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    Optimum design of sunken reinforced enclosures under buckling condition

    , Article Applied Sciences (Switzerland) ; Volume 10, Issue 23 , 2020 , Pages 1-14 Omidi Bidgoli, M ; Kashyzadeh, K. R ; Rahimian Koloor, S. S ; Petrů, M ; Amiri, N ; Sharif University of Technology
    MDPI AG  2020
    Abstract
    Increasing the lifetime and improving the performance of structures through redesign and optimization are important, especially in marine structures. In general, there are two main groups of marine structures: onshore and offshore structures. Most marine structures are offshore, and these are divided into two categories: floating or sunken. One of the important parameters in the design of sunken structures is the critical load resulting from the buckling of walls, which can cause damage to the structure. In the present paper, three rectangular aluminum and steel compartments of different conditions and sizes were modeled using design analysis methods. Then, different finite element analyses... 

    Field observation and vulnerability assessment of gonbad-e qbus

    , Article Journal of Architectural Engineering ; Volume 23, Issue 4 , 2017 ; 10760431 (ISSN) Ebrahimiyan, M ; Golabchi, M ; Yekrangnia, M ; Sharif University of Technology
    Abstract
    Gonbad-e Qabus, with a height of 52.8 m that makes it the tallest pure-brick tower in the world, located in the northern part of Iran, represents one of the most magnificent structures of the early Islamic centuries. This structure is still standing among the chaos of urban life and construction, catching the eyes of beholders even from far distances. This paper summarizes the historical and architectural background of this monumental structure and the important restorations carried out mainly in the past century. Various types of existing and potential structural and architectural damages are classified and elaborated in detail, and for each problem, a series of proposed solutions are... 

    A Mechanobiological model for damage-induced growth in arterial tissue with application to in-stent restenosis

    , Article Journal of the Mechanics and Physics of Solids ; Volume 101 , 2017 , Pages 311-327 ; 00225096 (ISSN) Fereidoonnezhad, B ; Naghdabadi, R ; Sohrabpour, S ; Holzapfel, G. A ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    In-stent restenosis (ISR) is one of the main drawbacks of stent implementation which limits the long-term success of the procedure. Morphological changes occurring within the arterial wall due to stent-induced mechanical injury are a major cause for activation of vascular smooth muscle cells (VSMCs), and the subsequent development of ISR. Considering the theory of volumetric mass growth and adopting a multiplicative decomposition of the deformation gradient into an elastic part and a growth part, we present a mechanobiological model for ISR. An evolution equation is developed for mass growth of the neointima, in which the activation of VSMCs due to stent-induced damage (injury) and the... 

    Mechanical Simulation of Corneal Ring Implant Surgery for Keratoconus Treatment

    , M.Sc. Thesis Sharif University of Technology Bagheri Tadi, Hamid Reza (Author) ; Asghari, Mohsen (Supervisor)
    Abstract
    Keratoconus is a progressive disease in which the cornea becomes thin and due to the presence of internal pressure in the eye and its application to the cornea, the cornea becomes bulging and conical. In recent years, due to the relatively large number of patients with keratoconus and also the ability of this disease to progress over time, the need to study and research on the treatment of this disease is noticeable. Early and non-surgical methods for the treatment of keratocous are use glass and contact lenses, but since the disease is progressive and usually appears more severely over time, ophthalmologists use the method of corneal ring implant for treatment.In this study, 9 types of... 

    An approach to relate shot peening finite element simulation to the actual coverage

    , Article Surface and Coatings Technology ; Vol. 243 , 2014 , pp. 39-45 ; ISSN: 02578972 Gangaraj, S. M. H ; Guagliano, M ; Farrahi, G. H ; Sharif University of Technology
    Abstract
    Coverage is one of the most important parameters which is always used in practice to characterize a shot peening process. At the same time however, it is the most missing parameter in the finite element simulations of this process. This study aims to relate shot peening simulation to the actual coverage that is developed during the process. Accordingly, two important models from literature are re-simulated and their capability to predict an actual coverage is assessed. Results of this study illustrate that full coverage situation is not captured by these models. Thereafter, a random finite element simulation along with a step by step examination of the treated surface is adopted in order to... 

    Characterization of the static behavior of micromirrors under the effect of capillary force, an analytical approach

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 226, Issue 9 , January , 2012 , Pages 2361-2372 ; 09544062 (ISSN) Moeenfard, H ; Darvishian, A ; Zohoor, H ; Ahmadian, M. T ; Sharif University of Technology
    SAGE  2012
    Abstract
    In this article, the static behavior of micromirrors under the effect of capillary force is studied. The dimensionless equations governing the static behavior and the pull-in state of the micromirror under capillary force are obtained, and the effects of different geometrical parameters on the pull-in angle of micromirrors are investigated. The static behavior of micromirrors is studied both numerically and analytically using the homotopy perturbation method. It is observed that with increasing the instability number defined in this article, the rotation angle of the micromirror is increased and suddenly the pull-in occurs. The results of the presented model are then verified by comparing... 

    Effect of capillary tube's shape on capillary rising regime for viscos fluids

    , Article 2017 International Conference on Nanomaterials and Biomaterials, ICNB 2017, 11 December 2017 through 13 December 2017 ; Volume 350, Issue 1 , 2018 ; 17578981 (ISSN) Soroush, F ; Moosavi, A ; Sharif University of Technology
    Institute of Physics Publishing  2018
    Abstract
    When properties of the displacing fluid are considered, the rising profile of the penetrating fluid in a capillary tube deviates from its classical Lucas-Washburn profile. Also, shape of capillary tube can affect the rising profile in different aspects. In this article, effect of capillary tube's shape on the vertical capillary motion in presence of gravity is investigated by considering the properties of the displacing fluid. According to the fact that the differential equation of the capillary rising for a non-simple wall type is very difficult to solve analytically, a finite element simulation model is used for this study. After validation of the simulation model with an experiment that... 

    Study of Direct Joining of Nanostructured-Zirconia to 430L Stainless Steel Produced by Co-sintering Process

    , Ph.D. Dissertation Sharif University of Technology Dourandish Yazdi, Mahdi (Author) ; Simchi, Abdolreza (Supervisor)
    Abstract
    In this study, the joint of co-sintered zirconia/stainless steel is investigated. To this end ZrO2-3mol%Y2O3 (TZP) and 430L stainless steel powders were utilized. The joining parameters of co-sintering in zirconia/metal were studied. In order to study the microstructure, diffusion and probable reactions at the joint boundary, HRSEM, HRTEM, EPMA and micro-focused XRD methods were employed. Shear strength of the joint was also measured. Finite element simulation of residual stresses and thermodynamic studies are utilized in the next step to analyze the experimental results. It is found that the direct joining of zirconia to 430L stainless steel is feasible by co-sintering at 1350 °C under low... 

    Numerical Simulation of Al-Si Alloy Fatigue Behavior under Thermo-Mechanical and Isothermal Loads

    , M.Sc. Thesis Sharif University of Technology Ghodrati Ghalati, Mohammad (Author) ; Farrahi, Gholamhossein (Supervisor) ; Asghari, Mohsen (Co-Advisor)
    Abstract
    The main purpose in this thesis is the finite element simulation of the stress-strain behavior in an aluminum-silicon-magnesium alloy, subjected to low cycle fatigue and thermo-mechanical fatigue loadings. This finite element modeling is performed in the ABAQUS software. Two time-dependent and time-independent models are used to simulate the behavior of the material. The time-independent model is the combined nonlinear isotropic/kinematic hardening model, which predicts the mean stress relaxation behavior, the cyclic softening or hardening and the translation of the yield surface, while it ignores the effect of the strain rate. Time-dependent models include Johnson-Cook and the two-layer... 

    Simulating the Insertion of Intrastromal Corneal Ring Segments in Keratoconic Corneas

    , M.Sc. Thesis Sharif University of Technology Dashti, Azadeh (Author) ; Zohoor, Hassan (Supervisor) ; Ahmadian, Mohammad Taghi ($item.subfieldsMap.e)
    Abstract
    Keratoconus is a progressive corneal illness that appears due to reduced thickness of cornea in some area. Normal cornea has semi sphere shape with uniform thickness from center of cornea to the limbus. However, keratoconic cornea’s shape becomes conic. One of the treatments in moderate state of keratoconus is implantation of IntraStromal Corneal Ring Segments( ICRS). Ring Segments are made of PMMA and inserted in 0/7- 0/8 of depth of cornea.In this study, before surgery data from 3 patient’s cornea images were prepared in order to 3D modeling of cornea, for importing to FEM software( ABAQUS). Material properties of cornea is considered hyperelastic second-order Ogden Model; elastic... 

    Design and Manufacturing of Water Jet Apparatus for Cutting Soft Tissue and Interaction Analysis

    , M.Sc. Thesis Sharif University of Technology Vatani, Pouyan (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Assempour, Ahmad (Supervisor)
    Abstract
    Cancer is one of the deadliest diseases of the modern era and accounts for 13% of all deaths in humans. Most cancers and lesions in the human body are related to soft tissue. Many soft-tissue cancers and lesions occur in sensitive areas of the body, such as the brain, pituitary, and intestine. The pituitary gland is located in the human head and near the optic nerves. Surgery in a typical way can result in risks such as heat loss of the optic nerve or injuries to healthy tissues due to the sharpness of the surgery tool. One of the alternatives to conventional surgery is water jet surgery. This method minimizes the risks of human error. In the present study, a water jet machine was designed... 

    Optimization and Continuous Synthesis of Artemisinin Using Core-Shell Nano-Catalysts by Means of Micro-Rector

    , Ph.D. Dissertation Sharif University of Technology Tamtaji, Mohsen (Author) ; Kazemeini, Mohammad (Supervisor)
    Abstract
    Artemisinin as a natural peroxide possess a high anti parasite, and antivirus (Covid-19) properties which could be synthesized through the photooxygenation of dihydroartemisinic acid. This production possesses a lot of difficulties, for example, homogeneous catalyst is used for the photooxygenation reaction which makes photocatalyst and solvent non-reusable. In addition, separation of products from solvent and photocatalysts is difficult. Photooxygenation needs high pressure and low temperature which is very costly. Besides, because of several by-products which are producing during photooxygenation and protonation reactions, Artemisinin yield decreases. The aim of this study is to optimize... 

    Design, modeling and optimization of a novel two DOF polymeric electro-thermal micro-actuator

    , Article Applied Mechanics and Materials ; Vol. 307 , 2013 , pp. 112-116 ; ISSN: 16609336 ; ISBN: 9783037856598 Sheikhbahaie, R ; Alasty, A ; Salarieh, H ; Sharif University of Technology
    Abstract
    In this paper, design, simulation and optimization of a novel electrothermally-activated polymeric microactuator capable of generating combination of bidirectional lateral and rotational motions are presented. The composite structure of this actuator is consisted of a symmetric meandered shape silicon skeleton, a SU8 thermal expandable polymer and a thin film chrome layer heater. This actuator is controlled by applying appropriate voltages on its four terminals. With the purpose of dimension optimization, a numerical parametric study is executed. The modeled actuator which is 1560 ?m long, 156 ?m wide and 30 ?m thick, demonstrates a remarkable lateral displacement of 23 ?m at power... 

    Finite element simulation of ultrasonic-assisted machining: a review

    , Article International Journal of Advanced Manufacturing Technology ; Volume 116, Issue 9-10 , 2021 , Pages 2777-2796 ; 02683768 (ISSN) Lotfi, M ; Akbari, J ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    Ultrasonic-assisted machining is an advanced method which could improve the process of machining. Besides, simulation modeling process is a method to help the researchers analyze different aspects of the process with more details in a shorter time. Simulation of ultrasonic-assisted machining is also a field of research that is of interest to researchers working in the field of machining processes. In recent years, a variety of papers have been published where cutting forces, chip formation, tool wear and temperature, and microstructure changes were simulated. That being the case, a review paper is required to represent the advances implemented by researchers in the simulation of... 

    Biomimetic ultraflexible piezoresistive flow sensor based on graphene nanosheets and PVA hydrogel

    , Article Advanced Materials Technologies ; 2021 ; 2365709X (ISSN) Abolpour Moshizi, S ; Moradi, H ; Wu, S ; Han, Z. J ; Razmjou, A ; Asadnia, M ; Sharif University of Technology
    John Wiley and Sons Inc  2021
    Abstract
    Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

    Biomimetic ultraflexible piezoresistive flow sensor based on graphene nanosheets and PVA hydrogel

    , Article Advanced Materials Technologies ; 2021 ; 2365709X (ISSN) Abolpour Moshizi, S ; Moradi, H ; Wu, S ; Han, Z. J ; Razmjou, A ; Asadnia, M ; Sharif University of Technology
    John Wiley and Sons Inc  2021
    Abstract
    Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

    Accurate analytical model for determination of effective diffusion coefficient of polymer electrolyte fuel cells by designing compact Loschmidt cells

    , Article Fuel ; Volume 199 , 2017 , Pages 551-561 ; 00162361 (ISSN) Izadmehr, M ; Abbasi, M ; Mansouri, M ; Kazemi, A ; Nakhaee, A ; Daryasafar, A ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    Effective diffusion coefficient is an important parameter which needs to be determined in different fields of study, such as cathode catalyst layers of PEM fuel. For this purpose, a Loschmidt diffusion cell can be used. When a porous medium is placed in Loschmidt apparatus, the effective gas diffusion coefficient (EGDC) of this section must be correlated by diffusion coefficient in absence of a porous medium. In the previous researches studying the Loschmidt diffusion cell, a simplifying infinite-length assumption was used in the analytical solution. Therefore, the solution is only applicable for a short time range, and this can result in high error. In order to overcome this challenge, the... 

    Experimental and numerical investigation of fixture time on distortion of welded part

    , Article International Journal of Advanced Manufacturing Technology ; Volume 104, Issue 1-4 , 2019 , Pages 1121-1131 ; 02683768 (ISSN) Gharib, A. R ; Biglari, F. R ; Shafaie, M ; Kokabi, A. H ; Sharif University of Technology
    Springer London  2019
    Abstract
    In this paper, the effect of clamping time on welding distortion is studied. The welding process has been done in austenitic stainless steel 304L butt-welded joint by TIG welding method. The numerical thermo-mechanical analysis is performed using commercial finite element software ABAQUS. The welding simulation is performed using the birth and death of elements technique. The heat source model that used in this study is the Goldak double-ellipsoidal model. At last, for verifying numerical results, a set of experimental tests have been carried out and welding distortion has been measured. The experimental measured data are compared with numerical (FEM) results. The results showed that the... 

    Vibration band gap properties of a periodic beam-like structure using the combination of GDQ and GDQR methods

    , Article Waves in Random and Complex Media ; 2019 ; 17455030 (ISSN) Hajhosseini, M ; Mahdian Parrany, A ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters.... 

    Vibration band gap properties of a periodic beam-like structure using the combination of GDQ and GDQR methods

    , Article Waves in Random and Complex Media ; 2019 ; 17455030 (ISSN) Hajhosseini, M ; Mahdian Parrany, A ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters....