Nitrogen quadrupole resonance studies have so far followed two major directions of investigation on the one hand, quadrupole coupling constants are interpreted in terms of the distribution of the bonding electrons, with many attempts to use the available molecular orbitals computed from models of various degrees of sophistication on the other hand, the effect of temperature on resonances yields information on the molecular motions and relaxation processes. [Pg.79]

The main processing options open to the crystallizer designer are the solubility gap (transition temperature, acid content), the operating temperature and the values of the rate coefficients (affected by Impurities) and crystal surface areas (eg. altering crystal content). The computer model generated In this study allows these effects to be evaluated. [Pg.299]

Finally, this study provides an extensive set of data on thick wood pyrolysis which can be better interpreted and generalized by the use of mathematical models taking into account the effects of transport phenomena and chemical reactions. Models including such features are already available in the literature (for instance, see References 23,24) and have proven to give quantitative predictions of temperature dynamics, but product yield predictions are still unacceptable, mainly because of unreliable kinetic constants. Therefore, this issue deserves further investigation before extensive computer simulation and/or development of more advanced physical models of thick wood pyrolysis are proposed. [Pg.1156]

The Duffing Equation 14.4 seems to be a model in order to describe the nonlinear behavior of the resonant system. A better agreement between experimentally recorded and calculated phase portraits can be obtained by consideration of nonlinear effects of higher order in the dielectric properties and of nonlinear losses (e.g. [6], [7]). In order to construct the effective thermodynamic potential near the structural phase transition the phase portraits were recorded at different temperatures above and below the phase transition. The coefficients in the Duffing Equation 14.4 were derived by the fitted computer simulation. Figure 14.6 shows the effective thermodynamic potential of a TGS-crystal with the transition from a one minimum potential to a double-well potential. So the tools of the nonlinear dynamics provide a new approach to the study of structural phase transitions. [Pg.268]

Kinetics and Mechanism of the Thermal DeNOx Reaction The discovery of the Thermal DeNOx reaction was followed by studies of its mechanism by the author and his coworkers and by other research groups. The former efforts culminated in the development of a kinetic data base and of a computer model2. The data base consisted of 742 data points distributed over a range of temperatures, reaction times, and initial concentrations of NO, NH3, 02, H2 and H2 O. The computer model used a set of 31 elementary reaction rates. Of these 31 reactions 27 had rate constants which were accurately known or could reasonably be estimated because they had little effect on the model s predictions. By using the remaining 4 reaction rate constants as adjustable parameters it was possible to fit the data base with its 7% experimental uncertainty. [Pg.3]

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