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81.
实例教学法在AutoCAD教学中的应用 总被引:1,自引:0,他引:1
本文分析了AutoCAD传统教学方法的不足,介绍了实例教学法的优点及具体实施的几个要点。 相似文献
82.
本文从实验室认可的角度,来谈检测实验室仪器设备的全过程管理,探讨了如何按照GB/T15481-2000《检测和校准实验室能力的通用要求》做好实验室仪器设备的管理。 相似文献
83.
Zhen-Han Tu 《Mathematische Zeitschrift》2002,240(1):13-35
We prove that any proper holomorphic mapping from to is necessarily a totally geodesic isometric embedding with respect to their Bergman metrics and therefore is the standard
linear embedding up to their automorphisms. The proof of the main result in this paper will be achieved by a differential-geometric
study of a special class of complex geodesic curves on the bounded symmetric domains with respect to their Bergman metrics.
Received: 31 October 2000; in final form: 2 July 2001/ Published online: 4 April 2002 相似文献
84.
Ekkehard Krätzel 《Monatshefte für Mathematik》2002,137(3):197-211
In this article we investigate the number of lattice points in a three-dimensional convex body which contains non-isolated
points with Gaussian curvature zero but a finite number of flat points at the boundary. Especially, in case of rational tangential
planes in these points we investigate not only the influence of the flat points but also of the other points with Gaussian
curvature zero on the estimation of the lattice rest.
Received 19 June 2001; in revised form 17 January 2002
RID="a"
ID="a" Dedicated to Professor Edmund Hlawka on the occasion of his 85th birthday 相似文献
85.
Bruno Sévennec 《Mathematische Annalen》2002,324(1):195-211
We improve – roughly by a factor 2 – the known bound on the multiplicity of the second eigenvalue of Schr?dinger operators
(i.e. Laplace plus potential) on closed surfaces. This gives four new topological types of surfaces for which Colin de Verdière's
conjecture relating the maximal multiplicity to the chromatic number of the surface is verified. The proof goes by defining
a space of "nodal splittings” of the surface, equipped with a double covering to which a Borsuk-Ulam type theorem is applied.
Received: 19 June 2001; revised version: 18 March 2002 /Published online: 17 June 2002 相似文献
86.
Michael Capalbo 《Combinatorica》2002,22(3):345-359
For all positive integers N and k, let denote the family of planar graphs on N or fewer vertices, and with maximum degree k. For all positive integers N and k, we construct a -universal graph of size . This construction answers with an explicit construction the previously open question of the existence of such a graph.
Received July 8, 1998
RID="*"
ID="*" Supported by NSF grant CCR98210-58 and ARO grant DAAH04-96-1-0013. 相似文献
87.
Dedicated to the memory of Paul Erdős
A graph is called -free if it contains no cycle of length four as an induced subgraph. We prove that if a -free graph has n vertices and at least edges then it has a complete subgraph of vertices, where depends only on . We also give estimates on and show that a similar result does not hold for H-free graphs––unless H is an induced subgraph of . The best value of is determined for chordal graphs.
Received October 25, 1999
RID="*"
ID="*" Supported by OTKA grant T029074.
RID="**"
ID="**" Supported by TKI grant stochastics@TUB and by OTKA grant T026203. 相似文献
88.
Alexandr V. Kostochka 《Combinatorica》2002,22(2):275-285
Dedicated to the memory of Paul Erdős
Let f(r,p,t) (p > t >= 1, r >= 2) be the maximum of the cardinality of a minimum transversal over all r-uniform hypergraphs possessing the property that every subhypergraph of with p edges has a transversal of size t. The values of f(r,p,2) for p = 3, 4, 5, 6 were found in [1] and bounds on f(r,7,2) are given in [3]. Here we prove that for large p and huge r.
Received September 23, 1999
RID="*"
ID="*" This work was partially supported by the grant 99-01-00581 of the Russian Foundation for Fundamental Research and the
Dutch–Russian Grant NWO-047-008-006. 相似文献
89.
Amnon Ta-Shma 《Combinatorica》2002,22(1):123-145
A disperser is a bipartite graph with the property that every subset A of of cardinality at least K, has at least fraction of the vertices of as neighbors. Such graphs have many applications in derandomization. Saks, Srinivasan and Zhou presented an explicit construction
of a disperser with an almost optimal degree , for every . We extend their result for every parameter .
Received November 12, 1998/Revised June 20, 2000
RID="*"
ID="*" This work was partially done while the author was at the Department of Computer Science, Weizmann Institute of Science,
Rehovot, Israel. This work was supported by a Phil Zacharia postdoctoral fellowship. 相似文献
90.
In a category with injective hulls and a cogenerator, the embeddings into injective hulls can never form a natural transformation,
unless all objects are injective. In particular, assigning to a field its algebraic closure, to a poset or Boolean algebra
its Mac-Neille completion, and to an R-module its injective envelope is not functorial, if one wants the respective embeddings to form a natural transformation.
Received January 21, 2000; accepted in final form August 10, 2001.
RID="h1"
RID="h2"
RID="h3"
ID="h1"The hospitality of York University is gratefully acknowledged by the first author.
ID="h2"Third author partially supported by the Grant Agency of the Czech Republic under Grant no. 201/99/0310, and the hospitality
of York University is also acknowledged.
ID="h3"Partial financial assistance by the Natural Sciences and Engineering Councel of Canada is acknowledged by the fourth
author. 相似文献