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Previous publications2–5 have examined the phenomenon of level crossings as predicted by the semiempirical techniques CNDO/26, IMDO7, and MINDO/38 for certain molecules when the total energy is viewed as a function of some conformational property. The purpose of this article is to examine this same phenomenon using the extended Hückel method(EHM)9, the iterated extended Hückel method(IEHM), and an ab-initio procedure with a minimal STO-3G basis set. The molecule chosen for this study is CO2 due to its structural simplicity and since previous calculations2–5 have demonstrated level crossing with this molecule. 相似文献
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Dr. Erik Frank Dipl.‐Chem. Lisa M. Steudle Dr. Denis Ingildeev Dipl.‐Chem. Johanna M. Spörl Prof. Michael R. Buchmeiser 《Angewandte Chemie (International ed. in English)》2014,53(21):5262-5298
This Review gives an overview of precursor systems, their processing, and the final precursor‐dependent structure of carbon fibers (CFs) including new developments in precursor systems for low‐cost CFs. The following CF precursor systems are discussed: poly(acrylonitrile)‐based copolymers, pitch, cellulose, lignin, poly(ethylene), and new synthetic polymeric precursors for high‐end CFs. In addition, structure–property relationships and the different models for describing both the structure and morphology of CFs will be presented. 相似文献
998.
We discuss the length of the longest directed cycle in the sparse random digraph , constant. We show that for large there exists a function such that a.s. The function where is a polynomial in . We are only able to explicitly give the values , although we could in principle compute any . 相似文献
999.
Xing Zhao Gary Shultis Ryan Hurley Michael Sutton William Fourney Uli Leiste Xiaomin Deng 《Experimental Mechanics》2014,54(4):539-555
Small scale models representing key vehicle structural elements, including both floorboards and bottom-mounted, downward V-shape hulls in various configurations, have been manufactured and subjected to a range of buried blast loading conditions. By varying surface stand-off distance and depth of burial for several hull and structure configurations, the input-scaled response of aluminum full-scale vehicle floorboards has been quantified using high speed stereo-vision. Specifically, the maximum vertical acceleration on the floorboard and the corresponding Head Injury Criterion (HIC15) are quantified as metrics to assess the severity of the blast event. Results show standard V-shaped hulls provide essential blast mitigation, with reductions in floorboard measurements up to 47X in maximum acceleration and HIC15. Though variations in protective hull geometry provide modest reductions in the severity of a floorboard blast event, results also show that personnel on typical floorboard structures during blast loading events will incur unacceptable shock loading conditions, resulting in either serious or fatal injury. A more appropriate design scenario would be to consider situations that employ frame-mounted passenger seating to reduce the potential for injury. A second set of experiments will be presented in Part II that focuses on frame motions and accelerations when steel frames and steel structures are employed with various frame connections and coatings for frame blast mitigation. 相似文献
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Stefanie K. Fehler Gerald Pratsch Walter Huber Alain Gast Remo Hochstrasser Michael Hennig Markus R. Heinrich 《Tetrahedron letters》2012,53(17):2189-2194
3-Aryltyramines were prepared in one single step from tyramine and various arenediazonium salts by radical arylation. Binding as well as enzyme inhibition data of the 14 compounds do not prove true interaction with BACE-1. In contrast, with BACE-2 inhibition and binding could be confirmed indicating that 3-aryltyramines are potential starting points for a drug discovery effort. 相似文献