In Proton Exchange Membrane Fuel Cells (PEMFC), methods for measuring the reaction temperature of the Proton Exchange Membrane (PEM) can be classified into contact and non-contact methods. Non-contact methods, such as infrared thermometry and thermographic phosphor, fail to accurately capture the transient temperatures of the PEM due to their low spatiotemporal resolution. Existing contact methods are limited by the large size of the measurement devices, poor heat resistance, and poor corrosion resistance, which affect both PEM reactions and the accuracy of temperature measurements. We have developed a new method that applies NiCr/NiSi thin-film thermocouples to the PEM using physical vapor deposition technology, allowing for accurate measurement of transient temperatures. These thermocouples, with their micrometer-scale structures, are suitable for contact measurements in sealed environments, preserving the integrity of the seal. They provide a rapid response of 2.91 mu s, effectively capturing transient temperatures. Experimental results show that these custommade thermocouples measure a stable reaction temperature of 79.7 degrees C, which is more accurate than the 78.8 degrees C measured by infrared methods. The authors also reveal that the reactor's central cathode temperature is 1.7 degrees C higher than the edges, and the anode temperature is 1.8 degrees C higher. This provides a new approach for achieving high spatiotemporal accuracy in temperature measurements during PEM reactions in the next generation of fuel cells.

Aiming to solve the problems of excessive leakage and insufficient gas film stiffness of high-speed dry gas seals, a bidirectional rotating triangular step groove sealing structure was developed, based on the spiral groove sealing principle and combined with bidirectional rotation and step groove design. The finite difference method was employed to solve the hydrodynamic lubrication equation, which can systematic study the influence of operating conditions and structural parameters on lubrication performance. Meanwhile, the coupling effect between the number of groove layers and the opening angle on seal optimization was examined. The results indicate that optimized groove design significantly enhances sealing efficiency. Increasing the opening angle of a single-layer groove can improve film stiffness and increase the opening force by 1.75%. Moreover, adding step layers effectively reduces leakage, decreasing the leakage rate by 2.04%. Among the tested configurations, “Type 3” grooves were preferable for applications requiring high opening force, whereas “Type 1” grooves achieve an optimal compromise between opening force and leakage control. Furthermore, an appropriate number of step layers (e.g., two layers) optimises gas film pressure distribution, enhances seal stability, and increases opening force, whereas excessive layering may negatively impact performance. This sealing structure demonstrates exceptional performance under high-speed and complex operating conditions, making it highly suitable for aerospace, energy, power generation, and precision machinery applications. It proviedes a solid foundation for advancing high-performance dry gas sealing technology.

Breaking through the speed of high-performance bearings is one of the important studies in the development of high-end equipment. The study of wear performance under various gases is helpful to improve the speed of series bearings. In this study, the analysis of shape-position error and surface performance of high-speed petal magnetic rotor series bearings (HPMRSBs) in vacuum service at 120000 rpm was carried out, and the fretting wear mechanism under various gases is evaluated. The HPMRSBs inner ring raceway subsurface wear was 1.5-2.5 times greater than the outer raceway subsurface wear. After the wear failure of the inner ring raceway of HPMRSBs, a nanocrystalline layer with a thickness of about 1500 nm appeared on the surface, which was 3.75 times that of the outer ring raceway. The outer ring was single crystal structure. The nanocrystalline layer of the outer ring raceway of the HPMRSBs contains 97.9 % Fe, 1.69 % C and 0.41 % O. The poor lubrication and decarburization effect of inner and outer race raceways of HPMRSBs. The formation of the decarburized layer will lead to the decrease of the surface hardness, the aggravation of wear, and then the increase of temperature, forming a vicious circle. The hardness of the nanocrystalline layer of the inner and outer raceways were 12.816 GPa and 10.268 GPa respectively. For air, argon and nitrogen environments, the coefficient of friction (COF) was relatively stable, and the maximum changes of the three were 0.93, 1.16 and 1.01, respectively. Therefore, different gas environments can be selected according to the working conditions. Combined with analytical data, the comprehensive mechanism analysis of grinding processing, surface integrity and service life was carried out. The research conclusion of this paper will provide theoretical guidance and data support for the design, manufacture and service failure of high-performance bearings (in different environments).

With the continuous increase in the heat flux density of electronic devices, the development of highly efficient and compact heat dissipation structures has become a major research focus. Inspired by the natural scallop shell structure, a three-dimensional bionic shell-structured microchannel is proposed in this study. Numerical simulations were conducted to systematically investigate the effects of the shell structure spacing (S/H = 3.0–4.5) and rotation angle (α = 0°–90°) on the flow and heat transfer characteristics. The results indicate that, within the inlet velocity range of 0.3–1.5 m/s (Re ≈ 183–914), the maximum Nusselt number (Nu) of the shell-structured microchannel is enhanced by up to 144.7% compared with that of the smooth microchannel, while the performance evaluation criterion (PEC) remains greater than 1, reaching a maximum value of 1.65. Under the same boundary conditions, the shell-structured microchannel exhibits consistently higher PEC values than the single-row circular pin-fin microchannel (NRM), demonstrating the significant comprehensive advantage of its unique curved geometry in enhancing heat transfer while controlling flow resistance. The optimal structural parameters exhibit distinct Reynolds number-dependent characteristics. At low and moderate Reynolds numbers (Re ≤ 700), the configuration with S/H = 3.75 and α = 0° achieves the best overall performance, whereas at high Reynolds numbers (Re ≥ 700), the configuration with S/H = 4.5 and α = 90° provides the highest heat transfer performance (Nu ≈ 97.70, PEC ≈ 1.65). The analysis reveals that the shell structure induces flow bypass, flow separation, reattachment, and multiple pairs of counter-rotating longitudinal vortices, which effectively enhance fluid mixing and weaken the thermal boundary layer, thereby serving as the primary mechanisms responsible for achieving efficient heat transfer enhancement with relatively low flow resistance.

PurposeA novel diamond cross-section groove design inspired by the structural features of diamond cross-sections is proposed to optimize the performance of dry gas seals.Design/methodology/approachThe groove geometry imitates diamond-like hydrodynamics, effectively guiding flow, suppressing turbulence and reducing pressure loss. Three-dimensional numerical simulations using ANSYS were conducted to evaluate flow field characteristics and sealing behavior under various operating conditions.FindingsThe results show that the diamond grooves generate stable vortices and strengthen hydrodynamic pressure in the gas film. Their symmetric structure provides load capacity in both rotational directions, overcoming the limitation of conventional spiral grooves under reverse operation. At high rotational speeds, the geometry stabilizes the flow field, suppresses turbulence and pressure fluctuations and achieves a microscale self-sealing effect, thereby reducing leakage. Turbulence increases the opening force by about 12%, while slip effects reduces it by about 5%, with the most significant effect under laminar flow. Leakage increases markedly with large film thickness, with turbulence combined with slip effects producing values nearly 50% higher than laminar flow, indicating a strong coupling between microscale gas dynamics and macroscopic flow. Frictional torque is about 15% higher in turbulence compared to laminar flow, whereas slip effects reduces it by about 10%, reflecting multiscale regulatory effects.Originality/valueThese findings provide an effective pathway for achieving efficient, low-leakage and low-friction design optimization of dry gas seals.

This study addresses the issues with traditional rolling protection bearings in vertical magnetic levitation flywheel energy storage systems (FESSs), which are prone to impact, wear, and temperature rise under abnormal conditions, such as drops. It designed a permanent magnet axial protection bearing based on a Halbach array, utilizing N42SH permanent magnet material. The five-layer Halbach array achieved a maximum axial magnetic force of 86 KN and a maximum air gap magnetic flux density of 2.2 T, meeting the application requirements. Simulation results, combined with rotor drop dynamics and thermal analysis, show that under an 8000 rpm drop condition, the permanent magnet bearing reduces radial and axial contact forces by approximately 60% and 54%, respectively, and wear by around 70%. Additionally, the maximum system temperature decreases from 109 °C to 74 °C, with a 32% reduction in temperature rise. Friction experimental analysis indicates that low frequency, low load, and moderate temperatures improve friction stability and reduce wear. Overall, the permanent magnet axial protective bearing effectively mitigates drop impact, reduces friction heat and wear, and enhances the safety and reliability of the flywheel energy storage system under abnormal working conditions, providing valuable theoretical support and a design reference for engineering applications.

P2 is the highest standard for the accuracy level of rolling bearings in the world, which is mainly used in the fields of aerospace, high-end equipment, precision/ultra-precision spindles/electric spindles and other rotary components. In this study, P2 high performance aerospace spindle bearing raceway was tested for up to 6000 h in high service. The failure mode after service was analyzed by means of SEM, EDS and EBSD. A series of research results show that the temperature of high-performance bearings was basically stable between 25 °C and 55 °C. The “4-ring” wear failure structure appears from the surface to the subsurface of the outer ring raceway of high performance bearings, and the maximum wear depth of the first, second, and third layers were 130 μm, 210 μm, and 230 μm, respectively. The outer ring raceway of high performance bearing raceway contained 46.9

GCr15 is mainly used as bearing ring material. In the traditional precision bearing machining method, the control of grinding force and grinding temperature (GF GT) often depends on operator’s “experience”, and its measurement method is quite simple. In this study, the basic analysis of different brands and types of precision bearings was carried out, and the potential coupling of GF GT in bearing grinding was investigated. Through the coupling experiment and simulation analysis of GF GT of bearing raceway, the following conclusions were repeatedly proved and obtained: (a) GF GT had great influence on retained austenite content and metamorphic layer thickness of precision bearing raceway. (b) The thickness of the metamorphic layer of Bearing B was smaller than that of Bearing A when the retained austenite content was about 10

This study presents the calibration methodology of NiCr-NiSi thin-film thermocouples and evaluates their application in real-time temperature monitoring and characterization of fuel cell thermal behavior. Experimental results reveal that the Seebeck coefficients of the NiCr-NiSi thin films remain stable after multiple calibration cycles, indicating good reliability and repeatability. Furthermore, the thermocouples demonstrate an ultrafast response time of less than 15 microseconds and reach thermal equilibrium within 200 microseconds under transient thermal inputs. These characteristics enable accurate and rapid temperature measurement of fuel cell plates up to 100 °C, which is critical for maintaining the safe and efficient operation of fuel cells.

Thin-film thermocouples are widely used in microelectronics, precision instrumentation, and aerospace because of their fast response, small size, and light weight. However, accurate temperature measurement cannot be separated from accurate calibration. This paper systematically studies the calibration method of NiCr–NiSi thin-film thermocouples, discusses the main factors affecting the calibration accuracy, and proposes specific measures to optimize the calibration process. Through experimental verification, the optimized calibration method significantly improves the measurement accuracy and stability of the thin-film thermocouple.

Thin Film Growth In article number 2404829, Wanyu Ding, Zixi Wang, and co-workers established a three-layer NiCr/NiSi thin-film thermocouple temperature measurement system in TiO2 film growth processes, to measure the temperature gradient from TiO2 film growth surface to substrate. The temperature of substrate was about 132.05 °C, while the temperature difference between TiO2 film growth surface and substrate could reach to was about 144.71 °C.

The dynamic response of proton exchange membrane fuel cell (PEMFC) is a crucial metric for evaluating these systems in vehicular applications. The forced convection effect can significantly enhance the dynamic response capabilities of proton exchange membrane fuel cells. In this study, we propose the application of the forced convection effect within a parallel flow field. This approach retains the advantages of low pressure drop at the inlets and outlets of the parallel flow field and facilitates rapid distribution of reaction gases, while simultaneously enhancing the dynamic response of actual PEMFC stacks without compromising drainage efficiency. we propose an innovative 3D wave channel design for PEMFC. Specifically, we design and assemble a stack optimized for performance. The proposed design is tested against the traditional 2D straight channel stack, with the 3D wave channel stack demonstrating an increase in peak power density by 8.05% to 33.92% across a relative humidity range of 20% to 100%. This novel design outperforms the 2D straight channel design in terms of gas distribution uniformity, and enhancedmass transfer to the diffusion layer, as well as reduction of concentration polarization in the PEMFC. It also enhances self-humidification under low humidity conditions. Most importantly, the 3D wave channel stack exhibits a superior dynamic response, with voltage fluctuations after current loading being 74.36% to 91.15% lower than those of the 2D straight channel stack. Furthermore, the 3D wave channel stack maintains superior voltage stability under starvation conditions. The findings from this study contribute significantly to optimizing the dynamic response capability of PEMFC systems, highlighting the potential of the 3D wave channel design in enhancing PEMFC performance.

Accurate size information measurement of the sealing components of proton exchange membrane fuel cell stacks is essential for preventing the escape of reactive gases from the cell reaction zone.Consequently,this study proposes a three-dimensional(3D)reconstruction method for flexible thin-walled parts based on a laser point cloud.By designing groove calibration objects and nonchamfered measuring blocks,the calibration object features are extracted from the contour data collected by each line laser contour sensor.Subsequently,the relative positional relationship of these features is used to accurately calibrate the optical plane and linear guide motion direction.We set overlapping areas and employ an improved point-to-surface iterative nearest point algorithm to fuse the point cloud data during the motion process of a single sensor.Combined with the calibration object characteristics,the transformation relationship between the different sensor optical plane coordinate systems is calculated by employing the principal component analysis method and consequently constructing the covariance matrix.The results demonstrate that the standard deviation of the system measurement results is approximately 0.01 mm.Furthermore,the proposed method accurately measures the 3D morphology and thickness information of flexible thin-walled test objects,and the measurement efficiency and accuracy satisfy the requirements of proton exchange membrane fuel cell stack seals in the industry.

This study proposes an enhanced algorithm based on guided filter and multi-scale fusion that detects surface defects of mosaic ceramics, allowing to tackle the small and difficult-to-detect surface reflection problem. This method first combines the gathered multi-angle light source images to obtain the highlight removal image. The guided filter then separates the image into base and detail images. Afterwards, the contrast limited adaptive histogram equalization (CLAHE) algorithm is used to enhance the detailed image. Taplacian contrast weights, saliency weights, and saturation weights are then introduced for the multi-scale fusion of the base and detail images. Finally, defects are extracted by non-linear enhancement, threshold segmentation, morphological processing, and the Canny operator. The proposed algorithm can effectively remove the mosaic ceramic surface highlights, enhance the details of the defect edges, remove the noise interference, improve the overall image quality, and perform rapid detection of defects on the surface of mosaic ceramics. Experiments are then conducted to verify the efficiency of the proposed algorithm. The results show that it has high performance, and it reaches a mosaic ceramic defect detection accuracy of 97.9 % with low leakage and false detection rates of 2.1 % and 1 %.

Gas dynamic bearing (GDB) has been extensively utilized in micro high-speed rotating machinery. However, the majority of existing research has been confined to conventional air environments. This study aims to address this gap by conducting a comprehensive investigation. Firstly, we compare and monitor the friction/wear characteristics between the bump foil strip and the top foil strip. Secondly, we explore the stiffness characteristics of the elastic support structure in GDB. Additionally, we examine the static and dynamic bearing performance of GDB in both oxygen-free and conventional air environments. Results reveal that in an oxygen-free atmosphere, the friction coefficient between the bump foil strip and the top foil strip, the stiffness of the elastic support structure, the load-carrying capacity, and the dynamic bearing stiffness of GDB are significantly higher than those observed in conventional air environment.

Rotating machinery is a core component of modern industry, and its operational state directly affects system safety and reliability. In order to achieve intelligent fault diagnosis of bearings under complex working conditions, the health management of bearings has become an important issue. Although deep learning has shown remarkable advantages, its performance still relies on the assumption that the training and testing data share the same distribution, which often deteriorates in real applications due to variations in load and rotational speed. This study focused on the scenario of domain generalization (DG) and proposed a Meta-Learning with Gradient Alignment and Data Augmentation (MGADA) method for cross-domain bearing fault diagnosis. Within the meta-learning framework, Mixup-based data augmentation was performed on the support set in the inner loop to alleviate overfitting under small-sample conditions and enhanced task-level data diversity. In the outer loop optimization stage, an arithmetic gradient alignment constraint was introduced to ensure consistent update directions across different source domains, thereby reducing cross-domain optimization conflicts. Meanwhile, a centroid convergence constraint was incorporated to enforce samples of the same class from different domains to converge to a shared centroid in the feature space, thus enhancing intra-class compactness and semantic consistency. Cross-working-condition experiments conducted on the Case Western Reserve University (CWRU) bearing dataset demonstrate that the proposed method achieves high classification accuracy across different target domains, with an average accuracy of 98.89%. Furthermore, ablation studies confirm the necessity of each module (Mixup, gradient alignment, and centroid convergence), while t-SNE and confusion matrix visualizations further illustrate that the proposed approach effectively achieves cross-domain feature alignment and intra-class aggregation. The proposed method provides an efficient and robust solution for bearing fault diagnosis under complex working conditions and offers new insights and theoretical references for promoting domain generalization in practical industrial applications.

Curved mosaic ceramics are the primary materials in creating three-dimensional mosaic ceramic artworks. However, they must be thoroughly inspected for defects to ensure the high quality of the final products. The unique small size, high reflectivity, and curved structure of these ceramics pose significant challenges for surface defects detection. Therefore, this paper proposes a deep-learning defect detection method based on an improved version of YOLOv7. Initially, highlights in the images are removed using minimum image fusion, followed by enhancement with the removed highlights. The model incorporates the Spatial and Channel-reconstruction Convolution (SCConv) module, the Centralized Feature Pyramid Network (CFPNet) module, and the Multi-Scale Dilated Transformer attention mechanism (Dilateformer) to create the YOLOv7-SCD model. Subsequently, defects are detected and identified. Experimental results indicate that YOLOv7-SCD increases detection accuracy and reduces missed detections compared to YOLOv7. The accuracy of this method in detecting surface defects in curved mosaic ceramics reaches 99%, with a detection time of 18.3 ms per ceramic piece. Thus, it provides accurate and rapid detection of surface defects, meeting industrial real-time detection requirements.

Microchannel heat exchangers have compact structure and very high heat transfer performance, making them a key technology addressing the heat dissipation challenges of high-power-density electronic devices. It has been shown that the optimization of the geometry of microchannels allows to increase the convective heat transfer coefficient during heat transfer, and to enhance the uniformity of the flow field distribution. However, the increase of the heat transfer performance often comes at the expense of high pressure drop and manufacturing costs. Performing coordinated optimization of heat transfer efficiency, flow resistance, and economic benefits has become a key challenge. Thus, this paper reviews the impacts of the microchannel geometry and surface roughness on the heat transfer performance, and explores the progress of the studies on biomimetic and composite microchannels for heat transfer enhancement. It also reviews the emerging applications of intelligent design methods to the performance prediction and multi-objective optimization, such as machine learning. Finally, it summarizes the existing studies and future development trends of high-performance microchannel heat exchangers. This paper provides a theoretical reference for the design of next-generation high-efficiency, low-resistance, and high-reliability thermal management systems.

The precision machining process caused by material removal and wear behavior is called grinding. Grinding force and grinding temperature (GF>) in precision/ultra-precision grinding directly affect the surface performances. In this study, the metamorphic layer, element content, hardness, residual stress and retained austenite of the finished thin-walled rolling bearing of rotary vector (RV) reducer were analyzed. Instead of the traditional method of indirect collecting GF>, a wireless sensing cubic boron nitride (CBN) raceway grinding wheel (WSCBN-RGW) with embedded force and temperature sensors was innovatively designed. The hardness, residual stress and retained austenite of the grinding surface were analyzed. With the increase of bearing raceway diameter, the thickness of "dark layer" decreases. The innovative design of WS-CBN-RGW solves the problem that GF> of bearing raceway are difficult to be collected directly. The ideal hardness, residual stress and retained austenite content can be obtained by controlling grinding parameters. After performance control, the raceway hardness, tangential and axial residual stress and residual austenite dispersion are reduced by 63.6 %, 34.6 %, 74.9 % and 31.5 %, respectively. Therefore, the problem of performance control can be solved by controlling GF>.