Sharif Digital Repository

In the present study, Friction Stir Process (FSP) was used to refine the microstructure of pure commercial copper in order to improve the mechanical properties. Since FSP can be considered as a hot deformation process, theoretical Models were utilized to simulate both thermal history and strain rate distribution. Zener-Hollomon parameter (Z) was then utilized to predict the microstructure of Stir Zone (SZ) which undergoes the Dynamic Recrystallization (DRX). Temperature distribution was formulated and solved by a commercial software COMSOL Multiphysics. Strain rate was analyzed using theoretical models and the codes were written by MATLAB. The predicted grain size was not in a good agreement... 

Resiliency is, now, recognized as a vital characteristics of every urban transportation network. This is so, because transportation network is considered as a life-line in disastrous events, such as major earthquakes. In this respect, design of networks may be considered (1) before the incident, (2) after the incident for 72 hours, and (3) from this 72 hours on. From the point of view of (1), design of the network may be considered as strengthening important links under budget constraints to withstand the design incident, in order to be able to function properly (to help the affected people, to evacuate the populated area, etc.).Design of network based on the point of view of (2), the one... 

In this project, Dissimilar Friction Stir Welding (FSW) between aluminum alloys (1100-H12 and 5083-O) and Magnesium alloy (AZ31B-O) with 3mm thickness were butt joined. Fusion welding of aluminum/magnesium alloys has failed because of forming much more intermetallic compounds. By using friction stir welded samples, effect of welding parameters such as tool travel speed, tool rotation rate, tool position respect to weld centerline, and sheet position respect to tool direction on mechanical (tensile strength, yield strength and elongation) and microstructural properties of the welds were investigated. After several tests, range of optimum parameters were obtained. In both 1100 and 5083 alloys,... 

This study develops a new framework for the assessment of land subsidence occurrence rate. The proposed framework considers the combined effects of saturated and unsaturated soil behavior. Accordingly, the biot consolidation theory was used for investigating subsidence in the saturated zone while the soil shrinkage curve, i.e., the void ratio-suction curve, was used in the determination of unsaturated zone subsidence. Specifically, groundwater decline and land climate change were used as the main contributing factor in investigating the land subsidence in the saturated and unsaturated zone, respectively. The approach presented in this study is based on using numerical modeling in PLAXIS 2D... 

Transferred Electron Device is a semiconductor device being capable of generating oscillation in microwave frequencies. Applying a bias voltage to the device and putting it in a resonant circuit, a periodic waveform in the output current is observed. The cause of the generation of oscillation in the device is related to the characteristics of velocity-field in the device. In some part of the characteristics, it is observed that increasing the field inside the device causes the velocity of electrons to be reduced. This causes the generation of the negative conductance and the oscillation of the output current under some conditions. The purpose of this thesis is to represent an equivalent... 

Domain shift is an inevitable issue when histopathological images are analyzed in a standard laboratory. This is due to the variations in tissue handling, manual procedures for sample preparation, and differences in scanners. This can result in reduced performance of machine learning algorithms trained on images from one laboratory when applied to another. In this framework, the goal of utilizing domain generalization techniques in machine learning is to develop models that perform well in different domains. This research examines various methods of dealing with the domain shift challenges within the context of detecting mitotic cells, and proposes algorithms to improve domain generalization... 

The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel... 

Aluminum Bronzes have many applications in marine environments. These alloys suffer from both hot cracking and cold cracking. In order to overcome the hot cracking and cold cracking, Semisolid Stir Joining method and a proper thermal cycle was used respectively. Effects of temperature, stirring rate, and tool type were investigated in Semisolid Stir joining method. In this method, butt joint design was used in order to place specimens, and the specimens were heated up to specific temperatures (920, 925, 930°C). A stirrer (Cylindrical and Grooved tool) with three rotational speeds (800, 1200, 1600 RPM) was introduced into the stir weld seam. Welded specimens were cooled to the 900°C... 

Nowadays, one of the problems of network designers and users is the correctness of network equipment functionality. Since routers play an important role in information transfer between various networks and communicate with each other through a routing protocol, any violation of such protocol can result in the network's failure or defective transfer of data. Thus, being assured of the conformance of the implemented protocol in a router with what has been defined in the protocol's standard is of great significance. To this end, before using or exposing a router, network equipment testers should run protocol conformance tests on it and insure its correct functionality. This brings up the... 

In order to increase the network performance, to discover network security threats, to guarantee the quality of services, to simulate networks and develop new network protocols, network designers and operators need software tools to analyze the network traffic. The first step to do this analysis is network monitoring. This can be done by using various software and hardware tools.
In this research we developed a tool which analyzes the network traffic using appropriate statistical methods. The models which are analyzed in this application are: Poisson, Self-similar and Weibull. This application analyzes the network traffic based on this statistical models and calculates their parameters.... 

The increasing number of road accidents and fatalities have yielded the introduction of several solutions by related industries such as automobile manufacture. Proposed solutions can be classified into two categories: passive, such as airbags, and active such as ABS ad ITS-based technologies. Inter vehicles communication let the communication between vehicles(V2V) or between vehicles and road infrastructure (V2I) by relying on DSRC technology and standards. Intelligent Transportation System (ITS) has three main types of applications namely safety, traffic and commercial. Safety applications are the main goal of vehicular communication, and real time guarantee in safety applications is so... 

In real-time systems, jobs that miss their deadline are considered worthless or ineffective. Nowadays, real-time applications (such as multimedia) that communicate through software-defined networks (SDN) are widely used and will continue to expand in the future. SDN is an emerging network architecture in which control plane is separated from data plane to manage it directly. In this research, we make changes to the controller and the switch used in such network to deliver real time packets or real-time flows (such as video) on time, as much as possible. As missed deadline packets are worthless and they waste bandwidth, dropping them is a solution. Moreover, the controller can drop flows that... 

Network Function Virtualization (NFV) is a new paradigm in computer networks for implementing network functions on general-purpose common-of-the-shelf processors. The revolutionized NFV architecture has shown to be a suitable replacement for hardware middleboxes. NFV is in high demand because of its lower costs, increased flexibility, and more scalability. However, the ever-growing volume of network traffic and increased data transfer speed in computer networks have made achieving high performance the major issue in this area. With thousands of processing cores and high memory bandwidth, Graphical Processing Units (GPUs) are potentially an appropriate solution to accelerate network... 

Today, with the increasing expansion and development of computer networks and information technology, network security has become an important concern for experts and researchers in this field. One of the main elements in the field of information and network security are intrusion detection systems. To maintain the accuracy and quality of these systems, we need to test and evaluate them frequently. The datasets of intrusion detection systems are one of the main tools for evaluating these systems. The quality and accuracy of these systems in detecting anomalies and attacks in the network largely rely on rich and complete data. Also, the main component of this datasets is the traffic data,... 

Nowadays, power systems and substations are the most important components of the vital infrastructure of a country, which handle the production, transmission and distribution of the electrical energy. Automation systems increase the efficiency of the power industry while making remote control possible, but the use of computer-based control systems is a potential field for cyberattacks which may cause equipment destruction and electricity network destabilization. One of the main requirements for the utilization of digital substations is the synchronization between different equipment used in it. Several algorithms and protocols have been proposed so far for time synchronization in distributed...