Face-centred central composite

Occasionally c = 1 is selected which creates a so-called face-centred central composite design. An alternative to the central composite designs, which, as far as we know, has not been used in chromatography, is the Box-Behnken 52) design. 

Face-centred central composite design with three factors... 

The latest DoE was focussing on the axial and swirl stream temperature (Tswiri) the rotation speed (n) in a face-centred central composite (CCF) response surface design with those three factors (/=3) on three levels. Levels were set linearly as mentioned in section Improved Experimental Setup so that N = 2 +2/+1 = 15 experiments were required for this model. The centre point was repeated five times to ensure reproducibility and reasonable model validity. Particle size, span, particle shape, surface roughness, flowabDity and BET surface area were chosen as responses to evaluate the significant effects of the factors on these particle properties [34, 35]. 

The Central Composite Designs Similar to the factorial designs, but with lines radiating from the centre of the figure, perpendicular to the faces and terminating outside. 

The three-factor central composite may be represented as a cube, with a centre point, experiments at each vertex and at the ends of axes radiating out from the centre through the middle of each face. The vertices will be designated as +1 or -1 for each factor. It is suggested that six runs be made at the centre, This design can be represented as indicated below the diagram,... 

Sometimes known as Box-Wilson designs, these are the same as the central composite designs for the spherical domain, except for the positioning of the axial points. These are face-centred, with a = 1. An example is given for 3 factors in table A3.4. They may be derived easily by applying the rules given in chapter 5. 

To develop a dispersive liquid-liquid microextraction method for Te determination several variables were optimised. A half fractional factorial design (32 experiments) was used to estimate the most effective parameters on the enrichment factor. Then, a half fractional central composite face centred design for five factors was performed to optimise the parameters. 

In the Circumscribed Central Composite Design the length of the arms of the star is the square root of the number of variables. In that case, each variable has five levels (vs. the three levels of the Face-Centred Design), all the points are equidistant from the centre and the design spans a spherical domain... 

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