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    3D numerical investigation of the effects of driving of the new mechanized tunnel on existing segmental linings and ground surface settlements - a case study: Shiraz metro line 2

    , Article International Journal of Geotechnical Engineering ; 2020 Pirastehfar, K ; Shivaei, S ; Sadaghiani, M. H ; Nikooee, E ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors... 

    Effect of nanoclays on the mechanical properties and durability of novolac phenolic resin/woven glass fiber composite at various chemical environments

    , Article Composites Part A: Applied Science and Manufacturing ; Vol. 63 , 2014 , pp. 149-158 ; ISSN: 1359835X Eesaee, M ; Shojaei, A ; Sharif University of Technology
    Abstract
    Both natural montmorilonite (CN) and organically modified montmorilonite (CB) improved significantly the mechanical performance of novolac phenolic resin (PF)/woven glass-fiber (GF) composites due to their nanodispersion and good interfacial interaction with the matrix. It was revealed that the incorporation of 2.5 wt% of the clays enhances the elastic modulus up to 38% for CN and 43% for CB. Aging of PF/GF composites at various aqueous solutions, i.e. water, brine and acidic environments, increased stiffness of the composite (∼100-250% increase in elastic modulus) due to possible secondary crosslinking caused by water molecules and hydroxyl groups of PF resin. However, aging led to the... 

    Bridged single-walled carbon nanotube-based atomic-scale mass sensors

    , Article Applied Physics A: Materials Science and Processing ; Volume 122, Issue 8 , Volume 122, Issue 8 , 2016 ; 09478396 (ISSN) Ali Akbari, H. R ; Shaat, M ; Abdelkefi, A ; Sharif University of Technology
    Springer Verlag 
    Abstract
    The potentials of carbon nanotubes (CNTs) as mechanical resonators for atomic-scale mass sensing are presented. To this aim, a nonlocal continuum-based model is proposed to study the dynamic behavior of bridged single-walled carbon nanotube-based mass nanosensors. The carbon nanotube (CNT) is considered as an elastic Euler–Bernoulli beam with von Kármán type geometric nonlinearity. Eringen’s nonlocal elastic field theory is utilized to model the interatomic long-range interactions within the structure of the CNT. This developed model accounts for the arbitrary position of the deposited atomic-mass. The natural frequencies and associated mode shapes are determined based on an eigenvalue... 

    Ionic interdiffusion as interaction mechanism between Al and Si3N4

    , Article Journal of the American Ceramic Society ; Volume 102, Issue 8 , 2019 , Pages 4835-4847 ; 00027820 (ISSN) Adabifiroozjaei, E ; Koshy, P ; Emadi, F ; Mofarah, S. S ; Ma, H ; Rastkerdar, E ; Lim, S ; Webster, R. F ; Mitchell, D. R. G ; Sorrell, C. C ; Sharif University of Technology
    Blackwell Publishing Inc  2019
    Abstract
    Al-Si3N4 couples were heat-treated at 850-1150°C for 250 hours. The thickness of the interacted area was measured by scanning electron microscopy (SEM) and scanning/transmission electron microscopy (TEM/STEM). The interaction rate increases exponentially with inverse temperature, with an activation energy of 194.23 kJ/mol and diffusion pre-coefficient of 5 × 10−9 m2/s, indicating that the interaction is diffusion-dependent. As the results showed, the interfacial area is comprised of Al alloy channels, Si precipitates, and AlN grains. Al-Si transfer through the solid solution (Si3-xAlxN4-y) at the interface of Al alloy and β-Si3N4 grains controls the kinetic of the interaction. When... 

    Chitosan interphase around nanodiamond: Insight from equilibrium molecular dynamics

    , Article Diamond and Related Materials ; Volume 104 , 2020 Aranifard, S ; Shojaei, A ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    In the context of nanodiamond/chitosan (ND/CS) nanocomposites and utilizing atomistic molecular dynamics, the interaction mechanism of adsorbed CS layer around a model ND has been investigated at three level of hydration: in bulk of water, water as a droplet, and completely dry condition. The effect of amination and carboxylation of ND has been studied. To ensure that the comparison of these model systems is meaningful (energetically and geometrically), the CS interphases around NDs were characterized through holistic concentration profiles and density distribution maps. Our results revealed that in a completely dry condition or hydrated by a molecularly small droplet, both of the... 

    Gamma irradiated electro-conductive polylactic acid/polyaniline nanofibers

    , Article Synthetic Metals ; Volume 259 , 2020 Ashraf, S. S ; Frounchi, M ; Dadbin, S ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    In this study, polyaniline nanoparticles (PANI NPs) in emeraldine base (EB) form were prepared by a modified method and characterized by FTIR and UV–vis spectroscopies. The average size of the nanoparticles was 140 nm measured by DLS method. The nanoparticles were embedded into polylactic acid (PLA) nanofibers prepared by electrospinning method. It was found that inclusion of PANI NPs in PLA resulted in reduced diameter of the fibers during the electrospinning process. Also, the surface of nanofibers appeared smooth in FE-SEM images without formation of beads. Improvement in mechanical and electrical properties of PLA/PANI nanofibers over the neat PLA nanofibers implied a good dispersion of... 

    3D numerical investigation of the effects of driving of the new mechanized tunnel on existing segmental linings and ground surface settlements - a case study: Shiraz metro line 2

    , Article International Journal of Geotechnical Engineering ; Volume 16, Issue 7 , 2022 , Pages 878-889 ; 19386362 (ISSN) Pirastehfar, K ; Shivaei, S ; Sadaghiani, M. H ; Nikooee, E ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors... 

    Introducing shell formation and a thermodynamics-inspired concept for swarm robotic systems

    , Article Robotics and Autonomous Systems ; Volume 148 , 2022 ; 09218890 (ISSN) Parrany, A. M ; Alasty, A ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    In this article, a new formation for swarm robotic systems is introduced. This formation, which is made up of a portion of swarm members and encircles the whole swarm, is called the shell formation. In this regard, an effective algorithm for developing the shell formation in swarm robotic systems is established. The interaction mechanism among swarm agents is based on the method of artificial potential fields and the local rule of the nearest neighbor. Subsequently, inspired by the thermodynamic science and based on the introduced shell formation, the thermodynamic concept of pressure is generalized to swarm robotic systems. Finally, the efficacy of the introduced shell formation in solving... 

    A mechanical model for morphological response of endothelial cells under combined wall shear stress and cyclic stretch loadings

    , Article Biomechanics and Modeling in Mechanobiology ; Volume 15, Issue 5 , 2016 , Pages 1229-1243 ; 16177959 (ISSN) Pakravan, H. A ; Saidi, M. S ; Firoozabadi, B ; Sharif University of Technology
    Springer Verlag 
    Abstract
    The shape and morphology of endothelial cells (ECs) lining the blood vessels are a good indicator for atheroprone and atheroprotected sites. ECs of blood vessels experience both wall shear stress (WSS) and cyclic stretch (CS). These mechanical stimuli influence the shape and morphology of ECs. A few models have been proposed for predicting the morphology of ECs under WSS or CS. In the present study, a mathematical cell population model is developed to simulate the morphology of ECs under combined WSS and CS conditions. The model considers the cytoskeletal filaments, cell–cell interactions, and cell–extracellular matrix interactions. In addition, the reorientation and polymerization of... 

    Dynamic stability analysis of single walled carbon nanocone conveying fluid

    , Article Computational Materials Science ; Volume 113 , 2016 , Pages 123-132 ; 09270256 (ISSN) Rasouli Gandomani, M ; Noorian, M. A ; Haddadpour, H ; Fotouhi, M. M ; Sharif University of Technology
    Elsevier  2016
    Abstract
    This report aims the study of dynamic stability of single walled carbon nanocone for some axial length conditions and declination angles of 60°, 120°and 240°. For dynamic stability analysis of Single Walled Carbon Nanocone (SWCNC), the mode shapes and frequencies of the carbon nanocone are extracted using the molecular mechanics approach. The mechanical properties of SWCNC were obtained by the Molecular Mechanics (MM) method. The obtained parameters are used for extraction of the conical shell virtual model of nanocone with the same dimensions. The equations of coupled fluid-structural dynamics of SWCNC are derived using the modal expansion for the structural displacements of the conical... 

    Optimizing the mechanical and physical properties of thermoplastic starch via tuning the molecular microstructure through co-plasticization by sorbitol and glycerol

    , Article Polymer International ; Volume 66, Issue 6 , 2017 , Pages 809-819 ; 09598103 (ISSN) Esmaeili, M ; Pircheraghi, G ; Bagheri, R ; Sharif University of Technology
    John Wiley and Sons Ltd  2017
    Abstract
    Nowadays, environmental hazards caused by plastic wastes are a major concern in academia and industry. Utilization of biodegradable polymers derived from renewable sources for replacing common petroleum-based plastics is a potential solution for reducing the problem. In this regard, starch has become one of the most promising alternatives to non-biodegradable polymers for depleting plastic waste thanks to its low expense, abundance, renewability and biodegradability. However, the main drawbacks of starch are its poor processability, weak mechanical properties and severe hydrophilicity. In this work, thermoplastic starch (TPS) samples have been prepared using glycerol and sorbitol as... 

    3D numerical investigation of the coupled interaction behavior between mechanized twin tunnels and groundwater – A case study: Shiraz metro line 2

    , Article Tunnelling and Underground Space Technology ; Volume 103 , 2020 Shivaei, S ; Hataf, N ; Pirastehfar, K ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Mechanized tunneling method using Tunnel Boring Machine (TBM) is being extensively employed in urban areas, especially when excavation takes place underneath the groundwater table. In this study, three-dimensional coupled Finite Element Analyses (FEA) have been performed to investigate the interaction mechanism between mechanized twin tunnels construction of Shiraz metro (line 2) and groundwater. Firstly, two soil constitutive models (Mohr-Coulomb and Modified Cam-Clay model) of Shiraz lean clay are validated against drained triaxial compression test data. Varying the permeability of the grout layer within the specified range, the base numerical model is then calibrated by the field data of... 

    How does the central nervous system address the kinetic redundancy in the lumbar spine? Three-dimensional isometric exertions with 18 Hill-model-based muscle fascicles at the L4-L5 level

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 224, Issue 3 , 2010 , Pages 487-501 ; 09544119 (ISSN) Rashedi, E ; Khalaf, K ; Nassajian, M. R ; Nasseroleslami, B ; Parnianpour, M ; Sharif University of Technology
    2010
    Abstract
    The human motor system is organized for execution of various motor tasks in a different and flexible manner. The kinetic redundancy in the human musculoskeletal system is a significant property by which the central nervous system achieves many complementary goals. An equilibrium-based biomechanical model of isometric three-dimensional exertions of trunk muscles has been developed. Following the definition and role of the uncontrolled manifold, the kinetic redundancy concept is explored in mathematical terms. The null space of the kinetically redundant system when a certain joint moment and/or stiffness are needed is derived and discussed. The aforementioned concepts have been illustrated,...