Search for: computer-simulation
Total 1232 records
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...
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 ; 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...
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...
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 ; 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...
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 ; 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...
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...
Subject-specific loads on the lumbar spine in detailed finite element models scaled geometrically and kinematic-driven by radiography images, Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 35, Issue 4 , 2019 ; 20407939 (ISSN) ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
Traditional load-control musculoskeletal and finite element (FE) models of the spine fail to accurately predict in vivo intervertebral joint loads due mainly to the simplifications and assumptions when estimating redundant trunk muscle forces. An alternative powerful protocol that bypasses the calculation of muscle forces is to drive the detailed FE models by image-based in vivo displacements. Development of subject-specific models, however, both involves the risk of extensive radiation exposures while imaging in supine and upright postures and is time consuming in terms of the reconstruction of the vertebrae, discs, ligaments, and facets geometries. This study therefore aimed to introduce a...
Rigid-bar loading on pregnant uterus and development of pregnant abdominal response corridor based on finite element biomechanical model, Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 36, Issue 1 , January , 2020 ; Ahmadian, M. T ; Mohammadi, H ; Sharif University of Technology
During pregnancy, traumas can threaten maternal and fetal health. Various trauma effects on a pregnant uterus are little investigated. In the present study, a finite element model of a uterus along with a fetus, placenta, amniotic fluid, and two most effective ligament sets is developed. This model allows numerical evaluation of various loading on a pregnant uterus. The model geometry is developed based on CT-scan data and validated using anthropometric data. Applying Ogden hyper-elastic theory, material properties of uterine wall and placenta are developed. After simulating the “rigid-bar” abdominal loading, the impact force and abdominal penetration are investigated. Findings are compared...
Effect of microthread design of dental implants on stress and strain patterns: A three-dimensional finite element analysis, Article Biomedizinische Technik ; Volume 58, Issue 5 , September , 2013 , Pages 457-467 ; 00135585 (ISSN) ; Raoofi, S ; Kadkhodazadeh, M ; Movahhedi, M. R ; Khademi, M ; Sharif University of Technology
Walter de Gruyter and Co 2013
The aim of this study was to use finite element analysis (FEA) to assess the influence of microthread design at the implant neck on stress distribution in the surrounding bone. A commercially available implant with 3.5 mm diameter and 10.5 mm length was selected and used as a model. For the purpose of designing the microthread implant model, microthreads were added to the implant neck in a computerized model. A force measuring 100 N was then applied to the entire surface of the abutment in the vertical direction. The results showed that in both models, stress was mainly concentrated at the cortical bone adjacent to the neck of the implant. Maximum stress values in the cortical bone...
Article Periodica Polytechnica Transportation Engineering ; Volume 33, Issue 1-2 , 2005 , Pages 125-137 ; 03037800 (ISSN) ; Kermanshah, M ; Sharif University of Technology
Technical University of Budapest 2005
The use of traffic information in the form of radio reports, as a solution to the problem of congestion, is one of the issues, which are of particular importance for large cities like Tehran. In this study, factors affecting the use of traffic information in the context of a developing country are examined for commuters in the city of Tehran using ordered logit models. Results based on the particular survey designed for this purpose are compared to those of a developed country. Regarding the use of information in the form of listening to the radio traffic reports, the models show that older commuters, commuters who adjust their departure time according to traffic conditions (those who are...
Effect of intervertebral translational flexibilities on estimations of trunk muscle forces, kinematics, loads, and stability, Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 18, Issue 16 , Sep , 2015 , Pages 1760-1767 ; 10255842 (ISSN) ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
Taylor and Francis Ltd 2015
Due to the complexity of the human spinal motion segments, the intervertebral joints are often simulated in the musculoskeletal trunk models as pivots thus allowing no translational degrees of freedom (DOFs). This work aims to investigate, for the first time, the effect of such widely used assumption on trunk muscle forces, spinal loads, kinematics, and stability during a number of static activities. To address this, the shear deformable beam elements used in our nonlinear finite element (OFE) musculoskeletal model of the trunk were either substantially stiffened in translational directions (SFE model) or replaced by hinge joints interconnected through rotational springs (HFE model). Results...
Numerical simulations of turbulent flow around side-by-side circular piles with different spacing ratios, Article International Journal of River Basin Management ; Volume 15, Issue 2 , 2017 , Pages 227-238 ; 15715124 (ISSN) ; Ataie Ashtiani, B ; Dashtpeyma, H ; Sharif University of Technology
Taylor and Francis Ltd 2017
Numerical simulations of the turbulent flow around single and side-by-side piles at different spacing ratios (centre-to-centre distance to the pile diameter) with flow Reynolds number of 105 on the fixed flat-bed are presented. The calculations are performed using the computational fluid dynamics model, FLOW-3D, which solves the Navier–Stokes equations in three dimensions with a finite-volume method. The numerical results of time-averaged flow patterns around single and side-by-side piles are validated using the available experimental measurements. At the downstream of the single pile, dimensionless vortex shedding frequency (Strouhal number) is estimated as 0.22. The maximum values of bed...
Article International Journal of Geotechnical Engineering ; Volume 14, Issue 6 , 2020 , Pages 644-652 ; Ahmadi, M. M ; Sharif University of Technology
Taylor and Francis Ltd 2020
This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs...
Article Communications in Statistics: Simulation and Computation ; Volume 50, Issue 11 , 2021 , Pages 3436-3464 ; 03610918 (ISSN) ; Akhavan Niaki, T ; Khedmati, M ; Sharif University of Technology
Taylor and Francis Ltd 2021
In some quality control applications, processes consist of multiple components, stations or stages to finish the final products or the services. Some quality characteristics in each stage of these processes (called multistage processes) can be represented by a relationship between a response and one or more explanatory variables which is named as profile. In this paper, a general model is proposed for monitoring multivariate profiles in multistage processes. To this aim, the multivariate form of the U transformation approach is first used to remove the effect of the cascade property between the stages. Then, three control schemes are employed to monitor the parameters of multivariate simple...
Numerical study of stiff diaphragm walls used to improve the performance of rocking foundation systems, Article Journal of Earthquake Engineering ; Volume 25, Issue 13 , 2021 , Pages 2628-2650 ; 13632469 (ISSN) ; Fadaee, M ; Ghannad, M. A ; Jahankhah, H ; Sharif University of Technology
Taylor and Francis Ltd 2021
This research explores the effectiveness of the use of stiff diaphragm walls next to a rocking foundation through numerical simulation. This improvement technique is used as a means to increase in subsoil peripheral confinement and reduce rocking-induced settlement. The numerical model was verified by the centrifuge test of rocking shallow foundations on clay under cyclic loading. A parametric study was conducted to explore the effect of three stiff wall shapes on the performance of a rocking system. The general conclusion of the parametric investigation is that the use of stiff diaphragm walls reduced the sinking-dominated settlement response of the rocking system. © 2019 Taylor & Francis...
Article Communications in Statistics: Simulation and Computation ; Volume 46, Issue 6 , 2017 , Pages 4465-4489 ; 03610918 (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
Taylor and Francis Inc 2017
In this article, the general linear profile-monitoring problem in multistage processes is addressed. An approach based on the U statistic is first proposed to remove the effect of the cascade property in multistage processes. Then, the T2 chart and a likelihood ratio test (LRT)-based scheme on the adjusted parameters are constructed for Phase-I monitoring of the parameters of general linear profiles in each stage. Using simulation experiments, the performance of the proposed methods is evaluated and compared in terms of the signal probability for both weak and strong autocorrelations, for processes with two and three stages, as well as for two sample sizes. According to the results, the...