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71.
Let F be an infinite field of characteristic different from 2 and G a torsion group. Write 𝒰+(FG) for the set of units in the group ring FG that are symmetric with respect to the classical involution induced from the map g ? g ?1, for all g ∈ G. We classify the groups such that ?𝒰+(FG)? is n-Engel. 相似文献
72.
Let be a field of positive characteristic and the group algebra of a group . It is known that, if is Lie nilpotent, then its upper (and lower) Lie nilpotency index is at most , where is the order of the commutator subgroup. The authors previously determined those groups for which this index is maximal and here they determine the groups for which it is `almost maximal', that is, it takes the next highest possible value, namely .Presented by V. Dl a b.Dedicated to Professor Vjacheslav Rudko on his 65th birthday.The research was supported by OTKA No. T 037202, No. T 038059 and Italian National Research Project “Group Theory and Application.” 相似文献
73.
Alberto Caprara Andrea Lodi Silvano Martello Michele Monaci 《Discrete Optimization》2006,3(4):317-326
We address the problem of packing a given set of rectangles into the minimum size square. We consider three versions of the problem, arising when the rectangles (i) are squares; (ii) have a fixed orientation; (iii) can be rotated by 90. For each case we study lower bounds, and analyze their worst-case performance ratio. In addition, we evaluate through computational experiments their average performance on instances from the literature. 相似文献
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75.
Yves Crama Michel Grabisch Silvano Martello 《4OR: A Quarterly Journal of Operations Research》2016,14(4):333-336
We recall some cases of ethical misconduct that occurred in the recent years, and we report a new trick that was recently attempted to cheat the journal in order to obtain the publication of an article through usurped identity. 相似文献
76.
We consider the generalization of the classical P||Cmax problem (assign n jobs to m identical parallel processors by minimizing the makespan) arising when the number of jobs that can be assigned to each processor cannot exceed a given integer k. The problem is strongly NP-hard for any fixed k > 2. We briefly survey lower and upper bounds from the literature. We introduce greedy heuristics, local search and a scatter search approach. The effectiveness of these approaches is evaluated through extensive computational comparison with a depth-first branch-and-bound algorithm that includes new lower bounds and dominance criteria. 相似文献
77.
The graph of a function f is subjected to non-homogeneous dilatations around (x0;f(x0)), related to the Taylor expansion of f at x0. Some natural questions about convergence are considered and answered. Finally, it is provided a counterexample to a statement which was presumed to be true in former literature.Mathematics Subject Classification (1991): Primary 41A10, 49Q15, 53A05, 54G20; Secondary 28A75, 28A78, 28A33, 54C20 相似文献
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Algorithms and codes for the assignment problem 总被引:1,自引:0,他引:1
This paper analyzes the most efficient algorithms for the Linear Min-Sum Assignment Problem and shows that they derive from a common basic procedure. For each algorithm, we evaluate the computational complexity and the average performance on randomly-generated test problems. Efficient FORTRAN implementations for the case of complete and sparse matrices are given.Research supported by C.N.R., Progetto Finalizzato Informatica-SOFMAT, Italy. 相似文献