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    Reversibility of Asphaltene Aggregation in Live Oils: Qualitative and Quantitative Evaluation

    , Article Journal of Chemical and Engineering Data ; Volume 60, Issue 9 , August , 2015 , Pages 2646-2654 ; 00219568 (ISSN) Mohammadi, S ; Rashidi, F ; Mousavi Dehghani, S. A ; Ghazanfari, M. H ; Sharif University of Technology
    American Chemical Society  2015
    Despite the numerous experimental studies concerning asphaltene, the extent of reversibility of asphaltene aggregation at reservoir conditions remains still an elusive and controversial issue in the available literature. In this work, a series of depressurization and repressurization experiments were performed on three different live oils for qualitative and quantitative evaluation of the reversibility of asphaltene aggregation under typical pressure and temperature conditions of oil fields. The obtained results reveal that the kinetics and the extent of reversibility of asphaltene aggregation at elevated pressure and temperature are majorly controlled by the characteristics of the reservoir... 

    Fluctuation relation for heat exchange in Markovian open quantum systems

    , Article Physical Review E ; Volume 97, Issue 4 , April , 2018 ; 24700045 (ISSN) Ramezani, M ; Golshani, M ; Tayefeh Rezakhani, A ; Sharif University of Technology
    American Physical Society  2018
    A fluctuation relation for the heat exchange of an open quantum system under a thermalizing Markovian dynamics is derived. We show that the probability that the system absorbs an amount of heat from its bath, at a given time interval, divided by the probability of the reverse process (releasing the same amount of heat to the bath) is given by an exponential factor which depends on the amount of heat and the difference between the temperatures of the system and the bath. Interestingly, this relation is akin to the standard form of the fluctuation relation (for forward-backward dynamics). We also argue that the probability of the violation of the second law of thermodynamics in the form of the... 

    Effects of temperature and torsion speed on torsional properties of single-walled carbon nanotubes

    , Article Materials Science and Engineering C ; Volume 31, Issue 2 , March , 2011 , Pages 452-457 ; 09284931 (ISSN) Khoei, A. R ; Ban, E ; Banihashemi, P ; Abdolhosseini Qomi, M. J ; Sharif University of Technology
    Carbon nanotubes (CNTs) are excellent candidates for torsional elements used in nanoelectro-mechanical systems (NEMS). Simulations show that after being twisted to a certain angle, they buckle and lose their mechanical strength. In this paper, classical molecular dynamics simulations are performed on single-walled carbon nanotubes (CNTs) to investigate the effects of torsion speed and temperature on CNT torsional properties. The AIREBO potential is employed to describe the bonded interactions between carbon atoms. The MD simulations clearly show that the buckling of CNTs in torsion is a reversible process, in which by unloading the buckled CNT in opposite direction, it returns to its...