Rasht, Iran
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New and novel ionic liquid (3-methyl-1-sulfonic acid imidazolium hydrogen sulfate) is a recyclable and eco-benign catalyst for the chemoselective trimethylsilyl protection of hydroxyl groups under solvent-free conditions to afford trimethylsilanes in excellent yields (92-100%) and in very short reaction times (1-8 min). The catalyst was characterized by FT-IR, 1H NMR and 13C NMR studies. All the products were extensively characterized by 1H NMR, IR, GC-MS and melting point analyses. A mechanism for the catalytic activity is proposed. The catalyst can be recovered and reused without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification. © 2011 Elsevier B.V. All rights reserved.


Karami A.,Guilan University
International Journal of Electrical Power and Energy Systems | Year: 2011

This paper proposes a methodology for estimating a normalized power system transient stability margin (ΔV n) using multi-layered perceptron (MLP) neural network with a fast training approach. The nonlinear mapping relation between the ΔV n and operating conditions of the power system is established using the MLP neural network. The potential energy boundary surface (PEBS) method along with a time-domain simulation technique is used to obtain the training set of the neural network. Results on the New England 10-machine 39-bus system demonstrate that the proposed method provides a fast and accurate tool to evaluate online power system transient stability with acceptable accuracy. In addition, based on the examination of generators rotor angles after faults, a method is presented to select the power system operating conditions that most effect the ΔVn for each fault. © 2011 Elsevier Ltd. All rights reserved.


A simple and facile synthesis of 12-aryl-12H-indeno[1,2-b]naphtho[3,2-e] pyran-5,11,13-trione derivatives was accomplished via the one-pot condensation of 2-hydroxynaphthalene-1,4-dione, aldehydes, and 2H-indene-1,3-dione at 100 °C under solvent-free conditions in the presence of the solid acid catalyst, poly(4-vinylpyridinium) hydrogensulfate. This method has the advantages of high yields, clean reactions, simple methodology, and short reaction times. The catalyst could be recycled and reused four times without significant loss of activity. The structures of the novel compounds were confirmed by IR, 1H NMR, and elemental analysis. © 2011 Elsevier Ltd. All rights reserved.


Arabani M.,Guilan University
Construction and Building Materials | Year: 2011

The stiffness modulus is one of the most important parameters for the prediction of pavement strength against dynamic loads. Previous research indicated that glass can reduce the construction costs of asphalt concrete pavements while providing better dynamic behaviour because of its unique properties. In this research, the behaviour of Hot Mix Asphalt (HMA) in different temperature conditions depending on the variation of the admixture contents and the gradation of the aggregates will be evaluated. Afterwards, for the first time, models for the prediction of the stiffness modulus of waste glass-asphalt in terms of three different parameters including temperature, percentage of additives and the aggregate gradation will be presented. The results of this research are indicative of an improvement in the dynamic behaviour of glass-asphalt mixture in comparison with conventional HMA mixtures. © 2010 Elsevier Ltd. All rights reserved.


3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an acidic task-specific ionic liquid for Pechmann condensation reaction. The coumarin products could simply be separated and the ionic liquid could be recycled and reused several times without noticeable decrease in the catalytic activity. © 2012 The Royal Society of Chemistry.


A simple and convenient procedure for the synthesis of 14-aryl-14H- dibenzo[a,j]xanthenes is described through a one-pot condensation of 2-naphthol with aryl aldehydes in the presence of poly(4-vinylpyridinium)hydrogen sulfate as an efficient, cheap, readily synthesized and eco-friendly catalyst in a solvent free media using conventional heating and ultrasound irradiation. © 2011 Elsevier B.V. All rights reserved.


A simple and convenient procedure for the synthesis of xanthene derivatives is described through a one-pot condensation of 2-naphthol {2- hydroxynaphthalene-1,4-dione or the mixture of 2-naphthol and 2-hydroxynaphthalene-1,4-dione} with aryl aldehydes in the presence of poly(4-vinylpyridinium)hydrogen sulfate as an efficient, cheap, easily synthesised and eco-friendly catalyst under solvent-free conditions. Further, the catalyst can be reused and recovered several times without any variations in the yield of the product. This journal is © 2012 The Royal Society of Chemistry.


Ramezani S.,Guilan University
International Journal of Mechanical Sciences | Year: 2012

In this study, a first order shear deformation micro-plate model based on strain gradient elasticity theory is developed. The most general form of Mindlins linear isotropic strain gradient elasticity is employed and a general micro-plate formulation is obtained. The governing equations of motion and all possible boundary conditions are determined using the variational method. For some specific values of the gradient-based material parameters, the general plate formulation can be reduced to those based on simple forms of the strain gradient elasticity theory. Accordingly, a simple form of the plate formulation is introduced. To illustrate the behavior of a micro-plate predicted by the new plate formulation, the static bending and free vibration problems of a simply supported micro plate are investigated. Numerical results reveal that the plate defection decreases and natural frequencies increase remarkably when the plate thickness becomes comparable to its material length scale parameter. These size effects decrease or even diminish as the thickness of the plate is far greater than the material length scale parameter. It was also observed that the effects of shear deformation are more sensible at micro scales. © 2012 Elsevier Ltd. All rights reserved.


Reliable and accurate forecasts of river flow is needed in many water resources planning, design development, operation and maintenance activities. In this study, the relative accuracy of artificial neural network (ANN) and support vector regression (SVR) models coupled with wavelet transform in monthly river flow forecasting is investigated, and compared to regular ANN and SVR models, respectively. The relative performance of regular ANN and SVR models is also compared to each other. For this, monthly river flow data of Kharjegil and Ponel stations in Northern Iran are used. The comparison of the results reveals that both ANN and SVR models coupled with wavelet transform, are able to provide more accurate forecasting results than the regular ANN and SVR models. However, it is found that SVR models coupled with wavelet transform provide better forecasting results than ANN models coupled with wavelet transform. The results also indicate that regular SVR models perform slightly better than regular ANN models. © 2012 Elsevier Ltd.


Ramezani S.,Guilan University
International Journal of Non-Linear Mechanics | Year: 2012

In this study, a micro scale non-linear Timoshenko beam model based on a general form of strain gradient elasticity theory is developed. The von Karman strain tensor is used to capture the geometric non-linearity. Governing equations of motion and boundary conditions are derived using Hamiltons principle. For some specific values of the gradient-based material parameters, the general beam formulation can be specialized to those based on simple forms of strain gradient elasticity. Accordingly, a simple form of the microbeam formulation is introduced. In order to investigate the behavior of the beam formulation, the problem of non-linear free vibration of a simply-supported microbeam is solved. It is shown that both strain gradient effect and that of geometric non-linearity increase the beam natural frequency. Numerical results reveal that for a microbeam with a thickness comparable to its material length scale parameter, the effect of strain gradient is higher than that of the geometric non-linearity. However, as the beam thickness increases, the difference between the results of the classical beam formulation and those of the gradient-based formulations become negligible. In other words, geometric non-linearity plays the essential role on increasing the natural frequency of a microbeam having a large thickness-to-length parameter ratio. In addition, it is shown that for some microbeams, both geometric non-linearity and size effect have significant contributions on increasing the natural frequency of non-linear vibrations. © 2012 Elsevier Ltd.

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