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1
Maaløe, S. "Melt dynamics of a layered mantle plume source." Contributions to Mineralogy and Petrology 133, no. 1-2 (October 1998): 83–95. http://dx.doi.org/10.1007/s004100050439.
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Moallemi, M. K., and R. Viskanta. "Melting Around a Migrating Heat Source." Journal of Heat Transfer 107, no. 2 (May 1, 1985): 451–58. http://dx.doi.org/10.1115/1.3247436.
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The problem of melting around a moving heat source arises in many different situations such as nuclear reactor technology (i.e., “self-burial” process of nuclear waste materials and reactor core “melt-down”), process metallurgy, and geophysics. Experiments were undertaken with a horizontal cylindrical heat source that melted its way through a phase-change material (n-octadecane) under its own weight. The heat source velocity and solid-liquid interface motion for a constant surface temperature source were measured. Effects of heat source density and surface temperature as well as the effects of the initial subcooling of the solid were investigated and are reported. The flow structure in the melt was visualized using a dye. Timewise variation of temperature distribution in the solid and the melt were also measured and are discussed. Results for the heat source migration velocity and the volume of the material melted are correlated in terms of the relevant problem parameters.
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Searle, M. P., J. M. Cottle, M. J. Streule, and D. J. Waters. "Crustal melt granites and migmatites along the Himalaya: melt source, segregation, transport and granite emplacement mechanisms." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 219–33. http://dx.doi.org/10.1017/s175569100901617x.
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ABSTRACTIndia–Asia collision resulted in crustal thickening and shortening, metamorphism and partial melting along the 2200 km-long Himalayan range. In the core of the Greater Himalaya, widespread in situ partial melting in sillimanite+K-feldspar gneisses resulted in formation of migmatites and Ms+Bt+Grt+Tur±Crd±Sil leucogranites, mainly by muscovite dehydration melting. Melting occurred at shallow depths (4–6 kbar; 15–20 km depth) in the middle crust, but not in the lower crust. 87Sr/86Sr ratios of leucogranites are very high (0·74–0·79) and heterogeneous, indicating a 100 crustal protolith. Melts were sourced from fertile muscovite-bearing pelites and quartzo-feldspathic gneisses of the Neo-Proterozoic Haimanta–Cheka Formations. Melting was induced through a combination of thermal relaxation due to crustal thickening and from high internal heat production rates within the Proterozoic source rocks in the middle crust. Himalayan granites have highly radiogenic Pb isotopes and extremely high uranium concentrations. Little or no heat was derived either from the mantle or from shear heating along thrust faults. Mid-crustal melting triggered southward ductile extrusion (channel flow) of a mid-crustal layer bounded by a crustal-scale thrust fault and shear zone (Main Central Thrust; MCT) along the base, and a low-angle ductile shear zone and normal fault (South Tibetan Detachment; STD) along the top. Multi-system thermochronology (U–Pb, Sm–Nd, 40Ar–39Ar and fission track dating) show that partial melting spanned ̃24–15 Ma and triggered mid-crustal flow between the simultaneously active shear zones of the MCT and STD. Granite melting was restricted in both time (Early Miocene) and space (middle crust) along the entire length of the Himalaya. Melts were channelled up via hydraulic fracturing into sheeted sill complexes from the underthrust Indian plate source beneath southern Tibet, and intruded for up to 100 km parallel to the foliation in the host sillimanite gneisses. Crystallisation of the leucogranites was immediately followed by rapid exhumation, cooling and enhanced erosion during the Early–Middle Miocene.
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Guo, Kai, Yunping Ji, Yiming Li, Xueliang Kang, Huiyi Bai, and Huiping Ren. "Numerical Simulation of Temperature Field and Melt Pool Characteristics of CP-Ti Manufactured by Laser Powder Bed Fusion." Metals 13, no. 1 (December 20, 2022): 11. http://dx.doi.org/10.3390/met13010011.
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A coupled heat source model that combined a Gauss surface heat source with a Gauss cylindrical volumetric heat source was introduced to simulate temperature field distribution and melt pool characteristics using a finite element simulation (FEM) method for the deep and narrow melt pools formed in laser powder bed fusion (L-PBF) aiming at commercial pure titanium (CP-Ti). For comparison, the same simulations using the Gauss surface heat source model and the double ellipsoid heat source model were also performed. The simulated melt pool geometries using the coupled heat source model match well with the measurements, with an average error of 1% for the melt pool depth and 7% for the width. Based on the single-track experimental results, it was found by comparing the simulated results from the three heat source models that the coupled heat source model had better accuracy than the other two. Then, the temperature field and the melt pool geometries of CP-Ti fabricated at different laser power levels from 300 W to 500 W and scanning speeds from 600 mm/s to 4000 mm/s were simulated. According to the simulated maximum temperature and geometries of the melt pool, a suitable process parameters map for CP-Ti was obtained. The reported experimental results agree well with the simulated map. The coupled heat source model is more accurate and applicable for the deep and narrow melt pools formed during L-PBF.
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Knapp, J. A., L. R. Thompson, and G. J. Collins. "The role of radiation in melt stability in zone-melt recrystallization of SOI." Journal of Materials Research 5, no. 5 (May 1990): 998–1002. http://dx.doi.org/10.1557/jmr.1990.0998.
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Under circumstances in Zone-Melt-Recrystallization (ZMR) of Si-on-Insulator (SOI) structures where radiative heat loss is significant, the ∼50% decrease in emissivity when Si melts destabilizes the Si molten zone. We have demonstrated this both experimentally using a slowly scanned e-beam line source and numerically with a finite-element computational simulation. The resulting instability narrows the process window and tightens requirements on beam control and background heating uniformity, both for e-beam ZMR systems and optically-coupled systems such as a graphite strip heater.
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Wieser, Penny, Maurizio Petrelli, Jordan Lubbers, Eric Wieser, Sinan Ozaydin, Adam Kent, and Christy Till. "Thermobar: An open-source Python3 tool for thermobarometry and hygrometry." Volcanica 5, no. 2 (November 9, 2022): 349–84. http://dx.doi.org/10.30909/vol.05.02.349384.
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We present Thermobar, a new open-source Python3 package for calculating pressures, temperatures, and melt compositions from mineral and mineral-melt equilibrium. Thermobar allows users to perform calculations with >100 popular parametrizations involving liquid, olivine-liquid, olivine-spinel, pyroxene only, pyroxene-liquid, two pyroxene, feldspar-liquid, two feldspar, amphibole only, amphibole-liquid, and garnet equilibria. Thermobar is the first open-source tool which can match up all possible pairs of phases from a given region, and apply various equilibrium tests to identify pairs from which to calculate pressures and temperatures (e.g. pyroxene-liquid, two pyroxene, feldspar-liquid, two feldspar, amphibole-liquid). Thermobar also contains functions allowing users to propagate analytical errors using Monte-Carlo methods, convert pressures to depths using different crustal density profiles, plot mineral classification and mineral-melt equilibrium diagrams, calculate liquid viscosities, and convert between oxygen fugacity values, buffer positions and Fe speciation in a silicate melt. Thermobar can be downloaded using pip and extensive documentation is available at https://thermobar.readthedocs.io/.
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Maaløe, S. "Extraction of melt from veined mantle source regions during eruptions." Journal of Volcanology and Geothermal Research 147, no. 3-4 (October 2005): 377–90. http://dx.doi.org/10.1016/j.jvolgeores.2005.04.016.
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Diener, Johann F. A., Richard W. White, and Timothy J. M. Hudson. "Melt production, redistribution and accumulation in mid-crustal source rocks, with implications for crustal-scale melt transfer." Lithos 200-201 (July 2014): 212–25. http://dx.doi.org/10.1016/j.lithos.2014.04.021.
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Kirdyashkin, A. A., A. G. Kirdyashkin, V. E. Distanov, and I. N. Gladkov. "ON HEAT SOURCE IN SUBDUCTION ZONE." Geodynamics & Tectonophysics 12, no. 3 (September 17, 2021): 471–84. http://dx.doi.org/10.5800/gt-2021-12-3-0534.
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The subduction of an oceanic plate is studied as the motion of a high-viscosity Newtonian fluid. The subducting plate spreads along the 670-km depth boundary under the influence of oppositely directed horizontal forces. These forces are due to oppositely directed horizontal temperature gradients. We consider the flow structure and heat transfer in the layer that includes both the oceanic lithosphere and the crust and moves underneath a continent. The heat flow is estimated at the contact between the subducting plate and the surrounding mantle in the continental limb of the subduction zone. Our study results show that the crustal layer of the subducting plate can melt and a thermochemical plume can form at the 670-km boundary. Our model of a thermochemical plume in the subduction zone shows the following: (1) formation of a plume conduit in the crustal layer of the subducting plate; (2) formation of a primary magmatic chamber in the area wherein the melting rate equals the rate of subduction; (3) origination of a vertical plume conduit from the primary chamber melting through the continent; (4) plume eruption through the crustal layer to the surface, i.e. formation of a volcano. Our experiments are aimed to model the plume conduit melting in an inclined flat layer above a local heat source. The melt flow structure in the plume conduit is described. Laboratory modeling have revealed that the mechanisms of melt eruption from the plume conduit differ depending on whether a gas cushion is present or absent at the plume roof.
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Ayoola, W. A., W. J. Suder, and S. W. Williams. "Comparison of Theoretical Disc and Point Source Profiles with Actual-Melt Source Profile in Conduction Welding." Nigerian Journal of Technological Development 19, no. 3 (September 23, 2022): 260–65. http://dx.doi.org/10.4314/njtd.v19i3.8.
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Prediction of fusion zone in numerical modelling of welds using a modified heat transfer model requires experimental results for validation. Primarily, the modified heat transfer models are developed from the point and disc source heat models which can be assumed to be a semi-circle or spherical shape. In this study, a simple relationship between melt areas, the depth of penetration and weld width was proposed for point and disc source profiles to represent the actual weld profile. The results obtained for focused and defocused laser beams indicate that the actual weld profile is closer to a point source than the disc source. The transition between the conduction and keyhole regimes was achieved when the actual weld depth of penetration is below that of the point source.
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Janeschitz-Kriegl, H., E. Ratajski, and G. Eder. "Unlimited Shear as a Source of Information in Polymer Melt Processing." International Polymer Processing 29, no. 3 (July 30, 2014): 402–11. http://dx.doi.org/10.3139/217.2859.
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Ohlanders, N., M. Rodriguez, and J. McPhee. "Stable water isotope variation in a Central Andean watershed dominated by glacier and snowmelt." Hydrology and Earth System Sciences 17, no. 3 (March 7, 2013): 1035–50. http://dx.doi.org/10.5194/hess-17-1035-2013.
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Abstract. Central Chile is an economically important region for which water supply is dependent on snow- and ice melt. Nevertheless, the relative contribution of water supplied by each of those two sources remains largely unknown. This study represents the first attempt to estimate the region's water balance using stable isotopes of water in streamflow and its sources. Isotopic ratios of both H and O were monitored during one year in a high-altitude basin with a moderate glacier cover (11.5%). We found that the steep altitude gradient of the studied catchment caused a corresponding gradient in snowpack isotopic composition and that this spatial variation had a profound effect on the temporal evolution of streamflow isotopic composition during snowmelt. Glacier melt and snowmelt contributions to streamflow in the studied basin were determined using a quantitative analysis of the isotopic composition of streamflow and its sources, resulting in a glacier melt contribution of 50–90% for the unusually dry melt year of 2011/2012. This suggests that in (La Niña) years with little precipitation, glacier melt is an important water source for central Chile. Predicted decreases in glacier melt due to global warming may therefore have a negative long-term impact on water availability in the Central Andes. The pronounced seasonal pattern in streamflow isotope composition and its close relation to the variability in snow cover and discharge presents a potentially powerful tool to relate discharge variability in mountainous, melt-dominated catchments with related factors such as contributions of sources to streamflow and snowmelt transit times.
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Kirdyashkin, А., and A. Kirdyashkin. "Forces generating crystallization differentiation, and the evolution of the melt composition on the example of plagioclase." Transbaikal State University Journal 26, no. 7 (2020): 44–52. http://dx.doi.org/10.21209/2227-9245-2020-26-7-44-52.
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Crystallization differentiation processes in the melt volume are investigated for albite-anorthite continuous solid solution series. It has shown that crystallization differentiation occurs in the isothermal melt volume due to hydrodynamic instability of the melt/solid particles system. The time of particle settling in a 10 cm thick melt layer is estimated for different particle sizes. In terrestrial conditions, the existence of large melt volumes with long lifetime is possible in the case of a long-lived heat source of high thermal power. This source is a mantle thermochemical plume with a mushroom-shaped head. The particle settling time is estimated for the melt layer thickness, i. e. plume head thickness equal to 10 km. A calculation technique is presented for composition of the melt remaining after settling of plagioclase particles. The results of calculations of changes in the melt composition due to crystallization differentiation at a temperature T = 1410 °C and a pressure P = 6,3 kbar are presented. For a melt whose composition corresponds to N 47,5 (weight percentage of anorthite is 47,5 %), the oxide content in the settled plagioclase, the composition of the melt in its intercrystalline spaces, and the residual melt composition are calculated. At constant temperature, the crystallization differentiation of the melt whose composition corresponds to plagioclase leads to the compositional changes in the initial melt. Calculations of the melt composition have shown that the melt is depleted in anorthite component owing to settling of plagioclase particles. The composition of plagioclase therewith shifts to the liquidus line, reaching its limit on this line
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Nabelek, Peter I., and Cindy D. Bartlett. "Fertility of metapelites and metagraywackes during leucogranite generation: an example from the Black Hills, U.S.A." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 91, no. 1-2 (2000): 1–14. http://dx.doi.org/10.1017/s0263593300007252.
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In order to elucidate how mineralogy and composition of crustal sources influences production of leucogranite magmas, we modelled the potential fertility of a sequence of metapelites and metagraywackes from the Black Hills, South Dakota, U.S.A., using a least-squares mixing approach. Rocks analogous to the Black Hills schists were the sources of the Harney Peak leucogranite. Both muscovite and biotite fluid-absent melting reactions (MM and BM, respectively) were investigated. Using the Harney Peak Granite composition as the melt analogue and mineral compositions from the schists for mixing calculations, it is shown that MM of metapelites would lead to highly variable residue mineralogy in the investigated samples. The average residue includes 36 wt.% biotite, 32 wt.% quartz, 12 wt.% plagioclase, 8 wt.% K-feldspar, 9 wt.% sillimanite and 2 wt.% garnet. Melt production ranges from 5% to 23% with an average of 14%. It is limited by the amount of H2O that must be in the melt at the conditions of melting, relative to the amount that is in muscovite in the source rocks. Plagioclase-rich metagraywackes contain little to no muscovite, thus MM cannot occur in them.Although BM is continuous over a wide temperature range, for the purposes of modelling melting at 975°C and 10kbar was chosen. The temperature is near the terminal stability of biotite, thus the calculations give near-maximum melt production. At this temperature, the mineralogy of the model residues from both metapelites and metagraywackes is dominated by garnet. The potential melt production in the metapelites ranges from 0% to 58% with an average of 32%. It is limited by the availability of plagioclase in the source rocks. Potential melt production in the metagraywackes ranges from 9% to 37% with an average of 23%. At the chosen conditions of melting, melt production is limited by the available K in biotite, although at lower temperatures, the available H2O limits melt production. The total potential melt production (MM + BM) in the metapelites is higher because they have on average a low normative An/Ab ratio (0·14) that approaches the ratio in the leucogranites (0·04). The paragonite component in muscovite significantly contributes to the low ratio in the metapelites. The higher ration (0·27) in the metagraywackes is denned by the feldspar composition.Using the calculated melt fractions and residue mineralogies, we modelled the concentrations of Rb, Sr and Ba in the melts, as these elements are important indicators of melt-generating processes. The results indicate that both Sr and Ba are likely to be heterogeneous in extracted melt batches and will be depleted in partial melts relative to their pelitic sources, irrespective of whether the melting is fluid-absent or fluid-present.
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Kiran, Abhilash, Ying Li, Josef Hodek, Michal Brázda, Miroslav Urbánek, and Jan Džugan. "Heat Source Modeling and Residual Stress Analysis for Metal Directed Energy Deposition Additive Manufacturing." Materials 15, no. 7 (March 30, 2022): 2545. http://dx.doi.org/10.3390/ma15072545.
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The advancement in additive manufacturing encourages the development of simplified tools for deep and swift research of the technology. Several approaches were developed to reduce the complexity of multi-track modeling for additive manufacturing. In the present work, a simple heat source model called concentrated heat source was evaluated for single- and multi-track deposition for directed energy deposition. The concentrated heat source model was compared with the widely accepted Goldak heat source model. The concentrated heat source does not require melt pool dimension measurement for thermal model simulation. Thus, it reduces the considerable time for preprocessing. The shape of the melt pool and temperature contour around the heat source was analyzed for single-track deposition. A good agreement was noticed for the concentrated heat source model melt pool, with an experimentally determined melt pool, using an optical microscope. Two heat source models were applied to multi-track 3D solid structure thermo-mechanical simulation. The results of the two models, for thermal history and residual stress, were compared with experimentally determined data. A good agreement was found for both models. The concentrated heat source model reported less than the half the computational time required for the Goldak model. The validated model, for 3D solid structure thermo-mechanical simulation, was used to analyze thermal stress evolution during the deposition process. The material deposition on the base plate at room temperature results in lower peak temperatures in the layers near the base plate. Consequently, the higher thermal stress in the layers near the base plate was found, compared to the upper layers during the deposition process.
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Hu, Wen-Jun, Mei-Fu Zhou, John Malpas, and Zhong-Yuan Ren. "High-Ca boninitic melt inclusions in lavas of the Troodos ophiolite and a reappraisal of genetic relationships between different lava types." GSA Bulletin 133, no. 9-10 (January 6, 2021): 1831–50. http://dx.doi.org/10.1130/b35717.1.
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Abstract Boninites in many supra-subduction zone ophiolites are thought to mark the early stage of subduction. The Troodos ophiolite in Cyprus contains a variety of volcanic rocks including the lower pillow lavas and the boninite-bearing upper pillow lavas (UPL). Here we present major, trace element and Pb isotope data for melt inclusions in olivine from the UPL on the northern flank of the Troodos ophiolite. Melt inclusions hosted by high-Mg (Fo = 89.4–93.5) olivine grains have typical high-Ca boninitic compositions with high MgO (11.2–18.4 wt%) and SiO2 (51.2–55.0 wt%) and low TiO2 (0.2–0.6 wt%) contents, in line with the existence of boninites in the northern part of the ophiolite. The melt inclusions have trace element compositions similar to the Troodos boninitic lavas and can be regarded as representing the parental magma of the boninites. The boninitic magmas were derived from high-degrees of partial melting of a refractory source at 1400 °C and 1.5 GPa based on thermobarometers and phase equilibria. The melt inclusions have significantly variable Pb isotopic compositions (208Pb/206Pb = 2.059–2.122; 207Pb/206Pb = 0.828–0.862) and are enriched in fluid-mobile trace elements (e.g., U, Sr, and Pb), indicating that the refractory source was metasomatized by slab fluids. In comparison, recalculation of literature data suggests that the lower pillow lavas were derived from a less refractory and shallower source. We propose a subduction initiation model in which melting of two unique sources was needed to form the chemostratigraphy of lavas in the Troodos ophiolite.
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Zabel, I. H. H., K. C. Jezek, P. A. Baggeroer, and S. P. Gogineni. "Ground-based radar observations of snow stratigraphy and melt processes in the percolation facies of the Greenland ice sheet." Annals of Glaciology 21 (1995): 40–44. http://dx.doi.org/10.3189/s0260305500015573.
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Summer melt is a primary source of mass loss on the Greenland ice sheet. An understanding of melt processes on the ice sheet, their connection with atmospheric processes, and the redistribution of meltwater is important for ascertaining the mass balance of the ice sheet. High-resolution radar measurements made in the percolation zone of the Greenland ice sheet reveal the evolving radar signature of summer surface melting and subsequent refreezing of meltwater. A traverse over the snow surface has resulted in the first radar map of snow stratigraphy over an extended distance. The dominant sources of back-scatter in the study area are the snow surface and effectively continuous annual ice layers. We suggest applications of our results to help define the extent of the percolation zone and to discriminate between regions where surface melt is lost to the sea and those where melt refreezes nearly in place.
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Zabel, I. H. H., K. C. Jezek, P. A. Baggeroer, and S. P. Gogineni. "Ground-based radar observations of snow stratigraphy and melt processes in the percolation facies of the Greenland ice sheet." Annals of Glaciology 21 (1995): 40–44. http://dx.doi.org/10.1017/s0260305500015573.
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Summer melt is a primary source of mass loss on the Greenland ice sheet. An understanding of melt processes on the ice sheet, their connection with atmospheric processes, and the redistribution of meltwater is important for ascertaining the mass balance of the ice sheet. High-resolution radar measurements made in the percolation zone of the Greenland ice sheet reveal the evolving radar signature of summer surface melting and subsequent refreezing of meltwater. A traverse over the snow surface has resulted in the first radar map of snow stratigraphy over an extended distance. The dominant sources of back-scatter in the study area are the snow surface and effectively continuous annual ice layers. We suggest applications of our results to help define the extent of the percolation zone and to discriminate between regions where surface melt is lost to the sea and those where melt refreezes nearly in place.
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Walowski, K. J., L. A. Kirstein, J. C. M. De Hoog, T. R. Elliott, I. P. Savov, and R. E. Jones. "Investigating ocean island mantle source heterogeneity with boron isotopes in melt inclusions." Earth and Planetary Science Letters 508 (February 2019): 97–108. http://dx.doi.org/10.1016/j.epsl.2018.12.005.
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Weinstein, Oleg, and Simon Brandon. "Dynamics of partially faceted melt/crystal interfaces II: multiple step–source calculations." Journal of Crystal Growth 270, no. 1-2 (September 2004): 232–49. http://dx.doi.org/10.1016/j.jcrysgro.2004.06.002.
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Hopkinson, Thomas, Nigel Harris, Nick M. W. Roberts, Clare J. Warren, Sam Hammond, Christopher J. Spencer, and Randall R. Parrish. "Evolution of the melt source during protracted crustal anatexis: An example from the Bhutan Himalaya." Geology 48, no. 1 (November 19, 2019): 87–91. http://dx.doi.org/10.1130/g47078.1.
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Abstract The chemical compositions of magmatic zircon growth zones provide powerful insight into evolving magma compositions due to their ability to record both time and the local chemical environment. In situ U-Pb and Hf isotope analyses of zircon rims from Oligocene–Miocene leucogranites of the Bhutan Himalaya reveal, for the first time, an evolution in melt composition between 32 and 12 Ma. The data indicate a uniform melt source from 32 Ma to 17 Ma, and the progressive addition of an older source component to the melt from at least ca. 17 Ma. Age-corrected ɛHf ratios decrease from between −10 and −15 down to values as low as −23 by 12 Ma. Complementary whole-rock Nd isotope data corroborate the Hf data, with a progressive decrease in ɛNd(t) from ca. 18 to 12 Ma. Published zircon and whole-rock Nd data from different lithotectonic units in the Himalaya suggest a chemical distinction between the younger Greater Himalayan Series (GHS) and the older Lesser Himalayan Series (LHS). The time-dependent isotopic evolution shown in the leucogranites demonstrates a progressive increase in melt contribution from older lithologies, suggestive of increasing LHS involvement in Himalayan melting over time. The time-resolved data are consistent with LHS material being progressively accreted to the base of the GHS from ca. 17 Ma, facilitated by deformation along the Main Central thrust. From 17 Ma, decompression, which had triggered anatexis in the GHS since the Paleogene, enabled melting in older sources from the accreted LHS, now forming the lowermost hanging wall of the thrust.
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Rushmer, Tracy. "Melt segregation in the lower crust: how have experiments helped us?" Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, no. 1-2 (1996): 73–83. http://dx.doi.org/10.1017/s0263593300006490.
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ABSTRACT:The rheological and chemical behaviour of the lower crust during anatexis has been a major focus of geological investigations for many years. Modern studies of crustal evolution require significant knowledge, not only of the potential source regions for granites, but also of the transport paths and emplacement mechanisms operating during granite genesis. We have gained significant insights into the segregation and transport of granitoid melts from the results of experimental studies on rock behaviour during partial melting. Experiments performed on crustal rock cores under both hydrostatic conditions and during deformation have led, in part, to two conclusions. (1) The interfacial energy controlling melt distribution is anisotropic and, as a result, the textures deviate significantly from those predicted for ideal systems—planar solid-melt interfaces are developed in addition to triple junction melt pockets. The ideal dihedral angle model for melt distribution cannot be used as a constraint to predict melt migration in the lower crust. (2) The ‘critical melt fraction’ model, which requires viscous, granitic melt to remain in the source until melt fractions reach >25 vol%, is not a reliable model for melt segregation. The most recent experimental results on crustal rock cores which have helped advance our understanding of melt segregation processes have shown that melt segregation is controlled by several variables, including the depth of melting, the type of reaction and the volume change associated with that reaction. Larger scale processes such as tectonic environment determine the rate at which the lower crust heats and deforms, thus the tectonic setting controls the melt fraction at which segregation takes place, in addition to the pressure and temperature of the potential melting reactions. Melt migration therefore can occur at a variety of different melt fractions depending on the tectonic environment; these results have significant implications for the predicted geochemistry of the magmas themselves.
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Lawson, E. C., J. L. Wadham, M. Tranter, M. Stibal, G. P. Lis, C. E. H. Butler, J. Laybourn-Parry, P. Nienow, D. Chandler, and P. Dewsbury. "Greenland Ice Sheet exports labile organic carbon to the Arctic oceans." Biogeosciences 11, no. 14 (July 31, 2014): 4015–28. http://dx.doi.org/10.5194/bg-11-4015-2014.
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Abstract. Runoff from small glacier systems contains dissolved organic carbon (DOC) rich in protein-like, low molecular weight (LMW) compounds, designating glaciers as an important source of bioavailable carbon for downstream heterotrophic activity. Fluxes of DOC and particulate organic carbon (POC) exported from large Greenland catchments, however, remain unquantified, despite the Greenland Ice Sheet (GrIS) being the largest source of global glacial runoff (ca. 400 km3 yr−1). We report high and episodic fluxes of POC and DOC from a large (>600 km2) GrIS catchment during contrasting melt seasons. POC dominates organic carbon (OC) export (70–89% on average), is sourced from the ice sheet bed, and contains a significant bioreactive component (9% carbohydrates). A major source of the "bioavailable" (free carbohydrate) LMW–DOC fraction is microbial activity on the ice sheet surface, with some further addition of LMW–DOC to meltwaters by biogeochemical processes at the ice sheet bed. The bioavailability of the exported DOC (26–53%) to downstream marine microorganisms is similar to that reported from other glacial watersheds. Annual fluxes of DOC and free carbohydrates during two melt seasons were similar, despite the approximately two-fold difference in runoff fluxes, suggesting production-limited DOC sources. POC fluxes were also insensitive to an increase in seasonal runoff volumes, indicating a supply limitation in suspended sediment in runoff. Scaled to the GrIS, the combined DOC (0.13–0.17 Tg C yr−1 (±13%)) and POC fluxes (mean = 0.36–1.52 Tg C yr−1 (±14%)) are of a similar order of magnitude to a large Arctic river system, and hence may represent an important OC source to the near-coastal North Atlantic, Greenland and Labrador seas.
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Lawson, E. C., J. L. Wadham, M. Tranter, M. Stibal, G. P. Lis, C. E. H. Butler, J. Laybourn-Parry, P. Nienow, D. Chandler, and P. Dewsbury. "Greenland Ice Sheet exports labile organic carbon to the Arctic oceans." Biogeosciences Discussions 10, no. 12 (December 10, 2013): 19311–45. http://dx.doi.org/10.5194/bgd-10-19311-2013.
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Abstract. Runoff from small glacier systems contains dissolved organic carbon (DOC), rich in protein-like, low molecular weight (LMW) compounds, designating glaciers as an important source of bioavailable carbon for downstream heterotrophic activity. Fluxes of DOC and particulate organic carbon (POC) exported from large Greenland catchments, however, remain unquantified, despite the Greenland Ice Sheet (GrIS) being the largest source of global glacial runoff (ca. 400 km3 yr−1). We report high and episodic fluxes of POC and DOC from a large (1200 km2) GrIS catchment during contrasting melt seasons. POC dominates organic carbon (OC) export (70–89% on average), is sourced from the ice sheet bed and contains a significant bioreactive component (9% carbohydrates). A major source for the "bioavailable" (free carbohydrates) LMW-DOC fraction is microbial activity on the ice sheet surface, with some further addition of LMW-DOC to meltwaters by biogeochemical processes at the ice sheet bed. The bioavailability of the exported DOC (30–58%) to downstream marine microorganisms is similar to that reported from other glacial watersheds. Annual fluxes of DOC and free carbohydrates during two melt seasons were similar, despite the ~ 2 fold difference in runoff fluxes, suggesting production-limited DOC sources. POC fluxes were also insensitive to an increase in seasonal runoff volumes, indicating supply-limitation of suspended sediment in runoff. Scaled to the GrIS, the combined DOC and POC fluxes (0.13–0.17 Tg C yr−1 DOC, 0.36–1.52 Tg C yr−1 mean POC) are of a similar order of magnitude to a large Arctic river system, and hence represent an important OC source to the North Atlantic, Greenland and Labrador Seas.
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Chung, Woo-Sik, André Häusler, Marc Hummel, Alexander Olowinsky, Arnold Gillner, Felix Beckmann, and Julian Moosmann. "In-situ x-ray phase contrast observation of the full penetration spot welding on limited aluminum material thickness." Journal of Laser Applications 34, no. 4 (November 2022): 042019. http://dx.doi.org/10.2351/7.0000772.
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The laser-spot welding process of aluminum alloy 1050A with a limited thickness is observed with the x-ray phase contrast method to investigate the melt dynamic especially when the melt penetrates the material. The laser-spot welding is investigated with two different wavelengths of the laser beam source: 515 and 1030 nm to investigate the influence of the absorptivity. The melt progressively penetrates the material during the spot-welding process until reaching the bottom side of the material and when the melt penetrates the lower side of the material, the so-called “lens-like” melt appears at the lower side due to the surface tension. At a comparable beam intensity value, the oscillation of the “lens-like” melt at the lower side of the material is driven by the expansion of vapor capillary. This expansion occurs inside of the material and directly above the “lens-like” melt. The shape of the expanded vapor determines the volume as well as the geometry of the resulting melt volume. Furthermore, the transition from the heat conduction welding mode to the keyhole welding mode is investigated by defocusing the laser beam for the beam source with a 515 nm wavelength. At a given variation, a clear difference between either mode is observed with the x-ray phase contrast method.
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Sawyer, E. W. "Melt segregation and magma flow in migmatites: implications for the generation of granite magmas." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, no. 1-2 (1996): 85–94. http://dx.doi.org/10.1017/s0263593300006507.
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ABSTRACT:To form a granite pluton, the felsic melt produced by partial melting of the middle and lower continental crust must separate from its source and residuum. This can happen in three ways: (1) simple melt segregation, where only the melt fraction moves; (2) magma mobility, in which all the melt and residuum move together; and (3) magma mobility with melt segregation, in which the melt and residuum move together as a magma, but become separated during flow. The first mechanism applies to metatexite migmatites and the other two to diatexite migmatites, but the primary driving forces for each are deviatoric stresses related to regional-scale deformation. Neither of the first two mechanisms generates parental granite magmas. In the first mechanism segregation is so effective that the resulting magmas are too depleted in FeOT, MgO, Rb, Zr, Th and the REEs, and in the second no segregation occurs. Only the third mechanism produces magmas with compositions comparable with parental granites, and occurs at a large enough scale in the highest grade parts of migmatite terranes, to be considered representative of the segregation processes occurring in the source regions of granites.
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Mayne, Matthew J., Gary Stevens, and Jean-François Moyen. "A phase equilibrium investigation of selected source controls on the composition of melt batches generated by sequential melting of an average metapelite." Geological Society, London, Special Publications 491, no. 1 (August 2, 2019): 223–41. http://dx.doi.org/10.1144/sp491-2018-121.
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AbstractThe ability of Rcrust software to conduct path-dependent phase equilibrium modelling with automated changing bulk compositions allows for a phase equilibrium approach to investigate an array of source controls for their effect on the bulk compositions of melts produced by sequential melting events. The following source controls of the rock system are considered: (1) initial magnesium and iron content; (2) initial sodium and calcium content; (3) pressure–temperature path followed by the system; and (4) threshold by which melt extractions in the system are triggered. These source controls are investigated in a water-restricted system and a water-in-excess system. The permutation of these cases resulted in 128 different modelled pressure–temperature bulk composition paths investigating the melting of an average pelite composition. The resultant melt compositions are compared to that of a natural granite dataset and provide a good fit for the incompatible elements Na2O and K2O with the allowance that granites most likely form as magmas consisting of melt and ferromagnesian-rich crystals. The fluid state of the system is shown to have the strongest control on melt compositions, with the pressure–temperature path having subordinate control on the volume and composition of melts produced.
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Guo, Lei, Xiaochun Wen, and Zhancheng Guo. "Kinetic Models for the in Situ Reaction between Cu-Ti Melt and Graphite." Metals 10, no. 2 (February 18, 2020): 267. http://dx.doi.org/10.3390/met10020267.
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The in situ reaction method for preparing metal matrix composites has the advantages of a simple process, good combination of the reinforcing phase and matrix, etc. Based on the mechanism of forming TiCx particles via the dissolution reaction of solid carbon (C) particles in Cu-Ti melt, the kinetic models for C particle dissolution reaction were established. The kinetic models of the dissolution reaction of spherical, cylindrical, and flat C source particles in Cu-Ti melt were deduced, and the expressions of the time for the complete reaction of C source particles of different sizes were obtained. The mathematical relationship between the degree of reaction of C source and the reaction time was deduced by introducing the shape factor. By immersing a cylindrical C rod in a Cu-Ti melt and placing it in a super-gravity field for the dissolution reaction, it was found that the super-gravity field could cause the precipitated TiCx particles to aggregate toward the upper part of the sample under the action of buoyancy. Therefore, the consuming rate of the C rod was significantly accelerated. Based on the flat C source reaction kinetic model, the relationship between the floating speed of TiCx particles in the Cu-Ti melt and the centrifugal velocity (or the coefficient of super-gravity G) was derived. It was proven that, when the centrifugal velocity exceeded a critical value, the super-gravity field could completely avoid the accumulation behavior of TiCx particles on the surface of the C source, thereby speeding up the formation reaction of TiCx. The goal of this study is to better understand and evaluate the generating process of TiCx particles, thus finding possible methods to increase the reaction efficiency
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Gourdal, Margaux, Martine Lizotte, Guillaume Massé, Michel Gosselin, Michel Poulin, Michael Scarratt, Joannie Charette, and Maurice Levasseur. "Dimethyl sulfide dynamics in first-year sea ice melt ponds in the Canadian Arctic Archipelago." Biogeosciences 15, no. 10 (May 29, 2018): 3169–88. http://dx.doi.org/10.5194/bg-15-3169-2018.
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Abstract. Melt pond formation is a seasonal pan-Arctic process. During the thawing season, melt ponds may cover up to 90 % of the Arctic first-year sea ice (FYI) and 15 to 25 % of the multi-year sea ice (MYI). These pools of water lying at the surface of the sea ice cover are habitats for microorganisms and represent a potential source of the biogenic gas dimethyl sulfide (DMS) for the atmosphere. Here we report on the concentrations and dynamics of DMS in nine melt ponds sampled in July 2014 in the Canadian Arctic Archipelago. DMS concentrations were under the detection limit (< 0.01 nmol L−1) in freshwater melt ponds and increased linearly with salinity (rs = 0.84, p ≤ 0.05) from ∼ 3 up to ∼ 6 nmol L−1 (avg. 3.7 ± 1.6 nmol L−1) in brackish melt ponds. This relationship suggests that the intrusion of seawater in melt ponds is a key physical mechanism responsible for the presence of DMS. Experiments were conducted with water from three melt ponds incubated for 24 h with and without the addition of two stable isotope-labelled precursors of DMS (dimethylsulfoniopropionate), (D6-DMSP) and dimethylsulfoxide (13C-DMSO). Results show that de novo biological production of DMS can take place within brackish melt ponds through bacterial DMSP uptake and cleavage. Our data suggest that FYI melt ponds could represent a reservoir of DMS available for potential flux to the atmosphere. The importance of this ice-related source of DMS for the Arctic atmosphere is expected to increase as a response to the thinning of sea ice and the areal and temporal expansion of melt ponds on Arctic FYI.
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Wendl, I. A., A. Eichler, E. Isaksson, T. Martma, and M. Schwikowski. "800 year ice-core record of nitrogen deposition in Svalbard linked to ocean productivity and biogenic emissions." Atmospheric Chemistry and Physics Discussions 14, no. 17 (September 25, 2014): 24667–700. http://dx.doi.org/10.5194/acpd-14-24667-2014.
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Abstract. We present the records of the two nitrogen species nitrate (NO3−) and ammonium (NH4+) analysed in a new ice core from Lomonosovfonna, Svalbard, in the Eurasian Arctic covering the period 1222–2009. We investigate the emission sources and the influence of melt on the records. During the 20th century both records are influenced by anthropogenic pollution from Eurasia. In pre-industrial times NO3− is highly correlated with methane-sulfonate (MSA) on decadal time-scales, which we explain by a fertilising effect. Enhanced atmospheric NO3− concentrations and the corresponding nitrogen input to the ocean trigger the growth of dimethyl-sulfide-(DMS)-producing phytoplankton. Increased DMS production results in elevated fluxes to the atmosphere where it is oxidised to MSA. Eurasia was presumably the main source area also for pre-industrial NO3−, but a more exact source apportionment could not be performed based on our data. This is different for NH4+, where biogenic ammonia (NH3) emissions from Siberian boreal forests were identified as the dominant source of pre-industrial NH4+. Changes in melt at the Lomonosovfonna glacier are excluded as major driving force for the decadal variations of the investigated compounds.
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Ohlanders, N., M. Rodriguez, and J. McPhee. "Stable water isotope variation in a Central Andean watershed dominated by glacier- and snowmelt." Hydrology and Earth System Sciences Discussions 9, no. 10 (October 30, 2012): 12227–69. http://dx.doi.org/10.5194/hessd-9-12227-2012.
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Abstract. Central Chile is an economically important region for which water supply is dependent on snow- and ice melt. Nevertheless, the fraction of water supplied by each of those two sources remains largely unknown. This study represents the first attempt to estimate the region's water balance using stable isotopes of water in streamflow and its sources; isotopic ratios of both H and O were monitored during one year in a high-altitude basin with a relatively high glacial cover (11.5%). We found that the steep altitude gradient of the studied catchment caused a corresponding gradient in snowpack isotopic composition and that this spatial variation had a profound effect on the temporal evolution of streamflow isotopic composition during snowmelt. Glacier- and snowmelt contributions to streamflow in the studied basin were calculated using a quantitative analysis of the isotopic composition of streamflow and its sources, resulting in a glacier melt contribution of 50–80% for the unusually dry melt year of 2011/12. This suggests that in (la Niña) years with little precipitation, glacier melt is an important water source for Central Chile. Predicted decreases in glacier melt due to global warming may therefore have a negative impact on water availability in the Central Andes as well as in comparable semi-arid regions of the world; this impact is non-commensurable with areal glacial cover or with the relative areal influence coverage of glacier versus seasonal snowpack. The pronounced seasonal pattern in streamflow isotope composition and its close relation to the evolution of snow cover and to discharge presents a potentially powerful tool for relating discharge evolution in mountainous, melt-dominated catchments with related factors such as contributions of sources to streamflow and snowmelt transit times.
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Cheng, Zhiguo, Tong Hou, Jakob K. Keiding, Ilya V. Veksler, Vadim S. Kamenetsky, Marko Hornschu, and Robert B. Trumbull. "Comparative Geothermometry in High-Mg Magmas from the Etendeka Province and Constraints on their Mantle Source." Journal of Petrology 60, no. 12 (December 1, 2019): 2509–28. http://dx.doi.org/10.1093/petrology/egaa016.
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Abstract There is still debate whether Large Igneous Provinces (LIPs) are caused by high mantle temperatures induced by thermal plumes or by other factors that enhance melt production from the mantle. A prerequisite for assessing the thermal plume model is a reliable estimate of liquidus temperatures of the magmas produced, preferably based on more than one method of geothermometry. The study reported here compares multiple geothermometers for the Etendeka LIP, which is among the largest Phanerozoic examples and one that shows several features suggestive of a plume origin (continental flood basalt province linked via an age-progressive volcanic ridge to an active hotspot). Magnesium (Mg)-rich magmas emplaced as dikes in NW Namibia are the most primitive rocks known from this province and are thus best suited to determine the composition and melting conditions of their mantle source. Earlier studies of the Etendeka Mg-rich dikes reported high liquidus temperatures based on olivine-melt Mg–Fe equilibria. We extend that work to a larger set of samples and compare the results of olivine-melt Mg–Fe thermometry with other methods based on spinel-melt and spinel–olivine equilibria (Al-in-olivine thermometry), as well as olivine-melt trace-element exchange (Sc/Y thermometry and V oxybarometry). All methods used the same starting assumptions of nominally anhydrous melts and a crystallization pressure of 0·5 GPa. Only mineral-melt or mineral-mineral pairs consistent with compositional equilibrium were used for calculating temperatures. The trace-element compositions of olivine are also used to discuss the relative proportion of peridotite and pyroxenite in the mantle source for these magmas. Twelve dike samples were studied, with whole-rock MgO concentrations ranging from 8·4 to 19·4 wt %. Diagnostic element ratios of transition metals in olivine (e.g., Mn/Fe, Mn/Zn, Zn/Fe) indicate a peridotite-dominated mantle source for the magmas, which is consistent with the other indicators based on whole-rock data e.g., 10 000×Zn/Fe, CaO–MgO trend, FeO/MnO and FC3MS (FeO/CaO–3×MgO/SiO2). The temperature variations show a positive correlation with the Fo-content of host olivines, and values from high-Fo olivine agree well with olivine and spinel liquidus temperatures calculated from thermodynamic models of bulk-rock composition. All methods and most samples yielded a temperature range between 1300 °C and 1400 °C. An exceptional few samples returned temperatures below 1300 °C, the minimum being 1193 °C, whereas several samples yielded temperatures above 1400 °C, the upper range being 1420–1440°C, which we consider to be a robust estimate of the maximum liquidus temperatures for the high-Mg magmas studied. The conversion to mantle potential temperatures is complicated by uncertain depth and degree of melting, but the functional relationship between Tp and primary melt MgO contents, using melt inclusions from olivine phenocrysts with of Fo > 90, indicate a Tp range from 1414 to 1525 °C ( 42 °C), which is 100–150°C higher than estimates of ambient upper mantle Tp in the South Atlantic today.
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Hasbi Nasution, Nur'afifah. "THE NATURE OF TRANSLATION (CASE STUDY ON TRANSLATING COMPUTER TEXT)." Journal MELT (Medium for English Language Teaching) 2, no. 1 (May 24, 2018): 1. http://dx.doi.org/10.22303/melt.2.1.2017.1-10.
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<em>Translation is dealing with transferring meaning from source language into target language. In simple cases, it can be translating word by word. While for some cases, such translation may seem awkward or even confusing and funny. It may happen when certain words are translated into inappropriate equivalent words. The translation, then, fails to transfer the meaning from source language. Based on the aim, it is necessary to catch the idea of the text. English as the language of science, including computer, is used widely in many textbooks. In fact, there are many words which have no equivalent words in Indonesian. This study analyzes the process of translating English into Indonesian on computer text. The object of the study is English articles used by Faculty of Engineering and Computer Science of Potensi Utama University. The study shows that there are two things to be paid attention in translating English computer text into Indonesian; finding the appropriate equivalent words, and keeping non-equivalent words as they are.</em>
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Zhu, Guofeng, Lei Wang, Yuwei Liu, Mohd Aadil Bhat, Dongdong Qiu, Kailiang Zhao, Liyuan Sang, Xinrui Lin, and Linlin Ye. "Snow-melt water: An important water source for Picea crassifolia in Qilian Mountains." Journal of Hydrology 613 (October 2022): 128441. http://dx.doi.org/10.1016/j.jhydrol.2022.128441.
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Sleptsov, S. D., N. A. Savvinova, and M. A. Grishin. "Mathematical modeling of ice melt during irradiation by selective source of thermal radiation." Journal of Physics: Conference Series 1382 (November 2019): 012188. http://dx.doi.org/10.1088/1742-6596/1382/1/012188.
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Kenny, Gavin G., Martin J. Whitehouse, and Balz S. Kamber. "Differentiated impact melt sheets may be a potential source of Hadean detrital zircon." Geology 44, no. 6 (April 28, 2016): 435–38. http://dx.doi.org/10.1130/g37898.1.
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Norman, Marc D., Michael O. Garcia, Vadim S. Kamenetsky, and Roger L. Nielsen. "Olivine-hosted melt inclusions in Hawaiian picrites: equilibration, melting, and plume source characteristics." Chemical Geology 183, no. 1-4 (March 2002): 143–68. http://dx.doi.org/10.1016/s0009-2541(01)00376-x.
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Liu, Peixing, Huiqiang Liu, and Yisheng Zhang. "A new thin sheet heat source model for active gas melt laser cutting." International Journal of Advanced Manufacturing Technology 77, no. 5-8 (November 12, 2014): 1475–81. http://dx.doi.org/10.1007/s00170-014-6478-z.
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Vowinkel, Steffen, Frank Malz, Karsten Rode, and Markus Gallei. "Single-source macroporous hybrid materials by melt-shear organization of core–shell particles." Journal of Materials Science 52, no. 19 (February 10, 2017): 11179–90. http://dx.doi.org/10.1007/s10853-017-0891-2.
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Xu, Yixuan, Dongyun Zhang, Junyuan Deng, Xuping Wu, Lingshan Li, Yinkai Xie, Reinhart Poprawe, Johannes Henrich Schleifenbaum, and Stephan Ziegler. "Numerical Simulation in the Melt Pool Evolution of Laser Powder Bed Fusion Process for Ti6Al4V." Materials 15, no. 21 (October 28, 2022): 7585. http://dx.doi.org/10.3390/ma15217585.
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In order to track the free interface of the melt pool and understand the evolution of the melt pool, the flow of fluid, and the interface behavior of gas and liquid, a physical model is developed by using the VOF method in this paper. Its characteristics are a combined heat source model, including a parabolic rotation and a cylindrical distribution, and a powder bed stochastic distributed model with powder particle size. The unit interface between the metallic and gas phase in the laser–powder interaction zone can only be loaded by the heat source. Only the first and second laser scanning tracks are simulated to reduce the calculation time. The simulation results show that process parameters such as laser power and scanning speed have significant effects on the fluid flow and surface morphology in the melt pool, which are in good agreement with the experimental results. Compared with the first track, the second track has larger melt pool geometry, higher melt temperature, and faster fluid flow. The melt flows intensely at the initial position due to the high flow rate in the limited melt space. Because there is enough space for the metal flow, the second track can obtain smooth surface morphology more easily compared to the first track. The melt pool temperature at the laser beam center fluctuates during the laser scanning process. This depends on the effects of the interaction between heat conduction or heat accumulation or the interaction between heat accumulation and violent fluid flow. The temperature distribution and fluid flow in the melt pool benefit the analysis and understanding of the evolution mechanism of the melt pool geometry and surface topography and further allow regulation of the L-PBF process of Ti6Al4V.
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Juliana, Juliana. "DOMESTICATION AND FOREIGNIZATION OF JAVANESE TERMS IN THE YEARS OF THE VOICELESS NOVEL." Journal MELT (Medium for English Language Teaching) 4, no. 1 (June 4, 2019): 12. http://dx.doi.org/10.22303/melt.4.1.2019.12-23.
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<p>This research analyses domestication and foreignization strategies in translating the Javanese cultural words in Years of the Voiceless novel. The objective of this research was to obtain the most frequent strategies used in altering Javanese cultural words that influence the ideology used in the translation of the Years of the Voiceles novel. This research was a qualitative descriptive method. The data collection was by reading source and target texts with note taking techniques. The method of data analysis used content analysis with a comparison strategy of translated text in the novel and source text. The theory used to analyze the translation ideology was Venuti (2008) while the theory used to analyze Javanese cultural words was Newmark's theory of cultural categories. The result of the research showed that there was an influence of domestication ideology in the translation of the novel the years of the voiceless at the Javanese cultural words. The domestication was the dominant strategy used in translating Javanese cultural words in the Years of Voiceless novel. Therefore, It indicates the translator tend to maintain Javanese cultural words in ST into English culture words in TT.</p>
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Liu, Zhaofei, Zhijun Yao, and Rui Wang. "Contribution of glacial melt to river runoff as determined by stable isotopes at the source region of the Yangtze River, China." Hydrology Research 47, no. 2 (October 22, 2015): 442–53. http://dx.doi.org/10.2166/nh.2015.089.
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The primary objective of this study was to quantify the contribution of glacial melt to total runoff in the Gaerqu River catchment, which is located in the source region of the Yangtze River, China. The isotope hydrograph separation method was used to separate glacier melt runoff from total runoff in the catchment. The degree-day method was used to investigate temporal variations in glacial melt runoff. The results showed that the contribution of glacial melt runoff to total runoff was 15.0%. The uncertainty of the separation was ± 3.7% at the confidence level of 95%. Glacial melt runoff was mainly generated in June, July, and August. The runoff coefficient was 0.23 for the catchment. Precipitation-induced runoff constituted 19.9% of the total precipitation, meaning that precipitation loss was >80% across the study period (a hydrological year). The Local Meteoric Water Line (LMWL) of the catchment was fitted as δ2H = 7.75 δ18O + 5.93. This line has a smaller slope and intercept than the Global Meteoric Water Line. The regression-lines for the δ18O and δ2H values of stream water indicated that evaporation was greater over the entire catchment than it was for the upstream region alone.
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Kimura, Satoshi, Paul R. Holland, Adrian Jenkins, and Matthew Piggott. "The Effect of Meltwater Plumes on the Melting of a Vertical Glacier Face." Journal of Physical Oceanography 44, no. 12 (November 26, 2014): 3099–117. http://dx.doi.org/10.1175/jpo-d-13-0219.1.
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Abstract Freshwater produced by the surface melting of ice sheets is commonly discharged into ocean fjords from the bottom of deep fjord-terminating glaciers. The discharge of the freshwater forms upwelling plumes in front of the glacier calving face. This study simulates the meltwater plumes emanated into an unstratified environment using a nonhydrostatic ocean model with an unstructured mesh and subgrid-scale mixing calibrated by comparison to established plume theory. The presence of an ice face reduces the entrainment of seawater into the meltwater plumes, so the plumes remain attached to the ice front, in contrast to previous simple models. Ice melting increases with height above the discharge, also in contrast to some simple models, and the authors speculate that this “overcutting” may contribute to the tendency of icebergs to topple inwards toward the ice face upon calving. The overall melt rate is found to increase with discharge flux only up to a critical value, which depends on the channel size. The melt rate is not a simple function of the subglacial discharge flux, as assumed by many previous studies. For a given discharge flux, the geometry of the plume source also significantly affects the melting, with higher melt rates obtained for a thinner, wider source. In a wider channel, two plumes are emanated near the source and these plumes eventually coalesce. Such merged meltwater plumes ascend faster and increase the maximum melt rate near the center of the channel. The melt rate per unit discharge decreases as the subglacial system becomes more channelized.
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Bons, Paul D., Jens K. Becker, Marlina A. Elburg, and Kristjan Urtson. "Granite formation: Stepwise accumulation of melt or connected networks?" Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 105–15. http://dx.doi.org/10.1017/s175569100901603x.
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ABSTRACTSeveral authors have proposed that granitic melt accumulation and transport from the source region occurs in networks of connected melt-filled veins and dykes. These models envisage the smallest leucosomes as ‘rivulets’ that connect to feed larger dykes that form the ‘rivers’ through which magma ascends through the sub-solidus crust. This paper critically reviews this ‘rivulets-feeding-rivers’ model. It is argued that such melt-filled networks are unlikely to develop in nature, because melt flows and accumulates well before a fully connected network can be established. In the alternative stepwise accumulation model, flow and accumulation is transient in both space and time. Observations on migmatites at Port Navalo, France, that were used to support the existence of melt-filled networks are discussed and reinterpreted. In this interpretation, the structures in these migmatites are consistent with the collapse and draining of individual melt batches, supporting the stepwise accumulation model.
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Cranston, Ray E. "Marine sediments as a source of atmospheric methane." Bulletin of the Geological Society of Denmark 41 (March 30, 1994): 101–9. http://dx.doi.org/10.37570/bgsd-1995-41-11.
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Methane sources and sinks have been evaluated at 10 sites off the east coasts of Canada and Russia. More than 99% of the diffusive methane flux from marine sediments appears to be consumed by microbial oxidation when dissolved sulfate is present. At 3 sites, methane bubble vents were found. Two of the vents, located in the Okhotsk Sea, appear to result from gas being released along faults. The third plume site was located in a shallow harbour where a large amount of organic carbon is deposited in shallow water. The global diffusive and advective (bubbles) release of methane to the atmosphere from marine sediments is estimated to fall into the range of 1 - 10 TgC a-1 (1 Tg = 1012 g). Researchers have speculated that marine gas hydrate deposits hold vast quantitites of methane that may melt and be released as a result of global warming. A warmer atmosphere could directly heat the ocean and/or change ocean current systems, which could bring warmer water to some areas. Hydrate samples were recovered from two sites in the Okhotsk Sea. These deposits, in 700 to 800 m of water, would require water temperatures to increase by 8°C in order to melt the hydrate. Quantitative estimates of hydrate reservoirs near the minimum pressure stability zone are needed to remove the uncertainty whether this will be a significant positive feedback loop for global warming.
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Rushmer, Tracy, and Matt Jackson. "Impact of melt segregation on tonalite-trondhjemite-granodiorite (TTG) petrogenesis." Transactions of the Royal Society of Edinburgh: Earth Sciences 97, no. 4 (2008): 325–36. http://dx.doi.org/10.1017/s0263593300001486.
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Abstract“In searching for the origin of granites, it is tempting to view them as purely chemical systems”(Pitcher 1979, p. 90)Although sophisticated geochemical studies tell us that tonolite-trondhjemite-granodiorite (TTG) plutonic complexes must be formed by partial melting of metabasaltic source material, they cannot tell us the tectonic regime in which this crust was formed, nor how large volumes of TTG magma can be generated. This study suggests that a solution to TTG arc crust formation requires a strongly interdisciplinary approach, to resolve the tectonic setting (slab melt verses mafic lowermost crust sources), the time and length scales for melting and extraction, and the role of melt segregation mechanisms in the formation of both Archean TTGs and more recent adakite-like magmas. The aim of this paper is to present an experimental approach which, when coupled with numerical models, allows some of these issues to be addressed. The experiments are designed to reproduce the local changes in bulk composition that are predicted to occur in response to buoyancy-driven melt segregation along grain edges and associated compaction of the solid residue. The preliminary study presented here documents the changes we observe in the melt composition and melt and solid phase modes between earlier direct partial melting and the new segregation equilibration experiments on metabasalt bulk compositions. The results suggest that if dynamic melt segregation and equilibrium processes are active, they may modify the normally robust geochemical indicators, such as Mg-numbers, which are typically used to develop models of TTG petrogenesis.
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Miller, Calvin F., E. Bruce Watson, and T. Mark Harrison. "Perspectives on the source, segregation and transport of granitoid magmas." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 79, no. 2-3 (1988): 135–56. http://dx.doi.org/10.1017/s0263593300014176.
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ABSTRACTThe pursuit of a comprehensive theory for the origin and evolution of granitoids is hindered by our incomplete understanding of the nature of the source and the mechanisms by which the magma is segregated and transported. This paper is a collection of three largely independent and necessarily incomplete perspectives on these outstanding issues. Lower to mid-crustal regions, which contain the principal source material for granitoid magmas, are highly heterogeneous. Consideration of available transfer mechanisms suggests that (1) this heterogeneity survives all foreseeable lower crustal processes; (2) closure is on very different scales for different chemical systems (e.g. Pb, Nd, Sr and O isotopes); in almost all cases, however, closure scale is much smaller than the scale of magma extraction zones for plutons; and (3) pluton-wide homogenisation of magmas by diffusion is precluded by low diffusivities in felsic melts. Thus, granitoid magmas begin life as aggregates of small, isolated chemical domains; homogenisation occurs only through (and on the scale of) effective stirring by convection. Because of variability in local conditions as well as in bulk composition, crustal regions undergoing anatexis must be patchworks with variable melt fractions and melt compositions. The way in which magma is extracted from and coalesces with this patchwork exerts a critical influence on the nature of granitoid magmas. Decoupling and unusual coupling of compositional parameters and isotopic heterogeneity within plutons are to be expected in crust-derived granitoids and do not require contamination. Granites image their sources, but these sources are ill-defined and do not correspond to simple, easily-recognised materials. Extent and patterns of heterogeneity remaining in crystallised plutons may be effective indicators of the ascent process.The efforts of materials scientists in characterising the nature and evolution of solid-phase interconnectivity in partially-molten materials may offer some insights into crustal magmatic processes. In particular, the rheological properties of partially-molten crustal rocks are probably strongly affected by the contiguity of the solid grains in the system (i.e. the fraction of their surface area that is shared with other grains). Theory and experimental data for simple alloy systems reveal that contiguity depends principally upon melt fraction and upon the characteristic wetting angle (θ) of the system. Measured θ's in granitoids (∼50° on average) imply contiguities as high as ∼0·2 for melt fractions of 0·5 or greater. This value in turn suggests that, at least under static conditions, a continuous skeleton of solid grains is maintained to quite high degrees of melting in the crust. Consequently, regions consisting of 50% or more of melt can, in principle, maintain not only high yield strength, but also high viscosity (provided the strain rate is sufficiently low to avoid disrupting contiguity).Despite the fact that on some time scale the continuous solid skeleton of a partially-molten region resists deformation, it is itself subject to textural evolution that could lead to the upward migration of melt. Occasional detachment of grains from the skeleton and subsequent “microsettling” within the partially-molten column may lead eventually to compaction of the solid (without plastic deformation) and net upward displacement of melt.Proposed granite transport mechanisms are discussed, although several are viewed as having historical interest only. In the absence of tectonic transport, diapirism appears to be the most compelling of these processes. However, considerable diversity exists in the literature regarding a pivotal requirement for this mechanism. Structural studies have tended to conclude that the granite diapir must be highly crystallised in order to ascend, whereas results of physical modelling yield contradictory results. For ascent to occur in these models, the magmas must be sufficiently fluid to allow convective circulation. Indeed, heat loss associated with diapirism is so efficient as to be a significant restriction on overall ascent. The resolution of these contrasting views appears to be that they reflect different phases of the ascent/emplacement continuum. Understanding the emplacement history of a southeastern Australian pluton allows assessment, via the diapir model, of the flow properties of the rock within the deformation aureole. Results suggest rock viscosities about an order of magnitude lower than those predicted by laboratory experiments, perhaps reflecting difficulties in reproducing natural conditions in the laboratory.
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Bash, Eleanor A., and Shawn J. Marshall. "Estimation of glacial melt contributions to the Bow River, Alberta, Canada, using a radiation-temperature melt model." Annals of Glaciology 55, no. 66 (2014): 138–52. http://dx.doi.org/10.3189/2014aog66a226.
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AbstractAlberta’s Bow River has its headwaters in the glaciated eastern slopes of the Canadian Rockies and is a major source of water in southern Alberta. Glacial retreat, declining snowpacks and increased water demand are all expected in the coming century, yet there are relatively few studies focusing on quantifying glacial meltwater in the Bow River. We develop a new radiation-temperature melt model for modelling distributed glacier mass balance and runoff in the Bow River basin. The model reflects physical processes through the incorporation of near-surface air temperature and absorbed radiation, while avoiding problems of collinearity through the use of a radiation-decorrelated temperature index. The model is calibrated at Haig Glacier in the southern portion of the basin and validated at Haig and Peyto Glaciers. Application of the model to the entire Bow River basin for 2000-09 shows glacier ice melt is equivalent to 3% of annual discharge in Calgary on average. Modelled ice melt in August is equal to 8-20% of the August Bow River discharge in Calgary. This emphasizes the importance of glacier runoff to late-summer streamflow in the region, particularly in warm, dry years.
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Rozhkov, Konstantin A., Sergey S. Starikov, Stepan V. Varushkin, Dmitry N. Trushnikov, and Irina A. Zubko. "ON IMPROVING THE METHOD OF ELECTRON-BEAM DEPOSITION." Journal of Physics: Conference Series 2077, no. 1 (November 1, 2021): 012017. http://dx.doi.org/10.1088/1742-6596/2077/1/012017.
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Abstract The paper deals with improvement of the electron-beam additive forming of metal products using a vertically fed filler wire in vacuum with two electron beams as a heating source. We compared the importance of the power of the heat source required for fusing the layers with each other and the calculated power of the heat source required to melt the filler wire and the surface of the product. Within the experimental conditions of the multilayer electron beam deposition using side wire feeding, the electron beam power of 2.4 kW was required to ensure fusion without the defect formation between the layers during the deposition of Ti-6Al-4V titanium alloy. At the same time, approximate calculations of the minimum power of the heat source required to melt the filler wire and the surface of the product showed a level of 730 W.
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Andriani, Nova. "THE ANALYSIS OF THE TEXT IN SIBOLGA HISTORY BROCHURE BY USING SISTEMIC FUNCTIONAL LINGUISTIC." Journal MELT (Medium for English Language Teaching) 1, no. 2 (May 24, 2018): 144. http://dx.doi.org/10.22303/melt.1.2.2016.144-154.
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This Study deals with textual functions in the text of Sibolga History. The objectives of the study were to: (1) describe the types of themes in the text of Sibolga History brochure and (2) identify the social contexts in the text of Sibolga History brochure. This research applied qualitative descriptive design to describe the data analysis. The qualitative analysis was applied in order to find out theoretically related to the research questions. The source of data was the text of Sibolga History brochure which consists of 22 paragraphs. The source was taken through documents that were written in the text of Sibolga History. The data was analyzed by Miles and Huberman model. The theme focused on Topical theme and there are 103 clauses of theme. The text was analyzed with the reference to the theories of Systemic Functional Linguistic (SFL). The finding showed that the proportions are: (1) Marked Simple Theme is 53 %, (2) Marked Multiple Theme is 5%, (3) Unmarked Simple Theme is 41 % and the last (4) Unmarked Multiple Theme wascan not found. It was concluded that the Marked Simple Theme are used in large number and Marked MultipleTheme are used in smaller number. The social context in this text can be seen through the field, tenor and mode of the text of Sibolga History brochure.