Zheng Zhang’s research while affiliated with Harbin Institute of Technology and other places

Self-supervised 3D occupancy prediction offers a promising solution for understanding complex driving scenes without requiring costly 3D annotations. However, training dense voxel decoders to capture fine-grained geometry and semantics can demand hundreds of GPU hours, and such models often fail to adapt to varying voxel resolutions or new classes without extensive retraining. To overcome these limitations, we propose a practical and flexible test-time occupancy prediction framework termed TT-GaussOcc. Our approach incrementally optimizes time-aware 3D Gaussians instantiated from raw sensor streams at runtime, enabling voxelization at arbitrary user-specified resolution. Specifically, TT-GaussOcc operates in a "lift-move-voxel" symphony: we first "lift" surrounding-view semantics obtained from 2D vision foundation models (VLMs) to instantiate Gaussians at non-empty 3D space; Next, we "move" dynamic Gaussians from previous frames along estimated Gaussian scene flow to complete appearance and eliminate trailing artifacts of fast-moving objects, while accumulating static Gaussians to enforce temporal consistency; Finally, we mitigate inherent noises in semantic predictions and scene flow vectors by periodically smoothing neighboring Gaussians during optimization, using proposed trilateral RBF kernels that jointly consider color, semantic, and spatial affinities. The historical static and current dynamic Gaussians are then combined and voxelized to generate occupancy prediction. Extensive experiments on Occ3D and nuCraft with varying voxel resolutions demonstrate that TT-GaussOcc surpasses self-supervised baselines by 46% on mIoU without any offline training, and supports finer voxel resolutions at 2.6 FPS inference speed.

In web data, advertising images are crucial for capturing user attention and improving advertising effectiveness. Most existing methods generate background for products primarily focus on the aesthetic quality, which may fail to achieve satisfactory online performance. To address this limitation, we explore the use of Multimodal Large Language Models (MLLMs) for generating advertising images by optimizing for Click-Through Rate (CTR) as the primary objective. Firstly, we build targeted pre-training tasks, and leverage a large-scale e-commerce multimodal dataset to equip MLLMs with initial capabilities for advertising image generation tasks. To further improve the CTR of generated images, we propose a novel reward model to fine-tune pre-trained MLLMs through Reinforcement Learning (RL), which can jointly utilize multimodal features and accurately reflect user click preferences. Meanwhile, a product-centric preference optimization strategy is developed to ensure that the generated background content aligns with the product characteristics after fine-tuning, enhancing the overall relevance and effectiveness of the advertising images. Extensive experiments have demonstrated that our method achieves state-of-the-art performance in both online and offline metrics. Our code and pre-trained models are publicly available at: https://github.com/Chenguoz/CAIG.

Linear attention has emerged as a promising alternative to softmax-based attention, leveraging kernelized feature maps to reduce complexity from quadratic to linear in sequence length. However, the non-negative constraint on feature maps and the relaxed exponential function used in approximation lead to significant information loss compared to the original query-key dot products, resulting in less discriminative attention maps with higher entropy. To address the missing interactions driven by negative values in query-key pairs, we propose a polarity-aware linear attention mechanism that explicitly models both same-signed and opposite-signed query-key interactions, ensuring comprehensive coverage of relational information. Furthermore, to restore the spiky properties of attention maps, we provide a theoretical analysis proving the existence of a class of element-wise functions (with positive first and second derivatives) that can reduce entropy in the attention distribution. For simplicity, and recognizing the distinct contributions of each dimension, we employ a learnable power function for rescaling, allowing strong and weak attention signals to be effectively separated. Extensive experiments demonstrate that the proposed PolaFormer improves performance on various vision tasks, enhancing both expressiveness and efficiency by up to 4.6%.

Compositional Zero-shot Learning (CZSL) aims to identify novel compositions via known attribute-object pairs. The primary challenge in CZSL tasks lies in the significant discrepancies introduced by the complex interaction between the visual primitives of attribute and object, consequently decreasing the classification performance towards novel compositions. Previous remarkable works primarily addressed this issue by focusing on disentangling strategy or utilizing object-based conditional probabilities to constrain the selection space of attributes. Unfortunately, few studies have explored the problem from the perspective of modeling the mechanism of visual primitive interactions. Inspired by the success of vanilla adversarial learning in Cross-Domain Few-Shot Learning, we take a step further and devise a model-agnostic and P rimitive- B ased Adv ersarial training (PBadv) method to deal with this problem. Besides, the latest studies highlight the weakness of the perception of hard compositions even under data-balanced conditions. To this end, we propose a novel over-sampling strategy with object-similarity guidance to augment target compositional training data. We performed detailed quantitative analysis and retrieval experiments on well-established datasets, such as UT-Zappos50K, MIT-States, and C-GQA, to validate the effectiveness of our proposed method, and the state-of-the-art (SOTA) performance demonstrates the superiority of our approach. The code is available at https://github.com/lisuyi/PBadv_czsl .

With the exponential surge in diverse multimodal data, traditional unimodal retrieval methods struggle to meet the needs of users seeking access to data across various modalities. To address this, cross-modal retrieval has emerged, enabling interaction across modalities, facilitating semantic matching, and leveraging complementarity and consistency between heterogeneous data. Although prior literature has reviewed the field of cross-modal retrieval, it suffers from numerous deficiencies in terms of timeliness, taxonomy, and comprehensiveness. This article conducts a comprehensive review of cross-modal retrieval’s evolution, spanning from shallow statistical analysis techniques to vision-language pretraining (VLP) models. Commencing with a comprehensive taxonomy grounded in machine learning paradigms, mechanisms, and models, this article delves deeply into the principles and architectures underpinning existing cross-modal retrieval methods. Furthermore, it offers an overview of widely used benchmarks, metrics, and performances. Lastly, this article probes the prospects and challenges that confront contemporary cross-modal retrieval, while engaging in a discourse on potential directions for further progress in the field. To facilitate the ongoing research on cross-modal retrieval, we develop a user-friendly toolbox and an open-source repository at https://cross-modal-retrieval.github.io.

The success of current deep cross-modal hashing admits a default assumption of the fully-observed cross-modal data. However, such a rigorous common policy is hardly guaranteed for practical large-scale cases, which directly disable the training of prevalent cross-modal retrieval methods with incomplete cross-modal instances and unpaired relations. The main challenges come from the collapsed semantic- and modality-level similarity learning as well as uncertain cross-modal correspondence. In this paper, we propose a Contrastive Incomplete Cross-modal Hashing (CICH) network, which simultaneously determines the cross-modal semantic coordination, unbalanced similarity calibration, and contextual correspondence alignment. Specifically, we design a prototypical semantic similarity coordination module to globally rebuild partially-observed cross-modal similarities under an asymmetric learning scheme. Meanwhile, a semantic-aware contrastive hashing module is established to adaptively perceive and remedy the unbalanced similarities across different modalities with the semantic transition for generating discriminative hash codes. Additionally, a contextual correspondence alignment module is conceived to maximally capture shared knowledge across modalities and eliminate the correspondence uncertainty via a dual contextual information bottleneck formula. To the best of our knowledge, this is the first successful attempt of enabling contrastive learning to incomplete deep cross-modal hashing. Extensive experiments validate the superiority of our CICH against state-of-the-art methods. Our code is available at https://github.com/DarrenZZhang/CICH .

Deep cross-modal hashing, as a promising fast similarity search technique, has attracted broad interest and obtained great success owing to its outstanding representation capability and computational efficiency. Since the inconsistent feature representations and distributions of different modalities (i.e., image and text), prior studies primarily focus on preserving pairwise similarity with global embedding, but fail to further utilize detailed local representations to effectively align such heterogeneous data to jointly bridge the heterogeneous and semantic gaps across modalities. Meanwhile, typical learning networks can learn only one fixed-length hash code rather than multi-length ones, leading to extremely limited flexibility and scalability. To tackle these issues, this paper proposes a novel Contrastive Multi-bit Collaborative Learning (CMCL) network, which hierarchically aligns both global and local features among different modalities and simultaneously generates multi-length hash codes (i.e., 16-, 32-, 64-bits) in one unified transformer-based framework. Specifically, we design a novel cross-modal contrastive alignment module to simultaneously bridge the heterogeneous and semantic gaps across modalities via global and local contrastive learning. Moreover, we propose a multi-bit collaborative optimization module to synchronously produce multi-length hash codes under the explicit guidance of one auxiliary online hash learner with a longer length (i.e., 128-bit). As such, our CMCL framework can jointly alleviate the heterogeneity among modalities from a hierarchical perspective and collaboratively explore the correlations between multi-bit hash codes, thereby yielding multi-length discriminative hash codes in a one-stop learning manner. Comprehensive experiments demonstrate the consistent superiority of our CMCL in multi-bit hash code learning over the state-of-the-art cross-modal hashing baselines.