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    Small-scale analysis of plates with thermoelastic damping based on the modified couple stress theory and the dual-phase-lag heat conduction model

    , Article Acta Mechanica ; Volume 229, Issue 9 , 2018 , Pages 3869-3884 ; 00015970 (ISSN) Borjalilou, V ; Asghari, M ; Sharif University of Technology
    Springer-Verlag Wien  2018
    Abstract
    Thermoelastic damping (TED) is one of the main energy dissipation mechanisms in structures with small scales. On the other hand, the classical continuum theory is not capable of describing the mechanical behavior of small-scale structures. In this paper, small-scale effects on the thermoelastic damping in microplates are studied. To this end, the coupled governing equations of motion and heat conduction are obtained based on the non-classical continuum theory of the modified couple stress and the dual-phase-lag heat conduction model. By solving these coupled equations, an explicit expression including small-scale effects for calculating TED in microplates is derived. The results are compared... 

    Universal rotation of nanowires in static uniform electric fields in viscous dielectric liquids

    , Article Applied Physics Letters ; Volume 113, Issue 6 , 2018 ; 00036951 (ISSN) Farain, K ; Esfandiar, A ; Moshfegh, A. Z ; Sharif University of Technology
    American Institute of Physics Inc  2018
    Abstract
    The wide utilization of nanomanipulation as a promising approach in microorganisms, nanoelectromechanical systems, and assembly of nanostructures remarks the importance of nanostructures' motion in electric fields. Here, we study the rotational dynamics of metallic and non-metallic nanowires (NWs) in a static uniform electric field in viscous dielectric liquids. For metallic NWs, it has been theoretically shown that the electric field-induced rotation is practically independent of the geometrical dimensions and the electrical properties of NWs. Our experimental results for suspended silver (Ag) NWs in microscope oil are perfectly in agreement with this model. However, in the case of TiO2... 

    Experimental and analytical study of block slit damper

    , Article Journal of Constructional Steel Research ; Volume 141 , February , 2018 , Pages 167-178 ; 0143974X (ISSN) Ahmadie Amiri, H ; Pournamazian Najafabadi, E ; Esmaeilpour Estekanchi, H ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    This study proposes a novel type of metallic yielding damper called block slit damper or BSD. This damper is a slit damper with very low height to thickness ratio. This device has high shear capacities, and is more economical than SSD devices with high height to thickness ratios. Based on theoretical analysis the formulation for the BSD device's main parameters is derived. Then to investigate the hysteretic behavior of the proposed devices, 5 specimens with different aspect ratios (height-width ratios) were manufactured and tested in a quasi-static manner. The tests revealed that by reducing the aspect ratios, the shear and energy dissipation capacity increases while the displacement... 

    Facile preparation of branched hierarchical ZnO nanowire arrays with enhanced photocatalytic activity: a photodegradation kinetic model

    , Article Applied Surface Science ; Volume 435 , 2018 , Pages 108-116 ; 01694332 (ISSN) Ebrahimi, M ; Yousefzadeh, S ; Samadi, M ; Dong, C ; Zhang, J ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    Branched hierarchical zinc oxide nanowires (BH-ZnO NWs) were fabricated successfully by a facile and rapid synthesis using two-step growth process. Initially, ZnO NWs have been prepared by anodizing zinc foil at room temperature and followed by annealing treatment. Then, the BH- ZnO NWs were grown on the ZnO NWs by a solution based method at very low temperature (31 oC). The BH- ZnO NWs with different aspect ratio were obtained by varying reaction time (0.5, 2, 5, 10 h). Photocatalytic activity of the samples was studied under both UV and visible light. The results indicated that the optimized BH-ZnO NWs (5 h) as a photocatalyst exhibited the highest photoactivity with about 3 times higher... 

    HPGR effect on the particle size and shape of iron ore pellet feed using response surface methodology

    , Article Mineral Processing and Extractive Metallurgy: Transactions of the Institute of Mining and Metallurgy ; Volume 127, Issue 1 , 2018 , Pages 40-48 ; 25726641 (ISSN) Abazarpoor, A ; Halali, M ; Hejazi, R ; Saghaeian, M ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    In this study the effect of HPGR operational parameters on the dimensional properties of pellet feed was examined and optimized using factorial methodology. The operational parameters considered include feed moisture, specific pressure and roll speed. For this study, size and shape of particles with Blaine number in the range 1800–2200 cm2g−1 was thoroughly investigated. It was deduced that increasing the specific pressure and decreasing the roll speed would result in reduction of D80 but would increase the Blaine number. The circularity, aspect ratio and roughness descriptors of the particles were measured by SEM micrographs and image analysis software. It was observed that particles tended... 

    Study on the effect of jets geometry in liquid atomization based on nonlinear stability analysis

    , Article ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, GT 2018, 11 June 2018 through 15 June 2018 ; Volume 4A-2018 , 2018 ; 9780791851050 (ISBN) Jafari, S ; Nehzati, T ; International Gas Turbine Institute ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2018
    Abstract
    In this paper, nonlinear instability of an elliptical jet is investigated by considering the impacts of orifice geometry variations using regular perturbation method. In the breakup mechanisms, created disturbances on the jet interfaces will grow owing to the nonlinear dynamics of fluid. In this study, a scrutiny of nonlinear cylindrical jet breakup is done initially. Next, Cosserat equations as a low order form of Navies-Stokes equations are solved on the nonlinear form to exert the impacts of orifice deformation on various aspect ratios. These nonlinear equations, Cosserat equations, are linearly solved in the past papers. As a result, the dispersion equation is derived to find the most... 

    Inertial particle focusing in serpentine channels on a centrifugal platform

    , Article Physics of Fluids ; Volume 30, Issue 1 , 2018 ; 10706631 (ISSN) Shamloo, A ; Mashhadian, A ; Sharif University of Technology
    American Institute of Physics Inc  2018
    Abstract
    Inertial particle focusing as a powerful passive method is widely used in diagnostic test devices. It is common to use a curved channel in this approach to achieve particle focusing through balancing of the secondary flow drag force and the inertial lift force. Here, we present a focusing device on a disk based on the interaction of secondary flow drag force, inertial lift force, and centrifugal forces to focus particles. By choosing a channel whose cross section has a low aspect ratio, the mixing effect of the secondary flow becomes negligible. To calculate inertial lift force, which is exerted on the particle from the fluid, the interaction between the fluid and particle is investigated... 

    Friction factor and nusselt number in annular flows with smooth and slotted surface

    , Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; 2018 ; 09477411 (ISSN) Nouri Borujerdi, A ; Erfanian Nakhchi, M ; Sharif University of Technology
    Springer Verlag  2018
    Abstract
    The purpose of this experimental work is to study the effect of slot depth to width ratio, rotational motion and inlet velocity on friction factor and Nusselt number in an annular flow between two concentric cylinders with smooth and slotted surface. The heated outer surface is stationary and the unheated inner one is rotating. This configuration is popular in industrial applications such as internal air system of gas turbine engines, cooling of rotating machinery, techniques of chemical vapor deposition and solidification of pure metals. The results show that the ratio of average slotted surface friction factor to that of the smooth one enhances by increasing the slot depth to width ratio... 

    A UHF variable gain amplifier for direct-conversion DVB-H receivers

    , Article 2009 IEEE Radio Frequency Integrated Circuits Symposium, RFIC 2009, Boston, MA, 7 June 2009 through 9 June 2009 ; 2009 , Pages 551-554 ; 15292517 (ISSN); 9781424433780 (ISBN) Meghdadi, M ; Sharif Bakhtiar, M ; Medi, A ; IEEE Microwave Theory and Techniques Society; IEEE Electron Devices Society; IEEE Solid-State Circuits Society ; Sharif University of Technology
    2009
    Abstract
    A CMOS fully differential UHF variable gain amplifier for use in a direct-conversion DVB-H receiver is presented employing input devices with variable aspect ratios. High linearity is achieved by reducing the transconductance of the input transistors for lower gain settings. It is shown that this technique has better linearity and noise performance compared to the conventional methods in which the gain reduction is performed at preceding stages. Implemented in TSMC 0.18-μm CMOS process, the inductorless RF VGA covers a voltage gain ranging from 15.5 dB to -6.5 dB with a maximum IIP3 of +24 dBm. The amplifier achieves a 3-dB bandwidth of 1.4 GHz and a minimum noise figure of 5.8 dB while... 

    Exploring contraction–expansion inertial microfluidic-based particle separation devices integrated with curved channels

    , Article AIChE Journal ; Volume 65, Issue 11 , 2019 ; 00011541 (ISSN) Shamloo, A ; Abdorahimzadeh, S ; Nasiri, R ; Sharif University of Technology
    John Wiley and Sons Inc  2019
    Abstract
    Separation of particles or cells has various applications in biotechnology, pharmaceutical and chemical industry. Inertial cell separation, in particular, has been gaining a great attention in the recent years since it has exhibited a label-free, high-throughput and efficient performance. In this work, first, an inertial contraction–expansion array microchannel device, capable of passively separating two particles with diameters of 4 and 10 μm, was numerically studied. Then, the validated model was combined with curved geometries in order to investigate the effect of curve features on the separation process. The overall purpose was to investigate the interaction between the two different... 

    Enhancing active electro-kinetic micro-mixer efficiency by introducing vertical electrodes and modifying chamber aspect ratio

    , Article Chemical Engineering and Processing - Process Intensification ; Volume 142 , 2019 ; 02552701 (ISSN) Maleki Bagherabadi, K ; Sani, M ; Saidi, M. S ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    Micro-mixers are considered as vital components of Micro Total Analysis systems (μTAS). Major objective in the design of micro-mixers is achieving high mixing quality in short mixing times. In this paper, numerical simulation of some micro-mixer designs has been carried out to understand the detailed flow pattern and thereby to propose modifications for improving mixing efficiency. It is well known that inducing convection will provide turbulent like behavior with corresponding mixing enhancement. In micro systems to drive the flow, electro-osmotic force is usually used by introducing electrodes. In this work, mixing electrodes have been implemented to induce convection and eddies. This... 

    Small-scale thermoelastic damping in micro-beams utilizing the modified couple stress theory and the dual-phase-lag heat conduction model

    , Article Journal of Thermal Stresses ; Volume 42, Issue 7 , 2019 , Pages 801-814 ; 01495739 (ISSN) Borjalilou, V ; Asghari, M ; Bagheri, E ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    In this article, the size-dependent behavior of micro-beams with the thermoelastic damping (TED) phenomenon is studied. The coupled thermoelasticity equations are derived on the basis of the modified couple stress theory (MCST) and dual-phase-lag (DPL) heat conduction model. By solving these coupled equations simultaneously, a closed-form expression for the TED parameter in micro-beams is presented which considers the small-scale effects incorporation. Then, the effect of various parameters on TED in micro-beams, such as micro-beam height, the type of material, boundary conditions, and aspect ratio is investigated. The results show that the influence of utilizing non-classical continuum and... 

    Steel plate shear walls having door openings with different arrangements of stiffeners

    , Article Advances in Structural Engineering ; Volume 22, Issue 10 , 2019 , Pages 2222-2235 ; 13694332 (ISSN) Rostami, P ; Mofid, M ; Sharif University of Technology
    SAGE Publications Inc  2019
    Abstract
    As steel plate shear walls are typically used in the building central cores around the elevators and stairs, introduction of an opening as door seems to be inevitable in steel plate shear wall spans. Due to the weakening of the steel plate shear walls’ performance caused by this particular type of opening, the use of stiffeners around the opening is necessary. Nevertheless, introduction of stiffeners around all sides of the opening, which does continue to boundary elements, is very expensive and inefficient. Therefore, the study on the effect of different arrangements of stiffeners on the behavior of steel plate shear walls is significant. In this research, a number of steel plate shear... 

    Friction factor and nusselt number in annular flows with smooth and slotted surface

    , Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 55, Issue 3 , 2019 , Pages 645-653 ; 09477411 (ISSN) Nouri Borujerdi, A ; Erfanian Nakhchi, M ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    The purpose of this experimental work is to study the effect of slot depth to width ratio, rotational motion and inlet velocity on friction factor and Nusselt number in an annular flow between two concentric cylinders with smooth and slotted surface. The heated outer surface is stationary and the unheated inner one is rotating. This configuration is popular in industrial applications such as internal air system of gas turbine engines, cooling of rotating machinery, techniques of chemical vapor deposition and solidification of pure metals. The results show that the ratio of average slotted surface friction factor to that of the smooth one enhances by increasing the slot depth to width ratio... 

    Investigation of iron ore particle size and shape on green pellet quality

    , Article Canadian Metallurgical Quarterly ; Volume 59, Issue 2 , 2020 , Pages 242-250 Abazarpoor, A ; Halali, M ; Hejazi, R ; Saghaeian, M ; Sheikh Zadeh, V ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    Particle size and shape of iron ore concentrate are effective parameters in the production of quality green pellets. In this research, the effect of particle morphology on green pellet quality was studied. It was concluded that pellet quality improved with increasing specific surface area. Drop number and green compression strength of pellets ground by HPGR were found to be superior over those ground in the ball mill. The chief reasons were related to particle shape and the fraction of fine particles. Smaller particle size results in a higher order of bonding between particles and therefore the formation of a stronger system. Also, the rougher and less circular shape of particles resulted in... 

    Effects of cone angle and length of nanopores on the resistive pulse quality

    , Article Physical Chemistry Chemical Physics ; Volume 22, Issue 43 , 2020 , Pages 25306-25314 Bakouei, M ; Abdorahimzadeh, S ; Taghipoor, M ; Sharif University of Technology
    Royal Society of Chemistry  2020
    Abstract
    Resistive pulse sensing (RPS) has proved to be a viable method for the detection and characterization of micro and nano particles. Modern fabrication methods have introduced different nanopore geometries for resistive pulse sensors. In this paper, we have numerically studied the effects of membrane thickness and the pore's cone angle, as the main geometrical parameters, on the sensing performance of the nanopores used for nanoparticle detection in the resistive pulse sensing method. To compare the sensing performance, three resistive pulse quality parameters were investigated-sensitivity, pulse duration and pulse amplitude. The thorough investigation on the relations between the geometrical... 

    An optimal architecture of magneto-plasmonic core-shell nanoparticles for potential photothermal applications

    , Article Physical Chemistry Chemical Physics ; Volume 22, Issue 25 , 2020 , Pages 14318-14328 Hadilou, N ; Souri, S ; Navid, H. A ; Sadighi Bonabi, R ; Anvari, A ; Palpant, B ; Sharif University of Technology
    Royal Society of Chemistry  2020
    Abstract
    In this work, the optical responses of Fe3O4@Au and Fe3O4@Ag are comprehensively investigated using the discrete dipole approximation. It is found that the resonance wavelength and absorption efficiency strongly depend on the composition of the core and shell, geometry of the nanoparticles, core to particle volume ratio, core radius and shell thickness. The strongest impact is due to the shell material, the shape of the nanoparticles and their combination. When the composition of the shell is changed from gold to silver, instead of one fundamental resonance peak the absorption spectrum shows two, corresponding to the bonding plasmon mode at the nanoparticle-environment interface and... 

    The effect of the second excitation frequency mode under different conditions on the fluid streaming and microparticles acoustophoresis with the aim of separating biological cells

    , Article Computer Methods and Programs in Biomedicine ; Volume 184 , 2020 Hosseini, M ; Hasani, M. A ; Biglarian, M ; Amoei, A. H ; Toghraie, D ; Mehrizi, A. A ; Rostami, S ; Sharif University of Technology
    Elsevier Ireland Ltd  2020
    Abstract
    Background and objective: In this study, the effect of the second excitation frequency mode under different conditions on the fluid streaming and its microparticles displacement is investigated. Methods: For this purpose, some variable parameters such as the particle diameter, microchannel aspect ratio, and applied frequency modes have been selected to study. The resulted acoustic streaming was scrutinized to understand the physics of the problem under different geometrical and input conditions. Finally, the effect of the increasing the microparticle size and aspect ratio of the microchannel, simultaneously, has been evaluated. Results: The results demonstrated that increasing the... 

    Composites of reduced graphene oxide/nickel submicrorods for non-enzymatic electrochemical biosensing: application to amperometric glucose detection

    , Article Journal of the Electrochemical Society ; Volume 167, Issue 8 , 2020 Mohammadzadeh, A ; Mazaheri, M ; Sedighian, A ; Ghanbari, H ; Simchi, A ; Sharif University of Technology
    Institute of Physics Publishing  2020
    Abstract
    For the rapid detection of hyperglycemia in human blood, we adopted a facile and two-step electrochemical procedure to prepare nickel/reduced graphene oxide (rGO) hybrid electrodes in the framework of a three-dimensional (3D) nanostructure. High-density and vertically-aligned nickel submicrorods with an average diameter of 155 ± 15 nm and a length of 7 ± 1 μm (an aspect ratio of about 40-50) were prepared by template-mediated electrochemical deposition techniques. Networks of rGO nanosheets between the rod-shaped arrays were formed by the cathodic electrophoretic deposition method. The synergistic effect of nickel morphology (planar and high-density rod-shaped arrays) and graphene oxide... 

    Ductile steel plate external end diaphragms for steel tub girder straight highway bridges

    , Article Earthquake Engineering and Engineering Vibration ; Volume 19, Issue 3 , July , 2020 , Pages 759-777 Maleki, S ; Dolati, A ; Sharif University of Technology
    Institute of Engineering Mechanics (IEM)  2020
    Abstract
    The end diaphragm of bridges are normally designed to resist lateral seismic forces imposed on the superstructure in earthquake prone regions. Using ductile diaphragms with high deformation capacity could reduce the seismic demands on the substructure and prevent costly damage under strong ground motions. The end diaphragms of steel tub girder bridges with high lateral stiffness and dominant shear behavior have a potential to be used as ductile fuse elements. In this study, a steel plate shear diaphragm (SPSD) is introduced as an external end diaphragm of tub girder steel bridges to reduce the seismic demands imposed on the substructure. Quasi static nonlinear analyses were conducted to...