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moradi--sepehr
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Viral cascade probability estimation and maximization in diffusion networks
, Article IEEE Transactions on Knowledge and Data Engineering ; 28 May , 2018 ; 10414347 (ISSN) ; Beigy, H ; Sharif University of Technology
IEEE Computer Society
2018
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 viral cascade If so, can we find a set of users that are more likely to trigger viral cascades These estimation and maximization problems are very challenging since both rare-event nature of viral cascades and efficiency requirement should be considered. Unfortunately, this problem still remains largely unexplored to date. In this paper, given temporal dynamics of a network, we first develop an efficient viral cascade probability estimation method, VICE, that leverages an special importance sampling approximation to achieve high...
Viral cascade probability estimation and maximization in diffusion networks
, Article IEEE Transactions on Knowledge and Data Engineering ; Volume 31, Issue 3 , 2019 , Pages 589-600 ; 10414347 (ISSN) ; Beigy, H ; Sharif University of Technology
IEEE Computer Society
2019
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 viral cascade? If so, can we find a set of users that are more likely to trigger viral cascades? These estimation and maximization problems are very challenging since both rare-event nature of viral cascades and efficiency requirement should be considered. Unfortunately, this problem still remains largely unexplored to date. In this paper, given temporal dynamics of a network, we first develop an efficient viral cascade probability estimation method, ViCE, that leverages an special importance sampling approximation to achieve high...
Structural virality estimation and maximization in diffusion networks
, Article Expert Systems with Applications ; Volume 206 , 2022 ; 09574174 (ISSN) ; Beigy, H ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Social media usage is one of the most popular online activities and people shares millions of message in a short time; however this information rarely goes viral. The diffusion process begins with an initial set of source nodes and continues with other nodes. In addition, the viral cascade is triggered when the number of infected nodes exceeds a specific threshold. Then, we find an initial set of source nodes that maximizes the number of infected nodes given the source nodes. This study aims to answer the following questions: how does a spread like a viral cascade propagate in a network? Do the structural properties of the propagation pattern play an important role in virality? If so, can we...
Multi-cass Semi-srvised Classification of Data Streams
, M.Sc. Thesis Sharif University of Technology ; Beigy, Hamid (Supervisor)
Abstract
Recent advances in storage and processing have provided the ability of automatic gathering of information which in turn leads to fast and contineous flow of data. The data which are produced and stored in this way are named data streams. It has many applications such as processing financial transactions, the recorded data of various sensors or the collected data by web sevices. Data streams are produced with high speed, large size and much dynamism and have some unique properties which make them applicable in precise modeling of many real data mining applications. The main challenge of data streams is the occurrence of concept drift which can be in four types: sudden, gradual, incremental or...
Fault-tolerant Attitude Control of Sattelite Using Neural Networks
, M.Sc. Thesis Sharif University of Technology ; Asadian, Nima (Supervisor)
Abstract
This research aims to introduce a new integrated fault tolerant attitude control system of satellites based on the neural networks. First, a linear controller and an optimal controller are designed assuming that no fault occurs in the reaction wheels of the satellite. It is obvious that these controllers are not able to respond properly when a fault occurs. Therefore, artificial neural networks are employed in the fault tolerant controller design. Neural networks are well-known for their adaptiveness and the ability to learn the dynamics of a system. Therefore, they can be used to predict the faulty conditions. In this research two approaches are examined to deal with the faulty conditions....
Information and Influence Diffusion in Social Network
,
Ph.D. Dissertation
Sharif University of Technology
;
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...
An analytical model for evaluation of wireless mesh networks
, Article 2008 International Symposium on Telecommunications, IST 2008, Tehran, 27 August 2008 through 28 August 2008 ; October , 2008 , Pages 295-300 ; 9781424427512 (ISBN) ; Ashtiani, F ; Sharif University of Technology
2008
Abstract
Wireless mesh networks (WMNs) are well-promising future networks especially for ubiquitous connection to Internet. In this paper, we propose an analytical model in order to evaluate the maximum stable throughput of a WMN based on a simplified version of IEEE 802.11s MAC protocol. Our modeling approach is based on a multi-class open queueing network. In this respect, we map some of the important features of IEEE 802.11s MAC protocol, esp., its contention-based and contention-free periods onto different parameters of the proposed queueing network. By solving the related traffic equations and applying the stability condition, we determine the maximum stable throughput, i.e., the maximum packet...
Three-phase Model for a Fixed-bed Laboratory Scale Diesel Hydrotreating Reactor
, M.Sc. Thesis Sharif University of Technology ; Khorasheh, Fahad (Supervisor) ; Sadighi, Sepehr (Supervisor)
Abstract
The harmful environmental effects of gases resulting from the combustion of sulfur compounds in fuel, poisoning of catalysts, corrosion of equipment, as well as the intensification of environmental considerations and new standards adopted for the maximum amount of sulfur, have made the desulfurization of fuels important; Meanwhile, the desulfurization method using hydrogen has a high potential to remove sulfur compounds. For example, diesel fuel contains a variety of impurities such as sulfur, nitrogen (basic and Non-basic), and aromatic compounds, the sulfur in diesel fuel causes many problems related to environmental pollution and corrosion of engine components. Also, due to the high...
Prediction of wax disappearance temperature using artificial neural networks
, Article Journal of Petroleum Science and Engineering ; Volume 108 , 2013 , Pages 74-81 ; 09204105 (ISSN) ; Mohadesi, M ; Moradi, M. R ; Sharif University of Technology
2013
Abstract
In this study, the artificial neural network (ANN) was used for the prediction of WDT. The inputs to network are molar mass and pressure, and the output is WDT at each input. A two-layer network with different hidden neurons and different learning algorithms such as LM, SCG, GDA and BR were examined. The network with 16 hidden neurons and Levenberg-Marquardt (LM) train function showed the best results in comparison with the other networks. Also, the predicted results of this network were compared with the thermodynamic models and better accordance with experimental data for ANN was concluded
Biodiesel production using CaO/γ-Al2 O3 catalyst synthesized by sol-gel method
,
Article
Canadian Journal of Chemical Engineering
;
Volume 93, Issue 9
,
July
,
2015
,
Pages 1531-1538
;
00084034 (ISSN)
; Mohadesi, M
; Rezaei, R
; Moradi, R
;
Sharif University of Technology
Wiley-Liss Inc
2015
Abstract
In this study, 40% CaO/γ-Al2 O3 catalyst was used for biodiesel production from corn oil. A transesterification reaction was done for 5h at a temperature of 65°C in the presence of corn oil, methanol (methanol to oil molar ratio of 12:1), and CaO/γ-Al2 O3 catalyst (0.06g/g (6wt%)). Catalyst used in this study was synthesized using the sol-gel method. In this method, two parameters of gelation temperature and nitric acid concentration were used as variables in the catalyst synthesis step, and experiments were designed using central composite design (CCD). The results indicate that the optimal point is achieved at a gelation temperature of 70°C and...
Study the Interaction between Cytoskleton and Cell Membrane
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor) ; Salarieh, Hassasn (Supervisor)
Abstract
In this project the main aim is to model the interaction between the cytoskeleton and cell membrane. In order to model the membrane and cytoskeleton it is used a discrete model, which contains several beads. For modeling the interaction between the beads it is used different kinds of energies. It is used four potentials in a 2D model for modeling the interaction between the membrane beads and it is used SSLJ potential in order to model the interaction between the cytoskeleton and cell membrane. Furthermore, this potential is used to model the interaction between the cytoskeleton filaments. Due to this potential, the cytoskeleton filaments can cross each other in the 2D model. For modeling...
DM Water Plant Sedimentation as a Cheap and Waste Source of Catalyst for Biodiesel Production
, Article International Journal of Chemical Reactor Engineering ; Volume 14, Issue 1 , 2016 , Pages 113-124 ; 15426580 (ISSN) ; Mohadesi, M ; Hosseini, S ; Davood Beygi, Y ; Moradi, R ; Sharif University of Technology
Walter de Gruyter GmbH
2016
Abstract
Transesterification reaction was performed in the presence of soybean oil, methanol, and Demineralized water plant sedimentation catalyst at 60°C for 8 h in this study. Central composite design method was used to study the effect of catalyst concentration and methanol to oil molar ratio on purity and yield of produced biodiesel. The results showed catalyst concentration of 9.08 wt% and methanol to oil molar ratio of 22.49 as the optimum condition in which the values of purity and yield of the produced biodiesel in the second-order models were 99.89% and 81.83%, respectively. Experiments are in good agreement with the mentioned values as corresponded values are 99.95% and 86.68%,...
State estimation, positioning and anti-swing robust control of traveling crane-lifter system
, Article Applied Mathematical Modelling ; March , 2015 ; 0307904X (ISSN) ; Vossoughi, G ; Sharif University of Technology
Elsevier Inc
2015
Abstract
Under different loading conditions, the over-head cranes may experience a wide range of model parameters variation. A robust control strategy is developed to achieve the high positioning accuracy, short transportation time and suppression of swing angle for an uncertain over-head crane system. Over-head crane is modeled as a three degrees of freedom system and control problem is investigated for two cases: a system with a single control input (the force on trolley) and a system with two control inputs (the force on trolley and the torque on lifter). Regulator and observer systems are designed. To achieve the tracking objectives, an optimal robust controller is designed based on μ-synthesis...
Analysis of nonlinear oscillations in spur gear pairs with approximated modelling of backlash nonlinearity
, Article Mechanism and Machine Theory ; Volume 51 , 2012 , Pages 14-31 ; 0094114X (ISSN) ; Salarieh, H ; Sharif University of Technology
2012
Abstract
Due to international competition and strict limitations of standards regarding the noise level, investigation of gear vibration is of great importance. In this paper, nonlinear oscillations of spur gear pairs including the backlash nonlinearity is studied. Dynamic system is described through the classical single degree of freedom (SDOF) model in terms of dynamic transmission error (DTE). Using multiple scale method, forced vibration responses of the gear system including primary, super-harmonic and sub-harmonic resonances are investigated. In each case, the jump phenomenon and stability analysis are studied. In addition, the effect of dynamic and manufacturing parameters of the gear system...
Nonlinear forced oscillations and stability analysis of the automotive gearbox system
, Article Proceedings of the ASME Design Engineering Technical Conference, 15 August 2010 through 18 August 2010 ; Volume 5 , 2010 , Pages 1013-1020 ; 9780791844137 (ISBN) ; Salarieh, H ; Sharif University of Technology
2010
Abstract
In this paper, nonlinear oscillation of the automobile gear system is studied. The backlash dynamic parameter is included in the nonlinear mathematical modeling of the problem. Using multiple scale method, forced vibration responses of the gear system including Primary, Subharmonic and Super-harmonic resonances are investigated. In each case, the jump phenomenon and stability analysis are studied. In addition, the effect of dynamic and manufacturing parameters of the gear system on the time responses are analyzed. Simulation and nonlinear analysis of the problem are developed in MAPLE and MATLAB environments
State estimation, positioning and anti-swing robust control of traveling crane-lifter system
, Article Applied Mathematical Modelling ; Volume 39, Issue 22 , 2015 , Pages 6990-7007 ; 0307904X (ISSN) ; Vossoughi, G ; Sharif University of Technology
Elsevier Inc
2015
Abstract
Under different loading conditions, the over-head cranes may experience a wide range of model parameters variation. A robust control strategy is developed to achieve the high positioning accuracy, short transportation time and suppression of swing angle for an uncertain over-head crane system. Over-head crane is modeled as a three degrees of freedom system and control problem is investigated for two cases: a system with a single control input (the force on trolley) and a system with two control inputs (the force on trolley and the torque on lifter). Regulator and observer systems are designed. To achieve the tracking objectives, an optimal robust controller is designed based on μ-synthesis...
Robust control of the variable speed wind turbines in the presence of uncertainties: A comparison between H∞ and PID controllers
, Article Energy ; Volume 90 , October , 2015 , Pages 1508-1521 ; 03605442 (ISSN) ; Vossoughi, G ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
To achieve a cost-effective and reliable use of wind power generation, advanced control techniques are required. In this paper, the application of two control strategies for the improvement of wind turbine power output is investigated in the presence of model/environmental uncertainties. Rotational speed of the wind turbine and consequently its power output are controlled via manipulation of blades pitch angle (at a constant generator torque). First, the classical PID controller is designed based on root locus analysis while in the second scheme, an H∞-robust controller is designed via μ-synthesis based on DKiteration algorithm. Performance of the two controllers in tracking of the desired...
Multivariable optimal control of an industrial nonlinear boiler–turbine unit
, Article Meccanica ; Volume 51, Issue 4 , 2016 , Pages 859-875 ; 00256455 (ISSN) ; Vossoughi, G ; Sharif University of Technology
2016
Abstract
Performance control of a boiler–turbine unit is of great importance due to demands for the economical operations of power plants and environmental awareness. In this paper, an optimal control strategy is designed to achieve the desired performance of a boiler–turbine unit. A multivariable nonlinear model of a utility boiler–turbine unit is considered. By manipulation of valves position for the fuel, steam and feed-water flows; output variables including the drum pressure, electric output and fluid density (and consequently drum water level) are controlled. Performance measure of the problem is defined such that the control efforts are minimized while the tracking objectives are obtained. In...
Multivariable control of the bifurcation and harmonic perturbations to improve the performance of air-handling units
, Article ISA Transactions ; Volume 60 , 2016 , Pages 119-127 ; 00190578 (ISSN) ; Vossoughi, G ; Sharif University of Technology
ISA - Instrumentation, Systems, and Automation Society
2016
Abstract
In this research, nonlinear dynamics of an air-ehandling unit (AHU) is studied for tracking objectives, in the presence of harmonic perturbations. Three arbitrary realistic set-paths are considered for the indoor temperature and relative humidity. Two controllers based on feedback linearization (FBL) and pole placement approaches are designed to preserve the dynamic system around the desired tracking paths. It is shown that FBL controller works efficiently in bifurcation control and transforms the quasi-periodic limit cycles into the periodic ones (and consequently comfortable indoor conditions). In addition, FBL controller guarantees suppression of larger periodic limit cycles into the...
A robust reliability-based scheduling for the maintenance activities during planned shutdown under uncertainty of activity duration
, Article Computers and Chemical Engineering ; Volume 130 , 2019 ; 00981354 (ISSN) ; Shadrokh, S ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Scheduling of the maintenance activities is considered, in which the duration of activities is uncertain, delivery date of the maintenance shutdown is predefined, and activities are multi-mode. The problem is a multi-mode time-constrained project scheduling problem (MTCPSP). The glycol regeneration unit in a gas refinery is as the case study. Based on the effect of equipment or sub-equipment on the system reliability, the importance value of equipment and sub-equipment within the system is determined, and these values are used in a heuristic algorithm as a priority rule for choosing activities in the schedule. Outcomes demonstrate the performance of the algorithm in early or on time delivery...