Sharif Digital Repository

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... 

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... 

Recently, macroporous polymers have gained wide acceptance for applications such as filters, membranes, biodegradable scaffolds, retention media, sound mufflers and etc. In this research, by keeping in mind the importance of the pore structure in the functionality of the porous part, three dimensional images of the pore structure during sintering was obtained using an optimized manual serial sectioning technique. Then, using the Euler number as a property of the topology of the pore surface, evolution of the three dimensional pore structure was scrutinized for two types of powders, powder A with a mean particle size of 200 micron and melt flow index of 0.2 (g/10 min) and powder B with a mean... 

Due to the increasing use of data storage systems and volume of digital data, fast information access and retrieval has significant effect on performance of storage-bound systems. Operating systems utilize the spare space in the main memory as a cache to speed up access to the storage subsystem. Due to the large performance gap between hard disk and main memory, any improvement in this caching layer can greatly affect the performance of the entire system. Page replacement algorithms are one of the important mechanisms in the virtual memory management layer. Several algorithms have been proposed for the eviction of pages from the virtual memory cache and few of them have also been implemented... 

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... 

By definition, Mobile Clouds are networks of mobile nodes, which are connected together using short-range communication links, and at the same time keep their connection with the long-range cellular networks. Short-range communication links in Mobile Clouds provide the opportunity of Resource Sharing, which can result in new services for end-users. These services are beyond the boundaries of traditional networks.
In the following report, we aim at focusing on some problems related to Mobile Clouds. First, we present a centralized model for managing the mobility of the nodes; then we try to propose algorithms for efficient data update and processing; and finally, we introduce a novel... 

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... 

Optical fibers with the high amount of nonlinearity, or length such as highly nonlinear fibers (HNLF) and long optical transmission lines could not be simply modeled as linear systems; and, in fact, the propagation of signal through these types of mediums is governed by the nonlinear Schrödinger equation (NLSE). From the statistical point of view, the interaction between signal, noise, and Kerr nonlinearity along the fiber leads to an output random process that is not well studied in the literatures and the exploration in this area may play an important role in solving different practical problems. In order to investigate the aforementioned output random process, this thesis obtains the most... 

In most real combustion systems, flow is turbulent (e.g., diesel engines). Therefore, a reliable turbulence modeling approach is necessary to design and analyze a system with turbulent flow. Direct numerical simulation (DNS), Large eddy simulation (LES), and Reynolds-averaged Navier-Stokes (RANS) are the three most mature Computational fluid dynamics (CFD) methods for turbulent flow simulations. Because of LES’s good accuracy and acceptable computational cost. In this project, LES is chosen to simulate the turbulent flow field.Modeled turbulence subgrid scales' interaction with nonlinear flow parameters, needs modeling. In supercritical and transcritical conditions, Equation-of-state is a... 

Modeling and simulation of acid transport in fractured porous medium and the formation of wormholes are the main goals of this dissertation. Injection of acid in rocks is one of the enhanced oil recovery methods which is extensively used in industry. The flow of acid in a porous medium produces a highly permeable path which is called wormholes. The formation of these wormholes is dependent on parameters of rock, acid and injection properties. As a result, simulation and prediction of this phenomenon are very important for optimization. Some researches developed methods to model this phenomenon in porous media but few of them investigated discontinuities in a medium. This research uses... 

One of the challenging issues in machine learning is the problem of data imbalance. Data imbalance occurs when the number of samples from one or more classes significantly exceeds or falls behind that of other classes. The existence of data imbalance in a dataset often leads to misleading accuracy of models, inadequate prediction of minority class, and a lack of generalization. Data imbalance can be observed in various datasets such as fraud detection, disease diagnosis, email spam detection, and fake news detection. To address this issue, various methods have been proposed, categorized into four groups: data-level, algorithm-level, cost-sensitive, and ensemble approaches. In this study, two...