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Chong Liu

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21 papers
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21

AAAI Conference 2026 Conference Paper

De-biased Natural Language Egocentric Task Verification via Prototypical Evidence Learning

  • Chong Liu
  • Xun Jiang
  • Fumin Shen
  • Lei Zhu
  • Jingkuan Song
  • Heng Tao Shen
  • Xing Xu

Natural Language-based Egocentric Task Verification (NLETV) aims to verify the alignment between action sequences in egocentric videos and their corresponding textual descriptions. However, existing NLETV approaches are still facing two critical challenges: (1) These methods are designed for simulating environments, ignoring the domain gap between synthetic and realistic data. (2) The matching processes are regarded as a simple binary classification problem, which undermines model reliability due to evaluation bias and uncalibrated decision settings. To address these challenges, we propose a novel method termed Prototypical Evidential Learning (PEL), which can be adapted to existing NLETV approaches and boost the model generalization and mitigate prediction bias. Our method leverages prototypes to guide cross-domain alignment and evidence collection. Specifically, PEL consists of two key components: (1) Prototypical Domain Adaptation module enabling cross-domain feature alignment and intra-domain prototype preservation between synthetic and realistic domains; (2) Matching Evidence Collector module, which quantifies prediction uncertainty on the prototypical representations through evidential deep learning. It enforces the model to collect the vision-text consistency and discrepancy evidence, thus addressing the issues of biased decisions in binary classification. Extensive experiments on two public datasets demonstrate that our PEL method outperforms existing state-of-the-art NLETV methods and shows remarkable generalizability.

AAAI Conference 2026 Conference Paper

Quantum Non-Linear Bandit Optimization

  • Zakaria Shams Siam
  • Chaowen Guan
  • Chong Liu

We study non-linear bandit optimization where the learner maximizes a black-box function with zeroth order function oracle, which has been successfully applied in many critical applications such as drug discovery and materials design. Existing works have showed that with the aid of quantum computing, it is possible to break the classical Ω(√T) regret lower bound and achieve the new O(poly log T) upper bound. However, they usually assume that the objective function sits within the reproducing kernel Hilbert space and their algorithms suffer from the curse of dimensionality. In this paper, we propose the new Q-NLB-UCB algorithm which enjoys an input dimension-free O(poly log T) upper bound, making it applicable for high-dimensional tasks. At the heart of our algorithm design are quantum Monte Carlo mean estimator, parametric function approximation technique, and a new quantum non-linear regression oracle, which can be of independent interests in more quantum machine learning problems. Our algorithm is also validated for its efficiency compared with other quantum algorithms on both high-dimensional synthetic and real-world tasks.

UAI Conference 2025 Conference Paper

Bayesian Optimization with Inexact Acquisition: Is Random Grid Search Sufficient?

  • Hwanwoo Kim
  • Chong Liu
  • Yuxin Chen

Bayesian optimization (BO) is a widely used iterative algorithm for optimizing black-box functions. Each iteration requires maximizing an acquisition function, such as the upper confidence bound (UCB) or a sample path from the Gaussian process (GP) posterior, as in Thompson sampling (TS). However, finding an exact solution to these maximization problems is often intractable and computationally expensive. Reflecting such realistic situations, in this paper, we delve into the effect of inexact maximizers of the acquisition functions. Defining a measure of inaccuracy in acquisition solutions, we establish cumulative regret bounds for both GP-UCB and GP-TS without requiring exact solutions of acquisition function maximization. Our results show that under appropriate conditions on accumulated inaccuracy, inexact BO algorithms can still achieve sublinear cumulative regret. Motivated from such findings, we provide both theoretical justification and numerical validation for random grid search as an effective and computationally efficient acquisition function solver.

AAAI Conference 2025 Conference Paper

Black-Box Optimization with Implicit Constraints for Public Policy

  • Wenqian Xing
  • JungHo Lee
  • Chong Liu
  • Shixiang Zhu

Black-box optimization (BBO) has become increasingly relevant for tackling complex decision-making problems, especially in public policy domains such as police redistricting. However, its broader application in public policymaking is hindered by the complexity of defining feasible regions and the high-dimensionality of decisions. This paper introduces a novel BBO framework, termed as the Conditional And Generative Black-box Optimization (CageBO). This approach leverages a conditional variational autoencoder to learn the distribution of feasible decisions, enabling a two-way mapping between the original decision space and a simplified, constraint-free latent space. The CageBO efficiently handles the implicit constraints often found in public policy applications, allowing for optimization in the latent space while evaluating objectives in the original space. We validate our method through a case study on large-scale police redistricting problems in Atlanta, Georgia. Our results reveal that our CageBO offers notable improvements in performance and efficiency compared to the baselines.

ICLR Conference 2025 Conference Paper

Rational Decision-Making Agent with Learning Internal Utility Judgment

  • Yining Ye
  • Xin Cong
  • Shizuo Tian
  • Yujia Qin
  • Chong Liu
  • Yankai Lin 0001
  • Zhiyuan Liu 0001
  • Maosong Sun 0001

With remarkable advancements, large language models (LLMs) have attracted significant efforts to develop LLM-based agents capable of executing intricate multi-step decision-making tasks. Existing approaches predominantly build upon the external performance measure to guide the decision-making process but the reliance on the external performance measure as prior is problematic in real-world scenarios, where such prior may be unavailable, flawed, or even erroneous. For genuine autonomous decision-making for LLM-based agents, it is imperative to develop rationality from their posterior experiences to judge the utility of each decision independently. In this work, we propose RaDAgent (Rational Decision-Making Agent), which fosters the development of its rationality through an iterative framework involving Experience Exploration and Utility Learning. Within this framework, Elo-based Utility Learning is devised to assign Elo scores to individual decision steps to judge their utilities via pairwise comparisons. Consequently, these Elo scores guide the decision-making process to derive optimal outcomes. Experimental results on the Game of 24, WebShop, ToolBench and RestBench datasets demonstrate RaDAgent’s superiority over baselines, achieving about 7.8% improvement on average. Besides, RaDAgent also can reduce costs (ChatGPT API calls), highlighting its effectiveness and efficiency.

NeurIPS Conference 2024 Conference Paper

High Rank Path Development: an approach to learning the filtration of stochastic processes

  • Jiajie Tao
  • Hao Ni
  • Chong Liu

Since the weak convergence for stochastic processes does not account for the growth of information over time which is represented by the underlying filtration, a slightly erroneous stochastic model in weak topology may cause huge loss in multi-periods decision making problems. To address such discontinuities, Aldous introduced the extended weak convergence, which can fully characterise all essential properties, including the filtration, of stochastic processes; however, it was considered to be hard to find efficient numerical implementations. In this paper, we introduce a novel metric called High Rank PCF Distance (HRPCFD) for extended weak convergence based on the high rank path development method from rough path theory, which also defines the characteristic function for measure-valued processes. We then show that such HRPCFD admits many favourable analytic properties which allows us to design an efficient algorithm for training HRPCFD from data and construct the HRPCF-GAN by using HRPCFD as the discriminator for conditional time series generation. Our numerical experiments on both hypothesis testing and generative modelling validate the out-performance of our approach compared with several state-of-the-art methods, highlighting its potential in broad applications of synthetic time series generation and in addressing classic financial and economic challenges, such as optimal stopping or utility maximisation problems. Code is available at https: //github. com/DeepIntoStreams/High-Rank-PCF-GAN. git.

ECAI Conference 2024 Conference Paper

Sinogram-Image Dual-Domain Network for Robust Metal Artifact Reduction in CT Image

  • Chong Liu
  • Yuhan Huang
  • Bo Li
  • Hui Ding

Computed tomography (CT) utilizes X-ray technology for internal body imaging. However, the presence of metal objects often results in artifacts due to their significant absorption and scattering of X-rays, thus obstructing lesion diagnosis, especially in the presence of multiple metals. Existing artifact reduction methods often suffer from deficiencies in completeness and preservation of fine detail. To address this limitation, we propose a novel sinogram and image dual-domain network. Specifically, in the sinogram domain, two enhancement modules are designed: one for extracting information from regions affected by metal traces, and the other for learning to restore the sinogram corresponding to these metal traces. Subsequently, utilizing filtered back projection (FBP), artifact removal images are reconstructed in the image domain. Quantitative and qualitative analyses of synthetic images show our framework’s superiority over conventional Metal Artifact Reduction (MAR) methods in both synthetic and clinical settings.

AAAI Conference 2023 Conference Paper

Dialogue State Distillation Network with Inter-slot Contrastive Learning for Dialogue State Tracking

  • Jing Xu
  • Dandan Song
  • Chong Liu
  • Siu Cheung Hui
  • Fei Li
  • Qiang Ju
  • Xiaonan He
  • Jian Xie

In task-oriented dialogue systems, Dialogue State Tracking (DST) aims to extract users' intentions from the dialogue history. Currently, most existing approaches suffer from error propagation and are unable to dynamically select relevant information when utilizing previous dialogue states. Moreover, the relations between the updates of different slots provide vital clues for DST. However, the existing approaches rely only on predefined graphs to indirectly capture the relations. In this paper, we propose a Dialogue State Distillation Network (DSDN) to utilize relevant information of previous dialogue states and migrate the gap of utilization between training and testing. Thus, it can dynamically exploit previous dialogue states and avoid introducing error propagation simultaneously. Further, we propose an inter-slot contrastive learning loss to effectively capture the slot co-update relations from dialogue context. Experiments are conducted on the widely used MultiWOZ 2.0 and MultiWOZ 2.1 datasets. The experimental results show that our proposed model achieves the state-of-the-art performance for DST.

JAIR Journal 2022 Journal Article

Doubly Robust Crowdsourcing

  • Chong Liu
  • Yu-Xiang Wang

Large-scale labeled dataset is the indispensable fuel that ignites the AI revolution as we see today. Most such datasets are constructed using crowdsourcing services such as Amazon Mechanical Turk which provides noisy labels from non-experts at a fair price. The sheer size of such datasets mandates that it is only feasible to collect a few labels per data point. We formulate the problem of test-time label aggregation as a statistical estimation problem of inferring the expected voting score. By imitating workers with supervised learners and using them in a doubly robust estimation framework, we prove that the variance of estimation can be substantially reduced, even if the learner is a poor approximation. Synthetic and real-world experiments show that by combining the doubly robust approach with adaptive worker/item selection rules, we often need much lower label cost to achieve nearly the same accuracy as in the ideal world where all workers label all data points.

NeurIPS Conference 2021 Conference Paper

Higher Order Kernel Mean Embeddings to Capture Filtrations of Stochastic Processes

  • Cristopher Salvi
  • Maud Lemercier
  • Chong Liu
  • Blanka Horvath
  • Theodoros Damoulas
  • Terry Lyons

Stochastic processes are random variables with values in some space of paths. However, reducing a stochastic process to a path-valued random variable ignores its filtration, i. e. the flow of information carried by the process through time. By conditioning the process on its filtration, we introduce a family of higher order kernel mean embeddings (KMEs) that generalizes the notion of KME to capture additional information related to the filtration. We derive empirical estimators for the associated higher order maximum mean discrepancies (MMDs) and prove consistency. We then construct a filtration-sensitive kernel two-sample test able to capture information that gets missed by the standard MMD test. In addition, leveraging our higher order MMDs we construct a family of universal kernels on stochastic processes that allows to solve real-world calibration and optimal stopping problems in quantitative finance (such as the pricing of American options) via classical kernel-based regression methods. Finally, adapting existing tests for conditional independence to the case of stochastic processes, we design a causal-discovery algorithm to recover the causal graph of structural dependencies among interacting bodies solely from observations of their multidimensional trajectories.

JMLR Journal 2021 Journal Article

Revisiting Model-Agnostic Private Learning: Faster Rates and Active Learning

  • Chong Liu
  • Yuqing Zhu
  • Kamalika Chaudhuri
  • Yu-Xiang Wang

The Private Aggregation of Teacher Ensembles (PATE) framework is one of the most promising recent approaches in differentially private learning. Existing theoretical analysis shows that PATE consistently learns any VC-classes in the realizable setting, but falls short in explaining its success in more general cases where the error rate of the optimal classifier is bounded away from zero. We fill in this gap by introducing the Tsybakov Noise Condition (TNC) and establish stronger and more interpretable learning bounds. These bounds provide new insights into when PATE works and improve over existing results even in the narrower realizable setting. We also investigate the compelling idea of using active learning for saving privacy budget, and empirical studies show the effectiveness of this new idea. The novel components in the proofs include a more refined analysis of the majority voting classifier --- which could be of independent interest --- and an observation that the synthetic "student" learning problem is nearly realizable by construction under the Tsybakov noise condition. [abs] [ pdf ][ bib ] &copy JMLR 2021. ( edit, beta )

AAAI Conference 2018 Conference Paper

Dual Set Multi-Label Learning

  • Chong Liu
  • Peng Zhao
  • Sheng-Jun Huang
  • Yuan Jiang
  • Zhi-Hua Zhou

In this paper, we propose a new learning framework named dual set multi-label learning, where there are two sets of labels, and an object has one and only one positive label in each set. Compared to general multi-label learning, the exclusive relationship among labels within the same set, and the pairwise inter-set label relationship are much more explicit and more likely to be fully exploited. To handle such kind of problems, a novel boosting style algorithm with model-reuse and distribution adjusting mechanisms is proposed to make the two label sets help each other. In addition, theoretical analyses are presented to show the superiority of learning from dual label sets to learning directly from all labels. To empirically evaluate the performance of our approach, we conduct experiments on two manually collected real-world datasets along with an adapted dataset. Experimental results validate the effectiveness of our approach for dual set multi-label learning.

ICRA Conference 2014 Conference Paper

Development of a high throughput robot-aided cell injection system for human cells

  • Yu Ting Chow
  • Shuxun Chen
  • Chong Liu
  • Shuk Han Cheng
  • Ronald A. Li
  • Dong Sun 0001

Few of the current injection technologies can be applied to those human cells whose diameters are ranged about 10-25 (im only. This paper reports our most recent effort in developing a robot-aided microinjection system to solve the challenging problem of automated injection on human cells. A unique microfluidic cell holding chip is designed and fabricated to trap the single cells in the predefined docking area. Imaging processing technique is used to recognize automatically the target cells to be injected. A microrobot system equipped with a micropipette is used to perform the injection tasks on these target cells. Injection experiments on human embryonic stem cells (hESCs) (ranged about 17-25μm) are performed to demonstrate the effectiveness of the proposed microinjection system.

ICRA Conference 2009 Conference Paper

A force control based cell injection approach in a bio-robotics system

  • Yu Xie 0013
  • Dong Sun 0001
  • Chong Liu
  • Shuk Han Cheng
  • Yun H. Liu

Robotic cell injection is a technique that employs automated device to insert substances into a single living cell with a fine needle. Most existing microinjection methods are based on position control without explicit regulation of the injection force. The injection force, if not controlled properly, may destroy the cell and lead to death of the cells. In this paper, we propose a force control based cell injection technology to explicitly regulate the injection force to follow the desired force trajectory during the injection. Any desired force trajectory that is twice continuously differentiable can be realized by the proposed approach. The convergence of the force tracking algorithm is provably guaranteed. Experiments performed on a laboratorial robotic cell injection system demonstrate the effectiveness of the proposed approach.

IROS Conference 2009 Conference Paper

Penetration force measurement and control in robotic cell microinjection

  • Yu Xie 0013
  • Dong Sun 0001
  • Chong Liu

In a robotic cell injection system, the penetration force applied on the cell reflects the changes of the physical behavior of the cell. The force, if not controlled properly, may damage to the cells or even lead to death of the cells. The current cellular force measurement is limited by the inherent cantilever structure of the sensor, which may not be applicable to a practical cell injection system. In this paper, a simply supported beam structure based PVDF force sensor is first presented. The proportion relation is established between the penetration force and the sensor output after compensation. Using the designed force sensor, the force applied on the cell can be measured, and a force control based cell injection system is constructed. The experimental results performed on zebrafish embryos demonstrate the effectiveness of the micro force sensor and the force based control framework.

IROS Conference 2008 Conference Paper

An adaptive impedance force control approach for robotic cell microinjection

  • Yu Xie 0013
  • Dong Sun 0001
  • Chong Liu
  • Shuk Han Cheng

Robotic cell microinjection is a technique that employs an automatic method to insert substances into a single living cell with a fine needle. Most available microinjection methods are based on position/velocity tracking, which make it incapable of controlling the injection force. The uncontrolled injection force, however, may destroy the cell and lead to the death of the cell. In this paper, a new adaptive force tracking algorithm within the impedance control framework is proposed to control the injection force applied on the cell. A target impedance is specified in the inner-loop and a trajectory modifying controller is design in the outer-loop for time varying ramp force tracking. The adaptive technique is also used to compensate for the uncertainty of the cell membranepsilas stiffness, the convergence of the system is provably guaranteed. Experiments performed on a laboratorial robotic cell injection system demonstrate the effectiveness of the approach.

IROS Conference 2006 Conference Paper

Vision-Based Assembly of Capillary for Microfluidic Device

  • Xiaodong Wang 0021
  • Xiujun Wang
  • Yi Luo
  • Chong Liu
  • Liqun Ma

The application of plastic microfluidic chips can be extended with quartz capillaries connected at the end of their microchannels, e. g. UV absorption detection method can be carried out, which responds to almost 80% chemical compounds in detection. A vision-based experiment system for automatically assembling capillaries to plastic microfluidic chips was set up. UN-curing adhesive is used for the joining procedure. Visual feedback is implemented in the assembly system and the control algorithm is briefly introduced. The methods for obtaining the spatial position deviation between the capillary and the end of the chip's micro channel are described. The deviation information in x-y plane is obtained by performing image processing and converting pixels into actual distance with calibrated data. Two methods for recovering vertical deviation information were explored, and both are feasible for application, one is the depth-in-focus, the other is with the use of microscopic stereovision.