Sharif Digital Repository

Amount of strain has been always considered as the primary parameter affecting the microstructural and strength evolutions during Severe Plastic Deformation (SPD). However, these evolutions unavoidably saturate in large strains under deformation with constant conditions, i.e. constant deformation temperature, strain rate and strain path. In this study, effects of these factors on the microstructural and flow behavior of Ultra-Fine Grain (UFG) aluminum (AA 1050 and AA 5052) processed by Accumulative Roll-Bonding (ARB) are investigated. The flow behavior and its time-dependent aspect are evaluated up to large strains by Plane Strain Compression (PSC) and Stress Relaxation (SR) tests. ... 

Over the past several years, TiO2 has become a focus of considerable researches as it possesses unique optical, catalytic and electrical properties in different applications such as sensors, water purification and dye-sensitized solar cells (DSSC). The goal of this research was synthesis of 1-Dimentional TiO2 nanostructure with suitable properties for DSSC applications. Two different TiO2 powders including micron-size anatase and mesoporous powders (produced from reaction of TiC and HNO3) along with KOH or NaOH were employed in hydrothermal process. The process was performed in two different containers including autoclave and balloon-shaped flask. The products were characterized by X-Ray... 

This project presents an outline of the crack tip stress fields in the presence of a plastic enclave around a growing fatigue crack using RKPM and Drucker-Prager criterion for pressure sensitive materials such as concrete and rock. Two distinguished features of RKPM are the arbitrarily high order smoothness and the interpolation property of the shape function which has kronecker delta property at the associated nodes. This method has proved to handle extreme material deformation and moving discontinuities. For the frictional materials such as rock in geotechnical engineering, a non-associated or associated Drucker- Prager plasticity model is appropriate for modeling its constitutive... 

In this thesis selection criteria are present for types, numbers and locations of sensors for structural health monitoring of offshore jacket platform in the Persian Gulf. The selection criteria are chosen by studying structural health monitoring of various structures in civil and aerospace industries. Knowing the types of sensors that can be used, a new approach of inverse vibration problem is introduced for structural health monitoring of offshore jacket platforms. In the previous studies, significant numbers of frequencies and mode shapes are usually used to detect damages by updating components of stiffness matrix. Considering the fact that offshore platforms are composed of a heavy... 

In this paper, we introduce a novel decision making strategy on how to assign markets to a multi-item newsvendor’s problem. We present a new formulation method based on the integration of news-vendor problem and dynamic programming approach alongside an efficient solution method. Suppose there are n distinct products and corresponding time intervals for selling them in different markets. These products will be worthless (perishable) at the end of each interval. Our proposed framework represents a trade-off between costs associated with staying in a market for further periods and costs of relocating the business in a new market. The objective is to maximize the total profit of our decisions... 

Despite significant progress in cancer treatment, drug resistance remains a major challenge. Synergistic drug combinations offer a promising approach to overcome drug resistance and reduce side effects. Still, despite high-throughput testing technologies, existing drug combination databases suffer from biases and a lack of diversity in tested cancer cell lines, which challenges the prediction of drug response on novel cell targets. To address this critical need, we designed a two-level deep learning method that uses large-scale gene expression datasets to estimate the score and synergy of drug compounds on a wide variety of cancer cell lines. Our model includes an auto-encoder that train on... 

ZnO semiconductor has a wide band gap (3.3eV) and high electron mobility, making it a possible candidate for an effective structure-based Dye-sensitized solar cell (DSSC) semiconductor. Efficiency of DSSC based on ZnO is lower than TiO2 due to its low chemical satability. It is well known that the energy conversion efficiency of DSSC depends on the electron transport in the photoelectrode so in this investigation we fabricated high transport photoelectrode by doping Al in ZnO nanostructures. DSSC based on Al doped and undoped ZnO nanosheet synthesized by electrochemical deposition. Current density-voltage (J-V) characterizations indicate that Al-doping in ZnO crystal structure increases... 

This thesis is focused on flight dynamics modeling and analysis of an articulated Flapping Micro Air Vehicle (FMAV), where the articulating joint is placed near the wing mid chord span. The articulation modeling, its results and verification due to added degrees of freedom are considered the key motivation and novelties of this project. Initial analyses indicated that a simple articulation device such as joint is not appropriate and will not be efficient for flying FMAV. As a corrective action, a spring-damper mechanism was utilized beside the articulation. Subsequently, the kinematics’ equations are developed and verified using the MSC Automated Dynamic Analysis of Mechanical Systems... 

Increasing of human demanding for energy and limiting of fossil fuels and bio-logical problems, it seems necessary to access new and clean source of ener-gy. For instance, one of these sources of energy is sun. If we can impart from this infinite energy source so health and natural life can be pictured for human. Nanostructure dye sensitized solar cells in compare with other photovoltaic cells are more economical and practical as a result of lower material cost and simpler manufacturing process. In general, a typical dye sensitized solar cell is a sandwich structure based on two transparent conducting oxide (FTO) glasses. The FTO glass substrates are expensive and account for most of... 

To protect mild steel against corrosion, an intelligent self-healing epoxy (EP) coating including carbon nanofiber (CNF) modified with polydopamine (PDA)-La (III) complex was successfully fabricated. The high aspect ratio and unique thermal and electrical characteristics of CNF made it an ideal physical barrier against the penetration of corrosive ions. Due to the poor dispersion of CNF, its surface was modified using PDA. PDA, which contains functional groups such as catechol, amine, and imine, can mitigate corrosion reaction by generating the Fe-Catechol complex and also boost the coating's adherence to the metal surface, in addition to anchoring La3+ inorganic corrosion inhibitor.... 

Because of increasing demands for using of rotating systems in high accuracy and high speed applications, in addition of specific condition of rotating systems, it is necessary to analysis these rotating systems characteristics. In addition to the dimensional and geometrical errors of mechanical system parts and assembly errors, manufacturing quality directly depends on Non Repetitive Run-Out (NRRO) errors; so the results of NRRO errors as an ultra-precision characteristic should be studied in required outputs. In this paper by analyzing dimensional and geometrical tolerances as tolerance zone, the variations of system outputs because of tolerances is calculated in both static and dynamic... 

In this study reliability and sensitivity analysis of the parameters of a concrete gravity dam have been proposed regarding to their probabilistic behavior. At first, the uncertainty of concrete fracture energy (GF), Foundation’s elasticity modulus (E_f), and the Peak ground acceleration (PGA) are considered according to their probability density function (pdf). The uncertainty sources are inserted in the model using the Latin Hyper Cube Sampling method (LHS) in order to do reliability analysis of the model. Monte Carlo method is one of the most popular methods for reliability analysis of numerical models. Taking this method in uncertainty analysis would evaluate the effects of the inputs on... 

It is believed that the carbon dioxide emissions are likely to be the dominant drivers of climate change over the coming century. Geological sequestration in saline aquifers is a potential technology for mitigating carbon dioxide emission in atmosphere. In this study, computer simulation is combined with experimental design to perform sensitivity analysis and estimation of carbon dioxide sequestration in saline aquifers. For this purpose, horizontal permeability, vertical to horizontal permeability ratio, porosity, depth, pressure gradient, temperature gradient, water salinity, formation thickness, diffusivity coefficient, dip, irreducible water saturation, water Corey exponent, gas Corey... 

Natural gas liquefaction is a gas refrigeration technology, which enables the export of natural gas worldwide, in liquids formed and stored at very low temperatures. In this project, a plate-fin type of heat exchanger, which is used for liquefaction of natural gas (mainly methane) at very low temperatures, has been investigated. The most important and effective part of this gas refrigeration cycle is the cold box heat exchanger. The cold box consists of two or more floors in which some sorts of fins are installed in each floor. In this simulation, the three-sream heat exchanger is designed in such a way that the input temperature of the natural gas is about 200 K and the output is 145 K at a... 

This dissertation studies the intertemporal decisions on private consumption and its relationship with financial markets. The main focus here is on using micro-data and heterogeneities. The first chapter gives a brief review on the literature. In the second chapter, we present estimates of the Elasticity of Intertemporal Substitution (EIS) for Iranian households using synthetic cohort panels based on household micro-data. Results show significant difference with the common values used in Dynamic Stochastic General Equilibrium (DSGE) models which are originally based on estimated values for developed countries. We show that this difference has important theoretical and practical implications.... 

In today's life, we look at each other, seeing different networks, such as power networks, telecommunication networks, transportation networks (freeways, roads, streets), rail networks, air service networks, shipping networks, Logistics networks (networks of construction and distribution), computer networks, Internet networks (e-commerce, banking networks), airline reservation networks, social networks and so on. In all of these networks, an entity such as man, product, car, electricity, message, information, aircraft, etc. from one source into a destination is moved according to the network's purposes and objectives.This thesis analyzes the sensitivity analysis and optimization of... 

As petroleum resources are not steadily distributed in the world and all industries and manufacturing sections are dependent on these resources, petroleum transportation is very important to the extent that availability of these resources occurs in the fastest time and costing the least possible. The objective of this study is to study the petroleum distribution through time in the world and assess its transportation efficacy during 1965-2005 in 173 countries. Collecting information about petroleum distribution between exporting countries to importing ones helped to complete the study data base. Also in this study two transportation networks, sea and land multimodal transportation network... 

One of the major problems in cancer treatment is side effects of treatments. Today, scientists have developed smart nanocarrier for diagnosis and drug delivery that can circulate in the bloodstream, pass the body's immune system to kill cancer cells and attach to the cancer cells to deliver drugs, without the side effects that are in other treatments, such as chemotherapy. magnetic nanoparticles coated by biodegradable polymers are one of the smart polymers. In this study, iron oxide nanoparticles with amine group on their surface are coated by starch modified by methyl acrylate then reacted with hydrazine and hydrazide functional group is formed that can chemically be bonded with the... 

A numerical algorithm for the optimal design of two components functionally graded materials under thermomechanical loadings is introduced in the present study. It is based on the topology optimization method. The objective function, to be minimized, is defined as the weighted combination of the thermal and mechanical compliance of structure. The design variables are defined as the local volume fractions of contributing phases. The set of constraints includes bound constraints on local volume fractions and a global constraint on the total volume fraction of the matrix phase. The corresponding heat and elasticity equations are solved by the finite element method. The local material properties...