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sadeghi-arjmand--saeed
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Homogenization of Hamilton - Jacobi Equations
, M.Sc. Thesis Sharif University of Technology ; Fotouhi, Morteza (Supervisor)
Abstract
The aim of homogenization theory is to establish the macroscopic behaviour of a system which is ‘microscopically’ heterogeneous, in order to describe some characteristics of the heterogeneous medium (for instance, its thermal or electrical conductivity). This means that the heterogeneous material is replaced by a homogeneous fictitious one (the ‘homogenized’ material), whose global (or overall) characteristics are a good approximation of the initial ones. From the mathematical point of view, this signifies mainly that the solutions of a boundary value problem, depending on a small parameter, converge to the solution of a limit boundary value problem which is explicitly described. In...
Casing Design Optimization Considering Drilling and Production Conditions
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeed (Supervisor) ; Shad, Saeed (Supervisor)
Abstract
Casing design is one of the most expensive parts in the drilling of oil wells, and any cost reduction with the basic design of these casing strings will significantly reduce the total cost of the operation. In recent years, occurring scenarios-based casing design has become popular; Because in many cases, it eliminates non-occurring scenarios such as gas kick and saves on drilling costs. In this study, we have tried to investigate all scenarios that may occur during the lifetime of the well, whether drilling or production, and for each well, based on its own field information, possible scenarios for each casing part are selected separately and the applying loads are calculated. For this...
Investigation and Evaluation of Rehabilitation by Lowerlimb Exoskeleton Based on Patient Intention Detection
,
M.Sc. Thesis
Sharif University of Technology
;
Behzadipour, Saeed
(Supervisor)
Abstract
Rehabilitation of individuals with gait impairments—especially those caused by spinal cord injury or accidents—requires timely and effective interventions. Lower-limb exoskeletons, as advanced rehabilitation tools, enable precise, safe, and repeatable movement execution, thereby enhancing training efficiency and accelerating motor recovery. Mental engagement during such training is known to promote neuroplasticity and improve functional outcomes. This study investigates the integration of a brain–computer interface (BCI) based on electroencephalographic (EEG) signals with a lower-limb exoskeleton to control movement based on the user's motor intention. The main objective is to evaluate the...
Durability Investigation and Fatigue Life Prediction Modelling for Pre-orroded AZ31 Alloy
, Ph.D. Dissertation Sharif University of Technology ; Adib Nazari, Saeed (Supervisor)
Abstract
This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The...
Cerebrovascular Attack Detection Using Artificial Intelligent Neural Network
, M.Sc. Thesis Sharif University of Technology ; Bagheri Shouraki, Saeed (Supervisor) ; Haj Sadeghi, Khosrow (Co-Advisor)
Abstract
Cerebrovascular Attack has been ranked the second or third of top 10 death causes in Taiwan. It has caused about 13,000 deaths every year since 1986. Once Cerebrovascular Attack (CVA) occurs, it not only leads to the huge cost of medical care, but even death. All developed countries in the world put CVA prevention and treatment in high priority. However, it is necessary to build a detective model to enhance the accurate diagnosis of CVA. From this detective model, CVA classification rules were extracted and used to improve the diagnosis and detection of CVA. This study acquired 2449 valid samples from this CVA prevention and treatment program, and adopted three classification algorithms,...
Implementation of Accurate Bio-Inspired Spiking Neural Network Using Fuzzy Methods
, M.Sc. Thesis Sharif University of Technology ; Bagheri Shouraki, Saeed (Supervisor) ; Haj Sadeghi, Khosrow (Supervisor)
Abstract
Neuron models are the elementary units, which determine the performance of an Artificial Spiking Neural Network (ASNN) as they are known to be a particular class of machine learning methods. The ASNNs that are inspired by the features of biological neurons and organizational structure of biological nervous system as the third generation of Artificial Neural Networks (ANN). This thesis concentrates on study of biologically plausible neuron; based on Fuzzy approach and tries to develop fuzzy state of Leaky Integrate and Fire (LIF) model, in order to resemble closely the neuron-electrical dynamics for ASNN in most efficient way. In this study, the Fuzzy methods including TAKAGI-SUGENO-KANG...
Enhanced active/barrier corrosion protective properties of epoxy coatings containing eco-friendly green inorganic/organic hybrid pigments based on zinc cations/Ferula Asafoetida leaves
, Article Journal of Molecular Liquids ; 2020 ; Ghaderi, S ; Sadeghi, M ; Gorji, B ; Ahmadijokani, F ; Ramazani S.A., A ; Mahdavian, M ; Arjmand, M ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this study, a novel inorganic/organic hybrid pigment based on zinc cations/Ferula Asafoetida leaves extract (Zn-FALE) was synthesized, and its corrosion protection properties were investigated in a saline solution and an organic coating. Interactions of components between Zn2+ cations and FALE were assessed by thermo-gravimetric analysis (TGA) and ultraviolet-visible (UV–visible) spectroscopy. Corrosion inhibitive performance of FALE and Zn-FALE pigments in the solution phase and coating phase was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). TGA and UV–visible results revealed the proper chelation between inorganic and organic components of...
Enhanced active/barrier corrosion protective properties of epoxy coatings containing eco-friendly green inorganic/organic hybrid pigments based on zinc cations/Ferula Asafoetida leaves
, Article Journal of Molecular Liquids ; Volume 323 , 2021 ; 01677322 (ISSN) ; Ghaderi, S ; Sadeghi, M ; Gorji, B ; Ahmadijokani, F ; Ramazani Saadatabadi, A ; Mahdavian, M ; Arjmand, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In this study, a novel inorganic/organic hybrid pigment based on zinc cations/Ferula Asafoetida leaves extract (Zn-FALE) was synthesized, and its corrosion protection properties were investigated in a saline solution and an organic coating. Interactions of components between Zn2+ cations and FALE were assessed by thermo-gravimetric analysis (TGA) and ultraviolet-visible (UV–visible) spectroscopy. Corrosion inhibitive performance of FALE and Zn-FALE pigments in the solution phase and coating phase was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). TGA and UV–visible results revealed the proper chelation between inorganic and organic components of...
Corrigendum to “enhanced active/barrier corrosion protective properties of epoxy coatings containing eco-friendly green inorganic/organic hybrid pigments based on zinc cations/ferula asafoetida leaves” [J. mol. liquids 323 (2021) 114584] (journal of molecular liquids (2021) 323, (S0167732220353344), (10.1016/j.molliq.2020.114584))
, Article Journal of Molecular Liquids ; Volume 386 , 2023 ; 01677322 (ISSN) ; Ghaderi, S ; Sadeghi, M ; Gorji, B ; Ahmadijokani, F ; Ramazani Saadatabadi, A. A ; Mahdavian, M ; Arjmand, M ; Sharif University of Technology
Elsevier B.V
2023
Abstract
The authors wish to clarify a previous error regarding the scale bar in Figures 8(a2), 8(b2), and 8(c2). Initially, the scale bar was inaccurately labeled as "5 µm". The correct scale bar is “2 µm”. The revised version of Figure 8, now featuring updated scale bar, is presented below. It's important to emphasize that this modification does not affect other sections of the article. The authors would like to apologize for any inconvenience caused. © 2023 Elsevier B.V
Simulation of wetting tendency of fluids with high density ratios using RK Lattice Boltzmann method
, Article 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019, 14 October 2019 through 18 October 2019 ; 2020 ; Pak, A ; Sadeghi, H ; Sharif University of Technology
Asian Regional Conference on Soil Mechanics and Geotechnical Engineering
2020
Abstract
Several lattice Boltzmann models for multi-phase flow have been developed, but few of them are capable of modeling fluid flows with high density ratio in the order of 1000. Therefore, an advanced chromodynamics, Rothmann-Keller (RK) type model is employed in current study, which can handle liquid-gas density ratio in the order of 1000 and viscosity ratio in the order of 100. Other distinctive characteristics of the proposed model are high stability, and capability of setting parameters such as surface tension independently. In spite of these benefits, the original RK model fails to model wetting tendency of the fluids. As a result, it is impossible to correctly simulate two-fluid phase flow...
Mechanical behavior during aging of plastically deformed AA6061-SiCp composite in different temperatures
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 226, Issue 4 , 2012 , Pages 322-329 ; 14644207 (ISSN) ; Serajzadeh, S
SAGE
2012
Abstract
In this study, the kinetics of aging in AA6061 and AA6061 with 5% volume fraction SiCp were studied and compared. The composite was first produced and homogenized using stir casting technique followed by hot extrusion with the ratio of 18:1. Then, both AA6061 and the composite were aged at three different temperatures including room temperature, 170 °C and 240 °C, while mechanical properties during aging were evaluated employing hardness measurements and tensile testing. Moreover, in order to assess the effect of plastic deformation on the kinetics of aging, a series of samples were first deformed by equal-channel angular pressing immediately after solution treatment and then aged in the...
Electroosmotic flow and ionic conductance in a pH-regulated rectangular nanochannel
, Article Physics of Fluids ; Volume 29, Issue 6 , 2017 ; 10706631 (ISSN) ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
2017
Abstract
Infinite series solutions are obtained for electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties of long pH-regulated rectangular nanochannels of low surface potential utilizing the double finite Fourier transform method. Closed form expressions are also obtained for channels of large height to width ratio for which the depthwise variations vanish. Neglecting the Stern layer impact, the effects of EDL (Electric Double Layer) overlap, multiple ionic species, and association/dissociation reactions on the surface are all taken into account. Moreover, finite-element-based numerical simulations are conducted to account for the end effects as well...
Geotechnical characterization and collapsibility of a natural dispersive loess
, Article Engineering Geology ; Volume 250 , 2019 , Pages 89-100 ; 00137952 (ISSN) ; Kiani, M ; Sadeghi, M ; Jafarzadeh, F ; Sharif University of Technology
Elsevier B.V
2019
Abstract
During preliminary investigation phase of the national Chabahar-Zahedan railway line, serious geotechnical problems including non-uniform settlements, tensile cracks, and local collapse were reported in parts of the path near the coastline. A follow-up field investigation revealed that the in-situ soil at construction site has a metastable structure being sensitive to saturation and loading. Therefore, a comprehensive series of physical, chemical, electro-chemical, and geotechnical tests were conducted to classify and characterize the soil properties and behavior in its natural state. The natural soil was classified as a clayey loess with moderately dispersive to dispersive characteristics....
Tribological characteristics of rubber-based friction materials
, Article Tribology Letters ; Volume 41, Issue 2 , October , 2011 , Pages 325-336 ; 10238883 (ISSN) ; Shojaei, A ; Sharif University of Technology
2011
Abstract
This article deals with the rubber-based friction materials (RBFMs) which can be used in brake system. The physico-mechanical and tribological properties of a series of fiber filled RBFMs containing steel wool and aramid pulp at different concentrations along with a fiber-free reference material were characterized. Rubber-glass transition induced at higher sliding velocities was identified based on the friction fade behavior of the RBFMs. The rubber-glass transition which is inherently originated by viscoelastic response of polymeric binder was found to be influential on the tribological properties of the RBFMs. It was revealed that steel wool increased coefficient of friction (COF) and...
Lumbopelvic Rhythm during Forward and Backward Sagittal Trunk Rotations; in vivo Measurements Using Inertial Sensors
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
Direct in vivo measurements of spinal loads and muscle forces are invasive. Investigators have thus used musculoskeletal biomechanical models that require kinematic data including trunk and pelvis angular movements as their inputs. . Novel devices measure anglular movements using both inertial sensors (such as gyroscopes and accelerometers) and miniature magnetometers. Relative low cost, portability, and accuracy are among specific characteristics of inertial tracking devices. The main objective of the present study was set to measure spinal kinematics including the lumbopelvic rhythm as the ratio of total lumbar rotation over pelvic rotation during trunk sagittal movement which is essential...
Numerical Simulation and Investigation of Gas Explosion in the Confined Spaces
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
Generally speaking, there are two types of self-propagating combustion waves: deflagrations and detonations. deflagrations waves propagate at relatively low subsonic velocities with respect to the reactants ahead of it. The propagation velocity in deflagration wave is of order of 1 to 10 meters per second depend on laminar or turbulent regime. On the other hand, the detonation wave is a supersonic combustion wave (of the order of 2000 m/s) across which the thermodynamic states (e.g., pressure and temperature) increase sharply. It can be considered as a reacting shock wave where reactants transform into products, accompanied by an energy release across it. Due to drastic changes that...
Evaluation of 1991 NIOSH Lifting Equation in Controlling the Biomechanical Loads of the Human Spine
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
The 1991 NIOSH Lifting Equation (NLE) is widely used to assess risk of injury to the spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses two biomechanical models of the spine to verify whether the RWL generates L5-S1 loads within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in some studies).Severallifting activities are simulated here to evaluate the RWL by the NLE and the L5-S1 loads by the models. In lifting activities involving moderate to large forward trunk flexion, the estimated RWL generates L5-S1 spine loads exceeding the recommended limits. The NIOSH vertical multiplier is the likely...
Sagittal Range of Motion of the Thoracic Spine Using Inertial Tracking Device and Effect of Measurement Errors on Model Predictions
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
Range of motion (ROM) of the thoracic spine has implications in patient discrimination for diagnostic purposes and in biomechanical models for predictions of spinal loads. Few previous studies have reported quite different thoracic ROMs. Total (T1-T12), lower (T5-T12) and upper (T1-T5) thoracic, lumbar (T12-S1), pelvis, and entire trunk (T1) ROMs were measured using an inertial tracking device as asymptomatic subjects flexed forward from their neutral upright position to full forward flexion. Correlations between body height and the ROMs were conducted. Effect of measurement errors of the trunk flexion (T1) on the model-predicted spinal loads was investigated. Mean of peak voluntary total...
A Detailed Finite Element Model of the Lumbar Spine under Muscle Forces
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
Etiological studies proves the fact that Low Back Pain (LBP) is one of the most expensive and prevalent desease all over the world. This fact illustrates the reqiurment of the special effort in ordet to reducing the pain due to this problem. Finite element modeling of human spine is one the suitable methods to simulate the behavior of human spine in different loading conditions. These conditions could be different daily occupational tasks. There is two general viewpoint toward finite element modeling of human spine. The fisrt method focuses on the detailed geometry and mechanical properties of spine, while the other complexities such as detailed muscle forces are overlooked. The latter...
A Hyrid EMG-optimization Based Model of the Lumbar Spine to Estimate Muscle Forces in Different Tasks
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor)
Abstract
Low back pains (LBP) are prevalent and costly. One of the important factors causing LBP is excessive axial compression and shear forces that are applied on the intervertebral discs during different activities. Due to lack of direct in vivo measurement methods for estimating these loads, musculoskeletal biomechanical models have been emerged as indispensable tools under various activities. Different biomechanical models have been suggested to estimate muscle forces and spinal loads base on optimization, EMG and hybrid (EMG assisted optimization, EMGAO) methods. Although there have been a number of studies on the differences between various optimization and EMG-based methods, there has been no...