Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Prediction description

Petersen, J. N., and Davison, B. H., Development of a Predictive Description of an Immobilized-Cell, Three-Phase, Fluidized-Bed Bioreactor, Biotechnol. Bioeng., 46 139 (1995)... [Pg.675]

A two-zone engine simulation, which divides the cylinder volume into burned and unburned regions, each spatially uniform, provides the simplest predictive description. In early work Hirst and Kirsch [155] applied the Shell model to the unburned region and showed that autoignition in a CFR engine could be predicted, and the model used to investigate the factors that influence fuel sensitivity (Section 7.2.3). The burning rate, a... [Pg.719]

An Ideal predictive description of the percutaneous absorption process should include not only the ability to predict the time course of the penetration process through the skin and absorption into the systemic circulation, but also an ability to predict the residual amounts remaining both on the skin surface and within the skin which are still available for absorption. In the latter half of this paper, a potentially useful pharmacokinetic model, which has this broad predictive capability, will be presented, together with data suggesting that solid substances deposited on the skin surface In volatile solvents are partially solubilized before the solvent has evaporated more rapid absorption of the solubilized fraction is then likely. [Pg.5]

Models of rubber elasticity have been reviewed for finite deformation and compared with experimental data by Boyce and Arruda (2000). A hybrid model of the Flory-Erman model for low stretch deformation and the Arruda-Boyce model for large stretch deformation is shown to give an accurate predictive description of Treloar s classic data over the entire stretch range for all deformation states. [Pg.179]

Circulation forecasts Predictive description of circulation processes into the future, through numerical... [Pg.66]

The nucleation rate, growth rate, and transformation rate equations that we developed in the preceding sections are sufficient to provide a general, semiquantitative understanding of nucleation- and growth-based phase transformations. However, it is important to understand that the kinetic models developed in this introductory text are generally not sufficient to provide a microstructurally predictive description of phase transformation for a specific materials system. It is also important to understand that real phase transformation processes often do not reach completion or do not attain complete equilibrium. In fact, extended defects such as grain boundaries or pores should not exist in a true equilibrium solid, so nearly all materials exist in some sort of metastable condition. Many phase transformation processes produce microstructures that depart wildly from our equilibrium expectation. The limited atomic mobilities associated with solid-state diffusion can frequently cause (and preserve) such nonequilibrium structures. In this section, we will focus more deeply on solidification (a liquid-solid phase transformation) as a way to discuss some of these issues. In particular, we will examine a few kinetic concepts/models... [Pg.232]

One lesson of these examples is that multiscale modeling is neither the exclusive domain of computational model building nor a fundamentally new idea. Indeed, in the deepest sense, the sentiment that animates all efforts at model building, whether analytical or computational, is of finding a minimal but predictive description of the problem of interest. [Pg.78]

When one tries to account for real polymer systems in terms of models of the type of Eqs. (1.1)-(1.8) the situation is rather unsatisfactory however, when one fits data on the coexistence curve or on (0 (AF/kBT)/0(() )j., the latter quantity being experimentally accessible via small angle scattering, one finds that one typically needs an effective y-parameter that does not simply scale proportional to inverse temperature, as Eq. (1.5) suggests. Moreover, there seems to be a pronounced (])-dependence of x, in particular for (]) — 1. Near (]) = (]) ", on the other hand, there are critical fluctuations (which have been intensely studied by Monte Carlo simulations [11-13,15] and also in careful experiments of polymer blends [16-18] and polymer solutions [19]). Sometimes in the literature a dependence of the x parameter on pressure [18] or even chain length is reported, too. Thus, there is broad consensus that the Flory-Huggins theory and its closely related extensions [20] are too crude as models to provide predictive descriptions of real polymer solutions and blends. A more promising approach is the lattice cluster approach of Freed and coworkers [21-23], where effective monomers block several sites on the lattice and have complicated shapes to somehow mimic the local chemical structure. However, this approach requires rather cumbersome numerical calculations, and is still of a mean-field character, as... [Pg.3]

Van Oene]. Currently, neither the phenomenological nor the structural approach to the determination of constitutive equations has yet shown itself to be capable of producing useful and predictive description of the majority of teehnologically important complex fluids. [Pg.1725]

An adequate prediction of multicomponent vapor-liquid equilibria requires an accurate description of the phase equilibria for the binary systems. We have reduced a large body of binary data including a variety of systems containing, for example, alcohols, ethers, ketones, organic acids, water, and hydrocarbons with the UNIQUAC equation. Experience has shown it to do as well as any of the other common models. V7hen all types of mixtures are considered, including partially miscible systems, the... [Pg.48]

Introduction and Commercial Application The objective of reservoir geology is the description and quantification of geologically controlled reservoir parameters and the prediction of their lateral variation. Three parameters broadly define the reservoir geology of a field ... [Pg.76]

The reservoir model will usually be a computer based simulation model, such as the 3D model described in Section 8. As production continues, the monitoring programme generates a data base containing information on the performance of the field. The reservoir model is used to check whether the initial assumptions and description of the reservoir were correct. Where inconsistencies between the predicted and observed behaviour occur, the model is reviewed and adjusted until a new match (a so-called history match ) is achieved. The updated model is then used to predict future performance of the field, and as such is a very useful tool for generating production forecasts. In addition, the model is used to predict the outcome of alternative future development plans. The criterion used for selection is typically profitability (or any other stated objective of the operating company). [Pg.333]

One of the most significant achievements of the twentieth century is the description of the quantum mechanical laws that govern the properties of matter. It is relatively easy to write down the Hamiltonian for interacting fennions. Obtaining a solution to the problem that is sufficient to make predictions is another matter. [Pg.87]

Onsager s reaction field model in its original fonn offers a description of major aspects of equilibrium solvation effects on reaction rates in solution that includes the basic physical ideas, but the inlierent simplifications seriously limit its practical use for quantitative predictions. It smce has been extended along several lines, some of which are briefly sunnnarized in the next section. [Pg.837]

Wlrile tire Bms fonnula can be used to locate tire spectral position of tire excitonic state, tliere is no equivalent a priori description of the spectral widtli of tliis state. These bandwidtlis have been attributed to a combination of effects, including inlromogeneous broadening arising from size dispersion, optical dephasing from exciton-surface and exciton-phonon scattering, and fast lifetimes resulting from surface localization 1167, 168, 170, 1711. Due to tire complex nature of tliese line shapes, tliere have been few quantitative calculations of absorjDtion spectra. This situation is in contrast witli tliat of metal nanoparticles, where a more quantitative level of prediction is possible. [Pg.2910]

In this section, the adiabatic picture will be extended to include the non-adiabatic terais that couple the states. After this has been done, a diabatic picture will be developed that enables the basic topology of the coupled surfaces to be investigated. Of particular interest are the intersection regions, which may form what are called conical intersections. These are a multimode phenomena, that is, they do not occur in ID systems, and the name comes from their shape— in a special 2D space it has the fomi of a double cone. Finally, a model Flamiltonian will be introduced that can describe the coupled surfaces. This enables a global description of the surfaces, and gives both insight and predictive power to the fomration of conical intersections. More detailed review on conical intersections and their properties can be found in [1,14,65,176-178]. [Pg.277]

Abstract. Molecular dynamics (MD) simulations of proteins provide descriptions of atomic motions, which allow to relate observable properties of proteins to microscopic processes. Unfortunately, such MD simulations require an enormous amount of computer time and, therefore, are limited to time scales of nanoseconds. We describe first a fast multiple time step structure adapted multipole method (FA-MUSAMM) to speed up the evaluation of the computationally most demanding Coulomb interactions in solvated protein models, secondly an application of this method aiming at a microscopic understanding of single molecule atomic force microscopy experiments, and, thirdly, a new method to predict slow conformational motions at microsecond time scales. [Pg.78]

Table 2. Predicted intrinsic and apparent pKa values for the Cys403 residue in Yersinia phosphatase for different models of the structure the data refer to a temperature of 293 K and an ionic strength corresponding to 150 mM of monovalent salt. See the text for the detailed description of the conditions under which each pK estimation was made. The experimentally determined value is 4.67 [39]... Table 2. Predicted intrinsic and apparent pKa values for the Cys403 residue in Yersinia phosphatase for different models of the structure the data refer to a temperature of 293 K and an ionic strength corresponding to 150 mM of monovalent salt. See the text for the detailed description of the conditions under which each pK estimation was made. The experimentally determined value is 4.67 [39]...
Neural networks were trained on the basis of these codes to predict chiralit> -dependent properties in enantioselective reactions [42] and in chiral chromatography [43]. A detailed description of the chirality codes is given in the Tutorial in Section 8,6,... [Pg.420]

Data mining can fulfill various different tasks such as classification, clustering and similarity detection, prediction, estimation, or description retrieval, which are described in Sections 9.8.1-9.8.5. [Pg.472]

The electron configuration is the orbital description of the locations of the electrons in an unexcited atom. Using principles of physics, chemists can predict how atoms will react based upon the electron configuration. They can predict properties such as stability, boiling point, and conductivity. Typically, only the outermost electron shells matter in chemistry, so we truncate the inner electron shell notation by replacing the long-hand orbital description with the symbol for a noble gas in brackets. This method of notation vastly simplifies the description for large molecules. [Pg.220]

The term theoretical chemistry may be defined as the mathematical description of chemistry. The term computational chemistry is generally used when a mathematical method is sufficiently well developed that it can be automated for implementation on a computer. Note that the words exact and perfect do not appear in these definitions. Very few aspects of chemistry can be computed exactly, but almost every aspect of chemistry has been described in a qualitative or approximately quantitative computational scheme. The biggest mistake a computational chemist can make is to assume that any computed number is exact. However, just as not all spectra are perfectly resolved, often a qualitative or approximate computation can give useful insight into chemistry if the researcher understands what it does and does not predict. [Pg.1]

One of the most commonly used constructs is a model. A model is a simple way of describing and predicting scientific results, which is known to be an incorrect or incomplete description. Models might be simple mathematical descriptions or completely nonmathematical. Models are very useful because they allow us to predict and understand phenomena without the work of performing the complex mathematical manipulations dictated by a rigorous theory. Experienced researchers continue to use models that were taught to them in high school and freshmen chemistry courses. However, they also realize that there will always be exceptions to the rules of these models. [Pg.2]

Quantum mechanics (QM) is the correct mathematical description of the behavior of electrons and thus of chemistry. In theory, QM can predict any property of an individual atom or molecule exactly. In practice, the QM equations have only been solved exactly for one electron systems. A myriad collection of methods has been developed for approximating the solution for multiple electron systems. These approximations can be very useful, but this requires an amount of sophistication on the part of the researcher to know when each approximation is valid and how accurate the results are likely to be. A significant portion of this book addresses these questions. [Pg.10]

The wave function T is a function of the electron and nuclear positions. As the name implies, this is the description of an electron as a wave. This is a probabilistic description of electron behavior. As such, it can describe the probability of electrons being in certain locations, but it cannot predict exactly where electrons are located. The wave function is also called a probability amplitude because it is the square of the wave function that yields probabilities. This is the only rigorously correct meaning of a wave function. In order to obtain a physically relevant solution of the Schrodinger equation, the wave function must be continuous, single-valued, normalizable, and antisymmetric with respect to the interchange of electrons. [Pg.10]

To a first approximation, the activation energy can be obtained by subtracting the energies of the reactants and transition structure. The hard-sphere theory gives an intuitive description of reaction mechanisms however, the predicted rate constants are quite poor for many reactions. [Pg.166]


See other pages where Prediction description is mentioned: [Pg.4]    [Pg.226]    [Pg.137]    [Pg.89]    [Pg.169]    [Pg.357]    [Pg.3]    [Pg.4]    [Pg.226]    [Pg.137]    [Pg.89]    [Pg.169]    [Pg.357]    [Pg.3]    [Pg.72]    [Pg.89]    [Pg.189]    [Pg.24]    [Pg.25]    [Pg.564]    [Pg.1591]    [Pg.1925]    [Pg.2164]    [Pg.2227]    [Pg.2827]    [Pg.2908]    [Pg.78]    [Pg.100]    [Pg.517]    [Pg.530]    [Pg.21]    [Pg.2]   
See also in sourсe #XX -- [ Pg.4 , Pg.5 ]




SEARCH



Model predictive control description

© 2024 chempedia.info