U-CORE: A Unified Deep Cluster-wise Contrastive Framework for Open Relation Extraction Jie Zhou author Shenpo Dong author Yunxin Huang author Meihan Wu author Haili Li author Jingnan Wang author Hongkui Tu author Xiaodong Wang author 2023 text journal article Transactions of the Association for Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal zhou-etal-2023-u 10.1162/tacl_a_00604 https://aclanthology.org/2023.tacl-1.74/ 2023 11 1301 1315