In Federated Learning (FL), data communication among clients is denied. However, it is difficult to learn from the decentralized client data, which is under-sampled, especially for segmentation tasks that need to extract enough contextual semantic information. Existing FL studies always average client models to one global model in segmentation tasks while neglecting the diverse knowledge extracted by the models. To maintain and utilize the diverse knowledge, we propose a novel training paradigm called Federated Learning with Z-average and Cross-teaching (FedZaCt) to deal with segmentation tasks. From the model parameters’ aspect, the Z-average method constructs individual client models, which maintain diverse knowledge from multiple client data. From the model distillation aspect, the Cross-teaching method transfers the other client models’ knowledge to supervise the local client model. In particular, FedZaCt does not have the global model during the training process. After training, all client models are aggregated into the global model by averaging all client model parameters. The proposed methods are applied to two medical image segmentation datasets including our private aortic dataset and a public HAM10000 dataset. Experimental results demonstrate that our methods can achieve higher Intersection over Union values and Dice scores.
The development of social networks provides a broad platform for the dissemination of information and also leads to the proliferation of fake news and false information, which we collectively refer to as rumors. The spread of rumors causes unnecessary panic and loss to individuals and society. To reduce the negative impacts of rumors, an appropriate rumor control strategy is necessary. To come up with some reasonable strategies, we need to have a clearer understanding of the spread of rumors. In this paper, we analyze crowd attitudes during the spreading of rumors by setting the misinformation prevalent progress on the social network as a dynamic system. Considering that most people do not have a clear supportive or opposing attitude when exposed to rumor information, we introduce a new group, stiflers who remain neutral, based on the infectious disease model scheme. By deriving the mean-field equation describing the rumor propagation process, we judge the stability of the constructed model. Finally, we use the model to fit the real-world data related to COVID-19, and based on this, we discuss the properties of the model and propose related strategies.
Segmenting heart components in the apical four-chamber view of fetal echocardiography is of critical significance in clinical practice. However, it is difficult to recognize these components due to small-scale components and the imbalanced ventricular apex orientation. In this study, a novel segmentation framework is proposed to segment ten general fetal heart components for the first time. This framework consists of a multi-directional fine-density (MDFD) data augmentation method and a coarse-to-fine cascade network (CFCN). MDFD enhances the apex orientation diversity and balances the orientation distribution. CFCN has two stages including a coarse network and a fine network. These two stages have similar structures that consist of a feature extractor and a feature refined layer named as Element-Wise Power with Dynamic Exponent layer (EWPDE). EWPDE which is a plug-and-play module for segmentation refines the features from the feature extractor to position small components accurately. By adopting EWPDE, the influence of each pixel is adjusted and hard pixels of small components are segmented precisely. Based on the dataset, the method is proved to be effective with the high mean intersection over union (mIoU) value and low missing ratio (MR). With MDFD and EWPDE, CFCN that adopts DeepLabV3+ as the feature extractor outperforms the best segmentation results (mIoU:0.480, MR:0.035). Compared to the original performance (mIoU:0.407, MR:0.085) of DeepLabV3+, the method improves the results significantly.
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