Current Issue : October-December Volume : 2026 Issue Number : 4 Articles : 5 Articles
Space weather events triggered by solar activity impact critical technologies like the Global Navigation Satellite System (GNSS) by causing atmospheric imbalances that alter ionospheric electron density. This study investigates the upper atmosphere response to the severe geomagnetic storms of October 2024, focusing on the coupling and compositional exchange between the ionosphere and thermosphere. Data were analysed from two midlatitude African stations, Rabat (RABT) and Hermanus (HNUS), using GNSS-Total Electron Content (TEC) measurements alongside thermospheric circulation observations from NASA-GOLD and solar wind indices from OMNIWeb. The October 2024 storm, which reached a minimum Dst of −333 nT, drove a negative ionospheric storm phase marked by TEC depletions exceeding 50 TECU. This response was driven by storm-time thermospheric upwelling of N2-rich air, which lowered the O/N2 ratio and accelerated plasma loss via charge-exchange reactions. Furthermore, a distinct hemispheric asymmetry was observed, as the equatorward thermospheric circulation in the Northern Hemisphere arrived before that of the Southern Hemisphere. Direct post-processing of the Earth-Centred Earth-Fixed (ECEF) coordinates using RTKLIB single-point position revealed that, while positioning accuracy significantly degraded at HNUS with errors increasing by up to 270%, it counterintuitively improved at RABT, where errors reached their minimum during the main and early recovery phases of the storm. These findings highlight that the technological impact of severe space weather is determined not just by storm magnitude but by the specific sign and spatial structure of the regional ionospheric response....
The demand for reliable Positioning, Navigation, and Timing (PNT) solutions is rapidly increasing due to the growing need for precision, efficiency, and safety in unmanned systems. As operations become more autonomous, the reliance on accurate and continuous PNT data becomes critical for maintaining system integrity. The Global Navigation Satellite System (GNSS), while serving as the primary global PNT service, is vulnerable to interference, jamming, and spoofing attacks. This raises serious concerns, particularly for safety-critical applications, and urgently requires resilient Alternative PNT (A-PNT) solutions. An existing worldwide infrastructure, the Distance Measuring Equipment (DME) system, is considered one of the most promising candidates for A-PNT to address GNSS vulnerabilities. Utilising the carrier phase of the DME signal enables distance measurements with centimetre-level accuracy. However, due to the pulse system nature of DME transmissions and the sparsity of phase observations, conventional carrier tracking loops such as PLLs and FLLs struggle to maintain a reliable phase lock. To address these challenges, this work proposes a zero-crossing-integrated Kalman filter-based approach to track the DME carrier signal at an irregular rate. The performance of the proposed algorithm is validated through a series of drone tests at Cranfield University, UK. The validation results demonstrate that the proposed enhanced carrier tracking approach consistently delivers stable and accurate performance....
Science centres support informal learning by offering interactive environments that promote hands-on experiences. While prior research has examined motivation and cognitive engagement, the role of spatial configuration on navigation behaviour remains underexplored. This study investigates how spatial metrics—syntactic, isovist, and radial—shape the navigation patterns of middle school students within a virtual science centre. Eighty participants were divided into two groups: one completed a task-based activity, while the other navigated freely. Spatial characteristics of individual navigation routes were calculated, and independent-samples t-tests were used to compare group differences. Results showed that task-oriented students, who perceived the activity as game-like, followed shorter paths and interacted more with visible, shallow regions of the environment. The task variable exerted a stronger influence on spatial behaviour than free exploration. These findings underscore the value of task-driven, game-like designs in supporting goal-directed navigation and point to spatial features that can inform the design of informal learning environments....
Introduction Imageless navigation is widely used in total hip arthroplasty (THA), yet evidence for procedures in the lateral decubitus position remains limited because pelvic orientation and registration differ from the supine position. This study evaluated the accuracy of imageless navigation for acetabular component positioning in lateral-position primary THA, using postoperative EOS-based 3D assessment as a postoperative reference method for agreement analysis. Methods The study comprised in-vitro pretests and an in-vivo cohort. In vitro, a pelvic model was systematically rotated along all axes to assess effects on navigated cup inclination and anteversion. In vivo, 70 patients undergoing primary THA in lateral decubitus were included. Intraoperative imageless navigation values were compared with postoperative EOS-3D-measurements. Results In vitro, z-axis (tilt) variations substantially altered both parameters. In vivo, inclination showed a small but statistically significant inter-method difference (mean 1.4°, p = 0.036, Cohen’s d = 0.26), whereas anteversion demonstrated a larger systematic underestimation by imageless navigation (mean −7.5°, p < 0.001, Cohen’s d = −0.78) with poor inter-method agreement (ICC = 0.168). Conclusion Imageless navigation demonstrated acceptable inclination agreement with postoperative EOS assessment, whereas anteversion showed a larger systematic deviation and poor inter-method agreement; sagittal pelvic tilt and positional frame-of-reference differences appear to be major contributing factors. Clinical trial registration The study was registered in the German Clinical Trials Register with the registration number DRKS00026749....
The key parameters of atmospheric convective stability, the K index (KI) and the Showalter index (SI), are important indicators for severe convective weather warnings. This study adopts a variational mode decomposition, bidirectional gated recurrent unit, and attention mechanism weighting combined model (VMD–BiGRU–Attention) to optimize core hyperparameters and verify model stability. Global Navigation Satellite Systemderived precipitable water vapor (PWV) and relative humidity (RH) are incorporated as key parameters representing atmospheric water vapor conditions, thereby assisting VMD decomposition in accurately separating effective signals related to severe convection. The results show that the optimal VMD decomposition parameter K for the KI is 10 (minimum root mean square error [RMSE] = 3.96), whereas the optimal K for the SI is 11 (minimum RMSE = 1.87), verifying the applicability of VMD decomposition. In the validation using extreme rainfall events (2021–2025) at three meteorological stations in Guangxi (Baise,Nanning, and Hepu), the model, with the auxiliary contributions of PWV and RH, stably and accurately predicts the KI and SI for the next three hours, effectively capturing the critical characteristics of severe convection. The predicted results are consistent with the observed precipitation, demonstrating significant practical application value....
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