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    A note on the algebraic connectivity of a graph and its complement

    , Article Linear and Multilinear Algebra ; 2019 ; 03081087 (ISSN) Afshari, B ; Akbari, S
    Taylor and Francis Ltd  2019
    Abstract
    For a graph G, let λ2(G) denote its second smallest Laplacian eigenvalue. It was conjectured that (Formula presented.), where (Formula presented.) is the complement of G. In this paper, it is shown that (Formula presented.). © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group  

    A reconfigurable fault-tolerant routing algorithm to optimize the network-on-chip performance and latency in presence of intermittent and permanent faults

    , Article Proceedings - IEEE International Conference on Computer Design: VLSI in Computers and Processors ; 2011 , Pages 433-434 ; 10636404 (ISSN) ; 9781457719523 (ISBN) Jabbarvand Behrouz, R ; Modarressi, M ; Sarbazi Azad, H ; Sharif University of Technology
    2011
    Abstract
    As the semiconductor industry advances to the deep sub-micron and nano technology points, the on-chip components are more prone to the defects during manufacturing and faults during system operation. Consequently, fault tolerant techniques are essential to improve the yield of modern complex chips. We propose a fault-tolerant routing algorithm that keeps the negative effect of faulty components on the NoC power and performance as low as possible. Targeting intermittent faults, we achieve fault tolerance by employing a simple and fast mechanism composed of two processes: NoC monitoring and route adaption. Experimental results show the effectiveness of the proposed technique, in that it offers... 

    Dynamic Modeling and Congestion Control in Computer Networks

    , M.Sc. Thesis Sharif University of Technology Kahe, Ghasem (Author) ; Jahangir, Amir Hossein (Supervisor) ; Ebrahim, Behrouz (Co-Advisor)
    Abstract
    Active queue management (AQM) is a key factor in congestion control and should provide appropriate feedback for flow control in traffic sources to overcome the congestion problem. Beside providing congestion control, achieving predictable queuing delay, maximizing link utilization, simplicity and robustness are also the main objectives of an AQM controller. We propose in this thesis an improved queue dynamic model while incorporating the packet drop probability as well. The proposed model is evaluated using ns2 platform. By applying the improved model, a new compensated proportionalintegral- derivative (PID) AQM controller is developed for TCP network. The time-varying nature of the network... 

    Application of a Thermo-Plastic Constitutive Model for Coupled THM Analysis of Behavior of Saturated Soils

    , M.Sc. Thesis Sharif University of Technology Afshari, Kioumars (Author) ; Pak, Ali (Supervisor)
    Abstract
    Effects of temperature on the behavior of soils and rocks have been studied widely in recent years. Following the need for understanding the effects of temperature on the behavior of clayey soils, several experimental and numerical studies on thermo-mechanical behavior of clayey soils have been carried out and a number of thermo-mechanical constitutive models have been developed for saturated and unsaturated clayey soils. In this research, a two-yield surface thermo-plastic constitutive model developed by Abuel-Naga et al. (2007, 2009), has been chosen for THM analysis of the behavior of saturated clayey soils. This constitutive model is based on Modified Cam-Clay (MCC) model. The MCC model... 

    Simulation of static recrystallization after cold side-pressing of low carbon steels using cellular automata

    , Article Journal of Materials Engineering and Performance ; Volume 21, Issue 8 , 2012 , Pages 1553-1561 ; 10599495 (ISSN) Afshari, E ; Serajzadeh, S ; Sharif University of Technology
    2012
    Abstract
    In this article, the finite element and cellular automata models are coupled to determine static recrystallization kinetics after cold deformation of low carbon steels. The deformation analysis is first performed to predict the strain, stress, and stored energy distributions within the deformed steel employing the finite element software, ABAQUS. Then, the kinetics of static recrystallization and distribution of recrystallized grain size are evaluated by means of a cellular automata model together with the stored energy calculated by the deformation analysis. To examine the predictions, the experimental results of recrystallized fractions and grain sizes after cold side-pressing of low... 

    Investigating the Response Reduction Factor of Steel 3-D Braced Frames with Eccentricity

    , M.Sc. Thesis Sharif University of Technology Afshari, Behrouz (Author) ; Khonsari, Vahid (Supervisor)
    Abstract
    Studying the performance of irregular structures in past earthquakes reveals that due to their severe vulnerability, we need to accurately assess the behavioral characteristics of such structures. On the other hand, all existing seismic codes recommend the use of response modification factor to determine the base shear, design forces of the members, and the design drift ratios, which seem to have limited comprehensiveness. Moreover, the response modification factor for a structural system is discussed in a general manner and the effect of factors such as number of bays, number of stories, span length, story height and irregularities are not considered. In this research, the effects of... 

    A note on the algebraic connectivity of a graph and its complement

    , Article Linear and Multilinear Algebra ; 2019 ; 03081087 (ISSN) Afshari, B ; Akbari, S ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    For a graph G, let λ2(G) denote its second smallest Laplacian eigenvalue. It was conjectured that (Formula presented.), where (Formula presented.) is the complement of G. In this paper, it is shown that (Formula presented.). © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group  

    Directed functional networks in Alzheimer's disease: disruption of global and local connectivity measures

    , Article IEEE Journal of Biomedical and Health Informatics ; Volume 21, Issue 4 , 2017 , Pages 949-955 ; 21682194 (ISSN) Afshari, S ; Jalili, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    Techniques available in graph theory can be applied to signals recorded from human brain. In network analysis of EEG signals, the individual nodes are EEG sensor locations and the edges correspond to functional relations between them that are extracted from EEG time series. In this paper, we study EEG-based directed functional networks in Alzheimer's disease (AD). To this end, directed connectivity matrices of 25 AD patients and 26 healthy subjects are processed and a number of meaningful graph theory metrics are studied. Our data show that functional networks of AD brains have significantly reduced global connectivity in alpha and beta bands (P < 0.05). The AD brains have significantly... 

    Some results on the Laplacian spread conjecture

    , Article Linear Algebra and Its Applications ; Volume 574 , 2019 , Pages 22-29 ; 00243795 (ISSN) Afshari, B ; Akbari, S ; Sharif University of Technology
    Elsevier Inc  2019
    Abstract
    For a graph G of order n, let λ 2 (G) denote its second smallest Laplacian eigenvalue. It was conjectured that λ 2 (G)+λ 2 (G‾)≥1, where G‾ is the complement of G. For any x∈R n , let ∇ x ∈R (n2) be the vector whose {i,j}-th entry is |x i −x j |. In this paper, we show the aforementioned conjecture is equivalent to prove that every two orthonormal vectors f,g∈R n with zero mean satisfy ‖∇ f −∇ g ‖ 2 ≥2. In this article, it is shown that for the validity of the conjecture it suffices to prove that the conjecture holds for all permutation graphs. © 2019 Elsevier Inc  

    Information resource management maturity model

    , Article World Academy of Science, Engineering and Technology ; Volume 37 , 2009 , Pages 258-262 ; 2010376X (ISSN) Afshari, H ; Khosravi, Sh ; Sharif University of Technology
    2009
    Abstract
    Nowadays there are more than thirty maturity models in different knowledge areas. Maturity model is an area of interest that contributes organizations to find out where they are in a specific knowledge area and how to improve it. As Information Resource Management (IRM) is the concept that information is a major corporate resource and must be managed using the same basic principles used to manage other assets, assessment of the current IRM status and reveal the improvement points can play a critical role in developing an appropriate information structure in organizations. In this paper we proposed a framework for information resource management maturity model (IRM3) that includes ten best... 

    New Jacobian matrix and equations of motion for a 6 d.o.f cable-driven robot

    , Article International Journal of Advanced Robotic Systems ; Volume 4, Issue 1 , 2007 , Pages 63-68 ; 17298806 (ISSN) Afshari, A ; Meghdari, A ; Sharif University of Technology
    InTech Europe  2007
    Abstract
    In this paper, we introduce a new method and new motion variables to study kinematics and dynamics of a 6 d.o.f cable-driven robot. Using these new variables and Lagrange equations, we achieve new equations of motion which are different in appearance and several aspects from conventional equations usually used to study 6 d.o.f cable robots. Then, we introduce a new Jacobian matrix which expresses kinematical relations of the robot via a new approach and is basically different from the conventional Jacobian matrix. One of the important characteristics of the new method is computational efficiency in comparison with the conventional method. It is demonstrated that using the new method instead... 

    On Dinur’s Proof of the PCP Theorem

    , M.Sc. Thesis Sharif University of Technology Afshari, Behnam (Author) ; Daneshgar, Amir (Supervisor)
    Abstract
    The PCP theorem is the result of a line of work on interactive proofs and probabilistically checkable proofs. The first theorem relating standard proofs and probabilistically checkable proofs is NEXP?PCP[poly(n),poly(n)] . Subsequently, the method used in the proof of this statement were extended to yield a proof of the PCP theorem. However, this proof is relatively long and complicated. The PCP theorem is equivalent to hardness of approximation of some optimization problems. In 2006, Irit Dinur discovered a different proof of the PCP theorem. Dinur’s proof is a rather shorter and simpler than original proof. The main purpose of this survey is to present the main concepts and tools used in... 

    Experimental Study of Bond in Curved FRP-Strengthed Beams

    , M.Sc. Thesis Sharif University of Technology Afshari, Majid (Author) ; Vafai, Abolhassan (Supervisor)
    Abstract
    Through the recent years application of FRP material in structural engineering has been developed significantly. According to possible changes of a building function during its lifetime or alteration of the building codes, building structures usually need to be strengthened. Referring to merits of FRP material, its application seems to be a convenient idea toward the cited requirement. Curved beam and slab are known as highly used elements in building structures. Bridges composed of horizontal or vertical arches could be noted as common examples which need to be reinforced by FRP. However curved concrete surfaces, reinforced by FRP plates, seem to be studied than it is really required; For,... 

    A note on the algebraic connectivity of a graph and its complement

    , Article Linear and Multilinear Algebra ; Volume 69, Issue 7 , 2021 , Pages 1248-1254 ; 03081087 (ISSN) Afshari, B ; Akbari, S ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Abstract
    For a graph G, let (Formula presented.) denote its second smallest Laplacian eigenvalue. It was conjectured that (Formula presented.), where (Formula presented.) is the complement of G. In this paper, it is shown that (Formula presented.). © 2019 Informa UK Limited, trading as Taylor & Francis Group  

    A note on the algebraic connectivity of a graph and its complement

    , Article Linear and Multilinear Algebra ; Volume 69, Issue 7 , 2021 , Pages 1248-1254 ; 03081087 (ISSN) Afshari, B ; Akbari, S ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Abstract
    For a graph G, let (Formula presented.) denote its second smallest Laplacian eigenvalue. It was conjectured that (Formula presented.), where (Formula presented.) is the complement of G. In this paper, it is shown that (Formula presented.). © 2019 Informa UK Limited, trading as Taylor & Francis Group  

    Recovery of Uranium(VI) from UCF Waste by Selective Transportacross Aliquid Membrane

    , M.Sc. Thesis Sharif University of Technology Soltani Behrouz, Masoud (Author) ; Samadfam, Mohammad (Supervisor) ; Fasihi, Javad (Supervisor)
    Abstract
    Due to environmental and economical impacts, recovery of the uranium from nuclear wastes is of continuing interest.This work reports the separation of uranyl ionusing transport technique through chloroform liquid membrane containing a mixture of DBDA15C4 and oleic acidas cooperative carrier.The pH of the feed phase (10-4 M of UO22+) was adjusted with nitric acid and acetic acid/NaOH for pHrange of 2-6.The receiving phase was hydrochloric acid 1M.The organic phase was chloroform which includesthe carrier DBDA15C4 (0.0001 M) and also the oleic acid (0.015M).The results showed that the transport increased with increasing pH and reached to maximumat pH of 5.Maximum cooperative effect of oleic... 

    Effect of Strain Path on Static Recrystallization Behavior of a Steel

    , M.Sc. Thesis Sharif University of Technology Afshari, Elham (Author) ; Serajzadeh, Siamak (Supervisor)
    Abstract
    Static recrystllization in low carbon steel after two type of deformation –sidepress as an inhomogeneous deformation and rolling as a common industrial process - has been simulated using Cellular Automata (CA). The finite element method was utilized to compute the strain and stored energy distribution due to deformation. The initial microstructures were created by simulation of recrystallization with homogeneous site-saturated nucleation and topologic deformation was also considered in model. Subsequently using the result of FEM, stored energy of deformation was calculated and transferred into a two dimensional CA lattice. Nucleation rate and grain boundary velocity were considered... 

    Effects of temperature variations on the performance of a space imaging system baffle

    , Article Proceedings of SPIE - The International Society for Optical Engineering, 7 September 2015 through 10 September 2015 ; Volume 9626 , 2015 ; 0277786X (ISSN) ; 9781628418156 (ISBN) Haghshenas, J ; Mohasel Afshari, B ; Sharif University of Technology
    SPIE  2015
    Abstract
    All the star trackers must be composed of a baffle system to removes stray lights intensity. The baffle is designed to mount in front of the optical system. The performance of a star tracker is often limited by the stray light level on the detector. According to the space conditions, the baffle may deflect due to the temperature variation during the mission. Sun heat flux imposed to the baffle from one side and heat radiates from baffle to the space in all sides. In our case, the baffle is fixed to the satellite structure by four titanium screw. A finite element model has been used to modeling the baffle and temperature distribution and deflection is obtained in worst cold and hot... 

    Corporate Social Responsibility in Iranian Companies Listed in Tehran Stock Exchange (2009)

    , M.Sc. Thesis Sharif University of Technology Afshari, Davoud (Author) ; Sharbat Oghli, Ahmad (Supervisor)
    Abstract
    In this thesis, type and importance of corporate social responsibility (CSR) based on Carroll’s framework was investigated among companies of Tehran Stock Exchange. Beside, the types of companies’ motivation to engage in CSR base on model of Garriga & Mele (2004) were studied. In addition, hypothesis 1) instrument motivation for companies of Tehran Bourse is more attractive than the other type of motivations 2) companies that have higher income, have higher costs in CSR was tested. Using questionnaire tool and help of descriptive and inferential statistical analysis, questions and assumptions was studied and results illustrated that legal and ethical dimensions is most-widely used definition... 

    Active Reliability Based Failure Prediction and Control of a Wing Structure via Online SHM Using Hybrid Algorithm and Experimental Data

    , Ph.D. Dissertation Sharif University of Technology Saraygord Afshari, Sajad (Author) ; Pourtakdoust, Hossein (Supervisor)
    Abstract
    Reliability evaluation is a key factor in serviceability and safety analysis of air vehicles. Structural health monitoring methods have grown to a degree of maturity in many industries. However, there is a challenging interest to tie in SHM with reliability assessment. In this respect, consideration of stochastic structural dynamics with SHM data and random loadings opens a new chapter in failure prevention. The current study focuses on the stochastic behavior of structures as a way to relate SHM data with reliability. In this respect, uncertain factors such as atmospheric turbulence, structural parameters, and sensor outputs are considered in the process of reliability assessment. Firstly,...