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91.
W. Mader 《Combinatorica》2001,21(2):251-265
Dedicated to the memory of Paul Erdős
It is proved that for every finite graph H of maximal degree and every , there is an integer such that every finite graph of average degree at least and of girth at least contains a subdivision of H.
Received May 5, 1999 相似文献
92.
Chemical oxygen demand (COD) is one of the most relevant chemical parameters for the management of wastewater treatment facilities including the control of the quality of an effluent. The adequacy of decisions based on COD values relies on the quality of the measurements. Cost effective management of the minor sources of uncertainty can be applied to the analytical procedure without affecting measurement quality. This work presents a detailed assessment of the determination of COD values in wastewaters, according to ISO6060:1989 standard, which can support reduction of both measurement uncertainty and cost of analysis. This assessment includes the definition of the measurement traceability chain and the validation of the measurement procedure supported on sound and objective criteria. Detailed models of the measurement performance, including uncertainty, developed from the Differential Approach, were successfully validated by proficiency tests. The assumption of the measurement function linearity of the uncertainty propagation law was tested through the comparison with the numerical Kragten method. The gathered information supported the definition of strategies for measurement uncertainty or cost reduction. The developed models are available as electronic supplementary material, in an MS-Excel file, to be updated with the user's data. 相似文献
93.
We investigate constant mean curvature complete vertical graphs in a warped product, which is supposed to satisfy an appropriated convergence condition. In this setting, under suitable restrictions on the values of the mean curvature and the norm of the gradient of the height function, we obtain rigidity theorems concerning to such graphs. Furthermore, applications to the hyperbolic and Euclidean spaces are given. 相似文献
94.
We prove that any H-minor-free graph, for a fixed graph H, of treewidth w has an Ω(w) × Ω(w) grid graph as a minor. Thus grid minors suffice to certify that H-minorfree graphs have large treewidth, up to constant factors. This strong relationship was previously known for the special
cases of planar graphs and bounded-genus graphs, and is known not to hold for general graphs. The approach of this paper can
be viewed more generally as a framework for extending combinatorial results on planar graphs to hold on H-minor-free graphs for any fixed H. Our result has many combinatorial consequences on bidimensionality theory, parameter-treewidth bounds, separator theorems,
and bounded local treewidth; each of these combinatorial results has several algorithmic consequences including subexponential
fixed-parameter algorithms and approximation algorithms.
A preliminary version of this paper appeared in the ACM-SIAM Symposium on Discrete Algorithms (SODA 2005) [16]. 相似文献
95.
G. S. Asanov 《Aequationes Mathematicae》1994,48(1):86-99
Summary The metric torsionless connection coefficients are found in an explicit way in the case of static spherically symmetric spaces defined in a generalized-Finslerian way. The connection coefficients are determined in terms of the metric tensor and its first derivatives. 相似文献
96.
K. L. Duggal 《Acta Appl Math》1989,17(2):171-193
This paper deals with Cauchy-Riemann (CR) submanifolds and their interaction with relativity. We lay the foundations of Lorentz CR submanifolds followed by some new applicable results. In particular, we study a new class of CR submanifolds with light-like distributions whose local geometry is quite different from what is known on this subject. Finally, we propose a research problem related to pseudo-conformal mappings and relativity. The paper contains several new results of geometric/physical significance. 相似文献
97.
Wolfgang Mader 《Combinatorica》2005,25(4):425-438
We determine all graphs on n ≥ 3 vertices with 3n-6 edges which do not contain a subdivision of K5. These are exactly the graphs which one gets from any number of disjoint maximal planar graphs by successively pasting along
triangles. 相似文献
98.
Presently there are a lot of activities in the study of overpartitions, objects that were discussed by MacMahon, and which
have recently proven useful in several combinatorial studies of basic hypergeometric series. In this paper we study some similar
objects, which we name m-ary overpartitions. We consider divisibility properties of the number of m-ary overpartitions of a natural number, and we prove a theorem which is a lifting to general m of the well-known Churchhouse congruences for the binary partition function.
Received October 11, 2004 相似文献
99.
C. Angosto 《Journal of Mathematical Analysis and Applications》2008,343(1):479-491
We establish here some inequalities between distances of pointwise bounded subsets H of RX to the space of real-valued continuous functions C(X) that allow us to examine the quantitative difference between (pointwise) countable compactness and compactness of H relative to C(X). We prove, amongst other things, that if X is a countably K-determined space the worst distance of the pointwise closure of H to C(X) is at most 5 times the worst distance of the sets of cluster points of sequences in H to C(X): here distance refers to the metric of uniform convergence in RX. We study the quantitative behavior of sequences in H approximating points in . As a particular case we obtain the results known about angelicity for these Cp(X) spaces obtained by Orihuela. We indeed prove our results for spaces C(X,Z) (hence for Banach-valued functions) and we give examples that show when our estimates are sharp. 相似文献
100.
Abel's lemma on summation by parts is reformulated to investigate systematically terminating theta hypergeometric series. Most of the known identities are reviewed and several new transformation and summation formulae are established. The authors are convinced by the exhibited examples that the iterating machinery based on the modified Abel lemma is powerful and a natural choice for dealing with terminating theta hypergeometric series. 相似文献