Sharif Digital Repository

Domino accidents are those which are initiated from one equipment and extend to neighbor equipments or units and as a result the consequence of the primary accident is increased. Risk management is one of the tools for reducing risk of accidents and Quantitative Risk Analysis is a crucial stage in risk management. Despite the importance and severity of domino accidents, in most of QRA studies the effect of these accidents on risk is not considered. In the present work tools for Quantitative Risk Analysis with considering domino accidents has been developed. Two major methods for this reason are used; analytical method and simulation. First, software based on analytical method was developed... 

The aim of this study is to evaluate post-earthquake travel behavior in Tehran. After a horrible disaster, like earthquake, people’s travel behavior may change substantially in comparison with normal condition. If people’s travel behavior can be predicted after an earthquake, then authorities can manage travels for emergency medical services in a more efficient way, so the casualties are profoundly diminished. To collect a formation, a questionnaire about socio-economic characteristics of people and their post-earthquake travel behavior was designed. According to the obtained results, time of occurrence and severity of the earthquake are of the utmost importance. So if the earthquake occurs... 

Metal matrix composites (MMCs) reinforced with ceramic particulates have been attractive as high specific strength materials utilized in automobile and aerospace industries. In order to enhance refinement and dispersibility of the ceramic particulates, the synthesis process with in-situ reactions has been investigated. The in-situ synthesis can avoid complexity and harmfulness.processes of powder handling and produce fine inclusions in the matrix with rather lower costs than conventional fabrication methods. In this study, the Al-based composites with TiC, TiB2 and Al2O3 particulates have been prepared by the by mechanically activated self-propagating high-temperature synthesis (MASHS) on... 

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... 

Modification by crumb rubber is a useful means of improving the resistance of asphalt binders and mixtures against rutting, fatigue cracking, and low temperature cracking. Increase binder viscosity and decrease stability at high temperatures are accompanied by most modifiers, and crumb rubber is no exception. Recent research efforts have shown that development of cross bonds across polymer chains and sulfur can improve the storage stability of modified binders. Also, WMA additives can considerably decrease the binder viscosity. This research showed that addition of small amount of sulfur during the crumb rubber modification can improve the workability and storage stability of this binder.... 

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... 

Recently, there has been a great interest toward site–specific modeling of outdoor radio wave propagation. Wave propagation in very large environments compared to a wavelength builds up an important category of electromagnetic wave propagation problems which occurs in
versatile criteria from optical devices to long wireless microwave links. Well-known methods such as different ray tracing schemes used in these problems suffer from long execution time and great amount of needed memory. A new method has been proposed in this thesis to overcome such difficulties for high frequency wave propagation in large scale problems. The proposed method is based on tracing 3D vectorial Gaussian beam.... 

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... 

Heat transfer enhancement in heat transfer equipment, such as heat exchangers, has been widely studied. There are plenty of techniques to increase heat transfer in tubular heat exchangers. One of these techniques is applying a porous medium. These media have a great interface with fluids which can enhance the heat transfer rate. Meanwhile, the thermal conductivity of these media is usually greater than that of the studied fluid. Thus, by adding a kind of highly conductive porous insert to a heat exchanger, we are able to save the material used to construct the device and the space occupied by it.
Shell-and-tube heat exchangers are one of the most widely-used types of exchangers in... 

The level of current and voltage harmonics in power networks has been increased due to the widespread use of power electronic equipment. This increase may, in turn, result in damage to power system equipment in addition to extra power losses in the network. In order to assess the level of harmonics, it is required to monitor power networks using power quality analyzers. However, due to the high costs, only limited number of measurements can be used in practice. The task of harmonic state estimation is to identify the location and magnitude of harmonic sources and to estimate the harmonic voltage and current by partial measurements. Due to the high price of measurement instruments and... 

Nowadays, the significance of securing data and information is undeniable. Cryptography is being used to provide data security. In addition, cryptanalysis is required to evaluate the effectiveness of cryptography methods, and hence, it is an essential concept for securing data. In general, the cryptography functions shall be designed in a way to impose a high load of time-intensive operations to prevent an adversary from accessing the main data from the encrypted data. As a result, cryptography and cryptanalysis algorithms need high performance computations. So far, a number of methods have been proposed to support the required performance. These methods include: distributed computing and...