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aghajani-zadeh--zahra
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Approximation Algorithms for Clustering Points in the Distributed Model
, M.Sc. Thesis Sharif University of Technology ; Zarrabi Zadeh, Hamid (Supervisor)
Abstract
Clustering is one of the most well-known fundamental problems in computer science. In this thesis we have focused on a particular version of such problem, called capacititated k-center, and we analyze and survey them in the distributed model, when massive data is given. Our contribution in this research includes a new approximation algorithms with constant approximate factors for such problems in the distributed model, as well as improving the best available algorithm for capacitated k-center problem. Composable coreset as one of the most important techniques in distributed and streaming model is our primary tools in designing these algorithms. This technique gives the opportunity of solving...
EEG-Based Markers of Major Depressive Disorder in Reinforcement Learning
, M.Sc. Thesis Sharif University of Technology ; Vosoughi Vahdat, Bijan (Supervisor) ; Karbalaei Aghajan, Hamid (Co-Supervisor)
Abstract
Major Depressive Disorder (MDD) is a common and serious mental health disorder characterized not only by mood disturbances but also by deficits in cognitive functions and decision-making processes. This disorder can affect all aspects of an individual’s life, including their relationships with family, friends, and society. Recent electroencephalography (EEG) studies have demonstrated that certain neuropsychiatric disruptions lead to alterations in specific brain signal metrics, which can serve as markers of brain dysfunction. Many studies have explored traditional linear EEG metrics, such as frequency band power, asymmetry in frequency band activity, and event-related potential components,...
Assessing the explanatory power of naturalism in addressing ultimate questions
, Article Vestnik Sankt-Peterburgskogo Universiteta, Filosofiia i Konfliktologiia ; Volume 37, Issue 2 , 2021 , Pages 217-228 ; 25422278 (ISSN) ; Sharif University of Technology
Saint Petersburg State University
2021
Abstract
A typical scientist has no responsibility other than to explain how a natural event occurred. However, when a philosopher asks about the conditions under which a scientist’s explanation is true, he is, in fact, raising an ultimate question, the concept which Karl Popper used for the first time. Answering this question requires that no elements are neglected in the explanation, and no significant factors in the explanation are overlooked. In other words, in explaining a phenomenon, at any level of its explanation, there should be no remainder. These requirements can be achieved through the full explanation. In the present article, by drawing on concepts such as theory-ladenness of...
Metaphysical necessity in the neo-sadraian school and assessment of necessitarian theories of the laws of nature
, Article Teorie Vedy / Theory of Science ; Volume 43, Issue 1 , 2021 , Pages 33-57 ; 12100250 (ISSN) ; Sharif University of Technology
Czech Academy of Sciences
2021
Abstract
To differentiate between the laws of nature and accidental generalizations, we must adopt a view of necessity that is capable of being realized in relationships existing among natural objects. In neo-Sadraian Islamic philosophy, metaphysical necessity is accepted as part of the cause-effect relationship. This paper compares the neo-Sadraian interpretation of necessity and necessitarian theories about the laws of nature, particularly essentialism and universal theory. By resorting to specific forms al-shûrat al-naw’iyyah, the origin of the essential properties of natural objects, I argue that neo-Sadraians have proposed a perspective on metaphysical necessity that is epistemologically a...
Assessing the explanatory power of naturalism in addressing ultimate questions
, Article Vestnik Sankt-Peterburgskogo Universiteta, Filosofiia i Konfliktologiia ; Volume 37, Issue 2 , 2021 , Pages 217-228 ; 25422278 (ISSN) ; Sharif University of Technology
Saint Petersburg State University
2021
Abstract
A typical scientist has no responsibility other than to explain how a natural event occurred. However, when a philosopher asks about the conditions under which a scientist’s explanation is true, he is, in fact, raising an ultimate question, the concept which Karl Popper used for the first time. Answering this question requires that no elements are neglected in the explanation, and no significant factors in the explanation are overlooked. In other words, in explaining a phenomenon, at any level of its explanation, there should be no remainder. These requirements can be achieved through the full explanation. In the present article, by drawing on concepts such as theory-ladenness of...
Metaphysical necessity in the neo-sadraian school and assessment of necessitarian theories of the laws of nature
, Article Teorie Vedy / Theory of Science ; Volume 43, Issue 1 , 2021 , Pages 33-57 ; 12100250 (ISSN) ; Sharif University of Technology
Czech Academy of Sciences
2021
Abstract
To differentiate between the laws of nature and accidental generalizations, we must adopt a view of necessity that is capable of being realized in relationships existing among natural objects. In neo-Sadraian Islamic philosophy, metaphysical necessity is accepted as part of the cause-effect relationship. This paper compares the neo-Sadraian interpretation of necessity and necessitarian theories about the laws of nature, particularly essentialism and universal theory. By resorting to specific forms al-shûrat al-naw’iyyah, the origin of the essential properties of natural objects, I argue that neo-Sadraians have proposed a perspective on metaphysical necessity that is epistemologically a...
A comparative study of cognitive science of religion and reformed epistemology
, Article Journal of Philosophical Theological Research ; Volume 24, Issue 1 , 2022 , Pages 5-20 ; 17359791 (ISSN) ; Sharif University of Technology
University of Qom
2022
Abstract
Reformed epistemology, based on the reliability of the functions of cognitive faculties, holds that one can believe in God directly without argument or evidence. Alvin Plantinga, one of the proponents of this view, replaces justification with warrant in the classical definition of knowledge and considers true belief, which has a warrant as knowledge. On this basis, he considers it reasonable to believe in the existence of God because it has a warrant and arises from our healthy cognitive faculties without the need for an independent argument. Some defenders of the cognitive science of religion also seek to provide evidence from cognitive science to explain religious beliefs in such a way as...
Muslims’ lifeworld during the pandemic and humanistic interpretation of religions
, Article Contemporary Islam ; 2023 ; 18720218 (ISSN) ; Sharif University of Technology
Springer Science and Business Media B.V
2023
Abstract
Some proponents of new atheism, including Dawkins, claim that religion, especially Islam, is the cause of the war because it encourages divisiveness and labeling. In this article, in the first step, I will show that Islam is not the cause of war, but rather it is a misconception of Islam that is the cause of divisiveness and eventually war. Then, I will demonstrate that the COVID-19 pandemic and its impact on societies and religious behaviors somehow could, and still can, modify this misconception and blur divisions. This effect occurs in two ways: firstly, a pandemic creates common human problems for all people worldwide, making people more aware of their common points that Islam refers to...
Resilient cities, a key solution to safeguard the environment
, Article Scientia Iranica ; Volume 23, Issue 5 , 2016 , Pages 2067-2076 ; 10263098 (ISSN) ; Abbaspour, M ; Mohammadi, A ; Reza Soltani, S ; Aghajani, D ; Ahmadi, A ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
In the 21st century, the world population is growing at a spiraling pace. Much of this growth is occurring in developing countries, where access to food, sanitary water, education, and health is severely limited. The ever-increasing urbanization highlighted the need for sustainable development based on human-environment interaction. The excessive and unplanned expansion of cities has resulted in numerous environmental predicaments due to clearly emphasized economic issues at the expense of social and environmental concerns. The most significant features of megacities are indicated in this paper and the environmental, social, physical, and economic criteria are addressed in order to attain...
Influence of In situ thermal processing strategies on the weldability of martensitic stainless steel resistance spot welds: effect of second pulse current on the weld microstructure and mechanical properties
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 50, Issue 11 , 2019 , Pages 5191-5209 ; 10735623 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Springer Boston
2019
Abstract
Martensitic stainless steel (MSS) welds are notorious for their susceptibility to low-energy failure due to the formation of brittle martensitic structure in the fusion zone. The unique approach to enhance the mechanical properties of MSS resistance spot welds during both the tensile-shear and the cross-tension loading is to improve the fracture toughness of the fusion zone. In the present study, the effect of double-pulse welding on the microstructure-mechanical properties relationship of the AISI420 MSS resistance spot welds is investigated. Depending on the second pulse current level, various metallurgical phenomena was observed including (i) rapid tempering of martensite in the fusion...
A pathway to produce strong and tough martensitic stainless steels resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 24, Issue 3 , 2019 , Pages 185-192 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Martensitic stainless steel (MSS) resistance spot welds are prone to quasi-cleavage interfacial failure with very low energy absorption capability due to formation of hard and brittle carbon and chromium rich martensite in the fusion zone (FZ). In this work, a new pathway is proposed to enhance strength/toughness of the MSS resistance spot welds based on modification of the FZ composition/microstructure via introducing a nickel interlayer. This altered the FZ microstructure from dual phase microstructure of martensite and δ-ferrite to austenitic microstructure with finely dispersed ultra-fine chromium rich carbides. Formation of a tough predominately austenitic microstructure in the FZ...
Oscillation of solutions of second-order nonlinear differential equations of Euler type
, Article Journal of Mathematical Analysis and Applications ; Volume 326, Issue 2 , 2007 , Pages 1076-1089 ; 0022247X (ISSN) ; Moradifam, A ; Sharif University of Technology
2007
Abstract
We consider the nonlinear Euler differential equation t2 x″ + g (x) = 0. Here g (x) satisfies x g (x) > 0 for x ≠ 0, but is not assumed to be sublinear or superlinear. We present implicit necessary and sufficient condition for all nontrivial solutions of this system to be oscillatory or nonoscillatory. Also we prove that solutions of this system are all oscillatory or all nonoscillatory and cannot be both. We derive explicit conditions and improve the results presented in the previous literature. We extend our results to the extended equation t2 x″ + a (t) g (x) = 0. © 2006 Elsevier Inc. All rights reserved
On the structure of detonation waves in magnetohydrodynamics
, Article Applied Mathematics Research eXpress ; Volume 2006 , 2006 ; 16871200 (ISSN) ; Hesaaraki, M ; Sharif University of Technology
2006
Some sufficient conditions for the intersection with the vertical isocline in the Liénard plane
, Article Applied Mathematics Letters ; Volume 19, Issue 5 , 2006 , Pages 491-497 ; 08939659 (ISSN) ; Moradifam, A ; Sharif University of Technology
2006
Abstract
In this work we study the problem of whether all trajectories of the system ẋ=y-F(x) and ẏ=-g(x) cross the vertical isocline, which is very important for the existence of periodic solutions and oscillation theory. Sufficient conditions are given for all trajectories to cross the vertical isocline. © 2005 Elsevier Ltd. All rights reserved
Nonexistence of limit cycles in two classes of predator-prey systems
, Article Applied Mathematics and Computation ; Volume 175, Issue 1 , 2006 , Pages 356-365 ; 00963003 (ISSN) ; Moradifam, A ; Sharif University of Technology
2006
Abstract
This paper deals with the question of nonexistence of limit cycles in two famous classes of predator-prey systems. We present some sufficient conditions for the nonexistence of limit cycles in these systems. Our results extend and improve the results presented by Moghadas. © 2005 Elsevier Inc. All rights reserved
On the structure of ionizing shock waves in magnetofluiddynamics
, Article International Journal of Mathematics and Mathematical Sciences ; Volume 29, Issue 7 , 2002 , Pages 395-415 ; 01611712 (ISSN) ; Hesaaraki, M ; Sharif University of Technology
2002
Abstract
Ionizing shock waves in magnetofluiddynamics occur when the coefficient of electrical conductivity is very small ahead of the shock and very large behind it. For planner motion of plasma, the structure of such shock waves are stated in terms of a system of four-dimensional equations. In this paper, we show that for the above electrical conductivity as well as for limiting cases, that is, when this coefficient is zero ahead of the shock and/or is infinity behind it, ionizing fast, slow, switch-on and switch-off shocks admit structure. This means that physically these shocks occur. © 2002 Hindawi Publishing Corporation. All rights reserved
Probing the Electrochemical Properties of Gold Electrode Modified with Edge-Functionalized Graphene and its Application
, M.Sc. Thesis Sharif University of Technology ; Shahrokhian, Saeed (Supervisor)
Abstract
In the present work, edge-functionalaized graphene was used as electrode material and its electrochemical properties were systematically characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Two methods were applied to modify the gold electrode surface. First method was the self assembling process of graphene nanosheets on gold electrode surface. Second method was simply casting specific amounts of graphene suspension on the gold electrode surface. Nyquist plots show decrease of the charge transfer resistance on the electrode surface at both cases. In cyclic voltammetry studies, first electrode shows no significant changes while the second electrode exhibits...
A Distance Vector Based Routing Protocol for Named Data Networking
, M.Sc. Thesis Sharif University of Technology ; Movaghar, Ali (Supervisor)
Abstract
Named Data Networking is the most promisicing content centric Architecture for the future of Internet. In this architecture, content can be accessed regardless of where it is.Routing is one of the most important and challenging issues in these networks. An efficient router improves the efficiency of network by reducing routers convergence time, stored data related to routing and exchanged routing data traffic. It also reduces the state each router keeps due to routing information. In Named Data Networking routers are smart and some of routing protocol responsibilities can be done by forwarding plane. Therefor netwok churns can be handeled by forwarding plane. Considering this responsibility...
Experimental and thermomechanical analysis of friction stir welding of poly(methyl methacrylate) sheets
, Article Science and Technology of Welding and Joining ; Volume 23, Issue 3 , 2018 , Pages 209-218 ; 13621718 (ISSN) ; Simchi, A ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
In the present work, the feasibility of friction stir welding (FSW) of poly(methyl methacrylate) sheets was studied experimentally and theoretically by employing thermomechanical simulations. The effect of processing parameters including tool plunge depth, tilt angle, tool rotational speed (w), and transverse velocity (v) was investigated to determine suitable conditions to attain sound and defect-free joints. It is shown that a low tool plunge depth of 0.2 mm and a tilt angle of 2° provide suitable material flow to gain sound joints. By controlling the heat input into stir zone by increasing the tool rotational speed and decreasing linear velocity, the formation of defects can be minimised....
An investigation on the dissimilar friction stir welding of T-joints between AA5754 aluminum alloy and poly(methyl methacrylate)
, Article Thin-Walled Structures ; Volume 135 , 2019 , Pages 376-384 ; 02638231 (ISSN) ; Simchi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Process optimization to prepare T-joints of poly methyl methacrylate (PMMA) and AA5754 alloy by friction stir welding (FSW) was performed. Effects of processing parameters including tool rotational velocity, traverse speed, tilt angle and plunge depth (TP) were studied. The material flow and formation of interaction layer upon FSW were evaluated and the tensile strength and hardness of the joints were examined. It is shown that by controlling the heat input into stir zone through increasing the rotational velocity or decreasing travelling speed, less defects are formed while the thickness of the interaction layer increases. The optimum condition is attained at 1600 rpm/30 mm min−1 with a...