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modeling-and-optimization
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Total 167 records
Dynamic Simulation of the Biped Normal and Amputee Human Gait
, M.Sc. Thesis Sharif University of Technology ; Farahmand, Farzam (Supervisor) ; Zohour, Hassan (Supervisor)
Abstract
One of the best methods of gait analysis is to use analytical models. In this project, first, the normal human gait was simulated using a two-dimensional biped model with 7 segments, i.e., a HAT segment representing head, arms and trunk, and 6 segments representing thighs, shanks and feet of the two legs. The foot-ground contact was simulated using a five-point penetration contact model. The elastic impact and friction effects are considered in the ground reaction force modeling. Optimization of the normal human walking model provided constant coefficients for simple PD controllers’ (driving torque) equations that could reasonably reproduce the normal kinematical pattern. Then, in the second...
Dynamic Simulation of Running Human Normal and with Below-Knee Prosthesis
, M.Sc. Thesis Sharif University of Technology ; Firoozbakhsh, Keykhosro (Supervisor) ; Zohoor, Hassan (Supervisor)
Abstract
Researches in the field of human gait have a lot of applications in medicine, ergonomics, sport science and technology. Lower limb prostheses design is one of the fields in which human gait is important. One of the best methods of gait analysis is to use analytical models. In this project, first, the normal human was simulated using a two-dimensional biped model with 7 segments, i.e., a HAT segment representing head, arms and trunk, and 6 segments representing thighs, shanks and feet of the two legs. In this model the foot-ground contact was is estimated using Taylor series after running experiment and it’s analysis which is expendable to people with different ages and different weight and...
Ant colony optimisation for finding the optimal railroad path
, Article Proceedings of the Institution of Civil Engineers: Transport ; Volume 170, Issue 4 , 2017 , Pages 218-230 ; 0965092X (ISSN) ; Shafahi, Y ; Sharif University of Technology
Thomas Telford Services Ltd
2017
Abstract
Engineers have applied mathematical models to find the optimal railway path in order to minimise the total cost subject to the railway limitations. There are two main issues for this problem. First, this approach results in a complex formulation for real-life applications, mainly because there are a huge number of variables and constraints. Second, to compute the total cost, different types of data are required, such as topography, right-of-way unit cost, forbidden zones and geology. Because various administrations are often responsible for preparing these data with their own standards, there is much inconsistency in the data. This paper deals with the first issue by proposing a...
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
Abstract
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...
Assessment of optimal reaction progress variable characteristics for partially premixed flames
, Article Combustion Theory and Modelling ; Volume 26, Issue 5 , 2022 , Pages 797-830 ; 13647830 (ISSN) ; Ommi, F ; Farshchi, M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
The reaction progress variable is a crucial concept in the advanced flamelet combustion models. As a controlling variable, a well-defined progress variable must consider the essential features of the combustion process. It is usually a heuristically defined linear combination of some major chemical species mass fractions. However, such a simple definition could lead to inaccurate results for the fuel-rich reactive mixtures or complicated fuels, due to the vast number of chemical species in the combustion process. In this paper, a new method for generating a reaction progress variable is proposed through solving a constrained optimisation problem. The proposed method uses a genetic algorithm...
Computational-based approach for predicting porosity of electrospun nanofiber mats using response surface methodology and artificial neural network methods
, Article Journal of Macromolecular Science, Part B: Physics ; Volume 54, Issue 11 , 2015 , Pages 1404-1425 ; 00222348 (ISSN) ; Khodaparast Haghi, A ; Kasaei, S ; Hasanzadeh, M ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
Comparative studies between response surface methodology (RSM) and artificial neural network (ANN) methods to find the effects of electrospinning parameters on the porosity of nanofiber mats is described. The four important electrospinning parameters studied included solution concentration (wt.%), applied voltage (kV), spinning distance (cm) and volume flow rate (mL/h). It was found that the applied voltage and solution concentration are the two critical parameters affecting the porosity of the nanofiber mats. The two approaches were compared for their modeling and optimization capabilities with the modeling capability of RSM showing superiority over ANN, having comparatively lower values of...
Personalized design of ankle-foot prosthesis based on computer modeling of amputee locomotion
, Article Assistive Technology ; September , 2018 ; 10400435 (ISSN) ; Mohammadi Moghaddam, M ; Farahmand, F ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
This study proposes a computer modeling approach to find the optimal damping coefficients of the viscoelastic ankle-foot prostheses for each specific amputee. A two-dimensional locomotion model was developed for a transtibial amputee and personalized using his body measures and the reference gait pattern of an equivalent able-bodied subject. By employing the forward dynamic simulation, the amputee’s locomotion was synthesized for different prosthetic settings to find the optimal damping coefficients, based on a kinematics and a total work cost function. Results indicated a good agreement between the model predictions and the experimental observations. © 2018, © 2018 RESNA
Personalized design of ankle-foot prosthesis based on computer modeling of amputee locomotion
, Article Assistive Technology ; Volume 32, Issue 2 , 2020 , Pages 100-108 ; Mohammadi Moghaddam, M ; Farahmand, F ; Sharif University of Technology
Taylor and Francis Inc
2020
Abstract
This study proposes a computer modeling approach to find the optimal damping coefficients of the viscoelastic ankle-foot prostheses for each specific amputee. A two-dimensional locomotion model was developed for a transtibial amputee and personalized using his body measures and the reference gait pattern of an equivalent able-bodied subject. By employing the forward dynamic simulation, the amputee’s locomotion was synthesized for different prosthetic settings to find the optimal damping coefficients, based on a kinematics and a total work cost function. Results indicated a good agreement between the model predictions and the experimental observations. © 2018, © 2018 RESNA
An optimization study of a palm oil-based regional bio-energy supply chain under carbon pricing and trading policies
, Article Clean Technologies and Environmental Policy ; Volume 20, Issue 1 , 2018 , Pages 113-125 ; 1618954X (ISSN) ; Ahmad, R ; Abdul Rahim, A. R ; Akbari Jokar, M. R ; Sharif University of Technology
Springer Verlag
2018
Abstract
Biomass residues due to their low bulk density typically require frequent transportation from biomass plantations in rural areas to conversion bio-energy power plants. This issue contrasts with environmental protection strategies, especially when power plants are facing different carbon reduction policies that enforce them to emit less than a given specific carbon amount. Although several researchers have investigated bio-energy supply chains concerning environmental policies, the majority of studies have been devoted to strategic decisions over a single planning period. This paper presents a multi-period bio-energy supply chain under carbon pricing (carbon tax) and carbon trading...
An agent-based model for optimal voltage control and power quality by electrical vehicles in smart grids
, Article 15th International Conference on Distributed Computing and Artificial Intelligence, DCAI 2018, 20 June 2018 through 22 June 2018 ; Volume 801 , 2019 , Pages 388-394 ; 21945357 (ISSN); 9783319996073 (ISBN) ; Sharif University of Technology
Springer Verlag
2019
Abstract
The electric power industry is the main part of Science development, and today, with the advent of technology, the demand for electric power has been expanded. On the other hand, smart grids are developing heavily. One of the notable features of these networks is the presence of a plug-in hybrid electric vehicle (PHEV). The addition of these cars to the network has its own advantages and disadvantages. One of the most important issues in smart grids is network management and control of critical system parameters. In this paper the effect of these cars on the grid is investigated. These vehicles impose an increase in production capacity in the uncontrolled charge mode. They also have the...
An agent-based model for optimal voltage control and power quality by electrical vehicles in smart grids
, Article 15th International Conference on Distributed Computing and Artificial Intelligence, DCAI 2018, 20 June 2018 through 22 June 2018 ; Volume 801 , 2019 , Pages 388-394 ; 21945357 (ISSN); 9783319996073 (ISBN) ; Sharif University of Technology
Springer Verlag
2019
Abstract
The electric power industry is the main part of Science development, and today, with the advent of technology, the demand for electric power has been expanded. On the other hand, smart grids are developing heavily. One of the notable features of these networks is the presence of a plug-in hybrid electric vehicle (PHEV). The addition of these cars to the network has its own advantages and disadvantages. One of the most important issues in smart grids is network management and control of critical system parameters. In this paper the effect of these cars on the grid is investigated. These vehicles impose an increase in production capacity in the uncontrolled charge mode. They also have the...
A robust multi-objective optimization model for project scheduling considering risk and sustainable development criteria
, Article Environment, Development and Sustainability ; Volume 23, Issue 8 , 2021 , Pages 11494-11524 ; 1387585X (ISSN) ; Abbasianjahromi, H. R ; Sepehri, M ; Zeighami, E ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
There is limited research that considers the sustainability aspect of the projects’ schedule. The present study proposes a model to cover this gap by considering sustainable development criteria. A multi-objective model with four objective functions, including minimizing cost, risk, and socio-environmental impacts, has been presented to decrease the project’s delay. Since some of the parameters are considered under conditions of uncertainty for the proximity of problems to real projects, the robust programming method is used to deal with the uncertainty, and the epsilon-constraint method was applied to solve the multi-objective model. Several scenarios are also defined to analyze the...
Optimal control of molecular weight and particle size distributions in a batch suspension polymerization reactor
, Article Iranian Polymer Journal (English Edition) ; Volume 28, Issue 9 , 2019 , Pages 735-745 ; 10261265 (ISSN) ; Shahrokhi, M ; Farahzadi, H ; Sharif University of Technology
Springer London
2019
Abstract
Mechanistic modelling is an engineering approach to simulate reasonable physical and chemical processes to develop a model to describe the behaviour of a system. Mathematical models are commonly adopted to explore the physical limits of a process, and are applied to process development, optimization and control. In this work, the population balance model and the moment technique have been utilized to model a suspension polymerization reactor and predict the dynamic evolution of particle size and molecular weight distributions. These distributions are two important factors that affect the physical, rheological and mechanical properties of a polymer, and its final product quality. The cell...
The development of a novel multi-objective optimization framework for non-vertical well placement based on a modified non-dominated sorting genetic algorithm-II
, Article Computational Geosciences ; Volume 23, Issue 5 , 2019 , Pages 1065-1085 ; 14200597 (ISSN) ; Jamshidi, S ; Zirbes, E ; Sharif University of Technology
Springer International Publishing
2019
Abstract
A single-objective well placement problem is one of the classical optimization problems in oilfield development and has been studied for many years, by researchers worldwide. However, the necessity to face practical applications and handle insufficient data in a single-objective optimization leads to the introduction of a multi-objective optimization framework, which consequently allows an engineer to manage more information. In this study, for the very first time, a multi-objective well placement optimization framework, based on a Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is utilized with a similarity-based mating scheme. To represent the power of this mating procedure, it is...
Analyzing the price skimming strategy for new product pricing
, Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 2099-2108 ; 10263098 (ISSN) ; Zare, A. G ; Sharif University of Technology
Sharif University of Technology
2013
Abstract
This article presents a new model for pricing a new product considering a skimming pricing strategy in the presence of competition. We consider two periods for price setting, including skimming and an economy period. The problem is to decide on skimming as well as economy price, in order to maximize total profit. The derived model is a non-linear programming model and we have analyzed the structure and properties of an optimal solution to develop a solution method. Analytical results, as well as managerial insights, are presented by mathematical and numerical analyses
Evaluation of planing craft maneuverability using mathematical modeling under the action of the rudder
, Article Scientia Iranica ; Volume 24, Issue 1 , 2017 , Pages 293-301 ; 10263098 (ISSN) ; Seif, M. S ; Mehdigholi, H ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
In the recent years, different mathematical models have been suggested for maneuvering of displacement vessels, which are capable to estimate maneuvering of the vessel with acceptable precision. But, simulation of planing craft maneuverability through a mathematical model has not been developed yet. In this paper, a mathematical model is developed for maneuvering of the planing craft by including the rudder forces and moments. Different maneuvers, such as straight-line stability, course keeping, and turning circle, are executed through the mathematical model. Simulation results are validated with the published experimental results and it is shown that they are in good agreement. Finally, the...
Robust model and solution algorithm for the railroad blocking problem under uncertainty
, Article Scientia Iranica ; Volume 25, Issue 4 , 2018 , Pages 1916-1930 ; 10263098 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Sharif University of Technology
2018
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 optimal paths for freight cars in a rail network. Often, demand and supply resource indicators are assumed certain; hence, the solution obtained from a certain model might not be optimal or even feasible in practice due to the stochastic nature of these parameters. To address this issue, this paper develops a robust model for this problem with uncertain demand and travel time as supply resource indicators. Since the model combines integer variables and nonlinear functions, a branch-And-cut algorithm is used to solve the...
Optimizing multi-response statistical problems using a genetic algorithm
, Article Scientia Iranica ; Volume 13, Issue 1 , 2006 , Pages 50-59 ; 10263098 (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
Sharif University of Technology
2006
Abstract
In this paper, two methods to solve multi-response statistical problems are presented. In these methods, desirability function, genetic algorithm and simulation methodology are applied. The desirability function is responsible for modeling the multi-response statistical problem, the genetic algorithm tries to optimize the model and, finally, the simulation approach generates the required input data from a simulated system. The methods differ from each other in controlling the randomness of the problem. In the first method, replications control this randomness, while, in the second method, the randomness is controlled by a statistical test. Furthermore, these methods are compared by designed...
Optimized age dependent clustering algorithm for prognosis: A case study on gas turbines
, Article Scientia Iranica ; Volume 28, Issue 3 B , 2021 , Pages 1245-1258 ; 10263098 (ISSN) ; Durali, M ; Abbasian Najafabadi, T ; Saadat Foumani, M ; Sharif University of Technology
Sharif University of Technology
2021
Abstract
This paper proposes an Age-Dependent Clustering (ADC) structure to be used for prognostics. To achieve this aim, a step-by-step methodology is introduced, that includes clustering, reproduction, mapping, and finally estimation of Remaining Useful Life (RUL). In the mapping step, a neural fitting tool is used. To clarify the age-based clustering concept, the main elements of the ADC model is discussed. A Genetic algorithm (GA) is used to find the elements of the optimal model. Lastly, the fuzzy technique is applied to modify the clustering. By investigating a case study on the health monitoring of some turbofan engines, the efficacy of the proposed method is demonstrated. The results showed...
Application of the Pitzer and the MSA-based models in predicting the activity and the osmotic coefficients of aqueous electrolyte solutions
, Article Scientia Iranica ; Volume 12, Issue 3 , 2005 , Pages 280-289 ; 10263098 (ISSN) ; Ghotbi, C ; Taghikhani, V ; Sharif University of Technology
Sharif University of Technology
2005
Abstract
The GV-MSA, the BMCSL-MSA and the Pitzer models were used to correlate the individual, the mean ionic activity coefficients and the osmotic coefficients of symmetric and asymmetric electrolyte solutions. In order to compare the results obtained from the GV-MSA with those obtained from the Pitzer and the BMCSL-MSA models, the same experimental data and the same minimization procedure were used and the new sets of parameters for the BMCSL-MSA and the Pitzer models were also reported. The values for the osmotic coefficients of electrolyte solutions were calculated directly using the values of the mean ionic activity coefficients obtained from the models studied in this work. The results for the...