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941.
942.
943.
Herbert Fischer 《Computational Optimization and Applications》1992,1(3):327-344
This paper is concerned with automatic differentiation methods for computing the reduced gradient M
t
G and the reduced Hessian matrix M
t
HM. Hereby G is the gradient and H is the Hessian matrix of a real function F of n variables, and M is a matrix with n rows and k columns where kn. The reduced quantities are of particular interest in constrained optimization with objective function F. Two automatic differentiation methods are described, a standard method that produces G and H as intermediate results, and an economical method that takes a shortcut directly to the reduced quantites. The two methods are compared on the basis of the reqired computing time and storage. It is shown that the costs for the economical method are less than (k
2+3k+2)/(n
2+3n+2) times the expenses for the standard method. 相似文献
944.
945.
946.
947.
E. Jäger K. Bürkmann B. Fischer H. -P. Frank B. Ittermann G. Sulzer H. -J. Stöckmann H. Ackermann 《Zeitschrift für Physik B Condensed Matter》1992,86(3):389-395
The spin-lattice relaxation of12B in single-crystal aluminum was measured by NMR in the temperature range 290 to 700 K. The total relaxation rate was separated into two well understood contributions caused by the interaction with conduction electrons and by12B diffusion, and into a third unexplained part at high temperatures. From the comparison of the diffusional relaxation rate with theoretical calculations it was concluded that the nearest neighbours of12B, trapped in the octahedral interstitial site, are displaced away by 8.8 (30)%. 相似文献
948.
949.
Tomáš Malatinský Zsófia Puhová Matej Babjak Jana Doháňošová Ján Moncol Štefan Marchalín Róbert Fischer 《Tetrahedron letters》2018,59(43):3867-3871
Two new five-membered cyclic d-talo-configured nitrones were synthesized from d-mannose, and examined in 1,3-dipolar cycloadditions with vinyl acetate and vinylene carbonate. The stereoselectivity of the cycloadditions depends greatly on the protecting group of the vicinal diol attached to the nitrone C-5 carbon atom. Methyl protection resulted in limited syn/anti-selectivity, giving mixtures of the two isomeric exo-syn and exo-anti isoxazolidines in comparable amounts. On the other hand, the cyclohexylidene-substituted nitrone reacted more selectively in favour of the syn isomer. The difference in the diastereoselectivity was attributed to the specific spatial orientation of the nitrone C-5 substituent. 相似文献
950.
Gartner B. Ackerbauer P. Breunlich W. H. Cargnelli M. Fischer A. Kammel P. King R. Kminek G. Lauss B. Marton J. Prymas W. Steininger E. Zmeskal J. Petitjean C. Chatellard D. Egger J. -P. Jeannet E. Hartmann F. J. Kosak A. Mühlbauer M. von Egidy T. Piller C. Schaller L. A. Schellenberg L. Schneuwly H. Thalmann Y. -A. Tresch S. Werthmüller A. 《Hyperfine Interactions》1996,101(1):249-255
Muon transfer from the ground state of muonic deuterium to a helium atom proceeds mainly via the formation of a muonic molecule in an excited state. A large number of decay X rays ( 6.8 keV) from these (dµHe)* molecules were observed for the4He as well as for the3He case. The time distributions of these X rays allow the determination of the ground state transfer rate. The simultaneous employment of Ge/Si-detectors and CCDs for the same target conditions allows the determination of the branching ratio of radiative to nonradiative decay for the first time. 相似文献