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    Drag Reduction Using Geometrically Structured Surfaces for Non-newtonian Multi-phase Fluids

    , M.Sc. Thesis Sharif University of Technology Javaherchian, Javaneh (Author) ; Moosavi, Ali (Supervisor)
    Abstract
    With the advancement of the industry, microscale devices use due to its unique characteristics. On the other hand, it is essential to find ways to reduce drag inside microchannels because of The importance of energy. One of the methods is to optimize the contact surface using structured geometric surfaces. These hydrophobic surfaces reduce drag by trapping the air in roughness and creating a two-phase flow. The purpose of this project is to reduce the drag within the microchannel using structured geometric surfaces for non-Newtonian and multiphase flows. In most previous studies, with simplification, Newtonian and two-phase flows have been investigated. While most industrial fluids show... 

    Pressure drop reduction of power-law fluids in hydrophobic microgrooved channels

    , Article Physics of Fluids ; Volume 31, Issue 7 , 2019 ; 10706631 (ISSN) Javaherchian, J ; Moosavi, A ; Sharif University of Technology
    American Institute of Physics Inc  2019
    Abstract
    Using hydrophobic surfaces is one of the efficient methods to preserve energy in fluid transfer systems. However, the studies have been concentrated on Newtonian fluids despite the wide applications of non-Newtonian fluids in daily life and many industries such as the biological, foodstuff, chemical, petroleum, cosmetic, and lab on a chip fields. In this study, we consider power-law fluids as a typical example of non-Newtonian fluids and investigate the effect of hydrophobic microgrooves on the pressure drop in channels by utilizing the phase field method. We demonstrate that the optimum size of the rectangular microgrooves in which the maximum pressure drop reduction (PDR) happens for both... 

    Functional compartmentalization in the hemocoel of insects

    , Article Scientific Reports ; Volume 9, Issue 1 , 2019 ; 20452322 (ISSN) Pendar, H ; Aviles, J ; Adjerid, K ; Schoenewald, C ; Socha, J. J ; Sharif University of Technology
    Nature Publishing Group  2019
    Abstract
    The insect circulatory system contains an open hemocoel, in which the mechanism of hemolymph flow control is ambiguous. As a continuous fluidic structure, this cavity should exhibit pressure changes that propagate quickly. Narrow-waisted insects create sustained pressure differences across segments, but their constricted waist provides an evident mechanism for compartmentalization. Insects with no obvious constrictions between segments may be capable of functionally compartmentalizing the body, which could explain complex hemolymph flows. Here, we test the hypothesis of functional compartmentalization by measuring pressures in a beetle and recording abdominal movements. We found that the... 

    Linear index coding via graph homomorphism

    , Article Proceedings - 2014 International Conference on Control, Decision and Information Technologies, CoDIT 2014 ; 2014 , pp. 158-163 ; ISBN: 9781479967735 Ebrahimi, J. B ; Siavoshani, M. J ; Sharif University of Technology
    2014
    Abstract
    In [1], [2] it is shown that the minimum broadcast rate of a linear index code over a finite field Fq is equal to an algebraic invariant of the underlying digraph, called minrankq. In [3], it is proved that for F2 and any positive integer k, minrankq(G) ≤ k if and only if there exists a homomorphism from the complement of the graph G to the complement of a particular undirected graph family called 'graph family {Gk}'. As observed in [2], by combining these two results one can relate the linear index coding problem of undirected graphs to the graph homomorphism problem. In [4], a direct connection between linear index coding problem and graph homomorphism problem is introduced. In contrast to... 

    Emerging OCDMA communication systems and data networks [electronic resource]

    , Article Journal of Optical Networking ; Volume 6, Issue 9, 1 September 2007, Pages 1138-1178 Salehi, J. A ; Sharif University Of Technology
    Abstract
    I present an in-depth review of the trends and the directions taken by researchers worldwide in optical code-division multiple-access (OCDMA) systems. I highlight those trends and features that I believe are essential to the successful introduction of various OCDMA techniques in communication systems and data networks in the near future. In particular I begin by giving a comprehensive review of the construction of optical orthogonal codes (OOCs). Specifically I discuss the recently developed algorithms that are based on matrix algebra, which simplify and enhance the efficiencies of algorithms in OOC generation. In communication systems studies I first focus on and discuss various OCDMA... 

    Network delay analysis of a (σ, ρ) - Regular traffic stream over multiple paths in a network of fair-queuing servers

    , Article 2013 Iran Workshop on Communication and Information Theory ; May , 2013 , Page(s): 1 - 6 ; 9781467350235 (ISBN) Ashar, J. K ; Golestani, S. J ; Sharif University of Technology
    2013
    Abstract
    In this paper, we analyze the worst-case delay performance of a network of fair queuing servers in case of multiple-paths between source-destination pairs. In order to develop worst-case delay analysis for the multiple-path scenario, two challenging events should be addressed: merging different sub-streams of a session as well as distributing a traffic stream among different paths (traffic partitioning). Specifically, we propose to merge incoming sub-streams of a session to a node according to a limited rate Fair Queuing (FQ) scheme. Although the merged stream is treated as a unity, this approach results in a guaranteed level of service to each sub-stream. In addition, an algorithm is... 

    Effects of tool rake angle and tool nose radius on surface quality of ultraprecision diamond-turned porous silicon

    , Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 321-331 ; 15266125 (ISSN) Heidari, M ; Akbari, J ; Yan, J ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the... 

    Effects of tool rake angle and tool nose radius on surface quality of ultraprecision diamond-turned porous silicon

    , Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 321-331 ; 15266125 (ISSN) Heidari, M ; Akbari, J ; Yan, J ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the... 

    Precipitate strengthening of pyramidal slip in Mg–Zn alloys

    , Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) Alizadeh, R ; Wang, J ; LLorca, J ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V  

    Precipitate strengthening of pyramidal slip in Mg–Zn alloys

    , Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) Alizadeh, R ; Wang, J ; LLorca, J ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V  

    Comparative study on the microstructures and properties of wire+arc additively manufactured 5356 aluminium alloy with argon and nitrogen as the shielding gas

    , Article Additive Manufacturing ; Volume 34 , August , 2020 Li, S ; Zhang, L. J ; Ning, J ; Wang, X ; Zhang, G. F ; Zhang, J. X ; Na, S. J ; Fatemeh, B ; Sharif University of Technology
    Elsevier B. V  2020
    Abstract
    This research explored the influences of shielding gases on the appearance of weld beads and the microstructures and mechanical properties of thin-wall samples using conventional gas metal arc welding as the heat source by using 5356 aluminium alloy welding wire as the raw materials and nitrogen (N2) and argon (Ar) as the shielding gases. The results showed that under the same parameters and after mono-layer single-bead welding was performed using N2 as the shielding gas, the bead height was higher, the bead width was narrower, and the penetration depth was shallower. The grain size of the thin-wall sample protected by N2 was 43.5–47.8 % smaller than that obtained under Ar protection.... 

    Solid products characterization in a multi-step mineralization process

    , Article Chemical Engineering Journal ; Vol. 252 , 2014 , Pages 210-219 ; ISSN: 13858947 Hemmati, A ; Shayegan, J ; Sharratt, P ; Yeo, T. Y ; Bu, J
    2014
    Abstract
    In this paper, we describe a carbon dioxide mineralization process and its associated solid products. These solid products include amorphous silica, iron hydroxides and magnesium carbonates. These products were subjected to various characterization tests, and the results are published here. It was found that the iron hydroxides from this process can have different crystalline properties, and their formation depended very much on the pH of the reaction conditions. Different forms of magnesium carbonate were also obtained, and the type of carbonate precipitated was found to be dependent on the carbonation temperature. Hydromagnesite was obtained mainly at low temperatures, while dypingite was... 

    Experimental and numerical investigation of pulse-shaped split Hopkinson pressure bar test

    , Article Materials Science and Engineering A ; Volume 539 , 2012 , Pages 285-293 ; 09215093 (ISSN) Naghdabadi, R ; Ashrafi, M. J ; Arghavani, J ; Sharif University of Technology
    2012
    Abstract
    Employing a proper pulse shaper in the conventional split Hopkinson pressure bar (SHPB) test helps to achieve dynamic equilibrium condition and to fulfill a constant strain rate condition in the test specimen. To this end, the parameters affecting the incident pulse shape, i.e., pulse shaper thickness, pulse shaper diameter, striker bar length and striker bar velocity are experimentally studied. Moreover, simulation results, validated by experimental data together with wave propagation analysis, are exploited to provide general guidelines to properly design a pulse shaper. It is recommended to use a relatively large diameter pulse shaper for testing work-hardening materials. Also, for... 

    Investigating and modeling the cleaning-in-place process for retrieving the membrane permeate flux: Case study of hydrophilic polyethersulfone (PES)

    , Article Journal of the Taiwan Institute of Chemical Engineers ; Volume 62 , May , 2016 , Pages 150–157 ; 18761070 (ISSN) Hedayati Moghaddam, A ; Shayegan, J ; Sargolzaei, J ; Sharif University of Technology
    Taiwan Institute of Chemical Engineers  2016
    Abstract
    In this work the effects of backwash pressure, duration of acid and sodium hydroxide backwashing, sodium hydroxide concentration, and the duration of forward washing on performance of permeate flux recovery (PFR) were investigated. A two-level fractional factorial design (FFD) was used to design the experiments. The ability of back propagation neural network (BPNN) and radial basis function neural network (RBFNN) in predicting the performance of cleaning-in-place (CIP) of hydrophilic polyethersulfone (PES) membrane were investigated. It is found that BPNN has better ability in predicting the PFR performance than RBFNN. The best architecture of BPNN was a network consisting of 1 hidden layer... 

    Development of DESHIMA: A redshift machine based on a superconducting on-chip filterbank

    , Article Proceedings of SPIE - The International Society for Optical Engineering ; Volume 8452 , 2012 ; 0277786X (ISSN) ; 9780819491534 (ISBN) Endo, A ; Baselmans, J. J. A ; Van Der Werf, P. P ; Knoors, B ; Javadzadeh, S. M. H ; Yates, S. J. C ; Thoen, D. J ; Ferrari, L ; Baryshev, A. M ; Lankwarden, Y. J. Y ; De Visser, P. J ; Janssen, R. M. J ; Klapwijk, T. M ; Sharif University of Technology
    2012
    Abstract
    Distant, dusty and extremely luminous galaxies form a key component of the high redshift universe, tracing the period of intense cosmic activity that ultimately gave rise to the present-day universe. These highly luminous galaxies, first detected in the ground-based submillimeter region, are however optically very faint, which hampers identification of the optical counterpart and the measurement of a redshift. We are developing a new direct-detection submm spectrograph DESHIMA. By taking advantage of the rapidly advancing technology of superconducting microresonators, DESHIMA will revolutionize the appearance and capabilities of a submm spectrograph. There will no longer be large grating... 

    Organic compound characterization and source apportionment of indoor and outdoor quasi-ultrafine particulate matter in retirement homes of the Los Angeles Basin

    , Article Indoor Air ; Volume 20, Issue 1 , 2010 , Pages 17-30 ; 09056947 (ISSN) Arhami, M ; Minguillón, M. C ; Polidori, A ; Schauer, J. J ; Delfino, R. J ; Sioutas, C ; Sharif University of Technology
    2010
    Abstract
    Quasi-ultrafine (quasi-UF) particulate matter (PM0.25) and its components were measured in indoor and outdoor environments at four retirement communities in Los Angeles Basin, California, as part of the Cardiovascular Health and Air Pollution Study (CHAPS). The present paper focuses on the characterization of the sources, organic constituents and indoor and outdoor relationships of quasi-UF PM. The average indoor/outdoor ratios of most of the measured polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes were close to or slightly lower than 1, and the corresponding indoor-outdoor correlation coefficients (R) were always positive and, for the most part, moderately strong (median R... 

    Sensitive spectrophotometric detection of dopamine, levodopa and adrenaline using surface plasmon resonance band of silver nanoparticles

    , Article Journal of the Iranian Chemical Society ; Volume 7, Issue SUPPL. 1 , 2010 , Pages S83-S91 ; 1735207X (ISSN) Hormozi Nezhad, M. R ; Tashkhourian, J ; Khodaveisi, J ; Sharif University of Technology
    2010
    Abstract
    A simple and effective procedure is proposed for spectrophotometric determination of catecholamines; Dopamine (1), L-Dopa (2) and Adrenaline (3). It was found that the reduction of Ag+ to silver nanoparticles (Ag-NPs) by these catecholamines in the presence of polyvinylpyrrolidone (PVP) as a stabilizing agent produced very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs allows the quantitative spectrophotometric detection of the catecholamines. The calibration curves derived from the changes in absorbance at λ = 440 nm were linear with concentration of Dopamine, Levodopa and Adrenaline in the range of 3.2×10-6- 2.0x10-5 M, 1.6x10-7 - 1.0×10-5 M,... 

    Detection of top-K central nodes in social networks: A compressive sensing approach

    , Article Proceedings of the 2015 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining, ASONAM 2015, 25 August 2015 through 28 August 2015 ; 2015 , Pages 902-909 ; 9781450338547 (ISBN) Mahyar, H ; Pei, J ; Tang, J ; Silvestri, F ; Sharif University of Technology
    Association for Computing Machinery, Inc  2015
    Abstract
    In analysing the structural organization of a social network, identifying important nodes has been a fundamental problem. The concept of network centrality deals with the assessment of the relative importance of a particular node within the network. Most of the traditional network centrality definitions have a high computational cost and require full knowledge of network topological structure. On the one hand, in many applications we are only interested in detecting the top-k central nodes of the network with the largest values considering a specific centrality metric. On the other hand, it is not feasible to efficiently identify central nodes in a large real-world social network via... 

    Bounds for the Huckel energy of a graph

    , Article Electronic Journal of Combinatorics ; Volume 16, Issue 1 R , 2009 ; 10778926 (ISSN) Ghorbani, E ; Koolen, J. H ; Yang, J. Y ; Sharif University of Technology
    2009
    Abstract
    Let G be a graph on n vertices with r := [n/2] and let γ 1 ≥ · · · ≥ γ n be adjacency eigenvalues of G. Then the Ḧuckel energy of G, HE(G), is defined as [Equation presented] The concept of Hückel energy was introduced by Coulson as it gives a good approximation for the π-electron energy of molecular graphs. We obtain two upper bounds and a lower bound for HE(G). When n is even, it is shown that equality holds in both upper bounds if and only if G is a strongly regular graph with parameters (n, k, γ, μ) = (4t2 + 4t + 2, 2t2 + 3t + 1, t2 + 2t, t2 + 2t + 1), for positive integer t. Furthermore, we will give an infinite family of these strongly regular graph whose construction was communicated... 

    Nonlinear ultrasound propagation through layered liquid and tissue-equivalent media: Computational and experimental results at high frequency

    , Article Physics in Medicine and Biology ; Volume 51, Issue 22 , 2006 , Pages 5809-5824 ; 00319155 (ISSN) Williams, R ; Cherin, E ; Lam, T. Y. J ; Tavakkoli, J ; Zemp, R. J ; Foster, F. S ; Sharif University of Technology
    2006
    Abstract
    Nonlinear propagation has been demonstrated to have a significant impact on ultrasound imaging. An efficient computational algorithm is presented to simulate nonlinear ultrasound propagation through layered liquid and tissue-equivalent media. Results are compared with hydrophone measurements. This study was undertaken to investigate the role of nonlinear propagation in high frequency ultrasound micro-imaging. The acoustic field of a focused transducer (20 MHz centre frequency, f-number 2.5) was simulated for layered media consisting of water and tissue-mimicking phantom, for several wide-bandwidth source pulses. The simulation model accounted for the effects of diffraction, attenuation and...