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Entropy, Volume 7, Issue 4 (December 2005), Pages 199-313

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Research

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Open AccessArticle Two-way thermodynamics: Could it really happen?
Entropy 2005, 7(4), 208-220; doi:10.3390/e7040208
Received: 15 April 2005 / Accepted: 20 September 2005 / Published: 6 October 2005
Cited by 4 | PDF Full-text (133 KB)
Abstract In previous publications I have suggested that opposite thermodynamic arrows of time could coexist in our universe. This letter responds to the comments of H. D. Zeh (previous letter in this journal). Full article
(This article belongs to the Special Issue Recent Advances in Entanglement and Quantum Information Theory)
Open AccessArticle A Computer's Arrow of Time
Entropy 2005, 7(4), 221-233; doi:10.3390/e7040221
Received: 15 April 2005 / Accepted: 20 September 2005 / Published: 6 October 2005
Cited by 5 | PDF Full-text (134 KB)
Abstract
Some researchers believe that the psychological or consciousness arrow of time is a consequence of the thermodynamic arrow. Some don't. As for many issues in this area, the disagreement revolves about fundamental and undebatable assumptions. As a contribution to this standoff I consider
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Some researchers believe that the psychological or consciousness arrow of time is a consequence of the thermodynamic arrow. Some don't. As for many issues in this area, the disagreement revolves about fundamental and undebatable assumptions. As a contribution to this standoff I consider the extent to which a computer---presumably governed by nothing more than the thermodynamic arrow---can be said to possess a psychological arrow. My contention is that the parallels are sufficiently strong as to leave little room for an independent psychological arrow. Reservations are nevertheless expressed on the complete objectivity of the thermodynamic arrow. Full article
Open AccessArticle Numerical Prediction of Entropy Generation in Separated Flows
Entropy 2005, 7(4), 234-252; doi:10.3390/e7040234
Received: 17 July 2005 / Accepted: 5 September 2005 / Published: 6 October 2005
Cited by 11 | PDF Full-text (437 KB)
Abstract
The present research investigates second law analysis of laminar flow over a backward facing step (BFS). Entropy generation due to separation, reattachment, recirculation and heat transfer is studied numerically. Local entropy generation distributions were obtained by solving momentum, energy, and entropy generation equations.
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The present research investigates second law analysis of laminar flow over a backward facing step (BFS). Entropy generation due to separation, reattachment, recirculation and heat transfer is studied numerically. Local entropy generation distributions were obtained by solving momentum, energy, and entropy generation equations. The effect of dimensionless temperature difference number (τ) and Brinkman number (Br) on the total entropy generation number (Ns) was investigated. Moreover, the effect of Reynolds number (Re) on the value of Ns was reported. It was found that as Re increased the value of Ns increased. Also, as Br increased the value of Ns increased. However, it was found that as τ increased the value of Ns decreased. For the bottom wall of the channel, the maximum value of Ns occurs inside the recirculation zone and reduces to a minimum value at the point of reattachment point. Also, for Re ≥ 500, a second peak of entropy generation appears after the reattachment point. For the top wall of the channel, the value of Ns has a maximum value directly above the step and its value reduced downstream the step. The contribution of the top wall to Ns downstream the point of reattachment was relatively small. Full article
Open AccessArticle Second law analysis of laminar flow in a channel filled with saturated porous media: a numerical solution
Entropy 2005, 7(4), 300-307; doi:10.3390/e7040300
Received: 2 November 2005 / Accepted: 8 December 2005 / Published: 9 December 2005
Cited by 13 | PDF Full-text (446 KB)
Abstract
This paper investigates entropy generation due to forced convection in a porous medium sandwiched between two parallel plates one of them being subjected to a uniform heat flux and the other one insulated. Our results showed that viscous dissipation will affect the entropy
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This paper investigates entropy generation due to forced convection in a porous medium sandwiched between two parallel plates one of them being subjected to a uniform heat flux and the other one insulated. Our results showed that viscous dissipation will affect the entropy generation rate at the centerline of the channel since viscous dissipation is a quadratic function of velocity [1-3]. Neglecting the Darcy dissipation term in comparison with the terms added by Al-Hadrami et al. [4], will lead to the misunderstanding that fluid friction has no effect on the entropy generation rate at the tube centerline where the velocity derivative vanishes due to symmetry. Though the term added by [4] is O(Da) compared to the Darcy term one should not drop it unless the clear flow solution is sought [5-7]. Moreover, as stated by Nield [1], one should not use just the term involving velocity derivatives, as some authors have done in the past, for example [8-11]. Though in this paper the viscous dissipation effects in the energy equation are neglected, we have take them into account when it came to the entropy generation analysis. Full article

Review

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Open AccessReview Differential entropy and time
Entropy 2005, 7(4), 253-299; doi:10.3390/e7040253
Received: 22 August 2005 / Accepted: 17 October 2005 / Published: 18 October 2005
Cited by 20 | PDF Full-text (323 KB)
Abstract
We give a detailed analysis of the Gibbs-type entropy notion and its dynamical behavior in case of time-dependent continuous probability distributions of varied origins: related to classical and quantum systems. The purpose-dependent usage of conditional Kullback-Leibler and Gibbs (Shannon) entropies is explained in
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We give a detailed analysis of the Gibbs-type entropy notion and its dynamical behavior in case of time-dependent continuous probability distributions of varied origins: related to classical and quantum systems. The purpose-dependent usage of conditional Kullback-Leibler and Gibbs (Shannon) entropies is explained in case of non-equilibrium Smoluchowski processes. A very different temporal behavior of Gibbs and Kullback entropies is confronted. A specific conceptual niche is addressed, where quantum von Neumann, classical Kullback-Leibler and Gibbs entropies can be consistently introduced as information measures for the same physical system. If the dynamics of probability densities is driven by the Schrödinger picture wave-packet evolution, Gibbs-type and related Fisher information functionals appear to quantify nontrivial power transfer processes in the mean. This observation is found to extend to classical dissipative processes and supports the view that the Shannon entropy dynamics provides an insight into physically relevant non-equilibrium phenomena, which are inaccessible in terms of the Kullback-Leibler entropy and typically ignored in the literature. Full article

Other

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Open AccessLetter Remarks on the Compatibility of Opposite Arrows of Time
Entropy 2005, 7(4), 199-207; doi:10.3390/e7040199
Received: 15 August 2005 / Accepted: 20 September 2005 / Published: 23 September 2005
Cited by 5 | PDF Full-text (173 KB)
Abstract I argue that opposite arrows of time, while being logically possible, cannot realistically be assumed to exist during one and the same epoch of our universe. Full article
(This article belongs to the Special Issue Recent Advances in Entanglement and Quantum Information Theory)
Open AccessCommentary The Symmetry Principle
Entropy 2005, 7(4), 308-313; doi:10.3390/e7040308
Received: 13 December 2005 / Accepted: 14 December 2005 / Published: 15 December 2005
Cited by 7 | PDF Full-text (47 KB) | HTML Full-text | XML Full-text
Abstract The symmetry principle is described in this paper. The full details are given in the book: J. Rosen, Symmetry in Science: An Introduction to the General Theory (Springer-Verlag, New York, 1995). Full article
(This article belongs to the Special Issue Symmetry and Entropy)

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