Table 6.

Simulated levels and results of quadratic regression orthogonal rotating test.

No	X1	X2	X3	Angle of repose/(°)
1	1	1	1	63.86
2	1	1	-1	44.95
3	1	-1	1	57.42
4	1	-1	-1	38.05
5	-1	1	1	52.39
6	-1	1	-1	41.28
7	-1	-1	1	53.44
8	-1	-1	-1	27.62
9	2	0	0	48.73
10	-2	0	0	35.47
11	0	2	0	68.11
12	0	-2	0	36.90
13	0	0	2	74.55
14	0	0	-2	31.83
15	0	0	0	54.15
16	0	0	0	54.35
17	0	0	0	55.82
18	0	0	0	53.21
19	0	0	0	54.27
20	0	0	0	53.71
21	0	0	0	53.25
22	0	0	0	53.68
23	0	0	0	54.01