5 Application of the model to the case study
5.2 An overview Company
Company chosen for this research study is a famous open frame manufacturing industry located in the United States California. The company planned to improve the quality of the product. They planned to purchase the quality raw material at low cost and at a short duration of time. Instead of purchasing the material from the single supplier they noted that five alternative suppliers, namely supplier 1 (S1), supplier 2 (S2), supplier 3 (S3), supplier 4 (S4), and supplier 5 (S5) were taken into consideration. Top manager of te company needs to decide to choose the most preferred supplier among these suppliers based on the quality and the fuzzy sample data. Let us consider the fuzzy sample data of the light transmission rate with size 20 have been collected from each supplier listed in Table 4.
Table 4: Triangular fuzzy data collected from the suppliers (unit: %)
S1 S2 S3 S4 S5
( 87, 90, 93 ) ( 90, 93, 94 ) ( 88, 91, 92 ) ( 89, 90, 91 ) ( 88, 91, 92 ) ( 88, 92, 93 ) ( 91, 92, 95 ) ( 89, 90, 93 ) ( 91, 92, 94 ) ( 89, 91, 93 ) ( 89, 92, 95 ) ( 88, 91, 95 ) ( 86, 89, 92 ) ( 87, 89, 91 ) ( 86, 89, 92 ) ( 90, 91, 92 ) ( 90, 91, 92 ) ( 90, 91, 92 ) ( 85, 89, 97 ) ( 89, 90, 91 ) ( 86, 90, 93 ) ( 91, 92, 95 ) ( 89, 90, 93 ) ( 90, 92, 93 ) ( 88, 91, 93 ) ( 88, 91, 92 ) ( 92, 93, 94 ) ( 90, 91, 92 ) ( 85, 89, 97 ) ( 90, 91, 92 ) ( 90, 93, 94 ) ( 92, 94, 95 ) ( 80, 82, 83 ) ( 91, 92, 93 ) ( 91, 92, 93 ) ( 90, 91, 92 ) ( 91, 93, 94 ) ( 89, 91, 92 ) ( 88, 89, 96 ) ( 89, 91, 92 )
15
( 88, 91, 93 ) ( 91, 93, 94 ) ( 89, 91, 92 ) ( 90, 91, 95 ) ( 90, 91, 92 ) ( 88, 92, 93 ) ( 90, 91, 92 ) ( 88, 89, 90 ) ( 77, 79, 83 ) ( 88, 89, 90 ) ( 89, 90, 93 ) ( 91, 92, 93 ) ( 89, 90, 91 ) ( 92, 93, 94 ) ( 82, 86, 88 ) ( 93, 94, 95 ) ( 93, 94, 96 ) ( 91, 92, 94 ) ( 91, 92, 95 ) ( 90, 91, 92 ) ( 88, 90, 92 ) ( 89, 91, 93 ) ( 87, 89, 91 ) ( 90, 91, 95 ) ( 88, 90, 91 ) ( 86, 89, 90 ) ( 87, 91, 92 ) ( 85, 89, 90 ) ( 90, 91, 92 ) ( 85, 89, 90 ) ( 91, 93, 94 ) ( 92, 94, 95 ) ( 90, 92, 93 ) ( 91, 92, 95 ) ( 91, 92, 94 ) ( 88, 89, 92 ) ( 88, 91, 94 ) ( 86, 89, 92 ) ( 92, 93, 94 ) ( 88, 89, 92 ) ( 90, 92, 93 ) ( 93, 94, 95 ) ( 91, 92, 93 ) ( 92, 94, 95 ) ( 90, 92, 93 ) ( 89, 91, 92 ) ( 90, 91, 92 ) ( 88, 89, 90 ) ( 91, 93, 94 ) ( 89, 90, 91 ) ( 89, 91, 93 ) ( 90, 93, 94 ) ( 88, 91, 92 ) ( 91, 93, 94 ) ( 89, 90, 92 ) ( 80,85, 89 ) ( 79, 81, 85 ) ( 77, 79, 83 ) ( 90, 91, 92 ) ( 87, 89, 90 )
The upper and lower specification limits of light transmission rate are set as USL = 95%
and LSL = 85% respectively. And the target value is set at τ= 90%. Then the estimates of statistics
x
iαL ,s
iLα , cˆLpmiαx
iUα ,s
iUα , and cˆUpmiα in the α-level sense of the five suppliers are shown in Table 5.Table 5: The α-level estimates of Cpmi S1
α-level L
xiα siLα cˆLpmiα xiUα siUα cˆUpmiα
0.0 88.35 2.56 0.44 92.65 1.42 0.55
0.1 88.60 2.48 0.48 92.47 1.45 0.58
0.2 88.85 2.40 0.54 92.29 1.48 0.61
0.3 89.10 2.32 0.59 92.11 1.51 0.64
0.4 89.35 2.24 0.65 91.93 1.56 0.66
0.5 89.60 2.17 0.71 91.75 1.60 0.68
0.6 89.85 2.11 0.77 91.57 1.65 0.69
0.7 90.10 2.05 0.80 91.39 1.71 0.70
0.8 90.35 1.99 0.78 91.21 1.77 0.71
0.9 90.60 1.94 0.75 91.03 1.83 0.72
1.0 90.85 1.90 0.73 90.85 1.90 0.73
S2
α-level L
xiα siLα cˆLpmiα xiUα siUα cˆUpmiα
0.0 89.90 3.02 0.54 93.45 2.33 0.22
0.1 90.09 2.99 0.55 93.28 2.36 0.24
0.2 90.27 2.96 0.53 93.11 2.39 0.26
0.3 90.46 2.92 0.52 92.94 2.43 0.28
0.4 90.64 2.90 0.50 92.77 2.47 0.30
0.5 90.83 2.87 0.48 92.60 2.51 0.32
0.6 91.01 2.85 0.47 92.43 2.56 0.33
0.7 91.20 2.83 0.45 92.26 2.61 0.35
0.8 91.38 2.81 0.43 92.09 2.67 0.36
0.9 91.57 2.80 0.41 91.92 2.73 0.38
1.0 91.75 2.79 0.39 91.75 2.79 0.39
S3
α-level L
xiα siLα cˆLpmiα xiUα siUα cˆUpmiα
0.0 87.50 3.50 0.24 91.00 2.94 0.45
0.1 87.69 3.47 0.26 90.84 2.96 0.47
0.2 87.87 3.43 0.28 90.67 2.98 0.48
0.3 88.06 3.40 0.30 90.51 3.00 0.50
0.4 88.24 3.37 0.32 90.34 3.03 0.51
0.5 88.43 3.35 0.34 90.18 3.06 0.53
0.6 88.61 3.32 0.36 90.01 3.09 0.54
0.7 88.80 3.30 0.38 89.85 3.13 0.52
0.8 88.98 3.28 0.40 89.68 3.16 0.49
0.9 89.17 3.26 0.43 89.52 3.21 0.47
1.0 89.35 3.25 0.45 89.35 3.25 0.45
S4
α-level L
xiα siLα cˆLpmiα xiUα siUα cˆUpmiα
0.0 89.15 3.53 0.39 93.50 3.00 0.17
0.1 89.31 3.48 0.41 93.23 2.93 0.20
16
0.2 89.47 3.44 0.43 92.95 2.88 0.24
0.3 89.63 3.39 0.45 92.68 2.84 0.27
0.4 89.79 3.35 0.48 92.40 2.83 0.31
0.5 89.95 3.32 0.50 92.13 2.84 0.34
0.6 90.11 3.28 0.50 91.85 2.86 0.37
0.7 90.27 3.25 0.49 91.58 2.91 0.39
0.8 90.43 3.22 0.47 91.30 2.98 0.41
0.9 90.59 3.19 0.46 91.03 3.06 0.43
1.0 90.75 3.16 0.45 90.75 3.16 0.45
S5
α-level L
xiα siLα cˆLpmiα xiUα siUα cˆUpmiα
0.0 88.35 2.13 0.52 91.65 1.39 0.81
0.1 88.54 2.05 0.57 91.51 1.38 0.85
0.2 88.72 1.97 0.63 91.36 1.37 0.89
0.3 88.91 1.89 0.69 91.22 1.37 0.92
0.4 89.09 1.82 0.75 91.07 1.37 0.96
0.5 89.28 1.74 0.82 90.93 1.37 0.99
0.6 89.46 1.67 0.89 90.78 1.38 1.02
0.7 89.65 1.61 0.96 90.64 1.39 1.05
0.8 89.83 1.55 1.04 90.49 1.40 1.07
0.9 90.02 1.49 1.12 90.35 1.42 1.10
1.0 90.20 1.44 1.11 90.20 1.44 1.11
5.3 Result Analysis
Using the commercial software MATLAB, can calculate the α-level sets, the graphs of membership functions of fuzzy estimates ˆ
c
pmi for i =1 ,…, 5 can be constructed and shown as Fig. 8.After pair-wise comparisons were obtained and entered into data matrices. The value of Δ and ij Δ are tabulated in the 2nd and 3rd column in Table 7, and the values of the fuzzy ji preference relation FPR
( c
ˆpmi,c
ˆpmj)
and FPR( c
ˆpmj,c
ˆpmi)
=1- FPR( c
ˆpmi,c
ˆpmj)
for i =1,2,3,4 and i< j are tabulated in the 4th and 5th column in Table 7.
Table 7 : Value of the fuzzy preference relation
Pairwise Comparison
Δij Δji FPR
(
cˆpmi,cˆpmj)
FPR(
cˆpmj,cˆpmi)
S1 and S2 ( i=1 and j=2 ) 0.7635 0.0373 0.9534 0.0466 S1 and S3 ( i=1 and j=3 ) 0.7623 0.0343 0.9569 0.0431 S1 and S4 ( i=1 and j=4 ) 0.7509 0.0287 0.9632 0.0368 S1 and S5 ( i=1 and j=5 ) 0.1047 1.0211 0.0930 0.9070 S2 and S3 ( i=2 and j=3 ) 0.1664 0.1646 0.5028 0.4972
0.4 0.6 0.8 1 1.2 1.4 1.6
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Cpm
Figure 8 : The membership functions of fuzzy estimates of 5 suppliers S1 S5
S2 S3
S4
α
S1 S2
S4 S5 S3
17
S2 and S4 ( i=2 and j=4 ) 0.1589 0.1629 0.4938 0.5062 S2 and S5 ( i=2 and j=5 ) 0.0105 1.3105 0.0079 0.9921 S3 and S4 ( i=3 and j=4 ) 0.1492 0.1550 0.4904 0.5096 S3 and S5 ( i=3 and j=5 ) 0.0098 1.3117 0.0074 0.9926 S4 and S5 ( i=4 and j=5 ) 0.0060 1.3021 0.0046 0.9954
(1) After finding the values of the fuzzy preference relation FPR
( c
ˆpmi,c
ˆpmj)
andFPR
( c
ˆpmj,c
ˆpmi)
=1- FPR( c
ˆpmi,c
ˆpmj)
for i =1,2,3,4 and i < j. We draw an analogy of the value ofγ
is set to be 0.50. In the light of Step 2 in the above procedure, the sequence of suppliers arranged by considering the preference of selection is given by { S5,S1,S4,S2,S3 }. On the basis of the result of the sorting we are convinced that Supplier 5 is the most preferred choice and Supplier 3 is the worst choice among all five suppliers with the preference degree 0.50.(2) Furthermore, if the value of
γ
is set to be 0.65, then the sequence goes for { ( S2,S3 ), ( S2,S4 ), ( S3,S4 )}, in which S2 is indifferent fromS3, S2 is indifferent fromS4, and S3 is indifferent fromS4 with indifference degrees (0.65,0.35), that can be written as below.0.35≤ FPR
( c
ˆpm2,c
ˆpm3)
≤ 0.65 and 0.35 ≤ FPR( c
ˆpm3,c
ˆpm2)
≤ 0.65and
0.35≤ FPR
( c
ˆpm2,c
ˆpm4)
≤ 0.65 and 0.35 ≤ FPR( c
ˆpm4,c
ˆpm2)
≤ 0.65and
0.35≤ FPR
( c
ˆpm3,c
ˆpm4)
≤ 0.65 and 0.35 ≤ FPR( c
ˆpm4,c
ˆpm3)
≤ 0.65In other words, supplier S5 and supplier S1 is still the most preferred supplier with the preference degree 0.65. In this case, the manger may randomly select one of supplier S5 and supplier S1 as the most preferred supplier, or provide some other criteria to select the most preferred supplier form supplier S5 and supplier S1. Surely, if the company is allowed to select more than one supplier to supply this particular touch screen for manufacturing, then both suppliers S5 and supplier S1 are the most preferred supplier.
6. Conclusions
Fuzzy logic is a powerful problem-solving methodology with a myriad of applications in embedded control and information processing. Fuzzy provides a remarkably simple way to draw definite conclusions from vague, ambiguous or imprecise information. In a sense, fuzzy logic resembles human decision making with its ability to work from approximate data and find precise solutions. This paper proposed an approach for the selection of suppliers, which model is capable of handling fuzzy data and was not seriously treated by the researchers.
The quality-based supplier selection and evaluation using the imprecise sample data has been applied for supplier selection. A general method is proposed to obtain the fuzzy estimate of the capability index
C
pmi of supplier i using “resolution identity” in fuzzy sets theory.In order to derive the membership degree of any given
γ
of fuzzy estimate ˆc
pmi , the original problem is transformed into the optimization problems. After obtaining the fuzzy18
estimates
{ c
ˆpm1,...,c
ˆpmq}
of respective supplier{ S
1,..., qS }
, we follow the ranking method proposed by Yuan (1991) to choose the most preferred supplier. The application model/case study taken from the touch screen application is provided illustrated the applicability of the proposed methodology.The results show that the model has the capability to be flexible and deal with fuzzy data to choose their supplier. The final priority of each alternative will lead to a recommended best option. It can be concluded that the model could facilitate decision making. The approach could help in reduced time consuming efforts in the supplier selection process.
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