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Si Chen

23 accepted papers

2026

Adaptive Testing for LLM Evaluation: A Psychometric Alternative to Static Benchmarks

ICML 2026spotlight

Evaluating large language models (LLMs) typically requires thousands of benchmark items, making the process expensive, slow, and increasingly impractical at scale. Existing evaluation protocols rely on average accuracy over fixed item sets, treating all items as equally informative despite substanti…

Cited by 0SourceScholar
2026

Adversarial Attacks Already Tell the Answer: Directional Bias-Guided Test-time Defense for Vision-Language Models

ICLR 2026poster

Vision-Language Models (VLMs), such as CLIP, have shown strong zero-shot generalization but remain highly vulnerable to adversarial perturbations, posing serious risks in real-world applications. Test-time defenses for VLMs have recently emerged as a promising and efficient approach to defend agains…

Cited by 0SourceScholar
2026

Fair Facial Attribute Recognition via Group-Decoupled Vision Transformer with Mask-Guided Correlation Suppression

AAAI 2026technical

Facial Attribute Recognition (FAR) holds significant potential for wide-ranging applications. However, traditionally trained FAR models exhibit unfairness, largely due to data bias—where certain sensitive attributes correlate statistically with target attributes. To address this, we propose a group-

Cited by 0SourcePDFScholar
2026

Graph Label Denoising via Neighborhood Agreement–Guided Expectation Maximization

IJCAI 2026

Graph Neural Networks are susceptible to label noise, in which message-passing mechanisms serve as conduits for propagating erroneous supervision. Current mitigation techniques typically recover clean labels via heuristics that lack theoretical grounding, which often leads to ineffective denoising.

Cited by 0Scholar
2026

PAMDP: Interact to Persona Alignment via a Partially Observable Markov Decision Process

ICLR 2026poster

The interaction process of comprehending user-specific nuances and adapting to their preferences represents a pivotal consideration for Persona Large Language Models, as it more authentically mirrors genuine dialogue dynamics than adherence to general human value alignment. In this paper, we concept…

Cited by 0SourceScholar
2025

BeyondMix: Leveraging Structural Priors and Long-Range Dependencies for Domain-Invariant LiDAR Segmentation

NeurIPS 2025poster

Domain adaptation for LiDAR semantic segmentation remains challenging due to the complex structural properties of point cloud data. While mix-based paradigms have shown promise, they often fail to fully leverage the rich structural priors inherent in 3D LiDAR point clouds. In this paper, we identify…

Cited by 0SourceScholar
2025

Exploring the Better Multimodal Synergy Strategy for Vision-Language Models

AAAI 2025technical

Vision-Language models (VLMs) have shown great potential in enhancing open-world visual concept comprehension. Recent researches focus on an optimum multimodal collaboration strategy that significantly advances CLIP-based few-shot tasks. However, existing prompt-based solutions suffer from unidirect…

Cited by 0SourcePDFScholar
2025

Just Enough Shifts: Mitigating Over-Refusal in Aligned Language Models with Targeted Representation Fine-Tuning

ICML 2025poster

Safety alignment is crucial for Large Language Models (LLMs) to resist malicious instructions but often results in over-refusals, where benign prompts are unnecessarily rejected, impairing user experience and model utility. To this end, we introduce **ACTOR** (Activation-Based Training for Over-Refu…

Cited by 0SourcePDFScholar
2025

SocialSim: Towards Socialized Simulation of Emotional Support Conversation

AAAI 2025technical

Emotional support conversation (ESC) helps reduce people's psychological stress and provide emotional value through interactive dialogues. Due to the high cost of crowdsourcing a large ESC corpus, recent attempts use large language models for dialogue augmentation. However, existing approaches large…

Cited by 0SourcePDFScholar
2024

FASTTRACK: Reliable Fact Tracing via Clustering and LLM-Powered Evidence Validation

EMNLP 2024finding

Fact tracing seeks to identify specific training examples that serve as the knowledge source for a given query. Existing approaches to fact tracing rely on assessing the similarity between each training sample and the query along a certain dimension, such as lexical similarity, gradient, or embeddin…

2024

High-Order Structure Based Middle-Feature Learning for Visible-Infrared Person Re-identification

AAAI 2024technical

Visible-infrared person re-identification (VI-ReID) aims to retrieve images of the same persons captured by visible (VIS) and infrared (IR) cameras. Existing VI-ReID methods ignore high-order structure information of features while being relatively difficult to learn a reasonable common feature spac…

2024

Learning to Rank for Active Learning via Multi-Task Bilevel Optimization

UAI 2024poster

Active learning is a promising paradigm for reducing labeling costs by strategically requesting labels to improve model performance. However, existing active learning methods often rely on expensive acquisition functions, extensive model retraining, and multiple rounds of interaction with annotators…

Cited by 1SourcePDFScholar
2022

Adversarial Unlearning of Backdoors via Implicit Hypergradient

ICLR 2022poster

We propose a minimax formulation for removing backdoors from a given poisoned model based on a small set of clean data. This formulation encompasses much of prior work on backdoor removal. We propose the Implicit Backdoor Adversarial Unlearning (I-BAU) algorithm to solve the minimax. Unlike previous…

2022

Just Fine-tune Twice: Selective Differential Privacy for Large Language Models

EMNLP 2022main

Protecting large language models from privacy leakage is becoming increasingly crucial with their wide adoption in real-world products. Yet applying *differential privacy* (DP), a canonical notion with provable privacy guarantees for machine learning models, to those models remains challenging due t…

2022

Learn-to-Decompose: Cascaded Decomposition Network for Cross-Domain Few-Shot Facial Expression Recognition

ECCV 2022poster

"Most existing compound facial expression recognition (FER) methods rely on large-scale labeled compound expression data for training. However, collecting such data is labor-intensive and time-consuming. In this paper, we address the compound FER task in the cross-domain few-shot learning (FSL) sett…

2022

SASH: Efficient secure aggregation based on SHPRG for federated learning

UAI 2022poster

To prevent private training data leakage in Federated Learning systems, we propose a novel secure aggregation scheme based on seed homomorphic pseudo-random generator (SHPRG), named SASH. SASH leverages the homomorphic property of SHPRG to simplify the masking and demasking scheme, which for each of…

Cited by 20SourcePDFScholar
2022

When Facial Expression Recognition Meets Few-Shot Learning: A Joint and Alternate Learning Framework

AAAI 2022technical

Human emotions involve basic and compound facial expressions. However, current research on facial expression recognition (FER) mainly focuses on basic expressions, and thus fails to address the diversity of human emotions in practical scenarios. Meanwhile, existing work on compound FER relies heavil…

Cited by 18SourcePDFScholar
2021

Learning Spatial-Semantic Relationship for Facial Attribute Recognition With Limited Labeled Data

CVPR 2021poster

Recent advances in deep learning have demonstrated excellent results for Facial Attribute Recognition (FAR), typically trained with large-scale labeled data. However, in many real-world FAR applications, only limited labeled data are available, leading to remarkable deterioration in performance for…

Cited by 41PDFScholar
2015

Scene Classification With Semantic Fisher Vectors

CVPR 2015poster

With the help of a convolutional neural network~(CNN) trained to recognize objects, a scene image is represented as a bag of semantics (BoS). This involves classifying image patches using the network and considering the class posterior probability vectors as locally extracted semantic descriptors. T…

Cited by 180SourcePDFScholar