Search Results (938)

Practical training on embedded systems is a very good way to assess the skills of students in firmware development, real-time programming and hardware–software co-design. However, many low- and middle-income institutions still use closed, proprietary boards, such as the Altera DE series, which hide the physical behavior. To address this, a low-cost, fully reconfigurable Microcontroller Test Board (MTB) was designed and technically validated for application in undergraduate laboratories. The MTB is manufactured as a one-sided through-hole PCB via toner transfer and FeCl3 etching, with a PIC18F2550 in-circuit programmer and support for 28- and 40-pin targets including the PIC16F877A. The MTB integrates six functional blocks, providing five canonical input/output modalities on a single regulated 5 V/0.56 A rail: (1) an ICSP programmer; (2) a multiplexed seven-segment display; (3) an 8 × 8 LED matrix; (4) a matrix keypad with LCD calculator; and (5) a 10-bit ADC stage. All subsystems operate with a flicker-free refresh rate > 122 Hz. The total board power consumption is 6.72 W at 12 V DC, with the linear regulator dissipating 3.92 W under full load. Probe points allow for signal transparency. Models for regulator dissipation, ADC quantization, multiplex refresh duty cycle, LED current limiting, oscillator timing, matrix-scanning latency, LCD timing, keypad response and Fe³⁺ with Cu etch kinetics were first-principles. Bench measurements agree with model predictions to less than 3% error, and confirm worst-case design margins. The MTB provides analytical rigor with accessible hardware to enable measurable experiments in microcontroller labs. The platform is cost-effective, with a material cost of less than USD 18. Each signal is routed to probe points, providing significant cost reduction from commercial trainers, and a transparent hands-on laboratory resource for engineering curricula with limited resources. Full article

Background/Objectives: Accurate intraoperative tumour localisation remains challenging in minimally invasive colorectal surgery because tactile palpation is lost and conventional markers can migrate or provide imprecise localisation. Building on a preceding tri-frequency study that identified 13.56 MHz as the preferred RFID band for the intended application, this work develops a shaft-compatible NFC antenna–reader platform and evaluates its electromagnetic behaviour from bench-top reference media to five-layer tissue-equivalent phantoms. Methods: A Ø3 × 25 mm Fair-Rite Material 67 ferrite-rod antenna was designed from material and geometric parameters using finite-rod demagnetisation, inductance, resonance, and field calculations, followed by FEM cross-validation and experimental characterisation. The primary dataset comprised 480 detection distance measurements (2 media × 4 tag angles × 30 repetitions × 2 encapsulation variants). Phantom testing added 1440 measurements at 22 °C and 600 measurements at 37 °C across three fabrication batches, with the 37 °C non-coaxial subset limited to one batch. Results: The fabricated antenna measured 16.9 µH versus a 17.4 µH analytical estimate (−2.9%), with loaded Q = 23. The coaxial detection range was 16.45 ± 0.29 mm in air and 16.26 ± 0.21 mm in saline; angle was the dominant determinant of range (partial η² = 0.989). In the multi-layer phantom, detection was 100% at 0 and 10 mm perirectal fat thickness under coaxial alignment at 22 °C, whereas performance declined markedly with angular misalignment and no detections occurred at fat thicknesses ≥ 20 mm. Across detectable phantom configurations, FEM showed r² = 0.994, RMSE = 0.81 mm, and mean bias +0.70 mm. Bare and resin-overcoated tags showed no statistically detectable range difference. Multi-tag discrimination reached 100% for up to three tags separated by ≥20 mm under coaxial alignment, but deteriorated with angular misalignment. Conclusions: The study demonstrates a physics-informed route from antenna miniaturisation to measured system performance, and defines the present operating envelope under controlled bench and tissue-equivalent phantom conditions. The electromagnetic measurements apply to the antenna–electronics subassembly; integrated-shaft, multi-prototype, multi-operator, ex vivo, and in vivo validation remain necessary before clinical performance can be determined. Full article

The knot-forming motions of knotters are difficult to directly observe, and knotting tests are labor-intensive and time-consuming. To address these issues, a novel test bench motion scheme was proposed to simulate the bundling process of a bale, and a performance test bench for a single-knot knotter was developed under controllable indoor conditions. The bench can verify the working principles of different knotters and assess the knotting success rate. To meet the requirements of unattended and safe operations for long-term continuous knotting tests, an automatic control process for the test bench was constructed to identify the knot-releasing failure and twine breakage fault based on monitoring the pressure of the simulated bale. By establishing the corresponding relationships between knotting actions and image states, a test and analysis method for detecting the motion timing sequences of the knotter was developed. This allowed us to obtain a motion timing diagram of the knotter, which can provide references for its reverse design or performance evaluation. The results of the continuous knotting tests show that the tested knotter achieved a knotting success rate of 99.57%, and the test bench can meet the performance testing requirements of the knotter. Full article

Objective. The main objective of this study was to examine the effects of transcutaneous auricular vagus nerve stimulation (taVNS) on psychological, sleep, and performance outcomes in powerlifters. Previous research has primarily focused on taVNS in clinical or healthy samples and showed improvements in psychological functioning, recovery, and sleep. Evidence for beneficial effects of taVNS in healthy athletes, however, is missing so far. Methods. Over the course of 4 weeks, 10 healthy adult powerlifters self-administered taVNS five times a week for 30 min after strength training or before bedtime, in an uncontrolled, single-arm pilot design without a sham or control condition. Measurements were taken at three time points: before the intervention phase (pre), immediately after the 4-week intervention phase (post) and 1 month after the post-assessment (follow-up). Pre, post, and follow-up measurements included various subjective psychological domains (recovery, stress, perceived stress, affect, memory, attention, anxiety, and well-being), objective sleep domains (nocturnal HRV, sleep score, sleep duration, and subjective sleep quality), and submaximal strength performance outcomes in squat, bench press, and deadlift. The small sample size required non-parametric testing. Additionally, a responder analysis was conducted to explore individual differences in outcome-specific responses. Results. Results showed nominally significant pre-post improvements (uncorrected for multiple comparisons) in positive affect and self-reported attentional difficulties, both revealing large effect sizes; however, given the absence of a control group and the lack of correction for multiple comparisons across multiple outcomes tested, these findings should be interpreted as exploratory and hypothesis-generating rather than confirmatory. The remaining psychological domains and sleep outcomes did not show meaningful changes. Regarding performance, only two of the ten participants provided complete baseline training data, so no reliable conclusions about a beneficial effect of taVNS on strength performance could be drawn. The responder analysis was consistent with the two nominally significant findings but did not reveal a clear overall pattern of taVNS effectiveness. Conclusions. The current study is the first to implement a 4-week taVNS intervention in strength training and demonstrate differences in domain-specific responsiveness to taVNS in athletes for psychological health and self-reported cognitive performance. These findings offer important insights into the feasibility and practical application of taVNS in sports settings. Further studies with larger, sham-controlled samples, a pre-registered primary outcome and a longer intervention period are needed to determine whether these preliminary, hypothesis-generating findings reflect genuine effects of taVNS. Full article

This article examines the problem of assessing the reliability of stamped-welded freight car bogie components based on fatigue strength criteria under operational loads. The theoretical framework utilizes the principles of the linear fatigue damage summation hypothesis, the power-law fatigue curve, the probabilistic description of the fatigue limit, and Rayleigh’s law for the distribution of dynamic stress amplitudes. An algorithm for calculating reliability indicators in a closed analytical form has been developed, enabling durability prediction at the design stage in the absence of complete information on the structural loading. The experimental part included strain gauge studies of the side frames and bolsters of freight car bogies, as well as fatigue bench tests of specimens under various cyclic load levels. Statistical processing of the test results was performed, determining the parameters of the fatigue curves, fatigue limits, and variation coefficients. It was established that the use of equivalent operational load amplitudes ensures a more accurate determination of the fatigue curve parameter and improves the reliability of the reliability assessment. A significant influence of the fatigue curve parameter on the estimated failure probability during the structural life cycle is demonstrated. The obtained results can be used in the design of advanced freight bogies and in improving regulatory methods for assessing the reliability of railcar structures. The scientific novelty of the study lies in the development of a closed-form algorithm for calculating reliability indicators and the substantiation of a method for processing fatigue test results, taking into account actual operating conditions. The article shows that when statistically processing the results of fatigue tests of the side frame, the transition from actual to equivalent load amplitudes leads to a change in the parameter of the power curve of fatigue (m) from 7.36 to 7.92. The average value of the endurance limit changes from 183.5 to 199.4 kN, the minimum value of the endurance limit—from 143.7 to 158.8 kN, and the coefficient of variation—from 0.1318 to 0.1237. It was also found that the difference in parameter (m) significantly affects the predicted reliability indicators: for the long service life under consideration, the estimated probability of failure was 2.0% and 1.1%, respectively; that is, it differed almost twofold. Full article

Background: Large language models (LLMs) can produce clinically plausible recommendations that are not adequately supported by authoritative evidence. Objectives: We introduce GuidelineGuard, a modular multi-agent retrieval-augmented generation pipeline in which a separate Auditor verifies claim–sentence support before a recommendation is surfaced. Methods: The original evaluation used a 73-sentence guideline corpus and GG-Bench-60, with replication across three open-weight backbones. In response to reviewer concerns about benchmark size and selective evaluation, we added a source-traceable GG-Bench-200 stress test and the complete 500-case held-out PQA-L test split of PubMedQA. The revision experiments compare single-pass RAG, a paired multi-agent no-Auditor ablation, and GuidelineGuard; the paired runner is designed to share the Planner–Retriever–Clinician draft so that the Auditor is the only intervention. Checkpoint verification confirmed an identical observable pre-audit state for all 200 GG-Bench cases and 496/500 PubMedQA cases; four PubMedQA cases were regenerated after quota-interrupted resumption and were correct commitments in both arms. Because the originally used hosted Llama endpoints became unavailable after the initial experiments, the expanded runs use openai/gpt-oss-20b for generation and openai/gpt-oss-120b for the Auditor. Results: On GG-Bench-200, single-pass RAG achieved 0.970 operational accuracy, while the no-Auditor and GuidelineGuard arms achieved 0.955 and 0.925, respectively. GuidelineGuard committed on 186/200 cases (coverage 0.930) and was correct on 185/186 commitments (selective accuracy 0.995); all 186 commitments cited at least one gold evidence identifier. Relative to the paired no-Auditor arm, the gate rejected six otherwise-correct commitments and no incorrect commitment. On PubMedQA-500, single-pass RAG achieved 0.644 operational accuracy at 0.950 coverage, the no-Auditor arm 0.638 at 0.896 coverage, and GuidelineGuard 0.550 at 0.736 coverage. Selective accuracy increased across those operating points from 0.678 to 0.712 to 0.747. Within the 496 PubMedQA cases with verified-identical observable pre-audit state, the gate rejected 36 incorrect and 45 correct pre-audit commitments, demonstrating both error enrichment and a substantial false-rejection cost. Conclusions: The expanded results support GuidelineGuard as a selective claim–evidence verification mechanism, not as a universally more accurate generator. Its value is the explicit, auditable coverage–risk trade-off; the appropriate verification threshold is task- and cost-dependent and requires prospective clinical validation. Full article

The increasing performance requirements of electric vehicle powertrains demand lightweight, efficient, and low-noise transmission systems. High-speed electric drive unit concepts offer significant potential for reducing motor size and mass by shifting torque generation to higher rotational speeds. However, this approach places increased demands on gearbox power density, efficiency, and noise, vibration, and harshness (NVH) performance. This work investigates the NVH behaviour of a compact, high-speed automotive gearbox with a focus on planetary gear stages. Although planetary stages offer high compactness, their complex kinematics can lead to pronounced NVH challenges. In particular, sequentially phased gear meshing results in characteristic sideband components whose orders can be predicted analytically, while their amplitudes remain difficult to estimate reliably during the design phase, necessitating experimental validation. Several NVH-oriented design measures, including high-contact-ratio gearing and low-NVH microgeometry, are applied to a two-stage gearbox comprising a planetary and a cylindrical gear stage. Peak-to-peak transmission error is used as a primary NVH design metric. The planetary stage is analysed in detail to assess the influence of sequential phasing on sideband components in the dynamic response and resulting vibration behaviour. The NVH-oriented gearbox is tested on a bench, with housing accelerations used to analyse planetary sidebands, providing insights into the NVH potential of compact, high-speed gearboxes and the role of sequential phasing in the vibration response. Full article

This study investigates the optimization of airflow distribution and pressure drops in H14 HEPA minipleat filters through the introduction of the hot-melt cell as the fundamental hydraulic unit governing local flow behavior. A coupled analytical framework integrating Falkner–Skan boundary-layer theory, Darcy–Weisbach channel friction, and Darcy porous-medium flow was developed and experimentally tested using velocity measurements obtained in a 600 m³/h test bench operating at a frontal velocity of 0.45 m/s under laminar-flow conditions. Ten primary geometric configurations and 21 hot-melt distribution scenarios (totaling 31 cases plus an optimized design case) were systematically evaluated by varying cell width (W), inlet height (H_i), and pleat length (L). Experimental and analytical results reveal significant velocity heterogeneity in the vicinity of the filter surface, which progressively decreases with distance from the filter, while localized velocity amplification is observed near the hot-melt separators. The analysis demonstrates that hydraulic diameter, pleat angle, and hot-melt spacing are the dominant parameters governing pressure drop generation and flow redistribution. Among the configurations investigated, a model-predicted optimized design (W = 46.25 mm, L = 55.00 mm, 230 pleats) yields a theoretical pressure drop reduction of up to 29.23% without significantly compromising the effective filtration area. These results provide an analytical framework for pre-prototyping optimization, although experimental verification of physical prototype validation for mechanical integrity and the preservation of initial efficiency, among other governing physical quantities, remains essential. The results demonstrate that the proposed hot-melt cell concept provides a practical engineering framework for the aerodynamic optimization of minipleat HEPA filters, enabling improved flow uniformity and reduced energy consumption in cleanroom applications. Full article

The automated transplanting of bare-root strawberry seedlings faces challenges, including a high reliance on manual feeding and a lack of adaptable equipment. Moreover, existing picking mechanisms are typically limited to plug seedlings rather than multi-stem crops. To overcome these limitations, this study proposes an automatic seedling picking and feeding system synergizing an intermittent conveying device and a manipulator. First, the physical and mechanical properties of bare-root strawberry seedlings were measured. Through radial stem compression tests, a non-destructive clamping safety threshold bounded by a bio-yield point of 28 N was determined. Secondly, an intermittent conveying device based on variable-span V-shaped supports was designed. Furthermore, based on the clamping safety threshold and spatial kinematic modeling, a seedling picking end-effector was developed. This end-effector adopts a “gather first, clamp later” operation strategy to guarantee grasping accuracy and ensure reliability by preventing seedling detachment during transportation. Finally, a system test bench was built to conduct a three-factor, three-level orthogonal experiment to investigate the effects of seedling picking frequency, gripping position, and clamping gap on operation quality. At a seedling pick-up frequency of 20 plants/min, gripping position of 25 mm, and gripping gap of 5 mm, the system reached 98% success rate in picking and feeding, validating its stability and providing core equipment and theoretical support for fully automatic strawberry transplanters. Full article

Fertilizer clusters tend to lose their agglomerated state upon ground contact, which reduces fertilizer use efficiency. To address this, we designed a gravity-constrained fertilizer guide tube. Based on the principle of minimum friction, we designed a trapezoidal groove. By analyzing the motion of the fertilizer as it dropped and contacted the ground, we identified the key factors affecting hole formation such as the fertilizer guiding angle, groove angle, and forward velocity. We used the discrete element method to determine the optimal combination of parameters: with a fertilizer guiding angle of 60°, a groove angle of 80°, and a forward velocity of 6 km/h, the average hole length was 87.6 mm, the coefficient of variation of hole length was 6.51%, and the coefficient of variation of hole spacing was 1.76%. Bench test results indicated that under conditions of a target fertilizer dosage per hole of 6.0 g, a forward velocity of 4–10 km/h, and a target hole spacing of 0.20–0.30 m, the fertilizer clusters consistently maintained their agglomerated state during descent. Field test results showed that under conditions of a target fertilizer dosage per hole of 2.0–8.0 g, a forward velocity of 4–10 km/h, and a target hole spacing of 0.20–0.30 m, the average hole length ranged from 94.5 to 223.0 mm, with a coefficient of variation of hole length of 7.17–11.16% and a coefficient of variation of hole spacing of 2.95–6.06%. Although hole formation performance was somewhat reduced in the field, the fertilizer in each hole remained in an aggregated state and was distributed uniformly. The collision between the fertilizer and the soil was the key factor affecting hole formation. The results of this study can provide insights and references for the design and optimization of fertilizer-hole-applied discharge devices. Full article

The cleaning system of combine harvesters is an important component whose efficiency directly depends on the uniform distribution of the air velocity profile on the sieve surface. However, the experimental evaluation of the air flow rate is often limited by the high cost and the impossibility of simultaneous multi-point acquisition using commercial anemometers. This paper presents the design, development, and calibration of a low-cost anemometric sensor, based on an NTC thermistor, intended for aerodynamic optimization in the design and laboratory testing phase of cleaning systems. The proposed system replaces the need to use Wheatstone bridges by combining a constant current source, a 16-bit ADC converter, and an RC filter, allowing it to resolve fine voltage variations at low velocity. The algorithm integrates temperature compensation in the 3rd degree polynomial equation by simultaneously reading the environmental temperature using a digital sensor with an accuracy of ±0.1 °C. Experimental validation on the bench against the reference anemometer testo 405i showed excellent agreement (R² = 0.998, mean bias = 0.017 m/s, and a maximum error of ±0.08 m/s), falling within the tolerance of the reference anemometer. By the ability to use multiple sensors and parallel acquisition in real time, the proposed solution offers an alternative for 2D/3D aerodynamic mapping of sieves under controlled laboratory conditions for the design of combine harvester cleaning systems. Full article

The dynamic distribution of braking forces between front and rear axles in electric commercial vehicles represents a critical multi-objective optimization challenge requiring simultaneous satisfaction of regulatory safety compliance, regenerative energy recovery, thermal stability, and actuator coordination under varying load and road conditions. This paper addresses this challenge through the development and experimental validation of an integrated adaptive brake force distribution strategy combining model predictive control (MPC) with Particle Swarm Optimization (PSO) within a unified framework that ensures compliance with ECE Regulation No. 13. A comprehensive experimental test bench was designed and instrumented, integrating three independent braking mechanisms: magnetic brakes with front and rear torque coefficients of 4.73 N·m/A and 3.65 N·m/A, respectively; an eddy current retarder with coefficient $k_0=$ 2.220 × 10⁻⁴ N·m·s/(A²·rad), producing braking torque that is quadratic in excitation current and linear in rotor speed; a regenerative braking system with 82–90% efficiency; and a switchable magnetic clutch for FWD/4WD operation. The MPC controller was formulated with a prediction horizon $N_p$ = 20, control horizon $N_c$ = 5, and sampling time $T_s$ = 20 ms. PSO was employed for systematic tuning of MPC weights using 30 particles over 50 iterations with cognitive and social coefficients $c_1$ = $c_2$ = 2.0 and linearly decreasing inertia from 0.8 to 0.4. A vehicle state estimation module using Kalman Filtering was developed for real-time estimation of vehicle mass (<3% error), road slope (<0.3% error), and road friction coefficient (<5% error). Experimental validation across eight comprehensive test scenarios demonstrates that the PSO-optimized MPC controller achieves 43% reduction in front RMSE (from 2.65 Nm to 1.52 Nm), 44% reduction in rear RMSE (from 0.78 Nm to 0.44 Nm), 100% ECE R13 compliance (improved from 67.5%), 57% settling time improvement (from 4.2 s to 1.8 s), 92% overshoot reduction (from 67% to 5%), and average recovered energy improvement from 3.51 kJ to 4.04 kJ. The proposed framework provides a comprehensive solution for next-generation electric commercial vehicle brake management systems. Full article

Cross-domain distribution shifts severely degrade the diagnostic performance of rolling bearing models under unseen variable operating scenarios. Single-source domain generalization (SDG) builds fault diagnosis models using only single-source vibration data, which fits the practical limitations of industrial data collection. Existing contrastive learning methods adopt uniform spectral perturbations for data augmentation, which easily corrupt fault harmonic characteristics and require massive, labeled training samples. To tackle these drawbacks, this paper proposes an unsupervised contrastive learning framework named FDACL. An adaptive frequency-domain augmentation (AFA) module equipped with learnable weights is designed to separate fault-critical frequency bands from noise components. Differentiated amplitude perturbations are applied to two categories of spectral signals to generate diverse pseudo-samples while retaining intrinsic fault information. A shared encoder is trained with combined InfoNCE contrast loss and classification loss to learn domain-invariant fault representations. Validations are carried out on three datasets, namely Case Western Reserve University (CWRU), Paderborn University (PU), and the industrial CRRC Qingdao Sifang railway wheelset bearing dataset acquired from physical test benches. FDACL achieves average cross-speed diagnostic accuracies of 92.68% and 77.85% on CWRU and PU, respectively, and maintains competitive performance on the Qingdao Sifang industrial dataset. It outperforms state-of-the-art baselines by 4.23–8.71% across all SDG transfer tasks. Ablation experiments and hyperparameter analysis verify the efficacy of the AFA module and contrastive learning scheme, providing an unsupervised diagnostic approach for railway bearings under unknown working conditions. Full article

Discharge uniformity and metering accuracy are essential for precision fertilization. An inclined screw fertilizer metering device with a spherical buffering outlet was designed and optimized using the discrete element method (DEM) and bench experiments. A particle-flow model was established using EDEM (DEM simulation software) to evaluate the effects of conveying inclination angle and outlet accumulation length on discharge performance using the coefficient of variation (CV), standard deviation, amplitude, and pulsation degree. Single-factor tests indicated that an inclination angle of 12° and an accumulation length of 32 mm produced favorable discharge performance. Two-factor optimization identified 13.5° and 40 mm as the optimal combination, yielding the lowest CV (2.36%) and standard deviation (51.88). Bench experiments further verified the performance of the optimized device. Compared with a conventional fluted-wheel fertilizer metering device, the optimized screw device reduced the average discharge error from 8.94% to 3.35% and achieved average CV values of 5.91%, 4.39%, and 4.44% under low-, medium-, and high-discharge-rate conditions, respectively. These results show that optimizing the inclination angle and outlet accumulation length can effectively improve fertilizer discharge uniformity and metering accuracy. Full article

To address large fluctuations in fertilizer flow and the difficulty of real-time quantitative blockage monitoring during fertilization by an integrated tillage, land preparation, and seeding machine, a fertilization monitoring system combining real-time detection and intelligent alarm functions was designed and developed. The system uses an STC32G12K128 microcontroller as the core control unit and integrates fiber-optic sensors, fiber-optic amplifiers, and associated peripheral hardware. Supporting host computer software was also developed on the Python3.13 platform. Based on the light-blocking principle, the optical signal generated by fertilizer particles passing through the sensing area is converted into a digital signal by the fiber-optic amplifier. A quantitative correlation model between the amount of blocked light and the fertilizer discharge rate was then established, enabling indirect and non-contact measurement of the fertilizer discharge rate. Indoor bench tests demonstrated a highly significant positive linear correlation between the amount of blocked light and the fertilizer discharge rate. The overall mean absolute percentage error of the fitted model was below 10%. Based on this detection system, a fertilization monitoring and alarm module was further developed for indoor bench conditions, together with discrimination logic for fertilizer blockage and fertilizer shortage. At rotational speeds of 30–50 r/min, the system achieved an average blockage detection rate of 98%, an average false alarm rate of 4.4%, and an alarm response time of no more than 3 s. Full article