Search for: computer-simulation
Total 1232 records
Introducing a New Boundary Condition Method in Dissipative Particle Dynamics and Simulation of Dilute Polymer Solution, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Saeid ; Saidi, Mohammad Hassan ; Shafiee, Mohammad Behshad
Dissipative particle dynamics (DPD) is an emerging mesoscopic computational method in which the interparticle forces arise because of coarse-graining at the molecular level. In the asymptotic limit of large length scales, the governing equations of continuum are reproduced, as demonstrated in this work. This method of simulation has the capability of simulating larger order of time and space in compare with dynamic molecular method. One of the important applications of DPD is simulating the dilute polymer solution. In this project, we developed a general code to simulate dilute polymer behavior which consists of polymeric forces and different types of usual DPD boundary conditions. This code...
Modeling and Solution Algorithm for Multi-Path Railroad Blocking Problem under Demand and Travel Time Uncertainty, Ph.D. Dissertation Sharif University of Technology ; Shafahi, Yousef
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...
M.Sc. Thesis Sharif University of Technology ; Farahmand, Farzam ; Parnianpour, Mohammad
Knee pain and injuries are very common in athletes. Anterior cruciate ligament (ACL) injury is one of the most important reason of knee acute and chronic pains. As ACL plays a significant role in knee stability and due to amount of reported ACL related injuries, much effort has been placed on finding proper and on time diagnosis and treatment of these injuries. Arthrometric methods are the most non-invasive reliable diagnosis option; however they are not fully capable of separating partial injuries from intact joint. This weakness can be investigated by quantifying the tests using computer simulations; so far few studies have been conducted toward this goal. In this study a two dimensional...
M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rouhollah
Physical and mechanical properties of cast alloys is partly a function of the morphology and volume fraction of phases from freezing. The microstructure of the eutectic solidification is function of physical properties (especially mobility and surface tension) and the volume fraction of phases involved in the evolution. The prediction of solidification microstructures will be very helpful for improving the mechanical properties of casting alloys and designing of new families of alloys. The theoretical study of the formation of eutectic microstructures is very difficult and almost impossible in general cases and empirical studies are expensive. The purpose of this study is to predict the...
M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza
We carry out computer simulations in the hope of understanding the properties of assemblies of molecules in terms of their structure and the microscopic interactions between them. This serves as a complement to conventional experiments, enabling us to learn something new, something that cannot be found out in other ways. One of the main families of simulation technique are molecular dynamics (MD). Over the last decade , nanoscience and nanotechnology have emerged as two of the pillars of the research that will lead us to the next industrial revolution. The fundamental entities of interest to nanoscience and nanotechnology are the isolated individual nanostructures and their assemblies. Nano...
M.Sc. Thesis Sharif University of Technology ; Hajilouy Benisi, Ali ; Mozafari, Ali Asghar
Nowadays internal combustion engines play an important role in the power generation as well as transportation fields all over the world. By using the turbocharger in internal combustion engine, more power is obtained in compare with aspirated engine having the same size, which is limited for gasoline engines. In this research, by a three-zone computer simulation code and experimental tests, the power boost limitations of the gasoline turbocharged engine are investigated. The results of single cylinder aspirated gasoline engine tests are used for validation the natural aspirated part of the code. For validating the turbocharged engine simulation, the results of a four cylinders gasoline...
Recursive Feasibility of Distributed Model Predictive Control: Application to Automated Irrigation Networks, M.Sc. Thesis Sharif University of Technology ; Farhadi, Alireza
The following thesis is concerned with the control of automated irrigation channel using model predictive control in order to eliminate upstream transient error propagation and amplification phenomenon. It is illustrated in the literature that one way of dealing with this phenomenon is to solve a constrained optimization problem at each receding horizon. However, this problem becomes infeasible for automated irrigation channels. Several methods in the literature have been proposed that exploit terminal constraints to guarantee the feasibility of this problem. Finding these constraints, however, is extremely time-consuming as well as impractical for large-scale automated irrigation channels....
M.Sc. Thesis Sharif University of Technology ; Goudarznia, Iraj
Increasing of industrial society's need to refinery's product, high consuming energy in distillation process and pollution product in it cause to researchers investigate about the alternative process for crude oil refinery. At this time, supercritical fluid extraction was regard as a less energy consuming process. The aim of this work was prepare to a computerized model for simulating of crude oil refinery's process. In this work effects of temperature and pressure on the supercritical extraction were investigated. The experiment was done at four temperatures (35, 40, 45, 50°C) and four pressures (100, 120, 140, 160 bar) by supercritical carbon dioxide and obtained samples were analyzed by...
Simultaneously Evaluate the Safety And Productivity of Construction Operations Using Computer Simulation, M.Sc. Thesis Sharif University of Technology ; Alvanchi, Amin
In order to respond to the concerns of safety and productivity of construction operations, in this research, the model based on discrete event simulation has been proposed. In this model, with simulation of different scenarios of construction operation in planning and designing phases, before starting construction operation, the level of safety and productivity of each scenario evaluates concurrently. The Scenario that best meets the safety and productivity concerns concurrently has been selected for operation. In order to evaluate the feasibility of the model in construction operation, the model has been implemented in a fabrical example. The operation of installing tiles on the sloping...
Article Computers in Biology and Medicine ; Volume 106 , 2019 , Pages 106-113 ; 00104825 (ISSN) ; Hasani Bidgoli, M ; Motahari, S. A ; Sedaghat, N ; Modarressi, M. H ; Sharif University of Technology
Elsevier Ltd 2019
Background: Nutrigenomic has revolutionized our understanding of nutrition. As plants make up a noticeable part of our diet, in the present study we chose microRNAs of edible plants and investigated if they can perfectly match human genes, indicating potential regulatory functionalities. Methods: miRNAs were obtained using the PNRD database. Edible plants were separated and microRNAs in common in at least four of them entered our analysis. Using vmatchPattern, these 64 miRNAs went through four steps of refinement to improve target prediction: Alignment with the whole genome (2581 results), filtered for those in gene regions (1371 results), filtered for exon regions (66 results) and finally...
Article IEEE Journal on Selected Areas in Communications ; Volume 27, Issue 9 , 2009 , Pages 1676-1686 ; 07338716 (ISSN) ; Matinfar, M. D ; Salehi, J. A ; Sharif University of Technology
In this paper we present and investigate a digital design and implementational details of a wireless optical CDMA (OCDMA) system based on generalized optical orthogonal codes (OOCs). A detailed digital implementation analysis and transmitter/receiver architectures in the context of the above design are fully studied. We analyze various subsystems for a wireless OCDMA system including detector and receiver structure, acquisition, and tracking blocks as well as evaluating their performance in a typical wireless OCDMA communication system. By analyzing two main parts of the system, namely, chip-level detector and OCDMA receiver blocks we evaluate the performance of the overall system....
Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 446-448 ; 0780395867 (ISBN); 9780780395862 (ISBN) ; Mousavi, M ; Emadi, M ; Nayebi, M. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2006
Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE
Whole cell mechanical property characterization based on mechanical properties of its cytoplasm and bio membrane, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 9 November 2012 through 15 November 2012 ; Volume 2 , November , 2012 , Pages 545-551 ; 9780791845189 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
Analysis and investigation of the relation between different parts of biological cells such as biomembrane, cytoplasm and nucleus can help to better understand their behaviors and material properties. In this paper, first, the whole elastic properties of mouse oocyte and embryo cells have been computed by inverse finite element and Levenberg-Marquardt optimization algorithm and second, using the derived mechanical properties and the mechanical properties of its bio membrane from the literature, the mechanical properties of its cytoplasm has been characterized. It has been assumed that the cell behavior is as continues, isotropic, nonlinear and homogenous material for modeling. Matching the...
Article Control Engineering Practice ; Volume 19, Issue 12 , December , 2011 , Pages 1408-1422 ; 09670661 (ISSN) ; Haeri, M ; Sharif University of Technology
A predictive functional controller based on ARMarkov model structure has been designed to control welding current and arc voltage in a GMAW process. The closed loop system performance is investigated through computer simulations and is compared by those achieved from implementing two commonly used controllers i.e. PI and feedback linearization based PID. The local stability of the closed loop system is analyzed in the presence of uncertainties in the linearized model of the process as well as the control parameters. Finally it is shown that the proposed controller performs like a PI controller along with a pre-filter compensator
Article Signal Processing ; Volume 88, Issue 3 , 2008 , Pages 558-570 ; 01651684 (ISSN) ; Taban, M. R ; Nayebi, M. M ; Norouzi, Y ; Sharif University of Technology
Order statistic (OS) CFAR processor is a powerful detector, but similar to many other CFAR detectors, suffers from clutter edge as well as interfering targets. To overcome these problems, two derivations of this detector have been developed. These are order statistic greatest of (OSGO) and order statistic smallest of (OSSO) CFAR processors. The cost, paid for this improvement, is a considerable decrease in detection probability for homogenous Weibull clutter. Furthermore, a substantial performance degradation of OSGO in interfering target (high target masking effect) and an excessive false alarm of OSSO in clutter edge, also, occur. This behavior is a result of non-soft rules used in these...
Wavelet packet decomposition of a new filter -based on underlying neural activity- for ERP classification, Article 29th Annual International Conference of IEEE-EMBS, Engineering in Medicine and Biology Society, EMBC'07, Lyon, 23 August 2007 through 26 August 2007 ; 2007 , Pages 1876-1879 ; 05891019 (ISSN) ; 1424407885 (ISBN); 9781424407880 (ISBN) ; Shamsollahi, M. B ; Hashemi, M. R ; Rezazadeh, I ; Sharif University of Technology
This paper introduces a wavelet packet algorithm based on a new wavelet like filter created by a neural mass model in place of wavelet. The hypothesis is that the performance of an ERP based BCI system can be improved by choosing an optimal wavelet derived from underlying mechanism of ERPs. The wavelet packet transform has been chosen for its generalization in comparison to wavelet. We compared the performance of proposed algorithm with existing standard wavelets as Db4, Bior4.4 and Coif3 in wavelet packet platform. The results showed a lowest cross validation error for the new filter in classification of two different kinds of ERP datasets via a SVM classifier. © 2007 IEEE
Article Journal of Petroleum Science and Engineering ; Volume 59, Issue 3-4 , 2007 , Pages 271-288 ; 09204105 (ISSN) ; Firoozabadi, B ; Mahani, H ; Khoozan, D ; Sharif University of Technology
Coarse grid generation from finely gridded geological model is a main step in reservoir simulation. Coarse grid generation algorithms aim at optimizing size, number and location of the grid blocks by identifying the important geological and flow features which control flow in porous media. By optimizing coarse grid structure we can improve accuracy of the coarse scale simulation results to reproduce fine grid behavior. A number of techniques have been proposed in the literature. We present a novel coarse grid generation procedure based on vorticity preservation between fine and coarse grids. In the procedure, the coarse grid mesh tries to capture variations in both permeability and fluid...
Article Asian Simulation Conference 2005, ASC 2005 and the 6th International Conference on System Simulation and Scientific Computing, ICSC 2005, Beijing, 24 October 2005 through 27 October 2005 ; 2005 , Pages 248-252 ; Farhad, M ; Mohammadpanah, A ; Sharif University of Technology
World Publishing Corporation 2005
Riding comfort, driving stability and drivability are important factors in good vehicle performance. These factors are heavily subject to low frequency vibration generated by engine. A recent tendency in engine mounting system design is the insertion of a sub-frame. In this paper a complete model of a typical vehicle is simulated with and without sub-frame. An acceleration analysis is studied for three important parts; steering roll, pedals and beneath of the deriver's feet. Also the effect and importance of existence of engine mount is studied by removing one engine mount. The results are presented graphically and show how using sub-frame improve the isolation of body vibration due to the...
Vibration analysis of axially loaded bridges traversed by accelerating vehicles with passenger dynamics, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 2 , 2004 , Pages 275-280 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Mehdigholi, H ; Esmailzadeh, E ; Sharif University of Technology
An investigation into the dynamics of vehicle-passenger-structure-induced vibration of suspension bridges traversed by accelerating vehicles is carried out. The vehicle including the driver and passengers is modeled as a half-car planer model with six degrees-of-freedom. In addition, the stiffness of compliant bushings at the connecting points of the shock absorbers to the body is considered. The bridge is assumed to obey the Timoshenko beam theory with axial load and arbitrary conventional boundary conditions. The roughness of the bridge is assumed as a differentiable function of location. Due to continuously moving the location of the variable loads on the bridge, and in the presence of...
Vibration analysis of a graphene nanoribbon under harmonic lorentz force using a hybrid modal-molecular dynamics method, Article International Journal of Structural Stability and Dynamics ; Vol. 14, issue. 2 , 2014 ; ISSN: 02194554 ; Mohammadkhani, H ; Amini, H ; Sharif University of Technology
An efficient hybrid modal-molecular dynamics method is developed for the vibration analysis of large scale nanostructures. Using the reduced order method, presented in this paper, linear and nonlinear vibrations of a suspended graphene nanoribbon (GNR) carrying an electric current in a harmonic magnetic field are investigated. The resonance frequencies as well as the nonlinear vibration response obtained by the present technique and direct molecular dynamic simulations are in very good agreement. Also, the obtained results illustrate the hardening behavior of nonlinear vibrations which is diminished by stretching the GNR