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211.
Hao CHEN 《Frontiers of Mathematics in China》2014,9(6):1253-1260
The restricted parameter range set cover problem is a weak form of the NP-hard set cover problem with the restricted range of parameters. We give a polynomial time algorithm for this problem by lattices. 相似文献
212.
为了研究垃圾填埋场内部生物降解产生的气体(以甲烷为主) 和氧气等在非饱和覆盖层中的运移规律,建立了气体在成层非饱和覆盖层中的一维扩散模型. 该模型考虑了覆盖层含水量瞬态变化和气体扩散的耦合作用. 采用有限元多物理场耦合分析软件COMSOL Multiphysics 4.3进行求解. 其计算结果与前人实验结果能符合得很好. 研究结果表明,对典型垃圾填埋场中厚度为1m的非饱和黏土覆盖层,含水量变化对覆盖层中气体污染物的扩散运移有显著影响. 与含水量稳态变化情况相比,20 d到100 d的运移时间内同一覆盖层深度处耦合含水量作用下,气体相对浓度可以相差接近8倍. 含水量是气体在非饱和覆盖层中不稳定运移的重要影响因素. 相似文献
213.
Themba Dube 《Applied Categorical Structures》2009,17(1):63-73
Coz-unique frames were defined and characterized by Banaschewski and Gilmour (J Pure Appl Algebra 157:1–22, 2001). In this note we give further characterizations of these frames along the lines of characterizations of absolutely z-embedded spaces obtained by Blair and Hager (Math Z 136:41–52, 1974) on the one hand, and by Hager and Johnson (Canad J Math 20:389–393, 1968) on the other. We also extend to frames certain characterizations of z-embedded spaces; namely, we give a characterization of coz-onto frame homomorphisms in terms of normal covers.
相似文献
214.
A strong defensive alliance in a graph G=(V,E) is a set of vertices A⊆V, for which every vertex v∈A has at least as many neighbors in A as in V−A. We call a partition A,B of vertices to be an alliance-free partition, if neither A nor B contains a strong defensive alliance as a subset. We prove that a connected graph G has an alliance-free partition exactly when G has a block that is other than an odd clique or an odd cycle. 相似文献
215.
We give examples of failure of the existence of co-fibered products in the category of algebraic curves.
相似文献
216.
Li-Chien Lin 《Optics Communications》2008,281(5):1008-1016
Digitalization enables and expertise storage and transmission of holographic data. However, the reconstructed object image is vulnerable to transmission errors over the noisy channel. We present a novel algorithm of what we believe is the first approach to reduction of noise effects on digital holograms corrupted by transmission errors. To accomplish this work, we exploit new interdependencies on the interference holograms and develop a detection-based algorithm to detect error points and to identify the corresponding interference holograms with the largest errors. In the reconstruction process, the conventional four-step algorithm is used for the recovery of error-free points. In contrast, a three-step algorithm is employed to reconstruct error points by removing the largest error holograms. With accurate detection, the proposed algorithm is capable of recovering the object image from digital holograms with severe transmission errors. It is shown that the proposed algorithm provides much better reconstruction performances than the conventional four-step reconstruction algorithm in an error-prone environment. 相似文献
217.
218.
STRONG EMBEDDINGS OF PLANAR GRAPHS ON HIGHER SURFACES 总被引:1,自引:0,他引:1
In this paper, the authors discuss the upper bound for the genus of strong embeddings for 3-connected planar graphs on higher surfaces. It is shown that the problem of determining the upper bound for the strong embedding of 3-connected planar near-triangulations on higher non-orientable surfaces is NP-hard. As a corollary, a theorem of Richter, Seymour and Siran about the strong embedding of 3-connected planar graphs is generalized to orientable surface. 相似文献
219.
Let Y be a Fano manifold of dimension n ? 3 with b2(Y and index n – 1 and let A be a projective manifold which is a double cover of Y. We determine which complex projective manifolds can admit A among their hyperplane sections. 相似文献
220.
设G是无割边三正则图,θ={C1,C2,…,Ck)是G一个圈覆盖,定义一新图G(θ)=(V,E),这里V={C1,C2,…,Ck),(Ci,Cj)∈E当且仅当E(Ci)∩E(Cj)≠φ(1≤i≠j≤k).那么G是三边着色的充分必要条件是G有一个圈的一或二次覆盖θ并且G(θ)是二或三点着色.这个结论给出了一个判定无割边三正则图是三边着色的方法。 相似文献