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1.
Polyvinylpolypyrrolidone-supported boron trifluoride has been studied for synthesis of 4-methyl coumarin by the Pechmann reaction. The reaction proceeded smoothly with hydroxyl phenols and ethyl acetoacetate in good yields in ethanol at reflux conditions. The polyvinylpolypyrrolidone-boron trifluoride complex is a non-corrosive and stable solid catalyst elevated Lewis acid property. 相似文献
2.
Hamed Rashidi Ali Ahmadpour Fatemeh F. Bamoharram Seyed Mojtaba Zebarjad Majid M. Heravi Faranak Tayari 《Chemical Papers》2014,68(4):516-524
ZnO nanostructures were synthesised in a hydrothermal reaction of zinc acetate in the presence of molybdophosphoric acid (H3[PMo12O40]) as well as its vanadium-substituted acid (H4[PMo11VO40]) at various times, temperatures, and concentrations. The ZnO nanostructures were characterised by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results demonstrated that the synthesised products are crystalline with a zincite hexagonal phase. Various ZnO nanostructures, such as nanoparticles, microrods, and nanosheets, were produced by changing the experimental conditions. The photocatalytic degradation of methyl orange was also investigated using the ZnO nanoparticles thus prepared. These particles exhibited high performance in the photocatalytic degradation of MO and almost 100 % decolourisation occurred within only 20 min. 相似文献
3.
In this work, TiO2 and doped TiO2 photocatalysts (Fe/TiO2 and Cu/TiO2) were synthesized by the sol–gel method. The main objective of this study was to investigate the influence of dopants on the structure, morphology, and activity of the catalysts in powder and immobilized states. XRF, XRD, and SEM methods were used to characterize the catalysts. The structure and phase distribution of the nanocrystalline powders were identified by XRD. Nanoparticles crystallite size and the degree of crystallinity were affected by doping. The anatase contents of catalysts were achieved as follows: TiO2 (5.89 %) < Fe/TiO2 (42.17 %) < Cu/TiO2 (70.28 %). It was indicated that the activity of the catalysts strongly depends on the anatase content. Under the same circumstances, copper-modified TiO2 exhibited a twofold higher photocatalytic activity compared with TiO2. The nanostructured catalysts were immobilized on light expanded clay aggregate (LECA) granules in order to investigate the effect of a novel support on the activity of the catalysts. Morphological changes are recognizable in the SEM images. Activity tests indicated that the best catalytic performance was assigned to Cu/TiO2/LECA. After 120 min of irradiation, 61 % degradation of phenol in synthetic wastewater was achieved. The high photocatalytic activity of Cu/TiO2/LECA confirms that LECA is as an excellent support. 相似文献
4.
Jean M. J. Tronchet Françoise Barbalat-Rey Jeannine F. Tronchet Faranak Raehidzadeh 《Journal of carbohydrate chemistry》2013,32(2):193-204
Replacement of the alkyl group of l-aryl-3-alkyltriazenes with a sugar moiety did not significantly modify their tautomeric behaviour. The same replacement done on 1-aryl-3-alkyl-3-methyl-triazenes did not affect to any large extent their rotameric properties. In contrast, the most prominent biological properties, anticancer activity and toxicity, of 1-aryl-3-methyltria-zenes disappeared on replacement of the methyl group with a sugar moiety. Unexpectedly, the N-acetyltriazene 15 was highly cyto-toxic. 相似文献
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6.
Applications of traditional data envelopments analysis (DEA) models require knowledge of crisp input and output data. However, the real-world problems often deal with imprecise or ambiguous data. In this paper, the problem of considering uncertainty in the equality constraints is analyzed and by using the equivalent form of CCR model, a suitable robust DEA model is derived in order to analyze the efficiency of decision-making units (DMUs) under the assumption of uncertainty in both input and output spaces. The new model based on the robust optimization approach is suggested. Using the proposed model, it is possible to evaluate the efficiency of the DMUs in the presence of uncertainty in a fewer steps compared to other models. In addition, using the new proposed robust DEA model and envelopment form of CCR model, two linear robust super-efficiency models for complete ranking of DMUs are proposed. Two different case studies of different contexts are taken as numerical examples in order to compare the proposed model with other approaches. The examples also illustrate various possible applications of new models. 相似文献
7.
This paper is concerned with the elastic buckling of stiffened cylindrical shells by rings and stringers made of functionally graded materials subjected to axial compression loading. The shell properties are assumed to vary continuously through the thickness direction. Fundamental relations, the equilibrium and stability equations are derived using the Sander’s assumption. Resulting equations are employed to obtain the closed-form solution for the critical buckling loads. The results show that the inhomogeneity parameter and geometry of shell significantly affect the critical buckling loads. The analytical results are compared and validated using the finite element method. 相似文献
8.
Faranak Pahlevani 《国际流体数值方法杂志》2006,52(4):381-392
This paper presents a numerical study of the sensitivity of an eddy viscosity model with respect to the variation of the eddy viscosity parameter for the two‐dimensional driven cavity problem and flow around a cylinder. The main objective is to provide a comparison between computing the sensitivity using sensitivity equation and computing the sensitivity using finite difference methods and also numerically illustrate the application of the sensitivity computations in improving drag flow functional. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
9.
Buckling of 2D-FG Cylindrical Shells under Combined External Pressure and Axial Compression 下载免费PDF全文
R. Mohammadzadeh M. M. Najafizadeh & M. Nejati 《advances in applied mathematics and mechanics.》2013,5(3):391-406
This paper presents the stability of two-dimensional functionally graded (2D-FG)
cylindrical shells subjected to combined external pressure and axial compression loads,
based on classical shell theory. The material properties of functionally graded cylindrical
shell are graded in two directional (radial and axial) and determined by the rule of mixture.
The Euler's equation is employed to derive the stability equations, which are solved by GDQ
method to obtain the critical mechanical buckling loads of the 2D-FG cylindrical shells. The
effects of shell geometry, the mechanical properties distribution in radial and axial direction
on the critical buckling load are studied and compared with a cylindrical shell made of 1D-FGM.
The numerical results reveal that the 2D-FGM has a significant effect on the critical buckling load. 相似文献
10.
Omid Bagheri Faranak Sadegh Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor‐Baltork Mahsa Safiri 《应用有机金属化学》2014,28(5):337-346
The tetrakis(4‐N‐methylpyridinium)porphyrinatopalladium(II) iodide, [Pd(TMPyP)]I4, supported on Dowex 50WX8 and Amberlite IR‐120 ion‐exchange resins, was used as heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura and Heck cross‐coupling reactions. These catalysts were applied to coupling of various aryl halides with phenylboronic acid and styrene in Suzuki and Heck reactions, respectively, and the corresponding products were obtained in excellent yields and short reaction times. The catalysts could be recovered easily by simple filtration and reused several times without significant loss of their catalytic activity. The catalysts were characterized by diffuse‐reflectance UV–visible spectroscopy and scanning electron microscopy, and their stability was confirmed by TGA. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献