Search for: geometrical-modeling
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    Information Flow in Random Wireless Networks

    , Ph.D. Dissertation Sharif University of Technology Shariatpanahi, Pooya (Author) ; Hossein Khalaj, Babak (Supervisor)
    We analyze the fundamental communication limits and capabilities of random wireless networks. In order to achieve this goal, we investigate and analyze efficient communication strategies in such networks. The traffic model considered is unicasting. Also, we consider two different channel models, namely, the geometric channel model and the random connections model.
    In networks with random connection model, channel powers between different nodes are drawn from a common distribution in an independent manner. We assume an on-off strategy for operation of transmitters, and show that finding the optimum transmission strategy problem is an NP-hard problem. Thus, we propose a heuristic algorithm... 

    Flying Vehicle Attitude Determination through Optical Flow Interpretation by Neural Network

    , M.Sc. Thesis Sharif University of Technology Tasouji Zadeh Aghdam, Ramin (Author) ; Saghafi, Fariborz (Supervisor)
    Attitude estimation means calculating the state variables during the flight, especially in landing and takeoff phases. If we can extract the optical flow using the sensors mounted on the flying object, due to the fact that the optical flow is created by linear and rotational speed of the object relative to the surrounding, we are able to calculate the relative attitude by analyzing the optical flow. Indeed the purpose is developing this idea by using artificial neural networks.
    First, we find the optical flow patterns for every attitude condition near the ground, using geometrical calculations. Then we produce an optimal neural network by these patterns. This network has the ability to... 

    Optimization of Scaled Composite Wing of Aircraft Jas-39 By Genetic Algorithm

    , M.Sc. Thesis Sharif University of Technology Zamani, Vahid (Author) ; Abedian, Ali (Supervisor)
    Popular usage of composite materials in aerospace, civil and defense industries in the last decades has been caused more attention to optimization of composite problems. Due to natural complexity of composite problems, i.e. discrete nature, complex dependence between design variables, existence of too much local optimum and etc., traditional methods of optimization are inefficient and it is necessary to use a powerful method to work cost effectively. Genetic algorithm as a technique through evolutionary algorithms is the most popular methods of tackling composite problems. The success of a genetic algorithm can be quantified by estimating the cost, time required and the quality of final... 

    A sensitivity study of FILTERSIM algorithm when applied to DFN modeling

    , Article Journal of Petroleum Exploration and Production Technology ; Vol. 4, issue. 2 , June , 2014 , p. 153-174 ; ISSN: 21900558 Ahmadi, R ; Masihi, M ; Rasaei, M. R ; Eskandaridalvand, K ; Shahalipour, R ; Sharif University of Technology
    Realistic description of fractured reservoirs demands primarily for a comprehensive understanding of fracture networks and their geometry including various individual fracture parameters as well as network connectivities. Newly developed multiple-point geostatistical simulation methods like SIMPAT and FILTERSIM are able to model connectivity and complexity of fracture networks more effectively than traditional variogrambased methods. This approach is therefore adopted to be used in this paper. Among the multiple-point statistics algorithms, FILTERSIM has the priority of less computational effort than does SIMPAT by applying filters and modern dimensionality reduction techniques to the... 

    Aerodynamic Optimization of Axial Transonic Compressor Blade by Adjoint Method Using Bump/ Local Blowing

    , Ph.D. Dissertation Sharif University of Technology Khatibi Rad, Saeedeh (Author) ; Mazaheri, Karim (Supervisor)
    Transonic flow compressors are widely used today. In these systems, the occurrence of shock waves, interaction of the shock and the boundary layer, thickening of the boundary layer and separation are some challenges which can severely affect the aerodynamic performance. Here we use a numerical analysis and an optimization algorithm to optimize the aerodynamic shape of a transonic axial compressor blade section. The total pressure loss through a cascade of blade sections is selected as the cost function. A continuous adjoint optimization method is used along with a RANS solver to find the new blade section shape. Application of three different geometric modelling of a compressor blade section... 

    Geometrical analysis of localization error in stereo vision systems

    , Article IEEE Sensors Journal ; Volume 13, Issue 11 , 2013 , Pages 4236-4246 ; 1530437X (ISSN) Fooladgar, F ; Samavi, S ; Soroushmehr, S. M. R ; Shirani, S ; Sharif University of Technology
    Determining an object location in a specific region is an important task in many machine vision applications. Different parameters affect the accuracy of the localization process. The quantization process in charge-coupled device of a camera is one of the sources of error that causes estimation rather than identifying the exact position of the observed object. A cluster of points, in the field of view of a camera are mapped into a pixel. These points form an uncertainty region. In this paper, we present a geometrical model to analyze the volume of this uncertainty region as a criterion for object localization error. The proposed approach models the field of view of each pixel as an oblique... 

    Modelling and analysis of the effect of angular velocity and acceleration on brain strain field in traumatic brain injury

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3 A , 2013 ; 9780791856215 (ISBN) Hoursan, H ; Ahmadian, M. T ; Barari, A ; Beidokhti, H. N ; Sharif University of Technology
    Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. A presentation of a model of what happens in the process has been under study for many years; and yet it remains a question due to physiological, geometrical and computational complications. Although the facilities for soft tissue modeling have improved and the precise CT-imaging of human head has revealed novel details of brain, skull and the interface (the meninges), a comprehensive FEM model of TBI is still being studied. This study aims to present an optimized model of human head including the brain, skull, and the meninges after a comprehensive study of the previous models.... 

    Geometric optimization of parabolic trough solar collector based on the local concentration ratio using the Monte Carlo method

    , Article Energy Conversion and Management ; Volume 175 , 2018 , Pages 278-287 ; 01968904 (ISSN) Hoseinzadeh, H ; Kasaeian, A ; Behshad Shafii, M ; Sharif University of Technology
    Elsevier Ltd  2018
    This research is aimed at geometric analysis of parabolic trough solar collector (PTC) in different sizes of the main components of the system. The rate of the Local Concentration Ratio (LCR) on the receiver tube and optical efficiency are two main features in geometric optimization of the parabolic trough solar collectors. In this work, parabolic trough solar collector was optimized for different sizes with three design variables: the receiver diameter, the collector aperture width and the rim angle. The method used in this research was the Monte Carlo Method (MCM) in MATLAB. The optical and geometric modeling was developed for coding in MATLAB. For the case study, a parabolic trough solar... 

    Monte-Carlo-based simulation and investigation of 230 kV transmission lines outage due to lightning

    , Article High Voltage ; Volume 5, Issue 1 , 2020 , Pages 83-91 Karami, E ; Khalilinia, A ; Bali, A ; Rouzbehi, K ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    Here, using the probabilistic evaluation based on the Monte Carlo method, back-flashover rate and shielding failure flashover rate of 230 kV overhead transmission lines in the western regions of Iran are evaluated. To such an aim, first, the number of thunderstorm days per year is collected from the reported weather information in order to determine the ground flash density. Then, using MRU-200 equipment, the tower-footing resistance of several towers is measured. Matlab® software is used in order to produce lightning surges considering its probabilistic nature and randomly distribution on the ground to evaluate striking distance based on the geometric model. Then, calculated parameters are... 

    Computational modeling of drug distribution in the posterior segment of the eye: Effects of device variables and positions

    , Article Mathematical Biosciences ; Vol. 255, issue. 1 , 2014 , p. 11-20 Jooybar, E ; Abdekhodaie, M. J ; Farhadi F ; Cheng Y. L ; Sharif University of Technology
    A computational model was developed to simulate drug distribution in the posterior segment of the eye after intravitreal injection and ocular implantation. The effects of important factors in intravitreal injection such as injection time, needle gauge and needle angle on the ocular drug distribution were studied. Also, the influences of the position and the type of implant on the concentration profile in the posterior segment were investigated. Computational Fluid Dynamics (CFD) calculations were conducted to describe the 3D convective-diffusive transport. The geometrical model was constructed based on the human eye dimensions. To simulate intravitreal injection, unlike previous studies... 

    Facial expression recognition using geometric normalization and appearance representation

    , Article Iranian Conference on Machine Vision and Image Processing, MVIP ; 2013 , Pages 159-163 ; 21666776 (ISSN) ; 9781467361842 (ISBN) Sadeghi, H ; Raie, A. A ; Mohammadi, M. R ; Sharif University of Technology
    IEEE Computer Society  2013
    Facial expression recognition is a challenging and interesting problem in computer vision and pattern recognition. Geometric variability in both emotion expression and neutral face is a fundamental challenge in facial expression recognition problem. This variability not only directly affects geometric facial expression recognition methods, but also is a critical problem in appearance methods. To overcome this problem, this paper presents an approach which eliminates geometric variability in emotion expression; thus, appearance features can be accurately used for facial expression recognition. Therefore, a fixed geometric model is used for geometric normalization of facial images. This model... 

    Fabrication of sintered porous polymeric materials: effect of chain interdiffusion time on mechanical properties

    , Article Polymer International ; Volume 67, Issue 4 , 2018 , Pages 422-430 ; 09598103 (ISSN) Salari, M ; Pircheraghi, G ; Sharif University of Technology
    John Wiley and Sons Ltd  2018
    In this study, sintered porous polymeric materials made of high density polyethylene (HDPE) were fabricated through controlling the chain interdiffusion time at the transition temperature of semicrystalline and melt states. At this intermediate state, where both crystalline and amorphous phases coexist, the interfacial welding of HDPE particles is facilitated thanks to interdiffusion caused by chain relaxation phenomena. Then, by assuming a spherical shape and a cubic packing configuration of particles, a geometrical model was developed to predict porosity variations as sintering progresses. Moreover, the HDPE used, as a broad molecular weight distributed polymer, has different family chains...