Search Results (2,334)

This study demonstrates the positive impact of scatterometer wind-based bogus vortex initialization on forecasts of Typhoon Doksuri (2023). In this scheme, the NCEP analysis vortex in the initial conditions is replaced with a bogus vortex. A regression model links the scatterometer wind-derived 34 kt wind radius with the radius of maximum sea-level pressure gradient, a required parameter in Fujita’s bogus formula. The cyclonic circulation center identified in the scatterometer wind field is designated as the typhoon center. The resulting bogus vortex provides a more realistic representation of the low-level circulation, center location, and intensity. Numerical experiments with the WRF model, configured with two-way nested domains (9–3 km) and 115 vertical levels below the model top at 1 hPa, show that the scatterometer wind-bogus scheme effectively improves the initial vortex position and minimum sea-level pressure, slightly enhances track forecasts, and substantially improves intensity forecasts, particularly during rapid intensification and weakening stages of Typhoon Doksuri over the western North Pacific. Furthermore, comparisons with Himawari-9 AHI infrared observations indicate that forecasts with bogus vortex initialization better reproduce the eye, eyewall, and spiral rainband structures than forecasts without it. These results underscore the value of scatterometer observations for improving typhoon forecasts. Full article

In this paper, the synergistic strengthening mechanism of a new type of prefabricated knee brace to semi-rigid steel frame lateral resistance was experimentally and numerically analyzed. Five full-scale specimens with a control steel frame and four knee-braced configurations were tested under pseudo-static cyclic loading in order to understand the stiffness evolution, failure mode, and energy dissipation characteristics of the specimens. Results show the following: (1) The innovative integrated knee braces increase initial lateral stiffness and yield capacity by 184–242% and 91–154% compared to conventional semi-rigid frames with acceptable ductility; (2) Three different failure modes coupled brace-joint yielding (Type I), brace dominated instability (Type II) and beam buckling brace connections (Type III) are identified; (3) Finite element simulations using ABAQUS with isotropic/kinetic hardening models show good agreement with experiments for their hysteretic responses confirming In particular the ultimate failure location is identified at the lateral screw holes of beam flanges located near brace supports where the local stress is greater than 1.8f_y. The study further proposes a BIM-integrated design workflow. These results give a theoretical basis and some practical recommendations for the application of knee-braced semi-rigid systems in earthquake-resistant steel buildings. Full article

Within the scope of the study, the parameters of friction pendulum-type (FPS) isolators used or planned to be used in different projects were evaluated specifically for the project and its location. The evaluations were conducted within a performance-based seismic design framework using displacement, re-centering, and force-based operability criteria, as implemented through the Türkiye Building Earthquake Code (TBDY) 2018. The friction coefficient and radius of curvature were evaluated, along with the lower and upper limit specifications determined according to TBDY 2018. The planned control points were the period of the isolator system, the isolator re-centering control, and the ratio of the base shear force to the structure weight. Within the scope of the study, isolator groups with different axial load values and different spectra were evaluated. A dataset was prepared by using the parameters obtained from the re-centering, period, and shear force analyses to determine the conditions in which the isolator continued to operate and those in which conditions prevented its operation. Machine learning models were developed to identify FPS isolator configurations that do not satisfy the code-based operability criteria, based on isolator properties, spectral acceleration coefficients corresponding to different earthquake levels, mean dead and live loads, and the number of isolators. The resulting Bagging model predicted an isolator’s operability with a high degree of accuracy, reaching 96%. Full article

Accurately estimating the absolute position of robots under external loads is challenging due to nonlinear dynamics, posture-dependent manipulability, and structural sensitivities. This study investigates a data-driven approach for absolute position prediction of a 2-DOF planar delta robot by learning time-series force signals generated during manipulability-driven free motion. Constant torques of opposite directions were applied to the robot without any position or trajectory control, allowing the mechanism to move naturally according to its configuration-dependent manipulability. Reaction forces measured at the end-effector and relative encoder variations were collected across a grid of workspace locations and used to construct a 12-channel time-series input. A hybrid deep learning architecture combining 1D convolutional layers and a bidirectional LSTM network was trained to regress the robot’s absolute X–Y position. Experimental results demonstrate that the predicted trajectories closely match the measured paths in the workspace, yielding overall RMSE values of 3.81 mm(X) and 2.94 mm(Y). Statistical evaluation using RMSE shows that approximately 83.73% of all test sequences achieve an error below 5 mm. The findings confirm that LSTM models can effectively learn posture-dependent dynamic behavior and force-manipulability relationships. Full article

On 2021, in the intensive care unit of a County Emergency Hospital where oxygen therapy treatment was applied to COVID patients, located in the municipality of Ploiesti, Prahova County, a fire occurred that resulted in the destruction by burning of the ICU room, the death of two people, and the injury of a medical professional. In order to elucidate the accelerating causes of the combustion phenomenon of materials in the ICU room, a combustion stand was designed whose atmosphere can be controlled in terms of achieving high oxygen concentrations of 40% vol., in accordance with the treatment schemes applied to the patients and with the configuration of the room and the frequency of use of the access door. In this experimental stand, a series of combustion tests of flexible polyurethane foam samples were performed, which highlighted the acceleration of combustion and the complete consumption of the mass. The purpose of this work is to explain the rapidity of the fire in a hospital ward, both with experimental methods and with the help of FDS. Full article

Wind and sand pose a significant threat to operational safety along the route of the Golmud-Korla Railway. To combat the adverse effects of these hazards, numerous sand retaining dikes and sand intercepting ditches have been constructed along the railway corridor. However, the deposition and erosion mechanisms of sand particles in close proximity to these structures have yet to be fully investigated. Therefore, it uses numerical simulations to study the structure of the wind-sand flow field around the sand retaining dike and the sand intercepting ditch, under varying spacing conditions, with an analysis of sand deposition and erosion laws. The results indicate that vortices form on the leeward side and within the sand intercepting ditch. Among these, the vortex flow occurring on the downstream side of the sand retaining dike exhibits a flow reattachment phenomenon at specific locations (i.e., attachment points). As the spacing increases, clockwise vortices Rd1 and Rd2, develop on the leeward side and inside the ditch, respectively. The leeward side of the spacing range of 0–8H is characterized by reverse erosion and deposition processes. When the spacing is 10–15H, a forward erosion zone emerges and expands progressively with the increase in spacing. When the spacing exceeds 10H, i.e., as the sand intercepting ditch is positioned downstream of the vortex reattachment point of the sand retaining dike, its sand interception efficiency is markedly enhanced. It not only elucidates the wind-sand flow and deposition patterns surrounding sand retaining dike and sand intercepting ditch under various spacing configurations but also offers valuable insights for the future design and implementation of protective structures for railways in wind-sand affected regions. Full article

The deployment of wireless seismic nodal systems necessitates the efficient identification of optimal locations for sensor installation, considering factors such as ground stability and the absence of interference. Semantic segmentation of satellite imagery has advanced significantly, and its application to this specific task remains unexplored. This work presents a baseline empirical evaluation of the U-Net architecture for the semantic segmentation of surfaces applicable for seismic sensor installation. We utilize a novel dataset of Sentinel-2 multispectral images, specifically labeled for this purpose. The study investigates the impact of pretrained encoders (EfficientNetB2, Cross-Stage Partial Darknet53—CSPDarknet53, and Multi-Axis Vision Transformer—MAxViT), different combinations of Sentinel-2 spectral bands (Red, Green, Blue (RGB), RGB+Near Infrared (NIR), 10-bands with 10 and 20 m/pix spatial resolution, full 13-band), and a technique for improving small object segmentation by modifying the input convolutional layer stride. Experimental results demonstrate that the CSPDarknet53 encoder generally outperforms the others (IoU = 0.534, Precision = 0.716, Recall = 0.635). The combination of RGB and Near-Infrared bands (10 m/pixel resolution) yielded the most robust performance across most configurations. Reducing the input stride from 2 to 1 proved beneficial for segmenting small linear objects like roads. The findings establish a baseline for this novel task and provide practical insights for optimizing deep learning models in the context of automated seismic nodal network installation planning. Full article

This paper presents an extensive experimental study on the hydrodynamic behavior of vertical cylinders representative of the structural elements of offshore floating photovoltaic (OFPV) platforms under both wave and steady-current conditions. The objectives are to determine reliable hydrodynamic coefficients for Morison-type formulations and to analyze the wake effects between cylinders for modular floating configurations. Tests under regular waves are conducted in a 25 m long wave flume at the Energy Engineering Department of the Bilbao School of Engineering. The obtained inertia and drag coefficients follow the expected trends for a wide range of Keulegan–Carpenter (KC) numbers, aligning well with classical experimental studies. Steady-current experiments are conducted in the same flume using a towing tank method. Again, the obtained drag coefficients align well with previous studies. As for the wake provoked by the first cylinder on the second cylinder located downstream at one of four different distances, in the wave cases, the wake attenuation is minimal and rapid recovery of the flow is observed for a wide range of KC values, while in the steady-current cases, the wake is stronger and affects the forces acting on the second cylinder. Full article

The worldwide transition to renewable energy systems is motivated by diminishing fossil fuel availability and the intensifying consequences of climate change. This study presents a Mixed-Integer Linear Programming (MILP) model for designing and optimising the bio-fuel and electricity supply chain in Colombia, using sugarcane as the main feedstock and integrating microalgae cultivation in vinasse. Six alternative biorefinery configurations and four microalgae conversion pathways were evaluated to inform strategic planning. The optimisation results indicate that microalgae achieve higher energy yields per unit of land than sugarcane. Ethanol production from sugarcane could meet all of Colombia’s gasoline demand, while diesel and sustainable aviation fuel derived from microalgae could supply around 9% and 16%, respectively, of the country’s consumption. Further-more, pelletised bagasse emerges as a viable alternative to replace part of the coal used in thermoelectric plants. From an economic perspective, all scenarios achieve a positive net present value, confirming their profitability. Sensitivity analysis highlights the critical factors influencing the deployment of distilleries as ethanol price, algae productivity, and sugarcane cost. Furthermore, transportation costs play a decisive role in the geographic location of microalgae-based facilities and the distribution of their products. Full article

Background/Objectives: To investigate whether healthcare workers present different characteristics of musculoskeletal symptoms depending on the level of complexity in which these professionals work in the Brazilian Unified Health System. Methods: Health professionals were recruited from 24 health institutions, using probabilistic stratified sampling. Data were collected using the Nordic Musculoskeletal Questionnaire. We obtained the questionnaire scores through exploratory factor analysis. Based on the scores, individuals could be grouped into symptom configurations using a non-hierarchical clustering algorithm (K-means). Results: The created groups differed in symptom intensity and location but did not differ by level of work complexity, as defined by Brazil’s healthcare sector division. Therefore, regardless of the level of complexity at which professionals perform their activities in the Brazilian Unified Health System, the burden of musculoskeletal symptoms related to the factor under analysis is similar. We developed distinct symptom profiles for each group, accompanied by targeted occupational intervention recommendations. Conclusions: This study challenges conventional assumptions by demonstrating that musculoskeletal symptom burden remains consistent across varying levels of work complexity, while providing a practical framework for developing targeted interventions based on symptom profiles. Full article

This study proposes an arc-circular lightweight honeycomb structure. Three different configurations of honeycomb specimens, namely arched honeycombs (AHs), arc-circular honeycombs with a first-order hierarchical configuration (ACH-1), and arc-circular honeycombs with a second-order hierarchical configuration (ACH-2), are prepared using metal additive manufacturing technology, and quasi-static compression tests are conducted. The results show that all configurations exhibit significant multi-stage load responses, with the ACH-2 configuration, which incorporates smaller sub-cells, demonstrating higher compressive stress and energy absorption potential. The specific energy absorption (SEA) of ACH-2 is enhanced by 210% compared to the baseline AH. The effectiveness of the finite element analysis is validated against experimental results. Further parametric analysis of the wall thickness parameters, cell number, and macroscopic dimensions of ACH-2 reveals significant variations in how wall thickness at different local locations affects the mechanical properties. Additionally, although increasing the macroscopic dimension significantly enhances the energy absorption capacity, the effect of increasing the number of cells on the overall energy absorption performance at the same relative density is limited. Finally, a reverse design framework for ACH-2 with multi-stage plateau stress is established. The effectiveness of this performance design framework is validated through experiments, providing a feasible technical approach for the design of honeycomb structures with multi-stage plateau stress characteristics. Full article

This paper presents a novel method for the precise localization of remote radio-signal sources using a formation of unmanned aerial vehicles (UAVs). The approach is based on time-difference-of-arrival (TDoA) measurements and the geometric analysis of hyperbolas formed by pairs of UAVs. By studying the asymptotic intersections of these hyperbolas, the method ensures unique determination of the source position, even in the presence of multiple intersection points. Theoretical analysis confirms that the correct intersection point is located at a significantly larger distance from the UAV formation center compared to spurious intersections, providing a rigorous criterion for resolving localization ambiguity. The proposed framework also addresses secure inter-UAV communication via optical-fiber links and supports expansion of UAV groups with directional antennas and low-power signal relays. Additionally, the study discusses practical UAV configurations, including hybrid propulsion and jet-assisted kamikaze platforms, demonstrating the applicability of the method in contested environments. The results indicate that this approach provides a robust mathematical basis for unambiguous emitter localization and enables scalable, secure, and resilient multi-UAV systems, with potential applications in electronic-warfare scenarios, surveillance, and tactical operations. Full article

The stability of the Fe/Zn interface during the hot-dip galvanizing process critically influences the coating’s quality and service performance. In this investigation, the impact of silicon atom positioning on the stability, bonding strength, and electronic structure of the Fe/Zn interface was systematically examined through first-principles calculations grounded in density functional theory, employing the CASTEP software and the GGA-PBE functional. By constructing the FeSi and ZnSi disordered solid solution models, low-energy stable configurations were selected, and 24 ZnSi/FeSi interface models (misfit < 5%) were further established. The interfacial adhesion work, interfacial energy, and electronic structure parameters were systematically calculated. The findings indicate that the position of Si atoms significantly affects interface stability, with Si atoms located on the Zn side exerting a more pronounced influence than those on the Fe side. The interfacial stability is optimal when the Si on the Fe side is far away from the interface and the Si on the Zn side is located at the interface. Notably, the S11Z32 model exhibited the highest adhesion work (4.763 J/m²) and the lowest interface energy (0.022 J/m²). This study elucidates the regulatory role of Si atoms in stabilizing the Fe/Zn interface and provides a theoretical foundation for optimizing the hot-dip galvanizing process and guiding the design of novel materials. Full article

The stability of underground excavations is a critical factor in the safety and efficiency of mining operations, particularly in structurally complex and geomechanically variable rock mass. This study presents a comparative evaluation of empirical and numerical methods for the design of tunnel support systems in the Gilar underground mine, located in the Gedabek Contract Area of Azerbaijan. To validate and optimize the empirical Q-system-based support designs, Finite Element Method (FEM) simulations were conducted using RS2 software. These simulations enabled the modeling of stress distribution, deformation, and support–rock interaction under in situ conditions. Critical sections along the main ramp were analyzed in detail to determine safety factors during excavation and post-support installation. The study reveals that, although the Q-system provides a practical and time-efficient method for support selection, it may underestimate the reinforcement required in highly fractured or low-strength zones. Numerical modeling proved to be essential in identifying zones with low strength factors and in optimizing support configurations by adjusting rockbolt spacing and shotcrete thickness. The hybrid approach adopted in this study—empirical classification followed by numerical verification and optimization—demonstrated significant improvements in long-term tunnel stability. This research highlights the importance of integrating empirical and numerical approaches for robust ground support design in underground mining. The proposed methodology not only enhances the accuracy of support recommendations but also provides a more reliable basis for decision-making in complex geological settings. The results are particularly relevant for deep and geologically active mines requiring long-term stability of access tunnels. Full article

Over the last decade, numerical simulations and experiments have confirmed the existence of a novel class of vibrationally excited solid-particle attractors in cubic cavities containing a fluid in non-isothermal conditions. The diversity of emerging particle structures, in both morphology and multiplicity, depends strongly on the uni- or multi-directional nature of the imposed temperature gradients. The present study seeks to broaden this theoretical framework by further increasing the complexity of the thermal “information” coded along the external boundary of the fluid container. In particular, in place of the thermal inhomogeneities located in the center of otherwise uniformly cooled or heated walls, here, a cubic cavity with temperature boundary conditions satisfying the D₂h (in Schoenflies notation) or “mmm” (in Hermann–Mauguin notation) symmetry is considered. This configuration, equivalent to a bipartite vertex coloring of a cube leading to a total of 24 thermally controlled planar surfaces, possesses three mutually perpendicular twofold rotation axes and inversion symmetry through the cube’s center. To reduce the problem complexity by suppressing potential asymmetries due to fluid-dynamic instabilities of inertial nature, the numerical analysis is carried out under the assumption of dilute particle suspension and one-way solid–liquid phase coupling. The results show that a kaleidoscope of new particle structures is enabled, whose main distinguishing mark is the essentially one-dimensional (filamentary) nature. These show up as physically disjoint or intertwined particle circuits in striking contrast to the single-curvature or double-curvature spatially extended accumulation surfaces reported in earlier investigations. Full article