Search Results (129)

Hand rehabilitation exoskeletons play a critical role in restoring motor function in patients with stroke or hand injuries. However, most existing designs rely on fixed-axis assumptions, neglecting the rolling–sliding coupling of finger joints that causes instantaneous center of rotation (ICOR) drift, leading to kinematic misalignment and localized pressure concentrations. This study proposes the Instant Radius Method (IRM) based on medical imaging to continuously model ICOR trajectories of the MCP, PIP, and DIP joints, followed by the construction of an equivalent ICOR through curve fitting. Crossing-type biomimetic kinematic pairs were designed according to the equivalent ICOR and integrated into a three-loop ten-linkage exoskeleton capable of dual DOFs per finger (flexion–extension and abduction–adduction, 10 DOFs in total). Kinematic validation was performed using IMU sensors (Delsys) to capture joint angles, and interface pressure distribution at MCP and PIP was measured using thin-film pressure sensors. Experimental results demonstrated that with biomimetic kinematic pairs, the exoskeleton’s fingertip trajectories matched physiological trajectories more closely, with significantly reduced RMSE. Pressure measurements showed a reduction of approximately 15–25% in mean pressure and 20–30% in peak pressure at MCP and PIP, with more uniform distributions. The integrated framework of IRM-based modeling–equivalent ICOR–biomimetic kinematic pairs–multi-DOF exoskeleton design effectively enhanced kinematic alignment and human–machine compatibility. This work highlights the importance and feasibility of ICOR alignment in rehabilitation robotics and provides a promising pathway toward personalized rehabilitation and clinical translation. Full article

Objectives: This study aimed to compare the clinical, functional, and radiological outcomes of three different fixation techniques—dorsal locking plate, crossed cortical screw, and a combination of both—used in first metatarsophalangeal (MTP) joint arthrodesis for advanced-stage hallux rigidus. The goal was to provide evidence-based guidance for surgical technique selection. Methods: This retrospective cohort study included 52 patients with advanced hallux rigidus (stage III–IV, Coughlin–Shurnas classification) who underwent surgical treatment between 2023 and 2025 at the Department of Orthopedics and Traumatology of Ankara Etlik City Hospital, with a minimum follow-up of one year. Patients were categorized into three groups according to the fixation technique used. Visual Analog Scale (VAS), American Orthopaedic Foot & Ankle Society (AOFAS) score, and Foot Function Index (FFI) were assessed using validated Turkish-language versions of the questionnaires. Radiological parameters included hallux valgus angle, first toe dorsiflexion angle, distal interphalangeal (DIP) arthritis, and radiographic union—defined as trabecular bridging across at least three cortices on weight-bearing anteroposterior and lateral radiographs. ANCOVA was performed with age as a covariate. Results: A total of 52 patients were included: Group 1 (dorsal plate fixation, n = 19), Group 2 (crossed cortical screw fixation, n = 16), and Group 3 (combined fixation, n = 17). Group 1 patients were significantly older (mean age: 64 ± 6 vs. 55 ± 6 and 59 ± 5 years; p < 0.001). After age adjustment, VAS pain scores were significantly higher in Group 1 compared to Group 3 (mean VAS: 2.8 ± 0.6 vs. 1.9 ± 0.5; p = 0.010). AOFAS scores did not differ significantly (p = 0.166), although Group 2 showed the highest median value (90 [70–93]). FFI scores differed significantly (p < 0.001), with Group 1 reporting worse outcomes (19 [17–31]) than Group 2 (15 [13–22], p = 0.03) and Group 3 (15 [11–16], p = 0.01). Dorsiflexion angle was significantly lower in Group 2 than Group 1 (median 19° vs. 27°; p = 0.04), though all remained within the physiological range. Radiographic union was achieved in 50/52 patients (96.2%), without significant intergroup differences (p = 0.612). Complications included two cases of wound dehiscence in Group 1; no infections, symptomatic non-union, malalignment, or hardware irritation were observed. Conclusions: Crossed cortical screw fixation yielded the most favorable functional outcomes, whereas the combined technique achieved the lowest postoperative pain scores. Dorsal plate fixation alone consistently underperformed. While outcomes were adjusted for age, residual confounding cannot be excluded. These results highlight the importance of tailoring fixation strategy to patient profile, with crossed screw and combined methods representing reliable choices for optimizing postoperative outcomes in advanced hallux rigidus. Full article

Concrete–fractured rock composites (CFRCs) are critical load-bearing systems in tunnels, dams, and other underground structures. Previous studies have not fully characterized how fracture geometry and confining pressure jointly influence crack propagation and failure modes. In this study, the particle flow discrete element method is employed to develop a heterogeneous concrete–fractured rock composite model in which the parallel bond model (PBM) is integrated with the smooth-joint model (SJM). The effects of fracture inclination (0–90°) and confining pressure (1–20 MPa) on the composite’s strength characteristics, crack propagation, and failure modes are systematically investigated. It is demonstrated that composite strength is markedly enhanced by confining pressure. Fracture inclination governs the evolution of the failure mode: as the inclination angle increases from 0° to 90°, overall composite strength increases. Confining pressure further modulates the failure path by altering the threshold for crack initiation. Specifically, under low confinement (<10 MPa), the shear-to-tensile crack ratio decreases with increasing dip angle, marking a transition from shear-dominated to tension-dominated mechanisms. At 20 MPa, the ratio remains relatively constant, with tensile failure being dominant. These findings establish a confining pressure–fracture geometry–failure framework for concrete–rock composites and suggest design strategies for deep tunnels, shallow structures, and inclination-specific reinforcement. Full article

Objectives: This study investigates the biomechanics of the bench press and overhead press exercises by modeling the trunk and upper limbs as a kinematic chain of rigid links connected by revolute joints and actuated by single- and two-joint muscles, with motion constrained by the barbell. The aims were to (i) assess the different contributions of shoulder and elbow torques during lifting, (ii) identify the parameters influencing joint loads, (iii) explain the origin of the sticking region, and (iv) validate the model against experimental barbell kinematics. Methods: Equations of motion and joint reaction forces were derived analytically in closed form. Dynamic simulations produced vertical barbell velocity profiles under various conditions. A waveform similarity analysis was used to compare simulated profiles with experimental data from maximal bench press trials. Results: The sticking region occurred when shoulder torque dropped below a critical threshold, resulting in a local velocity minimum. Adding elbow torque reduced this dip and shifted the velocity minimum from 38 cm to 23 cm above the chest, although it prolonged the time needed to overcome it. Static analysis revealed that grip width and barbell constraint had a greater effect on shaping the sticking region than muscle architecture parameters. Elbow extensors contributed minimally during early lift phases but became dominant near full extension. Model predictions showed high similarity to experimental data in the pre-sticking (SI = 0.962, p = 0.028) and sticking (SI = 0.949, p = 0.014) phases, with reduced, non-significant similarity post-sticking (SI = 0.881, p > 0.05) due to the assumption of constant torques. Conclusions: The model offers biomechanical insight into how joint torques and barbell constraints shape movement. The findings support training strategies that target shoulder strength early in the lift and elbow strength near lockout to minimize sticking and improve performance. Full article

Understanding the dynamic response and failure mechanisms of rock slopes during earthquakes is crucial in sustainable geohazard prevention and mitigation engineering. The initiation of landslides involves complex interactions between seismic wave propagation, dynamic rock mass behavior, and crack network evolution, and these interactions are heavily influenced by the slope geometry, lithology, and structural parameters of the slope. However, systematic studies remain limited due to experimental challenges and the inherent variability of landslide scenarios. This study employs Discrete Element Method (DEM) modeling to comprehensively investigate how geological structure parameters control the dynamic amplification and deformation characteristic of typical bedding/anti-dip layered slopes consist of parallel distributed rock masses and joint faces, with calibrated mechanical properties. A soft-bond model (SBM) is utilized to accurately simulate the quasi-brittle rock behavior. Numerical results reveal distinct dynamic responses between bedding and anti-dip slopes, where local amplification zones (LAZs) act as seismic energy concentrators, while potential sliding zones (PSZs) exhibit hindering effects. Parametric analyses of strata dip angles and thicknesses identify a critical dip range where slope stability drastically decreases, highlighting high-risk configurations for earthquake-induced landslides. By linking the slope failure mechanism to seismic risk reduction strategies, this work provides practical guidelines for sustainable slope design and landslide mitigation in tectonically active regions. Full article

Introduction: Finger injuries are common in pediatric patients and typically heal well with conservative management. However, rare fracture patterns involving significant displacement and physeal injury, such as the one described in this case, require specialized surgical intervention to ensure proper healing and prevent long-term complications. Case Presentation: A 12-year-old left-hand-dominant female presented with pain, swelling, and deformity at the distal interphalangeal (DIP) joint following hyperextension of the left fifth digit. Initial radiographs revealed a volar displaced intra-articular fracture with physis involvement, confirmed by computed tomography (CT) imaging. Conservative management with closed reduction and splinting failed to achieve adequate alignment. Surgical intervention was performed via a dorsal approach, utilizing ORIF with K-wire fixation to restore joint congruity and ensure anatomic alignment. Outcomes: Postoperative follow-up demonstrated satisfactory healing, maintained reduction, and resolution of pain with no complications. The patient regained functional use of the digit with minimal stiffness, and the growth plate remained uninvolved during the recovery period. Discussion: This case underscores the importance of advanced imaging, early referral, and tailored surgical intervention for rare mallet fractures involving volar displacement and physeal injury. ORIF provided reliable stabilization and optimal outcomes in this complex case. Conclusions: Volar displaced Salter–Harris III fractures of the DIP joint are rare and challenging injuries in pediatric patients. This case highlights the role of ORIF in achieving successful outcomes and emphasizes the importance of precise reduction and stabilization to prevent long-term complications. Full article

Background: The knee joint performs a vital function in human movement, supporting significant loads and ensuring stability during daily activities. Methods: The objective of this study was to develop and validate a subject-specific framework to model knee flexion–extension by integrating 3D gait data with individualized musculoskeletal (MS) and finite element (FE) models. In this proof of concept, gait data were collected from a 52-year-old woman using Xsens inertial sensors. The MS model was based on the same subject to define realistic loading, while the 3D knee FE model, built from another individual’s MRI, included all major anatomical structures, as subject-specific morphing was not possible due to unavailable scans. Results: The FE simulation showed principal stresses from –28.67 to +44.95 MPa, with compressive stresses between 2 and 8 MPa predominating in the tibial plateaus, consistent with normal gait. In the ACL, peak stress of 1.45 MPa occurred near the femoral insertion, decreasing non-uniformly with a compressive dip around –3.0 MPa. Displacement reached 0.99 mm in the distal tibia and decreased proximally. ACL displacement ranged from 0.45 to 0.80 mm, following a non-linear pattern likely due to ligament geometry and local constraints. Conclusions: These results support the model’s ability to replicate realistic, patient-specific joint mechanics. Full article

This study departs from conventional stochastic statistical approaches for rock mass structural modeling. Based on deterministic structural surface parameters, including orientation (dip and dip direction), trace length, trace center coordinates, and spacing between structural surface sets, this research investigates the relationships among volumetric density, areal density, structural surface persistence, and inter-set spacing. With a focus on model domain dimensions, positioning of the model center, and mitigation of boundary effects, the methodology systematically addresses key considerations in modeling joints, layers, and faults. A deterministic Discrete Fracture Network (DFN) modeling approach is proposed accordingly. In this framework, joints are represented by disks, whereas lithological interfaces such as layers and faults are modeled as flat planes. The proposed method was applied to the Qingdao Metro Line 15 project. Validation results demonstrate that the surrounding rock classification derived from the model is in good agreement with field geological investigation data. Full article

Double-arch tunnels in inclined layered jointed rock masses face risks of lining cracking and collapse under bedding-inclined asymmetric stress (BIAS); however, related studies remain limited. Based on a case study of an expressway tunnel case in Zhejiang Province, a three-dimensional discrete element model of a double-arch tunnel was developed using Three-Dimensional Distinct Element Code (3DEC) (version 7.0, Itasca Consulting Group, Inc., Minneapolis, MN, USA). The impacts of joint dip angle (0–90°) and spacing (0.5–6.5 m) on deformation, BIAS evolution, and middle partition wall stability were analyzed. Key findings reveal that joint presence significantly amplifies surrounding rock deformation, with pronounced displacement increases observed on the counter-dip side. The BIAS intensity follows a unimodal distribution with joint dip angles, peaking within the 30–60° range. Increasing joint spacing reduces BIAS effects, with a 57.1% decrease in asymmetric deformation observed when spacing increases from 0.5 m to 6.5 m. The implementation of dip-side pilot excavation with the main tunnel full-face method, combined with an optimized support strategy (installing dip-side bolts perpendicular to joints and extending counter-dip side bolt lengths from 4 m to 6 m), achieved a near-unity stress ratio between tunnel sides under equivalent overburden depths compared to conventional methods. These findings offer theoretical and technical insights for optimizing excavation and reinforcement in similar tunnel engineering contexts. Full article

The rapidly evolving field of functional yarns has garnered substantial research attention due to their exceptional potential in enabling next-generation electronic textiles for wearable health monitoring, human–machine interfaces, and soft robotics. Despite notable advancements, the development of yarn-based strain sensors that simultaneously achieve high flexibility, stretchability, superior comfort, extended operational stability, and exceptional electrical performance remains a critical challenge, hindered by material limitations and structural design constraints. Here, we present a bioinspired, hierarchically structured core-sheath yarn sensor (CSSYS) engineered through an efficient dip-coating process, which synergistically integrates the two-dimensional conductive MXene nanosheets and one-dimensional silver nanowires (AgNWs). Furthermore, the sensor is encapsulated using a yarn-based protective layer, which not only preserves its inherent flexibility and wearability but also effectively mitigates oxidative degradation of the sensitive materials, thereby significantly enhancing long-term durability. Drawing inspiration from the natural architecture of plant stems—where the inner core provides structural integrity while a flexible outer sheath ensures adaptive protection—the CSSYS exhibits outstanding mechanical and electrical performance, including an ultralow strain detection limit (0.05%), an ultrahigh gauge factor (up to 744.45), rapid response kinetics (80 ms), a broad sensing range (0–230% strain), and exceptional cyclic stability (>20,000 cycles). These remarkable characteristics enable the CSSYS to precisely capture a broad spectrum of physiological signals, ranging from subtle arterial pulsations and respiratory rhythms to large-scale joint movements, demonstrating its immense potential for next-generation wearable health monitoring systems. Full article

Background: Syndactyly, the congenital fusion of digits, compromises hand function and esthetics. Although surgical separation is the standard treatment, the optimal timing of the intervention remains controversial. Methods: We prospectively analyzed 20 pediatric patients (86 operated fingers) undergoing syndactyly repair, comparing early (≤24 months) versus delayed (>24 months) surgery. Outcome measures included range of motion (ROM) at the metacarpophalangeal (MP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints; complications (synostosis, nail deformities, finger length disparity, webbing); and patient-reported outcomes assessed by the Disabilities of the Arm, Shoulder, and Hand (DASH) and overall esthetic satisfaction scores. Results: The median age at surgery was 31 months (IQR25/75: 24.75–36.5), with a median follow-up of 72 months (IQR25/75: 42.0–86.25). Notably, digits III (28.24%) and IV (29.41%) were predominantly affected. Delayed surgery resulted in significantly improved MP ROM (90.98° ± 8.44° vs. 73.13° ± 22.37°, p = 0.004) and DIP ROM (76.28° ± 22.24° vs. 67.19° ± 22.78°, p = 0.028), with a non-significant trend toward better PIP ROM (93.00° ± 25.18° vs. 77.37° ± 30.29°, p = 0.075). Furthermore, the incidence of synostosis was markedly reduced in the delayed surgery group (6.0% vs. 38.9%, p = 0.001). Despite superior joint function associated with delayed intervention, early surgery patients reported higher satisfaction with cosmetic results (3.00 vs. 2.80, p = 0.028), while the DASH scores remained comparably low between groups (0.00 vs. 0.24, p = 0.141). Finger length disparities and webbing were minimal. Conclusions: Our study challenges the conventional advocacy for early syndactyly repair, by demonstrating that delaying surgery beyond 24 months significantly enhances joint mobility and reduces the synostosis rate. However, the higher satisfaction observed as a result of early intervention suggests that surgical timing should be individualized for affected fingers, joints, and severities to balance the functional and cosmetic outcomes. Further studies are needed to define the optimal surgical timing and techniques for pediatric syndactyly. Full article

In this study, the dissimilar joining of aluminum to high-melting-point alloys, including steel, titanium, and copper, was successfully achieved through hot-dipping. By precisely controlling the dipping temperature at 670 °C and maintaining a dipping time of 5 s, uniform aluminum layers with a thickness of 3–4 mm were successfully formed on the surfaces of high-melting-point alloys. This process enabled effective dissimilar metal joining between Al/steel, Al/Ti, and Al/Cu. Metallurgical bonding at the joining interfaces was achieved through the formation of uniform intermetallic compounds, specifically Fe₄Al₁₃, TiAl₃, Al₂Cu, and Al₃Cu₄, respectively. The different joints exhibited varying mechanical properties: the Al/Cu joint demonstrated the highest shear strength at 79.1 MPa, while the Fe₄Al₁₃-containing joint exhibited the highest hardness, reaching 604.4 HV. Numerical simulations revealed that an obvious decrease in interfacial temperature triggered the solidification and growth of the aluminum layer. Additionally, the specific heat and thermal conductivity of the high-melting-point alloys were found to significantly influence the thickness of the aluminum layer. The hot-dip joining technology is well suited for dissimilar metal bonding involving large contact areas and significant differences in melting points. Full article

The question of at which energy the transition from galactic to extra-galactic cosmic rays takes place has been a long-standing conundrum in cosmic ray physics. The sun stands out as the closest and clearest astrophysical accelerator of cosmic rays, while other objects within and beyond the galaxy remain enigmatic. It is probable that the cosmic ray spectrum and mass components from these celestial sources share similarities, offering a novel approach to study their origin. In this study, we perform joint analysis of spectra and mass in the energy range from MeV to 10 EeV, and find the following: (1) $⟨\mathrm{lnA}⟩$ demonstrates three clear peaks, tagging component transition; (2) a critical variable $\Delta$ is adopted to define the location of the transition; (3) for protons, the knee is located at ∼1.8 PeV, and the boundary between the galaxy and extra-galaxy occurs at ∼60 PeV, marked by a spectral dip; and (4) the all-particle spectrum exhibits hardening at ∼60 PeV due to the contribution of nearby galaxies, and the extra-galaxy dominates ∼0.8 EeV. We hope the LHAASO experiment can perform spectral measurements of individual species to validate these specific observations. Full article

The fracture evolution and the strength characteristics of a jointed rock mass under hydro-mechanical coupling are key issues that affect the safety and stability of underground engineering. In this study, a kind of transparent rock-like resin was adopted to investigate the crack initiation and propagation modes of the 3D flaw under hydro-mechanical coupling. The influences of the water pressure and the flaw dip angle on the fracture modes of the 3D flaw and the strength properties of the specimen were analyzed. The experiment results indicated that under the initiation and propagation modes, the 3D flaw presented two types of modes: the low-water-pressure type and the high-water-pressure type. The increase in the water pressure had a significant promoting effect on the crack initiation and propagation, which changed the overall failure mode of the specimen. With the increase in the flaw dip angle, the critical growth length of the wing crack decreased and the initiation moment of the fin-like crack showed a hysteretic tendency. The influences of the water pressure on the crack initiation stress and failure strength had thresholds. When lower than the threshold, the crack initiation stress increased slightly and the failure strength decreased gradually with the increase in the water pressure. Once the threshold was exceeded, both the crack initiation stress and the failure strength decreased significantly with the increase in the water pressure. With the increase in the flaw dip angle, both the crack initiation stress and the failure strength showed a first decreasing and then increasing tendency. The lowest crack initiation stress and the failure strength were found for the specimen containing the 45° flaw, while the highest were found for the specimen containing the 75° flaw. This study helps to deepen the understanding of the fracture mechanism of the engineering rock mass under hydro-mechanical coupling and has certain theoretical and applied value in engineering design and construction safety. Full article

To investigate the dynamic wave propagation characteristics and dynamic response of heterogeneous layered slopes under a blasting vibration, a modeling method considering the slope’s layered dip angle and heterogeneity was proposed. Different dip jointed slope models were established using the Weibull random distribution function introduced to realize the stochastic distribution of rock mechanics parameters, representing heterogeneity. Taking the background project of the Sijiaying Yanshan Open-Pit Iron Mine as an example, through numerical simulation, the effects of different joint dip angles and rock hardness on the slope’s dynamic response were analyzed in detail. The sensitivity of the elastic modulus, cohesion, and friction angle to the slope dynamic response was also investigated. A comparative analysis of the amplification effects between a jointed slope and heterogeneous slope was conducted. Finally, the dynamic stability of the jointed slope and heterogeneous slope under a blasting load was analyzed. The results indicate that the Peak Ground Acceleration (PGA) of jointed slopes with dip angles of 45° and 60° is generally higher than that of slopes with a 0° dip angle and without joints. The smaller the rock mass heterogeneity, the smaller the PGA at the measuring points, and the less sensitive the PGA is to variations in the three quantities. Under the same physical and mechanical parameters of the rock, the amplification factor of jointed slopes is generally greater than that of heterogeneous slopes. Under the blasting load, the overall dynamic time-series safety factors of both slopes decrease first and then increase, with the safety factor reaching its lowest value at the location of the strongest blasting vibration wave. This study can provide guidance for the blasting design and safety protection of layered dip slopes and serve as a reference for the analysis of blasting impact laws in similar mines. Full article