Forward strategy

In the first strategy, a forward strategy, one could start with the feature with the highest A-value and then successively add further features. In the second strategy, a backward strategy, one could start with all features. Then the feature with the lowest discriminating power is deleted first from the entire set, and so on. 

In Tab. 5-13 we report the results of both mentioned strategies for the selection process. In both procedures the WILKS lambda varies monotonously and each set has a significant meaning. We may, therefore, stop the selection process following the misclassification rate. In the forward strategy the first zero error rate appears with the feature set Ti, Mg, Ca in step 3 (Fig. 5-25) whereas in the backward strategy the zero error rate is obtained with the remaining elements Si, Ca, Al, Mg in step 3. Now it is up to the expert to decide which feature set to retain in the future. 

The dynamic model was validated both in steady and unsteady-state conditions, which is quite interesting in case that a control based on feed-forward strategy is applied. The prediction of the final concentration of Orange II from the initial data would allow the system control to modify the flow rate of MnP, Orange II or H2O2, in order to adapt the conditions to the desired final value. 

The forward strategy can be used to imply the forward price, provided that the current price of the underlying and the money market interest rate are known. FIGURE 6.2 illustrates how this works, using the one-year forward contract whose profit/loss profile is graphed in figure 6.1 and assuming an initial spot price, P, of 50, a risk-free rate, r, of 1.05 percent, and a payout yield, R, of 1 percent. 

The feedforward control strategy (Fig. lb) addresses the disadvantages of the feedback control strategy. The feedforward control strategy measures the disturbance before it affects the output of the process. A model of the process determines the adjustment ia the manipulated variables(s) to compensate for the disturbance. The information flow is therefore forward from the disturbances, before the process is affected, to the manipulated variable iaputs. 

Strategy Write the rate expression for the rate-determining second step. This will involve the unstable intermediate, O. To get rid of [O], use the feet that reactants and products are in equilibrium in step 1, so forward and reverse reactions occur at the same rate. 

STRATEGY Calculate the reaction quotient and substitute it and the standard Gibbs free energy of reaction into Eq. 5. If AGr < 0, the forward reaction is spontaneous at the given composition. If AGr > 0, the reverse reaction is spontaneous at the given composition. If AGr = 0, there is no tendency to react in either direction the reaction is at equilibrium. At 298.15 K, RT = 2.479 kJ-moF h... 

STRATEGY Raising the temperature of an equilibrium mixture will tend to shift its composition in the endothermic direction of the reaction. A positive reaction enthalpy indicates that the reaction is endothermic in the forward direction. A negative reaction enthalpy indicates that the reaction is endothermic in the reverse direction. To find the standard reaction enthalpy, use the standard enthalpies of formation given in Appendix 2A. 

In this short initial communication we wish to describe a general purpose continuous-flow stirred-tank reactor (CSTR) system which incorporates a digital computer for supervisory control purposes and which has been constructed for use with radical and other polymerization processes. The performance of the system has been tested by attempting to control the MWD of the product from free-radically initiated solution polymerizations of methyl methacrylate (MMA) using oscillatory feed-forward control strategies for the reagent feeds. This reaction has been selected for study because of the ease of experimentation which it affords and because the theoretical aspects of the control of MWD in radical polymerizations has attracted much attention in the scientific literature. 

Feedback control can never be perfect as it only reacts to the disturbances which are already measured in the system output. The feed-forward method tries to eliminate this drawback by an alternative approach. Instead of using the process output, the measured variable is taken as the measured inlet disturbances and its effect on the process is anticipated via the use of a model. The action is taken on the manipulated variable using the model to relate the measured variable at the inlet, the manipulated variable and the process output. The success of this control strategy depends largely on the accuracy of the model prediction, which is often imperfect as models can rarely predict the... 

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