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Total 177 records

    Modeling of HV Substation Automation Systems and Evaluating of Operation Failure

    , M.Sc. Thesis Sharif University of Technology Falahati, Bamdad (Author) ; Vakilian, Mehdi (Supervisor)
    Abstract
    In two past decades, a revolution has occurred by emerging of substation automation system in field of substation control and protection system. The traditional control system has changed to the modern automation systems which are based on computer networks. The development of this project become possible by having experience in and being familiar with automation systems, studying equipment specifications, tasks, and criteria and analyzing operation of various systems. The main target of this thesis is evaluating the automation system precisely and exhaustively and developing a model based on mathematical relations. This model is founded based on the application and analysis of the networks.... 

    Short-Term Traffic Volume Estimation Based on Macroscopic Flow Characteristics

    , M.Sc. Thesis Sharif University of Technology Tajalli, Mehrdad (Author) ; Poorzahedy, Hossein (Supervisor)
    Abstract
    Traffic volume is the most important characteristic in most traffic studies, which is regularly measured by sampling methods for a given road. Traffic volume has determining effect in specifying network origin-destination demand, improvement of roads, traffic distributions over the network, improving road parameters, air pollution and in other aspects of flow in the network. There are many ways to measure traffic volume in different situations. However, most of them are expensive to implement and in cases which take a long time to do the survey, or the number of locations are excessive, the operation would not be cost-effective. In this research we investigate using macroscopic... 

    Accident Prediction Model Based on Macroscopic Traffic Characteristics

    , M.Sc. Thesis Sharif University of Technology Mohamadian Amiri, Amir (Author) ; Nassiri, Habibollah (Supervisor)
    Abstract
    Lately, there has been a great attention to accident prediction methods in traffic management. The importance of predicting an accident is because of its enormous effect on reducing casualties, injuries, property damages and delays. The main objectivein this study was to identify the relationship between accidents frequency rates and geometric design variables, climatic parameters and traffic characteristics using probabilistic models. The other objective was to evaluate the crash severity and crash type. Therefore, the 1997 traffic accident statistics of city of Mashhad in Iran was used for the for the modeling of different highway classification. Probabilistic models are used for... 

    Economic Analysis of Energy Supply Security based on Energy Security Indices

    , Ph.D. Dissertation Sharif University of Technology Kanani Maman, Yaser (Author) ; Maleki, Abbas (Supervisor)
    Abstract
    As a problem, generally, energy security components do not interfere with the calculation of the optimal energy supply situation. In this paper, we are looking to find a solution to make a framework of the impact of energy security on energy supply in order to obtain comprehensive analysis of the economic optimal point. Method is based on the competition of energy costs to meet demand during the study period. Threats that have been addressed in the energy security are seen as risky and stochastic parameters in the model. The nature of these parameters is of uncertainty type, therefore, based on the probable scenarios of the stochastic model, the perspective of the energy supply system is... 

    Stochastic Model for Optimal Participation of Wind Power Producers in Electricity Market Considering Risk Factors

    , M.Sc. Thesis Sharif University of Technology Shamsi Gushki, Amin (Author) ; Ehsan, Mehdi (Supervisor)
    Abstract
    This thesis presents a new method for scheduling wind generation companies to participate in day-ahead market. The assumed market structure of this thesis, considers day-ahead energy market and balancing market, simultaneously. The stochastic model of this, implements a robust function to face the uncertainties of these markets. The risk of participation in these market are controlled with Information Gap Decision Theory (IGDT). Finally the allowable percent of each uncertain parameters are introduced to met an specific level of profit for the company  

    Study of Statistical Behavior of Chaotic Maps and Design of Stochastic Models for Reconstruction and Prediction of Behavioral Patterns of Chaotic Systems

    , M.Sc. Thesis Sharif University of Technology Jokar, Meysam (Author) ; Salarieh, Hassan (Supervisor) ; Alasty, Aria (Supervisor)
    Abstract
    Chaotic time series analysis, study of statistical behavior of chaotic maps and eventually an attempt to reconstruction and prediction of dynamical and statistical properties of output data of chaotic systems using stochastic models such as Markov models and autoregressive-moving average models are the main purposes of the present research. Examples of chaotic time series abound in the output of economics, engineering systems, the natural sciences (especially geophysics and meteorology) and social sciences. An intrinsic feature of an output time series of a dynamic system is that, adjacent observations are dependent. Time series analysis is concerned with techniques for the analysis of this... 

    Modeling and Solution Algorithm for Multi-Path Railroad Blocking Problem under Demand and Travel Time Uncertainty

    , Ph.D. Dissertation Sharif University of Technology Mohammad Hassani, Reza (Author) ; Shafahi, Yousef (Supervisor)
    Abstract
    The railroad blocking problem emerges as an important issue at the tactical level of planning in freight rail transportation. This problem consists of determining the paths of each shipment which minimize the total cost subject to the key constraints such as limitation on travel time, limitation on number of dispatched trains, and limitation on the number of cars classified at each station. The multi-path railroad blocking model is developed and then a new heuristic algorithm based on the Lagrangian relaxation technique to solve the realistic rail network is introduced.To consider the uncertainty which is inherent in the demand and travel time (as a supply indicator of rail system), a... 

    Stochastic Modeling of Online Advertising System

    , M.Sc. Thesis Sharif University of Technology Divsalar, Mohammad Reza (Author) ; Nobakhti, Amin (Supervisor) ; Babazadeh, Maryam (Supervisor)
    Abstract
    Television, radio, newspaper, magazines, and billboards are among the major channels that traditionally place ads, however, the advancement of the Internet enables users to seek information online. In display and mobile advertising, the most significant technical development in recent years is the growth of Real-Time Bidding (RTB), which facilitates a real-time auction for a display opportunity. Real-time means the auction is per impression and the process usually occurs less than 300 milliseconds before the ad is placed. RTB has fundamentally changed the landscape of the digital media market by scaling the buying process across a large number of available inventories among publishers in an... 

    Information and Influence Diffusion in Social Network

    , Ph.D. Dissertation Sharif University of Technology Sepehr, Arman (Author) ; Beigy, Hamid (Supervisor)
    Abstract
    People use social networks to share millions of stories every day, but these stories rarely become viral. Can we estimate the probability that a story becomes a u/rof cascade? If so, can we find a set of users that are more likely to trigger viral cascades? There are many factors influenced the message virality. In this thesis, we investigate the effect of graph structure, diffusion pattern as well as the message text on virality measure. Finally, the authors solve both source localization and inferring COVID-19 network via propsed methods.First, the authors investigate probability estimation and maximization of cascade virality. In this section, we develop an efficient viral cascade... 

    Energy Management Optimization in Samart Home

    , M.Sc. Thesis Sharif University of Technology Shaefi, Mojtaba (Author) ; Fotuhi Firouzabad, Mahmud (Supervisor) ; Rajabi Qahnuyeh, Abbas (Co-Advisor)
    Abstract
    Smart consumers have a major role in the development of the smart grid. On the other hand, increasing need for more flexibility in DGs highlights the consumer’s role. This is possible with the development of smart appliance and appropriate communications infrastructure to active consumers. Today, with the development of smart grids, it is possible to control different parts of home energy systems and manage energy consumption. In this project a comprehensive model has been developed to optimize energy consumption in smart home. In the next phase of the thesis, due to the random nature of solar energy and electric vehicles, stochastic model of smart home energy system is discussed. At this... 

    A multi-peak evolutionary model for stochastic simulation of ground motions based on time-domain features

    , Article Journal of Earthquake Engineering ; 2018 ; 13632469 (ISSN) Waezi, Z ; Rofooei, F. R ; Hashemi, M. J ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    This paper introduces an efficient stochastic method to produce fully nonstationary records having multiple peaks in power spectrum. The zero-crossing characteristics of the acceleration, velocity, and displacement time histories of the output signal are used to estimate the model parameters. This procedure is utilized to resimulate 252 non-pulse-like, horizontal near-field records with rupture distance of less than 10 km and strike–slip mechanism. The model parameters are regressed against moment magnitude, rupture distance, hypo-central depth, and shear wave velocity, enabling the scenario-based simulation of the records. The response spectra of the simulated records are compared with... 

    Stochastic model predictive control-based countermeasure methodology for satellites against indirect kinetic cyber-attacks

    , Article International Journal of Control ; 2022 ; 00207179 (ISSN) Amin Alandihallaj, M ; Assadian, N ; Khorasani, K ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    The objective of this paper is to provide a stochastic framework to optimally avoid collision between a maneuverable spacecraft and a space object or debris. The satellite collision can be caused through a cyber-attack on a satellite by colliding it with a considered strategic satellite. Consequently, it is highly imperative that critical operational space assets be provided with autonomous collision avoidance systems. The collision avoidance methodology proposed in this paper will reduce the collision probability to an acceptable level and protect the satellite against indirect kinetic cyber-attacks initiated by designing optimal collision avoidance maneuvers using a stochastic model... 

    New model for simulating random synthetic stochastic earthquake scenarios

    , Article Journal of Earthquake Engineering ; Volume 26, Issue 2 , 2022 , Pages 1072-1089 ; 13632469 (ISSN) Khansefid, A ; Bakhshi, A ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    This research attempts to propose a new simulating model capable of generating synthetic stochastic earthquake scenario including both seismological, and acceleration signal properties. The Iranian plateau is selected as a mainland for developing the model due to the existence of high-quality earthquake databases. This model is composed of two sub-models. The first one generates random seismic event scenarios including mainshocks and aftershocks. The second one procreates 3-dimensional synthetic stochastic accelerograms for each of the previously simulated events. This scenario-based predictive model offers a powerful tool to the risk modelers interested in lifetime seismic risk assessment... 

    Developing a wide easy-to-generate class of bivariate copulas

    , Article Communications in Statistics - Theory and Methods ; Volume 37, Issue 12 , Volume 37, Issue 12 , 2008 , Pages 1919-1929 ; 03610926 (ISSN) Izady, N ; Mahlooji, H ; Sharif University of Technology
    Taylor and Francis Inc  2008
    Abstract
    As of late, copulas have drawn great attention in stochastic simulation, financial engineering, and risk management. Their power lies under their ability of modeling dependent random variables. Using a known theorem in probability which proves that the fractional part of the sum of a uniform and an arbitrary independent continuous random variable follows a uniform distribution, we construct a wide class of bivariate copulas in which bivariate random vector generation can be performed easily. Some important members of this new class and their properties together with two invariant correlation measures and some insights in their application are presented. © Taylor & Francis Group, LLC  

    Experimental and analytical model analysis of Babolsar's steel arch bridge

    , Article 3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost, Porto, 16 July 2006 through 19 July 2006 ; 2006 , Pages 235-237 ; 0415403154 (ISBN); 9780415403153 (ISBN) Beygi, M. H. A ; Kazemi, M. T ; Lark, B ; Tabrizian, Z ; Sharif University of Technology
    Taylor and Francis/ Balkema  2006
    Abstract
    The paper presents the experimental and analytical model analysis of a steel-girder arch bridge. The field test is carried out by ambient vibration testing under traffic excitations. Both the peak picking method in the frequency domain and the stochastic subspace identification method in the time domain are used for the output-only model identification. A good agreement in identified frequencies has been found between the two methods. It is further demonstrated that the stochastic subspace method provides better mode shapes. The three-dimensional finite element models are constructed and an analytical model analysis is then performed to generate natural frequencies and mode shapes in the... 

    Modeling performance of hadoop applications: A journey from queueing networks to stochastic well formed nets

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 14 December 2016 through 16 December 2016 ; Volume 10048 LNCS , 2016 , Pages 599-613 ; 03029743 (ISSN) ; 9783319495828 (ISBN) Ardagna, D ; Bernardi, S ; Gianniti, E ; Karimian Aliabadi, S ; Perez Palacin, D ; Requeno, J. I ; Carretero, J ; Nakano, K ; Ko, R ; Mueller, P ; Garcia Blas, J ; Sharif University of Technology
    Springer Verlag  2016
    Abstract
    Nowadays, many enterprises commit to the extraction of actionable knowledge from huge datasets as part of their core business activities. Applications belong to very different domains such as fraud detection or one-to-one marketing, and encompass business analytics and support to decision making in both private and public sectors. In these scenarios, a central place is held by the MapReduce framework and in particular its open source implementation, Apache Hadoop. In such environments, new challenges arise in the area of jobs performance prediction, with the needs to provide Service Level Agreement guarantees to the enduser and to avoid waste of computational resources. In this paper we... 

    Bi-objective location problem with balanced allocation of customers and Bernoulli demands: two solution approaches

    , Article Soft Computing ; Volume 23, Issue 13 , 2018 , Pages 1-20 ; 14327643 (ISSN) Shiripour, S ; Mahdavi-Amiri, N ; Sharif University of Technology
    Springer Verlag  2018
    Abstract
    A bi-objective stochastic capacitated multi-facility location–allocation problem is presented where the customer demands have Bernoulli distributions. The capacity of a facility for accepting customers is limited so that if the number of allocated customers to the facility is more than its capacity, a shortage will occur. The problem is formulated as a bi-objective mathematical programming model. The first objective is to find optimal locations of facilities among potential locations and optimal allocations of stochastic customers to the facilities so that the total sum of fixed costs of establishment of the facilities and the expected values of servicing and shortage costs is minimized. The... 

    Apnea bradycardia detection based on new coupled hidden semi Markov model

    , Article Medical and Biological Engineering and Computing ; 12 November , 2020 Montazeri Ghahjaverestan, N ; Shamsollahi, M. B ; Ge, D ; Beuchee, A ; Hernandez, A. I ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2020
    Abstract
    In this paper, a method for apnea bradycardia detection in preterm infants is presented based on coupled hidden semi Markov model (CHSMM). CHSMM is a generalization of hidden Markov models (HMM) used for modeling mutual interactions among different observations of a stochastic process through using finite number of hidden states with corresponding resting time. We introduce a new set of equations for CHSMM to be integrated in a detection algorithm. The detection algorithm was evaluated on a simulated data to detect a specific dynamic and on a clinical dataset of electrocardiogram signals collected from preterm infants for early detection of apnea bradycardia episodes. For simulated data, the... 

    Empirical predictive model for generating synthetic non-stationary stochastic accelerogram of the Iranian plateau: including far- and near-field effects as well as mainshock and aftershock categorization

    , Article Bulletin of Earthquake Engineering ; Volume 17, Issue 7 , 2019 , Pages 3681-3708 ; 1570761X (ISSN) Khansefid, A ; Bakhshi, A ; Ansari, A ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    This work proposes comprehensive empirical predictive equations for generating stochastic synthetic 3-dimensional accelerograms for the Iranian plateau based on the existing database. First, the databank of Iranian accelerograms is collected, sorted, processed, declustered and categorized into the pulse-like and non-pulse-like data. To simulate the artificial accelerograms, a stochastic model capable of handling both the temporal and spectral non-stationarity of accelerograms is adopted. By implementing nonlinear curve fitting, parameters of the stochastic model are estimated. Then, the recorded events are categorized into eight distinct groups based on the existence of pulse-like... 

    Performance aware scheduling considering resource availability in grid computing

    , Article Engineering with Computers ; Volume 33, Issue 2 , 2017 , Pages 191-206 ; 01770667 (ISSN) Entezari Maleki, R ; Bagheri, M ; Mehri, S ; Movaghar, A ; Sharif University of Technology
    Springer London  2017
    Abstract
    This paper presents a mathematical model using Stochastic Activity Networks (SANs) to model a grid resource, and compute the throughput of a resource in servicing grid tasks, wherein the failure–repair behavior of the processors inside the resource is taken into account. The proposed SAN models the structural behavior of a grid resource and evaluates the combined performance and availability measure of the resource. Afterwards, the curve fitting technique is used to find a suitable function fitted to the throughput of a resource for grid tasks. Having this function and the size of each grid job based on its tasks, an algorithm is proposed to compute the makespan of each available resource to...