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171.
Johnny Henderson 《Journal of Difference Equations and Applications》2013,19(7):1005-1018
We study the existence and non-existence of positive solutions of a system of nonlinear second-order difference equations with eigenvalues subject to multi-point boundary conditions. 相似文献
172.
Mohammad Mehdi Khodaei Davood Kordestani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2403-2405
Abstract Direct conversion of acylals to the corresponding bisulfites can be easily performed in the presence of bismuth (III) nitrate pentahydrate in ethanol at room temperature in good yields. 相似文献
173.
《应用有机金属化学》2017,31(3)
Polystyrene‐supported N ,N ‐dimethylethylenediamine Pd(II) complex C was used as an efficient catalyst for the synthesis of aromatic ketones via ortho ‐acylation of sp2 C─H bonds of 2‐arylpyridines with alcohols as effective coupling partners. The alcohols were oxidized with tert ‐butyl hydroperoxide to their corresponding aldehydes in situ and efficiently coupled with 2‐arylpyridines to form aryl ketones under solvent‐free conditions. Furthermore, catalyst C could be easily recovered by simple filtration and reused for five cycles without any significant decrease in its activity. 相似文献
174.
Synthesis and Characterization of Novel Biodegradable Di‐ and Tri‐Block Copolymers Based on Ethylene Carbonate Polymer as Hydrophobic Segment 下载免费PDF全文
Rubina Abdul‐Karim Syed Ghulam Musharraf Muhammad Imran Malik 《Journal of polymer science. Part A, Polymer chemistry》2017,55(11):1887-1893
Synthesis of novel amphiphilic biodegradable block copolymers based on ethylene carbonate is reported in this study. Polyethylene glycol monomethyl ether (MeO‐PEO) and polyethylene glycol (PEG) of varying molar masses are used as macro‐initiator for ring‐opening polymerization of ethylene carbonate in the presence of sodium stannate trihydrate as a heterogeneous transesterification catalyst. Earlier elution of block copolymer from macro‐initiator in size exclusion chromatography (SEC) indicated the successful synthesis of the block copolymers. Ratios of both types of blocks are varied systematically. Liquid chromatography at critical conditions is used for the analysis of the non‐critical individual blocks, and if there are any critical segments that are not attached to the non‐critical block. To the best of our knowledge, this is the first report on the synthesis of ethylene carbonate‐based amphiphilic block copolymers. Chromatographic critical conditions of the ethylene carbonate polymer are also reported for the first time. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1887–1893 相似文献
175.
Ali Ramazani Ebrahim Ahmadi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):565-567
Magnesium hydrogen sulfate powder was found to catalyze stereoselective conversion of dialkyl 2-(imido-N-yl)-3-(triphenylphosphorany-lidene)butanedioates to electron-poor (Z)-N-vinylimides in solvent-free conditions at 95°C 1 h in high conversions. Microwave also was found to catalyze the same reactions in the presence of magnesium hydrogen sulfate powder in solvent-free conditions in 3 min. 相似文献
176.
《International Journal of Solids and Structures》2014,51(15-16):2865-2877
This paper proposes a procedure to deal with n-layered inclusion based composites with imperfect interfaces (which conditions consist of displacement or stress vector jumps) respecting spherical symmetry. For that purpose, “discontinuity matrices” have been introduced. These matrices have been derived for several classical interface-models and an asymptotic method has been used to determine some of them. A self-consistent condition based on a strain-energy equivalence in the case of inclusion-matrix type composite materials is restated for n-layered inclusions with imperfect interfaces and applied to get estimates of such composites materials. The remarkable feature of the presently self consistent approach is that it does not need any tedious algebra providing the attached interface models respect the spherical symmetry. The present Generalized Self Consistent Model (GSCM) is then used to study size effects and mismatch in composites reinforced by coated inclusions. 相似文献
177.
178.
Farhad Shirini Nader Ghaffari Khaligh Gholam Hossein Imanzadeh Parisa Ghods Ghasem-Abadi 《中国化学快报》2012,23(10):1145-1148
1,3-Dibromo-5,5-dimethylhydantoin,has been used as an efficient catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes in the presence of kaolin.All reactions are performed in the absence of solvent in relatively short reaction times in good to high yields. 相似文献
179.
In this paper, we prove controllability results for a two-dimensional semilinear heat equation with mixed boundary conditions. It is well-known that mixed boundary conditions can present a singular behaviour of the solution. First, we will prove global Carleman estimates then we will use these inequalities to obtain controllability results. 相似文献
180.
《Optimization》2012,61(4):527-537
Using a special scalarization, we give necessary optimality conditions for fractional multiobjective optimization problems. Under a generalized invexity, sufficient optimality conditions are also given. All over the article, the data are assumed to be continuous but not necessarily Lipschitz. 相似文献