In certain types of finite element computations the application of isoparametric mapping may require transformation of second-order as well as the first-order derivatives. Isoparametric transformation of second (or higher)-order derivatives is not straightforward and requires lengthy algebraic manipulations. Details of a convenient procedure for the isoparametric transformation of second-order derivatives are given by Petera et a . (1993). [Pg.38]

In the earlier versions of the streamline upwinding scheme the modified weight function was only applied to the convection tenns (i.e. first-order derivatives in the hyperbolic equations) while all other terms were weighted in the usual manner. This is called selective or inconsistent upwinding. Selective upwinding can be interpreted as the introduction of an artificial diffusion in addition to the physical diffusion to the weighted residual statement of the differential equation. This improves the stability of the scheme but the accuracy of the solution declines. [Pg.54]

The first order derivative in Equation (2.80) corresponds to the convection in a field problem and the examples shown in Figure 2.26 illustraTes the ina bility of the standard Galerkin method to produce meaningful results for convection-dominated equations. As described in the previous section to resolve this difficulty, in the solution of hyperbolic (convection-dominated) equations, upwind-ing or Petrov-Galerkin methods are employed. To demonstrate the application of upwinding we consider the case where only the weight function applied to the first-order derivative in the weak variational statement of the problem, represented by Equation (2.82), is modified. [Pg.58]

In the simple one-dimensional example considered here the upwinded weight function found using Equation (2.89) is reduced to W = N + j3 dNldx). Therefore, the modified weight functions applied to the first order derivative term in Equation (2.91) can be written as... [Pg.59]

Therefore the second-order derivative of/ appearing in the original form of / is replaced by a term involving first-order derivatives of w and/plus a boundary term. The boundary terms are, normally, cancelled out through the assembly of the elemental stiffness equations over the common nodes on the shared interior element sides and only appear on the outside boundaries of the solution domain. However, as is shown later in this chapter, the appropriate treatment of these integrals along the outside boundaries of the flow domain depends on the prescribed boundary conditions. [Pg.78]

In practice, in order to maintain the symmetry of elemental coefficient matrices, some of the first order derivatives in the discretized equations may also be integrated by parts. [Pg.78]

Suppose that, near some fixed point G F, dT, the graph F, is a straight line segment parallel to the x axis. Let G (0, T) be an arbitrary fixed point and let Re C denote the ball of a sufficiently small radius with centre (a °,t°). First, we examine the smoothness of the function X = (IF, w). Let D stand for a first-order derivative and let (p denote an arbitrary smooth function in i 2s such that p = 0 outside Rzeji 0 < (> < 1, and dpidy = 0 on F. ... [Pg.208]

A solvent free, fast and environmentally friendly near infrared-based methodology was developed for the determination and quality control of 11 pesticides in commercially available formulations. This methodology was based on the direct measurement of the diffuse reflectance spectra of solid samples inside glass vials and a multivariate calibration model to determine the active principle concentration in agrochemicals. The proposed PLS model was made using 11 known commercial and 22 doped samples (11 under and 11 over dosed) for calibration and 22 different formulations as the validation set. For Buprofezin, Chlorsulfuron, Cyromazine, Daminozide, Diuron and Iprodione determination, the information in the spectral range between 1618 and 2630 nm of the reflectance spectra was employed. On the other hand, for Bensulfuron, Fenoxycarb, Metalaxyl, Procymidone and Tricyclazole determination, the first order derivative spectra in the range between 1618 and 2630 nm was used. In both cases, a linear remove correction was applied. Mean accuracy errors between 0.5 and 3.1% were obtained for the validation set. [Pg.92]

The module of ratio of the second-order derivative d fi/dx to the first-order derivative dfi/dx is... [Pg.444]

The Laplace transform of a first-order derivative is defined consistently with eq. (39.48) by means of the integral ... [Pg.478]

First order derivative, df/dt, and the second order derivative,... [Pg.13]

The method of steepest descent uses only first-order derivatives to determine the search direction. Alternatively, Newton s method for single-variable optimization can be adapted to carry out multivariable optimization, taking advantage of both first- and second-order derivatives to obtain better search directions1. However, second-order derivatives must be evaluated, either analytically or numerically, and multimodal functions can make the method unstable. Therefore, while this method is potentially very powerful, it also has some practical difficulties. [Pg.40]

If each of these reactions is regarded as irreversible pseudo first-order, derive equations for the time dependence of each species in terms of the initial concentrations and the appropriate rate constants. [Pg.166]

The F(t) curve for a system consisting of a plug flow reactor followed by a continuous stirred tank reactor is identical to that of a system in which the CSTR precedes the PFR. Show that the overall fraction conversions obtained in these two combinations are different when the reactions are other than first-order. Derive appropriate expressions for the case of second-order irreversible reactions and indicate how the reactors should be ordered so as to maximize the conversion achieved. [Pg.420]

In both calculations, the boundary conditions are linear with respect to 0 and its first-order derivatives. The solution of the Fourier equation, with respect to the space variables, may be developed in a series of orthogonal functions, winch are exponential with respect to the time variable [for the solution of similar problems, see (45)]- The time-dependance of the temperature distribution along a single space variable r, resulting from a unit pulse, is therefore given by... [Pg.212]

Oppenheimer approximation, 517-542 Coulomb interaction, 527-542 first-order derivatives, 529-535 second-order derivatives, 535-542 normalization factor, 517 nuclei interaction terms, 519-527 overlap integrals, 518-519 permutational symmetry, group theoretical properties, 670—674... [Pg.67]

Let us first investigate the properties of equations that involve only first-order derivatives, i.e., equations such that... [Pg.85]

The polarizability coefficients can now be derived by differentiation of the forms (31) to (34), to give first order derivatives... [Pg.98]

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