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ghasemalizadeh--o
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Experimental Investigation of the Durability of Rammed Earth Materials in Different Environments
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Rammed earth structures have attracted the attention of engineers and researchers in recent years due to their economic advantages, sustainable development, and environmental sustainability. One of the main concerns for public opinion for acceptance of Rammed Earth as a reliable construction material is their durability. Previous studies have investigated the durability of rammed earth materials by conducting wet and dry cycle test, accelerated erosion test, and rain simulation in the laboratory environment. This research studied the durability of cement stabilized rammed earth (CSRE) for one year under the aggressive environments. Three cement contents were considered for preparing the CSRE...
Exact modeling of cardiovascular system using lumped method
, Article 2008 International Conference on Bioinformatics and Computational Biology, BIOCOMP 2008, Las Vegas, NV, 14 July 2008 through 17 July 2008 ; 2008 , Pages 408-417 ; 1601320558 (ISBN); 9781601320551 (ISBN) ; Mirzaee, M. R ; Firoozabadi, B ; Hassani, K ; Sharif University of Technology
2008
Abstract
Electrical analogy (Lumped method) is an easy way to model human cardiovascular system. In this paper Lumped method is used for simulating a complete model. It describes a 36-vessel model and cardiac system of human body with details that could show hydrodynamic parameters of cardiovascular system. Also this paper includes modeling of pulmonary, atrium, left and right ventricles with their equivalent circuits. Exact modeling of right and left ventricles pressure increases the accuracy of our simulation. In this paper we show that a calculated pressure for aorta from our complex circuit is near to measured pressure by using advanced medical instruments
Simulating dynamic plastic continuous neural networks by finite elements
, Article IEEE Transactions on Neural Networks and Learning Systems ; Volume 25, Issue 8 , August , 2014 , Pages 1583-1587 ; ISSN: 2162237X ; Torghabehi, O. O ; Sharif University of Technology
2014
Abstract
We introduce dynamic plastic continuous neural network (DPCNN), which is comprised of neurons distributed in a nonlinear plastic medium where wire-like connections of neural networks are replaced with the continuous medium. We use finite element method to model the dynamic phenomenon of information processing within the DPCNNs. During the training, instead of weights, the properties of the continuous material at its different locations and some properties of neurons are modified. Input and output can be vectors and/or continuous functions over lines and/or areas. Delay and feedback from neurons to themselves and from outputs occur in the DPCNNs. We model a simple form of the DPCNN where the...
Vertically aligned ZnO@CdS nanorod heterostructures for visible light photoinactivation of bacteria
, Article Journal of Alloys and Compounds ; Vol. 590 , 2014 , pp. 507-513 ; ISSN: 09258388 ; Akhavan, O ; Moradlou, O ; Nien, Y. T ; Moshfegh, A. Z ; Sharif University of Technology
2014
Abstract
Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (Eg) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with Eg ∼2.5-2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve...
Metallurgical and mechanical properties of underwater friction stir welds of Al7075 aluminum alloy
, Article Journal of Materials Processing Technology ; Volume 262 , 2018 , Pages 239-256 ; 09240136 (ISSN) ; Kokabi, A. H ; Sabet, H ; Paidar, M ; Ojo, O. O ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Travel speeds between 25–300 mm/min and tool rotational speeds of 800 and 1250 rpm were employed for this study. The microstructure, mechanical properties and fracture surfaces of the joints were studied. Underwater environment and an increase in travel speed significantly increase the precipitates’ volume fraction, reduce the average grain and precipitate sizes of the weld nugget zones. A critical travel speed of 150 mm/min is attained in underwater welds beyond which the average grain sizes remain relatively the same. Average grain and precipitate sizes have linear relationships with the tool rotational and travel speed ratio. Optimum weld strengths of 396 and 360 MPa were obtained in the...
Pre-threaded hole friction stir spot welding of AA2219/PP-C30S sheets
, Article Journal of Materials Processing Technology ; Volume 273 , 2019 ; 09240136 (ISSN) ; Ojo, O. O ; Moghanian, A ; Karami Pabandi, H ; Elsa, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper examines the use of pre-fabricated interlocking arms/threading in enhancing the strength of friction stir spot welded hybrid joints of AA2219/PP-C30S polypropylene polymer by varying parameter combination. The process involves the fabrication of a pre-threaded hole on the Al alloy prior to the joining process, and the threading/crest-pitch profile aids mechanical interlocking. The peak temperature, crest-pitch interlocked profiles, microstructural and mechanical properties of the joints were examined. The results show that an increase in the tool rotational speed increases the thickness of the reaction layer (between the Al and the polymer substrates), the shear-tensile load...
Flexible bactericidal graphene oxide–chitosan layers for stem cell proliferation [electronic resource]
, Article Journal of Applied Surface Science ; 15 May 2014, Volume 301, Pages 456–462 ; Akhavan, O ; Simchi, A. (Abdolreza) ; Sharif University of Technology
Abstract
Graphene oxide (GO)–chitosan composite layers with stacked layer structures were synthesized using chemically exfoliated GO sheets (with lateral dimensions of ∼1 μm and thickness of ∼1 nm), and applied as antibacterial and flexible nanostructured templates for stem cell proliferation. By increasing the GO content from zero to 6 wt%, the strength and elastic modulus of the layers increased ∼80% and 45%, respectively. Similar to the chitosan layer, the GO–chitosan composite layers showed significant antibacterial activity (>77% inactivation after only 3 h) against Staphylococcus aureus bacteria. Surface density of the actin cytoskeleton fibers of human mesenchymal stem cells (hMSCs) cultured...
Superparamagnetic zinc ferrite spinel-graphene nanostructures for fast wastewater purification
, Article Carbon ; Vol. 69 , April , 2014 , pp. 230-238 ; ISSN: 00086223 ; Akhavan, O ; Sharif University of Technology
2014
Abstract
Superparamagnetic ZnFe2O4/reduced graphene oxide (rGO) composites containing ZnFe2O4 nanoparticles (with ∼5-20 nm sizes) attached onto rGO sheets (with ∼1 μm lateral dimensions) were synthesized by hydrothermal reaction method. By increasing the graphene content of the composite from 0 to 40 wt%, the size as well as the number of the ZnFe2O4 nanoparticles decreased and the saturated magnetization of the composites reduced from 10.2 to 1.8 emu/g, resulting in lower responses to external magnetic fields. Concerning this, the time needed for 90% separation of ZnFe2O4/rGO (40 wt%) composite from its solution (2 mg/mL in ethanol) was found 60 min in the presence of an external magnetic field (∼1...
Visible light-induced photocatalytic reduction of graphene oxide by tungsten oxide thin films
, Article Applied Surface Science ; Volume 276 , 2013 , Pages 628-634 ; 01694332 (ISSN) ; Akhavan, O ; Sharif University of Technology
2013
Abstract
Tungsten oxide thin films (deposited by thermal evaporation or sol gel method) were used for photocatalytic reduction of graphene oxide (GO) platelets (synthesized through a chemical exfoliation method) on surface of the films under UV or visible light of the environment, in the absence of any aqueous ambient at room temperature. Atomic force microscopy (AFM) technique was employed to characterize surface morphology of the GO sheets and the tungsten oxide films. Moreover, using X-ray photoelectron spectroscopy (XPS), chemical state of the tungsten oxide films and the photocatalytic reduction of the GO platelets were quantitatively investigated. The better performance of the sol-gel tungsten...
Ethylbenzene dehydrogenation to styrene over fresh and used commercial catalysts
, Article AIChE Annual Meeting, Conference Proceedings ; 2011 ; 9780816910670 (ISBN) ; Ebrahimpour, O ; Sharif University of Technology
2011
Abstract
Dehydrogenation of ethylbenzene (EB) to produce styrene (ST) monomer is commercially performed over potassium-promoted iron oxide catalysts. Catalyst deactivation due to coke deposition and loss of potassium is a major operation and economic drawback in this process. To better evaluate the performance change of these catalysts over their life-cycle, dehydrogenation of EB to ST over the fresh and used commercial catalysts was experimentally investigated at temperatures from 590 to 639°C under atmospheric pressure. The fresh and the used catalysts were obtained from a styrene plant. The used catalyst had been continuously operated for two years under severe plant conditions. The catalyst...
Improving the photocatalytic activity of graphene oxide/ZnO nanorod films by UV irradiation
, Article Applied Surface Science ; Volume 371 , 2016 , Pages 592-595 ; 01694332 (ISSN) ; Akhavan, O ; Sharif University of Technology
Elsevier
2016
Abstract
Graphene oxide (GO) sheets with a low concentration (∼1 wt%) were deposited on surface of hydrothermally synthesized ZnO nanorod films. The deposited films were heat treated at 450 °C in order to achieve suitable GO/ZnO hybrid thin films for photocatalytic purposes. The photocatalytic activity of the nanocomposite films was investigated based on degradation of methylene blue (MB) dye which is a typical pollutant model. The GO/ZnO hybrid thin films could degrade higher MB (∼90%) than the bare ZnO nanorods (which showed only ∼75% degradation) after 450 min UV irradiation. A further significant improvement (resulting in a nearly complete degradation of MB) was achieved by exposing the GO/ZnO...
Roles of surface coverage increase and re-peening on properties of AISI 1045 carbon steel in conventional and severe shot peening processes
, Article Surfaces and Interfaces ; Volume 11 , 2018 , Pages 82-90 ; 24680230 (ISSN) ; Unal, O ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Surface coverage as one of the most effective parameters of shot peening process has substantial influence on the functionality of the peened component. The aim of this study is to investigate the effects of surface coverage increase on the properties of treated specimens experimentally before and after re-shot peening. Different shot peening treatments from conventional to severe; were performed on the AISI 1045 steel. Microstructural observations and XRD measurements were applied to characterize the circumstance of microstructure changes. In order to investigate the mechanical properties, microhardness profiles were achieved, surface roughness was evaluated and the residual stresses...
Ultrahigh permeable C2N-inspired graphene nanomesh membranes versus highly strained c2n for reverse osmosis desalination
, Article Journal of Physical Chemistry B ; Volume 123, Issue 41 , 2019 , Pages 8740-8752 ; 15206106 (ISSN) ; Akhavan, O ; Sharif University of Technology
American Chemical Society
2019
Abstract
The reverse osmosis (RO) desalination capability of hydrogenated and hydroxylated graphene nanomesh membranes (GNMs) inspired by the morphology of carbon nitride (C2N) has been studied by using molecular dynamics simulation. As an advantage, water permeance of the GNMs is found to be several orders of magnitude higher than that of the available RO filters and comparable with highly strained C2N (S-C2N) as follows: 6,6-H,OH > 12-H > S-C2N > 5,5-H,OH > 10-H. The reverse order is found for salt rejection, regardless of S-C2N. The hydrophilic character of the incorporated -OH functional group is believed to be responsible for linking the water molecules in feed and permeate sides via the...
Laminar forced convection simulation at different boundary conditions with averaging scheme (numerical and theoretical research)
, Article Mathematical Modelling of Engineering Problems ; Volume 6, Issue 4 , 2019 , Pages 519-526 ; 23690739 (ISSN) ; Adibi, O ; Sharif University of Technology
International Information and Engineering Technology Association
2019
Abstract
In this paper, cavity flow is simulated numerically. Forced convection in different Reynolds numbers between 100 and 5000 is simulated. Different and complex thermal boundary conditions are applied and various parameters are calculated numerically. Up and down walls are in constant temperature and left and right walls are thermal insulation in the first thermal boundary condition. The Left and the down walls are in constant temperature and the temperature of the up and the right walls changes linearly in the second thermal boundary condition. For the third thermal boundary condition, the left and the down walls are in constant temperature and the temperature of the up and the right walls...
On the way of policy making to reduce the reliance of fossil fuels: Case study of Iran
, Article Sustainability (Switzerland) ; Volume 12, Issue 24 , 2020 , Pages 1-28 ; Mahdavi, O ; Sharif University of Technology
MDPI AG
2020
Abstract
Nowadays, fossil fuels are well known as a predominant source of energy in the planet. Located in the Middle East region, Iran holds one of the largest fossil fuel reservoirs in the world. The country has abundant oil and natural gas fields in various regions; some of them are shared between other countries and have not reached their operational capacity yet. Meanwhile, during recent years and due to global warming followed by environmental global contracts such as Kyoto protocol, using fossil fuels is being criticized to a large extent around the world. Therefore, the global interest has been focused toward clean energy resources. Furthermore, endowed with sundry geographical pattern...
Optimization of shot peening effective parameters on surface hardness improvement
, Article Metals and Materials International ; June , 2020 ; Unal, O ; Sharif University of Technology
Korean Institute of Metals and Materials
2020
Abstract
Abstract: Shot peening is well-known process for mechanical properties integrity in metallic materials. In present study influences of different shot peening treatments on the surface hardness of different carbon steels were investigated experimentally and then alternative approach by using artificial neural network is presented for hardness prediction of the shot peened surface. After modeling a comprehensive parametric investigations and sensitivity analysis were applied according to the influence of the related effective parameters on surface hardness improvements. Graphic Abstract: [Figure not available: see fulltext.] © 2020, The Korean Institute of Metals and Materials
Fatigue limit prediction and analysis of nano-structured AISI 304 steel by severe shot peening via ANN
, Article Engineering with Computers ; February , 2020 ; Unal, O ; Sharif University of Technology
Springer
2020
Abstract
AISI 304 stainless steel is very widely used for industrial applications due to its good integrated performance and corrosion resistance. However, shot peening (SP) is known as one of the effectual surface treatments processes to provide superior properties in metallic materials. In the present study, a comprehensive study on SP of AISI 304 steel including 42 different SP treatments with a wide range of Almen intensities of 14–36 A and various coverage of 100–2000% was carried out. Varieties of experiments were accomplished for the investigation of the microstructure, grain size, surface topography, hardness and residual stresses as well as axial fatigue behavior. After experimental...
Laminar forced convection simulation at different boundary conditions with averaging scheme (numerical and theoretical research)
, Article Mathematical Modelling of Engineering Problems ; Volume 6, Issue 4 , 2019 , Pages 519-526 ; 23690739 (ISSN) ; Adibi, O ; Sharif University of Technology
International Information and Engineering Technology Association
2019
Abstract
In this paper, cavity flow is simulated numerically. Forced convection in different Reynolds numbers between 100 and 5000 is simulated. Different and complex thermal boundary conditions are applied and various parameters are calculated numerically. Up and down walls are in constant temperature and left and right walls are thermal insulation in the first thermal boundary condition. The Left and the down walls are in constant temperature and the temperature of the up and the right walls changes linearly in the second thermal boundary condition. For the third thermal boundary condition, the left and the down walls are in constant temperature and the temperature of the up and the right walls...
Structural changes and surface activities of ethylbenzene dehydrogenation catalysts during deactivation
, Article Applied Catalysis A: General ; Volume 326, Issue 2 , 2007 , Pages 143-151 ; 0926860X (ISSN) ; Ebrahimpour, O ; Sharif University of Technology
2007
Abstract
Industrial dehydrogenation of ethylbenzene to styrene is performed using potassium-promoted iron oxide catalyst. Many attempts have been made to understand the deactivation mechanism of the catalyst based on the chemical differences between the fresh and used catalysts. In the present work, in addition to the effect of chemical changes, the effect of structural changes of the internal areas on the catalyst activity was investigated. A fresh and used commercial catalyst from an industrial reactor which had been continuously used for two years under severe conditions (LHSV = 1 h-1, T = 610 °C, mass ratio of steam to ethylbenzene = 1.2, P = 1.2 atm) was studied. Nitrogen adsorption, Hg...
Common coding of expected value and value uncertainty memories in the prefrontal cortex and basal ganglia output
, Article Science Advances ; Volume 7, Issue 20 , 2021 ; 23752548 (ISSN) ; Hikosaka, O ; Sharif University of Technology
American Association for the Advancement of Science
2021
Abstract
Recent evidence implicates both basal ganglia and ventrolateral prefrontal cortex (vlPFC) in encoding value memories. However, comparative roles of cortical and basal nodes in value memory are not well understood. Here, single-unit recordings in vlPFC and substantia nigra reticulata (SNr), within macaque monkeys, revealed a larger value signal in SNr that was nevertheless correlated with and had a comparable onset to the vlPFC value signal. The value signal was maintained for many objects (>90) many weeks after reward learning and was resistant to extinction in both regions and to repetition suppression in vlPFC. Both regions showed comparable granularity in encoding expected value and value...