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    Current Distribution and Nonlinearity of Open-Ends and Gaps in Superconducting Microstrip Structures

    , Article Journal of Superconductivity and Novel Magnetism ; Volume 26, Issue 5 , May , 2012 , PP, 1821-1825 ; 15571939 (ISSN) Javadzadeh, S. M. H ; Farzaneh, F ; Fardmanesh, M ; Sharif University of Technology
    2012
    Abstract
    Superconducting devices are known to produce nonlinear effects. In planar structures, these nonlinearities depend on the current distribution on the strip, which definitely depends on the structure of device. This paper used a numerical method based on 3D-FEM to obtain the current distribution in the open-ends and gaps in the superconducting microstrip structures. This is used to present the nonlinear distributed circuit modeling of these discontinuities and its impact on the nonlinear phenomenon. This nonlinear circuit model is used in the Harmonic Balance (HB) method to analyze nonlinearity in the superconducting microwave devices. Therefore, this simple accurate enough nonlinear circuit... 

    Linear and Non-Linear Modeling of Electrophoretic Mobility of Peptides

    , M.Sc. Thesis Sharif University of Technology Darvizeh, Fatemeh (Author) ; Jalali Heravi, Mehdi (Supervisor)
    Abstract
    Regarding the importance of biological systems in daily life and the complexity of these systems, this project is concerned with this problem and especially with applications of chemometrics in proteomics. In this respect, specific importance of peptides has been taken into account in the process of construction of especial and necessary proteins for human body. Due to the risks involved in some experimental investigations, it is quite preferable to utilize modeling approaches using different sets of data. Achieving a number of specific descriptors, a powerful can be established. This model could be quiet comprehensive for the prediction of the electrophoretic mobility of peptides. This... 

    Robustness investigation of a ducted-fan aerial vehicle control, using linear, adaptive, and model predictive controllers

    , Article International Journal of Advanced Mechatronic Systems ; Volume 6, Issue 2-3 , 2015 , Pages 108-117 ; 17568412 (ISSN) Emami, S. A ; Banazadeh, A ; Sharif University of Technology
    Inderscience Publishers  2015
    Abstract
    A comparison of three common controllers for stabilising a vertical take-off and landing air vehicle is presented. RMIT is a small sized tail-sitter ducted fan air vehicle with a particular configuration layout, multiple control surfaces, low weight, and high-speed flight capability. The main problem here is control effectiveness at low flight speeds and transition manoeuvres because of the inherent instability. In the current study, a comprehensive nonlinear model is firstly developed for RMIT, followed by a validation process. Subsequently, linear, adaptive and model predictive controllers are designed in vertical flight. Based on the simulation results, it is shown that the linear... 

    Application of Nonlinear System Identification Techniques in the Modeling of Agile Fighter Aircraft Dynamics

    , Ph.D. Dissertation Sharif University of Technology Roudbari, Alireza (Author) ; Saghafi, Fariborz (Supervisor)
    Abstract
    Modeling and simulation are widely used as essential tools to predict and analyze complex systems in various scientific and engineering fields. For an aerospace system such as aircraft, mathematical models are useful used to carry out such tasks as dynamic analysis, autopilot development and combination of flight control laws, hazardous behaviors prediction, the controller design and validation, the study of the handling qualities, or the implementing simulators used for training pilots and many other tasks. In general, the aircraft flight dynamics is a nonlinear and coupled system whose dynamic modeling, in addition to pilot control inputs, depends on flight conditions (i.e., Mach and... 

    Control effectiveness investigation of a ducted-fan aerial vehicle using model predictive controller

    , Article International Conference on Advanced Mechatronic Systems, ICAMechS ; 2014 , pp. 532-537 Banazadeh, A ; Emami, S. A ; Sharif University of Technology
    Abstract
    Special attention is given to vertical takeoff and landing air vehicles due to their unique capabilities and versatile missions. The main problem here is control effectiveness at low flight speeds and transition maneuvers because of the inherent instability. RMIT is a small sized tail-sitter ducted fan air vehicle with a particular configuration layout, multiple control surfaces, low weight, and high-speed flight capability. In the current study, a comprehensive nonlinear model is firstly developed for RMIT, followed by a validation process. This model consists of all parts including aerodynamic forces and moments, control surfaces term together with the gravity and driving fan forces.... 

    Analysis of the convergence and closed loop stability in EDMC

    , Article Scientia Iranica ; Volume 12, Issue 1 , 2005 , Pages 43-54 ; 10263098 (ISSN) Haeri, M ; Zadehmorshed Beik, H ; Sharif University of Technology
    Sharif University of Technology  2005
    Abstract
    In this paper, the convergence and stability conditions of extended DMC in the control of nonlinear SISO and MIMO systems are investigated. The formulations are based on the ordinary DMC in which, with successive linearization of the nonlinear model and new interpretation of disturbance, the nonlinear extension is deduced. In addition, new convergence and stability criteria are derived for SISO and MIMO systems. These criteria include convergence and stability in the case of longer control (M > 1) and prediction (P > 1) horizons, as well as the finite and infinite sampling time. Finally, the simulation results for a MIMO (3 × 3) model, based on a power unit nonlinear plant, are presented. ©... 

    Adaptive Attitude and Position Control of a Rigid Body Insect-Like Flapping Wing

    , M.Sc. Thesis Sharif University of Technology Taymourtash, Neda (Author) ; Banazadeh, Afshin (Supervisor)
    Abstract
    In this study, adaptive control of attitude and position of a rigid body insect-like flapping wing is investigated. For this purpose, a non-linear dynamic and time varying modeling and simulation is carried out initially with six degrees of freedom, and then the accuracy of the simulation is evaluated during different test cases. In order to design the controller, non-linear and time varying dynamic is transformed into non-linear and time-invariant dynamic using theory of averaging. Then, a non-linear controller is designed based on Lyapunov stability theory. Due to the inefficiency of the aforementioned controller under disturbances and unknown uncertainties in the model, an adaptive... 

    Investigation of Strength and Ductility of Hinged Khorjini Connection

    , M.Sc. Thesis Sharif University of Technology Hosseini, Sajjad (Author) ; Moghaddam, Hassan (Supervisor) ; Eskandari, Morteza (Co-Advisor)
    Abstract
    Khorjini connection is a type of connection in steel frames, in which the beam remains continuous at the intersection with column. In its ordinary form, this beam is connected to the face of column section using upper and lower angles. This type of connection is frequently used in construction of steel frames in Iran due to economic advantages and ease of fabrication. However since it is rarely used in other countries, its behavior and method of design is not described in international references and standards. The failure of the connections is a dominant type of seismic fraction in a building (The main reason of structural failures in Manjil and Roudbar earthquake – 1990). Contrary to the... 

    Nonlinear Analysis of 3D Irregular concrete Structures by Endurance Time Method

    , M.Sc. Thesis Sharif University of Technology Khaki, Ali (Author) ; Esmaeil Pourestekanchi, Homayun (Supervisor)
    Abstract
    The structure performances during past earthquakes indicate the importance of predicting behaviors of irregular structures under earthquakes. If the irregularity exceeds an expected limit, a seismic analysis should be carried out by a dynamic analysis method. The Endurance Time (ET) is a time-history method, base on dynamic analysis for seismic analyzing and designing the structures, in which structures are subjected to intensifying accelerogram functions and their Endurance Time is measured. One of the most applicable methods for RCF analysis is the Concentrated Hinge Model which is used in this research too. The needed parameters for modeling plasticity in concentrated hinge are achieved... 

    A Comparative Approach between Deep Learning and MLE for Monitoring Multivariate Processes with Chaotic Trends

    , M.Sc. Thesis Sharif University of Technology Rahimi Movassagh, Maryam (Author) ; Akhavan Niaki, Taghi (Supervisor)
    Abstract
    There are a variety of multivariate industrial processes in real world problems. It seems to be necessary to control them through strong tools such as control charts. One of the state-of-the-art methods to monitor processes is neural network. Neural networks are data processing systems inspired by human brain and they are capable of processing data with a variety of small processors working in parallel forming an integrated network to solve a problem. Chaotic models, one of the states of being out of control, are deterministic non-linear models which have extremely complex behavior under determined assumption. Researches have shown neural networks have excellent performance in such systems.... 

    Safety Assessment of the Transmission Towers Subjected to Natural Loads Including Earthquakes, Floods, Storms and Ice

    , M.Sc. Thesis Sharif University of Technology Zandevakili, Ali (Author) ; Ghaemian, Mohsen (Supervisor)
    Abstract
    Electrical power is an inseparable part of human life. Therefore, design and analysis of electrical transmission towers have always been important for scientists. In common design methods due to the lightness of these structures only the wind load is considered and earthquake effects are neglected. On the other hand, regarding regulation No.2800 a lot of areas of Iran are located in earthquake zones. Therefore, it is necessary to evaluate the performance of these structures against earthquakes. In this research, regarding conducted studies, we decided to use incremental dynamic analysis method (IDA) in order to evaluate seismic performance of the tower. In sake of thoroughness of the... 

    Attitude Control of a 3DOF Quadrotor Stand Using a Heuristic Nonlinear Controller

    , M.Sc. Thesis Sharif University of Technology Alizad Arabolye Bishe, Meysam (Author) ; Nobahari, Hadi (Supervisor)
    Abstract
    A new heuristic controller, called nonlinear model predictive control based on gravitational search algorithm, is proposed for nonlinear systems. Nonlinear model predictive control involves the solution at each sampling instant of a finite horizon optimal control problem subject to nonlinear system dynamics and constraints. The new controller formulates nonlinear model predictive control problem as a single stochastic dynamic optimization problem and uses a system of virtual masses to find the best control signal at each sampling instant. For this purpose, a cost function is defined to evaluate each point of the search space. This function minimizes simultaneously the tracking error, control... 

    Suppression of nonlinear regenerative chatter in milling process via robust optimal control

    , Article Journal of Process Control ; Volume 23, Issue 5 , 2013 , Pages 631-648 ; 09591524 (ISSN) Moradi, H ; Vossoughi, G ; Movahhedy, M. R ; Salarieh, H ; Sharif University of Technology
    2013
    Abstract
    During the milling process, self-excited vibration or chatter adversely affects tool life, surface quality and productivity rate. In this paper, nonlinear cutting forces of milling process are considered as a function of chip thickness with a complete third order polynomial (instead of the common linear dependency). An optimal control strategy is developed for chatter suppression of the system described through nonlinear delay differential equations. Counterbalance forces exerted by actuators in x and y directions are the control inputs. For optimal control problem, an appropriate performance index is defined such that the regenerative chatter is suppressed while control efforts are... 

    Vibration absorber design to suppress regenerative chatter in nonlinear milling process: Application for machining of cantilever plates

    , Article Applied Mathematical Modelling ; Volume 39, Issue 2 , 2015 , Pages 600-620 ; 0307904X (ISSN) Moradi, H ; Vossoughi, G ; Behzad, M ; Movahhedy, M. R ; Sharif University of Technology
    Elsevier Inc  2015
    Abstract
    In this paper, a tunable vibration absorber (TVA) is designed to suppress regenerative chatter in milling of cantilever plates. In machining industry, the majority of work-piece materials or the interaction of work-piece/cutting tool causes the cutting forces to demonstrate nonlinear behavior. The application of TVA (as a semi-active controller) is investigated for the process with an extensive nonlinear model of cutting forces. Under regenerative chatter conditions, optimum values of the absorber position and its spring stiffness are found such that the plate vibration is minimized. For this purpose, an optimal algorithm is developed based on mode summation approach. Results are presented... 

    Developing a conjunctive nonlinear model for inflow prediction using wavelet transforms and artificial neural networks: A case study of Dez reservoir dam, Iran

    , Article Operations Management 2006, Sacramento, CA, 14 August 2006 through 16 August 2006 ; Volume 2006 , 2006 , Pages 69-78 ; 0784408750 (ISBN); 9780784408759 (ISBN) Mehdikhani, H ; Abrishamchi, A ; Khodaei, H ; Sharif University of Technology
    2006
    Abstract
    Dez reservoir dam is one of the famous dams in Khuzestan province in southwestern part of Iran. Operation of Dez reservoir dam and it's strategic position has an important role regard to providing country's net power, it's long precedence in operation, Dam dimension, multidisciplinary uses and existence of essential land use in downstream. Thus inflow forecasting could have a great role in effective operation of dam, flood non-structural and risk management by applying an effective flood warning. The more accurate the forecasting of inflow to reservoir will be results the less peak outflow and less risk to downstream. This paper presents a new Conjunctive nonlinear model using Wavelet... 

    Application of extended DMC for nonlinear MIMO systems

    , Article Computers and Chemical Engineering ; Volume 29, Issue 9 , 2005 , Pages 1867-1874 ; 00981354 (ISSN) Haeri, M ; Zadehmorshed Beik, H ; Sharif University of Technology
    2005
    Abstract
    In this paper, an extended approach to the nonlinear DMC algorithm is proposed, which can handle constrained and MIMO systems under some defined conditions. This extension also admits higher control horizon, M and prediction horizon, P that are required to increase the performance of the controller in the most practical applications. Simulation results of the proposed method in the control of a stirred tank reactor with 2 inputs, 2 outputs nonlinear model and also a power unit nonlinear model with 3 inputs, 3 outputs are presented to illustrate effectiveness of the method and its justification. © 2005 Elsevier Ltd. All rights reserved  

    Performance Based Seismic Assessment of Concrete Dual Structures using Endurance Time Method

    , M.Sc. Thesis Sharif University of Technology Ebrahimkhanlou, Arvin (Author) ; Esmaeil Pourestekanchi, Homayun (Supervisor)
    Abstract
    The expansion of new analytical methods along with evolving computational tools has accelerated the recognition of obscured nonlinear behavior of structures. In this process, the innovative Endurance Time method is a great step which presents a comprehensive assessment of structural behavior with less computational cost. The accuracy of this method among the unpredictable nature of earthquake engineering, as well as its fastness and simplicity, has attracted the attention of researchers. This research is part of a project on introducing and assessing the capacities and restrictions of the Endurance Time method, which investigates its usage in analyzing performance of concrete structures with... 

    Project Planning and Management Under Resource Constraint and Stochastic Activity Duration

    , M.Sc. Thesis Sharif University of Technology Seifzadeh Dorabadi, Hossein (Author) ; Kianfar, Farhad (Supervisor)
    Abstract
    Most of the researches on project planning and scheduling have supposed that there is a complete and fixed information about the activities duration and amount of resources needed for project, but in reality we face lots of uncertainty in activities duration and required resources. In previous researches there are some cases which lead to more than one schedule for project, but in most of them they offer no solution for choosing between the schedules. In this project we are trying to make a nonlinear model of project environment by using Weibull distribution as activities duration and then we determine the input information by using the methods of probability encoding in decision analysis.... 

    The Application of Chaos Theory and Nonlinear Structures in Financial Time Series

    , M.Sc. Thesis Sharif University of Technology Hosseini Tash, Fatemeh Sadat (Author) ; Modarres Yazdi, Mohammad (Supervisor)
    Abstract
    Financial and monetary markets are appropriate areas of applying Chaos Theory. Firstly, current theories of financial and monetary economics state that economic and financial variables such as exchange rates and stock prices are stochastic, so forecasting them is almost impossible. Secondly, if we find the hidden ordered and deterministic trends, we can achieve considerable profits. In this piece of research, we evaluate different methods and tests of detecting chaos in financial time series, and choose the most applicable methods to test financial markets’ indices. The main three indices of Tehran Stock Exchange, including Price, Finance and Industry indices, are examined. A sample of the... 

    Seismic Performance of Friction Damped Bracing Systems

    , M.Sc. Thesis Sharif University of Technology Moini, Bardia (Author) ; Moghaddam, Hassan (Supervisor)
    Abstract
    In recent years a large number of passive energy dissipating systems developed in accordance with pioneering work on friction dampers which was firstly reported by pall(1979). Uusing Friction dampers reduce the inelastic demand of the structure during severe earthquake motions by sliping and a large portion of input energy dissipated mechanically in friction instead of yielding the main components of the structure. Based on economical purposes, it is valuable to know in which storey and slip force should be employ the friction devices to have an optimized performance of the structure. Due to kinematic conditions of slip and stick stages, as well as transition zones between them in friction...