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- Slama, J, et al.
(författare)
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Plešovice zircon – A new natural standard for U-Pb and Hf isotopic microanalysis
- 2007
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Ingår i: Goldschmidt Conference Abstracts.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Increasing number of geological applications requires theuse of well-characterized and widely available referencematerials for in situ analysis. We have established a newnatural zircon standard (“Plešovice”) for U-Pb dating and Hfisotopic analysis by laser ablation ICP-MS.The ID-TIMS U-Pb age of the Plešovice zircon has beendetermined to 336.9±0.2 Ma (95% confidence limits; mean206Pb/238U age). The U-Pb ages obtained by LA ICP-MS (3labs) and SIMS techniques show larger spread but within theiranalytical uncertainties they are consistent with the TIMS age.Hafnium isotopic composition of the Plešovice zircon appearsto be homogenous within and between grains. Combined laserablation and solution MC ICP-MS analyses gave a mean176Hf/177Hf value of 0.282481±0.000013 (95% confidencelimits, 87 analyses). Cathodoluminescence and BSE imagingand chemical analyses revealed that discrete zones in thePlešovice zircon are enriched in trace elements and especiallyin U and Th. Raman spectroscopy suggests that these highlyradiation-damaged areas have not undergone any annealing.Our LA ICP-MS analyses did not indicate any Pb-loss but thehigh intensities of measured U signal require that these areasare avoided during routine U-Pb isotopic analysis.
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- Fritsch, Daniel J., et al.
(författare)
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Experimental and Computational Study of 2D Smooth Wall Turbulent Boundary Layers in Pressure Gradient
- 2022
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Ingår i: AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- This paper describes a collaborative experimental and computational study of smooth wall boundary layers in a systematic family of favorable and adverse pressure gradients. The objective is to advance turbulence modeling of these flows, in particular the effects of pressure gradients that can be classified as non-equilibrium. This collaboration is a component of the larger NATO AVT-349 Research Task Group. Experiments under this effort are conducted at Virginia Tech and computational efforts are presented from Virginia Tech, the German Aerospace Center (DLR), the University of Melbourne, Chalmers University of Technology, the Maritime Research Institute Netherlands (MARIN) in conjunction with the University of Lisbon Instituto Superior Técnico (IST) (MARIN/IST), and the Sirehna Naval Group. This paper describes some of the key elements of the experimental and computational approaches, the efforts made for cross-discipline collaboration, verification, and validation, and reports on some initial results and findings. The agreement between various RANS solutions and RANS turbulence models and between RANS solutions and experiment are generally good, but questions remain as to the efficacy of RANS modeling for non-equilibrium boundary layer flows and some potential directions for future investigations are suggested.
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- de Hoogh, Kees, et al.
(författare)
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Development of West-European PM2.5 and NO2 land use regression models incorporating satellite-derived and chemical transport modelling data
- 2016
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Ingår i: Environmental Research. - : Elsevier BV. - 0013-9351 .- 1096-0953. ; 151, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Satellite-derived (SAT) and chemical transport model (CTM) estimates of PM2.5 and NO2 are increasingly used in combination with Land Use Regression (LUR) models. We aimed to compare the contribution of SAT and CTM data to the performance of LUR PM2.5 and NO2 models for Europe. Four sets of models, all including local traffic and land use variables, were compared (LUR without SAT or CTM, with SAT only, with CTM only, and with both SAT and CTM). LUR models were developed using two monitoring data sets: PM2.5 and NO2 ground level measurements from the European Study of Cohorts for Air Pollution Effects (ESCAPE) and from the European AIRBASE network. LUR PM2.5 models including SAT and SAT+CTM explained ~60% of spatial variation in measured PM2.5 concentrations, substantially more than the LUR model without SAT and CTM (adjR(2): 0.33-0.38). For NO2 CTM improved prediction modestly (adjR(2): 0.58) compared to models without SAT and CTM (adjR(2): 0.47-0.51). Both monitoring networks are capable of producing models explaining the spatial variance over a large study area. SAT and CTM estimates of PM2.5 and NO2 significantly improved the performance of high spatial resolution LUR models at the European scale for use in large epidemiological studies.
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