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Total 177 records

    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... 

    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... 

    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... 

    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.... 

    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  

    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... 

    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... 

    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... 

    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... 

    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... 

    Multi-objective dynamic cell formation problem: A stochastic programming approach

    , Article Computers and Industrial Engineering ; Volume 98 , 2016 , Pages 323-332 ; 03608352 (ISSN) Zohrevand, A. M ; Rafiei, H ; Zohrevand, A. H ; Sharif University of Technology
    Elsevier Ltd 
    Abstract
    This paper addresses dynamic cell formation problem (DCFP) which has been explored vastly for several years. Although a considerable body of literature in this filed, two remarkable aspects have been significantly ignored so far, as uncertainty and human-related issues. In order to compensate such a shortage, this paper develops a bi-objective stochastic model. The first objective function of the developed model seeks to minimize total cost of machine procurement, machine relocation, inter-cell moves, overtime utilization, worker hiring/laying-off, and worker moves between cells; while the second objective function maximizes labor utilization of the cellular manufacturing system. In the... 

    Fabrication and surface stochastic analysis of enhanced photoelectrochemical activity of a tuneable MoS2-CdS thin film heterojunction

    , Article RSC Advances ; Volume 6, Issue 20 , 2016 , Pages 16711-16719 ; 20462069 (ISSN) Zirak, M ; Ebrahimi, M ; Zhao, M ; Moradlou, O ; Samadi, M ; Bayat, A ; Zhang, H. L ; Moshfegh, A. Z ; Sharif University of Technology
    Royal Society of Chemistry  2016
    Abstract
    A very simple and well-controlled procedure was employed to prepare CdS nanoparticle/few-layer MoS2 nanosheet/Indium tin oxide (ITO) thin film heterostructures. To tune and fabricate the CdS/MoS2(t)/ITO thin films with various surface topographies, first electrophoretic deposition (EPD) was used to deposit MoS2 nanosheets on the ITO substrate under an optimized applied potential difference (8 V) for different deposition times (t) of 30, 60, 120 and 240 s. Then, CdS nanoparticles were deposited via a successive ion layer adsorption and reaction (SILAR) technique. The highest photo-current density of 285 μA cm-2 was measured for the CdS/MoS2(60 s)/ITO sample, which was about 2.3 times higher... 

    A fuzzy-stochastic OWA model for robust multi-criteria decision making

    , Article Fuzzy Optimization and Decision Making ; Volume 7, Issue 1 , 2008 , Pages 1-15 ; 15684539 (ISSN) Zarghami, M ; Szidarovszky, F ; Ardakanian, R ; Sharif University of Technology
    2008
    Abstract
    All realistic Multi-Criteria Decision Making (MCDM) problems face various kinds of uncertainty. Since the evaluations of alternatives with respect to the criteria are uncertain they will be assumed to have stochastic nature. To obtain the uncertain optimism degree of the decision maker fuzzy linguistic quantifiers will be used. Then a new approach for fuzzy-stochastic modeling of MCDM problems will be introduced by merging the stochastic and fuzzy approaches into the OWA operator. The results of the new approach, entitled FSOWA, give the expected value and the variance of the combined goodness measure for each alternative. Robust decision depends on the combined goodness measures of... 

    Recurrent spatio-temporal modeling of check-ins in location-based social networks

    , Article PLOS ONE ; Volume 13, Issue 5 , 23 May , 2018 ; 19326203 (ISSN) Zarezade, A ; Jafarzadeh, S ; Rabiee, H. R ; Sharif University of Technology
    Public Library of Science  2018
    Abstract
    Social networks are getting closer to our real physical world. People share the exact location and time of their check-ins and are influenced by their friends. Modeling the spatio-temporal behavior of users in social networks is of great importance for predicting the future behavior of users, controlling the users’ movements, and finding the latent influence network. It is observed that users have periodic patterns in their movements. Also, they are influenced by the locations that their close friends recently visited. Leveraging these two observations, we propose a probabilistic model based on a doubly stochastic point process with a periodic-decaying kernel for the time of check-ins and a... 

    Steering social activity: a stochastic optimal control point of view

    , Article Journal of Machine Learning Research ; Volume 18 , 2018 , Pages 1-35 ; 15324435 (ISSN) Zarezade, A ; De, A ; Upadhyay, U ; Rabiee, H.R ; Gomez Rodriguez, M ; Sharif University of Technology
    Microtome Publishing  2018
    Abstract
    User engagement in online social networking depends critically on the level of social activity in the corresponding platform-the number of online actions, such as posts, shares or replies, taken by their users. Can we design data-driven algorithms to increase social activity? At a user level, such algorithms may increase activity by helping users decide when to take an action to be more likely to be noticed by their peers. At a network level, they may increase activity by incentivizing a few influential users to take more actions, which in turn will trigger additional actions by other users. In this paper, we model social activity using the framework of marked temporal point processes,... 

    A risk-based resilient distribution system planning model against extreme weather events

    , Article IET Renewable Power Generation ; Volume 16, Issue 10 , 2022 , Pages 2125-2135 ; 17521416 (ISSN) Zare Bahramabadi, M ; Ehsan, M ; Farzin, H ; Sharif University of Technology
    John Wiley and Sons Inc  2022
    Abstract
    Due to the accelerated climate change, it is anticipated that the number and severity of natural disasters such as hurricanes, blizzards, and floods will be increased in the coming years. In this regard, this paper presents a distribution system planning model to improve the system resilience against hurricane. A scenario-based mathematical model is proposed to capture the random nature of weather events. Moreover, a stochastic optimization model is developed to simultaneously harden the distribution lines and place different types of distributed generation (DG) units such as microturbines (MTs), wind turbines (WTs), and photovoltaic cells (PVs). The conditional value at risk (CVaR) is used... 

    Stochastic non-stationary model for ground motion simulation based on higher-order crossing of linear time variant systems

    , Article Journal of Earthquake Engineering ; Volume 21, Issue 1 , 2017 , Pages 123-150 ; 13632469 (ISSN) Waezi, Z ; Rofooei, F. R ; Sharif University of Technology
    Abstract
    This article introduces a new time-varying model to generate synthetic non-stationary acceleration records using the modified Kanaii-Tajimi model with time-variant parameters. The proposed method can capture two different dominant frequencies per time which makes it suitable for synthesizing the near-field no-pulse earthquake records. A number of closed-form relationships are developed to describe the frequency dependent time-domain level crossings of the simulated records under white noise excitation. The model parameters are optimized using the crossing and Arias intensity properties of the synthetic and target records. The efficiency of the proposed model is demonstrated using a data base... 

    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... 

    An approach to divide wind power capacity between day-ahead energy and intraday reserve power markets

    , Article IEEE Systems Journal ; Volume 16, Issue 1 , 2022 , Pages 1123-1134 ; 19328184 (ISSN) Tavakkoli, M ; Fattaheian Dehkordi, S ; Pourakbari Kasmaei, M ; Liski, M ; Lehtonen, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Abstract
    Wind power producers have recently gained a significant penetration in the electric power network, which might cause some challenges for the system operation due to the uncertainties in the generated power. In this way, wind power owners may offer different services, such as providing reserve capacity besides their conventional role of delivering just energy. Currently, conventional generators are the main responsible for providing some reserve in case of uncertainty in renewable generation and demand changes. Therefore, this article introduces a novel approach that allows wind power producers to participate in both energy and reserve markets alongside conventional generators. A two-stage... 

    Replenish-up-to multi-chance-constraint inventory control system under fuzzy random lost-sale and backordered quantities

    , Article Knowledge-Based Systems ; Volume 53 , 2013 , Pages 147-156 ; 09507051 (ISSN) Taleizadeh, A. A ; Niaki, S. T. A ; Meibodi, R. G ; Sharif University of Technology
    2013
    Abstract
    In this paper, a multiproduct multi-chance constraint stochastic inventory control problem is considered, in which the time-periods between two replenishments are assumed independent and identically distributed random variables. For the problem at hand, the decision variables are of integer-type, the service-level is a chance constraint for each product, and the space limitation is another constraint of the problem. Furthermore, shortages are allowed in the forms of fuzzy random quantities of lost sale that are backordered. The developed mathematical formulation of the problem is shown to be a fuzzy random integer-nonlinear programming model. The aim is to determine the maximum level of...