462
X. Chen et al.
Table 30.8 Trapezoid MF parameters for importance weight
Importance weight
MF parameters
a L
a LM
a RM
a R
Very small
0
0
0.1
0.2
Small
0.1
0.2
0.3
0.5
Fair
0.3
0.5
0.5
0.7
Big
0.5
0.7
0.8
0.9
Very big
0.8
0.9
1.0
1.0
30.3 Application of Fuzzy Linguistic Approach
We use the pre-defined MFs to transfer the linguistic terms to fuzzy numbers, in
order to assess the criticality of three raw materials: Cobalt, Tungsten and Yttrium,
as follows:
Step 1. Define the membership functions for risk metrics and importance weight,
shown in Table 30.7 and Table 30.8;
Step 2. Use linguistic terms to assess the risk level of each metric (Table 30.9)
and its corresponding importance weight (Table 30.10);
Step 3. Aggregate the MFs of metrics and importance weights by Eq. 30.3;
Equation 30.3: Aggregation of membership functions
Table 30.9 Risk levels of
three critical materials
1 Risk metric
Critical material
Cobalt
Tungsten
Yttrium
Abundance risk
M (2, 3, 4)
M (2, 3, 4)
M (2, 3, 4)
Conflict material
risk
L (1, 2, 3)
H (3, 4, 5)
L (1, 2, 3)
Environmental
country risk
L (1, 2, 3)
M (2, 3, 4)
VH (4, 5, 5)
Price volatility
risk
VL (0, 1, 2) VL (0, 1, 2) M (2, 3, 4)
Sourcing and
geopolitical risk
M (2, 3, 4)
H (3, 4, 5)
VH (4, 5, 5)
Monopoly of
supply risk
L (1, 2, 3)
H (3, 4, 5)
VH (4, 5, 5)