Sharif Digital Repository

In fact knot theory is working by an elastic string. A knot is A smooth embedding of in . We say that two knots are equivalent if there is an ambient isotopic between them. In knot theory we study equivalent classes of knots. As it seems from its name, a dynamical system is the study of motions, mechanics and dynamics of a system. We will observe some systems and stability of orbits in theme. Then we define templates which contain orbits in themselves. At last, we observe relations between discrete dynamical systems and knot theory. Then for any arbitrary chaotic knot we observe that there exist an universal template that contain a copy of any kind of not. Finally we will study some open... 

We study wavelet transformation for use in pattern recognition. Feature extraction is a crucial processing step for pattern recognition. Feature extraction is based on finding mathematical methods for reducing dimensionality of pattern representation. Two most important features to be extracted are edges and textures. Edges and textures are not absolute concepts and change with scale. Moreover, local characteristics of edges are needed. In recent decades, wavelet transformation as a mathematical tool has captured the attention of many scientists in signal processing and mathematics. Wavelet basis can provide efficient and useful description of a function or signal since it has local... 

Dependence of some magnetic properties such as core loss and permeability on temper rolling was studied in this thesis. It is shown that with a proper temper rolling sharper textures are obtained in the electrical steel and the magnetic properties in the longitudinal and traverse directions are improved. By texture analysis, it is shown that because of temper rolling, shear strain on the surface of the sheet is the main factor for abnormal grain growth and shear texture formation on the surface. The result of formation of this texture is enhancement of the {100} intensity and reduction of the {111} intensity, leading to the improvement of the permeability. Temper rolling is always... 

In content based image retrieval, low level features are used to find similar image. To do this, many system has been proposed by other people, in which in many of them, combination of features in the same time are used as a step of retrieval to increase accuracy. Feature combination are divied in two category: vector based and weight based which in weight based approach, features can get different weight, based on their importance and role in retrieval accuracy. Each image contain different partition, which some of them like background, base on their lower discrimintivity power, have lower importance. Based on our study, some image have powerfull color features and some of them have... 

Content Based Image Retrieval (CBIR) is a research area in computer vision. This area comprises of two main steps, low level feature extraction such as color, texture and shape extraction and also similarity measures for comparison of images. The challenge in this system is the existence semantic gap between the low level visual features and the high level image semantics. The aim of research in this field is to reduce this semantic gap. In this study the images are divided into regions using Meanshift method, for color segmentation and then moments of each region as color feature are calculated. Also for extracting texture the images are divided into regions using Jseg method, and then... 

During recent years, decay, fraction, corrosion and leakage of oil pipe lines have resulted in soil pollution. Gas oil is one of the main causes of soil pollution in different places. Soil and pollutant interaction results in varying soil geotechnical properties which causes shear strength, permeability, etc. to change drastically. After careful recognition of the problem, it should be encountered in a good manner. Therefore, comprehensive investigation regarding the effect of oil production on soil should be done. In this thesis, properties of combination of sand, kaolinite and pollutant in different situation such as different fine grain content, different relative compaction, and... 

In this study, non-isothermal annealing of multi-directionally forged (MDF) aluminum alloy 2024 has been investigated. Two initial heat treatments have been considered, the solution treated (without S′/S (Al2CuMg)) and the over-aged (with S′/S (Al2CuMg)) conditions. DSC curves have shown that GPB zones/Cu-Mg co-clusters have been dynamically formed during MDF. This dynamic formation of these meta-stable phases has been modeled and in the presented model volume fraction of meta-stable phases has been calculated and its effect on the dislocation density has been considered. Although, hardness of solution treated sample has been increased by two-fold after MDF, hardness of over-aged sample has...