Search Results (5,165)

Exoskeleton-assisted bodyweight support training (BWST) has demonstrated enhanced neurorehabilitation outcomes in which joint motion prediction serves as the critical foundation for adaptive human–machine interactive control. However, joint angle prediction under dynamic unloading conditions remains unexplored. This study introduces an adaptive wavelet-denoising fusion (AWDF) model to predict lower-limb joint angles during BWST. Utilizing a custom human-tracking bodyweight support system, time series data of surface electromyography (sEMG), and inertial measurement unit (IMU) from ten adults were collected across graded bodyweight support levels (BWSLs) ranging from 0% to 40%. Systematic comparative experiments evaluated joint angle prediction performance among five models: the sEMG-based model, kinematic fusion model, wavelet-enhanced fusion model, late fusion model, and the proposed AWDF model, tested across prediction time horizons of 30–150 ms and BWSL gradients. Experimental results demonstrate that increasing BWSLs prolonged gait cycle duration and modified muscle activation patterns, with a concomitant decrease in the fractal dimension of sEMG signals. Extended prediction time degraded joint angle estimation accuracy, with 90 ms identified as the optimal tradeoff between system latency and prediction advancement. Crucially, this study reveals an enhancement in prediction performance with increased BWSLs. The proposed AWDF model demonstrated robust cross-condition adaptability for hip and knee angle prediction, achieving average root mean square errors (RMSE) of 1.468° and 2.626°, Pearson correlation coefficients (CC) of 0.983 and 0.973, and adjusted R² values of 0.992 and 0.986, respectively. This work establishes the first computational framework for BWSL-adaptive joint prediction, advancing human–machine interaction in exoskeleton-assisted neurorehabilitation. Full article

As the world is technologically advancing, the integration of FSO communication in
non-terrestrial platforms is transforming the landscape of global connectivity. By enabling
high-data-rate inter-satellite links, secure UAV–ground channels, and efficient HAPS
backhaul, FSO technology is paving the way for sustainable 6G non-terrestrial networks.
However, the stringent requirement for precise line-of-sight (LoS) alignment between
the optical transmitter and receivers poses a hindrance in practical deployment. As
non-terrestrial missions require continuous movement across the mission area, the platform
is subject to vibrations, dynamic motion, and environmental disturbances. This makes
maintaining the LoS between the transceivers difficult. While fine-pointing mechanisms
such as fast steering mirrors and adaptive optics are effective for microradian angular
corrections, they rely heavily on an initial coarse alignment to maintain the LoS. Coarse
pointing modules or gimbals serve as the primary mechanical interface for steering
and stabilizing the optical beam over wide angular ranges. This survey presents a
comprehensive analysis of coarse pointing and gimbal modules that are being used in
FSO communication systems for non-terrestrial platforms. The paper classifies gimbal
architectures based on actuation type, degrees of freedom, and stabilization strategies.
Key design trade-offs are examined, including angular precision, mechanical inertia,
bandwidth, and power consumption, which directly impact system responsiveness and
tracking accuracy. This paper also highlights emerging trends such as AI-driven pointing
prediction and lightweight gimbal design for SWap-constrained platforms. The final part
of the paper discusses open challenges and research directions in developing scalable and
resilient coarse pointing systems for aerial FSO networks Full article

To address the altitude control requirements of high-altitude latex balloons, this paper proposes a novel lightweight electromagnetically actuated valve design. The valve employs a permanent magnet–electromagnet–spring composite structure to achieve rapid opening/closing motions through electromagnetic force control, enabling precise regulation of balloon gas venting. 3D electromagnetic field simulations were conducted to validate the magnetic flux density distribution, while computational fluid dynamics (CFD) simulations based on the Reynolds-averaged Navier–Stokes equations were employed to evaluate the valve’s aerodynamic characteristics. The CFD results confirmed stable venting performance, with near-linear flow–pressure relationships and localized jet structures that support reliable operation under stratospheric conditions. A multidisciplinary optimization framework was further applied to achieve a lightweight structural design of critical components. Experimental results demonstrate that the optimized valve achieves a total mass of 984.69 g with an actuation force of 15.263 N, maintaining stable performance across a temperature range of −60 °C to 25 °C. This study provides an innovative and systematically validated solution for micro-valve design in lighter-than-air vehicles. Full article

Precise estimate of antenna location is essential for high-quality three-dimensional (3D) radar imaging, especially under sparse sampling schemes. In scenarios involving synchronized scanning and rotational motion, small deviations in the radar’s transmitting position can lead to significant phase errors, thereby degrading image fidelity or even causing image failure. To address this challenge, we propose a novel trajectory estimation method based on microwave three-point ranging. The method utilizes three fixed microwave-reflective calibration spheres positioned outside the imaging scene. By measuring the one-dimensional radial distances between the radar and each of the three spheres, and geometrically constructing three intersecting spheres in space, the radar’s spatial position can be uniquely determined at each sampling moment. This external reference-based localization scheme significantly reduces positioning errors without requiring precise synchronization control between scanning and rotation. Furthermore, the proposed approach enhances the robustness and flexibility of sparse sampling strategies in near-field radar imaging. Beyond ground-based setups, the method also holds promise for drone-borne 3D imaging applications, enabling accurate localization of onboard radar systems during flight. Simulation results and error analysis demonstrate that the proposed method improves trajectory accuracy and supports high-fidelity 3D reconstruction under non-ideal sampling conditions. Full article

Background: Unicompartmental knee arthroplasty (UKA) represents a well-recognized treatment option for isolated medial compartment osteoarthritis; however, the debate regarding the superiority of fixed-bearing versus mobile-bearing designs continues. We aimed to evaluate the mid- to long-term outcomes of medial UKA comparing mobile- versus fixed-bearing designs within a single institution over an average 10-year follow-up. Methods: This retrospective study included 81 consecutive patients who underwent primary medial UKA (45 fixed-bearing and 36 mobile-bearing) with a minimum five-year follow-up. Clinical outcomes were measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and range of motion (ROM). Radiological measurements included hip-knee-ankle axis angle (HKA) and osteoarthritis progression. Implant survivorship was evaluated using Kaplan–Meier analysis, with failure defined as either conversion to total knee arthroplasty (TKA) or polyethylene (PE) exchange. Results: At a mean follow-up of 10.6 years, WOMAC scores, ROM, and radiological outcomes showed no statistically significant differences between the fixed-bearing and mobile-bearing groups. Significantly higher failure rates were observed in the mobile-bearing group, both when considering conversion only (p = 0.041) and when including conversion or PE exchange (p = 0.009). Survival analysis demonstrated 10-year rates of 97.8% for fixed-bearing and 88.9% for mobile-bearing with TKA conversion defined as failure (p = 0.066). Using combined failure criteria of TKA conversion or PE exchange, 10-year survival rates were 97.8% for fixed-bearing and 83.3% for mobile-bearing (p = 0.015). Conclusions: At a mean 10.6-year follow-up, clinical and radiological outcomes were comparable, but fixed-bearing UKA demonstrated superior survivorship. Full article

This paper presents the results of seakeeping tests conducted on the Tritor, a remotely controlled autonomous unmanned surface vehicle (USV) featuring a trimaran hull design known as the Three Slender Cylinders Hull (3SCH) and equipped with electric propulsion. Previous research focused on the vehicle’s design, prototype development, and initial functional testing. Tritor is characterised by its simple design and construction, reliable propulsion system, and excellent stability and manoeuvrability. Its control and navigation systems have demonstrated effective performance in both remote-controlled and fully autonomous modes. In the present study, seakeeping tests were carried out in a towing tank, with repeated trials conducted at various speeds and wavelengths. The selected wavelengths were close to the vehicle’s length, where the most significant responses were expected. Test speeds ranged from 1.0 to 2.5 m per second, based on prior operational experience with the vehicle. Due to the constraints of the towing tank, all wave directions were limited to head seas. Measurements included heave and pitch motions. Vertical accelerations at the vehicle’s centre of gravity were derived from the heave data and used as a key indicator of seakeeping performance. The results were evaluated against established seakeeping criteria related to vessel operability and structural safety. Full article

Background/Objectives: Children with myelomeningocele (MMC) often experience lower extremity muscular contractures, which can impact their functional mobility. While standing programs have demonstrated benefits for children with other neuromuscular conditions, there is limited evidence on their use in ambulatory children with MMC who have joint deformities. This single-subject design study examined the impact of a home-based standing program on two ambulatory children with MMC, focusing on lower extremity muscle flexibility, functional movement quality, gait velocity, and participation in daily activities. Methods: Two children participated in a multi-phase single-subject (ABABA) withdrawal design beginning with the baseline phase and then alternating between the intervention and withdrawal phases. The intervention consisted of 60-minute standing sessions, five days a week, using a sit-to-stand stander (STSS) with support and supervision from a physical therapist (PT) and the parent. Primary outcomes included goniometric passive range of motion (PROM) and 10-Meter Walk Test (10 MWT). Secondary outcomes included the Pediatric Neuromuscular Recovery Scale (Peds NRS) and the Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT). Results: Improvements in hip and knee muscle flexibility were observed during the intervention phases, with some loss during the withdrawal phase. Functional movement quality improved in both children. Gait velocity and participation in daily activity scores remained stable during intervention phases. Parental feedback reflected increased independence and high engagement with the home program. One child discontinued due to a heel injury, highlighting the need for individualized support. Conclusions: Personalized standing programs may improve muscle flexibility and functional movement quality in ambulatory children with MMC. Further research is warranted to determine the optimal dosing regimen, ensure safety, and assess long-term functional outcomes. Full article

The upper limb stretching device plays a key role in enhancing physical function. Current commercial upper limb stretching devices often suffer from limited functionality and are poorly aligned with the biomechanics of the human arm. To address these limitations, this paper presents the design of an ergonomic device for upper limb stretching. Firstly, the development of a regression model for the upper limb force test was carried out through the Box–Behnken Design (BBD) response surface methodology. Secondly, the Denavit-Hartenberg (D-H) method was adopted for the kinematic analysis of the human upper limb stretching mechanism. Subsequently, a kinematic model was established by coupling the data from Creo Parametric and ADAMS models. The kinematic characteristics were then investigated throughout the entire range of motion, yielding the corresponding kinematic parameter curves. Next, the finite element method was employed within ABAQUS to model the upper limb stretching mechanism, to allow for a detailed strength analysis of its key components. Finally, a prototype was manufactured and tested through upper limb stretching experiments to validate its performance. The results demonstrate that the designed stretching mechanism achieved the desired range of motion, with its angular velocity and angular acceleration exhibiting smooth variations. The maximum stress observed is 195.2 MPa, which meets the design requirements. This study provides a valuable reference for the development of future human stretching devices. Full article

Background: Healthcare professionals are at significant risk of musculoskeletal injuries due to the physically demanding nature of patient-handling tasks. While various ergonomic interventions have been introduced to mitigate these risks, comprehensive methods for assessing and addressing musculoskeletal hazards remain limited. Purpose: This study presents a novel approach to evaluating musculoskeletal injury risks among healthcare workers, marking the first instance in which two motion tracking systems are used simultaneously. This dual-system setup enables a more comprehensive and dynamic analysis of worker interactions in real time. Healthcare professionals were divided into three groups to perform patient transfer tasks. Three key poses within the task, associated with peak lumbar forces, were identified and analyzed. Results: The resulting compressive forces on the participants’ lower back ranged from 581.0 N to 3589.1 N, and the Anterior–Posterior (A/P) shear forces ranged from 33.1 N to 912.3 N across the three poses. Relative differences in trunk flexion showed strong correlations with compressive and A/P shear forces at each pose, respectively. Discussion and conclusion: Strong associations were found between lumbar loads and participant’s anthropometrics. Recommendations for optimal postures and partner pairings were developed to help reduce the risk of lower back injuries during patient handling. Full article

This paper presents the third-generation design of Bimu, a compact wearable inertial measurement unit (IMU) tailored for advanced human motion tracking. Building on prior iterations, Bimu R2 focuses on enhancing thermal stability, data integrity, and energy efficiency by integrating onboard memory, redesigning the power management system, and optimizing the communication interfaces. A detailed performance evaluation—including noise, bias, scale factor, power consumption, and drift—demonstrates the device’s reliability and readiness for deployment in real-world applications ranging from clinical gait analysis to high-speed motion capture. The improvements introduced offer valuable insights for researchers and engineers developing robust wearable sensing solutions. Full article

Seven groups of long-period ground motions (LPGMs) and three groups of ordinary ground motions (OGMs) were selected and bidirectionally input into a high-rise structure; the energy distribution and dissipation characteristics of the structure were studied comparatively. The results show that at the same seismic level, the input energy of the structure under LPGMs is significantly greater than that under OGMs. Under OGMs, the structure mainly dissipates energy through damping energy, while under LPGMs, hysteretic energy becomes the main way of energy dissipation. During an 8-degree frequent earthquake, coupling beams are the main energy dissipation members, the floors below 2/3 of the structural height mainly dissipate hysteresis energy by coupling beams, with the hysteretic energy ratio ranging from 61% to 99.9%, and the floors above 2/3 of the structural height mainly dissipate hysteretic energy by frame beams. During 8-degree design and rare earthquakes, the hysteretic energy ratio of coupling beams significantly decreases, and frame beams are the main energy-dissipating members; the hysteresis energy on the first to second floors is mainly dissipated by shear walls, while on floors above the third floor, the hysteresis energy is mainly borne by frame beams, the hysteretic energy ratio from the fifth to the twelfth accounts for 56% to 89%, and above the twelfth floor accounts for more than 85% to 90% on that floor. Full article

In children under 4, septic arthritis of the hip (SAH) caused by Kingella kingae (SAH-KK) can be misdiagnosed, as it does not meet classic septic joint criteria (fever > 38.5°, pain, limited range of motion, and inability to bear weight). The objective of this study was to report clinical and paraclinical characteristics in a large cohort of children with confirmed SAH-KK and to evaluate the reliability of the Kocher (KC) and Caird criteria (CC) in predicting SAH-KK. Medical records of 140 children with confirmed SAH-KK were collected. Data on sex, age, temperature on admission, weight-bearing status, white blood cell (WBC) count, platelet count, C-reactive protein (CRP) value, and erythrocyte sedimentation rate (ESR) were extracted. The study focused on the sensitivity of KC (body temperature, refusal to bear weight, leukocytosis, and ESR) and CC (KC criteria plus CRP level). All patients had bacteriologically confirmed SAH-KK; most had mild symptoms and near-normal inflammatory markers. CRP (76.2%) had the highest sensitivity, followed by weight-bearing status (73.8%) and WBC count (69.6%). Body temperature and ESR exceeded cutoff values in less than 50% of cases. Among 77 patients fulfilling all KC, 49 (63.5%) had less than a 40% probability of SAH. Of 50 children with complete CC, 20 (40%) had a 62.4% or lower probability of SAH. KC and CC are not sufficiently accurate to confidently exclude SAH-KK in preschool-aged children due to heterogeneous clinical presentations. Further studies are needed to redefine diagnostic criteria based on patient age and causative pathogens. Full article

Due to their potential to reduce greenhouse gas emissions, light-frame timber buildings (LFTBs) are widely used in seismically active regions. However, their construction in these areas remains limited, primarily due to the high costs associated with continuous anchor tie systems (ATSs), which are required to withstand significant seismic forces. To address this challenge, frictional seismic isolation offers an alternative by enhancing seismic protection. Although frictional base isolation is an effective mitigation strategy, its performance can be compromised by extreme ground motions that induce large lateral displacements, resulting in impacts between the sliders and the perimeter protection ring. The effects of these internal lateral impacts on base-isolated LFTBs remain largely unexplored. To fill this knowledge gap, this study evaluates the collapse capacity of a set of base-isolated LFTBs representative of Chilean real estate developments. Nonlinear numerical models were developed in the OpenSeesPy platform to capture the nonlinear behavior of the superstructure, including the impact effects within the frictional isolation system. Incremental dynamic analyses following the FEMA P695 methodology were performed using subduction ground motions. Collapse margin ratios (CMRs) and fragility curves were derived to quantify seismic performance. Results indicate that frictional base-isolated LFTBs can achieve acceptable collapse safety without ATS, even with compact-size bearings. Code-conforming archetypes achieved CMRs ranging from 1.24 to 1.55, indicating sufficient safety margins. These findings support the cost-effective implementation of frictional base isolation in mid-rise timber construction for high-seismic regions. Full article

The motion of ships in the ocean follows six degrees of freedom, and accurately measuring this motion is crucial for improving marine engineering operations. Among the six degree-of-freedom movement of ships, the change in ship heave freedom has the worst impact on offshore lifting operations. At present, the most common method for measuring heave displacement is by integrating heave acceleration twice. The heave motion of ships belongs to low-frequency motion, but the low-frequency band range is often easily overlooked. This paper first analyzes the wave spectrum to determine the dominant frequency range of ship heave motion under typical wind speeds, which is found to be between 0.22 Hz and 0.45 Hz. The accuracy of low-frequency ship heave displacement signals largely depends on the heave acceleration signal, and filtering acceleration signals in the low-frequency range is particularly difficult. To address this challenge, this paper proposes a low-frequency component filtering method for heave acceleration signal of marine ships, which effectively avoids the phase and peak-to-peak errors introduced by traditional filters. This method further improves the filtering performance of acceleration signals in the 0.2 Hz to 0.5 Hz low-frequency range and can provide the crane driver with a motion reference for the heave of the ship when the ship is performing lifting operations. Full article

Background: Glenoid radiolucenct lines (gRLL) and glenoid component subsidence (gSC) after anatomic total shoulder arthroplasty (aTSA) have traditionally been linked to implant loosening and functional decline. However, their impact on long-term clinical outcomes remains unclear. This study aimed to evaluate whether gRLL and gSC are associated with inferior clinical or functional results in patients without revision surgery. Methods: In this retrospective study, 52 aTSA cases (2008–2015) were analyzed with a minimum of five years of clinical and radiographic follow-up. Based on final imaging, patients were categorized according to the presence and extent of gRLL and gSC. Clinical outcomes included the Constant-Murley Score, DASH, VAS for pain, and range of motion (ROM). Radiographic parameters included the critical shoulder angle (CSA), acromiohumeral distance (AHD), lateral offset (LO), humeral head-stem index (HSI), and cranial humeral head decentration (DC). Group comparisons were conducted between: (1) ≤2 vs. 3 gRLL zones, (2) 0 vs. 1 zone, (3) 0 vs. 3 zones, (4) gSC vs. no gSC, and (5) DC vs. no DC. Results: Demographics and baseline characteristics were comparable across groups. Functional scores (Constant, DASH), pain (VAS), and ROM were largely similar. Patients with extensive gRLL showed reduced external rotation (p = 0.01), but the difference remained below the MCID. Similarly, gSC was associated with lower forward elevation (p = 0.04) and external rotation (p = 0.03), both below MCID thresholds. No significant differences were observed for DC. Conclusions: Neither extensive gRLL nor gSC significantly impaired long-term clinical or functional outcomes. As these radiographic changes can occur in the absence of symptoms, regular radiographic monitoring is essential, and revision decisions should be made individually in cases of progressive bone loss. Full article