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排序方式: 共有297条查询结果,搜索用时 328 毫秒
31.
Daniele Simoni Giuseppe GianniniPier Giovanni Baraldi Romeo RomagnoliMarinella Roberti Riccardo RondaninRiccardo Baruchello Giuseppina GrisoliaMarcello Rossi Danilo MirizziFrancesco Paolo Invidiata Stefania GrimaudoManlio Tolomeo 《Tetrahedron letters》2003,44(14):3005-3008
A double Suzuki cross-coupling protocol has been devised as a practical route to a variety of terphenyls. Good chemoselectivity was observed. Unsymmetrically substituted triphenylenes were also easily prepared. 相似文献
32.
Romeo Rizzi 《Discrete Mathematics》2006,306(13):1390-1404
We consider graphs which contain both directed and undirected edges (partially directed graphs). We show that the problem of covering the edges of such graphs with a minimum number of edge-disjoint directed paths respecting the orientations of the directed edges is polynomially solvable. We exhibit a good characterization for this problem in the form of a min-max theorem. We introduce a more general problem including weights on possible orientations of the undirected edges. We show that this more general weighted formulation is equivalent to the weighted bipartite b-factor problem. This implies the existence of a strongly polynomial algorithm for this weighted generalization of Euler's problem to partially directed graphs (compare this with the negative results for the mixed Chinese postman problem). We also provide a compact linear programming formulation for the weighted generalization that we propose. 相似文献
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Maria Stella Mongioví Silvana Romeo 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1996,47(1):144-161
A dissipative model of helium II was built up in previous works, using a 13-field extended thermodynamic theory formulated by Liu and Müller. In this work a generalization of such model is presented, where an extended thermodynamics with 14 fields due to Kremer is used. It is shown that the fourteenth field is able to account for the experimental data concerning the second sound attenuation. Further, the proposed theory is able to explain the Osborne experiment. Finally, a comparison with the two-fluid model is performed, emphasizing the different ways in which the dissipative phenomena are explained by the two theories. 相似文献
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Giuseppe Chidichimo Marcello Longeri Giuseppina Menniti Giovanni Romeo Alida Ferlazzo 《Magnetic resonance in chemistry : MRC》1984,22(1):52-54
The ring mobility of some 1,5-benzodiazepine-2,4-diones and 1,4-benzodiazepin-2-one has been investigated by the temperature dependence of their 1H NMR spectra. The activation parameters have been obtained, and the influence of N-1 substitution on the ring mobility is discussed, taking into account previously reported data for similar compounds. 相似文献
37.
Bianco A Dezzi S Bonadies F Romeo G Scarpati ML Uccella N 《Natural product research》2006,20(5):475-478
Aroma of olive oil is a very complex mixture of components. Analysis of head space of a series of virgin olive oil samples indicate a great variability of volatile substances composition in olives and these data probably should be related to the story of olives after collecting. 相似文献
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The paper presents preliminary results of a work in progress addressing the hydrodynamic stability of swirling flows problems in ducts with variable radius which imply mathematical modeling, dynamic and stability investigations. The proposed quasi-analytical method aims to obtain the velocity profiles with a low order approximation method of which the computation costs were neglijable and regain the central stagnation zone developed in the fluid. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
40.
Romeo Brunetti Klaus Fredenhagen Katarzyna Rejzner 《Communications in Mathematical Physics》2016,345(3):741-779
We construct perturbative quantum gravity in a generally covariant way. In particular our construction is background independent. It is based on the locally covariant approach to quantum field theory and the renormalized Batalin–Vilkovisky formalism. We do not touch the problem of nonrenormalizability and interpret the theory as an effective theory at large length scales. 相似文献