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Structure Formation and Galactic Dynamics in Modified Gravity (MOG)
, Ph.D. Dissertation Sharif University of Technology ; Rahvar, Sohrab (Supervisor) ; Mohammad Movahed, Sadegh (Co-Advisor)
Abstract
The standard model of Cosmology (SM), based on Einstein’s theory of general relativity (GR), is the best model in describing the cosmic-scale observations. In galactic scales, however, galactic dynamics show a discrepancy between the observed luminous mass and the predicted value from the theory. Two approaches are suggested to eliminate this inconsistency: assuming the existence of dark matter within the context of GR, or modifying the theory of gravity in galactic scales, like MOND or MOG. In this thesis, we study the spherical collapse and the formation of shell galaxies in MOG, in comparison with SM. We introduce the action and the field equations of MOG and the equation of motion of a...
Erratum: Multifractal detrended fluctuation analysis of sunspot time series (Journal of statistical mechanics: Theory and experiment)
, Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2011, Issue 9 , 2011 ; 17425468 (ISSN) ; Jafari, G. R ; Ghasemi, F ; Rahvar, S ; Reza Rahimi Tabar, M ; Sharif University of Technology
2011
Effecive & efficient DSM configuration guidelines for low-cost development of complex systems
, Article Gain Competitive Advantage by Managing Complexity - Proceedings of the 14th International Dependency and Structure Modelling Conference, DSM 2012, 13 September 2012 through 14 September 2012 ; 2012 , Pages 125-137 ; 9783446433540 (ISBN) ; Sharif University of Technology
Institution of Engineering Designers
2012
Abstract
With the proliferation of more complex systems has come the need to find better solutions in both technical and management domains. Such complex systems are usually larger in size, have more parallel operations and contain more complex interfaces (Eisner, 2005). The Design Structure Matrix is a very useful tool in handling such complexities, provided that the system designer can use it properly. This paper addresses how effectiveness & efficiency are defined for a DSM and how these two important characteristics can be achieved. The importance of understanding the solution space in constructing an effective & efficient DSM is discussed and general guidelines are given on configuring the DSM...
Observational constraints on a variable dark energy model
, Article Physical Review D - Particles, Fields, Gravitation and Cosmology ; Volume 73, Issue 8 , 2006 ; 15507998 (ISSN) ; Rahvar, S ; Sharif University of Technology
2006
Abstract
We study the effect of a phenomenological parameterized quintessence model on low, intermediate and high redshift observations. At low and intermediate redshifts, we use the Gold sample of supernova Type Ia (SNIa) data and recently observed size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), to put constraint on the parameters of the quintessence model. At the high redshift, the same fitting procedure is done using WAMP data, comparing the location of acoustic peak with that obtain from the dark energy model. As a complementary analysis in a flat universe, we combine the results from the SNIa, CMB and SDSS. The best fit values for the model parameters are Ωm=0.27-0.02+0.02...
Observational constraints with recent data on the DGP modified gravity
, Article International Journal of Theoretical Physics ; Volume 48, Issue 4 , 2009 , Pages 1203-1230 ; 00207748 (ISSN) ; Farhang, M ; Rahvar, S ; Sharif University of Technology
2009
Abstract
We study one of the simplest covariant modified-gravity models based on the Dvali-Gabadadze-Porrati (DGP) brane cosmology, a self-accelerating universe. In this model gravitational leakage into extra dimensions is responsible of late-time acceleration. We mainly focus on the effects of the model parameters on the geometry and the age of universe. Also we investigate the evolution of matter density perturbations in the modified gravity model, and obtain an analytical expression for the growth index, f. We show that increasing Ωrcleads to less growth of the density contrast δ, and also decreases the growth index. We give a fitting formula for the growth index at the present time and indicate...
A novel secure bilinear pairing based remote user authentication scheme with smart card
, Article Proceedings - IEEE/IFIP International Conference on Embedded and Ubiquitous Computing, EUC 2010, 11 December 2010 through 13 December 2010 ; 2010 , Pages 578-582 ; 9780769543222 (ISBN) ; Sabzinejad, M ; Movahed, A ; Sharif University of Technology
2010
Abstract
Authentication schemes play vital roles in computer and communication security. In order to authenticate the remote users, password based schemes have been widely used. In this paper we introduce a secure remote user authentication scheme based on bilinear pairing that satisfies all security requirements which are mentioned for password based authentication schemes using smart card
The O (n) model in the n → 0 limit (self-avoiding-walks) and logarithmic conformal field theory
, Article Nuclear Physics B ; Volume 707, Issue 3 , 2005 , Pages 405-420 ; 05503213 (ISSN) ; Saadat, M ; Rahimi Tabar, M. R ; Sharif University of Technology
2005
Abstract
We consider the O (n) theory in the n → 0 limit. We show that the theory is described by logarithmic conformal field theory, and that the correlation functions have logarithmic singularities. The explicit forms of the two-, three- and four-point correlation functions of the scaling fields and the corresponding logarithmic partners are derived. © 2004 Elsevier B.V. All rights reserved
Fractal Analysis of Cosmic Microwave Background Radiation
, Article Houches-Ecole d'Ete de Physique Theorique ; Volume 86, Issue C , 2007 , Pages 552- ; 09248099 (ISSN) ; Sharif University of Technology
2007
Consistency of f(R)=R2-R02 gravity with cosmological observations in the palatini formalism
, Article Physical Review D - Particles, Fields, Gravitation and Cosmology ; Volume 76, Issue 4 , 2007 ; 15507998 (ISSN) ; Baghram, S ; Rahvar, S ; Sharif University of Technology
2007
Abstract
In this work we study the dynamics of the Universe in f(R)=R2-R02 modified gravity with the Palatini formalism. We use data from recent observations, such as the supernova type Ia Gold sample and Supernova Legacy Survey data, the size of the baryonic acoustic peak from the Sloan Digital Sky Survey, the position of the acoustic peak from the cosmic microwave background observations, and large-scale structure formation from the 2dFGRS survey, to put constraints on the parameters of the model. To check the consistency of this action, we compare the age of old cosmological objects with the age of the Universe. In the combined analysis with all the observations, we find the parameters of the...
Miniaturized salting-out liquid-liquid extraction in a coupled-syringe system combined with HPLC-UV for extraction and determination of sulfanilamide
, Article Talanta ; Vol. 121 , April , 2014 , pp. 199-204 ; ISSN: 00399140 ; Khosraviani, M ; Sadegh Amini-Fazl, M ; Sharif University of Technology
2014
Abstract
In salting-out liquid-liquid extraction (SALLE) technique, water-miscible organic solvents are used for extraction of polar analytes from saline solutions. In this study, for the first time, a coupled 1-mL syringes system was utilized to perform a miniaturized SALLE method. Sulfanilamide antibiotic was extracted and determined via the developed method followed by high performance liquid chromatography-ultraviolet detection (HPLC-UV). The extraction process was carried out by rapid shooting of acetonitrile as extraction solvent (syringe B) into saline aqueous sample solution (syringe A), and then the shooting was repeated several times at a rate of 1 cycle s-1. Thereby, an extremely large...
A coarse relative-partitioned index theorem
, Article Bulletin des Sciences Mathematiques ; Volume 153 , 2019 , Pages 57-71 ; 00074497 (ISSN) ; Esfahani Zadeh, M ; Sadegh, A ; Sharif University of Technology
Elsevier Masson SAS
2019
Abstract
It seems that the index theory for non-compact spaces has found its ultimate formulation in the realm of coarse spaces and K-theory of related operator algebras. Relative and partitioned index theorems may be mentioned as two important and interesting examples of this program. In this paper we formulate a combination of these two theorems and establish a partitioned-relative index theorem. © 2019 Elsevier Masson SAS
Long-range correlation in cosmic microwave background radiation
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 84, Issue 2 , 2011 ; 15393755 (ISSN) ; Ghasemi, F ; Rahvar, S ; Tabar, M. R. R ; Sharif University of Technology
2011
Abstract
We investigate the statistical anisotropy and Gaussianity of temperature fluctuations of Cosmic Microwave Background (CMB) radiation data from the Wilkinson Microwave Anisotropy Probe survey, using the Multifractal Detrended Fluctuation Analysis, Rescaled Range, and Scaled Windowed Variance methods. Multifractal Detrended Fluctuation Analysis shows that CMB fluctuations has a long-range correlation function with a multifractal behavior. By comparing the shuffled and surrogate series of CMB data, we conclude that the multifractality nature of the temperature fluctuation of CMB radiation is mainly due to the long-range correlations, and the map is consistent with a Gaussian distribution
Techno-economic optimization of biogas-fueled micro gas turbine cogeneration systems in sewage treatment plant
, Article Energy Conversion and Management ; Volume 218 , 15 August , 2020 ; Avami, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The aim of this paper is to investigate the feasibility of a combined cooling, heating, and power generation system with a micro turbine using biogas as the fuel to supply the heat and electricity demands in a real wastewater treatment plant. The plant is optimized using the system's total cost rate and the amount of the produced biogas as objective functions. The anaerobic digester is modeled using the ADM1 model. The optimization variables include digester hydraulic retention time, compressor pressure ratio, isentropic compressor efficiency, recuperator pinch time temperature, turbine isentropic efficiency, turbine input temperature, and the number of micro turbines. In the first scenario...
An Intrusion Detection System for the Grid Environment
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasool (Supervisor)
Abstract
Existing Intrusion Detection Systems (IDSs) are not designed to deal with all categories of processing environments. This thesis focuses on IDSs for the Grid computing environment, and concentrates on feature selection and performance. An existing framework, Globus, is used as the basis for the consideration and development of the research issue in Grid computing. The system is based on two engine designs: (a) Signature and (b) Support Vector Machine; SVM has been selected for pattern discovery in traffic analysis. We found that the performance of the system greatly depends on the efficiency of the underlying framework and the number of Intrusion Detection System instances. We demonstrate...
The effect of additives on anode passivation in electrorefining of copper
, Article Chemical Engineering and Processing: Process Intensification ; Volume 46, Issue 8 , 2007 , Pages 757-763 ; 02552701 (ISSN) ; Yoozbashizadeh, H ; Sadegh Safarzadeh, M ; Sharif University of Technology
2007
Abstract
In copper electrorefining process, some additives are added to the electrolyte to improve the morphology of cathode deposits as well as the quality of products. In the present investigation, the effects of thiourea, glue and chloride ions (as additives) on the passivation of industrial copper anodes under high current densities have been reported. Experiments were conducted at 65 °C; using a synthetic electrolyte containing 40 g/l Cu2+ and 160 g/l H2SO4. Results obtained from chronopotentiometry experiments showed that increasing the concentration of chloride ion leads to increase in passivation time. The results also indicated that from a certain level on, namely 2 ppm, the increase in...
Level crossing analysis of Burgers equation in 1 + 1 dimensions
, Article Journal of Physics A: Mathematical and General ; Volume 39, Issue 15 , 2006 , Pages 3903-3909 ; 03054470 (ISSN) ; Bahraminasab, A ; Rezazadeh, H ; Masoudi, A. A ; Sharif University of Technology
2006
Abstract
We investigate the average frequency of positive slope ν +α, crossing the velocity field in the Burgers equation. The level crossing analysis in the inviscid limit and the total number of positive crossings of the velocity field before the creation of singularities are given. The main goal of this paper is to show that this quantity, ν+α, is a good measure for the fluctuations of velocity fields in the Burgers turbulence. © 2006 IOP Publishing Ltd
Characterization of interfacial hydrodynamics in a single cell of shaken microtiter plate bioreactors applying computational fluid dynamics technique
, Article Procedia Engineering ; Volume 42 , 2012 , Pages 924-930 ; 18777058 (ISSN) ; Amoabediny, G ; Sadegh Saghafinia, M ; Haji Abbas, M. P ; Sharif University of Technology
2012
Abstract
Development of orbital shaking technology for enhanced mixing with lower mechanical demand has been receiving significant attention since the advent of advanced mixing schemes. Amongst shaken bioreactors, microtiter plates play significant role both for research and industrial purposes due to their capability of handling tiny amount of liquid in parallel experimentations. Detailed understanding of complicated Flow hydrodynamics thus seems to be considered a continual effort, as it is responsible for efficient gas-liquid mass transfer. Computational fluid dynamics (CFD) technique is shown to be a suitable numerical method in particular for discovering concealed flow facts, which can reliably...
Fractal analysis of discharge current fluctuations
, Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2009, Issue 3 , 2009 ; 17425468 (ISSN) ; Sadegh Movahed, M ; Khorram, S ; Sobhanian, S ; Rahimi Tabar, M. R ; Sharif University of Technology
Institute of Physics Publishing
2009
Abstract
We use multifractal detrended fluctuation analysis (MF-DFA) to study the electrical discharge current fluctuations in plasma and show that it has multifractal properties and behaves as a weak anti-correlated process. Comparison of the MF-DFA results for the original series with those for the shuffled and surrogate series shows that correlation of the fluctuations is responsible for the multifractal nature of the electrical discharge current. © 2009 IOP Publishing Ltd. and SISSA
Thin Film Thickness Measurement Using Colors of Interference Fringes
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
There are several methods for measuring thin film thickness, however, for the analysis of liquid film motors [1] we need a method which is capable of measuring the thickness using a single image of the film. In this work, we use the colors that appear on thin films, such as soup bubbles, which is a result of light interference to calculate the thickness of the layer
Measure for Macroscopic Quantumness via Quantum Coherence and Macroscopic Distinction
, M.Sc. Thesis Sharif University of Technology ; Raeisi, Sadegh (Supervisor)
Abstract
One of the most elusive problems in quantum mechanics is the transition between classical and quantum physics. This problem can be traced back to the Schrodinger's cat. A key element that lies at the center of this problem is the lack of a clear understanding and characterization of macroscopic quantum states. Our understanding of Macroscopic Quantumness relies on states such as the Greenberger-Horne-Zeilinger(GHZ) or the NOON state. Here we take a first principle approach to this problem. We start from coherence as the key quantity that captures the notion of quantumness and demand the quantumness to be collective and macroscopic. To this end, we introduce macroscopic coherence which is the...