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    Flow visualization of internal waves and wakes of a streamlined body in a stratified fluid

    , Article Journal of Applied Fluid Mechanics ; Volume 9, Issue 2 , 2016 , Pages 635-641 ; 17353572 (ISSN) Bidokhti, A. A ; Bidokhti, A. A ; Sharif University of Technology
    Isfahan University of Technology  2016
    Abstract
    The wake and internal waves of a moving three dimensional (3D) airfoil body in a stratified fluid has been investigated in a large stratified tank with a finite depth using movies of shadowgraphs of the flow fields. Typical Reynolds and Froude numbers of the flow varied between 103 and 104, and 0.3 and 2 respectively. The flows are generated often by towing the body in a uniformly stratified flow, while limited cases are carried out with body stationary and the channel was in recirculating mode. For some experiments the density profile had a stepped like shape. The wake flow is often consisted of internal waves including random and coherent ones. Distortion of density fields was also... 

    Investigation on the wear properties of Ti/TiC/TiN composite coatings prepared by powder cored wires through TIG method at nitrogen atmosphere on titanium substrate

    , Article Materials Research ; Volume 22, Issue 2 , 2019 ; 15161439 (ISSN) Kokabi, A. H ; Allahyari, A. A ; Sharif University of Technology
    Universidade Federal de Sao Carlos  2019
    Abstract
    In this present study, Tungsten Inert Gas (TIG) welding and powder filled cored wires with nitrogen shielding gas were utilized to produce TiC and TiN surface composite coatings on the titanium (Ti) sheet substrate. The TIG procedure was done at same welding parameters for all of prepared samples. Phase analysis and microstructures were done by X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The obtained results from XRD and EDS demonstrated that the presence of crystalline phases of TiC, TiN and Ti. SEM and OM exhibited formation of the spherical and dendritic TiC particles in a martensitic matrix and also,... 

    Ultimate strength analysis of jacket type offshore platforms due to wave, current and wind loading

    , Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 15 June 2008 through 20 June 2008, Berlin ; Volume 1 , 2008 , Pages 779-786 ; 9780791848234 (ISBN) Mirzadeh Niasar, J ; Aghakouchak, A. A ; Samadani, S ; Aghakouchak, A
    2008
    Abstract
    As the result of safety factors considered in load and resistant values for the design of new offshore platforms, a higher resistance compared to the 100 year return period environmental loading, is achieved in the structure. This type of design is usually performed using linear methods of structural analysis. In this case the structure practically has a high reserve capacity which is disregarded in the design phase but may be considered in special cases. One of these important cases is when an existing structure is assessed and evaluated after elapse of its structural life. In this case using the platforms reserve capacity, through a non-linear analysis such as push-over, would be logical... 

    Possible role for growth hormone in suppressing acylated ghrelin and hunger ratings during and after intermittent exercise of different intensities in obese individuals

    , Article Acta Medica Iranica ; Vol. 52, Issue. 1 , 2014 , pp. 29-37 ; ISSN: 1735-9694 Gholipour, M ; Kordi, M. R ; Taghikhani, M ; Ravasi, A. A ; Gaeini, A. A ; Tabrizi, A ; Sharif University of Technology
    2014
    Abstract
    Body weight is influenced by both food intake and energy expenditure. Acylated ghrelin enhances appetite, and its circulating level is suppressed by Growth Hormone. Data on the acylated ghrelin responses to exercise of different intensities in obese individuals are currently not available. This study examined the effects of an intermittent exercise protocol on acylated ghrelin levels and hunger ratings in obese people. Nine inactive male ran on the treadmill at 0900 with progressive intensities of 50, 60, 70, and 80% of VO2max for 10, 10, 5, and 2 min respectively. Blood samples were collected before the exercise at 0845 (-15 min as the resting values), after each workload (10, 23, 31, and... 

    Electrical behaviour of glass/ carbon- phenolic conductive hybrid composite woven used in electrostatics precipitator filter

    , Article International Journal of Electrochemical Science ; Vol. 9, issue. 11 , 2014 , p. 6416-6430 Neyestanak, A. A. L ; Nazari, S. A ; Sadeghbeigi, N ; Karimzadeh, A ; Sharif University of Technology
    2014
    Abstract
    Electrical behavior of hybrid conductive composites made of phenolic resin, graphite woven, glass woven and graphite nano powder has been studied for the first time in the present research to apply as collecting plates in electro static precipitators. To this purpose, two types of four-layer composites smeared with phenolic resin by different amounts of graphite nano powder then produced at 120°C and 200 bars with proper curing cycle. Finally, electrical resistivity of all the plates undergoing impact loading after different rapping cycles was measured by means of a repetitive rapping tester system particularly manufactured for this task. This study performs changes in mechanical behavior of... 

    Analysis of Capillary-Viscous-Gravity Forces in Biopolymer Flooding with a Sensitivity Analysis on Polymer and Porous Medium Parameters

    , Article Journal of Dispersion Science and Technology ; Vol. 35, issue. 12 , Aug , 2014 , p. 1764-1773 Hamidpour, E ; Mirzaei-Paiaman, A ; Ramazani, S. A. A ; Hatami, A ; Sharif University of Technology
    2014
    Abstract
    Gravity, viscous, and capillary are three main forces affecting flow characteristics in porous media. No analytical solution can be found to model the flow by considering all these forces. In this work, by considering all these forces, the polymer-flooding process is modeled by using a numerical simulation approach. For characterizing the polymer, the modified Blake-Kozeny model is chosen, which benefits consideration of the permeability reduction due to polymer adsorption on the rock surface  

    Topological code autotune

    , Article Physical Review X ; Volume 2, Issue 4 , October , 2012 ; 21603308 (ISSN) Fowler, A. G ; Whiteside, A. C ; McInnes, A. L ; Rabbani, A ; Sharif University of Technology
    2012
    Abstract
    Many quantum systems are being investigated in the hope of building a large-scale quantum computer. All of these systems suffer from decoherence, resulting in errors during the execution of quantum gates. Quantum error correction enables reliable quantum computation given unreliable hardware. Unoptimized topological quantum error correction (TQEC), while still effective, performs very suboptimally, especially at low error rates. Hand optimizing the classical processing associated with a TQEC scheme for a specific system to achieve better error tolerance can be extremely laborious. We describe a tool, AUTOTUNE, capable of performing this optimization automatically, and give two highly... 

    Linear quadratic Gaussian application and clipped optimal algorithm using for semi active vibration of passenger car

    , Article 2011 IEEE International Conference on Mechatronics, ICM 2011, Istanbul, 13 April 2011 through 15 April 2011 ; 2011 , Pages 122-127 ; 9781612849836 (ISBN) Zareh, S. H ; Sarrafan, A ; Jahromi, A. F ; Khayyat, A. A ; Sharif University of Technology
    2011
    Abstract
    A novel semi active control system for eleven Degrees of Freedom passenger car's suspension system using Magneto rheological damper is presented. The considered suspension system is modeled using mass spring damper model. The semi active vibration control is designed to reduce the amplitude of vehicle's vibration due to by road profile. The applied control strategies are based on a Linear Quadratic Gaussian optimal control algorithm to obtain desired damping forces of MR dampers. In considered system, the damping coefficient of the shock absorber changes actively through inducing magnetic field. The necessary input voltage to MR dampers to generate desired damping forces are derived using... 

    Neuro-fuzzy control strategy for an offshore steel jacket platform subjected to wave-induced forces using magnetorheological dampers

    , Article Journal of Mechanical Science and Technology ; Volume 26, Issue 4 , 2012 , Pages 1179-1196 ; 1738494X (ISSN) Sarrafan, A ; Zareh, S. H ; Khayyat, A. A. A ; Zabihollah, A ; Sharif University of Technology
    2012
    Abstract
    Magnetorheological (MR) damper is a prominent semi-active control device to vibrate mitigation of structures. Due to the inherent non-linear nature of MR damper, an intelligent non-linear neuro-fuzzy control strategy is designed to control wave-induced vibration of an offshore steel jacket platform equipped with MR dampers. In the proposed control system, a dynamic-feedback neural network is adapted to model non-linear dynamic system, and the fuzzy logic controller is used to determine the control forces of MR dampers. By use of two feedforward neural networks required voltages and actual MR damper forces are obtained, in which the first neural network and the second one acts as the inverse... 

    Experimental investigation of spray characteristics of a modified bio-diesel in a direct injection combustion chamber

    , Article Experimental Thermal and Fluid Science ; 2016 ; 08941777 (ISSN) Ghahremani, A. R ; Saidi, M. H ; Hajinezhad, A ; Mozafari, A. A ; Sharif University of Technology
    Elsevier Inc  2016
    Abstract
    Macroscopic and microscopic characteristics of spray of a Modified Bio-diesel Fuel (MBF), applying direct injection system have been explored and compared with those of conventional diesel fuel. MBF is a new combination of bio-diesel, molasses bio-ethanol, and water, which has been kept as a single-phase bio-fuel, employing an emulsifier. Lower emissions and production costs, higher oxygen content and cetane number are the key advantages of the MBF to be replaced by conventional fossil fuels in internal combustion engines. Applying atomization model, the spray atomization properties such as Ohnesorge number and Sauter Mean Diameter (SMD) have been investigated. Air entrainment analysis has... 

    The effects of homogenization time and cooling environment on microstructure and transformation temperatures of Ni-42.5wt%Ti-7.5wt%Cu alloy

    , Article Defect and Diffusion Forum ; Volume 297-301 , 2010 , Pages 344-350 ; 10120386 (ISSN); 3908451809 (ISBN); 9783908451808 (ISBN) Omrani, E ; Shokuhfar, A ; Etaati, A ; Dorri M., A ; Saatian, A ; Sharif University of Technology
    Trans Tech Publications Ltd  2010
    Abstract
    The present paper deals with different effects of homogenization time and cooling environment on Ni-42.5wt%Ti-7.5wt%Cu alloy. The alloy was prepared by vacuum arc melting. Afterwards, three homogenization times (half, one and two hour) and three cooling environments (water, air and furnace) at 1373 K were selected. Optical and Scanning Electron Microscopic methods, EDX, DSC and hardness tests have been used to evaluate the microstructure, transformation temperatures and hardness. Results indicate that specimens that were cooled in air are super-saturated. Also, the microstructure from furnace cooling has many disparities with the other cooling environments' microstructure and two types of... 

    Modeling of pressure line behavior of a common rail diesel engine due to injection and fuel variation

    , Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 39, Issue 3 , 2017 , Pages 661-669 ; 16785878 (ISSN) Mohebbi, M ; Aziz, A. A ; Hamidi, A ; Hajialimohammadi, A ; Hosseini, V ; Sharif University of Technology
    Springer Verlag  2017
    Abstract
    Common rail diesel engines with electronic fuel injection can accurately meter the fuel injection quantity with more accurate fuel injection control capability. In this work a common rail fuel injection system of a single cylinder diesel engine has been proposed and the important parameters like injection pressure, energizing time and high pressure pipes diameter and length are designed such that to be compatible with the engine basic design in case of pressure waves and injected mass variations. A one-dimensional approach has been used to model the injector using AMESim code in which Adiabatic models have been used to model injector system. Injected mass quantity has been calculated for... 

    Mechanical, rheological and oxygen barrier properties of ethylene vinyl acetate/diamond nanocomposites for packaging applications

    , Article Diamond and Related Materials ; Volume 99 , 2019 ; 09259635 (ISSN) Amini, M ; Ramazani S. A., A ; Haddadi, S. A ; Kheradmand, A ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    In this work, the effects of the surface-modified nanodiamond particles (NDs) on the barrier, rheological, mechanical and thermal properties of ethylene vinyl acetate (EVA) composites for the packaging applications were investigated. Fourier transform infrared spectroscopy, as well as thermal gravimetric analysis were employed to study the grafting of vinyltriethoxy silane (VTS) on the surface of NDs. Afterwards, EVA samples containing 0, 0.1, 0.5, 1, 1.5 and 2 wt% of surface-modified NDs were prepared by a two-stage process including the solution and injection processes. In order to evaluate the physicochemical, rheological, mechanical and thermal properties of the EVA/NDs samples, field... 

    Experimental investigation of spray characteristics of a modified bio-diesel in a direct injection combustion chamber

    , Article Experimental Thermal and Fluid Science ; Volume 81 , 2017 , Pages 445-453 ; 08941777 (ISSN) Ghahremani, A. R ; Saidi, M. H ; Hajinezhad, A ; Mozafari, A. A ; Sharif University of Technology
    Elsevier Inc  2017
    Abstract
    Macroscopic and microscopic characteristics of spray of a Modified Bio-diesel Fuel (MBF), applying direct injection system have been explored and compared with those of conventional diesel fuel. MBF is a new combination of bio-diesel, molasses bio-ethanol, and water, which has been kept as a single-phase bio-fuel, employing an emulsifier. Lower emissions and production costs, higher oxygen content and cetane number are the key advantages of the MBF to be replaced by conventional fossil fuels in internal combustion engines. Applying atomization model, the spray atomization properties such as Ohnesorge number and Sauter Mean Diameter (SMD) have been investigated. Air entrainment analysis has... 

    Crack initiation and kinking behaviours of spot welded coach peel specimens under cyclic loading

    , Article Science and Technology of Welding and Joining ; Volume 12, Issue 8 , 2007 , Pages 696-702 ; 13621718 (ISSN) Daneshpour, S ; Kokabi, A. H ; Ekrami, A. A ; Motarjemi, A. K ; Sharif University of Technology
    2007
    Abstract
    The present study Is carried out to investigate fatigue crack initiation and kinking behaviours of spot welded coach peel (CP) specimens of low carbon steel sheets subjected to cyclic loading by experimental and finite element analysis methods. Evaluations of fatigue crack growth stages were performed by crack tip plastic strains and J integral analyses and also by microhardness measurements on process zone. According to the experimental and analytical results, fatigue crack initiation and growing stages in the spot welded CP specimens can be divided to three stages. Stage I corresponds to 'gap sharpening stage' observed at the beginning steps of cyclic loading with crack growing on the... 

    Review - Towards the two-dimensional hexagonal boron nitride (2D h-BN) electrochemical sensing platforms

    , Article Journal of the Electrochemical Society ; Volume 167, Issue 12 , 2020 Angizi, S ; Khalaj, M ; Alem, S. A. A ; Pakdel, A ; Willander, M ; Hatamie, A ; Simchi, A ; Sharif University of Technology
    IOP Publishing Ltd  2020
    Abstract
    Electrochemical sensing performance of two-dimensional hexagonal boron nitride (2D h-BN) has traditionally been suppressed by their intrinsic electrical insulation and deficient electron transportation mechanism. However, the excellent electrocatalytic activity, high specific surface area, N- and B-active edges, structural defects, adjustable band gap through interaction with other nanomaterials, and chemical functionalization, makes 2D h-BN ideal for many sensing applications. Therefore, finding a pathway to modulate the electronic properties of 2D h-BN while the intrinsic characteristics are well preserved, will evolve a new generation of highly sensitive and selective electrochemical... 

    X-ray diffraction analysis and williamson-hall method in usdm model for estimating more accurate values of stress-strain of unit cell and super cells (2 × 2 × 2) of hydroxyapatite, confirmed by ultrasonic pulse-echo test

    , Article Materials ; Volume 14, Issue 11 , 2021 ; 19961944 (ISSN) Rabiei, M ; Palevicius, A ; Dashti, A ; Nasiri, S ; Monshi, A ; Doustmohammadi, A ; Vilkauskas, A ; Janusas, G ; Sharif University of Technology
    MDPI AG  2021
    Abstract
    Taking into account X-ray diffraction, one of the well-known methods for calculating the stress-strain of crystals is Williamson-Hall (W–H). The W-H method has three models, namely (1) Uniform deformation model (UDM); (2) Uniform stress deformation model (USDM); and (3) Uniform deformation energy density model (UDEDM). The USDM and UDEDM models are directly related to the modulus of elasticity (E). Young’s modulus is a key parameter in engineering design and materials development. Young’s modulus is considered in USDM and UDEDM models, but in all previous studies, researchers used the average values of Young’s modulus or they calculated Young’s modulus only for a sharp peak of an XRD pattern... 

    Fuzzy project scheduling with discounted cash flows

    , Article Economic Computation and Economic Cybernetics Studies and Research ; Volume 5 , 2012 ; 0424267X (ISSN) Shavandi, H ; Najafi, A. A ; Moslehirad, A ; Sharif University of Technology
    2012
    Abstract
    Project scheduling to maximize the net present value of the cash flows has been a topic of recent research. These researches assume that the duration of activities is known either with certitude or at least with some probability. However, in many applications the structure of the duration of activities is imprecise. In this paper, the project scheduling problem with discounted cash flows under fuzzy environment is considered. The duration of activities are assumed triangular fuzzy numbers. The derived mathematical model is a multi-objective non-linear programming model and for solving it the Taylor expansion is used to transform the objective function to a linear form. To interpret the fuzzy... 

    Bandwidth adapted hierarchical multicast overlay

    , Article Proceedings - 5th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2010, 20 September 2010 through 25 September 2010 ; 2010 , Pages 262-267 ; 9780769541815 (ISBN) Bagheri, M ; Movaghar, A ; Khodaparast, A. A ; Sharif University of Technology
    2010
    Abstract
    As the infrastructure-centric model of peer-to-peer streaming, recent overlay construction schemes compose a hierarchical topology of peers by grouping them into clusters. There is a server in each cluster that receives data from the source and relays it to its cluster members. In this paper, we propose an alternative infrastructure-centric peer-to-peer framework called BAHMO that constructs a hierarchical multicast tree. BAHMO does not utilize server bandwidth and rely only on peer bandwidth for data transfers. It achieves both the stability of the infrastructure-centric model and the bandwidth efficiency of the fully-distributed model. Bandwidth assignment for inter-cluster data transfers... 

    FDTD analysis of distributed amplifiers based on the fully distributed model

    , Article 2007 Asia-Pacific Conference on Applied Electromagnetics, APACE2007, Melaka, 4 December 2007 through 6 December 2007 ; 2007 ; 1424414350 (ISBN); 9781424414352 (ISBN) Mirzavand, R ; Abdipour, A ; Shishegar, A. A ; Sharif University of Technology
    2007
    Abstract
    In this paper a wave approach has been introduced to study the performance of a distributed amplifier. The time domain response of a FET is obtained by means of the fully distributed model. By applying the procedure to a pi-gate GaAs MESFET, the S matrix is computed from time domain results over a frequency range of 2-20 GHz. Scattering parameters of gate and drain lines are extracted from three-dimensional FDTD simulation. The result obtained by this wave approach is compared with device lumped model and Quasi static approach of transmission line. © 2007 IEEE