The Experts below are selected from a list of 6012 Experts worldwide ranked by ideXlab platform
Jainagesh A Sekhar - One of the best experts on this subject based on the ideXlab platform.
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morphological assessment with the maximum entropy production rate mepr postulate
Current opinion in chemical engineering, 2014Co-Authors: Yaw Delali Bensah, Jainagesh A SekharAbstract:The three established techniques that are currently employed for the prediction of solidification bifurcations and the shape of cast microstructures are reviewed. The main limitations of these established techniques are discussed with examples. A more recent model called the maximum entropy production rate (MEPR) postulate is also reviewed as to its ability to predict patterns, especially those that form during positive temperature gradient solidification. The principle of MEPR states that if there are sufficient degrees of freedom within a System, it will adopt a stable state at which the entropy generation rate is maximized in an Open Thermodynamic System. In the context of steady state solidification, pathway selections are reflected in the overall steady-state morphological features and shape-bifurcations that are noted with a change in the rate of solidification.
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The description of morphologically stable regimes for steady state solidification based on the maximum entropy production rate postulate
Journal of Materials Science, 2011Co-Authors: Jainagesh A SekharAbstract:The maximum entropy production rate (MEPR) in the solid–liquid zone is developed and tested as a possible postulate for predicting the stable morphology for the special case of steady state directional solidification (DS). The principle of MEPR states that, if there are sufficient degrees of freedom within a System, it will adopt a stable state at which the entropy generation (production) rate is maximized. Where feasible, the System will also try and adopt a steady state. The MEPR postulate determines the most probable state and therefore allows pathway selections to occur in an Open Thermodynamic System. In the context of steady state solidification, pathway selections are reflected in the corresponding morphological selections made by the System in the solid–liquid (mushy) zone in order to cope with the required entropy production. Steady state solidification is feasible at both close to, and far from equilibrium conditions. Based on MEPR, a model is proposed for examining the stability of various morphologies that have been experimentally observed during steady state directional solidification. This model employs a control volume approach for entropy balance, including the entropy generation term ( S _gen), which depends on the diffuse zone and average temperature of the solid–liquid region within the control volume. In this manner, the model takes a different approach from the successful kinetic models that have been able to predict key features of stable morphological patterns. Unstable planar interfaces, faceted cellular arrays, cell–dendrite transitions, half cells both faceted and smooth, and other transitions such as the absolute stability transition at high solid/liquid velocities are examined with the model. Uncommon solidification morphological features such as non - crystallographic dendrites and discontinuous cell-tip splitting are also examined with the model. The preferred morphological change-direction for the emergence of the stable morphological feature is inferred with the MEPR postulate in a manner analogous to the free energy minimization principle(s) when used for predicting phase stability and metastable phase formation. Aspects of mixed-mode order transformation characteristics are also discussed for non-equilibrium solidification containing a diffuse interface, in contrast to classifying solidification as purely a first order transformation. The MEPR model predictions are shown to follow the experimental transitions observed to date in several historical studies.
Yaw Delali Bensah - One of the best experts on this subject based on the ideXlab platform.
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morphological assessment with the maximum entropy production rate mepr postulate
Current opinion in chemical engineering, 2014Co-Authors: Yaw Delali Bensah, Jainagesh A SekharAbstract:The three established techniques that are currently employed for the prediction of solidification bifurcations and the shape of cast microstructures are reviewed. The main limitations of these established techniques are discussed with examples. A more recent model called the maximum entropy production rate (MEPR) postulate is also reviewed as to its ability to predict patterns, especially those that form during positive temperature gradient solidification. The principle of MEPR states that if there are sufficient degrees of freedom within a System, it will adopt a stable state at which the entropy generation rate is maximized in an Open Thermodynamic System. In the context of steady state solidification, pathway selections are reflected in the overall steady-state morphological features and shape-bifurcations that are noted with a change in the rate of solidification.
A Holas - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic extension of density functional theory i canonical massieu planck function its legendre and massieu planck transforms for equilibrium state in terms of density matrix
arXiv: Chemical Physics, 2009Co-Authors: Robert Balawender, A HolasAbstract:A general formulation of the equilibrium state of a many-electron System in terms of a (mixed-state, ensemble) density matrix operator in the Fock space, based on the maximum entropy principle, is introduced. Various characteristic functions/functionals are defined and investigated: the basic Massieu function for fully Open Thermodynamic System (ensemble), the effective action function for the fully closed (isolated) System, and a series of Legendre transforms for partially Open/closed ones - the Massieu functions. Convexity and/or concavity properties of these functions are determined, their first and second derivatives with respect to all arguments are obtained. Other characteristic functions - the Gibbs-Helmholtz functions - are obtained from previous ones as their Massieu-Planck transforms, i.e. by specific transformation of arguments (which involves the temperature) and by applying the temperature with the minus as a prefactor. Such functions are closer to traditional (Gibbs, Helmholtz) Thermodynamic potentials. However, the first and second derivatives of these functions represent more complicated expressions than derivatives of the Massieu functions. All introduced functions are suitable for application to the extensions of the density functional theory, both at finite and zero temperature.
Robert Balawender - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic extension of density functional theory i canonical massieu planck function its legendre and massieu planck transforms for equilibrium state in terms of density matrix
arXiv: Chemical Physics, 2009Co-Authors: Robert Balawender, A HolasAbstract:A general formulation of the equilibrium state of a many-electron System in terms of a (mixed-state, ensemble) density matrix operator in the Fock space, based on the maximum entropy principle, is introduced. Various characteristic functions/functionals are defined and investigated: the basic Massieu function for fully Open Thermodynamic System (ensemble), the effective action function for the fully closed (isolated) System, and a series of Legendre transforms for partially Open/closed ones - the Massieu functions. Convexity and/or concavity properties of these functions are determined, their first and second derivatives with respect to all arguments are obtained. Other characteristic functions - the Gibbs-Helmholtz functions - are obtained from previous ones as their Massieu-Planck transforms, i.e. by specific transformation of arguments (which involves the temperature) and by applying the temperature with the minus as a prefactor. Such functions are closer to traditional (Gibbs, Helmholtz) Thermodynamic potentials. However, the first and second derivatives of these functions represent more complicated expressions than derivatives of the Massieu functions. All introduced functions are suitable for application to the extensions of the density functional theory, both at finite and zero temperature.
Ihsan Dagtekin - One of the best experts on this subject based on the ideXlab platform.
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energetic exergetic economic analyses of a cogeneration thermic power plant in turkey
International Communications in Heat and Mass Transfer, 2009Co-Authors: Omer Faruk Can, Nevin Celik, Ihsan DagtekinAbstract:Abstract In present study the exergy and economical analysis of a cogeneration plant System in Turkey (Esenyurt Thermic Power Plant) was performed based on the measured data during the operation time of the System. First and second laws of Thermodynamics are adapted to the measured data. Furthermore, fuel-utilization efficiency, rate of power heat and rate of process heat are determined. The System is considered as a steady-state Open Thermodynamic System. As a result, it is found that the second law efficiency is 89.5% which is accepted as an agreeable value in archival journals. The pay back period of the plant is found 3.5 years, which is favorable time period for well designed plants in terms of the economical analysis.
