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    Modeling for Sensing Behavior of SnO2-CuO Nanostructures toward H2S Gas

    , Ph.D. Dissertation Sharif University of Technology Boroun, Zhoubin (Author) ; Ghorbani, Mohammad (Supervisor) ; Moosavi, Ali (Supervisor) ; Mohammadpour, Raheleh (Supervisor)
    Abstract
    H2S is a toxic and corrosive gas which is detrimental for both human’s health and some of important industries such as oil and gas. Based on different experimental research among various systems, resistive sensors fabricated from SnO2-CuO nanostructures have promising performance toward detection of this gas. High sensitivity and selectivity, response time of order of seconds, recovery times of order of tens of seconds and determining concentration of H2S gas below ppm level are advantages of this system. Unfortunately due to lack of a theoretical model, current experimental researches are excessively based on “trial and error” methodology. In this research some of the basic questions which... 

    On-fiber standardization technique for solid-coated solid-phase microextraction

    , Article Analytical Chemistry ; Volume 79, Issue 3 , 2007 , Pages 1221-1230 ; 00032700 (ISSN) Zhou, S. N ; Zhang, X ; Ouyang, G ; Es-haghi, A ; Pawliszyn, J ; Sharif University of Technology
    2007
    Abstract
    The on-fiber standardization technique for solid-coated solid-phase microextraction (SPME) was studied, and a theoretical model is proposed for the isotropic behavior of adsorption and desorption, based on Fick's law of diffusion and the Langmuir model. The isotropy of the adsorption and desorption of analytes onto and from the surface of porous solid SPME fiber was validated with the use of a commercially available fiber, a 50-μm Carbowax/ templated resin for carbamate pesticide analysis in various sample matrixes, and a self-made polypyrrole fiber for diazepam analysis in blood samples. Time constants were comparable for the adsorption and desorption processes. Equilibrium constants and... 

    Modeling of a nonlinear Euler-Bernoulli flexible beam actuated by two active shape memory alloy actuators

    , Article Journal of Intelligent Material Systems and Structures ; Volume 22, Issue 11 , 2011 , Pages 1249-1268 ; 1045389X (ISSN) Zakerzadeh, M. R ; Salehi, H ; Sayyaadi, H ; Sharif University of Technology
    2011
    Abstract
    There are two different ways of using shape memory alloy (SMA) wire as an actuator for shape control of flexible structures: it can be either embedded within the composite laminate or externally attached to the structure. As the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, considerabnle shape changes with the same magnitude of actuation force compared with the embedded type. Such a configuration also provides faster heat transfer rate owing to convection, which is very important in shape control applications that require a highfrequency response of SMA actuators. Although combination and physics-based... 

    An optimization based approach embedded in a fuzzy connectivity algorithm for airway tree segmentation

    , Article Proceedings of the 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'08 - "Personalized Healthcare through Technology", 20 August 2008 through 25 August 2008, Vancouver, BC ; 2008 , Pages 4011-4014 ; 9781424418152 (ISBN) Yousefi Rizi, F ; Ahmadian, A. R ; Fatemizadeh, E ; Alirezaie, J ; Sharif University of Technology
    2008
    Abstract
    The main problem with airway segmentation methods which significantly influences their accuracy is leakage into the extra-luminal regions due to thinness of the airway wall during the process of segmentation. This phenomenon potentially makes large regions of lungparenchyma to be wrongly identified as airways. A solution to this problem in the previous methods was based on leak detection followed by reducing leakage during the segmentation process. This has been dealt with adjusting the segmentation parameters and performing the re-segmentation process on the pre-segmented area. This makes the algorithm very exhaustive and more dependent on the user interaction. The method presented here is... 

    Higher-order four-wave mixing modeling in DWDM networks

    , Article Physica Scripta, Belgrade ; Volume T157 , 15 November , 2013 ; 02811847 (ISSN) Yazdani, A ; Noshad, M ; Sharif University of Technology
    2013
    Abstract
    In this paper, we derive a theoretical model for the higher-order four-wave mixing (FWM) power in wavelength division multiplexing networks with non-zero dispersion shifted fibers for the first time. We have investigated the higher-order FWM power theoretically and by numerical simulations. Dividing the fiber into a finite number of elements and applying the boundary conditions allow us to derive an expression for the second-order power penalty. At the end of each element, we derive the first-order FWM power for all wavelengths and use these values to calculate the second-order FWM power in the next element. Consequently, for each channel we can compute the total second-order FWM power... 

    Theoretical modeling and simulation of higher order FWM crosstalks in multichannel WDM optical communication systems

    , Article Advanced Materials Research, Xiamen ; Volume 660 , 2013 , Pages 130-134 ; 10226680 (ISSN) ; 9783037856413 (ISBN) Yazdani, A ; Noshad, M ; Farrokhi, A ; Sharif University of Technology
    2013
    Abstract
    In this paper, we derive a theoretical model for the higher order FWM power in WDM networks with NZDSF fibers for the first time. We have investigated the higher order FWM power theoretically and by numerical simulations. Dividing the fiber into finite number of elements and applying the boundary conditions, allow us derive an expression for second order power penalty. At the end of each element we derive the first order FWM power for all wavelengths and use these values to calculate the second order FWM power in the next element. Consequently, for each channel we can compute the total second order FWM power penalty at the end of the fiber  

    Smart meters big data: Game theoretic model for fair data sharing in deregulated smart grids

    , Article IEEE Access ; Volume 3 , December , 2015 , Pages 2743-2754 ; 21693536 (ISSN) Yassine, A ; Nazari Shirehjini, A. A ; Shirmohammadi, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Aggregating fine-granular data measurements from smart meters presents an opportunity for utility companies to learn about consumers' power consumption patterns. Several research studies have shown that power consumption patterns can reveal a range of information about consumers, such as how many people are in the home, the types of appliances they use, their eating and sleeping routines, and even the TV programs they watch. As we move toward liberalized energy markets, many different parties are interested in gaining access to such data, which has enormous economical, societal, and environmental benefits. However, the main concern is that many such beneficial uses of smart meter big data... 

    Methods to Derive the Differential Equation of the Free Surface Boundary

    , Article Ground Water ; Volume 49, Issue 2 , 2011 , Pages 133-143 ; 0017467X (ISSN) Wang, X. S ; Neuman, S. P ; Strack, O. D. L ; Verruijt, A ; Jamali, M ; Seymour, B ; Bear, J ; Cheng, A. H. D ; Chen, C ; Kuang, X ; Jiao, J. J ; Sharif University of Technology
    2011

    Investigation of the equivalent material properties and failure stress of the re-entrant composite lattice structures using an analytical model

    , Article Composite Structures ; 2020 Veisi, H ; Farrokhabadi, A ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    In the present study, a novel theoretical model is developed, based on classical laminate theory, to predict the equivalent mechanical properties of the re-entrant lattice structures, which composed of continuous fiber reinforced composite struts. Three main mechanism of stretching, flexing and hinging are considered and a general closed-form formulation is derived to estimate the auxetic honeycomb's elastic and shear modulus as well as Poisson's ratios. In spite of previous studies in which the response of honeycomb structures is modeled using beam theory, here, each strut of unit cell is expressed as a composite laminate with orthotropic mechanical properties and classical laminate theory... 

    Study on the catalytic activity and theoretical modeling of a novel dual acidic mesoporous silica

    , Article RSC Advances ; Volume 4, Issue 32, 2014 , 2014 , Pages 16647-16654 ; ISSN: 20462069 Vafaeezadeh, M ; Fattahi, A ; Sharif University of Technology
    Abstract
    A novel mesoporous silica-functionalized dual Brønsted acidic species has been introduced as an efficient catalyst for solvent-free esterification of fatty acids with ethanol. The structure of the catalyst has been characterized by FT-IR spectroscopy, thermal gravimetric analysis (TGA), TEM and N2 adsorption-desorption. TGA of catalyst 1 showed no weight loss before 200 °C, indicating a high degree of hydrophobicity of the surface of the mesoporous silica. TEM images and nitrogen adsorption-desorption showed no noticeable changes to the structure of the catalyst before and after acid treatment. pH metric analysis was performed for the catalyst to determine the loading of the acidic sites.... 

    Mesoporous silica-functionalized dual Brønsted acidic ionic liquid as an efficient catalyst for thioacetalization of carbonyl compounds in water

    , Article Catalysis Communications ; Volume 41 , 2013 , Pages 96-100 ; 15667367 (ISSN) Vafaeezadeh, M ; Dizicheh, Z. B ; Hashemi, M. M ; Sharif University of Technology
    2013
    Abstract
    A novel silica-functionalized dual Brønsted acidic ionic liquid (ionic liquid with two Brønsted acidic species) has been reported as a highly efficient catalyst for thioacetalization of carbonyl compounds. The reaction was efficiently performed in water as an environmentally benign solvent with good to high yields. Thermal gravimetric analysis showed that the catalyst is stable at least up to 350 C. Furthermore, the catalyst can be recycled and reused for six runs of reaction without appreciable loss of activity. The structure of the catalyst is modelized to gain more realistic structural insight about the functionalized ionic liquid  

    Behavior of polymer concrete beam/pile confined with CFRP sleeves

    , Article Mechanics of Advanced Materials and Structures ; 2017 , Pages 1-8 ; 15376494 (ISSN) Toufigh, V ; Toufigh, V ; Saadatmanesh, H ; Ahmari, S ; Kabiri, E ; Sharif University of Technology
    Abstract
    This research investigates the flexural behavior of a polymer concrete beam/pile encased with carbon fiber sleeve. The mechanical properties of carbon fiber sleeves in tension and cement and polymer concrete in compression were determined. Polymer concrete beams were tested in flexure to determine the bending moment capacity. Then, the test results were compared to the theoretical model results. Finally, a parametric study was conducted to determine the influence of beam/pile parameters on the capacity of the element. Based on the investigation, carbon fiber sleeve filled with polymer concrete exhibits outstanding structural performance including ductility and bending capacity. © 2017 Taylor... 

    Behavior of polymer concrete beam/pile confined with CFRP sleeves

    , Article Mechanics of Advanced Materials and Structures ; Volume 26, Issue 4 , 2019 , Pages 333-340 ; 15376494 (ISSN) Toufigh, V ; Toufigh, V ; Saadatmanesh, H ; Ahmari, S ; Kabiri, E ; Sharif University of Technology
    Taylor and Francis Inc  2019
    Abstract
    This research investigates the flexural behavior of a polymer concrete beam/pile encased with carbon fiber sleeve. The mechanical properties of carbon fiber sleeves in tension and cement and polymer concrete in compression were determined. Polymer concrete beams were tested in flexure to determine the bending moment capacity. Then, the test results were compared to the theoretical model results. Finally, a parametric study was conducted to determine the influence of beam/pile parameters on the capacity of the element. Based on the investigation, carbon fiber sleeve filled with polymer concrete exhibits outstanding structural performance including ductility and bending capacity  

    Theoretical model for visible light saturable absorber nanolithography

    , Article Journal of Optics (United Kingdom) ; Volume 14, Issue 12 , 2012 ; 20408978 (ISSN) Tofighi, S ; Bahrampour, A. R ; Sharif University of Technology
    2012
    Abstract
    In this paper a saturable absorber medium is employed as an optical limiter to reduce the spot size to the range of several tens of nanometres. The characteristics of a Gaussian beam are theoretically analysed upon propagation through the saturable absorber medium. Based on Maxwell equations a system of coupled nonlinear ordinary differential equations for intensity, beam radius and beam curvature is obtained. Theoretical analyses and numerical results show that the behaviour of a Gaussian beam in a saturable absorber medium strongly depends on the initial characteristics of the laser beam. Numerical results indicate that, depending on the initial conditions and a suitable saturable absorber... 

    Prediction of stratified charge divided chamber engine performance

    , Article Scientia Iranica ; Volume 16, Issue 1 , 2009 , Pages 92-100 ; 10263098 (ISSN) Tiourad, M ; Mozafari, A ; Sharif University of Technology
    2009
    Abstract
    Certain stratified charge divided chamber engines have a very small pre-chamber, equipped with a spark plug and a main chamber connected to the pre-chamber through nozzles, A theoretical model is presented in this research to predict ignition delay and initiation of combustion in the pre-chamber. It considers flame progress in the pre-chamber up to the point where the flame penetrates the main chamber through the connecting nozzles. Step by step calculations then continue in the main chamber and the mass fraction burned and the energy release rate are calculated. The process continues to the point where all the fuel is burned. At each step, due to a one degree rotation of the crank shaft,... 

    Fractional order model reduction approach based on retention of the dominant dynamics: Application in IMC based tuning of FOPI and FOPID controllers

    , Article ISA Transactions ; Volume 50, Issue 3 , July , 2011 , Pages 432-442 ; 00190578 (ISSN) Tavakoli Kakhki, M ; Haeri, M ; Sharif University of Technology
    2011
    Abstract
    Fractional order PI and PID controllers are the most common fractional order controllers used in practice. In this paper, a simple analytical method is proposed for tuning the parameters of these controllers. The proposed method is useful in designing fractional order PI and PID controllers for control of complicated fractional order systems. To achieve the goal, at first a reduction technique is presented for approximating complicated fractional order models. Then, based on the obtained reduced models some analytical rules are suggested to determine the parameters of fractional order PI and PID controllers. Finally, numerical results are given to show the efficiency of the proposed tuning... 

    Analysis of microchannel heat sink performance using nanofluids in turbulent and laminar flow regimes and its simulation using artificial neural network

    , Article 10th International Conference on Computer Modelling and Simulation, EUROSIM/UKSim2008, Cambridge, 1 April 2008 through 3 April 2008 ; 2008 , Pages 623-628 ; 0769531148 (ISBN); 9780769531144 (ISBN) Shokouhmand, H ; Ghazvini, M ; Shabanian, J ; Sharif University of Technology
    2008
    Abstract
    In this study, silicon microchannel heat sink (MCHS) performance using nanofluids as coolants was analyzed. The nanofluid was a mixture of nanoscale Cu particles and pure water with various volume fractions. Based on theoretical models and experimental correlations, the heat transfer and friction coefficients required in the analysis were used. In the theoretical model, nanofluid was treated as a single-phase fluid. In the experimental correlation, thermal dispersion due to particle random motion was included. The microchannel heat sink performances for a specific geometries with Wch = W fin = 100 μm and Lch =300 μm is examined. In this study, flow in laminar and turbulent regimes using the... 

    A density functional study of strong local magnetism creation on MoS 2 nanoribbon by sulfur vacancy

    , Article Nanoscale ; Volume 2, Issue 8 , 2010 , Pages 1429-1435 ; 20403364 (ISSN) Shidpour, R ; Manteghian, M ; Sharif University of Technology
    2010
    Abstract
    In this study a low-width MoS2 ribbon has been used for probing the electronic structure and local magnetic moment near vacancies. A theoretical study with the full-potential Density Functional Theory (DFT) approach (Wien2K code) have shown that when the dimension of MoS2 is reduced from 2-D to 1-D the nonmagnetic semi-conductor MoS2 becomes a magnetic conductor. Our study has shown that a vacancy on the S-edge with 50% coverage intensifies the magnetization of the edge of the MoS2 nanoribbon but such a vacancy on S-edge with 100% coverage causes this magnetic property to disappear. It is concluded that in both of them, there are positive or negative strong gradients of local magnetic moment... 

    Moon shadow on high energy cosmic ray in data of a small extensive air shower array

    , Article Astroparticle Physics ; Volume 33, Issue 5-6 , 2010 , Pages 330-334 ; 09276505 (ISSN) Sheidaei, F ; Bahmanabadi, M ; Samimi, J ; Sharif University of Technology
    2010
    Abstract
    Data from a small air shower array were used to examine the cosmic ray shadow of the Moon at energies more than 100 TeV. A simple technique has been used for the analysis of this data. In this technique the number of EAS events with arrival directions falling in error circles centered about the moving moon is compared to the mean number of events falling in error circles with centers randomly chosen in the sky. For any assumed angular radius of the error circle the deficit in EAS event count in the direction of moon which is a moon-related effect is interpreted as the shadow of the moon. A simple theoretical model has been developed to relate the mean number of EAS events, Nsky, to the... 

    Electrical bending instability in electrospinning visco-elastic solutions

    , Article Journal of Polymer Science, Part B: Polymer Physics ; Volume 54, Issue 11 , 2016 , Pages 1036-1042 ; 08876266 (ISSN) Shariatpanahi, S. P ; Bonn, D ; Ejtehadi, M. R ; Iraji Zad, A ; Sharif University of Technology
    John Wiley and Sons Inc 
    Abstract
    The electrical bending instability in charged liquid jets is the phenomenon determining the process of electrospinning. A model of this phenomenon is lacking however, mostly due to the complicated interplay between the viscosity and elasticity of the solution. To investigate the bending instability, we performed electrospinning experiments with a solution of polyethylene oxide in water/ethanol. Using a fast camera and sensitive multimeter, we deduced an experimental dispersion relation describing the helix pitch length as a function of surface charge. To understand this relation, we developed a theoretical model for the instability for a wide range of visco-elastic materials, from conducting...