High-resolution x-ray absorption spectroscopy was used to probe the chemical and structural environments of sulfur in coal. Measurement of the sulfur Kedge spectra down to 2472.0 electron volts under nonvacuum conditions was made possible in an all-helium path, and a Stern-Heald type ion chamber was used for fluorescence detection. For a number of selected sulfur-containing minerals and organic model compounds, results show that near-edge spectral features are diagnostic for sulfur in specific organic moieties such as thiols, disulfides, and various heterocyclics, as well as in mineral sulfide and sulfate phases. The spectrum of a model system containing 35 percent iron pyrite and 65 percent benzothiophene was found to match the observed spectral features of a bituminous coal from the eastern United States.
A transonic turbine airfoil design is optimized using an artificial intelligence engineering design shell coupled with an inviscid, adaptive grid, CFD solver. The objective of the optimization is to minimize the downstream static pressure variation resulting from the trailing edge shock structure. Cascade test results verify the analytical predictions. Techniques are described which were used to couple the optimization shell to the 2-D turbine airfoil shape to allow the search for optimal designs and indicate the quality of those designs. The emphasis of the discussion is upon the application of these techniques rather than the physical details of the resulting blade design.
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By employing the Xa-scattering.av'e methnt4 ',4tb a..Cu cluster to model the cheniisorption of CO on a one-fold site of a Cu(100) surfa e. a simple interpretation 9ftesatellite structure observed in the x-ray photoelectron spectrum (XPS) in UNCLASSIFIED that the present Cu 0 cluster is the better model, however.Experimentally, a three peak structure is observed in both the Ols and Cls hole sepctra. The "first" peak, at lowest binding energy, is followed by a second peak at 2-3 eV higher binding energy and the third peak is at 7-8 eV higher binding energy with respect to the first peak.The theoretical model derived here suggests that tfhe unoccupied 2w level of isolated CO is split into two levels 2i_ and 2*f on interaction with the Cu meta In the neutral ground state neither of these leels is occupied. On the introduction of a core hole in the chemisorbed CO(e.g. the Cls hole) the 2* h and 2* a orbitals change their character quite significantly to become 2if; and . The former is now partially occupied and closely resembles the isolated 2 orbitals of CO, and the latter is unoccupied with significant metal character and less CO content. The character of the 1w level of isolated CO is basically the same for the chemisorbed ground state (where it is labeled 1W). However, it changes rather dramatically (label: W*') after the removal of the core electron, as it shiftsto screen the core hole.A description of the final states which give rise to the three peaks observ d in the experimental spectrun can be given in terms of the occupancies of the three orbitals 1', 2i, and 2W'; there is of Course a ls hole in each of the final states. The assignment oF the final state configuration corresponding to the three observed peaks (in order of increasing binding energy) is as follows:.4 ~1 0 (1' 4 (2 0 ( 1 an .3 2 ,0 1.) (1* ) (2wb) ( 2 ) O 2.) (1b)(2%)0(2Fr) and 3.) (1W ) (2%) (2%)The last final state corresponds to the final state configuration found in the isolated CO molecule due to a 17r' 2w' shake-up. Reproduction in whole or in part is permitted for any purpost ,.e United States Government. This document has been approved for public release and sale; its distribution is unlimited. Experimentally, a three peak structure is observed in both the 01 and Cls hole spectra. The "first" peak, at lowest binding energy, is followed by a second peak at 2-3eV higher binding energy and the third peak is at 7-8eV higher binding energy with respect to the first peak.The theoretical model derived here suggests that the unoccupied 2W level of isolated CO is split into two levels 2 wa and 2 "'b on interaction with the Cu metal. In the neutral ground state neither of these levels is occupied. On the introduction of a core hole in the chemisorbed CO (e.g.the CIs hole) the 2w b and 2W a orbitals change their character quite significantly to become :rw and Cw a . The former is now partially occupied and b closely resembles the isolated 2w orbitals of CO, and the latter is unoccupied vith significant metal character nd less CO content. The cha...
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