Search for: modelling-and-analysis
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    Reliable clustering of Bernoulli mixture models

    , Article Bernoulli ; Volume 26, Issue 2 , May , 2020 , Pages 1535-1559 Najafi, A ; Motahari, S. A ; Rabiee, H. R ; Sharif University of Technology
    International Statistical Institute  2020
    A Bernoulli Mixture Model (BMM) is a finite mixture of random binary vectors with independent dimensions. The problem of clustering BMM data arises in a variety of real-world applications, ranging from population genetics to activity analysis in social networks. In this paper, we analyze the clusterability of BMMs from a theoretical perspective, when the number of clusters is unknown. In particular, we stipulate a set of conditions on the sample complexity and dimension of the model in order to guarantee the Probably Approximately Correct (PAC)-clusterability of a dataset. To the best of our knowledge, these findings are the first non-asymptotic bounds on the sample complexity of learning or... 

    Reliability analysis of rotating cracked blade using modal data

    , Article 2017 International Conference on Mechanical, System and Control Engineering, ICMSC 2017, 19 May 2017 through 21 May 2017 ; 2017 , Pages 78-84 ; 9781509065295 (ISBN) Heidari, S ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    This paper deals with vibrational behaviors of blades with cracks which are key components in rotating machines. However, since modelling and analysis of real blade is a complex problem, a simplified cantilever beam with both chordwise (in X-Y plane) and flapwise (in X-Z plane) motion are modeled instead. Finite Element Method (FEM) is used to model beam and to investigate its natural frequencies with a crack. Finally a limit function using modal data is developed and reliability analysis of beam model is performed. © 2017 IEEE  

    A new model for deformed carbon nanotubes using Green's function

    , Article Applied Physics A: Materials Science and Processing ; Volume 105, Issue 4 , 2011 , Pages 875-880 ; 09478396 (ISSN) Fathi, D ; Sarvari, R ; Sharif University of Technology
    A new method for modeling and analysis of deformed carbon nanotubes (CNTs) using Green's function, is presented in this paper, for the first time. Using the proposed method, a new circuit model is obtained for the deformation region of a deformed single-walled CNT (SWCNT), which the values of its elements depend on the type of deformation and also the deformation parameters such as the coupling matrices and the energy variations of deformation region. The comparison between the obtained results from the analysis of proposed model and the literature gives a good match which approves the accuracy and correctness of the proposed model  

    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.... 

    Stochastic geometry modeling and analysis of single- and multi-cluster wireless networks

    , Article IEEE Transactions on Communications ; Volume 66, Issue 10 , 2018 , Pages 4981-4996 ; 00906778 (ISSN) Azimi Abarghouyi, S. M ; Makki, B ; Haenggi, M ; Nasiri Kenari, M ; Svensson, T ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    This paper develops a stochastic geometry-based approach for the modeling and analysis of single- and multi-cluster wireless networks. We first define finite homogeneous Poisson point processes to model the number and locations of the transmitters in a confined region as a single-cluster wireless network. We study the coverage probability for a reference receiver for two strategies; closest-selection, where the receiver is served by the closest transmitter among all transmitters, and uniform-selection, where the serving transmitter is selected randomly with uniform distribution. Second, using Matern cluster processes, we extend our model and analysis to multi-cluster wireless networks. Here,... 

    Coverage analysis of finite cellular networks: A stochastic geometry approach

    , Article 2018 Iran Workshop on Communication and Information Theory, IWCIT 2018, 25 April 2018 through 26 April 2018 ; 2018 , Pages 1-5 ; 9781538641491 (ISBN) Azimi Abarghouyi, S. M ; Makki, B ; Haenggi, M ; Nasiri Kenari, M ; Svensson, T ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    This paper develops a tractable modeling and analysis framework for finite cellular wireless networks using stochastic geometry. Defining finite homogeneous Poisson point processes to model the number and locations of access points in a confined region, we study the coverage probability for an arbitrarily-located reference user that is served by the closest access point. The distance distribution and the Laplace transform (LT) of the interference are derived. We also derive a closed-form lower bound on the LT of the interference. Our analyses reveal that a higher path loss exponent improves the coverage probability and that there is a location where the coverage probability is maximized. ©... 

    Excavation plan and preliminary support design of an underground control room using 3D analysis in soft and weathered rocks

    , Article 6th European Conference on Numerical Methods in Geotechnical Engineering - Numerical Methods in Geotechnical Engineering, Graz, 6 September 2006 through 8 September 2006 ; 2006 , Pages 359-365 ; 0415408229 (ISBN); 9780415408226 (ISBN) Vahedi Fard, F ; Talebi, M ; Jafarzadeh, F ; Dianat Nejad, M ; Sharif University of Technology
    Taylor and Francis/ Balkema  2006
    In this paper, proper and safe planning of excavation method and design of support system in very weak rocks with case study of control room of Silveh dam are discussed. Silveh earth-storage dam, with 102 m height; is under construction in North-West of Iran. Due to numerous and various tectonic occurrences, the area of dam site is known as a high activity zone of Iran. In purposed location of control room, bedrock contains mostly weathered and crushed Shale and Schist. 60 m overburden and finite aquifers are another specific concern of this project. In this paper by using 3D finite element modeling, different stages of excavation and support system installation have been analyzed for the... 

    Technical and economic feasibility study of using Micro CHP in the different climate zones of Iran

    , Article Energy ; Volume 36, Issue 8 , August , 2011 , Pages 4790-4798 ; 03605442 (ISSN) Teymouri Hamzehkolaei, F ; Sattari, S ; Sharif University of Technology
    The growing worldwide demand for less polluting shapes of energy have led to a renewed interest in the use of Micro Combined Heat and Power (Micro CHP) technologies in the residential sector. Micro CHP have been introduced around Iran recently, and expected to diffuse more and more.In this paper, technical and economic studies for the use of Micro CHP in the different climate zones of Iran are executed. These zones are categorized in to five; Tehran, Rasht, Bandar Abbas, Ardebil and Yazd, based on weather conditions. Later on using an economic model, both annual energy savings and percentage of system profitability in each zone are calculated as well as reduction in annual emissions. It... 

    Analysis of random capacitor mismatch errors in pipeline analog-to-digital converters

    , Article Proceedings - IEEE International Symposium on Circuits and Systems ; 2011 , Pages 514-517 ; 02714310 (ISSN) ; 9781424494736 (ISBN) Nikandish, G ; Medi, A ; Sharif University of Technology
    A new modeling and analysis of the nonlinearities caused by the capacitor mismatch errors in the pipeline analog-to-digital converters (ADCs) is presented. Error in each stage is modeled by an input-referred gain error and a nonlinear term. A method is proposed for calculation of the ADC integral nonlinearity (INL) from the total input referred error. Analytical expressions for estimation of the ADC INL in terms of standard deviation of random capacitor mismatch errors are derived. The proposed model is verified by system-level Monte Carlo simulations  

    The effects of postural difficulty conditions on variability of joint kinematic patterns during sit to stand task in normals and patients with non-specific chronic low back pain

    , Article 2011 1st Middle East Conference on Biomedical Engineering, MECBME 2011, 21 February 2011 through 24 February 2011, Sharjah ; 2011 , Pages 300-303 ; 9781424470006 (ISBN) Tajali, S ; Negahban, H ; Yazdi, M. J. S ; Salehi, R ; Mehravar, M ; Parnianpour, M ; Sharif University of Technology
    Sit to stand (STS) is one of the most important activities of daily living that is shown to be affected in low back pain (LBP) patients. It requires a fundamental coordination action among all segments (DOFs) of the body in order to control important performance variables such as body's center of mass (CM) within base of support (BOS). In this study, possible differences in joint coordination and variability patterns between chronic LBP and healthy control subjects were investigated during STS task. Eleven adults with nonspecific chronic LBP and 12 healthy controls were recruited in the study. The participants performed the task in 3 exerimental conditions including: rigid surface, open eyes... 

    A generalized technique of modeling, analysis, and control of a matrix converter using SVD

    , Article IEEE Transactions on Industrial Electronics ; Volume 58, Issue 3 , 2011 , Pages 949-959 ; 02780046 (ISSN) Hojabri, H ; Mokhtari, H ; Chang, L ; Sharif University of Technology
    In this paper, a new simple and complete technique of modeling and analysis of a matrix converter is presented based on the singular value decomposition (SVD) of modulation matrix. The proposed modeling method yields a new limitation between the matrix converter gain and its input power factor, which is more relaxed as compared to the limits reported so far in the literature. The SVD of the modulation matrix leads to a unified modulation technique which achieves the full capability of a matrix converter. It is shown that this approach is general and all other modulation methods established for a matrix converter are specific cases of this technique. The proposed modulation method can be used... 

    A mathematical model of nanoparticulate mixed oxide pseudocapacitors; part I: model description and particle size effects

    , Article Journal of Solid State Electrochemistry ; Volume 13, Issue 3 , 2009 , Pages 433-443 ; 14328488 (ISSN) Farsi, H ; Gobal, F ; Sharif University of Technology
    A mathematical model was developed to describe the performance of nanoparticulate mixed oxide pseudocapacitors based on RuO 2-MO 2 (M being another suitable transition metal) under galvanostatic charge/discharge regime. Both double layer and faradaic processes were taken into account. The effects of the active material's particle size and composition were examined. Furthermore, the influence of discharge current on the extents of double layer and faradaic contributions was analyzed. The model analysis showed that the energy density declined upon increasing the volume fraction of larger particles. © 2008 Springer-Verlag  

    Modeling and analysis of power conversion system for high temperature gas cooled reactor with cogeneration

    , Article 2008 ASME Turbo Expo, Berlin, 9 June 2008 through 13 June 2008 ; Volume 2 , August , 2008 , Pages 649-655 ; 9780791843123 (ISBN) Afrazeh, A ; Khaledi, H ; Ghofrani, M. B ; International Gas Turbine Institute ; Sharif University of Technology
    A gas turbine in combination with a nuclear heat source has been subject of study for some years. This paper describes the advantages of a gas turbine combined with an inherently safe and well-proven nuclear heat source. The design of the power conversion system is based on a regenerative, non-intercooled, closed, direct Brayton cycle with high temperature gas-cooled reactor (HTGR), as heat source and helium gas as the working fluid. The plant produces electricity and hot water for district heating (DH). Variation of specific heat, enthalpy and entropy of working fluid with pressure and temperature are included in this model. Advanced blade cooling technology is used in order to allow for a... 

    Shear-flexural interaction in analysis of Reduced web section beams using VM link element

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 20, Issue 1 , 2007 , Pages 23-35 ; 1728-144X (ISSN) Erfani, S ; Kazemi, M. T ; Sharif University of Technology
    Materials and Energy Research Center  2007
    Reduced web section beams in shear-yielding moment-resistant steel frames are used for energy dissipating of earthquakes. The finite element analysis indicates that failure mode of these beams are governed by the combination of shear force and flexural moment. Therefore the analysis of frames with reduced web section beams needs consideration of shear-flexural interaction in those sections. In the present paper, modeling and analysis of reduced web section beams are investigated by using a special element which is called VM link element. The elastic and inelastic shear and flexural deformations and tangential stiffnesses in this link element are considered by using the multi- surfaces... 

    Hierarchical stochastic activity networks: Formal definitions and behaviour

    , Article International Journal of Simulation: Systems, Science and Technology ; Volume 6, Issue 1-2 , 2005 , Pages 56-66 ; 14738031 (ISSN) Azgomi, M. A ; Movaghar, A ; Sharif University of Technology
    UK Simulation Society  2005
    Stochastic activity networks (SANs) are a powerful and flexible extension of Petri nets. These models can be used for the modelling and analysis of various kinds and different aspects of distributed real-time systems. Similar to other classical extensions of Petri nets, SANs have some limitations for modelling complex and large-scale systems. In order to remove some of these limitations and provide high-level modelling constructs, we have defined a new extension for SANs, called hierarchical stochastic activity networks (HSANs). HSAN models provide a construct for composing a hierarchy of SAN submodels that is called macro activity. HSANs encapsulate hierarchies and a key benefit of these... 

    Application of a new cylindrical element formulation in finite element structural analysis of FGM hollow cylinders

    , Article 2008 ASME International Mechanical Engineering Congress and Exposition, IMECE 2008, Boston, MA, 31 October 2008 through 6 November 2008 ; Volume 14 , 2009 , Pages 21-25 ; 9780791848753 (ISBN) Ahmadian, M. T ; Taghvaeipour, A ; Bonakdar, M ; Sharif University of Technology
    Functionally graded materials are advanced composite materials consisting two or more material ingredients that are engineered to have a continuous spatial variation of properties. There are a few analytical methods available to solve the governing equations of FGM made structures, confined to some specific and limited shapes, loadings and boundary conditions. Hence the numerical methods such as FEM are used to treat these materials. In previous studies the finite element method was used to solve thin walled FG structures like shells and plates by modification of the conventional shell and plate elements. Solving the thick walled FG structures confronts some difficulties. One of the methods...