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    On the complexity of isoperimetric problems on trees [electronic resource]

    , Article Discrete Applied Mathematics ; Volume 160 Issue 1-2, January, 2012 Pages 116-131 Daneshgar, A. (Amir) ; Javadi, Ramin ; Sharif Univercity of Technology
    Abstract
    This paper is aimed at investigating some computational aspects of different isoperimetric problems on weighted trees. In this regard, we consider different connectivity parameters called minimum normalized cuts/isoperimetric numbers defined through taking the minimum of the maximum or the mean of the normalized outgoing flows from a set of subdomains of vertices, where these subdomains constitute a partition/subpartition. We show that the decision problem for the case of taking k-partitions and the maximum (called the max normalized cut problem NCP^M), and the other two decision problems for the mean version (referred to as IPP^m and NCP^m) are NP-complete problems for weighted trees. On... 

    A polynomial time branch and bound algorithm for the single item economic lot sizing problem with all units discount and resale [electronic resource]

    , Article International Journal of Optimization in Civil Engineering ; 2012, 2(2): 183-202 Mirmohammadi, S. H. (S. Hamid) ; Shadrokh, Sh ; Eshghi, Kourosh ; Sharif University of Technology
    Abstract
    The purpose of this paper is to present a polynomial time algorithm which determines the lot sizes for purchase component in Material Requirement Planning (MRP) environments with deterministic time-phased demand with zero lead time. In this model, backlog is not permitted, the unit purchasing price is based on the all-units discount system and resale of the excess units is possible at the ordering time. The properties of an optimal order policy are argued and on the basis of them, a branch and bound algorithm is presented to construct an optimal sequence of order policies. In the proposed B&B algorithm, some useful fathoming rules have been proven to make the algorithm very efficient. By... 

    Power and performance efficient partial circuits in packet-switched networks-on-chip

    , Article Proceedings of the 2013 21st Euromicro International Conference on Parallel, Distributed, and Network-Based Processing, PDP 2013 ; 27 February - 1 March , 2013 , pp. 509-513 ; Print ISBN: 9781467353212 Teimouri, N ; Modarressi, M ; Sarbazi-Azad, H ; Sharif University of Technology
    Abstract
    In this paper, we propose a hybrid packet-circuit switching for networks-on-chip to benefit from the advantages of both switching mechanisms. Integrating circuit and packet switching into a single NoC is achieved by partitioning the link bandwidth and router data-path and control-path elements into two parts and allocating each part to one of the switching methods. In this NoC, during injection in the source node, packets are initially forwarded on the packet-switched sub-network, but keep requesting a circuit towards the destination node. The circuit-switched part, at each cycle, collects the circuit construction requests, performs arbitration among the conflicting requests, and constructs... 

    Exploration of temperature constraints for thermal aware mapping of 3D networks on chip

    , Article Proceedings - 20th Euromicro International Conference on Parallel, Distributed and Network-Based Processing, PDP 2012 ; 15-17 February , 2012 , pp. 499-506 ; ISBN: 9780769546339 Hamedani, P. K ; Hessabi, S ; Sarbazi-Azad, H ; Jerger, N. E ; Sharif University of Technology
    Abstract
    This paper proposes three ILP-based static thermalaware mapping algorithms for 3D Networks on Chip (NoC) to explore the thermal constraints and their effects on temperature and performance. Through complexity analysis, we show that the first algorithm, an optimal one, is not suitable for 3D NoC. Therefore, we develop two approximation algorithms and analyze their algorithmic complexities to show their proficiency. As the simulation results show, the mapping algorithms that employ direct thermal calculation to minimize the temperature reduce the peak temperature by up to 24% and 22%, for the benchmarks that have the highest communication rate and largest number of tasks, respectively. This... 

    Inverse and forward dynamics of N-3RPS manipulator with lockable joints

    , Article Robotica ; 2015 ; ISSN: 02635747 Taherifar, A ; Salarieh, H ; Alasty, A ; Honarvar, M ; Sharif University of Technology
    Abstract
    The N-3 Revolute-Prismatic-Spherical (N-3RPS) manipulator is a kind of serial-parallel manipulator and has higher stiffness and accuracy compared with serial mechanisms, and a larger workspace compared with parallel mechanisms. The locking mechanism in each joint allows the manipulator to be controlled by only three wires. Modeling the dynamics of this manipulator presents an inherent complexity due to its closed-loop structure and kinematic constraints. In the first part of this paper, the inverse kinematics of the manipulator, which consists of position, velocity, and acceleration, is studied. In the second part, the inverse and forward dynamics of the manipulator is formulated based on... 

    A sensitivity study of FILTERSIM algorithm when applied to DFN modeling

    , Article Journal of Petroleum Exploration and Production Technology ; Vol. 4, issue. 2 , June , 2014 , p. 153-174 ; ISSN: 21900558 Ahmadi, R ; Masihi, M ; Rasaei, M. R ; Eskandaridalvand, K ; Shahalipour, R ; Sharif University of Technology
    Abstract
    Realistic description of fractured reservoirs demands primarily for a comprehensive understanding of fracture networks and their geometry including various individual fracture parameters as well as network connectivities. Newly developed multiple-point geostatistical simulation methods like SIMPAT and FILTERSIM are able to model connectivity and complexity of fracture networks more effectively than traditional variogrambased methods. This approach is therefore adopted to be used in this paper. Among the multiple-point statistics algorithms, FILTERSIM has the priority of less computational effort than does SIMPAT by applying filters and modern dimensionality reduction techniques to the... 

    Well Placement optimization using hybrid optimization technique combined with fuzzy inference system

    , Article Petroleum Science and Technology ; Vol. 31, issue. 5 , Dec , 2009 , p. 481-491 ; ISSN: 10916466 Darabi, H ; Masihi, M ; Sharif University of Technology
    Abstract
    Decision on the location of new wells through infill drilling projects is a complex problem that depends on the reservoir rock and fluid properties, well and surface facilities specifications, and economic measures. Conventional approach to address this is a direct optimization that uses the numerical flow simulation. However, this is computationally very extensive. In this study the authors use a hybrid genetic algorithm (HGA) optimization technique based on the genetic algorithm (GA) with helper functions based on the polytope algorithm and the neural network. This hybridization introduces hill-climbing into the stochastic search and makes use of proxies created and calibrated iteratively... 

    A novel iron complex containing an N,O-type bidentate oxazoline ligand: Synthesis, X-ray studies, DFT calculations and catalytic activity

    , Article Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy ; Vol. 133, issue , Jun , 2014 , p. 432-438 Amini, M ; Arab, A ; Derakhshandeh, P. G ; Bagherzadeh, M ; Ellern, A ; Woo, L. K ; Sharif University of Technology
    Abstract
    A five-coordinated Fe(III) complex with the distorted trigonal bipyramidal configuration was synthesized by reactions of FeCl36H2O and 2-(2′-hydroxyphenyl)oxazoline (Hphox) as a bidentate ON donor oxazoline ligand. Complex [Fe(phox)2Cl] was fully characterized, including by single-crystal X-ray structure analysis. DFT calculations were accompanied with experimental results in order to obtain a deeper insight into the electronic structure and vibrational normal modes of complex. Oxidation of sulfides to sulfoxides in one-step was conducted by this complex as catalyst using urea hydrogen peroxide (UHP) in mixture of CH2Cl 2/CH3OH (1:1) under air at room temperature. The results show that using... 

    An optimal hardware implementation for active learning method based on memristor crossbar structures

    , Article IEEE Systems Journal ; Vol. 8, issue. 4 , 2014 , pp. 1190-1199 ; ISSN: 19328184 Esmaili Paeen Afrakoti, I ; Shouraki, S. B ; Haghighat, B ; Sharif University of Technology
    Abstract
    This paper presents a new inference algorithm for active learning method (ALM). ALM is a pattern-based algorithm for soft computing, which uses the ink drop spread (IDS) algorithm as its main engine for feature extraction. In this paper, a fuzzy number is extracted from each IDS plane rather than from the narrow path and the spread, as in previous approaches. This leads to a significant reduction in the hardware required to implement the inference part of the algorithm and real-time computation of the implemented hardware. A modified version of the memristor crossbar structure is used to solve the problem of varying shapes of the ink drops, as reported in previous studies. In order to... 

    Versatile low-Reynolds-number swimmer with three-dimensional maneuverability

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Vol. 90, issue. 5 , 2014 ; ISSN: 15393755 Jalali, M. A ; Alam, M. R ; Mousavi, S ; Sharif University of Technology
    Abstract
    We design and simulate the motion of a swimmer, the Quadroar, with three-dimensional translation and reorientation capabilities in low-Reynolds-number conditions. The Quadroar is composed of an I-shaped frame whose body link is a simple linear actuator and four disks that can rotate about the axes of flange links. The time symmetry is broken by a combination of disk rotations and the one-dimensional expansion or contraction of the body link. The Quadroar propels on forward and transverse straight lines and performs full three-dimensional reorientation maneuvers, which enable it to swim along arbitrary trajectories. We find continuous operation modes that propel the swimmer on planar and... 

    A sensitive and selective colorimetric method for detection of copper ions based on anti-aggregation of unmodified gold nanoparticles

    , Article Talanta ; Vol. 129, issue , 2014 , pp. 227-232 ; ISSN: 00399140 Hormozi-Nezhad, M. R ; Abbasi-Moayed, S ; Sharif University of Technology
    Abstract
    A highly sensitive and selective colorimetric method for detection of copper ions, based on anti-aggregation of D-penicillamine (D-PC) induced aggregated gold nanoparticles (AuNPs) was developed. Copper ions can hinder the aggregation of AuNPs induced by D-PC, through formation of mixed-valence complex with D-PC that is a selective copper chelator. In the presence of a fixed amount of D-PC, the aggregation of AuNPs decreases with increasing concentrations of Cu2+ along with a color change from blue to red in AuNPs solution and an increase in the absorption ratio (A520/A 650). Under the optimum experimental conditions (pH 7, [AuNPs] =3.0 nmol L-1 and [NaCl]=25 mmol L-1), a linear calibration... 

    Homoleptic tetraazaphenanthrene-based copper(I) complexes: Synthesis, spectroscopic characterization, crystal structures and computational studies

    , Article Inorganica Chimica Acta ; Vol. 423, issue. PA , 2014 , pp. 348-357 ; ISSN :0020-1693 Kia, R ; Scholz, M ; Raithby, P. R ; Techert, S ; Sharif University of Technology
    Abstract
    Three new Cu(I) complexes containing bidentate N^N donor ligands with the general formula [Cu(N^N)2][PF6] (N^N = 2,3-diphenyl-6,7-di-p-tolyl-1,4,5,8-tetraazaphenanthrene (L1), 2,3-diphenyl-6,7-di(2-thienyl)-1,4,5,8-tetraazaphenanthrene (L2), and 2,3-diphenyl-6,7-di-p-fluorophenyl-1,4,5,8-tetraazaphenanthrene (L3), were prepared by the reaction of [Cu(CH3CN)4][PF6] with two equivalents of the N^N ligand. Single-crystal X-ray diffraction analysis confirmed that in each complex the metal displays a distorted tetrahedral geometry surrounded by the four N atoms of the two sterically hindered substituted tetraazaphenanthrene (TAP) ligands. Density functional theory (DFT) and time-dependent density... 

    Low-data complexity biclique cryptanalysis of block ciphers with application to piccolo and HIGHT

    , Article IEEE Transactions on Information Forensics and Security ; Vol. 9, Issue. 10 , 2005 , Pages 1641-1652 Ahmadi, S ; Ahmadian, Z ; Mohajeri, J ; Aref, M. R ; Sharif University of Technology
    Abstract
    In this paper, we present a framework for biclique cryptanalysis of block ciphers which extremely requires a low amount of data. To that end, we enjoy a new representation of biclique attack based on a new concept of cutset that describes our attack more clearly. Then, an algorithm for choosing two differential characteristics is presented to simultaneously minimize the data complexity and control the computational complexity. Then, we characterize those block ciphers that are vulnerable to this technique and among them, we apply this attack on lightweight block ciphers Piccolo-80, Piccolo-128, and HIGHT. The data complexity of these attacks is only 16-plaintext-ciphertext pairs, which is... 

    An investigation of the oxidative dehydrogenation of propane kinetics over a vanadium-graphene catalyst aiming at minimizing of the COx species

    , Article Chemical Engineering Journal ; Vol. 250 , 2014 , Pages 14-24 ; ISSN: 13858947 Fattahi, M ; Kazemeini, M ; Khorasheh, F ; Rashidi, A ; Sharif University of Technology
    Abstract
    Application of the DOE with the ANN in kinetic study of the ODHP was investigated.•The catalyst of vanadium/graphene synthesized through the hydrothermal technique.•The ANN and RSM's simulations were utilized to generate the extra data points.•Power law models and corresponding parameters determined to describe the reactions.•The optimization conducted in order to minimize the COx production. In the current investigation, an application of the design of experiments (DOE) along with the artificial neural networks (ANN) in a kinetic study of oxidative dehydrogenation of propane (ODHP) reaction over a synthesized vanadium-graphene catalyst at 400-500. °C presented aiming at minimizing the CO. x... 

    Transesterification of waste cooking oil to biodiesel using KOH/γ-Al2O3 catalyst in a new two-impinging-jets reactor

    , Article Industrial and Engineering Chemistry Research ; Vol. 53, Issue. 31 , 2014 , Pages 12238-12248 ; ISSN: 08885885 Ghasemi, M ; Molaei Dehkordi, A ; Sharif University of Technology
    Abstract
    In this article, the transesterification of waste cooking oil (WCO) to biodiesel fuel (BDF) has been studied using KOH loaded on millimetric γ-Al2O3 particles in a novel type of two-impinging-jets reactor (TIJR). The effects of various parameters such as KOH loading (wt %), catalyst loading, and methanol-to-oil molar ratio on the BDF yield were studied. The catalyst particles with a KOH loading of 25 wt % at appropriate reaction conditions (i.e., catalyst loading = 4 wt % and methanol-to-oil molar ratio = 15:1) and at 65 °C were used in the TIJR. The influences of various operating and design parameters such as jet Reynolds number value, feed flow rate, jet diameter, and the internozzle... 

    Kinetic modeling of oxidative dehydrogenation of propane (ODHP) over a vanadium-graphene catalyst: Application of the DOE and ANN methodologies

    , Article Journal of Industrial and Engineering Chemistry ; Vol. 20, issue. 4 , July , 2014 , p. 2236-2247 ; ISSN: 1226086X Fattahi, M ; Kazemeini, M ; Khorasheh, F ; Rashidi, A ; Sharif University of Technology
    Abstract
    In this research the application of design of experiment (DOE) coupled with the artificial neural networks (ANN) in kinetic study of oxidative dehydrogenation of propane (ODHP) over a vanadium-graphene catalyst at 400-500 °C and a method of data collection/fitting for the experiments were presented. The proposed reaction network composed of consecutive and simultaneous reactions with kinetics expressed by simple power law equations involving a total of 20 unknown parameters (10 reaction orders and 5 rate constants each expressed in terms of a pre-exponential factors and activation energies) determined through non-linear regression analysis. Because of the complex nature of the system, neural... 

    Synthesis, X-ray studies, and catalytic activity of tridentate Schiff base dioxo-molybdenum(VI)

    , Article Journal of Coordination Chemistry ; Volume 67, Issue 14 , 2014 ; ISSN: 00958972 Amini, M ; Khaksar, M ; Boghaei, D. M ; Bagherzadeh, M ; Ellern, A ; Woo, L. K ; Sharif University of Technology
    Abstract
    The reaction of a solution of MoO2(acac)2 in CH3OH and salicylidene 2-picoloyl hydrazone as a tridentate ONO donor Schiff base (ONO) afford a six-coordinated Mo(VI) complex [MoO2(ONO)(CH3OH)], with a distorted octahedral configuration. [MoO2(ONO)(CH3OH)] was isolated as an air-stable crystalline solid and fully characterized by single-crystal X-ray structure analysis. [MoO2(ONO)(CH3OH)] shows reactivity in the oxidation of sulfides to their corresponding sulfoxides using urea hydrogen peroxide as the oxidant at room temperature under air  

    Synthesis, characterizations and catalytic studies of a new two-dimensional metal-organic framework based on Co-carboxylate secondary building units

    , Article Journal of Solid State Chemistry ; Volume 223, March , 2014 , Pages 32-37 ; ISSN: 00224596 Bagherzadeh, M ; Ashouri, F ; Dakovic, M ; Sharif University of Technology
    Abstract
    A metal-organic framework [Co3(BDC)3(DMF)2(H2O)2] was synthesized and structurally characterized. X-ray single crystal analysis revealed that the framework contains a 2D polymeric chain through coordination of 1,4-benzenedicarboxylic acid linker ligand to cobalt centers. The polymer crystallize in monoclinic P21 /n space group with a=13.989(3) Å, b=9.6728(17) Å, c=16.707(3) Å, and Z=2. The polymer features a framework based on the perfect octahedral Co-O6 secondary building units. The catalytic activities of [Co3(BDC)3(DMF)2(H2O)2]n for olefins oxidation was conducted. The heterogeneous catalyst could be facilely separated from the reaction mixture, and reused three times without significant... 

    On the Complexity of Deciding Whether the Regular Number is at Most Two

    , Article Graphs and Combinatorics ; Volume 31, Issue 5 , September , 2014 , pp 1359-1365 ; ISSN: 09110119 Dehghan, A ; Sadeghi, M. R ; Ahadi, A ; Sharif University of Technology
    Abstract
    The regular number of a graph (Formula presented.) denoted by (Formula presented.) is the minimum number of subsets into which the edge set of (Formula presented.) can be partitioned so that the subgraph induced by each subset is regular. In this work we answer to the problem posed as an open problem in Ganesan et al. (J Discrete Math Sci Cryptogr 15(2-3):49-157, 2012) about the complexity of determining the regular number of graphs. We show that computation of the regular number for connected bipartite graphs is NP-hard. Furthermore, we show that, determining whether (Formula presented.) for a given connected (Formula presented.)-colorable graph (Formula presented.) is NP-complete. Also, we... 

    Influence of β-lactoglobulin and its surfactant mixtures on velocity of the rising bubbles

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Vol. 460 , October , 2014 , pp. 361-368 ; ISSN: 09277757 Ulaganathan, V ; Krzan, M ; Lotfi, M ; Dukhin, S. S ; Kovalchuk, V. I ; Javadi, A ; Gunes, D. Z ; Gehin-Delval, C ; Malysa, K ; Miller, R ; Sharif University of Technology
    Abstract
    The rising velocity of air bubbles in surfactant solutions is a sensitive measure for the formation of a dynamic adsorption layer (DAL) at the bubble surface. Due to a certain surface coverage by adsorbed species the bubble surface starts to become immobilized and the rising velocity is retarded. There is a large difference in the retardation effect in presence of the protein β-lactoglobulin (BLG) alone and its mixed solutions with surfactants. In presence of added surfactants BLG forms complexes, which adsorb and retard the bubble rising velocity according to their respective surface activity and adsorption kinetics. While the nonionic surfactant C12DMPO does not show significant increase...