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    Clustering and Embedding Graphs into Trees

    , M.Sc. Thesis Sharif University of Technology Nodehi Sabet, Amirhossein (Author) ; Daneshgar, Amir (Supervisor)
    In this thesis, we study the following question stating that “how well a tree structure can approximate the clustering structure of a graph”.To do this, we first focus on the DJS algorithm proposed by Daneshgar et.al. and second we consider the minimum distortion tree approximation algorithm proposed by Abraham et.al.We conclude, using some experimental results, that the minimum spanning tree algorithm extracts some geometric aspects of the data set that the Abraham et.al. algorithm can not track  

    Application of Coding in Multi-party Computation for Massive Operations

    , M.Sc. Thesis Sharif University of Technology Akbari Nodehi, Hanzaleh (Author) ; Maddah-Ali, Mohammad Ali (Supervisor)
    In this thesis, we introduce limited-sharing multi-party computation; in which there is a network of workers (processors) and a set of sources, each having access to a massive matrix as a private input. These sources aim to offload the task of computing a polynomial function of the matrices to the workers, while preserving the privacy of data. We also assume that the load of the link between each source and each worker is upper bounded by a fraction of each input. The objective is to minimize the number of workers needed to perform the computation, such that even if an arbitrary subset of t 1 workers, for some t 2 N, collude, they cannot gain any information about the input matrices. This... 

    Solving Detour-Based Fuel Stations Location Problems

    , Article Computer-Aided Civil and Infrastructure Engineering ; Volume 31, Issue 2 , 2016 , Pages 132-144 ; 10939687 (ISSN) Zockaie, A ; Aashtiani, H. Z ; Ghamami, M ; Marco Nie, Y ; Sharif University of Technology
    Blackwell Publishing Inc  2016
    This article studies the problem of locating fuel stations to minimize the extra cost spent in refueling detours, which belongs to a class of discretionary service facility location problems. Unlike many studies of similar problems in the literature, the proposed model considers capacity constraints and compares different ways to incorporate them in the formulation. Note that ignoring the capacity constraint results in nonoptimal and unrealistic solutions. The proposed models are solved using both an off-the-shelf solver (CPLEX) and a specialized meta-heuristic method (Simulated Annealing) developed in this study. The solution methods are tested and compared in two case studies; a test... 

    Vertically aligned ZnO@CdS nanorod heterostructures for visible light photoinactivation of bacteria

    , Article Journal of Alloys and Compounds ; Vol. 590 , 2014 , pp. 507-513 ; ISSN: 09258388 Zirak, M ; Akhavan, O ; Moradlou, O ; Nien, Y. T ; Moshfegh, A. Z ; Sharif University of Technology
    Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (Eg) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with Eg ∼2.5-2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve... 

    On the growth and photocatalytic activity of the vertically aligned ZnO nanorods grafted by CdS shells

    , Article Applied Surface Science ; Volume 273 , July , 2013 , Pages 391-398 ; 01694332 (ISSN) Zirak, M ; Moradlou, O ; Bayati, M. R ; Nien, Y. T ; Moshfegh, A. Z ; Sharif University of Technology
    We have studied systematically photocatalytic properties of the vertically aligned ZnO@CdS core-shell nanorods where the features were grown through a multistep procedure including sol-gel for the formation of ZnO seed layer, hydrothermal process to grow ZnO nanorods, and successive ion layer adsorption and reaction (SILAR) process to deposit CdS nanoshells onto the ZnO nanorods. Formation of the ZnO seed layer and vertically aligned ZnO nanorods (d ∼ 40 nm) with a hexagonal cross-section was confirmed by AFM and SEM imaging. Successful capping of ZnO nanorods with homogeneous CdS nanocrystallites (∼5 nm) was ascertained by HRTEM diffraction and imaging. Optical properties of the samples... 

    Controlled engineering of WS2 nanosheets-CdS nanoparticle heterojunction with enhanced photoelectrochemical activity

    , Article Solar Energy Materials and Solar Cells ; Volume 141 , 2015 , Pages 260-269 ; 09270248 (ISSN) Zirak, M ; Zhao, M ; Moradlou, O ; Samadi, M ; Sarikhani, N ; Wang, Q ; Zhang, H. L ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier  2015
    Abstract We report the well-controlled preparation of WS2 nanosheets-CdS nanoparticle heterojunction for photoelectrochemical (PEC) water splitting application. The WS2 nanosheets with an average thickness of ~5 nm and lateral dimensions of ~200 nm were synthesized via liquid phase exfoliation of bulk WS2 in water/ethanol solution, followed by deposition onto ITO substrate via electrophoretic method. CdS nanoparticles were grown via facile successive ion layer absorption and reaction (SILAR) method. Using these two well-controlled methods, CdS/WS2/ITO and WS2/CdS/ITO systems were fabricated. The loading of WS2 nanosheets was... 

    Fabrication and surface stochastic analysis of enhanced photoelectrochemical activity of a tuneable MoS2-CdS thin film heterojunction

    , Article RSC Advances ; Volume 6, Issue 20 , 2016 , Pages 16711-16719 ; 20462069 (ISSN) Zirak, M ; Ebrahimi, M ; Zhao, M ; Moradlou, O ; Samadi, M ; Bayat, A ; Zhang, H. L ; Moshfegh, A. Z ; Sharif University of Technology
    Royal Society of Chemistry  2016
    A very simple and well-controlled procedure was employed to prepare CdS nanoparticle/few-layer MoS2 nanosheet/Indium tin oxide (ITO) thin film heterostructures. To tune and fabricate the CdS/MoS2(t)/ITO thin films with various surface topographies, first electrophoretic deposition (EPD) was used to deposit MoS2 nanosheets on the ITO substrate under an optimized applied potential difference (8 V) for different deposition times (t) of 30, 60, 120 and 240 s. Then, CdS nanoparticles were deposited via a successive ion layer adsorption and reaction (SILAR) technique. The highest photo-current density of 285 μA cm-2 was measured for the CdS/MoS2(60 s)/ITO sample, which was about 2.3 times higher... 

    The effect of silver oxidation on the photocatalytic activity of Ag/ZnO hybrid plasmonic/metal-oxide nanostructures under visible light and in the dark

    , Article Scientific Reports ; Volume 9, Issue 1 , 2019 ; 20452322 (ISSN) Ziashahabi, A ; Prato, M ; Dang, Z ; Poursalehi, R ; Naseri, N ; Sharif University of Technology
    Nature Publishing Group  2019
    A new synergetic hybrid Ag/ZnO nanostructure was fabricated which is able to cause photocatalytic degradation (in high yields) of methylene blue under visible light as well as in the dark. In this nanostructure, ZnO was synthesized using the arc discharge method in water and was coupled with Ag via a chemical reduction method. X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy results confirmed the existence of defects in ZnO in the hybrid nanostructures; these defects act as electron traps and inhibit the recombination of electron-hole pairs. The absorption edge of the hybrid nanostructure shifts toward the visible region of the spectrum due to a combination of the Ag... 

    Theoretical and experimental study of cascade solar stills

    , Article Solar Energy ; Volume 90 , April , 2013 , Pages 205-211 ; 0038092X (ISSN) Ziabari, F. B ; Sharak, A. Z ; Moghadam, H ; Tabrizi, F. F ; Sharif University of Technology
    Most part of Iran is dominated by arid and semi-arid areas due to low annual rainfall. The need for production of fresh water from brackish water is considerably high, especially in dry regions. In this study 1 month daily-based experimental data from a solar still site has been reported. The technical and operational problems of this site which finally contributed to the total cease of the site are described. Then a detailed analysis is investigated on progress of a prototype which constructed in order to solve the site's problems. The results of 1 month of experimental data of the final design showed that the last prototype could be used to solve the current problems of the site. The... 

    Unexpected optical limiting properties from MoS2 nanosheets modified by a semiconductive polymer

    , Article Chemical Communications ; Volume 51, Issue 61 , Jun , 2015 , Pages 12262-12265 ; 13597345 (ISSN) Zhao, M ; Chang, M. J ; Wang, Q ; Zhu, Z. T ; Zhai, X. P ; Zirak, M ; Moshfegh, A. Z ; Song, Y. L ; Zhang, H. L ; Sharif University of Technology
    Royal Society of Chemistry  2015
    Direct solvent exfoliation of bulk MoS2 with the assistance of poly(3-hexylthiophene) (P3HT) produces a novel two-dimensional organic/inorganic semiconductor hetero-junction. The obtained P3HT-MoS2 nanohybrid exhibits unexpected optical limiting properties in contrast to the saturated absorption behavior of both P3HT and MoS2, showing potential in future photoelectric applications  

    Enhanced electromagnetic wave dissipation features of magnetic Ni microspheres by developing core-double shells structure

    , Article Ceramics International ; Volume 48, Issue 1 , 2022 , Pages 446-454 ; 02728842 (ISSN) Zhang, B ; Mahariq, I ; Tran, N ; Mahmoud, M. Z ; Akhtar, M. N ; Sharif University of Technology
    Elsevier Ltd  2022
    Readily oxidization of magnetic particles is a common drawback of these type of materials which reduce their electromagnetic wave dissipation performance. In this study, the magnetic core-double shells structured (Ni/SiO2/Polyaniline) composite has been developed for protection of the core from oxidation and in consequent improvement the complex permittivity. Solvothermal and in-situ polymerization methods were utilized for decorating Ni micro-particles with SiO2 and conductive polyaniline polymer respectively. All physico-chemical, magnetic and electromagnetic features were evaluated via XRD, FTIR, XPS, FESEM, VSM and VNA analysis. The double shells composite possesses significant... 

    Effect of front double wishbone strut position on vehicle steering and suspension performance

    , Article Proceedings of 2012 IEEE Conference on Control, Systems and Industrial Informatics, ICCSII 2012 ; 2012 , Pages 151-154 ; 9781467310239 (ISBN) Zeinali, M ; Darus, I. Z. M ; Taghavi, A. H ; IEEE Indonesia Section ; Sharif University of Technology
    The front double wishbone suspension parameters are related as a multi-body model. By replacing the new suspension and steering hard points, the performance of the suspension system is studied using CATIA and MSC ADAMS software for modeling and analyzing, respectively. In this case two tests were done, steady state circular test in ADAMS/View and parallel wheel travel in ADAMS/Car. The strut position is directly related to Kingpin inclination angle and scrub radius. The increase the amount of these two parameters has an effect on steering performance in low speed and negative displacement, such as camber, caster and Kingpin inclination angles in negative displacement of wheels. Moreover, the... 

    Incorporating aspect ratio in a new modeling approach for strengthening of MMCs and its extension from micro to nano scale

    , Article Advanced Composite Materials ; Volume 19, Issue 4 , Apr , 2010 , Pages 299-316 ; 09243046 (ISSN) Zehtab Yazdi, A ; Bagheri, R ; Zebarjad, S. M ; Razavi Hesabi, Z ; Sharif University of Technology
    The strengthening behavior of particle reinforced metal-matrix composites is primarily attributed to the dislocation strengthening effect and the load transfer effect. To account for these two effects in a unified way, a new multi-scale approach is developed in this paper incorporating the aspect ratio effect into the geometrically necessary dislocation strengthening relationships. By making use of this multi-scale approach, the deformation behavior of metal-matrix composites (MMCs) and metal-matrix nanocomposites (MMNCs) as a function of size, volume fraction, aspect ratio, etc. of the particles has been investigated. Comparison with the previously proposed models and the available... 

    Complementarity formulation and solution algorithm for auto-transit assignment problem

    , Article Transportation Research Record ; Volume 2673, Issue 4 , 2019 , Pages 384-397 ; 03611981 (ISSN) Zarrinmehr, A ; Aashtiani, H. Z ; Nie, Y. M ; Azizian, H ; Sharif University of Technology
    SAGE Publications Ltd  2019
    In this paper, a combined model of auto-transit assignment is introduced based on two complementarity formulations in the literature. The model accounts for interactions between the auto and transit modes through non-separable asymmetric demand and cost functions. A path-based solution algorithm is presented based on the three ideas of decomposition, column generation, and linearization, which have proved to be effective in tackling large-size networks. Numerical results over the Chicago sketch network suggest that the algorithm converges quickly within the first iterations, but is less effective as the solution gets closer to the neighborhood of the equilibrium solution. The sluggish... 

    Dissociation of C-H molecular bond of methane by pulse shaped ultra-intense laser field

    , Article Chemical Physics Letters ; Volume 560 , 2013 , Pages 60-65 ; 00092614 (ISSN) Zare, S ; Irani, E ; Navid, H. A ; Dehghani, Z ; Anvari, A ; Sadighi Bonabi, R ; Sharif University of Technology
    The effects of laser field and laser pulse width on the dissociation probability of C-H bond of CH4 have been investigated. Calculation of time dependent Schrödinger equation by grid spectral method is carried out and it is produced optimistic results in comparison to the earlier Quasi-classical calculations. The results show that there is an excellent match with experimental data. In this work, a number of results in the emerging field of laser with intensity of I = 8 × 1013 W cm-2 and pulse duration of 100 fs are presented. The present modulated field leads to more than 20% improvement in the dissociation probability  

    Immobilization of a molybdenum complex on the surface of magnetic nanoparticles for the catalytic epoxidation of olefins

    , Article New Journal of Chemistry ; Volume 40, Issue 2 , 2016 , Pages 1580-1586 ; 11440546 (ISSN) Zare, M ; Moradi Shoeili, Z ; Bagher Zadeh, M ; Akbayrak, S ; Özkar, S ; Sharif University of Technology
    Royal Society of Chemistry  2016
    Novel organic-inorganic hybrid heterogeneous nanocatalysts were obtained by covalent anchoring of a molybdenum(vi) complex of salicylidene 2-picoloyl hydrazine, MoO2(sal-phz)(CH3OH), (1) on the surface of magnetic nanoparticles functionalized by one of two routes: in the first method, the surface of magnetic nanoparticles is directly modified with 3-chloropropyltrimethoxysilane yielding 1A. In the second method, magnetic nanoparticles were silica-coated with tetraethoxysilane and then with 3-chloropropyltrimethoxysilane yielding the intermediate 2B. Then complex 1 was grafted on the surface of 1A or 2B through covalent interaction yielding 2A or 3B, respectively. The nanocatalysts 2A and 3B... 

    Oxazine containing molybdenum(VI)–oxodiperoxo complex immobilized on SBA-15 as highly active and selective catalyst in the oxidation of alkenes to epoxides under solvent-free conditions

    , Article Microporous and Mesoporous Materials ; Volume 251 , 2017 , Pages 173-180 ; 13871811 (ISSN) Zare, M ; Moradi Shoeili, Z ; Esmailpour, P ; Akbayrak, S ; Özkar, S ; Sharif University of Technology
    Elsevier B.V  2017
    Molybdenum(VI)–oxodiperoxo complex containing an oxazine ligand, ([MoO(O2)2(phox)], phox: 2-(2′-hydroxyphenyl)-5,6-dihydro-1,3-oxazine) was conveniently synthesized and immobilized onto chloro-functionalized mesoporous silica SBA-15 by covalent bonding between the chloropropyl group on the internal surface of the pores and the nitrogen atom of oxazine ligand yielding [MoO(O2)2(phox)]/SBA-15. The resulting material was characterized by FT-IR, TGA, XRD, SEM, TEM, EDX, ICP-AES, BET and UV–vis spectroscopy. The heterogeneous catalyst [MoO(O2)2(phox)]/SBA-15 was employed in the epoxidation of alkenes, exhibiting high catalytic performance and selectivity for epoxide similar to that of homogeneous... 

    Heterogeneous SBA-15-supported oxoperoxomolybdenum(VI) complex for enhanced olefin epoxidation

    , Article Catalysis Communications ; Volume 88 , 2017 , Pages 9-12 ; 15667367 (ISSN) Zare, M ; Moradi Shoeili, Z ; Ashouri, F ; Bagherzadeh, M ; Sharif University of Technology
    Heterogeneous nanoscale catalyst was successfully synthesized via anchoring of oxoperoxo molybdenum(VI) complex on the chloro-functionalized SBA-15. The mesoporous nanomaterials, MoO3(sal-phz)/SBA-15 (where sal-phz is salicylidene 2-picoloyl hydrazine) were identified by several characterization techniques. MoO3(sal-phz)/SBA-15 and MoO3(sal-phz) were also treated as catalysts in the olefins epoxidation reactions. Both homogenous and heterogeneous catalysts exhibit outstanding activity and selectivity for epoxide with tert-BuOOH in decane as oxidant at 95 °C. In addition, the heterogeneous nanocatalyst was chemically stable and can be efficiently reused for at least six cycles without a... 

    Presentation of a novel variable reluctance tubular resolver

    , Article IEEE Transactions on Industrial Electronics ; Volume 69, Issue 12 , 2022 , Pages 13773-13780 ; 02780046 (ISSN) Zare, F ; Keyvannia, A ; Nasiri Gheidari, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Encoders and resolvers are the most common position sensors in controlling electrical machines. However, due to their ability to work under harsh conditions, resolvers are more preferred. In linear position detection, the transversal edge effects and the longitudinal end-effects adversely affect the accuracy of conventional linear resolvers. On the contrary, due to the cylindrical symmetry of tubular machines, they are not subject to the edge effects. With this idea, this article presents a novel linear VR resolver with a tubular structure to achieve higher accuracy than the existing linear resolvers. A magnetic equivalent circuit model is then developed to prove the correct performance of... 

    Helical motion wound-rotor resolver

    , Article IEEE Sensors Journal ; Volume 22, Issue 10 , 2022 , Pages 9371-9377 ; 1530437X (ISSN) Zare, F ; Nasiri Gheidari, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    In this paper an integrated core, high reliability, linear-rotational resolver with a simple slotless configuration is proposed. The moving part of the proposed resolver has only one helical winding. While, its stator needs at least two individual windings to be able to determine the linear and angular position in simultaneous linear and rotational, helical, motions. Three different configurations are proposed for the stator's windings: (1) helical and horizontally skewed winding (2) helical and vertically skewed winding (3) horizontally and vertically skewed windings. The influence of the mentioned configurations is discussed in the terms of sensor's accuracy in independent and simultaneous...