Sharif Digital Repository

The price that customers pay for electric energy is determined by cost of generation, transmission and distribution parts. In Practice all customer have main concern about reliability of electric energy, because of it’s major effect on different aspect of life. Although customers are interested to have fully reliable service, but power companies are aware that it is impossible to achieve this goal from technical and economical aspect. The utilities and customer benefits can be achieved through minimization of the total investment cost of network, while improving the reliability and quality of electric service. This also requires to minimize the customers service interruption time. To meet... 

Widespread growth in popularity of Android apps stimulates malware authors to consider Android-based devices as an atractive target platform. To defend against this severe increase of Android malwares and help users make a beter evaluation of apps, several approaches have been proposed. However, most of them suffer from some shortcomings such as being computationally expensive, not being general, or not being robust enough.According to obfuscation, encryption, and transformation techniques used in malwares, the static detection techniques are not efficient. Another approach is to use dynamic detection techniques, but existing dynamic techniques suffer from lack of atention to semantic... 

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... 

The concept of symmetry has long been the focus of numerous debates in different fields; some have come up with an artistic approach looking for a beautiful notion germane to the concept of symmetry. Others have examined this issue from a philosophical viewpoint and studied the ontology of symmetry and philosophers like Kant moved beyond the limits and have given their symmetry a transcendental position. On the other hand, in an anti-realist position relying on the fact that the goal of science is not truth but merely it’s an empirical adequacy, Van Fraassen argued that “science was rapidly gaining autonomy not only from theology but from all of philosophy, and was exploiting concepts and... 

The severe wildfires in California, Australia, Canada, and Iran have interrupted the power system operation, caused multiple blackouts, took many lives, and caused damages to power grid infrastructure to the extent of millions and billions of dollars. Most of the recent wildfires occur in the distribution system. Therefore, enhancing power system distribution resilience against wildfire is crucial.To this end, two groups of measures are proposed: the hardening of the power network and the operational measures. The past published papers mainly studied the resilience enhancement strategies against wildfire from an operational perspective. There is a considerable gap between the past works... 

Todays, thanks to the positive effects of electric vehicles, (against the vehicles which use patrol as their fuel), reduction of the Earth temperature and its climate change; the manufacturing, sale and use of electric vehicles experience a sharp increase. In addition to decreasing the air pollution, due to their abundant smart implications, they have been dramatically propagated. Massive use of these devices has raised the concern about the loss of the security which is indispensable part of the infrastructure. None of the past publications and works have taken the cyber-attack on the charging price rate and other data into account. In this thesis, charging methods of electric vehicles are... 

This thesis presents turbulent partially premixed combustion modeling behind a bluff-body by using the Flamelet Generated Manifold. The objective of the present work is to develop a 4D FGM program to simulate partially premixed combustion at a reasonable computational cost. Pre-tabulated data of this manifold is obtained by using a correlated joint PDF. An in-house code is developed to build a pre-tabulated library in conjunction with a correlated PDF. Also, an exclusive OpenFOAM solver is created by employing the PIMPLE algorithm. This solver provides the link of the computational domain with the pre-tabulated chemistry. This program is used to simulate Cambridge-Sandia stratified burner... 

The increased need for experimental verification of the seismic performance of conventional and novel structural systems has resulted in highly sophisticated dynamic test procedures. Hybrid simulation is one of the most efficient experimental methods for assessment of dynamic and rate-dependent behavior of large-scale structural systems under earthquake excitation. Compared to earthquake simulations using shake tables, hybrid simulation may have significant advantages in terms of cost, scale, geometry, and required physical mass of structures. However, recent hybrid simulations have been limited to simplified structural models with only a few degrees of freedom. Currently, the major... 

Ball bearings diagnosis increases the efficiency and reliability of industrial machinery. Data driven is one of the most effective and highly applicable method in this field. In this way, it is usually assumed that the sensor is mounted on the bearing housing, but in many cases there is no direct access to some of the machine bearings, and in such cases, the bearing can not be monitored and checked. In this project, with simplifications in order to inaccessible bearings diagnostic, a shaft with several supports is considered. The purpose of this project is to diagnose the bearing by the sensors located on the other bearing's housing. In order to achieve this goal, continuous wavelet... 

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... 

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... 

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... 

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... 

With the rapid growth of Internet popularity, web applications are growing in usage and complexity, and therefore, are attractive targets for attackers. Increasing number of services and amount of information stored in the Internet, stimulates attackers to focus on these kind of applications. On the other hand, security specialists are deploying different solutions to mitigate such threats. One of these solutions are Honeypot systems. In contrast with other security solutions, honeypots are not designed to defend against attackers directly. Honeypots, rather, are planned to gather data about what attackers do. This information can help security administrators to learn and understand... 

Network forensic analysts employ Payload Attribution Systems (PAS) as an investigative tool. With such tool large amount of network traffic, including full packet payload, is summarized and stored. Hence an investigator could query the system for a specific string and see whether any packets transmitted previously in the network contained that specific string. Wildcards are an important type of query that allows the investigator to locate strings in the payload when only part of the string is known. In this thesis we present a new payload attribution technique, named character based bloom filter, which in addition to improving on previously proposed techniques is able to support wildcard... 

Bearing capacity of foundations is one of the most controversial issues in foundation engineering. In this study regarding to the previous researches which has done by the other researchers the bearing capacity factors of a footing has calculatedusing finite element method. On the next step of this study some footings has modeled on different positions near slopes with different angles and bearing capacity of them has calculated, then some strip foundation has modeled and bearing capacity of them has calculated and compared with the values of the footings in this study and strip foundations of the other researches. Furthermore some foundations have modeled on the solpe and bearing capacity... 

Three-dimensional cell culture and forming multicellular aggregates is superior over traditional monolayer approaches due to better mimicking in vivo conditions and hence functions of a tissue. A considerable amount of attention has been devoted to devising efficient methods for the rapid formation of uniform sized multicellular aggregates. Restoring cartilage to healthy state is difficult due to low cell density and hence low regenerative capacity. Currently used platforms are not compatible with clinical translation and require dedicated handling of trained personnel. However, when engineering and implanting cell microaggregates in a higher concentration, new cartilage is efficiently... 

An a priori analysis is performed to assess the performances of Laminar Flamelet Decomposition (LFD) and Conditional Source-term Estimation (CSE) methods in predicting conditional and unconditional filtered production rates and mass fractions for turbulent premixed flames over a wide range of Karlovitz numbers, which is an indicator for the level of turbulence-chemistry interaction in premixed combustion.In LFD, it is assumed that a turbulent flame is composed of strained laminar flamelets. By presuming the functional form of the probability density function (PDF) of the progress variable and inverting the integral equation for the unconditional filtered mass fractions of one of the species,...