Sharif Digital Repository

In recent decades the use of FRP materials for strengthening structures has been developed extensively, thanks to their high strength, sufficient stiffness, high durablity, and ease of use. A great deal of research has been conducted on strengthening reinforced concrete beams and columns with FRP composites. By contrast, not many researches are performed on slabs, especially two-way slabs. In these few researches, the loading and boundary conditions are limited to simplest ones. Therefore, in this thesis, the focus of attention is on strengthening reinforced concrete slabs under various loads and boundary conditions using FRP composites.
In this thesis, first, FRP composites and their... 

Supplier selection is a strategic decision that has a key impact on the success of the supply chain. Due to the nature of goods and storage conditions in the cold supply chain has a great impact on environmental pollution compared to other chains, and it also has the possibility of disrupting the chain due to the importance of temperature and time conditions. Currently, due to the spread of international pressures on the observance of environmental and social principles, the issue of choosing a sustainable supplier has been raised. Also, the expansion of supply chains has caused the challenges and risks faced by supply chains to expand and disrupt the chain, so the decision of supply chain... 

Reinforced concrete (RC) shear walls with a curved cross-section are appealing structural elements to architects and engineers due to the aesthetic and structural advantages. Owing to the paucity of decent experimental research on curved RC shear walls (CRCSWs), the seismic response of these structural elements is essentially unknown. In that regard, this study includes research on a high-demanding type of structural element, which has found its application in North America, Europe, Asia, and to some extent in the Middle East with relatively no design specifications and laboratory research, structural analysis, and design methodology. Therefore, in order to provide an insight into the... 

Over the last few years, several economical and environmental reasons have caused many countries throughout the world to plan to replace conventional gasoline vehicles with different types of electric vehicles, and hence, it is anticipated that using these vehicles will quickly be developed in near future. Widespread use of electric vehicles calls for a comprehensive network of easily accessible charging stations being capable of replenishing their batteries. In this regard, municipal public parking decks, because of their characteristics, can be considered as proper candidates for installing charging equipment. However, as a large number of electric vehicles can be parked at a public... 

The use of nano-fluid, which is a stable solid liquid mixture, has been proposed as a new strategy for heat transfer operations. Much research has been done on heat transfer of nano-fluids until now, whereas the study of phenomena associated with phase change, such as boiling where there is heat transfer in larger scales is very necessary. The boiling process based on its potential for transferring high amounts of heat at low temperatures is a very effective and common mechanism, and it occurs in many engineering systems, including boilers at plants, evaporators in refrigeration systems and nuclear reactors. Also, a considerable amount of research was done recently in the field of... 

With the advancement of technology, the volume of network traffic has also increased dramatically. The optical network, as the main part of the backbone communication system, plays a significant role in the transmission of network traffic. Due to the limited network resources, an efficient resource allocation in optical networks is required to increase network performance and reduce costs. To solve resource allocation optimization problems, an effective tool is needed to provide a suitable solution in a reasonable time. Resource allocation problems are usually developed on a graph, which is derived from network topology or other properties of the network. As a result, graph-based tools seem to... 

In this research we focus on study and fabrication of ZnO composite nanofibers by electrospinning method for photocatalytic application. The most important challenges in the field of photocatalyst are photocatalytic activity under the visible light and efficiency enhancement. ZnO is a wide band gap semiconductor and it is not active under the visible light. In Iran, we have more than 300 sunny days in a year. Therefore fabrication and application of photocatalytic material with activity under the sun light that contained 40% of visible light is so vital in our country. In the first part of this project, ZnO-CNT nanofibers were fabricated and carbon doped in the crystal lattice of the ZnO.... 

Internet and the market based on this new product and service has penetrated in all aspects of today’s modern life of human being. After invention of this market each day a new innovation revolutionized this market and industry. High speed internet based on ADSL technology was one of these innovations. The high-speed internet service has achieved a remarkable increase in penetration in recent years. In order to survive in this competitive market, companies should continue to improve their service performance. The high level of service performance is believed to be an effective way to improve customer satisfaction and loyalty. In recent years, the high-speed internet service, based on the... 

Decimal multiplication is a frequent operation with inherent complexity in implementation. Commercial and financial applications require their data to be precise while binary number system cannot ensure precision. Existing research works on parallel decimal multipliers have mainly focused on latency and area as two major factors to be improved. However, energy/power consumption is another prominent issue in today’s digital systems. Hence, in this thesis we present a comparative study of parallel decimal multipliers, considering energy/power consumption (leakage and dynamic power consumption), latency and area. Furthermore, we present two novel techniques to reduce energy/power consumption of... 

In this study some experiments were performed to investigate the effect of sweep angle on the transition location of laminar flow to turbulent flow. Three half wing models were used, each having a different sweep angle but with the same aspect ratio in various angles of attack. Two flat plates were used at the ends of the swept wing models to prevent the flow from rolling up over the wing. By simulating flow over infinity swept wing by eliminating tip vertices, the effect of sweep angle on flow transition phenomenon was investigated.
The experiments included the study of transition flow via hot-film sensors, which were glued on the wing surface. We found that the small leading-edge... 

In building construction, a rigid vertical diaphragm is capable of transferring lateral forces from exterior walls, roofs and floors to the ground foundation in a direction parallel to its planes.[1] Refractory elements against lateral forces contain moment frames, shear walls or a combination of them. In this research, shear walls are discussed. Nowadays, in cities having old contexture, some of the buildings should be destructed. Thus, modern buildings should be built. Due to the limitation of adequate space and lack of symmetrical plan, buildings must be built in asymmetrical form. To design the structures with asymmetrical plan, it is necessary to study buildings with presence of... 

Hydrogen bond is a type of molecular bond which occurs between hydrogen and a highly electronegative atom (usually F, N and O) and results in special properties.Alkyl phosphonic acids and their derivatives have several applications as pesticides, antibiotics and anti-viruses. Furthermore, some chemicals in human nervous system hydrolyze to alkyl phosphonates and finally to methyl phosphonic acid. Linear alkyl phosphonic acids and their saults have both organic nonpolar hydrophobic groups and inorganic hydrophilic groups and used as surfactants.Different substituents can affect the acidity of alkyl phosphonic acids. Investigation have shown that hydroxyl functional group can increase the... 

In this thesis, a shape optimization technique is presented for powder forming processes based on the genetic algorithm approach. The numerical modeling of powder compaction simulation is applied based on a large deformation formulation, powder plasticity behavior, and frictional contact algorithm. A Lagrangian finite element formulation is employed for large powder deformations. A cap plasticity model is used in numerical simulation of nonlinear powder behavior. The influence of powder-tool friction is simulated by the use of penalty approach in which a plasticity theory of friction is incorporated to model sliding resistance at the powder-tool interface. For hot compaction process coupled... 

Hydrogen bonding is an important weak interaction encountered in gas, liquid, as well as solid phases. The hydrogen bond plays a very vital role in many life processes and is one of the most frequently used terms in chemistry and biology.
Polyols or polyhydric alcohols are, strictly speaking, simply organic chemicals containing more than two hydroxyl groups. Each hydroxyl is attached to separate carbon atoms of an aliphatic skeleton.They may also contain ester, ether, amide, acrylic, metal, metalloid and other functionalities; along with hydroxyl groups. Polyols are obtained from many plant and animal sources and are synthesized by a variety of methods. Among important properties of... 

Refractory metals (W,Re,Ta,Mo,Nb) and their alloys can exhibit exceptional properties at elevated temperatures. However, refectory metals tend to be relatively heavy and, in some cases, can be relatively difficult to form in complex shapes at low cost. Light composites of refractory metals with high-melting ceramics, which can be fabricated into dense, near net shapes at low temperatures, would be particularly attractive for advanced aerospace applications. In this project, WC powders have been pressed and shaped to cylindrical preforms. Secondly, these performs have been sintered slightly(presintered) into porous, rigid ones with about 50% open porosity. Finally, in order to reach dense... 

Lightweight clients are a type of blockchain users who do not store all the blocks in the blockchain due to limited resources. These users store only a small part of each block and when needed, request transactions from full nodes that store the entire blockchain. These users have no role in block validation and only want to receive transactions related to their addresses with proof of the inclusion in the block from full nodes.Since light clients rely on full nodes for receiving transactions, their privacy against full nodes is important. The current implementation of Bitcoin uses Bloom filters for privacy, but this offers very little privacy to the users.In this thesis, we study the... 

Optical ¬memories are one of the most important elements in photonic integrated circuits (PCI). Usually these memories have been designed in type of inactive and were based on nonlinear optic effects such as saturation absorption and Kerr effect in Micro¬ ring resonator. Semiconductor Micro¬ ring laser is appropriate candidate for designing and constructing of optical memories. Bifurcation analysis indicates that semiconductor Micro ring laser coupled with waveguide in the presence of external optical feedback from end face of waveguide has two stable modes. Phase differences of clockwise and counter clockwise fields of these modes in the coupling point for one of them is zero (in phase... 

Growing demand on energy and limitation and consequence of fossil fuels have caused to utilize the clean and renewable energy sources. Hydrogen is a clean energy carrier which produced just water vapor during combustion. Today, methods which are usually used to produce this fuel are based on using fossil fuel compounds. Therefore, utilizing new production methods is unavoidable. One of these methods is using semiconductors such as TiO2 to spilt water and produce H2 by solar irradiation. Reducing the energy gap of these semiconductors to match the solar spectrum, specially in its visible range, modification of their structures, surfaces and stability are the main challenges in hydrogen...