Safety provision is a crucial application for the vehicular ad hoc networks (VANETs). In the VANETs, vehicles periodically broadcast their geographic information. Therefore, collisions can be avoided. In this paper, we address the issue of large computation overhead caused by the safety message authentication. A cooperative message authentication protocol(CMAP) is presented to alleviate vehicles' computation burden. In the protocol, because vehicles share their verification results with each other in a cooperative way, the number of safety messages that each vehicle needs to verify will be reduced greatly. A new research issue of the protocol is how to select verifiers in the city road scenario. Thus, we propose three verifiers selection algorithms, n-nearest method, most-even distributed method and the compound method for the CMAP. Based on the simulation results from NS2, comparisons between these three methods and the existing work are given at the end of the paper to demonstrate the performance of our protocol.

Video captioning, a challenging task that entails generating natural language descriptions of visual content, often fails to effectively grasp the essence of action semantics. To harness the power of action detection to facilitate a deeper understanding of the video content, we propose an action-driven method, named Hierarchical Semantic Representation and Aggregation (HSRA) network. This method explicitly exploits action clues with a hierarchical semantic representation module, which models visual semantics in a three-level structure: “object-action-event”. By employing learnable action queries, our approach injects extensive action semantics into the model, thereby enabling more accurate and context-rich captions. To further enhance semantic alignment and understanding, we introduce a semantic aggregation composed of a semantic interaction module and a semantic refinement module. This component facilitates the alignment of semantics across different levels and emphasizes key information, ultimately leading to significant improvements in semantic consistency between the video and generated captions. We performed extensive evaluations on two well-established public datasets, MSVD and MSR-VTT, and the findings consistently demonstrate that our proposed HSRA network outperforms contemporary state-of-the-art methods.

This work aims to address the multi-view perspective RGB generation from text prompts given Bird-Eye-View(BEV) semantics. Unlike prior methods that neglect layout consistency, lack the ability to handle detailed text prompts, or are incapable of generalizing to unseen view points, MVPbev simultaneously generates cross-view consistent images of different perspective views with a two-stage design, allowing object-level control and novel view generation at test-time. Specifically, MVPbev firstly projects given BEV semantics to perspective view with camera parameters, empowering the model to generalize to unseen view points. Then we introduce a multi-view attention module where special initialization and de-noising processes are introduced to explicitly enforce local consistency among overlapping views w.r.t. cross-view homography. Last but not least, MVPbev further allows test-time instance-level controllability by refining a pre-trained text-to-image diffusion model. Our extensive experiments on NuScenes demonstrate that our method is capable of generating high-resolution photorealistic images from text descriptions with thousands of training samples, surpassing the state-of-the-art methods under various evaluation metrics. We further demonstrate the advances of our method in terms of generalizability and controllability with the help of novel evaluation metrics and comprehensive human analysis.

Video summarization remains a challenging task despite increasing research efforts. Traditional methods focus solely on long-range temporal modeling of video frames, overlooking important local motion information that cannot be captured by frame-level video representations. In this article, we propose the Parameter-free Motion Attention Module (PMAM) to exploit the crucial motion clues potentially contained in adjacent video frames, using a multi-head attention architecture. The PMAM requires no additional training for model parameters, leading to an efficient and effective understanding of video dynamics. Moreover, we introduce the Multi-feature Motion Attention Network (MMAN), integrating the PMAM with local and global multi-head attention based on object-centric and scene-centric video representations. The synergistic combination of local motion information, extracted by the proposed PMAM, with long-range interactions modeled by the local and global multi-head attention mechanism, can significantly enhance the performance of video summarization. Extensive experimental results on the benchmark datasets, SumMe and TVSum, demonstrate that the proposed MMAN outperforms other state-of-the-art methods, resulting in remarkable performance gains.