Sharif Digital Repository

In oil industry, increment of drilling mud viscosity is of great importance. Water based polymers are widely use as drilling fluid to achieve this goal. Formation damages can be occurred by invading polymer solution into the formation in different ways such as scale and precipitation. These damages appear in different shapes such as reduction in relative permeability and productivity index reduction. In this study we have proposed, designed and fabricated a novel device, called sand pack, to measure the damage of the reservoir which enable us to calculate relative permeability and recovery factor by means of pressure difference and flow rate. Using this lab-scaled device we have measured... 

In this work, polyvinylidene difluoride (PVDF) as a ferroelectric polymer, polyaniline (PANI) and polypyrrole (PPy) as conductive polymer additives are used to fabricate high performance mesoporous CH3NH3PbI3-xClx mixed-halide perovskite solar cells in a sequential deposition method. Using polymer additives in perovskite precursor solution leads to modification of perovskite layer morphology by changing nucleation and growth of perovskite grains. Besides, conductive polymer additives in perovskite layer help to more charge carrier transfer. Power conversion efficiency has been enhanced from 10.40 % to 16.51% and to 13.21 % in ambient atmosphere in the presence of 1.0 wt. % of PVDF and PPy... 

In the present work, the experiments were carried out for two types of PAM (3330 and 3630) with three distinct concentrations (25, 40 and 55 ppm) and TiO_2-water nanofluid for four concentrations (1.5, 2, 2.5 and 3 vol. %), and the Nusselt number and friction factor for each of them expressed separately. The Reynolds number was in the range from 11000 to 21000. The steady state turbulent convective heat transfer and friction factor of the combination of TiO_2-water nanofluid and polymer 3330 in the coiled tube were investigated. The effects of the Reynolds number for 2 vol. % nanoparticles which consists of 25 ppm PAM (3330) determined at the constant temperature of 24°C. It was observed... 

Recently, conductive nanocomposites have found great deals of attentions due to their vast applications in different fields. According to the definition of nanocomposite, the filler component should be in the range of 10-100 nm. In this study, silver nanoparticles was used as filler with 4 nm size and synthesized by microemulsion method that is known as the best approach for fabricating silver nanoparticles with small sizes, narrow size distribution and high stability.
Copoly (ortho-phenylenediamine/dopamine) was used as matrix component. Ortho-phenylenediamine is one of the conductive polymers that was used less than other conductive polymers such as polyaniline in this research area.... 

Corrosion is caused through chemical interactions between metal and gases in the surrounding environment. Conductive polymers are used for corrosion protection, polyaniline is the most environmentally stable out of all the conductive polymers, the most studied of this materials, is highly stable, synthesized easily, highly conducting, and readily converted between its various oxidation states.
In this study we prepared nanoporous polyaniline coating on carbon steel to corrosion protection. Coating was included nanopouros polyaniline with doping molybdate (PANI-MoO_4^(-2)). To increase adhesion between steel and PANI-MoO_4^(-2) layer, oxalic acid was used. Polystyrene nanoparticle layer... 

Nervous system plays an intricate biological process of man body.Damage of nervous system has serious consequences and is hard to recover, as well as the other parts of the body may not work properly. Many strategies have been used to repair spinal cord injuries in which the main objective is to improve the regeneration of axons and functional recovery. The purpose of this research is introducing neural tissue engineering concepts (e.g. scaffolds, stimulation and etc.) and also design and fabrication suitable for neural tissue engineering. For this purpose the combination of biodegradable polymers (chitosan),conductive polymer (poly-aniline) and carbon nanosheets (graphene) was chosen as the... 

The rehabilitation of old structures holds a lot of importance, as many structures with a life span of over 30 years are prone to severe damage and even collapse. To overcome this problem, the use of FRP sheets to strengthen structures is suggested. RC-arches have been used in many structures such as bridges and require specific consideration in terms of strengthening. So far, the influence of the number of FRP layers and location, the height of arch and percentage of reinforcement on strengthened arch behavior have not been investigated. In this research, reinforced concrete arch members strengthened with GFRP and CFRP were investigated. A total of 28 Specimens, including four... 

Despite extensive studies on the behavior of reinforced concrete slabs, especially those reinforced with steel rebars, no comprehensive studies have been conducted on the behavior of concrete slabs reinforced with FRP rebars. Therefore, there are some ambiguities regarding the tensile and compressive behavior of these rebars in the load-bearing capacity of reinforced concrete slabs (depending on their amount in the slab and their combination with steel rebars). Hence, in this study, in order to ensure the accuracy of numerical simulations, the numerical 3D simulation of a one-way concrete slab reinforced with tensile FRP rebars was performed using the finite element Abaqus software.... 

A brief overview of the proposed research, its aims, engineering relevance and applications; as well as expected achievements compared to the present state of the art:The plastic hinge length and ultimate drift calculations of frames are required in the performance based design of reinforce concrete structure. FRP-confinement increases the column’s shear resistance and ductility. FRP-confinement prevents concrete cover from spalling and increases the inelastic deformability of concrete in the potential plastic hinge region. GU et al. 2012 [24] studied the existing experimental results of confinement effects on the plastic hinge length. Mortezaei and Ronagh, 2012 [25], studied the plastic... 

This study has investigated the effects of different environmental conditions on the bond at the interface between two fiber reinforced polymer (FRP) layers. A total of 945 single lap splice coupons with three bond length were made using wet lay-up technic. There were used three unidirectional fabrics and one type of epoxy resin. A Uniaxial tensile test was performed on samples after 2, 4, 12, 20, 28, 36 and 48 weeks of exposure. Also series of test were conducted in order to determine the minimum lap splice length of single splice FRP samples. The experimental results indicated reduction of bond strength in glass specimens that was 17 % after 48 weeks of exposure while for same amount of... 

Most of the investigations during the two past decades focused on the effect of moisture and temperature on the bond at the interface of carbon or glass-fabrics and concrete, masonry or timber. Few investigations have studied the effect of chemical solutions, dry heat exposure and ultravilolent (UV) radiation on the bond at the interface of other types of fiber reinforced-polymers (FRPs) and masonry, timber and concrete in the short and long terms. Therefore, this research aims to investigate the effect of five chemical solutions with pH of 2.5±0.1, 7±0.1, 7.25±0.1, 10±0.1 and 12.5±0.1 on the interfacial bond strength between seven types of FRPs (unidirectional, bidirectional and hybrids)... 

Masonry structures are complex systems that require a thorough and detailed knowledge for analysis and designing, and especially maintaining their capability. Since the old historical masonry structures have cultural value, maintenance of such structures against natural disasters that cause destruction is important. The goal of this research is to find a method for protection of the historical masonry structure of Daniel shrine that is located in susa region in Khuzestan. According to the reference structures of architectural heritage, a number of challenges in conservation, diagnosis, analysis, monitoring, repair and strengthening are presented that limit the application of modern codes... 

Precise numerical models to predict responses and damage of FRP strengthened RC slabs to impact loads are limited in the literature. The behavior of (RC) slabs strengthened by FRP sheets is investigated. The behavior of strengthened RC slabs under impact load is analyzed using finite elements method. In this study, the effects of FRP strengthening of RC slabs to resist impact loads have been performed using ANSYS software. RC slabs without/with different FRP strengthening measures have been simulated in this study. RC slab without strengthening and RC slab strengthened with FRP sheets applied to the tension face of the slab have been included in the model. Each slab is subjected to repeated... 

The investigation of non-prestressed concrete components subjected to impact loadings has been reported in the literature. However, the knowledge on the impact-resistant capacity of pre-stressed concrete components is very limited. In this study, behavior of pre-stressed concrete slabs strengthened by FRP sheets is investigated. The behavior of strengthened pre-stressed concrete slabs under impact load is analyzed using finite elements method. The effects of FRP strengthening of pre-stressed concrete slabs to resist impact loads have been studied using ANSYS software. Pre-stressed concrete slabs have been modeled without/with different FRP strengthening measures. Pre-stressed concrete slab... 

Although considerable researches have been conducted on strengthening RC structures using FRP method during past years, a few researches have been reported on RC arch or curved structures strengthened by FRP. In this study, behavior of RC arches strengthened by FRP strips is investigated. The behavior of strengthened RC arches under gravitational load is analyzed using finite elements method. The arches are modeled by appropriate software in order to evaluate the behavior. The structural behavior of arches is more complicated. So, the estimation of the effect of strengthening using FRP technique on such structures is hard in comparison with traditional RC beams. In this study, the effect of... 

The purpose of this study is to determine the effects of some strengthening methods such as steel jacketing, concrete jacketing and FRP wraps in the overall behavior of structures and introducing the most appropriate method. For this purpose a 14 story building with intentionally weak designed shear walls was considered, subsequently each of the strengthening methods were followed for the shear walls and relative structural outcomes like total stiffness and lateral movements were calculated, studied and compared and finally a guideline for choosing the most appropriate strengthening method for concrete shear walls is resulted. It is established that for the system with steel jacketing... 

The research shows that the compressive strength of concrete reduced by replacing crumb rubber in concrete mix design compared to normal concrete mix design. However, there have been a couple of utilizations investigated to date for the structural utilization of these materials. Crumb rubber is usually provided from recycled rubber from automotive and truck scrap tires. During the recycling process steel and triviality are removed, leaving tire rubber with a granulose cohesiveness. The additional crumb-rubber aggregate has a significant effect on concrete mix porosity which affects both the plastic state workability and hardened state mechanical properties. This research depicts an... 

Reinforced concrete (RC) column in building often needs strengthening either due to defects in the column themselves, having to support higher loads than those foreseen in the initial design of the structure or as the result of ageing or accidental damage such as earthquake force. The use of FRP wrapping, steel caging or reinforce concrete jacketing for this purpose is now a common practice in many countries throughout the world. Even though a considerable number of researches have been conducted on retrofitting methods during past years, but very limited researches have been done to compare these methods. This research has investigated the effect of jacketing from different views. The... 

Fiber Reinforced Polymer (FRP) tendons are suitable to be used in concrete beams exposed to aggressive environments. This study proceeds the design and it presents the flexural capacity (in relation to the moment-curvature) for composite sections (reinforced with steel bars and pre-stressed FRP) rectangular, T-section which has been bent and broken. The failure is in attending with strain softening, stress hardening of fiber reinforced concrete (FRC) and reinforcing with steel bars and polymer. Using the predicted moment-curvature relationship, a numerical method is used to estimate the load deflection response at sample beams under concentrated and uniform loads. A parametric study will be... 

The strengthening of reinforced concrete structures with externally bonded fibre reinforced polymer (FRP) laminates has shown excellent performance, so this technology is rapidly replacing externally bonded steel plates, steel or concrete jackets, and many traditional techniques available. In this study strengthening of reinforced concrete beams by GFRP to reduce creep deflection is investigated by mathematical method using available relations. Five RC beams with different dimensions, with and without strengthening with GFRP laminate, were investigated for their creep deflection. The creep coefficient of beams selected from experimental result that were mentioned in RILEM DATA BANK. In this...