Search Results (1,185)

The purpose of this study was threefold: (a) to analyze differences in mean force, impulse, mean concentric and eccentric velocity, and peak concentric velocity across six repetitions of the flywheel deadlift exercise, with a particular focus on the first repetition initiated from zero momentum; (b) to explore relationships between these kinetic and kinematic variables and one-repetition maximum (1-RM) performance in the free-weight deadlift; (c) to examine the effects of different flywheel inertial loads on the relationships among mean force (MF), impulse, time under tension (TUT), and velocity, with the aim of identifying the most valid and reliable parameter for flywheel load prescription. Thirteen resistance-trained men (24.7 ± 5.0 y; 82.2 ± 11.7 kg; 1-RM deadlift: 174 ± 24 kg) performed six repetitions of the flywheel deadlift against six inertial loads (0.025 to 0.145 kg∙m²) on a kBox 5 device. Results showed that although the first repetition had 25–30% lower mean concentric velocity and 7–11% lower mean force compared to subsequent repetitions (p < 0.001), it exhibited 4–8% higher impulse due to the 14–20% longer time under tension. MF, velocity, and impulse in the first repetition showed moderate-to-strong correlations with 1-RM (r = 0.58 to 0.85, p < 0.05), particularly at the two higher inertia loads. MF plateaued at moderate inertia loads, while impulse and TUT increased linearly with increasing inertial load and demonstrated the strongest and most consistent relationships with inertial load (r = 0.99 ± 0.01 and 0.97 ± 0.02, p < 0.001), enabling individualized flywheel training prescription. This study highlights the distinct value of the first repetition in flywheel deadlifts and its practical value for both assessment and training. Also, it suggests that impulse and TUT may be used as simple and practical flywheel exercise prescription variables. Full article

Metal powder compaction in rigid dies often suffers from high ejection forces, non-uniform density, and accelerated tool wear. We investigate an elastic-sleeve die concept in which a conical shrink-fit sleeve provides controllable radial confinement during pressing and elastic relaxation during extraction. An extensive experimental program on Fe-based and 316L powders, carried out in parallel with finite element analyses (SolidWorks Simulation version 2021; Marc Mentat 2005), quantified the roles of taper angle (α = 1–4°), axial pretension (Δh = 0.5–1.5 mm), and friction. Contact pressure increased from ≈52 MPa at α = 1° to ≈200 MPa at α = 3°, with negligible gains beyond 3°. For 316L, relative density reached ρ ≈ 0.889 at 325 kN with Δh = 1.5 mm; Fe–Cu–C achieved ρ ≈ 0.865 under identical conditions. The experimental results provided direct validation of the FEM, with calibrated viscoplastic simulations reproducing density–force trends within ≈±5% (mean density error ≈ 4.6%), while mid-stroke force differences (≈15–20%) reflected rearrangement/friction effects not captured by the constitutive law. The combined evidence identifies an optimal window of α ≈ 3° and Δh ≈ 1.0–1.5 mm that maximizes contact pressure and densification without overstressing the sleeve. Elastic relaxation of the sleeve facilitates extraction and suggests reduced ejection effort compared with rigid dies. These findings support elastic dies as a practical route to improved densification and tool life in powder metallurgy. Full article

Permanent magnet synchronous motors (PMSMs) are widely favored by manufacturers for use in electric vehicles (EVs) because of their many benefits, which include high power density at high speeds, ruggedness, potential for high efficiency, and reduced control complexity. However, since the Back Electromotive Force (EMF) increases proportionally with the motor’s rotational speed, it must be carefully controlled at high speeds. Flux-weakening (FW) control is required to avoid excessive electromagnetic flux beyond the power source and inverter’s voltage restrictions. This paper aims to compare various FW control strategies and analyze their effectiveness in maximizing the speed of PMSMs in EV applications while ensuring stable and reliable performance. Various FW approaches, such as voltage-based control, current-based control, and advanced predictive control methods, are examined to determine how each method balances speed enhancement with torque output and efficiency. In addition, other control strategies are crucial for optimizing the performance of PMSMs in electric vehicles. Among the most popular methods for controlling torque and speed in PMSMs are Field-Oriented Control (FOC), Direct Torque Control (DTC), and Vector Current Control (VCC). Each control technique has advantages and is frequently cited in the literature as a crucial instrument for improving EV motor control. This article provides a comprehensive evaluation of FW methods, highlighting their respective advantages and disadvantages by synthesizing the findings of numerous studies. In addition to outlining future research directions in FW control for EV applications, this study provides essential insights and valuable suggestions to help select FW control techniques for various PMSM types and operating conditions. Full article

This study aimed to monitor the biomechanical development of an artistic swimming duet across a macrocycle through an individualised training approach. Two swimmers (17.5 ± 0.5 years), members of the Los Angeles 2028 National Olympic Project, were assessed in December 2023 (M1) and April 2024 (M2), corresponding to the beginning and the end of the macrocycle. Maximal (Fmax) and mean (Fmean) force in the prone sculling and kick pull action were measured using a 20 s tethered test. Split velocity (vSplit) was assessed in free format based on video recording. Dry-land strength included assessments of internal (IR) and external (ER) shoulder rotation strength of the dominant (D) and non-dominant (ND) limbs, and countermovement jump (CMJ) power. The standard duet choreography was analysed in competition at both time points. Percentage variation (∆%) between swimmers was calculated for M1 vs. M2. Results showed convergence (M1 vs. M2) in Fmean of the sculling (21.6% vs. 9.9%) and kick pull (45.1% vs. 29.1%), accompanied by greater similarity in vSplit (15.9% vs. 15.5%). Further convergence was observed in IR_ND (33.7% vs. 13.9%), ER_D (11.6% vs. 4.4%) and CMJ (7.4% vs. 3.6%). The duet’s competition score increased from 168.9943 to 190.7183 points. It can be concluded that individualised training was useful for the duet to become more homogeneous in in-water strength, in-water kinematics and dryland strength, resulting in improved competitive performance. Full article

This paper addresses the cruise range maximization problem for hypersonic drones by proposing a combined aerodynamic force/thrust vector trajectory optimization method. A novel continuous linear parameterization strategy for trajectory optimization is innovatively developed, achieving continuous thrust vector trajectory optimization throughout the entire flight using only 21 parameters through recursive linear function design. This approach reduces parameter dimensionality and effectively addresses sparse rewards and training difficulties in reinforcement learning. The study integrates the Deep Deterministic Policy Gradient (DDPG) algorithm with deep residual networks for trajectory optimization, systematically exploring the impact mechanisms of different aerodynamic force and thrust vector combination modes on range performance. Through collaborative trajectory optimization of thrust vectors and flight height, simulation results demonstrate that the combined trajectory optimization strategy achieves a total range enhancement of approximately 146.14 km compared to pure aerodynamic control, with continuous linearly parameterized thrust vector trajectory optimization providing superior performance over traditional segmented methods. These results verify the significant advantages of the proposed trajectory optimization approach and the effectiveness of the deep reinforcement learning framework. Full article

A novel rolling scheme incorporating an inclined oval-caliber configuration is proposed to enhance plastic deformation mechanisms in the traditional oval–round rolling sequence. Finite Element Method (FEM) simulations were performed using DEFORM-3D to evaluate and optimize this new scheme across multiple objectives: maximizing average effective strain, minimizing strain non-uniformity (captured via the standard deviation of effective strain), and minimizing rolling force. Numerical modeling was conducted for calibration angles of γ = 0°, 25°, 35°, and 45°, from which Pareto-optimal solutions were identified based on classical non-dominance criteria. Pairwise 2D projections of the Pareto front enabled visualization of trade-offs and revealed γ = 35° as the Pareto knee-point, representing the most balanced compromise among high deformation intensity, increased uniformity, and reduced energy consumption. This optimal angle was further corroborated through a normalized weighted sum of the objective functions. The findings provide a validated reference for designing prototype deforming tools and support future experimental validation. Full article

The stability of ceramic suspensions is a key factor in the preparation and shaping of ceramic bodies. The presented work offers an experimental determination of ceramics suspensions stability using the LUMiSizer analytical centrifuge, focusing on kinetic behaviour using transmission profiles and instability indexes. Multiple ceramic systems comprising corundum, metakaolin, and zirconia suspensions were experimentally examined under varying solid contents, dispersant dosages, and additive concentrations. Results showed that highly loaded corundum suspensions with dispersant (Dolapix CE64) achieved excellent stability, with an instability index below 0.05. Compared to classical sedimentation tests, which are time-consuming and not highly sensitive, LUMiSizer offers a suitable alternative by guaranteeing correct kinetic data and instability indexes indicating suspension behaviour using centrifugal force. Comparisons of the LUMiSizer results and data obtained using the modified Stokes law confirmed increased terminal velocities in experiments with metakaolin suspensions, indicating the sensitivity of the centrifuge to the effect of dispersion medium shape. The influence of porogen (waste coffee grounds) on the stability of corundum suspensions was also investigated, followed by slip casting to create and characterize a ceramic body, confirming the possibility of shaping based on stability results. Furthermore, instability indices are suggested as a rapid, quantitative method for comparing system stability and as an auxiliary criterion to the rheological measurements. Optimal dispersant concentration for zirconia-based photocurable suspensions was identified as 8.5 wt.%, which minimized viscosity and, at the same time, assured maximal kinetic stability. Integrating the LUMiSizer analytical centrifuge with standard methods, including sedimentation tests and rheological measurements, highlights its value as a powerful tool for characterizing and optimizing ceramic suspensions. Full article

Pressure on fresh water resources has been aggravated in recent decades, basically due to population growth, rapid urbanization, and global warming. Integrated engineering solutions and the circular economy, considering the urban water cycle as a whole, are becoming fundamental, particularly in arid and semi-arid regions under permanent or recurrent hydric deficit. This study aims to develop and present an integrated engineering solution for water supply, wastewater collection, and treated wastewater reuse for landscape irrigation in a large, topographically complex, and arid to semi-arid coastal urban region at the south of Santiago Island, Cape Verde. The region is one of the driest and most arid of the Island, with a current average annual precipitation between about 100 and 200 mm, and has very limited underground water resources. The main study area, with about 600 ha, has altitudes ranging from values close to sea level up to about 115 m and has several topographic difficulties, including several relatively rugged zones. The devised water supply system considers four altimetric distribution levels, three main reservoirs connected to each other by a serial system of pipelines with successive pumping, a fourth downstream reservoir for pressure balance in one of the levels, and desalinated water as the source. The sanitary sewer pipes of the urbanizations drain to an interceptor system that operates predominantly in open channel flow in a closed pipe. The long interceptor crosses laterally along the coast several very dug valleys in the path to the Praia Wastewater Treatment Plant in the east, and requires several conduits working under pressure for the crossings, either lifting or governed by gravity. The under-pressure pipeline system of recycled water is partially forced and partially ruled by gravity and transports the treated wastewater from the plant in the opposite direction of the interceptor to a natural reservoir or lake located in the region of urbanizations and the main green spaces to be irrigated. The conceived design of the interceptor and recycled water pipeline minimizes the construction and operation costs, maximizing their hydraulic performance. Full article

High-performance sports cars rely on aerodynamics for stability and speed, but developing aero packages is challenging when wind tunnel testing is limited. In this study, we employed a simulation-guided design loop to maximize downforce and minimize drag on a sports car using Computational Fluid Dynamics (CFD). Thirteen aerodynamic modifications—including splitters, ducts, diffusers, and a Drag Reduction System (DRS)—were iteratively tested using CFD. To ensure numerical reliability, a mesh independence study and convergence analysis were performed, confirming stable aerodynamic predictions. The final configuration achieved an ~11× increase in downforce at 120 km/h (from about 320 N to 3588 N), meeting the design goal of roughly 2000 kg of downforce at 177 mph when scaled. This extreme downforce came with higher drag ($C_D$ ≈ 0.83), so a dual-mode approach was developed: a DRS configuration provides moderate downforce with 50% less drag ($C_D$ ≈ 0.41) for high-speed efficiency. A 1:12-scale wind tunnel test qualitatively supported the CFD predictions by visualizing wake narrowing and improved flow attachment. While quantitative force validation was not possible due to Reynolds mismatch and facility constraints, the qualitative results increased confidence in the CFD-based findings. Overall, the study demonstrates that substantial aerodynamic gains can be achieved under resource constraints, offering a practical framework for motorsport engineers and manufacturers to optimize aero kits when conventional full-scale testing is not accessible. Full article

Background: The gut–muscle axis is believed to influence training adaptations through microbiota-derived signals and the regulation of inflammation, but evidence in elite swimmers is limited and mixed. This study aims to determine whether synbiotic supplementation (probiotics + omega-3) combined with ultra-short race-pace training (USRPT) improves sprint-related upper-body strength. Methods: In a randomized, double-blind, 8-week trial of male elite sprint freestyle swimmers, participants completed USRPT and were allocated to either synbiotic supplementation or its single-component arms (probiotic or omega-3) or placebo. Primary outcomes indexed dynamic/explosive strength (isokinetic shoulder torque and power at 180°/s, rate of force development, time-to-peak torque); secondary outcomes included maximal strength (MVIC; 60°/s) and field/strength-endurance tests (dead-hang, handgrip, medicine-ball throw). Analyses reported p-values with effect sizes. Results: The synbiotic group showed greater improvements in high-velocity, sprint-relevant measures versus comparators—higher 180°/s torque and power, increased rate of force development, and shorter time-to-peak torque (Time × Group p < 0.05 across domains; effects in the medium–large range). Changes in handgrip and medicine-ball throw were small and not different between groups (p > 0.05). Conclusions: Synbiotic supplementation concurrent with USRPT preferentially enhances dynamic (explosive) upper-body strength in elite sprint swimmers, whereas non-stroke-embedded field tests show limited added value. Any reference to gut–muscle-axis modulation is hypothesis-generating, as stool sequencing and metabolite profiling were not performed. Larger, sex-inclusive trials incorporating in-water, stroke-embedded assessments and microbiome/metabolomic profiling are warranted. Full article

Introduction: Rheumatoid arthritis (RA) is known to affect the musculoskeletal system and, consequently, may lead to sarcopenia, but the role of respiratory muscle involvement in RA patients is unclear. Methods: This prospective, exploratory, single-center, matched-pair analysis study was designed to compare respiratory muscle strength and handgrip strength in RA patients and controls. Results: RA patients with low disease activity as estimated from the Disease Activity Score 28 (2.3 ± 1.2) and without signs of interstitial lung disease (n = 36, 72% female, 28% smoker, mean age 48 + 15 years, mean forced vital capacity 3.9 ± 1.0 L, 98% ± 11% predicted) and control subjects (n = 36, 72% female, 11% smoker, mean age 48 + 14 years, mean forced vital capacity 4.1 ± 1.1 L, 98% ± 16% predicted) were well balanced. Maximal inspiratory mouth pressure (PImax, primary endpoint) tended to be lower in RA patients, but this was statistically not significant (−0.9 kPa; 95%CI = −2.11/0.32). However, RA patients more frequently had PImax values below the lower limit of normal (OR 1.74 kPa; 95% CI 0.65/4.77). RA patients had lower handgrip strength (−5.97 kg; 95%CI = −9.43/−2.50). In addition, PImax was correlated to handgrip strength both in RA patients (R = 0.51, p = 0.0017) and controls (R = 0.48, p = 0.0029) and to the 6-minute walking distance (RA-patients: R = 0.30, p = 0.075; controls: R = 0.52, p = 0.0012). Conclusions: Even though the primary endpoint has not been reached, an impairment of respiratory muscle strength in RA cannot be excluded at least in a subset of patients. Further studies also involving RA patients with more disease activity are needed. Full article

The population activity of grid cells from a single module is topologically constrained to a toroidal manifold. Our work proposes an improved version of Gardner’s earlier model, which can account for both geometric properties and force field dynamics. Employing methods from Differential Geometry, we have derived Lagrangian densities that—under very general assumptions and avoiding dimensionful constants—provide a rationale for the trajectories associated with the synaptic spacetime as a global solution to the Einstein–Maxwell field equations. Then, we investigate the helical solutions to show that the synaptic toroidal topological space, as a locally flat Minkowski spacetime, with a Lorentzian metric is geodesically complete and, therefore, exhibits maximal stability. Finally, we consider a Lorentzian metric with curved spacetimes that give rise to Lorentzian tori admitting curvature spacetime singularities. Full article

Background: This study examined the impact of aerobic capacity on force–velocity (F–v) variables and repeated-sprint (RS) performance in male national-level sprinters (SPRs, n = 8; 177.0 ± 4.3 cm; 74.0 ± 5.0 kg; maximal oxygen uptake [VO₂max]: 55.4 ± 3.0 mL/kg/min) and middle-distance runners (MDRs; n = 8; 179.0 ± 5.1 cm; 67.2 ± 5.0 kg; VO₂max: 64.3 ± 3.3 mL/kg/min). Method: Participants underwent assessments of aerobic capacity, mechanical F-v profiling in sprinting 2 × 60 m with full recovery, and a 10 × 60 m repeated-sprint test with 30 s recovery. Results: MDRs exhibited significantly higher VO₂max (p < 0.001) and speed at VO₂max (vVO₂max, p < 0.001), while SPRs demonstrated greater anaerobic speed reserve (ASR, p < 0.001), maximal theoretical horizontal force (F₀, p = 0.012), and power output (P_max, p < 0.01). During the RS test, SPRs displayed a 16.6% performance decrement (p = 0.002) and failed to complete all sprints with voluntary withdrawal after 5–8 sprints due to exhaustion, whereas MDRs maintained consistent performance. SPRs exhibited a larger decrease in v₀ compared to MDRs (p < 0.01), whereas no differences were observed on F₀ (p = 0.519) and P_max (p = 0.758). Blood lactate accumulation was higher in SPRs (p < 0.001). Multiple linear regression analysis on the pooled sample identified vVO₂max (p = 0.003) and not ASR (p = 0.482) as a key predictor of fatigue resistance. Conclusions: These findings underscore the critical role of aerobic capacity in sustaining RS performance. Aerobic capacity, specifically vVO₂max, emerged as the primary determinant of fatigue resistance during repeated sprints, underscoring its critical role in sustaining RS performance over mechanical variables such as v₀ but not F₀ and P_max. Full article

Super high-rise buildings of 400 m and above are currently rare globally, making their design and construction data invaluable. Due to their enormous size, the structural safety, architectural effect, and construction cost are key concerns of all parties. This study employs parametric analysis to research the lateral force-resisting system and key local structural issues of a 400 m under-construction super-high-rise structure. The overall analysis results show that the 8-mega-column scheme can relatively well balance architectural effect and structural performance; the 5-belt truss design minimizes the steel consumption. The local research results indicate that the inward inclination of bottom columns leads to increased axial forces in floor beams significantly, necessitating reinforcement; horizontal braces directly connected to the core tube enhance folded belt truss integrity under rare earthquakes; failure of bottom gravity columns in the folded secondary frame increases beam bending moments and axial forces substantially. Steel consumption sensitivity analysis shows that when the structural first-order period is reduced by 0.1 s, adjusting the section sizes of the members in the belt truss minimizes the increase in steel consumption, while adjusting steel beams maximizes it. These findings provide essential design insights for similar super-high-rise projects. Full article

Compared with conventional RC frame buildings, staggered-story frame buildings are prone to the formation of short columns due to the vertical staggering of beam members, which exerts an adverse impact on the seismic performance of the building. Therefore, steel tube-reinforced concrete (ST-RC) columns are usually adopted to address the issue of the insufficient ductility of short columns. For this purpose, to investigate the seismic performance of partial staggered-story RC frame buildings, an elastic–plastic model is established based on a specific practical building, with ST-RC columns installed in the staggered-story area. By varying the confinement coefficients of the ST-RC columns (1.087, 1.152, 1.224, and 1.307) and classifying the member-level performance states, the seismic performance of ST-RC columns in staggered-story buildings under different confinement coefficients is evaluated. The research results indicate the following: in the statistical analysis of the performance states of the positive sections of the ST-RC columns, the degree of damage of the ST-RC columns first decreases and then increases sharply with an increase in the confinement coefficient, and the member damage is minimized when the confinement coefficient is 1.224. In the statistical analysis of the performance states of the inclined sections of the ST-RC columns, the damage state of the ST-RC columns shows a decreasing trend as the confinement coefficient increases; when the confinement coefficients are 1.224 and 1.307, the ST-RC columns are completely in the elastic state. With an increase in the confinement coefficient, the shear force borne by the ST-RC columns first increases and then decreases, while the tensile strain and compressive strain generally show a decreasing trend. When the confinement coefficient is 1.224, the tensile strain and compressive strain of the ST-RC columns are the smallest. Therefore, when arranging ST-RC columns in staggered-story buildings, it is necessary to select an appropriate confinement coefficient according to the actual project conditions to maximize the ductility of the short columns. Full article