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This work is to deposit (CrNbTiAlV)CN/MoN coatings by alternating sputtering with multiple targets. The hardness and elastic modulus of the (CrNbTiAlV)CN/MoN multilayer coatings gradually increase with the decreasing of the modulation period from 420 to 110 nm; however, the values decrease on the multilayer coating with a modulation period of 50 nm. As the modulation period decreases, the characteristic of MoO3 debris changes from large flakes to smooth transfer tribolayers and then to small particles. The coating with a modulation period of 110 nm has a minimum friction coefficient and wear rate of about 0.11 and 4.4 × 10–6 mm3/(N m) at 500°C, respectively. This can be attributed to the fact that it has the best resistance to plastic deformation and tends to form smooth transfer tribolayers. [ABSTRACT FROM AUTHOR]

Macroscale superlubricity on engineering steel surfaces offers a promising solution for minimizing friction and wear in engineering applications. However, achieving superlubricity typically requires a long running‐in period, which may result in significant wear for the friction pair. Herein, a new lubricant with superlubricating properties is rationally designed by using polyethylene glycol (PEG) and critic acid (CA) under complexing effect with a running‐in period of about 800 s. Importantly, the introduction of carbon quantum dots (CQDs) obtained from the pyrolysis of CA into PEG aqueous solution shortens the running‐in period for achieving macroscale superlubricity (µ ≈ 0.005) between steel/steel contact to 44 s. The corresponding wear rate (1.15 × 10−7 mm3 N−1 m−1) on the steel disk is reduced by 77% due to the shorter running‐in time. Furthermore, the surface analysis combined with the molecular dynamics simulations demonstrates that CQDs easily adsorb on the surface of the friction pair, forming a carbon film that reduces interaction energy between the lubricant molecules and the substrate. This work provides new insights into the lubrication mechanism of CQDs and contributes to the design of liquid superlubricants with short running‐in periods and low wear rates on engineering steel surfaces. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the effect of V doping on the microstructure, chemical stability, mechanical and vacuum tribological behavior of sputtered MoS2 coatings. Design/methodology/approach: The MoS2-V coatings are fabricated via tuning V target current by magnetron sputtering technique. The structural characteristic and elemental content of the coatings are measured by field emission scanning electron microscopy, X-ray diffractometer, electron probe X-ray micro-analyzer, Raman, X-ray photoelectron spectroscopy, high resolution transmission electron microscope and energy dispersive spectrometer. The hardness of the deposited coatings are tested by a nanoindentation technique. The vacuum tribological properties of MoS2-V coatings are studied by a ball-on-disc tribometer. Findings: Introducing V into the MoS2 coatings results in a more compact microstructure. The hardness of the coatings increases with the doping of V. The MoS2-V coating deposited at a current of 0.2 A obtains the lowest friction coefficient (0.043) under vacuum. As the amount of V doping increases, the wear rate of the coating decreases first and then increases, among which the coating deposited at a current of 0.5 A has the lowest wear rate of 2.2 × 10–6 mm3/N·m. Originality/value: This work elucidates the role of V doping on the lubrication mechanism of MoS2 coatings in a vacuum environment, and the MoS2-V coating is expected to be applied as a solid lubricant in space environment. [ABSTRACT FROM AUTHOR]

The multi-sensor scheduling problem of dual unmanned flight platforms has a complex coupling relationship, and how to reasonably match flight segments, sensors and targets is an intricate part of the problem. To solve the multi-sensor scheduling problem of dual unmanned flight platforms, a flight segment task allocation mechanism was proposed in this study, which assigned tasks through the position relationship between the flight segment and the target. This mechanism could effectively split the tasks and solve the task coupling problem of the two platforms. Pre-processing targets and sensors were carried out to identify scarce sensor resources and independent targets in advance to guide subsequent scheduling matching. Then, sensor-target matching was carried out to plan the scheduling of sensors based on the task revenue. The scheduling of conflicting segments was adjusted according to the availability of sensor resources. Finally, task migration was carried out for targets that still need to complete their assigned tasks. The available free sensors in the corresponding flight segments were matched according to the target task remaining to improve the task revenue. In order to verify the effectiveness of the proposed algorithm in this study, existing algorithms were compared through simulation experiments on 10 test problems. The experimental results showed that this algorithm outperformed existing algorithms in task revenue and stability with a significant reduction in running time. [ABSTRACT FROM AUTHOR]

The turnover rate of social workers is extremely high and the predictive roles of professional identity and job burnout on turnover intention have not been explored in China. The study examined the relationship between professional identity and turnover intention, mediated by job burnout and moderated by a social work degree, amongst social workers in China. Based on a sample of 829 participants and the structural equation model method, the findings confirmed that professional identity per se was not related to turnover intention, and a mediating role of job burnout and a moderating role of a social work degree were identified. [ABSTRACT FROM AUTHOR]

Low pay and the absence of professional identity (PI) are often blamed as major antecedents related to the turnover of social workers in China, yet no study has provided any consideration of the two antecedents together in predicting the turnover intention (TI) of social workers and comparing them, which acts as a more powerful predictor. Based on a sample of 819 participants and by using structural equation models, the current study indicated whether pay satisfaction (PS) or PI could predict TI; the results show that PS plays a stronger role. The findings identified the mediating role of PI in the relationship between PS and TI, but the moderating role of the type of sector (TS) was not supported. The findings suggest that it is necessary to advocate for adequate pay for social workers all over the world. Additionally, PI should be a top priority in social work education, training, exams and practice. Meanwhile, the government should strengthen the purchase of social work services, and a greater proportion of purchase money should be used to pay social workers. Furthermore, the government could offer subsidies for social workers employed in the private sector, similar to those employed in the public sector. [ABSTRACT FROM AUTHOR]

Thick diamond‐like carbon (DLC) coatings with different silicon (Si) transition layer thickness are deposited by hollow cathode plasma immersion coating technology. The results show that the internal stress of the coating can be tuned by changing the deposition time of Si transition layer, thereby obtaining good adhesion strength. Friction and wear results show that all coatings have good tribological properties. The coating with 8 min Si transition layer (Si‐8) demonstrates the lowest friction coefficient (μ ≈ 0.03), even achieves ultralow friction (μ ≈ 0.008) for a short time. However, the wear rate of Si‐8 coating is found to be the largest (2.1 × 10−16 m3 (N m)−1. The low friction coefficient of Si‐8 coating is related to its high degree of graphitization, complete transfer film and fine wear debris. In contrast, the Si‐16 coating has the lowest wear rate of about 5.6 × 10−17 m3 (N m)−1 with a relatively high friction coefficient (μ ≈ 0.1). This is due to its high hardness and the formation of a nano‐twisted double helix carbon debris during the friction process. This nano‐twisted double helix structure can consume additional plastic deformation energy, while reducing the interface contact area and increasing the interface bearing capacity, thereby improving the wear resistance of the thick DLC coating. [ABSTRACT FROM AUTHOR]

This paper studies the effects of Ag atomic segregation from the inner (100) or (111) planes on the melting of Ag-Pd clusters with different sizes by a molecular dynamics simulation. The results show that Ag segregation leads to the atomic energy decreases with increasing the temperature. Furthermore, the effect of the (100) segregation is larger than that of the (111) segregation. Meanwhile, the influence of segregation on the energy decreases with increasing the cluster size. The melting points of the clusters without segregation are the largest, followed by the clusters with a (111) and (100) segregation. [ABSTRACT FROM AUTHOR]

The formation of bcc and fcc during the coalescence of free and supported Fe and Ni clusters has been studied by molecular dynamics simulation using an embedded atom method. Structural evolution of the clusters, coalesced under varying temperature, Ni content and substrate conditions, was explored by interatomic energy, snapshots, pair distribution functions and bond order parameters. The results show that the formation of bcc and fcc is strongly related to Ni content, substrate and coalescence temperature. Free clusters coalesced at 1200 K form bcc at lower Ni contents with fcc forming at higher Ni concentrations and no observable coexistence of bcc and fcc. Differences in coalescence at 1000 K result from the coexistence of bcc and fcc within the Ni range of 50–70%. Free clusters supported on disordered Ni substrates were shown to transform from spherical morphology to islands of supported clusters with preferred epitaxial orientation. The Ni content required to form bcc and fcc coexistence on supported clusters at 1000 K decreased to 30–50% Ni. Free clusters possessing bcc and fcc generally stacked along the bcc (110) and fcc (111) facets, whereas supported clusters stacked along the (111) bcc and (100) fcc planes. Structural transformation was induced by clusters containing greater numbers of atoms. Spread over the substrate enhanced interatomic energy, order substrates affect the epitaxial growth direction and increase the melting points of the supported clusters. This study can be used to predict the nature of fcc and bcc formation in Fe–Ni films. [ABSTRACT FROM AUTHOR]

Fe-based amorphous alloys (FAA) have excellent anti-corrosion and anti-abrasive comprehensive performances. However, sprayed thin FAA coatings with high porosity cannot provide efficient protection, or even accelerate the corrosion rate of the substrate due to galvanic corrosion. Laser re-melting densifying is usually used to improve the anti-corrosion performance of sprayed coatings. There are two disadvantages of the common laser re-melting method, including crystallization and residual stress. In the present paper, a low density energy laser re-melting method was used to improve the performance of cold spraying (CS) FeCoCrMoBCY FAA coating on 40Cr substrate. The results show that the CS FAA coatings were crystallized partially during the melting process. The hardness of the coating is improved at the melting zone after laser re-melting, which improves the anti-abrasive performance. Potentiodynamic test results show that laser re-melting can decrease the corrosion rate, but the salt spray test indicates that low energy density re-melting cannot eliminate penetrated diffusion passage. Further optimization should be conducted to improve the anticorrosion performance for this method. [ABSTRACT FROM AUTHOR]