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3D modeling of cohesive crack growth in partially saturated porous media: A parametric study
, Article Engineering Fracture Mechanics ; Vol. 124-125, issue , 2014 , pp. 272-286 ; ISSN: 00137944 ; Khoei, A. R ; Sharif University of Technology
2014
Abstract
In this paper, the 3D cohesive crack propagation is presented in partially saturated porous media. The double-nodded zero-thickness cohesive interface elements are employed to capture the mixed mode fracture behavior. In order to describe the behavior of fractured media, two balance equations are applied similar to those employed for the mixture of solid-fluid phase in semi-saturated media, including: the momentum balance of fractured media, and the balance of fluid mass within the fracture. Crack permeability is modified based on the data obtained from experimental results to consider the roughness of fracture walls effect
Modeling of cohesive crack growth in partially saturated porous media; A study on the permeability of cohesive fracture
, Article International Journal of Fracture ; Volume 167, Issue 1 , Jan , 2011 , Pages 15-31 ; 03769429 (ISSN) ; Khoei, A. R ; Mofid, M ; Sharif University of Technology
2011
Abstract
Modeling the water flow in cohesive fracture is a fundamental issue in the crack growth simulation of cracked concrete gravity dams and hydraulic fracture problems. In this paper, a mathematical model is presented for the analysis of fracture propagation in the semi-saturated porous media. The solid behavior incorporates a discrete cohesive fracture model, coupled with the flow in porous media through the fracture network. The double-nodded zero-thickness cohesive interface element is employed for the mixed mode fracture behavior in tension and contact behavior in compression. The modified crack permeability is applied in fracture propagation based on the data obtained from experimental...
Modeling of cohesive crack growth using an adaptive mesh refinement via the modified-SPR technique
, Article International Journal of Fracture ; Volume 159, Issue 1 , 2009 , Pages 21-41 ; 03769429 (ISSN) ; Moslemi, H ; Majd Ardakany, K ; Barani, O. R ; Azadi, H ; Sharif University of Technology
2009
Abstract
In this paper, an adaptive finite element procedure is presented in modeling of mixed-mode cohesive crack propagation via the modified superconvergent path recovery technique. The adaptive mesh refinement is performed based on the Zienkiewicz-Zhu error estimator. The weighted-SPR recovery technique is employed to improve the accuracy of error estimation. The Espinosa-Zavattieri bilinear cohesive zone model is applied to implement the traction-separation law. It is worth mentioning that no previous information is necessary for the path of crack growth and no region of the domain is necessary to be filled by the cohesive elements. The maximum principal stress criterion is employed for...
Concrete basic creep predi ction based on time-temperature equivalence relation and short-term tests
, Article Arabian Journal for Science and Engineering ; Volume 35, Issue 2 A , 2010 , Pages 105-121 ; 13198025 (ISSN) ; Mostofinejaad, D ; Saadatpour, M. M ; Shekarchi, M ; Sharif University of Technology
2010
Abstract
Using temperature as an accelerator of reactions in short-term tests for the prediction of concrete creep is the main idea of this paper. The application of a time-temperature equivalence relation is examined with reference to creep in concrete under constant moisture conditions. A mathematical model is developed which uses short-term tests to predict long-term creep deformation of concrete under constant moisture conditions, taking into account aging of concrete and the influence of temperature. The thermal activation is assumed to be governed by the Arrhenius principle, and the activation energy of the viscosity of water is found to be applicable in the analysis of the experimental data....
Numerical Study of Combustion of H2-O2 Cryogenic Propellant under Supercritical Condition
, M.Sc. Thesis Sharif University of Technology ; Mardani, Amir (Supervisor)
Abstract
In order to improve performance and optimize design of high pressure combustion devices such as liquid rocket engine, gas turbine engine, and diesel engine there is a need for comprehensive understanding of injection, mixing and combustion in supercritical condition. Under this condition chamber pressure is higher than critical pressure of fuel and oxidizer. The characteristic of supercritical condition, include changing thermophysical properties such as density, CP, and compressibility factor. Therefore under this condition ideal state equation cannot correctly predict the mentioned properties. These characteristics make supercritical combustion different from other combustion regimes....
Modeling of Cohesive Crack Propagation in Saturated and Semi Saturated Porous Media
, Ph.D. Dissertation Sharif University of Technology ; Khoei, Amir Reza (Supervisor) ; Mofid, Massoud (Supervisor)
Abstract
Modeling the water flow in cohesive fracture is a fundamental issue in the crack growth simulation of cracked concrete gravity dams and hydraulic fracture problems. Discontinuities in porous materials such as concrete, soil and rock have important role on the mechanical and hydraulic behavior of a multiphase system. The creation and propagation of discontinuities, such as cracks in a multi-physics system, lead to a complex non-linear coupled problem with continuous topological changes in the domain.In this study, a mathematical model is presented for for the analysis of dynamic fracture propagation in the saturated and semi-saturated porous media. The solid behavior incorporates a discrete...
On the performance of an innovative electronic chipset thermal management module based on energy storage unit concept utilizing nano-additive phase change material (NPCM)
, Article Journal of Energy Storage ; Volume 50 , 2022 ; 2352152X (ISSN) ; Alimohammadi, M ; Barani, E ; Taheri, A ; Passandideh Fard, M ; Sardarabadi, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Due to size minimization and increment in the frequency of electronic devices, efficient and reliable methods for thermal management are required to reduce operating temperature, enhance stability, increase lifetime and user comfort. To prevent the damages of leakage and corrosion which occur in conventional heat sinks, proposing innovative thermal management methods has always been welcomed. Regarding these issues and based on the energy storage unit concept, in this study, a passive heat sink (HS) is fabricated and characterized for electronic chipset cooling with heat fluxes of 2000 to 4000 W/m2 utilizing phase change material (PCM) and nano-additive PCM (NPCM). The presented cooling...
Corrigendum to "Finite element analysis of machine and workpiece instability in turning". [Int. J. Mach. Tools Manuf. 45 (2005) 753-760] (DOI:10.1016/j.ijmachtools.2004.11.017)
, Article International Journal of Machine Tools and Manufacture ; Volume 48, Issue 2 , 2008 , Pages 260- ; 08906955 (ISSN) ; Ghorbanian, O ; Movahhedy, M. R ; Sharif University of Technology
2008
A polygonal-FEM technique in modeling large sliding contact on non-conformal meshes: A study on polygonal shape functions
, Article Engineering Computations (Swansea, Wales) ; Volume 32, Issue 5 , 2015 , Pages 1391-1431 ; 02644401 (ISSN) ; Yasbolaghi, R ; Biabanaki, S. O. R ; Sharif University of Technology
2015
Abstract
Purpose - In this paper, the polygonal-FEM technique is presented in modeling large deformation - large sliding contact on non-conformal meshes. The purpose of this paper is to present a new technique in modeling arbitrary interfaces and discontinuities for non-linear contact problems by capturing discontinuous deformations in elements cut by the contact surface in uniform non-conformal meshes. Design/methodology/approach - The geometry of contact surface is used to produce various polygonal elements at the intersection of the interface with the regular FE mesh, in which the extra degrees-of-freedom are defined along the interface. The contact constraints are imposed between polygonal...
A polygonal finite element method for modeling crack propagation with minimum remeshing
, Article International Journal of Fracture ; Volume 194, Issue 2 , 2015 ; 03769429 (ISSN) ; Yasbolaghi, R ; Biabanaki, S. O. R ; Sharif University of Technology
Kluwer Academic Publishers
2015
Abstract
In this paper, a polygonal finite element method is presented for crack growth simulation with minimum remeshing. A local polygonal mesh strategy is performed employing polygonal finite element method to model the crack propagation. In order to model the singular crack tip fields, the convex and concave polygonal elements are modified based on the singular quarter point isoparametric concept that improves the accuracy of the stress intensity factors. Numerical simulations are performed to demonstrate the efficiency of various polygonal shape functions, including the Wachspress, metric, Laplace and mean value shape functions, in modeling the crack tip fields. Eventually, analogy of the...
Review of Oxygenation with Nanobubbles: Possible Treatment for Hypoxic COVID-19 Patients
, Article ACS Applied Nano Materials ; Volume 4, Issue 11 , 2021 , Pages 11386-11412 ; 25740970 (ISSN) ; Akhavan, O ; Hamblin, M. R ; Varma, R. S ; Sharif University of Technology
American Chemical Society
2021
Abstract
The coronavirus disease (COVID-19) pandemic, which has spread around the world, caused the death of many affected patients, partly because of the lack of oxygen arising from impaired respiration or blood circulation. Thus, maintaining an appropriate level of oxygen in the patients' blood by devising alternatives to ventilator systems is a top priority goal for clinicians. The present review highlights the ever-increasing application of nanobubbles (NBs), miniature gaseous vesicles, for the oxygenation of hypoxic patients. Oxygen-containing NBs can exert a range of beneficial physiologic and pharmacologic effects that include tissue oxygenation, as well as tissue repair mechanisms,...
Review of oxygenation with nanobubbles: possible treatment for hypoxic covid-19 patients
, Article ACS Applied Nano Materials ; Volume 4, Issue 11 , 2021 , Pages 11386-11412 ; 25740970 (ISSN) ; Akhavan, O ; Hamblin, M. R ; Varma, R. S ; Sharif University of Technology
American Chemical Society
2021
Abstract
The coronavirus disease (COVID-19) pandemic, which has spread around the world, caused the death of many affected patients, partly because of the lack of oxygen arising from impaired respiration or blood circulation. Thus, maintaining an appropriate level of oxygen in the patients' blood by devising alternatives to ventilator systems is a top priority goal for clinicians. The present review highlights the ever-increasing application of nanobubbles (NBs), miniature gaseous vesicles, for the oxygenation of hypoxic patients. Oxygen-containing NBs can exert a range of beneficial physiologic and pharmacologic effects that include tissue oxygenation, as well as tissue repair mechanisms,...
KF/Al2O3-mediated Michael addition of thiols to electron-deficient olefins
, Article Synthetic Communications ; Volume 35, Issue 18 , 2005 , Pages 2427-2433 ; 00397911 (ISSN) ; Bardajee, G. R ; Veranlou, R. O. C ; Sharif University of Technology
2005
Abstract
Potassium fluoride supported on alumina efficiently catalyzes Michael addition of aromatic and aliphatic thiols to a variety of conjugated alkenes such as α,β-unsaturated carbonyl compounds, carboxylic esters, amides, nitriles and chalcones. The Michael adducts are produced in good to excellent yields and relatively in short times. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency. Copyright © Taylor & Francis, Inc
A polygonal finite element method for modeling arbitrary interfaces in large deformation problems
, Article Computational Mechanics ; Volume 50, Issue 1 , 2012 , Pages 19-33 ; 01787675 (ISSN) ; Khoei, A. R ; Sharif University of Technology
2012
Abstract
In this paper, a polygonal-FEM technique is presented in modeling of arbitrary interfaces in large deformations. The method is used to model the internal interfaces and arbitrary geometries using a uniform non-conformal mesh. The technique is applied to capture discontinuous deformations in the non-conformal elements, which are cut by the interface in a uniform regular mesh. In this approach, a uniform non-conformal mesh is decomposed into sub-elements that conform to the internal interfaces. The geometry of interface is used to produce various triangular, quadrilateral and pentagonal elements at the intersection of interface with regular FE mesh, in which the extra degrees-of-freedom are...
A generalized finite element method for modeling arbitrary interfaces in large deformation problems
, Article Computational Plasticity XI - Fundamentals and Applications, COMPLAS XI, 7 September 2011 through 9 September 2011 ; September , 2011 , Pages 1306-1317 ; 9788489925731 (ISBN) ; Khoei, A. R ; Sharif University of Technology
2011
Abstract
In this paper, a generalized-FEM technique is presented in modeling of arbitrary interfaces in large deformations. The method is used to model the internal interfaces and arbitrary geometries using a uniform non-conformal mesh. The technique is applied to capture independent deformations at both sides of separated element cut by the interface in a uniform regular mesh. In this approach, a uniform non-conformal mesh is decomposed into subelements that conform to the internal interfaces. The geometry of interface is used to produce various triangular, quadrilateral and pentagonal elements at the intersection of interface with regular FE mesh, in which the extra degrees-of-freedom are defined...
A case study in vapor phase synthesis of Mg-Al alloy nanoparticles by plasma arc evaporation technique
, Article Chemical Engineering Journal ; Volume 259 , 2015 , Pages 918-926 ; 13858947 (ISSN) ; Derakhshan, R ; Mirzaee, O ; Sharif University of Technology
Elsevier
2015
Abstract
Alloy nanoparticles in the Mg-Al system were prepared by plasma arc discharge method from the Mgx to Al (45%
Effects of conventional, severe, over, and re-shot peening processes on the fatigue behavior of mild carbon steel
, Article Surface and Coatings Technology ; Volume 344 , 25 June , 2018 , Pages 62-74 ; 02578972 (ISSN) ; Unal, O ; Kashyzadeh, K. R ; Sharif University of Technology
Elsevier B.V
2018
Abstract
The present study investigates experimentally the effects of different shot peening treatments, including conventional, severe, over, and re-shot peening on microstructure, mechanical properties, and fatigue behavior of AISI 1050 mild carbon steel. Different shot peening treatments were performed using various effective parameters by considering the influences of increasing Almen intensity and coverage. Optical microscopy and field emission scanning electron microscopy observations and X-Ray diffraction measurements were carried out to analyze grains refinement in each shot peening treatment. Microhardness and residual stress measurements were taken from shot peened surfaces to the core...
Optical properties and surface morphology of evaporated (WO 3)1-x-(Fe2O3)x thin films
, Article Thin Solid Films ; Volume 484, Issue 1-2 , 2005 , Pages 124-131 ; 00406090 (ISSN) ; Azimirad, R ; Akhavan, O ; Sharif University of Technology
2005
Abstract
Thin films of (WO3)1 - x-(Fe2O 3)x composition were deposited by thermal evaporation on glass substrates and then all samples were annealed at 400 °C in air. Optical properties such as transmittance, reflectance, and optical bandgap energy of the "as deposited" and the annealed films were studied using ultraviolet-visible spectrophotometry. It was shown that the annealing process did not substantially change the optical transmittance and reflectance of all the films except the films having x = 0.75. By increasing Fe2O 3 content in the films from x = 0 to x = 0.75, optical bandgap energy decreased from 3.4 to about 1.3 eV and from 3.1 to 2.1 eV for the "as deposited" and the annealed samples,...
Green products from herbal medicine wastes by subcritical water treatment
, Article Journal of Hazardous Materials ; Volume 424 , 2022 ; 03043894 (ISSN) ; Tavakoli, O ; Sarkhanpour, R ; Sajadi, S. M ; Zarrintaj, P ; Rabiee, N ; Akhavan, O ; Lima, E. C ; Saeb, M. R ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Herbal medicine wastes (HMWs) are byproducts of medicine factories, which are mainly landfilled for their environmental problems. Only bearing in mind the contamination and concerns caused by the COVID-19 pandemic and environmental emissions, the worth of herbal medicine wastes management and conversion to green products can be understood. In this work, subcritical water treatment was carried out batch-wise in a stainless tube reactor in the pressure range of 0.792–30.0 MPa, varying the temperature (127–327 °C) and time (1–60 min) of extraction. This resulted in new and green material sources, including organic acids, amino acids, and sugars. Amazingly, at very low extraction times (below 5...
Detection of movement related cortical potential: Effects of causal vs. non-causal processing
, Article 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 16 August 2016 through 20 August 2016 ; Volume 2016-October , 2016 , Pages 5733-5736 ; 1557170X (ISSN); 9781457702204 (ISBN) ; Chavarriaga, R ; Shamsollahi, M. B ; Millan, J. D. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Movement Related Cortical Potentials (MRCP) have been the subject of numerous studies. They accompany many self-initiated movements and this makes them a good candidate for incorporation in BCI paradigms. In this work we propose a novel experimental protocol involving natural controlling of a computer mouse and based on EEG recordings from 5 subjects, show that it elicits MRCP. We also show the feasibility of online detection of MRCP by implementing a classification based detection framework. Additionally, we discuss the adverse effects of causality restriction on detection performance by implementing an additional offline approach relaxing those restrictions and comparing the results. The...