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A novel approach using Monte Carlo method applied to simulation of low‐density polyethylene (LDPE) polymerization in tubular reactor showing topological characteristics, and the comprehensive kinetic mechanism has been taken into consideration. The results show the precise details of the structure of a chain in the three levels of the backbone, the main branches, and branches on branch. The chain types include dead polymer, dead polymer with unsaturated end, and live polymer with primary radical, secondary radical, and tertiary radical. In this work, the branches on branch were identified in terms of number, length, and position of the branch. Sixty percent of branches on branch are 1 to 5 carbons long, and the longest branch on branch is about 50 carbons. Thus, this study provides a tool for more accurately mapping the polymer chains architecture, superior to determine the number, and position of long‐ and short‐chain branches in past researches. Finally, this approach will advance the prediction of microstructure‐related properties of polymer one step further. 相似文献
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Zeinab Abdeveiszadeh Siamak Noorizadeh 《International journal of quantum chemistry》2020,120(11):e26185
DFT calculations are performed to investigate the structure, stability, and nature of chemical bonding of some neutral noble gas insertion compounds containing a Xe-Xe bond; including HXeXeR, FXeXeR as well as RXeXeR (R = CN, NC, CCH, and BS). Geometry optimization of the considered molecules anticipate the existence of just four stable compounds (HXeXeCN, HXeXeNC, FXeXeCN, and FXeXeCCH); and rest of the molecules dissociate during the structural optimization. The results of NBO and AIM calculations show that a H(F)XeXeR molecule has a covalent H(F)-Xe bond in the H(F)XeXe+ fragment, which is bonded to R− mainly through columbic interaction. Thermodynamic study indicates that all of the considered unimolecular dissociation channels for decomposition of H(F)XeXeR molecules to neutral fragments are both exothermic and exorergic; but dissociation to ionic species (H(F)XeXe+ and R−) is endothermic. Also kinetic study of the most probable dissociation reaction shows that FXeXeR molecules are metastable with respect to the global minimum F-R + 2Xe. Therefore, FXeXeCN molecule is more kinetically protected against the decomposition reaction than the other molecules and its experimental detection is more likely. 相似文献
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Siamak Yassemi 《Czechoslovak Mathematical Journal》1997,47(4):585-592
It is shown that for any Artinian modules M, M
is the greatest integer i such that
(M
) 0. 相似文献
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In this paper we show that a quasi-forest is shellable if and only if its h-triangle satisfies ${h_{i,j}(\Delta)=0 \quad \forall i, \forall j >1 }$ . In addition, it will be shown that a quasi-forest is sequentially Cohen-Macaulay if and only if it is shellable. 相似文献
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Irregularities are widespread in large databases and often lead to erroneous conclusions with respect to data mining and statistical
analysis. For example, considerable bias is often resulted from many parameter estimation procedures without properly handling
significant irregularities. Most data cleaning tools assume one known type of irregularity. This paper proposes a generic
Irregularity Enlightenment (IE) framework for dealing with the situation when multiple irregularities are hidden in large
volumes of data in general and cross sectional time series in particular. It develops an automatic data mining platform to
capture key irregularities and classify them based on their importance in a database. By decomposing time series data into
basic components, we propose to optimize a penalized least square loss function to aid the selection of key irregularities
in consecutive steps and cluster time series into different groups until an acceptable level of variation reduction is achieved.
Finally visualization tools are developed to help analysts interpret and understand the nature of data better and faster before
further data modeling and analysis. 相似文献
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