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961.
AKi is a complete subgraph of size i. A Ki-cover of a graph G(V, E) is a set C of Ki?1s of G such that every Ki in G contains at least one Ki?1 in C . ci(G) is the cardinality of a smallest Ki-cover of G. A Ki-packing of G is a set of Kis such that no two Kis have i ? 1 nodes in common. pi(G) is the cardinality of a largest Ki-packing of G. Let F i(G) denote the set of Kis in G and define ci(F) and pi(F) analogously for F ? F i(G). G is Ki-perfect if ?F ? F i(G), ci(F) = pi(F). The K2-perfect graphs are precisely the bipartite graphs. We present a characterization of Ki-perfect graphs that is similar to the Strong Perfect Graph Conjecture, and explore the relationships between Ki-perfect graphs and normal hypergraphs. Furthermore, if iA denotes the 0 ? 1 matrix of G where the rows are the elements of F i?1(G) that belong to at least one Ki and the columns are the elements of F i(G), then we show that iA is perfect iff G is a Ki-perfect graph. We also characterize the Ki-perfect graphs for which iAis balanced. 相似文献
962.
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964.
The problem of partitioning a set of independent and simultaneously available jobs into batches and sequencing them for processing on a single machine is presented. Jobs in the same batch are to be delivered together, upon completion of the last job in the batch. Jobs finished before this time have to wait until delivery. There are a delivery cost depending on the number of batches formed and an earliness cost for jobs finished before delivery. The dynamic programming approach to minimizing the total cost is considered, yielding two pseudopolynomial algorithms when the number of batches has a fixed upper bound. A polynomial algorithm for a special case of the problem is also presented. 相似文献
965.
A classification of the ovoids inPG(3, 32) is completed with the aid of a computer. The ovoids are examined in terms of which ovals can possibly appear as secant plane sections. A weak necessary condition for two ovals to appear together as plane sections of an ovoid surprisingly turns out to be sufficient to demonstrate that the only possible secant plane sections are translation ovals. A known result regarding ovoids with such plane sections then identifies the ovoids as either elliptic quadrics or Tits ovoids. 相似文献
966.
967.
Error estimates needed for the selection of order in Adams codes are studied in the presence of propagated errors. A new derivation of the Nordsieck form of the Adams methods reveals that codes based on this form have changed order incorrectly and shows how to do it properly. 相似文献
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969.
Mark S. Gordon 《Chemical physics letters》1980,76(1):163-168
Geometries, relative energies, and electron density distributions in silacyclopropane and five of its isomers are investigated using ab initio methods. VinyIsilane is found to be the most stable isomer, and methyl substitution is preferred at the silicon end of both silaethylene and methyl silylene. 相似文献
970.