Search Results (1,151)

Understanding hand–paddle interaction is essential for optimizing performance and preventing injury in kayaking, yet coaches still lack objective, practical tools. We present a soft, instrumented glove that measures and dynamically maps palmar pressure throughout the stroke cycle. A matrix of piezoresistive sensors is integrated into the glove and connected to dedicated electronics housed in a waterproof enclosure. A viscoelastic model converts sensor resistance into forces, enabling time-resolved 3D mapping of contact mechanics. Data are transmitted via Bluetooth Low Energy (BLE). Experimental validation on a kayak ergometer across multiple cadences demonstrated accurate measurements (per-sensor root mean square error (RMSE) of ±2 N), clear delineation of pull and push phases, evolving pressure distribution over the motion, and a peak total right-hand force of 186 N at high cadence. Beyond feasibility, these results position the glove as a practical training aid: it supports athlete-specific load monitoring and the early detection of potentially problematic movement patterns. Full article

Currently, the study of individual parameters’ influence on the energy efficiency of hydraulic systems is one of the leading research directions for these types of drives. Determining the influence of individual components and system architectures on the energy efficiency parameter for exemplary objects and systems is a new body of knowledge that allows for the development of a basic and general method for determining the energy efficiency of hydrostatic systems. The method developed and presented in this article extends this knowledge, making it possible to determine the influence of liquid parameters and individual system components on the energy efficiencies achieved by hydrostatic systems. The method used for determining individual factors’ influence on achieved system energy efficiencies is utilitarian and allows for the determination of how changes in specific parameters affect the efficiency of operational systems based on the results of pressure and motion speed measurements. Experimental tests were conducted to determine total power variations and the quantitative relationship between volumetric and flow resistance losses as the oil temperature increased from 25 °C to 75 °C. Full article

This paper provides comprehensive numerical and experimental studies on the unsteady resistance of the world’s first battery-driven, zero-emissions high-speed catamaran, the MS Medstraum, in accelerated forward speed motion. These studies suggest that for a certain speed range of around Froude 0.50 (the so-called last hump of wave resistance), the corresponding unsteady resistance is significantly less than the originally anticipated value, namely, up to 40% less when adding to the steady resistance, the conventional added mass term. This surprising result could be explained by both experimental resistance tests and CFD calculations, as well as by inspection of the numerically generated wave patterns. Thus, care must be taken when applying the traditional approach to the unsteady resistance of a ship in accelerated or decelerated forward speed motion. As such, this positively affects the estimation of the required power capacity to accelerate the ship to full operational speed. This leads to reduced (fitted) battery weight and positively affects the ship’s displacement, allowing the vessel to achieve higher speeds. The present research finally yielded notable results of interest for seakeeping and ship maneuvering simulation studies; namely, comprehensive CFD simulations for the studied slender catamaran have shown that calculated added mass values for surge motion in real-flow conditions are up to six times higher than those initially estimated by ideal flow potential theory methods. Full article

The dynamic reliability of steam-turbine governing systems is essential for the safe operation of nuclear power units. As a key regulating and protection component, the reheat valve must complete rapid closure under abnormal operating conditions. This study addresses the closing timeout problem observed in a nuclear reheat-valve oil-motor actuator after domestic substitution, with particular attention to sluggish motion and discontinuous closing at small openings. A coupled hydraulic–mechanical model was then established by integrating the coned-disc spring assembly, hydraulic circuit, cartridge valve, gear–rack transmission, and load resistance based on the mathematical model. The model was used to identify the dominant parameters controlling the fast-closing process, and the optimization strategy was subsequently verified by experiments on an actual actuator platform. The results show that coned-disc spring degradation is a critical source of closing timeout risk. When the equivalent elastic modulus decreases to approximately 195 GPa, the fast-closing time approaches the critical limit of 0.8 s, while further degradation results in evident timeout. The C0 throttling orifice has the strongest influence on the effective closing time by governing the pressure-relief capacity of the working chamber. A coordinated correction strategy, involving coned-disc spring force compensation and throttling parameter adjustment, restores the closing margin, shortens the fast-closing time to 0.78 s, and improves closing smoothness. This work provides the practical guidance for design verification, field commissioning, and domestic improvement of nuclear reheat-valve oil-motor actuator systems. Full article

This study presents field measurements for a non-conventional mobile square cylinder fish enclosure, with permeable ends, evaluated under both towed and moored conditions at a semi-open ocean test site. Novelty lies within the enclosure design that enables both mobility and control of internal flow through the incorporation of an adjustable aft-end perimeter constriction to regulate internal flow and support fish welfare by enabling control of swimming conditions. Enclosure motion, internal flow speeds and hydrodynamic loads were measured for three constrictions (0%, 40% and 60%). The primary objective was to assess the effectiveness of aft-end constriction in regulating internal flow to levels compatible with sustainable swimming speeds for finfish culture. The enclosure remained stable at approximately 9 m depth across all vessel speeds and constriction settings in both towed and moored scenarios. During towing, increasing constriction to 40% reduced time-averaged internal flow by up to 24% without a significant increase in hydrodynamic load. A 60% constriction achieved a larger reduction (~51%) but resulted in a substantial load increase (~90% relative to 0% constriction), indicating a trade-off between flow control and towing resistance. Under moored conditions, aft-end constriction had minimal influence on both internal flow and hydrodynamic load. Mooring loads showed no clear relationship with wave height and only a weak correlation with ambient current speed. Overall, the results demonstrate that aft-end constriction is an effective mechanism for controlling internal flow during towing, but has limited impact when moored. The enclosure’s stability and controllability highlight its potential advantages over conventional gravity cages for mobile open-ocean finfish aquaculture applications. Full article

The present work focuses on the nonlinear seismic response of transmission tower systems when subjected to successive earthquake ground motions. To this end, nonlinear time-history analyses were carried out by applying multiple ground motion records in sequence, thereby replicating realistic scenarios in which structures endure repeated seismic loading during and following major earthquakes. The structural behavior was examined through two distinct modeling frameworks: a pinned configuration, where tower members are considered to resist axial forces only, and an SSI-based model, which captures the interaction between the structure and the supporting soil. Both frameworks were assessed in terms of several critical response quantities, namely peak displacements, permanent displacements following each seismic event, acceleration demands, and base shear forces developed at the foundation level. The comparative evaluation of the two models brought to light considerable discrepancies in the computed response, confirming that the dynamic characteristics of the soil and its coupling with the structure have a pronounced effect on the overall seismic performance of transmission towers. In addition, it was shown that the cumulative effect of successive seismic excitations drives a gradual buildup of deformations, yielding displacement demands that far exceed those obtained from conventional single-earthquake analyses. These outcomes point to the necessity of incorporating SSI and multi-sequence seismic loading into both the design and the seismic assessment of transmission infrastructure, as approaches relying solely on single-event excitation are likely to significantly underestimate the true seismic demand imposed on such structures. Full article

The accurate prediction of resistance and running attitudes of high-speed planing crafts is of great significance for the improvement of ship hydrodynamics. In this study, the lab model tests and computational fluid dynamics (CFD) methods are employed to investigate the effects of volumetric Froude number and longitudinal center of gravity (LCG) position on the resistance performance, motion characteristics, and free-surface wave patterns for a planing craft. The capability of the CFD model was validated through towing tank resistance tests conducted under various LCG conditions. A systematic analysis of the influence mechanism of LCG variation on the hydrodynamic performance of the craft was conducted. The results indicate that an aftward LCG position can improve the resistance performance; however, it also leads to an increase in the pitch angle. These findings can provide a foundation for the optimization design of high-speed planing craft. Full article

Studying Bingham flows in permeable media under a periodic magnetic field enhances the understanding of yield-stress fluids for applications like oil recovery and filtration. This study combines non-Newtonian behavior with porous-medium resistance and magnetic variations, facilitating the analysis of complex flow phenomena, including oscillatory yielding and improved flow control in porous structures. The viscous potential theory is employed to streamline the mathematical processes. The utilization of linear governing partial differential equations of motion, along with appropriate nonlinear boundary conditions, yields additional simplifications. The investigation yields a nonlinear Mathieu oscillator that governs the interfacial displacement. A non-perturbative method is used to convert this nonlinear ordinary differential equation into a linear equation. A non-dimensional formulation minimizes the fundamental variables required to characterize the system by establishing a collection of dimensionless physical characteristics. The study analyzes a nonlinear Mathieu oscillator with complex coefficients to explore system dynamics related to elevation. By simplifying the variable coefficients, it enhances the examination of stability and resonance behavior. Despite inherent complexities, the work effectively clarifies fundamental concepts, contributing to a more coherent understanding of the subject. The Hartman number, magnetic field, and magnetic permeability ratio exert a destabilizing effect. Conversely, the Bingham parameter, Weber number, and periodic frequency exert a stabilizing influence. Full article

To address the limitations of the centralized hydraulic steering system used in the first-generation heavy-duty wheeled platform developed by our team, this study proposes a fully electrified steering system based on a compact direct-drive electro-mechanical actuator (DEMA) architecture. Compared with the original hydraulic system, the proposed solution reduces the steering-system weight from approximately 150 kg to 32 kg in the single-channel configuration and 40 kg in the dual-channel configuration, while significantly improving system integration and maintainability. For the single-channel DEMA steering system, a composite control strategy combining three-loop PID control with feedforward compensation is developed to improve dynamic response and position-tracking accuracy. AMESim simulation results under a steering resistance torque of 6000 ± 500 Nm show that the system achieves an overshoot below 2%, a steady-state error below 0.1°, and a tracking error below 0.4°. To reduce motor power and thermal-management requirements, a dual-channel DEMA steering architecture is further proposed. Considering inter-channel parameter differences, a primary–secondary synchronization control strategy is developed to suppress force-fighting behavior and improve motion consistency. Simulation results demonstrate that the proposed strategy effectively reduces synchronization errors and maintains highly consistent force output between channels while preserving excellent steering accuracy and tracking performance. The proposed fully electrified steering system and synchronization control strategy provide an effective solution for improving the dynamic performance, lightweight design, and reliability of heavy-duty wheeled platforms. Full article

The seismic fragility of reinforced concrete (RC) bridge piers is critical for urban rail transport systems, as severe pier damage may interrupt post-earthquake operation and threaten network safety. Compared with conventional highway bridge piers, urban rail transport RC solid piers usually have lower axial load ratios, larger cross-sections, and stricter serviceability requirements. However, the combined effects of geometric parameters, reinforcement detailing, and material strength on their cyclic behavior, dynamic response, and seismic fragility remain insufficiently understood. To address this issue, seven 1/4-scale RC solid pier specimens were tested under quasi-static cyclic loading to examine the effects of pier height, transverse reinforcement ratio, and longitudinal reinforcement ratio on damage evolution, hysteretic response, skeleton curves, and energy dissipation. A fiber-based OpenSees model considering bond-slip effects was then established, validated against the tests, and extended to a full-scale prototype pier for parametric analysis. The effects of aspect ratio, axial load ratio, longitudinal reinforcement ratio, stirrup ratio, steel yield strength, and concrete strength were evaluated under cyclic loading and nonlinear dynamic time-history excitations. An incremental dynamic analysis-based probabilistic seismic demand model was further developed using 30 near-fault ground motions, with peak ground acceleration as the intensity measure and displacement ductility as the engineering demand parameter. The results showed that increasing the aspect ratio changed the failure mode from flexure-shear-dominated to flexure-dominated behavior, increasing the ultimate displacement from 122 mm to 155 mm while reducing the peak lateral strength from 263 kN to 248 kN. Increasing the longitudinal reinforcement ratio improved both peak strength and ultimate displacement, from 226 kN to 262 kN and from 120 mm to 160 mm, respectively. The numerical results indicated that aspect ratio, axial load ratio, and longitudinal reinforcement ratio had more pronounced effects on seismic demand and fragility than stirrup ratio. Increasing steel yield strength generally reduced seismic fragility, whereas increasing concrete strength enhanced lateral resistance but did not necessarily improve fragility performance. These findings suggest that the seismic performance of urban rail transport RC solid piers should be evaluated by combining cyclic response, dynamic demand, and fragility-based performance, rather than by maximizing any single design parameter. Full article

Achieving precise docking, reliable locking and damage-free emergency unlocking under complex ocean current conditions remains a key challenge for deep-water multi-way quick connectors (MQCs). This study proposes a novel MQC prototype characterised by a tiered tolerance guidance mechanism, an innovative L-shaped spatial helical cam locking system, and a real-time visual attitude indicator. Using Ansys 2023 R2 and its tools, the safe operating limits were determined through explicit non-linear finite element collision analysis. The results demonstrate that, under a controlled docking speed of 10 mm/s, the hierarchical guidance mechanism successfully accommodated extreme initial misalignments (25 mm lateral offset, 5° horizontal rotation and 15° axial rotation), whilst keeping the peak collision stress within the elastic limit. Furthermore, the L-shaped locking guide was analysed using a fifth-order polynomial motion law and a macro-micro elastoplastic Hertzian contact mechanics model, effectively eliminating rigid-flexible impact forces. Under extreme separation loads of 10,000 psi, the maximum equivalent plastic strain at the base of the locking shaft was strictly controlled at 0.00926. This is well below the failure threshold of 0.0865 specified by ASME, providing a substantial safety margin and completely preventing local yielding. Crucially, the emergency release strategy based on precision locating pins was validated through full-scale prototype testing. Destructive tests conducted under simulated severe jamming conditions demonstrated clean, damage-free disengagement under shear torques ranging from 2100 Nm to 2200 Nm. This threshold ensures that accidental triggering will absolutely not occur during routine operations (1400 Nm) and establishes a safe underwater robotic (ROV) operating speed of ≤4 r/min. This study provides a robust theoretical framework and empirical data for the future design of yield-resistant subsea connectors and safe emergency recovery. Full article

Background/Objectives: Rigidity has been defined as an increase in muscle tone that is independent of the velocity of the stretch in Parkinson’s disease (PD). However, there is an ongoing debate about this non-velocity-dependent nature of rigidity in PD. To investigate the behaviour of axial muscle tone at different examination velocities using isokinetic dynamometry, and to determine whether trunk muscle resistance is velocity-dependent in people with PD compared with healthy controls (HCs). Methods: A cross-sectional study was conducted with HC and people with PD (I–III stages of Hoehn and Yahr and assessed by the UPDRS, Section III: motor aspects) by a senior neurologist. The trunk extension–flexion component of an isokinetic dynamometer measured axial muscle tone over a range of 50° (S: 30-50-80). The continuous passive mode with three angular speeds (30°/s, 45°/s and 60°/s) was used to assess muscle tone. Peak torque (N), work (J) and work recorded in the first and in the last third of the explored trunk range of motion were calculated (J) were registered. All these outcomes were performed within 1–3 h of the administration of anti-Parkinsonian medication (ON phase) in the PD sample. Results: People with PD (N = 36) and healthy controls (N = 20) completed the study. Our results showed largely similar behaviour in work and peak torque registered in both groups, by which, resistance measures, like peak torque, weakly increased with mobilisation speed from 30°/s to 45°/s, without reaching statistical significance, but increased from 45°/s to 60°/s, only in the flexors. No clear increase was observed in the work. Furthermore, greater torque measures in PD than controls were only observed for peak torque at 30°/s. Conclusions: Peak torque of trunk flexors–extensors tends to increase as the angular speed increases in both PD and controls. This may suggest that the (relatively slow) tested speeds were likely evaluating the non-neural component of muscle tone. This has implications for the clinical assessment of axial rigidity in PD. Full article

The triboelectric nanogenerator (TENG), which converts mechanical energy into electrical energy through the coupled effect of triboelectrification and electrostatic induction, has garnered significant interest among researchers due to its portability and self-powered characteristics. Despite its evident development potential, TENG continues to face challenges, including the necessity to enhance its triboelectric performance through the optimization of structures, materials, and manufacturing techniques to improve energy conversion efficiency. Additionally, its environmental stability and durability also need to be improved. TENGs designed inspired by non-human animals and plants offer feasible solutions to address these limitations. These bio-inspired TENGs optimize the structural design of TENGs and the materials of the triboelectric layers by imitating the structures, functions, and behaviors of organisms, thereby further improving the energy conversion efficiency, sensitivity, wear resistance, adaptability to special environments, biocompatibility, and wearing comfort of TENGs. This paper expounds on the progress of TENGs inspired by non-human animals and plants applied in environmental energy harvesting, human health and motion monitoring. It also discusses the current challenges, with a view to providing insights for the interdisciplinary integration and development of bionics and TENGs. Full article

Magnetorheological (MR) dampers enable semi-active control in prosthetic knees by providing rapidly adjustable resistance with low mechanical complexity. This paper evaluates three torque level control methodologies for a transfemoral prosthetic leg incorporating an MR damper: a model-based feedforward strategy, an adaptive inverse-dynamics controller, and a robust inverse-dynamics controller. A Lagrange-based planar leg model with explicit force-to-torque mapping is formulated, and a reference knee trajectory is estimated from measurable gait variables using a cubic polynomial model whose order is selected through least-squares RMSE analysis. Each controller is assessed using knee-angle tracking accuracy and control effort to capture the practical trade-off between motion quality and energy demand. Results demonstrated that the adaptive inverse-dynamics controller has the smallest tracking error but requires the highest effort, whereas the robust inverse-dynamics approach realizes approximately the same tracking performance with reduced effort, thereby suggesting the best accuracy–effort compromise in the present work. Results, likewise, examined actuator feasibility by considering the MR damper as the primary dissipative element and the DC motor as a supplemental active actuator required when damping alone cannot satisfy the commanded knee torque. Full article

Two methods of accounting for the motion of the bodies—the deforming mesh method and the method of overlapping meshes (or overset mesh method)—are compared using problems with floating bodies, which are typical for the shipbuilding industry. Three problems are considered: oscillation of the cylinder on the water surface, movement of the box under the influence of waves, and heaving and pitching of the ship model in head waves. Numerical computations are carried out in the LOGOS software package, the simulation methodology used is based on the solution of a system of Reynolds-averaged Navier-Stokes equations, and the Volume of fluid (VOF) method to take into account the free surface. In all problems, the characteristics of the movement of bodies are evaluated; the resistance force of the ship model is also determined in the third problem; control values obtained using two methods of accounting for moving bodies are compared with the available experimental data. The results of numerical simulation have shown that both methods predict body movement parameters well; the accuracy in determining the resistance force in the task of streamlining the ship’s hull is also comparable: the difference between the maximum deviations of the resistance coefficient in the computations with deformation and overlapping computation meshes is 0.5%. In the case of computations of the three-dimensional problem, the time spent when using the mesh-deformation method turned out to be 10% more; therefore, the method of overlapping meshes can be considered more optimal when solving such shipbuilding tasks as self-propelled tests and streamlining the ship’s hull with and without wind and wave loads. Full article