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The spin density distributions in the radical anions of nitrobenzene and some para substituted nitrobenzenes are calculated using the unrestricted Hatree-Fock formalism of Amos and Snyder. A parameter scheme which gives satisfactory account of the electronic transitions and molecular ionisation potentials of substituted benzenes (nitrobenzene, toluene, aniline, benzaldehyde and benzonitrile) is used for spin density calculations of the nitro radical anions. The importance of spin densities on neighbouring atoms on the hyperfine splitting of nitrogen atom is discussed. It is seen that although Karplus-Fraenkel theory gives a better estimate of14N splitting constant, the simple McConnell-type of relation is approximately valid for the nitro group-nitrogen. The--parameters for use with unrestricted Hartree-Fock spin densities for the prediction of nitrogen hyperfine couplings in nitro, amino and cyano groups are summarised.
Zusammenfassung Die Spindichteverteilungen in den Radikalanionen des Nitrobenzols und einiger parasubstituierter Nitrobenzole werden mit Hilfe des UHF-Formalismus von Amos und Snyder berechnet. Zur Ermittlung der Spindichte der nitroaromatischen Radikalanionen wird ein Parameterschema benutzt, das zufriedenstellende Darstellung der Elektronenübergänge und der molekularen Ionisationspotentiale von substituierten Benzolen (Nitrobenzol, Toluol, Anilin, Benzaldehyd, Benzonitril) gestattet. Der Einfluß der Spins von benachbarten Atomen auf die Hyperfeinaufspaltung des Stickstoffatoms wird diskutiert. Es zeigt sich, daß zur näherungsweisen Beschreibung des Stickstoffs der Nitrogruppe eine einfache Gleichung des McCornell-Typs ausreicht, wenn auch die Karplus-Fraenkel-Theorie eine bessere Abschätzung der14N-Aufspaltungskonstanten ermöglicht. Die --Parameter, die zur Voraussage der Stickstoff-Hyperfeinkopplung in Nitro-, Amino- und Cyanogruppen mit Hilfe der UHF-Spindichten erforderlich sind, werden zusammengestellt.相似文献
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The dependence of the conversion efficiency of a piezoelectric transducer on its frequency and the input electrical power has been examined and it is found that the efficiency is dependent not on the input power but on frequency and the nature of the liquid 相似文献
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Conclusion The quantitative agreement with experimental barrier height and the extra stabilization energy of cis-N2F2 over trans-N2F2 may not be considered to be very good, but this is only to be expected as small differences between large quantities are being calculated. It appears from our present calculations that the use of Cusachs relation for evaluating the off-diagonal matrix elements in this system is open to question since the experimentally observed planarity of N2F2 is not correctly predicted by the use of this relation. We therefore prefer the use of the Wolfsberg-Helmholz relation in this system. A value of K= 1.75 appears to be preferable. The results of all the E.H.T. calculations made here for difluorodiazine clearly show that a twisted transition state is more probable than a linear one (LT or LC) in the isomerization of trans-N2F2 to cis-N2F2. This conclusion also receives further support from a consideration of the high preexponential factor in the rate equation [1] and the multiplicity of the transition state. 相似文献
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Supplier development involves efforts undertaken by manufacturing firms to improve their suppliers’ capabilities and performance. These improvement efforts can be targeted at a variety of areas such as quality management, product development, and cost reduction. Since supplier development requires investments on the part of the manufacturer, it is important to optimally allocate investment dollars among multiple suppliers to minimize risk while maintaining an acceptable level of return. This paper presents a set of optimization models that address this issue. We consider two scenarios: single-manufacturer and multiple suppliers (SMMS) and two-manufacturer and multiple suppliers (TMMS). In the SMMS case, we suggest optimal investments in various suppliers by effectively considering risk and return. The TMMS case investigates whether manufacturers with differing capabilities could gain risk reduction benefits from cooperating with each other in supplier development. Through illustrative applications, we identify conditions in which both cooperation and non-cooperation are beneficial for manufacturers. Under conditions of cooperation, we propose optimal investments for manufacturers to achieve high levels of risk reduction benefits. 相似文献