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Barati E.,Khayyam Higher Education Institute | Esfahani J.A.,Ferdowsi University of Mashhad
Journal of Food Engineering | Year: 2013

The paper deals with modeling the convective drying process. A relevant and reliable mathematical model that captures the history and distribution of temperature is presented. The attention is focused on the simultaneous heat and mass transfer occurring during drying where dry and hot air flows about the food. In the present study, external resistance to mass transfer is considered negligible. As a result, the drying curve is almost independent of the boundary conditions, which means that drying is diffusion-controlled. The main connotation of present study regards to undertake analytical procedure to establish the novel model for practical applications. The results show that the temperature evolution can be evaluated from an advanced analytical solution in a quick and efficient manner. The model is validated with the literature experimental data obtained for carrot and mango slabs. A good agreement is obtained between the model predictions and the available experimental results. © 2012 Elsevier Ltd. All rights reserved. Source

Karimi H.,University of Technology Malaysia | Rahmani R.,University of Technology Malaysia | Mashayekhi R.,Khayyam Higher Education Institute | Ranjbari L.,University of Technology Malaysia | And 5 more authors.
Beilstein Journal of Nanotechnology | Year: 2014

Graphene, which as a new carbon material shows great potential for a range of applications because of its exceptional electronic and mechanical properties, becomes a matter of attention in these years. The use of graphene in nanoscale devices plays an important role in achieving more accurate and faster devices. Although there are lots of experimental studies in this area, there is a lack of analytical models. Quantum capacitance as one of the important properties of field effect transistors (FETs) is in our focus. The quantum capacitance of electrolyte-gated transistors (EGFETs) along with a relevant equivalent circuit is suggested in terms of Fermi velocity, carrier density, and fundamental physical quantities. The analytical model is compared with the experimental data and the mean absolute percentage error (MAPE) is calculated to be 11.82. In order to decrease the error, a new function of E composed of α and β parameters is suggested. In another attempt, the ant colony optimization (ACO) algorithm is implemented for optimization and development of an analytical model to obtain a more accurate capacitance model. To further confirm this viewpoint, based on the given results, the accuracy of the optimized model is more than 97% which is in an acceptable range of accuracy. © 2014 Karimi et al; licensee Beilstein-Institut. Source

Esfahani J.A.,Ferdowsi University of Mashhad | Barati E.,Khayyam Higher Education Institute | Karbasian H.R.,Ferdowsi University of Mashhad
Journal of Naval Architecture and Marine Engineering | Year: 2013

In flapping underwater vehicles the propulsive performance of harmonically sinusoidal heaving and pitching foil will be degraded by some awkward changes in effective angle of attack profile, as the Strouhal number increases. This paper surveys different angle of attack profiles (Sinusoidal, Square, Sawtooth and Cosine) and considers their thrust production ability. In the wide range of Strouhal numbers, thrust production of Square profile is considerable but it has a discontinuity in heave velocity profile, in which an infinite acceleration exists. This problem poses a significant defect in control of flapping foil. A novel profile function is proposed to omit sharp changes in heave velocity and acceleration. Furthermore, an optimum profile is found for different Strouhal numbers with respect to Square angle of attack profile. © 2013 ANAME Publication. All rights reserved. Source

Esfahani J.A.,Ferdowsi University of Mashhad | Karbasian H.R.,Ferdowsi University of Mashhad | Kangarshahi A.F.,University of Tehran | Barati E.,Khayyam Higher Education Institute
CFD Letters | Year: 2013

One of the problems may be occurred in the Town Border Station (TBS) for reducing of natural gas pressure is a serious damage which follows the bends. In this paper the bend erosion by gas-particle flows is investigated. The process is simulated using Computational Fluid Dynamics (CFD) and solved by k-ε model. The particles momentum can easily transfer to surface of the bend and it increases the rate of erosion by disorder in pressure distribution and gas high velocity. For protecting bend form erosion a novel method is proposed. A multistage diffuser is installed before the bend, which influence on gas momentum and spread the velocity profile in pipe. Additionally, this process produces local turbulence, which helps erosion to drop. Overall results show the proposed method can notably reduce the rate of erosion until 51% and may be used as a procedure to reduce erosion in units where the gas pressure drop is their major duty, such as TBS. © 2013 All rights reserved. ISSR Journals. Source

Esfahani J.A.,Ferdowsi University of Mashhad | Barati E.,Khayyam Higher Education Institute | Karbasian H.R.,Ferdowsi University of Mashhad
Applied Ocean Research | Year: 2013

In the present study the effect of caudal length on hydrodynamic performance of flapping foil is investigated. According to reality of swimming of fishes, the kinematics of their oscillation tail is involved with two rotational motions where one of them causes the tail to move in circular direction and the other leads the tail to pitch around its pitch axis. With this concept, a generalized kinematic model is considered. According to simulation of the motion trajectory of flapping foil, it is shown that the length of caudal may affect the hydrodynamic performance. It is shown that at lower and higher Strouhal numbers (St < 0.2 and St > 0.6) the hydrodynamic performance of flapping foil is optimum when the length of caudal is infinitive. It should be noted that at higher caudal length the variation of propulsive efficiency and produced thrust are stopped and these hydrodynamic parameters are kept at constant values. Additionally, it is demonstrated that there is the possibility of improving propulsive efficiency at moderate Strouhal numbers (0.2 < St < 0.6) by manipulation of caudal length. Furthermore, it is shown that in some cases the manipulation of caudal length may increase thrust coefficient as the propulsive efficiency is also increased. © 2013 Elsevier Ltd. Source

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