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991.
Based on the number of k-matching m(G,k) of a graph G, Gutman and Zhang introduced an order relation of graphs: for graphs G
1 and G
2, if m(G
1,k) ≥ m(G
2,k) for all k. The order relation has important applications in comparing Hosaya indices and energies of molecular graphs and has been
widely studied. Especially, Gutman and Zhang gave complete orders of six classes of graphs with respect to the relation . In this paper, we consider a class of graphs with special structure, which is a generalization of a class of graphs studied
by Gutman and Zhang. Some order relations in the class of graphs are given, and the maximum and minimum elements with respect
to the order relation are determined. The new results can be applied to order some classes of graphs by their matching numbers. 相似文献
992.
Experimental studies of supermolecular structures and localized flow birefringence in solutions of high-molecular weight polymer are described. Advantage is taken of poly(ethylene oxide) and polyisobutylene. Supermolecular structures are examined with the aid of optical microscopy using freeze-dried samples of the polymer solutions. Birefringence is investigated that arises in planar elongational flow in a cross-slot cell. Flow velocities at which the onset of the localized birefringence occurs are determined. Then these velocities are correlated with viscoelastic characteristics of the solutions. The presence of a liquid-crystalline fibrillar network in the polymer solutions exhibiting flow birefringence is ascertained. The fibrils are birefringent objects. The fibrils are birefringent objects. The localized birefringence phenomenon is explained in term of the orientation of the fibrils in elongational flow. It has been shown that the onset of localized birefringence occurs at a critical Weissenberg number, the value of which is close to unity. 相似文献
993.
N. A. Mel’nichenko 《Journal of Structural Chemistry》2007,48(3):479-485
Hydration numbers of basic ions in sea water (SW) are found from a proton relaxation rate of 1/T 1 in SW and model solutions. A possibility for the formation of three-layer hydrate shells around main SW cations and two-layer shells around anions is ascertained. About half of water molecules is in influence zones of ions in sea water that correlates with a double shift in the baric dependence maximum of T 1 to a smaller pressure in SW relative to pure water. 相似文献
994.
Momentum transfer was investigated in an unbaffled agitated vessel of inner diameter 0.3 m equipped with different off-centred
impellers. The distribution of the shear rate on the tank wall as a function of the impeller type and Reynolds number was
studied in the turbulent regime of the Newtonian liquid flow. The dependences of the averaged dimensionless shear rate, friction
coefficient, and dissipated energy on the Reynolds number and eccentricity ratio were approximated using four-parameter equations.
Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May
2006. 相似文献
995.
Preben C. Mrk John Ugelstad Jan Ole Aasen 《Journal of polymer science. Part A, Polymer chemistry》1995,33(11):1759-1765
Expressions for calculating the stationary state distribution of radicals in compartmentalized systems with a constant number of reaction loci containing an oil-soluble initiator are given. Besides pairwise formation of radicals in the particles, desorption and reabsorption, water phase termination, solubility of the initiator in the aqueous phase, and the possibility of formation of a single radical species are taken into consideration. The calculation is based on a probabilistic analysis leading to a third-order recurrence relation solved using confluent, hypergeometric Kummer functions. Some calculated curves illustrating the de-pendence of the average number of radicals per particle on various relevant parameters are included. © 1995 John Wiley & Sons, Inc. 相似文献
996.
Dany Brouillette Gérald Perron Jacques E. Desnoyers 《Journal of solution chemistry》1998,27(2):151-182
Lithium bis(trifluoromethylsulfone)imide (LiTFSI) is a promising electrolyte for high-energy lithium batteries due to its high solubility in most solvents and electrochemical stability. To characterize this electrolyte in solution, its conductance and apparent molar volume and heat capacity were measured over a wide range of concentration in glymes, tetraethylsulfamide (TESA), acetonitrile, -butyrolactone, and propylene carbonate at 25°C and were compared with those of LiClO4 in the same solvents. The glymes or n(ethylene glycol) dimethyl ethers (nEGDME), which have the chemical structure CH3–O–(CH2–CH2–O)
n
–CH3 for n = 1 to 4, are particularly interesting since they are electrochemically stable, have a good redox window, and are analogs of the polyethylene oxides used in polymer-electrolyte batteries. TESA is a good plasticizer for polymer-electrolyte batteries. Whenever required, the following properties of the pure solvents were measured: compressibilities, expansibilities, temperature and pressure dependences of the dielectric constant, acceptor number, and donor number. These data were used in particular to calculate the limiting Debye-Hückel parameters for volumes and heat capacities. The infinite dilution properties of LiTFSI are quite similar to those of other lithium salts. At low concentrations, LiTFSI is strongly associated in the glymes and moderately associated in TESA. At intermediate concentrations, the thermodynamic data suggests that a stable solvate of LiTFSI in EGDME exists in the solution state. At high concentrations, the thermodynamic properties of the two lithium salts approach those of the molten salts. These salts have a reasonably high specific conductivity in most of the solvents. This suggests that the conductance of ions at high concentration in solvents of low dielectric constant is due to a charge transfer process rather than to the migration of free ions. 相似文献
997.
The apparent molar volumes, V
φ
, of glycine, L-alanine and L-serine were obtained in aqueous 0 to ∼4 mol⋅kg−1 N,N-dimethylacetamide (DMA) solutions from density measurements at 298.15 and 308.15 K. The standard partial molar volume,
V
φ
o, and standard partial molar volumes of transfer, Δtr
V
φ
o, were determined for these amino acids. It has been shown that hydrophilic-hydrophilic interactions between charged groups
of the amino acids and the —CON= group of DMA are predominant in the case of glycine and L-serine, but for L-alanine the interactions
between its side group (—CH3) and DMA are predominant. An increase in temperature increases the standard partial molar volumes but decreases the transfer
volumes of the amino acids. The results have been interpreted in terms of cosphere overlap model. 相似文献
998.
999.
1000.
用具有流通池的分光光度计作测定装置,建立了由平衡移动法测定络合反应中质子释放数的新方法。方法简单、快速,仅用一个标准溶液,适于在变更pH值范围内金属离子不发生水解和没有其他副反应的体系。 相似文献