Undesired processing

Decoupling Control Systems Decoupling control systems provide an alternative approach for reducing control loop interactions. The basic idea is to use additional controllers called decouplers to compensate for undesirable process interactions. 

The function of the decouplers is to compensate for the undesirable process interactions represented by Gpi9 and Gp9i. Suppose that the process transfer functions are all known. Then the ide design equations are ... 

Error recovery by the operators is only one of several layers of protection to prevent undesired consequences (see Figure 2.1). Process and equipment designs (discussed in previous chapters) that prevent undesired process excursions are inherently safer than designs that require operator intervention. Likewise, designs that enable the operators to intervene before an upset becomes serious are inherently safer than those that do not. 

The dissolution of semiconductors is usually an undesirable process since it diminishes the stability of the electrode and limits their use... 

The recovered sulfur industry has come of age in the last twD decades and is now a major world source of this essential element Much progress has been made in the improvement of various process steps, particularly those related to overall recovery efficiency. These improvements continue to reduce undesirable process losses to atmosphere and the environmental impact of the industry. As... 

P. W. Bramer Tom George did indeed do significant work in control of reactions. However, if I recall correctly, his approach required extremely high field strengths and, as such, induced undesirable processes that competed with control (e.g., molecule ionization). 

Fermentation proceeds via the development of microorganisms that the food industry controls and corrects to obtain the desired results. The main substratum that is transformed is made up of carbohydrates, which may undergo various types of fermentation, with the production of more simple substances that are very important in the determination of the quality of the final product. In some cases, the formation of some substances may indicate undesired processes. There is, therefore, the need to intervene rapidly so that the necessary corrections may be made to the process. Fast analytical methods are required that can in most cases ascertain the content of various sugars, organic acids, glycerol, and alcohols (for example, methanol, ethanol, higher alcohols). 

A number of undesirable processes can occur in competition with the formation of the optically active product (1) alkylation of the wrong ion-pair leading to the enantiomer of the desired product (step c) (2) side-reactions of either the starting substrate [e.g., ester saponifi-... 

The formation of a-naphthylamines 140 and 153 in reactions of 2-benzopyrylium salts with ammonia and primary amines is not always an undesirable process. The synthetic application of a-naphthylamines is connected with the chemistry of benzo[c]phenanthridine alkaloids 132 (78MI1 81H474). 

This limiting current, /liin, is the maximum current that can be employed in an electrodialysis process. If the potential required to produce this current is exceeded, the extra current will be carried by other processes, first by transport of anions through the cationic membrane and, at higher potentials, by hydrogen and hydroxyl ions formed by dissociation of water. Both of these undesirable processes consume power without producing any separation. This decreases the current efficiency of the process, that is, the separation achieved per unit of power consumed. A more detailed discussion of the effect of the limiting current density on electrodialysis performance is given by Krol et al. [20],... 

Active forms of oxygen, formed by reactions (9.1) and (9.2), are not yet ready for selective interaction with the substrate because, in principle, they may enter various reactions, including undesired processes ... 

A multipole cell at pressures around 1 to 15 mtorr, placed between the sampler-skimmer interface and the mass spectrometer, can serve two functions reduce the kinetic energy of the ions to nearly thermal energies (<0.5 eV) and carry out reactions with analyte or background ions. Of particular interest for ICP-MS are reactions that would dramatically reduce spectral overlaps due to elemental or polyatomic ions. Two potentially undesirable processes must be considered for successful use of a collision-reaction cell. Scattering losses can be severe if the mass of the collision or reaction gas is high compared to that of the analyte ion... 

Hypochlorous acid formed at the anode by hydrolysis of dissolved chlorine reacts with hypochlorite according to the equation (XII I-14). This undesirable process can be partially suppressed by maintaining a low temperature of the electrolyte. The cooling of the solution is still more important when higher current densities are used. A low temperature is, however, disadvantageous as far as energy consumption is concerned, as the ohmic resistance of the electrolyte increases. 

To prevent the undesirable processes mentioned above, it would be necessary to maintain during electrolysis a neutral reaction by gradually introducing just the right amount of concentrated sulphuric acid into the stirred electrolyte to neutralize the ammonia. As, however, this measure is industrially difficult to comply with, the method of operating in a neutral solution is not suitable for commercial exploitation. 

There are two undesirable processes that these surface layers should prevent ... 

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