Sharif Digital Repository

In Economic literature, investigating effective determinants of driving offences is discussed in Economics of Crime. In this field the effect of economic and sometimes non-economic parameters on offences are investigated. Economics of Crime was introduced as a branch of economics after Becker (1968). Since then different studies have been done and many theories have been made to discuss the relation between economic Variables and crimes in the society. In this study we use a cross-province panel data of driving offences to investigate the Effective Determinants of these offences. The most important result is the deterring effect of the penalty. For example in the regression for the seventeen... 

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... 

CO2 separation from air was investigated in this work. An immobilized liquid membrane (ILM) which contains triethylene glycol (TEG) and diethanolamine (DEA) was used for this purpose. In this kind of membranes a liquid, which improves permeability of gas species through the membrane, fills the pores of a polymeric membrane as support. Because of low vapor pressure of solution, liquid loss was negligible. Transport of CO2 was facilitated due to reversible chemical reaction between CO2 and amine solution. A polyvinylidene fluoride (PVDF) membrane was chosen to have chemical resistance against the solution and prevent destruction of polymer by solution. A flat sheet and hydrophilic PVDF was... 

In this research, initially the Triethylene glycol and Diglycol amine liquid membrane which is supported by PVDF, was prepared in order to separate the Carbone dioxide from CO2-Air mixture. A polyvinylidene fluoride (PVDF) membrane was chosen to have chemical resistance to solution. The effect of Pressure, Concentration of TEG and DGA solution and the percentage of carbon dioxide in feed; in rate and permeability of CO2, N2 and O2 and also selectivity of CO2/ N2 , CO2/ O2 and N2/ O2 was investigated. Transport of CO2 was facilitated due to reversible chemical reaction between CO2 and amine solution. The experiments were done in 0.4, 0.6 and 0.8bar and different concentration of solution.... 

In various industries, for energy production, fossil fuels are burned. Oxygen needed for combustion, taken directly from the ambient air; So that the inert gas is about 80%. The presence of this inert gas, mainly nitrogen, reduce combustion efficiency and increase the use of combustible material. In this project with the help of membrane technology, was used to remove the amount of nitrogen in the air so that the incoming air into the combustion chamber is enriched with oxygen. For this purpose, several gas separation membrane was applied and evaluated. Then, according to the oxygen enrichment, fuel efficiency and the amount of savings, increasing chamber temperature, reduction manufacturing... 

In the present study, a heat recovery system for a distributed generation plant (DG) with a 1 MW gas combustion engine has been designed. The purpose of this designing is converting the power plant to a CHP system. For the existing heat recovery system, a shell & tube heat exchanger is designed to recover the thermal energy from exhaust gases and a plate heat exchanger is designed to recover the thermal energy from the engine jacket cooling fluid. The heat exchanger design has been calculated manually and also by use of software. In the software calculation, the heat exchanger design has been done by use of the Aspen HTFS +2006.5 software. In the manual one, the Kern equation (1950) was... 

The main objective of this project is to study the effect of the presence of nanoparticles on mass transfer in liquid-liquid systems. To do this research, TiO2/water, Al2O3/water, CNTs/water and CNTs/toluene have been used as nanofluids. The experiments of TiO2/water nanofluid were been carried out in water-acetone-toluene system at two weigh percents of TiO2 nanoparticles. The result showed that mass transfer decreased in 0.5wt% of TiO2, compared to base fluid, and it increase in 1 %wt. Also in 0.5%wt the decrease in interfacial tension decreased diameter of drops and as a result mass transfer decreased too. In 1%wt the increase in viscosity increased the diameter of drops and then the... 

Liquid-liquid extraction is one of the common chemical processes in the industry which its application is increasing day by day. Taking trend of increase of energy resources, chemical materials and industrial system into account, the necessity use of least energy consumption and material for achieving highest output and purity of products in different industries is attracted researches and industerialists.In this research we have studied the effect of presence of nano particles on both disperses and continuous liquids phases on hydrodynamic of deoplets specially their investigated system in this project was watter, toluene and acetone, and chosen nanoparticles wer carbon nanotubes and TiO2.... 

Different modeling and simulation techniques, new numerical methods and analyzing effects of different parameters on operation of bubble columns are continuously under study for optimized design, scale-up and prediction of industrial bubble columns. Tools for analyzing and developing gas-liquid systems are experimental techniques and computational fluid dynamics (CFD). In order to describe accurately the fluid dynamics of complex gas-liquid systems, more advanced mathematical models are required. To obtain a feasible numerical solution, efficient numerical techniques must be devised. One of such models that considerably reduces the assumptions and consequently increases the accuracy of... 

The separation ofacetic acids in binary water solutions hasbeenstudied using a reverse osmosis (RO) membrane. Thin film composite polyamide membrane is used in this study.Thin-film composite (TFC) membrane was prepared through the interfacial polymerization between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on the polysulphone support membrane.The solute permeation was carried out under applied pressure of 5 bar at 25°C. In this work the effect of various synthesis conditions on the membrane performance was investigated. Parametric studies were conducted by varyingconcentration of reactants, reaction time, curing time and curing temperature. By suitable combination of these... 

Tissue engineering aims to produce artificial tissues and organs to treat the damaged part, by implant in body of patients, is an important issue in research and development. In cases that tissue damage is sever or due to genetic defects or congenital disease, tissue in the body are not fully formed, tissue engineering can be used to regenerate, repair or replace organs or tissues. Cell culture on the scaffold and put it in the bioreactor is a critical step in the formation of tissues or organs. Among various bioreactors, perfusion bioreactor due to increase of convection in the structure of cell-scaffold is widely used. Enhancement of convection increases shear stress on the cells that is... 

In this study, aqueous two-phase systems (ATPS) containing Tween 20 as a biocompatible nonionic surfactant and three different salts (NH4HPO4, NH4CH3COO and Mg(CH3COO)2 ) were prepared and their extractive potential for Lysozyme enzyme was evaluated. These systems have surfactant-rich top phase and salt-rich bottom phase. Phase equilibrium diagrams at 23 ° C were obtained by using the cloud point method and the results were successfully fitted to the Merchuk correlation and their trends were correlated with the effective excluded volume (EEV) parameter. Afterward, the partitioning behavior of the lysozyme and its extraction efficiency in the systems of Tween 20/diammonium hydrogen phosphate,... 

Core-shell structures of Ag@Pt nanoparticles (NPs) dispersed on Carbon Vulcan XC-72, Multiwalled carbon nanotube and reduced graphene oxide (rGO) support containing different Ag:Pt mass ratios and applied to the oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell (PEMFC) were synthesized by the ultrasonic and reduction treatment method. The morphology of as-prepared catalysts characterized by the high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and induced coupled plasma atomic emission spectroscopy (ICP-OES). The ORR activities and stabilities of catalysts were studied through electrochemical measurements utilizing the Cyclic Voltammetry... 

Surface phenomena and dynamic interfacial properties plays a significant role in multiphase gas-liquid & liquid-liquid processes applied in different industrial applications. However, current laboratory equipment and represented methods for dynamic and unsteady state condition caused by motivation of interface of two phases (like rising bubble), in purpose of qualitative investigation of interphase properties are not satisfying enough. Also, common modeling methods are represented with lots of modified assumptions which are not validated properly with experimental results. In current thesis, with development of laboratory tools and applying the “rising bubble method” for investigating the... 

The present study has been performed for better understanding about the dynamic behavior of fluid interfaces in presence of surfactants, nanoparticles and their interactions in gas-liquid dispersion systems. One of the main purposes of this work is to investigate the influence of surface modified nanoparticles on the dynamic behavior of gas-liquid interfaces. For this purpose, the rising bubble experiment was used as one of the most conventional procedures. Local velocities of bubbles rising in nanoparticle solutions were determined experimentally. Influences of silica nanoparticles which were modified via three approaches were investigated in these experiments. Heat treatment was applied to... 

Today reverse osmosis (RO) is the dominant technology for desalination. Most of commercially available RO membranes are polyamide thin film composite (TFC) types which exhibit good performance. However, the major obstacle for application of polyamide TFC RO membranes is fouling which can be mitigate by surface modification.In this research, surface modification of fabricated aromatic polyamide TFC RO membranes was carried out using UV-initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g/L). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm)... 

In this research, a novel nanofiltration membrane was used to separate nitrate from water as a nitrogen-containing compound. The membrane was fabricated by interfacial polymerization on the modified polysulfone substrate. To improve the efficiency of nitrate removal, several surface and bulk modifiers were used. As modified with LiCl and PVP polymer, the substrate matrix was modified to have the highest porosity to reduce the mass transfer resistance and the much surface area to form a polyamide layer on it. The polyamide layer was then synthesized by interfacial polymerization using a blend of MPD and PIP in different ratios (1: 1 optimum ratio) in reaction with TMC (optimum concentration... 

It is necessary to monitor pollutants in aquatic samples, because many of these compounds can pose threats to human health and the ecosystem. Separation technology based on magnetic materials has received considerable attention in recent years. The magnetic extraction method is not only convenient, economical and highly efficient, but it also overcomes problems with conventional solid-phase extraction. In order to remove anionic dyes from single and ternary systems, zinc ferrite nanoparticle was synthesized using co-precipitation method and its surface was modified by Cetyltrimethyl ammonium bromide (CTAB) cationic surfactant. Surface characteristics of ZFN-CTAB was studied using Fourier... 

This research studies a 3D channeled myocardium scaffold with computational fluid dynamics. It proposes a mathematical model to evaluate the impact of oxygen carriers and scaffold geometry on cell growth in a 3D cardiac construct. The modeling results show that using 5.4% perfluorocarbon oxygen carrier (PFC) has increased cardiac cells density 15% of the initial seeded cells comparing to pure culture medium without PFC supplementation. Effects of the scaffold geometry on cell density in the construct were examined by increasing channel numbers and changing the construct length. The results show that increasing channel numbers (by 50% decreasing channels diameter and wall to wall spacing) the... 

In this study, modification of Polyvinylidene fluoride membrane in order to reduce membrane fouling in membrane bioreactors is investiged. To achieve this goal, chemical modification and grafting methods were used. Initially, by chemical modification, the reaction was made to make hydroxyl groups on the membrane surface. The hydroxyl functional groups were used as a site for connecting of subsequent monomers. Finally, the lysozyme enzyme was used as the main modifier to improve the hydrophilicity and antibacterial properties of the membrane surface. To evaluate the performance of the modified membrane in comparison with the pristine membrane, different tests, such as water contact angle...