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afshari--behnam
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A note on the algebraic connectivity of a graph and its complement
, Article Linear and Multilinear Algebra ; 2019 ; 03081087 (ISSN) ; 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
Examination of a solar desalination system equipped with an air bubble column humidifier, evacuated tube collectors and thermosyphon heat pipes
, Article Desalination ; Volume 397 , 2016 , Pages 30-37 ; 00119164 (ISSN) ; Behshad Shafii, M ; Sharif University of Technology
Elsevier
2016
Abstract
In this paper, the performance of a novel HDH solar desalination system equipped with a combination of heat pipe (HP), evacuated tube collector (ETC) and air bubble column humidifier is experimentally investigated. This novel HDH system uses advantages of ETC-HP as a highly efficient thermal absorption and conductor device, and at the same time employs the advantages of an air bubble column humidifier, i.e. high interface area and effective mixing in order to heat the water and humidify the air, respectively. The effects of various parameters including incoming air flow rate into the humidifier, initial depth of water in the humidifier, and adding fluids such as oil and water in the space...
MRI-PET image fusion based on NSCT transform using local energy and local variance fusion rules
, Article Journal of Medical Engineering and Technology ; Vol. 38, issue. 4 , 2014 , p. 211-219 ; Fatemizadeh, E ; Behnam, H ; Sharif University of Technology
2014
Abstract
Image fusion means to integrate information from one image to another image. Medical images according to the nature of the images are divided into structural (such as CT and MRI) and functional (such as SPECT, PET). This article fused MRI and PET images and the purpose is adding structural information from MRI to functional information of PET images. The images decomposed with Nonsubsampled Contourlet Transform and then two images were fused with applying fusion rules. The coefficients of the low frequency band are combined by a maximal energy rule and coefficients of the high frequency bands are combined by a maximal variance rule. Finally, visual and quantitative criteria were used to...
A robust dual source level set method for three-dimensional echocardiography image segmentation
, Article Journal of Theoretical and Applied Information Technology ; Volume 95, Issue 21 , 2017 , Pages 5701-5710 ; 19928645 (ISSN) ; Fatemizadeh, E ; Behnam, H ; Sharif University of Technology
2017
Abstract
Echocardiography as a common place device has been widely used for diagnosis. Segmentation of left ventricle just using the standard level set formulation based on the magnitude of intensity cannot restrict the contour evolution completely due to the lack of sharp edges. This paper aims to introduce a robust method for segmentation of three-dimensional echocardiography images based on two boundary maps namely distance map and probabilistic map as stopping criteria of contour evolution which are extracted using two different approaches. The distance map is extracted by applying Free Form Deformation (FFD) method on manually determined landmarks of initial spherical volume to register the...
An optimized probabilistic edge based level set method for left ventricle segmentation in echocardiography images
, Article Biomedical Research (India) ; Volume 28, Issue 8 , 2017 , Pages 3788-3793 ; 0970938X (ISSN) ; Fatemizadeh, E ; Behnam, H ; Sharif University of Technology
Scientific Publishers of India
2017
Abstract
In this paper, an efficient approach for ultrasonic object segmentation with special application for left ventricle segmentation in echocardiography images is proposed. At first, an efficient hybrid trend for ultrasonic image edge detection is suggested. Then, a modified level set approach is introduced based on the extracted edges and the computed probabilistic map as the stopping criteria for the contour evolution. Both synthetic and clinical images are utilized as validation measures with respect to the prior techniques which indicate outperform results quantitatively and qualitatively. Left ventricle segmentation using proposed method illustrates expert-approved performance, providing a...
A review on state-of-the-art applications of data-driven methods in desalination systems
, Article Desalination ; Volume 532 , 2022 ; 00119164 (ISSN) ; Faegh, M ; Khiadani, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
The substitution of conventional mathematical models with fast and accurate modeling tools can result in the further development of desalination technologies and tackling the need for freshwater. Due to the great capability of data-driven methods in analyzing complex systems, several attempts have been made to study various desalination systems using data-driven approaches. In this state-of-the-art review, the application of various artificial intelligence and design of experiment data-driven methods for analyzing different desalination technologies have been thoroughly investigated. According to the applications of data-driven methods in the field of desalination, the reviewed...
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) ; 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...
Information resource management maturity model
, Article World Academy of Science, Engineering and Technology ; Volume 37 , 2009 , Pages 258-262 ; 2010376X (ISSN) ; 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...
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) ; 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) ; 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
A note on the algebraic connectivity of a graph and its complement
, Article Linear and Multilinear Algebra ; 2019 ; 03081087 (ISSN) ; 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
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) ; 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
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) ; 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...
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) ; 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
On Dinur’s Proof of the PCP Theorem
, M.Sc. Thesis Sharif University of Technology ; 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...
Application of a Thermo-Plastic Constitutive Model for Coupled THM Analysis of Behavior of Saturated Soils
, M.Sc. Thesis Sharif University of Technology ; 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...
Experimental Study of Bond in Curved FRP-Strengthed Beams
, M.Sc. Thesis Sharif University of Technology ; 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,...
Investigating the Response Reduction Factor of Steel 3-D Braced Frames with Eccentricity
, M.Sc. Thesis Sharif University of Technology ; 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...
Influence of Beta Nucleation Method with the Use of Calcium Pimelate on Low-Temperature Toughness of Polypropylene Block Copolymer
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza (Supervisor)
Abstract
One drawback of polypropylene (PP) as a widely-used semicrystalline thermoplastic is its low toughness at sub-zero temperatures. Along with adding elastomers to PP as impact modifiers, modification of PP’s crystalline structure by means of beta-phase nucleating agents —beta being the toughest polymorph of PP —is a standard method of improving PP’s toughness. Nucleation efficiency is highly dependent on the optimum dispersion of the nucleating agent. Therefore, improving the dispersion of the nucleating agents assumes an essential role. The objective of this study is to determine the influence of the incorporation method of calcium pimelate (CaPi), a highly-selective beta nucleating agent, on...
Automatic segmentation of brain MRI in high-dimensional local and non-local feature space based on sparse representation
, Article Magnetic Resonance Imaging ; Volume 31, Issue 5 , 2013 , Pages 733-741 ; 0730725X (ISSN) ; Fatemizadeh, E ; Behnam, H ; Sharif University of Technology
2013
Abstract
Automatic extraction of the varying regions of magnetic resonance images is required as a prior step in a diagnostic intelligent system. The sparsest representation and high-dimensional feature are provided based on learned dictionary. The classification is done by employing the technique that computes the reconstruction error locally and non-locally of each pixel. The acquired results from the real and simulated images are superior to the best MRI segmentation method with regard to the stability advantages. In addition, it is segmented exactly through a formula taken from the distance and sparse factors. Also, it is done automatically taking sparse factor in unsupervised clustering methods...