Capacity-based approach

However, as we have demonstrated in our previous examples, this design is usually not the one that provides the best control, i.e., the least variability of product quality. What we need is a way to incorporate quantitatively (in terms of dollars/year) this variability into the economic calculations. We discuss in this section a method called the capacity-based approach that accomplishes this objective. It should be emphasized that the method provides an analysis tool, not a synthesis tool. It can provide a quantitative assessment of a proposed flowsheet or set of parameter values or even a proposed control structure. But it does not generate the besf flowsheet or parameter values it only evaluates proposed systems. 

Now let us apply the capacity-based approach. Positive and negative 10 percent disturbances are made in the fresh feed flow rate Fg and in the fresh feed composition Zq. Dynamic simulations (confirmed by frequency-domain analysis, to be discussed in Chapter 10) show that the variability in product quality xb is decreased by increasing reactor volume or by decreasing the number of trays in the stripper. 

Several approaches have been proposed, and some of the more practical are briefly reviewed in this section. The capacity-based approach discussed in Section 7.3 appears to offer a fairly simple, logical and effective methodology for achieving the goals of simultaneous design. 

The capacity-based approach is a practical and effective method for incorporating dynamic controllability into the design of a chemical plant. All the tools needed for the job are available in the commercial flowsheeting simulation software. 

Geometry-based approach from a geometrical point of view, a cavity is a concave empty space that can be described using 2D (surface) or 3D shape descriptors (19-21). We consider three regions in the protein environment the protein bulk, the bulk solvent and the cavity space. The protein bulk is the space filled by the protein atoms. The bulk solvent is the space outside the protein which differentiates from the space inside the protein which defines the cavity where the drug-like molecule is supposed to bind. The identification of protein pockets by numerical methods suppose the capacity to discriminate first the protein bulk from the rest... 

ECVAM is the leading international center for alternative test method validation. Hartung et al. (29) summarized the modular steps necessary to accomplish stage 3 (test validation). The seven modular steps are (I) test definition, (2) within-laboratory variability, (3) transferability, (4) between-laboratory variability, (5) predictive capacity, (6) applicability domain, and (7) performance standards (29). Steps 2-4 evaluate the test s reliability steps 5 and 6 evaluate the relevance of the test. Successful completion of all seven steps is necessary to proceed to stage 4 (independent assessment or peer review). This modular approach allows flexibility for the validation process where information on the test method can be gathered either prospectively or retrospectively. The approach is applicable not only to in vitro test methods but also to in silico approaches (e.g., computer-based approaches such as quantitative structure-activity relationships or QSAR) and pattern-based systems (e.g., genomics and proteomics). 

Noipa T, Srijaranai S, Tuntulani T, Ngeontae W. New approach for evaluation of the antioxidant capacity based on scavenging DPPH free radical in micelle systems. Food Research International. 2011 44(3) 798-806. 

See T. R. Elliott, M. L. Luyben, and W. L. Luyben, Application of the capacity-based economic approach to an industrial-scale process, Ind. Eng Chem. Research 36, 1727 (1997). 

Polylactide (PLA) is the leading polymer type among biodegradables with global production capacity for this material amounting to about 250,000 tonnes per annum in 2005. Starch-based polymer capacity is approaching 60,000 tonnes per annum. 

There has been some useful work in developing methods for comparing the economics of alternative designs, using both steady-state and dynamic considerations. The capacity-based economic approach of Elliott et al. (1997) provides a technique for quantitatively comparing the profitability of alternative processes. 

Alternative Approaches / 5.62 Basic Concepts of the Capacity-Based Method / 5.6.3 Reactor-Column-Recycle Example... 

Two trans-sialidases isolated from the animal-pathogenic Afiican trypanosome T. Congo lense show pronounced differences in their capacity for sialic acid transfer as compared with the hydrolytic activity. Partial sequences were obtained from these two enzymes by a PCR-based approach, showing 50% identity with each oflier, but are similar to viral, bacterial, animal siahdases and other trans-sialidases. Most of the critical active-site residues common to other trypanosomal siahdases and TS are conserved This similarity, together with the amino acid difference at the active site, between American and African (trans-)siahdases is depicted in the pubUcation. ... 

Eppen, G.D., Martin, R.K., and Schrage, L.E. A Scenario-Based Approach to Capacity Planning. Operations Research, 37(4) 517—527, July-August 1989. 

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