Sharif Digital Repository

The goal of this thesis is to represent some application of algebraic topology specially homology and simplicial structures in data analysis and image processing. First the notion of topological persistence will be introduced and next for computing that several efficient algorithms will be proposed. Also complexity of the algorithms base on the topological spaces and by some algebraic topology tools. And it will be tried to test this theorical algorithms on real data and represent some application of topology in real data analysis. To do that, at the begining the tools of algebraic topology will be reviewed and the notions like singular complexes and singular homology and some related... 

In general, the output power of the gas turbines decreases as the ambient temperature increases. One of the ways to deal with such a performance loss is to use a wet compression system, which reduces the air temperature rise throughout the compressor. In this system, the water droplets are injected into the compressor inlet and evaporated throughout the stages. As a result, the work of the compressor decreases, and the power and efficiency of the whole engine increase. Most of the researchers in this field have tried to develop mathematical models to investigate the effects of this system on compressor and gas turbine performance in steady-state conditions. However, it is necessary to... 

The goal of the present study is to analyze the effect of CaF2 and nano-TiO2 as additives on formulation and properties of common dental glass-ceramics. To achieve the goal, a glass system based on SiO2-Al2O3-Li2O-K2O-P2O5-ZnO-ZrO2 was considered to produce glass-ceramic samples and the additives, nano-TiO2 and CaF2, with the 0.5, 1, and 1.5 %Wt was added to the system. After the melting process, the glass samples poured in the water and ferrite was produced. In the next step, the ferrite was milled and pressed. In the heat treatment step, the samples were treated in the temperature range of 650-850°C in order to gain lithium disilicate glass-ceramics. In the last step, the chemical... 

This study presents a Machine Learning framework for post-earthquake structural damage state and economic loss estimation. The framework is proposed to rapidly determine whether a structure is safe or unsafe to be occupied following a seismic event, to predict the detailed structural response, and finally to evaluate the economic loss of the buildings. An extensive database is developed by analyzing twelve low-rise, mid-rise, and high-rise eccentrically braced frames (EBFs) under 44 scaled ground motion records through incremental dynamic analysis (IDA) to train the Machine Learning algorithms. Machine Learning algorithms are employed to classify the structural damage state of the buildings... 

The Reconfigurable manufacturing system (RMS) was first introduced in 1996 with the ability to respond quickly to market changes and in response to global competition between companies. The effort of this research is to expand the problem presented in the Moghaddam et al. (2019) by introducing the concept of raw materials for the production of parts and related issues such as purchasing and warehousing raw materials, and providing a suitable solution to the problem. In the basic article, the RMS should utilize the best combination of machines and their configurations in proportion to the demand of the products in order to minimize the cost and produce all the demand. In this study, a large... 

Final control elements usually have nonlinear dynamics which affect the stability of the closed- loop system. Four most common types of these nonlinearities are dead-zone, backlash, hysteresis and saturation. Because most of final control elements especially in chemical processes are subjected to saturation constraint and also due to lack of generaland practical control scheme to handle this limitation, our concentration will be focused on saturation nonlinearity. In this work, based on sliding mode control strategy, a control scheme for multi-input multi-state systems in the presence of input saturation is presented. Some numerical simulations are carried out to show the effectiveness of... 

Dead Reckoning navigation, as an infrastructure-independent approach, plays a key role in scenarios where access to the Global Navigation Satellite System (GNSS) is unavailable; however, its performance is consistently affected by the accumulation of errors in inertial measurement unit (IMU) sensors. In this research, a novel approach is proposed to enhance the accuracy of this method. In the first stage, sensor noise modeling is performed using three innovative approaches. The first approach involves a static tuning based on an adaptive Extended Kalman Filter (AEKF). In this method, the discrete process noise covariance matrix is adaptively estimated, and the continuous-time process noise... 

Pipe freezing has become well established in industry as a method of short-termisolation in order to carry out maintenance or repairs. It is often necessary to repair system components without plant shutdown or drainage of system having many piping structures which may have hazardous or expensive fluid. Therefore, a series of tests has been arranged to investigate the ice plug formation in two standard pipes with different diameter size. The freeze zone on the pipe has been created by means of an aluminum jacket which liquid nitrogen flows in it. In the tests the freezing time, amount of liquid nitrogen usage andthe pressure tolerance of ice plug have been determined. Moreover, the numerical... 

TiO2 and TiO2-Graphene have been synthesized by hydrothermal method. Their physical, chemical and morphological properties have been investigated using XPS, XRD, FTIR, TEM, EDX, UV-Vis and AFM analyses. Moreover, photocatalytic efficiency of prepared materials has been examined using degradation of methylene blue. AFM image exhibited that monolayer GO with thickness of 10 nm was synthesized using modified Hummer’s method. FTIR analysis represented main characteristic peak of oxygen bond on the surface of GO, whereas for TiO2-Graphene most of oxygen functionalities on the surface were removed partially or completely. Photocatalytic degradation of MB proved this extension of light absorption.... 

In recent years, the area of research on micro flying robots has been developed due to the development in micro manufacturing technologies. Due to extra advantages of these flying robots, they are implemented in military and civilian missions such as identifying, espionage, aerial relays, traffic surveillance, rescue, aid, etc. Ability to fly in specified areas, without human injuries, low manufacturing and energy costs, easy and fast implementation, Easy Maintenance, etc, which are some advantages of these robots. We can control these robots manually by remote controllers (RC) or by Auto guidance systems. On the other hand, these robots are used in research laboratories for testing new... 

Range Profile (RP) is known as one of the most important tools for radar target recognition. The main problem with range profile for radar target recognition is its sensitivity to aspect angle. To overcome this problem, range profiles are assumed to have the same statistical characteristics in small frames of aspect angles or context dependent models such as HMM may be used. All methods presented, seems to have some shortcomings to offer a model based on physical circumstances of target maneuver. For example in such models, consecutive samples of RPs in an aspect frame are assumed to be statistically independent with the same distribution (IID). Here we propose dynamic system (DS) for... 

The present thesis aims at investigating the dynamic interaction of slosh and aeroelasticity in the fuel contained aero vehicles. The main approach in this research is to develop reduced order models for description of the coupled system. In this regard, boundary element method is used to develop slosh dynamic model. Axisymmetric boundary element method with non-symmetric boundary conditions is used to develop slosh dynamic model for axisymmetric containers. Zoning method is used to develop slosh dynamic model for the multi-baffled tanks and based on it, slosh equivalent mechanical model is developed for multi-baffled tanks. Finite element method along with modal technique is used to develop... 

There are numerous ways available to achieve low temperatures that cryocoolers might be among the most important of them. In the meantime, the pulse tube refrigerator has a special place due to its simple geometry and not be using any moving parts. This simple property make the pulse tube refrigerator one of the most popular methods to achieve low temperatures. Nowadays, a pulse tube refrigerator is used for cooling in the range of 4 to 123 Kelvin in two form of one-stage and two-stage and up to an approximate power of 1 KW. Today, due to the temperature and the amount of power required for cooling, as well as the time it takes to reach that temperature, this chiller is used in medical,... 

In modeling of biological systems and chemical reaction networks, analy-sis the existence of multiple equilibria is important. Our interest in using dynamical system in such analyses comes from biology. So, we will study the qualitative properties of a dynamical system, described by a system of ordinary differential equations. In this thesis we will discuss the question of how to decide when a general chemical reaction system is incapable of admitting multiple euilibria, regardless of parameter values such as reaction rate constants. We will relate different graphs to chemical reaction systems, and by means of its paths and circuits, we will introduce some sufficient conditions for... 

This thesis presents an investigation of the dynamics of two coupled non-identical FitzHugh–Nagumo neurons. It is known that signal transmission in coupled neurons is not instantaneous in general, and time delay is inevitable in signal transmission for real neurons. Therefore we consider the system of two coupled neurons with delayed synaptic connection. We consider coupling strength and time delay as bifurcation parameters, and try to classify all possible dynamics which is fairly rich and we will study the excitability of the neurons. By bifurcation study of the system the coupling strength and delay-dependent stability regions are illustrated in the parameter plane, to describe typical... 

During the last few years, the study of urban environment structures is considered as a research field of interest in remote sensing. In satellite observations of the earth's surface, continuous imaging in terms of time and space has caused the remote sensing technique to be proposed as a useful and efficient tool for the analysis of urban areas. Obtaining quantitative spatial information from the urban environment in fields such as determining the height of buildings plays an essential role in urban planning, monitoring damage to buildings, establishing communication bases and digital cities. During the last two decades, the use of Tomosar approach in order to reconstruct the structures of... 

In synthetic aperture radar (SAR) satellites, the nadir echo is defined as the backscattered signal from the point directly below the satellite on the earth surface. If the timing of the radar is such that the nadir echo arrives at the receiver while the receiver is turned on for receiving the desired signal, it could damage the receiver or disrupt the resulting SAR image, unless it is suppressed enough by proper design of antenna radiation pattern. In current SAR satellites, ”avoiding” this phenomenon is associated with two problems: 1) limiting the swath width, 2) imposing stringent restrictions on the selection of pulse repeatition frequency (PRF). Therefore, ”suppressing” the nadir echo,...