排序方式: 共有45条查询结果,搜索用时 15 毫秒
41.
Some hyperbranched aromatic polyamides have been synthesized by direct polycondensation using the modified Higashi's method. Structures of the above polymers have been realized taking in proper account the analogies with amide group sequences of poly(p-phenyleneterephthalamide) (PPDT) and poly(p-benzamide) (PBA). Therefore, AB2- type monomers as well as suitable combinations of different bi- and trifunctional reactants (AA + B3) (e.g., p-phenylenediamine + trimesic acid or other trifunctional acids) have been considered. For the latter systems, network formation has been minimized. In the present paper, our results on their direct polyamidation together with some preliminary characterization data on the resultant hyperbranched aramids are given. 相似文献
42.
Habib Ammari Hyeonbae Kang Habib Zribi 《计算数学(英文版)》2007,25(3):244-251
In this paper, we consider conductivity inclusions inside a homogeneous background conductor. We provide a complete asymptotic expansion of the solution of such problems in terms of small variations in the electrical conductivity of the inclusion. Our method is based on a boundary integral perturbation theory. Our results are valid for both high and low contrast inclusions. 相似文献
43.
Facile one-pot synthesis of new [1,2,4]triazolo[1,5-a]pyridine derivatives by ultrasonic irradiation
Herein, we report an ultrasonic promoted facile and convenient “one-pot” procedure for the synthesis of new [1,2,4]triazolo[1,5-a]pyridine derivatives 3, 4 and 5, using Amberlite IRA-400, in short reaction times and high yields and its comparison with classical reaction conditions. The structures of new compounds were assigned with the help of analytical 1H, 13C NMR, and mass spectral studies. 相似文献
44.
The coordination chemistry of the water soluble phosphane oxide ligand tris[2‐isopropylimidazol‐4(5)‐yl]phosphane oxide, 4‐TIPOiPr, has been explored. A variety of 3d‐metal halide complexes have been prepared and the crystal structures of the solvates [(4‐TIPOiPr)ZnCl2]·MeOH·1/2dioxane ( 1 ·MeOH·1/2dioxane), [(4‐TIPOiPr)CoCl2]·H2O·2dioxane ( 2 ·H2O·2dioxane) and [(4‐TIPOiPr)2Ni(MeOH)2]Cl2·2MeOH ( 3 ·2MeOH) have been determined. All three structures show unprecedented coordination modes of the 4‐TIPOiPr ligand. Both zinc and cobalt complexes are coordinated in a bidentate κ2N fashion, whereas the nickel atom is coordinated by two ligands in a κN,O mode using one imidazolyl substituent and the P=O oxygen atom. 相似文献
45.
Asymptotic expansions for currents caused by small interface changes of an electromagnetic inclusion
Habib Zribi 《Applicable analysis》2013,92(1):172-190
We consider solutions to the Helmholtz equation in two dimensions. The aim of this article is to advance the development of high-order asymptotic expansions for boundary perturbations of currents caused by small perturbations of the shape of an inhomogeneity with 𝒞2-boundary. The work represents a natural completion of Ammari et al. [H. Ammari, H. Kang, M. Lim, and H. Zribi, Conductivity interface problems. Part I: Small perturbations of an interface, Trans. Am. Math. Soc. 363 (2010), pp. 2901–2922], where the solution for the Helmholtz equation is represented by a system and the proof of our asymptotic expansion is radically different from Ammari et al. (2010). Our derivation is rigorous and is based on the field expansion method. Its proof relies on layer potential techniques. It plays a key role in developing effective algorithms to determine certain properties of the shape of an inhomogeneity based on boundary measurements. 相似文献