Search Results (391)

This paper proposes a method for reducing the initial azimuth estimation time of a north-finding system employing low-cost sensors and a compact 3-axis turntable. The system is capable of operating in non-horizontal environments, magnetically disturbed environments, and environments where Global Navigation Satellite System (GNSS) signals are unavailable. Detection of due north without prior azimuth information was evaluated through indoor experiments under the aforementioned conditions. During each rotation, the compact 3-axis turntable was kept horizontal and the acceleration and angular velocity were measured in 16 directions at 22.5${}^{\circ }$ intervals. By including the final position coinciding with the initial one, a total of 17 measurement points were obtained per lap. This process was repeated for 77 laps. For statistical evaluation, 5000 bootstrap replications were generated. Detection of due north was then performed using these datasets and the relationship between the number of laps and the estimation error was statistically analyzed. Consequently, it was confirmed that the root mean square (RMS) error becomes less than 1${}^{\circ }$ after ten laps, corresponding to a data acquisition time of approximately 1.3 h. Compared to our previous study, the required estimation time is reduced by approximately 2 h. Full article

For single-motor Formula Student Electric China (FSEC) race cars, current powertrain design methodologies commonly suffer from the disconnection among parameter matching, dynamic simulation, and structural optimization: gear ratio selection is mostly based on static theoretical calculations, lightweight design does not incorporate full-vehicle dynamic load spectra constraints, and the simulation toolchain (CarSim 2024, OptimumLap version 5, ANSYS 2022) lacks a standardized data closed-loop, leading to prolonged iteration cycles and unquantifiable reliability. To address these issues, this paper takes the Nanning University electric formula race car E66 as the research object and proposes a three-phase integrated design framework of “requirement-driven, multi-simulation co-validation, and lightweight iteration.” The study includes three core contributions: (1) establishing a powertrain parameter matching method based on power boundary calculations and multi-dimensional selection criteria, achieving the integrated selection of the Emrax 228 motor (power density 9.2 kW/kg, Emrax d.o.o., Kamnik, Slovenia) and the Unitek-D3 controller through comparative analysis with the JJE motor (5.7 kW/kg, Jing-Jin Electric Technologies Co., Ltd., Beijing, China); (2) constructing a co-simulation mechanism combining OptimumLap version 5 and CarSim 2024, completing the closed-loop optimization of the gear ratio from the range of 1.6–4.3 to the optimal value of 3.9 under the Hefei NIO track operating conditions, with a 75 m acceleration simulation result of 4.4 s and an endurance lap time of 86 s; (3) introducing ANSYS 2022 topology optimization technology to perform two-iteration lightweight design on the 7075 aluminum alloy main sprocket, achieving 35% mass reduction and 40% volume reduction while maintaining the maximum principal stress at 73.16 MPa (below yield strength). The expected outcome is a replicable development paradigm for single-motor powertrain systems, transforming drivetrain matching from experience-driven to simulation-driven, providing reliable data boundaries for physical vehicle commissioning, and effectively reducing trial-and-error costs. Full article

Accurate short-term precipitation nowcasting remains challenging in complex terrain regions, where storm displacement, evolution, and orographic enhancement strongly affect precipitation distribution. This study evaluates three precipitation nowcasting schemes initialized from LAPS analysis fields: first-order advection (Control), advection–diffusion (AD), and advection–diffusion coupled with the linear theory of orographic precipitation (ADLOP). The schemes are tested over the Attica region of Greece using three high-impact precipitation events representing different synoptic weather regimes and verified against high-resolution weather radar observations. Forecast performance is assessed using continuous, categorical, and neighborhood-based spatial verification metrics. Results show that the Control performs competitively for light precipitation and at larger neighborhood sizes in localized events. The inclusion of diffusion in the AD scheme generally reduces random errors. In this limited three-case sample, aggregated results show that ADLOP reduces systematic bias, with reductions reaching approximately 33% at longer lead times and showing higher detection scores. However, its added value is strongly dependent on the terrain-influenced precipitation regime and may be accompanied by increased error at longer lead times. Overall, the benefits of incorporating diffusion and simplified linear orographic forcing depend on precipitation regime, lead time, and verification metric; therefore, the results should be interpreted as diagnostic case-study evidence rather than as a general assessment of ADLOP performance. Full article

This study proposes a reduced-complexity nonlinear model predictive control (NMPC) framework for high-performance path tracking of a four-wheel-drive (4WD) autonomous vehicle. A 4WD sports car equipped with four independent wheel motors is used as the test vehicle. Although the vehicle has four motors, the proposed NMPC directly optimizes the front-wheel steering command and the rear-left and rear-right wheel torque commands, while the front-wheel torques are generated using a gain-based virtual 4WD distribution law. Trajectory optimization (TRO) is performed offline to generate the reference racing line and velocity profile, while the online NMPC controller tracks the optimized reference trajectory using the front-wheel steering command and the rear-left and rear-right wheel torque commands as control inputs. This structure reduces the control complexity while maintaining the ability to improve traction utilization and yaw response. Under the investigated simulation conditions on the Shanghai International Circuit, the proposed reduced-dimensional NMPC with rear-dominant virtual 4WD torque distribution reduces the simulated lap time while maintaining bounded path-tracking errors and satisfying the track-boundary constraints. As the torque distribution gain $K_r$ increases from 0 to 0.5, the lap time is reduced by approximately 10.3% (from 182.08 s to 163.30 s), while the maximum lateral tracking error remains below 0.33 m and the maximum heading-angle error remains below 2.95 deg for all stable cases. However, further increasing $K_r$ beyond 0.5 leads to degraded tracking performance or loss of stable path following because excessive front-wheel longitudinal force reduces the available lateral tire force for steering. These results indicate that an appropriate torque distribution gain can improve corner-exit acceleration and overall lap-time performance, whereas excessive front torque assistance may degrade tracking accuracy and vehicle stability. Full article

Introduction: Cross-country running performance is influenced by a complex interaction of physiological, biomechanical, and morphological factors. Recently, infrared thermography (IRT) has emerged as a non-invasive method to assess skin temperature (TSK) and detect potential asymmetries associated with neuromuscular status, fatigue, and injury risk. However, limited evidence exists regarding its relationship with competitive performance in endurance athletes. Methods: An observational study, conducted with STROBE guidelines, included 24 national-level cross-country athletes competing in the 2026 Spanish National Championships. Pre-competition assessments comprised bilateral thermographic analysis of the anterior and posterior thigh and leg regions, alongside some anthropometric measurements (thigh and leg circumferences) following ISAK standards. Performance was evaluated using official race times. Independent t-tests and linear regression models were applied to assess sex differences and associations between variables. Results: No significant sex differences were observed in thigh circumference, whereas males presented significantly greater leg volume (right p = 0.020; left p = 0.042). Thermographic analysis showed no differences in bilateral thermal asymmetry (ΔTSK) between sex quadriceps (p = 0.077), hamstrings (p = 0.695), shins (p = 0.510), and calves (p = 0.194); however, higher absolute temperatures were observed in males in specific thigh regions (right anterior p = 0.039, right posterior p = 0.015, left posterior p = 0.020). Males achieved significantly faster race times during the first four laps, t1 (p ≤ 0.001), t2 (p = 0.002), t3 (p = 0.002), and t4 (p = 0.008), but there was no difference in the fifth lap, t5 (p = 0.179). Statistically significant correlations were observed between temperature differences in the various anatomical regions and competition results during the first four laps, in three of the four regions analyzed (anterior thigh p = 0.035, posterior thigh p = 0.010, anterior leg p ≤ 0.001). Conclusions: Pre-competition thermal asymmetry of the lower limbs appears to be negatively associated with endurance performance, potentially reflecting suboptimal neuromuscular status or incomplete recovery. IRT represents a practical and sensitive tool for monitoring athletes’ physiological readiness. Full article

Background: Efficient and safe instrument exchange remains an important challenge in robot-assisted laparoscopic surgery (RALS). Current workflows require human assistance, increasing staff workload and contamination risk. The modular design of the AdLap robotic laparoscopic instruments enables automated exchange of instrument shafts. This study presents the development and validation of the Instrument Carousel Exchange System (ICES). Methods: An automatic ICES was developed for the AdLap robotic surgery platform of the Delft University of Technology. The prototype was designed to hold six Shaft-Actuated Tip-Articulating (SATA) modular instrument shafts (SATA instrument line, SATA Medical, Amsterdam, The Netherlands) and focused on compactness, robustness, modularity, and rapid disassembly for cleaning and sterilization. System performance was evaluated using repeated autonomous instrument exchange cycles without user interaction. Reliability, alignment tolerance, safety, and exchange duration were assessed. Results: The ICES prototype was successfully designed, manufactured, and tested. Repeated functional testing demonstrated reliable autonomous instrument shaft exchange without human intervention. The system tolerated minor alignment deviations while maintaining stable and safe operation. The mean time for a complete instrument shaft exchange was 84 s (SD = 10 s). The modular architecture allowed straightforward disassembly and maintenance while preserving structural integrity and compact design. Conclusions: The developed ICES represents a substantial step toward fully automated modular instrument handling in RALS. Automated instrument exchange may reduce staff workload and minimize contamination risk during procedures. Future work will focus on improving automation speed, alignment efficiency, and autonomous reinsertion of the instrument shaft through the trocar to further enhance clinical applicability. Full article

Optimizing a high-fidelity GT3 race car setup is a serious dimensional, nonlinear problem in which small changes to mechanical parameters can affect lap time, handling balance, and vehicle stability. Existing motorsport AI studies largely emphasize racing line optimization, autonomous control, race strategy, or offline vehicle dynamics estimation, while the mechanical setup layer is often treated as fixed or tuned manually. This paper presents a staged simulator-based setup optimization framework augmented with setup-conditioned telemetry response modeling. Using the virtual BMW Z4 GT3 vehicle model implemented within the Assetto Corsa (v1.16.4) simulation environment as a controlled GT3 test platform, 134 setup configurations were evaluated at the Red Bull Ring under a fixed simulator AI driving policy. The staged search improved the best lap time from 91.430 s to 91.040 s, corresponding to a 0.390 s reduction. To move beyond a single aggregate lap-time claim, the full telemetry corpus was processed into 585 stable laps and 29,250 track-position segment samples. A setup-conditioned LightGBM model was trained to predict segment time and local vehicle response metrics from setup parameters and segment context, using five-fold GroupKFold validation by telemetry file to avoid random row leakage. The setup-conditioned segment model reconstructed held-out file-level lap time with 0.223 s mean absolute error and Spearman correlation of 0.961, outperforming a setup-only model at 0.288 s, a track-only segment model at 0.687 s, and a shuffled-setup placebo at 0.776 s. The same setup-conditioned model also improved the prediction of segment-level speed, slip angle, tire load spread, rake (defined here as rear-front ride height difference), tire temperature, yaw response, and lateral acceleration. These results show that high-frequency telemetry can support not only staged setup search, but also quantifiable learning of where and how setup changes alter vehicle behavior around the lap. Full article

This study investigates the effect of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) passivation time on the adhesive bonding performance of aluminum substrates using an epoxy adhesive. Alkaline etching was used to generate a chemically active surface prior to silane treatment. GPTMS passivation led to the formation of silane-derived species on the aluminum surface. SEM/EDS indicated the presence of silicon-containing species. ATR-FTIR analysis showed the progressive development of siloxane (Si–O–Si) bonding with increasing passivation time. The mechanical performance of the bonded joints was evaluated using single-lap shear (SLS) testing. The SLS strength increased from 4.3 ± 1.0 MPa in the as-received substrate to 5.5 ± 1.2 MPa after etching. After GPTMS passivation, the strength reached a plateau beginning at 3 min, with a value of 13.5 ± 1.8 MPa. This corresponds to increases of 28% after etching and 223% after GPTMS passivation. This plateau behavior indicates a self-limiting interfacial process. The improved adhesion is attributed to siloxane formation within the silane layer and the chemical compatibility between GPTMS and the epoxy adhesive. A first-order conceptual semi-quantitative model was developed to relate silane surface coverage to adhesion strength. The results demonstrate that adhesion depends on both surface coverage and the development of siloxane bonding within the silane layer. This study highlights the importance of controlled passivation time in improving adhesion performance under the present experimental conditions. Full article

Real-time telemetry is essential for performance optimization and safety in motorcycle racing, yet commercial solutions remain proprietary, expensive, and poorly extensible. This paper presents the design, implementation, and experimental evaluation of an open-architecture embedded telemetry unit built around the STM32H745 dual-core microcontroller. The system integrates a u-blox ZED-F9P RTK-GNSS receiver, a Bosch BNO085 9-DoF IMU with on-chip sensor fusion, a CAN-FD interface for powertrain data acquisition, and a SIM7600E-H 4G/LTE module for real-time remote streaming, all housed in a 3D-printed vibration-resistant enclosure. The firmware employs deterministic dual-core task partitioning: the Cortex-M7 core handles sensor fusion and CAN-FD at high frequency, while the Cortex-M4 core manages 4G communication and microSD logging. We explicitly delimit the scope of the evidence presented: CAN-FD powertrain acquisition and end-to-end operational reliability are experimentally validated on real circuit data spanning four campaigns, over 100 laps, and 5.8 h of logging—with sustained acquisition of 13 powertrain channels at speeds up to 185 km/h and zero system resets or data-integrity errors. In contrast, RTK positioning accuracy (2.5 cm CEP), sensor-fusion latency (sub-2 ms at the 99th percentile), 4G-uplink reliability, and thermal margins are characterized through manufacturer specifications, Monte Carlo simulation, and analytical models, with a fully instrumented end-to-end measurement campaign identified as the immediate next step. The 50 Hz effective positioning rate combines 25 Hz GNSS with IMU interpolation. With a bill of materials of approximately EUR 265, the platform offers an order-of-magnitude cost reduction over commercial alternatives while providing full openness and extensibility for distributed intelligence applications. Full article

Background/Objectives: Weaning failure from mechanical ventilation affects 10–20% of critically ill patients. Cardiovascular dysfunction—particularly diastolic dysfunction with elevated left atrial pressure (LAP)—underlies up to 50–60% of failed spontaneous breathing trials (SBTs) and frequently remains undetected without targeted echocardiographic assessment. This narrative review synthesises current evidence on the echocardiographic evaluation of weaning failure, with emphasis on LAP estimation, right ventricular (RV) dysfunction, and the integration of lung and diaphragm ultrasound. Methods: A structured literature search of PubMed/MEDLINE and EMBASE was performed for publications from January 2000 to April 2026, supplemented by hand-searching of reference lists and current society guidelines. This article is reported as a narrative review; no formal systematic review protocol was registered. A qualitative synthesis emphasising pathophysiological mechanisms, echocardiographic phenotypes, and clinical applicability was performed. Results: Positive pressure ventilation with PEEP provides active LV afterload reduction; extubation abruptly removes this unloading and may precipitate acute filling pressure elevation in vulnerable patients. Multiparametric echocardiographic LAP assessment—integrating the E/e’ ratio, deceleration time, and pulmonary vein flow—supports pre-extubation risk stratification. The dynamic PEEP reduction test, although not yet standardised or multicentre-validated, may identify patients with load-dependent cardiac decompensation before extubation. RV dysfunction is present in 20–50% of ventilated patients and worsens weaning outcomes through ventricular interdependence. Complementary lung ultrasound B-line quantification and diaphragm thickening fraction assessment together support a phenotype-specific diagnostic approach. Conclusions: A structured multimodal ultrasound framework integrating echocardiography, lung ultrasound, and diaphragm ultrasound may support identification and targeted treatment of the dominant mechanism of weaning failure before extubation. Prospective multicentre validation of the integrated protocol as a whole remains a priority research need. Full article

Adhesive joints are widely used in structural applications. However, they are susceptible to degradation under service loads and adverse environmental conditions, leading to eventual catastrophic failure. Thus, the advancement of monitoring tools that can deliver real-time data on the deterioration of adhesive joints is crucial for enhancing the reliability of structures. This study investigated the feasibility of using electrical impedance responses to monitor integrity degradation under tensile and fatigue loading in single-lap adhesive joints in aluminum alloy and carbon fiber-reinforced polymer (CFRP) specimens. Previous works on electrical impedance monitoring of adhesive joint integrity invariably employed conductive adhesives. Theoretical considerations based on the concept of a capacitive system indicate that electrical impedance monitoring may still be feasible even if the joint is non-conductive. This has important implications as it suggests that the structural health of many existing ordinary adhesive joints may be amenable to impedance-based monitoring. To test this possibility, neat epoxy adhesive joints without the addition of conductive constituents were fabricated with aluminum and composite adherends. The specimens were subjected to tensile and fatigue degradation while the impedance responses under different excitation frequencies were monitored. The results showed that impedance monitoring is insensitive for detecting damage during tensile failure because the onset of debonding that produces a detectable impedance change occurs too close to the unstable final failure. For fatigue cycling, debonding developed at an early stage and evolved in a stable manner, and the impedance gradually increased with the number of fatigue cycles, reflecting the development of fatigue damage. These findings indicate that impedance-based monitoring on non-conductive adhesive joints has strong potential for tracking structural integrity degradation, particularly for fatigue loading. Full article

Lithium niobate (LiNbO₃, LN) single crystal is widely used in optoelectronic fields due to its excellent performance. However, its low hardness, high brittleness, and strong anisotropy lead to low processing efficiency and poor surface quality. Hydrophilic fixed abrasive lapping technology was adopted for the thinning of LN wafers in this research. The effects of lapping pressure on the thinning process were investigated comprehensively in terms of the material removal rate (MRR), surface quality, and subsurface damage (SSD). The results show that lapping pressure exerted a significant influence on the machining performance. High pressure contributed to improving the MRR but aggravated surface roughness (Ra) and SSD. With low pressure, material removal was dominated by ductile removal machining, with fine scratches as the main damage form, which was favorable for obtaining low Ra and low SSD. The root mean square (RMS) of the acoustic emission (AE) signal rose with the increase in pressure, increasing slowly in the ductile removal regime and rising abnormally in the brittle removal regime. It was positively correlated with the MRR and SSD and can be used as an in situ monitoring indicator. After a comprehensive comparison of five groups of experiments, 7 kPa was determined to be the optimal lapping pressure, with the following corresponding parameters: wafer speed: 100 rpm; lapping table speed: 80 rpm; slurry flow rate: 100 mL/min; eccentricity: 60 mm; soft lapping pad; abrasive mass fraction: 50%; and lapping time: 5 min. Under these conditions, the Ra value was approximately 30 nm, the MRR exceeded 1 μm/min, and SSD was as low as 3.3 μm, realizing the synergistic optimization of high-efficiency and low-damage machining. It provides a favorable foundation for the subsequent processing of LN substrates, such as ultra-precision polishing, thin-film transfer, and bonding. Full article

This study investigates the mechanical performance of resistance spot-welded titanium lap joints made of Grade 1 and Grade 5 alloys. Experimental tests were combined with artificial neural network modeling to predict joint load-bearing capacity based on welding current and welding time. Three models were developed for Grade 1/Grade 1, Grade 1/Grade 5, and Grade 5/Grade 5 joints. The mixed Grade 1/Grade 5 joint achieved the highest predictive accuracy, with an R² value of 0.9289. Statistical evaluation confirmed high model reliability, with mean relative errors between four and six percent. The most accurate model was optimized using a genetic algorithm. The algorithm identified an optimal parameter set consisting of a welding current of 2.89 kA and a welding time of five pulses. This configuration produced a predicted load-bearing capacity of 3.2 kN, which meets the required threshold of three kilonewtons. Contour maps showed that the optimal point lies near the boundary of the high-strength region and corresponds to the lowest welding current and shortest welding time that still ensure sufficient joint quality. The results demonstrate that combining neural network modeling with evolutionary optimization is an effective approach for designing efficient welding processes for dissimilar titanium joints. Full article

This study investigates how the adhesive curing state before riveting influences material flow during riveting, joint formation, and the mechanical performance of CFRP/aluminum hybrid joints. Hybrid joints were fabricated in a single-lap configuration using electromagnetic self-piercing riveting (E-SPR) at curing times of 0, 20, 40, 60, and 80 min, and the adhesive distribution, joint geometry, load–displacement behavior, energy absorption, and failure mode were examined. As curing time increased, adhesive squeeze-out decreased and adhesive displacement during riveting was progressively restricted, leaving more adhesive near the contact point. Consequently, the head height increased from 0.12 to 0.21 mm, whereas the interlock distance decreased from 0.67 to 0.54 mm. In the bonded region, the peak load increased with curing time, and a peak load of 11.15 kN was observed at 40 min, indicating an increased contribution of the adhesive layer. In contrast, the load in the riveted region decreased at 60 and 80 min because the increased resistance of the adhesive interlayer limited the rivet deformation and mechanical interlocking. A maximum energy absorption of 32.13 J was observed at 40 min, where the joint exhibited relative contributions of the adhesive and the rivet. Failure analysis showed bearing failure at 40 min, whereas rivet pull-out was observed at 60 min, consistent with the curing-dependent changes in joint formation. These results indicate that curing-induced changes in adhesive behavior govern the interaction between adhesive flow and rivet deformation, thereby influencing joint formation and mechanical performance. Full article

Background: Contemporary pediatric oncology confronts medical staff with challenges that are not only clinical but also ethical and existential in nature. The aim of this study was to identify the cognitive and affective factors associated with medical professionals’ attitudes toward fertility preservation procedures (oncofertility) in pediatric patients. In particular, the association of “existential vacuum” (lack of life goals, sense of meaninglessness), value systems, and religiosity on the level of competence and emotional acceptance of these procedures was examined. Methods: A cross-sectional observational study was conducted between January and September 2024 in pediatric oncology centers in Poland (Gdańsk, Lublin, Łódź, and Poznań). The study group consisted of 62 medical professionals (62.9% physicians and 37.1% nurses) selected using purposive sampling. The research protocol included an Author-Designed Questionnaire, the Scheler Value Scale (SVS), the Life Attitude Profile—Revised (LAP-R), and the Centrality of Religiosity Scale (CRS-15). Statistical analyses comprised Pearson’s r correlations, multiple regression analysis, and cluster analysis using the k-means method. Results: Participants demonstrated a moderate level of substantive competence in oncofertility (M = 2.31 on a 5-point scale). Regression analysis revealed that “existential vacuum” was the strongest negative predictor of competence (B = −0.34; p = 0.001), which was found to be a significant negative correlate of professional development in this area. In the affective domain, a pronounced normative conflict was observed: religiosity was negatively correlated with emotional acceptance of the procedures (r = −0.42; p < 0.001), indicating tension between medical imperatives and worldview-based beliefs. At the same time, the regression model showed that internalized religiosity and moral values might theoretically function as an “axiological buffer”; however, due to the severe psychometric limitations of the emotional acceptance measure (α = 0.268), these affective associations are highly tentative and unstable. Alternative measurement strategies are required to validate this hypothesis. Exploratory cluster analysis suggested the potential existence of two professional profiles: “Axiologically Integrated” staff members and a larger group of “Existential Skeptics”, who exhibited higher “existential vacuum” and lower psychosocial resources. Conclusions: Viewed through a dual-process interpretative lens, a theoretical phenomenon of cognitive–affective dissociation was explored. The highly tentative data suggest that “existential vacuum” might represent a hypothesized barrier to competence acquisition. Furthermore, findings regarding the affective domain—limited by the low reliability of the emotional measure—suggest religiosity could act as a potential source of normative tension. These exploratory profiles serve as hypotheses for future intervention designs rather than definitive clinical mechanisms. Full article