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71.
Optimal competence set expansion using deduction graphs 总被引:1,自引:0,他引:1
A competence set is a collection of skills used to solve a problem. Based on deduction graph concepts, this paper proposes a method of finding an optimal process so as to expand a decision maker's competence set to enable him to solve his problem confidently. Using the concept of minimum spanning tree, Yu and Zhang addressed the problem of the optimal expansion of competence sets. In contrast, the method proposed here enjoys the following advantages: it can deal with more general problems involving intermediate skills and compound skills; it can find the optimal solution by utilizing a 0–1 integer program; and it can be directly extended to treat multilevel competence set problems, and thus is more practically useful.This work was supported by the National Science Council, Taipei, Taiwan, Republic of China, Grant No. NSC-81-0301-H-009-501. 相似文献
72.
Kinkar Ch. Das 《Graphs and Combinatorics》2007,23(6):625-632
Let G = (V,E) be a simple graph with n vertices, e edges and d1 be the highest degree. Further let λi, i = 1,2,...,n be the non-increasing eigenvalues of the Laplacian matrix of the graph G. In this paper, we obtain the following result: For connected graph G, λ2 = λ3 = ... = λn-1 if and only if G is a complete graph or a star graph or a (d1,d1) complete bipartite graph.
Also we establish the following upper bound for the number of spanning trees of G on n, e and d1 only:
The equality holds if and only if G is a star graph or a complete graph. Earlier bounds by Grimmett [5], Grone and Merris [6], Nosal [11], and Kelmans [2] were
sharp for complete graphs only. Also our bound depends on n, e and d1 only.
This work was done while the author was doing postdoctoral research in LRI, Université Paris-XI, Orsay, France. 相似文献
73.
We investigate algorithms to find the first vertex in large trees generated by either the uniform attachment or preferential attachment model. We require the algorithm to output a set of K vertices, such that, with probability at least , the first vertex is in this set. We show that for any ε, there exist such algorithms with K independent of the size of the input tree. Moreover, we provide almost tight bounds for the best value of K as a function of ε. In the uniform attachment case we show that the optimal K is subpolynomial in , and that it has to be at least superpolylogarithmic. On the other hand, the preferential attachment case is exponentially harder, as we prove that the best K is polynomial in . We conclude the paper with several open problems. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 50, 158–172, 2017 相似文献
74.
Henning Sulzbach 《Random Structures and Algorithms》2017,50(3):493-508
For a martingale (Xn) converging almost surely to a random variable X, the sequence (Xn– X) is called martingale tail sum. Recently, Neininger (Random Structures Algorithms 46 (2015), 346–361) proved a central limit theorem for the martingale tail sum of Régnier's martingale for the path length in random binary search trees. Grübel and Kabluchko (in press) gave an alternative proof also conjecturing a corresponding law of the iterated logarithm. We prove the central limit theorem with convergence of higher moments and the law of the iterated logarithm for a family of trees containing binary search trees, recursive trees and plane‐oriented recursive trees. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 50, 493–508, 2017 相似文献
75.
Gabriel Berzunza 《Random Structures and Algorithms》2017,51(3):404-427
We destroy a finite tree of size n by cutting its edges one after the other and in uniform random order. Informally, the associated cut‐tree describes the genealogy of the connected components created by this destruction process. We provide a general criterion for the convergence of the rescaled cut‐tree in the Gromov‐Prohorov topology to an interval endowed with the Euclidean distance and a certain probability measure, when the underlying tree has branching points close to the root and height of order . In particular, we consider uniform random recursive trees, binary search trees, scale‐free random trees and a mixture of regular trees. This yields extensions of a result in Bertoin (Probab Stat 5 (2015), 478–488) for the cut‐tree of uniform random recursive trees and also allows us to generalize some results of Kuba and Panholzer (Online J Anal Combin (2014), 26) on the multiple isolation of vertices. The approach relies in the close relationship between the destruction process and Bernoulli bond percolation, which may be useful for studying the cut‐tree of other classes of trees. © 2017 Wiley Periodicals, Inc. Random Struct. Alg., 51, 404–427, 2017 相似文献
76.
气液两相涡街稳定性的研究 总被引:6,自引:1,他引:6
通过气液两相涡街试验研究和理论分析,首次得出了当有稳定的气液两相涡街发生时,气液两相涡街结构参数的取值及变化规律 相似文献
77.
On drag, Strouhal number and vortex-street structure 总被引:5,自引:0,他引:5
A phenomenological model for the vortex-shedding process behind bluff cylindrical bodies is proposed. Relationships between Strouhal frequency St, drag coefficient cD, Reynolds number Re and geometric wake parameters are obtained from mass conservation, momentum conservation in the transverse direction and energy considerations. For the first time, Roshko's (Technical Report TN 3169, NACA, US Government Printing Office, Washington DC, 1954) experimental discovery of vortex-street similarity behind different cylinders is analytically derived. In addition, the empirically obtained Strouhal-frequency laws of Roshko (Technical Report TN1191, NACA, US Government Printing Office, Washington DC, 1954) and Fey (Phys. fluids A 10 (1998) 1547) are also reproduced. Measurements of St and cD including their Re dependency for flows around cylinders with circular, square, triangular, semi-circular and other cross sections agree favorably with the proposed model. 相似文献
78.
G. Godard F. Weiss M. Gonzalez P. Paranthoën 《Experimental Thermal and Fluid Science》2005,29(8):947-956
This experimental study is devoted to the diffusion of a passive scalar downstream a line source located in a Bénard–von Kármán street. Measurements of velocity and temperature have been performed using LDA and cold wire thermometer with a phase reference. Information on the initial evolution of mean, fluctuating velocity and temperature and associated shear-stresses and heat fluxes fields are presented for two locations of the source: ( and 1). The results show that the velocity field in the wake is strongly related to the geometric structure of vortices while the temperature field is controlled by both the time scale of rotation of the vortices and the location of the heated fluid within the vortex street. 相似文献
79.
Philippe Nadeau 《Journal of Combinatorial Theory, Series A》2011,118(5):1638-1660
In this paper we study alternative tableaux introduced by Viennot [X. Viennot, Alternative tableaux, permutations and partially asymmetric exclusion process, talk in Cambridge, 2008]. These tableaux are in simple bijection with permutation tableaux, defined previously by Postnikov [A. Postnikov, Total positivity, Grassmannians, and networks, arXiv:math/0609764v1 [math.CO], 2006].We exhibit a simple recursive structure for alternative tableaux, from which we can easily deduce a number of enumerative results. We also give bijections between these tableaux and certain classes of labeled trees. Finally, we exhibit a bijection with permutations, and relate it to some other bijections that already appeared in the literature. 相似文献
80.