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    Simplified Methods to Estimate the Response of Non-linear Soil-structure Interaction Systems

    , M.Sc. Thesis Sharif University of Technology Bahador, Hossein (Author) ; Ghannad, Mohammad Ali (Supervisor)
    Abstract
    Usually the structures are designed based on the fixed-base assumption; however thisassumption is not always correct and the bed flexibility should be considered. This effectwhich is called soil-structure interaction, change the response of structure on both elasticand inelastic behavior. In the regulations for the design of structures on flexible base,generally soil-structure system is replaced with an equivalent fixed base structure; in theway that the design force of soil-structure system with reasonable accuracy can beestimated by equivalent fixed-base structure. In some regulations, dynamic characteristicsof equivalent structure have been determined on elastic state and the results have... 

    Damage Detection of Offshore Jacket Platforms Using Fitting Vibration Data

    , M.Sc. Thesis Sharif University of Technology Bahador, Mohammad Mahdi (Author) ; Ali Akbar, Golafshani (Supervisor)
    Abstract
    In the regard of structural health monitoring the identification of the structural modal parameters is essential. Since the different sources (wind, waves, Devices …) induce vibration on an offshore platform, it is impossible to determine the portion of each source in vibration. Thus the methods that analyze vibrations needless of input measurements are more efficient. These methods apply the ambient factors and obtain the modal properties from the structural response. This procedure has no unwanted effect on the serviceability of structure and by placement of sensors on the platform; one can monitor the structural health.
    In the present work a two dimensional jacket offshore platform... 

    Reliability of slope stability analysis using fuzzy set

    , Article Annual Conference of the Canadian Society for Civil Engineering 2007: Where the Road Ends, Ingenuity Begins, Yellowknife, NT, 6 June 2007 through 9 June 2007 ; Volume 1 , 2007 , Pages 11-20 Bahador, M ; Sharif University of Technology
    2007
    Abstract
    In this research, theory of fuzzy sets is used to deal with the uncertain nature of soil parameters and the inaccuracy involved in the analysis simultaneously. Soil parameters are defined using suitable fuzzy sets and the uncertainty inherent in the value of factor of safety is assessed. It is believed that this approach accounts for the uncertainty in soil parameters more realistically compared to the conventional probabilistic approaches reported in the literature. The proposed method is applied to a case study and the results are discussed subsequently  

    Small-strain shear modulus of cement-admixed kaolinite

    , Article Geotechnical and Geological Engineering ; Volume 30, Issue 1 , Oct , 2012 , Pages 163-171 ; 09603182 (ISSN) Bahador, M ; Pak, A ; Sharif University of Technology
    2012
    Abstract
    An experimental study is conducted to measure small-strain shear modulus of clay-cement mixture using bender element apparatus setup in a triaxial cell. Bender element tests were conducted on cement-treated soils and the results were analyzed to study the variation of shear modulus properties of soil specimens at different cement contents, confining pressures, curing times, and compaction moisture contents. Based on the obtained results increasing the cement ratio has a significant effect on the small-strain shear modulus of the treated soils, and this effect signifies with increasing the moisture content and curing time. Rates of shear modulus enhancements due to cement content, curing... 

    Waveform Design for Joint Radar-Communication Systems

    , Ph.D. Dissertation Sharif University of Technology Rezaei, Omid (Author) ; Nayebi, Mohammad Mahdi (Supervisor) ; Naghsh, Mohammad Mahdi (Co-Supervisor) ; Karbasi, Mohammad (Co-Supervisor)
    Abstract
    The integration of radar and communication functionalities into a unified Joint Radar-Communication (JRC) system offers enhanced spectral efficiency and reduced hardware complexity. Recognized as a key enabler for next-generation wireless networks, JRC systems require a careful balance between radar and communication demands, where waveform design plays a pivotal role in achieving this equilibrium. Although waveform design has been extensively studied separately in radar and communication domains, the requirements of modern networks necessitate a unified approach that simultaneously addresses the needs of both systems. This thesis advances waveform design methodologies for JRC systems,... 

    Radar Target Parameter Estimation Using Frequency and Space Diversity

    , Ph.D. Dissertation Sharif University of Technology Sebt, Mohammad Ali (Author) ; Nayebi, Mohammad Mahdi (Supervisor)
    Abstract
    In this dissertation, the application of frequency and space diversities in radar target parameter estimation are investigated. On this basis, multi-frequency signal is used to improve the range resolution, array structure is used to increase the angle estimation accuracy and the merger of the multi-frequency signal and array structure are used to increase the maximum number of targets that can be uniquely identified.Considering the desirable properties of multi-frequency signals such as high bandwidth efficiency, high range resolution achievement without chip length decrease and …, there has been increased interest in the vast area of research on the design of such signals that has... 

    Using the Echo of Rotating Parts to Recognize a Radar Target

    , M.Sc. Thesis Sharif University of Technology Johari, Mohammad Mahdi (Author) ; Nayebi, Mohammad Mahdi (Supervisor)
    Abstract
    Target recognition techniques based on micro Doppler phenomenon are popular because they are applicable even on low resolution radars, in contrast to other techniques such as High Resolution Range Profile (HRRP) which need high resolution in range or angle. Usually, main purpose of such techniques is generating robust features against target initial state, velocity, aspect angle, etc. rather than features which exactly identify a target. Main approaches in the literature are based on time-frequency transforms (TFT) such as spectrogram in order to generate features to classify targets, but in this thesis, we propose a totally different method using Recurrence Plot for generating features... 

    Numerical Analysis of Mechanized Tunneling Effects in Different Conditions on Internal Forces and Settlement of Superstructures

    , M.Sc. Thesis Sharif University of Technology Shirazi, Mohammad Hassan (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Abstract
    In this research with Finite Element Methods in ABAQUS, numerical modeling has done in three-dimensions, which can be used to determine the effect of different factors on the surface settlement. Also, various factors such as geotechnical conditions, tunnel diameter,tunnel depth, the impact of the thickness of the segments and the amount of eccentricity of the structure relative to the longitudinal axis of the tunnel considered in this study. Face Pressure Supports, and Grout Injection Pressures are taken into account, too.Tunnel drilling causes a change in the displacement area and creates a changing zone around the tunnel. In this regard, not only adjacent buildings will be affected by... 

    Design and Implementation of Proton Precession Magnetometer

    , M.Sc. Thesis Sharif University of Technology Kamrani, Mohammad Hamed (Author) ; Fardmanesh, Mahdi (Supervisor)
    Abstract
    Proton precession magnetometers are one of the most sensitive scalar magnetic sensors. Their function is based on Zeeman effect and also nuclear magnetic resonance phenomena. In this project we have designed and implemented needed coils, swithching and signal detection circuits. Because of extremely high sensitivity of this sensor to induced noises and also gradient of earth’s magnetic fileld, detection of precession signal needs design of low noise electronic circuits with special EMC considerations. The implemented system in this project contains different blocks, such as switching circuit and its related control unit, amplifier, filter and frequency meter. Using this system, the obtained... 

    Positivity Bounds on Effective Field Theories: Galileon Theories as a Case Study

    , M.Sc. Thesis Sharif University of Technology Jalali, Mohammad Hossein (Author) ; Torabian, Mahdi (Supervisor)
    Abstract
    Effective field theory is a practical method for model building and explaining experimental/observational data. These theories are constructed based on knowing low energy degrees of freedom and symmetries (accidental or fundamental). By construction, these theories are applicable up to a cut-off scale and their predictions beyond that are not reliable. For applications to higher energies a UV completion is needed through which modifications are applied or new heavy degrees of freedom are introduced. In order to complete a theory in a Wilsonian approach, scattering amplitudes must satisfy some constraints. These constraints are derived from basic assumptions like Lorentz invariance,... 

    Numerical Study of Pile Behavior under Seismic Loading

    , M.Sc. Thesis Sharif University of Technology Mashinchian, Mohammad Javad (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Abstract
    Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of... 

    Identifying and Ranking Factors Affecting High Rise Concrete Construction Productivity (Study Current Situation and Strategies to Improve productivity)

    , M.Sc. Thesis Sharif University of Technology Mostavi, Amir (Author) ; Mortaheb, Mohammad Mahdi (Supervisor)
    Abstract
    The current global economy challenges and the importance of maintaining a sustainable development strategy has increasingly bolded the importance of construction productivity measures. This research describes the results of a running research that is to find the most critical factors affecting the productivity of high rise concrete building projects in developing countries. To achieve that, we have conducted Delphi method in two phases. In the first phase we had a brainstorming program with construction experts from owner organizations, construction contractors and designing engineers to identify factors that have influenced productivity in recent concrete building construction projects.50... 

    Multi-period Value-at-Risk Forecasting

    , M.Sc. Thesis Sharif University of Technology Rezaei, Mohammad Hosein (Author) ; Barakchian, Mahdi (Supervisor)
    Abstract
    Multi-period Value-at-Risk (VaR) forecasting is important for risk management. Financial institutions especially commercial banks according to Basel Committee regulations for capital adequacy in “Internal Approach”, should forecast their VaR for multi-period horizons (longer than one day). The most conventional approach for forecasting multi-period VaR is scaling one-day forecasted VaR that is called “square root of time rule”; therefore most works in this area have been focused on forecasting one-day VaR. In this study, we review performance of a wide range of different methods in forecasting multi-period VaR. The results of our study show that historical simulation performs weakly in... 

    Beamforming Through Array Thinning

    , M.Sc. Thesis Sharif University of Technology Tohidi, Ehsan (Author) ; Nayebi, Mohammad Mahdi (Supervisor)
    Abstract
    Modern communication and space systems such as satellite communication devices, radars, SAR and radio astronomy interferometers are realized with large antenna arrays since this kind of radiating systems are able to generate radiation patterns with high directivity and resolution. In such a framework, conventional arrays with uniform inter-element spacing could be not satisfactory in terms of costs and dimensions. An interesting alternative is to reduce the array elements obtaining the so called ‘ thinned arrays’. Large thinned arrays have been exploited because of their advantages in terms of weight,consumption, hardware complexity, and cost over the... 

    Effects of Soil-Pile-Structure Interaction on the Seismic Response of a Bridges

    , M.Sc. Thesis Sharif University of Technology Tamaddoni, Nima (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Abstract
    A large number of structures subjected to the seismic loading have been damaged or have experienced failure in different parts such as the pile structure or even in the entire structure due to unanticipated effects of the soil-pile-structure interaction.The complexity of problems regarding the soil-pile-structure interaction is an influencing factor in prediction of the behavior of structure during the earthquakes. In this study, the effect of the interaction on the dynamic response of bridges was investigated using the finite element software ABAQUS. The primary purpose of this study, as previously described, is to study the effects of the soil-structure interaction on a bridge located on a... 

    Fully Homomorphic Encryption Implementation

    , M.Sc. Thesis Sharif University of Technology Heydarian, Mohammad Javad (Author) ; Shabany, Mahdi (Supervisor)
    Abstract
    After being introduced in 2009, the first fully homomorphic encryption (FHE) scheme has created significant excitement in academia and industry. Despite rapid advances in the last 6 years, FHE schemes are still not ready for deployment due to an efficiency bottleneck. Here we introduce a hardware/software codesign, in fact a hardware accelerator optimized for a class of reconfigurable logic to bring homomorphic encryption schemes one step closer to deployment in real-life applications. The accelerator we present is connected via a fast PCIe interface to a CPU platform to provide homomorphic evaluation services to any application that needs to support blinde computations. Specifically we... 

    Application of Adaptive Neural Network Systems in Controller Design of Nonlinear Processes

    , M.Sc. Thesis Sharif University of Technology Talkhoncheh, Mahdi Khajeh (Author) ; Shahrokhi, Mohammad (Supervisor)
    Abstract
    In this project design of adaptive neural network controller for uncertain nonlinear systems in the presence of different restrictions has been investigated. After providing introduction and motivation, two general forms of nonlinear systems including strict- feedback and pure- feedback have been introduced. In order to solve the problem caused by each restriction, a solution has been proposed. For the strict- feedback nonlinear systems several restrictions are considered such as, unknown dynamic model, unmeasured state, input saturation, unknown control directions, time delays in states and input. Stability analysis based on the Lyapunov theorem has been established. In addition, two kinds... 

    A Numerical Study of Train-induced Vibration and the Screening Effectiveness of Shredded-tire-Infilled Trenches

    , M.Sc. Thesis Sharif University of Technology Koocheki, Kianoosh (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Abstract
    Train-induced vibrations can disturb the residential areas close to the rail as well as making ground-borne noises that can create problems for sensitive apparatus and devices. To reduce these problems, there need to be an evaluation of the amplitude of the ground-borne vibrations. The goal in this study is creating a suitable finite difference model in order to predict the intensity of train induced vibrations propagating inside or on the surface of the soil using FLAC (Fast Lagrangian Analysis of Continua) software as well as assessing the effectiveness of recycled shredded tires in reducing the surface vibrations by using these material as the filler for vibration isolation trenches. The... 

    Numerical Modeling of the Bearing Capacity of Suction Caisson by Finite Element Method

    , M.Sc. Thesis Sharif University of Technology Hejazian, Maryam (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Abstract
    Suction caisson is a relatively new technology which was introduced about 30 years ago for the first time and after several investigations, was found its position in the oil industry and construction of anchorages, during previous decade. So nowadays, it is the most effective and economical choice as the mooring of offshore structures in comparison with the other foundations. Suction caisson is a hollow cylinder with an open bottom and a closed top. After placement on the seafloor, the caisson first penetrates into the soil by its self weight and then inserts into the ground by pumping water out of it. Although many researchers have attempted to understand the behavior of suction caissons... 

    Optimum Location of Re-closers, and Fault Indicators in a Distribution Network for Improvement of Reliability Parameters

    , M.Sc. Thesis Sharif University of Technology Asghari, Mohammad Omid (Author) ; Vakilian, Mahdi (Supervisor)
    Abstract
    Nowadays, due to the indensible role of electrical energy in life of societies, the reliability of service should be provided in an economic form. Researches has shown that, about 80% of faults occur in the distribution network. In a distribution network that is equipped with automation systems, through the acceleration in the determination of the fault location, and also possibility of reacting against transient and steady faults, the electricity interruption time duration is minimized. This thesis aims to determine the number and to locate the auto reclosers and fault indicators in a distribution network optimally. To make it economically feasible, a limited number of these devices and...