Onion design

Olsson, I.-M., Gottfries, J. and Wold, S. (2004) D-optimal onion designs in statistical molecular design. Chemometr. Intell. Lab. Syst., 73, 37. 

Recently, Kriegl et al. used a set of 967 diverse drug-like compounds with IC50 values between 0.4 and 50 xM to derive multivariate models of CYP3A4 inhibition [100]. After removal of outliers, a D-optimal onion design strategy was used... 

Five- and three-layer onion designs were performed for A and B matrices, respectively and a careful layer filling was planned in order to achieve the best coverage of the space. 

FIGURE 2 Scores plot, PCI versus PC2 versus PCS, of A (in plane) matrix. Grey circles represent the 70 sites, selected by means of D-optimal Onion Design. 

The synthesis of the correct structure and the optimization of parameters in the design of the reaction and separation systems are often the single most important tasks of process design. Usually there are many options, and it is impossible to fully evaluate them unless a complete design is furnished for the outer layers of the onion. For example, it is not possible to assess which is better. 

Figure 1.6 The onion model of process design. A reactor design is needed before the separation ind recycle system can be designed, and so on. (From Smith and Linnhoff, Trans. IChemE, CkERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...

Having found the best nonintegrated sequence, most designers would then heat integrate. In other words, the total problem is not solved simultaneously but in two steps. Moving outward from the center of the onion (see Fig. 1.6), the separation layer is addressed first, followed by the heat exchanger network layer. 

Once a design is known for the first two layers of the onion (i.e., reactors and separators only), the overall total cost of this design for all four layers of the onion (i.e., reactors, separators, heat exchanger network, and utilities) is simply the total cost of all reactors and separators (evaluated explicitly) plus the total cost target for heat exchanger network and utilities. 

All too often safety and health (and environmental) considerations are left to the final stages of the design. Returning to the hierarchy of design illustrated by the onion diagram in Fig. 1.6, such considerations would add another layer in the diagram outside the utilities layer. This approach leaves much to be desired. 

Chemical Designations - Synonyms No common synonyms Chemical Formula (CH3)jS04. Observable Characteristics - Physical State (as normally shipped) Liquid Color. Colorless Odor. No characteristic odor slight, not distinctive weak onion. 

Hollow carbon nanostructures are exciting new systems for research and for the design of potential nano-electronic devices. Their atomic structures are closely related to their outer shapes and are described by hex-agonal/pentagonal network configttrations. The surfaces of such structures are atomically smooth and perfect. The most prominent of these objects are ftil-lerenes and nanotubesjl]. Other such novel structures are carbon onions[2] and nanocones[3]. 

This hierarchy can be represented symbolically by the layers of the onion diagram shown in Figure 1.76. The diagram emphasizes the sequential, or hierarchical, nature of process design. Other ways to represent the hierarchy have also been suggested4. 

Figure 1.7 The onion model of process design. A reactor is needed before the separation and recycle system can be designed and so on. 

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