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Boundary layer solution for the turbulent swirling decay flow through a fixed pipe: SBR at the inlet
, Article International Journal of Engineering Science ; Volume 43, Issue 1-2 , 2005 , Pages 107-120 ; 00207225 (ISSN) ; Saidi, M. H ; Sadeghipour, M. S ; Souhar, M ; Sharif University of Technology
Elsevier Ltd
2005
Abstract
In this study the developing turbulent swirling pipe flow is investigated both numerically and analytically. Governing equations are derived accompanying the boundary layer assumptions. Uniform and solid body rotation (SBR) distributions are taken into account for the axial and tangential velocities at the inlet of the pipe, respectively. Beyond the boundary layers, the flow pattern is considered to be the potential flow. Making use of the fourth-order Runge-Kutta scheme, the numerical solution of the differential equations is obtained. Further more, by simplifying the governing equations for large Rossby number, the analytical solution is performed. The results of numerical and analytical...
Numerical analysis of turbulent swirling decay pipe flow
, Article International Communications in Heat and Mass Transfer ; Volume 32, Issue 5 , 2005 , Pages 627-638 ; 07351933 (ISSN) ; Saidi, M. H ; Sadeghipour, M. S ; Souhar, M ; Sharif University of Technology
2005
Abstract
Turbulent swirling decay pipe flow has been investigated numerically in a vertical straight fixed pipe. The swirling flow is created by means of a rotating honeycomb which produces the solid body rotation at the inlet of the fixed pipe. Since there are no experimental data at the inlet of the fixed pipe; different axi-symmetric approaches may be considered to model the honeycomb effects at the downstream flow. Considering the appropriate approach and using the resulting flow field properties from the exit of the modeled swirl generator which are applied as the inlet boundary condition for the fixed pipe, several high Reynolds turbulence models are used to predict this type of the swirling...
Experimental and numerical hydrodynamic modeling of an underwater manipulator
, Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED ; Volume 256 , 2000 , Pages 291-296 ; 08888116 (ISSN) ; Tehranian, A ; Meghdari, A ; Sadeghipour, M. S ; Sharif University of Technology
2000
Abstract
This paper presents the kinematics and dynamic modeling of a three-link (3-DOF) underwater manipulator where the effects of hydrodynamic forces are investigated. In our investigation, drag and added mass coefficients are not considered as constants. In contrast, the drag coefficient is a variable with respect to all relative parameters. Experiments were conducted to validate the hydrodynamic model for a one degree-of-freedom manipulator up to a three degrees-of-freedom manipulator. Finally, the numerical and experimental results are compared and thoroughly discussed
Efffects of confining walls on laminar natural convection from a horizontal cylinder
, Article 35th Intersociety Energy Conversion Engineering Conference and Exhibit 2000, Las Vegas, NV, 24 July 2000 through 28 July 2000 ; 2000 ; Pedram Razi, Y ; Sharif University of Technology
2000
Abstract
The laminar natural convection from an isothermal horizontal cylinder confined between vertical walls is investigated by experimental and numerical methods. The experimental and numerical data are well correlated, independently, to equations which give the average Nusselt number in terms of the wail spacing to cylinder diameter ratio, t/D, and the Rayleigh number, Ra, for two different values of the wall height to cylinder diameter ratios, H/D=7 and 15.2. For the low Rayleigh numbers considered (Ra<1000), there are certain conditions for the confining walls under which heat transfer from the cylinder is maximum. Results are compared with the reported numerical and/or experimental results...
Effects of confining walls on laminar natural convection from a horizontal cylinder
, Article Proceedings of the Intersociety Energy Conversion Engineering Conference ; Volume 2 , 2000 , Pages 1261-1267 ; 0146955X (ISSN) ; Razi, Y. P ; Sharif University of Technology
2000
Abstract
The laminar natural convection from an isothermal horizontal cylinder confined between vertical walls is investigated by experimental and numerical methods. The experimental and numerical data are well correlated, independently, to equations which give the average Nusselt number in terms of the wall spacing to cylinder diameter ratio, t/D, and the Rayleigh number, Ra, for two different values of the wall height to cylinder diameter ratios, H/D=7 and 15.2. For the low Rayleigh numbers considered (Ra<1000), there are certain conditions for the confining walls under which heat transfer from the cylinder is maximum. Results are compared with the reported numerical and/or experimental results...
An adaptive thresholding approach for image denoising using redundant representations
, Article Machine Learning for Signal Processing XIX - Proceedings of the 2009 IEEE Signal Processing Society Workshop, MLSP 2009, 2 September 2009 through 4 September 2009, Grenoble ; 2009 ; 9781424449484 (ISBN) ; Babaie Zadeh, M ; Jutten, C ; Sharif University of Technology
2009
Abstract
A frequently used approach for denoising is the shrinkage of coefficients of the noisy signal representation in a transform domain. Although the use of shrinkage is optimal for Gaussian white noise with complete and unitary transforms, it has already been shown that shrinkage has promising results even with redundant transforms. In this paper, we propose using adaptive thresholding of redundant representations of the noisy image for image denoising. In the proposed thresholding scheme, a different threshold is used for each representation coefficient of the noisy image in an overcomplete transform. In this method, each threshold is automatically set based on statistical properties of the...
Seismic Performance Evaluation of Vertcial Irregular Structures through Nonlinear Time History Analysis
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Incremental Dynamic Analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. Using IDA , the objective is to study the effect of the irregular distribution of stiffness and strength along the height of a 9 story 3D steel structure model. The reference and each modified structure are hence forced to show the complete spectrum of behavior from elasticity to final global instability, allowing the estimation of capacities for the full range of limit-states and enabling a straightforward comparison without needing to “tune” the structures to the same fundamental period and/or the...
Natural convection from a confined horizontal cylinder: The optimum distance between the confining walls
, Article International Journal of Heat and Mass Transfer ; Volume 44, Issue 2 , 2001 , Pages 367-374 ; 00179310 (ISSN) ; Razi, Y. P ; Sharif University of Technology
2001
Abstract
The laminar natural convection from an isothermal horizontal cylinder confined between vertical walls, at low Rayleigh numbers, is investigated by theoretical, experimental and numerical methods. The height of the walls is kept constant, however, their distance is changed to study its effect on the rate of the heat transfer. Results are incorporated into a single equation which gives the Nusselt number as a function of the ratio of the wall distance to cylinder diameter, t/D, and the Rayleigh number. There is an optimum distance between the walls for which heat transfer is maximum. © 2000 Elsevier Science Ltd. All rights reserved
Image Enhancement via Sparse Decomposition
, M.Sc. Thesis Sharif University of Technology ; Babaiezadeh, Massoud (Supervisor)
Abstract
Sparse decomposition has recently attracted the attention of many researchers in dierent areas of signal processing. In mathematical viewpoint, sparse decomposition is nding a sparse solution of an Underdetermined System of Linear Equations (USLE). This concept has many applications in dierent signal processing elds including blind sourse separation, optical character recognition and image processing. In this thesis, we investigate the application of sparse decomposition in image denoising. One of the image denoising methods which is related to sparse decomposition concepts is the \transfrom domain method". In this method, the noisy image is rst transformed to another domain, and then noise...
Design and development of a miniaturized roto-translational motion platform for microaerial vehicle identification
, Article IEEE Aerospace and Electronic Systems Magazine ; Volume 39, Issue 12 , 2024 , Pages 24-35 ; 08858985 (ISSN) ; Pourtakdoust, S. H ; Mousavi, S. M. S
IEEE
2024
Abstract
Accurate system identification (SI) is essential for flight controller design of unmanned aerial vehicles and microaerial vehicles (MAVs). SI can be performed either in frequency or time domain using flight test data. As flight testing is often costly and may even lead to catastrophic events before some flight stability analysis is at hand, a low-cost 5 degree-of-freedom free motion platform (FMP) is designed and used for initial identification of MAVs via wind tunnel testing. A typical MAV is constructed as a test case and equipped with inertial sensors for testing and validation purposes. The proposed FMP allows for both rotational as well as translational motions that in turn provide for...
Non-fragile control and synchronization of a new fractional order chaotic system
, Article Applied Mathematics and Computation ; Volume 222 , 2013 , Pages 712-721 ; 00963003 (ISSN) ; Delshad, S. S ; Hamidi Beheshti, M. T ; Tavazoei, M. S ; Sharif University of Technology
2013
Abstract
In this paper, we address global non-fragile control and synchronization of a new fractional order chaotic system. First we inspect the chaotic behavior of the fractional order system under study and also find the lowest order (2.49) for the introduced dynamics to remain chaotic. Then, a necessary and sufficient condition which can be easily extended to other fractional-order systems is proposed in terms of Linear Matrix Inequality (LMI) to check whether the candidate state feedback controller with parameter uncertainty can guarantee zero convergence of error or not. In addition, the proposed method provides a global zero attraction of error that guarantees stability around all existing...
A Mechanical model for flexible exercise bars to study the influence of the initial position of the bar on lumbar discs and muscles forces
, Article Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, 25 August 2015 through 29 August 2015 ; Volume 2015-November , 2015 , Pages 3917-3920 ; 1557170X (ISSN) ; 9781424492718 (ISBN) ; Abdollahi, M ; Nikkhoo, M ; Hoviattalab, M ; Asghari, M ; Ashouri, S ; Nikpour, S ; Kahrizi, S ; Parnianpour, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
A single-degree-of-freedom model is considered for flexible exercise bars based on the lumped-element approach. By considering the side segment of a flexible bar as a cantilever beam with an equivalent mass at the free end, its free-vibration response, as well as the forced response under the excitation of the grip, are expressed parametrically. Experiments are performed on a particular flexible bar (FLEXI-BAR) in order to obtain numerical values for quantifying the model's parameters. The model is also computationally simulated to study the response of the flexible bar to various excitations. The results are imported into a multi-segment musculoskeletal software (AnyBody), where the effect...
Parameters calculation of transformer winding detailed model based on finite element method to study partial discharge
, Article International Review on Modelling and Simulations ; Volume 5, Issue 5 , October , 2012 , Pages 1995-2000 ; 19749821 (ISSN) ; Vakilian, M ; Enjavimadar, S. M ; Sharif University of Technology
Praise Worthy Prize
2012
Abstract
The first step to locate Partial Discharge in power transformers is to find a model that can clearly explain the behavior of the winding in high-frequency. The detailed model is one of the models used for the study of PD. One of the fundamental problems of the described model is to find its parameters. And the accuracy in calculating these parameters has significant impact on reducing the simulation error and PD locating. The current paper seeks to calculate the parameters of the detailed model 20kv distribution transformer winding by using the finite element method (FEM). Comparing the results of this model with pulse waveforms obtained from the PD to the winding in the laboratory...
Magnetoelectric nanocomposite scaffold for high yield differentiation of mesenchymal stem cells to neural-like cells
, Article Journal of Cellular Physiology ; Volume 234, Issue 8 , 2019 , Pages 13617-13628 ; 00219541 (ISSN) ; Soleimani, M ; Ghiass, M. A ; Hatamie, S ; Vakilian, S ; Zomorrod, M. S ; Sadeghzadeh, N ; Vossoughi, M ; Hosseinzadeh, S ; Sharif University of Technology
Wiley-Liss Inc
2019
Abstract
While the differentiation factors have been widely used to differentiate mesenchymal stem cells (MSCs) into various cell types, they can cause harm at the same time. Therefore, it is beneficial to propose methods to differentiate MSCs without factors. Herein, magnetoelectric (ME) nanofibers were synthesized as the scaffold for the growth of MSCs and their differentiation into neural cells without factors. This nanocomposite takes the advantage of the synergies of the magnetostrictive filler, CoFe 2 O 4 nanoparticles (CFO), and piezoelectric polymer, polyvinylidene difluoride (PVDF). Graphene oxide nanosheets were decorated with CFO nanoparticles for a proper dispersion in the polymer through...
Hydrogenated graphene oxide (H-G-SiO2) Janus structure: Experimental and computational study of strong piezo-electricity response
, Article Journal of Physics D: Applied Physics ; Volume 53, Issue 17 , 2020 ; Alidoosti, M ; Hosseinzadeh, A ; Seyyedi, S. M. S ; Elahi, M ; Pourfath, M ; Mohajerzadeh, S ; Sharif University of Technology
Institute of Physics Publishing
2020
Abstract
We have investigated the piezoelectric response of the hydrogenated graphene oxide (H-G-SiO2) stacks both experimentally and theoretically. The piezoresponse force microscopy method and density-functional theory (DFT) calculations were used to study the piezoresponse effect of this structure from both experimental and computational point of views. A mono-layer graphene, made by chemical vapour deposition method, is deposited on Si/SiO2 substrate and its surface is then functionalized with hydrogen atoms. The vertical piezoresponse, observed by piezoresponse force microscopy, is measured to be about 2146 pC N-1, that is comparable to the reported state of the art piezoelectric materials such...
An ultra-wideband 3-dB quadrature hybrid with multisection broadside stripline tandem structure
, Article Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering ; Volume 77 LNICST , 2012 , Pages 672-681 ; 18678211 (ISSN) ; 9783642351549 (ISBN) ; Majedi, S. M. S ; Farzaneh, F ; Sharif University of Technology
2012
Abstract
Design of an Ultra-Wideband 3-dB quadrature (90°) Hybrid using ADS and HFSS softwares plus Measurement report are presented. Simultaneous Use of these two softwares lead to fast and accurate design procedure. The coupler is realized in broadside stripline and with the connection of coupled regions in tandem structure. The measured data agrees well with the expected values from simulations, and shows a good ultra wide bandwidth response over the frequency range of 1-10 GHz. Measurements showed an amplitude unbalance of ±1.5 dB, a phase unbalance of 90°±7° , and an isolation and a return loss characteristics of more than 14 dB over the frequency of 1 to 10 GHz
Broadside coupler Channels 1 to 10 GHz
, Article Microwaves and RF ; Volume 51, Issue 1 , 2012 ; 07452993 (ISSN) ; Majedi, S. M. S ; Farzaneh, F ; Sharif University of Technology
2012
Tensile deformation mechanisms at different temperatures in the Ni-base superalloy GTD-111
, Article Journal of Materials Processing Technology ; Volume 155-156, Issue 1-3 , 2004 , Pages 1900-1904 ; 09240136 (ISSN) ; Nategh, S ; Isac, M ; Zebarjad, S. M ; Sharif University of Technology
2004
Abstract
The Ni-base superalloy GTD-111 is employed in high-power stationary gas turbines because of its high temperature strength and oxidation resistance. The temperature dependence of the tensile behavior of GTD-111 has been studied by tensile tests in the temperature range of 25-900°C with a constant strain rate of 10-4s-1. The results showed an abnormal tensile property variation with increasing temperature. The yield strength decreased slightly with temperature up to about 650°C and then increased between 650 and 750°C. Above 750°C, a rapid decrease in the yield strength was found. The tensile strength showed a similar behavior except for its maximum that occurred at 650°C. The elongation...
Cell-imprinted substrates act as an artificial niche for skin regeneration
, Article ACS Applied Materials and Interfaces ; Vol. 6, Issue. 15 , 2014 , Pages 13280-13292 ; ISSN: 19448244 ; Bonakdar, S ; Taghinejad, H ; Satarifard, V ; Heidari, M ; Majidi, M ; Sharifi, S ; Peirovi, A ; Saffar, S ; Taghinejad, M ; Abdolahad, M ; Mohajerzadeh, S ; Shokrgozar, M. A ; Rezayat, S. M ; Ejtehadi M. R ; Dalby, M. J ; Mahmoudi, M ; Sharif University of Technology
2014
Abstract
Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed...
Development of grid resource discovery service based on semantic information
, Article SpringSim '07: Proceedings of the 2007 spring simulaiton multiconference ; Volume 1 , 2007 , Pages 141-148 ; 07359276 (ISSN) ; 1565553128 (ISBN); 9781565553125 (ISBN) ; Moshkenani, M. S ; Sharif University of Technology
2007
Abstract
Grid computing is a type of parallel and distributed system that provides the possibility of sharing, choosing and collecting the autonomous resources (such as computer, software, databases, and equipments) that are distributed geographically. Resource discovery is one of the key subjects in distributed systems and especially Grids. We should consider that Grid consists of different applications that each of them consist of different hardware and software resources, therefore recognizing these resources is important in a Grid system. Classical approaches to Grid resource discovery are either centralized or hierarchical [1] (and will maybe prove inefficient as the scale of Grid systems...