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ZverovichIE ZverovichOI 《高校应用数学学报(英文版)》2004,19(2):125-132
Two new hereditary classes of P5-free graphs where the stability number can be found in polynomial time are proposed. They generalize several known results. 相似文献
2.
Surface tensions (σ) and densities (ρ) of 4-methyl-2-pentanone/ethyl benzoate binary mixtures have been measured over the entire composition range at 278.15, 288.15,
298.15, and 308.15 K. Values of the excess surface tensions (σE) and excess molar volumes (VE) have been calculated. The σE and VE values were fitted by to the Redlich–Kister polynomial equation and the Ak coefficients have been derived. The standard deviations between the calculated and the experimental excess properties have
also been derived. The surface tension values have been further used to calculate the surface entropies (SS) and surface enthalpies (HS) per unit surface area. The lyophobicity (β) and the surface mole fractions (x1S) of the surfactant 4-methyl-2-pentanone have been derived using the extended Langmuir model. The obtained results are discussed
from the viewpoint of the existence of specific interactions between unlike molecules in the bulk region and the surface. 相似文献
3.
The molar conductivities (Λ) of solutions of n-tetrabutylammonium tetraphenylborate (NBu4BPh4) in 3-pentanone have been measured in the temperature range from 283.15 to 329.15 K. The conductance data have been analyzed
using the Lee-Wheaton conductivity equation with the distance parameter (a) set at Bjerrum’s pairing distance, and the limiting molar conductivities (Λo) and the association equilibrium constants (K
A) have been derived. The limiting ion conductivities (λ_±o) have been evaluated according to the method of Krumgalz. The λ+
o values have been compared with λ+
o values calculated from the empirical equation of Gill. The thermodynamic functions, Gibbs energy (Δ G
A
o), enthalpy (Δ H
A
o) and entropy (Δ S
A
o) for the process of ion-pair formation as well as the activation energy of the ionic movement (ΔH
∗) have been evaluated. The obtained results are discussed in terms of ion-ion and ion-solvent interactions. 相似文献
4.
Zverovich I E 《高校应用数学学报(英文版)》2004,19(3):239-244
§1 IntroductionLet G be a graph with vertex-set V(G) ={ v1 ,v2 ,...,vn} .A labeling of G is a bijectionL:V(G)→{ 1,2 ,...,n} ,where L (vi) is the label of a vertex vi.A labeled graph is anordered pair (G,L) consisting of a graph G and its labeling L.Definition1.An increasing nonconsecutive path in a labeled graph(G,L) is a path(u1 ,u2 ,...,uk) in G such thatL(ui) + 1相似文献
5.
通过在NF-3低速风洞专门研制的翼型模型及相应的俯仰和沉浮振动机构,选用NACA0012翼型进行大迎角下不同频率的振动实验,研究了模型振动平均状态下对其气动力特性的影响情况,并在N-S方程基础上对振动流场进行了初步分析。实验与计算研究的结果表明:在临近定常失速迎角的大迎角条件下,翼型的振动可以引起旋涡分离,导致翼型升力减小和失速迎角的提前;就所讨论的两种振动模式而言,俯仰振动的影响大于沉浮振动。所以,为了提高飞机模型,尤其是大展弦比飞机模型的风洞实验精准度,在模型设计和加工时要特别注意加强机翼弦向的扭转刚度。 相似文献
6.
Nikos G. Tsierkezos Ioanna E. Molinou Alexander C. Filippou 《Journal of solution chemistry》2005,34(12):1371-1386
The excess molar volumes (VE), excess surface tensions (σE), and deviations in molar refraction (RE) and isentropic compressibility (ksE) of binary mixtures of cyclohexanone with methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol have been determined over
the entire composition range at 293.15 K. The results were fitted by the Redlich–Kister polynomial equation and the corresponding
binary coefficients Ak have been derived. The standard deviations between the calculated and the experimental excess properties have been determined.
The results provide information on the interactions of the molecules in the pure liquids as well as in the binary mixtures. 相似文献
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Tsierkezos NG Roithova J Schröder D Molinou IE Schwarz H 《The journal of physical chemistry. B》2008,112(14):4365-4371
The solvation of copper(II) sulfate in binary mixtures of water and N,N-dimethylformamide (DMF) is studied by a combined approach using electrochemical studies in solution and a mass spectrometric assay of the solvated ions formed from these solutions upon electrospray ionization (ESI). In the condensed phase, the limiting transference numbers (t(+/-)(o)) and the apparent ion association constants (K(A)'s) of CuSO(4) have been determined in water/DMF solutions at 20 degrees C. The t(+)(o) values decrease with increasing DMF content, demonstrating a gradual solvation of Cu(2+) by DMF molecules. The association constants indicate that aggregation becomes more pronounced as the DMF content increases. In order to achieve complementary insight, the intrinsic interactions among the ions and solvent molecules are investigated in gas-phase experiments of the CuSO(4)/water/DMF system using ESI mass spectrometry. Under the conditions used, the dications [Cu(DMF)(n)](2+) (n = 3-6), [Cu(2)(DMF)(n)SO(4)](2+) (n = 2-7), and [Cu(3)(DMF)(n)(SO(4))(2)](2+) (n = 2-7), and the monocations [Cu(OH)(DMF)(n)](+), [Cu(DMF)(n)(HSO(4))](+) (both, n = 1-3), and [Cu(DMF)(n)](+) (n = 1, 2), are formed as the leading copper-containing cations. Likewise, polynuclear copper clusters observed in the anion ESI spectra support partial aggregation occurring in solution. The gas-phase studies clearly support the conclusions that (i) DMF is a highly preferred ligand for CuII in comparison to water and that (ii) DMF supports ion association for which the mass spectrometric data suggest the formation of polynuclear copper clusters. 相似文献
8.
Molinou IE Tsierkezos NG 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):954-958
Raman spectra of water+N,N-dimethylformamide (DMF) mixtures and their solutions with NaNCS, KNCS and NH(4)NCS were obtained. The bands of nu(CO) stretching, delta(OCN) bending, r(CH(3)) rocking and nu(N-CH)(3)) stretching of the DMF molecule with and without salts were studied. The dependence of the vibration frequencies and Raman intensities of the bands on the composition of the mixed solvent was discussed. The change of the band frequencies as a result of the presence of the salts and the solvation of the cations by the solvent molecules was examined. The stronger cation solvation by the aprotic solvent molecules instead of the water molecules in DMF concentrated solutions was discussed. The nu(CN) and nu(CS) vibrations of the SCN(-) ions were observed as a function of the cation present and the solvent composition. The presence of the SCN(-) ions as "free", contact ion pairs, or solvent separated pairs, was discussed. 相似文献
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