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Clinical validation of a smartphone-based handheld ECG device: A validation study
, Article Critical Pathways in Cardiology ; Volume 21, Issue 4 , 2022 , Pages 165-171 ; 1535282X (ISSN) ; Gharebaghi, M ; Kamalian, E ; Hajghassem, H ; Ghanbari, A ; Karimi, A ; Mansoury, B ; Dayari, M. S ; Khatmi Nemati, M ; Karimi, A ; Zarghami, M. H ; Vasheghani Farahani, A ; Sharif University of Technology
Lippincott Williams and Wilkins
2022
Abstract
Background: Remote cardiac monitoring and screening have already become an integral telemedicine component. The wide usage of several different wireless electrocardiography (ECG) devices warrants a validation study on their accuracy and reliability. Methods: Totally, 300 inpatients with the Nabz Hooshmand-1 handheld ECG device and the GE MAC 1200 ECG system (as the reference) were studied to check the accuracy of the devices in 1 and 6-limb lead performance. Simultaneous 10-second resting ECGs were assessed for the most common ECG parameters in lead I. Afterward, 6-lead ECGs (limb leads), were performed immediately and studied for their morphologies. Results: Of the 300 patients, 297 had...
Behaviour of End-Plate Connections in 3D Frames Under Fire Conditions: Experimental Study
, Article International Journal of Steel Structures ; Volume 18, Issue 3 , 2018 , Pages 734-749 ; 15982351 (ISSN) ; Vosough Grayli, P ; Ghorbani, A ; Roshani Moghaddam, A ; Sharif University of Technology
Korean Society of Steel Construction
2018
Abstract
Due to high vulnerability of steel structures to elevated temperatures and the need for taking adequate and effective measures to reduce human and financial losses in fires, a thorough understanding of such behaviour is of utmost importance. In this research, a half-scale 3D model, comprising moment-resisting frames, equipped with flush end-plate connections, in one direction, and braced frames in the other, was subjected to a scaled ISO 834 standard fire. The maximum attained temperature was 1055 °C. The results showed that the structure tolerates high temperatures for an appreciable amount of time before collapsing. Moreover, for thick flush end-plates, which were used in this study, the...
Investigation into the 3D behaviour of split-level steel building structures: introducing the LBDM
, Article International Journal of Steel Structures ; Volume 22, Issue 3 , 2022 , Pages 833-850 ; 15982351 (ISSN) ; Eskandaritorbaghan, F ; Sharif University of Technology
Korean Society of Steel Construction
2022
Abstract
Irregular buildings constitute a large portion of the modern urban structures. Based on experiences of past earthquakes, irregular configuration of buildings or asymmetrical distribution of structural properties trigger an increase in seismic demand, intensifying the vulnerability of the structure. In this work, the effects of splitting in levels, classified as vertical irregularity, on the seismic behaviour of some 3D steel structures are studied. Studied models consisted of five-, ten- and fifteen-storey 3D steel special moment-resisting frames, split just in one direction, with six different plans. Equivalent static method together with a special pattern for distributing the base shear,...
Inverse emulsion polymerization of triple monomers of acrylamide, maleic anhydride, and styrene to achieve highly hydrophilic–hydrophobic modified polyacrylamide
, Article Journal of Applied Polymer Science ; Volume 136, Issue 29 , 2019 ; 00218995 (ISSN) ; Ramazani S. A., A ; Tamsilian, Y ; Shirazi, M ; Sharif University of Technology
John Wiley and Sons Inc
2019
Abstract
The purpose of this study was the production of copolymers and terpolymers with highly hydrophilic–hydrophobic properties, using inexpensive and available monomers as potential enhancing oil recovery (EOR) and water production control agents for high-temperature and high-salinity (HTHS) oil reservoirs. For this purpose, several copolymers and terpolymers with different molar percentage of acrylamide/styrene, acrylamide/maleic anhydride, and acrylamide/styrene/maleic anhydride were synthesized by the inverse emulsion polymerization technique. The presence of hydrophobic styrene and hydrophilic maleic anhydride monomers in the copolymer and terpolymer structure, provided some unique properties...
Strength of SCLC recycle springs and fibers concrete subject to high temperatures
, Article Structural Concrete ; 2021 ; 14644177 (ISSN) ; Toufigh, V ; Sharif University of Technology
John Wiley and Sons Inc
2021
Abstract
In this article, the self-compacting lightweight concretes (SCLC) with different fibers were prepared and exposed to elevated temperatures, and their mechanical properties were investigated. Three types of fibers were steel fibers (SF), polypropylene fibers (PPF), and metal springs with a volume fraction of 0.4%. One hundred and fifty cylindrical specimens were prepared, and the compression, tensile and flexural tests were carried out on them after exposure to high temperatures ranging from 25 to 700°C. The findings indicate that incorporation of steel fibers and springs enhanced the compressive strength of concrete by 20% compared to the control specimen. Meanwhile, the polypropylene fibers...
Cementitious mortars containing pozzolana under elevated temperatures
, Article Structural Concrete ; Volume 23, Issue 5 , 2022 , Pages 3294-3312 ; 14644177 (ISSN) ; Pachideh, G ; Sharif University of Technology
John Wiley and Sons Inc
2022
Abstract
In recent years, pozzolana are being increasingly used in different types of concretes and mortars. This investigation aims to evaluate the effect of replacing 7, 14, 21, and 28% cement (by weight) with silica fume (SF), granulated blast furnace slag (GBFS), zeolite, and fly ash (FA) under elevated temperatures. Forty mix designs were built with various water-to-cement ratios and plasticizers. Three hundred and six specimens were prepared, and the flexural, uniaxial compression and tensile tests were performed on specimens after exposure to elevated temperatures between 25°C and 900°C. The X-ray diffraction (XRD) test was then performed on the two series of specimens. Accordingly, the...
Strength of SCLC recycled springs and fibers concrete subject to high temperatures
, Article Structural Concrete ; Volume 23, Issue 1 , 2022 , Pages 285-299 ; 14644177 (ISSN) ; Toufigh, V ; Sharif University of Technology
John Wiley and Sons Inc
2022
Abstract
In this article, the self-compacting lightweight concretes (SCLC) with different fibers were prepared and exposed to elevated temperatures, and their mechanical properties were investigated. Three types of fibers were steel fibers (SF), polypropylene fibers (PPF), and metal springs with a volume fraction of 0.4%. One hundred and fifty cylindrical specimens were prepared, and the compression, tensile and flexural tests were carried out on them after exposure to high temperatures ranging from 25 to 700°C. The findings indicate that incorporation of steel fibers and springs enhanced the compressive strength of concrete by 20% compared to the control specimen. Meanwhile, the polypropylene fibers...
Target localization in distributed MIMO radar from time delays, doppler shifts, azimuth and elevation angles of arrival
, Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 1498-1503 ; 9781728115085 (ISBN) ; Navebi, M. M ; Amiri, R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, we focus on the moving target localization problem in a multiple-input multiple-output radar with widely separated antennas. By exploiting jointly different types of information including time delay, Doppler shift and azimuth and elevation angles of arrival, we develop an algebraic closed-form two-stage weighted least squares solution for the problem. The proposed algorithm is shown analytically to attain the CramerRao lower bound accuracy under the small Gaussian noise assumption. Numerical simulations are included to examine the algorithm's performance and corroborate the theoretical developments
Particle filtering-based low-elevation target tracking with multipath interference over the ocean surface
, Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 56, Issue 4 , 2020 , Pages 3044-3054 ; Taheri, A ; Cecen, T ; Celik, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
As radar signals propagate above the ocean surface to determine the trajectory of a target, the signals that are reflected directly from the target arrive at the receiver along with indirect signals reflected from the ocean surface. These unwanted signals must be properly filtered; otherwise, their interference may mislead the signal receiver and significantly degrade the tracking performance of the radar. To this end, we propose a low-elevation target tracking mechanism considering the specular and diffuse reflection effects of multipath propagation over the ocean surface simultaneously. The proposed mechanism consists of a state-space model and a particle filtering algorithm and promises...
Processing of Al-20Si-5Fe-2X(X=Cu, Ni, Cr) alloys by melt-spinning and hot-pressing
, Article European International Powder Metallurgy Congress and Exhibition, Euro PM 2008, Mannheim, 29 September 2008 through 1 October 2008 ; Volume 2 , 2008 , Pages 99-104 ; 9781899072033 (ISBN) ; Simchi, A ; Davami, P ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2008
Abstract
Al-20Si-5Fe-2X (X=Cu, Ni, Cr) ribbons were produced by melt-spinning and consolidated by hot pressing at 400°C for 60 min. Optical and transmission electron microscopy (TEM), X-ray diffractometry (XRD), and hardness test were used to evaluate the microstructure and mechanical strength of the ribbons and hot consolidated specimens. The compressive strength of the specimens at ambient and elevated temperatures was also examined. The microstructure of the ribbons exhibited featureless and dendritic zones, and contains spherically-shaped Si particles with an average diameter of 20 nm. After hot-pressing, ultrafine Si (110-150 nm) and iron-containing intermetallic particles were formed. The...
The effect of elevated temperatures on the tensile performance of GFRP and CFRP sheets
, Article Construction and Building Materials ; Volume 190 , 2018 , Pages 38-52 ; 09500618 (ISSN) ; Pournamazian Najafabadi, E ; Houshmand Khaneghahi, M ; Vatani Oskouei, A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this study, the effects of fiber type (i.e., carbon and glass fibers) and intumescent paint on the tensile performance of fiber reinforced polymer (FRP) sheets at elevated temperatures are investigated. For this purpose, a series of tensile tests were conducted on the glass and carbon fiber reinforced polymer (GFRP and CFRP) sheets, with and without intumescent fire retardant paint, at different elevated temperatures. The studied temperatures ranged from 25 °C to 600 °C. Scanning electron microscopy was also used to examine the effects of elevated temperatures on FRP sheets and the fire protecting mechanism of the intumescent paint. Based on the test results, the tensile strength of the...
Drying shrinkage in alkali-activated binders – A critical review
, Article Construction and Building Materials ; Volume 190 , 2018 , Pages 533-550 ; 09500618 (ISSN) ; Kinnunen, P ; Dalvand, A ; Mohammadi Firouz, R ; Illikainen, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Alkali-activated binders have been proposed and have emerged as an alternative to ordinary Portland cement (OPC) binders with acceptable mechanical and durability performances in addition to positive environmental impacts. These alternative binders use a wide range of aluminosilicate precursors, with differing availabilities, reactivities, costs and CO2 emissions. Despite all the studies published on improving the characteristics of these materials in the last decades, some aspects of alkali-activated binders require further investigations. For instance, shrinkage in alkali-activated binders due to the different chemical processes being involved is more complicated than OPC composites and it...
Geopolymers vs. alkali-activated materials (AAMs): A comparative study on durability, microstructure, and resistance to elevated temperatures of lightweight mortars
, Article Construction and Building Materials ; Volume 222 , 2019 , Pages 49-63 ; 09500618 (ISSN) ; Shoaei, P ; Zareei, S. A ; Behforouz, B ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper studied the durability, microstructure, and fire behavior of lightweight mortars based on cement, metakaolin (MK), ultrafine ground granulated blast furnace slag (UGGBFS), ceramic waste powder (CWP), and clay brick waste powder (CBWP). Two sets of mixes were prepared with two types of lightweight aggregate including lightweight expanded clay aggregate (LECA) and pumice aggregate. Regarding the durability assessment, the electrical resistivity and water absorption of the mortars were measured. The UGGBFS-based alkali-activated mortar with pumice aggregate exhibited the highest electrical resistivity and lowest water absorption, while CBWP-based geopolymer mortar with LECA showed...
The tensile performance of FRP bars embedded in concrete under elevated temperatures
, Article Construction and Building Materials ; Volume 211 , 2019 , Pages 1138-1152 ; 09500618 (ISSN) ; Vatani Oskouei, A ; Khaneghahi, M. H ; Shoaei, P ; Ozbakkaloglu, T ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this research, the mechanical properties of glass and carbon fiber reinforced polymer (FRP) bars with epoxy resin matrices embedded in concrete were investigated under an extensive range of elevated temperatures (i.e., 25–800 °C). Embedded FRP bars with various bar diameters were studied in order to determine bar diameter influence on the results. In addition, analysis of variance (ANOVA) was performed on the experimental results to investigate the contribution of exposure temperature and bar diameter to the tensile behavior of embedded in concrete FRP bars at elevated temperatures. The results show that the tensile strength of embedded FRP bars generally decreases with increasing...
Effect of fibers configuration and thickness on tensile behavior of GFRP laminates subjected to elevated temperatures
, Article Construction and Building Materials ; Volume 202 , 2019 , Pages 189-207 ; 09500618 (ISSN) ; Bazli, M ; Ashrafi, H ; Vatani Oskouei, A ; Azhari, S ; Zhao, X. L ; Gholipour, H ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This study was aimed at gaining an improved understanding of the behavior of glass fiber-reinforced polymer laminates at elevated temperatures by means of testing laminate specimens with unidirectional, woven, and randomly distributed (chopped strand mat) fibers. The testing parameters were temperature, the type of fiber, and the thickness of the laminates. The failure modes of the specimens and their elasticity moduli at ambient temperature were investigated, and analysis of variance was conducted to determine the contribution of each parameter to the behavioral test results. The findings showed that among the parameters, an increase in temperature exerted the strongest effect on the...
Recycled ceramic waste high strength concrete containing wollastonite particles and micro-silica: A comprehensive experimental study
, Article Construction and Building Materials ; Volume 201 , 2019 , Pages 11-32 ; 09500618 (ISSN) ; Ameri, F ; Shoaei, P ; Bahrami, N ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This study investigated the effects of combined utilization of wollastonite particles and recycled waste ceramic aggregate (RWCA) on high strength concrete (HSC) properties. Two groups of mixtures were manufactured: 1) concrete mixtures in which cement was partially replaced with wollastonite at values ranging from 10% to 50%, and 2) mixtures in which wollastonite was used at the aforementioned dosages and 50% of natural coarse aggregate was replaced with RWCA. In addition, 10% of cement weight micro-silica was added to all mixtures. The concrete behavior in terms of strength, durability, resistance against acidic environment, and performance under elevated temperatures ranging from 20 °C to...
Experimental investigation and probabilistic models for residual mechanical properties of GFRP pultruded profiles exposed to elevated temperatures
, Article Composite Structures ; Volume 211 , 2019 , Pages 610-629 ; 02638223 (ISSN) ; Houshmand Khaneghahi, M ; Ahmadie Amiri, H ; Esmaeilpour Estekanchi, H ; Ozbakkaloglu, T ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Here, we investigate the influence of elevated temperatures with negligible ambient oxygen on mechanical properties of various embedded glass fiber reinforced polymer (GFRP) profiles, as well as the application of a predictive Bayesian model for predicting these properties. Both the flexural and compressive properties of FRP profiles were investigated through the tests of I-shaped and box-shaped profiles. To determine the impact of low and high elevated temperature, the profiles were exposed to a wide range of temperatures (i.e., 25–550 °C); effects of the exposure time were also investigated. Experiments showed that specimens exposed to higher elevated temperatures for longer time periods...
Effect of thickness and reinforcement configuration on flexural and impact behaviour of GFRP laminates after exposure to elevated temperatures
, Article Composites Part B: Engineering ; Volume 157 , 2019 , Pages 76-99 ; 13598368 (ISSN) ; Ashrafi, H ; Jafari, A ; Zhao, X.-L ; Gholipour, H ; Oskouei, A. V ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This study investigates the flexural and impact behaviour of GFRP laminates after exposure to elevated temperatures. The effect of fibre's length and orientation, laminate's thickness, and exposure time is studied. A total number of 540 tests in terms of three-point bending and Charpy impact tests were conducted to obtain the mechanical properties. In addition, SEM analyses were carried out to investigate the degradation mechanisms. Finally, statistical study was conducted to investigate the contribution of each variable and develop probabilistic models using ANOVA and linear Bayesian regression method. The results showed that generally the flexural and impact properties of GFRP laminates...
Synthesis and morphology optimization of electrospun SiBNC nanofibers
, Article Ceramics International ; Volume 46, Issue 5 , 2020 , Pages 6052-6059 ; Mehdinavaz Aghdam, R ; Shahedi Asl, M ; Faghihi Sani, M. A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
SiBNC nanofibers were synthesized through the polymeric route by a one-pot synthesis approach. DMTA (dichloroboryl methyl trichlorosilyl amine) polymer was selected as pre-ceramic for SiBNC, which was shaped into nanofibers by electrospinning. Then, the nanofibers were cured in an inert atmosphere in order to obtain the final ceramic. By changing the curing atmosphere, the compound of final ceramic has been manipulated. In addition, the ceramic yield of DMTA as a preceramic was increased in the nitrogen atmosphere. The effects of applied voltage, solution concentration, and feeding rate on the morphology of final electrospun ceramic nanofibers were also investigated. Final ceramic remains...
Tensile properties of GFRP laminates after exposure to elevated temperatures: Effect of fiber configuration, sample thickness, and time of exposure
, Article Composite Structures ; Volume 238 , 2020 ; Bazli, M ; Jafari, A ; Ozbakkaloglu, T ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This study investigates the tensile properties of various GFRP laminates after exposure to elevated temperatures. Fiber configuration, exposure temperature and laminate thickness were considered as the test variables. A total number of 180 specimens were tested in tension to obtain the mechanical properties of GFRP laminates. Alongside the mechanical tests, SEM analyses were conducted on selected samples before testing to investigate the resin, fiber, and their interface damages. Regardless of the sample type, it was generally observed that the reduction rate in the tensile strength increased with an increase in the exposure time and a decrease in the laminates’ thickness. The results of...