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    Parametric study on mixing process in an in-plane spiral micromixer utilizing chaotic advection

    , Article Analytica Chimica Acta ; Volume 1022 , 2018 , Pages 96-105 ; 00032670 (ISSN) Vatankhah, P ; Shamloo, A ; Sharif University of Technology
    Abstract
    Recent advances in the field of microfabrication have made the application of high-throughput microfluidics feasible. Mixing which is an essential part of any miniaturized standalone system remains the key challenge. This paper proposes a geometrically simple micromixer for efficient mixing for high-throughput microfluidic devices. The proposed micromixer utilizes a curved microchannel (spiral microchannel) to induce chaotic advection and enhance the mixing process. It is shown that the spiral microchannel is more efficient in comparison to a straight microchannel, mixing wise. The pressure drop in the spiral microchannel is only slightly higher than that in the straight microchannel. It is... 

    The laser-assisted field effect transistor gas sensor based on morphological zinc-excited tin-doped in2o3 nanowires

    , Article Surface Review and Letters ; Volume 24, Issue 8 , 2017 ; 0218625X (ISSN) Shariati, M ; Khosravinejad, F ; Sharif University of Technology
    Abstract
    The gas nanosensor of indium oxide nanowires in laser assisted approach, doped with tin and zinc for gas sensing and 1D growth purposes respectively, was reported. The nanowires were very sensitive to H2S gas in low concentration of 20 ppb gas at room temperature. The fast dynamic intensive and sensitive response to gas was in a few seconds with an on/off sensitivity ratio of around 10. The square cross-section indium oxide nanowires were fabricated through physical vapor deposition (PVD) mechanism and annealing approach. The field emission scanning electron microscopy (FESEM) observations indicated that the annealing temperature was vital in nanostructures' morphology. The fabricated... 

    Wideband and polarisation-independent antireflection coating using metamaterials

    , Article IET Optoelectronics ; Volume 14, Issue 5 , 2020 , Pages 266-273 Sepehripour, F ; Karimi, P ; Khavasi, A ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    Abstract
    Here, the authors propose a new approach for realising wideband and polarisation-independent antireflection coating, based on a metamaterial composed of a subwavelength array of metallic pillars with a square cross-section. The effective impedance of the array can be duly adjusted by the size and distance of the pillars. As such, the authors design the effective impedance of the antireflection coating to be the geometrical mean of the impedance of upper and lower media and choose its height to be quarter of operating wavelength. Doing so, the reflection vanishes at the desired frequency and fractional bandwidth of 56% is achieved with a criterion of 10% reflectance (the refractive index of... 

    Shear-rate-dependent rheology effects on mass transport and surface reactions in biomicrofluidic devices

    , Article AIChE Journal ; Volume 61, Issue 6 , 2015 , Pages 1912-1924 ; 00011541 (ISSN) Sadeghi, A ; Amini, Y ; Saidi, M. H ; Yavari, H ; Sharif University of Technology
    John Wiley and Sons Inc  2015
    Abstract
    Consideration is given to shear-rate-dependent rheology effects on mass transport in a heterogeneous microreactor of rectangular cross section, utilizing both numerical and analytical approaches. The carrier liquid obeys the power-law viscosity model and is actuated primarily by an electrokinetic pumping mechanism. It is discovered that, considering the shear-thinning biofluids to be Newtonian fluids gives rise to an overestimation of the saturation time. The degree of overestimation is higher in the presence of large Damkohler numbers and electric double layer thicknesses. It is also increased by the application of a favorable pressure gradient, whereas the opposite is true when an opposed... 

    System and method for analysis of involving factors in the demisting cyclone efficiency

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), San Diego, CA ; Volume 15 , November , 2013 ; 9780791856444 (ISBN) Najafabadi, M. M ; Ehteram, M. A ; Ahmadian, M. T ; Barari, A ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Abstract
    In this study a system for real-time analysis of some involving factors in the efficiency of gas-liquid separators is developed based on the weighing method. An ultrasonic atomizer generates water drops in a size range of 1-10 μm with the same frequency during the test. A cyclone separator is selected and effect of the developing flow rate and shape of the mini-riser as a part of connecting assembly to the cyclone separator is investigated. Further an efficient electrostatic precipitator (ESP) with outcome of single-phase airflow is employed in the downstream of the cyclone to separate remaining droplets and produce the same pressure loss during the test. Circular, triangular, rectangular... 

    Numerical study of external flow over ducts with various cross-sections

    , Article Defect and Diffusion Forum ; Volume 366 , 2016 , Pages 10-16 ; 10120386 (ISSN) Maleki, E ; Sadrhosseini, H ; Sharif University of Technology
    Trans Tech Publications Ltd 
    Abstract
    In this article a comprehensive numerical study is performed to compare the effect of fluid flow across a duct with various cross sectional shapes and with different velocities of the flow. Circular, elliptical and rectangular cross sections have been chosen for the ducts and air flows across them with four values of low Reynolds numbers in the range of Re = 1 to Re = 1000. Continuity and momentum equations with proper boundary conditions are solved in two dimensions. Streamlines, pressure distribution and Velocity profiles are obtained and creation of vortices, boundary layers, separation region, wake region, reattachment point and stagnation points are studied in detail and the results are...