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vakili--masoumeh
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Recommendations on enhancing the efficiency of algebraic multigrid preconditioned GMRES in solving coupled fluid flow equations
, Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 55, Issue 3 , 2009 , Pages 232-256 ; 10407790 (ISSN) ; Darbandi, M ; Sharif University of Technology
2009
Abstract
The algebraic multigrid (AMG) algorithm as a preconditioner to the Krylov subspace methods has drawn the attention of many researchers in solving fluid flow and heat transfer problems. However, the efficient employment of this solver needs experience, because users have to quantify several important parameters. In this work, we choose a hybrid finite-volume element method and quantify the optimum magnitudes for those parameters. To generalize our results, two sets of fluid flow governing equations, the thermobuoyant flow and confined diffusion flame, are studied and the optimum values are determined. The results indicate that the AMG can be very effective if a proper storage method is chosen...
Evaluation of The Informational Efficiency of Tehran Securities Market
, M.Sc. Thesis Sharif University of Technology ; Zamani, Shiva (Supervisor)
Abstract
In the present research, the weak level efficiency of securitise market is reviewed and examined .Therefore the “Random Walk Hypothesis” has been examined on the time series of daily efficiency index of TEHRAN SECURITISE MARKET. The main difference between this research and the previous researches which have been performed previously in Iran, is the method of Hypothesis Test. The” Variance Ratio Test” has been used as a method of Hypothesis’ Test. In the second chapter, the theoretical and experimental literatures of this research has been described in detail. In parallel with the ” Variance Ratio Test”, the impact of the Day of week and the “HETROSCEDASITY TEST” also has been...
Production of Nanostructured Composite Sheets of AA1100/St37 Using ARB Technique and Evaluation of Heat Treatment Effect on Grains Structure
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
In present work, nanostructured multilayer composites produced from AA1100 and St37 alloys and mechanical properties of resulted samples characterized using tension and micro hardness tests. Also dispersion pattern of second phase in matrix studied via optical microscopy. Thickness of second phase layers showed a little reduction after 2 ARB cycles; but their length decrease gradually. With increasing number of ARB cycles up to 6 cycles, sample's tensile strength first decrease rapidly and after that increased, but never reached initial value. In order to evaluation of heat treatment effects on samples grain structure, samples heat treated and tensile test carried on them. Annealing at 300...
Why and How did Philosophy of Science Come to Iran?
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
The history of an Episteme is part of that Episteme. Without understanding the history of Episteme, one cannot get the right understanding of the Episteme. In order to understand the current coordinates of philosophy in Iran (as well as understanding the current state of philosophy in Iran), it must examine the history of its emergence and development. Part of the sources of recognition of this history is the “Erlbnis” of those who lived the event. Those who have been trying for its birth and development. Some other sources in understanding this history are the previous published works in this area. Another is the educational effort and the establishment and development of the institutions...
Design of adaptive proportional-integral-weighted (PIw) controllers for control of a class of nonlinear uncertain systems
, Article 2017 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 923-926 ; 9781509059638 (ISBN) ; Tavazoei, M. S ; Sharif University of Technology
2017
Abstract
Study on the potential abilities of the proportional-integral-weighted (PIw) controllers, as a recently proposed generalization for proportional-integral (PI) controllers, can be useful for improving the performance of traditional control systems. In this paper, adaptive PI and adaptive PIw controllers are designed to be used in control of a special class of nonlinear uncertain systems based on the Lyapanuv stability theorem. The effectiveness of the proposed controllers is illustrated by applying the proposed schemes to a Continuous Stirred-Tank Reactor (CSTR) system with an unknown parameter. Simulation results indicate that using adaptive PIw controllers, in comparison to using the...
Type i shell galaxies as a test of gravity models
, Article Astrophysical Journal ; Volume 848, Issue 1 , 2017 ; 0004637X (ISSN) ; Kroupa, P ; Rahvar, S ; Sharif University of Technology
2017
Abstract
Shell galaxies are understood to form through the collision of a dwarf galaxy with an elliptical galaxy. Shell structures and kinematics have been noted to be independent tools to measure the gravitational potential of the shell galaxies. We compare theoretically the formation of shells in Type I shell galaxies in different gravity theories in this work because this is so far missing in the literature. We include Newtonian plus dark halo gravity, and two non-Newtonian gravity models, MOG and MOND, in identical initial systems. We investigate the effect of dynamical friction, which by slowing down the dwarf galaxy in the dark halo models limits the range of shell radii to low values. Under...
Frameworks, quantitative indicators, characters, and modeling approaches to analysis of energy system resilience: A review
, Article Renewable and Sustainable Energy Reviews ; Volume 144 , 2021 ; 13640321 (ISSN) ; Saboohi, Y ; Vakili, A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The rise of the damage to energy systems caused by both natural and man-made disruptive events and the connection between energy systems and socio-economic systems have motivated the study of energy system resilience. This paper conceptualizes and comprehensively presents a systematic review of the recent literature focused on the analytical, technical, and mathematical points from the standpoint of the energy systems facing disruptive events. To this end, five phases are developed. Firstly, the concept of the energy system resilience is presented, and then the energy resilience characters and the resilience states are introduced and connected. Thirdly, the formulation and indicators of the...
Frameworks, quantitative indicators, characters, and modeling approaches to analysis of energy system resilience: A review
, Article Renewable and Sustainable Energy Reviews ; Volume 144 , 2021 ; 13640321 (ISSN) ; Saboohi, Y ; Vakili, A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The rise of the damage to energy systems caused by both natural and man-made disruptive events and the connection between energy systems and socio-economic systems have motivated the study of energy system resilience. This paper conceptualizes and comprehensively presents a systematic review of the recent literature focused on the analytical, technical, and mathematical points from the standpoint of the energy systems facing disruptive events. To this end, five phases are developed. Firstly, the concept of the energy system resilience is presented, and then the energy resilience characters and the resilience states are introduced and connected. Thirdly, the formulation and indicators of the...
Performance Analysis of PIw Controllers in Improving the Efficiency of Nonlinear Control Systems
, M.Sc. Thesis Sharif University of Technology ; Tavazoei, Mohmmad Saleh (Supervisor)
Abstract
In this thesis, the performance of a special type of controllers, called Proportional-Integral weighted (PIw) controllers, in control of nonlinear systems is studied. To this aim, the domain of attraction of polynomial nonlinear control systems in the presence of PIw and Proportional-Integral (PI) controllers is estimated and compared with each other. For this estimation, two different methods are used, and the obtained results are compared. Next, adaptive PIw and adaptive PI controllers are designed to be used in control of nonlinear systems. The effectiveness of the proposed controllers is illustrated for a Continuous-Stirred-Tank-Reactor (CSTR) that has an uncertain parameter in its...
Data-Oriented Verification of Programs
, M.Sc. Thesis Sharif University of Technology ; Ardeshir, Mohammad (Supervisor)
Abstract
The verification of programs is one of the most important subjects in Computer Science. In this thesis, after reviewing preliminary subjects, While-Programming computational model is presented and its semantics is discussed. Next, the axiomatic method of Hoare is presented, which is a deduction system for verification of programs. With the help of Hoare method, the idea of Data-Oriented verification of programs is developed
Differentially Detection in UWB Communicatio Systems without Reference Transmission
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
In recent years, UWB multiple access communication systems have received a great attention due to its many advantages. The most important advantages of a UWB system can be summarized as its high data rates, low power consumption, fading immunity and high precision routing. One of the important problems in a UWB system implementation is in its receiver part in which in order to use a coherent RAKE receiver, the channel coefficients have to be estimated. Since UWB channel is a dense multipath fading channel with a very high number of resolvable paths, the channel coefficient estimation based on using training sequence is very complicated. To resolve this problem, transmit reference (TR)...
Cooperative Communications in Free-Space Optical Networks
, Ph.D. Dissertation Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
With recent successes in laboratory tests, and in atmosphere and space demonstrations, there is no doubt that the free-space optical (FSO) communications is ready for operational deployment. Large bandwidth, unlicensed spectrum, excellent security, and quick and inexpensive setup are among its most attractive features. Despite their attractive features, FSO communications suffer from several challenges in practical deployment; the major of them is fading or scintillation and path loss. To overcome such limitations, Channel Coding along with MIMO and Cooperative techniques have been proposed. Although the promising effects of cooperative transmissions in RF communications have greatly been...
Harnessing Interference in Cooperative Communication Networks
, Ph.D. Dissertation Sharif University of Technology ; Nasiri-Kenari, Masoumeh (Supervisor)
Abstract
The compute-and-forward (CMF) method has shown a great promise as an innovative approach to exploit interference towards achieving higher network throughput. Here, instead of recovering single messages, the relays attempt to reliably decode (compute) and pass an integer linear combination of the transmitted messages, referred to as an equation, to the destination. By receiving sufficient equations,the destination can solve the linear equation system to recover the desired messages.Two main challenges of the CMF methods are the computational complexity and the rank failure problem at the destination. In this thesis, to decrease the implementation as well as the computational complexity of the...
Multiple-Access Techniques for Wireless Indooor Infrared Communication with Dispersive Link
, Ph.D. Dissertation Sharif University of Technology ; Nasiri-Kenari, Masoumeh (Supervisor)
Abstract
Infrared wireless local area networks are a suitable choice for a fast and cheap wireless network, providing rates over 10 Mbps with access to unregulated bandwidth. Among multiple-access techniques for infrared wireless networks, CDMA1 has attracted the most interest, due to its simple structure and power ecency. However, spreading the spectrum in CDMA prohibits exploiting the low-rate strong channel codes. The other limiting factor in infrared networks is the channel dispersion. In this thesis, these two issues are considered and an internally coded scheme for time-hopping CDMA, suitable for wireless infrared communication is proposed and with accurate modelling of infrared dispersive...
Spectrum Sensing in Cognitive Radio Networks
, Ph.D. Dissertation Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
In this thesis, we consider the problem of spectrum sensing in cognitive radio networks. First, the collaborative energy detectors based spectrum sensing are investigated in the case of known noise variance for two models of primary user (PU) signal, i.e. random and unknown deterministic signals. Since the derived optimum collaborative energy detector requires the signal-to-noise ratio (SNR) of secondary users (SU) and it has complex structure, the generalized likelihood ratio (GLR) detector is proposed for both models of PU signal which leads to the same decision rules for both models. Simulation results show that the performance of the proposed GLR detector is near to that of optimal...
Efficient Transmission and Reception in Wireless Communication Systems based on NOMA
, Ph.D. Dissertation Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
Multiple access technologies are one of the key features of different generations of wireless communication. From the first generation to the fourth generation, orthogonal multiple access (OMA) schemes have been utilized to serve multiple users in different orthogonal resource blocks in time, frequency or code domain. However, the new application scenarios for the fifth generation impose the requirements of higher system throughput, massive connectivity, and low latency, which can not be fulfilled with OMA schemes. Therefore, non-orthogonal multiple access (NOMA) schemes have attracted increasing attention in both industry and academia. In NOMA, multiple users may occupy the same resource...
Analysis of Cache-aided Wireless Communications Systems in the Presence of IRS
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
Future mobile networks are expected to not only bring more wireless connectivity and higher data rates, but also to support several high-quality services including low-latency, ultra-reliable, and energy-efficient communications. To support these needs, intelligent reflecting surfaces (IRSs) have recently attracted a lot of attention due to their potential for reconfiguring the wireless channel and are considered as a promising solution for future mobile generations. On the other hand, the exponential growth of network traffic, and its non-uniform distribution result in network congestion during peak-traffic times and network underutilization during off-peak times. Caching or content...
Dark energy from fifth-dimensional brans-dicke theory
, Article International Journal of Modern Physics D ; Volume 22, Issue 10 , 2013 ; 02182718 (ISSN) ; Farhoudi, M ; Vakili, H ; Sharif University of Technology
2013
Abstract
Following the approach of the induced-matter theory, we investigate the cosmological implications of a five-dimensional Brans-Dicke (BD) theory, and propose to explain the acceleration of the universe. After inducing in a four-dimensional hypersurface, we classify the energy-momentum tensor into two parts in a way that, one part represents all kind of the matter (the baryonic and dark) and the other one contains every extra terms emerging from the scale factor of the fifth dimension and the scalar field, which we consider as the energy-momentum tensor of dark energy. We also separate the energy-momentum conservation equation into two conservation equations, one for matter and the other for...
Modeling dual-channel supply chain based on fuzzy system and genetic algorithm
, Article International Journal of Uncertainty, Fuzziness and Knowlege-Based Systems ; Volume 25, Issue 4 , 2017 , Pages 573-598 ; 02184885 (ISSN) ; Shavandi, H ; Vakili, M. R ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2017
Abstract
In this paper, we have proposed a dual-channel supply chain model in uncertain environment to analyze the demand of manufacturer and retailer demand in which the profit being maximized. Linguistic terms are also utilized to establish two fuzzy systems for estimating the demand in direct and retail channels. In order to do that, a mathematical model is proposed based on decentralized situation of supply chain. To solve the model, we have developed a hybrid solution method of genetic algorithm, fuzzy system, and L-P metric. Finally, several test problems are first generated; then, the computational results are analyzed. © 2017 World Scientific Publishing Company
Resisting dynamic structures in shifting toward "systems thinking"
, Article 51st Annual Meeting of the International Society for the Systems Sciences, ISSS 2007, Tokyo, 5 August 2007 through 10 August 2007 ; 2007 , Pages 593-611 ; 9781605600437 (ISBN) ; Fakhar Izadi, E ; Moteabbed, S ; Sharif University of Technology
2007
Abstract
There is a unanimous agreement that "systems thinking" helps both individuals and organizations make more intelligent and more effective decisions. On the other hand, the unsatisfactory rate of systems thinking evolution among managers, collegians, students and other stratums raises this question that, why such a useful, discriminating and tasteful concept in theory, does not spread with the desirable pace in practice. Where exactly does the problem originate from? The tragedy is more sensible when noting the fact that even those who know the concept methodically do not apply it in action and in their decisions. Unfortunately, despite relatively numerous literatures on changing beliefs,...