Sharif Digital Repository

Automated dimensional inspection is commonly expensive because of the requirement for high-precision measurement devices. To perform a precision measurement, the technician must be highly skilled and fully understands the operation of the equipment. Moreover, automation of the mentioned process to reduce dimensional measurement time is a complicated task due to restrictions of precise equipment such as CMM. With the expansion of the use of cameras in the industry, the measurement method with the help of machine vision systems is one of the cost-effective methods that can be achieved with the development of a suitable image processing algorithm to achieve acceptable accuracy compared to... 

Walking with lower-limb exoskeletons, particularly in individuals with limited motor abilities, presents numerous challenges. One of the most critical limitations is the absence of an active ankle joint in many commercial exoskeletons. This deficiency prevents users from naturally transferring their center of mass over the peak of potential energy, as the ankle normally plays a crucial role in generating forward propulsion and transferring energy between steps. The lack of this energy source forces users to adopt compensatory strategies that have not yet been thoroughly identified or analyzed. In this study, aiming to precisely analyze the gait mechanism in the presence of an exoskeleton... 

In this work, the glassy carbon electrode (GCE) was modified with a thin layer of multi-walled carbon nanotubes (MWCNTs) and consequently, electrochemically deposited poly-pyrrole. The electrochemical behavior of mesalazine was studied on the surface of the modified electrode by applying linear sweep voltammetry (LSV). The electro-polymerization process and the electrochemical response toward mesalazine were investigated in the presence of different aromatic anion dopants including, benzenesulfonic acid (BSA), 1,3-benzenedisulfonic acid (1,3-BDSA), 1,5-naphthalenedisulfonic acid (1,5-NDSA) and new coccine (NC). By using 1,5-NDSA as dopant, a significant increase (∼418 times) was observed in... 

This dissertation proposes a probabilistic framework for optimal calibration of design provisions based on the minimization of lifecycle cost (LCC) and its uncertainty. Subsequently, this framework is utilized to determine the optimal robust design base shear coefficient of building structures, and propose a methodology for codifying it while preserving the current structure of the base shear equation. In the first part of the proposed methodology, various structures are designed with different seismic base shears. Then, at each site, their LCC comprising the construction costs and seismic losses is calculated. Various types of seismic loss considered in this study include the direct... 

Turbochargers are industrial devices that widely are used in aviation, marine and automotive industry. Manufacturing cost and technology of their components vary according to their application fields. One of the most important components of these devices is turbine wheel, which needs to be solid, strong and have a high resistance in critical extraordinary conditions. In these days, it can be seen that superalloys are used remarkably in manufacturing of turbine wheels. When this part of turbine is damaged due to some different reasons, turbine wheel must be quit of circle Process according to repair instructions. In these conditions either turbine must be repaired or replaced by a new one;... 

A numerical simulation of fluid flow in gas condensate wellbore, which annular flow is dominant, is performed. A three fluid model is used for annular two phase flow. The model is based on conservation equations of mass, momentum and energy for gas phase, dispersed phase (droplets) and the film. The friction between phases and with wellbore wall and also mass transfer between phases, which conservation equations rely on them, are considered. Computer programming of obtained system of equations is performed in Matlab. The Reimann method is used for solving our system of hyperbolic equations and simulation is performed for both steady and unsteady state. Transforming system of nonlinear... 

Today, due to a massive increase in accuracy of reservoir characterization models, multiphase flow simulation on real permeability fields faces a serious challenge. Using multiscale methods in reservoir flow simulation of a heterogeneous environment has led to huge speed-up of the simulation. In multiscale methods, instead of replacing a heterogeneous medium by an equivalent homogeneous medium, used in upscaling, the problem is solved on the original resolution. In this thesis, multiscale finite volume method (MSFV) has been used to simulate flow and saturation behavior of a black oil model. Unlike the original multiscale finite volume methods that were unable to solve compressible fluid... 

The mud loss and its impact on the formation play a vital role in the productivity of the formation and the near wellbore area. Despite the importance of the use of mud during the drilling process, one cannot overlook the issues that may be caused by losing mud into the formation. In addition to the formation damage caused by mud loss, the cost associated with such phenomenon and drilling operational issues and challenges has motivated the industry to look into different avenues to resolve the mud loss issue or reduce its impact. Evaluating the impact of such a phenomenon on these issues requires accurate modeling. In this study different models have been developed to evaluate the impact of... 

In petroleum related drilling, Barite particles settling and Barite sag as major problems in drilling wells can potentially impose significant operational issues. In this study, a computational fluid dynamics (CFD) and experimental investigation of Barite settlement in annular space were conducted in both static and dynamic conditions. The Euler-Euler approach was used to model the multiphase flow of solid Barite particles and drilling fluid. In this approach, the momentum lost between phases has been taken into account by means of particle-particle and particle-fluid exchange coefficients. The governing equations were numerically solved using finite volume method by CFD software package... 

Particulates are a group of air pollutants. They can enter the respiratory system by breathing and cause adverse effects on its performance. Also, inhaled drugs, recently have found many applications in the field of drug delivery. Prediction of particle deposition in the lungs during breathing, can provide useful information on the effects of deposited particles on the respiratory system. When a person is exposed to breathable particulates, after a while with completion of a few respiratory cycles, particle deposition rate, reaches a certain amount at the quasi-steady state. A lot of researchers have investigated particle deposition in the lung, but all of them have studied a single... 

Transport phenomena in porous media play important role in many areas of subsurface hydrology, geo-physics, environment, energy and petroleum. The work in the field of numerical modeling of fractured porous media is yet an open area of research. The classic finite element method (FEM) has some limitations in modeling of discontinuities like fracture. FEM mesh should conform with the geometry of the fracture. Presence of fracture imposes discontinuity in pressure field of fluid phases and displacement field of solid phase (rock). To represent the fractures, the extended finite element method (X-FEM) can be used in which the standard finite element approximation of the field variables is... 

This research focuses on determining the optimal base shear coefficient for the design of conventional steel buildings based on the minimization of lifecycle cost (LCC) and associated uncertainties throughout the service life of the building. Current seismic design codes are calibrated based on engineering judgment, acceptable societal risk, or past earthquake experiences. However, technical literature has shown that such calibration does not lead to a design that optimally balances construction costs and seismic damage. As a solution, lifecycle cost-based calibration has been proposed. In this study, the optimal range of the base shear coefficient is determined by minimizing the expected... 

The goal of the present study is to investigate the effect of rejuvenation treatment on microstructure and creep properties of damaged IN738LC superalloy. Virgin alloy was damaged by interrupted creep tests at 926°C and 170 MPa for 100, 200 and 250 hours. The results obtained showed that damaging the virgin alloy by interrupted creep tests resulted in microstructural deterioration (consisting of coarsening of ' precipitates, formation of continuous films of ' on grain boundary regions and formation of transition zone around MC carbides) and, consequently, degradation of creep properties. Rejuvenation treatment was carried out with the purpose of healing the damaged alloy and restoration of... 

This paper develops a novel insight and procedure that includes a variety of algorithms for finding the best solution in a structured multi-agent system with internal communications and a global purpose. In other words, it finds the optimal communication structure among agents and the optimal policy in this structure. First, a unique reinforcement learning algorithm is proposed to find the optimal policy of each agent in a fixed structure with non-linear function approximation like artificial neural networks (ANN) and eligibility traces. Secondly, a mechanism is presented to perform self-organization based on the information of the learned policy. Finally, an algorithm that can discover an...