排序方式: 共有204条查询结果,搜索用时 15 毫秒
191.
Fariba Jam 《Tetrahedron》2007,63(39):9881-9889
A general and efficient method for the synthesis of spiro-2,5-diketopiperazines (spiro-DKPs) is described. Cyclization of Boc-protected dipeptides containing spiro-amino acids by microwave assisted heating in water furnished the corresponding spiro-DKPs. The spiro-amino acids were prepared by combining stereoselective alkylation reactions using the Schöllkopf methodology for amino acid construction with Grubbs ring-closing metathesis (RCM) methodology using ruthenium complexes. The RCM reactions and all subsequent transformations to the spiro-DKPs were run with microwave assisted heating, resulting in high yields and short reaction times for all steps. 相似文献
192.
An efficient one-pot method has been developed for the synthesis of 1,2,4-oxadiazoles through a one-pot reaction of nitriles with hydroxylamine hydrochloride in the presence of magnesia-supported sodium carbonate followed by reaction with acyl halides under solvent-free conditions using microwave irradiation. This method is easy, rapid and good yielding. 相似文献
193.
A combination of molybdatophosphoric acid and sodium nitrite in the presence of wet SiO2 was used as an effective nitrosating agent for the nitrosation of secondary amines under mild and heterogeneous conditions in good to excellent yields. Also, the results of a computational study are investigated in the gas phase for geometry and properties of proposed structures. 相似文献
194.
Extension of TOPSIS for decision-making problems with interval data: Interval efficiency 总被引:1,自引:0,他引:1
G.R. Jahanshahloo F. Hosseinzadeh Lotfi A.R. Davoodi 《Mathematical and Computer Modelling》2009,49(5-6):1137-1142
There are some methods for solving Multiple Criteria Decision-Making problems, of which one is the TOPSIS method. When data is nondeterministic like interval data, the method must be modified to show the correct result. In this research we present a new TOPSIS method for ranking DMUs with interval data yielding the interval score for each alternative, and in the end we show that when data is deterministic, our new method is the same as the conventional one. 相似文献
195.
Connections between the covector mapping theorem and convergence of pseudospectral methods for optimal control 总被引:2,自引:0,他引:2
Qi Gong I. Michael Ross Wei Kang Fariba Fahroo 《Computational Optimization and Applications》2008,41(3):307-335
In recent years, many practical nonlinear optimal control problems have been solved by pseudospectral (PS) methods. In particular,
the Legendre PS method offers a Covector Mapping Theorem that blurs the distinction between traditional direct and indirect
methods for optimal control. In an effort to better understand the PS approach for solving control problems, we present consistency
results for nonlinear optimal control problems with mixed state and control constraints. A set of sufficient conditions is
proved under which a solution of the discretized optimal control problem converges to the continuous solution. Convergence
of the primal variables does not necessarily imply the convergence of the duals. This leads to a clarification of the Covector
Mapping Theorem in its relationship to the convergence properties of PS methods and its connections to constraint qualifications.
Conditions for the convergence of the duals are described and illustrated. An application of the ideas to the optimal attitude
control of NPSAT1, a highly nonlinear spacecraft, shows that the method performs well for real-world problems.
The research was supported in part by NPS, the Secretary of the Air Force, and AFOSR under grant number, F1ATA0-60-6-2G002. 相似文献
196.
Mehdi D. Esrafili Parisasadat Mousavian Fariba Mohammadian-Sabet 《Molecular physics》2019,117(1):58-66
Using high-level ab initio calculations, the cooperativity effects between an aerogen-bonding and a pnicogen- or chalcogen-bonding interactions are studied in ternary Y···PH2CN···ZO3 and Y···SHCN···ZO3 complexes (Y?=?NH3, N2 and Z?=?Ar, Kr, Xe). A detailed analysis of the structures, interaction energies and bonding properties is performed on these systems. For each set of the complexes, a favourable cooperativity is observed between Z···N and P/S···N interactions, especially in complexes involving NH3 and XeO3 molecules. It is found that for a given Y or Z, the amount of cooperativity effects in Y···PH2CN···ZO3 complexes are important than Y···SHCN···ZO3 ones. For each ternary complex considered, the effect of a Z···N aerogen bond on a P/S···N bond is more pronounced than that of a P/S···N bond on a Z···N bond. The mechanism of the cooperativity effects in the ternary complexes is studied by electron density difference, quantum theory of atoms in molecules and natural bond orbital analyses. The solvent effects are also studied on the interaction energy and cooperativity of Z···N and P/S···N bonds in the ternary systems. 相似文献
197.
Dadkhoda?GhazanfariEmail author Fariba?Najafizadeh Fereshteh?Khosravi 《Monatshefte für Chemie / Chemical Monthly》2004,135(11):1409-1413
Summary. 4-Aminoperoxybenzoic acid supported on silica gel in presence of air was found to be a selective and convenient oxidant for the oxidation of methylene groups in aryl ketones to convert them to -diketones. 相似文献
198.
Mazloum-Ardakani Mohammad Sabaghian Fariba Naderi Hamidreza Ebadi Azra Mohammadian-Sarcheshmeh Hamideh 《Journal of Solid State Electrochemistry》2020,24(3):571-582
Journal of Solid State Electrochemistry - A graphene aerogel cross-linked by p-phenylenediamine (PPDA) composite with Sm2O3 nanoparticles (AP.Sm) was synthesized as a novel nanocomposite via a... 相似文献
199.
A carbon ionic liquid electrode (CILE) was used for the investigation of the electrochemical oxidation of phenolic compounds in acidic media using cyclic voltammetry, chronoamperometry and square wave voltammetry techniques. The results indicate that, contrary to many other electrodes, the oxidation of phenolic compounds on CILE is highly stable and does not result in electrode fouling. Cyclic voltammetry showed that phenolic compounds such as phenol, 2,4-dichlorophenol and catechol were oxidized at CILE and remained electroactive after multiple cycles and at high concentrations of phenol. The cyclic voltammetric response of the CILE is very stable with more than 99% of the initial activity remaining after 20 s of stirring of a 0.5 mM solution of phenol. 相似文献
200.
Rapid green synthesis of gold nanoparticles using Rosa hybrida petal extract at room temperature 总被引:1,自引:0,他引:1
Noruzi M Zare D Khoshnevisan K Davoodi D 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1461-1465
This study reports a green method for the synthesis of gold nanoparticles using the aqueous extract of rose petals. The effects of gold salt concentration, extract concentration and extract quantity were investigated on nanoparticles synthesis. Gold nanoparticles were characterized with different techniques such as UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, dynamic light scattering and transmission electron microscopy. Transmission electron microscopy experiments showed that these nanoparticles are formed with various shapes. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary amine group (-NH2), carbonyl group, -OH groups and other stabilizing functional groups. X-ray diffraction pattern showed high purity and face centered cubic structure of gold nanoparticles. Dynamic light scattering technique was used for particle size measurement, and it was found to be about 10nm. The rate of the reaction was high and it was completed within 5 min. 相似文献