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A new integration scheme for application to seismic hybrid simulation
, Article Earthquake Engineering and Engineering Vibration ; Volume 16, Issue 1 , 2017 , Pages 69-81 ; 16713664 (ISSN) ; Tasnimi, A. A ; Ahmadizadeh, M ; Sharif University of Technology
Institute of Engineering Mechanics (IEM)
2017
Abstract
Hybrid simulation is a powerful test method for evaluating the seismic performance of structural systems. This method makes it feasible that only critical components of a structure be experimentally tested. This paper presents a newly proposed integration algorithm for seismic hybrid simulation which is aimed to extend its capabilities to a wide range of systems where existing methods encounter some limitations. In the proposed method, which is termed the variable time step (VTS) integration method, an implicit scheme is employed for hybrid simulation by eliminating the iterative phase on experimental element, the phase which is necessary in regular implicit applications. In order to study...
Multiscale Modeling of Crack Propagation under Thermal Fatigue in Nano-Structured Materials
, Ph.D. Dissertation Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In this research, various molecular dynamics simulations have been carried out and sensitivity of the crack propagation process to the simulation parameters including the load pattern, maximum applied strain, temperature, loading frequency, and percentage of defects is investigated. Moreover, the crack propagation in poly-crystalline structure is studied using a larger model consisting of several atomic crystals and the effect of the presence of crystals on crack growth is investigated. In the next step, a novel coupling technique is developed in the continuum–atomistic multi-scale analysis of temperature field problems. In this manner, a new thermostat is introduced based on the single-atom...
Chain deformation in translocation phenomena
, Article Soft Matter ; Volume 9, Issue 9 , 2013 , Pages 2750-2759 ; 1744683X (ISSN) ; Maleknejad, A ; Varnik, F ; Ejtehadi, M. R ; Sharif University of Technology
2013
Abstract
Deformation of single stranded DNA in a translocation process before reaching the pore is investigated. By solving the Laplace equation in a suitable coordinate system and with appropriate boundary conditions, an approximate solution for the electric field inside and outside a narrow pore is obtained. With an analysis based on the "electrohydrodynamic equivalence" we determine the possibility of the extension of a charged polymer due to the presence of an electric field gradient in the vicinity of the pore entrance. With a multi-scale hybrid simulation (LB-MD), it is shown that an effective deformation before reaching the pore occurs, which facilitates the process of finding the entrance for...
Reliable nonlinear hybrid simulation using modified operator splitting technique
, Article Structural Control and Health Monitoring ; 2018 ; 15452255 (ISSN) ; Tasnimi, A. A ; Ahmadizadeh, M ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
One of the main challenges of hybrid simulation is developing integration methods that not only provide accurate and stable results but also are compatible with the hybrid simulation circumstances. This paper presents a novel enhanced integration technique for hybrid simulation termed “modified operator splitting” (MOS) method. The main aim of the MOS technique is to improve the precision of the operator splitting (OS) method by reducing the corrector step length, where initial stiffness is utilized instead of actual stiffness. For this purpose, a new algorithm is proposed, which makes a more precise estimation of the predictor displacement; thus minimizes the effect of the corrective...
Reliable nonlinear hybrid simulation using modified operator splitting technique
, Article Structural Control and Health Monitoring ; Volume 26, Issue 1 , 2019 ; 15452255 (ISSN) ; Tasnimi, A. A ; Ahmadizadeh, M ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
One of the main challenges of hybrid simulation is developing integration methods that not only provide accurate and stable results but also are compatible with the hybrid simulation circumstances. This paper presents a novel enhanced integration technique for hybrid simulation termed “modified operator splitting” (MOS) method. The main aim of the MOS technique is to improve the precision of the operator splitting (OS) method by reducing the corrector step length, where initial stiffness is utilized instead of actual stiffness. For this purpose, a new algorithm is proposed, which makes a more precise estimation of the predictor displacement; thus minimizes the effect of the corrective...
Reliable nonlinear hybrid simulation using modified operator splitting technique
, Article Structural Control and Health Monitoring ; Volume 26, Issue 1 , 2019 ; 15452255 (ISSN) ; Tasnimi, A. A ; Ahmadizadeh, M ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
One of the main challenges of hybrid simulation is developing integration methods that not only provide accurate and stable results but also are compatible with the hybrid simulation circumstances. This paper presents a novel enhanced integration technique for hybrid simulation termed “modified operator splitting” (MOS) method. The main aim of the MOS technique is to improve the precision of the operator splitting (OS) method by reducing the corrector step length, where initial stiffness is utilized instead of actual stiffness. For this purpose, a new algorithm is proposed, which makes a more precise estimation of the predictor displacement; thus minimizes the effect of the corrective...
A resilience-based practical platform and novel index for rapid evaluation of urban water distribution network using hybrid simulation
, Article Sustainable Cities and Society ; Volume 82 , 2022 ; 22106707 (ISSN) ; Mortaheb, M. M ; Hassani, N ; Taghizadeh yazdi, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
This article proposes a novel index along with a user-friendly platform for resilience evaluation of the urban water distribution networks (WDN). WDN is of great importance in preserving the safety and sustainability of communities and cities. Resilience of a given system results in its sustainability. In recent years, many studies have focused on resilient urban WDN. However, these studies did not provide a comprehensive evaluation index and platform that could simultaneously consider hydraulic analysis, resilience parameters, and significant uncertainties. In this study, a novel resilience index was defined, and a user-friendly and practical platform (REWAT) was developed to calculate the...
Analysis of Organizational Learning Using Hybrid Simulation Involving Agent-based and System Dynamics Models
, M.Sc. Thesis Sharif University of Technology ; Akhavan Niaki, Taghi (Supervisor) ; Mashayekhi, Alinaghi (Co-Advisor)
Abstract
Integrated modeling of learning makes happen simultaneous investigation and analysis of the interaction among different scales, abstraction levels and contexts within an organization. Enquiry of the organization, organizational unit and individual employee scales at levels of low and high abstraction within temporal, spatial and event-driven contexts may have conspicuous impact on perspicuousness of learning concept, as well as the creation of productive policy making opportunities which improves system performance measurements and their influencing causes. By development in multi-method approach to system modeling, integrated representation of learning has got recently feasible. Thus, a...
Extending a hybrid continuum-molecular simulation method to solve the micro/nanoscale gas mixing problems
, Article ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting, FEDSM 2018, 15 July 2018 through 20 July 2018 ; Volume 3 , 2018 ; 08888116 (ISSN); 9780791851579 (ISBN) ; Darbandi, M ; Schneider, G. E ; Fluids Engineering Division ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2018
Abstract
Despite vast efforts in developing hybrid continuum-molecular methods, there has been no specific work focused on the gas mixture flow simulations including the mixing and/or separation of species. In present study, we extend a hybrid method to analyze such phenomena suitably and study the gas mixing problems in micro/nano length scales reliably. The results of current hybrid simulations are compared against the results of full-molecular simulations to evaluate the physical accuracy of developed hybrid method. The effect of continuum breakdown criterion is investigated to find out the achieved accuracy of developed hybrid simulation method from different perspectives. The current results...
Iterative implicit integration procedure for hybrid simulation of large nonlinear structures
, Article Earthquake Engineering and Structural Dynamics ; Volume 40, Issue 9 , October , 2011 , Pages 945-960 ; 00988847 (ISSN) ; Ahmadizadeh, M ; Sharif University of Technology
2011
Abstract
A fully implicit iterative integration procedure is presented for local and geographically distributed hybrid simulation of the seismic response of complex structural systems with distributed nonlinear behavior. The purpose of this procedure is to seamlessly incorporate experimental elements in simulations using existing fully implicit integration algorithms designed for pure numerical simulations. The difficulties of implementing implicit integrators in a hybrid simulation are addressed at the element level by introducing a safe iteration strategy and using an efficient procedure for online estimation of the experimental tangent stiffness matrix. In order to avoid physical application of...
A hybrid simulation-adaptive network based fuzzy inference system for improvement of electricity consumption estimation
, Article Expert Systems with Applications ; Volume 36, Issue 8 , 2009 , Pages 11108-11117 ; 09574174 (ISSN) ; Saberi, M ; Gitiforouz, A ; Saberi, Z ; Sharif University of Technology
2009
Abstract
This paper presents a hybrid adaptive network based fuzzy inference system (ANFIS), computer simulation and time series algorithm to estimate and predict electricity consumption estimation. The difficulty with electricity consumption estimation modeling approach such as time series is the reason for proposing the hybrid approach of this study. The algorithm is ideal for uncertain, ambiguous and complex estimation and forecasting. Computer simulation is developed to generate random variables for monthly electricity consumption. Various structures of ANFIS are examined and the preferred model is selected for estimation by the proposed algorithm. Finally, the preferred ANFIS and time series...