Recommender system (RS) aims to capture personalized preferences from massive user behaviors, making them pivotal in the era of information explosion. However, the presence of “information cocoons,” interaction sparsity, cold-start problem, and feedback loops inherent in RS make users interact with a limited number of items. Conventional recommendation algorithms typically focus on the positive historical behaviors, while neglecting the essential role of negative feedback in user preference understanding. As a promising but easy-to-ignored area, negative sampling is proficient in revealing the genuine negative aspect inherent in user behaviors, emerging as an inescapable procedure in RS. In this survey, we first discuss existing user feedback, the critical role of negative sampling and the optimization objectives in RS, and thoroughly analyze challenges that consistently impede its progress. Then, we conduct an extensive literature review on the existing negative sampling strategies in RS and classify them into five categories with their discrepant techniques. Finally, we detail the insights of the tailored negative sampling strategies in diverse RS scenarios and outline an overview of the prospective research directions toward which the community may engage and benefit.

Personalized outfit generation aims to construct a set of compatible and personalized fashion items as an outfit. Recently, generative AI models have received widespread attention, as they can generate fashion items for users to complete an incomplete outfit or create a complete outfit. However, they have limitations in terms of lacking diversity and relying on the supervised learning paradigm. Recognizing this gap, we propose a novel framework FashionDPO, which fine-tunes the fashion outfit generation model using direct preference optimization. This framework aims to provide a general fine-tuning approach to fashion generative models, refining a pre-trained fashion outfit generation model using automatically generated feedback, without the need to design a task-specific reward function. To make sure that the feedback is comprehensive and objective, we design a multi-expert feedback generation module which covers three evaluation perspectives, i.e., quality, compatibility and personalization. Experiments on two established datasets, i.e., iFashion and Polyvore-U, demonstrate the effectiveness of our framework in enhancing the model's ability to align with users' personalized preferences while adhering to fashion compatibility principles. Our code and model checkpoints are available at https://github.com/Yzcreator/FashionDPO.

The development of virtual try-on has revolutionized online shopping by allowing customers to visualize themselves in various fashion items, thus extending the in-store try-on experience to the cyber space. Although virtual try-on has attracted considerable research initiatives, existing systems only focus on the quality of image generation, overlooking whether the fashion item is a good match to the given person and clothes. Recognizing this gap, we propose to design a one-stop Smart Fitting Room, with the novel formulation of matching-aware virtual try-on. Following this formulation, we design a Hybrid Matching-aware Virtual Try-On Framework (HMaVTON), which combines retrieval-based and generative methods to foster a more personalized virtual try-on experience. This framework integrates a hybrid mix-and-match module and an enhanced virtual try-on module. The former can recommend fashion items available on the platform to boost sales and generate clothes that meets the diverse tastes of consumers. The latter provides high-quality try-on effects, delivering a one-stop shopping service. To validate the effectiveness of our approach, we enlist the expertise of fashion designers for a professional evaluation, assessing the rationality and diversity of the clothes combinations and conducting an evaluation matrix analysis. Our method significantly enhances the practicality of virtual try-on. The code is available at https://github.com/Yzcreator/HMaVTON.

Cross-domain recommendation (CDR) aims at leveraging the correlation of users’ behaviors in both the source and target domains to improve the user preference modeling in the target domain. Conventional CDR methods typically explore the dual-relations between the source and target domains’ behaviors. However, this may ignore the informative mixed behaviors that naturally reflect the user’s global preference. To address this issue, we present a novel framework, termed triple sequence learning for cross-domain recommendation (Tri-CDR), which jointly models the source, target, and mixed behavior sequences to highlight the global and target preference and precisely model the triple correlation in CDR. Specifically, Tri-CDR independently models the hidden representations for the triple behavior sequences and proposes a triple cross-domain attention (TCA) method to emphasize the informative knowledge related to both user’s global and target-domain preference. To comprehensively explore the cross-domain correlations, we design a triple contrastive learning (TCL) strategy that simultaneously considers the coarse-grained similarities and fine-grained distinctions among the triple sequences, ensuring the alignment while preserving information diversity in multi-domain. We conduct extensive experiments and analyses on six cross-domain settings. The significant improvements of Tri-CDR with different sequential encoders verify its effectiveness and universality. The source code is available at https://github.com/hulkima/Tri-CDR .

Deep learning has been proven to be effective in image classification tasks. However, existing methods may face difficulties in distinguishing complex images due to the distraction caused by diverse image content. To overcome this challenge, we propose a class-aware convolution and attentive aggregation (CA-Net) framework that improves the effectiveness of representation learning and reduces the influence of irrelevant background. CA-Net includes three main modules: the discrete representation learning (DRL) module that uses a group learning method to learn discriminative representations, the class-aware score of discrete representation (CSDR) module that infers class-aware scores to generate weights for representation learners, and the class-aware representation fusion module(CRF) that aggregates class-aware representations using the class-aware scores as a guide. Our experimental results on three benchmarking datasets show that CA-Net improves the performance of state-of-the-art backbones and enhances feature extraction robustness.

Negative Sampling in recommendation aims to capture informative negative instances for the sparse user-item interactions to improve the performance. Conventional negative sampling methods tend to select informative hard negative samples (HNS) besides the default random samples. However, these hard negative sampling methods usually struggle with false hard negative samples (FHNS), which happens when a user-item interaction has not been observed yet and is picked as a negative sample, while the user will actually interact with this item once exposed to it. Such FHNS issues may seriously confuse the model training, while most conventional hard negative sampling methods do not systematically explore and distinguish FHNS from HNS. To address this issue, we propose a novel model-agnostic Real Hard Negative Sampling (RealHNS) framework specially for cross-domain recommendation (CDR), which aims to discover the false and refine the real from all HNS via both general and cross-domain real hard negative sample selectors. For the general part, we conduct the coarse- and fine-grained real HNS selectors sequentially, armed with a dynamic item-based FHNS filter to find high-quality HNS. For the cross-domain part, we further design a new cross-domain HNS for alleviating negative transfer in CDR and discover its corresponding FHNS via a dynamic user-based FHNS filter to keep its power. We conduct experiments on four datasets based on three representative hard negative sampling methods, along with extensive model analyses, ablation studies, and universality analyses. The consistent improvements indicate the effectiveness, robustness, and universality of RealHNS, which is also easy-to-deploy in real-world systems as a plug-and-play strategy. The source code is avaliable in https://github.com/hulkima/RealHNS.

In this paper, we focus on generating photo-realistic images from given text descriptions. Current methods first generate an initial image and then progressively refine it to a high-resolution one. These methods typically indiscriminately refine all granularity features output from the previous stage. However, the ability to express different granularity features in each stage is not consistent, and it is difficult to express precise semantics by further refining the features with poor quality generated in the previous stage. Current methods cannot refine different granularity features independently, resulting in that it is challenging to clearly express all factors of semantics in generated image, and some features even become worse. To address this issue, we propose a Hierarchical Disentangled Representations Generative Adversarial Networks (HDR-GAN) to generate photo-realistic images by explicitly disentangling and individually modeling the factors of semantics in the image. HDR-GAN introduces a novel component called multi-granularity feature disentangled encoder to represent image information comprehensively through explicitly disentangling multi-granularity features including pose, shape and texture. Moreover, we develop a novel Multi-granularity Feature Refinement (MFR) containing a Coarse-grained Feature Refinement (CFR) model and a Fine-grained Feature Refinement (FFR) model. CFR utilizes coarse-grained disentangled representations (e.g., pose and shape) to clarify category information, while FFR employs fine-grained disentangled representations (e.g., texture) to reflect instance-level details. Extensive experiments on two well-studied and publicly available datasets (i.e., CUB-200 and CLEVR-SV) demonstrate the rationality and superiority of our method.

Haze classification has gained much attention recently as a cost-effective solution for air quality monitoring. Different from conventional image classification tasks, it requires the classifier to capture the haze patterns of different severity degrees. Existing efforts typically focus on the extraction of effective haze features, such as the dark channel and deep features. However, it is observed that the light-haze images are often mis-classified due to the presence of diverse background scenes. To address this issue, this paper presents an unsupervised contrastive masking (UCM) algorithm to segment the haze regions without any supervision, and develops a dual-channel model-agnostic framework, termed magnifier neural network (MagNet), to effectively use the segmented haze regions to enhance the learning of haze features by conventional deep learning models. Specifically, MagNet employs the haze regions to provide the pixel- and feature-level visual information via three strategies, including Input Augmentation, Network Constraint, and Feature Enhancement, which work as a soft-attention regularizer to alleviates the trade-off between capturing the global scene information and the local information in the haze regions. Experiments were conducted on two datasets in terms of performance comparison, parameter estimation, ablation studies, and case studies, and the results verified that UCM can accurately and rapidly segment the haze regions, and the proposed three strategies of MagNet consistently improve the performance of the state-of-the-art deep learning backbones.

The automatic generation of Chinese fonts is challenging due to the large quantity and complex structure of Chinese characters. When there are insufficient reference samples for the target font, existing deep learning-based methods cannot avoid overfitting caused by too few samples, resulting in blurred glyphs and incomplete strokes. To address these problems, this paper proposes a novel deep meta-learning-based font generation method (MLFont) for few-shot Chinese font generation, which leverages existing fonts to improve the generalization capability of the model for new fonts. Existing deep meta-learning methods mainly focus on few-shot image classification. To apply meta-learning to font generation, we present a meta-training strategy based on Model-Agnostic Meta-Learning (MAML) and a task organization method for font generation. The meta-training makes the font generator easy to fine-tune for new font generation tasks. Through random font generation tasks and extraction of glyph content and style separately, the font generator learns the prior knowledge of character structure in the meta-training stage, and then quickly adapts to the generation of new fonts with a few samples by fine-tuning of adversarial training. Extensive experiments demonstrate that our method outperforms the state-of-the-art methods with more complete strokes and less noise in the generated character images.

Weak supervisory information of web images, such as captions, tags, and descriptions, make it possible to better understand images at the semantic level. In this paper, we propose a novel online multimodal co-indexing algorithm based on Adaptive Resonance Theory, named OMC-ART, for the automatic co-indexing and retrieval of images using their multimodal information. Compared with existing studies, OMC-ART has several distinct characteristics. First, OMC-ART is able to perform online learning of sequential data. Second, OMC-ART builds a two-layer indexing structure, in which the first layer co-indexes the images by the key visual and textual features based on the generalized distributions of clusters they belong to; while in the second layer, images are co-indexed by their own feature distributions. Third, OMC-ART enables flexible multimodal search by using either visual features, keywords, or a combination of both. Fourth, OMC-ART employs a ranking algorithm that does not need to go through the whole indexing system when only a limited number of images need to be retrieved. Experiments on two published data sets demonstrate the efficiency and effectiveness of our proposed approach.

Discovering social communities of web users through clustering analysis of heterogeneous link associations has drawn much attention. However, existing approaches typically require the number of clusters a prior, do not address the weighting problem for fusing heterogeneous types of links and have a heavy computational cost. In this paper, we explore the feasibility of a newly proposed heterogeneous data clustering algorithm, called Generalized Heterogeneous Fusion Adaptive Resonance Theory (GHF-ART), for discovering user communities in social networks. Different from existing algorithms, GHF-ART performs real-time matching of patterns and one-pass learning which guarantee its low computational cost. With a vigilance parameter to restrain the intra-cluster similarity, GHF-ART does not need the number of clusters a prior. To achieve a better fusion of multiple types of links, GHF-ART employs a weighting function to incrementally assess the importance of all the feature channels. Extensive experiments have been conducted to analyze the performance of GHF-ART on two heterogeneous social network data sets. The promising results comparing with existing methods demonstrate the effectiveness and efficiency of GHF-ART.

Co-clustering is a commonly used technique for tapping the rich meta-information of multimedia web documents, including category, annotation, and description, for associative discovery. However, most co-clustering methods proposed for heterogeneous data do not consider the representation problem of short and noisy text and their performance is limited by the empirical weighting of the multi-modal features. In this paper, we propose a generalized form of Heterogeneous Fusion Adaptive Resonance Theory, called GHF-ART, for co-clustering of large-scale web multimedia documents. By extending the two-channel Heterogeneous Fusion ART (HF-ART) to multiple channels, GHF-ART is designed to handle multimedia data with an arbitrarily rich level of meta-information. For handling short and noisy text, GHF-ART does not learn directly from the textual features. Instead, it identifies key tags by learning the probabilistic distribution of tag occurrences. More importantly, GHF-ART incorporates an adaptive method for effective fusion of multi-modal features, which weights the features of multiple data sources by incrementally measuring the importance of feature modalities through the intra-cluster scatters. Extensive experiments on two web image data sets and one text document set have shown that GHF-ART achieves significantly better clustering performance and is much faster than many existing state-of-the-art algorithms.