Search Results (13,737)

Cylindrical gears are used extensively due to their significant advantages including high efficiency, high load-bearing capacity, and long lifespan. However, the machining accuracy of cylindrical gears is significantly affected by motion errors and force-induced errors of machine tools. In this study, a motion error model of the machine tools was established based on multi-body system theory and homogeneous coordinate transformation method, quantifying the contributions and variation patterns of 12 key errors in the A and B-axes to workpiece geometric errors. Then, by using the stiffness analytical model and the spatial meshing theory, the influence of the force-induced elastic deformation of the shaft of rolling wheel and the springback of the workpiece tooth flank on the geometric error was revealed. Finally, taking the through rolling of a spur cylindrical gear with a module of 1.75 mm, a pressure angle of 20°, and 46 teeth as an example, the force-induced elastic deformation model of the shaft was verified by the rolling tests. Results show that for 40CrNiMo steel, the total profile deviation, total helix deviation, and single pitch deviation in the X-direction caused by rolling forces are 32.48 µm, 32.13 µm and 32.13 µm, respectively, with a maximum contact rebound is δ_c = 28.27. The relative error between theoretical and measured X-direction spindle deformation is 8.26%. This study provides theoretical foundation and experimental support for improving the precision of rolling process. Full article

In the field of high-temperature in situ sensing, highly reflective Fabry–Perot (F-P) cavity mirrors with thermal stress matching are urgently needed. The quartz-based volume Bragg grating (VBG) can replace the dielectric high-reflection film to prepare a high-temperature and high-precision F-P cavity sensitive unit by virtue of the integrated structure of homogeneous materials. The reflectivity of the VBG is a key parameter determining the performance of the F-P cavity, and its accurate measurement is very important for the pre-evaluation of the device’s sensing ability. Based on the reflectivity measurement of quartz-based VBG with a large aspect ratio, a free-space optical path reflective measurement system is proposed. The ZEMAX simulation is used to optimize the optical transmission path and determine the position of each component when the optimal spot size is achieved. After completing the construction of the VBG reflectivity measurement system, the measurement error is calibrated by measuring the optical path loss, and the maximum error is only 1.2%. Finally, the reflectivity of the VBG measured by the calibrated system is 30.84%, which is basically consistent with the multi-physical field simulation results, showing a deviation as low as 0.85%. The experimental results fully verify the availability and high measurement accuracy of the reflectivity measurement system. This research work provides a new method for testing the characteristics of micron-scale grating size VBGs. Additionally, this work combines optical characterization methods to verify the good effect of VBG preparation technology, providing core technical support for the realization of subsequent homogeneous integrated Fabry–Perot cavity sensors. Furthermore, it holds important application value in the field of optical sensing and micro-nano integration. Full article

Objectives: This work investigated the influence of anthropometric height on oculo-manual ability during a visuo-motor reaction time task. The aim was to determine whether aligning test configurations with individual stature changes performance outcomes. Methods: In the first phase, 450 participants completed a standardized reaction task using a fixed panel, and correlations were explored between anthropometric measures and performance. The results revealed significant inverse correlations between height and both reaction time total time, and reaction time intertime. A second experimental phase involved an additional group of 36 individuals, who completed the same task using both the fixed and adjustable panels, designed to align visual stimuli with each participant’s central line of sight and arm length. Results: A paired-sample t-test showed a statistically significant reduction in both reaction time total time, total time required to deactivate all 54 lights targets, ($32.1\pm 3.26$ s to $30.7\pm 2.58$ s, $p<0.05$) and reaction time intertime, average time interval between successive light deactivations out of a total of 54 lights, ($0.31\pm 0.123$ s to $0.21\pm 0.149$ s, $p<0.01$), time total time, total time required to deactivate all 54 lights targets, ($32.1\pm 3.26$ s to $30.7\pm 2.58$ s, $p<0.05$) and reaction time intertime, average time interval between successive light deactivations out of a total of 54 lights, ($0.31\pm 0.123$ s to $0.21\pm 0.149$ s, $p<0.01$) under the adjustable panel configuration. Conclusions: These findings suggest that standard testing configurations may disadvantage individuals with shorter stature and highlight the benefits of personalized setups for assessing and enhancing oculo-manual coordination. Full article

In the search for lightweight and sustainable engineering approaches, enhancing the surface wear resistance of structural materials, such as 6061-T6 aluminum alloy, has become increasingly important. This study investigates the effect of coverage rates on the tribological properties of shot-peened 6061-T6 alloy, aiming to improve its usage in industries where weight reduction and durability are important, such as aerospace, automotive, railway, and renewable energy systems. A shot peening process was applied at four different coverage rates of 100%, 200%, 500%, and 1500% for comprehensive evaluation. A series of experimental analyses were conducted, including microhardness tests, ball-on-plate wear tests, residual stress measurements, and surface roughness evaluations. Furthermore, microstructural analysis was performed to investigate subsurface deformation, and scanning electron microscopy (SEM) was carried out to identify the wear mechanisms of the worn surfaces in detail. The results demonstrated a clear trend of gradual improvement in wear resistance with increasing shot peen coverage. The sample treated at a 1500% coverage rate exhibited 1.34 times higher hardness and 19 times higher wear resistance compared to the untreated sample. This study highlights that shot peening is an effective and feasible surface engineering method for enhancing the wear performance of 6061-T6 alloy. The findings offer valuable contributions for the development of lightweight and wear-resistant components considering sustainable material design. Full article

Multimode VCSELs coupled into waveguides can be a practical path toward realizing commercially viable photonic interposer chips. The experimental coupling of multimode VCSEL light to a non-silicon waveguide fabricated using a CMOS-compatible process is demonstrated. The GaP prism was tested and adopted as a coupling method. Both conventional and cavity-type optical waveguides, fabricated from CMOS-compatible PECVD SiO₂, Si₃N₄, and SiO_xN_y materials, were evaluated. The average propagation loss transmitted through the cavity-type waveguide was measured as 0.444 dB/cm. A polyimide micro-lens, cavity-type waveguide, and a GaP prism coupler are developed to inject the multimode VCSEL light into the waveguide measuring the net coupling loss of 0.762 dB. The packaged size of VCSEL has an area of 0.4 mm² and a height of 0.64 mm. MUX/DeMUX was designed on the bottom of the prism. A light source, a modulator, and MUX/DeMUX are all located in the same area of the prism bottom in VCSEL-based interconnections. Full article

With the global climate warming, the temperature conditions in permafrost regions have changed significantly, and the stability of permafrost slopes is facing serious threats. This paper focuses on the construction of the instability mechanism and prediction model of permafrost slopes considering the influence of temperature. By analyzing the thermokarst collapse process of permafrost slopes, the characteristics and causes of stages such as the soil loosening period and the surface sloughing period were studied. Based on the Mohr–Coulomb strength criterion, combined with the simplified Bishop method and the Morgenstern–Price method, a mechanical analysis of the critical state was carried out, and a safety factor formula applicable to the critical state of permafrost slopes was derived. From the curves of the total cohesion and effective internal friction angle of the experimental soil changing with temperature, an influence model of temperature on the strength parameters was fitted. Considering the factor of freeze–thaw cycles, a safety factor model for permafrost slopes was constructed. Through a large amount of data calculation and analysis of the model, the reliability of the model was verified. This model can be used to predict slope states in practical assessments and optimize slope support structure design parameters in cold regions, providing important references for ensuring engineering safety, reducing geological disasters, and promoting sustainability in cold regions. Finally, potential mitigation measures for frozen soil slope instability based on the findings are briefly discussed. Full article

In the context of rapid advancements in big data and artificial intelligence, similarity measurement methods between samples have been widely applied in data mining, pattern recognition, medical diagnosis, financial risk control, and other fields. The Mahalanobis distance, due to its effectiveness in capturing correlations within high-dimensional data, has become a crucial tool in many practical scenarios. However, sample data often contains sensitive privacy information, making it essential to achieve secure and privacy-preserving computation of Mahalanobis distance. This paper proposes a secure Mahalanobis distance calculation scheme tailored for sample vectors that effectively resists malicious cheating behaviors. The designed multi-party computation algorithms ensure privacy protection while maintaining computational efficiency and minimizing communication overhead. The experimental results compare three algorithms in terms of execution time and communication delay across varying sample sizes and vector dimensions. The results demonstrate that our proposed scheme achieves a favorable balance between security and performance. This research provides a practical and robust solution for similarity measurement under privacy constraints and lays a theoretical and practical foundation for secure data collaboration in multi-party computing environments, offering significant application potential. Full article

As a key parameter that defines the spectral characteristics of lasers, the precise measurement of laser linewidth is crucial for a wide range of advanced applications. This review systematically summarizes recent advances in laser linewidth measurement techniques, covering methods applicable from GHz-level broad linewidths to sub-Hz ultranarrow regimes. We begin by presenting representative applications of lasers with varying linewidth requirements, followed by the physical definition of linewidth and a discussion of the fundamental principles underlying its measurement. For broader linewidth regimes, we review two established techniques: direct spectral measurement using high-resolution spectrometers and Fabry–Pérot interferometer-based analysis. In the context of narrow-linewidth lasers, particular emphasis is placed on the optical beating method. A detailed comparison is provided between two dominant approaches: power spectral density (PSD) analysis of the beat signal and phase-noise-based linewidth evaluation. For each technique, we discuss the working principles, experimental configurations, achievable resolution, and limitations, along with comparative assessments of their advantages and drawbacks. Additionally, we critically examine recent innovations in ultra-high-precision linewidth metrology. This review aims to serve as a comprehensive technical reference for the development, characterization, and application of lasers across diverse spectral regimes. Full article

Metal-oxide surge arresters (MOSAs) are critical devices for overvoltage protection in power systems, and the aging characteristics of their zinc oxide (ZnO) varistors under impulse and power-frequency voltages exhibit significant differences. However, traditional methods for monitoring the aging state of surge arresters suffer from limitations such as insufficient sensitivity and vulnerability to harmonic interference. Therefore, this study conducted accelerated aging experiments on ZnO varistor samples under negative-polarity impulse currents. Key parameters were measured, including the DC reference voltage, the DC leakage current, nonlinear coefficients, and the full current under harmonic-containing power-frequency voltage at a voltage ratio of 0.6. The resistive component was accurately extracted from the full current using a separation method based on the Levenberg–Marquardt (LM) optimization algorithm. Spectral analysis was then performed on both the full current and the extracted resistive current components. The experimental results demonstrate a significant polarity effect in the aging of ZnO varistors under unipolar impulse currents. The LM optimization algorithm enables precise extraction of the resistive current component from the full current. Furthermore, compared to the fundamental and third harmonic components, the amplitude of the DC component within the resistive current exhibits the highest sensitivity to aging, establishing it as a viable aging criterion. Full article

The multi-wing centrifugal fan is an important part of air conditioning systems, particularly in the automotive domain. Due to the compact structure and short blade passage of the fan, it may reduce the aerodynamic performance and generate noise. As a key part of the multi-wing centrifugal fan, the volute tongue has an important impact on the aerodynamic performance and noise of the multi-wing centrifugal fan. In this paper, the volute tongue of a multi-wing centrifugal fan is modified for air conditioning systems, and a novel gradient-radius volute tongue is designed. Specifically, a simulation calculation model for the multi-wing centrifugal fan is developed based on the Realizable $k-\epsilon$ turbulence model and the Ffowcs Williams–Hawkings (FW-H) equation. The simulation results are analyzed, and the reliability of the proposed method is assessed by comparing the total pressure efficiency and noise levels with the corresponding experimental measurements. Subsequently, the aerodynamic performance and noise characteristics of the gradient-radius volute tongue are investigated, with particular attention given to variations in the flow field, pressure pulsation, and noise before and after the modification. The results indicate that the gradient-radius volute tongue effectively attenuates the pressure pulsations arising from the interaction between the volute and the airflow, thereby reducing the tongue-region noise. Compared with the original fan, a noise reduction of 3.5 dB is achieved through the implementation of the gradient-radius volute tongue. Full article

Objectives. The present study aimed to quantify changes in spinal kinematics during Nordic walking compared to regular walking (RW) for 60 s on a training path among physically fit young males (n = 20, aged 19–22 years). Methods. Two walking speeds were analyzed: 3 km/h and 5 km/h. The experimental setup was designed to assess spinal angular rotations using five kinematic parameters: upper spine, lower spine, thoracic region, lumbar region, and pelvis. Results. The data were acquired from 9 compact inertial sensors and the following motion analysis is carried out using 3D MioMotion IMU sensor’s analysis system. The differences in the obtained cyclic biomechanical parameters were detected using functional data analysis (FDA) statistical tests. Conclusions. The key finding of the study is that Nordic walking significantly alters the angular kinematic pattern of spinal movement as it revealed significant differences in all five measured parameters when compared to normal walking. Notably, the most pronounced changes were observed in the upper spine and pelvis motion. Additionally, Nordic walking increased stance phase duration and velocity: (i) significantly increased the duration of the stance phase in all three planes of motion; (ii) significantly increased the velocity during the stance phase across all three planes. These reported findings highlight the biomechanical, preventive, therapeutic, and rehabilitative potential of Nordic walking. Full article

In modern industrial manufacturing, the mechanical properties of large bearing housing castings are critical to equipment reliability and lifespan. Traditional prediction methods relying on experimental testing and empirical formulas face challenges such as high costs, limited samples, and inadequate generalization capabilities. This study presents a machine learning approach for predicting mechanical properties of ZG270-500 cast steel, integrating multivariate data (chemical composition, process parameters) to establish an efficient predictive model. Utilizing real-world production data from a certain foundry and forging plant, the research implemented preprocessing steps including outlier handling, data balancing, and normalization. A systematic comparison was conducted on the performance of four algorithms: Backpropagation Neural Network (BPNN), Support Vector Regression (SVR), Random Forest (RF), and Extreme Gradient Boosting (XGBoost). The results indicate that under small-sample conditions, the SVR model outperforms other models, achieving a coefficient of determination (R²) between 0.85 and 0.95 on the test set for mechanical properties. The root mean square errors (RMSE) for yield strength, tensile strength, elongation, reduction in area, and impact energy are 7.59 MPa, 7.52 MPa, 0.68%, 1.47%, and 5.51 J, respectively. Experimental validation confirmed relative errors between predicted and measured values below 4%. SHAP value analysis elucidated the influence mechanisms of key process parameters (e.g., pouring speed, normalization holding time) and elemental composition on mechanical properties. This research establishes an efficient data-driven approach for large casting performance prediction and provides a theoretical foundation for guiding process optimization, thereby addressing the research gap in performance prediction for large bearing housing castings. Full article

This work develops a Boundary Element Method (BEM) formulation for simulating bioheat transfer in perfused biological tissues using the Atangana–Baleanu fractional derivative in the Caputo sense (ABC). The ABC operator incorporates a nonsingular Mittag–Leffler kernel to model thermal memory effects while preserving compatibility with standard boundary conditions. The formulation combines boundary discretization with cell-based domain integration to account for volumetric heat sources, and a recursive time-stepping scheme to efficiently evaluate the fractional term. The model is applied to a one-dimensional cylindrical tissue domain subjected to metabolic heating and external energy deposition. Simulations are performed for multiple fractional orders, and the results are compared with classical BEM $(a=1.0)$, Caputo-based fractional BEM, and in vitro experimental temperature data. The fractional order $a\approx 0.894$ yields the best agreement with experimental measurements, reducing the maximum temperature error to 1.2% while maintaining moderate computational cost. These results indicate that the proposed BEM–ABC framework effectively captures nonlocal and time-delayed heat conduction effects in biological tissues and provides an efficient alternative to conventional fractional models for thermal analysis in biomedical applications. Full article

This article presents a preliminary study on the potential application of artificial intelligence methods for assessing the durability of HTS tapes in superconducting fault current limiters (SFCLs). Despite their importance for the selectivity and reliability of power networks, these devices remain at the prototype testing stage, and the phenomena occurring in HTS tapes during their operation—particularly the degradation of tapes due to cyclic transitions into the resistive state—are difficult to model owing to their highly non-linear and dynamic nature. A concept of an engineering decision support system (EDSS) has been proposed, which, based on macroscopically measurable parameters (dissipated energy and the number of transitions), aims to enable the prediction of tape parameter degradation. Within the scope of the study, five approaches were tested and compared: Gaussian process regression (GPR) with various kernel functions, k-nearest neighbours (k-NN) regression, the random forest (RF) algorithm, piecewise cubic hermite interpolating polynomial (PCHIP) interpolation, and polynomial approximation. All models were trained on a limited set of experimental data. Despite the quantitative limitations and simplicity of the adopted methods, the results indicate that even simple GPR models can support the detection of HTS tape degradation in scenarios where direct measurement of the critical current is not feasible. This work constitutes a first step towards the construction of a complete EDSS and outlines directions for further research, including the need to expand the dataset, improve validation, analyse uncertainty, and incorporate physical constraints into the models. Full article

This paper presents an automatic oil sampling system designed for vertical cylindrical oil tanks on land, focusing primarily on the structural design and control optimization for oil level measurement and liquid sampling inside the tank. First, the key structure and control architecture of the automatic sampler are introduced, explaining the collaborative working principles of its components to ensure good stability in system structure and motion control. On this basis, an improved Sparrow Search Algorithm (CSSA) is proposed, which integrates the Coati Optimization Algorithm (COA) and the traditional Sparrow Search Algorithm (SSA). This algorithm is used to optimize the parameters of the Proportional–Integral–Derivative (PID) control system in the oil sampler, aiming to address issues such as response delay, large overshoot, and insufficient stability that commonly occur in traditional PID control under complex conditions. This method achieves consistent response behavior over time and adaptiveness in the control process by dynamically adjusting the PID parameters in real time. To verify the effectiveness of the proposed control strategy, system simulations were conducted in the MATLAB 2024B environment, and a physical experimental platform was built for testing. The simulation compares the CSSA-PID controller with traditional PID, COA-PID, and SSA-PID control methods. In addition, a load disturbance was introduced at 300 ms to perform anti-interference comparative simulations. The results show that under CSSA-PID control, the system response time was shortened by up to 112 ms, the convergence speed improved by 72.3%, the global optimization capability was significantly enhanced, and the anti-interference ability was stronger. In the actual tests, the average error was reduced by approximately 45.3%. These results indicate that CSSA-PID can significantly enhance the stability and response speed of the control system. The efficient control of the automatic oil sampler will greatly enhance the intelligence and efficiency of oil level detection in tanks and reduce labor costs, having significant implications for the development of the grain and oil storage industry. Full article