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Effects of stress invariants and reverse loading on ductile fracture initiation
, Article International Journal of Solids and Structures ; Volume 49, Issue 13 , 2012 , Pages 1541-1556 ; 00207683 (ISSN) ; Hoseini, S. H ; Farrahi, G. H ; Sharif University of Technology
2012
Abstract
Recent research studies on ductile fracture of metals have shown that the ductile fracture initiation is significantly affected by the stress state. In this study, the effects of the stress invariants as well as the effect of the reverse loading on ductile fracture are considered. To estimate the reduction of load carrying capacity and ductile fracture initiation, a scalar damage expression is proposed. This scalar damage is a function of the accumulated plastic strain, the first stress invariant and the Lode angle. To incorporate the effect of the reverse loading, the accumulated plastic strain is divided into the tension and compression components and each component has a different weight...
A plasticity model for metals with dependency on all the stress invariants
, Article Journal of Engineering Materials and Technology, Transactions of the ASME ; Volume 135, Issue 1 , 2013 ; 00944289 (ISSN) ; Hoseini, S. H ; Farrahi, G. H ; Sharif University of Technology
2013
Abstract
Recent experiments on metals have shown that all of the stress invariants should be involved in the constitutive description of the material in plasticity. In this paper, a plasticity model for metals is defined for isotropic materials, which is a function of the first stress invariant in addition to the second and the third invariants of the deviatoric stress tensor. For this purpose, the Drucker-Prager yield criterion is extended by addition of a new term containing the second and the third deviatoric stress invariants. Furthermore for estimating the cyclic behavior, new terms are incorporated into the Chaboche's hardening evolution equation. These modifications are applied by adding new...
Calibration of gurson–tvergaard–needleman model parameters of a niti alloy using response surface method
, Article Journal of Materials Engineering and Performance ; Volume 32, Issue 18 , 2023 , Pages 8467-8477 ; 10599495 (ISSN) ; Bahrami, H ; Hoseini, H ; Sharif University of Technology
Springer
2023
Abstract
The GTN micromechanical fracture model is frequently used to predict the ductile fracture. This model is based on the microscopic mechanism of void nucleation, growth and coalescence in ductile material. GTN model includes many parameters that need to be precisely calibrated in order to obtain the maximum accuracy. In this study, an indirect approach is used to determine the GTN model parameters of a NiTi alloy by using the response surface method, RSM. This method is implemented in combination with the polynomial regression method. A quadratic polynomial equation is employed to obtain a relationship between the experimental results of smooth and notched round bar tensile tests with GTN...
Fracture analysis of shape memory alloy considering the effect of Ti-rich areas
, Article Engineering Failure Analysis ; Volume 143 , 2023 ; 13506307 (ISSN) ; Bahrami, H ; Hoseini, H ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
In this paper, the effect of Ti-rich areas on the fracture of NiTi alloys has been studied. To carry out this investigation, a series of experimental tests, as well as numerical analyses are conducted. In the experimental plan, NiTi smooth and notched bars with various notch sizes are subjected to tensile load until fracture. Moreover, the corresponding SEM observation and EDX analyses of fracture surface are utilized to investigate the fracture process of these alloys. Simultaneously, a numerical procedure based on the Gurson-Tvergaard-Needleman micro-mechanical model, GTN, is implemented. The numerical procedure is implemented using the finite element method. The tensile test of each...
Calculation of the transport properties of dense fluids using modified Enskog theory and an appropriate equation of state
, Article Fluid Phase Equilibria ; Volume 253, Issue 2 , 2007 , Pages 108-117 ; 03783812 (ISSN) ; Kalantar, Z ; Sharif University of Technology
2007
Abstract
In this work, a new method based on the modified Enskog theory (MET) is presented for calculation of transport properties at high densities (ρ > ρc). The main limitation of using the MET is lack of experimental data for co-volume, b0. We have substituted b0 from hard sphere (HS) theory and zero density transport properties from the kinetic theory of gases for HS in the MET expression, because of the fact that dense fluids behave more and less like a HS fluid. As a result, a simple linear expression for the self diffusion (D) and quadratic expressions for viscosity (η) and thermal conductivity (λ) coefficients have been obtained in terms of Y at high densities (ρ > ρc), where Y = (T (∂ p / ∂...
Extension of linear isotherm regularity to long chain primary, secondary and tertiary alcohols, ketones and 1-carboxylic acids by group contribution method
, Article Fluid Phase Equilibria ; Volume 234, Issue 1-2 , 2005 , Pages 11-21 ; 03783812 (ISSN) ; Kalantar, Z ; Sharif University of Technology
2005
Abstract
In this work, the group contribution approach has been used in combination with the linear isotherm regularity (LIR) equation of state to estimate pvT properties of primary, secondary and tertiary alcohols, ketones and 1-carboxylic acid. In addition, the isothermal compressibility and thermal expansion coefficient of these compounds have been predicted. We assume each of these organic compounds as a hypothetical mixture of methyl, methylene and a functional group, in which the interaction potential of each pair is assumed to be the average effective pair potential. Then, the LIR equation of state (EOS) has been extended to such a hypothetical mixture. Three basic compounds, namely propane,...
Residual stress analyses of re-autofrettaged thick-walled tubes
, Article International Journal of Pressure Vessels and Piping ; Volume 98 , 2012 , Pages 57-64 ; 03080161 (ISSN) ; Voyiadjis, G. Z ; Hoseini, S. H ; Hosseinian, E ; Sharif University of Technology
Elsevier
2012
Abstract
In this paper the effect of the re-autofrettage process on the residual stress distribution at the wall of a thick-walled tube is considered. For accurate material behavior modeling, it is assumed that the yield surface is a function of all the stress invariants. Also for estimating the behavior of the material under loading-unloading process, a modified Chaboche's hardening model is applied. For evaluation of this unloading behavior model a series of loading-unloading tests are conducted on specimens that are made of the high strength steel, DIN1.6959. In addition the finite element simulations are implemented to simulate the re-autofrettage process and to estimate the residual stresses....
Biodegradation of cyanide by a new isolated strain under alkaline conditions and optimization by response surface methodology (RSM)
, Article Journal of Environmental Health Science and Engineering ; Vol. 12, issue. 1 , 2014 ; Yaghmaei, S ; Nejad, Z. G ; Sharif University of Technology
2014
Abstract
Background: Biodegradation of free cyanide from industrial wastewaters has been proven as a viable and robust method for treatment of wastewaters containing cyanide. Results: Cyanide degrading bacteria were isolated from a wastewater treatment plant for coke-oven-gas condensate by enrichment culture technique. Five strains were able to use cyanide as the sole nitrogen source under alkaline conditions and among them; one strain (C2) was selected for further studies on the basis of the higher efficiency of cyanide degradation. The bacterium was able to tolerate free cyanide at concentrations of up to 500 ppm which makes it a good potentially candidate for the biological treatment of cyanide...
ACM: Accurate crosstalk modeling to predict channel delay in Network-on-Chips
, Article 2016 IEEE 22nd International Symposium on On-Line Testing and Robust System Design, IOLTS 2016, 4 July 2016 through 6 July 2016 ; 2016 , Pages 7-8 ; 9781509015061 (ISBN) ; Shirmohammadi, Z ; Miremadi, S. G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
The severity of timing delay in the communication channels of Network on Chip (NoC) depends on the transition patterns appearing on the wires. An analytical model can estimate the timing delay in NoC channels in the presence of crosstalk faults. However, recently proposed analytical model does not have enough accuracy and is based on 3-wire delay model. In this paper, an Accurate Crosstalk Model (ACM) based on 5-wire delay model is proposed to estimate the delay of communication channels in the presence of crosstalk faults. ACM is more accurate due to considering more wires in the delay model and also considering the overlaps between locations of transition patterns
Surface modification of exchange-coupled Co/NiO x magnetic bilayer by bias sputtering
, Article Applied Surface Science ; Volume 252, Issue 2 , 2005 , Pages 466-473 ; 01694332 (ISSN) ; Akhavan, O ; Moshfegh, A. Z ; Jafari, G. R ; Kavei, G ; Sharif University of Technology
Elsevier
2005
Abstract
We have investigated the effect of bias voltage on sheet resistance, surface roughness and surface coverage of Co/NiO x magnetic bilayer. In addition, interface topography and corrosion resistance of the Ta/Co/Cu/Co/NiO x /Si(1 0 0) system have been studied for Co layers deposited at an optimum bias voltage. Atomic force microscopy (AFM) and four point probe sheet resistance (Rs) measurement have been used to determine surface and electrical properties of the sputtered Co layer at different bias voltages ranging from 0 to -80 V. The Co/NiO x bilayer exhibits a minimum surface roughness and low sheet resistance value with a maximum surface coverage at Vb=-60 V resulted in a slight increase of...
A non-intrusive portable fault injection framework to assess reliability of FPGA-based designs
, Article FPT 2013 - Proceedings of the 2013 International Conference on Field Programmable Technology ; 2013 , Pages 398-401 ; 9781479921990 (ISBN) ; Ghaderi, Z ; Miremadi, S. G ; Sharif University of Technology
2013
Abstract
This paper proposes a full-featured fault injection framework to assess reliability of FPGA-based designs. The framework provides non-intrusiveness, portability, flexibility and performance in reliability evaluation of FPGA-based designs against adverse effects of SEUs. It works in a non-intrusive manner, allowing the reliability of ready-to-be-released designs to be assessed independently, without any intrusion into their place and route characteristics. We have studied implications of framework's intrusiveness into design under test by comparing proposed non-intrusive framework with previous intrusive methods; up to 5% deviation in the number of effective faults is observed in intrusive...
Multifunctional Ag/AgCl/ZnTiO3 structures as highly efficient photocatalysts for the removal of nitrophenols, CO2 photoreduction, biomedical waste treatment, and bacteria inactivation
, Article Applied Catalysis A: General ; Volume 643 , 2022 ; 0926860X (ISSN) ; Ghasemi, S ; Hajiahmadi, S ; Rhimi, B ; Nejad, Z. G ; Karima, S ; Shahsavari, Z ; Wang, C ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Over the past few decades, biological hazards and organic pollution have become major environmental concerns. Photocatalysis has been found to be effective in minimizing the negative impacts of these issues in air and water. Lozenge shape Ag/AgCl/ZnTiO3 photocatalysts were fabricated by a facile two-step synthesis method, including hydrothermal and coprecipitation. The physicochemical characteristics and morphological properties of the structures were comprehensively described taking advantage of a multi-technique approach. The prepared photocatalysts offered excellent nitrophenol mineralization (>90%) after 90 min of visible light irradiation. Based on the spin-trapping ESR technique, •O2̅–...
Magnetic/pH-sensitive κ-carrageenan/sodium alginate hydrogel nanocomposite beads: Preparation, swelling behavior, and drug delivery
, Article Journal of Biomaterials Science, Polymer Edition ; Vol. 25, issue. 17 , 2014 , p. 1891-1906 ; Rahmani, Z ; Karami, S ; Pourjavadi, A ; Sharif University of Technology
2014
Abstract
This work describes the preparation of magnetic and pH-sensitive beads based on κ-carrageenan and sodium alginate for use as drug-targeting carriers. Physical cross-linking using K+/Ca2+ ions was applied to obtain ionic cross-linked magnetic hydrogel beads. The produced magnetite beads were thoroughly characterized by TEM, SEM/EDS, XRD, FTIR, and VSM techniques. While the water absorbency (WA) of magnetic beads was enhanced by increasing the weight ratio of κ-carrageenan, introducing magnetic nanoparticles caused a decrease in WA capacity from 15.4 to 6.3 g/g. Investigation on the swelling of the hydrogel beads in NaCl, KCl, and CaCl2 solutions revealed the disintegration of beads depending...
A superabsorbent hydrogel network based on poly ((2-dimethylaminoethyl) methacrylate) and sodium alginate obtained by γ-radiation: Synthesis and characterization
, Article Iranian Polymer Journal (English Edition) ; Volume 21, Issue 12 , 2012 , Pages 829-836 ; 10261265 (ISSN) ; Hooshyar, Z ; Zehtabi, F ; Pourjavadi, A ; Sharif University of Technology
2012
Abstract
In this study, the synthesis and characterization of a novel nano-porous superabsorbent hydrogel with high water swelling capacity is described. A nano-porous hydrogel was prepared by employing (2-dimethylaminoethyl) methacrylate (PDMAEMA) as a pH sensitive monomer and sodium alginate (SA) as a water soluble polysaccharide under γ-ray irradiation. The polymerization reaction was performed at room temperature in the absence of chemically toxic crosslinking agent and initiators. The interactive parameters including biopolymer backbone concentration, monomer concentration and γ-irradiation dose were selected as major factors in the synthesis of superabsorbent and three levels for each factor...
Meta hybrid density functional theory study of adsorption of imidazolium and ammonium based ionic liquids on graphene sheet
, Article Journal of Physical Chemistry C ; Volume 119, Issue 13 , March , 2015 , Pages 7095-7108 ; 19327447 (ISSN) ; Jamshidi, Z ; Bayat, A ; Kamath, G ; Sharif University of Technology
American Chemical Society
2015
Abstract
In this study, two types of ionic liquids (ILs) based on 1 butyl 3 methylimidazolium [Bmim]+ and butyltrimethylammonium [Btma]+ cations, paired to tetrafluoroborate [BF4], hexafluorophosphate [PF6], dicyanamide [DCA], and bis(trifluoromethylsilfonyl)imide [Tf2N] anions, were chosen as adsorbates to investigate the influence of cation and anion type on the adsorption of ILs on the graphene surface. The adsorption process on the graphene surface (circumcoronene) was studied using M06 2X/cc pVDZ level of theory. Empirical dispersion correction (D3) was also added to the M06 2X functional to investigate the effects of dispersion on the binding energy values. The graphene···IL configurations,...
A fault-tolerant and energy-aware mechanism for cluster-based routing algorithm of WSNs
, Article Proceedings of the 2015 IFIP/IEEE International Symposium on Integrated Network Management, IM 2015, 11 May 2015 through 15 May 2015 ; May , 2015 , Pages 659-664 ; 9783901882760 (ISBN) ; Shirmohammdi, Z ; Rohbani, N ; Miremadi, S. G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Wireless Sensor Networks (WSNs) are prone to faults due to battery depletion of nodes. A node failure can disturb routing as it plays a key role in transferring sensed data to the end users. This paper presents a Fault-Tolerant and Energy-Aware Mechanism (FTEAM), which prolongs the lifetime of WSNs. This mechanism can be applied to cluster-based WSN protocols. The main idea behind the FTEAM is to identify overlapped nodes and configure the most powerful ones to the sleep mode to save their energy for the purpose of replacing a failed Cluster Head (CH) with them. FTEAM not only provides fault tolerant sensor nodes, but also tackles the problem of emerging dead area in the network. Our...
LAXY: a location-based aging-resilient Xy-Yx routing algorithm for network on chip
, Article IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems ; Volume 36, Issue 10 , 2017 , Pages 1725-1738 ; 02780070 (ISSN) ; Shirmohammadi, Z ; Zare, M ; Miremadi, S. G ; Sharif University of Technology
2017
Abstract
Network on chip (NoC) is a scalable interconnection architecture for ever increasing communication demand between processing cores. However, in nanoscale technology size, NoC lifetime is limited due to aging processes of negative bias temperature instability, hot carrier injection, and electromigration. Usually, because of unbalanced utilization of NoC resources, some parts of the network experience more thermal stress and duty cycle in comparison with other parts, which may accelerate chip failure. To slow down the aging rate of NoC, this paper proposes an oblivious routing algorithm called location-based aging-resilient Xy-Yx (LAXY) to distribute packet flow over entire network. LAXY is...
Using the group method for the synthesis of copper/ZrO2 nanocomposites to achieve high wear resistance by ball milling and spark plasma sintering
, Article Ceramics International ; Volume 48, Issue 12 , 2022 , Pages 17576-17588 ; 02728842 (ISSN) ; Hasani, A ; Amiri, Z ; Khayati, G. R ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The use of ZrO2 nanoparticles is common in the Cu matrix to manufacture Cu/ZrO2 nanocomposites. Many approaches and parameters produce Cu/ZrO2 nanocomposites with an appropriate wear rate and other properties. Hence, proposing an accurate and reliable model was imperative. The main goal of this paper is to find out the best models among the ant colony optimization (ACO), gene expression programming (GEP), artificial bee colony (ABC), and gray wolf optimization algorithm (GWOA) to predict the wear rate of/ZrO2 nanocomposites. To the best of our knowledge, this is the first research that predicts Cu/ZrO2 nanocomposites wear rate using group modeling. To develop models, 105 data were collected...
On endurance and performance of erasure codes in SSD-based storage systems
, Article Microelectronics Reliability ; Volume 55, Issue 11 , 2015 , Pages 2453-2467 ; 00262714 (ISSN) ; Delavari, Z ; Miremadi, S. G ; Asadi, H ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Erasure codes are widely used in data storage systems to protect against disk failures. Employing erasure codes in an array of Solid-State Drives (SSDs) in storage systems necessitates designers to revisit different characteristics in comparison to Hard Disk Drives (HDDs), due to non-mechanical property of SSDs. One of the most important characteristics of SSDs is their limitation on the number of Program/Erase (P/E) cycles. By taking into account the characteristics of SSDs, this paper presents a comprehensive analysis to investigate the effects of three well-known erasure codes on the endurance and performance of SSD-based disk subsystems. The three erasure codes, i.e., Reed-Solomon,...
Balanced equi-n-squares
, Article Electronic Journal of Combinatorics ; Volume 27, Issue 4 , 2020 , Pages 1-35 ; Marbach, T. G ; Stones, R. J ; Wu, Z ; Sharif University of Technology
Australian National University
2020
Abstract
We define a d-balanced equi-n-square L = (lij ), for some divisor d of n, as an n×n matrix containing symbols from Zn in which any symbol that occurs in a row or column, occurs exactly d times in that row or column. We show how to construct a d-balanced equi-n-square from a partition of a Latin square of order n into d×(n/d) subrectangles. In design theory, L is equivalent to a decomposition of Kn,n into d-regular spanning subgraphs of Kn/d,n/d . We also study when L is diagonally cyclic, defined as when l(i+1)(j+1) = lij + 1 for all i, j ∈ Zn, which corresponds to cyclic such decompositions of Kn,n (and thus α-labellings). We identify necessary conditions for the existence of (a) d-balanced...