Low-Rank Adaptation (LoRA) is a widely adopted approach for parameter-efficient fine-tuning of large language models, enabling effective adaptation with a small number of trainable parameters. However, its reliance on linear low-rank projections restricts adaptation to linear subspaces, which can limit flexibility on complex downstream tasks. To address this, we propose RanLoRA, a Residual-aware nonlinear Low-Rank Adaptation approach that leverages the decomposition structure of pretrained weights. We used Singular Value Decomposition (SVD) to decompose pretrained weights into principal components that are kept frozen and residual components that are used for task-specific adaptation. To enhance the expressiveness of linear low-rank updates, RanLoRA incorporates a nonlinear activation layer together with a Hadamard-product-based vector modulation. This design supports an implicit progressive adaptation behavior, where optimization evolves from coarse approximation of dominant components toward residual alignment and fine-grained nonlinear refinement. Experiments on benchmarks covering commonsense reasoning, natural language understanding, image classification, and mathematical reasoning show that RanLoRA consistently outperforms vanilla LoRA and representative variants under comparable parameter budgets. These results suggest that incorporating structured nonlinearity into adapter design can enhance representational flexibility and generalization across tasks in large models.

Joint entity and relation extraction tasks aim to recognize named entities and extract relations simultaneously. Suffering from a variety of data biases, such as data selection bias, and distribution bias (out of distribution, long-tail distribution), serious concerns can be witnessed to threaten the model’s transferability, robustness, and generalization. In this work, we address the above problems from a causality perspective. We propose a novel causal framework called c ̲ovariance and  ̲variance  ̲optimization framework (OVO) to optimize feature representations and conduct general debiasing. In particular, the proposed  ̲covariance  ̲optimizing (COP) minimizes characterizing features’ covariance for alleviating the selection and distribution bias and enhances feature representation in the feature space. Furthermore, based on the causal backdoor adjustment, we propose \\underlinevariance  ̲optimizing (VOP) separates samples in terms of label information and minimizes the variance of each dimension in the feature vectors of the same class label for mitigating the distribution bias further. By applying it to three strong baselines in two widely used datasets, the results demonstrate the effectiveness and generalization of OVO for joint entity and relation extraction tasks. Furthermore, a fine-grained analysis reveals that OVO possesses the capability to mitigate the impact of long-tail distribution.

Few-shot named entity recognition (NER) systems aim to recognize new classes of entities with limited labeled samples. However, these systems face a significant challenge of overfitting compared to tasks with abundant samples. This overfitting is mainly caused by the spurious correlation resulting from the bias in selecting a few samples. To address this issue, we propose a causal intervention-based few-shot NER method in this paper. Our method, based on the prototypical network, intervenes in the context to block the backdoor path between context and label. In the one-shot scenario, where no additional context is available for intervention, we employ incremental learning to intervene on the prototype, which also helps mitigate catastrophic forgetting. Our experiments on various benchmarks demonstrate that our approach achieves new state-of-the-art results.