排序方式: 共有28条查询结果,搜索用时 15 毫秒
1.
Ovanes Mekenyan Danail Bonchev Alexandru Balaban 《Journal of mathematical chemistry》1988,2(4):347-375
Whereas the internal fragment topological index (IFTI) is calculated in the normal manner as for any molecule, the external fragment topological index (EFTI) is calculated so as to reflect the interaction between the excised fragment F and the remainder of the molecule (G-F). For selected topological indices (TIs), a survey of EFTI values, formulas and examples is presented. Some requirements as to the fragment indices are formulated and examined. In the discussion of the results, it is shown that for some TIs regularities exist in the dependence of EFTI values upon the branching of fragment F, or upon the marginal versus central position of the fragment F in the graph G. New vortex invariants can be computed as EFTI values for one-atom fragments over all graph vertices; by iteration, it is in principle possible to devise an infinite number of now vertex invariants. 相似文献
2.
Ovanes Mekenyan Danail Bonchev Alexandru T. Balaban 《Journal of computational chemistry》1984,5(6):629-639
The vertex numbering obtained by application of the HOC algorithm can be converted into two sequences of numbers: If each vertex starting with vertex 1 is only counted once, the sums of numberings of adjacent vertices form sequence Si (i = 1?N), while the sums of Si values form sequence Mi (i = 1?N). These two sequences can be used for (i) two new topological indices, ?? and ??, the latter being of extremely low degeneracy, and the former correlating with boiling points of alkanes; (ii) a criterion based on sequence Si for ordering graphs which possess the same number N of vertices; and (iii) a quantitative measure, also based on sequence Si, for appreciating the similarity or dissimilarity of pairs of graphs. Comparisons with other topological indices, ordering criteria, and similarity measures for graphs show that the newly devised procedures compare favorably with those known previously. 相似文献
3.
Alexandry T. Balaban Danail Bonchev William A. Scitz 《Journal of Molecular Structure》1993,280(2-3):253-260
A set of priority rules is defined for obtaining the graph center in multigraphs, i.e. in molecular graphs with multiple bonds. In order to obtain closer agreement between experimental bond distances in molecules and the relative magnitudes of entries in the distance matrix, a new type of distance is defined, called the “chemical distance”: CD = bt-14, where b is the conventional bond multiplicity. 相似文献
4.
Alexandru T. Balaban Ovanes Mekenyan Danail Bonchev 《Journal of computational chemistry》1985,6(6):562-569
A topological code is devised on the basis of the unique topological representation of the molecule described in the preceding two parts of this series.1 By adding to the topological code additional chemical information on atoms and/or bonds, as well as stereochemical information, a chemical and respectively stereochemical code (SHOC) are also constructed. The advantages of the new linear codes are that they are convention-free codes, preserving the symmetry of molecular graph, and easily implemented either manually or by means of computer programs. By concentrating all topological, chemical, and stereochemical information, our code (SHOC) is more compact and more general than the codes based on several separate lists. 相似文献
5.
Nikolai Ralev Stoyan Karabunarliev Ovanes Mekenyan Danail Bonchev Alexandru T. Balaban 《Journal of computational chemistry》1985,6(6):587-591
The computer implementation of the HOC procedures presented in Parts I, II and III of this series is based on the module principle. It contains a main program and seventeen subroutines in Fortran IV. The system is able to provide unique atom numbering and code for all kinds of chemical compounds in their tremendous variety of structures. 相似文献
6.
Philippe Kobel Danail Obreschkow Aurèle de Bosset Nicolas Dorsaz Mohamed Farhat 《Experiments in fluids》2009,47(1):39-48
This paper describes the techniques and physical parameters used to produce stable centimetric water drops in microgravity,
and to study single cavitation bubbles inside such drops (Parabolic Flight Campaigns, European Space Agency ESA). While the
main scientific results have been presented in a previous paper, we shall herein provide the necessary technical background,
with potential applications to other experiments. First, we present an original method to produce and capture large stable
drops in microgravity. This technique succeeded in generating quasi-spherical water drops with volumes up to 8 ml, despite
the residual g-jitter. We find that the equilibrium of the drops is essentially dictated by the ratio between the drop volume
and the contact surface used to capture the drop, and formulate a simple stability criterion. In a second part, we present
a setup for creating and studying single cavitation bubbles inside those drops. In addition, we analyze the influence of the
bubble size and position on the drop behaviour after collapse, i.e., jets and surface perturbations. 相似文献
7.
We study locally mass conservative approximations of coupled Darcy and Stokes flows on polygonal and polyhedral meshes. The discontinuous Galerkin (DG) finite element method is used in the Stokes region and the mimetic finite difference method is used in the Darcy region. DG finite element spaces are defined on polygonal and polyhedral grids by introducing lifting operators mapping mimetic degrees of freedom to functional spaces. Optimal convergence estimates for the numerical scheme are derived. Results from computational experiments supporting the theory are presented. 相似文献
8.
9.
Doz. Dr. Danail Bonchev Verginia Kamenska Dimitar Kamenski 《Monatshefte für Chemie / Chemical Monthly》1977,108(2):477-487
The information approach for describing electronic structures of atoms was developed and different information characteristics of chemical elements were determined on this basis. The information functions display interesting features and correlate with the properties of chemical elements. The spin information of the elements having a closed electron shell, expressed in bits, was found to be equal to the atomic number of the element.
Mit 8 Abbildungen 相似文献
Mit 8 Abbildungen 相似文献
10.
Two novel highly photostable blue-emitting 1,8-naphthalimides, containing active fragments of a hindered amine radical scavenger and an s-triazine UV absorber were designed as multifunctional additives capable of simultaneous fluorescent brightening and photostabilization of polymers. Their light absorption and fluorescence properties have been determined and discussed. The ability of the combined fluorescent brighteners to copolymerize with acrylonitrile was demonstrated by obtaining acrylonitrile copolymers with an intense blue fluorescence. Photodegradation of the new fluorophores and their influence on the photostability of the fluorescent copolymers have been studied and compared to other similar 1,8-naphthalimides, not containing either UV absorber or hindered amine fragment in their molecules as well as not containing both of them. Novel fluorophores showed the best photostability in both solution and polymer. A significant photostabilizing effect towards photodegradation of polyacrylonitrile was found. 相似文献