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    ABSTRACT: Mechanical properties of NiTi shape memory alloy (SMA) were obtained using uniaxial tensile testing and dog-bone specimens. Critical crack tip opening displacement (CTOD) was measured at room temperature on compact tension (CT) specimens using experimental methods of elastic-plastic fracture mechanics (EPFM). To observe the effect of martensitic phase transformation on CTOD, tests were also carried out above martensite deformation temperature (Md). To obtain the displacement and strain fields around the crack tip, under Mode-I loading, digital image correlation (DIC) was used. The extent of transformation zone was calculated using the measured strain field. Finite element analyses were carried out to solve the 2D CT specimen problem under Mode-I loading. Critical CTOD values were calculated for both superelastic and austenitic NiTi for comparison purposes. Size of the transformation zone at the crack tip was also calculated together with crack face opening displacement. The computational and experimental results were compared and discussed. CTOD measurements showed that the phase transformation ahead of the crack tip, improves the fracture behavior of NiTi.
    Full-text · Article · Dec 2015
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    ABSTRACT: The study aims to analyse the selective ability and market timing ability of Polish equity fund managers during the period from January 2009 to November 2014. After the global financial crisis of 2008, in this period of quantitative easing (QE), thanks to an increase in the money supply, a capital flow from developed countries to developing countries was observed. In this study, Polish equity fund manager performances are analysed by using Jensen (1968) alpha measure and Treynor&Mazuy (1966) regression analysis method. Jensen alpha (1968) and Treynor&Mazuy (1966) models provide us the selectivity skills and market timing ability of fund managers, respectively. A total of 14 Polish equity funds have been evaluated during the study period. Among 14 funds, only two funds have positive Jensen alpha, but none of them are statistically significant. Similarly, Treynor&Mazuy (1966) regression analysis indicated that again two other funds have positive yet insignificant market timing ability.
    Full-text · Article · Dec 2015 · Procedia - Social and Behavioral Sciences
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    ABSTRACT: The Northern Aegean Earthquake (Mw=6.9 \ ML=6.5) took place on May 24, 2014 between the islands of Gokceada, Turkey and Samothraki, Greece. The tremors were felt as far as in Istanbul, about 300 km on the East – Northeast (ENE) side of the epicenter. Kandilli Observatory and Earthquake Research Institute (KOERI) of Bogazici University, Turkey operate three downhole arrays in Istanbul, namely Atakoy (ATK), Fatih (FTH) and Zeytinburnu (ZYT) arrays. In this study, waveforms and site response observed at the KOERI operated seismic downhole arrays during the May 2014 Northern Aegean Earthquake (NAE2014) are analyzed in detail and presented. Evaluation of the acceleration records have shown low amplitude but long period and long duration motions at Istanbul. Furthermore, the analyses of the recordings suggest that V s30 alone may not be a sufficient parameter for the characterization of site amplification.
    Full-text · Article · Oct 2015 · Soil Dynamics and Earthquake Engineering

Information

  • Address
    İstanbul, Turkey
  • Head of Institution
    Prof. Gulay Barbarosoglu
  • Website
    www.boun.edu.tr
  • Phone
    +90 212 359 54 00
  • Fax
    +90 212 265 63 57
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Top publications last week by reads

 
The Leadership Quarterly 01/1999; 10(2):219-256.
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International Journal of Information Management 04/2010; 30(2-30):144-151. DOI:10.1016/j.ijinfomgt.2009.08.009
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