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排序方式: 共有268条查询结果,搜索用时 31 毫秒
81.
In this paper, epsilon and Ritz methods are applied for solving a general class of fractional constrained optimization problems. The goal is to minimize a functional subject to a number of constraints. The functional and constraints can have multiple dependent variables, multiorder fractional derivatives, and a group of initial and boundary conditions. The fractional derivative in the problem is in the Caputo sense. The constrained optimization problems include isoperimetric fractional variational problems (IFVPs) and fractional optimal control problems (FOCPs). In the presented approach, first by implementing epsilon method, we transform the given constrained optimization problem into an unconstrained problem, then by applying Ritz method and polynomial basis functions, we reduce the optimization problem to the problem of optimizing a real value function. The choice of polynomial basis functions provides the method with such a flexibility that initial and boundary conditions can be easily imposed. The convergence of the method is analytically studied and some illustrative examples including IFVPs and FOCPs are presented to demonstrate validity and applicability of the new technique. 相似文献
82.
Lotfi Aroua 《合成通讯》2013,43(11):1935-1942
The synthesis of bis(oxazolidinone)polyoxyethylene derivatives 2a–h from oligoethylene glycols diglycidyl ethers 1a–e and isocyanates is reported. The reaction was achieved by lithium bromide and tributylphosphine oxide. These bis‐oxazolidinones may have important antibacterial activity. 相似文献
83.
Forouzan Aboufazeli Hamid Reza Lotfi Zadeh Zhad Omid Sadeghi Mohammad Karimi Ezzatolla Najafi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1):18-24
In this work, MCM-41 (Mobil Composition of Matter number 41) nanoporous silica has been synthesized and characterized by X-ray powder diffraction and IR spectroscopy. In the next step, poly-thiophene was coated on the nanoporous silica in order to increase its surface area. This composite was characterized by X-Ray powder diffraction, High resolution transmission electronic microscopy micrograph (HRTEM), elemental analysis (CHNS) and Thermal analysis (TG/DTA). The application of this composite was investigated in mercury ions removal from waste water prior to determination by inductively coupled plasma atomic emission spectroscopy (ICP-OES). In order to investigate the effect of nanoporous structure on the efficiency of this composite, the same composite without porous structure has been synthesized and the results were compared. 相似文献
84.
Nessrine Salah Youssef Arfaoui Mohamed Bahri Mohamed Lotfi Efrit Azaiez Ben Akacha 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):609-622
Abstract The addition of hydrazine and its derivatives to cycloalkoxyphosphinallenes leads to β-(5,5-dialkyl-2-oxo-1,3,2-dioxaphosphoranyl)-hydrazones in good yields. The structure of the obtained compounds were elucidated by the NMR (1H, 13C, 31P) spectroscopy and density functional theory (DFT) calculations at B3LYP/6-311++G (2d, 2p) level of theory. 相似文献
85.
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87.
Ramin Ghorbani-Vaghei Lotfi Shiri Arash Ghorbani-Choghamarani 《Comptes Rendus Chimie》2014,17(10):1002-1006
A new method is described for the reduction of sulfoxides to sulfides using N,N,N’,N’-tetrabromobenzene-1,3-disulfonamide [TBBDA] in combination with triphenylphosphine. Good to excellent yields, short reaction times, high efficiency and facile isolation of the desired products are the advantages of this method. 相似文献
88.
The reaction of N-thiocarbamoylimidates 1 with methyl thioglycolate leads to the formation of 4-arylamino-5-methoxycarbonylthiazoles 2. The condensation of the same imidates 1 on ethyl bromoacetate, benzyl bromide and chloroacetonitrile provides the corresponding 2-arylaminothiazoles 4. 相似文献
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90.
Gholam Reza Jahanshahloo Hélcio Vieira Junior Farhad Hosseinzadeh Lotfi Darush Akbarian 《European Journal of Operational Research》2007
This research proposes a new ranking system for extreme efficient DMUs (Decision Making Units) based upon the omission of these efficient DMUs from reference set of the inefficient DMUs. We state and prove some facts related to our model. A numerical example where the proposed method is compared with traditional ranking approaches is shown. 相似文献