object description. The indiscernibility relation (similarity), which is a mathematical basis of the rough set theory, induces a partition of the universe in to blocks of indiscernible objects, called elementary sets, which can be used to build knowledge about a real or abstract world. Precise condition rules can be extracted from a discernibility matrix. Application of RST in different fields of the applied sciences has been reported (Pal et al., 2004). 

## 2. Experimental:

Experiments were conducted with the hydrocyclone Test Rig C705 (Figure1a).The verification data is divided into hydrocyclone operations according to the different pressure drop (psi) and solid percent, as the tests run with constant geometrical parameters (diameters of the hydrocyclone=50.8cm, overflow=30m, underflow=7mm). 

![0_image_0.png](0_image_0.png)

The sample that used in this study was collected from Qara Ağac kaolin mining of Iran, where the density of our sample is 2.17 g/cm3. 

The process has four manipulating variables: Pressure drop (psi), solid percent 
(%), size fraction (-m) and overflow or underflow state (ascribed 0, 1codes, respectively). The main output of this model is cumulate passing percent (%) that used to control of the split size (d50) and, as a direct result, calculation of Imperfection coefficient in the hydrocyclone operations, can be evaluated (Figure1b). 