Sharif Digital Repository

This research answers two questions: First, what effect does the increase in the number of children have on women's employment? Second, what is the magnitude of the effect of increasing the number of children on the potential employment rate of Iranian women? To address the first question, we use Heckman's reduced form regression along with a structural model of female labor supply. We use the Simulated Method Moments (SMM) to estimate the structural equations. Our data for the empirical analysis are taken from the Iranian Households’ Income and Expenditures Surveys in urban areas over the years 1990 to 2020. We use the estimated model to measure the potential increase in female employment... 

Propylene Copolymers and terpolymers with small amount of 1-butene& ethylene can greatly improve the properties of polypropylene material such as low temperature toughness, printing performance, transparency, process ability and so on, leading to expanding of its application. Poly(propylene-co-1-butene) performance intensely relies on its composition and chain structure. The copolymerization catalyzed by Ziegler-Natta catalyst, which is a multy-active central system. The Ziegler-Natta catalyst TiCl4/ Mg(OEt)2/ DIBP was used for copolymerization. The microstructure of copolymers were characterized by FTIR. The influence of different comonomer ratios on the copolymerization has been... 

Smart heat-sensitive polymers play a unique role in drug delivery systems due to reversible behavior in response to environmental changes, especially temperature changes. Among the heat-sensitive polymers, UCST polymers due to their specific behavior and very little-known polymers with this feature are the subject of many new researches. In the present study, New designed temperature-sensitive polymers with UCST capability based on acrylamide and vinyl acetate were synthesized. These copolymers were synthesized in different percentages of acrylamide by free radical polymerization in solution conditions. All polymers compounds were characterized by H-NMR, FT-IR, DSC and GPC measurements. The... 

Blending can be used as one of the ways of producing materials with appropriate properties, which have many relative advantages in comparison with other methods like polymerization. Among the existing blends in the market and scientific areas, blends of polyurethane thermoplastic and polypropylene have been also studied because of its commercial importance and scientific interest. This blending can improve the mechanical properties, friction resistance, improvement of impact strength at low temperatures and improvement of plasticity properties. In this research, blends with different ratios of TPU/PP is produced by melt mixing, and for improving properties of blends, two kinds of nano fumed ... 

In this work, the viscoelastic fluids flow and their short fiber suspensions has been modeled in contraction geometry using conformation models, these models predict behavior of polymeric chains in contraction geometry. Prediction of viscoelastic fluids flow through a contraction is very important, especially in polymer processing where a polymer melt in barrel of an extruder is going to pass through a narrow die. We expect to see an eddy in each corner of barrel. The result has shown that increasing of De number enhances the eddy magnitude; also with making acute angle, we see decreasing of eddy magnitude. Normal stresses and velocity were investigated in contraction and their results had... 

In this study, biodiesel production using enzymatic method for transestrification of castor oil was investigated. It was found that the yield of biodiesel production is affected by methanol to oil molar ratio, temperature, enzyme amount, water content and reaction time. Effective factors were determined first, using two-factorial design method. Methanol to oil molar ratio was found as the most effective factor. Response surface methodology coupled with central composite design was utilized for statistical modeling of enzymatic biodiesel production and the reaction time was found as a non-significant factor. In another attempt, three factors including methanol to oil molar ratio, temperature,... 

The main object of this thesis is preparation and investigation of polyolophine/graphene oxide nanocomposites by using bi-supported Ziegler-Natta catalytic system and in-situ polymerization. Magnesium ethoxide and graphene oxide were used as supports of catalyst. TiCl4 was accompanied by triisobutyl aluminum (tibia) and diisobutyl phthalate (DIBP) as an electron donor constituting Ziegler-Natta catalytic system. Preparation of catalyst and polymerization were taken place in slurry phase under the argon atmosphere. At the beginning of the polymerization experiment, several type of nanocomposites were made under various conditions (such as different Al/Ti molar ratio) to find optimum condition... 

Electrospinning process has been widely used to produce nanofibers from polymer blends. Poly(vinyl alcohol) (PVA) and chitosan (CS) have numerous biomedical applications such as wound healing and tissue engineering. Nanofibers of CS/PVA have been prepared by many works, however, a complete physicochemical and mechanical characterization as well as cell behavior has not been reported. In this study, Non-toxic, biodegradable, and biocompatible chitosan/poly(vinyl alcohol)(PVA)/nano silica nanofibers were prepared by electrospinning. The properties of the nanofibers at various blend ratios were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR)... 

The nervous system is the most complex body system and controls other body systems. Damages of the peripheral nervous system will interfere with the functioning of the body. Tissue engineering is used as one of the most effective methods for repairing damaged tissues,by providing 3-dimensional (scaffold) bedding with proper properties, allows the proliferation of Myelin sheath and proliferation of axons. In this study, we used a continuous extrusion process, sodium alginate with different percentages of Polyaniline-Graphene nanoparticle (synthesized by solvent emulsion) was extruded and its properties were determined by FTIR, SEM, MTT, tensile properties, Conductivity, contact angles and...