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81.
A. V. Men’shov 《Siberian Mathematical Journal》2014,55(3):440-450
We study the solvability of random systems of equations on the free abelian group ? m of rank m. Denote by SAT(? m , k, n) and \(SAT_{\mathbb{Q}^m } (\mathbb{Z}^m ,k,n)\) the sets of all systems of n equations of k unknowns in ? m satisfiable in ? m and ? m respectively. We prove that the asymptotic density \(\rho \left( {SAT_{\mathbb{Q}^m } (\mathbb{Z}^m ,k,n)} \right)\) of the set \(SAT_{\mathbb{Q}^m } (\mathbb{Z}^m ,k,n)\) equals 1 for n ≤ k and 0 for n > k. As regards, SAT(? m , k, n) for n < k, some new estimates are obtained for the lower and upper asymptotic densities and it is proved that they lie between (Π j=k?n+1 k ζ(j))?1 and \(\left( {\tfrac{{\zeta (k + m)}} {{\zeta (k)}}} \right)^n\) , where ξ(s) is the Riemann zeta function. For n ≤ k, a connection is established between the asymptotic density of SAT(? m , k, n) and the sums of inverse greater divisors over matrices of full rank. Starting from this result, we make a conjecture about the asymptotic density of SAT(? m , n, n). We prove that ρ(SAT(? m , k, n)) = 0 for n > k. 相似文献
82.
R. V. Men’shova S. P. Ermakova S. M. Rachidi A. H. Al-Hajje T. N. Zvyagintseva H. M. Kanaan 《Chemistry of Natural Compounds》2012,47(6):870-875
The variation of the polysaccharide composition of the brown alga Padina pavonica from the Mediterranean Sea was studied as a function of the collection season (April–July). It was shown that the principal
polysaccharide (8.0-13.3% of dry alga weight) was alginic acid. Its content did not undergo significant changes from April
to July. The content of water-soluble polysaccharides (laminarans and fucoidans) was low (<0.3% of dry alga weight). Water-soluble
polysaccharides of the studied alga were practically pure fucoidan. The amount of laminarans was insignificant (<0.01% of
dry alga weight). The content of fucoidans increased in alga samples from May through July. It was shown that P. pavonica is a promising source of alginic acids, which have a high capacity for gelation, and fucoidans, which exhibit antitumor action
against RPMI-7951 human melanoma cells. 相似文献
83.
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85.
Violeta Yeguas Gloria Inés Cárdenas-Jirón María Isabel Menéndez Ramón López 《Journal of mathematical chemistry》2010,48(1):137-144
The B3LYP density functional theory methodology in conjunction with the 6-31G(d,p) basis set has been used to characterize
triply N-confused meso-tetraphenylporphyrins. According to our computations, there is no a direct correlation between stability and aromaticity
as already found for non-substituted confused porphyrins. The inclusion of these substituents in the calculations provokes
a decrease of the planarity and aromaticity of these macrocycles along with a notable rise of their relative stability with
respect to the non-substituted case. Steric repulsions, both among phenyl rings and β atoms in the pyrrolic rings, and among H atoms in the core of the macrocycles, dominate over aromaticity in the establishment
of the most stable conformation of each isomer. 相似文献
86.
A. V. Fedorov A. L. Mikhailov A. V. Men’shikh D. V. Nazarov S. A. Finyushin V. A. Davydov 《Russian Journal of Physical Chemistry B, Focus on Physics》2007,1(6):600-605
The stability of the detonation front and the detonation parameters of composite liquid HEs of fueloxidizer type prepared from tetranitromethane, nitrobenzene, and nitromethane are studied using laser interferometry. 相似文献
87.
本文依据工科数学第十卷(1994年8月)数学建模MCM—89问题A的数据,用Fisher判别方法建立数学模型,进行分类,识别新样品的类别,其结论与复杂的原解法一致,此方法一般本科生就可以去作,而且没有更多的假设。 相似文献
88.
本文出了8Mbps数字电视编解码器的硬件实现方案,包括视频、音频信道三个部分,同时给出了样机的测试结果,最后略地介绍了此编解码器的应用情况。 相似文献
89.
研究了磁控溅射制备的Ag5In5Te47Sb33相变薄膜的光谱及短波长静态记录性能。研究结果表明,晶态薄膜反射率较高,并在600~900nm波长范围内,晶态与非晶态的反射率和折射率相差很大。在CD-E系统的工作波长780nm处,晶态反射率高达50%,光学常数为5.34-1.0i;非晶态反射率为23%,光学常数为2.5-1.03i。从这一角度讲,Ag5In5Te47Sb33相变薄膜适于做CD-E系统的记录介质。另外,采用波长为514.4nm的短波长光学静态记录测试仪对Ag5In5Te47Sb33薄膜的记录性能进行了测试,结果表明,这种薄膜短波长记录性能较好,它在较低功率和短脉宽的激光束作用下就可得到较高的反射率对比度。 相似文献
90.
A system of boundary integral equations that allows evaluating the displacement and stress fields for an interfacial crack
under harmonic loading is presented. Expressions for the integral kernels are obtained. A numerical solution for a penny-shaped
crack between steel and aluminum half-spaces under normally incident compression-rarefaction wave is given
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 8, pp. 47–56, July 2007. 相似文献