Search for: mechanical-stability
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    Reliability Analysis of MSE Wall

    , M.Sc. Thesis Sharif University of Technology Pahlavani, Helda (Author) ; Toufigh, Vahab (Supervisor)
    This study investigates the reliability analysis of mechanically stabilized earth (MSE) wall and takes into account the uncertainty associated in the mechanical properties of soil and geogrid, the magnetude of surcharge load and the soil-geosynthetic interface friction angle. In addition, the effect of number, length and place of the geogrid layers on the performance of this wall has been evaluated. The failure modes related to external stability, internal stability and horizontal displacement of the wall were considerd. In order to determine the probabilistic characteristics and the probability distribution function of soil and soil-geosynthetic interface friction angle, direct shear test... 

    Boundary stabilization of non-classical micro-scale beams

    , Article Applied Mathematical Modelling ; Volume 37, Issue 20-21 , 2013 , Pages 8709-8724 ; 0307904X (ISSN) Vatankhah, R ; Najafi, A ; Salarieh, H ; Alasty, A ; Sharif University of Technology
    In this paper, the problem of boundary stabilization of a vibrating non-classical micro-scale Euler-Bernoulli beam is considered. In non-classical micro-beams, the governing Partial Differential Equation (PDE) of motion is obtained based on the non-classical continuum mechanics which introduces material length scale parameters. In this research, linear boundary control laws are constructed to stabilize the free vibration of non-classical micro-beams which its governing PDE is derived based on the modified strain gradient theory as one of the most inclusive non-classical continuum theories. Well-posedness and asymptotic stabilization of the closed loop system are investigated for both cases... 

    Toward multiscale modeling of wave propagation in arteries

    , Article Journal of Mechanics in Medicine and Biology ; Volume 16, Issue 3 , 2016 ; 02195194 (ISSN) Raustin, R ; Mohammadi, H ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd 
    In this study, we apply a novel numerical technique for modeling the propagation of mechanical wave in the human arteries using the multiscale method. We define a particle region characterized by molecular dynamics (MD) method which is surrounded by a continuous region characterized by a finite element (FE) method. The interface between the two models are defined so as to minimize spurious reflections at the interface. This is a preliminary work for the modeling of the mechanical stability of atherosclerosis plaques using multiscale method. The model offered has extensive application in cell mechanics  

    Multi-porous Co3O4 nanoflakes @ sponge-like few-layer partially reduced graphene oxide hybrids: towards highly stable asymmetric supercapacitors

    , Article Journal of Materials Chemistry A ; Volume 5, Issue 24 , 2017 , Pages 12569-12577 ; 20507488 (ISSN) Qorbani, M ; Chou, T. C ; Lee, Y. H ; Samireddi, S ; Naseri, N ; Ganguly, A ; Esfandiar, A ; Wang, C. H ; Chen, L. C ; Chen, K. H ; Moshfegh, A. Z ; Sharif University of Technology
    The controlled growth of metal oxide nanostructures within hierarchically porous conductive carbon-based frameworks is critically important to achieving high volumetric performance and appropriate channel size for energy storage applications. Herein, we grow cobalt oxide (Co3O4) nanoflakes, using a sequential-electrodeposition process, into spherically porous sponge-like few-layer partially reduced graphene oxide (SrGO) synthesized by template-directed ordered assembly. Maximum specific/volumetric capacitances of 1112 F gCo3O4-1 (at 3.3 A gCo3O4-1), 178 F cm-3 (at 2.6 A cm-2), and 406 F gtotal-1 (at 1 A gtotal-1) and sensible rate capability (80% retention by increasing the charge/discharge... 

    High-Performance, flexible, all-solid-state wire-shaped asymmetric micro-supercapacitors based on three dimensional CoNi2S4 nanosheets decorated-nanoporous Ni-Zn-P Film/Cu wire

    , Article Journal of Physical Chemistry C ; Volume 123, Issue 35 , 2019 , Pages 21353-21366 ; 19327447 (ISSN) Shahrokhian, S ; Naderi, L ; Sharif University of Technology
    American Chemical Society  2019
    Demand increasing for next generation portable and miniaturized electronics has aroused much interest to explore microscale and lightweight energy storage devices. Herein, we demonstrate successful development of flexible wire-shaped micro-supercapacitors (micro-SCs) based on novel CoNi2S4/E-NZP film@Cu wire electrode. The etched Ni-Zn-P (E-NZP) film was synthesized by directly deposition of NZP film on Cu wire, followed by a chemical etching process. Alkaline etching treatment provides a micro- and mesoporous structure with high surface area and facilitates the penetration of electrolyte ions into the electrode matrix. Then, CoNi2S4 nanosheets as electroactive material are electrochemically... 

    Trunk dynamic stability assessment for individuals with and without nonspecific low back pain during repetitive movement

    , Article Human Factors ; 2020 Asgari, M ; Mokhtarinia, H. R ; Sanjari, M. A ; Kahrizi, S ; Philip, G. C ; Parnianpour, M ; Khalaf, K ; Sharif University of Technology
    SAGE Publications Inc  2020
    Objective: This study aimed to employ nonlinear dynamic approaches to assess trunk dynamic stability with speed, symmetry, and load during repetitive flexion-extension (FE) movements for individuals with and without nonspecific low back pain (NSLBP). Background: Repetitive trunk FE movement is a typical work-related LBP risk factor contingent on speed, symmetry, and load. Improper settings/adjustments of these control parameters could undermine the dynamic stability of the trunk, hence leading to low back injuries. The underlying stability mechanisms and associated control impairments during such dynamic movements remain elusive. Method: Thirty-eight male volunteers (19 healthy, 19 NSLBP)... 

    Construction of a ternary nanocomposite, polypyrrole/fe-co sulfide-reduced graphene oxide/nickel foam, as a novel binder-free electrode for high-performance asymmetric supercapacitors

    , Article Journal of Physical Chemistry C ; Volume 124, Issue 8 , 2020 , Pages 4393-4407 Karimi, A ; Kazeminezhad, I ; Naderi, L ; Shahrokhian, S ; Sharif University of Technology
    American Chemical Society  2020
    The development of asymmetric supercapacitors requires the design of electrode construction and the utilization of new electroactive materials. In this regard, an effective strategy is the loading of active materials on an integrated 3D porous graphene-based substrate such as graphene foam (GF). Herein, we successfully designed and fabricated a novel ternary binder-free nanocomposite consisting of polypyrrole, Fe-Co sulfide, and reduced graphene oxide on a nickel foam electrode (PPy/FeCoS-rGO/NF) via a facile, cost-effective, and powerful electrodeposition method for application in high-performance asymmetric supercapacitors. The monolithic 3D porous graphene foam (GF) obtained by the facile... 

    Comparing half-metallic, MOKE, and thermoelectric behavior of the CrTiZ (Z = As, P) half-Heuslers: A DFT study

    , Article Materials Research Express ; Volume 8, Issue 4 , 2021 ; 20531591 (ISSN) Sadeghi, M ; Zelati, A ; Boochani, A ; Arman, A ; Mirzaei, S ; Sharif University of Technology
    IOP Publishing Ltd  2021
    Structural, half-metallic, magneto-optic, and thermoelectric properties of CrTiZ (Z = As, P) half-Heusleres compounds are investigated based on density functional theory. These compounds have mechanical stability in the ferromagnetic state with a high bulk modulus. They are often half-metallic with a large and integer magnetic moment and are very attractive in spintronics, magneto-optics applications. The magnetic moments of CrTiAs and CrTiP were 2.9865 μB and 3.00 μB, respectively, which were attributed to their ferromagnetic phase. Additionally, the positive sign of the phonon branches indicates the dynamic stability of these compounds. Applying both GGA and mBJ approximations, CrTiAs and... 

    Friction Stir Welding of Severely Deformed Aluminum Using Hybrid Powders

    , M.Sc. Thesis Sharif University of Technology Moosavi, Ezzatollah (Author) ; Movahedi, Mojtaba (Supervisor) ; Kazeminezhad, Mohsen (Supervisor)
    Severe plastic deformation (SPD) is an ideal approach to fabricate light-weight alloys, such as aluminum alloys, with ultrafine-grained (UFG) structure up to nano-scale. Thus, it is known as a process that boosts the strength of materials. This method is also adopted to enhance the specific strength of materials, which is essential in the transportation and aerospace industries. Because of limitations like load capacity, and as a result, low-size productions, it is not possible to use them in industries. A practical solution is to join the productions and fabricate them on bigger scales. Welding of SPDed materials by employing solid-state welding techniques is appropriate for joining UFG... 

    Seismic Performance Evaluation of MSE Wall Reinforced with Geotextile

    , M.Sc. Thesis Sharif University of Technology Salehi, Sina (Author) ; Toufigh, Vahab (Supervisor)
    This study aims to evaluate the seismic behavior of geotextile-reinforced soil retaining walls by using incremental dynamic analysis and endurance time analysis methods. Five different wall models with variables of length and the modulus of elasticity of reinforcements have been constructed in the ABAQUS finite element software. In this study, the soil behavior and the interaction between the soil and reinforcement are modeled using a fully plastic linear elastic behavior model based on the Mohr-Coulomb yield criterion. Despite reinforced retaining walls' numerous benefits and extensive use, there is an obvious need for more precise design and a better knowledge of these structures' static... 

    Fabrication of granulated NaY zeolite nanoparticles using a new method and study the adsorption properties

    , Article Powder Technology ; Volume 231 , November , 2012 , Pages 1-6 ; 00325910 (ISSN) Charkhi, A ; Kazemeini, M ; Ahmadi, S. J ; Kazemian, H ; Sharif University of Technology
    NaY zeolite nanoparticles were synthesized and shaped into the uniform spherical granules using a developed novel and simple two-step granulation technique. First, the alginate/nanozeolite or alginate/nanozeolite-bentonite spherical hybrid was successfully fabricated, and then the alginate was decomposed by calcinations resulting uniform spherical granules. To improve the mechanical stability of the prepared granules, bentonite was added as an inorganic binder at different ratios of 20wt.% to 40wt.%. Moreover, the effect of binder on the ion exchange properties of the prepared granules was studied. Increasing of binder content from 20wt.% to 40wt.% linearly enhanced the mechanical stability... 

    Chemically modified organic/inorganic nanoporous composite particles for the adsorption of reactive black 5 from aqueous solution

    , Article Reactive and Functional Polymers ; Volume 86 , 2015 , Pages 7-15 ; 13815148 (ISSN) Nematollahzadeh, A ; Shojaei, A ; Karimi, M ; Sharif University of Technology
    Elsevier  2015
    In the present work, we report a chemically modified polyacrylamide/silica nanoporous composite adsorbent for the removal of reactive black 5 (RB5) azo dye from aqueous solutions. The composite adsorbent was synthesized in a packed bed and modified by ethylenediamine (EDA). The adsorbent was characterized by Fourier transformation infrared (FT-IR), thermogravimetric analysis (TGA), thermoporometry, Brunauer, Emmett and Teller (BET) method and scanning electron microscopy (SEM). Mechanical stability of the adsorbent was examined in a packed bed by following the back-pressure of the column. Pore diameter of the composite adsorbent in dry and wet states was estimated to be about 18.71 nm and... 

    Fabrication of gas ionization sensor using carbon nanotube arrays grown on porous silicon substrate

    , Article Sensors and Actuators, A: Physical ; Volume 162, Issue 1 , 2010 , Pages 24-28 ; 09244247 (ISSN) Nikfarjam, A ; Iraji Zad, A ; Razi, F ; Mortazavi, S. Z ; Sharif University of Technology
    We fabricated gas sensors based on field ionization from multiwalled carbon nanotube (MWCNT) arrays grown on porous silicon templates. MWCNTs were grown through thermal chemical vapor deposition. We measured breakdown voltages, discharge and pre-discharge currents of the device for various gases in different concentrations. Our gas ionization sensors (GIS) presented good sensitivity, selectivity and short response time. The GISs based on porous substrates showed higher discharge current and good mechanical stability in comparison to those which were fabricated on polished silicon substrates. Additionally, we applied a high electric field to align CNTs. This increased the pre-breakdown... 

    Finite element analysis of a CFRP reinforced retaining wall

    , Article Geomechanics and Engineering ; Volume 10, Issue 6 , 2016 , Pages 757-774 ; 2005307X (ISSN) Ouria, A ; Toufigh, V ; Desai, C ; Toufigh, V ; Saadatmanesh, H ; Sharif University of Technology
    Techno Press 
    Soils are usually weak in tension therefore different materials such as geosynthetics are used to address this inadequacy. Worldwide annual consumption of geosynthetics is close to 1000 million m2, and the value of these materials is probably close to US$1500 million. Since the total cost of the construction is at least four or five times the cost of the geosynthetic itself, the impact of these materials on civil engineering construction is very large indeed. Nevertheless, there are several significant problems associated with geosynthetics, such as creep, low modulus of elasticity, and susceptibility to aggressive environment. Carbon fiber reinforced polymer (CFRP) was introduced over two... 

    Mechanical reinforcement of urinary bladder matrix by electrospun polycaprolactone nanofibers

    , Article Scientia Iranica ; Volume 24, Issue 6 , 2017 , Pages 3476-3480 ; 10263098 (ISSN) Ghafari, A. M ; Rajabi Zeleti, S ; Naji, M ; Ghanian, M. H ; Baharvand, H ; Sharif University of Technology
    For a successful repair and reconstruction of bladder tissue, fabrication of scaffolds with proper biochemical and biomechanical characteristics is necessary. Decellularized bladder tissue has been proposed in previous studies as a gold standard material for scaffold fabrication. However, weak mechanical properties of such a load-bearing tissue has remained a challenge. Incorporation of both biological and synthetic materials has been known as an effective strategy for improving mechanical and biological properties of the scaffolds. In the present work, a simple process was developed to fabricate hybrid hydrogel scaffolds with a biomimetic architecture from the natural urinary bladder... 

    Enhancement of surface properties and performance of reverse osmosis membranes after surface modification: a review

    , Article Desalination ; Volume 420 , 2017 , Pages 330-383 ; 00119164 (ISSN) Asadollahi, M ; Bastani, D ; Musavi, S. A ; Sharif University of Technology
    Reverse osmosis (RO) membrane process has become the most promising technology for desalination to produce purified water. Among numerous polymeric materials used to fabricate RO membranes, aromatic polyamide thin film composite (TFC) membranes are dominant in commercial RO membrane processes because of their high salt rejection and water permeability as well as their excellent chemical, thermal, and mechanical stability. However, the major hindrance to the effective application of polyamide TFC RO membranes is membrane fouling. Furthermore, polyamide TFC RO membranes have limited stability to chlorine, which is commonly used as disinfect to control membrane biofouling. These two factors... 

    High-Performance fiber-shaped flexible asymmetric microsupercapacitor based on ni(oh)2 nanoparticles-decorated porous dendritic ni-cu film/cu wire and reduced graphene oxide/carbon fiber electrodes

    , Article ACS Sustainable Chemistry and Engineering ; Volume 6, Issue 11 , 2018 , Pages 14574-14588 ; 21680485 (ISSN) Shahrokhian, S ; Naderi, L ; Mohammadi, R ; Sharif University of Technology
    American Chemical Society  2018
    Miniaturization of electronic devices with portable, flexible and wearable characteristics created a great demand for high-performance microscale energy storage devices with lightweight and flexible properties. Among the energy storage devices, wire-shaped supercapacitors (WSSCs) have recently received tremendous attention due to their tiny volume, wearability, high flexibility and potential applications in the next-generation portable/wearable electronic devices. Herein, we successfully fabricated a porous dendritic Ni-Cu film on Cu wire substrate (CWE) for fabrication of high-performance wire-type supercapacitors. The porous structure with dendritic morphology provides a high surface area,... 

    Study the effect of viscoelastic matrix model on the stability of CNT/polymer composites by multiscale modeling

    , Article Polymer Composites ; Volume 30, Issue 11 , 2009 , Pages 1545-1551 ; 02728397 (ISSN) Montazeri, A ; Naghdabadi, R ; Sharif University of Technology
    In this article, a Molecular Structural Mechanics/Finite Element (MSM/FE) multiscale modeling of carbon nanotube/polymer composites with viscoelastic (VE) polymer matrix is introduced. The nanotube is modeled at the atomistic scale using structural molecular mechanics. The matrix deformation is analyzed by nonlinear finite element method considering VE behavior. The nanotube and matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones potential at the interface. Using the MSM/FE multiscale model, we investigate the effect of carbon nanotube (CNT) on the improvement of mechanical stability of the nanocomposite. Also, the buckling behavior of these... 

    Flexible and mechanically durable asymmetric supercapacitor based on nico-layered double hydroxide and nitrogen-doped graphene using a simple fabrication method

    , Article Energy Technology ; Volume 7, Issue 5 , 2019 ; 21944288 (ISSN) Mehrabimatin, B ; Gilshteyn, E. P ; Melandsø Buan, M. E ; Sorsa, O ; Jiang, H ; Iraji zad, A ; Shahrokhian, S ; Nasibulin, A. G ; Kallio, T ; Sharif University of Technology
    Wiley-VCH Verlag  2019
    A high-performing, lightweight, and flexible asymmetric supercapacitor (ASC) using NiCo-layered double hydroxide (NiCo LDH) supported on 3D nitrogen-doped graphene (NG) as a positive electrode and NG as a negative electrode is demonstrated. Highly conductive NG provides fast electron transfer and facilitates (dis)charging of NiCo LDH deposited on it. The composite electrode of NiCo LDH@NG exhibits a high specific capacitance of 1421 F g −1 at 2 A g −1 . Moreover, the as-obtained hybrid electrode shows an excellent rate capability with a specific capacitance of 1397 F g −1 at a high current density of 10 A g −1 , which is about 98% of the capacitance obtained at 2 A g −1 . The flexible ASC... 

    Magneto-mechanical stability of axially functionally graded supported nanotubes

    , Article Materials Research Express ; Volume 6, Issue 12 , 2019 ; 20531591 (ISSN) Ebrahimi Mamaghani, A ; Mirtalebi, H ; Ahmadian, M. T ; Sharif University of Technology
    Institute of Physics Publishing  2019
    In this paper, size-dependent vibration analysis of axially functionally graded (AFG) supported nanotubes conveying nanoflow under longitudinal magnetic fields are performed, aiming at performance improvement of fluid-interaction nanosystems. Either the density or the elastic modulus of the AFG nanotube varies linearly or exponentially along the axial direction. Based on the nonlocal continuum theory, the higher-order dynamical equation of motion of the system is derived considering no-slip boundary condition. Galerkin discretization technique and eigenvalue analysis are implemented to solve the modeled equation. The validity of the simplified model is justified by comparing the results with...