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sajjadi--hashem
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Finite element modeling of trolling-mode AFM
, Article Ultramicroscopy ; Volume 189 , 2018 , Pages 24-38 ; 03043991 (ISSN) ; Nejat Pishkenari, H ; Vossoughi, G
Elsevier B.V
2018
Abstract
Trolling mode atomic force microscopy (TR-AFM) has overcome many imaging problems in liquid environments by considerably reducing the liquid-resonator interaction forces. The finite element model of the TR-AFM resonator considering the effects of fluid and nanoneedle flexibility is presented in this research, for the first time. The model is verified by ABAQUS software. The effect of installation angle of the microbeam relative to the horizon and the effect of fluid on the system behavior are investigated. Using the finite element model, frequency response curve of the system is obtained and validated around the frequency of the operating mode by the available experimental results, in air...
A Formal Semantics for CORBA Interface Definition Language
, M.Sc. Thesis Sharif University of Technology ; Izadi, Mohammad (Supervisor)
Abstract
Common Object Request Broker Architecture (CORBA) is a standard for hybrid applications that is designed and supported by Object Management Group (OMG). This standard defines protocols and Relational Data Model Objects / Services which can be connected into heterogeneous software (written in different languages). So we can use CORBA to share the distributed object platform, without worrying about where they are located or who has designed them. CORBA can package the codes (in some programming languages) and add the packaging information, such as the ability to execute the codes and how to implement them. So this package or object code can execute some other programs or CORBA objects that...
Complexity of density dependencies of thermal and internal pressure compared to that of total pressure
, Article Industrial and Engineering Chemistry Research ; Volume 52, Issue 23 , May , 2013 , Pages 8034-8045 ; 08885885 (ISSN) ; Parsafar, G ; Sharif University of Technology
2013
Abstract
A simple equation of state (EoS) has recently been introduced (J. Phys. Chem. B2009, 113, 11977-11987) as (Z - 1)v2 = e + f/ρ + gρ2, where Z ≡ pv/RT is the compressibility factor, v = 1/ρ is molar volume, and e, f, and g are temperature dependent parameters. This EoS has been found to be accurate for all types of nano and bulk solids and bulk fluids, in the entire temperature and pressure ranges for which experimental data are reported, except for the isotherms within 1 ≤ T r = T/Tc ≤ 1.1 for the spherical and near spherical species and for a wider temperature range for the cylindrical molecules. The aim of this work is to investigate the validity of a three-term expression similar to the...
Simulation of chatter vibrations in reaming
, Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 3 , 2008 , Pages 441-447 ; 0791842975 (ISBN); 9780791842973 (ISBN) ; Movahhedy, M. R ; Sharif University of Technology
2008
Abstract
A time domain approach is used to study the cutting conditions in reaming process that leads the system to regenerative chatter vibrations. The dynamic analysis of the system includes inertia of the tool, centripetal and Coriolis terms, damping and the first mode bending of reamer. A model of cutting forces proportional to chip cross sectional area and process damping proportional to cutting speed is considered. Numerical simulation based on the Euler integration scheme is carried out to obtain time domain solution of the equation. Despite linearization in force modelling, the model is nonlinear due to the change in the tool engagement area. Another nonlinearity included in the model jumping...
Simulation of chatter vibrations in reaming
, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 3 , 2007 , Pages 441-447 ; 0791842975 (ISBN) ; Movahhedy, M. R ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007
Abstract
A time domain approach is used to study the cutting conditions in reaming process that leads the system to regenerative chatter vibrations. The dynamic analysis of the system includes inertia of the tool, centripetal and Coriolis terms, damping and the first mode bending of reamer. A model of cutting forces proportional to chip cross sectional area and process damping proportional to cutting speed is considered. Numerical simulation based on the Euler integration scheme is carried out to obtain time domain solution of the equation. Despite linearization in force modelling, the model is nonlinear due to the change in the tool engagement area. Another nonlinearity included in the model jumping...
Haptic Design for Steering Mechanism in a System for Remote Vehicle Driving
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor)
Abstract
The purpose of this thesis is to design haptic control system for vehicle steering mechanism in a tele-driving system. Thus the subject is a developed subject in comparison with a steer by wire system. The difference is that in the steer by wire system, due to the lack of delay in sending and receiving data, possibility of instability is very low. This subject makes haptic control more difficult in vehicle tele-driving. Control of vehicle tele-driving steering system has been done by different bilateral control structures available in the literature. simulation results of the case that there is no delay in the transmission block suggest that used different control structures in order to...
Social distancing in pedestrian dynamics and its effect on disease spreading
, Article Physical Review E ; Volume 104, Issue 1 , 2021 ; 24700045 (ISSN) ; Hashemi, A ; Ghanbarnejad, F ; Sharif University of Technology
American Physical Society
2021
Abstract
Nonpharmaceutical measures such as social distancing can play an important role in controlling the spread of an epidemic. In this paper, we use a mathematical model combining human mobility and disease spreading. For the mobility dynamics, we design an agent-based model consisting of pedestrian dynamics with a novel type of force to resemble social distancing in crowded sites. For the spreading dynamics, we consider the compartmental susceptible-exposed-infective (SEI) dynamics plus an indirect transmission with the footprints of the infectious pedestrians being the contagion factor. We show that the increase in the intensity of social distancing has a significant effect on the exposure...
Active Control of Vibrations Transmitted to the Human Body in the Vehicle and in the Presence of Uncertainties Using the Robust Control Method
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
With the advent of new technologies in everyday human life, issues related to the use of vehicles have become crucial subjects of investigation. In this context, vibrations transmitted from the vehicle to the human body, especially in terms of long-term health effects, have garnered special attention and significance. The main objective of this research is to develop a control system for the active control of vibrations transmitted to the human body. To achieve this goal, a 5-DOF model of the human body has been employed as the study system. Considering the uncertainties in the parameters and dynamics of this model, H∞ and µ-synthesis methods have been utilized for robust control design. The...
Hardware Acceleration of Convolutional Neural Networks by Computational Prediction
, M.Sc. Thesis Sharif University of Technology ; Bayatsarmadi, Siavash (Supervisor)
Abstract
Recently, Convolutional neural networks (CNNs) are widely used in many artificial intelligence applications such as image processing, speech processing and robotics. The neural networks superior accuracy comes at the cost of high computational complexity. Recent studies show that these operations can be performed in parallel. Therefore, as graphic processing units (GPUs) offer the best performance in terms of computational power and throughput, they are widely used to implement and accelerate neural networks. Nevertheless, the high price and power consumption of these processors have resulted in drawing more attraction towards Field-Programmable Arrays (FPGAs). In order to improve resource...
Predictive Process Control Using a Hierachical Method Based on Regression Analysis and Artificial Neural Networks (case study: Spray Drying in Tile Industry)
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
This is the first attempt at process modeling in terms of predictive control using a hierachical method based on regression analysis and artificial neural networks(ANNs).This hierachical use leads to the reliability improvement of neural model of process in prediction (extrapolation and interpolation) of process output. such an outlook makes it possible to predict the proper input settings which achieved a desired process output by designing various senarios for process set up. This approach was applied in Tile industry for spray dring process and in order to indicate the achieved improvement,three models:(i) regression model of process using multiple linear regression,(ii)Neural model of...
Comparison Between Methods Of Synchronization In A Queue With Finite Customer Population
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
One technique to reduce variance of output in comparing two or more systems via simulation is random number synchronization. the primary technique for achieving synchronization is to assign an independent seed to each random process and then use the same collection of seeds across all systems . Another way of synchronization in systems with limited customer population is to assign different seed to each customer (transaction) and then use the same collection of seeds across all systems. The main Question to be considered here is which of these methods of synchronization can better reduce variance of output in a queue with finite customer population
Reliability Optimization of Series-Parallel System with Redundancy Allocation and Stochastic Failure Rate
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
This thesis presents a method to solve a redundancy allocation problem for the series-parallel system. The modeling formulation deals with the choice of the best redundancy strategy, component and redundancy level for each subsystem in order to maximize the system reliability under system-level constraints. Majority of the solution methods for the general redundancy allocation problems assume that the failure rate of components is determined. However, in practice variable failure rate may be used. The complexity of this problem is known as NP-hard and therefore the optimal solution is not accessible in the normal course of events. It is demonstrated in this thesis that genetic algorithm is...
Interpretation of the Seven Errors in Bulk Material Sampling with the Aim of Providing a Guideline (Protocol) for Sampling From Liquids - Case of Edible Oil
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
Sampling is so deep-rooted in our habits that it usually takes place unconsciously. A large number of books and articles have been published in this field. The connection between sampling and quality control is the reason that many industries have focused their attention on sampling; however, only a few numbersare familiar with bulk material sampling related issues. Describing this theory along with its seven errors is the main object of this research. Using this theory, characteristics of the lot of interest was analyzed. Creating necessary conditions for assuring sampling correctness is very critical and if these conditions cannot be provided, implementing some part of the theory issues...
Using Multivariate Tukey distribution in Multivariare Process Capability Indices
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
In this thesis we will provide a comprehensive study of process capability indices, and we use multivariate g-and-h Tukey distribution for calculating process capability indices of multivariate non-normal processes. Univariate process capability indices have been used commonly in literature for measuring the capability of a process. However, there are several processes with more than one quality characteristic. When these characteristics are independent, we can use univariate process capability indices, but when the characteristics are dependent we should use multivariate methods for measuring process capability. There have been several studies about multivariate process capability indices,...
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
In some statistical process control applications, quality of a process or product 1s characterized by a relationship between a response variable and one or more explanatory variables which is referred to as profile by researchers. In some applications such as calibration, this relationship is characterized by a simple linear regression. However, in some situations, more complicated models are needed. It seems that there is a little attention to monitoring of profiles with binary response variables. Furthermore, the extensive applications of binary response variables in real industrial worlds make it necessary to concentrate on this kind of profiles. In this ...
A Novel Metamodel-based Simulation Optimization Algorithm using a Hybrid Sequential Experimental Design
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
In this work, we propose a metamodel-based simulation optimization algorithm using a novel hybrid sequential experimental design. The algorithm starts with a metamodel construction phase in which at each stage, a sequential experimental design is used to select a new sample point from the search space using a hybrid exploration-exploitation search strategy. Based on the available design points at each stage, a metamodel is constructed using Artificial Neural Network (ANN) and Kriging interpolation techniques. The resulting metamodel is then used in the optimization process to evaluate new solutions. We use Imperialist Competitive Algorithm (ICA) which is a powerful population-based...
Nurse Scheduling of an Emergency Department in Order to Decreasing Patients Waiting Time Using Simulation and Genetic Algorithm
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
This work attempt to analyze the impact of changes in nurse scheduling on quality of services at emergency department of Emam Khomeini Hospital Complex. In nurse scheduling some constraints such as maximum working hours per week and unacceptable working sequences must be considered. A simulation model is developed to cover the complete flow for the patient through the emergency department. Emergency department of Emam Khomeini is simulated in order to obtain the patient average waiting time for each nurse roster. Then a genetic algorithm is integrated with the simulation model. In each iteration genetic algorithm produces many nurse rosters . For each roster the patient average waiting time...
Robust Optimization for Simulated Systems Using Risk Management and Kriging
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
Many simulation optimization problems are defined in random settings and their inputs have uncertainty. Therefore, in defining an optimal solution for these problems, uncertainties should be taken into account. The primary way of dealing with this , is Robust Optimization which finds solution immune to these changing settings. Aiming at finding a new approach for simulation optimization problems, this study investigates these uncertainties and robust methods. In the optimization problem, the goal and constraints are considered with separate risk measures and a related problem is defined as follows: Minimizing the weighted sum of all risks subject to the problem constraints. To solve the...
Change Point Estimation of Multivariate Multiple Linear Profiles, under Multiple Linear Drifts and Step Changes
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
Control charts are the most popular Statistical Process Control tools used to monitor process changes. However, they are not capable of identifying the real time of a process change, which is essential for diagnosing assignable causes of the change. Therefore, a number of methods of change-point estimation have been developed. In the literature, relatively little study has been done on multiple changes. In this research, a new method based on Maximum Likelihood Estimator (MLE) is introduced to identify linear drifts and step changes in multivariate multiple linear profiles. Due to the massive increase in the amount and time of the calculations along with the growth of the number of the...
An Integrated Simulation-DEA Approach to Multi-criteria Ranking of Scenarios for Execution of Operations in a Construction Project
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
Before a construction project gets under way an attempt is made to examine different ways and scenarios for its implementation. Through such a process the more appropriate scenarios should be selected based on several criteria that are not necessarily at the same level in terms of importance. The purpose of this study is to examine different scenarios for implementing operations in the pre-construction phase of a project, based on several competing criteria with different importance levels in order to achieve a more efficient execution plan. This paper presents a new framework that integrates discrete event simulation (DES) and data envelopment analysis (DEA) to rank different scenarios for...