Search Results (972)

As a key technology for the fifth-generation of mobile communications, massive MIMO systems enable massive user access via large-scale arrays. However, their dense deployment extends the near-field (NF) region, introducing new localization complexities. Based on an exact spherical wavefront model, this paper proposes a multiple-cumulant-matrices-based method for NF source localization using a Co-centered Orthogonal Loop and Dipole (COLD) array. Firstly, following the physical numbering of array elements, we can construct multiple polarization cumulant matrices, which can then be cascaded into a long matrix. Next, the signal subspace can be obtained through eigen-decomposition of this long matrix, from which the horizontal and vertical components can be further separated. By applying ESPRIT, joint angle, range, and polarization parameters can be estimated. In addition, the asymptotic variances for joint spatial and polarization parameters are analyzed. Compared with existing NF polarization algorithms, the proposed method exhibits better parameter estimation and is consistent with a theoretical asymptotic performance. Full article

Neurological disorders like stroke are one of the main causes of motor dysfunction and gait function disabilities in humans. These disorders impact the mobility of patients often leading to weakened and impaired ankle joints which further compromise their balance and walking abilities. Over the span of the last twenty years, there has been a rising interest in designing, developing, and using rehabilitative robots for patients suffering from various ankle joint disabilities. These robotic devices are developed by employing diverse mechanical designs, materials, and control strategies. The aim of this study is to provide a detailed overview of the recent developments in mechanical design, actuation, and control strategies of ankle rehabilitation robots. Experimental evaluation of the discussed ankle robots has also been carried out discussing their results and limitations. This article concludes by highlighting future challenges and opportunities for the advancement of ankle rehabilitation robots, stressing the need for robust and effective devices to better serve patients. Full article

In the context of aging populations, it has become necessary to develop new methods and devices for the daily home-based self-rehabilitation of elderly people. To this end, this paper proposes and evaluates the use of an easy-to-use single battery-powered device including a 3D accelerometer and a 3D gyroscope, where light algorithms, such as the complementary filter and the Kalman filter, are implemented to estimate the elbow joint angle. During experiments, a robotic arm and a human arm were used to obtain an error interval for each tested algorithm; the robotic arm allows for reproducible movements and reproducible results, which allows us to independently verify the impact of parameters such as the sensor’s movement speed on the algorithm precision. The experimental results show that the algorithm that uses only accelerometer data is one of the most relevant since it allows us to obtain a Root Mean Square Error between 1.83° and 5.52° at a sensor data rate of 100 Hz, which is similar to the results obtained using the data fusion algorithms tested. Nevertheless, it has a lower power consumption since it requires only 58 cycles when using an ARM Cortex-M4 processor (which is lower than that of the other data fusion algorithms tested by a factor of at least two), and it does not necessitate the additional sensor required by the other data fusion algorithms tested (such as a gyroscope or a magnetometer). The algorithm using only accelerometer data also seems to be the algorithm with the lowest power consumption and should be preferred. Moreover, its power consumption can be reduced by more than the increase in the error when reducing the rate of the data output by the sensor. In this work, a reduction in the data rate from 100 Hz to 10 Hz increased the RMSE by a factor of 1.8 but could reduce the power consumption associated with the sensor and the algorithm’s computation by a factor of 10. Finally, the experimental results show that the higher the speed of the sensor’s motion, the higher the error obtained using only accelerometer data. Nevertheless, the algorithm that uses only accelerometer data remains well suited to rehabilitation exercises or mobility evaluations since the speed of the sensor’s movement is also moderate. Full article

The General Movements Assessment provides early insight into motor development’s range of motion; however, its relationship with joint kinematics, such as hip abduction range of motion, remains underexplored. This study analyzed hip abduction kinematics during General Movements, evaluating potential sex differences and variations in movement patterns (Fidgety vs. Writhing), and aimed to provide quantitative data that complement qualitative pediatric assessments. This cross-sectional observational study analyzed video recordings of spontaneous motor activity in 32 infants under three months of corrected age. Hip abduction range of motion was extracted using biomechanical analysis during General Movements. Interrater reliability was evaluated using Fleiss’s Kappa. Correlations were assessed using Pearson’s test, and a two-way ANOVA examined the effects of sex and the type of movements on range of motion. Interrater reliability for movement classification was excellent (Kappa = 0.909, p < 0.001). No significant correlations were found between sex or General Movements type and hip abduction range of motion (p > 0.68). Two-way ANOVA showed no significant effects of sex, movement pattern, or their interaction on range of motion in either hip (right: p = 0.726, left: p = 0.823), with small effect sizes (η² < 0.013). A minor asymmetry favoring the right hip was observed but was not clinically significant. Sex and General Movements type did not significantly influence hip abduction range of motion in infants under three months. Early joint mobility appears consistent across sexes and movement patterns, supporting its reliability as a biomechanical marker of typical development. Full article

Total Hip Arthroplasty (THA) is a widely used surgical procedure to restore mobility and reduce pain in patients with hip joint disorders. Implant success and longevity are influenced by the selection of appropriate materials. This study presents a comprehensive literature review based on structured searches in Scopus and Web of Science, focusing on material selection criteria and methods in THA. The inclusion criteria targeted original studies and reviews addressing material properties, selection techniques, and clinical performance. A bibliometric analysis and keyword co-occurrence network were used to highlight major research themes. The review examines traditional materials such as Metal-on-Polyethylene (MoP), as well as advanced options like ceramics, composites, and Functionally Graded Materials (FGMs). Key challenges discussed include aseptic loosening, wear resistance, and stress shielding. Selection methodologies such as Multi-Criteria Decision-Making (MCDM), Weighted Properties Methods (WPM), and computational tools like Ashby charts and CES Selector are analyzed. The findings from international arthroplasty registries show that more than half of implant failures are linked to material-related factors. This study therefore aims to guide material selection processes in THA by aligning clinical performance with biomechanical and biological requirements, supporting improved implant outcomes and long-term surgical success. Future developments should focus on patient-specific solutions and continuous innovation. Full article

The demand for electric mobility has driven the development of advanced laser welding technologies such as dual beam welding and beam shaping. Nevertheless, some intrinsic characteristics present challenges to exploring all its benefits. In this sense, this study investigates the effect of the laser welding parameters employed on the weld quality in busbar–battery interconnects. Dual beam and beam shaping strategies were applied in Al-Al (AA1050 H24) and Al-Cu (AA1050 H24 and C11000) overlap joint configurations adopting statistical methods. For Al-Al joints, welding speed was the most significant parameter influencing interface width, whereas in Al-Cu joints, core power was the only significant parameter affecting both interface width and penetration in the studied configuration. Common defects, such as porosity and cracks, were observed in both material combinations. In Al-Al joints, higher welding speeds resulted in up to a 16% (65.6 HV) increase in hardness, while, in Al-Cu joints, the peak value reached around 900 HV in the interface zone due to the formation of intermetallic compounds (IMCs). In addition, IMCs with complex structures and significant compositional variations, including Cu₉Al₄ and CuAl₂ were identified. Full article

Background and Objective: This study aimed to compare functional and clinical outcomes between patients with chronic non-specific lower back pain (NSLBP) with restricted hip extension mobility who performed spinal stabilization exercises with hip mobilization either with or without additional hip exercises. Methods: A total of 42 patients with chronic NSLBP with restricted hip extension mobility were enrolled (21 with and 21 without additional hip exercises). Functional and clinical outcomes were assessed based on hip joint mobility, back extensor endurance, postural stability, and patient-reported outcomes, including visual analog scale (VAS) and Oswestry disability index (ODI) scores. Results: A significant group–time interaction was identified for postural stability (Rt: p < 0.001, Lt: p = 0.002) and the ODI (p = 0.004). After the intervention, the group with additional hip exercises demonstrated significantly greater improvements in postural stability (Rt: p < 0.001; Lt: p = 0.01) and ODI scores (p < 0.001) compared with the group without additional hip exercises. However, no significant main group effect or group–time interaction was observed for the hip joint mobility, back extensor endurance, or VAS scores (all p > 0.05). Furthermore, the ODI score (r² = 0.123, p = 0.023) was an independent predictor of hip joint mobility but not the VAS score (p > 0.05). Conclusions: Hip exercises may improve postural stability and function in patients with chronic NSLBP with restricted hip extension mobility. Notably, clinicians and therapists must recognize the importance of hip exercises during rehabilitation of patients with chronic NSLBP with restricted hip extension mobility. Full article

Mobile edge computing (MEC) has become an effective framework for latency-sensitive and computation-intensive applications by deploying computing resources at network edge. The unmanned aerial vehicle (UAV)-assisted MEC leverages UAV mobility and communication advantages to enable services in dynamic environments, where frequent adjustments to flight trajectories and user association are required due to dynamic factors such as time-varying task requirements, user mobility, and communication environment variation. This paper addresses the joint optimization problem of UAV flight trajectory control and user association in dynamic environments, which explicitly incorporates the constraints governed by UAV flight dynamics. The joint problem is formulated as a non-convex optimization formulation that involves continuous–discrete hybrid decision variables. To overcome the inherent complexity of this problem, a novel proximal policy optimization-based dynamic control (PPO-DC) algorithm is developed. This algorithm aims to reduce the weighted combination of delay and energy consumption by dynamically controlling the UAV trajectory and user association. The numerical results validate that the PPO-DC algorithm successfully enables real-time UAV trajectory control under flight dynamics constraints, ensuring feasible and efficient flight trajectory. Compared to the state-of-the-art hybrid-action deep reinforcement learning (DRL) algorithms or metaheuristics, the PPO-DC achieves notable improvements in system performance by simultaneously lowering system delay and energy consumption. Full article

Osteoarthritis (OA) is a chronically progressive degenerative arthropathy characterized by the loss of cartilage, changes in subchondral architecture, and ongoing inflammation resulting in reduced mobility and pain. This study assessed the treatment potential of a combination of chondroitin and glucosamine enriched with Curcumin C3 Complex (C3GC) in modulating the pathophysiological features in mouse models with surgically induced OA and in dogs with naturally occurring OA. A cohort of 24 male C57BL/6 mice aged 3 months old were surgically destabilized with medial meniscus (DMM) to cause osteoarthritis. These animals underwent a nutritional intervention with C3GC or with GC over a course of 8 weeks. In order to evaluate cartilage health and subchondral bone structure, we carried out a combination of behavioral tests, micro-computed tomography (micro-CT), and histopathological examinations. In addition, a cohort of 12 OA-diagnosed retired police dogs were administered C3GC supplements or conventional care over a course of 30 days, with pain measurement and serum concentrations of MMP-3 and TNF-α determined before and after treatment. According to our findings, the administration of C3GC was determined to preserve subchondral microarchitectural structure integrity (p < 0.05) and resulted in better motor function in comparison with GC. In animals taking nutritional supplements, the OARSI scores of joint tissue sections were reduced, with the medial tibial plateau OARSI score being particularly low in the C3GC group (p < 0.0001). In dogs, treatment with C3GC resulted in a 24.5% reduction in serum MMP-3 levels (p < 0.01), and there was also a 20.8% decrease in serum TNF-α levels (p < 0.05), along with a decrease in subjective pain assessment. The results are in support of the chondroprotective, anti-inflammatory, and analgesic properties of C3GC and justify future research on the potential utility of C3GC in treating osteoarthritis. Full article

The purpose of this study was to investigate the benefits of a 12-week plyometric training program intervention on lower limb joint mobility, explosive strength, advanced layup success rates, and injury rates. The study recruited 15 collegiate male basketball players as participants. They underwent basketball training five times per week, each lasting two hours, and additionally received plyometric training twice a week. The study utilized image processing software (ImageJ, version 1.54f, National Institutes of Health, Bethesda, MD, USA) to measure the lower limb joint mobility during the take-off phase of a layup and employed a force plate to assess the explosive strength of the lower limbs during the jump. Furthermore, the study examined the success rate and injury rate of advanced layups—including crossover layups, spin layups, and straight-line layups—as well as the sports injury rate. The results demonstrated that plyometric training significantly enhanced the hip, knee, and ankle joint mobility as well as lower limb explosive strength, with a strong positive correlation between these variables. Furthermore, plyometric training improved joint mobility and lower limb explosive strength. The success rate of advanced layups increased from 50% to 72%, while the sports injury rate decreased from 18% to 8%. In conclusion, plyometric training significantly improved participants’ lower limb joint mobility and explosive strength, which in turn enhanced advanced layup performance and reduced the sports injury rate. Although this study provided preliminary evidence supporting the effectiveness of plyometric training, further research is needed to examine its long-term effects and other influencing factors. Full article

The global aging trend increases chronic diseases and lowers quality of life. Exercise is vital for physiological, cognitive, and mental health, countering age-related decline. Outdoor multidomain interventions enhance adherence, motivation, and resilience, supporting independence and well-being. Objectives: This paper aimed to apply an outdoor exercise protocol for middle-aged and older people and to study its preliminary effects on cognitive state, body composition, cardiovascular health, physical fitness, physiological function, physical activity, frailty, incidence of sarcopenia, and satisfaction with life. Methods: This protocol describes an eighteen-week, two-pronged, parallel, single-blind randomized controlled trial. This paper complies with the Consort and SPIRIT guidelines. A cohort comprising a minimum of fifty-two older adults from the University for Seniors program will be equally allocated to a multidomain training group (TG) and a passive control group (CG). Intervention: The TG will follow a multidomain outdoor intervention twice a week for a complete duration of 18 weeks, with recommendations for additional autonomous cardiorespiratory training. The supervised sessions will be divided into a 10-min warm-up session focusing on activation and joint mobility, followed by 40 min of resistance training, cardiorespiratory training, and balance and coordination; and it concludes with a 10-min cool-down featuring flexibility, relaxation, and playful emotional intelligence tasks. Cognitive training will be integrated across different parts of the session. Conclusions: This preliminary study aims to explore the feasibility and potential effectiveness of outdoor multidomain training in improving the health of older adults. Importantly, by including late middle-aged adults from the age of 55, this study also aims to explore the potential of preventive strategies initiated before reaching old age. This reflects a broader conceptualization of healthy aging as a lifelong process, where early interventions may help mitigate decline and extend independence into later life. The partnership between health professionals and physical activity fosters independence for older adults, addressing the increasing burden on health services. Full article

Objective: To assess the associations between academic study- and non-study-related sedentary behaviors and the risk of overweight/obesity in children and adolescents, as well as their joint association with sugar-sweetened beverage (SSB) consumption. Methods: Sedentary behaviors and SSB consumption were assessed using self-reported questionnaires. Overweight/obesity were defined by age- and sex-specific body mass index cut-off values according to the criteria of “Screening for overweight and obesity among school-age children and adolescents” in China. Poisson regression with robust error variance was used to assess the associations of sedentary behaviors and/or SSB consumption with the risk of overweight/obesity, yielding relative risks (RRs) and 95% confidence intervals (CIs). The Shapley additive explanations (SHAP) method was used to rank the contribution of five specific sedentary behaviors to obesity risk. Results: Among 47,148 participants with a 3-year follow-up, longer durations of screen-related, academic study-related, and total sedentary time were each associated with a higher risk of overweight/obesity (adjusted RR (95% CI) per hour increment: 1.01 (1.00–1.02), 1.03 (1.01–1.06), and 1.02 (1.01–1.03)). After mutual adjustment, the associations of engaging in homework, attending tutorial classes, and using mobile electronic devices remained significantly associated with higher overweight/obesity risk. The SHAP summary plot shows that using mobile electronic devices, attending tutorial classes, and doing homework were the three most important sedentary obesogenic contributors. A significant interaction of age with sedentary time was found (p for interaction < 0.05). No significant interaction was found between SSB consumption and sedentary time. Conclusions: Excessive sedentary behaviors were associated with a higher risk of overweight/obesity, particularly due to mobile electronic device use, attending tutorial classes, and doing homework. Full article

This work proposes a power-efficient framework for adaptive video streaming in UAV-assisted wireless networks specially designed for disaster-hit areas where existing base stations are nonfunctional. Delivering high-quality videos requires higher video rates and more resources, which leads to increased power consumption. With the increasing demand of mobile video, efficient bandwidth allocation becomes essential. In shared networks, users with lower bitrates experience poor video quality when high-bitrate users occupy most of the bandwidth, leading to a degraded and unfair user experience. Additionally, frequent video rate switching can significantly impact user experience, making the video rates’ smooth transition essential. The aim of this research is to maximize the overall users’ quality of experience in terms of power-efficient adaptive video streaming by fair distribution and smooth transition of video rates. The joint optimization includes power minimization, efficient resource allocation, i.e., transmit power and bandwidth, and efficient two-dimensional positioning of the UAV while meeting system constraints. The formulated problem is non-convex and difficult to solve with conventional methods. Therefore, to avoid the curse of complexity, the block coordinate descent method, successive convex approximation technique, and efficient iterative algorithm are applied. Extensive simulations are performed to verify the effectiveness of the proposed solution method. The simulation results reveal that the proposed method outperforms 95–97% over equal allocation, 77–89% over random allocation, and 17–40% over joint allocation schemes. Full article

Background: The role of the periarticular muscles of the knee joint in ensuring body balance is still ambiguous. Therefore, we conducted clinical and biomechanical assessments on 52 older adults (36 women and 16 men, age of 67.58 ± 7.30 years, body weight of 75.10 ± 13.42 kg, and height of 163.92 ± 8.80 cm) to determine the role of the knee muscles in balance maintenance. Methods: The clinical examination included the Dizziness Handicap Inventory (DHI), the Geriatric Depression Scale (GDS), the Performance-Oriented Mobility Assessment (POMA), the Functional Reach Test (FRT), the Falls Efficacy Scale—International (FES-I), and bioimpedance parameters (skeletal muscle mass—SMM—and its derived parameter—Diff SMM). The biomechanical assessment involved parameters that characterize muscle torques of knee joint extensors and flexors in isokinetic and isometric conditions, as well as changes in the centre of pressure (COP) position while standing with eyes open and closed. Results: Based on treatment history and DHI results (>10 points), 26 participants were identified as having balance disorders, while the remaining participants formed the control group. Statistical analysis was performed to determine differences between the groups. The groups significantly differed in terms of the results obtained from the DHI (p < 0.001) and GDS (p = 0.04) questionnaires as well as FES-I (p < 0.001) and POMA (p = 0.002) tests. While SMM (p = 0.012) was similar in the groups, Diff SMM (p = 0.04) significantly differed. The multiple regression analysis confirmed the knee joint extensor parameters’ significant role in predicting the COP path (p = 0.03 and p = 0.04 for two assumed models). Conclusions: The obtained results proved that the muscle torques of knee extensors can be used in the diagnostic process of older patients with balance disorders, indicating possible rehabilitation directions. Full article

This paper proposes a novel approach to the virtual 3D modeling of articulated mechanisms. It follows the widespread use of XML (eXtensible Markup Language) for various applications and defines a version of XML that is specially designed for the description of 3D geometric models of articulated bodies. In addition, it shows how the 3D geometric model of a mechanism can be gradually developed through the use of suitably defined elements and stored in a corresponding XML file. The developed XML model is processed, and using a powerful VTK (Visualization Toolkit) library, the corresponding virtual model is built and shown on the computer screen. To drive the virtual model, the dynamic model of the mechanism is developed using Bond Graph modeling techniques. Virtual 3D geometric and dynamic models are created using the corresponding software packages: BonSim3D 2023 Visual and BondSim 2023. The models are interconnected by a two-way named pipe. During the simulation of the dynamic model, the parameters necessary to drive the virtual model (e.g., the joint displacements) are collected and sent to the virtual model over the pipe. When the virtual model receives a package, the computer screen is updated by showing the new state of the mechanism. The approach is demonstrated using the example of a holonomic omnidirectional mobile robot. Full article