Loading...
Search for:
mohammadi--a
0.148 seconds
Total 14422 records
Sol-gel nanostructured titanium dioxide: Controlling the crystal structure, crystallite size, phase transformation, packing and ordering
, Article Microporous and Mesoporous Materials ; Volume 112, Issue 1-3 , 2008 , Pages 392-402 ; 13871811 (ISSN) ; Fray, D. J ; Mohammadi, A ; Sharif University of Technology
2008
Abstract
The anatase phase of titania was stabilised with physically modifying particulate sol-gel process. Two major parameters, peptisation temperature and drying temperature, were identified which were responsible for retarding the anatase to rutile phase transformation, crystal growth and packing of primary particles. The critical nucleus size of transformation was controlled by natural (at 25 °C) and artificial (at 50 and 70 °C) peptisation techniques. Moreover, sintering of primary particles was controlled by cool (at 0 and 5 °C) and normal (at 25 °C) drying techniques. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that a full conversion of titanium isopropoxide is obtained...
Data-driven model-free adaptive control of z-source inverters
, Article Sensors ; Volume 21, Issue 22 , 2021 ; 14248220 (ISSN) ; Ahmadi, A ; Mohammadi, S ; Moradi Amani , A ; Marzband, M ; Mohammadi Ivatloo, B ; Sharif University of Technology
MDPI
2021
Abstract
The universal paradigm shift towards green energy has accelerated the development of modern algorithms and technologies, among them converters such as Z-Source Inverters (ZSI) are playing an important role. ZSIs are single-stage inverters which are capable of performing both buck and boost operations through an impedance network that enables the shoot-through state. Despite all advantages, these inverters are associated with the non-minimum phase feature imposing heavy restrictions on their closed-loop response. Moreover, uncertainties such as parameter perturbation, unmodeled dynamics, and load disturbances may degrade their performance or even lead to instability, especially when...
Fluid-structure interaction simulation of blood flow and cerebral aneurysm: effect of partly blocked vessel
, Article Journal of Vascular Research ; Volume 56, Issue 6 , 2019 , Pages 296-307 ; 10181172 (ISSN) ; Shamloo, A ; Mohammadi, A ; Sharif University of Technology
S. Karger AG
2019
Abstract
In this study, using fluid-structure interaction (FSI), 3-dimensional blood flow in an aneurysm in the circle of Willis-which is located in the middle cerebral artery (MCA)-has been simulated. The purpose of this study is to evaluate the effect of a partly blocked vessel on an aneurysm. To achieve this purpose, two cases have been investigated using the FSI method: in the first case, an ideal geometry of aneurysm in the MCA has been simulated; in the second case, modeling is performed for an ideal geometry of the aneurysm in the MCA with a partly blocked vessel. All boundary conditions, properties and modeling methods were considered the same for both cases. The only difference between the...
Modification of nanostructured anodized aluminum coatings by pulse current mode
, Article Surface and Coatings Technology ; Volume 278 , 2015 , Pages 48-55 ; 02578972 (ISSN) ; Afshar, A ; Sharif University of Technology
Elsevier
2015
Abstract
In this study, the effects of pulse current mode on corrosion resistance and mechanical properties of anodized coatings were explored. Thickness and hardness measurements, polarization and electrochemical impedance spectroscopy were employed to take mechanical and corrosion behaviors of the anodized coatings into consideration. Also, field-emission scanning electron microscopy (FE-SEM) was utilized to characterize the surface morphology of the coatings. It was shown that in short anodizing times, coating thickness is controlled by the heat concentrated on coating. Although at prolonged anodizing times, the coating thickness is affected by average current density. Hardness measurements showed...
Microstructure and mechanical properties of pure Cu interlayer TLP joints of 304 stainless steel to dual phase steel
, Article Journal of Materials Processing Technology ; Volume 275 , January , 2020 ; Ekrami, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Bonding was carried out at 1150 °C for holding times of 60 and 90 min followed by water quenching. At the bonding time of 60 min, Cu remained at the bond region resulting in an unstable liquid/solid interface with a sinusoidal microstructure. Isothermal solidification completed at the holding time of 90 min. Unidirectional solidification was observed from the stainless steel side toward the low carbon manganese steel and abnormal grain growth of stainless steel was seen at the bond region due to temperature gradient which originated from different electrical properties of the parent alloys. Joints made at the bonding time of 90 min were homogenized at 730 °C for 75 min and quenched in water...
A simple particulate sol-gel route to synthesize nanostructural TiO2-Ta2O5 binary oxides and their characteristics
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 142, Issue 1 , 2007 , Pages 16-27 ; 09215107 (ISSN) ; Fray, D. J ; Sadrnezhaad, S. K ; Mohammadi, A ; Sharif University of Technology
2007
Abstract
Nanostructured and mesoporous TiO2-Ta2O5 films and powders with various TiO2:Ta2O5 molar ratios and high specific surface area (SSA) have been prepared by a straightforward particulate sol-gel route. Titanium isopropoxide and tantalum ethoxide were used as precursors and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the SSA. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that powders contained both hexagonal δ-Ta2O5 and monoclinic β-Ta2O5 phases, as well as anatase and rutile. It was observed that Ta2O5 retarded anatase-to-rutile transformation. Furthermore, δ → β phase transformation temperature increased...
Multi-sensory balance board for children with spd & adhd disorders
, Article Journal of Biomedical Physics and Engineering ; Volume 11, Issue 6 , 2021 , Pages 761-768 ; 22517200 (ISSN) ; Selk Ghafari , A ; Zabihol Lah, A ; Mohammadi Moghaddam, S ; Mohammadi Laal Abadi , Z ; Sharif University of Technology
Shriaz University of Medical Sciences
2021
Abstract
Nowadays, as technology grows, human life formation changes every second. These changes sometimes create harmful habits and affect our lifestyle, which unfortunately bring various diseases and disorders. ADHD (Attention Deficit Hyperactivity Disorder) & SPD (Sensory Processing Disorder) are common disorders in children. By giving children the right treatment at the younger ages, we can help them overcome their disabilities and not face any symptoms in their adulthood. The multi-sensory balance board is designed and developed to help medics diagnose the disorders in patients at early stages and monitor the treatment progress. The balance board uses multiple sensors to detect common human...
Fractal structure of Hastings-Levitov patterns restricted in a sector geometry
, Article Journal of Physics A: Mathematical and Theoretical ; Volume 43, Issue 37 , August , 2010 ; 17518113 (ISSN) ; Saberi, A. A ; Rouhani, S ; Sharif University of Technology
2010
Abstract
A generalized form of the Hastings and Levitov algorithm for the simulation of diffusion-limited aggregation (DLA) restricted in a sector geometry is studied. It is found that this generalization with uniform measure produces 'wedge-like' fractal patterns in the physical space, whose fractal dimension and anisotropy exponent depend significantly on the opening angle β of the sector. The morphological properties and the overall shape of the patterns are analyzed by computing the angular two-point density correlation function of the patterns. We also find that the fractal dimension of the patterns with sinusoidal distributed measure depends weakly on β with almost the same dimension as the...
Scaling and multiscaling behavior of the perimeter of a diffusion-limited aggregation generated by the Hastings-Levitov method
, Article Journal of Physics Condensed Matter ; Volume 21, Issue 37 , 2009 ; 09538984 (ISSN) ; Saberi, A. A ; Rouhani, S ; Sharif University of Technology
2009
Abstract
In this paper, we analyze the scaling behavior of a diffusion-limited aggregation (DLA) simulated by the Hastings-Levitov method. We obtain the fractal dimension of the clusters by direct analysis of the geometrical patterns, in good agreement with one obtained from an analytical approach. We compute the two-point density correlation function and we show that, in the large-size limit, it agrees with the obtained fractal dimension. These support the statistical agreement between the patterns and DLA clusters. We also investigate the scaling properties of various length scales and their fluctuations, related to the boundary of the cluster. We find that all of the length scales do not have a...
Experimental investigation of thermal resistance of a ferrofluidic closed-loop pulsating heat pipe
, Article Heat Transfer Engineering ; Vol. 35, issue. 1 , 2014 , pp. 25-33 ; ISSN: 01457632 ; Mohammadi, M ; Ghahremani, A. R ; Shafii, M. B ; Mohammadi, N ; Sharif University of Technology
2014
Abstract
For the present article, a pulsating heat pipe (PHP) is fabricated and tested experimentally by bending a copper tube. The effects of working fluid, heat input, charging ratio, inclination angle, magnets location, and ferrofluid (magnetic nanofluid) volumetric concentration have been investigated on the thermal performance of this PHP. Experimental results show that using ferrofluid as a working fluid improves the thermal performance of the PHP significantly. Moreover, applying a magnetic field on a ferrofluidic PHP reduces its thermal resistance. By changing the inclination angle of the PHP from vertical mode to angles close to the horizontal mode, the present PHP has a constant and...
Performance-based assessment of an innovative braced tube system for tall buildings
, Article Bulletin of Earthquake Engineering ; 2017 , Pages 1-22 ; 1570761X (ISSN) ; Toufigh, V ; Golafshani, A. A ; Arzeytoon, A ; Sharif University of Technology
2017
Abstract
In this paper, an innovative seismic lateral force resisting system for tall buildings is introduced. In this system, a novel supplemental part, ribbed bracing system (RBSyst), is attached to Braced Tube System, creating a modified BTS. RBSyst is a supplemental part which is attached to the conventional bracing members to eliminate buckling problem. The behavior of RBSyst under tensile force is similar to that of the conventional braces. However, in compression, it prevents the braces from buckling by length reduction. In order to evaluate the efficiency of this new BTS system by performance-based assessment, two typical 40-story tall buildings with different story modules equipped with this...
Experimental evaluation of pinned frame equipped with ribbed bracing system
, Article Journal of Earthquake Engineering ; 2017 , Pages 1-21 ; 13632469 (ISSN) ; Toufigh, V ; Golafshani, A. A ; Arzeytoon, A ; Sharif University of Technology
2017
Abstract
This study presents the experimental investigation of half-scale, one-story, one-bay pinned frames equipped with a ribbed bracing system (RBS). The RBS is a newly developed passive control system designed to eliminate buckling and enhance the seismic behavior of structures. Here, mechanical models of this bracing system were designed and constructed. Pinned frames equipped with the RBS were cyclically tested. The hysteretic behavior and energy absorbing capacities of the frames were evaluated. Based on the results, the full plastic capacity of the brace was achieved and no buckling occurred. The RBS frame illustrated proper hysteretic behavior and energy dissipation capacity up to 4% story...
Experimental evaluation of pinned frame equipped with ribbed bracing system
, Article Journal of Earthquake Engineering ; Volume 23, Issue 8 , 2019 , Pages 1297-1317 ; 13632469 (ISSN) ; Toufigh, V ; Golafshani, A. A ; Arzeytoon, A ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
This study presents the experimental investigation of half-scale, one-story, one-bay pinned frames equipped with a ribbed bracing system (RBS). The RBS is a newly developed passive control system designed to eliminate buckling and enhance the seismic behavior of structures. Here, mechanical models of this bracing system were designed and constructed. Pinned frames equipped with the RBS were cyclically tested. The hysteretic behavior and energy absorbing capacities of the frames were evaluated. Based on the results, the full plastic capacity of the brace was achieved and no buckling occurred. The RBS frame illustrated proper hysteretic behavior and energy dissipation capacity up to 4% story...
Performance-based assessment of an innovative braced tube system for tall buildings
, Article Bulletin of Earthquake Engineering ; Volume 16, Issue 2 , February , 2018 , Pages 731-752 ; 1570761X (ISSN) ; Toufigh, V ; Golafshani, A. A ; Arzeytoon, A ; Sharif University of Technology
Springer Netherlands
2018
Abstract
In this paper, an innovative seismic lateral force resisting system for tall buildings is introduced. In this system, a novel supplemental part, ribbed bracing system (RBSyst), is attached to Braced Tube System, creating a modified BTS. RBSyst is a supplemental part which is attached to the conventional bracing members to eliminate buckling problem. The behavior of RBSyst under tensile force is similar to that of the conventional braces. However, in compression, it prevents the braces from buckling by length reduction. In order to evaluate the efficiency of this new BTS system by performance- based assessment, two typical 40-story tall buildings with different story modules equipped with...
Synthesis and characterization of pure metallic titanium nanoparticles by an electromagnetic levitation melting gas condensation method
, Article RSC Advances ; Vol. 4, issue. 14 , 2014 , pp. 7104-7108 ; ISSN: 20462069 ; Halali, M ; Sharif University of Technology
2014
Abstract
Pure titanium nanoparticles were synthesized by utilizing an Electromagnetic Levitation Melting Gas Condensation (ELM-GC) method. Pure bulk titanium samples were melted and evaporated by electromagnetic levitation technique in an inert gas atmosphere in a silica tube. Titanium nanoparticles were formed from ascending vapor by employing high purity argon and helium as carrier gases and cooling agents. Particle size and morphology of the produced nanoparticles were studied by Field-Emission Scanning Electron Microscopy (FE-SEM) and Dynamic Light Scattering (DLS) analysis. Results showed almost spherical nanoparticles with a narrow size distribution under both cooling atmospheres. The purity of...
An efficient run-based method for connected component labeling
, Article 9th Iranian Conference on Machine Vision and Image Processing, 18 November 2015 through 19 November 2015 ; Volume 2016-February , 2015 , Pages 100-104 ; 21666776 (ISSN) ; 9781467385398 (ISBN) ; Gaffari, A ; Sharif University of Technology
IEEE Computer Society
2015
Abstract
This paper presents a new run-based algorithm for labeling connected components in a binary image. The algorithm removes assumption on all border pixels of image are background. Also it does not use merging operation for resolving label equivalences among provisional labels (sets), but it uses post processing stage. The post processing stage reduces complexity for resolving label equivalency. During the first scan, provisional labels are assigned to the connected components. After the first scan, the post processing is done to resolve label equivalency. The smallest provisional label among all provisional labels that are assigned to a connected component is considered as a representative...
Missile aerodynamic identification using a two step estimation procedure
, Article Scientia Iranica ; Volume 9, Issue 4 , 2002 , Pages 354-363 ; 10263098 (ISSN) ; Massoumnia, M. A ; Sharif University of Technology
Sharif University of Technology
2002
Abstract
In this paper, the performance of EAM (Estimation After Modeling) and EBM (Estimation Before Modeling) techniques for aerodynamic parameter identification are compared. The results clearly show that EAM has a superior performance over EBM, but both techniques fail when there is considerable modeling uncertainty. Given this shortcoming, a two-step procedure is used that is a combination of EAM and EBM for estimating the aerodynamic parameters. Simulation results show that this new technique outperforms EAM when modeling uncertainties are considered. This technique will be applied to the problem of identifying the aerodynamic parameters of an anti-tank missile and its performance is compared...
Meshless solution of 2D fluid flow problems by subdomain variational method using MLPG method with radial basis functions (RBFS)
, Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 1 SYMPOSIA , 2006 , Pages 333-341 ; 0791847500 (ISBN); 9780791847503 (ISBN) ; Shamsai, A ; Sharif University of Technology
2006
Abstract
This paper deals with the solution of two-dimensional fluid flow problems using the truly meshless Local Petrov-Galerkin (MLPG) method. The present method is a truly meshless method based only on a number of randomly located nodes. Radial basis functions (RBF) are employed for constructing trial functions in the local weighted meshless local Petrov-Galerkin method for two-dimensional transient viscous fluid flow problems. No boundary integration is needed, no element matrix assembly is required and no special treatment is needed to impose the essential boundary conditions due to satisfaction of kronecker delta property in RBFs. Three different radial basis functions (RBFs), i.e....
Design, modeling and optimization of a piezoelectric pressure sensor based on thin-film PZT diaphragm contain of nanocrystalline powders
, Article 2009 6th International Symposium on Mechatronics and its Applications, ISMA 2009, Sharjah, 23 March 2009 through 26 March 2009 ; 2009 ; 9781424434817 (ISBN) ; Sheikhi, M. H ; Torkian, S ; Barzegar, A ; Masumi, E ; Mohammadi, S ; Sharif University of Technology
2009
Abstract
In this paper fabrication of a 0-3 ceramic/ceramic composite lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 thin film has been presented and then a pressure sensor based on multilayer thin-film PZT diaphragm contain of Lead Zirconate Titanate nanocrystalline powders was designed, modeled and optimized. This multilayer diaphragm in general acts as sensor or actuator. ANSYS was used for simulation of diaphragm. Dynamics characteristics of this multilayer diaphragm have been investigated. By this simulation the effective parameters of the multilayer PZT diaphragm for improving the performance of a pressure sensor in different ranges of pressure are optimized. The optimized thickness ratio of PZT...
Facial expression recognition using geometric normalization and appearance representation
, Article Iranian Conference on Machine Vision and Image Processing, MVIP ; 2013 , Pages 159-163 ; 21666776 (ISSN) ; 9781467361842 (ISBN) ; Raie, A. A ; Mohammadi, M. R ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
Facial expression recognition is a challenging and interesting problem in computer vision and pattern recognition. Geometric variability in both emotion expression and neutral face is a fundamental challenge in facial expression recognition problem. This variability not only directly affects geometric facial expression recognition methods, but also is a critical problem in appearance methods. To overcome this problem, this paper presents an approach which eliminates geometric variability in emotion expression; thus, appearance features can be accurately used for facial expression recognition. Therefore, a fixed geometric model is used for geometric normalization of facial images. This model...