社会建议利用社会关系来增强建议的代表性学习。大多数社会推荐模型都将用户互动（协作领域）和社会关系（社会领域）的用户表示统一。但是，这种方法可能无法模拟用户在两个域中的异质行为模式，从而损害了用户表示的表现力。在这项工作中，为了解决这种局限性，我们为社会建议提出了一个新颖的截面对比度学习框架DCREC。更具体地说，我们建议从项目和社会域中学习分开的用户表示。此外，分离的对比度学习旨在在分散的用户表示之间进行社交建议之间的知识转移。各种现实世界数据集的全面实验证明了我们提出的模型的优势。

最近的研究表明，基于神经网络的深度推荐系统容易受到对抗性攻击的影响，攻击者可以将精心制作的虚假用户配置文件（即，伪造用户与之互动的一组项目）注入目标推荐系统，以实现恶意目的，例如促进或降低一组目标项目。由于安全性和隐私问题，在黑框设置下执行对抗性攻击更为实用，在黑框设置下，攻击者无法轻松访问目标系统的体系结构/参数和培训数据。但是，在Black-Box设置下生成高质量的假用户配置文件，对于目标系统的资源有限，这是一项挑战。为了应对这一挑战，在这项工作中，我们通过利用项目的属性信息（即项目知识图）引入了一种新颖的策略，这些信息可以公开访问并提供丰富的辅助知识来增强伪造用户配置文件的产生。更具体地说，我们提出了一项知识增强的黑框攻击框架（KGATTACK），以通过深度强化学习技术有效地学习攻击政策，其中知识图无缝集成到层次结构策略网络中，以生成伪造的用户配置文件，以表演对抗性黑色 - 黑色 - - 黑色 - 黑色 - 盒子攻击。在各种现实世界数据集上进行的全面实验证明了在黑框设置下提出的攻击框架的有效性。

Deep learning methods have contributed substantially to the rapid advancement of medical image segmentation, the quality of which relies on the suitable design of loss functions. Popular loss functions, including the cross-entropy and dice losses, often fall short of boundary detection, thereby limiting high-resolution downstream applications such as automated diagnoses and procedures. We developed a novel loss function that is tailored to reflect the boundary information to enhance the boundary detection. As the contrast between segmentation and background regions along the classification boundary naturally induces heterogeneity over the pixels, we propose the piece-wise two-sample t-test augmented (PTA) loss that is infused with the statistical test for such heterogeneity. We demonstrate the improved boundary detection power of the PTA loss compared to benchmark losses without a t-test component.

尽管最近在开发动画全身化身方面取得了进展，但服装的现实建模（人类自我表达的核心方面之一）仍然是一个开放的挑战。最先进的物理模拟方法可以以交互速度产生现实行为的服装几何形状。但是，建模光真逼真的外观通常需要基于物理的渲染，这对于交互式应用来说太昂贵了。另一方面，数据驱动的深度外观模型能够有效地产生逼真的外观，但在合成高度动态服装的几何形状和处理具有挑战性的身体套构型方面挣扎。为此，我们通过对服装的明确建模介绍了姿势驱动的化身，这些化身表现出逼真的服装动力学和从现实世界数据中学到的逼真的外观。关键的想法是引入一个在显式几何形状之上运行的神经服装外观模型：在火车时，我们使用高保真跟踪，而在动画时期，我们依靠物理模拟的几何形状。我们的关键贡献是一个具有物理启发的外观网络，能够生成具有视图依赖性和动态阴影效果的影像逼真的外观，即使对于看不见的身体透明构型也是如此。我们对我们的模型进行了彻底的评估，并在几种受试者和不同类型的衣服上展示了不同的动画结果。与以前关于影迷全身化身的工作不同，我们的方法甚至可以为宽松的衣服产生更丰富的动力和更现实的变形。我们还证明，我们的配方自然允许服装与不同人的头像一起使用，同时保持完全动画，因此首次可以采用新颖的衣服来实现逼真的化身。

Deep learning models can achieve high accuracy when trained on large amounts of labeled data. However, real-world scenarios often involve several challenges: Training data may become available in installments, may originate from multiple different domains, and may not contain labels for training. Certain settings, for instance medical applications, often involve further restrictions that prohibit retention of previously seen data due to privacy regulations. In this work, to address such challenges, we study unsupervised segmentation in continual learning scenarios that involve domain shift. To that end, we introduce GarDA (Generative Appearance Replay for continual Domain Adaptation), a generative-replay based approach that can adapt a segmentation model sequentially to new domains with unlabeled data. In contrast to single-step unsupervised domain adaptation (UDA), continual adaptation to a sequence of domains enables leveraging and consolidation of information from multiple domains. Unlike previous approaches in incremental UDA, our method does not require access to previously seen data, making it applicable in many practical scenarios. We evaluate GarDA on two datasets with different organs and modalities, where it substantially outperforms existing techniques.

The development of social media user stance detection and bot detection methods rely heavily on large-scale and high-quality benchmarks. However, in addition to low annotation quality, existing benchmarks generally have incomplete user relationships, suppressing graph-based account detection research. To address these issues, we propose a Multi-Relational Graph-Based Twitter Account Detection Benchmark (MGTAB), the first standardized graph-based benchmark for account detection. To our knowledge, MGTAB was built based on the largest original data in the field, with over 1.55 million users and 130 million tweets. MGTAB contains 10,199 expert-annotated users and 7 types of relationships, ensuring high-quality annotation and diversified relations. In MGTAB, we extracted the 20 user property features with the greatest information gain and user tweet features as the user features. In addition, we performed a thorough evaluation of MGTAB and other public datasets. Our experiments found that graph-based approaches are generally more effective than feature-based approaches and perform better when introducing multiple relations. By analyzing experiment results, we identify effective approaches for account detection and provide potential future research directions in this field. Our benchmark and standardized evaluation procedures are freely available at: https://github.com/GraphDetec/MGTAB.

As one of the prevalent methods to achieve automation systems, Imitation Learning (IL) presents a promising performance in a wide range of domains. However, despite the considerable improvement in policy performance, the corresponding research on the explainability of IL models is still limited. Inspired by the recent approaches in explainable artificial intelligence methods, we proposed a model-agnostic explaining framework for IL models called R2RISE. R2RISE aims to explain the overall policy performance with respect to the frames in demonstrations. It iteratively retrains the black-box IL model from the randomized masked demonstrations and uses the conventional evaluation outcome environment returns as the coefficient to build an importance map. We also conducted experiments to investigate three major questions concerning frames' importance equality, the effectiveness of the importance map, and connections between importance maps from different IL models. The result shows that R2RISE successfully distinguishes important frames from the demonstrations.

Compressed videos often exhibit visually annoying artifacts, known as Perceivable Encoding Artifacts (PEAs), which dramatically degrade video visual quality. Subjective and objective measures capable of identifying and quantifying various types of PEAs are critical in improving visual quality. In this paper, we investigate the influence of four spatial PEAs (i.e. blurring, blocking, bleeding, and ringing) and two temporal PEAs (i.e. flickering and floating) on video quality. For spatial artifacts, we propose a visual saliency model with a low computational cost and higher consistency with human visual perception. In terms of temporal artifacts, self-attention based TimeSFormer is improved to detect temporal artifacts. Based on the six types of PEAs, a quality metric called Saliency-Aware Spatio-Temporal Artifacts Measurement (SSTAM) is proposed. Experimental results demonstrate that the proposed method outperforms state-of-the-art metrics. We believe that SSTAM will be beneficial for optimizing video coding techniques.

We propose a distributionally robust return-risk model for Markov decision processes (MDPs) under risk and reward ambiguity. The proposed model optimizes the weighted average of mean and percentile performances, and it covers the distributionally robust MDPs and the distributionally robust chance-constrained MDPs (both under reward ambiguity) as special cases. By considering that the unknown reward distribution lies in a Wasserstein ambiguity set, we derive the tractable reformulation for our model. In particular, we show that that the return-risk model can also account for risk from uncertain transition kernel when one only seeks deterministic policies, and that a distributionally robust MDP under the percentile criterion can be reformulated as its nominal counterpart at an adjusted risk level. A scalable first-order algorithm is designed to solve large-scale problems, and we demonstrate the advantages of our proposed model and algorithm through numerical experiments.

Witnessing the impressive achievements of pre-training techniques on large-scale data in the field of computer vision and natural language processing, we wonder whether this idea could be adapted in a grab-and-go spirit, and mitigate the sample inefficiency problem for visuomotor driving. Given the highly dynamic and variant nature of the input, the visuomotor driving task inherently lacks view and translation invariance, and the visual input contains massive irrelevant information for decision making, resulting in predominant pre-training approaches from general vision less suitable for the autonomous driving task. To this end, we propose PPGeo (Policy Pre-training via Geometric modeling), an intuitive and straightforward fully self-supervised framework curated for the policy pretraining in visuomotor driving. We aim at learning policy representations as a powerful abstraction by modeling 3D geometric scenes on large-scale unlabeled and uncalibrated YouTube driving videos. The proposed PPGeo is performed in two stages to support effective self-supervised training. In the first stage, the geometric modeling framework generates pose and depth predictions simultaneously, with two consecutive frames as input. In the second stage, the visual encoder learns driving policy representation by predicting the future ego-motion and optimizing with the photometric error based on current visual observation only. As such, the pre-trained visual encoder is equipped with rich driving policy related representations and thereby competent for multiple visuomotor driving tasks. Extensive experiments covering a wide span of challenging scenarios have demonstrated the superiority of our proposed approach, where improvements range from 2% to even over 100% with very limited data. Code and models will be available at https://github.com/OpenDriveLab/PPGeo.