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Inertial measurement units (IMUs) are being recognized in clinical and rehabilitation settings for their ability to assess movement-related disorders of the spine for better guidance of treatment-planning and tracking of recovery. This study evaluated the Mbientlab MetaMotionR IMUs, relative to Vicon motion capture equipment in measuring local dynamic stability of the spine (quantified using maximum finite-time Lyapunov exponent; λmax), lumbopelvic coordination (quantified using mean absolute relative phase; MARP), and intersegmental motor variability (quantified using deviation phase; DP) of lumbopelvic segments in 10 participants during 35 cycles of repetitive spine flexion–extension (FE). Intraclass correlations were strong between systems when using both the FE angle time-series and the sum of squares (SS) time-series to measure local dynamic stability (0.807 ≤ICC2,1λmax,FE ≤ 0.919; 0.738 ≤ ICC2,1λmax,SS ≤ 0.868), sagittal-plane lumbopelvic coordination (0.961 ≤ICC2,1MARP ≤ 0.963), and sagittal-plane lumbopelvic variability (0.961 ≤ICC2,1DP ≤ 0.963). It was concluded that the MetaMotionR IMUs can be reliably used for measuring features associated with spine movement quality and motor control during a repetitive FE task. Future work will assess the reliability of sensor placement, performance during multi-directional movements, and ability to discern clinical and healthy populations based on assessment of movement quality and control.

The machining of aerospace deep cavity parts was prone to issues such as chatter. Currently, discrete-edge end mills are commonly employed in milling these parts, yet the vibration reduction mechanism of the cutter and the rationality of the distribution position of the chip-split groove have not been systematically studied. Consequently, a design method of distribution position of chip-split groove of discrete-edge end mill was proposed. Initially, the correlation between the discrete parameters of discrete-edge end mills and the eigenvalue of cutting vibration was examined to elucidate how the structural characteristics of discrete-edge end mills impact vibration. Subsequently, the impact of discrete-edge end mill structure, tool-work contact system, and cutting parameters on vibration was sequentially assessed. The effect of discrete parameters on the dynamic characteristics and cutting forces of the end mill was investigated, and the vibration reduction mechanism of discrete-edge end mill was revealed. Furthermore, the distribution position of chip-split groove of the discrete-edge end mill was optimized based on the Improved Grey Wolf Algorithm (I-GWO). The optimized parameters were as follows: a width of 1 mm, a total of 4 grooves, arranged alternately with varying density. Finally, the design method of distribution position of chip-split groove of discrete edge end mill was proposed, and the effectiveness of the method was verified by experiments. This method serves as a foundational reference for the design and production of discrete-edge end mills.

Assessment of gait parameters is commonly performed through the high-end motion tracking systems, which limits the measurement to sophisticated laboratory settings due to its excessive cost. Recently, Microsoft Kinect (v2) sensor has become popular in clinical gait analysis due to its low-cost. But, determining the accuracy of its RGB-D image data stream in measuring the joint kinematics and local dynamic stability remains an unsolved problem. This study examined the suitability of Kinect(v2) RGB-D image data stream in assessing those gait parameters. Fifteen healthy participants walked on a treadmill during which lower body kinematics were measured by a Kinect(v2) sensor and a optophotogrametric tracking system, simultaneously. Extended Kalman filter was used to extract the lower extremity joint angles from Kinect, while inverse kinematics was used for the gold standard system. For both systems, local dynamic stability was assessed using maximal Lyapunov exponent. Sprague’s validation metrics, root mean square error (RMSE) and normalized RMSE were computed to confirm the difference between the joint angles time series of the two systems while relative agreement between them was investigated through Pearson’s correlation coefficient (pr). Fisher’s Exact Test was performed on maximal Lyapunov exponent to investigate the data independence while reliability was assessed using intraclass correlation coefficients. This study concludes that the RGB-D data stream of Kinect sensor is efficient in estimating joint kinematics, but not suitable for measuring the local dynamic stability.

Previous work has identified that individuals adopt different dynamic lumbar spine stability responses when experiencing back muscle fatigue, and that the neuromuscular system adjusts multi-joint coordination in response to fatigue. Therefore, this study was designed to determine whether distinct differences in coordination and coordination variability would be observed for those who stabilize, destabilize, or demonstrate no change in dynamic stability when their back muscles are fatigued. Thirty participants completed two repetitive trunk flexion–extension trials (Rested, Fatigued) during which lumbar flexion–extension dynamic stability, thorax-pelvis movement coordination, and coupling angle variability (CAV) were assessed. Dynamic stability was evaluated using maximum Lyapunov exponents (λmax) with participants being allotted to stabilizer, destabilizer, or no change groups based on their stability response to fatigue. Each flexion–extension repetition was further segregated into two phases (flexion, extension) and vector coding analyses were implemented to determine thorax-pelvis coordination and CAV during each movement phase. Results demonstrated that when fatigued, ∼30% of individuals adopted more stable (lower λmax) flexion–extension movements and greater CAV during the extension phase, ∼17% of individuals became less stable (higher λmax) and exhibited decreased CAV during the extension phase, and the remaining ∼53% of individuals expressed no change in dynamic stability or CAV. Additionally, more in-phase coordination patterns were generally observed across all individuals when fatigued. Altogether, this study highlights the heterogeneous nature of lumbar spine movement behaviours within a healthy population in response to fatigue.

Context In this study, the authors have investigated the structural, optoelectronic, thermoelectric, and thermodynamic properties of Ca 2 NaIO 6 and Sr 2 NaIO 6 double perovskite oxides. Both materials exhibit semiconductor behavior with direct band gaps ( E g ) of 0.353 eV and 0.263 eV, respectively. Optical parameters like absorption coefficient α(ω), reflectivity R(ω), dielectric constants, and refractive index have been calculated. The most notable absorption peaks are identified at 5.52 eV (equal to 108.33 × 10 4  cm −1 ) in the case of Ca 2 NaIO 6 and at 11.16 eV (equivalent to 118.17 × 10 4  cm −1 ) for Sr 2 NaIO 6 . These findings suggest a promising outlook for applications in optoelectronics. Moreover, their commendably low thermal conductivity and a high figure of merit, particularly at low temperatures (100 K), indicate their effectiveness as thermoelectric materials. This analysis underscores that these materials hold potential as suitable candidates for n-type doping, making them well-suited for use in thermoelectric devices. Studying thermal properties, including thermal expansion, bulk modulus, acoustic Debye temperature, entropy, and heat capacity, contributes to understanding the materials’ thermodynamic stability. The titled materials are dynamically stable. The analysis of these double perovskite materials highlights their potential across various technological applications due to their advantageous structural, electronic, optical, and transport properties, offering new possibilities in material science and technology development. Methods The study utilized the full potential linearized augmented plane wave (FP-LAPW) method in conjunction with density functional theory within the WIEN2k simulation code. This approach is widely recognized as one of the most dependable methods for evaluating the photovoltaic characteristics of semiconducting perovskites. The thermoelectric properties were ascertained using the rigid band approach and the constant scattering time approximation, both implemented in the BoltzTraP computational code.

Concussed individuals commonly exhibit locomotor deficits during dual-task gait that can last substantially longer than clinical signs and symptoms. Previous studies have examined traditional stability measures, but nonlinear stability may offer further information about the health of the motor control system post-concussion. For up to one year post-concussion, this study longitudinally examined the local dynamic stability of five concussed athletes and four matched healthy controls during single- and dual-task gait. Local dynamic stability (LDS) was estimated using short-term, finite-time maximum Lyapunov exponents calculated from tri-axial accelerometers placed on the trunk and head. No main effects of group or task were found for LDS or stride time variability, but significant group*task interactions were apparent for trunk stability and stride time variability. Concussed individuals exhibited decreased trunk LDS and increased stride time variability during dual-task walking compared to matched controls despite similar single-task stability and variability. These preliminary results reinforce previous reports that concussions persistently affect dual-task processes even when single-tasks may be unaffected. Furthermore, the decreased local dynamic stability during dual-task gait indicates the concussed group attenuated local disturbances less than their healthy teammates. The decreased dynamic stability during dual-task activities was present after the athletes were cleared for competition and may be a contributing factor in the higher rates of musculoskeletal injuries in athletes post-concussion.

A large amount of underground cavities nowadays exists throughout the Apulian region (south-eastern Italy) as a result of mining processes of soft calcarenite, which frequently followed the “room and pillar” technique. In these cave systems, pillars and septa are critical structures, whose failure can lead to a significant increment of the sinkhole hazard. The behaviour of these rocky structures in the dynamic field is poorly studied in literature, and the present study aims to investigate their dynamic stability, according to regional seismicity data. For this purpose, ideal pillar geometries were considered, for which the evolution of the stress–strain field under dynamic inputs was observed in both 2D and 3- configurations by means of parametrical finite element analysis. For shallow cavities, slender septa were found to be the most affected by the influence of seismic loading. For deep cavities, dynamic instability is observed only for rather squat septa, with the cavity width also influencing the dynamic behaviour. To quantitatively assess the septum stability, a stability index was also proposed in 2D models. Moreover, three-dimensional analyses showed a stabilizing effect in the pillar exerted by the stress component perpendicular to the earthquake.

To address the problem of brittle damage of CGACs under seismic loads, a C&S-RAC and an EB-SAC were developed. Multiple sets of shaking table model tests of anchored slopes under the excitation of El Centro, Landers and sine waves were carried out. The effect of the type and frequency of seismic waves on the dynamic response law of the C&S-RAC and EB-SAC reinforced slopes was clarified, and a new method for evaluating the dynamic stability of anchored slopes based on GMM was established. The results show that the shock-absorbing devices of the C&S-RAC and EB-SAC can effectively reduce the shock effect of earthquakes on slopes and reduce the whiplash effect of anchored slopes. The seismic reinforcement performance of each type of anti-seismic anchor cable differs at different seismic frequencies, and the influence of the seismic wave frequency should be considered when selecting anti-seismic anchor cables in the seismic reinforcement design of slopes. The EB-SAC buffer cushion effectively decreases the vibration intensity of the anchor plate and has a stronger seismic isolation effect on high-frequency seismic waves. The research results provide more references for the selection of anchor cables for slope reinforcement in high seismic intensity areas and the stability evaluation of anchored slopes during earthquakes.

Architected cellular structures are designed by tessellating unit cells in a periodic fashion. The optimisation of the cellular structures ensures their compatibility with engineering applications in which mechanical properties are highly customised to meet a specific requirement while preserving considerable lightweight. The present paper aims to explore the dynamic buckling behaviour of the imperfect sandwich plate with an architected cellular core. The homogeneous method is adopted to obtain the effective material properties of the cellular core with various unit cell configurations. Different impact loading cases, namely, the sinusoidal, exponential, rectangular, and damping impulses, have been simulated. Meanwhile, two common types of boundary restraints (i.e., simply supported and clamped) are embraced in the investigation. The governing equation system is built based on the first-order shear deformation plate theory with the Von Karman nonlinearity and then resolved by the Galerkin and the fourth-order Runge-Kutta methods. Volmir criterion is employed to determine the critical dynamic buckling load. Several validations are made before conducting systematic numerical experiments. The correlations between the dynamic buckling load of the sandwich model and a number of crucial factors, such as the geometry and relative density of the cell unit, the initial imperfection and boundary conditions of the sandwich plate, elastic foundation coefficients, and damping, are discussed. In addition, the load-to-weight ratio is shown, which will aid in determining the optimal unit cell design and relative density for light-weighting a specific technical component.

In distributed wireless systems enabled by multimodal sensing and semantic communication, heterogeneous modalities provide richer task-relevant information but simultaneously introduce asynchronous updates due to modality-dependent sensing, processing, and transmission delays. How such asynchronous multimodal communication affects the dynamic stability of the overall system remains insufficiently understood. This paper investigates the fundamental relationship between semantic information richness and system stability in distributed multimodal wireless communication. To this end, a unified system model is developed in which multimodal semantic streams are embedded into the continuous-time task state evolution, explicitly accounting for heterogeneous delays and MIMO transmission effects. The resulting system is formulated as a delay-coupled dynamic model, and Lyapunov–Krasovskii analysis is employed to characterize the stability conditions under asynchronous semantic updates. An explicit stability perturbation metric is derived to quantify how delayed multimodal information influences system dynamics. The analysis reveals a fundamental trade-off between semantic information richness and dynamic stability: incorporating additional modalities does not always improve system performance and may destabilize the system when asynchronous delays accumulate. Based on this insight, a stability-aware optimization framework is proposed to regulate modality participation and precoding design. The results highlight the necessity of stability-driven multimodal communication design for future distributed wireless and 6G intelligent systems.