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reduction-method
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Assessment of foundation mass and earthquake input mechanism effect on dam–reservoir–foundation system response
, Article International Journal of Civil Engineering ; Volume 17, Issue 4 , 2019 , Pages 473-480 ; 17350522 (ISSN) ; Noorzad, A ; Mohammadnezhad, H ; Sharif University of Technology
Springer International Publishing
2019
Abstract
Concrete dams are one of the most important infrastructures in every country and the seismic safety assessment of them is a major task in dam engineering field. Dam–foundation–reservoir system analysis is a complex interaction problem because this system consists of three domains with different behaviors. For accurate analysis of this system, some important factors should be considered such as foundation mass and earthquake input mechanism. In this paper, the effect of foundation mass and earthquake input mechanism on seismic response of concrete gravity dam is investigated. For this purpose, two different methods are introduced for modeling of massed semi-infinite foundation in finite...
Calculation of Pulse Height Distribution by Deterministic and Monte Carlo Methods
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
Radiation detection techniques have important applications including prompt gamma neutron activation analysis (PGNAA), radiotherapy dose measurement, medical imaging and homeland security. Pulse height distribution is also a useful parameter in Radionuclide identification. Gamma ray spectroscopy analysis is a common technique in measuring of radiation field to identify the radioactive source.
Probabilistic methods are commonly used for numerical simulation of Pulse height distribution. In Monte Carlo methods, each history is individually tracked and details of interactions are available. Using the Monte Carlo methods for calculation of pulse height distribution leads to more real...
Probabilistic methods are commonly used for numerical simulation of Pulse height distribution. In Monte Carlo methods, each history is individually tracked and details of interactions are available. Using the Monte Carlo methods for calculation of pulse height distribution leads to more real...
A comprehensive study on noise reduction methods of marine propellers and design procedures
, Article Applied Acoustics ; Volume 150 , 2019 , Pages 55-69 ; 0003682X (ISSN) ; Razaghian, A. H ; Seif, M. S ; Zahedi, F ; Nouri Borujerdi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The noise generated by the propeller is one of the most important components of the vessels noise. Therefore, reducing this noise will significantly decrease the total noise of the vessel. Underwater noise of vessels has destructive effects on marine life. In addition, this noise affects the health and comfort of the crew and passengers of the ship. Moreover, high noise may cause warships to be detected easily. In this paper, first, common methods of noise reduction, including blade coating, modern propellers, propeller hub modification and ducted propellers are investigated. Then, relevant optimization methods are presented. Next, the effects of the geometric parameters like number of...
Stochastic unit commitment of wind farms integrated in power system
, Article Electric Power Systems Research ; Volume 80, Issue 9 , Jan , 2010 , Pages 1006-1017 ; 03787796 (ISSN) ; Vakilian, M ; Sharif University of Technology
2010
Abstract
Integration of wind power generation creates new concerns for operation engineers in a power system. Unlike conventional power generation sources, wind power generators supply intermittent power due to uncertainty in parameters of wind such as its velocity. This paper presents probabilistic model for load and wind power uncertainty which can be used in operation planning (with durations up to one or two years). A stochastic model is proposed to simulate the status of units that are directly affected by the load and wind power generation uncertainties. This paper develops a solution method for generation scheduling of power system, while taking into account the stochastic behavior of the load...
Domain reduction method for seismic analysis of dam-foundation-fault system
, Article Scientia Iranica ; Volume 26, Issue 1A , 2019 , Pages 145-156 ; 10263098 (ISSN) ; Zafarani, H ; Ghaemian, M ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Numerical simulation of dam-foundation-fault system, considering the earthquake source, propagation path, and local site effects, was carried out for realistic and reasonable seismic safety analysis of concrete dams. The Domain Reduction Method (DRM) was used for seismic analysis of Dam-Foundation-Fault (DFF) system, in which a modular two-step methodology for reducing the computational costs in large domain analysis was introduced. In this method, seismic excitation is directly applied to the computational domain such that assigning artificial boundary to the finite element models is more comfortable. In order to verify the implementation of the DRM in Finite Element Method (FEM), a simple...
Domain reduction method for seismic analysis of dam-foundation-fault system
, Article Scientia Iranica ; Volume 26, Issue 1A , 2019 , Pages 145-156 ; 10263098 (ISSN) ; Zafarani, H ; Ghaemian, M ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Numerical simulation of dam-foundation-fault system, considering the earthquake source, propagation path, and local site effects, was carried out for realistic and reasonable seismic safety analysis of concrete dams. The Domain Reduction Method (DRM) was used for seismic analysis of Dam-Foundation-Fault (DFF) system, in which a modular two-step methodology for reducing the computational costs in large domain analysis was introduced. In this method, seismic excitation is directly applied to the computational domain such that assigning artificial boundary to the finite element models is more comfortable. In order to verify the implementation of the DRM in Finite Element Method (FEM), a simple...
Detecting and Estimating the Time of Change Point in Parameters Vector of Multi-Attribute Processes
, M.Sc. Thesis Sharif University of Technology ; Akhavan Niaki, Taghi (Supervisor)
Abstract
Control charts are one of the most important statistical process control tools used in monitoring processes and improving the quality by decreasing the variability of processes. In spite of various applications for multi-attribute control charts in industries and service sectors, only a few research efforts have been performed in developing this type of control charts. The developed multivariate control charts are all based on the assumption that the quality characteristics follow a multivariate Normal distribution while, in many applications the correlated quality characteristics that have to be monitored simultaneously are of attribute type and follow distributions such as multivariate...
Seismic Analysis of Concrete Dam based on Numerical Modeling of Wave Propagation from Seismic Source to Site
, Ph.D. Dissertation Sharif University of Technology ; Ghaemian, Mohsen (Supervisor) ; Zafarani, Hamid (Co-Advisor)
Abstract
Safety assessment of existing dams and analysis and design of new dams as an important part of infrastructures of any country, hinges on proper and precise modeling of coupled system of dam-foundation-reservoir under appropriate seismic excitation. In this dissertation, effective methodology for seismic analysis of concrete dam, using finite element method, is presented which takes account for numerical modeling of wave propagation from excitation source to site and interactions between dam, foundation and reservoir. To model the effects of mass, wave propagation and radiotional damping in unbounded foundation as well as modeling the fault itself, two boundary conditions namely, free-field...
Mathematical Frameworks for the Study of Oscillatory Networks in Neuroscience
, M.Sc. Thesis Sharif University of Technology ; Fotouhi Firouzabad, Morteza (Supervisor)
Abstract
In this thesis, we first introduce the required biological preparations and popular models for modeling single neuron, synapse and cable. Then by introduction of limit cycle oscillators and the necessary prerequisites, investigations are limited to systems involving weakly coupled oscillators. As two examples of such models, famous Kuramoto and Wilson- Cowan models are described. In the following, we introduce some methods for reduction dimension of weakly coupled oscillators and finally we apply one of the expressed methods on the dynamics of cortical network
Manifold learning for ECG arrhythmia recognition
, Article 2013 20th Iranian Conference on Biomedical Engineering, ICBME 2013 ; 2013 , Pages 126-131 ; Jahed, M ; Khalaj, B ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
Heart is a complex system and we can find its function in electrocardiogram (ECG) signal. The records show high mortality rate of heart diseases. So it is essential to detect and recognize ECG arrhythmias. The problem with ECG analysis is the vast variations among morphologies of ECG signals. Premature Ventricular Contractions (PVC) is a common type of arrhythmia which may lead to critical situations and contains risk. This study, proposes a novel approach for detecting PVC and visualizing data with respect to ECG morphologies by using manifold learning. To this end, the Laplacian Eigenmaps - One of the reduction method and it is in the nonlinear category - is used to extract important...
MMRO: A feature selection criterion for MR images based on alpha stable filter responses
, Article 2011 7th Iranian Conference on Machine Vision and Image Processing, MVIP 2011 - Proceedings ; 2011 ; 9781457715358 (ISBN) ; Fatemizadeh, E ; Sharif University of Technology
Abstract
In feature-based image registration, feature selection and reduction methods play an important role in decreasing computational burden of these operations. In this paper, a new approach is introduced to reduce the dimension of extracted feature vectors of MR images. This approach is based on the selection of the maximum and minimum responses of the alpha stable filter for the MR images over the extracted features with different orientation in frequency domain. This algorithm selects the rotation invariant features which are suitable for image registration purposes. It has been shown that these features could efficiently describe the image elements. The discriminating ability of the features...
Temperature control of a cutting process using fractional order proportional-integral-derivative controller
, Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 133, Issue 5 , March , 2011 ; 00220434 (ISSN) ; Haeri, M ; Sharif University of Technology
2011
Abstract
In this paper, the fractionalized differentiating method is implemented to reduce commensurate fractional order models complexity. The prominent properties of this method are its simplicity and guarantee of preserving the stability of a specific class of fractional order models in their reduced counterparts. The presented reduction method is employed in simplifying complicated fractional order controllers to a fractional order PID (FOPID) controller and proposing tuning rules for its parameters adjustment. Finally, the efficiency of the FOPID tuning rule obtained based on the proposed reduction method is shown in the temperature control of a cutting process
Fractional order model reduction approach based on retention of the dominant dynamics: Application in IMC based tuning of FOPI and FOPID controllers
, Article ISA Transactions ; Volume 50, Issue 3 , July , 2011 , Pages 432-442 ; 00190578 (ISSN) ; Haeri, M ; Sharif University of Technology
2011
Abstract
Fractional order PI and PID controllers are the most common fractional order controllers used in practice. In this paper, a simple analytical method is proposed for tuning the parameters of these controllers. The proposed method is useful in designing fractional order PI and PID controllers for control of complicated fractional order systems. To achieve the goal, at first a reduction technique is presented for approximating complicated fractional order models. Then, based on the obtained reduced models some analytical rules are suggested to determine the parameters of fractional order PI and PID controllers. Finally, numerical results are given to show the efficiency of the proposed tuning...
Dimension reduction of remote sensing images by incorporating spatial and spectral properties
, Article AEU - International Journal of Electronics and Communications ; Volume 64, Issue 8 , 2010 , Pages 729-732 ; 14348411 (ISSN) ; Kasaei, S ; Sharif University of Technology
Abstract
A new and efficient dimension reduction method is introduced in this paper. The proposed method, almost the same as the well-known principal component analysis (PCA) method, enjoys the properties of uncorrelatedness of resulting components and orthogonality of transform coefficients. In addition, by incorporating spatial and spectral properties among image pixels, the method obtains more accurate classification results with less computational cost
On the effect of inducted negative correlation rate for beta acceptance–rejection algorithms
, Article Communications in Statistics: Simulation and Computation ; Volume 46, Issue 3 , 2017 , Pages 2152-2167 ; 03610918 (ISSN) ; Akhavan Niaki, S. T ; Bootaki, B ; Bakhshesh, D ; Sharif University of Technology
Taylor and Francis Inc
2017
Abstract
One of the variance reduction methods in simulation experiments is negative correlation induction, and in particular the use of the antithetic variates. The simultaneous use of antithetic variates and an acceptance–rejection method has been studied in some papers, where the inducted negative correlation has been calculated. In this study, the factors affecting the inducted negative correlation rate are addressed. To do this, the beta distribution is first selected to generate negatively correlated random variates using the acceptance–rejection method. The effects of both the efficiency of the acceptance–rejection method and the initial negative correlation rate on the inducted negative...
Model reduction in commensurate fractional-order linear systems
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 223, Issue 4 , 2009 , Pages 493-505 ; 09596518 (ISSN) ; Haeri, M ; Sharif University of Technology
2009
Abstract
In this paper, some commonly used model reduction methods for integer-order systems are employed to approximate commensurate fractional-order linear systems. In comparison with the original system, the approximating model possesses a smaller inner dimension, while its fractional order is the same as that of the original system. The applied methods fall into the global reduction category, such as direct truncation and singular perturbation methods, and into the local reduction category, such as Pade approximation, partial realization, shifted Pade approximation, and rational interpolation methods. The applicability of these methods is illustrated by approximating a sample high-dimensional,...
Measurement, Analysis and Reduction Methods of Ship Vibration
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor) ; Ghoreishi, Reza (Supervisor)
Abstract
This thesis addresses the main stages of ship vibration analysis and introduces applied strategies for vibration reduction of an existing ship. First, the basic theory of ship vibration is considered and the main sources of ship vibration are enumerated. Then, the manner and the steps of vibration measurement on ship structure are presented and a summary of vibration measurement guidelines is mentioned. Afterward, the procedure how to analyze the measured data of ship vibration is outlined and a comparison between the measured data and standard limits for vibration level considering structural vibration, machinery vibration and human comfort is done. Next, human response to vibration and the...
Sensor Network Localization Using Semidefinite Representations and Facial Reductions
, M.Sc. Thesis Sharif University of Technology ; Mahdavi Amiri, Nezamoddin (Supervisor)
Abstract
Use of wireless sensor networks (WSNs) to record environmental data such as temperature, sound level, and light intensity has grown dramatically. The specification of the locations of sensors is important. Using tools such as global positioning system (GPS) to find the location of sensors is not economical. Sensors can record their distances from neighboring sensors. On the other hand, the locations of some sensors are fixed. In wireless sensor network localization (SNL), we want to find the location of sensors using the available information. An approach for solving the SNL problem is to model the problem as an optimization problem and use an interior point method for its solution. Interior...
Comparison of classification and dimensionality reduction methods used in fMRI decoding
, Article Iranian Conference on Machine Vision and Image Processing, MVIP ; 2013 , Pages 175-179 ; 21666776 (ISSN) ; 9781467361842 (ISBN) ; Fatemizadeh, E ; Sharif University of Technology
2013
Abstract
In the last few years there has been growing interest in the use of functional Magnetic Resonance Imaging (fMRI) for brain mapping. To decode brain patterns in fMRI data, we need reliable and accurate classifiers. Towards this goal, we compared performance of eleven popular pattern recognition methods. Before performing pattern recognition, applying the dimensionality reduction methods can improve the classification performance; therefore, seven methods in region of interest (RDI) have been compared to answer the following question: which dimensionality reduction procedure performs best? In both tasks, in addition to measuring prediction accuracy, we estimated standard deviation of...
Reliability-constrained unit commitment using stochastic mixed-integer programming
, Article 2010 IEEE 11th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2010, 14 June 2010 through 17 June 2010 ; June , 2010 , Pages 200-205 ; 9781424457236 (ISBN) ; Fotuhi Firuzabad, M ; Aminifar, F ; Abiri Jahromi, A ; Sharif University of Technology
2010
Abstract
This paper proposes a stochastic mixed-integer programming (SMIP) model for the reliability-constrained unit commitment (RCUC) problem. The major objective of the paper is to examine both features of accuracy and efficiency of the proposed SMIP model of RCUC. The spinning reserve of generating units is considered as the only available reserve provision resource; however, the proposed formulation can be readily extended to comprise the other kind of reserve facilities. Expected load not served (ELNS) and loss of load probability (LOLP) are accommodated as the reliability constraints. Binding either or both reliability indices ensures the security of operation incorporating the stochastic...