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    Iran atlas of offshore renewable energies

    , Article Renewable Energy ; Volume 36, Issue 1 , January , 2011 , Pages 388-398 ; 09601481 (ISSN) Abbaspour, M ; Rahimi, R ; Sharif University of Technology
    The aim of the present study is to provide an Atlas of IRAN Offshore Renewable Energy Resources (hereafter called 'the Atlas') to map out wave and tidal resources at a national scale, extending over the area of the Persian Gulf and Sea of Oman. Such an Atlas can provide necessary tools to identify the areas with greatest resource potential and within reach of present technology development. To estimate available tidal energy resources at the site, a two-dimensional tidally driven hydrodynamic numerical model of Persian Gulf was developed using the hydrodynamic model in the MIKE 21 Flow Model (MIKE 21HD), with validation using tidal elevation measurements and tidal stream diamonds from... 

    Compressive and Bond Behavior of Concrete-Filled Pultruded GFRP and PE Tubes Under Elevated Temperatures

    , Ph.D. Dissertation Sharif University of Technology Tabatabaeian Nimavard, Mojtaba (Author) ; Khaloo, Alireza (Supervisor)
    Concrete-filled GFRP and PE tubes are composite systems using the polymeric tubes as confinement for the marine structures to extend their service life. However, elevated temperatures and thermal cycles in marine environments can affect the behavior of such composite systems. In this investigation, the effect of elevated temperatures and thermal cycles on the performance of concrete-filled pultruded GFRP tubes (CFPGT) and concrete-filled polyethylene tubes (CFPT) is assessed, respectively. For this, different parameters such as concrete core strength (30 and 60 MPa), exposure temperature (25, 100, 200, 300, and 400°C), time exposure (60 and 120 min.), number of thermal cycles (50, 100, and... 

    Multi criteria site selection model for wind-compressed air energy storage power plants in Iran

    , Article Renewable and Sustainable Energy Reviews ; Vol. 32 , April , 2014 , pp. 579-590 ; ISSN: 13640321 Satkin, M ; Noorollahi, Y ; Abbaspour, M ; Yousefi, H ; Sharif University of Technology
    In this research, a site selection method for wind-compressed air energy storage (wind-CAES) power plants was developed and Iran was selected as a case study for modeling. The parameters delineated criteria for potential wind development localities for wind-CAES power plant sites. One important consequence of this research was the identification of the wind energy potential for wind-CAES sites. The theoretical wind energy potential of Iran of greater than 50 W/m2 was identified from a wind atlas of Iran. The model produced factor maps by considering the boundary conditions of the input data and created geo-databases from the outputs maps. The main factor maps were electrical grids and... 

    Hydroxyapatite nanocomposites: Synthesis, sintering and mechanical properties

    , Article Ceramics International ; Volume 39, Issue 3 , April , 2013 , Pages 2197-2206 ; 02728842 (ISSN) Aminzare, M ; Eskandari, A ; Baroonian, M. H ; Berenov, A ; Razavi Hesabi, Z ; Taheri, M ; Sadrnezhaad, S. K ; Sharif University of Technology
    Two different hydroxyapatite based composites reinforced by oxide ceramic (20 wt%) nano crystals were synthesized by high-energy ball milling and sintered by pressure less technique. Alumina and titania nanoparticles as secondary phases improved densification and mechanical behavior of apatite and postponed its decomposition to the tricalcium phosphate (TCP) phases at elevated temperatures. Increasing the relative density of apatite using nano reinforcements leads to enhance the bending strength by more than 40% and 27% (as compared to the pure HA) and increase the hardness from 2.52 to 5.12 (Al2O3 composite) and 4.21 (TiO2 addition) GPa, respectively. Transmission electron microscopy (TEM),... 

    Production of net-shaped dense metal-carbide-based composites through an infiltration process at intermediate temperature

    , Article International Journal of Refractory Metals and Hard Materials ; Volume 38 , 2013 , Pages 35-39 ; 02634368 (ISSN) Davarpanah, A ; Sani, M. A. F ; Shabani, K ; Bodaghi, M ; Sharif University of Technology
    Tungsten composites are interesting materials for high temperature applications. These composites are conventionally produced by solid state reaction, where elevated temperatures and long sintering processes are inevitable, and generally produce volatile components that increase defects and impair the properties of the composites for high temperature applications. In the present paper, synthesis of dense near net-shaped transition metal-metal carbide by reaction casting is studied, which creates a potential application for the composite at 2000 C. Since the pores of the ceramic preform are filled with reaction products, this technique is referred to as displacive compensation porosity (DCP).... 

    Tribological characterization of electroless Ni-10% P coatings at elevated test temperature under dry conditions

    , Article International Journal of Advanced Manufacturing Technology ; Volume 62, Issue 9-12 , October , 2012 , Pages 1063-1070 ; 02683768 (ISSN) Masoumi, F ; Ghasemi, H. R ; Ziaei, A. A ; Shahriari, D ; Sharif University of Technology
    Springer  2012
    An experimental study of wear characteristics of electroless Ni-10% P coating sliding against hard AISI 52100 steel pin is investigated. Experiments are carried out at room and 550°C temperatures. Heat treatment effects on tribological behavior of this coating are studied. The wear surface and the microstructure of the coatings are analyzed using optical microscopy, scanning electron microscopy, energy dispersion analysis X-ray, and microhardness testing equipment. It is observed that the forming of continuous oxide film on contacting surfaces of pin and disk improves wear resistance and decreases friction coefficient of the Ni-10% P coating. The results indicate that the wear resistance of... 

    A trace-time framework for prediction of elevation angle over land mobile LEO satellites networks

    , Article Wireless Personal Communications ; Volume 62, Issue 4 , February , 2012 , Pages 793-804 ; 09296212 (ISSN) Seyedi, Y ; Rahimi, F ; Sharif University of Technology
    Elevation angle is one of the most significant parameters of land mobile satellite channels, subject to rapid variations in the case of Low Earth Orbit (LEO) satellite systems. In this paper a novel trace-based framework is proposed and analyzed which is capable of predicting elevation angle as a function of time during satellite visibility window. Trace-time based modeling makes the framework practical for real-time evaluation of elevation angle and its alteration incurred by communication links in LEO satellite systems. The proposed method is particularly suitable for development of communication channel models and services in mobile LEO satellite networks where path variability is of... 

    Constitutive modeling of temperature and strain rate dependent elastoplastic hardening materials using a corotational rate associated with the plastic deformation

    , Article International Journal of Plasticity ; Volume 27, Issue 9 , 2011 , Pages 1445-1455 ; 07496419 (ISSN) Ghavam, K ; Naghdabadi, R ; Sharif University of Technology
    In this paper, a constitutive model with a temperature and strain rate dependent flow stress (Bergstrom hardening rule) and modified Armstrong-Frederick kinematic evolution equation for elastoplastic hardening materials is introduced. Based on the multiplicative decomposition of the deformation gradient,new kinematic relations for the elastic and plastic left stretch tensors as well as the plastic deformation-dependent spin tensor are proposed. Also, a closed-form solution has been obtained for the elastic and plastic left stretch tensors for the simple shear problem.To evaluate model validity, results are compared with known experimental data for SUS 304 stainless steel, which shows a good... 

    Phase formation during sintering of nanocrystalline zirconia/stainless steel functionally graded composite layers

    , Article Materials Letters ; Volume 65, Issue 3 , February , 2011 , Pages 523-526 ; 0167577X (ISSN) Dourandish, M ; Simchi, A ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
    Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the... 

    The performance of bolted slant endplate connections subjected to temperature increase

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010l ; Volume 2 , July , 2010 , Pages 207-217 ; 9780791849163 (ISBN) Zahmatkesh, F ; Talebi, E ; Sharif University of Technology
    In this paper the main goal is to evaluate the vertical and slant bolted endplate connections performance in steel moment frame structures under thermal effect in elastic field, and by a finite element software. the connections are simulated to complete and verify simple modeling of analytical and numerical analysis of the behavior of vertical and slant bolted endplate connections due to increase in temperature. The results that are obtained from performance of a vertical bolted endplate connection and a slant bolted endplate connection due to increase in temperature will be compared  

    Dynamic ageing and the mechanical response of Al-Mg-Si alloy through equal channel angular pressing

    , Article Materials and Design ; Volume 31, Issue 9 , October , 2010 , Pages 4076-4082 ; 02641275 (ISSN) Vaseghi, M ; Karimi Taheri, A ; Ig Hong, S ; Seop Kim, H ; Sharif University of Technology
    In this paper, dynamic ageing characteristics associated with the application of equal channel angular pressing (ECAP) to Al6061 alloy at elevated temperatures was investigated. Followed by ECAP, Vickers microhardness measurement on the cross-sectional planes and microstructural observations were undertaken using transmission electron microscopy. The combination of the ECAP process with dynamic ageing at both 100°C and 150°C resulted in a significant increase in hardness. The grain size was measured as ∼160. nm after four passes. A comparison with the published data on the same alloy processed by ECAP at room temperature and statically aged, suggests several advantages in incorporating... 

    Oxidation behavior of AISI 321, AISI 316, and AISI 409 stainless steels: Kinetic, thermodynamic, and diffusion studies

    , Article Journal of Materials Research ; 2016 , Pages 1-9 ; 08842914 Movahedi Rad, A ; Pelaseyed, S.S ; Attarian, M ; Shokrallahzadeh, R ; Sharif University of Technology
    Cambridge University Press  2016
    The oxidation behavior of three types of stainless steels, namely AISI 321, AISI 316, and AISI 409, was compared. In all stainless steels, oxide layers were formed and their masses and thicknesses increased with oxidation time. Among them, AISI 409 ferritic stainless steel demonstrated higher oxidation rate. According to the kinetical oxidation behavior of them at elevated temperatures, the oxidation mechanism was determined. Among them, the AISI 409 ferritic stainless steel showed the lowest and AISI 321 austenitic stainless steel demonstrated the highest oxidation resistance. Based on the experimental results, it was suggested that the kinetic of oxide growth in stainless steels was... 

    Effect of silicon carbide nanoparticles on hot deformation of ultrafine-grained aluminium nanocomposites prepared by hot powder extrusion process

    , Article Powder Metallurgy ; Volume 59, Issue 4 , 2016 , Pages 262-270 ; 00325899 (ISSN) Mobarhan Bonab, M. A ; Simchi, A ; Sharif University of Technology
    Taylor and Francis Ltd 
    The flow behaviour of Al–SiC nanocomposites prepared by mechanical milling and hot powder extrusion methods was studied at different temperatures (350–500°C) and strain rates (0.005–0.5 s−1). The flow of the Powder metallurgy nanocomposites exhibited a peak stress followed by a dynamic flow softening behaviour. It was shown that mechanical milling increased high-temperature strain rate sensitivity of ultrafine-grained (UFG) aluminium while decreasing its flow dependence to temperature. Constitutive analysis of the hot deformation process by Zener–Hollomon parameter (Z) also indicated a remarkable increase in the deformation activation energy (about 40%). Likewise, SiC nanoparticles (up to... 

    The effect of mechanical and thermal properties of FRP bars on their tensile performance under elevated temperatures

    , Article Construction and Building Materials ; Volume 157 , 2017 , Pages 1001-1010 ; 09500618 (ISSN) Ashrafi, H ; Bazli, M ; Najafabadi, E. P ; Vatani Oskouei, A ; Sharif University of Technology
    In this experimental study the effect of physical and thermal properties of various FRP bars on their performance under elevated temperatures are investigated. The parameters included the bars' diameter, type of fiber, type of resin, fiber to matrix ratio, and thermal properties were studied. Moreover, ANOVA (ANalysis Of VAriance) was performed in order to investigate the contribution of each variable on the obtained results. The results showed that in addition to the temperature, the bars' diameter, type of fiber, type of resin, and thermal properties (Tg and Td) of the FRP bars have contributions to the results, while the fiber to matrix ratio was found to be an ineffective factor. It was... 

    SPH numerical simulation of tsunami wave forces impinged on bridge superstructures

    , Article Coastal Engineering ; Volume 121 , 2017 , Pages 145-157 ; 03783839 (ISSN) Sarfaraz, M ; Pak, A ; Sharif University of Technology
    Elsevier B.V  2017
    This paper addresses numerically-derived tsunami wave loads on bridge superstructures using smoothed particle hydrodynamics (SPH), which is a type of mesh-free methods. Although there exist some relationships for the case of impinged loads on bridges exerted by regular (sinusoidal) waves, for the case of solitary waves such as tsunamis, no relation has yet been proposed in the literature. This shortcoming is partly due to the lack of understanding the mechanism of wave action on the bridge superstructures. In this study, three water depths, three wave amplitudes and four submergence depths of the deck are considered for the process of numerical investigation of tsunami-induced loads on... 

    Deformation behavior of severely deformed al and related mechanisms through warm tensile test

    , Article Journal of Materials Engineering and Performance ; Volume 26, Issue 3 , 2017 , Pages 1311-1324 ; 10599495 (ISSN) Charkhesht, V ; Kazeminezhad, M ; Sharif University of Technology
    Springer New York LLC  2017
    Flow stress and ductility behaviors of the annealed and severely deformed Al were investigated at warm deformation temperatures. Constrained groove pressing (CGP) method as a severe plastic deformation process was used. The tensile test was carried out at the temperature range of the 298-573 K and strain rate range of 0.001-0.1 s−1 to present the elevated temperature deformation behavior utilizing hyperbolic sine constitutive equation. The flow stress of the CGPed sample is increased with the number of CGP passes and decreased with temperature. Dynamic recovery and strain softening are found as main restoration mechanisms. Flow stress amounts are not remarkably affected by the strain rate.... 

    Drying shrinkage in alkali-activated binders – A critical review

    , Article Construction and Building Materials ; Volume 190 , 2018 , Pages 533-550 ; 09500618 (ISSN) Mastali, M ; Kinnunen, P ; Dalvand, A ; Mohammadi Firouz, R ; Illikainen, M ; Sharif University of Technology
    Elsevier Ltd  2018
    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... 

    Effect of rare earth elements addition and T6 heat treatment on creep properties of Mg-Al-Zn alloy

    , Article Magnesium Technology 2009, San Francisco, CA, 15 February 2009 through 19 February 2009 ; 2009 , Pages 483-488 ; 15454150 (ISSN); 9780873397308 (ISBN) Meshinchi Asl, K ; Khomamizadeh, F ; Magnesium Committee of the Light Metals Division; Minerals, Metals and Materials Society, TMS ; Sharif University of Technology
    This paper focuses on creep properties of AZ91-RE and heat treated AZ91 magnesium alloy. Influence of heat treatment and rare earths addition on microstructure and mechanical properties were investigated. Creep behavior is dependent on the stability of the near grain boundary microstructure and is improved by rare earth addition. The results show that sliding of grain boundaries has an important part in the deformation mechanism in AZ91 alloy at elevated temperatures which is greatly suppressed by the rare earths addition  

    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) Noroozi, A ; Navebi, M. M ; Amiri, R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    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  

    Mechanical strength of CFRP and GFRP composites filled with APP fire retardant powder exposed to elevated temperature

    , Article Fire Safety Journal ; Volume 115 , 2020 Shekarchi, M ; Majdabadi Farahani, E ; Yekrangnia, M ; Ozbakkaloglu, T ; Sharif University of Technology
    Elsevier Ltd  2020
    Ammonium polyphosphate (APP) is one of the most widely used halogen-free flame retardant, added in various resins to improve the fire properties, such as flame and smoke spread ratings and LOI, of fiber-reinforced polymer (FRP) composites. This paper experimentally investigates the effects of using APP, as a fire-retardant filler, on mechanical properties (i.e. ultimate tensile, flexural, and bond strength) of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites. Based on two fiber types (i.e. carbon and glass) and three different APP mass fractions in resin (i.e. 0, 20, and 40% of total weight of matrix), six sets of specimens were prepared for each...