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    Exact Solution for Electrical Impedance Tomography using DSP

    , M.Sc. Thesis Sharif University of Technology Soltani, Farnoosh (Author) ; Vosoughi Vahdat, Bijan (Supervisor)
    There are some problems in calculation of heavy and huge equations which are ill-posed and nonlinear. They need to be solved by the processors. The errors are important in our measurements because this precision is very important in calculation. The Block Method approach solving Forward Problem in Electrical Impedance Tomography (EIT) results produce an exact solution only if the measurements are done with enough accuracy. In this thesis, a 3D model of EIT with Block Method is implemented by means of Digital Signal Processor (DSP) to obtain exact results. In this work it has used a powerful processor called TMS320C6416DSK to reduce the measurement error in equations. It has used Code... 

    Dynamic modelling and control of a sphere-based micro robot with adjustable arm

    , Article MARSS 2018 - International Conference on Manipulation, Automation and Robotics at Small Scales, 4 July 2018 through 8 July 2018 ; 2018 ; 9781538648414 (ISBN) Esfandbod, A ; Nejat Pishkenari, H ; Meghdari, A ; Sharif University of Technology
    In this article, we propose a three-dimensional model of a low-Reynolds-number swimmer that consists of three small spheres connected to a larger sphere via three perpendicular adjustable rods which enable the micro robot to swim along arbitrary trajectories. Then we focus on dynamic modelling of the swimmer and propose a control method to control the position of the micro swimmer in a low Reynolds number flow. The control aim intended in this article is that the middle sphere to follow a desired trajectory and respective simulation results from control indicates successful accomplishment in application. © 2018 IEEE  

    Numerical assessment of new compound restrainer for seismic retrofit of bridges

    , Article Structure and Infrastructure Engineering ; Volume 14, Issue 5 , 2018 , Pages 652-671 ; 15732479 (ISSN) Joghataie, A ; Pahlavan Yali, A ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one... 

    Performance-based assessment of an innovative braced tube system for tall buildings

    , Article Bulletin of Earthquake Engineering ; Volume 16, Issue 2 , February , 2018 , Pages 731-752 ; 1570761X (ISSN) Mohammadi, H ; Toufigh, V ; Golafshani, A. A ; Arzeytoon, A ; Sharif University of Technology
    Springer Netherlands  2018
    In this paper, an innovative seismic lateral force resisting system for tall buildings is introduced. In this system, a novel supplemental part, ribbed bracing system (RBSyst), is attached to Braced Tube System, creating a modified BTS. RBSyst is a supplemental part which is attached to the conventional bracing members to eliminate buckling problem. The behavior of RBSyst under tensile force is similar to that of the conventional braces. However, in compression, it prevents the braces from buckling by length reduction. In order to evaluate the efficiency of this new BTS system by performance- based assessment, two typical 40-story tall buildings with different story modules equipped with... 

    Evaluation the Surface Settlement and Interaction Between Tunnelinline2 and Metro Station Inline1 of Mashhad Metro at Intersection Using 3-D Numerical Modeling

    , M.Sc. Thesis Sharif University of Technology Ghasempour, Hamid (Author) ; Sadaghiani, Mohammad Hossein (Supervisor)
    In this study, the interaction of tunneling of line 2 of Mashhad metro and existing metro station (Shariati station) in line 1 has been investigated. To produce the stress and displacement which is caused by excavation of station, the process of station excavation has been modeled by method of cut and cover.This method is the common method for station construction at Shallow depth and is used in several cases in line 1 of Mashhad metro. The piled-raft system is used in foundation of central part of the station to reduce the settlements and the effects of interactions between the station and new tunnel. The new tunnel under the station is surrounded by two rows of lateral piles with distance... 

    Developing three dimensional potential solver for investigation of propulsion performance of rigid and flexible oscillating foils

    , Article Ocean Engineering ; Volume 147 , 2018 , Pages 121-131 ; 00298018 (ISSN) Abbaspour, M ; Najafi, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Heave and pitch motion of an oscillating airfoil in uniform flow will cause generation of forwarding thrust. Applying a combination of these two motions on flexible foil, one can increase thrust and therefore the efficiency. This is the way that most fishes and other flying animals uses to consume less energy. In this paper, hydrodynamic forces and efficiency of an oscillating airfoil is investigated. A code is developed based on potential flow formulation in combination with Time Stepping Method (TSM) with nonlinear free shear layer dynamic approach to predict the wake behind the lifting bodies. A linear Morino type Kutta condition has been implemented on panels adjacent to trailing edge.... 

    Feasibility of infrared tracking of beating heart motion for robotic assisted beating heart surgery

    , Article International Journal of Medical Robotics and Computer Assisted Surgery ; Volume 14, Issue 1 , February , 2018 ; 14785951 (ISSN) Mansouri, S ; Farahmand, F ; Vossoughi, G ; Ghavidel, A. A ; Rezayat, M ; Sharif University of Technology
    John Wiley and Sons Ltd  2018
    Background: Accurate tracking of the heart surface motion is a major requirement for robot assisted beating heart surgery. Method: The feasibility of a stereo infrared tracking system for measuring the free beating heart motion was investigated by experiments on a heart motion simulator, as well as model surgery on a dog. Results: Simulator experiments revealed a high tracking accuracy (81 μm root mean square error) when the capturing times were synchronized and the tracker pointed at the target from a 100 cm distance. The animal experiment revealed the applicability of the infrared tracker with passive markers in practical heart surgery conditions. Conclusion: With the current technology,... 

    Two-Stage Axial Compressor Design Software

    , M.Sc. Thesis Sharif University of Technology Peyvan, Ahmad (Author) ; Hajilou Benisi, Ali (Supervisor)
    Axial-flow compressor is one of the most basic components of gas turbine engines. Consequently, it is essential to design this machine appropriately. Full three dimensional analyses of axial-flow compressors is time consuming due to the flow field complexity, so a method with minimum running time and producing an acceptable design is required. One dimensional design method is a low cost procedure with acceptable results for preliminary stages of design. It receives inlet flow conditions, such as total pressure ratio, mass flow and rotational speed and designs a compressor which satisfies the desired input data. Too many efforts have been accomplished to predict energy losses, design... 

    Towards simulation of 3D nonlinear high-speed vessels motion

    , Article Ocean Engineering ; Volume 36, Issue 3-4 , 2009 , Pages 256-265 ; 00298018 (ISSN) Panahi, R ; Jahanbakhsh, E ; Seif, M. S ; Sharif University of Technology
    A numerical simulation algorithm based on the finite volume discretisation is presented for analyzing ship motions. The algorithm employs a fractional step method to deal with the coupling between the pressure and velocity fields. The free surface capturing is fulfilled by using a volume of fluid method in which the interface between the liquid (water) and gas (air) phases are computed by solving a scalar transport equation for the volume fraction of the liquid phase. The computed velocity field is employed to evaluate the acting forces and moments on the vessel. Using the strategy of boundary-fitted body-attached mesh and calculating all six degrees-of-freedom of motion in each time step,... 

    Evaluation of dike-type causeway impacts on the flow and salinity regimes in Urmia Lake, Iran

    , Article Journal of Great Lakes Research ; Volume 35, Issue 1 , 2009 , Pages 13-22 ; 03801330 (ISSN) Zeinoddini, M ; Tofighi, M. A ; Vafaee, F ; Sharif University of Technology
    Urmia Lake, located in a closed basin in north-west Iran, is the largest lake (5000-6000 km2) in the Middle East. It is very saline with total dissolved salts reaching 200 g/l compared with a normal seawater salinity of about 35 g/l. The construction of a causeway, which was initiated in 1979 but then abandoned until the early 2000s, is near completion and will provide road access between the western and eastern provinces. The causeway has an opening 1.25 km long and divides Urmia Lake into a northern and southern basin and restricts water exchange. The flow and salinity regimes are affected by the presence of this new causeway, and there are concerns over the well being of the Artemia... 

    The Behavior of Supporting Structures with Pretension Anchors by Geotechnical Softwares

    , M.Sc. Thesis Sharif University of Technology Ahmadi, Alireza (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    In recent years, due to urban expansion and population growth, number of floors and excavations depth has increased. Stabilization of excavations is one of the most important issues in geotechnical engineering. Today, one of the most widely used methods that is used in deep excavations is brace soil by steels and pretension them. In this thesis tries to evaluate static behavior of flexible supporting structures with pretension anchors by using PLAXIS2D, FLAC3D and GEOSTUDIO softwares. The objective of this modeling is better understanding the static behavior of walls, comparing the two and three dimensional modeling and the effect of corners of excavation on deformation. The results shows... 

    Shaking table test of a 1: 2.35 scale 4-story building constructed with a 3D panel system

    , Article Scientia Iranica ; Volume 16, Issue 3 , 2009 , Pages 199-215 ; 10263098 (ISSN) Rezaifar, O ; Zaman Kabir, M ; Bakhshi, A ; Sharif University of Technology
    The seismic behaviour of a 4-story building is investigated under horizontal excitation of simulated earthquakes. The model has been constructed with a 3D sandwich panel system without any conventional frame system in four storeys on a shaking table. The building has been modelled before construction. Due to the table limit, the scale factor of the model is chosen as 1: 2.35 of a prototype. The shaking table test of the scaled model of the building is carried out under several ground motions to verify the safety of the system. The simulated motions were applied to the model in two-perpendicular directions, simultaneously. The failure mechanism and dynamic behaviour of the model, as a... 

    3D model for evaluation of pollutant concentration distributions from land-based sources of the Caspian Sea region - Regional study, southern part of the Caspian Sea

    , Article Journal of Environmental Informatics ; Volume 14, Issue 1 , 2009 , Pages 51-65 ; 17262135 (ISSN) Abbaspour, M ; Nobakhti, M. H ; Sharif University of Technology
    An unstructured grid, finite-volume, and three-dimensional (3D) primitive equation ocean model has been developed to predict oceanic pollutant dispersions in depth and surface of the Caspian Sea for non-chemical reactions of dissolved constituents. The model consists of momentum, continuity, temperature, salinity, and density equations. Physical and mathematical closure has been achieved using Mellor and Yamada turbulent closure sub-models. Since determining a practical definition of salinity that enjoys acceptable accuracy is difficult; therefore, various definitions have been used in this work. A recent definition of salinity stated in the UNESCO Practical Salinity Scale of 1978, PSS78,... 

    Parametric Analysis of Interaction Between Crossing Tunnels at Different Level

    , M.Sc. Thesis Sharif University of Technology Tohidi, Amin (Author) ; Sadagiani, Mohammad Hossein (Supervisor)
    Sensibility of parameters that influence the Interaction between crossing tunnel at different level such as Soil charactristic, Construction procedure,Method of excavation,Rigidity of lining,Distance between tunnels and angle of intersection is studied. For comparison above parameters the surface settlement and bending moment during the excavation is measured .In order to simulate the Interaction between Crossing tunnels, use 3D finite element model with Abaqus program. The soil govern elasto-plastic mohr-coloumb constitutive equation.Parametric Analysis shows the great and different influence of each parameter that we can able to minimize this interaction with correct choose of this... 

    Fuzzy-Pade' Method for Approximating the Aerodynamic Forces in Dynamic Modeling of the Flexible Flapping Wing

    , Ph.D. Dissertation Sharif University of Technology Abedinnasab, Mohammad Hossein (Author) ; Zohoor, Hassan (Supervisor)
    In this thesis, we have derived the exact equations of motion for flexible beams. The derived equations are compared with similar equations reported in the literature, and they demonstrate significant power in prediction of the numerical results. The model for planar beams is verified by the performed experiments on carbon fiber rods. A new highly convergent, efficient technique which is quite fast is also developed for both approximating and controlling a system, entitled as fuzzy-Pade method. We then have studied effects of the wing flexibility on enhancing the lift and trust coefficients in the flapping flight. Aerodynamic force generation due to flapping is simulated for both the... 

    CFD Modeling of Fixed Bed Reactor for Direct Synthesis of DME from Syngas and Carbon Dioxide

    , M.Sc. Thesis Sharif University of Technology Moradi, Fazel (Author) ; Kazemeini, Mohammad (Supervisor)
    Today, the global environmental restrictions as well as; energy problems have directed researchers toward developing ideas of producing a clean liquid fuel from coal or natural gas as a major research topic. In this regard, a special attention is paid to the dimethyl ether (DME) as a clean material containing 34.8% oxygen possessing enough positive potential to replace the diesel and LPG fuels. One of the most economic routes for producing the DME is known to be the direct conversion of the synthesis gases and carbon dioxide first to the methanol and then its dehydration to the DME. Moreover, the DME is not limited to a particular country or resource area since small reservoirs of natural... 

    Physical-Phenomenological Constitutive Modeling and Numerical Analysis of Magnetic Shape Memory Alloys

    , M.Sc. Thesis Sharif University of Technology Mousavi, Mohammad Reza (Author) ; Arghavani, Jamal (Supervisor) ; Sohrabpour, Saeed (Supervisor) ; Naghdabadi, Reza (Co-Advisor)
    Magnetic shape memory alloys (MSMAs) are a new class of smart materials that exhibit characteristics of large recoverable strains and high frequency. These unique characteristics, make MSMAs interesting materials for applications such as actuators, sensors, and energy harvesters. This thesis presents a three-dimensional phenomenological constitutive model for MSMAs, developed within the framework of irreversible continuum thermodynamics. To this end, a proper set of internal variables is introduced to reflect the microstructural consequences on the material macroscopic behavior. Moreover, a stress-dependent thermodynamic force threshold needed for variant reorientation is introduced which... 

    Study the Effect of Staged Construction and Behavior of Concave Corner of Excavation Stabilized by Soldier Piles with Pretensioned Anchor by 3D Numerical Modeling

    , M.Sc. Thesis Sharif University of Technology Mehdizadeh, Mehdi (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    In recent years, due to the development of cities and population growth, the number of underground floors and the depth of excavations have increased. Sustainability of excavation and control of deformation due to excavation process has always been considered as one of the important issues in geotechnical engineering. One of the most commonly used systems for deep excavation, especially in urban areas, is the soldier pile wall with tiebacks. This system consists of anchoring on soldier piles that are performed at horizontal distances around the excavation range. The cables have two parts. Unbond and bond length that, when pretensioned, have the task of transfering load out of the wedge of... 

    Three-dimensional modeling of density current in a straight channel

    , Article Journal of Hydraulic Engineering ; Volume 135, Issue 5 , 2009 , Pages 393-402 ; 07339429 (ISSN) Firoozabadi, B ; Afshin, H ; Aram, E ; Sharif University of Technology
    Dense underflows are continuous currents that move downslope due to their density being heavier than that of the ambient water. In this work, a steady density current with a uniform velocity and concentration from a narrow sluice gate enters into a wide channel of lighter ambient fluid and moves forward downslope. Experiments varying inlet velocity and concentration and hence inlet Richardson numbers were conducted. Numerical simulations were also performed with a low-Reynolds number k-ε model. The results of numerical simulation agree well with the experimental data. © 2009 ASCE  

    Study of the Interaction of Non-level Crossing Tunnels, Case Study of Crossing of Tunnels of Line 1 and Line 7 of Tehran Metro

    , M.Sc. Thesis Sharif University of Technology Pourjavadi, Sobhan (Author) ; Sadaghiani, Mohammad Hosein (Supervisor)
    As the crowded cities require public transportation and because of lack of space on the ground, Subway and boring underground tunnels encountered. In this thesis the interaction of boring the line 7 of Tehran metro with the existing station of line 1 of Tehran metro (Molavi station) is studied. By changing the soil specification, The surface settlement is significant so the soil specification is one of the important parameters of the interaction. For comparinf the effect of these parameters, the soil settlement and bending moments is investigated in different parts of station while the lower tunnel is passing beneath it. The 3D Abaqus software is used for modeling this interaction. In...