Search Results (92)

This contribution presents a thermal analysis of a Hyundai i10 exposed to solar radiation and investigates the greenhouse effect, which causes the air temperature inside the parked car to rise well above the ambient temperature. Experimental measurements of the effects of customized window inserts on the temperature and heat absorption inside the car were carried out by thermal camera and thermal probes. The probes recorded the temperature at three locations inside the car—in the footwell of the rear seat, on the windscreen, and at the driver’s head height—on two consecutive days with similar weather conditions. The results show that the inserts effectively reduced heat build-up in the interior. Full article

Background: Strength and the strength–power continuum may increase athletic performance, although data are scarce regarding the effects of long-term periodized training on the athletic performance of adolescent track and field athletes. The purpose of this study was to investigate performance modifications following 8 weeks of strength and strength–power resistance training, focusing on the athletic performance of adolescent track and field athletes. Methods: Following an equivalent single-arm pre–post intervention design, 16 adolescent athletes (age: 16.3 ± 0.5 years; mass: 56.5 ± 10.4 kg; height: 1.67 ± 0.07 m) participated in the study. Athletes followed an 8-week periodized resistance training program aiming to increase strength and strength–power. Measurements were performed before (T1), at the middle (T2) and at the end of the training period (T3) and included the standing long jump, single-leg standing long jump, five-step long jump, seated medicine ball throw, 0–80 m sprint and 1RM in the bench press and parallel squat. Results: The standing long jump (F_(2,14) = 109.564; η² = 0.940; p = 0.001), single-leg long jump (F_(2,14) > 41.801; η² = 0.857; p = 0.001) and five-step long jump (F_(2,14) = 148.564; η² = 0.955; p = 0.001) improved significantly from T1 to T2 (p < 0.001) and from T2 to T3 (p < 0.001). The seated medicine ball throw (F_(2,14) = 124.305; η² = 0.947; p = 0.001) and sprinting performance (F_(2,14) = 51.581; η² = 0.828; p = 0.001) were significantly enhanced from T1 to T2 (p < 0.001) and from T2 to T3 (p < 0.001). The 1RM in the bench press (F_(2,14) = 36.280; η² = 0.838, p = 0.001) and in the parallel squat (F_(2,14) = 48.165; η² = 0.873, p = 0.001) increased significantly from T1 to T2 (p < 0.001) and from T2 to T3 (p < 0.01). Conclusions: Strength and the strength–power continuum appear to have a positive effect on the physical fitness of adolescent track and field athletes, which highlights the importance of strength-based resistance training programs in adolescent athletes. Full article

High rock slopes are extensively distributed in areas of major engineering constructions, such as transportation infrastructure, hydraulic projects, and mining operations. The stability and failure evolution mechanism during their multi-stage excavation process have consistently been a crucial research topic in geotechnical engineering. In this paper, a series of two-dimensional rock slope models, incorporating various combinations of slope height and slope angle, were established utilizing the Discrete Element Method (DEM) software PFC2D. This systematic investigation delves into the meso-mechanical response of the slopes during multi-stage excavation. The Parallel Bond Model (PBM) was employed to simulate the contact and fracture behavior between particles. Parameter calibration was performed to ensure that the simulation results align with the actual mechanical properties of the rock mass. The research primarily focuses on analyzing the evolution of displacement, the failure modes, and the changing characteristics of the force chain structure under different geometric conditions. The results indicate that as both the slope height and slope angle increase, the inter-particle deformation of the slope intensifies significantly, and the shear band progressively extends deeper into the slope mass. The failure mode transitions from shallow localized sliding to deep-seated overall failure. Prior to instability, the force chain system exhibits an evolutionary pattern characterized by “bundling–reconfiguration–fracturing,” serving as a critical indicator for characterizing the micro-scale failure mechanism of the slope body. Full article

Background: The objective of this study was to analyze the absolute and relative reliability intersession for a maximal isometric muscle strength protocol in the bilateral seated bench press (BSBP), bilateral seated row (BSR), unilateral seated knee right extension (USKER) and unilateral seated knee left extension (USKEL) in a population of older adults. Methods: Eighteen older adults (age = 69.38 ± 5.06 years; weight = 75.79 ± 14.18 kg; height = 1.61 ± 0.08 m; BMI = 28.98 ± 5.04 kg/m². The maximal isometric muscle strength assessment was performed in a seated position. Participants were asked to exert maximum effort during the exercise. The BSBP and BSR assessments were performed bilaterally with shoulders and elbows at 90°, while the USKER and USKEL assessments were performed unilaterally. Three sets of 5 secondswere performed with a 3 minutes rest between measurements until maximum isometric strength was reached in all four measurements. Results: In the inter-session reliability measurements, acceptable absolute reliability was presented for BSR and USKER, and extremely high reliability for the BSBP and USKEL measures. In addition, extremely high relative reliability was reported for all assessments of maximum isometric muscle strength, with no significant differences were observed (p > 0.05) and an ES classified as null (ES < 0.12). Conclusions: The main results of this study show that maximal isometric muscle strength in bilateral seated bench press, bilateral seated row, and unilateral seated right and left knee extension, assessed using the Chronojump Force Sensor Kit, is reliable and reproducible for the elderly population. Full article

Background: Seated shot put is a core Paralympic event in which lower-limb-impaired athletes generate throwing power primarily through the trunk and upper limbs. The configuration of the throwing frame may influence performance stability and biomechanics. This study aimed to evaluate the effect of two seated orientations on throwing performance, kinematics, and within-subject reliability in a Paralympic F55 athlete using markerless motion capture. Methods: A para-athlete F55-class (age: 37 years; body mass: 93 kg; height: 180 cm; training experience: 20 years) performed 20 throws (10 per seat position: perpendicular and 54.5° rotated). Kinematic data were recorded with an eight-camera, 250 Hz markerless motion capture system. Variables included throw distance, trial time, release angle, wrist acceleration and velocity, and torso angular velocities. Reliability was assessed using intraclass correlation coefficients (ICC), standard error of measurement (SEM), coefficient of variation (CV%), Bland–Altman analysis, and ROC curve discrimination. Results: Throw distance did not differ significantly between positions (p = 0.1086), but trial duration was significantly shorter in the rotated position (p = 0.0114). Most kinematic variables showed poor-to-moderate reliability (ICC = −0.51 to 0.40). Bland–Altman and ROC analyses indicated stable performance measures but higher variability in torso motion, with torso rotation (AUC = 0.72) showing the strongest discriminative ability. Conclusions: Seated orientation minimally affected performance but influenced trunk kinematics and reliability, emphasizing the need for individualized biomechanical assessment in Paralympic shot put training. Full article

This study proposes and evaluates a car seat-integrated heat pump as localized air conditioning system for electric vehicles (EVs). The proposed system uses R1234yf and comprises a compressor, microchannel heat exchangers, an electronic expansion valve, and a four-way reversing valve for bidirectional operation, delivering conditioned air through the internal seat ducts to the cushion and backrest. A horizontal twin-rotary compressor was developed, which exhibits high isentropic and volumetric efficiencies. The compact module, with a height of 145 mm, a width of 330 mm, a length of 484 mm, and a mass of 20 kg, can be installed under the seat while satisfying the standard SgRP/H30 envelope constraints. Testing was conducted in controlled environmental chambers across representative operating conditions with various airflow rates at different temperatures of 30 °C and 35 °C for cooling and 7 °C and 15 °C for heating. At a typical compressor speed of 4000 rpm, the proposed system achieved coefficient of performance (COP) values of 3.5–5.5 and 4.5–8 in cooling and heating modes and cooling and heating capacities of 650–900 W and 400–600 W, respectively. Concentrating thermal control at the seat is expected to provide rapid, occupant-level cooling/heating with favorable efficiency, indicating a practical path to EV energy savings and thermal comfort. Full article

Background/Objective: Postural stability and motor coordination require precise regulation of agonist and antagonist muscle activities. Jaw clenching modulates neuromuscular control during static and reactive postural tasks. However, its effects on dynamic voluntary movement remain unclear. This pilot study aimed to investigate the effects of jaw clenching on muscle activity and kinematics during repetitive single-leg sit-to-stand task performance. Methods: Eleven healthy adults (age: 21.2 ± 0.4 years; 6 males and 5 females; height: 167.9 ± 9.6 cm; body weight: 59.7 ± 8.1 kg) performed repetitive single-leg sit-to-stand tasks for 30 s under jaw-clenching and control conditions. Electromyography (EMG) signals from eight muscles and kinematic data from 16 inertial measurement unit sensors were analyzed, focusing on the seat-off phase. Results: Jaw clenching resulted in a significantly lower success rate than the control condition (success rate: 0.96 ± 0.13 vs. 0.78 ± 0.29, p = 0.047). Under the jaw clenching condition, failed trials exhibited higher medial gastrocnemius and masseter EMG activity (p < 0.001), lower erector spinae longus EMG activity (p < 0.001), and altered kinematics, including increased trunk yaw and roll angles (p < 0.001). Jaw clenching increased the coactivation of the gastrocnemius and tibialis anterior muscles (p < 0.001), disrupting the reciprocal muscle patterns critical for task performance. Conclusions: These findings suggest that jaw clenching may reduce task performance by altering neuromuscular coordination during dynamic postural tasks. Full article

Background: The study evaluated the acute effect of dryland maximum strength (MS) training on water polo performance. Methods: Twelve female players (20.3 ± 1.4 years) underwent initial assessments, including a head-out 20 m swim and a one-repetition maximum (1RM) strength test in three exercises: bench press, seated pull row, and half squat. These exercises were used as the experimental (EXP) condition. During the main testing sessions, participants completed the EXP and a control (CON) condition. In the EXP, players completed MS training (three sets of six repetitions at 80% 1RM), followed 15 min later by in-water testing. In the CON, only the in-water tests were performed. These included a 10 s tethered swim to measure force, a 20 m head-out swim at maximum intensity to measure performance time, ten goal-targeted throws to reach the highest accuracy and throwing velocity, and three in-water vertical jumps as high as possible. Results: The performance time in the head-out 20 m swim (EXP: 14.21 ± 0.4, CON: 14.18 ± 0.5 s), tethered swimming force (EXP: 86.85 ± 14.82, CON: 89.58 ± 15.92 N), shooting velocity (EXP: 14.67 ± 1.19, CON: 14.91 ± 0.32 m·s⁻¹), shooting accuracy (EXP: 16.5 ± 5.4, CON: 19.0 ± 5.1 points), and in-water vertical jump height (EXP: 51.7 ± 5.6, CON: 52.9 ± 4.2 cm) were no different between conditions (p > 0.05). Conclusions: Dryland maximum strength training performed with high loads (80% 1RM) does not impair subsequent performance during sport-specific testing in female water polo players. These findings suggest that such MS training can be safely implemented 15 min prior to in-water training sessions. Full article

The effectiveness of mixing ventilation for contaminant removal and maintaining indoor air quality remains an active topic of debate. In shared multi-person spaces, it is common for occupants to experience uneven exposure levels due to variations in system configuration and seating arrangements. Previous studies have primarily considered static occupancy schemes, leaving a gap in understanding how dynamic patterns of use interact with ventilation design. This study investigates the combined effects of system settings and occupancy patterns on ventilation effectiveness (VE), while also exploring whether lower ventilation rates can still sustain acceptable air quality. Validated Computational Fluid Dynamics (CFD) models were developed to simulate multiple scenarios involving three ceiling heights, two inlet and exhaust configurations, and three occupancy patterns. Analysis of air quality at the breathing zone reveals that the spatial arrangement of ventilation inlets and exhausts substantially influences VE, with optimized layouts improved system effectiveness by approximately 20%. Seating arrangement was similarly important, with favorable positioning relative to inlets improving perceived air quality by up to 25%. In addition, modest increases in ceiling height reduced the ventilation rate needed to maintain equivalent air quality, suggesting opportunities for energy savings without compromising occupant health. Overall, this study demonstrates that the interaction between system configuration and occupancy has a stronger impact on ventilation performance. These findings underscore the importance of integrated design strategies that align ventilation layout with occupant distribution to achieve both efficiency and equity in indoor environments. Full article

Adopting a human-centered approach, this study investigates the influence of seat parameters on comfort for elderly users. Twenty healthy older adults (61–70 years) assessed age-friendly seats with varying seat heights (knee popliteal height H mm, H − 50 mm, H − 25 mm, H + 25 mm, and H + 50 mm) and backrest inclinations (90°, 105°, 120°, 135°). Body pressure distribution analysis and subjective comfort evaluations were conducted to assess the impact of these parameters. Key findings demonstrated that optimal subjective and objective comfort ratings were achieved at a seat height of H mm or H − 25 mm combined with a backrest inclination of 105°. Seat height showed a positive correlation with contact area, while exhibiting negative correlations with average pressure and maximum pressure. Regional comfort (feet, calves, coccyx, anterior thighs) exhibited significant positive correlations with overall comfort (p < 0.01). Furthermore, increasing the backrest inclination angle led to a higher-pressure gradient, and slippage perception negatively correlated with comfort (p < 0.05). This research confirms that the parameter optimization—specifically height and backrest inclination—effectively optimizes pressure distribution and significantly enhances sitting comfort for the elderly. The findings provide a scientific basis for designing comfortable, age-friendly seating solutions that support sustainable quality of life. Full article

Gravity anomalies caused by tectonics are commonly assumed to be static, based on the argument that the motions are slow enough for the induced mass changes over time to be negligible. We exploit this concept in the context of rifting and subduction by showing that the horizontal motions of density contrasts occurring at active and passive margins are responsible for sizable amounts of gravity rate of change. These findings are obtained via 2D finite element modeling of the two tectonic mechanisms in a vertical cross-section perpendicular to the ocean–continent transition as well as through evaluating the time-dependent gravity disturbance at a reference height caused by mass readjustment underneath. This disturbance originates from deep-seated changing density anomalies and dynamic topography with respect to a reference normal Earth. The gravity rate of change is proven to scale linearly with extensional and trench migration velocity; the peak-to-peak values between the largest maxima and minima are 0.08 μGal/yr and 0.21 μGal/yr, for a velocity of 1 cm/yr. For both tectonic mechanisms, the dominant positive rate of change is due to the horizontal motion of a density contrast of about 300–400 kg/m³. We also consider the role of dynamic topography in comparison to that of deep-seated changing density anomalies. Full article

Isometric strength is widely used to monitor training adaptations, assess neuromuscular fatigue, and play a critical role in the maintenance of muscle health. This study assessed repeatability (intra-session) and reliability (inter-session) of a force production machine in different exercises: Isometric Mid-Thigh Pull (IMTP), Knee Flexion (KF) at 30°, and Seated Calf Raise (SCR). Parameters measured included Peak Force (PF), RFD at 0–50, 0–100, 0–150, 0–200, 50–100, 100–150 and 150–200 ms. Thirty male individuals (IMTP = 30; KF = 11 and SCR = 30) participated (age: 20.6 ± 3.6 years, mass: 75.3 ± 7.5 kg, height: 1.80 ± 0.64 m). Repeatability and reliability were calculated for bilateral PF and RFD for IMTP and SCR, and unilateral for KF. PF demonstrated good to excellent repeatability in all exercises: IMTP (ICC = 0.93), KF (left: ICC = 0.98; right: ICC = 0.97), SCR (ICC = 0.84). RFD displayed poor to good repeatability in IMTP (ICC = 0.45–0.87) and SCR (ICC = 0.40–0.85), moderate to excellent repeatability in KF (left: ICC = 0.53–0.96; right: ICC = 0.61–0.92). PF reliability was excellent in IMTP (ICC = 0.93) and KF (left: ICC = 0.99; right: ICC = 0.97), and moderate in SCR (ICC = 0.64). RFD reliability was moderate to excellent in IMTP (ICC = 0.58–0.94), poor to good in SCR (ICC = 0.13–0.64), and poor to excellent in KF (left: ICC = 0.33–0.96; right: ICC = −0.19–0.95). This study shows that portable dynamometry can measure maximal and explosive strength in different exercises, demonstrating good reliability for most parameters in IMTP and KF. Full article

Road infrastructure plays a crucial role in economic development across Latin America, yet outdated design standards in Ecuador compromise both safety and efficiency. Despite a national road network exceeding 61,000 km, Ecuador’s geometric design guidelines have not been formally updated since 2003 and fail to reflect recent changes in vehicle configurations or driver characteristics. This study proposes a data-driven methodology to update two key geometric parameters: vehicle dimensions and driver eye height. A database of 1170 vehicles across 36 categories was developed using 2023 registration records and technical specifications. Driver eye height was estimated using two complementary approaches: (1) combining vehicle seat height and ground clearance data with Ecuador-specific anthropometric measurements from the country’s five main ethnic groups, and (2) virtually assigning anthropometric profiles to the national fleet. The results show that the average eye height of light vehicle drivers is approximately 0.95 m, which is lower than the current design standards in Ecuador (1.15 m) and AASHTO (1.08 m). Estimates for heavy vehicles are also lower (1.70 m versus 2.0 and 2.4 m, respectively). These findings reveal a mismatch between the current design assumptions and real-world conditions. The proposed framework is scalable and replicable, supporting the modernization of road design standards in Ecuador and other Latin American countries. Full article

This study proposes an equivalent furniture fire model based on standard combustible assembly and verifies its feasibility as a substitute for real furniture through full-scale experiments and numerical simulations. Experiments show that the peak heat release rate and total heat release of the standard combustible assembly are highly consistent with those of the single-seat sofa. The numerical model has been verified by experimental data. The dynamic characteristics of the heat release rate (HRR) curve are consistent with the temperature evolution process, confirming its reliability for the numerical model. The research on optimizing fire extinguishing parameters is carried out based on this numerical simulation. The results show that the response time of the horizontal sprinkler is 22 s shorter than that of the vertical sprinkler, and the fire extinguishing efficiency is improved. Reducing the sprinkler height to 3 m can accelerate activation and reduce CO₂ release. A flow rate of 91.4 L/min can effectively control the fire, but when it exceeds 150 L/min, the fire extinguishing efficiency is significantly reduced. The low response time index sprinkler starts up 88 s faster than the standard type, significantly enhancing the initial fire suppression capability. This scheme provides a safe, economical, and repeatable standardized combustible assembly for fire training and offers theoretical support for the parameter design of intelligent fire extinguishing systems. Full article

The Red River Jig is a traditional Métis dance practiced among Indigenous and non-Indigenous Peoples. While exercise improves physical health and fitness, the impacts of cultural dances on wholistic health are less clear. This study aimed to investigate the psychosocial (cultural and mental), social, physical function, and physical fitness benefits of a Red River Jig intervention. In partnership with Li Toneur Nimiyitoohk Métis Dance Group, Indigenous and non-Indigenous adults (N = 40, 39 ± 15 years, 32 females) completed an 8-week Red River Jig intervention. Social support, cultural identity, memory, and mental wellbeing questionnaires, seated blood pressure and heart rate, weight, pulse-wave velocity, heart rate variability, baroreceptor sensitivity, jump height, sit-and-reach flexibility, one-leg and tandem balance, and six-minute walk test were assessed pre- and post-intervention. Community, family, and friend support scores, six-minute walk distance (553.0 ± 88.7 m vs. 602.2 ± 138.6 m, p = 0.002), jump, leg power, and systolic blood pressure low-to-high-frequency ratio increased after the intervention. Ethnic identity remained the same while affirmation and belonging declined, leading to declines in overall cultural identity, as learning about Métis culture through the Red River Jig may highlight gaps in cultural knowledge. Seated systolic blood pressure (116.5 ± 7.3 mmHg vs. 112.5 ± 10.7 mmHg, p = 0.01) and lower peripheral pulse-wave velocity (10.0 ± 2.0 m·s⁻¹ vs. 9.4 ± 1.9 m·s⁻¹, p = 0.04) decreased after the intervention. Red River Jig dance training can improve social support, physical function, and physical fitness for Indigenous and non-Indigenous adults. Full article