Tribological performance and lubrication mechanism of contact-charged electrostatic spray lubrication technique

To minimize friction at the chip-tool interface and the amount of lubricant usage, a new near-dry machining technique called "contact-charged electrostatic spray lubrication (CCESL) technique" was proposed. The chargeability, penetrability, and wettability of lubricant droplets under CCESL condition were analyzed. The atomization and tribological performance of the CCESL technique were compared with those of the existing minimal quantity lubrication (MQL) technique under different testing conditions. The experimental results suggest that the CCESL technique considerably improves the anti-wear and anti-friction properties compared with the existing MQL technique. In addition, to understand its lubrication mechanism, the morphology and main elements of the worn surface were characterized using an optical microscope and X-ray photoelectron spectroscopy, respectively. In the CCESL technique, an ordered molecule layer which provides effective lubrication is formed on the rubbing surface as polar functional groups in the lubricant molecule are oriented. The enhanced tribological performance is attributed to the fact that the technique can provide more abundant lubricant and oxygen for the interface of frictional pairs to promote the formation of an abundant lubricating layer comprising adsorption and oxide films, which improve the worn surface quality

Disturbance Observer-Based Backstepping Control of PMSM for the Mine Traction Electric Locomotive

For the Permanent Magnet Synchronous Motor (PMSM) control system of the Mine Traction Electric Locomotive (MTEL), the fluctuation of the load will lead to the resonance of the velocity of the MTEL. In addition, the speed sensor is easy to be damaged due to the moisture, dust, and vibration. To solve the above problems, a disturbance observer-based (DOB) backstepping control of PMSM for the MTEL is proposed in this paper. First, a full-dimensional Luenberger observer for PMSM is designed and the asymptotically stability of the observer is proved. Next, through the designing of the virtual control input that includes the reconstruction disturbances and using backstepping control strategy, the DOB controller is proposed. The obtained controller can achieve high precision speed tracking and disturbance rejection. Finally, the effectiveness and feasibility of the designed system are verified by Matlab simulation and experiment results

Grinding performance and self-lubrication mechanism of phenolic resin-bonded grinding wheel filled with inclusion complex of β-cyclodextrin and dialkyl pentasulfide

To minimize friction at the grinding wheel-workpiece interface, a nanosized lubricant complex of β-cyclodextrin (β-CD) and dialkyl pentasulfide (RC2540) was proposed as filler to phenolic resin-bonded grinding wheels. Complex-filled grinding wheels with different filling content (5, 10, 15, and 20 wt%) were prepared by the cold compression method and the tribological properties of the wheel specimens were investigated under different speed and load conditions. The grinding performance of the complex-filled grinding wheels was compared with that of an ordinary grinding wheel under different liquid coolant conditions (water and emulsified liquid). The experimental results suggest that the complex-filled grinding wheel considerably improves the tribological and grinding performance compared with those of the ordinary grinding wheel. A complex-filled wheel with 10 wt% complex is recommended because it provides not only higher grinding ratio and lower grinding force but also better surface finish. In addition, XPS analysis was used to investigate the workpiece surface. RC2540 is found to be released as the complex decomposes. The enhanced tribological and grinding performances of the wheel are attributed to the formation of an anti-friction and anti-wear self-lubricating layer comprising sulfide and carbon-deposited films, which improve the surface quality

Classification and Quantitative Evaluation of Eddy Current Based on Kernel-PCA and ELM for Defects in Metal Component

Eddy current testing technology is widely used in the defect detection of metal components and the integrity evaluation of critical components. However, at present, the evaluation and analysis of defect signals are still mostly based on artificial evaluation. Therefore, the evaluation of defects is often subjectively affected by human factors, which may lead to a lack in objectivity, accuracy, and reliability. In this paper, the feature extraction of non-linear signals is carried out. First, using the kernel-based principal component analysis (KPCA) algorithm. Secondly, based on the feature vectors of defects, the classification of an extreme learning machine (ELM) for different defects is studied. Compared with traditional classifiers, such as artificial neural network (ANN) and support vector machine (SVM), the accuracy and rapidity of ELM are more advantageous. Based on the accurate classification of defects, the linear least-squares fitting is used to further quantitatively evaluate the defects. Finally, the experimental results have verified the effectiveness of the proposed method, which involves automatic defect classification and quantitative analysis

Osthole improves collagen-induced arthritis in a rat model through inhibiting inflammation and cellular stress

Abstract Background Osthole is a natural product that has multiple bioactive functions and has been reported to exert potent immunosuppressive effects. However, the therapeutic effect of osthole on arthritis has not been explored. In the present study, a collagen-induced arthritis rat model, IL-1β-stimulated SW982 cells, and RA-like fibroblast-like synoviocytes (FLS) were employed to investigate the effect and possible mechanism of osthole on arthritis in vivo and in vitro. Results 20 and 40 mg/kg osthole significantly alleviated collagen-induced arthritic symptoms based on histopathology and clinical arthritis scores, and improved erosion using HE staining. 20 and 40 mg/kg osthole decreased the level of IL-1β, TNF-α and IL-6 in rats and ameliorated oxidative stress in serum evaluated using ELISA kits. In addition, treatment with 50 and 100 μM osthole for 48 h inhibited 10 ng/ml IL-1β-stimulated proliferation and migration of SW982, and significantly inhibited the expression of matrix metalloproteinases, such as MMP-1, MMP-3 and MMP-13, as detected by western blot. 50 and 100 μM osthole also blocked the generation of IL-6 and TNF-α in IL-1β-stimulated SW982 cells. The NF-κB and MAPK pathways were also inhibited by osthole in IL-1β-treated SW982 cells. Conclusion These results collectively demonstrated that osthole improves collagen-induced arthritis in a rat model and IL-1β-treated SW982 cells through inhibiting inflammation and cellular stress in vivo and in vitro, and osthole might be a promising therapeutic agent for RA

Monthly Climatologies of Oceanic Friction Velocity Cubed

Abstract Different measures of wind influence the ocean in different ways. In particular, the time-averaged mixed layer turbulent energy production rate is proportional to 〈u3*〉, where u* is the “oceanic friction velocity” that is based on wind stress. Estimating 〈u3*〉 from monthly averages of wind stress or wind speed may introduce large biases due to the day-to-day variability of the direction and magnitude of the wind. The authors create monthly climatologies of 〈u3*〉 from daily wind stress measurements obtained from the Goddard Satellite-based Surface Turbulent Fluxes version 2 (GSSTF2; based on satellite microwave measurements), the Quick Scatterometer (QuikSCAT; based on satellite scatterometry measurements), and the National Centers for Environmental Prediction (NCEP) reanalysis wind. The differences among zonal averages of these climatologies and of a similar climatology based on the da Silva version of the Comprehensive Ocean–Atmosphere Data Set (COADS) have a complex dependence on latitude. These differences are typically 10%–30% of the climatological values. The GSSTF2 data confirm that 〈u3*〉 is much larger than estimates from monthly averaged wind stress or wind speed, especially outside the Tropics

Research on Eddy Current Imaging Detection of Surface Defects of Metal Plates Based on Compressive Sensing

Accurate detection and quantitative evaluation of defects and damage in metal plates is a crucial task in a range of technological applications, such as maintaining the integrity, enhancing the safety, and assuring the reliability of structures. There is scope for improving eddy current testing methods by incorporating compressive sensing (CS) in the inspection process. The key scientific problems in eddy current imaging of defects of metal plates are sparse representations and transform domain mapping, sparse testing constraints, and sparse image reconstruction. The main research content of this paper is as follows. We first provide basic theory based on research of sparse representations, transform domain mapping, sparse matrices, sparse transform matrices, and signal recovery a priori errors. We then propose information-recovery methods for completing compressive sensing. Third, we establish an experimental system for validating theories and methods. Finally, we establish theories and methods for eddy current imaging of metal plates

Galileo triple-frequency uncombined precise orbit determination: model and quality assessment

Multi-frequency signals have brought new opportunities and challenges to global navigation satellite system (GNSS) precise data processing. In this contribution, the uncombined (UC) observation model suitable for multi-frequency precise orbit determination (POD) was derived, and the double-differenced constraining strategy for multi-frequency UC ambiguity was given. Afterwards, Galileo POD was carried out by using the observation data of 150 multi-GNSS experiment (MGEX) stations. Different solutions using E1/E5a double-frequency, E1/E5b double-frequency and E1/E1a/E5b triple-frequency observations based on UC model and the traditional ionosphere free (IF) model respectively are applied to generate Galileo orbits.The comparison with external precise orbit products, orbit boundary discontinuities comparison and satellite laser ranging (SLR) validation were used to evaluate the orbit accuracy of different solutions. The results showed that the UC model and IF model having comparable orbit accuracy for double-frequency solutions.The differences of orbit accuracy between UC and IF model are within 1 mm, and the differences of the estimated satellite clock and SLR residuals are within 0.01 ns and 2 mm, respectively. When triple-frequency observations (E1/E5a/E5b) were used, the accuracy of float UC and float IF solutions can be improved by 1~2 mm compared to that using E1/E5b observations