共查询到20条相似文献,搜索用时 31 毫秒
1.
运用量子力学PM3方法模拟α-环己基扁桃酸((R/S)-CHMA)与β-环糊精(β-CD)的主客体相互作用,探讨(R/S)-CHMA在β-CD上的手性识别机理.模拟结果能够准确预测色谱出峰顺序从而能从原子层次上对手性识别机制给予理论解释.PM3方法的计算结果表明:(S)-CHMA与β-CD形成的结合物比(R)-CHMA与β-CD形成的结合物稳定.从模拟包结物的构型可以看出(R/S)-CHMA与β-CD结合方式完全不同:(R)-CHMA是将苯环插入β-CD空腔形成包结物,而(S)-CHMA是将环己基插入β-CD空腔形成包结物.此外,(S)-CHMA除了自身的分子内氢键外,与β-CD分子之间还存在分子间氢键作用;而(R)-CHMA与β-CD之间没有分子间氢键作用.从而说明疏水作用以及弱的分子间氢键作用是造成手性识别的主要驱动力. 相似文献
2.
《Computers & Mathematics with Applications》2003,45(6-9):1087-1099
We investigate the global character of solutions of the equation in the title with non-negative parameters and nonnegative initial conditions. 相似文献
3.
Over the last decades, the α-stable distribution has proved to be a very efficient model for impulsive data. In this paper, we propose an extension of stable distributions, namely mixture of α-stable distributions to model multimodal, skewed and impulsive data. A fully Bayesian framework is presented for the estimation of the stable density parameters and the mixture parameters. As opposed to most previous work on mixture models, the model order is assumed unknown and is estimated using reversible jump Markov chain Monte Carlo. It is important to note that the Gaussian mixture model is a special case of the presented model which provides additional flexibility to model skewed and impulsive phenomena. The algorithm is tested using synthetic and real data, accurately estimating α-stable parameters, mixture coefficients and the number of components in the mixture. 相似文献
4.
从7月初始,北京市软件产业促进中心将正式向社会启动“1+1+1”工程。该工程是一项有针对性培养Linux人才的教育项目,将在从今年开始的三年内有计划地培养100名linux教师,1000名linux技术人员和10000名linux基础应用人员,故简称为“1+1+1”工程。该工程的启动得到包括IBM在内的国 相似文献
5.
《Information Processing Letters》1987,25(4):241-245
This paper presents parallel algorithms for coloring a constant-degree graph with a maximum degree of Δ using Δ + 1 colors and for finding a maximal independent set in a constant-degree graph. Given a graph with n vertices, the algorithms run in O(lg1n) time on an EREW PRAM with O(n) processors. The algorithms use only local communication and achieve the same complexity bounds when implemented in a distributed model of parallel computation. 相似文献
6.
郝慧君 《中国信息技术教育》2021,(8):98-100
本文针对课程教学中存在的一些关键问题,统筹规划教学课堂,从项目式分组、“学生教师”授课和交叉互评出发,组织全新的课堂,促进生生、组组、师生交流,激发学生学习的热情。采用项目式驱动的1+1+1+1教学模式,着重培养学生沟通表达能力、项目经理职业素养与实践管理技能,并能运用管理与软件知识解决实际问题(如统筹规划项目实施计划等)。 相似文献
7.
Ellison和McNealy这两个偏执狂终于促成了Oracle和Sun的联姻。至此在这场历时4年耗资近500亿美元先后收购了52家软件公司的收购大战后,Oracle"打败"了蓝色巨人IBM成功收购了另一个巨头—Sun,以软件业红色巨人的姿态屹立在人们面前。 相似文献
8.
9.
10.
An ab initio study of the cooperativity in XH2P⋯NCH⋯Z and XH2P⋯CNH⋯Z complexes (X = F, Cl, Br, CN, NC; Z = C2H2, C6H6) connected by pnicogen-bonding and H⋯π interactions is carried out by means of MP2 computational method. A detailed analysis of the structures, interaction energies and bonding properties is performed on these systems. For each set of the complexes considered, a favorable cooperativity is observed, especially in X = F and CN complexes. However, for a given X or Z, the amount of cooperativity effects in XH2P⋯CNH⋯Z complexes are more important than XH2P⋯NCH⋯Z counterparts. Besides, the influence of a H⋯π interaction on a P⋯N (C) bond is more pronounced than that of a P⋯N (C) bond on a H⋯π bond. The quantum theory of atoms in molecules shows that ternary complexes have increased electron densities at their bond critical points relative to the corresponding binary systems. The results also indicate that the strength of the P⋯N(C) and H⋯π interactions increases in the presence of the solvent. 相似文献
11.
12.
13.
14.
《Information Sciences》1987,43(3):161-168
Mechanical and logical systems admit an “additive” law of measures, while biological and social system may not. We consider generalized additive models which under the sum property get transformed into a generalized functional equation. Solutions of this generalized functional equation characterize the generalized information measures with preference order β. Some particular cases are studied. 相似文献
15.
在分析多处理机调度问题的基础上,提出了α-平坦的概念,并将其引入到多处理机调度问题中;基于此,提出了一种新的基于α-平坦的求解多处理机调度问题的算法.算法首先对作业集合做平坦化处理,然后再对处理后所得的新问题进行求解,最终获得原调度问题的一个近似解.实验结果表明,通过该算法可以求得较好的结果,相对于其它启发式算法,该算法具有较好的稳定性. 相似文献
16.
17.
18.
19.