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Bilayered heparinized vascular graft fabricated by combining electrospinning and freeze drying methods
, Article Materials Science and Engineering C ; Volume 94 , 2019 , Pages 1067-1076 ; 09284931 (ISSN) ; Shamloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin...
Bilayered heparinized vascular graft fabricated by combining electrospinning and freeze drying methods
, Article Materials Science and Engineering C ; Volume 94 , 2019 , Pages 1067-1076 ; 09284931 (ISSN) ; Shamloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin...
Secure data transmission using qubits
, Article 6th IEEE International Conference on Computer and Information Technology, CIT 2006, Seoul, 20 September 2006 through 22 September 2006 ; 2006 ; 076952687X (ISBN); 9780769526874 (ISBN) ; Hosseini Khayat, S ; Sharif University of Technology
2006
Abstract
A quantum protocol for secure transmission of data using qubits is presented. This protocol sends one qubit in a round-trip to transmit one bit of data. The protocol offers an improvement over the BB84 QKD protocol. BB84, in conjunction with one-time pad encryption, has been shown to be unconditionally secure. However its security relies on the assumption that the qubit source device does not emit multiple replicas of the same qubit for each transmitted bit. If this happens a multi-qubit emission attack can be launched. In addition, BB84 cannot be used to send predetermined bit strings as it generates a random bit string in the process. Our protocol does not have the above drawbacks, but...
Conceptual duct shape design for horizontal-axis hydrokinetic turbines
, Article Scientia Iranica ; Volume 23, Issue 5 , 2016 , Pages 2113-2124 ; 10263098 (ISSN) ; Rad, M ; Khayat, M ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
In the present paper, conceptual duct shape design for kinetic energy extraction with hydrokinetic turbines is discussed. The goal is to find a single-passage axisymmetric geometry that holds stable flow with maximum kinetic energy flux at duct throat. For finding the optimum duct shape, the fluid flow was numerically simulated in a wedge shaped space with Flow-Simulation Software. In a multi-stage conceptual design, tabulated configurations were employed to study each geometrical characteristic separately. These include curvature of profile camber, trailing edge shape, profile tip shape, and duct exit cross sectional area. The revolved profile of each duct consists of a well constrained...
COVID-19 and health inequality: the nexus of race, income and mortality in New York City
, Article International Journal of Human Rights in Healthcare ; 2021 ; 20564902 (ISSN) ; Teron, L ; Rasoulyan, F ; Sharif University of Technology
Emerald Group Holdings Ltd
2021
Abstract
Purpose: The purpose of this paper is to evaluate socioeconomic factors related to COVID-19 mortality rates in New York City (NYC) to understand the connections between socioeconomic variables, including race and income and the disease. Design/methodology/approach: Using multivariable negative binomial regression, the association between health and mortality disparities related to COVID-19 and socioeconomic conditions is evaluated. The authors obtained ZIP code-level data from the NYC Department of Health and Mental Hygiene and the US Census Bureau. Findings: This study concludes that the mortality rate rises in areas with a higher proportion of Hispanic and Black residents, whereas areas...
COVID-19 and health inequality: the nexus of race, income and mortality in New York City
, Article International Journal of Human Rights in Healthcare ; Volume 15, Issue 4 , 2022 , Pages 363-372 ; 20564902 (ISSN) ; Teron, L ; Rasoulyan, F ; Sharif University of Technology
Emerald Group Holdings Ltd
2022
Abstract
Purpose: The purpose of this paper is to evaluate socioeconomic factors related to COVID-19 mortality rates in New York City (NYC) to understand the connections between socioeconomic variables, including race and income and the disease. Design/methodology/approach: Using multivariable negative binomial regression, the association between health and mortality disparities related to COVID-19 and socioeconomic conditions is evaluated. The authors obtained ZIP code-level data from the NYC Department of Health and Mental Hygiene and the US Census Bureau. Findings: This study concludes that the mortality rate rises in areas with a higher proportion of Hispanic and Black residents, whereas areas...
Design and Fabrication of Engineered Biomaterials for Tissue Engineering Applications such as Cardiovascular System
, M.Sc. Thesis Sharif University of Technology ; Shamlou, Amir (Supervisor)
Abstract
Cardiovascular diseases are the leading cause of death all over the world, even more common than cancers. The first reason of mortality in Iran according to statistics is the occlusion of coronary arteries. Unfortunately almost one third of patients doesn’t have enough blood vessels to be used in the bypass surgery and need artificial vessels. These artificial blood vessels with small diameters (less than 6 mm) will fail quickly. As a result there is an increasing demand for tissue engineered blood vessels which are capable of enduring high blood pressures. An artificial blood vessel should mimic both structure and mechanical properties of the real one. Blood vessels have layered structures,...
Numerical and experimental investigations for design of a high performance microhydro-kinetic turbine
, Article International Journal of Engineering, Transactions B: Applications ; Volume 30, Issue 5 , 2017 , Pages 785-790 ; 1728144X (ISSN) ; Rad, M ; Khayat, M ; Sharif University of Technology
2017
Abstract
Design and manufacturing of a high performance micro-hydro-kinetic turbine is discussed in the present paper. The main goal is manufacturing an equipped experimental model of hydro-kinetic turbine with highest energy absorption from water current. A multi-shape ducted turbine comprised of a multi-part diffuser was manufactured that can be converted to many experimental models for studying various diffuser enhancing effects. Turbine's rotor included a three-blade axial propeller and a mixed six-blade propeller with high power coefficient. Simple experiments on propeller were performed for flow visualization, torque measurement and illustrating dynamic balance at high speed rotation in air and...
Experimental and numerical investigations of a single turn pulsating heat pipe using distilled water including micro-coppers
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 59, Issue 9 , 2023 , Pages 1601-1619 ; 09477411 (ISSN) ; Zareh, M ; Shafii, M. B ; Khayat, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2023
Abstract
In this work, experimental and numerical investigations were performed to evaluate the heat transfer efficiency of a single turn pulsating heat pipe by using distilled water as base fluid and distilled water with micro particles (micro-coppers). The pulsating heat pipe was manufactured with copper capillary tube by choosing the internal and external diameter 4 mm and 6 mm, respectively. The effect of filling ratio (40, 50 and 60%), heat input (20, 30, 40, 50 and 60 W) and concentrations of micro-coppers (0.0625 g ml−1 and 0.125 g ml−1) in distilled water as base fluid were studied. Experimental findings displayed that the thermal resistance of the system using micro-coppers declined with...
Prediction of hydrate formation for the systems containing single and mixed electrolyte solutions
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 26, Issue 1 , 2007 , Pages 35-45 ; 10219986 (ISSN) ; Rashtchian, D ; Ghotbi, C ; Taghikhani, V ; Khayat, G ; Sharif University of Technology
Iranian Journal of Chemistry and Chemical Engineering
2007
Abstract
In this work the effect of electrolytes on hydrate formation was investigated. To do so, a new model was used in predicting the hydrate formation conditions in presence of both single and mixed electrolyte solutions. The new model is based on the van der Waals - Platteeuw hydrate equation of state. In order to evaluate the values for the activity of water in electrolyte solutions the simplified version of the Ghotbi-Vera Mean Spherical Approximation (SGV-MSA) model was used. According to the SGV-MSA model the ions in the solutions are considered as charged hard spheres with different sizes. The values of the parameters for the SGV-MSA model are independent of temperature and depend only on...
A novel hybrid algorithm for creating self-organizing fuzzy neural networks
, Article Neurocomputing ; Volume 73, Issue 1-3 , 2009 , Pages 517-524 ; 09252312 (ISSN) ; Ebadzadeh, M. M ; Shahdoosti, H. R ; Rajaei, R ; Khajehnasiri, I ; Sharif University of Technology
2009
Abstract
A novel hybrid algorithm based on a genetic algorithm and particle swarm optimization to design a fuzzy neural network, named self-organizing fuzzy neural network based on GA and PSO (SOFNNGAPSO), to implement Takagi-Sugeno (TS) type fuzzy models is proposed in this paper. The proposed algorithm, as a new hybrid algorithm, consists of two phases. A tuning based on TS's fuzzy model is applied to identify the fuzzy structure, and also a fuzzy cluster validity index is utilized to determine the optimal number of clusters. To obtain a more precision model, GA and PSO are performed to conduct fine tuning for the obtained parameter set of the premise parts and consequent parts in the...
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...
A Deep Learning Approach for Detecting Covid-19 Using the Chest X-Ray Images
, Article Computers, Materials and Continua ; Volume 74, Issue 1 , 2023 , Pages 751-768 ; 15462218 (ISSN) ; Rostami, O ; Yi, M. K ; Hwang, S. O ; Sharif University of Technology
Tech Science Press
2023
Abstract
Real-time detection of Covid-19 has definitely been the most widely-used world-wide classification problem since the start of the pandemic from 2020 until now. In the meantime, airspace opacities spreads related to lung have been of the most challenging problems in this area. A common approach to do on that score has been using chest X-ray images to better diagnose positive Covid-19 cases. Similar to most other classification problems, machine learning-based approaches have been the first/most-used candidates in this application. Many schemes based on machine/deep learning have been proposed in recent years though increasing the performance and accuracy of the system has still remained an...
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...