Sharif Digital Repository

Considering the advantages and disadvantages of reported micropumps, we aimed to introduce a novel idea to diminish the disadvantages and promote the advantages of Magnetohydrodynamic (MHD) micropumps. This novel idea operates based on a mercury slug rotation in a circular microchannel. This cyclic motion of the mercury slug which is similar to a piston, push the fluid in the microchannel and pump the flow. However, to bring this idea into the practice, it must be integrated with a specific valve. Fluid has not to go through this specific valve. In contrary, mercury slug has to pass across this valve. These two specifications must be considered during the design process of the valve. On the... 

It is widely accepted that under reservoir conditions there exists some degree of block-to-block interaction that may lead to capillary continuity. The formation of liquid bridges causing capillary continuity between blocks will significantly affect the ultimate oil recovery. However, accurate modeling of the growth and detachment of traveling liquid bridges which causes capillary continuity between blocks remains a controversial topic. In this work the generalized continuity and momentum equations along with fracture capillary pressure are combined to develop a mechanistic model for formation of traveling liquid bridges between blocks. Firoozabadi and Ishimoto (1994) model is considered for... 

With altering natural state and increasing impervious surfaces, traditional urbanization leads to deteriorating the environment and water catchments. During the years most efforts in order to control the urban runoff outflow, have been focused on quantity; and awareness about improving water quality has been raised just in the last few years and, which emphasizes on pollution source control. Standard water quality sampling methods are time consuming, expensive and because of sampling in broad geographic areas, difficult; however modeling is a more efficient way in assessing water quality and as worries about non-point source pollution grows, different kinds of models have been used to... 

The continual deterioration and insufficient strength of reinforced concrete (RC) structures has been a vital problem in the field of civil engineering such an extent that traditional methods of strengthening found to be inconvenient. Nowadays by increasing demands for retrofitting of structures, it necessitates the application of efficient, inexpensive and unobtrusive methods of strengthening. Common way on retrofitting was to use of steel plates externally bonded to RC members. Although this technique has proven to be reasonably effective, it has several distinct disadvantages such as susceptibility of the steel plates to corrode and the excessive weight of steel plates when used in... 

Arc welding is one of the key processes in the industry. Its vocational status in manufacturing industry comes to third place. From applicable standpoint gas metal arc welding (GMAW) has especial place between various electrode arcs. Base on the mode of transferring welding drop from electrode into welding pool the GMAW process could be categorized. The physics of metal transfer is not yet well understood, due to the facts that the arcs area is too small, the temperatures is too high and the metal transferring is at too high rate. However, physical behavior of process of each model is different from another. So equations that express each of them, need to reform toward others. The conditions... 

In this research, the partitioning of Penicillin G-Acylase in aqueous two-phase systems (ATPS) containing poly ethylene glycol (PEG) 20000 or 35000 and potassium di-hydrogen phosphate (KH2PO4) or sodium citrate (C6H5Na3O7.5H2O) is measured at three temperature (301.2, 307.2 and 310.2) K. The effects of temperature, polymer molecular weight, polymer and salt concentrations on partitioning of Penicillin G in the aqueous two-phase systems are studied. The experimental data showed that composition of salt has a large effect on partitioning of Penicillin G in ATPS and temperature of system has small effect on the partitioning. The modified local composition model was used to obtain the activity... 

This study has been carried out for investigating the need for an appropriate and fast seismic analysis method to be applied in performance based design (PBD), and show the application of Endurance Time (ET) method and its advantages in PBD. The major goal of this project is analysis and study of behavior of concrete frames with retrofitted shear walls with FRP by ET method with acceleration functions which are compatible with actual earthquake and comparation with time history analysis, forand comparation of whole results with shear wall frames that are not retrofitted. Performance criteria of FEMA code were used fore comparation of two frame categories (retrofitted and not retrofitted).... 

In this study biological denitrification method by moving bed biofilm reactor is investigated. The main advantage of MBBR reactor is due to their capacity for high removal rates and low operational problems such as clogging. Two MBBRs in series with 3 liter volume each, were designed in experimental set up and used in this research. Nitrification reactor worked under aerobic conditions and denitrification reactor operated under anaerobic conditions. Methanol was used as carbon source in the reactors throughout the study. Fifty percent of each reactor volume was occupied with KMT1 packing. To finding the optimum nitrate loading rate, the concentration of ammonium and nitrate were changed from... 

In a polyvinyl alcohol (PVA) plant, equal moles of methyl acetate are produced as byproduct for every mole of PVA. Since there is a little demand for impure methyl acetate, it is converted to methanol and acetic acid as raw materials of PVA plant via hydrolysis reaction. Duo to the small equilibrium constant of hydrolysis reaction of methyl acetate, the conventional process (including reaction and separation sections) suffers some problems such as large recycle flow and high energy consumption. Therefore, reactive distillation is introduced as an alternative for these processes. Since the reactive distillation integrates both reaction and separation in a single vessel, it has more complex... 

The aerial vehicle capable of vertical takeoff and landing (VTOL), have created an interest in the community of researchers and admirers of Unmanned Aerial Vehicles. Among the existing UAV's, those with the capability of vertical takeoff and landing are prominent due to their higher maneuverability and hover capability. Quadrotors mostly have been considered as a flying robot for save and rescue operations in dangerous and unreachable places in addition to its military application. In cross shape of Quadrotor platform on each edge is appointed an electric motor with light rotors that usually are controled by considering motor rates as their only inputs. This thesis aims, to simulate and... 

Complex networks science have become the major method in the modeling of topological features of networks and graphs. Although file sharing Peer-to-Peer systems can be modeled by networks with un-weighted nodes and links, using these networks for Peer-to-Peer streaming systems have not led to a suitable model.In this research, we aim to model Peer-to-Peer streaming networks with weighted nodes and weighted links so that present the performance of nodes and the amount of streaming that is transmitted between nodes respectively. Due to lack of information about upload bandwidth distribution in networks we assume this distribution as uniform. Because of dynamics of network, this distribution... 

In this project, the continuous phase mass transfer and backflow coefficients are optimized, using the experimental data from two RDC columns. The continuous and dispersed phases are modeled by stage wise and forward mixing model, respectively. Genetic Algorithm is applied to find the optimized parameters of the model. Olney model is employed to find the slip velocities of drops. The dispersed phase mass transfer coefficients were calculated using Handlos-Baron model. In the other part of the project, the Rigid Drop model was modified to predict the mass transfer coefficients of dispersed phase and the modification parameter was optimized by genetic algorithm. The effect of rotor speed and... 

Nowadays, most of businesses are becoming computer-based. This trend causes the organizations to become more vulnerable to internal and external threats. Internal threats are done through insiders. Insiders unlike outsiders have capabilities which aid them to easily carry out their illicit activities. Unfortunately, most of research in computer security has focused on the outsider threats, whereas the most damaging is the result of insiders’ illicit activities.This dissertation addresses three primary necessities of the research in the area of insider threat: a consistent definition of insider threat, a classification of types of insider threats, and a classification of vulnerabilities which... 

In this research, a simple yet efficient two-dimensional model of proton exchange membrane fuel cell (PEMFC) is developed using stream function-vorticity formulation. The model accounts for the fluid flow and masstransport processes in cathode gas channel and gas diffuser layer. The governing equations are decoupled and solved usingtwo efficient approaches, Alternating Direction Implicit (ADI) and False Transient Method (FTM) in a modified geometry to simulate the fully-developed condition consistently. An in-house code was developed to perform a parametric study of fuel cell performance. The results show the variations of important parameters along the cathode channel such as velocity... 

One of the most common diseases associated with musculo-skeletal ailment is low back pain which is epidemic among general public so that billions of dollars is spent annually to treat this disease. There are back pain prevention strategies include training on correct lifting, ergonomic tool design, and industrial automation amongst others. In recent years, assistive devices have also been used to prevent back pain. There are assistive devices that can be installed on the body and significantly have reduced forces required for Erector Spinae muscle and Lumbar moments. In this research, at first the anatomy of the spine and muscles and method of processing Electromyography (EMG) of muscles... 

One of the beautiful branches of Astrophysics is studing of binary systems and specially eclipsing binary sytems which is included transiting eclipsing extrasolar planets. Detecting of extrasolar planets with transit method is based on which a planet orbits around a star and when its orbit alignment is such that planet along our line of sight across disk of star, it causes eclipse of star and a drop in star’s brightness and from this we can find the existence of a planet. In analysis of observational light curve (obtained from data acquisition with photometry method) a synthetic light curve, constructed from a theoretical model which is based on transit, planet and star geometry, is... 

This thesis describes different neural networks models and an approximation based neural network controller for autonomous underwater vehicles (AUVs). The online multilayer perceptron neural networks (OMLPNN) have been designed to perform modeling of AUVs of which the dynamics are highly nonlinear and time varying. The online recurrent multilayer perceptron neural networks (ORMLPNN) have been additionally designed to generate a memory to pervious states and increase the performance of the modeling. The designed OMLPNN and ORMLPNN with the use of backpropagation learning algorithm have advantages and robustness to model the highly nonlinear functions. The proposed neural networks architecture... 

Oil and gas upstream, is one of the major parts of the energy chain in the world. Processes of production, transportation, processing and conversion of energy carriers are the main parts of this sector. Process units of oil and gas upstream industry are some of most local and global pollution resources in the world. In this research, the consideration of the pollutions from the production, processing and conversion of fossil fuels sector and the optimization of the management choices of each pollutant is subjected. Consideration of the pollutants related to the upstream sector, pollution control and management choices, cost accounting of the environmental impacts, the methods of accounting... 

Mold/metal interfacial heat transfer coefficient (IHTC) is the most important parameter that influences the solidification and the mechanical properties of a solidified product. The present work focuses on the determination and evaluation of pressure effect on interfacial heat transfer coefficient from the experimental cooling curves during unidirectional solidification of A356 alloy against water cooled Gray iron mold (chill). For this purpose, inverse heat conduction method is used. The results showed that IHTC is not constant, but varies with time, temperature and pressure during solidification. IHTC variation is related to coherency and critical solid fraction during... 

Diesel engines have widely used in past hundred years. During this time costly and extensive researches have been done to improve engine performance, which is going on. Important issues of these engines are higher specific power and efficiency and lower specific fuel consumption and pollutions formation. One of the best methods for engine performance improvement is matching a convenient turbocharger on engine. A turbocharger increases the engine air mass flow rate by increasing the inlet pressure and density. Due to increase of fresh air mass flow rate, fuel mass flow rate and power would increase. The aim of this research is to choose the convenient turbocharger for the OM355 naturally...