Search Results (306)

Apple harvesting faces increasing challenges owing to rising labor costs and the limited seasonal workforce availability, highlighting the need for robotic harvesting solutions in precision agriculture. This study presents a 6-DOF robotic arm system designed for harvesting in dwarf hedge-planted orchards, featuring a lightweight perception module, a task-adaptive motion planner, and an adaptive soft gripper. A lightweight approach was introduced by integrating the Faster module within the C2f module of the You Only Look Once (YOLO) v8n architecture to optimize the real-time apple detection efficiency. For motion planning, a Dynamic Temperature Simplified Transition Adaptive Cost Bidirectional Transition-Based Rapidly Exploring Random Tree (DSA-BiTRRT) algorithm was developed, demonstrating significant improvements in the path planning performance. The adaptive soft gripper was evaluated for its detachment and load-bearing capacities. Field experiments revealed that the direct-pull method at 150 mN·m torque outperformed the rotation-pull method at both 100 mN·m and 150 mN·m. A custom control system integrating all components was validated in partially controlled orchards, where obstacle clearance and thinning were conducted to ensure operation safety. Tests conducted on 80 apples showed a 52.5% detachment success rate and a 47.5% overall harvesting success rate, with average detachment and full-cycle times of 7.7 s and 15.3 s per apple, respectively. These results highlight the system’s potential for advancing robotic fruit harvesting and contribute to the ongoing development of autonomous agricultural technologies. Full article

Implementing energy-efficient solutions and developing energy complexes to decentralise power supply are key objectives for enhancing national security in Ukraine and Eastern Europe. This study compares the design, numerical, and experimental parameters of a channel-type jet-reaction turbine. A steam turbogenerator unit and a pilot industrial experimental test bench were developed to conduct full-scale testing of the unit. The article presents experimental data on the operation of a steam turbogenerator unit with a capacity of up to 475 kW, based on a channel-type steam jet-reaction turbine (JRT), and includes the validation of a computational fluid dynamics (CFD) model against the obtained results. For testing, a pilot-scale experimental facility and a turbogenerator were developed. The turbogenerator consists of two parallel-mounted JRTs operating on a single electric generator. During experimental testing, the system achieved an electrical output power of 404 kW at a turbine rotor speed of 25,000 rpm. Numerical modelling of the steam flow in the flow path of the jet-reaction turbine was performed using ANSYS CFX 25 R1 software. The geometry and mesh setup were described, boundary conditions were defined, and computational calculations were performed. The experimental results were compared with those obtained from numerical simulations. In particular, the discrepancy in the determination of the power and torque on the shaft of the jet-reaction turbine between the numerical and full-scale experimental results was 1.6%, and the discrepancy in determining the mass flow rate of steam at the turbine inlet was 1.34%. JRTs show strong potential for the development of energy-efficient, low-power turbogenerators. The research results confirm the feasibility of using such units for decentralised energy supply and recovering secondary energy resources. This contributes to improved energy security, reduces environmental impact, and supports sustainable development goals. Full article

This study explored the effects of adding a newly developed type of polydextrose on the appearance, sensory score, and textural parameters of steamed bread and the microstructure of dough, as well as the pasting, thermal, and thermal mechanical properties of high-gluten wheat flours. The results revealed that, compared with a control sample, 3–10% of polydextrose addition significantly increased the hardness, adhesiveness, gumminess, and chewiness of steamed bread, but other textural parameters like springiness, cohesiveness, and resilience remained basically the same. Further, in contrast to the control sample, 3–10% polydextrose addition significantly reduced the specific volume and width/height ratio of steamed bread but increased the brightness index, yellowish color, and color difference; improved the internal structure; and maintained the other sensory parameters and total score. Polydextrose addition decreased the peak, trough, final, breakdown, and setback viscosity of the pasting of wheat flour suspension solutions but increased the pasting temperature. Polydextrose additions significantly reduced the enthalpy of gelatinization and the aging rate of flour paste but increased the peak temperature of gelatinization. A Mixolab revealed that, with increases in the amount of added polydextrose, the dough’s development time and heating rate increased, but the proteins weakened, and the peak torque of gelatinization, starch breakdown, and starch setback torque all decreased. Polydextrose additions increased the crystalline regions of starch, the interaction between proteins and starch, and the β-sheet percentage of wheat dough without yeast and of steamed bread. The amorphous regions of starch were increased in dough through adding polydextrose, but they were decreased in steamed bread. Further, 3–10%of polydextrose addition decreased the random coils, α-helixes, and β-turns in dough, but the 3–7% polydextrose addition maintained or increased these conformations in steamed bread, while 10% polydextrose decreased them. In unfermented dough, as a hydrogel, the 5–7% polydextrose addition resulted in the formation of a continuous three-dimensional network structure with certain adhesiveness and elasticity, with increases in the porosity and gas-holding capacity of the product. Moreover, the 10% polydextrose addition further increased the viscosity, freshness, and looseness of the dough, with smaller and more numerous holes and indistinct boundaries between starch granules. These results indicate that the 3–10% polydextrose addition increases the chewiness and freshness of steamed bread by improving the gluten network structure. This study will promote the addition of polydextrose in steamed bread to improve shelf-life and dietary fiber contents. Full article

Traditional three-row roller YRT turntable bearings exhibit high friction torque during operation, which limits their performance in high-precision and high-response applications. To address this issue, a novel ball–roller composite turntable bearing is proposed that effectively reduces friction torque while maintaining a high load capacity. A mechanical model based on statics is established, and the Newton–Raphson method is employed to calculate the contact load. The formation mechanism of friction torque is analyzed, and a corresponding computational model is developed and validated using experimental data. The effects of axial load, eccentricity, overturning moment, rotational speed, and axial clearance on friction torque are systematically studied. Results indicate that friction torque increases with these parameters. Axial clearance has a significant influence, and an optimal clearance value between the balls and rollers is determined. Additionally, a reasonable range for the raceway curvature radius coefficient is proposed. When the numerical ratio of balls to rollers is 1, the bearing exhibits optimal friction performance. Among various roller crowning strategies, logarithmic crowning yields the best results. This study provides a theoretical basis and technical support for the optimized design of ball–roller composite turntable bearings. Full article

Background/Objectives: The objective of this study was to compare muscular strength and neuromuscular activation characteristics between male gymnasts and physical education (PE) students during isometric shoulder extension and flexion tasks. Methods: Thirteen competitive male gymnasts (age: 19.59 ± 1.90 years; body mass: 66.54 ± 6.10 kg; height: 169.38 ± 6.28 cm; mean ± SD) and thirteen male physical education (PE) students (age: 20.96 ± 2.30 years; body mass: 74.00 ± 8.69 kg; height: 174.96 ± 4.93 cm) voluntarily participated in the study. Peak torque (PT), rate of torque development (RTD), RTD normalized to body mass (RTD/BM), and muscle activation assessed via surface electromyography (EMG), normalized to maximal EMG activity (EMG/EMGmax), were evaluated during bilateral isometric shoulder extension and flexion at a joint angle of 45°. Measurements were analyzed across the following time intervals: −50 to 0 ms (pre-tension), 0–30 ms, 0–50 ms, 0–100 ms, and 0–200 ms relative to contraction onset. Custom MATLAB R2024b scripts were used for data processing and visualization. One-way and two-way multivariate analyses of variance (MANOVAs) were conducted to test for group differences. Results: Gymnasts exhibit higher values of PT, PT/BM, RTD, and RTD/BM particularly within the early contraction phases (i.e., 0–50 ms and 0–100 ms) compared to PE students (p < 0.05 to <0.001; η² = 0.04–0.66). Additionally, EMG activity normalized to maximal activation (EMG/EMGmax) was significantly greater in gymnasts during both early and mid-to-late contraction phases (0–100 ms and 0–200 ms), (p < 0.05 to <0.001; η² = 0.04–0.48). Conclusions: These findings highlight gymnasts’ superior explosive neuromuscular capacity. Metrics like RTD, RTD/BM, and EMG offer valuable insights into rapid force production and neural activation, supporting performance monitoring, training optimization, and injury prevention across both athletic and general populations. Full article

This paper analyzes the electromagnetic characteristics of an interior permanent magnet synchronous motor (IPMSM) for electric vehicle traction under various control imbalance conditions in a twin inverter system, assuming that one of the inverters fails to operate properly. The imbalance conditions are first investigated through dynamometer experiments and then applied to finite element method (FEM) simulations to evaluate their electromagnetic effects. Since the focus is on scenarios where a single inverter malfunctions, a stator winding configuration is first redefined to ensure stable operation in a single inverter system by preventing voltage and current imbalances within the circuit. When the stator winding is configured with eight parallel paths, the dynamometer test results show a phase voltage imbalance. However, when the number of parallel circuits is reduced to four, this voltage imbalance disappears. Using this configuration, a twin inverter system is constructed, and various imbalance conditions are applied to intuitively examine the electromagnetic characteristics when one inverter fails to accurately control current magnitude or phase angle. The simulation results showed that applying unbalanced conditions to the current and current phase angle led to a decrease in torque and an increase in torque ripple. In addition, when one of the inverters was completely disconnected, the motor performance analysis showed that it operated with approximately half of its original performance. Based on dynamometer experiments and finite element method (FEM) simulations, the electromagnetic characteristics under inverter fault conditions and appropriate stator winding configurations were analyzed. When an optimal number of parallel circuits is applied to the stator winding and a twin inverter system is employed, the load on each individual inverter is reduced, enabling accurate control. This makes the application to high-voltage and high-current systems feasible, allowing higher performance. Moreover, even if one inverter fails, the system can still operate at approximately half its capacity, ensuring high operational reliability. Full article

In order to improve the efficiency of highway tunnel construction and ensure the construction quality, the design concept of a prefabricated inverted arch and partial cast-in-place lining of highway tunnels by a mining method is put forward. During the assembly of prefabricated tunnel invert arches, the longitudinal joints between adjacent invert sections were subjected to shear forces due to the combined effects of the invert’s self-weight and construction equipment loads. This study investigated the shear performance of these longitudinal joints under construction loads, with a particular focus on the influence of bolt-tightening torque. Three longitudinal joint specimens were designed and fabricated, varying the bolt-tightening torque as a key parameter, and subjected to shear tests. The failure modes, load–slip behavior, and shear capacity of the joints were analyzed in relation to the tightening torque of high-strength bolts. The results indicate that when the bolt-tightening torque was set to 50% and 70% of the standard torque, the upper bolts of the joint sheared off, while the threads of the lower bolts were damaged. When the torque reached the standard value, all bolts were sheared off. The ultimate shear capacity of the longitudinal joints increased with higher bolt-tightening torque, with the optimal torque range identified as 70% to 85% of the specified standard. Ultimately, a method of calculation for evaluating the shear-bearing capacity of inverted arch longitudinal joints was proposed, with computational outcomes demonstrating a conservative bias that aligns with structural safety requirements. Full article

This study aimed to investigate the effects of Nano-cAMP on growth performance, gut development, and microbiota composition in broilers. A total of 108 21-day-old yellow-feathered female chicks were randomly divided into three groups with six replicates per group and six chicks per replicate according to the principle of consistent body weight. Experimental treatments included the following: (1) CON group (basal diet), (2) cAMP group (basal diet + 0.02 g/kg cAMP), and (3) Nano-cAMP group (basal diet + 0.37 g/kg Nano-cAMP liposomes). After a 21-day experimental period, results revealed the following: Compared with the CON group, the Nano-cAMP group exhibited a significantly reduced feed-to-gain ratio (p < 0.05). The cAMP group exhibited a significant increase in duodenal index (p < 0.05), whereas the Nano-cAMP group demonstrated greater jejunal villus height (p < 0.05). Both treatment groups showed significant upregulation of cholecystokinin (CCK) and secretin gene expression (p < 0.05). Analysis of alpha-diversity indices (Chao1, Shannon, Simpson) revealed no significant differences in jejunal and cecal microbiota composition between experimental groups (p > 0.05). Notably, the relative abundance of Firmicutes significantly increased (p < 0.05) in the cAMP and Nano-cAMP groups, whereas Proteobacteria, Gemmatimonadota, and Chloroflexi significantly decreased (p< 0.05). The combined relative abundance of three Lactobacillus genera and Bifidobacterium was obviously elevated. Linear discriminant analysis identified Bifidobacterium, Ruminococcus torques group, and uncultured_Thermoanaerobacterales_bacterium as dominant genera in the intestinal tract of Nano-cAMP group. In conclusion, dietary addition of Nano-cAMP promotes jejunal development, modulates appetite hormones mRNA expression, enhances absorption capacity, increases the relative abundance of intestinal probiotics such as Bifidobacterium and cellulose-degrading bacteria such as Ruminococcus torques group, optimizes gut microbiota composition, and ultimately reduces the feed-to-gain ratio in broilers. Full article

The response to perturbations in the gait of elderly and young individuals can differ due to various factors, such as age-related changes in sensorimotor function, muscle strength, and balance control. This study aimed to identify and compare compensatory kinematic and kinetic gait strategies in response to sudden treadmill perturbations applied during the Pre-Swing phase in young and older adults. The analysis focused on determining age-related differences in joint behavior and force production under perturbation stress, with implications for fall prevention. Twenty-one young and an equal number of elderly healthy females walked on a treadmill in a virtual environment (GRAIL, Motek). Unexpected perturbations were applied five times. Principal Component Analysis (PCA) and k-means clustering identified three distinct compensatory strategies per limb. Young adults primarily employed Strategies I (42.2%) and II (40%), while older adults most often selected Strategy II (45.5%). Statistical analysis (SPM and Mann-Whitney U test, p = 0.05) showed significant between-group differences in joint angles and torques across the gait cycle. For instance, in Strategy I, young participants had significantly lower ankle plantarflexion angles (p < 0.01) and hip extension torques (p < 0.05) compared to the elderly. Strategy II in older adults showed significantly higher vGRF minimums (p < 0.01) and anterior-posterior GRF peaks (p < 0.001). The elderly adopted strategies compatible with their neuromuscular capacity rather than those minimizing joint load, as observed in the young group. These findings offer novel insights into age-related compensatory mechanisms and highlight the importance of tailored fall-prevention strategies based on biomechanical response patterns. Full article

With the increasing capacity of wind turbines, key components including the rotor diameter, tower height, and tower radius expand correspondingly. This heightened inertia extends the response time of pitch actuators during rapid wind speed variations occurring above the rated wind speed. Consequently, wind turbines encounter significant output power oscillations and complex structural loading challenges. To address these issues, this paper proposes a novel pitch control strategy combining an effective wind speed estimation with the inverse system method. The developed control system aims to stabilize the power output and rotational speed despite wind speed fluctuations. Central to this approach is the estimation of the aerodynamic rotor torque using an extended Kalman filter (EKF) applied to the drive train model. The estimated torque is then utilized to compute the effective wind speed at the rotor plane via a differential method. Leveraging this wind speed estimate, the inverse system technique transforms the nonlinear wind turbine dynamics into a linearized, decoupled pseudo-linear system. This linearization facilitates the design of a more agile pitch controller. Simulation outcomes demonstrate that the proposed strategy markedly enhances the pitch response speed, diminishes output power oscillations, and alleviates structural loads, notably at the tower base. These improvements bolster operational safety and stability under the above-rated wind speed conditions. Full article

To address the limitations of traditional single-motor bionic ornithopters in terms of environmental adaptability and lift capacity, this study proposes a dual-motor independently driven system utilizing a cross-shaft single-gear crank mechanism to achieve adjustable flap speed and wing frequency, thereby enabling asymmetric flapping for enhanced environmental adaptability. The design integrates a two-stage reduction gear group to optimize torque transmission and an S1223 high-lift airfoil to improve aerodynamic efficiency. Multiphysics simulations combining computational fluid dynamics (CFD) and finite element analysis (FEA) demonstrate that, under flapping frequencies of 1–3.45 Hz and wind speeds of 1.2–3 m/s, the optimized model achieves 50% and 60% improvements in lift and thrust coefficients, respectively, compared to the baseline. Concurrently, peak stress in critical components (e.g., cam disks and wing rods) is reduced by 37% to 41 MPa, with significantly improved stress uniformity. These results validate the dual-motor system’s capability to dynamically adapt to turbulent airflow through the precise control of wing kinematics, offering innovative solutions for applications such as aerial inspection and precision agriculture. Full article

Achieving the appropriate primary stability for immediate or early loading in areas with low-density bone, such as the posterior maxilla, is challenging. A three-dimensional (3D) stabilization implant design featuring a tapered body with continuous cutting flutes along the length of the external thread form, with a combination of curved and linear geometric surfaces on the thread’s crest, has the capacity to enhance early biomechanical and osseointegration outcomes compared to implants with traditional buttressed thread profiles. Commercially available implants with a buttress thread design (TP), and an experimental implant that incorporated the 3D stabilization trimmed-thread design (TP 3DS) were used in this study. Six osteotomies were surgically created in the ilium of adult sheep (N = 14). Osteotomy sites were randomized to receive either the TP or TP 3DS implant to reduce site bias. Subjects were allowed to heal for either 3 or 12 weeks (N = 7 sheep/time point), after which samples were collected en bloc (including the implants and surrounding bone) and implants were either subjected to bench-top biomechanical testing (e.g., lateral loading), histological/histomorphometric analysis, or nanoindentation testing. Both implant designs yielded high insertion torque (ITV ≥ 30 N⋅cm) and implant stability quotient (ISQ ≥ 70) values, indicative of high primary stability. Qualitative histomorphological analysis revealed that the TP 3DS group exhibited a continuous bone–implant interface along the threaded region, in contrast to the TP group at the early, 3-week, healing time point. Furthermore, TP 3DS’s cutting flutes along the entire length of the implant permitted the distribution of autologous bone chips within the healing chambers. Histological evaluation at 12 weeks revealed an increase in woven bone containing a greater presence of lacunae within the healing chambers in both groups, consistent with an intramembranous-like healing pattern and absence of bone dieback. The TP 3DS macrogeometry yielded a ~66% increase in average lateral load during pushout testing at baseline (T = 0 weeks, p = 0.036) and significantly higher bone-to-implant contact (BIC) values at 3 weeks post-implantation (p = 0.006), relative to the traditional TP implant. In a low-density (Type IV) bone model, the TP 3DS implant demonstrated improved performance compared to the conventional TP, as evidenced by an increase in baseline lateral loading capacity and increased BIC during the early stages of osseointegration. These findings indicate that the modified implant configuration of the TP 3DS facilitates more favorable biomechanical integration and may promote more rapid and stable bone anchorage under compromised bone quality conditions. Therefore, such improvements could have important clinical implications for the success and longevity of dental implants placed in regions with low bone density. Full article

Aiming at the problems of excessive dependence on manual operations, unquantifiable parameters, low hoisting efficiency, and low level of automation and informatization in the lifting process of spacecraft, a novel cable-driven parallel automatic leveling robot with a two-stage adjustment function is proposed. It contains a cable-driven parallel mechanism and a counterweight compensation mechanism and has the advantages of high load-bearing capacity and better posture adjustment. Its kinematics and leveling performance are studied systematically. First, a geometric model of the robot is established, and the inverse position is derived. Second, the system’s eccentric coordinates are solved based on the inclination angles of the moving platform. A theoretical model of the cable adjustment length is established according to the eccentric coordinates, and the cable adjustment scheme is analyzed and optimized. Third, according to the optimal cable adjustment scheme, the relationship between the inclination angles and the counterweight’s adjustment displacement is established to better improve the leveling accuracy based on the force and torque balance principle. Finally, the kinematics and leveling performance are verified through MATLAB numerical calculations, ADAMS simulation, and experimental study, proving that the robot could realize the hoisting and leveling task. Full article

Alginate hydrogels offer distinct advantages as ionically crosslinked, biocompatible networks that can be shaped into spherical beads with high compositional flexibility. These spherical architectures provide isotropic geometry, modularity and the capacity for encapsulation, making them ideal platforms for scalable, stimuli-responsive actuation. Their ability to respond to thermal, magnetic, electrical, optical and chemical stimuli has enabled applications in targeted delivery, artificial muscles, microrobotics and environmental interfaces. This review examines recent advances in alginate sphere-based actuators, focusing on fabrication methods such as droplet microfluidics, coaxial flow and functional surface patterning, and strategies for introducing multi-stimuli responsiveness using smart polymers, nanoparticles and biologically active components. Actuation behaviours are understood and correlated with physical mechanisms including swelling kinetics, photothermal effects and the field-induced torque, supported by analytical and multiphysics models. Their demonstrated functionalities include shape transformation, locomotion and mechano-optical feedback. The review concludes with an outlook on the existing limitations, such as the material stability, cyclic durability and integration complexity, and proposes future directions toward the development of autonomous, multifunctional soft systems. Full article

Wind turbines align with the wind direction and adjust to wind speed by rotating their nacelle and blades using electromechanical or hydraulic actuators. Due to the fact that the rated capacity of wind turbines is increasing and that the actuators are reaching some size limits, the current solution is to install several actuators at each joint until the required torque is reached. The problem with this approach is that, despite the fact the actuators can be selected from the same type and series, they typically have distinct parameters, resulting in different behaviours. The synchronisation of actuators of wind turbines has still not been studied in the specialised literature. Therefore, a control approach for the synchronisation of the pitch actuators is proposed in this work. Two cases are considered: the synchronisation of torque outputs and the synchronisation of position angle. The simulation results indicate that the proposed solution is effective for synchronising actuators, either when they are placed together on the same blade or when they are on separate blades while simultaneously following the collective pitch control command. Full article