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261.
Necessary and sufficient conditions are obtained for a bipartitegraph to admit a matching which includes a preassigned set ofedges and excludes another preassigned set of edges. 1991 MathematicsSubject Classification 05C70. 相似文献
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An experimental study has been performed shedding light on the conformational energies of the asymmetric ether n-butyl ethyl ether. Rotational spectroscopy between 7.8 GHz and 16.2 GHz has identified two conformers of n-butyl ethyl ether, C4H9OC2H5. In these experiments spectra were observed as the target compound participated in an argon expansion from high to low pressure causing molecular rotational temperatures to be below 4 K. For one conformer, 95 pure rotational transitions have been recorded, for the second conformer, 20 pure rotational transitions were recorded. Rotational constants and centrifugal distortion constants are presented for both butyl ethyl ether conformers. The structures of both conformers have been identified by exploring the multi-dimensional molecular potential energy surface using ab initio calculations. From the numerous low energy conformers identified using ab initio methods, the three lowest conformers were pursued at increasingly higher levels of theory, i.e. complete basis set extrapolations, coupled cluster methods, and also taking into consideration zero point vibrational energies. The two conformers observed experimentally are only revealed to be the two lowest energy conformers when high levels of quantum chemical methodologies are employed. 相似文献
264.
C.T. Dewberry G.S. Grubbs II M.M. Serafin S.A. Cooke 《Journal of Molecular Spectroscopy》2008,248(1):20-25
A Fourier transform microwave spectrometer has been used to make high resolution measurements on the J = 1-0 rotational transition for 11 isotopomers of SnO. For the most abundant isotopomer the transition was observed in the v = 0, 1, 2, and 3 states. Magnetic hyperfine structure was observed in the transitions for 115Sn16O, 117Sn16O and 119Sn16O. The nuclear spin-rotation constant CI(Sn) has been determined for these isotopomers for the first time and these constants have been related to nmr shielding parameters. A multi-isotopomer analysis, including data from the 120Sn17O and 120Sn18O isotopomers, has been performed on the data. Born-Oppenheimer breakdown parameters were required in the fit and these parameters have been compared to those for the other Sn-chalcogenides. 相似文献
265.
Distance measures for dynamic citation networks 总被引:1,自引:0,他引:1
Michael J. Bommarito II Daniel Martin Katz Jonathan L. Zelner James H. Fowler 《Physica A》2010,389(19):4201-4208
Acyclic digraphs arise in many natural and artificial processes. Among the broader set, dynamic citation networks represent an important type of acyclic digraph. For example, the study of such networks includes the spread of ideas through academic citations, the spread of innovation through patent citations, and the development of precedent in common law systems. The specific dynamics that produce such acyclic digraphs not only differentiate them from other classes of graphs, but also provide guidance for the development of meaningful distance measures. In this article, we develop and apply our sink distance measure together with the single-linkage hierarchical clustering algorithm to both a two-dimensional directed preferential attachment model as well as empirical data drawn from the first quarter-century of decisions of the United States Supreme Court. Despite applying the simplest combination of distance measure and clustering algorithm, analysis reveals that more accurate and more interpretable clusterings are produced by this scheme. 相似文献
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Gregory F. Meyers Michael T. Dineen Edward O. Shaffer II Ted Stokich Jr. Jang‐hi Im 《Macromolecular Symposia》2001,167(1):213-226
Scanning probe microscopy (SPM) techniques are used to characterize surfaces related to the processing of benzocyclobutene (BCB) dielectric thin films. Thermally cured resins and photodefineable resins are sold under the trade name CYLCOTENETM1) for electronic applications. TappingMode AFM (TMAFM) imaging is used to follow changes in adhesion promoter morphology upon baking to help explain adhesion performance. Power spectral density (PSD) analysis of TMAFM images of plasma treated BCB surfaces are unique and can be used to ‘fingerprint’ processes. Selective oxidation of the BCB surface can be used to fabricate a phase imaging standard for TMAFM. Near surface modulus of the BCB materials is 3.6 ± 0.2 GPa and the hardness is 0.38 ± 0.2 GPa measured by depth‐sensing nanoindentation. Creep recovery of indents can be used to qualitatively distinguish between thermal and photocureable materials. A heated tip in a scanning thermal microscope can induce the thermal curing of BCB over micron sized areas. Local thermal analysis with the same probe allows the measurement of the changes in the glass transition, Tg, at the surface with cure temperature. 相似文献
269.
Manish K. Saraf Louis M. Wojcinski II Karen A. Kennedy Sylvain Gerard Paul A. Charpentier Joseph M. DeSimone George W. Roberts 《Macromolecular Symposia》2002,182(1):119-129
The surfactant-free precipitation polymerization of vinylidene fluoride (VF2) in supercritical carbon dioxide was studied in a continuous stirred autoclave. The polymerization temperature ranged from 65 to 85°C, the average residence time in the reactor varied from 10 to 50 min., and the pressure was between 210 and 305 bar. Diethyl peroxydicarbonate was used as the initiator. The fractional conversion of monomer varied from 7 to 26%, the number-average molecular weight of the polymer was between about 14,000 and 79,000, and the weight-average molecular weight was between about 21,000 and 700,000. In many cases, the polymer exhibited a bimodal molecular-weight distribution, especially at high monomer concentrations. 相似文献