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Theoretical and experimental modeling of vortex engine in ramjet application
, Article 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2 August 2009 through 5 August 2009, Denver, CO ; 2009 ; 9781563479762 (ISBN) ; Ghafourian, A ; Saidi, M. H ; Mozafari, A. A ; Sharif University of Technology
2009
Abstract
A new experimental facility was designed, fabricated and tested to model and study the possibility of applying the bidirectional swirl flow on the combustion chamber of airbreathing subsonic ramjet engine. Appropriate intake was designed to convert axial external air to tangential swirl flow inside the combustion chamber. Inlets with appropriate angles conduct the swirl flow into the chamber and create bidirectional swirl flow field in the combustion chamber. This flow field has been modeled theoretically to determine the velocity field characteristics by previous researchers. Bidirectional swirl flow in liquid fuel ramjet engines has the proven advantage of keeping the combustion chamber...
Theoretical and Experimental Modeling of Vortex Engine in Ramjet Application
, M.Sc. Thesis Sharif University of Technology ; Ghafourian, Akbar (Supervisor) ; Saeedi, Mohsen (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
Abstract
Heat transfer to combustion chamber walls is an unwanted phenomenon. Reduction of this heat transfer by using bidirectional swirl flow, as proved in past studies, can result in time and cost saving methods in design and fabrication of combustion chambers. Bidirectional Swirl flow, existing in vortex engine, maintains the chamber wall cool. This characteristic of such flow field, among with many other advantages for it, makes researchers more interested in studying the propulsion of it as well as its other applications. Bidirectional swirl flow in liquid fuel ramjet engines has the proven advantage of keeping the combustion chamber walls cool and in solid fuel ramjet engines in increasing the...
Adding backlash to the connection elements can improve the performance of a robotic exoskeleton
, Article Mechanism and Machine Theory ; Volume 152 , 2020 ; Behzadipour, S ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Kinematic mismatch between exoskeletons and human body results in excess internal forces/torques and hence discomfort as well as increase the power consumption. The connection stiffness has been shown to have potentials for minimizing the kinematic mismatch effects. However, realization of a desired stiffness in the connection element seems difficult if not impractical. In this work, adding controlled backlash to the exoskeleton-body connection is investigated as a possible solution for the kinematic mismatch challenge. A stiffness model which includes backlash parameters was formulated and identified experimentally using three male subjects on a typical lower extremity exoskeleton. A...
Experimental study on macro segregation behavior in short and wide range solidification of different aluminum alloys
, Article Materials Science and Technology Conference and Exhibition 2013, MS and T 2013 ; Volume 2 , 2013 , Pages 822-829 ; 9781629933092 (ISBN) ; Mohammad Salehi, E ; Hassan Nejad, H ; Shafiei Zadeh, S ; Sharif University of Technology
2013
Abstract
Data are presented on the solidification of aluminum alloys and their macro segregation behavior. Three alloys with different solidification ranges were prepared in two temperatures. Two types of molds were also prepared by sand and metallic materials. The solidification of Al alloys were studied and the effects of four parameters were determined, including cooling rate, casting temperature, degassing and nucleation effects on solidification and a comparison was conducted to Scheil model performance. Three types of aluminum alloys (Al-12.1%Si, Al-6.9%Si and Al-4.4% Cu) with short, medium and wide solidification ranges were studied and the results showed that degassing, nucleation, increasing...
Determination of Coefficient of Lateral Pressure of Sandy Soil at Rest Using Results of Calibration of Cone Penetration Test and Artificial Neural Network
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
The estimation of soil parameters in geotechnical practice is always an important and challenging task for the geotechnical engineer. Obtaining undisturbed samples from sands is generally very difficult and expensive, and in some cases impractical. A good prediction of sands parameters from insitu tests such as Cone Penetration Test (CPT) is one of the most challenging problems in geotechnical engineering. Using Calibration Chambers, a soil with predefined parameters is tested by cone penetrometer and some relationships are developed between CPT results and soil parameters. Using these relationships, in-situ results are interpreted.
In this thesis, after introducing previously developed...
In this thesis, after introducing previously developed...
Estimating time-dependent origin-destination demand from traffic counts: Extended gradient method
, Article Transportation Letters ; Volume 7, Issue 4 , 2015 , Pages 210-218 ; 19427867 (ISSN) ; Nazemi, M ; Seyedabrishami, S ; Sharif University of Technology
Maney Publishing
2015
Abstract
Time-dependent origin-destination (TDOD) demand is a key input of dynamic traffic assignment (DTA) in advanced traffic management systems. Model reliability is highly dependent on the accuracy of this information. One method to achieve TDOD demand matrices is to use a primary demand matrix and traffic volume counts in some links of a network. This paper proposes a bi-level model to correct the TDOD demand matrix. The extended gradient method (EGM) - an iterative method that minimizes the discrepancy between the counted and estimated traffic volumes - is a suggested means to solve this problem. The methodology is first tested on a small synthetic network to verify its performance. Then, it is...
Thermo-mechanical vibration of rotating axially functionally graded nonlocal Timoshenko beam
, Article Applied Physics A: Materials Science and Processing ; Volume 123, Issue 1 , 2017 ; 09478396 (ISSN) ; Mirjavadi, S. S ; Shafiei, N ; Hamouda, A. M. S ; Sharif University of Technology
Springer Verlag
2017
Abstract
The free vibration analysis of rotating axially functionally graded nanobeams under an in-plane nonlinear thermal loading is provided for the first time in this paper. The formulations are based on Timoshenko beam theory through Hamilton’s principle. The small-scale effect has been considered using the nonlocal Eringen’s elasticity theory. Then, the governing equations are solved by generalized differential quadrature method. It is supposed that the thermal distribution is considered as nonlinear, material properties are temperature dependent, and the power-law form is the basis of the variation of the material properties through the axial of beam. Free vibration frequencies obtained are...
Vibration of two-dimensional imperfect functionally graded (2D-FG) porous nano-/micro-beams
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 322 , 2017 , Pages 615-632 ; 00457825 (ISSN) ; Mirjavadi, S. S ; MohaselAfshari, B ; Rabby, S ; Kazemi, M ; Sharif University of Technology
Elsevier B.V
2017
Abstract
This study presents analysis on the vibration behavior of the two-dimensional functionally graded (2D-FG) nano and microbeams which are made of two kinds of porous materials for the first time, based on Timoshenko beam theory. The material of the nano and microbeams is modeled as 2D-FGMs according to the power law. The Eringen's nonlocal elasticity and the modified couple stress theories are used, respectively in case of nano and microbeams. The boundary conditions are considered as clamped (CC), simply supported (SS), clamped–simply supported (CS), and cantilever (CF). The governing equations are solved using the generalized differential quadrature method (GDQM). The effects of FG power...
Erratum to: thermo-mechanical vibration of rotating axially functionally graded nonlocal Timoshenko beam (Erratum to: Appl. Phys. A, (2017), 123, (104), 10.1007/s00339-016-0712-5)
, Article Applied Physics A: Materials Science and Processing ; Volume 123, Issue 2 , 2017 ; 09478396 (ISSN) ; Mirjavadi, S. S ; Shafiei, N ; Hamouda, A. M. S ; Sharif University of Technology
Springer Verlag
2017
Abstract
The original version of this article unfortunately contained a mistake. The affiliation 3 was incorrect. The correct affiliation 3 is: Department of Mechanical Engineering, Payame Noor University (PNU), P. O. Box 19395-3697, Tehran, Iran. © 2016, Indian Society of Haematology & Transfusion Medicine
A study of liquid drainage rate from foam with population balance equation: impact of bubble evolution
, Article Colloid and Polymer Science ; Volume 296, Issue 6 , 2018 , Pages 1097-1108 ; 0303402X (ISSN) ; Ghazanfari, M. H ; Seyyedsar, S. M ; Sharif University of Technology
Springer Verlag
2018
Abstract
A significant challenge of foam injection is the stability of the foam in formations. In this study, the modeling of liquid drainage and the impact of some parameters (i.e., concentration of surfactants, nano-particles, and monovalent ions) on the liquid drainage rate and foam stability were investigated by using a population balance model. First, foam bubble size distribution was experimentally measured and used as input for the population balance model. The population balance equations were solved numerically, and the number density of bubble size distribution as a function of time was obtained. Then, the liquid drainage rate was calculated using volume balance equations. It is shown that...
Vibration of rotating functionally graded timoshenko nano-beams with nonlinear thermal distribution
, Article Mechanics of Advanced Materials and Structures ; 2017 , Pages 1-14 ; 15376494 (ISSN) ; Mirjavadi, S. S ; Shafiei, N ; Hamouda, A. M. S ; Davari, E ; Sharif University of Technology
2017
Abstract
The vibration analysis of rotating, functionally graded Timoshenko nano-beams under an in-plane nonlinear thermal loading is studied for the first time. The formulation is based on Eringen's nonlocal elasticity theory. Hamilton's principle is used for the derivation of the equations. The governing equations are solved by the differential quadrature method. The nano-beam is under axial load due to the rotation and thermal effects, and the boundary conditions are considered as cantilever and propped cantilever. The thermal distribution is considered to be nonlinear and material properties are temperature-dependent and are changing continuously through the thickness according to the power-law...
Thermal buckling behavior of two-dimensional imperfect functionally graded microscale-tapered porous beam
, Article Journal of Thermal Stresses ; Volume 40, Issue 10 , 2017 , Pages 1201-1214 ; 01495739 (ISSN) ; Matin, A ; Shafiei, N ; Rabby, S ; Mohasel Afshari, B ; Sharif University of Technology
2017
Abstract
This article presents a study on the thermal buckling behavior of two-dimensional functionally graded microbeams made of porous materials. The material composition varies along thickness and length of the microbeam based on the power law distribution. The microbeam is modeled within the framework of Euler–Bernoulli beam theory. The microbeam is considered having variable material composition along thickness. The equations are derived using the modified couple stress theory and the solving process is based on the generalized differential quadrature method. The validity of the results is shown through comparison of the results with the results of other published research. © 2017 Taylor &...
On size-dependent free vibration and thermal buckling of axially functionally graded nanobeams in thermal environment
, Article Applied Physics A: Materials Science and Processing ; Volume 123, Issue 5 , 2017 , 315 ; 09478396 (ISSN) ; Rabby, S ; Shafiei, N ; Mohasel Afshari, B ; Kazemi, M ; Sharif University of Technology
Springer Verlag
2017
Abstract
This article aims to study the buckling and free vibrational behavior of axially functionally graded (AFG) nanobeam under thermal effect for the first time. The temperature is considered to be constant and variable along thickness and different boundary conditions. The governing equation is developed using the Hamilton’s principle considering the axial force. The Euler–Bernoulli beam theory is used to model the nanobeam, and Eringen’s nonlocal elasticity theory is utilized to consider the nano-size effect. The generalized differential quadrature method (GDQM) is used to solve the equations. The small-scale parameter, AFG power index, thermal distribution, different functions of temperature...
Effect of temperature and porosity on the vibration behavior of two-dimensional functionally graded micro-scale timoshenko beam
, Article JVC/Journal of Vibration and Control ; Volume 24, Issue 18 , 2018 , Pages 4211-4225 ; 10775463 (ISSN) ; Mohasel Afshari, B ; Shafiei, N ; Rabby, S ; Kazemi, M ; Sharif University of Technology
2018
Abstract
This work is aimed to present analysis on the thermal vibrational behavior of two-dimensional functionally graded porous microbeams based on Timoshenko beam theory. According to the power law function, the material composition and so the material properties are varying along thickness and axis of the microbeam. The governing equations are derived on the basis of the couple stress theory and the generalized differential quadrature method is used to solve the equations. The temperature gradient is considered to be uniform and nonuniform across the thickness of the microbeam. The results are presented to show the effect of temperature change, porosity, functionally graded and axially...
Template-directed hydrothermal synthesis of dandelion-like hydroxyapatite in the presence of cetyltrimethylammonium bromide and polyethylene glycol
, Article Ceramics International ; Volume 35, Issue 7 , 2009 , Pages 2563-2569 ; 02728842 (ISSN) ; Solati Hashjin, M ; Shafiei, S. S ; Salarian, R ; Nemati, Z. A ; Sharif University of Technology
2009
Abstract
A template-directed synthetic method, using surfactant cetyltrimethylammonium bromide (CTAB) as a template and co-surfactant polyethylene glycol (PEG600) as a co-template under hydrothermal conditions, has been applied to obtain dandelion-like HAp. The morphology, size, crystalline phase, chemical composition, physical characteristics, and thermal behavior of the product were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier ransform infrared spectroscopy (FTIR), induced coupled plasma spectroscopy (ICP), BET (Brunauer, Emmett, and Teller) method, and simultaneous thermal analysis (STA). SEM and TEM...
A highly efficient MIL-101(Cr)–Graphene–molybdenum oxide nano composite for selective oxidation of hydrogen sulfide into elemental sulfur
, Article Journal of Industrial and Engineering Chemistry ; Volume 71 , 2019 , Pages 308-317 ; 1226086X (ISSN) ; Askari, S ; Rashidi, A ; Fakhraie, S ; Kooti, M ; Shafiei Alavijeh, M ; Sharif University of Technology
Korean Society of Industrial Engineering Chemistry
2019
Abstract
Hybrid composites of MIL-101(Cr) and Nanoporous Graphene with ratios in the range of 10–50% were prepared via hydrothermal synthesis method. This study deals with an experimental investigation on selective oxidation of H2S into elemental sulfur in the range of 200–270 °C, the catalyst activity and selectivity toward sulfur was studied. High-temperature reactor tests indicated that the MIL-101(Cr)–NPG50–Mo could be a promising candidate with conversion and selectivity of 100% and 99.5% at 200 °C. The MIL-101(Cr)–NPG50–Mo stability showed there were not any significant changes in physical properties, the activity was evaluated after 20 h which was completely stable without any changes
prediction of time to failure in stress corrosion cracking of 304 stainless steel in aqueous chloride solution by artificial neural network
, Article Protection of Metals and Physical Chemistry of Surfaces ; Volume 45, Issue 5 , 2009 , Pages 610-615 ; 20702051 (ISSN) ; Shahrabi, T ; Baigi, V ; Shafiei, A. M ; Sharif University of Technology
2009
Abstract
Despite the numerous researches in Stress Corrosion Cracking (SCC) risk of austenitic stainless steels in aqueous chloride solution, no formulation or reliable method for prediction of time to failure as a result of SCC has yet been defined. In this paper, the capability of artificial neural network for estimation of the time to failure for SCC of 304 stainless steel in aqueous chloride solution together with sensitivity analysis has been expressed. The output results showed that artificial neural network can predict the time to failure for about 74% of the variance of SCC experimental data. Furthermore, the sensitivity analysis also demonstrated the effects of input parameters (Temperature,...
A new model for the effect of grain size on the elastic modulus of nanocrystalline materials
, Article Materials Science- Poland ; Volume 27, Issue 1 , 2009 , Pages 279-285 ; 01371339 (ISSN) ; Sharif University of Technology
2009
Abstract
A new model is developed for the structure of nanocrystalline materials. Based on the developed model, a new approach for investigating the effect of grain size on the elastic moduli of nanocrystalline materials is introduced. The predictions of the model are strongly correlated with the experimental results reported in the existing literature
Nonlinear vibration and buckling of functionally graded porous nanoscaled beams
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 40, Issue 7 , July , 2018 ; 16785878 (ISSN) ; Mohasel Afshari, B ; Khezel, M ; Shafiei, N ; Rabby, S ; Kordnejad, M ; Sharif University of Technology
Springer Verlag
2018
Abstract
Although many researchers have studied the vibration and buckling behavior of porous materials, the behavior of porous nanobeams is still a needed issue to be studied. This paper is focused on the buckling and nonlinear vibration of functionally graded (FG) porous nanobeam for the first time. Nonlinear Von Kármán strains are put into consideration to study the nonlinear behavior of nanobeam based on the Euler–Bernoulli beam theory. The nonlocal Eringen’s theory is used to study the size effects. The mechanical properties of ceramic and metal are used to model the functionally graded material through thickness, and the boundary conditions are considered as clamped–clamped (CC) and simply...
Optimisation of an integrated parallel distribution system by including network marketing
, Article International Journal of Logistics Systems and Management ; Volume 36, Issue 2 , 2020 , Pages 305-318 ; Modarres, M ; Sharif University of Technology
Inderscience Publishers
2020
Abstract
Network marketing is a business model that depends upon a network of distributors for growth, such as in multilevel marketing. A direct selling method features independent agents that make up a distribution network for goods and services. This paper provides a framework to study the network marketing by adopting the traditional channel. To motivate all distributers in network marketing as well as retailers, it is required to design a well-balanced distribution and pricing system. The allocated commission for distributers in different layers of network marketing is part of pricing system, which is vital. In this paper, we develop an approach to determine all elements of system, including...