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991.
In this paper we study the degenerate Cauchy-Riemann equation in Gevrey classes. We first prove the local solvability in Gevrey
classes of functions and ultra-distributions. Using microlocal techniques with Fourier integral operators of infinite order
and microlocal energy estimates, we prove a result of propagation of singularities along one dimensional bicharacteristics.
相似文献
992.
We present two numerical methods to approximate the shortest path or a geodesic between two points on a three-dimensional parametric surface. The first one consists of minimizing the path length, working in the parameter domain, where the approximation class is composed of Bézier curves. In the second approach, we consider Bézier surfaces and their control net. The numerical implementation is based on finding the shortest path on the successive control net subdivisions. The convergence property of the Bézier net to the surface gives an approximation of the required shortest path. These approximations, also called pseudo-geodesics, are then applied to the creation of pseudo-geodesic meshes. Experimental results are also provided. 相似文献
993.
In this work, the mechanical behaviour of millimetre-scale, bulk single crystalline, nanoporous gold at room temperature is reported for the first time. Tension and compression tests were performed with a custom-designed test system that accommodates small-scale samples. The absence of grain boundaries in the specimens allowed measurement of the inherent strength of millimetre-scale nanoporous gold in tension. The elastic modulus and strength values in tension and compression were found to be significantly lower than values measured with nanoindentation-based techniques and previously reported in the literature, but close to those reported for millimetre-scale polycrystalline samples tested using traditional compression techniques. Fracture toughness was found to be very low, in agreement with the macroscopic brittleness of nanoporous gold, but this is due to the localization of deformation to a narrow zone of ligaments, which individually exhibit significant plasticity and necking. 相似文献
994.
N-Arylazetidines are efficiently obtained in a three-step procedure, providing a wide diversity of derivatives on multigram scale with overall yields of 21–55%. Cheap or easily available acetanilides are used in an adapted aldolization with aldehydes, furnishing β-hydroxyamides with an 81% average yield over 21 examples. Special Mitsunobu conditions have been developed to ensure the cyclization of these hydroxyamides, giving β-lactams with an 73% average yield over 16 examples. A reduction then provided the N-arylazetidines in high yields. 相似文献
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