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    A case study in vapor phase synthesis of Mg-Al alloy nanoparticles by plasma arc evaporation technique

    , Article Chemical Engineering Journal ; Volume 259 , 2015 , Pages 918-926 ; 13858947 (ISSN) Karbalaei Akbari, M ; Derakhshan, R ; Mirzaee, O ; Sharif University of Technology
    Elsevier  2015
    Abstract
    Alloy nanoparticles in the Mg-Al system were prepared by plasma arc discharge method from the Mgx to Al (45%

    Wear and friction behavior of nanosized TiB2 and TiO2 particle-reinforced casting A356 aluminum nanocomposites: A comparative study focusing on particle capture in matrix

    , Article Journal of Composite Materials ; Volume 49, Issue 29 , 2015 , Pages 3665-3681 ; 00219983 (ISSN) Karbalaei Akbari, M ; Rajabi, S ; Shirvanimoghaddam, K ; Baharvandi, H. R ; Sharif University of Technology
    SAGE Publications Ltd  2015
    Abstract
    In the present study, regarding the theoretical and practical aspects of nanoparticle capture in liquid-state processing of aluminum composite, different volume fractions of TiB 2 and TiO 2 nanopowders were incorporated into aluminum alloy via stir casting method. Hardness and sliding wear test were carried out to evaluate the mechanical properties of composites. The effects of wear load and reinforcement content on wear rate and friction coefficient of composites were examined. Microstructural studied showed that particle distribution in A356- TiB 2 composites was more favorable than that of the A356- TiO 2 samples. Results showed that nanoparticles were partially captured by aluminum... 

    Poncelet Theorem

    , M.Sc. Thesis Sharif University of Technology Karbalaei Harofte, Dorna (Author) ; Jafari, Amir (Supervisor)
    Abstract
    In this thesis the theorems of Poncelet and Cayley will be discussed. We will use algebraic geometry and in particular the theory of elliptic curves to present a proof following the works of Griffiths and Harris (refrence 1).
    The P2-version of poncelet’s theorem that we prove in our thesis says:let C , D be smooth conic in general position. Suppose there is an n-sided olygon inscribed in C and circumscribed about D.Then for any point of C, there exists an n-sided polygen, also inscribed in C and circumscribe about D, which has this point for one of its vertics.the Cayley’s theorem provides a criterion on the existence of such an n-gon given the conics C and D as above  

    A Novel Approach for Seizure Prediction using EEG Signals

    , M.Sc. Thesis Sharif University of Technology Shahbazi, Mohammad (Author) ; Karbalaei Aghajan, Hamid (Supervisor)
    Abstract
    As the fourth most common neurological disorder, epilepsy affects lots of people all around the world, some of whom have to live with unpredictable seizures uncontrollable by surgery or medication. Hence, Developing systems for detection and prediction of the epileptic seizures will help the patients to avoid the possible damages caused by sudden seizures. This study addresses the task of epileptic seizure prediction, using three different novel approaches. The first approach, which is based on anomaly detection, contains three steps: feature extraction from EEG signals, training a one-class SVM classifier, and a post-processing step. The second method exploits a recurrent neural network to... 

    Speech-Driven Facial Reenactment

    , M.Sc. Thesis Sharif University of Technology Jalalifar, Ali (Author) ; Karbalaei Aghajan, Hamid (Supervisor)
    Abstract
    Creating talking heads from audio input is interesting from both scientific and practical viewpoints, e.g. constructing virtual computer generated characters, aiding hearing-impaired people, live dubbing of videos with translated audio, etc. Due to its wide variety of applications, audio to video has been the focus of intensive research in recent years. Mapping audio to facial images with accurate lip-sync is an extremely difficult task because it is a mapping form 2-Dimensional to 3-Dimensional space and also because humans are expert at detecting any out-of-sync lip movements with respect to an audio.Approaches to automatically generating natural looking speech animation usually involve... 

    Solution of Compressible Flow Using Finite Volume Lattice Boltzmann Method on Unstructured Meshes

    , M.Sc. Thesis Sharif University of Technology Karbalaei baba, Ali Reza (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In this study, the solution of compressible flows is performed using finite volume lattice Boltzmann method (FVLBM). A model associated with 13 discrete velocity vectors and 2 energy levels is used and the Boltzmann transport equation is solved using a cell-centered finite volume on structured meshes. The values of distribution functions on each cell faceare determined by averaging from their values at the two control points located on the center of two neighboring cells. The fourth-order Runge-Kutta time-stepping scheme is applied to discretize temporal derivative term. The second- and fourth-order numerical dissipation termsareadded to the algorithm to stabilize the solution when solving... 

    Effects of 40Hz Auditory Entrainment on Phase-Amplitude Coupling and Connectivity Parameters of the Brain

    , M.Sc. Thesis Sharif University of Technology Eshaghi, Amir Masoud (Author) ; Karbalaei Aghajan, Hamid (Supervisor)
    Abstract
    Alzheimer's disease is the most common type of dementia, which has been recognized as the seventh most common fatal disease in the elderly over 65 years of age. Despite all the research done to recognize and treat this disease, so far there is no cure for this disease, and even most of the chemical treatments that are prescribed for Alzheimer's patients are only effective towards reducing the symptoms of this disease and lose their effectiveness as it progresses. Therefore, in the last two decades, in order to find a way to better understand and even treat AD, scientists have reached a concept called brain frequency stimulation, which can improve people's cognitive performance without the... 

    Differentiating Signals Recorded from Rat Brain in Response to Different Olfactory Stimuli

    , M.Sc. Thesis Sharif University of Technology Arman Mehr, Matin (Author) ; Karbalaei Aghajan, Hamid (Supervisor)
    Abstract
    The olfactory sense in rats provides crucial information for identifying food sources, detecting threats, and facilitating social interactions. The olfactory bulb is one of the key brain regions involved in the initial processing of olfactory information and its transmission to higher brain areas for more complex processing. However, more advanced cognitive processes such as evaluation and decision-making rely on interactions between other brain regions. Among these, the striatum, as a part of the basal ganglia, plays a role in reward evaluation, reward-based learning, and shaping behaviors associated with sensory stimuli. This region contributes to learning, decision-making, and action... 

    Differences of the Brain’s Surprise Response Due to the Habituation Effect in Neurodegenerative Patients and Healthy People

    , M.Sc. Thesis Sharif University of Technology Hosseinpour Khaledian, Kamyab (Author) ; Karbalaei Aghajan, Hamid (Supervisor)
    Abstract
    The brain is constantly placed in stochastic environments. This leads to the brain developing a probabilistic model for the environment. However, sometimes unexpected events occur that lead to surprise and a need for updating the probabilistic model. It can be concluded from this argument that reduction in brian’s surprise is a sign of learning. On the other hand, a probability distribution obtained from a probabilistic model contains an amount of uncertainty. Reducing this uncertainty can also be considered a sign of learning. Surprise and uncertainty can be obtained from a probability distribution using information theory concepts. Another important issue in learning is habituation, which... 

    Efficiency enhancement of time-modulated arrays with optimized switching sequences

    , Article IEEE Transactions on Antennas and Propagation ; Volume 66, Issue 7 , July , 2018 , Pages 3411-3420 ; 0018926X (ISSN) Mazaheri, M. H ; Fakharzadeh, M ; Akbari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    The conventional time-modulated arrays (TMAs) have a low radiation efficiency, since each antenna turns off at specific time slots. In this paper, first, the efficiency of TMA is investigated analytically. Next, the optimized switching sequences are proposed to enhance the radiation efficiency of a specific sideband, while preserving the level of the other sidebands. The practical hardware limitations are considered in the switching sequence design. Moreover, a low-cost flexible eight-element printed dipole array operating at 1.2-1.4 GHz is implemented to verify the proposed algorithms. The measured radiation patterns indicate that by applying the proposed sequences, the TMA efficiency... 

    Electrified BPS giants: BPS configurations on giant gravitons with static electric field

    , Article Journal of High Energy Physics ; Volume 2007, Issue 10 , 2007 ; 11266708 (ISSN) Akbari, M. A ; Sheikh Jabbari, M. M ; Sharif University of Technology
    2007
    Abstract
    We consider D3-brane action in the maximally supersymmetric type IIB plane-wave background. Upon fixing the light-cone gauge, we obtain the light-cone Hamiltonian which is manifestly supersymmetric. The 1/2 BPS solutions of this theory (solutions which preserve 16 supercharges) are either of the form of spherical three branes, the giant gravitons, or zero size point like branes. We then construct specific classes of 1/4 BPS solutions of this theory in which static electric field on the brane is turned on. These solutions are deformations about either of the two 1/2 BPS solutions. In particular, we study in some detail 1/4 BPS configurations with electric dipole on the three sphere giant,... 

    Chromatic number and clique number of subgraphs of regular graph of matrix algebras

    , Article Linear Algebra and Its Applications ; Volume 436, Issue 7 , 2012 , Pages 2419-2424 ; 00243795 (ISSN) Akbari, S ; Aryapoor, M ; Jamaali, M ; Sharif University of Technology
    2012
    Abstract
    Let R be a ring and X R be a non-empty set. The regular graph of X, Γ(X), is defined to be the graph with regular elements of X (non-zero divisors of X) as the set of vertices and two vertices are adjacent if their sum is a zero divisor. There is an interesting question posed in BCC22. For a field F, is the chromatic number of Γ( GLn(F)) finite? In this paper, we show that if G is a soluble subgroup of GLn(F), then χ(Γ(G))<∞. Also, we show that for every field F, χ(Γ( Mn(F)))=χ(Γ( Mn(F(x)))), where x is an indeterminate. Finally, for every algebraically closed field F, we determine the maximum value of the clique number of Γ(), where denotes the subgroup generated by A∈ GLn(F)  

    Correlation of shear wave velocity with liquefaction resistance for silty sand based on laboratory study

    , Article 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability, 9 November 2015 through 13 November 2015 ; 2015 , Pages 794-799 Akbari-Paydar, N ; Ahmadi, M. M ; Sharif University of Technology
    Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  2015
    Abstract
    Several methods have been used for the evaluation of liquefaction potential, among which the simplified method is mostly used. In this method, which is mainly based on standard penetration test (SPT), cone penetration test (CPT) and shear wave velocity (Vs) measurement, a boundary curve is provided to separate the liquefiable and non-liquefiable soil zones. Vs measurement is a good alternative method of penetration-based methods (SPT and CPT). This is especially true in micro-zonation of liquefaction potential. Although relatively large studies have been carried out to establish the correlation between Vs and liquefaction resistance for sands; there are uncertainties about the effects of... 

    Effect of fines type and content of sand on correlation between shear wave velocity and liquefaction resistance

    , Article Geotechnical and Geological Engineering ; 2016 , Pages 1-20 ; 09603182 (ISSN) Akbari Paydar, N ; Ahmadi, M. M ; Sharif University of Technology
    Springer International Publishing  2016
    Abstract
    The use of shear wave velocity (Vs) measurements as an in situ test for evaluation of liquefaction potential has increased substantially due to its advantages. Relatively large numbers of studies have been performed to establish the correlation between Vs and liquefaction resistance (CRR) of clean sands. Usually, natural sands contain silt and/or clay, and previous studies have shown that both the amount of fines and their nature influence the values of CRR as well as Vs. Therefore, the CRR–Vs correlations may also be affected by fines content and type of sandy soils. However, effect of fines content and especially fines type of sandy soils on the correlation between Vs and CRR is... 

    Cost evaluation of a two-echelon inventory system with lost sales and approximately normal demand

    , Article Scientia Iranica ; Volume 13, Issue 1 , 2006 , Pages 105-112 ; 10263098 (ISSN) Akbari Jokar, M. R ; Seifbarghy, M ; Sharif University of Technology
    Sharif University of Technology  2006
    Abstract
    The inventory system under consideration consists of one central warehouse and an arbitrary number of retailers controlled by a continuous review inventory policy (R,Q). Independent Poisson demands are assumed with constant transportation times for all retailers and a constant lead time for replenishing orders from an external supplier for the warehouse. Unsatisfied demands are assumed to be lost in the retailers and unsatisfied retailer orders are backordered in the warehouse. An approximate cost function is developed to find optimal reorder points for given batch sizes in all installations and the related accuracy is assessed through simulation. © Sharif University of Technology, January... 

    {k, r - k}-Factors of r-Regular Graphs

    , Article Graphs and Combinatorics ; Vol. 30, issue. 4 , 2014 , pp. 821-826 ; ISSN: 0911-0119 Akbari, S ; Kano, M ; Sharif University of Technology
    2014
    Abstract
    For a set S of positive integers, a spanning subgraph F of a graph G is called an S-factor of G if degF(x) ∈ S for all vertices x of G, where degF(x) denotes the degree of x in F. We prove the following theorem on {a, b}-factors of regular graphs. Let r ≥ 5 be an odd integer and k be either an even integer such that 2 ≤ k < r/2 or an odd integer such that r/3 ≤ k < r/2. Then every r-regular graph G has a {k, r-k}-factor. Moreover, for every edge e of G, G has a {k, r-k}-factor containing e and another {k, r-k}-factor avoiding e  

    Visibility maintenance of a moving segment observer inside polygons with holes

    , Article Proceedings of the 22nd Annual Canadian Conference on Computational Geometry, CCCG 2010, 9 August 2010 through 11 August 2010, Winnipeg, MB ; 2010 , Pages 117-120 Akbari, H ; Ghodsi, M ; Sharif University of Technology
    2010
    Abstract
    We analyze how to efficiently maintain and update the visibility polygons for a segment observer moving in a polygonal domain. The space and time requirements for preprocessing are O(n2) and after preprocessing, visibil- ity change events for weak and strong visibility can be handled in O(log VP) and O(log(VP1 + VP2)) re- spectively, or O(log n) in which VP is the size of the line segment's visibility polygon and VP 1 and VP2 represent the number of vertices in the visibility poly- gons of the line segment endpoints  

    Failure analysis of a first stage gas turbine blade

    , Article Engineering Failure Analysis ; 2010 ; 13506307 (ISSN) Kazempour Liacy, H ; Abouali, S ; Akbari Garakani, M
    2010

    On linear transformations preserving at least one eigenvalue

    , Article Proceedings of the American Mathematical Society ; Volume 132, Issue 6 , 2004 , Pages 1621-1625 ; 00029939 (ISSN) Akbari, S ; Aryapoor, M ; Sharif University of Technology
    2004
    Abstract
    Let F be an algebraically closed field and T: Mn(F) → Mn(F) be a linear transformation. In this paper we show that if T preserves at least one eigenvalue of each matrix, then T preserves all eigenvalues of each matrix. Moreover, for any infinite field F (not necessarily algebraically closed) we prove that if T: Mn(F) → M n(F) is a linear transformation and for any A ∈ Mn(F) with at least an eigenvalue in F, A and T(A) have at least one common eigenvalue in F, then T preserves the characteristic polynomial  

    The Chromatic Index of a Graph Whose Core is a Cycle of Order at Most 13

    , Article Graphs and Combinatorics ; Vol. 30, issue. 4 , 2014 , p. 801-819 Akbari, S ; Ghanbari, M ; Nikmehr, M. J ; Sharif University of Technology
    2014
    Abstract
    Let G be a graph. The core of G, denoted by GΔ, is the subgraph of G induced by the vertices of degree Δ(G), where Δ(G) denotes the maximum degree of G. A k -edge coloring of G is a function f: E(G) → L such that {pipe}L{pipe} = k and f(e1) ≠ f(e2) for all two adjacent edges e1 and e2 of G. The chromatic index of G, denoted by χ′(G), is the minimum number k for which G has a k-edge coloring. A graph G is said to be Class 1 if χ′(G) = Δ(G) and Class 2 if χ′(G) = Δ(G) + 1. In this paper it is shown that every connected graph G of even order whose core is a cycle of order at most 13 is Class 1