Search for: entropy
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    Entropy production and non-markovian dynamical maps

    , Article Scientific Reports ; Volume 7, Issue 1 , 2017 ; 20452322 (ISSN) Marcantoni, S ; Alipour, S ; Benatti, F ; Floreanini, R ; Rezakhani, A. T ; Sharif University of Technology
    In the weak-coupling limit approach to open quantum systems, the presence of the bath is eliminated and accounted for by a master equation that introduces dissipative contributions to the system reduced dynamics: within this framework, there are no bath entropy contributions to the entropy balance. We show that, as a consequence, the entropy production fails to be positive for a class of physically legitimate, that is completely positive and trace preserving, non-Markovian dynamical maps. Moreover, in absence of the semigroup property, if the reduced dynamics has a thermal asymptotic state, this need not be stationary. Then even the integrated entropy production becomes negative. These... 

    Series solution of entropy generation toward an isothermal flat plate

    , Article Thermal Science ; Volume 16, Issue 5 , 2012 , Pages 1289-1295 ; 03549836 (ISSN) Malvandi, A ; Ganji, D. D ; Hedayati, F ; Kaffash, M. H ; Jamshidi, M ; Sharif University of Technology
    The steady 2-D boundary layer flow over a flat plate is studied analytically by homotopy perturbation method to analyze the entropy generation inside the boundary layer with constant wall temperature. By the transformations of go-verning equations including continuity, momentum, and energy by similarity va-riables, a dimensionless equation for entropy generation inside the boundary layer is obtained. The effects of important parameters such as Reynolds and Eck-ert numbers are investigated and the physical interpretations of the results are explained in details  

    Calculation of melting temperature and transition curve for dickerson DNA dodecamer on the basis of configurational entropy, hydrogen bonding energy, and heat capacity: A molecular dynamics simulation study

    , Article Journal of the Iranian Chemical Society ; Volume 8, Issue 3 , 2011 , Pages 708-716 ; 1735207X (ISSN) Izanloo, C ; Parsafar, G. A ; Abroshan, H ; Akbarzade, H ; Sharif University of Technology
    A familiarity with denaturation process is highly significant in understanding the DNA replication, manipulation, and interactions involving DNA double helix stability. We have performed molecular dynamics simulation on B-DNA duplex (CGCGAATTGCGC) at different temperatures. At each temperature, configurational entropy was estimated using the covariance matrix of atom-positional fluctuations. By plotting the configuration entropy versus temperature, we calculated the melting temperature which was found to be 329.7 K. We also calculated the hydrogen bonding energy and heat capacity for the atoms participating in the hydrogen bonding between two strands of DNA. Moreover, their temperature... 

    Correlations in quantum thermodynamics: Heat, work, and entropy production

    , Article Scientific Reports ; Volume 6 , 2016 ; 20452322 (ISSN) Alipour, S ; Benatti, F ; Bakhshinezhad, F ; Marcantoni, S ; Rezakhani, A. T ; Sharif University of Technology
    Nature Publishing Group  2016
    We provide a characterization of energy in the form of exchanged heat and work between two interacting constituents of a closed, bipartite, correlated quantum system. By defining a binding energy we derive a consistent quantum formulation of the first law of thermodynamics, in which the role of correlations becomes evident, and this formulation reduces to the standard classical picture in relevant systems. We next discuss the emergence of the second law of thermodynamics under certain-but fairly general-conditions such as the Markovian assumption. We illustrate the role of correlations and interactions in thermodynamics through two examples  

    Entropy-based video steganalysis of motion vectors

    , Article Entropy ; Volume 20, Issue 4 , 2018 ; 10994300 (ISSN) Sadat, E. S ; Faez, K ; Saffari Pour, M ; Sharif University of Technology
    MDPI AG  2018
    In this paper, a new method is proposed for motion vector steganalysis using the entropy value and its combination with the features of the optimized motion vector. In this method, the entropy of blocks is calculated to determine their texture and the precision of their motion vectors. Then, by using a fuzzy cluster, the blocks are clustered into the blocks with high and low texture, while the membership function of each block to a high texture class indicates the texture of that block. These membership functions are used to weight the effective features that are extracted by reconstructing the motion estimation equations. Characteristics of the results indicate that the use of entropy and... 

    A review of quantum thermodynamics

    , Article Iranian Journal of Physics Research ; Volume 19, Issue 3 , 2019 , Pages 489-521 ; 16826957 (ISSN) Shahidani, S ; Rezakhani, A ; Sharif University of Technology
    Isfahan University of Technology  2019
    In this article, we present a brief and elementary review of quantum thermodynamics and its achievements and challenges. This review includes an introduction to some fundamental concepts such as internal energy, heat, work, entropy, entropy production, thermal equilibrium, second law of quantum thermodynamics, relation between thermodynamics and information theory, as well as a discussion of how quantum effects such as entanglement and correlations affect performance of quantum heat engines. © 2019 by the authors. Licensee MDPI, Basel, Switzerland  

    Double-horizon limit, AdS geometry and entropy function

    , Article Nuclear Physics B ; Volume 802, Issue 3 , 2008 , Pages 405-420 ; 05503213 (ISSN) Arfaei, H ; Fareghbal, R ; Sharif University of Technology
    We start from a generic metric which describes four-dimensional stationary black holes in an arbitrary theory of gravity and show that the AdS2 part of the near-horizon geometry is a consequence of the double-horizon limit and finiteness. We also show that the field configurations of the near horizon are determined if the same conditions are applied to the equations of motion. This is done by showing that in the double-horizon limit field equations at the horizon decouple from the bulk of the space. Solving these equations gives the near-horizon field configurations. It is shown that these decoupled equations can be obtained from an action derived from the original action by applying the... 

    Full characterization of a spin liquid phase: From topological entropy to robustness and braid statistics

    , Article Journal of Physics A: Mathematical and Theoretical ; Volume 50, Issue 14 , 2017 ; 17518113 (ISSN) Jahromi, S. S ; Langari, A ; Sharif University of Technology
    Institute of Physics Publishing  2017
    We use the topological entanglement entropy (TEE) as an efficient tool to fully characterize the Abelian phase of a Z2 ×Z2 spin liquid emerging as the ground state of topological color code (TCC), which is a class of stabilizer states on the honeycomb lattice. We provide the fusion rules of the quasiparticle (QP) excitations of the model by introducing single- or two-body operators on physical spins for each fusion process which justify the corresponding fusion outcome. Besides this, we extract the TEE from Renyi entanglement entropy (EE) of the TCC, analytically and numerically by finite size exact diagonalization on the disk shape regions with contractible boundaries. We obtain that the EE... 

    Playing games with bounded entropy

    , Article Games and Economic Behavior ; Volume 115 , 2019 , Pages 363-380 ; 08998256 (ISSN) Valizadeh, M ; Gohari, A ; Sharif University of Technology
    Academic Press Inc  2019
    We study zero-sum repeated games in which the maximizer (player or team) is restricted to strategies with limited randomness. Particularly, we analyze the maxmin payoff of the maximizer in two models: the first model forces the maximizer to randomize her actions just by conditioning them to the outcomes of an observed random source. In the second model, the maximizer is a team of players who are free to privately randomize their corresponding actions but do not have access to any explicit source of shared randomness needed for coordination. While prior works adopted the method of types to address these problems, we use the idea of random hashing being the core of randomness extractors. In... 

    Renormalization of entanglement in the anisotropic Heisenberg (XXZ) model

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 77, Issue 3 , 2008 ; 10502947 (ISSN) Kargarian, M ; Jafari, R ; Langari, A ; Sharif University of Technology
    We have applied our recent approach to study the quantum-information properties of the anisotropic s=1/2 Heisenberg chain. We have investigated the underlying quantum-information properties such as the evolution of concurrence, entanglement entropy, nonanalytic behaviors, and the scaling close to the quantum critical point of the model. Both the concurrence and the entanglement entropy develop two saturated values after enough iterations of the renormalization of coupling constants. These values are associated with the two different phases, i.e., Néel and spin liquid phases. The nonanalytic behavior comes from the divergence of the first derivative of both measures of entanglement as the... 

    Entropy generation minimisation analysis of cross-flow heat exchangers used in indirect evaporative air conditioners

    , Article International Journal of Exergy ; Volume 6, Issue 1 , 2009 , Pages 61-79 ; 17428297 (ISSN) Eslamian, M ; Heydari, A ; Ghezelbash, P ; Sharif University of Technology
    In this paper, entropy generation in heat exchangers used in Indirect Evaporative Coolers (IDECs) is studied. First, expressions for the rate of entropy generation in tube-type and plate-type cross-flow heat exchangers used as IDECs are obtained. Then, by introducing appropriate geometric constraints and employing thermohydraulic design equations, the variation of the rate of entropy generation within the heat exchangers is investigated. The maximum EER, outlet temperatures and the optimum sizes are obtained for several cases. The results of several experiments conducted on an optimum tube-type experimental prototype are presented and compared with the numerical data. Copyright © 2009... 

    Irreversibility of nanomaterial due to MHD via numerical approach

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 144, Issue 3 , 2021 , Pages 1041-1050 ; 13886150 (ISSN) Balazadeh, N ; Shafee, A ; Tlili, I ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    In current research, MAPLE software was utilized to scrutinize the heat transfer of copper–H2O nanomaterial migration over a sheet. Entropy production in existence of magnetic field was scrutinized, and Bejan number was reported as main outputs. Converting PDEs into ODEs was done via similarity transformation, and final ODEs were analyzed via RK4. The influence of different variables, including fraction of nanomaterial and Lorentz force on flow distribution and temperature field, also on surface tension and Nu was demonstrated. Besides, Be and NG were calculated for various ranges of scrutinized variables. © 2020, Akadémiai Kiadó, Budapest, Hungary  

    Minimum entropy control of chaos via online particle swarm optimization method

    , Article Applied Mathematical Modelling ; Vol. 36, Issue. 8 , 2012 , pp. 3931-3940 ; ISSN: 0307904X Sadeghpour, M ; Salarieh, H ; Alasty, A ; Sharif University of Technology
    One of the recently developed approaches for control of chaos is the minimum entropy (ME) control technique. In this method an entropy function based on the Shannon definition, is defined for a chaotic system. The control action is designed such that the entropy as a cost function is minimized which results in more regular pattern of motion for the system trajectories. In this paper an online optimization technique using particle swarm optimization (PSO) method is developed to calculate the control action based on ME strategy. The method is examined on some standard chaotic maps with error feedback and delayed feedback forms. Considering the fact that the optimization is online, simulation... 

    The value of help bits in randomized and average-case complexity

    , Article Computational Complexity ; Volume 26, Issue 1 , 2017 , Pages 119-145 ; 10163328 (ISSN) Beigi, S ; Etesami, O ; Gohari, A ; Sharif University of Technology
    Birkhauser Verlag AG  2017
    “Help bits" are some limited trusted information about an instance or instances of a computational problem that may reduce the computational complexity of solving that instance or instances. In this paper, we study the value of help bits in the settings of randomized and average-case complexity. If k instances of a decision problem can be efficiently solved using ℓ< k help bits, then without access to help bits one can efficiently compute a k-bit vector that is not equal to the k-bit vector of solutions to the k instances. A decision problem with this property is called k-membership comparable. Amir, Beigel, and Gasarch (1990) show that for constant k, all k-membership comparable languages... 

    How compressible are innovation processes?

    , Article IEEE Transactions on Information Theory ; Volume 64, Issue 7 , 2018 , Pages 4843-4871 ; 00189448 (ISSN) Ghourchian, H ; Amini, A ; Gohari, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    The sparsity and compressibility of finite-dimensional signals are of great interest in fields, such as compressed sensing. The notion of compressibility is also extended to infinite sequences of independent identically distributed or ergodic random variables based on the observed error in their nonlinear $k$ -term approximation. In this paper, we use the entropy measure to study the compressibility of continuous-domain innovation processes (alternatively known as white noise). Specifically, we define such a measure as the entropy limit of the doubly quantized (time and amplitude) process. This provides a tool to compare the compressibility of various innovation processes. It also allows us... 

    Existence of a unique positive entropy solution to a singular fractional Laplacian

    , Article Complex Variables and Elliptic Equations ; 2020 Bayrami Aminlouee, M ; Hesaaraki, M ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    In this paper, we study the existence of a positive solution to the elliptic problem: (Formula presented.) Here (Formula presented.) (N>2s) is an open bounded domain with smooth boundary, (Formula presented.) and (Formula presented.). For (Formula presented.), we take advantage of the convexity of Ω. The operator (Formula presented.) indicates the restricted fractional Laplacian, and μ is a non-negative Radon measure as a source term. The assumptions on f and h will be precised later. Besides, we will discuss the notion of entropy solution and its uniqueness for some specific measures. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group  

    Numerical and experimental investigation of the flow and performance characteristics of twin-entry radial turbine under full and partial admission conditions

    , Article 2008 ASME Turbo Expo, Berlin, 9 June 2008 through 13 June 2008 ; Volume 6, Issue PART B , June , 2008 ; 9780791843161 (ISBN) Shahhosseini, M. R ; Hajilouy Benisi, A ; Rad, M ; International Gas Turbine Institute ; Sharif University of Technology
    In this paper, numerical and experimental investigation of the performance and internal flow field characteristics of the twinentry radial inflow turbine under full and partial admission conditions are presented. The turbine is tested on a turbocharger test facility, which was developed for small and medium size turbochargers. The flow pattern in the volute and impeller of a twin-entry turbine is analyzed using fully three-dimensional viscous program. The computational performance results are compared with the experimental results, and good agreement is found. The flow field at the outlet of the turbine is investigated using a five-hole pressure probe. The tests are performed for both full... 

    On the relationship between entropy and information

    , Article Physics Essays ; Volume 20, Issue 3 , 2007 , Pages 487-493 ; 08361398 (ISSN) Shafiee, A ; Karimi, M ; Sharif University of Technology
    In this paper we analyze the relationship between entropy and information in the context of the mixing process of two identical ideal gases. We will argue that entropy has a special information-based feature that is enfolded in the statistical entropy, but the second law does not include it directly. Therefore, in some given processes in thermodynamics where there is no matter and energy interaction between the system and the environment, the state of the system may go toward a situation of lower probability to increase the observer's information about the environment. This is a kind of information-based interaction in which the total entropy is not constrained by the second law  

    Bell's inequality and contextual information

    , Article International Journal of Quantum Information ; Volume 4, Issue 4 , 2006 , Pages 641-651 ; 02197499 (ISSN) Safinejad, F ; Shafiee, A ; Maleeh, R ; Sharif University of Technology
    The properties of the Shannon entropy (concavity and strong additivity) are satisfied in both classical and quantum experiments, if the context of experiment is considered appropriately. We show that these properties hold true in a classical model with the feature of being contextual, where a correlation is observed between events. Our results show that the classical example is similar to an entangled singlet state for spin-1/2 particles. But, contrary to general opinion, Icorrentgld > 1 is not a necessary and sufficient condition for violating Bell's inequality, since it has been obtained on the basis of a common cause pattern. In other words, it is possible to reconstruct the amount of... 

    Optimized cooling system for pem fuel cell stack based on entropy generation minimization

    , Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 1 , 2004 , Pages 97-103 ; 0791841731 (ISBN); 9780791841730 (ISBN) Saidi, M. H ; Mozafari, A. A ; Sharifian, L ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    Cell temperature in fuel cells is an important parameter which highly affects fuel cell stack efficiency. A suitable cooling system should satisfy an acceptable temperature range. In this research a relevant cooling system for a specified PEM fuel cell stack has been proposed complying with the criteria and cooling requirements of the fuel cell. The effect of various parameters on the entropy generation and temperature distribution in the cooling plates are surveyed. The number of cooling plates, the number of channels in each cooling plate and the channel width is determined. Two flow regimes namely laminar and turbulent flows of the cooling fluid in channels are analyzed and a design...