Sharif Digital Repository

Due to the increasing concentration of greenhouse gases in the earth's atmosphere and their destructive consequences, many scientists and researchers have turned to preventing the emission of greenhouse gases, such as carbon dioxide. One of the primary sources of carbon dioxide emissions is flue gases. Carbon dioxide is one of the most important greenhouse gases, the release of which causes global temperature increase and climate change. One of the options for reducing carbon dioxide emissions from gas streams is using reactive amine solvents, considered the most critical technologies for carbon dioxide removal. The only commercially available carbon dioxide separation method is absorption... 

Electrodeposion of Zn-Ni Alloy Nanometer Multilayer has been studied. The investigations show that Multilayer coatings have more corrosion resistance than a Monolayer. The electrodeposition of the multilayer coatings was performed with the single bath technique. The sulfate-borate bath has been used for electrodeposition of the Multilayer coatings. The switching cathode density current has been used for the multilayer coatings in cathode current densities of 20, 30, 40, and 50 mA.cm-2. The number of layers with constant overall thickness of 2 µm was 20, 40, 80, and 100. The composition of layers varied between 5-11% wt Ni with the values of cathode current densities. The Response Surface... 

Content delivery networks play a significant role in improving the quality of internet services by placing the necessary content closer to users on servers. Currently, over half of internet traffic is delivered through these networks to end users. The efficiency of a content delivery network depends on various parameters, including the type of requested content, workload distribution methods, network topology, routing algorithms, caching policies, network server configurations, and resource allocation (shared or dedicated hardware resources). Additionally, the requests made to a content delivery network vary based on the type of service and even the time of day, making optimization a... 

Thrust vector control as a method toward increasing of the aircrafts’ maneuverability and expanding the flight envelope into poor aerodynamic conditions, is considered a major field of academic and industrial appeal. Older methods based upon an approach of utilizing a mechanical instrument, impose quite a large amount of cost onto the design, prototyping and operation of the aircraft, even though they lead to improve in maneuverability. Having taken these setbacks into account, to simplify the manufacturing process and to reduce the thrust losses due to mechanical control of the thrust vector, the direction of research was set toward realizing and employing the flow control procedures. In... 

One of the most important problems of quantum information theory is to try to determine the channel capacity of noisy quantum channels. Alice would like to send Bob information over many uses of a noisy quantum communication link. As the line is usually noisy, this cannot be done perfectly, and so they must use suitable coding methods to minimize the error. Different coding methods yield different rates of information transition and different errors, the channel capacity is defined as the maximum rate at which information may be transferred with vanishing error in the limit of a large number of channel uses. There are a variety of different capacities, depending upon whether Alice and Bob... 

In the present work storage of hydrogen molecules in hybrid nanostructures has been evaluated. Hybrid nanostructures consist of carbon structure bases which have been doped by metal atoms. Carbon structures used in this thesis include graphene and metal organic frameworks (MOFs). Carbon structures have superior properties such as very low density, while metal atoms are considered to enhance the interactions and increase the hydrogen storage capacity. In the first step of the work, Monte Carlo method was applied to model the system. To develop the Monte Carlo method for hydrogen adsorption on graphene sheets, Feynman-Hibbs corrections were added to Lennard-Jones potential. However in the next... 

In a typical rigid robot manipulator, joint angels and velocities are often considered as system states. Joint angels are usually measured by precise Shaft Encoders. However, lack of velocity measurement sensors “Tachometers” and their undesired characteristics in most of existing robotic systems make it difficult to have access to full system states. As full access to the system states in various applications is inevitable, velocity observers can be used to reconstruct or estimate the unmeasured velocity signals. This thesis presents an observer for global estimation of joint velocities in robot manipulators. A non-minimal model of a robotic manipulator is introduced to design an... 

Considering the high growth potential of creative industry as well as the increasing trend of e-business, content-oriented digital business has been the main focus of this research. These enterprises are a subset of the creative industry that are primarily developed in the digital context. After reviewing the literature, it was observed that the keyword "value creation" in this type of business has been less considered by research.On the other hand, in conversations with managers who are active in the industry, a practical vacuum was revealed on how to create value in these firms; Because a comprehensive review of value creation processes in these firms can ultimately lead to more profitable... 

Functionally graded porous structures are very close to the bone tissue. Parameters that are related to the pore size and other parameters that determine mechanical properties, can closely represent properties of bone tissue. These parameters contain the percentage of the porosity and the pore size on the porosity side, and modulus of elasticity and yield stress from mechanical view. Calibrated structures with complex geometries, containing porous material, also can be produced by 3D printing technology. One application of porous structures is in production of dental implant with a cylindrical shape, containing a dense core, surrounded by a porous region. The aim of the present study is to... 

Composite quantum systems are generally correlated and these correlations may have classical or quantum nature. Entanglement is only a special type of quantum correlations and separable states may be quantum correlated. Quantum discord, local quantum uncertainty and the rank of the correlation matrix are the most important measures of quantum correlations beyond entanglement. Regarding the various applications of discordant separable states in the field of quantum information, the important problem is how to produce discordant separable states and what is the resource which should be used for this preparation. In this thesis we present a method of preparation for such states in two qubit... 

In this study, thermal and rheological properties of nanofluids of water/carbon nanotubes, water/spherical silica nanoparticles and water/hybrid nanoparticles (hybrid of carbon nanotubes and spherical silica nanoparticles) have been investigated. To do so, carbon nanotubes have been synthesized by CCVD process and spherical silica nanoparticles and hybrid nanoparticles by wet chemical method. After synthesis of nanomaterials, nanofluids have been prepared by using SDBS as a dispersant with the concentration of 1.5 times of concentration of nanomaterials and then thermal conductivity, kinematic viscosity, dynamic viscosity and density of nanofluids have been investigated. As the results show,...