Sharif Digital Repository

Nowadays, According to the improvement of technology, especially in power electronics, electric shipboards are preferred over traditional ones. Better maneuverability, lower emission, higher efficiency and reliability are the most conspicuous merits of this type of ships. Notwithstanding the fact that electric shipboards have many advantages, some serious problems may arise in these ships. Since the thruster motors of these ships are usually induction motors and they are fed by the microgrid of the ship, and taking into ACcount that thruster motors consume a huge amount of the generated power by the synchronous generators, the concept of infinite bus is inexistent in these microgrids. Hence,... 

In this study closed cell aluminum foam was manufactured through accumulative roll bonding (ARB). In this method, aluminum AA1050 strip was used as the matrix and calcium carbonate was selected as blowing agent powder. The strips were roll-bonded with reduction of 50% during each pass. The produced composite was then subjected to different foaming conditions in order to achieve foams with maximum porosity. Subsequently, influences of content of the blowing agent, time, pressure, number of rolling passes and heating rate on the percentage of porosities were evaluated. In optimum condition quantity of the blowing agent, foaming temperature, holding time and number of ARB passes were equal to 1... 

In safe and economic designing of deep foundations for any structure, there are several factors affecting the behavior and response of a pile under seismic loads. These factors can be divided into three main categories: geometrical factors (e.g. Dimensions of the pile, soil, and mesh scheme), material properties (e.g. shear modulus, bulk modulus, soil elasticity, soil density, and shear strength) and earthquake load characteristics (e.g. frequency range, PGA, duration of excitation(. Studying the effects and importance of these factors in the final response of the pile (i.e. ultimate forces and displacements ) can help the design engineers of these foundations to optimize their designs.... 

Subwavelength localization of electromagnetic energy with intense local fields, also known as electromagnetic hotspots, has received significant attention over the past few decades. In most cases the hotspot is achieved through the resonant concentration of electromagnetic fields. One way recently considered to get hotspot is through reflection of electromagnetic waves in nonreciprocal one-way structures, in plasmonics and via magneto optic effect.However these hotspots are less confined compared to hotspots caused by resonances. So combining nonreciprocal structures with resonance can provide better hotspots.Our aim in this thesis is to study nonreciprocal resonant structures using coupled... 

With the advances in technology, Nowadays digital cameras are everywhere. As a result very large amount of images are on the web. Searching through these images intelligently and purposively is an essential need. Recently the possibility of retrieving images with some conceptual words along side of content based image retrieval has been studied in computer vision. For this purpose it’s required that for each image several words that describe its content be assigned automatically. One of the main problems for this task is semantic gap, meaning that the low level features such as color, texture,… don’t have the ability to describe the high level concepts in images which are comprehensible by... 

Human activity recognition is an important and useful area in computer vision that application include surveillance systems, patient monitoring systems, human-computer interaction and analyse video data from big websites.Traditional Human action recognition use the RGB videos as default input that unable describe motion and action as full. On the other hand Kinect camera sendsthe RGB data to output in addition to the Depth Data that allows us to extract skeleton of human easily. Recently Space-time features have been particulary popular in RGB Videos because of their structure. These features are describedby their descriptor and send the good and important information to output.Finally we... 

Setar is a traditional Persian musical instrument. Nowadays, Setar is one of the most common musical instruments in Persian music. A systematic method for Setar production modification has not been introduced yet. This work is the first scientific work about analysis of this instrument. The aim of this study is to undertake early steps for Setar quality improvement. In this thesis, after analysis of the wood using in Setar construction, numerical and experimental methods have been utilized to analyze this instrument. After that, some works has been performed to extract an objective function which can judge about Setar quality. The results show good agreement between experimental and... 

Melanoma is a malignant skin cancer which is caused by cancerous growth of melanocytes. If not treated at its early development stages, melanoma is the deadliest form of cancer. The best way to cure melanoma is to treat it in its earliest stage of development. Since a melanoma leasion is similar to benign moles (regaring its shape and appearance) at its early stages of development, it is often mistaken for moles and left untreated. Therefore, automatic melanoma detection can increase the survival rate of patients by detecting melanoma in its early stages. In this thesis, a new method for automatic diagnosis of melanoma using segmented dermoscopic images is provided. Almost all related... 

Nowadays, digital images are easy to manipulate and edit due to availability of powerful image processing and editing software. It is possible to add or remove important features to the image without leaving any obvious traces of tampering. Therefore, proving the authenticity and integrity of digital media becomes increasingly important. In this study, we focus on detection of a special type of digital forgery, the copy-move attack, in which a part of the image is copied and pasted somewhere else in the image with the intent to cover an important image features or to add some fake feature. In this way we propose some novel methods that work in spatial domain, Discrete Cosine domain and... 

The ability of measuring colors of objects, independent of light source illumination, is called color constancy which is an important field in machine vision and image processing. In this thesis, we propose five new combinantional ways in color constansy fields. The first two proposed methods use neural networks to combining basic methods. The third and forth proposed methods use fuzzy measures and integrals for combining color constancy methods. And finally fifth method combines methods with indoor outdoor classification this method has the best result (3.01 median angular error) in proposed methods and past methods in color constancy fields. It is shown in this article that the proposed... 

Shadows are one of the most important details in graphical images. There exist many shadow generation algorithms each of which suffers from some problems. High processing time and ill-shaped shadow borders, known as alasing, are some of such problems. In this paper, we propose a heuristic method based on standard shadow map technique, named rotated shadow maps, to generate excellent hard shadows. Our method uses some shadow maps which are generated from the same view but objects are slightly rotated around the center of view area. Rotated shadow maps can be considered as an independent hard shadow generation algorithm. Also it can be combined with other shadow map based approaches. Utilizing... 

In recent years with advancement of Robotics, the applications of wide scale use of robots in our homes is not as far-fetched as it was before. One of the important problems for an indoor robot is moving inside a new and unknown environment. To achieve this, the robot should, with the help of its sensors, not only calculate its location; but should also build a map of the environment for later use. Additionally, the robot must be able to explore this unknown environment. The most important drawbacks of the classical solutions to these problems are long computation times, heavy memory usage and absence of precision. In recent years, large amount of research effort has put on solving these...