排序方式: 共有29条查询结果,搜索用时 765 毫秒
1.
We study the high‐contrast biharmonic plate equation with Hsieh–Clough–Tocher discretization. We construct a preconditioner that is robust with respect to contrast size and mesh size simultaneously based on the preconditioner proposed by Aksoylu et al. (Comput. Vis. Sci. 2008; 11 :319–331). By extending the devised singular perturbation analysis from linear finite element discretization to the above discretization, we prove and numerically demonstrate the robustness of the preconditioner. Therefore, we accomplish a desirable preconditioning design goal by using the same family of preconditioners to solve the elliptic family of PDEs with varying discretizations. We also present a strategy on how to generalize the proposed preconditioner to cover high‐contrast elliptic PDEs of order 2k, k>2. Moreover, we prove a fundamental qualitative property of the solution to the high‐contrast biharmonic plate equation. Namely, the solution over the highly bending island becomes a linear polynomial asymptotically. The effectiveness of our preconditioner is largely due to the integration of this qualitative understanding of the underlying PDE into its construction. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
2.
Niiket
cal Feray Aydoan idem Yolaan Zuhal Turgut 《Journal of heterocyclic chemistry》2003,40(4):721-724
Alkyl and aryl substituted furothiazolidine derivatives have been synthesized by the reaction of Wittig reagent with benzylidene derivatives of 4‐thiazolidinones obtained from aldimines and thioglicolic acid. 相似文献
3.
Summary: Conducting polypyrrole (PPy) nanoparticles were synthesized via microemulsion polymerization. PP/PPy nanocomposites were prepared by melt-mixing of polypyrrole with polypropylene (PP) and processed with injection molding. Tensile tests have revealed that increasing amount of PPy increased the strength and the stiffness of the nanocomposite while limiting the elongation of PP. Thermal gravimetric analysis has showed that incorporation of PPy nanoparticles has improved the thermal stability of the nanocomposites. Increasing amount of PPy nanoparticles increases the conductivity of nonconductive PP up to 2,4.10−4 Scm−1. The same techniques were used to characterize nanocomposites containing 2% w dispersant. Composites prepared with dispersant have involved smaller dimension PPy nanoparticles and exhibited improvement in some mechanical and thermal properties. 相似文献
4.
A series of N-ethylpiperazine substitute thioureas [C6N2H13NHCSNHR], where R = -C3H5 (L 1 ), -C10H7 (L 2 ), and -C7H7 (L 3 ), and their copper (II) complexes have been synthesized. These ligands and complexes have been characterized by elemental analyses, IR, 1H and 13C-NMR spectra, UV-Vis, magnetic susceptibility, thermogravimetrical analyses, and MALDI-TOF MS. In vitro antitumor activity of ligands and their complexes has been screened toward several tumor cell lines. The effects on these complexes of the growth of L1210 and MCF7 were studied comparatively with that of free ligands. Antioxidant and radical scavenging activities of synthesized compounds were determined by various in vitro assays including 1,1-diphenyl-2-picryl-hydrazyl free radicals (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid radicals (ABTS+), and ferrous ion (Fe2+) chelating activities. Moreover, these activities were compared to synthetic and standard antioxidant trolox. The results showed that the synthesized compounds had effective antioxidant power. 相似文献
5.
The reductive metallation of 6-methyl-2,3-diphenylquinoxaline 1 with sodium metal in tetrahydrofuran and inert atmosphere to a monomeric dianion 2 has been explored and the nucleophilicity of this disodium adduct was investigated with various alkylation and acylation reagents. An annulation of the pyrazine ring system was accomplished by treating the dianion with polymethylene chlorides, Cl(CH2)nCl, n = 3,4. 相似文献
6.
Canan Aksu Canbay Soner Ozgen Zuhal Karagoz Genc 《Applied Physics A: Materials Science & Processing》2014,117(2):767-771
There are many studies to improve the properties of Cu–Al–Mn shape memory alloys, such as high transformation temperatures, ductility and workability. Most of them have been performed by adding a quaternary component to the alloy. In this study, the effect of trace Mg addition on transformation temperatures and microstructures of three different quaternary Cu–Al–Mn–Mg alloys has been investigated using thermal analysis, optical microscopy and XRD techniques. The transformation temperatures are within the range of 120–180 °C, and they have not changed significantly on decreasing the Mn content, replacing with Mg. The fine precipitates have been observed in the alloys with the Mg content up to 1.64 at%. Calculated entropy change and XRD analysis reveal that the alloys with high Al content have mainly 18R-type structure which could be responsible for good ductility and workability. 相似文献
7.
Abstract Solution properties of poly(acenaphthylene) (PACN) were investigated in a theta solvent (1,2-dichloroethane) and a good solvent (chloroform). The viscosity exponent α was found to be 0.50 at both 35 and 41 °C in 1,2-dichloroethane. Unperturbed dimensions found from viscometric measurements were compared with those of other vinyl aromatic polymers. Calculation of the chain flexibility parameters led to the conclusion that PACN is a rather stiff chain compared to other vinyl polymers with its characteristic ratio C∞ of 18.2 and chain flexibility parameter λ of 7. 相似文献
8.
The synthesis of new 2,3,5,6-aryl substituted tetrahydro-2H-pyrazolo[3,4-d]- thiazoles 4a-j as potential biologically active compounds by the cyclocondensation of phenyl hydrazine with new 5-arylidene derivatives 2a-j of 2,3-disubstituted-1,3- thiazolidin-4-ones 1a-e is reported. 相似文献
9.
Parham Taslimi Fikret Türkan Kadir Turhan Halide Sedef Karaman Zuhal Turgut İlhami Gulcin 《Journal of heterocyclic chemistry》2020,57(8):3116-3125
In this study, substituted 2H-indazolo[2,1-b]phthalazine-1,6,11-trione compounds ( 4a–d ) obtained via one-pot three-component condensation reaction of aromatic aldehydes, cyclic 1,3-dione, and phthalhydrazide in ethanol catalyzed by Y(OTf)3 showed satisfactory inhibitory effects against some important enzymes. Also, these molecules had Ki values in the row of 185.92 ± 36.03-294.82 ± 50.76 nM vs carbonic anhydrase I (CA I), 204.93 ± 46.90-374.10 ± 83.63 nM against human CA II, 937.16 ± 205.82-1021.83 ± 193.66 nM against α-glycosidase (α-Gly), respectively. For cholinesterase enzymes, the Ki values were found in the range of 47.26 ± 9.62-72.05 ± 19.47 nM against acetylcholinesterase (AChE) and 65.03 ± 9.88-102.83 ± 25.04 nM against butyrylcholinesterase (BChE), respectively. The inhibition effects of these compounds against enzymes whose name are AChE, BChE, α-Gly, hCA I, and hCA II, were compared with control molecules like tacrine, acarbose, and acetazolamide. 相似文献
10.
Synthesis,antioxidant activity and SAR study of novel spiro-isatin-based Schiff bases 总被引:1,自引:0,他引:1
Sonmez Fatih Gunesli Zuhal Kurt Belma Zengin Gazioglu Isil Avci Davut Kucukislamoglu Mustafa 《Molecular diversity》2019,23(4):829-844
Molecular Diversity - A new series of 21 Schiff bases of spiro-isatin was synthesized, and their DPPH, CUPRAC and ABTS cation radical scavenging abilities were investigated for antioxidant... 相似文献