Retinal vessel segmentation is an important task in medical image analysis that can aid doctors in diagnosing various eye diseases. However, due to the complexity and blurred boundaries of retinal vessel structures, existing methods face many challenges in practical applications. To overcome these challenges, this paper proposes a retina vessel segmentation algorithm based on an attention mechanism, called CAS-UNet. Firstly, the Cross-Fusion Channel Attention mechanism is introduced, and the Structured Convolutional Attention block is used to replace the original convolutional block of U-Net to achieve channel enhancement for retinal blood vessels. Secondly, an Additive Attention Gate is added to the skip-connection layer of the network to achieve spatial enhancement for retinal blood vessels. Finally, the SoftPool pooling method is used to reduce information loss. Experimental results using the CHASEDB1 and DRIVE datasets show that the proposed algorithm achieves an accuracy of 96.68% and 95.86%, and a sensitivity of 83.21% and 83.75%, respectively. The proposed CAS-UNet thus outperforms the existing U-Net-based classic algorithms.

Image segmentation is a fundamental task in image processing and is still a challenging problem when processing images with high noise, low resolution and intensity inhomogeneity. In this paper, a weighted region-based level set method, which is based on the techniques of local statistical theory, level set theory and curve evolution, is proposed. Specifically, a new weighted pressure force function (WPF) is first presented to flexibly drive the closed contour to shrink or expand outside and inside of the object. Second, a faster and smoother regularization term is added to ensure the stability of the curve evolution and that there is no need for initialization in curve evolution. Third, the WPF is integrated into the region-based level set framework to accelerate the speed of the curve evolution and improve the accuracy of image segmentation. Experimental results on medical and natural images demonstrate that the proposed segmentation model is more efficient and robust to noise than other state-of-the-art models.

The goal of this study is to improve the quality and diversity of text paraphrase generation, a critical task in Natural Language Generation (NLG) that requires producing semantically equivalent sentences with varied structures and expressions. Existing approaches often fail to generate paraphrases that are both high-quality and diverse, limiting their applicability in tasks such as machine translation, dialogue systems, and automated content rewriting. To address this gap, we introduce two self-contrastive learning models designed to enhance paraphrase generation: the Contrastive Generative Adversarial Network (ContraGAN) for supervised learning and the Contrastive Model with Metrics (ContraMetrics) for unsupervised learning. ContraGAN leverages a learnable discriminator within an adversarial framework to refine the quality of generated paraphrases, while ContraMetrics incorporates multi-metric filtering and keyword-guided prompts to improve unsupervised generation diversity. Experiments on benchmark datasets demonstrate that both models achieve significant improvements over state-of-the-art methods. ContraGAN enhances semantic fidelity with a 0.46 gain in BERTScore and improves fluency with a 1.57 reduction in perplexity. In addition, ContraMetrics achieves gains of 0.37 and 3.34 in iBLEU and P-BLEU, respectively, reflecting greater diversity and lexical richness. These results validate the effectiveness of our models in addressing key challenges in paraphrase generation, offering practical solutions for diverse NLG applications.

In the field of image segmentation, there are still some technical problems, such as the segmentation accuracy of the image with intensity inhomogeneity is not high enough. Level set method has the advantages of solid theoretical foundation and stable algorithm for segmentation of small sample data, so far it has played a significant role in image segmentation. In this paper, with the level set method for the research framework, we present a new approach to segment noise and weak boundary images that is supported by an adaptive velocity correction function. Based on the properties analysis of noise and edge information, this correction function is replaced the original constant to largely improve the segmentation accuracy. In addition, on the basis of some theoretical analysis, we use the edge stop function constructed by entropy to effectively improve the accuracy of image segmentation. Finally, a large number of challenging image experiments show that the proposed segmentation model performs better than other classical models in segmentation accuracy.