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161.
We show that in every r-coloring of the edges of K n there is a monochromatic double star with at least \(\frac{n(r+1)+r-1}{r^2}\) vertices. This result is sharp in asymptotic for r = 2 and for r≥ 3 improves a bound of Mubayi for the largest monochromatic subgraph of diameter at most three. When r-colorings are replaced by local r-colorings, our bound is \(\frac{n(r+1)+r-1}{r^2+1}\). 相似文献
162.
163.
B-SERIES METHODS CANNOT BE VOLUME-PRESERVING 总被引:1,自引:0,他引:1
Volume preservation is one of the qualitative characteristics common to many dynamical systems. However, it has been proved by Kang and Shang that e.g. Runge–Kutta (RK) methods can not preserve volume for all linear source-free ODEs (let alone nonlinear ODEs). On the other hand, certain so-called Exponential Runge–Kutta (ERK) methods do preserve volume for all linear source-free ODEs. Do such ERK methods perhaps also preserve volume for all nonlinear ODEs? Here we prove that the answer to this question is negative; B-series methods (which include RK, ERK and several more classes of methods) cannot preserve volume for all source-free ODEs. The proof is presented via the theory of K-loops, which is an extension of the theory of classical rooted trees. 相似文献
164.
基于分形理论的红外图像边缘检测 总被引:19,自引:5,他引:14
提出了利用分形理论进行红外图像边缘检测的方法,比较了根据单一分形维数和根据多尺度分形维数两种方法的边缘检测结果,从而得出:分表理论可以用于红外图像的边缘检测,并且根据多尺度维数的方法能获得较好的边缘检测结果。 相似文献
165.
Olga
wider Micha Wjcicki Marzena Bujak Edyta Juszczuk-Kubiak Magdalena Szczepaska Marek . Roszko 《Molecules (Basel, Switzerland)》2021,26(19)
Salt concentrations in brine and temperature are the major environmental factors that affect activity of microorganisms and, thus may affect formation of biogenic amines (BAs) during the fermentation process. A model system to ferment cucumbers with low salt (0.5%, 1.5% or 5.0% NaCl) at two temperatures (11 or 23 °C) was used to study the ability of indigenous microbiota to produce biogenic amines and metabolize amino acid precursors. Colony counts for presumptive Enterococcus and Enterobacteriaceae increased by 4 and up to 2 log of CFU∙mL−1, respectively, and remained viable for more than 10 days. 16S rRNA sequencing showed that Lactobacillus and Enterobacter were dominant in fermented cucumbers with 0.5% and 1.5% salt concentrations after storage. The initial content of BAs in raw material of 25.44 ± 4.03 mg∙kg−1 fluctuated throughout experiment, but after 6 months there were no significant differences between tested variants. The most abundant BA was putrescine, that reached a maximum concentration of 158.02 ± 25.11 mg∙kg−1. The Biogenic Amines Index (BAI) calculated for all samples was significantly below that needed to induce undesirable effects upon consumption. The highest value was calculated for the 23 °C/5.0% NaCl brine variant after 192 h of fermentation (223.93 ± 54.40). Results presented in this work indicate that possibilities to control spontaneous fermentation by changing salt concentration and temperature to inhibit the formation of BAs are very limited. 相似文献
166.
167.
168.
Monk [1970] extended the notion of the completion of a Boolean algebra to Boolean algebras with operators. Under the assumption
that the operators of such an algebra are completely additive, he showed that the completion of always exists and is unique up to isomorphisms over . Moreover, strictly positive equations are preserved under completions a strictly positive equation that holds in must hold in the completion of . In this paper we extend Monk’s preservation theorem by proving that certain kinds of Sahlqvist equations (as well as some
other types of equations and implications) are preserved under completions. An example is given that shows that arbitrary
Sahlqvist equations need not be preserved.
Received May 3, 1998; accepted in final form October 7, 1998. 相似文献
169.
胡杏云 《宁波大学学报(理工版)》2005,18(4):500-505
针对古村落发展面临的现实和潜在的问题,以四明山腹地宁渡余姚柿林村为例,探讨了古村落在市场经济条件下的管理制度与保护机制. 相似文献
170.
用4种不同浓度的条浒苔多酚(Enteromorpha clathrata polyphenols, ECPs)溶液处理新鲜加州鲈鱼块后置于4℃贮藏,结合感官评分、菌落总数、挥发性盐基氮(TVB-N)、硫代巴比妥酸(TBA)值、肌原纤维蛋白巯基含量、表面疏水性、肌肉色差和质地剖面分析(TPA)等指标,综合评估其对鱼块货架期的影响.结果表明,在4℃贮藏条件下, ECPs处理能有效抑制鲈鱼贮藏期间TVB-N值、TBA值和菌落总数的增加,减缓蛋白氧化和品质劣化进程,从而达到延长货架期的作用.当ECPs浓度为0.20%时,其对鲈鱼鱼块的保鲜效果最佳,能延长鲈鱼货架期6 d. 相似文献