Sharif Digital Repository

As it is known, one of the dangerous consequences of the earthquake is the possibility of fire. In recent years in our country special attention have been paid to design and retrofit buildings against earthquakes, but have not done to understand the behavior and design concepts of structures against fire. One of the reasons is the lack of information and the absence of a specific standard for design of structures against fire. Since the beam-to-column connections play an important role in the performance of structures, in this study, the behavior of the moment frame with flush end plate was investigated by testing on a small scale structural model (half scale). It is observed that, the test... 

In this study, the stability and vibrations of the rotor with initial bow and crack were investigated. Using a model developed to calculate the Euler-Bernoulli rotor motion equations with four degrees of freedom at each node, the occurrence of transverse cracks, their breathing, and initial bow, and the effect of these defects on the stability and response of the system were investigated. The occurrence of transverse cracks in rotating systems can threaten their performance and health and affect the stability and vibrations of the system. Initial bow caused by loading can lead to unwanted vibrations or serious failures. These defects are often caused by material, manufacturing, or assembly... 

This work numerically simulates pressure drop and heat transfer for flow in a pipe with porous wall. Incompressible two dimensional, ax symmetric laminar or turbulence flow with constant mass flow rate is considered. It is assumed that there is no thermal equilibrium in the porous media region between solid and fluid phase. Effect of porous wall thickness and Darcy number on the rate of heat transfer and pressure drop were investigated. The Darcy number varies from to and porous wall thickness can fill entire pipe. the turbulent model is used to calculate the fluid flow and heat transfer characteristics in turbulent flow. Nusselt number can enhance about ... 

Performance of reinforced concrete frames is highly dependent on detailing of the joint connections between its members, such as beams and columns. To have a good structural behavior, joints must show ductile behavior and designed based on the philosophy of strong column-weak beam. In the case of sever lacking ductility, strength or even rigidity of the connections, or having a weak column-strong beam, in the existing structures, there is a need for seismic upgrading of the connection. There are several ways for seismic upgrading of this type of connections.In this research, using steel plates for seismic upgrading of Concrete Beam-Column connections subjected to axial and cyclic loads has... 

Nowadays, using of microwave integrated circuits in military and industry applications has been became popular, especially with the advent of monolithic microwave integrated circuits which provide possibility of fabrication of amplifiers in large volume with high precision and appropriate cost. Power amplifiers as the last block of transmitters, are such circuits that are too attractive in this area. Since high power amplifiers consume a lot of power in transistors, large amount of heat will be in the surface of chip. Loss of some of consumed power in amplifiers results increasing transistor’s channel and chip surface temperature. Increase in channel temperature results degradation in... 

A droplet placed on the boundary of two solids with different wettabilities will move to the more wettable part. This is a well-known phenomenon and has been extensively used in a variety of processes and applications ranging from biological systems and ink jet printing to the commercial lab-on-a-chip. Because of its importance, many studies are conducted around this phenomenon. The difference between the equilibrium contact angles of the droplet on the two parts gives rise to an interfacial driving force which moves the droplet. Such a motion is not continuous as the droplet slides to the more wettable area, the driving force diminishes and consequently the droplet stops. A non-stop motion... 

Although unsaturated soils exist all around the world, civil engineers are not familiar with unsaturated soil behavior; consequently, the soil structures they design may neither be safe nor economical. Thus, implementing unsaturated soil constitutive models to practical computer softwares can be very beneficial for geotechnical engineers. Geotechnical engineering softwares normally consider soil in saturated or dry conditions. So, their built-in constitutive models do not usually consider unsaturated soils. In this study, Barcelona Basic Model (BBM), which is developed using critical states soils mechanics principles, is implemented to the FLAC2D software. This model can simulate complex... 

Lifetime extension would be a necessary preventive action to halt micro cracks expansion on the airplane external surface. To decide about whether to perform this operation, one should examine technological maturity, costs and technical parameters. Technical status in lifetime extension is one of the major drivers of this decision which should be considered in the first step of technology management process which is known as the technology attractiveness step. In this research, major technologies of rejuvenation is examined and categorized by the technology mapping. Also, key processes of rejuvenation and technological fields ranking has been determined by the procedural view tools of the... 

Magnesia-doloma refractories are alkaline products made by combining sintered or fused dolomite and magnesite. These refractories contain 50-80 wt% magnesium and a higher percentage of magnesium oxide, provides desirable properties such as improved refractoriness and resistance to air moisture absorption. Magnesia-doloma refractories have significant weaknesses, including rapid hydration due to the presence of CaO and MgO phases. These refractories are also primarily used with carbon additives in the industry, where increasing the carbon weight percentage in these refractories weakens their strength and some of mechanical properties. In the present study, the effect of adding carbon... 

Centrifugal compressors have wide applications in the turbochargers, aircraft propulsion and petrochemical industry. Therefore it is important to design high efficiency centrifugal compressor. Knowledge of compressor performance at different conditions, energy losses and the contribution of each component of compressor in efficiency losses have of great importance.
In this research, different loss models of the centrifugal compressor were reviewed and investigated. Then 1D codes were developed based on the loss models, and performance characteristics of S2B Schweitzer and GT4082 Garret compressors at different conditions were achieved. In order to evaluate the modeling results,... 

Nowadays, video on demand causes a drastic increase in network traffic that it is expected that network traffic surpasses 45 exabytes per month until 2022; consequently, utilizing distributed memories known as caches across the network to alleviate the communication load during peak hours is inevitable. Coded caching is a promising approach to mitigate and smooth traffic during peak hours in the communication network in a way that it creates coded multicasting opportunities in addition to delivering content to users locally. However, it suffers from imposed delay resulting from coding that makes this approach infeasible for delay-sensitive contents, namely video streaming applications. So... 

In the era of the internet and with the emergence of online stores, the possibility of changing prices for these e-commerce platforms has become simple and virtually cost-free. This allows them to adjust prices optimally in response to environmental and surrounding factors, maximizing their revenue from product sales. This development has led to numerous applications of statistical learning methods, particularly online learning, in these markets. In this thesis, we explore the issue of online pricing from various perspectives. One aspect is that product pricing is based on their features, which can be numerous. This leads us to the use of online learning methods and statistical learning in... 

Today, with the development of micro-technology in chemical reactions, the use of appropriate systems for the separation and purification of synthesized chemicals seems to be necessary. In this study, the continuous synthesis of bromide-lithium exchange reaction and the separation of organic and aqueous phase products in micro systems was investigated.The method used to construct micro-separator and micro reactor, a laser engraving technique, and thermal bonding of glass to glass.In the first step, the factors affecting the separation of organic and aqueous phase in the capillary micro-separator, such as the width of the capillary, the length of the capillary, the number of capillaries and... 

Today, the world energy crisis, the need to optimize its consumption and discussion to reduce fuel consumption has become a vital issue. The conventional vehicle air conditioning system due to compressor in refrigeration cycle, which has causes a severe loss in engine useful power, increasing fuel consumption, etc. Therefore, the main goal of this project is the feasibility of the vehicle cooler replacement with the vapor jet refrigeration cycle. In this cycle, the energy required for completing the refrigeration cycle is provided from the heat of the water inside the radiator that is possible with conventional refrigeration cycle. The first stage of this project includes design and... 

The electric field induced response of a charged droplet in an uncharged gel is calculated theoretically. For modeling, the gel is considered as a soft porous solid that is saturated with a Newtonian electrolyte and modeled as a continuum that contains 3 phases: a porous, soft and compressible solid, an incompressible Newtonian fluid and the ions inside fluid. Droplet is modeled as a charged incompressible Newtonian fluid immiscible with the gel. The droplet-gel interface is considered as a surface with electrostatic potential ζ . After obtaining governing equations, they solved by using perturbation methodology and linear superposition. Boundary conditions, especially at the droplet-gel... 

Nanoparticles can be applied as chemical agent in enhnaced oil recovery like surfactants and polymers. One of nanoparticles usefull capabilities is modification of their surface. This research investigates this capabilty of nanoparticles in enhanced oil recovery. Surface modification of nanoparticles with both agents can bring new abilities to these materials. Here surface of silica nanoparticles is modified by hydrophilic agent comprising PEG groups, hydrophobic agent comprising propyl group and both agents. FT-IR tests showed that grafting of modifiyng agents on surface of nanoparticles is well done. To investigate effect of nanoparticles surface modification on nanoparticles capability in... 

Important features of the nanoparticles properties are their high superficial area and being able to reform their surface. In this study, the repairable property used to reform surface of silica nanoparticles (Those are used more frequently than other nanoparticles). Repairing of surface are doing to use nanoparticles as a surface-active material in enhanced oil recovery. Silane compounds with different chain length are used to create hydrophobic nanoparticles and PEG compounds are used to create hydrophilic nanoparticles. Also amphiphilic nanoparticles are created with a combination of both hydrophilic and hydrophobic compounds. To investigate the usefulness of nanofluids are made up of the... 

The main purposes of this project are simulation, design, and fabrication of a microfluidic system based on dielectrophoresis (DEP) exploiting AC voltages for separation of microparticles. Generally, this project can be divided into two parts. First, the engineering section including design and fabrication of microchip, and second biological samples preparation for investigating the system performance. The main advantages of proposed system are eliminating joule heating, a significant problem in insulating based dielectrophoresis systems, overcoming problems related to metal contamination in biological samples, the main problem of conventional dielectrophoresis platforms, and removing... 

Production of nanocrystalline (under 100nm) or submicron materials (100-1000nm), has been created to one of the most important problems in engineering. A well-known method to create Ultra-Fined Grains (UFG) is imposing high strains to metals in order to break the structure. Among lots of ways forproducing UFG metals, Equal Channel Angular Pressing (ECAP) is one of the most famous and common ways. On the other hand, Shot Peening has been being used for a long time to improve mechanical properties of metals by introducing nanocrystalline layer at the surface of specimen. The aim of the work, is investigation of the effect of combination of ECAP and Shot Peening on High Cycle Fatigue of 6082... 

In some activities, an almost free of any vibration environment is needed. Semi conductor production process and microelectronic microscopes are two examples in which a quiet environment is essential. The goal of this thesis is to attenuate ambient vibrations effectively and to prepare a suitable environment for two microelectronic microscopes. The designed system must be practical, economical and capable of being made in a short time interval. Considering mentioned properties a steel table with bolt connections supported on 4 air springs was built. To investigate dynamic properties, modal analysis was performed with the aid of finite element packages and experiments. To extract oscillations...