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41.
42.
Yousef Alavi Gary Chartrand F. R. K. Chung Paul Erds R. L. Graham Ortrud R. Oellermann 《Journal of Graph Theory》1987,11(2):235-249
A connected graph is highly irregular if each of its vertices is adjacent only to vertices with distinct degrees. In this paper we investigate several problems concerning the existence and enumeration of highly irregular graphs as well as their independence numbers, with particular focus on the corresponding problems for highly irregular trees. 相似文献
43.
Yousef Hashem Zahran 《国际流体数值方法杂志》2008,57(6):745-760
We describe a hybrid method for the solution of hyperbolic conservation laws. A third‐order total variation diminishing (TVD) finite difference scheme is conjugated with a random choice method (RCM) in a grid‐based adaptive way. An efficient multi‐resolution technique is used to detect the high gradient regions of the numerical solution in order to capture the shock with RCM while the smooth regions are computed with the more efficient TVD scheme. The hybrid scheme captures correctly the discontinuities of the solution and saves CPU time. Numerical experiments with one‐ and two‐dimensional problems are presented. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
44.
In this research, we study linear difference equations with constant coefficients subject to boundary conditions. Necessary and/or sufficient conditions for the existence of a unique solution will be established. The proofs of the existence and uniqueness theorems are established by means of special types of determinants called Mosaic Vandermonde determinants. 相似文献
45.
We introduce a functor Sph, the spherical spectrum, which assigns to a graded ringG a space Sph(G) of homogeneous orderings ofG. It combines ideas of concrete geometry in theN-sphere defined by positively homogeneous polynomial equations and inequalities with the abstract notion of the real spectrum of a ring to give a counterpart for real semialgebraic geometry of the functor Proj. 相似文献
46.
Salamin YI 《Optics letters》2007,32(1):90-92
Fields of a radially polarized laser beam developed recently [Y. I. Salamin, Opt. Lett.31, 2619 (2006)] are employed to show that electrons produced by atomic ionization near the focus may be accelerated to GeV energies. Conditions for producing a mono-energetic and well-collimated electron beam are discussed. 相似文献
47.
Novel thiono and seleno phosphoramidate compounds with the general formula (X)(Y)P(C6H5)2; (X = NMe2 & Y = S, 1a; X = NEt2 & Y = S, 2a; X = NMe(CH2Ph) & Y = S, 3a; X = NH(CH2Ph) & Y = S, 4a; X = NEt(CH2Ph) & Y = S, 5a; X = N(C(Me)3) (CH2Ph) & Y = S, 6a; X = N(CH2Ph)2 & Y = S, 7a; X = NMe2 & Y = Se, 1b; X = NEt2 & Y = Se, 2b; X = NMe(CH2Ph) & Y = Se, 3b; X = NH (CH2Ph) & Y = Se, 4b; X = NEt(CH2Ph) & Y = Se, 5b; X = N(C(Me)3)(CH2Ph) & Y = Se, 6b and X = N(CH2Ph)2 & Y = Se, 7b) were prepared and characterized by 1H, 31P and 13C NMR and IR spectroscopy and elemental analysis. 31P chemical shift of thiono and seleno derivatives didn’t show significant different because of their little difference in
electronegativity sulfur and selenium. Hydrophobic parameter of compounds was determined by measurement of octanol-water partition
coefficient by shake-flask technique. Determination of human erythrocyte acetylcholinesterase (hAChE) activity was carried
out according to the Ellman’s modified kinetic method. IC50 values of the selected thiono and seleno compounds varied from 3.4 to 0.11 and 9.9 to 5.1 mM, respectively. The seleno compounds
show lower affinities for hAChE relative to the thino compounds. These results demonstrate that hydrophobic and electronic
factors of the organophosphorus compounds play a key role on the inhibitory potency. 相似文献
48.
In this work a facile hydrothermal route has been employed to prepare a multiwall carbon nanotube wrapped in a chelating resin. 8-Hydroxyquinoline and p-formaldehyde were used as monomer and linker for polymer synthesis. The prepared composite was employed as an efficient adsorbent for lead adsorption and preconcentration from various matrices. Effective parameters on lead adsorption have been optimized by central composite design. Results showed that equilibrium adsorption was obtained at pH = 4, with a shacking time of 15 min and adsorbent dosage of 15 mg. Isotherm study showed that the sorbent has adsorbent capacity of 250 mg g?1; moreover, the process followed a Langmuir isotherm model. Thermodynamic investigation confirmed that lead adsorption is spontaneous, as well as follows endothermic path. 相似文献
49.
Ultrasonic welding (USW) is an alternative solution for the bonding process especially in automotive industry. Ultrasonic welding of metals is a joining technique as a combination of applying pressure and frictional vibrations within the range of ultrasonic frequencies. In automotive industry, ultrasonic welding is often used for wired connections. As an alternative for crimping technology of multi-strand aluminum cables in wire bonding, ultrasonic welding is used. This work presents a thermomechanical analysis of the interface between two mating parts in USW. For this reason, the temperature distribution at bonding locations inside a wire bundle due to frictional vibrations and pressure is investigated using the finite element method (FEM). The obvious difference in microsections from different welding samples, which originates from different local temperature rises, was the motivation for this study to further investigate the thermomechanical aspects of the USW by use of finite element simulations. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献