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Sample records for p-to-s mantle converted

  1. Three-dimensional, prestack, plane wave migration of teleseismic P-to-S converted phases: 2. Stacking multiple events

    Science.gov (United States)

    Poppeliers, Christian; Pavlis, Gary L.

    2003-05-01

    In part 1 we developed the theoretical foundations of a prestack migration procedure to image forward scattered P to S (PdS) converted waves in the coda of teleseismic P waves. This paper addresses the issue of how to optimally stack data from multiple events migrated by this procedure. We apply matrix perturbation theory to develop an objective way to quantify noise in deconvolved PdS data. Application of the theory demonstrates that an optimal stack requires weighting the migrated data from each event by a signal-to-noise ratio criterion. We also find that the migrated PdS images have to be binned by back azimuth and balanced prior to the final stack. This is necessary to mitigate coherent noise that results from aliased microseism noise that is enhanced by our processing method. We processed 23 events recorded by the Lodore array in northwestern Colorado with our procedure. The results indicate the presence of a major, lithospheric scale discontinuity defined by a south dipping boundary within the crust that we interpret as the subsurface expression of the Cheyenne Belt. The suture is also marked by a transition in crustal thickness from 35 km on the Archean side to over 40 km on the Colorado Plateau side. We also observe a strong difference in the lithospheric mantle PdS conversion signature on opposite sides of the suture that suggests delamination and northward convergence of the Colorado lithosphere beneath the Wyoming province.

  2. Prestack planewave migration of teleseismic P-to-S converted phases

    Science.gov (United States)

    Poppeliers, Christian John

    This research presents a new prestack migration technique to image the Earth with forward scattered teleseismic P-to-S converted phases (receiver functions). The method builds on the pseudostation stacking technique presented by Neal and Pavlis [1999 and a planewave decomposition-based migration technique introduced by Treitel et al. [1982]. We apply this procedure to dozens of teleseismic earthquakes recorded by the Lodore array in northwestern Colorado, which was deployed to image the subsurface structure of the Cheyenne belt. The Cheyenne belt has been interpreted as the surface expression of a suture zone between the Archean-age Wyoming province and the Proterozoic-age Colorado Plateau. The end result of applying planewave migration to many events recorded by the Lodore array is that we obtain a high resolution image which suggests the presence of a major, lithospheric scale discontinuity between the Wyoming province and the Colorado Plateau. The imaged discontinuity extends to a depth of at least 90km, which is the maximum depth that we can image with the Lodore array. Additionally, we apply planewave migration to approximately one dozen teleseismic earthquakes recorded by a large array in the Tien Shan mountains (Asia) to image a major suture zone there. Based the two different datasets provided by the Lodore array and the Tien Shan array, we suggest that scars from continental sutures extend to depths greater than 200 km and remain as distinct features for hundreds of millions of years. In a separate study, we analyze data from 35 three-component seismic recording instruments deployed in a 5 x 7 grid over a steep slope. The array was deployed to record to site response of the steep slope and recorded ten underwater explosions detonated in a lake which was adjacent to the slope. The explosions were approximately 800 meters from the array. We found that the slope crest had a local acceleration approximately twice that of the surrounding flat ground

  3. Three-dimensional, prestack, plane wave migration of teleseismic P-to-S converted phases: 1. Theory

    Science.gov (United States)

    Poppeliers, Christian; Pavlis, Gary L.

    2003-02-01

    We present the theoretical foundations for a prestack migration technique to image teleseismic P-to-S converted phases. The method builds on teleseismic P wave deconvolution, pseudostation stacking [, 1999] and on the idea of using a plane wave decomposition for imaging as introduced by [1982]. Deconvolution operators are constructed by pseudostation stacking of the array aligned to the incident P wave arrival times to produce a space-variable deconvolution operator. The resulting data are then muted to remove the deconvolved direct P wave pulse and pseudostation stacked over a grid of feasible slowness vectors. The pseudostation stack interpolates the wave field onto a regular grid along Earth's surface producing a series (one per slowness vector) of uniformly sampled three-dimensional data cubes (two space variables and time). The plane wave components can be propagated downward using a form of approximate ray tracing with a three-dimensional Earth model. This yields a series of distorted cubes topologically equivalent to the original uniformly sampled data cubes. These data volumes are summed as a weighted stack with the weights derived from an integration formula for inverse scattering based on the generalized Radon transform. This allows an image of the subsurface to be constructed on an event by event basis beneath the array. We apply this technique to data from the Lodore array that was deployed in northwestern Colorado. The results suggest the presence of a major lithospheric-scale discontinuity defined by a south dipping boundary.

  4. Searching for structure in the mid-mantle: Observations of converted phases beneath Iceland and Europe

    Science.gov (United States)

    Jenkins, J.; Deuss, A. F.; Cottaar, S.

    2016-12-01

    Until recently, most of the lower mantle was considered to be well-mixed with strong heterogeneity restricted to the lowermost several hundred kilometers above the core-mantle boundary, also known as the D'' layer. However, several recent studies have started to hint at a potential change in earth structure at mid-mantle depths, with evidence from both seismic tomography (Fukao and Obayashi 2013, French and Romanowichz, 2015) and global viscosity structure (Rudolph et al., 2015). We present the first continental-wide search for mid-mantle P to S wave converted phases and find most observations come from approximately 1000 km depth beneath Iceland and Western Europe. Conversions are identified using a data set of 50,000 high quality receiver functions which are systematically searched for robust signals from the mid-mantle. Potential P to s conversions are analysed in terms of slowness to determine whether they are true observations from depth or simply surface multiples arriving at similar times. We find broad regions with robust signals from approximately 1000 km depth in several locations; beneath Iceland and across Western Europe, beneath Ireland, Scotland, Eifel and south towards NW Italy and Spain. Similar observations have previously been observed mainly in subduction zone settings, and have been hypothesised to be caused by down-going oceanic crustal material. Here we present observations which correlate with slow seismic velocities in recent tomographic models (Rickers et al., (2013); French and Romanowicz, (2015)). These low velocities appear to be a channel deviating from the broad mantle plume beneath Iceland at mid-mantle depths. We hypothesise that the mid-mantle seismic signals we observe are caused by either a phase transition occurring locally in a specific composition or by small-scale chemical heterogeneities swept along with upwelling material and ponding around 1000 km.

  5. Converted phases from sharp 1000 km depth mid-mantle heterogeneity beneath Western Europe

    Science.gov (United States)

    Jenkins, J.; Deuss, A.; Cottaar, S.

    2017-02-01

    Until recently, most of the lower mantle was generally considered to be well-mixed with strong heterogeneity restricted to the lowermost several hundred kilometres above the core-mantle boundary, known as the D″ layer. However several recent studies have started to hint at a potential change in Earth's structure at mid-mantle depths beneath the transition zone. Here we present a continental-wide search of Europe and the North Atlantic for mid-mantle P-to-s wave converted phases. Our data set consists of close to 50,000 high quality receiver functions. These are combined in slowness and depth stacks to identify seismic discontinuities in the range of 800-1400 km depth to determine at which depths and in which tectonic settings these features exist. Receiver functions are computed in different frequency bands to resolve the sharpness of the observed discontinuities. We find most seismic velocity jumps are observed between 975-1050 km depth, localised beneath western Europe and Iceland. The shear wave velocity jumps are roughly 1-2.5% velocity increase with depth occurring over less than 8 km in width. The most robust observations are coincident with areas of active upwelling (under Iceland) and an elongate lateral low velocity anomaly imaged in recent tomographic models which has been interpreted as diverted plume material at depth. The lack of any suggested phase change in a normal pyrolitic mantle composition at around 1000 km depth indicates the presence of regional chemical heterogeneity within the mid-mantle, potentially caused by diverted plume material. We hypothesise that our observations represent either a phase change within chemically distinct plume material itself, or are caused by small scale chemical heterogeneities entrained within the upwelling plume, either in the form of recycled basaltic material or deep sourced chemically distinct material from LLSVPs. Our observations, which cannot be directly linked to an area of either active or ancient

  6. Imaging P-to-S conversions with multichannel receiver functions

    Science.gov (United States)

    Neal, Scott L.; Pavlis, Gary L.

    We present a new methodology in the direct imaging of P-to-S converted phases recorded on broadband seismic arrays. Our approach is based on conventional three-component array processing and receiver function techniques with the key addition of a weighted stack based on an aerial smoothing function. This creates synthetic arrays with a specified aperture whose image points vary continuously across the array. With this approach, it is possible to interpolate data from an array of broadband stations onto an arbitrarily fine grid. We have applied this technique to a single deep event recorded by the Lodore broadband array, located in northern Colorado and southern Wyoming. The resulting images show distinct differences in crustal structure across the array, and also image major upper mantle discontinuities.

  7. Three-dimensional Kirchhoff-approximate generalized Radon transform imaging using teleseismic P-to-S scattered waves

    Science.gov (United States)

    Liu, Kaijian; Levander, Alan

    2013-03-01

    Teleseismic imaging techniques utilizing mode converted/scattered waves are gaining importance due to the deployment of increasingly dense broad-band seismograph arrays. Although common-conversion point (CCP) stacking is widely used to determine structure from Ps or Sp scattered wavefields isolated by receiver function (RF) processing, this method is limited due to its assumption of a layered medium: Dipping events and diffractions are not treated correctly. As an extension of previous 2-D generalized Radon transform (GRT) imaging methods, we present a 3-D Kirchhoff-approximate imaging technique to migrate scattered waves in 3-D. We first derive the 3-D migration formula for P-to-S conversions using the GRT solution to the linear inverse elastic wave scattering problem. Then we illustrate the Kirchhoff method using finite-difference synthetic seismograms from several 3-D models. Next, we apply the method to two portable broad-band array data sets in the western United States to image the Mendocino Triple Junction and the High Lava Plains (HLP) crust and uppermost mantle structures. From the HLP data, we construct the Ps transmission coefficient images with three-component Green's functions. The 1.0 and 0.5 Hz images show a continuous undulating Moho, as well as three negative upper-mantle events at 50-80 km depth. Compared to the CCP images, the Moho is more clearly imaged, particularly near 117.5°W-117.8°W at the western edge of the Owyhee Plateau. The three negative events in the upper mantle correlate well with the top of three low-Vs zones (-3 per cent contour) in the Rayleigh wave tomography model. The migrated Ps RF data from Mendocino clearly image the rapid decrease in depth of the lithosphere-asthenosphere boundary from ˜65 km beneath the subducting Gorda Plate to 30-50 km beneath the Coast Ranges slab window. The final image is consistent with, but has higher resolution than the Vs structure determined from joint receiver function/Rayleigh wave

  8. Oceanic mantle alteration in the trench-outer rise region of the Japan trench

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    Fujie, G.; Takahashi, T.; Kodaira, S.; Obana, K.; Yamada, T.

    2014-12-01

    Dehydration processes and the expulsion of the water from the subducting oceanic plate affect various subduction-zone processes, including arc volcanism and generation of earthquakes and tremor. Since the amount of chemically bound water in the oceanic plate is highest in serpentinized mantle, it is important to reveal the degree of oceanic mantle serpentinization prior to subduction.In 2009 and 2013, to reveal the structural evolution of the incoming oceanic plate prior to subduction, we conducted wide-angle seismic structural surveys in the trench-outer rise region of the Japan trench. We found P-wave velocity (Vp) within the oceanic crust and mantle gradually decreases toward the trench axis, especially beneath the well-developed horst and grabens. Generally, reduction of Vp suggests two possibilities; one is a fracturing (dry mechanism) and the other is fracturing and water penetration (wet mechanism). The Vp/Vs ratio is a key to distinguish these two possibilities. Using P-to-S converted phases, we successfully modeled Vs within the oceanic crust by the travel-time inversion, and we found the Vp/Vs ratio within the oceanic crust gradually increases toward the trench, suggesting the water infiltration into the oceanic crust. However, it is not straightforward to determine Vs within the oceanic mantle because signal-to-noise ratio of S-wave mantle refraction was too poor to pick arrival times. Therefore, we calculated S-wave mantle refractions by assuming wide variety of Vp/Vs ratio within the oceanic mantle and compared with the observed horizontal data. Although S-wave mantle refraction was observed at only limited number of OBSs, we found that Vp/Vs ratio within the oceanic mantle did not change even in the area where mantle Vp become lower. This implies that the mantle Vp reduction in our seismic profile is mainly governed by the "dry mechanism" or mantle hydration might be confined in only topmost mantle.

  9. Singular spectrum analysis and its applications in mapping mantle seismic structure

    Science.gov (United States)

    Dokht, Ramin M. H.; Gu, Yu Jeffrey; Sacchi, Mauricio D.

    2017-03-01

    Seismic discontinuities are fundamental to the understanding of mantle composition and dynamics. Their depths and impedance contrasts are generally determined using secondary phases such as SS precursors and P-to-S converted waves. However, analysing and interpreting these weak signals often suffer from incomplete data coverage, high noise levels and interfering seismic arrivals, especially near tectonically complex regions such as subduction zones. To overcome these pitfalls, we adopt a singular spectrum analysis (SSA) method to remove random noise, reconstruct missing traces and enhance the robustness of SS precursors and P-to-S conversions from mantle seismic discontinuities. Our method takes advantage of the predictability of time series in the frequency-space domain and performs rank reduction using a singular value decomposition of the trajectory matrix. We apply SSA to synthetic record sections as well as the observations of (1) SS precursors beneath the northwestern Pacific subduction zones, and (2) P-to-S converted waves from southwestern Canada. In comparison with raw or interpolated data, the SSA enhanced seismic sections exhibit greater resolution due to the suppression of random noise (which reduces signal amplitude during standard averaging procedures) through rank reduction. SSA also enables an effective separation of the SS precursors from the postcursors of S-wave core diffractions. This method will greatly benefit future analyses of weak crustal and mantle seismic phases, especially when data coverages are less than ideal.

  10. Mapping the Hawaiian plume conduit with converted seismic waves

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    Li; Kind; Priestley; Sobolev; Tilmann; Yuan; Weber

    2000-06-22

    The volcanic edifice of the Hawaiian islands and seamounts, as well as the surrounding area of shallow sea floor known as the Hawaiian swell, are believed to result from the passage of the oceanic lithosphere over a mantle hotspot. Although geochemical and gravity observations indicate the existence of a mantle thermal plume beneath Hawaii, no direct seismic evidence for such a plume in the upper mantle has yet been found. Here we present an analysis of compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations on the Hawaiian islands, that indicate a zone of very low shear-wave velocity (effects of the Hawaiian plume conduit in the asthenosphere and mantle transition zone with excess temperature of approximately 300 degrees C. Large variations in the transition-zone thickness suggest a lower-mantle origin of the Hawaiian plume similar to the Iceland plume, but our results indicate a 100 degrees C higher temperature for the Hawaiian plume.

  11. Seismic structure of the crust and upper mantle in central-eastern Greenland

    DEFF Research Database (Denmark)

    Kraft, Helene Anja

    on the very first regional passive seismic study in central-Eastern Greenland, focusing on the area between Scoresby Sund and Summit. The study aims to image the structure of subsurface Greenland starting from the crust and down to the mantle transition zone. Furthermore, the thesis links these observations...... with topographic features, the recent uplift history of the North Atlantic region, break-up related processes, and the possible track of the Iceland hotspot. The core of this study are P to S- and S to P- receiver functions, which image the difference in arrival time between not-converted and converted phases......Geophysical and geological knowledge of the interior of Greenland is very limited. The lack of knowledge arises mainly due to the logistical challenges related to conducting geophysical fieldwork on the up to 3400 m thick ice sheet, which covers around 80% of the land area. This PhD thesis is based...

  12. Mantle transition zone thickness in the Central South-American Subduction Zone

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    Braunmiller, Jochen; van der Lee, Suzan; Doermann, Lindsey

    We used receiver functions to determine lateral variations in mantle transition zone thickness and sharpness of the 410- and 660-km discontinuities in the presence of subducting lithosphere. The mantle beneath the central Andes of South America provides an ideal study site owing to its long-lived subduction history and the availability of broadband seismic data from the dense BANJO/SEDA temporary networks and the permanent station LPAZ. For LPAZ, we analyzed 26 earthquakes between 1993-2003 and stacked the depth-migrated receiver functions. For temporary stations operating for only about one year (1994-1995), station stacks were not robust. We thus stacked receiver functions for close-by stations forming five groups that span the subduction zone from west to east, each containing 12 to 25 events. We found signal significant at the 2σ level for several station groups from P to S conversions that originate near 520- and 850-900 km depth, but most prominently from the 410- and 660-km discontinuities. For the latter, the P to S converted signal is clear in stacks for western groups and LPAZ, lack of coherent signal for two eastern groups is possibly due to incoherent stacking and does not necessitate the absence of converted energy. The thickness of the mantle transition zone increases progressively from a near-normal 255 km at the Pacific coast to about 295 km beneath station LPAZ in the Eastern Cordillera. Beneath LPAZ, the 410-km discontinuity appears elevated by nearly 40 km, thus thickening the transition zone. We compared signal amplitudes from receiver function stacks calculated at different low-pass frequencies to study frequency dependence and possibly associated discontinuity sharpness of the P to S converted signals. We found that both the 410- and 660-km discontinuities exhibit amplitude increase with decreasing frequency. Synthetic receiver function calculations for discontinuity topography mimicking observed topography show that the observed steep

  13. Imaging P-to-S conversions with broad-band seismic arrays using multichannel time-domain deconvolution

    Science.gov (United States)

    Neal, Scott L.; Pavlis, Gary L.

    2001-09-01

    This paper describes a series of innovations in the problem of deconvolving forward scattered P-to-S conversions. We introduce a theoretical foundation for a recently developed multichannel stacking technique and show that this process is equivalent to a spatial convolution of the incident wavefield with the discretely sampled set of station locations. We then show that deconvolution of the stacked data is a form of multichannel deconvolution with a spatially variable set of weights equal to those used in stacking. This result is independent of the particular deconvolution method that is used. A second innovation focuses on the design of deconvolution operators that correctly account for the loss of high frequency components of P-to-S conversions caused by differential attenuation of P and S waves. We describe two complimentary methods to implement this: (1) through the use of a regularization operator that penalizes high frequencies and increases with P-to-S lag time, or (2) through the use of a quelling operator. For the latter, we introduce the use of a t* operator that is applied to the deconvolution matrix operator. The t* operator progressively filters the vertical component seismogram with increasing P-to-S lag time and is based on an earth model of body wave attenuation. Both techniques produce progressively smoother solutions for increasing P-to-S lag times. The quelling approach has two advantages: (1) it is based on the physical principle that this solution is designed to address, and (2) it provides a unified inversion framework for the combination of stacking and deconvolution. This combination may be interpreted as a three-dimensional quelling (smoothing) operator that is applied to the full wavefield to stabilize the inversion. Application of this procedure to synthetic data shows that while the addition of a time dependent component to the deconvolution tends to decrease the frequency content of the solution, the amplitude of background ringing is

  14. Mantle wedge dynamics from seismic anisotropy (Invited)

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    Long, M. D.; Wirth, E. A.

    2013-12-01

    The mantle wedge above subducting slabs plays a critical role in many of the physical processes associated with subduction, including water transport into the upper mantle and the generation and transport of melts. Our understanding of mantle wedge dynamics is incomplete; in particular, the mantle flow field above subducting slabs remains poorly understood. Because seismic anisotropy is a consequence of deformation, observations of anisotropy (such as shear wave splitting and P-to-SH converted waves) can constrain the geometry of the wedge flow field. Additionally, because the presence of water (either in nominally anhydrous minerals or as hydrous phases) can have a large effect on anisotropic structure, a detailed understanding of mantle wedge anisotropy can help to constrain processes related to water cycling in subduction systems. We present a global, synoptic view of anisotropy observations in subduction zone mantle wedges, compiled from a large number of individual studies, with the goal of understanding the first-order controls on wedge anisotropy and flow patterns. This compilation allows us to explicitly test the predictions made by many different conceptual models for wedge anisotropy, as well as to explore the relationships between observed anisotropy parameters and other parameters that describe subduction. We find that no simple model can explain all of the trends observed in the global data set. Mantle wedge flow is likely controlled by a combination of downdip motion of the slab, trench migration, ambient mantle flow, small-scale convection, proximity to slab edges, and slab morphology, with the relative contributions of these in any given subduction system controlled by the subduction kinematics and mantle rheology. There is also a likely contribution from B-type olivine and/or serpentinite fabric in many subduction zones, governed by the local thermal structure and volatile distribution.

  15. Wavelength Converters

    DEFF Research Database (Denmark)

    Kloch, Allan; Hansen, Peter Bukhave; Wolfson, David;

    1999-01-01

    at 2.5 Gbit/s, the regeneration causes a reduction of the required input power to an in-line EDFA of ~6 dB for a power penalty of 1 dB at a bit error rate of 10-9. If two converters are concatenated the power requirement is reduced ~8 dB. Obviously, the power reduction allows for longer spans between....... It is predicted that jitter accumulation can be minimised by using a 9-10 dB ratio between the signal and CW power also assuring a high extinction ratio. Using this guideline simulations show that 20 cross-gain modulation converters can be cascaded at 10 Gbit/s with only ~20 ps of accumulated jitter...... and an extinction ratio of ~10 dB.The regenerative capabilities of the cross-phase converters are described and verified experimentally at 20 Gbit/s, where the noise redistribution and improvement of the signal-to-noise ratio clearly is demonstrated by controlling the input power to an EDFA. In a similar experiment...

  16. The mantle transition zone beneath the Afar Depression and adjacent regions: implications for mantle plumes and hydration

    Science.gov (United States)

    Reed, C. A.; Gao, S. S.; Liu, K. H.; Yu, Y.

    2016-06-01

    The Afar Depression and its adjacent areas are underlain by an upper mantle marked by some of the world's largest negative velocity anomalies, which are frequently attributed to the thermal influences of a lower-mantle plume. In spite of numerous studies, however, the existence of a plume beneath the area remains enigmatic, partially due to inadequate quantities of broad-band seismic data and the limited vertical resolution at the mantle transition zone (MTZ) depth of the techniques employed by previous investigations. In this study, we use an unprecedented quantity (over 14 500) of P-to-S receiver functions (RFs) recorded by 139 stations from 12 networks to image the 410 and 660 km discontinuities and map the spatial variation of the thickness of the MTZ. Non-linear stacking of the RFs under a 1-D velocity model shows robust P-to-S conversions from both discontinuities, and their apparent depths indicate the presence of an upper-mantle low-velocity zone beneath the entire study area. The Afar Depression and the northern Main Ethiopian Rift are characterized by an apparent 40-60 km depression of both MTZ discontinuities and a normal MTZ thickness. The simplest and most probable interpretation of these observations is that the apparent depressions are solely caused by velocity perturbations in the upper mantle and not by deeper processes causing temperature or hydration anomalies within the MTZ. Thickening of the MTZ on the order of 15 km beneath the southern Arabian Plate, southern Red Sea and western Gulf of Aden, which comprise the southward extension of the Afro-Arabian Dome, could reflect long-term hydration of the MTZ. A 20 km thinning of the MTZ beneath the western Ethiopian Plateau is observed and interpreted as evidence for a possible mantle plume stem originating from the lower mantle.

  17. Subduction and collision processes in the Central Andes constrained by converted seismic phases.

    Science.gov (United States)

    Yuan, X; Sobolev, S V; Kind, R; Oncken, O; Bock, G; Asch, G; Schurr, B; Graeber, F; Rudloff, A; Hanka, W; Wylegalla, K; Tibi, R; Haberland, C; Rietbrock, A; Giese, P; Wigger, P; Röwer, P; Zandt, G; Beck, S; Wallace, T; Pardo, M; Comte, D

    The Central Andes are the Earth's highest mountain belt formed by ocean-continent collision. Most of this uplift is thought to have occurred in the past 20 Myr, owing mainly to thickening of the continental crust, dominated by tectonic shortening. Here we use P-to-S (compressional-to-shear) converted teleseismic waves observed on several temporary networks in the Central Andes to image the deep structure associated with these tectonic processes. We find that the Moho (the Mohorovicić discontinuity--generally thought to separate crust from mantle) ranges from a depth of 75 km under the Altiplano plateau to 50 km beneath the 4-km-high Puna plateau. This relatively thin crust below such a high-elevation region indicates that thinning of the lithospheric mantle may have contributed to the uplift of the Puna plateau. We have also imaged the subducted crust of the Nazca oceanic plate down to 120 km depth, where it becomes invisible to converted teleseismic waves, probably owing to completion of the gabbro-eclogite transformation; this is direct evidence for the presence of kinetically delayed metamorphic reactions in subducting plates. Most of the intermediate-depth seismicity in the subducting plate stops at 120 km depth as well, suggesting a relation with this transformation. We see an intracrustal low-velocity zone, 10-20 km thick, below the entire Altiplano and Puna plateaux, which we interpret as a zone of continuing metamorphism and partial melting that decouples upper-crustal imbrication from lower-crustal thickening.

  18. Zoned mantle convection.

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    Albarède, Francis; Van Der Hilst, Rob D

    2002-11-15

    We review the present state of our understanding of mantle convection with respect to geochemical and geophysical evidence and we suggest a model for mantle convection and its evolution over the Earth's history that can reconcile this evidence. Whole-mantle convection, even with material segregated within the D" region just above the core-mantle boundary, is incompatible with the budget of argon and helium and with the inventory of heat sources required by the thermal evolution of the Earth. We show that the deep-mantle composition in lithophilic incompatible elements is inconsistent with the storage of old plates of ordinary oceanic lithosphere, i.e. with the concept of a plate graveyard. Isotopic inventories indicate that the deep-mantle composition is not correctly accounted for by continental debris, primitive material or subducted slabs containing normal oceanic crust. Seismological observations have begun to hint at compositional heterogeneity in the bottom 1000 km or so of the mantle, but there is no compelling evidence in support of an interface between deep and shallow mantle at mid-depth. We suggest that in a system of thermochemical convection, lithospheric plates subduct to a depth that depends - in a complicated fashion - on their composition and thermal structure. The thermal structure of the sinking plates is primarily determined by the direction and rate of convergence, the age of the lithosphere at the trench, the sinking rate and the variation of these parameters over time (i.e. plate-tectonic history) and is not the same for all subduction systems. The sinking rate in the mantle is determined by a combination of thermal (negative) and compositional buoyancy and as regards the latter we consider in particular the effect of the loading of plates with basaltic plateaux produced by plume heads. Barren oceanic plates are relatively buoyant and may be recycled preferentially in the shallow mantle. Oceanic plateau-laden plates have a more pronounced

  19. Where is mantle's carbon?

    Science.gov (United States)

    Oganov, A. R.; Ono, S.; Ma, Y.

    2008-12-01

    Due to the strongly reducing conditions (the presence of metallic iron was suggested both by experiments [1] and theory [2]), diamond was believed to be the main host of carbon through most of the lower mantle [3]. We showed [4] that cementite Fe3C is another good candidate to be the main host of "reduced" carbon in the mantle, reinforcing an earlier hypothesis [5]. The fate of "oxidised" carbon (in subducted slabs) is of particular importance - if carbonates decompose producing fluid CO2, this would have important implications for the chemistry and rheology of the mantle. Knowledge of crystal structures and phase diagrams of carbonates is crucial here. The high-pressure structures of CaCO3 were predicted [6] and subsequently verified by experiments. For MgCO3, Isshiki et al. [7] found a new phase above 110 GPa, and several attempts were made to solve it [8,9]. Here [4], using an evolutionary algorithm for crystal structure prediction [10], we show that there are two post-magnesite phases at mantle-relevant pressure range, one stable at 82-138 GPa, and the other from 138 GPa to ~160 GPa. Both are based on threefold rings of CO4-tetrahedra and are more favourable than all previously proposed structures. We show that through most of the P-T conditions of the mantle, MgCO3 is the major host of oxidized carbon in the Earth. We predict the possibility of CO2 release at the very bottom of the mantle (in SiO2-rich basaltic part of subducted slabs), which could enhance partial melting of rocks and be related to the geodynamical differences between the Earth and Venus. 1.Frost D.J., Liebske C., Langenhorst F., McCammon C.A., Tronnes R.G., Rubie D.C. (2004). Experimental evidence for the existence of iron-rich metal in the Earth's lower mantle. Nature 428, 409-412. 2.Zhang F., Oganov A.R. (2006). Valence and spin states of iron impurities in mantle-forming silicates. Earth Planet. Sci. Lett. 249, 436-443. 3.Luth R.W. (1999). Carbon and carbonates in the mantle. In: Mantle

  20. Shear-wave velocity structure of the crust and upper mantle beneath the Kola Peninsula

    Science.gov (United States)

    Dricker, I. G.; Roecker, S. W.; Kosarev, G. L.; Vinnik, L. P.

    We determined the shear-wave velocity structure of the crust and upper mantle beneath the central part of the Kola peninsula from the analysis of P-wave receiver functions and mantle P-SV converted phases recorded at stations Apatity (APA) and Lovozero (LVZ). The times of P-SV converted phases from the 410 and 660 km discontinuities are close to those predicted by the IASP91 model. Phase conversions at the crust-mantle boundary beneath the Baltic shield northeast of LVZ and southwest of APA are consistent with a sharp transition from crust to mantle at a depth of 40 km, while conversions from the intervening Khibina plutonic region are consistent with a gradual transition between depths of 20 and 40 km. We infer that short (∼50 km) wavelength lateral variations in the crust-mantle transition persist in this region, despite the inactivity of the Kola peninsula since Devonian times.

  1. The mantle transition zone and the upper mantle in Central-Eastern Greenland

    Science.gov (United States)

    Anja Kraft, Helene; Thybo, Hans; Vinnik, Lev

    2016-04-01

    We present a receiver function (RF) study of the mantle transition zone (MTZ) and upper mantle in central-eastern Greenland. Our results are based on data from 18 temporary broad-band seismometers and 5 additional stations from the GLISN and GLATIS networks. The stations were operating in the region between Scoresby Sund and Summit (~ 70 ° N) with half of them installed on ice, the other half on bedrock. For our analysis we calculated low frequency PRF and SRF, which use the difference in travel times between converted and not converted phases at discontinuities. We see clear signals from P410s and P660s in most of our PRF and from S410p in the SRF. Their delay times suggest a surprisingly thin MTZ for most parts of the study area with up to 25 km of thinning compared to standard Earth models. The only exception is a small region in the centre of the study area, which shows times close to standard. It is mainly the delay time for P410s, that varies, while P660s is stable throughout our study area. This indicates, that the thinning of the MTZ is mainly due to topography on the 410-discontinuity. We furthermore observe an M-shaped signal for P410s at stations in the western part around Summit. A similar, complicated signal has been observed previously in different settings and is interpreted as a thin low velocity layer between 410 km and 520 km. In addition we jointly inverted the PRF and SRF for upper mantle velocities. These results show velocities slower than IASP91 for the entire study area. Both the low velocities in the upper mantle and the thinning of the MTZ are in contrary to simple models of old continental shields and might indicate a fairly recent heating event.

  2. Tracing Mantle Plumes: Quantifying their Morphology and Behavior from Seismic Tomography

    Science.gov (United States)

    O'Farrell, K. A.; Eakin, C. M.; Jones, T. D.; Garcia, E.; Robson, A.; Mittal, T.; Lithgow-Bertelloni, C. R.; Jackson, M. G.; Lekic, V.; Rudolph, M. L.

    2016-12-01

    Hotspot volcanism provides a direct link between the deep mantle and the surface, but the location, depth and source of the mantle plumes that feed hotspots are highly controversial. In order to address this issue it is important to understand the journey along which plumes have travelled through the mantle. The general behavior of plumes in the mantle also has the potential to tell us about the vigor of mantle convection, net rotation of the mantle, the role of thermal versus chemical anomalies, and important bulk physical properties of the mantle such as the viscosity profile. To address these questions we developed an algorithm to trace plume-like features in shear-wave (Vs) seismic tomographic models based on picking local minima in velocity and searching for continuous features with depth. We apply this method to several of the latest tomographic models and can recover 30 or more continuous plume conduits that are >750 km long. Around half of these can be associated with a known hotspot at the surface. We study the morphology of these plume chains and find that the largest lateral deflections occur near the base of the lower mantle and in the upper mantle. We analyze the preferred orientation of the plume deflections and their gradient to infer large scale mantle flow patterns and the depth of viscosity contrasts in the mantle respectively. We also retrieve Vs profiles for our traced plumes and compare with velocity profiles predicted for different mantle adiabat temperatures. We use this to constrain the thermal anomaly associated with these plumes. This thermal anomaly is then converted to a density anomaly and an upwelling velocity is derived. We compare this to buoyancy fluxes calculated at the surface and use this in conjunction with our measured plume tilts/deflections to estimate the strength of the "mantle wind".

  3. Wavelength converter technology

    DEFF Research Database (Denmark)

    Kloch, Allan; Hansen, Peter Bukhave; Poulsen, Henrik Nørskov;

    1999-01-01

    Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on all-optical wavelength converter types based on semiconductor optical amplifiers....

  4. Wavelength converter technology

    DEFF Research Database (Denmark)

    Kloch, Allan; Hansen, Peter Bukhave; Poulsen, Henrik Nørskov;

    1999-01-01

    Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on air-optical wavelength converter types based on semiconductor optical amplifiers....

  5. Technologies for converter topologies

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yan; Zhang, Haiyu

    2017-02-28

    In some embodiments of the disclosed inverter topologies, an inverter may include a full bridge LLC resonant converter, a first boost converter, and a second boost converter. In such embodiments, the first and second boost converters operate in an interleaved manner. In other disclosed embodiments, the inverter may include a half-bridge inverter circuit, a resonant circuit, a capacitor divider circuit, and a transformer.

  6. Power Converters for Accelerators

    CERN Document Server

    Visintini, R

    2015-01-01

    Particle accelerators use a great variety of power converters for energizing their sub-systems; while the total number of power converters usually depends on the size of the accelerator or combination of accelerators (including the experimental setup), the characteristics of power converters depend on their loads and on the particle physics requirements: this paper aims to provide an overview of the magnet power converters in use in several facilities worldwide.

  7. Mantle hydrocarbons: abiotic or biotic?

    Science.gov (United States)

    Sugisaki, R; Mimura, K

    1994-06-01

    Analyses of 227 rocks from fifty localities throughout the world showed that mantle derived rocks such as tectonized peridotites in ophiolite sequences (tectonites) arid peridotite xenoliths in alkali basalts contain heavier hydrocarbons (n-alkanes), whereas igneous rocks produced by magmas such as gabbro arid granite lack them. The occurrence of hydrocarbons indicates that they were not derived either from laboratory contamination or from held contamination; these compounds found in the mantle-derived rocks are called here "mantle hydrocarbons." The existence of hydrocarbons correlates with petrogenesis. For example, peridotite cumulates produced by magmatic differentiation lack hydrocarbons whereas peridotite xenoliths derived from the mantle contain them. Gas chromatographic-mass spectrometric records of the mantle hydrocarbons resemble those of aliphatics in meteorites and in petroleum. Features of the hydrocarbons are that (a) the mantle hydrocarbons reside mainly along grain boundaries and in fluid inclusions of minerals; (b) heavier isoprenoids such as pristane and phytane are present; and (c) delta 13C of the mantle hydrocarbons is uniform (about -27%). Possible origins for the mantle hydrocarbons are as follows. (1) They were in organically synthesized by Fischer-Tropsch type reaction in the mantle. (2) They were delivered by meteorites and comets to the early Earth. (3) They were recycled by subduction. The mantle hydrocarbons in the cases of (1) and (2) are abiogenic and those in (3) are mainly biogenic. It appears that hydrocarbons may survive high pressures and temperatures in the mantle, but they are decomposed into lighter hydrocarbon gases such as CH4 at lower pressures when magmas intrude into the crust; consequently, peridotite cumulates do not contain heavier hydrocarbons but possess hydrocarbon gases up to C4H10.

  8. The Mantle Transition Zone in Central-Eastern Greenland

    Science.gov (United States)

    Kraft, H. A.; Thybo, H.; Vinnik, L. P.

    2015-12-01

    We present results of a Receiver Function (RF) study of the mantle transition zone (TZ) in Central-Eastern Greenland. The base of this study is data from 19 broad-band seismometers, which were temporarily installed from 2009 to 2012 in the region between Scoresbysund and Summit (~ 70º N) plus 5 permanent stations from the GLISN network. One half of these stations were installed on the ice, the other half on bedrock.Our analysis is based on low frequency PRF, which use the difference in travel times between converted and not converted phasesat discontinuities. Most of our RFs show clear signals for P410s and P660s. Their delay times suggest a surprisingly thin mantle transition zone for most parts of the study area in comparison to standard Earth models, and much thinner than below other continental shield and platform areas. This could indicate a fairly recent heating of the TZ. Another observation is an M-shaped signal around the 410 km - discontinuity at some of the stations mainly in the western part around Summit. This observation is contrary to the expected simple negative signal. It may indicate a thin low velocity layer between 410 km and 520 km, as it has previously been observed in several settings based on converted waves and also explosion data. Most of our stations show positive travel time anomalies for the upper mantle, which again is contrary to simple models of old continental shields.

  9. Iron geochemistry of the mantle

    Science.gov (United States)

    Humayun, M.; Campbell, T. J.; Brandon, A. D.; Davis, F. A.; Hirschmann, M. M.

    2011-12-01

    The Fe/Mg ratio is an important constraint on the compositionally controlled density of the mantle. However, this ratio cannot be inferred from erupted lavas from OIB or MORB sources, but must be determined directly from mantle peridotites. Recently, the Fe/Mn ratio of erupted lavas has been used as an indicator of potential Fe variability in the mantle driven by core-mantle interaction, recycled oceanic crust, or even variations in the temperature of mantle melting. The classic compilation of McDonough & Sun (1995) provided the currently accepted Fe/Mn ratio of the upper mantle, 60±10. The uncertainty on this ratio allows for 15-30% variability in mantle iron abundances, which is equivalent to a density variation larger than observed by seismic tomography in the mantle. To better understand the relationship between mantle peridotites and erupted lavas, and to search for real variability in the Fe/Mn ratio of mantle peridotites, we report precise new ICP-MS measurements of the transition element geochemistry of suites of mantle xenoliths that have known Fe/Mg ratios. For 12 Kilbourne Hole xenoliths, we observe a clear correlation between Fe/Mn and MgO (or Fe/Mg) over an Fe/Mn range of 59-72. Extrapolation of this trend to a Primitive Mantle (PM) MgO content of 37.8 yields an Fe/Mn of 59±1 for the PM. Our new analyses of KLB-1 powder and fused glass beads yield an Fe/Mn of 61.4 for both samples, which plots on the Kilbourne Hole Fe/Mn vs. MgO trend. A set of ten xenoliths from San Carlos yield a wide range of Fe/Mn (56-65) not correlated with MgO content. The San Carlos xenoliths may have experienced a metasomatic effect that imprinted variable Fe/Mn. A clinopyroxene-rich lithology from San Carlos yields an Fe/Mn of 38, which plots on an extension of the Kilbourne Hole Fe/Mn vs. MgO trend. These new results, and those from other xenolith localities being measured in our lab, provide new constraints on the compositional variability of the Earth's upper mantle. Mc

  10. The photoelectric displacement converter

    Science.gov (United States)

    Dragoner, Valeriu V.

    2005-02-01

    In the article are examined questions of constructing photoelectric displacement converter satisfying demands that are stated above. Converter has channels of approximate and precise readings. The approximate reading may be accomplished either by the method of reading from a code mask or by the method of the consecutive calculation of optical scale gaps number. Phase interpolator of mouar strips" gaps is determined as a precise measuring. It is shown mathematical model of converter that allow evaluating errors and operating speed of conversion.

  11. Mapping the mass distribution of Earth's mantle using satellite-derived gravity gradients

    Science.gov (United States)

    Panet, Isabelle; Pajot-Métivier, Gwendoline; Greff-Lefftz, Marianne; Métivier, Laurent; Diament, Michel; Mandea, Mioara

    2014-02-01

    The dynamics of Earth's mantle are not well known. Deciphering mantle flow patterns requires an understanding of the global distribution of mantle density. Seismic tomography has been used to derive mantle density distributions, but converting seismic velocities into densities is not straightforward. Here we show that data from the GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission can be used to probe our planet's deep mass structure. We construct global anomaly maps of the Earth's gravitational gradients at satellite altitude and use a sensitivity analysis to show that these gravitational gradients image the geometry of mantle mass down to mid-mantle depths. Our maps highlight north-south-elongated gravity gradient anomalies over Asia and America that follow a belt of ancient subduction boundaries, as well as gravity gradient anomalies over the central Pacific Ocean and south of Africa that coincide with the locations of deep mantle plumes. We interpret these anomalies as sinking tectonic plates and convective instabilities between 1,000 and 2,500km depth, consistent with seismic tomography results. Along the former Tethyan Margin, our data also identify an east-west-oriented mass anomaly likely in the upper mantle. We suggest that by combining gravity gradients with seismic and geodynamic data, an integrated dynamic model for Earth can be achieved.

  12. A sharp and flat section of the core-mantle boundary

    Science.gov (United States)

    Vidale, J.E.; Benz, H.M.

    1992-01-01

    THE transition zone between the Earth's core and mantle plays an important role as a boundary layer for mantle and core convection1. This zone conducts a large amount of heat from the core to the mantle, and contains at least one thermal boundary layer2,3; the proximity of reactive silicates and molten iron leads to the possibility of zones of intermediate composition4. Here we investigate one region of the core-mantle boundary using seismic waves that are converted from shear to compressional waves by reflection at the boundary. The use of this phase (known as ScP), the large number of receiving stations, and the large aperture of our array all provide higher resolution than has previously been possible5-7. For the 350-km-long section of the core-mantle boundary under the northeast Pacific sampled by the reflections, the local boundary topography has an amplitude of less than 500 m, no sharp radial gradients exist in the 400 km above the boundary, and the mantle-lo-core transition occurs over less than 1 km. The simplicity of the structure near and above the core-mantle boundary argues against chemical heterogeneity at the base of the mantle in this location.

  13. Compositional Evolution of the Mantle

    Science.gov (United States)

    Bennett, V. C.

    2003-12-01

    The mantle is the Earth's largest chemical reservoir comprising 82% of its total volume and 65% of its mass. The mantle constitutes almost all of the silicate Earth, extending from the base of the crust (which comprises only 0.6% of the silicate mass) to the top of the metallic core at 2,900 km depth. The chemical compositions of direct mantle samples such as abyssal peridotites (Chapter 2.04) and peridotite xenoliths (Chapter 2.05), and of indirect probes of the mantle such as basalts from mid-ocean ridge basalts (MORBs) and ocean island basalts (OIBs) (Chapter 2.03), and some types of primitive granites, tell us about the compositional state of the modern mantle, with ever increasingly detailed information providing strong evidence for chemical complexity and heterogeneity at all scales (Chapter 2.03). This chemical heterogeneity must reflect the complex physical interplay of a number of distinct long-lived geochemical reservoirs that are identified primarily by their radiogenic isotopic compositions.Many of the chapters in this volume provide detailed images of the current chemical and physical state of the Earth's mantle, whereas other contributions examine the starting composition for the Earth (Chapter 2.01). This chapter attempts to link these two areas by tracking the composition of the mantle through time. The first part of this chapter is a summary of the empirical evidence for secular change in the chemical composition of the mantle from the formation of the Earth at 4.56 Ga throughto the present day. The emphasis is on results from the long-lived radiogenic isotopic systems, in particular 147Sm-143Nd, 176Lu-176Hf, 87Rb-87Sr, and 187Re-187Os systems as these isotopic data provide some of the best constraints on the composition of the mantle in the first half of Earth history, and the timing and extent of chemical differentiation that has affected the mantle over geologic time. Selected trace element data and the "short-lived" 146Sm-142Nd isotopic systems

  14. High speed data converters

    CERN Document Server

    Ali, Ahmed MA

    2016-01-01

    This book covers high speed data converters from the perspective of a leading high speed ADC designer and architect, with a strong emphasis on high speed Nyquist A/D converters. For our purposes, the term 'high speed' is defined as sampling rates that are greater than 10 MS/s.

  15. Electrical Power Converter

    NARCIS (Netherlands)

    Ferreira, J.A.

    2014-01-01

    Electrical power converter for converting electrical power of a power source connected or connectable at an input to electrical DC-power at an output, wherein between the input and the output a first circuit of submodules is provided, wherein said first circuit of submodules and the power source for

  16. Redox conditions for mantle plumes

    Science.gov (United States)

    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

  17. Cascaded resonant bridge converters

    Science.gov (United States)

    Stuart, Thomas A. (Inventor)

    1989-01-01

    A converter for converting a low voltage direct current power source to a higher voltage, high frequency alternating current output for use in an electrical system where it is desired to use low weight cables and other circuit elements. The converter has a first stage series resonant (Schwarz) converter which converts the direct current power source to an alternating current by means of switching elements that are operated by a variable frequency voltage regulator, a transformer to step up the voltage of the alternating current, and a rectifier bridge to convert the alternating current to a direct current first stage output. The converter further has a second stage series resonant (Schwarz) converter which is connected in series to the first stage converter to receive its direct current output and convert it to a second stage high frequency alternating current output by means of switching elements that are operated by a fixed frequency oscillator. The voltage of the second stage output is controlled at a relatively constant value by controlling the first stage output voltage, which is accomplished by controlling the frequency of the first stage variable frequency voltage controller in response to second stage voltage. Fault tolerance in the event of a load short circuit is provided by making the operation of the first stage variable frequency voltage controller responsive to first and second stage current limiting devices. The second stage output is connected to a rectifier bridge whose output is connected to the input of the second stage to provide good regulation of output voltage wave form at low system loads.

  18. Mantle Volatiles - Distribution and Consequences

    Science.gov (United States)

    Luth, R. W.

    2003-12-01

    Volatiles in the mantle have, for many years, been the subject of intensive study from a number of perspectives. They are of interest because of their potential effects on melting relationships, on transport of major and trace elements, and on the rheological and other physical properties of the mantle. By convention, "volatiles" in this context are constituents that are liquid or gaseous at normal Earth surface conditions. This review will look at the behavior of C-O-H-S-halogen volatiles, beginning with H2O and C-O volatiles.There have been tremendous strides made recently towards understanding how volatiles in general and water in particular is transported and stored in the mantle. This progress is based on research on a number of fronts: studies of mantle-derived samples have provided insight into the nature and occurrence of hydrous phases such as amphibole, mica, and chlorite, and have provided constraints on the capacity of nominally anhydrous minerals (NAMs) such as olivine, pyroxenes, and garnet to contain "water" by a variety of substitution mechanisms. Experimental studies on mantle-derived magmas have provided constraints on volatile contents in their source regions. Other studies have constrained the pressure, temperature, and composition conditions over which hydrous phases are stable in the mantle.Fundamental questions remain about the geochemical cycling of volatiles in the mantle, and between the mantle and the surface. Much attention has focused on the capability of hydrous phases such as amphibole, mica, serpentine, chlorite, and a family of "dense hydrous magnesian silicates" (DHMSs) to act as carriers of water in subducting slabs back into the mantle. It has been clear since the work of Ito et al. (1983) that there is a discrepancy between the amount of volatiles subducted into the mantle and those returned to the surface by arc magmatism. A recent overview of volatile cycling in subduction systems by Bebout (1996) suggests that 5-15% of the H2

  19. Converting Nonclassicality into Entanglement

    Science.gov (United States)

    Killoran, N.; Steinhoff, F. E. S.; Plenio, M. B.

    2016-02-01

    Quantum mechanics exhibits a wide range of nonclassical features, of which entanglement in multipartite systems takes a central place. In several specific settings, it is well known that nonclassicality (e.g., squeezing, spin squeezing, coherence) can be converted into entanglement. In this work, we present a general framework, based on superposition, for structurally connecting and converting nonclassicality to entanglement. In addition to capturing the previously known results, this framework also allows us to uncover new entanglement convertibility theorems in two broad scenarios, one which is discrete and one which is continuous. In the discrete setting, the classical states can be any finite linearly independent set. For the continuous setting, the pertinent classical states are "symmetric coherent states," connected with symmetric representations of the group S U (K ). These results generalize and link convertibility properties from the resource theory of coherence, spin coherent states, and optical coherent states, while also revealing important connections between local and nonlocal pictures of nonclassicality.

  20. Improving Power Converter Reliability

    DEFF Research Database (Denmark)

    Ghimire, Pramod; de Vega, Angel Ruiz; Beczkowski, Szymon

    2014-01-01

    The real-time junction temperature monitoring of a high-power insulated-gate bipolar transistor (IGBT) module is important to increase the overall reliability of power converters for industrial applications. This article proposes a new method to measure the on-state collector?emitter voltage...... of a high-power IGBT module during converter operation, which may play a vital role in improving the reliability of the power converters. The measured voltage is used to estimate the module average junction temperature of the high and low-voltage side of a half-bridge IGBT separately in every fundamental...... is measured in a wind power converter at a low fundamental frequency. To illustrate more, the test method as well as the performance of the measurement circuit are also presented. This measurement is also useful to indicate failure mechanisms such as bond wire lift-off and solder layer degradation...

  1. Converting Nonclassicality into Entanglement.

    Science.gov (United States)

    Killoran, N; Steinhoff, F E S; Plenio, M B

    2016-02-26

    Quantum mechanics exhibits a wide range of nonclassical features, of which entanglement in multipartite systems takes a central place. In several specific settings, it is well known that nonclassicality (e.g., squeezing, spin squeezing, coherence) can be converted into entanglement. In this work, we present a general framework, based on superposition, for structurally connecting and converting nonclassicality to entanglement. In addition to capturing the previously known results, this framework also allows us to uncover new entanglement convertibility theorems in two broad scenarios, one which is discrete and one which is continuous. In the discrete setting, the classical states can be any finite linearly independent set. For the continuous setting, the pertinent classical states are "symmetric coherent states," connected with symmetric representations of the group SU(K). These results generalize and link convertibility properties from the resource theory of coherence, spin coherent states, and optical coherent states, while also revealing important connections between local and nonlocal pictures of nonclassicality.

  2. Thermionic photovoltaic energy converter

    Science.gov (United States)

    Chubb, D. L. (Inventor)

    1985-01-01

    A thermionic photovoltaic energy conversion device comprises a thermionic diode mounted within a hollow tubular photovoltaic converter. The thermionic diode maintains a cesium discharge for producing excited atoms that emit line radiation in the wavelength region of 850 nm to 890 nm. The photovoltaic converter is a silicon or gallium arsenide photovoltaic cell having bandgap energies in this same wavelength region for optimum cell efficiency.

  3. Rogue mantle helium and neon.

    Science.gov (United States)

    Albarède, Francis

    2008-02-15

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

  4. Determining upper mantle structures using gravity, seismology, and GIA modelling in Fennoscandia

    Science.gov (United States)

    Root, B. C.; van der Wal, W.; Vermeersen, B. L. A.

    2015-12-01

    The 3D structure of the upper mantle plays a large role in Glacial Isostatic Adjustment (GIA). Finite-element software is able to model this 3D structure, but knowledge of the upper mantle is needed to make these models realistic. Nowadays, global maps are made of the crustal structure and temperature of the upper mantle from seismic observations. Also, satellite gravity missions, such as GOCE and GRACE, determine global gravity fields. Combining these data sets could give new insights in Glacial Isostatic Adjustment and explain some discrepancies seen in currents geological observations with 1D rheology Earth models. We obtain upper mantle models that fit gravity observations. Then, the upper mantle seismic velocities are converted to temperature profiles; that are used to determine the amount of strain according to diffusion and dislocation creep in the upper mantle. The obtained 3D rheology models are used in a finite element GIA model to observe the effect of the 3D structures during GIA. The GIA model results are compared to geological observations of the sea level change, GPS uplift rates, and ongoing gravity change in the area. This study specifically studies the effect of compositional differences in the upper mantle on the modelled remaining uplift and gravity signal. Molecular conversion relations for primitive mantle rock composition, Garnet Lherzolite rock composition, and Archon, iron depleted rock composition are used to compute the temperature and density profiles. The Fennoscandian lithosphere is believed to contain these three types of composition, yet, it is not yet known in what relative amounts and locations. An iterative approach is used to find the best compositional structure to fit the GIA observables in the Fenoscandian upper mantle.

  5. Angiotensin-converting enzyme

    DEFF Research Database (Denmark)

    Sørensen, P G; Rømer, F K; Cortes, D

    1984-01-01

    In order to evaluate bleomycin-associated lung damage in humans, lung function parameters and serum levels of the endothelial-bound angiotensin-converting enzyme (ACE) were determined by serial measurements in 11 patients who were treated for testicular cancer. None developed clinical or radiolog......In order to evaluate bleomycin-associated lung damage in humans, lung function parameters and serum levels of the endothelial-bound angiotensin-converting enzyme (ACE) were determined by serial measurements in 11 patients who were treated for testicular cancer. None developed clinical...

  6. Mantle superplumes induce geomagnetic superchrons

    Directory of Open Access Journals (Sweden)

    Peter eOlson

    2015-07-01

    Full Text Available We use polarity reversal systematics from numerical dynamos to quantify the hypothesis that the modulation of geomagnetic reversal frequency, including geomagnetic superchrons, results from changes in core heat flux related to growth and collapse of lower mantle superplumes. We parameterize the reversal frequency sensitivity from numerical dynamos in terms of average core heat flux normalized by the difference between the present-day core heat flux and the core heat flux at geomagnetic superchron onset. A low-order polynomial fit to the 0-300 Ma Geomagnetic Polarity Time Scale (GPTS reveals that a decrease in core heat flux relative to present-day of approximately 30% can account for the Cretaceous Normal Polarity and Kiaman Reverse Polarity Superchrons, whereas the hyper-reversing periods in the Jurassic require a core heat flux equal to or higher than present-day. Possible links between GPTS transitions, large igneous provinces (LIPs, and the two lower mantle superplumes are explored. Lower mantle superplume growth and collapse induce GPTS transitions by increasing and decreasing core heat flux, respectively. Age clusters of major LIPs postdate transitions from hyper-reversing to superchron geodynamo states by 30-60 Myr, suggesting that superchron onset may be contemporaneous with LIP-forming instabilities produced during collapses of lower mantle superplumes.

  7. Converting the reset

    NARCIS (Netherlands)

    Hoogland, J.K.; Neumann, C.D.D.; Bloch, D.

    2001-01-01

    We give a simple algorithm to incorporate the effects of resets in convertible bond prices, without having to add an extra factor to take into account the value of the reset. Furthermore we show that the effect of a notice period, and additional make-whole features, can be treated in a straightforwa

  8. An Electromagnetic Beam Converter

    DEFF Research Database (Denmark)

    2009-01-01

    The present invention relates to an electromagnetic beam converter and a method for conversion of an input beam of electromagnetic radiation having a bell shaped intensity profile a(x,y) into an output beam having a prescribed target intensity profile l(x',y') based on a further development...

  9. Definition of Power Converters

    CERN Document Server

    Bordry, F

    2015-01-01

    The paper is intended to introduce power conversion principles and to define common terms in the domain. The concept s of sources and switches are defined and classified. From the basic laws of source interconnections, a generic method of power converter synthesis is presented. Some examples illustrate this systematic method. Finally, the commutation cell and soft commuta tion are introduced and discussedd.

  10. Convertible Proxy Signcryption Scheme

    Institute of Scientific and Technical Information of China (English)

    李继国; 李建中; 曹珍富; 张亦辰

    2004-01-01

    In 1996, Mambo et al introduced the concept of proxy signature. However, proxy signature can only provide the delegated authenticity and cannot provide confidentiality. Recently, Gamage et al and Chan and Wei proposed different proxy signcryption schemes respectively, which extended the concept of proxy signature.However, only the specified receiver can decrypt and verify the validity of proxy signcryption in their schemes.To protect the receiver' s benefit in case of a later dispute, Wu and Hsu proposed a convertible authenticated encryption scheme, which carn enable the receiver to convert signature into an ordinary one that can be verified by anyone. Based on Wu and Hsu' s scheme and improved Kim' s scheme, we propose a convertible proxy signcryption scheme. The security of the proposed scheme is based on the intractability of reversing the one-way hash function and solving the discrete logarithm problem. The proposed scheme can satisfy all properties of strong proxy signature and withstand the public key substitution attack and does not use secure channel. In addition, the proposed scheme can be extended to convertible threshold proxy signcryption scheme.

  11. The Convertible Arbitrage Strategy Analyzed

    NARCIS (Netherlands)

    Loncarski, I.; Ter Horst, J.R.; Veld, C.H.

    2006-01-01

    This paper analyzes convertible bond arbitrage on the Canadian market for the period 1998 to 2004.Convertible bond arbitrage is the combination of a long position in convertible bonds and a short position in the underlying stocks. Convertible arbitrage has been one of the most successful strategies

  12. Advanced DC/DC converters

    CERN Document Server

    Luo, Fang Lin

    2003-01-01

    INTRODUCTIONHistorical ReviewMultiple Quadrant ChoppersPump CircuitsDevelopment of DC/DC Conversion TechniqueCategorize Prototypes and DC/DC Converters Family TreeVOLTAGE-LIFT CONVERTERSIntroductionSeven Self-Lift ConvertersPositive Output Luo-ConvertersNegative Output Luo-ConvertersModified Positive Output Luo-Converters Double Output Luo-ConvertersPOSITIVE OUTPUT SUPER-LIFT LUO-CONVERTERS IntroductionMain SeriesAdditional SeriesEnhanced Series Re-Enhanced Series Multiple-Enhanced Series Summary of Positive Output

  13. Microprocessor controlled static converter

    Directory of Open Access Journals (Sweden)

    Stefan Szabo

    2005-10-01

    Full Text Available This paper wants to demonstrate a way of implementing a microcontroller into an DC motor speed control loop. The static power converter is a fully controlled rectifier bridge, using standard SCR's. The bridge's control signals are supplied by the microcontroller and are phase-angle or burst types. The automation loop contains a software PI-style regulator. All the experimental results shows that this aproach is flexibile enough to be used on a large scale.

  14. DSP controlled power converter

    OpenAIRE

    Chan, CH; Pong, MH

    1995-01-01

    A digital controller is designed and implemented by a Digital Signal Processor (DSP) to replace the Pulse Width Modulator (PWM) and error amplifier compensation network in a two wheeler forward converter. The DSP controller is designed in three approaches: a) Discretization of analog controller - the design is based on the transfer function of the error amplifier compensation network. b) Digital PID controller design - the design is based on the general form of the pulse transfer function of ...

  15. SSG Wave Energy Converter

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Vicinanza, Diego; Frigaard, Peter

    2008-01-01

    head hydroturbines are converting the potential energy of the stored water into power. A key to success for the SSG will be the low cost of the structure and its robustness. The construction of the pilot plant is scheduled and this paper aims to describe the concept of the SSG wave energy converter...... and the studies behind the process that leads to its construction. The pilot plant is an on-shore full scale module in 3 levels with an expected power production of 320 MWh/y in the North Sea. Location, wave climate and laboratory tests results will be used here to describe the pilot plant and its characteristics.......The SSG (Sea Slot-cone Generator) is a wave energy converter of the overtopping type. The structure consists of a number of reservoirs one on the top of each others above the mean water level, in which the water of incoming waves is stored temporary. In each reservoir, expressively designed low...

  16. How stratified is mantle convection?

    Science.gov (United States)

    Puster, Peter; Jordan, Thomas H.

    1997-04-01

    We quantify the flow stratification in the Earth's mid-mantle (600-1500 km) in terms of a stratification index for the vertical mass flux, Sƒ (z) = 1 - ƒ(z) / ƒref (z), in which the reference value ƒref(z) approximates the local flux at depth z expected for unstratified convection (Sƒ=0). Although this flux stratification index cannot be directly constrained by observations, we show from a series of two-dimensional convection simulations that its value can be related to a thermal stratification index ST(Z) defined in terms of the radial correlation length of the temperature-perturbation field δT(z, Ω). ST is a good proxy for Sƒ at low stratifications (SƒUniformitarian Principle. The bound obtained here from global tomography is consistent with local seismological evidence for slab flux into the lower mantle; however, the total material flux has to be significantly greater (by a factor of 2-3) than that due to slabs alone. A stratification index, Sƒ≲0.2, is sufficient to exclude many stratified convection models still under active consideration, including most forms of chemical layering between the upper and lower mantle, as well as the more extreme versions of avalanching convection governed by a strong endothermic phase change.

  17. Mid-mantle heterogeneities and iron spin transition in the lower mantle: Implications for mid-mantle slab stagnation

    Science.gov (United States)

    Shahnas, M. H.; Yuen, D. A.; Pysklywec, R. N.

    2017-01-01

    Recent high pressure experimental results reveal that the elastic and transport properties of mantle materials are impacted by the electronic spin transition in iron under lower mantle pressure and temperature conditions. The electronic transition in ferropericlase (Fp), the second major constituent mineral of the lower mantle material, is associated with a smooth increase in density starting from the mid-mantle depth to the core-mantle boundary (CMB). The transition also yields softening in the elastic moduli and an increase in the thermal expansivity over the transition zone in the lower mantle. Although there is not yet robust experimental evidence for spin-transition induced density change in the perovskite (Pv) phase (the major constituent mineral in the lower mantle), the spin transition in the octahedral (B) site in Al-free perovskite causes a bulk modulus hardening (increase in the bulk modulus) in the mineral. We have incorporated these physical processes into high resolution 3D-spherical control volume models for mantle convection. A series of numerical experiments explore how the electronic spin transition in iron modifies the mantle flow, and in particular the fate of sinking cold slabs. Such mid-mantle stagnations are prevalent globally in seismic tomographic inversions, but previous explanations for their existence are not satisfactory. Employing density anomalies from the iron spin transition in ferropericlase and density anomaly models for perovskite, we study the influence of the spin transition in the minerals of the lower mantle on mantle flow. Our model results reveal that while the spin transition-induced property variations in ferropericlase enhance mixing in the lower depths of the mantle, the density anomaly arising from the hardening in the bulk modulus of Al-free perovskite can be effective in slowing the descent of slabs and may cause stagnation at mid-mantle levels. A viscosity hill in the lower mantle may further enhance the stagnation

  18. Mantle wedge serpentinization effects on slab dips

    Directory of Open Access Journals (Sweden)

    Eh Tan

    2017-01-01

    Full Text Available The mechanical coupling between a subducting slab and the overlying mantle wedge is an important factor in controlling the subduction dip angle and the flow in mantel wedge. This paper investigates the role of the amount of mantle serpentinization on the subduction zone evolution. With numerical thermos-mechanical models with elasto-visco-plastic rheology, we vary the thickness and depth extent of mantle serpentinization in the mantle wedge to control the degree of coupling between the slab and mantle wedge. A thin serpentinized mantle layer is required for stable subduction. For models with stable subduction, we find that the slab dip is affected by the down-dip extent and the mantle serpentinization thickness. A critical down-dip extent exists in mantle serpentinization, determined by the thickness of the overriding lithosphere. If the down-dip extent does not exceed the critical depth, the slab is partially coupled to the overriding lithosphere and has a constant dip angle regardless of the mantle serpentinization thickness. However, if the down-dip extent exceeds the critical depth, the slab and the base of the overriding lithosphere would be separated and decoupled by a thick layer of serpentinized peridotite. This allows further slab bending and results in steeper slab dip. Increasing mantle serpentinization thickness will also result in larger slab dip. We also find that with weak mantle wedge, there is no material flowing from the asthenosphere into the serpentinized mantle wedge. All of these results indicate that serpentinization is an important ingredient when studying the subduction dynamics in the mantle wedge.

  19. The amount of recycled crust in sources of mantle-derived melts.

    Science.gov (United States)

    Sobolev, Alexander V; Hofmann, Albrecht W; Kuzmin, Dmitry V; Yaxley, Gregory M; Arndt, Nicholas T; Chung, Sun-Lin; Danyushevsky, Leonid V; Elliott, Tim; Frey, Frederick A; Garcia, Michael O; Gurenko, Andrey A; Kamenetsky, Vadim S; Kerr, Andrew C; Krivolutskaya, Nadezhda A; Matvienkov, Vladimir V; Nikogosian, Igor K; Rocholl, Alexander; Sigurdsson, Ingvar A; Sushchevskaya, Nadezhda M; Teklay, Mengist

    2007-04-20

    Plate tectonic processes introduce basaltic crust (as eclogite) into the peridotitic mantle. The proportions of these two sources in mantle melts are poorly understood. Silica-rich melts formed from eclogite react with peridotite, converting it to olivine-free pyroxenite. Partial melts of this hybrid pyroxenite are higher in nickel and silicon but poorer in manganese, calcium, and magnesium than melts of peridotite. Olivine phenocrysts' compositions record these differences and were used to quantify the contributions of pyroxenite-derived melts in mid-ocean ridge basalts (10 to 30%), ocean island and continental basalts (many >60%), and komatiites (20 to 30%). These results imply involvement of 2 to 20% (up to 28%) of recycled crust in mantle melting.

  20. X-Y Converter Family

    DEFF Research Database (Denmark)

    Bhaskar, Mahajan Sagar; Sanjeevikumar, Padmanaban; Wheeler, Patrick

    2016-01-01

    A New breed of a buck boost converter, named as the XY converter family is proposed in this article. In the XY family, 16 topologies are presented which are highly suitable for renewable energy applications which require a high ratio of DC-DC converter; such as a photovoltaic multilevel inverter...... system, high voltage automotive applications and industrial drives. Compared to the traditional boost converter and existing recent converters, the proposed XY converter family has the ability to provide a higher output voltage by using less number of power devices and reactive components. Other distinct...... features of the XY converter family are i) Single control switch ii) Provide negative output voltage iii) Non-isolated topologies iv) High conversion ratio without making the use of high duty cycle and v) modular structure. XY family is compared with the recent high step-up converters and the detailed...

  1. Radioactivity released from burning gas lantern mantles.

    Science.gov (United States)

    Luetzelschwab, J W; Googins, S W

    1984-04-01

    Gas lantern mantles contain thorium to produce incandescence when lantern fuel is burned on the mantle. Although only thorium is initially present on the mantle, the thorium daughters build up, some over a period of weeks and some over a period of years, and significant quantities of these daughters are present when the mantle is used. Some of these daughters are released when the lantern fuel is burned on the mantle. The amounts of radioactivity released during burning is studied by measuring the gamma radiation emitted by the daughters. Results of this study show that some of the radium (224Ra and 228Ra) and more than half the 212Pb and 212Bi is released during the first hour of a burn. The actual amounts release depend on the age of the mantle.

  2. Resonant power converters

    CERN Document Server

    Kazimierczuk, Marian K

    2012-01-01

    This book is devoted to resonant energy conversion in power electronics. It is a practical, systematic guide to the analysis and design of various dc-dc resonant inverters, high-frequency rectifiers, and dc-dc resonant converters that are building blocks of many of today's high-frequency energy processors. Designed to function as both a superior senior-to-graduate level textbook for electrical engineering courses and a valuable professional reference for practicing engineers, it provides students and engineers with a solid grasp of existing high-frequency technology, while acquainting them wit

  3. Cycloidal Wave Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Stefan G. Siegel, Ph.D.

    2012-11-30

    This program allowed further advancing the development of a novel type of wave energy converter, a Cycloidal Wave Energy Converter or CycWEC. A CycWEC consists of one or more hydrofoils rotating around a central shaft, and operates fully submerged beneath the water surface. It operates under feedback control sensing the incoming waves, and converts wave power to shaft power directly without any intermediate power take off system. Previous research consisting of numerical simulations and two dimensional small 1:300 scale wave flume experiments had indicated wave cancellation efficiencies beyond 95%. The present work was centered on construction and testing of a 1:10 scale model and conducting two testing campaigns in a three dimensional wave basin. These experiments allowed for the first time for direct measurement of electrical power generated as well as the interaction of the CycWEC in a three dimensional environment. The Atargis team successfully conducted two testing campaigns at the Texas A&M Offshore Technology Research Center and was able to demonstrate electricity generation. In addition, three dimensional wave diffraction results show the ability to achieve wave focusing, thus increasing the amount of wave power that can be extracted beyond what was expected from earlier two dimensional investigations. Numerical results showed wave cancellation efficiencies for irregular waves to be on par with results for regular waves over a wide range of wave lengths. Using the results from previous simulations and experiments a full scale prototype was designed and its performance in a North Atlantic wave climate of average 30kW/m of wave crest was estimated. A full scale WEC with a blade span of 150m will deliver a design power of 5MW at an estimated levelized cost of energy (LCOE) in the range of 10-17 US cents per kWh. Based on the new results achieved in the 1:10 scale experiments these estimates appear conservative and the likely performance at full scale will

  4. Thermal Stratification in Vertical Mantle Tanks

    DEFF Research Database (Denmark)

    Knudsen, Søren; Furbo, Simon

    2001-01-01

    It is well known that it is important to have a high degree of thermal stratification in the hot water storage tank to achieve a high thermal performance of SDHW systems. This study is concentrated on thermal stratification in vertical mantle tanks. Experiments based on typical operation conditions...... are carried out to investigate how the thermal stratification is affected by different placements of the mantle inlet. The heat transfer between the solar collector fluid in the mantle and the domestic water in the inner tank is analysed by CFD-simulations. Furthermore, the flow pattern in the vertical mantle...... tank is investigated....

  5. Bidirectional buck boost converter

    Science.gov (United States)

    Esser, Albert Andreas Maria

    1998-03-31

    A bidirectional buck boost converter and method of operating the same allows regulation of power flow between first and second voltage sources in which the voltage level at each source is subject to change and power flow is independent of relative voltage levels. In one embodiment, the converter is designed for hard switching while another embodiment implements soft switching of the switching devices. In both embodiments, first and second switching devices are serially coupled between a relatively positive terminal and a relatively negative terminal of a first voltage source with third and fourth switching devices serially coupled between a relatively positive terminal and a relatively negative terminal of a second voltage source. A free-wheeling diode is coupled, respectively, in parallel opposition with respective ones of the switching devices. An inductor is coupled between a junction of the first and second switching devices and a junction of the third and fourth switching devices. Gating pulses supplied by a gating circuit selectively enable operation of the switching devices for transferring power between the voltage sources. In the second embodiment, each switching device is shunted by a capacitor and the switching devices are operated when voltage across the device is substantially zero.

  6. Gallium phosphide energy converters

    Energy Technology Data Exchange (ETDEWEB)

    Sims, P.E.; Dinetta, L.C.; Goetz, M.A.

    1995-10-01

    Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp {minus}17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

  7. Diamond growth in mantle fluids

    Science.gov (United States)

    Bureau, Hélène; Frost, Daniel J.; Bolfan-Casanova, Nathalie; Leroy, Clémence; Esteve, Imène; Cordier, Patrick

    2016-11-01

    In the upper mantle, diamonds can potentially grow from various forms of media (solid, gas, fluid) with a range of compositions (e.g. graphite, C-O-H fluids, silicate or carbonate melts). Inclusions trapped in diamonds are one of the few diagnostic tools that can constrain diamond growth conditions in the Earth's mantle. In this study, inclusion-bearing diamonds have been synthesized to understand the growth conditions of natural diamonds in the upper mantle. Diamonds containing syngenetic inclusions were synthesized in multi-anvil presses employing starting mixtures of carbonates, and silicate compositions in the presence of pure water and saline fluids (H2O-NaCl). Experiments were performed at conditions compatible with the Earth's geotherm (7 GPa, 1300-1400 °C). Results show that within the timescale of the experiments (6 to 30 h) diamond growth occurs if water and carbonates are present in the fluid phase. Water promotes faster diamond growth (up to 14 mm/year at 1400 °C, 7 GPa, 10 g/l NaCl), which is favorable to the inclusion trapping process. At 7 GPa, temperature and fluid composition are the main factors controlling diamond growth. In these experiments, diamonds grew in the presence of two fluids: an aqueous fluid and a hydrous silicate melt. The carbon source for diamond growth must be carbonate (CO32) dissolved in the melt or carbon dioxide species in the aqueous fluid (CO2aq). The presence of NaCl affects the growth kinetics but is not a prerequisite for inclusion-bearing diamond formation. The presence of small discrete or isolated volumes of water-rich fluids is necessary to grow inclusion-bearing peridotitic, eclogitic, fibrous, cloudy and coated diamonds, and may also be involved in the growth of ultradeep, ultrahigh-pressure metamorphic diamonds.

  8. Mantle plumes and continental tectonics.

    Science.gov (United States)

    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.

  9. Manufacturing method of photoelectric converter

    Energy Technology Data Exchange (ETDEWEB)

    Yamazaki, Shunpei; Suzuki, Kunio; Fukada, Takeshi; Kanehana, Mikio

    1987-06-25

    This is a photoelectric converter wherein a photoelectromotive force is generated by utilizing the shorter wavelength side by the 1st converter and by utilizing the longer wavelength side by the 2nd converter; as a whole, wider wavelength range of light can be converted into electricity. In the 1st. converter, an electrode on the side of semi-incident surface is made transparent as well as an electrode equipped on the back of a non-mono-crystalline semiconductor. Light which passed this is introduced into the 2nd converter to generate an electromotive force. This invention especially relates with a method of forming this 2nd converter. In preparing I-type non-mono-crystalline semiconductor among the semiconductors having PIN junction, PCVD method is used by means of ECR (Electron Cyclotron Resonance) by using a hydrogen- or halogen- added Si-semiconductor instead of using expensive Ge, etc, which are common in the conventional method. (3 figs)

  10. Unity power factor converter

    Science.gov (United States)

    Wester, Gene W. (Inventor)

    1980-01-01

    A unity power factor converter capable of effecting either inversion (dc-to-dc) or rectification (ac-to-dc), and capable of providing bilateral power control from a DC source (or load) through an AC transmission line to a DC load (or source) for power flow in either direction, is comprised of comparators for comparing the AC current i with an AC signal i.sub.ref (or its phase inversion) derived from the AC ports to generate control signals to operate a switch control circuit for high speed switching to shape the AC current waveform to a sine waveform, and synchronize it in phase and frequency with the AC voltage at the AC ports, by selectively switching the connections to a series inductor as required to increase or decrease the current i.

  11. Electromagnetic wave energy converter

    Science.gov (United States)

    Bailey, R. L. (Inventor)

    1973-01-01

    Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive dc output power.

  12. A case for mantle plumes

    Institute of Scientific and Technical Information of China (English)

    Geoffrey F. Davies

    2005-01-01

    The existence of at least several plumes in the Earth's mantle can be inferred with few assumptions from well-established observations. As well, thermal mantle plumes can be predicted from well-established and quantified fluid dynamics and a plausible assumption about the Earth's early thermal state. Some additional important observations, especially of flood basalts and rift-related magmatism, have been shown to be plausibly consistent with the physical theory. Recent claims to have detected plumes using seismic tomography may comprise the most direct evidence for plumes, but plume tails are likely to be difficult to resolve definitively and the claims need to be well tested. Although significant questions remain about its viability, the plume hypothesis thus seems to be well worth continued investigation. Nevertheless there are many non-plate-related magmatic phenomena whose association with plumes is unclear or unlikely. Compositional buoyancy has recently been shown potentially to substantially complicate the dynamics of plumes, and this may lead to explanations for a wider range of phenomena, including "headless" hotspot tracks, than purely thermal plumes.

  13. Integrated power electronic converters and digital control

    CERN Document Server

    Emadi, Ali; Nie, Zhong

    2009-01-01

    Non-isolated DC-DC ConvertersBuck ConverterBoost ConverterBuck-Boost ConverterIsolated DC-DC ConvertersFlyback ConverterForward ConverterPush-Pull ConverterFull-Bridge ConverterHalf-Bridge ConverterPower Factor CorrectionConcept of PFCGeneral Classification of PFC CircuitsHigh Switching Frequency Topologies for PFCApplication of PFC in Advanced Motor DrivesIntegrated Switched-Mode Power ConvertersSwitched-Mode Power SuppliesThe Concept of Integrated ConverterDefinition of Integrated Switched-Mode Power Supplies (ISMPS)Boost-Type Integrated TopologiesGeneral Structure of Boost-Type Integrated T

  14. Advanced power electronics converters PWM converters processing AC voltages

    CERN Document Server

    dos Santos, Euzeli

    2014-01-01

    This book covers power electronics, in depth, by presenting the basic principles and application details, which can be used both as a textbook and reference book.  Introduces a new method to present power electronics converters called Power Blocks Geometry. Applicable for courses focusing on power electronics, power electronics converters, and advanced power converters. Offers a comprehensive set of simulation results to help understand the circuits presented throughout the book

  15. Numerical modeling of mantle plume diffusion

    Science.gov (United States)

    Krupsky, D.; Ismail-Zadeh, A.

    2004-12-01

    To clarify the influence of the heat diffusion on the mantle plume evolution, we develop a two-dimensional numerical model of the plume diffusion and relevant efficient numerical algorithm and code to compute the model. The numerical approach is based on the finite-difference method and modified splitting algorithm. We consider both von Neumann and Direchlet conditions at the model boundaries. The thermal diffusivity depends on pressure in the model. Our results show that the plume is disappearing from the bottom up - the plume tail at first and its head later - because of the mantle plume geometry (a thin tail and wide head) and higher heat conductivity in the lower mantle. We study also an effect of a lateral mantle flow associated with the plate motion on the distortion of the diffusing mantle plume. A number of mantle plumes recently identified by seismic tomography seem to disappear in the mid-mantle. We explain this disappearance as the effect of heat diffusion on the evolution of mantle plume.

  16. Deep Mantle Seismic Modeling and Imaging

    Science.gov (United States)

    Lay, Thorne; Garnero, Edward J.

    2011-05-01

    Detailed seismic modeling and imaging of Earth's deep interior is providing key information about lower-mantle structures and processes, including heat flow across the core-mantle boundary, the configuration of mantle upwellings and downwellings, phase equilibria and transport properties of deep mantle materials, and mechanisms of core-mantle coupling. Multichannel seismic wave analysis methods that provide the highest-resolution deep mantle structural information include network waveform modeling and stacking, array processing, and 3D migrations of P- and S-wave seismograms. These methods detect and identify weak signals from structures that cannot be resolved by global seismic tomography. Some methods are adapted from oil exploration seismology, but all are constrained by the source and receiver distributions, long travel paths, and strong attenuation experienced by seismic waves that penetrate to the deep mantle. Large- and small-scale structures, with velocity variations ranging from a fraction of a percent to tens of percent, have been detected and are guiding geophysicists to new perspectives of thermochemical mantle convection and evolution.

  17. The effects of wetting layer on electronic and optical properties of intersubband P-to-S transitions in strained dome-shaped InAs/GaAs quantum dots

    Directory of Open Access Journals (Sweden)

    Mohammadreza Shahzadeh

    2014-06-01

    Full Text Available The authors report on the impact of wetting layer thickness and quantum dot size on the electronic and optical properties of dome-shaped InAs/GaAs quantum dots (QDs with strained potential. Two wetting layer thicknesses of 0.5 and 2.0 nm were compared. A strong size dependence of P-to-S transition energy, transition dipole moment, oscillator strength, and linear and third-order nonlinear susceptibilities were concluded. The P-to-S transition dipole moment was shown to be purely in-plane polarization. The linear and nonlinear absorption and dispersion showed a red shift when the wetting layer thickness was increased. Our results revealed that the nonlinear susceptibility is much more sensitive to QD size compared to the linear susceptibility. An interpretation of the results was presented based on the probability density of finding the electron inside the dot and wetting layer. The results are in good agreement with previously reported experimental data.

  18. Heat transfer correlations in mantle tanks

    DEFF Research Database (Denmark)

    Furbo, Simon; Knudsen, Søren

    2005-01-01

    Small solar domestic hot water systems are best designed as low flow systems based on vertical mantle tanks. Theoretical investigations of the heat transfer in differently designed vertical mantle tanks during different operation conditions have been carried out. The investigations are based...... of the inner hot water tank and the domestic water in all levels of the tank. The heat transfer analysis showed that the heat transfer near the mantle inlet port between the solar collector fluid in the mantle and the walls surrounding the mantle is in the mixed convection regime, and as the distance from...... the inlet increases, natural convection starts to dominate. The heat transfer between the wall of the inner hot water tank and the domestic water is governed by natural convection. The results of the CFD-calculations are used to determine improved heat transfer correlations based on dimensionless analysis...

  19. Viscosity jump in Earth's mid-mantle.

    Science.gov (United States)

    Rudolph, Maxwell L; Lekić, Vedran; Lithgow-Bertelloni, Carolina

    2015-12-11

    The viscosity structure of Earth's deep mantle affects the thermal evolution of Earth, the ascent of mantle plumes, settling of subducted oceanic lithosphere, and the mixing of compositional heterogeneities in the mantle. Based on a reanalysis of the long-wavelength nonhydrostatic geoid, we infer viscous layering of the mantle using a method that allows us to avoid a priori assumptions about its variation with depth. We detect an increase in viscosity at 800- to 1200-kilometers depth, far greater than the depth of the mineral phase transformations that define the mantle transition zone. The viscosity increase is coincident in depth with regions where seismic tomography has imaged slab stagnation, plume deflection, and changes in large-scale structure and offers a simple explanation of these phenomena.

  20. Nanostructure Neutron Converter Layer Development

    Science.gov (United States)

    Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Kang, Jin Ho (Inventor); Lowther, Sharon E. (Inventor); Thibeault, Sheila A. (Inventor); Bryant, Robert G. (Inventor)

    2016-01-01

    Methods for making a neutron converter layer are provided. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development.

  1. Impedance source power electronic converters

    CERN Document Server

    Liu, Yushan; Ge, Baoming; Blaabjerg, Frede; Ellabban, Omar; Loh, Poh Chiang

    2016-01-01

    Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key features: Comprehensive analysis of the impedance source converter/inverter topologies, including typical topologies and derived topologies. Fully explains the design and control techniques of impedance source converters/inverters, including hardware design and control parameter design for corresponding control methods. Presents the latest power conversion solutions that aim to advance the role of pow...

  2. A thermochemical energy converter

    Energy Technology Data Exchange (ETDEWEB)

    Toyeguti, K.; Indzima, T.

    1982-08-09

    Mercury is used as the active mass of the anode in the converter and 0/sub 2/ is used as the active cathode material. The reaction of Mercury + 1/2 0/sub 2/-Hg0 occurs with a discharge. With heating to 500/sup 0/C the regeneration of the Mercury, Hg0 yields Mercury + 1/2 0/sub 2/, occurs. The device for performing the thermochenical conversion of energy contains an element body, an oxygen chamber, an oxygen electrode, a chamber with an alkaline liquid electrolyte, a separator, an auxiliary separator, an electrode and a chamber with the Mercury. The thermochemical reaction occurs in the reactor to which the Hg0 is transported along a pipe which has a refrigerator and a valve. The Mercury is fed into the element from a reservoir. The Mercury reduced in the reactor and in a reaction tower is fed into it through a closed cycle. The bellows is connected with the reactor by a pipe with a refrigerator. Through it the 0/sub 2/ goes in a closed cycle to the chamber. The current forming reactions are Hg + 20H-anion yields Hg0 + H/sub 2/0 + 2e and 1/2 0/sub 2/ + H/sub 2/0 + 2e yields 20H-anion. The voltage on the outleads of the element is approximately 0.3 volts.

  3. DC to DC converters: operation; Hacheurs: fonctionnement

    Energy Technology Data Exchange (ETDEWEB)

    Bernot, F. [Ecole d' Ingenieurs de Tours, 37 (France)

    2002-05-01

    This article deals with pulse width modulation (PWM) and pulse position modulation (PPM) DC to DC converters. A tri-phase PWM converter is made of 6 simple DC/DC converters grouped together into 3 reversible converters of the same type: 1 - single-quadrant voltage lowering converters (hydraulic analogy, study with ideal elements, full scheme with input and output filters); 2 - single-quadrant voltage raising converters (hydraulic analogy, operation); 3 - two quadrants reversible converters (structure construction, quadrants of operation, reversible converter connected to a DC motor); 4 - four-quadrants reversible converters; 5 - other converters structure (current converters and converters with intermediate storage, asymmetrical converters, converters with capacitive storage, insulated converters, resonating converters, status); 6 - conclusion. (J.S.)

  4. Upper and mid mantle fabric developing during subduction-induced mantle flow

    Science.gov (United States)

    Faccenda, Manuele

    2013-04-01

    Subduction zones are convergent margins where the rigid lithosphere sinks into the Earth's mantle inducing complex 3D flow patterns. Seismic anisotropy generated by strain-induced lattice/crystal preferred orientation (LPO/CPO) of intrinsically anisotropic minerals is commonly used to study flow in the mantle and its relations with plate motions. We computed the seismic anisotropy of the upper and mid mantle due to strain-induced LPO in 3D mechanical models of dynamic subduction by using, respectively, D-Rex and Underworld. Subsequently, FSTRACK was used to compute seismogram synthetics and SKS splitting patterns. Strong anisotropy develops in the upper mantle, while weak or null seismic anisotropy is formed in the upper transition zone/lower mantle and lower transition zone, respectively. The distribution of the fabric in the mantle depends on the distribution and amount of the deformation, and not on the rate at which the slab subducts. The SKS splitting patterns are controlled by the anisotropy in the upper mantle because SKS waves are more sensitive to the anisotropy in the shallowest layers. Horizontally propagating shear waves in the mid mantle originating from local earthquakes are characterized by significant splitting that is mostly due to the fabric in the uppermost lower mantle. We discuss the implications of our results for real subduction settings like Tonga, where a discrete amount of observations have been collected in the past 10 years on the anisotropy in the upper and mid mantle.

  5. Primary magmas and mantle temperatures through time

    Science.gov (United States)

    Ganne, Jérôme; Feng, Xiaojun

    2017-03-01

    Chemical composition of mafic magmas is a critical indicator of physicochemical conditions, such as pressure, temperature, and fluid availability, accompanying melt production in the mantle and its evolution in the continental or oceanic lithosphere. Recovering this information has fundamental implications in constraining the thermal state of the mantle and the physics of mantle convection throughout the Earth's history. Here a statistical approach is applied to a geochemical database of about 22,000 samples from the mafic magma record. Potential temperatures (Tps) of the mantle derived from this database, assuming melting by adiabatic decompression and a Ti-dependent (Fe2O3/TiO2 = 0.5) or constant redox condition (Fe2+/∑Fe = 0.9 or 0.8) in the magmatic source, are thought to be representative of different thermal "horizons" (or thermal heterogeneities) in the ambient mantle, ranging in depth from a shallow sublithospheric mantle (Tp minima) to a lower thermal boundary layer (Tp maxima). The difference of temperature (ΔTp) observed between Tp maxima and minima did not change significantly with time (˜170°C). Conversely, a progressive but limited cooling of ˜150°C is proposed since ˜2.5 Gyr for the Earth's ambient mantle, which falls in the lower limit proposed by Herzberg et al. [2010] (˜150-250°C hotter than today). Cooling of the ambient mantle after 2.5 Ga is preceded by a high-temperature plateau evolution and a transition from dominant plumes to a plate tectonics geodynamic regime, suggesting that subductions stabilized temperatures in the Archaean mantle that was in warming mode at that time.abstract type="synopsis">Plain Language SummaryThe Earth's upper mantle constitutes a major interface between inner and outer envelops of the planet. We explore at high resolution its thermal state evolution (potential temperature of the ambient mantle, Tp) in depth and time using a multi-dimensional database of mafic lavas chemistry (>22,000 samples formed in

  6. Proposed electromagnetic wave energy converter

    Science.gov (United States)

    Bailey, R. L.

    1973-01-01

    Device converts wave energy into electric power through array of insulated absorber elements responsive to field of impinging electromagnetic radiation. Device could also serve as solar energy converter that is potentially less expensive and fragile than solar cells, yet substantially more efficient.

  7. Geodynamically Consistent Interpretation of Seismic Tomography for Thermal and Thermochemical Mantle Plumes

    Science.gov (United States)

    Samuel, H.; Bercovici, D.

    2006-05-01

    Recent theoretical developments as well as increased data quality and coverage have allowed seismic tomographic imaging to better resolve narrower structures at both shallow and deep mantle depths. However, despite these improvements, the interpretation of tomographic images remains problematic mainly because of: (1) the trade off between temperature and composition and their different influence on mantle flow; (2) the difficulty in determining the extent and continuity of structures revealed by seismic tomography. We present two geodynamic studies on mantle plumes which illustrate the need to consider both geodynamic and mineral physics for a consistent interpretation of tomographic images in terms of temperature composition and flow. The first study aims to investigate the coupled effect of pressure and composition on thermochemical plumes. Using both high resolution 2D numerical modeling and simple analytical theory we show that the coupled effect of composition and pressure have a first order impact on the dynamics of mantle thermochemical plumes in the lower mantle: (1) For low Si enrichment of the plume relative to a reference pyrolitic mantle, an oscillatory behavior of the plume head is observed; (2) For Si-enriched plume compositions, the chemical density excess of the plume increases with height, leading to stagnation of large plume heads at various depths in the lower mantle. As a consequence, these thermochemical plumes may display broad (~ 1200 km wide and more) negative seismic velocity anomalies at various lower mantle depths, which may not necessarily be associated with upwelling currents. The second study focuses on the identification of thermal mantle plumes by seismic tomography beneath the Hawaiian hot spot: we performed a set of 3D numerical experiments in a spherical shell to model a rising plume beneath a moving plate. The thermal structure obtained is converted into P and S wave seismic velocities using mineral physics considerations. We

  8. Impedance Source Power Electronic Converters

    DEFF Research Database (Denmark)

    Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming

    Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable...... and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key...... control methods. Presents the latest power conversion solutions that aim to advance the role of power electronics into industries and sustainable energy conversion systems. Compares impedance source converter/inverter applications in renewable energy power generation and electric vehicles as well...

  9. Characteristics of Vertical Mantle Heat Exchangers for Solar Water Heaters

    DEFF Research Database (Denmark)

    Shah, Louise Jivan; Morrison, G.L.; Behnia, M.

    1999-01-01

    exchangers was also developed for detailed evaluation of the heat flux distribution over the mantle surface. Both the experimental and simulation results indicate that distribution of the flow around the mantle gap is governed by buoyancy driven recirculation in the mantle. The operation of the mantle...

  10. Trace-element geochemistry of mantle olivine and application to mantle petrogenesis and geothermobarometry

    OpenAIRE

    De Hoog, Cees-Jan; Gall, Louise; Cornell, David H.

    2010-01-01

    Trace-element compositions of olivine from 75 mantle rocks of diverse origin, including xenoliths from kimberlites, basaltic lavas and orogenic peridotites, were determined by laser ablation ICP-MS to study systematic variations between mantle lithologies, partitioning mechanisms in olivine and their potential for geothermobarometry and unravelling mantle processes. Samples were selected to cover a wide range of forsterite contents (89.1-93.4), equilibration temperatures and pressures (750-14...

  11. Thermoconvective waves in the earth's mantle

    Science.gov (United States)

    Birger, B. I.

    1980-06-01

    The thermoconvective instability of the Earth's mantle is analysed. The mantle is modelled as an infinite horizontal layer with a free upper surface, heated from below. The creep in the mantle is supposed to be transient when strains are small. This transient creep is described by Lomnitz's law modified by Jeffreys (1958a). It is shown that disturbances, in the form of thermoconvective waves with a period of 10 8 - 10 9y and wavelength of the order 10 3 km, can propagate through the mantle without attenuation. These waves induce oscillations of the Earth's surface. The pattern of flows differs greatly from that suggested by plate tectonics. An attempt is made to give a new explanation for the linear magnetic anomalies over oceanic ridges.

  12. Can mantle convection be self-regulated?

    Science.gov (United States)

    Korenaga, Jun

    2016-08-01

    The notion of self-regulating mantle convection, in which heat loss from the surface is constantly adjusted to follow internal radiogenic heat production, has been popular for the past six decades since Urey first advocated the idea. Thanks to its intuitive appeal, this notion has pervaded the solid earth sciences in various forms, but approach to a self-regulating state critically depends on the relation between the thermal adjustment rate and mantle temperature. I show that, if the effect of mantle melting on viscosity is taken into account, the adjustment rate cannot be sufficiently high to achieve self-regulation, regardless of the style of mantle convection. The evolution of terrestrial planets is thus likely to be far from thermal equilibrium and be sensitive to the peculiarities of their formation histories. Chance factors in planetary formation are suggested to become more important for the evolution of planets that are more massive than Earth.

  13. How mantle slabs drive plate tectonics.

    Science.gov (United States)

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-04

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction.

  14. MODELLING MANTLE TANKS FOR SDHW SYSTEMS USING PIV AND CFD

    DEFF Research Database (Denmark)

    Shah, Louise Jivan; Morrison, G.L.; Behnia, Masud

    1999-01-01

    Characteristics of vertical mantle heat exchanger tanks for SDHW systems have been investigated experimentally and theoretically using particle image velocimetry (PIV) and CFD modelling. A glass model of a mantle heat exchanger tank was constructed so that the flow distribution in the mantle could...... be studied using the PIV test facility. Two transient three-dimensional CFD-models of the glass model mantle tank were developed using the CFD-programmes CFX and FLUENT.The experimental results illustrate that the mantle flow structure in the mantle is complicated and the distribution of flow in the mantle...

  15. Comparisons between radioactive and non-radioactive gas lantern mantles.

    Science.gov (United States)

    Furuta, E; Yoshizawa, Y; Aburai, T

    2000-12-01

    Gas lantern mantles containing radioactive thorium have been used for more than 100 years. Although thorium was once believed to be indispensable for giving a bright light, non-radioactive mantles are now available. From the radioactivities of the daughter nuclides, we estimated the levels of radioactivity of 232Th and 228Th in 11 mantles. The mantles contained various levels of radioactivity from background levels to 1410 +/- 140 Bq. Our finding that radioactive and non-radioactive mantles are equally bright suggests that there is no advantage in using radioactive mantles. A remaining problem is that gas lantern mantles are sold without any information about radioactivity.

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

    Science.gov (United States)

    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 (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.

  17. Radiation tolerant power converter controls

    CERN Document Server

    Todd, B; King, Q; Uznanski, S

    2012-01-01

    The Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is the world's most powerful particle collider. The LHC has several thousand magnets, both warm and super-conducting, which are supplied with current by power converters. Each converter is controlled by a purpose-built electronic module called a Function Generator Controller (FGC). The FGC allows remote control of the power converter and forms the central part of a closed-loop control system where the power converter voltage is set, based on the converter output current and magnet-circuit characteristics. Some power converters and FGCs are located in areas which are exposed to beam-induced radiation. There are numerous radiation induced effects, some of which lead to a loss of control of the power converter, having a direct impact upon the accelerator's availability. Following the first long shut down (LS1), the LHC will be able to run with higher intensity beams and higher beam energy. This is expected to lead to signifi...

  18. Power converter simulation and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ghazy, M.A.

    1989-01-01

    There has been a great deal of progress made in computer aided design and analysis in the power electronic field. Many of the simulation packages are inefficient and time consuming in simulating switching converters. This thesis proposes an efficient, simple, general simulation approach to simulate any power converter with less computation time and space requirements on computer. In this approach the equations of power converters are formulated using network topology. In this thesis several procedures have been explained for the steady-state computation of power electronic circuits. Also, the steady-state analyses have been accomplished by a new technique called Fourier series method. For a complete system consisting of converters, filters, and electric machines, the simulation is complicated if a frequency domain technique is used. This thesis introduces a better technique which decouples the system into subsystems and simulates it in the time domain. The design of power converters using optimization techniques is presented in this thesis. Finally, the theory of Variable Structured Systems has been applied to power converters. Sliding mode control for DC-DC and DC-AC power converters is introduced as a tool to accomplish desired characteristics.

  19. Subduction and volatile recycling in Earth's mantle

    Science.gov (United States)

    King, S. D.; Ita, J. J.; Staudigel, H.

    1994-01-01

    The subduction of water and other volatiles into the mantle from oceanic sediments and altered oceanic crust is the major source of volatile recycling in the mantle. Until now, the geotherms that have been used to estimate the amount of volatiles that are recycled at subduction zones have been produced using the hypothesis that the slab is rigid and undergoes no internal deformation. On the other hand, most fluid dynamical mantle flow calculations assume that the slab has no greater strength than the surrounding mantle. Both of these views are inconsistent with laboratory work on the deformation of mantle minerals at high pressures. We consider the effects of the strength of the slab using two-dimensional calculations of a slab-like thermal downwelling with an endothermic phase change. Because the rheology and composition of subducting slabs are uncertain, we consider a range of Clapeyron slopes which bound current laboratory estimates of the spinel to perovskite plus magnesiowustite phase transition and simple temperature-dependent rheologies based on an Arrhenius law diffusion mechanism. In uniform viscosity convection models, subducted material piles up above the phase change until the pile becomes gravitationally unstable and sinks into the lower mantle (the avalanche). Strong slabs moderate the 'catastrophic' effects of the instabilities seen in many constant-viscosity convection calculations; however, even in the strongest slabs we consider, there is some retardation of the slab descent due to the presence of the phase change.

  20. Archimedean Proof of the Physical Impossibility of Earth Mantle Convection

    CERN Document Server

    Herndon, J Marvin

    2010-01-01

    Eight decades ago, Arthur Holmes introducted the idea of mantle convection as a mechanism for continental drift. Five decades ago, continental drift was modified to become plate tectonics theory, which included mantle convection as an absolutely critical component. Using the submarine design and operation concept of "neutral buoyancy", which follows from Archimedes' discoveries, the concept of mantle convection is proven to be incorrect, concomitantly refuting plate tectonics, refuting all mantle convection models, and refuting all models that depend upon mantle convection.

  1. PWM DC/DC Converter

    OpenAIRE

    Chen, Juan

    2008-01-01

    This report is the result of a Master Thesis work done at Seaward Electronics Inc. in Beijing, China from June to December in 2007. The main goal for this thesis is to verify and improve the performance of Honey-PWM DC-DC converter, which has been fabricated by a standard 0.6um CMOS processes. The project was started with studying of Buck converter structure. After the understanding of the converter structure, the project goes in to the analyses phase for each sub-cells, including the theory,...

  2. Laser system with wavelength converter

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention relates to an apparatus comprising a diode laser (10) providing radiation in a first wavelength interval, a radiation conversion unit (12) having an input and an output, the radiation converter configured to receive the radiation in the first wavelength interval from the diode...... laser at the input, the radiation conversion unit configured to convert the radiation in the first wavelength interval to radiation in a second wavelength interval and the output configured to output the converted radiation, the second wavelength interval having one end point outside the first...... wavelength interval. Further, the invention relates to a method of optically pumping a target laser (14) in a laser system, the laser system comprising a laser source providing radiation at a first frequency, the laser source being optically connected to an input of a frequency converter, the frequency...

  3. Time-to-digital converters

    CERN Document Server

    Henzler, Stephan

    2010-01-01

    This text covers the fundamentals of time-to-digital converters on analog and digital conversion principles. It includes a theoretical investigation into quantization, linearity, noise and variability, and it details a range of advanced TDC architectures.

  4. Teaching machines to find mantle composition

    Science.gov (United States)

    Atkins, Suzanne; Tackley, Paul; Trampert, Jeannot; Valentine, Andrew

    2017-04-01

    The composition of the mantle affects many geodynamical processes by altering factors such as the density, the location of phase changes, and melting temperature. The inferences we make about mantle composition also determine how we interpret the changes in velocity, reflections, attenuation and scattering seen by seismologists. However, the bulk composition of the mantle is very poorly constrained. Inferences are made from meteorite samples, rock samples from the Earth and inferences made from geophysical data. All of these approaches require significant assumptions and the inferences made are subject to large uncertainties. Here we present a new method for inferring mantle composition, based on pattern recognition machine learning, which uses large scale in situ observations of the mantle to make fully probabilistic inferences of composition for convection simulations. Our method has an advantage over other petrological approaches because we use large scale geophysical observations. This means that we average over much greater length scales and do not need to rely on extrapolating from localised samples of the mantle or planetary disk. Another major advantage of our method is that it is fully probabilistic. This allows us to include all of the uncertainties inherent in the inference process, giving us far more information about the reliability of the result than other methods. Finally our method includes the impact of composition on mantle convection. This allows us to make much more precise inferences from geophysical data than other geophysical approaches, which attempt to invert one observation with no consideration of the relationship between convection and composition. We use a sampling based inversion method, using hundreds of convection simulations run using StagYY with self consistent mineral physics properties calculated using the PerpleX package. The observations from these simulations are used to train a neural network to make a probabilistic inference

  5. Shear wave splitting and subcontinental mantle deformation

    Science.gov (United States)

    Silver, Paul G.; Chan, W. Winston

    1991-09-01

    We have made measurements of shear wave splitting in the phases SKS and SKKS at 21 broadband stations in North America, South America, Europe, Asia, and Africa. Measurements are made using a retrieval scheme that yields the azimuth of the fast polarization direction ϕ and delay time δt of the split shear wave plus uncertainties. Detectable anisotropy was found at most stations, suggesting that it is a general feature of the subcontinental mantle. Delay times range from 0.65 s to 1.70 s and average about 1 s. Somewhat surprisingly, the largest delay time is found in the 2.7 b.y.-old Western Superior Province of the Canadian Shield. The splitting observations are interpreted in terms of the strain-induced lattice preferred orientation of mantle minerals, especially olivine. We consider three hypotheses concerning the origin of the continental anisotropy: (1) strain associated with absolute plate motion, as in the oceanic upper mantle, (2) crustal stress, and (3) the past and present internal deformation of the subcontinental upper mantle by tectonic episodes. It is found that the last hypothesis is the most successful, namely that the most recent significant episode of internal deformation appears to be the best predictor of ϕ. For stable continental regions, this is interpreted as "fossil" anisotropy, whereas for presently active regions, such as Alaska, the anisotropy reflects present-day tectonic activity. In the stable portion of North America there is a good correlation between delay time and lithospheric thickness; this is consistent with the anisotropy being localized in the subcontinental lithosphere and suggests that intrinsic anisotropy is approximately constant. The acceptance of this hypothesis has several implications for subcontinental mantle deformation. First, it argues for coherent deformation of the continental lithosphere (crust and mantle) during orogenies. This implies that the anisotropic portion of the lithosphere was present since the

  6. Boron nitride converted carbon fiber

    Science.gov (United States)

    Rousseas, Michael; Mickelson, William; Zettl, Alexander K.

    2016-04-05

    This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.

  7. Photoelectric converters with quantum coherence

    OpenAIRE

    Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can

    2016-01-01

    Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nano-sized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We sh...

  8. Radiation tolerant power converter controls

    Science.gov (United States)

    Todd, B.; Dinius, A.; King, Q.; Uznanski, S.

    2012-11-01

    The Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is the world's most powerful particle collider. The LHC has several thousand magnets, both warm and super-conducting, which are supplied with current by power converters. Each converter is controlled by a purpose-built electronic module called a Function Generator Controller (FGC). The FGC allows remote control of the power converter and forms the central part of a closed-loop control system where the power converter voltage is set, based on the converter output current and magnet-circuit characteristics. Some power converters and FGCs are located in areas which are exposed to beam-induced radiation. There are numerous radiation induced effects, some of which lead to a loss of control of the power converter, having a direct impact upon the accelerator's availability. Following the first long shut down (LS1), the LHC will be able to run with higher intensity beams and higher beam energy. This is expected to lead to significantly increased radiation induced effects in materials close to the accelerator, including the FGC. Recent radiation tests indicate that the current FGC would not be sufficiently reliable. A so-called FGClite is being designed to work reliably in the radiation environment in the post-LS1 era. This paper outlines the concepts of power converter controls for machines such as the LHC, introduces the risks related to radiation and a radiation tolerant project flow. The FGClite is then described, with its key concepts and challenges: aiming for high reliability in a radiation field.

  9. Transformerless dc-Isolated Converter

    Science.gov (United States)

    Rippel, Wally E.

    1987-01-01

    Efficient voltage converter employs capacitive instead of transformer coupling to provide dc isolation. Offers buck/boost operation, minimal filtering, and low parts count, with possible application in photovoltaic power inverters, power supplies and battery charges. In photovoltaic inverter circuit with transformerless converter, Q2, Q3, Q4, and Q5 form line-commutated inverter. Switching losses and stresses nil because switching performed when current is zero.

  10. Wave energy converter test application

    OpenAIRE

    Hottola, Niko

    2016-01-01

    This thesis was made for wave energy company Wello Oy. Given assignment was to find the suitable generator and frequency converter for a wave energy converter test application. The primary objective was to find a suitable generator for direct drive, in order to avoid the weight of the test application rising too high. In this thesis the possible machine types for test application are presented and what are their advenatages and disadvantages. In addition, the operation of the frequency co...

  11. Multiscale seismic tomography and mantle dynamics

    Science.gov (United States)

    Zhao, Dapeng

    2010-05-01

    Multiscale (local, regional and global) tomographic studies are made to determine the 3-D structure of the Earth, particularly for imaging mantle plumes and subducting slabs. Plume-like slow anomalies are clearly visible under the major hotspot regions in most parts of the mantle, in particular, under Hawaii, Iceland, Kerguelen, South Pacific and Africa (Zhao, 2001, 2004, 2009). The slow anomalies under South Pacific and Africa have lateral extensions of over 1000 km and exist in the entire mantle, representing two superplumes. The Pacific superplume has a larger spatial extent and stronger slow anomalies than that of the Africa superplume. The Hawaiian plume is not part of the Pacific superplume but an independent whole-mantle plume (Zhao, 2004, 2009). The slow anomalies under hotspots usually do not show a straight pillar shape, but exhibit winding images, suggesting that plumes are not fixed in the mantle but can be deflected by the mantle flow. As a consequence, hotspots are not really fixed but can wander on the Earth's surface, as evidenced by the recent paleomagnetic and numeric modeling studies. Wider and more prominent slow anomalies are visible at the core-mantle boundary (CMB) than most of the lower mantle, and there is a good correlation between the distribution of slow anomalies at the CMB and that of hotspots on the surface, suggesting that most of the strong mantle plumes under the hotspots originate from the CMB. However, there are some small-scaled, weak plumes originating from the transition zone or mid mantle depths (Zhao et al., 2006; Zhao, 2009; Lei et al., 2009; Gupta et al., 2009). Clear images of subducting slabs and magma chambers in the upper-mantle wedge beneath active arc volcanoes are obtained, indicating that geodynamic systems associated with arc magmatism and back-arc spreading are related to deep processes, such as convective circulation in the mantle wedge and dehydration reactions of the subducting slab (Zhao et al., 2002, 2007

  12. Slab mantle dehydrates beneath Kamchatka—Yet recycles water into the deep mantle

    Science.gov (United States)

    Konrad-Schmolke, Matthias; Halama, Ralf; Manea, Vlad C.

    2016-08-01

    The subduction of hydrated slab mantle is the most important and yet weakly constrained factor in the quantification of the Earth's deep geologic water cycle. The most critical unknowns are the initial hydration state and the dehydration behavior of the subducted oceanic mantle. Here we present a combined thermomechanical, thermodynamic, and geochemical model of the Kamchatka subduction zone that indicates significant dehydration of subducted slab mantle beneath Kamchatka. Evidence for the subduction of hydrated oceanic mantle comes from across-arc trends of boron concentrations and isotopic compositions in arc volcanic rocks. Our thermodynamic-geochemical models successfully predict the complex geochemical patterns and the spatial distribution of arc volcanoes in Kamchatka assuming the subduction of hydrated oceanic mantle. Our results show that water content and dehydration behavior of the slab mantle beneath Kamchatka can be directly linked to compositional features in arc volcanic rocks. Depending on hydration depth of the slab mantle, our models yield water recycling rates between 1.1 × 103 and 7.4 × 103 Tg/Ma/km corresponding to values between 0.75 × 106 and 5.2 × 106 Tg/Ma for the entire Kamchatkan subduction zone. These values are up to one order of magnitude lower than previous estimates for Kamchatka, but clearly show that subducted hydrated slab mantle significantly contributes to the water budget in the Kamchatkan subduction zone.

  13. Mantle strength of the San Andreas fault system and the role of mantle-crust feedbacks

    NARCIS (Netherlands)

    Chatzaras, V.; Tikoff, B.; Newman, J.; Withers, A.C.; Drury, M.R.

    2015-01-01

    In lithospheric-scale strike-slip fault zones, upper crustal strength is well constrained from borehole observations and fault rock deformation experiments, but mantle strength is less well known. Using peridotite xenoliths, we show that the upper mantle below the San Andreas fault system (Californi

  14. Radiation effects on DC-DC Converters

    Science.gov (United States)

    Zhang, Dexin; Attia, John O.; Kankam, Mark D. (Technical Monitor)

    2000-01-01

    DC-DC switching converters are circuits that can be used to convert a DC voltage of one value to another by switching action. They are increasing being used in space systems. Most of the popular DC-DC switching converters utilize power MOSFETs. However power MOSFETs, when subjected to radiation, are susceptible to degradation of device characteristics or catastrophic failure. This work focuses on the effects of total ionizing dose on converter performance. Four fundamental switching converters (buck converter, buck-boost converter, cuk converter, and flyback converter) were built using Harris IRF250 power MOSFETs. These converters were designed for converting an input of 60 volts to an output of about 12 volts with a switching frequency of 100 kHz. The four converters were irradiated with a Co-60 gamma source at dose rate of 217 rad/min. The performances of the four converters were examined during the exposure to the radiation. The experimental results show that the output voltage of the converters increases as total dose increases. However, the increases of the output voltage were different for the four different converters, with the buck converter and cuk converter the highest and the flyback converter the lowest. We observed significant increases in output voltage for cuk converter at a total dose of 24 krad (si).

  15. Binary/BCD-to-ASCII data converter

    Science.gov (United States)

    Miller, A. J.

    1977-01-01

    Converter inputs multiple precision binary words, converts data to multiple precision binary-coded decimal, and routes data back to computer. Converter base can be readily changed without need for new gate structure for each base changeover.

  16. Melting and Crystallization at Core Mantle Boundary

    Science.gov (United States)

    Fiquet, G.; Pradhan, G. K.; Siebert, J.; Auzende, A. L.; Morard, G.; Antonangeli, D.; Garbarino, G.

    2015-12-01

    Early crystallization of magma oceans may generate original compositional heterogeneities in the mantle. Dense basal melts may also be trapped in the lowermost mantle and explain mantle regions with ultralow seismic velocities (ULVZs) near the core-mantle boundary [1]. To test this hypothesis, we first constructed the solidus curve of a natural peridotite between 36 and 140 gigapascals using laser-heated diamond anvil cells. In our experiments, melting at core-mantle boundary pressures occurs around 4100 ± 150 K, which is a value that can match estimated mantle geotherms. Similar results were found for a chondritic mantle [2] whereas much lower pyrolitic melting temperatures were recently proposed from textural and chemical characterizations of quenched samples [3]. We also investigated the melting properties of natural mid ocean ridge basalt (MORB) up to core-mantle boundary (CMB) pressures. At CMB pressure (135 GPa), we obtain a MORB solidus temperature of 3950 ±150 K. If our solidus temperatures are in good agreement with recent results proposed for a similar composition [4], the textural and chemical characterizations of our recovered samples made by analytical transmission electron microscope indicate that CaSiO3 perovskite (CaPv) is the liquidus phase in the entire pressure range up to CMB. The partial melt composition is enriched in FeO, which suggests that such partial melts could be gravitationnally stable at the core mantle boundary. Our observations are tested against calculations made using a self-consistent thermodynamic database for the MgO-FeO-SiO2 system from 20 GPa to 140 GPa [5]. These observations and calculations provide a first step towards a consistent thermodynamic modelling of the crystallization sequence of the magma ocean, which shows that the existence of a dense iron rich and fusible layer above the CMB at the end of the crystallization is plausible [5], which is in contradiction with the conclusions drawn in [4]. [1] Williams

  17. Ferrous iron partitioning in the lower mantle

    Science.gov (United States)

    Muir, Joshua M. R.; Brodholt, John P.

    2016-08-01

    We used density functional theory (DFT) to examine the partitioning of ferrous iron between periclase and bridgmanite under lower mantle conditions. To study the effects of the three major variables - pressure, temperature and concentration - these have been varied from 0 to 150 GPa, from 1000 to 4000 K and from 0 to 100% total iron content. We find that increasing temperature increases KD, increasing iron concentration decreases KD, while pressure can both increase and decrease KD. We find that KD decreases slowly from about 0.32 to 0.06 with depth under lower mantle conditions. We also find that KD increases sharply to 0.15 in the very lowermost mantle due to the strong temperature increases near the CMB. Spin transitions have a large effect on the activity of ferropericlase which causes KD to vary with pressure in a peak-like fashion. Despite the apparently large changes in KD through the mantle, this actually results in relatively small changes in total iron content in the two phases, with XFefp ranging from about 0.20 to 0.35, before decreasing again to about 0.28 at the CMB, and XFebd has a pretty constant value of about 0.04-0.07 throughout the lower mantle. For the very high Fe concentrations suggested for ULVZs, Fe partitions very strongly into ferropericlase.

  18. PWM Converter Power Density Barriers

    Science.gov (United States)

    Kolar, Johann W.; Drofenik, Uwe; Biela, Juergen; Heldwein, Marcelo; Ertl, Hans; Friedli, Thomas; Round, Simon

    Power density of power electronic converters has roughly doubled every 10 years since 1970. Behind this trajectory is the continuous advancement of power semiconductor devices, which has increased the converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts and passive components are major barriers for a continuation of this trend. To identify such technological barriers, this paper investigates the volume of the cooling system and passive components as a function of the switching frequency for power electronic converters and determines the switching frequency that minimizes the total volume. A power density limit of 28kW/dm3 at 300kHz is calculated for an isolated DC-DC converter, 44kW/dm3 at 820kHz for a three-phase unity power factor PWM rectifier, and 26kW/dm3 at 21kHz for a sparse matrix converter. For single-phase AC-DC conversion a general limit of 35kW/dm3 results from the DC link capacitor. These power density limits highlight the need to broaden the scope of power electronics research to include cooling systems, high frequency electromagnetics, interconnection and packaging technology, and multi-domain modelling and simulation to ensure further advancement along the power density trajectory.

  19. Testing the reference Moon model in respect of the thermal regime and chemical composition of the mantle: Thermodynamics versus seismology

    Science.gov (United States)

    Kuskov, O. L.; Kronrod, V. A.; Kronrod, E. V.

    2016-05-01

    The VPREMOON seismic reference Moon model (Garcia et al., 2011) has been tested with respect to the thermal regime and chemical composition of the mantle. Based on a self-consistent thermodynamic approach and petrological models of the lunar mantle covering a wide range of concentrations of CaO, Al2O3, and FeO, we convert the P- and S-wave velocity profiles to the temperature-depth profiles. The solution procedure relies on the method of the Gibbs free energy minimization and the equations of state for the mantle material which take into account the effects of phase transformations, anharmonicity, and anelasticity. We find that regardless of the chemical composition, the positive P- and S-wave velocity gradient in the lunar mantle leads to a negative temperature gradient, which has no physical basis. For adequate mantle temperatures, the P- and S-wave velocities should remain almost constant or slightly decrease with depth (especially V S ) as a result of the effects of the temperature, which grows faster than pressure. These findings underscore the importance of the relationship of the thermodynamics and physics of minerals with seismology.

  20. Post combustion in converter steelmaking

    Energy Technology Data Exchange (ETDEWEB)

    Oghbasilasie, H.; Holappa, L.

    1997-12-31

    The purpose of this work is to study the fundamentals of post combustion and the effect of different process parameters on the post combustion ratio (PCR) and heat transfer efficiency (HTE) in converter steelmaking process. The PCR and HTE have been determined under normal operating conditions. Trials assessed the effect of lance height, vessel volume, foaming slag and pellet additions on PCR and HTE. Based on enthalpy considerations, post combustion of CO gas is regarded as one of the most effective means of increasing the heat supply to the BOP. The thermodynamic study of gas-metal-slag reactions gives the limiting conditions for post combustion inside the converter reactor. Different process parameters influencing both thermodynamic equilibria and kinetic conditions can greatly affect the post combustion ratio. Different features of converter processes as well smelting reduction processes utilizing post combustion have been reviewed. (orig.) SULA 2 Research Programme; 26 refs.

  1. Deep mantle mineralogy and novel materials synthesis using multianvil high-pressure technology (Robert Wilhelm Bunsen Medal Lecture)

    Science.gov (United States)

    Tetsuo, Irifune

    2016-04-01

    Phase relations in mantle and slab materials have been studied using Kawai-type multianvil apparatus (KMA) under pressure and temperature conditions of the mantle transition region and the uppermost lower mantle of the Earth. The associated density and sound velocity changes of these materials have also been determined using the KMA technology combined with synchrotron in situ X-ray and ultrasonic interferometry measurements. The results show that the mantle transition region is made of a pyrolitic composition, while the presence of a harzburgite-rich layer is suggested in the lower parts of this region. Use of sintered diamond anvils for KMA has allowed expansion of these measurements toward deeper region of the lower mantle. Our preliminary results of such measurements indicate that at least upper part of the lower mantle is made of the pyrolitic composition contrary to a recent study based on Brillouin scattering measurements in diamond anvil cell, which concluded a more Si-rich lower mantle. On the other hand, we have been applying KMA technology to synthesis of novel functional materials utilizing its capability of producing very high static pressures and homogeneous temperatures in relatively large sample volumes. These include ultrahard nano-polycrystalline diamond (NPD) directly converted from graphite, which is now being used for applications to abrasive and cutting tools as well as for some scientific applications such as anvils for some high-pressure devices. Another example of such a novel material is hard and tough nano-polycrystalline stishovite (NPS), which is also potentially important for some industrial applications. Moreover, we recently succeeded in making highly transparent nano-polycrystalline garnet (NPG), which is ideal for the measurements of sound velocities by various methods, such as Brillouin scattering and GHz ultrasonic interferometry. Thus, the KMA technology opens the door to the synthesis of transparent nano

  2. Redox-induced lower mantle density contrast and effect on mantle structure and primitive oxygen

    Science.gov (United States)

    Gu, Tingting; Li, Mingming; McCammon, Catherine; Lee, Kanani K. M.

    2016-09-01

    The mantle comprises nearly three-quarters of Earth's volume and through convection connects the deep interior with the lithosphere and atmosphere. The composition of the mantle determines volcanic emissions, which are intimately linked to evolution of the primitive atmosphere. Fundamental questions remain on how and when the proto-Earth mantle became oxidized, and whether redox state is homogeneous or developed large-scale structures. Here we present experiments in which we subjected two synthetic samples of nearly identical composition that are representative of the lower mantle (enstatite chondrite), but synthesized under different oxygen fugacities, to pressures and temperatures up to 90 GPa and 2,400 K. In addition to the mineral bridgmanite, compression of the more reduced material also produced Al2O3 as a separate phase, and the resulting assemblage is about 1 to 1.5% denser than in experiments with the more oxidized material. Our geodynamic simulations suggest that such a density difference can cause a rapid ascent and accumulation of oxidized material in the upper mantle, with descent of the denser reduced material to the core-mantle boundary. We suggest that the resulting heterogeneous redox conditions in Earth's interior can contribute to the large low-shear velocity provinces in the lower mantle and the evolution of atmospheric oxygen.

  3. Mantle flow in subduction systems: The mantle wedge flow field and implications for wedge processes

    Science.gov (United States)

    Long, Maureen D.; Wirth, Erin A.

    2013-02-01

    The mantle wedge above subducting slabs is associated with many important processes, including the transport of melt and volatiles. Our understanding of mantle wedge dynamics is incomplete, as the mantle flow field above subducting slabs remains poorly understood. Because seismic anisotropy is a consequence of deformation, measurements of shear wave splitting can constrain the geometry of mantle flow. In order to identify processes that make first-order contributions to the pattern of wedge flow, we have compiled a data set of local S splitting measurements from mantle wedges worldwide. There is a large amount of variability in splitting parameters, with average delay times ranging from ~0.1 to 0.3 s up to ~1.0-1.5 s and large variations in fast directions. We tested for relationships between splitting parameters and a variety of parameters related to subduction processes. We also explicitly tested the predictions made by 10 different models that have been proposed to explain splitting patterns in the mantle wedge. We find that no simple model can explain all of the trends observed in the global data set. Mantle wedge flow is likely controlled by a combination of downdip motion of the slab, trench migration, ambient mantle flow, small-scale convection, proximity to slab edges, and slab morphology, with the relative contributions of these in any given subduction system controlled by the subduction kinematics and mantle rheology. There is also a likely contribution from B-type olivine and/or serpentinite fabric in many subduction zones, governed by the local thermal structure and volatile distribution.

  4. Stirling Converters For Solar Power

    Science.gov (United States)

    Shaltens, Richard K.; Schreiber, Jeffrey G.

    1993-01-01

    Two designs expected to meet long-term goals for performance and cost. Proposed for advanced systems to convert solar thermal power to electrical power. Each system, designed to operate with 11-m-diameter paraboloidal reflector, includes solar-energy receiver, liquid-metal heat-transport subsystem, free-piston Stirling engine, cooling subsystem, alternator or generator coupled directly or indirectly to commercial electric-power system, and control and power-conditioning circuitry. System converts approximately 75 kW of input solar thermal power falling on collector to about 25 kW of output electrical power.

  5. Simplified design of data converters

    CERN Document Server

    Lenk, John

    1997-01-01

    Simplified Design of Data Converters shows how to design and experiment with data converters, both analog-to-digital and digital to analog. The design approach here is the same one used in all of John Lenk's best-selling books on simplified and practical design. Throughout the book, design problems start with guidelines for selecting all components on a trial-value basis, assuming a specific design goal and set of conditions. Then, using the guideline values in experimental circuits, the desired results are produced by varying the experimental component values, if needed.If you are a w

  6. Watching dehydration: transient vein-shaped porosity in the oceanic mantle of the subducting Nazca slab

    Science.gov (United States)

    Bloch, Wasja; John, Timm; Kummerow, Jörn; Wigger, Peter; Salazar, Pablo; Shapiro, Serge

    2016-04-01

    Subduction zones around the world show the common pattern of a Double Seismicity Zone, where seismicity is organized in the form of two sub-parallel planes, one at the plate contact and the other one, 10 to 30 km below, in the mantle of the oceanic lithosphere (Lower Seismicity Zone, LSZ). A commonly held hypothesis states that dehydration processes and the associated mineral reactions promote the earthquakes of the LSZ. Fluids filling a porespace strongly alter the petropyhsical properties of a rock. Especially the seismic P- to S-wave velocity ratio (Vp/Vs) has been shown to be sensitive to the presence of fluid-filled porosity. It transforms uniquely to Poisson's ratio. To test the mineral-dehydration-hypothesis, we use local earthquake data to measure Vp/Vs in the oceanic mantle of the subducting Nazca slab at 21°S. We determine it as the slope of the de-meaned differential P- vs. S-wave arrivaltimes of a dense seismicity cluster in the LSZ. This measurement yields a value for Vp/Vs of 2.10 ± 0.09, i.e. a Poisson's ratio of ˜0.35. This value clearly exceeds the range of Vp/Vs values expected for oceanic mantle rocks in their purely solid form at ˜50km depth. We follow a poroelastic approach to model the rock's elastic properties, including Vp/Vs, as a function of porosity and porespace-geometry. This results in a porespace model for the target volume having a vein-like porosity occupying only a minor volume fraction. Porosity is in the order of 0.1%. These findings are in very good agreement with field surveys and laboratory experiments of mantle dehydration. The pore-geometry is close to the geometrical percolation threshold, where long-ranged interconnectivity statistically emerges, suggesting good draining capabilities. Indeed, porosity is soft so that the amount of porosity and, consequently, permeability is very sensitive to local fluid pressure. We conclude that in the oceanic mantle of the subducting Nazca slab, mineral dehydration reactions are

  7. Design and Control for the Buck-Boost Converter Combining 1-Plus-D Converter and Synchronous Rectified Buck Converters

    OpenAIRE

    2015-01-01

    In this paper, a design and control for the buck-boost converter, i.e., 1-plus-D converter with a positive output voltage, is presented, which combines the 1-plus-D converter and the synchronous rectified (SR) buck converter. By doing so, the problem in voltage bucking of the 1-plus-D converter can be solved, thereby increasing the application capability of the 1-plus-D converter. Since such a converter operates in continuous conduction mode inherently, it possesses the nonpulsating output cu...

  8. AC-DC PFC Converter Using Combination of Flyback Converter and Full-bridge DC-DC Converter

    Directory of Open Access Journals (Sweden)

    Moh. Zaenal Efendi

    2014-06-01

    Full Text Available This paper presents a combination of power factor correction converter using Flyback converter and Full-bridge dc-dc converter in series connection. Flyback converter is operated in discontinuous conduction mode so that it can serve as a power factor correction converter and meanwhile Full-bridge dc-dc converter is used for dc regulator. This converter system is designed to produce a 86 Volt of output voltage and 2 A of output current. Both simulation and experiment results show that the power factor of this converter achieves up to 0.99 and meets harmonic standard of IEC61000-3-2. Keywords: Flyback Converter, Full-bridge DC-DC Converter, Power Factor Correction.

  9. Melting of subducted basalt at the core-mantle boundary.

    Science.gov (United States)

    Andrault, Denis; Pesce, Giacomo; Bouhifd, Mohamed Ali; Bolfan-Casanova, Nathalie; Hénot, Jean-Marc; Mezouar, Mohamed

    2014-05-23

    The geological materials in Earth's lowermost mantle control the characteristics and interpretation of seismic ultra-low velocity zones at the base of the core-mantle boundary. Partial melting of the bulk lower mantle is often advocated as the cause, but this does not explain the nonubiquitous character of these regional seismic features. We explored the melting properties of mid-oceanic ridge basalt (MORB), which can reach the lowermost mantle after subduction of oceanic crust. At a pressure representative of the core-mantle boundary (135 gigapascals), the onset of melting occurs at ~3800 kelvin, which is ~350 kelvin below the mantle solidus. The SiO2-rich liquid generated either remains trapped in the MORB material or solidifies after reacting with the surrounding MgO-rich mantle, remixing subducted MORB with the lowermost mantle.

  10. Mixing properties of thermal convection in the earth's mantle

    NARCIS (Netherlands)

    Schmalzl, J.T.

    1996-01-01

    The structure of mantle convection will greatly influence the generation and the survival of compositional heterogeneities. Conversely, geochemical observations can be used to obtain information about heterogeneities in the mantle and then, with certain model assumptions, information about the patte

  11. OPTIMISATION OF MANTLE TANKS FOR LOW FLOW SOLAR HEATING SYSTEMS

    DEFF Research Database (Denmark)

    Shah, Louise Jivan; Furbo, Simon

    1996-01-01

    A model, describing the heat transfer coefficients in the mantle of a mantle tank has been developed. The model is validated by means of measurements with varying operational conditions for different designed mantle tanks. The model has been implemented in an existing detailed mathematical...... programme that simulates the thermal behaviour of low flow SDHW systems. The yearly thermal performance of low flow SDHW systems with different designed mantle tanks has been calculated. The influence of the mantle tank design on the thermal performance is investigated by means of the calculations...... with the programme and by means of tests of three SDHW systems with different designed mantle tanks. Based on the investigations design rules for mantle tanks are proposed. The model, describing the heat transfer coefficients in the mantle is approximate. In addition, the measurements have revealed...

  12. The Earth's heterogeneous mantle a geophysical, geodynamical, and geochemical perspective

    CERN Document Server

    Khan, Amir

    2015-01-01

    This book highlights and discusses recent developments that have contributed to an improved understanding of observed mantle heterogeneities and their relation to the thermo-chemical state of Earth's mantle, which ultimately holds the key to unlocking the secrets of the evolution of our planet. This series of topical reviews and original contributions address 4 themes. Theme 1 covers topics in geophysics, including global and regional seismic tomography, electrical conductivity and seismic imaging of mantle discontinuities and heterogeneities in the upper mantle, transition zone and lower mantle. Theme 2 addresses geochemical views of the mantle including lithospheric evolution from analysis of mantle xenoliths, composition of the deep Earth and the effect of water on subduction-zone processes. Theme 3 discusses geodynamical perspectives on the global thermo-chemical structure of the deep mantle. Theme 4 covers application of mineral physics data and phase equilibrium computations to infer the regional-scale ...

  13. Seismic structure of the lithosphere and upper mantle beneath the ocean islands near mid-oceanic ridges

    Science.gov (United States)

    Haldar, C.; Kumar, P.; Kumar, M. Ravi

    2014-05-01

    Deciphering the seismic character of the young lithosphere near mid-oceanic ridges (MORs) is a challenging endeavor. In this study, we determine the seismic structure of the oceanic plate near the MORs using the P-to-S conversions isolated from quality data recorded at five broadband seismological stations situated on ocean islands in their vicinity. Estimates of the crustal and lithospheric thickness values from waveform inversion of the P-receiver function stacks at individual stations reveal that the Moho depth varies between ~ 10 ± 1 km and ~ 20 ± 1 km with the depths of the lithosphere-asthenosphere boundary (LAB) varying between ~ 40 ± 4 and ~ 65 ± 7 km. We found evidence for an additional low-velocity layer below the expected LAB depths at stations on Ascension, São Jorge and Easter islands. The layer probably relates to the presence of a hot spot corresponding to a magma chamber. Further, thinning of the upper mantle transition zone suggests a hotter mantle transition zone due to the possible presence of plumes in the mantle beneath the stations.

  14. Multiresolution imaging of mantle reflectivity structure using SS and P'P' precursors

    Science.gov (United States)

    Schultz, Ryan; Gu, Yu J.

    2013-10-01

    Knowledge of the mantle reflectivity structure is highly dependent on our ability to efficiently extract, and properly interpret, small seismic arrivals. Among the various data types and techniques, long-period SS/PP precursors and high-frequency receiver functions are routinely utilized to increase the confidence of the recovered mantle stratifications at distinct spatial scales. However, low resolution and a complex Fresnel zone are glaring weaknesses of SS precursors, while over-reliance on receiver distribution is a formidable challenge for the analysis of converted waves from oceanic regions. A promising high frequency alternative to receiver functions is P'P' precursors, which are capable of resolving mantle structures at vertical and lateral resolution of ˜5 and ˜200 km, respectively, owing to their spectral content, shallow angle of incidence and near-symmetric Fresnel zones. This study presents a novel processing method for both SS (or PP) and P'P' precursors based on deconvolution, stacking, Radon transform and depth migration. A suite of synthetic tests is performed to quantify the fidelity and stability of this method under different data conditions. Our multiresolution survey of the mantle at targeted areas near Nazca-South America subduction zone reveal both olivine and garnet related transitions at depths below 400 km. We attribute a depressed 660 to thermal variations, whereas compositional variations atop the upper-mantle transition zone are needed to explain the diminished or highly complex reflected/scattered signals from the 410 km discontinuity. We also observe prominent P'P' reflections within the transition zone, and the anomalous amplitudes near the plate boundary zone indicate a sharp (˜10 km thick) transition that likely resonates with the frequency content of P'P' precursors. The migration of SS precursors in this study shows no evidence of split 660 reflections, but potential majorite-ilmenite (590-640 km) and ilmenite

  15. XML Docbook to Mediawiki Converter

    Directory of Open Access Journals (Sweden)

    Maria Chiara Pievatolo

    2013-05-01

    Full Text Available A Perl script, based on the work of Stefano Selleri, to migrate XML-Docbook 4.X documents to Wiki markup. I added some lines to meet my need to convert my Kant translations from Docbook to MediaWiki. A sample of the output can be...

  16. Charge-pump voltage converter

    Science.gov (United States)

    Brainard, John P.; Christenson, Todd R.

    2009-11-03

    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  17. High-Performance Data Converters

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    Novel techniques for multi-bit oversampled data conversion are described. State-of-the-art oversampled data converters are analyzed, leading to the conclusion that their performance is limited mainly by low-resolution signal representation. To increase the resolution, high-performance, high...

  18. Steady-state creep in the mantle

    Directory of Open Access Journals (Sweden)

    G. RANALLI

    1977-06-01

    Full Text Available SUMMARY - The creep equations for steady-state flow of olivine at high
    pressure and temperature are compared in an attempt to elucidate the rheological
    behaviour of the mantle. Results are presented in terms of applied deformation
    maps and curves of effective viscosity v depth.
    In the upper mantle, the transition stress between dislocation and diffusion
    creep is between 10 to 102 bar (as orders of magnitude for grain sizes from
    0.01 to 1 cm. The asthenosphere under continents is deeper, and has higher
    viscosity, than under oceans. Predominance of one creep mechanism above the
    others depends on grain size, strain rate, and volume fraction of melt; the
    rheological response can be different for different geodynamic processes.
    In the lower mantle, on the other hand, dislocation creep is predominant
    at all realistic grain sizes and strain rates. If the effective viscosity has to be only
    slightly higher than in the upper mantle, as some interpretations of glacioisostatic
    rebound suggest, then the activation volume cannot be larger than
    11 cm3 mole^1.

  19. Volcanism, Earth Degassing and Replenished Lithosphere Mantle

    Science.gov (United States)

    Bailey, D. K.

    1980-07-01

    Volcanism that pierces plate interiors is characteristically rich in alkalis and volatiles, and its cause and persistence are essentially expressions of the Earth's outgassing. The general balance of mobile elements (such as H, C, F and Cl) rules out recycling of sea floor, hydrosphere, sediments or atmosphere: furthermore, it is not in accord with accepted planet degassing budgets. The typical eruptive mode of volatile-rich magmatism means that the observed regional chemical variations, and even differences between adjacent volcanoes, must largely reflect source heterogeneity. In a broader context, this magmatism is also at odds with a concept of continental crust underlain by strongly depleted (refractory) mantle. Repetition of activity along crustal zones of weakness shows that the lithosphere mantle (a) is structurally complex and (b) still holds continuing (or continual) rich reserves of mobile elements. Unbroken lithosphere muffles the evolutionary escape of volatiles from the deep mantle: any lesion that appears then offers easy escape channels, whereby volatiles are drained from a large mantle region and funnelled through the plate. Horizontal movement of thick continental lithosphere releases volatiles from deep sources, imparting some of the special chemical characteristics of the stable continental magmatism. Present evidence requires consideration of the continental lithosphere as a site of primordial heterogeneity that has been accentuated rather than diminished by geological processes.

  20. Explosion of Ultrahigh Pressure Minerals in Mantle

    Institute of Scientific and Technical Information of China (English)

    BAI Wenji; YANG Jingsui; FANG Qingsong; YAN Binggang; ZHANG Zhongming

    2001-01-01

    @@ The microexplosion stucture of ultrahigh pressure minerals was found for the first time in podform chromitites within the mantle peridotite facies of Luobusa ophiolite along the Yarlung Zangbo suture zone.The explosion stuctures of high-energy silicate inclusions are commonly seen in thin sections (see figure).

  1. Geodynamo Modeling of Core-Mantle Interactions

    Science.gov (United States)

    Kuang, Wei-Jia; Chao, Benjamin F.; Smith, David E. (Technical Monitor)

    2001-01-01

    Angular momentum exchange between the Earth's mantle and core influences the Earth's rotation on time scales of decades and longer, in particular in the length of day (LOD) which have been measured with progressively increasing accuracy for the last two centuries. There are four possible coupling mechanisms for transferring the axial angular momentum across the core-mantle boundary (CMB): viscous, magnetic, topography, and gravitational torques. Here we use our scalable, modularized, fully dynamic geodynamo model for the core to assess the importance of these torques. This numerical model, as an extension of the Kuang-Bloxham model that has successfully simulated the generation of the Earth's magnetic field, is used to obtain numerical results in various physical conditions in terms of specific parameterization consistent with the dynamical processes in the fluid outer core. The results show that depending on the electrical conductivity of the lower mantle and the amplitude of the boundary topography at CMB, both magnetic and topographic couplings can contribute significantly to the angular momentum exchange. This implies that the core-mantle interactions are far more complex than has been assumed and that there is unlikely a single dominant coupling mechanism for the observed decadal LOD variation.

  2. Elasticity of ferropericlase at lower mantle conditions

    Science.gov (United States)

    Wu, Z.; Justo, J. F.; Wentzcovitch, R. M.

    2014-12-01

    Clarification of the effect of the iron spin change on properties of Fp is important to address the relative abundance of Fp in the lower mantle. However, recent reports to this question show completely different conclusions. The calculated density of a pyrolite aggregate with spin crossover-related change in iron partitioning up to 45 GPa compared well with the density in PREM [1]. On the other hand, Murakami et al's analysis of VS in aggregates with variable amounts of Fp concluded the opposite - the lower mantle is more perovskitic than pyrolitic [2]. We investigated thermoelasticity of Fp with first principles DFT+U calculations. The calculated thermoelasticity are in good consitence with the available experimental data on samples with various iron concentrations. The results can well explain discrepancy on softening of the shear modulus of Fp among different experiments[3,4]. We predict velocities of Fp at lower mantle conditions and suggest that pyrolite is a reasonable compositional model for the lower mantle. Our results show the importance of constraining the elastic properties of minerals without extrapolations for analyses of the thermochemical state of this region[5]. [1] Irifune et al., Science 327, 193 (2010). [2] Murakami et al., Nature 485, 90 (2012). [3] Crowhurst et al., Science 319, 451 (2008). [4] Marquardt et al., Science 324, 224 (2009). [5]Wu et al., Phys. Rev. Lett. 110. 228501 (2013)

  3. The lithospheric mantle below southern West Greenland

    DEFF Research Database (Denmark)

    Sand, Karina Krarup; Waight, Tod Earle; Pearson, D. Graham

    2009-01-01

    Geothermobarometry of primarily garnet lherzolitic xenoliths from several localities in southern West Greenland is applied to address the diamond potential, pressure and temperature distribution and the stratigraphy of the subcontinental lithospheric mantle ~600 Ma ago. The samples are from kimbe...... into the reworked Archean North of the Naqssugtoqidian deformation front....

  4. Plate tectonics: Delayed response to mantle pull

    Science.gov (United States)

    Nedimović, Mladen R.

    2016-08-01

    At mid-ocean ridges, the directions in which plates spread and the underlying mantle flows were thought to broadly align. A synthesis of results from ridges that spread at a variety of rates reveals that instead there may be a systematic skew.

  5. Chondritic Xenon in the Earth's mantle: new constrains on a mantle plume below central Europe

    Science.gov (United States)

    Caracausi, Antonio; Avice, Guillaume; Bernard, Peter; Furi, Evelin; Marty, Bernard

    2016-04-01

    Due to their inertness, their low abundances, and the presence of several different radiochronometers in their isotope systematics, the noble gases are excellent tracers of mantle dynamics, heterogeneity and differentiation with respect to the atmosphere. Xenon deserves particular attention because its isotope systematic can be related to specific processes during terrestrial accretion (e.g., Marty, 1989; Mukhopadhyay, 2012). The origin of heavy noble gases in the Earth's mantle is still debated, and might not be solar (Holland et al., 2009). Mantle-derived CO2-rich gases are particularly powerful resources for investigating mantle-derived noble gases as large quantities of these elements are available and permit high precision isotope analysis. Here, we report high precision xenon isotopic measurements in gases from a CO2 well in the Eifel volcanic region (Germany), where volcanic activity occurred between 700 ka and 11 ka years ago. Our Xe isotope data (normalized to 130Xe) show deviations at all masses compared to the Xe isotope composition of the modern atmosphere. The improved analytical precision of the present study, and the nature of the sample, constrains the primordial Xe end-member as being "chondritic", and not solar, in the Eifel mantle source. This is consistent with an asteroidal origin for the volatile elements in Earth's mantle and it implies that volatiles in the atmosphere and in the mantle originated from distinct cosmochemical sources. Despite a significant fraction of recycled atmospheric xenon in the mantle, primordial Xe signatures still survive in the mantle. This is also a demonstration of a primordial component in a plume reservoir. Our data also show that the reservoir below the Eifel region contains heavy-radiogenic/fissiogenic xenon isotopes, whose ratios are typical of plume-derived reservoirs. The fissiogenic Pu-Xe contribution is 2.26±0.28 %, the UXe contribution is negligible, the remainder being atmospheric plus primordial. Our

  6. Shear wave speeds at the base of the mantle

    NARCIS (Netherlands)

    Castle, John C.; Hilst, R.D. van der; Creager, K.C.; Winchester, John P.

    2006-01-01

    We inverted 4864 ScS-S and 1671 S(diff)-SKS residual travel times for shear wave speed anomalies at the base of the Earth's mantle. We applied ellipticity corrections, accounted for mantle structure outside of the basal layer using mantle tomography models, and employed finite size sensitivity kerne

  7. Global correlation of lower mantle structure and past subduction

    NARCIS (Netherlands)

    Domeier, M.; Doubrovine, Pavel V.; Torsvik, Trond H.; Spakman, W.|info:eu-repo/dai/nl/074103164; Bull, A.L.

    2016-01-01

    Advances in global seismic tomography have increasingly motivated identification of subducted lithosphere in Earth's deep mantle, creating novel opportunities to link plate tectonics and mantle evolution. Chief among those is the quest for a robust subduction reference frame, wherein the mantle asse

  8. Shear wave speeds at the base of the mantle

    NARCIS (Netherlands)

    Castle, John C.; Hilst, R.D. van der; Creager, K.C.; Winchester, John P.

    2000-01-01

    We inverted 4864 ScS-S and 1671 S(diff)-SKS residual travel times for shear wave speed anomalies at the base of the Earth's mantle. We applied ellipticity corrections, accounted for mantle structure outside of the basal layer using mantle tomography models, and employed finite size sensitivity

  9. European Lithospheric Mantle; geochemical, petrological and geophysical processes

    Science.gov (United States)

    Ntaflos, Th.; Puziewicz, J.; Downes, H.; Matusiak-Małek, M.

    2017-04-01

    The second European Mantle Workshop occurred at the end of August 2015, in Wroclaw, Poland, attended by leading scientists in the study the lithospheric mantle from around the world. It built upon the results of the first European Mantle Workshop (held in 2007, in Ferrara, Italy) published in the Geological Society of London Special Publication 293 (Coltorti & Gregoire, 2008).

  10. Mantle Temperature, Mantle Composition, Mantle Heterogeneity, and the Composition of the Upper Mantle: The View from a Global Synthesis of MORB

    Science.gov (United States)

    Langmuir, C. H.; Gale, A.; Dalton, C. A.

    2012-12-01

    A new comprehensive review of global MORB can address outstanding issues such mantle temperature vs. mantle composition in controlling MORB compositions, the mean composition of ocean ridge basalts, the K/U ratio of the MORB reservoir, and the implications for silicate Earth mass balance of the composition of the upper mantle. We created a global catalogue of ridge segments to assign every sample to a segment. We carried out interlaboratory corrections for major elements, and examined data from each segment to ensure appropriate fractionation correction. We included large unpublished data sets from the Langmuir and Schilling laboratories, assembling the most comprehensive data set for MORB. Data averaged by segment permit calculation of averages that include weighting by segment length and spreading rate. The segment-based approach, comprehensive data set, individualized fractionation correction and interlaboratory corrections distinguish these results from earlier efforts. We also carried out bootstrapping statistical tests for meaningful errors on average compositions. The mean composition of the ocean crust is best determined by a segment length and spreading rate weighted arithmetic mean. As with other recent efforts, notably Su (2002) and also Arevalo and McDonough (2009), the mean composition is substantially more enriched than previous MORB estimates. Average MORB implies a MORB mantle Sm/Nd and Nd isotopic composition similar to the 'non-chondritic primitive mantle' composition based on 142Nd. Then continental crust/MORB mantle mass balance is not possible using a non-chondritic (depleted) bulk silicate earth composition, unless there is a large unsampled depleted reservoir. In contrast to Arevalo and McDonough, who suggested a K/U ratio for MORB of 19,000, we find K/U of 12,340±810, in line with earlier estimates. The discrepancy can be understood from contrasts in methodology, as we determine average K/ average U, while they determine average K/U. To

  11. Mantle Convection Models Constrained by Seismic Tomography

    Science.gov (United States)

    Durbin, C. J.; Shahnas, M.; Peltier, W. R.; Woodhouse, J. H.

    2011-12-01

    Although available three dimensional models of the lateral heterogeneity of the mantle, based upon the latest advances in seismic tomographic imaging (e.g. Ritsema et al., 2004, JGR) have provided profound insights into aspects of the mantle general circulation that drives continental drift, the compatibility of the tomography with explicit models of mantle mixing has remained illusive. For example, it remains a significant issue as to whether hydrodynamic models of the mixing process alone are able to reconcile the observed detailed pattern of surface plate velocities or whether explicit account must be taken of elastic fracture processes to account for the observed equipartition of kinetic energy between the poloidal and toroidal components of the surface velocity pattern (e.g. Forte and Peltier, 1987, JGR). It is also an issue as to the significance of the role of mantle chemical heterogeneity in determining the buoyancy distribution that drives mantle flow, especially given the expected importance of the spin transition of iron that onsets in the mid-lower mantle, at least in the ferropericlase component of the mineralogy. In this paper we focus upon the application of data assimilation techniques to the development of a model of mantle mixing that is consistent with a modern three dimensional tomography based model of seismic body wave heterogeneity. Beginning with the simplest possible scenario, that chemical heterogeneity is irrelevant to first order, we employ a three dimensional version of the recently published control volume based convection model of Shahnas and Peltier (2010, JGR) as the basis for the assimilation of a three dimensional density field inferred from our preferred tomography model (Ritsema et al., 2004, JGR). The convection model fully incorporates the dynamical influence of the Olivine-Spinel and Spinel-Perovskite+Magnesiowustite solid-solid phase transformations that bracket the mantle transition zone as well as the recently discovered

  12. Bidirectional dc-to-dc Power Converter

    Science.gov (United States)

    Griesbach, C. R.

    1986-01-01

    Solid-state, series-resonant converter uses high-voltage thyristors. Converter used either to convert high-voltage, low-current dc power to lowvoltage, high current power or reverse. Taking advantage of newly-available high-voltage thyristors to provide better reliability and efficiency than traditional converters that use vacuum tubes as power switches. New converter essentially maintenance free and provides greatly increased mean time between failures. Attractive in industrial applications whether or not bidirectional capability is required.

  13. Parametric study of laser photovoltaic energy converters

    Science.gov (United States)

    Walker, G. H.; Heinbockel, J. H.

    1987-01-01

    Photovoltaic converters are of interest for converting laser power to electrical power in a space-based laser power system. This paper describes a model for photovoltaic laser converters and the application of this model to a neodymium laser silicon photovoltaic converter system. A parametric study which defines the sensitivity of the photovoltaic parameters is described. An optimized silicon photovoltaic converter has an efficiency greater than 50 percent for 1000 W/sq cm of neodymium laser radiation.

  14. Compositions of Upper Mantle Fluids Beneath Eastern China:Implications for Mantle Evolution

    Institute of Scientific and Technical Information of China (English)

    ZHANG Mingjie; WANG Xianbin; LIU Gang; ZHANG Tongwei; BO Wenrui

    2004-01-01

    The composition of gases trapped in olivine, orthopyroxene and clinopyroxene in lherzolite xenoliths collected from different locations in eastern China has been measured by the vacuum stepped-heating mass spectrometry.These xenoliths are hosted in alkali basalts and considered as residues of partial melting of the upper mantle, and may contain evidence of mantle evolution. The results show that various kinds of fluid inclusions in lherzolite xenoliths have been released at distinct times, which could be related to different stages of mantle evolution. In general, primitive fluids of the upper mantle (PFUM) beneath eastern China are dominated by H2, CO2 and CO, and are characterized by high contents of H2 and reduced gases. The compositions of PFUM are highly variable and related to tectonic settings. CO, CO2 and H2 are the main components of the PFUM beneath cratons; the PFUM in the mantle enriched in potassic metasomatism in the northern part of northeastern China has a high content of H2, while CO2 and SO2 are the dominant components of the PFUM in the Su-Lu-Wan (Jiangsu-Shandong-Anhui) region, where recycled crustal fluids were mixed with deeper mantle components. There are several fluids with distinct compositions beneath eastern China, such as primitive fluids of upper mantle (CO, CO2 and H2), partial melting fluids (CO2 and CO) and metasomatic fluids mixed with recycled crustal fluids (CO2, N2, 8O2 and CH4) etc. Fluids of the upper mantle beneath the North China craton are different from that of the South China craton in total gases and chemical compositions: the contents of the reduced gases of the PFUM in the NCC are higher than those in the SCC.

  15. Finding the patterns in mantle convection

    Science.gov (United States)

    Atkins, Suzanne; Rozel, Antoine; Valentine, Andrew; Tackley, Paul; Trampert, Jeannot

    2016-04-01

    Inverting mantle flow for past configurations is one of the great outstanding problems in geodynamics. We demonstrate a new method for probabilistic inversion of present-day Earth observations for mantle properties and history. Convection is a non-linear and chaotic, thwarting most standard inversion methods. Because of its chaotic and unpredictable nature, small errors in initial conditions, parameter selection, and computational precision can all significantly change the results produced by mantle convection simulations. However, some patterns and statistics of convection contain the signature of the parameters used in the simulations over long time-scales. Geodynamical studies often vary these parameters to investigate their effects on the patterns produced. We show that with a large enough set of simulations, we can investigate the relationship between input parameters and convection patterns in a more rigorous way. Probabilistic inversion is the only way to approach highly non-linear problems. We use neural networks to represent the probability density function linking convection simulation input parameters and the patterns they produce. This allows us to find input parameters, whilst taking into account all of the uncertainties that are inherent in the inversion of any Earth system: how well do we understand the physics of the process; what do we already know about the input parameters; and how certain are our observations? We show that the mantle structures produced by 4.5 Gyr of convection simulations contain enough information on yield stress, viscosity coefficients, mantle heating rate, and the initial state of primordial material that we can infer them directly without requiring any other information, such as plate velocity.

  16. Nitrogen speciation in mantle and crustal fluids

    Science.gov (United States)

    Li, Yuan; Keppler, Hans

    2014-03-01

    Seventy-nine experiments have been carried out at 600-1400 °C, 2-35 kbar, and oxygen fugacities ranging from the Fe-FeO to the Re-ReO2 buffer to investigate the nitrogen speciation in mantle and crustal N-H-O fluids. Laser Raman analyses of fluid inclusions trapped in situ in quartz and olivine crystals show that N2 and/or NH3 are the only detectable nitrogen species in the fluids at the conditions of the present study. The results further show that in the fluids of the oxidized shallow upper mantle, nitrogen is mostly present as N2, while in the deep reduced upper mantle, NH3 is the dominant nitrogen species. Nitrogen speciation in subduction zone fluids is also calculated from the experimental data to constrain the efficiency of nitrogen recycling. The data show that a hot, oxidized slab is an efficient barrier for deep nitrogen subduction, while a cold, reduced slab would favor recycling nitrogen into the deep mantle. The nitrogen species in magmatic fluids of mid-ocean ridge basalt and arc magmas are predominantly N2, but a significant fraction of nitrogen can be NH3 at certain conditions. The nitrogen species in fluids released from the solidifying magma ocean and the reduced young mantle may have been mostly NH3. The release of such fluids may have created a reduced atmosphere on the every early Earth, with an elevated concentration of NH3. This may not only resolve the faint young Sun paradox but may also have created favorable conditions for the formation of biomolecules through Miller-Urey type reactions.

  17. Nickel isotopic composition of the mantle

    Science.gov (United States)

    Gall, Louise; Williams, Helen M.; Halliday, Alex N.; Kerr, Andrew C.

    2017-02-01

    This paper presents a detailed high-precision study of Ni isotope variations in mantle peridotites and their minerals, komatiites as well as chondritic and iron meteorites. Ultramafic rocks display a relatively large range in δ60 Ni (permil deviation in 60 Ni /58 Ni relative to the NIST SRM 986 Ni isotope standard) for this environment, from 0.15 ± 0.07‰ to 0.36 ± 0.08‰, with olivine-rich rocks such as dunite and olivine cumulates showing lighter isotope compositions than komatiite, lherzolite and pyroxenite samples. The data for the mineral separates shed light on the origin of these variations. Olivine and orthopyroxene display light δ60 Ni whereas clinopyroxene and garnet are isotopically heavy. This indicates that peridotite whole-rock δ60 Ni may be controlled by variations in modal mineralogy, with the prediction that mantle melts will display variable δ60 Ni values due to variations in residual mantle and cumulate mineralogy. Based on fertile peridotite xenoliths and Phanerozoic komatiite samples it is concluded that the upper mantle has a relatively homogeneous Ni isotope composition, with the best estimate of δ60Nimantle being 0.23 ± 0.06‰ (2 s.d.). Given that >99% of the Ni in the silicate Earth is located in the mantle, this also defines the Ni isotope composition of the Bulk Silicate Earth (BSE). This value is nearly identical to the results obtained for a suite of chondrites and iron meteorites (mean δ60 Ni 0.26 ± 0.12‰ and 0.29 ± 0.10‰, respectively) showing that the BSE is chondritic with respect to its Ni isotope composition, with little to no Ni mass-dependent isotope fractionation resulting from core formation.

  18. Water in the Cratonic Mantle Lithosphere

    Science.gov (United States)

    Peslier, A. H.

    2016-01-01

    The fact that Archean and Proterozoic cratons are underlain by the thickest (>200 km) lithosphere on Earth has always puzzled scientists because the dynamic convection of the surrounding asthenosphere would be expected to delaminate and erode these mantle lithospheric "keels" over time. Although density and temperature of the cratonic lithosphere certainly play a role in its strength and longevity, the role of water has only been recently addressed with data on actual mantle samples. Water in mantle lithologies (primarily peridotites and pyroxenites) is mainly stored in nominally anhydrous minerals (olivine, pyroxene, garnet) where it is incorporated as hydrogen bonded to structural oxygen in lattice defects. The property of hydrolytic weakening of olivine [4] has generated the hypothesis that olivine, the main mineral of the upper mantle, may be dehydrated in cratonic mantle lithospheres, contributing to its strength. This presentation will review the distribution of water concentrations in four cratonic lithospheres. The distribution of water contents in olivine from peridotite xenoliths found in kimberlites is different in each craton (Figure 1). The range of water contents of olivine, pyroxene and garnet at each xenolith location appears linked to local metasomatic events, some of which occurred later then the Archean and Proterozoic when these peridotites initially formed via melting. Although the low olivine water contents ( 6 GPa at the base of the Kaapvaal cratonic lithosphere may contribute to its strength, and prevent its delamination, the wide range of those from Siberian xenoliths is not compatible with providing a high enough viscosity contrast with the asthenophere. The water content in olivine inclusions from Siberian diamonds, on the other hand, have systematically low water contents (water contents. The olivine inclusions, however, may have been protected from metasomatism by their host diamond and record the overall low olivine water content of

  19. Cosmochemical Estimates of Mantle Composition

    Science.gov (United States)

    Palme, H.; O'Neill, H. St. C.

    2003-12-01

    In 1794 the German physicist Chladni published a small book in which he suggested the extraterrestrial origin of meteorites. The response was skepticism and disbelief. Only after additional witnessed falls of meteorites did scientists begin to consider Chladni's hypothesis seriously. The first chemical analyses of meteorites were published by the English chemist Howard in 1802, and shortly afterwards by Klaproth, a professor of chemistry in Berlin. These early investigations led to the important conclusion that meteorites contained the same elements that were known from analyses of terrestrial rocks. By the year 1850, 18 elements had been identified in meteorites: carbon, oxygen, sodium, magnesium, aluminum, silicon, phosphorous, sulfur, potassium, calcium, titanium, chromium, manganese, iron, cobalt, nickel, copper, and tin (Burke, 1986). A popular hypothesis, which arose after the discovery of the first asteroid Ceres on January 1, 1801 by Piazzi, held that meteorites came from a single disrupted planet between Mars and Jupiter. In 1847 the French geologist Boisse (1810-1896) proposed an elaborate model that attempted to account for all known types of meteorites from a single planet. He envisioned a planet with layers in sequence of decreasing densities from the center to the surface. The core of the planet consisted of metallic iron surrounded by a mixed iron-olivine zone. The region overlying the core contained material similar to stony meteorites with ferromagnesian silicates and disseminated grains of metal gradually extending into shallower layers with aluminous silicates and less iron. The uppermost layer consisted of metal-free stony meteorites, i.e., eucrites or meteoritic basalts. About 20 years later, Daubrée (1814-1896) carried out experiments by melting and cooling meteorites. On the basis of his results, he came to similar conclusions as Boisse, namely that meteorites come from a single, differentiated planet with a metal core, a silicate mantle

  20. Ultra-low velocity zone heterogeneities at the core-mantle boundary from diffracted PKKPab waves

    Science.gov (United States)

    Ma, Xiaolong; Sun, Xinlei

    2017-08-01

    Diffracted waves around Earth's core could provide important information of the lowermost mantle that other seismic waves may not. We examined PKKPab diffraction waves from 52 earthquakes occurring at the western Pacific region and recorded by USArray to probe the velocity structure along the core-mantle boundary (CMB). These diffracted waves emerge at distances up to 10° past the theoretical cutoff epicentral distance and show comparable amplitudes. We measured the ray parameters of PKKPab diffraction waves by Radon transform analysis that is suitable for large-aperture arrays. These ray parameters show a wide range of values from 4.250 to 4.840 s/deg, suggesting strong lateral heterogeneities in sampling regions at the base of the mantle. We further estimated the P-wave velocity variations by converting these ray parameters and found the CMB regions beneath the northwestern edge of African Anomaly (Ritsma et al. in Science 286:1925-1928, 1999) and southern Sumatra Islands exhibit velocity reductions up to 8.5% relative to PREM. We suggest that these low velocity regions are Ultra-low velocity zones, which may be related to partial melt or iron-enriched solids.[Figure not available: see fulltext.

  1. Photoelectric converters with quantum coherence

    Science.gov (United States)

    Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can

    2016-05-01

    Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency ηCA. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to ηCA through manipulation of carefully controlled quantum coherences.

  2. Photoelectric converter; Koden henkan soshi

    Energy Technology Data Exchange (ETDEWEB)

    Sawayama, I.

    1995-04-07

    The conventional solar cell module wherein plural photovoltaic elements formed on a metal substrate are connected and coated by weatherproof and translucent resin has defects such as pinholes, and separation because moisture infiltrating from the outside causes dissolution of such conductive matrix as silver in the collecting electrode. This invention relates to a photoelectric converter which has little decrease in the output under the environment of light irradiation, wherein a photoelectric converting semiconductor, a transparent conductive layer on the above-mentioned semiconductor, and conductive member containing water repellent fine powder grains on this transparent conductive layer are laminated successively. Polytetrafluoroethylene, polydimethyl siloxane, polyethylene, and nylon are desirable to be employed as the water repellent fine powder grains. The fine powder grains are mixed with conductive filler and binder to produce conductive paste, pattern-applied by a screen printing machine, and subjected to thermal treatment to form a conductive member. 3 figs., 1 tab.

  3. Photoelectric converters with quantum coherence.

    Science.gov (United States)

    Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can

    2016-05-01

    Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency η_{CA}. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to η_{CA} through manipulation of carefully controlled quantum coherences.

  4. Importance of Mantle Viscosity in Interseismic Deformation

    Science.gov (United States)

    Wang, K.; He, J.; Hu, Y.

    2012-12-01

    The role of mantle viscosity in subduction earthquake cycles was postulated when the plate tectonics theory had just gained wide acceptance. The process was described using Elsasser's 1-D model for diffusion of stress from the subduction boundary to the plate interior. Main features of interseismic surface deformation predicted by this elegantly simple model were later verified by GPS observations following giant subduction earthquakes. However, and intriguingly, the vast majority of interseismic deformation models developed in the era of space geodesy assume an elastic Earth, incorrectly regarding interseismic deformation as a subdued mirror image of coseismic deformation. The reason is four-fold. (1) The 1-D model and subsequent 2-D viscoelastic models failed to recognize the role of rupture length in the strike direction and could not self-consistently explain deformation following medium and small earthquakes. (2) Based on global mantle viscosity models derived from glacial isostatic adjustment studies, the viscoelastic mantle should indeed behave elastically in earthquake cycles of a few hundred years. (3) The effect of viscous mantle deformation can often be equivalently described by deep fault creep in a purely elastic Earth. (4) The use of an elastic model provides convenience in inverting geodetic data to determine fault locking and creep. Here we use 3D finite element models to show that the main characteristics of surface deformation following subduction earthquakes of all sizes can be explained with a viscoelastic Earth in which the mantle wedge is less viscous than global upper-mantle average of 1020 - 1021 Pa s by one to two orders of magnitude. Following giant earthquakes, such as 1700 Cascadia, 1960 Chile, 1964 Alaska, 2004 Sumatra, and 2011 Japan, upper-plate land deformation undergoes phases of wholesale seaward motion, opposing motion of coastal and inland areas, and wholesale landward motion. The "speed" of the evolution scales inversely with

  5. Simplified dc to dc converter

    Science.gov (United States)

    Gruber, R. P. (Inventor)

    1984-01-01

    A dc to dc converter which can start with a shorted output and which regulates output voltage and current is described. Voltage controlled switches directed current through the primary of a transformer the secondary of which includes virtual reactance. The switching frequency of the switches is appropriately varied to increase the voltage drop across the virtual reactance in the secondary winding to which there is connected a low impedance load. A starting circuit suitable for voltage switching devices is provided.

  6. Biomass compounds converted to gasoline

    Energy Technology Data Exchange (ETDEWEB)

    1979-10-08

    It is claimed that corn, castor, and jojoba oils as well as Hevea latex can be converted in high yields to gasoline by passage over zeolite catalysts at 450 degrees to 500 degrees centigrade. Gasoline yields are 60% from corn oil (essentially tristearin), compared with 50% yields from methanol. Latex depolymerizes before conversion. Fat and oil molecules adopt conformations that enable them to enter zeolite interstices, resulting in high yields of C6 to C9 aromatics.

  7. Workshop 4 Converter cooling & recuperation

    Science.gov (United States)

    Iles, Peter; Hindman, Don

    1995-01-01

    Cooling the PV converter increases the overall TPV system efficiency, and more than offsets the losses incurred in providing cooling systems. Convective air flow methods may be sufficient, and several standard water cooling systems, including thermo-syphon radiators, capillary pumps or microchannel plates, are available. Recuperation is used to increase system efficiency, rather than to increase the emitter temperature. Recuperators operating at comparable high temperatures, such as in high temperature turbines have worked effectively.

  8. Computerized simulation of converter process

    Energy Technology Data Exchange (ETDEWEB)

    Jalkanen, H.; Suomi, M.L.; Wallgren, M. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Metallurgy

    1996-12-31

    Converter process is essentially an oxidising refining process aiming in addition to (1) the primary refining action, decarburisation of high carbon iron melt, also to (2) maximal elimination of impurity elements, especially silicon, phosphorus and sulphur, (3) melting of substantial amounts of scrap using the extra heat released in oxidation reactions and (4) to exact final steel temperature control, optimal for further treatments. `Quantitative modelling of such a complex non-stationary chemical process as oxygen converting necessitates extensive formulation of chemical and thermal evolution of the process in connection with the technological properties of the reactor and the process control measures. A comprehensive converter simulation program like CONSIM-3. 1 and its preceding versions that is based on the theoretical and practical knowledge on the process can be used for (1) educating specialists and smelter personnel, (2) planning of the blowing programs, (3) developing and testing of process control systems and after some elaboration and restructuring (4) it can be integrated to static or dynamic process control systems. (orig.) SULA 2 Research Programme; 10 refs.

  9. Design and Control for the Buck-Boost Converter Combining 1-Plus-D Converter and Synchronous Rectified Buck Converters

    Directory of Open Access Journals (Sweden)

    Jeevan Naik

    2015-06-01

    Full Text Available In this paper, a design and control for the buck-boost converter, i.e., 1-plus-D converter with a positive output voltage, is presented, which combines the 1-plus-D converter and the synchronous rectified (SR buck converter. By doing so, the problem in voltage bucking of the 1-plus-D converter can be solved, thereby increasing the application capability of the 1-plus-D converter. Since such a converter operates in continuous conduction mode inherently, it possesses the nonpulsating output current, thereby not only decreasing the current stress on the output capacitor but also reducing the output voltage ripple. Above all, both the 1-plus-D converter and the SR buck converter, combined into a buck–boost converter with no right-half plane zero, use the same power switches, thereby causing the required circuit to be compact and the corresponding cost to be down. Furthermore, during the magnetization period, the input voltage of the 1-plus-D converter comes from the input voltage source, whereas during the demagnetization period, the input voltage of the 1-plus-D converter comes from the output voltage of the SR buck converter.

  10. Geophysical and geochemical constraints on geoneutrino fluxes from Earth's mantle

    CERN Document Server

    Šrámek, Ondřej; Kite, Edwin S; Lekić, Vedran; Dye, Steve; Zhong, Shijie

    2012-01-01

    Knowledge of the amount and distribution of radiogenic heating in the mantle is crucial for understanding the dynamics of the Earth, including its thermal evolution, the style and planform of mantle convection, and the energetics of the core. Although the flux of heat from the surface of the planet is robustly estimated, the contributions of radiogenic heating and secular cooling remain poorly defined. Constraining the amount of heat-producing elements in the Earth will provide clues to understanding nebula condensation and planetary formation processes in early Solar System. Mantle radioactivity supplies power for mantle convection and plate tectonics, but estimates of mantle radiogenic heat production vary by a factor of up to 30. Recent experimental results demonstrate the potential for direct assessment of mantle radioactivity through observations of geoneutrinos, which are emitted by naturally occurring radionuclides. Predictions of the geoneutrino signal from the mantle exist for several established est...

  11. Role of mantle flow in Nubia-Somalia plate divergence

    Science.gov (United States)

    Stamps, D. S.; Iaffaldano, G.; Calais, E.

    2015-01-01

    Present-day continental extension along the East African Rift System (EARS) has often been attributed to diverging sublithospheric mantle flow associated with the African Superplume. This implies a degree of viscous coupling between mantle and lithosphere that remains poorly constrained. Recent advances in estimating present-day opening rates along the EARS from geodesy offer an opportunity to address this issue with geodynamic modeling of the mantle-lithosphere system. Here we use numerical models of the global mantle-plates coupled system to test the role of present-day mantle flow in Nubia-Somalia plate divergence across the EARS. The scenario yielding the best fit to geodetic observations is one where torques associated with gradients of gravitational potential energy stored in the African highlands are resisted by weak continental faults and mantle basal drag. These results suggest that shear tractions from diverging mantle flow play a minor role in present-day Nubia-Somalia divergence.

  12. Simulation Results of Double Forward Converter

    Directory of Open Access Journals (Sweden)

    P. Vijaya KUMAR

    2009-12-01

    Full Text Available This work aims to find a better forward converter for DC to DC conversion.Simulation of double forward converter in SMPS system is discussed in this paper. Aforward converter with RCD snubber to synchronous rectifier and/or to current doubleris also discussed. The evolution of the forward converter is first reviewed in a tutorialfashion. Performance parameters are discussed including operating principle, voltageconversion ratio, efficiency, device stress, small-signal dynamics, noise and EMI. Itscircuit operation and its performance characteristics of the forward converter with RCDsnubber and double forward converter are described and the simulation results arepresented.

  13. Eight good reasons why the uppermost mantle could be magnetic

    Science.gov (United States)

    Ferré, Eric C.; Friedman, Sarah A.; Martín-Hernández, Fatíma; Feinberg, Joshua M.; Till, Jessica L.; Ionov, Dmitri A.; Conder, James A.

    2014-06-01

    Wasilewski et al. (1979) concluded that no magnetic remanence existed in the uppermost mantle and that even if present, such sources would be at temperatures too high to contribute to long wavelength magnetic anomalies (LWMA). However, new collections of unaltered mantle xenoliths indicate that the uppermost mantle could contain ferromagnetic minerals. 1. The analysis of some LWMA over cratons and forearcs suggest magnetic sources in the uppermost mantle. 2. The most common ferromagnetic phase in the uppermost mantle is stoichiometric magnetite. Assuming a 30 km-thick crust, and crustal and mantle geotherms of 15 °C/km and 5 °C/km, respectively, the 600 °C Curie temperature implies a 30 km-thick layer of mantle. 3. The uppermost mantle is cooler than 600 °C in Archean and Proterozoic shields (> 350 °C), subduction zones (> 300 °C) and old oceanic basins (> 250 °C). 4. Recently investigated sets of unaltered mantle xenoliths contain pure magnetite inclusions in olivine and pyroxene formed in equilibrium with the host silicate. 5. The ascent of mantle xenoliths occurs in less than a day. Diffusion rates in olivine suggest that the growth of magnetite possible within this time frame cannot account for the size and distribution of magnetite particles in our samples. 6. Demagnetization of natural remanent magnetization (NRM) of unaltered mantle xenoliths unambiguously indicates only a single component acquired upon cooling at the Earth's surface. This is most easily explained as a thermoremanent magnetization acquired by pre-existing ferromagnetic minerals as xenoliths cool rapidly at the Earth's surface from magmatic temperatures, acquired during ascent. 7. Modern experimental data suggest that the wüstite-magnetite oxygen buffer and the fayalite-magnetite-quartz oxygen buffer extend several tens of km within the uppermost mantle. 8. The magnetic properties of mantle xenoliths vary consistently across tectonic settings. In conclusion, the model of a uniformly

  14. Mantle plumes: Why the current skepticism?

    Institute of Scientific and Technical Information of China (English)

    Gillian R. Foulger

    2005-01-01

    The present reappraisal of the mantle plume hypothesis is perhaps the most exciting current debate in Earth science. Nevertheless, the fundamental reasons for why it has arisen are often not well understood. They are that 1) many observations do not agree with the predictions of the original model, 2) it is possible that convection of the sort required to generate thermal plumes in the Earth's mantle does not occur, 3) so many variants of the original model have been invoked to accommodate conflicting data that the plume hypthesis is in practice no longer testable, and 4) alternative models are viable, though these have been largely neglected by researchers. Regardless of the final outcome, the present vigorous debate is to be welcomed since it is likely to stimulate new discoveries in a way that unquestioning acceptance of the conventional plume model will not.

  15. A Consensus on Mantle Potential Temperatures? (Invited)

    Science.gov (United States)

    Putirka, K. D.

    2009-12-01

    Recent publications may indicate a mounting consensus regarding mantle temperatures - an agreement that can be crucial for improving our understanding of mantle dynamics. To compare temperatures at various localities, McKenzie & Bickle (1988) proposed the concept of a mantle potential temperature (Tp) as a reference; Tp is the temperature the mantle would have at the surface, if it ascended along an adiabat without undergoing melting. Perhaps the most precise method to estimate Tp involves estimating the conditions of partial melting, and then correcting for the heat of fusion. The several sources of error include estimation of: a parental liquid, an equilibrium mantle olivine, the degree of partial melting (F), and the depth at which the parental melt is generated. There is also model error inherent to any thermometer. And when correcting for the heat of fusion we assume that we are correcting up to the convective adiabat, but if the parental melt was generated within the conductive lithosphere, Tp will be low. In any case, if we accept that the highest Tp estimates at Hawaii are of most interest (since magmas generated away from a plume centerline will not reflect the full heat content of a high T source), then in spite of these sources of error, recent estimates, published over a span of 10 months by three independent research groups, indicate considerable convergence. At Hawaii maximum Tp values are: 1600 deg. C by Herzberg & Asimow (2008), ca. 1630 deg. C by Lee et al. (2009; their Fig. 2B), and using two slightly different equation sets, 1687 deg. C by Putirka (2008; Geology) and 1660 deg. C by Putirka (2008; RiMG volume 69), yielding an average of 1644±38oC. Similarly, there is convergence for mean Tp at MORs (accepting that MORs are not isothermal; Klein and Langmuir, 1987): Herzberg & Asimow (2008) and Lee et al. (2009) estimate that Tp is ca. 1350 deg. C, and Putirka (2008; Geology) estimates a Tp of 1396 deg. C; these estimates average to 1365±26o

  16. Lunar maria - result of mantle plume activity?

    Science.gov (United States)

    Sharkov, E.

    It is generally accepted that lunar maria are the result of catastrophic impact events. However, comparative studying of the Earth's and the Moon's tectonomagmatic evolution could evidence about another way of these specific structures origin. Such studies showed that the both planetary bodies evolved on the close scenario: their geological development began after solidification of global magmatic oceans which led to appearance of their primordial crusts: granitic on the Earth and anorthositic - on the Moon. The further evolution of the both bodies occurred in two stages. For their first stages, lasted ˜2.5 mlrd. years on the Earth and ˜1.5 mlrd. years on the Moon, were typical melts, generated in depleted mantle (Bogatikov et al., 2000). However, at the boundary 2.2-2.0 Ga ago on the Earth and 3.9-3.8 Ga on the Moon another type of magmas appeared: geochemical enriched Fe-Ti picrites and basalts, characteristic for the terrestrial Phanerozoic plume-related situations, and basaltic mare magmatism with high-Ti varieties on the Moon. It suggests that evolution of the Earth's magmatism was linked with ascending of mantle plumes (superplumes) of two generation: (1) generated in the mantle, depleted during solidification of magmatic ocean and Archean magmatic activity, and (2) generated at the core-mantle boundary (CMB). The latter were enriched in the mantle fluid components (Fe, Ti, alkalies, etc); this lighter material could ascend to shallower depths, leading to change of tectonic processes, in particular, to appearance of plate tectonics as the major type of tectonomagmatic activity till now (Bogatikov et al., 2000). By analogy to the Earth, magmatism of the Moon was also linked with ascending of mantle plumes: (1) generated in the depleted mantle (magnesian suite) and (2) generated at the lunar CMB with liquid at that time metallic core (mare basalt and picrites with high-Ti varieties). Like on the Earth, these plumes were lighter than the older plumes, and

  17. Constitution and structure of earth's mantle

    DEFF Research Database (Denmark)

    Zunino, Andrea; Khan, Amir; Cupillard, Paul

    2016-01-01

    This chapter describes a quantitative approach that integrates data and results from mineral physics, petrological analyses, and geophysical inverse calculations to map geophysical data directly for mantle composition and thermal state. Seismic tomography has proved an important tool to image...... the inaccessible parts of the Earth. Computation of physical properties using thermodynamic models is described and discussed, and an application of the joint inverse methodology is illustrated in a case study where mantle composition and thermal state beneath continental Australia is determined directly from...... seismic data. There is a growing consensus that the cause of the imaged wavespeed anomalies not only relates to variations in temperature, but also bears a strong compositional component. However, separation of thermal and chemical effects from seismic wave speeds alone is difficult and is further...

  18. Si Bule Masuk Islam: Western Converts to Islam in Indonesia - more than just Converts of Convenience?

    OpenAIRE

    M. A. Kevin Brice

    2015-01-01

    In discussing converts to Islam, two different types of converts are often identified based on the reason for conversion: converts of convenience and converts of conviction. The common view is that in most (if not all) cases, conversion to Islam in Indonesia by Westerners is about facilitating marriage and so the converts should be classified as converts of convenience. Evidence of the commonality of this view is considered by reference to advice offered to Westerners about marriage to Indone...

  19. Hydrogen storage in Earth's mantle and core

    Science.gov (United States)

    Prewitt, Charles T.

    1994-01-01

    Two different approaches to explaining how hydrogen might be stored in the mantle are illustrated by a number of papers published over the past 25-30 years, but there has been little attempt to provide objective comparisons of the two. One approach invokes the presence in the mantle of dense hydrous magnesium silicates (DHMS) stable at elevated pressures and temperatures. The other involves nominally anhydrous minerals (NAM) that contain hydrogen as a minor constituent on the ppm level. Experimental studies on DHMS indicate these phases may be stable to pressures and temperatures as high at 16 GPa and 1200 C. This temperature is lower than that indicated by a mantle geotherm at 16 GPa, but may be reasonable for a subducting slab. It is possible that other DHMS could be stable to even higher pressures, but little is known about maximum temperature limits. For NAM, small amounts of hydrogen (up to several hundred ppm) have been detected in olivine, orthopyroxene, clinopyroxene, and garnet recovered from xenoliths in kimberlites, eclogites, and alkali basalts; it has been demonstrated that synthetic wadsleyite and perovskite can accommodate significant amounts of hydrogen. A number of problems are associated with each possibility. For NAM originating in the mantle, one would like to assume that the hydrogen measured in samples recovered on Earth's surface was incorporated when the phase-crystallized at high temperatures and pressures, but it could have been introduced during transport to the surface. Major problems for the DHMS proponents are that none of these phases have been found as minerals and little is yet known about their stabilities in systems containing other cations such as Fe, Al, and Ca.

  20. Thermal Conductivity Measurement of Synthesized Mantle Minerals

    Science.gov (United States)

    Asimow, P. D.; Luo, S.; Mosenfelder, J. L.; Liu, W.; Staneff, G. D.; Ahrens, T. J.; Chen, G.

    2002-12-01

    Direct thermal conductivity (k) measurement of mantle minerals is crucial to constrain the thermal profile of the Earth as well as geodynamic studies of the mantle (e.g., to determine the Rayleigh number). We have embarked on systematic multi-anvil syntheses of dense polycrystalline specimens of mantle phases of adequate size and zero porosity for precise thermal conductivity measurements by the 3ω method (\\textit{Cahill and Pohl, Phys. Rev. B, 1987}) under elevated temperatures (T). Coesite and stishovite (see \\textit{Luo et al., GRL, 2002}) as well as majorite and wadsleyite have been synthesized; ringwoodite and perovskite are scheduled. Preliminary thermal conductivity measurements at ambient pressure on coesite (120 - 300 K, 9.53 Wm-1K-1 at 300 K) are consistent with prior room temperature data (\\textit{Yukutake & Shimada, PEPI, 1978}), while our stishovite data at 300 K appear to be low (1.96 Wm-1K-1). Efforts are being made to extend the measurement to higher temperatures (e.g., above Debye temperature Θ D), thus allowing determination of k(T) relationship (say, k~ T-n); success will depend on the decomposition kinetics of these metastable phases. The pressure dependence of k of these synthesized samples can also be measured (\\textit{e.g., Osako et al., HPMPS-6, 2002; Xu et al., EOS, 2001}). Recent thermal conductivity measurement on LiF and Al2O_3 from shock wave loading (\\textit{Holland & Ahrens, 1998}) is consistent with the modeling on MgO and Al2O_3 (\\textit{Manga & Jeanloz, JGR, 1997}) with classical theories. Thus, k values at modest pressures and T (say, above Θ D) would allow extrapolation of k to appropriate mantle conditions.

  1. Seismic Discontinuities within the Crust and Mantle Beneath Indonesia as Inferred from P Receiver Functions

    Science.gov (United States)

    Woelbern, I.; Rumpker, G.

    2015-12-01

    Indonesia is situated at the southern margin of SE Asia, which comprises an assemblage of Gondwana-derived continental terranes, suture zones and volcanic arcs. The formation of SE Asia is believed to have started in Early Devonian. Its complex history involves the opening and closure of three distinct Tethys oceans, each accompanied by the rifting of continental fragments. We apply the receiver function technique to data of the temporary MERAMEX network operated in Central Java from May to October 2004 by the GeoForschungsZentrum Potsdam. The network consisted of 112 mobile stations with a spacing of about 10 km covering the full width of the island between the southern and northern coast lines. The tectonic history is reflected in a complex crustal structure of Central Java exhibiting strong topography of the Moho discontinuity related to different tectonic units. A discontinuity of negative impedance contrast is observed throughout the mid-crust interpreted as the top of a low-velocity layer which shows no depth correlation with the Moho interface. Converted phases generated at greater depth beneath Indonesia indicate the existence of multiple seismic discontinuities within the upper mantle and even below. The strongest signal originates from the base of the mantle transition zone, i.e. the 660 km discontinuity. The phase related to the 410 km discontinuity is less pronounced, but clearly identifiable as well. The derived thickness of the mantle-transition zone is in good agreement with the IASP91 velocity model. Additional phases are observed at roughly 33 s and 90 s relative to the P onset, corresponding to about 300 km and 920 km, respectively. A signal of reversed polarity indicates the top of a low velocity layer at about 370 km depth overlying the mantle transition zone.

  2. The role of thermodynamics in mantle convection: is mantle-layering intermittent?

    Science.gov (United States)

    Stixrude, L. P.; Cagney, N.; Lithgow-Bertelloni, C. R.

    2016-12-01

    We examine the thermal evolution of the Earth using a 1D model in which mixing length theory is used to characterise the role of thermal convection. Unlike previous work, our model accounts for the complex role of thermodynamics and phase changes through the use of HeFESTo (Stixrude & Lithgow-Bertelloni, Geophys. J. Int. 184, 2011), a comprehensive thermodynamic model that enables self-consistent computation of phase equilibria, physical properties (e.g. density, thermal expansivity etc.) and mantle isentropes. Our model also accounts for the freezing of the inner core, radiogenic heating and Arrhenius rheology, and is validated by comparing our results to observations, including the present-day size of the inner core and the heat flux at the surface.If phase changes and the various thermodynamic effects on mantle properties are neglected, the results are weakly dependent on the initial conditions, as has been observed in several previous studies. However, when these effects are accounted for, the initial temperature profile has a strong influence on the thermal evolution of the mantle, because small changes in the temperature and phase-assemblage can lead to large changes in the local physical properties and the adiabatic gradient.The inclusion of thermodynamic effects leads to some new and interesting insights. We demonstrate that the Clapeyron slope and the thermal gradient at the transition zone both vary significantly with time; this causes the mantle to switch between a layered state, in which convection across the transition zone is weak or negligible, and an un-layered state, in which there is no resistance to mass transfer between the upper and lower mantles.Various plume models describe plumes either rising directly from the CMB to the lithosphere, or stalling at the transition zone before spawning new plumes in the upper mantle. The observance of switching behaviour indicates that both models may be applicable depending on the state of the mantle: plumes

  3. Modeling mantle convection in the spherical annulus

    Science.gov (United States)

    Hernlund, John W.; Tackley, Paul J.

    2008-12-01

    Most methods for modeling mantle convection in a two-dimensional (2D) circular annular domain suffer from innate shortcomings in their ability to capture several characteristics of the spherical shell geometry of planetary mantles. While methods such as rescaling the inner and outer radius to reduce anomalous effects in a 2D polar cylindrical coordinate system have been introduced and widely implemented, such fixes may have other drawbacks that adversely affect the outcome of some kinds of mantle convection studies. Here we propose a new approach that we term the "spherical annulus," which is a 2D slice that bisects the spherical shell and is quantitatively formulated at the equator of a spherical polar coordinate system after neglecting terms in the governing equations related to variations in latitude. Spherical scaling is retained in this approximation since the Jacobian function remains proportional to the square of the radius. We present example calculations to show that the behavior of convection in the spherical annulus compares favorably against calculations performed in other 2D annular domains when measured relative to those in a fully three-dimensional (3D) spherical shell.

  4. Echocardiographic Assessment of Mantle Radiation Mitral Stenosis.

    Science.gov (United States)

    Bastiaenen, Rachel; Sneddon, James; Sharma, Rajan

    2016-02-01

    The long-term sequelae of mantle radiotherapy include lung disease and cardiac disorders. Dyspnea on exertion is a common complaint and can be due to one or more pathologies. We describe a case of mantle radiotherapy-induced mitral stenosis, characterized by aorto-mitral continuity calcification and absent commissural fusion which precludes balloon valvotomy. The latency period is long, and this patient presented 42 years after radiotherapy. Importantly, as previously described with radiation-induced valve disease, significant mitral stenosis developed 10 years after surgery for significant aortic stenosis. Two-dimensional and three-dimensional transthoracic and transesophageal echocardiography should be considered during assessment of symptomatic survivors of Hodgkin's disease where the index of suspicion for valvular stenosis increases over time. Given the natural history of mantle radiation valvular disease, a lower threshold for surgical intervention in radiation-induced mitral stenosis may need to be considered if cardiac surgery is planned for other reasons in order to avoid repeated sternotomy in patients with prior irradiation.

  5. Mantle updrafts and mechanisms of oceanic volcanism

    Science.gov (United States)

    Anderson, Don L.; Natland, James H.

    2014-10-01

    Convection in an isolated planet is characterized by narrow downwellings and broad updrafts-consequences of Archimedes' principle, the cooling required by the second law of thermodynamics, and the effect of compression on material properties. A mature cooling planet with a conductive low-viscosity core develops a thick insulating surface boundary layer with a thermal maximum, a subadiabatic interior, and a cooling highly conductive but thin boundary layer above the core. Parts of the surface layer sink into the interior, displacing older, colder material, which is entrained by spreading ridges. Magma characteristics of intraplate volcanoes are derived from within the upper boundary layer. Upper mantle features revealed by seismic tomography and that are apparently related to surface volcanoes are intrinsically broad and are not due to unresolved narrow jets. Their morphology, aspect ratio, inferred ascent rate, and temperature show that they are passively responding to downward fluxes, as appropriate for a cooling planet that is losing more heat through its surface than is being provided from its core or from radioactive heating. Response to doward flux is the inverse of the heat-pipe/mantle-plume mode of planetary cooling. Shear-driven melt extraction from the surface boundary layer explains volcanic provinces such as Yellowstone, Hawaii, and Samoa. Passive upwellings from deeper in the upper mantle feed ridges and near-ridge hotspots, and others interact with the sheared and metasomatized surface layer. Normal plate tectonic processes are responsible both for plate boundary and intraplate swells and volcanism.

  6. Density profile of pyrolitic lower mantle

    Science.gov (United States)

    Sinmyo, R.; Hirose, K.; Ohishi, Y.

    2010-12-01

    Density profile of pyrolite at lower mantle high-pressure (P) and -temperature (T) conditions was investigated by using laser-heated diamond-anvil cell up to 117 GPa and 2800 K. The density was determined from chemical composition and unit-cell volume of each constituent mineral (MgSiO3-rich perovskite, ferropericlase and CaSiO3-rich perovskite). The chemical compositions of coexisting phases were analyzed by transmission electron microscope, and their volumes were obtained by in-situ X-ray diffraction measurements. To avoid extensive chemical segregation during laser-heating, sample was coated by gold that worked as a laser absorber (Sinmyo and Hirose 2010 PEPI). Results of chemical analyses show that Mg-Fe (total Fe) partitioning coefficient between MgSiO3-rich perovskite and ferropericlase [K* = (Fe*/Mg)Pv/(Fe*/Mg)Fp] is about 0.6, slightly higher than the value previously reported in the pyrolitic bulk composition (Murakami et al. 2005 GRL). The lower K* value in the previous study may be attributed to the chemical heterogeneity in the sample induced by strong temperature gradient during laser heating. The calculated density profile of pyrolite is indeed in good agreement with the PREM model within experimental errors, in contrast with the mismatch reported by the previous study (Ricolleau et al. 2009 GRL). Our results support the lower mantle has pyrolitic bulk composition, and thus it is not necessary to suppose the chemically stratification in the lower mantle.

  7. Mantle transition zone shear velocity gradients beneath USArray

    Science.gov (United States)

    Schmandt, Brandon

    2012-11-01

    Broadband P-to-s scattering isolated by teleseismic receiver function analysis is used to investigate shear velocity (VS) gradients in the mantle transition zone beneath USArray. Receiver functions from 2244 stations were filtered in multiple frequency bands and migrated to depth through P and S tomography models. The depth-migrated receiver functions were stacked along their local 410 and 660 km discontinuity depths to reduce stack incoherence and more accurately recover the frequency-dependent amplitudes of P410s and P660s. The stacked waveforms were inverted for one-dimensional VS between 320 and 840 km depth. First, a gradient-based inversion was used to find a least-squares solution and a subsequent Monte Carlo search about that solution constrained the range of VS profiles that provide an acceptable fit to the receiver function stacks. Relative to standard references models, all the acceptable models have diminished VS gradients surrounding the 410, a local VS gradient maximum at 490-500 km depth, and an enhanced VS gradient above the 660. The total 410 VS increase of 6.3% is greater than in reference models, and it occurs over a thickness of 20 km. However, 60% of this VS increase occurs over only 6 km. The 20 km total thickness of the 410 and diminished VS gradients surrounding the 410 are potential indications of high water content in the regional transition zone. An enhanced VS gradient overlying the 660 likely results from remnants of subduction lingering at the base of the transition zone. Cool temperatures from slabs subducted since the late Cretaceous and longer-term accumulation of former ocean crust both may contribute to the high gradient above the 660. The shallow depth of the 520 km discontinuity, 490-500 km, implies that the regional mean temperature in the transition zone is 110-160 K cooler than the global mean. A concentrated Vs gradient maximum centered near 660 km depth and a low VS gradient below 675 km confirms that the ringwoodite to

  8. multilevel buck converter for automotive electrical load

    African Journals Online (AJOL)

    user

    development of DCM based buck converter and its applications in the HEVs/EVs using ... The paper also highlights the implications of implementing a single stage buck converter, and ..... instance when the saw tooth signal within the internal.

  9. Converting pest insects into food

    DEFF Research Database (Denmark)

    Offenberg, Hans Joachim; Wiwatwittaya, Decha

    2010-01-01

    on management, 32-115 kg ant brood (mainly new queens) was harvested per ha per year without detrimental effect on colony survival and worker ant densities. This suggest that ant biocontrol and ant harvest can be sustainable integrated in plantations and double benefits derived. As ant production is fuelled...... by pest insects, problematic pests are converted into food and additional earnings. To assess the profitability of providing additional food for the ants, O. smaragdina food conversion efficiency (ECI) was estimated in the laboratory. This estimate suggests the feeding of weaver ants in ant farms...

  10. Power electronics converters and regulators

    CERN Document Server

    Dokić, Branko L

    2015-01-01

    This book is the result of the extensive experience the authors gained through their year-long occupation at the Faculty of Electrical Engineering at the University of Banja Luka. Starting at the fundamental basics of electrical engineering, the book guides the reader into this field and covers all the relevant types of converters and regulators. Understanding is enhanced by the given examples, exercises and solutions. Thus this book can be used as a textbook for students, for self-study or as a reference book for professionals.

  11. Converting pest insects into food

    DEFF Research Database (Denmark)

    Offenberg, Hans Joachim; Wiwatwittaya, Decha

    2010-01-01

    Canopy dwelling weaver ants (Oecophylla spp.) are used to control a variety of pests in a number of tropical tree crops. What is less familiar is the existence of commercial markets where these ants and their brood are sold for (i) human consumption, (ii) pet food or (iii) traditional medicine...... by pest insects, problematic pests are converted into food and additional earnings. To assess the profitability of providing additional food for the ants, O. smaragdina food conversion efficiency (ECI) was estimated in the laboratory. This estimate suggests the feeding of weaver ants in ant farms...

  12. OAM mode converter in twisted fibers

    DEFF Research Database (Denmark)

    Usuga Castaneda, Mario A.; Beltran-Mejia, Felipe; Cordeiro, Cristiano

    2014-01-01

    We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA.......We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA....

  13. Analysis and design of converters in Matlab

    OpenAIRE

    Lorente Sanjurjo, Rodrigo

    2010-01-01

    This project will try to provide better understanding of data converters, more specifically in the mathematical representation and coding of non idealities of the converter. As programming tool it will be used the MATLAB environment, with which will carry out the coding and the analysis of the behavior of the converters by adding diverse nonlinearities, taking advantage of the simplicity, clarity, and extensibility that provides this environment. Summarizing, it is going to study the converte...

  14. The effect of water to mantle rheology and convection

    Science.gov (United States)

    Brändli, Stefan

    2016-04-01

    Water has a significant influence to mantle rheology and therefore also to the convection of the mantle and the plate tectonics. The viscosity of the mantle can be decreased by up to two orders of magnitude when water is present. Another effect of the water is the change in the solidus of the mantle and therefore the melting regime. These two effects of water in the mantle have a significant influence on mantle convection and plate tectonics. The influx of water to the mantle is driven by plate tectonics as wet oceanic lithosphere is subducted into the mantle, then water is brought back to the lithosphere and the surface by MOR-, arc- and hotspot volcanism. Studies show that the amount of water in the mantle is about three times bigger than the water in the oceans. To model this water cycle multiple additions to our simulation code StagYY are necessary. A water diffusion to complement the water transport due to advection, and water dependent viscosity law are implemented. This additions to StagYY will be followed by implementations of a pressure-temperature law for maximum water content, additional transport mechanisms for water, water dependent solidus functions and the implementation of recent values for plate velocities and water capacities in subducting slabs. This will allow us to research the influence of water to the mantle convection and rheology over the past 200Ma.

  15. Pattern recognition constrains mantle properties, past and present

    Science.gov (United States)

    Atkins, S.; Rozel, A. B.; Valentine, A. P.; Tackley, P.; Trampert, J.

    2015-12-01

    Understanding and modelling mantle convection requires knowledge of many mantle properties, such as viscosity, chemical structure and thermal proerties such as radiogenic heating rate. However, many of these parameters are only poorly constrained. We demonstrate a new method for inverting present day Earth observations for mantle properties. We use neural networks to represent the posterior probability density functions of many different mantle properties given the present structure of the mantle. We construct these probability density functions by sampling a wide range of possible mantle properties and running forward simulations, using the convection code StagYY. Our approach is particularly powerful because of its flexibility. Our samples are selected in the prior space, rather than being targeted towards a particular observation, as would normally be the case for probabilistic inversion. This means that the same suite of simulations can be used for inversions using a wide range of geophysical observations without the need to resample. Our method is probabilistic and non-linear and is therefore compatible with non-linear convection, avoiding some of the limitations associated with other methods for inverting mantle flow. This allows us to consider the entire history of the mantle. We also need relatively few samples for our inversion, making our approach computationally tractable when considering long periods of mantle history. Using the present thermal and density structure of the mantle, we can constrain rheological and compositional parameters such as viscosity and yield stress. We can also use the present day mantle structure to make inferences about the initial conditions for convection 4.5 Gyr ago. We can constrain initial mantle conditions including the initial concentration of heat producing elements in the mantle and the initial thickness of primordial material at the CMB. Currently we use density and temperature structure for our inversions, but we can

  16. Mineralogy and composition of the oceanic mantle

    Science.gov (United States)

    Putirka, Keith; Ryerson, F.J.; Perfit, Michael; Ridley, W. Ian

    2011-01-01

    The mineralogy of the oceanic basalt source region is examined by testing whether a peridotite mineralogy can yield observed whole-rock and olivine compositions from (1) the Hawaiian Islands, our type example of a mantle plume, and (2) the Siqueiros Transform, which provides primitive samples of normal mid-ocean ridge basalt. New olivine compositional data from phase 2 of the Hawaii Scientific Drilling Project (HSDP2) show that higher Ni-in-olivine at the Hawaiian Islands is due to higher temperatures (T) of melt generation and processing (by c. 300°C) related to the Hawaiian mantle plume. DNi is low at high T, so parental Hawaiian basalts are enriched in NiO. When Hawaiian (picritic) parental magmas are transported to shallow depths, olivine precipitation occurs at lower temperatures, where DNi is high, leading to high Ni-in-olivine. Similarly, variations in Mn and Fe/Mn ratios in olivines are explained by contrasts in the temperatures of magma processing. Using the most mafic rocks to delimit Siqueiros and Hawaiian Co and Ni contents in parental magmas and mantle source compositions also shows that both suites can be derived from natural peridotites, but are inconsistent with partial melting of natural pyroxenites. Whole-rock compositions at Hawaii and Siqueiros are also matched by partial melting experiments conducted on peridotite bulk compositions. Hawaiian whole-rocks have elevated FeO contents compared with Siqueiros, which can be explained if Hawaiian parental magmas are generated from peridotite at 4-5 GPa, in contrast to pressures of slightly greater than 1 GPa for melt generation at Siqueiros; these pressures are consistent with olivine thermometry, as described in an earlier paper. SiO2-enriched Koolau compositions are reproduced if high-Fe Hawaiian parental magmas re-equilibrate at 1-1·5 GPa. Peridotite partial melts from experimental studies also reproduce the CaO and Al2O3 contents of Hawaiian (and Siqueiros) whole-rocks. Hawaiian magmas have TiO2

  17. Ecologically Optimal Solution of Power Semiconductors Converters

    Directory of Open Access Journals (Sweden)

    Ivan Lokseninec

    2003-01-01

    Full Text Available One of the relevant scientific programs of Department of Power Electrical Systems is research of ecologically optimal topologies main circuits of power converters. This paper presents some methods how to reduce unfavourable influences of power converters on the grid. The achieved results were applieed in praxis, especially in the power converters produced by Electrotechnical Research and Projecting Institute in Nova Dubnica.

  18. Electrical conductivity of mantle peridotite at the uppermost lower mantle condition

    Energy Technology Data Exchange (ETDEWEB)

    Yoshino, T; Katsura, T; Yamazaki, D; Ito, E, E-mail: tyoshino@misasa.okayama-u.ac.j [Institute for Study of the Earth' s Interior, Okayama University, 827 Yamada, Misasa, Tottori 682-1093 (Japan)

    2010-03-01

    Electrical conductivity of mantle peridotite was measured at 25 GPa and temperature up to 1800 K in a Kawai-type multi-anvil apparatus. The starting material was gel with a composition of fertile spinel lherzolite (KLB1). After the conductivity measurement, mineral phases of run products are composed of magnesium silicate perovskite, ferro-periclase and Ca perovskite. The conductivity value of the peridotite is distinctly higher than those of post-spinel and magnesian silicate perovskite with a composition of (Mg{sub 0.9},Fe{sub 0.1})SiO{sub 3}, but lower than that of ferro-periclase. Both absolute values and change in activation enthalpy for the conductivity of the mantle peridotite are similar to those for the silicate perovskite. A presence of aluminous perovskite with substantial amount of ferric iron in crystal structure would enhance bulk conductivity of the lower mantle.

  19. A dc to dc converter

    Science.gov (United States)

    Willis, A. E.; Gould, J. M.; Matheney, J. L.; Garrett, H. (Inventor)

    1984-01-01

    The object of the invention is to provide an improved converter for converting one direct current voltage to another. A plurality of phased square wave voltages are provided from a ring counter through amplifiers to a like plurality of output transformers. Each of these transformers has two windings, and S(1) winding and an S(2) winding. The S(1) windings are connected in series, then the S(2) windings are connected in series, and finally, the two sets of windings are connected in series. One of six SCRs is connected between each two series connected windings to a positive output terminal and one of diodes is connected between each set of two windings of a zero output terminal. By virtue of this configuration, a quite high average direct current voltage is obtained, which varies between full voltage and two-thirds full voltage rather than from full voltage to zero. Further, its variation, ripple frequency, is reduced to one-sixth of that present in a single phase system. Application to raising battery voltage for an ion propulsion system is mentioned.

  20. Numerical modeling of mantle wedge processes and exhumation of UHP mantle in subduction zones

    Science.gov (United States)

    Gorczyk, W.; Gerya, T. V.; Guillot, S.; Connolly, J. A.; Yuen, D.

    2007-12-01

    The upwelling of subduction generated partially molten rocks is potentially a mechanism for the exhumation of UHP rocks through the mantle wedge. We investigated this processes using a 2-D coupled petrological- thermomechanical model that incorporates slab dehydration and water transport as well as partial melting of mantle and crustal rocks. This approach allows us to study the dynamics of mantle wedge processes including evolution of partially molten plumes and their interaction with surrounding dry mantle. To study the internal structure of the plumes we used ultra-high resolution numerical simulations with 10 billion active markers to detail the internal structure of natural plumes originating from the slab. The plumes consist of partially molten hydrated peridotite, dry solid mantle and subducted oceanic crust, which may comprise up to 12 volume % of the plume. As the 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 strongly layered lithologically mixed (marble cake) structure of asthenospheric mantle wedges. The recent discovery of garnet bearing peridotites in the subduction zone of the Great Antilles in Hispaniola has raised questions about the process that leads to their exhumation. To evaluate whether upwelling plumes are a plausible exhumation mechanism we investigated the dynamics of subduction of slow spreading ridges. The results show that subduction of strongly serpentinized oceanic plate causes strong dehydration of the slab and leads to a rheological weakening of the interface between subducting and overriding plate. This weakening triggers trench retreat and massive asthenospheric upwelling into the gap between the

  1. Seismic anisotropy of upper mantle in eastern Tibetan Plateau and related crust-mantle coupling pattern

    Institute of Scientific and Technical Information of China (English)

    Paul; SILVER; Lucy; FLESCH

    2007-01-01

    By using the polarization analysis of teleseismic SKS waveform data recorded at 116 seismic stations which respectively involved in China National Digital Seismograph Network, and Yunnan, Sichuan, Gansu and Qinghai regional digital networks, and portable broadband seismic networks deployed in Sichuan, Yunnan and Tibet, we obtained the SKS fast-wave direction and the delay time between fast and slow waves of each station by use of the stacking analysis method, and finally acquired the fine image of upper mantle anisotropy in the eastern Tibetan Plateau and its adjacent regions. We analyzed the crust-mantle coupling deformation on the basis of combining the GPS observation results and the upper mantle anisotropy distribution in the study area. The Yunnan region out of the plateau has dif-ferent features of crust-mantle deformation from the inside plateau. There exists a lateral transitional zone of crust-mantle coupling in the eastern edge of the Tibetan Plateau, which is located in the region between 26° and 27°N in the west of Sichuan and Yunnan. To the south of transitional zone, the fast-wave direction is gradually turned from S60°―70°E in southwestern Yunnan to near EW in south-eastern Yunnan. To the north of transitional zone in northwestern Yunnan and the south of western Sichuan, the fast-wave direction is nearly NS. From crust to upper mantle, the geophysical parameters (e.g. the crustal thickness, the Bouguer gravity anomaly, and tectonic stress direction) show the feature of lateral variation in the transitional zone, although the fault trend on the ground surface is inconsis-tent with the fast-wave direction. This transitional zone is close by the eastern Himalayan syntaxis, and it may play an important role in the plate boundary dynamics.

  2. Seismic anisotropy of upper mantle in eastern Tibetan Plateau and related crust-mantle coupling pattern

    Institute of Scientific and Technical Information of China (English)

    WANG ChunYong; CHANG LiJun; L(U) ZhiYong; QIN JiaZheng; SU Wei; Paul SILVER; Lucy FLESCH

    2007-01-01

    By using the polarization analysis of teleseismic SKS waveform data recorded at 116 seismic stations which respectively involved in China National Digital Seismograph Network, and Yunnan, Sichuan,Gansu and Qinghai regional digital networks, and portable broadband seismic networks deployed in Sichuan, Yunnan and Tibet, we obtained the SKS fast-wave direction and the delay time between fast and slow waves of each station by use of the stacking analysis method, and finally acquired the fine image of upper mantle anisotropy in the eastern Tibetan Plateau and its adjacent regions. We analyzed the crust-mantle coupling deformation on the basis of combining the GPS observation results and the upper mantle anisotropy distribution in the study area. The Yunnan region out of the plateau has different features of crust-mantle deformation from the inside plateau. There exists a lateral transitional zone of crust-mantle coupling in the eastern edge of the Tibetan Plateau, which is located in the region between 26° and 27°N in the west of Sichuan and Yunnan. To the south of transitional zone, the fast-wave direction is gradually turned from S60°-70°E in southwestern Yunnan to near EW in southeastern Yunnan. To the north of transitional zone in northwestern Yunnan and the south of western Sichuan, the fast-wave direction is nearly NS. From crust to upper mantle, the geophysical parameters(e.g. the crustal thickness, the Bouguer gravity anomaly, and tectonic stress direction) show the feature of lateral variation in the transitional zone, although the fault trend on the ground surface is inconsistent with the fast-wave direction. This transitional zone is close by the eastern Himalayan syntaxis, and it may play an important role in the plate boundary dynamics.

  3. Dihedral angle of carbonatite melts in mantle residue near the upper mantle and transition zone

    Science.gov (United States)

    Ghosh, S. K.; Rohrbach, A.; Schmidt, M. W.

    2015-12-01

    Carbonate melts are thought to be ideal metasomatic agents in the deep upper mantle (Green & Wallace, 1988) and these melts are low in viscosities (10-1-10-3 Pa·s) compared to primitive basalt (101-102 Pa·s), furthermore the ability to form an interconnected grain-edge melt network at low melt fractions (3 GPa (Dasgupta et al. 2006, Ghosh et al., 2009), dissolve a number of geochemically incompatible elements much better than silicate melts (Blundy and Dalton, 2000). Previous studies of carbonate melt dihedral angles in olivine-dominated matrices yielded 25-30oat 1-3 GPa, relatively independent of melt composition (Watson et al., 1990) and temperature (Hunter and McKenzie, 1989). Dihedral angles of carbonate melts in contact with deep mantle silicate phases (e.g. garnet, wadsleyite, and ringwoodite) which constitute more than 70 % of the deep upper mantle and transition zone have not been studied yet. We have performed multi-anvil experiments on carbonate-bearing peridotites with 5.0 wt% CO2 from 13.5 to 20 GPa 1550 oC to investigate the dihedral angle of magnesio-carbonatite melts in equilibrium with garnet, olivine (and its high-pressure polymorphs), and clinoenstatite. The dihedral angle of carbonate melts in the deep upper mantle and transition zone is ~30° for majorite garnet and olivine (and its polymorphs) dominated matrices. It does not change with increasing pressure in the range 13.5-20 GPa. Our results suggest that very low melt fractions of carbonatite melt forming in the deep upper mantle and transition zone are interconnected at melt fractions less than 0.01. Consistent with geophysical observations, this could possibly explain low velocity regions in the deep mantle and transition zone.

  4. Determining resolvability of mantle plumes with synthetic seismic modeling

    Science.gov (United States)

    Maguire, R.; Van Keken, P. E.; Ritsema, J.; Fichtner, A.; Goes, S. D. B.

    2014-12-01

    Hotspot volcanism in locations such as Hawaii and Iceland is commonly thought to be associated with plumes rising from the deep mantle. In theory these dynamic upwellings should be visible in seismic data due to their reduced seismic velocity and their effect on mantle transition zone thickness. Numerous studies have attempted to image plumes [1,2,3], but their deep mantle origin remains unclear. In addition, a debate continues as to whether lower mantle plumes are visible in the form of body wave travel time delays, or whether such delays will be erased due to wavefront healing. Here we combine geodynamic modeling of mantle plumes with synthetic seismic waveform modeling in order to quantitatively determine under what conditions mantle plumes should be seismically visible. We model compressible plumes with phase changes at 410 km and 670 km, and a viscosity reduction in the upper mantle. These plumes thin from greater than 600 km in diameter in the lower mantle, to 200 - 400 km in the upper mantle. Plume excess potential temperature is 375 K, which maps to seismic velocity reductions of 4 - 12 % in the upper mantle, and 2 - 4 % in the lower mantle. Previous work that was limited to an axisymmetric spherical geometry suggested that these plumes would not be visible in the lower mantle [4]. Here we extend this approach to full 3D spherical wave propagation modeling. Initial results using a simplified cylindrical plume conduit suggest that mantle plumes with a diameter of 1000 km or greater will retain a deep mantle seismic signature. References[1] Wolfe, Cecily J., et al. "Seismic structure of the Iceland mantle plume." Nature 385.6613 (1997): 245-247. [2] Montelli, Raffaella, et al. "Finite-frequency tomography reveals a variety of plumes in the mantle." Science 303.5656 (2004): 338-343. [3] Schmandt, Brandon, et al. "Hot mantle upwelling across the 660 beneath Yellowstone." Earth and Planetary Science Letters 331 (2012): 224-236. [4] Hwang, Yong Keun, et al

  5. Valuing Convertible Bonds Based on LSRQM Method

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2014-01-01

    Full Text Available Convertible bonds are one of the essential financial products for corporate finance, while the pricing theory is the key problem to the theoretical research of convertible bonds. This paper demonstrates how to price convertible bonds with call and put provisions using Least-Squares Randomized Quasi-Monte Carlo (LSRQM method. We consider the financial market with stochastic interest rates and credit risk and present a detailed description on calculating steps of convertible bonds value. The empirical results show that the model fits well the market prices of convertible bonds in China’s market and the LSRQM method is effective.

  6. Can the mantle control the core?: Energetics and dynamics

    Science.gov (United States)

    Nakagawa, T.

    2011-12-01

    The sustainability of magnetic field generation is discussed from a coupled model of numerical mantle convection simulation and core energetics theory. The pattern of geomagnetic field could be also controlled as a consequence of mantle convection [e.g. Amit and Choblet, 2009]. Our previous studies have suggested that the best-fit scenario for explaining both sustainability of magnetic field generation caused by dynamo actions and the size of inner core would be strongly controlled by the heat transfer of mantle convection with strongly compositional heterogeneities [Nakagawa and Tackley, 2004; Nakagawa and Tackley, 2010]. Here we investigate effects of initial mantle temperature and radioactive heat source in a convecting mantle with extremely high initial temperature at the core-mantle boundary that has been suggested from the hypothesis of early Earth [Labrosse et al., 2007] for checking how the mantle can control the thermal evolution of the core. Main consequence is that the amount of heat production rate and initial mantle temperature are not very sensitive to the thermal evolution of Earth's core but the convective vigor seems to be sensitive to the results. For the mantle side, the Urey ratio is not very good constraint for understanding thermal evolution of the whole Earth. In addition, we also show an example of numerical dynamo simulations with both a stably stratified layer and lateral variation of heat flux across the core-mantle boundary (CMB), which expands a paper by Nakagawa [2011], evaluated from numerical mantle convection simulations for checking how the mantle can control the dynamics of the core, which checks dead or alive for the magnetic field generated by dynamo actions with strongly lateral variation of CMB heat flux.

  7. Archimedean Proof of the Physical Impossibility of Earth Mantle Convection

    OpenAIRE

    Herndon, J. Marvin

    2010-01-01

    Eight decades ago, Arthur Holmes introducted the idea of mantle convection as a mechanism for continental drift. Five decades ago, continental drift was modified to become plate tectonics theory, which included mantle convection as an absolutely critical component. Using the submarine design and operation concept of "neutral buoyancy", which follows from Archimedes' discoveries, the concept of mantle convection is proven to be incorrect, concomitantly refuting plate tectonics, refuting all ma...

  8. Scales of Heterogeneities in the Continental Crust and Upper Mantle

    OpenAIRE

    M. Tittgemeyer; F. Wenzel; Trond Ryberg; Fuchs, K

    1999-01-01

    A seismological characterization of crust and upper mantle can refer to large-scale averages of seismic velocities or to fluctuations of elastic parameters. Large is understood here relative to the wavelength used to probe the earth. In this paper we try to characterize crust and upper mantle by the fluctuations in media properties rather than by their average velocities. As such it becomes evident that different scales of heterogeneities prevail in different layers of crust mantle. Although ...

  9. Water concentrations in mantle peridotite minerals

    Science.gov (United States)

    Warren, J. M.; Hauri, E. H.

    2010-12-01

    The concentration and distribution of volatiles in the mantle is important for constraining many key properties, including melting systematics at ridges and subduction zones. We present measurements of water concentrations in nominally anhydrous minerals from abyssal, orogenic and xenolith peridotites. Analyses of fresh and altered samples from a variety of locations are used to assess the extent to which mineral water concentrations reflect primary mantle compositions, versus diffusive loss and/or hydration due to secondary processes. Water concentrations were measured in olivine (Ol), orthopyroxene (Opx) and clinopyroxene (Cpx) by ion microprobe, using mineral specific standards and monitoring background concentrations by analysis of synthetic forsterite. Analytical reproducibility, based on 11 repeat analyses of an Ol grain, is 10%, while background H2O levels varied from 7-19 ppm. Samples include xenoliths from Pali Aike, Samoa and Spitsbergen, along with unusually fresh oceanic peridotites from the Gakkel Ridge and the Tonga Trench. In addition, samples were analyzed from the Southwest Indian Ridge (SWIR) and the Josephine Peridotite, both of which have moderate degrees of alteration. In olivine, water concentrations are Pali Aike xenoliths, which have water concentrations of 16-33 ppm. On average, peridotite Opx have 187 ppm and Cpx have 474 ppm. Pyroxenite veins from the Southwest Indian Ridge have systematically lower concentrations, with an average of 12 ppm in Opx and 55 ppm in Cpx. Water partition coefficients for Opx/Ol have an average value of 28 and Cpx/Ol of 57, significantly higher than previous estimates (e.g., Hirth and Kohlstedt, 1996). Excluding the pyroxenites, the average Cpx/Opx partition coefficient is 2, in agreement with published estimates. This suggests that Cpx and Opx preserve mantle water concentrations, whereas Ol has undergone hydrogen loss. Mineral rims have water concentrations that are within error of core concentrations. The

  10. The composition of mantle plumes and the deep Earth

    Science.gov (United States)

    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.

  11. Efficiency of Capacitively Loaded Converters

    DEFF Research Database (Denmark)

    Andersen, Thomas; Huang, Lina; Andersen, Michael A. E.;

    2012-01-01

    This paper explores the characteristic of capacitance versus voltage for dielectric electro active polymer (DEAP) actuator, 2kV polypropylene film capacitor as well as 3kV X7R multi layer ceramic capacitor (MLCC) at the beginning. An energy efficiency for capacitively loaded converters...... is introduced as a definition of efficiency. The calculated and measured efficiency curves for charging DEAP actuator, polypropylene film capacitor and X7R MLCC are provided and compared. The attention has to be paid for the voltage dependent capacitive load, like X7R MLCC, when evaluating the charging...... polypropylene film capacitor can be the equivalent capacitive load. Because of the voltage dependent characteristic, X7R MLCC cannot be used to replace the DEAP actuator. However, this type of capacitor can be used to substitute the capacitive actuator with voltage dependent property at the development phase....

  12. Reliability of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon

    . Structural reliability considerations and optimizations impact operation and maintenance (O&M) costs as well as the initial investment costs. Furthermore, there is a control system for WEC applications which defines the harvested energy but also the loads onto the structure. Therefore, extreme loads but also...... WEPTOS. Calibration of safety factors are performed for welded structures at theWavestar device including different control systems for harvesting energy from waves. In addition, a case study of different O&M strategies for WECs is discussed, and an example of reliability-based structural optimization......There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs to become successful and more competitive to other renewable electricity sources, the consideration of the structural reliability of WECs is essential...

  13. Reliability of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon

    for welded structures at the Wavestar device includingdifferent control systems for harvesting energy from waves. In addition, a casestudy of different O&M strategies for WECs is discussed, and an example ofreliability-based structural optimization of the Wavestar foundation ispresented. The work performed......There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs tobecome successful and more competitive to other renewable electricity sources,the consideration of the structural reliability of WECs is essential.......Structural reliability considerations and optimizations impact operation andmaintenance (O&M) costs as well as the initial investment costs.Furthermore, there is a control system for WEC applications which defines theharvested energy but also the loads onto the structure. Therefore, extremeloads but also fatigue loads...

  14. Reliability of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon

    There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs to become successful and more competitive to other renewable electricity sources, the consideration of the structural reliability of WECs is essential....... Structural reliability considerations and optimizations impact operation and maintenance (O&M) costs as well as the initial investment costs. Furthermore, there is a control system for WEC applications which defines the harvested energy but also the loads onto the structure. Therefore, extreme loads but also...... of the Wavestar foundation is presented. The work performed in this thesis focuses on the Wavestar and WEPTOS WEC devices which are only two working principles out of a large diversity. Therefore, in order to gain general statements and give advice for standards for structural WEC designs, more working principles...

  15. Manufacturing method of photoelectric converter

    Energy Technology Data Exchange (ETDEWEB)

    Toda, Koji; Niwa, Yasuo

    1987-06-24

    In a method of making a thin film for a photoelectric converter by a method to form an electroconductive layer by burning a mixture of lead oxide and chromic oxide, thickness of the film was limited and the poreless uniform film was not obtainable. The intransparency of the film gave low conversion efficiency only. This invention enabled to obtain a transparent film wherein an oxide (containing lead and chrome) is used as a target to form, in vacuum, a thin film of the oxide, and then this thin film is heat-treated in an atmosphere at least containing lead. Thin transparent film was obtained enhancing the conversion efficiency. High quality and high reliability are ensured because a poreless uniform film can be obtained. Cost was reduced because mass-production was made possible by the use of a vacuum technique. (5 figs)

  16. The SSG Wave Energy Converter

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Margheritini, Lucia; Kofoed, Jens Peter

    2012-01-01

    The Sea-wave Slot-cone Generator concept (SSG) is a Wave Energy Converter based on the wave overtopping principle utilizing several reservoirs placed on top of each other, in which the energy of the incoming wave will be stored as potential energy. The water captured in the reservoirs will then run...... through turbines for electricity production. The system utilizes a wide spectrum of different wave conditions by means of multiple reservoirs, located at different levels above the still water level. Thereby, it obtains a high overall efficiency and it can be suitable for shoreline and breakwater...... applications, presenting particular advantages such as: sharing structure costs, availability of grid connection and infrastructures, recirculation of water inside the harbor, as the outlet of the turbines is on the rear part of the system. Recently, plans for the SSG pilot installation were in progress...

  17. Mantle Structure Beneath Central South America

    Science.gov (United States)

    Vandecar, J. C.; Silver, P. G.; James, D. E.; Assumpcao, M.; Schimmel, M.; Zandt, G.

    2003-12-01

    Making use of 60 digital broadband seismic stations that have operated across central South America in recent years, we have undertaken an inversion for the upper- and uppermost lower-mantle P- and S-wave velocity structures beneath the region. We have combined data from four portable PASSCAL-type experiments as well as the 3 GTSN permanent stations (LPAZ, BDFB and CPUP) and 1 Geoscope station (SPB) located in the region. The portable data were deployed at various times between 1992 and 1999 and include: 28 sites from the Brazilian Lithosphere Seismic Project (BLSP: Carnegie Institution of Washington and Universidade de Sao Paulo), 16 sites from the Broadband ANdean JOint experiment (BANJO: Carnegie Institution of Washington and University of Arizona), 8 sites from the Seismic Exploration of the Deep Altiplano project (SEDA: Lawrence Livermore National Laboratory) and 4 sites from the University of Brasilia. The P- and S-wave relative delay times are independently obtained via a multi-channel cross correlation of band-passed waveforms for each teleseismic event. These data are then inverted using an iterative, robust, non-linear scheme which parameterizes the 3-D velocity variations as splines under tension constrained at over 120,000 nodes across South America between latitudes of 15 and 30 degrees South. Amongst other features, we robustly image the high-velocity subducting Nazca plate penetrating into the lower mantle and the high-velocity root of the ~3.2 Gyr old Sao Francisco Craton extending to depths of 200-300 km. We will discuss the consistency between our tomographic models and predictions of dynamic mantle models based on plate tectonic reconstructions of subduction.

  18. How Depleted is the MORB mantle?

    Science.gov (United States)

    Hofmann, A. W.; Hart, S. R.

    2015-12-01

    Knowledge of the degree of mantle depletion of highly incompatible elements is critically important for assessing Earth's internal heat production and Urey number. Current views of the degree of MORB source depletion are dominated by Salters and Stracke (2004), and Workman and Hart (2005). The first is based on an assessment of average MORB compositions, whereas the second considers trace element data of oceanic peridotites. Both require an independent determination of one absolute concentration, Lu (Salters & Stracke), or Nd (Workman & Hart). Both use parent-daughter ratios Lu/Hf, Sm/Nd, and Rb/Sr calculated from MORB isotopes combined with continental-crust extraction models, as well as "canonical" trace element ratios, to boot-strap the full range of trace element abundances. We show that the single most important factor in determining the ultimate degree of incompatible element depletion in the MORB source lies in the assumptions about the timing of continent extraction, exemplified by continuous extraction versus simple two-stage models. Continued crust extraction generates additional, recent mantle depletion, without affecting the isotopic composition of the residual mantle significantly. Previous emphasis on chemical compositions of MORB and/or peridotites has tended to obscure this. We will explore the effect of different continent extraction models on the degree of U, Th, and K depletion in the MORB source. Given the uncertainties of the two most popular models, the uncertainties of U and Th in DMM are at least ±50%, and this impacts the constraints on the terrestrial Urey ratio. Salters, F.J.M. and Stracke, A., 2004, Geochem. Geophys. Geosyst. 5, Q05004. Workman, R.K. and Hart, S.R., 2005, EPSL 231, 53-72.

  19. Trans-Pacific whole mantle structure

    Science.gov (United States)

    Liu, Lijun; Tan, Ying; Sun, Daoyuan; Chen, Min; Helmberger, Don

    2011-04-01

    Recent reports on modeling USArray data reveal mostly vertical microplates with little resemblance to preliminary reference Earth model (PREM). Such complexity at plate boundaries makes it difficult to form reliable images of ocean basins using global paths. Here, we report on modeling stacked seismograms obtained from the first broadband array (TriNet) situated on the edge of the Pacific Plate, southern California, with no major subduction zone blocking its view. Extended records, including multi-S and ScS waves up to four bounces from 18 Tonga-Fiji deep events (140 to 620 km) are analyzed to check the validity of existing models and derive the whole mantle shear velocity structure along this corridor. Synthetics generated from 3-D tomographic models do not fit the upper mantle triplication data or the mantle reverberations associated with the ScS multiples as well as the 1-D model PAC06. We construct a hybrid model (HPAC), which remains one dimensional down to 800 km (PAC06). The lower portion of HPAC is essentially the tomography model S20RTS with velocity variation inflated by a factor of 2 for the lowermost 600 km. Thus, the mid-Pacific large low shear velocity province (LLSVP) has a lower shear velocity of about 2% relative to PREM and extends into the midmantle, similar to that beneath South Africa. Moreover, rapid changes in the differential (ScS-S) and (ScS2-S) times as a function of distance suggest ultra low velocity zones near the eastern edge and under the LLSVP, again similar to that found beneath Africa.

  20. Is there seismic attenuation in the mantle?

    Science.gov (United States)

    Ricard, Y.; Durand, S.; Montagner, J.-P.; Chambat, F.

    2014-02-01

    The small scale heterogeneity of the mantle is mostly due to the mixing of petrological heterogeneities by a smooth but chaotic convection and should consist in a laminated structure (marble cake) with a power spectrum S(k) varying as 1/k, where k is the wavenumber of the anomalies. This distribution of heterogeneities during convective stirring with negligible diffusion, called Batchelor regime is documented by fluid dynamic experiments and corresponds to what can be inferred from geochemistry and seismic tomography. This laminated structure imposes density, seismic velocity and potentially, anisotropic heterogeneities with similar 1/k spectra. A seismic wave of wavenumber k0 crossing such a medium is partly reflected by the heterogeneities and we show that the scattered energy is proportional to k0S(2k0). The reduction of energy for the propagating wave appears therefore equivalent to a quality factor 1/Q∝k0S(2k0). With the specific 1/k spectrum of the mantle, the resulting apparent attenuation should therefore be frequency independent. We show that the total contribution of 6-9% RMS density, velocity and anisotropy would explain the observed S and P attenuation of the mantle. Although these values are large, they are not unreasonable and we discuss how they depend on the range of frequencies over which the attenuation is explained. If such a level of heterogeneity were present, most of the attenuation of the Earth would be due to small scale scattering by laminations, not by intrinsic dissipation. Intrinsic dissipation must certainly exist but might correspond to a larger, yet unobserved Q. This provocative result would explain the very weak frequency dependence of the attenuation, and the fact that bulk attenuation seems negligible, two observations that have been difficult to explain for 50 years.

  1. Sizes of mantle heteogeneities and seismic attenuation

    Science.gov (United States)

    Ricard, Y. R.; durand, S.; Chambat, F.; Montagner, J.

    2013-12-01

    The small scale heterogeneity of the mantle, being mostly due to the mixing of petrological heterogeneities by a smooth but chaotic convection should consist in a laminated structure (marble cake) with a power spectrum S(k) varying as 1/k, where k is the wavenumber of the anomalies. This distribution of heterogeneities during convective stirring with negligible diffusion, called Batchelor regime is documented by fluid dynamic experiments and corresponds to what can be inferred from geochemistry and seismic tomography. This laminated structure imposes density, seismic velocity and potentially, anisotropic heterogeneities with similar 1/k spectrums. We show that a seismic wave of wavenumber k_0 crossing such medium is partly reflected by the heterogeneities and the scattered energy has an energy found proportional to k_0 S(2k_0). The reduction of energy for the propagating wave appears therefore equivalent to a quality factor 1/Q proportional to k_0 S(2k_0). With the specific 1/k spectrum of the mantle, the resulting apparent attenuation should therefore be frequency independent. We show that the total contribution of 6-9% RMS density, velocity and anisotropy would explain the observed S and P attenuation of the mantle. Although these values are large there are not unreasonable and we discuss how they are likely overestimated. In this case, most of the attenuation of the Earth would be due to small scale scattering by laminations not by intrinsic dissipation. Intrinsic dissipation must certainly exists but might correspond to a larger, yet unobserved Q. This provocative result would explain the observed very weak frequency dependence of the attenuation, and the fact that bulk attenuation seems negligeable, two observations that have been difficult to explain for 50 years.

  2. Pyroxenes as tracers of mantle water variations

    Science.gov (United States)

    Warren, Jessica M.; Hauri, Erik H.

    2014-03-01

    The concentration and distribution of volatiles in the Earth's mantle influence properties such as melting temperature, conductivity, and viscosity. To constrain upper mantle water content, concentrations of H2O, P, and F were measured in olivine, orthopyroxene, and clinopyroxene in mantle peridotites by secondary ion mass spectrometry. Analyzed peridotites are xenoliths (Pali Aike, Spitsbergen, Samoa), orogenic peridotites (Josephine Peridotite), and abyssal peridotites (Gakkel Ridge, Southwest Indian Ridge, Tonga Trench). The comparison of fresh and altered peridotites demonstrates that low to moderate levels of alteration do not affect H2O concentrations, in agreement with mineral diffusion data. Olivines have diffusively lost water during emplacement, as demonstrated by disequilibrium between olivine and coexisting pyroxenes. In contrast, clinopyroxene and orthopyroxene preserve their high-temperature water contents, and their partitioning agrees with published experiments and other xenoliths. Hence, olivine water concentrations can be determined from pyroxene concentrations using mineral-mineral partition coefficients. Clinopyroxenes have 60-670 ppm H2O, while orthopyroxenes have 10-300 ppm, which gives calculated olivine concentrations of 8-34 ppm. The highest olivine water concentration translates to an effective viscosity of 6 × 1019 Pa s at 1250°C and ~15 km depth, compared to a dry effective viscosity of 2.5 × 1021 Pa s. Bulk rock water concentrations, calculated using mineral modes, are 20-220 ppm and correlate with peridotite indices of melt depletion. However, trace element melt modeling indicates that peridotites have too much water relative to their rare earth element concentrations, which may be explained by late-stage melt addition, during which only hydrogen diffuses fast enough for reequilibration.

  3. Primary mantle cell lymphoma of the trachea.

    Science.gov (United States)

    Guddati, Achuta K; Marak, Creticus P

    2012-12-01

    Primary mantle cell lymphoma (MCL) is a controversial entity. It is difficult to diagnose MCL in a single organ without lymph node involvement. However, with the advent of PET-CT scans and large panels of immunohistochemistry markers, there have been increasing reports of primary MCL detected in various organs of which the GI tract is the most common. In this case report, we describe the diagnosis and clinical course of a patient who presented with "B symptoms" and respiratory distress. On further investigation, he was found to have a mass in his trachea, which was diagnosed as primary MCL.

  4. Cratonic lithospheric mantle: Is anything subducted?

    Institute of Scientific and Technical Information of China (English)

    William L. Griffin; Suzanne Y. O'ReiUy

    2007-01-01

    @@ If the subcontinental lithospheric mantle (SCLM) formed through the repeated underthrusting of oceanic slabs, peridotitic SCLM should resemble oceanic peridotites, and mafic rocks (eclogites, s.l.) should be distributed throughout the SCLM. However, cratonic peridotites (both exposed massifs and xenoliths) differ markedly from oceanic and ophiolitic peridotites in their Fe-Cr-Al relationships and abundances of trace elements (Li and B) diagnostic of subduction. "Typical"cratonic peridotites have experienced extensive metaso matism; modelling of their refractory protoliths indicates high-degree melting at high P, perhaps a uniquely Archean process.

  5. Geochemical Characterization of Endmember Mantle Components

    Science.gov (United States)

    2005-06-01

    in Figs. 7 & 8). Production of the EM component by deep mantle fractionations involving high-pressure phases such as Ca or Mg perovskite likewise... Hafnium isotopes in basalts from the southern Mid-Atlantic Ridge from 40°S to 55°S: Discovery and Shona plume-ridge interactions and the role of recycled...171 (1999) 49-61. Bowring, S. A. and T. Housh, The Earth’s Early Evolution, Science 269 (1995) 1535-1540. Chauvel, C. and J. Blichert-Toft, A hafnium

  6. Intraplate volcanism and mantle dynamics in East Asia: Big mantle wedge (BMW) model (Invited)

    Science.gov (United States)

    Zhao, D.

    2009-12-01

    In the East Asia continent there are many Cenozoic volcanoes, but only a few are still active now, such as the Changbai, Wudalianchi, and Tengchong volcanoes which have erupted several times in the past 1000 years. Although many studies have been made by using various approaches, the origin of the intraplate volcanoes in East Asia is still not very clear. Recently we used regional and global seismic tomography to determine high-resolution 3-D mantle structure under Western Pacific to East Asia (Zhao, 2004; Huang and Zhao, 2006; Zhao et al., 2009). Our results show prominent low-velocity anomalies from the surface down to 410 km depth beneath the intraplate volcanoes and a broad high-velocity anomaly in the mantle transition zone under East Asia. Focal-mechanism solutions of deep earthquakes indicate that the subducting Pacific slab under the Japan Sea and the East Asia margin is subject to compressive stress regime. These results suggest that the Pacific slab meets strong resistance at the 660-km discontinuity and so it becomes stagnant in the mantle transition zone under East Asia. The Philippine Sea slab has also subducted down to the mantle transition zone under western Japan and the Ryukyu back-arc region. The western edge of the stagnant slab is generally parallel with the Japan trench and the Ryukyu trench and roughly coincides with a prominent surface topography and gravity boundary in East China, which is located approximately 1800 km west of the trenches. The upper mantle under East Asia has formed a big mantle wedge (BMW) above the stagnant slab. The BMW exhibits low seismic-velocity and high electrical-conductivity, which is hot and wet because of the deep dehydration reactions of the stagnant slab and the convective circulation process in the BMW. These processes lead to the upwelling of hot and wet asthenospheric materials and thinning and fracturing of the continental lithosphere, leading to the formation of the active intraplate volcanoes in East

  7. Three-phase AC-AC power converters based on matrix converter topology matrix-reactance frequency converters concept

    CERN Document Server

    Szczesniak, Pawel

    2013-01-01

    AC voltage frequency changes is one of the most important functions of solid state power converters. The most desirable features in frequency converters are the ability to generate load voltages with arbitrary amplitude and frequency, sinusoidal currents and voltages waveforms; the possibility of providing unity power factor for any load; and, finally, a simple and compact power circuit. Over the past decades, a number of different frequency converter topologies have appeared in the literature, but only the converters with either a voltage or current DC link are commonly used in industrial app

  8. Thermal and compositional structure of the upper mantle

    Science.gov (United States)

    Gilbert, Hersh Joseph

    Constraints for models of the convective, thermal, and mineralogical structure within the mantle depend heavily on seismic observations of the deep, and otherwise inaccessible, Earth. Studies presented within this dissertation focus primarily on the upper mantle discontinuities that bound the transition zone between the upper and lower mantle at the nominal depths of 410 and 660 km. These discontinuities are attributed to phase transitions of the mantle mineral olivine to denser configurations. Additionally, they may demark compositional layers within the mantle. This region figures prominently in the convective style of the planet. I address the questions of whether the 660-km discontinuity in some way inhibits flow from crossing between the upper and lower mantle and, more specifically, if it coincides with a compositional barrier in the mantle. Thermal variations associated with warm-rising and cool-sinking material in the mantle produce observable variations in the depths of the discontinuities. If rising or sinking materials cross the entire extent of the mantle, then the transition zone should respond to its associated thermal perturbations in a correlated manner. If instead, convection were divided between the upper and lower mantle, then thermal perturbations in the transition zone need not be spatially correlated. Observations presented in this dissertation display regions in which both the 410- and 660-km discontinuities possess greater than 20 km of peak-to-peak topography that is not correlated between the two. Studying the upper mantle below the western United States, I find no correlation between the upper mantle and the surface tectonics of the region. The topography on both discontinuities in this region is nearly as pronounced as that found where the cold subducting Tonga slab interacts with the upper mantle, suggesting the presence of a similar thermal anomaly. Additionally, amplitudes of the velocity jumps associated with the discontinuities

  9. Application of Core Dynamics Modeling to Core-Mantle Interactions

    Science.gov (United States)

    Kuang, Weijia

    2003-01-01

    Observations have demonstrated that length of day (LOD) variation on decadal time scales results from exchange of axial angular momentum between the solid mantle and the core. There are in general four core-mantle interaction mechanisms that couple the core and the mantle. Of which, three have been suggested likely the dominant coupling mechanism for the decadal core-mantle angular momentum exchange, namely, gravitational core-mantle coupling arising from density anomalies in the mantle and in the core (including the inner core), the electromagnetic coupling arising from Lorentz force in the electrically conducting lower mantle (e.g. D-layer), and the topographic coupling arising from non-hydrostatic pressure acting on the core-mantle boundary (CMB) topography. In the past decades, most effort has been on estimating the coupling torques from surface geomagnetic observations (kinematic approach), which has provided insights on the core dynamical processes. In the meantime, it also creates questions and concerns on approximations in the studies that may invalidate the corresponding conclusions. The most serious problem is perhaps the approximations that are inconsistent with dynamical processes in the core, such as inconsistencies between the core surface flow beneath the CMB and the CMB topography, and that between the D-layer electric conductivity and the approximations on toroidal field at the CMB. These inconsistencies can only be addressed with numerical core dynamics modeling. In the past few years, we applied our MoSST (Modular, Scalable, Self-consistent and Three-dimensional) core dynamics model to study core-mantle interactions together with geodynamo simulation, aiming at assessing the effect of the dynamical inconsistencies in the kinematic studies on core-mantle coupling torques. We focus on topographic and electromagnetic core-mantle couplings and find that, for the topographic coupling, the consistency between the core flow and the CMB topography is

  10. Geochemistry on mantle-derived volatiles in natural gases from eastern China oil/gas provinces (I )——Helium, argon and hydrocarbons in mantle volatiles

    Institute of Scientific and Technical Information of China (English)

    徐永昌; 沈平; 陶明信; 刘文汇

    1997-01-01

    Researches on helium, argon, carbon dioxide and methane are very significant in studies of mantle substance characteristics and mantle evolution. A < -shaped pattern of the isotope composition distribution of helium and argon sourced from the mantle and the crust, abundance distribution, isotopic composition and reservoir formation of carbon dioxide, and mantle-sourced methane are discussed.

  11. Water pumping in mantle shear zones

    Science.gov (United States)

    Précigout, Jacques; Prigent, Cécile; Palasse, Laurie; Pochon, Anthony

    2017-06-01

    Water plays an important role in geological processes. Providing constraints on what may influence the distribution of aqueous fluids is thus crucial to understanding how water impacts Earth's geodynamics. Here we demonstrate that ductile flow exerts a dynamic control on water-rich fluid circulation in mantle shear zones. Based on amphibole distribution and using dislocation slip-systems as a proxy for syn-tectonic water content in olivine, we highlight fluid accumulation around fine-grained layers dominated by grain-size-sensitive creep. This fluid aggregation correlates with dislocation creep-accommodated strain that localizes in water-rich layers. We also give evidence of cracking induced by fluid pressure where the highest amount of water is expected. These results emphasize long-term fluid pumping attributed to creep cavitation and associated phase nucleation during grain size reduction. Considering the ubiquitous process of grain size reduction during strain localization, our findings shed light on multiple fluid reservoirs in the crust and mantle.

  12. Towards a Global Upper Mantle Attenuation Model

    Science.gov (United States)

    Karaoglu, Haydar; Romanowicz, Barbara

    2015-04-01

    Global anelastic tomography is crucial for addressing the nature of heterogeneity in the Earth's interior. The intrinsic attenuation manifests itself through dispersion and amplitude decay. These are contaminated by elastic effects such as (de)focusing and scattering. Therefore, mapping anelasticity accurately requires separation of elastic effects from the anelastic ones. To achieve this, a possible approach is to try and first predict elastic effects through the computation of seismic waveforms in a high resolution 3D elastic model, which can now be achieved accurately using numerical wavefield computations. Building upon the recent construction of such a whole mantle elastic and radially anisotropic shear velocity model (SEMUCB_WM1, French and Romanowicz, 2014), which will be used as starting model, our goal is to develop a higher resolution 3D attenuation model of the upper mantle based on full waveform inversion. As in the development of SEMUCB_WM1, forward modeling will be performed using the spectral element method, while the inverse problem will be treated approximately, using normal mode asymptotics. Both fundamental and overtone time domain long period waveforms (T>60s) will be used from a dataset of over 200 events observed at several hundred stations globally. Here we present preliminary results of synthetic tests, exploring different iterative inversion strategies.

  13. Radiation-Tolerant DC-DC Converters

    Science.gov (United States)

    Skutt, Glenn; Sable, Dan; Leslie, Leonard; Graham, Shawn

    2012-01-01

    A document discusses power converters suitable for space use that meet the DSCC MIL-PRF-38534 Appendix G radiation hardness level P classification. A method for qualifying commercially produced electronic parts for DC-DC converters per the Defense Supply Center Columbus (DSCC) radiation hardened assurance requirements was developed. Development and compliance testing of standard hybrid converters suitable for space use were completed for missions with total dose radiation requirements of up to 30 kRad. This innovation provides the same overall performance as standard hybrid converters, but includes assurance of radiation- tolerant design through components and design compliance testing. This availability of design-certified radiation-tolerant converters can significantly reduce total cost and delivery time for power converters for space applications that fit the appropriate DSCC classification (30 kRad).

  14. Converting Relational Database Into Xml Document

    Directory of Open Access Journals (Sweden)

    Kanagaraj.S

    2012-03-01

    Full Text Available XML (Extensible Markup Language is emerging and gradually accepted as the standard for data interchange in the Internet world. Interoperation of relational database and XML database involves schema and data translations. Through EER (extended entity relationship model can convert the schema of relational database into XML. The semantics of the relational database, captured in EER diagram, are mapped to XML schema using stepwise procedures and mapped to XML document under the definitions of the XML schema. Converting Relational Database into XML Document is a process of converting the existing databases into XML file format. Existing conversion techniques convert a single database into xml. The proposed approach performs the conversion of databases like Ms-Access, MS-SQL to XML file format. Read the tables information from the corresponding database and generate code for the appropriate databases and convert the tables into XML flat file format. This converted XML file is been presented to the user.

  15. Ocean floor mounting of wave energy converters

    Science.gov (United States)

    Siegel, Stefan G

    2015-01-20

    A system for mounting a set of wave energy converters in the ocean includes a pole attached to a floor of an ocean and a slider mounted on the pole in a manner that permits the slider to move vertically along the pole and rotate about the pole. The wave energy converters can then be mounted on the slider to allow adjustment of the depth and orientation of the wave energy converters.

  16. Development of a Modular Power Converter

    Science.gov (United States)

    Stepanov, A.; Biesenieks, L.; Sokolovs, A.; Galkin, I.

    2009-01-01

    This report describes the most important details of elaboration of a versatile power module that can be utilized as a part of various converters. Two or more modules connected together can form a frequency converter or multilevel converter or 3-phase inverter/rectifier etc. Initially the module was developed for fast prototyping of uninterruptible power supplies and energy systems with alternative energy sources. The module can be used also as a basis for laboratory equipment of the power electronics course.

  17. Regeneration of ZVS converter with Resonant inductor

    Directory of Open Access Journals (Sweden)

    J.Sivavara Prasad

    2011-09-01

    Full Text Available This paper presents an analysis of the regeneration of zero-voltage-switching converter with resonant inductor, quasi-resonant converters, and full-bridge zero-voltage-switched PWM Converter. The design of a clamping circuit considering a saturable resonant inductor is presented and compared with the design of a clamping circuit with a linear resonant inductor. A diode model with reverse recovery is employed to simulate the effects.

  18. The maximum water storage capacities in nominally anhydrous minerals in the mantle transition zone and lower mantle

    Science.gov (United States)

    Inoue, T.; Yurimoto, H.

    2012-12-01

    Water is the most important volatile component in the Earth, and affects the physicochemical properties of mantle minerals, e.g. density, elastic property, electrical conductivity, thermal conductivity, rheological property, melting temperature, melt composition, element partitioning, etc. So many high pressure experiments have been conducted so far to determine the effect of water on mantle minerals. To clarify the maximum water storage capacity in nominally anhydrous mantle minerals in the mantle transition zone and lower mantle is an important issue to discuss the possibility of the existence of water reservoir in the Earth mantle. So we have been clarifying the maximum water storage capacity in mantle minerals using MA-8 type (KAWAI-type) high pressure apparatus and SIMS (secondary ion mass spectroscopy). Upper mantle mineral, olivine can contain ~0.9 wt% H2O in the condition just above 410 km discontinuity in maximum (e.g. Chen et al., 2002; Smyth et al., 2006). On the other hand, mantle transition zone mineral, wadsleyite and ringwoodite can contain significant amount (about 2-3 wt.%) of H2O (e.g. Inoue et al., 1995, 1998, 2010; Kawamoto et al., 1996; Ohtani et al., 2000). But the lower mantle mineral, perovskite can not contain significant amount of H2O, less than ~0.1 wt% (e.g. Murakami et al., 2002; Inoue et al., 2010). In addition, garnet and stishovite also can not contain significant amount of H2O (e.g. Katayama et al., 2003; Mookherjee and Karato, 2010; Litasov et al., 2007). On the other hand, the water storage capacities of mantle minerals are supposed to be significantly coupled with Al by a substitution with Mg2+, Si4+ or Mg2+ + Si4+, because Al3+ is the trivalent cation, and H+ is the monovalent cation. To clarify the degree of the substitution, the water contents and the chemical compositions of Al-bearing minerals in the mantle transition zone and the lower mantle were also determined in the Al-bearing systems with H2O. We will introduce the

  19. Strong, Multi-Scale Heterogeneity in Earth's Lowermost Mantle.

    Science.gov (United States)

    Tkalčić, Hrvoje; Young, Mallory; Muir, Jack B; Davies, D Rhodri; Mattesini, Maurizio

    2015-12-17

    The core mantle boundary (CMB) separates Earth's liquid iron outer core from the solid but slowly convecting mantle. The detailed structure and dynamics of the mantle within ~300 km of this interface remain enigmatic: it is a complex region, which exhibits thermal, compositional and phase-related heterogeneity, isolated pockets of partial melt and strong variations in seismic velocity and anisotropy. Nonetheless, characterising the structure of this region is crucial to a better understanding of the mantle's thermo-chemical evolution and the nature of core-mantle interactions. In this study, we examine the heterogeneity spectrum from a recent P-wave tomographic model, which is based upon trans-dimensional and hierarchical Bayesian imaging. Our tomographic technique avoids explicit model parameterization, smoothing and damping. Spectral analyses reveal a multi-scale wavelength content and a power of heterogeneity that is three times larger than previous estimates. Inter alia, the resulting heterogeneity spectrum gives a more complete picture of the lowermost mantle and provides a bridge between the long-wavelength features obtained in global S-wave models and the short-scale dimensions of seismic scatterers. The evidence that we present for strong, multi-scale lowermost mantle heterogeneity has important implications for the nature of lower mantle dynamics and prescribes complex boundary conditions for Earth's geodynamo.

  20. Solar combi system based on a mantle tank

    DEFF Research Database (Denmark)

    Yazdanshenas, Eshagh; Furbo, Simon

    2007-01-01

    . The thermal performance of the solar combisystem is compared to the thermal performance of a solar domestic hot water system based on a mantle tank. In the experimental study, tank temperatures and the heat transfer coefficient for the top mantle for a discharge test is determined. The investigations showed...

  1. Tectonic evolution and mantle structure of the Caribbean

    NARCIS (Netherlands)

    van Benthem, S.; Govers, R.; Spakman, W.; Wortel, R.

    2013-01-01

    We investigate whether predictions of mantle structure from tectonic reconstructions are in agreement with a detailed tomographic image of seismic P wave velocity structure under the Caribbean region. In the upper mantle, positive seismic anomalies are imaged under the Lesser Antilles and Puerto Ric

  2. Waves in the core and mechanical core-mantle interactions

    DEFF Research Database (Denmark)

    Jault, D.; Finlay, Chris

    2015-01-01

    the motions in the direction parallel to the Earth'srotation axis. This property accounts for the signicance of the core-mantle topography.In addition, the stiening of the uid in the direction parallel to the rotation axis gives riseto a magnetic diusion layer attached to the core-mantle boundary, which would...

  3. Abundant carbon in the mantle beneath Hawai`i

    Science.gov (United States)

    Anderson, Kyle R.; Poland, Michael

    2017-01-01

    Estimates of carbon concentrations in Earth’s mantle vary over more than an order of magnitude, hindering our ability to understand mantle structure and mineralogy, partial melting, and the carbon cycle. CO2 concentrations in mantle-derived magmas supplying hotspot ocean island volcanoes yield our most direct constraints on mantle carbon, but are extensively modified by degassing during ascent. Here we show that undegassed magmatic and mantle carbon concentrations may be estimated in a Bayesian framework using diverse geologic information at an ocean island volcano. Our CO2 concentration estimates do not rely upon complex degassing models, geochemical tracer elements, assumed magma supply rates, or rare undegassed rock samples. Rather, we couple volcanic CO2 emission rates with probabilistic magma supply rates, which are obtained indirectly from magma storage and eruption rates. We estimate that the CO2content of mantle-derived magma supplying Hawai‘i’s active volcanoes is 0.97−0.19+0.25 wt%—roughly 40% higher than previously believed—and is supplied from a mantle source region with a carbon concentration of 263−62+81 ppm. Our results suggest that mantle plumes and ocean island basalts are carbon-rich. Our data also shed light on helium isotope abundances, CO2/Nb ratios, and may imply higher CO2 emission rates from ocean island volcanoes.

  4. Hf isotope evidence for a hidden mantle reservoir

    DEFF Research Database (Denmark)

    Bizzarro, Martin; Simonetti, A.; Stevenson, R.K.

    2002-01-01

    High-precision Hf isotopic analyses and U-Pb ages of carbonatites and kimberlites from Greenland and eastern North America, including Earth's oldest known carbonatite (3 Ga), indicate derivation from an enriched mantle source. This previously unidentified mantle reservoir-marked by an unradiogeni...

  5. Fundamentals and hard-switching converters

    CERN Document Server

    Ioinovici, Adrian

    2013-01-01

    Volume 1 Fundamentals and Hard-switching Converters introduces the key challenges in power electronics from basic components to operation principles and presents classical hard- and soft-switching DC to DC converters, rectifiers and inverters. At a more advanced level, it provides comprehensive analysis of DC and AC models comparing the available approaches for their derivation and results. A full treatment of DC to DC hard-switching converters is given, from fundamentals to modern industrial solutions and practical engineering insight. The author elucidates various contradictions and misunderstandings in the literature, for example, in the treatment of the discontinuous conduction operation or in deriving AC small-signal models of converters.

  6. DC/DC Converter Stability Testing Study

    Science.gov (United States)

    Wang, Bright L.

    2008-01-01

    This report presents study results on hybrid DC/DC converter stability testing methods. An input impedance measurement method and a gain/phase margin measurement method were evaluated to be effective to determine front-end oscillation and feedback loop oscillation. In particular, certain channel power levels of converter input noises have been found to have high degree correlation with the gain/phase margins. It becomes a potential new method to evaluate stability levels of all type of DC/DC converters by utilizing the spectral analysis on converter input noises.

  7. Commutation Processes in Multiresonant ZVS Bridge Converter

    Directory of Open Access Journals (Sweden)

    Miroslaw Luft

    2008-01-01

    Full Text Available The analysis of the multiresonant ZVS DC/DC bridge converter is presented. The control system of the converter is basedon the method of frequency control at the constant time of transistor turn-off with a phase shift. The operation of the circuit is givenand the operating range of the converter is defined where ZVS switching operation is assured. Control characteristics are given andthe converter’s efficiency is defined. The circuit’s operation is analysed on the basis of results of the converter simulation tests using Simplorer programme.

  8. Reliability of Power Electronic Converter Systems

    DEFF Research Database (Denmark)

    -link capacitance in power electronic converter systems; wind turbine systems; smart control strategies for improved reliability of power electronics system; lifetime modelling; power module lifetime test and state monitoring; tools for performance and reliability analysis of power electronics systems; fault......-tolerant adjustable speed drive systems; mission profile oriented reliability design in wind turbine and photovoltaic systems; reliability of power conversion systems in photovoltaic applications; power supplies for computers; and high-power converters. Reliability of Power Electronic Converter Systems is essential...... reading for researchers, professionals and students working with power electronics and their applications, particularly those specializing in the development and application of power electronic converters and systems....

  9. Cascaded Evolution of Mantle Plumes and Metallogenesis of Core- and Mantle-derived Elements

    Institute of Scientific and Technical Information of China (English)

    NIU Shuyin; HOU Quanlin; HOU Zengqian; SUN Aiqun; WANG Baode; LI Hongyang; XU Chuanshi

    2003-01-01

    Mineral deposits are unevenly distributed in the Earth's crust, which is closely related to the formation andevolution of the Earth. In the early history of the Earth, controlled by the gravitational contraction and thermal expansion,lighter elements, such as radioactive, halogen-family, rare and rare earth elements and alkali metals. migrated upwards;whereas heavier elements, such as iron-family and platinum-family elements, base metals and noble metals, had atendency of sinking to the Earth's core, so that the elements iron, nickel, gold and silver are mainly concentrated in theEarth's core. However, during the formation of the stratified structure of the Earth, the existence of temperature, pressureand viscosity differences inside and outside the Earth resulted in vertical material movement manifested mainly bycascaded evolution of mantle plumes in the Earth. The stratifications and vertical movement of the Earth wereinterdependent and constituted the motive force of the mantle-core movement. The cascaded evolution of mantle plumesopens the passageways for the migration of deep-seated ore-forming material, and thus elements such as gold and silverconcentrated in the core and on the core-mantle boundary migrate as the gaseous state together with the hot material flowof mantle plumes against the gravitational force through the passageways to the lithosphere, then migrate as the mixed gas-liquid state to the near-surface level and finally are concentrated in favorable structural expansion zones, forming mineraldeposits. This is possibly the important metallogenic mechanism for gold, silver, lead, zinc, copper and other manyelements. Take for example the NE-plunging crown of the Fuping mantle-branch structure, the paper analyzes ductile-brittle shear zone-type gold fields (Weijiayu) at the core of the magmatic-metamorphic complex, principal detachment-type gold fields (Shangmingyu) and hanging-wall cover fissure-vein-type lead-zinc polymetallic ore fields

  10. Global correlation of lower mantle structure and past subduction

    Science.gov (United States)

    Domeier, Mathew; Doubrovine, Pavel V.; Torsvik, Trond H.; Spakman, Wim; Bull, Abigail L.

    2016-05-01

    Advances in global seismic tomography have increasingly motivated identification of subducted lithosphere in Earth's deep mantle, creating novel opportunities to link plate tectonics and mantle evolution. Chief among those is the quest for a robust subduction reference frame, wherein the mantle assemblage of subducted lithosphere is used to reconstruct past surface tectonics in an absolute framework anchored in the deep Earth. However, the associations heretofore drawn between lower mantle structure and past subduction have been qualitative and conflicting, so the very assumption of a correlation has yet to be quantitatively corroborated. Here we show that a significant, time-depth progressive correlation can be drawn between reconstructed subduction zones of the last 130 Myr and positive S wave velocity anomalies at 600-2300 km depth, but that further correlation between greater times and depths is not presently demonstrable. This correlation suggests that lower mantle slab sinking rates average between 1.1 and 1.9 cm yr-1.

  11. Mantle circulation and the lateral migration of subducted slabs

    Science.gov (United States)

    Garfunkel, Z.; Anderson, C. A.; Schubert, G.

    1986-01-01

    The geometry of transverse migration of subducted lithospheric slabs is examined, and the way in which this influences the flow in the mantle is studied. The migration of subducted slabs generally appears to be retrograde (at rates of 10-25 mm/yr), so that the descent of material is actually steeper than the slab dip. Retrograde slab migration is probably caused by the tendence of negatively buoyant slabs to sink in the surrounding mantle. The properties of the flow driven by such retrograde slab migration are explored in simple two-dimensional models. The results are used as a guide to infer the contribution of retrograde slab motion to the more complex mantle flow and to examine some consequences of the additional component of mantle flow. It is shown that slab migration is an important factor that causes mantle flow to be geometrically complex and time dependent.

  12. Molybdenum isotope fractionation in the mantle

    Science.gov (United States)

    Liang, Yu-Hsuan; Halliday, Alex N.; Siebert, Chris; Fitton, J. Godfrey; Burton, Kevin W.; Wang, Kuo-Lung; Harvey, Jason

    2017-02-01

    We report double-spike molybdenum (Mo) isotope data for forty-two mafic and fifteen ultramafic rocks from diverse locations and compare these with results for five chondrites. The δ98/95Mo values (normalized to NIST SRM 3134) range from -0.59 ± 0.04 to +0.10 ± 0.08‰. The compositions of one carbonaceous (CI) and four ordinary chondrites are relatively uniform (-0.14 ± 0.01‰, 95% ci (confidence interval)) in excellent agreement with previous data. These values are just resolvable from the mean of 10 mid-ocean ridge basalts (MORBs) (0.00 ± 0.02‰, 95% ci). The compositions of 13 mantle-derived ultramafic xenoliths from Kilbourne Hole, Tariat and Vitim are more diverse (-0.39 to -0.07‰) with a mean of -0.22 ± 0.06‰ (95% ci). On this basis, the isotopic composition of the bulk silicate Earth (BSE or Primitive Mantle) is within error identical to chondrites. The mean Mo concentration of the ultramafic xenoliths (0.19 ± 0.07 ppm, 95% ci) is similar in magnitude to that of MORB (0.48 ± 0.13 ppm, 95% ci), providing evidence, either for a more compatible behaviour than previously thought or for selective Mo enrichment of the subcontinental lithospheric mantle. Intraplate and ocean island basalts (OIBs) display significant isotopic variability within a single locality from MORB-like to strongly negative (-0.59 ± 0.04‰). The most extreme values measured are for nephelinites from the Cameroon Line and Trinidade, which also have anomalously high Ce/Pb and low Mo/Ce relative to normal oceanic basalts. δ98/95Mo correlates negatively with Ce/Pb and U/Pb, and positively with Mo/Ce, explicable if a phase such as an oxide or a sulphide liquid selectively retains isotopically heavy Mo in the mantle and fractionates its isotopic composition in low degree partial melts. If residual phases retain Mo during partial melting, it is possible that the [Mo] for the BSE may be misrepresented by values estimated from basalts. This would be consistent with the high Mo

  13. Petrology of periodotites as a tool of insight into mantle processes: a review. Jobu mantle kanrangan no gansekigaku (ikani mantle process wo yomitoruka)

    Energy Technology Data Exchange (ETDEWEB)

    Arai, S. (Kanazawa University, Ishikawa (Japan). Faculty of Science)

    1992-09-05

    Petrological studies of the upper mantle materials are reviewed mainly in terms of recent topics. Along with on increase in depletion degree (degree of slipped-out magma) of resistate which remains after magma slipped out from the upper mantle materials, a series from lherzolite to Harzburgites is obtained and as an example, the Horoman peridotite complex which intrudes into the Hidaka metamorphic belt (Hokkaido) is shown. In this connection, a theory is introduced where the bedded structure of this peridotite complex was formed by a series of processes accompanied by the cracks generated in the mantle peridotite. Then, the following topics are explained: strongly incompatible trace elements can be enriched in resistate with high depletion degree (REE paradox); and the recent research trend on issues which relates to the interaction between the magma and mantle, such as the formation of dunites, the origin of picrite basalt, and the origin of chromitite are described. 40 refs., 13 figs.

  14. How Irreversible Heat Transport Processes Drive Earth's Interdependent Thermal, Structural, and Chemical Evolution Providing a Strongly Heterogeneous, Layered Mantle

    Science.gov (United States)

    Hofmeister, A.; Criss, R. E.

    2013-12-01

    Because magmatism conveys radioactive isotopes plus latent heat rapidly upwards while advecting heat, this process links and controls the thermal and chemical evolution of Earth. We present evidence that the lower mantle-upper mantle boundary is a profound chemical discontinuity, leading to observed heterogeneities in the outermost layers that can be directly sampled, and construct an alternative view of Earth's internal workings. Earth's beginning involved cooling via explosive outgassing of substantial ice (mainly CO) buried with dust during accretion. High carbon content is expected from Solar abundances and ice in comets. Reaction of CO with metal provided a carbide-rich core while converting MgSiO3 to olivine via oxidizing reactions. Because thermodynamic law (and buoyancy of hot particles) indicates that primordial heat from gravitational segregation is neither large nor carried downwards, whereas differentiation forced radioactive elements upwards, formation of the core and lower mantle greatly cooled the Earth. Reference conductive geotherms, calculated using accurate and new thermal diffusivity data, require that heat-producing elements are sequestered above 670 km which limits convection to the upper mantle. These irreversible beginnings limit secular cooling to radioactive wind-down, permiting deduction of Earth's inventory of heat-producing elements from today's heat flux. Coupling our estimate for heat producing elements with meteoritic data indicates that Earth's oxide content has been underestimated. Density sorting segregated a Si-rich, peridotitic upper mantle from a refractory, oxide lower mantle with high Ca, Al and Ti contents, consistent with diamond inclusion mineralogy. Early and rapid differentiation means that internal temperatures have long been buffered by freezing of the inner core, allowing survival of crust as old as ca.4 Ga. Magmatism remains important. Melt escaping though stress-induced fractures in the rigid lithosphere imparts a

  15. Mantle differentiation and chemical cycling in the Archean (Invited)

    Science.gov (United States)

    Lee, C.

    2010-12-01

    Differentiation of Earth’s silicate mantle is largely controlled by solid-state convection. Today, upwelling mantle leads to decompression melting. Melts, being of low density, rise to form the continental and oceanic crusts. Because many trace elements, such as heat-producing U, Th and K, as well as the noble gases, preferentially partition into melts, melt extraction concentrates these elements into the crust or atmosphere. However, one by-product of whole-mantle convection is that melting during the Earth’s first billion years was likely deep and hot. Such high pressure melts may have been dense, allowing them to stall, crystallize and later founder back into the lower mantle. These sunken lithologies would have ‘primordial’ chemical signatures despite a non-primordial origin. As the Earth cools, the proportion of upwards melt segregation relative to downwards melt segregation increases, removing volatiles and other incompatible elements to the surface. Recycling of these elements back into the Earth’s interior occurs by subduction, but because of chemical weathering, hydrothermal alteration and photosynthetic reactions occurring in the Earth’s exosphere, these recycled materials may re-enter the mantle already chemically transformed. In particular, photosynthetic production of oxygen and, especially, the progressive oxygenation of the Earth’s atmosphere require removal of reduced carbon from the Earth’s surface. If such removal occurred by subduction, the mantle would have become progressively reduced. During the Archean and early Proterozoic, much of this material may have contributed to making cratonic mantle, and if so, cratonic mantle may have been assembled by reduced building blocks, perhaps explaining the origin of diamonds with organic carbon isotopic signatures. The origin of peridotitic diamonds in cratonic mantle could then be explained if the underlying convecting mantle was in fact more oxidizing such that carbonatitic liquids

  16. Iron-carbonate interaction at Earth's core-mantle boundary

    Science.gov (United States)

    Dorfman, S. M.; Badro, J.; Nabiei, F.; Prakapenka, V.; Gillet, P.

    2015-12-01

    Carbon storage and flux in the deep Earth are moderated by oxygen fugacity and interactions with iron-bearing phases. The amount of carbon stored in Earth's mantle versus the core depends on carbon-iron chemistry at the core-mantle boundary. Oxidized carbonates subducted from Earth's surface to the lowermost mantle may encounter reduced Fe0 metal from disproportionation of Fe2+ in lower mantle silicates or mixing with the core. To understand the fate of carbonates in the lowermost mantle, we have performed experiments on sandwiches of single-crystal (Ca0.6Mg0.4)CO3 dolomite and Fe foil in the laser-heated diamond anvil cell at lower mantle conditions of 49-110 GPa and 1800-2500 K. Syntheses were conducted with in situ synchrotron X-ray diffraction to identify phase assemblages. After quench to ambient conditions, samples were sectioned with a focused Ga+ ion beam for composition analysis with transmission electron microscopy. At the centers of the heated spots, iron melted and reacted completely with the carbonate to form magnesiowüstite, iron carbide, diamond, magnesium-rich carbonate and calcium carbonate. In samples heated at 49 and 64 GPa, the two carbonates exhibit a eutectoid texture. In the sample heated at 110 GPa, the carbonates form rounded ~150-nm-diameter grains with a higher modal proportion of interspersed diamonds. The presence of reduced iron in the deep lower mantle and core-mantle boundary region will promote the formation of diamonds in carbonate-bearing subducted slabs. The complete reaction of metallic iron to oxides and carbides in the presence of mantle carbonate supports the formation of these phases at the Earth's core-mantle boundary and in ultra-low velocity zones.

  17. Whole-mantle convection with tectonic plates preserves long-term global patterns of upper mantle geochemistry.

    Science.gov (United States)

    Barry, T L; Davies, J H; Wolstencroft, M; Millar, I L; Zhao, Z; Jian, P; Safonova, I; Price, M

    2017-05-12

    The evolution of the planetary interior during plate tectonics is controlled by slow convection within the mantle. Global-scale geochemical differences across the upper mantle are known, but how they are preserved during convection has not been adequately explained. We demonstrate that the geographic patterns of chemical variations around the Earth's mantle endure as a direct result of whole-mantle convection within largely isolated cells defined by subducting plates. New 3D spherical numerical models embedded with the latest geological paleo-tectonic reconstructions and ground-truthed with new Hf-Nd isotope data, suggest that uppermost mantle at one location (e.g. under Indian Ocean) circulates down to the core-mantle boundary (CMB), but returns within ≥100 Myrs via large-scale convection to its approximate starting location. Modelled tracers pool at the CMB but do not disperse ubiquitously around it. Similarly, mantle beneath the Pacific does not spread to surrounding regions of the planet. The models fit global patterns of isotope data and may explain features such as the DUPAL anomaly and long-standing differences between Indian and Pacific Ocean crust. Indeed, the geochemical data suggests this mode of convection could have influenced the evolution of mantle composition since 550 Ma and potentially since the onset of plate tectonics.

  18. Can Lower Mantle Slab-like Seismic Anomalies be Explained by Thermal Coupling Between the Upper and Lower Mantles?

    NARCIS (Netherlands)

    Cízková, H. (Hana); Cadek, O.; Berg, A.P. van den; Vlaar, N.J.

    1999-01-01

    Below subduction zones, high resolution seismic tomographic models resolve fast anomalies that often extend into the deep lower mantle. These anomalies are generally interpreted as slabs penetrating through the 660-km seismic discontinuity, evidence in support of whole-mantle convection. However, th

  19. Crustal and upper mantle seismic structure of the Svalbard Archipelago from the receiver function analysis

    Directory of Open Access Journals (Sweden)

    Wilde−Piórko Monika

    2015-06-01

    Full Text Available Receiver function provides the signature of sharp seismic discontinuities and the information about the shear wave (S−wave velocity distribution beneath the seismic station. This information is very valuable in areas where any or few reflection and/or refraction studies are available and global and/or regional models give only rough information about the seismic velocities. The data recorded by broadband seismic stations have been analysed to investigate the crustal and upper mantle structure of the Svalbard Archipelago. Svalbard Archipelago is a group of islands located in Arctic, at the north−western part of the Barents Sea continental platform, which is bordered to the west and to the north by passive continental margins. The new procedure of parameterization and selection of receiver functions (RFs has been proposed. The back−azimuthal sections of RF show a strong variation for the HSPB and KBS stations. Significant amplitudes of transversal component of RF (T−RF for the HSPB station indicate a shallow dipping layer towards the southwest. The structure of the crust beneath the SPITS array seems to be less heterogeneous, with very low amplitudes of converted phase comparing to the KBS and HSPB stations. Forward modelling by trial−and−error method shows a division of the crust into 3-4 layers beneath all stations and layering of the uppermost mantle beneath the SPITS array and the HSPB stations. The thickness of the mantle transition zone is larger for western part of archipelago and smaller for eastern part comparing to iasp91 model.

  20. Mantle xenoliths from Marosticano area (Northern Italy): a comparison with Veneto Volcanic Province lithospheric mantle

    Science.gov (United States)

    Brombin, Valentina; Bonadiman, Costanza; Coltorti, Massimo

    2016-04-01

    The Tertiary Magmatic Province of Veneto, known as Veneto Volcanic Province (VVP), in the North-East of Italy, represents the most important volcanic distric of Adria Plate. It is composed by five volcanic bodies: Val d'Adige, Marosticano, Mts. Lessini, Berici Hills and Euganean Hills. Most of the volcanic products are relatively undifferentiated lavas and range in composition from nephelinites to tholeiites. Often VVP nephelinites and basanites carry mantle xenoliths (mainly harzburgites and lherzolite). This study reports petrological comparison between Marosticano xenoliths (new outcrop) and xenoliths from the Lessinean and Val d'Adige areas already studied by many Authors (Siena & Coltorti 1989; Beccaluva et al., 2001, Gasperini et al., 2006). Mineral major elements analyses show that the Marosticano lherzolites and harzburgites reflect "more restitic" composition than the mantle domain beneath the other VVP districts (Lessini Mts. and Val d'Adige). In fact, olivine and pyroxene of Marosticano xenoliths have the highest mg# values of the entire district (Marosticano→90-93; literature→86-92). At comparable mg# (45-85 wt%) Marosticano spinels tend to be higher in Cr2O3 (23-44 wt%) contents with respect to the other VVP sp (7-25 wt%). It is worth noting that, Ni contents of Marosticano olivines in both harzburgites and lherzolites are higher (2650-3620 ppm) than those of the Lessinean xenoliths (1500- 3450 ppm), and similar to that of Val d'Adige lherzolites (3000-3500 ppm), approaching the contents of Archean cratonic mantle (Kelemen, 1998). In turn, Lessinean olivines properly fall in the Ni-mg# Phanerozoic field. At fixed pressure of 15 kbar, the equilibration temperature of Marosticano xenoliths are similar (Brey & Köhler: 920-1120°C) to those of Lessini (O'Neill & Wall: 990-1110°C; Beccaluva et al., 2007), but higher than those of Val d'Adige (Wells: 909-956°C; Gasperini et al., 2006). Finally, Marosticano mantle fragment show similar relatively high

  1. The North American upper mantle: density, composition, and evolution

    Science.gov (United States)

    Mooney, Walter D.; Kaban, Mikhail K.

    2010-01-01

    The upper mantle of North America has been well studied using various seismic methods. Here we investigate the density structure of the North American (NA) upper mantle based on the integrative use of the gravity field and seismic data. The basis of our study is the removal of the gravitational effect of the crust to determine the mantle gravity anomalies. The effect of the crust is removed in three steps by subtracting the gravitational contributions of (1) topography and bathymetry, (2) low-density sedimentary accumulations, and (3) the three-dimensional density structure of the crystalline crust as determined by seismic observations. Information regarding sedimentary accumulations, including thickness and density, are taken from published maps and summaries of borehole measurements of densities; the seismic structure of the crust is based on a recent compilation, with layer densities estimated from P-wave velocities. The resultant mantle gravity anomaly map shows a pronounced negative anomaly (−50 to −400 mGal) beneath western North America and the adjacent oceanic region and positive anomalies (+50 to +350 mGal) east of the NA Cordillera. This pattern reflects the well-known division of North America into the stable eastern region and the tectonically active western region. The close correlation of large-scale features of the mantle anomaly map with those of the topographic map indicates that a significant amount of the topographic uplift in western NA is due to buoyancy in the hot upper mantle, a conclusion supported by previous investigations. To separate the contributions of mantle temperature anomalies from mantle compositional anomalies, we apply an additional correction to the mantle anomaly map for the thermal structure of the uppermost mantle. The thermal model is based on the conversion of seismic shear-wave velocities to temperature and is consistent with mantle temperatures that are independently estimated from heat flow and heat production data

  2. Molecular pathogenesis of mantle cell lymphoma

    Science.gov (United States)

    Jares, Pedro; Colomer, Dolors; Campo, Elias

    2012-01-01

    Mantle cell lymphoma is a B cell malignancy in which constitutive dysregulation of cyclin D1 and the cell cycle, disruption of DNA damage response pathways, and activation of cell survival mechanisms contribute to oncogenesis. A small number of tumors lack cyclin D1 overexpression, suggesting that its dysregulation is always not required for tumor initiation. Some cases have hypermutated IGHV and stable karyotypes, a predominant nonnodal disease, and an indolent clinical evolution, which suggests that they may correspond to distinct subtypes of the disease. In this review, we discuss the molecular pathways that contribute to pathogenesis, and how improved understanding of these molecular mechanisms offers new perspectives for the treatment of patients. PMID:23023712

  3. MicroRNAs in mantle cell lymphoma

    DEFF Research Database (Denmark)

    Husby, Simon; Geisler, Christian; Grønbæk, Kirsten

    2013-01-01

    Mantle cell lymphoma (MCL) is a rare and aggressive subtype of non-Hodgkin lymphoma. New treatment modalities, including intensive induction regimens with immunochemotherapy and autologous stem cell transplant, have improved survival. However, many patients still relapse, and there is a need...... for novel therapeutic strategies. Recent progress has been made in the understanding of the role of microRNAs (miRNAs) in MCL. Comparisons of tumor samples from patients with MCL with their normal counterparts (naive B-cells) have identified differentially expressed miRNAs with roles in cellular growth...... and survival pathways, as demonstrated in various biological model systems. In addition, MCL clinico-pathological and prognostic subtypes can be identified using individual miRNAs or miRNA classifiers. miRNA based therapies have now shown efficacy in animal models, and many efforts are currently being made...

  4. P-V-T equations of state of lower mantle minerals: Constraints on mantle composition models

    Science.gov (United States)

    Fei, Y.; Zhang, L.; Frank, M.; Corgne, A.; Wheeler, K.; Meng, Y.

    2004-12-01

    Ferropericlase (Mg,Fe)O is likely a stable phase coexisting with silicate perovskite in the Earth's lower mantle. Determination of a reliable P-V-T equation-of-state of this phase is therefore crucial for developing compositional and mineralogical models of the Earth's interior. In this study, we report new compression data on ferropericlase up to 136 GPa, covering the entire pressure range of the lower mantle. The experiments were performed at the HPCAT 16-ID-B beamline (Advanced Photon Source), using monochromatic X-radiation and a CCD area detector. We used (Mg0.6Fe0.4)O as the starting material. The powdered sample was sandwiched between NaCl and a mixture of NaCl-Au in an externally heated high-temperature diamond anvil cell. The sample was annealed at each pressure increment by laser heating. High-quality diffraction data were collected up to 136 GPa. The same starting material was also studied up to 27 GPa and 2173 K in a multi-anvil apparatus by X-ray diffraction. A reliable P-V-T equation of state for (Mg0.6Fe0.4)O was developed by combining the two data sets. The new results, together with our recent P-V-T data for Al-bearing perovskite up to 105 GPa and 1000 K, provide solid density measurements for the two most important lower mantle minerals under simultaneous high pressure and temperature conditions. The new data are used to model the density profile of the lower mantle and provide tight constraints on its chemical composition.

  5. Crust-Mantle Structures and Gold Enrichment Mechanism of Mantle Fluid System

    Institute of Scientific and Technical Information of China (English)

    邓军; 孙忠实; 王庆飞; 韦延光

    2003-01-01

    Gold enrichment mechanism of ore-forming fluid is the essence of gold metallization.This paper summarizes the distinguishing symbols of mantle fluid and effect of crust-mantlestructure on fluid movement. Fluid moving processes include osmosis, surge, gas-liquid alterna-tion and mutation of fluid speed. During fluid movement, gold will be enriched gradually. Final-ly, a layered circulatory system is illustrated in this paper.

  6. Multilevel converters for 10 MW Wind Turbines

    DEFF Research Database (Denmark)

    Ma, Ke; Blaabjerg, Frede

    2011-01-01

    Several promising multi-level converter configurations for 10 MW Wind Turbines both with direct drive and one-stage gear box drive using Permanent Magnet Synchronous Generator (PMSG) are proposed, designed and compared. Reliability is a crucial indicator for large scale wind power converters...

  7. Present trends in HVDC converter station design

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, Lennart; Asplund, Gunnar; Bjorklund, Hans; Flisberg, Gunnar [ABB Power Systems AB, Ludvika (Sweden)

    1994-12-31

    HVDC converter station technology has developed rapidly to satisfy increasing requirements during past 10 - 15 years, but there has not been any dramatic changes since thyristor valves were introduced in the mid 70s. This paper describes some recent and expected future developments, that will substantiality change and simplify future converter stations. (author) 4 refs., 7 figs.

  8. High-Efficiency dc/dc Converter

    Science.gov (United States)

    Sturman, J.

    1982-01-01

    High-efficiency dc/dc converter has been developed that provides commonly used voltages of plus or minus 12 Volts from an unregulated dc source of from 14 to 40 Volts. Unique features of converter are its high efficiency at low power level and ability to provide output either larger or smaller than input voltage.

  9. Power Converters Secure Electronics in Harsh Environments

    Science.gov (United States)

    2013-01-01

    In order to harden power converters for the rigors of space, NASA awarded multiple SBIR contracts to Blacksburg, Virginia-based VPT Inc. The resulting hybrid DC-DC converters have proven valuable in aerospace applications, and as a result the company has generated millions in revenue from the product line and created four high-tech jobs to handle production.

  10. High Precision Current Measurement for Power Converters

    CERN Document Server

    Cerqueira Bastos, M

    2015-01-01

    The accurate measurement of power converter currents is essential to controlling and delivering stable and repeatable currents to magnets in particle accelerators. This paper reviews the most commonly used devices for the measurement of power converter currents and discusses test and calibration methods.

  11. Time-Interleaved Analog to Digital Converters

    NARCIS (Netherlands)

    Louwsma, S.M.; van Tuijl, Adrianus Johannes Maria; Nauta, Bram

    2010-01-01

    This book describes the research carried out by our PhD student Simon Louwsma at the University of Twente, The Netherlands in the field of high-speed Analogto- Digital (AD) converters. AD converters are crucial circuits for modern systems where information is stored or processed in digital form. Due

  12. Input-output rearrangement of isolated converters

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Kovacevic, Milovan; Mønster, Jakob Døllner;

    2015-01-01

    is not a requirement. The proposed technique is particularly valuable in power conversion at very high frequencies, and may be combined with other stress reduction methods. Finally, the new arrangements are experimentally verified both on off the shelf converters and on a VHF resonant SEPIC converter. All results...

  13. Modeling and Simulation of Matrix Converter

    DEFF Research Database (Denmark)

    Liu, Fu-rong; Klumpner, Christian; Blaabjerg, Frede

    2005-01-01

    This paper discusses the modeling and simulation of matrix converter. Two models of matrix converter are presented: one is based on indirect space vector modulation and the other is based on power balance equation. The basis of these two models is• given and the process on modeling is introduced...

  14. Formation and modification of chromitites in the mantle

    Science.gov (United States)

    Arai, Shoji; Miura, Makoto

    2016-11-01

    Podiform chromitites have long supplied us with unrivaled information on various mantle processes, including the peridotite-magma reaction, deep-seated magmatic evolution, and mantle dynamics. The recent discovery of ultrahigh-pressure (UHP) chromitites not only sheds light on a different aspect of podiform chromitites, but also changes our understanding of the whole picture of podiform chromitite genesis. In addition, new evidence was recently presented for hydrothermal modification/formation chromite/chromitite in the mantle, which is a classical but innovative issue. In this context, we present here an urgently needed comprehensive review of podiform chromitites in the upper mantle. Wall-rock control on podiform chromitite genesis demonstrates that the peridotite-magma reaction at the upper mantle condition is an indispensable process. We may need a large system in the mantle, far larger than the size of outcrops or mining areas, to fulfill the Cr budget requirement for podiform chromitite genesis. The peridotite-magma reaction over a large area may form a melt enriched with Na and other incompatible elements, which mixes with a less evolved magma supplied from the depth to create chromite-oversaturated magma. The incompatible-element-rich magma trapped by the chromite mainly precipitates pargasite and aspidolite (Na analogue of phlogopite), which are stable under upper mantle conditions. Moderately depleted harzburgites, which contain chromite with a moderate Cr# (0.4-0.6) and a small amount of clinopyroxene, are the best reactants for the chromitite-forming reaction, and are the best hosts for podiform chromitites. Arc-type chromitites are dominant in ophiolites, but some are of the mid-ocean ridge type; chromitites may be common beneath the ocean floor, although it has not yet been explored for chromitite. The low-pressure (upper mantle) igneous chromitites were conveyed through mantle convection or subduction down to the mantle transition zone to form

  15. Radiation Effects on DC-DC Converters

    Science.gov (United States)

    Zhang, De-Xin; AbdulMazid, M. D.; Attia, John O.; Kankam, Mark D. (Technical Monitor)

    2001-01-01

    In this work, several DC-DC converters were designed and built. The converters are Buck Buck-Boost, Cuk, Flyback, and full-bridge zero-voltage switched. The total ionizing dose radiation and single event effects on the converters were investigated. The experimental results for the TID effects tests show that the voltages of the Buck Buck-Boost, Cuk, and Flyback converters increase as total dose increased when using power MOSFET IRF250 as a switching transistor. The change in output voltage with total dose is highest for the Buck converter and the lowest for Flyback converter. The trend of increase in output voltages with total dose in the present work agrees with those of the literature. The trends of the experimental results also agree with those obtained from PSPICE simulation. For the full-bridge zero-voltage switch converter, it was observed that the dc-dc converter with IRF250 power MOSFET did not show a significant change of output voltage with total dose. In addition, for the dc-dc converter with FSF254R4 radiation-hardened power MOSFET, the output voltage did not change significantly with total dose. The experimental results were confirmed by PSPICE simulation that showed that FB-ZVS converter with IRF250 power MOSFET's was not affected with the increase in total ionizing dose. Single Event Effects (SEE) radiation tests were performed on FB-ZVS converters. It was observed that the FB-ZVS converter with the IRF250 power MOSFET, when the device was irradiated with Krypton ion with ion-energy of 150 MeV and LET of 41.3 MeV-square cm/mg, the output voltage increased with the increase in fluence. However, for Krypton with ion-energy of 600 MeV and LET of 33.65 MeV-square cm/mg, and two out of four transistors of the converter were permanently damaged. The dc-dc converter with FSF254R4 radiation hardened power MOSFET's did not show significant change at the output voltage with fluence while being irradiated by Krypton with ion energy of 1.20 GeV and LET of 25

  16. Thermal evolution of Earth's mantle and core: Influence of reference viscosity and concentration of radioactive elements in the mantle

    Science.gov (United States)

    Nakagawa, T.; Tackley, P. J.

    2010-12-01

    In a series of studies on the thermal evolution of Earth’s mantle and core [Nakagawa and Tackley, 2004; 2005; 2010], we have assumed a reference viscosity (at T=1600 K and P=0) of 1022 Pa.s and a concentration of radioactive elements based on the surface heat flux of the Earth’s mantle (6x10-12 W/kg). In addition, the initial mantle temperature in these studies was also based on the mantle adiabat estimated from present potential temperature (1600 K). Problems with these models are that (1) the average mantle temperature increases in the initial phase of the calculation and (2) the final (present-day) surface heat flux is a factor of two lower than expected from observational constraints (46 TW [Jaupart et al., 2007]), which means the Urey ratio is higher than the expected value (~0.3) [Jaupert et al., 2007; Korenaga, 2007]. Here we present results of a coupled model of thermo-chemical mantle convection in a 2-D spherical annulus and parameterized core heat balance, in which we vary (i) the reference viscosity down to 1020 Pa.s, giving a "surface" Rayleigh number of 109, (ii) the concentration of radioactive heat-producing elements in the mantle are tried (either a theoretical estimate [Schubert et al., 2001; 25 TW], geochemical estimate [McDonough and Sun, 1995; 20 TW] and modified geochemical estimate [Lyubetskaya and Korenaga, 2006; 16 TW]) and (iii) the initial mantle adiabat (up to 2500 K at the surface). Preliminary results indicate a preference for an initial mantle adiabat of more than 2500 K and the modified geochemical estimate of radioactive element concentration, in order to understand the current thermal state of Earth’s mantle when the reference viscosity is 1022 Pa s. Results with lower reference viscosity will be presented.

  17. Modelling, analyses and design of switching converters

    Science.gov (United States)

    Cuk, S. M.; Middlebrook, R. D.

    1978-01-01

    A state-space averaging method for modelling switching dc-to-dc converters for both continuous and discontinuous conduction mode is developed. In each case the starting point is the unified state-space representation, and the end result is a complete linear circuit model, for each conduction mode, which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small-signal). While the method is generally applicable to any switching converter, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model. The insights that emerge from the general state-space modelling approach lead to the design of new converter topologies through the study of generic properties of the cascade connection of basic buck and boost converters.

  18. Qualitative model of a plasma photoelectric converter

    Science.gov (United States)

    Gorbunov, N. A.; Flamant, G.

    2009-01-01

    A converter of focused optical radiation into electric current is considered on the basis of the photovoltaic effect in plasmas. The converter model is based on analysis of asymmetric spatial distributions of charge particle number density and ambipolar potential in the photoplasma produced by external optical radiation focused in a heat pipe filled with a mixture of alkali vapor and a heavy inert gas. Energy balance in the plasma photoelectric converter is analyzed. The conditions in which the external radiation energy is effectively absorbed in the converter are indicated. The plasma parameters for which the energy of absorbed optical radiation is mainly spent on sustaining the ambipolar field in the plasma are determined. It is shown that the plasma photoelectric converter makes it possible to attain a high conversion efficiency for focused solar radiation.

  19. Transformer Isolated Buck-Boost Converters

    Directory of Open Access Journals (Sweden)

    Barry W. Williams

    2016-12-01

    Full Text Available Of the single-switch dc-to-dc converters, those with the buck-boost voltage transfer function offer most potential for transformer coupling, hence isolation, at the kilowatt level. This paper highlights the limitations of the traditional magnetic coupled, buck-boost topology. Then four split-capacitor transformer-coupled topologies (specifically the Cuk, sepic, zeta, and a new, converters with a common ac equivalent circuit are explored, that do not temporarily store core magnetic energy as does the traditional isolated buck-boost converter nor have a core dc magnetizing current bias, as with the sepic and zeta transformer coupled topologies. Core dc bias capacitive voltage compensation is a practical design constraint in three of the four topologies, while all four must cater for stray and leakage inductance effects. Simulations and experimental results for the new converter at 408W support the transformer-coupled, single-switch dc-to-dc converter concepts investigated.

  20. Periodic Control of Power Electronic Converters

    DEFF Research Database (Denmark)

    Zhou, Keliang; Danwei, Wang; Yang, Yongheng

    Advanced power electronic converters convert, control and condition electricity. Power converters require control strategies for periodic signal compensation to assure good power quality and stable power system operation. This comprehensive text presents the most recent internal model principle...... based periodic control technology, which offers the perfect periodic control solution for power electronic conversion. It also provides complete analysis and synthesis methods for periodic control systems, and plenty of practical examples to demonstrate the validity of proposed periodic control...... technology for power converters. It proposes a unified framework for housing periodic control schemes for power converters, and provides a general proportional-integral-derivative control solution to periodic signal compensation in extensive engineering applications. Periodic Control of Power Electronic...

  1. SPECTRAL ANALYSIS OF BUCK AND SEPIC CONVERTERS

    Directory of Open Access Journals (Sweden)

    CHAKIB ALAOUI

    2011-02-01

    Full Text Available Switched mode power converters generate harmonic currents, which will be injected into the utility grid, causing distortion of the utility waveform. They also become a source for the generation of EMI, which may affect the communication systems. This work is about the design and evaluation of the two most frequently used SMPS used in step down mode of operation: the Buck converter and the Sepic converter working in step-down mode of operation. These converters were designed using optimized equations for their components ratings. Simulation results show that although the Buck output voltage is low in harmonics, it has high harmonic contents in currents circulating in its inductor and diode, and hence requires strong filtering. The Sepic converterhas lower harmonic contents than the Buck converter.

  2. A novel power converter for photovoltaic applications

    Science.gov (United States)

    Yuvarajan, S.; Yu, Dachuan; Xu, Shanguang

    A simple and economical power conditioner to convert the power available from solar panels into 60 Hz ac voltage is described. The raw dc voltage from the solar panels is converted to a regulated dc voltage using a boost converter and a large capacitor and the dc output is then converted to 60 Hz ac using a bridge inverter. The ratio between the load current and the short-circuit current of a PV panel at maximum power point is nearly constant for different insolation (light) levels and this property is utilized in designing a simple maximum power point tracking (MPPT) controller. The controller includes a novel arrangement for sensing the short-circuit current without disturbing the operation of the PV panel and implementing MPPT. The switching losses in the inverter are reduced by using snubbers. The results obtained on an experimental converter are presented.

  3. The Effect of Lower Mantle Metallization on Magnetic Field Generation in Rocky Exoplanets

    CERN Document Server

    Vilim, Ryan; Elkins-Tanton, Linda

    2013-01-01

    Recent theoretical and experimental evidence indicates that many of the materials that are thought to exist in the mantles of terrestrial exoplanets will metallize and become good conductors of electricity at mantle pressures. This allows for strong electromagnetic coupling of the core and the mantle in these planets. We use a numerical dynamo model to study the effect of a metallized lower mantle on the dynamos of terrestrial exoplanets using several inner core sizes and mantle conductivities. We find that the addition of an electrically conducting mantle results in stronger core-mantle boundary fields because of the increase in magnetic field stretching. We also find that a metallized mantle destabilizes the dynamo resulting in less dipolar, less axisymmetric poloidal magnetic fields at the core-mantle boundary. The conducting mantle efficiently screens these fields to produce weaker surface fields. We conclude that a conducting mantle will make the detection of extrasolar terrestrial magnetic fields more d...

  4. PERFORMANCE ANALYSIS OF 2D CONVERTER BY COMBINING SR & KY CONVERTERS

    Directory of Open Access Journals (Sweden)

    V. Manoj Kumar

    2014-03-01

    Full Text Available Most of the portable equipments use battery as power source. The increasing use of low voltage portable devices and growing requirements of functionalities embedded into such devices. Thus an efficient power management technique is needed for longer battery life for them. Highly variable nature of batteries systems often require supply voltages to be both higher and lower than the battery. This is most efficiently generated by a buck-boost switching converter. But here the converter efficiency is decreased since the power loss occurs in the storage devices. Step by step, process of designing, feedback control and simulation of a novel voltage-buck boost converter, combining KY and synchronous Rectifier buck converter for battery power applications. Unlike the traditional buck–boost converter, this converter has the positive output voltage and system is stable, different from the negative output voltage and low stable of the traditional inverting buck–boost converters. Since such a converter operates in continuous conduction mode. Also it possesses the non-pulsating output current, thereby not only decreasing the current stress on the output capacitor but also reducing the output voltage ripple. Both the KY converter and the synchronous buck converter, combined into a positive buck– boost converter, uses the same power switches. Here it makes the circuit to be compact and the corresponding cost to be down. Voltage conversion ratio is 2D,so it is also called 2D converter.

  5. Tracing recycled volatiles in a heterogeneous mantle with boron isotopes

    Science.gov (United States)

    Walowski, Kristina; Kirstein, Linda; de Hoog, Cees-Jan; Elliot, Tim; Savov, Ivan; Devey, Colin

    2016-04-01

    Recycling of oceanic lithosphere drives the chemical evolution of the Earth's mantle supplying both solids and volatiles to the Earth's interior. Yet, how subducted material influences mantle composition remains unclear. A perfect tracer for slab recycling should be only fractionated at the Earth's surface, have a strong influence on mantle compositions but be resistant to perturbations en route back to the surface. Current understanding suggests that boron concentrations linked to B isotope determinations fulfil all these requirements and should be an excellent tracer of heterogeneity in the deep mantle. Here, we present the trace element, volatile and the B isotope composition of basaltic glasses and melt inclusions in olivine from distinct end-member ocean island basalts (OIB) to track the fate of recycled lithosphere and ultimately document how recycling contributes to mantle heterogeneity. The chosen samples represent the different end member OIB compositions and include: EMI (Pitcairn), EMII (MacDonald), HIMU (St. Helena), and FOZO (Cape Verde & Reunion). The data is derived from both submarine and subaerial deposits, with B isotope determination of both basaltic glass and melt inclusions from each locality. Preliminary results suggest OIB have B isotopic compositions that overlap the MORB array (-7.5‰±0.7; Marschall et al., 2015) but extend to both lighter and heavier values. These results suggest that B isotopes will be useful for resolving mantle source heterogeneity at different ocean islands and contribute to our understanding of the volatile budget of the deep mantle.

  6. Propagating buoyant mantle upwelling on the Reykjanes Ridge

    Science.gov (United States)

    Martinez, Fernando; Hey, Richard

    2017-01-01

    Crustal features of the Reykjanes Ridge have been attributed to mantle plume flow radiating outward from the Iceland hotspot. This model requires very rapid mantle upwelling and a "rheological boundary" at the solidus to deflect plume material laterally and prevent extreme melting above the plume stem. Here we propose an alternative explanation in which shallow buoyant mantle upwelling instabilities propagate along axis to form the crustal features of the ridge and flanks. As only the locus of buoyant upwelling propagates this mechanism removes the need for rapid mantle plume flow. Based on new geophysical mapping we show that a persistent sub-axial low viscosity channel supporting buoyant mantle upwelling can explain the current oblique geometry of the ridge as a reestablishment of its original configuration following an abrupt change in opening direction. This mechanism further explains the replacement of ridge-orthogonal crustal segmentation with V-shaped crustal ridges and troughs. Our findings indicate that crustal features of the Reykjanes Ridge and flanks are formed by shallow buoyant mantle instabilities, fundamentally like at other slow spreading ridges, and need not reflect deep mantle plume flow.

  7. Limited latitudinal mantle plume motion for the Louisville hotspot

    Science.gov (United States)

    Koppers, Anthony A. P.; Yamazaki, Toshitsugu; Geldmacher, Jörg; Gee, Jeffrey S.; Pressling, Nicola; Koppers, Anthony A. P.; Yamazaki, Toshitsugu; Geldmacher, Jörg; Gee, Jeffrey S.; Pressling, Nicola; Hoshi, Hiroyuki; Anderson, L.; Beier, C.; Buchs, D. M.; Chen, L.-H.; Cohen, B. E.; Deschamps, F.; Dorais, M. J.; Ebuna, D.; Ehmann, S.; Fitton, J. G.; Fulton, P. M.; Ganbat, E.; Hamelin, C.; Hanyu, T.; Kalnins, L.; Kell, J.; Machida, S.; Mahoney, J. J.; Moriya, K.; Nichols, A. R. L.; Rausch, S.; Sano, S.-I.; Sylvan, J. B.; Williams, R.

    2012-12-01

    Hotspots that form above upwelling plumes of hot material from the deep mantle typically leave narrow trails of volcanic seamounts as a tectonic plate moves over their location. These seamount trails are excellent recorders of Earth's deep processes and allow us to untangle ancient mantle plume motions. During ascent it is likely that mantle plumes are pushed away from their vertical upwelling trajectories by mantle convection forces. It has been proposed that a large-scale lateral displacement, termed the mantle wind, existed in the Pacific between about 80 and 50 million years ago, and shifted the Hawaiian mantle plume southwards by about 15° of latitude. Here we use 40Ar/39Ar age dating and palaeomagnetic inclination data from four seamounts associated with the Louisville hotspot in the South Pacific Ocean to show that this hotspot has been relatively stable in terms of its location. Specifically, the Louisville hotspot--the southern hemisphere counterpart of Hawai'i--has remained within 3-5° of its present-day latitude of about 51°S between 70 and 50 million years ago. Although we cannot exclude a more significant southward motion before that time, we suggest that the Louisville and Hawaiian hotspots are moving independently, and not as part of a large-scale mantle wind in the Pacific.

  8. ON THE VIGOR OF MANTLE CONVECTION IN SUPER-EARTHS

    Energy Technology Data Exchange (ETDEWEB)

    Miyagoshi, Takehiro [Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama 236-0001 (Japan); Tachinami, Chihiro [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Kameyama, Masanori [Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577 (Japan); Ogawa, Masaki, E-mail: miyagoshi@jamstec.go.jp, E-mail: ctchnm.geo@gmail.com, E-mail: kameyama@sci.ehime-u.ac.jp, E-mail: cmaogawa@mail.ecc.u-tokyo.ac.jp [Department of Earth Sciences and Astronomy, University of Tokyo at Komaba, 3-8-1 Komaba, Meguro, Tokyo 153-8902 (Japan)

    2014-01-01

    Numerical models are presented to clarify how adiabatic compression affects thermal convection in the mantle of super-Earths ten times the Earth's mass. The viscosity strongly depends on temperature, and the Rayleigh number is much higher than that of the Earth's mantle. The strong effect of adiabatic compression reduces the activity of mantle convection; hot plumes ascending from the bottom of the mantle lose their thermal buoyancy in the middle of the mantle owing to adiabatic decompression, and do not reach the surface. A thick lithosphere, as thick as 0.1 times the depth of the mantle, develops along the surface boundary, and the efficiency of convective heat transport measured by the Nusselt number is reduced by a factor of about four compared with the Nusselt number for thermal convection of incompressible fluid. The strong effect of adiabatic decompression is likely to inhibit hot spot volcanism on the surface and is also likely to affect the thermal history of the mantle, and hence, the generation of magnetic field in super-Earths.

  9. Water Distribution in the Continental and Oceanic Upper Mantle

    Science.gov (United States)

    Peslier, Anne H.

    2015-01-01

    Nominally anhydrous minerals such as olivine, pyroxene and garnet can accommodate tens to hundreds of ppm H2O in the form of hydrogen bonded to structural oxygen in lattice defects. Although in seemingly small amounts, this water can significantly alter chemical and physical properties of the minerals and rocks. Water in particular can modify their rheological properties and its distribution in the mantle derives from melting and metasomatic processes and lithology repartition (pyroxenite vs peridotite). These effects will be examined here using Fourier transform infrared spectrometry (FTIR) water analyses on minerals from mantle xenoliths from cratons, plume-influenced cratons and oceanic settings. In particular, our results on xenoliths from three different cratons will be compared. Each craton has a different water distribution and only the mantle root of Kaapvaal has evidence for dry olivine at its base. This challenges the link between olivine water content and survival of Archean cratonic mantle, and questions whether xenoliths are representative of the whole cratonic mantle. We will also present our latest data on Hawaii and Tanzanian craton xenoliths which both suggest the intriguing result that mantle lithosphere is not enriched in water when it interacts with melts from deep mantle upwellings (plumes).

  10. The ruthenium isotopic composition of the oceanic mantle

    Science.gov (United States)

    Bermingham, K. R.; Walker, R. J.

    2017-09-01

    The approximately chondritic relative, and comparatively high absolute mantle abundances of the highly siderophile elements (HSE), suggest that their concentrations in the bulk silicate Earth were primarily established during a final ∼0.5 to 1% of ;late accretion; to the mantle, following the cessation of core segregation. Consequently, the isotopic composition of the HSE Ru in the mantle reflects an amalgamation of the isotopic compositions of late accretionary contributions to the silicate portion of the Earth. Among cosmochemical materials, Ru is characterized by considerable mass-independent isotopic variability, making it a powerful genetic tracer of Earth's late accretionary building blocks. To define the Ru isotopic composition of the oceanic mantle, the largest portion of the accessible mantle, we report Ru isotopic data for materials from one Archean and seven Phanerozoic oceanic mantle domains. A sample from a continental lithospheric mantle domain is also examined. All samples have identical Ru isotopic compositions, within analytical uncertainties, indicating that Ru isotopes are well mixed in the oceanic mantle, defining a μ100Ru value of 1.2 ± 7.2 (2SD). The only known meteorites with the same Ru isotopic composition are enstatite chondrites and, when corrected for the effects of cosmic ray exposure, members of the Main Group and sLL subgroup of the IAB iron meteorite complex which have a collective CRE corrected μ100Ru value of 0.9 ± 3.0. This suggests that materials from the region(s) of the solar nebula sampled by these meteorites likely contributed the dominant portion of late accreted materials to Earth's mantle.

  11. Moho vs crust-mantle boundary: Evolution of an idea

    Science.gov (United States)

    O'Reilly, Suzanne Y.; Griffin, W. L.

    2013-12-01

    The concept that the Mohorovicic Discontinuity (Moho) does not necessarily coincide with the base of the continental crust as defined by rock-type compositions was introduced in the early 1980s. This had an important impact on understanding the nature of the crust-mantle boundary using information from seismology and from deep-seated samples brought to the surface as xenoliths in magmas, or as tectonic terranes. The use of empirically-constrained P-T estimates to plot the locus of temperature vs depth for xenoliths defined a variety of geotherms depending on tectonic environment. The xenolith geotherms provided a framework for constructing lithological sections through the deep lithosphere, and revealed that the crust-mantle boundary in off-craton regions commonly is transitional over a depth range of about 5-20 km. Early seismic-reflection data showed common layering near the Moho, correlating with the petrological observation of multiple episodes of basaltic intrusion around the crust-mantle boundary. Developments in seismology, petrophysics and experimental petrology have refined interpretation of lithospheric domains. The expansion of in situ geochronology (especially zircon U-Pb ages and Hf-isotopes; Os isotopes of mantle sulfides) has defined tectonic events that affected whole crust-mantle sections, and revealed that the crust-mantle boundary can change in depth through time. However, the nature of the crust-mantle boundary in cratonic regions remains enigmatic, mainly due to lack of key xenoliths or exposed sections. The observation that the Moho may lie significantly deeper than the crust-mantle boundary has important implications for modeling the volume of the crust. Mapping the crust using seismic techniques alone, without consideration of the petrological problems, may lead to an overestimation of crustal thickness by 15-30%. This will propagate to large uncertainties in the calculation of elemental mass balances relevant to crust-formation processes

  12. Conflicting Geophysical and Geochemical Indicators of Mantle Temperature Beneath Tibet

    Science.gov (United States)

    Klemperer, S. L.

    2013-12-01

    In Tibet a small number of earthquakes occurs at 75-100 km depth, spanning the Moho, reaching >350 km and >550 km north of the Himalayan front in south-eastern Tibet and western Tibet respectively. 'Earthquake thermometry' implies these deep earthquakes occur in anhydrous lower lithosphere, either anorthitic or ultramafic, at 0.1RA (~1% mantle fluid) are conventionally taken to imply an unequivocal mantle component. Time-averaged upward flow rates calculated from measured 3He/4He ratios (R) and [4He] range from ~1-15 cm/a, implying transport times of 0.5-7 Ma through a 70-km thick crust. Discussion of 3He in Tibet in the western literature has been dominated by a single paper (Hoke et al., EPSL, 2000) that reported modest mantle helium (0.110% mantle fluids are reported 120 km and 150 km south of the northern limit of deep earthquakes in southeastern and western Tibet respectively. These hot springs apparently sampled mantle with T>800°C south of the locations where earthquake thermometry implies Moho temperatures India, Nepal and Pakistan, even though the 800°C isotherm is substantially shallower there than beneath southern Tibet? More plausibly the mantle helium is derived from an Asian mantle wedge above the region of deep earthquakes, in which case underthrusting Indian lithosphere is not intact, but breaks into an upper layer forming the lower crust of the Tibetan Plateau, and a lower seismogenic layer that is subducted more deeply into the mantle. Based on the geothermal springs, an Asian mantle wedge extended south of the Indus Tsangpo suture in SE Tibet and to the Karakoram fault in W Tibet until the latest Miocene, or even more recently.

  13. Seismic anisotropy: tracing plate dynamics in the mantle.

    Science.gov (United States)

    Park, Jeffrey; Levin, Vadim

    2002-04-19

    Elastic anisotropy is present where the speed of a seismic wave depends on its direction. In Earth's mantle, elastic anisotropy is induced by minerals that are preferentially oriented in a directional flow or deformation. Earthquakes generate two seismic wave types: compressional (P) and shear (S) waves, whose coupling in anisotropic rocks leads to scattering, birefringence, and waves with hybrid polarizations. This varied behavior is helping geophysicists explore rock textures within Earth's mantle and crust, map present-day upper-mantle convection, and study the formation of lithospheric plates and the accretion of continents in Earth history.

  14. Mantle structure and tectonic history of SE Asia

    Science.gov (United States)

    Hall, Robert; Spakman, Wim

    2015-09-01

    Seismic travel-time tomography of the mantle under SE Asia reveals patterns of subduction-related seismic P-wave velocity anomalies that are of great value in helping to understand the region's tectonic development. We discuss tomography and tectonic interpretations of an area centred on Indonesia and including Malaysia, parts of the Philippines, New Guinea and northern Australia. We begin with an explanation of seismic tomography and causes of velocity anomalies in the mantle, and discuss assessment of model quality for tomographic models created from P-wave travel times. We then introduce the global P-wave velocity anomaly model UU-P07 and the tectonic model used in this paper and give an overview of previous interpretations of mantle structure. The slab-related velocity anomalies we identify in the upper and lower mantle based on the UU-P07 model are interpreted in terms of the tectonic model and illustrated with figures and movies. Finally, we discuss where tomographic and tectonic models for SE Asia converge or diverge, and identify the most important conclusions concerning the history of the region. The tomographic images of the mantle record subduction beneath the SE Asian region to depths of approximately 1600 km. In the upper mantle anomalies mainly record subduction during the last 10 to 25 Ma, depending on the region considered. We interpret a vertical slab tear crossing the entire upper mantle north of west Sumatra where there is a strong lateral kink in slab morphology, slab holes between c.200-400 km below East Java and Sumbawa, and offer a new three-slab explanation for subduction in the North Sulawesi region. There is a different structure in the lower mantle compared to the upper mantle and the deep structure changes from west to east. What was imaged in earlier models as a broad and deep anomaly below SE Asia has a clear internal structure and we argue that many features can be identified as older subduction zones. We identify remnants of slabs

  15. Mercury's Plasma Mantle – a survey of MESSENGER observations

    Science.gov (United States)

    Jasinski, Jamie Matthew; Slavin, James A.; Raines, Jim; DiBraccio, Gina

    2016-10-01

    The plasma mantle is a region of solar wind plasma entry into the nightside high-latitude magnetosphere. We present a survey of plasma mantles identified in particle and magnetic field measurements from four years of MESSENGER spacecraft observations of Mercury's magnetosphere. The two common observational signatures of this region are ion energy latitude dispersions as well as diamagnetic depressions. From these observations we estimate the contribution of plasma from the solar wind via the mantle and infer magnitude and variability in the cross-magnetospheric electric fields present at Mercury's dynamic magnetosphere.

  16. Electromagnetic Compatibility of Matrix Converter System

    Directory of Open Access Journals (Sweden)

    S. Fligl

    2006-12-01

    Full Text Available The presented paper deals with matrix converters pulse width modulation strategies design with emphasis on the electromagnetic compatibility. Matrix converters provide an all-silicon solution to the problem of converting AC power from one frequency to another, offering almost all the features required of an ideal static frequency changer. They possess many advantages compared to the conventional voltage or current source inverters. A matrix converter does not require energy storage components as a bulky capacitor or an inductance in the DC-link, and enables the bi-directional power flow between the power supply and load. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. The perspective of matrix converters regarding EMC in comparison with other types of converters is brightly evident because it is no need to use any equipment for power factor correction and current and voltage harmonics reduction. Such converter with proper control is properly compatible both with the supply mains and with the supplied load. A special digital control system was developed for the realized experimental test bed which makes it possible to achieve greater throughput of the digital control system and its variability.

  17. Underwater noise from a wave energy converter

    DEFF Research Database (Denmark)

    Tougaard, Jakob

    A recent addition to the anthropogenic sources of underwater noise is offshore wave energy converters. Underwater noise was recorded from the Wavestar wave energy converter located at Hastholm, Denmark (57°7.73´N, 8°37.23´E). The Wavestar is a full-scale test and demonstration converter...... in full operation and start and stop of the converter. Median broad band (10 Hz – 20 kHz) sound pressure level (Leq) was 123 dB re. 1 Pa, irrespective of status of the wave energy converter (stopped, running or starting/stopping). The most pronounced peak in the third-octave spectrum was in the 160 Hz...... significant noise above ambient could be detected above the 250 Hz band. The absolute increase in noise above ambient was very small. L50 third-octave levels in the four bands with the converter running were thus only 1-2 dB above ambient L50 levels. The noise recorded 25 m from the wave energy converter...

  18. Volatile cycling and the thermal evolution of planetary mantle

    Science.gov (United States)

    Sandu, Constantin

    The thermal histories of terrestrial planets are investigated using two parameterized mantle convection models for either Earth like planets and planets with no active plate tectonics. Using parameterized models of mantle convection, we performed computer simulations of planetary cooling and volatile cycling. The models estimate the amount of volatile in mantle reservoir, and calculate the outgassing and regassing rates. A linear model of volatile concentration-dependent is assumed for the activation energy of the solid-state creep in the mantle. The kinematic viscosity of the mantle is thus dynamically affected by the activation energy through a variable concentration in volatile. Mantle temperature and heat flux is calculated using a model derived from classic thermal boundary layer theory of a single layered mantle with temperature dependent viscosity. The rate of volatile exchanged between mantle and surface is calculated by balancing the amount of volatiles degassed in the atmosphere by volcanic and spreading related processes and the amount of volatiles recycled back in the mantle by the subduction process. In the cases that lack plate tectonics, the degassing efficiency is dramatically reduced and the regassing process is absent. The degassing effect is dependent on average spreading rate of tectonic plates and on the amount of volatile in the melt extract in the transition zone between mantle and upper boundary laver. The regassing effect is dependent on the subduction rate and on the amount of volatile present on a hydrated layer on top of the subducting slab. The degassing and regassing parameters are all related to the intensity of the convection in the mantle and to the surface temperature of the planet, and they are regulated by the amount of volatiles in reservoir. Comparative study with the previous models display significant differences and improve the versatility of the model. The optimum efficiency factors found are in the range of 0.01--0.06 for

  19. Accumulation of 'anti-continent' at the base of the mantle and its recycling in mantle plumes

    Science.gov (United States)

    Tatsumi, Yoshiyuki; Suzuki, Toshihiro; Ozawa, Haruka; Hirose, Kei; Hanyu, Takeshi; Ohishi, Yasuo

    2014-10-01

    The continental crust is a unique reservoir of light elements in the solid Earth; it possesses an intermediate composition and is believed to have been created principally along volcanic arcs, which are major sites of terrestrial andesitic magmatism. Mantle-derived arc magmas are, however, generally mafic or basaltic. A simple mechanism to overcome this apparent dilemma and generate andesitic melts in such a setting is through the partial remelting of an initial mafic arc crust by heat supplied from underplating basaltic magmas. An antithesis to the formation of continental crust in this way should be the production of refractory melting residue, here referred to as 'anti-continent'. This anti-continent is likely to detach from arc crust as a result of a density inversion and descend into the upper mantle. High-pressure experiments demonstrate that sinking anti-continent is, in contrast to the subducting oceanic crust, always denser than the surrounding mantle, suggesting that it penetrates through the upper-lower mantle boundary, without stagnation, and accumulates at the base of the mantle to form a 200-400 km thick mass known as the D″ layer. Geochemical modeling provides further evidence that this accumulating anti-continent contributes to a deep-seated hotspot source. Therefore, through complementary processes, Earth creates buoyant continents and dense anti-continents at the top and the base of the mantle, respectively, and has recycled portions of anti-continent in mantle plumes.

  20. Global-scale water circulation in the Earth's mantle: Implications for the mantle water budget in the early Earth

    Science.gov (United States)

    Nakagawa, Takashi; Spiegelman, Marc W.

    2017-04-01

    We investigate the influence of the mantle water content in the early Earth on that in the present mantle using numerical convection simulations that include three processes for redistribution of water: dehydration, partitioning of water into partially molten mantle, and regassing assuming an infinite water reservoir at the surface. These models suggest that the water content of the present mantle is insensitive to that of the early Earth. The initial water stored during planetary formation is regulated up to 1.2 OMs (OM = Ocean Mass; 1.4 ×1021 kg), which is reasonable for early Earth. However, the mantle water content is sensitive to the rheological dependence on the water content and can range from 1.2 to 3 OMs at the present day. To explain the evolution of mantle water content, we computed water fluxes due to subducting plates (regassing), degassing and dehydration. For weakly water dependent viscosity, the net water flux is almost balanced with those three fluxes but, for strongly water dependent viscosity, the regassing dominates the water cycle system because the surface plate activity is more vigorous. The increased convection is due to enhanced lubrication of the plates caused by a weak hydrous crust for strongly water dependent viscosity. The degassing history is insensitive to the initial water content of the early Earth as well as rheological strength. The degassing flux from Earth's surface is calculated to be approximately O (1013) kg /yr, consistent with a coupled model of climate evolution and mantle thermal evolution.

  1. Propagation characteristics of converted refracted wave and its application in static correction of converted wave

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Three-component seismic exploration through P-wave source and three-component geophone is an effective technique used in complicated reservoir exploration. In three-component seismic exploration data processing,one of the difficulties is static correction of converted wave. This paper analyzes propagation characteristics of non-converted and converted refracted waves,and discovers a favor-able condition for the formation of converted refracted wave,i.e. the velocity of overlaying medium S wave is much lower than that of underlying medium S wave. In addition,the paper proposes the static correction method of converted wave based on PPS converted refracted wave,and processes the real three-component seismic data with better results of static correction of converted wave.

  2. High-power converters and AC drives

    CERN Document Server

    Wu, Bin

    2017-01-01

    This new edition reflects the recent technological advancements in the MV drive industry, such as advanced multilevel converters and drive configurations. It includes three new chapters, Control of Synchronous Motor Drives, Transformerless MV Drives, and Matrix Converter Fed Drives. In addition, there are extensively revised chapters on Multilevel Voltage Source Inverters and Voltage Source Inverter-Fed Drives. This book includes a systematic analysis on a variety of high-power multilevel converters, illustrates important concepts with simulations and experiments, introduces various megawatt drives produced by world leading drive manufacturers, and addresses practical problems and their mitigations methods.

  3. Data Converter for Multistandard Mobile Phones

    DEFF Research Database (Denmark)

    Yurttas, Aziz; Bruun, Erik; Jensen, Rasmus Glarborg

    2004-01-01

    This paper describes an analog to digital converter (ADC) for mobile communication systems using a direct down conversion architecture. The ADC can be programmed to meet the requirements of different communication standards, including GSM (Global System for Mobile communication) and WCDMA (Wideband...... Code Division Multiple Access). The ADC is realized with a pipeline ADC architecture for WCDMA and a Sigma-Delta architecture for GSM. In order to have an optimized area and power consumption, the basic building blocks (opamps) of the converters are shared between the two converter architectures...

  4. Selective harmonic control for power converters

    DEFF Research Database (Denmark)

    Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede;

    2014-01-01

    This paper proposes an Internal Model Principle (IMP) based Selective Harmonic Controller (SHC) for power converters. The proposed SHC offers an optimal control solution for power converters to mitigate power harmonics. It makes a good trade-off among cost, complexity and performance. It has high...... accuracy and fast transient response, and it is cost-effective, easy for real-time implementation, and compatible for design rules-of-thumb. An application on a three-phase PWM converter has confirmed the effectiveness of the proposed control scheme in terms of harmonic mitigation....

  5. Time interleaved counter analog to digital converters

    OpenAIRE

    Danesh, Seyed Amir Ali

    2011-01-01

    The work explores extending time interleaving in A/D converters, by applying a high-level of parallelism to one of the slowest and simplest types of data-converters, the counter ADC. The motivation for the work is to realise high-performance re-configurable A/D converters for use in multi-standard and multi-PHY communication receivers with signal bandwidths in the 10s to 100s of MHz. The counter ADC requires only a comparator, a ramp signal, and a digital counter, where the ...

  6. Large Scale, High Resolution, Mantle Dynamics Modeling

    Science.gov (United States)

    Geenen, T.; Berg, A. V.; Spakman, W.

    2007-12-01

    To model the geodynamic evolution of plate convergence, subduction and collision and to allow for a connection to various types of observational data, geophysical, geodetical and geological, we developed a 4D (space-time) numerical mantle convection code. The model is based on a spherical 3D Eulerian fem model, with quadratic elements, on top of which we constructed a 3D Lagrangian particle in cell(PIC) method. We use the PIC method to transport material properties and to incorporate a viscoelastic rheology. Since capturing small scale processes associated with localization phenomena require a high resolution, we spend a considerable effort on implementing solvers suitable to solve for models with over 100 million degrees of freedom. We implemented Additive Schwartz type ILU based methods in combination with a Krylov solver, GMRES. However we found that for problems with over 500 thousend degrees of freedom the convergence of the solver degraded severely. This observation is known from the literature [Saad, 2003] and results from the local character of the ILU preconditioner resulting in a poor approximation of the inverse of A for large A. The size of A for which ILU is no longer usable depends on the condition of A and on the amount of fill in allowed for the ILU preconditioner. We found that for our problems with over 5×105 degrees of freedom convergence became to slow to solve the system within an acceptable amount of walltime, one minute, even when allowing for considerable amount of fill in. We also implemented MUMPS and found good scaling results for problems up to 107 degrees of freedom for up to 32 CPU¡¯s. For problems with over 100 million degrees of freedom we implemented Algebraic Multigrid type methods (AMG) from the ML library [Sala, 2006]. Since multigrid methods are most effective for single parameter problems, we rebuild our model to use the SIMPLE method in the Stokes solver [Patankar, 1980]. We present scaling results from these solvers for 3D

  7. P-V-T Equation of State of (Al,Fe)-bearing Mantle Perovskite and its Implications for Mantle Models

    Science.gov (United States)

    Fei, Y.; Ricolleau, A.; Litasov, K.; Prakapenka, V.

    2008-12-01

    We have made significant progress on accurate measurements of P-V-T equations-of-state of mantle minerals that are of fundamental importance for developing compositional and mineralogical models of the Earth's mantle. In this study, we report new compression data on (Al,Fe)-bearing mantle perovskite up to simultaneous pressure and temperature of 113 GPa and 2120 K. The mantle perovskite was synthesized in the multi-anvil apparatus at 27 GPa and 2073 K, with chemical compositions expected in a peridotitic mantle. It contains 5.86 wt% FeO and 3.84 wt% Al2O3. The pre-synthesized perovsite mixed with Au powder was compressed in neon pressure medium in a symmetric diamond anvil cell. The sample was heated with a double-sided laser-heating system at the GSECARS 13-ID-D beamline (Advanced Photon Source). We performed 8 heating cycles in the pressure range of 30-113 GPa and temperatures up to 2560 K. In-situ synchrotron X-ray diffraction data were collected within a uniformly heated area, using a MAR-CCD area detector. The diffraction pattern contains peaks of orthorhombic perovskite, internal standard Au, and pressure medium Ne. The triplet (020, 112, and 200 diffraction peaks) of the orthorhombic perovskite is well resolve. The present dataset covers the entire P-T range of the lower mantle and requires no extrapolation to compare the mantle density profile derived from seismic observations. In light of the new P-V-T data on the (Al,Fe)-bearing mantle perovskite combined with our recent density data and spin transition of ferropericlase, we finally discuss the compositional and mineralogical models of the lower mantle.

  8. European upper mantle tomography: adaptively parameterized models

    Science.gov (United States)

    Schäfer, J.; Boschi, L.

    2009-04-01

    We have devised a new algorithm for upper-mantle surface-wave tomography based on adaptive parameterization: i.e. the size of each parameterization pixel depends on the local density of seismic data coverage. The advantage in using this kind of parameterization is that a high resolution can be achieved in regions with dense data coverage while a lower (and cheaper) resolution is kept in regions with low coverage. This way, parameterization is everywhere optimal, both in terms of its computational cost, and of model resolution. This is especially important for data sets with inhomogenous data coverage, as it is usually the case for global seismic databases. The data set we use has an especially good coverage around Switzerland and over central Europe. We focus on periods from 35s to 150s. The final goal of the project is to determine a new model of seismic velocities for the upper mantle underlying Europe and the Mediterranean Basin, of resolution higher than what is currently found in the literature. Our inversions involve regularization via norm and roughness minimization, and this in turn requires that discrete norm and roughness operators associated with our adaptive grid be precisely defined. The discretization of the roughness damping operator in the case of adaptive parameterizations is not as trivial as it is for the uniform ones; important complications arise from the significant lateral variations in the size of pixels. We chose to first define the roughness operator in a spherical harmonic framework, and subsequently translate it to discrete pixels via a linear transformation. Since the smallest pixels we allow in our parameterization have a size of 0.625 °, the spherical-harmonic roughness operator has to be defined up to harmonic degree 899, corresponding to 810.000 harmonic coefficients. This results in considerable computational costs: we conduct the harmonic-pixel transformations on a small Beowulf cluster. We validate our implementation of adaptive

  9. Density structure of the cratonic mantle in southern Africa

    DEFF Research Database (Denmark)

    Artemieva, Irina; Vinnik, Lev P.

    2016-01-01

    . An unusually high topography may be caused by a low density (high depletion) of the cratonic lithospheric mantle and/or by the dynamic support of the mantle with origin below the depth of isostatic compensation (assumed here to be at the lithosphere base). We use free-board constraints to examine the relative...... contributions of the both factors to surface topography in the cratons of southern Africa. Our analysis takes advantage of the SASE seismic experiment which provided high resolution regional models of the crustal thickness.We calculate the model of density structure of the lithospheric mantle in southern Africa...... and show that it has an overall agreement with xenolith-based data for lithospheric terranes of different ages. Density of lithospheric mantle has significant short-wavelength variations in all tectonic blocks of southern Africa and has typical SPT values of ca. 3.37-3.41g/cm3 in the Cape Fold and Namaqua...

  10. Inference of mantle viscosity for depth resolutions of GIA observations

    Science.gov (United States)

    Nakada, Masao; Okuno, Jun'ichi

    2016-11-01

    Inference of the mantle viscosity from observations for glacial isostatic adjustment (GIA) process has usually been conducted through the analyses based on the simple three-layer viscosity model characterized by lithospheric thickness, upper- and lower-mantle viscosities. Here, we examine the viscosity structures for the simple three-layer viscosity model and also for the two-layer lower-mantle viscosity model defined by viscosities of η670,D (670-D km depth) and ηD,2891 (D-2891 km depth) with D-values of 1191, 1691 and 2191 km. The upper-mantle rheological parameters for the two-layer lower-mantle viscosity model are the same as those for the simple three-layer one. For the simple three-layer viscosity model, rate of change of degree-two zonal harmonics of geopotential due to GIA process (GIA-induced J˙2) of -(6.0-6.5) × 10-11 yr-1 provides two permissible viscosity solutions for the lower mantle, (7-20) × 1021 and (5-9) × 1022 Pa s, and the analyses with observational constraints of the J˙2 and Last Glacial Maximum (LGM) sea levels at Barbados and Bonaparte Gulf indicate (5-9) × 1022 Pa s for the lower mantle. However, the analyses for the J˙2 based on the two-layer lower-mantle viscosity model only require a viscosity layer higher than (5-10) × 1021 Pa s for a depth above the core-mantle boundary (CMB), in which the value of (5-10) × 1021 Pa s corresponds to the solution of (7-20) × 1021 Pa s for the simple three-layer one. Moreover, the analyses with the J˙2 and LGM sea level constraints for the two-layer lower-mantle viscosity model indicate two viscosity solutions: η670,1191 > 3 × 1021 and η1191,2891 ˜ (5-10) × 1022 Pa s, and η670,1691 > 1022 and η1691,2891 ˜ (5-10) × 1022 Pa s. The inferred upper-mantle viscosity for such solutions is (1-4) × 1020 Pa s similar to the estimate for the simple three-layer viscosity model. That is, these analyses require a high viscosity layer of (5-10) × 1022 Pa s at least in the deep mantle, and suggest

  11. Coupling surface and mantle dynamics: A novel experimental approach

    Science.gov (United States)

    Kiraly, Agnes; Faccenna, Claudio; Funiciello, Francesca; Sembroni, Andrea

    2015-05-01

    Recent modeling shows that surface processes, such as erosion and deposition, may drive the deformation of the Earth's surface, interfering with deeper crustal and mantle signals. To investigate the coupling between the surface and deep process, we designed a three-dimensional laboratory apparatus, to analyze the role of erosion and sedimentation, triggered by deep mantle instability. The setup is constituted and scaled down to natural gravity field using a thin viscous sheet model, with mantle and lithosphere simulated by Newtonian viscous glucose syrup and silicon putty, respectively. The surface process is simulated assuming a simple erosion law producing the downhill flow of a thin viscous material away from high topography. The deep mantle upwelling is triggered by the rise of a buoyant sphere. The results of these models along with the parametric analysis show how surface processes influence uplift velocity and topography signals.

  12. Mantle structure beneath the western edge of the Colorado Plateau

    Science.gov (United States)

    Sine, C.R.; Wilson, D.; Gao, W.; Grand, S.P.; Aster, R.; Ni, J.; Baldridge, W.S.

    2008-01-01

    Teleseismic traveltime data are inverted for mantle Vp and Vs variations beneath a 1400 km long line of broadband seismometers extending from eastern New Mexico to western Utah. The model spans 600 km beneath the moho with resolution of ???50 km. Inversions show a sharp, large-magnitude velocity contrast across the Colorado Plateau-Great Basin transition extending ???200 km below the crust. Also imaged is a fast anomaly 300 to 600 km beneath the NW portion of the array. Very slow velocities beneath the Great Basin imply partial melting and/or anomalously wet mantle. We propose that the sharp contrast in mantle velocities across the western edge of the Plateau corresponds to differential lithospheric modification, during and following Farallon subduction, across a boundary defining the western extent of unmodified Proterozoic mantle lithosphere. The deep fast anomaly corresponds to thickened Farallon plate or detached continental lithosphere at transition zone depths. Copyright 2008 by the American Geophysical Union.

  13. Thermochemical structure of the Earth's mantle and continental crust

    DEFF Research Database (Denmark)

    Guerri, Mattia

    A detailed knowledge of the Earth's thermal structure and chemical composition is fundamental in order to understand the processes driving the planet ormation and evolution. The inaccessibility of most of the Earth's interior makes the determination of its thermo-chemical conditions a challenging...... in determining crustal seismic discontinuities. In the second chapter, I deal about the possibility to disentangle the dynamic and isostatic contribution in shaping the Earth's surface topography. Dynamic topography is directly linked to mantle convection driven by mantle thermo-chemical anomalies, and can...... argue therefore that our understandings of the lithosphere density structure, needed to determine the isostatic topography, and of the mantle density and viscosity, required to compute the dynamic topography, are still too limited to allow a robust determination of mantle convection effects on the Earth...

  14. Generation and control of thoron emanated from lantern mantles

    Science.gov (United States)

    Sorimachi, Atsuyuki; Sahoo, Sarata Kumar; Tokonami, Shinji

    2009-01-01

    This paper describes the performance of a thoron (R220n) flowthrough source made of a commercially available lantern mantle. This R220n source is easy to construct and operate and has a negligible radon (R222n) gas generated when the air was passed through the source. We studied the R220n concentration generated from the lantern mantles in terms of the variability in concentration associated with both the total weight of the lantern mantles used in the source and the air flow rate used in the experimental chamber. We found that the concentration of R220n generated in air ranged from 0.9 to 150 kBq m-3 and exponentially depended on the absolute humidity. The R220n concentration increased linearly with increasing total weight of the lantern mantles, but variations in the rate of air flow passed through the source had no influence on the observed R220n concentration.

  15. On the deep-mantle origin of the Deccan Traps

    Science.gov (United States)

    Glišović, Petar; Forte, Alessandro M.

    2017-02-01

    The Deccan Traps in west-central India constitute one of Earth’s largest continental flood basalt provinces, whose eruption played a role in the Cretaceous-Paleogene extinction event. The unknown mantle structure under the Indian Ocean at the start of the Cenozoic presents a challenge for connecting the event to a deep mantle origin. We used a back-and-forth iterative method for time-reversed convection modeling, which incorporates tomography-based, present-day mantle heterogeneity to reconstruct mantle structure at the start of the Cenozoic. We show a very low-density, deep-seated upwelling that ascends beneath the Réunion hot spot at the time of the Deccan eruptions. We found a second active upwelling below the Comores hot spot that likely contributed to the region of partial melt feeding the massive eruption.

  16. New PWM switched-mode converter topologies

    Science.gov (United States)

    Hua, Gui-Chao; Huang, Shi-Peng

    Two augmented switching cells are proposed from which four novel topologies can be derived: an augmented buck converter, an augmented boost converter, a novel switching power amplifier, and a novel switching controlled rectifier. The augmented buck and the augmented boost converters realize higher step-down and step-up ratios, respectively, under a given switch duty ratio by proper design of the turn ratios of the transformer and coupled inductor. The switching power amplifier achieves four-quadrant output by the use of two bidirectional current switches and a single power supply, while the inverse converter can be used as a switching controlled rectifier. The experimental verification of the power amplifier is presented.

  17. "Forback" Dc-To-Dc Converters

    Science.gov (United States)

    Lukemire, Alan T.

    1992-01-01

    Dc-to-dc power-converter circuits called "forback" resemble circuits of standard configurations called "forward", "flyback", and "Cuk". Circuit employs minor modifications to existing topologies, combines advantages, while eliminating disadvantages, of older circuits.

  18. A three-port direct current converter

    DEFF Research Database (Denmark)

    2016-01-01

    The three-port direct current converter comprising: at least one input direct current source; at least one storage battery; a primary side circuit; a secondary side circuit; a first single magnetic component shared by the primary side circuit and the secondary side circuit, wherein the primary side...... circuit comprises a connection between the at least one input direct current source and the at least one storage battery, the primary side circuit configured for operating as a buck converter; a second magnetic component serially coupled to the first single magnetic component, wherein the first and second...... magnetic components are configured to perform a voltage step-up, wherein the secondary side circuit comprises a connection between the at least one storage battery and at least one load, the secondary side configured for operating as a tapped boost converter; wherein the three-port direct current converter...

  19. Interface of magnetoresistive converter of active power

    Directory of Open Access Journals (Sweden)

    A. I. Vytiaganets

    2009-10-01

    Full Text Available The vehicle and programmatic interfaces of magnetoresistive converter of active power are considered, the results of statistical treatment of the multiple measuring of active-power are analysed.

  20. Catalytic converters as a source of platinum

    Directory of Open Access Journals (Sweden)

    A. Fornalczyk

    2011-10-01

    Full Text Available The increase of Platinum Group Metals demand in automotive industry is connected with growing amount of cars equipped with the catalytic converters. The paper presents the review of available technologies during recycling process. The possibility of removing platinum from the used catalytic converters applying pyrometallurgical and hyrdometallurgical methods were also investigated. Metals such as Cu, Pb, Ca, Mg, Cd were used in the pyrometallurgical research (catalytic converter was melted with Cu, Pb and Ca or Mg and Cd vapours were blown through the whole carrier. In hydrometallurgical research catalytic converters was dissolved in aqua regia. Analysis of Pt contents in the carrier before and after the process was performed by means of atomic absorption spectroscopy. Obtained result were discussed.

  1. Reliability of power electronic converter systems

    CERN Document Server

    Chung, Henry Shu-hung; Blaabjerg, Frede; Pecht, Michael

    2016-01-01

    This book outlines current research into the scientific modeling, experimentation, and remedial measures for advancing the reliability, availability, system robustness, and maintainability of Power Electronic Converter Systems (PECS) at different levels of complexity.

  2. State estimation for wave energy converters

    Energy Technology Data Exchange (ETDEWEB)

    Bacelli, Giorgio; Coe, Ryan Geoffrey

    2017-04-01

    This report gives a brief discussion and examples on the topic of state estimation for wave energy converters (WECs). These methods are intended for use to enable real-time closed loop control of WECs.

  3. Lithology and temperature: How key mantle variables control rift volcanism

    Science.gov (United States)

    Shorttle, O.; Hoggard, M.; Matthews, S.; Maclennan, J.

    2015-12-01

    Continental rifting is often associated with extensive magmatic activity, emplacing millions of cubic kilometres of basalt and triggering environmental change. The lasting geological record of this volcanic catastrophism are the large igneous provinces found at the margins of many continents and abrupt extinctions in the fossil record, most strikingly that found at the Permo-Triassic boundary. Rather than being considered purely a passive plate tectonic phenomenon, these episodes are frequently explained by the involvement of mantle plumes, upwellings of mantle rock made buoyant by their high temperatures. However, there has been debate over the relative role of the mantle's temperature and composition in generating the large volumes of magma involved in rift and intra-plate volcanism, and even when the mantle is inferred to be hot, this has been variously attributed to mantle plumes or continental insulation effects. To help resolve these uncertainties we have combined geochemical, geophysical and modelling results in a two stage approach: Firstly, we have investigated how mantle composition and temperature contribute to melting beneath Iceland, the present day manifestation of the mantle plume implicated in the 54Ma break up of the North Atlantic. By considering both the igneous crustal production on Iceland and the chemistry of its basalts we have been able to place stringent constraints on the viable temperature and lithology of the Icelandic mantle. Although a >100°C excess temperature is required to generate Iceland's thick igneous crust, geochemistry also indicates that pyroxenite comprises 10% of its source. Therefore, the dynamics of rifting on Iceland are modulated both by thermal and compositional mantle anomalies. Secondly, we have performed a global assessment of the mantle's post break-up thermal history to determine the amplitude and longevity of continental insulation in driving excess volcanism. Using seismically constrained igneous crustal

  4. Role of the subduction filter in mantle recycling

    Science.gov (United States)

    Kimura, J. I.; Skora, S. E.; Gill, J.; Van Keken, P. E.

    2015-12-01

    Subduction modifies the descending basaltic and sedimentary oceanic crust and generates felsic arc materials and continental crust. Studies of element mass balances in the subduction zone therefore reveal the evolution of the Earth's two major geochemical reservoirs: the continent crust and mantle. We use the Arc Basalt Simulator ver.4 (ABS4) to model the geochemical mass balance during dehydration by prograde metamorphism and melting of the slab followed by subsequent flux melting of the wedge mantle caused by the addition of slab-derived liquids. The geochemistry of high-Mg andesite or adakite formed in a hot subduction zone is akin to the present-day bulk continental crust and to the Archean (>2 Ga) Tonalite-Trondjhemite-Granodiorite composition. Therefore, the residual slab and the metasomatized mantle wedge at hot subduction zones should be the most plausible sources for materials recycled back into the deep mantle. Model calculations of isotopic growth in the residual slab and mantle formed in hot subduction zones reproduce fairly well the EM1-FOZO-HIMU isotope arrays found in ocean island basalts (OIBs) of deep mantle plume origin, although FOZO with high 3He/4He is not generated by this slab recycling process. The recycled materials are bulk igneous ocean crust for HIMU and metasomatized mantle wedge peridotite for EM1. In contrast, the EM2-FOZO array can be generated in a cold subduction zone with igneous oceanic crust for FOZO and sediment for EM2 sources. Necessary residence time are ~2 Ga to form HIMU-FOZO-EM1 and ~1 Ga to form EM2-FOZO. The subducted oceanic crust (forming HIMU) and mantle wedge peridotite (forming EM1) may have travelled in the mantle together. They then melted together in an upwelling mantle plume to form the EM1-FOZO-HIMU isotopic variations found frequently in OIBs. In contrast, the less frequent EM2-FOZO array suggests a separate source and recycling path. These recycling ages are consistent with the change in the mantle potential

  5. Mantle flow influence on the evolution of subduction systems.

    Science.gov (United States)

    Chertova, Maria; Spakman, Wim; Steinberger, Bernhard

    2016-04-01

    Evolution of the subducting slab has been widely investigated in the past two decades be means of numerical and laboratory modeling, including analysis of the factors controlling its behavior. However, until present, relatively little attention has been paid to the influence of the mantle flow. While for large subduction zones, due to the high slab buoyancy force, this effect might be small, mantle flow might be a primary factor controlling the evolution of a regional subduction zone. Here we investigate the impact of prescribed mantle flow on the evolution of both generic and real-Earth subduction models by means of 3D thermo-mechanical numerical modeling. The generic setup consists of a laterally symmetric subduction model using a 3000×2000×1000 km modeling domain with a lateral slab width varying from 500 to 1500 km. Non-linear rheology is implemented including diffusion, dislocation creep and a viscosity-limiter. To satisfy mass conservation, while implementing mantle inflow on some side boundaries, we keep other sides open (Chertova et al. 2012). To test the mantle flow influence on the dynamics of real-Earth subduction zone we adopt the numerical model from Chertova et al. (2014) for the evolution of the western Mediterranean subduction since 35 Ma. First, this model was tested with the arbitrary mantle flow prescribed on one of the four side boundaries or for the combination of two boundaries. In the last set of experiments, for side boundary conditions we use time-dependent estimates of actual mantle flow in the region based on Steinberger (2015) given for every 1 My. We demonstrate that for the western-Mediterranean subduction, the surrounding mantle flow is of second-order compared to slab buoyancy in controlling the dynamics of the subducting slab. Introducing mantle flow on the side boundaries might, however, improve the fit between the modeled and real slab imaged by tomography, although this may also trade-off with varying rheological parameters of

  6. Predicting lower mantle heterogeneity from 4-D Earth models

    Science.gov (United States)

    Flament, Nicolas; Williams, Simon; Müller, Dietmar; Gurnis, Michael; Bower, Dan J.

    2016-04-01

    The Earth's lower mantle is characterized by two large-low-shear velocity provinces (LLSVPs), approximately ˜15000 km in diameter and 500-1000 km high, located under Africa and the Pacific Ocean. The spatial stability and chemical nature of these LLSVPs are debated. Here, we compare the lower mantle structure predicted by forward global mantle flow models constrained by tectonic reconstructions (Bower et al., 2015) to an analysis of five global tomography models. In the dynamic models, spanning 230 million years, slabs subducting deep into the mantle deform an initially uniform basal layer containing 2% of the volume of the mantle. Basal density, convective vigour (Rayleigh number Ra), mantle viscosity, absolute plate motions, and relative plate motions are varied in a series of model cases. We use cluster analysis to classify a set of equally-spaced points (average separation ˜0.45°) on the Earth's surface into two groups of points with similar variations in present-day temperature between 1000-2800 km depth, for each model case. Below ˜2400 km depth, this procedure reveals a high-temperature cluster in which mantle temperature is significantly larger than ambient and a low-temperature cluster in which mantle temperature is lower than ambient. The spatial extent of the high-temperature cluster is in first-order agreement with the outlines of the African and Pacific LLSVPs revealed by a similar cluster analysis of five tomography models (Lekic et al., 2012). Model success is quantified by computing the accuracy and sensitivity of the predicted temperature clusters in predicting the low-velocity cluster obtained from tomography (Lekic et al., 2012). In these cases, the accuracy varies between 0.61-0.80, where a value of 0.5 represents the random case, and the sensitivity ranges between 0.18-0.83. The largest accuracies and sensitivities are obtained for models with Ra ≈ 5 x 107, no asthenosphere (or an asthenosphere restricted to the oceanic domain), and a

  7. The origin of volatiles in the Earth's mantle

    Science.gov (United States)

    Hier-Majumder, Saswata; Hirschmann, Marc M.

    2017-08-01

    The Earth's deep interior contains significant reservoirs of volatiles such as H, C, and N. Due to the incompatible nature of these volatile species, it has been difficult to reconcile their storage in the residual mantle immediately following crystallization of the terrestrial magma ocean (MO). As the magma ocean freezes, it is commonly assumed that very small amounts of melt are retained in the residual mantle, limiting the trapped volatile concentration in the primordial mantle. In this article, we show that inefficient melt drainage out of the freezing front can retain large amounts of volatiles hosted in the trapped melt in the residual mantle while creating a thick early atmosphere. Using a two-phase flow model, we demonstrate that compaction within the moving freezing front is inefficient over time scales characteristic of magma ocean solidification. We employ a scaling relation between the trapped melt fraction, the rate of compaction, and the rate of freezing in our magma ocean evolution model. For cosmochemically plausible fractions of volatiles delivered during the later stages of accretion, our calculations suggest that up to 77% of total H2O and 12% of CO2 could have been trapped in the mantle during magma ocean crystallization. The assumption of a constant trapped melt fraction underestimates the mass of volatiles in the residual mantle by more than an order of magnitude.Plain Language SummaryThe Earth's deep interior contains substantial amounts of volatile elements like C, H, and N. How these elements got sequestered in the Earth's interior has long been a topic of debate. It is generally assumed that most of these elements escaped the interior of the Earth during the first few hundred thousand years to create a primitive atmosphere, leaving the mantle reservoir nearly empty. In this work, we show that the key to this paradox involves the very early stages of crystallization of the mantle from a global magma ocean. Using numerical models, we show

  8. Water content in the Martian mantle: A Nakhla perspective

    Science.gov (United States)

    Weis, Franz A.; Bellucci, Jeremy J.; Skogby, Henrik; Stalder, Roland; Nemchin, Alexander A.; Whitehouse, Martin J.

    2017-09-01

    Water contents of the Martian mantle have previously been investigated using Martian meteorites, with several comprehensive studies estimating the water content in the parental melts and mantle source regions of the shergottites and Chassigny. However, no detailed studies have been performed on the Nakhla meteorite. One possible way to determine the water content of a crystallizing melt is to use the water content in nominally anhydrous minerals (NAMs) such as clinopyroxene and olivine. During or after eruption on the surface of a planetary body and during residence in a degassing magma, these minerals may dehydrate. By reversing this process experimentally, original (pre-dehydration) water concentrations can be quantified. In this study, hydrothermal rehydration experiments were performed at 2 kbar and 700 °C on potentially dehydrated Nakhla clinopyroxene crystals. Rehydrated clinopyroxene crystals exhibit water contents of 130 ± 26 (2σ) ppm and are thus similar to values observed in similar phenocrysts from terrestrial basalts. Utilizing clinopyroxene/melt partition coefficients, both the water content of the Nakhla parent melt and mantle source region were estimated. Despite previous assumptions of a relatively dry melt, the basaltic magma crystallizing Nakhla may have had up to 1.42 ± 0.28 (2σ) wt.% H2O. Based on an assumed low degree of partial melting, this estimate can be used to calculate a minimum estimate of the water content for Nakhla's mantle source region of 72 ± 16 ppm. Combining this value with values determined for other SNC mantle sources, by alternative methods, gives an average mantle value of 102 ± 9 (2σ) ppm H2O for the Martian upper mantle throughout geologic time. This value is lower than the bulk water content of Earth's upper mantle (∼250 ppm H2O) but similar to Earth's MORB source (54-330 ppm, average ∼130 ppm H2O).

  9. Execution of mantle field with multileaf collimator: A simple approach

    Directory of Open Access Journals (Sweden)

    Prabhakar Ramachandran

    2008-01-01

    Full Text Available Background: Until very recently mantle field radiotherapy remained the gold standard for the treatment of favorable early-stage Hodgkin′s lymphoma. The classic mantle includes all the major lymph nodes above the diaphragm and extends from the inferior portion of the mandible to the level of the insertion of the diaphragm. Aims: To describe a simple technique that has been devised to treat the mantle field with the help of multileaf collimator and using computed tomography (CT-based treatment planning. Materials and Methods: CT scan was performed with the patient in the supine position and the datasets were transferred to the Eclipse™ treatment planning system. Elekta Precise™ linear accelerator equipped with 40 pairs of multileaf collimator (MLC was used for the execution of the mantle field. The MLC′s shapes were designed to take the shape of the conventional customized blocks used for treatment of mantle field. The anterior mantle field was divided into three separate MLC segments with the collimator kept at 0°. The first MLC segment was shaped to cover the neck, clavicular regions, and mediastinum. The second and the third MLC segments covered the right and left axilla, respectively. The posterior fields were opposed to the anterior subfields in a similar fashion. The dose was prescribed at the midplane, using reference points. Results and Conclusion: The technique described in this study is very simple, easy to implement, and avoids unnecessary delay in the execution of the mantle field. The mantle field can be easily shaped with the multileaf collimators, without any collimator rotation.

  10. Initial Feasibility Study to Drill and Core the Ocean Mantle

    OpenAIRE

    2011-01-01

    An initial feasibility study (Pilisi and Whitney, 2011) of drilling through the Mohorovičić discontinuity (Moho) into the oceanic mantle specifically focused on future requirements for planning, drilling and coring a hole 500 m into the oceanic mantle from three candidate locations in the Pacific Ocean (Cocos Plate, Baja California, and offshore Hawaii). The study points out some of the critical issues that need to be resolved before embarking upon such a challengingproject. It was conducted ...

  11. Origin of geochemical mantle components: Role of subduction filter

    Science.gov (United States)

    Kimura, Jun-Ichi; Gill, James B.; Skora, Susanne; van Keken, Peter E.; Kawabata, Hiroshi

    2016-08-01

    We quantitatively explore element redistribution at subduction zones using numerical mass balance models to evaluate the roles of the subduction zone filter in the Earth's geochemical cycle. Our models of slab residues after arc magma genesis differ from previous ones by being internally consistent with geodynamic models of modern arcs that successfully explain arc magma genesis and include element fluxes from the dehydration/melting of each underlying slab component. We assume that the mantle potential temperature (Tp) was 1400-1650°C at 3.5-1.7 Ga and gradually decreased to 1300-1350°C today. Hot subduction zones with Tp ˜1650°C have a thermal structure like modern SW Japan where high-Mg andesite is formed which is chemically like continental crust. After 2.5-1.7 Gyr of storage in the mantle, the residual igneous oceanic crust from hot subduction zones can evolve isotopically to the HIMU mantle component, the residual base of the mantle wedge to EMI, the residual sediment becomes an essential part of EMII, and the residual top of the mantle wedge can become the subcontinental lithosphere component. The Common or Focal Zone component is a stable mixture of the first three residues occasionally mixed with early depleted mantle. Slab residues that recycled earlier (˜2.5 Ga) form the DUPAL anomaly in the southern hemisphere, whereas residues of more recent recycling (˜1.7 Ga) underlie the northern hemisphere. These ages correspond to major continental crust forming events. The east-west heterogeneity of the depleted upper mantle involves subcontinental mantle except in the Pacific.

  12. Alpine Lithosphere and Upper Mantle Passive Seismic Monitoring

    OpenAIRE

    Brückl, Ewald; Hausmann, Helmut; Behm, Michael; Lippitsch, Regina; Mitterbauer, Ulrike; Institute of Geodesy and Geophysics Vienna University of Technology (Hrsg.)

    2008-01-01

    The project ALPASS is a passive seismic monitoring project aiming to reveal upper mantle, lower lithosphere, and asthenosphere beneath the wider Eastern Alpine region, including the Bohemian Massive, the Carpathians, the Pannonian Basin, and the Dinarides. A 3D seismic model which will provide crustal corrections to the seismic travel times has been generated in this area down to the Moho and the uppermost mantle from data of former projects CELEBRATION 2000 and ALP 2002. ALPASS will yield in...

  13. Properties of the Plasma Mantle in the Earth's Magnetotail

    Science.gov (United States)

    Shodhan-Shah, Sheela

    1998-04-01

    The plasma mantle is the site where the solar wind enters the Earth's magnetosphere. As yet, the mantle in the magnetotail (downstream part of the magnetosphere) has remained an enigma, for this region is remote and inaccessible. However, new results from the GEOTAIL spacecraft have yielded data on the mantle, making its study possible. The research reported in this dissertation uses the measurements made by the GEOTAIL spacecraft when it was beyond 100 Re (1 Re = Earth radius) in the magnetotail to determine the global geometrical and dynamical properties of the mantle. The model and the data together provide a cross-sectional picture of the mantle, as well as its extent into the tail and along the circumference of the tail. The model assesses the mass and momentum flux flowing through the mantle and merging with the plasma sheet (a relatively dense region that separates the oppositely directed fields of the tail lobes). In this way, the thesis examines the importance of the mantle as a source that replenishes and moves the plasma sheet. Moreover, it addresses the relative importance of the global dynamical modes of the tail. The analysis finds that the tail's 'breathing' mode, of shape change, occurs on a timescale of tens of minutes while a windsock-type motion, responding to changes in the solar wind direction, occurs on a scale of hours. The mantle extends about 140o around the circumference of the tail rather than 90o as previously thought and is about 20 ± 9 Re thick. It is capable of feeding the plasma sheet with sufficient particles to make up for those lost and can drag it away with a force that compares with the Earthward force on it. The rate at which the energy flows through the tail at 100 Re is about 10% of that in the solar wind and is a factor of 10 higher than the energy dissipated.

  14. Lower mantle heterogeneity, dynamic topography and the geoid

    Science.gov (United States)

    Hager, B. H.; Clayton, R. W.; Richards, M. A.; Comer, R. P.; Dziewonski, A. M.

    1985-01-01

    Density contrasts in the lower mantle, recently imaged using seismic tomography, drive convective flow which results in kilometers of dynamically maintained topography at the core-mantle boundary and at the earth's surface. The total gravity field due to interior density constrasts and boundary topography predicts the largest wavelength components of the geoid remarkably well. Neglecting dynamic surface deformation leads to geoid anomalies of opposite sign than are observed.

  15. New design trends in photovoltaic converters

    OpenAIRE

    Van den Bossche, Alex

    2013-01-01

    The reason to look at new trends in PV converters is that, in the total cost of ownership the converter is more expensive than the PV panel. Another trend is that one uses them without transformer to increase efficiency, but one has to take into account safety. One can increase the switching frequency and at the same time reducing the switching losses using SiC components, but still good cost effective solutions can be made with Si-IGBTs.

  16. Industrial application, 1MHz, quasi resonant converter

    OpenAIRE

    Carrasco Solís, Juan Manuel; Pérez Ridao, Francisco; Quero Reboul, José Manuel; Janer Jiménez, Carlos; García Franquelo, Leopoldo

    1993-01-01

    An industrial multi-output QRC converter is presented. Its main designing constraints are low cost, small in size, reduced EMI and EMC, high efficiency and severe dynamic behaviour in all outputs. Accomplishing this last restriction proved to be a difficult task. This has been done by means of a classical controller and cross regulation. The actual performance was tested on a 1MHz prototype rated at 50W. The low cost developed converter is characterized by its simplicity of design and operati...

  17. AC – AC Converters for UPS

    Directory of Open Access Journals (Sweden)

    Rusalin Lucian R. Păun

    2008-05-01

    Full Text Available This paper propose a new control technique forsingle – phase AC – AC converters used for a on-line UPSwith a good dynamic response, a reduced-partscomponents, a good output characteristic, a good powerfactorcorrection(PFC. This converter no needs anisolation transformer. A power factor correction rectifierand an inverter with the proposed control scheme has beendesigned and simulated using Caspoc2007, validating theconcept.

  18. Switching power converters medium and high power

    CERN Document Server

    Neacsu, Dorin O

    2013-01-01

    An examination of all of the multidisciplinary aspects of medium- and high-power converter systems, including basic power electronics, digital control and hardware, sensors, analog preprocessing of signals, protection devices and fault management, and pulse-width-modulation (PWM) algorithms, Switching Power Converters: Medium and High Power, Second Edition discusses the actual use of industrial technology and its related subassemblies and components, covering facets of implementation otherwise overlooked by theoretical textbooks. The updated Second Edition contains many new figures, as well as

  19. Local Bifurcations in DC-DC Converters

    OpenAIRE

    2012-01-01

    Three local bifurcations in DC-DC converters are reviewed. They are period-doubling bifurcation, saddle-node bifurcation, and Neimark bifurcation. A general sampled-data model is employed to study the types of loss of stability of the nominal (periodic) solution and their connection with local bifurcations. More accurate prediction of instability and bifurcation than using the averaging approach is obtained. Examples of bifurcations associated with instabilities in DC-DC converters are given.

  20. Mercurian impact ejecta: Meterorites and mantle

    CERN Document Server

    Gladman, B

    2008-01-01

    We have examined the fate of impact ejecta liberated from the surface of Mercury due to impacts by comets or asteroids, in order to study (1) meteorite transfer to Earth, and (2) re-accumulation of an expelled mantle in giant-impact scenarios seeking to explain Mercury's large core. In the context of meteorite transfer, we note that Mercury's impact ejecta leave the planet's surface much faster (on average) than other planet's in the Solar System because it is the only planet where impact speeds routinely range from 5-20 times the planet's escape speed. Thus, a large fraction of mercurian ejecta may reach heliocentric orbit with speeds sufficiently high for Earth-crossing orbits to exist immediately after impact, resulting in larger fractions of the ejecta reaching Earth as meteorites. We calculate the delivery rate to Earth on a time scale of 30 Myr and show that several percent of the high-speed ejecta reach Earth (a factor of -3 less than typical launches from Mars); this is one to two orders of magnitude ...

  1. Deuterium enrichment of the interstellar grain mantle

    CERN Document Server

    Das, Ankan; Chakrabarti, Sandip K

    2015-01-01

    We carry out Monte-Carlo simulation to study deuterium enrichment of interstellar grain mantles under various physical conditions. Based on the physical properties, various types of clouds are considered. We find that in diffuse cloud regions, very strong radiation fields persists and hardly a few layers of surface species are formed. In translucent cloud regions with a moderate radiation field, significant number of layers would be produced and surface coverage is mainly dominated by photo-dissociation products such as, C,CH_3,CH_2D,OH and OD. In the intermediate dense cloud regions (having number density of total hydrogen nuclei in all forms ~ 2 x 10^4 cm^-3), water and methanol along with their deuterated derivatives are efficiently formed. For much higher density regions (~ 10^6 cm^-3), water and methanol productions are suppressed but surface coverage of CO,CO_2,O_2,O_3 are dramatically increased. We find a very high degree of fractionation of water and methanol. Observational results support a high frac...

  2. Petrological features of suprasubuction mantle: evidence from northern, central and southern Patagonian mantle xenoliths

    Science.gov (United States)

    Melchiorre, M.; Coltorti, M.; Gregoire, M.; Benoit, M.

    2012-04-01

    Patagonia has a number of outcrops where xenoliths-bearing lavas can be found. It thus represents a good opportunity to study mantle material in supra-subduction environment both on arc and back-arc position, from as near as 300 km to as far as 600 km from the Chile trench. A wealth of data is nowadays available on these xenoliths, starting from petrographic observations, whole-rock and mineral major and trace element analyses plus few isotopic analyses on whole rock and mineral separates. To this already large dataset the petrological features of another locality (Estancia Sol de Mayo, ESM) were added, allowing a comparison between as much as eight localities coming from northern (Cerro Aznare, Praguaniyeu, Cerro Rio Chubut, Cerro de los Chenques), central (Cerro Clark and Gobernador Gregores) and southern Patagonia (Pali Aike), covering approximately an area of 1000 x 300 km. Most xenoliths are harzburgites, with minor amount of lherzolites, wehrlites and dunites. In the Al2O3 vs mg# [MgO/(MgO+FeO) mol %] diagram clinopyroxene (cpx) compositions highlight three different trends, with orthopyroxene (opx) compositions plotting on two of these. In the first trend Al2O3 content increases at almost constant mg# mol % (trend 1). The second trend comprises only cpx from wehrlites (trend 2) and is situated between the first and the third trend. In the third trend the slight increases of Al2O3 is associated with a remarkable decrease in mg# (trend 3). LREE and LILE abundances in cpx from Tres Lagos and Cerro Rio Chubut are directly correlated to the Al2O3, while they are inversely correlated at Cerro de Los Chenques and Cerro Fraile. In the first case it is likely that a metasomatic process affects the mantle domains beneath those areas, while in the second case a refertilization event caused by a tholeiitic melt is favorite. In other cases, as for Gobernador Gregores, a more complex situation is recorded, with two groups of samples showing both negative and positive

  3. LHC Power Converters: A Precision Game

    CERN Multimedia

    2001-01-01

    The LHC test-bed, String 2, is close to commissioning and one important element to get a first chance to prove what it can do is the power converter system. In String 2 there are 16 converters, in the full LHC there will be almost 1800. This article takes a look at what is so special about the power converters for the LHC. The 13 000 Amps power converters with the watercooled cables going to the String 2 feedboxes. The LHC's superconducting magnets will be the pinnacle of high technology. But to work, they'll need the help of high-precision power converters to supply them with extremely stable DC current. Perfection will be the name of the game, with an accuracy of just 1-2 parts per million (ppm) required. LEP, for the sake of comparison, could live with 10-20 ppm. The LHC's power converters will be very different from those of LEP or the SPS since the new accelerator's magnets are mostly superconducting. That means that they require much higher currents at a lower voltage since superconductors have no re...

  4. Low arc drop hybrid mode thermionic converter

    Science.gov (United States)

    Shimada, K.

    1977-01-01

    The hybrid mode operation for the reduction of plasma drops is being investigated. This report discusses the results obtained from two molybdenum emitter converters. One converter had a molybdenum collector and the other a nickel collector. The molybdenum collector converter was operated in a hybrid mode (at an interelectrode distance of 1.7 mm) and produced a minimum barrier index of 1.96 eV at an emitter temperature of 1500 K. The arc drop was calculated to be 0.14 eV, using the published results for a molybdenum collector. On the other hand, the nickel collector converter was operated in a conventional ignited mode (at an interelectrode distance of 0.5 mm) and produced a minimum barrier index of 2.1 eV at an emitter temperature of 1700 K. It is tentatively concluded that a large-gap operation of the hybrid mode converter permits the diffusion of cesium ions to a distance in the order of one millimeter for an effective neutralization of electron space charge. By employing a low work function collector (1.55 eV) in a hybrid mode converter with an arc drop of 0.14 eV, it appears that a barrier index as low as 1.69 eV could be achieved.

  5. Deep mantle forces and the uplift of the Colorado Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Moucha, R; Forte, A M; Rowley, D B; Mitrovica, J X; Simmons, N A; Grand, S P

    2009-06-23

    Since the advent of plate tectonics, it has been speculated that the northern extension of the East Pacific Rise, specifically its mantle source, has been over-ridden by the North American Plate in the last 30 Myrs. Consequently, it has also been postulated that the opening of the Gulf of California, the extension in the Basin and Range province, and the uplift of the Colorado Plateau are the resulting continental expressions of the over-ridden mantle source of the East Pacific Rise. However, only qualitative models based solely on surface observations and heuristic, simplified conceptions of mantle convection have been used in support or against this hypothesis. We introduce a quantitative model of mantle convection that reconstructs the detailed motion of a warm mantle upwelling over the last 30 Myrs and its relative advance towards the interior of the southwestern USA. The onset and evolution of the crustal uplift in the central Basin and Range province and the Colorado Plateau is determined by tracking the topographic swell due to this mantle upwelling through time. We show that (1) the extension and magmatism in the central Basin and Range province between 25 and 10 Ma coincides with the reconstructed past position of this focused upwelling, and (2) the southwestern portion of the Colorado Plateau experienced significant uplift between 10 Ma and 5 Ma that progressed towards the northeastern portion of the plateau. These uplift estimates are consistent with a young, ca. 6 Ma, Grand Canyon model and the recent commencement of mafic magmatism.

  6. Oceanic crust recycling and the formation of lower mantle heterogeneity

    Science.gov (United States)

    van Keken, Peter E.; Ritsema, Jeroen; Haugland, Sam; Goes, Saskia; Kaneshima, Satoshi

    2016-04-01

    The Earth's lower mantle is heterogeneous at multiple scales as demonstrated for example by the degree-2 distribution of LLSVPs seen in global tomography and widespread distribution of small scale heterogeneity as seen in seismic scattering. The origin of this heterogeneity is generally attributed to leftovers from Earth's formation, the recycling of oceanic crust, or a combination thereof. Here we will explore the consequences of long-term oceanic crust extraction and recycling by plate tectonics. We use geodynamical models of mantle convection that simulate plates in an energetically consistent manner. The recycling of oceanic crust over the age of the Earth produces persistent lower mantle heterogeneity while the upper mantle tends to be significantly more homogeneous. We quantitatively compare the predicted heterogeneity to that of the present day Earth by tomographic filtering of the geodynamical models and comparison with S40RTS. We also predict the scattering characteristics from S-P conversions and compare these to global scattering observations. The geophysical comparison shows that lower mantle heterogeneity is likely dominated by long-term oceanic crust recycling. The models also demonstrate reasonable agreement with the geochemically observed spread between HIMU-EM1-DMM in ocean island basalts as well as the long-term gradual depletion of the upper mantle as observed in Lu-Hf systematics.

  7. [Biochemistry and functional characterization of squid mantle meat (Dosidicus gigas)].

    Science.gov (United States)

    Abugoch, L; Guarda, A; María Pérez, L; Isabel Donghi, M

    2000-12-01

    A study for the characterization of frozen giant squid mantle (meat) protein stored at -25 degrees C for 8 month was started. In the present research, the following functional properties were investigate: emulsifying, water holding and gel forming capacities. Optimal conditions for the separation and differentiation of miofibrillar and sarcoplasmatic proteins were also studied. It was found that the unfrozen giant squid mantle meat es capable of emulifying 2.817,4 g of oil/g of protein and holding capacity was 3.64 g of water/g of protein. Related to the gel forming capacity, it was not obtain, probably due to excessive storage of the meat. With regard to miofibrilar protein obtention of the squid mantle meat, it was found that two low ionic strength washings (I = 0.05), the sarcoplasmic proteins were practically eliminated from the protein matrix. The differentiation of miofibrilar and sarcoplasmatic proteins was obtained by PAGE-SDS of the squid mantle meat extracted at two different ionic strength (I = 0.05 and I = 0.5). This work demonstrates that the giant squid mantle protein has a high emulsifying and water holding capacity, and it can be used, as a raw material, for the improvement of sausage products. About the gelling products, more studies will be necessary with fresh squid mantle meat to conclude about this functional property.

  8. Mantle Xenoliths of Cerro Mercedes, Costa Rica, Central America

    Science.gov (United States)

    Lindsay, F. N.; Carr, M. J.; Herzberg, C. T.; Feigenson, M. D.

    2003-12-01

    Mantle peridotite occurs as xenoliths in lavas and bombs at Cerro Mercedes, a Plio-Quaternary potassic alkaline basalt volcano approximately 70 km behind the volcanic front of northern Costa Rica (Tournon and Alvarado, 1997). Mineral exploration led to the first discovery of abundant mantle xenoliths in Central America (Vargas and Alfaro, 1992). The compositions of 71 xenoliths recovered in January 2003 include dunite, harzburgite, lherzolite and olivine websterite. Twenty xenoliths have a diameter of at least 3 cm. The nodules are abundant in basalt outcrops and the rare bombs. In spite of substantial soil development in a rain forest environment, both xenoliths and host lava remain well preserved. Olivine, pyroxenes and spinel are common, plagioclase is present and garnet appears to be absent. There is no obvious shearing or deformation and several pyroxenes are as much as 1 cm in diameter. The mineralogy suggests a relatively shallow upper mantle source, within either the lithosphere or possibly the uppermost asthenosphere. Cerro Mercedes, at latitude 10° 58' N and longitude 82° 21' W, lies along the Rio San Juan, which is locally the border between Nicaragua and Costa Rica, Central America. This location approximately coincides with a boundary between dominantly depleted mantle to the northwest and OIB or Galapagos-like mantle to the southeast. We will use mineralogical data to better define the likely depths and oxidation states of representative nodules and isotopic data to define the type of mantle source.

  9. Seismic scatterers in the mid-lower mantle

    Science.gov (United States)

    Kaneshima, Satoshi

    2016-08-01

    Recent seismological studies have revealed that rocks with significantly different elastic properties are juxtaposed in the mid-lower mantle and often scatter seismic waves efficiently enough to be detected by seismic array analyses. Seismic networks all over the world with various aperture and geometry have been utilized for detecting scattered waves. A large number of objects that act as scatterers in the mid-lower mantle have been mapped out by analyzing several different types of scattered waves, mostly of short period: S-to-P scattering, P-to-P scattering prior to PP waves, P-to-P scattering prior to P‧P‧, P-to-P scattering in P coda waves, and P-to-P scattering prior to PKP. The scatterers have a lesser size that is smaller than the wavelengths (∼10 km), and probably extend several tens of kilometers at least. The mid-mantle scatterers are most likely to represent basaltic rocks that subducted into the lower mantle. Revealing the elastic properties relative to the surrounding rocks and the geometry of the individual scatterers, as well as the global distribution of the scatterers, should shed new light on the style of mantle convection. Relevant observations of mid-lower mantle scatterers are reviewed, and the directions of future progress are suggested.

  10. The benefits of extended plate motion history in mantle circulation models

    Science.gov (United States)

    Webb, Peter; Davies, Huw; Davies, Rhodri; Hochard, Cyril; Stampfli, Gerard

    2010-05-01

    Mantle Circulation Models (MCMs) are mantle convection simulations conditioned with plate motion history. Due to difficulties in reconstructing plate motions beyond ≈ 120 Ma, MCMs often only incorporate the most recent 120 Myr of plate tectonic evolution. We find that such models are strongly influenced by initial conditions. The development of a new series of tectonic reconstructions extending back to the Triassic (230 Ma) and including careful reconstruction of the oceanic parts of the plates (modified from Stampfli and Borel, 2004, Stampfli et al. 2008 and references therein) should prove to be of huge importance to MCMs. In this study we present a comparison between the traditionally used 120 Myr and the latest 230 Myr plate motion histories. We use the three-dimensional spherical mantle convection code TERRA (Bunge et al., 2003) to simulate convection at Earth like vigour. Here we apply the plate motion history as a surface velocity boundary condition to drive the internal convection of an already well-mixed system. The forward models from a chosen starting point to present day yield information on mantle temperature (as well as pressure, velocity and material properties) throughout the volume. One of the ways to validate our results is to compare these with tomographic models. Seismic tomography provides us with a snapshot of Earth's mantle at present day. Assuming that the mantle is driven largely by thermal convection, we can assume that the seismically fast regions are associated with cooler, denser material. The most significant of these can be interpreted as remnants of subducted slabs (Hafkenscheid et al 2006, van der Meer et al. 2010). We convert the temperatures predicted by the MCM to seismic velocities using the latest techniques (e.g. Cobden et al., 2008) and compare the calculated velocities to a range of seismic tomography models (both P and S wave). This way we can examine the validity of the surface velocity boundary condition and identify

  11. Reconstructing the Cenozoic evolution of the mantle: Implications for mantle plume dynamics under the Pacific and Indian plates

    Science.gov (United States)

    Glišović, Petar; Forte, Alessandro M.

    2014-03-01

    The lack of knowledge of the initial thermal state of the mantle in the geological past is an outstanding problem in mantle convection. The resolution of this problem also requires the modelling of 3-D mantle evolution that yields maximum consistency with a wide suite of geophysical constraints. Quantifying the robustness of the reconstructed thermal evolution is another major concern. To solve and estimate the robustness of the time-reversed (inverse) problem of mantle convection, we analyse two different numerical techniques: the quasi-reversible (QRV) and the backward advection (BAD) methods. Our investigation extends over the 65 Myr interval encompassing the Cenozoic era using a pseudo-spectral solution for compressible-flow thermal convection in 3-D spherical geometry. We find that the two dominant issues for solving the inverse problem of mantle convection are the choice of horizontally-averaged temperature (i.e., geotherm) and mechanical surface boundary conditions. We find, in particular, that the inclusion of thermal boundary layers that yield Earth-like heat flux at the top and bottom of the mantle has a critical impact on the reconstruction of mantle evolution. We have developed a new regularisation scheme for the QRV method using a time-dependent regularisation function. This revised implementation of the QRV method delivers time-dependent reconstructions of mantle heterogeneity that reveal: (1) the stability of Pacific and African ‘large low shear velocity provinces’ (LLSVP) over the last 65 Myr; (2) strong upward deflections of the CMB topography at 65 Ma beneath: the North Atlantic, the south-central Pacific, the East Pacific Rise (EPR) and the eastern Antarctica; (3) an anchored deep-mantle plume ascending directly under the EPR (Easter and Pitcairn hotspots) throughout the Cenozoic era; and (4) the appearance of the transient Reunion plume head beneath the western edge of the Deccan Plateau at 65 Ma. Our reconstructions of Cenozoic mantle

  12. Simulation of Multi output Fly back Converter with Integrated Auxiliary Buck Converter with reduced components

    Directory of Open Access Journals (Sweden)

    J.KOMATHI

    2015-04-01

    Full Text Available The fly back converter has been widely used for multi outputs due to the simple structure and low cost in low-power applications. This paper presents a new multi output converter. It consists of a half-bridge inverter with boost converter in primary side and a fly back rectifier that is integrated with an auxiliary buck converter in secondary side. The boost converter is used to generate high voltage dc from Low voltage PV cells. The primary switches control the main output voltage and the secondary synchronous switches control the auxiliary output voltage. The main advantages of the proposed converter are that the transformer size can be reduced due to the less magnetizing offset current, all the power switches including synchronous ones can achieve the zero-voltage switching (ZVS and it has no output cross regulation problems. The circuit is simulated using MATLAB. The performance is verified with simulation results.

  13. Melting curve of the deep mantle applied to properties of early magma ocean and actual core-mantle boundary

    Science.gov (United States)

    Andrault, Denis; Lo Nigro, Giacomo; Bolfan-Casanova, Nathalie; Bouhifd, Mohamed A.; Garbarino, Gaston; Mezouar, Mohamed

    2010-05-01

    Our planet experienced partial melting early in its history as a consequence of energy release due to accretion. Partial mantle melting could still happen today in the lowermost mantle. Occurrence of melting is primordial for the chemical segregation between the different Earth's reservoirs and for the dynamics of the whole planet. Melting of iron-alloys is relatively easy to achieve, but the silicated mantle happens to be more refractory. We investigated experimentally melting properties of two starting material, forsterite and chondritic-mantle, at pressures ranging from 25 to 140 GPa, using laser-heated diamond anvil cell coupled with synchrotron radiation. We show that partial melting in the lowermost mantle, as suggested by seismology on the basis of the ultra-low velocity zones (ULVZ), requires temperatures above 4200 K at the core-mantle boundary. At low pressures, our curve plots significantly lower than previous reports. Compared to recent estimates of mantle geotherm, while this temperature remains possible if the Earth's core is very hot, it is more likely that ULVZs correspond to high concentration of incompatible elements driven down to the D"-layer by subducting slabs or extracted out from the outer core. When our chondritic melting curve is coupled with recent isentropic temperature profiles for a magma ocean, we obtain a correlation between magma ocean depth and the potential temperature (Tp) at its surface; an ocean depth of 1000 km (equivalent to ~40 GPa) corresponds to Tp=2000 K, which happens to be significantly hotter than the estimated surface temperature of a sustained magma ocean. It emphasizes the importance of a lid at the magma ocean surface at an epoch as early as that of core-mantle segregation.

  14. Trace element mass balance in hydrous adiabatic mantle melting: The Hydrous Adiabatic Mantle Melting Simulator version 1 (HAMMS1)

    Science.gov (United States)

    Kimura, Jun-Ichi; Kawabata, Hiroshi

    2014-06-01

    numerical mass balance calculation model for the adiabatic melting of a dry to hydrous peridotite has been programmed in order to simulate the trace element compositions of basalts from mid-ocean ridges, back-arc basins, ocean islands, and large igneous provinces. The Excel spreadsheet-based calculator, Hydrous Adiabatic Mantle Melting Simulator version 1 (HAMMS1) uses (1) a thermodynamic model of fractional adiabatic melting of mantle peridotite, with (2) the parameterized experimental melting relationships of primitive to depleted mantle sources in terms of pressure, temperature, water content, and degree of partial melting. The trace element composition of the model basalt is calculated from the accumulated incremental melts within the adiabatic melting regime, with consideration for source depletion. The mineralogic mode in the primitive to depleted source mantle in adiabat is calculated using parameterized experimental results. Partition coefficients of the trace elements of mantle minerals are parameterized to melt temperature mostly from a lattice strain model and are tested using the latest compilations of experimental results. The parameters that control the composition of trace elements in the model are as follows: (1) mantle potential temperature, (2) water content in the source mantle, (3) depth of termination of adiabatic melting, and (4) source mantle depletion. HAMMS1 enables us to obtain the above controlling parameters using Monte Carlo fitting calculations and by comparing the calculated basalt compositions to primary basalt compositions. Additionally, HAMMS1 compares melting parameters with a major element model, which uses petrogenetic grids formulated from experimental results, thus providing better constraints on the source conditions.

  15. High-pressure phase of brucite stable at Earth's mantle transition zone and lower mantle conditions

    Science.gov (United States)

    Hermann, Andreas; Mookherjee, Mainak

    2016-12-01

    We investigate the high-pressure phase diagram of the hydrous mineral brucite, Mg(OH)2, using structure search algorithms and ab initio simulations. We predict a high-pressure phase stable at pressure and temperature conditions found in cold subducting slabs in Earth’s mantle transition zone and lower mantle. This prediction implies that brucite can play a much more important role in water transport and storage in Earth’s interior than hitherto thought. The predicted high-pressure phase, stable in calculations between 20 and 35 GPa and up to 800 K, features MgO6 octahedral units arranged in the anatase–TiO2 structure. Our findings suggest that brucite will transform from a layered to a compact 3D network structure before eventual decomposition into periclase and ice. We show that the high-pressure phase has unique spectroscopic fingerprints that should allow for straightforward detection in experiments. The phase also has distinct elastic properties that might make its direct detection in the deep Earth possible with geophysical methods.

  16. Magnesium stable isotope composition of Earth's upper mantle

    Science.gov (United States)

    Handler, Monica R.; Baker, Joel A.; Schiller, Martin; Bennett, Vickie C.; Yaxley, Gregory M.

    2009-05-01

    The mantle is Earth's largest reservoir of Mg containing > 99% of Earth's Mg inventory. However, no consensus exists on the stable Mg isotope composition of the Earth's mantle or how variable it is and, in particular, whether the mantle has the same stable Mg isotope composition as chondrite meteorites. We have determined the Mg isotope composition of olivine from 22 mantle peridotites from eastern Australia, west Antarctica, Jordan, Yemen and southwest Greenland by pseudo-high-resolution MC-ICP-MS on Mg purified to > 99%. The samples include fertile lherzolites, depleted harzburgites and dunites, cryptically metasomatised ('dry') peridotites and modally metasomatised apatite ± amphibole-bearing harzburgites and wehrlites. Olivine from these samples of early Archaean through to Permian lithospheric mantle have δ25Mg DSM-3 = - 0.22 to - 0.08‰. These data indicate the bulk upper mantle as represented by peridotite olivine is homogeneous within current analytical uncertainties (external reproducibility ≤ ± 0.07‰ [2 sd]). We find no systematic δ25Mg variations with location, lithospheric age, peridotite fertility, or degree or nature of mantle metasomatism. Although pyroxene may have slightly heavier δ25Mg than coexisting olivine, any fractionation between mantle pyroxene and olivine is also within current analytical uncertainties with a mean Δ25Mg pyr-ol = +0.06 ± 0.10‰ (2 sd; n = 5). Our average mantle olivine δ25Mg DSM-3 = - 0.14 ± 0.07‰ and δ26Mg DSM-3 = - 0.27 ± 0.14‰ (2 sd) are indistinguishable from the average of data previously reported for terrestrial basalts, confirming that basalts have stable Mg isotope compositions representative of the mantle. Olivine from five pallasite meteorites have δ25Mg DSM-3 = - 0.16 to - 0.11‰ that are identical to terrestrial olivine and indistinguishable from the average δ25Mg previously reported for chondrites. These data provide no evidence for measurable heterogeneity in the stable Mg isotope

  17. Subduction History and the Evolution of Earth's Lower Mantle

    Science.gov (United States)

    Bull, Abigail; Shephard, Grace; Torsvik, Trond

    2016-04-01

    Understanding the complex structure, dynamics and evolution of the deep mantle is a fundamental goal in solid Earth geophysics. Close to the core-mantle boundary, seismic images reveal a mantle characterised by (1) higher than average shear wave speeds beneath Asia and encircling the Pacific, consistent with sub ducting lithosphere beneath regions of ancient subduction, and (2) large regions of anomalously low seismic wavespeeds beneath Africa and the Central Pacific. The anomalously slow areas are often referred to as Large Low Shear Velocity Provinces (LLSVPs) due to the reduced velocity of seismic waves passing through them. The origin, composition and long-term evolution of the LLSVPs remain enigmatic. Geochemical inferences of multiple chemical reservoirs at depth, strong seismic contrasts, increased density, and an anticorrelation of shear wave velocity to bulk sound velocity in the anomalous regions imply that heterogeneities in both temperature and composition may be required to explain the seismic observations. Consequently, heterogeneous mantle models place the anomalies into the context of thermochemical piles, characterised by an anomalous component whose intrinsic density is a few percent higher relative to that of the surrounding mantle. Several hypotheses have arisen to explain the LLSVPs in the context of large-scale mantle convection. One end member scenario suggests that the LLSVPs are relatively mobile features over short timescales and thus are strongly affected by supercontinent cycles and Earth's plate motion history. In this scenario, the African LLSVP formed as a result of return flow in the mantle due to circum-Pangean subduction (~240 Ma), contrasting a much older Pacific LLSVP, which may be linked to the Rodinia supercontinent and is implied to have remained largely unchanged since Rodinian breakup (~750-700 Ma). This propounds that Earth's plate motion history plays a controlling role in LLSVP development, suggesting that the location

  18. Comparing the nature of the western and eastern Azores mantle

    Science.gov (United States)

    Genske, Felix S.; Beier, Christoph; Stracke, Andreas; Turner, Simon P.; Pearson, Norman J.; Hauff, Folkmar; Schaefer, Bruce F.; Haase, Karsten M.

    2016-01-01

    The Azores islands in the central North-Atlantic originate from a regional melting anomaly, probably created by melting hot, unusually hydrous and geochemically enriched mantle. Here, we present Hf, Pb and Os isotopic data in geochemically well-characterised primitive lavas from the islands Flores and Corvo that are located west of the Mid-Atlantic Ridge (MAR), as well as submarine samples from a subsided island west of Flores and from Deep Sea Drilling Project (DSDP) holes drilled in the western part of the Azores platform and beyond. These are compared to existing data from the Azores islands east of the MAR. The geodynamic origin of the two islands west of the ridge axis and furthest from the inferred plume centre in the central part of the plateau is enigmatic. The new data constrain the source compositions of the Flores and Corvo lavas and show that the western and eastern Azores mantle is isotopically similar, with the exception of an enriched component found exclusively on eastern São Miguel. Trace element ratios involving high field strength elements (HFSE) are distinctly different in the western islands (e.g. twofold higher Nb/Zr) compared to any of the islands east of the MAR. A similar signature is observed in MAR basalts to the south of the Azores platform and inferred to originate from (auto-) metasomatic enrichment of the sub-ridge mantle (Gale et al., 2011, 2013). In a similar fashion, low degree melts from an enriched source component may metasomatise the ambient plume mantle underneath the western Azores islands. Melting such a modified plume mantle can explain the chemical differences between lavas from the western and eastern Azores islands without the need for additional plume components. Recent re-enrichment and intra melting column modification of the upwelling mantle can cause local to regional scale geochemical differences in mantle-derived melts.

  19. Sulfur in Earth's Mantle and Its Behavior During Core Formation

    Science.gov (United States)

    Chabot, Nancy L.; Righter,Kevin

    2006-01-01

    The density of Earth's outer core requires that about 5-10% of the outer core be composed of elements lighter than Fe-Ni; proposed choices for the "light element" component of Earth's core include H, C, O, Si, S, and combinations of these elements [e.g. 1]. Though samples of Earth's core are not available, mantle samples contain elemental signatures left behind from the formation of Earth's core. The abundances of siderophile (metal-loving) elements in Earth's mantle have been used to gain insight into the early accretion and differentiation history of Earth, the process by which the core and mantle formed, and the composition of the core [e.g. 2-4]. Similarly, the abundance of potential light elements in Earth's mantle could also provide constraints on Earth's evolution and core composition. The S abundance in Earth's mantle is 250 ( 50) ppm [5]. It has been suggested that 250 ppm S is too high to be due to equilibrium core formation in a high pressure, high temperature magma ocean on early Earth and that the addition of S to the mantle from the subsequent accretion of a late veneer is consequently required [6]. However, this earlier work of Li and Agee [6] did not parameterize the metalsilicate partitioning behavior of S as a function of thermodynamic variables, limiting the different pressure and temperature conditions during core formation that could be explored. Here, the question of explaining the mantle abundance of S is revisited, through parameterizing existing metal-silicate partitioning data for S and applying the parameterization to core formation in Earth.

  20. Ensemble data assimilation for the reconstruction of mantle circulation

    Science.gov (United States)

    Bocher, Marie; Coltice, Nicolas; Fournier, Alexandre; Tackley, Paul

    2016-04-01

    The surface tectonics of the Earth is the result of mantle dynamics. This link between internal and surface dynamics can be used to reconstruct the evolution of mantle circulation. This is classically done by imposing plate tectonics reconstructions as boundary conditions on numerical models of mantle convection. However, this technique does not account for uncertainties in plate tectonics reconstructions and does not allow any dynamical feedback of mantle dynamics on surface tectonics to develop. Mantle convection models are now able to produce surface tectonics comparable to that of the Earth to first order. We capitalize on these convection models to propose a more consistent integration of plate tectonics reconstructions into mantle convection models. For this purpose, we use the ensemble Kalman filter. This method has been developed and successfully applied to meteorology, oceanography and even more recently outer core dynamics. It consists in integrating sequentially a time series of data into a numerical model, starting from an ensemble of possible initial states. The initial ensemble of states is designed to represent an approximation of the probability density function (pdf) of the a priori state of the system. Whenever new observations are available, each member of the ensemble states is corrected considering both the approximated pdf of the state, and the pdf of the new data. Between two observation times, each ensemble member evolution is computed independently, using the convection model. This technique provides at each time an approximation of the pdf of the state of the system, in the form of a finite ensemble of states. We perform synthetic experiments to assess the efficiency of this method for the reconstruction of mantle circulation.

  1. Iron carbonates in the Earth's lower mantle: reality or imagination?

    Science.gov (United States)

    Cerantola, V.; McCammon, C. A.; Merlini, M.; Bykova, E.; Kupenko, I.; Ismailova, L.; Chumakov, A. I.; Kantor, I.; Dubrovinsky, L. S.; Prescher, C.

    2015-12-01

    Carbonates play a fundamental role in the recycling of carbon inside our planet due to their presence in oceanic slabs that sink through the Earth's interior. Through this process, iron carbonates are potential stable carbon-bearing minerals in the deep mantle in part due to spin crossover of ferrous iron. Our goal is to identify which minerals may be the dominant carriers of carbon into the deep mantle at the relevant conditions of fO2, P and T. All experiments were performed using synthetic FeCO3 and MgFeCO3 single crystals in laser heated diamond anvil cells up to 100 GPa and 3000 K in order to simulate the conditions prevailing in the Earth's lower mantle. Transformation and decomposition products of the original carbonates were characterized at different synchrotron facilities by means of single-crystal XRD, synchrotron Mössbauer source spectroscopy and XANES techniques. At deep lower mantle conditions, we observed the transformation of FeCO3 to two new HP-carbonate structures, monoclinic Fe22+Fe23+C4O13 and trigonal Fe43+(CO4)3, both characterized by the presence of CO4 tetrahedra with different degrees of polymerization. At shallower depths in the lower mantle where temperatures are lower following the geotherm, Fe-carbonates decompose to different Fe-oxides instead of new HP-carbonates. However, at slab temperatures several hundred degrees lower than the surrounding mantle, carbonates could be stabilized until reaching conditions that trigger their transformation to HP-structures. We postulate that Fe-rich carbonates could exist in regions down to the core-mantle boundary in the proximity of subducting slabs, i.e., a "cold" environment with relatively high fO2.

  2. Materials technology for Stirling space power converters

    Science.gov (United States)

    Baggenstoss, William; Mittendorf, Donald

    1992-01-01

    This program was conducted in support of the NASA LeRC development of the Stirling power converter (SPC) for space power applications. The objectives of this contract were: (1) to perform a technology review and analyses to support the evaluation of materials issues for the SPC; (2) to evaluate liquid metal compatibility issues of the SPC; (3) to evaluate and define a transient liquid phase diffusion bonding (TLPDB) process for the SPC joints to the Udimet 720 heater head; and (4) to evaluate alternative (to the TLPDB) joining techniques. In the technology review, several aspects of the current Stirling design were examined including the power converter assembly process, materials joining, gas bearings, and heat exchangers. The supporting analyses included GLIMPS power converter simulation in support of the materials studies, and system level analysis in support of the technology review. The liquid metal compatibility study evaluated process parameters for use in the Stirling power converter. The alternative joining techniques study looked at the applicability of various joining techniques to the Stirling power converter requirements.

  3. Efficiency of Thermionic and Thermoelectric Converters

    Science.gov (United States)

    Gerstenmaier, York Christian; Wachutka, Gerhard

    2007-02-01

    Thermoelectric and thermionic converters — also in micro- and nano-meter design — are considered for power generation and cooling applications. The potential of thermionic vacuum gap converters is investigated precisely by a new advanced theory with inclusion of backward currents from the 2nd electrode, losses due to thermal radiation and ohmic resistance in the electrodes, tunneling through the gap, image forces, and space charge effects. The efficiency of nano-meter gap thermionic converters is by far higher than for thermoelectric devices (including nano-structured superlattices) for operating temperatures above 800°K, however, there is no chance of realization with today's technology. For a vacuum gap width of about 1 μm the performance is higher than for hypothetical bulk- thermoelectric generators (TEGs) with ZT = 1 for T > 1000°K and also higher than for hypothetical nano-structured superlattices (ZT = 2.4) for T > 1200°K. A thermionic converter with gap width of 5μm has lower performance than a TEG with ZT = 1, however, also operates at T > 1200°K. Reasonable performance of thermionic converters at T ⩽ 500°K necessitates materials with workfunctions ⩽ 0.5 eV.

  4. Understanding delta-sigma data converters

    CERN Document Server

    Pavan, Shanti; Temes, Gabor C

    2017-01-01

    This new edition introduces novel analysis and design techniques for delta-sigma (ΔΣ) converters in physical and conceptual terms, and includes new chapters that explore developments in the field over the last decade. This book explains the principles and operation of delta-sigma analog-to-digital converters (ADCs) in physical and conceptual terms in accordance with the most recent developments in the field. The interest of ΔΣ converter designers has shifted significantly over the past decade, due to many new applications for data converters at the far ends of the frequency spectrum. Continuous-time delta-sigma A/D converters with GHz clocks, of both lowpass and bandpass types, are required for wireless applications. At the other extreme, multiplexed ADCs with very narrow (sometimes 10 Hz wide) signal bandwidths, but very high accuracy are needed in the interfaces of biomedical and environmental sensors. To reflect the changing eeds of designers, the second edition includes significant new material on bo...

  5. Analysis of the flow structure and heat transfer in a vertical mantle heat exchanger

    DEFF Research Database (Denmark)

    Knudsen, Søren; Morrison, GL; Behnia, M

    2005-01-01

    initially mixed and initially stratified inner tank and mantle. The analysis of the heat transfer showed that the flow in the mantle near the inlet is mixed convection flow and that the heat transfer is dependent on the mantle inlet temperature relative to the core tank temperature at the mantle level. (C......The flow structure inside the inner tank and inside the mantle of a vertical mantle heat exchanger was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the inner tank and in the mantle were measured using a Particle Image...... Velocimetry (PIV) system. A Computational Fluid Dynamics (CFD) model of the vertical mantle heat exchanger was also developed for a detailed evaluation of the heat flux at the mantle wall and at the tank wall. The flow structure was evaluated for both high and low temperature incoming flows and for both...

  6. A linear temperature-to-frequency converter

    DEFF Research Database (Denmark)

    Løvborg, Leif

    1965-01-01

    The possibility of converting temperature into a frequency signal by means of a thermistor which is part of the frequency-determining network of an RC oscillator is investigated. It is shown that a temperature - frequency characteristic which has a point of inflection may be realized, and that th......The possibility of converting temperature into a frequency signal by means of a thermistor which is part of the frequency-determining network of an RC oscillator is investigated. It is shown that a temperature - frequency characteristic which has a point of inflection may be realized......, and that the maximum value of the temperature-frequency coefficient beta in this point is-1/3 alpha, where a is the temperature coefficient of the thermistor at the corresponding temperature. Curves showing the range in which the converter is expected to be linear to within plusmn0.1 degC are given. A laboratory...

  7. Converters for Distributed Power Generation Systems

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Yang, Yongheng

    2015-01-01

    Power electronics technology has become the enabling technology for the integration of distributed power generation systems (DPGS) such as offshore wind turbine power systems and commercial photovoltaic power plants. Depending on the applications, a vast array of DPGS-based power converter...... presents an overview of the power converters for the DPGS, mainly based on wind turbine systems and photovoltaic systems, covering a wide range of applications. Moreover, the modulation schemes and interfacing power filters for the power converters are also exemplified. Finally, the general control...... topologies has been developed and more are coming into the market in order to achieve an efficient and reliable power conversion from the renewables. In addition, stringent demands from both the distribution system operators and the consumers have been imposed on the renewable-based DPGS. This article...

  8. CMOS Integrated Capacitive DC-DC Converters

    CERN Document Server

    Van Breussegem, Tom

    2013-01-01

    This book provides a detailed analysis of all aspects of capacitive DC-DC converter design: topology selection, control loop design and noise mitigation. Readers will benefit from the authors’ systematic overview that starts from the ground up, in-depth circuit analysis and a thorough review of recently proposed techniques and design methodologies.  Not only design techniques are discussed, but also implementation in CMOS is shown, by pinpointing the technological opportunities of CMOS and demonstrating the implementation based on four state-of-the-art prototypes.  Provides a detailed analysis of all aspects of capacitive DC-DC converter design;  Analyzes the potential of this type of DC-DC converter and introduces a number of techniques to unleash their full potential; Combines system theory with practical implementation techniques; Includes unique analysis of CMOS technology for this application; Provides in-depth analysis of four fabricated prototypes.

  9. External ionization mechanisms for advanced thermionic converters

    Science.gov (United States)

    Hatziprokopiou, M. E.

    Ion generation and recombination mechanisms in the cesium plasma were investigated as they pertain to the advanced mode thermionic energy converters. The changes in plasma density and temperature within the converter were studied under the influence of several promising auxiliary ionization candidate sources. Three novel approaches of external cesium ion generation were investigated in some detail, namely vibrationally excited N2 as an energy source of ionization of Cs ions in a DC discharge, microwave power as a means of resonant sustenance of the cesium plasma, and ion generation in a pulse N2-Cs mixture. The experimental data obtained and discussed in this work show that all three techniques--i.e. the non-LTE high-voltage pulsing, the energy transfer from vibrationally excited diatomic gases, and the external pumping with a microwave power--have considerable promise as schemes in auxiliary ion generation applicable to the advanced thermionic energy converter.

  10. Data Converter for Multistandard Mobile Phones

    DEFF Research Database (Denmark)

    Yurttas, Aziz; Bruun, Erik; Jensen, Rasmus Glarborg

    2004-01-01

    This paper describes an analog to digital converter (ADC) for mobile communication systems using a direct down conversion architecture. The ADC can be programmed to meet the requirements of different communication standards, including GSM (Global System for Mobile communication) and WCDMA (Wideband...... Code Division Multiple Access). The ADC is realized with a pipeline ADC architecture for WCDMA and a Sigma-Delta architecture for GSM. In order to have an optimized area and power consumption, the basic building blocks (opamps) of the converters are shared between the two converter architectures....... The entire ADC consumes about 5.5 mW and occupies an active area of about 0.36 mm(2). A test circuit has been developed and fabricated and measurements show that both the required programmability and the required performance can be obtained using the proposed configurations....

  11. Power system applications for PASC converter systems

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, M.K. [Pacific Northwest Lab., Richland, WA (United States); Johnson, R.M. [Montana State Univ., Bozeman, MT (United States)

    1994-04-01

    This paper shows, using computer EMTP simulations, some preliminary results of applying pulse amplitude synthesis and control (PASC) technology to single-source level voltage converter system. The method can be applied to any single terminal pair source with appropriate modifications in power extraction interface and computer control program to match source and load impedance characteristics. The PASC realization as discussed here employs banks of transformers, one bank per phase, in which the primaries are connected in parallel through a switch matrix to the dc source. Two opposite polarity primaries per transformer are pulsed alternatively in time to produce an oscillatory sinusoidal output waveform. PASC conversion system capabilities to produce both leading and lagging power factor power output in single-phase and three-phase {Delta} or Y configurations are illustrated. EMTP simulations are used to demonstrate the converter capabilities. Also included are discussions regarding harmonics and potential control strategies to adapt the converter to an application or to minimize harmonics.

  12. Self-oscillating resonant power converter

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to resonant power converters and inverters comprising a self-oscillating feedback loop coupled from a switch output to a control input of a switching network comprising one or more semiconductor switches. The self-oscillating feedback loop sets a switching frequency...... of the power converter and comprises a first intrinsic switch capacitance coupled between a switch output and a control input of the switching network and a first inductor. The first inductor is coupled in-between a first bias voltage source and the control input of the switching network and has...... a substantially fixed inductance. The first bias voltage source is configured to generate an adjustable bias voltage applied to the first inductor. The output voltage of the power converter is controlled in a flexible and rapid manner by controlling the adjustable bias voltage....

  13. High Efficiency Reversible Fuel Cell Power Converter

    DEFF Research Database (Denmark)

    Pittini, Riccardo

    The large scale integration of renewable energy sources requires suitable energy storage systems to balance energy production and demand in the electrical grid. Bidirectional fuel cells are an attractive technology for energy storage systems due to the high energy density of fuel. Compared...... entitled "High Efficiency Reversible Fuel Cell Power Converter" and it presents the design of a high efficiency dc-dc converter developed and optimized for bidirectional fuel cell applications. First, a brief overview of fuel cell and energy storage technologies is presented. Different system topologies...... to traditional unidirectional fuel cell, bidirectional fuel cells have increased operating voltage and current ranges. These characteristics increase the stresses on dc-dc and dc-ac converters in the electrical system, which require proper design and advanced optimization. This work is part of the PhD project...

  14. Contamination of the Convecting Mantle in Eastern Tethyan 'Subduction Factories'

    Science.gov (United States)

    Flower, M. F.; Nguyen, T. H.

    2003-04-01

    As subduction gives way to collision at the end of a Wilson Cycle the associated magmatic activity becomes increasingly enriched in potassium and other large-ion lithophile elements. This is usually attributed to the addition of continental crust-derived material to the convecting mantle wedge. Corresponding depletions in high-field strength elements (Ti and Nb) are more commonly explained in terms of accessory phase buffering or protracted reaction of melts with mantle wallrock. It is increasingly apparent that mantle wedge magmatic sources range from 'fertile' (lherzolitic) to 'refractory' (harzburgitic) although the extent to which this corresponds to the LILE and HFSE variation is unclear. Mantle wedge mass balances clearly hold clues to enrichment-depletion histories of the convecting asthenosphere with respect to both the overriding and subducting plates. With a view to better understanding these effects we have used the MELTS algorithm to calculate hypothetical partial melt compositions as a function of source fertility and H2O content, in the pressure range, 0-1.0 GPa as a basis comparison for natural partial melts. Primitive magmas characterizing the Mariana (western Pacific) and Sunda-Banda (Indonesia) arcs, and the northeastern syntaxis of the India-Asia collision suture (Yunnan) appear to resemble calculated equilibrium melts of refractory (basalt-depleted) peridotite, variably enriched in lithophile and light rare earth elements. These comparisons lead to three observations. 1) HFSE and Fe abundances in primitive MORB, calcalkaline, and boninite magmas, and their respective high-potassium variants are consistent with those implied by phase equilibria associated with partial melting and fractionation, suggesting accessory phases, wall-rock reaction, and slab contamination are probably not important as causes of HFSE depletions. 2) Magmatic sources at convergent and colliding margins are typically refractory (basalt-depleted) compared to those yielding

  15. Anatomy of mantle plumes: hot heads and cold stems

    Science.gov (United States)

    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

  16. Isotopic constraints of mantle derived carbonatitic melts from Calatrava, Spain

    Science.gov (United States)

    Humphreys, E. R.; Bailey, K.; Hawkesworth, C. J.; Wall, F.; Avanzinelli, R.

    2010-12-01

    Carbonatite volcanism is typically associated both spatially and temporally with alkaline, ultramafic volcanism (Woolley & Church, 2005). Recent discoveries in Calatrava, Spain illustrate the activity of carbonatite in the source melts of leucitite volcanism. Melilitite pyroclastic lapilli tuffs also show a clear association with volcanic carbonate. Carbonatitic activity has been shown to initiate at depths greater than 100km (Humphreys et al., 2010) despite a maximum estimate of lithospheric thickness of 80km. The presence of aragonite and abundant mantle xenoliths in many deposits are clear indication of the rapid emplacement rates of such magmas. Carbonatitic activity in the source of the leucitite melts is indicated by carbonate inclusions within olivine xenocrysts and the presence of occasional carbonatite lenses. The composition of lead and strontium isotope ratios in the bulk rock, and spatially resolved analysis of carbonate from the groundmass and from inclusions demonstrates a genetic affinity between the inclusions and the related bulk rock composition. Lead and strontium isotopic analysis suggest that such melts do not represent the composition of convecting asthenospheric mantle. 87Sr/86Sr (0.7055-0.7068) values are higher than those of MORB and most OIB. Lead isotope ratios show a trend displaced to higher 207Pb/204Pb relative to MORB and OIB. Carbonate inclusions have less radiogenic lead values than the more radiogenic bulk rocks. Our data indicate that carbonatitic activity in the mantle is intrinsic in the generation of the leucitite lava. However, petrographic and isotopic evidence suggest a complex melt history. Olivine xenocrysts are not in equilibrium with the host leucitite, despite inclusions within olivine showing an isotopic affinity to the bulk rock. We suggest that in this example, alkaline magmatism was induced by the presence of CO2 in the mantle source. Isotopic evidence shows that the mantle producing such melts was not

  17. Mapping small-scale mantle heterogeneities using seismic arrays

    Science.gov (United States)

    Bentham, H. L.; Rost, S.

    2012-12-01

    In recent years array seismology has been used extensively to detect and locate the small scale (~10 km) structure of the Earth. In the mantle, small scale structure likely represents chemical heterogeneity and is essential in our understanding of mechanical mixing processes within mantle convection. As subducted crust is chemically distinct from the background mantle, imaging the remains of the crust provides a tracer for convectional flow. Evidence for heterogeneities has been found in the lower mantle in previous seismology studies but the arrivals associated with such heterogeneities are difficult to detect in the seismic data as they are typically low amplitude and are often masked by a multitude of larger amplitude arrivals. In this study we find global and regional seismic heterogeneities in the mantle by processing teleseismic earthquake data through array seismology methods. We find global patterns of heterogeneity using a stacking approach. To locate regional heterogeneities, we target the "quiet" window prior to the PP arrival for earthquakes with epicentral distances of 90-110°. Within this time window, we enhance the weak coherent energy that arrives off great circle path by calculating the observed directivity (slowness and backazimuth) and using a semblance weighted beampower measure. We use the directivity and travel times of suitable precursors to back-trace the energy to the origin of P-to-P reflections, using a 1D raytracer. Most of the P-to-P reflections that we observe have reflection origins in the upper/mid mantle. Beneath the western Pacific subduction zones, such reflections show a good correlation with subduction zone contours that are derived from subduction zone seismicity, and correlate well with tomography gradients of 0.01-0.5% per degree, interpreted as the edge of the slab. Deep mantle reflections (>600 km) are also observed to depths of ~1900 km. The locations of these heterogeneities are combined with previous seismological

  18. Single phase AC-DC power factor corrected converter with high frequency isolation using buck converter

    Directory of Open Access Journals (Sweden)

    R. Ramesh,

    2014-03-01

    Full Text Available Single phase ac-dc converters having high frequency isolation are implemented in buck, boost, buck-boost configuration with improving the power quality in terms of reducing the harmonics of input current. The paperpropose the circuit configuration, control mechanism, and simulation result for the single phase ac-dc converter.

  19. Dual Converter Fed Open-End Transformer Topology with Parallel Converters and Integrated Magnetics

    DEFF Research Database (Denmark)

    Gohil, Ghanshyamsinh Vijaysinh; Bede, Lorand; Teodorescu, Remus

    2016-01-01

    A converter system for high power applications, connected to a medium-voltage network using a stepup transformer, is presented in this paper. The converterside winding of the transformer is configured as an openend and both the ends of the windings are fed from two different converter groups. Each...

  20. Si Bule Masuk Islam: Western Converts to Islam in Indonesia - more than just Converts of Convenience?

    Directory of Open Access Journals (Sweden)

    M. A. Kevin Brice

    2015-04-01

    Full Text Available In discussing converts to Islam, two different types of converts are often identified based on the reason for conversion: converts of convenience and converts of conviction. The common view is that in most (if not all cases, conversion to Islam in Indonesia by Westerners is about facilitating marriage and so the converts should be classified as converts of convenience. Evidence of the commonality of this view is considered by reference to advice offered to Westerners about marriage to Indonesians on specialist web sites and examples of coverage of the topic in Indonesian social media. By considering a number of brief case studies, the common view is challenged. The binary of “convert of convenience” versus “convert of conviction” is revisited to suggest that individuals may move between the types over a period of time. Finally the paper will consider whether there is anything about Islam in Indonesia which contributes to the phenomenon of “transnational” conversion by Westerners in Indonesia.DOI: 10.15408/sdi.v22i1.1386

  1. Nd-isotopes in selected mantle-derived rocks and minerals and their implications for mantle evolution

    Science.gov (United States)

    Basu, A.R.; Tatsumoto, M.

    1980-01-01

    The Sm-Nd systematics in a variety of mantle-derived samples including kimberlites, alnoite, carbonatite, pyroxene and amphibole inclusions in alkali basalts and xenolithic eclogites, granulites and a pyroxene megacryst in kimberlites are reported. The additional data on kimberlites strengthen our earlier conclusion that kimberlites are derived from a relatively undifferentiated chondritic mantle source. This conclusion is based on the observation that the e{open}Nd values of most of the kimberlites are near zero. In contrast with the kimberlites, their garnet lherzolite inclusions show both time-averaged Nd enrichment and depletion with respect to Sm. Separated clinopyroxenes in eclogite xenoliths from the Roberts Victor kimberlite pipe show both positive and negative e{open}Nd values suggesting different genetic history. A whole rock lower crustal scapolite granulite xenolith from the Matsoku kimberlite pipe shows a negative e{open}Nd value of -4.2, possibly representative of the base of the crust in Lesotho. It appears that all inclusions, mafic and ultramafic, in kimberlites are unrelated to their kimberlite host. The above data and additional Sm-Nd data on xenoliths in alkali basalts, alpine peridotite and alnoite-carbonatites are used to construct a model for the upper 200 km of the earth's mantle - both oceanic and continental. The essential feature of this model is the increasing degree of fertility of the mantle with depth. The kimberlite's source at depths below 200 km in the subcontinental mantle is the most primitive in this model, and this primitive layer is also extended to the suboceanic mantle. However, it is clear from the Nd-isotopic data in the xenoliths of the continental kimberlites that above 200 km the continental mantle is distinctly different from their suboceanic counterpart. ?? 1980 Springer-Verlag.

  2. Tomography of core-mantle boundary and lowermost mantle coupled by geodynamics: joint models of shear and compressional velocity

    Directory of Open Access Journals (Sweden)

    Gaia Soldati

    2015-03-01

    Full Text Available We conduct joint tomographic inversions of P and S travel time observations to obtain models of delta v_P  and delta v_S in the entire mantle. We adopt a recently published method which takes into account the geodynamic coupling between mantle heterogeneity and core-mantle boundary (CMB topography by viscous flow, where sensitivity of the seismic travel times to the CMB is accounted for implicitly in the inversion (i.e. the CMB topography is not explicitly inverted for. The seismic maps of the Earth's mantle and CMB topography that we derive can explain the inverted seismic data while being physically consistent with each other. The approach involved scaling P-wave velocity (more sensitive to the CMB to density anomalies, in the assumption that mantle heterogeneity has a purely thermal origin, so that velocity and density heterogeneity are proportional to one another. On the other hand, it has sometimes been suggested that S-wave velocity might be more directly sensitive to temperature, while P heterogeneity is more strongly influenced by chemical composition. In the present study, we use only S-, and not P-velocity, to estimate density heterogeneity through linear scaling, and hence the sensitivity of core-reflected P phases to mantle structure. Regardless of whether density is more closely related to P- or S-velocity, we think it is worthwhile to explore both scaling approaches in our efforts to explain seismic data. The similarity of the results presented in this study to those obtained by scaling P-velocity to density suggests that compositional anomaly has a limited impact on viscous flow in the deep mantle.

  3. Blending geological observations and convection models to reconstruct mantle dynamics

    Science.gov (United States)

    Coltice, Nicolas; Bocher, Marie; Fournier, Alexandre; Tackley, Paul

    2015-04-01

    Knowledge of the state of the Earth mantle and its temporal evolution is fundamental to a variety of disciplines in Earth Sciences, from the internal dynamics to its many expressions in the geological record (postglacial rebound, sea level change, ore deposit, tectonics or geomagnetic reversals). Mantle convection theory is the centerpiece to unravel the present and past state of the mantle. For the past 40 years considerable efforts have been made to improve the quality of numerical models of mantle convection. However, they are still sparsely used to estimate the convective history of the solid Earth, in comparison to ocean or atmospheric models for weather and climate prediction. The main shortcoming is their inability to successfully produce Earth-like seafloor spreading and continental drift self-consistently. Recent convection models have begun to successfully predict these processes. Such breakthrough opens the opportunity to retrieve the recent dynamics of the Earth's mantle by blending convection models together with advanced geological datasets. A proof of concept will be presented, consisting in a synthetic test based on a sequential data assimilation methodology.

  4. Mantle decarbonation and Archean high-Mg magmas

    Science.gov (United States)

    Edwards, Garth R.

    1992-10-01

    Magnesium-rich mane to ultramafic extrusions were most common in the Archean and pose interesting petrological problems. The high Mg content of komatiites (>18 wt%, for example, is usually interpreted as indicating an origin at higher temperatures than exist in mantle melting zones in the modern Earth. Current contrasting models for the origin of komatiites in the mantle require either high degrees of melting or lower degrees of melting at great depth. A potential complementary mechanism for Mg enrichment in magmas involves the melting of magnesite-bearing garnet Iherxolite. In this model, the ascending primary mafic or ultramafic magma is enriched in MgO by the loss of some off the CO2 to the adjacent mantle at pressures of ˜2.2 GPa, where the magma becomes saturated with CO2. To generate komatiite in this way from a picritelike parent, for example, requires that the primary magma lose some of its major and trace element components to the adjacent mantle concurrently with the CO2. Production of magnesian magmas by magnesite breakdown may not have required the heat or depth of those produced by other means; this mechanism may help to explain some apparently low Archean geothermal gradients, as well as the contemporaneity of Archean diamonds and komatites. The mantle magnesite could have formed by direct reaction of primordial CO2 or CO with hot, protomantle material during Earth's accretionary period.

  5. Laboratory-based electrical conductivity at Martian mantle conditions

    Science.gov (United States)

    Verhoeven, Olivier; Vacher, Pierre

    2016-12-01

    Information on temperature and composition of planetary mantles can be obtained from electrical conductivity profiles derived from induced magnetic field analysis. This requires a modeling of the conductivity for each mineral phase at conditions relevant to planetary interiors. Interpretation of iron-rich Martian mantle conductivity profile therefore requires a careful modeling of the conductivity of iron-bearing minerals. In this paper, we show that conduction mechanism called small polaron is the dominant conduction mechanism at temperature, water and iron content conditions relevant to Mars mantle. We then review the different measurements performed on mineral phases with various iron content. We show that, for all measurements of mineral conductivity reported so far, the effect of iron content on the activation energy governing the exponential decrease in the Arrhenius law can be modeled as the cubic square root of the iron content. We recast all laboratory results on a common generalized Arrhenius law for iron-bearing minerals, anchored on Earth's mantle values. We then use this modeling to compute a new synthetic profile of Martian mantle electrical conductivity. This new profile matches perfectly, in the depth range [100,1000] km, the electrical conductivity profile recently derived from the study of Mars Global Surveyor magnetic field measurements.

  6. Seismic anisotropy of upper mantle in Sichuan and adjacent regions

    Institute of Scientific and Technical Information of China (English)

    CHANG LiJun; WANG ChunYong; DING ZhiFeng

    2008-01-01

    Based on the polarization analysis of teleseismic SKS waveform data recorded at 94 broadband seismic stations in Sichuan and adjacent regions, the SKS fast-wave direction and the delay time between the fast and slow shear waves were determined at each station using the grid searching method of minimum transverse energy and the stacking analysis method, and the image of upper mantle anisotropy was acquired. The fast-wave polarization directions are mainly NW-SE in the study area,NWW-SEE to its northeast and NS to its west. The delay time falls into the interval [0.47 s, 1.68 s]. The spatial variation of the fast-wave directions is similar to the variation of GPS velocity directions. The anisotropic image indicates that the regional tectonic stress field has resulted in deformation and flow of upper mantle material, and made the alignment of upper mantle peridotite lattice parallel to the direction of material deformation. The crust-upper mantle deformation in Sichuan and adjacent regions accords with the mode of vertically coherent deformation. In the eastern Tibetan Plateau, the crustal material was extruded to east or southeast clue to SE traction force of the upper mantle material. The extrusion might be obstructed by a rigid block under the Sichuan Basin and the crust has been deformed. After a long-term accumulation of tectonic strain energy, the accumulative energy suddenly released in Yingxiu town of the Longmenshan region, and Wenchuan Ms8.0 earthquake occurred.

  7. On the consistency of seismically imaged lower mantle slabs.

    Science.gov (United States)

    Shephard, G E; Matthews, K J; Hosseini, K; Domeier, M

    2017-09-08

    The geoscience community is increasingly utilizing seismic tomography to interpret mantle heterogeneity and its links to past tectonic and geodynamic processes. To assess the robustness and distribution of positive seismic anomalies, inferred as subducted slabs, we create a set of vote maps for the lower mantle with 14 global P-wave or S-wave tomography models. Based on a depth-dependent threshold metric, an average of 20% of any given tomography model depth is identified as a potential slab. However, upon combining the 14 models, the most consistent positive wavespeed features are identified by an increasing vote count. An overall peak in the most robust anomalies is found between 1000-1400 km depth, followed by a decline to a minimum around 2000 km. While this trend could reflect reduced tomographic resolution in the middle mantle, we show that it may alternatively relate to real changes in the time-dependent subduction flux and/or a mid-lower mantle viscosity increase. An apparent secondary peak in agreement below 2500 km depth may reflect the degree-two lower mantle slow seismic structures. Vote maps illustrate the potential shortcomings of using a limited number or type of tomography models and slab threshold criteria.

  8. Solar energy converter using surface plasma waves

    Science.gov (United States)

    Anderson, L. M. (Inventor)

    1984-01-01

    Sunlight is dispersed over a diffraction grating formed on the surface of a conducting film on a substrate. The angular dispersion controls the effective grating period so that a matching spectrum of surface plasmons is excited for parallel processing on the conducting film. The resulting surface plasmons carry energy to an array of inelastic tunnel diodes. This solar energy converter does not require different materials for each frequency band, and sunlight is directly converted to electricity in an efficient manner by extracting more energy from the more energetic photons.

  9. Modeling and Simulation of Matrix Converter

    DEFF Research Database (Denmark)

    Liu, Fu-rong; Klumpner, Christian; Blaabjerg, Frede

    2005-01-01

    This paper discusses the modeling and simulation of matrix converter. Two models of matrix converter are presented: one is based on indirect space vector modulation and the other is based on power balance equation. The basis of these two models is• given and the process on modeling is introduced...... in details. The results of simulations developed for different researches reveal that different mdel may be suitable for different purpose, thus the model should be chosen different carefully. Some details and tricks in modeling are also introduced which give a reference for further research....

  10. Combination solar photovoltaic heat engine energy converter

    Science.gov (United States)

    Chubb, Donald L.

    1987-01-01

    A combination solar photovoltaic heat engine converter is proposed. Such a system is suitable for either terrestrial or space power applications. The combination system has a higher efficiency than either the photovoltaic array or the heat engine alone can attain. Advantages in concentrator and radiator area and receiver mass of the photovoltaic heat engine system over a heat-engine-only system are estimated. A mass and area comparison between the proposed space station organic Rankine power system and a combination PV-heat engine system is made. The critical problem for the proposed converter is the necessity for high temperature photovoltaic array operation. Estimates of the required photovoltaic temperature are presented.

  11. Metamaterial polarization converter analysis: limits of performance

    DEFF Research Database (Denmark)

    Markovich, Dmitry L.; Andryieuski, Andrei; Zalkovskij, Maksim;

    2013-01-01

    In this paper, we analyze the theoretical limits of a metamaterial-based converter with orthogonal linear eigenpolarizations that allow linear-to-elliptical polarization transformation with any desired ellipticity and ellipse orientation. We employ the transmission line approach providing a needed...... and a single layer with a ground plane can have 100 % polarization conversion efficiency. We tested our conclusions numerically reaching the designated limits of efficiency using a simple metamaterial design. Our general analysis provides useful guidelines for the metamaterial polarization converter design...

  12. Is China Ready for Full Yuan Convertibility?

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Although China has made headway in reforming the exchange rate regime of its currency,the yuan,and expanding the use of it in cross-border trade during the past year,the yuan is far from fully convertible.Huang Yiping,a professor at the National School of Development of Peking University,said in an article for Beijing Review that China has the conditions for capital account liberalization and should strive for basic convertibility within five years. Edited excerpts follow

  13. Generalized modular multilevel converter and modulation

    DEFF Research Database (Denmark)

    Liu, Hui; Loh, Poh Chiang; Blaabjerg, Frede

    2014-01-01

    Modular multilevel converter (MMC) has gained popularity recently with its modulation, capacitor voltage balancing and circulating current issues widely discussed. Contributing to this effort, a study is presented here to show how the MMC topology can be derived from the viewpoint of two series...... converters regulating a power grid. The generalized topology derived and notated as GMMC can then be altered to create various types of MMC, including the traditional topology that is presently well-known. This effort has not been previously discussed, and may smoothen the understanding of MMC operation...

  14. The 5 GPa mantle solidus revisited

    Science.gov (United States)

    Lesher, C. E.; Pickering-Witter, J.; Baxter, G.; Walter, M. J.

    2001-12-01

    We critically examine the recent claim that interlaboratory discrepancies in the solidus temperatures of nominally dry, fertile mantle peridotite between 4 and 6 GPa are related to encapsulating material (Re- foil capsules [1] versus graphite-lined Pt capsules [2]). Herzberg et al. [1] argue that reaction between silicate and graphite produces CO2, which causes a substantial freezing point depression of the peridotite solidus (>50\\deg~C at 5 GPa). We report results of a direct experimental comparison of peridotite melting in Re-foil and graphite-lined Pt capsules. We locate both capsules, containing fertile peridotite KR4003 [2], into the central portion of a stepped graphite heater, where thermal gradients are modest and well-characterized. Our experiments are performed in a MA6/8 multianvil, using octahedra of Ceramacast 584 cast with fins to fit 10-mm truncated edge length carbide anvils and calibrated by [3]. We insert axial W-Re (D-type) thermocouples into both ends of the furnace; butting thermocouple leads against the metal capsules to complete the circuit. This arrangement closely matches the thermocouple configurations used in the studies of [1] and [2]. Thermocouple voltage, power consumption, and load are recorded continuously during the experiment. Temperature is controlled by the thermocouple connected through the Pt capsule. We find that the voltage from the second thermocouple drifts significantly above 1650\\deg~C, and gives false temperatures after only 10 minutes at the set point temperature. We also find that the phase assemblages in both capsules of a given experiment are identical down to conditions with trace amounts of quenched melt. At 1670\\deg~C, based on the control thermocouple, KR4003 was partially melted to ~35% and has a residual mineralogy of olivine, orthopyroxene, and garnet. This run temperature is 15\\deg~C below the 5 GPa solidus of [1]. Extrapolation of melt fraction versus temperature data gives a solidus temperature for KR

  15. Tomographic imaging of the Nazca slab and surrounding mantle in the mantle transition zone beneath the Central Andes

    Science.gov (United States)

    Scire, A. C.; Biryol, C. B.; Zandt, G.; Beck, S. L.; Wagner, L. S.; Long, M. D.; Minaya, E.; Tavera, H.

    2013-12-01

    The central Andes in South America is an ideal location to investigate the interaction between a subducting slab and the surrounding mantle to the base of the mantle transition zone (MTZ). We used finite-frequency teleseismic P-wave tomography to image velocity anomalies in the mantle from 100 - 700 km between 10° and 28°S in the central Andes by combining data from twelve separate networks deployed in the region between 1994 and 2013. P- and PKIKP- (diffracted PKP) arrivals were picked in multiple frequency bands for earthquakes at distances between 30° and 90° and between 155° to 180° from the array, respectively. The tomographic algorithm used calculates approximate finite frequency kernels for each ray, providing additional sampling for each model layer to potentially increase the resolution of our images. The trench-parallel, fast anomaly which appears to correspond with the subducting Nazca slab is the most prominent anomaly in our tomograms. Variations in the width of the slab anomaly in the deeper parts of the model show evidence for deformation of the slab between 300 and 660 km. Our results show localized thickening of the Nazca slab in the MTZ north of 14°S, between 16° and 18°S, and south of 25°S, in agreement with the idea that the Nazca slab stagnates at least temporarily in the transition zone before resuming subduction into the lower mantle. Our images of the deeply subducted Nazca slab also show evidence of varying degrees of thinning in the mantle transition zone, particularly at 20° and 24°S, possibly indicating that the stress state changes along strike as the slab deforms in the MTZ before resuming subduction into the lower mantle. We also image along-strike variations in the sub-slab mantle in the MTZ including a strong low velocity anomaly between 22° and 28°S which is similar to those seen in other subduction zones, and is interpreted as either a local thermal anomaly or a region of hydrated material in the MTZ. A similar

  16. Upper mantle viscosity and lithospheric thickness under Iceland determined from a microphysical modelling approach of mantle rheology

    Science.gov (United States)

    Barnhoorn, A.; van der Wal, W.; Drury, M. R.

    2012-04-01

    The Vatnajökull glacier, located in the south-east of Iceland is the largest ice cap of Iceland having a mean radius of ~50 km covering an area of ˜8100 km2. The Vatnajökull glacier is situated directly on top of the spreading axis in the eastern volcanic zone (EVZ) of the Icelandic mid-ocean ridge and near the inferred center of the Icelandic hotspot. Due to the vicinity of the glacier to the active tectonic area, the response of the solid earth to melting of the ice cap is strongly controlled by the properties of the hot newly formed upper mantle underneath the mid-ocean ridge. The relatively high temperatures in the mantle during rifting result in relatively low upper mantle viscosities and fast relaxation times in comparison with tectonically inactive glaciated areas such as in. In this study, estimates for lithospheric thickness and upper mantle viscosity under Iceland are produced by a microphysical modelling approach using the theoretical temperature distribution under mid-ocean ridges combined with olivine diffusion and dislocation creep flow laws. Large lateral variations in upper mantle viscosity and especially lithospheric thickness are expected for Iceland perpendicular to the ridge axis due to the large changes in temperatures away from the ridge axis. The lithospheric thickness (27-40 km) and upper mantle viscosity (2 × 1018-1019 Pa s) outcomes for the recent glaciation are consistent with previous reports of viscosity and lithospheric thickness from glacial isostatic adjustment studies. A combination of a 40 km thick elastic lithosphere and an average upper mantle viscosity of 5 × 1018 Pa s would suggest that the upper mantle under Iceland is most likely dry. Also, the results indicate that the presence of a plume under Iceland cannot explain the recent low viscosity values reported for Iceland. Using a larger extent and larger thickness of the Icelandic icecap during the Weichselian glaciation event (˜10,000 BP) this study predicts that during

  17. Upper mantle geotherm for eastern China and its geological implications

    Institute of Scientific and Technical Information of China (English)

    徐义刚; 林传勇; 史兰斌; J-C.C.Mercier; J.V.Ross

    1995-01-01

    The equilibrium temperature and pressure of both spinel and garnet peridotite xenolithsfrom eastern China have been estimated by using different geothermobarometers that are currentlyconsidered to be reliable.Based on these data,the upper mantle geotherm for eastern China has beenconstructed.The obtained geotherm is higher than that for old craton regions,but is similar to that for southeasternAustralia.The most prominent feature of the geotherm is that there is a slight gradient at about 60 kmdepth,and the inflection of the geotherm just passes through the transition line between spinel and garnetfacies.It is likely that the inflection represents the botmdary between the lithosphere and asthenosphere.Thestructures of the upper mantle beneath eastern China have also been discussed by combining the results ofpetrologic,rheological and dynamical studies of the upper mantle.

  18. Mantle Degassing and Diamond Genesis:A Carbon Isotope Perspective

    Institute of Scientific and Technical Information of China (English)

    郑永飞

    1994-01-01

    The effect of Co2 and CH4 degassing from the mantle on the carbon isotopic composition of diamond has been quantitatively modeled in terms of the principles of Rayleigh distillation.Assuming the δ13 C value of -5‰ for the mantle,the outgassing of CO2 can result in the large negative δ13 C values of diamond,whereas the outgassing of CH4 can drive the δ13C values of diamond in the positive direction.The theoretical expectations can be used to explain the full range of δ13 C values from-34.4‰5 to+5‰ observed for natural diamonds.It is possible that diamond formation was triggered by the degassing of Co2 and/or CH4 from the mantle and the associated fractional crystallization of carbonate-bearing melt.

  19. An olivine-free mantle source of Hawaiian shield basalts.

    Science.gov (United States)

    Sobolev, Alexander V; Hofmann, Albrecht W; Sobolev, Stephan V; Nikogosian, Igor K

    2005-03-31

    More than 50 per cent of the Earth's upper mantle consists of olivine and it is generally thought that mantle-derived melts are generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. This can be resolved if the olivine of the mantle peridotite is consumed by reaction with melts derived from recycled oceanic crust, to form a secondary pyroxenitic source. Our modelling shows that more than half of Hawaiian magmas formed during the past 1 Myr came from this source. In addition, we estimate that the proportion of recycled (oceanic) crust varies from 30 per cent near the plume centre to insignificant levels at the plume edge. These results are also consistent with volcano volumes, magma volume flux and seismological observations.

  20. Large gem diamonds from metallic liquid in Earth's deep mantle.

    Science.gov (United States)

    Smith, Evan M; Shirey, Steven B; Nestola, Fabrizio; Bullock, Emma S; Wang, Jianhua; Richardson, Stephen H; Wang, Wuyi

    2016-12-16

    The redox state of Earth's convecting mantle, masked by the lithospheric plates and basaltic magmatism of plate tectonics, is a key unknown in the evolutionary history of our planet. Here we report that large, exceptional gem diamonds like the Cullinan, Constellation, and Koh-i-Noor carry direct evidence of crystallization from a redox-sensitive metallic liquid phase in the deep mantle. These sublithospheric diamonds contain inclusions of solidified iron-nickel-carbon-sulfur melt, accompanied by a thin fluid layer of methane ± hydrogen, and sometimes majoritic garnet or former calcium silicate perovskite. The metal-dominated mineral assemblages and reduced volatiles in large gem diamonds indicate formation under metal-saturated conditions. We verify previous predictions that Earth has highly reducing deep mantle regions capable of precipitating a metallic iron phase that contains dissolved carbon and hydrogen.

  1. Estimating Upper Mantle Hydration from In Situ Electrical Conductivity

    Science.gov (United States)

    Behrens, J.; Constable, S.; Heinson, G.; Everett, M.; Weiss, C.; Key, K.

    2004-12-01

    The electrical conductivity of 35-40 Ma Pacific plate has been measured in situ; one robust result is the presence of bulk anisotropy in the lithospheric upper mantle. We interpret this anisotropy to be a result of hydrothermal circulation into the upper mantle along spreading-ridge-parallel normal faults: the associated zones of serpentinized peridotite provide the pathways of enhanced electrical conductivity required by the data. Our modeling bounds the range of possible anisotropic ratios, which are then used to estimate the amount of water required to serpentinize the requisite amounts of peridotite. These data sets, however, do not indicate anisotropy in the bulk conductivity of the crust, nor in the asthenospheric mantle. This second point is significant, as recent measurements of sub-continental asthenospheric conductivity have been interpreted to indicate anisotropy aligned with present plate motion, with the diffusion of hydrogen through olivine advanced as an explanation.

  2. Mantle olivine xenocrysts entrained in Mesozoic basalts from the North China craton:Implication for replacement process of lithospheric mantle

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hongfu; YING Jifeng; XU Ping; MA Yuguang

    2004-01-01

    Mesoxzoic(125 Ma) Fangcheng basalts from Shandong Province contain clearly zoned olivines that are rare in terrestrial samples and provide first evidence for the replacement of lithospheric mantle from high-Mg peridotites to low-Mg peridotites through peridotite-melt reaction. Zoned olivines have compostions in the core(Mg#=87.2-90.7)similar to those olivines from the mantle peridotitic xenoliths entrained in Cenozoic basalts from the North China craton and in the rim (Mg#=76.8-83.9)close to olivine phenocrysts of the host basalts (75.7-79.0).These compositional features as well as rounded crystal shapes and smaller grain sizes (300-800μm)demonstrate that these zoned olivines are mantle xenocrysts ,I.e.an important type of the replacement of lithospheric mantle.The reaction resulted in the transformation of the Paleozoic refractory (high-Mg)peridotites to the late Mesozoic fertile (low-Mg) and radiogenic isotope-enriched peridotites,leading to the loss of old lithospheric mantle.

  3. Efficient, lightweight dc/dc switching converter

    Science.gov (United States)

    Cuk, S.; Middlebrook, R. D.

    1981-01-01

    Converters have input properties of boost power stage and output properties of buck power stage, yet they perform general conversion function with high efficiency. Other features include non-pulsating input/output currents, use of capacitive energy transfer, low output voltage ripple, reduced EMI, and small size.

  4. Power electronics converters for wind turbine systems

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Liserre, Marco; Ma, Ke

    2011-01-01

    The steady growth of installed wind power which reached 200 GW capacity in 2010, together with the up-scaling of the single wind turbine power capability - 7 MW’s has been announced by manufacturers - has pushed the research and development of power converters towards full scale power conversion,...

  5. Power Electronics Converters for Wind Turbine Systems

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Liserre, Marco; Ma, Ke

    2012-01-01

    The steady growth of installed wind power together with the upscaling of the single wind turbine power capability has pushed the research and development of power converters toward full-scale power conversion, lowered cost pr kW, increased power density, and also the need for higher reliability. ...

  6. China to Gradually Make Capital Account Convertible

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ China is pushing forward its currency Renminbi (RMB)'s capital account convertibility gradually and in a stable manner, said an official with the State Administration of Foreign Exchange (SAFE), ruling out both an adventurous leap and conservative cautiousness, according to a report of Xinhua on April 12.

  7. China to Gradually Make Capital Account Convertible

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

      China is pushing forward its currency Renminbi (RMB)'s capital account convertibility gradually and in a stable manner, said an official with the State Administration of Foreign Exchange (SAFE), ruling out both an adventurous leap and conservative cautiousness, according to a report of Xinhua on April 12.……

  8. Power electronics converters for wind turbine systems

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Liserre, Marco; Ma, Ke

    2011-01-01

    The steady growth of installed wind power which reached 200 GW capacity in 2010, together with the up-scaling of the single wind turbine power capability - 7 MW’s has been announced by manufacturers - has pushed the research and development of power converters towards full scale power conversion,...

  9. Mathematical modeling of the flash converting process

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-31

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

  10. Development of the Wave Energy Converter

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter; Sørensen, Hans Christian

    2000-01-01

    The development of the wave energy converter Wave Dragon (WD) is presented. The WD is based on the overtopping principle. Initially a description of the WD is given. Then the development over time in terms of the various research and development projects working with the concept is described...

  11. Aquabuoy Wave Energy Converter

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Margheritini, Lucia; Frigaard, Peter

    The work reported here is part of the contract agreement between the Finavera Renewables Ocean Energy Ltd. and the Department of Civil Engineering Hydraulics and Coastal Engineering Laboratory to instrument a model in scale 1:10 to prototype of the AquaBuOY (AB) wave energy converter and to analyse...

  12. Fast Constant Weight Codeword to Index Converter

    Science.gov (United States)

    2011-08-01

    is achievable; a 64-out- of-128 bit converter uses only 9% of the available ALMs. The large values of n required special Verilog programming. For...n r ) in a MATLAB program and wrote it to a header file that was included in the Verilog code. III. COMPLEX DISJOINT DECOMPOSITION SOLUTION It can

  13. Low-power variable frequency PFC converters

    Energy Technology Data Exchange (ETDEWEB)

    Li Yani; Yang Yintang; Zhu Zhangming, E-mail: yanili@mail.xidian.edu.c [Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices of the Ministry of Education, Institute of Microelectronics, Xidian University, Xi' an 710071 (China)

    2010-01-15

    Based on the SinoMOS 1 {mu}m 40 V CMOS process, a novel power factor contention (PFC) converter with a low-power variable frequency function is presented. The circuit introduces a multi-vector error amplifier and a programmable oscillator to achieve frequency modulation, which provides a rapid dynamic response and precise output voltage clamping with low power in the entire load. According to the external load variation, the system can modulate the circuit operating frequency linearly, thereby ensuring that the PFC converter can work in frequency conversion-mode. Measured results show that the normal operating frequency of the PFC converter is 5-6 kHz, the start-up current is 36 {mu}A, the stable operating current is only 2.43 mA, the efficiency is 97.3%, the power factor (PF) is 0.988, THD is 3.8%, the load adjust rate is 3%, and the linear adjust rate is less than 1%. Both theoretical and practical results reveal that the power consumption of the whole supply system is reduced efficiently, especially when the load varies. The active die area of the PFC converter chip is 1.61 x 1.52 mm{sup 2}. (semiconductor integrated circuits)

  14. Oxygen activity measurements in simulated converter matte

    CSIR Research Space (South Africa)

    Tshilombo, KG

    2007-01-01

    Full Text Available to the composition of the gas atmosphere over the melt. The measured oxygen activity was generally close to that predicted by FactSage calculations. This indicates that such oxygen activity measurements could be useful to monitor iron removal during converting...

  15. Online Scheduling in Distributed Message Converter Systems

    NARCIS (Netherlands)

    Risse, Thomas; Wombacher, Andreas; Surridge, Mike; Taylor, Steve; Aberer, Karl

    2001-01-01

    The optimal distribution of jobs among hosts in distributed environments is an important factor to achieve high performance. The optimal strategy depends on the application. In this paper we present a new online scheduling strategy for distributed EDI converter system. The strategy is based on the B

  16. Converting Student Support Services to Online Delivery.

    Science.gov (United States)

    Brigham, David E.

    2001-01-01

    Uses a systems framework to analyze the creation of student support services for distance education at Regents College: electronic advising, electronic peer network, online course database, online bookstore, virtual library, and alumni services website. Addresses the issues involved in converting distance education programs from print-based and…

  17. Online Scheduling in Distributed Message Converter Systems

    NARCIS (Netherlands)

    Risse, Thomas; Wombacher, Andreas; Surridge, Mike; Taylor, Steve; Aberer, Karl

    2001-01-01

    The optimal distribution of jobs among hosts in distributed environments is an important factor to achieve high performance. The optimal strategy depends on the application. In this paper we present a new online scheduling strategy for distributed EDI converter system. The strategy is based on the B

  18. Online Scheduling in Distributed Message Converter Systems

    NARCIS (Netherlands)

    Risse, Thomas; Wombacher, Andreas; Surridge, Mike; Taylor, Steve; Aberer, Karl

    The optimal distribution of jobs among hosts in distributed environments is an important factor to achieve high performance. The optimal strategy depends on the application. In this paper we present a new online scheduling strategy for distributed EDI converter system. The strategy is based on the

  19. Near-Shore Floating Wave Energy Converters

    DEFF Research Database (Denmark)

    Ruol, Piero; Zanuttigh, Barbara; Martinelli, Luca

    2011-01-01

    Aim of this note is to analyse the possible application of a Wave Energy Converter (WEC) as a combined tool to protect the coast and harvest energy. Physical model tests are used to evaluate wave transmission past a near-shore floating WEC of the wave activated body type, named DEXA. Efficiency...

  20. Hybrid switch for resonant power converters

    Science.gov (United States)

    Lai, Jih-Sheng; Yu, Wensong

    2014-09-09

    A hybrid switch comprising two semiconductor switches connected in parallel but having different voltage drop characteristics as a function of current facilitates attainment of zero voltage switching and reduces conduction losses to complement reduction of switching losses achieved through zero voltage switching in power converters such as high-current inverters.

  1. Mantle fluids in the Karakoram fault: Helium isotope evidence

    Science.gov (United States)

    Klemperer, Simon L.; Kennedy, B. Mack; Sastry, Siva R.; Makovsky, Yizhaq; Harinarayana, T.; Leech, Mary L.

    2013-03-01

    The Karakoram fault (KKF) is the 1000 km-long strike-slip fault separating the western Himalaya from the Tibetan Plateau. From geologic and geodetic data, the KKF is argued either to be a lithospheric-scale fault with hundreds of km of offset at several cm/a, or to be almost inactive with cumulative offset of only a few tens of kilometers and to be just the upper-crustal localization of distributed deformation at depth. Here we show 3He/4He ratios in geothermal springs along a 500-km segment of the KKF are 3-100 times the normal ratio in continental crust, providing unequivocal evidence that a component of these hydrologic systems is derived from tectonically active mantle. Mantle enrichment is absent along the Indus-Yarlung suture zone (ISZ) just 35 km southwest of the KKF, suggesting that the mantle fluids flow only within the KKF. Within the last few Ma, the KKF must have accessed tectonically active Tibetan mantle northeast of the "mantle suture" which we therefore locate vertically beneath the KKF, very close to the surface trace of the ISZ. Hence, in southwestern Tibet, Indian crust may not now be underthrusting substantially north of the ISZ, even though Miocene underthrusting may have placed Indian crust north of the ISZ in the lower half of the Tibetan Plateau crust. This is in significant contrast to central and eastern Tibet where underthrust Indian material not only forms the lower half of the Tibetan crust but is also currently underthrusting for ∼200 km north of the ISZ. Our new constraint on KKF penetration to the mantle allows an improved description of the continuously evolving Karakoram fault, as a tectonically significant yet perhaps geologically ephemeral lithospheric structure.

  2. West Antarctic Mantle Plume Hypothesis and Basal Water Generation

    Science.gov (United States)

    Ivins, Erik; Seroussi, Helene; Wiens, Doug; Bondzio, Johannes

    2017-04-01

    The hypothesis of a deep mantle plume that manifests Pliocene and Quaternary volcanism and present-day seismicity in West Antarctica has been speculated for more than 30 years. Recent seismic images support the plume hypothesis as the cause of Marie Byrd Land (MBL) volcanism and geophysical structure [ Lloyd et al., 2015; Ramirez et al., 2016]. Mantle plumes can more that double the geothermal heat flux, qGHF, above nominal continental values at their axial peak position and raise qGHF in the surrounding plume head to 60 mW/m2 or higher. Unfortunately, there is a dearth of in-situ basal ice sheet data that sample the heat flux. Consequently, we examine a realistic distribution of heat flux associated with a late-Cenozoic mantle plume in West Antarctica and explore its impact on thermal and melt conditions near the ice sheet base. The solid Earth model assumes a parameterized deep mantle plume and head. The 3-D ice flow model includes an enthalpy framework and full-Stokes stress balance. Both the putative plume location and extent are uncertain. Therefore, we perform broadly scoped experiments to characterize plume related basal conditions. The experiments show that mantle plumes have an important local impact on the ice sheet, with basal melting rates reaching several centimeters per year directly above the hotspot. The downstream active lake system of Whillans Ice Stream suggests a rift-related source of anomalous mantle heat. However, the lack of lake and stream activity in MBL suggests a relatively weak plume: one that delivers less flux by 35% below the heat flux to the crustal surface at the site of the Yellowstone hotspot [e.g., DeNosaquo et al., 2009], with peak value no higher than about 145 mW/m2.

  3. Mantle flow and dynamic topography associated with slab window opening

    Science.gov (United States)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-05-01

    A slab window is defined as an 'hole' in the subducting lithosphere. In the classical view, slab windows develop where a spreading ridge intersects a subduction zone. The main consequences of this phenomenon are the modifications of the physical, chemical and thermal conditions in the backarc mantle that in turn affect the tectonic and magmatic evolution of the overriding plate. In this work, we perform dynamically self-consistent mantle-scale laboratory models, to evaluate how the opening of a window in the subducting panel influences the geometry and the kinematics of the slab, the mantle circulation pattern and, finally, the overriding plate dynamic topography. The adopted setup consists in a two-layer linearly viscous system simulating the roll-back of a fixed subducting plate (simulated using silicone putty) into the upper mantle (simulated using glucose syrup). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We find that the geometry and the kinematics of the slab are only minorly affected by the opening of a slab window. On the contrary, slab induced mantle circulation, quantified using Feature Tracking image analysis technique, is strongly modified and produces a peculiar non-isostatic topographic signal on the overriding plate. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compare them to the Patagonian subduction zone finding that anomalous backarc volcanism that developed since middle Miocene could result from the lateral flowage of subslab mantle, and that part of the Patagonian uplift could be dynamically supported.

  4. Vertical velocity of mantle flow of East Asia and adjacent areas

    Institute of Scientific and Technical Information of China (English)

    CHENG Xianqiong; ZHU Jieshou; CAI Xuelin

    2007-01-01

    Based on the high-resolution body wave tomo- graphic image and relevant geophysical data, we calculated the form and the vertical and tangential velocities of mantle flow. We obtained the pattern of mantle convection for East Asia and the West Pacific. Some important results and under- standings are gained from the images of the vertical velocity of mantle flow for East Asia and the West Pacific. There is an upwelling plume beneath East Asia and West Pacific, which is the earth's deep origin for the huge rift valley there. We have especially outlined the tectonic features of the South China Sea, which is of the "工" type in the upper mantle shield type in the middle and divergent in the lower; the Siberian clod downwelling dives from the surface to near Core and mantle bounary (CMB), which is convergent in the upper mantle and divergent in the lower mantle; the Tethyan subduction region, centered in the Qinghai-Tibet plateau, is visible from 300 to 2 000 km, which is also convergent in the upper mantle and divergent in the lower mantle. The three regions of mantle convection beneath East Asia and the West Pacific are in accordance with the West Pacific, Ancient Asia and the Tethyan structure regions. The mantle upwelling orig- inates from the core-mantle boundary and mostly occurs in the middle mantle and the lower part of the upper mantle. The velocities of the vertical mantle flow are about 1-4 cm per year and the tangential velocities are 1-10 cm per year. The mantle flow has an effect on controlling the movement of plates and the distributions of ocean ridges, subduction zones and collision zones. The mantle upwelling regions are clearly related with the locations ofhotspots on the earth's surface.

  5. A New Hard Switching Bidirectional Converter With High Power Density

    Directory of Open Access Journals (Sweden)

    Bahador Fani

    2010-01-01

    Full Text Available In this paper, a new isolated dc-dc bidirectional converter is proposed. This converter consists of two transformers (flyback and forward and only one switch in primary side and one switch in secondary side of transformers. In this converter energy transfers to the output in both on and off switch states so power density of this converter is high This converter controlled by PWM signal. Also this converter operates over a wide input voltage range. Theoretical analysis is presented and computer simulation and experimental results verify the converter analysis.

  6. Bidirectional converter interface for a battery energy storage test bench

    DEFF Research Database (Denmark)

    Trintis, Ionut; Thomas, Stephan; Blank, Tobias;

    2011-01-01

    This paper presents the bidirectional converter interface for a 6 kV battery energy storage test bench. The power electronic interface consists a two stage converter topology having a low voltage dc-ac grid connected converter and a new dual active bridge dc-dc converter with high transformation...... ratio. The dc-dc converter controls the battery charge/discharge current while the grid converter controls the common dc-link voltage and the grid current. The applied control structures and the hardware implementation of both converters are presented, together with their interaction. Experimental...

  7. Bidirectional converter interface for a battery energy storage test bench

    DEFF Research Database (Denmark)

    Trintis, Ionut; Thomas, Stephan; Blank, Tobias

    2011-01-01

    This paper presents the bidirectional converter interface for a 6 kV battery energy storage test bench. The power electronic interface consists a two stage converter topology having a low voltage dc-ac grid connected converter and a new dual active bridge dc-dc converter with high transformation...... ratio. The dc-dc converter controls the battery charge/discharge current while the grid converter controls the common dc-link voltage and the grid current. The applied control structures and the hardware implementation of both converters are presented, together with their interaction. Experimental...

  8. Seismic Constraints on the Mantle Viscosity Structure beneath Antarctica

    Science.gov (United States)

    Wiens, Douglas; Heeszel, David; Aster, Richard; Nyblade, Andrew; Wilson, Terry

    2015-04-01

    Lateral variations in upper mantle viscosity structure can have first order effects on glacial isostatic adjustment. These variations are expected to be particularly large for the Antarctic continent because of the stark geological contrast between ancient cratonic and recent tectonically active terrains in East and West Antarctica, respectively. A large misfit between observed and predicted GPS rates for West Antarctica probably results in part from the use of a laterally uniform viscosity structure. Although not linked by a simple relationship, mantle seismic velocities can provide important constraints on mantle viscosity structure, as they are both largely controlled by temperature and water content. Recent higher resolution seismic models for the Antarctic mantle, derived from data acquired by new seismic stations deployed in the AGAP/GAMSEIS and ANET/POLENET projects, offer the opportunity to use the seismic velocity structure to place new constraints on the viscosity of the Antarctic upper mantle. We use an Antarctic shear wave velocity model derived from array analysis of Rayleigh wave phase velocities [Heeszel et al, in prep] and examine a variety of methodologies for relating seismic, thermal and rheological parameters to compute a suite of viscosity models for the Antarctic mantle. A wide variety of viscosity structures can be derived using various assumptions, but they share several robust common elements. There is a viscosity contrast of at least two orders of magnitude between East and West Antarctica at depths of 80-250 km, reflecting the boundary between cold cratonic lithosphere in East Antarctica and warm upper mantle in West Antarctica. The region beneath the Ellsworth-Whitmore Mtns and extending to the Pensacola Mtns. shows intermediate viscosity between the extremes of East and West Antarctica. There are also significant variations between different parts of West Antarctica, with the lowest viscosity occurring beneath the Marie Byrd Land (MBL

  9. A New Carbonate Chemistry in the Earth's Lower Mantle

    Science.gov (United States)

    Boulard, E.; Gloter, A.; Corgne, A.; Antonangeli, D.; Auzende, A.; Perrillat, J.; Guyot, F. J.; Fiquet, G.

    2010-12-01

    The global geochemical carbon cycle involves exchange between the Earth’s mantle and the surface. Carbon (C) is recycled into the mantle via subduction and released to the atmosphere via volcanic outgassing. Carbonates are the main C-bearing minerals that are transported deep in the Earth’s mantle via subduction of the oceanic lithosphere [1]. The way C is recycled and its contribution to the lower mantle reservoir is however largely unknown [ e.g 2, 3]. In this respect, it is important to assess if carbonates can be preserved in the deep mantle, or if decarbonatation, melting or reduction play a role in the deep carbon cycle. To clarify the fate of carbonates in the deep mantle, we carried out high-pressure and high-temperature experiments up to 105 GPa and 2850 K. Natural Fe-Mg carbonates or oxide mixtures of (Mg,Fe)O + CO2 were loaded into laser heated diamond anvil cells. In situ characterizations were done by X-ray Diffraction (XRD) using synchrotron radiation at the high-pressure beamline ID27 of the European Synchrotron Radiation Facility. A focused ion beam technique was then used to prepare the recovered samples for electron energy loss spectroscopy in a dedicated scanning transmission electron microscope (EELS-STEM) and scanning transmission X-ray microscopy (STXM). In situ XRD clearly shows the transformation of the initial carbonate phase into a new Mg-Fe high pressure carbonate phase at lower mantle conditions. We also provide direct evidence for recombination of CO2 with (Mg,Fe)O to form this new carbonate structure. In addition, subsequent EELS-STEM and STXM spectroscopies carried out on recovered samples yields C K-edge and stoechiometry characteristic to this new carbonate structure. This new high pressure phase concentrates a large amount of Fe(III), as a result of redox reactions within the siderite-rich carbonate. The oxidation of iron is balanced by partial reduction of carbon into CO groups and/or diamond. These reactions may provide an

  10. Evidence for Little Shallow Entrainment in Starting Mantle Plumes

    Science.gov (United States)

    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

  11. Primary cutaneous blastoid mantle cell lymphoma-case report.

    Science.gov (United States)

    Estrozi, Bruna; Sanches, José A; Varela, Paulo C S; Bacchi, Carlos E

    2009-06-01

    Mantle cell lymphoma (MCL) commonly involves extranodal sites, usually as a manifestation of disseminated disease. In rare cases, MCLs may arise as a primary tumor in the skin. Blastoid mantle cell lymphoma (BV-MCL) is a rare variant and has a more aggressive clinical course. The phenotype of BV-MCL is characterized as CD20+, CD5+, cyclin D1+, CD23-, and CD10-. Interphase fluorescence in situ hybridization shows a characteristic t(11;14) fusion pattern. We report a case of a BV-MCL arising in skin as primary cutaneous MCL with the characteristic immunophenotype and translocation.

  12. Seismic determination of elastic anisotropy and mantle flow.

    Science.gov (United States)

    Park, J; Yu, Y

    1993-08-27

    When deformed, many rocks develop anisotropic elastic properties. On many seismic records, a long-period (100 to 250 seconds), "quasi-Love" wave with elliptical polarization arrives slightly after the Love wave but before the Rayleigh wave. Mantle anisotropy is sufficient to explain these observations qualitatively as long as the "fast" axis of symmetry is approximately horizontal. Quasi-Love observations for several propagation paths near Pacific Ocean subduction zones are consistent with either flow variations in the mantle within or beneath subducting plates or variations in the direction of fossil spreading in older parts of the Pacific plate.

  13. Helium isotopic systematics of oceanic islands and mantle heterogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Kurz, M.D.; Jenkins, W.J. (Woods Hole Oceanographic Institution, MA (USA)); Hart, S.R. (Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Earth and Planetary Sciences)

    1982-05-06

    The results of helium isotopic analyses in basaltic phenocrysts from the islands of Gough and Tristan da Cunha are reported which seem to indicate that the mantle beneath these islands are not primitive or undepleted relative to mid-ocean ridge basalt (MORB). New analyses from Loihi Seamount are also reported which do indicate a more primitive source. When these data are combined with values for MORBs previously obtained and plotted with respect to /sup 87/Sr//sup 86/Sr, the observed trends offer insight into the different source regions for oceanic island basalts and the nature of mantle heterogeneity.

  14. Water contents in pyroxenes of intraplate lithospheric mantle

    Science.gov (United States)

    Bonadiman, C.; Hao, Y.-T.; Coltorti, M.; Dallai, L.; Faccini, B.; Hu, H.; Qunke, X.

    2009-04-01

    Water contents of clinopyroxene and orthopyroxene in mantle peridotites from various xenolith occurrences in intraplate settings (both oceanic and continental) were determined by Fourier Transform Infrared Spectroscopy (FTIR). The localities are as follow: Sal Island (Cape Verde Archipelago); Baker Rocks and Greene Point (Northern Victoria Land, Antarctica); Panshishan and Lianshan (Subei Basin, Eastern China). They represent well-known localities where detailed petrographical and geochemical studies have already been carried out or areas which are currently under investigation. The water incorporated in these pyroxenes is low (cpx, 37-399ppm; opx: 9-166ppm)(or very low as in Greene Point, Antarctica; cpx, 5-16ppm; opx: 9-16ppm) and, among each population, no clear correlation with melting parameters (MgO contents) in single mineral is evident. Results are compared with the available literature data on water contents in mantle pyroxene which includes peridotites from on-craton (hosted by kimberlitic-type magmas) and off-craton (hosted by alkaline basic magmas), as well as subarc mantle settings. The "relatively dry" (cpx: 140-528 ppm; opx: 38-280 ppm) sub-arc mantle xenoliths (Peslier et al., 2002) are shown to be wetter than the intraplate (off-craton) xenoliths. Cratonic mantle pyroxenes are only represented by a few determinations on garnet peridotites and eclogite from Kaapvaal and Colorado Plateau. They record the highest water contents (cpx: 342-1012 ppm; opx: 180-491 ppm) so far measured in mantle pyroxenes from various tectonic settings. Despite the limited data set, the indication that the cratonic mantle is strongly hydrated is compelling. Rehydration for the Colorado Plateau craton may be due to the Farallon plate subduction (Li et al., 2008), while for Kaapvaal Craton it might be related to young (<100Ma) metasomatic enrichments (Griffin et al., 2003a; Kobussen et al., 2008). If this is the case then the Archean mantle water content needs to be

  15. A mantle plume below the Eifel volcanic fields, Germany

    OpenAIRE

    Ritter, Joachim R. R.; Jordan, Michael; Christensen, Ulrich R.; Achauer, Ulrich

    2001-01-01

    We present seismic images of the upper mantle below the Quaternary Eifel volcanic fields, Germany, determined by teleseismic travel time tomography. The data were measured at a dedicated network of more than 200 stations. Our results show a columnar low P-velocity anomaly in the upper mantle with a lateral contrast of up to 2%. The 100 km wide structure extends to at least 400 km depth and is equivalent to about 150–200 K excess temperature. This clear evidence for a plume below a region of c...

  16. Role of viscoelasticity in mantle convection models

    Science.gov (United States)

    Patocka, Vojtech; Cadek, Ondrej; Tackley, Paul

    2015-04-01

    constitutive equations in a way more suitable for global studies, which is different from the method refered to earlier. The computational domain is expected to be composed of two parts: One in which elastic effects are important and where material does not move significantly within one elastic time step and one where elastic effects are not important, where material is allowed to move across many cells within one elastic time step. Local accumulation of stress in viscoelastic simulations is observed, suggesting elasticity could e.g. trigger plasticity in realistic cases. References Moresi L., Dufour F., Mühlhaus H.-B., 2003: A Lagrangian integration point finite element method for large deformation modeling of viscoelastic geomaterials, Journal of Computational Physics, 184 (2003), 476 - 497 Tackley P., 2008: Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid, Physics of the Earth and Planetary Interiors, 171 (2008), 7-18

  17. Multi-output DC-DC converters based on diode-clamped converters configuration

    DEFF Research Database (Denmark)

    Nami, A.; Zare, F.; Ghosh, A.;

    2010-01-01

    for a diode-clamed inverter in the grid connection systems, where boosting low rectified output-voltage and series DC link capacitors is required. To verify the proposed topology, steady-state and dynamic analyses of a MOB converter are examined. A simple control strategy has been proposed to demonstrate...... the performance of the proposed topology for a double-output boost converter. The topology and its control strategy can easily be extended to offer multiple outputs. Simulation and experimental results are presented to show the validity of the control strategy for the proposed converter....

  18. Emissions Tests Of Two Dc-To-Dc Converters

    Science.gov (United States)

    Mclyman, W. T.

    1992-01-01

    Report describes tests to characterize unwanted electric and magnetic fields, at frequencies up to few megahertz, radiated by two dc-to-dc converters, one 20-kHz square-wave converter; the other, a 33-kHz sine-wave converter. Part of effort to develop "quiet" power converter for use aboard spacecraft. Converter required to interfere minimally with delicate instruments measuring electric and magnetic fields.

  19. Coordinated Control of Wave Energy Converters Subject to Motion Constraints

    OpenAIRE

    2016-01-01

    In this paper, a generic coordinated control method for wave energy converters is proposed, and the constraints on motion amplitudes and the hydrodynamic interaction between converters are considered. The objective of the control problem is to maximize the energy converted from ocean waves, and this is achieved by coordinating the power take-off (PTO) damping of each wave energy converter in the frequency domain in each sea state. In a case study, a wave energy farm consisting of four convert...

  20. Research on Converter Valve Overvoltage Mechanism and Calculation Conditions of ± 800 kV Converter Station

    Institute of Scientific and Technical Information of China (English)

    WANG Dongju; DENG Xu; ZHOU Hao; CHEN Xilei; XU Anwen; SHEN Yang

    2012-01-01

    The thyristor converter valve is the key equipment of commutation in ultra high voltage direct current (UHVDC) transmission systems. Owing to the limited voltage and current overload capacity, any transient overvoltage may cause permanent damage to the thyristor converter valve. In order to specify the converter valves' overvoltage levels of the ±800 kV UHVDC transmission system, the mechanisms of its generation and development are discussed in detail, from which the calculation conditions for the highest stresses of the converter valves are given. Finally, the converter valve's overvoltage of Xiluodu UHV converter station is simulated. The research results show that the overvoltages of the converter valves in the upper 3-pulse group of the high voltage(HV) and low voltage(LV) 12-pulse converter are generated jointly by the DC line voltage and the converter transformer's voltage at its valve side. Calculation conditions for this overvoltage are: DC system in bipolar operation mode, converter station operating as rectifier, maximum DC system operating voltage, minimum DC current, minimum AC system voltage of the converter station. Furthermore, the other converter valves' overvoltage is caused by the phase-to-phase switching surge generated at the converter station's AC side, penetrating into the valve hall. Overall, the maximum overvoltages of Xiluodu converter station in the upper 3-pulse group of the HV and LV 12-pulse converter are 379.1 kV and 384.9 kV, for other converter valves the maximum overvoltage is 375.3 kV.

  1. Imbalance between pulmonary angiotensin-converting enzyme and angiotensin-converting enzyme 2 activity in acute respiratory distress syndrome

    NARCIS (Netherlands)

    Wosten-van Asperen, Roelie M.; Bos, Albert; Bem, Reinout A.; Dierdorp, Barbara S.; Dekker, Tamara; van Goor, Harry; Kamilic, Jelena; van der Loos, Chris M.; van den Berg, Elske; Bruijn, Martijn; van Woensel, Job B.; Lutter, Rene

    2013-01-01

    Objective: Angiotensin-converting enzyme and its effector peptide angiotensin II have been implicated in the pathogenesis of acute respiratory distress syndrome. Recently, angiotensin-converting enzyme 2 was identified as the counter-regulatory enzyme of angiotensin-converting enzyme that converts

  2. Imbalance between pulmonary angiotensin-converting enzyme and angiotensin-converting enzyme 2 activity in acute respiratory distress syndrome

    NARCIS (Netherlands)

    Wosten-van Asperen, Roelie M.; Bos, Albert; Bem, Reinout A.; Dierdorp, Barbara S.; Dekker, Tamara; van Goor, Harry; Kamilic, Jelena; van der Loos, Chris M.; van den Berg, Elske; Bruijn, Martijn; van Woensel, Job B.; Lutter, Rene

    2013-01-01

    Objective: Angiotensin-converting enzyme and its effector peptide angiotensin II have been implicated in the pathogenesis of acute respiratory distress syndrome. Recently, angiotensin-converting enzyme 2 was identified as the counter-regulatory enzyme of angiotensin-converting enzyme that converts a

  3. The initiation, temporal evolution and dynamics of deep mantle heterogeneities

    Science.gov (United States)

    Bull-Aller, Abigail; Torsvik, Trond; Domeier, Mathew; Doubrovine, Pavel

    2013-04-01

    Understanding the first-order dynamical structure and temporal evolution of Earth's mantle is a fundamental goal in solid-earth geophysics. Recent tomographic observations reveal a lower mantle characterised by higher-than-average shear-wave speeds beneath Asia and encircling the Pacific, consistent with cold slabs of descending lithosphere beneath regions of ancient subduction, and lower-than-average shear-wave speeds in broad regional areas beneath Africa and the Central Pacific (LLSVPs). The LLSVPs, although not as easily understood from a dynamical perspective, are inferred to be broad upwelling centres between Mesozoic and Cenozoic subduction zones. Heterogeneous mantle models place these anomalies into the context of thermochemical piles, characterised by an anomalously dense component, with their location and geometry being controlled by the movement of subducting slabs. The origin and temporal evolution of the LLSVPs remain enigmatic. Recent numerical studies propose that the LLSVP beneath Africa formed as a result of return flow in the mantle due to circum-Pacific subduction beneath the Pangean supercontinent. This suggests that prior to the formation of Pangea, the lower mantle was dominated by a degree-1 convection pattern, with a major upwelling centred close to the present-day Pacific LLSVP and subduction concentrated in the antipodal hemisphere. The African LLSVP would thus have developed within the time frame of the Pangean supercontinent (i.e., 300Ma-180Ma), in contrast to a much older Pacific LLSVP. It is further proposed that a cyclic alternation between a degree-1 pattern and a degree-2 pattern of mantle convection may accompany the supercontinent cycle and characterise the temporal convective evolution of Earth's mantle. In contrast, a more long-term persistence for both the African and Pacific LLSVPs, and thus for the planform of mantle convection within the Earth as a whole, is suggested by recent palaeomagnetic studies, which show that over

  4. Experimental study of diamond resorption during mantle metasomatism

    Science.gov (United States)

    Fedorchuk, Yana; Schmidt, Max W.; Liebske, Christian

    2014-05-01

    Many of kimberlite-derived diamonds are partially dissolved to various degree but show similar resorption style. This resorption style has been observed in experiments with aqueous fluid at the conditions corresponding to kimberlite emplacement (1-2 GPa). At the same time, each diamond population has more than ten percent of diamond crystals with several drastically different resorption styles, which have not been observed in experiments, and may represent partial dissolution of diamonds during metasomatism in different mantle domains. Metasomatic processes modify the composition of subcratonic mantle, may trigger the formation of kimberlite magma, and result in the growth and partial dissolution of diamonds. Composition of metasomatic agents as constrained from studies of the reaction rims on mantle minerals (garnet, clinopyroxene) and experimental studies vary between carbonatitic melt, aqueous silicate melt, and CHO fluid. However, complex chemical pattern of mantle minerals and estimates of redox regime in subcratonic mantle allow different interpretations. Here we explore diamond dissolution morphology as an indicator of the composition of mantle metasomatic agents. Towards this end we examine diamond dissolution morphologies developed in experiments at the conditions of mantle metasomatism in different reacting media and compare them to the mantle-derived dissolution features of natural diamonds. The experiments were conducted in multi-anvil (Walker-Type) apparatus at 6 GPa and 1200-1500oC. Dissolution morphology of natural octahedral diamond crystals (0.5 mg) was examined in various compositions in synthetic system MgO-CaO- SiO2-CO2-H2O. The runs had the following phases present: solid crystals with fluid (various ratio of H2O-CO2-SiO2, and in the air), carbonate melt, carbonate-silicate melt, and carbonate melt with CHO fluid. Experiments produced three different styles of diamond resorption. In the presence of a fluid phase with variable proportions of H2O

  5. Deep mantle heat flow and thermal evolution of the Earth's core based on thermo-chemical mantle convection

    Science.gov (United States)

    Nakagawa, T.; Tackley, P.; Buffett, B.

    2004-12-01

    A coupled core-mantle evolution model that combines the global heat balance in the core with a fully-dynamical thermo-chemical mantle convection [Nakagawa and Tackley, 2004 published in EPSL] is used to investigate the deep mantle heat flow that is required to sustain the magnetic field generated by the geodynamo process. Effects of a radioactive heat source due to potassium in the core are also included in the global heat balance in the Earth??s core. Two important parameters are checked in this study; (1) density variation between depleted hartzbergite and basaltic material (0 to 3 percent) and (2) concentration of radioactive potassium in the core alloy (0ppm to 400ppm). The parameter set that most closely satisfies the criteria of size of the inner core (1220km at present time) is around 2 percent of density difference in a convecting mantle and 200ppm of radioactive heat source in the core. The concentration of potassium in the core is consistent with the geochemical approach [Murthy et al., 2003] but smaller than other successful thermal evolution models [Labrosse, 2003; Nimmo et al., 2004]. Heat flow through the core-mantle boundary and the contribution of radioactive heat sources in the core are consistent with theoretical estimates [e.g. Buffett, 2002] and geochemical constraints [Gessmann and Wood, 2002]. The power available to the geodynamo, based on the predicted heat flow through the core-mantle boundary, is approximately four times greater than the value predicted by numerical models of the geodynamo [Christensen and Kutzner, 2004] but closer to theoretical estimates [e.g. Buffett, 2002].

  6. Layering of the lithospheric mantle beneath the Siberian Craton: Modeling using thermobarometry of mantle xenolith and xenocrysts

    Science.gov (United States)

    Ashchepkov, I. V.; Vladykin, N. N.; Ntaflos, T.; Kostrovitsky, S. I.; Prokopiev, S. A.; Downes, H.; Smelov, A. P.; Agashev, A. M.; Logvinova, A. M.; Kuligin, S. S.; Tychkov, N. S.; Salikhov, R. F.; Stegnitsky, Yu. B.; Alymova, N. V.; Vavilov, M. A.; Minin, V. A.; Babushkina, S. A.; Ovchinnikov, Yu. I.; Karpenko, M. A.; Tolstov, A. V.; Shmarov, G. P.

    2014-11-01

    Single-grain thermobarometric studies of xenocrysts were used to compile local SCLM transects through the major regions of kimberlite magmatism in Siberia and longer transects through the subcontinental mantle lithosphere (SCLM) beneath the Siberian craton. The mantle structure was obtained using P-Fe#, Ca in garnets, oxygen fugacity values fO2 and calculated temperatures T°C. The most detail transect obtained for the Daldyn field on the Udachnaya-Zarnitsa reveals layering showing an inclination of > 35° to Udachnaya. Mantle layering beneath the Alakit field determined from the Krasnopresnenskaya-Sytykanskaya transect shows a moderate inclination from N to S. The inflection near Yubileinaya-Aykhal is also supported by the extreme depletion in peridotites with low-Fe sub-Ca garnets. Beneath the Malo-Botuobinsky field the sharply layered mantle section starts from 5.5 GPa and reveals step-like P-Fe#Ol trends for garnets and ilmenites. The deeper part of SCLM in this field was originally highly depleted but has been regenerated by percolation of protokimberlites and hybrid melts especially beneath Internationalnaya pipe. The three global transects reveal flat layering in granite-greenstone terranes and fluctuations in the granulite-orthogneiss Daldyn collision terranes. The mantle layering beneath the Daldyn - Alakite region may have been created by marginal accretion. Most of southern fields including the Malo-Botuobinsky field reveal flat layering. The primary subduction layering is smoothed beneath the Alakit field. Lower Jurassic kimberlites from the Kharamai-Anabar kimberlite fields reveal a small decrease of the thickness of the SCLM and heating of its base. The Jurassic Kuoyka field shows an uneven base of the SCLM inclined from west to east. SCLM sequences sampled at this time started mainly from depths of 130 km, but some pipes still showed mantle roots to 250 km. The garnet series demonstrates an inclined straight line pyroxenite P-Fe# trend due to

  7. Efficient Wide Range Converters (EWiRaC): A new family of high efficient AC-DC Converters

    DEFF Research Database (Denmark)

    Petersen, Lars; Andersen, Michael Andreas E.

    2006-01-01

    The performance in terms of efficiency of the existing power supplies used for PFC is very dependent on the input voltage range. The boost converter is the most commonly used PFC converter because of its simplicity and high efficiency. But, the boost converter as well as other known converters...... the converter topology according to the input voltage. This new converter type has been named: efficient wide range converter (EWiRaC). The performance of the EWiRaC is experimental verified in a universal input range (90-270VAC) application with an output voltage of 185VDC capable of 500W output power. The EWi...

  8. Rhenium - osmium heterogeneity of enriched mantle basalts explained by composition and behaviour of mantle-derived sulfides

    Science.gov (United States)

    Harvey, J.; Dale, C. W.; Gannoun, A.; Burton, K. W.

    2010-12-01

    Analyses of enriched mantle (EM) -basalts, using lithophile element-based isotope systems have long provided evidence for discrete, but variable mantle reservoirs [1]. Upon partial melting, the isotopic fingerprint of each reservoir is imparted upon the partial melt produced. However, recent work involving the Re-Os isotope systematics of EM-basalts [2] suggests that it may not be so simple to delimit these previously well defined mantle reservoirs; the “mantle zoo” [3] may contain more reservoirs than previously envisaged. However, a simple model, with varying contributions from two populations of compositionally distinct mantle sulfides can readily account for the observed heterogeneities in Re-Os isotope systematics of such basalts without additional mantle reservoirs. Rhenium-osmium elemental and isotopic analyses of individual sulfide grains separated from spinel lherzolites from Kilbourne Hole, NM, USA demonstrate that two discrete populations of mantle sulfide exist in terms of both Re-Os systematics and textural relationship with co-existing silicates. One population, with a rounded morphology, is preserved in silicate grains and typically possesses high [Os], low [Re] with unradiogenic, typically sub-chondritic, 187Os/188Os attributable to long term isolation in a low-Re environment. By contrast, irregular-shaped sulfides, preserved along silicate grain boundaries, possess low [Os], higher [Re] and a wider range of, but generally supra-chondritic, 187Os/188Os ([Os] typically ≤ 1-2 ppm, 187Os/188Os ≤ 0.3729; this study). This population is thought to represent metasomatic sulfide (e.g. [4,5]). Uncontaminated silicate phases contain negligible Os (mobilized and incorporated into the melt, adding their radiogenic 187Os/188Os signature. Only when sulfides armored within silicates are exposed to the melt through continued partial melting will enclosed sulfides add their high [Os] and unradiogenic 187Os/188Os to the aggregate melt. Platinum-group element

  9. Analog-digital converters for industrial applications including an introduction to digital-analog converters

    CERN Document Server

    Ohnhäuser, Frank

    2015-01-01

    This book offers students and those new to the topic of analog-to-digital converters (ADCs) a broad introduction, before going into details of the state-of-the-art design techniques for SAR and DS converters, including the latest research topics, which are valuable for IC design engineers as well as users of ADCs in applications. The book then addresses important topics, such as correct connectivity of ADCs in an application, the verification, characterization and testing of ADCs that ensure high-quality end products. Analog-to-digital converters are the central element in any data processing system and regulation loops such as modems or electrical motor drives. They significantly affect the performance and resolution of a system or end product. System development engineers need to be familiar with the performance parameters of the converters and understand the advantages and disadvantages of the various architectures. Integrated circuit development engineers have to overcome the problem of achieving high per...

  10. TiConverter: A training image converting tool for multiple-point geostatistics

    Science.gov (United States)

    Fadlelmula F., Mohamed M.; Killough, John; Fraim, Michael

    2016-11-01

    TiConverter is a tool developed to ease the application of multiple-point geostatistics whether by the open source Stanford Geostatistical Modeling Software (SGeMS) or other available commercial software. TiConverter has a user-friendly interface and it allows the conversion of 2D training images into numerical representations in four different file formats without the need for additional code writing. These are the ASCII (.txt), the geostatistical software library (GSLIB) (.txt), the Isatis (.dat), and the VTK formats. It performs the conversion based on the RGB color system. In addition, TiConverter offers several useful tools including image resizing, smoothing, and segmenting tools. The purpose of this study is to introduce the TiConverter, and to demonstrate its application and advantages with several examples from the literature.

  11. The Elephants' Graveyard: Constraints from Mantle Plumes on the Fate of Subducted Slabs and Implications for the Style of Mantle Convection

    Science.gov (United States)

    Lassiter, J. C.

    2007-12-01

    The style of mantle convection (e.g., layered- vs. whole-mantle convection) is one of the most hotly contested questions in the Geological Sciences. Geochemical arguments for and against mantle layering have largely focused on mass-balance evidence for the existence of "hidden" geochemical reservoirs. However, the size and location of such reservoirs are largely unconstrained, and most geochemical arguments for mantle layering are consistent with a depleted mantle comprising most of the mantle mass and a comparatively small volume of enriched, hidden material either within D" or within seismically anomalous "piles" beneath southern Africa and the South Pacific. The mass flux associated with subduction of oceanic lithosphere is large and plate subduction is an efficient driver of convective mixing in the mantle. Therefore, the depth to which oceanic lithosphere descends into the mantle is effectively the depth of the upper mantle in any layered mantle model. Numerous geochemical studies provide convincing evidence that many mantle plumes contain material which at one point resided close to the Earth's surface (e.g., recycled oceanic crust ± sediments, possibly subduction-modified mantle wedge material). Fluid dynamic models further reveal that only the central cores of mantle plumes are involved in melt generation. The presence of recycled material in the sources of many ocean island basalts therefore cannot be explained by entrainment of this material during plume ascent, but requires that recycled material resides within or immediately above the thermo-chemical boundary layer(s) that generates mantle plumes. More recent Os- isotope studies of mantle xenoliths from OIB settings reveal the presence not only of recycled crust in mantle plumes, but also ancient melt-depleted harzburgite interpreted to represent ancient recycled oceanic lithosphere [1]. Thus, there is increasing evidence that subducted slabs accumulate in the boundary layer(s) that provide the source

  12. Radiation effects in power converters: Design of a radiation hardened integrated switching DC/DC converter

    Science.gov (United States)

    Adell, Philippe

    When electronic devices are used in space and military systems, they may be exposed to various types of radiation, including photons, electrons, protons, neutrons, and heavy ions. The effects of radiation on the semiconductor devices within the systems range from gradual degradation to catastrophic failure. In order to design and produce reliable systems for space or military applications, it is necessary to understand the device-level effects of radiation and develop appropriate strategies for reducing system susceptibility. This research focuses on understanding radiation effects in power converters for space and military applications. We show that power converters are very sensitive to radiation (total-dose, single event effects and displacement damage) and that their radiation response is dependent on input bias conditions and load conditions. We compared the radiation hardness of various power converter topologies using experiments and simulations. Evaluation of these designs under different modes of operation is demonstrated to be critical for determining radiation hardness. We emphasize the correlation between radiation effects and the role of the dynamic response of these topologies. For instance, total dose exposure has been found to degrade loop gain and affect regulation in some converters. We propose several radiation-hardening solutions to improve the radiation response of these designs. For instance, we demonstrate the design of a digitally controlled boost converter suitable for space applications based on an SRAM FPGA. A design hardening solution has been developed and successfully applied through VHDL simulations and experiments to assure the continuous operation of the converter in the presence of SEES (more precisely SEFIs). This research led to the design of a digitally controlled radiation hardened integrated switching buck converter. The proposed design is suitable for micro-satellite applications and is based on a high-voltage/CMOS process

  13. Parametric study of minimum converter loss in an energy-storage dc-to-dc converter

    Science.gov (United States)

    Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.

    1982-01-01

    Through a combination of analytical and numerical minimization procedures, a converter design that results in the minimum total converter loss (including core loss, winding loss, capacitor and energy-storage-reactor loss, and various losses in the semiconductor switches) is obtained. Because the initial phase involves analytical minimization, the computation time required by the subsequent phase of numerical minimization is considerably reduced in this combination approach. The effects of various loss parameters on the optimum values of the design variables are also examined.

  14. Evolution of the Oxidation State of the Earth's Mantle

    Science.gov (United States)

    Danielson, L. R.; Righter, K.; Keller, L.; Christoffersen, E.; Rahman, Z.

    2015-01-01

    The oxidation state of the Earth's mantle during formation remains an unresolved question, whether it was constant throughout planetary accretion, transitioned from reduced to oxidized, or from oxidized to reduced. We investigate the stability of Fe3(+) at depth, in order to constrain processes (water, late accretion, dissociation of FeO) which may reduce or oxidize the Earth's mantle. In our previous experiments on shergottite compositions, variable fO2, T, and P less than 4 GPa, Fe3(+)/sigma Fe decreased slightly with increasing P, similar to terrestrial basalt. For oxidizing experiments less than 7GPa, Fe3(+)/sigma Fe decreased as well, but it's unclear from previous modelling whether the deeper mantle could retain significant Fe3(+). Our current experiments expand our pressure range deeper into the Earth's mantle and focus on compositions and conditions relevant to the early Earth. Preliminary multi-anvil experiments with Knippa basalt as the starting composition were conducted at 5-7 GPa and 1800 C, using a molybdenum capsule to set the fO2 near IW, by buffering with Mo-MoO3. TEM and EELS analyses revealed the run products quenched to polycrystalline phases, with the major phase pyroxene containing approximately equal to Fe3(+)/2(+). Experiments are underway to produce glassy samples that can be measured by EELS and XANES, and are conducted at higher pressures.

  15. Olivine crystals align during diffusion creep of Earth's upper mantle.

    Science.gov (United States)

    Miyazaki, Tomonori; Sueyoshi, Kenta; Hiraga, Takehiko

    2013-10-17

    The crystallographic preferred orientation (CPO) of olivine produced during dislocation creep is considered to be the primary cause of elastic anisotropy in Earth's upper mantle and is often used to determine the direction of mantle flow. A fundamental question remains, however, as to whether the alignment of olivine crystals is uniquely produced by dislocation creep. Here we report the development of CPO in iron-free olivine (that is, forsterite) during diffusion creep; the intensity and pattern of CPO depend on temperature and the presence of melt, which control the appearance of crystallographic planes on grain boundaries. Grain boundary sliding on these crystallography-controlled boundaries accommodated by diffusion contributes to grain rotation, resulting in a CPO. We show that strong radial anisotropy is anticipated at temperatures corresponding to depths where melting initiates to depths where strongly anisotropic and low seismic velocities are detected. Conversely, weak anisotropy is anticipated at temperatures corresponding to depths where almost isotropic mantle is found. We propose diffusion creep to be the primary means of mantle flow.

  16. Experimental Constraints on the Chemical Differentiation of Mercurys Mantle

    Science.gov (United States)

    Boujibar, A.; Righter, K.; Pando, K.; Danielson, L.

    2015-01-01

    Mercury is known as being the most reduced terrestrial planet with the highest core/mantle ratio. Results from MESSENGER spacecraft have shown that its surface is FeO-poor (2-4 wt%) and S-rich (up to 6-7 wt%), which confirms the reducing nature of its silicate mantle. In addition several features suggest important melting stages of the Mercurian mantle: widespread volcanic deposits on its surface, a high crustal thickness (approximately 10% of the planet's volume) and chemical compositions of its surface suggesting several stages of differentiation and remelting processes. Therefore it is likely that igneous processes like magma ocean crystallization and continuous melting have induced chemical and mineralogical heterogeneities in the Mercurian mantle. The extent and nature of compositional variations produced by partial melting remains poorly constrained for the particular compositions of Mercury (very reducing conditions, low FeO-contents and high sulfur-contents). Melting experiments with bulk Mercury-analogue compositions are scarce and with poorly con-trolled starting compositions. Therefore additional experimental data are needed to better understand the differentiation processes that lead to the observed chemical compositions of Mercury's surface.

  17. Dehydrogenation of goethite in Earth’s deep lower mantle

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qingyang; Kim, Duck Young; Liu, Jin; Meng, Yue; Yang, Liuxiang; Zhang, Dongzhou; Mao, Wendy L.; Mao, Ho-kwang

    2017-01-31

    The cycling of hydrogen influences the structure, composition, and stratification of Earth’s interior. Our recent discovery of pyrite-structured iron peroxide (designated as the P phase) and the formation of the P phase from dehydrogenation of goethite FeO2H implies the separation of the oxygen and hydrogen cycles in the deep lower mantle beneath 1,800 km. Here we further characterize the residual hydrogen, x, in the P-phase FeO2Hx. Using a combination of theoretical simulations and high-pressure–temperature experiments, we calibrated the x dependence of molar volume of the P phase. Within the current range of experimental conditions, we observed a compositional range of P phase of 0.39 < x < 0.81, corresponding to 19–61% dehydrogenation. Increasing temperature and heating time will help release hydrogen and lower x, suggesting that dehydrogenation could be approaching completion at the high-temperature conditions of the lower mantle over extended geological time. Our observations indicate a fundamental change in the mode of hydrogen release from dehydration in the upper mantle to dehydrogenation in the deep lower mantle, thus differentiating the deep hydrogen and hydrous cycles.

  18. Petrological evidence for secular cooling in mantle plumes.

    Science.gov (United States)

    Herzberg, Claude; Gazel, Esteban

    2009-04-02

    Geological mapping and geochronological studies have shown much lower eruption rates for ocean island basalts (OIBs) in comparison with those of lavas from large igneous provinces (LIPs) such as oceanic plateaux and continental flood provinces. However, a quantitative petrological comparison has never been made between mantle source temperature and the extent of melting for OIB and LIP sources. Here we show that the MgO and FeO contents of Galapagos-related lavas and their primary magmas have decreased since the Cretaceous period. From petrological modelling, we infer that these changes reflect a cooling of the Galapagos mantle plume from a potential temperature of 1,560-1,620 degrees C in the Cretaceous to 1,500 degrees C at present. Iceland also exhibits secular cooling, in agreement with previous studies. Our work provides quantitative petrological evidence that, in general, mantle plumes for LIPs with Palaeocene-Permian ages were hotter and melted more extensively than plumes of more modern ocean islands. We interpret this to reflect episodic flow from lower-mantle domains that are lithologically and geochemically heterogeneous.

  19. Origin of azimuthal seismic anisotropy in oceanic plates and mantle

    Science.gov (United States)

    Becker, Thorsten W.; Conrad, Clinton P.; Schaeffer, Andrew J.; Lebedev, Sergei

    2014-09-01

    Seismic anisotropy is ubiquitous in the Earth's mantle but strongest in its thermo-mechanical boundary layers. Azimuthal anisotropy in the oceanic lithosphere and asthenosphere can be imaged by surface waves and should be particularly straightforward to relate to well-understood plate kinematics and large-scale mantle flow. However, previous studies have come to mixed conclusions as to the depth extent of the applicability of paleo-spreading and mantle flow models of anisotropy, and no simple, globally valid, relationships exist. Here, we show that lattice preferred orientation (LPO) inferred from mantle flow computations produces a plausible global background model for asthenospheric anisotropy underneath oceanic lithosphere. The same is not true for absolute plate motion (APM) models. A ˜200 km thick layer where the flow model LPO matches observations from tomography lies just below the ˜1200 °C isotherm of a half-space cooling model, indicating strong temperature-dependence of the processes that control the development of azimuthal anisotropy. We infer that the depth extent of shear, and hence the thickness of a relatively strong oceanic lithosphere, can be mapped this way. These findings for the background model, and ocean-basin specific deviations from the half-space cooling pattern, are found in all of the three recent and independent tomographic models considered. Further exploration of deviations from the background model may be useful for general studies of oceanic plate formation and dynamics as well as regional-scale tectonic analyses.

  20. Geochemical heterogeneity in the Arctic mantle at Gakkel Ridge

    Science.gov (United States)

    D'Errico, M. E.; Warren, J. M.; Godard, M.

    2014-12-01

    Conductive cooling due to ultraslow spreading has been suggested to limit partial melting of the mantle and crustal production at Gakkel Ridge. In addition, the thick lithosphere induced by cooling should significantly control melt migration and extraction. To explore these effects at ultraslow spreading rates, major and trace element concentrations in pyroxene minerals are presented for 14 dredged Gakkel abyssal peridotites. Samples from the same dredge and among dredges reveal wide compositional variation. Trace element compositions of lherzolites reflect 4-6% non-modal fractional mantle melting. However, these high degrees of melting without a corresponding amount of oceanic crust suggest the occurrence of infertile mantle due to ancient melting event(s). In addition, high degrees of melt depletion at short length-scales (earth elements that can be fit by 6 to ≥13% non-modal melting, but this results in modeled light rare earth element contents that are too low relative to observed concentrations. Instead, harzburgite trace element patterns require open-system melting involving interaction with a percolating melt. Extreme enrichments in highly incompatible elements also suggest the occurrence of late-stage refertilization and melt entrapment. Modeling of several different source melt compositions indicates that the trapped melt was generated from garnet field-equilibrated peridotite. Overall, the compositional variability in Gakkel peridotite samples reflects a heterogeneous mantle resulting from inherited depletion and recent melt percolation and entrapment.

  1. Using pattern recognition to infer parameters governing mantle convection

    Science.gov (United States)

    Atkins, Suzanne; Valentine, Andrew P.; Tackley, Paul J.; Trampert, Jeannot

    2016-08-01

    The results of mantle convection simulations are fully determined by the input parameters and boundary conditions used. These input parameters can be for initialisation, such as initial mantle temperature, or can be constant values, such as viscosity exponents. However, knowledge of Earth-like values for many input parameters are very poorly constrained, introducing large uncertainties into the simulation of mantle flow. Convection is highly non-linear, therefore linearised inversion methods cannot be used to recover past configurations over more than very short periods of time, which makes finding both initial and constant simulation input parameters very difficult. In this paper, we demonstrate a new method for making inferences about simulation input parameters from observations of the mantle temperature field after billions of years of convection. The method is fully probabilistic. We use prior sampling to construct probability density functions for convection simulation input parameters, which are represented using neural networks. Assuming smoothness, we need relatively few samples to make inferences, making this approach much more computationally tractable than other probabilistic inversion methods. As a proof of concept, we show that our method can invert the amplitude spectra of temperature fields from 2D convection simulations, to constrain yield stress, surface reference viscosity and the initial thickness of primordial material at the CMB, for our synthetic test cases. The best constrained parameter is yield stress. The reference viscosity and initial thickness of primordial material can also be inferred reasonably well after several billion years of convection.

  2. Investigations of Eurasian Seismic Sources and Upper Mantle Structure

    Science.gov (United States)

    1989-05-25

    in classical Earth models include the free surface, the Mohorovicic (M) discontinuity, the core-mantle boundary (CMB), and the inner core-outer core...rather to the superposition of first- and higher-order reverberations generated at the Mohorovicic (M) discontinuity. Figure 3.1 depicts the effect of

  3. Electrical Conductivity of the Lower-Mantle Ferropericlase

    Energy Technology Data Exchange (ETDEWEB)

    Lin, J F; Weir, S T; Jackson, D D; Evans, W J; Vohra, Y K; Qiu, W; Yoo, C S

    2007-04-19

    Electrical conductivity of the lower-mantle ferropericlase-(Mg{sub 0.75},Fe{sub 0.25})O has been studied using designer diamond anvils to pressures over one megabar and temperatures up to 500 K. The electrical conductivity of (Mg{sub 0.75},Fe{sub 0.25})O gradually rises by an order of magnitude up to 50 GPa but decreases by a factor of approximately three between 50 to 70 GPa. This decrease in the electrical conductivity is attributed to the electronic high-spin to low-spin transition of iron in ferropericlase. That is, the electronic spin transition of iron results in a decrease in the mobility and/or density of the charge transfer carriers in the low-spin ferropericlase. The activation energy of the low-spin ferropericlase is 0.27 eV at 101 GPa, similar to that of the high-spin ferropericlase at relatively low temperatures. Our results indicate that low-spin ferropericlase exhibits lower electrical conductivity than high-spin ferropericlase, which needs to be considered in future geomagnetic models for the lower mantle. The extrapolated electrical conductivity of the low-spin ferropericlase, together with that of silicate perovskite, at the lower mantle pressure-temperature conditions is consistent with the model electrical conductivity profile of the lower mantle.

  4. Seismic structure of the mantle ; from subduction zone to craton

    NARCIS (Netherlands)

    Kennett, B.L.N.; Hilst, R.D. van der

    1998-01-01

    Seismological techniques have provided much of the currently available information on the internal structure of the Earth, and in particular on the mantle. Early studies revealed the need for an increase in seismic velocity with depth in the Earth, and by 1915 Gutenberg was able to make a good estim

  5. Upper mantle viscosity and lithospheric thickness under Iceland

    NARCIS (Netherlands)

    Barnhoorn, A.; Wal, W. van der; Drury, M.R.

    2011-01-01

    Deglaciation during the Holocene on Iceland caused uplift due to glacial isostatic adjustment. Relatively low estimates for the upper mantle viscosity and lithospheric thickness result in rapid uplift responses to the deglaciation cycles on Iceland. The relatively high temperatures of the upper mant

  6. Trench migration, net rotation and slab mantle coupling

    Science.gov (United States)

    Funiciello, F.; Faccenna, C.; Heuret, A.; Lallemand, S.; Di Giuseppe, E.; Becker, T. W.

    2008-07-01

    Laboratory models have been conducted to improve our understanding of the role that the resistance of the slab to bending and its coupling to the ambient mantle play in subduction dynamics over geological time scales. Our models are set up with a viscous plate of silicone (lithosphere) subducting under negative buoyancy in a viscous layer of glucose syrup (mantle). For our study, the lithosphere/upper mantle viscosity contrast has been systematically varied, from ~ 10 to ~ 10 5 in order to explore the parameter space between weak and strong slab dynamics. We found that subduction is characterized by a retreating mode for viscosity ratios > 10 4, by the coexistence of a retreating mode and an advancing mode for viscosity ratios between ~ 10 4 and ~ 10 2, and quasi-stationary, Rayleigh-Taylor like behaviour for ratios < 10 2. By combining our experimental results and kinematic data from current subduction zones in four reference frames which differ in the amount of net rotation, we infer that a lithosphere/upper mantle viscosity contrast of 150-500 is necessary to obtain realistic trench/subducting plate velocity ratios as well as the variability of subduction styles observed in nature.

  7. Treatment of older patients with mantle-cell lymphoma

    DEFF Research Database (Denmark)

    Kluin-Nelemans, H C; Hoster, E; Hermine, O;

    2012-01-01

    The long-term prognosis for older patients with mantle-cell lymphoma is poor. Chemoimmunotherapy results in low rates of complete remission, and most patients have a relapse. We investigated whether a fludarabine-containing induction regimen improved the complete-remission rate and whether mainte...

  8. Pitfalls in modeling mantle convection with internal heat production

    Science.gov (United States)

    Korenaga, Jun

    2017-05-01

    The mantle of the Earth, and probably of other terrestrial planets as well, is heated from below and within. The heating mode of mantle convection is thus mixed heating, and it is also time dependent because the amount of heat-producing isotopes in the mantle is steadily decreasing by radioactive decay and because the basal heat flux originating in the cooling of the core can vary with time. This mode of transient mixed heating presents its own challenges to the study of mantle convection, but such difficulties are not always appreciated in the recent literature. The purpose of this tutorial is to clarify the issue of heating mode by explaining relevant concepts in a coherent manner, including the internal heating ratio, the Urey ratio, secular cooling, and the connection between the thermal budget of the Earth and the geochemical models of the Earth. The importance of such basic concepts will be explained with some illustrative examples in the context of the thermal evolution of the Earth, and a summary of common pitfalls will be provided, with a possible strategy for how to avoid them.

  9. Mantle geoneutrinos in KamLAND and Borexino

    CERN Document Server

    Fiorentini, G; Lisi, E; Mantovani, F; Rotunno, A M

    2012-01-01

    The KamLAND and Borexino experiments have observed, each at ~4 sigma level, signals of electron antineutrinos produced in the decay chains of thorium and uranium in the Earth's crust and mantle (Th and U geoneutrinos). Various pieces of geochemical and geophysical information allow an estimation of the crustal geoneutrino flux components with relatively small uncertainties. The mantle component may then be inferred by subtracting the estimated crustal flux from the measured total flux. To this purpose, we analyze in detail the experimental Th and U geoneutrino event rates in KamLAND and Borexino, including neutrino oscillation effects. We estimate the crustal flux at the two detector sites, using state-of-the-art information about the Th and U distribution on global and local scales. We find that crust-subtracted signals show hints of a residual mantle component, emerging at ~2.4 sigma level by combining the KamLAND and Borexino data. The inferred mantle flux slightly favors scenarios with relatively high Th ...

  10. Mantle structure and tectonic history of SE Asia

    NARCIS (Netherlands)

    Hall, Robert; Spakman, Wim|info:eu-repo/dai/nl/074103164

    2015-01-01

    Seismic travel-time tomography of the mantle under SE Asia reveals patterns of subduction-related seismic P-wave velocity anomalies that are of great value in helping to understand the region's tectonic development. We discuss tomography and tectonic interpretations of an area centred on Indonesia

  11. Modeling the effect of water on mantle rheology

    Science.gov (United States)

    Bounama, CH.; Franck, S.

    1994-01-01

    To study the thermal history of the Earth we use a parameterized model of mantle convection. This model includes a mathematical description of de- and regassing processes of water from the Earth's mantle. The rates of this processes are considered to be directly proportional to the seafloor spreading rate. The kinematic viscosity of the mantle depends on the temperature/pressure as well as on the volatile content. Dissolved volatiles such as water weaken the minerals by reducing their activation energy for solid state creep. Karato and Toriumi showed a power law dependence between creep rate and water fugacity derived from experimental results. Therefore, we use such flow parameters of diffusion creep in olivine under wet and dry conditions to calculate the mantle viscosity as a function of the water content. Because the creep rate is proportional to the concentration of water-related point deflects we assume that the water fugacity is proportional to the water weight fraction. An equation for the steady-state strain rate under wet conditions is established. To assess the unknown constant K in this equation, we use flow law parameters given by Karato and Wu as well as the results of McGovern and Schubert.

  12. Mantle cell lymphoma in the orbital and adnexal region

    DEFF Research Database (Denmark)

    Rasmussen, Peter Kristian; Sjö, L D; Prause, J U

    2009-01-01

    AIMS: To characterise clinicopathological features of mantle cell lymphoma (MCL) in the orbital and adnexal region. METHODS: Data on lymphoid lesions were retrieved searching the Danish Ocular Lymphoma Database 1980-2005. Specimens were collected from Danish pathological departments and re-evalua...

  13. Laboratory-Scale Simulation of Spiral Plumes in the Mantle

    CERN Document Server

    Sharifulin, A N

    2012-01-01

    On the basis of laboratory simulation a mechanism is established for the formation of the upper mantle convection spiral plumes from a hot point in the presence of a roll-type large-scale convective flow. The observed plume has horizontal sections near the upper limit, which may lead to the formation of chains of volcanic islands.

  14. Zinc isotope fractionation during mantle melting and constraints on the Zn isotope composition of Earth's upper mantle

    Science.gov (United States)

    Wang, Ze-Zhou; Liu, Sheng-Ao; Liu, Jingao; Huang, Jian; Xiao, Yan; Chu, Zhu-Yin; Zhao, Xin-Miao; Tang, Limei

    2017-02-01

    The zinc (Zn) stable isotope system has great potential for tracing planetary formation and differentiation processes due to its chalcophile, lithophile and moderately volatile character. As an initial approach, the terrestrial mantle, and by inference, the bulk silicate Earth (BSE), have previously been suggested to have an average δ66Zn value of ∼+0.28‰ (relative to JMC 3-0749L) primarily based on oceanic basalts. Nevertheless, data for mantle peridotites are relatively scarce and it remains unclear whether Zn isotopes are fractionated during mantle melting. To address this issue, we report high-precision (±0.04‰; 2SD) Zn isotope data for well-characterized peridotites (n = 47) from cratonic and orogenic settings, as well as their mineral separates. Basalts including mid-ocean ridge basalts (MORB) and ocean island basalts (OIB) were also measured to avoid inter-laboratory bias. The MORB analyzed have homogeneous δ66Zn values of +0.28 ± 0.03‰ (here and throughout the text, errors are given as 2SD), similar to those of OIB obtained in this study and in the literature (+0.31 ± 0.09‰). Excluding the metasomatized peridotites that exhibit a wide δ66Zn range of -0.44‰ to +0.42‰, the non-metasomatized peridotites have relatively uniform δ66Zn value of +0.18 ± 0.06‰, which is lighter than both MORB and OIB. This difference suggests a small but detectable Zn isotope fractionation (∼0.1‰) during mantle partial melting. The magnitude of inter-mineral fractionation between olivine and pyroxene is, on average, close to zero, but spinels are always isotopically heavier than coexisting olivines (Δ66ZnSpl-Ol = +0.12 ± 0.07‰) due to the stiffer Zn-O bonds in spinel than silicate minerals (Ol, Opx and Cpx). Zinc concentrations in spinels are 11-88 times higher than those in silicate minerals, and our modelling suggests that spinel consumption during mantle melting plays a key role in generating high Zn concentrations and heavy Zn isotopic

  15. Improved design of mantle tanks for small low flow SDHW systems

    DEFF Research Database (Denmark)

    Furbo, Simon; Knudsen, Søren

    2006-01-01

    Side-by-side tests of two small low flow SDHW systems based on mantle tanks have been carried out under the same test conditions in a laboratory test facility. The systems are identical with exception of the mantle tanks. One of the mantle tanks has the mantle inlet port located at the top...... of the mantle and the other mantle tank has the mantle inlet port moved 0.175 m down from the top of the mantle. The thermal performance is almost the same for the two systems in the measuring period of 252 days. The solar fractions were 0.66 and 0.68 for the two systems. The tests showed also that the system...... with the low mantle inlet perform better than the system with the high mantle inlet in periods with low solar fractions, that is in less sunny periods. Further, calculations with a simulation model for low flow SDHW systems based on mantle tanks showed that mantle tanks currently marketed can be greatly...

  16. Mapping mantle flow during retreating subduction: Laboratory models analyzed by feature tracking

    Science.gov (United States)

    Funiciello, F.; Moroni, M.; Piromallo, C.; Faccenna, C.; Cenedese, A.; Bui, H. A.

    2006-03-01

    Three-dimensional dynamically consistent laboratory models are carried out to model the large-scale mantle circulation induced by subduction of a laterally migrating slab. A laboratory analogue of a slab-upper mantle system is set up with two linearly viscous layers of silicone putty and glucose syrup in a tank. The circulation pattern is continuously monitored and quantitatively estimated using a feature tracking image analysis technique. The effects of plate width and mantle viscosity/density on mantle circulation are systematically considered. The experiments show that rollback subduction generates a complex three-dimensional time-dependent mantle circulation pattern characterized by the presence of two distinct components: the poloidal and the toroidal circulation. The poloidal component is the answer to the viscous coupling between the slab motion and the mantle, while the toroidal one is produced by lateral slab migration. Spatial and temporal features of mantle circulation are carefully analyzed. These models show that (1) poloidal and toroidal mantle circulation are both active since the beginning of the subduction process, (2) mantle circulation is intermittent, (3) plate width affects the velocity and the dimension of subduction induced mantle circulation area, and (4) mantle flow in subduction zones cannot be correctly described by models assuming a two-dimensional steady state process. We show that the intermittent toroidal component of mantle circulation, missed in those models, plays a crucial role in modifying the geometry and the efficiency of the poloidal component.

  17. MAGIC: Model and Graphic Information Converter

    Science.gov (United States)

    Herbert, W. C.

    2009-01-01

    MAGIC is a software tool capable of converting highly detailed 3D models from an open, standard format, VRML 2.0/97, into the proprietary DTS file format used by the Torque Game Engine from GarageGames. MAGIC is used to convert 3D simulations from authoritative sources into the data needed to run the simulations in NASA's Distributed Observer Network. The Distributed Observer Network (DON) is a simulation presentation tool built by NASA to facilitate the simulation sharing requirements of the Data Presentation and Visualization effort within the Constellation Program. DON is built on top of the Torque Game Engine (TGE) and has chosen TGE's Dynamix Three Space (DTS) file format to represent 3D objects within simulations.

  18. Faults and Diagnosis Systems in Power Converters

    DEFF Research Database (Denmark)

    Lee, Kyo-Beum; Choi, Uimin

    2014-01-01

    efforts have been put into making these systems better in terms of reliability in order to achieve high power source availability, reduce the cost of energy and also increase the reliability of overall systems. Among the components used in power converters, a power device and a capacitor fault occurs most......A power converter is needed in almost all kinds of renewable energy systems and drive systems. It is used both for controlling the renewable source and for interfacing with the load, which can be grid-connected or working in standalone mode. Further, it drives the motors efficiently. Increasing...... frequently. Therefore, it is important to monitor the power device and capacitor fault to increase the reliability of power electronics. In this chapter, the diagnosis methods for power device fault will be discussed by dividing into open- and short-circuit faults. Then, the condition monitoring methods...

  19. Strained quantum well photovoltaic energy converter

    Science.gov (United States)

    Freundlich, Alexandre (Inventor); Renaud, Philippe (Inventor); Vilela, Mauro Francisco (Inventor); Bensaoula, Abdelhak (Inventor)

    1998-01-01

    An indium phosphide photovoltaic cell is provided where one or more quantum wells are introduced between the conventional p-conductivity and n-conductivity indium phosphide layer. The approach allows the cell to convert the light over a wider range of wavelengths than a conventional single junction cell and in particular convert efficiently transparency losses of the indium phosphide conventional cell. The approach hence may be used to increase the cell current output. A method of fabrication of photovoltaic devices is provided where ternary InAsP and InGaAs alloys are used as well material in the quantum well region and results in an increase of the cell current output.

  20. Component technology for Stirling power converters

    Science.gov (United States)

    Thieme, Lanny G.

    NASA Lewis Research Center has organized a component technology program as part of the efforts to develop Stirling converter technology for space power applications. The Stirling Space Power Program is part of the NASA High Capacity Power Project of the Civil Space Technology Initiative (CSTI). NASA Lewis is also providing technical management for the DOE/Sandia program to develop Stirling converters for solar terrestrial power producing electricity for the utility grid. The primary contractors for the space power and solar terrestrial programs develop component technologies directly related to their goals. This Lewis component technology effort, while coordinated with the main programs, aims at longer term issues, advanced technologies, and independent assessments. An overview of work on linear alternators, engine/alternator/load interactions and controls, heat exchangers, materials, life and reliability, and bearings is presented.

  1. A Variational Inequality from Pricing Convertible Bond

    Directory of Open Access Journals (Sweden)

    Yan Huiwen

    2011-01-01

    Full Text Available The model of pricing American-style convertible bond is formulated as a zero-sum Dynkin game, which can be transformed into a parabolic variational inequality (PVI. The fundamental variable in this model is the stock price of the firm which issued the bond, and the differential operator in PVI is linear. The optimal call and conversion strategies correspond to the free boundaries of PVI. Some properties of the free boundaries are studied in this paper. We show that the bondholder should convert the bond if and only if the price of the stock is equal to a fixed value, and the firm should call the bond back if and only if the price is equal to a strictly decreasing function of time. Moreover, we prove that the free boundaries are smooth and bounded. Eventually we give some numerical results.

  2. MOCCASIN: converting MATLAB ODE models to SBML.

    Science.gov (United States)

    Gómez, Harold F; Hucka, Michael; Keating, Sarah M; Nudelman, German; Iber, Dagmar; Sealfon, Stuart C

    2016-06-15

    MATLAB is popular in biological research for creating and simulating models that use ordinary differential equations (ODEs). However, sharing or using these models outside of MATLAB is often problematic. A community standard such as Systems Biology Markup Language (SBML) can serve as a neutral exchange format, but translating models from MATLAB to SBML can be challenging-especially for legacy models not written with translation in mind. We developed MOCCASIN (Model ODE Converter for Creating Automated SBML INteroperability) to help. MOCCASIN can convert ODE-based MATLAB models of biochemical reaction networks into the SBML format. MOCCASIN is available under the terms of the LGPL 2.1 license (http://www.gnu.org/licenses/lgpl-2.1.html). Source code, binaries and test cases can be freely obtained from https://github.com/sbmlteam/moccasin : mhucka@caltech.edu More information is available at https://github.com/sbmlteam/moccasin. © The Author 2016. Published by Oxford University Press.

  3. Dynamics of Pre-3 Ga Crust-Mantle Evolution

    Science.gov (United States)

    Patchett, P. J.; Chase, C. G.; Vervoort, J. D.

    2004-05-01

    During 3.0 to 2.7 Ga, the Earth's crust underwent a non-uniformitarian change from a pre-3.0 Ga environment where long-term preservation of cratons was rare and difficult, to post-2.7 Ga conditions where cratons were established and new continental crust generation took place largely at craton margins. Many models view the Earth's surface during pre-3 Ga time as broadly equivalent to the post 2.7 Ga regime. Any such uniformitarian or gradual evolution cannot explain the conundrum that only a tiny amount of pre-3 Ga crust is preserved today coupled with the fact that very little pre-3 Ga crust was incorporated into the large amount of new craton that came into existence during 3.0-2.7 Ga. If large volumes of pre-3 Ga continental crust existed, it disappeared either just prior to 3 Ga, or during 3.0-2.7 Ga. To explain sudden appearance of surviving but dominantly juvenile continental crust in a model where continents were large prior to 3 Ga, it would be necessary either that pre-3 Ga continent was recycled into the mantle at sites systematically different from those where new 3.0-2.7 Ga crust was made, or that widespread continent destruction preceded the 3.0-2.7 Ga crustal genesis. From expected mantle overturn in response to the heat budget, it is likely that most pre-3 Ga crust was both more mafic and shorter-lived than after 3 Ga. Although Nd and Hf ratios for pre-3 Ga rocks are uncertain due to polymetamorphism, it appears that depleted upper mantle was widespread by 2.7 Ga, even pre-3 Ga. Depletion may have been largely achieved by formation, subduction and storage of mafic crust for periods of 200-500 m.y. The rapid change to large surviving continents during 3.0-2.7 Ga was due to declining mantle overturn, and particularly to development of the ability to maintain subduction in one zone of the earth's surface for the time needed to allow evolution to felsic igneous rock compositions. In as much as storage of subducted slabs is probably occurring today, and

  4. Morphology of seismically slow lower-mantle structures

    Science.gov (United States)

    Cottaar, Sanne; Lekic, Vedran

    2016-11-01

    Large low shear velocity provinces (LLSVPs), whose origin and dynamic implication remain enigmatic, dominate the lowermost mantle. For decades, seismologists have created increasingly detailed pictures of the LLSVPs through tomographic models constructed with different modeling methodologies, data sets, parametrizations and regularizations. Here, we extend the cluster analysis methodology of Lekic et al., to classify seismic mantle structure in five recent global shear wave speed (VS) tomographic models into three groups. By restricting the analysis to moving depth windows of the radial profiles of VS, we assess the vertical extent of features. We also show that three clusters are better than two (or four) when representing the entire lower mantle, as the boundaries of the three clusters more closely follow regions of high lateral VS gradients. Qualitatively, we relate the anomalously slow cluster to the LLSVPs, the anomalously fast cluster to slab material entering the lower mantle and the neutral cluster to `background' lower mantle material. We obtain compatible results by repeating the analysis on recent global P-wave speed (VP) models, although we find less agreement across VP models. We systematically show that the clustering results, even in detail, agree remarkably well with a wide range of local waveform studies. This suggests that the two LLSVPs consist of multiple internal anomalies with a wide variety of morphologies, including shallowly to steeply sloping, and even overhanging, boundaries. Additionally, there are indications of previously unrecognized meso-scale features, which, like the Perm anomaly, are separated from the two main LLSVPs beneath the Pacific and Africa. The observed wide variety of structure size and morphology offers a challenge to recreate in geodynamic models; potentially, the variety can result from various degrees of mixing of several compositionally distinct components. Finally, we obtain new, much larger estimates of the volume

  5. Mantle Sulfur Cycle: A Case for Non-Steady State ?

    Science.gov (United States)

    Cartigny, Pierre; Labidi, Jabrane

    2016-04-01

    Data published over the last 5 years show that the early inference that mantle is isotopically homogeneous is no more valid. Instead, new generation data on lavas range over a significant 34S/32S variability of up to 5‰ with δ 34S values often correlated to Sr- and Nd-isotope compositions. This new set of data also reveals the Earth's mantle to have a sub-chondritic 34S/32S ratio, by about ˜ 1‰. We will present at the conference our published and unpublished data on samples characterizing the different mantle components (i.e. EM1, EM2, HIMU and LOMU). All illustrate 34S-enrichments compared to MORB with Δ 33S and Δ 36S values indistinguishable from CDT or chondrites at the 0.03‰ level. These data are consistent with the recycling of subducted components carrying sulfur with Δ 33S and Δ 36S-values close to zero. Archean rocks commonly display Δ 33S and Δ 36S values deviating from zero by 1 to 10 ‰. The lack of variations for Δ 33S and Δ 36S values in present day lava argue against the sampling of any subducted protolith of Archean age in their mantle source. Instead, our data are consistent with the occurrence of Proterozoic subducted sulfur in the source of the EM1, EM2, LOMU and HIMU endmember at the St-Helena island. This is in agreement with the age of those components early derived through the use of the Pb isotope systematic. Currently, the negative δ 34S-values of the depleted mantle seem to be associated with mostly positive values of enriched components. This would be inconsistent with the concept a steady state of sulfur. Assuming that the overall observations of recycled sulfur are not biased, the origin of such a non-steady state remains unclear. It could be related to the relatively compatible behavior of sulfur during partial melting, as the residue of present-day melting can be shown to always contain significant amounts of sulfide (50{%} of what is observed in a fertile source). This typical behavior likely prevents an efficient

  6. Bases of the Mantle-Carbonatite Conception of Diamond Genesis

    Science.gov (United States)

    Litvin, Yuriy; Spivak, Anna; Kuzyura, Anastasia

    2016-04-01

    In the mantle-carbonatite conception of diamond genesis, the results of physic-chemical experiments are coordinated with the data of analytic mineralogy of primary inclusions in natural diamonds. Generalization of the solutions of principal genetic problems constitutes the bases of the conception. The solutions are following: (1) it is grounded that diamond-parental melts of the upper mantle have peridotite/eclogite - carbonatite - carbon compositions, of the transition zone - (wadsleite↔ringwoodite) - majorite - stishovite - carbonatite - carbon compositions, and of the lower mantle - periclase/wustite - bridgmanite - Ca-perovskite -stishovite - carbonatite - carbon compositions; (2) a construction of generalized diagrams for the diamond-parental media, which reveal changeable compositions of the growth melts of diamonds and associated phases, their genetic relations to the mantle substance, and classification connections of the primary inclusions in natural diamonds; (3) experimental equilibrium phase diagrams of syngenesis of diamonds and primary inclusions, which characterize the nucleation and growth conditions of diamonds and a capture of paragenetic and xenogenetic minerals by the growing diamonds; (4) a determination of the phase diagrams of diamonds and inclusions syngenesis under the regime of fractional crystallization, which discover the regularities of ultrabasic-basic evolution and paragenesis transitions in the diamond-forming systems of the upper and lower mantle. The evidence of the physic-chemically united mode of diamond genesis at the mantle depths with different mineralogy is obtained. References. Litvin Yu.A. (2007). High-pressure mineralogy of diamond genesis. In: Advances in High-Pressure Mineralogy (edited by Eiji Ohtani), Geological Society of America Special paper 421, 83-103. Litvin Yu.A. (2012). Experimental study of physic-chemical conditions of natural diamond formation on an example of the eclogite

  7. Europium and strontium anomalies in the MORB source mantle

    Science.gov (United States)

    Tang, Ming; McDonough, William F.; Ash, Richard D.

    2017-01-01

    Lower crustal recycling depletes the continental crust of Eu and Sr and returns Eu and Sr enriched materials into the mantle (e.g., Tang et al., 2015, Geology). To test the hypothesis that the MORB source mantle balances the Eu and Sr deficits in the continental crust, we carried out high precision Eu/Eu∗ and Sr/Sr∗ measurement for 72 MORB glasses with MgO >8.5% from the Pacific, Indian, and Atlantic mid-ocean ridges. MORB glasses with MgO ⩾ 9 wt.% have a mean Eu/Eu∗ of 1.025 ± 0.025 (2 σm, n = 46) and Sr/Sr∗ of 1.242 ± 0.093 (2 σm, n = 41) and these ratios are positively correlated. These samples show both positive and negative Eu and Sr anomalies, with no correlations between Eu/Eu∗ vs. MgO or Sr/Sr∗ vs. MgO, suggesting that the anomalies are not produced by plagioclase fractionation at MgO >9 wt.% and, thus, other processes must be responsible for generating the anomalies. We term these MORB samples primitive MORBs, as they record the melt Eu/Eu∗ and Sr/Sr∗ before plagioclase fractionation. Consequently, the mean oceanic crust, including cumulates, has a bulk Eu/Eu∗ of ∼1 and 20% Sr excess. Considering that divalent Sr and Eu(II) diffuse faster than trivalent Pr, Nd, Sm, and Gd, we evaluated this kinetic effect on Sm-Eu-Gd and Pr-Sr-Nd fractionations during spinel peridotite partial melting in the MORB source mantle. Our modeling shows that the correlated Eu and Sr anomalies seen in primitive MORBs may result from disequilibrium mantle melting. Melt fractions produced during early- and late-stage melting may carry positive and negative Eu and Sr anomalies, respectively, that overlap with the ranges documented in primitive MORBs. Because the net effect of disequilibrium melting is to produce partial melts with bulk positive Eu and Sr anomalies, the MORB source mantle must have Eu/Eu∗ continental crustal materials, which have positive Eu and Sr anomalies, are partially mixed into the upper mantle (i.e., MORB source region), a

  8. Multiport Resonant DC-DC Converter

    OpenAIRE

    Tran, Yan-Kim; Dujic, Drazen; Barrade, Philippe

    2015-01-01

    his paper presents a multiport galvanically isolated LLC resonant DC-DC converter suitable for DC applications. A three-port structure is analyzed, with full bidirectional power flow capabilities, simple control and behavior similar to that expected from a DC transformer. Each port is equipped with half-bridge modules accompanied with tuned resonant tank, partly realized with elements of a multi- winding high frequency transformer. With some restrictions that are explained in the paper, each ...

  9. Converting Student Support Services to Online Delivery

    OpenAIRE

    David E. Brigham

    2001-01-01

    This case study describes how Regents College (soon to be Excelsior College), an accredited, private, distance education institution with administrative offices in Albany, New York addressed the structural, management, and resource issues that came into play when converting distance education programs from print-based and telephone delivery to online delivery. The study uses a systems framework to describe and analyze the circumstances and issues surrounding the creation of six student suppor...

  10. Reversible thyristor converters of brushless synchronous compensators

    Directory of Open Access Journals (Sweden)

    А.М.Galynovskiy

    2013-12-01

    Full Text Available Behavior of models of three-phase-to-single-phase rotary reversible thyristor converters of brushless synchronous compensators in a circuit simulation system is analyzed. It is shown that combined control mode of opposite-connected thyristors may result in the exciter armature winding short circuits both at the thyristor feed-forward and lagging current delay angles. It must be taken into consideration when developing brushless compensator excitation systems.

  11. (Convertible) Undeniable Signatures Without Random Oracles

    Science.gov (United States)

    Yuen, Tsz Hon; Au, Man Ho; Liu, Joseph K.; Susilo, Willy

    We propose a convertible undeniable signature scheme without random oracles. Our construction is based on Waters' and Kurosawa and Heng's schemes that were proposed in Eurocrypt 2005. The security of our scheme is based on the CDH and the decision linear assumption. Comparing only the part of undeniable signatures, our scheme uses more standard assumptions than the existing undeniable signatures without random oracles due to Laguillamie and Vergnaud.

  12. Fracture imaging with converted elastic waves

    Energy Technology Data Exchange (ETDEWEB)

    Nihei, K.T.; Nakagawa, S.; Myer, L.R.

    2001-05-29

    This paper examines the seismic signatures of discrete, finite-length fractures, and outlines an approach for elastic, prestack reverse-time imaging of discrete fractures. The results of this study highlight the importance of incorporating fracture-generated P-S converted waves into the imaging method, and presents an alternate imaging condition that can be used in elastic reverse-time imaging when a direct wave is recorded (e.g., for crosswell and VSP acquisition geometries).

  13. Spectral converters and luminescent solar concentrators

    CERN Document Server

    Scudo, Petra F; Fusco, Roberto

    2009-01-01

    In this paper we present a comprehensive theoretical description of molecular spectral converters in the specific context of Luminescent Solar Concentrators (LSCs). The theoretical model is an extension to a three-level system interacting with a solar radiation bath of the standard quantum theory of atomic radiative processes. We derive the equilibrium equations of the conversion process and provide specific examples of application of this principle to the development of solar concentration devices.

  14. The CERN Control Protocol for power converters

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, I.; Benincasa, G.; Berrig, O.; Brun, R.; Burla, P.; Coudert, G.; Pett, J.G.; Pittin, R.; Royer, J.P.; Trofimov, N. (CERN, Geneva (Switzerland))

    1993-08-01

    The Control Protocols provide, for a class of similar devices, a unique and standard access procedure from the control system. Behavioral models have been proposed for the different kinds of Power Converters and the corresponding functionalities, with their parameters, variables and attributes have been identified. The resulting data structures have been presented using the ISO ASN.1 metalanguage, that permits universal representation independent of any computer environment. Implementations in the UNIX-based CERN accelerator control systems are under development.

  15. Study on a Novel High-Efficiency Bridgeless PFC Converter

    Directory of Open Access Journals (Sweden)

    Cao Taiqiang

    2014-01-01

    Full Text Available In order to implement a high-efficiency bridgeless power factor correction converter, a new topology and operation principles of continuous conduction mode (CCM and DC steady-state character of the converter are analyzed, which show that the converter not only has bipolar-gain characteristic but also has the same characteristic as the traditional Boost converter, while the voltage transfer ratio is not related with the resonant branch parameters and switching frequency. Based on the above topology, a novel bridgeless Bipolar-Gain Pseudo-Boost PFC converter is proposed. With this converter, the diode rectifier bridge of traditional AC-DC converter is eliminated, and zero-current switching of fast recovery diode is achieved. Thus, the efficiency is improved. Next, we also propose the one-cycle control policy of this converter. Finally, experiments are provided to verify the accuracy and feasibility of the proposed converter.

  16. Subduction-zone cycling of nitrogen in serpentinized mantle rocks

    Science.gov (United States)

    Halama, R.; Bebout, G. E.; John, T.; Scambelluri, M.

    2010-12-01

    Nitrogen (N) has shown great potential as a geochemical tracer of volatiles recycling, in part because of large differences in the N isotope composition of the various Earth reservoirs. The subduction flux of N in serpentinized oceanic mantle could be as important as N input flux in oceanic crust and even sediment because, although its N concentrations are lower, its volume is potentially far greater than that of the crust/sediment. However, recycling of oceanic mantle rocks is still poorly constrained for the N cycle, and N isotope data for subduction-related ultramafic rocks are scarce [1]. The primary goal of this study is to characterize the subduction flux of N in subducting altered oceanic mantle by documenting concentrations and isotopic compositions of N in mantle rocks that reflect different stages of the metamorphic subduction zone cycle. The results are crucial to assess the composition of N recycled into the mantle, to determine the extent to which N can be retained in subducted mantle rocks to depths approaching those beneath arcs, and to balance N subduction-zone inputs with outputs in arc volcanic gases. Moreover, information has been gained regarding the redistribution and isotope fractionation of N via ultramafic dehydration and metamorphic fluid-rock interaction. The samples analyzed in this study are ultramafic rocks from shallow oceanic environments to increasing P-T conditions up to depths of ~70 km. Three distinct metamorphic grades, reflecting seafloor fluid uptake, water release due to brucite breakdown and the final antigorite breakdown, were investigated: 1. Pre-subduction serpentinized mantle peridotite from non-subducted ophiolite sequences from the Northern Apennines, Italy (Monte Nero). 2. Eclogite-facies antigorite serpentinites from the Ligurian Alps, Italy (Erro Tobbio). 3. Eclogite-facies chlorite harzburgites derived from dehydration of serpentinites from the Betic Cordillera, Spain (Cerro de Almirez). The pre

  17. Numerical Modeling of Deep Mantle Flow: Thermochemical Convection and Entrainment

    Science.gov (United States)

    Mulyukova, Elvira; Steinberger, Bernhard; Dabrowski, Marcin; Sobolev, Stephan

    2013-04-01

    One of the most robust results from tomographic studies is the existence of two antipodally located Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle, which appear to be chemically denser than the ambient mantle. Results from reconstruction studies (Torsvik et al., 2006) infer that the LLSVPs are stable, long-lived, and are sampled by deep mantle plumes that rise predominantly from their margins. The origin of the dense material is debated, but generally falls within three categories: (i) a primitive layer that formed during magma ocean crystallization, (ii) accumulation of a dense eclogitic component from the recycled oceanic crust, and (iii) outer core material leaking into the lower mantle. A dense layer underlying a less dense ambient mantle is gravitationally stable. However, the flow due to thermal density variations, i.e. hot rising plumes and cold downwelling slabs, may deform the layer into piles with higher topography. Further deformation may lead to entrainment of the dense layer, its mixing with the ambient material, and even complete homogenisation with the rest of the mantle. The amount of the anomalous LLSVP-material that gets entrained into the rising plumes poses a constraint on the survival time of the LLSVPs, as well as on the plume buoyancy, on the lithospheric uplift associated with plume interaction and geochemical signature of the erupted lavas observed at the Earth's surface. Recent estimates for the plume responsible for the formation of the Siberian Flood Basalts give about 15% of entrained dense recycled oceanic crust, which made the hot mantle plume almost neutrally buoyant (Sobolev et al., 2011). In this numerical study we investigate the mechanics of entrainment of a dense basal layer by convective mantle flow. We observe that the types of flow that promote entrainment of the dense layer are (i) upwelling of the dense layer when it gets heated enough to overcome its stabilizing chemical density anomaly, (ii

  18. Mantle hydrous-fluid interaction with Archaean granite.

    Science.gov (United States)

    Słaby, E.; Martin, H.; Hamada, M.; Śmigielski, M.; Domonik, A.; Götze, J.; Hoefs, J.; Hałas, S.; Simon, K.; Devidal, J.-L.; Moyen, J.-F.; Jayananda, M.

    2012-04-01

    Water content/species in alkali feldspars from late Archaean Closepet igneous bodies as well as growth and re-growth textures, trace element and oxygen isotope composition have been studied (Słaby et al., 2011). Both processes growth and re-growth are deterministic, however they differ showing increasing persistency in element behaviour during interaction with fluids. The re-growth process fertilized domains and didn't change their oxygen-isotope signature. Water speciation showed persistent behaviour during heating at least up to 600oC. Carbonate crystals with mantle isotope signature are associated with the recrystallized feldspar domains. Fluid-affected domains in apatite provide evidence of halide exchange. The data testify that the observed recrystallization was a high-temperature reaction with fertilized, halide-rich H2O-CO2 mantle-derived fluids of high water activity. A wet mantle being able to generate hydrous plumes, which appear to be hotter during the Archean in comparison to the present time is supposed by Shimizu et al. (2001). Usually hot fluids, which can be strongly carbonic, precede asthenospheric mantle upwelling. They are supposed to be parental to most recognized compositions, which can be derived by their immiscible separation into saline aqueous-silicic and carbonatitic members (Klein-BenDavid et al., 2007). The aqueous fractions are halogen-rich with a significant proportion of CO2. Both admixed fractions are supposed to be fertile. The Closepet granite emplaced in a major shear zone that delimitates two different terrains. Generally such shear zones, at many places, are supposed to be rooted deep into the mantle. The drain, that favoured and controlled magma ascent and emplacement, seemed to remain efficient after granite crystallization. In the southern part of the Closepet batholiths an evidence of intensive interaction of a lower crust fluid (of high CO2 activity) is provided by the extensive charnockitization of amphibolite facies (St

  19. Optimizing Design of UHVDC Converter Stations

    Institute of Scientific and Technical Information of China (English)

    MA Weimin; NIE Dingzhen; CAO Yanming

    2012-01-01

    Based on the consultation and study for Xiangjiaba-Shanghai ±800 kV UHVDC(ultra high voltage direct current) project, this paper presents an optimal design for key technique solutions. In this paper, the DC system electrical scheme design, the DC filter design, the DC harmonic component suppression, the over voltage and insulation coordination, the requirements for converter station equipment, the main equipment technical parameters of equipment (including thyristor valve, converter transformer, smoothing reactor, DC breaker), the configuration of measuring device and DC control protection system, and the de-icing operation design are investigated. According to the UHVDC technology researched conclusions and the development of the project construction, the UHVDC system design for converter stations becomes an optimal combination. The optimized design solves numbers of technical problems of the world's first UHVDC project, and it is applied to the project's construction. Under the actual operating condition, the optimized design is proved to be correct and superior. These optimal design conclusions are impartment for developing UHVDC technique and equipment, and provide reference for future UHVDC projects.

  20. Converter fed sub sea motor drives

    Energy Technology Data Exchange (ETDEWEB)

    Raad, R.O.

    1995-09-01

    Minor offshore gas and oil resources located 20-50 km from existing installations may often be commercially exploited only by use of complete sub sea solutions. This thesis deals with analyses of a sub sea adjustable speed electric motor which is fed by a frequency converter via a long cable (up to 50 km) between the converter and the motor. The author develops a general model for analysing such motor drive systems with the objective of verifying the feasibility of specific applications and of specifying the requirements on the system components. The simulation model is used to identify the critical frequency ranges in which the converter must not generate significant harmonics, to verify the start-up strategy chosen, and to verify the stability with potential disturbances applied to the system. Simulation models are developed for both transient and steady state analyses. They are accurate up to 5 kHz and can incorporate the frequency dependency of the motor and cable parameters. Ideal thyristors and diodes are used. The models are implemented in existing simulation tools. Most of the results relate to a base case with a 670 kW squirrel cage motor fed from a 30 km long cable, but cases with 3 MW rating or with 50 km cable have also been analyzed and found to be feasible. Each specific application must be separately studied. Results of simulation calculations are presented and conclusions given. 53 refs., 124 figs., 23 tabs.