Sharif Digital Repository

In this thesis one of the sensorless methods which exploits the existing anisotropies of the rotor is utilized to estimate rotor position. In order to implement this method, first a high frequency voltage is injected in a specific, time-varying direction and then the corresponding current response would be observed in order to estimate the rotor saliency position. The estimation of rotor position would be more precise as the magnetic anisotropy due to rotor saliency increases and as a result the effect of noise and different disturbances in estimation of rotor position would be decresed. The effect of stator resistence is one of these disturbances which is usually neglected as a result of... 

This study investigated the effect of Robot Assisted Language Learning (RALL) on the vocabulary learning and retention as well as anxiety and attitude of Iranian English as Foreign Language (EFL) junior high school students in Tehran-Iran. After taking a vocabulary pretest, 46 beginner level female students at the age of 12, studying in their first year of junior-high participated in two groups of RALL (30 students) and non-RALL (16 students) in this study. The textbook used was the English book (Prospect-1) devised by the Iranian Ministry of Education for 7th graders, and the vocabulary taught and tested (pretest and posttest) were taken from this book. Moreover, the treatment given by a... 

Considering uncertainty is of great importance in the design of controllers for dynamical systems because the existence of uncertainty is inevitable in the modeling of almost all real-world systems. There are numerous methods and strategies for dealing with the control of uncertain systems in control systems theory including adaptive and robust approaches. The former one is more suitable for cases in which the information about uncertainty is very poor compared to robust techniques that are applicable in the cases more data is available about uncertainty. For instance, where there is no data about the direction in the actuator model, adaptive control methods are the only applicable choices.... 

Increasing the power of a turbocharged diesel engine without changing main engine components is important in industrial applications, with economic benefits. The engine power can be increased by higher boost pressure. In this research, the turbocharged diesel engine performance improvement was investigated to increase the engine power. As a case study, the performance improvement of OM355A turbocharged diesel engine carried out. For this purpose, the engine was modeled in boost module of the AVL software. First, naturally aspirated OM355 and turbocharged OM355A diesel engines were modeled. Then the simulation results were evaluated in compare with engine tests data. Maximum difference in... 

Natural language processing has been used in solving the problems of humanities, including linguistics and analysis of religious books, such as the Bible, the Torah, and the Quran. One of the challenges in this field is the analysis of issues using the Quran. The problem in this issue is that a person becomes prejudiced in order to analyze the issues and makes incorrect judgements either inadvertently or intentionally based on his/her intellectual background. The same applies to analysis of issues based on the Quran. The method of analysis in this research is to produce an Arabic text based on the language of the Quran by receiving subjects in Persian. In order to achieve this goal, three... 

In this thesis, we study the fate and consequences of the existence of edges or domain walls with non-zero thickness and how the properties of edge modes arising from symmetry-protected topological (SPT) phases and consequently the bulk dynamics of these phases changes due to this thickness. This general study is specifically examined in the context of anomalous quantum Hall effect (QAHE) systems as an example of these topological phases. Symmetry-protected topological phases are an important category of gapped material topological phases that, although lacking long-range order, exhibit non-trivial properties in the presence of boundaries. These non-trivial properties arise due to the... 

The three-phase Dual Active Bridge DC-DC converter, by virtue of its various advantages, has been widely used in numerous industrial and sensitive applications. However, this converter includes a large number of power switching devices, which are the most fragile components in Power Electronics, and therefore, can pose a threat to appropriateness of the converter for such applications. Accordingly, introducing a fault-tolerant scheme for this converter is necessary, in order to meet the demands of high reliability and service continuity in aforementioned applications. In this thesis, firstly, the converter is studied during normal operation as well as under switch open-circuit fault, and the... 

The Fukushima accident is one of the reasons why the spent fuel pool (SFP) is an important safety element. The large amount of spent fuel inside the spent fuel pool has made it a source of hydrogen and radioactive material in the accident of any disturbance to pool cooling. Although the loss of spent fuel pool cooling system accident has a slow transient, it can lead to disasters if you ignore it. In this project, spent fuel pool of Bushehr Power Plant unit ‘I’ was simulated by Ansys Fluent and the natural circulation of fluids in the absence of cooling system was investigated. The distribution of water temperature in the pool was investigated for the worst possible spent fuel pool loading... 

Steganalysis is the process of discovering existence of hidden data in a file or image. Recent advances in steganographic methods result in their wide use in secure communications applications. Reports of using information hiding by criminals to send messages, and malwares to communicate to servers, emphasizes importance of steganalysis in real time applications. Due to wide use of JPEG images in social media and internet, steganalysis of JPEG images is a highly active research topic in information hiding. Number of steganographic tools available for steganography in JPEG domain, shows importance of steganalysis of this image format. Classic Steganalysis techniques combine feature... 

In this study, we intend to examine the effect of physicians’ leisure and parents’ preferences on the choice of the date of C-section. According to the literature, the comfort and convenience of the physician is one of the main factors contributing to the fact that less C-sections are scheduled on weekends compared to other days. On the other hand, avoidance of C-section on the 13th of the month as well as increase of C-section on certain special dates has been observed in different counties. In this study, we use national birth data in Iran from 2013 through 2017. During this period, cesarean rate was about 50% nationwide. According to the results, C-section is reduced by 72%, 42% and 12%... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

In his book “Groundwork for the Metaphysic of Morals ”, Kant tries to pesent a formula for the supreme pinciple of morality. He ends up introducing three formulae that he thinks are all the same and just pesenting one formula In three different ways. After publishing this book, many criticisms were levelled against both his way of argument and the efficacy of his proposed formulae. In this enquiry, by focusing on the first two chapters of Kant’s book, and by considering the universal law formula and the humanity formula, we try to answer these criticisms. In the way, we make use of the new reading of Kant’s view- the critical reading- proposed by Samuel Kerstein, according to which Kant’s... 

In geotechnical engineering, collapsible soils as a part of problematic soils has an extreme importance since as a mutual effects of applying load and increasing their water content, Soil’s inter-particle forces become weak, and therefore, the soil experiences sudden large volumetric change known as collapse. Foundations built on these soils might experience sudden, large settlement. Collapsible soils exist in almost all continents, and many damages are reported due to the collapse phenomenon of these soils.
Due to the importance of this issue, and lack of comprehensive studies related to the volumetric and shear behavior of these soils, in this study, triaxial wetting test are performed... 

In nature, tidal currents are visible in gorges and in saltwater and freshwater collisions. In the study of behavior of different types of flow, it is usually assumed that the pressure is hydrostatic and the equations are solved based on this assumption. In the Approach Controlled regime observed during the double layer in 1993, the modeling performed using the equations derived from this assumption did not fit the results of the experiments. This demonstrates the inability of the hydrostatic pressure assumption to solve this particular regime. Hence, the equations were written on the basis of non-hydrostatic pressure and then the observed results were in accordance with the results of the... 

In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without... 

The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction...