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Modeling the Nonlinear Behavior of Nano-Materials Via Hierarchical RVE-based Multi-Scale Method
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In this paper, a hierarchical RVE-based continuum-atomistic multiscale framework is established on the basis of the nonlinear finite element method and molecular dynamics simulation in order to model the geometric and material nonlinearities of deformable solids. In this framework, the coarse scale material properties required for nonlinear finite element method are directly exploited via fine scale atomistic simulation of atomic RVEs designated for each coarse scale integration point and required boundary conditions for atomic RVE simulation are achieved from the coarse scale kinematical response. In order to ensure the kinematical and energetic consistency between the two scales, the...
Electrodeposition of the Ni-P by Pulse Plating
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Ni-P alloy coatings were electrodeposited using pulse current in a watt type bath in various conditions. The influences of different parameters were investigated and optimized for the highest amount of coating hardness using the Design Of Experiment (DOE) method. The optimized deposition parameters were current density 23.7 A/dm2, duty cycle 75%, frequency equal to 188 Hz, temperature equal to 70ºC and 17.5 gr/l of H3PO3. The DOE prediction of hardness for the optimized coatings was between 700 and 750 the achieved micro-hardness was about 725.8 HV. It was obtained that an increase of the current density will improve micro-hardness, decreases P content and increase deposition rate. Also, the...
Plasmonic fractals: Ultrabroadband light trapping in thin film solar cells by a Sierpinski nanocarpet
, Article Optical and Quantum Electronics ; Vol. 46, issue. 6 , 2014 , pp. 751-757 ; ISSN: 03068919 ; Khavasi, A ; Sharif University of Technology
2014
Abstract
Plasmonic Sierpinski nanocarpet as back structure for a thin film Si solar cell is investigated. We demonstrate that ultra-broadband light trapping can be obtained by placing square metallic nanoridges with Sierpinski pattern on the back contact of the thin film solar cell. The multiple-scale plasmonic fractal structure allows excitation of localized surface plasmons and surface plasmon polaritons in multiple wavelengths leading to obvious absorption enhancements in a wide frequency range. Full wave simulations show that 109 % increase of the short-circuit current density for a 200 nm thick solar cell, is achievable by the proposed fractal back structure. The amount of light absorbed in the...
Effect of traffic-load dependent vehicle routing algorithm on the connectivity in VANETs
, Article IEEE Vehicular Technology Conference, 15 May 2011 through 18 May 2011 ; May , 2011 , Page(s): 1 - 5 ; 15502252 (ISSN) ; 9781424483310 (ISBN) ; Ashtiani, F ; Sharif University of Technology
2011
Abstract
In this paper, we evaluate how traffic-load dependent vehicle routing at intersections is able to improve the connectivity status of all streets. To this end, we consider a VANET scenario, comprised of several streets and intersections. Then, we focus on two vehicle routing algorithms, one based on the distance to destination, i.e., traffic-load independent (TLI) algorithm, and another one based on both distance to destination and traffic load status of the local streets, i.e., traffic-load dependent (TLD) algorithm. By employing a simple mobility model based on an open BCMP queueing network, we derive the spatial traffic distribution at two cases. Afterwards, we propose a simple algorithm...
Modeling and Design of CCHP System for Sharif Energy Research Institute
, M.Sc. Thesis Sharif University of Technology ; Sabbohi, Yadollah (Supervisor)
Abstract
The aim of the present research project has been techno-economical analysis of using a CCHP (Combined Cooling Heating and Power) technology at the building of Sharif Energy Research Institute (SERI). The CCHP at SERI is supposed to supply energy required at the building. Useful energy demand at the building include heating in winter, cooling and air conditioning in summer, lighting and power requirement of electric appliance and equipments. Since there are many technologies that could be utilized as CCHP, an optimal model of energy supply system of the building has been developed in order to identify the most appropriate technology. The application of model has enabled techno logical...
Experimental evaluation of ship squat in shallow waters
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Vol. 36, Issue. 3 , 2014 , pp. 559-569 ; ISSN: 1806-3691 ; Seif, M. S ; Sharif University of Technology
2014
Abstract
Enlargement of ship size in recent decades and no change in the harbors and approach channels have resulted in global attention toward navigation in shallow and confined waters. A phenomenon which restricts ship navigation in shallow waters is reduction of under-keel clearance in terms of sinkage and dynamic trim, which is called squatting. Due to the complexity of flow around the ship hull, one of the best methods for predicting the ship squat is the experimental approach based on systematic model tests in the towing tank. In this study, model tests for tanker ship model and traditional Persian Gulf and Oman Sea vessel called dhow had been performed in the towing tank and the squat of the...
Experimental study of a tanker ship squat in shallow water
, Article Jurnal Teknologi (Sciences and Engineering) ; Vol. 66, Issue. 2 , 2014 , pp. 15-20 ; ISSN: 01279696 ; Seif, M. S ; Sharif University of Technology
2014
Abstract
One of the phenomena restricting the tanker navigation in shallow waters is reduction of under keel clearance in the terms of sinkage and dynamic trim that is called squatting. According to the complexity of flow around ship hull, one of the best methods to predict the ship squat is experimental approach based on model tests in the towing tank. In this study model tests for tanker ship model had been held in the towing tank and squat of the model are measured and analyzed. Based on experimental results suitable formulae for prediction of these types of ship squat in fairways are obtained
Simulation of turbulent flow through porous media employing a v2f model
, Article Scientia Iranica ; Volume 16, Issue 2 B , 2009 , Pages 159-167 ; 10263098 (ISSN) ; Kazemzadeh Hannani, S ; Sharif University of Technology
2009
Abstract
In this article, a v2f model is employed to conduct a series of computations of incompressible flow in a periodic array of square cylinders simulating a porous media. A Galerkin/least-squares finite element formulation employing equal order velocity-pressure elements is used to discretize the governing equations. The Reynolds number is varied from 1000 to 84,000 and different values of porosities are considered in the calculations. Results are compared to the available data in the literature. The v2f model exhibits superior accuracy with respect to κ - ε results and is closer to LES calculations. The macroscopic pressure gradients for all porosities studied showed a good agreement with...
On the scale effects of resistance model tests of high-speed monohulls
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 41, Issue 4 , 2019 ; 16785878 (ISSN) ; Seif, M. S ; Sharif University of Technology
Springer Verlag
2019
Abstract
Scaled model test in towing tank is a common method to predict the ship resistance in calm water. The scale effects are dominant in these tests because the Reynolds and Froude numbers of the model and full-scale ship cannot be equal. There is a sufficient amount of knowledge about the displacement hulls which have limited speed ranges in most cases. However, scarcity of published data on high-speed crafts is noticed. The influence of the model length on ship resistance varies in different speeds, so it should be studied in more detail. The extrapolation method of model ship resistance to full scale is studied in this paper for high-speed monohulls. Resistance model tests of semi-displacement...
Simulation of turbulent flow through porous media employing a v2f model
, Article AIP Conference Proceedings- International Conference on Computational Methods in Science and Engineering 2007, ICCMSE 2007, Corfu, 25 September 2007 through 30 September 2007 ; Volume 963, Issue 2 , 2007 , Pages 1257-1260 ; 0094243X (ISSN) ; 9780735404786 (ISBN) ; Kazemzadeh Hannani, S ; Sharif University of Technology
2007
Abstract
In this article a v2f model is employed to conduct a series of computations of incompressible flow in a periodic array of square cylinders simulating a porous media. Galerkin/Least-Squares finite element formulation employing equal order velocity-pressure elements is used to discretize the governing equations. The Reynolds number is varied from 1000 to 50,000 and different values of porosities are considered in the calculations. Results are compared with the available data in the literature. v2f model exhibits superior accuracy with respect to k - ε results and is closer to LES calculations. The macroscopic pressure gradients for all porosities studied, showed a good agreement with...
Numerical Simulation of Displacement of the Fluid Phases in Porous Media
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Nowadays, oil has an important role in our life and most of its role can be seen on the transportation. Discovering and extraction of oil are very important to produce oil and receive it to costumer. When oil is discovered, the oil companies used to drill the ground to extract the oil but they can’t extract all of oil from its reservoir. So, researchers proposed to inject another fluid like water to the oil reservoir to extract oil. Oil is trapped in the porous media which has a lot of pores and some of them have a micro scale size and they contain oil. When water is injected to the reservoir it flows in this pore and interfaces with oil and they create a multiphase flow. The governing...
Nanostructured ternary composites of PPy/CNT/NiFe2O4 and PPy/CNT/CoFe2O4: Delineating and improving microwave absorption
, Article Comptes Rendus Chimie ; Volume 21, Issue 9 , 2018 , Pages 862-871 ; 16310748 (ISSN) ; Kheirjou, S ; Asgari, S ; Kazerooni, H ; Sharif University of Technology
Elsevier Masson SAS
2018
Abstract
Two different ternary nanocomposites, PPy/CNT/CoFe2O4 and PPy/CNT/NiFe2O4, were synthesized by in situ polymerization method. The resulting composites were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. They were evaluated with the aim of investigating microwave absorption properties. The results showed that the value of microwave reflection decreases as that of prepared nanocomposites increases. This happens with increase in the PPy content and polymerization on the surface. © 2018 Académie des sciences
A continuum-atomistic multi-scale technique for nonlinear behavior of nano-materials
, Article International Journal of Mechanical Sciences ; Volume 148 , 2018 , Pages 191-208 ; 00207403 (ISSN) ; Sameti, A. R ; Kazerooni, Y. N ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this paper, a hierarchical RVE-based continuum-atomistic multi-scale procedure is developed to model the nonlinear behavior of nano-materials. The atomistic RVE is accomplished in consonance with the underlying atomistic structure, and the inter-scale consistency principals, i.e. kinematic and energetic consistency principals, are exploited. To ensure the kinematic compatibility between the fine- and coarse-scales, the implementation of periodic boundary conditions is elucidated for the fully atomistic method. The material properties of coarse-scale are modeled with the nonlinear finite element method, in which the stress tensor and tangent modulus are computed using the Hill-Mandel...
Maneuvering & Dynamic Stability Study of Planing Hulls
, Ph.D. Dissertation Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor)
Abstract
Planing hulls have been under rapid development during recent years and their maximum speed has increased significantly thanks to advancements in high power engines and light weight hull construction methods. In the past two decades, the main concern have been hydrodynamic characteristics and stability of the planing hulls in straight-line motion in calm and rough water, and no applied mathematical model is proposed for their dynamic motions in different maneuvers in contrast to displacement hulls. Moreover, control loss at high speeds is very prevalent and in most cases this leads to economy and human losses. The main target of this thesis is to develop and validate a mathematical model to...
A general model for I/O system theory, Proceedings of AIMC31 [electronic resource]
, Article Iranian Journal of Fuzzy Systems ; 2006, Volume 3, Issue 2, Page 1-19 ; Hashem, Amir ; Sharif University of TechnologyExperimental and Numerical Study of Spray Combustion under Hot-diluted Conditions
, M.Sc. Thesis Sharif University of Technology ; Mardani, Amir (Supervisor)
Abstract
In this thesis, combustion of liquid fuel spray under the condition of hot and diluted oxidizer, has been investigated. To this end, a novel type laboratory-scale test rig was designed to study the physics governing the MILD-Spray combustion conditions with an applied approach. The underlined test rig eliminates the operational problems of its predecessor test stands and is used for a heavier fuel with much more complex chemical composition (kerosene). The test section is axially symmetrical, in which the fuel is injected by a pressure-swirl atomizer in the direction of hot and diluted co-flowing air. With the use of the aforesaid test rig, the effect of variables such as oxygen...
General theory of translation invariant systems [electronic resource]
, Article Mathematics and Its Applications ; Volume 329, 1995, pp 77-89 ; Sharif University of Technology
Abstract
The basic goal of this article is to present an abstract system-theoretic approach to morphological filtering and the theory of translation invariant systems which is mainly based on residuated semigroups. Some new results as well as a number of basic questions are also introduced
Duality in a generalized model for translation invariant systems [electronic resource]
, Article Fuzzy Sets and Systems ; 1996, Volume 83, Issue 3, Pages 347–352 ; Sharif University of Technology
Abstract
In a previous paper we introduced a generalized model for translation invariant (TI) operators. In this model we considered the space, φ of all maps from an abelian group G to ω U {-∞}, called LG-fuzzy sets, where ω is a complete lattice-ordered group; and we defined TI operators on this space. Also, in that paper, we proved strong reconstruction theorem to show the consistency of this model. This theorem states that for an order-preserving TI operator Y one can explicitly compute Y(A), for any A, from a specific subset of φ called the base of Y. In this paper duality is considered in the same general framework, and in this regard, continuous TI operators are studied. This kind of operators...
Reconstruction in a generalized model for translation invariant systems [electronic resource]
, Article Fuzzy Sets and Systems ; 1996, Volume 83, Issue 1, Pages 51–55 ; Sharif University of Technology
Abstract
We consider translation invariant (TI) operators on Φ, the set of maps from an abelian group G to Ω ∪ {−∞} , called LG-fuzzy sets, where 0 is a complete lattice ordered group. By defining Minkowski and morphological operations on Φ and considering order preserving operators, we prove a reconstruction theorem. This theorem, which is called the Strong Reconstruction Theorem (SRT), is similar to the Convolution Theorem in the theory of linear and shift invariant systems and states that for an order preserving TI operator Y one can explicitly compute Y ( A ), for any A , from a specific subset of Φ called the base of Y . The introduced framework is a general model for the theory of translation...
Residuated semigroups and morphological aspects of translation invariant systems [electronic resource]
, Article 1997, Volume 90, Issue 1, Pages 69–81 ; Fuzzy Sets and Systems ; Sharif University of Technology
Abstract
The main goal of this paper is to verify classical properties of morphological operators within the general model of translation invariant (TI) systems. In this model, TI operators are defined on the space of LG-fuzzy sets Φ i.e. Φ = {A: G → Ω ∪ {− ∞}} in which G is an abelian group and Ω is a complete lattice ordered group. A TI operator Y is an operator on Φ which is invariant under translation on G and Ω as groups. We consider the generalization of Minkowski addition (D on Φ and we emphasize that (Φ,⊛) is an involutive residuated topological monoid. We verify all properties of traditional (set-theoretic) morphological operators as well as classical representations (Matheron, 1967) for...