Sharif Digital Repository

A basic highway design problem is to find the most economical alignment connecting two given end points based on topography, soil conditions, socioeconomic factors and environmental impacts, while satisfying a set of design and operational constraints. The cost function complexity and numerous limitations such as highway design criteria have made this problem a NP-hard one. In this study, a swarm based searching algorithm has been applied to a three dimensional highway alignment optimization model. The spatial data has been exploited from a GIS databases using a heuristic swift approach. In addition, the majority of cost items that depend on highway design have been extended in a practical... 

As a robust and accurate classification of tumors is necessary for successful treatment of cancer, classification of DNA microarray data has been widely used in successful diagnosis of cancers and some other biological diseases. But the main challenge in classification of microarray data is the extreme asymmetry between the dimensionality of features (usually thousands or even tens of thousands of genes) and that of tissues (few hundreds of samples). Because of such curse of dimensionality, a class prediction model could be very successful in classifying one type of dataset but may fail to perform well in some other ones. Overfitting is another problem that prevents conventional learning... 

In this research, portfolio risk management methodology has been developed based on the portfolio management standard. This document is applicable as a template and standard for the organizations managing their projects in a portfolio structure since the methodology is based on portfolio standards and risk management, and it is being benefitted from their synergy. The most essential goal of portfolio management is to protect the organization against damages and to prepare it for responding to risks. In order to realize the goal of portfolio risk management, a well-developed and operational framework shall be provided. Therefore, the purpose of this study is to express the details of the... 

Roll bonding process is commonly used for the production of multilayer sheets. In the present study, using the roll bonding process, two layer sheets of copper - stainless steel were produced. In this case bonding strength was measured by peeling test at different statges and the quality of bonding was evaluated by SEM and Stereo Electron Microscope. The cross-sections of the bonding of rolled and annealed samples was investigated by optical microscopy. Also using EDAX analysis and EDS, the chemical composition of formed transition layer and the size of its interface at different temperature are measured respectively and the change in mechanical properties was investigated by tensile test... 

In the present thesis, the issue of locating end devices in the LoRa IoT network is examined using the received signal strength (RSS) approach. Recent advancements in machine learning techniques have revolutionized the localization field, enabling researchers to achieve better performance in non-line-of-sight (NLOS) and multipath interference conditions compared to traditional methods such as RSS and time difference of arrival (TDOA). This research first aims to reduce the position estimation error by appropriately scaling the received signal strength values on the public Antwerp dataset and to obtain a trained model for real-time localization of end devices. After introducing an appropriate... 

Crude oil production could cause the thermodynamic equilibrium of the crude oil to be disturbed in the well column which results in asphaltene precipitation and deposition. The thickness of the deposited material grows over time until it completely blocks the well column.Due to the hard and insoluble nature of deposited asphaltene, the two main chemical and mechanical methods are found to be more effective. It should be noted that the actual organic sediments in the piping are not pure and consist of three components: asphaltene, resin and paraffin. Therefore, it is very important to know the composition of the deposited material before selecting the appropriate chemical solvent.The samples... 

The continuous rise in electricity demand and the ever growing power generation in different power networks over the world have caused the short circuit level in the power systems to exceed the operational rating of the installed power devices (including cables, circuit breakers and buses). Replacing these devices with new higher rating devices is an expensive solution. From this point of view, utilizing fault current limiters is an economical solution. Superconducting fault current limiters form an efficient category of current limiters. This type is expected to be studied and used widely in future due to their advantages. In this thesis, the first chapter reviews the superconductivity... 

Terahertz waves which includes frequencies between 100 GHz to 10 THz of electromagnetic spectrum have found many applications in science, medical treatments and industry. One of the recent methods to produce these waves is using nonlinear properties of superconductors based on Josephson junctions which inherently appear in some superconductors called BSCCO. Stack of intrinsic junctions of these superconducting materials can radiate terahertz waves by only applying a DC voltage across them. This Thesis investigates some of these structures based on Josephson junctions to produce coherent radiation of terahertz waves. For the optimization of the radiation power, this study also investigates... 

There are different approaches in modifications of General Relativity as the theory of gravity. The modified theories of gravity are important cases in this context, which mostly start by modifying the Einstein-Hilbert action, while keeping the general covariance. Within the modified theories of gravity, we consider two cases. The first is the f(R) theories of gravity, and the second is curvature squared theories of gravity with an action like S = ∫d4x pg( 116GR + (R)2 + R2 +(R)2). Curvature squared theories of gravity have interesting feautures, most important of which is renormalizability, in contrast with General Relativity. But this advantage, as noted by K.S. Stelle in 1977 comes at... 

Near Horizon Extremal Geometries (NHEG), are geometries which may appear in the near horizon region of the extremal black holes. These geometries have SL(2;R)U(1)n isometry, and constitute a family of solutions to the theory under consideration. In the first part of this report,their thermodynamic properties are reviewed, and their three universal laws are derived. In addition, at the end of the first part, the role of these laws in black hole thermodynamics is presented. In the second part of this thesis, we review building their classical phase space in the Einstein-Hilbert theory. The elements in the NHEG phase space manifold are built by appropriately chosen coordinate transformations of... 

Multiverse scenario has been recently addressed by physicists and they have found it useful in many areas of physics. In this dissertation, I have treated some issues about multiverse such as the kinds of multiverses, the arguments for or against multiverse, areas in which multiverse is introduced, etc. This dissertation has six chapters and an appendix. In the chapter one, some classifications of multiverse is introduced, and also some definitions of the concept of a world is presented. Then, my classification and definition of a multiverse and a world is introduced. In the chapter two, the concept of possible worlds in philosophy and its relationship with multiverse hypothesis is examined.... 

Employing high-temperature superconducting (HTS) tapes, instead of copper or aluminum wires for winding in a superconducting transformer, results in a series of significant advantages; such as: smaller volume, lighter weight, higher efficieny, greatly extended overload capability, better voltage regulation, lower life cycle cost, fault current limiting capability, lower environmental pollution and lower risk potential against fire hazards.In this thesis, optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers has been performed. Then, multilayered flux diverters have been proposed for reduction of weight and losses. The impact of... 

Valve leak detection is very important due to bad direct effects on parts life and engine power. Acoustic emission (AE) has a good known ability on leak detection between fault detection methods. The aim of this thesis is presenting the ability of AE method for valve leak detection in internal combustion engines. The research method in a general framework based on the idea that firstly some evaluations were done in static tests for leakage due to three faults including clearance, quasi-crack and notch. Then, the evaluations were continued with dynamic analysis of rotational speeds and different loads on the engine. Finally, the neural network approach was used to automatically detect all... 

Inrush Current is a form of over-current that occurs during energization of a transformer. For power transformers, the magnitude of the first peak of inrush current is initially several times the rated load current but slowly decreases until it finally reaches the normal exciting current value. This process typically takes several minutes. Time-variant axial and radial electromagnetic forces under inrush current and short-circuit current are calculated (by finite element method; FEM), and compared. An analytic method is presented for computation of inrush current in transformer. The simulation results obtained by this proposed method are compared with the measured values. A compact... 

The goal of this thesis is to evaluate the strengths and weaknesses of the two existing formulations of Bohmian mechanics. The first one was proposed by Bohm, and emphasizes on the dynamics being second-order, and in which, the key tool for explaining the quantum phenomena is a non-classical potential, called "the quantum potential". In this approach, the postulates of de Broglie's "pilot-wave" theory, which now is known as Bohmian mechanics, are non-fundamental and are special to the atomic level. The possibility is proposed that these postulates become subjected to some modifications at the nuclear or lower levels, but no particular way for performing such modifications is suggested. The...