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981.
The Lovász Local Lemma is a useful tool in the “probabilistic method” that has found many applications in combinatorics. In this paper, we discuss applications of the Lovász Local Lemma to some combinatorial set systems and arrays, including perfect hash families, separating hash families, ?-free systems, splitting systems, and generalized cover-free families. We obtain improved bounds for some of these set sytems. Also, we compare some of the bounds obtained from the local lemma to those using the basic probabilistic method as well as the well-known “expurgation” method. Finally, we briefly consider a “high probability” variation of the method, wherein a desired object is obtained with high probability in a suitable space. 相似文献
982.
983.
A novel communication technique is proposed, which utilizes a set ofmutually distinguishable optical pat terns instead of convergent facula to transmit information. Then the capacity is increased by exploiting the optical spatial bandwidth resources. At last, we experimentally demonstrate the proposed communication technique based on four 8 × 8 spatial pattern signals by using lenslet array processor. 相似文献
984.
Xiaobo Deng Rong Luo Hualin Chen Bailing Liu Yujun Feng Yuhai Sun 《Colloid and polymer science》2007,285(8):923-930
Composite latex particles of acrylate and polydimethylsiloxane (PDMS) with high PDMS content was prepared by emulsion copolymerization
and characterized by particle size analyzer, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR).
With gemini surfactant as the co-emulsifier in the system, the PDMS content in the system reached 50%, which was far higher
than the other reported values. Through the characterization of the particle size analyzer, the particle size augmented with
the increase of the amount of PDMS, which could be said that the polysiloxane had participated into the reaction and had been
introduced into the colloid particle. The results of FTIR indicated that almost all the monomer had been exhausted in the
reaction because there was no C=C and D4 characteristic peaks in the spectrum. Besides the surface properties also were measured by surface tension analysis, water
absorption, and the static contact angle, it could be found that with the increase of polysiloxane content, the excellent
properties acquired by PDMS were clearly revealed by the findings, such as the decrease of surface tension and water absorption,
and the increase of static contact angle. All the measurements were consistent with the conclusion that the composite latex
particles of polysiloxane and acrylate with high siloxane content had been prepared successfully. 相似文献
985.
986.
987.
一个近-三角剖分嵌入是指一个曲面上的嵌入图使得几乎所有的面都是三角形,至多只有一个可能的例外.文中作者证明了如下结论:如果一个图G 在球面S0(或环面S1)上有近-三角剖分嵌入,那么G在每一个可定向曲面Sk有近-三角剖分嵌入,其中k=h,h+1,\cdots ,\lfloor\frac{\beta(G)}{2}\rfloor$, 而h=0(或1)并且β(G)是图G的Betti数.特别地,G是上可嵌入的. 相似文献
988.
This paper considers the existence and uniqueness of solutions of an age-structured population model in a spatially heterogeneous bounded environment. The model describes individual organism movement of diffusion and advection in the older life stage but assumes stationarity of individuals in the embryonic stage. The mathematical formulation is a nonlinear degenerate parabolic partial differential problem with non-locally integro-type initial-boundary conditions. 相似文献
989.
An efficient preconditioner for electromagnetic integral equations using predefined wavelet packet basis 总被引:1,自引:0,他引:1
Hai Deng Hao Ling 《Antennas and Propagation, IEEE Transactions on》2002,50(11):1633-1640
An approximate-inverse preconditioner based on the predefined wavelet packet (PWP) basis is proposed for the fast iterative solution of electromagnetic integral equations. The PWP basis is designed to achieve a sparse representation of the moment matrix and the preconditioner is constructed by inverting the block-diagonal approximation of the PWP-based moment matrix and transforming the results into the space domain. Numerical results show that the PWP preconditioner is effective in accelerating the convergence rate of iterative solution to moment equations. It is also demonstrated that by properly designing the block-diagonal matrix and computing the matrix elements, the total computational complexity and memory costs for the preconditioner can be kept to O(NlogN). 相似文献
990.