Sharif Digital Repository

In this study, in order to indicate the best airfoil profile for the different sections of a blade, five airfoils including S8xx, FFA, and AH series were studied. Among the most popular wind power blades for this application were selected, in order to find the optimum performance. Nowadays, modern wind turbines are using blades with multi-airfoils at different sections. On the large scale profile, SST K-ω model with different wind speed at large-scale profile was applied to the simulation of horizontal axis wind turbines (HAWT). The aerodynamic simulation was accomplished using the computational fluid dynamic (CFD) method based on the finite volume method. The governing equations applied in... 

The present study focuses on the simulation of two dimensional unsteady cavitating flows. For simulation of unsteady behaviors of cavitation which have practical applications, the development of unsteady PISO algorithm based on the non-conservative approach is utilized. For multi-phase simulation, single-fluid Navier-Stokes equations, along with the volume fraction transport equation, are employed. The bubble dynamics model is utilized to simulate phase change between vapor and liquid phases of the water. Unsteady simulation of cavitation around NACA66(MOD) and supercavitation around a flat plate normal to flow direction are performed to clarify accuracy of presented model. Numerical results... 

A carbon nanotube field effect transistor (CNTFET) has been studied based on the SchrödingerPoisson formalism. To improve the saturation range in the output characteristics, new structures for CNTFETs are proposed. These structures are simulated and compared with the conventional structure. Simulations show that these structures have a wider output saturation range. With this, larger drain-source voltage (Vds) can be used, which results in higher output power. In the digital circuits, higher Vds increases noise immunity. © 2009 World Scientific Publishing Company  

The qualitative effects of residual stress parameters on fatigue crack growth are investigated using Monte Carlo probabilistic analysis technique. These parameters include the maximum residual stress,σ0, half-width of the tensile residual stress region, b, and the redistribution of residual stress parameter, β. A normal distribution is assumed for all parameters considered in the investigation and fatigue life is determined using Forman equation. The results indicate that: (i) fatigue life decreases nonlinearly if the mean of random maximum residual stress and the half-width of tensile residual stress region increases; (ii) fatigue life increases nonlinearly if the rate of residual stress... 

Molecular dynamics (MD) simulation was utilized to study the role of asphaltene extracted from Gachsaran (an Iranian oilfield) at the synthetic oil-water interface. In agreement with experimental data, IFTs predicted by MD simulation for heptol/brine system showed a minima at around 50 vol.% n-heptane, reflecting the highest contribution of asphaltene into the interface. At greater n-heptane fractions, IFT was increased steadily. Simulation results suggest the asphaltene propensity for remaining in the bulk heptol phase rather related to the fraction of toluene in the mixture. Heptol ingredients, i.e., toluene and heptane, act differently with respect to asphaltene, where former tends to... 

In this paper, the advantages of numerical simulation to improve the process of copper electroforming are demonstrated. In this regard, the finite element model of copper electroforming for a rotating cone electrode was first prepared and then, the effect of the key parameters, such as applied current density, solution conductivity, electrode spacing, and anode height, on the uniformity of the thickness was investigated. The model combines tertiary current distribution with Bulter–Volmer electrode kinetics and computational fluid dynamics at the turbulent condition. In order to validate the model, a cone-shaped shell was produced by electroforming method in the laboratory. The obtained... 

Simulation has been shown to be one of the most powerful tools in many areas of the health-care system, a system which attracted the attention of researchers due to its intricacy. The main goal of this study is to evaluate the patients' flow in an emergency department (ED). Discrete event simulation (DES)has been used as the core of this research so that it offers various ways to reduce the length of stay (LOS)of patients in different segments of ED by assessing various scenarios. In particular, a new approach for verification of the simulated model will be discussed. This study reports on the results that extracted from a case study on patient record data in one of the EDs located in Tehran... 

Driving simulators can provide safe real-world driving conditions that may help researchers study driving behavior; however, driving simulator sickness (DSS) has been recognized as one of the most frequent challenges associated with using driving simulators. The DSS issue may affect the validity and reliability of results obtained during the driving simulator experience. Therefore, it is necessary to understand the potential consequences of DSS in the virtual environment of a driving simulator. The goal of this study is to analyze DSS symptoms among participants of a driving simulator by their demographics. The samples of four simulator studies were combined, including a total of 259... 

In this research, we simulate the corrosive behavior of steel reinforcements on 5 different mixtures to investigate the effect of two powerful protective methods, including pozzolanic additives and corrosion inhibitor on concrete, by artificial neural networks (ANNs). Related to this model, fly ash (FA), micro silica (MS), and slag were used as pozzolanic materials at an optimum 25%, 10%, and 25% of cement weight, respectively. Moreover, Ferrogard 901 as an inhibitor was also utilized. The producer recommends using12 kg/m3 to get the best possible results. The non-linear corrosion of concrete into a marine solution (3.5% NaCl) was simulated by the feed forward back propagation (FFBP)... 

In this research, we simulate the corrosive behavior of steel reinforcements on 5 different mixtures to investigate the effect of two powerful protective methods, including pozzolanic additives and corrosion inhibitor on concrete, by artificial neural networks (ANNs). Related to this model, fly ash (FA), micro silica (MS), and slag were used as pozzolanic materials at an optimum 25%, 10%, and 25% of cement weight, respectively. Moreover, Ferrogard 901 as an inhibitor was also utilized. The producer recommends using12 kg/m3 to get the best possible results. The non-linear corrosion of concrete into a marine solution (3.5% NaCl) was simulated by the feed forward back propagation (FFBP)... 

Interleukin 1 Receptor type I (IL-1RI) is a multi-domain transmembrane receptor that triggers the inflammatory response. Understanding its detailed mechanism of action is crucial for treating immune disorders. IL-1RI is activated upon formation of its functional assembly that occurs by binding of the IL-1 cytokine and the accessory protein (Il-1RAcP) to it. X-ray crystallography, small-Angle X-ray Scattering and molecular dynamics simulation studies showed that IL-1RI adopts two types of ‘compact’ and ‘extended’ conformational states in its dynamical pattern. Furthermore, glycosylation has shown to play a critical role in its activation process. Here, classical and accelerated atomistic... 

Increasing the lifetime and improving the performance of structures through redesign and optimization are important, especially in marine structures. In general, there are two main groups of marine structures: onshore and offshore structures. Most marine structures are offshore, and these are divided into two categories: floating or sunken. One of the important parameters in the design of sunken structures is the critical load resulting from the buckling of walls, which can cause damage to the structure. In the present paper, three rectangular aluminum and steel compartments of different conditions and sizes were modeled using design analysis methods. Then, different finite element analyses... 

In this study, we present results of a mathematical model in which the governing equations of electroforming process were solved using a robust finite element solver (COMSOL Multiphysics). The effects of different parameters including applied current density, solution electrical conductivity, electrode spacing, and anode height on the copper electroforming process have been investigated. An electroforming experiment using copper electroforming cell was conducted to verify the developed model. The obtained results show that by increasing the applied current density, the electroforming process takes place faster, thereby resulting in a higher thickness of the electroformed layer. In addition,... 

In this study, transient 2D/axisymmetric simulations of cavitating flows are performed using a modified 'Volume-of-Fluid' (VOF) technique. Simulation of the cavitation is based on a homogenous equilibrium flow model. To predict the shape of the cavity, the Navier-Stokes equations in addition to an advection equation for the liquid volume fraction are solved. Mass transfer between the phases is treated as a sink term in the VOF equation. The numerical method is used for different geometries in a wide range of cavitation numbers. Computed shapes of cavities were found to be in good agreement with those of the reported experiments. The simulation results also compared well with those obtained... 

In this paper we analyses the energy consumption of well known family of asynchronous circuits and present a new methodology for energy estimation of these circuits at intermediate-level of abstraction. Energy estimation is performed by simulating the intermediate format of the design. The number of Read and Write accesses on the ports of the concurrent processes are counted by analyzing the conditional and computational portion during the simulation which is the base of our estimation methodology. Our proposed power estimation scheme is faster than usual post-synthesis power estimation by an order of 9, while the estimated power resides in a boundary of 11% total imprecision. © 2007 IEEE  

With IoT devices becoming abundant and WSN applications becoming evermore present, the once dream of ubiquitous connectivity is closer to realization than ever before. but this realization is hindered by many technical problems and lengthy time to markets. Currently, our best practice of feasibility analysis relies in the same simulators used to model and develop the network applications. Because of their broad range and immense usability challenges, these jack-of-all-trades simulators tend to be computation-intensive and hard to work with.Here, we propose a relatively light-weight simulator based on the analytical models of different parts of the network to aid in rapid development and ease... 

For large and complex reacting systems, computational efficiency becomes a critical issue in process simulation, optimization and model-based control. Mechanism simplification is often a necessity to improve computational speed. We present a novel approach to simplification of reaction networks that formulates the model reduction problem as an optimization problem and solves it using genetic algorithm (GA).The aim of simplification kinetics modeling is to derive the simplest reaction system, which retains the essential features of the full system. Numerical results for H2/O2 combustion reaction mechanism illustrate the potential and proficiency of this approach  

The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. Specific consideration was given to dynamic simulations of viscoelastic fibers in which the fluid flow is predicted by a method that is a hybrid between Direct Numerical Simulations (DNS) and Large Eddy Simulation techniques (LES), and fluid fibrous structure interactions (FSI) will be taken into account. Numerical results are presented for which focus is on fiber floc deformation by hydrodynamic forces in turbulent flows. Dynamics of simple fiber networks in a shearing flow of water in a channel flow illustrate that the... 

Taylor Expansion Diagram (TED) has been recently introduced as a compact and canonical representation for arithmetic functions with finite Taylor series. It can represent Boolean logic interacting with arithmetic functions canonically. One of the main disadvantages of TED is that relations must be bit expanded to be represented in TED. This paper represents a method for high-level symbolic simulation and property checking based on integer equations. Functionality of design is represented in Conditional TED (CTED), which is our enhancement of TED to represent relations without bit expansion. This way, a more compact structure is achieved for high-level designs, containing control path... 

The demands for mobile communication services are growing rapidly. In heavily populated areas, cell splits are necessary to increase the capacity of cellular systems. Cell splitting causes a cellular system to have mixed cell sizes. Calculation of the reverse link capacity of CDMA cellular systems with mixed cell sizes and imperfect power control is presented in this paper. When a macro cell is split into micro cells, the capacity of a non-uniform cellular system has been calculated, together with the calculation of micro and neighboring macro cell capacity. The computer simulation results show that with the reduction in radius of a micro cell, its capacity increases, while that of the...