Sharif Digital Repository

In this thesis we would like to investigate structural disorder of Graphene and its effect on electronic properties. Graphene is a one-layer crystal of Carbon atoms which was the first two dimensional crystal observed experimentally. Low energy current carriers on Graphene behave like mass-less Dirac fermions and this interesting electronic property attracts much attention on studying Graphene. Structural disorder of Graphene highly affects its electronic properties. We study thermal fluctuations of Graphene sheet, disorder super lattice, and static ripples, as structural disorders of Graphene. Disorders due to thermal fluctuations of graphene induce a disordered gauge field on the graphene... 

Today, communication sciences are advancing very rapidly; one of these advances is mobile location determination, means finding position of a mobile station. there are some method to location determination; one of these methods is Signal Strength (Power of Arrivals); In this research, Mobile Location Determination using Signal strength measurements in a Location grid will be describe; In this method there is a Mobile Location Server (MLS); In MLS, there re comparable records in database which have been collected from Location grid. When a MS needs to be located, its signaling data (fingerprint) is transmitted to MLS; In MLS, the fingerprints are compared to Data which is store in signature... 

In recent years, unmanned vehicles have intensively been developed to reduce human dangers for marine applications. Predicting the hydrodynamic coefficients of an autonomous underwater vehicle is important during the vehicle’s design phase. In other words to design an AUV, one must clarify its maneuverability and controllability based on a mathematical model. The mathematical model contains various hydrodynamic forces and moments expressed collectively in terms of hydrodynamic coefficients. Therefore, the correct values of the coefficients must be known to precisely design the controller of AUVs.SUT-2 is an AUV, being developed by Marine Engineering Laboratory of Sharif University of... 

Wireless sensor networks have a wide range of applications in the world. In most of the applications, collected data is not usable without the knowledge about the localization of events. There are two approaches to specifying the location of a sensor: using hardware solutions such as GPS, which is an expensive solution, and using the localization algorithm. Therefore, localization has an important role in sensor networks. Most of the current localization algorithms are non-adaptive and proposed for fixed wireless sensor networks. Recently, adaptive localization algorithms have been considered because of their simple implementation, fast result and low computation overhead for each node. In... 

Plant layout and siting are the earliest steps in any process design that may have significant effects on the further required level of safety and costs. Extensive carried out studies have been published in literatures in which, the safety factor has been taken into account in the form of prediction the severity of likely accidents. Majority of these studies are based on the accident consequence and other important parameters such as the accident frequency and the density of vulnerable items have been ignored. This recent negligence may lead to over conservative designs. To eliminate this recent deficiency, quantitative risk assessment (QRA) is the best procedure than can be suggested.... 

Disorders with creating the localized states, which are the states with limited spatial distribution, cause carriers of these states become limited to small part of space and cannot participate in the transport. If energy of these states is near the Fermi energy, the Anderson metal-insulator phase transition occurs. In this thesis,we studied type of disorders and determining their Hamiltonian and by studying definition of localization from different aspects, we attained a better explanation of disorders effects on materials. With studying the localization scaling theory, we ex-amined conditions of localization in different dimensions. Then for determining the green function and therefor the... 

In this thesis, the problem of locating a source based on the time difference of arrival (TDOA) has been studied and three different methods have been presented to improve the precision of the positioning. The first method is a solution to the least square error (LSE) by utilizing a convex problem. Generally, the mentioned problem is a non-convex problem; however, it is possible to convert it to a convex one by some relaxation in the constraints. By some justifiable and insightful relaxation, not only we obtain a convex problem, but also the exact solution of the main problem is derived. The second method is using high perturbed TDOA measurements which severely affected the localization.... 

Node localization is an important issue in dynamic environments for location-dependent applications of Wireless Sensor Networks (WSNs). Geographical location information is necessary in many WSN applications. The goal of localization algorithm is to assign geographical coordinates to each unknown node position. Among different localization algorithms, DV-hop is one of the well- known algorithms. DV-hop algorithm is a range-free algorithm and has significant error in node location estimation. Since the node deployment is stochastic, minimizing this error has a critical role in location estimation accuracy of the algorithm. Increasing communication radius and number of anchors, to the certain... 

In recent years, hardware Trojans (HTs) have become one of the main challenging concerns within the chain of manufacturing digital integrated circuit chips. Because of their diversity in chips, HTs are difficult to detect and locate. This thesis attempted to propose a new improved method for detection and localization of HTs based on the real-time logical values of nodes. The algorithm extracts the nodes with special attributes. At the next stage, the nodes with the greatest similarity in terms of logical value are selected as targets. Depending on the size of the circuit, the extraction continues until a sufficient number of similar nodes has been selected. The logical relationship between... 

Sharing secret key is an essential prerequisite of symmetric key cryptography. So, we consider a source model for information theoretic secret key agreement based on the distance among the nodes. Secret key agreement based on information theory, unlike computational models, guarantee full information secrecy, eavesdropper receives no efficient information. The model is a basic system consisting of two legitimate users and an eavesdropper. The legitimate nodes try to agree on a reliable and secure key based on their noisy observation of distance between them. Eavesdropper observes the distance, too. First, we model distance estimation by the nodes to study performance of the system (secret... 

Decision-making about make or buy is one of important and strategic decisions. Any wrong decisions in this regard can cause high costs to organizations. About this make or buy decision, there is rich literature and experts of different scientific fields such as economy, sociology, industrial engineering, and management, etc. study about it. According to importance of make or buy decisions in research organization and self- sufficiency Jihad as a supportive organ from IRIB in order to make needed products of this organization, the main purpose of this research is to provide and present a conceptual framework to help make or buy decisions for this organization. The research method in this... 

The research field of localization with high precision (precision of 10 micrometers) has greatly attracted attentions in recent years. Optical flow sensor is one of the inexpensive solutions for the localization of robot, which have been used in computer mice. The most important application of this thesis is to localize walking micro robot. The main challenge of previous research is the fact that sensor's precision is highly dependent on the surface texture. The aim of this research is to implement an appropriate algorithm on optical flow sensor in order to increase the robustness of sensor's precision to surface texture. In this regard, firstly experimental hardware has been designed and... 

Recent experimental progress in approximating closed quantum many-body systems such as ultra-cold atomic gases, has leads to surge of interest in the dynamics of closed quantum systems. In addition, driving a closed quantum system out of its equilibrium can create an appropriate conditions in order to archive novel phases of matter such as discrete Time-Crystals.In the present work, following a brief introduction, we start with basic principles of the Floquet theory. According to the matrix representation of the Floquet theory, we examine solutions of a quantum system which is driven by external periodic perturbation.We then turn to study of thermalization in closed quantum system and... 

In this thesis, in order to improve the performance of the mobile robot navigation, a Fuzzy approach is used for making a safe path in the cluttered environment with hurdles in the work space of the robot. To this end, based on data collected from instantaneous location of the robot and location of the robot, heuristic rules are extracted. Also, in order to obtain optimal data fusion of the sensors, Kalman filter is used to localize the robot. In this regards, by using the kinematics of the robot and supposing the white noise in the process and measurements, the position and orientation of the mobile robot are estimated in a real-time and adaptive manner  

The use of conventional multi-scale models for materials that exhibit softening behavior is not possible due to the phenomenon of localization, because the fundamental assumptions of homogenization are no longer satisfying around the localization region, and therefore the macro-scale results depend on the size of the representative volume element and the macro-scale mesh discretization. Also, if the finite elements mesh be fine enough, the solution does not converge to acceptable physical values. This research concerns the multi-scale study of failure and proposes an appropriate method for computational homogenization of that. The main idea is to apply the enhanced homogenization method to... 

Endoscopy is a medical operation in which a camera is sent into the patient's body and the physician starts taking pictures at specified times. In the traditional endoscopic procedure, a camera is sent into the body by a guiding wire. This can cause severe pain to the patient. In the newer method, a camera is mounted on a small capsule and the patient swallows the capsule. Then the camera inside the capsule starts taking photos and sends them out. This procedure, in addition to being painless, allows the physician to access the innermost parts of the body or the digestive tract.In capsule endoscopy, unlike the older method, one has to find the position and orientation of the capsule at any... 

Positioning refers to the process of estimating the receiver coordinates aiming for an accurate understanding of the surrounding environment. This branch of science has attracted considerable attention in recent years. Today, the influence sphere of positioning is so expanded that encompasses applications in daily life (e.g., navigation) as well as commercial and even military fields. Global Positioning System (GPS) is the most widely used tool in real-time positioning. Because GPS imposes great measurement errors in challenging conditions (e.g., turbulent water environments), alternative methods such as methods based on Wi-Fi, Bluetooth, and visible light have been proposed. Benefiting... 

Drive Test is a known technique witch network operators use to optimize and evaluate their mobile network infra in terms of capacity, coverage, and quality of service. Conducting Drive tests in outdoor areas is time-consuming and increases CAPEX and OPEX. Also, in areas with many giant physical obstacles, like towers and buildings in cities, Drive test is nearly impossible. In this paper, based on data and measurements provided by various Drive tests and TEMS MDT solution, we use an advanced processing algorithm in our database to bring signal coverage map practically to the users' cellphones. By taking advantage of grid-based signal fingerprinting technique, and filtering geo-tagged... 

Ultralight aircraft (VLA category) are usually piloted by novice pilots under Visual Flight Rules (VFR). In this work, we demonstrate how newly developed techniques in robotics could be used to enhance flight safety in this category of aircraft, especially during landing around sunset. In this research we have investigated the ability of Simultaneous Localization And Mapping (SLAM) algorithms in low level flight just before touch-down. Different case-studies show that SLAM algorithm is efficient in detecting the runway threshold. Comparing five different methods of parameterizations for landmarks detection including: (1) Plucker, (2) Anchored Plucker, (3) Homogeneous, (4) Anchored... 

According to the goals of new generation of wireless communication networks, which include increasing data transfer speed, reducing latency, optimizing power consumption, and increasing the quality of communication, the use of intelligent surfaces to change and control the wireless transmission environment to achieve the goals of new wireless networks has emerged as an effective solution. Finding the location of a user connected to a wireless network for issues like navigation or traffic control has also long been under consideration, and a variety of business systems have been introduced for positioning. Given that the accuracy and speed of finding the user's position is one of the...