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| 1 | +--- |
| 2 | +title: 'SCS-SupCon: Sigmoid-based common and style supervised contrastive learning |
| 3 | + with adaptive decision boundaries' |
| 4 | +authors: |
| 5 | +- Bin Wang |
| 6 | +- Fadi Dornaika |
| 7 | +- Jinan Charafeddine |
| 8 | +date: '2026-01-01' |
| 9 | +publishDate: '2026-04-14T13:10:00.976472Z' |
| 10 | +publication_types: |
| 11 | +- article-journal |
| 12 | +publication: '*Expert Systems with Applications*' |
| 13 | +doi: https://doi.org/10.1016/j.eswa.2026.131308 |
| 14 | +abstract: Image classification can be inherently challenging due to subtle inter-class |
| 15 | + differences and substantial intra-class variations, limiting the effectiveness of |
| 16 | + existing contrastive learning approaches. In particular, supervised contrastive |
| 17 | + methods based on the InfoNCE loss often suffer from the negative-sample dilution |
| 18 | + issue and lack explicit mechanisms for adaptive decision-boundary control, significantly |
| 19 | + weakening their discriminative capability on fine-grained image classification tasks. |
| 20 | + To address these challenges, we propose a novel supervised contrastive learning |
| 21 | + framework, termed Sigmoid-based Common and Style Supervised Contrastive Learning |
| 22 | + (SCS-SupCon). In this framework, we introduce a sigmoid-based pairwise contrastive |
| 23 | + loss with adaptive decision boundaries, explicitly parameterized by learnable temperature |
| 24 | + and bias terms. This design places greater emphasis on critical discriminative information |
| 25 | + from hard negatives, thereby alleviating the problem of negative-sample dilution |
| 26 | + while fully leveraging supervision signals in contrastive learning. Furthermore, |
| 27 | + we incorporate an explicit style-distance constraint to disentangle style and content |
| 28 | + representations, leading to more robust and discriminative feature learning. Comprehensive |
| 29 | + experiments on six benchmark datasets, including prominent fine-grained datasets |
| 30 | + such as CUB200-2011 and Stanford Dogs, consistently demonstrate that our proposed |
| 31 | + SCS-SupCon achieves superior performance over the most closely related InfoNCE-based |
| 32 | + supervised contrastive baselines (SupCon, SelfCon, CS-SupCon and its overlapping |
| 33 | + variant) across diverse CNN and Transformer backbones. In particular, on CIFAR-100 |
| 34 | + with a ResNet-50 encoder, SCS-SupCon improves the mean top-1 accuracy over SupCon |
| 35 | + by about 3.9 percentage points and over CS-SupCon by about 1.7 percentage points |
| 36 | + under a five-fold cross-validation protocol. On challenging fine-grained datasets |
| 37 | + such as CUB200-2011 and Stanford Dogs with both CNN and Transformer architectures, |
| 38 | + our method achieves absolute improvements of approximately 0.4–3.0 percentage points |
| 39 | + over CS-SupCon. Extensive ablation studies and paired statistical tests further |
| 40 | + confirm the robustness and effectiveness of our framework, and a Friedman test with |
| 41 | + Nemenyi post-hoc analysis shows that SCS-SupCon attains the best average rank among |
| 42 | + the evaluated methods, even though pairwise differences with other strong competitors |
| 43 | + are not always statistically significant at the 0.05 level. |
| 44 | +tags: |
| 45 | +- Supervised contrastive learning |
| 46 | +- Fine-grained classification |
| 47 | +- Negative sample dilution |
| 48 | +- Feature disentanglement |
| 49 | +- Decision boundary adjustment |
| 50 | +links: |
| 51 | +- name: URL |
| 52 | + url: https://www.sciencedirect.com/science/article/pii/S0957417426002216 |
| 53 | +--- |
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