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hassanian--hamed
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Elastic field of a nano disk shape defect in an fcc thin film
, Article 2007 2nd IEEE International Conference on Nano/Micro Engineered and Molecular Systems, IEEE NEMS 2007, Bangkok, 16 January 2007 through 19 January 2007 ; 2007 , Pages 142-146 ; 1424406102 (ISBN) ; 9781424406104 (ISBN) ; Pahlevani, L ; Hamed, E ; Sharif University of Technology
2007
Abstract
In this paper, we develop a theory to study the nano defects of various geometries within thin films. The considered thin films have face centered cubic (fee) structure. The eigenstrain method is combined with the long-range Sutton-Chen (SC) inter-atomic potential function which is appropriate for fee crystals. The disturbance caused by a defect in a thin film is determined from the equilibrium equation using the discrete Fourier transformation. The disturbed field is also determined using three dimensional (3D) Molecular Dynamics (MD) simulation in which the constant NVT ensemble is applied to the atomic system. For illustration, the problem of nano disk shape defect in thin film is studied...
Inclusion problems associated with thin fcc films: linkage between eigenstrain and inter-atomic potential
, Article Mechanics of Materials ; Volume 39, Issue 8 , 2007 , Pages 803-818 ; 01676636 (ISSN) ; Pahlevani, L ; Hamed, E ; Sharif University of Technology
2007
Abstract
Often, during fabrication of thin films on substrates, different types of defects may be introduced into the films. Recently, the determination of the elastic fields due to the self-assembly of quantum dots or strained islands in thin films has been of major concern. In the micromechanical studies, such strained islands are modeled by inclusions. This paper aims to develop a theory pertaining to the presence of nano-inclusions of various geometries within thin films having face centered cubic (fcc) structure. To this end, the notion of eigenstrain is combined with a many body inter-atomic potential suitable for fcc crystals. The interaction between atoms is modeled via Sutton-Chen (SC)...
Development of a New Analytical Model based on Soil-water Retention Curve Microstructure Considering the Effects of Osmotic Potential
, M.Sc. Thesis Sharif University of Technology ; Sadeghi, Hamed (Supervisor)
Abstract
The soil-water retention curves (SWRC) is an unsaturated soil mechanics hydro chemical state surface, which expresses the relationship between the soil suction and water content. The soil-water retention curve could describe the water adsorption and desorption process that happened in soils. The difference between the desorption or drying retention curve and the adsorption or wetting retention curves in a specific soil specimen indicates the hydraulic hysteresis phenomenon. Generally, the amount of water remaining in the drying process is greater than the amount of water adsorbed in the wetting process at a certain amount of suction. Suction due to the combined effects of capillary and...
Optimization Based on Opinion Consensus in Complex Networks
, M.Sc. Thesis Sharif University of Technology ; Jalili, Mahdi (Supervisor)
Abstract
In this thesis a method based on opinion formation in complex networks aiming to solve unconstrained optimization problem has been studied. Unconstrained optimization problem is the problem of searching for the best solution in the solution space. Optimization problems have many applications in various fields that due to advances in data storage and also appearance of new big data applications solving these problems in large scales gained much importance. Different methods have been proposed in order to solve such problems but because of high computational complexity, many of them do not show good performance. A category of methods called stochastic search methods are used to overcome the...
Identification and Analysis of Root Causes of Construction Cost Overruns
, M.Sc. Thesis Sharif University of Technology ; Haj Kazem Kashani, Hamed (Supervisor)
Abstract
Project cost overrun is one of the most frequently occurring issues in the construction industry. Past research studies have investigated the project cost overrun problem from various perspectives. However, to date, only a few studies have focused on the identification of the root causes of projects cost overruns. A close review of these studies reveals that the studies often provide limited insight into the root causes of project cost overrun. These studies fail to consider the impact of project delivery system as a defining project characteristic that may influence construction cost overruns. In addition, past studies have relied on surveys that are not necessarily precise and highly...
Design and Comparison of an Adaptive and Robust Control Strategy to Improve the Boiler-Turbine unit Performance and Reduction of Make-Up Water
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor) ; Vossoughi, Gholamreza (Supervisor)
Abstract
There is many sources of uncertainty in the power plants such as continuous changes of the ambient temperature and the climate condition. The controller of the boiler-turbine unite should be robust against uncertainties and overcome the changes in the operating condition. In this regard, a robust adaptive variable structure control scheme (RAVCS) is proposed to control a nonlinear multi-input multi-output (MIMO) model of industrial boiler-turbine unite, in the presence of unknown parameters and bounded uncertainties as well as external disturbances. Moreover, a robust controller based on and in the presence of rational deviation in parameters, is designed. To investigate the zero...
Comparing the Performance of Several Control Methods on the Air Handling unit in Special Condition
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor) ; Alasti, Aria (Supervisor)
Abstract
Air-handling unit (AHU) is one of the installations that is responsible to control the temperature and humidity inside a space using the heating, cooling, humidifier and drying air. At present, energy efficiency in building is an important issue to maintain the comfort conditions. One of the most common ways to optimize the performance of industrial installations is the use of control systems, which leads to the reduction in both of the costs and energy consumption. In this research, a multivariable nonlinear dynamic model of the AHU with one zone in the VAV (variable air volume) system for working in summer is considered. At first, introduction, limitations and driving the equations for the...
Numerical Simulation of Displacement of the Fluid Phases in Porous Media
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Nowadays, oil has an important role in our life and most of its role can be seen on the transportation. Discovering and extraction of oil are very important to produce oil and receive it to costumer. When oil is discovered, the oil companies used to drill the ground to extract the oil but they can’t extract all of oil from its reservoir. So, researchers proposed to inject another fluid like water to the oil reservoir to extract oil. Oil is trapped in the porous media which has a lot of pores and some of them have a micro scale size and they contain oil. When water is injected to the reservoir it flows in this pore and interfaces with oil and they create a multiphase flow. The governing...
A novel optimization method based on opinion formation in complex networks
, Article 2016 IEEE International Symposium on Circuits and Systems, ISCAS 2016, 22 May 2016 through 25 May 2016 ; Volume 2016-July , 2016 , Pages 882-885 ; 02714310 (ISSN); 9781479953400 (ISBN) ; Jalili, M ; Yu, X ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper we introduce a novel population-based binary optimization technique, which works based on consensus of interacting multi-agent systems. The agents, each associated with an opinion vector, are connected through a network. They can influence each other, and thus their opinions can be updated. The agents work collectively with their neighbors to solve an optimization task. Here we consider a specific opinion update rule and various topologies for the connection network. Our experiments on a number of benchmark non-convex cost functions show that ring topology results in the best performance as compared to others. We also compare the performance of the proposed method with a number...
On the Assessment of a Novel Exemplary Metallic Yielding Damper
,
M.Sc. Thesis
Sharif University of Technology
;
Mofid, Massood
(Supervisor)
;
Khezrzadeh, Hamed
(Co-Advisor)
Abstract
One of the passive control systems that are used widely in today’s buildings are metallic yielding dampers. Metallic yielding dampers by absorbing earthquake input energy, prevent inelastic defromations form in beams and columns. In this research, the behavior of an innovated metallic yielding damper, named pistonic damper is investigated. This damper consists of a number of circular parallel plates with constant or variable thickness that dissipate seismic input energy by flexure yielding in small displacements. at large displacements stress field in plates is changed and this caused the stiffness and strength of damper are increased and show shell behavior. this kind of behavior...
Design and Implementation of a Control System for Stable and Transparent Endoscopic Sinus Surgery Simulator
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor) ; Moradi, Hamed (Supervisor)
Abstract
The main goal of this project is to design and implement an Endoscopic Sinus Surgery Simulator using a nonlinear model relating the force and displacement of the surgery tool interacting with the virtual sinus tissue. This model approximately matches the force-displacement data attained from the experiments conducted on the real sinus tissues. To simulate the behavior of the sinus tissue in a virtual environment, a haptic device is utilized which imitates the behavior of the surgery tool interacting with the tissue model. The haptic device in this project is a Falcon Robot. Because of the uncertainties in the parameters of the robot and the operator’s hand model (which is considered in the...
Design and Implimentation of an Online Robust Model Predictive Controller for Stabilization and Transparency of Sinus Surgery Haptic Simulator
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor) ; Moradi, Hamed (Supervisor)
Abstract
No one bears thinking about undergoing a surgery by an unexpirienced surgeon, the consideration of which implies the prominence of effective surgical trainings. The advent of utilizing haptic interfaces as a novelty in this field has led to a more promising surgery education. These haptic interfaces consist of three communicating parts namely: operator’s hand, haptic robot, and tissue virtual environment. Design and implementation of a proper controller in order to stabilize the haptic interface during surgery simulation, with acceptable transparency, is still novel an otherwise challenging research field. In this thesis we consider an appropriate nonlinear model for both virtual tissue as...
Assessment of Approaches to Economical Definition of Public Infrastructure Projects
, M.Sc. Thesis Sharif University of Technology ; Haj Hazem Kashani, Hamed (Supervisor)
Abstract
In this study, reform strategies to enhance private sector participation in infrastructure projects is provided. The study is presented in the form of words that government institutions could use in the highest level. the pattern used for this study is based on system thinking in which all components are in causal relationship with each other. It was made effort to policies and upstream objectives of the country be respected. To provide research content, content analysis of successful experiences in the world was done. Finally, obtained strategies was presented to the experts, reformed and important cases was investigated. Lack of information and difficult access to country's infrastructure...
Combined Optical flow Algorithm and Simultaneous Localization and Mapping for Localization Robust to Surface Texture Variations
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Gholamreza (Supervisor) ; Moradi, Hamed (Supervisor)
Abstract
The research field of localization with high precision (precision of 10 micrometers) has greatly attracted attentions in recent years. Optical flow sensor is one of the inexpensive solutions for the localization of robot, which have been used in computer mice. The most important application of this thesis is to localize walking micro robot. The main challenge of previous research is the fact that sensor's precision is highly dependent on the surface texture. The aim of this research is to implement an appropriate algorithm on optical flow sensor in order to increase the robustness of sensor's precision to surface texture. In this regard, firstly experimental hardware has been designed and...
Design and Implementation of a Control Strategy to Sustain Postural Stability for a Lower Limb Exoskeleton
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Gholamreza (Supervisor) ; Moradi, Hamed (Supervisor)
Abstract
Nowadays, the developments in control and robotics provide rehabilitation and power augmentation applications for the exoskeleton robots. In the rehabilitation applications, the goal is to help elderly and persons with paraplegia to do their daily activities and movements. One of this applications is to help these individuals for postural stability and recovering balance after receiving perturbations. In this research, we propose a control strategy for a lower limb exoskeleton to help the wearer to recover balance after a perturbation without using crutches. Here, we concentrate on the stance phase when a push is exerted to the robot and try to make the system quite upright. Therefore, a...
A Framework to Assess Effect of Interdependent Infrastructures' Disruption on Operation of Hospital during Natural Disasters
, M.Sc. Thesis Sharif University of Technology ; Haj Kazem Kashani, Hamed (Supervisor)
Abstract
In earthquake-prone communities, the post-earthquake functionality of hospitals is crucial. Hospitals can dramatically reduce earthquake casualties if they can remain functional and retain service continuity. A variety of earthquake-induced problems such as damage to hospital components, unavailability of medical staff, disruption in medicine supply, and failure of supporting infrastructure systems can negatively affect the functionality of a hospital. Hospital administrators and facility managers require appropriate tools to assess the effect of these problems on hospital functionality. This research presents a probabilistic framework to assess the functionality of hospitals following...
Obstacles to Implementation of the FIDIC Contracts in Iran and the Solutions
, M.Sc. Thesis Sharif University of Technology ; Haj Kazem Kashani, Hamed (Supervisor)
Abstract
FIDIC as a proposed model for a contract and including patterns of regular international contract projects. In Iran, many giant construction projects such as petroleum projects, power plants, roads and water networks was signed based on FIDIC contract pattern and These projects have been faced with many challenges .The main challenges for this contract are not ready. Improper translation of the original, traditional look owners to contractors, FIDIC modern approach depends on the project parties (owner - Consulting - contractors), Iran's judicial laws, lack of private land ownership and the absence of allocated budget that indicates the appropriate use of this model contracts in Iran. To...
Modeling and Control of Vibrations in Horizontal Drill String with Coupled Axial and Torsional Vibrations
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor) ; Vossoughi, Gholamreza (Supervisor)
Abstract
Oil and natural gas today are one of the most important sources of human energy supply, so that crude oil Percentage and natural gas provide 25% of the world's energy. Until now, vertical drilling methods have been used to extract oil and gas. In recent years, due to vertical drilling constraints, for extraction and access to places that can not be achieved by vertical drilling, Horizontal drilling has been increased. In horizontal drilling, a variety of vibrations including longitudinal, torsional, and lateral take place. These vibrations, if not controlled, can damage the equipment and the drilling field, as well as reduce the efficiency of the drilling process and increase the process...
Investment Valuation Model for Retrofit of Infrastructure under Uncertainty
, M.Sc. Thesis Sharif University of Technology ; Haj Kazem Kashani, Hamed (Supervisor)
Abstract
Infrastructure systems play a critical role in the economic and social activities of a community. Effective and continuous performance of these infrastructure systems is essential to the welfare and prosperity of the communities. Infrastructure systems comprise networks of interdependent assets that are built through a long and costly process. These assets are subject to a variety of factors that reduce the performance and reliability over time. These factors also increase the vulnerability of infrastructure assets in face of future probable hazards. In order to ensure the continuous and uninterrupted performance of infrastructure assets in post-hazard situations, asset managers should plan...
Model Predictive Control of the Wind Turbines with Uncertainties for the Switching between Operating Regions
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
Through the last decades, due to environmental issues and to confine CO2 emission and also dependency to the fossil fuels, renewable energy resources has been developed. It’s been expected up to 2035, the renewable energy resources will be scaled three times and among those resources, the wind energy will stand prominently. Out of this king of renewable resource, the horizontal wind turbine has been subjected in this research. The focus of is to design the controller in third of a 2 MW turbine operation by which stable rotor speed and nominal output power to be attained. Besides, to enhance the accuracy of the wind turbine profiles, the TURBSIM software (At the National Renewable Energy...