Cavitation erosion is a predominant failure mode of austenitic stainless steels in corrosive fluid environments, severely limiting their durability in nuclear piping and hydraulic components. In this study, five 316LN steels with 0.008–0.34 wt.% nitrogen content were fabricated, and both short-term (2 h) and long-term (24 h) cavitation tests were performed to elucidate the effect and mechanism of nitrogen. Increasing nitrogen markedly enhanced cavitation resistance: after 24 h, the cumulative mass loss decreased by 36%, 52%, 60%, and 71% for 09N, 17N, 22N, and 34N relative to 00N, accompanied by lower surface roughness, shallower pit depth, and a prolonged incubation stage. SEM revealed a progressive damage process from twin/high-angle grain boundaries to intragranular deformation bands and finally to spalling at slip intersections, whereas high-N steels exhibited only slight local detachment. TEM demonstrated that nitrogen transformed dislocations from random networks into dense slip bands and planar arrays with stacking faults, raising hardness from ~140 HV to ~260 HV. EBSD further confirmed strain-induced martensite transformation under severe deformation, providing additional strengthening. These results reveal that nitrogen improves cavitation resistance by tailoring dislocation structures and enhancing strength–plasticity compatibility, offering guidance for the design of high-performance austenitic stainless steels in cavitation environments.

This study developed and evaluated a novel upper-limb rehabilitation device that integrates piano playing into task-oriented occupational therapy, addressing the limitations of traditional continuous passive motion (CPM) training in patient engagement and functional recovery. The system features a bi-axial sliding platform for precise 61-key positioning and a ten-link, four-loop robotic hand for key striking. A hierarchical control framework incorporates MIDI-based task mapping, finger optimization using an improved Hungarian algorithm, and impedance–admittance hybrid control for adaptive force–position modulation. An 8-week randomized controlled trial demonstrated that the experimental group significantly outperformed the control group, with a 74.7% increase in Fugl–Meyer scores (50.5 ± 2.5), a 14.6-point improvement in the box and block test (BBT), a 20.2-s reduction in nine-hole peg test (NHPT) time, and a 72.6% increase in rehabilitation motivation scale (RMS) scores (55.4 ± 3.8). The results indicate that combining piano playing with robotic rehabilitation enhances neuroplasticity and engagement, significantly improving motor function, daily activity performance, and rehabilitation adherence. This mechanical-control synergy introduces a new paradigm for music-interactive rehabilitation, with potential applications in home-based remote therapy and multimodal treatment integration.

Piano-based occupational therapy has emerged as an engaging and effective rehabilitation strategy for improving upper limb motor functions. However, a lack of comprehensive biomechanical modeling, objective rehabilitation assessment, and real-time fatigue monitoring has limited its clinical optimization. This study developed a comprehensive “key–finger–exoskeleton” biomechanical model based on Hill-type muscle dynamics and rigid-body kinematics. A three-dimensional muscle synergy analysis method using non-negative tensor factorization (NTF) was proposed to quantitatively assess rehabilitation effectiveness. Furthermore, a real-time Comprehensive Muscle Fatigue Index (CMFI) based on multi-muscle coordination was designed for fatigue monitoring during therapy. Experimental validations demonstrated that the biomechanical model accurately predicted interaction forces during piano-playing tasks. After three weeks of therapy, patients exhibited increased synergy modes and significantly improved similarities with healthy subjects across spatial, temporal, and frequency domains, particularly in the temporal domain. The CMFI showed strong correlation (r > 0.83, p < 0.001) with subjective fatigue ratings, confirming its effectiveness in real-time fatigue assessment and training adjustment. The integration of biomechanical modeling, synergy-based rehabilitation evaluation, and real-time fatigue monitoring offers an objective, quantitative framework for optimizing piano-based rehabilitation. These findings provide important foundations for developing intelligent, adaptive rehabilitation systems.