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Model Parameter Estimation (model + parameter_estimation)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Reactive Flow Model Parameter Estimation Using Genetic Algorithms

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 3 2010
Jose Baranda, Ribeiro
Abstract An original real-coded genetic algorithm methodology that has been developed for the estimation of the parameters of the Tarver reactive flow model of shock initiation and detonation of heterogeneous solid explosives is described in detail. This methodology allows, in a single optimisation procedure and without the need for a starting solution, to search for the 15 parameters of the reaction rate law of the reactive flow model that fit the numerical results to the experimental ones. The developed methodology was applied and tested with an experimental situation, described in detail in the literature, involving the acceleration of a tantalum metal plate by an LX-17 explosive charge. The obtained parameters allow a very good description of the experimental results and are close to the ones originally used by Tarver and co-authors in their simulation of the phenomenon. [source]

Dynamic cerebral autoregulation in healthy adolescents

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2002
M. S. Vavilala
Background: There is little information on the limits of cerebral autoregulation and the autoregulatory capacity in children. The aim of this study was to compare dynamic cerebral autoregulation between healthy adolescents and adults. Methods: Seventeen healthy volunteers 12,17 years (n = 8) and 25,45 years (n = 9) were enrolled in this study. Bilateral mean middle cerebral artery flow velocities (Vmca; (cm/s)) were measured using transcranial Doppler ultrasonography (TCD). Mean arterial blood pressure (MAP) and end-tidal carbon dioxide were measured continuously during dynamic cerebral autoregulation studies. Blood pressure cuffs were placed around both thighs and inflated to 30 mmHg above the systolic blood pressure for 3 min and then rapidly deflated, resulting in transient systemic hypotension. The change of Vmca to change in MAP constitutes the autoregulatory response, and the speed of this response was quantified using computer model parameter estimation. The dynamic autoregulatory index (ARI) was averaged between the two sides. Results: Adolescents had significantly lower ARI (3.9 ± 2.1 vs. 5.3 ± 0.8; P=0.05), and higher Vmca (75.2 ± 15.2 vs. 57.6 ± 15.0; P<0.001) than adults. Conclusion: The autoregulatory index is physiologically lower in normal adolescents 12,17 years of age than in adults. [source]

Soil model parameter estimation with ensemble data assimilation

ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009
Biljana Orescanin
Abstract A parameter estimation problem in context of ensemble data assimilation is addressed. In an example using a one-point soil temperature model, the parameters corresponding to the emissivity and to the effective depth between the surface and the lowest atmospheric model level are estimated together with the initial conditions for temperature. The nonlinear synthetic observations representing various fluxes are assimilated using the Maximum Likelihood Ensemble Filter (MLEF). The results indicate a benefit of simultaneous assimilation of initial conditions and parameters. The estimated uncertainties are in general agreement with actual uncertainties. Copyright © 2009 Royal Meteorological Society [source]

Effects of physical properties estimation on process design: a case study using AspenPlus

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
Loic Cadoret
Abstract This study focuses on the physical property model parameters estimation in order to accurately simulate separation processes for a given set of components. The non-random two-liquid (NRTL) model was chosen and parameters were calculated using different methods: experimental data regression and UNIFAC and COSMO-SAC (conductor-like screening model, segment activity coefficient) predictive models. The vapor-liquid equilibrium (VLE) obtained from these different models was compared and results showed that COSMO-SAC can be a reliable tool when data or functional groups are missing. Results also showed that the use of UNIFAC to estimate activity coefficients at infinite dilution can, in some cases, leads to inaccurate results and strongly impact process simulation results. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]