Search Results (783)

The Cooperative-Intelligent Transport Systems (C-ITS) require emerging Vehicular-to-Everything (V2X) applications, such as Advanced Driving Systems (ADS) and Connected Autonomous Driving (CAD), to support efficient road safety measures. These applications often require high reliability, throughput, and low latency by exchanging a significant amount of data among End-to-End (E2E) vehicles. However, current V2X communication technologies, such as DSRC and C-V2X, are not able to meet these stringent demands. Two or more Radio Access Technologies (RATs) are essential to guarantee the required Quality of Service (QoS) in high-density vehicular environments. To address this critical gap, this survey presents the 3M Framework—a hybrid vehicular architecture approach based on Multi-Radio Access Technology (M-RAT), Mobility Management, and Machine Learning (ML). The manuscript provides a detailed overview of V2X Multi-RAT evolutions, analyzing their state-of-the-art and limitations in heterogeneous scenarios. We specifically highlight that the existing Long Term Evolution (LTE)-based mobility management fails to meet V2X handover requirements for high-speed vehicles, necessitating a comprehensive overview of Vertical Handover (VHO). Furthermore, the survey details how the integration of ML promotes the prediction of network states, enabling optimized context-aware decisions for connectivity and resource allocation, thereby reducing Handover Failures (HoFs) and enhancing reliability using techniques like Deep Reinforcement Learning (DRL). Finally, based on a comprehensive review of existing methods, the paper identifies critical research directions and challenges required to realize intelligent, hyper-fast, and ultra-reliable Beyond 5G (B5G) and Sixth Generation (6G) V2X networks, delivering a more profound understanding for future endeavors. Full article

All existing Satellite-Based Augmentation Systems (SBAS) are regional, leading to discontinuous global coverage and significant service gaps. To overcome the inherent coverage limitations of SBAS caused by regional ground station distribution, this study integrates Low Earth Orbit (LEO) satellites with ground-based networks to enable global SBAS coverage. Using real observational data from eight LEO satellites, we demonstrate their feasibility as space-based monitoring stations. The results show that incorporating LEO satellites reduces the dual-frequency range error (DFRE) and significantly increases the number of available augmented satellites within the service region. Compared with Standard Point Positioning (SPP), this augmentation reduces the 95th-percentile horizontal and vertical positioning errors by approximately 51.4% and 44.2%, respectively. Furthermore, all stations satisfy the Approach with Vertical guidance I (APV-I) availability requirements, and no Hazardous Misleading Information (HMI) events are observed. Based on the observation data from eight LEO satellites, we construct an eight-satellite simulated constellation that matches the real satellites’ orbital characteristics, thereby validating the consistency between real-data findings and simulation-based assessments. Subsequently, we built a hybrid LEO constellation (108 Walker + 60 polar) as space-based monitoring stations integrated with ground stations to evaluate global SBAS service performance. The results show that with LEO satellite augmentation, the global number of available augmented satellites remains above nine. The 95th-percentile horizontal and vertical positioning accuracies are better than 0.75 m and 1.6 m. All global evaluation stations achieve APV-I availability above 99%. In addition, sensitivity analysis reveals that dissemination delay is a critical factor affecting protection levels and service availability, particularly at high latitudes. Overall, both real-data experiments and global simulations validate the significant benefit of LEO augmentation in improving global SBAS service performance. Full article

Indoor climbing gyms are high-occupancy settings, yet integrated indoor air quality (IAQ) studies that analyze objective exposure and occupant perception remain scarce. The novelty consists of combining user perception with multi-zone, high-resolution IAQ measurements. We investigated a climbing gym in Romania to (i) quantify particulate matter (PM₁, PM_2.5, PM₁₀) and carbon dioxide (CO₂), (ii) compare natural and mechanical ventilation under real operating conditions with per capita normalization, (iii) relate exposure to occupancy and user perception, and (iv) coupling continuous optical monitoring with 24 h gravimetric and morphological/chemical analyses (scanning electron microscopy, confocal microscopy, X-ray fluorescence, and inductively coupled plasma mass spectrometry). The gravimetric 24 h reference measurements (EN 12341:2014) showed that daily means for PM_2.5 and PM₁₀ were 1.9–2.0× and 2.3–2.8× higher than the WHO guideline values, which confirms persistent daily particulate loads. Mechanical ventilation reduced coarse PM and CO₂, but absolute PM remained elevated and fine fractions persisted. CO₂ revealed a near-uniform vertical mixing, confirming dilution but indicating that CO₂ is not a surrogate for particulate exposure. Survey responses from occupants revealed a gap between perception and reality: most of the users rated IAQ as good despite high PM. This study is among the few integrations of perception of IAQ for climbing gyms and the first comprehensive assessment in Romania, providing evidence-based recommendations on ventilation and filtration upgrades, chalk use management, and dust-reservoir control, thus creating sparkling interest for IAQ researchers, building services engineers, sports facilities operators, and policymakers. Full article

The emergence of low-cost GNSS hardware and affordable RTK correction services has made high-precision positioning more accessible. While prior studies have investigated RTK capabilities using smartphones, most rely on professional geodetic infrastructures. This study shifts the focus toward evaluating smartphone-based RTK positioning within low-cost GNSS networks and comparing the performance against traditional geodetic network setups. The research investigates two main configurations: (1) a smartphone functioning as an RTK rover within a low-cost GNSS network, using a low-cost base station and publicly available or inexpensive correction services, and (2) the same smartphone setup operating within a traditional geodetic network with high-grade base stations. The study aims to assess the viability of smartphones as RTK rovers in low cost networks, exploring metrics such as horizontal and vertical positioning accuracy, fix reliability, initialization time, and system responsiveness. Preliminary findings suggest that smartphones integrated with low-cost GNSS receivers can deliver sub-meter accuracy under favorable conditions, though some trade-offs are noted when compared with geodetic-grade infrastructure. The study emphasizes the potential of cost-effective RTK configurations for practical applications where high precision is required. By comparing performance across traditional and low-cost network configurations, this research demonstrates the increasing potential of using smartphones and low-cost GNSS systems to make high-precision positioning more accessible. Full article

An increased interest in decreasing the environmental impact of the construction sector and in vertical urbanization has renewed attention to timber as a primary structural material in multi-story buildings. This study investigated whether an existing 10-story reinforced concrete (RC) residential building can be redesigned as an equivalent mass-timber structure while satisfying the same structural performance requirements. It addressed the lack of like-for-like building-scale comparisons that redesigned an existing multi-story RC residential building into a functionally equivalent mass-timber scheme. A real RC building in Gävle, Sweden, was modeled, analyzed, and designed using StruSoft FEM-Design software in accordance with the Eurocodes and the Swedish National Annex, after which all main structural elements were systematically replaced with timber. Through iterative adjustments of member sizes, support conditions, and added reinforcing elements, both the RC and timber schemes were verified with respect to load-bearing capacity, serviceability, and global stability under identical load combinations. The RC and timber buildings reached maximum utilization ratios of 99% and 98%, respectively; displacements were higher in the timber building but remained within serviceability limits, and both systems were classified as globally stable. The timber alternative reduced the total structural weight to about 19% of the RC building and roughly halved the maximum vertical reaction forces, at the expense of additional beams, columns, and basement wall segments. Moreover, this article developed an equivalent-design methodology for material substitution, a bottom-up reinforcing elements logic that resolved serviceability and stability constraints in tall timber, and a performance trade-off map based on structural performance, offering guidance for future mass-timber design. Full article

This study examines a top-chord-free open-web steel-truss composite floor in which the concrete slab functionally replaces the traditional top chord and works jointly with vertical square-tube web members and a square-tube bottom chord. Two scaled specimens—with and without concrete infill in the end shear-bending blocks—were fabricated and tested under static loading. The load–deflection response delineates three stages: elastic, elastic–plastic, and failure. Tests show that infilling the shear-bending blocks does not enhance global mechanical performance. In the elastic range, the mid-span open-web section satisfies the plane-section assumption with a linear strain profile, whereas the solid-web section exhibits a bilinear distribution. A validated ANSYS finite-element model reproduces the measured responses and supports a parametric study showing that span-to-depth ratio, opening-to-span ratio, slab (flange) thickness, and width-to-span ratio significantly affect ultimate capacity and deflection. Design recommendations are proposed: span-to-depth ratios of 11–14 and opening-to-span ratios of 0.04–0.07. An equivalent-stiffness-based simplified linear-elastic deflection formula with a reduction factor is derived, which accurately tracks deflection evolution and enables serviceability-driven selection of web spacing and overall structural depth. Full article

Enhancing carbon sink capacity and optimizing urban blue-green infrastructure (UBGI) are crucial for urban planning and sustainable development. Based on the ArcGIS 10.8 platform and the InVEST model, this study comprehensively evaluates the spatiotemporal evolution characteristics of three ecosystem services (carbon storage, habitat quality, and water retention) in Guilin. By applying the coupling coordination degree model, bivariate spatial autocorrelation, and K-means clustering methods, it systematically reveals the synergistic and trade-off relationships among multiple ecosystem services in karst cities, identifies the spatial differentiation pattern of ecological spaces, and proposes UBGI optimization strategies. The results show that the three types of ecosystem services in Guilin exhibited a spatiotemporal differentiation pattern of stable high values in mountainous areas and continuous expansion of low values around urban areas from 1993 to 2023, with their changes mainly driven by the significant negative impact of human activity intensity (nighttime light, population density). Guilin’s ecological space can be divided into four functional zones: Ecological Core Cluster (77.50%), Degraded Carbon-Poor Cluster (1.47%), Habitat Protection Cluster (0.46%), and Buffer Balance Cluster (20.58%). Carbon storage, habitat quality, and water retention showed significant spatial gradient differences (Kruskal–Wallis nonparametric test, p < 0.001) and local decoupling characteristics. Furthermore, the study proposed key ecological management thresholds, such as impervious surface ratio < 15% and forestland ratio > 30%, and constructed a differentiated “zoning-classification-grading” UBGI optimization strategy system based on the four functional zones, including ecological corridor construction, promotion of vertical greening and sponge facilities, supplementary planting of native vegetation, and integration of ecological agriculture. These strategies aim to enhance the synergistic efficiency of ecosystem services, improve regional carbon sink capacity, and provide a scientific basis for Guilin’s ecological planning, the implementation of “dual carbon” goals, and the construction of the National Innovation Demonstration Zone for Sustainable Development Agenda. Full article

Network slicing is a cornerstone of 5G/6G vertical services, yet practical deployments require mobile network operators (MNOs) to adjust slice service level agreement (SLA) weights based on quality of experience (QoE), causing rapid non-stationary objective changes that can destabilize deep reinforcement learning (DRL) slicing policies and necessitate retraining. This paper proposes Continual Mixture of Experts (CoMEx) for fast policy adaptation. CoMEx pre-trains and freezes multiple expert policies under diverse SLA preferences, explicitly appends the SLA weight vector to observations, and trains a DRL-based gating network to fuse expert actions at the step level for fast adaptation to unseen SLA configurations. To broaden coverage without degrading existing experts, CoMEx further incorporates a masked expert expansion mechanism that incrementally adds new experts and fine-tunes the gate. Step-level DRL gating demonstrates superior generalization in RAN slicing, attaining a mean score of 78.95 under unseen SLA weights—surpassing episode-level and supervised gating by 2.40% and 27.67%, respectively. Moreover, CoMEx’s extensibility is highlighted by a 7.08% performance boost (reaching 84.54) upon the addition of a fourth expert. Such results confirm the framework’s capacity for timely and robust policy adaptation in non-stationary SLA environments. Full article

High-platform timber structures represent a typical structural form in ancient Chinese architecture, where the platform and the upper timber structure constitute a mechanically coupled system with interacting mechanical properties and response behaviors. However, a systematic understanding of their global coupling mechanism and its impact on structural response remains unclear. This study investigates a representative high-platform timber structure, i.e., Xi’an Bell Tower, to analyze the static and dynamic response characteristics of the platform–superstructure system using in situ dynamic testing and finite element simulation. The results indicate that the simulated first two natural frequencies align well with in situ measurements, validating the model’s rationality. The global coupling effect alters the system’s mass and stiffness distribution, leading to an overall lengthening of the structural natural periods. Structural self-weight is identified as the dominant factor inducing vertical deformation under serviceability conditions, with significant deformation observed at the platform’s edges and corners. Under lateral loads, deformations concentrate in the second story of the timber superstructure, with seismic actions exerting a more pronounced influence than wind loads. Under rare earthquake conditions, the maximum inter-story drift ratio reaches 1/70. Local tensile stresses at the joints, architrave ends, and the Dou-Gong layer exceed the timber’s tensile strength parallel to the grain, identifying these components as the weak links in the structure’s seismic performance. Full article

In order to study the influence of the under-track foundation disease on the track system, based on the CRTS II slab ballastless track in ABAQUS, this paper analyzes the influence of the overall temperature, temperature gradient, CA mortar layer stiffness and voiding, and fastener system stiffness changes on the track system. The results show that the tensile stress of the track slab, the vertical displacement of the rail and the track slab and the vertical compressive stress of the mortar layer are all linearly related to the change of the temperature field, and increase with the increase of the temperature load. The stiffness of the fastener mainly affects the deformation of the rail. The damage of the CA mortar layer deteriorates the service performance of the track structure. The stiffness of the CA mortar layer has a great influence on the transverse tensile stress of the track slab. Both the length and width of the void have adverse effects on the rail, track slab and mortar layer. And when the void width reaches 1.5 m, the transverse tensile stress of the track slab reaches the maximum value, while the impact of the void height on the track system is relatively small. The outcomes provide a quantitative basis for establishing scientific maintenance thresholds and optimizing repair strategies, essential for ensuring the long-term serviceability of high-speed railway infrastructure. Full article

The agrarian sector, as the key source of livelihood in Sub-Saharan Africa (SSA), has become highly vulnerable to changes in extension service deliveries. Farmers mainly lack access to technical advice, financial credits, farming inputs and mechanization tools while environmental challenges reinforce the adaptation of sustainable management practices. Therefore, an understanding how multi-functional actor relationships determine agricultural knowledge and information (AKI) sharing is required. This study contributes to filling this gap by characterizing horizontal and vertical interactions. By applying a social network analysis, we mapped actor relations along public–private-community co-operations to provide insights into structural dependencies at different administrative levels. Related to three sites distributed over Burkina Faso and Ghana, local perceptions were collected in stakeholder workshops to generate social network narratives. These narratives were analyzed by various metrics to identify patterns of partnerships and key actors. Study results reveal for Burkina Faso a slight shared network topology, while both sites in Ghana reflect a top-down flow of AKI. The statistical findings indicate that agricultural extension services are primarily delivered to farmers through a few key actors such as NGOs and farm-based organizations/cooperatives. Especially at the community level, the results show many reciprocal links between farmers, business actors and NGOs. This highlights a shift toward a pluralistic agricultural extension service system and underpins the demand for policies to support the long-term viability of these actors, in particular for regions where public extension agents are under-represented. Full article

The Galileo High Accuracy Service (HAS) offers free, real-time precise point positioning (PPP) corrections via Galileo (E6-B) and internet, supporting Galileo (E1, E5a, E5b, E6) and GPS (L1, L5) signals. As of Service Level 1, HAS provides SSR orbit, clock corrections, and biases, achieving decimeter-level accuracy (20 cm horizontal, 40 cm vertical) within 300 s (95th percntile), per the HAS ICD. This study compares HAS products with other analysis centers, verifying declared accuracy. Using a Septentrio Mosaic X5 GNSS receiver, real-time HAS data was collected over three weeks, verified against CODE products, and assessed for PPP performance under various scenarios to evaluate HAS reliability for high-accuracy positioning. The analysis has shown that HAS products provide superior accuracy for Galileo (9.6 cm URE) over GPS (14.0 cm URE) and enable decimeter-level positioning convergence within 3–5 min, although significant outliers were detected in the GPS clock corrections. Full article

Knee disorders are a major indication for musculoskeletal imaging, yet MRI reliability remains constrained by signal nonuniformity, motion artefacts, protocol variability, and reader-dependent effects. This study presents an integrated two-vector framework that couples (i) a fuzzy diagnostic control-risk model with (ii) a quantitative digital-maturity assessment to strengthen MRI-based diagnosis of knee pathology. The vertical vector characterizes organizational readiness through a weighted fuzzy aggregation of six capability agents (technical, information and analytical, mathematical/model, metrological, human resources, and software support). The horizontal vector estimates producer’s and consumer’s risks as misclassification probabilities relative to an acceptance boundary, driven by measurement/interpretation uncertainty, variability of the decision threshold, and the ratio of instrumental to physiological dispersion. Simulation results indicate that error probabilities increase sharply when threshold uncertainty exceeds 20–25% and rise by approximately 15–20% as the standard-deviation ratio approaches unity. To connect diagnostic reliability with downstream mechanics, a FE analysis of the tibial insert in TKA under $F=1150$ N at 0° flexion predicts a peak contact pressure of 85.449 MPa and a maximum UHMWPE von Mises stress of 43.686 MPa, identifying wear-critical contact zones. Overall, the proposed framework provides interpretable quantitative targets for QA, protocol refinement, and resource allocation in radiology services undergoing digital transformation, and offers a reproducible pathway for linking imaging reliability to biomechanical risk. Full article

Accurate braking-distance prediction for heavy-duty multi-axle trucks remains challenging due to the large gross vehicle weight, tandem-axle interactions, and strong transient load transfer during emergency braking. Recent studies on tire–road friction estimation, commercial-vehicle braking control (EBS/AEBS), and weigh-in-motion (WIM) sensing have highlighted that unmeasured vertical-load dynamics and time-varying friction are key sources of prediction uncertainty. To address these limitations, this study proposes an integrated sensing–simulation–AI framework that combines real-time axle-load estimation, full-scale robotic braking tests, fused road-friction sensing, and physics-consistent machine-learning modeling. A micro-electro-mechanical systems (MEMS)-based load-angle sensor was installed on the leaf-spring panel linking tandem axles, enabling the continuous estimation of dynamic vertical loads via a polynomial calibration model. Full-scale on-road braking tests were conducted at 40–60 km/h under systematically varied payloads (0–15.5 t) using an actuator-based braking robot to eliminate driver variability. A forward-looking optical friction module was synchronized with dynamic axle-load estimates and deceleration signals, and additional scenarios generated in a commercial ASM environment expanded the operational domain across a broader range of friction, grade, and loading conditions. A gradient-boosting regression model trained on the hybrid dataset reproduced measured stopping distances with a mean absolute error (MAE) of 1.58 m and a mean absolute percentage error (MAPE) of 2.46%, with most predictions falling within ±5 m across all test conditions. The results indicate that incorporating real-time dynamic axle-load sensing together with fused friction estimation improves braking-distance prediction compared with static-load assumptions and purely kinematic formulations. The proposed load-aware framework provides a scalable basis for advanced driver-assistance functions, autonomous emergency braking for heavy trucks, and infrastructure-integrated freight safety management. All full-scale braking tests were carried out at approximately 60% of the nominal service-brake pressure, representing non-panic but moderately severe braking conditions, and the proposed model is designed to accurately predict the resulting stopping distance under this prescribed braking regime rather than to minimize the absolute stopping distance itself. Full article

Conducting regular verticality inspections for thin tower structures is essential for ensuring structural safety, extending service life, and optimizing operation and maintenance strategies. However, the traditional theodolite inspection method, as a commonly used technique for verticality assessment, still has certain limitations, including strict requirements for station setup, the need for high-altitude contact-based operations, and difficulty in accurately resolving the tilt azimuth of the central axis. More importantly, the conventional method provides insufficient understanding of the overall verticality geometric characteristics of thin tower structures, particularly lacking in systematic approaches for characterizing the axis morphology under non-contact, full three-dimensional (3D) perception conditions. Therefore, this study proposes a refined method for inspecting the verticality of thin tower structures using the Marching Square algorithm. The tower body of a tower crane was selected as the experimental subject. Firstly, ground-based LiDAR was employed to scan and acquire the raw point cloud data of the tower crane. After point cloud registration and denoising, high-precision and valid point cloud data of the tower body were obtained. Secondly, a cross-sectional slicing segmentation strategy was designed for the point cloud of the tower body standard sections, and a slice-polygon-contour extraction method based on the Marching Square algorithm was proposed to extract the contour vertices and compute the coordinates of the contour centroids. Finally, a spatial line-fitting algorithm based on the least squares method was proposed to fit a 3D line to the coordinates of the contour centroids, thereby determining the direction vector of the central axis. The direction vector was then subjected to vector operations with the x-axis and z-axis in the station-center space coordinate system to derive the tilt azimuth and tilt angle of the central axis, thereby providing the verticality inspection results of the tower crane. The experimental results indicate that the four cross-section slicing segmentation schemes designed using the proposed method in this study yielded tower crane verticality values of 2.45‰, 2.35‰, 2.20‰, and 2.18‰. All verticality values meet the verticality requirement of no more than 4‰ specified in GB/T 5031-2019 (Tower Cranes). This verifies that the proposed method is feasible and effective, providing a novel, high-precision, and non-contact inspection method for inspecting the anti-overturning stability of thin tower structures. Full article