Sharif Digital Repository

Due to the increasing need for drinking water in the world, various membrane processes have been developing significantly over the past several years. The process of membrane distillation is one of the non-isothermal processes that cause steam to pass from the membrane due to the difference in temperature and the resulting difference in vapor pressure. Due to the lack of precision in the amount of flux and thermal efficiency in various operating conditions the membrane distillation process still needs development. This article attempted to examine the effects of flowrate, temperature, and module length on the performance of the membrane distillation process using computational fluid dynamics... 

We extend the construction and analysis of Raptor codes originally designed in [1] for the erasure channel to general symmetric channels. We explicitly calculate the asymptotic fraction of output nodes of degree one and two for capacity-achieving Raptor codes, and discuss techniques to optimize the output degree distribution  

In this paper, based on the high-order theory (HOT) of sandwich structures, the response of sandwich cylindrical shells with flexible core and any sort of boundary conditions under a general distributed static loading is investigated. The faces and the core are made of isotropic materials. The faces are modeled as thin cylindrical shells obeying the Kirchhoff–Love assumptions. For the core material, it is assumed to be thick and the in-plane stresses are negligible. The governing equations are derived using the principle of the stationary potential energy. Using harmonic differential quadrature method (HDQM), the equations are solved for deformation components. The obtained results are... 

Using harmonic differential quadrature method, an approach to analyze sandwich cylindrical shell panels with any sort of boundary conditions under a generally distributed static loading, undergoing elasto-plastic deformation is proposed. The faces of the sandwich shell panel are made of some isotropic materials with linear work hardening behavior while the core is assumed to be an isotropic material experiencing only elastic behavior. The faces are modeled as thin cylindrical shells obeying the Kirchhoff–Love assumptions. For the core material, it is assumed to be thick and the in-plane stresses are negligible. Upon application of an inner and outer general lateral loading, the governing... 

The effect of the nucleating agent masterbatch carrier resin on the nonisothermal crystallization of a pipe-grade polypropylene block copolymer was investigated at three different cooling rates using differential scanning calorimetry (DSC). Bis(3,4-dimethylibenzylidene) sorbitol (DMDBS), a well-known, third-generation sorbitol derivative, was used as a nucleating agent in this study. Crystallization kinetic parameters obtained from DSC cooling curves showed that incorporation of a nucleating agent by means of a masterbatch increased the crystallization rate by approximately two times compared to that of the sample with the same concentration of nucleating agent without the use of a... 

Vapor liquid equilibrium (VLE) data has significant role in designing processes which include vapor and liquid in equilibrium. Since it is impractical to measure equilibrium data at any desired temperature and pressure, particularly near critical region, thermodynamic models based on equation of state (EOS) are usually used for VLE estimating. In recent years due to the development of numerical tools like artificial intelligence methods, VLE prediction has been find new alternatives. In the present study a novel method called Least-Squares Support Vector Machine (LSSVM) used for predicting bubble/dew point pressures of binary mixtures containing carbon dioxide (CO 2) + cyclic compounds as... 

This work concerns experimentally quantifying finger behavior during miscible displacements in fractured porous media. A series of miscible tests were performed on five-spot fractured micromodels which were initially saturated with heavy crude oil, and the developed finger patterns were quantified using an image analysis technique. The results revealed that the numbers of macro fingers formed is well correlated with the square root of dimensionless time, while the rate of finger initiation is independent of fracture characteristics. The level of bypassed oil linearly decreases with dimensionless distance traveled by front precisely. The transient fractal dimension behavior experiences a... 

Multiple contact miscible floods such as injection of relatively inexpensive gases into oil reservoirs are considered as well-established enhanced oil recovery (EOR) techniques for conventional reservoirs. A fundamental factor in the design of gas injection project is the minimum miscibility pressure (MMP), whereas local sweep efficiency from gas injection is very much dependent on the MMP. Slim tube displacements, and rising bubble apparatus (RBA) are two main tests that are used for experimentally determination of MMP but these tests are both costly and time consuming. Hence, searching for quick and accurate mathematical determination of gas-oil MMP is inevitable. The objective of this... 

A new study is conducted with the aid of molecular dynamics (MD) simulation to investigate the effect of shear modulus value of the interlayer van der Waals (vdWs) interactions on free vibration of cantilever multi-layer graphene nanoribbons (MLGNRs). The corresponding calibrated nonlocal parameters of the nonlocal model are obtained accordingly. The vdWs interactions are treated as the cores between every two adjacent graphene layers and their equivalent shear modulus is calculated using MD simulation. The obtained resonant frequencies via the nonlocal sandwich model are compared to the MD simulation results to calibrate the nonlocal parameter. Results reveal a strong conclusion that the... 

The linear static elastic-plastic behavior of sandwich cylindrical shell panels under a generally distributed loading with thick flexible core is studied. The core modeling is based on high-order theory of sandwich structures in which the in-plane stresses of the core are neglected. The faces are modeled based on Kirchhoff-Love shell theory. The materials of the faces and the core are assumed to be isotropic with linear work hardening behavior. The incremental Prandtl-Reuss plastic flow theory is used in this analysis. Using the principle of virtual displacements, the governing equations are derived and solved for any sort of boundary conditions based on elastic-plastic harmonic differential... 

Demands for hydrocarbon production have been increasing in recent decades. As a tertiary production processes, chemical flooding is one of the effective technologies to increase oil recovery of hydrocarbon reservoirs. Retention of surfactants is one of the key parameters affecting the performance and economy of a chemical flooding process. The main parameters contribute to surfactant retention are mineralogy of rock, surfactant structure, pH, salinity, acidity of the oil, microemulsion viscosity, co-solvent concentration, and mobility. Despite various theoretical studies carried out so far, a comprehensive and reliable predictive model for surfactant retention is still found lacking. In this... 

One of the most promising methods for transporting natural gas and overcoming its low energy density is adsorbed natural gas (ANG) technology. ANG technology is highly dependent on the perfect conception of adsorption isotherms in different operational conditions and on different adsorbents. In this study, the utilization of a novel mathematical model of least squares support vector machine (LSSVM) for accurate prediction of adsorption isotherm has been examined. The considered variables were temperature, pressure and type of adsorbents. A data set containing 670 experimental data points of methane adsorption on 10 different adsorbents in a broad range of temperature and pressure were used... 

Multiphase flow meters (MPFMs) are utilized to provide quick and accurate well test data in numerous numbers of oil production applications like those in remote or unmanned locations topside exploitations that minimize platform space and subsea applications. Flow rates of phases (oil, gas and water) are most important parameter which is detected by MPFMs. Conventional MPFM data collecting is done in long periods; because of radioactive sources usage as detector and unmanned location due to wells far distance. In this paper, based on a real case of MPFM, a new method for oil rate prediction of wells base on Fuzzy logic, Artificial Neural Networks (ANN) and Imperialist Competitive Algorithm is... 

Appropriate execution of drilling operation, in particular for high pressure and high temperature wells, requires accurate knowledge of behavior of the drilling fluid density as a function of pressure and temperature. In this communication, a novel mathematicalbased approach is presented to develop a reliable model for predict the density of four drilling fluid including water-based, oil-based, Colloidal Gas Aphron (CGA) and synthetic. To pursue our objective, a predictive model is proposed using a robust soft computing approach namely least square support vector machine (LSSVM) modeling optimized with coupled simulated annealing (CSA) optimization tool. Moreover, leverage approach, in which...