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Xiang Ji

16 accepted papers

2025

Improving Vision-Language-Action Model with Online Reinforcement Learning

ICRA 2025

Recent studies have successfully integrated large vision-language models (VLMs) into low-level robotic control by supervised fine-tuning (SFT) with expert robotic datasets, resulting in what we term vision-language-action (VLA) models. Although the VLA models are powerful, how to improve these large

Cited by 78SourceScholar
2025

MATH-Perturb: Benchmarking LLMs' Math Reasoning Abilities against Hard Perturbations

ICML 2025poster

Large language models have demonstrated impressive performance on challenging mathematical reasoning tasks, which has triggered the discussion of whether the performance is achieved by true reasoning capability or memorization. To investigate this question, prior work has constructed mathematical be…

2025

Tree-NeRV: Efficient Non-Uniform Sampling for Neural Video Representation via Tree-Structured Feature Grids

ICCV 2025poster

Implicit Neural Representations for Videos (NeRV) have emerged as a powerful paradigm for video representation, enabling direct mappings from frame indices to video frames. However, existing NeRV-based methods do not fully exploit temporal redundancy, as they rely on uniform sampling along the tempo…

2024

Dual Enhancement in ODI Super-Resolution: Adapting Convolution and Upsampling to Projection Distortion

IJCAI 2024poster

Omnidirectional images (ODIs) demand considerably higher resolution to ensure high quality across all viewports. Traditional convolutional neural networks (CNN)-based single-image super-resolution (SISR) networks, however, are not effective for spherical ODIs. This is due to the uneven pixel density…

Cited by 0SourcePDFScholar
2024

Policy Evaluation for Reinforcement Learning from Human Feedback: A Sample Complexity Analysis

AISTATS 2024poster

A recently popular approach to solving reinforcement learning is with data from human preferences. In fact, human preference data are now used with classic reinforcement learning algorithms such as actor-critic methods, which involve evaluating an intermediate policy over a reward learned from human…

Cited by 3SourcePDFScholar
2024

RS-NeRF: Neural Radiance Fields from Rolling Shutter Images

ECCV 2024poster

"Neural Radiance Fields (NeRFs) have become increasingly popular because of their impressive ability for novel view synthesis. However, their effectiveness is hindered by the Rolling Shutter (RS) effects commonly found in most camera systems. To solve this, we present RS-NeRF, a method designed to s…

2023

Blur Interpolation Transformer for Real-World Motion From Blur

CVPR 2023poster

This paper studies the challenging problem of recovering motion from blur, also known as joint deblurring and interpolation or blur temporal super-resolution. The challenges are twofold: 1) the current methods still leave considerable room for improvement in terms of visual quality even on the synth…

2023

Rethinking Video Frame Interpolation from Shutter Mode Induced Degradation

ICCV 2023poster

Image restoration from various motion-related degradations, like blurry effects recorded by a global shutter (GS) and jello effects caused by a rolling shutter (RS), has been extensively studied. It has been recently recognized that such degradations encode temporal information, which can be exploit…

Cited by 8PDFScholar
2023

Sample Complexity of Nonparametric Off-Policy Evaluation on Low-Dimensional Manifolds using Deep Networks

ICLR 2023poster

We consider the off-policy evaluation problem of reinforcement learning using deep convolutional neural networks. We analyze the deep fitted Q-evaluation method for estimating the expected cumulative reward of a target policy, when the data are generated from an unknown behavior policy. We show that…

Cited by 21SourcePDFScholar
2022

Neural Global Shutter: Learn To Restore Video From a Rolling Shutter Camera With Global Reset Feature

CVPR 2022poster

Most computer vision systems assume distortion-free images as inputs. The widely used rolling-shutter (RS) image sensors, however, suffer from geometric distortion when the camera and object undergo motion during capture. Extensive researches have been conducted on correcting RS distortions. However…

Cited by 15PDFcodeScholar
2022

Optimal Estimation of Policy Gradient via Double Fitted Iteration

ICML 2022spotlight

Policy gradient (PG) estimation becomes a challenge when we are not allowed to sample with the target policy but only have access to a dataset generated by some unknown behavior policy. Conventional methods for off-policy PG estimation often suffer from either significant bias or exponentially large…

Cited by 4SourcePDFScholar
2021

Are Missing Links Predictable? An Inferential Benchmark for Knowledge Graph Completion

ACL 2021long

We present InferWiki, a Knowledge Graph Completion (KGC) dataset that improves upon existing benchmarks in inferential ability, assumptions, and patterns. First, each testing sample is predictable with supportive data in the training set. To ensure it, we propose to utilize rule-guided train/test ge…

2021

Bootstrapping Fitted Q-Evaluation for Off-Policy Inference

ICML 2021spotlight

Bootstrapping provides a flexible and effective approach for assessing the quality of batch reinforcement learning, yet its theoretical properties are poorly understood. In this paper, we study the use of bootstrapping in off-policy evaluation (OPE), and in particular, we focus on the fitted Q-evalu…

Cited by 52SourcePDFScholar