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F. Albarède - One of the best experts on this subject based on the ideXlab platform.
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Thermal evolution of planetesimals during accretion
Icarus, 2017Co-Authors: Yanick Ricard, David Bercovici, F. AlbarèdeAbstract:Abstract Although the Mass Distribution of planetesimals during the early stages of planetary formation has been discussed in various studies, this is not the case for their temperature Distribution. Mass and temperature Distributions are closely linked, since the ability of planetesimals to dissipate the heat produced by both radioactive decay and impacts is related to their size and hence Mass. Here, we propose a simple model of the evolution of the joint Mass-temperature Distribution through a formalism that encompasses the classic statistical approach of Wetherill (1990). We compute the statistical Distribution of planetesimals by using simple rules for aggregation. Although melting temperatures can be easily reached, the formation of molten planetary embryos requires that they be formed in only a few 100 kyr. Our aggregation model, which even ignores fragmentation during collision, predicts that planetesimals with radii less than approximately 20 km will not melt during their formation.
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Thermal evolution of planetesimals during accretion
Icarus, 2017Co-Authors: Yanick Ricard, David Bercovici, F. AlbarèdeAbstract:Although the Mass Distribution of planetesimals during the early stages of planetary formation has been discussed in various studies, this is not the case for their temperature Distribution. Mass and temperature Distributions are closely linked, since the ability of planetesimals to dissipate the heat produced by both radioactive decay and impacts is related to their size and hence Mass. Here, we propose a simple model of the evolution of the joint Mass-temperature Distribution through a formalism that encompasses the classic statistical approach of Wetherill (1990). We compute the statistical Distribution of planetesimals by using simple rules for aggregation. Although melting temperatures can be easily reached, the formation of molten planetary embryos requires that they be formed in only a few 100 kyr. Our aggregation model, which even ignores fragmentation during collision, predicts that planetesimals with radii less than approximately 20 km will not melt during their formation. © 2016 Elsevier Inc.
Yanick Ricard - One of the best experts on this subject based on the ideXlab platform.
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Thermal evolution of planetesimals during accretion
Icarus, 2017Co-Authors: Yanick Ricard, David Bercovici, F. AlbarèdeAbstract:Abstract Although the Mass Distribution of planetesimals during the early stages of planetary formation has been discussed in various studies, this is not the case for their temperature Distribution. Mass and temperature Distributions are closely linked, since the ability of planetesimals to dissipate the heat produced by both radioactive decay and impacts is related to their size and hence Mass. Here, we propose a simple model of the evolution of the joint Mass-temperature Distribution through a formalism that encompasses the classic statistical approach of Wetherill (1990). We compute the statistical Distribution of planetesimals by using simple rules for aggregation. Although melting temperatures can be easily reached, the formation of molten planetary embryos requires that they be formed in only a few 100 kyr. Our aggregation model, which even ignores fragmentation during collision, predicts that planetesimals with radii less than approximately 20 km will not melt during their formation.
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Thermal evolution of planetesimals during accretion
Icarus, 2017Co-Authors: Yanick Ricard, David Bercovici, F. AlbarèdeAbstract:Although the Mass Distribution of planetesimals during the early stages of planetary formation has been discussed in various studies, this is not the case for their temperature Distribution. Mass and temperature Distributions are closely linked, since the ability of planetesimals to dissipate the heat produced by both radioactive decay and impacts is related to their size and hence Mass. Here, we propose a simple model of the evolution of the joint Mass-temperature Distribution through a formalism that encompasses the classic statistical approach of Wetherill (1990). We compute the statistical Distribution of planetesimals by using simple rules for aggregation. Although melting temperatures can be easily reached, the formation of molten planetary embryos requires that they be formed in only a few 100 kyr. Our aggregation model, which even ignores fragmentation during collision, predicts that planetesimals with radii less than approximately 20 km will not melt during their formation. © 2016 Elsevier Inc.
Guangwen Chen - One of the best experts on this subject based on the ideXlab platform.
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Mass transfer in liquid-liquid Taylor flow in a microchannel: Local concentration Distribution, Mass transfer regime and the effect of fluid viscosity
Chemical Engineering Science, 2020Co-Authors: Chaoqun Yao, Qiankun Zhao, Yanyan Liu, Yuchao Zhao, Guangwen ChenAbstract:Abstract Mass transfer characteristics of liquid-liquid Taylor flow with various fluid pairs are investigated, in order to reveal the viscous effects of the fluids. The concentration pattern in continuous slugs, Mass transfer time and Mass transfer coefficient are discussed and analyzed. Several different concentration patterns originated from recirculation are observed at both straight channels and curved bends, respectively. It is shown that the Mass transfer coefficient (Ka and K) can increase with the increase in the viscosity of the continuous phase at large flow rates, which is explained by the increased contribution of the film at the lateral droplet side and its exchange with the bulk slug. Based on the dominance of different parts (i.e., film, cap), three Mass transfer regimes are distinguished. Correlations for each regime, which covers a wide range of fluid viscosity of 0.89–45.6 mPa·s, are developed to predict the Mass transfer coefficient.
Guangguo Ying - One of the best experts on this subject based on the ideXlab platform.
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biocides in the yangtze river of china spatiotemporal Distribution Mass load and risk assessment
Environmental Pollution, 2015Co-Authors: Jianliang Zhao, Zhifeng Chen, Yuanyuan Yang, Qianqian Zhang, Guangguo YingAbstract:Nineteen biocides were investigated in the Yangtze River to understand their spatiotemporal Distribution, Mass loads and ecological risks. Fourteen biocides were detected, with the highest concentrations up to 166 ng/L for DEET in surface water, and 54.3 ng/g dry weight (dw) for triclocarban in sediment. The dominant biocides were DEET and methylparaben, with their detection frequencies of 100% in both phases. An estimate of 152 t/y of 14 biocides was carried by the Yangtze River to the East China Sea. The Distribution of biocides in the aquatic environments was significantly correlated to Gross Domestic Product (GDP), total phosphorus (TP) and total nitrogen (TN), suggesting dominant input sources from domestic wastewater of the cities along the river. Risk assessment showed high ecological risks posed by carbendazim in both phases and by triclosan in sediment. Therefore, proper measures should be taken to reduce the input of biocides into the river systems.
A. Massling - One of the best experts on this subject based on the ideXlab platform.
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Size Distribution, Mass concentration, chemical and mineralogical composition and derived optical parameters of the boundary layer aerosol at Tinfou, Morocco, during SAMUM 2006
Tellus B: Chemical and Physical Meteorology, 2009Co-Authors: Konrad Kandler, Lothar Schütz, C. Deutscher, Martin Ebert, Heiko Hofmann, Simon Jäckel, Ruprecht Jaenicke, Peter Knippertz, K. Lieke, A. MasslingAbstract:During the SAMUM 2006 field campaign in southern Morocco, physical and chemical properties of desert aerosols were measured. Mass concentrations ranging from 30 μ gm −3 for PM2.5 under desert background conditions up to 300 000 μ gm −3 for total suspended particles (TSP) during moderate dust storms were measured. TSP dust concentrations are correlated with the local wind speed, whereas PM10 and PM2.5 concentrations are determined by advection from distant sources. Size Distributions were measured for particles with diameter between 20 nm and 500 μm (parametrizations are given). Two major regimes of the size spectrum can be distinguished. For particles smaller than 500 nm diameter, the Distributions show maxima around 80 nm, widely unaffected of varying meteorological and dust emission conditions. For particles larger than 500 nm, the range of variation may be up to one order of magnitude and up to three orders of magnitude for particles larger than 10 μm. The mineralogical composition of aerosol bulk samples was measured by X-ray powder diffraction. Major constituents of the aerosol are quartz, potassium feldspar, plagioclase, calcite, hematite and the clay minerals illite, kaolinite and chlorite. A small temporal variability of the bulk mineralogical composition was encountered. The chemical composition of approximately 74 000 particles was determined by electron microscopic single particle analysis. Three size regimes are identified: for smaller than 500 nm in diameter, the aerosol consists of sulphates and mineral dust. For larger than 500 nm up to 50 μm, mineral dust dominates, consisting mainly of silicates, and—to a lesser extent—carbonates and quartz. For diameters larger than 50 μm, approximately half of the particles consist of quartz. Time series of the elemental composition show a moderate temporal variability of the major compounds. Calcium-dominated particles are enhanced during advection from a prominent dust source in Northern Africa (Chott El Djerid and surroundings). The particle aspect ratio was measured for all analysed particles. Its size dependence reflects that of the chemical composition. For larger than 500 nm particle diameter, a median aspect ratio of 1.6 is measured. Towards smaller particles, it decreases to about 1.3 (parametrizations are given). From the chemical/mineralogical composition, the aerosol complex refractive index was determined for several wavelengths from ultraviolet to near-infrared. Both real and imaginary parts show lower values for particles smaller than 500 nm in diameter (1.55–2.8 × 10 −3 i at 530 nm) and slightly higher values for larger particles (1.57–3.7 × 10 −3 i at 530 nm).