Guangxue Li

Ultrawideband (UWB) technology is pivotal for centimeter-level indoor positioning, yet its accuracy is severely degraded by non-line-of-sight (NLOS) propagation in complex industrial environments. Existing NLOS identification methods face critical trade-offs between model accuracy, computational efficiency, and dynamic scenario adaptability. To address these challenges, we propose a novel lightweight framework named LightMamba that integrates selective state-space models (SSMs) with UWB channel impulse response (CIR) characteristics. LightMamba introduces three key innovations: 1) a dual-branch feature extraction module that combines segmented CIR projection with auxiliary channel feature alignment, preserving both local temporal dependencies and global environmental semantics; 2) a Mamba block with dynamic path selection, enabling adaptive focus on NLOS-induced multipath components while maintaining linear computational complexity and efficient processing of long sequences; 3) a resource-efficient architecture achieving millisecond-level inference latency without sacrificing accuracy. Extensive experiments on three real-world datasets (eWINE, IULCD, OIUD) demonstrate LightMamba’s superiority, achieving a high ${F}1$ -score of 95.20% on the OIUD dataset with only 22k parameters, outperforming baseline models while reducing the parameter number by 96% compared to long short-term memory (LSTM) with 545k parameters. This work provides a new solution for high-reliability UWB-based indoor positioning systems in industrial Internet of Things (IIoTs) applications.

The Bohai Sea is the region with the highest suspended sediment concentration (SSC) in the world. The transport of suspended sediment from the Bohai Sea to the open sea greatly affects the coastal biogeochemical processes. However, due to the limitations of long-term field observations, the temporal and spatial characteristics and mechanisms of the long-term changes in suspended sediment concentration and flux in the Bohai Sea remain unclear. Remote sensing results and numerical simulation analysis indicate that the transport of suspended sediment from the Bohai Sea to the open sea is decreasing. Further analysis shows that changes in the wind field are the main reason affecting the output of suspended sediment from the Bohai Sea. During the transport process of suspended sediment from the Bohai Sea to the open sea, both the SSC and the range of high concentration suspended sediment are showing a downward trend, with the 15 mg/L isopleth range gradually shrinking at a rate of 7.38 km/yr. The suspended sediment flux (SSF) from the Bohai Sea to the open sea shows a clear downward trend, and the decline rate gradually weakens from west to east, mainly controlled by the weakening of the northwesterly (NW) wind intensity in winter.

Sediment resuspension primarily occurs within the bottom boundary layer (BBL) of water bodies, particularly in silty coastal environments, and helps form the fluid mud layer (FML). In this study, we report data on the water level, waves, currents, and suspended sediment concentration (SSC) collected from the Bohai Sea over one year, at a vertical resolution of 4 cm, by using the acoustic wave and current profiler, acoustic Doppler current profiler, and an acoustic backscattering system. The aim was to investigate the mechanisms of formation and disappearance of the FML as driven by wave–current interactions on silty seabeds The findings revealed a thin and stable FML within 4–12 cm of the seabed in shallow waters. Strong waves contributed more significantly to sediment resuspension than strong currents. Moreover, the SSC near the seabed was generally governed by the currents, while waves were predominant in this regard in stormy conditions. The index of intensity of the bottom shear β—defined as the ratio of the wave–current-induced shear stress to the critical shear stress—was identified as a sensitive indicator of variations in the SSC. Significant sediment resuspension occurred in case of the coupling of large wave and current events on the fine-grained seabed, when the value of β exceeded 10 for more than 20 h and the Rouse number persisted below 0.01 for over 30 h. Following the storm (β < 10), the sediment gradually accumulated, and this led to the formation of the FML. Prolonged periods in which the value of β surpassed 10 for over 10 h while that of the Rouse number remained below 0.01 for more than 30 h resulted in considerable sediment resuspension and the destruction of the FML. Our results highlight the profound impacts of wave–current interactions on the formation and disappearance of the FML within the BBL in silty, shallow marine environments. The work here offers critical insights into the dynamics of fine-particle sediment, and provides suggestions for mitigating the negative effects associated with the FML.

Seabed liquefaction induced by wave loading poses considerable risks to marine structures and requires careful consideration in marine engineering design and construction. Traditional methods relying on statistical wave parameters for analyzing random waves often underestimate the potential for seabed liquefaction. To address this underestimation, the present study employs field observations and numerical simulations to examine wave characteristics and liquefaction distribution across various wave return periods in the Chengdao Sea area of the Yellow River subaqueous delta. The research results indicated that the wave decay phase exhibited a higher liquefaction potential than the growth phase, primarily because of the prevalence of low-frequency swell waves. The China Hydrological Code Spectrum (CHC Spectrum) effectively captured the wave characteristics in the study area, with parameterization grounded in measured data. The poro-elastic wave–sediment interaction model further elucidated the liquefaction distribution under extreme wave conditions, revealing a maximum liquefaction depth exceeding 3 m and prominent liquefaction zones at water depths of 5–15 m. Notably, seabed properties emerged as a critical factor for liquefaction and overshadowed water depth, with non-liquefaction zones occurring at water depths of less than 15 m at high clay content, highlighting the general liquefaction risk of silty seabed. This study enhances understanding of the seabed liquefaction process and offers valuable insights into engineering safety.

Mud deposits in cold water masses (CWMs) on continental shelves represent distinct units of suspended particulate matter (SPM); however, the generative mechanism and variation in SPM during source-sink processes remain unresolved. In this study, we measured the properties of SPM during transport among water masses into a CWM in the North Yellow Sea (NYS) based on grain-size distributions via laser in situ scattering and transmissometry (LISST). Our results show that this CWM is an important sink for SPM from the Bohai Sea and Chengshan Cape. The SPM in these source areas mainly consists of fine aggregates or flocs. Particles may bond to form coarse flocs when they pass through a high-temperature water mass, as the weak turbulent shear in these water masses facilitates flocculation. The subsequent transport of such coarse flocs into the marginal waters around the CWM, where temperatures are lower and turbulent shear is stronger, causes the coarse flocs to disaggregate into fine aggregates/flocs. These low-density fine flocs, which are mainly composed of organic matter, are subsequently transported toward the upper water body by upwelling; meanwhile, high-density fine aggregates, which are mainly inorganic, are transported toward a northern cold water mass, where they are deposited due to the quiescent near-bottom water. The results of our model provide new insights into the generative mechanisms of muddy deposits subject to cold vortices on continental shelves.

The Bohai Sea, known for being the lowest latitude seasonally frozen sea area in the world, experienced severe ice conditions with a 30-year recurrence period during the winter of 2009-2010. Water-sediment flux is a crucial parameter for water quality management in marine environment. Using a highly accurate three-dimensional hydrodynamic and sediment transport numerical model, the significant wave height (Hs), current velocity, suspended sediment concentration (SSC) and water-sediment flux in the Bohai Sea during ice-covered and ice-free conditions are compared. Our findings indicate that the current velocity and sediment resuspension decrease under the ice coverage, but increase at the edge of the ice. The net outflow tidal flux (TF) in winter under ice-free conditions accounts for 24.5% of the whole year. The net outflow TF increases by 32.7% during ice-covered conditions, primarily due to the pressure difference between high air pressure superimposing heavy sea ice in the northwest Bohai Sea and the low air pressure in Bohai Strait, resulting in increased ebb velocity and decreased flood velocity. The net outflow suspended sediment flux (SSF) during ice-free conditions in the winter is 2.32×10⁹ kg, while SSF increases by 1.24 times during ice-covered conditions, leading to worse water quality in the outer sea. The decrease of TF in the southern part of the Bohai Strait and the reduction of suspended sediment concentration by nearly 15 mg/l lead to the significant decrease in SSF. This study has significance guiding value for understanding the source-sink sedimentation system and water quality research in East China Sea.