Abstract:In the fields of intelligent manufacturing, aerospace, and robotics, control systems often operate under unknown dynamics. This significantly limits the effectiveness of traditional model-based control methods. Reinforcement learning (RL), as a data-driven intelligent control approach, enables policy learning and optimization through interaction with the environment, showing great potential for solving optimal control problems in such model-unknown scenarios. This survey focuses on the issue of unknown dynamic models in continuous-time systems and first reviews the development of general reinforcement learning algorithms and their application in model-known scenarios through industrial examples and theoretical analysis methods. It also summarizes representative methods for model-unknown scenarios, such as model-based RL, off-policy integral RL, and Q-learning approaches. The survey also introduces Lyapunov-based theoretical analysis tools and important assumptions. It discusses cutting-edge topics such as RL under partial observability using large language models, safe RL, and stability and robustness enhanced RL, while highlighting the challenges faced by existing methods.

Abstract:Fiber-based supercontinuum sources offer broad spectral bandwidth, high brightness, and excellent spatial coherence, showing great promise in applications such as electro-optical countermeasures, gas sensing, and optical coherence tomography. To address the diverse performance requirements of fiber-based supercontinuum imposed by different application scenarios, this review focuses on three key directions: power scaling, mid-infrared spectral extension, and suppression of intensity noise. We summarize recent advances in fiber-based supercontinuum generation, outline technical approaches tailored to enhance each specific performance metric, and provide an outlook on future developments, aiming to serve as a reference for the development and application of high-performance.

Abstract:In the era of big data intelligence, knowledge has become the fundamental driving force for technological development. Big data knowledge fusion, which constructs a unified knowledge system by associating multi-source fragmented data, serves as a key support for enhancing knowledge completeness and improving cognitive intelligence. Based on basic paradigms and classic methods, the research status of three key links—knowledge representation learning, knowledge alignment matching, and knowledge conflict resolution—was systematically summarized. Meanwhile, new progress in the context of big data was deeply explored, covering frontier directions such as temporal knowledge fusion, cross-modal knowledge fusion, and large language model knowledge fusion. Furthermore, future development trends were prospected, and potential research issues, including the fusion of symbolic and parametric knowledge as well as cross-modal temporal knowledge fusion, were highlighted. Through a panoramic review of basic links and emerging paradigms, important reference and guidance are provided for theoretical expansion and technological evolution in the field of big data knowledge fusion.

Abstract:Solid-state pulsed power driving sources are essential for compact, high-repetition-rate, and long-lifetime high-power microwave systems. This paper reviews the domestic and international research status of solid-state pulse power driver sources, focusing on the investigation and review of three mainstream modular superimposed technology routes: solid-state Marx pulse generators, solid-state linear transformer driver (LTD) sources, and solid-state stacked Blumlein line pulse generators. From the perspective of switches, this paper points out that the current technical challenges are mainly concentrated on three aspects: the constraining factors of switch operating characteristics and frequency enhancement, energy loss and thermal management, as well as driving and control. Meanwhile, the paper discusses the future development trends of high-repetition-rate solid-state pulsed driving sources, and provides references and basis for the research and exploration of technical routes of high-repetition-rate solid-state pulsed power driving sources.

Abstract:The rapid development of high-performance computing (HPC) and artificial intelligence (AI) demands networks with higher bandwidth, larger scale, and greater cost. As the core of interconnection networks, topology design is constrained by multiple factors, including the number of ports per router chip, the number of virtual channels, and packaging density. This study reviews approximately thirty topologies proposed by academia and industry, providing detailed analysis of the most representative and recent designs. It examines the design challenges of adaptive routing in high-radix networks, compares the performance and cost of multiple topologies, and provides recommendations for topology selection. Finally, the paper identifies key challenges in topology design and outlines future trends, including application-driven, cost-effective network topologies; power-supply-constrained designs that align with facility power capacity; the unification of intra-node network protocols; and the continual expansion of supernode scale. Future topologies are expected to integrate intra-node and inter-node designs in a coordinated manner.

Abstract:Absolute gravity measurement based on laser interferometry is the main means to establish gravity measurement reference, and it is also the gravity reference instrument used currently. In recent years, along with the development of quantum absolute gravity measurement techniques, new opportunities have been presented for establishing a gravity reference with higher accuracy. With the support of the National Development and Reform Commission, Huazhong University of Science and Technology had established the “precision gravity measurement facility (PGMF)” as a major national scientific and technological infrastructure. A key component of this facility's construction is the establishment of a micro-Gal level absolute gravity measurement reference station. This station provides a standardized reference for gravity measurement instruments and data, serving as a foundation for achieving high-precision measurements and applications in the gravitational field. High-precision gravity measurement instruments are the core equipment for PGMF to achieve gravity measurement reference. For this purpose, PGMF independently developed a reference quantum absolute gravimeter suitable for station measurement and a miniaturized quantum absolute gravimeter for reference extension. Furthermore, a gravity comparison field and a background physical environment monitoring system were established. Ultimately, a micro-Gal level gravity measurement reference station was established.

Abstract:Addressing the critical need for autonomous navigation of low-altitude unmanned aerial vehicles (UAVs) in Global Navigation Satellite System (GNSS)-denied environments, this paper presents a comprehensive survey on absolute visual localization techniques based on a "retrieval-matching-pose estimation" framework. It begins by analyzing the challenges inherent to low-altitude UAV observation, such as significant imaging disparities, rapid scene scale variations, and object occlusions, there by elucidating the advantages of the hier-archical framework for large-scale, long-endurance localization tasks. Subsequently, the review systematically examines the technological evolution and current state-of-the-art across three core components: cross-view image retrieval, pixel-level feature matching, and UAV pose estimation, tracing the progression from traditional handcrafted features to deep learning paradigms. Finally, considering the requirements for deployment on airborne edge-computing platforms, the paper discusses the limitations of existing technologies and outlines promising future research directions. This survey is intended to serve as a valuable reference for both research and practical applications in absolute visual localization for low-altitude UAVs.

Abstract:Currently, countries around the world are generally unable to defend effectively against high-speed vehicles, and related basic research is still in its infancy. Accelerating the development of high-speed target defense technology is crucial for maintaining aerospace security. Given the problems present in the near-space defense confrontation under this background, such as a narrow defensive posture, significant speed disadvantages, and limited single-missile defense capability, this paper reviews the current development status of the defense guidance law for high-speed near-space vehicles. It analyzes the deficiencies of the existing guidance law research from perspectives such as complex offensive and defensive confrontation scenarios, missile cooperative guidance mechanisms, and real environment effectiveness constraints. It also foresees the key development directions of future defense guidance laws for high-speed vehicles, aiming to offer references for the construction of future defense systems for high-speed vehicles and the frontier basic research in the field of precision guidance.

Abstract:During the high-speed flight of aircraft, raindrop impact erosion causes significant damage to surface materials, thereby seriously affecting flight performance and structural safety. This paper aims to systematically review the mechanical mechanisms, key influencing factors, and progress in corresponding protection technologies of high-speed raindrop impact erosion. In terms of experiments, current studies mainly rely on devices such as wind tunnels, rocket sleds, and rotating arms to construct simulated environments of real rain fields. Meanwhile, high-speed photography is used to record the dynamic erosion process, and laser velocimetry is employed to obtain raindrop impact velocity, thus achieving multi-dimensional observation of erosion behavior. In terms of numerical simulation, this paper focuses on introducing mainstream simulation techniques such as the finite element method (FEM) and the smoothed particle hydrodynamics (SPH) method. Additionally, an overview was provided of existing research methods and outcomes, which primarily involve establishing liquid-solid coupling models to analyze the propagation patterns of stress waves and the dynamic response characteristics of materials during impact processes. The research results show that raindrop impact velocity, impact angle, and mechanical properties of materials are the key factors affecting the erosion rate. Based on the actual flight envelope parameters of aircraft, targeted optimization design of rain erosion resistance performance can be carried out, which provides a theoretical basis and technical support for improving the service safety of aircraft in harsh meteorological environments.

Abstract:The aerodynamic environment in low-altitude regionsis characterised by complex flow field structures, diverse disturbance sources, and significant coupling effects. These factors have a significant impact on the aerodynamic performance and flight safety of unmanned aerial vehicles(UAVs), making them a key focus of research in the field of low-altitude UAV aerodynamics. Three typical scenarios have been systematical reviewed: complex low-altitude wind fields, spatially constrained environments, and multi-UAV environments. The fundamental characteristics and modelling approaches of complex low-altitude wind fields have been systematically outlined, and their effects on UAVs and key research methodologies have been summarised. Spatially constrained environments are categorised based on disturbance mechanisms and constraint types, and the review provides a comprehensive summary of the aerodynamic impacts on UAVs within such environments. Spatially constrained environments are categorised based on disturbance mechanisms and constraint types, and a comprehensive summary of the aerodynamic impacts on UAVs within such environments has been provided. The aerodynamic characteristics of UAVs in multi-UAV environments have been summarised, and the aerodynamic coupling mechanisms and research methodologies for cooperative and non-formation flight scenarios have been outlined. Building upon this foundation, the core issues and key challenges currently facing aerodynamic research on UAVs in low-altitude environments have been further refined, and future research priorities in this field have been outlined.