Search Results (1,140)

Background and Objectives: Assessing knee extensor (KE) strength is important for detecting muscle weakness in older adults, yet dynamometry is often impractical in community settings. This study examined whether smartphone-derived kinematics during the Five Times Sit-to-Stand Test (FTSST) could predict seated isometric KE strength. Materials and Methods: A cross-sectional study included 105 community-dwelling older adults (68.19 ± 5.85 years). A smartphone application extracted rising time, vertical velocity, and smartphone-estimated relative vertical power during the FTSST. KE strength was measured as maximum voluntary isometric contraction (MVIC) using fixed-frame dynamometry with a Lafayette dynamometer head. Bioelectrical impedance-derived body composition variables were reported descriptively but excluded from the primary prediction models to maintain a transparent movement-based model independent of device-specific body-composition estimates. Hierarchical regression models used smartphone-derived variables and transparent non-BIA covariates. Agreement was examined using Bland–Altman analysis. Results: Smartphone-estimated relative vertical power showed the strongest correlation with MVIC (r = 0.787, p < 0.001). The combined model including sex, age, femur length, and smartphone-estimated relative vertical power explained 71.6% of MVIC variance (adjusted R² = 0.716, SEE = 3.276 kg), outperforming vertical velocity, rising time, and total FTSST time models. Internal validation using repeated 10-fold cross-validation showed CV-R² = 0.701, CV-adjusted R² = 0.689, CV-RMSE = 3.343 kg, and CV-MAE = 2.739 kg. Bland–Altman analysis showed minimal mean bias (0.00 kg), 95% limits of agreement from −6.296 to 6.296 kg, and significant proportional bias (slope = −0.172, p = 0.002), indicating overestimation in weaker individuals and underestimation in stronger individuals. Conclusions: Consistent with our hypothesis, smartphone-estimated relative vertical power was the strongest kinematic predictor of seated isometric KE strength among the evaluated FTSST-derived variables. This approach may support community screening and monitoring, but it should not replace standardized dynamometry for precise individual-level strength quantification. Full article

Racing pigeons (Columba livia domestica) have been selectively bred for centuries for superior flight capacity. Yet, the quantitative structure of flight performance traits and the extent to which sex influences these parameters remain poorly characterized, particularly in Turkish populations. This study aimed to evaluate flight performance in racing pigeons raised in the South Marmara region of Türkiye using three key kinematic traits (flight duration, speed, and distance) and to explore the multivariate structure and individual variation of these parameters through an integrative machine learning framework. Data were compiled from 166 individually registered pigeons (77 females, 89 males), totaling 781 race records used for pattern analysis. A composite Flight Performance Score (FPS) was constructed using min–max normalized component variables, and its internal consistency was assessed via Cronbach’s alpha and principal component analysis. Univariate comparisons revealed no statistically significant sex-related differences in any of the three flight parameters (p > 0.05 for all traits). Principal component analysis confirmed substantial overlap between male and female individuals in multivariate trait space, and Random Forest classification failed to discriminate between sexes above chance level (accuracy = 0.490; ROC-AUC = 0.500), collectively indicating that sex is not a dominant determinant of flight performance in this population. Internal consistency analysis revealed that flight duration, speed, and distance are functionally independent dimensions (Cronbach’s α = 0.135; r = −0.749 between duration and speed), with PCA of the FPS component variables indicating an effectively two-dimensional variance structure (PC1: 60.1%; PC2: 39.7%). Pattern analysis of race records identified four biologically distinct flight performance profiles, characterized by differential trade-offs among flight duration, speed, and distance, suggesting that individual-level performance strategy, rather than sex, is the primary axis of variation in this dataset. These findings challenge common breeder assumptions about sex-based differences in performance and highlight the multidimensional, individual-specific nature of flight performance in racing pigeons. Full article

Background: The objective was to synthesize and critically appraise systematic reviews with meta-analysis evaluating the association between irrigation, instrumentation, and obturation procedures and post-operative endodontic pain. Methods: An umbrella review was conducted following PRISMA guidelines. Electronic searches identified systematic reviews published between 2016 and 2025. Eligible studies are systematic reviews that include meta-analyses, published in English and correlating the presence of post-operative pain in 3 different critical stages of root canal treatments, namely irrigation, instrumentation and obturation. Methodological quality was assessed using the AMSTAR 2 tool. Outcomes included pain prevalence and intensity at different time points. Results: Out of 368 records, 25 systematic reviews with meta-analysis met the inclusion criteria: 9 on irrigation, 8 on instrumentation, and 8 on obturation. NaOCl concentrations, irrigant activation, and intracanal cryotherapy were repeatedly reported as being associated with reduced short-term post-operative pain. For instrumentation, most reviews reported lower pain with rotary systems, but two studies found no difference or favored reciprocating kinematics. Apical patency did not appear to increase pain and foraminal enlargement may increase early pain. No clinically consistent differences were observed between bioceramic/calcium silicate-based and resin-based sealers, although calcium silicate sealers seem to support periapical healing. However, the certainty of these findings was limited by heterogeneity, methodological weaknesses, and overlap among primary studies. Methodological limitations were identified across reviews, mainly related to no protocol registration (n = 4), incomplete reporting of excluded studies with justification (n = 11), limited assessment of publication bias, and poor reporting of funding sources for primary studies. Conclusions: Based on current evidence, irrigation, instrumentation, and obturation procedures may influence short-term post-operative pain. However, these findings remain tentative because of heterogeneity, methodological weaknesses, variable review quality, and overlap among primary studies. Further high-quality reviews and clinical trials are needed. Full article

Variable-amplitude vibrating screens are widely adopted for screening frozen sea buckthorn berry particles. Investigating their motion characteristics and particle behaviors on the screen surface is essential for optimizing the screening process and improving equipment performance and screening efficiency. In this work, a variable-amplitude vibrating screen is taken as the research subject. Its structural composition and working principle are elaborated, and kinematic simulations are conducted via RecurDyn. The results reveal that the vertical amplitude and velocity of the screen surface increase gradually from the feed end to the discharge end, which facilitates rapid particle penetration. Meanwhile, the horizontal velocity remains stable across all sections of the screen. Specifically, crank length governs the screen amplitude, while crank rotational speed determines the vibration frequency. A dynamic model of particles and the screen surface is established by combining EDEM 2024 and RecurDyn V9R4, and two-way coupling of the discrete element model is realized. Coupled simulation results indicate that the dynamic screening efficiency rises with increasing crank length and rotational speed, reaching the maximum at a crank length of 20 mm and a rotational speed of 208 r/min. Crank parameters exert remarkable effects on the thickness of the particle layer and the quantity of penetrated particles: a thicker particle layer leads to a longer residence time of materials on the screen. Field tests are carried out to verify the model accuracy. It turns out that the simulation results are basically consistent with experimental data. In conclusion, crank length and rotational speed are critical influencing factors for variable-amplitude vibrating screens. Research on the screen’s motion characteristics and particle behaviors can provide a theoretical reference for its efficient operation and optimal design. Full article

This work presents an experimental comparison of three speed control strategies for a permanent magnet DC (PMDC) rover actuator implemented on a resource-constrained embedded microcontroller platform. The system operates under fixed-rate discrete control with quantized encoder velocity feedback, representative of low-cost embedded systems. The controllers evaluated are a classical PID, a PID controller designed via discrete pole placement, and a Mamdani fuzzy controller. Beyond conventional tracking and transient response metrics, the proposed evaluation framework incorporates jerk-based kinematic indicators to assess the mechanical activity induced by control actions under both nominal and mechanically disturbed operating conditions. Experimental validation was performed over a range of operating speeds using repeated trials, and the observed differences were evaluated through nonparametric statistical testing. The results show that controller rankings depend strongly on operating conditions: the classical PID provides smoother motion under nominal conditions, whereas the fuzzy and compensated PID controllers achieve superior disturbance rejection when external mechanical perturbations are introduced. These findings reveal a clear tradeoff between mechanical smoothness and tracking robustness, and demonstrate that controllers exhibiting better tracking performance do not necessarily produce the smoothest kinematic response. The principal contribution of this work is the experimental demonstration that jerk-based indicators provide essential complementary information to conventional performance metrics for the evaluation and selection of embedded speed controllers in mechatronic systems subject to variable mechanical loading. Full article

Background/Objectives: Alignment philosophy in total knee arthroplasty (TKA) may affect joints beyond the knee. Mechanical alignment (MA) targets a neutral mechanical axis, whereas kinematic alignment (KA) aims to restore native alignment and joint line obliquity (JLO). This study compares the effects of MA and KA on hip and ankle radiographic parameters and investigates the propagation of coronal correction along the lower limb. Methods: A retrospective comparative study evaluated 63 TKAs performed for varus deformity (KA: n = 32; MA: n = 31). Pre- and postoperative full-length standing radiographs were used to calculate changes (Δ), defined as the difference between postoperative and preoperative values, in hip offsets, mechanical and arithmetic hip–knee–ankle angles (mHKA, aHKA), medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), JLO, and ankle ground-referenced angles. Between-group differences and correlations were analysed. Interobserver reliability was assessed for all variables. Results: MA produced significantly greater limb correction than KA (ΔmHKA: 8.89° vs. 4.82°, p < 0.001), primarily due to increased tibial valgus correction (ΔMPTA: 6.26° vs. 2.41°, p < 0.001). JLO increased substantially with MA (+4.10°) but was preserved with KA (+0.30°, p < 0.001). MA resulted in significant valgus shifts at the ankle (ground talar dome angle (GTDA) −3.01°, ground tibial plafond angle (GTPA) −3.02°; p = 0.006 for both), whereas KA produced no significant ankle changes. Correlation analysis demonstrated limited knee–ankle biomechanical coupling, with a moderate negative correlation in MA (ΔmHKA vs. ΔGTDA: ρ = −0.479, p = 0.006) and a weak correlation in KA (ΔaHKA vs. ΔGTDA: ρ = −0.360, p = 0.043). Hip parameters remained unchanged in both groups. Conclusions: Mechanical alignment induces larger tibial-driven coronal corrections, increases joint line obliquity, and produces measurable valgus shift at the ankle. In contrast, kinematic alignment preserves native alignment and joint-line obliquity while minimising distal ankle compensatory changes. Full article

Most detraining research in swimming has focused on competitive athletes, whereas less is known about recreational university swimmers, a population commonly exposed to temporary interruptions in structured training. This study examined the effects of 4 weeks of naturally occurring detraining on anthropometric, body composition, biochemical, kinematic, and performance variables in recreational university swimmers. Sixteen young swimmers were assessed before and after detraining, following at least one year of participation in a structured university swimming training program. Anthropometric, body composition, biochemical, kinematic, and performance variables were assessed before and after the detraining period. After detraining, waist and hip circumferences, fat mass, and total cholesterol increased. In contrast, fasting glucose, triglycerides, post-exercise lactate, 50 m performance, and kinematic variables showed no statistically significant changes. These findings suggest that, in recreational university swimmers, anthropometric, body composition, and metabolic variables may be more sensitive to short-term detraining than sprint performance-related outcomes. However, the absence of statistically significant performance changes should be interpreted with caution. Full article

This paper develops a generalized kinematic model for a lever-link-type flat pressing mechanism used in food processing applications for compacting the coagulate. The study aims to highlight the influence of the geometric parameter that defines the position of the intermediate coupling on the driving element on the mechanism’s configuration and on the main kinematic variables of the active pressing point. Under an idealized representation—assuming rigid links, perfect joints, and a vertical constraint acting on the active element—general analytical expressions for displacement, velocity, and acceleration were established using the vector-kinematic method. The results show that modifying the position of the intermediate coupling produces nonlinear variations in the length of the connecting element, its spatial orientation, and the vertical motion of the active point. Increased values of this parameter are associated with a greater effective stroke and higher vertical velocities toward the end of the motion, while the calculated accelerations remain relatively low, indicating a smooth kinematic evolution. The model establishes analytical relationships that describe the influence of geometric parameters on the kinematic behavior of the mechanism and can serve as a basis for further developments involving dynamic analysis and experimental validation. Full article

Hurdle technique analysis requires accurate identification of key phases and kinematic features, but conventional biomechanical methods are often costly, equipment-dependent, and difficult to apply in front-line training. This study developed a low-cost monocular-video-based framework for rapid hurdle clearance analysis in practical training settings. Thirty-seven physical education college students with different hurdling skill levels were recruited as participants, and side-view videos of their hurdle clearance were recorded. The proposed pipeline combined YOLO26 hurdle detection, RTMPose markerless pose estimation, rule-based key-event detection, phase segmentation, and phase-specific kinematic feature extraction. The results showed that the hurdle detection model achieved high accuracy, with bounding-box mAP@0.5 of 0.992 and mask mAP@0.5 of 0.971. Pose estimation showed good agreement with manual annotations, with an overall RMSE of 8.25 px and PCK of 97.64%. The rule-based phase segmentation method achieved an overall event localization MAE of 0.74 frames and RMSE of 1.55 frames, outperforming LSTM and TCN temporal baselines. Core distance and most angle variables also showed high agreement with manually recalculated values. These findings indicate that monocular video and markerless pose estimation can provide an accurate, low-cost, and practical tool for hurdle phase segmentation and kinematic assessment in routine training contexts. Full article

The transition to bio-based fuels requires a thorough understanding of how molecular structure governs key physicochemical properties such as oxidation stability and viscosity. In this study, the combined influence of fatty acid composition and alcohol structure on biodiesel and biolubricant performance is investigated using a multivariate statistical approach. A dataset comprising 108 samples was analyzed, including 17 experimental samples produced in this work and 91 samples collected from peer-reviewed literature. Each sample was characterized by its fatty acid composition and at least one physicochemical property, namely oxidation stability (Rancimat induction time) and/or kinematic viscosity. Principal Component Analysis (PCA) was applied to identify dominant compositional patterns, followed by clustering (k-means) to define homogeneous compositional regions. Within these regions, a variance decomposition approach was used to quantify the relative contribution of alcohol type to property variability. The results show that fatty acid composition defines the primary structural framework governing oxidative stability, largely driven by the degree of unsaturation. In contrast, viscosity is more strongly influenced by the type of alcohol used, particularly in systems involving higher alcohols or polyols. The proposed approach provides a structured multivariate framework focused on analyzing oxidation stability and viscosity, enabling the systematic interpretation of the relative influence of fatty acid composition and alcohol structure on these key physicochemical properties. This study demonstrates that integrating PCA, clustering, and variance decomposition offers a robust strategy for analyzing complex bio-based systems, supporting the rational selection of feedstocks and processing conditions for the optimization of biodiesel and biolubricant formulations. Full article

The squat is a critical component of numerous rehabilitation and functional assessment protocols, playing a significant role in enhancing athletic performance and activities of daily living. Although some of the characteristics gathered during the squat need additional confirmation, Kinovea provides a free two-dimensional squat motion analysis tool that is simple to use in clinical practice. This analytical, cross-sectional reliability study aimed to evaluate the intra-rater and test–retest reliability (with a 20 min interval between performances) of loaded squat kinematics in a sample of women using Kinovea. Twenty women performed a loaded back squat; intra-rater reliability was assessed by re-analyzing the same video one week apart, and test–retest reliability was assessed across two performances separated by 20 min. The results showed good to excellent intra-rater reliability (ICC: 0.75–0.99; SEM: 0.16 cm to 5.14°; MDC: 0.44 cm to 14.24°), and moderate to excellent test–retest reliability (ICC: 0.64–0.98; SEM: 0.36 cm to 14.29°; MDC: 0.99 cm to 39.61°). Variables tracked in the sagittal plane showed high precision. Conversely, the head angle and knee angle in the frontal plane exhibited greater variability, reflected by higher SEM and MDC values. In conclusion, Kinovea is a reliable and accessible tool for clinical kinematic assessment of the squat, particularly in the sagittal plane parameters. However, due to the elevated measurement error observed in head angles and frontal-plane knee dynamics, the integration of 3D motion capture is recommended over 2D digital protocols for these variables. Full article

The majority of currently available hand kinematic databases have been gathered using expensive marker-based systems or are restricted to a particular gesture-recognition task, failing to capture the dynamic nature of joints when the hand is engaged with an object. To address this gap, we introduce the RGB-based Hand Joint Kinematics (RGB-HJK) dataset, a publicly available collection of continuous, frame-level 3D joint angle trajectories, recorded while ten healthy adults (six male, four female; age $25.8\pm 3.2$ years; BMI $22.8\pm 2.0$ kg/m²) performed five standardized object interaction grasps: Power Grasp (cylindrical bottle), Tripod Grasp (pen), Static Power Hold (smartphone), Precision Pinch (thin paper), and Lateral Pinch (book). Data were collected using a standard RGB camera and the MediaPipe Hands markerless pipeline at $26.95\pm 0.29$ Hz, a rate that was stable across all subjects. Each participant completed five trials for each grasp type. After filtering using active hold, 28,111 validated frames remained, with a 100% detection rate for all 250 trials. Intra-subject repeatability was good (mean SD $\le 7.9°$ across all joint grasp combinations) and inter-subject variability was within the range expected based on normal anatomical diversity. Importantly, kinematic validation of the Index Proximal Interphalangeal (PIP) joint (61.8° ± 18.4°) showed values consistent with ranges reported in previous studies using instrumented gloves and depth sensors. Principal Component Analysis (PCA) confirmed clear linear separability among the five grasp configurations. Unlike existing datasets, the RGB-HJK method does not compromise the natural sense of touch and is free of hardware occlusions, thereby providing an easily accessible ecological baseline. Full article

This paper introduces the research progress of path planning, trajectory tracking control, and multi-machine collaborative operation systems for agricultural robots. It summarizes the development laws of 3D terrain modeling and adaptive path planning algorithms for complex agricultural environments such as hills and mountains, and analyzes the dynamic disturbance characteristics of agricultural machinery under slip, sideslip, and dynamic load changes. Through comprehensive analysis, it is found that traditional kinematic control models have limitations in complex and unstructured environments. Combining soil mechanics mechanisms, variable load identification, and robust control strategies is key to improving trajectory tracking stability and operational quality. In terms of multi-machine collaboration, this paper discusses master–slave collaboration, distributed control, and task allocation modes. It further identifies that the stability of collaboration and interoperability standards between devices in weak network environments are currently the main bottlenecks limiting the large-scale application of this technology. Finally, this paper provides prospects for future research directions and suggests strengthening the closed-loop integration of perception, decision-making, and dynamic models, establishing industry unified standards, and enhancing the safety of the entire lifecycle of operations, providing suggestions for the unmanned application of agricultural robots. Full article

In precision gear manufacturing, longitudinal crowning on tooth flanks is commonly produced by applying diagonal feed in worm-type generating processes using tools such as variable-tooth-thickness hobs and dressable grinding worms. However, precise twist control remains difficult because the geometric parameters of the generating tool are strongly coupled with the machine feed settings in the underlying generating kinematics. In addition, direct numerical optimization becomes unreliable near the standard tool state, where the sensitivity of the diagonal-feed coefficient degenerates and conventional linearized solvers may lose effectiveness. To address these issues, this study proposes a multi-variable optimization framework for twist-constrained worm-type gear generation. An iterative singular value decomposition (SVD) scheme is developed to construct and update the sensitivity matrix, while a warm-start continuation strategy is introduced to overcome the local singularity and improve numerical robustness. Two closed-form expressions for the diagonal-feed coefficient are also proposed as practically useful initial estimates, corresponding respectively to the minimum SVD topographic residual and the minimum tooth-flank twist. Numerical validation over a 60-case parameter sweep shows maximum relative errors below 1.6% within the tested range. The proposed framework coordinates the tool-geometry design and diagonal-feed selection to generate tooth flanks with prescribed crowning characteristics while satisfying a specified twist requirement and limiting the required diagonal shift. Numerical examples show that the iterative framework reduces the root-mean-square (RMS) topographic error from 1.14 μm to 0.027 μm relative to the analytical setting of Hsu and Fong. These results indicate that the proposed method provides a reliable computational basis for twist control and process-parameter design in advanced CNC gear generation. From a manufacturing standpoint, because the three design criteria are accessed by adjusting only the diagonal-feed ratio on the machine, a single generating-tool design can serve a range of crowning and twist requirements without retooling, reducing setup and tooling efforts in production. Full article

Kinematic modeling and parameter identification are essential for achieving high-precision robot calibration. A widely used strategy involves utilizing the end-effector position error for parameter identification. However, the strong coupling between length and angular parameters often impedes calibration accuracy. In addition, substantial differences in their scales further exacerbate this issue. To overcome these limitations, following the variable projection method, this paper reformulates the conventional Modified Denavit–Hartenberg (MDH) model into a separable nonlinear structure. This allows independent identification of the two parameter types. Non-geometric errors such as joint compliance and backlash are also explicitly taken into account. The backlash errors are separated from the angular positions of each joint by modeling their bidirectional positioning errors with Chebyshev polynomials. This method enables the establishment of a comprehensive positioning error model to mitigate the influence of backlash errors. Based on the variable projection method, an improved variable projection with modified Gram–Schmidt (IVPMGS) identification method is proposed, which also eliminates redundant parameters that hinder identification robustness. Simulations indicate that the proposed method achieves faster convergence and higher identification accuracy. Compensation experiments demonstrate that the average absolute positioning error is reduced from 0.1804 mm to 0.0917 mm compared with the traditional MDH model, corresponding to a 49.17% improvement in positioning accuracy. These findings confirm the accuracy and effectiveness of the proposed approach. Full article