Search Results (45)

Background/Objectives: There is limited information on the interplay between passive joint motion and joint kinematics from three-dimensional gait analysis (3DGA) and its longitudinal evolution in cerebral palsy (CP). We aimed to associate clinical measurements and gait kinematics over time using a longitudinal study design. Methods: Ambulatory individuals with spastic CP, aged 4–18, who performed a minimum of two 3DGA at the Karolinska University Hospital between 2008 and 2025 were recruited. Primary outcomes were sagittal plane kinematics and maximum passive knee extension (pKE). Canonical correlation (R) with statistical parametric mapping was used to associate passive maximum knee extension with sagittal hip, knee, and ankle angles at two timepoints. Results: the 3DGA data of 31 children (age 4–17 years; mean age 10.4 +/− 2.9) with 22 bilateral (bCP, GMFCS I = 6; II = 13; III = 3) and 9 unilateral CP (uCP, GMFCS I = 8; II = 1) was included. For the whole and bCP groups, respectively, knee flexion/extension and pKE were correlated throughout stance (p < 0.001), with R between −0.47 and −0.57/−0.49 and −0.59 at T1 and between −0.46 and −0.72/−0.50 and −0.76 at T2. Hip flexion/extension and knee pKE were correlated from 17 to 62%/46–52% of the gait cycle (p < 0.001/p = 0.045) for the whole and bCP groups, respectively, with R between −0.41 and −0.57/−0.38 and −0.41 at T1 and from 15 to 64%/17 to 61% with R between −0.50 and −0.57/−0.42 and −0.57 at T2. Conclusions: Reported associations between structural knee properties and knee position during gait demonstrated progression over time, implying that a restricted range of motion may be driven by functional constraints. Combining knee contractures and their longitudinal development with 3DGA is a powerful approach for pre-intervention planning. Full article

This paper deals with a privacy-preserving human tracking system that uses multi-property infrared sensor arrays. In the growing field of intelligent elderly care, there is a critical need for monitoring systems that ensure safety without compromising personal privacy. While traditional camera-based systems offer detailed activity recognition, privacy-related concerns often limit their practical application and user acceptance. Consequently, approaches that protect privacy at the sensor level have gained increasing attention. The privacy-preserving human tracking system proposed in this paper protects privacy at the sensor level by fusing data from an ultra-low-resolution $8\times 8$ (64-pixel) passive thermal infrared (IR) sensor array and a similarly low-resolution $8\times 8$ active Time-of-Flight (ToF) sensor. The thermal sensor identifies human presence based on heat signature, while the ToF sensor provides a depth map of the environment. By integrating these complementary modalities through a convolutional neural network (CNN) enhanced with a cross-attention mechanism, our system achieves real-time three-dimensional human tracking. Compared to previous methods using ultra-low-resolution IR sensors, which mostly only obtained two-dimensional coordinates, the acquisition of the Z coordinate enables the system to analyze changes in a person’s vertical position. This allows for the detection and differentiation of critical events such as falls, sitting, and lying down, which are ambiguous to 2D systems. With a demonstrated mean absolute error (MAE) of 0.172 m in indoor tracking, our system provides the data required for privacy-preserving Ambient Assisted Living (AAL) applications. Full article

In 3.5 wt% NaCl solution used to simulate seawater, the individual (self-corrosion) and coupled (galvanic) corrosion behaviors of TA22 titanium alloy and 304 stainless steel were systematically investigated at 25 °C, 35 °C, 45 °C and 55 °C. Post-corrosion surfaces were characterized by scanning electron microscopy (SEM), three-dimensional profilometry and X-ray photoelectron spectroscopy (XPS). The results demonstrated that elevating temperature decreased the compactness and protective quality of the passive film on both alloys, as indicated by increasing donor densities and positive shifts in flat-band potentials. Distinct pitting corrosion occurred on 304 SS above 45 °C. Upon galvanic coupling, the passive film on TA22 was modified in both structure and composition, exhibiting a decreased TiO₂ content and increased lower valence oxides (Ti₂O₃, TiO). The galvanic effect intensified with temperature, leading to progressively aggravated corrosion of 304 SS, characterized by increased pit density, diameter, and depth compared to its self-corrosion state. Full article

Functional hydrogels are a growing class of soft materials. Functional hydrogels are characterized by their three-dimensional (3D) polymeric network and high water-retention capacity. Functional hydrogels are deliberately engineered with specific chemical groups, stimuli-responsive motifs, or crosslinking strategies that impart targeted biomedical or environmental roles (e.g., drug delivery, pollutant removal). Their capacity to imitate the extracellular matrix, and their biocompatibility and customizable physicochemical properties make them highly suitable for biomedical and environmental applications. In contrast, non-functional hydrogels are defined as passive polymer networks that primarily serve as water-swollen matrices without such application-oriented modifications. Recent progress includes stimuli-responsive hydrogel designs. Stimuli such as pH, temperature, enzymes, light, etc., enable controlled drug delivery and targeted therapy. Moreover, hydrogels have shown great potential in tissue engineering and regenerative medicine. The flexibility and biofunctionality of hydrogels improve cell adhesion and tissue integration. Functional hydrogels are being explored for water purification by heavy metal ion removal and pollutant detection. The surface functionalities of hydrogels have shown selective binding and adsorption, along with porous structures that make them effective for environmental remediation. However, hydrogels have long been postulated as potential candidates to be used in clinical advancements. The first reported clinical trial was in the 1980s; however, their exploration in the last two decades has still struggled to achieve positive results. In this review, we discuss the rational hydrogel designs, synthesis techniques, application-specific performance, and the hydrogel-based materials being used in ongoing clinical trials (FDA–approved) and their mechanism of action. We also elaborate on the key challenges remaining, such as biocompatibility, mechanical stability, scalability, and future directions, to unlocking their multifunctionality and responsiveness. Full article

Background: At present, the rotational function of the hip adductor muscle group remains unclear. This study aimed to clarify the rotational function and stabilizing role of the pectineus, adductor longus, and adductor brevis (adductor muscle group) based on anatomical findings and T₂ values (ms) obtained from magnetic resonance imaging (MRI). T₂ values are prolonged in tissues with higher water content, and in skeletal muscle, it has been demonstrated that T₂ values increase in proportion to exercise intensity. Methods: Using fixed specimens (n = 6, aged 61–96 years), we observed the three-dimensional arrangement of muscles in the neutral position of the hip joint and observed the extension or shortening of muscles associated with passive maximum internal and external rotation of the hip joint. In addition, we evaluated the activity of the adductor muscle group by T₂ values (ms) from MRI pre- and post-internal rotation (forward step with the left leg) and pre- and post-external rotation (backward step with the left leg) movements of the right hip joint in a standing position (n = 8, healthy adult subjects, mean age 29.1 ± 5.3 years). Results: Regarding functional anatomy, the arrangement of the gluteus minimus and adductor muscle groups was almost parallel across the femoral neck. In the evaluation of adductor muscle group activity using MRI, the percent change in T₂ values (%) of the pectineus was 6.38 ± 1.35 pre- and post-internal rotation and 1.35 ± 0.71 pre- and post-external rotation, whereas that of the adductor longus and brevis was 4.84 ± 1.31 pre- and post-internal rotation and 1.31 ± 0.68 pre- and post-external rotation. The percent change in T₂ values pre- and post-internal rotation exercise was significantly greater than that pre- and post-external rotation exercise in the pectineus, adductor longus, and brevis muscles (p < 0.05). Conclusions: The adductor muscle groups are suggested to contribute to joint stability in the coronal plane and provide joint internal rotation in the standing position. Full article

Forest trees have emerged as a promising passive solution for mitigating low-frequency ground vibrations generated by railway operations, offering ecological and cost-effective advantages. This study proposes a three-dimensional semi-analytical method developed for evaluating the dynamic responses of the coupled track–ground–tree system. The thin-layer method is employed to derive an explicit Green’s function corresponding to a har-monic point load acting on a layered half-space, which is subsequently applied to couple the foundation with the track system. The forest trees are modeled as surface oscillators coupled on the ground surface to evaluate the characteristics of multiple scattered wavefields. The vibration attenuation capacity of forest trees in mitigating railway-induced ground vibrations is systematically investigated using the proposed method. In the direction perpendicular to the track on the ground surface, a graded array of forest trees with varying heights is capable of forming a broad mitigation frequency band below 80 Hz. Due to the interaction of wave fields excited by harmonic point loads at multiple locations, the attenuation performance of the tree system varies significantly across different positions on the surface. The influence of variability in tree height, radius, and density on system performance is subsequently examined using a Monte Carlo simulation. Despite the inherent randomness in tree characteristics, the forest still demonstrates notable attenuation effectiveness at frequencies below 80 Hz. Among the considered parameters, variations in tree height exert the most pronounced effect on the uncertainty of attenuation performance, followed sequentially by variations in density and radius. Full article

A fully passive oscillating foil turbine on a swinging arm in a tandem configuration consisting of two NACA 0015 foils at both ends of its arm and operating in an incompressible flow at a Reynolds number of $3.9\times {10}^6$ is investigated with numerical simulations. The turbine is free to oscillate passively in response to hydrodynamic forces and structural reactions from springs and dampers. The passive motion of the tandem turbine arises from a transfer of energy from the flow, and this motion is solved using a fluid-structure algorithm coupling the Newtonian dynamics of the system with two-dimensional, unsteady, and Reynolds-averaged Navier–Stokes equations. The performance metrics, i.e., the efficiency and power coefficient, of the proposed turbine concept are explored with a momentum gradient ascent algorithm, which uses the near-optimal configuration of an equivalent single-foil concept from a previous study as a starting point. These starting configurations consist of tandem foils operating either under coupled flutter or stall flutter instabilities. The use of gears to adjust the equilibrium position of the pitching motion is also considered, resulting in a total of four baseline configurations. The best configuration found with the gradient ascent algorithm presents an efficiency value near $75\%$ and a power coefficient of $1.46$, showing the great potential of fully passive oscillating foil turbines operating in a tandem configuration and providing valuable insight for further development of this technology through three-dimensional simulations and prototype testing. Full article

This paper investigates the three-dimensional target localization problem in satellite–ground bistatic radar. In conventional bistatic radar systems, passive receivers struggle to directly acquire the altitude information of the target, making it difficult to achieve effective three-dimensional target localization. This paper uses the bistatic distance data obtained after signal processing to construct ellipsoidal constraints, thereafter combining azimuth data to compress the position solution space into a three-dimensional elliptical line. Introducing the assumption of short-term linear uniform motion of the target, the target trajectory and elliptical line constraints are projected onto a two-dimensional plane, establishing an optimization model to determine the target trajectory parameters, ultimately yielding the target’s three-dimensional coordinates and completing the positioning process. The simulation results demonstrate the efficacy and performance of the proposed method. Full article

This paper aims to enhance lightning positioning technology and data processing algorithms using very-high-frequency (VHF) lightning radar. It focuses on achieving three-dimensional imaging of plasma channels formed during lightning. By extracting key features from lightning echo signals received by VHF radar, we utilize a unique active and passive integrated positioning technology to locate the lightning radiation source. This algorithm effectively overcomes the limitations of traditional positioning methods. Experimental results show that the integrated positioning algorithm maintains accuracy while significantly increasing the number of positioning points, which supports subsequent imaging of lightning plasma channels. To illustrate the dendritic structure of the lightning channel, we employed a density-based clustering algorithm to eliminate noise points unrelated to the lightning source, enhancing imaging clarity. The methods presented in this study successfully meet the experiment’s goals and are significant for locating lightning radiation sources and understanding the dendritic structure changes in plasma channels during lightning propagation. Full article

High-precision, robust, and rapid three-dimensional (3D) passive positioning of the radiation source is critical for modern reconnaissance systems. While synthetic aperture technology has advanced 2D passive positioning performance, existing methods fail to achieve full 3D positioning with sufficient accuracy and computational efficiency. This is because of the inherent limitations of the single-station platform in resolving elevation-angle ambiguity. To address this gap, we propose a Cross-Track Interferometric Synthetic Aperture (CISA) 3D passive positioning algorithm. The algorithm innovatively realizes robust elevation-angle measurement by recursively deriving the long baseline unambiguous phase difference step-by-step from a virtual short baseline. The 3D positioning is achieved by combining passive synthetic aperture and interferometric angle measurement. Furthermore, we establish the incoherence model of synthetic aperture passive positioning for the first time and propose a compensation method based on static acquisition data to improve the practicability of CISA. Simulation and experimental results demonstrate that the proposed CISA algorithm achieves a positioning accuracy of 4.73‰R, improves computational efficiency by 1–2 orders of magnitude compared to conventional methods, and exhibits superior robustness to noise. The research can provide a reference for the method research and engineering realization of synthetic aperture 3D passive positioning. Full article

High-stability photovoltaic devices are crucial for low-power or passive applications in fields such as renewable energy, wearable electronics, and deep-space exploration. However, achieving stable and controllable doping in two-dimensional (2D) materials remains challenging, hindering the optimization of photovoltaic performance. Here, we fabricate three high-performance, self-driven photodetectors based on layered WSe₂ with varying doping concentrations. By leveraging asymmetric Schottky barriers and introducing a defect-free, high-bandgap intrinsic region with a long mean free path, we construct a positive–intrinsic–negative (PIN) vertical homojunction that significantly enhances the photogenerated voltage, photon absorption, and carrier transport efficiency. The resulting PIN junction exhibits a photogenerated voltage of up to 0.58 V, a responsivity of 0.35 A/W, and an external quantum efficiency of 83.9%. Moreover, it maintains a reverse saturation current as low as 0.2 nA at 430 K. These results provide a promising route toward the development of high-responsivity, high-stability van der Waals devices and highlight the potential for 2D material-based technologies to operate reliably under extreme conditions. Full article

The present research attempted to investigate the relationship between leadership styles and job satisfaction for civilian personnel of the Ministry of Defense. The research was carried out during the months of May and June in the year 2022. The Multifactor Leadership Questionnaire (M.L.Q.-5X) and the Employee Satisfaction Inventory (ESI) were given via the Internet in digital form to 127 participating technical employees and civilian personnel who served in this specific period in various services of the Ministry of National Defense of Greece. The survey data were statistically analyzed using SPSS program v.22. The results of the dimensional correlations between leadership styles and job satisfaction showed that idealized influence (both attributes and behavior), inspirational motivation, intellectual stimulation, individual consideration, and contingent rewards were positively related to overall employee satisfaction. In contrast, management by exception (active) was not correlated with overall satisfaction. Furthermore, management by exception (passive) and laissez-faire leadership were negatively correlated with overall job satisfaction. Accordingly, the statistical findings of the dimensional correlations concerning the relationship between the three dimensions of leadership outcomes and job satisfaction showed that extra effort, effectiveness, and satisfaction with leadership were positively related to overall satisfaction. Higher effect sizes were reported for the correlation between the contingent reward dimension of process leadership and employee satisfaction, indicating that processing leadership has a stronger effect on the satisfaction of the technical employees of the Ministry of National Defense compared to transformational leadership dimensions. We assume that this result is due to the special characteristics of the Ministry of National Defense workplace. Full article

Arm and hand function play a critical role in the successful completion of everyday tasks. Lost function due to neurological impairment impacts millions of lives worldwide. Despite improvements in the ability to assess and rehabilitate arm deficits, knowledge about underlying sources of impairment and related sequela remains limited. The comprehensive assessment of function requires the measurement of both biomechanics and neuromuscular contributors to performance during the completion of tasks that often use multiple joints and span three-dimensional workspaces. To our knowledge, the complexity of movement and diversity of measures required are beyond the capabilities of existing assessment systems. To bridge current gaps in assessment capability, a new exoskeleton instrument is developed with comprehensive bilateral assessment in mind. The development of the BiLateral Upper-limb Exoskeleton for Simultaneous Assessment of Biomechanical and Neuromuscular Output (BLUE SABINO) expands on prior iterations toward full-arm assessment during reach-and-grasp tasks through the development of a dual-arm and dual-hand system, with 9 active degrees of freedom per arm and 12 degrees of freedom (six active, six passive) per hand. Joints are powered by electric motors driven by a real-time control system with input from force and force/torque sensors located at all attachment points between the user and exoskeleton. Biosignals from electromyography and electroencephalography can be simultaneously measured to provide insight into neurological performance during unimanual or bimanual tasks involving arm reach and grasp. Design trade-offs achieve near-human performance in exoskeleton speed and strength, with positional measurement at the wrist having an error of less than 2 mm and supporting a range of motion approximately equivalent to the 50th-percentile human. The system adjustability in seat height, shoulder width, arm length, and orthosis width accommodate subjects from approximately the 5th-percentile female to the 95th-percentile male. Integration between precision actuation, human–robot-interaction force-torque sensing, and biosignal acquisition systems successfully provide the simultaneous measurement of human movement and neurological function. The bilateral design enables use with left- or right-side impairments as well as intra-subject performance comparisons. With the resulting instrument, the authors plan to investigate underlying neural and physiological correlates of arm function, impairment, learning, and recovery. Full article

Some passive sensors can provide only relative angles of a signal source. To obtain the signal source location, multiple passive sensors can be constructed into a passive sensor network through communication links. This paper investigates the source localization problem with angle-only measurements in three-dimensional space. First, we present an intersection localization method, which estimates the target position by minimizing the sum of distances between lines formed by angle-only measurements. It has the same target position estimate as the widely used least-squares (LS) method, but with a lower computational cost. Furthermore, considering the differences in measurement accuracy of sensors, the weighted least-squares (WLS) algorithm can achieve better localization performance than the LS method. Unfortunately, since the coefficient matrix and the noise vector are correlated, the WLS method is biased. The bias-compensation WLS (BCWLS) method is also presented in this paper to reduce the bias by estimating the correlation between the coefficient matrix and the pseudolinear noise vector. To evaluate the performance of the presented algorithms, numerical simulations are conducted, indicating that the superiority of the intersection localization method in computational cost and the superiority of the BCWLS method in localization accuracy. Full article

The functionalized graphene oxide (GO)-based composites as fillers added into organic coatings are desired for realizing the longstanding corrosion protection of carbon steel. Here, the pH-responsive two-dimensional/three-dimensional (2D/3D) GO-based composite (ZIF–90–AAP/GO) was developed by environmentally friendly corrosion inhibitor 4-aminoantipyrine (AAP) anchored on the in situ growth of zeolite imidazolate framework–90 (ZIF–90) on the GO surface (ZIF–90/GO) through the Schiff base reaction. The active filler (ZIF–90–AAP/GO) was incorporated into an epoxy coating (EP) to obtain a high-performance self-healing coating on the surface of carbon steel. ZIF–90–AAP can greatly improve dispersion and compatibility of GO in EP. The low-frequency impedance modulus of ZIF–90–AAP/GO–EP can still reach up to 1.35 × 10¹⁰ Ω⋅cm² after 40 days, which is about three orders of magnitude higher than that of the EP containing GO (GO–EP) relying on its passive and active corrosion protection. Meanwhile, ZIF–90–AAP/GO–EP exhibits excellent self-healing performance. The self-healing rate of ZIF–90–AAP/GO changes from negative to positive after 24 h, which results from the effective corrosion inhibition activity of ZIF–90–AAP for carbon steel based on the pH-triggered controlled release of AAP. The developed pH-responsive 2D/3D GO-based composite coating is very attractive for the corrosion protection of carbon steel. Full article