Table 1.
MobileNet Architecture
| Type/Stride | Filter Shape | Input Size |
|---|
| Conv/s2 | | |
| Conv dw/s1 | | |
| Conv/s1 | | |
| Conv dw/s2 | | |
| Conv/s1 | | |
| Conv dw/s1 | | |
| Conv/s1 | | |
| Conv dw/s2 | | |
| Conv/s1 | | |
| Conv dw/s1 | | |
| Conv/s1 | | |
| Conv dw/s2 | | |
| Conv/s1 | | |
| conv dw/s1 | | |
| conv/s1 | | |
| Conv dw/s2 | | |
| Conv/s1 | | |
| Conv dw/s2 | | |
| Conv/s1 | | |
| Avg pool/s1 | Pool | |
| FC/s1 | | |
| Softmax/s1 | Classifier | |
Table 2.
Performance Evaluation Results of Proposed Approaches Using GASF Time Series Encoding: Averaged Metrics from Fivefold Cross-Validation with Best Results Highlighted in Bold
| Approach | Acc (%) | Pre (%) | Re (%) | F1 (%) | Er (%) |
|---|
| Softmax approach (RGB method) | 98.5 | 98.6 | 98.5 | 98.5 | 1.5 |
| Softmax approach (appending method) | 97.75 | 97.8 | 97.7 | 97.7 | 2.25 |
| SVM approach (RGB method) | 99.4 | 99.5 | 99.4 | 99.4 | 0.55 |
| SVM approach (appending method) | 98.3 | 98.4 | 98.3 | 98.3 | 1.66 |
| FF approach | 99.6 | 99.7 | 99.68 | 99.68 | 0.3 |
Table 3.
Performance Evaluation Results of Proposed Approaches Using GADF Time Series Encoding: Averaged Metrics from Fivefold Cross-Validation with Best Results Highlighted in Bold
| Approach | Acc (%) | Pre (%) | Re (%) | F1 (%) | Er (%) |
|---|
| Softmax approach (RGB method) | 97 | 97.27 | 97 | 97 | 3 |
| Softmax approach (appending method) | 96.49 | 97.1 | 96.4 | 96.4 | 3.5 |
| SVM approach (RGB method) | 98.6 | 98.7 | 98.6 | 98.7 | 1.38 |
| SVM approach (appending method) | 98.3 | 98.4 | 98.3 | 98.3 | 1.6 |
| FF approach | 99.3 | 99.4 | 99.3 | 99.3 | 0.62 |
Table 4.
Comparative Analysis of SVM Performance with GASF Time Series Encoding across Various Image Appending Orders
| Appending Order | Acc (%) | F1 (%) | Er (%) |
|---|
| | 98.3 | 98.3 | 1.66 |
| | 98.6 | 98.6 | 1.38 |
| | 98.6 | 98.6 | 1.38 |
| | 98.6 | 98.6 | 1.38 |
| | 98 | 98 | 1.94 |
| | 98.3 | 98.3 | 1.66 |
Table 5.
Performance Comparison of Proposed Approaches Using GASF Encoding Time Series with RGB and Grayscale Channel Concatenation Methods
| Approach | Acc (%) | Pre (%) | Re (%) | F1 (%) | Er (%) |
|---|
| Softmax (RGB method) | 98.5 | 98.6 | 98.5 | 98.5 | 1.5 |
| Softmax (grayscale channel method) | 98.2 | 98.4 | 98.2 | 98.2 | 1.8 |
| SVM (RGB method) | 99.4 | 99.5 | 99.4 | 99.4 | 0.55 |
| SVM (grayscale channel method) | 99.1 | 99.2 | 99.1 | 99.1 | 0.83 |
Table 6.
Computational Complexity Comparison of Proposed Approaches in Terms of Training and Inference Time
| Approach | Average Training Time (s) | Average Inference Time per Sample (s) |
|---|
| Softmax approach | 23.7 | 0.002 |
| SVM approach | 0.8 | 0.0007 |
| FF approach | 37.97 | 0.004 |
Table 7.
Performance Assessment of the SVM and FF Approaches under Different Input Sizes
| Input Size | SVM Approach | FF Approach |
|---|
| | Acc | 53.6 | 95.9 |
| F1 | 53.6 | 95.7 |
| Er | 46.3 | 4.06 |
| | Acc | 95.83 | 97.16 |
| F1 | 95.8 | 96.7 |
| Er | 4.16 | 2.8 |
| | Acc | 97.7 | 99.3 |
| F1 | 97.7 | 99.3 |
| Er | 2.22 | 0.6 |
| | Acc | 98.9 | 99 |
| F1 | 98.9 | 99 |
| Er | 1.11 | 0.93 |
| | Acc | 99.4 | 99.6 |
| F1 | 99.4 | 99.6 |
| Er | 0.55 | 0.3 |
| | Acc | 99.16 | 99 |
| F1 | 99.1 | 99 |
| Er | 0.83 | 0.93 |
| | Acc | 98.6 | 98.1 |
| F1 | 98.6 | 98.1 |
| Er | 1.38 | 1.87 |
Table 8.
Comparative Analysis of Our Proposed Approaches with Traditional Methods
| Method | Acc (%) | F1 (%) | Er (%) |
|---|
| Decision tree | 87 | 86.8 | 13 |
| Naive Bayes | 89 | 89 | 11 |
| Logistic regression | 83 | 83 | 17 |
| KNN | 89 | 89 | 11 |
| SVM approach | 99.4 | 99.4 | 0.55 |
| FF approach | 99.6 | 99.68 | 0.3 |
Table 9.
Comparative Results of SVM-Based Transfer Learning Using Different Pre-trained CNN Models
| Pre-trained Model | Acc (%) | F1 (%) | Er (%) | (s) |
|---|
| VGG16 | 98 | 98 | 1.94 | 0.001 |
| ResNet50 | 99.1 | 99.1 | 0.83 | 0.002 |
| Inception | 98.8 | 98.8 | 1.11 | 0.002 |
| DenseNet | 98 | 98 | 1.94 | 0.0017 |
| MobileNet | 99.4 | 99.4 | 0.55 | 0.0007 |
Table 10.
Comparative Results of FF-Based Transfer Learning Using Different Pre-trained CNN Models
| Pre-trained Model | Acc (%) | F1 (%) | Er (%) | (s) |
|---|
| VGG16 | 97.8 | 97.8 | 2.18 | 0.005 |
| ResNet50 | 98.75 | 98.74 | 1.25 | 0.0047 |
| Inception | 97.8 | 97.8 | 2.18 | 0.005 |
| DenseNet | 95.3 | 93.7 | 4.68 | 0.0052 |
| MobileNet | 99.6 | 99.6 | 0.3 | 0.004 |
Table 11.
Robustness Analysis of Proposed Approaches across Various Test Datasets
| Data | Softmax | SVM | FF |
|---|
| Unseen dataset | Acc | 96 | 99.1 | 99.3 |
| Er | 3.96 | 0.86 | 0.68 |
| Synthetic data | Acc | 94 | 97 | 98 |
| Er | 6 | 3 | 2 |
| Noisy data | Acc | 94.1 | 98.8 | 98.4 |
| Er | 6.37 | 1.2 | 1.5 |