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Sample records for plume composition control

  1. CHLORINATED SOLVENT PLUME CONTROL

    EPA Science Inventory

    This lecture will cover recent success in controlling and assessing the treatment of shallow ground water plumes of chlorinated solvents, other halogenated organic compounds, and methyl tert-butyl ether (MTBE).

  2. CHLORINATED SOLVENT PLUME CONTROL

    EPA Science Inventory

    This lecture will cover recent success in controlling and assessing the treatment of shallow ground water plumes of chlorinated solvents, other halogenated organic compounds, and methyl tert-butyl ether (MTBE).

  3. Compositional differentiation of Enceladus' plume

    NASA Astrophysics Data System (ADS)

    Khawaja, N.; Postberg, F.; Schmidt, J.

    2014-04-01

    The Cosmic Dust Analyser (CDA) on board the Cassini spacecraft sampled Enceladus' plume ice particles emanated directly from Enceladus' fractured south polar terrain (SPT), the so-called "Tiger Stripes", during two consecutive flybys (E17 and E18) in 2012. The spacecraft passed through the dense plume with a moderate velocity of ~7.5km/s, horizontally to the SPT with a closest approach (CA) at an altitude of ~75km almost directly over the south pole. In both flybys, spectra were recorded during a time interval of ~ ±3 minutes with respect to the closest approach achieving an average sampling rate of about 0.6 sec-1. We assume that the spacecraft passed through the plume during an interval of about ±60(sec) from the CA. Particles encountered before and after this period are predominately from the E-ring background in which Enceladus is embedded. Most CDA TOF-mass spectra are identified as one of three compositional types: (i) almost pure water (ii) organic rich and (iii) salt rich [2]. A Boxcar Analysis (BCA) is performed from a count database for compositional mapping of the plume along the space-craft trajectory. In BCA, counts of each spectrum type are integrated for a certain interval of time (box size). The integral of counts represents frequencies of compositional types in absolute abundances, which are converted later into proportions. This technique has been proven to be a suitable for inferring the compositional profiles from an earlier flyby (E5) [1]. The inferred compositional profiles show similar trends on E17 and E18. The abundances of different compositional types in the plume clearly differ from the Ering background and imply a compositional differentiation inside the plume. Following up the work of Schmidt et al, 2008 and Postberg et al, 2011 we can link different compositional types to different origins. The E17/E18 results are compared with the E5 flyby in 2008, which yielded the currently best compositional profile [2] but was executed at much

  4. Deposition and composition-control of Mn-doped ZnO thin films by combinatorial pulsed laser deposition using two delayed plasma plumes

    SciTech Connect

    Sanchez-Ake, C.; Camacho, R.; Moreno, L.

    2012-08-15

    Thin films of ZnO doped with manganese were deposited by double-beam, combinatorial pulsed laser deposition. The laser-induced plasmas were studied by means of fast photography and using a Langmuir probe, whereas the films were analyzed by x-ray-diffraction and energy-dispersive x-ray spectroscopy. The effect of the relative delay between plasma plumes on the characteristics of the films was analyzed. It was found that using this parameter, it is possible to control the dopant content keeping the oriented wurtzite structure of the films. The minimum content of Mn was found for plume delays between 0 and 10 {mu}s as the interaction between plasmas scatters the dopant species away from the substrate, thus reducing the incorporation of Mn into the films. Results suggest that for delays shorter than {approx}100 {mu}s, the expansion of the second plume through the region behind the first plume affects the composition of the film.

  5. The composition of mantle plumes and the deep Earth

    NASA Astrophysics Data System (ADS)

    Hastie, Alan R.; Fitton, J. Godfrey; Kerr, Andrew C.; McDonald, Iain; Schwindrofska, Antje; Hoernle, Kaj

    2016-06-01

    Determining the composition and geochemical diversity of Earth's deep mantle and subsequent ascending mantle plumes is vital so that we can better understand how the Earth's primitive mantle reservoirs initially formed and how they have evolved over the last 4.6 billion years. Further data on the composition of mantle plumes, which generate voluminous eruptions on the planet's surface, are also essential to fully understand the evolution of the Earth's hydrosphere and atmosphere with links to surface environmental changes that may have led to mass extinction events. Here we present new major and trace element and Sr-Nd-Pb-Hf isotope data on basalts from Curacao, part of the Caribbean large igneous province. From these and literature data, we calculate combined major and trace element compositions for the mantle plumes that generated the Caribbean and Ontong Java large igneous provinces and use mass balance to determine the composition of the Earth's lower mantle. Incompatible element and isotope results indicate that mantle plumes have broadly distinctive depleted and enriched compositions that, in addition to the numerous mantle reservoirs already proposed in the literature, represent large planetary-scale geochemical heterogeneity in the Earth's deep mantle that are similar to non-chondritic Bulk Silicate Earth compositions.

  6. Distribution and composition of hydrothermal plume particles from the ASHES Vent Field at Axial Volcano, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Feely, R. A.; Geiselman, T. L.; Baker, E. T.; Massoth, G. J.; Hammond, S. R.

    1990-08-01

    In 1986 and 1987, buoyant and neutrally buoyant hydrothermal plume particles from the ASHES vent field within Axial Volcano were sampled to study their variations in composition with height above the seafloor. Individual mineral phases were identified using standard X ray diffraction procedures. Elemental composition and particle morphologies were determined by X ray fluorescence spectrometry and scanning electron microscopy/X ray energy spectrometry techniques. The vent particles were primarily composed of sphalerite, anhydrite, pyrite, pyrrhotite, chalcopyrite, barite, hydrous iron oxides, and amorphous silica. Grain size analyses of buoyant plume particles showed rapid particle growth in the first few centimeters above the vent orifice, followed by differential sedimentation of the larger sulfide and sulfate minerals out of the buoyant plume. The neutrally buoyant plume consisted of a lower plume, which was highly enriched in Fe, S, Zn, and Cu, and an upper plume, which was highly enriched in Fe and Mn. The upper plume was enriched in Fe and Mn oxyhydroxide particles, and the lower plume was enriched in suspended sulfide particles in addition to the Fe and Mn oxyhydroxide particles. The chemical data for the water column particles indicate that chemical scavenging and differential sedimentation processes are major factors controlling the composition of the dispersing hydrothermal particles. Short-term sediment trap experiments indicate that the fallout from the ASHES vent field is not as large as some of the other vent fields on the Juan de Fuca Ridge.

  7. Mapping of plume deposits and surface composition on Enceladus

    NASA Astrophysics Data System (ADS)

    Nordheim, T. A.; Scipioni, F.; Cruikshank, D. P.; Clark, R. N.,; Hand, K. P.

    2017-01-01

    A major result of the Cassini mission was the discovery that the small mid-sized moon Enceladus is presently geological active[Dougherty et al., 2006; Porco et al., 2006; Spencer et al., 2006; Hansen et al., 2008]. This activity results in plumes of water vapor and ice emanating from a series of fractures ("Tiger Stripes") at the moon's South Pole. Some fraction of plume material escapes the moon's gravity and populates the E-ring as well as ultimately providing a source of fresh plasma in the Saturnian magnetosphere [Pontius and Hill, 2006; Kempf et al., 2010]. However, a significant portion of plume material is redeposited on Enceladus and thus provides a source of surface contaminants. By studying the near-infrared spectral signatures of these contaminants we may put new constraints on the composition of the plumes and, ultimately, their source, which is currently believed to be Enceladus's global sub-surface ocean [Iess et al., 2014]. Here we present preliminary results from our analysis of observations from the Visual and Infrared Mapping Spectrometer (VIMS) [Brown et al., 2005] onboard Cassini and mapping of plume deposits across the surface of Enceladus. We have investigated the global variation of the water ice Fresnel peak at 3.1 μm, which may be used as an indicator of ice crystallinity [Hansen & McCord, 2004; Jaumann et al., 2008; Newman et al., 2008]. We have also investigated the slope of the 1.11-2.25 μm spectral region, which serves as an indicator of water ice grain size for small grains (< 100 μm) as well as the presence of contaminants [e.g. Filacchione et al., 2010]. Finally, we have identified and mapped an absorption feature centered at 3.25 μm that may be related to organic contaminants, represented by the band depth of the fundamental C-H stretch [e.g. Cruikshank et al., 2014; Scipioni et al., 2014].

  8. Organic-inorganic nano-composite films for photonic applications made by multi-beam multi-target pulsed laser deposition with remote control of the plume directions

    NASA Astrophysics Data System (ADS)

    Darwish, Abdalla M.; Moore, Shaelynn; Mohammed, Aziz; Alexander, Deonte'; Bastian, Tyler; Dorlus, Wydglif; Sarkisov, Sergey S.; Patel, Darayas N.; Mele, Paolo; Koplitz, Brent

    2016-09-01

    There has been an explosive interest in the technique of laser assisted deposition of polymer nano-composite films exploiting the matrix assisted pulsed laser evaporation (MAPLE) with regard to the polymer host as can be judged form recent publications.1-4 In MAPLE, a frozen solution of a polymer in a relatively volatile solvent is used as a laser target. The solvent and concentration are selected so that first, the polymer of interest can dissolve to form a dilute, particulate free solution, second, the majority of the laser energy is initially absorbed by the solvent molecules and not by the solute molecules, and third, there is no photochemical reaction between the solvent and the solute. The light-material interaction in MAPLE can be described as a photothermal process. The photon energy absorbed by the solvent is converted to thermal energy that causes the polymer to be heated but the solvent to vaporize. As the surface solvent molecules are evaporated into the gas phase, polymer molecules are exposed at the gas-target matrix interface. The polymer molecules attain sufficient kinetic energy through collective collisions with the evaporating solvent molecules, to be transferred into the gas phase. By careful optimization of the MAPLE deposition conditions (laser wavelength, repetition rate, solvent type, concentration, temperature, and background gas and gas pressure), this process can occur without any significant polymer decomposition. The MAPLE process proceeds layer-by-layer, depleting the target of solvent and polymer in the same concentration as the starting matrix. When a substrate is positioned directly in the path of the plume, a coating starts to form from the evaporated polymer molecules, while the volatile solvent molecules are evacuated by the pump from the deposition chamber. In case of fabrication of polymer nanocomposites, MAPLE targets are usually prepared as nano-colloids of the additives of interest in the initial polymer solutions. Mixing

  9. The interaction of plume heads with compositional discontinuities in the Earth's mantle

    NASA Technical Reports Server (NTRS)

    Manga, Michael; Stone, Howard A.; O'Connell, Richard J.

    1993-01-01

    The effects of compositional discontinuities of density and viscosity in the Earth's mantle on the ascent of mantle plume heads is studied using a boundary integral numerical technique. Three specific problems are considered: (1) a plume head rising away from a deformable interface, (2) a plume head passing through an interface, and (3) a plume head approaching the surface of the Earth. For the case of a plume attached to a free-surface, the calculated time-dependent plume shapesare compared with experimental results. Two principle modes of plume head deformation are observed: plume head elingation or the formation of a cavity inside the plume head. The inferred structure of mantle plumes, namely, a large plume head with a long tail, is characteristic of plumes attached to their source region, and also of buoyant material moving away from an interface and of buoyant material moving through an interface from a high- to low-viscosity region. As a rising plume head approaches the upper mantle, most of the lower mantle will quickly drain from the gap between the plume head and the upper mantle if the plume head enters the upper mantle. If the plume head moves from a high- to low-viscosity region, the plume head becomes significantly elongated and, for the viscosity contrasts thought to exist in the Earth, could extend from the 670 km discontinuity to the surface. Plume heads that are extended owing to a viscosity decrease in the upper mantle have a cylindrical geometry. The dynamic surface topography induced by plume heads is bell-shaped when the top of the plume head is at depths greater than about 0.1 plume head radii. As the plume head approaches the surface and spreads, the dynamic topography becomes plateau-shaped. The largest stresses are produced in the early stages of plume spreading when the plume head is still nearly spherical, and the surface expression of these stresses is likely to be dominated by radial extension. As the plume spreads, compressional

  10. Biodegradation at Dynamic Plume Fringes: Mixing Versus Reaction Control

    NASA Astrophysics Data System (ADS)

    Cirpka, O. A.; Eckert, D.; Griebler, C.; Haberer, C.; Kürzinger, P.; Bauer, R.; Mellage, A.

    2014-12-01

    Biodegradation of continuously emitted plumes is known to be most pronounced at the plume fringe, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. Under steady-state conditions, physical mixing of contaminant and electron acceptor by transverse dispersion was shown to be the major bottleneck for biodegradation, with plume lengths scaling inversely with the bulk transverse dispersivity in quasi two-dimensional settings. Under these conditions, the presence of suitable microbes is essential but the biokinetic parameters do not play an important role. When the location of the plume shifts (caused, e.g., by a fluctuating groundwater table), however, the bacteria are no more situated at the plume fringe and biomass growth, decay, activation and deactivation determine the time lag until the fringe-controlled steady state is approached again. During this time lag, degradation is incomplete. The objective of the presented study was to analyze to which extent flow and transport dynamics diminish effectiveness of fringe-controlled biodegradation and which microbial processes and related biokinetic parameters determine the system response in overall degradation to hydraulic fluctuations. We performed experiments in quasi-two-dimensional flow through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth and maintenance (often subsumed as "biomass decay") microbial dormancy (that is, change into a metabolically inactive state) and

  11. Plume and surface feature structure and compositional effects on Europa's global exosphere: Preliminary Europa mission predictions

    NASA Astrophysics Data System (ADS)

    Teolis, B. D.; Wyrick, D. Y.; Bouquet, A.; Magee, B. A.; Waite, J. H.

    2017-03-01

    A Europa plume source, if present, may produce a global exosphere with complex spatial structure and temporal variability in its density and composition. To investigate this interaction we have integrated a water plume source containing multiple organic and nitrile species into a Europan Monte Carlo exosphere model, considering the effect of Europa's gravity in returning plume ejecta to the surface, and the subsequent spreading of adsorbed and exospheric material by thermal desorption and re-sputtering across the entire body. We consider sputtered, radiolytic and potential plume sources, together with surface adsorption, regolith diffusion, polar cold trapping, and re-sputtering of adsorbed materials, and examine the spatial distribution and temporal evolution of the exospheric density and composition. These models provide a predictive basis for telescopic observations (e.g. HST, JWST) and planned missions to the Jovian system by NASA and ESA. We apply spacecraft trajectories to our model to explore possible exospheric compositions which may be encountered along proposed flybys of Europa to inform the spatial and temporal relationship of spacecraft measurements to surface and plume source compositions. For the present preliminary study, we have considered four cases: Case A: an equatorial flyby through a sputtered only exosphere (no plumes), Case B: a flyby over a localized sputtered 'macula' terrain enriched in non-ice species, Case C: a south polar plume with an Enceladus-like composition, equatorial flyby, and Case D: a south polar plume, flyby directly through the plume.

  12. The He isotope composition of the earliest picrites erupted by the Ethiopia plume, implications for mantle plume source

    NASA Astrophysics Data System (ADS)

    Stuart, Finlay; Rogers, Nick; Davies, Marc

    2016-04-01

    The earliest basalts erupted by mantle plumes are Mg-rich, and typically derived from mantle with higher potential temperature than those derived from the convecting upper mantle at mid-ocean ridges and ocean islands. The chemistry and isotopic composition of picrites from CFB provide constraints on the composition of deep Earth and thus the origin and differentiation history. We report new He-Sr-Nd-Pb isotopic composition of the picrites from the Ethiopian flood basalt province from the Dilb (Chinese Road) section. They are characterized by high Fe and Ti contents for MgO = 10-22 wt. % implying that the parent magma was derived from a high temperature low melt fraction, most probably from the Afar plume head. The picrite 3He/4He does not exceed 21 Ra, and there is a negative correlation with MgO, the highest 3He/4He corresponding to MgO = 15.4 wt. %. Age-corrected 87Sr/86Sr (0.70392-0.70408) and 143Nd/144Nd (0.512912-0.512987) display little variation and are distinct from MORB and OIB. Age-corrected Pb isotopes display a significant range (e.g. 206Pb/204Pb = 18.70-19.04) and plot above the NHRL. These values contrast with estimates of the modern Afar mantle plume which has lower 3He/4He and Sr, Nd and Pb isotope ratios that are more comparable with typical OIB. These results imply either interaction between melts derived from the Afar mantle plume and a lithospheric component, or that the original Afar mantle plume had a rather unique radiogenic isotope composition. Regardless of the details of the origins of this unusual signal, our observations place a minimum 3He/4He value of 21 Ra for the Afar mantle plume, significantly greater than the present day value of 16 Ra, implying a significant reduction over 30 Myr. In addition the Afar source was less degassed than convecting mantle but more degassed than mantle sampled by the proto-Iceland plume (3He/4He ~50 Ra). This suggests that the largest mantle plumes are not sourced in a single deep mantle domain with a

  13. Plume and plate controlled hotspot trails in the South Atlantic

    NASA Astrophysics Data System (ADS)

    O'Connor, John; Jokat, Wilfried; le Roex, Anton; Class, Cornelia; Wijbrans, Jan; Keßling, Stefanie; Kuiper, Klaudia; Nebel, Oliver

    2013-04-01

    Discovering if hotspots observed on the Earth's surface are explained by underlying plumes rising from the deep mantle or by shallow plate-driven processes continues to be an essential goal in Earth Science. Key evidence underpinning the mantle plume concept is the existence of age-progressive volcanic trails recording past plate motion relative to surface hotspots and their causal plumes. Using the icebreaker RV Polarstern, we sampled scattered hotspot trails on the 2,000 km-wide southeast Atlantic hotspot swell, which projects down to one of the Earth's two largest and deepest regions of slower-than-average seismic wave speed - the Africa Low Shear Wave Velocity Province - caused by a massive thermo-chemical 'pile' on the core-mantle boundary. We showed recently using Ar/Ar isotopic ages - and crustal structure and seafloor ages - that these hotspot trails are age progressive and formed synchronously across the swell, consistent with African plate motion over plumes rising from the stable edge of a Low Shear Wave Velocity Province (LLSVP) (O'Connor et al., 2012). We showed furthermore that hotspot trails formed initially only at spreading boundaries at the outer edges of the swell until roughly 44 million years ago, when they started forming across the swell, far from spreading boundaries in lithosphere that was sufficiently weak (young) for plume melts to reach the surface. We concluded that if plume melts formed synchronous age progressive hotspot trails whenever they could penetrate the lithosphere, then hotspot trails in the South Atlantic are controlled by the interplay between deep plumes and the shallow motion and structure of the African plate. If the distribution of hotspot trails reflects where plume melts could or could not penetrate the continental or oceanic lithosphere then plumes could have been active for significantly longer than indicated by their volcanic chains. This provides a mechanism for extended late stage interplay between deep mantle

  14. Plume composition and volatile flux from Nyamulagira volcano

    NASA Astrophysics Data System (ADS)

    Calabrese, Sergio; Bobrowski, Nicole; Giuffrida, Giovanni Bruno; Scaglione, Sarah; Liotta, Marcello; Brusca, Lorenzo; D'Alessandro, Walter; Arellano, Santiago; Yalire, Matiew; Galle, Bo; Tedesco, Dario

    2015-04-01

    Nyamulagira, in the Virunga volcanic province (VVP), Democratic Republic of Congo, is one of the most active volcanoes in Africa. The volcano is located about 25 km north-northwest of Lake Kivu in the Western Branch of the East African Rift System (EARS). The activity is characterized by frequent eruptions (on average, one eruption every 2-4 years) which occur both from the summit crater and from the flanks (31 flank eruptions over the last 110 years). Due to the peculiar low viscosity of its lava and its location in the floor of the rift, Nyamulagira morphology is characterized by a wide lava field that covers over 1100 km2 and contains more than 100 flank cones. Indeed, Nyamulagira is a SiO2- undersaturated and alkali-rich basaltic shield volcano with a 3058 m high summit caldera with an extension of about 2 km in diameter. In November 2014 a field expedition was carried out at Nyamulagira volcano and we report here the first assessment of the plume composition and volatile flux from Nyamulagira volcano. Helicopter flights and field observations allowed us to recognize the presence of lava fountains inside an about 350-meter wide pit crater. The lava fountains originated from an extended area of about 20 to 40 m2, in the northeast sector of the central caldera. A second smaller source, close to the previous described one, was clearly visible with vigorous spattering activity. There was no evidence of a lave lake but the persistence of intense activity and the geometry of the bottom of the caldera might evolve in a new lava lake. Using a variety of in situ and remote sensing techniques, we determined the bulk plume concentrations of major volatiles, halogens and trace elements. We deployed a portable MultiGAS station at the rim of Nyamulagira crater, measuring (at 0.5 Hz for about 3 hours) the concentrations of major volcanogenic gas species in the plume (H2O, CO2, SO2, H2S). Simultaneously, scanning differential optical absorption spectroscopy instruments were

  15. Opposing authigenic controls on the isotopic signature of dissolved iron in hydrothermal plumes

    NASA Astrophysics Data System (ADS)

    Lough, A. J. M.; Klar, J. K.; Homoky, W. B.; Comer-Warner, S. A.; Milton, J. A.; Connelly, D. P.; James, R. H.; Mills, R. A.

    2017-04-01

    Iron is a scarce but essential micronutrient in the oceans that limits primary productivity in many regions of the surface ocean. The mechanisms and rates of Fe supply to the ocean interior are still poorly understood and quantified. Iron isotope ratios of different Fe pools can potentially be used to trace sources and sinks of the global Fe biogeochemical cycle if these boundary fluxes have distinct signatures. Seafloor hydrothermal vents emit metal rich fluids from mid-ocean ridges into the deep ocean. Iron isotope ratios have the potential to be used to trace the input of hydrothermal dissolved iron to the oceans if the local controls on the fractionation of Fe isotopes during plume dispersal in the deep ocean are understood. In this study we assess the behaviour of Fe isotopes in a Southern Ocean hydrothermal plume using a sampling program of Total Dissolvable Fe (TDFe), and dissolved Fe (dFe). We demonstrate that δ56Fe values of dFe (δ56dFe) within the hydrothermal plume change dramatically during early plume dispersal, ranging from -2.39 ± 0.05‰ to -0.13 ± 0.06‰ (2 SD). The isotopic composition of TDFe (δ56TDFe) was consistently heavier than dFe values, ranging from -0.31 ± 0.03‰ to 0.78 ± 0.05‰, consistent with Fe oxyhydroxide precipitation as the plume samples age. The dFe present in the hydrothermal plume includes stabilised dFe species with potential to be transported to the deep ocean. We estimate that stable dFe exported from the plume will have a δ56Fe of -0.28 ± 0.17‰. Further, we show that the proportion of authigenic iron-sulfide and iron-oxyhydroxide minerals precipitating in the buoyant plume exert opposing controls on the resultant isotope composition of dissolved Fe passed into the neutrally buoyant plume. We show that such controls yield variable dissolved Fe isotope signatures under the authigenic conditions reported from modern vent sites elsewhere, and so ought to be considered during iron isotope reconstructions of past

  16. El Chichon - Composition of plume gases and particles

    NASA Astrophysics Data System (ADS)

    Kotra, J. P.; Finnegan, D. L.; Zoller, W. H.; Hart, M. A.; Moyers, J. L.

    1983-12-01

    Aircraft measurements were made of trace gases, atmospheric particles, and condensed acid volatiles in the plume of El Chichon volcano, Chiapas, Mexico, in November 1982. Hydrogen sulfide was the primary gaseous sulfur species in the plume at the time of collection. Concentrations of 28 elements were determined by neutron activation analysis of particulate material from the plume. The volatile elements sulfur, chlorine, arsenic, selenium, bromine, antimony, iodine, tungsten, and mercury were enriched relative to bulk pyroclastic material by factors of 60 to 20,000. Arsenic, antimony, and selenium were associated predominantly with small (not greater than 3 micrometer) particles. Calcium and sodium were present almost exclusively on larger particles and aluminum and manganese were bimodally distributed. Ashladen particulate material injected into the stratosphere during the early violent eruptions was enriched by factors of 10 to 30 relative to ash in some of the same elements observed in the quiescent plume.

  17. El Chichon - Composition of plume gases and particles

    NASA Technical Reports Server (NTRS)

    Kotra, J. P.; Finnegan, D. L.; Zoller, W. H.; Hart, M. A.; Moyers, J. L.

    1983-01-01

    Aircraft measurements were made of trace gases, atmospheric particles, and condensed acid volatiles in the plume of El Chichon volcano, Chiapas, Mexico, in November 1982. Hydrogen sulfide was the primary gaseous sulfur species in the plume at the time of collection. Concentrations of 28 elements were determined by neutron activation analysis of particulate material from the plume. The volatile elements sulfur, chlorine, arsenic, selenium, bromine, antimony, iodine, tungsten, and mercury were enriched relative to bulk pyroclastic material by factors of 60 to 20,000. Arsenic, antimony, and selenium were associated predominantly with small (not greater than 3 micrometer) particles. Calcium and sodium were present almost exclusively on larger particles and aluminum and manganese were bimodally distributed. Ashladen particulate material injected into the stratosphere during the early violent eruptions was enriched by factors of 10 to 30 relative to ash in some of the same elements observed in the quiescent plume.

  18. El Chichon - Composition of plume gases and particles

    NASA Technical Reports Server (NTRS)

    Kotra, J. P.; Finnegan, D. L.; Zoller, W. H.; Hart, M. A.; Moyers, J. L.

    1983-01-01

    Aircraft measurements were made of trace gases, atmospheric particles, and condensed acid volatiles in the plume of El Chichon volcano, Chiapas, Mexico, in November 1982. Hydrogen sulfide was the primary gaseous sulfur species in the plume at the time of collection. Concentrations of 28 elements were determined by neutron activation analysis of particulate material from the plume. The volatile elements sulfur, chlorine, arsenic, selenium, bromine, antimony, iodine, tungsten, and mercury were enriched relative to bulk pyroclastic material by factors of 60 to 20,000. Arsenic, antimony, and selenium were associated predominantly with small (not greater than 3 micrometer) particles. Calcium and sodium were present almost exclusively on larger particles and aluminum and manganese were bimodally distributed. Ashladen particulate material injected into the stratosphere during the early violent eruptions was enriched by factors of 10 to 30 relative to ash in some of the same elements observed in the quiescent plume.

  19. Distribution and composition of hydrothermal plume particles from the ASHES vent field at Axial Volcano, Juan de Fuca Ridge. [Axial Seamount Hydrothermal Emission Study

    SciTech Connect

    Feely, R.A.; Geiselman, T.L.; Baker, E.T.; Massoth, G.J. ); Hammond, S.R. )

    1990-08-10

    In 1986 and 1987, buoyant and neutrally buoyant hydrothermal plume particles from the ASHES vent field within Axial Volcano were sampled to study their variations in composition with height above the seafloor. Individual mineral phases were identified using standard X ray diffraction procedures. Elemental composition and particle morphologies were determined by X ray fluorescence spectrometry and scanning electron microscopy/X ray energy spectrometry techniques. The vent particles were primarily composed of sphalerite, anhydrite, pyrite, pyrrhotite, chalcopyrite, barite, hydrous iron oxides, and amorphous silica. Grain size analyses of buoyant plume particles showed rapid particle growth in the first few centimeters above the vent orifice, followed by differential sedimentation of the larger sulfide and sulfate minerals out of the buoyant plume. The neutrally buoyant plume consisted of a lower plume, which was highly enriched in Fe, S, Zn, and Cu, and an upper plume, which was highly enriched in Fe and Mn. The upper plume was enriched in Fe and Mn oxyhydroxide particles, and the lower plume was enriched in suspended sulfide particles in addition to the Fe and Mn oxyhydroxide particles. The chemical data for the water column particles indicate that chemical scavenging and differential sedimentation processes are major factors controlling the composition of the dispersing hydrothermal particles. Short-term sediment trap experiments indicate that the fallout from the ASHES vent field is not as large as some of the other vent fields on the Juan de Fuca Ridge.

  20. Fine scale mapping of the structure and composition of the Elkhorn Slough (California, USA) tidal plume

    NASA Astrophysics Data System (ADS)

    Fischer, Andrew M.; Ryan, John P.; Rienecker, Erich V.

    2017-01-01

    Fine scale mapping of the structure and composition of a tidal ebb plume from a highly modified coastal lagoon (Elkhorn Slough, California, USA) was conducted by combining in situ, observational data sets from surface underway mapping, autonomous underwater vehicle (AUV) profiles, drifter tracking and the analysis of plume structure indices. The results reveal a 6-m-deep, jet-like, sediment laden plume extending one km offshore at low tide, which becomes entrained in the prevailing nearshore circulation. The plume that exits the slough is significantly different from the water that enters the slough. The rapidly evolving discharge plume is associated with elevated and highly correlated (r = 0.93) concentrations of dissolved organic matter and nitrate. While dissolved constituents remain in the shallow plume and are transported northward with the prevailing current, sediment may settle quickly through the water column and can be transported southwestward with the littoral currents. This study illustrates the applications of AUVs, when coupled with additional datasets, for generating higher resolution observational snapshots of dynamic and ephemeral tidal plumes. The results provide unique perspective on small-scale dynamics of an estuarine plume and its influence on coastal ecology.

  1. Shuttle primary reaction control system engine exhaust plume contamination effects

    NASA Technical Reports Server (NTRS)

    Koontz, Steve; Ehlers, Horst; Pedley, Mike; Cross, John; Hakes, Charles

    1993-01-01

    Space Shuttle proximity operations constitute an important part of the SSF induced external environment. The impingement of primary reaction control system (PRCS) engine plumes on SSF functional surfaces during docking or berthing and separation leads to concerns about molecular contamination and high speed particle impact. The Shuttle Plume Impingement flight Experiment (SPIE) was designed to provide a direct measure of both the molecular contamination and particle impact rates produced by Shuttle PRCS engines in the LEO environment. The measured permanent deposition produced by PRCS engine firings was less than that assumed in current SSF programatic assessments. Only two to three possible high velocity particle impact pits were observed on the RMS end effector hardware.

  2. Shuttle primary reaction control system engine exhaust plume contamination effects

    NASA Technical Reports Server (NTRS)

    Koontz, Steve; Ehlers, Horst; Pedley, Mike; Cross, John; Hakes, Charles

    1993-01-01

    Space Shuttle proximity operations constitute an important part of the SSF induced external environment. The impingement of primary reaction control system (PRCS) engine plumes on SSF functional surfaces during docking or berthing and separation leads to concerns about molecular contamination and high speed particle impact. The Shuttle Plume Impingement flight Experiment (SPIE) was designed to provide a direct measure of both the molecular contamination and particle impact rates produced by Shuttle PRCS engines in the LEO environment. The measured permanent deposition produced by PRCS engine firings was less than that assumed in current SSF programatic assessments. Only two to three possible high velocity particle impact pits were observed on the RMS end effector hardware.

  3. Method and device for controlling plume during laser welding

    DOEpatents

    Fuerschbach, Phillip W.; Jellison, James L.; Keicher, David M.; Oberkampf, William L.

    1991-01-01

    A method and apparatus for enhancing the weldment of a laser welding system is provided. The laser weld plume control device includes a cylindrical body defining an upside-down cone cavity; the upper surface of the body circumscribes the base of the cone cavity, and the vertex of the cone cavity forms an orifice concentrically located with respect to the laser beam and the plume which forms as a result of the welding operation. According to the method of the invention, gas is directed radially inward through inlets in the upper surface of the body into and through channels in the wall of the body and finally through the orifice of the body, and downward onto the surface of the weldment. The gas flow is then converted by the orifice of the device from radial flow to an axisymmetric gas jet flowing away from the weldment surface in a direction perpendicular to the surface and opposite to that of the laser.

  4. A salt-water reservoir as the source of a compositionally stratified plume on Enceladus.

    PubMed

    Postberg, F; Schmidt, J; Hillier, J; Kempf, S; Srama, R

    2011-06-22

    The discovery of a plume of water vapour and ice particles emerging from warm fractures ('tiger stripes') in Saturn's small, icy moon Enceladus raised the question of whether the plume emerges from a subsurface liquid source or from the decomposition of ice. Previous compositional analyses of particles injected by the plume into Saturn's diffuse E ring have already indicated the presence of liquid water, but the mechanisms driving the plume emission are still debated. Here we report an analysis of the composition of freshly ejected particles close to the sources. Salt-rich ice particles are found to dominate the total mass flux of ejected solids (more than 99 per cent) but they are depleted in the population escaping into Saturn's E ring. Ice grains containing organic compounds are found to be more abundant in dense parts of the plume. Whereas previous Cassini observations were compatible with a variety of plume formation mechanisms, these data eliminate or severely constrain non-liquid models and strongly imply that a salt-water reservoir with a large evaporating surface provides nearly all of the matter in the plume.

  5. El Chichon: Composition of Plume Gases and Particles

    NASA Astrophysics Data System (ADS)

    Phelan Kotra, Janet; Finnegan, David L.; Zoller, William H.; Hart, Mark A.; Moyers, Jarvis L.

    1983-12-01

    Aircraft measurements were made of trace gases, atmospheric particles, and condensed acid volatiles in the plume of El Chichon volcano, Chiapas, Mexico, in November 1982. Hydrogen sulfide was the primary gaseous sulfur species in the plume at the time of collection. Concentrations of 28 elements were determined by neutron activation analysis of particulate material from the plume. Rates of trace element emission to the atmosphere for each species were estimated by normalization to the simultaneously determined total sulfur emission rate. The volatile elements sulfur, chlorine, arsenic, selenium, bromine, antimony, iodine, tungsten, and mercury were enriched relative to bulk pyroclastic material by factors of 60 to 20,000. Arsenic, antimony, and selenium were associated predominantly with small (<= 3 micrometer) particles. Calcium and sodium were present almost exclusively on larger particles and aluminum and manganese were bimodally distributed. Ashladen particulate material injected into the stratosphere during the early violent eruptions was enriched by factors of 10 to 30 relative to ash in some of the same elements observed in the quiescent plume.

  6. Statistical analyses of plume composition and deposited radionuclide mixture ratios

    SciTech Connect

    Kraus, Terrence D.; Sallaberry, Cedric Jean-Marie; Eckert-Gallup, Aubrey Celia; Brito, Roxanne; Hunt, Brian D.; Osborn, Douglas M.

    2014-01-01

    A proposed method is considered to classify the regions in the close neighborhood of selected measurements according to the ratio of two radionuclides measured from either a radioactive plume or a deposited radionuclide mixture. The subsequent associated locations are then considered in the area of interest with a representative ratio class. This method allows for a more comprehensive and meaningful understanding of the data sampled following a radiological incident.

  7. The dynamics and composition of a Pele-type plume

    NASA Astrophysics Data System (ADS)

    Wong, M. C.

    2001-11-01

    The primary sources of Io's tenuous atmosphere are thought to be frost sublimation and volcanic eruption. The relative contribution from these two sources is not clear. Earlier model calculations (Wong and Johnson 1996; Wong and Smyth 2000) have shown the importance of a sublimation source. In this paper, we will discuss the relative importance of a volcanic source in Io's atmosphere. In particular, recent observations of Pele plume (Spencer et al 2000) will be used as physical constraints for our model calculations.

  8. The origin of the Line Islands: plate or plume controlled volcanism?

    NASA Astrophysics Data System (ADS)

    Storm, L. P.; Konter, J. G.; Koppers, A. A.

    2011-12-01

    Geochemical compositions of melts produced in the Earth's mantle provide key data for our understanding of the Earth's internal structure. Particularly, the range in compositions for oceanic intraplate volcanism has fueled the ongoing debate on the dynamic origin of hotspots. Traditionally, hotspots have been interpreted to originate from narrow, upwelling plumes of hot mantle material that reach the bottom of the tectonic plates. Progressively younger volcanoes, as seen at, for example, Hawaii, are then derived from plume melts. However, such a plume may originate from the core-mantle boundary, the top of seismically defined superplumes, or the origin may not lie in a buoyantly upwelling plume at all. The presence of an age progressive volcanic chain and a large igneous province, a high buoyancy flux, the geochemical composition of the erupted lavas, and seismically slow velocities have been used to distinguish different hotspot origins. Volcanic chains that lack most of these features may originate from the eruption of shallow melts along lithospherically controlled cracks. A unique area to study this type of volcanism is the Line Islands. These islands define a complex chain of volcanoes south of Hawaii that morphologically define multiple sub-groups. Moreover, recent age dating has revealed a complex geochronology. Combined geochronological and geochemical data from the Line Islands allude to the presence of shallow mantle melts that feed eruptions where there are weaknesses in the plates due to fractures or fissures. The Line Islands consist of elongated ridges, seamounts, atolls and islands that form the northern segment of the Line-Tuamotu chain of volcanoes. The volcanic chain is divided into three morphologically distinct regions; the northern, central and southern provinces. Long en echelon ridges of the Line Islands Cross Trend intersect the northern province at 14-16°N, which consists of the section between the Molokai and Clarion fracture zones. The

  9. The link between Hawaiian mantle plume composition, magmatic flux, and deep mantle geodynamics

    NASA Astrophysics Data System (ADS)

    Harrison, Lauren N.; Weis, Dominique; Garcia, Michael O.

    2017-04-01

    Oceanic island basalts sample mantle reservoirs that are isotopically and compositionally heterogeneous. The Hawaiian-Emperor chain represents ∼85 Myr of volcanism supplied by a deep mantle plume. Two geographically and geochemically delineated trends, Kea and Loa, are well documented within the Hawaiian Islands. Enriched Loa compositions originate from subduction recycled or primordial material stored in deep mantle reservoirs such as the large low shear velocity province (LLSVP) below Hawai'i. Loa compositions have not been observed along the Emperor Seamounts (>50 Ma), whereas lavas on the Hawaiian Islands (<6.5 Ma) sample both Kea and Loa sources. Lead isotopes in shield lavas along the Northwest Hawaiian Ridge (NWHR) spanning ∼42 Myr between the bend in the chain and the Hawaiian Islands record the geochemical evolution of the Hawaiian mantle plume over a time period when many geophysical parameters (volcanic propagation rate, magmatic flux, mantle potential temperature) increased significantly. Along the NWHR, the Loa geochemical component appears ephemerally, which we link to the sampling of different lower mantle compositional domains by the Hawaiian mantle plume. The plume initially sampled only the deep Pacific mantle (Kea component) from outside the LLSVP during the formation of the Emperor Seamounts. Southward migration and anchoring of the plume on the LLSVP led to entrainment of increasing amounts of LLSVP material (Loa component) along the NWHR as documented by an increase in 208Pb*/206Pb* with decreasing age. The correlation between 208Pb*/206Pb* and magmatic flux suggests source composition affects the magmatic flux, and explains why the Hawaiian mantle plume has dramatically strengthened through time.

  10. Composite structure of plumes in stratus-topped boundary layers

    SciTech Connect

    Moeng, C.H. ); Schumann, U. )

    1991-10-15

    Knowledge of convective plumes within the clear convective boundary layer (CBL) is quite advanced owing to direct measurements, tank experiments, and large-eddy simulation studies. As a result, modeling of the CBL is relatively successful. Progress for the stratus-topped boundary layer (STBL), however, is slow. This study compares the plume structure of the surface-heated CBL with that of the cloud-top-cooled STBL in the hope of extending knowledge of the CBL to the STBL. A conditional sampling technique is applied to the STBL flow fields that are generated through large-eddy simulations, so that the structures of typical updrafts and downdrafts may be derived. For the purpose of comparing the surface-heated CBL and the cloud-top-cooled STBL, an idealized STBL, the compensating updrafts are nearly as strong as the top-cooling-generated downdrafts, and they contribute a significant amount to the heat, moisture, and momentum transports. This differs very much from the CBL, where the compensating downdrafts are much weaker than the surface-heating-generated updrafts and contribute much less to the transports. The mechanism that results in such an asymmetry between the CBL and STBL is examined, and suggestions on how the asymmetry affects the entrainment process are made. 25 refs., 26 figs.

  11. Deriving the Structure and Composition of Enceladus’ Plume from Cassini UVIS Observations

    NASA Astrophysics Data System (ADS)

    Hansen, Candice; Esposito, Larry; Colwell, Josh; Hendrix, Amanda; Portyankina, Ganna; Shemansky, Don; West, Robert

    2015-11-01

    Cassini’s Ultraviolet Imaging Spectrograph (UVIS) has observed 4 stellar and one solar occultation by Enceladus’ water vapor plume. The July 2005 occultation observation established that water is the primary constituent of the plume [1], and allowed us to calculate the flux of water coming from the plume; the 2007 occultation showed super-sonic jets of gas imbedded within the plume [2]. The solar occultation observation set upper limits for N2 as a constituent of the plume and provided higher resolution data on the jets [3]. On 19 October 2011, epsilon and zeta Orionis were simultaneously occulted by the plume. The stars were in separate pixels on the detector, separated by 24 mrad, or ~20 km, with the lower altitude star (epsilon Orionis) 18 km above the limb at its closest point. The profile at two altitudes shows evidence for a new gas jet location, possibly between dust jet #50 and #51 identified in [4].Results from the assemblage of these data sets, with implications for the composition and vertical structure of the plume and jets, will be described. Gas being expelled from the “tiger stripe” fissures is largely on a vertical escape trajectory away from Enceladus. Upper limits are set for water vapor near the limb at latitudes well away from the south pole at 3 x 1015 cm-2. Upper limits are set for the amount of ethylene and H2 in the plume, two species of interest to the chemistry of the plume [5]. No hydrogen or oxygen emission features have been observed from Enceladus’ water vapor plume, in contrast to the purported plumes at Europa, probably due to the very different plasma environment at Saturn. Data have now been processed consistently for all occultations with slightly different results for water vapor supply to the Saturn magnetosphere than previously reported. Overall, eruptive activity has been steady to within ~20% from 2005 to 2011.References: [1] Hansen, C. J. et al., Science 311:1422 (2006). Hansen, C. J. et al., Nature 456:477 (2008

  12. Plume impingement study for reaction control system of the Orbital Maneuvering Vehicle

    NASA Technical Reports Server (NTRS)

    Mcgregor, R. D.; Lohn, P. D.; Haflinger, D. E.

    1990-01-01

    A study has been performed to assess plume impingement effects from the reaction control system of NASA's OMV. A key aspect of this modeling effort has been the use of the direct Monte Carlo method as an integral part of the nozzle/plume flowfield modeling and to compute the impingement effects for configurations in which vehicle structure or multiple plumes resulted in highly three-dimensional rarefied plume flowfields. The calculation of the flowfield for a pair of interacting thruster plumes has shown that backflow in the region between the thrusters is greatly enhanced by the interaction of the two plumes. Although the present analyses have focussed on impingement force and heating effects, this methodology would also be valuable for contamination assessments since it properly accounts for the species separation effects that are inherent in the nonequilibrium nature of rarefied gas flows.

  13. Geochemistry of rainfall at Stromboli volcano (Aeolian Islands): Isotopic composition and plume-rain interaction

    NASA Astrophysics Data System (ADS)

    Liotta, M.; Brusca, L.; Grassa, F.; Inguaggiato, S.; Longo, M.; Madonia, P.

    2006-07-01

    The chemical and isotopic compositions of the precipitation at Stromboli Island, Italy, were investigated between October 2003 and October 2005. We employed a rain gauge network designed to cover the range in exposures and elevations of the volcanic edifice. The hydrogen and oxygen isotopic ratios vary greatly on a seasonal basis and correlate with air temperature. Deuterium excess values show a positive correlation with altitude. No direct contribution of volcanogenic H or O is evident in the isotopic composition of the rainwater. The chemical composition of the rainwater is principally controlled by the sea aerosol contribution at the coastal sites, whereas it is significantly influenced by volcanic activity near the summit vents. Interaction with volcanic acid gases is indicated by the pH, which is usually 1-2 units lower near the craters than at the coastal sites. The S/Cl, Cl/F, and S/F molar ratios in rainwater 1.5 km from the craters are consistent with those measured in the volcanic plume using other methods (diffusive tubes and Fourier transform infrared spectroscopy). Rising of undegassed magmas changes these molar ratios because of the differential degassing of sulphur, chlorine, and fluorine from the magma. We therefore propose that the chemical composition of precipitation, within 1.5 km of the craters, provides additional information that is useful for monitoring volcanic activity at Stromboli Island. Moreover, this paper presents estimates of the fluxes of F, Cl, S, Na, K, Ca, and Mg to the soil that could be useful for geochemical studies on groundwater.

  14. Orion Service Module Reaction Control System Plume Impingement Analysis Using PLIMP/RAMP2

    NASA Technical Reports Server (NTRS)

    Wang, Xiao-Yen; Lumpkin, Forrest E., III; Gati, Frank; Yuko, James R.; Motil, Brian J.

    2009-01-01

    The Orion Crew Exploration Vehicle Service Module Reaction Control System engine plume impingement was computed using the plume impingement program (PLIMP). PLIMP uses the plume solution from RAMP2, which is the refined version of the reacting and multiphase program (RAMP) code. The heating rate and pressure (force and moment) on surfaces or components of the Service Module were computed. The RAMP2 solution of the flow field inside the engine and the plume was compared with those computed using GASP, a computational fluid dynamics code, showing reasonable agreement. The computed heating rate and pressure using PLIMP were compared with the Reaction Control System plume model (RPM) solution and the plume impingement dynamics (PIDYN) solution. RPM uses the GASP-based plume solution, whereas PIDYN uses the SCARF plume solution. Three sets of the heating rate and pressure solutions agree well. Further thermal analysis on the avionic ring of the Service Module was performed using MSC Patran/Pthermal. The obtained temperature results showed that thermal protection is necessary because of significant heating from the plume.

  15. Orion Service Module Reaction Control System Plume Impingement Analysis Using PLIMP/RAMP2

    NASA Technical Reports Server (NTRS)

    Wang, Xiao-Yen J.; Gati, Frank; Yuko, James R.; Motil, Brian J.; Lumpkin, Forrest E.

    2009-01-01

    The Orion Crew Exploration Vehicle Service Module Reaction Control System engine plume impingement was computed using the plume impingement program (PLIMP). PLIMP uses the plume solution from RAMP2, which is the refined version of the reacting and multiphase program (RAMP) code. The heating rate and pressure (force and moment) on surfaces or components of the Service Module were computed. The RAMP2 solution of the flow field inside the engine and the plume was compared with those computed using GASP, a computational fluid dynamics code, showing reasonable agreement. The computed heating rate and pressure using PLIMP were compared with the Reaction Control System plume model (RPM) solution and the plume impingement dynamics (PIDYN) solution. RPM uses the GASP-based plume solution, whereas PIDYN uses the SCARF plume solution. Three sets of the heating rate and pressure solutions agree well. Further thermal analysis on the avionic ring of the Service Module showed that thermal protection is necessary because of significant heating from the plume.

  16. Estimation and Modeling of Enceladus Plume Jet Density Using Reaction Wheel Control Data

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.; Wang, Eric K.; Pilinski, Emily B.; Macala, Glenn A.; Feldman, Antonette

    2010-01-01

    The Cassini spacecraft was launched on October 15, 1997 by a Titan 4B launch vehicle. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. In 2005, Cassini completed three flybys of Enceladus, a small, icy satellite of Saturn. Observations made during these flybys confirmed the existence of a water vapor plume in the south polar region of Enceladus. Five additional low-altitude flybys of Enceladus were successfully executed in 2008-9 to better characterize these watery plumes. The first of these flybys was the 50-km Enceladus-3 (E3) flyby executed on March 12, 2008. During the E3 flyby, the spacecraft attitude was controlled by a set of three reaction wheels. During the flyby, multiple plume jets imparted disturbance torque on the spacecraft resulting in small but visible attitude control errors. Using the known and unique transfer function between the disturbance torque and the attitude control error, the collected attitude control error telemetry could be used to estimate the disturbance torque. The effectiveness of this methodology is confirmed using the E3 telemetry data. Given good estimates of spacecraft's projected area, center of pressure location, and spacecraft velocity, the time history of the Enceladus plume density is reconstructed accordingly. The 1-sigma uncertainty of the estimated density is 7.7%. Next, we modeled the density due to each plume jet as a function of both the radial and angular distances of the spacecraft from the plume source. We also conjecture that the total plume density experienced by the spacecraft is the sum of the component plume densities. By comparing the time history of the reconstructed E3 plume density with that predicted by the plume model, values of the plume model parameters are determined. Results obtained are compared with those determined by other Cassini science instruments.

  17. Estimation and Modeling of Enceladus Plume Jet Density Using Reaction Wheel Control Data

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.; Wang, Eric K.; Pilinski, Emily B.; Macala, Glenn A.; Feldman, Antonette

    2010-01-01

    The Cassini spacecraft was launched on October 15, 1997 by a Titan 4B launch vehicle. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. In 2005, Cassini completed three flybys of Enceladus, a small, icy satellite of Saturn. Observations made during these flybys confirmed the existence of a water vapor plume in the south polar region of Enceladus. Five additional low-altitude flybys of Enceladus were successfully executed in 2008-9 to better characterize these watery plumes. The first of these flybys was the 50-km Enceladus-3 (E3) flyby executed on March 12, 2008. During the E3 flyby, the spacecraft attitude was controlled by a set of three reaction wheels. During the flyby, multiple plume jets imparted disturbance torque on the spacecraft resulting in small but visible attitude control errors. Using the known and unique transfer function between the disturbance torque and the attitude control error, the collected attitude control error telemetry could be used to estimate the disturbance torque. The effectiveness of this methodology is confirmed using the E3 telemetry data. Given good estimates of spacecraft's projected area, center of pressure location, and spacecraft velocity, the time history of the Enceladus plume density is reconstructed accordingly. The 1 sigma uncertainty of the estimated density is 7.7%. Next, we modeled the density due to each plume jet as a function of both the radial and angular distances of the spacecraft from the plume source. We also conjecture that the total plume density experienced by the spacecraft is the sum of the component plume densities. By comparing the time history of the reconstructed E3 plume density with that predicted by the plume model, values of the plume model parameters are determined. Results obtained are compared with those determined by other Cassini science instruments.

  18. Estimation and Modeling of Enceladus Plume Jet Density Using Reaction Wheel Control Data

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.; Wang, Eric K.; Pilinski, Emily B.; Macala, Glenn A.; Feldman, Antonette

    2010-01-01

    The Cassini spacecraft was launched on October 15, 1997 by a Titan 4B launch vehicle. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. In 2005, Cassini completed three flybys of Enceladus, a small, icy satellite of Saturn. Observations made during these flybys confirmed the existence of a water vapor plume in the south polar region of Enceladus. Five additional low-altitude flybys of Enceladus were successfully executed in 2008-9 to better characterize these watery plumes. The first of these flybys was the 50-km Enceladus-3 (E3) flyby executed on March 12, 2008. During the E3 flyby, the spacecraft attitude was controlled by a set of three reaction wheels. During the flyby, multiple plume jets imparted disturbance torque on the spacecraft resulting in small but visible attitude control errors. Using the known and unique transfer function between the disturbance torque and the attitude control error, the collected attitude control error telemetry could be used to estimate the disturbance torque. The effectiveness of this methodology is confirmed using the E3 telemetry data. Given good estimates of spacecraft's projected area, center of pressure location, and spacecraft velocity, the time history of the Enceladus plume density is reconstructed accordingly. The 1-sigma uncertainty of the estimated density is 7.7%. Next, we modeled the density due to each plume jet as a function of both the radial and angular distances of the spacecraft from the plume source. We also conjecture that the total plume density experienced by the spacecraft is the sum of the component plume densities. By comparing the time history of the reconstructed E3 plume density with that predicted by the plume model, values of the plume model parameters are determined. Results obtained are compared with those determined by other Cassini science instruments.

  19. Estimation and Modeling of Enceladus Plume Jet Density Using Reaction Wheel Control Data

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.; Wang, Eric K.; Pilinski, Emily B.; Macala, Glenn A.; Feldman, Antonette

    2010-01-01

    The Cassini spacecraft was launched on October 15, 1997 by a Titan 4B launch vehicle. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. In 2005, Cassini completed three flybys of Enceladus, a small, icy satellite of Saturn. Observations made during these flybys confirmed the existence of a water vapor plume in the south polar region of Enceladus. Five additional low-altitude flybys of Enceladus were successfully executed in 2008-9 to better characterize these watery plumes. The first of these flybys was the 50-km Enceladus-3 (E3) flyby executed on March 12, 2008. During the E3 flyby, the spacecraft attitude was controlled by a set of three reaction wheels. During the flyby, multiple plume jets imparted disturbance torque on the spacecraft resulting in small but visible attitude control errors. Using the known and unique transfer function between the disturbance torque and the attitude control error, the collected attitude control error telemetry could be used to estimate the disturbance torque. The effectiveness of this methodology is confirmed using the E3 telemetry data. Given good estimates of spacecraft's projected area, center of pressure location, and spacecraft velocity, the time history of the Enceladus plume density is reconstructed accordingly. The 1 sigma uncertainty of the estimated density is 7.7%. Next, we modeled the density due to each plume jet as a function of both the radial and angular distances of the spacecraft from the plume source. We also conjecture that the total plume density experienced by the spacecraft is the sum of the component plume densities. By comparing the time history of the reconstructed E3 plume density with that predicted by the plume model, values of the plume model parameters are determined. Results obtained are compared with those determined by other Cassini science instruments.

  20. Simulating the Black Saturday 2009 UTLS Smoke Plume with an Interactive Composition-Climate Model

    NASA Astrophysics Data System (ADS)

    Field, R. D.; Luo, M.; Fromm, M. D.; Voulgarakis, A.; Mangeon, S.; Worden, J. R.

    2015-12-01

    Pyroconvective smoke plumes from large fires can be injected directly into the geostrophic flow and dry air at high altitudes. As a result, they are usually longer-lived, can be transported thousands of kilometers, and can cross the tropopause into the lower stratosphere. Because the emissions pulses are so abrupt relative to other non-volcanic sources, their evolution and decay can be easily separated from background levels of aerosols and trace gases. This makes them interesting natural experiments against which to evaluate models, and understand the fate and effects of surface emissions pulses. We have simulated the well-observed February 2009 Black Saturday smoke plume from southeast Australia using the NASA GISS Earth System Model. To the best of our knowledge, this represents the first simulation of a high altitude smoke plume with a full-complexity composition-climate model. We compared simulated CO to a joint retrieval from the Aura Tropospheric Emission Spectrometer and Microwave Limb Sounder instruments. Using an upper tropospheric injection height, we were able to simulate the plume's eastward transport and ascent over New Zealand, anticyclonic circulation and ascent over the Coral Sea, westward transport in the lower tropical stratosphere, and arrival over Africa at the end of February. Simulations were improved by taking into account hourly variability in emissions associated with extreme fire behavior observed by fire management agencies. We considered a range of emissions amounts, based on different assumptions about which of the Black Saturday fires were explosive enough to inject smoke to high altitudes, and accounting for emissions factor uncertainty. The best agreement between plume concentrations at the end of February was found for the highest emissions scenario. Three days after the fire, there was a linear relationship between emissions amount and plume concentration. Three weeks after the fire, the relationship was non-linear; we discuss

  1. Trace element composition of the mount st. Helens plume: stratospheric samples from the 18 may eruption.

    PubMed

    Vossler, T; Anderson, D L; Aras, N K; Phelan, J M; Zoller, W H

    1981-02-20

    Atmospheric particulate material collected from the stratosphere in the plume of the 18 May 1980 eruption of the Mount St. Helens volcano was quite similar in composition to that of ash that fell to the ground in western Washington. However, there were small but significant differences in concentrations of some elements with altitude, indicating that the stratospheric material was primarily produced from fresh magma, not fragments of the mountain.

  2. Trace element composition of the Mount St. Helens plume: stratospheric samples from the 18 May eruption

    SciTech Connect

    Vossler, T.; Anderson, D.L.; Aras, N.K.; Phelan, J.M.; Zoller, W.H.

    1981-01-01

    Atmospheric particulate material collected from the stratosphere in plume of the 18 May 1980 eruption of the Mount St. Helens volcano was quite similar in composition to that of ash that fell to the ground in western Washington. However, there were small but significant differences in concentrations of some elements with altitude, indicating that the statospheric material was primarily produced from fresh magma, but fragments of the mountain.

  3. Impact of rocket exhaust plumes on atmospheric composition and climate ― an overview

    NASA Astrophysics Data System (ADS)

    Voigt, Ch.; Schumann, U.; Graf, K.; Gottschaldt, K.-D.

    2013-03-01

    Rockets are the only direct anthropogenic emission sources into the upper atmosphere. Gaseous rocket emissions include CO, N2, H2, H2O, and CO2, while solid rocket motors (SRM) additionally inject significant amounts of aluminum oxide (Al2O3) particles and gaseous chlorine species into the atmosphere. These emissions strongly perturb local atmospheric trace gas and aerosol distributions. Here, previous aircraft measurements in various rocket exhaust plumes including several large space shuttle launch vehicles are compiled. The observed changes of the lower stratospheric composition in the near field are summarized. The injection of chlorine species and particles into the stratosphere can lead to ozone loss in rocket exhaust plumes. Local observations are compared with global model simulations of the effects of rocket emissions on stratospheric ozone concentrations. Large uncertainties remain concerning individual ozone loss reaction rates and the impact of small-scale plume effects on global chemistry. Further, remote sensing data from satellite indicate that rocket exhaust plumes regionally increase iron and water vapor concentrations in the mesosphere potentially leading to the formation of mesospheric clouds at 80- to 90-kilometer altitude. These satellite observations are summarized and the rocket emission inventory is compared with other natural and anthropogenic sources to the stratosphere such as volcanism, meteoritic material, and aviation.

  4. Groundwater plume control with phytotechnologies at Argonne National Laboratory.

    SciTech Connect

    Rock, S.; Negri, M. C.; Quinn, J.; Wozniak, J.,; McPherson, J.

    2002-07-16

    In 1999, Argonne National Laboratory-East (ANL-E) designed and installed a series of engineered plantings consisting of a vegetative cover system and approximately 800 hybrid poplars and willows rooting at various predetermined depths. The plants were installed using various methods including Applied Natural Science's TreeWell{reg_sign} system. The goal of the installation was to protect downgradient surface and groundwater by hydraulic control of the contaminated plume. This goal was to be accomplished by intercepting the contaminated groundwater with the tree roots, removing moisture from the upgradient soil area, reducing water infiltration, preventing soil erosion, degrading and/or transpiring the residual VOCs, and removing tritium from the subsoil and groundwater. The U.S. EPA Superfund Innovative Technology Evaluation Program (SITE) and ANL-E evaluated the demonstration. The effectiveness of the various plantings was monitored directly through groundwater measurements and samples, and indirectly via soil moisture probes, plant tissue analysis, microbial studies, geochemical analysis, and sap flow monitoring. A weather station with data logging equipment was installed. ANL-E modeled the predicted effect of the plants on the groundwater using MODFLOW. The demonstration has lasted three growing seasons and continues. This paper presents the results of the sampling, monitoring, and modeling efforts to date. The project was not only successful in reducing the groundwater contaminant flow and the contaminants at the source; it also provides insight into the techniques that are useful for measuring and predicting the effectiveness of future similar projects.

  5. Enceladus Plume Density Modeling and Reconstruction for Cassini Attitude Control System

    NASA Technical Reports Server (NTRS)

    Sarani, Siamak

    2010-01-01

    In 2005, Cassini detected jets composed mostly of water, spouting from a set of nearly parallel rifts in the crust of Enceladus, an icy moon of Saturn. During an Enceladus flyby, either reaction wheels or attitude control thrusters on the Cassini spacecraft are used to overcome the external torque imparted on Cassini due to Enceladus plume or jets, as well as to slew the spacecraft in order to meet the pointing needs of the on-board science instruments. If the estimated imparted torque is larger than it can be controlled by the reaction wheel control system, thrusters are used to control the spacecraft. Having an engineering model that can predict and simulate the external torque imparted on Cassini spacecraft due to the plume density during all projected low-altitude Enceladus flybys is important. Equally important is being able to reconstruct the plume density after each flyby in order to calibrate the model. This paper describes an engineering model of the Enceladus plume density, as a function of the flyby altitude, developed for the Cassini Attitude and Articulation Control Subsystem, and novel methodologies that use guidance, navigation, and control data to estimate the external torque imparted on the spacecraft due to the Enceladus plume and jets. The plume density is determined accordingly. The methodologies described have already been used to reconstruct the plume density for three low-altitude Enceladus flybys of Cassini in 2008 and will continue to be used on all remaining low-altitude Enceladus flybys in Cassini's extended missions.

  6. Secular trends in plume composition of Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Ilanko, Tehnuka; Oppenheimer, Clive; Kyle, Philip; Burgisser, Alain

    2015-04-01

    Long-lived active lava lakes, such as that in the summit crater of Erebus volcano, Antarctica, provide a rare insight into sustained magma convection and degassing over long timescales. Erebus lava lake has been persistently active since 1972, and potentially for several decades or more previously (Ross, 1847). Since the 1970s, regular scientific expeditions, lasting a few weeks in the austral summers, have made observations of the lake activity. Annual Fourier transform infrared (FTIR) spectroscopic gas measurements began in 2004 (Oppenheimer and Kyle, 2008; Oppenheimer et al., 2009), yielding an extensive, if discontinuous, time series of infrared absorption spectra. These data, once processed, provide insights into temporal evolution of the gas geochemistry in terms of seven molecular species: H2O, CO2, CO, SO2, HCl, HF, and OCS. FTIR spectroscopic data are now available over ten field seasons, totalling roughly 1.8 million spectra and increasing each year. This period spans changes to crater morphology, fluctuations in lava lake surface area (Jones et al., 2014), and two episodes of increased explosive activity (2005-06 and 2013). The dataset captures both long-term degassing trends and short-lived features, such as cyclicity in gas emissions during passive degassing (Ilanko et al., 2015) and compositions released by explosive bubble-burst eruptions. We consider the longer-term changes to gas ratios occurring within (i.e. over days to weeks) and between annual field seasons, their potential causes, and their relationship to observations of eruptive behaviour and crater morphology.

  7. Contamination control and plume assessment of low-energy thrusters

    NASA Technical Reports Server (NTRS)

    Scialdone, John J.

    1993-01-01

    Potential contamination of a spacecraft cryogenic surface by a xenon (Xe) ion generator was evaluated. The analysis involves the description of the plume exhausted from the generator with its relative component fluxes on the spacecraft surfaces, and verification of the conditions for condensation, adsorption, and sputtering at those locations. The data describing the plume fluxes and their effects on surfaces were obtained from two sources: the tests carried out with the Xe generator in a small vacuum chamber to indicate deposits and sputter on monitor slides; and the extensive tests with a mercury (Hg) ion thruster in a large vacuum chamber. The Hg thruster tests provided data on the neutrals, on low-energy ion fluxes, on high-energy ion fluxes, and on sputtered materials at several locations within the plume.

  8. Magnetic Detachment and Plume Control in Escaping Magnetized Plasma

    SciTech Connect

    P. F. Schmit and N. J. Fisch

    2008-11-05

    The model of two-fluid, axisymmetric, ambipolar magnetized plasma detachment from thruster guide fields is extended to include plasmas with non-zero injection angular velocity profiles. Certain plasma injection angular velocity profiles are shown to narrow the plasma plume, thereby increasing exhaust efficiency. As an example, we consider a magnetic guide field arising from a simple current ring and demonstrate plasma injection schemes that more than double the fraction of useful exhaust aperture area, more than halve the exhaust plume angle, and enhance magnetized plasma detachment.

  9. Magnetic Detachment and Plume Control in Escaping Magnetized Plasma

    SciTech Connect

    P. F. Schmit and N. J. Fisch

    2008-11-05

    The model of two-fluid, axisymmetric, ambipolar magnetized plasma detachment from thruster guide fields is extended to include plasmas with non-zero injection angular velocity profiles. Certain plasma injection angular velocity profiles are shown to narrow the plasma plume, thereby increasing exhaust efficiency. As an example, we consider a magnetic guide field arising from a simple current ring and demonstrate plasma injection schemes that more than double the fraction of useful exhaust aperture area, more than halve the exhaust plume angle, and enhance magnetized plasma detachment.

  10. Estuarine and coastal water dynamics controlling sediment movement and plume development in Long Island Sound

    NASA Technical Reports Server (NTRS)

    Ruggles, F. H., Jr. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. As the Connecticut River flows into Long Island Sound, large plumes develop during the mixing of ocean and estuarine waters. Plumes were delineated for July 28, October 8, October 27, and December 2, 1972, by analyzing ERTS-1 imagery with the SRI Electronic Satellite Image Analysis Console (ESIAC). Because the chemical and physical composition of the plume and ocean water were not too different, the ESIAC was utilized to expand the scenes and subject the transparencies to varying combinations of viewing techniques to identify and delineate the plumes. Best results were obtained when band 5 transparencies were used. Indications are, when the scene being analyzed is predominantly in the first two steps of the gray scale, it is best to use the negative transparencies. When the analysis is being done above the first two steps of the gray scale, it is best to use the positive transparencies.

  11. First in-situ sensing of volcanic gas plume composition at Boiling Lake (Dominica, West Indies)

    NASA Astrophysics Data System (ADS)

    Di Napoli, R.; Aiuppa, A.; Allard, P.

    2012-12-01

    Dominica, a small Caribbean island between Martinique (to the South) and Guadeloupe (to the North), is, because of the high number of potentially active volcanic centres, one of the most susceptible sites to volcanic risk in the Lesser Antilles arc. Seven major volcanic centres, active during the last 10ka, are considered likely to erupt again, and one of these is the Valley of Desolation volcanic complex. This is an area of 0.5 km2, located in on SW Dominica, where a number of small explosion craters, hot springs, bubbling pools and fumaroles testify for vigorous and persistent hydrothermal activity. Two main phreatic explosions have been documented in historical time (1880 and 1997), and the most likely centre of future activity is the Boiling Lake, a nearby high-T volcanic crater lake produced by an undated phreatic/phreato-magmatic explosion. Hot (80 to 90°C) and acidic (4-6) waters normally characterize the steady-state activity of the lake, whereby which vigorous gas upwelling in the lake's centre feeds a persistent steaming plume. Stability of the Boiling Lake has occasionally been interrupted in the past (since 1876) by crises, the most recent in 2004, involving rapid draining of the lake and changes in water temperature and pH, likely as a result of drastic decrease of hydrothermal fluid input into the lake. While the chemical and isotopic composition of the lake waters is well characterised, there are no compositional data available for the gas plume leaving the lake, due to inherent difficulties in direct gas sampling. Here, we present the results of the first direct measurements of the Boiling Lake's plume, performed by using the MultiGAS technique in February 2012. We acquired 0.5 Hz time-series of H2O, CO2, H2S and SO2 plume concentrations, which were seen to peak (with maximum background-corrected concentrations of 3680, 101 and 25 ppm for respectively H2O, CO2 and H2S) during phases of visible increase in lake outgassing. SO2 was virtually absent

  12. Plume composition changes during the birth of a new lava lake - Nyamulagira volcano, DR Congo

    NASA Astrophysics Data System (ADS)

    Bobrowski, Nicole; Giuffrida, Giovanni Bruno; Calabrese, Sergio; Scaglione, Sarah; Yalire, Mathieu; Liotta, Marcello; Brusca, Lorenzo; Arellano, Santiago; Rüdiger, Julian; Galle, Bo; Castro, Jonathan; Tedesco, Dario

    2016-04-01

    Nyamulagira, in the Virunga Volcanic Province (VVP), Democratic Republic of Congo, is one of the most active volcanoes in Africa. The volcano is located about 25 km north-northwest of Lake Kivu in the Western Branch of the East African Rift System (EARS) with a distance of only 15 km to Nyiragongo, which is well known for its decades-old active lava lake. Nyamulagira is a shield volcano with a 3058 m high and ~2000 m wide summit caldera. The volcano is characterized by frequent eruptions, which occur both from the summit crater and from the flanks (31 flank eruptions over the last 110 years). Due to the low viscosity lava, although significantly higher than the one of Nyiragongo, wide lava fields cover over 1100 km2 and lava flows often reach > 20 km length. More than 100 flank cones can be counted around the summit crater. A part from its frequent eruptions Nyamulagira had a long period of lava lake activity in the past, at least from 1912 to 1938. During the past decades, gas emissions from Nyamulagira have been only reported during eruptions. This changed in 2012, however, when Nyamulagira began emitting a persistent gas plume above its crater. By the end of 2014, and beginning in 2015, a lava lake was born, a feature that - as of the time of this writing - is still growing. To date, very little is known about gas emissions of Nyamulagira volcano with the only exception for SO2. Very few studies have been conducted regarding the volatile chemistry of Nyamulagira. We try to fill this gap by reporting gas composition measurements of Nyamulagira's volcanic plume during the birth of the lava lake, and in the first year of the lake's activity. Two field surveys have been carried out, the first one on November 1st, 2014 and the second one October 13th - 15th, 2015. Applying the broad toolbox of volcanic gas composition measurement techniques offered us the opportunity to characterize Nyamulagira's plume in excruciating detail. Nyamulagira is known to be a significant

  13. Spatial and Temporal Investigations of Laser Ablation Plasma Plume Density and Composition

    NASA Astrophysics Data System (ADS)

    Iratcabal, Jeremy; Bach, Bernhard; Beatty, Cuyler; Dutra, Eric; Darling, Timothy; Wiewior, Piotr; Covington, Aaron

    2016-10-01

    Laser ablation of solid targets with laser intensities of the order of 108-1011 W/cm2 provides a rich platform for investigating the density and composition of coexisting molecular, atomic, and ion species in the resulting plasma plume. Experiments measuring the spatial- and temporal-evolution of laser ablation plumes have been performed to simultaneously characterize the multiple parameters related to the energy and momentum partitioning of the incident laser energy as the ablation process occurs. The temperature, density, and relative populations of different molecular, atomic, and ion species can be determined by the simultaneous measurement of optical and charged particle spectroscopy, fast imaging cameras, and optical interferometric diagnostics. Additionally, background gas pressure, density, and species were carefully varied. A comparison of density measurements obtained with multiple interferometric, spectroscopic, and fast imaging diagnostics for a carbon ablation plume expanding into vacuum and into background gases with different Reynolds numbers will be presented. Atomic, molecular, and ion species population evolution will be presented as measured with optical and charged particle spectroscopy. This work was supported by the U.S. DOE NNSA Cooperative Agreement No. DE-NA0002075 and National Securities Technologies, LLC under Contract No. DE-AC52-06NA25946/subcontract No. 165819.

  14. Flow field description of the Space Shuttle Vernier reaction control system exhaust plumes

    NASA Technical Reports Server (NTRS)

    Cerimele, Mary P.; Alred, John W.

    1987-01-01

    The flow field for the Vernier Reaction Control System (VRCS) jets of the Space Shuttle Orbiter has been calculated from the nozzle throat to the far-field region. The calculations involved the use of recently improved rocket engine nozzle/plume codes. The flow field is discussed, and a brief overview of the calculation techniques is presented. In addition, a proposed on-orbit plume measurement experiment, designed to improve future estimations of the Vernier flow field, is addressed.

  15. Observations of ozone formation in power plant plumes and implications for ozone control strategies.

    PubMed

    Ryerson, T B; Trainer, M; Holloway, J S; Parrish, D D; Huey, L G; Sueper, D T; Frost, G J; Donnelly, S G; Schauffler, S; Atlas, E L; Kuster, W C; Goldan, P D; Hubler, G; Meagher, J F; Fehsenfeld, F C

    2001-04-27

    Data taken in aircraft transects of emissions plumes from rural U.S. coal-fired power plants were used to confirm and quantify the nonlinear dependence of tropospheric ozone formation on plume NO(x) (NO plus NO(2)) concentration, which is determined by plant NO(x) emission rate and atmospheric dispersion. The ambient availability of reactive volatile organic compounds, principally biogenic isoprene, was also found to modulate ozone production rate and yield in these rural plumes. Differences of a factor of 2 or greater in plume ozone formation rates and yields as a function of NO(x) and volatile organic compound concentrations were consistently observed. These large differences suggest that consideration of power plant NO(x) emission rates and geographic locations in current and future U.S. ozone control strategies could substantially enhance the efficacy of NO(x) reductions from these sources.

  16. Inferences of Particle Size and Composition From Video-like Images Based on Acoustic Data: Grotto Plume, Main Endeavor Field

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Rona, P. A.; Santilli, K.; Dastur, J.; Silver, D.

    2004-12-01

    Optical and acoustic scattering from particles in a seafloor hydrothermal plume can be related if the particle properties and scattering mechanisms are known. We assume Rayleigh backscattering of sound and Mie forward scattering of light. We then use the particle concentrations implicit in the observed acoustic backscatter intensity to recreate the optical image a camera would see given a particular lighting level. The motivation for this study is to discover what information on particle size and composition in the buoyant plume can be inferred from a comparison of the calculated optical images (based on acoustic data) with actual video images from the acoustic acquisition cruise and the IMAX film "Volcanoes of the Deep Sea" (Stephen Low Productions, Inc.). Because the geologists, biologists and oceanographers involved in the study of seafloor hydrothermal plumes all "see" plumes in different ways, an additional motivation is to create more realistic plume images from the acoustic data. By using visualization techniques, with realistic lighting models, we can convert the plume image from mechanical waves (sound) to electromagnetic waves (light). The resulting image depends on assumptions about the particle size distribution and composition. Conversion of the volume scattering coefficients from Rayleigh to Mie scattering is accomplished by an extinction scale factor that depends on the wavelengths of light and sound and on the average particle size. We also make an adjustment to the scattered light based on the particles reflectivity (albedo) and color. We present a series of images of acoustic data for Grotto Plume, Main Endeavour Field (within the Endeavour ISS Site) using both realistic lighting models and traditional visualization techniques to investigate the dependence of the images on assumptions about particle composition and size. Sensitivity analysis suggests that the visibility of the buoyant plume increases as the intensity of supplied light increases

  17. Analysis of Plume Impingement Effects from Orion Crew Service Module Dual Reaction Control System Engine Firings

    NASA Astrophysics Data System (ADS)

    Prisbell, A.; Marichalar, J.; Lumpkin, F.; LeBeau, G.

    2011-05-01

    Plume impingement effects on the Orion Crew Service Module (CSM) were analyzed for various dual Reaction Control System (RCS) engine firings and various configurations of the solar arrays. The study was performed using a decoupled computational fluid dynamics (CFD) and Direct Simulation Monte Carlo (DSMC) approach. This approach included a single jet plume solution for the R1E RCS engine computed with the General Aerodynamic Simulation Program (GASP) CFD code. The CFD solution was used to create an inflow surface for the DSMC solution based on the Bird continuum breakdown parameter. The DSMC solution was then used to model the dual RCS plume impingement effects on the entire CSM geometry with deployed solar arrays. However, because the continuum breakdown parameter of 0.05 could not be achieved due to geometrical constraints and because high resolution in the plume shock interaction region is desired, a focused DSMC simulation modeling only the plumes and the shock interaction region was performed. This high resolution intermediate solution was then used as the inflow to the larger DSMC solution to obtain plume impingement heating, forces, and moments on the CSM and the solar arrays for a total of 21 cases that were analyzed. The results of these simulations were used to populate the Orion CSM Aerothermal Database.

  18. Analysis of Plume Impingement Effects from Orion Crew Service Module Dual Reaction Control System Engine Firings

    NASA Technical Reports Server (NTRS)

    Prisbell, Andrew; Marichalar, J.; Lumpkin, F.; LeBeau, G.

    2010-01-01

    Plume impingement effects on the Orion Crew Service Module (CSM) were analyzed for various dual Reaction Control System (RCS) engine firings and various configurations of the solar arrays. The study was performed using a decoupled computational fluid dynamics (CFD) and Direct Simulation Monte Carlo (DSMC) approach. This approach included a single jet plume solution for the R1E RCS engine computed with the General Aerodynamic Simulation Program (GASP) CFD code. The CFD solution was used to create an inflow surface for the DSMC solution based on the Bird continuum breakdown parameter. The DSMC solution was then used to model the dual RCS plume impingement effects on the entire CSM geometry with deployed solar arrays. However, because the continuum breakdown parameter of 0.5 could not be achieved due to geometrical constraints and because high resolution in the plume shock interaction region is desired, a focused DSMC simulation modeling only the plumes and the shock interaction region was performed. This high resolution intermediate solution was then used as the inflow to the larger DSMC solution to obtain plume impingement heating, forces, and moments on the CSM and the solar arrays for a total of 21 cases that were analyzed. The results of these simulations were used to populate the Orion CSM Aerothermal Database.

  19. Wind forcing controls on river plume spreading on a tropical continental shelf

    NASA Astrophysics Data System (ADS)

    Tarya, A.; van der Vegt, M.; Hoitink, A. J. F.

    2015-01-01

    Berau Continental Shelf is located close to the Equator in the Indonesian Archipelago, hosting a complex of coral reefs along its oceanic edge. The Berau coral reefs have a very high biodiversity, but the area is under serious risk due to river-derived nutrients and sediments. The region is characterized by weak winds, moderate tides, and almost absent Coriolis forcing. Existing knowledge about river plume behavior in tropical environments is limited. The aim of this paper is to investigate the influence of the subtle physical forcing on the dynamics of the Berau river plume. A three-dimensional model (ECOMSED) was calibrated with observational data. The model was forced by freshwater input from the Berau river distributaries, tides at the open boundaries, and measured hourly wind. The model reproduces the freshwater dynamics on the shelf adequately and highlights that the river plume spreads symmetrically for river forcing only. Tides cause vertical mixing and suppress the cross-shelf spreading of the river plume. However, the spreading of the river plume over the shelf is mainly controlled by the weak monsoonal winds, resulting in a seasonal development. During the Southeast Monsoon, the southerly winds push the plume northeastward and cause a stratified water column in the northern part of the continental shelf. Northerly winds during the Northwest Monsoon disperse the plume to the south, promoting a vertically well-mixed water column. The results can be used to predict the possible impact of land-use changes in the steadily developing Berau region on coral reef health.

  20. Near-realtime monitoring of the 2014 Holuhraun volcanic plume, its composition and dispersion.

    NASA Astrophysics Data System (ADS)

    Björk Jónasdóttir, Elín; Barsotti, Sara; Bergsson, Baldur; Pfeffer, Melissa Anne; Arason, Þórður; Björnsson, Halldór; Nína Petersen, Guðrún; Þorsteinsson, Hróbjartur; Yeo, Richard; Arngrímsson, Hermann; Jóhannsson, Þorsteinn

    2015-04-01

    Icelandic Civil Protection Authorities. Samples of rainwater and snow are also collected and analyzed for acidity and chemical composition. The SO2 emission rate has been measured since the start of the eruption using DOASes. Three scanning DOASes capable of streaming data in near real-time were installed less than 15 km from the fissure. Long-distance traverses with a car-mounted DOAS are made along the ring road down-wind from the eruption as well as near-source traverses when conditions allow. The plume composition is measured by FTIR, MultiGAS, DOAS and filter packs when conditions allow. Forecasting of the volcanic gas dispersion has developed rapidly since the onset of the eruption. CALPUFF dispersion model was set up in early September and the forecast duty meteorologists produce gas dispersion forecasts twice a day and issue both a text forecast as well as a foreacast map indicating where levels of ground concentration fo SO2 might exceed health limits.

  1. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Technical Reports Server (NTRS)

    Woronowicz, Michael

    2011-01-01

    We have learned it is conceivable that the Neutral Mass Spectrometer on board the Lunarr Atmosphere Dust Environment Explorer (LADEE) could measure gases from surface-reflected Attitude Control System (ACS) thruster plume. At minimum altitude, the measurement would be maximized, and gravitational influence minimized ("short" time-of-flight (TOF) situation) Could use to verify aspects of thruster plume modeling Model the transient disturbance to NMS measurements due to ACS gases reflected from lunar surface Observe evolution of various model characteristics as measured by NMS Species magnitudes, TOF measurements, angular distribution, species separation effects

  2. Splash Plumes

    NASA Astrophysics Data System (ADS)

    Davies, J. H.

    2006-12-01

    I have discovered a new class of thermal upwellings in mantle convection simulations which are not rooted in a thermal boundary layer (ref 1). Since they look a bit like water droplet splashes, I have abbreviated these `plumes not rooted in thermal boundary layers' as `splash plumes'. These mantle convection simulations are high resolution ( ~ 22km spacing) 3D spherical simulations at Earth-like vigour. They have a chondritic rate of internal heating and bottom heating that straddles expected Earth values. There is a realistic depth variation in viscosity, with a lithosphere and lower mantle more viscous than upper mantle. The mantle is compressible with the coefficient of thermal expansion decreasing with depth. Some models have phase transitions. The surface of the models is driven by 119Myr of recent plate motion history. At the end of most simulations (present day) we discover many examples of hot mid-mantle thermal anomalies in the shape of bowls which have hot cylindrical plumes rising from the rim. They originate at a range of depths and are not rooted in thermal boundary layers. These splash plumes are formed from hot mantle collecting beneath the surface, and then a cold instability from the surface descending onto the sheet of hot underlying material pushing it down into the mantle and forming a bowl. The plumes are formed by instabilities coming from the bowl rim edge. In fact the downwellings can push the sheets all the way to the core mantle boundary in certain cases where it is then difficult to tell splash plumes apart from `traditional plumes'. Splash plumes might provide explanations for weak, short-lived plumes that do not seem to have deep roots (e.g. Eifel). If the surface boundary condition is made free-slip (ref 2), rather than be driven by recent plate motion history, we do not discover splash plumes but rather large steady strong thermal boundary layer plumes. Therefore while the discovery of splash plumes is interesting, potentially a more

  3. Leachate analyses of volcanic ashes from Stromboli volcano: A proxy for the volcanic gas plume composition?

    NASA Astrophysics Data System (ADS)

    Bagnato, E.; Aiuppa, A.; Andronico, D.; Cristaldi, A.; Liotta, M.; Brusca, L.; Miraglia, L.

    2011-09-01

    Many volcanoes show a change in chemical composition of the gas phase prior to periods of eruptive activity. Fine-grained tephra erupted from active vents and transported through volcanic plumes can adsorb, and therefore rapidly scavenge, volatile elements such as sulfur, halogens, and metal species in the form of soluble salts adhering to ash surfaces. Analysis of such water-soluble surface materials is a suitable supplement for remote monitoring of volcanic gases at inaccessible volcanoes. In this work, ash samples of the 2004 to 2009 eruptive activity of Stromboli volcano were sampled, leached, and analyzed for major and trace elements. Data analysis and interpretation was focused on determining the relationship between chemical composition of water-soluble components adhering to volcanic ash and the volcano's activity state. First results show significant temporal variations in ash leachate compositions, reflecting changes in the eruptive style of the volcano. In particular, we reveal that ash leachates S/F and Mg/Na ratios showed marked increases prior to a large-scale explosion on 15 March 2007.

  4. Mixing-controlled biodegradation in a toluene plume — Results from two-dimensional laboratory experiments

    NASA Astrophysics Data System (ADS)

    Bauer, Robert D.; Maloszewski, Piotr; Zhang, Yanchun; Meckenstock, Rainer U.; Griebler, Christian

    2008-02-01

    Various abiotic and biotic processes such as sorption, dilution, and degradation are known to affect the fate of organic contaminants, such as petroleum hydrocarbons in saturated porous media. Reactive transport modeling of such plumes indicates that the biodegradation of organic pollutants is, in many cases, controlled by mixing and therefore occurs locally at the plume's fringes, where electron donors and electron-acceptors mix. Herein, we aim to test whether this hypothesis can be verified by experimental results obtained from aerobic and anaerobic degradation experiments in two-dimensional sediment microcosms. Toluene was selected as a model compound for oxidizable contaminants. The two-dimensional microcosm was filled with quartz sand and operated under controlled flow conditions simulating a contaminant plume in otherwise uncontaminated groundwater. Aerobic degradation of toluene by Pseudomonas putida mt-2 reduced a continuous 8.7 mg L - 1 toluene concentration by 35% over a transport distance of 78 cm in 15.5 h. In comparison, under similar conditions Aromatoleum aromaticum strain EbN1 degraded 98% of the toluene infiltrated using nitrate (68.5 ± 6.2 mg L - 1 ) as electron acceptor. A major part of the biodegradation activity was located at the plume fringes and the slope of the electron-acceptor gradient was steeper during periods of active biodegradation. The distribution of toluene and the significant overlap of nitrate at the plume's fringe indicate that biokinetic and/or microscale transport processes may constitute additional limiting factors. Experimental data is corroborated with results from a reactive transport model using double Monod kinetics. The outcome of the study shows that in order to simulate degradation in contaminant plumes, detailed data sets are required to test the applicability of models. These will have to deal with the incorporation of existing parameters coding for substrate conversion kinetics and microbial growth.

  5. Impingement effect of service module reaction control system engine plumes. Results of service module reaction control system plume model force field application to an inflight Skylab mission proximity operation situation with the inflight Skylab response

    NASA Technical Reports Server (NTRS)

    Lobb, J. D., Jr.

    1978-01-01

    Plume impingement effects of the service module reaction control system thruster firings were studied to determine if previous flight experience would support the current plume impingement model for the orbiter reaction control system engines. The orbiter reaction control system is used for rotational and translational maneuvers such as those required during rendezvous, braking, docking, and station keeping. Therefore, an understanding of the characteristics and effects of the plume force fields generated by the reaction control system thruster firings were examined to develop the procedures for orbiter/payload proximity operations.

  6. Short wavelength heterogeneity in the Galápagos plume: Evidence from compositionally diverse basalts on Isla Santiago

    NASA Astrophysics Data System (ADS)

    Gibson, S. A.; Geist, D. G.; Day, J. A.; Dale, C. W.

    2012-09-01

    Analyses of basalts from the Galápagos archipelago and adjacent spreading center have shown that the underlying mantle plume is isotopically heterogeneous over length scales of 10s to 100s of km. We show that the convecting mantle is also compositionally heterogeneous on smaller length scales (kms). Our evidence comes from recent small-volume mildly alkaline and tholeiitic basalts on Isla Santiago, central Galápagos. Flows from volcanic vents <5 km apart are homogeneous in terms of incompatible-trace element and isotopic ratios but inter-vent variations in these ratios are large, such that Santiago basalts display some of the most extensive ranges known for any Galápagos island. Geochemical indexes of depth of melting correlate with an eastward decrease in geophysical estimates of lithospheric thickness-from 55 to 43 km over a ˜10 km horizontal distance beneath Isla Santiago-suggesting that melts have not undergone significant lateral transport in the underlying crust. This lithospheric `step' below the center of the island generally results in a greater proportion of enriched mantle melts contributing to basalts from west Santiago, than to those in the east, due to less melting of more depleted mantle as the plume upwells beneath thicker lithosphere. Nevertheless, the sporadic occurrence of isotopically enriched flows with low [Sm/Yb]n, and more isotopically depleted compositions with elevated [Sm/Yb]n, across Santiago suggests that portions of the underlying Galápagos plume are compositionally heterogeneous in terms of enriched and depleted reservoirs over short length scales (kilometers). In this respect the Galápagos mantle plume is similar to plumes beneath Hawaii and Canary Islands.

  7. Controls of Plume Dispersal at the Slow Spreading Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Walter, M.; Mertens, C.; Koehler, J.; Sueltenfuss, J.; Rhein, M.; Keir, R. S.; Schmale, O.; Schneider v. Deimling, J.; German, C. R.; Yoerger, D. R.; Baker, E. T.

    2011-12-01

    valley since the depth of the valley exceeds the rise height of the plume. Velocities observed with a Lowered Acoustic Doppler Current Profiler (LADCP), and the gradient of the stratification across the sill show a hydraulic control of the background flow over the sill, resulting in a northward advection of plume material. Downstream, the particle plume is modified by a dominant across-valley tide, and strong vertical mixing in the wake of the hydraulic jump. The Logatchev hydrothermal field (14°45'N) consists of seven vent sites, mostly smoking craters, located up on the eastern flank of the axial graben. The current field as observed with LADCP is irregular, but follows to some extent the topography in the range of the particle plume. This plume is sheared in the vertical, indicating the influence of the local tides.

  8. Lithium Isotopic Composition of Mantle Plumes and the Distribution of Lithium Isotopes Among Earth's Reservoirs

    NASA Astrophysics Data System (ADS)

    Chan, L.; Hart, S. R.; Blusztajn, J. S.; Lassiter, J. C.; Frey, F. A.; Hauri, E. H.

    2006-12-01

    We have determined lithium isotopic compositions of seventy nearly unaltered basaltic lavas from the Samoan and Cook-Austral volcanic chains, and Pitcairn Island. In addition, the Li isotope record of Mauna Kea has been extended from 3.1 km to 3.3 km using the newly recovered deep drill core of Hawaii Scientific Drilling Project (HSDP-2). From the results of the Hawaii and South Pacific hotspots, we examine the source components of mantle plumes and consider the distribution of Li isotopes among Earth's major reservoirs. The total δ^{7}Li range observed in South Pacific and Hawaiian islands is 2.5 to 7.5‰, suggesting considerable heterogeneity in the deep mantle. The Hawaiian plume occupies the lower range, 2.5 to 5.7‰. Cook-Austral samples depict mixing between HIMU and depleted mantle (DM) components. The DM endmember has δ^{7}Li values of 3.2 to 4.2‰, identical to MORB. HIMU type lavas are isotopically heavier than MORB, reflecting the influence of recycled oceanic crust. The most extreme HIMU signature was observed at Mangaia (7.4‰; Nishio et al., 2005). The EM1 composition shown by Pitcairn is relatively light (3.3 to 4.1‰) and resembles the global average of subducting sediments (~3‰). Malumalu seamount of the Samoan chain defines the most extreme composition of the EM2 mantle; δ^{7}Li range from 4.5 to 5.6‰. High 3He/4He samples of Ofu Island (R/Ra = 24 to 33.7) suggest that the least degassed mantle has δ^{7}Li of about 3‰. In addition to these classic mantle endmembers, we observe an additional component that elevates Samoan lavas above the typical mantle baseline (~3‰) up to 7.5‰. The source of this enrichment is likely mantle wedge material that has been metasomatized by 7Li-rich slab fluids (Elliott et al., 2004). On the other hand, recent studies suggest that a large portion of subducted Li can be retained in high-pressure metamorphosed slab (Marschall et al., in press). This implies that deeply subducted slab need not be

  9. CFD Simulation of the Space Shuttle Launch Vehicle with Booster Separation Motor and Reaction Control Plumes

    NASA Technical Reports Server (NTRS)

    Gea, L. M.; Vicker, D.

    2006-01-01

    The primary objective of this paper is to demonstrate the capability of computational fluid dynamics (CFD) to simulate a very complicated flow field encountered during the space shuttle ascent. The flow field features nozzle plumes from booster separation motor (BSM) and reaction control system (RCS) jets with a supersonic incoming cross flow at speed of Mach 4. The overset Navier-Stokes code OVERFLOW, was used to simulate the flow field surrounding the entire space shuttle launch vehicle (SSLV) with high geometric fidelity. The variable gamma option was chosen due to the high temperature nature of nozzle flows and different plume species. CFD predicted Mach contours are in good agreement with the schlieren photos from wind tunnel test. Flow fields are discussed in detail and the results are used to support the debris analysis for the space shuttle Return To Flight (RTF) task.

  10. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Technical Reports Server (NTRS)

    Woronowicz, M. S.

    2010-01-01

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cu cm. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  11. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    SciTech Connect

    Woronowicz, M. S.

    2011-05-20

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cm{sup 3}. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  12. CFD Simulation of the Space Shuttle Launch Vehicle with Booster Separation Motor and Reaction Control Plumes

    NASA Technical Reports Server (NTRS)

    Gea, L. M.; Vicker, D.

    2006-01-01

    The primary objective of this paper is to demonstrate the capability of computational fluid dynamics (CFD) to simulate a very complicated flow field encountered during the space shuttle ascent. The flow field features nozzle plumes from booster separation motor (BSM) and reaction control system (RCS) jets with a supersonic incoming cross flow at speed of Mach 4. The overset Navier-Stokes code OVERFLOW, was used to simulate the flow field surrounding the entire space shuttle launch vehicle (SSLV) with high geometric fidelity. The variable gamma option was chosen due to the high temperature nature of nozzle flows and different plume species. CFD predicted Mach contours are in good agreement with the schlieren photos from wind tunnel test. Flow fields are discussed in detail and the results are used to support the debris analysis for the space shuttle Return To Flight (RTF) task.

  13. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Astrophysics Data System (ADS)

    Woronowicz, M. S.

    2011-05-01

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cm3. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  14. Role of the deep mantle in generating the compositional asymmetry of the Hawaiian mantle plume

    NASA Astrophysics Data System (ADS)

    Weis, Dominique; Garcia, Michael O.; Rhodes, J. Michael; Jellinek, Mark; Scoates, James S.

    2011-12-01

    Linear chains of volcanic ocean islands are one of the most distinctive features on our planet. The longest, the Hawaiian-Emperor Chain, has been active for more than 80 million years, and is thought to have formed as the Pacific Plate moved across the Hawaiian mantle plume, the hottest and most productive of Earth's plumes. Volcanoes fed by the plume today form two adjacent trends, including Mauna Kea and Mauna Loa, that exhibit strikingly different geochemical characteristics. An extensive data set of isotopic analyses shows that lavas with these distinct characteristics have erupted in parallel along the Kea and Loa trends for at least 5 million years. Seismological data suggest that the Hawaiian mantle plume, when projected into the deep mantle, overlies the boundary between typical Pacific lower mantle and a sharply defined layer of apparently different material. This layer exhibits low seismic shear velocities and occurs on the Loa side of the plume. We conclude that the geochemical differences between the Kea and Loa trends reflect preferential sampling of these two distinct sources of deep mantle material. Similar indications of preferential sampling at the limit of a large anomalous low-velocity zone are found in Kerguelen and Tristan da Cunha basalts in the Indian and Atlantic oceans, respectively. We infer that the anomalous low-velocity zones at the core-mantle boundary are storing geochemical anomalies that are enriched in recycled material and sampled by strong mantle plumes.

  15. Chemical composition of fine particles in fresh smoke plumes from boreal wild-land fires in Europe.

    PubMed

    Saarnio, Karri; Aurela, Minna; Timonen, Hilkka; Saarikoski, Sanna; Teinilä, Kimmo; Mäkelä, Timo; Sofiev, Mikhail; Koskinen, Jarkko; Aalto, Pasi P; Kulmala, Markku; Kukkonen, Jaakko; Hillamo, Risto

    2010-05-15

    A series of smoke plumes was detected in Helsinki, Finland, during a one-month-lasting period in August 2006. The smoke plumes originated from wildfires close to Finland, and they were short-term and had a high particulate matter (PM) concentration. Physical and chemical properties of fine particles in those smokes were characterised by a wide range of real-time measurements that enabled the examination of individual plume events. Concurrently PM(1) filter samples were collected and analysed off-line. Satellite observations employing MODIS sensor on board of NASA EOS Terra satellite with the dispersion model SILAM and the Fire Assimilation System were used for evaluation of the emission fluxes from wildfires. The model predicted well the timing of the plumes but the predicted PM concentrations differed from the observed. The measurements showed that the major growth in PM concentration was caused by submicrometer particles consisting mainly of particulate organic matter (POM). POM had not totally oxidised during the transport based on the low WSOC-to-OC ratio. The fresh plumes were compared to another major smoke episode that was observed in Helsinki during April-May 2006. The duration and the source areas of the two episode periods differed. The episode in April-May was a period of nearly constantly upraised level of long-range transported PM and it was composed of aged particles when arriving in Helsinki. The two episodes had differences also in the chemical composition of PM. The mass concentrations of biomass burning tracers (levoglucosan, potassium, and oxalate) increased during both the episodes but different concentration levels of elemental carbon and potassium indicated that the episodes differed in the form of burning as well as in the burning material. In spring dry crop residue and hay from the previous season were burnt whereas in August smokes from smouldering and incomplete burning of fresh vegetation were detected.

  16. Controls on Turbulent Mixing in a Strongly Stratified and Sheared Tidal River Plume

    SciTech Connect

    Jurisa, Joseph T.; Nash, Jonathan D.; Moum, James N.; Kilcher, Levi F.

    2016-08-01

    Considerable effort has been made to parameterize turbulent kinetic energy (TKE) dissipation rate ..epsilon.. and mixing in buoyant plumes and stratified shear flows. Here, a parameterization based on Kunze et al. is examined, which estimates ..epsilon.. as the amount of energy contained in an unstable shear layer (Ri < Ric) that must be dissipated to increase the Richardson number Ri = N2/S2 to a critical value Ric within a turbulent decay time scale. Observations from the tidal Columbia River plume are used to quantitatively assess the relevant parameters controlling ..epsilon.. over a range of tidal and river discharge forcings. Observed ..epsilon.. is found to be characterized by Kunze et al.'s form within a factor of 2, while exhibiting slightly decreased skill near Ri = Ric. Observed dissipation rates are compared to estimates from a constant interfacial drag formulation that neglects the direct effects of stratification. This is found to be appropriate in energetic regimes when the bulk-averaged Richardson number Rib is less than Ric/4. However, when Rib > Ric/4, the effects of stratification must be included. Similarly, ..epsilon.. scaled by the bulk velocity and density differences over the plume displays a clear dependence on Rib, decreasing as Rib approaches Ric. The Kunze et al. ..epsilon.. parameterization is modified to form an expression for the nondimensional dissipation rate that is solely a function of Rib, displaying good agreement with the observations. It is suggested that this formulation is broadly applicable for unstable to marginally unstable stratified shear flows.

  17. Global heat transport scaling in plume-controlled regime in turbulent Rayleigh-Bénard convection

    NASA Astrophysics Data System (ADS)

    Chong, Kai Leong; Huang, Shi-Di; Xia, Ke-Qing

    2016-11-01

    Previous study by Chong et al. has introduced a normalized aspect-ratio Γ /Γopt (Γopt = 29 . 37 Ra - 0 . 31) where the plume coverage at fixed Γ /Γopt is invariant with respect to Ra in the so-called plume-controlled regime in Rayleigh-Bénard convection. We have studied the global heat transport scaling (expressed as Nusselt number Nu) at fixed Γ /Γopt with the Rayleigh number Ra between 107 and 1010 at fixed Prandtl number Pr = 4 . 38 by direct numerical simulations. It is found that at Γ /Γopt = 1 where the thermal plume becomes highly coherent and system-sized, Nu exhibits the scaling Nu - 1 Ra 0 . 327 +/- 0 . 001 over three decades of Ra . This scaling is different from that found at Γ = 1 for which Nu - 1 Ra 0 . 308 +/- 0 . 001 , and this difference in scaling can be shown evidently in the compensated plots. This work was supported by RGC of HKSAR (No. CUHK404513), CUHK Direct Grant (No. 3132740) and through a HKPhD Fellowship.

  18. The structure, dynamics, and chemical composition of noneruptive plumes from Mount St. Helens, 1980-1988

    USGS Publications Warehouse

    McGee, K.A.

    1992-01-01

    From May 1980 to September 1988, more than 1000 fixed-wing aircraft flights were made with a correlation spectrometer to measure the sulfur dioxide flux from Mount St. Helens volcano. These flights also provided valuable data on the structure and dynamics of noneruptive plumes emanating from Mount St. Helens. During 1980 and part of 1981, an infrared spectrometer was also used to measure carbon dioxide emission rates. At distances up to 25 km from Mount St. Helens, plume widths can range up to 20 km or more, with width/thickness ratios from 3 to about 30. Maximum sulfur dioxide concentrations in these plumes depend on wind speed and are typically under 5 ppm and usually 1 ppm or less. Close examination of the plume data reveals that the characteristics of quiescent plumes from Mount St. Helens are strongly affected by certain meteorological conditions such as thermal and wind stratification in the troposphere, as well as by the topography of the volcano. ?? 1992.

  19. Fast changes in chemical composition and size distribution of fine particles during the near-field transport of industrial plumes.

    PubMed

    Marris, Hélène; Deboudt, Karine; Augustin, Patrick; Flament, Pascal; Blond, François; Fiani, Emmanuel; Fourmentin, Marc; Delbarre, Hervé

    2012-06-15

    Aerosol sampling was performed inside the chimneys and in the close environment of a FeMn alloys manufacturing plant. The number size distributions show a higher abundance of ultrafine aerosols (10-100 nm) inside the plume than upwind of the plant, indicating the emissions of nanoparticles by the industrial process. Individual analysis of particles collected inside the plume shows a high proportion of metal bearing particles (Mn-/Fe-) consisting essentially of internally mixed aluminosilicate and metallic compounds. These particles evolve rapidly (in a few minutes) after emission by adsorption of VOC gas and sulfuric acid emitted by the plant but also by agglomeration with pre-existing particles. At the moment, municipalities require a monitoring of industrial emissions inside the chimneys from manufacturers. However those measures are insufficient to report such rapid changes in chemical composition and thus to evaluate the real impact of industrial plumes in the close environment of plants (when those particles leave the industrial site). Consequently, environmental authorities will have to consider such fast evolutions and then to adapt future regulations on air pollution sources. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Simulating the Black Saturday 2009 smoke plume with an interactive composition-climate model: Sensitivity to emissions amount, timing, and injection height

    NASA Astrophysics Data System (ADS)

    Field, Robert D.; Luo, Ming; Fromm, Mike; Voulgarakis, Apostolos; Mangeon, Stéphane; Worden, John

    2016-04-01

    We simulated the high-altitude smoke plume from the early February 2009 Black Saturday bushfires in southeastern Australia using the NASA Goddard Institute for Space Studies ModelE2. To the best of our knowledge, this is the first single-plume analysis of biomass burning emissions injected directly into the upper troposphere/lower stratosphere (UTLS) using a full-complexity composition-climate model. We compared simulated carbon monoxide (CO) to a new Aura Tropospheric Emission Spectrometer/Microwave Limb Sounder joint CO retrieval, focusing on the plume's initial transport eastward, anticyclonic circulation to the north of New Zealand, westward transport in the lower stratospheric easterlies, and arrival over Africa at the end of February. Our goal was to determine the sensitivity of the simulated plume to prescribed injection height, emissions amount, and emissions timing from different sources for a full-complexity model when compared to Aura. The most realistic plumes were obtained using injection heights in the UTLS, including one drawn from ground-based radar data. A 6 h emissions pulse or emissions tied to independent estimates of hourly fire behavior produced a more realistic plume in the lower stratosphere compared to the same emissions amount being released evenly over 12 or 24 h. Simulated CO in the plume was highly sensitive to the differences between emissions amounts estimated from the Global Fire Emissions Database and from detailed, ground-based estimates of fire growth. The emissions amount determined not only the CO concentration of the plume but also the proportion of the plume that entered the stratosphere. We speculate that this is due to either or both nonlinear CO loss with a weakened OH sink or plume self-lofting driven by shortwave absorption of the coemitted aerosols.

  1. Lithospheric inhomogeneity - the main factor controlling the Permo/Triassic Siberian plume location

    NASA Astrophysics Data System (ADS)

    Nikishin, Anatoly; Sobornov, Konstantin; Pravikova, Natalia

    2010-05-01

    Northwestern part of the Siberian platform is one of the interesting places to study the relations between the intraplate tectonics and the short-term large scale magmatic events. We will focus on four events which affected nearly the same area: (1) Vendian(~Ediacaran) to Early Paleozoic rapid subsidence without rifting; (2) Late Carboniferous to Early Permiam syncompressional subsidence; (3) Permo/Triassic large-scale Siberian (Tunguska) plume-related basaltic magmatism; (4) large-scale intraplate inversional tectonic events, close to the Triassic/Jurassic boundary. During the Riphean, several large sedimentary rift-related and passive margin related basins occupied the marginal parts of the platform. The total thicknesses of sediments locally exceeds 10 km. Approximately at the Riphean-Vendian boundary (630-620 Ma), a major collision took place along the northern (Taymyr), western (the Enisey Ridge) and southeastern (Transbaikal area) parts of the platform. The compression was transmitted to the inner domains of the platform, causing the long-wavelength intraplate basement-involved folding and thrusting, followed by general uplift and erosion. This compression was followed by rapid regional Vendian to Silurian subsidence, with the vertical amplitude of up to 5-7 km. This subsidence is likely thermally controlled, and does not reveal any relation with rifting. We propose this subsidence was related with lithosphere cooling which followed the postcollisional delamination (figure). Rapid subsidence occured at nearly the same place during the Late Carboniferous-Early Permian times, synchronously with the main Uralian-West Siberian orogeny. It could have a syncompressional nature. The depocentre of Permo/Triassic Siberian traps (flood basalts) is located rather close to the depocentre of previous, Vendian to Permian, subsidence. So we can imagine that the location of mantle plume intrusion in the lithosphere was not occasional. At the same time, the Permo

  2. Support to Aviation Control Service (SACS): an online service for near real-time satellite monitoring of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Brenot, H.; Theys, N.; Clarisse, L.; van Geffen, J.; van Gent, J.; Van Roozendael, M.; van der A, R.; Hurtmans, D.; Coheur, P.-F.; Clerbaux, C.; Valks, P.; Hedelt, P.; Prata, F.; Rasson, O.; Sievers, K.; Zehner, C.

    2013-10-01

    Volcanic eruptions emit plumes of ash and gases in the atmosphere, potentially at very high altitudes. Ash rich plumes are hazardous for airplanes as ash is very abrasive and easily melts inside their engines. With more than 50 active volcanoes per year and the ever increasing number of commercial flights, the safety of airplanes is a real concern. Satellite measurements are ideal for monitoring global volcanic activity and, in combination with atmospheric dispersion models, to track and forecast volcanic plumes. Here we present the Support to Aviation Control Service (SACS, http://sacs.aeronomie.be), which is a free online service initiated by ESA for the near real-time (NRT) satellite monitoring of volcanic plumes of SO2 and ash. It combines data from two UV-visible (OMI, GOME-2) and two infrared (AIRS, IASI) spectrometers. This new multi-sensor warning system of volcanic plumes, running since April 2012, is based on the detection of SO2 and is optimised to avoid false alerts while at the same time limiting the number of notifications in case of large plumes. The system shows successful results with 95% of our notifications corresponding to true volcanic activity.

  3. Characterizing the Chemical Composition of the Columbia River Plume: the use of Silicic Acid, Nitrate, Manganese and Salinity as Tracers of Sources of Waters Contributing to the Plume.

    NASA Astrophysics Data System (ADS)

    Bruland, K. W.; Aguilar-Islas, A. M.; Lohan, M. C.

    2004-12-01

    The RISE program is examining the influence of the Columbia River plume on the coastal waters off Washington and Oregon. It is important to define the macro and micro nutrient chemistry of the plume as it enters these coastal waters. Low salinity waters of the Columbia River are encountered just a short distance inside the mouth of the Columbia River estuary. These low salinity waters (salinities of 1 to 5) are low in nitrate (3 to 10 μ M), high in silicic acid (140 to 160 μ M), high in dissolved manganese and relatively high in dissolved iron. Within a remarkably short distance of exiting the mouth of the estuary into the coastal waters, the plume has attained salinities of roughly 13 to 22. The source of seawater that is entrained together with the river water in this near-field mixing regime to form the Columbia River plume can be defined using silicic acid, nitrate, manganese and salinity as tracers. During June and July of 2004, it appears that the seawater being initially entrained with the plume is subsurface, high salinity (>33), nutrient rich (nitrate 25 μ M and silicic acid 35 μ M) water. This is particularly important for the macronutrient nitrate, as this adds a substantial amount of additional nitrate to the plume. The plume water then advects and mixes further away from the source. The combination of these same tracers is useful in identifying the far-field mixing as well. We will present examples of these processes and tracers using data from the 2004 RISE cruises.

  4. Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure.

    PubMed

    Waite, J Hunter; Combi, Michael R; Ip, Wing-Huen; Cravens, Thomas E; McNutt, Ralph L; Kasprzak, Wayne; Yelle, Roger; Luhmann, Janet; Niemann, Hasso; Gell, David; Magee, Brian; Fletcher, Greg; Lunine, Jonathan; Tseng, Wei-Ling

    2006-03-10

    The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (<1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby.

  5. Mantle plume capture, anchoring, and outflow during Galápagos plume-ridge interaction

    NASA Astrophysics Data System (ADS)

    Gibson, S. A.; Geist, D. J.; Richards, M. A.

    2015-05-01

    Compositions of basalts erupted between the main zone of Galápagos plume upwelling and adjacent Galápagos Spreading Center (GSC) provide important constraints on dynamic processes involved in transfer of deep-mantle-sourced material to mid-ocean ridges. We examine recent basalts from central and northeast Galápagos including some that have less radiogenic Sr, Nd, and Pb isotopic compositions than plume-influenced basalts (E-MORB) from the nearby ridge. We show that the location of E-MORB, greatest crustal thickness, and elevated topography on the GSC correlates with a confined zone of low-velocity, high-temperature mantle connecting the plume stem and ridge at depths of ˜100 km. At this site on the ridge, plume-driven upwelling involving deep melting of partially dehydrated, recycled ancient oceanic crust, plus plate-limited shallow melting of anhydrous peridotite, generate E-MORB and larger amounts of melt than elsewhere on the GSC. The first-order control on plume stem to ridge flow is rheological rather than gravitational, and strongly influenced by flow regimes initiated when the plume was on axis (>5 Ma). During subsequent northeast ridge migration material upwelling in the plume stem appears to have remained "anchored" to a contact point on the GSC. This deep, confined NE plume stem-to-ridge flow occurs via a network of melt channels, embedded within the normal spreading and advection of plume material beneath the Nazca plate, and coincides with locations of historic volcanism. Our observations require a more dynamically complex model than proposed by most studies, which rely on radial solid-state outflow of heterogeneous plume material to the ridge.

  6. Measurements of the stratospheric plume from the Mount St. Helens eruption: radioactivity and chemical composition

    SciTech Connect

    Leifer, R.; Hinchliffe, L.; Fisenne, I.; Franklin, H.; Knutson, E.; Olden, M.; Sedlacek, W.; Mroz, E.; Cahill, T.

    1981-11-20

    Gas measurements made in the stratospheric plume from the eruption of Mount St. Helens on 18 May 1980 were not consistent with a reported large injection of radon-222 into the atmosphere. No enrichment in the volatile element polonium was found in filter samples, and the ratio of polonium-210 to lead-210 was not different from background values. Data obtained with an experimental impactor, flown shortly after the eruption, showed an increase of 10/sup 3/ in the stratospheric number concentration of submicrometer sulfate particles compared to concentrations before the eruption.

  7. Measurements of the stratospheric plume from the mount st. Helens eruption: radioactivity and chemical composition.

    PubMed

    Leifer, R; Hinchliffe, L; Fisenne, I; Franklin, H; Knutson, E; Olden, M; Sedlacek, W; Mroz, E; Cahill, T

    1981-11-20

    Gas measurements made in the stratospheric plume from the eruption of Mount St. Helens on 18 May 1980 were not consistent with a reported large injection of radon-222 into the atmosphere. No enrichment in the volatile element polonium was found in filter samples, and the ratio of polonium-210 to lead-210 was not different from background values. Data obtained with an experimental impactor, flown shortly after the eruption, showed an increase of 10(3) in the stratospheric number concentration of submicrometer sulfate particles compared to concentrations before the eruption.

  8. Measurements of the stratospheric plume from the Mount St. Helens eruption - Radioactivity and chemical composition

    NASA Astrophysics Data System (ADS)

    Leifer, R.; Hinchliffe, L.; Fisenne, I.; Franklin, H.; Knutson, E.; Olden, M.; Sedlacek, W.; Mroz, E.; Cahill, T.

    1981-11-01

    Gas measurements made in the stratospheric plume from the eruption of Mount St. Helens on 18 May 1980 were not consistent with a reported large injection of radon-222 into the atmosphere. No enrichment in the volatile element polonium was found in filter samples, and the ratio of polonium-210 to lead-210 was not different from background values. Data obtained with an experimental impactor, flown shortly after the eruption, showed an increase of 10 to the 3rd in the stratospheric number concentration of submicrometer sulfate particles compared to concentrations before the eruption.

  9. Measurements of the stratospheric plume from the Mount St. Helens eruption: radioactivity and chemical composition

    SciTech Connect

    Leifer, R.; Hinchliffe, L.; Fisenne, I.; Franklin, H.; Knutson, E.; Olden, M.; Sedlacek, W.; Mroz, E.; Cahill, T.

    1981-11-20

    Gas measurements made in the stratospheric plume from the eruption of Mount St. Helens on 18 May 1980 were not consistent with a reported large injection of radon-222 into the atmosphere. No enrichment in the volatile element polonium was found in filter samples, and the ratio of polonium-210 to lead-210 was not different from background values. Data obtained with an experimental impactor, flown shortly after the eruption, showed an increase of 10/sup 3/ in the stratospheric number concentration of submicrometer sulfate particles compared to concentrations before the eruption.

  10. Effects of the Orion Launch Abort Vehicle Plumes on Aerodynamics and Controllability

    NASA Technical Reports Server (NTRS)

    Vicker, Darby; Childs, Robert; Rogers,Stuart E.; McMullen, Matthew; Garcia, Joseph; Greathouse, James

    2013-01-01

    Characterization of the launch abort system of the Multi-purpose Crew Vehicle (MPCV) for control design and accurate simulation has provided a significant challenge to aerodynamicists and design engineers. The design space of the launch abort vehicle (LAV) includes operational altitudes from ground level to approximately 300,000 feet, Mach numbers from 0-9, and peak dynamic pressure near 1300psf during transonic flight. Further complicating the characterization of the aerodynamics and the resultant vehicle controllability is the interaction of the vehicle flowfield with the plumes of the two solid propellant motors that provide attitude control and the main propulsive impulse for the LAV. These interactions are a function of flight parameters such as Mach number, altitude, dynamic pressure, vehicle attitude, as well as parameters relating to the operation of the motors themselves - either as a function of time for the AM, or as a result of the flight control system requests for control torque from the ACM. This paper discusses the computational aerodynamic modeling of the aerodynamic interaction caused by main abort motor and the attitude control motor of the MPCV LAV, showing the effects of these interactions on vehicle controllability.

  11. Mapping methane plumes and the delta C-13 composition of anthropogenic sources in southwest Germany

    NASA Astrophysics Data System (ADS)

    Schmidt, Martina; Yeman, Christiane; Dinger, Florian; Ars, Sebastien; Yver Kwok, Camille

    2016-04-01

    A mobile analyser based on Cavity-Ring-Down Spectroscopy was installed on a vehicle, together with a GPS receiver. This allows us to measure atmospheric methane and carbon dioxide mole fractions and the C-13 isotopes of both gases while driving. Methane mole fraction measurements show a good repeatability even for high frequency measurements whereas the 13CH4 measurements need a longer averaging time of 1 minute for 1 ‰ repeatability and 15 minutes for 0.23 ‰ repeatability. Driving through an emission plume, the signal is typically only 60 seconds long. To overcome the precision problem for the isotope measurements we filled a 25 m tubing when driving through the plume, which was then flushed back through our analyser during 30 minutes. During several campaigns we visited a land fill site, a biogas plant, a dairy cow farm and a natural gas storage and measured an averaged isotopic methane signature(C-13) of -58.3 ±3 ‰, -62.5 ± 1‰, -62.2 ± 2‰, -51 ± 7‰, respectively.

  12. The Effect of Reaction Control System Thruster Plume Impingement on Orion Service Module Solar Array Power Production

    NASA Technical Reports Server (NTRS)

    Bury, Kristen M.; Kerslake, Thomas W.

    2008-01-01

    NASA's new Orion Crew Exploration Vehicle has geometry that orients the reaction control system (RCS) thrusters such that they can impinge upon the surface of Orion's solar array wings (SAW). Plume impingement can cause Paschen discharge, chemical contamination, thermal loading, erosion, and force loading on the SAW surface, especially when the SAWs are in a worst-case orientation (pointed 45 towards the aft end of the vehicle). Preliminary plume impingement assessment methods were needed to determine whether in-depth, timeconsuming calculations were required to assess power loss. Simple methods for assessing power loss as a result of these anomalies were developed to determine whether plume impingement induced power losses were below the assumed contamination loss budget of 2 percent. This paper details the methods that were developed and applies them to Orion's worst-case orientation.

  13. Dynamics of thermochemical plumes: 2. Complexity of plume structures and its implications for mapping mantle plumes

    NASA Astrophysics Data System (ADS)

    Lin, Shu-Chuan; van Keken, Peter E.

    2006-03-01

    The mantle plume hypothesis provides explanations for several major observations of surface volcanism. The dynamics of plumes with purely thermal origin has been well established, but our understanding of the role of compositional variations in the Earth's mantle on plume formation is still incomplete. In this study we explore the structures of plumes originating from a thermochemical boundary layer at the base of the mantle in an attempt to complement fluid dynamical studies of purely thermal plumes. Our numerical experiments reveal diverse characteristics of thermochemical plumes that frequently deviate from the classic features of plumes. In addition, owing to the interplay between the thermal and compositional buoyancy forces, the morphology, temperature, and flow fields in both the plume head and plume conduit are strongly time-dependent. The entrainment of the dense layer and secondary instabilities developed in the boundary layer contribute to lateral heterogeneities and enhance stirring processes in the plume head. Our models show that substantial topography of the compositional layer can develop simultaneously with the plumes. In addition, plumes may be present in the lower mantle for more than 70 million years. These features may contribute to the large low seismic velocity provinces beneath the south central Pacific, the southern Atlantic Ocean, and Africa. Our model results support the idea that the dynamics of mantle plumes is much more complicated than conventional thinking based on studies of purely thermal plumes. The widely used criteria for mapping mantle plumes, such as a vertically continuous low seismic velocity signature and strong surface topography swell, may not be universally applicable. We propose that the intrinsic density contrast of the distinct composition may reduce the associated topography of some large igneous provinces such as Ontong Java.

  14. Mobile colloid generation induced by a cementitious plume: mineral surface-charge controls on mobilization.

    PubMed

    Li, Dien; Kaplan, Daniel I; Roberts, Kimberly A; Seaman, John C

    2012-03-06

    Cementitious materials are increasingly used as engineered barriers and waste forms for radiological waste disposal. Yet their potential effect on mobile colloid generation is not well-known, especially as it may influence colloid-facilitated contaminant transport. Whereas previous papers have studied the introduction of cement colloids into sediments, this study examined the influence of cement leachate chemistry on the mobilization of colloids from a subsurface sediment collected from the Savannah River Site, USA. A sharp mobile colloid plume formed with the introduction of a cement leachate simulant. Colloid concentrations decreased to background concentrations even though the aqueous chemical conditions (pH and ionic strength) remained unchanged. Mobile colloids were mainly goethite and to a lesser extent kaolinite. The released colloids had negative surface charges and the mean particle sizes ranged primarily from 200 to 470 nm. Inherent mineralogical electrostatic forces appeared to be the controlling colloid removal mechanism in this system. In the background pH of ~6.0, goethite had a positive surface charge, whereas quartz (the dominant mineral in the immobile sediment) and kaolinite had negative surface charges. Goethite acted as a cementing agent, holding kaolinite and itself onto the quartz surfaces due to the electrostatic attraction. Once the pH of the system was elevated, as in the cementitious high pH plume front, the goethite reversed to a negative charge, along with quartz and kaolinite, then goethite and kaolinite colloids were mobilized and a sharp spike in turbidity was observed. Simulating conditions away from the cementitious source, essentially no colloids were mobilized at 1:1000 dilution of the cement leachate or when the leachate pH was ≤ 8. Extreme alkaline pH environments of cementitious leachate may change mineral surface charges, temporarily promoting the formation of mobile colloids.

  15. Transient river flow into a fjord and its control of plume energy partitioning

    NASA Astrophysics Data System (ADS)

    O'Callaghan, J. M.; Stevens, C. L.

    2015-05-01

    The influence of variable inflows on near-field plume dynamics and energy partitioning was examined using observations of a controlled flow into Doubtful Sound, New Zealand. The high temporal changes in flows passing through the Manapouri hydroelectric power station mimic the magnitude and variability seen in small mountainous river systems (SMRS) globally. The variable flow coupled with strong vertical density gradients akin to ambient conditions in coastal systems enabled plume behavior to be characterized for differing flow, wind, and tidal inputs in a quasi-idealized "laboratory" system. Comparisons of the frequency distributions of energy for different forcing conditions showed that baroclinic and barotropic processes were closely intertwined for transient forcing. The periodicity of density due to tidal oscillations was initially absent; headwaters of the fjord absorbed the momentum when inflows were substantially increased from the mean of ˜420 m3 s-1. From the buoyancy frequency squared N2, six events were identified when N2 was greater than 0.07 s-2. Seven occurrences of supercritical flow (Froude number, Fri > 1) and associated transitions to subcritical flow were observed over the duration of mooring deployment. Transient inflows induced internal hydraulic jumps in the near-field region which lead to a rapid breakdown of vertical stratification. The horizontal length scale of an internal hydraulic jump is O (1 km). Not all transitions from Fri > 1 to <1 are explained by transient forcing and the role of strong, up-fjord wind stress is likely to initiate supercritical flows via setup at the head of the fjord.

  16. Lead isotope composition of Central American volcanoes: Influence of the Galapagos plume

    NASA Astrophysics Data System (ADS)

    Feigenson, Mark D.; Carr, Michael J.; Maharaj, Susan V.; Juliano, Scott; Bolge, Louise L.

    2004-06-01

    Lead isotopic analyses of lavas from Central America, both along and behind the volcanic arc, help to clarify source components in the mantle wedge. Analysis of previous Pb isotopic data had implied that little or no marine sediment lead was added to the Central American source region, as all samples fell within the MORB field, in contrast to other information (e.g., Ba/La, 10Be, 87Sr/86Sr) that indicated a high subduction component. The data presented here include several analyses of local marine sediment, showing it to be exceptionally unradiogenic in Pb and thus permitting high sediment contributions to the mantle source region without significant changes in Pb isotopes. Combined Pb-Nd and Pb-Sr isotopic diagrams clearly illustrate the influence of crustal contamination for samples from Guatemala and Honduras, and of subducted sediment for all lavas of the volcanic front. Samples collected behind the volcanic front are derived from mixing between enriched and depleted mantle sources, and in central Costa Rica (extending to the back arc) overlap Pb, Sr and Nd isotope values for both Cocos Island and some components of the Galapagos hot spot. The restricted geographical occurrence of the enriched mantle signature in Central America, coupled with the persistence of the signal well into the back arc region, imply that these lavas are sampling Galapagos plume-influenced mantle. The presence of this plume component beneath southern Central America and extending to the northeast beneath the Caribbean confirms a Galapagos hot spot origin for this part of Caribbean Plate.

  17. Investigation of the effects of solid rocket motor propellant composition on plume signature

    NASA Astrophysics Data System (ADS)

    Snaza, Clay J.

    1994-06-01

    Three propellants with aluminum/silicon weight percentages of 18/0%, 13.5/4.5%, and 12/6% were fired in a subscale motor to determine if the plume infrared signature could be reduced without a significant loss in specific impulse. Spectral measurements from 2.5 to 5.5 micrometers and thermal measurements from 3.5 to 5.0 micrometers were made. Plume particle size measurements showed that only particles with small diameters (less than 1.93 micrometers) were present with any significant volume. Replacing a portion of the aluminum in a highly metallized solid propellant with silicon was found to eliminate the Al2O3 in favor of SiO2 and Al6SiO13, without any change in particulate mass concentration or any large change in particle size distribution. These particulates were found to have significantly lower absorptivity than Al2O3. An additional investigation was conducted to determine the particle size distribution at the nozzle entrance. Malvern ensemble scattering, phase-Doppler single particle scattering, and laser transmittance measurements made through windows in the combustion chamber at the nozzle entrance indicated that large particles were present (to 250 micrometers). However, most of the mass of the particles was contained in particles with diameters smaller than 5 micrometers. Approximate calculations made with the measured data showed that if 100 micrometer particles are present with the smoke (particles with diameters less than 2 micrometers) they could account for only approximately 10% of the article volume.

  18. The Composition and Structure of Enceladus' Plume from a Cassini UVIS Observation of a Solar Occultation

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Shemansky, D. E.; Esposito, L. W.; Stewart, I.; Hendrix, A. R.

    2010-12-01

    The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed an occultation of the sun by Enceladus’ water vapor plume on May 18, 2010. UVIS used its extreme ultraviolet (EUV) channel for this new observation, to detect absorptions in the wavelength range 55 to 110 nm. Molecular nitrogen and water vapor have absorptions in this range. The N2 b(3,0) line is at 97.2 nm, extinguishing the solar H Lyman gamma emission. Cassini’s Ion and Neutral Mass Spectrometer (INMS) detected a species with an atomic mass of 28 amu, which could be CO, C2H4 or N2 [1, 2]. Definitive UVIS detection of N2 was important to clear up this ambiguity, and this was an important goal of the observation, as the presence or lack of N2 is key to models of the geochemistry in the interior [3, 4, 5]. UVIS did not detect N2 and we set an upper limit for the column density of 3 x 10^13 cm^-2. The absorption features in the spectrum are best fit by a water vapor column density of 0.9 x 10^16 cm^-2. This column density is in family with previous UVIS measurements from stellar occultations in 2005 and 2007 at far ultraviolet wavelengths, suggesting that Enceladus’ activity has been stable for the last 5 years [6, 7]. We used fluctuations in the signal to probe the structure of the gas jets again, as was analyzed in the 2007 occultation of zeta Orionis [7]. Gas jets are correlated to the dust jets detected by Cassini’s Imaging Science Subsystem [8]. The path of the sun cut through the jets horizontally at an altitude above the limb of ~15 km at the closest point. The resolution of the solar occultation is higher than the stellar occultation, and collimation of the gas jets observed in the solar occultation is greater than estimated in 2007. The observed collimation allows us to derive a mach number of ~4 for the ratio of the vertical velocity in the jet to the thermal velocity of the plume gas. The new opportunity afforded by this solar occultation is used to further model the structure and

  19. Enceladus' water vapor plume.

    PubMed

    Hansen, Candice J; Esposito, L; Stewart, A I F; Colwell, J; Hendrix, A; Pryor, W; Shemansky, D; West, R

    2006-03-10

    The Cassini spacecraft flew close to Saturn's small moon Enceladus three times in 2005. Cassini's UltraViolet Imaging Spectrograph observed stellar occultations on two flybys and confirmed the existence, composition, and regionally confined nature of a water vapor plume in the south polar region of Enceladus. This plume provides an adequate amount of water to resupply losses from Saturn's E ring and to be the dominant source of the neutral OH and atomic oxygen that fill the Saturnian system.

  20. Adaptive management for subsurface pressure and plume control in application to geological CO2 storage

    NASA Astrophysics Data System (ADS)

    Gonzalez-Nicolas, A.; Cihan, A.; Birkholzer, J. T.; Petrusak, R.; Zhou, Q.; Riestenberg, D. E.; Trautz, R. C.; Godec, M.

    2016-12-01

    Industrial-scale injection of CO2 into the subsurface can cause reservoir pressure increases that must be properly controlled to prevent any potential environmental impact. Excessive pressure buildup in reservoir may result in ground water contamination stemming from leakage through conductive pathways, such as improperly plugged abandoned wells or distant faults, and the potential for fault reactivation and possibly seal breaching. Brine extraction is a viable approach for managing formation pressure, effective stress, and plume movement during industrial-scale CO2 injection projects. The main objectives of this study are to investigate suitable different pressure management strategies involving active brine extraction and passive pressure relief wells. Adaptive optimized management of CO2 storage projects utilizes the advanced automated optimization algorithms and suitable process models. The adaptive management integrates monitoring, forward modeling, inversion modeling and optimization through an iterative process. In this study, we employ an adaptive framework to understand primarily the effects of initial site characterization and frequency of the model update (calibration) and optimization calculations for controlling extraction rates based on the monitoring data on the accuracy and the success of the management without violating pressure buildup constraints in the subsurface reservoir system. We will present results of applying the adaptive framework to test appropriateness of different management strategies for a realistic field injection project.

  1. Using Hydrothermal Plumes and Their Chemical Composition to Identify and Understand Hydrothermal Activity at Explorer Ridge

    NASA Astrophysics Data System (ADS)

    Resing, J.; Lebon, G.; Baker, E.; Walker, S.; Nakamura, K.; Silvers, B.

    2002-12-01

    During June and July, 2002, an extensive survey of the hydrothermal systems of the Explorer Ridge was made aboard the R/V Thomas Thompson. This survey employed hydrocasts and the Autonomous Benthic Explorer (ABE) to locate and map hydrothermal vent fields. A total of 28 hydrocasts (17 verticals and 11 tow-yos) were used to search for hydrothermal activity from 49.5°N to 50.3°N on the Explorer Ridge. During the hydrocasts continuous measurements were made of conductivity, temperature, pressure, light backscatter, eH, Fe, Mn, and pH. Discrete samples were collected for total dissolved Fe and Mn, methane, pH, total CO2, and particulate matter. Most of the strong hydrothermal venting was near the Magic Mountain area of the Explorer Ridge at ~49.76° N, 130.26° W, where strong particulate backscatter signals (~0.130 NTUs) and moderate temperature anomalies (~ 0.05 °C) were detected. The particulate matter causing the backscatter was made up primarily of volatile particulate sulfur (PS) with little to no hydrothermal PFe. PS:PFe ratios exceeded 25 in the areas of most intense venting, . These PFe and PS data suggest that the hydrothermal Fe, if any, is deposited as sulfide minerals beneath the sea floor and that S is far in excess of Fe in the hydrothermal fluids. In the most intense plumes,total dissolvable Fe and Mn were between 20 and 30 nM, pH anomalies exceeded 0.025 pH units (indicating an increase of ~10uM CO2), and methane reached 16nM. These results suggest that the fluids exiting the sea floor are metal-poor and moderately gas-rich.

  2. Control of trichloroethylene plume migration using a biobarrier system: a field-scale study.

    PubMed

    Kuo, Y C; Wang, S Y; Chang, Y M; Chen, S H; Kao, C M

    2014-01-01

    The objective of this field-scale study was to evaluate the effectiveness of controlling trichloroethylene (TCE) plume migration using the polycolloid substrate (PS) biobarrier. The developed PS (containing soybean oil, lactate and surfactants) could release substrate to enhance the TCE dechlorination. In this study, a biobarrier comprising PS injection wells was installed. Injection wells were installed at 5-m intervals, and approximately 15 L of PS was injected into each well. Results show that TCE concentrations in the injection wells dropped from an average of 87 μg/L to below 1 μg/L after 35 days of PS injection. The total organic carbon concentrations in the injection wells increased from an average of 2.1-543 mg/L after 30 days of PS injection. The dissolved oxygen (DO) concentrations and oxidation-reduction potential (ORP) values dropped from an average of 1.6 mg/L to below 0.1 mg/L and from 124 mv to -14 mv after 20 days of injection, respectively. The DO and ORP remained in anaerobic conditions during the remaining 100 days of the operational period. TCE degradation by-products were observed in groundwater samples during the operational period. This reveals that the addition of PS could effectively enhance the reductive dechlorinating of TCE.

  3. Lithospheric Controls on Magma Composition along Earth's Longest Continental Hotspot-Track

    NASA Astrophysics Data System (ADS)

    Rawlinson, N.; Davies, R.; Iaffaldano, G.; Campbell, I. H.

    2014-12-01

    Hotspots are anomalous regions of volcanism at Earth's surface that show no obvious association with tectonic plate boundaries. Classic examples include the Hawaiian-Emperor chain and the Yellowstone-Snake River Plain province. The majority are believed to form as Earth's tectonic plates move over long-lived mantle plumes: buoyant upwellings that bring hot material from Earth's deep-mantle to its surface. It has long been recognised that lithospheric thickness limits the rise height of plumes and, thereby, their minimum melting pressure. It should, therefore, have a controlling influence on the geochemistry of plume-related magmas, although unambiguous evidence of this has, thus far, been lacking. Here we integrate observational constraints from surface geology, geochronology, plate-motion reconstructions, geochemistry and seismology to ascertain plume melting depths beneath Earth's longest continental hotspot-track, a ~2000 km long track in eastern Australia that displays a record of volcanic activity between ~33 and ~9 Ma, which we call the Cosgrove track. Our analyses highlight a strong correlation between lithospheric thickness and magma composition along this track, with: (i) standard basaltic compositions in regions where lithospheric thickness is less than ~110 km; (ii) volcanic gaps in regions where lithospheric thickness exceeds ~150 km; and (iii) low-volume, leucitite-bearing volcanism in regions of intermediate lithospheric thickness. Trace-element concentrations from samples along this track support the notion that these compositional variations result from different degrees of partial-melting, which is controlled by the thickness of overlying lithosphere. Our results place the first observational constraints on the subcontinental melting depth of mantle plumes and provide direct evidence that lithospheric thickness has a dominant influence on the volume and chemical composition of plume-derived magmas.

  4. Lithospheric Controls on Magma Composition along Earth's Longest Continental Hotspot-Track

    NASA Astrophysics Data System (ADS)

    Rawlinson, N.; Davies, R.; Iaffaldano, G.; Campbell, I. H.

    2015-12-01

    Hotspots are anomalous regions of volcanism at Earth's surface that show no obvious association with tectonic plate boundaries. Classic examples include the Hawaiian-Emperor chain and the Yellowstone-Snake River Plain province. The majority are believed to form as Earth's tectonic plates move over long-lived mantle plumes: buoyant upwellings that bring hot material from Earth's deep-mantle to its surface. It has long been recognised that lithospheric thickness limits the rise height of plumes and, thereby, their minimum melting pressure. It should, therefore, have a controlling influence on the geochemistry of plume-related magmas, although unambiguous evidence of this has, thus far, been lacking. Here we integrate observational constraints from surface geology, geochronology, plate-motion reconstructions, geochemistry and seismology to ascertain plume melting depths beneath Earth's longest continental hotspot-track, a ~2000 km long track in eastern Australia that displays a record of volcanic activity between ~33 and ~9 Ma, which we call the Cosgrove track. Our analyses highlight a strong correlation between lithospheric thickness and magma composition along this track, with: (i) standard basaltic compositions in regions where lithospheric thickness is less than ~110 km; (ii) volcanic gaps in regions where lithospheric thickness exceeds ~150 km; and (iii) low-volume, leucitite-bearing volcanism in regions of intermediate lithospheric thickness. Trace-element concentrations from samples along this track support the notion that these compositional variations result from different degrees of partial-melting, which is controlled by the thickness of overlying lithosphere. Our results place the first observational constraints on the subcontinental melting depth of mantle plumes and provide direct evidence that lithospheric thickness has a dominant influence on the volume and chemical composition of plume-derived magmas.

  5. Lithospheric controls on magma composition along Earth's longest continental hotspot track

    NASA Astrophysics Data System (ADS)

    Davies, D. R.; Rawlinson, N.; Iaffaldano, G.; Campbell, I. H.

    2015-09-01

    Hotspots are anomalous regions of volcanism at Earth's surface that show no obvious association with tectonic plate boundaries. Classic examples include the Hawaiian-Emperor chain and the Yellowstone-Snake River Plain province. The majority are believed to form as Earth's tectonic plates move over long-lived mantle plumes: buoyant upwellings that bring hot material from Earth's deep mantle to its surface. It has long been recognized that lithospheric thickness limits the rise height of plumes and, thereby, their minimum melting pressure. It should, therefore, have a controlling influence on the geochemistry of plume-related magmas, although unambiguous evidence of this has, so far, been lacking. Here we integrate observational constraints from surface geology, geochronology, plate-motion reconstructions, geochemistry and seismology to ascertain plume melting depths beneath Earth's longest continental hotspot track, a 2,000-kilometre-long track in eastern Australia that displays a record of volcanic activity between 33 and 9 million years ago, which we call the Cosgrove track. Our analyses highlight a strong correlation between lithospheric thickness and magma composition along this track, with: (1) standard basaltic compositions in regions where lithospheric thickness is less than 110 kilometres; (2) volcanic gaps in regions where lithospheric thickness exceeds 150 kilometres; and (3) low-volume, leucitite-bearing volcanism in regions of intermediate lithospheric thickness. Trace-element concentrations from samples along this track support the notion that these compositional variations result from different degrees of partial melting, which is controlled by the thickness of overlying lithosphere. Our results place the first observational constraints on the sub-continental melting depth of mantle plumes and provide direct evidence that lithospheric thickness has a dominant influence on the volume and chemical composition of plume-derived magmas.

  6. Lithospheric controls on magma composition along Earth's longest continental hotspot track.

    PubMed

    Davies, D R; Rawlinson, N; Iaffaldano, G; Campbell, I H

    2015-09-24

    Hotspots are anomalous regions of volcanism at Earth's surface that show no obvious association with tectonic plate boundaries. Classic examples include the Hawaiian-Emperor chain and the Yellowstone-Snake River Plain province. The majority are believed to form as Earth's tectonic plates move over long-lived mantle plumes: buoyant upwellings that bring hot material from Earth's deep mantle to its surface. It has long been recognized that lithospheric thickness limits the rise height of plumes and, thereby, their minimum melting pressure. It should, therefore, have a controlling influence on the geochemistry of plume-related magmas, although unambiguous evidence of this has, so far, been lacking. Here we integrate observational constraints from surface geology, geochronology, plate-motion reconstructions, geochemistry and seismology to ascertain plume melting depths beneath Earth's longest continental hotspot track, a 2,000-kilometre-long track in eastern Australia that displays a record of volcanic activity between 33 and 9 million years ago, which we call the Cosgrove track. Our analyses highlight a strong correlation between lithospheric thickness and magma composition along this track, with: (1) standard basaltic compositions in regions where lithospheric thickness is less than 110 kilometres; (2) volcanic gaps in regions where lithospheric thickness exceeds 150 kilometres; and (3) low-volume, leucitite-bearing volcanism in regions of intermediate lithospheric thickness. Trace-element concentrations from samples along this track support the notion that these compositional variations result from different degrees of partial melting, which is controlled by the thickness of overlying lithosphere. Our results place the first observational constraints on the sub-continental melting depth of mantle plumes and provide direct evidence that lithospheric thickness has a dominant influence on the volume and chemical composition of plume-derived magmas.

  7. Support to Aviation Control Service (SACS): an online service for near-real-time satellite monitoring of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Brenot, H.; Theys, N.; Clarisse, L.; van Geffen, J.; van Gent, J.; Van Roozendael, M.; van der A, R.; Hurtmans, D.; Coheur, P.-F.; Clerbaux, C.; Valks, P.; Hedelt, P.; Prata, F.; Rasson, O.; Sievers, K.; Zehner, C.

    2014-05-01

    Volcanic eruptions emit plumes of ash and gases into the atmosphere, potentially at very high altitudes. Ash-rich plumes are hazardous for airplanes as ash is very abrasive and easily melts inside their engines. With more than 50 active volcanoes per year and the ever-increasing number of commercial flights, the safety of airplanes is a real concern. Satellite measurements are ideal for monitoring global volcanic activity and, in combination with atmospheric dispersion models, to track and forecast volcanic plumes. Here we present the Support to Aviation Control Service (SACS, http://sacs.aeronomie.be/ecosystem), which is a free online service initiated by the European Space Agency (ESA) for the near-real-time (NRT) satellite monitoring of volcanic plumes of SO2 and ash. It combines data from three ultraviolet (UV)-visible and three infrared (IR) spectrometers. The UV-vis sensors are the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2) on-board the two polar orbiting meteorological satellites (MetOp-A & MetOp-B) operated by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). The IR sensors are the Atmospheric InfraRed Sounder (AIRS) and the Infrared Atmospheric Sounding Interferometer (IASI) on-board MetOp-A & MetOp-B. This new multi-sensor warning system of volcanic emissions is based on the selective detection of SO2 and ash. This system is optimised to avoid false alerts while at the same time limiting the number of notifications in case of large plumes. A successful rate with more than 95% of notifications corresponding to true volcanic activity is obtained by the SACS system.

  8. A controlled-release molasses barrier system for controlling nitrate plume in groundwater: A large flow-tank study

    NASA Astrophysics Data System (ADS)

    Lee, B. S.; Um, J. Y.; Lee, K. Y.; Kim, Y. B.; Nam, K.; Woo, N. C.; Kim, J. H.; Lee, J. M.

    2009-04-01

    A well-type permeable barrier system containing controlled-release molasses as a reactive material to promote the indigenous denitrifying activity (termed CRM system hereafter) has been developed for controlling nitrate plume in groundwater. To control the release of molasses as an extra carbon and energy source, CRM rod (OD x L = 4 cm x 30 cm) was manufactured using molding technique by dispersing molasses in paraffin wax-cellulose-silica matrix. A large scale flow-tank (L x W x D = 8 m x 4 m x 1 m, 95 m3 of sands, porosity of 0.45) was prepared to test the CRM system (L x W x D = 3 m x 4 m x 1 m) in destroying nitrate, which was consisted of three layers of discrete barriers installed at 1-m interval. Nitrate plume (1.2 m/d of velocity, 142 mg/L of nitrate) was generated by introducing both tap water (1.1 m3/d) and diluted nitrate solution (0.5 m3/d, 312 mg/L of nitrate) daily. Changes in nitrate concentrations were monitored at 30 monitoring points across the flow-tank. For 14 (i.e., the first test), 21 (i.e., the second test), and 42 (i.e., the third test) days, 80, 140, and 140 CRM rods were placed into the barriers to construct the CRM system, respectively. An indigenous microorganism Ensifer adhaerens (97% similarity) was identified from the flow-tank sands, which was probably the main denitrifier in the system. After the second test, a heterotrophic denitrifier Pseudomonas sp. KY1 was inoculated to increase destruction efficiency into the flow-tank sands for the third test. For the first test, nitrate concentrations decreased by 29, 59, and 80% after the 1st, 2nd, and 3rd barriers, respectively. For the second and third tests, nitrate concentrations decreased by 32 and 26% for the 1st, 68 and 74% for the 2nd, and 84 and 81% for the 3rd barrier, indicating little effects of inoculating KY1 on destruction efficiencies. At 5.5 m downstream (i.e., 1.75 m behind the 3rd barrier), nitrate concentrations decreased by 81, 90, and 90% at the first, second, and third

  9. The effects of 1 kW class arcjet thruster plumes on spacecraft charging and spacecraft thermal control materials

    NASA Technical Reports Server (NTRS)

    Bogorad, A.; Lichtin, D. A.; Bowman, C.; Armenti, J.; Pencil, E.; Sarmiento, C.

    1992-01-01

    Arcjet thrusters are soon to be used for north/south stationkeeping on commercial communications satellites. A series of tests was performed to evaluate the possible effects of these thrusters on spacecraft charging and the degradation of thermal control material. During the tests the interaction between arcjet plumes and both charged and uncharged surfaces did not cause any significant material degradation. In addition, firing an arcjet thruster benignly reduced the potential of charged surfaces to near zero.

  10. A controlled field experiment on groundwater contamination by a multicomponent DNAPL: creation of the emplaced-source and overview of dissolved plume development.

    PubMed

    Rivett, M O; Feenstra, S; Cherry, J A

    2001-05-01

    A unique field experiment has been undertaken at the CFB Borden research site to investigate the development of dissolved chlorinated solvent plumes from a residual dense non-aqueous phase liquid (DNAPL) source. The "emplaced-source" tracer test methodology involved a controlled emplacement of a block-shaped source of sand containing chlorinated solvents below the water table. The gradual dissolution of this residual DNAPL solvent source under natural aquifer conditions caused dissolved solvent plumes of trichloromethane (TCM), trichloroethene (TCE) and perchloroethene (PCE) to continuously develop down gradient. Source dissolution and 3-D plume development were successfully monitored via 173 multilevel samplers over a 475-day tracer test period prior to site remediation research being initiated. Detailed groundwater level and hydraulic conductivity data were collected. Development of plumes with concentrations spanning 1-700,000 micrograms/1 is described and key processes controlling their migration identified. Plumes were observed to be narrow due to the weakness of transverse dispersion processes and long due to advection and significant longitudinal dispersion, very limited sorptive retardation and negligible, if any, attenuation due to biodegradation or abiotic reaction. TCM was shown to be essentially conservative, TCE very nearly conservative and PCE, consistent with its greater hydrophobicity, more retarded yet having a greater mobility than observed in previous Borden field tests. The absence of biodegradation was ascribed to the prevailing aerobic conditions and lack of any additional biodegradable carbon substrates. The transient groundwater flow regime caused significant transverse lateral plume movement, plume asymmetry and was likely responsible for most of the, albeit limited, transverse horizontal plume spreading. In agreement with the widespread incidence of extensive TCE and PCE plumes throughout the industrialized world, the experiment indicates

  11. Composition and size distribution of submicrometer aerosol particles observed on Mt. Fuji in the volcanic plumes from Miyakejima

    NASA Astrophysics Data System (ADS)

    Naoe, Hiroaki; Heintzenberg, Jost; Okada, Kikuo; Zaizen, Yuji; Hayashi, Kazuhiko; Tateishi, Takahiro; Igarashi, Yasuhito; Dokiya, Yukiko; Kinoshita, Kisei

    An aerosol observation campaign was conducted at the summit of Mt. Fuji (at an altitude of 3776 m), which is located 170 km northwest of Miyakejima. Individual aerosol particles were collected with an electrostatic aerosol sampler and the number-size distribution and composition were examined by electron microscopy. Number-size distributions were measured with the combination of a diffusion battery (DB) and a condensation particle counter. Sulfate and sulfur dioxide concentrations were also determined. During the first half of the campaign (13-15 September 2000), high number fractions of sulfuric-acid containing particles with a mode radius around 0.06 μm were observed in the radius range of 0.02-0.2 μm coincident with a humid maritime air mass originated from the south. Sulfate and sulfur dioxide also showed high concentrations in this period. These results suggested that the volcanic plumes of Miyakejima were transported up to the summit of Mt. Fuji. Number-size distributions determined by electron microscope were consistent with those derived using the DB. During the later half of the experiment (18-20 September), low fractions of sulfuric-acid containing particles represented only a small fraction of the total particle number, coincident with a dry continental air mass originating from the west.

  12. Influence of Chemical Composition on Microbial Communities in Deep Water Plumes After the Deepwater Horizon Oil Spill

    NASA Astrophysics Data System (ADS)

    Redmond, M. C.; Valentine, D. L.

    2012-12-01

    After the Deepwater Horizon oil spill, large amounts of natural gas and oil remained dissolved or suspended in the deep Gulf of Mexico. These deep water plumes were preferentially enriched in soluble hydrocarbons, including methane, ethane, propane, cyclohexane, benzene, toluene, and xylenes. Microbial communities responded rapidly to the influx of hydrocarbons, and were initially dominated by a novel group of Oceanospirillales. As the summer progressed, Colwellia and Cycloclasticus became more abundant, followed by an increase in methanotrophs and methylotrophs. DNA stable isotope probing experiments showed that Colwellia spp. were the primary bacteria assimilating carbon from ethane and propane, suggesting that the presence of natural gas had a significant effect on the microbes that responded to the spill. Additional incubation experiments suggested that Colwellia could also consume benzene and other hydrocarbons in crude oil, but it was unclear whether the presence of natural gas stimulated or inhibited the consumption of other hydrocarbons. In order to determine the effect of natural gas on microbial community composition and the degradation of petroleum hydrocarbons, we conducted a series of incubation experiments with seawater from the deep Gulf of Mexico. We also conducted experiments to determine the effect of individual hydrocarbon compounds on the microbial community response. We will present results from both sets of experiments.

  13. CFD Simulation of the Space Shuttle Launch Vehicle with Booster Separation Motor and Reaction Control System Plumes

    NASA Technical Reports Server (NTRS)

    Gea, L. M.; Vicker, D.

    2006-01-01

    The primary objective of this paper is to demonstrate the capability of computational fluid dynamics (CFD) to simulate a very complicated flow field encountered during the space shuttle ascent. The flow field features nozzle plumes from booster separation motor (BSM) and reaction control system (RCS) jets with a supersonic incoming cross flow at speed of Mach 4. The overset Navier-Stokes code OVERFLOW, was used to simulate the flow field surrounding the entire space shuttle launch vehicle (SSLV) with high geometric fidelity. The variable gamma option was chosen due to the high temperature nature of nozzle flows and different plume species. CFD predicted Mach contours are in good agreement with the schlieren photos from wind tunnel test. Flow fields are discussed in detail and the results are used to support the debris analysis for the space shuttle Return To Flight (RTF) task.

  14. CFD Simulation of the Space Shuttle Launch Vehicle with Booster Separation Motor and Reaction Control System Plumes

    NASA Technical Reports Server (NTRS)

    Gea, L. M.; Vicker, D.

    2006-01-01

    The primary objective of this paper is to demonstrate the capability of computational fluid dynamics (CFD) to simulate a very complicated flow field encountered during the space shuttle ascent. The flow field features nozzle plumes from booster separation motor (BSM) and reaction control system (RCS) jets with a supersonic incoming cross flow at speed of Mach 4. The overset Navier-Stokes code OVERFLOW, was used to simulate the flow field surrounding the entire space shuttle launch vehicle (SSLV) with high geometric fidelity. The variable gamma option was chosen due to the high temperature nature of nozzle flows and different plume species. CFD predicted Mach contours are in good agreement with the schlieren photos from wind tunnel test. Flow fields are discussed in detail and the results are used to support the debris analysis for the space shuttle Return To Flight (RTF) task.

  15. Composition of the Tarim mantle plume: Constraints from clinopyroxene antecrysts in the early Permian Xiaohaizi dykes, NW China

    NASA Astrophysics Data System (ADS)

    Wei, Xun; Xu, Yi-Gang; Luo, Zhen-Yu; Zhao, Jian-Xin; Feng, Yue-Xing

    2015-08-01

    Numerous alkaline basaltic dykes crosscut the Early Permian Xiaohaizi wehrlite in drill-cores and syenite intrusion in the Tarim large igneous province, NW China. One basaltic dyke contains abundant clinopyroxene macrocrysts with strong resorption textures. Such a textural disequilibrium is consistent with their contrasting chemistry between the macrocrysts (Mg# = 80-89) and the host dyke (Mg# = 39, corresponding to Mg# = 73 of clinopyroxene in equilibrium with the dyke), indicating that they are not phenocrysts. The clinopyroxene macrocrysts are characterized by low TiO2 (0.26-1.09 wt.%), Al2O3 (1.15-3.10 wt.%) and Na2O (0.16-0.37 wt.%), unlike those in mantle peridotites but resembling those in layered mafic intrusions in the same area. The clinopyroxene macrocrysts and the clinopyroxenes from the Xiaohaizi cumulate wehrlites define a coherent compositional trend and have identical trace element patterns, pointing to a comagmatic origin for these crystals. Accordingly, the macrocrysts cannot be xenocrysts foreign to the magmatic system. Rather they are antecrysts that crystallized from progenitor magmas and have been reincorporated into the host dyke before intrusion. The 87Sr/86Sri (0.7035-0.7037) and εNdi (4.5-4.8) of the clinopyroxene macrocrysts with high Mg# (80-89) are apparently lower and higher than their respective ratios of the clinopyroxenes in the wehrlites (Mg# = 75-84, 87Sr/86Sri = 0.7038-0.7041, εNdi = 1.0-1.9). This difference in isotopes can be accounted for by assimilation and fractional crystallization (AFC) process operated during the formation of the Xiaohaizi intrusion. In this sense, the clinopyroxene macrocrysts record the composition of the uncontaminated Tarim plume-derived melts.

  16. Plume magmatism in the northeastern part of the Altai-Sayan region: Stages, source compositions, and geodynamics (exemplified by the Minusinsk Depression)

    NASA Astrophysics Data System (ADS)

    Vorontsov, A. A.; Perfilova, O. Yu.; Buslov, M. M.; Travin, A. V.; Makhlaev, M. L.; Dril, S. I.; Katraevskaya, Ya. I.

    2017-02-01

    The results of geochronological (U-Pb, Ar-Ar), geochemical, and isotopic (Sr, Nd) studies of the Ordovician and Devonian mafic volcanic-subvolcanic rock associations of the Minusinsk Depression are presented. The obtained ages of magmatic associations and the basite composition, considering previous studies, witness to the impact of two mantle plumes different in age (Late Cambrian-Ordovician and Devonian) on suprasubduction rock complexes in active continental margin settings.

  17. The composition and distribution of the rejuvenated component across the Hawaiian plume: Hf-Nd-Sr-Pb isotope systematics of Kaula lavas and pyroxenite xenoliths

    NASA Astrophysics Data System (ADS)

    Bizimis, Michael; Salters, Vincent J. M.; Garcia, Michael O.; Norman, Marc D.

    2013-10-01

    Rejuvenated volcanism refers to the reemergence of volcanism after a hiatus of 0.5-2 Ma following the voluminous shield building stage of Hawaiian volcanoes. The composition of the rejuvenated source and its distribution relative to the center of the plume provide important constraints on the origin of rejuvenated volcanism. Near-contemporaneous lavas from the Kaula-Niihau-Kauai ridge and the North Arch volcanic field that are aligned approximately orthogonally to the plume track can constrain the lateral geochemical heterogeneity and distribution of the rejuvenated source across the volcanic chain. Nephelinites, phonolites and pyroxenite xenoliths from Kaula Island have radiogenic Hf, Nd and unradiogenic Sr isotope compositions consistent with a time-integrated depleted mantle source. The pyroxenites and nephelinites extend to the lowest 208Pb/204Pb reported in Hawaiian rocks. These data, along with new Pb isotope data from pyroxenites from the Salt Lake Crater (Oahu) redefine the composition of the depleted end-member of the Hawaiian rejuvenated source at 208Pb/204Pb=37.35±0.05, 206Pb/204Pb = 17.75±0.03, ɛNd = 9-10, ɛHf ˜16-17 and 87Sr/88Sr <0.70305. The revised isotope composition also suggests that this depleted component may contribute to LOA and KEA trend shield stage Hawaiian lavas, consistent with the rejuvenated source being part of the Hawaiian plume and not entrained upper mantle. The isotope systematics of rejuvenated magmas along the Kaula-Niihau-Kauai-North Arch transect are consistent with a larger proportion of the rejuvenated depleted component in the periphery of the plume track rather than along its axis.

  18. Compositions of Hawaiian Double Track Volcanoes: Shallow or Deep Controls?

    NASA Astrophysics Data System (ADS)

    Hofmann, A. W.; Farnetani, C. G.; Class, C.

    2012-12-01

    At least three mechanisms have been proposed to explain the compositional differences between the two parallel chains of Hawaiian volcanoes known as Loa and Kea trends, respectively: (1) The Hawaiian plume is concentrically zoned, and Loa trend volcanoes tap the central portions, whereas Kea trend volcanoes tap more peripheral portions of the plume. (2) Variations in lithospheric thickness control the depth and extent of melt extraction, and therefore the specific compositional mix between enriched and depleted components distributed uniformly throughout an otherwise unzoned plume. (3) The two tracks sample a large-scale compositional gradient initially located in the plume source, the thermal boundary layer near the base of the mantle. Model (1) is inconsistent with the observation that both pre-shield and post-shield Loa-trend volcanoes, which sample the periphery of the plume, have Loa-type, not Kea-type, isotopic characteristics. Model (2), as proposed by Ballmer et al. (2011), invokes systematically higher extents of melting for Kea-trend volcanoes. This conflicts with geochemical evidence, such as La/Yb ratios that are consistently higher in Kea-trend shield volcanoes than in corresponding Loa-shields, indicating lower, not higher extents of melting for Kea-shields. It also conflicts with radiogenic 208Pb*/206Pb* ratios of pre-shield Loihi, which, in spite of a large difference in melt fraction, are similar to Loa-shield lavas. Model (3) has recently been linked to the isotopic DUPAL anomaly and the edge of the large, lower-mantle shear-wave velocity anomaly in the Pacific (Weis et al., 2011). Using geodynamic modeling, we show how an isotopic gradient in the lower-mantle thermal boundary layer is drawn into the plume conduit and sampled by the two volcano tracks. An isotopic gradient or sharp boundary, even when initially located away from the plume conduit by hundreds of kilometers, will nevertheless ultimately be drawn into the center of the conduit. This

  19. Application of natural attenuation for the control of petroleum hydrocarbon plume: Mechanisms and effectiveness evaluation

    NASA Astrophysics Data System (ADS)

    Chiu, H. Y.; Hong, A.; Lin, S. L.; Surampalli, R. Y.; Kao, C. M.

    2013-11-01

    The effectiveness and mechanisms of NA were evaluated in the field-scale study.Significant BTEX removal was observed via different intrinsic bioremediation processes.The calculated biodegradation capacity confirmed that NA can effectively contain the plume.BTEX-degrading bacteria appeared in groundwater via PCR/nucleotide sequence analyses.

  20. Vertically Discontinuous Seismic Signatures From Continuous Thermochemical Plumes

    NASA Astrophysics Data System (ADS)

    Harris, A. C.; Kincaid, C.; Savage, B.

    2008-12-01

    To interpret seismic signatures associated with mantle upwellings, we must understand the distribution of thermochemical heterogeneities within mantle plumes. Thermochemical heterogeneities are expected to arise within plumes by the incorporation of subducted lithosphere (Eclogite and Harzburgite) that has reached the plume source region (thermal boundary layers in the mantle). We analyze laboratory experiments in conjunction with seismic velocity models to predict the seismic signature of thermochemical plumes. Laboratory experiments are fully three-dimensional and use glucose syrup (Rayleigh number: 106) to model the mantle and a two-layer subducted lithosphere, where composition (viscosity and density) is controlled by water content. Experiments show heterogeneous upwellings with variations in both temperature and composition that are more complex than predicted in previous plume models. Spatial distributions for temperature and composition in representative, repeatable types of thermochemical upwellings are tracked through time, scaled to mantle values and used to calculate predicted seismic velocities. Apparent seismic velocity signals are estimated for patterns in thermochemical heterogeneity with length scales ranging from 1 to 300 km and excess temperatures from 50 to 300°C. Results show that if plumes are purely thermal they can be identified in the usual way, by slow velocities. However, if plumes are a mixture of compositions, as predicted by laboratory models, their velocity structure is more complex. An Ecolgite lens within a plume at ~300km depth with an excess temperature of 250°C can have the same velocity as regular mantle with no excess temperature. A Harzburgite lobe of a plume head (up to half of the plume volume) at 300km depth with an excess temperature of 225°C can have the same Vs as regular mantle with no excess temperature, but can only mask up to 55°C in Vp. Spatial variations in temperature control velocity structure above 300km

  1. Compositional variation in aging volcanic plumes - Analysis of gaseous SO2, CO2 and halogen species in volcanic emissions using an Unmanned Aerial Vehicle (UAV).

    NASA Astrophysics Data System (ADS)

    Rüdiger, Julian; Lukas, Tirpitz; Bobrowski, Nicole; Gutmann, Alexandra; Liotta, Marcello; de Moor, Maarten; Hoffmann, Thorsten

    2017-04-01

    Volcanoes are a large source for several reactive atmospheric trace gases including sulfur and halogen containing species. The detailed understanding of volcanic plume chemistry is needed to draw information from gas measurements on subsurface processes. This knowledge is essential for using gas measurements as a monitoring tool for volcanic activity. The reactive bromine species bromine monoxide (BrO) is of particular interest, because BrO as well as SO2 are readily measurable from safe distance by spectroscopic remote sensing techniques. BrO is not directly emitted, but is formed in the plume by a multiphase reaction mechanism. The abundance of BrO changes as a function of the distance from the vent as well as the spatial position in the plume. The precursor substance for the formation of BrO is HBr with Br2as an intermediate product. In this study we present the application of a UAV as a carrier for a remote-controlled sampling system for halogen species (Br2, HBr, BrCl, etc), based on the gas diffusion denuder technique, which allows speciation and enrichment by selective organic reactions. For the analysis of gaseous SO2 and CO2 an in-situ gas monitoring system was additionally mounted. This setup was deployed into the gas plumes of Stromboli Volcano (Italy), Masaya Volcano (Nicaragua) and Turrialba Volcano (Costa Rica) in 2016, to investigate the halogen chemistry at distant locations in the plume further downwind to the emission source, which are in most cases not accessible by other approaches. Flights into the plume were conducted with ascents of up to 1000 m. From telemetrically transmitted SO2 mixing ratios, areas of dense plume where localized to keep the UAV stationary for up to 10 minutes of sampling time. Additionally, ground based samples were taken at the crater rim (at Masaya and Turrialba) using alkaline traps, denuder and gas sensors for comparison with airborne-collected data. Herein we will present time and spatial resolved gas mixing ratio

  2. Shuttle active thermal control system development testing. Volume 6: Water ejector plume tests

    NASA Technical Reports Server (NTRS)

    Mcginnis, F. K.; Summerhays, R. M.

    1973-01-01

    Results are given of vacuum testing of nozzles designed to eject water vapor away from the space shuttle to prevent contamination of the spacecraft surfaces and payload. The water vapor is generated by an active cooling system which evaporates excess fuel cell water to supplement a modular radiator system (MRS). The complete heat rejection system including the MRS, flash evaporator or sublimator and nozzle were first tested to demonstrate the system operational characteristics. The plume tests were performed in two phases and the objectives of this test series were: (1) to determine the effectiveness of a supersonic nozzle and a plugged nozzle in minimizing impingement upon the spacecraft of water vapor exhausted by an active device (flash evaporator or sublimator); and (2) to obtain basic data on the flow fields of exhaust plumes generated by these active devices, both with and without nozzles installed.

  3. Evolution of North Atlantic Passive Margins Controlled by the Iceland Mantle Plume

    NASA Astrophysics Data System (ADS)

    Parnell-Turner, R. E.; White, N. J.; Henstock, T.; Murton, B. J.; Jones, S. M.

    2015-12-01

    Evolution of North Atlantic passive margins has been profoundly influenced by the Iceland mantle plume over the past 60 Ma. Residual depth anomalies of oceanic lithosphere, long wavelength gravity anomalies and seismic tomographic models show that upwelling mantle material extends from Baffin Bay to Western Norway. At fringing passive margins such as Northwest Scotland, there is evidence for present-day dynamic support of the crust. The Iceland plume is bisected by the Reykjanes Ridge ridge, which acts as a tape-recorder of the temporal variability of the plume. We present regional seismic reflection profiles that traverse the oceanic basin between northwest Europe and Greenland. A diachronous pattern of V-shaped ridges and troughs are imaged beneath marine sediments, revealing a complete record of transient periodicity that can be traced continuously back to ~55 Myrs. This periodicity increases from ~3 to ~8 Ma with clear evidence for minor, but systematic, asymmetric crustal accretion. V-shaped ridges grow with time and reflect small (5-30°C) changes in mantle temperature, consistent with episodic generation of hot solitary waves triggered by growth of thermal boundary layer instabilities within the mantle. Our continuous record of convective activity suggests that the otherwise uniform thermal subsidence of sedimentary basins, which fringe the North Atlantic Ocean, has been punctuated by periods of variable dynamic topography. This record can explain a set of diverse observations from the geologic record. Paleogene unconformities in the Faroe-Shetland Basin, the punctuated deposition of contourite drifts and variations in deep-water current strength can all be explained by transient mantle plume behavior. These signals of convective activity should lead to improved insights into the fluid dynamics of the mantle, and into the evolution of volcanic passive margins.

  4. Multi-sensor satellite monitoring of ash and SO2 volcanic plume in support to aviation control

    NASA Astrophysics Data System (ADS)

    Brenot, Hugues; Theys, Nicolas; Clarisse, Lieven; van Geffen, Jos; van Gent, Jeroen; Van Roozendael, Michel; van der A, Ronald; Hurtmans, Daniel; Coheur, Pierre-Francois; Clerbaux, Cathy; Valks, Pieter; Hedelt, Pascal; Prata, Fred; Rasson, Olivier; Sievers, Klaus; Zehner, Claus

    2014-05-01

    The 'Support to Aviation Control Service' (SACS; http://sacs.aeronomie.be) is an ESA-funded project hosted by the Belgian Institute for Space Aeronomy since 2007. The service provides near real-time (NRT) global volcanic ash and SO2 observations, as well as notifications in case of volcanic eruptions (success rate >95% for ash and SO2). SACS is based on the combined use of UV-visible (OMI, GOME-2 MetOp-A, GOME-2 MetOp-B) and infrared (AIRS, IASI MetOp-A, IASI MetOp-B) satellite instruments. The SACS service is primarily designed to support the Volcanic Ash Advisory Centers (VAACs) in their mandate to gather information on volcanic clouds and give advice to airline and air traffic control organisations. SACS also serves other users that subscribe to the service, in particular local volcano observatories, research scientists and airliner pilots. When a volcanic eruption is detected, SACS issues a warning that takes the form of a notification sent by e-mail to users. The SACS notification points to a dedicated web page where all relevant information is available and can be visualised with user-friendly tools. Information about the volcanic plume height from GOME-2 (MetOp-A and MetOp-B) are also available. The strength of a multi-sensor approach relies in the use of satellite data with different overpasses times, minimising the time-lag for detection and enhancing the reliability of such alerts. This presentation will give an overview of the SACS service, and of the different techniques used to detect volcanic plumes (ash, SO2 and plume height). It will also highlight the strengths and limitations of the service and measurements, and some perspectives.

  5. Factors controlling pollutant plume length downwind of major roadways in nocturnal surface inversions

    NASA Astrophysics Data System (ADS)

    Choi, W.; Winer, A. M.; Paulson, S. E.

    2013-09-01

    A curve fit method using a Gaussian dispersion model solution was successfully applied to obtain both dispersion coefficients and a particle number emission factor (PNEF) directly from ultrafine particle (UFP) concentration profiles observed downwind of major roadways in California's South Coast Air Basin (SoCAB). The Briggs' formulation for the vertical dispersion parameter σz was adopted in this study due to its better performance in describing the observed profiles compared to other formulations examined. The two dispersion coefficients in Briggs' formulation, α and β, ranged from 0.02 to 0.07 and from -0.5 × 10-3 to 2.8 × 10-3, respectively, for the four freeway transects studied and are significantly different for freeways passing over vs. under the street on which measurements of the freeway plume were made. These ranges are wider than literature values for α and β under stable conditions. The dispersion coefficients derived from observations showed strong correlations with both surface meteorology (wind speed/direction, temperature, and air stability) and differences in concentrations between the background and plume peak. The relationships were applied to predict freeway plume transport using a multivariate regression, and produced excellent agreement with observed UFP concentration profiles. The mean PNEF for a mixed vehicle fleet on the four freeways was estimated as 1.2 × 1014 particles mi-1 vehicle-1, which is about 15% of the value estimated in 2001 for the I-405 freeway, implying significant reductions in UFP emissions over the past decade in the SoCAB.

  6. Factors controlling pollutant plume length downwind of major roadways in nocturnal surface inversions

    NASA Astrophysics Data System (ADS)

    Choi, W.; Winer, A. M.; Paulson, S. E.

    2014-07-01

    A fitting method using a semi-empirical Gaussian dispersion model solution was successfully applied to obtain both dispersion coefficients and a particle number emission factor (PNEF) directly from ultrafine particle (UFP; particles smaller than <0.1 μm in diameter) concentration profiles observed downwind of major roadways in California's South Coast Air Basin (SoCAB). The effective Briggs' formulation for the vertical dispersion parameter σz was adopted in this study due to its better performance in describing the observed profiles compared to other formulations examined. The two dispersion coefficients in Briggs' formulation, α and β, ranged from 0.02 to 0.07 and from -0.5 × 10-3 to 2.8 × 10-3, respectively, for the four freeway transects studied and are significantly different for freeways passing over vs. under the street on which measurements of the freeway plume were made. These ranges are wider than literature values for α and β under stable conditions. The dispersion coefficients derived from observations showed strong correlations with both surface meteorology (wind speed/direction, temperature, and air stability) and differences in concentrations between the background and plume peak. The relationships were applied to predict freeway plume transport using a multivariate regression, and produced excellent agreement with observed UFP concentration profiles. The mean PNEF for a mixed vehicle fleet on the four freeways was estimated as 7.5 × 1013 particles km-1 vehicle-1, which is about 15% of the value estimated in 2001 for the I-405 freeway, implying significant reductions in UFP emissions over the past decade in the SoCAB.

  7. Tvashtar's Plume

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This dramatic image of Io was taken by the Long Range Reconnaissance Imager (LORRI) on New Horizons at 11:04 Universal Time on February 28, 2007, just about 5 hours after the spacecraft's closest approach to Jupiter. The distance to Io was 2.5 million kilometers (1.5 million miles) and the image is centered at 85 degrees west longitude. At this distance, one LORRI pixel subtends 12 kilometers (7.4 miles) on Io.

    This processed image provides the best view yet of the enormous 290-kilometer (180-mile) high plume from the volcano Tvashtar, in the 11 o'clock direction near Io's north pole. The plume was first seen by the Hubble Space Telescope two weeks ago and then by New Horizons on February 26; this image is clearer than the February 26 image because Io was closer to the spacecraft, the plume was more backlit by the Sun, and a longer exposure time (75 milliseconds versus 20 milliseconds) was used. Io's dayside was deliberately overexposed in this picture to image the faint plumes, and the long exposure also provided an excellent view of Io's night side, illuminated by Jupiter. The remarkable filamentary structure in the Tvashtar plume is similar to details glimpsed faintly in 1979 Voyager images of a similar plume produced by Io's volcano Pele. However, no previous image by any spacecraft has shown these mysterious structures so clearly.

    The image also shows the much smaller symmetrical fountain of the plume, about 60 kilometers (or 40 miles) high, from the Prometheus volcano in the 9 o'clock direction. The top of a third volcanic plume, from the volcano Masubi, erupts high enough to catch the setting Sun on the night side near the bottom of the image, appearing as an irregular bright patch against Io's Jupiter-lit surface. Several Everest-sized mountains are highlighted by the setting Sun along the terminator, the line between day and night.

    This is the last of a handful of LORRI images that New Horizons is sending 'home' during its busy close

  8. Tvashtar's Plume

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This dramatic image of Io was taken by the Long Range Reconnaissance Imager (LORRI) on New Horizons at 11:04 Universal Time on February 28, 2007, just about 5 hours after the spacecraft's closest approach to Jupiter. The distance to Io was 2.5 million kilometers (1.5 million miles) and the image is centered at 85 degrees west longitude. At this distance, one LORRI pixel subtends 12 kilometers (7.4 miles) on Io.

    This processed image provides the best view yet of the enormous 290-kilometer (180-mile) high plume from the volcano Tvashtar, in the 11 o'clock direction near Io's north pole. The plume was first seen by the Hubble Space Telescope two weeks ago and then by New Horizons on February 26; this image is clearer than the February 26 image because Io was closer to the spacecraft, the plume was more backlit by the Sun, and a longer exposure time (75 milliseconds versus 20 milliseconds) was used. Io's dayside was deliberately overexposed in this picture to image the faint plumes, and the long exposure also provided an excellent view of Io's night side, illuminated by Jupiter. The remarkable filamentary structure in the Tvashtar plume is similar to details glimpsed faintly in 1979 Voyager images of a similar plume produced by Io's volcano Pele. However, no previous image by any spacecraft has shown these mysterious structures so clearly.

    The image also shows the much smaller symmetrical fountain of the plume, about 60 kilometers (or 40 miles) high, from the Prometheus volcano in the 9 o'clock direction. The top of a third volcanic plume, from the volcano Masubi, erupts high enough to catch the setting Sun on the night side near the bottom of the image, appearing as an irregular bright patch against Io's Jupiter-lit surface. Several Everest-sized mountains are highlighted by the setting Sun along the terminator, the line between day and night.

    This is the last of a handful of LORRI images that New Horizons is sending 'home' during its busy close

  9. Two views of Hawaiian plume structure

    NASA Astrophysics Data System (ADS)

    Hofmann, Albrecht W.; Farnetani, Cinzia G.

    2013-12-01

    Fundamentally contradictory interpretations of the isotopic compositions of Hawaiian basalts persist, even among authors who agree that the Hawaiian hotspot is caused by a deep-mantle plume. One view holds that the regional isotopic pattern of the volcanoes reflects large-scale heterogeneities in the basal thermal boundary layer of the mantle. These are drawn into the rising plume conduit, where they are vertically stretched and ultimately sampled by volcanoes. The alternative view is that the plume resembles a "uniformly heterogeneous plum pudding," with fertile plums of pyroxenite and/or enriched peridotite scattered in a matrix of more refractory peridotite. In a rising plume, the plums melt before the matrix, and the final melt composition is controlled significantly by the bulk melt fraction. Here we show that the uniformly heterogeneous plum pudding model is inconsistent with several geochemical observations: (1) the relative melt fractions inferred from La/Yb ratios in shield-stage basalts of the two parallel (Kea- and Loa-) volcanic chains, (2) the systematic Pb-isotopic differences between the chains, and the absence of such differences between shield and postshield phases, (3) the systematic shift to uniformly depleted Nd-isotopic compositions during rejuvenated volcanism. We extend our previous numerical simulation to the low melt production rates calculated far downstream (200-400 km) from shield volcanism. Part of these melts, feeding rejuvenated volcanism, are formed at pressures of ˜5 GPa in the previously unmelted underside of the plume, from material that originally constituted the uppermost part of the thermal boundary layer at the base of the mantle.

  10. Plume flowfield analysis of the shuttle primary Reaction Control System (RCS) rocket engine

    NASA Technical Reports Server (NTRS)

    Hueser, J. E.; Brock, F. J.

    1990-01-01

    A solution was generated for the physical properties of the Shuttle RCS 4000 N (900 lb) rocket engine exhaust plume flowfield. The modeled exhaust gas consists of the five most abundant molecular species, H2, N2, H2O, CO, and CO2. The solution is for a bare RCS engine firing into a vacuum; the only additional hardware surface in the flowfield is a cylinder (=engine mount) which coincides with the nozzle lip outer corner at X = 0, extends to the flowfield outer boundary at X = -137 m and is coaxial with the negative symmetry axis. Continuum gas dynamic methods and the Direct Simulation Monte Carlo (DSMC) method were combined in an iterative procedure to produce a selfconsistent solution. Continuum methods were used in the RCS nozzle and in the plume as far as the P = 0.03 breakdown contour; the DSMC method was used downstream of this continuum flow boundary. The DSMC flowfield extends beyond 100 m from the nozzle exit and thus the solution includes the farfield flow properties, but substantial information is developed on lip flow dynamics and thus results are also presented for the flow properties in the vicinity of the nozzle lip.

  11. Where Plumes Live

    NASA Astrophysics Data System (ADS)

    King, S. D.

    2004-12-01

    From the perspective of fluid dynamics, `Plumes or not?' might be the wrong question. Let me begin by defining a few terms. Plume with a `P' is the well-known thermal structure with thin (order 100 km) tail and large, bulbous head that originates at the core-mantle boundary. The thin tail/large, bulbous-head morphology has been generated in a number of laboratory and numerical experiments. It can be seen, for example, on the cover of the famous fluid dynamics text by Batchelor. There is a clearly-defined range of parameters for which this structure is the preferred solution for instabilities arising from a bottom boundary layer in a convecting fluid. For example, a strong temperature-dependent rheology is needed. By contrast, plume with a `p' is any cylindrical or quasi-cylindrical instability originating from a thermal (or thermo-chemical) boundary layer. In fluid dynamics plume is sometimes used interchangeable with jet. Unless there is a very small temperature drop across the core-mantle boundary or a rather remarkable balance between temperature and composition at the base of the mantle, there are almost certainly plumes. (Note the little p.) Are these plumes the thermal structures with thin (order 100 km) tails and large bulbous heads or could they be broad, hot regions such as the degree 2 pattern seen in global seismic tomography images of the lower mantle, or the disconnected droplets seen in chaotic convection? To study this question, I will present a sequence of numerical `experiments' that illustrate the morphology of instabilities from a basal thermal boundary layer, i.e., plumes. Some of the aspects I will present include: spherical geometry, temperature-and pressure-dependence of rheology, internal heating, pressure-dependent coefficient of thermal expansion, variable coefficient of thermal diffusivity, phase transformations, and compositional layering at the base of the mantle. The goal is to map out the parameters and conditions where Plumes live

  12. Compositional Controls on Melt Polymerization

    NASA Astrophysics Data System (ADS)

    Brugger, C.; Hammer, J.

    2005-12-01

    The structure and rheology of silicate melts are strongly controlled by composition, namely the concentrations of network-forming and -modifying cations. Melt viscosity is implicated in kinetic theories of phase transformations as a proxy for component mobility, which partly controls rates of crystal and bubble nucleation and growth. To anticipate reaction kinetics in magmas and focus experimental work on key variables, compositional controls on melt structure are systematically investigated using NBO/T (Mysen, 1988), the ratio of non-bridging oxygens to tetrahedrally coordinated cations. Silicon, ferric iron, and aluminum are network-formers, whereas alkalis and divalent cations are network-modifiers unless needed to charge-balance trivalent cations in tetrahedral coordination. NBO/T calculations are performed over 4D composition space (alkalis, silica, divalent and trivalent cations), in which 3 components are varied independently, creating a cube. We assess the effects of individual components using slices through the cube contoured for NBO/T. Ratios are also calculated for naturally occurring liquids and MELTS-generated liquid lines of descent derived from basalts with similar silica contents but varying in alkalis. Naturally occurring melts are highly polymerized (NBO/T of 0-1) compared to silicate minerals (0-4). Calculations show that replacing network-modifiers with network-formers decreases NBO/T; conversely, replacing formers with modifiers increases the ratio. However, polymerization increases when alumina replaces silica or when alkalis replace divalent cations. Natural alkali-rich melts tend to have fewer divalent cations than alkali-poor melts at similar silica contents, thus they are more polymerized and have higher viscosities. Contrary to common perception, the lower viscosities of highly differentiated alkalic melts (e.g. trachytes, phonolites) compared to silica-rich rhyolites are attributed to lower silica rather than greater alkalis. In fact

  13. Evaluation of diesel fleet emissions and control policies from plume chasing measurements of on-road vehicles

    NASA Astrophysics Data System (ADS)

    Lau, Chui Fong; Rakowska, Agata; Townsend, Thomas; Brimblecombe, Peter; Chan, Tat Leung; Yam, Yat Shing; Močnik, Griša; Ning, Zhi

    2015-12-01

    Vehicle emissions are an important source of urban air pollution. Diesel fuelled vehicles, although constituting a relatively small fraction of fleet population in many cities, are significant contributors to the emission inventory due to their often long mileage for goods and public transport. Recent classification of diesel exhaust as carcinogenic by the World Health Organization also raises attention to more stringent control of diesel emissions to protect public health. Although various mandatory and voluntary based emission control measures have been implemented in Hong Kong, there have been few investigations to evaluate if the fleet emission characteristics have met desired emission reduction objectives and if adoption of an Inspection/Maintenance (I/M) programme has been effective in achieving these objectives. The limitations are partially due to the lack of cost-effective approaches for the large scale characterisation of fleet based emissions to assess the effectiveness of control measures and policy. This study has used a plume chasing method to collect a large amount of on-road vehicle emission data of Hong Kong highways and a detailed analysis was carried out to provide a quantitative evaluation of the emission characteristics in terms of the role of high and super-emitters in total emission reduction, impact of after-treatment on the multi-pollutants reduction strategy and the trend of NO2 emissions with newer emission standards. The study revealed that not all the high-emitters are from those vehicles of older Euro emission standards. Meanwhile, there is clear evidence that high-emitters for one pollutant may not be a high-emitter for another pollutant. Multi-pollutant control strategy needs to be considered in the enactment of the emission control policy which requires more comprehensive retrofitting technological solutions and matching I/M programme to ensure the proper maintenance of fleets. The plume chasing approach used in this study also

  14. Automated ablation of dental composite using an IR pulsed laser coupled to a plume emission spectral feedback system.

    PubMed

    Jang, Andrew T; Chan, Kenneth H; Fried, Daniel

    2017-09-01

    The purpose of this study is to assemble a laser system for the selective removal of dental composite from tooth surfaces, that is feasible for clinical use incorporating a spectral feedback system, a scanning system, articulating arm and a clinical hand-piece, and evaluate the performance of that system on extracted teeth. Ten extracted teeth were collected and small fillings were placed on the occlusal surface of each tooth. A clinical system featuring a CO2 laser operating at 50 Hz and spectral optical feedback was used to remove the composite. Removal was confirmed using a cross polarized optical coherence tomography (CP-OCT) system designed for clinical use. The system was capable of rapidly removing composite from small preparations on tooth occlusal surfaces with a mean loss of enamel of less than 20 μm. We have demonstrated that spectral feedback can be successfully employed in an automated system for composite removal by incorporating dual photodiodes and a galvanometer controlled CO2 laser. Additionally, the use of registered OCT images presents as a viable method for volumetric benchmarking. Overall, this study represents the first implementation of spectral feedback into a clinical hand-piece and serves as a benchmark for a future clinical study. Lasers Surg. Med. 49:658-665, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  15. Evaluation of Visible Plumes.

    ERIC Educational Resources Information Center

    Brennan, Thomas

    Developed for presentation at the 12th Conference on Methods in Air Pollution and Industrial Hygiene Studies, University of Southern California, April, 1971, this outline discusses plumes with contaminants that are visible to the naked eye. Information covers: (1) history of air pollution control regulations, (2) need for methods of evaluating…

  16. Evaluation of Visible Plumes.

    ERIC Educational Resources Information Center

    Brennan, Thomas

    Developed for presentation at the 12th Conference on Methods in Air Pollution and Industrial Hygiene Studies, University of Southern California, April, 1971, this outline discusses plumes with contaminants that are visible to the naked eye. Information covers: (1) history of air pollution control regulations, (2) need for methods of evaluating…

  17. The chemical structure of the Hawaiian mantle plume.

    PubMed

    Ren, Zhong-Yuan; Ingle, Stephanie; Takahashi, Eiichi; Hirano, Naoto; Hirata, Takafumi

    2005-08-11

    The Hawaiian-Emperor volcanic island and seamount chain is usually attributed to a hot mantle plume, located beneath the Pacific lithosphere, that delivers material sourced from deep in the mantle to the surface. The shield volcanoes of the Hawaiian islands are distributed in two curvilinear, parallel trends (termed 'Kea' and 'Loa'), whose rocks are characterized by general geochemical differences. This has led to the proposition that Hawaiian volcanoes sample compositionally distinct, concentrically zoned, regions of the underlying mantle plume. Melt inclusions, or samples of local magma 'frozen' in olivine phenocrysts during crystallization, may record complexities of mantle sources, thereby providing better insight into the chemical structure of plumes. Here we report the discovery of both Kea- and Loa-like major and trace element compositions in olivine-hosted melt inclusions in individual, shield-stage Hawaiian volcanoes--even within single rock samples. We infer from these data that one mantle source component may dominate a single lava flow, but that the two mantle source components are consistently represented to some extent in all lavas, regardless of the specific geographic location of the volcano. We therefore suggest that the Hawaiian mantle plume is unlikely to be compositionally concentrically zoned. Instead, the observed chemical variation is probably controlled by the thermal structure of the plume.

  18. Influence of fuel sulfur on the composition of aircraft exhaust plumes: The experiments SULFUR 1-7

    NASA Astrophysics Data System (ADS)

    Schumann, U.; Arnold, F.; Busen, R.; Curtius, J.; Kärcher, B.; Kiendler, A.; Petzold, A.; Schlager, H.; Schröder, F.; Wohlfrom, K.-H.

    2002-08-01

    The series of SULFUR experiments was performed to determine the aerosol particle and contrail formation properties of aircraft exhaust plumes for different fuel sulfur contents (FSC, from 2 to 5500 μg/g), flight conditions, and aircraft (ATTAS, A310, A340, B707, B747, B737, DC8, DC10). This paper describes the experiments and summarizes the results obtained, including new results from SULFUR 7. The conversion fraction ɛ of fuel sulfur to sulfuric acid is measured in the range 0.34 to 4.5% for an older (Mk501) and 3.3 +/- 1.8% for a modern engine (CFM56-3B1). For low FSC, ɛ is considerably smaller than what is implied by the volume of volatile particles in the exhaust. For FSC >= 100 μg/g and ɛ as measured, sulfuric acid is the most important precursor of volatile aerosols formed in aircraft exhaust plumes of modern engines. The aerosol measured in the plumes of various aircraft and models suggests ɛ to vary between 0.5 and 10% depending on the engine and its state of operation. The number of particles emitted from various subsonic aircraft engines or formed in the exhaust plume per unit mass of burned fuel varies from 2 × 1014 to 3 × 1015 kg-1 for nonvolatile particles (mainly black carbon or soot) and is of order 2 × 1017 kg-1 for volatile particles >1.5 nm at plume ages of a few seconds. Chemiions (CIs) formed in kerosene combustion are found to be quite abundant and massive. CIs contain sulfur-bearing molecules and organic matter. The concentration of CIs at engine exit is nearly 109 cm-3. Positive and negative CIs are found with masses partially exceeding 8500 atomic mass units. The measured number of volatile particles cannot be explained with binary homogeneous nucleation theory but is strongly related to the number of CIs. The number of ice particles in young contrails is close to the number of soot particles at low FSC and increases with increasing FSC. Changes in soot particles and FSC have little impact on the threshold temperature for contrail

  19. Effect of In-Plume Aerosol Processing on the Efficacy of Marine Cloud Albedo Enhancement from Controlled Sea-Spray Injections

    NASA Astrophysics Data System (ADS)

    Stuart, G. S.; Stevens, R. G.; Spracklen, D. V.; Korhonen, H.; Pierce, J. R.

    2012-12-01

    The intentional enhancement of cloud albedo via controlled sea-spray injection from ships has been proposed as a possible method to control anthropogenic global warming (1); however, there remains significant uncertainty in the efficacy of this method due to uncertainties in aerosol and cloud microphysics. A major assumption used in multiple recent studies (2,3) is that all sea-spray was emitted uniformly into some oceanic grid boxes, and thus did not account for sub-grid aerosol microphysics within the sea-spray plumes. However, as a consequence of the fast sea-spray injection rates which are proposed, in the order of 10^17 1/s (1), particle concentrations in these plumes may be quite high and particle coagulation may significantly reduce the number of emitted particles and increase their average size. Therefore, it is possible that the emissions necessary to reach a desired cooling may be even larger than currently assumed. We explore the evolution of these sea-salt plumes using a multi-shelled Gaussian plume model with size-resolved aerosol coagulation. We determine how the final number and size of particles depends on the emission rate and size distribution of the emitted sea-spray plume and local atmospheric conditions, including wind speed and boundary-layer stability. Under the injection rates reported in (1) and typical marine conditions, we find that the number of aerosol particles is reduced by about 40%. This fraction decreases for decreasing emission rates or increasing wind speeds due to lower particle concentrations in the plume. Finally, we make suggestions for effective size-resolved emissions for use in climate models. (1) Salter, S. et al., Phil. Trans. R. Soc. A., 2008. (2) Korhonen, H. et al., Atmos. Chem. Phys., 10, 4133-4143, 2010. (3) Partanen, A.-I. et al., J. Geophys. Res., 117, D02203, 2012.

  20. Evaporation monitoring and composition control of alloy systems with widely differing vapor pressures

    SciTech Connect

    Anklam, T.M.; Berzins, L.V.; Braun, D.G.; Haynam, C.; McClelland, M.A.; Meier, T.

    1994-10-01

    Lawrence Livermore National Laboratory is developing sensors and controls to improve and extend electron beam materials processing technology to alloy systems with constituents of widely varying vapor pressure. The approach under development involves using tunable lasers to measure the density and composition of the vapor plume. A laser based vaporizer control system for vaporization of a uranium-iron alloy has been previously demonstrated in multi-hundred hour, high rate vaporization experiments at LLNL. This paper reviews the design and performance of the uranium vaporization sensor and control system and discusses the extension of the technology to monitoring of uranium vaporization. Data is presented from an experiment in which titanium wire was fed into a molten niobium pool. Laser data is compared to deposited film composition and film cross sections. Finally, the potential for using this technique for composition control in melting applications is discussed.

  1. Species separation in rocket exhaust plumes and analytic plume flow models

    NASA Astrophysics Data System (ADS)

    Koppenwallner, G.

    2001-08-01

    Species separation in the exhaust plume of control thrusters of satellites is of main importance for the contamination analysis. Contamination concerns mainly scientific instruments or sensitive surfaces.. In continuum fluid dynamics a multi- component gas mixture can be treated as mixture with mean properties and with a flow field independent composition. This basic feature of continuum flow ceases to be valid in the rarefied flow regimes. In this regime there are two main mechanism which cause a separation of species in the flow field. a. Strong velocity gradients or streamline curvature. Strong stream line curvatures with large centrifugal forces exist close to the nozzle throat of sonic free jets [Sherman] or at the nozzle lip. Heavy gas constituents will not be able to follow these strong stream line curvatures. b. Different thermal velocity or thermal diffusivity of heavy and light gas constituents The transition from continuum to free molecular plume expansion can approximately be described by the sudden freeze model of Bird. At the freezing point molecular collisions suddenly cease and the further expansion is given by the velocity vector of the individual molecules at this freezing point. As light molecules have a larger thermal speed c than the heavy ones their spreading potential is also higher. This mechanism will also produce an enrichment of the plume boundary with light molecules. The approaches to model species separation in exhaust plumes as result of the above mechanism will be reviewed. To gain more insight into the separation the following cases are analyzed in detail: [B ]The free molecular supersonic expansion from a freezing plane. □ The various analytic plume flow models and their capability to predict the lateral spreading at the plume boundary (e.g. Simmons, Boynton, Brook, DLR) □ DSMC test case calculations of single and two-species plumes with mass separation. (M. Ivanov, ITAM) Based on this analysis a new 3 region model for species

  2. Intraply Hybrid Composites Would Contain Control Strips

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Shiao, Chi-Yu

    1996-01-01

    "Smart" structural components with sensors and/or actuators distributed throughout their volumes made of intraply hybrid composite materials, according to proposal. Strips of hybrid control material interspersed with strips of ordinary (passive) composite material in some layers, providing distributed control capability. For example, near and far edges of plate bent upward by commanding bottom control strips to expand and simultaneously commanding upper control strips to contract.

  3. Plume-derived rare gases in 380 Ma carbonatites from the Kola region (Russia) and the argon isotopic composition in the deep mantle

    NASA Astrophysics Data System (ADS)

    Marty, Bernard; Tolstikhin, Igor; Kamensky, Igor L.; Nivin, Valentin; Balaganskaya, Elena; Zimmermann, Jean-Louis

    1998-12-01

    * ratios are close to values expected for radiogenic production and accumulation in the mantle source. It may rather represent a characteristic of the plume source. The isotope composition of light noble gases in samples from ultrabasic-alkaline rocks of the Kola Peninsula, and associated carbonatites, indicate a contribution of material with lower time-integrated (U + Th)/( 3He, 22Ne) and ( 40K/ 36Ar) ratios than those in the asthenospheric upper mantle, the subcontinental lithosphere, and the continental crust. The location of such material is likely to be below the convective mantle supplying MORB magmas, and reflects the contribution of a plume source material to Kola carbonatitic magmatism. These data support models which advocate a structure of the Earth heterogeneous in its refractory/volatile content.

  4. The planet beyond the plume hypothesis

    NASA Astrophysics Data System (ADS)

    Smith, Alan D.; Lewis, Charles

    1999-12-01

    Acceptance of the theory of plate tectonics was accompanied by the rise of the mantle plume/hotspot concept which has come to dominate geodynamics from its use both as an explanation for the origin of intraplate volcanism and as a reference frame for plate motions. However, even with a large degree of flexibility permitted in plume composition, temperature, size, and depth of origin, adoption of any limited number of hotspots means the plume model cannot account for all occurrences of the type of volcanism it was devised to explain. While scientific protocol would normally demand that an alternative explanation be sought, there have been few challenges to "plume theory" on account of a series of intricate controls set up by the plume model which makes plumes seem to be an essential feature of the Earth. The hotspot frame acts not only as a reference but also controls plate tectonics. Accommodating plumes relegates mantle convection to a weak, sluggish effect such that basal drag appears as a minor, resisting force, with plates having to move themselves by boundary forces and continents having to be rifted by plumes. Correspondingly, the geochemical evolution of the mantle is controlled by the requirement to isolate subducted crust into plume sources which limits potential buffers on the composition of the MORB-source to plume- or lower mantle material. Crustal growth and Precambrian tectonics are controlled by interpretations of greenstone belts as oceanic plateaus generated by plumes. Challenges to any aspect of the plume model are thus liable to be dismissed unless a counter explanation is offered across the geodynamic spectrum influenced by "plume theory". Nonetheless, an alternative synthesis can be made based on longstanding petrological evidence for derivation of intraplate volcanism from volatile-bearing sources (wetspots) in conjunction with concepts dismissed for being incompatible or superfluous to "plume theory". In the alternative Earth, the sources for

  5. Pilot study of laser induced breakdown spectroscopy for tissue differentiation by monitoring the plume created during laser surgery — An approach on a feedback Laser control mechanism

    NASA Astrophysics Data System (ADS)

    Kanawade, Rajesh; Mehari, Fanuel; Knipfer, Christian; Rohde, Maximilian; Tangermann-Gerk, Katja; Schmidt, Michael; Stelzle, Florian

    2013-09-01

    This study focuses on tissue differentiation using 'Laser Induced Breakdown Spectroscopy' (LIBS) by monitoring the plasma plume created during laser surgery processes. This technique is aimed at controlling a laser surgery feedback system in real time. An Excimer laser (Ar-F 193 nm) was used for the ablation of tissue samples. Fat, muscle, nerve and skin tissue samples of bisected ex-vivo pig heads were prepared as test objects for the ablation procedure. A single fiber was used to collect emissions and deliver them to a spectrometer. The obtained LIBS spectra in the measured emissions were analyzed to determine each tissue type according to their chemical composition. The elements found in the samples and their emission spectra were in agreement with those described in literature. The collected LIBS spectra were analyzed to differentiate the tissues using statistical data analysis: Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Receiver Operating Characteristics (ROC). The obtained preliminary results suggest a successful differentiation of the target tissues with high sensitivity and specificity. The main goal of this study was to qualitatively identify tissue types during laser ablation, which will provide a real time feedback mechanism for clinical Laser surgery applications to significantly improve the accuracy and safety of laser surgery procedures.

  6. Plume Electrification: Laboratory and Numerical Experiments

    NASA Astrophysics Data System (ADS)

    Mendez, J. S.; Dufek, J.

    2012-12-01

    The spectacular lightning strokes observed during eruptions testify to the enormous potentials that can be generated within plumes. Related to the charging of individual ash particles, large electric fields and volcanic lightning have been observed at Eyjafjallajokull, Redoubt, and Chaiten, among other volcanoes. A number of mechanisms have been proposed for plume electrification, including triboelectric charging, charging from the brittle failure of rock, and charging due to phase change as material is carried aloft. While the overall electrification of the plume likely results from a combination of these processes, in the following work we focus on triboelectric charging—how a plume charges as particles collide with each other. To explore the role of triboelectric effects in plume charging we have conducted a number of small scale laboratory experiments similar to those designed by Forward et al (2009). Succinctly, the experiments consist of fluidizing an ash bed with nitrogen and monitoring the resulting currents induced by the moving particles. It is important to note that the reaction chamber only allows particle-particle interactions. The entire experimental setup is enclosed in a vacuum chamber, allowing us to carefully control the environment during experiments. Runs were carried out for different ash compositions, and driving pressures. We particularly focused on natural grain size distributions of ash and on quantifying not only the net charge but also the charging rate. Furthermore, we report on our progress to incorporate the collected data, namely charging rates, into a large eularian-eularian-lagrangian multiphase eruption dynamic model. Finally, to validate these results, we present our plans to deploy a large wireless sensor network of electrometers and magnetometers around active volcanoes to directly map the overhead E- and M-fields as an eruption occurs.

  7. Laser ablation of (GeSe2)100-x(Sb2Se3)x chalcogenide glasses: Influence of the target composition on the plasma plume dynamics

    NASA Astrophysics Data System (ADS)

    Irimiciuc, S.; Boidin, R.; Bulai, G.; Gurlui, S.; Nemec, P.; Nazabal, V.; Focsa, C.

    2017-10-01

    The dynamics and properties of the (GeSe2)100-x(Sb2Se3)x laser-induced plasma were investigated by fast ICCD imaging and space- and time-resolved optical emission spectroscopy (OES). The experiments were performed at 10-6 Torr background pressure, using the second harmonic (532 nm) of the Nd-YAG laser (10 ns, 10 Hz). For all investigated samples, the ICCD images revealed a splitting of the plasma plume into three components with distinct dynamics. Based on OES measurements, the first and second plasma structures were found to be represented mainly by ionic and neutral species, respectively. As the Sb2Se3 content of the samples increases, the three structures present an increase in their velocities. This dynamic variation and also the compositional dependence of the excitation temperature obtained from Boltzmann plots were correlated to the changes in the structure and electrical/thermal properties of the bulk chalcogenide glasses.

  8. Elastic flexure controls magma trajectories and explains the offset of primary volcanic activity upstream of mantle plume axis at la Réunion and Hawaii hotspot islands

    NASA Astrophysics Data System (ADS)

    Gerbault, Muriel; Fontaine, Fabrice J.; Rabinowicz, Michel; Bystricky, Misha

    2017-03-01

    Surface volcanism at la Réunion and Hawaii occurs with an offset of 150-180 km upstream to the plume axis with respect to the plate motion. This striking observation raises questions about the forcing of plume-lithosphere thermo-mechanical interactions on melt trajectories beneath these islands. Based on visco-elasto-plastic numerical models handled at kilometric resolution, we propose to explain this offset by the development of compressional stresses at the base of the lithosphere, that result from elastic plate bending above the upward load exerted by the plume head. This horizontal compression adopts a disc shape centered around the plume axis: (i) it is 20 km thick, (ii) it has a 150 km radius, (iii) it lays at the base of the elastic part of the lithosphere, i.e., around ∼50-70 km depth where the temperature varies from ∼600 °C to ∼750 °C, (iv) it lasts for 5 to 10 My in an oceanic plate of age greater than 70 My, and (vi) it is controlled by the visco-elastic relaxation time at ∼50-70 km depth. This period of time exceeds the time during which both the Somalian/East-African and Pacific plates drift over the Reunion and Hawaii plumes, respectively. This indicates that this basal compression is actually a persistent feature. It is inferred that the buoyant melts percolating in the plume head pond below this zone of compression and eventually spread laterally until the most compressive principal elastic stresses reverse to the vertical, i.e., ∼150 km away from the plume head. There, melts propagate through dikes upwards to ∼35 km depth, where the plate curvature reverses and ambient compression diminishes. This 30-35 km depth may thus host a magmatic reservoir where melts transported by dykes pond. Only after further magmatic differentiation can dykes resume their ascension up to the surface and begin forming a volcanic edifice. As the volcano grows because of melt accumulation at the top of the plate, the lithosphere is flexed downwards

  9. Fractures, not Plumes, Have Controlled Major Seamount Volcanism in the Pacific over 170 Million Years

    NASA Astrophysics Data System (ADS)

    Natland, J. H.; Winterer, E. L.

    2003-12-01

    shift laterally in response to whatever was occurring along its eastern spreading boundaries. A very consistent and strong stress regime therefore developed across the Pacific plate with a NNE direction of least principal stress. The change in stress orientation may have taken up to 10 million years, during an interval marked by little or no volcanic productivity at the western end of the Hawaiian chain. Since that time, the predominant alignment of both linear island chains and Puka Puka-type ridges, from the Kodiak-Bowie chain in the Gulf of Alaska to the Louisville Ridge south of the Antarctic convergence, has been orthogonal to this direction. Development of large-volume persistent chains and shorter small-volume chains indicates patterns of differential stress in the plate, variable fertility and geochemistry of the asthenosphere and/or shallow convective overturn of the asthenosphere rather than the action of mantle plumes of different sizes and depths of origin. Tapping of enriched mantle by widespread volcano clusters during the Mesozoic suggests the presence of a shallow asthenospheric source layer rather than multiple narrow conduits. (1) Hieronymus, C.F., and Bercovici, D. 2000. Earth Planet. Sci. Lett. 181, 539-554. (2) Davis, A.S., Gray, L.B., Clague, D.A., and Hein, J.R., 2002 Geochem. Geophys. Geosyst. 3: 10.1029/2001GC0000190, 1-28.

  10. Constraining the source of mantle plumes

    NASA Astrophysics Data System (ADS)

    Cagney, N.; Crameri, F.; Newsome, W. H.; Lithgow-Bertelloni, C.; Cotel, A.; Hart, S. R.; Whitehead, J. A.

    2016-02-01

    In order to link the geochemical signature of hot spot basalts to Earth's deep interior, it is first necessary to understand how plumes sample different regions of the mantle. Here, we investigate the relative amounts of deep and shallow mantle material that are entrained by an ascending plume and constrain its source region. The plumes are generated in a viscous syrup using an isolated heater for a range of Rayleigh numbers. The velocity fields are measured using stereoscopic Particle-Image Velocimetry, and the concept of the 'vortex ring bubble' is used to provide an objective definition of the plume geometry. Using this plume geometry, the plume composition can be analysed in terms of the proportion of material that has been entrained from different depths. We show that the plume composition can be well described using a simple empirical relationship, which depends only on a single parameter, the sampling coefficient, sc. High-sc plumes are composed of material which originated from very deep in the fluid domain, while low-sc plumes contain material entrained from a range of depths. The analysis is also used to show that the geometry of the plume can be described using a similarity solution, in agreement with previous studies. Finally, numerical simulations are used to vary both the Rayleigh number and viscosity contrast independently. The simulations allow us to predict the value of the sampling coefficient for mantle plumes; we find that as a plume reaches the lithosphere, 90% of its composition has been derived from the lowermost 260-750 km in the mantle, and negligible amounts are derived from the shallow half of the lower mantle. This result implies that isotope geochemistry cannot provide direct information about this unsampled region, and that the various known geochemical reservoirs must lie in the deepest few hundred kilometres of the mantle.

  11. Buckling of Chemical Wave Plumes

    NASA Astrophysics Data System (ADS)

    Rogers, Michael C.; Morris, Stephen W.

    2004-03-01

    Chemical wave fronts are found in many autocatalytic chemical reactions, such as the iodate oxidation of arsenous acid. In vertical capillary tubes, ascending chemical wave fronts show convective behavior when a dimensionless driving parameter S exceeds a critical value Sc ˜ 100. S ∝ a^3, where a is the radius of the tube. In the iodate arsenous-acid reaction, the density jump that drives convection is created by both the partial molal density decrease of the product solution and by thermal expansion due to the slight exothermicity of the reaction. We observed strongly supercritical ascending chemical wave plumes in vertical tubes with S 10^7. We report on the motion of these plumes in experiments where both the viscosity and the temperature of the reactant fluid are control parameters. We find experimentally that the background temperature of the reactant fluid has a significant influence on the behavior of the plumes. Above a critical temperature, plumes rise straight up the tube, whereas below this temperature, plumes go through an initial stage of buckling before they surrender to straight rising motion. The flow induced by the chemical plumes can be visualized using tracer particles. The buckling behavior of the plumes may arise from the Kelvin-Helmholtz instability, as in the case of a fluid jet descending through stratified surroundings [Pesci et al., Phys. Rev. E, 68, 056305 (2003)].

  12. Controlled Composition in the Teaching of Style.

    ERIC Educational Resources Information Center

    Miller, Edmund

    Intended for students in regular and advanced composition classes, each of the four controlled composition exercises presented in this paper aims at teaching writing style through carefully constructed short passages that concentrate on an isolated problem in style such as parallel structure, relative clauses, pseudo-relative clauses, and…

  13. Radiation Chemistry of Potential Europa Plumes

    NASA Astrophysics Data System (ADS)

    Gudipati, M. S.; Henderson, B. L.

    2014-12-01

    Recent detection of atomic hydrogen and atomic oxygen and their correlation to potential water plumes on Europa [Roth, Saur et al. 2014] invoked significant interest in further understanding of these potential/putative plumes on Europa. Unlike on Enceladus, Europa receives significant amount of electron and particle radiation. If the plumes come from trailing hemisphere and in the high radiation flux regions, then it is expected that the plume molecules be subjected to radiation processing. Our interest is to understand to what extent such radiation alterations occur and how they can be correlated to the plume original composition, whether organic or inorganic in nature. We will present laboratory studies [Henderson and Gudipati 2014] involving pulsed infrared laser ablation of ice that generates plumes similar to those observed on Enceladus [Hansen, Esposito et al. 2006; Hansen, Shemansky et al. 2011] and expected to be similar on Europa as a starting point; demonstrating the applicability of laser ablation to simulate plumes of Europa and Enceladus. We will present results from electron irradiation of these plumes to determine how organic and inorganic composition is altered due to radiation. Acknowledgments:This research was enabled through partial funding from NASA funding through Planetary Atmospheres, and the Europa Clipper Pre-Project. B.L.H. acknowledges funding from the NASA Postdoctoral Program for an NPP fellowship. Hansen, C. J., L. Esposito, et al. (2006). "Enceladus' water vapor plume." Science 311(5766): 1422-1425. Hansen, C. J., D. E. Shemansky, et al. (2011). "The composition and structure of the Enceladus plume." Geophysical Research Letters 38. Henderson, B. L. and M. S. Gudipati (2014). "Plume Composition and Evolution in Multicomponent Ices Using Resonant Two-Step Laser Ablation and Ionization Mass Spectrometry." The Journal of Physical Chemistry A 118(29): 5454-5463. Roth, L., J. Saur, et al. (2014). "Transient Water Vapor at Europa's South

  14. Orbital Maneuvering Vehicle (OMV) plume and plume effects study

    NASA Technical Reports Server (NTRS)

    Smith, Sheldon D.

    1991-01-01

    The objective was to characterize the Orbital Maneuvering Vehicle (OMV) propulsion and attitude control system engine exhaust plumes and predict the resultant plume impingement pressure, heat loads, forces, and moments. Detailed description is provided of the OMV gaseous nitrogen (GN2) thruster exhaust plume flow field characteristics calculated with the RAMP2 snd SFPGEN computer codes. Brief descriptions are included of the two models, GN2 thruster characteristics and RAMP2 input data files. The RAMP2 flow field could be recalculated by other organizations using the information presented. The GN2 flow field can be readily used by other organizations who are interested in GN2 plume induced environments which require local flow field properties which can be supplied using the SFPGEN GN2 model.

  15. ASSESSMENT OF PLUME DIVING

    EPA Science Inventory

    This presentation presents an assessment of plume diving. Observations included: vertical plume delineation at East Patchogue, NY showed BTEX and MTBE plumes sinking on either side of a gravel pit; Lake Druid TCE plume sank beneath unlined drainage ditch; and aquifer recharge/dis...

  16. Seawater subduction controls the heavy noble gas composition of the mantle.

    PubMed

    Holland, Greg; Ballentine, Chris J

    2006-05-11

    The relationship between solar volatiles and those now in the Earth's atmosphere and mantle reservoirs provides insight into the processes controlling the acquisition of volatiles during planetary accretion and their subsequent evolution. Whereas the light noble gases (helium and neon) in the Earth's mantle preserve a solar-like isotopic composition, heavy noble gases (argon, krypton and xenon) have an isotopic composition very similar to that of the modern atmosphere, with radiogenic and (in the case of xenon) solar contributions. Mantle noble gases in a magmatic CO2 natural gas field have been previously corrected for shallow atmosphere/groundwater and crustal additions. Here we analyse new data from this field and show that the elemental composition of non-radiogenic heavy noble gases in the mantle is remarkably similar to that of sea water. We challenge the popular concept of a noble gas 'subduction barrier'--the convecting mantle noble gas isotopic and elemental composition is explained by subduction of sediment and seawater-dominated pore fluids. This accounts for approximately 100% of the non-radiogenic argon and krypton and 80% of the xenon. Approximately 50% of the convecting mantle water concentration can then be explained by this mechanism. Enhanced recycling of subducted material to the mantle plume source region then accounts for the lower ratio of radiogenic to non-radiogenic heavy noble gas isotopes and higher water content of plume-derived basalts.

  17. Fuel compositions containing deposit control additives

    SciTech Connect

    Lilburn, J.E.

    1980-11-18

    Fuel compositions are provided which contain a deposit control additive. The deposit control additive is produced by reacting a hydrocarbylpoly(oxyalkylene) alcohol with excess phosgene and an excess amount of certain polyamines. The product comprises hydrocarbylpoly(oxyalkylene) ureylene carbamates.

  18. Nonlinear Optical Pulsed Control of Composite Metamaterials

    DTIC Science & Technology

    2011-10-07

    Final report for project entitled "Nonlinear optical pulsed control of composite metamaterials", under Grant no. AOARD - 094042 The stated...pump (control) radiation. 2. Study temporal pulse dynamics in order to optimize pump probe delays, intensities, carrier frequencies and the pulse ...nanostructures using simple time and cost effective lithographic technique termed as ‘Laser Interference Lithography’. Figure-1 below shows a

  19. JV Task 104 - Risk Reduction Using Innovative Vacuum-Enhanced Plume Controls

    SciTech Connect

    Jaroslav Solc; Barry Botnen

    2009-03-01

    The Energy & Environmental Research Center (EERC) conducted remediation of hydrocarbon-contaminated soils and groundwater at the Vining Oil site in Carrington, North Dakota. The primary technological synergies included (1) contaminant recovery using simultaneous operation of multiphase recovery and high-vacuum soil vapor extraction (SVE) and (2) vacuum-controlled air and ozone sparging on the periphery of an induced hydraulic and pneumatic depression. Final risk reduction steps included design and retrofit for the municipal well. The successful remediation effort resulted in the reduction of long-term health risks associated with rate-limited contaminant release within the capture zone for the municipal well and allowed for its reintegration into the water supply system. Contaminant recovery for the remediation period of September 2006 to June 2008 totaled over 12,653 lb (5,740 kg) of hydrocarbons, an equivalent to 2022 gallons (7653 l) of product. Integration of the air-sparging subsystem operated simultaneously with multiphase extraction and SVE systems resulted in accelerated volatile organic contaminant transport from the saturated zone and increased contaminants of concern recovery. Delivery of over 7.7 million ft{sup 3} of oxygen (219.8 thousand m{sup 3}) into the contaminated aquifer would translate into in situ biodegradation of 2007 kg (4424 lb) of benzene and provide for long term stimulation of the natural attenuation process.

  20. Active Volcanic Plumes on Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This color image, acquired during Galileo's ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon (see inset at upper right), erupting over a caldera (volcanic depression) named Pillan Patera after a South American god of thunder, fire and volcanoes. The plume seen by Galileo is 140 kilometers (86 miles) high and was also detected by the Hubble Space Telescope. The Galileo spacecraft will pass almost directly over Pillan Patera in 1999 at a range of only 600 kilometers (373 miles).

    The second plume, seen near the terminator (boundary between day and night), is called Prometheus after the Greek fire god (see inset at lower right). The shadow of the 75-kilometer (45- mile) high airborne plume can be seen extending to the right of the eruption vent. The vent is near the center of the bright and dark rings. Plumes on Io have a blue color, so the plume shadow is reddish. The Prometheus plume can be seen in every Galileo image with the appropriate geometry, as well as every such Voyager image acquired in 1979. It is possible that this plume has been continuously active for more than 18 years. In contrast, a plume has never been seen at Pillan Patera prior to the recent Galileo and Hubble Space Telescope images.

    North is toward the top of the picture. The resolution is about 6 kilometers (3.7 miles) per picture element. This composite uses images taken with the green, violet and near infrared filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. The images were obtained on June 28, 1997, at a range of more than 600,000 kilometers (372,000 miles).

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page

  1. Nutrient controls on new production in the Bodega Bay, California, coastal upwelling plume

    NASA Astrophysics Data System (ADS)

    Dugdale, R. C.; Wilkerson, F. P.; Hogue, V. E.; Marchi, A.

    2006-12-01

    A theoretical framework for the time-dependent processes leading to the high rates of new production in eastern boundary upwelling systems has been assembled from a series of past upwelling studies. As part of the CoOP WEST (Wind Events and Shelf Transport) study, new production in the Bodega Bay upwelling area and it's control by ambient nitrate and ammonium concentrations and the advective wind regime are described. Data and analyses are focused primarily on the WEST 2001 cruise (May-June 2001) when the two legs differed greatly in wind regimes but not nutrient concentrations. Elevated concentrations of ammonium in upwelled water with high nitrate were observed in both legs. Nitrate uptake by phytoplankton as a function of nitrate concentration was linear rather than Michaelis-Menten-like, modulated by inhibitory levels of ammonium, yielding coefficients that enable the specific nitrate uptake element of new production to be estimated from nutrient concentrations. The range of specific nitrate uptake rates for the two legs of WEST 2001 were similar, essentially a physiological response to nutrient conditions. However, the low "realization" of new production i.e. incorporation of biomass as particulate nitrogen that occurred in this system compared to the theoretical maximum possible was determined by the strong advective and turbulent conditions that dominated the second leg of the WEST 2001 study. These data are compared with other upwelling areas using a physiological shift-up model [Dugdale, R.C., Wilkerson, F.P., Morel, A. 1990. Realization of new production in coastal upwelling areas: a means to compare relative performance. Limnology and Oceanography 35, 822-829].

  2. Automated ablation of dental composite using an IR pulsed laser coupled to a plume emission spectral feedback system

    NASA Astrophysics Data System (ADS)

    Jang, Andrew T.; Chan, Kenneth H.; Fried, Daniel

    2017-02-01

    Dental composites are used as restorative materials for filling cavities, shaping, and covering teeth for esthetic purposes, and as adhesives. Dentists spend more time replacing existing restorations that fail than they do placing new restorations. Tooth colored restorations are difficult to differentiate from the surrounding tooth structure making them challenging to remove without damaging healthy tooth structure. Previous studies have demonstrated that CO2 lasers in conjunction with spectral feedback can be used to selectively remove composite from tooth surfaces. The purpose of this study is to assemble a system that is feasible for clinical use incorporating a spectral feedback system, a scanning system, articulating arm and a clinical handpiece and then evaluate the performance of that system on extracted teeth. In addition, the selectivity of composite removal was analyzed using a high-speed optical coherence tomography system that is suitable for clinical use. The system was capable of rapidly removing composite from small preparations on tooth occlusal surfaces with a mean loss of enamel of less than 20-μm.

  3. Effect of In-Plume Aerosol Processing on the Efficacy of Marine Cloud Albedo Enhancement from Controlled Sea-Spray Injections

    NASA Astrophysics Data System (ADS)

    Stevens, R. G.; Spracklen, D.; Korhonen, H.; Pierce, J. R.

    2010-12-01

    The intentional enhancement of cloud albedo via controlled sea-spray injection from ships has been suggested as a possible means to control anthropogenic global warming (1); however, there remains significant uncertainty in the efficacy of this method due to uncertainties in aerosol and cloud microphysics. Recent analysis showed that more sea-spray may be necessary than previously assumed to reach a desired cooling due to nonlinearities in the aerosol/cloud microphysics (2). A major assumption used in (2) is that all sea-spray was emitted uniformly into some oceanic grid boxes, and thus did not account for sub-grid aerosol microphysics within the sea-spray plumes. However, as a consequnce of the fast sea-spray injection rates which are proposed, in the order of 1x10^17 1/s (1), particle concentrations in these plumes may be quite high and particle coagulation may significantly reduce the number of emitted particles and increase their average size. Therefore, it is possible that the emissions necessary to reach a desired cooling may be even larger than currently assumed. We explore the processing of the freshly emitted sea-spray plumes in the Large-Eddy Simulation (LES)/Cloud Resolving Model (CRM) the System for Atmospheric Modelling (SAM, 3) with the online aerosol microphysics module TOMAS (4). We determine how the final number and size of particles (once well mixed with background air) depends on the emission rate and size distribution of the sea-spray plume and on the pre-existing aerosol concentrations and local atmospheric conditions. Finally, we make suggestions for effective size-resolved emissions for use in climate models. (1) Salter, S. et al., Phil. Trans. R. Soc. A., 2008. (2) Korhonen, H. et al., Atmos. Chem. Phys., 10, 4133-4143, 2010. (3) Khairoutdinov, M., and Randall, D.,. J. Atmos. Sci., 60, 607-625, 2003. (4) Pierce, J. and Adams, P., Atmos. Chem. Phys., 9, 1339-1356, 2009.

  4. Multiple Scale Studies to Understand Mass Transfer Controlled Uranium Migration in a Dynamic Groundwater Plume Influenced by Water Table Fluctuations (Invited)

    NASA Astrophysics Data System (ADS)

    Zachara, J. M.

    2009-12-01

    The 300 A uranium (U) plume at the U.S. DOE Hanford site shows complex seasonal behavior as a result of groundwater-surface water interaction. The plume, which is under regulatory mandated clean-up, has persisted far longer than anticipated and is inadequately described by previous modeling approaches. A field experimental site consisting of 37 wells has been installed within the plume to understand hydrologic and geochemical processes controlling: i.) U resupply to the groundwater, and ii.) U concentrations, migration velocities, and directions in the saturated zone. The site supports various field activities including high-volume saturated zone injections, and monitoring based experiments along hydrologic and geochemical gradients. A project goal is to develop a reactive transport simulator, based on geochemical retardation by kinetically controlled surface surface complexation, to forecast long term plume dynamics, quantify potential U fluxes to the nearby Columbia River, and evaluate the efficacy of proposed remediation strategies. A hierarchical characterization scheme involving laboratory measurements and studies of retrieved core materials, and field hydrologic and geophysical measurements of different kinds is being applied to develop site geostatistical models of hydrologic properties, U distribution, and kinetic and thermodynamic reaction parameters. This presentation will briefly summarize these various activities as background, with subsequent focus on multi-scale studies, measurements, and modeling of U mass transfer that is a dominant coupled process influencing the behavior of U at this site. Our approach to develop a field scale understanding of the roles of mass transfer from the particle to facies scale will be highlighted through discussion of key laboratory and field experimental results.

  5. Synchronisation control of composite chaotic systems

    NASA Astrophysics Data System (ADS)

    Zha, Jindao; Li, Chunbiao; Song, Bing; Hu, Wen

    2016-12-01

    Synchronisation conditions are studied for composite chaotic systems with complex compound structure and the signum function based on the theorem of zero-solution stability for a class of linear time-varying systems with countable discontinuous points. The synchronisation controller and its gain range are deduced according to the stability theorem, where the gain of the controller can speed synchronisation. Numerical simulation further proves the control theory and the validity of the synchronisation controller. The proposed controller can be widely applied in those chaotic systems with switch functions or other hybrid chaotic systems.

  6. Thermal Analysis on Plume Heating of the Main Engine on the Crew Exploration Vehicle Service Module

    NASA Technical Reports Server (NTRS)

    Wang, Xiao-Yen J.; Yuko, James R.

    2007-01-01

    The crew exploration vehicle (CEV) service module (SM) main engine plume heating is analyzed using multiple numerical tools. The chemical equilibrium compositions and applications (CEA) code is used to compute the flow field inside the engine nozzle. The plume expansion into ambient atmosphere is simulated using an axisymmetric space-time conservation element and solution element (CE/SE) Euler code, a computational fluid dynamics (CFD) software. The thermal analysis including both convection and radiation heat transfers from the hot gas inside the engine nozzle and gas radiation from the plume is performed using Thermal Desktop. Three SM configurations, Lockheed Martin (LM) designed 604, 605, and 606 configurations, are considered. Design of multilayer insulation (MLI) for the stowed solar arrays, which is subject to plume heating from the main engine, among the passive thermal control system (PTCS), are proposed and validated.

  7. Mantle plumes in the vicinity of subduction zones

    NASA Astrophysics Data System (ADS)

    Mériaux, C. A.; Mériaux, A.-S.; Schellart, W. P.; Duarte, J. C.; Duarte, S. S.; Chen, Z.

    2016-11-01

    We present three-dimensional deep-mantle laboratory models of a compositional plume within the vicinity of a buoyancy-driven subducting plate with a fixed trailing edge. We modelled front plumes (in the mantle wedge), rear plumes (beneath the subducting plate) and side plumes with slab/plume systems of buoyancy flux ratio spanning a range from 2 to 100 that overlaps the ratios in nature of 0.2-100. This study shows that 1) rising side and front plumes can be dragged over thousands of kilometres into the mantle wedge, 2) flattening of rear plumes in the trench-normal direction can be initiated 700 km away from the trench, and a plume material layer of lesser density and viscosity can ultimately almost entirely underlay a retreating slab after slab/plume impact, 3) while side and rear plumes are not tilted until they reach ∼600 km depth, front plumes can be tilted at increasing depths as their plume buoyancy is lessened, and rise at a slower rate when subjected to a slab-induced downwelling, 4) rear plumes whose buoyancy flux is close to that of a slab, can retard subduction until the slab is 600 km long, and 5) slab-plume interaction can lead to a diversity of spatial plume material distributions into the mantle wedge. We discuss natural slab/plume systems of the Cascadia/Bowie-Cobb, and Nazca/San Felix-Juan Fernandez systems on the basis of our experiments and each geodynamic context and assess the influence of slab downwelling at depths for the starting plumes of Java, Coral Sea and East Solomon. Overall, this study shows how slab/plume interactions can result in a variety of geological, geophysical and geochemical signatures.

  8. Evapotranspiration And Geochemical Controls On Groundwater Plumes At Arid Sites: Toward Innovative Alternate End-States For Uranium Processing And Tailings Facilities

    SciTech Connect

    Looney, Brian B.; Denham, Miles E.; Eddy-Dilek, Carol A.; Millings, Margaret R.; Kautsky, Mark

    2014-01-08

    Management of legacy tailings/waste and groundwater contamination are ongoing at the former uranium milling site in Tuba City AZ. The tailings have been consolidated and effectively isolated using an engineered cover system. For the existing groundwater plume, a system of recovery wells extracts contaminated groundwater for treatment using an advanced distillation process. The ten years of pump and treat (P&T) operations have had minimal impact on the contaminant plume – primarily due to geochemical and hydrological limits. A flow net analysis demonstrates that groundwater contamination beneath the former processing site flows in the uppermost portion of the aquifer and exits the groundwater as the plume transits into and beneath a lower terrace in the landscape. The evaluation indicates that contaminated water will not reach Moenkopi Wash, a locally important stream. Instead, shallow groundwater in arid settings such as Tuba City is transferred into the vadose zone and atmosphere via evaporation, transpiration and diffuse seepage. The dissolved constituents are projected to precipitate and accumulate as minerals such as calcite and gypsum in the deep vadose zone (near the capillary fringe), around the roots of phreatophyte plants, and near seeps. The natural hydrologic and geochemical controls common in arid environments such as Tuba City work together to limit the size of the groundwater plume, to naturally attenuate and detoxify groundwater contaminants, and to reduce risks to humans, livestock and the environment. The technical evaluation supports an alternative beneficial reuse (“brownfield”) scenario for Tuba City. This alternative approach would have low risks, similar to the current P&T scenario, but would eliminate the energy and expense associated with the active treatment and convert the former uranium processing site into a resource for future employment of local citizens and ongoing benefit to the Native American Nations.

  9. The Cocos and Carnegie Ridges: A Record of Long-term Galapagos Plume-Ridge Interaction

    NASA Astrophysics Data System (ADS)

    Harpp, K. S.; Wanless, V.; Hoernle, K.

    2001-12-01

    The present-day Galapagos Archipelago exhibits an astonishingly wide variety of geochemical compositions, from enriched, hotspot-like signatures in the west and south to MORB-like lavas in the central and northern regions. The distinctive spatial zonation has been attributed to a heterogeneous plume and its extensive interaction with the asthenosphere. One of the controversial questions about the Galapagos system is whether the geochemical zonation in the present-day archipelago is a long-term phenomenon due to inherent plume heterogeneity or only the recent result of short-lived mantle contamination. The aseismic Cocos and Carnegie Ridges record the last 20 Ma of plume activity as the Cocos and Nazca plates, respectively, have moved over the hotspot. During the 1999 PAGANINI expedition, we collected over 80 dredge samples from the ridges to explore the temporal variations of the Galapagos plume. Preliminary results suggested that lavas dredged off the west coast of Central America preserve the geochemical zonation observed in the Galapagos Archipelago today. Trace element determinations from dredge sites along the Cocos and Carnegie Ridges indicate, however, that the situation is (not surprisingly) more complex. Instead, the geochemical variations observed along the ridges may be controlled predominantly by the relative positions of the Galapagos plume and the Galapagos Spreading Center (GSC). The GSC has been migrating to the NE relative to the hotspot. For the oldest portions of the Cocos Ridge, the plume was located beneath the Nazca plate and did not interact with the GSC. Lavas produced during this time therefore represent pristine plume, with compositions more enriched than those of the present-day Galapagos; these are observed NE of Cocos Island. As the ridge migrates closer to the hotspot, plume-mid-ocean ridge interaction intensifies, resulting in the dilution of hotspot lavas by entrained, depleted asthenosphere. Consistently, younger lavas along the

  10. Plume-asthenosphere-lithosphere Interactions Within a Plume-fed Asthenosphere: Implications for Hawaii- and Iceland-type Plume-linked Topography, Melting and Geoid Anomalies

    NASA Astrophysics Data System (ADS)

    Shi, C.; Morgan, J. P.; Hasenclever, J.

    2010-12-01

    The competing view of the upper mantle is that the asthenosphere is the region where temperature and pressure conditions result in the lowest viscosity region of the mantle. We think the suboceanic asthenosphere exists for a different reason, that it is the “graveyard” for rising plumes of hotter-than-average mantle. This Plume-fed Asthenosphere (PFA) system could have significant effects on: 1) global mantle convection flow pattern as a decoupling mechanism and fast path between shallow and deep mantle, 2) dynamic topography and geoid anomalies through plume-asthenosphere-lithosphere interaction, and 3) dynamic relief at the base of a buoyant asthenosphere. In the past years we have presented observational evidence and a suite of 2D and 3D numerical experiments which suggest that in Earth’s mantle there exists a buoyant asthenosphere layer fed by upwelling in mantle plumes, and consumed by ridge upwelling and melt-extraction to make new compositional lithosphere, plate cooling to make new thermal lithosphere, and slab dragdown (Shi and Phipps Morgan, 2007-2009). Our PFA model may provide a possible explanation to the recent observations of underside reflections from a ~250-350km-deep reflector in ocean basins (Cao et al., 2010), the 200 degree hotter-than-underlying-mantle suboceanic asthenosphere (Cammarano and Romanowicz, 2007), and the “fast halo” seen in the recent PLUME seismic experiment (Wolfe et al., 2009). For this study, we study the effects of on- and off-axis deep-mantle plumes with thermal and compositional density and viscosity controlled by thermal and melt-extraction processes -- rather than only assuming that temperature controls density and an Arrhenius-type viscosity. The code we use is a parallel Matlab-based 3-D Finite Element code we have developed, which utilizes unstructured tetrahedral meshes, and which can handle large and abrupt (6 orders of magnitude) viscosity contrast. We will show the results of: 1) the necessary conditions

  11. Constraints on the noble gas composition of the Icelandic plume source by laser analyses of individual vesicles in the volcanic glass DICE 11

    NASA Astrophysics Data System (ADS)

    Colin, A. P.; Moreira, M. A.; Gautheron, C.; Burnard, P.

    2014-12-01

    Models of Earth's volatile acquisition and evolution attempt to reproduce the current noble gas abundances and isotopic composition of the mantle reservoirs. The volatile composition of the OIB reservoir - assumed to preserve a higher proportion of primordial noble gases than the degassed MORB reservoir - is a strong constraint for those models. However, the correct values of the neon and argon isotopic ratios in OIBs are still a subject of debate, because of the contamination of the samples by air-derived noble gases. Although there is no consensus on the origin of this contamination - is it empty vesicles or cracks in volcanic glasses filled with seawater; air dissolution in the magma at the timing of magma eruption; assimilation of oceanic crust in the magma chamber?- targeting directly with a laser the vesicle to analyse in volcanic glasses is an efficient way to reduce this contamination. Here we present analyses of individual vesicles of an Icelandic volcanic glass, DICE 11, that was extensively studied in the past by crushing pieces of the volcanic glass under vacuum, because it was considered to have a pure plume origin. The mm-sized sample was imaged tomographically with a 5μm resolution. For opening bubbles, we used a 193nm Excimer laser to avoid diffusion of noble gases by local heating. CO2 contents were estimated by pressure measurement in the laser cell using a sensitive manometer. We analysed He and Ar isotopes, plus 22Ne abundance on a Helix SFT mass-spectrometer. We also present new He, Ne and Ar compositions obtained by step crushing on similar samples (DICE 10 and DICE 11). 3He/4He isotopic ratios are homogeneous in all the vesicles and consistent with analyses by crushing, about 18Ra. Precise 40Ar/36Ar isotopic ratios were obtained on the largest vesicles only, due to high blank contribution to the smallest vesicles, and are about 9000, i.e. the highest values obtained by step-crushing. Considering that the Ar and He isotopic compositions

  12. A composite control scheme for 6DOF spacecraft formation control

    NASA Astrophysics Data System (ADS)

    Sun, Haibin; Li, Shihua; Fei, Shumin

    2011-09-01

    In this paper, a 6DOF spacecraft formation control problem is investigated via a composite control method, which consists of a feedback control law based on a finite time control technique and a feedforward compensator based on a nonlinear disturbance observer technique. The composite controller can guarantee that the closed-loop error system is globally asymptotically stable with respect to a set of two equilibria, that is, the 6DOF spacecraft can reach the desired formation. Simulation results are provided to demonstrate the effectiveness of the proposed method. The results show that the control performance of the proposed method in terms of both stabilization and disturbance rejection are considerably better than the traditional method.

  13. A plume beneath western Ethiopia!

    NASA Astrophysics Data System (ADS)

    Keranen, K. M.; Hariharan, A.; Alemayehu, S.; Ayele, A.; Bastow, I. D.

    2016-12-01

    Body-wave tomography, receiver functions, and measurements of seismic anisotropy reveal a profound impact of magmatic systems on the crust and upper mantle beneath the Ethiopian highlands. Finite-frequency tomography (using the method of Schmandt et al., 2010) reveals a low-velocity conduit-like structure in the upper mantle beneath the Ethiopian highlands. We interpret the anomaly as a probable plume stem and the likely source of the Ethiopian flood basalts. This "plume" is located 300-km west of the actively-extending Main Ethiopian Rift (MER) and 700-km southwest of the suggested Afar plume. Within the lithosphere, the anomaly separates into multiple fingers, rising beneath previously enigmatic regions of off-rift Quaternary faulting and volcanism far west of the MER. One finger underlies the Lake Tana graben, within the highlands 400-km from the rift, and another finger rises beneath a lineament of faulting and volcanism known as the Yerer-Tullu Wellel lineament (YTVL). The YTVL runs along the southern edge of the Ethiopian highlands, between the interpreted plume source and the MER. We suggest that the Quaternary volcanism in the YTVL and the Tana regions is related to melt associated with these lithospheric velocity anomalies. At shallower depths, receiver function estimates indicate a concentrated zone of 40-45 km thick crust near the Lake Tana anomaly, thicker than the 30-35 km thick crust elsewhere beneath the Ethiopian Plateau. This crustal thickening, likely from magmatic underplating, and the recent Quaternary volcanism occur within the projected borders of a northwest-southeast trending Mesozoic Blue Nile rift system, suggesting control on magmatic ascent above the plume by the existing rift structure. The MER itself may have been influenced by both the plume beneath the Ethiopian highlands, and by a similar plume stem beneath Afar.

  14. Long-term mass transfer and mixing-controlled reactions of a DNAPL plume from persistent residuals

    NASA Astrophysics Data System (ADS)

    Liu, Yuan; Illangasekare, Tissa H.; Kitanidis, Peter K.

    2014-02-01

    Understanding and being able to predict the long-term behavior of DNAPL (i.e., PCE and TCE) residuals after active remediation has ceased have become increasingly important as attention at many sites turns from aggressive remediation to monitored natural attenuation and long-term stewardship. However, plume behavior due to mass loading and reactions during these later phases is less studied as they involve large spatial and temporal scales. We apply both theoretical analysis and pore-scale simulations to investigate mass transfer from DNAPL residuals and subsequent reactions within the generated plume, and, in particular, to show the differences between early- and late-time behaviors of the plume. In the zone of entry of the DNAPL entrapment zone where the concentration boundary layer in the flowing groundwater has not fully developed, the pore-scale simulations confirm the past findings based on laboratory studies that the mass transfer increases as a power-law function of the Peclét number, and is enhanced due to reactions in the plume. Away from the entry zone and further down gradient, the long-term reactions are limited by the available additive and mixing in the porous medium, thereby behave considerably differently from the entry zone. For the reaction between the contaminant and an additive with intrinsic second-order bimolecular kinetics, the late-time reaction demonstrates a first-order decay macroscopically with respect to the mass of the limiting additive, not with respect to that of the contaminant. The late-time decay rate only depends on the intrinsic reaction rate and the solubility of the entrapped DNAPL. At the intermediate time, the additive decays exponentially with the square of time (t2), instead of time (t). Moreover, the intermediate decay rate also depends on the initial conditions, the spatial distribution of DNAPL residuals, and the effective dispersion coefficient.

  15. Simulation of Europa's water plume .

    NASA Astrophysics Data System (ADS)

    Lucchetti, A.; Cremonese, G.; Schneider, N. M.; Plainaki, C.; Mazzotta Epifani, E.; Zusi, M.; Palumbo, P.

    Plumes on Europa would be extremely interesting science and mission targets, particularly due to the unique opportunity to obtain direct information on the subsurface composition, thereby addressing Europa's potential habitability. The existence of water plume on the Jupiter's moon Europa has been long speculated until the recent discover. HST imaged surpluses of hydrogen Lyman alpha and oxygen emissions above the southern hemisphere in December 2012 that are consistent with two 200 km high plumes of water vapor (Roth et al. 2013). In previous works ballistic cryovolcanism has been considered and modeled as a possible mechanism for the formation of low-albedo features on Europa's surface (Fagents et al. 2000). Our simulation agrees with the model of Fagents et al. (2000) and consists of icy particles that follow ballistic trajectories. The goal of such an analysis is to define the height, the distribution and the extension of the icy particles falling on the moon's surface as well as the thickness of the deposited layer. We expect to observe high albedo regions in contrast with the background albedo of Europa surface since we consider that material falling after a cryovolcanic plume consists of snow. In order to understand if this phenomenon is detectable we convert the particles deposit in a pixel image of albedo data. We consider also the limb view of the plume because, even if this detection requires optimal viewing geometry, it is easier detectable in principle against sky. Furthermore, we are studying the loss rates due to impact electron dissociation and ionization to understand how these reactions decrease the intensity of the phenomenon. We expect to obtain constraints on imaging requirements necessary to detect potential plumes that could be useful for ESA's JUICE mission, and in particular for the JANUS camera (Palumbo et al. 2014).

  16. Controlled Angiogenesis in Peptide Nanofiber Composite Hydrogels.

    PubMed

    Wickremasinghe, Navindee C; Kumar, Vivek A; Shi, Siyu; Hartgerink, Jeffrey D

    2015-09-14

    Multidomain peptide (MDP) nanofibers create scaffolds that can present bioactive cues to promote biological responses. Orthogonal self-assembly of MDPs and growth-factor-loaded liposomes generate supramolecular composite hydrogels. These composites can act as delivery vehicles with time-controlled release. Here we examine the controlled release of placental growth factor-1 (PlGF-1) for its ability to induce angiogenic responses. PlGF-1 was loaded either in MDP matrices or within liposomes bound inside MDP matrices. Scaffolds showed expected rapid infiltration of macrophages. When released through liposomes incorporated in MDP gels (MDP(Lipo)), PlGF-1 modulates HUVEC VEGF receptor activation in vitro and robust vessel formation in vivo. These loaded MDP(Lipo) hydrogels induce a high level of growth-factor-mediated neovascular maturity. MDP(Lipo) hydrogels offer a biocompatible and injectable platform to tailor drug delivery and treat ischemic tissue diseases.

  17. Dust Plume off Mauritania

    NASA Technical Reports Server (NTRS)

    2007-01-01

    A thick plume of dust blew off the coast of Mauritania in western Africa on October 2, 2007. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite observed the dust plume as it headed toward the southwest over the Atlantic Ocean. In this image, the dust varies in color from nearly white to medium tan. The dust plume is easier to see over the dark background of the ocean, but the plume stretches across the land surface to the east, as well. The dust plume's structure is clearest along the coastline, where relatively clear air pockets separate distinct puffs of dust. West of that, individual pillows of dust push together to form a more homogeneous plume. Near its southwest tip, the plume takes on yet another shape, with stripes of pale dust fanning out toward the northwest. Occasional tiny white clouds dot the sky overhead, but skies are otherwise clear.

  18. Modeling Europa's dust plumes

    NASA Astrophysics Data System (ADS)

    Southworth, B. S.; Kempf, S.; Schmidt, J.

    2015-12-01

    The discovery of Jupiter's moon Europa maintaining a probably sporadic water vapor plume constitutes a huge scientific opportunity for NASA's upcoming mission to this Galilean moon. Measuring properties of material emerging from interior sources offers a unique chance to understand conditions at Europa's subsurface ocean. Exploiting results obtained for the Enceladus plume, we simulate possible Europa plume configurations, analyze particle number density and surface deposition results, and estimate the expected flux of ice grains on a spacecraft. Due to Europa's high escape speed, observing an active plume will require low-altitude flybys, preferably at altitudes of 5-100 km. At higher altitudes a plume may escape detection. Our simulations provide an extensive library documenting the possible structure of Europa dust plumes, which can be quickly refined as more data on Europa dust plumes are collected.

  19. Particle-resolved simulation of aerosol size, composition, mixing state, and the associated optical and cloud condensation nuclei activation properties in an evolving urban plume

    SciTech Connect

    Zaveri, Rahul A.; Barnard, James C.; Easter, Richard C.; Riemer, Nicole; West, Matthew

    2010-09-11

    The recently developed particle-resolved aerosol box model PartMC-MOSAIC was used to simulate the evolution of aerosol mixing state and the associated optical and cloud condensation nuclei (CCN) activation properties in an idealized urban plume. The model explicitly resolved the size and composition of individual particles from a number of sources and tracked their evolution due to condensation/evaporation, coagulation, emission, and dilution. The ensemble black carbon (BC) specific absorption cross section increased by 40% over the course of two days as a result of BC aging by condensation and coagulation. Three- and four-fold enhancements in CCN/CN ratios were predicted to occur within 6 hours for 0.2% and 0.5% supersaturations (S), respectively. The particle-resolved results were used to evaluate the errors in the optical and CCN activation properties that would be predicted by a conventional sectional framework that assumes monodisperse, internally-mixed particles within each bin. This assumption artificially increased the ensemble BC specific absorption by 14-30% and decreased the single scattering albedo by 0.03-0.07 while the bin resolution had a negligible effect. In contrast, the errors in CCN/CN ratios were sensitive to the bin resolution, and they depended on the chosen supersaturation. For S = 0.2%, the CCN/CN ratio predicted using 100 internally-mixed bins was up to 25% higher than the particle-resolved results, while it was up to 125% higher using 10 internally-mixed bins. Errors introduced in the predicted optical and CCN properties by neglecting coagulation were also quantified.

  20. Process and control systems for composites manufacturing

    NASA Technical Reports Server (NTRS)

    Tsiang, T. H.; Wanamaker, John L.

    1992-01-01

    A precise control of composite material processing would not only improve part quality, but it would also directly reduce the overall manufacturing cost. The development and incorporation of sensors will help to generate real-time information for material processing relationships and equipment characteristics. In the present work, the thermocouple, pressure transducer, and dielectrometer technologies were investigated. The monitoring sensors were integrated with the computerized control system in three non-autoclave fabrication techniques: hot-press, self contained tool (self heating and pressurizing), and pressure vessel). The sensors were implemented in the parts and tools.

  1. Identifying key controls on the behavior of an acidic-U(VI) plume in the Savannah River Site using reactive transport modeling.

    PubMed

    Bea, Sergio A; Wainwright, Haruko; Spycher, Nicolas; Faybishenko, Boris; Hubbard, Susan S; Denham, Miles E

    2013-08-01

    Acidic low-level waste radioactive waste solutions were discharged to three unlined seepage basins at the F-Area of the Department of Energy (DOE) Savannah River Site (SRS), South Carolina, USA, from 1955 through 1989. Despite many years of active remediation, the groundwater remains acidic and contaminated with significant levels of U(VI) and other radionuclides. Monitored Natural Attenuation (MNA) is a desired closure strategy for the site, based on the premise that regional flow of clean background groundwater will eventually neutralize the groundwater acidity, immobilizing U(VI) through adsorption. An in situ treatment system is currently in place to accelerate this in the downgradient portion of the plume and similar measures could be taken upgradient if necessary. Understanding the long-term pH and U(VI) adsorption behavior at the site is critical to assess feasibility of MNA along with the in-situ remediation treatments. This paper presents a reactive transport (RT) model and uncertainty quantification (UQ) analyses to explore key controls on the U(VI)-plume evolution and long-term mobility at this site. Two-dimensional numerical RT simulations are run including the saturated and unsaturated (vadose) zones, U(VI) and H(+) adsorption (surface complexation) onto sediments, dissolution and precipitation of Al and Fe minerals, and key hydrodynamic processes are considered. UQ techniques are applied using a new open-source tool that is part of the developing ASCEM reactive transport modeling and analysis framework to: (1) identify the complex physical and geochemical processes that control the U(VI) plume migration in the pH range where the plume is highly mobile, (2) evaluate those physical and geochemical parameters that are most controlling, and (3) predict the future plume evolution constrained by historical, chemical and hydrological data. The RT simulation results show a good agreement with the observed historical pH and concentrations of U(VI), nitrates

  2. Identifying key controls on the behavior of an acidic-U(VI) plume in the Savannah River Site using reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Bea, Sergio A.; Wainwright, Haruko; Spycher, Nicolas; Faybishenko, Boris; Hubbard, Susan S.; Denham, Miles E.

    2013-08-01

    Acidic low-level waste radioactive waste solutions were discharged to three unlined seepage basins at the F-Area of the Department of Energy (DOE) Savannah River Site (SRS), South Carolina, USA, from 1955 through 1989. Despite many years of active remediation, the groundwater remains acidic and contaminated with significant levels of U(VI) and other radionuclides. Monitored Natural Attenuation (MNA) is a desired closure strategy for the site, based on the premise that regional flow of clean background groundwater will eventually neutralize the groundwater acidity, immobilizing U(VI) through adsorption. An in situ treatment system is currently in place to accelerate this in the downgradient portion of the plume and similar measures could be taken upgradient if necessary. Understanding the long-term pH and U(VI) adsorption behavior at the site is critical to assess feasibility of MNA along with the in-situ remediation treatments. This paper presents a reactive transport (RT) model and uncertainty quantification (UQ) analyses to explore key controls on the U(VI)-plume evolution and long-term mobility at this site. Two-dimensional numerical RT simulations are run including the saturated and unsaturated (vadose) zones, U(VI) and H+ adsorption (surface complexation) onto sediments, dissolution and precipitation of Al and Fe minerals, and key hydrodynamic processes are considered. UQ techniques are applied using a new open-source tool that is part of the developing ASCEM reactive transport modeling and analysis framework to: (1) identify the complex physical and geochemical processes that control the U(VI) plume migration in the pH range where the plume is highly mobile, (2) evaluate those physical and geochemical parameters that are most controlling, and (3) predict the future plume evolution constrained by historical, chemical and hydrological data. The RT simulation results show a good agreement with the observed historical pH and concentrations of U(VI), nitrates and

  3. Hybrid plume plasma rocket

    NASA Technical Reports Server (NTRS)

    Chang, Franklin R. (Inventor)

    1989-01-01

    A technique for producing thrust by generating a hybrid plume plasma exhaust is disclosed. A plasma flow is generated and introduced into a nozzle which features one or more inlets positioned to direct a flow of neutral gas about the interior of the nozzle. When such a neutral gas flow is combined with the plasma flow within the nozzle, a hybrid plume is constructed including a flow of hot plasma along the center of the nozzle surrounded by a generally annular flow of neutral gas, with an annular transition region between the pure plasma and the neutral gas. The temperature of the outer gas layer is below that of the pure plasma and generally separates the pure plasma from the interior surfaces of the nozzle. The neutral gas flow both insulates the nozzle wall from the high temperatures of the plasma flow and adds to the mass flow rate of the hybrid exhaust. The rate of flow of neutral gas into the interior of the nozzle may be selectively adjusted to control the thrust and specific impulse of the device.

  4. Source components of the Hawaiian shield lavas and their distribution in the plume

    NASA Astrophysics Data System (ADS)

    Ren, Z.; Hanyu, T.; Chang, Q.; Kawabata, H.; Miyazaki, T.; Takahashi, T.; Hirahara, Y.; Tatsumi, Y.

    2006-12-01

    We examined major, trace elements and Sr-, Nd-, Pb-, He- isotope compositions in a suite of fresh lavas from the submarine Koolau, Kilauea and Loihi volcanoes, as these volcanoes are believed to have sampled the three distinct Hawaiian plume components. The trace element ratios and isotopic variations imply that, to a first order, the composition of the Hawaiian shield lavas appears to be dominated by a mixture of two components: a relatively enriched component (Koolau) and a relatively depleted component (Loihi). The Koolau component consists of a higher proportion of ancient recycled oceanic crust (lower crust); the Loihi and Kea component contains a higher proportion relatively depleted FOZO like component that is from the lower mantle. On the basis of our new data involving previous whole rock (Ren et al., J. Petrol., 2004; 2006) and melt inclusion data (Ren et al., 2005, Nature), combined with the geochemical evolutions of the individual shield volcanoes, we propose a Hawaiian mantle plume characterized by more random heterogeneity than would be present in a simple compositionally zoned mantle plume. The plume may have a peridotite matrix from the lower mantle with recycled oceanic crust that may remain distinct geochemistry, forming streaks or ribbons distributed throughout the entire plume. The dominant component sampled at a given stage of the shield volcanoes is likely to be controlled by the thermal structure of the plume and the melting points of the different materials in the plume. References: (1)Ren, Z.-Y., Takahashi, E., Orihashi, Y., K. M. T. Johnson (2004), J. Petrol., 45, 2067-2099. (2)Ren, Z.-Y., T. Shibata, M. Yoshikawa, K. Johnson, E. Takahashi (2006), J. Petrol., 47, 255-275. (3)Ren, Z.-Y., S. Stephanie, E. Takahashi, N. Hirano, T. Hirata (2005), Nature, 436, 837-840.

  5. Volcanic Plume Chemistry: Models, Observations and Impacts

    NASA Astrophysics Data System (ADS)

    Roberts, Tjarda; Martin, Robert; Oppenheimer, Clive; Griffiths, Paul; Braban, Christine; Cox, Tony; Jones, Rod; Durant, Adam; Kelly, Peter

    2010-05-01

    mercury. Excitingly, we can now begin to compare the model simulations to very recently reported in-situ aircraft and balloon measurements in downwind volcanic plumes, which found e.g. ozone depletion at Redoubt, ozone depletion and elevated HNO3 at Erebus and sulfate-H2O interactions at Kilauea. Satellite observations of volcanic BrO, and DOAS observations of BrO under varying plume conditions have also recently been reported. Such comparisons may highlight additional chemistry (e.g. HO2NO2 at Erebus), identify further underlying processes (e.g. the role of plume dispersion and gas fluxes in controlling plume chemistry), guide future field-observation strategies, and support and improve the model simulations that aim to understand volcanic emissions, plume chemistry, and predict the environmental impacts of volcanic plumes.

  6. Mantle source of the 2.44-2.50-Ga mantle plume-related magmatism in the Fennoscandian Shield: evidence from Os, Nd, and Sr isotope compositions of the Monchepluton and Kemi intrusions

    NASA Astrophysics Data System (ADS)

    Yang, Sheng-Hong; Hanski, Eero; Li, Chao; Maier, Wolfgang D.; Huhma, Hannu; Mokrushin, Artem V.; Latypov, Rais; Lahaye, Yann; O'Brien, Hugh; Qu, Wen-Jun

    2016-12-01

    Significant PGE and Cr mineralization occurs in a number of 2.44-2.50-Ga mafic layered intrusions located across the Karelian and Kola cratons. The intrusions have been interpreted to be related to mantle plume activity. Most of the intrusions have negative ɛNd values of about -1 to -2 and slightly radiogenic initial Sr isotope compositions of about 0.702 to 0.703. One potential explanation is crustal contamination of a magma derived from a mantle plume, but another possibility is that the magma was derived from metasomatized sub-continental lithospheric mantle. Samples from the upper chromitite layers of the Kemi intrusion and most samples from the previously studied Koitelainen and Akanvaara intrusions have supra-chondritic γOs values indicating some crustal contamination, which may have contributed to the formation of chromitites in these intrusions. Chromite separates from the main ore zone of the Kemi and Monchepluton intrusions show nearly chondritic γOs, similar to the coeval Vetreny belt komatiites. We suggest that the Os isotope composition of the primitive magma was not significantly changed by crustal contamination due to a high Os content of the magma and a low Os content of the contaminant. Modeling suggests that the Os and Nd isotope compositions of the Monchepluton and Kemi intrusions cannot be explained by assuming a magma source in the sub-continental lithospheric mantle with sub-chondritic γOs. A better match for the isotope data would be a plume mantle source with chondritic Re/Os and Os isotope composition, followed by crustal contamination.

  7. Supervisory control of drilling of composite materials

    NASA Astrophysics Data System (ADS)

    Ozaki, Motoyoshi

    Composite materials have attractive features, such as high ratios of strength-to-weight and stiffness-to-weight. However, they are easily damaged when they are machined. A typical damage is delamination, which can occur when fiber reinforced composite laminates are drilled. The objective of this research is to study the drilling processes of carbon fiber reinforced laminates, and to develop and test a supervisory control strategy for their delamination-free drilling. Characterization of thrust force and torque is achieved through constant feedrate drilling experiments. The average values of thrust force and torque during the full engagement of the drill are utilized to obtain the Shaw's equations' parameters. The thrust force profile just before exit is given special attention. The Hocheng-Dharan equations, which give conservative values of delamination at the entrance and at the exit, are modified to express the influence of one lamina thickness explicitly. They are utilized not only for the characterization of thrust force but also for the determination of the thrust force reference for force control. In the design of the controllers of thrust force and torque, both thrust force and torque are assumed to be proportional to FPHR (Feed Per Half Revolution). A discrete-time dynamic model is established for the case when the time interval for a half revolution of the drill is divided by the sampling time, and the model is extended to the case of general spindle speeds. PI controllers are designed for the dynamic models of thrust force and torque. Root-locus techniques are used in the analysis. The phases of the drilling process are introduced and the control strategy at each phase is explained. The supervisory controller chooses not only the best control strategy for each phase, but also the reference value and the controller gain that are suitable at each drill position. Drilling experiments are conducted to show the usefulness of the concepts introduced in this

  8. Time delay control of hysteretic composite plate

    NASA Astrophysics Data System (ADS)

    Chen, Long-Xiang; Li, Shi-Hong; Liu, Kun; Cai, Guo-Ping; Li, Hong-Guang

    2015-04-01

    Due to boosting usage of flexible and damping materials, it is of great significance for both science and engineering to explore active control methods for vibration within time-delayed hysteretic structures. This paper conducts theoretical and experimental research on a time-delayed controller for a flexible plate with a single-layer rubber glued on its back. First of all, the dynamic equation for a composite plate is given on the base of the Kirchhoff-Love assumption, where damping-restoring force is described by the Bouc-Wen hysteresis model. Then, the influence of time delay is taken into account and the state equation of the plate with time delay is obtained. Next, a standard state equation, with implicit time delay, is derived using one specific form of integral transformation and vector augmentation. Finally, an instantaneous optimal control method is used to design an active controller. This controller does not only involve state feedback of the current step, but also a linear addition of former state feedbacks within several steps. In order to verify this method, experimental work is conducted. Problems encountered like differential computation and lifting of displacement signal are also handled. According to a comparison between simulations and experiments, the control method given in this paper is feasible and valid, and it is available for both small and large time delay.

  9. Robust control of ionic polymer metal composites

    NASA Astrophysics Data System (ADS)

    Kang, Sunhyuk; Shin, Jongho; Kim, Seong Jun; Kim, H. Jin; Hyup Kim, Yong

    2007-12-01

    Ionic polymer-metal composites (IPMCs) have been considered for various applications due to their light weight, large bending, and low actuation voltage requirements. However, their response can be slow and vary widely, depending on various factors such as fabrication processes, water content, and contact conditions with the electrodes. In order to utilize their capability in various high-performance microelectromechanical systems, controllers need to address this uncertainty and non-repeatability while improving the response speed. In this work, we identified an empirical model for the dynamic relationship between the applied voltage and the IPMC beam deflection, which includes the uncertainties and variations of the response. Then, four types of controller were designed, and their performances were compared: a proportional-integral-derivative (PID) controller with optimized gains using a co-evolutionary algorithm, and three types of robust controller based on H_\\infty , H_\\infty with loop shaping, and μ-synthesis, respectively. Our results show that the robust control techniques can significantly improve the IPMC performance against non-repeatability or parametric uncertainties, in terms of the faster response and lower overshoot than the PID control, using lower actuation voltage.

  10. Modeling Europa's Dust Plumes

    NASA Astrophysics Data System (ADS)

    Southworth, B.; Kempf, S.; Schmidt, J.

    2015-12-01

    The discovery of Europa maintaining a probably sporadic water vapor plume constitutes a huge scientific opportunity for NASA's upcoming mission to this Galilean moon. Measuring the properties of material emerging from interior sources offers a unique chance to understand conditions at Europa's subsurface ocean. Exploiting results obtained for the Enceladus plume, we adjust the ejection model by Schmidt et al. [2008] to the conditions at Europa. In this way, we estimate properties of a possible, yet unobserved dust component of the Europa plume. For a size-dependent speed distribution of emerging ice particles we use the model from Kempf et al. [2010] for grain dynamics, modified to run simulations of plumes on Europa. Specifically, we model emission from the two plume locations determined from observations by Roth et al. [2014] and also from other locations chosen at the closest approach of low-altitude flybys investigated in the Europa Clipper study. This allows us to estimate expected fluxes of ice grains on the spacecraft. We then explore the parameter space of Europa dust plumes with regard to particle speed distribution parameters, plume location, and spacecraft flyby elevation. Each parameter set results in a 3-dimensional particle density structure through which we simulate flybys, and a map of particle fallback ('snowfall') on the surface of Europa. Due to the moon's high escape speed, a Europa plume will eject few to no particles that can escape its gravity, which has several further consequences: (i) For given ejection velocity a Europa plume will have a smaller scale height, with a higher particle number densities than the plume on Enceladus, (ii) plume particles will not feed the diffuse Galilean dust ring, (iii) the snowfall pattern on the surface will be more localized about the plume location, and will not induce a global m = 2 pattern as seen on Enceladus, and (iv) safely observing an active plume will require low altitude flybys, preferably at 50

  11. Reservoir Architecture Control on the Geometry of a CO2 Plume Using 4D Seismic, Sleipner Field.

    NASA Astrophysics Data System (ADS)

    Bitrus, Roy; Iacopini, David; Bond, Clare

    2017-04-01

    Time lapse seismic from the Sleipner field, Norwegian North Sea represents a unique database to understand the geometry of a saline aquifer, the Utsira Sand Formation, and its role in containing sequestered CO2. The heterogeneous high permeability Utsira Sand formation bounded by an overlying seal is surrounded by impermeable to semi-permeable intra-reservoir thin shale units that influence the migration of injected CO2. It is important to understand and verify the dynamics of injected CO2 plume migration as this ensures close to accurate predictions of the evolving and stable state of CO2 in storage projects. Previous detailed interpretation results of the thin shale units and permeability flow path chimneys within the Utsira Formation have been used in this research. The Utsira Cap rock, IUTS1 and IUTS1 (Intra-Utsira Shale Units) are the top three units that affect the containment and upward migration path of injected CO2. They are combined with seismic geobodies of the CO2 plume across time lapse data. Here, these seismic geobodies are created using 2 methods to delineate the 3D shape and the cubic volume occupancy of the CO2 plume within the reservoir. Method 1 employs the use of an envelope attribute volume, where samples are extracted from voxels that contain seismic trace amplitude values of injected CO2 across the 3D data. These extracted samples are then tracked throughout the target area and then classed and quantified as a CO2 geobodies. Method 2 applies the same concept; the only difference is the samples extracted from voxels are classed based on the proximity and connectivity of pre-defined amplitude values. Both methods employ the use of a Bayesian classifier which defines the probability density function used to categorise the extracted threshold values. Our result of the 3D geobody shapes are compared against the internal geometry of the reservoir which shows the influence of the cap rock and intra-reservoir thin shales on the CO2 plume acting as

  12. Control of DWPF melter feed composition

    SciTech Connect

    Brown, K.G.; Edwards, R.E.; Postles, R.L.; Randall, C.T.

    1989-12-31

    The Defense Waste Processing Facility will be used to immobilize Savannah River Site high-level waste into a stable borosilicate glass for disposal in a geologic repository. Proper control of the melter feed composition in this facility is essential to the production of glass which meets product durability constraints dictated by repository regulations and facility processing constraints dictated by melter design. A technique has been developed which utilizes glass property models to determine acceptable processing regions based on the multiple constraints imposed on the glass product and to display these regions graphically. This system along with the batch simulation of the process is being used to form the basis for the statistical process control system for the facility.

  13. Control of DWPF melter feed composition

    SciTech Connect

    Brown, K.G.; Edwards, R.E.; Postles, R.L.; Randall, C.T.

    1989-01-01

    The Defense Waste Processing Facility will be used to immobilize Savannah River Site high-level waste into a stable borosilicate glass for disposal in a geologic repository. Proper control of the melter feed composition in this facility is essential to the production of glass which meets product durability constraints dictated by repository regulations and facility processing constraints dictated by melter design. A technique has been developed which utilizes glass property models to determine acceptable processing regions based on the multiple constraints imposed on the glass product and to display these regions graphically. This system along with the batch simulation of the process is being used to form the basis for the statistical process control system for the facility.

  14. Near-glacier surveying of a subglacial discharge plume: Implications for plume parameterizations

    NASA Astrophysics Data System (ADS)

    Jackson, R. H.; Shroyer, E. L.; Nash, J. D.; Sutherland, D. A.; Carroll, D.; Fried, M. J.; Catania, G. A.; Bartholomaus, T. C.; Stearns, L. A.

    2017-07-01

    At tidewater glaciers, plume dynamics affect submarine melting, fjord circulation, and the mixing of meltwater. Models often rely on buoyant plume theory to parameterize plumes and submarine melting; however, these parameterizations are largely untested due to a dearth of near-glacier measurements. Here we present a high-resolution ocean survey by ship and remotely operated boat near the terminus of Kangerlussuup Sermia in west Greenland. These novel observations reveal the 3-D structure and transport of a near-surface plume, originating at a large undercut conduit in the glacier terminus, that is inconsistent with axisymmetric plume theory, the most common representation of plumes in ocean-glacier models. Instead, the observations suggest a wider upwelling plume—a "truncated" line plume of ˜200 m width—with higher entrainment and plume-driven melt compared to the typical axisymmetric representation. Our results highlight the importance of a subglacial outlet's geometry in controlling plume dynamics, with implications for parameterizing the exchange flow and submarine melt in glacial fjord models.

  15. Solar Jetlets and Plumes

    NASA Astrophysics Data System (ADS)

    DeForest, Craig; Antiochos, Spiro K.; DeVore, C. Richard; Karpen, Judith T.; Kumar, Pankaj; Raouafi, Nour-Eddine; Roberts, Merrill; Uritsky, Vadim; Wyper, Peter

    2017-08-01

    We present results of a careful deep-field (low-noise) analysis of evolution and structure of solar plumes using multiple wavelength channels from SDO/AIA. Using new noise-reduction techniques on SDO/AIA images, we reveal myriad small, heating events that appear to be the primary basis of plume formation and sustenance. These events ("jetlets") comprise a dynamic tapestry that forms the more distributed plume itself. We identify the "jetlets" with ejecta that have been previously observed spectroscopically, and distinguish them from the quasi-periodic slow mode waves that are seen as large collective motions. We speculate that the jetlets themselves, which are consistent with multiple interchange reconnection events near the base of the plume, are the primary energy driver heating plasma in the plume envelope.Solar polar (and low-latitude) plumes have been analyzed by many authors over many years. Plumes are bright, persistent vertical structures embedded in coronal holes over quasi-unipolar magnetic flux concentrations. They are EUV-bright in the ~1MK lines, slightly cooler (by ionization fraction) than the surrounding coronal hole, persistent on short timescales of a few hours, and recurrent on timescales of a few days. Their onset has been associated with large X-ray jets, although not all plumes are formed that way. Plumes appear to comprise myriad small "threads" or "strands", and may (or may not) contribute significantly to the solar wind, though they have been associated with myriad small, frequent eruptive ejection events.Our results are new and interesting because they are the lowest-noise, time-resolved observations of polar plumes to date; and they reveal the deep association between small-scale magnetic activity and the formation of the plumes themselves.

  16. Evidence for Little Shallow Entrainment in Starting Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Lohmann, F. C.; Phipps Morgan, J.; Hort, M.

    2005-12-01

    Basalts from intraplate or hotspot ocean islands show distinct geochemical signatures. Their diversity in composition is generally believed to result from the upwelling plume entraining shallow mantle material during ascent, while potentially also entraining other deep regions of the mantle. Here we present results from analogue laboratory experiments and numerical modelling that there is evidence for little shallow entrainment into ascending mantle plumes, i.e. most of the plume signature is inherited from the source. We conducted laboratory experiments using glucose syrup contaminated with glass beads to visualize fluid flow and origin. The plume is initiated by heating from below or by injecting hot, uncontaminated syrup. Particle movement is captured by a CCD camera. In our numerical experiments we solve the Stokes equations for a viscous fluid at infinite Prandtl number with passive tracer particles being used to track fluid flow and entrainment rates, simulating laboratory as well as mantle conditions. In both analogue experiments and numerical models we observe the classical plume structure being embedded in a `sheath' of material from the plume source region that retains little of the original temperature anomaly of the plume source. Yet, this sheath ascends in the `slipstream' of the plume at speeds close to the ascent speed of the plume head, and effectively prevents the entrainment of surrounding material into the plume head or plume tail. We find that the source region is most effectively sampled by an ascending plume and that compositional variations in the source region are preserved during plume ascent. The plume center and plume sheath combined are composed of up to 85% source material. However, there is also evidence of significant entrainment of up to 30% of surrounding material into the outer layers of the plume sheath. Entrainment rates are found to be influenced by mantle composition and structure, with the radial viscosity profile of the

  17. Dynamics and Deposits of Coignimbrite Plumes

    NASA Astrophysics Data System (ADS)

    Engwell, Samantha; de'Michieli Vitturi, Mattia; Esposti Ongaro, Tomaso; Neri, Augusto

    2014-05-01

    Fine ash in the atmosphere poses a significant hazard, with potentially disastrous consequences for aviation and, on deposition, health and infrastructure. Fine-grained particles form a large proportion of ejecta in Plinian volcanic clouds. However, another common, but poorly studied phenomena exists whereby large amounts of fine ash are injected into the atmosphere. Coignimbrite plumes form as material is elutriated from the top of pyroclastic density currents. The ash in these plumes is considerably finer grained than that in Plinian plumes and can be distributed over thousands of kilometres in the atmosphere. Despite their significance, very little is known regarding coignimbrite plume formation and dispersion, predominantly due to the poor preservation of resultant deposits. As a result, consequences of coignimbrite plume formation are usually overlooked when conducting hazard and risk analysis. In this study, deposit characteristics and numerical models of plumes are combined to investigate the conditions required for coignimbrite plume formation. Coignimbrite deposits from the Campanian Ignimbrite eruption (Magnitude 7.7, 39 ka) are well sorted and very fine, with a mode of between 30 and 50 microns, and a significant component of respirable ash (less than 10 microns). Analogous distributions are found for coignimbrite deposits from Tungurahua 2006 and Volcan de Colima (2004-2006), amongst others, regardless of magnitude, type or chemistry of eruption. These results indicate that elutriation processes are the dominant control on coignimbrite grainsize distribution. To further investigate elutriation and coignimbrite plume dynamics, the numerical plume model of Bursik (2001) is applied. Model sensitivity analysis demonstrates that neutral buoyancy conditions (required for the formation of the plume) are controlled by a balance between temperature and gas mass flux in the upper most parts of the pyroclastic density current. In addition, results emphasize the

  18. Dissolved and particulate Fe in a hydrothermal plume at 9{degree}45 minutes N, East Pacific Rise: Slow Fe (II) oxidation kinetics in Pacific plumes

    SciTech Connect

    Field, M.P.; Sherrell, R.M.

    2000-02-01

    Production of Fe(III) particles in hydrothermal plumes is of fundamental importance to the long-term effect of hydrothermal circulation on seawater composition. To elucidate the fundamental controls on Fe redox kinetics and solution/particle partitioning in neutrally buoyant plumes, the authors sampled near-field (<3 km) plume particles at 9{degree}45 minutes N on the East Pacific Rise in 1996, returning in 1997 to sample both particulate and dissolved phases (0.40 {micro}m filter). Concentrations of dissolved Fe varied from 320 to 20 nM in proximal (<0.3 km from vent site) to distal samples (1--3 km downfield), constituting {approximately}85--50% of total Fe, respectively. Based on vent fluid dilution factors calculated from dissolved Mn, a mass balance for vent fluid Fe at this site indicates that {approximately}65% of Fe is lost to particulate sulfide settling in the buoyant plume, and that particulate Fe in distal (1--3 km) samples is twice as concentrated as predicted from dilution of particles in proximal plume water. These observations are consistent with a calculated Fe(II) oxidation half-time of 3.3 h, long enough that Fe(III) colloid production and aggregation occurs primarily in the neutrally buoyant plume at relatively high dilutions, preventing generation of high particular Fe concentrations (11--56 nM observed). A general investigation of Fe(II) oxidation rates in plumes worldwide gives Fe(II) oxidation half-lives as short as 17 min at some Atlantic sites, and as long as 6 h at some Pacific sites. The calculations indicate that the distribution of Fe particles in plumes depends chiefly on inter-basin differences in ambient deep water chemistry (primarily pH and dissolved O{sub 2}) and on local currents driving plume dilution, and to a much lesser extent on variations in primary vent fluid composition. Long-term changes in thermohaline circulation or ocean biogeochemistry may therefore alter Fe dynamics and minor element fluxes associated with global

  19. Heat sources for mantle plumes

    NASA Astrophysics Data System (ADS)

    Beier, C.; Rushmer, T.; Turner, S. P.

    2008-06-01

    Islands, and the Azores). We also find no correlation between Fe and buoyancy flux. The apparent lack of correlations suggests that excess heat may be a result of conductive heat contribution from the core or from the adjacent boundary layer. Thus, the formation of mantle plumes along the core-mantle boundary may be largely controlled by distance of enriched material from the core-mantle boundary.

  20. Randomized Control Trial of Composite Cuspal Restorations

    PubMed Central

    Fennis, W.M.; Kuijs, R.H.; Roeters, F.J.; Creugers, N.H.; Kreulen, C.M.

    2014-01-01

    The objective of this randomized control trial was to compare the five-year clinical performance of direct and indirect resin composite restorations replacing cusps. In 157 patients, 176 restorations were made to restore maxillary premolars with Class II cavities and one missing cusp. Ninety-two direct and 84 indirect resin composite restorations were placed by two operators, following a strict protocol. Treatment technique and operator were assigned randomly. Follow-up period was at least 4.5 yrs. Survival rates were determined with time to reparable failure and complete failure as endpoints. Kaplan-Meier five-year survival rates were 86.6% (SE 0.27%) for reparable failure and 87.2% (SE 0.27%) for complete failure. Differences between survival rates of direct and indirect restorations [89.9% (SE 0.34%) vs. 83.2% (SE 0.42%) for reparable failure and 91.2% (SE 0.32%) vs. 83.2% (SE 0.42%) for complete failure] were not statistically significant (p = .23 for reparable failure; p = .15 for complete failure). Mode of failure was predominantly adhesive. The results suggest that direct and indirect techniques provide comparable results over the long term (trial registration number: ISRCTN29200848). PMID:24155264

  1. DWPF waste glass Product Composition Control System

    SciTech Connect

    Brown, K.G.; Postles, R.L.

    1992-01-01

    The Defense Waste Processing Facility (DWPF) will be used to blend aqueous radwaste (PHA) with solid radwaste (Sludge) in a waste receipt vessel (the SRAT). The resulting SRAT material is transferred to the SME an there blended with ground glass (Frit) to produce a batch of melter feed slurry. The SME material is passed to a hold tank (the MFT) which is used to continuously feed the DWPF melter. The melter. The melter produces a molten glass wasteform which is poured into stainless steel canisters for cooling and, ultimately, shipment to and storage in a geologic repository. The Product Composition Control System (PCCS) is the system intended to ensure that the melt will be processible and that the glass wasteform will be acceptable. This document provides a description of this system.

  2. DWPF waste glass Product Composition Control System

    SciTech Connect

    Brown, K.G.; Postles, R.L.

    1992-07-01

    The Defense Waste Processing Facility (DWPF) will be used to blend aqueous radwaste (PHA) with solid radwaste (Sludge) in a waste receipt vessel (the SRAT). The resulting SRAT material is transferred to the SME an there blended with ground glass (Frit) to produce a batch of melter feed slurry. The SME material is passed to a hold tank (the MFT) which is used to continuously feed the DWPF melter. The melter. The melter produces a molten glass wasteform which is poured into stainless steel canisters for cooling and, ultimately, shipment to and storage in a geologic repository. The Product Composition Control System (PCCS) is the system intended to ensure that the melt will be processible and that the glass wasteform will be acceptable. This document provides a description of this system.

  3. Plumes on Enceladus: Lessons for Europa?

    NASA Astrophysics Data System (ADS)

    Nimmo, F.

    2014-12-01

    The possible detection of a water vapour plume on Europa [1] suggests resemblances to Enceladus, a cryovolcanically active satellite [2]. How does this activity work, and what lesson does Enceladus have for plumes on Europa? The inferred vapour column densities of the Europa [1] and Enceladus [3] plumes are similar, but the inferred velocity and mass flux of the former are higher. At Enceladus, the inferred plume strength is modulated by its orbital position [4,5], suggesting that tides opening and closing cracks control the eruption behaviour [6,7]. An additional source of stress potentially driving eruptions is the effect of slow freezing of the ice shell above[7,8]. The original detection of the Europa plume was close to apocentre, when polar fractures are expected to be in tension [1]. Follow-up observations at the same orbital phase did not detect a plume [9], although the Galileo E12 magnetometer data may provide evidence for an earlier plume [Khurana, pers. comm.]. One possible explanation for the plume's disappearance is that longer-period tidal effects are playing a role; there are hints of similar secular changes in the Enceladus data [4,5]. Another is that detectability of the Europa plumein the aurora observations also depends on variations in electron density (which affects the UV emission flux) [9]. Or it may simply be that eruptive activity on Europa is highly time-variable, as on Io. At Enceladus, the plume scale height is independent of orbital position and plume brightness [5]. This suggests that the vapour velocity does not depend on crack width, consistent with supersonic flow through a near-surface throat. The large scale height inferred for the Europa plume likewise suggests supersonic behaviour. Continuous fallback of solid plume material at Enceladus affects both the colour [10] and surface texture [2] of near-polar regions. Less frequent plume activity would produce subtler effects; whether the sparse available imagery at Europa [11

  4. The ice plumes of Europa

    NASA Astrophysics Data System (ADS)

    Sparks, William

    2014-10-01

    It is of extreme interest to NASA and the scientific community that evidence has been found for plumes of water ice venting from the polar regions of Europa (Roth et al 2014) - spectroscopic detection of off-limb line emission from the dissociation products of water. We were awarded Cycle 21 time to seek direct images of the Europa exosphere, including Enceladus-like plumes if present, basing our study on FUV images of Europa as it transits the smooth face of Jupiter. We also obtained a necessary FUV image of Europa out of transit. These observations provide additional evidence for the presence of ice plumes on Europa. Here, we propose to augment our previous imaging work and to seek an initial, efficient characterization of off-limb emission as Europa orbits Jupiter. Such images provide sensitive flux and column density limits, with exceptional spatial resolution. In transit, our strategy can place firm limits on, or measurements of, absorbing columns, their distribution with altitude above the surface of Europa, and constrain their wavelength dependence and hence composition. Out of transit, geometrical and surface brightness considerations can help us distinguish between continuum FUV emission from forward- or back-scattering, from line emission, or, though we might prefer otherwise, from more subtle instrumental artifacts than hitherto understood. If the ice fountains of Europa arise from the deep ocean, we have gained access to probably the most astrobiologically interesting location in the Solar System.

  5. Slowly released molasses barrier system for controlling nitrate plumes in groundwater: a pilot-scale tank study.

    PubMed

    Lee, Byung Sun; Lee, Kyuyeon; Um, Jae Yeon; Nam, Kyoungphile

    2014-02-01

    A well-type barrier system containing solidified molasses as a reactive medium was developed to promote the indigenous denitrifying activity and to treat nitrate plumes in groundwater. Three slowly released molasses (SRM) barrier systems harboring 60, 120, and 120 SRM rods, which were named System A, B, and C, respectively, were operated to examine nitrate removal efficiency in a pilot-scale sandy tank. These SRM systems induced a consistent removal of nitrate without pore clogging and hydraulic disturbance during the test period. The initial nitrate concentration was 142mgL(-1), and the concentrations decreased by 80%, 84%, and 79% in System A, B, and C, respectively. In particular, System C was inoculated with heterotrophic denitrifiers, but the nitrate removal efficiency was not enhanced compared to System B, probably due to the prior existence of indigenous denitrifiers in the sandy tank. The presence of nitrite reductase-encoding gene (i.e. nirK) at the site was confirmed by denatured gradient gel electrophoresis analysis.

  6. A global sensitivity analysis of the PlumeRise model of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Woodhouse, Mark J.; Hogg, Andrew J.; Phillips, Jeremy C.

    2016-10-01

    Integral models of volcanic plumes allow predictions of plume dynamics to be made and the rapid estimation of volcanic source conditions from observations of the plume height by model inversion. Here we introduce PlumeRise, an integral model of volcanic plumes that incorporates a description of the state of the atmosphere, includes the effects of wind and the phase change of water, and has been developed as a freely available web-based tool. The model can be used to estimate the height of a volcanic plume when the source conditions are specified, or to infer the strength of the source from an observed plume height through a model inversion. The predictions of the volcanic plume dynamics produced by the model are analysed in four case studies in which the atmospheric conditions and the strength of the source are varied. A global sensitivity analysis of the model to a selection of model inputs is performed and the results are analysed using parallel coordinate plots for visualisation and variance-based sensitivity indices to quantify the sensitivity of model outputs. We find that if the atmospheric conditions do not vary widely then there is a small set of model inputs that strongly influence the model predictions. When estimating the height of the plume, the source mass flux has a controlling influence on the model prediction, while variations in the plume height strongly effect the inferred value of the source mass flux when performing inversion studies. The values taken for the entrainment coefficients have a particularly important effect on the quantitative predictions. The dependencies of the model outputs to variations in the inputs are discussed and compared to simple algebraic expressions that relate source conditions to the height of the plume.

  7. Hubble Sees Recurring Plume Erupting From Europa

    NASA Image and Video Library

    2017-04-13

    These composite images show a suspected plume of material erupting two years apart from the same location on Jupiter's icy moon Europa. The images bolster evidence that the plumes are a real phenomenon, flaring up intermittently in the same region on the satellite. Both plumes, photographed in ultraviolet light by NASA's Hubble's Space Telescope Imaging Spectrograph, were seen in silhouette as the moon passed in front of Jupiter. The newly imaged plume, shown at right, rises about 62 miles (100 kilometers) above Europa's frozen surface. The image was taken Feb. 22, 2016. The plume in the image at left, observed by Hubble on March 17, 2014, originates from the same location. It is estimated to be about 30 miles (50 kilometers) high. The snapshot of Europa, superimposed on the Hubble image, was assembled from data from NASA's Galileo mission to Jupiter. The plumes correspond to the location of an unusually warm spot on the moon's icy crust, seen in the late 1990s by the Galileo spacecraft (see PIA21444). Researchers speculate that this might be circumstantial evidence for water venting from the moon's subsurface. The material could be associated with the global ocean that is believed to be present beneath the frozen crust. https://photojournal.jpl.nasa.gov/catalog/PIA21443

  8. RELATIVE ABUNDANCE MEASUREMENTS IN PLUMES AND INTERPLUMES

    SciTech Connect

    Guennou, C.; Hahn, M.; Savin, D. W.

    2015-07-10

    We present measurements of relative elemental abundances in plumes and interplumes. Plumes are bright, narrow structures in coronal holes that extend along open magnetic field lines far out into the corona. Previous work has found that in some coronal structures the abundances of elements with a low first ionization potential (FIP) <10 eV are enhanced relative to their photospheric abundances. This coronal-to-photospheric abundance ratio, commonly called the FIP bias, is typically 1 for elements with a high-FIP (>10 eV). We have used Extreme Ultraviolet Imaging Spectrometer observations made on 2007 March 13 and 14 over a ≈24 hr period to characterize abundance variations in plumes and interplumes. To assess their elemental composition, we used a differential emission measure analysis, which accounts for the thermal structure of the observed plasma. We used lines from ions of iron, silicon, and sulfur. From these we estimated the ratio of the iron and silicon FIP bias relative to that for sulfur. From the results, we have created FIP-bias-ratio maps. We find that the FIP-bias ratio is sometimes higher in plumes than in interplumes and that this enhancement can be time dependent. These results may help to identify whether plumes or interplumes contribute to the fast solar wind observed in situ and may also provide constraints on the formation and heating mechanisms of plumes.

  9. Remote Diagnostic Measurements of Hall Thruster Plumes

    DTIC Science & Technology

    2009-08-14

    distribution Angle Relative to Thruster Centerline (degrees) Summary and Conclusions 1. Plasma diagnostics designed, developed, and fabricated 2. Calibrated... Thruster Plumes 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Casey C. Farnell ( Plasma Controls); Daniel L. Brown (AFRL/RZSS); Garret...measurements of Hall thruster plumes that characterize ion energy distributions and charge state fractions using remotely located plasma diagnostics

  10. Entrainment by Lazy Plumes

    NASA Astrophysics Data System (ADS)

    Kaye, Nigel; Hunt, Gary

    2004-11-01

    We consider plumes with source conditions that have a net momentum flux deficit compared to a pure plume - so called lazy plumes. We examine both the case of constant buoyancy flux and buoyancy flux linearly increasing with height. By re-casting the plume conservation equations (Morton, Taylor & Turner 1956) for a constant entrainment coefficient ((α)) in terms of the plume radius (β) and the dimensionless parameter (Γ=frac5Q^2 B4α M^5/2) we show that the far-field flow in a plume with a linear internal buoyancy flux gain is a constant velocity lazy plume with reduced entrainment and radial growth rate. For highly lazy source conditions we derive first-order approximate solutions which indicate a region of zero entrainment near the source. These phenomena have previously been observed, however, it has often been assumed that reduced entrainment implies a reduced (α). We demonstrate that a constant (α) formulation is able to capture the behaviour of these reduced entrainment flows. Morton, B. R., Taylor, G. I. & Turner, J. S. (1956), Turbulent gravitational convection from maintained and instantaneous sources.', Proc. Roy. Soc. 234, 1-23.

  11. Methane Plumes on Mars

    NASA Image and Video Library

    Spectrometer instruments attached to several telescopes detect plumes of methane emitted from Mars during its summer and spring seasons. High levels of methane are indicated by warmer colors. The m...

  12. Genome-resolved metagenomics reveals that sulfur metabolism dominates the microbial ecology of rising hydrothermal plumes

    NASA Astrophysics Data System (ADS)

    Anantharaman, K.; Breier, J. A., Jr.; Jain, S.; Reed, D. C.; Dick, G.

    2015-12-01

    Deep-sea hydrothermal plumes occur when hot fluids from hydrothermal vents replete with chemically reduced elements and compounds like sulfide, methane, hydrogen, ammonia, iron and manganese mix with cold, oxic seawater. Chemosynthetic microbes use these reduced chemicals to power primary production and are pervasive throughout the deep sea, even at sites far removed from hydrothermal vents. Although neutrally-buoyant hydrothermal plumes have been well-studied, rising hydrothermal plumes have received little attention even though they represent an important interface in the deep-sea where microbial metabolism and particle formation processes control the transformation of important elements and impact global biogeochemical cycles. In this study, we used genome-resolved metagenomic analyses and thermodynamic-bioenergetic modeling to study the microbial ecology of rising hydrothermal plumes at five different hydrothermal vents spanning a range of geochemical gradients at the Eastern Lau Spreading Center (ELSC) in the Western Pacific Ocean. Our analyses show that differences in the geochemistry of hydrothermal vents do not manifest in microbial diversity and community composition, both of which display only minor variance across ELSC hydrothermal plumes. Microbial metabolism is dominated by oxidation of reduced sulfur species and supports a diversity of bacteria, archaea and viruses that provide intriguing insights into metabolic plasticity and virus-mediated horizontal gene transfer in the microbial community. The manifestation of sulfur oxidation genes in hydrogen and methane oxidizing organisms hints at metabolic opportunism in deep-sea microbes that would enable them to respond to varying redox conditions in hydrothermal plumes. Finally, we infer that the abundance, diversity and metabolic versatility of microbes associated with sulfur oxidation impart functional redundancy that could allow it to persist in the dynamic settings of hydrothermal plumes.

  13. Sulfur plumes off Namibia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Sulfur plumes rising up from the bottom of the ocean floor produce colorful swirls in the waters off the coast of Namibia in southern Africa. The plumes come from the breakdown of marine plant matter by anaerobic bacteria that do not need oxygen to live. This image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on April 24, 2002 Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  14. Sulfur plumes off Namibia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Sulfur plumes rising up from the bottom of the ocean floor produce colorful swirls in the waters off the coast of Namibia in southern Africa. The plumes come from the breakdown of marine plant matter by anaerobic bacteria that do not need oxygen to live. This image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on April 24, 2002 Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  15. Plume Measurement System (PLUMES) Calibration Experiment

    DTIC Science & Technology

    1994-08-01

    Atle Lohrmann SonTek, Inc. 7940 Silverton Avenue, No. 105 San Diego, California 92126 and Craig Huhta JIMAR University of Hawaii, Honolulu, Hawaii 96822...Measurement System (PLUMES) Calibration Experiment by Age Lohrmann SonTek, Inc. 7940 Silverton Avenue, No. 105 San Diego, CA 92126 Craig Huhta JIMAR...PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) &. PERFORMING ORGANIZATION SonTek, Inc., 7940 Silverton Avenue, No. 105, San Diego, CA 92126 REPORT NUMBER

  16. Hubble Captures Volcanic Eruption Plume From Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Hubble Space Telescope has snapped a picture of a 400-km-high (250-mile-high) plume of gas and dust from a volcanic eruption on Io, Jupiter's large innermost moon.

    Io was passing in front of Jupiter when this image was taken by the Wide Field and Planetary Camera 2 in July 1996. The plume appears as an orange patch just off the edge of Io in the eight o'clock position, against the blue background of Jupiter's clouds. Io's volcanic eruptions blasts material hundreds of kilometers into space in giant plumes of gas and dust. In this image, material must have been blown out of the volcano at more than 2,000 mph to form a plume of this size, which is the largest yet seen on Io.

    Until now, these plumes have only been seen by spacecraft near Jupiter, and their detection from the Earth-orbiting Hubble Space Telescope opens up new opportunities for long-term studies of these remarkable phenomena.

    The plume seen here is from Pele, one of Io's most powerful volcanos. Pele's eruptions have been seen before. In March 1979, the Voyager 1 spacecraft recorded a 300-km-high eruption cloud from Pele. But the volcano was inactive when the Voyager 2 spacecraft flew by Jupiter in July 1979. This Hubble observation is the first glimpse of a Pele eruption plume since the Voyager expeditions.

    Io's volcanic plumes are much taller than those produced by terrestrial volcanos because of a combination of factors. The moon's thin atmosphere offers no resistance to the expanding volcanic gases; its weak gravity (one-sixth that of Earth) allows material to climb higher before falling; and its biggest volcanos are more powerful than most of Earth's volcanos.

    This image is a contrast-enhanced composite of an ultraviolet image (2600 Angstrom wavelength), shown in blue, and a violet image (4100 Angstrom wavelength), shown in orange. The orange color probably occurs because of the absorption and/or scattering of ultraviolet light in the plume. This light from Jupiter passes through

  17. Plume-induced subduction

    NASA Astrophysics Data System (ADS)

    Gerya, T.; Stern, R. J.; Baes, M.; Sobolev, S. V.; Whattam, S. A.

    2016-12-01

    Dominant present-day subduction initiation mechanisms require acting plate forces and/or pre-existing zones of lithospheric weakness, which are themselves consequences of plate tectonics. In contrast, recently discovered plume-induced subduction initiation could have started the first subduction zone without pre-existing plate tectonics. Here, we investigate this new mechanism with high-resolution 3D numerical thermomechanical modeling experiments. We show that typical plume-induced subduction dynamics is subdivided into five different stages: (1) oceanic plateau formation by arrival of a mantle plume head; (2) formation of an incipient trench and a descending nearly-circular slab at the plateau margins; (3) tearing of the circular slab; (4) formation of several self-sustained retreating subduction zones and (5) cooling and spreading of the new lithosphere formed between the retreating subduction zones. At the final stage of plume-induced subduction initiation, a mosaic of independently moving, growing and cooling small oceanic plates heading toward individual retreating subduction zones forms. The plates are separated by spreading centers, triple junctions and transform faults and thus the newly formed multi-slab subduction system operates as an embryonic plate tectonic cell. We demonstrate that three key physical factors combine to trigger self-sustained plume-induced subduction: (1) old negatively buoyant oceanic lithosphere; (2) intense weakening of the lithosphere by plume-derived magmas; and (3) lubrication of the forming subduction interface by hydrated oceanic crust. We furthermore discuss that plume-induced subduction, which is rare at present day conditions, may have been common in the Precambrian time and likely started global plate tectonics on Earth.

  18. Coronal Plumes in the Fast Solar Wind

    NASA Technical Reports Server (NTRS)

    Velli, Marco; Lionello, Roberto; Linker, Jon A.; Mikic, Zoran

    2011-01-01

    The expansion of a coronal hole filled with a discrete number of higher density coronal plumes is simulated using a time-dependent two-dimensional code. A solar wind model including an exponential coronal heating function and a flux of Alfven waves propagating both inside and outside the structures is taken as a basic state. Different plasma plume profiles are obtained by using different scale heights for the heating rates. Remote sensing and solar wind in situ observations are used to constrain the parameter range of the study. Time dependence due to plume ignition and disappearance is also discussed. Velocity differences of the order of approximately 50 km/s, such as those found in microstreams in the high-speed solar wind, may be easily explained by slightly different heat deposition profiles in different plumes. Statistical pressure balance in the fast wind data may be masked by the large variety of body and surface waves which the higher density filaments may carry, so the absence of pressure balance in the microstreams should not rule out their interpretation as the extension of coronal plumes into interplanetary space. Mixing of plume-interplume material via the Kelvin-Helmholtz instability seems to be possible within the parameter ranges of the models defined here, only at large di stances from the Sun, beyond 0.2-0.3 AU. Plasma and composition measurements in the inner heliosphere, such as those which will become available with Solar Orbiter and Solar Probe Plus, should therefore definitely be able to identify plume remnants in the solar wind.

  19. Coronal Plumes in the Fast Solar Wind

    NASA Technical Reports Server (NTRS)

    Velli, Marco; Lionello, Roberto; Linker, Jon A.; Mikic, Zoran

    2011-01-01

    The expansion of a coronal hole filled with a discrete number of higher density coronal plumes is simulated using a time-dependent two-dimensional code. A solar wind model including an exponential coronal heating function and a flux of Alfven waves propagating both inside and outside the structures is taken as a basic state. Different plasma plume profiles are obtained by using different scale heights for the heating rates. Remote sensing and solar wind in situ observations are used to constrain the parameter range of the study. Time dependence due to plume ignition and disappearance is also discussed. Velocity differences of the order of approximately 50 km/s, such as those found in microstreams in the high-speed solar wind, may be easily explained by slightly different heat deposition profiles in different plumes. Statistical pressure balance in the fast wind data may be masked by the large variety of body and surface waves which the higher density filaments may carry, so the absence of pressure balance in the microstreams should not rule out their interpretation as the extension of coronal plumes into interplanetary space. Mixing of plume-interplume material via the Kelvin-Helmholtz instability seems to be possible within the parameter ranges of the models defined here, only at large di stances from the Sun, beyond 0.2-0.3 AU. Plasma and composition measurements in the inner heliosphere, such as those which will become available with Solar Orbiter and Solar Probe Plus, should therefore definitely be able to identify plume remnants in the solar wind.

  20. Composite flight-control actuator development

    NASA Technical Reports Server (NTRS)

    Bott, Richard; Ching, Fred

    1992-01-01

    The composite actuator is 'jam resistant', satisfying a survivability requirement for the Navy. Typically, the push-pull force needed to drive through the wound area of the composite actuator is 73 percent less than that of an all-metal actuator. In addition to improving the aircraft's combat survivability, significant weight savings were realized. The current design of the survivable, composite actuator cylinder is 36 percent lighter than that of the production steel cylinder, which equates to a 15 percent overall actuator weight savings.

  1. Isotopically enriched N-MORB: a new geochemical signature for plume-ridge interaction

    NASA Astrophysics Data System (ADS)

    Yang, A. Y.; Zhao, T.; Zhou, M. F.

    2016-12-01

    The presence of E-MORB (mid-ocean ridge basalts with enrichments in light rare earth elements (LREE)) at MOR has long been considered as the necessary geochemical evidence for plume-ridge interaction, because plume materials are normally more enriched in both trace elements and isotopic compositions than the source of N-MORB (normal-MORB). However, global MORB compilation indicates that MORB erupted on the ridge segments within 200 km of hotspots do not always show obvious E-MORB signatures. Therefore, is it true that E-MORB is the only possible geochemical signature of such interaction? Alternatively, isotopic enriched N-MORB in this study, combined with MORB of such kind worldwide, would potentially provide a new perspective on our understanding on the geochemical expression of plume-ridge interactions. Interaction between the Southwest Indian Ridge (46°E and 52°20'E) and Crozet hotspot has been proposed by geophysical studies, but remains controversial mostly due to the lack of E-MORB. 47 new samples collected from this region during the RV Dayang Yihao Cruise, including 15 from the segment 27 centered at 50°28'E with 10-km thick crust, are all N-MORB and can be classified into two groups: a high-Al group only at 50°28'E and a Main group widespread. The former, with higher Al2O3 and lower TiO2 and SiO2, have slightly enriched Sr-Nd-Hf-Pb isotopic compositions. Considering almost twice the thickness of the segment 27 than nearby segments for at least 3 Ma, the enriched isotopic compositions call for the presence of a hot and isotopically enriched source with previous melt extraction to deplete the incompatible elements. Neither melting residue related to the Madagascar and Karoo flood basalts nor local mantle heterogeneity can meet such requirements. The Crozet plume melting residues, alternatively, are the likely source. The isotopically enriched N-MORB formed by re-melting of the Crozet hotspot with previous melt extraction likely during transportation

  2. Implementing Controlled Composition to Improve Vocabulary Mastery of EFL Students

    ERIC Educational Resources Information Center

    Juriah

    2015-01-01

    The purposes of this study was to know how (1) Controlled composition teaching techniques implemented by the English teacher at SDN 027 Samarinda to improve vocabulary mastery, and (2) Controlled composition teaching techniques improves vocabulary mastery of the sixth grade students of SDN 027 Samarinda. This research used a Classroom Action…

  3. A Brilliant Plume

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Long Range Reconnaissance Imager (LORRI) on New Horizons captured another dramatic picture of Jupiter's moon Io and its volcanic plumes, 19 hours after the spacecraft's closest approach to Jupiter on Feb. 28, 2007. LORRI took this 75 millisecond exposure at 0035 Universal Time on March 1, 2007, when Io was 2.3 million kilometers (1.4 million miles) from the spacecraft.

    Io's dayside is deliberately overexposed to bring out faint details in the plumes and on the moon's night side. The continuing eruption of the volcano Tvashtar, at the 1 o'clock position, produces an enormous plume roughly 330 kilometers (200 miles) high, which is illuminated both by sunlight and 'Jupiter light.'

    The shadow of Io, cast by the Sun, slices across the plume. The plume is quite asymmetrical and has a complicated wispy texture, for reasons that are still mysterious. At the heart of the eruption incandescent lava, seen here as a brilliant point of light, is reminding scientists of the fire fountains spotted by the Galileo Jupiter orbiter at Tvashtar in 1999.

    The sunlit plume faintly illuminates the surface underneath. 'New Horizons and Io continue to astonish us with these unprecedented views of the solar system's most geologically active body' says John Spencer, deputy leader of the New Horizons Jupiter Encounter Science Team and an Io expert from Southwest Research Institute.

    Because this image shows the side of Io that faces away from Jupiter, the large planet does not illuminate the moon's night side except for an extremely thin crescent outlining the edge of the disk at lower right. Another plume, likely from the volcano Masubi, is illuminated by Jupiter just above this lower right edge. A third and much fainter plume, barely visible at the 2 o'clock position, could be the first plume seen from the volcano Zal Patera.

    As in other New Horizons images of Io, mountains catch the setting Sun just beyond the terminator (the line dividing day and night

  4. A Brilliant Plume

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Long Range Reconnaissance Imager (LORRI) on New Horizons captured another dramatic picture of Jupiter's moon Io and its volcanic plumes, 19 hours after the spacecraft's closest approach to Jupiter on Feb. 28, 2007. LORRI took this 75 millisecond exposure at 0035 Universal Time on March 1, 2007, when Io was 2.3 million kilometers (1.4 million miles) from the spacecraft.

    Io's dayside is deliberately overexposed to bring out faint details in the plumes and on the moon's night side. The continuing eruption of the volcano Tvashtar, at the 1 o'clock position, produces an enormous plume roughly 330 kilometers (200 miles) high, which is illuminated both by sunlight and 'Jupiter light.'

    The shadow of Io, cast by the Sun, slices across the plume. The plume is quite asymmetrical and has a complicated wispy texture, for reasons that are still mysterious. At the heart of the eruption incandescent lava, seen here as a brilliant point of light, is reminding scientists of the fire fountains spotted by the Galileo Jupiter orbiter at Tvashtar in 1999.

    The sunlit plume faintly illuminates the surface underneath. 'New Horizons and Io continue to astonish us with these unprecedented views of the solar system's most geologically active body' says John Spencer, deputy leader of the New Horizons Jupiter Encounter Science Team and an Io expert from Southwest Research Institute.

    Because this image shows the side of Io that faces away from Jupiter, the large planet does not illuminate the moon's night side except for an extremely thin crescent outlining the edge of the disk at lower right. Another plume, likely from the volcano Masubi, is illuminated by Jupiter just above this lower right edge. A third and much fainter plume, barely visible at the 2 o'clock position, could be the first plume seen from the volcano Zal Patera.

    As in other New Horizons images of Io, mountains catch the setting Sun just beyond the terminator (the line dividing day and night

  5. Modeling the Enceladus Plume--Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Fleshman, B. L.; Delamere, P. A.; Bagenal, F.

    2009-12-01

    We investigate the chemical interaction between Saturn's corotating plasma and Enceladus' volcanic plumes. The evolution of a parcel of ambient plasma passing through a prescribed H2O plume is estimated using a physical chemistry model based on the Io torus chemistry but adapted for water-group reactions. The flow field is assumed to be that of a plasma around an electrically-conducting obstacle centered on Enceladus and aligned with Saturn's magnetic field, consistent with Cassini magnetometer data. Our results suggest that charge exchange dominates the local chemistry and that H3O+ dominates the water-group composition downstream of the Enceladus plumes. We explore the effects on the physical chemistry of (1) a small population of hot electrons and (2) a flow decelerated in response to the pickup of fresh ions near the plumes. Charge exchange dominates the local interaction, leading to an H3O+-dominated local water-group chemistry. Pickup Rate/(kg s-1) Pickup rate from the plasma--plume interaction. We emphasize: (1) The possibility of hot electron beams at Enceladus, given the contraints on charge exchange + impact ionization pickup [0.2--3 kg s-1, Khurana et al. (2007); Saur et al. (2007); Burger et al. (2008)]. (2) Charge exchange dominates the local chemistry.

  6. Particle Characterization in Rocket Exhaust Plumes

    NASA Technical Reports Server (NTRS)

    Callen, E. Eugene, Jr.; Fisher, J. Scott

    1997-01-01

    A method to characterize particles in rocket exhaust plumes is developed. The particle velocity, size, and material composition are determined from crater characteristics resulting from impacts into aluminum and copper targets passed through the plume. The targets are mounted on a steel arm approximately 21 inches (53 cm) long which is rotated through the plume at sufficient velocity to prevent material failure resulting from thermal effects. A Scanning Electron Microscope (SEM) with secondary x-ray detectors is used to determine the particle material, and a standard optical measurement microscope is used to determine the crater diameter and depth. The crater diameter and depth are used in turn, as inputs to a ballistics computer code to estimate the velocity and size of the particle. The target has a safe residence time in the plume of approximately 50 ms before reaching an unacceptably high temperature. The = must mach a velocity of 104 ft/s (32 m/s) before entering the plume to produce the design residence time of 20 ms. The arm is actuated by a torsion spring with a 5-inch (13 cm) outer diameter, 0.625-inch (16 mm wire diameter, and 11 coils. A prototype of the entire rocket exhaust particle impact characterization system (PICS) was constructed and statically tested.

  7. Martian Atmospheric Plumes: Behavior, Detectability and Plume Tracing

    NASA Astrophysics Data System (ADS)

    Banfield, Don; Mischna, M.; Sykes, R.; Dissly, R.

    2013-10-01

    We will present our recent work simulating neutrally buoyant plumes in the martian atmosphere. This work is primarily directed at understanding the behavior of discrete plumes of biogenic tracer gases, and thus increasing our understanding of their detectability (both from orbit and from in situ measurements), and finally how to use the plumes to identify their precise source locations. We have modeled the detailed behavior of martian atmospheric plumes using MarsWRF for the atmospheric dynamics and SCIPUFF (a terrestrial state of the art plume modeling code that we have modified to represent martian conditions) for the plume dynamics. This combination of tools allows us to accurately simulate plumes not only from a regional scale from which an orbital observing platform would witness the plume, but also from an in situ perspective, with the instantaneous concentration variations that a turbulent flow would present to a point sampler in situ instrument. Our initial work has focused on the detectability of discrete plumes from an orbital perspective and we will present those results for a variety of notional orbital trace gas detection instruments. We have also begun simulating the behavior of the plumes from the perspective of a sampler on a rover within the martian atmospheric boundary layer. The detectability of plumes within the boundary layer has a very strong dependence on the atmospheric stability, with plume concentrations increasing by a factor of 10-1000 during nighttime when compared to daytime. In the equatorial regions of the planet where we have simulated plumes, the diurnal tidal “clocking” of the winds is strongly evident in the plume trail, which similarly “clocks” around its source. This behavior, combined with the strong diurnal concentration variations suggests that a rover hunting a plume source would be well suited to approach it from a particular azimuth (downwind at night) to maximize detectability of the plume and the ability to

  8. Volcanic Plume Measurements with UAV (Invited)

    NASA Astrophysics Data System (ADS)

    Shinohara, H.; Kaneko, T.; Ohminato, T.

    2013-12-01

    Volatiles in magmas are the driving force of volcanic eruptions and quantification of volcanic gas flux and composition is important for the volcano monitoring. Recently we developed a portable gas sensor system (Multi-GAS) to quantify the volcanic gas composition by measuring volcanic plumes and obtained volcanic gas compositions of actively degassing volcanoes. As the Multi-GAS measures variation of volcanic gas component concentrations in the pumped air (volcanic plume), we need to bring the apparatus into the volcanic plume. Commonly the observer brings the apparatus to the summit crater by himself but such measurements are not possible under conditions of high risk of volcanic eruption or difficulty to approach the summit due to topography etc. In order to overcome these difficulties, volcanic plume measurements were performed by using manned and unmanned aerial vehicles. The volcanic plume measurements by manned aerial vehicles, however, are also not possible under high risk of eruption. The strict regulation against the modification of the aircraft, such as installing sampling pipes, also causes difficulty due to the high cost. Application of the UAVs for the volcanic plume measurements has a big advantage to avoid these problems. The Multi-GAS consists of IR-CO2 and H2O gas analyzer, SO2-H2O chemical sensors and H2 semiconductor sensor and the total weight ranges 3-6 kg including batteries. The necessary conditions of the UAV for the volcanic plumes measurements with the Multi-GAS are the payloads larger than 3 kg, maximum altitude larger than the plume height and installation of the sampling pipe without contamination of the exhaust gases, as the exhaust gases contain high concentrations of H2, SO2 and CO2. Up to now, three different types of UAVs were applied for the measurements; Kite-plane (Sky Remote) at Miyakejima operated by JMA, Unmanned airplane (Air Photo Service) at Shinomoedake, Kirishima volcano, and Unmanned helicopter (Yamaha) at Sakurajima

  9. Redox conditions for mantle plumes

    NASA Astrophysics Data System (ADS)

    Heister, L. E.; Lesher, C. E.

    2005-12-01

    The vanadium to scandium ratio (V/Sc) for basalts from mid-ocean ridge (MOR) and arc environments has been proposed as a proxy for fO2 conditions during partial melting (e.g. [1] and [2]). Contrary to barometric measurements of the fO2 of primitive lavas, the V/Sc ratio of the upper mantle at mid-ocean ridges and arcs is similar, leading previous authors to propose that the upper mantle has uniform redox potential and is well-buffered. We have attempted to broaden the applicability of the V/Sc parameter to plume-influenced localities (both oceanic and continental), where mantle heterogeneities associated with recycled sediments, mafic crust, and metasomatized mantle, whether of shallow or deep origin, exist. We find that primitive basalts from the North Atlantic Igneous Province (NAIP), Hawaii (both the Loa and Kea trends), Deccan, Columbia River, and Siberian Traps show a range of V/Sc ratios that are generally higher (average ~9) than those for MOR (average ~ 6.7) or arc (average ~7) lavas. Based on forward polybaric decompression modeling, we attribute these differences to polybaric melting and melt segregation within the garnet stability field rather than the presence of a more oxidized mantle in plume-influenced settings. Like MORB, the V/Sc ratios for plume-influenced basalts can be accounted for by an oxidation state approximately one log unit below the Ni-NiO buffer (NNO-1). Our analysis suggests that source heterogeneities have little, if any, resolvable influence on mantle redox conditions, although they have significant influence on the trace element and isotopic composition of mantle-derived melts. We suggest that variations in the redox of erupted lavas is largely a function of shallow lithospheric processes rather than intrinsic to the mantle source, regardless of tectonic setting. [1] Li and Lee (2004) EPSL, [2] Lee et al. (2005) J. of Petrology

  10. Ridge suction drives plume-ridge interactions

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Hékinian, R.

    2003-04-01

    geochemical anomalies extend < 400 km along the slower (20 to 13 mm/yr northward) spreading South Kolbeinsey Ridge, but > 1500 km along the faster (20 to 25 mm/yr southward) spreading Reykjanes Ridge. 4. The spreading-rate dependent ridge suction force also explains the first-order differences between the fast-spreading East Pacific Rise (EPR) and the slow-spreading Mid-Atlantic Ridge (MAR). Identified mantle plumes/hotspots are abundant near the MAR (e.g., Iceland, Azores, Ascension, Tristan, Gough, Shona and Bouvet), but rare along the entire EPR (notably, the Easter hotspot at ˜27^oS on the Nazca plate). Such apparent unequal hotspot distribution would allow a prediction of more enriched MORB at the MAR than at the EPR. However, the mean compositions between MAR-MORB and EPR-MORB are the same in terms of incompatible element abundances, and are identical in terms of Sr-Nd-Pb isotopic ratios. This suggests similar extents of mantle plume contributions to EPR and MAR MORB. We consider that the apparent rarity of near-EPR plumes/hotspots results from fast spreading. The fast spreading creates large ridge suction forces that do not allow the development of surface expressions of mantle plumes as such, but draw plume materials to a broad zone of sub-ridge upwelling, giving rise to random distribution of abundant enriched MORB and elevated and smooth axial topography along the EPR (vs. MAR). One of the important implications is that the asthenospheric flow is necessarily decoupled from its overlaying oceanic lithospheric plate. This decoupling increases with increasing spreading rate.

  11. Plume primary smoke

    NASA Astrophysics Data System (ADS)

    Chastenet, J. C.

    1993-06-01

    The exhaust from a solid propellant rocket motor usually contains condensed species. These particles, also called 'Primary Smoke', are often prejudicial to missile detectability and to the guidance system. To avoid operational problems it is necessary to know and quantify the effects of particles on all aspects of missile deployment. A brief description of the origin of the primary smoke is given. It continues with details of the interaction between particles and light as function of both particles and light properties (nature, size, wavelength, etc). The effects of particles on plume visibility, attenuation of an optical beam propagated through the plume and the contribution of particles on optical signatures of the plume are also described. Finally, various methods used in NATO countries to quantify the primary smoke effects are discussed.

  12. African Equatorial and Subtropical Ozone Plumes: Recurrences Timescales of the Brown Cloud Trans-African Plumes and Other Plumes

    NASA Technical Reports Server (NTRS)

    Chatfield, Robert B.; Thompson, Anne M.; Guan, Hong; Witte, Jacquelyn C.

    2004-01-01

    We have found repeated illustrations in the maps of Total Tropospheric Ozone (TTO) of apparent transport of ozone from the Indian Ocean to the Equatorial Atlantic Ocean. Most interesting are examples that coincide with the INDOEX observations of late northern winter, 1999. Three soundings associated with the SHADOZ (Southern Hemisphere Additional Ozonesondes) network help confirm and quantify degree of influence of pollution, lightning, and stratospheric sources, suggesting that perhaps 40% of increased Atlantic ozone could be Asian pollution during periods of maximum identified in the TTO maps. We outline recurrent periods of apparent ozone transport from Indian to Atlantic Ocean regions both during and outside the late-winter period. These are placed in the context of some general observations about factors controlling recurrence timescales for the expression of both equatorial and subtropical plumes. Low-level subtropical plumes are often controlled by frontal systems approaching the Namib coast; these direct mid-level air into either easterly equatorial plumes or westerly mid- troposphere plumes. Equatorial plumes of ozone cross Africa on an easterly path due to the occasional coincidence of two phenomena: (1) lofting of ozone to mid and upper levels, often in the Western Indian Ocean, and (2) the eastward extension of an Equatorial African easterly jet.

  13. African Equatorial and Subtropical Ozone Plumes: Recurrence Timescales of the Brown Cloud Trans-African Plume and Other Plumes

    NASA Astrophysics Data System (ADS)

    Chatfield, R. B.; Guan, H.; Thompson, A. M.; Witte, J.

    2004-05-01

    We have found repeated illustrations in the maps of Total Tropospheric Ozone (TTO) of apparent transport of ozone from the Indian Ocean to the Equatorial Atlantic Ocean. Most interesting are examples that coincide with the INDOEX observations of late northern winter, 1999. Three soundings associated with the SHADOZ (Southern Hemisphere Additional Ozonesondes) network help confirm and quantify degree of influence of pollution, lightning, and stratospheric sources, suggesting that perhaps 40% of increased Atlantic ozone could be Asian pollution during periods of maximum identified in the TTO maps. We outline recurrent periods of apparent ozone transport from Indian to Atlantic Ocean regions both during and outside the late-winter period. These are placed in the context of some general observations about factors controlling recurrence timescales for the expression of both equatorial and subtropical plumes. Low-level subtropical plumes are often controlled by frontal systems approaching the Namib coast; these direct mid-level air into eithier easterly equatorial plumes or westerly mid-troposphere plumes. Equatorial plumes of ozone cross Africa on an easterly path due to the occasional coincidence of two phenomena: (1) lofting of ozone to mid and upper levels, often in the Western Indian Ocean, and (2) the eastward extension of an Equatorial African easterly jet.

  14. African Equatorial and Subtropical Ozone Plumes: Recurrences Timescales of the Brown Cloud Trans-African Plumes and Other Plumes

    NASA Technical Reports Server (NTRS)

    Chatfield, Robert B.; Thompson, Anne M.; Guan, Hong; Witte, Jacquelyn C.

    2004-01-01

    We have found repeated illustrations in the maps of Total Tropospheric Ozone (TTO) of apparent transport of ozone from the Indian Ocean to the Equatorial Atlantic Ocean. Most interesting are examples that coincide with the INDOEX observations of late northern winter, 1999. Three soundings associated with the SHADOZ (Southern Hemisphere Additional Ozonesondes) network help confirm and quantify degree of influence of pollution, lightning, and stratospheric sources, suggesting that perhaps 40% of increased Atlantic ozone could be Asian pollution during periods of maximum identified in the TTO maps. We outline recurrent periods of apparent ozone transport from Indian to Atlantic Ocean regions both during and outside the late-winter period. These are placed in the context of some general observations about factors controlling recurrence timescales for the expression of both equatorial and subtropical plumes. Low-level subtropical plumes are often controlled by frontal systems approaching the Namib coast; these direct mid-level air into either easterly equatorial plumes or westerly mid- troposphere plumes. Equatorial plumes of ozone cross Africa on an easterly path due to the occasional coincidence of two phenomena: (1) lofting of ozone to mid and upper levels, often in the Western Indian Ocean, and (2) the eastward extension of an Equatorial African easterly jet.

  15. Investigation of power-plant plume photochemistry using a reactive plume model

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Kim, H. S.; Song, C. H.

    2016-12-01

    Emissions from large-scale point sources have continuously increased due to the rapid industrial growth. In particular, primary and secondary air pollutants are directly relevant to atmospheric environment and human health. Thus, we tried to precisely describe the atmospheric photochemical conversion from primary to secondary air pollutants inside the plumes emitted from large-scale point sources. A reactive plume model (RPM) was developed to comprehensively consider power-plant plume photochemistry with 255 condensed photochemical reactions. The RPM can simulate two main components of power-plant plumes: turbulent dispersion of plumes and compositional changes of plumes via photochemical reactions. In order to evaluate the performance of the RPM developed in the present study, two sets of observational data obtained from the TexAQS II 2006 (Texas Air Quality Study II 2006) campaign were compared with RPM-simulated data. Comparison shows that the RPM produces relatively accurate concentrations for major primary and secondary in-plume species such as NO2, SO2, ozone, and H2SO4. Statistical analyses show good correlation, with correlation coefficients (R) ranging from 0.61 to 0.92, and good agreement with the Index of Agreement (IOA) ranging from 0.70 to 0.95. Following evaluation of the performance of the RPM, a demonstration was also carried out to show the applicability of the RPM. The RPM can calculate NOx photochemical lifetimes inside the two plumes (Monticello and Welsh power plants). Further applicability and possible uses of the RPM are also discussed together with some limitations of the current version of the RPM.

  16. Rocket plume burn hazard.

    PubMed

    Stoll, A M; Piergallini, J R; Chianta, M A

    1980-05-01

    By use of miniature rocket engines, the burn hazard posed by exposure to ejection seat rocket plume flames was determined in the anaesthetized rat. A reference chart is provided for predicting equivalent effects in human skin based on extrapolation of earlier direct measurements of heat input for rat and human burns. The chart is intended to be used in conjunction with thermocouple temperature measurements of the plume environment for design and modification of escape seat system to avoid thermal injury on ejection from multiplace aircraft.

  17. Eiffel Tower Plume

    NASA Image and Video Library

    2015-08-19

    This still image from an animation from NASA GSFC Solar Dynamics Observatory shows a single plume of plasma, many times taller than the diameter of Earth, spewing streams of particles for over two days Aug. 17-19, 2015 before breaking apart. At times, its shape resembled the Eiffel Tower. Other lesser plumes and streams of particles can be seen dancing above the solar surface as well. The action was observed in a wavelength of extreme ultraviolet light. http://photojournal.jpl.nasa.gov/catalog/PIA19875

  18. A Composite Discrete/Continuous Control of Robot Manipulators

    DTIC Science & Technology

    1991-04-01

    technical 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS A Composite Discrete/Continuous Control of Robot Manipulators 6. AUTHOR(S) Ju-Jang Lee and...Yangsheng Xu 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) B. PERFORMING ORGANIZATION REPORT NUMBER The Robotics Institute Carnegie Mellon University CMU...13. ABSTRACT ’Maximum ,CO wors;A In this report, a composite control scheme for the control of robot manipulators is proposed. Due to the modeling

  19. Vibration control of pre-twisted rotating composite thin-walled beams with piezoelectric fiber composites

    NASA Astrophysics Data System (ADS)

    Choi, Seung-Chan; Park, Jae-Sang; Kim, Ji-Hwan

    2007-02-01

    Rotating composite beam structures like blades are applied in many fields of aerospace and mechanical engineering. In this research, bending vibration control of the pre-twisted rotating composite thin-walled beam is studied. The formulation is based on single cell composite beam including a warping function, centrifugal force, Coriolis acceleration, pre-twist angle and piezoelectric effect. A negative velocity feedback control algorithm is applied to realize the adaptive capability of the beam. Using a finite-element method, numerical simulations show that macro-fiber composite (MFC) actuators which are piezoelectric fiber composites and PVDF sensors can generate active vibration control effect. Relations between active vibration control effect and design parameters of beams such as rotating speeds, pre-twist angles and fiber orientations in a host structure are investigated in detail. Besides, a case study conformed that the effective damping performance can be obtained by suitable arrangement and distribution of the sensor and actuator pairs.

  20. Sulfur chemistry in a copper smelter plume

    NASA Astrophysics Data System (ADS)

    Eatough, D. J.; Christensen, J. J.; Eatough, N. I.; Hill, M. W.; Major, T. D.; Mangelson, N. F.; Post, M. E.; Ryder, J. F.; Hansen, L. D.; Meisenheimer, R. G.; Fischer, J. W.

    Sulfur transformation chemistry was studied in the plume of the Utah smelter of Kennecott Copper Corporation from April to October 1977. Samples were taken at up to four locations from 4 to 60 km from the stacks. Data collected at each station included: SO 2 concentration, low-volume collected total paniculate matter, high-volume collected size fractionated paniculate matter, wind velocity and direction, temperature, and relative humidity. Paniculate samples were analyzed for S(IV). sulfate, strong acid, anions, cations, and elemental concentrations using calorimetric, ion Chromatographie, FIXE, ESCA, ion microprobe, and SEM-ion microprobe techniques. The concentration of As in the paniculate matter was used as a conservative plume tracer. The ratios Mo/As, Pb/As, and Zn/As were constant in particulate matter collected at all sampling sites for any particle size. Strong mineral acid was neutralized by background metal oxide and/or carbonate particulates within 40km of the smelter. This neutralization process is limited only by the rate of incorporation of basic material into the plume. Two distinct metal-S(IV) species similar to those observed in laboratory aerosol experiments were found in the plume. The formation of paniculate S(IV) species occurs by interaction of SO 2 (g) with both ambient and plume derived aerosol and is equilibrium controlled. The extent of formation of S(IV) complexes in the aerosol is directly proportional to the SO 2(g) and paniculate (Cu + Fe) concentration and inversely proportional to the paniculate acidity. S(IV) species were stable in collected paniculate matter only in the neutralized material, but with proper sampling techniques could be demonstrated to also be present in very acidic particles at high ambient SO 2(g) concentrations. Reduction of arsenate to arsenite by the aerosol S(IV) complexes during plume transport is suggested. The SO 2(g)-sulfate conversion process in the plume is described by a mechanism which is first order

  1. Modeling the Effects of Aircraft Emissions on Atmospheric Photochemistry Using Layered Plume Dynamics

    NASA Astrophysics Data System (ADS)

    Cameron, M. A.; Jacobson, M. Z.; Naiman, A. D.; Lele, S. K.

    2012-12-01

    Aviation is an expanding industry, experiencing continued growth and playing an increasingly noticed role in upper tropospheric/lower stratospheric composition. Nitrogen oxides and other gas-phase emissions from aircraft react to affect ozone photochemistry. This research investigates the effects of treating aircraft gas-phase chemistry within an expanding layered plume versus at the grid scale. SMVGEAR II, a sparse-matrix, vectorized Gear-type solver for ordinary differential equations, is used to solve chemical equations at both the grid scale and subgrid scale. A Subgrid Plume Model (SPM) is used to advance the expanding plume, accounting for wind shear and diffusion. Simulations suggest that using a layered plume approach results in noticeably different final NOx concentrations, demonstrating the importance of these plume dynamics in predicting the effects of aircraft on ozone concentrations. Results showing the effects of a layered plume, single plume, and no plume on ozone after several hours will be presented.

  2. Active Volcanic Plumes on Io

    NASA Image and Video Library

    1998-03-26

    This color image, acquired during NASA Galileo ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon, erupting over a caldera volcanic depression named Pillan Patera.

  3. Hydrostatic Modeling of Buoyant Plumes

    NASA Astrophysics Data System (ADS)

    Stroman, A.; Dewar, W. K.; Wienders, N.; Deremble, B.

    2014-12-01

    The Deepwater Horizon oil spill in the Gulf of Mexico has led to increased interest in understanding point source convection dynamics. Most of the existing oil plume models use a Lagrangian based approach, which computes integral measures such as plume centerline trajectory and plume radius. However, this approach doesn't account for feedbacks of the buoyant plume on the ambient environment. Instead, we employ an Eulerian based approach to acquire a better understanding of the dynamics of buoyant plumes. We have performed a series of hydrostatic modeling simulations using the MITgcm. Our results show that there is a dynamical response caused by the presence of the buoyant plume, in that there is a modification of the background flow. We find that the buoyant plume becomes baroclinically unstable and sheds eddies at the neutral buoyancy layer. We also explore different scenarios to determine the effect of the buoyancy source and the temperature stratification on the evolution of buoyant plumes.

  4. LAMP Observes the LCROSS Plume

    NASA Image and Video Library

    This video shows LAMP’s view of the LCROSS plume. The first half of the animation shows the LAMP viewport scanning across the horizon, passing through the plume, and moving on. The second half of...

  5. EUV analysis of polar plumes

    NASA Technical Reports Server (NTRS)

    Ahmad, I. A.; Withbroe, G. L.

    1977-01-01

    Three polar plumes were studied using Skylab Mg X and O VI data. The plumes lie within the boundaries of a polar coronal hole. We find that the mean temperature of the plumes is about 1.1 million K and that they have a small vertical temperature gradient. Densities are determined and found consistent with white light analyses. The variation of density with height in the plumes is compared with that expected for hydrostatic equilibrium. As is the case for other coronal features, polar plumes will be a source of solar wind if the magnetic field lines are open. On the basis of the derived plume model and estimates of the numbers of plumes in polar coronal holes, it appears that polar plumes contain about 15% of the mass in a typical polar hole and occupy about 10% of the volume.

  6. Semi-Passive Oxidation-Based Approaches for Control of Large, Dilute Groundwater Plumes of Chlorinated Ethylenes

    DTIC Science & Technology

    2014-04-01

    landfill. Chemosphere 89, 680-687. Crank, J., 1975. The mathematics of diffusion. 2nd ed. Oxford University Press, GB, ISBN 0198533446. 85 Criado...groundwater remediation. Chemosphere 66, 2058-66. doi:10.1016/j.chemosphere.2006.09.093. Lee, E.S. and Schwartz, F.W., 2007b. Characterization and...optimization of long-term controlled release system for groundwater remediation: A generalized modeling approach. Chemosphere 69, 247-253. Lee, E.S

  7. Parameters of thermochemical plumes responsible for the formation of batholiths: Results of experimental simulation

    NASA Astrophysics Data System (ADS)

    Kirdyashkin, A. A.; Kirdyashkin, A. G.; Gurov, V. V.

    2017-07-01

    Based on laboratory and theoretical modeling results, we present the thermal and hydrodynamical structure of the plume conduit during plume ascent and eruption on the Earth's surface. The modeling results show that a mushroom-shaped plume head forms after melt eruption on the surface for 1.9 < Ka < 10. Such plumes can be responsible for the formation of large intrusive bodies, including batholiths. The results of laboratory modeling of plumes with mushroom-shaped heads are presented for Ka = 8.7 for a constant viscosity and uniform melt composition. Images of flow patterns are obtained, as well as flow velocity profiles in the melt of the conduit and the head of the model plume. Based on the laboratory modeling data, we present a scheme of a thermochemical plume with a mushroom-shaped head responsible for the formation of a large intrusive body (batholith). After plume eruption to the surface, melting occurs along the base of the massif above the plume head, resulting in a mushroom-shaped plume head. A possible mechanism for the formation of localized surface manifestations of batholiths is presented. The parameters of some plumes with mushroom-shaped heads (plumes of the Altay-Sayan and Barguzin-Vitim large-igneous provinces, and Khangai and Khentei plumes) are estimated using geological data, including age intervals and volumes of magma melts.

  8. The composition of heterogeneous control laws

    NASA Technical Reports Server (NTRS)

    Kuipers, Benjamin; Astrom, Karl

    1991-01-01

    The fuzzy control literature and industrial practice provide certain nonlinear methods for combining heterogeneous control laws, but these methods have been very difficult to analyze theoretically. An alternate formulation and extension of this approach is presented that has several practical and theoretical benefits. An example of heterogeneous control is given and two alternate analysis methods are presented.

  9. Permeability measurement and control for epoxy composites

    NASA Astrophysics Data System (ADS)

    Chang, Tsun-Hsu; Tsai, Cheng-Hung; Wong, Wei-Syuan; Chen, Yen-Ren; Chao, Hsien-Wen

    2017-08-01

    The coupling of the electric and magnetic fields leads to a strong interplay in materials' permittivity and permeability. Here, we proposed a specially designed cavity, called the mu cavity. The mu cavity, consisting of a mushroom structure inside a cylindrical resonator, is exclusively sensitive to permeability, but not to permittivity. It decouples materials' electromagnetic properties and allows an accurate measurement of the permeability. With the help of an epsilon cavity, these two cavities jointly determine the complex permeability and permittivity of the materials at microwave frequencies. Homemade epoxy-based composite materials were prepared and tested. Measurement and manipulation of the permeability and permittivity of the epoxy composites will be shown. The results will be compared with the effective medium theories.

  10. PLUME and research sotware

    NASA Astrophysics Data System (ADS)

    Baudin, Veronique; Gomez-Diaz, Teresa

    2013-04-01

    The PLUME open platform (https://www.projet-plume.org) has as first goal to share competences and to value the knowledge of software experts within the French higher education and research communities. The project proposes in its platform the access to more than 380 index cards describing useful and economic software for this community, with open access to everybody. The second goal of PLUME focuses on to improve the visibility of software produced by research laboratories within the higher education and research communities. The "development-ESR" index cards briefly describe the main features of the software, including references to research publications associated to it. The platform counts more than 300 cards describing research software, where 89 cards have an English version. In this talk we describe the theme classification and the taxonomy of the index cards and the evolution with new themes added to the project. We will also focus on the organisation of PLUME as an open project and its interests in the promotion of free/open source software from and for research, contributing to the creation of a community of shared knowledge.

  11. Buoyant plume calculations

    SciTech Connect

    Penner, J.E.; Haselman, L.C.; Edwards, L.L.

    1985-01-01

    Smoke from raging fires produced in the aftermath of a major nuclear exchange has been predicted to cause large decreases in surface temperatures. However, the extent of the decrease and even the sign of the temperature change, depend on how the smoke is distributed with altitude. We present a model capable of evaluating the initial distribution of lofted smoke above a massive fire. Calculations are shown for a two-dimensional slab version of the model and a full three-dimensional version. The model has been evaluated by simulating smoke heights for the Hamburg firestorm of 1943 and a smaller scale oil fire which occurred in Long Beach in 1958. Our plume heights for these fires are compared to those predicted by the classical Morton-Taylor-Turner theory for weakly buoyant plumes. We consider the effect of the added buoyancy caused by condensation of water-laden ground level air being carried to high altitude with the convection column as well as the effects of background wind on the calculated smoke plume heights for several fire intensities. We find that the rise height of the plume depends on the assumed background atmospheric conditions as well as the fire intensity. Little smoke is injected into the stratosphere unless the fire is unusually intense, or atmospheric conditions are more unstable than we have assumed. For intense fires significant amounts of water vapor are condensed raising the possibility of early scavenging of smoke particles by precipitation. 26 references, 11 figures.

  12. Enceladus' Water Vapour Plumes

    NASA Technical Reports Server (NTRS)

    Hansen, Candice J.; Esposito, L.; Colwell, J.; Hendrix, A.; Matson, Dennis; Parkinson, C.; Pryor, W.; Shemansky, D.; Stewart, I.; Tew, J.; Yung, Y.

    2006-01-01

    A viewgraph presentation on the discovery of Enceladus water vapor plumes is shown. Conservative modeling of this water vapor is also presented and also shows that Enceladus is the source of most of the water required to supply the neutrals in Saturn's system and resupply the E-ring against losses.

  13. Enceladus' Water Vapour Plumes

    NASA Technical Reports Server (NTRS)

    Hansen, Candice J.; Esposito, L.; Colwell, J.; Hendrix, A.; Matson, Dennis; Parkinson, C.; Pryor, W.; Shemansky, D.; Stewart, I.; Tew, J.; hide

    2006-01-01

    A viewgraph presentation on the discovery of Enceladus water vapor plumes is shown. Conservative modeling of this water vapor is also presented and also shows that Enceladus is the source of most of the water required to supply the neutrals in Saturn's system and resupply the E-ring against losses.

  14. Double Diffusive Plumes

    NASA Astrophysics Data System (ADS)

    Sutherland, Bruce; Lee, Brace

    2008-11-01

    Sour gas flares attempt to dispose of deadly H2S gas through combustion. What does not burn rises as a buoyant plume. But the gas is heavier than air at room temperature, so as the rising gas cools eventually it becomes negatively buoyant and descends back to the ground. Ultimately, our intent is to predict the concentrations of the gas at ground level in realistic atmospheric conditions. As a first step towards this goal we have performed laboratory experiments examining the structure of a steady state plume of hot and salty water that rises buoyantly near the source and descends as a fountain after it has cooled sufficiently. We call this a double-diffusive plume because its evolution is dictated by the different (turbulent) diffusivities of heat and salt. A temperature and conductivity probe measures both the salinity and temperature along the centreline of the plume. The supposed axisymmetric structure of the salinity concentration as it changes with height is determined by light-attenuation methods. To help interpret the results, a theory has been successfully adapted from the work of Bloomfield and Kerr (2000), who developed coupled equations describing the structure of fountains. Introducing a new empirical parameter for the relative rates of turbulent heat and salt diffusion, the predictions are found to agree favourably with experimental results.

  15. Enceladus Plume Movie

    NASA Image and Video Library

    2005-12-06

    Jets of icy particles burst from Saturn’s moon Enceladus in this brief movie sequence of four images taken on Nov. 27, 2005. The sensational discovery of active eruptions on a third outer solar system body (Io and Triton are the others) is surely one of the great highlights of the Cassini mission. Imaging scientists, as reported in the journal Science on March 10, 2006, believe that the jets are geysers erupting from pressurized subsurface reservoirs of liquid water above 273 degrees Kelvin (0 degrees Celsius). Images taken in January 2005 appeared to show the plume emanating from the fractured south polar region of Enceladus, but the visible plume was only slightly brighter than the background noise in the image, because the lighting geometry was not suitable to reveal the true details of the feature. This potential sighting, in addition to the detection of the icy particles in the plume by other Cassini instruments, prompted imaging scientists to target Enceladus again with exposures designed to confirm the validity of the earlier plume sighting. The new views show individual jets, or plume sources, that contribute to the plume with much greater visibility than the earlier images. The full plume towers over the 505-kilometer-wide (314-mile) moon and is at least as tall as the moon's diameter. The four 10-second exposures were taken over the course of about 36 minutes at approximately 12 minute intervals. Enceladus rotates about 7.5 degrees in longitude over the course of the frames, and most of the observed changes in the appearances of the jets is likely attributable to changes in the viewing geometry. However, some of the changes may be due to actual variation in the flow from the jets on a time scale of tens of minutes. Additionally, the shift of the sources seen here should provide information about their location in front of and behind the visible limb (edge) of Enceladus. These images were obtained using the Cassini spacecraft narrow-angle camera at

  16. Plume Collection Strategies for Icy World Sample Return

    NASA Technical Reports Server (NTRS)

    Neveu, M.; Glavin, D. P.; Tsou, P.; Anbar, A. D.; Williams, P.

    2015-01-01

    Three icy worlds in the solar system display evidence of pluming activity. Water vapor and ice particles emanate from cracks near the south pole of Saturn's moon Enceladus. The plume gas contains simple hydrocarbons that could be fragments of larger, more complex organics. More recently, observations using the Hubble and Herschel space telescopes have hinted at transient water vapor plumes at Jupiter's moon Europa and the dwarf planet Ceres. Plume materials may be ejected directly from possible sub-surface oceans, at least on Enceladus. In such oceans, liquid water, organics, and energy may co-exist, making these environments habitable. The venting of habitable ocean material into space provides a unique opportunity to capture this material during a relatively simple flyby mission and return it to Earth. Plume collection strategies should enable investigations of evidence for life in the returned samples via laboratory analyses of the structure, distribution, isotopic composition, and chirality of the chemical components (including biomolecules) of plume materials. Here, we discuss approaches for the collection of dust and volatiles during flybys through Enceladus' plume, based on Cassini results and lessons learned from the Stardust comet sample return mission. We also highlight areas where sample collector and containment technology development and testing may be needed for future plume sample return missions.

  17. Paducah Gaseous Diffusion Plant Northwest Plume interceptor system evaluation

    SciTech Connect

    Laase, A.D.; Clausen, J.L.

    1998-07-01

    The Paducah Gaseous Diffusion Plant (PGDP) recently installed an interceptor system consisting of four wells, evenly divided between two well fields, to contain the Northwest Plume. As stated in the Northwest Plume Record of Decision (ROD), groundwater will be pumped at a rate to reduce further contamination and initiate control of the northwest contaminant plume. The objective of this evaluation was to determine the optimum (minimal) well field pumping rates required for plume hotspot containment. Plume hotspot, as defined in the Northwest Plume ROD and throughout this report, is that portion of the plume with trichloroethene (TCE) concentrations greater than 1,000 {micro}g/L. An existing 3-dimensional groundwater model was modified and used to perform capture zone analyses of the north and south interceptor system well fields. Model results suggest that the plume hotspot is not contained at the system design pumping rate of 100 gallons per minute (gal/min) per well field. Rather, the modeling determined that north and south well field pumping rates of 400 and 150 gal/min, respectively, are necessary for plume hotspot containment. The difference between the design and optimal pumping rates required for containment can be attributed to the discovery of a highly transmissive zone in the vicinity of the two well fields.

  18. Numerical modeling of the Patos Lagoon coastal plume, Brazil

    NASA Astrophysics Data System (ADS)

    Marques, W. C.; Fernandes, E. H.; Monteiro, I. O.; Möller, O. O.

    2009-03-01

    The Southern Brazilian Shelf (SBS) is a freshwater-influenced region, but studies on the dynamics of coastal plumes are sparse and lack in space-time resolution. Studies on the dynamics of the Patos Lagoon plume are even more limited. The aim of this paper is to investigate the influence of the principal physical forcing for the formation and behavior of the Patos Lagoon coastal plume. The study is carried out through 3D numerical modeling experiments and empirical orthogonal function (EOF) analysis. Results showed that the amount of freshwater is the principal physical forcing controlling the plume formation. The Coriolis effect enhances the northward transport over the shelf, while the tidal effects contribute to intensify horizontal and vertical mixing, which are responsible for spreading the freshwater over the shelf. The wind effect, on the other hand, is the main mechanism controlling the behavior of the Patos Lagoon coastal plume over the inner SBS in synoptic time scales. Southeasterly and southwesterly winds contribute to the northeastward displacement of the plume, breaking the vertical stratification of the inner continental shelf. Northeasterly and northwesterly winds favor ebb conditions in the Patos Lagoon, contributing to the southwestward displacement of the plume enhancing the vertical stratification along and across-shore. The EOF analysis reveals two modes controlling the variability of the plume on the surface. The first mode (explaining 70% of the variability) is associated to the southwestward transportation of the plume due to the dominance of north quadrant winds, while the second mode (explaining 19% of the variability) is associated to the intermittent migration of the plume northeastward due to the passage of frontal systems over the area. Large scale plumes can be expected during winter and spring months, and are enhanced during El Niño events.

  19. Composite Gauss-Legendre Quadrature with Error Control

    ERIC Educational Resources Information Center

    Prentice, J. S. C.

    2011-01-01

    We describe composite Gauss-Legendre quadrature for determining definite integrals, including a means of controlling the approximation error. We compare the form and performance of the algorithm with standard Newton-Cotes quadrature. (Contains 1 table.)

  20. Composite Gauss-Legendre Quadrature with Error Control

    ERIC Educational Resources Information Center

    Prentice, J. S. C.

    2011-01-01

    We describe composite Gauss-Legendre quadrature for determining definite integrals, including a means of controlling the approximation error. We compare the form and performance of the algorithm with standard Newton-Cotes quadrature. (Contains 1 table.)

  1. Nighttime chemistry in the Houston urban plume

    NASA Astrophysics Data System (ADS)

    Luria, Menachem; Valente, Ralph J.; Bairai, Solomon; Parkhurst, William J.; Tanner, Roger L.

    A late afternoon polluted air parcel transported from the Houston metropolitan area was monitored by an instrumented aircraft throughout the night of 21-22 July, 2005. Sampling was conducted during three flight segments over several downwind areas that were identified by a controllable meteorological balloon released from the Houston area at sundown. Samples were taken for approximately 2 h over each area. Using carbon monoxide as a tracer of the urban plume, it was revealed that the dilution inside the plume was relatively small. Ozone levels of up to 120 ppb were found in the plume at the furthest downwind distance, some 250 km northwest of Houston, with plume transport in the direction of the Dallas metropolitan area. The data further suggest that the nighttime conversion of NO x to NO z was very rapid, with complete (˜100%) conversion by the end of the night. At two locations the urban plume mixed with fresh emissions from power plants. At these sampling points ˜50% of the NO y had already been converted to NO z, thus indicating very rapid oxidation at night.

  2. Composition control in laser surface alloying

    NASA Astrophysics Data System (ADS)

    Chande, T.; Mazumder, J.

    1983-06-01

    Laser surface alloying, a process of growing interest for local surface modification, relies upon a suitable composition and microstructure for satisfactory on-the-job performance. This paper reports the results of an initial systematic study of laser surface alloying nickel onto AISI 1020 steel substrates using a statistical experimental design technique. The objective was to relate processing conditions to dimensions, solute content, and microstructural refinement of the laser alloyed zones. Solute content was of principal concern as it is the single most important factor affecting the properties of laser surface alloys. The effects of varying the laser power, beam diameter, and speed on the width, depth, nickel content, and fluctuations in nickel content are reported. Interactions between process parameters are discussed, the reproducibility assessed, contour plots for solute content drawn. Dimensionless plots are developed that relate average solute content and microstructural refinement to process parameters. Previously published data for alloying chromium into 1018 steels are shown to contain similar trends. It is felt that such an approach would facilitate selection of processing conditions to obtain reproducibly the compositions and microstructures necessary for gainful utilization of laser surface alloys.

  3. Plume impingement forces on inclined flat plates

    NASA Astrophysics Data System (ADS)

    Legge, H.

    Plume impingement from spacecraft control thrusters on vehicles in space is simulated in wind tunnel scale experiments. Pressure and shear stress are measured on flat plates inclined to the plume axis between 0 and 90 deg. In addition to a nozzle of a 0.5N thruster, a free jet from a thin plate orifice was used, by which the flow regime from nearly free molecular flow to continuum flow was covered. Simple pressure and shear stress laws are given by which the impingement pressure and shear stress can be estimated for engineering applications.

  4. CALIOP-derived Smoke Plume Injection Height

    NASA Astrophysics Data System (ADS)

    Soja, A. J.; Winker, D. M.; Choi, H. D.; Fairlie, T. D.; Westberg, D. J.; Roller, C. M.; Pouliot, G.; Vaughan, M.; Pierce, T. E.; Trepte, C. R.; Rao, V.

    2014-12-01

    Biomass burning is a dominant natural and anthropogenic disturbance that feeds back to the climate system. Fire regimes, ecosystem fuels, fire severity and intensity vary widely, even within the same system, largely under the control of weather and climate. These strongly influence fire plume injection height and thus the transport of related biomass burning emissions, affecting air quality, human health and the climate system. If our knowledge of plume injection height is incorrect, transport models of those emissions will likewise be incorrect, adversely affecting our ability to analyze and predict climate feedbacks (i.e. black carbon to the Arctic, precipitation, cloud-radiation relationships) and public health (air quality forecast). Historically, plume height was based on the pioneering work of G.A. Briggs [1969; 1971] and verified with limited field campaigns. However, we currently have two satellite instruments, Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) onboard CALIPSO (afternoon overpass) and Multi-angle Imaging SpectroRadiometer (MISR) onboard TERRA (morning overpass), that can provide the statistics necessary to verify our assumptions and improve fire plume injection height estimates for use in both small- and large-scale models. We have developed a methodology to assess fire plume injection height using the Langley Trajectory Model (LaTM), CALIOP, Hazard Mapping System (HMS) smoke plume, and MODerate Resolution Imaging Spectrometer (MODIS) thermal anomaly data that is capable of generating two distinct types of verification data. A single CALIOP smoke-filled aerosol envelop can be traced back to numerous fire events, and using multiple CALIOP transects from numerous days, a daily smoke plume injection height evolution from a single fire can be defined. Additionally, we have linked the smoke plumes to ecosystems and the meteorological variables that define fire weather. In concert, CALIOP and MISR data can produce the statistical knowledge

  5. Hydrothermal outflow plume of Valles caldera, New Mexico, and a comparison with other outflow plumes

    SciTech Connect

    Goff, F.; Shevenell, L.; Gardner, J.N.; Vuataz, F.; Grigsby, C.O.

    1988-06-10

    Stratigraphic, temperature gradient, hydrogeochemical, and hydrologic data have been integrated with geologic data from previous studies to show the structural configuration of the Valles caldera hydrothermal outflow plume. Hydrologic data suggest that 25--50% of the discharge of the Valles outflow is confined to the Jemez fault zone, which predates caldera formation. Thermal gradient data from bores penetrating the plume show that shallow gradients are highest in the vicinity of the Jemez fault zone (up to 190 /sup 0/C/km). Shallow heat flow above the hydrothermal plume is as high as 500 mW m/sup -2/ near core hole VC-1 (Jemez fault zone) to 200 mW m/sup -2/ at Fenton Hill (Jemez Plateau). Chemical and isotopic data indicate that two source reservoirs within the caldera (Redondo Creek and Sulphur Springs reservoirs) are parents to mixed fluids flowing in the hydrothermal plume. However, isotopic data, borehole data, basic geology, and inverse relations between temperature and chloride content at major hot springs indicate that no single reservoir fluid and no single diluting fluid are involved in mixing. The Valles caldera hydrothermal plume is structurally dominated by lateral flow through a belt of vertical conduits (Jemez fault zone) that strike away from the source reservoir. Stratigraphically confined flow is present but dispersed over a wide area in relatively impermeable rocks. The Valles configuration is contrasted with the configuration of the hydrothermal plume at Roosevelt Hot Springs, which is dominated by lateral flow through a near-surface, widespread, permeable aquifer. Data from 12 other representative geothermal systems show that outflow plumes occur in a variety of magmatic and tectonic settings, have varying reservoir compositions, and have different flow characteristics.

  6. Plasma Rocket With Hybrid Exhaust Plume

    NASA Technical Reports Server (NTRS)

    Chang, Franklin R.

    1987-01-01

    Proposed plasma rocket, described in report, generates hybrid exhaust plume comprising annular layer of relatively cool neutral gas around plasma core. Plasma and gas intermix, providing gradual radial transition between the two. Amount of gas injected adjusted to control propulsive efficiency; relatively cool gas boundary layer at surface of nozzle insulates nozzle from high plasma temperature.

  7. Computer controlled processing of composites utilizing dielectric signature curves

    NASA Astrophysics Data System (ADS)

    Keller, L. B.; Dominski, Marty

    1992-10-01

    Three composite materials for aircraft applications are experimentally developed by using automated computer control of the autoclave fabrication process. The computer-control methodology is an expert system based on data regarding the correlation of dielectric information and physicochemical changes in polymer matrices during processing. Thermal and rheological analyses are conducted with thermocouples and dielectric sensors, and real-time data are sent to the computer to control the autoclave processing. Sample laminates including PEEK APC-2/AS-4, SC-1008 phenolic, and PMR-15 polyimide are studied for density, resin/void content, and fiber volume. Critical process events are identified which contribute to the production of high-quality composites, and the process-control technique is shown to reduce scrap and enhance uniformity in the samples. The study demonstrates the utility of dielectric signature curves as the basis for computer-controlled composite processing.

  8. Sampling by mantle plumes : the legacy of the plume source

    NASA Astrophysics Data System (ADS)

    Brandeis, G.; Touitou, F.; Davaille, A.

    2013-12-01

    Plumes in the Earth's mantle are considered to be at the origin of intraplate volcanism (or hotspots). They continue to fascinate the scientific community by the heterogeneity of the material they sample on the surface of our planet. To characterize what part of the mantle is sampled by plumes, we have developed a laboratory model for laminar thermal plumes at high Prandtl number, in a fluid whose viscosity depends strongly on the temperature. This study describes the precise phenomenology of the plume and proposes scaling laws for the speed and temperature of the conduit of the plume. We show a strong dependence of these features of the plume with the Rayleigh number and viscosity ratio. Our visualization technique allows for the simultaneous non-intrusive measurements of the temperature, deformation and velocity fields. By calculating numerically the advection of passive markers through the experimental velocity field, we found that (1) the hot center of the plume conduit only consists of fluid which has passed through the thermal boundary layer ("TBL") at the bottom of the tank from which the plume was issued. Moreover, as material is stretched by velocity gradients, it is also in the thermal boundary layer that most of the material stretching occurs (2). The fluid is then transported in the conduit without lateral mixing, and further stretched vertically by the lateral velocity gradients. Since it is only the hot upwelling plume center which melts and therefore is sampled by volcanic activity, (1) implies that the plume geochemical signature is representative of the material located in the deep TBL of the mantle from which the plume is issued. On the other hand, (2) implies that filaments, pancakes, and concentric or bimodal zonation of the plume at the surface all result from different distributions of the heterogeneities in the plume source, filaments being the most generic case. Finally, we apply the scaling laws to the case of Hawaii.

  9. Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFRC Focused on Hanford’s 300 Area Uranium Plume January 2010 to January 2011

    SciTech Connect

    Zachara, John M.; Bjornstad, Bruce N.; Christensen, John N.; Conrad, Mark S.; Fredrickson, Jim K.; Freshley, Mark D.; Haggerty, Roy; Hammond, Glenn E.; Kent, Douglas B.; Konopka, Allan; Lichtner, Peter C.; Liu, Chongxuan; McKinley, James P.; Murray, Christopher J.; Rockhold, Mark L.; Rubin, Yoram; Vermeul, Vincent R.; Versteeg, Roelof J.; Ward, Anderson L.; Zheng, Chunmiao

    2011-02-01

    The Integrated Field Research Challenge (IFRC) at the Hanford Site 300 Area uranium (U) plume addresses multi-scale mass transfer processes in a complex subsurface hydrogeologic setting where groundwater and riverwater interact. A series of forefront science questions on reactive mass transfer focus research. These questions relate to the effect of spatial heterogeneities; the importance of scale; coupled interactions between biogeochemical, hydrologic, and mass transfer processes; and measurements and approaches needed to characterize and model a mass-transfer dominated system. The project was initiated in February 2007, with CY 2007, CY 2008, and CY 2009 progress summarized in preceding reports. A project peer review was held in March 2010, and the IFRC project has responded to all suggestions and recommendations made in consequence by reviewers and SBR/DOE. These responses have included the development of “Modeling” and “Well-Field Mitigation” plans that are now posted on the Hanford IFRC web-site. The site has 35 instrumented wells, and an extensive monitoring system. It includes a deep borehole for microbiologic and biogeochemical research that sampled the entire thickness of the unconfined 300 A aquifer. Significant, impactful progress has been made in CY 2010 including the quantification of well-bore flows in the fully screened wells and the testing of means to mitigate them; the development of site geostatistical models of hydrologic and geochemical properties including the distribution of U; developing and parameterizing a reactive transport model of the smear zone that supplies contaminant U to the groundwater plume; performance of a second passive experiment of the spring water table rise and fall event with a associated multi-point tracer test; performance of downhole biogeochemical experiments where colonization substrates and discrete water and gas samplers were deployed to the lower aquifer zone; and modeling of past injection experiments for

  10. Colloid Formation at Waste Plume Fronts

    SciTech Connect

    Wan, Jiamin; Tokunaga, Tetsu K.; Saiz, Eduardo; Larsen, Joern T.; Zheng, Zuoping; Couture, Rex A.

    2004-05-22

    Highly saline and caustic tank waste solutions containing radionuclides and toxic metals have leaked into sediments at U. S. Department of Energy (DOE) facilities such as the Hanford Site (Washington State). Colloid transport is frequently invoked to explain migration of radionuclides and metals in the subsurface. To understand colloid formation during interactions between highly reactive fluids and sediments and its impact on contaminant transport, we simulated tank waste solution (TWS) leakage processes in laboratory columns at ambient and elevated (70 C) temperatures. We found that maximum formation of mobile colloids occurred at the plume fronts (hundreds to thousands times higher than within the plume bodies or during later leaching). Concentrations of suspended solids were as high as 3 mass%, and their particle-sizes ranged from tens of nm to a few {micro}m. Colloid chemical composition and mineralogy depended on temperature. During infiltration of the leaked high Na{sup +} waste solution, rapid and completed Na{sup +} replacement of exchangeable Ca{sup 2+} and Mg{sup 2+} from the sediment caused accumulation of these divalent cations at the moving plume front. Precipitation of supersaturated Ca{sup 2+}/Mg{sup 2+}-bearing minerals caused dramatic pH reduction at the plume front. In turn, the reduced pH caused precipitation of other minerals. This understanding can help predict the behavior of contaminant trace elements carried by the tank waste solutions, and could not have been obtained through conventional batch studies.

  11. Three Dimensional Volcanic Plume Simulations on Early Mars

    NASA Astrophysics Data System (ADS)

    Fisher, M. A.; Kobs-Nawotniak, S. E.

    2016-12-01

    Current explosive volcanic plume models for early Mars are thought to overestimate plume height by tens of kilometers. They are based on 1D empirical terrestrial plume models, which determine plume rise using Morton-style convection. Not only do these models fail to account for turbulent mixing processes, but the Martian versions also violate assumptions regarding the speed of sound, radial expansion, and availability of ambient air for entrainment. Since volcanically derived volatiles are hypothesized to have increased early Martian warming, it is vital to understand how high these volatiles can be injected into the atmosphere. Active Tracer High-resolution Atmospheric Model (ATHAM; Oberhuber et al., 1998) is a 3D plume simulator that circumvents the underlying assumptions of the current Martian plume models by solving the Navier-Stokes equations. Martian-ATHAM (M-ATHAM) simulates Martian volcanic eruptions by replacing terrestrial planetary and atmospheric conditions with those appropriate for early Mars. In particular we evaluate three different atmospheric compositions with unique temperature and density profiles: 99.5% CO2/0.5% SO2 and 85% CO2/15% H2 representing a "warm and wet" climate and 100% CO2 representing a "cold and wet" climate. We evaluated for mass eruption rates from 10^3 kg/s to 10^10 kg/s using the Idaho National Laboratory's supercomputer Falcon in order determine what conditions produced stable eruption columns. Of the three different atmospheric compositions, 100% CO2 and 99.5% CO2/0.5% SO2 produced stable plumes for the same mass eruption rates whereas the 85% CO2/15% H2 atmosphere produced stable plumes for a slightly higher range of mass eruption rates. The tallest plumes were produced by 85% CO2/15% H2 atmosphere, producing plumes 5% taller than the revised empirical models, suggesting closer agreement than previously assumed under certain conditions. In comparison to terrestrial plumes, all early Martian plumes needed higher mass

  12. Estimation of Ship-plume Ozone Production Efficiency: ITCT 2K2 Case Study

    NASA Astrophysics Data System (ADS)

    Kim, H.; Kim, Y.; Song, C.

    2013-12-01

    The Ozone Production Efficiency (OPE) of ship plume was evaluated in this study, based on ship-plume photochemical/dynamic model simulations and the ship-plume composition data measured during the ITCT 2K2 (Intercontinental Transport and Chemical Transformation 2002) aircraft campaign. The averaged instantaneous OPEs (OPEi ) estimated via the ship-plume photochemical/dynamic modeling for the ITCT 2K2 ship-plume ranged between 4.61 and 18.92, showing that the values vary with the extent of chemical evolution (or chemical stage) of the ship plume and the stability classes of the marine boundary layer (MBL). Together with OPEi, the equivalent OPEs (OPEe) for the entire ITCT 2K2 ship-plume were also estimated. The OPEe values varied between 9.73 (for the stable MBL) and 12.73 (for the moderately stable MBL), which agreed well with the OPEe of 12.85 estimated based on the ITCT 2K2 ship-plume observations. It was also found that both the model-simulated and observation-based OPEe inside the ship-plume were 0.29-0.38 times smaller than the OPEe calculated/measured outside the ITCT 2K2 ship-plume. Lower OPEs insides the ship plume were due to the high levels of NOx. Possible implications of this ship-plume OPE study in the global chemistry-transport modeling are also discussed in this study.

  13. Colloid Formation and Transport at Waste Plume Fronts

    NASA Astrophysics Data System (ADS)

    Wan, J.; Tokunaga, T. K.; Larsen, J. T.; Zheng, Z.

    2004-12-01

    We have recently identified the phenomenon of massive colloid formation and transport within moving waste plume fronts during infiltration of high-salinity waste solutions into sediments. Colloid formation and transport was thousands of times higher within a narrow zone at the moving plume front than in the plume body and the leaching stage. The newly formed plume front colloids were primarily in the size range from tens of nm to a few micron meters. The underlying process begins with rapid and completed cation exchange of Na+ from the infiltrating waste solution replacing Ca2+ and Mg2+ from the sediments, coupled with flow of the infiltrating waste solution enriched these divalent cations within the moving plume front. Subsequent precipitation of colloids containing these divalent cations released protons and reduced the plume front pH to as low as neutral. This substantially reduced pH in turn promoted precipitation of other pH sensitive minerals and amorphous phases as colloids. This plume front colloid generation phenomenon can occur under a wide range of conditions including sediment type, waste solution pH, temperature, and chemical composition, with the only necessary condition being that of a high ionic strength waste solution. Because of the large mass of suspended colloids generated, this phenomenon could significantly affect the fate and transport of the contaminant trace elements contained within the waste plumes. Depending on the chemical properties of the individual radionuclide or toxic metal, it can co-precipitate with or adsorb onto the plume front colloids. As an example, uranium was predicted and found preferentially precipitated as a mobile colloid phase within a uranium waste plume front. Funding of this research was provided by the Geosciences Research Program of Basic Energy Science, U.S. Department of Energy.

  14. Recycled crust and the secular cooling of mantle plumes

    NASA Astrophysics Data System (ADS)

    Gazel Dondi, E.; Herzberg, C. T.; Vidito, C. A.

    2012-12-01

    Current models suggest that the massive basaltic production responsible for the emplacement of Large Igneous Provinces (LIPS) during the Permian-Paleocene may represent the initial phases of some of the mantle plumes that feed the current ocean island basalts (OIB). In some cases this magmatism was so voluminous that it produced global environmental impacts. Recent petrological, geochemical and geophysical studies of some of these localities like Samoa, Hawaii, Galapagos provide evidence that melting is related to a true mantle plume that originates from a boundary layer beneath the upper mantle. Thus, plume-related magmas produced in OIB and LIPS and their connecting plume tracks provide evidence on mantle temperature, size and composition of heterogeneities, and deep geochemical cycles. Although a lot of work has been done on LIPS and OIB, no complete record of the evolution of a mantle plume is available to this point. Galapagos-related lavas provide a complete record of the evolution of a mantle plume since the plume's initial stages in the Cretaceous. In the case of the Galapagos, our work suggests a decrease from TP(max) of 1650 °C in the Cretaceous to 1500 °C in the present day. Our recent work on the Galapagos Islands and the preliminary work on older Galapagos-related terranes suggest that this secular cooling is related with increasing amounts of recycled crust in the plume. Detailed olivine chemistry shows that although peridotite is the dominant source lithology of the Galapagos Plume, a recycled pyroxenite component is also significant in both isotopically enriched and depleted domains of the archipelago. We suggest that this possibly represents two separate bodies of recycled crust within the Galapagos mantle plume.

  15. The Chemistry of Hydrothermal Plumes Along the Galapagos Spreading Center

    NASA Astrophysics Data System (ADS)

    Resing, J.; Baker, E.; Lebon, G.; Walker, S.; Haymon, R.; Nakamura, K.; Lupton, J.

    2006-12-01

    During the 2005-06 GalAPAGoS expedition, we conducted nested sonar, plume, and camera surveys along a 300 n.m.-long portion of the Galapagos Spreading Center (GSC) where the ridge intersects the Galapagos hotspot between 94.5° and 89.5°W. Hydrothermal plumes were located by placing a variety of sensors on the clump weight of the DSL-120, which was towed approximately 100 m above the seafloor. These sensors included the vents in situ analyzer (nee SUAVE), which measured Fe, Mn, and pH; a redox potential (Eh) sensor; an optical backscatter sensor; a METs methane analyzer; and a CTD. These sensors were uploaded in real time allowing us to monitor for plumes during the tow. In addition, the tow line of the DSL-120 carried a vertical array of optical backscatter sensors (MAPRs). Almost all of the plumes found were identified solely from the data uploaded to the ship in real time and were confirmed from the vertical MAPR array. The MAPR array provided information on the rise height and vertical extent of the plumes. Many plumes were then also located and sampled by vertical and towed CTD hydrocasts. The CTD hydrocast samples were sampled for Fe, Mn, pH, helium isotopes, methane, and total suspended matter composition. Many of the plumes were characterized by fairly low amounts of total dissolved metals and variable Fe:Mn ratios. Plumes over the discovered black smoker vents carried elevated total dissolved metals and Fe:Mn ratios typical of other midocean ridge plumes. Data will be presented on the chemical makeup of the plumes from the sensors on the DSL-120 clump weight and from the CTD hydrocast samples.

  16. Chemical plume source localization.

    PubMed

    Pang, Shuo; Farrell, Jay A

    2006-10-01

    This paper addresses the problem of estimating a likelihood map for the location of the source of a chemical plume using an autonomous vehicle as a sensor probe in a fluid flow. The fluid flow is assumed to have a high Reynolds number. Therefore, the dispersion of the chemical is dominated by turbulence, resulting in an intermittent chemical signal. The vehicle is capable of detecting above-threshold chemical concentration and sensing the fluid flow velocity at the vehicle location. This paper reviews instances of biological plume tracing and reviews previous strategies for a vehicle-based plume tracing. The main contribution is a new source-likelihood mapping approach based on Bayesian inference methods. Using this Bayesian methodology, the source-likelihood map is propagated through time and updated in response to both detection and nondetection events. Examples are included that use data from in-water testing to compare the mapping approach derived herein with the map derived using a previously existing technique.

  17. The Kea- and Loa- trends and magma genesis in the Hawaiian mantle plume

    NASA Astrophysics Data System (ADS)

    Ren, Z.; Ingle, S.; Takahashi, E.; Hirano, N.; Hirata, T.; Tatsumi, Y.

    2005-12-01

    the shield volcanoes likely reflect different mixing proportions of subducted recycled gabbroic oceanic crust and peridotite from the lower mantle. The dominant component sampled at a given shield volcano is likely controlled by the thermal structure. As the volcano grows, it migrates away from the hot plume axis with plate motion. In the plume core, higher temperatures are able to generate melts with Kea-like composition from the more refractory component (i.e. peridotite from lower mantle) during the early shield stages. In contrast, lavas from some of the late-stages of the Hawaiian shields are Loa-like with isotopically enriched characteristics, implying that the proportion of the subducted oceanic crust (eclogite) component contributing to the melt may be higher relative to the peridotitic matrix. This is because during the generation of the later-stage lavas, their mantle source is located significantly away from the mantle plume axis where the temperature is lower than in the center of plume, and therefore the lower melting point component (eclogite) is preferentially sampled by the melt.

  18. Persistence of a Groundwater Contaminant Plume after Hydraulic Source Containment at a Chlorinated-Solvent Contaminated Site

    NASA Astrophysics Data System (ADS)

    Matthieu, D. E.; Plaschke, M.; Carroll, K. C.; Brinker, F.; Brusseau, M. L.

    2013-12-01

    Hydraulic containment is one approach available for management of source zones contaminated by chlorinated solvents and other organic liquids. The objective of this study was to characterize the behavior of a groundwater contaminant plume containing TCE and other organic contaminants after implementation of a source-containment operation at a site in Arizona. The plume is approximately 600 m long and 250 m wide, and it resides in a quasi three-layer system comprising a sand/gravel unit bounded on the top and bottom by relatively thick silty clayey layers. The system was monitored for 60 months beginning at start-up in 2007 to measure the change in contaminant concentrations within the plume, the change in plume area, the mass of contaminant removed, and the integrated contaminant mass discharge. Operation of two source-control wells appears to have established containment of the source area, which has resulted in isolation of the source from the contaminant plume. Concentrations of trichloroethene in groundwater pumped from the plume extraction wells have declined over the course of operation, as have concentrations for groundwater sampled from 45 monitoring wells located within the plume. The total contaminant mass discharge associated with operation of the plume extraction wells peaked at 0.23 kg/d, decreased significantly within one year, and thereafter began an asymptotic decline to a current value of approximately 0.03 kg/d. Despite an 87% reduction in contaminant mass and a comparable 87% reduction in contaminant mass discharge, the spatial area encompassed by the plume has decreased by only approximately 50%. This is much less than would be anticipated based on ideal flushing and mass-removal behavior. Trichloroethene concentrations in groundwater sampled from monitoring wells screened in the clayey units showed a composite decrease of less than 50%, compared to a ~90% reduction for the wells screened in the sand/gravel unit. This observation suggests that

  19. Optimized Field Sampling and Monitoring of Airborne Hazardous Transport Plumes; A Geostatistical Simulation Approach

    SciTech Connect

    Chen, DI-WEN

    2001-11-21

    Airborne hazardous plumes inadvertently released during nuclear/chemical/biological incidents are mostly of unknown composition and concentration until measurements are taken of post-accident ground concentrations from plume-ground deposition of constituents. Unfortunately, measurements often are days post-incident and rely on hazardous manned air-vehicle measurements. Before this happens, computational plume migration models are the only source of information on the plume characteristics, constituents, concentrations, directions of travel, ground deposition, etc. A mobile ''lighter than air'' (LTA) system is being developed at Oak Ridge National Laboratory that will be part of the first response in emergency conditions. These interactive and remote unmanned air vehicles will carry light-weight detectors and weather instrumentation to measure the conditions during and after plume release. This requires a cooperative computationally organized, GPS-controlled set of LTA's that self-coordinate around the objectives in an emergency situation in restricted time frames. A critical step before an optimum and cost-effective field sampling and monitoring program proceeds is the collection of data that provides statistically significant information, collected in a reliable and expeditious manner. Efficient aerial arrangements of the detectors taking the data (for active airborne release conditions) are necessary for plume identification, computational 3-dimensional reconstruction, and source distribution functions. This report describes the application of stochastic or geostatistical simulations to delineate the plume for guiding subsequent sampling and monitoring designs. A case study is presented of building digital plume images, based on existing ''hard'' experimental data and ''soft'' preliminary transport modeling results of Prairie Grass Trials Site. Markov Bayes Simulation, a coupled Bayesian/geostatistical methodology, quantitatively combines soft information

  20. Past Plate Motions and The Evolution of Earth's Lower Mantle: Relating LLSVPs and Plume Distribution

    NASA Astrophysics Data System (ADS)

    Bull, A. L.; Torsvik, T. H.; Shephard, G. E.

    2015-12-01

    Seismic tomography elucidates broad, low shear-wave velocity structures in the lower mantle beneath Africa and the central Pacific with uncertain physical and compositional origins. The anomalously slow areas, which cover nearly 50% of the core-mantle boundary, are often referred to as Large Low Shear Velocity Provinces (LLSVPs) due to the reduced velocity of seismic waves passing through them. Several hypotheses have arisen to explain the LLSVPs in the context of large-scale mantle convection. One end-member scenario infers a spatial correlation between LLSVP margins at depth and the reconstructed surface eruption sites of hotspots, kimberlites, and Large Igneous Provinces. Such a correlation has been explained by the preferential triggering of plumes at LLSVP margins by impingement of the subducting lithosphere upon the lower thermal boundary layer at the interface between ambient mantle and the higher density structures. This scenario propounds that Earth's plate motion history plays a controlling role in plume development, and that the location, geometry and morphology of plumes may be influenced by the movement of subducting slabs. Here, we investigate what is necessary to create such a pattern of plume distribution in relation to LLSVPs. We consider what effect past plate motions may have had on the evolution of Earth's lower mantle, and discuss the development of mantle plumes in terms of subduction dynamics. We integrate plate tectonic histories and numerical models of mantle convection to investigate the role that subduction history plays in the development and evolution of plumes in the presence of LLSVPs. To test whether an interaction exists between the surface location of subduction and plume eruption sites, and if so, to what degree over time, we apply varying shifts to the absolute reference frame of the plate reconstruction. With this method, we are able to change the location of subduction at the surface and thus the global flow field. This in turn

  1. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures.

    PubMed

    Hu, Liangfa; O'Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-10-18

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42-83 μm, 77-276 μm, and 167-545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed.

  2. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

    PubMed Central

    Hu, Liangfa; O’Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-01-01

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42–83 μm, 77–276 μm, and 167–545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed. PMID:27752106

  3. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

    NASA Astrophysics Data System (ADS)

    Hu, Liangfa; O’Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-10-01

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42–83 μm, 77–276 μm, and 167–545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed.

  4. Enceladus Plumes: A Boiling Liquid Model

    NASA Astrophysics Data System (ADS)

    Nakajima, Miki; Ingersoll, A. P.

    2012-10-01

    Following the discovery of H2O vapor and particle plumes from the tiger stripes at the south pole of Enceladus (Porco et al., 2006), observational and theoretical studies have been conducted to understand the plume mechanism (e.g., Schmidt et al., 2008; Kieffer et al., 2009; Ingersoll and Pankine, 2010). Although the “Ice Chamber Model”, which assumes that ice sublimation under the stripes causes the plumes, has successfully explained the plume mass flux (e.g., Nimmo et al., 2007; Ingersoll and Pankine, 2010), it cannot explain the high salinity in the plume (Postberg et al., 2009). Ice particles condensing from a vapor are relatively salt free, but ice particles derived from a salty liquid can have high salinity. Therefore we have investigated the “Boiling Liquid Model”, which assumes that liquid H2O under the stripes causes the plumes. With conservation of mass, momentum and energy, we built a simple atmospheric model that includes controlled boiling and gas-ice wall interaction. We first assumed that the heat radiated to space comes entirely from the heat generated by condensation of the gas onto the ice wall. We varied the width (0.1-1 m) and the height (5-4000 m) of the crack as parameters. We find that the escaping vapor flux can be relatively close to the observed value (250±100 kg/s, Hansen et al., 2006, 2008) but the radiated heat flux is only 1 GW, which is much less than the observed value (15.8 GW, Howett et al., 2011). Other models (Nimmo et al., 2007; Abramov and Spencer, 2009) also have the same difficulty accounting for the observed value. We then investigated the additional heat radiated by the particles after they come out of the crack. We built a simple model to estimate the size distributions of these condensed ice particles and their radiative properties.

  5. Simultaneous 2-D Measurements of Transient Velocity and Temperature Fields in a Thermal Starting Plume: Laboratory Models of Entrainment and Structure of Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Kumagai, I.; Yanagisawa, T.; Kurita, K.

    2002-12-01

    Both numerical and experimental models of thermal plumes suggest that mantle plumes entrain surrounding mantle and their morphology (temperature and compositional fields in the plume head) evolves as they rise. Recent geochemical and isotopic studies of mantle plume products have revealed mixing of the ambient mantle with the primitive plume source. In order to make a quantitative comparison of the geophysical modeling with geological evidences, it is desired to show a precise image of spatial and temporal evolution of temperature and compositional fields in the plumes. Here, we present preliminary results of our laboratory experiments on thermal starting plumes using a quantitative technique of digital image processing. By coupling Particle Image Velocimetry (PIV) with Laser Induced Fluorescence (LIF) we can measure simultaneous 2-dimensional transient velocity and temperature fields in a thermal plume. Our experiments were conducted in a transparent rectangular tank containing a viscous fluid. Buoyancy in the form of heat was injected into the fluid by operating a heater at the base of the tank. The flow was marked with tracer particles for velocity and with the fluorescence dye, Rhodamine B, for temperature measurements. The particles and the fluorescence dye were illuminated and exited by a thin vertical sheet of laser light that was oriented to contain the axis of symmetry. We succeeded in simultaneous measurements of ascent velocity of the plume head, precise velocity field within the plume head, and evolution of the temperature field. This makes clear their relation and is useful for considering the entrainment process of plumes. Our aim of this study is to clarify the physics of entrainment and mixing phenomena of starting plumes, and to make quantitative geophysical models of mantle plumes connecting with geological and seismic evidences. In this presentation, we will show that this quantitative technique is a powerful tool for approaching these issues.

  6. The system controlling the composition of clastic sediments

    USGS Publications Warehouse

    Johnsson, Mark J.

    1993-01-01

    The composition of clastic sediments and rocks is controlled by a complex suite of parameters operating during pedogenesis, erosion, transport, deposition, and burial. The principal first-order parameters include source rock composition, modification by chemical weathering, mechanical disaggregation and abrasion, authigenic inputs, hydrodynamic sorting, and diagenesis. Each of these first-order parameters is influenced to varying degrees by such factors as the tectonic settings of the source region, transportational system and depositional environment, climate, vegetation, relief, slope, and the nature and energy of transportational and depositional systems. These factors are not independent; rather a complicated web of interrelationships and feedback mechanisms causes many factors to be modulated by others. Accordingly, processes controlling the composition of clastic sediments are best viewed as constituting a system, and in evaluating compositional information the dynamics of the system must be considered as whole.

  7. Formation of secondary aerosols from biomass burning plumes: chamber simulation study

    NASA Astrophysics Data System (ADS)

    Wang, X.; Hu, Q.; Fang, Z.; Deng, W.

    2015-12-01

    Biomass burning contributed substantially to carbonaceous aerosols in China's ambient air, even in its highly industrialized megacities, based on recent source attributions by receptor modeling or by molecular and isotopic tracers. Although chemical evolution of biomass burning plumes in the ambient is a vital issue for the study of climatic and health effects, the understanding of secondary pollutants formation during the aging of biomass burning plumes is far from complete. Here we collected typical agriculture residues and forest plant branches in the Pearl River Delta in south China, and got them burned in laboratory-controlled conditions and introduced the plumes from burning these biomass directly into the GIGCAS indoor smog chamber with a reactor of 30 m3 to investigate the photochemical aging of the plumes. The inorganic trace gases, including SO2, NOx, NH3 and O3, were monitored online with chemiluminescence gas analyzers, precursor volatile organic compounds (VOCs) were monitor online with a PTR-ToF-MS and offline by a preconcentrator coupled with a gas chromatography-mass selective detector/flame ionization detector/electron capture detector (GC-MSD/FID/ECD), particle number concentrations and size distributions were obtained using a scanning mobility particle sizer (SMPS), and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) was used to measure the chemical compositions and evolutions of submicron aerosols and to trace the change in the average element ratios of organics, like H/C, O/C, and N/C. The results from the study were summarized in the following aspects: 1) primary emission factors of gaseous and particulate pollutants from burning of typical biomass including agricultural remains and forest wood plants; 2) yields of secondary pollutants, including secondary inorganic and organic aerosols and gaseous products (like O3) during photochemical aging of biomass burning plumes; 3) relationship between the formed secondary

  8. Polymer-xerogel composites for controlled release wound dressings.

    PubMed

    Costache, Marius C; Qu, Haibo; Ducheyne, Paul; Devore, David I

    2010-08-01

    Many polymers and composites have been used to prepare active wound dressings. These materials have typically exhibited potentially toxic burst release of the drugs within the first few hours followed by a much slower, potentially ineffective drug release rate thereafter. Many of these materials also degraded to produce inflammatory and cytotoxic products. To overcome these limitations, composite active wound dressings were prepared here from two fully biodegradable and tissue compatible components, silicon oxide sol-gel (xerogel) microparticles that were embedded in tyrosine-poly(ethylene glycol)-derived poly(ether carbonate) copolymer matrices. Sustained, controlled release of drugs from these composites was demonstrated in vitro using bupivacaine and mepivacaine, two water-soluble local anesthetics commonly used in clinical applications. By systematically varying independent compositional parameters of the composites, including the hydrophilic:hydrophobic balance of the tyrosine-derived monomers and poly(ethylene glycol) in the copolymers and the porosity, weight ratio and drug content of the xerogels, drug release kinetics approaching zero-order were obtained. Composites with xerogel mass fractions up to 75% and drug payloads as high as 13% by weight in the final material were fabricated without compromising the physical integrity or the controlled release kinetics. The copolymer-xerogel composites thus provided a unique solution for the sustained delivery of therapeutic agents from tissue compatible wound dressings. 2010 Elsevier Ltd. All rights reserved.

  9. Biogeochemistry and isotope geochemistry of a landfill leachate plume.

    PubMed

    van Breukelen, Boris M; Röling, Wilfred F M; Groen, Jacobus; Griffioen, Jasper; van Verseveld, Henk W

    2003-09-01

    The biogeochemical processes were identified which improved the leachate composition in the flow direction of a landfill leachate plume (Banisveld, The Netherlands). Groundwater observation wells were placed at specific locations after delineating the leachate plume using geophysical tests to map subsurface conductivity. Redox processes were determined using the distribution of solid and soluble redox species, hydrogen concentrations, concentration of dissolved gases (N(2), Ar, and CH(4)), and stable isotopes (delta15N-NO(3), delta34S-SO(4), delta13C-CH(4), delta2H-CH(4), and delta13C of dissolved organic and inorganic carbon (DOC and DIC, respectively)). The combined application of these techniques improved the redox interpretation considerably. Dissolved organic carbon (DOC) decreased downstream in association with increasing delta13C-DOC values confirming the occurrence of degradation. Degradation of DOC was coupled to iron reduction inside the plume, while denitrification could be an important redox process at the top fringe of the plume. Stable carbon and hydrogen isotope signatures of methane indicated that methane was formed inside the landfill and not in the plume. Total gas pressure exceeded hydrostatic pressure in the plume, and methane seems subject to degassing. Quantitative proof for DOC degradation under iron-reducing conditions could only be obtained if the geochemical processes cation exchange and precipitation of carbonate minerals (siderite and calcite) were considered and incorporated in an inverse geochemical model of the plume. Simulation of delta13C-DIC confirmed that precipitation of carbonate minerals happened.

  10. The interaction of Io's plumes and sublimation atmosphere

    NASA Astrophysics Data System (ADS)

    McDoniel, William J.; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.

    2017-09-01

    Io's volcanic plumes are the ultimate source of its SO2 atmosphere, but past eruptions have covered the moon in surface frost which sublimates in sunlight. Today, Io's atmosphere is a result of some combination of volcanism and sublimation, but it is unknown exactly how these processes work together to create the observed atmosphere. We use the direct simulation Monte Carlo (DSMC) method to model the interaction of giant plumes with a sublimation atmosphere. Axisymmetric plume/atmosphere simulations demonstrate that the total mass of SO2 above Io's surface is only poorly approximated as the sum of independent volcanic and sublimated components. A simple analytic model is developed to show how variation in the mass of erupting gas above Io's surface can counteract variation in the mass of its hydrostatic atmosphere as surface temperature changes over a Jupiter year. Three-dimensional, unsteady simulations of giant plumes over an Io day are also presented, showing how plume material becomes suspended in the sublimation atmosphere. We find that a plume which produces some total mass above Io's surface at night will cause a net increase in the noon-time atmosphere of only a fraction of the night-time value. However, as much as seven times the night-side mass of the plume will become suspended in the sublimation atmosphere, altering its composition and displacing sublimated material.

  11. Biogeochemistry and isotope geochemistry of a landfill leachate plume

    NASA Astrophysics Data System (ADS)

    van Breukelen, Boris M.; Röling, Wilfred F. M.; Groen, Jacobus; Griffioen, Jasper; van Verseveld, Henk W.

    2003-09-01

    The biogeochemical processes were identified which improved the leachate composition in the flow direction of a landfill leachate plume (Banisveld, The Netherlands). Groundwater observation wells were placed at specific locations after delineating the leachate plume using geophysical tests to map subsurface conductivity. Redox processes were determined using the distribution of solid and soluble redox species, hydrogen concentrations, concentration of dissolved gases (N 2, Ar, and CH 4), and stable isotopes ( δ15N-NO 3, δ34S-SO 4, δ13C-CH 4, δ2H-CH 4, and δ13C of dissolved organic and inorganic carbon (DOC and DIC, respectively)). The combined application of these techniques improved the redox interpretation considerably. Dissolved organic carbon (DOC) decreased downstream in association with increasing δ13C-DOC values confirming the occurrence of degradation. Degradation of DOC was coupled to iron reduction inside the plume, while denitrification could be an important redox process at the top fringe of the plume. Stable carbon and hydrogen isotope signatures of methane indicated that methane was formed inside the landfill and not in the plume. Total gas pressure exceeded hydrostatic pressure in the plume, and methane seems subject to degassing. Quantitative proof for DOC degradation under iron-reducing conditions could only be obtained if the geochemical processes cation exchange and precipitation of carbonate minerals (siderite and calcite) were considered and incorporated in an inverse geochemical model of the plume. Simulation of δ13C-DIC confirmed that precipitation of carbonate minerals happened.

  12. Seismic Imaging of Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Nataf, Henri-Claude

    The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

  13. Low altitude plume impingement handbook

    NASA Technical Reports Server (NTRS)

    Smith, Sheldon D.

    1991-01-01

    Plume Impingement modeling is required whenever an object immersed in a rocket exhaust plume must survive or remain undamaged within specified limits, due to thermal and pressure environments induced by the plume. At high altitudes inviscid plume models, Monte Carlo techniques along with the Plume Impingement Program can be used to predict reasonably accurate environments since there are usually no strong flowfield/body interactions or atmospheric effects. However, at low altitudes there is plume-atmospheric mixing and potential large flowfield perturbations due to plume-structure interaction. If the impinged surface is large relative to the flowfield and the flowfield is supersonic, the shock near the surface can stand off the surface several exit radii. This results in an effective total pressure that is higher than that which exists in the free plume at the surface. Additionally, in two phase plumes, there can be strong particle-gas interaction in the flowfield immediately ahead of the surface. To date there have been three levels of sophistication that have been used for low altitude plume induced environment predictions. Level 1 calculations rely on empirical characterizations of the flowfield and relatively simple impingement modeling. An example of this technique is described by Piesik. A Level 2 approach consists of characterizing the viscous plume using the SPF/2 code or RAMP2/LAMP and using the Plume Impingement Program to predict the environments. A Level 3 analysis would consist of using a Navier-Stokes code such as the FDNS code to model the flowfield and structure during a single calculation. To date, Level 1 and Level 2 type analyses have been primarily used to perform environment calculations. The recent advances in CFD modeling and computer resources allow Level 2 type analysis to be used for final design studies. Following some background on low altitude impingement, Level 1, 2, and 3 type analysis will be described.

  14. Constraints on Structure and Melting of Heterogeneous Plumes From Laboratory Experiments With Three Components

    NASA Astrophysics Data System (ADS)

    Harris, A. C.; Kincaid, C.; Kelley, K. A.

    2007-12-01

    Many studies of chemical geodynamics consider the fate of a single, compositionally distinct layer at the base of the mantle, but subducted oceanic lithosphere introduces two distinct lithologies (higher-density eclogite and lower-density harzburgite) into the mantle (a third lithology, intermediate-density lherzolitic peridotite). To address the dynamic complexities of interactions between these materials, we conducted three-dimensional laboratory experiments that use glucose syrup (Rayleigh number: 106\\)) to model the mantle and a two-layer subducted lithosphere. The viscosity and density of the syrup are controlled by its water content, which is varied to simulate the distinct physical properties of each of the three lithologies. Experiments were conducted in a 20cc tank, heated from below to create a basal thermal boundary layer (BTBL). The two-layer glucose slab was frozen and placed within the tank, where it sank into the BTBL. These experiments produced heterogeneous upwellings with temporal and spatial variations in both temperature and composition that are much more complex than predicted by classic plume theory. Temperature, composition, and distribution of material in the tank through space and time were recorded during each experiment. We scale these data to mantle-equivalent conditions and address the observational implication for melting such heterogeneous plumes, both within larger (200 - 600 km) plume heads and smaller (<100 km) trailing conduits. Results show length scales of chemical heterogeneity range from <10 km up to 300 km. Thermal heterogeneity was often correlated with composition, where the denser, eclogite analog had higher temperatures than the lighter, harzburgite analog. Distinct domains form within plumes and melting begins at different depths, dependent on the temperature and composition of each domain and the solidus of each composition (e.g. eclogite melts at lower temperatures than harzburgite). The combination of thermo

  15. Cellulose, chitosan, and keratin composite materials. Controlled drug release.

    PubMed

    Tran, Chieu D; Mututuvari, Tamutsiwa M

    2015-02-03

    A method was developed in which cellulose (CEL) and/or chitosan (CS) were added to keratin (KER) to enable [CEL/CS+KER] composites to have better mechanical strength and wider utilization. Butylmethylimmidazolium chloride ([BMIm(+)Cl(-)]), an ionic liquid, was used as the sole solvent, and because the [BMIm(+)Cl(-)] used was recovered, the method is green and recyclable. Fourier transform infrared spectroscopy results confirm that KER, CS, and CEL remain chemically intact in the composites. Tensile strength results expectedly show that adding CEL or CS into KER substantially increases the mechanical strength of the composites. We found that CEL, CS, and KER can encapsulate drugs such as ciprofloxacin (CPX) and then release the drug either as a single or as two- or three-component composites. Interestingly, release rates of CPX by CEL and CS either as a single or as [CEL+CS] composite are faster and independent of concentration of CS and CEL. Conversely, the release rate by KER is much slower, and when incorporated into CEL, CS, or CEL+CS, it substantially slows the rate as well. Furthermore, the reducing rate was found to correlate with the concentration of KER in the composites. KER, a protein, is known to have secondary structure, whereas CEL and CS exist only in random form. This makes KER structurally denser than CEL and CS; hence, KER releases the drug slower than CEL and CS. The results clearly indicate that drug release can be controlled and adjusted at any rate by judiciously selecting the concentration of KER in the composites. Furthermore, the fact that the [CEL+CS+KER] composite has combined properties of its components, namely, superior mechanical strength (CEL), hemostasis and bactericide (CS), and controlled drug release (KER), indicates that this novel composite can be used in ways which hitherto were not possible, e.g., as a high-performance bandage to treat chronic and ulcerous wounds.

  16. Cellulose, Chitosan, and Keratin Composite Materials. Controlled Drug Release

    PubMed Central

    2015-01-01

    A method was developed in which cellulose (CEL) and/or chitosan (CS) were added to keratin (KER) to enable [CEL/CS+KER] composites to have better mechanical strength and wider utilization. Butylmethylimmidazolium chloride ([BMIm+Cl–]), an ionic liquid, was used as the sole solvent, and because the [BMIm+Cl–] used was recovered, the method is green and recyclable. Fourier transform infrared spectroscopy results confirm that KER, CS, and CEL remain chemically intact in the composites. Tensile strength results expectedly show that adding CEL or CS into KER substantially increases the mechanical strength of the composites. We found that CEL, CS, and KER can encapsulate drugs such as ciprofloxacin (CPX) and then release the drug either as a single or as two- or three-component composites. Interestingly, release rates of CPX by CEL and CS either as a single or as [CEL+CS] composite are faster and independent of concentration of CS and CEL. Conversely, the release rate by KER is much slower, and when incorporated into CEL, CS, or CEL+CS, it substantially slows the rate as well. Furthermore, the reducing rate was found to correlate with the concentration of KER in the composites. KER, a protein, is known to have secondary structure, whereas CEL and CS exist only in random form. This makes KER structurally denser than CEL and CS; hence, KER releases the drug slower than CEL and CS. The results clearly indicate that drug release can be controlled and adjusted at any rate by judiciously selecting the concentration of KER in the composites. Furthermore, the fact that the [CEL+CS+KER] composite has combined properties of its components, namely, superior mechanical strength (CEL), hemostasis and bactericide (CS), and controlled drug release (KER), indicates that this novel composite can be used in ways which hitherto were not possible, e.g., as a high-performance bandage to treat chronic and ulcerous wounds. PMID:25548871

  17. Mantle plumes and continental tectonics.

    PubMed

    Hill, R I; Campbell, I H; Davies, G F; Griffiths, R W

    1992-04-10

    Mantle plumes and plate tectonics, the result of two distinct modes of convection within the Earth, operate largely independently. Although plumes are secondary in terms of heat transport, they have probably played an important role in continental geology. A new plume starts with a large spherical head that can cause uplift and flood basalt volcanism, and may be responsible for regional-scale metamorphism or crustal melting and varying amounts of crustal extension. Plume heads are followed by narrow tails that give rise to the familiar hot-spot tracks. The cumulative effect of processes associated with tail volcanism may also significantly affect continental crust.

  18. Structure of axisymmetric mantle plumes

    NASA Technical Reports Server (NTRS)

    Olson, Peter; Schubert, Gerald; Anderson, Charles

    1993-01-01

    The structure of axisymmetric subsolidus thermal plumes in the earth's lower mantle is inferred from calculations of axisymmetric thermal plumes in an infinite Prandtl number fluid with thermally activated viscosity. The velocity and temperature distribution is determined for axisymmetric convection above a heated disk in an incompressible fluid cylinder 2,400 km in height and 1,200 km in diameter. Several calculations of plumes with heat transport in the range 100-400 GW, similar to the advective heat transport at the Hawaiian hotspot, are presented. Hotspot formation by plumes originating at the base of the mantle requires both large viscosity variations and a minimum heat transport.

  19. Effects of pressure and composition on Pt-Re-Os partitioning behavior between solid and liquid metal in the Fe-Ni-S system: Implication for Os isotopic anomalies in plume-derived lavas

    NASA Astrophysics Data System (ADS)

    Hayashi, H.; Ohtani, E.; Terasaki, H.; Ito, Y.

    2008-12-01

    Coupled 186Os/188Os and 187Os/188Os enrichments of plume-derived lavas have been suggested to reflect material contribution from the outer core (e.g., Brandon, 1998). This geochemical hypothesis is based on an assumption that the outer core shows coupled enrichments in 186Os/ 188Os and 187Os/ 188Os ratio, reflecting the decay of 190Pt and 187Re to 186Os and 187Os, respectively. In order to examine this hypothesis, partitioning experiments of Pt-Re-Os between solid metal and liquid metal were performed using an MA-8 Kawai-type multi-anvil apparatus at 5-20 GPa and 1250-1400C. Starting materials of Fe metal, Ni (7 wt.%) metal and FeS (5 wt.% S in the bulk) were doped with 3 wt.% of Pt, Re and Os metals. Concentrations of all elements were determined using JXA-8800M electron probe microanalyzer with wave-dispersive spectrometry. Measured partition coefficients of Pt, Re and Os increase with increasing sulfur content and almost constant with increasing pressure. Therefore, the effect of liquid composition on the partitioning behavior of highly siderophile elements is much more significant compared to the effect of pressure and temperature. On the basis of the present experimental results, it is unlikely to generate the required Pt-Re-Os fractionation during inner core crystallization assuming that the light element in the Earth"fs core is sulfur only.

  20. Development of a Reactive Plume Model for the Consideration of Power-Plant Plume Photochemistry and Its Applications.

    PubMed

    Kim, Yong H; Kim, Hyun S; Song, Chul H

    2017-02-07

    A reactive plume model (RPM) was developed to comprehensively consider power-plant plume photochemistry with 255 condensed photochemical reactions. The RPM can simulate two main components of power-plant plumes: turbulent dispersion of plumes and compositional changes of plumes via photochemical reactions. In order to evaluate the performance of the RPM developed in the present study, two sets of observational data obtained from the TexAQS II 2006 (Texas Air Quality Study II 2006) campaign were compared with RPM-simulated data. Comparison shows that the RPM produces relatively accurate concentrations for major primary and secondary in-plume species such as NO2, SO2, ozone, and H2SO4. Statistical analyses show good correlation, with correlation coefficients (R) ranging from 0.61 to 0.92, and good agreement with the Index of Agreement (IOA) ranging from 0.76 to 0.95. Following evaluation of the performance of the RPM, a demonstration was also carried out to show the applicability of the RPM. The RPM can calculate NOx photochemical lifetimes inside the two plumes (Monticello and Welsh power plants). Further applicability and possible uses of the RPM are also discussed together with some limitations of the current version of the RPM.

  1. A simple behaviour provides accuracy and flexibility in odour plume tracking--the robotic control of sensory-motor coupling in silkmoths.

    PubMed

    Ando, Noriyasu; Kanzaki, Ryohei

    2015-12-01

    Odour plume tracking is an essential behaviour for animal survival. A fundamental strategy for this is to move upstream and then across-stream. Male silkmoths, Bombyx mori, display this strategy as a pre-programmed sequential behaviour. They walk forward (surge) in response to the female sex pheromone and perform a zigzagging 'mating dance'. Though pre-programmed, the surge direction is modulated by bilateral olfactory input and optic flow. However, the nature of the interaction between these two sensory modalities and contribution of the resultant motor command to localizing an odour source are still unknown. We evaluated the ability of the silkmoth to localize an odour source under conditions of disturbed sensory-motor coupling, using a silkmoth-driven mobile robot. The significance of the bilateral olfaction of the moth was confirmed by inverting the olfactory input to the antennae, or its motor output. Inversion of the motor output induced consecutive circling, which was inhibited by covering the visual field of the moth. This suggests that the corollary discharge from the motor command and the reafference of self-generated optic flow generate compensatory signals to guide the surge accurately. Additionally, after inverting the olfactory input, the robot successfully tracked the odour plume by using a combination of behaviours. These results indicate that accurate guidance of the reflexive surge by integrating bilateral olfactory and visual information with innate pre-programmed behaviours increases the flexibility to track an odour plume even under disturbed circumstances. © 2015. Published by The Company of Biologists Ltd.

  2. A neural network controller for automated composite manufacturing

    NASA Technical Reports Server (NTRS)

    Lichtenwalner, Peter F.

    1994-01-01

    At McDonnell Douglas Aerospace (MDA), an artificial neural network based control system has been developed and implemented to control laser heating for the fiber placement composite manufacturing process. This neurocontroller learns an approximate inverse model of the process on-line to provide performance that improves with experience and exceeds that of conventional feedback control techniques. When untrained, the control system behaves as a proportional plus integral (PI) controller. However after learning from experience, the neural network feedforward control module provides control signals that greatly improve temperature tracking performance. Faster convergence to new temperature set points and reduced temperature deviation due to changing feed rate have been demonstrated on the machine. A Cerebellar Model Articulation Controller (CMAC) network is used for inverse modeling because of its rapid learning performance. This control system is implemented in an IBM compatible 386 PC with an A/D board interface to the machine.

  3. Controlled degradation pattern of hydroxyapatite/calcium carbonate composite microspheres.

    PubMed

    Yang, Ning; Zhong, Qiwei; Zhou, Ying; Kundu, Subhas C; Yao, Juming; Cai, Yurong

    2016-06-01

    Hydroxyapatite (HAP) is widely used in clinic due to its good biocompatibility and osteoconductivity except for its slow degradation speed. In the present study, spherical calcium carbonate (CaCO3 ) is fabricated in the presence of silk protein sericin, which is transmuted into HAP microsphere in phosphate solution with the assistance of microwave irradiation. The effect of reaction conditions on the conversion of CaCO3 is investigated including reaction time, chemical composition of phosphate solution, and microwave power to get a series of HAP/CaCO3 composites. The degradation property of the composites is evaluated in vitro. Results show the degradation speed of the composite with higher HAP content is slower. The degradation rate of the composite could be changed effectively by modulating the proportion of HAP and CaCO3 . This work provides a feasible method for the preparation of spherical HAP/CaCO3 composite with controllable degradability. The composite thus obtained may be an ideal material for bone tissue engineering application. Microsc. Res. Tech. 79:518-524, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  4. 3-D numerical modeling of plume-induced subduction initiation

    NASA Astrophysics Data System (ADS)

    Baes, Marzieh; Gerya, taras; Sobolev, Stephan

    2016-04-01

    Investigation of mechanisms involved in formation of a new subduction zone can help us to better understand plate tectonics. Despite numerous previous studies, it is still unclear how and where an old oceanic plate starts to subduct beneath the other plate. One of the proposed scenarios for nucleation of subduction is plume-induced subduction initiation, which was investigated in detail, using 2-D models, by Ueda et al. (2008). Recently. Gerya et al. (2015), using 3D numerical models, proposed that plume-lithosphere interaction in the Archean led to the subduction initiation and onset of plate tectonic. In this study, we aim to pursue work of Ueda et al. (2008) by incorporation of 3-D thermo-mechanical models to investigate conditions leading to oceanic subduction initiation as a result of thermal-chemical mantle plume-lithosphere interaction in the modern earth. Results of our experiments show four different deformation regimes in response to plume-lithosphere interaction, that are a) self-sustaining subduction initiation where subduction becomes self-sustained, b) freezing subduction initiation where subduction stops at shallow depths, c) slab break-off where subducting circular slab breaks off soon after formation and d) plume underplating where plume does not pass through the lithosphere but spreads beneath it (failed subduction initiation). These different regimes depend on several parameters such as plume's size, composition and temperature, lithospheric brittle/plastic strength, age of the oceanic lithosphere and presence/absence of lithospheric heterogeneities. Results show that subduction initiates and becomes self-sustained when lithosphere is older than 10 Myr and non-dimensional ratio of the plume buoyancy force and lithospheric strength above the plume is higher than 2.

  5. Processing of aerosol particles within the Habshan pollution plume

    NASA Astrophysics Data System (ADS)

    Semeniuk, T. A.; Bruintjes, R.; Salazar, V.; Breed, D.; Jensen, T.; Buseck, P. R.

    2015-03-01

    The Habshan industrial site in the United Arab Emirates produces a regional-scale pollution plume associated with oil and gas processing, discharging high loadings of sulfates and chlorides into the atmosphere, which interact with the ambient aerosol population. Aerosol particles and trace gas chemistry at this site were studied on two flights in the summer of 2002. Measurements were collected along vertical plume profiles to show changes associated with atmospheric processing of particle and gas components. Close to the outlet stack, particle concentrations were over 10,000 cm-3, dropping to <2000 cm-3 in more dilute plume around 1500 m above the stack. Particles collected close to the stack and within the dilute plume were individually measured for size, morphology, composition, and mixing state using transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. Close to the stack, most coarse particles consisted of mineral dust and NaCl crystals from burning oil brines, while sulfate droplets dominated the fine mode. In more dilute plume, at least 1500 m above the stack, the particle spectrum was more diverse, with a significant increase in internally mixed particle types. Dilute plume samples consisted of coarse NaCl/silicate aggregates or NaCl-rich droplets, often with a sulfate component, while fine-fraction particles were of mixed cation sulfates, also internally mixed with nanospherical soot or silicates. Thus, both chloride and sulfate components of the pollution plume rapidly reacted with ambient mineral dust to form coated and aggregate particles, enhancing particle size, hygroscopicity, and reactivity of the coarse mode. The fine-fraction sulfate-bearing particles formed in the plume contribute to regional transport of sulfates, while coarse sulfate-bearing fractions locally reduced the SO2 loading through sedimentation. The chloride- and sulfate-bearing internally mixed particles formed in the plume markedly changed the

  6. Fracture mechanisms and fracture control in composite structures

    NASA Astrophysics Data System (ADS)

    Kim, Wone-Chul

    Four basic failure modes--delamination, delamination buckling of composite sandwich panels, first-ply failure in cross-ply laminates, and compression failure--are analyzed using linear elastic fracture mechanics (LEFM) and the J-integral method. Structural failures, including those at the micromechanical level, are investigated with the aid of the models developed, and the critical strains for crack propagation for each mode are obtained. In the structural fracture analyses area, the fracture control schemes for delamination in a composite rib stiffener and delamination buckling in composite sandwich panels subjected to in-plane compression are determined. The critical fracture strains were predicted with the aid of LEFM for delamination and the J-integral method for delamination buckling. The use of toughened matrix systems has been recommended for improved damage tolerant design for delamination crack propagation. An experimental study was conducted to determine the onset of delamination buckling in composite sandwich panel containing flaws. The critical fracture loads computed using the proposed theoretical model and a numerical computational scheme closely followed the experimental measurements made on sandwich panel specimens of graphite/epoxy faceskins and aluminum honeycomb core with varying faceskin thicknesses and core sizes. Micromechanical models of fracture in composites are explored to predict transverse cracking of cross-ply laminates and compression fracture of unidirectional composites. A modified shear lag model which takes into account the important role of interlaminar shear zones between the 0 degree and 90 degree piles in cross-ply laminate is proposed and criteria for transverse cracking have been developed. For compressive failure of unidirectional composites, pre-existing defects play an important role. Using anisotropic elasticity, the stress state around a defect under a remotely applied compressive load is obtained. The experimentally

  7. Single SCA-plume dynamics

    NASA Astrophysics Data System (ADS)

    Yano, J.-I.; Baizig, Hichem

    2012-11-01

    A fully prognostic prototype of bulk mass-flux convection parameterization is presented. The bulk mass-flux parameterization is formulated by assuming a subgrid-scale system consisting only of a convective plume and environment. Both subcomponents (segments) are assumed to be homogeneous horizontally. This assumption is called the segmentally constant approximation (SCA). The present study introduces this purely geometrical constraint (SCA) into the full nonhydrostatic anelastic system. A continuous-space description of the full system is, thus, replaced by a discretization consisting only of two segments (plume and environment) in the horizontal direction. The resulting discretized system is mathematically equivalent to a 0th order finite volume formulation with the only two finite volumes. The model is presented under a two-dimensional configuration. Interfaces between the plume and the environment segments may either be fixed in time or Lagrangianly advected as two limiting cases. Under this framework, the single-plume dynamics is systematically investigated in a wide phase space of Richardson number, the aspect ratio, and a displacement rate of the plume interfaces relative to the Lagrangian displacement. Advantage of the present model is in evaluating the lateral mixing processes of the plume without invoking an entrainment-detrainment hypothesis. The fractional entrainment-detrainment rate diagnosed from the present model simulations highly varies both over space and time, suggesting a limitation of applying an entrainment-detrainment hypothesis to unsteady plumes, as in the present case, in which circulations of the plume scale dominates over the turbulent mixing process. Furthermore, when the entrainment-plume hypothesis of Morton et al. is adopted for defining the plume-interface displacement rate, the plume continuously expands with time without reaching equilibrium.

  8. Modelling of thruster plume induced erosion

    NASA Astrophysics Data System (ADS)

    Alred, John; Boeder, Paul; Mikatarian, Ron; Pankop, Courtney; Schmidl, William

    2003-09-01

    One source of external induced contamination on the International Space Station (ISS) is thruster plume exhausts. The contamination from these plumes onto ISS sensitive surfaces is due to liquid drops of unreacted or partially reacted propellants. However, the drag acceleration of these particles (drops) from the exhaust gases produces high velocity (~km/s) drops that will mechanically damage surfaces in the exhaust. Previous space flight experiments on the Space Shuttle Orbiter which studied thruster plume induced contamination also demonstrated the pitting nature of these particles. The External Contamination/Plasma Team of the Boeing ISS Program Office in Houston has developed an approach to modeling the mechanical erosion on surfaces due to the impact of particles in thruster plumes. This approach melds damage simulation data from a smooth particle hydrodynamics (SPH) code from Los Alamos National Laboratory (LANL) into Boeing's own contamination computer tool (NASAN-II). The Boeing team has conducted several analyses simulating bipropellant thruster droplets impacting ISS sensitive surfaces. Computational results of various thrusters firing onto the ISS, at different build-stages, were completed and show a concern for particular solar array orientations during attitude control firings. Mitigation techniques for minimizing the erosion effects have also been determined and are presented.

  9. Ash Plume from Shiveluch

    NASA Image and Video Library

    2017-09-27

    When NASA’s Terra satellite passed over Russia’s Kamchatka Peninsula at noon local time (00:00 Universal Time) on October 6, 2012, Shilveluch Volcano was quiet. By the time NASA’s Aqua satellite passed over the area two hours later (bottom image), the volcano had erupted and sent a plume of ash over the Kamchatskiy Zaliv. The plume traveled about 90 kilometers (55 miles) toward the south-southeast, where a change in wind direction began pushing the plume toward the east. On October 6, 2012, the Kamchatka Volcanic Emergency Response Team (KVERT) reported that the ash plume from Shiveluch reached an altitude of 3 kilometers (9,800 feet) above sea level, and had traveled some 220 kilometers (140 miles) from the volcano summit. Shiveluch (also spelled Sheveluch) ranks among the biggest and most active volcanoes on the Kamchatka Peninsula. Rising to 3,283 meters (10,771 feet) above sea level, Shiveluch is a stratovolcano composed of alternating layers of hardened lava, compacted ash, and rocks ejected by previous eruptions. The beige-colored expanse of rock on the volcano’s southern slopes (visible in both images) is due to an explosive eruption that occurred in 1964. Part of Shiveluch’s southern flank collapsed, and the light-colored rock is avalanche debris left by that event. High-resolution imagery of Shiveluch shows very little vegetation within that avalanche zone. On October 6, 2012, KVERT cited observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on Terra and Aqua in detecting the Shiveluch eruption. This was not the first time that MODIS observed a Shiveluch eruption shortly after it started. In 2007, MODIS captured an image within minutes of the eruption’s start, before winds could blow the ash away from the summit. When NASA’s Terra satellite passed over Russia’s Kamchatka Peninsula at noon local time (00:00 Universal Time) on October 6, 2012, Shilveluch Volcano was quiet (top image). By the time NASA

  10. Enceladus Plumes: Causes of Decadal Variability

    NASA Astrophysics Data System (ADS)

    Ingersoll, Andrew P.; Ewald, Shawn P.

    2016-10-01

    The Enceladus plumes have decreased over the decade that Cassini has been observing them. This long-term variation is superposed on the much shorter-term variation tied to the position of Enceladus in its orbit around Saturn. The observations are ISS and VIMS images, which reveal the particles in the plumes but not the gas. The decadal variability largely consists of a 2-fold decline in the mass of plume material, but there is a hint of a recent turnaround. Here we offer three hypotheses, each with its strengths and weaknesses, to explain the long-term variability. The first is seasonal change, from summer to fall in the southern hemisphere. The loss of sunlight could increase the build-up of ice around the tiger stripes. The weakness is that the sunlight is likely to have a small effect, e.g., decreasing the sublimation rate of the ice by only ~1 cm/year. The second hypothesis is a statistical fluctuation in the number of active plumes, which tend to turn themselves off due to build-up of ice at the throat of the vent. The weakness is that the plumes are likely to fluctuate independently, and if there are ~100 plumes, their sum will only fluctuate by 10%. The third hypothesis is that the variation is part of a well-known decadal cycle of orbital eccentricity, which varies by ±2.5% around a mean of 0.0047. The peak eccentricity occurred in 2009-2010, and the minimum occurred in 2015. Since eccentricity controls the short-term orbital cycle variations, it could also control the longer-term decadal variations. The weakness is that the eccentricity variation is small, from 0.0046 to 0.0048. It is not certain that such a small variation could cause a 2-fold variation in the strength of the plumes. An independent study, still in its infancy, is the possibility that liquid water reaches the surface during part of the orbital cycle.

  11. Chemical processing of volcanic ash within eruption plume and cloud: a numerical modeling approach

    NASA Astrophysics Data System (ADS)

    Hoshyaripour, Gholam Ali; Hort, Matthias; Langmann, Baerbel; Brasseur, Guy

    2015-04-01

    Volcanic ash is recently identified as an active chemical agent in the Earth system. Generated mainly through lithospheric processes and magma fragmentation, it can pose significant impacts upon different components of the Earth system for e.g. atmosphere and hydrosphere on various temporal and spatial scales. While airborne in the atmosphere, transition metals contained in the ash can catalyze the sulfur oxidation cycle thereby indirectly affecting the volcanic radiative forcing. Moreover, upon deposition on the surface ocean, ash can release soluble iron that fertilizes Fe-limited areas of the ocean and stimulate the marine productivity and CO2 drawdown. Such impacts are provoked through interfacial processes and thus, are mainly induced by the ash surface composition. Recent studies suggest that in-plume and in-cloud processing of volcanic ash primarily control its surface composition. Direct evidences concerning such processes are, however, lacking. Here we present the results of our recent investigations on in-plume and in-cloud processing of volcanic ash. A 1D numerical model is developed that simulates the gas-ash-aerosol interactions in volcanic eruption plume and cloud at temperatures between 600 C and 0 C focusing on iron, sulfur and halogen chemistry. Results show that sulfuric acid and water vapor condense at 150 C and 50 C, respectively, generating a liquid coating at the ash surface that scavenges the surrounding gases (>95extremely acidic (pH

  12. Linking Europa's plume activity to tides, tectonics, and liquid water

    NASA Astrophysics Data System (ADS)

    Rhoden, Alyssa Rose; Hurford, Terry A.; Roth, Lorenz; Retherford, Kurt

    2015-06-01

    Much of the geologic activity preserved on Europa's icy surface has been attributed to tidal deformation, mainly due to Europa's eccentric orbit. Although the surface is geologically young (30-80 Myr), there is little information as to whether tidally-driven surface processes are ongoing. However, a recent detection of water vapor near Europa's south pole suggests that it may be geologically active. Initial observations indicated that Europa's plume eruptions are time-variable and may be linked to its tidal cycle. Saturn's moon, Enceladus, which shares many similar traits with Europa, displays tidally-modulated plume eruptions, which bolstered this interpretation. However, additional observations of Europa at the same time in its orbit failed to yield a plume detection, casting doubt on the tidal control hypothesis. The purpose of this study is to analyze the timing of plume eruptions within the context of Europa's tidal cycle to determine whether such a link exists and examine the inferred similarities and differences between plume activity on Europa and Enceladus. To do this, we determine the locations and orientations of hypothetical tidally-driven fractures that best match the temporal variability of the plumes observed at Europa. Specifically, we identify model faults that are in tension at the time in Europa's orbit when a plume was detected and in compression at times when the plume was not detected. We find that tidal stress driven solely by eccentricity is incompatible with the observations unless additional mechanisms are controlling the eruption timing or restricting the longevity of the plumes. The addition of obliquity tides, and corresponding precession of the spin pole, can generate a number of model faults that are consistent with the pattern of plume detections. The locations and orientations of these hypothetical source fractures are robust across a broad range of precession rates and spin pole directions. Analysis of the stress variations across

  13. Advanced Polymer Composite Molding Through Intelligent Process Analysis and Control

    DTIC Science & Technology

    2007-03-30

    assisted resin transfer molding ( VARTM ) and Seemann Composite Resin Infusion Molding Process (SCRIMPT M). All variations of RTM are suitable for the...numerical simulations have been used to design the vent and gate locations for molds used for RTM , VARTM and SCRIMPTM [2,3,7-14]. Regardless of the research...200 Words) To prevent dry spot formation in RTM , a control interface and four different adaptive control algorithms were developed and tested with

  14. Atmospheric chemistry in volcanic plumes

    PubMed Central

    von Glasow, Roland

    2010-01-01

    Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis. PMID:20368458

  15. Atmospheric chemistry in volcanic plumes.

    PubMed

    von Glasow, Roland

    2010-04-13

    Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis.

  16. Plumes do not Exist: Plate Circulation is Confined to Upper Mantle

    NASA Astrophysics Data System (ADS)

    Hamilton, W. B.

    2002-12-01

    Plumes from deep mantle are widely conjectured to define an absolute reference frame, inaugurate rifting, drive plates, and profoundly modify oceans and continents. Mantle properties and composition are assumed to be whatever enables plumes. Nevertheless, purported critical evidence for plume speculation is false, and all data are better interpreted without plumes. Plume fantasies are made ever more complex and ad hoc to evade contradictory data, and have no predictive value because plumes do not exist. All plume conjecture derives from Hawaii and the guess that the Emperor-Hawaii inflection records a 60-degree change in Pacific plate direction at 45 Ma. Paleomagnetic latitudes and smooth Pacific spreading patterns disprove any such change. Rationales for other fixed plumes collapse when tested, and hypotheses of jumping, splitting, and gyrating plumes are specious. Thermal and physical properties of Hawaiian lithosphere falsify plume predictions. Purported tomographic support elsewhere represents artifacts and misleading presentations. Asthenosphere is everywhere near solidus temperature, so melt needs a tensional setting for egress but not local heat. Gradational and inconsistent contrasts between MORB and OIB are as required by depth-varying melt generation and behavior in contrasted settings and do not indicate systematically unlike sources. MORB melts rise, with minimal reaction, through hot asthenosphere, whereas OIB melts react with cool lithosphere, and lose mass, by crystallizing refractories and retaining and assimilating fusibles. The unfractionated lower mantle of plume conjecture is contrary to cosmologic and thermodynamic data, for mantle below 660 km is more refractory than that above. Subduction, due to density inversion by top-down cooling that forms oceanic lithosphere, drives plate tectonics and upper-mantle circulation. It organizes plate motions and lithosphere stress, which controls plate boundaries and volcanic chains. Hinge rollback is the

  17. Rocket Plume Scaling for Orion Wind Tunnel Testing

    NASA Technical Reports Server (NTRS)

    Brauckmann, Gregory J.; Greathouse, James S.; White, Molly E.

    2011-01-01

    A wind tunnel test program was undertaken to assess the jet interaction effects caused by the various solid rocket motors used on the Orion Launch Abort Vehicle (LAV). These interactions of the external flowfield and the various rocket plumes can cause localized aerodynamic disturbances yielding significant and highly non-linear control amplifications and attenuations. This paper discusses the scaling methodologies used to model the flight plumes in the wind tunnel using cold air as the simulant gas. Comparisons of predicted flight, predicted wind tunnel, and measured wind tunnel forces-and-moments and plume flowfields are made to assess the effectiveness of the selected scaling methodologies.

  18. Is the 'Fast Halo' around Hawaii as imaged in the PLUME experiment direct evidence for buoyant plume-fed asthenosphere?

    NASA Astrophysics Data System (ADS)

    Morgan, J. P.; Shi, C.; Hasenclever, J.

    2010-12-01

    An intriguing spatial pattern of variations in shear-wave arrival times has been mapped in the PLUME ocean bottom experiment (Wolfe et al., 2009) around Hawaii. The pattern consists of a halo of fast travel times surrounding a disk of slow arrivals from waves traveling up though the plume. We think it is directly sensing the pattern of dynamic uplift of the base of a buoyant asthenosphere - the buoyancy of the plume conduit lifting a 'rim' of the cooler, denser mantle that the plume rises through. The PLUME analysis inverted for lateral shear velocity variations beneath the lithosphere, after removing the assumed 1-D model velocity structure IASP91. They found that a slow plume-conduit extends to at least 1200 km below the Hawaiian hotspot. In this inversion the slow plume conduit is — quite surprisingly - surrounded by a fast wavespeed halo. A fast halo is impossible to explain as a thermal halo around the plume; this should lead to a slow wavespeed halo, not a fast one. Plume-related shearwave anisotropy also cannot simply explain this pattern — simple vertical strain around the plume conduit would result in an anisotropic slow shear-wavespeed halo, not a fast one. (Note the PLUME experiment’s uniform ‘fast-halo’ structure from 50-400km is likely to have strong vertical streaking in the seismic image; Pacific Plate-driven shear across a low-viscosity asthenosphere would be expected to disrupt and distort any cold sheet of vertical downwelling structure between 50-400km depths so that it would no longer be vertical as it is in the 2009 PLUME image with its extremely poor vertical depth control.) If the asthenosphere is plume-fed, hence more buoyant than underlying mantle, then there can be a simple explanation for this pattern. The anomaly would be due to faster traveltimes resulting from dynamic relief at the asthenosphere-mesosphere interface; uplift of the denser mesosphere by the buoyancy of the rising plume increases the distance a wave travels

  19. Synthesis and analysis of new humidity-controlling composite materials

    NASA Astrophysics Data System (ADS)

    Shang, Jian-li; Zong, Zhi-fang; Zhang, Hao

    2017-05-01

    Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.

  20. Scanning thermal plumes

    NASA Technical Reports Server (NTRS)

    Scarpace, F. L.; Madding, R. P.; Green, T., III

    1975-01-01

    Over a three-year period 800 thermal line scans of power plant plumes were made by an airborne scanner, with ground truth measured concurrently at the plants. Computations using centered finite differences in the thermal scanning imagery show a lower bound in the horizontal temperature gradient in excess of 1.6 C/m. Gradients persist to 3 m below the surface. Vector plots of the velocity of thermal fronts are constructed by tracing the front motion in successive thermal images. A procedure is outlined for the two-point ground calibration of a thermal scanner from an equation describing the scanner signal and the voltage for two known temperatures. The modulation transfer function is then calculated by input of a thermal step function and application of digital time analysis techniques using Fast Fourier Transforms to the voltage output. Field calibration tests are discussed. Data accuracy is limited by the level of ground truth effort chosen.

  1. Scanning thermal plumes

    NASA Technical Reports Server (NTRS)

    Scarpace, F. L.; Madding, R. P.; Green, T., III

    1975-01-01

    Over a three-year period 800 thermal line scans of power plant plumes were made by an airborne scanner, with ground truth measured concurrently at the plants. Computations using centered finite differences in the thermal scanning imagery show a lower bound in the horizontal temperature gradient in excess of 1.6 C/m. Gradients persist to 3 m below the surface. Vector plots of the velocity of thermal fronts are constructed by tracing the front motion in successive thermal images. A procedure is outlined for the two-point ground calibration of a thermal scanner from an equation describing the scanner signal and the voltage for two known temperatures. The modulation transfer function is then calculated by input of a thermal step function and application of digital time analysis techniques using Fast Fourier Transforms to the voltage output. Field calibration tests are discussed. Data accuracy is limited by the level of ground truth effort chosen.

  2. Groundwater contaminant plume ranking. [UMTRA Project

    SciTech Connect

    Not Available

    1988-08-01

    Containment plumes at Uranium Mill Tailings Remedial Action (UMTRA) Project sites were ranked to assist in Subpart B (i.e., restoration requirements of 40 CFR Part 192) compliance strategies for each site, to prioritize aquifer restoration, and to budget future requests and allocations. The rankings roughly estimate hazards to the environment and human health, and thus assist in determining for which sites cleanup, if appropriate, will provide the greatest benefits for funds available. The rankings are based on the scores that were obtained using the US Department of Energy's (DOE) Modified Hazard Ranking System (MHRS). The MHRS and HRS consider and score three hazard modes for a site: migration, fire and explosion, and direct contact. The migration hazard mode score reflects the potential for harm to humans or the environment from migration of a hazardous substance off a site by groundwater, surface water, and air; it is a composite of separate scores for each of these routes. For ranking the containment plumes at UMTRA Project sites, it was assumed that each site had been remediated in compliance with the EPA standards and that relict contaminant plumes were present. Therefore, only the groundwater route was scored, and the surface water and air routes were not considered. Section 2.0 of this document describes the assumptions and procedures used to score the groundwater route, and Section 3.0 provides the resulting scores for each site. 40 tabs.

  3. Aircraft-borne aerosol chemical composition measurements in the lower to middle troposphere over southern West Africa: Biomass burning, urban outflow plumes, and long-range transport.

    NASA Astrophysics Data System (ADS)

    Batenburg, Anneke; Schulz, Christiane; Schneider, Johannes; Sauer, Daniel; Schlager, Hans; Borrmann, Stephan

    2017-04-01

    During the DACCIWA field campaign in June and July 2016, aircraft-borne in-situ aerosol chemical composition measurements were performed over southern West Africa (SWA). This presentation will focus on the submicron particle measurements done with a Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF-AMS) on board of the DLR Falcon aircraft during twelve research flights from Lomé, Togo, covering the altitude range from the boundary layer (BL) to the middle troposphere (12 km). A preliminary analysis of the results shows typical baseline total non-refractory aerosol mass loadings of 1.5 to 2.8 μg m-3 in the BL, and 0.4 to 1.1 μg m-3above. Up to half of the baseline aerosol mass in the BL appears to consist of sulphate, compared to only 10 to 35 % above the BL; organic matter dominates in the middle troposphere. During several flights, the DLR Falcon crossed a pronounced and seemingly widespread aerosol layer at 2—4.5 km altitude, partly in or slightly above the BL. The AMS data indicate that about half of the non-refractory aerosol mass in the middle of this layer consisted of organic matter. We consider it likely that these aerosol particles were produced by biomass burning in Central Africa. Emissions from cities and industrial areas were also intercepted, as well as enhancements in some species at higher altitudes. Trajectory analysis suggests that an increase of the organics to more than 2.5 μg m-3 observed at 8 km during one flight came from the Arabian Peninsula. Several ammonium peaks during the same flight at higher altitudes were traced back to the Asian Summer Monsoon Anticyclone (ASMA).

  4. Composite predictive flight control for airbreathing hypersonic vehicles

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Zhao, Zhenhua; Li, Shihua; Zheng, Wei Xing

    2014-09-01

    The robust optimised tracking control problem for a generic airbreathing hypersonic vehicle (AHV) subject to nonvanishing mismatched disturbances/uncertainties is investigated in this paper. A baseline nonlinear model predictive control (MPC) method is firstly introduced for optimised tracking control of the nominal dynamics. A nonlinear-disturbance-observer-based control law is then developed for robustness enhancement in the presence of both external disturbances and uncertainties. Compared with the existing robust tracking control methods for AHVs, the proposed composite nonlinear MPC method obtains not only promising robustness and disturbance rejection performance but also optimised nominal tracking control performance. The merits of the proposed method are validated by implementing simulation studies on the AHV system.

  5. Access Control Model for Sharing Composite Electronic Health Records

    NASA Astrophysics Data System (ADS)

    Jin, Jing; Ahn, Gail-Joon; Covington, Michael J.; Zhang, Xinwen

    The adoption of electronically formatted medical records, so called Electronic Health Records (EHRs), has become extremely important in healthcare systems to enable the exchange of medical information among stakeholders. An EHR generally consists of data with different types and sensitivity degrees which must be selectively shared based on the need-to-know principle. Security mechanisms are required to guarantee that only authorized users have access to specific portions of such critical record for legitimate purposes. In this paper, we propose a novel approach for modelling access control scheme for composite EHRs. Our model formulates the semantics and structural composition of an EHR document, from which we introduce a notion of authorized zones of the composite EHR at different granularity levels, taking into consideration of several important criteria such as data types, intended purposes and information sensitivities.

  6. Optimized control of multistate quantum systems by composite pulse sequences

    SciTech Connect

    Genov, G. T.; Vitanov, N. V.; Torosov, B. T.

    2011-12-15

    We introduce a technique for derivation of high-fidelity composite pulse sequences for two types of multistate quantum systems: systems with the SU(2) and Morris-Shore dynamic symmetries. For the former type, we use the Majorana decomposition to reduce the dynamics to an effective two-state system, which allows us to find the propagator analytically and use the pool of available composite pulses for two-state systems. For the latter type of multistate systems, we use the Morris-Shore decomposition, which reduces the multistate dynamics to a set of two-state systems. We present examples which demonstrate that the multistate composite sequences open a variety of possibilities for coherent control of quantum systems with multiple states.

  7. Novel hybrid coatings with controlled wettability by composite nanoparticle aggregation

    NASA Astrophysics Data System (ADS)

    Hritcu, Doina; Dodi, Gianina; Iordache, Mirabela L.; Draganescu, Dan; Sava, Elena; Popa, Marcel I.

    2016-11-01

    The aim of this study is to evaluate novel hybrid materials as potential candidates for producing coatings with hierarchical roughness and controlled wetting behaviour. Magnetite (Fe3O4) nanoparticles obtained by co-precipitation were embedded in matrices synthesized by radical graft co-polymerization of butyl acrylate (BA), butyl methacrylate (BMA), hexyl acrylate (HA) or styrene (ST) with ethylene glycol di-methacrylate (EGDMA) onto previously modified chitosan bearing surface vinyl groups. The resulting composite particles were characterized regarding their average size, composition and magnetic properties. Hybrid thin films containing suspension of composite particles in ethanol and pre-hydrolysed hexadecyltrimethoxysilane (HDTS) as a coupling/crosslinking agent were deposited by spin coating or spraying. The films were cured by heating and subsequently characterized regarding their morphology (scanning electron microscopy), contact angle with water and adhesion to substrate (scratch test). The structure-property relationship is discussed.

  8. Seismic imaging of melt in a displaced Hawaiian plume

    NASA Astrophysics Data System (ADS)

    Rychert, Catherine A.; Laske, Gabi; Harmon, Nicholas; Shearer, Peter M.

    2013-08-01

    The Hawaiian Islands are the classic example of hotspot volcanism: the island chain formed progressively as the Pacific plate moved across a fixed mantle plume. However, some observations are inconsistent with simple, vertical upwelling beneath a thermally defined plate and the nature of plume-plate interaction is debated. Here we use S-to-P seismic receiver functions, measured using a network of land and seafloor seismometers, to image the base of a melt-rich zone located 110 to 155 km beneath Hawaii. We find that this melt-rich zone is deepest 100 km west of Hawaii, implying that the plume impinges on the plate here and causes melting at greater depths in the mantle, rather than directly beneath the island. We infer that the plume either naturally upwells vertically beneath western Hawaii, or that it is instead deflected westwards by a compositionally depleted root that was generated beneath the island as it formed. The offset of the Hawaiian plume adds complexity to the classical model of a fixed plume that ascends vertically to the surface, and suggests that mantle melts beneath intraplate volcanoes may be guided by pre-existing structures beneath the islands.

  9. Growth and mixing dynamics of mantle wedge plumes

    NASA Astrophysics Data System (ADS)

    Gorczyk, Weronika; Gerya, Taras V.; Connolly, James A. D.; Yuen, David A.

    2007-07-01

    Recent work suggests that hydrated partially molten thermal-chemical plumes that originate from subducted slab as a consequence of Rayleigh-Taylor instability are responsible for the heterogeneous composition of the mantle wedge. We use a two-dimensional ultrahigh-resolution numerical simulation involving 10 × 109 active markers to anticipate the detailed evolution of the internal structure of natural plumes beneath volcanic arcs in intraoceanic subduction settings. The plumes consist of partially molten hydrated peridotite, dry solid mantle, and subducted oceanic crust, which may compose as much as 12% of the plume. As plumes grow and mature these materials mix chaotically, resulting in attenuation and duplication of the original layering on scales of 1-1000 m. Comparison of numerical results with geological observations from the Horoman ultramafic complex in Japan suggests that mixing and differentiation processes related to development of partially molten plumes above slabs may be responsible for the strongly layered lithologically mixed (marble cake) structure of asthenospheric mantle wedges.

  10. Stratospheric aircraft exhaust plume and wake chemistry

    NASA Technical Reports Server (NTRS)

    Miake-Lye, R. C.; Martinez-Sanchez, M.; Brown, R. C.; Kolb, C. E.; Worsnop, D. R.; Zahniser, M. S.; Robinson, G. N.; Rodriguez, J. M.; Ko, M. K. W.; Shia, R-L.

    1993-01-01

    Progress to date in an ongoing study to analyze and model emissions leaving a proposed High Speed Civil Transport (HSCT) from when the exhaust gases leave the engine until they are deposited at atmospheric scales in the stratosphere is documented. A kinetic condensation model was implemented to predict heterogeneous condensation in the plume regime behind an HSCT flying in the lower stratosphere. Simulations were performed to illustrate the parametric dependence of contrail droplet growth on the exhaust condensation nuclei number density and size distribution. Model results indicate that the condensation of water vapor is strongly dependent on the number density of activated CN. Incorporation of estimates for dilution factors into a Lagrangian box model of the far-wake regime with scale-dependent diffusion indicates negligible decrease in ozone and enhancement of water concentrations of 6-13 times background, which decrease rapidly over 1-3 days. Radiative calculations indicate a net differential cooling rate of the plume about 3K/day at the beginning of the wake regime, with a total subsidence ranging between 0.4 and 1 km. Results from the Lagrangian plume model were used to estimate the effect of repeated superposition of aircraft plumes on the concentrations of water and NO(y) along a flight corridor. Results of laboratory studies of heterogeneous chemistry are also described. Kinetics of HCl, N2O5 and ClONO2 uptake on liquid sulfuric acid were measured as a function of composition and temperature. Refined measurements of the thermodynamics of nitric acid hydrates indicate that metastable dihydrate may play a role in the nucleation of more stable trihydrates PSC's.

  11. Phytoplankton assemblages within the Chesapeake Bay plume and adjacent waters of the continental shelf

    NASA Technical Reports Server (NTRS)

    Marshall, H. G.

    1981-01-01

    The Chesapeake Bay plume was identified and plotted in relation to the presence and high concentrations of phytoplankton assemblages. Seasonal differences occurred within the plume during the collection period, with Skeletonema costatum and an ultraplankton component the dominant forms. Patchiness was found along the transects, with variations in composition and concentrations common on consecutive day sampling within the plume in its movement along the shelf. The presence of 236 species is noted, with their presence indicated for plume and shelf stations during the March, June, and October 1980 collections.

  12. Bioinspired Composites with Spatial and Orientational Control of Reinforcement

    NASA Astrophysics Data System (ADS)

    Demiroers, Ahmet; Studart, Andre; Complex Materials Team

    Living organisms combine soft and hard components to fabricate composite materials with out-standing mechanical properties. The optimum design and assembly of the anisotropic components reinforce the material in specific directions against multidirectional external loads. Although nature does it quite readily, it is still a challenge for material scientists to control the orientation and position of the colloidal components in a matrix. Here, we use external electric and magnetic fields to achieve positional and orientational control over colloid-polymer composites to fabricate mechanically robust materials to capture some of the essential features of natural systems. We first investigated the assembly of spherical micron-sized colloids using dielectrophoresis, as these particles provided an easily accessible and instructive length scale for performing initial experiments. We used dielectrophoresis for spatial control of reinforcing anisotropic components and magnetic fields to provide control over the orientation of these reinforcing constituents. The obtained composites with different orientational and spatial reinforcement showed enhanced mechanical properties, such as wear resistance, which exhibits similarities to tooth enamel. SNSF Ambizione Grant PZ00P2_148040.

  13. Noise transmission properties and control strategies for composite structures

    NASA Technical Reports Server (NTRS)

    Silcox, Richard J.; Beyer, Todd B.; Lester, Harold C.

    1991-01-01

    A study of several component technologies required to apply active control techniques to reduce interior noise in composite aircraft structures is described. The mechanisms of noise transmission in an all composite, large-scale, fuselage model are studied in an experimental program and found similar to mechanisms found in conventional aircraft construction. Two primary conditions of structural acoustic response are found to account for the dominant interior acoustic response. A preliminary study of active noise control in cylinders used piezoceramic actuators as force inputs for a simple aluminum fuselage model. These actuators provided effective control for the same two conditions of noise transmission found in the composite fuselage structure. The use of piezoceramic actuators to apply force inputs overcomes the weight and structural requirements of conventional shaker actuators. Finally, in order to accurately simulate these types of actuators in a cylindrical shell, two analytical models are investigated that apply either in-plane forces or bending moments along the boundaries of a finite patch. It is shown that the bending model may not be as effective as the force model for exciting the low order azimuthal modes that typically dominate the structural acoustic response in these systems. This result will affect the arrangement and distribution of actuators required for effective active control systems.

  14. Plume Impingement Analysis for the European Service Module Propulsion System

    NASA Technical Reports Server (NTRS)

    Yim, John Tamin; Sibe, Fabien; Ierardo, Nicola

    2014-01-01

    Plume impingement analyses were performed for the European Service Module (ESM) propulsion system Orbital Maneuvering System engine (OMS-E), auxiliary engines, and reaction control system (RCS) engines. The heat flux from plume impingement on the solar arrays and other surfaces are evaluated. This information is used to provide inputs for the ESM thermal analyses and help determine the optimal configuration for the RCS engines.

  15. The impact of glacier geometry on meltwater plume structure and submarine melt in Greenland fjords

    NASA Astrophysics Data System (ADS)

    Carroll, D.; Sutherland, D. A.; Hudson, B.; Moon, T.; Catania, G. A.; Shroyer, E. L.; Nash, J. D.; Bartholomaus, T. C.; Felikson, D.; Stearns, L. A.; Noël, B. P. Y.; Broeke, M. R.

    2016-09-01

    Meltwater from the Greenland Ice Sheet often drains subglacially into fjords, driving upwelling plumes at glacier termini. Ocean models and observations of submarine termini suggest that plumes enhance melt and undercutting, leading to calving and potential glacier destabilization. Here we systematically evaluate how simulated plume structure and submarine melt during summer months depends on realistic ranges of subglacial discharge, glacier depth, and ocean stratification from 12 Greenland fjords. Our results show that grounding line depth is a strong control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-trapped plumes that can overcut termini. Due to sustained upwelling velocities, plumes in cold, shallow fjords can induce equivalent depth-averaged melt rates compared to warm, deep fjords. These results detail a direct ocean-ice feedback that can affect the Greenland Ice Sheet.

  16. A PCE groundwater plume discharging to a river: influence of the streambed and near-river zone on contaminant distributions.

    PubMed

    Conant, Brewster; Cherry, John A; Gillham, Robert W

    2004-09-01

    An investigation of a tetrachloroethene (PCE) groundwater plume originating at a dry cleaning facility on a sand aquifer and discharging to a river showed that the near-river zone strongly modified the distribution, concentration, and composition of the plume prior to discharging into the surface water. The plume, streambed concentration, and hydrogeology were extensively characterized using the Waterloo profiler, mini-profiler, conventional and driveable multilevel samplers (MLS), Ground Penetrating Radar (GPR) surveys, streambed temperature mapping (to identify discharge zones), drivepoint piezometers, and soil coring and testing. The plume observed in the shallow streambed deposits was significantly different from what would have been predicted based on the characteristics of the upgradient plume. Spatial and temporal variations in the plume entering the near-river zone contributed to the complex contaminant distribution observed in the streambed where concentrations varied by factors of 100 to 5000 over lateral distances of less than 1 to 3.5 m. Low hydraulic conductivity semi-confining deposits and geological heterogeneities at depth below the streambed controlled the pattern of groundwater discharge through the streambed and influenced where the plume discharged into the river (even causing the plume to spread out over the full width of the streambed at some locations). The most important effect of the near-river zone on the plume was the extensive anaerobic biodegradation that occurred in the top 2.5 m of the streambed, even though essentially no biodegradation of the PCE plume was observed in the upgradient aquifer. Approximately 54% of the area of the plume in the streambed consisted solely of PCE transformation products, primarily cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC). High concentrations in the interstitial water of the streambed did not correspond to high groundwater-discharge zones, but instead occurred in low discharge zones and are

  17. Life Cycle of Mantle Plumes: A perspective from the Galapagos Plume (Invited)

    NASA Astrophysics Data System (ADS)

    Gazel, E.; Herzberg, C. T.

    2009-12-01

    Hotspots are localized sources of heat and magmatism considered as modern-day evidence of mantle plumes. Some hotspots are related to massive magmatic production that generated Large Igneous Provinces (LIPS), an initial-peak phase of plume activity with a mantle source hotter and more magmatically productive than present-day hotspots. Geological mapping and geochronological studies have shown much lower eruption rates for OIB compared to lavas from Large Igneous Provinces LIPS such as oceanic plateaus and continental flood provinces. Our study is the first quantitative petrological comparison of mantle source temperatures and extent of melting for OIB and LIP sources. The wide range of primary magma compositions and inferred mantle potential temperatures for each LIP and OIB occurrence suggest that this rocks originated form a hotspot, a spatially localized source of heat and magmatism restricted in time. Extensive outcrops of basalt, picrite, and sometimes komatiite with circa 65-95 Ma ages occupy portions of the pacific shore of Central and South America included in the Caribbean Large Igneous Province (CLIP). There is general consensus of a Pacific-origin of CLIP and most studies suggest that it was produced by melting in the Galapagos mantle plume. The Galapagos connection is consistent with isotopic and geochemical similarities with lavas from the present-day Galapagos hotspot. A Galapagos link for rocks in South American oceanic complexes (eg. the island of Gorgona) is more controversial and requires future work. The MgO and FeO contents of lavas from the Galapagos related lavas and their primary magmas have decreased since the Cretaceous. From petrological modeling we infer that these changes reflect a cooling of the Galapagos mantle plume from a potential temperature of 1560-1620 C in the Cretaceous to 1500 C at the present time. These temperatures are higher than 1350 C for ambient mantle associated with oceanic ridges, and provide support for the mantle

  18. Photocatalytic studies of Ho–Zr–O nano-composite with controllable composition and defects

    SciTech Connect

    Du, Weimin; Zhao, Guoyan; Chang, Hongxun; Shi, Fei; Zhu, Zhaoqiang; Qian, Xuefeng

    2013-09-15

    With the help of sol–gel method assisted by melting salt, a series of Ho–Zr–O nano-composite with controllable composition and defects have been successfully prepared. Characterization results show that the positions, intensity, and width of the X-ray diffraction peaks of the products have a regular variation with the increase of zirconium element which implies the gradual changes of crystal spacing and product size. At the same time, the molar ratios between holmium and zirconium ions are consistent with the chemical formula and both of them are uniformly distributed in products further showing the perfect formation of targeted materials. Optical properties reveal that diversified defect forms of Ho–Zr–O nano-composite lead to the different absorptions of visible light. Photocatalytic experiments demonstrate Zr{sub 0.8}Ho{sub 0.2}O{sub 2−δ} nano-crystals have excellent visible-light-responsive photocatalytic activities on some familiar dyes (e.g.: methylene blue and Rhodamine B) which results from the special defect structure, better absorption of visible light and larger specific surface area. It follows that Zr{sub 0.8}Ho{sub 0.2}O{sub 2−δ} nano-crystals are a new kind of visible-light-responsive photocatalysts with better prospects in conversion and utilization of solar energy. Also, the present melting salt assisted route might be generalized to synthesize other AxByOz composite oxide nano-crystals with more complicated structures. - Highlights: • Ho–Zr–O nano-composite with controllable composition and defects has been obtained. • Diversified defect forms of products lead to the different visible light absorption. • Zr{sub 0.8}Ho{sub 0.2}O{sub 2−δ} nano-crystals have excellent photocatalytic activities.

  19. Composite fuzzy sliding mode control of nonlinear singularly perturbed systems.

    PubMed

    Nagarale, Ravindrakumar M; Patre, B M

    2014-05-01

    This paper deals with the robust asymptotic stabilization for a class of nonlinear singularly perturbed systems using the fuzzy sliding mode control technique. In the proposed approach the original system is decomposed into two subsystems as slow and fast models by the singularly perturbed method. The composite fuzzy sliding mode controller is designed for stabilizing the full order system by combining separately designed slow and fast fuzzy sliding mode controllers. The two-time scale design approach minimizes the effect of boundary layer system on the full order system. A stability analysis allows us to provide sufficient conditions for the asymptotic stability of the full order closed-loop system. The simulation results show improved system performance of the proposed controller as compared to existing methods. The experimentation results validate the effectiveness of the proposed controller.

  20. A robust composite nonlinear control scheme for servomotor speed regulation

    NASA Astrophysics Data System (ADS)

    Huang, Yanwei; Cheng, Guoqing

    2015-01-01

    A parameterised design of robust composite nonlinear controller is proposed for typical second-order servo systems subject to unknown constant disturbance and control input saturation. The control law consists of a linear feedback part for achieving fast response, a nonlinear feedback part for suppressing the overshoot, and a disturbance-compensation mechanism for erasing the steady-state error. An extended state observer is adopted to estimate the unknown disturbance. The closed-loop stability is analysed theoretically. The control scheme is applied to the speed regulation of permanent magnet synchronous motor, and numerical simulations are carried out. The results confirm that the proposed control scheme can achieve fast, smooth, and accurate speed regulation, and has a certain degree of robustness with respect to the amplitude of disturbances and the perturbations of system parameters.

  1. Modeling the Complex Photochemistry of Biomass Burning Plumes in Plume-Scale, Regional, and Global Air Quality Models

    NASA Astrophysics Data System (ADS)

    Alvarado, M. J.; Lonsdale, C. R.; Yokelson, R. J.; Travis, K.; Fischer, E. V.; Lin, J. C.

    2014-12-01

    Forecasting the impacts of biomass burning (BB) plumes on air quality is difficult due to the complex photochemistry that takes place in the concentrated young BB plumes. The spatial grid of global and regional scale Eulerian models is generally too large to resolve BB photochemistry, which can lead to errors in predicting the formation of secondary organic aerosol (SOA) and O3, as well as the partitioning of NOyspecies. AER's Aerosol Simulation Program (ASP v2.1) can be used within plume-scale Lagrangian models to simulate this complex photochemistry. We will present results of validation studies of the ASP model against aircraft observations of young BB smoke plumes. We will also present initial results from the coupling of ASP v2.1 into the Lagrangian particle dispersion model STILT-Chem in order to better examine the interactions between BB plume chemistry and dispersion. In addition, we have used ASP to develop a sub-grid scale parameterization of the near-source chemistry of BB plumes for use in regional and global air quality models. The parameterization takes inputs from the host model, such as solar zenith angle, temperature, and fire fuel type, and calculates enhancement ratios of O3, NOx, PAN, aerosol nitrate, and other NOy species, as well as organic aerosol (OA). We will present results from the ASP-based BB parameterization as well as its implementation into the global atmospheric composition model GEOS-Chem for the SEAC4RS campaign.

  2. Updated Conceptual Model for the 300 Area Uranium Groundwater Plume

    SciTech Connect

    Zachara, John M.; Freshley, Mark D.; Last, George V.; Peterson, Robert E.; Bjornstad, Bruce N.

    2012-11-01

    The 300 Area uranium groundwater plume in the 300-FF-5 Operable Unit is residual from past discharge of nuclear fuel fabrication wastes to a number of liquid (and solid) disposal sites. The source zones in the disposal sites were remediated by excavation and backfilled to grade, but sorbed uranium remains in deeper, unexcavated vadose zone sediments. In spite of source term removal, the groundwater plume has shown remarkable persistence, with concentrations exceeding the drinking water standard over an area of approximately 1 km2. The plume resides within a coupled vadose zone, groundwater, river zone system of immense complexity and scale. Interactions between geologic structure, the hydrologic system driven by the Columbia River, groundwater-river exchange points, and the geochemistry of uranium contribute to persistence of the plume. The U.S. Department of Energy (DOE) recently completed a Remedial Investigation/Feasibility Study (RI/FS) to document characterization of the 300 Area uranium plume and plan for beginning to implement proposed remedial actions. As part of the RI/FS document, a conceptual model was developed that integrates knowledge of the hydrogeologic and geochemical properties of the 300 Area and controlling processes to yield an understanding of how the system behaves and the variables that control it. Recent results from the Hanford Integrated Field Research Challenge site and the Subsurface Biogeochemistry Scientific Focus Area Project funded by the DOE Office of Science were used to update the conceptual model and provide an assessment of key factors controlling plume persistence.

  3. Emission control devices, fuel additive, and fuel composition changes.

    PubMed Central

    Piver, W T

    1977-01-01

    Emission control devices are installed to meet the exhaust standards of the Clean Air Act for carbon monoxide and hydrocarbons, and it is necessary to know, from a public health point of view, how exhaust emissions may be affected by changes in fuel additives and fuel composition. Since these topics are concerned with developing technologies, the available literature on exhaust emission characteristics and the limited information on health effects, is reviewed. PMID:71235

  4. Constitutive modeling and control of 1D smart composite structures

    NASA Astrophysics Data System (ADS)

    Briggs, Jonathan P.; Ostrowski, James P.; Ponte-Castaneda, Pedro

    1998-07-01

    Homogenization techniques for determining effective properties of composite materials may provide advantages for control of stiffness and strain in systems using hysteretic smart actuators embedded in a soft matrix. In this paper, a homogenized model of a 1D composite structure comprised of shape memory alloys and a rubber-like matrix is presented. With proportional and proportional/integral feedback, using current as the input state and global strain as an error state, implementation scenarios include the use of tractions on the boundaries and a nonlinear constitutive law for the matrix. The result is a simple model which captures the nonlinear behavior of the smart composite material system and is amenable to experiments with various control paradigms. The success of this approach in the context of the 1D model suggests that the homogenization method may prove useful in investigating control of more general smart structures. Applications of such materials could include active rehabilitation aids, e.g. wrist braces, as well as swimming/undulating robots, or adaptive molds for manufacturing processes.

  5. The Saturn hydrogen plume

    NASA Astrophysics Data System (ADS)

    Shemansky, D. E.; Liu, X.; Melin, H.

    2009-12-01

    Images of the Saturn atmosphere and magnetosphere in H Lyα emission during the Cassini spacecraft pre and post Saturn orbit insertion (SOI) event obtained using the UVIS experiment FUV spectrograph have revealed definitive evidence for the escape of H I atoms from the top of the thermosphere. An image at 0.1×0.1 Saturn equatorial radii ( RS) pixel resolution with an edge-on-view of the rings shows a distinctive structure (plume) with full width at half maximum (FWHM) of 0.56RS at the exobase sub-solar limb at ˜-13.5∘ latitude as part of the distributed outflow of H I from the sunlit hemisphere, with a counterpart on the antisolar side peaking near the equator above the exobase limb. The structure of the image indicates that part of the outflowing population is sub-orbital and re-enters the thermosphere in an approximate 5 h time scale. An evident larger more broadly distributed component fills the magnetosphere to beyond 45RS in the orbital plane in an asymmetric distribution in local time, similar to an image obtained at Voyager 1 post encounter in a different observational geometry. It has been found that H2 singlet ungerade Rydberg EUV/FUV emission spectra collected with the H Lyα into the image mosaic show a distinctive resonance property correlated with the H Lyα plume. The inferred approximate globally averaged energy deposition at the top of the thermosphere from the production of the hot atomic hydrogen accounts for the measured atmospheric temperature. The only known process capable of producing the atoms at the required few eV/atom kinetic energy appears to be the direct electron excitation of non-LTE H2XΣg+1( v:J) into the repulsive H2bΣu+3, although details of the processes need to be examined under the constraints imposed by the observations to determine compatibility with the current knowledge of hydrogen rate processes.

  6. Cruise Ship Plume Tracking Survey Report

    NASA Astrophysics Data System (ADS)

    2002-09-01

    The U. S. Environmental Protection Agency (EPA) is developing a Cruise Ship Discharge Assessment Report in response to a petition the agency received in March 2000. The petition requested that EPA assess and where necessary control discharges from cruise ships. Comments received during public hearings, in 2000, resulted in the EPA agreeing to conduct a survey to assess the discharge plumes resulting from cruise ships, operating in ocean waters off the Florida coast and to compare the results to the Alaska dispersion models. This survey report describes the daily activities of August 2001 Cruise Ship Plume Tracking Survey, and provides a synopsis of the observations from the survey. It also provides data that can be used to assess dispersion of cruise ship wastewater discharges, while in transit. A description of the survey methods is provided in Section 2. Survey results are presented in Section 3. Findings and conclusions are discussed in Section 4.

  7. COMPARING AND LINKING PLUMES ACROSS MODELING APPROACHES

    EPA Science Inventory

    River plumes carry many pollutants, including microorganisms, into lakes and the coastal ocean. The physical scales of many stream and river plumes often lie between the scales for mixing zone plume models, such as the EPA Visual Plumes model, and larger-sized grid scales for re...

  8. COMPARING AND LINKING PLUMES ACROSS MODELING APPROACHES

    EPA Science Inventory

    River plumes carry many pollutants, including microorganisms, into lakes and the coastal ocean. The physical scales of many stream and river plumes often lie between the scales for mixing zone plume models, such as the EPA Visual Plumes model, and larger-sized grid scales for re...

  9. The effect of recycled oceanic crust in the thermal evolution of the Galapagos Plume

    NASA Astrophysics Data System (ADS)

    Gazel, E.; Herzberg, C. T.; Vidito, C. A.

    2011-12-01

    Current models suggest that the massive basaltic production responsible for the emplacement of Large Igneous Provinces (LIPS) during the Permian-Paleocene may represent the initial phases (plume heads) of some of the mantle plumes that feed the current ocean island basalts (OIB). In many cases, magmatism associated with the initiation of mantle plumes was so voluminous that produced global environmental impacts. The origin of these intra-plate magmatism is still debated but recent petrological, geochemical and geophysical studies of some of these localities like Samoa, Hawaii, Galapagos, provide evidence that melting is related to a true mantle plume, representing a geochemically heterogeneous, hot-buoyant domain that originates from a boundary layer beneath the upper mantle. Thus, plume-related magmas produced in OIB and LIPS and their connecting plume tracks are windows into the Earth's mantle, providing evidence on mantle temperature, size and composition of heterogeneities, and the deep earth geochemical cycles. Our preliminary petrological modeling suggests that mantle plumes for LIPS with Permian-Paleocene ages were generally hotter and melted more extensively than plumes of more modern oceanic islands. Although a lot of work has been done on LIPS and OIB, no complete record of the evolution of a mantle plume is available to this point, mostly due to the inaccessibility of the submerged sections of almost all plume tracks. Galapagos-related lavas provide a complete record of the evolution of a mantle plume since the plume's initial stages in the Cretaceous. In the case of the Galapagos, our work suggests a decrease from TP(max) of1650 C in the Cretaceous to 1500 C in the present day. Our recent work on the Galapagos Islands and the preliminary work on older Galapagos-related terranes suggest that this secular cooling is directly related with increasing amounts of recycled crust in the plume.

  10. Ozone production efficiency of a ship-plume: ITCT 2K2 case study.

    PubMed

    Kim, Hyun S; Kim, Yong H; Han, Kyung M; Kim, Jhoon; Song, Chul H

    2016-01-01

    Ozone production efficiency (OPE) of ship plume was first evaluated in this study, based on ship-plume photochemical/dynamic model simulations and the ship-plume composition data measured during the ITCT 2K2 (Intercontinental Transport and Chemical Transformation 2002) aircraft campaign. The averaged instantaneous OPEs (OPE(i)‾) estimated via the ship-plume photochemical/dynamic modeling for the ITCT 2K2 ship-plume ranged between 4.61 and 18.92, showing that the values vary with the extent of chemical evolution (or chemical stage) of the ship plume and the stability classes of the marine boundary layer (MBL). Together with OPE(i)‾, the equivalent OPEs (OPE(e)‾) for the entire ITCT 2K2 ship-plume were also estimated. The OPE(e)‾ values varied between 9.73 (for the stable MBL) and 12.73 (for the moderately stable MBL), which agreed well with the OPE(e)‾ of 12.85 estimated based on the ITCT 2K2 ship-plume observations. It was also found that both the model-simulated and observation-based OPE(e)‾ inside the ship-plume were 0.29-0.38 times smaller than the OPE(e)‾ calculated/measured outside the ITCT 2K2 ship-plume. Such low OPEs insides the ship plume were due to the high levels of NO and non-liner ship-plume photochemistry. Possible implications of this ship-plume OPE study in the global chemistry-transport modeling are also discussed. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  11. 3-D thermo-mechanical modeling of plume-induced subduction initiation

    NASA Astrophysics Data System (ADS)

    Baes, M.; Gerya, T.; Sobolev, S. V.

    2016-11-01

    Here, we study the 3-D subduction initiation process induced by the interaction between a hot thermo-chemical mantle plume and oceanic lithosphere using thermo-mechanical viscoplastic finite difference marker-in-cell models. Our numerical modeling results show that self-sustaining subduction is induced by plume-lithosphere interaction when the plume is sufficiently buoyant, the oceanic lithosphere is sufficiently old and the plate is weak enough to allow the buoyant plume to pass through it. Subduction initiation occurs following penetration of the lithosphere by the hot plume and the downward displacement of broken, nearly circular segments of lithosphere (proto-slabs) as a result of partially molten plume rocks overriding the proto-slabs. Our experiments show four different deformation regimes in response to plume-lithosphere interaction: a) self-sustaining subduction initiation, in which subduction becomes self-sustaining; b) frozen subduction initiation, in which subduction stops at shallow depths; c) slab break-off, in which the subducting circular slab breaks off soon after formation; and d) plume underplating, in which the plume does not pass through the lithosphere and instead spreads beneath it (i.e., failed subduction initiation). These regimes depend on several parameters, such as the size, composition, and temperature of the plume, the brittle/plastic strength and age of the oceanic lithosphere, and the presence/absence of lithospheric heterogeneities. The results show that subduction initiates and becomes self-sustaining when the lithosphere is older than 10 Myr and the non-dimensional ratio of the plume buoyancy force and lithospheric strength above the plume is higher than approximately 2. The outcomes of our numerical experiments are applicable for subduction initiation in the modern and Precambrian Earth and for the origin of plume-related corona structures on Venus.

  12. Electrical charging of explosive volcanic plumes (Invited)

    NASA Astrophysics Data System (ADS)

    James, M. R.; Lane, S. J.; Gilbert, J. S.

    2010-12-01

    The lightning that accompanies many silicate-rich volcanic plumes is only one indicator of the electrical charging activity that occurs during explosive eruptions. Perturbations to the atmospheric electric gradient and direct measurements of electrical charge on sedimenting particles also indicate that, even in plumes not associated with lightning, significant electrical charging does occur. For a charging process to produce macro-scale electrification and detectable electric fields, the initial charge generation (representing atomic- or micro-scale separation of charge) must be followed by subsequent charge separation. In common with thunderclouds, the gravitational separation of particles or droplets with different fall velocities is assumed to dominate the charge separation process. However, charge generation is much less understood because the complex and poly-phase nature of plumes, which contain solid particles, liquid drops and gases of various chemical compositions, over wide ranges of temperatures and pressures, offers many possibilities in terms of charging mechanisms. We can consider charge generation processes as either primary (i.e. directly associated with the eruption process and dominantly located at the vent) or secondary (i.e. associated with in-plume and dispersion processes, and dominantly at some distance from the vent). For primary charge generation, both observations and measurements have indicated that high degrees of electrification are strongly correlated with events involving either vigorous water boiling or extensive magma fragmentation, or both. Neglecting boiling, since only a relatively few eruptions involve large amounts of external water, primary charging is dominantly attributed to solid-solid processes resulting from magma fragmentation. The most likely charging mechanism is fractoemission, in which charged atomic particles are released from fresh material surfaces during brittle fracture. During magma fragmentation to generate

  13. Active vibration control of smart composite plates using LQR algorithm

    NASA Astrophysics Data System (ADS)

    Suresh, R.; Venkateshwara Rao, G.

    2003-10-01

    The concept of using the actuators and sensors to form a self controlling and self monitoring smart system in advanced structural design has drawn considerable interest among the research community. The smart system has large number of active, light weight, distributed sensors and actuators either bonded or embedded in the structure for the purpose of vibration suppression, shape and acoustic controls as well as fault detection and mitigation. The present study addresses the issues related to the active vibration control schemes for the smart composite panels, with substrate as the fiber reinforced composite laminate and the piezo ceramic layers as the actuators and sensors, using LQR algorithm. The study involves the structural modelling, controller design, open and closed loop system response analysis. For this purpose, an eight noded isoparametric finite element with seven degrees of freedom, viz., three translations, two section rotations and two potential differences corresponding to the actuators and sensors is developed. The piezo-ceramic actuator and sensor layers are also considered as the load bearing components in the panel. The finite element equations are first transformed into the modal state space form and then are used to obtain the constant controller gains. These are used to obtain the closed loop responses.

  14. Electrical Charging of Volcanic Plumes

    NASA Astrophysics Data System (ADS)

    James, M. R.; Wilson, L.; Lane, S. J.; Gilbert, J. S.; Mather, T. A.; Harrison, R. G.; Martin, R. S.

    2008-06-01

    Many explosive terrestrial volcanic eruptions are accompanied by lightning and other atmospheric electrical phenomena. The plumes produced generate large perturbations in the surface atmospheric electric potential gradient and high charge densities have been measured on falling volcanic ash particles. The complex nature of volcanic plumes (which contain gases, solid particles, and liquid drops) provides several possible charging mechanisms. For plumes rich in solid silicate particles, fractoemission (the ejection of ions and atomic particles during fracture events) is probably the dominant source of charge generation. In other plumes, such as those created when lava enters the sea, different mechanisms, such as boiling, may be important. Further charging mechanisms may also subsequently operate, downwind of the vent. Other solar system bodies also show evidence for volcanism, with activity ongoing on Io. Consequently, volcanic electrification under different planetary scenarios (on Venus, Mars, Io, Moon, Enceladus, Tethys, Dione and Triton) is also discussed.

  15. Electrical Charging of Volcanic Plumes

    NASA Astrophysics Data System (ADS)

    James, M. R.; Wilson, L.; Lane, S. J.; Gilbert, J. S.; Mather, T. A.; Harrison, R. G.; Martin, R. S.

    Many explosive terrestrial volcanic eruptions are accompanied by lightning and other atmospheric electrical phenomena. The plumes produced generate large perturbations in the surface atmospheric electric potential gradient and high charge densities have been measured on falling volcanic ash particles. The complex nature of volcanic plumes (which contain gases, solid particles, and liquid drops) provides several possible charging mechanisms. For plumes rich in solid silicate particles, fractoemission (the ejection of ions and atomic particles during fracture events) is probably the dominant source of charge generation. In other plumes, such as those created when lava enters the sea, different mechanisms, such as boiling, may be important. Further charging mechanisms may also subsequently operate, downwind of the vent. Other solar system bodies also show evidence for volcanism, with activity ongoing on Io. Consequently, volcanic electrification under different planetary scenarios (on Venus, Mars, Io, Moon, Enceladus, Tethys, Dione and Triton) is also discussed.

  16. Collapsing plumes and resurrecting fountains

    NASA Astrophysics Data System (ADS)

    van den Bremer, Ton; Hunt, Gary

    2012-11-01

    We explore the range of behaviour predicted for steady plumes and fountains that undergo an increase or decrease in buoyancy which arise due to phase changes or chemical reactions. We model these changes in the simplest possible way by assuming a quadratic relationship between the density and the temperature of the fluid. We thereby extend the model of Caulfield & Woods (`95) to include the most recent developments in the literature on steady releases of buoyancy emitted vertically from horizontal area sources in unconfined quiescent environments of uniform density based on the plume model of Morton, Taylor & Turner (`56). We provide closed-form solutions and identify four classes of solution: collapsing plumes, resurrecting fountains, plumes with enhanced buoyancy and fountains with enhanced negative buoyancy. We provide criteria for each category of behaviour in terms of the source-value of two non-dimensional quantities: the Richardson number and a temperature parameter.

  17. Composite control for protecting two nonorthogonal qubit states against decoherence

    NASA Astrophysics Data System (ADS)

    Cao, Ya; Tian, Guojing; Zhang, Zhi-Chao; Yang, Ying-Hui; Wen, Qiao-Yan; Gao, Fei

    2017-03-01

    Quantum feedback control (QFBC) and quantum feedforward control (QFFC) are two of the major techniques for protecting two nonorthogonal qubit states against decoherence. In this paper, we propose a quantum composite control scheme for protecting such states, where QFBC and QFFC are combined. Note that the combination is deliberately devised, other than simply one plus one (i.e., the trivial combination). We show the performance of our scheme is better than that of both the previous control schemes and the trivially combined one for most states and noises in the sense that, for given success probability, our scheme can achieve the biggest fidelity, and for given fidelity, our scheme has the biggest success probability. Furthermore, our scheme can be experimentally implemented with current technologies.

  18. Composite disturbance rejection control based on generalized extended state observer.

    PubMed

    Zhang, Yanjun; Zhang, Jun; Wang, Lu; Su, Jianbo

    2016-07-01

    Traditional extended state observer (ESO) design method does not focus on analysis of system reconstruction strategy. The prior information of the controlled system cannot be used for ESO implementation to improve the control accuracy. In this paper, composite disturbance rejection control strategy is proposed based on generalized ESO. First, the disturbance rejection performance of traditional ESO is analyzed to show the essence of the reconstruction strategy. Then, the system is reconstructed based on the equivalent disturbance model. The generalized ESO is proposed based on the reconstructed model, while convergence of the proposed ESO is analyzed along with the outer loop feedback controller. Simulation results on a second order mechanical system show that the proposed generalized ESO can deal with the external disturbance with known model successfully. Experiment of attitude tracking task on an aircraft is also carried out to show the effectiveness of the proposed method. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  19. Space Station flexible dynamics under plume impingement

    NASA Technical Reports Server (NTRS)

    Williams, Trevor

    1993-01-01

    Assembly of the Space Station requires numerous construction flights by the Space Shuttle. A particularly challenging problem is that of control of each intermediate station configuration when the shuttle orbiter is approaching it to deliver the next component. The necessary braking maneuvers cause orbiter thruster plumes to impinge on the station, especially its solar arrays. This in turn causes both overall attitude errors and excitation of flexible-body vibration modes. These plume loads are predicted to lead to CMG saturation during the approach of the orbiter to the SC-5 station configuration, necessitating the use of the station RCS jets for desaturation. They are also expected to lead to significant excitation of solar array vibrations. It is therefore of great practical importance to investigate the effects of plume loads on the flexible dynamics of station configuration SC-5 as accurately as possible. However, this system possesses a great many flexible modes (89 below 5 rad/s), making analysis time-consuming and complicated. Model reduction techniques can be used to overcome this problem, reducing the system model to one which retains only the significant dynamics, i.e. those which are strongly excited by the control inputs or plume disturbance forces and which strongly couple with the measured outputs. The particular technique to be used in this study is the subsystem balancing approach which was previously developed by the present investigator. This method is very efficient computationally. Furthermore, it gives accurate results even for the difficult case where the structure has many closed-spaced natural frequencies, when standard modal truncation can give misleading results. Station configuration SC-5 is a good example of such a structure.

  20. A nitrogen-rich septage-effluent plume in a glacial aquifer, Cape Cod, Massachusetts, February 1990 through December 1992

    USGS Publications Warehouse

    DeSimone, Leslie A.; Barlow, Paul M.; Howes, Brian L.

    1996-01-01

    Physical, chemical, and microbial processes controlled transport of a nitrogen-rich ground-water plume through a glacial aquifer. Lithologic heterogeneity and vertical head gradients influenced plume movement and geometry. Nitrate was the predominant nitrogen form and oxygen was depleted in the ground-water plume. However, denitrification transformed only 2 percent of plume nitrogen because of limited organic-carbon availability. Aerobic respiration, nitrification and cation exchange (unsaturated zone) and ammonium sorption (saturated zone) had larger effects.

  1. Active Piezoelectric Vibration Control of Subscale Composite Fan Blades

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Min, James B.; Kray, Nicholas

    2012-01-01

    As part of the Fundamental Aeronautics program, researchers at NASA Glenn Research Center (GRC) are investigating new technologies supporting the development of lighter, quieter, and more efficient fans for turbomachinery applications. High performance fan blades designed to achieve such goals will be subjected to higher levels of aerodynamic excitations which could lead to more serious and complex vibration problems. Piezoelectric materials have been proposed as a means of decreasing engine blade vibration either through a passive damping scheme, or as part of an active vibration control system. For polymer matrix fiber composite blades, the piezoelectric elements could be embedded within the blade material, protecting the brittle piezoceramic material from the airflow and from debris. To investigate this idea, spin testing was performed on two General Electric Aviation (GE) subscale composite fan blades in the NASA GRC Dynamic Spin Rig Facility. The first bending mode (1B) was targeted for vibration control. Because these subscale blades are very thin, the piezoelectric material was surface-mounted on the blades. Three thin piezoelectric patches were applied to each blade two actuator patches and one small sensor patch. These flexible macro-fiber-composite patches were placed in a location of high resonant strain for the 1B mode. The blades were tested up to 5000 rpm, with patches used as sensors, as excitation for the blade, and as part of open- and closed-loop vibration control. Results show that with a single actuator patch, active vibration control causes the damping ratio to increase from a baseline of 0.3% critical damping to about 1.0% damping at 0 RPM. As the rotor speed approaches 5000 RPM, the actively controlled blade damping ratio decreases to about 0.5% damping. This occurs primarily because of centrifugal blade stiffening, and can be observed by the decrease in the generalized electromechanical coupling with rotor speed.

  2. Active Piezoelectric Vibration Control of Subscale Composite Fan Blades

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Min, James B.; Kray, Nicholas

    2012-01-01

    As part of the Fundamental Aeronautics program, researchers at NASA Glenn Research Center (GRC) are investigating new technologies supporting the development of lighter, quieter, and more efficient fans for turbomachinery applications. High performance fan blades designed to achieve such goals will be subjected to higher levels of aerodynamic excitations which could lead to more serious and complex vibration problems. Piezoelectric materials have been proposed as a means of decreasing engine blade vibration either through a passive damping scheme, or as part of an active vibration control system. For polymer matrix fiber composite blades, the piezoelectric elements could be embedded within the blade material, protecting the brittle piezoceramic material from the airflow and from debris. To investigate this idea, spin testing was performed on two General Electric Aviation (GE) subscale composite fan blades in the NASA GRC Dynamic Spin Rig Facility. The first bending mode (1B) was targeted for vibration control. Because these subscale blades are very thin, the piezoelectric material was surface-mounted on the blades. Three thin piezoelectric patches were applied to each blade two actuator patches and one small sensor patch. These flexible macro-fiber-composite patches were placed in a location of high resonant strain for the 1B mode. The blades were tested up to 5000 rpm, with patches used as sensors, as excitation for the blade, and as part of open- and closed-loop vibration control. Results show that with a single actuator patch, active vibration control causes the damping ratio to increase from a baseline of 0.3% critical damping to about 1.0% damping at 0 RPM. As the rotor speed approaches 5000 RPM, the actively controlled blade damping ratio decreases to about 0.5% damping. This occurs primarily because of centrifugal blade stiffening, and can be observed by the decrease in the generalized electromechanical coupling with rotor speed.

  3. Smoke plumes: Emissions and effects

    Treesearch

    Susan O' Neill; Shawn Urbanski; Scott Goodrick; Sim Larkin

    2017-01-01

    Smoke can manifest itself as a towering plume rising against the clear blue sky-or as a vast swath of thick haze, with fingers that settle into valleys overnight. It comes in many forms and colors, from fluffy and white to thick and black. Smoke plumes can rise high into the atmosphere and travel great distances across oceans and continents. Or smoke can remain close...

  4. Radiation-induced conductivity control in polyaniline blends/composites

    NASA Astrophysics Data System (ADS)

    Güven, Olgun

    2007-08-01

    Polyaniline (PANI) blends with chlorine-containing polymers and copolymers and composites with HCl-releasing compounds were prepared to investigate their radiation response in terms of induced conductivities. Blends of non-conductive PANI with poly(vinyl chloride) (PVC), poly(vinylidene chloride- co-vinyl acetate), [P(VDC- co-VAc)], poly(vinylidene chloride- co-vinyl chloride), [P(VDC- co-VC)] were prepared in the form of as-cast films. A number of blends which are different in composition were exposed to gamma radiation and accelerated electrons to various doses, and the effects of irradiation type and composition of polymers on the conductivity of films were investigated by using conductivity measurements and UV-vis and FT-IR spectroscopy. The results clearly showed that ionizing radiation is an effective tool to induce and control conductivity in the blends of PANI-base with chlorine-carrying polymers as well as its composites prepared from HCl-releasing compounds such as chloral hydrate. The main mechanism behind this radiation-induced conductivity is in situ doping of PANI-base with HCl released from partner polymers and low molecular weight compounds by the effect of radiation.

  5. Electrically controllable liquid crystal elastomer-graphite composite artifical muscles

    NASA Astrophysics Data System (ADS)

    Finkelmann, Heino; Shahinpoor, Mohsen

    2002-07-01

    Reported is the fabrication method and experimental results pertaining to a new class of liquid crystal elastometer- graphite (LCE-G) composites as electrically controllable biomimetic artificial muscles. These films (10mmx20mmx0.32mm) of monodomain nematic liquid side chain crystal elastomers graphite (LSCE-G) composites were transversely pressed between uniform layers of fine graphite powder of 2 microns average diameter under a stress of 100 kPa. The resulting composite expanded to (12 mmx24mmx0.33mm) and had about 53% by volume embedded graphite powder. The composite became a conductor and had an effective resistivity of about 2 ohms/square on its surface and about 1 ohmsquare across its thickness. Upon applying DC voltage of 0.5 to 5 volts to the samples for 4 seconds, under a stress if abiyt 10 kPa, the sample contracted quickly in about a second to about 18 mm lengthwise with an average linear strain of about 25%. The samples generally had negligible contractions in the thickness and transverse direction. The cooling was also quick and it took the sample about 4.4 seconds to revert back to its initial length.

  6. Active vibration control of basic structures using macro fiber composites

    NASA Astrophysics Data System (ADS)

    Yi, Guo; Wang, Jinming; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2011-03-01

    In the modern naval battle, as the anti-detection technique developing fleetly, enhancing submarine's hidden ability is becoming more and more important. However, in view of the worse control effect at low-frequency and weak adjustability to external influence, conventional passive vibration control can't satisfy the modern naval rigorous demands. Fortunately, active vibration control technology not only monitors the structure's real-time vibration, but also has more remarkable control effects and superior suitability. At the present time, it has a primary application in the vibration damping of ship engineering. In addition, due to functional materials rapidly developing, with the coming of piezoelectric composite materials, the advanced active control techniques have more applicability, lager damp amplitude and wider applied field, which basing on the piezoelectric-effect and inverse- piezoelectric-effect of piezoelectric materials. Especially, in the end of nineties, NASA had successfully manufactured the excellent macro fiber composite (MFC), which assembles actuating and sensing abilities. Comparing with the conventional piezoelectric ceramic materials, it provides the required durability, excellent flexibility, higher electromechanical coupling factors and stronger longitudinal actuating force by using interdigital electrodes. On the basis of the application of cantilever beam' active vibration control by using MFC actuators, this paper started with the mechanical characteristics of its actuating and sensing equations, and then investigated its piezoelectric feedback scale factor when equipped on the honeycomb aluminous panel. Finally, in order to validate the theoretical analysis method, the vibration control experiment of cantilever beam and honeycomb aluminous panel are built and tested with different activating force. The experimental results verify that MFC used in submarine structures' active vibration control are feasible and effective.

  7. Piezoceramics/CFRP composites for active vibration control and shape control of aerospace structures

    NASA Astrophysics Data System (ADS)

    Herold-Schmidt, Ursula; Schaefer, Wolfgang; Zaglauer, Helmut W.

    1996-04-01

    The application of piezoceramics/CFRP composites for active control of aerospace structures was investigated in a laboratory scale. Exemplary results are presented for active vibration damping of CFRP plates with integrated PZT sensors and actuators as well as for shape control of an antenna reflector shell using piezoelements.

  8. Geometry adaptive control of a composite reflector using PZT actuator

    NASA Astrophysics Data System (ADS)

    Lan, Lan; Jiang, Shuidong; Zhou, Yang; Fang, Houfei; Tan, Shujun; Wu, Zhigang

    2015-04-01

    Maintaining geometrical high precision for a graphite fiber reinforced composite (GFRC) reflector is a challenging task. Although great efforts have been placed to improve the fabrication precision, geometry adaptive control for a reflector is becoming more and more necessary. This paper studied geometry adaptive control for a GFRC reflector with piezoelectric ceramic transducer (PZT) actuators assembled on the ribs. In order to model the piezoelectric effect in finite element analysis (FEA), a thermal analogy was used in which the temperature was applied to simulate the actuation voltage, and the piezoelectric constant was mimicked by a Coefficient of Thermal Expansion (CTE). PZT actuator's equivalent model was validated by an experiment. The deformations of a triangular GFRC specimen with three PZT actuators were also measured experimentally and compared with that of simulation. This study developed a multidisciplinary analytical model, which includes the composite structure, thermal, thermal deformation and control system, to perform an optimization analysis and design for the adaptive GFRC reflector by considering the free vibration, gravity deformation and geometry controllability.

  9. Adaptive aeroelastic composite wings - Control and optimization issues

    NASA Technical Reports Server (NTRS)

    Weisshaar, Terrence A.; Ehlers, Steven M.

    1992-01-01

    High-performance aircraft are adaptive machines composed of internal structural skeletons to which are attached control surfaces operated by hydraulic muscles to allow them to maneuver. The flight crew, avionic sensors and systems function as the brain and nervous system to adapt the machine to changing flight conditions, such as take-off, cruise and landing. The development of new materials that can expand or contract on command or change stiffness on demand will blur the now distinct boundaries between the structure, actuators and the control system. This paper discusses the use of imbedded active piezoelectric materials to change the aeroelastic stiffness of a lifting surface to allow this surface to control the aircraft. Expressions are developed for the piezoelectric material effectiveness when these active materials are combined with advanced composite structural materials for a swept, high-aspect-ratio wing. The interaction between advanced composite material properties and piezoelectric electromechanical properties is examined. The importance of choosing the proper active control laws is also illustrated.

  10. Adaptive aeroelastic composite wings - Control and optimization issues

    NASA Technical Reports Server (NTRS)

    Weisshaar, Terrence A.; Ehlers, Steven M.

    1992-01-01

    High-performance aircraft are adaptive machines composed of internal structural skeletons to which are attached control surfaces operated by hydraulic muscles to allow them to maneuver. The flight crew, avionic sensors and systems function as the brain and nervous system to adapt the machine to changing flight conditions, such as take-off, cruise and landing. The development of new materials that can expand or contract on command or change stiffness on demand will blur the now distinct boundaries between the structure, actuators and the control system. This paper discusses the use of imbedded active piezoelectric materials to change the aeroelastic stiffness of a lifting surface to allow this surface to control the aircraft. Expressions are developed for the piezoelectric material effectiveness when these active materials are combined with advanced composite structural materials for a swept, high-aspect-ratio wing. The interaction between advanced composite material properties and piezoelectric electromechanical properties is examined. The importance of choosing the proper active control laws is also illustrated.

  11. Simulation of Deepwater Horizon oil plume reveals substrate specialization within a complex community of hydrocarbon degraders

    PubMed Central

    Hu, Ping; Probst, Alexander J.; Wang, Jian; Sieber, Christian M. K.; Tom, Lauren M.; Gardinali, Piero R.; Banfield, Jillian F.; Atlas, Ronald M.

    2017-01-01

    The Deepwater Horizon (DWH) accident released an estimated 4.1 million barrels of oil and 1010 mol of natural gas into the Gulf of Mexico, forming deep-sea plumes of dispersed oil droplets and dissolved gases that were largely degraded by bacteria. During the course of this 3-mo disaster a series of different bacterial taxa were enriched in succession within deep plumes, but the metabolic capabilities of the different populations that controlled degradation rates of crude oil components are poorly understood. We experimentally reproduced dispersed plumes of fine oil droplets in Gulf of Mexico seawater and successfully replicated the enrichment and succession of the principal oil-degrading bacteria observed during the DWH event. We recovered near-complete genomes, whose phylogeny matched those of the principal biodegrading taxa observed in the field, including the DWH Oceanospirillales (now identified as a Bermanella species), multiple species of Colwellia, Cycloclasticus, and other members of Gammaproteobacteria, Flavobacteria, and Rhodobacteria. Metabolic pathway analysis, combined with hydrocarbon compositional analysis and species abundance data, revealed substrate specialization that explained the successional pattern of oil-degrading bacteria. The fastest-growing bacteria used short-chain alkanes. The analyses also uncovered potential cooperative and competitive relationships, even among close relatives. We conclude that patterns of microbial succession following deep ocean hydrocarbon blowouts are predictable and primarily driven by the availability of liquid petroleum hydrocarbons rather than natural gases. PMID:28652349

  12. Simulation of Deepwater Horizon oil plume reveals substrate specialization within a complex community of hydrocarbon degraders.

    PubMed

    Hu, Ping; Dubinsky, Eric A; Probst, Alexander J; Wang, Jian; Sieber, Christian M K; Tom, Lauren M; Gardinali, Piero R; Banfield, Jillian F; Atlas, Ronald M; Andersen, Gary L

    2017-07-11

    The Deepwater Horizon (DWH) accident released an estimated 4.1 million barrels of oil and 10(10) mol of natural gas into the Gulf of Mexico, forming deep-sea plumes of dispersed oil droplets and dissolved gases that were largely degraded by bacteria. During the course of this 3-mo disaster a series of different bacterial taxa were enriched in succession within deep plumes, but the metabolic capabilities of the different populations that controlled degradation rates of crude oil components are poorly understood. We experimentally reproduced dispersed plumes of fine oil droplets in Gulf of Mexico seawater and successfully replicated the enrichment and succession of the principal oil-degrading bacteria observed during the DWH event. We recovered near-complete genomes, whose phylogeny matched those of the principal biodegrading taxa observed in the field, including the DWH Oceanospirillales (now identified as a Bermanella species), multiple species of Colwellia, Cycloclasticus, and other members of Gammaproteobacteria, Flavobacteria, and Rhodobacteria. Metabolic pathway analysis, combined with hydrocarbon compositional analysis and species abundance data, revealed substrate specialization that explained the successional pattern of oil-degrading bacteria. The fastest-growing bacteria used short-chain alkanes. The analyses also uncovered potential cooperative and competitive relationships, even among close relatives. We conclude that patterns of microbial succession following deep ocean hydrocarbon blowouts are predictable and primarily driven by the availability of liquid petroleum hydrocarbons rather than natural gases.

  13. Model based control of polymer composite manufacturing processes

    NASA Astrophysics Data System (ADS)

    Potaraju, Sairam

    2000-10-01

    The objective of this research is to develop tools that help process engineers design, analyze and control polymeric composite manufacturing processes to achieve higher productivity and cost reduction. Current techniques for process design and control of composite manufacturing suffer from the paucity of good process models that can accurately represent these non-linear systems. Existing models developed by researchers in the past are designed to be process and operation specific, hence generating new simulation models is time consuming and requires significant effort. To address this issue, an Object Oriented Design (OOD) approach is used to develop a component-based model building framework. Process models for two commonly used industrial processes (Injected Pultrusion and Autoclave Curing) are developed using this framework to demonstrate the flexibility. Steady state and dynamic validation of this simulator is performed using a bench scale injected pultrusion process. This simulator could not be implemented online for control due to computational constraints. Models that are fast enough for online implementation, with nearly the same degree of accuracy are developed using a two-tier scheme. First, lower dimensional models that captures essential resin flow, heat transfer and cure kinetics important from a process monitoring and control standpoint are formulated. The second step is to reduce these low dimensional models to Reduced Order Models (ROM) suited for online model based estimation, control and optimization. Model reduction is carried out using Proper Orthogonal Decomposition (POD) technique in conjunction with a Galerkin formulation procedure. Subsequently, a nonlinear model-based estimation and inferential control scheme based on the ROM is implemented. In particular, this research work contributes in the following general areas: (1) Design and implementation of versatile frameworks for modeling and simulation of manufacturing processes using object

  14. Dynamics and structure of thermo-chemical mantle plumes: Are numerical models consistent with observations?

    NASA Astrophysics Data System (ADS)

    Dannberg, J.; Sobolev, S. V.

    2013-12-01

    According to widely accepted models, plumes ascend from the core-mantle boundary and cause massive melting when they reach the base of the lithosphere. Most of these models consider plumes as purely thermal and predict flattening of the plume head to a disk-like structure, thin plume tails with a radius on the scale of 100 km and kilometer-scale topographic uplift before and during the eruption of flood basalts. However, several paleogeographic and paleotectonic field studies indicate significantly smaller surface uplift during the development of many LIPs, and seismic imaging reveals thicker plume tails as well as a more complex plume structure in the upper mantle including broad low-velocity anomalies up to 400 km depth and elongated low-velocity fingers. Moreover, geochemical data indicate a plume composition that differs from that of the average mantle and recent geodynamic models of plumes in the upper mantle show that plumes containing a large fraction of eclogite and therefore having very low buoyancy can explain the observations much better. Nevertheless, the question remains how such a low-buoyancy plume can rise through the whole mantle and how this ascent affects its dynamics. We perform numerical experiments in 2D axisymmetric geometry to systematically study the dynamics of the plume ascent as well as 2D and 3D models with prescribed velocity at the upper boundary to investigate the interaction between plume- and plate-driven flow. For that purpose, we use modified versions of the finite-element codes Citcom and Aspect. Our models employ complex material properties incorporating phase transitions with the accompanying density changes, Clapeyron slopes and latent heat effects for the peridotite and eclogite phase, mantle compressibility and a highly temperature- and depth-dependent viscosity. We study under which conditions (excess temperature, plume volume and eclogite content) thermo-chemical plumes can ascend through the whole mantle and what

  15. On fractional order composite model reference adaptive control

    NASA Astrophysics Data System (ADS)

    Wei, Yiheng; Sun, Zhenyuan; Hu, Yangsheng; Wang, Yong

    2016-08-01

    This paper presents a novel composite model reference adaptive control approach for a class of fractional order linear systems with unknown constant parameters. The method is extended from the model reference adaptive control. The parameter estimation error of our method depends on both the tracking error and the prediction error, whereas the existing method only depends on the tracking error, which makes our method has better transient performance in the sense of generating smooth system output. By the aid of the continuous frequency distributed model, stability of the proposed approach is established in the Lyapunov sense. Furthermore, the convergence property of the model parameters estimation is presented, on the premise that the closed-loop control system is stable. Finally, numerical simulation examples are given to demonstrate the effectiveness of the proposed schemes.

  16. Plume temperature emitted from metered dose inhalers.

    PubMed

    Brambilla, G; Church, T; Lewis, D; Meakin, B

    2011-02-28

    The temperature of the drug cloud emitted from a pressurised metered dose inhaler (pMDI) may result in patient discomfort and inconsistent or non-existent dose delivery to the lungs. The effects of variations in formulation (drug, propellant, co-solvent content) and device hardware (metering volume, actuator orifice diameter, add-on devices) upon the temperature of pMDI plumes, expressed as replicate mean minimum values (MMPT), collected into a pharmacopoeial dose unit sampling apparatus (DUSA), have been investigated. Ten commercially available and two development products, including chlorofluorocarbon (CFC) suspensions and hydrofluoroalkane (HFA) solutions or suspensions, were examined together with a number of drug products in late stage development and a variety of HFA 134a placebo pMDIs. Plume temperatures were observed to be lowest in the proximity of the product's actuator mouthpiece where rapid flashing and evaporation of the formulation's propellant and volatile excipients cause cooling. The ability to control plume temperature by judicious choice of formulation co-solvent content, metering volume and the actuator orifice diameter is identified. An ethanol based HFA 134a formulation delivered through a fine orifice is inherently warmer than one with 100% HFA 134a vehicle delivered through a coarse actuator orifice. Of the 10 commercial products evaluated, MMPTs ranged from -54 to +4°C and followed the formulation class rank order, HFA suspensionsplume temperature to that of the ambient surroundings by use of an add-on or integrated spacer device.

  17. Water vapour jets inside the plume of gas leaving Enceladus.

    PubMed

    Hansen, C J; Esposito, L W; Stewart, A I F; Meinke, B; Wallis, B; Colwell, J E; Hendrix, A R; Larsen, K; Pryor, W; Tian, F

    2008-11-27

    A plume of water vapour escapes from fissures crossing the south polar region of the Saturnian moon Enceladus. Tidal deformation of a thin surface crust above an internal ocean could result in tensile and compressive stresses that would affect the width of the fissures; therefore, the quantity of water vapour released at different locations in Enceladus' eccentric orbit is a crucial measurement of tidal control of venting. Here we report observations of an occultation of a star by the plume on 24 October 2007 that revealed four high-density gas jets superimposed on the background plume. The gas jet positions coincide with those of dust jets reported elsewhere inside the plume. The maximum water column density in the plume is about twice the density reported earlier. The density ratio does not agree with predictions-we should have seen less water than was observed in 2005. The ratio of the jets' bulk vertical velocities to their thermal velocities is 1.5 +/- 0.2, which supports the hypothesis that the source of the plume is liquid water, with gas accelerated to supersonic velocity in nozzle-like channels.

  18. Plumes, orogenesis, and supercontinental fragmentation

    NASA Astrophysics Data System (ADS)

    Dalziel, I. W. D.; Lawver, L. A.; Murphy, J. B.

    2000-05-01

    A time-space relationship between large igneous provinces (LIPS), present day hot spots, and the fragmentation of Pangea has been documented over several decades, but the cause of fragmentation has remained elusive. LIPS are regarded either as the result of impingement of a mantle plume on the base of the lithosphere, or as the initial products of adiabatic decompression melting of anomalously hot mantle. Do LIPS therefore constitute evidence of an active role for plumes from the deep mantle in supercontinental fragmentation, or are they merely the first indications of a large-scale but near-surface tectonic process? Two long recognized and enigmatic orogenic events may offer a solution to this geologically important 'chicken or egg' conundrum. The reconstructed early Mesozoic Gondwanide fold belt of South America, southern Africa, and Antarctica, could have resulted from 'plume-modified orogeny', flattening of a downgoing lithospheric slab due to the buoyancy of a plume rising beneath a continental margin subduction zone. If so, the ˜180 Ma Karroo and Ferrar LIPS associated with the opening of the ocean basin between East and West Gondwanaland at ˜165 Ma resulted from impingement of this plume and are unrelated to the thermal insulation of the shallow mantle beneath Gondwanaland. It would then follow that the plume itself played an active, possibly critical, role in the initial breakup of the supercontinent. The Late Paleozoic 'Ancestral Rockies' deformation in the southwestern United States could be yet another example of orogeny driven by a plume that initiated the break-up of Pangea approximately 15 Myr earlier in the Central Atlantic region.

  19. Composition Based Strategies for Controlling Radii in Lipid Nanotubes

    PubMed Central

    Kurczy, Michael E.; Mellander, Lisa J.; Najafinobar, Neda; Cans, Ann-Sofie

    2014-01-01

    Nature routinely carries out small-scale chemistry within lipid bound cells and organelles. Liposome–lipid nanotube networks are being developed by many researchers in attempt to imitate these membrane enclosed environments, with the goal to perform small-scale chemical studies. These systems are well characterized in terms of the diameter of the giant unilamellar vesicles they are constructed from and the length of the nanotubes connecting them. Here we evaluate two methods based on intrinsic curvature for adjusting the diameter of the nanotube, an aspect of the network that has not previously been controllable. This was done by altering the lipid composition of the network membrane with two different approaches. In the first, the composition of the membrane was altered via lipid incubation of exogenous lipids; either with the addition of the low intrinsic curvature lipid soy phosphatidylcholine (soy-PC) or the high intrinsic curvature lipid soy phosphatidylethanolamine (soy-PE). In the second approach, exogenous lipids were added to the total lipid composition during liposome formation. Here we show that for both lipid augmentation methods, we observed a decrease in nanotube diameter following soy-PE additions but no significant change in size following the addition of soy-PC. Our results demonstrate that the effect of soy-PE on nanotube diameter is independent of the method of addition and suggests that high curvature soy-PE molecules facilitate tube membrane curvature. PMID:24392077

  20. Three-dimensional laboratory modeling of the Tonga trench and Samoan plume interaction

    NASA Astrophysics Data System (ADS)

    Druken, K. A.; Kincaid, C. R.; Pockalny, R. A.; Griffiths, R. W.; Hart, S. R.

    2009-12-01

    Plume processes occurring near ridge centers (e.g. Iceland) or mid-plate (e.g. Hawaii) have been well studied; however, the behavior of a plume near a subducting plate is still poorly understood and may in fact differ from the typical expected plume surfacing patterns. We investigate how three-dimensional subduction-driven flow relates to the deformation and dispersal of nearby upwelling plume material and the associated geochemical spatial patterns, with site-specific comparisons to the Tonga trench and Samoan plume system. Eighteen plume-trench laboratory experiments were conducted with varied combinations of subduction motions (down-dip, trench rollback, slab steepening and back-arc extension) and plume parameters (position and temperature.) A phenolic plate and glucose syrup, with a temperature dependent viscosity, are used to model the slab and upper mantle, respectively. Hydraulic pistons control longitudinal, translational and steepening motions of the slab as a simplified kinematic approach to mimic dynamic experiments. Results show that the subduction-induced flow dominates the upwelling strength of the plume, causing a significant portion of the plume head to subduct before reaching the melt zone. The remaining material is entrained around the slab edge into the mantle wedge by the trench rollback-induced flow. The proportion of subducted verses entrained material is predominantly dependent on plume location (relative to the trench) and thermal strength, with additional effects from back-arc extension and plate steepening.

  1. Energetics and heat budget of the earth's mantle convection constrained by plume and slab dynamics

    NASA Astrophysics Data System (ADS)

    Leng, Wei

    Understanding the heat budget and energetics of the Earth's mantle convection is important for constraining the thermal evolution history and chemical composition of the Earth's core and mantle. Mantle plumes and subducted slabs are two most important agents for energy transfer in the Earth's mantle convection. With numerical modeling and theoretical analysis, here we show that surface observations of plumes and slabs can be used to constrain the internal heating ratio of the mantle, the core-mantle boundary (CMB) heat flux and the viscous dissipation in the plate bending zones. We also show that including more realistic physics may significantly affect the surface manifestation of the conventional mantle plume model. Our main conclusions are summarized as below. First, mantle plumes account for 80%-90% of the CMB heat flux. Due to the steeper adiabatic gradient of plumes compared with ambient mantle, plume heat flux and plume excess temperature decrease approximately by a factor of two during plumes' ascent. In order to reproduce surface plume-related observations, ˜70% internal heating ratio of the Earth's mantle, i.e. ˜11 TW of CMB heat flux, is required. Second, the total viscous dissipation and the total adiabatic heating balance out each other at any instant in time for compressible mantle convection. The viscous dissipation in the plate bending zones only account for <10% of the total viscous dissipation in the Earth's mantle, thus plays a minor role in Earth's thermal evolution history. Third, instead of causing surface uplift as suggested by convectional plume models, a plume head temporarily ponding below the 660-km phase boundary may cause significant surface subsidence over an extended time period before it reaches surface and generates flood basalt eruptions. Therefore, the observed surface subsidence history in many flood basalt provinces may be used as diagnostics for identifying plume-induced flood basalt events.

  2. Expression patterns of elemental cycling genes in the Amazon River Plume.

    PubMed

    Satinsky, Brandon M; Smith, Christa B; Sharma, Shalabh; Landa, Marine; Medeiros, Patricia M; Coles, Victoria J; Yager, Patricia L; Crump, Byron C; Moran, Mary Ann

    2017-04-07

    Metatranscriptomics and metagenomics data sets benchmarked with internal standards were used to characterize the expression patterns for biogeochemically relevant bacterial and archaeal genes mediating carbon, nitrogen, phosphorus and sulfur uptake and metabolism through the salinity gradient of the Amazon River Plume. The genes were identified in 48 metatranscriptomic and metagenomic data sets summing to >500 million quality-controlled reads from six locations in the plume ecosystem. The ratio of transcripts per gene copy (a direct measure of expression made possible by internal standard additions) showed that the free-living bacteria and archaea exhibited only small changes in the expression levels of biogeochemically relevant genes through the salinity and nutrient zones of the plume. In contrast, the expression levels of genes in particle-associated cells varied over orders of magnitude among the stations, with the largest differences measured for genes mediating aspects of nitrogen cycling (nifH, amtB and amoA) and phosphorus acquisition (pstC, phoX and phoU). Taxa varied in their baseline gene expression levels and extent of regulation, and most of the spatial variation in the expression level could be attributed to changes in gene regulation after removing the effect of shifting taxonomic composition. We hypothesize that changes in microbial element cycling along the Amazon River Plume are largely driven by shifting activities of particle-associated cells, with most activities peaking in the mesohaline regions where N2 fixation rates are elevated.The ISME Journal advance online publication, 7 April 2017; doi:10.1038/ismej.2017.46.

  3. The Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFC Focused on Hanford’s 300 Area Uranium Plume Quality Assurance Project Plan

    SciTech Connect

    Fix, N. J.

    2008-01-31

    The purpose of the project is to conduct research at an Integrated Field-Scale Research Challenge Site in the Hanford Site 300 Area, CERCLA OU 300-FF-5 (Figure 1), to investigate multi-scale mass transfer processes associated with a subsurface uranium plume impacting both the vadose zone and groundwater. The project will investigate a series of science questions posed for research related to the effect of spatial heterogeneities, the importance of scale, coupled interactions between biogeochemical, hydrologic, and mass transfer processes, and measurements/approaches needed to characterize a mass-transfer dominated system. The research will be conducted by evaluating three (3) different hypotheses focused on multi-scale mass transfer processes in the vadose zone and groundwater, their influence on field-scale U(VI) biogeochemistry and transport, and their implications to natural systems and remediation. The project also includes goals to 1) provide relevant materials and field experimental opportunities for other ERSD researchers and 2) generate a lasting, accessible, and high-quality field experimental database that can be used by the scientific community for testing and validation of new conceptual and numerical models of subsurface reactive transport.

  4. Magmatic plumbing system from lower mantle of Hainan plume

    NASA Astrophysics Data System (ADS)

    Xia, Shaohong; Sun, Jinlong; Xu, Huilong; Huang, Haibo; Cao, Jinghe

    2017-04-01

    Intraplate volcanism during Late Cenozoic in the Leiqiong area of southernmost South China, with basaltic lava flows covering a total of more than 7000 km2, has been attributed to an underlying Hainan plume. However, detailed features of Hainan plume, such as morphology of magmatic conduits, depth of magmatic pool in the upper mantle and pattern of mantle upwelling, are still enigmatic. Here we present seismic tomographic images of the upper 1100 km of the mantle beneath the southern South China. Our results show a mushroom-like continuous low-velocity anomaly characterized by a columnar tail with diameter of about 200-300 km that tilts downward to lower mantle beneath north of Hainan hotspot and a head that spreads laterally near the mantle transition zone, indicating a magmatic pool in the upper mantle. Further upward, this head is decomposed into small patches, but when encountering the base of the lithosphere, a pancake-like anomaly is shaped again to feed the Hainan volcanism. Our results challenge the classical model of a fixed thermal plume that rises vertically to the surface, and propose the new layering-style pattern of magmatic upwelling of Hainan plume. This work indicates the spatial complexities and differences of global mantle plumes probably due to heterogeneous compositions and changefully thermochemical structures of deep mantle.

  5. Stationary Plasma Thruster Plume Characteristics

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Manzella, David H.

    1994-01-01

    Stationary Plasma Thrusters (SPT's) are being investigated for application to a variety of near-term missions. This paper presents the results of a preliminary study of the thruster plume characteristics which are needed to assess spacecraft integration requirements. Langmuir probes, planar probes, Faraday cups, and a retarding potential analyzer were used to measure plume properties. For the design operating voltage of 300 V the centerline electron density was found to decrease from approximately 1.8 x 10 exp 17 cubic meters at a distance of 0.3 m to 1.8 X 10 exp 14 cubic meters at a distance of 4 m from the thruster. The electron temperature over the same region was between 1.7 and 3.5 eV. Ion current density measurements showed that the plume was sharply peaked, dropping by a factor of 2.6 within 22 degrees of centerline. The ion energy 4 m from the thruster and 15 degrees off-centerline was approximately 270 V. The thruster cathode flow rate and facility pressure were found to strongly affect the plume properties. In addition to the plume measurements, the data from the various probe types were used to assess the impact of probe design criteria

  6. Bromine oxidation in volcanic plumes

    NASA Astrophysics Data System (ADS)

    Bobrowski, N.; Vogel, L.; Kern, C.; Giuffrida, G. B.; Delgado-Granados, H.; Platt, U.

    2009-04-01

    Volcanoes are very strong sources of hydrogen, carbon, sulphur and halogen compounds, as well as of particles. Some gases only behave as passive tracers; others interact and affect the formation, growth or chemical characteristics of aerosol particles in a complex system. Recent measurements of halogen radicals in volcanic plumes showed that volcanic plumes are chemically very active. Kinetic considerations (Oppenheimer et al., 2006) and detailed calculations with an atmospheric chemistry model (Bobrowski et al., 2007) explain the halogen chemistry mainly with photochemical reactions involving both, the gas and particle phase. They reproduce the measured gas-phase concentrations quite well. However, temporal evolution of BrO in the early plume is not well described in the models. The understanding of chemical kinetics of BrO formation is still not complete. Recent measurement results (Vogel et al., 2008) do not fit with initial model calculation. The new data lead to the suggestion that the BrO formation could be much faster during the first few minutes after emission than initially suggested. Old and recent data sets will be confronted, compared and possible causes of their differences discussed. The measurements considered were taken at Mt. Etna (Italy), Villarica (Chile), and Popocatépetl (Mexico) volcanoes. Additionally, at Mt Etna the emission consists of up to four individual plumes from four summit craters. The differences between the individual plumes have been investigated during the last years and will be presented.

  7. Fluid dynamics of active heterogeneities in a mantle plume conduit

    NASA Astrophysics Data System (ADS)

    Farnetani, C. G.; Limare, A.; Hofmann, A. W.

    2015-12-01

    Laboratory experiments and numerical simulations indicate that the flow of a purely thermal plume preserves the azimuthal zonation of the source region, thus providing a framework to attribute a deep origin to the isotopic zonation of Hawaiian lavas. However, previous studies were limited to passive heterogeneities not affecting the flow. We go beyond this simplification by considering active heterogeneities which are compositionally denser, or more viscous, and we address the following questions: (1) How do active heterogeneities modify the axially symmetric velocity field of the plume conduit? (2) Under which conditions is the azimuthal zonation of the source region no longer preserved in the plume stem? (3) How do active heterogeneities deform during upwelling and what is their shape once at sublithospheric depths? We conducted both laboratory experiments, using a Particle Image Velocimetry (PIV) to calculate the velocity field, and high resolution three-dimensional simulations where millions of tracers keep track of the heterogeneous fluid. For compositionally denser heterogeneities we cover a range of buoyancy ratios 0plume axis. We find that by increasing λ, the shape of the heterogeneity changes from filament-like to blob-like characterized by internal rotation and little stretching. By increasing B the heterogeneity tends to spread at the base of the plume stem and to rise as a tendril close to the axis, so that the initial zonation may be poorly preserved. We also find that the plume velocity field can be profoundly modified by active heterogeneities, and we explore the relation between strain rates and the evolving shape of the upwelling heterogeneity.

  8. Multilayer electromechanical composites with controlled piezelectric coefficient distribution

    NASA Astrophysics Data System (ADS)

    Vartuli, James S.; Milius, David L.; Li, Xiaoping; Shih, Wan Y.; Shih, Wei-Heng; Prud'homme, Robert K.; Aksay, Ilhan A.

    1997-02-01

    We have fabricated multilayer electromechanical composites with controlled piezoelectric coefficient distributions using tape casting. Tapes of doped lead zirconate titanate were cut and stacked in accordance with their characteristic electromechanical coupling values and modulus of elasticity. This technique is an extremely versatile method to fabricate displacement actuators to fabricate monolithic ceramic parts with controlled material property gradients. To obtain a quantifiable method to optimize this type of transducer, we have devised a processing model. Given the functional distribution of the electromechanical coupling coefficient, d31, and the functional distribution of elastic modulus through the thickness of the transducer, the analysis predicts the displacement as a function of loading. The tape casting method coupled with the model provides an actuator that maximizes displacement and generated force for the given material properties.

  9. 1D nanocrystals with precisely controlled dimensions, compositions, and architectures.

    PubMed

    Pang, Xinchang; He, Yanjie; Jung, Jaehan; Lin, Zhiqun

    2016-09-16

    The ability to synthesize a diverse spectrum of one-dimensional (1D) nanocrystals presents an enticing prospect for exploring nanoscale size- and shape-dependent properties. Here we report a general strategy to craft a variety of plain nanorods, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors. These cylindrical unimolecular nanoreactors enable a high degree of control over the size, shape, architecture, surface chemistry, and properties of 1D nanocrystals. We demonstrate the synthesis of metallic, ferroelectric, upconversion, semiconducting, and thermoelectric 1D nanocrystals, among others, as well as combinations thereof.

  10. Active vibration control based on piezoelectric smart composite

    NASA Astrophysics Data System (ADS)

    Gao, Le; Lu, Qingqing; Fei, Fan; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2013-12-01

    An aircraft’s vertical fin may experience dramatic buffet loads in high angle of attack flight conditions, and these buffet loads would cause huge vibration and dynamic stress on the vertical fin structure. To reduce the dynamic vibration of the vertical fin structure, macro fiber composite (MFC) actuators were used in this paper. The drive moment equations and sensing voltage equations of the MFC actuators were developed. Finite element analysis models based on three kinds of models of simplified vertical fin structures with surface-bonded MFC actuators were established in ABAQUS. The equivalent damping ratio of the structure was employed in finite element analysis, in order to measure the effectiveness of vibration control. Further, an open-loop test for the active vibration control system of the vertical fin with MFC actuators was designed and developed. The experimental results validated the effectiveness of the MFC actuators as well as the developed methodology.

  11. Expert model process control of composite materials in a press

    NASA Astrophysics Data System (ADS)

    Saliba, Tony E.; Quinter, Suzanne R.; Abrams, Frances L.

    An expert model for the control of the press processing of thermoset composite materials has been developed. The knowledge base written using the PC PLUS expert system shell was interfaced with models written in FORTRAN. The expert model, which is running on a single computer with a single processor, takes advantage of the symbol-crunching capability of LISP and the number crunching capability of FORTRAN. The Expert Model control system is a qualitative-quantitative process automation (QQPA) system since it includes both quantitative model-based and qualitative rule-based expert system operations. Various physical and mechanical properties were measured from panels processed using the two cycles. Using QQPA, processing time has been reduced significantly without altering product quality.

  12. Controls over the strontium isotope composition of river water

    SciTech Connect

    Palmer, M.R. ); Edmond, J.M. )

    1992-05-01

    Strontium concentrations and isotope ratios have been measured in river and ground waters from the Granges, Orinoco, and Amazon river basins. When compared with major element concentrations, the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments: (1) typical drainage basins containing limestones, evaporites, shales, and alumino-silicate metamorphic and igneous rocks; (2) shield terrains containing no chemical or biogenic sediments; and (3) the flood plains that constitute the largest areas of many large rivers. The strontium concentration and isotope compositions of river waters are largely defined by mixing of strontium derived from limestones and evaporites with strontium derived from silicate rocks. The strontium isotope composition of the limestone end member generally lies within the Phanerozoic seawater range, which buffers the [sup 87]Sr/[sup 86]Sr ratios of major rivers. A major exception is provided by the rivers draining the Himalayas, where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic strontium derived from coexisting silicate rocks. The strontium isotope systematics of rivers draining shield areas are controlled by the intense, transport-limited, nature of the weathering reactions, and thereby limits variations in the strontium flux from these terrains. Flood plains are only a minor source of dissolved strontium to river waters, and precipitation of soil salts in some flood plains can reduce the riverine flux of dissolved strontium to the oceans.

  13. Insights into the formation and dynamics of coignimbrite plumes from one-dimensional models

    NASA Astrophysics Data System (ADS)

    Engwell, S. L.; de'Michieli Vitturi, M.; Esposti Ongaro, T.; Neri, A.

    2016-06-01

    Coignimbrite plumes provide a common and effective mechanism by which large volumes of fine-grained ash are injected into the atmosphere. Nevertheless, controls on formation of these plumes as a function of eruptive conditions are still poorly constrained. Herein, two 1-D axysymmetric steady state models were coupled, the first describing the parent pyroclastic density current and the second describing plume rise. Global sensitivity analysis is applied to investigate controls on coignimbrite plume formation and describe coignimbrite source and the maximum plume height attained. For a range of initial mass flow rates between 108 and 1010 kg/s, modeled liftoff distance (the distance at which neutral buoyancy is attained), assuming radial supercritical flow, is controlled by the initial flow radius, gas mass fraction, flow thickness, and temperature. The predicted decrease in median grain size between flow initiation and plume liftoff is negligible. Calculated initial plume vertical velocities, assuming uniform liftoff velocity over the pyroclastic density current invasion area, are much greater (several tens of m/s) than those previously used in modeling coignimbrite plumes (1 m/s). Such velocities are inconsistent with the fine grain size of particles lofted into coignimbrite plumes, highlighting an unavailability of large clasts, possibly due to particle segregation within the flow, prior to plume formation. Source radius and initial vertical velocity have the largest effect on maximum plume height, closely followed by initial temperature. Modeled plume heights are between 25 and 47 km, comparable with Plinian eruption columns, highlighting the potential of such events for distributing fine-grained ash over significant areas.

  14. High-altitude plume computer code development

    NASA Technical Reports Server (NTRS)

    Audeh, B. J.; Murphy, J. E.

    1985-01-01

    The flowfield codes that have been developed to predict rocket motor plumes at high altitude were used to predict plume properties for the RCS motor which show reasonable agreement with experimental data. A systematic technique was established for the calculation of high altitude plumes. The communication of data between the computer codes was standardized. It is recommended that these outlined procedures be more completed, documented and updated as the plume methodology is applied to the varied problems of plume flow and plume impingement encountered by space station design and operation.

  15. Method for continuous control of composition and doping of pulsed laser deposited films by pressure control

    DOEpatents

    Lowndes, Douglas H.; McCamy, James W.

    1996-01-01

    A method for growing a deposit upon a substrate of semiconductor material involves the utilization of pulsed laser deposition techniques within a low-pressure gas environment. The substrate and a target of a first material are positioned within a deposition chamber and a low-pressure gas atmosphere is developed within the chamber. The substrate is then heated, and the target is irradiated, so that atoms of the target material are ablated from the remainder of the target, while atoms of the gas simultaneously are adsorbed on the substrate/film surface. The ablated atoms build up upon the substrate, together with the adsorbed gas atoms to form the thin-film deposit on the substrate. By controlling the pressure of the gas of the chamber atmosphere, the composition of the formed deposit can be controlled, and films of continuously variable composition or doping can be grown from a single target of fixed composition.

  16. Estimation of Enceladus Plume Density Using Cassini Flight Data

    NASA Technical Reports Server (NTRS)

    Wang, Eric K.; Lee, Allan Y.

    2011-01-01

    The Cassini spacecraft was launched on October 15, 1997 by a Titan 4B launch vehicle. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. In 2005, Cassini completed three flybys of Enceladus, a small, icy satellite of Saturn. Observations made during these flybys confirmed the existence of water vapor plumes in the south polar region of Enceladus. Five additional low-altitude flybys of Enceladus were successfully executed in 2008-9 to better characterize these watery plumes. During some of these Enceladus flybys, the spacecraft attitude was controlled by a set of three reaction wheels. When the disturbance torque imparted on the spacecraft was predicted to exceed the control authority of the reaction wheels, thrusters were used to control the spacecraft attitude. Using telemetry data of reaction wheel rates or thruster on-times collected from four low-altitude Enceladus flybys (in 2008-10), one can reconstruct the time histories of the Enceladus plume jet density. The 1 sigma uncertainty of the estimated density is 5.9-6.7% (depending on the density estimation methodology employed). These plume density estimates could be used to confirm measurements made by other onboard science instruments and to support the modeling of Enceladus plume jets.

  17. Plume base flow simulation technology

    NASA Technical Reports Server (NTRS)

    Roberts, B. B.; Wallace, R. O.; Sims, J. L.

    1983-01-01

    A combined analytical/empirical approach was studied in an effort to define the plume simulation parameters for base flow. For design purposes, rocket exhaust simulation (i.e., plume simulation) is determined by wind tunnel testing. Cold gas testing was concluded to be a cost and schedule effective data base of substantial scope. The results fell short of the target, although work conducted was conclusive and advanced the state of the art. Comparisons of wind tunnel predictions with Space Transportation System (STS) flight data showed considerable differences. However, a review of the technology program data base has yielded an additional parameter that may correlate flight and cold gas test data. Data from the plume technology program and the NASA test flights are presented to substantiate the proposed simulation parameters.

  18. The Source and Lateral Motion of Mantle Plumes From 3D Mantle Dynamic Models

    NASA Astrophysics Data System (ADS)

    Li, M.; Zhong, S.

    2016-12-01

    Intraplate volcanism such as hotspots may be caused by anomalously hot upwelling mantle plumes. The reconstruction of past plate motion often relies on the location of hotspots, which itself is determined by where mantle plumes form and how mantle plumes move laterally as they rise to the surface. Previous studies suggest that the large igneous provinces (LIPs), which may be caused by plume heads, preferentially locate near the edges of the seismically observed large low shear velocity provinces (LLSVPs) in the lowermost mantle beneath Africa and Pacific. However, the mechanism that leads to this interesting distribution of LIPs related to the LLSVPs is unclear. Important questions that remain to be answered include: (1) what controls the source location of mantle plumes, or more specifically, under what condition mantle plumes form outside, near the edges or in the middle of LLSVPs and (2) how much is the lateral movement of mantle plumes as they rise to the surface? In this study, we perform 3D geodynamical calculations to study plume source locations and the lateral movement of plumes. We employ plate motion history from 458 Ma as surface velocity boundary condition in our models, and the LLSVPs are simulated by large scale thermochemical piles. We explore how parameters (i.e., viscosity, thermal expansivity, thermal diffusivity) in mantle convection models control the source of plumes. We also quantify the lateral movement of mantle plumes, and compare our results with that predicted by previous studies. We find an increase of thermal diffusivity and decrease of thermal expansivity with depth, which are more consistent with mineral physical studies, suppress plumes in cold regions at the core-mantle boundary and promote plumes forming in regions with thermochemical piles. While some stable plumes originate on top and in the middle of piles, more plumes are triggered near the edges of the piles and they show transient features, and are generally hotter than that

  19. Modeling Leaking Gas Plume Migration

    SciTech Connect

    Silin, Dmitriy; Patzek, Tad; Benson, Sally M.

    2007-08-20

    In this study, we obtain simple estimates of 1-D plume propagation velocity taking into account the density and viscosity contrast between CO{sub 2} and brine. Application of the Buckley-Leverett model to describe buoyancy-driven countercurrent flow of two immiscible phases leads to a transparent theory predicting the evolution of the plume. We obtain that the plume does not migrate upward like a gas bubble in bulk water. Rather, it stretches upward until it reaches a seal or until the fluids become immobile. A simple formula requiring no complex numerical calculations describes the velocity of plume propagation. This solution is a simplification of a more comprehensive theory of countercurrent plume migration that does not lend itself to a simple analytical solution (Silin et al., 2006). The range of applicability of the simplified solution is assessed and provided. This work is motivated by the growing interest in injecting carbon dioxide into deep geological formations as a means of avoiding its atmospheric emissions and consequent global warming. One of the potential problems associated with the geologic method of sequestration is leakage of CO{sub 2} from the underground storage reservoir into sources of drinking water. Ideally, the injected green-house gases will stay in the injection zone for a geologically long time and eventually will dissolve in the formation brine and remain trapped by mineralization. However, naturally present or inadvertently created conduits in the cap rock may result in a gas leak from primary storage. Even in supercritical state, the carbon dioxide viscosity and density are lower than those of the indigenous formation brine. Therefore, buoyancy will tend to drive the CO{sub 2} upward unless it is trapped beneath a low permeability seal. Theoretical and experimental studies of buoyancy-driven supercritical CO{sub 2} flow, including estimation of time scales associated with plume evolution, are critical for developing technology

  20. Compositional controls on hydrogen generation during serpentinization of ultramafic rocks

    NASA Astrophysics Data System (ADS)

    Klein, Frieder; Bach, Wolfgang; McCollom, Thomas M.

    2013-09-01

    Where ultramafic rocks are exposed to water at temperatures < 400 °C, they inevitably undergo serpentinization reactions to form serpentine ± brucite ± talc ± magnetite (in addition to minor or trace phase like chlorite, tremolite, secondary diopside, garnet, Ni-Fe sulfides, alloys). In many circumstances, this process releases substantial amounts of hydrogen. Since the compositional controls of the primary lithology on the secondary mineralogy, fluid composition, Fe-distribution, and H2 formation are not well established, we used thermodynamic computations to examine the equilibrium mineral assemblages, mineral compositions and the chemistry of fluids during serpentinization of 21 different ultramafic rock compositions and 10 distinct compositions of olivine between 25 °C and 400 °C at 50 MPa. Our models predict some systematic differences between serpentinization of olivine-dominated lithologies (i.e. peridotite) and of orthopyroxene-dominated lithologies (i.e. pyroxenite). Most notably, it is predicted that serpentinization of peridotite causes the formation of serpentine having elevated Fe+ 3/(Fe+ 3 + Fe+ 2) values, Fe-bearing brucite (at temperatures ≤ ca. 320 °C), and magnetite (at temperatures > ca. 200 °C), while serpentinization of pyroxenite does not produce magnetite, but instead forms Fe-rich serpentine with relative low Fe+ 3/(Fe+ 3 + Fe+ 2) values and Fe-poor talc. The predicted activities of dissolved hydrogen (aH2(aq)), dissolved silica (aSiO2(aq)), as well as the pH vary accordingly. At temperatures ≤ ca. 350 °C, fluids interacting with peridotite are more reducing, have lower aSiO2(aq) and higher pH than fluids interacting with pyroxenite. A direct correlation between the iron content of olivine, its stability relative to water, temperature and aH2(aq) is apparent from our calculations. In contrast to forsterite-rich olivine, fayalite-rich olivine can be stable to temperatures as low as 180 °C in the presence of water. As a

  1. Geological control of floristic composition in Amazonian forests.

    PubMed

    Higgins, Mark A; Ruokolainen, Kalle; Tuomisto, Hanna; Llerena, Nelly; Cardenas, Glenda; Phillips, Oliver L; Vásquez, Rodolfo; Räsänen, Matti

    2011-11-01

    AIM: Conservation and land-use planning require accurate maps of patterns in species composition and an understanding of the factors that control them. Substantial doubt exists, however, about the existence and determinants of large-area floristic divisions in Amazonia. Here we ask whether Amazonian forests are partitioned into broad-scale floristic units on the basis of geological formations and their edaphic properties. LOCATION: Western and central Amazonia. METHODS: We used Landsat imagery and Shuttle Radar Topography Mission (SRTM) digital elevation data to identify a possible floristic and geological discontinuity of over 300 km in northern Peru. We then used plant inventories and soil sampling to document changes in species composition and soil properties across this boundary. Data were obtained from 138 sites distributed along more than 450 km of road and river. On the basis of our findings, we used broad-scale Landsat and SRTM mosaics to identify similar patterns across western and central Amazonia. RESULTS: The discontinuity identified in Landsat and SRTM data corresponded to a 15-fold change in soil cation concentrations and an almost total change in plant species composition. This discontinuity appears to be caused by the widespread removal of cation-poor surface sediments by river incision to expose cation-rich sediments beneath. Examination of broad-scale Landsat and SRTM mosaics indicated that equivalent processes have generated a north-south discontinuity of over 1500 km in western Brazil. Due to similarities with our study area, we suggest that this discontinuity represents a chemical and ecological limit between western and central Amazonia. MAIN CONCLUSIONS: Our findings suggest that Amazonian forests are partitioned into large-area units on the basis of geological formations and their edaphic properties. The evolution of these units through geological time may provide a general mechanism for biotic diversification in Amazonia. These

  2. Geological control of floristic composition in Amazonian forests

    PubMed Central

    Higgins, Mark A; Ruokolainen, Kalle; Tuomisto, Hanna; Llerena, Nelly; Cardenas, Glenda; Phillips, Oliver L; Vásquez, Rodolfo; Räsänen, Matti

    2011-01-01

    Aim Conservation and land-use planning require accurate maps of patterns in species composition and an understanding of the factors that control them. Substantial doubt exists, however, about the existence and determinants of large-area floristic divisions in Amazonia. Here we ask whether Amazonian forests are partitioned into broad-scale floristic units on the basis of geological formations and their edaphic properties. Location Western and central Amazonia. Methods We used Landsat imagery and Shuttle Radar Topography Mission (SRTM) digital elevation data to identify a possible floristic and geological discontinuity of over 300 km in northern Peru. We then used plant inventories and soil sampling to document changes in species composition and soil properties across this boundary. Data were obtained from 138 sites distributed along more than 450 km of road and river. On the basis of our findings, we used broad-scale Landsat and SRTM mosaics to identify similar patterns across western and central Amazonia. Results The discontinuity identified in Landsat and SRTM data corresponded to a 15-fold change in soil cation concentrations and an almost total change in plant species composition. This discontinuity appears to be caused by the widespread removal of cation-poor surface sediments by river incision to expose cation-rich sediments beneath. Examination of broad-scale Landsat and SRTM mosaics indicated that equivalent processes have generated a north–south discontinuity of over 1500 km in western Brazil. Due to similarities with our study area, we suggest that this discontinuity represents a chemical and ecological limit between western and central Amazonia. Main conclusions Our findings suggest that Amazonian forests are partitioned into large-area units on the basis of geological formations and their edaphic properties. The evolution of these units through geological time may provide a general mechanism for biotic diversification in Amazonia. These compositional

  3. CaF{sub 2} ablation plumes as a source of CaF molecules for harmonic generation

    SciTech Connect

    Oujja, M.; Nalda, R. de; Castillejo, M.; Lopez-Arias, M.; Torres, R.; Marangos, J. P.

    2010-04-15

    Generation of low-order harmonics (third and fifth) of the fundamental radiation of a Q-switched Nd:YAG laser (1064 nm, pulse 15 ns) was observed in a CaF{sub 2} laser ablation plume. The ablation process is triggered by a second Q-switched Nd:YAG laser operating at 532 or 266 nm. In the scheme employed, the fundamental laser beam propagates parallel to the target surface at controllable distance and temporal delay, allowing to the probing of different regions of the freely expanding plume. The intensity of the harmonics is shown to decrease rapidly as the distance to the target is increased, and for each distance, an optimum time delay between the ablating laser pulse and the fundamental beam is found. In situ diagnosis of the plume by optical emission spectroscopy and laser-induced fluorescence serves to correlate the observed harmonic behavior with the temporally and spatially resolved composition and velocity of flight of species in the plume. It is concluded that harmonics are selectively generated by CaF species through a two-photon resonantly enhanced sum-mixing process exploiting the (B {sup 2{Sigma}+}-X {sup 2{Sigma}+}, {Delta}{nu}=0) transition of the molecule in the region of 530 nm. In this work polar molecules have been shown to be the dominating species for harmonic generation in an ablation plume. Implications of these results for the generation of high harmonics in strongly polar molecules which can be aligned in the ablation plasma are discussed.

  4. Europa's Atmosphere and Aurora: Recent Advances from HST-STIS and Plans for Plume Searches with JUICE-UVS

    NASA Astrophysics Data System (ADS)

    Retherford, K. D.; Gladstone, R.; Roth, L.; McGrath, M. A.; Saur, J.; Feldman, P. D.; Steffl, A. J.; Strobel, D. F.; Greathouse, T. K.; Spencer, J. R.; Bagenal, F.; Fletcher, L. N.; Eterno, J. S.

    2013-12-01

    Space Telescope Imaging System (STIS) images of Europa's neutral oxygen 130.4 nm and 135.6 nm emissions contain a wealth of information about the molecular oxygen atmosphere, discovered using previous Hubble far-UV observations. Europa's magnetospheric plasma interaction generates auroral emissions, which exhibit a morphology that has been difficult to interpret. Recent observations in Nov. & Dec. 2012 allow a new understanding of how Jupiter's magnetic field orientation and relation to the plasma sheet control the emission variability, yet explanations for this general behavior, including the likely role of ocean-induced magnetic fields and possible local atmospheric density enhancements, remain incomplete (cf. Roth et al. this meeting). NASA's Ultraviolet Spectrograph (UVS) instrument contribution to the ESA-led Jupiter Icy Moons Explorer (JUICE) mission will obtain excellent imaging of these atmospheric and auroral emissions from Europa during two flybys currently planned, with the objective of investigating these and other unanswered questions. UVS's stellar occultation technique will be used to characterize Europa's atmosphere structure and composition and to also search for local enhancements created by plumes. This stellar occultation technique, demonstrated by Cassini-UVIS at Enceladus, has the benefit of being useful at relatively large distances (several 10's of Jupiter radii) as well as during the Europa flyby sequences (several 10's of Europa radii). A robust search for plumes is planned in JUICE's first year at Jupiter to provide a roughly 30-degree grid of global coverage, followed by focused targeting of likely plumes/active-regions during early and late stages of the flyby sequences. High spatial resolution limb imaging is also planned near closest approaches, which could directly image plume gases in a manner analogous with plume aurora imaging of Io. A UV spectrograph on the planned Europa Clipper mission could perform an even more robust search

  5. Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFRC Focused on Hanford’s 300 Area Uranium Plume

    SciTech Connect

    Zachara, John M.; Bjornstad, Bruce N.; Christensen, John N.; Conrad, Mark E.; Fredrickson, Jim K.; Freshley, Mark D.; Haggerty, Roy; Hammon, Glenn; Kent, Douglas B.; Konopka, Allan; Lichtner, Peter C.; Liu, Chongxuan; McKinley, James P.; Murray, Christopher J.; Rockhold, Mark L.; Rubin, Yoram; Vermeul, Vincent R.; Versteeg, Roelof J.; Ward, Anderson L.; Zheng, Chunmiao

    2010-02-01

    The Integrated Field-Scale Subsurface Research Challenge (IFRC) at the Hanford Site 300 Area uranium (U) plume addresses multi-scale mass transfer processes in a complex hydrogeologic setting where groundwater and riverwater interact. A series of forefront science questions on mass transfer are posed for research which relate to the effect of spatial heterogeneities; the importance of scale; coupled interactions between biogeochemical, hydrologic, and mass transfer processes; and measurements and approaches needed to characterize and model a mass-transfer dominated system. The project was initiated in February 2007, with CY 2007 and CY 2008 progress summarized in preceding reports. The site has 35 instrumented wells, and an extensive monitoring system. It includes a deep borehole for microbiologic and biogeochemical research that sampled the entire thickness of the unconfined 300 A aquifer. Significant, impactful progress has been made in CY 2009 with completion of extensive laboratory measurements on field sediments, field hydrologic and geophysical characterization, four field experiments, and modeling. The laboratory characterization results are being subjected to geostatistical analyses to develop spatial heterogeneity models of U concentration and chemical, physical, and hydrologic properties needed for reactive transport modeling. The field experiments focused on: (1) physical characterization of the groundwater flow field during a period of stable hydrologic conditions in early spring, (2) comprehensive groundwater monitoring during spring to characterize the release of U(VI) from the lower vadose zone to the aquifer during water table rise and fall, (3) dynamic geophysical monitoring of salt-plume migration during summer, and (4) a U reactive tracer experiment (desorption) during the fall. Geophysical characterization of the well field was completed using the down-well Electrical Resistance Tomography (ERT) array, with results subjected to robust

  6. Mobile Bay turbidity plume study

    NASA Technical Reports Server (NTRS)

    Crozier, G. F.

    1976-01-01

    Laboratory and field transmissometer studies on the effect of suspended particulate material upon the appearance of water are reported. Quantitative correlations were developed between remotely sensed image density, optical sea truth data, and actual sediment load. Evaluation of satellite image sea truth data for an offshore plume projects contours of transmissivity for two different tidal phases. Data clearly demonstrate the speed of change and movement of the optical plume for water patterns associated with the mouth of Mobile bay in which relatively clear Gulf of Mexico water enters the bay on the eastern side. Data show that wind stress in excess of 15 knots has a marked impact in producing suspended sediment loads.

  7. Plume Detection and Plume Top Height Estimation using SLSTR

    NASA Astrophysics Data System (ADS)

    Virtanen, Timo H.; Kolmonen, Pekka; Sogacheva, Larisa; Rodriguez, Edith; Saponaro, Giulia; de Leeuw, Gerrit

    2017-04-01

    We present preliminary results on ash and desert dust plume detection and plume top height estimates based on satellite data from the Sea and Land Surface Temperature Radiometer (SLSTR) aboard Sentinel-3, launched in 2016. The methods are based on the previously developed AATSR Correlation Method (ACM) height estimation algorithm, which utilized the data of the preceding similar instrument, Advanced Along Track Scanning Radiometer (AATSR). The height estimate is based on the stereo-viewing capability of SLSTR, which allows to determine the parallax between the satellite's 55° backward and nadir views, and thus the corresponding height. The ash plume detection is based on the brightness temperature difference between between thermal infrared (TIR) channels centered at 11 and 12 μm, which show characteristic signals for both desert dust and ash plumes. The SLSTR instrument provides a unique combination of dual-view capability and a wavelength range from visible to thermal infrared, rendering it an ideal instrument for this work. Accurate information on the volcanic ash position is important for air traffic safety. The ACM algorithm can provide valuable data of both horizontal and vertical ash dispersion. These data may be useful for comparisons with other volcanic ash and desert dust retrieval methods and dispersion models. The current work is being carried out as part of the H2020 project EUNADICS-AV ("European Natural Disaster Coordination and Information System for Aviation"), which started in October 2016.

  8. Wind relaxation and a coastal buoyant plume north of Pt. Conception, CA: Observations, simulations, and scalings

    NASA Astrophysics Data System (ADS)

    Suanda, Sutara H.; Kumar, Nirnimesh; Miller, Arthur J.; Di Lorenzo, Emanuele; Haas, Kevin; Cai, Donghua; Edwards, Christopher A.; Washburn, Libe; Fewings, Melanie R.; Torres, Rachel; Feddersen, Falk

    2016-10-01

    In upwelling regions, wind relaxations lead to poleward propagating warm water plumes that are important to coastal ecosystems. The coastal ocean response to wind relaxation around Pt. Conception, CA is simulated with a Regional Ocean Model (ROMS) forced by realistic surface and lateral boundary conditions including tidal processes. The model reproduces well the statistics of observed subtidal water column temperature and velocity at both outer and inner-shelf mooring locations throughout the study. A poleward-propagating plume of Southern California Bight water that increases shelf water temperatures by ≈ 5°C is also reproduced. Modeled plume propagation speed, spatial scales, and flow structure are consistent with a theoretical scaling for coastal buoyant plumes with both surface-trapped and slope-controlled dynamics. Plume momentum balances are distinct between the offshore (>30 m depth) region where the plume is surface-trapped, and onshore of the 30 m isobath (within 5 km from shore) where the plume water mass extends to the bottom and is slope controlled. In the onshore region, bottom stress is important in the alongshore momentum equation and generates vertical vorticity that is an order of magnitude larger than the vorticity in the plume core. Numerical experiments without tidal forcing show that modeled surface temperatures are biased 0.5°C high, potentially affecting plume propagation distance and persistence.

  9. NASA/LaRC jet plume research

    NASA Technical Reports Server (NTRS)

    Seiner, John M.; Ponton, Michael K.; Manning, James C.

    1992-01-01

    The following provides a summary for research being conducted by NASA/LaRC and its contractors and grantees to develop jet engine noise suppression technology under the NASA High Speed Research (HSR) program for the High Speed Civil Transport (HSCT). The objective of this effort is to explore new innovative concepts for reducing noise to Federally mandated guidelines with minimum compromise on engine performance both in take-off and cruise. The research program is divided into four major technical areas: (1) jet noise research on advanced nozzles; (2) plume prediction and validation; (3) passive and active control; and (4) methodology for noise prediction.

  10. Three-Dimensional Composite Nanostructures for Lean NOx Emission Control

    SciTech Connect

    Gao, Pu-Xian

    2013-07-31

    This final report to the Department of Energy (DOE) and National Energy Technology Laboratory (NETL) for DE-EE0000210 covers the period from October 1, 2009 to July 31, 2013. Under this project, DOE awarded UConn about $1,248,242 to conduct the research and development on a new class of 3D composite nanostructure based catalysts for lean NOx emission control. Much of the material presented here has already been submitted to DOE/NETL in quarterly technical reports. In this project, through a scalable solution process, we have successfully fabricated a new class of catalytic reactors, i.e., the composite nanostructure array (nano-array) based catalytic converters. These nanocatalysts, distinct from traditional powder washcoat based catalytic converters, directly integrate monolithic substrates together with nanostructures with well-defined size and shape during the scalable hydrothermal process. The new monolithic nanocatalysts are demonstrated to be able to save raw materials including Pt-group metals and support metal oxides by an order of magnitude, while perform well at various oxidation (e.g., CO oxidation and NO oxidation) and reduction reactions (H{sub 2} reduction of NOx) involved in the lean NOx emissions. The size, shape and arrangement of the composite nanostructures within the monolithic substrates are found to be the key in enabling the drastically reduced materials usage while maintaining the good catalytic reactivity in the enabled devices. The further understanding of the reaction kinetics associated with the unique mass transport and surface chemistry behind is needed for further optimizing the design and fabrication of good nanostructure array based catalytic converters. On the other hand, the high temperature stability, hydrothermal aging stability, as well as S-poisoning resistance have been investigated in this project on the nanocatalysts, which revealed promising results toward good chemical and mechanical robustness, as well as S

  11. Controle de la fabrication des composites par injection sur renforts

    NASA Astrophysics Data System (ADS)

    Lebel, Francois

    Liquid Composite Molding (LCM) is an increasingly used class of processes to manufacture high performance composites. A multiscale study is presented in this thesis in order to better understand the fundamental physics of impregnation and air entrapment phenomena in dual scale fibrous reinforcements and thus propose practical solutions for process control engineers. First of all, an experimental setup is developed to study the saturation of fibrous reinforcements, at the macroscopic scale, during the Resin Transfer Molding (RTM). This setup is used to determine some key parameters of the part filling step and industrial post-filling strategies (mold bleeding and consolidation) that control the impregnation quality of fibrous reinforcements. These key parameters are identified using three series of experiments. These parameters are the flow front velocity, the inlet mold pressure and the bleeding flow rate. The analyses in these three series of experiments are based on an ASTM standard procedure for void content determination in the composite parts by carbonization (also called loss on ignition (LOI)). These three series of experiments have related a posteriori the key parameters of LCM processes to phenomena of void formation, migration and dissolution in composite parts made of E-glass non crimp fabric (NCF) and vinyl ester resin. The second part of this thesis aims to investigate, at the mesoscopic and microscopic scale, the impregnation mechanisms of fibrous reinforcements during LCM processes. This analysis focuses more specifically on wicking phenomenon in fiber tows and in fibrous laminates, namely here stacks of non crimp fabric plies. This experimental study is carried out to better understand the physics which explain that the impregnation velocity is one of the key parameters that control the quality of composite parts manufactured by LCM processes. This analysis also aims to identify the structural features of fiber tows and fibrous reinforcements that

  12. Exhaust Nozzle Plume and Shock Wave Interaction

    NASA Technical Reports Server (NTRS)

    Castner, Raymond S.; Elmiligui, Alaa; Cliff, Susan

    2013-01-01

    Fundamental research for sonic boom reduction is needed to quantify the interaction of shock waves generated from the aircraft wing or tail surfaces with the exhaust plume. Both the nozzle exhaust plume shape and the tail shock shape may be affected by an interaction that may alter the vehicle sonic boom signature. The plume and shock interaction was studied using Computational Fluid Dynamics simulation on two types of convergent-divergent nozzles and a simple wedge shock generator. The nozzle plume effects on the lower wedge compression region are evaluated for two- and three-dimensional nozzle plumes. Results show that the compression from the wedge deflects the nozzle plume and shocks form on the deflected lower plume boundary. The sonic boom pressure signature of the wedge is modified by the presence of the plume, and the computational predictions show significant (8 to 15 percent) changes in shock amplitude.

  13. Uncertainties in volcanic plume modeling: A parametric study using FPLUME

    NASA Astrophysics Data System (ADS)

    Macedonio, G.; Costa, A.; Folch, A.

    2016-10-01

    We carry out a parametric study in order to identify and quantify the effects of uncertainties on pivotal parameters controlling the dynamics of volcanic plumes. The study builds upon numerical simulations using FPLUME, an integral steady-state model based on the Buoyant Plume Theory generalized in order to account for volcanic processes (particle fallout and re-entrainment, water phase changes, effects of wind, etc). As reference cases for strong and weak plumes, we consider the cases defined during the IAVCEI Commission on tephra hazard modeling inter-comparison study (Costa et al., 2016). The parametric study quantifies the effect of typical uncertainties on total mass eruption rate, column height, mixture exit velocity, temperature and water content, and particle size. Moreover, a sensitivity study investigates the role of wind entrainment and intensity, atmospheric humidity, water phase changes, and particle fallout and re-entrainment. Results show that the leading-order parameters that control plume height are the mass eruption rate and the air entrainment coefficient, especially for weak plumes.

  14. What factors control the composition of andesitic sand?

    SciTech Connect

    Smith, G.A.; Lotosky, J.E.

    1995-01-02

    The modal composition of andesitic sand and sandstone is not only a function of source-area climate and transport processes typically considered for nonvolcanic sediment but is also strongly controlled by volcanic fragmentation and pyroclastic-transport processes. Most volcaniclastic sediment deposited penecontemporaneously with active volcanism is not epiclastic, and therefore its composition is not dependent on climate. Crystal-rich andesite sand cannot simply be regarded as the product of weathering in a humid climate. In fact, there is no relationship between precipitation and the ratio of crystals to rock fragments. Fluvial-transport abrasion demonstrably generates crystal-rich sand only in the case of porphyritic glassy rock fragments that are not durable during transport; holocrystalline pyroclastic fragments apparently do not disintegrate during transport to yield crystal-rich sand. Many sand-size primary volcanic deposits are crystal-rich as a result of eruptive processes that physical fractionate particles of different sizes and densities. Reworking of these deposits results in crystal-rich sand that is not a product of weathering or transport abrasion. The abundance of unaltered green hornblende is one measure of the importance of pyroclastic material in a volcanic sand because this mineral is not found in lava flows. Interpretation of volcaniclastic sandstone requires consideration of volcanic processes not typically considered by sedimentologists.

  15. Genetic network driven control of PHBV copolymer composition.

    PubMed

    Iadevaia, Sergio; Mantzaris, Nikos V

    2006-03-09

    We developed a detailed mathematical model describing the coupling between the molecular weight distribution dynamics of poly(3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV) copolymer chains with those of hydroxybutyrate (HB) and hydroxyvalerate (HV) monomer formation. Sensitivity analysis of the model revealed that both the monomer composition and the molecular weight distribution of the copolymer chains are strongly affected by the ratio between the rates at which the two-monomer units are incorporated into the chains. This ratio depends on the relative HB and HV availability, which in turn is a function of the expression levels of genes encoding enzymes that catalyze monomer formation. Regulation of gene expression was accomplished through the aid of an artificial genetic network, the patterns of expression of which can be controlled by appropriately tuning the concentration of an extracellular inducer. Extensive simulations were used to study the effects of operating conditions and parameter uncertainties on the range of achievable copolymer compositions. Since the predicted conditions fell in the range of feasible bioprocessing manipulations, it is expected that such strategy could be successfully employed. Thus, the presented model constitutes a powerful tool for designing genetic networks that can drive the formation of PHBV copolymer structures with desirable characteristics.

  16. Venus ionosphere: photochemical and thermal diffusion control of ion composition.

    PubMed

    Bauer, S J; Donahue, T M; Hartle, R E; Taylor, H A

    1979-07-06

    The major photochemical sources and sinks for ten of the ions measured by the ion mass spectrometer on the Pioneer Venus bus and orbiter spacecraft that are consistent with the neutral gas composition measured on the same spacecraft have been identified. The neutral gas temperature (Tn) as a function of solar zenith angle (chi) derived from measured ion distributions in photochemical equilibrium is given by Tn (K) = 323 cos(1/5)chi. Above 200 kilometers, the altitude behavior of ions is generally controlled by plasma diffusion, with important modifications for minor ions due to thermal diffusion resulting from the observed gradients of plasma temperatures. The dayside equilibrium distributions of ions are sometimes perturbed by plasma convection, while lateral transport of ions from the dayside seems to be a major source of the nightside ionosphere.

  17. Selection of optimal composition-control parameters for friable materials

    SciTech Connect

    Pak, Yu.N.; Vdovkin, A.V.

    1988-05-01

    A method for composition analysis of coal and minerals is proposed which uses scattered gamma radiation and does away with preliminary sample preparation to ensure homogeneous particle density, surface area, and size. Reduction of the error induced by material heterogeneity has previously been achieved by rotation of the control object during analysis. A further refinement is proposed which addresses the necessity that the contribution of the radiation scattered from each individual surface to the total intensity be the same. This is achieved by providing a constant linear rate of travel for the irradiated spot through back-and-forth motion of the sensor. An analytical expression is given for the laws of motion for the sensor and test tube which provides for uniform irradiated area movement along a path analogous to the Archimedes spiral. The relationships obtained permit optimization of measurement parameters in analyzing friable materials which are not uniform in grain size.

  18. Electrochemically-Controlled Compositional Oscillations of Oxide Surfaces

    SciTech Connect

    Mutoro, Eva; Crumlin, Ethan; Pöpke, Hendrik; Luerssen, Bjoern; Amati, Matteo; Abyaneh, Majid; Biegalski, Michael D; Christen, Hans M; Gregoratti, Luca; Janek, Jürgen; Shao-Horn, Yang

    2012-01-01

    Perovskite oxides can exhibit a wide range of interesting characteristics such as being catalytically active and electronically and/or ionically conducting, and thus they have been used in a number of solid-state devices such as solid oxide fuel cells and sensors. As the surface compositions of perovskites can greatly influence the catalytic properties, knowing and controlling their surface chemistries is crucial to enhance device performance. In this study, we demonstrate that the surface strontium (Sr) and cobalt (Co) concentrations of perovskite-based thin films can be controlled reversibly at elevated temperatures by applying small electrical potential biases. The surface chemistry changes of La0.8Sr0.2CoO3 (LSC113), LaSrCoO4 (LSC214), and LSC214-decorated LSC113 films (LSC113/214) were investigated in situ by utilizing synchrotron-based X-ray photoelectron spectroscopy (XPS), where the largest changes of surface Sr was found for the LSC113/214 surface. These findings offer the potential of reversibly controlling the surface functionality of perovskites.

  19. An evaluation of modeled plume injection height with satellite-derived observed plume height

    Treesearch

    Sean M. Raffuse; Kenneth J. Craig; Narasimhan K. Larkin; Tara T. Strand; Dana Coe Sullivan; Neil J.M. Wheeler; Robert. Solomon

    2012-01-01

    Plume injection height influences plume transport characteristics, such as range and potential for dilution. We evaluated plume injection height from a predictive wildland fire smoke transport model over the contiguous United States (U.S.) from 2006 to 2008 using satellite-derived information, including plume top heights from the Multi-angle Imaging SpectroRadiometer (...

  20. Controls over the strontium isotope composition of river water

    NASA Astrophysics Data System (ADS)

    Palmer, M. R.; Edmond, J. M.

    1992-05-01

    Strontium concentrations and isotope ratios have been measured in river and ground waters from the Ganges, Orinoco, and Amazon river basins. When compared with major element concentrations, the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments: (1) "typical" drainage basins containing limestones, evaporites, shales, and alumino-silicate metamorphic and igneous rocks; (2) shield terrains containing no chemical or biogenic sediments; and (3) the floodplains that constitute the largest areas of many large rivers. The strontium concentration and isotope composition of river waters are largely defined by mixing of strontium derived from limestones and evaporites with strontium derived from silicate rocks. The strontium isotope composition of the limestone endmember generally lies within the Phanerozoic seawater range, which buffers the 87Sr /86Sr ratios of major rivers. A major exception is provided by the rivers draining the Himalayas, where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic strontium derived from coexisting silicate rocks. The strontium isotope systematics of rivers draining shield areas are controlled by the intense, transportlimited, nature of the weathering reactions, and thereby limits variations in the strontium flux from these terrains. Floodplains are only a minor source of dissolved strontium to river waters, and precipitation of soil salts in some floodplains can reduce the riverine flux of dissolved strontium to the oceans. The most effective mechanisms for altering the isotope ratio and flux of riverine strontium to the oceans are increased glaciation and large-scale regional metamorphism of the type produced during continental collision. Both mechanisms provide a means for increasing the 87Sr /86Sr ratio of the global riverine flux.

  1. Active control of structures using macro-fiber composite (MFC)

    NASA Astrophysics Data System (ADS)

    Kovalovs, A.; Barkanov, E.; Gluhihs, S.

    2007-12-01

    This paper presents the use of macro-fiber composites (MFC) for vibration reduces of structures. The MFC consist of polyimid films with IDE-electrodes that are glued on the top and the bottom of rectangular piezoceramic fibers. The interdigitated electrodes deliver the electric field required to activate the piezoelectric effect in the fibers and allows to invoke the stronger longitudinal piezoelectric effect along the length of the fibers. When this actuator embedded in a surface or attached to flexible structures, the MFC actuator provides distributed solid-state deflection and vibration control. The major advantages of the piezoelectric fibre composite actuators are their high performance, flexibility, and durability when compared with the traditional piezoceramic (PZT) actuators. In addition, the ability of MFC devices to couple the electrical and mechanical fields is larger than in monolithic PZT. In this study, we showed the experimental results that an MFC could be used as actuator to find modal parameters and reduce vibration for structures such as an aluminium beam and metal music plate. Two MFC actuators were attached to the surfaces of test subjects. First MFC actuator used to supply a signal as exciter of vibration and second MFC show his application for reduction of vibration in the range of resonance frequencies. Experimental results of aluminium beam with MFC actuators compared with finite element model which modelled in ANSYS software. The applied voltage is modelled as a thermal load according to thermal analogy for MFC. The experimental and numerical results presented in this paper confirm the potential of MFC for use in the vibration control of structures.

  2. Capture of the Canary mantle plume material by the Gibraltar arc mantle wedge during slab rollback

    NASA Astrophysics Data System (ADS)

    Mériaux, C. A.; Duarte, J. C.; Duarte, S. S.; Schellart, W. P.; Chen, Z.; Rosas, F.; Mata, J.; Terrinha, P.

    2015-06-01

    Recent evidence suggests that a portion of the Canary plume travelled northeastwards below the lithosphere of the Atlas Mountains in North Africa towards the Alboran domain and was captured ˜10 Ma ago by the Gibraltar subduction system in the Western Mediterranean. The capture would have been associated with the mantle return flow induced by the westward-retreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the Gibraltar subduction zone. Such material eventually contaminated the subduction related volcanism in the Alboran region. In this work, we use scaled analogue models of slab-plume interaction to investigate the plausibility of the plume capture. An upper-mantle-scaled model combines a narrow (400 km) edge-fixed subduction plate with a laterally offset compositional plume. The subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 × 1350 km2. While the plume head initially spreads axisymmetrically, it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km, before getting dragged towards mantle wedge. When applied to the Canary plume-Gibraltar subduction system, our model supports the observationally based conceptual model that mantle plume material may have been dragged towards the mantle wedge by slab rollback-induced toroidal mantle flow. Using a scaling argument for the spreading of a gravity current within a channel, we also show that more than 1500 km of plume propagation in the sublithospheric Atlas corridor is dynamically plausible.

  3. Density and optical properties of SPARCS plumes

    NASA Technical Reports Server (NTRS)

    Brown, W. A.; Kumer, J. B.; Cooper, C. E., Jr.

    1972-01-01

    Propellant gases emitted by attitude control systems such as SPARCS (Solar Pointing Aerobee Rocket Control System) and possible interference with experiments aboard the payloads are discussed. The optical properties of seven actual and potential gases emitted by propellant systems (CF4, N2H4, NH3, N2, CO2, Ar, and He) are presented. A compilation of absorption coefficients from 1 Angstrom to 50 microns and a summary of fluorescent spectra and efficiencies are provided. Since Freon-14 (CF4) is of primary importance to SPARCS, an experimental search for the fluorescent spectrum of CF4 was performed by exciting the gas with 920 Angstrom UV photons. The result was compared with an electron impact induced spectrum of CF4, and conclusions drawn about the nature of the radiating species. A detailed study of the CF4 flow fields and plume densities for typical SPARCS controlled payloads was made using gas dynamic codes which included the effects of vehicle shading and condensation. The importance of the optical properties of CF4 plumes was investigated and it is concluded that absorption is negligible but fluoresence may be significant in some cases.

  4. Large Smoke Plumes, Alberta Canada

    Atmospheric Science Data Center

    2016-12-30

    ...     View Larger Image Devastating wildfires in Alberta Province, Canada, near the city of Fort McMurray began on ... a result of intense thermal heating emanating from surface wildfires. The intense heating drives convection within the smoke plume. At the ...

  5. Smoke Plume Over Eastern Canada

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In late May, a massive smoke plume hundreds of kilometers across blew eastward over New Brunswick toward the Atlantic Ocean. On May 26, 2007, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image at 11:40 a.m. local time. By the time MODIS took this picture, the smoke appeared to have completely detached itself from the source, a large fire burning in southwestern Quebec, beyond the western edge of this image. In this image, the smoke appears as a gray-beige opaque mass with fuzzy, translucent edges. The plume is thickest in the southwest and diminishes toward the northeast. Just southwest of the plume is a red outline indicating a hotspot an area where MODIS detected anomalously warm surface temperatures, such as those resulting from fires. This hotspot, however, is not the source for this smoke plume. According to a bulletin from the National Oceanic and Atmospheric Administration, the southwestern Quebec fire was the source. According to reports from the Canadian Interagency Forest Fire Centre on May 29, that fire was estimated at 63,211 hectares (156,197 acres), and it was classified as 'being held.' At the same time, more than 20 wildfires burned in Quebec, news sources reported, and firefighters from other Canadian provinces and the United States had been brought in to provide reinforcements for the area's firefighters.

  6. Profiling an electrospray plume by laser-induced fluorescence and Fraunhofer diffraction combined to mass spectrometry: influence of size and composition of droplets on charge-state distributions of electrosprayed proteins.

    PubMed

    Girod, Marion; Dagany, Xavier; Boutou, Véronique; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe; Mordehai, Alex; Love, Craig; Werlich, Mark; Fjeldsted, John; Stafford, George

    2012-07-14

    We investigated how physico-chemical properties of charged droplets are affected by the electrospray process, using simultaneous in situ measurements by laser-induced fluorescence (LIF), Fraunhofer diffraction and mass spectrometry. For this purpose, we implemented a laser-induced-fluorescence profiling setup in conjunction with a fast, high-resolution particle sizing scheme on a modified Agilent Jet Stream electrospray source coupled to a single quadrupole mass analyser. The optical setup permits us to profile the solvent fractionation and the size of the droplets as they evaporate in an electrospray plume by measuring both the angular scattering pattern and emission spectra of a solvatochromic fluorescent dye. Mass spectra are recorded simultaneously. These mass spectrometry and optical spectroscopy investigations allow us to study the relation between the observed charge-state distributions of protein anions and physico-chemical properties of evaporating droplets in the spray plume. By mixing water with methanol, a refolding of cytochrome C is observed as the water percentage increases in the plume due to the preponderant evaporation of volatile methanol.

  7. Types of thermal plumes in coastal waters

    NASA Technical Reports Server (NTRS)

    Green, T.; Madding, R.; Scarpace, F.

    1977-01-01

    A large number of thermal images of the surface temperatures of the thermal plumes associated with the once-through cooling of electric power plants show that four kinds of plume occur sufficiently often to be classified as distinct plume types. Each type has implications for both numerical models and measurement strategies.

  8. Chesapeake Bay plume dynamics from LANDSAT

    NASA Technical Reports Server (NTRS)

    Munday, J. C., Jr.; Fedosh, M. S.

    1981-01-01

    LANDSAT images with enhancement and density slicing show that the Chesapeake Bay plume usually frequents the Virginia coast south of the Bay mouth. Southwestern (compared to northern) winds spread the plume easterly over a large area. Ebb tide images (compared to flood tide images) show a more dispersed plume. Flooding waters produce high turbidity levels over the shallow northern portion of the Bay mouth.

  9. Downwelling wind, tides, and estuarine plume dynamics

    NASA Astrophysics Data System (ADS)

    Lai, Zhigang; Ma, Ronghua; Huang, Mingfen; Chen, Changsheng; Chen, Yong; Xie, Congbin; Beardsley, Robert C.

    2016-06-01

    The estuarine plume dynamics under a downwelling-favorable wind condition were examined in the windy dry season of the Pearl River Estuary (PRE) using the PRE primitive-equation Finite-Volume Community Ocean Model (FVCOM). The wind and tide-driven estuarine circulation had a significant influence on the plume dynamics on both local and remote scales. Specifically, the local effect of downwelling-favorable winds on the plume was similar to the theoretical descriptions of coastal plumes, narrowing the plume width, and setting up a vertically uniform downstream current at the plume edge. Tides tended to reduce these plume responses through local turbulent mixing and advection from upstream regions, resulting in an adjustment of the isohalines in the plume and a weakening of the vertically uniform downstream current. The remote effect of downwelling-favorable winds on the plume was due to the wind-induced estuarine sea surface height (SSH), which strengthened the estuarine circulation and enhanced the plume transport accordingly. Associated with these processes, tide-induced mixing tended to weaken the SSH gradient and thus the estuarine circulation over a remote influence scale. Overall, the typical features of downwelling-favorable wind-driven estuarine plumes revealed in this study enhanced our understanding of the estuarine plume dynamics under downwelling-favorable wind conditions.

  10. Estimation and Modeling of Enceladus Plume Density Using Attitude Control Data Collected by the Cassini Spacecraft During Low-Altitude Enceladus Flybys

    NASA Technical Reports Server (NTRS)

    Wang, Eric K.; Lee, Allan Y.

    2011-01-01

    The Cassini spacecraft was launched on 15 October 1997. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. Major science objectives of the Cassini mission include investigations of the configuration and dynamics of Saturn's magnetosphere, the structure and composition of the rings, the characterization of several of Saturn's icy satellites, and Titan's atmosphere constituent abundance

  11. Estimation and Modeling of Enceladus Plume Density Using Attitude Control Data Collected by the Cassini Spacecraft During Low-Altitude Enceladus Flybys

    NASA Technical Reports Server (NTRS)

    Wang, Eric K.; Lee, Allan Y.

    2011-01-01

    The Cassini spacecraft was launched on 15 October 1997. After an interplanetary cruise of almost seven years, it arrived at Saturn on June 30, 2004. Major science objectives of the Cassini mission include investigations of the configuration and dynamics of Saturn's magnetosphere, the structure and composition of the rings, the characterization of several of Saturn's icy satellites, and Titan's atmosphere constituent abundance

  12. Models of the Enceladus Plumes

    NASA Astrophysics Data System (ADS)

    Ingersoll, Andrew P.; Porco, C. C.; Helfenstein, P.; West, R. A.; Cassini ISS Team

    2006-09-01

    The gases in the plumes include H2O, CO2, N2, CH4, and possibly other hydrocarbons, according to the INMS team. The solid particles in the plumes are probably water ice, but the identification is less certain than for the gaseous components. The plumes emanate from warm cracks in the surface near the south pole. The gas has a scale height of 80 km, according to the UVIS team, and the particles have a scale height of 30 km, according to the ISS team. By integrating across the plumes in their images, the ISS team was able to infer the upward flux of particles vs. altitude. Close to the surface, the falloff of density with altitude is much steeper than that of an escaping atmosphere in which both the particles and the gas are moving upward with the thermal velocity of the gas. Thus some of the particles are falling back to the surface and some are escaping. The larger scale height of the gas implies that the escaping fraction is greater for the gas. I will present models that attempt to explain these plume data. The density of the gas and the size of the particles determine the degree of dynamical coupling between gas and particles. There are three models - a sublimating gas that picks up particles as it leaves the surface; sublimating gas that forms particles in flight as the pressure decreases; a boiling liquid that freezes by evaporative cooling as the pressure decreases. Each model has its own range of mass flux, density, particle size, and scale height for both gas and liquid. I will discuss the implications of the observations and models regarding the possibility of liquid water near the surface.

  13. Controlled-release fertilizer composition substantially coated with an impermeable layer

    SciTech Connect

    Ankeny, Mark

    2016-03-29

    A controlled-release fertilizer composition is provided that is substantially coated with an impermeable layer. The fertilizer composition may further include one or more hollow sections to allow for root penetration and efficient delivery of nutrients.

  14. Ground-based analysis of volcanic ash plumes using a new multispectral thermal infrared camera approach

    NASA Astrophysics Data System (ADS)

    Williams, D.; Ramsey, M. S.

    2015-12-01

    Volcanic plumes are complex mixtures of mineral, lithic and glass fragments of varying size, together with multiple gas species. These plumes vary in size dependent on a number of factors, including vent diameter, magma composition and the quantity of volatiles within a melt. However, determining the chemical and mineralogical properties of a volcanic plume immediately after an eruption is a great challenge. Thermal infrared (TIR) satellite remote sensing of these plumes is routinely used to calculate the volcanic ash particle size variations and sulfur dioxide concentration. These analyses are commonly performed using high temporal, low spatial resolution satellites, which can only reveal large scale trends. What is lacking is a high spatial resolution study specifically of the properties of the proximal plumes. Using the emissive properties of volcanic ash, a new method has been developed to determine the plume's particle size and petrology in spaceborne and ground-based TIR data. A multispectral adaptation of a FLIR TIR camera has been developed that simulates the TIR channels found on several current orbital instruments. Using this instrument, data of volcanic plumes from Fuego and Santiaguito volcanoes in Guatemala were recently obtained Preliminary results indicate that the camera is capable of detecting silicate absorption features in the emissivity spectra over the TIR wavelength range, which can be linked to both mineral chemistry and particle size. It is hoped that this technique can be expanded to isolate different volcanic species within a plume, validate the orbital data, and ultimately to use the results to better inform eruption dynamics modelling.

  15. Recycled gabbro signature in hotspot magmas unveiled by plume-ridge interactions

    NASA Astrophysics Data System (ADS)

    Stroncik, N. A.; Devey, C. W.

    2011-06-01

    Lavas erupted within plate interiors above upwelling mantle plumes have chemical signatures that are distinct from mid-ocean ridge lavas. When a plume interacts with a mid-ocean ridge, the compositions of both their lavas changes, but there is no consensus as to how this interaction occurs. For the past 15Myr, the Pacific-Antarctic mid-ocean ridge has been approaching the Foundation hotspot and erupted lavas have formed seamounts. Here we analyse the noble gas isotope and trace element signature of lava samples collected from the seamounts. We find that both intraplate and on-axis lavas have noble gas isotope signatures consistent with the contribution from a primitive plume source. In contrast, near-axis lavas show no primitive noble gas isotope signatures, but are enriched in strontium and lead, indicative of subducted former oceanic lower crust melting within the plume source. We propose that, in a near-ridge setting, primitive, plume-sourced magmas formed deep in the plume are preferentially channelled to and erupted at the ridge-axis. The remaining residue continues to rise and melt, forming the near-axis seamounts. With the deep melts removed, the geochemical signature of subduction contained within the residue becomes apparent. Lavas with strontium and lead enrichments are found worldwide where plumes meet mid-ocean ridges, suggesting that subducted lower crust is an important but previously unrecognised plume component.

  16. Photogrammetric and photometric investigation of a smoke plume viewed from space.

    NASA Technical Reports Server (NTRS)

    Randerson, D.; Garcia, J. G.; Whitehead, V. S.

    1971-01-01

    Use of detailed analyses of an Apollo 6 stereographic photograph of a smoke plume which originated in southern Arizona and crossed over into Mexico to illustrate how high-resolution photography can aid meteorologists in evaluating specific air pollution events. Photogrammetric analysis of the visible smoke plume revealed that the plume was 8.06 miles long and attained a maximum width of 4000 ft, 3.0 miles from the 570-ft chimney emitting the effluent. Stereometric analysis showed that the visible top of the plume rose nearly 2400 ft above stack top, attaining 90% of this total rise 1.75 miles downwind from the source. Photometric analysis of the plume revealed a field of plume optical density that portrayed leptokurtic and bimodal distributions rather than a true Gaussian distribution. A horizontal eddy diffusivity of about 650,000 sq cm/sec and a vertical eddy diffusivity of 230,000 sq cm/sec were determined from the plume dimensions. Neutron activation analysis of plume samples revealed the elemental composition of the smoke to be copper, arsenic, selenium, indium and antimony, with trace amounts of vanadium and scandium.

  17. Photogrammetric and photometric investigation of a smoke plume viewed from space.

    NASA Technical Reports Server (NTRS)

    Randerson, D.; Garcia, J. G.; Whitehead, V. S.

    1971-01-01

    Use of detailed analyses of an Apollo 6 stereographic photograph of a smoke plume which originated in southern Arizona and crossed over into Mexico to illustrate how high-resolution photography can aid meteorologists in evaluating specific air pollution events. Photogrammetric analysis of the visible smoke plume revealed that the plume was 8.06 miles long and attained a maximum width of 4000 ft, 3.0 miles from the 570-ft chimney emitting the effluent. Stereometric analysis showed that the visible top of the plume rose nearly 2400 ft above stack top, attaining 90% of this total rise 1.75 miles downwind from the source. Photometric analysis of the plume revealed a field of plume optical density that portrayed leptokurtic and bimodal distributions rather than a true Gaussian distribution. A horizontal eddy diffusivity of about 650,000 sq cm/sec and a vertical eddy diffusivity of 230,000 sq cm/sec were determined from the plume dimensions. Neutron activation analysis of plume samples revealed the elemental composition of the smoke to be copper, arsenic, selenium, indium and antimony, with trace amounts of vanadium and scandium.

  18. Hydrothermal plume particles and dissolved phosphate over the superfast-spreading southern East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Feely, R. A.; Baker, E. T.; Marumo, K.; Urabe, T.; Ishibashi, J.; Gendron, J.; Lebon, G. T.; Okamura, K.

    1996-07-01

    The distribution and elemental composition of hydrothermal plume particles were mapped along the superfast spreading southern East Pacific Rise from the Garret Transform Fault to ˜19°S. Hydrographic and optical data were obtained using a series of seven tow-yos and thirty vertical casts employing a rosette sampler with 19-L PVC bottles for collecting discrete samples of various dissolved and particulate hydrothermal species. The extent of hydrothermal plume coverage over the southern East Pacific Rise between 13°33' and 18°40'S is significantly greater than in other ridgecrest systems. The region south of 17°20'S is characterized by significant enrichments of volatile gases resulting from magmatic input of fresh lava at the seafloor. Between 17°20' and 18°40'S, the ratio of S/Fe in the plume particles is highly correlated with the dissolved gases in the neutrally-buoyant hydrothermal plumes. Plume inventories of Fe and S over this portion of the southern East Pacific Rise are 6-150 times higher than what has been observed over other vent fields because the total abundance of plumes is much greater. In addition, significant depletions (> 100 nmol/L) of dissolved phosphate over the ridge axis were observed at the depth of the hydrothermal plumes. These results provide clear evidence that this section of the southern East Pacific Rise maintains the most extensive complex of hydrothermal plumes observed thus far on the global ridgecrest system.

  19. A new method for GPS-based wind speed determinations during airborne volcanic plume measurements

    USGS Publications Warehouse

    Doukas, Michael P.

    2002-01-01

    locations on the ground. Most FTIR studies to date measure only gas compositions or ratios of gas species (Love and others, 1998; Francis and others, 1998; Horrocks and others, 1999). What all of these methods have in common, however, is the necessity to know plume velocities if accurate gas emission rates are to be calculated. Even open-path FTIR studies done in tandem with a COSPEC require knowledge of plume velocity in order to compute emission rates.

  20. Factors Controlling Stress Rupture of Fiber-Reinforced Ceramic Composites

    NASA Technical Reports Server (NTRS)

    DiCarlo, J. A.; Yun, H. M.

    1999-01-01

    The successful application of fiber-reinforced ceramic matrix composites (CMC) depends strongly on maximizing material rupture life over a wide range of temperatures and applied stresses. The objective of this paper is to examine the various intrinsic and extrinsic factors that control the high-temperature stress rupture of CMC for stresses below and above those required for cracking of the 0 C plies (Regions I and II, respectively). Using creep-rupture results for a variety of ceramic fibers and rupture data for CMC reinforced by these fibers, it is shown that in those cases where the matrix carries little structural load, CMC rupture conditions can be predicted very well from the fiber behavior measured under the appropriate test environment. As such, one can then examine the intrinsic characteristics of the fibers in order to develop design guidelines for selecting fibers and fiber microstructures in order to maximize CMC rupture life. For those cases where the fiber interfacial coatings are unstable in the test environment, CMC lives are generally worse than those predicted by fiber behavior alone. For those cases where the matrix can support structural load, CMC life can even be greater provided matrix creep behavior is properly controlled. Thus the achievement of long CMC rupture life requires understanding and optimizing the behavior of all constituents in the proper manner.

  1. Appearance and water quality of turbidity plumes produced by dredging in Tampa Bay, Florida

    USGS Publications Warehouse

    Goodwin, Carl R.; Michaelis, D.M.

    1984-01-01

    Turbidity plumes in Tampa Bay, Florida, produced during ship-channel dredging operations from February 1977 to August 1978, were monitored in order to document plume appearance and water quality, evaluate plume influence on the characteristics of Tampa Bay water, and provide a data base for comparison with other areas that have similar sediment, dredge, placement, containment, and tide conditions. The plumes investigated originated from the operation of one hopper dredge and three cutterhead-pipeline dredges. Composition of bottom sediment was found to vary from 85 percent sand and shell fragments to 60 percent silt and clay. Placement methods for dredged sediment included beach nourishment, stationary submerged discharge, oscillating surface discharge, and construction of emergent dikes. Tidal currents ranged from slack water to flow velocities of 0.60 meter per second. Plumes were monitored simultaneously by (1) oblique and vertical 35-millimeter aerial photography and (2) water-quality sampling to determine water clarity and concentrations of nutrients, metals, pesticides, and industrial compounds. Forty-nine photographs depict plumes ranging in length from a few tens of meters to several kilometers and ranging in turbidity level from <10 to 200,000 nephelometric turbidity units. The most visible turbidity plumes were produced by surface discharge of material with high sand content into unconfined placement areas during times of strong tidal currents. The least visible turbidity plumes were produced by discharge of material with high silt and clay content into areas enclosed by floating turbidity barriers during times of weak tidal currents. Beach nourishment from hopper-dredge unloading operations also produced plumes of low visibility. Primary turbidity plumes were produced directly by dredging and placement operations; secondary plumes were produced indirectly by resuspension of previously deposited material. Secondary plumes were formed both by erosion, in

  2. Liquid Booster Module (LBM) plume flowfield model

    NASA Technical Reports Server (NTRS)

    Smith, S. D.

    1981-01-01

    A complete definition of the LBM plume is important for many Shuttle design criteria. The exhaust plume shape has a significant effect on the vehicle base pressure. The LBM definition is also important to the Shuttle base heating, aerodynamics and the influence of the exhaust plume on the launch stand and environment. For these reasons a knowledge of the LBM plume characteristics is necessary. A definition of the sea level LBM plume as well as at several points along the Shuttle trajectory to LBM, burnout is presented.

  3. Turbulent forces within river plumes affect spread

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-08-01

    When rivers drain into oceans through narrow mouths, hydraulic forces squeeze the river water into buoyant plumes that are clearly visible in satellite images. Worldwide, river plumes not only disperse freshwater, sediments, and nutrients but also spread pollutants and organisms from estuaries into the open ocean. In the United States, the Columbia River—the largest river by volume draining into the Pacific Ocean from North America—generates a plume at its mouth that transports juvenile salmon and other fish into the ocean. Clearly, the behavior and spread of river plumes, such as the Columbia River plume, affect the nation's fishing industry as well as the global economy.

  4. Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFRC Focused on Hanford’s 300 Area Uranium Plume January 2011 to January 2012

    SciTech Connect

    Zachara, John M.; Bjornstad, Bruce N.; Christensen, John N.; Conrad, Mark S.; Fredrickson, Jim K.; Freshley, Mark D.; Haggerty, Roy; Hammond, Glenn E.; Kent, Douglas B.; Konopka, Allan; Lichtner, Peter C.; Liu, Chongxuan; McKinley, James P.; Murray, Christopher J.; Rockhold, Mark L.; Rubin, Yoram; Vermeul, Vincent R.; Versteeg, Roelof J.; Zheng, Chunmiao

    2012-03-05

    The Integrated Field Research Challenge (IFRC) at the Hanford Site 300 Area uranium (U) plume addresses multi-scale mass transfer processes in a complex subsurface biogeochemical setting where groundwater and riverwater interact. A series of forefront science questions on reactive mass transfer motivates research. These questions relate to the effect of spatial heterogeneities; the importance of scale; coupled interactions between biogeochemical, hydrologic, and mass transfer processes; and measurements and approaches needed to characterize and model a mass-transfer dominated biogeochemical system. The project was initiated in February 2007, with CY 2007, CY 2008, CY 2009, and CY 2010 progress summarized in preceding reports. A project peer review was held in March 2010, and the IFRC project acted upon all suggestions and recommendations made in consequence by reviewers and SBR/DOE. These responses have included the development of 'Modeling' and 'Well-Field Mitigation' plans that are now posted on the Hanford IFRC web-site, and modifications to the IFRC well-field completed in CY 2011. The site has 35 instrumented wells, and an extensive monitoring system. It includes a deep borehole for microbiologic and biogeochemical research that sampled the entire thickness of the unconfined 300 A aquifer. Significant, impactful progress has been made in CY 2011 including: (i) well modifications to eliminate well-bore flows, (ii) hydrologic testing of the modified well-field and upper aquifer, (iii) geophysical monitoring of winter precipitation infiltration through the U-contaminated vadose zone and spring river water intrusion to the IFRC, (iv) injection experimentation to probe the lower vadose zone and to evaluate the transport behavior of high U concentrations, (v) extended passive monitoring during the period of water table rise and fall, and (vi) collaborative down-hole experimentation with the PNNL SFA on the biogeochemistry of the 300 A Hanford-Ringold contact and the

  5. Carbon Dioxide Sealing Capacity: Textural or Compositional Controls?

    SciTech Connect

    Cranganu, Constantin; Soleymani, Hamidreza; Sadiqua, Soleymani; Watson, Kieva

    2013-11-30

    This research project is aiming to assess the carbon dioxide sealing capacity of most common seal-rocks, such as shales and non-fractured limestones, by analyzing the role of textural and compositional parameters of those rocks. We hypothesize that sealing capacity is controlled by textural and/or compositional pa-rameters of caprocks. In this research, we seek to evaluate the importance of textural and compositional parameters affecting the sealing capacity of caprocks. The conceptu-al framework involves two testable end-member hypotheses concerning the sealing ca-pacity of carbon dioxide reservoir caprocks. Better understanding of the elements controlling sealing quality will advance our knowledge regarding the sealing capacity of shales and carbonates. Due to relatively low permeability, shale and non-fractured carbonate units are considered relatively imper-meable formations which can retard reservoir fluid flow by forming high capillary pres-sure. Similarly, these unites can constitute reliable seals for carbon dioxide capture and sequestration purposes. This project is a part of the comprehensive project with the final aim of studying the caprock sealing properties and the relationship between microscopic and macroscopic characteristics of seal rocks in depleted gas fields of Oklahoma Pan-handle. Through this study we examined various seal rock characteristics to infer about their respective effects on sealing capacity in special case of replacing reservoir fluid with super critical carbon dioxide (scCO{sub 2}). To assess the effect of textural and compositional properties on scCO{sub 2} maximum reten-tion column height we collected 30 representative core samples in caprock formations in three counties (Cimarron, Texas, Beaver) in Oklahoma Panhandle. Core samples were collected from various seal formations (e.g., Cherokee, Keys, Morrowan) at different depths. We studied the compositional and textural properties of the core samples using several techniques

  6. The size of plume heterogeneities constrained by Marquesas isotopic stripes

    NASA Astrophysics Data System (ADS)

    Chauvel, Catherine; Maury, René C.; Blais, Sylvain; Lewin, Eric; Guillou, Hervé; Guille, GéRard; Rossi, Philippe; Gutscher, Marc-André

    2012-07-01

    The scale and geometry of chemical and isotopic heterogeneities in the source of plumes have important scientific implications on the nature, composition and origin of plumes and on the dynamics of mantle mixing over time. Here, we address these issues through the study of Marquesas Islands, one of the Archipelagoes in Polynesia. We present new Sr, Nd, Pb, Hf isotopes as well as trace element data on lavas from several Marquesas Islands and demonstrate that this archipelago consists of two adjacent and distinct rows of islands with significantly different isotopic compositions. For the entire 5.5 Ma construction period, the northern islands, hereafter called the Ua Huka group, has had systematically higher 87Sr/86Sr and lower 206Pb/204Pb ratios than the southern Fatu Hiva group at any given 143Nd/144Nd value. The shape and curvature of mixing arrays preclude the ambient depleted MORB mantle as one of the mixing end-members. We believe therefore that the entire isotopic heterogeneity originates in the plume itself. We suggest that the two Marquesas isotopic stripes originate from partial melting of two adjacent filaments contained in small plumes or "plumelets" that came from a large dome structure located deep in the mantle under Polynesia. Low-degree partial melting under Marquesas and other "weak" Polynesian hot spot chains (Pitcairn-Gambier, Austral-Cook, Society) sample small areas of the dome and preserve source heterogeneities. In contrast, more productive hot spots build up large islands such as Big Island in Hawaii or Réunion Island, and the higher degrees of melting blur the isotopic variability of the plume source.

  7. Iodine Plasma Species Measurements in a Hall Effect Thruster Plume

    DTIC Science & Technology

    2013-05-01

    divergence than Xe • High density – Stores at 2-3 times density of Xe – Modest heating to generate gas (sublimation) • Low feed system pressure – Tank ...point for Xe – 30 degrees encloses 86% of Xenon plume, 90% of Iodine plume • Tank pressure always lower with iodine Iodine 500 V, 2 A -90 -60 -30 0 30... pressure is 1000 times lower than Xe • Passive long term storage – I2 stores in the solid phase – No temperature control for inactive system • Low cost

  8. Teaching the Mantle Plumes Debate

    NASA Astrophysics Data System (ADS)

    Foulger, G. R.

    2010-12-01

    There is an ongoing debate regarding whether or not mantle plumes exist. This debate has highlighted a number of issues regarding how Earth science is currently practised, and how this feeds into approaches toward teaching students. The plume model is an hypothesis, not a proven fact. And yet many researchers assume a priori that plumes exist. This assumption feeds into teaching. That the plume model is unproven, and that many practising researchers are skeptical, may be at best only mentioned in passing to students, with most teachers assuming that plumes are proven to exist. There is typically little emphasis, in particular in undergraduate teaching, that the origin of melting anomalies is currently uncertain and that scientists do not know all the answers. Little encouragement is given to students to become involved in the debate and to consider the pros and cons for themselves. Typically teachers take the approach that “an answer” (or even “the answer”) must be taught to students. Such a pedagogic approach misses an excellent opportunity to allow students to participate in an important ongoing debate in Earth sciences. It also misses the opportunity to illustrate to students several critical aspects regarding correct application of the scientific method. The scientific method involves attempting to disprove hypotheses, not to prove them. A priori assumptions should be kept uppermost in mind and reconsidered at all stages. Multiple working hypotheses should be entertained. The predictions of a hypothesis should be tested, and unpredicted observations taken as weakening the original hypothesis. Hypotheses should not be endlessly adapted to fit unexpected observations. The difficulty with pedagogic treatment of the mantle plumes debate highlights a general uncertainty about how to teach issues in Earth science that are not yet resolved with certainty. It also represents a missed opportunity to let students experience how scientific theories evolve, warts

  9. Anatomy of mantle plumes: hot heads and cold stems

    NASA Astrophysics Data System (ADS)

    Davaille, A. B.; Kumagai, I.; Vatteville, J.; Touitou, F.; Brandeis, G.

    2012-12-01

    Recent petrological studies show evidences for secular cooling in mantle plumes: the source temperature of oceanic plateaus could be 100°C hotter than the source temperature of volcanic island chains (Herzberg and Gazel, Nature, 2009). In terms of mantle plumes, it would mean that the temperature of the plume head is hotter than that of the plume stem. This is at odd with a model where a plume head would entrain so much ambient mantle on its journey towards the Earth's surface that it would end up being considerably colder than its narrow stem. So we revisited the problem using laboratory experiments and new visualization techniques to measure in situ simultaneously the temperature, velocity and composition fields. At time t=0, a hot instability is created by heating a patch of a given radius at constant power or constant temperature. The fluids are mixtures of sugar syrups , with a strongly temperature-dependent viscosity, and salt. Rayleigh numbers were varied from 104 to 108, viscosity ratios between 1.8 and 4000, and buoyancy ratios between 0 and 2. After a stage where heat transport is by conduction only, the hot fluid gathers in a sphere and begins to rise, followed by a stem anchored on the hot patch. In all cases, temperatures in the head start with higher values than in the subsequent stem. This is also the case for the thermal instabilities rising from a infinite plate heated uniformly. However, the head also cools faster than the stem as they rise, so that they will eventually have the same temperature if the mantle is deep enough. Moreover, all the material sampled by partial melting in the plume head or stem would be coming from the heated area around the deep source, and very little entrainment from the ambient mantle is predicted. The difference in temperature between head and stem strongly depends on the mantle depth, the viscosity ratio and the buoyancy ratio. Our scaling laws predict that Earth's mantle plumes can indeed have hot heads and colder

  10. Plasma plume MHD power generator and method

    DOEpatents

    Hammer, James H.

    1993-01-01

    Highly-conducting plasma plumes are ejected across the interplanetary magnetic field from a situs that is moving relative to the solar wind, such as a spacecraft or an astral body, such as the moon, having no magnetosphere that excludes the solar wind. Discrete plasma plumes are generated by plasma guns at the situs extending in opposite directions to one another and at an angle, preferably orthogonal, to the magnetic field direction of the solar wind plasma. The opposed plumes are separately electrically connected to their source by a low impedance connection. The relative movement between the plasma plumes and the solar wind plasma creates a voltage drop across the plumes which is tapped by placing the desired electrical load between the electrical connections of the plumes to their sources. A portion of the energy produced may be used in generating the plasma plumes for sustained operation.

  11. Aerodynamic interactions with turbulent jet exhaust plumes

    NASA Technical Reports Server (NTRS)

    Wilmoth, R. G.

    1982-01-01

    The importance of aerodynamic interactions associated with external flow-field effects on turbulent jet exhaust plume structure is discussed. A viscous/inviscid prediction technique is presented which combines the overlaid mixing and inviscid plume components of the JANNAF Standardized Plume Flow-Field (SPF) model with inviscid external flow and boundary-layer analyses for treating nozzle afterbodies at subsonic/transonic speeds. Validation of the technique via comparisons between predictions and experiment for cold-air jet plumes is presented. Predicted spatial temperature distributions for hot, nonafterburning plumes are presented and compared to results obtained from more simplified prediction techniques in order to assess the importance of the aerodynamic interactions associated with external boundary layers and pressure gradients. It is demonstrated that these interactions play a significant role in determining the near-field turbulent mixing and inviscid plume shock structure. The implication of these results to plume radiation predictions is discussed.

  12. Plume capture by a migrating ridge: Analog geodynamic experiments

    NASA Astrophysics Data System (ADS)

    Mendez, J. S.; Hall, P.

    2010-12-01

    Paleomagnetic data from the Hawaii-Emperor Seamount Chain (HESC) suggests that the Hawaiian hotspot moved rapidly (~40 mm/yr) between 81 - 47 Ma but has remained relatively stationary since that time. This implies that the iconic bend in the HESC may in fact reflect the transition from a period of rapid hotspot motion to a stationary state, rather than a change in motion of the Pacific plate. Tarduno et al. (2009) have suggested that this period of rapid hotspot motion might be the surface expression of a plume conduit returning to a largely vertical orientation after having been “captured” and tilted by a migrating mid-ocean ridge. We report on a series of analog fluid dynamic experiments designed to characterize the interaction between a migrating spreading center and a thermally buoyant mantle plume. Experiments were conducted in a clear acrylic tank (100 cm x 70 cm x 50 cm) filled with commercial grade high-fructose corn syrup. Plate-driven flow is modeled by dragging two sheets of Mylar film (driven by independent DC motors) in opposite directions over the surface of the fluid. Ridge migration is achieved by moving the point at which the mylar sheets diverge using a separate motor drive. Buoyant plume flow is modeled using corn syrup introduced into the bottom of the tank from an external, heated, pressurized reservoir. Small (~2 mm diameter), neutrally buoyant Delrin spheres are mixed into reservoir of plume material to aid in visualization. Plate velocities and ridge migration rate are controlled and plume temperature monitored using LabView software. Experiments are recorded using digital video which is then analyzed using digital image analysis software to track the position and shape of the plume conduit throughout the course of the experiment. The intersection of the plume conduit with the surface of the fluid is taken as an analog for the locus of hotspot volcanism and tracked as a function of time to obtain a hotspot migration rate. Experiments are

  13. Understanding Plume Bending at Grotto Vent on the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Xu, G.; Rabinowitz, J.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

    2011-12-01

    Our improved understanding of black smoker plume bending derives from acoustic imaging of the plume at Grotto, a 30 m diameter vent cluster in the Main Endeavour Field, Juan de Fuca Ridge. In July 2000, the VIP2000 cruise collected 15 acoustic images over 24 hours. In September 2010, the Cabled Observatory Vent Imaging Sonar (COVIS) was connected to the NEPTUNE Canada Endeavour Observatory and acquired a 29 day time series capturing plume bending in 479 independent images. Inclination and declination are extracted for one or more plumes from the acoustic images using 2D Gaussian fitting. The bending of the large plume above the northwest end of Grotto is consistent with a dominant tidal sloshing and secondary rift valley inflow based a spectral analysis of the COVIS time series compared with a spectral analysis of current data from 2.9 km north of Grotto. The smaller plume above the eastern end of Grotto behaves in a more complicated fashion as it sometimes bends towards the larger plume. The overall shape of the larger plume is highly variable: sometimes the plume just leans in the direction of the presumed ambient current; other times, the plume bends-over and, in a few cases, the plume bends in two or more directions (forming a sinusoidal shape). Several factors influence bending direction, magnitude and shape. First, for a fluctuating plume, the instantaneous plume centerline wiggles around within the time-averaged plume boundaries; this will certainly produce a "sinusoidal" shape and may be the best explanation for the small scale multi-directional bending observed in individual acoustic images. Second, the transition from jet to plume could produce a change in bending magnitude (but not direction); however, this is unlikely to be visible on the acoustic images a