Zhang Han


2024

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Enhancing Sequence Representation for Personalized Search
Wang Shijun | Zhang Han | Yuan Zhe
Proceedings of the 23rd Chinese National Conference on Computational Linguistics (Volume 1: Main Conference)

“The critical process of personalized search is to reorder candidate documents of the current querybased on the user’s historical behavior sequence. There are many types of information containedin user historical information sequence, such as queries, documents, and clicks. Most existingpersonalized search approaches concatenate these types of information to get an overall userrepresentation, but they ignore the associations among them. We believe the associations ofdifferent information mentioned above are significant to personalized search. Based on a hierar-chical transformer as base architecture, we design three auxiliary tasks to capture the associationsof different information in user behavior sequence. Under the guidance of mutual information,we adjust the training loss, enabling our PSMIM model to better enhance the information rep-resentation in personalized search. Experimental results demonstrate that our proposed methodoutperforms some personalized search methods.”

2023

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Case Retrieval for Legal Judgment Prediction in Legal Artificial Intelligence
Zhang Han | Dou Zhicheng
Proceedings of the 22nd Chinese National Conference on Computational Linguistics

“Legal judgment prediction (LJP) is a basic task in legal artificial intelligence. It consists ofthree subtasks, which are relevant law article prediction, charge prediction and term of penaltyprediction, and gives the judgment results to assist the work of judges. In recent years, many deeplearning methods have emerged to improve the performance of the legal judgment prediction task. The previous methods mainly improve the performance by integrating law articles and the factdescription of a legal case. However, they rarely consider that the judges usually look up historicalcases before making a judgment in the actual scenario. To simulate this scenario, we propose ahistorical case retrieval framework for the legal judgment prediction task. Specifically, we selectsome historical cases which include all categories from the training dataset. Then, we retrieve themost similar Top-k historical cases of the current legal case and use the vector representation ofthese Top-k historical cases to help predict the judgment results. On two real-world legal datasets,our model achieves better results than several state-of-the-art baseline models.”

2021

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Few-Shot Charge Prediction with Multi-Grained Features and MutualInformation
Zhang Han | Zhu Yutao | Dou Zhicheng | Wen Ji-Rong
Proceedings of the 20th Chinese National Conference on Computational Linguistics

Charge prediction aims to predict the final charge for a case according to its fact descriptionand plays an important role in legal assistance systems. With deep learning based methods prediction on high-frequency charges has achieved promising results but that on few-shot chargesis still challenging. In this work we propose a framework with multi-grained features and mutual information for few-shot charge prediction. Specifically we extract coarse- and fine-grained features to enhance the model’s capability on representation based on which the few-shot chargescan be better distinguished. Furthermore we propose a loss function based on mutual information. This loss function leverages the prior distribution of the charges to tune their weights so the few-shot charges can contribute more on model optimization. Experimental results on several datasets demonstrate the effectiveness and robustness of our method. Besides our method can work wellon tiny datasets and has better efficiency in the training which provides better applicability in realscenarios.