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Richard E Ernst - One of the best experts on this subject based on the ideXlab platform.
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paleomagnetism and u pb age of the 2 4 ga erayinia mafic dykes in the south western yilgarn western australia paleogeographic and geodynamic implications
Precambrian Research, 2015Co-Authors: Sergei Pisarevsky, Bert De Waele, Sarah Jones, Ulf Soderlund, Richard E ErnstAbstract:We present results from a paleomagnetic study of the previously undated Erayinia dykes intruding the south-western Yilgarn Craton. The U-Pb TIMs baddeleyite age of these dykes is now 2401 +/- 1 Ma, which is about 10 m.y. younger than the 2418-2410 Ma Widgiemooltha dyke swarm. The paleomagnetic study isolated a stable primary remanence with steep Downward Direction, and the paleomagnetic pole (22.7 degrees S. 150.5 degrees E, A(95) = 11.4 degrees) is similar, but not identical to that of the previously studied Widgiemooltha dykes. We interpret this difference as the result of the movement of the Yilgam Craton toward the pole at similar to 1 degrees/m.y. angular speed, which is comparable with tectonic plates' velocities during the Phanerozoic. Paleomagnetic polarities of Widgiemooltha and Erayinia dykes suggest that at least one geomagnetic reversal occurred between these two magmatic events. The estimated amplitude of geomagnetic secular variations at c. 2400 Ma is slightly higher than predicted by the existing models for the last 5 m.y. at the c. 64 degrees latitude. The paleomagnetic data and patterns of c. 2.6-2.1 Ga mafic dyke swarms permit the recently suggested reconstruction of the Paleoproterozoic supercontinent. (C) 2014 Elsevier B.V. All rights reserved.
Sergei Pisarevsky - One of the best experts on this subject based on the ideXlab platform.
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paleomagnetism and u pb age of the 2 4 ga erayinia mafic dykes in the south western yilgarn western australia paleogeographic and geodynamic implications
Precambrian Research, 2015Co-Authors: Sergei Pisarevsky, Bert De Waele, Sarah Jones, Ulf Soderlund, Richard E ErnstAbstract:We present results from a paleomagnetic study of the previously undated Erayinia dykes intruding the south-western Yilgarn Craton. The U-Pb TIMs baddeleyite age of these dykes is now 2401 +/- 1 Ma, which is about 10 m.y. younger than the 2418-2410 Ma Widgiemooltha dyke swarm. The paleomagnetic study isolated a stable primary remanence with steep Downward Direction, and the paleomagnetic pole (22.7 degrees S. 150.5 degrees E, A(95) = 11.4 degrees) is similar, but not identical to that of the previously studied Widgiemooltha dykes. We interpret this difference as the result of the movement of the Yilgam Craton toward the pole at similar to 1 degrees/m.y. angular speed, which is comparable with tectonic plates' velocities during the Phanerozoic. Paleomagnetic polarities of Widgiemooltha and Erayinia dykes suggest that at least one geomagnetic reversal occurred between these two magmatic events. The estimated amplitude of geomagnetic secular variations at c. 2400 Ma is slightly higher than predicted by the existing models for the last 5 m.y. at the c. 64 degrees latitude. The paleomagnetic data and patterns of c. 2.6-2.1 Ga mafic dyke swarms permit the recently suggested reconstruction of the Paleoproterozoic supercontinent. (C) 2014 Elsevier B.V. All rights reserved.
Bimlesh Kumar - One of the best experts on this subject based on the ideXlab platform.
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experimentation on submerged flow over flexible vegetation patches with Downward seepage
Ecological Engineering, 2016Co-Authors: Thokchom Bebina Devi, Bimlesh KumarAbstract:Abstract The present study addresses the change in flow characteristics of alluvial channel occupied by submerged vegetated patches of different spacing under Downward seepage condition. Measurements show that velocity measured at upstream vegetation section is reduced in the range of 8–16% as the flow reaches the downstream vegetation section. An increase in the near bed velocity and Reynolds stresses has been observed with the application of Downward seepage. Reynolds stress profiles show that the maximum value exists near the top of the patches. When the flow enters the vegetation section, more erosion takes place at the upstream vegetation section and then decreases along the downstream section. The maximum turbulence intensities lie near the vegetation top and the turbulence created at the upstream vegetation section is reduced in the range 4–9% as the flow reached the downstream vegetation section. The presence of vegetation induces a local effect which leads to occurrence of erosion and deposition in the vegetated section. Third order moments highlights the Downward seepage effect on increasing the flux transport in Downward Direction and diffusion in the streamwise Direction which is shown by the governance of sweep event over ejection event from quadrant analysis. Drag coefficient decreases with the application of Downward seepage. The experiments have resulted that vegetation can provide considerable stability to channels by reducing channel erosion even with Downward seepage.
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Flow characteristics in an alluvial channel covered partially with submerged vegetation
Ecological Engineering, 2016Co-Authors: Thokchom Bebina Devi, Bimlesh KumarAbstract:Abstract The present study examines the flow characteristics in a stable alluvial channel partially covered with submerged Oryza sativa (rice) stems in a staggered pattern with Downward seepage. Measurements were taken in transect across the flume at the vegetated region, interface or junction of vegetated and unvegetated region an unvegetated region to explore the difference in flow characteristics in these regions. The presence of vegetation reduces the velocity, Reynolds stress and turbulent intensities at the downstream vegetated region even with Downward seepage which is an important finding for river restoration. An increase in the flow characteristics such as velocity, Reynolds stress and turbulent intensities are observed in the unvegetated region as the flow goes downstream which means that the reduction in the flow characteristics in the vegetated region is diverted towards the unvegetated region. Moment analysis shows that streamwise flux is occurring in the flow Direction and vertical flux is occurring in Downward Direction and increases with increase in seepage percentage. Integral scales also exhibit that with Downward seepage, the size of eddies increases. The maximum depth of erosion with Downward seepage is more than for the case of no seepage and erosion increases as the flow goes downstream.
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turbulent characteristics and evolution of sheet flow in an alluvial channel with Downward seepage
Geomorphology, 2015Co-Authors: Mahesh Patel, Vishal Deshpande, Bimlesh KumarAbstract:Abstract Experimental investigation of the flow hydrodynamics and temporal changes in the cross-sectional profile of an alluvial channel has been studied in the present work. Experiments were carried out in a curvilinear cross-sectional shaped channel with no seepage and with a Downward seepage condition to ascertain seepage effects on channel geometry and turbulent characteristics of flow. Measures of turbulent characteristics such as time-averaged near-bed velocities and Reynolds stresses were found to increase with the application of Downward seepage. Stream power and the value of Shields parameter are increased under the action of Downward seepage, causing bed particles to move in the form of a sheet layer. Integral scales of flow suggest that the size of eddies increases with the application of Downward seepage, which is linked to the evolution of the sheet layer. Sheet development causes reduction in flow depth and rapid channel widening. Cross-sectional parabolic shape of the threshold channel is transformed into a trapezoidal shape with the presence of the sheet layer. With the passage of time (11 h), the channel attains another equilibrium geometrical state with the value of Shields stress around 0.074 from the no seepage value of 0.0399. An empirical equation for sheet flow rate is derived with the consideration of seepage in the Downward Direction.
Praveen Linga - One of the best experts on this subject based on the ideXlab platform.
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investigation on the kinetics of methane hydrate formation in presence of methyl ester sulfonate
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Katipot Inkong, Hari Prakash Veluswamy, Santi Kulprathipanja, Pramoch Rangsunvigit, Praveen LingaAbstract:Abstract The kinetics of methane hydrate formation in the presence of methyl ester sulfonate (MES), a bio-based anionic surfactant, was evaluated in an unstirred reactor. MES concentration was varied from 1 mM to 8 mM (0.029 wt% to 0.232 wt%) and its effect on the kinetics of the methane hydrate formation was observed at 277.2 K and 8 MPa. MES drastically improved the kinetics of methane hydrate formation and methane consumption. The increase in the MES concentration dramatically decreased the induction time as well. In addition, the morphology of methane hydrate formation with the different MES concentrations was presented. Hydrate nucleation was observed at the interphase of gas/liquid phase followed by the hydrate growth in the upward Direction into the gas phase and then Downward Direction into the liquid phase, respectively. Dissociation characteristics and methane recovery were not significantly different for different MES concentrations.
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investigation on the kinetics of methane hydrate formation in the presence of methyl ester sulfonate
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Katipot Inkong, Hari Prakash Veluswamy, Santi Kulprathipanja, Pramoch Rangsunvigit, Praveen LingaAbstract:Abstract The kinetics of methane hydrate formation in the presence of methyl ester sulfonate (MES), a bio-based anionic surfactant, was evaluated in an unstirred reactor. MES concentration was varied from 1 mM to 8 mM (0.029 wt% to 0.232 wt%) and its effect on the kinetics of the methane hydrate formation was observed at 277.2 K and 8 MPa. MES drastically improved the kinetics of methane hydrate formation and methane consumption. The increase in the MES concentration dramatically decreased the induction time as well. In addition, the morphology of methane hydrate formation with the different MES concentrations was presented. Hydrate nucleation was observed at the interphase of gas/liquid phase followed by the hydrate growth in the upward Direction into the gas phase and then Downward Direction into the liquid phase, respectively. Dissociation characteristics and methane recovery were not significantly different for different MES concentrations.
David Schmid - One of the best experts on this subject based on the ideXlab platform.
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flow pattern observations and flow pattern map for adiabatic two phase flow of carbon dioxide in vertical upward and Downward Direction
Experimental Thermal and Fluid Science, 2022Co-Authors: David Schmid, B Verlaat, P Petagna, Remi Revellin, Jurg SchiffmannAbstract:Abstract A test facility to investigate flow pattern transitions of vertical two-phase flow of CO2 has been built within the scope of the high-luminosity detector upgrades at the European Organization for Nuclear Research (CERN). Adiabatic flow pattern observations for both vertical up- and downflow are recorded with high-speed imaging in tubes of 8 mm inner diameter, with saturation temperatures in the range of − 25 ° C to + 5 ° C and mass velocities ranging from 100 kg m − 2 s − 1 to 450 kg m − 2 s − 1 . A database of 431 flow pattern observations in upward and 123 in Downward Direction has been compiled. The recorded data have been analyzed with machine learning techniques and a previously trained Frame- and Flow-Regime-Classifier is used for the flow regime classification. The observed two-phase flow pattern transitions did not match the transition lines of existing flow pattern maps. As a consequence, new transition lines for the bubbly-to-slug, slug-to-churn and churn-to-annular transitions have been developed for both vertical upflow and downflow respectively and condensed into new flow pattern maps. It is concluded, that the flow regime transitions are strongly depended on vapour quality, mass velocity, the flow Direction and the fluid properties. Compared to horizontal flow, a dryout region is not observed and the liquid film of the annular flow regime dries out symmetrically at vapour qualities close to x = 1 .