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Quasi two-dimensional random site percolation model objects have been prepared using a synchrotron radiation lithography technique with a spatial resolution better than 50 microm and an aspect ratio of up to 17. Flow of water through the pore space was studied with the aid of an NMR velocity mapping method and compared with a computational fluid dynamics simulation. In order to be able to measure and map widely distributed flow velocities with microscopic resolution (typically 40 x 40 microm), an experimental protocol that permits one to cover an effectively very wide velocity field of view (0.6-10 mm/s) had to be developed. 相似文献
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Hydrodynamic flow and electric currents through model porous media were investigated. The transport rates through the individual pathways of the pore network are determined by the local width of the pore channels and by the driving mechanism. The model objects represent quasi two-dimensional random site percolation clusters. The calculated design was realized by milling the structure in polystyrene sheets. Velocity maps of stationary flow and current density maps of stationary currents through the cluster were acquired by magnetic resonance imaging methods. The findings were compared to the results of numerical simulations based on the same structure. Since the difference in the transport patterns of the different driving mechanisms are expected to be more pronounced in smaller pore spaces, ultra deep X-ray lithography has been used for the fabrication of downsized model objects with a spatial resolution of better than 50 microm and an aspect ratio as large as 20. First results obtained with these objects are reported. 相似文献
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Harries C. Hofmann Fritz Ditmar R. Backer H. J. Stark J. Ruggli P. Nierenstein M. Donath E. Indra A. Eisenlohr F. Pitaval M. R. Hoffmann F. Danneel H. Meyer J. Fischer Franz Rinne F. Block W. Riemann C. Buchner G. Hinneberg P. v. Meyer E. Engler C. Wöhler L. Wallach O. Luther R. Nernst W. Blanc M. Le Kossel A. Kellner O. Immendorff H. Witt O. N. 《Analytical and bioanalytical chemistry》1913,52(10-11):664-668
Analytical and Bioanalytical Chemistry - 相似文献
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W. Kossel 《Zeitschrift für Physik A Hadrons and Nuclei》1947,124(1-2):77-79
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Cyclic cross-polarization from a proton magnetization to 13C and from there back to proton coherences permits the indirect, 13C chemical shift selective detection of hydrocarbon compounds in the proton NMR channel. This excitation technique can be combined with elements of one-, two- or three-dimensional magnetic resonance imaging permitting the measurement of time-resolved spatial distributions of hydrocarbon components. Beginning this sort of CYCLCROP mapping experiment with a non-equilibrium distribution of the constituents in the system allows one to study the time evolution of the concentrations of all components that can be identified by characteristic 13C resonance lines. As applications, studies of ingress, mixing, gel formation, transport and metabolism in living plants, long-time inter- and self-diffusion in complex hydrocarbon systems are suggested. As a test experiment, the diffusion of methanol in swollen polymethylmethacrylate was examined. 相似文献