Search Results (3,181)

This study presents a system for precisely measuring pulsed magnetic fields with high amplitude and microsecond duration with minimal interference. The system comprises a probe with an advanced magnetic field sensor and a measurement unit for signal conversion, analysis, and digitization. The sensor uses a thin nanostructured manganite La-Sr-Mn-O film exhibiting colossal magnetoresistance, which enables precise magnetic field measurement independent of its orientation. Films with different compositions were optimized and tested in pulsed magnetic fields. The measurement unit includes a pulsed voltage generator, an ADC, a microcontroller, and an amplifier unit. Two versions of the measurement unit were developed: one with a separate amplifier unit configured for the sensor positioned more than 1 m away from the measurement unit, and the other with an integrated amplifier for the sensor positioned at a distance of less than 0.5 m. A bipolar pulsed voltage supplying the sensor minimized the parasitic effects of the electromotive force induced in the probe circuit. The data were transmitted via a fiber optic cable to a PC equipped with a special software for processing and recording. Tests with 20–30 μs pulses up to 15 T confirmed the effectiveness of the system for measuring high pulsed magnetic fields. Full article

Children with neurodevelopmental disabilities often struggle with motor control and stability, impacting their ability to perform functional tasks such as lifting and carrying objects. This study explores positional performance during bimanual box-lifting tasks in children aged 9–18 years with neurodevelopmental disabilities. A total of 83 participants, including 62 with unilateral spastic cerebral palsy and 21 with non-unilateral spastic cerebral palsy, performed tasks using the Activity of Daily Living Testing and Training Device. Tasks were conducted at maximal (80–100% force) and submaximal (40–80% force) levels of force control, with positional performance measured in six directions using Inertial Measurement Unit sensors. Statistical analyses included the Wilcoxon signed-rank test for levels of force control comparisons, Kruskal–Wallis tests for group differences, and Spearman correlations to assess relationships between maximal and submaximal performance. The results revealed that four of six positional parameters were worse in the maximal zone than in the submaximal zone ($p<0.05$), highlighting the challenges of higher force demands. Additionally, positive correlations between maximal and submaximal performance suggest consistency across levels of force control. Maximal levels of force control increased variability, with submaximal performance proven to be a reliable predictor of maximal capabilities. This finding offers a safer and more efficient method for assessing motor performance. Overall, these results underscore the importance of targeted rehabilitation strategies focused on improving stability and precision in children with neurodevelopmental disabilities so they can perform daily tasks more independently. Full article

This study investigates the structural and catalytic properties of pure and Sr-doped LaCoO₃ and LaFeO₃ thin films for potential use as resistive gas sensors. Thin films were deposited via pulsed laser deposition (PLD) and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), nanoindentation, and scratch tests. XRD analysis confirmed the formation of the desired perovskite phases without secondary phases. XPS revealed the presence of La³⁺, Co³⁺/Co⁴⁺, Fe³⁺/Fe⁴⁺, and Sr²⁺ oxidation states. SEM and AFM imaging showed compact, nanostructured surfaces with varying morphologies (shape and size of surface irregularities) depending on the composition. Sr doping led to surface refinement and increased nanohardness and adhesion. Transmission electron microscopy (TEM) analysis confirmed the columnar growth of nanocrystalline films. Sr-doped LaCoO₃ demonstrated enhanced sensitivity and stability in the presence of NO₂ gas compared to pure LaCoO₃, as evidenced by electrical resistivity measurements within 230 ÷ 440 °C. At the same time, it was found that Sr doping stabilizes the catalytic activity of LaFeO₃ (in the range of 300 ÷ 350 °C), although its behavior in the presence of NO₂ differs from that of LaCo(Sr)O₃—especially in terms of response and recovery times. These findings highlight the potential of Sr-doped LaCoO₃ and LaFeO₃ thin films for NO₂ sensing applications. Full article

Miniaturized components for enhanced integrated functionality or thin sheets for lightweight applications often consist of face-centered cubic metals. They exhibit good strength, corrosion resistance, formability and recyclability. Microfabrication technologies, however, may introduce cold work or detrimental heat-induced lattice defects into the material, with consequences for the mechanical properties. Austenitic stainless steels (1.4310, 1.4301) and aluminum alloys (EN AW-5005-H24, EN AW-6082-T6) were selected for this study. The influence of pulsed fiber laser cutting, microwaterjet cutting, and annealing on the strain–stress behavior was investigated. The micro-tensile test setup comprised a flex-structure force sensor, a laser extensometer, and a dedicated sample holder. Fiber laser cut 1.4310 samples exhibited early failure at low fracture strain in narrow shear band zones. The shear band zones were detectable on the sample surface, in the laser extensometer images, in the horizontal sections of the stress–strain curves, and in the microstructure. Inside the shear band zones, grains were strongly elongated and exhibited numerous parallel planar defects. Heat-induced chromium carbides, in combination with low stacking fault energy (SFE) and elevated carbon content, favored shear band zone formation in 1.4310. In contrast, microwaterjet cut high SFE materials EN AW-5005-H24 and EN AW-6082-T6, as well as low-carbon austenitic stainless steel 1.4301, exhibited uniform plastic deformation. Full article

Forcecardiography (FCG) uses force sensors to record the mechanical vibrations induced on the chest wall by cardiac and respiratory activities. FCG is usually performed via piezoelectric lead-zirconate titanate (PZT) sensors, which simultaneously record the very slow respiratory movements of the chest, the slow infrasonic vibrations due to emptying and filling of heart chambers, the faster infrasonic vibrations due to movements of heart valves, which are usually recorded via Seismocardiography (SCG), and the audible vibrations corresponding to heart sounds, commonly recorded via Phonocardiography (PCG). However, PZT sensors are not flexible and do not adapt very well to the deformations of soft tissues on the chest. This study presents a flexible FCG sensor based on a piezoelectric polyvinylidene fluoride (PVDF) transducer. The PVDF FCG sensor was compared with a well-assessed PZT FCG sensor, as well as with an electro-resistive respiratory band (ERB), an accelerometric SCG sensor, and an electronic stethoscope for PCG. Simultaneous recordings were acquired with these sensors and an electrocardiography (ECG) monitor from a cohort of 35 healthy subjects (16 males and 19 females). The PVDF sensor signals were compared in terms of morphology with those acquired simultaneously via the PZT sensor, the SCG sensor and the electronic stethoscope. Moreover, the estimation accuracies of PVDF and PZT sensors for inter-beat intervals (IBIs) and inter-breath intervals (IBrIs) were assessed against reference ECG and ERB measurements. The results of statistical analyses confirmed that the PVDF sensor provides FCG signals with very high similarity to those acquired via PZT sensors (median cross-correlation index of 0.96 across all subjects) as well as with SCG and PCG signals (median cross-correlation indices of 0.85 and 0.80, respectively). Moreover, the PVDF sensor provides very accurate estimates of IBIs, with R² > 0.99 and Bland–Altman limits of agreement (LoA) of [−5.30; 5.00] ms, and of IBrIs, with R² > 0.96 and LoA of [−0.510; 0.513] s. The flexibility of the PVDF sensor makes it more comfortable and ideal for wearable applications. Unlike PZT, PVDF is lead-free, which increases safety and biocompatibility for prolonged skin contact. Full article

In recent years, cold gas thrusters have been successfully deployed in numerous missions, showcasing their exceptional reliability and enabling ultra-precise space operations across a broad thrust range. This article introduces an integrated cold gas thruster that integrates flow, pressure, and displacement sensors. The thrust range of this thruster can exceed 1000 μN at most, and the resolution can reach up to 0.1 μN at low thrust. The results of the high-precision displacement sensor are good, showing that the thruster performs well in terms of flow control accuracy and thrust output sensitivity. The measurement accuracy of the force frame itself is also excellent, and it can detect small thrust changes of 0.1 μN. The thrust noise level of the thruster is good, comparable to the standard noise levels of the experimental environment. Full article

This study introduces an integrated lower limb robotic orthosis with near-field electrospinning (NFES) piezoelectric sensors and a fuzzy logic-based gait phase detection system to enhance mobility assistance and rehabilitation. The exoskeleton incorporates embedded pressure sensors within the insoles to capture ground reaction forces (GRFs) in real-time. A fuzzy logic inference system processes these signals, classifying gait phases such as stance, initial contact, mid-stance, and pre-swing. The NFES technique enables the fabrication of highly oriented nanofibers, improving sensor sensitivity and reliability. The system employs a master–slave control framework. A Texas Instruments (TI) TMS320F28069 microcontroller (Texas Instruments, Dallas, TX, USA) processes gait data and transmits actuation commands to motors and harmonic drives at the hip and knee joints. The control strategy follows a three-loop methodology, ensuring stable operation. Experimental validation assesses the system’s accuracy under various conditions, including no-load and loaded scenarios. Results demonstrate that the exoskeleton accurately detects gait phases, achieving a maximum tracking error of 4.23% in an 8-s gait cycle under no-load conditions and 4.34% when tested with a 68 kg user. Faster motion cycles introduce a maximum error of 6.79% for a 3-s gait cycle, confirming the system’s adaptability to dynamic walking conditions. These findings highlight the effectiveness of the developed exoskeleton in interpreting human motion intentions, positioning it as a promising solution for wearable rehabilitation and mobility assistance. Full article

This study systematically investigates the influence of heat treatment on the mechanical and magnetic properties of AISI 304 austenitic stainless steel following cold rolling. Experimental analyses were conducted on samples annealed at 50 °C to 1200 °C in 25 °C increments. The mechanical properties were characterized through chemical and metallographic analyses, microhardness testing, hardness measurements, and tear-off force evaluations. Magnetic properties were assessed using a fluxgate sensor to analyze the intrinsic magnetic field variations. The findings reveal that the magnetic field intensity peaks at an annealing temperature of 100 °C, followed by a progressive decline up to 700 °C. A pronounced reduction in magnetic properties was observed at 500 °C, with stabilization beyond 700 °C. Notably, the increase in magnetic field intensity at 100 °C suggests a potential transformation of deformation-induced martensite back into austenite. These results provide insights into the thermal stability of cold-rolled AISI 304 stainless steel and its structural evolution, contributing to a deeper understanding of its mechanical and magnetic behavior under varying heat treatment conditions. Full article

Nano-structures play a crucial role in advancing technology due to their unique properties and applications in various fields. This study examines the forced vibration behavior of an orthotropic nano-system consisting of an elastically connected nanoplate and a doubly curved shallow nano-shell. Both nano-elements are simply supported and embedded in a Winkler-type elastic medium. Utilizing the Eringen constitutive elastic relation, Kirchhoff–Love plate theory, and Novozhilov’s linear shallow shell theory, we derive a system of four coupled nonhomogeneous partial differential equations (PDEs) describing the forced transverse vibrations of the system. We perform forced vibration analysis using modal analysis. The developed model is a novel approach that has not been extensively researched by other authors. Therefore, we provide insights into the nano-system of an elastically connected nanoplate and a doubly curved shallow nano-shell, offering a detailed analytical and numerical analysis of the PDEs describing transverse oscillations. This includes a clear insight into natural frequency analysis and the effects of the nonlocal parameter. Additionally, damping proportional coefficients and external excitation significantly influence the transverse displacements of both the nanoplate and nano-shell. The proposed mathematical model of the ECSNPS aids in developing new nano-sensors that respond to transverse vibrations based on the geometry of the nano-shell element. These sensors are often used to adapt to curved surfaces in medical practice and gas sensing. Full article

This study developed a sustainable colorimetric pH sensor using chitosan derived from mealworm (Tenebrio molitor) biomass and anthocyanin extracted from red cabbage (Brassica oleracea). Chitosan was used as the substrate material, and anthocyanin served as the pH indicator dye, collectively forming the basis of the pH sensor. The resulting pH-responsive film effectively measures pH levels from 1 to 13, with a distinct color shift from pink to green. The sensor demonstrated remarkable stability, maintaining color fidelity after prolonged exposure to aqueous environments, and its practical functionality was confirmed through an ammonia detection assay, underscoring its utility in monitoring food freshness. Mechanistic investigations using Fourier-transform infrared spectroscopy (FTIR) and molecular modeling identified electrostatic and hydrophobic forces as key factors in anthocyanin binding to the chitosan matrix. Molecular modeling further revealed a minimal binding energy of −3 kcal/mol and an RMSD of 0 Å, indicating a strong interaction stability. The film exhibited high structural integrity, with tensile strength and elongation values of 8.8 MPa and 8.4%, respectively, and its flexibility suggests its suitability for diverse applications, including biomedical devices. The eco-friendly production process and the biocompatibility of this sensor provide a sustainable alternative to conventional pH measurement technologies. This innovation not only addresses ecological challenges but also expands the capabilities of colorimetric sensors for use in scientific research, biomedical applications, and other fields. Full article

Inertial measurement units (IMUs) are an example of practical technology for measuring countermovement jump (CMJ) performance, but there is a need to enhance their validity. One potential strategy to achieve this is advancing the literature on IMU placement. Many studies opt to position a single IMU on anatomical landmarks rather than determining placement based on anthropometric principles, despite the knowledge that linear mechanics act through the segmental centers of mass of the human body. The purpose of this study was to evaluate the impact of positioning IMU sensors to approximate the trunk and lower-extremity segmental centers of mass on the validity of vertical acceleration measurements and jump height (JH) estimation during CMJs. Thirty young adults (female n = 10, 21.3 (3.8) years, 166.1 (4.1) cm, 67.6 (11.3) kg; male n = 20, 22.0 (2.6) years, 179.2 (6.4) cm, 83.5 (17.1) kg) from a university setting participated in the study. Seven IMUs were positioned at the approximate centers of mass of the trunk, thighs, shanks, and feet. Using data from these sensors, 15 whole-body center of mass models were developed, including 1-, 2-, 3-, and 4-segment configurations derived from the trunk and three lower-body segments. The root mean square error (RMSE) of vertical acceleration was calculated for each IMU model by comparing its data against vertical acceleration measurements obtained from a force platform. JH estimates were calculated using the take-off velocity method and compared across IMU models and the force platform to evaluate for systematic bias. RMSE and JH values from the best-performing 1-, 2-, 3-, and 4-segment IMU models were analyzed for main effects using one-way analyses of variance. The best performing 2-segment (trunk and shanks; RMSE = 2.1 ± 1.3 m × s⁻²) and 3-segment (trunk, thighs, and feet; RMSE = 2.0 ± 1.2 m × s⁻²) IMU models returned significantly lower RMSE values compared to the 1- segment (trunk; RMSE = 3.0 ± 1.4 m × s⁻²) model (p = 0.021–0.041). No systematic bias was detected between the JH estimates derived from the best-performing IMU models and those obtained from the force platform (p = 0.91–0.99). Positioning multiple IMU sensors to approximate segmental centers of mass significantly improved the validity of vertical acceleration time-series data from CMJs. The findings highlight the importance of anthropometric-based IMU placement for enhancing measurement accuracy without introducing systematic bias. Full article

While automated-driving technology is advancing rapidly, human-centered research is still in its early stages. Research on negative user responses to automated driving is particularly limited in complex roadway environments such as roundabouts, where driving decisions typically depend on driver judgment and traffic conditions. In these environments, automated-driving vehicles may exhibit unstable behaviors, such as sudden stops or forced intersection entries. Since successful interaction between users and automated systems is critical for widespread adoption, understanding when and how automated driving negatively affects users is essential. This study investigated user psychological responses and corresponding physiological changes during unstable automated-driving situations. Using a virtual environment driving simulator, we compared two scenarios: sensor-only automated driving (A.D(S)), which exhibited unstable driving patterns; and cooperative automated driving (A.D(C)), which achieved more stable performance through infrastructure communication. We analyzed the responses of 30 participants using electromyography (EMG) measurements and pupil diameter tracking, supplemented by qualitative evaluations. Results showed that A.D(S) participants experienced higher levels of frustration during prolonged waiting times compared to A.D(C) participants. In addition, sudden braking events elicited startle responses characterized by pupil dilation and elevated arm-muscle EMG readings. This research advances our understanding of how automated-driving behaviors affect user experience and emphasizes the importance of human factors in the development of automated-driving technologies. Full article

As the end-effector of a humanoid robot, the dexterous hand plays a crucial role in the process of robot execution. However, due to the complicated and delicate structure of the human hand, it is difficult to replicate human hand functionality, balancing structural complexity, and cost. To address the problem, the article introduces the design and development of a multi-finger synergistic adaptive humanoid dexterous hand with underactuation flexible articulated fingers and integrated pressure sensors. The proposed hand achieves force feedback control, minimizes actuator use while enabling diverse grasping postures, and demonstrates the capability to handle everyday objects. It combines advanced bionics with innovative design to optimize flexibility, ease of manufacturing, and cost-effectiveness. Full article

A human gait recognition method based on the PSO-ELM algorithm is proposed in order to achieve coordinated movement between humans and lower limb exoskeletons. Ground reaction force (GRF) from the foot, and motion capture data (MCD) from two joints were collected through the exoskeleton device. The sample data were obtained through multiple experiments in different action scenarios, including standing still, walking on the flat, climbing up and down stairs, traveling up and down slopes, in addition to squatting down and standing up. The algorithm utilizes short-term posture data to recognize different posture movement patterns, with two advantages: (1) A user-friendly wearable device was constructed based on multi-source sensors distributed throughout the body, addressing multiple subjects with varying weights and heights, while being cost-effective and reliably and easily collecting data. (2) The PSO-ELM algorithm identifies key features of gait data, achieving a higher recognition accuracy than other advanced recognition methods, especially during arbitrary gait transition duration. Full article

A fault-tolerant collaborative control strategy for four-wheel-drive electric vehicles is proposed to address hidden safety issues caused by one or more in-wheel motor faults; the basic design scheme is that the control system is divided into two layers of motion tracking and torque distribution, and three systems, including driving, braking, and front-wheel steering are controlled collaboratively for four-wheel torque distribution. In the layer of motion tracking, a vehicle model with two-degree-of-freedom is employed to predict the control reference values of the longitudinal force and additional yaw moment required; four types of sensors, such as wheel speed, acceleration, gyroscope, and steering wheel angle, are used to calculate the actual values. At the torque distribution layer, SSOD and MSCD distribution schemes are designed to cope with two operating conditions, namely sufficient and insufficient output capacity after local hub motor failure, respectively, focusing on the objective function, constraints, and control variables of the MSCD control strategy. Finally, two operating environments, a straight-line track, and a DLC track, are set up to verify the effectiveness of the proposed control method. The results indicate that, compared with traditional methods, the average errors of the center of mass sideslip angle and yaw rate are reduced by at least 12.9% and 5.88%, respectively, in the straight-line track environment. In the DLC track environment, the average errors of the center of mass sideslip angle and yaw rate are reduced by at least 6% and 4.5%, respectively. The proposed fault-tolerant controller ensures that the four-wheel-drive electric vehicle meets the requirements of handling stability and safety under one or more hub motor failure conditions. Full article