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Roughening transition and universality of single step growth models in (2+1)-dimensions
, Article New Journal of Physics ; Volume 19, Issue 6 , 2017 ; 13672630 (ISSN) ; Saberi, A. A ; Rouhani, S ; Sharif University of Technology
2017
Abstract
We study (2+1)-dimensional single step model for crystal growth including both deposition and evaporation processes parametrized by a single control parameter p. Using extensive numerical simulations with a relatively high statistics, we estimate various interface exponents such as roughness, growth and dynamic exponents as well as various geometric and distribution exponents of height clusters and their boundaries (or iso-height lines) as function of p. We find that, in contrary to the general belief, there exists a critical value at which the model undergoes a roughening transition from a rough phase with in the Kardar-Parisi-Zhang universality to a smooth phase with , asymptotically in...
Statistics of toppling wave boundaries in deterministic and stochastic sandpile models
, Article Journal of Physics A: Mathematical and Theoretical ; Volume 45, Issue 4 , 2012 ; 17518113 (ISSN) ; Azimi Tafreshi, N ; Moghimi Araghi, S ; Sharif University of Technology
2012
Abstract
We study numerically the statistics of curves which form the boundaries of toppling wave clusters in the deterministic Bak, Tang and Wiesenfeld sandpile model and stochastic Manna model on a square lattice. We consider the Abelian version of each model. Multiple tests show that the boundary of toppling wave clusters in both deterministic and stochastic models can be described by SLE curves with diffusivity = 2
Direct evidence for conformal invariance of avalanche frontiers in sandpile models
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 79, Issue 3 , Volume 79, Issue 3 , 2009 ; 15393755 (ISSN) ; Moghimi-Araghi, S ; Dashti-Naserabadi, H ; Rouhani, S ; Sharif University of Technology
2009
Abstract
Appreciation of stochastic Loewner evolution (SLEκ), as a powerful tool to check for conformal invariant properties of geometrical features of critical systems has been rising. In this paper we use this method to check conformal invariance in sandpile models. Avalanche frontiers in Abelian sandpile model are numerically shown to be conformally invariant and can be described by SLE with diffusivity κ=2. This value is the same as value obtained for loop-erased random walks. The fractal dimension and Schramm's formula for left passage probability also suggest the same result. We also check the same properties for Zhang's sandpile model. © 2009 The American Physical Society
Classification of Two-dimensional Surface Growth Models using Schramm -Loewner Evolution
, Ph.D. Dissertation Sharif University of Technology ; Rohani, Shahin (Supervisor) ; Saberi, Abbas Ali (Co-Advisor)
Abstract
Rough surfaces and growth process are the important and significant problems of theoretical and condensed matter physics to model phenomena ranging from the extremely small (biological phenomena) to largest one (Earth’s relief). Although the equations that describe these processes are well defined, but the question of how to characterize these surfaces which display large fluctuations, is open. The existence of (often) scale invariant clusters and very large fluctuations in surface growth process are reminiscent of critical fluctuations in equilibrium systems. Therefore, it is natural to try characterizing the surface by means of critical exponents, i.e., by the scaling dimensions of various...
Stochastic nature of series of waiting times
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 6 , 2013 ; 15393755 (ISSN) ; Aghamohammadi, C ; Dashti Naserabadi, H ; Salehi, E ; Behjat, E ; Qorbani, M ; Khazaei Nezhad, M ; Zirak, M ; Hadjihosseini, A ; Peinke, J ; Tabar, M. R. R ; Sharif University of Technology
2013
Abstract
Although fluctuations in the waiting time series have been studied for a long time, some important issues such as its long-range memory and its stochastic features in the presence of nonstationarity have so far remained unstudied. Here we find that the "waiting times" series for a given increment level have long-range correlations with Hurst exponents belonging to the interval 1/2
Three-dimensional Ising model, percolation theory and conformal invariance
, Article EPL ; Volume 92, Issue 6 , 2010 ; 02955075 (ISSN) ; Dashti Naserabadi, H ; Sharif University of Technology
2010
Abstract
The fractal structure and scaling properties of a 2d slice of the 3d Ising model is studied using Monte Carlo techniques. The percolation transition of geometric spin (GS) clusters is found to occur at the Curie point, reflecting the critical behavior of the 3d model. The fractal dimension and the winding angle statistics of the perimeter and external perimeter of the geometric spin clusters at the critical point suggest that, if conformally invariant in the scaling limit, they can be described by the theory of Schramm-Löwner evolution (SLE κ) with diffusivity of κ=5 and 16/5, respectively, putting them in the same universality class as the interfaces in 2d tricritical Ising model. It is...
The Effect of Electroporation on Ultrasund Signals
, M.Sc. Thesis Sharif University of Technology ; Zahedi, Edmond (Supervisor)
Abstract
In this thesis, a cellular model of electroporation process and its detection by ultrasound signals is proposed. Electroporation is permeabilization of the cell membrane, caused by an external electric field. The resulted pores open cell’s membrane to large or hydrophilic molecules. The process of Electroporation has been used in Gene therapy and treatment of solid tumors. In this project, first we made a phantom of electroporated tissue and a phantom of normal tissue and then we simulated their responses to a linear array ultrasound transducer. By comparision of received signals from phantoms the probable effect of electroporation on ultrasound RF signals revealed. Results show up to 5 %...
Classification of (2+1 ) -dimensional growing surfaces using Schramm-Loewner evolution
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 82, Issue 2 , August , 2010 ; 15393755 (ISSN) ; Dashti Naserabadi, H ; Rouhani, S ; Sharif University of Technology
2010
Abstract
Statistical behavior and scaling properties of isoheight lines in three different saturated two-dimensional grown surfaces with controversial universality classes are investigated using ideas from Schramm-Loewner evolution (SLEκ). We present some evidence that the isoheight lines in the ballistic deposition (BD), Eden and restricted solid-on-solid (RSOS) models have conformally invariant properties all in the same universality class as the self-avoiding random walk (SAW), equivalently SLE8/3. This leads to the conclusion that all these discrete growth models fall into the same universality class as the Kardar-Parisi-Zhang (KPZ) equation in two dimensions
Modeling and simulation of olefin polymerization at microstructure level
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 27, Issue 2 , 2008 , Pages 13-22 ; 10219986 (ISSN) ; Ramezani Saadatabadi, A ; Sharif University of Technology
2008
Abstract
A new model based on a combination of the polymeric multigrain and multilayer models has been developed to predict the polymerization rate, particle growth, morphology, effective parameters on broadening of the molecular weight distribution, number and weight average of the molecular weight, isotacticity index and bulk density of polymer. Mathematical correlations and the kinetics used in this model are based on the polymeric multigrain and the multilayer models, respectively. In the modeling, multiplicity of active site using different kinetics parameters as well as Reactivation of catalyst during the polymerization have been considered,. Moreover, it considers mass transfer effects on...
The spatial asymmetric two-dimensional continuous Abelian sandpile model
, Article Journal of Physics A: Mathematical and Theoretical ; Volume 41, Issue 43 , 2008 ; 17518113 (ISSN) ; Dashti Naserabadi, H ; Moghimi Araghi, S ; Sharif University of Technology
2008
Abstract
We insert some asymmetries into the continuous Abelian sandpile models, such as directedness and ellipticity. We analyze probability distribution of different heights and also find the corresponding field theories. Also we find the fields associated with some height variables. © 2008 IOP Publishing Ltd
Development of a model for Planning and Management of flood in Multi-Reservoir and Multi-Purpose River Basin (Case Study: Karkheh river basin)
, M.Sc. Thesis Sharif University of Technology ; Abrishmachi, Ahmad (Supervisor)
Abstract
The study of flood control operation in large scale multipurpose reservoir systems is deals with various objectives, such as flood damage reduction, hydropower generation and reliability of the system for supplying demands after flood seasons. The introduction of these objectives, introduces a conflict in objective function where tradeoff must be made. The purpose of this study is helping to decision making process in evaluation, planning and operation phases through preparing the Pareto curves that include various optimum alternatives for operation. For this purpose, we develop a multiobjective optimization model, based on use the mixed-integer linear programming. This model considers two...
The Abelian sandpile model on the honeycomb lattice
, Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2010, Issue 2 , 2010 ; 17425468 (ISSN) ; Dashti Naserabadi, H ; Moghimi Araghi, S ; Ruelle, P ; Sharif University of Technology
2010
Abstract
We check the universality properties of the two-dimensional Abelian sandpile model by computing some of its properties on the honeycomb lattice. Exact expressions for unit-height correlation functions in the presence of boundaries and for different boundary conditions are derived. Also, we study the statistics of the boundaries of avalanche waves by using the theory of SLE and suggest that these curves are conformally invariant and described by SLE 2
Fracture characterizing and modeling of a porous fractured carbonate reservoir
, Article Society of Petroleum Engineers - SPE/EAGE Reservoir Characterization and Simulation Conference 2009 - Overcoming Modeling Challenges to Optimize Recovery, 19 October 2009 through 21 October 2009 ; Volume 1 , 2009 , Pages 303-319 ; 9781615677443 (ISBN) ; Bagheri, M. B ; Ulhaq, S ; Sharif University of Technology
2009
Abstract
Anisotropy and heterogeneity in reservoir properties introduce challenges during the development of hydrocarbon reservoirs in naturally fractured reservoirs. In reservoir simulations, grid-block properties are frequently assigned to obtain reasonable history matches. Even then, accuracy with regard to some aspects of the performance such as water or gas cuts, breakthrough times, and sweep efficiencies may be inadequate. In some cases, this could be caused by the presence of substantial flow through natural fractures. In this work the fracture characterization and modeling was performed in a highly fractured carbonate reservoir in SW Iran. It was observed that reservoir simulation based on...
Performance and exhaust emission characteristics of a spark ignition engine operated with gasoline and CNG blend
, Article Proceedings of the Spring Technical Conference of the ASME Internal Combustion Engine Division ; 2012 , Pages 179-187 ; 15296598 (ISSN) ; 9780791844663 (ISBN) ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
2012
Abstract
Using CNG as an additive for gasoline is a proper choice due to higher octane number of CNG enriched gasoline with respect to that of gasoline. As a result, it is possible to use gasoline with lower octane number in the engine. This would also mean the increase of compression ratio in SI engines resulting in higher performance and lower gasoline consumption. Over the years, the use of simulation codes to model the thermodynamic cycle of an internal combustion engine have developed tools for more efficient engine designs and fuel combustion. In this study, a thermodynamic cycle simulation of a conventional four-stroke spark-ignition engine has been developed. The model is used to study the...
Estimation of 3-D pore network coordination number of rocks from watershed segmentation of a single 2-D image
, Article Advances in Water Resources ; Volume 94 , 2016 , Pages 264-277 ; 03091708 (ISSN) ; Ayatollahi, S ; Kharrat, R ; Dashti, N ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this study, we have utilized 3-D micro-tomography images of real and synthetic rocks to introduce two mathematical correlations which estimate the distribution parameters of 3-D coordination number using a single 2-D cross-sectional image. By applying a watershed segmentation algorithm, it is found that the distribution of 3-D coordination number is acceptably predictable by statistical analysis of the network extracted from 2-D images. In this study, we have utilized 25 volumetric images of rocks in order to propose two mathematical formulas. These formulas aim to approximate the average and standard deviation of coordination number in 3-D pore networks. Then, the formulas are applied...
A comparative study of the performance of a SI engine fuelled by natural gas as alternative fuel by thermodynamic simulation
, Article 2009 ASME Internal Combustion Engine Division Fall Technical Conference, ICEF 2009, Lucerne, 27 September 2009 through 30 September 2009 ; 2009 , Pages 49-57 ; 9780791843635 (ISBN) ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2009
Abstract
With the declining energy resources and increase of pollutant emissions, a great deal of efforts has been focused on the development of alternatives for fossil fuels. One of the promising alternative fuels to gasoline in the internal combustion engine is natural gas [1-5]. The application of natural gas in current internal combustion engines is realistic due to its many benefits. The higher thermal efficiency due to the higher octane value and lower exhaust emissions including CO2 as a result of the lower carbon to hydrogen ratio of the fuel are the two important feature of using CNG as an alternative fuel. It is well known that computer simulation codes are valuable economically as a cost...
Development of a Framework for Software Architecture Extraction of Existing Projects Based on Their Requirements
, M.Sc. Thesis Sharif University of Technology ; Habibi, Jafar (Supervisor)
Abstract
The architecture of a software system, its elements and the way they interact is a valuable treasure for understanding the system. If architecture description of a system is not available, working on its extraction and reconstruction should be done. For a software with huge size and vast complexity, architecture extraction by hand and without any predefined method is nearly impossible. So, it is essential for software architecture extractor to use a framework and a well-defined process related to it, for extracting the software architecture. It can help him to use automated tools as much as possible in addition to havingauniquelogicalstructureforperformingthearchitectureextractionprocess. In...
Effect of anode compositions on the current efficiency of zinc electrowinning
, Article Proceedings - European Metallurgical Conference, EMC 2011 ; Volume 2 , 2011 , Pages 387-396 ; 9783940276377 (ISBN) ; Rashchi, F ; Vahidi, E ; Emami, M ; Khoshnevisan, A ; Sharif University of Technology
2011
Abstract
The main goals in zinc electrowinning process are decreasing of power consumption and increasing of current efficiency. The purpose of this research was to investigate effect of different alloy compositions used in production of lead-based anodes on the zinc electrowinning process. The anode compositions prepared and examined in this study were binary alloys Pb - (0.5 and 2 %) Ag and quaternary alloys Pb - 0.5 % Ag - 1 % Ca - 2 % Sn, Pb - 0.5 % Ag - 1 % Ca - 1 % Sn - 1 % Sb and Pb - 0.5 % Ag - 1 % Ca - 1 % Sn - 1 % Bi. The electrowinning experiments were conducted using a laboratory-scale apparatus, at a plating time of 4 hours, a current density of 500 to 1000 A/m2, industrial zinc sulfate...
A novel photometric glucose biosensor based on decolorizing of silver nanoparticles
, Article Sensors and Actuators, B: Chemical ; Volume 158, Issue 1 , November , 2011 , Pages 185-189 ; 09254005 (ISSN) ; Hormozi Nezhad, M. R ; Khodaveisi, J ; Dashti, R ; Sharif University of Technology
2011
Abstract
A novel glucose biosensor based on chromophore (silver nanoparticles) decolorizing for the photometric determination of glucose was developed. Silver nanoparticles are directly synthesized in the sol-gel matrix by a one-step method based on the reduction of the inorganic precursor AgNO3 and were used for the preparation, characterization and calibration of a highly sensitive and cost-effective localized surface plasmon resonance-based glucose biosensor. In the presence of glucose oxidase (GOx) and due to the enzyme-substrate (glucose) reaction, H2O2 was produced and silver nanoparticles in the sol-gel glass have the ability for the decomposition of hydrogen peroxide. Due to the degradation...
Mechanistic study to investigate the effects of different gas injection scenarios on the rate of asphaltene deposition: An experimental approach
, Article Fuel ; Volume 262 , 2020 ; Zanganeh, P ; Kord, S ; Ayatollahi, S ; Amiri, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Asphaltene deposition during enhanced oil recovery (EOR) processes is one of the most problematic challenges in the petroleum industry, potentially resulting in flow blockage. Our understanding of the deposition mechanism with emphasis on the rate of the asphaltene deposition is still in its infancy and must be developed through a range of experiments and modelling studies. This study aims to investigate the rate of asphaltene deposition through a visual study under different gas injection scenarios. To visualise the asphaltene deposition, a high-pressure setup was designed and constructed, which enables us to record high-quality images of the deposition process over time. Present research...