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    Evaluating Impact of Erasure Codes on Performance and Endurance of SSD-Based RAID Array

    , M.Sc. Thesis Sharif University of Technology Delavari, Ziba (Author) ; Asadi, Hossein (Supervisor)
    Abstract
    Performance and reliability are the major concerns in design of data storage systems. Using Redundant Array of Independent Disks (RAID) can enhance both performance and reliability. A commonly used configuration in RAID arrays is erasure codes to further enhance system reliability. Due to promising advantages of Solid-State Drives (SSDs)such as low power, shock resistance, and high I/O performance, designers have been encouraged to replace Hard Disk Drives (HDDs) by SSDs in RAID arrays. SSDs, however, suffer from limited endurance due to erase-before-write operation.In this thesis, we investigate the effect of stripe unite size and the number of disks of a RAID array on the endurance of SSDs... 

    Synthesis and Evaluation of Molybdenum Disulfide for Combined Photothermal-chemo Therapy

    , Ph.D. Dissertation Sharif University of Technology Salimi, Marzieh (Author) ; Vosoughi, Manouchehr (Supervisor) ; Shokrgozar, Mohammad Ali (Supervisor) ; Delavari, Hamid (Co-Supervisor)
    Abstract
    New methods of cancer treatment are always the attention of researchers all over the world, among which the photothermal treatment method is of particular importance. In addition to being easy, this treatment method has the least invasiveness. Studies have shown that combining this method with other methods such as chemotherapy not only can be very effective in destroying tumor tissue, but can significantly reduce the side effects of chemotherapy drugs.In order to apply the photothermal treatment method, an effective photothermal agent is needed. Molybdenum disulfide nanosheets have performed successfully in this field, which have been of great interest, due to their high efficiency in... 

    Study of the Static and Dynamic Behaviour of Tieback Walls

    , M.Sc. Thesis Sharif University of Technology Sasar, Mohammad Hassan (Author) ; Haeri, Mohsen (Supervisor)
    Abstract
    The commercially available finite element software, FLAC, was used to provide better understanding of the static and dynamic behavior of tieback and anchored walls. Many of the codes dealing with the design of these structures use empirical methods to estimate the amount of deformation under static conditions. Therefore, in terms of static behavior, this thesis mainly focuses on the deformation patterns of the wall and the retained soil. Mohr-Coulomb elasto-plastic constitutive model was used; however, in elastic part the nonlinear Duncan-Change was implemented. The efforts made for better representation of soil behavior resulted in the suggestion of a modification to Duncan-Chang’s... 

    Seismic Response of “Karroon III” DAM to Non-Uniform Ground Motions

    , M.Sc. Thesis Sharif University of Technology Pouya, Mohammad Reza (Author) ; Ghaemian, Mohsen (Supervisor)
    Abstract
    Usually in analysis of arch dams, applied seismic motions on dam-foundation interface are assumed to be uniform. This is while that recorded motions show non-uniform accelerations in dam-foundation interface. Analyzing of the dam under this non-uniform accelerations we can find the importance of this assumption in analysis of arch dams. Two earthquakes were excited “KAROON III” dam at 20.11.2007 and 21.11.2007. The respective motions were recorded by the array of accelerometers that has been installed on the dam. The recorded motions, indicated non-uniformity of excitations in accelerometers were installed near the dam-foundation interface. Therefore this data provided an opportunity to... 

    Nonlinear Vibration Analysis of Circular Microplate Based on Strain Gradient Theory

    , M.Sc. Thesis Sharif University of Technology Faghihi, Mohammad Amin (Author) ; Asghari, Mohsen (Supervisor)
    Abstract
    Nowadays the combination of mechanical and electronic systems in small scales is gaining attention. Micro electro-mechanical systems are widely used in various industries such as car manufacturing and electronic chips. In these devices, the most important and useful mechanical structures are beams and plates. Therefore, investigating the mechanical properties of these structures in very small scales (micro and nano) is of great importance. Decreasing the size to these scales leads to the dependence of the behavior of these structures to size. Accordingly, some theories for prediction of these behaviors have been presented, one of which is the strain gradient theory. This theory is used in... 

    Nonlinear Dynamic Analysis of Earth and Rockfill Dams Using the Finite Difference Method Considering the Effect of Vertical Earthquake Component

    , M.Sc. Thesis Sharif University of Technology Babaee, Mohammad Saeed (Author) ; Haeri, Mohsen (Supervisor)
    Abstract
    Earth and rockfill dams are enormous three-dimensional structures constructed from earth and rockfill materials. They are mainly built for water supply, agricultural land irrigation, electricity generation, and flood control. Earthquake is one of the most significant natural hazards affecting the stability of these dams. Nowadays, with the development of computers and software, the seismic behavior of most dams are assessed by dynamic analysis. In a considerable part of technical literature, dynamic analysis of earth and rockfill dams have been performed by applying only the horizontal component of the earthquakes, and the effects of vertical component of the earthquakes have often been... 

    Application of Data Mining Methods in Operation Theater Scheduling for Elective Patients

    , M.Sc. Thesis Sharif University of Technology Ahmadian, Mohammad Amin (Author) ; Varmazyar, Mohsen (Supervisor)
    Abstract
    According to the growing population and the need to make optimal use of available resources, the discussion of planning and scheduling in healthcare will be useful. One of the most expensive and lucrative sections in a hospital, which always spends a large percentage of renewable and non-renewable resources, is the Operating rooms (ORs). These ORs are the most important part of the hospital in terms of health and financial issues. In these scheduling problems, in order to be able to model the real situation, we needed to consider the recovery section integrated with the ORs. Also, the duration of surgery and stay in the recovery rooms are considered stochastic. In this study, we solve the... 

    Investigation of Modeling Arterial Tissue Growth and Remodeling Under Biaxial Loading Conditions

    , M.Sc. Thesis Sharif University of Technology Badiee, Mohammad Mehdi (Author) ; Asghari, Mohsen (Supervisor)
    Abstract
    Cardiovascular diseases are one of the leading causes of death in the world. Identifying the mechanical behavior of arteries and their growth and remodeling under applied loadings can help to better understand the progression of the disease and provide more effective clinical interventions. Therefore, many researchers in recent decades have turned their attention to modeling the process of stress-mediated growth and remodeling in soft tissues. Among the most important models proposed to study this process are the constrained mixture model proposed by Humphrey et al. and the volumetric growth model proposed by Hoger et al.. The constrained mixture model is based on the continuous turnover of... 

    Operating Theater Scheduling under Uncertainty with Machine Learning-Based Optimization Approach

    , M.Sc. Thesis Sharif University of Technology Rasouli, Mohammad Reza (Author) ; Varmazyar, Mohsen (Supervisor)
    Abstract
    Surgery theaters are one of the most important and expensive departments in hospitals. Since the operating theaters are connected with other departments, improving the efficiency in the operating theaters can affect other departments as well, so effective and efficient planning and scheduling of the operating theater It is necessary. In this research, we study and investigate the problem of planning and scheduling surgery theaters under the uncertainty of surgery duration, considering the open scheduling strategy and having the list of patients and limited resources after surgery. Let's say that the parameter of the duration of surgery is uncertain and we have little data about it. Some... 

    Adaptive second-order fractional sliding mode control with application to water tanks level control

    , Article Fractional Calculus: Applications ; 2015 , Pages 149-163 ; 9781634632331 (ISBN)9781634632218 (ISBN) Senejohnny, D ; Faieghi, M ; Delavari, H ; Sharif University of Technology
    Nova Science Publishers, Inc  2015
    Abstract
    Combining the fractional calculus with second-order sliding mode control,a novel type of control strategycalled second order fractional sliding mode control is introduced for a class of nonlinear dynamical systemssubject to uncertainty. A fractional-order switching manifold is proposed and the corresponding control law isformulated based on the Lyapunov stability theory to guarantee the sliding condition. A novel adaptation algorithm is derived to ensure perfect tracking, diminish chattering effect and steady state error by estimating switching controller parameters. Finally, numerical simulation results utilizing the dynamic model of interconnected twin tank system are presented to... 

    Fault Diagnosis of Crack Growth in Power Transmission Systems, using Neural Network

    , M.Sc. Thesis Sharif University of Technology Delavari, Mohammad Mohsen (Author) ; Selk Ghafari, Ali (Supervisor) ; Khayyat, Amir Ali Akbar ($item.subfieldsMap.e)
    Abstract
    Nowadays, industrial companies deal with a wide range of serious problems in the field of power transmission maintenance and also fault detection. A large amount of money and time is spent on these issues in order to solve them; consequently, there is an essential need for this subject. In this thesis, in order to tackle those major issues which were referred above, an artificial neural network is trained with only one hidden layer. Also, a suitable database for training an efficient neural network is needed. Thus, a one-stage gearbox system with appropriate degrees of freedom is used to set up referred database. In this system, a crack is imposed to a tooth of spur gear with different sizes... 

    Production planning problem with pricing under random yield: CVAR criterion [electronic resource]

    , Article Journal of Systems Science and Systems Engineering ; 2014 Eskandarzadeh, S. (Saman) ; Eshghi, Kourosh ; Modarres Yazdi, Mohammad ; Bahramgiri, Mohsen ; Sharif University of Technology
    Abstract
    In this paper, we address a basic production planning problem with price dependent demand and stochastic yield of production. We use price and target quantity as decision variables to lower the risk of low yield. The value of risk control becomes more important especially for products with short life cycle. This is because, the profit implications of low yield might be unbearable in the short run. We apply Conditional Value at Risk (CVaR) to model the risk. CVaR measure is a coherent risk measure and thereby having nice conceptual and mathematical underpinnings. It is also widely used in practice. We consider the problem under general demand function and general distribution function of... 

    The Effect of Hot and Cold Rolling on Microstructure and Mechanical Properties of Al-Mg6

    , M.Sc. Thesis Sharif University of Technology Mostafaei, Mohammad Ali (Author) ; Kazeminezhad, Mohsen (Supervisor)
    Abstract
    In this research, a comprehensive examination on hot and cold deformation of Al-Mg6 alloy has been performed. In order to find out hot deformation behavior of Al-Mg6, hot compression tests at 350, 450, and 550 oC and at strain rates of 0.001, 0.1, and 1 s-1 have been carried out. After the correction of the curves due to friction and adiabatic heating effects, constitutive equation of this alloy has been derived. Corrected curves show the occurrence of dynamic recovery. A new method for developing strain dependent constitutive equation has been employed using normalized stress and strain curve. After normalization, the curves at all deformation conditions follow a similar behavior.Rolling of... 

    , Ph.D. Dissertation Sharif University of Technology Farshidi, Mohammad Hassan (Author) ; Kazeminezhad, Mohsen (Supervisor)
    Abstract
    The aim of this study was improvement of mechanical properties and grain refinem ent of aluminum 6061 alloy tubes by combining pre and post heat treatments with Tube Channel Pre ssing (TC P) as a new severe plastic deformation process. For this purpose , the effect of geometr i cal parameters of TCP on deformation behavior was studied at first. Then , the effect of pre and post heat treatments on mechanical properties improvement and micro structure was invest i gated. Finally, the effect of TCP process on mechanical properties improvement and grain refinement was considered. Results show that the mandrel design must follow die design in TCP. As an illustration ,... 

    Mechanical Formulation for Pre-twisted Micro/Nano Beams Based on the Strain Gradient Theory

    , M.Sc. Thesis Sharif University of Technology Javadi Sigaroudi, Mohammad Javad (Author) ; Asghari, Mohsen (Supervisor)
    Abstract
    One of the extensively used, yet complex, structures in the industry is pre-twisted Micro/Nano beams. Studying their mechanical behavior helps to have a broader view of them. In this present study, explores and analyzes the behavior of a pre-twisted Micro/Nano beam with a quadrangular/rectangular cross-section using the strain gradient theory and modified couple stress theory. Using the calculus of variations and the Hamiltonian principle the elastodynamics governing partial differential equations of transverse deflection of the pre-twisted Micro/Nano beam with hinged-hinged boundary conditions are derived. Then the mechanical behavior of the pre-twisted Micro/Nano beam in static mode and... 

    The Effect of Ultra-rapid Annealing on Microstructure and Mechanical Properties of Severely Deformed Low-carbon Steel

    , Ph.D. Dissertation Sharif University of Technology Mostafaei, Mohammad Ali (Author) ; Kazeminezhad, Mohsen (Supervisor)
    Abstract
    Severe plastic deformation (SPD) can refine microstructure of steel and increase its strain energy. Ultra-rapid annealing (URA) influences on the temperature and kinetics of recrystallization and transformation, and causes to improve the mechanical properties of steel. In this research, low-carbon steel with the average grain size of 80 μm was subjected to SPD using 2 passes of constrained groove pressing (CGP) method and its grains size is reduced to 30 μm. Ultra-rapid annealing with the reference heating rate of 200 oC/s was performed on SPDed steel up to subcritical and intercritical temperature ranges. Other heating rates of 75 oC/s to 1800 oC/s were performed for further examinations.... 

    Flow Pattern Prediction in iPWR SMR with Natural Circulation by Coupling of RELAP and ANSYS CFX Code

    , M.Sc. Thesis Sharif University of Technology Emampour, Mohammad Hassan (Author) ; Ghafari, Mohsen (Supervisor)
    Abstract
    Selection of appropriate thermohydraulic tool for analyzing nuclear reactors is a trade of between accuracy and calculation run-time. Nuclear reactors analyses perform on two levels including system and sub-channel. In this regard or the system codes' one-dimensional approach is selected or the CFD codes for considering the three-dimensional and non-equilibrium phenomenon are employed. In this research a T-H tool for prediction of light-water cooled reactors core is developed. Although this code requires lower CPU and run-time in comparison with CFD codes, in contrast with system codes can report non-equilibrium and three-dimensional phenomenon. This code has a modular implementation based... 

    A simple model for the size and shape dependent Curie temperature of freestanding Ni and Fe nanoparticles based on the average coordination number and atomic cohesive energy

    , Article Chemical Physics ; Volume 383, Issue 1-3 , 2011 , Pages 1-5 ; 03010104 (ISSN) Delavari, H ; Madaah Hosseini, H ; Simchi, A ; Sharif University of Technology
    2011
    Abstract
    To study the effect of size and shape of metallic nanoparticle on their Curie temperature, an analytical model is proposed. The core average coordination number (CAC) and surface average coordination number (SAC) of freestanding nanoparticles are considered in the model. Clusters of icosahedral (IC) and body centred cubic (BCC) structure without any vacancies and defects are modelled. A critical Curie temperature is introduced for metallic clusters with a diameter of 2-3 nm. This critical diameter is related to clusters which the ratio of surface atoms to total atoms is about 50%. The "shape effect" is shown to be important at sizes less than 20 nm. The obtained results are supported by... 

    Experimental and Modeling Study of Controlled Salinity Water Injection for Enhanced Oil Recovery from one of Iranial Oil Reservoirs

    , M.Sc. Thesis Sharif University of Technology Shojaei, Mohammad Javad (Author) ; Ghazanfari, Mohammad Hossein (Supervisor) ; Masihi, Mohsen (Co-Advisor)
    Abstract
    From previous years, water injection was considered as one of the most common methods for enhanced oil recovery. But recently much attention has been paid on the use of low salinity water (LSW) as an enhanced oil recovery fluid. The main mechanism that causes improve oil recovery is wettability alteration to a more water wet state. The change observed in recovery factor during LSW flooding induced from changes in relative permeability and capillary pressure when different levels of salinity are used. However, a few researchers tried to evaluate how macroscopic flow functions depend on the salinity of injected water. To this end, a series oil displacements by water performed on sandstone rock... 

    Investigation of Carbon Nanotube-Polymer Composites Thermal Conductivity Using Molecular Dynamics Simulations

    , Ph.D. Dissertation Sharif University of Technology Gharib-Zahedi, Mohammad Reza (Author) ; Tafazzoli, Mohsen (Supervisor) ; Alaghemandi, Mohammad (Co-Advisor)
    Abstract
    In the present research, we have applied reverse non-equilibrium molecular dynamics (RNEMD) to investigate the thermal conductivity (λ) of carbon nanotube (CNT) bundles, CNT-polyamide (PA) nanocomposites, and nanoconfined PA in the vicinity of graphene layers. First, transversal heat transport in CNT bundles with and without intertube chemical bonds are examined. It is found that the transversal λ of samples with cross linkers can surprisingly increase ~9 times than that of neat CNT bundles (0.26 W m-1K-1). According to the simulation results, key parameters are overlapping vibrational density of state (DOS) profiles between the atoms forming the bridging units, cross linker in the direction...