed data from 2005 to 2009 for city of Aligoodarz in Iran was analyzed. • Wind power density and wind energy density of the region were estimated using Weibull distribution. • Performance of six different wind turbine models were analyzed. • Economic evaluation was performed and installing of E-3120 (50 kW) model turbine was suggested. - Abstract: This study evaluates the economic feasibility of electricity generation using wind turbines in city of Aligoodarz situated in the west part of Iran. For this purpose, the wind energy potential and its characteristics were assessed in terms of diurnal, monthly and annual analysis using five years measured wind speed data from 2005 to 2009 at 10 m height. The analysis results specified a nearly stable wind pattern in different hours and months of the year which demonstrated more suitability of the region for wind energy harnessing to meet the electricity demand in all time intervals throughout the year. According to Pacific Northwest Laboratory (PNL) wind power classification, the wind resource in Aligoodarz falls in class 3 and the location was recognized as a moderate location for wind energy development. The economic feasibility of six different wind turbines with rated powers ranging from 20 to 150 kW was evaluated. Among all turbines examined, the E-3120 wind turbine was introduced as the most attractive option for installation

  20. Wind energy resources assessment for Yanbo, Saudi Arabia

    International Nuclear Information System (INIS)

    Rehman, Shafiqur

    2004-01-01

    The paper presents long term wind data analysis in terms of annual, seasonal and diurnal variations at Yanbo, which is located on the west coast of Saudi Arabia. The wind speed and wind direction hourly data for a period of 14 years between 1970 and 1983 is used in the analysis. The analysis showed that the seasonal and diurnal pattern of wind speed matches the electricity load pattern of the location. Higher winds of the order of 5.0 m/s and more were observed during the summer months of the year and noon hours (09:00 to 16:00 h) of the day. The wind duration availability is discussed as the percent of hours during which the wind remained in certain wind speed intervals or bins. Wind energy calculations were performed using wind machines of sizes 150, 250, 600, 800, 1000, 1300, 1500, 2300 and 2500 kW rated power. Wind speed is found to remain above 3.5 m/s for 69% of the time during the year at 40, 50, 60, and 80 m above ground level. The energy production analysis showed higher production from wind machines of smaller sizes than the bigger ones for a wind farm of 30 MW installed capacity. Similarly, higher capacity factors were obtained for smaller wind machines compared to larger ones

  1. Wind energy information guide

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-04-01

    This book is divided into nine chapters. Chapters 1--8 provide background and annotated references on wind energy research, development, and commercialization. Chapter 9 lists additional sources of printed information and relevant organizations. Four indices provide alphabetical access to authors, organizations, computer models and design tools, and subjects. A list of abbreviations and acronyms is also included. Chapter topics include: introduction; economics of using wind energy; wind energy resources; wind turbine design, development, and testing; applications; environmental issues of wind power; institutional issues; and wind energy systems development.

  2. Arctic wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Peltola, E. [Kemijoki Oy (Finland); Holttinen, H.; Marjaniemi, M. [VTT Energy, Espoo (Finland); Tammelin, B. [Finnish Meteorological Institute, Helsinki (Finland)

    1998-12-31

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  3. Arctic wind energy

    International Nuclear Information System (INIS)

    Peltola, E.; Holttinen, H.; Marjaniemi, M.; Tammelin, B.

    1998-01-01

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  4. Wind power today

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    This publication highlights initiatives of the US DOE`s Wind Energy Program. 1997 yearly activities are also very briefly summarized. The first article describes a 6-megawatt wind power plant installed in Vermont. Another article summarizes technical advances in wind turbine technology, and describes next-generation utility and small wind turbines in the planning stages. A village power project in Alaska using three 50-kilowatt turbines is described. Very brief summaries of the Federal Wind Energy Program and the National Wind Technology Center are also included in the publication.

  5. Wind Power Career Chat

    Energy Technology Data Exchange (ETDEWEB)

    L. Flowers

    2011-01-01

    This document will teach students about careers in the wind energy industry. Wind energy, both land-based and offshore, is expected to provide thousands of new jobs in the next several decades. Wind energy companies are growing rapidly to meet America's demand for clean, renewable, and domestic energy. These companies need skilled professionals. Wind power careers will require educated people from a variety of areas. Trained and qualified workers manufacture, construct, operate, and manage wind energy facilities. The nation will also need skilled researchers, scientists, and engineers to plan and develop the next generation of wind energy technologies.

  6. Collision risk of birds with modern large wind turbines

    NARCIS (Netherlands)

    Krijgsveld, K.L.; Akershoek, K.; Schenk, F.; Dijk, van F.; Dirksen, J.

    2009-01-01

    We studied collision rate of birds with modern, large 1.65 MW wind turbines in three wind farms in The Netherlands during three months in autumn and winter. Collision rate, after correction for retrieval and disappearance rate, was 0.08 birds per turbine per day on average (range 0.05-0.19).

  7. Wind power development field test project at Ashibe-cho. Detailed wind characteristics survey; Ashibecho ni okeru furyoku kaihatsu field test jigyo (fukyo seisa) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-11-01

    A detailed wind characteristics survey was conducted at Ashibe-cho, Iki-gun, Nagasaki Prefecture, on the assumption that a wind power generation system would be constructed. The survey was a 1-year project from October 1998 through September 1999, and wind characteristics such as the average wind speed, average wind direction, standard deviation of wind velocity, and the maximum instantaneous wind speed were observed. The observation point was fixed at 20m above ground, the minimum time unit for observation was 10 minutes, and the 10-minute average value was defined as the measured value. For the maximum instantaneous wind speed, the minimum time unit for observation was set to be 2 seconds. The yearly average wind speed was 5.8m/s and the maximum wind speed in the period was 35m/s. Winds came from the prevailing direction of NE (21.3%), and then from NNE (14.7%) and ENE (7.9%). The wind axis was in the NE-SW direction, and the total wind direction occurrence rate from the 6 directions was 60.2%. Turbulence intensity was 0.19 at wind speed 2.0m/s or more and 0.17 at wind speed 4.0m/s or more. Estimated wind turbine yearly operating factors of 66-84% were obtained using rated values of a 150kW, 300kW, and 750kW-class wind turbines. (NEDO)

  8. Evolution of wind towards wind turbine

    NARCIS (Netherlands)

    Giyanani, A.H.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.

    2015-01-01

    Remote sensing of the atmospheric variables with the use of LiDAR is a relatively new technology field for wind resource assessment in wind energy. The validation of LiDAR measurements and comparisons is of high importance for further applications of the data.

  9. Urban Wind Energy

    DEFF Research Database (Denmark)

    Beller, Christina

    important for the implementation of wind energy conversion systems are the macro and micro wind climate, the siting within a micro wind climate and the choice of a wind turbine model most appropriate for the selected site. In the frame of this work, all these important elements are analyzed and a row......New trends e.g. in architecture and urban planning are to reduce energy needs. Several technologies are employed to achieve this, and one of the technologies, not new as such, is wind energy. Wind turbines are installed in cities, both by companies and private persons on both old and new buildings....... However, an overview of the energy content of the wind in cities and how consequently turbines shall be designed for such wind climates is lacking. The objective of the present work is to deliver an objective and fundamental overview of the social, practical and physical conditions relevant...

  10. Leadership Team | Wind | NREL

    Science.gov (United States)

    Leadership Team Leadership Team Learn more about the expertise and technical skills of the wind Initiative and provides leadership in the focus areas of high-fidelity modeling, wind power plant controls

  11. Danish Wind Power

    DEFF Research Database (Denmark)

    Lund, Henrik; Hvelplund, Frede; Østergaard, Poul Alberg

    In a normal wind year, Danish wind turbines generate the equivalent of approx. 20 percent of the Danish electricity demand. This paper argues that only approx. 1 percent of the wind power production is exported. The rest is used to meet domestic Danish electricity demands. The cost of wind power...... misleading. The cost of CO2 reduction by use of wind power in the period 2004-2008 was only 20 EUR/ton. Furthermore, the Danish wind turbines are not paid for by energy taxes. Danish wind turbines are given a subsidy via the electricity price which is paid by the electricity consumers. In the recent years...... is paid solely by the electricity consumers and the net influence on consumer prices was as low as 1-3 percent on average in the period 2004-2008. In 2008, the net influence even decreased the average consumer price, although only slightly. In Denmark, 20 percent wind power is integrated by using both...

  12. Superconducting Wind Turbine Generators

    Directory of Open Access Journals (Sweden)

    Yunying Pan

    2016-08-01

    Full Text Available Wind energy is well known as a renewable energy because its clean and less polluted characteristic, which is the foundation of development modern wind electricity. To find more efficient wind turbine is the focus of scientists around the world. Compared from conventional wind turbines, superconducting wind turbine generators have advantages at zero resistance, smaller size and lighter weight. Superconducting wind turbine will inevitably become the main trends in this area. This paper intends to introduce the basic concept and principle of superconductivity, and compare form traditional wind turbine to obtain superiority, then to summary three proposed machine concept.While superconductivity have difficulty  in modern technology and we also have proposed some challenges in achieving superconducting wind turbine finally.

  13. Influence of a stellar wind on the evolution of a star of 30 M/sub sun/

    International Nuclear Information System (INIS)

    Stothers, R.; Chin, C.

    1980-01-01

    A coarse grid of theoretical evolutionary tracks has been computed for a star of 30 M/sub sun/, in an attempt to delineate the role of mass loss in the star's evolution during core helium burning. For all of the tracks, Cox-Stewart opacities have been adopted, and the free parameters have included the rate of mass loss, criterion for convection, and initial chemical composition. With the use of the Schwarzschild criterion, the star suffers little mass loss during core helium burning and remains almost to the end, a blue supergiant, well separated from main-sequence stars on the H-R diagram. With the use of the Ledoux criterion, the same consequences are obtained only in the case of a relatively low initial hydrogen or initial metals abundance. Otherwise, the star evolves, first, into a red supergiant, whereupon rapid mass loss must be assumed to take place, if the observed paucity of very bright red supergiants is to be accounted for. The stellar remnant then consists of little more than the original helium core, and may appear, for a time, bluer than equally luminous main-sequence stars, provided that the the initial hydrogen and metals abundances are normal. Thus, a wide variety of possible evolutionary tracks can be obtained for an initial mass of 30 M/sub sun/ with reasonable choices of the free parameters

  14. Lake Michigan Offshore Wind Feasibility Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Boezaart, Arnold [GVSU; Edmonson, James [GVSU; Standridge, Charles [GVSU; Pervez, Nahid [GVSU; Desai, Neel [University of Michigan; Williams, Bruce [University of Delaware; Clark, Aaron [GVSU; Zeitler, David [GVSU; Kendall, Scott [GVSU; Biddanda, Bopi [GVSU; Steinman, Alan [GVSU; Klatt, Brian [Michigan State University; Gehring, J. L. [Michigan State University; Walter, K. [Michigan State University; Nordman, Erik E. [GVSU

    2014-06-30

    recording wind data technology at a at a high confidence level as compared to traditional anemometer cup technology. • During storms, mean Turbulent Kinetic Energy (TKE) increases with height above water; • Sufficient wind resources exist over Lake Michigan to generate 7,684 kWh of power using a 850 kW rated turbine at elevations between 90 - 125 meters, a height lower than originally anticipated for optimum power generation; • Based on initial assessments, wind characteristics are not significantly different at distant (thirty-two mile) offshore locations as compared to near-shore (six mile) locations; • Significant cost savings can be achieved in generation wind energy at lower turbine heights and locating closer to shore. • Siting must be sufficiently distant from shore to minimize visual impact and to address public sentiment about offshore wind development; • Project results show that birds and bats do frequent the middle of Lake Michigan, bats more so than birds; • Based on the wind resource assessment and depths of Lake Michigan encountered during the project, future turbine placement will most likely need to incorporate floating or anchored technology; • The most appropriate siting of offshore wind energy locations will enable direct routing of transmission cables to existing generating and transmission facilities located along the Michigan shoreline; • Wind turbine noise propagation from a wind energy generating facility at a five mile offshore location will not be audible at the shoreline over normal background sound levels.

  15. Wind speed reductions by large-scale wind turbine deployments lower turbine efficiencies and set low wind power potentials

    Science.gov (United States)

    Miller, Lee; Kleidon, Axel

    2017-04-01

    Wind turbines generate electricity by removing kinetic energy from the atmosphere. Large numbers of wind turbines are likely to reduce wind speeds, which lowers estimates of electricity generation from what would be presumed from unaffected conditions. Here, we test how well wind power potentials that account for this effect can be estimated without explicitly simulating atmospheric dynamics. We first use simulations with an atmospheric general circulation model (GCM) that explicitly simulates the effects of wind turbines to derive wind power limits (GCM estimate), and compare them to a simple approach derived from the climatological conditions without turbines [vertical kinetic energy (VKE) estimate]. On land, we find strong agreement between the VKE and GCM estimates with respect to electricity generation rates (0.32 and 0.37 We m-2) and wind speed reductions by 42 and 44%. Over ocean, the GCM estimate is about twice the VKE estimate (0.59 and 0.29 We m-2) and yet with comparable wind speed reductions (50 and 42%). We then show that this bias can be corrected by modifying the downward momentum flux to the surface. Thus, large-scale limits to wind power can be derived from climatological conditions without explicitly simulating atmospheric dynamics. Consistent with the GCM simulations, the approach estimates that only comparatively few land areas are suitable to generate more than 1 We m-2 of electricity and that larger deployment scales are likely to reduce the expected electricity generation rate of each turbine. We conclude that these atmospheric effects are relevant for planning the future expansion of wind power.

  16. DEVIATION OF STELLAR ORBITS FROM TEST PARTICLE TRAJECTORIES AROUND SGr A* DUE TO TIDES AND WINDS

    International Nuclear Information System (INIS)

    Psaltis, Dimitrios; Li, Gongjie; Loeb, Abraham

    2013-01-01

    Monitoring the orbits of stars around Sgr A* offers the possibility of detecting the precession of their orbital planes due to frame dragging, of measuring the spin and quadrupole moment of the black hole, and of testing the no-hair theorem. Here we investigate whether the deviations of stellar orbits from test-particle trajectories due to wind mass loss and tidal dissipation of the orbital energy compromise such measurements. We find that the effects of stellar winds are, in general, negligible. On the other hand, for the most eccentric orbits (e > 0.96) for which an optical interferometer, such as GRAVITY, will detect orbital plane precession due to frame dragging, the tidal dissipation of orbital energy occurs at timescales comparable to the timescale of precession due to the quadrupole moment of the black hole. As a result, this non-conservative effect is a potential source of systematic uncertainty in testing the no-hair theorem with stellar orbits

  17. DEVIATION OF STELLAR ORBITS FROM TEST PARTICLE TRAJECTORIES AROUND SGr A* DUE TO TIDES AND WINDS

    Energy Technology Data Exchange (ETDEWEB)

    Psaltis, Dimitrios [Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Li, Gongjie; Loeb, Abraham, E-mail: dpsaltis@email.arizona.edu, E-mail: gli@cfa.harvard.edu, E-mail: aloeb@cfa.harvard.edu [Institute for Theory and Computation, Harvard-Smithsonian CfA, 60 Garden Street, Cambridge, MA (United States)

    2013-11-01

    Monitoring the orbits of stars around Sgr A* offers the possibility of detecting the precession of their orbital planes due to frame dragging, of measuring the spin and quadrupole moment of the black hole, and of testing the no-hair theorem. Here we investigate whether the deviations of stellar orbits from test-particle trajectories due to wind mass loss and tidal dissipation of the orbital energy compromise such measurements. We find that the effects of stellar winds are, in general, negligible. On the other hand, for the most eccentric orbits (e > 0.96) for which an optical interferometer, such as GRAVITY, will detect orbital plane precession due to frame dragging, the tidal dissipation of orbital energy occurs at timescales comparable to the timescale of precession due to the quadrupole moment of the black hole. As a result, this non-conservative effect is a potential source of systematic uncertainty in testing the no-hair theorem with stellar orbits.

  18. An evaluation of the WindEye wind lidar

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Sjöholm, Mikael; Mann, Jakob

    Prevision of the wind field by remote sensing wind lidars has the potential to improve the performance of wind turbines. The functionality of a WindEye lidar developed by Windar Photonics A/S (Denmark) for the wind energy market was tested in a two months long field experiment. The WindEye sensor...... with a high accuracy during the whole campaign....

  19. Design of a wind turbine-generator system considering the conformability to wind velocity fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Wakui, Tetsuya; Hashizume, Takumi; Outa, Eisuke

    1999-07-01

    The conformability of the rated power output of the wind turbine-generator system and of the wind turbine type to wind velocity fluctuations are investigated with a simulation model. The authors examine three types of wind turbines: the Darrieus-Savonius hybrid, the Darrieus proper and the Propeller. These systems are mainly operated at a constant tip speed ratio, which refers to a maximum power coefficient points. As a computed result of the net extracting power, the Darrieus turbine proper has little conformability to wind velocity fluctuations because of its output characteristics. As for the other turbines, large-scale systems do not always have an advantage over small-scale systems as the effect of its dynamic characteristics. Furthermore, it is confirmed that the net extracting power of the Propeller turbine, under wind direction fluctuation, is much reduced when compared with the hybrid wind turbine. Thus, the authors conclude that the appropriate rated power output of the system exists with relation to the wind turbine type for each wind condition.

  20. Wind Power Utilization Guide.

    Science.gov (United States)

    1981-09-01

    The expres- sions for the rotor torque for a Darrieus machine can be found in Reference 4.16. The Darrieus wind turbine offers the following... turbine generators, wind -driven turbines , power conditioning, wind power, energy conservation, windmills, economic ana \\sis. 20 ABS 1"ACT (Conti,on... turbines , power conditioning requirements, siting requirements, and the economics of wind power under different conditions. Three examples are given to