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121.
Summary An enormous development has taken place within the last five years in synchronous teaching over the Internet, i.e. both the teacher and the students are simultaneously in direct communication with each other as in a normal class-room or auditorium. With this concept it is possible to communicate orally, to exchange Power Point Presentations, documents, programmes and live web-camera pictures. It is even possible to use an electronic black board on which both the teacher and the students can work simultaneously. The great advantage with this type of teaching is that it is not restricted to a single class-room/auditorium with limited access, but in a virtual room accessible to everybody in principle all over the world, and which certainly open up new possibilities in teaching. The purpose of this paper is to present and to discuss the concept of virtual class-room teaching, how the system operates in practice, its advantages and, finally, how its inherent limitations can be overcome.  相似文献   
122.
表面分散过程的分形研究   总被引:5,自引:0,他引:5  
盐类和氧化物等活性组分在一定条件下,可在高比表面载体上自发分散。研究这些过程对多相催化剂、吸附剂的制备过程理解和控制无疑是重要的。这类分散过程已被系统地研究,并提出了单层分散模型,对CuCl_2/γ-Al_2O_3、HgCl_2/活性炭等多种体系,测定了单层分散阈值。表面化学习惯上理解为就是二维的化学。早在1931年Tayor就指出表面是不均匀的,但这种不均匀性是作为对理想二维表面的修正而引入的,如TLK模型。表面科学的这些基本概念其数学基础是欧基里德几何学,其物理背景是晶体结构,不规则性就是指晶体结  相似文献   
123.
Properties such as shear modulus, gelation time, structure of supramolecular hydrogels are strongly dependent on self-assembly, gelation triggering mechanism and processes used to form the gel. In our work we extend reported rheology analysis methodologies to pH-triggered supramolecular gels to understand structural insight using a model system based on N−N’ Dibenzoyl-L-Cystine pH-triggered hydrogelator and Glucono-δ-Lactone as the trigger. We observed that Avrami growth model when applied to time-sweep rheological data of gels formed at lower trigger concentrations provide estimates of fractal dimension which agree well compared with visualization of the microstructure as seen via Confocal Laser Scanning Microscopy, for a range of gelator concentrations.  相似文献   
124.
In this paper we obtain several characterizations of the adjacency matrix of a probe interval graph. In course of this study we describe an easy method of obtaining interval representation of an interval bigraph from its adjacency matrix. Finally, we note that if we add a loop at every probe vertex of a probe interval graph, then the Ferrers dimension of the corresponding symmetric bipartite graph is at most 3.  相似文献   
125.
The concept of metric basis is useful for robot navigation. In graph G, a robot is aware of its current location by sending signals to obtain the distances between itself and the landmarks in G. Its position is determined uniquely in G if it knows its distances to sufficiently many landmarks. The metric basis of G is defined as the minimum set of landmarks such that all other vertices in G can be uniquely determined and the metric dimension of G is defined as the cardinality of the minimum set of landmarks. The major contribution of this paper is that we have partly solved the open problem proposed by Manuel et al. [9], by proving that the metric dimension of HDN1(n) and HDN2(n) are either 3 or 4. However, the problem of finding the exact metric dimension of HDN networks is still open.  相似文献   
126.
We leverage the results of the prequel [8], in combination with a theorem of D. Orlov to create a categorical covering picture for factorizations. As applications, we provide a conjectural geometric framework to further understand M. Kontsevich's Homological Mirror Symmetry conjecture and obtain new cases of a conjecture of Orlov concerning the Rouquier dimension of the bounded derived category of coherent sheaves on a smooth variety.  相似文献   
127.
For a commutative ringR, its related characterizations are given by investigating the structure and properties ofH 0 R. Furthermore, by virtue ofH 0 structure, some important characterizations of CPF properties and connected properties onK 0 R are obtained from related rings.  相似文献   
128.
金铁英 《数学杂志》2000,20(4):469-472
本文研究了一类多分子生化反应模型Dx=δ-ax-x^py^p,Dy=x^py^p-by当a≠0,p=3,q=2的情形,得出了不存在闭轨的参数区域;至少分支出两个极限环的参数区域以及极限的唯一性的参数区域的一些结果。  相似文献   
129.
In this article, we define and study the Gorenstein flat dimension and Gorenstein cotorsion dimension for unbounded complexes over GF-closed rings by constructions of resolutions of unbounded complexes. The behavior of the dimensions under change of rings is investigated.  相似文献   
130.
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