Shuai Guo

This paper systematically reviews the research status and future development trends of time synchronization technology in drone swarms. The paper first elaborates on the basic theory of time synchronization and defines the evaluation indicators for synchronization performance. Then, it deeply analyzes the characteristics and development status of time synchronization technologies such as centralized and distributed synchronization protocols, covering GPS time transfer, RBS, TPSN, FTSP, PTP, ATS, FF, and other synchronization protocols, as well as advanced directions such as time compensation technology under motion, communication technology, and hardware optimization technology. Finally, the paper summarizes the four major development trends of time synchronization technology: further improvement in accuracy, enhanced network robustness, faster clock servoing speed, and optimized communication resource allocation. This study provides an overview of the development of time synchronization technology in drone swarms under dynamic complex environments and analyzes possible future research directions.

Multi-drone systems demonstrate efficient coverage and task parallelism in fields such as disaster assessment, public safety, and environmental monitoring. However, path planning often involves multiple objectives, constraints, and environmental dynamics, and its complexity significantly limits the collective performance of the swarm. In this paper, within the unified MDP/PO-MDP framework, we systematically review the five main approaches for multi-drone path planning: classical algorithms, heuristic algorithms, meta-heuristic algorithms, machine learning algorithms, and hybrid algorithms. For each algorithm category, an eight-dimensional evaluation system was developed, covering time efficiency, computational cost, system complexity, convergence speed, adaptability to complex environments, scalability over large areas, trajectory smoothness, and obstacle avoidance capability, followed by a cross-comparison of representative algorithms. Based on the comparative analysis, this paper proposes the “method hybridization + directed optimization” paradigm, which enhances global-local coordination through strategies such as learning priors, swarm intelligence parallel search, and geometric pruning, and anticipates future research directions like learning-enhanced provable optimization, native 4D conflict-free trajectory planning, and decentralized collaborative decision-making, offering references for advancing multi-drone path planning from “feasible” to “usable.”

The fusion of synthetic aperture radar (SAR) and visible images offers complementary spatial and spectral information, enabling more reliable and comprehensive scene interpretation. However, SAR speckle noise and the intrinsic modality gap pose significant challenges for existing methods in extracting consistent and complementary features. To address these issues, we propose VGSRF-Net, a Retinex-guided SAR reconstruction-driven fusion network that leverages visible-image priors to refine SAR features. This approach effectively reduces modality discrepancies before fusion, enabling improved multi-modal representation. The cross-modality reconstruction module (CMRM) reconstructs SAR features guided by visible priors, effectively reducing modality discrepancies before fusion and enabling improved multi-modal representation. The multi-modal feature joint representation module (MFJRM) enhances cross-modal complementarity by integrating global contextual interactions and local dynamic convolution, thereby achieving further feature alignment. Finally, the feature enhancement module (FEM) refines multi-scale spatial features and selectively enhances high-frequency details in the frequency domain, improving structural clarity and texture fidelity. Extensive experiments on diverse real-world remote sensing datasets demonstrate that VGSRF-Net surpasses state-of-the-art methods in denoising, structural preservation, and generalization under varying noise and illumination conditions.

Novel-view synthesis with sparse input views is important for practical applications such as AR/VR and autonomous driving. Many works in this field have already integrated depth information into NeRF, utilizing depth priors for assistance in geometric and spatial understanding. However, most existing work tends to either overlook the inaccuracies in depth maps or only handle them roughly, limiting the effectiveness of the synthesis. To address this issue, we propose a depth-guided robust point cloud fusion NeRF for sparse input synthesis. We first construct a point cloud for each input view, with a novel point cloud representation based on learnable matrices and vectors. Then, through an additional lightweight scene fusion network, we fuse the point clouds from each input view to build a point cloud of the entire scene. By optimizing the point cloud representation and scene fusion network, inaccuracies in the depth map can be adjusted and refined, thereby achieving a more precise perception of the overall scene. Each voxel in the scene is determined by referencing the fused point cloud to establish its density and appearance. Experimental results demonstrate that our method outperforms state-of-the-art baselines.

Depth image-based rendering (DIBR) view synthesis is the most widely employed method in real-time FVV research. Despite recent progress, most DIBR-based FVV synthesis approaches are not sufficiently simple and effective in filling holes and artifacts. Additionally, they use RGB-D cameras, which are difficult to widely adopt or take considerable time to estimate high-quality depth images. This paper introduces a real-time FVV synthesis system based on DIBR and a depth estimation network. This system includes a 12-view synchronous camera system, a new multistage depth estimation network, a new GPU-accelerated DIBR algorithm, and a virtual view parameter generation method. This system provides the first real-time FVV solution for background-fixed fields based on DIBR and a depth estimation network. It can infer depth images for all camera views and synthesize any virtual view along the horizontal circular arc of the camera rig in real time. To our knowledge, we are the first to introduce background models and foreground masks and a refined multistage structure to address real-time high-quality depth estimation and DIBR FVV synthesis. We also build a high-quality multiview RGB-D synchronous dataset that has promising DIBR FVV synthesis performance to train and evaluate our system. The experimental results demonstrate the real-time and better performance of the proposed system.

Human body movements can convey a variety of emotions and even create advantages in some special life situations. However, how emotion is encoded in body movements has remained unclear. One reason is that there is a lack of public human body kinematic dataset regarding the expressing of various emotions. Therefore, we aimed to produce a comprehensive dataset to assist in recognizing cues from all parts of the body that indicate six basic emotions (happiness, sadness, anger, fear, disgust, surprise) and neutral expression. The present dataset was created using a portable wireless motion capture system. Twenty-two semi-professional actors (half male) completed performances according to the standardized guidance and preferred daily events. A total of 1402 recordings at 125 Hz were collected, consisting of the position and rotation data of 72 anatomical nodes. To our knowledge, this is now the largest emotional kinematic dataset of the human body. We hope this dataset will contribute to multiple fields of research and practice, including social neuroscience, psychiatry, computer vision, and biometric and information forensics.