The Experts below are selected from a list of 320814 Experts worldwide ranked by ideXlab platform
Sheetal Kalyani - One of the best experts on this subject based on the ideXlab platform.
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outage probability and Rate for kappa mu shadowed fading in interference limited scenario
IEEE Transactions on Wireless Communications, 2017Co-Authors: Suman Kumar, Sheetal KalyaniAbstract:The $\kappa$ - $\mu$ shadowed fading model is a very general fading model as it includes both $\kappa$ - $\mu$ and $\eta$ - $\mu$ as special cases. In this paper, we derive the Expression for outage probability when the signal-of-interest (SoI) and interferers both experience $\kappa$ - $\mu$ shadowed fading in an interference limited scenario. The derived Expression is valid for arbitrary SoI parameters, arbitrary $\kappa$ , and $\mu$ parameters for all interferers and any value of the parameter $m$ for the interferers excepting the limiting value of $m\rightarrow \infty$ . The Expression can be expressed in terms of Pochhammer integral, where the integrands of integral only contains elementary functions. The outage probability Expression is then simplified for various special cases, especially when SoI experiences $\eta$ - $\mu$ or $\kappa$ - $\mu$ fading. Furthermore, the Rate Expression is derived when the SoI experiences $\kappa$ - $\mu$ shadowed fading with the integer values of $\mu$ , and the interferers experience $\kappa$ - $\mu$ shadowed fading with arbitrary parameters. The Rate Expression can be expressed in terms of sum of Lauricella’s function of the fourth kind. The utility of our results is demonstRated by using the derived Expression to study and compare fractional frequency reuse and soft frequency reuse in the presence of $\kappa$ - $\mu$ shadowed fading. Extensive simulation results are provided and these further validate our theoretical results.
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outage probability and Rate for kappa mu shadowed fading in interference limited scenario
arXiv: Information Theory, 2017Co-Authors: Suman Kumar, Sheetal KalyaniAbstract:The $\kappa$-$\mu$ shadowed fading model is a very general fading model as it includes both $\kappa$-$\mu$ and $\eta$-$\mu$ as special cases. In this work, we derive the Expression for outage probability when the signal-of-interest (SoI) and interferers both experience $\kappa$-$\mu$ shadowed fading in an interference limited scenario. The derived Expression is valid for arbitrary SoI parameters, arbitrary $\kappa$ and $\mu$ parameters for all interferers and any value of the parameter $m$ for the interferers excepting the limiting value of $m\rightarrow \infty$. The Expression can be expressed in terms of Pochhammer integral where the integrands of integral only contains elementary functions. The outage probability Expression is then simplified for various special cases, especially when SoI experiences $\eta$-$\mu$ or $\kappa$-$\mu$ fading. Further, the Rate Expression is derived when the SoI experiences $\kappa$-$\mu$ shadowed fading with integer values of $\mu$, and interferers experience $\kappa$-$\mu$ shadowed fading with arbitrary parameters. The Rate Expression can be expressed in terms of sum of Lauricella's function of the fourth kind. The utility of our results is demonstRated by using the derived Expression to study and compare FFR and SFR in the presence of $\kappa$-$\mu$ shadowed fading. Extensive simulation results are provided and these further validate our theoretical results.
Kai Sundmacher - One of the best experts on this subject based on the ideXlab platform.
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derivation of Rate equations for equilibrium limited gas solid reactions
Chemical Engineering Science, 2019Co-Authors: Marcus Wenzel, Kai SundmacherAbstract:Abstract In this work the differences between the formulation of reaction Rate equations for equilibrium limited reactions in homogeneous and heterogeneous systems are investigated. A rigorous derivation for equilibrium limited gas-solid reactions is proposed based on the core ideas of homogeneous gas phase reactions. The resulting reaction Rate Expression allows for two distinct reaction Rate mechanisms for the forward and reverse reaction direction and is, therefore, valid in both reaction directions. The thermodynamic consistency and the validity of the proposed reaction Rate Expression is shown using a simple reactor model. The results are compared to traditional reaction Rate Expressions and it is explained why they are not able to appropriately describe the true reaction behavior in some cases. The implications and use cases for process modeling are investigated and suggestions are proposed for solving numerical challenges associated with the proposed reaction Rate equations.
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Rate Expression for electrochemical oxidation of methanol on a direct methanol fuel cell anode
Journal of Electroanalytical Chemistry, 2005Co-Authors: Tanja Vidakovic, Mihai Christov, Kai SundmacherAbstract:Abstract The kinetics of methanol oxidation at PtRu catalyst was investigated on a membrane electrode assembly (MEA) in a cyclone flow cell. Catalyst characterisation was done by means of cyclic voltammetry and CO stripping. The influence of the flow Rate (10–20 l/h), the methanol concentration (0.03–3 M) and the temperature (22–61 °C) was checked. The reaction order with respect to methanol was found to vary from zero (low potential, high concentrations) to close to unity (high potentials), where limiting currents are recorded. A model for the anodic oxidation of methanol, based on a bifunctional mechanism was presented, which includes methanol adsorption on the Pt sites, formation of OHads on the Ru sites and surface reaction between these adsorbed species. For Langmuir adsorption conditions it predicted reaction order, Tafel slopes and activation energies in qualitative agreement with the experimental observations. The kinetic parameters were determined by fitting the experimental curves. Some modifications of the model were tested as well – Sips adsorption conditions on the Pt sites; Frumkin adsorption conditions; diffusion through the back diffusion layer and the Nafion membrane. No significant improvement has been achieved, although Frumkin conditions seem to describe better the anodic behaviour outside of the limiting current region. From these simulations it is difficult to decide whether the reaction between adsorbed methanol and OHads depends on potential or not.
Dionisios G Vlachos - One of the best experts on this subject based on the ideXlab platform.
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a reduced mechanism for methane and one step Rate Expressions for fuel lean catalytic combustion of small alkanes on noble metals
Combustion and Flame, 2007Co-Authors: S R Deshmukh, Dionisios G VlachosAbstract:A reduced mechanism and a one-step Rate Expression for fuel-lean methane/air catalytic combustion on an Rh catalyst are proposed. These are developed from a detailed microkinetic model using a computer-aided model reduction stRategy that employs reaction path analysis, sensitivity analysis, partial equilibrium analysis, and simple algebra to deduce the most abundant reaction intermediate and the Rate-determining step. The mechanism and the one-step Rate Expression are then tested on Pt catalyst. It is found that the reaction proceeds effectively via the same mechanistic pathway on both noble metals, but the effective reaction orders differ due to the difference in the adsorption strength of oxygen. Based on the homologous series idea, the Rate Expression is extended to small alkanes (ethane and propane; butane is also briefly discussed) and is found to reasonably describe experimental data. Estimation of the relevant parameters in the Rate Expression for various fuels and catalysts using the semiempirical bond-order conservation theory, quantum mechanical density functional theory, and/or simple experiments is discussed. Finally, it is proposed that detailed microkinetic models with coverage-dependent parameters can assist in rationalizing the apparent discrepancies between experimental data from various research groups.
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is the water gas shift reaction on pt simple computer aided microkinetic model reduction lumped Rate Expression and Rate determining step
Catalysis Today, 2005Co-Authors: A B Mhadeshwar, Dionisios G VlachosAbstract:Abstract The water–gas shift (WGS) is an essential process in hydrogen production from hydrocarbon and biomass fuel processing. Recently, it was shown that the chemistry of the WGS reaction on Pt is complex and depends critically on the oxidation of CO by adsorbed OH and H2O, mainly via the carboxyl intermediate [A.B. Mhadeshwar, D.G. Vlachos, J. Phys. Chem. B 108 (2004) 15246]. On the other hand, previous one-step Rate Expressions in the literature have described experimental data reasonably well. Here, starting from a comprehensive microkinetic model, we derive a reduced microkinetic model consisting of elementary reaction steps using principal component analysis and then develop a one-step Rate Expression for WGS on Pt using a posteriori analysis. It is shown that the Rate-determining step of WGS on Pt is the oxidation of CO by H2O, but the effective reaction Rate constant and reaction orders are concentration dependent. Finally, the effect of uncertainty in reaction Rate constants on the Rate-determining step is discussed.
Harvey G Stenger - One of the best experts on this subject based on the ideXlab platform.
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water gas shift reaction kinetics and reactor modeling for fuel cell grade hydrogen
Journal of Power Sources, 2003Co-Authors: Yongtaek Choi, Harvey G StengerAbstract:Abstract The kinetics of the water gas shift reaction was studied to evaluate existing reaction mechanisms, test various Rate Expressions and simulate the performance in a methanol fuel processor for fuel cell applications. The reaction was carried out in a micro reactor testing unit using a commercial Sud-Chemie Cu/ZnO/Al 2 O 3 catalyst between 120 and 250 °C with a range of feed Rates and compositions. Using non-linear least squares optimization, the parameters in five Rate Expressions were fit to the experimental data. Based on a review of published work on the WGS reaction mechanism, our study found that a Rate Expression derived from a regenerative mechanism and another Rate Expression derived from adsorptive mechanism fit the experimental data equally well. Numerical integration of a one-dimensional PFR model was used for this parameter fitting. An empirical Rate Expression, r CO = kP CO P H 2 O (1− β ) with activation energy of 47.4 kJ/mol was also obtained from the experimental data. Reactor performance was simulated to determine catalyst loadings required to achieve specific CO conversions as a function of temperature and water feed Rate. These results are useful in studying the design trade offs available to reformer systems.
William Y. Svrcek - One of the best experts on this subject based on the ideXlab platform.
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New experimental data and kinetic Rate Expression for the Claus reaction
Chemical Engineering Science, 2000Co-Authors: Wayne D. Monnery, A Pollock, Kelly Hawboldt, William Y. SvrcekAbstract:The modi"ed Claus process is the most common method for the conversion to sulphur of the hydrogen sulphide contained in sour oil and natural gas. An important but relatively unstudied part of the Claus process are the reaction kinetics of the front-end reaction furnace in which sulphur production takes place, hydrocarbon contaminants are destroyed and reactions occur that prepare the sour gas for downstream catalytic processing. One of the key reactions that occurs in the front-end furnace is between H 2 S and SO 2 . This second part of the Claus reactions has been studied under catalytic but not thermal conditions. The purpose of this work was to study this reaction at actual Claus plant reaction furnace temperatures and residence times. The new kinetic data would then be used to develop a new reaction Rate Expression. Experiments were performed in a laboratory scale, isothermal, plug-#ow reactor at temperatures between 850 and 11503C and at residence times between 0.05 and 1.2 s. Overall conversion of H 2 S and SO 2 were measured and results are presented in this paper. The newly developed kinetic Rate Expression is as follows: r"A f expEaf@RTP H2S P0.52 !A r expEar@RTP H2O P0.752 , where A f "15,762 ($1200) mol cm~3 s~1 atm~1.5, E af "49.9 ($0.3) kcal mol~1, A r "506 ($50) mol cm~3 s~1 atm~1.75 and E ar "44.9 ($0.5) kcal mol~1. The new Rate Expression correlates experimental H 2 S and SO 2 conversion data within 12 and 18%, respectively. In addition, the predicted conversion for the new Rate Expression extrapolates correctly to equilibrium conversion values and the Arrhenius parameters predict the heat of reaction to within 0.05%. ( 2000 Elsevier Science Ltd. All rights reserved.
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new experimental data and kinetic Rate Expression for h2s pyrolysis and re association
Chemical Engineering Science, 2000Co-Authors: Kelly Hawboldt, Wayne D. Monnery, William Y. SvrcekAbstract:The pyrolysis and re-association of hydrogen sulphide is a key reaction in the Claus sulphur recovery process. In this paper, a new kinetic Rate Expression and its parameters for this reaction are derived under the conditions of the Claus reaction furnace. Experiments were performed with hydrogen sulphide using an isothermal, plug-#ow reactor at temperatures between 850}1153C and residence times of 50}1500 ms. The Rate constants for the forward (pyrolysis or cracking of H 2 S) and reverse (re-association of H 2 and S 2 ) were derived through numerical simulation based on the collected experimental data. The form of the Rate equation was determined to be r"A f e~Ef@RT P H2S P0.52 !A r e~Er@RTP H2 P S2 , where A f and E f , the forward parameters, are 5260 ($260) mol/cm3 s/atm1.5 and 45.0 ($0.3) kcal/mol, while the reverse parameters, A r and E r , were 14 ($1) mol/cm3 s/atm2 and 23.4 ($0.2) kcal/mol. The Rate equation not only agrees with the experimental data within 15% but also agrees very well with published data. In addition, the Rate Expression properly predicts equilibrium compositions and is thermodynamically consistent. ( 1999 Elsevier Science Ltd. All rights reserved.