Sharif Digital Repository

Sampling is the process of selecting and analyzing part of population and generalizing the results to estimate characteristics of the population. Time and cost considerations or the destructive nature of experiments are the main reasons why we study a sample instead of the whole population. In typical applications, sampling units are well-defined which means these units can be defined, selected and analyzed separately. This is the case in taking samples from a human population or products that consist of distinct units. If sampling units are not well-defined, as in the case of a bulk material (e.g., a pile of dust or other particulate materials, a tankful of liquid, the air or other gases)... 

Feature extraction in subspace domain for face recognition has attracted growing attention in recent years. Face image shown by a long vector usually belongs to a manifold of intrinsically low dimension. Researchers in face recognition field try to extract these manifolds using algebraic and statistical tools. Recently, the use of multilinear algebra and multidimensional data in various stages of feature extraction and recognition is considered. This approach reduces small sample size problem and computational cost by considering the spatial information in the image. Although these successes, the performance of the methods based of this idea in term of recognition rate in the applications... 

We have tried this for the first time to reperesent a comprehensive description of the evolution of a perfect fluid in inhomogeneous relativistic models.We solve Einstein equations using numerical methods.In this procedure we can evaluate the effect of pressure in perfect fluid evolution.Also we look at the behavior of the various horizons, and in the end we will present a cosmological model to a black hole  

In this thesis, we study the heterogeneous vehicles routing problem, which is a general-ization of the well-known travelling salesperson problem. In this problem, we are given a set of heterogeneous vehicles located in specific depots, along with a set of customers in the form of a graph. The vertices of the graph represent clients and depots, and the weight of edges represents the cost of travel between vertices of the graph. The goal is to find a subgraph for each vehicle so that the union of the subgraphs contain all customers and the total travel cost is minimized. The heterogeneity here means that the cost of traversing edges for each vehicle might be different. In this work, we briefly... 

In this thesis, first, random lasing in a three dimensional disordered medium has been simulated using FDTD method and some properties of random lasers which were observed by others in the previous experiments have theoretically been shown. Our simulation results show that when the density of particles increases to an upper limit, the intensity of lasing modes is enhanced. Also, the effects of pumping rate and particle size on the number of lasing modes and their intensity are studied. Lasing threshold of laser modes in different disordered systems is calculated and it is shown that by an appropriate selection of the central frequency of gain line-shape, the output power intensity of random... 

Water flooding is one of the improved oil recovery methods that has been used for past decades. The water flooding efficiency is calculated in two different scale; macroscopic scale and microscopic scale. The efficiency in macroscopic scale is called volume sweep efficiency (Ev) and in microscopic scale, displacement sweep efficiency (Ed). A special type of hydrocarbon reservoirs are composed of several permeable units in an impermeable shaley background in a way that hydrocarbon can just flow through the permeable units. The predominant feature of such reservoirs is continuity of permeable units that affecting the flow behavior. This simplification enables us to model such reservoirs by... 

In this work heterogenization of manganese porphyrins in ZIF-8 and Mg-Al-LDHs structures is performed, via host-guest interactions, and their catalytic activities for olefins epoxidation are also investigated.A heterogenized meso-tetrakis(2,3-dihydroxyphenyl)porphyrinatomanganese(III) acetate at zeolite imidazolate framework-8 (T(2,3-OHP)PorMn@ZIF-8) is investigated in the catalytic olefin epoxidation reactions at room temperature at the first part. Heterogenization is done through a non-classical hydrogen bond proposed between T(2,3-OHP)PorMn bearing O-H groups and C-H of the 2-methylimidazolate linkers in ZIF-8 structure. The aforementioned compound characterized by X-ray powder... 

This study aims to provide a multiscale model of traumatic brain injury including the three levels of macro, meso, and microscale information. In order to do this, a macroscale voxel-baed model of human head was constructed. The model was designed and generated to include mesoscale tissue information as well as a voxel-based approach to include voxel-based microscale data and to be coupled in a multiscale framework. Next, three different microscale models were constructed. The variations of fractional anisotropy within one standard deviation in the regions (including 60% to 70% of voxels) can change the stiffness of the tissue by up to the considerable amount of 40%. The microscale models... 

Geosteering is a process that is used in drilling oil and gas wells and its main goal is to reach hydrocarbon layers with high accuracy and optimal extraction from them. ROP is the distance drillied per unit of time, which has applications such as formation evaluation, boundary detection and maintaining the well path in geosteering. Gas ratio is another important parameter in this project which is strongly influenced by porosity, permeability and ROP. First, we give a brief introduction of various logs used in drilling like gamma-ray, density, neutron and sonic. Then in the literature review, we examine geosteering technologies such as automatic geosteering and machine learning. As we know,...