Uniform spread design

The first example of a "uniform spread" design in the study of solvent varation was applied to the Willgerodt-Kindler reaction.[3] It is not reproduced here, since it is very similar to the above example of amine variation. A very clear application of the principle of "uniform spread" is given in an example on the Fischer indole synthesis in the next chapter. 

A similar problem is encountered when a promising solvent has been found in a screening experiment, e.g. by a "uniform spread" design. It is reasonable to assume that the preferred solvent has properties which are similar to those of a promising candidate. The next step is then to explore the solvents projected in the vicinity of the promising candidate in the score plot. This can be accomplished by a small "uniform spread" selection around the winning candidate, or by a simplex search described below. 

When the objective is either to make a carful screening for finding a good candidate for future development, or to study whether a gradual change in the performance of the reaction could be traced to the properties of the reaction system, a design which affords a selection of test items which are uniformly spread in the score plot should be employed. An example of this principle is given in the study of the Fisher indole reaction below. 

The above example shows a selection of test systems by a design affording a uniform spread in the principal properties. The objective was to establish whether there was a gradual change in the performance of the reaction which could be related to the properties of the reaction system. The aim was to detennine those properties which have an influence on the selectivity so that these properties could be controlled. Both these objectives were attained. The results would have been very difficult to achieve without the PLS method and without using a multivariate design for selecting test items. 

The PLS method is also the appropriate tool for determining which properties of the reaction system have an influence on the experimental results. An extensive study of the Fischer indole synthesis was given as an example. For analysis of this type of problem, an experimental design which affords a uniform spread in the principal properties should be used. 

In the automated lay-up system, each layer of veneer (with exception of the top surface veneer) passes under an automatic adhesive appHcation system. This may be a spray appHcation, a curtain coater, or an extmder, each of which is designed to apply a uniform adhesive spread on the upper face of each veneer. After all except the top veneer have been spread with adhesive and laid together, the top veneer is added. The me of the veneer—adhesive assembly at this point should be about 8%. 

Example 2.11 An aluminium cantilever beam is SO mm wide, 80 mm long and 2 mm deep. The loading is 200 N spread uniformly over the cantilever. If the beam is to be replaced by one made from acetal and the design criteria is that the end deflections should be the same in each beam after one month, calculate the dimensions (a) of a solid acetal beam and (b) an acetal beam with unidirectional ribs. The modulus of the aluminium is 70 GN/m. ... 

Roughly speaking we see a 2% variation in growth rate with each degree change in wafer temperature. Therefore, if the uniformity needs to stay within 10% only a 5°C temperature spread across the wafer is allowed. With a proper design of the hot plate this is easy to accomplish. 

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