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571.
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Ulrike Tillmann 《Mathematische Annalen》2000,317(3):613-628
Abstract. The operad studied in conformal field theory and introduced ten years ago by G. Segal [S] is built out of moduli spaces of
Riemann surfaces. We show here that this operad which at first sight is a double loop space operad is indeed an infinite loop
space operad. This leads to a new proof of the fact that the classifying space of the stable mapping class group , is an infinite loop space after plus construction [T2]. This new approach has various advantages. In particular, the infinite
loop space structure is more explicid.
Received: 21 September 1998 / Revised: 30 August 1999 / Published online: 8 May 2000 相似文献
574.
Daniela Lürding Yavuz Ba
ar Ulrike Hansktter 《International Journal of Solids and Structures》2001,38(52)
The contribution deals with an extension of a classical Neo–Hookean model for compressible isotropic materials to transverse isotropy. With this enhancement for one preferred material direction there is a possibility to simulate large strains in volume changes of the isotropic basic continuum and supplementary in fiber direction. The integrity basis of polynomial invariants in case of transversely isotropic hyperelasticity consists of three principal invariants of the isotropic basic continuum and additionally of two principal invariants for the preferred material direction. The proposed stored energy function for transverse isotropy contains the classical theory near to the natural state and fulfills the restriction on polyconvexity and coerciveness.By numerical enforcement of the material model into shell kinematics without rotational variables a four-node isoparametric finite element is developed using special concepts to avoid locking. The capability of the algorithms proposed is demonstrated by a numerical example involving large strains as well as finite rotations. 相似文献
575.
Summary. The reaction of 1,5-diphenylpentanetrione, 4-chlorobenzaldehyde, and acetone in the presence of methylamine resulted in 2,6-dibenzoyl-5-(4-chlorphenyl)-3-methyl-cyclohex-2-en-1-one,
which was formed by a sequence of a Knoevenagel reaction, an aldol condensation, and a Michael addition in a one-pot reaction.
Received August 16, 2000. Accepted September 8, 2000 相似文献
576.
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579.
Ulrike Gambert Harald S. Conradt Manfred Nimtz Joachim Thiem 《Journal of carbohydrate chemistry》2013,32(4-5):621-629
ABSTRACT Transgalactosylation of chitobiose and chitotriose led to formation of terminally (β1-3)- and (β1-4)-galactosylated chitooligosaccharides ready for fucosylation to give Lewisa and Lewisx motifs. Their structures could be assigned employing HPAECPAD, methylation, ESI-MS/MS and NMR analyses. 相似文献
580.
In many bistable oscillating systems only one of the attractors is desired to possessing certain system performance. We present a method to drive a bistable system to a desired target attractor by annihilating the other one. This shift from bistability to monostability is achieved by augmentation of the nonlinear oscillator with a linear control system. For a proper choice of the control function one of the attractors disappears at a critical coupling strength in an control-induced boundary crisis. This transition from bistability to monostability is demonstrated with two paradigmatic examples, the autonomous Chua oscillator and a neuronal system with a periodic input signal. 相似文献