Sharif Digital Repository

Poly vinylidene fluoride (PVDF) as a fluorine polymer with acceptable thermal, chemical and physical property attractive create attention in membrane technology for water treatment application. However, with differential surface free energy between PVDF and water (∆G_s=30 mJ/m^2) PVDF polymer is divided as a hydrophobic materials, that is one of the basic problem for PVDF polymer. Due to its hydrophobicity the water molecules repulsion away from hydrophobic PVDF membrane surface as a spontaneous process with an entropy increasing and therefore pollutant molecules with hydrophobic functional group have tendency to adsorb onto membrane surface and dominate the boundary layer. In recent years... 

Charged particle lenses perform two types of operations. One purpose of lenses is to confine a beam, or maintain a constant or slowly varying radius. This is important in high-energy accelerators where particles must travel long distances through a small bore.A second function of lenses is to focus beams or compress them to the smallest possible radius. If the particles are initially parallel to the axis, a linear field lens aims them at a common point. Focusing leads to high particle flux or a highly localized beam spot. Focusing is important for applications such as scanning electron microscopy, ion microprobes, and ion-beam-induced inertial fusion. All modern lenses, have fully metal... 

Here we have used CFD to simulate the flow field around a DBD plasma active controller for flow control. Enhanced Electrostatic model is applied to model the plasma actuator, by solution of two elliptic equations to find electric field and charge density in whole flow field. So, it provided the body force by neglecting the magnetic forces in Lorentz equation. The body force is added to the momentum equation as a source term. A commercial software FLUENT is used for this simulation. To validate the algorithm, flow over a flat plate using DBD actuator is solved and results are compared with experimental and numerical results. Flow control around a cylinder with Reynolds number of 18,000 is... 

Micropumps are one of the most important devices in the field of microfluidics which have many applications in various fields of engineering. Electrostatic excitation is one of the types of excitation mechanisms in micropumps that is widely used in microelectromechanical systems due to its low power consumption and easier control. In this research, first, the physics of droplets on the surface studied, important dimensionless numbers and other factors influencing microfluidic phenomena are investigated. The effective parameters of the droplet motion and the mechanism of this motion are described. Besides, the phenomenon of electrowetting, one of the phenomena in the field of dynamics of... 

Electrostatic precipitators are widely used in cement plants to remove impurities and dust from the exhaust gases. The filtration mechanism is based on using high intensity electric fields which first ionize the particles and then absorb them toward the collecting electrodes. The corrosion effect is one of the major problems associated with electrostatic precipitators which not only can negatively affect their operation efficiency but also decreases their life-time through breakage occurrence in the corroded electrodes. One of the commonly used methods to suppress this negative effect and increase the total working hours of the device is to cut the bottom part of the first collecting plate... 

In order to investigate the effect of molecular-structural properties of asphaltene fraction on changes in wettability and flow of crude oil in the porous medium, four crude oil samples from oil fields in southern Iran were tested ;To know the characteristics of crude oil, molecular-structural properties of asphaltene fraction and the effect of asphaltene fraction on the wettability properties of surface, Experiments such as crude oil density and viscosity measurement, crude oil hydrocarbon analysis, asphaltene extraction with standard IP-143 method, elemental analysis and metal content, gel permeation chromatography, nuclear magnetic resonance, interaction between rock and asphaltene.... 

Particulate air pollution is one of the top environmental health risks. Industrial processes like power generation from fossil fuels and steel and cement manufacturing release a huge amount of particles into the atmosphere. Moreover, internal combustion engines produce a considerable amount of particulate matter in populated areas. The usual way to overcome this risk is using air-cleaning devices such as filters. Filters are designed for specific purposes like removing aerosol particles, aerosol sampling and collecting valuable particles. Because of its diverse applications, filtration has become an active area of research and many kinds of filters are currently available. One type of... 

Nano/Microelectromechanical systems have generated a great impact on industry and technology. There are many applications for these systems in micropumps, airbag accelerometers and inkjet printer heads. In theses systems mechanical and electrical fields are involved with each other, and complexities due to this involvement has prevented the scientific society from an effective tool for analysis of this systems in computational point of view. So the objective of this project is to use the Extended Kantorovich method to solve the equations of microplate deformation due to electrostatic actuation. This method is based on variational principals and it uses an initial guess function which doesn’t... 

The aim of this study is to develop an understanding of the role of the magnetic and electric forces on the filtration performance of wet granular beds. At first, the effect of wetting is considered by locating micro water film around the square channel for particles deposition in four different Reynolds Re=1 to Re=10 number, Typically 1000 particles in different sizes (100nm-10μm) were injected to microchannel when air and water formed completely on the surface of the block. The Drag force, Brownian force, Saffman`s lift force and the gravity force are affecting the particles. After that Dielectrophoretic and Magnetophoretic forces were included in the domain for investigating the role of...