Sharif Digital Repository

Due to the decrease in oil reserves in the world, increasing population and the growing demands for oil consumption in the world, increasing the oil recovery from oil reservoirs has become more important. Increasing the amount of oil production efficiency by using low salinity water/modified salinity water has been highly appreciated during the last two decades. Low-salt water is a new method, due to its advantages such as low cost, simplicity of operation and low environmental hazards. It is believed that low salinity water can alter the rock wettability from a more oil-wetting state to a more water-wetting state. In order to be able to predict the performance of low salinity water... 

Matrix acidizing as a well stimulation technique is performed to increase the production index by increasing the permeability and removing the formation damage in the near wellbore region. However, several challenges such as corrosion of the tubulars and iron precipitation in the formation are hindering this process. To encounter these challenges, different chemicals, or additives, such as corrosion inhibitors and iron control agents are added to the acid solution. Carbonate acidizing has been carried out using HCl-based stimulation fluids for decades. However, at high temperatures, HCl does not produce satisfactory results because of its fast reaction, acid penetration, and hence surface... 

Water coning is a complex phenomenon that depends on various parameters which include among: production rate, matrix and fracture permeability, perforation interval, aquifer size, mobility ratio, capillary pressure, etc. Production of water can greatly affect the productivity of a well and the reservoir at large volume. In naturally fractured reservoirs, this problem is more complex because permeability of the fractures in the porous media is too high. With this complexity of water coning behavior in naturally fractured reservoir, this phenomenon was studied by simulating a sector of a carbonate fractured reservoir supported by an aquifer using Eclipse-300 simulator. A sector of an Iranian... 

Understanding the flow of liquids and particularly water in nanochannels is important for scientific and technological applications, such as for filtration and drug delivery. In this study, we perform molecular dynamics simulations to investigate the transfer of single-file water molecules across straight or nonstraight single-walled carbon nanotubes (SWCNTs). In contrast with the macroscopic scenario, the nonstraight nanostructure can increase the water permeation. Remarkably, compared with the straight SWCNT, the nonstraight SWCNT with the minimal bending angle of 30° in the simulations can enhance the water transport up to 3.9 times. Also increasing length and diameter of carbon nanotubes... 

Nowadays, water desalination is a widely-used method for producing clean and fresh water. Recent researches in this area have mostly focused on Reverse Osmosis technology which is one of the most efficient technologies in water desalination. A new idea to increase the efficiency of a recently-designed reverse osmosis membrane called “Honeycomb Carbon Nanotube Membrane” is presented through molecular dynamics simulation. Although in this study only the inlet area of the honeycomb structure which is a Y-shaped entrance, is modeled and studied, but obviously, any improvement in the membrane inlet, equals better results at outlet which means a more efficient desalination process. Present thesis... 

The formation of droplets at a T-junction in a micro channel network is primarily influenced by the pressure difference across the interface in the squeezing regime. Accurate measurements of droplet velocity and pressure profiles are difficult to obtain experimentally, yet these are the basic parameters required. Droplet micro fluidics has shown great potential for biological assays, chemical reactions and polymer emulsions. High stability allows the droplets to work as stable and isolated reactors that open up for parallel and serial reactions where each droplet can be screened individually. The purpose was to fabricate such systems, establish stable droplet generation where droplet volumes... 

In most cases, material failures occur on their surfaces, such as fatigue fracture, wear and friction, fretting fatigue and corrosion, so surface modification is one of the most effective techniques to improve the strength of materials. Correction of near surface grain size to nanoscale is one of the effective ways to improve the strength, fatigue life, toughness and etc. With increasing evidences of novel properties in nanostructured materials, it is reasonable to propose to achieve surface modification by the generation of nanostructured surface layer so that the overall properties and behaviors of the material are significantly improved.By means of surface severe plastic deformation, the... 

This thesis is devoted to the simulation of biomolecules manipulation using Molecular dynamics (MD). In order to investigate the manipulation behavior, we have used the Ubiquitin as biomolecule, a single-walled carbon nanotube (SWCNT) as manipulation probe, a graphene sample as substrate. Along this line, a lot of simulations are conducted to study the effects of different conditions on the success of manipulation process. These conditions include tip diameter, vertical gap between tip and substrate, initial orientation of protein, and the simulation environment (dry or wet). The results demonstrate that tips with bigger diameters and smaller distances with respect to the substrate increase... 

Hole-transporter-free perovskite solar cells with structure of TiO2/ZrO2/C triple-layer scaffold filled with perovskite are great alternative to the conventional ones due to the possibility of making full printable low-cost and stable devices. In the present work, the impacts of the structures of the quadruple layer scaffold in the form of TiO2/ZrO2/NiO/C and triple layer scaffold in the form of TiO2/ZrO2/C on their photovoltaic performance are studied. In addition, the effects of thickness and deposition method of each layer were investigated as well as the effect of compounding of the carbon counter electrode. All devices were constructed by a simple printable method. Electrochemical... 

Corrosion is a main problem for oil and gas industries at refineries and petrochemical process. Presence of sulfur compounds in crude oil and creation a corrosive environment for steel structure, caused failure and unfortunate damages. H2S which present at cracking and sweetening process in sour feed obtain hydrogen atoms that can diffuse into steel structure which involve with its instruments and consequent to hydrogen damage .distribution and storage of these sour environments can be done by high strength low alloy steel (HSLA).Electrochemical hydrogen permeation test were performed to measure the hydrogen permeation current through A106/GR B pipeline steel in the electrolytes simulating... 

Electrochemical sensing of glucose has received paramount attention in recent years, particularly, the non-enzymatic glucose sensing is one of the trends in the whole biosensing world. In this research, synthesis and evaluation of a hybrid structure of vertical oriented nickel nanorod-reduced graphene oxide sheets as a non-enzymatic glucose sensor were performed. The 3D array of nickel nanorods was synthesized by electrodeposition of nickel sulfate electrolyte in track-etched polycarbonate template with 100 nm pore size and 6-10 μm thickness. The electrodeposition performed in various conditions, and the best result was achieved by application of potential of 3 V for 60 minutes. The shiny... 

This research describes a new and relatively general method to grow well-aligned carbon nanotubes (CNTs) on cobalt-deposited stainless steel by thermal chemical vapor deposition (CVD) of ethylenediamine precursor. The CNTs are vertically aligned at high density over large areas on the surface. Different effective parameters in growth of carbon nanotubes, as type of substrate, surface treatment, temperature of growth , feeding carbon supplies have been studied. Finally, aligned carbon nanotubes have been prepared by 100-150 nm diameter and 9µ length. CoOx•nH2O–MWCNTs nanocomposites were successfully synthesized, using a cathodic electrochemical reduction of H2O2 to deposit cobalt... 

In some concrete projects, the consolidation of concrete is quite challenging due to the congestion of rebar and the complex concrete placement. Self-compacting concrete (SCC) can overcome these problems. On the other hand, nanomaterials in concrete can be used to improve the engineering properties of concrete and adverse environmental effects. This study uses aluminum-nano oxide and carbon-nano tubes (by replacing 1, 3, and 5% by weight of cementitious materials) to enhance the physical and mechanical properties of SCC. Additionally, adverse environmental effects of SCC improve by replacing 35% of cement with combustion furnace slag. Experimental results showed that with increasing... 

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.... 

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)... 

Damming projects always have been important while construction, operation and even demolition due to their major effects on society, environment and economy. Although researchers have focused on one or a few phases of construction projects to develop sustainable infrastructures, the research community has to consider long term effects of developments too. There are a variety of such effects that ignoring them will cause construction of not convenient infrastructures i.e. air pollution and over-consumption of energy resources while construction, operation and demolition. Therefore, it is suggested to consider life cycle assessments to include all bad effects in all phases of a project. Dams... 

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... 

Carbon nanotubes are cylinders in Nano scale formed of carbon atoms with covalent bonds that contain a significant electrical and mechanical features. Carbon nanotubes are divided into two main types: multi-walled carbon nanotubes (MWCNTs) and single walled carbon nanotubes (SWCNTs). A SWCNT is a rolled graphene sheet (graphene is in fact a single sheet of graphite). SWCNTs has lately been considered as one of most interesting research cases. The reason why researchers have been fond of investigating about graphene has been its unconventional quantum hall effects, high room-temperature electrical conductivity and its mechanical stability despite of being composed of single layer atom...