Sharif Digital Repository

Providing high bandwidth network infrastructures for ever increasing need of data transport is of great importance. The underling infrastructure for many communication services such as GSM/3G/4G mobile networks and Internet services is Synchronous Digital Hierarchy (SDH) optical transport systems. SDH are standardized protocols that multiplex multiple lower rate digital bit streams, such as E1 and Ethernet, and transfer them synchronously over optical fiber using lasers or LEDs. In addition to high data transfer rates, flexible network management and protection mechanisms have great importance, hence are part of SDH standards. In order to obtain flexible network architecture and protected... 

Development of Smart Grid and deployment of smart meters in large scale has raised a lot of concerns regarding customers’ privacy. Consequently, several schemes have been proposed to overcome the above mentioned issue. These schemes mainly rely on data aggregation as a method of protecting users’ privacy from the grid operators. However, the main problem with most of these schemes is the fact that they require a large amount of processing power at the meter side. This, together with the fact that smart meters don’t usually have a powerful processor, can cause the unavailability of smart meter data at the required time for operators of the grid, and at the same time disables smart meters from... 

A liquid crystal is a state of matter composed of highly anisotropic building blocks. When liquid crystals are exposed to surfaces with given shapes and anchoring conditions, the orientation of their molecules gets spatially disordered and topological defects may form in the system. The interplay between liquid crystals and the geometry and topology of the colloidal particles has motivated extensive recent studies.In this thesis, we present the numerical modeling results for two faceted colloidal particles in a thermotropic nematic liquid crystal. To obtain the equilibrium nematic field with a finiteelement method, we numerically minimize the free energy of the system that based on the... 

With the fast-growing mobile networks, the need for network reliability increases. Various events like antenna failures, attacks on mobile networks, floods, sporting events cause abnormal behavior in mobile networks. Some events like antenna failures and attacks need consideration. But some of them like sporting events can be ignored. Right now, most mobile operators, detect these events manually which is a very time-consuming and costly task for them. To overcome this problem one idea is to predict future data by prediction algorithms. Then compare new data with the predicted one. If there exists significant deviation, there is an anomaly. But most of the failures and anomalies in mobile... 

Dynamic spectrum access with the aid of cognitive radio (CR) technology is a viable solution to spectrum scarcity. There are many military and emergency applications that require the use of cognitive radio ad-hoc networks (CRAHNs). In these net- works, nodes must first find each other in a wide spectrum and then exchange their desired data. The process of finding each other in a multichannel environment is a challenging task and is usually known as rendezvous. Since rendezvous is the first step in communication, disrupting will disable the nodes from establishing proper communication sessions. That results in a drastic degrade in the performance of the network. Therefore, it is important to... 

Spray-wall impingement is one of the phenomenon that associated in different subject such as spray cooling, combustion chamber and gas turbine. With the impingement of spray to the wall, liquid film begins to form. Wall film characteristics is still an important subject to study. Due to the various stages of liquid film formation from injection of spray till spray-wall impingement, the investigation of this phenomenon is far more complicated. This paper is meant to provide detailed data on spray-wall impingement and wall film formation physics with the help of computational analysis of OpenFOAM . A Lagrangian-Eulerian method based on discrete phase model (DPM) was employed to model... 

The seismic performance of a low-rise nonductile reinforced concrete (RC) building rehabilitated using eccentric steel bracing is investigated. At first three-story building was Modeled using sap 2000 computer program then analyzed and getting the results. The effectiveness of the eccentric steel bracing in rehabilitating the building was examined. The effect of distributing the steel bracing over the height of the RC frame on the seismic performance of the rehabilitated building was studied. The behavior of the nonductile RC frame members is represented by a beam–column element capable of modeling the strength deterioration and the effect of the axial force on the yield moment and the... 

The fiber reinforced polymers (FRP) are widely used for strengthening and rehabilitation of concrete and steel structures. One of the serious collapse mechanisms of the Carbon Fiber Reinforced Polymer (CFRP) strengthened steel beam is due to debonding of the CFRP laminates in the vicinity of high stress concentration regions, such as, at the ends of the laminates. There are several analytical solutions for stress analysis of this effect. Nevertheless, most of these methods are applicable only in the elastic range. In this thesis a simple and efficient analysis modeling will be proposed and investigated for reasonable predicting of the debonding effect. The simplified analytical result will... 

In the 1994 Northridge earthquake, connections in the resistant steel moment frames sustained unexpected brittle fractures in the beam to column connection region. One of the strategies to decrease the vulnerability of connections is reducing the beam section in a region, near the column face. Because to reach the plastic hinge in this region and decrease deformation in other region, like beam end, panel zone and columns. Reducing in beam section is caused some differences in seismic performance of steel frame. Although extensive numerical and experimental studies have conducted on this type of connection but limited studies have performed on the moment frame with reduced beam section... 

Today using cold-formed steel elements as members of light-weight structures is more common especially in low-rise residential and industrial buildings. Due to Thin-walled plates used to make these sections, members of the frame are prone to premature local buckling and they don’t show good ductility under seismic loadings. Beacause of these reasons, using cold-formed steel elements in moment frames has become a big challenge for scientists. Lots of numerical and experimental models have been presented.
In this study, we investigated the behavior of a beam-column moment connection, consists of two back to back channel sections with curved flanges, using a plate passing through the... 

Tumor markers are substances that are naturally found in blood and other fluids in body, but in abnormal conditions such as cancer and metastasis, their level increase. The aim of researching about tumor markers is to find a way for discovering cancer only with a blood test and replace with the current methods such as ELISA, and any type of cancer can be detected by these tests. In this study, molecular imprinted polymers were synthesized with biomolecules. To do that, silica microparticles were used as solid base and after functionalizing their surface, a thin film of polymer was synthesized on them. To optimize the components concentrations and the polymer thickness on the silica surface,... 

Composite systems consisting of concrete columns and steel beams are introduces as structural systems in recent years. These structural systems enjoy merits of both steel and concrete frames by efficiently combining the advantages of them. This study is allocated to lateral force resistance system using armed concrete and structural steel. Advantages of composite structures rather to those of two other conventional ones are among performance characteristics under ultimate loads, economical conservation, and higher speed of construction.In this research the aim is to study these frame under earthquake induced loads. The seismic performances of these composite frames with through column beams,... 

Although many aspects of helical strand have been carried out, there are still some situations which need more studies. Based on previous studies of wire rope the constitutive equations regarding the rope tension and torque to the rope deformations are carried out. In which constitutive constants depend on both the rope material and geometry of the rope. Equations of motion for straghit rope loaded simultaneously in tension and torque are derived, and with using extensional-torsional deformations in both side of the rope, dynamic stiffness matrix is derived. Some experimental results and currently models are compared with my research model numerically. Finally, mechanic response of helically... 

Recent earthquakes indicate the importance of retrofitting existing structures to achieve an acceptable level of performance. Use of bracing systems is a cost-effective method for seismic retrofitting of existing steel frames. In particular, Buckling Restrained Braces (BRBs) and Special Concentrically Bracing systems (SCB) are practical choices to be used because of their large energy dissipation capacity especially under moderate to severe earthquakes. Buckling restrained braces which yield in both tension and compression, exhibits stable and predictable hysteretic behavior. In this study several existing steel frames, which are designed based on older versions of the building codes, have... 

Passive energy dissipation systems are mechanical devices which could spread input energy, reduce response and decrease possible damage of the structure. Dampers were identified as a strong energy dissipation devices with cost efficiency and easy installation and maintanance. In this study, effects of using friction and metallic yield dampers to reduce structural responses are investigated. In addition, a comparison between these devices for reducing responses are conducted. Two 5 and 10 stories buildings with intermediate steel moment frames with and without damper are modeled and designed. It is seen, using of dampers could be reduce sections’ sizes. Seven pairs of earthquake records... 

Optimization and uncertainty are two main issues in the structure design. In engineering problems and specially the structure, loads are among those issues witch we cannot be commented definitively. The uncertainty also shows itself in material properties and structural shapes. Design optimization is inevitable in order to use resources effectively. In the past, structural design was based on experience and engineering judgment, which was conservative and sometimes structure weight was very high. But today, thanks to computers, high-volume calculations would not be out of reach. With considering uncertainty, we can have prosper sight toward constraints by maintaining proper distance from... 

Among different natural disasters, earthquake has always been known as one of the most effective ones on human lives, and this is only because we still cannot predict the exact time and place of its happening. So, giving special attention to the methods which can omit or minimize the damages of this natural event is needed for controlling the loss in the event of an earthquake. On the other hand schools are known as places which are full of people from younger ages for at least half of each day, and they are considered to be not well educated about how to react in an earthquake in comparison to older people and also considered vulnerable at the time of this natural event. According to what...