Sharif Digital Repository

Microstructural characteristics and mechanical properties of a friction stir welded cast Aluminum Bronze (Cu–9Al–1Fe), produced through sand casting method, have been investigated in this study at tool rotation of 850–1500 rpm and traverse speed of 50–100mm/min. The study also describes results obtained from microstructure evolution (optical microscopy and Clemex image analysis software) and mechanical properties of Aluminum Bronze welds produced by FSW process. Refinement of the primary coarse cast microstructure and elimination of the defects in base metal due to porosity and casting was seen clearly after friction stir welding. Microstructure of the stir zone was divided into four... 

Since random access networks can work in distributed manner they have found variety of applications in wireless local area networks and wireless sensor networks. Throughput maximization and calculation of optimal parameters of such networks are subject of many research but most of these researches have ignored delay and suffer from high packet delay. We investigate and analyze delay in random access and solve the delay constrained utility maximization problem. We define network utility as a combination of throughput and cost of energy consumption and solve “access network optimization with link delay constraint”, and “cross layer optimization of transport and access layer with end to end... 

The importance of routers in information transfer among networks is critical. Thus, vulnerabilities and security deficiencies in routers and the related services like routing protocols can be destructive not only for some hosts, but also for the whole network. Hence, it is necessary that 1) vulnerabilities related to the routers and their services be evaluated and analyzed, and 2) the functional aspects of routers related to the vulnerabilities be formally modeled and analyzed. In this thesis, we present a method for the evaluation and the analysis of OSPF routing protocol from the security point of view. First, reported vulnerabilities on the OSPF are collected and evaluated by a... 

Nowadays, extensive use of Hardware Trojan Horses (HTH) or backdoors is more prevalent than ever. We could count disruption, disabling, eavesdropping and sending out internal information as misuse.
In this project, we embed hardware trojan in a Programmable Logic Controller, and present different methods to detect and neutralize them. This is an important issue, as PLCs should work in a safe environment especially in industrial environments while keeping the information intact is significant as even a slight intentional malfunction could cause data to be lost or disclosed, and result in a catastrophe. Subsequently, features of hardware of PLCs should be examined and the right place of... 

Recently, security of integrated circuits has received more attention as ICs have become more complex and their usage has increased in safety critical systems. Many orgeniaztions use the ICs that made by third party companies. This is due to the high costs to build and maintain state-of-the-art semiconductor factories. This subject puts the trustworthiness of the ICs under the question. The chips might be maliciously modified in each stage of the manufacturing chain. This threat is called hardware backdoor in scientific community. The aim of this project is to assess the features embedded in a microprocessor and evaluate the side channel effect of various hardware backdoors. hardware... 

Security Protocols are a set of protocols for the exchange of messages that both side of communication use in order to create the secure communication channel. Usually in such a case, both sides agree on one encrypted key. The purpose of these protocols is to obtain some features such as Authentication, Secrecy, Integrity, Non Repudiation, privacy and freshness. Freshness is one of the most important and vital features in communication protocols which is gained with Challenge and Response, timestamp and sequence number methods. Can interpret freshness as new and up-to-date. From the perspective of a participating agent in execute of protocol, a phrase take into account as fresh when it... 

A concern in the production sour oil and gas is the corrosion caused by the acid gas H2S. Even though corrosion resistant alloys (CRA) have long been available as a material selection option that mitigates H2S corrosion, the carbon steel is in general more cost-effective for oil and gas facilities. The aim of this study is to investigate the mechanical properties of 410NiMo cladding on a low alloy steel substrate. In this investigation, two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps, Post Weld Heat Treatment (PWHT) was used. To characterize the mechanical properties of... 

With the expansion of network equipment including routers and wireless modems, these equipment have become more susceptible to backdoors and hacker attacks. One way to cause troubles to these systems is through backdoor insertion. Recently, several attacks via backdoor insertions have been reported by some of the major router companies. In this project, a complete description of routers, ways of intrusion to routers and how to change settings in routers in order to measure traffic intensity are explained. In this thesis we manually setup a backdoor in a router in order to observe its effects on local networks. Furthermore, we purposely attack a router in order to find the followings: 1. Ways... 

There is a plethora of research and implementations that intend to increase the performance and reduce implementation costs of network routers. In this work, we review previous designs and propose a new network router design that is based on software-defined networks. Our design separates the data plane and the control plane from each other and connects both parts by using OpenFlow protocol. The control plane consists of a general small computer that utilizes the Quagga software to enforce the routing protocols. The control plane translates routing decisions to OpenFlow instructions and sends them to the data plane. The data plane is based on a switch that supports the OpenFlow protocol... 

Today's modern industrial control systems (ICS) and SCADA infrastructures, use industrial networks to communicate with the sensors and actuators installed in the field. In recent years the increase in use of standard protocols in this networks, and also the connection of industrial networks to the internet introduced new challenges in the area of industrial network security. The difference in the property, size, and requirements of this networks in comparison to legacy computer networks have made the legacy security solutions such as firewalls and IDS to not have enough efficiency. Some researches work on implementing new solution to meet the requirements of industrial networks in the area... 

The effect of alloying elements such as Chrome, Molybdenum and Chrome-Molybdenum on microstructure and mechanical properties of submerged-arc weld of structural St37 and 4135 Chromoly Steel was investigated. Addition of alloying elements was done through flux and slag-weld metal reactions. Bonded flux was used to achieve this purpose. Mechanical properties were studied by means of Longitudinal Tensile, Hardness and Charpy V-notch tests. Microstructure was studied by means of Optical and Scanning Electron Microscope. The results show that chromium increase Ultimate Tensile Strength (UTS) and impairs Impact Toughness (IT), although it increases the percentage of acicular ferrite (AF). In the... 

The rapid advancement of information technology and computer networks raised concerns of the users and network administrators regarding security. The development of computer networks and the increase in the number of specialists in this field led to the increase in the number of people who seek to abuse these networks, people known as attackers. The attackers look for security defects in a network to penetrate and abuse it proportionate to their needs. Considering the risks of these attacks, it is necessary to have an intrusion detection system (IDS). IDSs are capable of detecting attack traffic or suspected traffic, then, they alert the network administrators, and consequently, stop the... 

Network dynamics, environmental changes, increasing number of users and their demand have made it necessary to continuously evaluate and optimize the network performance. Self organizing networks (SON) were introduced to add this capability to cellular networks. Among the SON functions, Coverage and Capacity Optimization (CCO) and Load Balancing (LB) are the most important ones. These two functions working collaboratively allows the operator to improve the network performance in terms of coverage and capacity while minimizing cell saturation and user dissatisfaction across the network. In this Thesis, a Two-Stage Optimization Approach has been proposed that enables the network to consider... 

Nowadays, electrical energy is a necessity and the use of intelligent power equipment is expanding. Of course, having a protocol for communicating between such equipment is not only useful but sometimes mandatory. In the past, each equipment manufacturer used its own method for communication, hence, the "IEC 61850" standard was proposed as a solution to solve the problem of communication between different equipment. In this research, we intend to design a tester to perform a performance test with for GOOSE messages. These messages are based on the IEC 61850 data set and have the ability to quickly and securely distribute input and output values at the system level, which are transmitted by a... 

Quality of Experience (QoE) indicates the overall quality of one service such as Voice over IP (VoIP) from users' point of view by considering several systems, human, and contextual factors. QoE measurement and prediction are more challenging than Quality of Service (QoS) which is only related to network parameters. There exist various objective and subjective methods for QoE prediction. This research investigates various features affecting QoE by proposing a comprehensive subjective evaluation by employing a large number of users. We show that many unconsidered factors including speaker specifications and signal properties, such as signal-to-noise ratio (SNR), can affect QoE so that the SNR... 

The purpose of this study is to simulate a turbulent premixed flame with the help of the Laminar Flamelet Decomposition method. Numerical simulation is considered the main approach for studying this flame. A Bunsen-type premixed burner, which has a novel approach to making different levels of turbulence, has been used for modeling the premixed flame. To reduce the cost of numerical calculations, the Reynolds-averaged Navier-Stokes approach has been chosen for the CFD simulation. In this study, the Laminar Flamelet Decomposition model is the main combustion model for analyzing the turbulent premixed flame and with this method, the rate of reactions for all the reaction species will be... 

In this research, the strength and wear resistance of aluminum 5083 was improved by using composites with magnesium oxide nanoparticles (MgO-20nm) and friction stir processing. The effect of the number of process passes and rotational speed variables, considering the number of one, three, and five passes at rotational speeds of 700, 1000, 1300, 1600, and 1900 rpm, was investigated on the mechanical properties and wear behavior of the composite. To determine the appropriate weight percentage of MgO powder, the longitudinal tensile strength of three composites with different weight percentages of 3, 4.7, and 6 were compared. The linear movement speed of the tool was selected as a constant... 

Oil and gas upstream, is one of the major parts of the energy chain in the world. Processes of production, transportation, processing and conversion of energy carriers are the main parts of this sector. Process units of oil and gas upstream industry are some of most local and global pollution resources in the world. In this research, the consideration of the pollutions from the production, processing and conversion of fossil fuels sector and the optimization of the management choices of each pollutant is subjected. Consideration of the pollutants related to the upstream sector, pollution control and management choices, cost accounting of the environmental impacts, the methods of accounting... 

Globally, bicycle sharing is one of the fast-growing solutions to climate change in the transport sector. However, what inequities may be reflected, exacerbated, or arose from its adoption and use? Relying on a qualitative research design involving interviews with bicycle sharing users, non-adopters, and daily observers of the cycling infrastructure (N = 36), site visits, and a literature review, we examine distributive, procedural, and recognition injustices in association with Bdood, an operating BSS in Iran, a developing country that allows for less-documented types of injustice to arise. In doing so, we utilize a comprehensive transport/mobility justice framework, drawn from the fields...