Zhicai Du, Qiang He, Hengcheng Wan, Lei Zhang, Zehua Xu, Yuan Xu and Guotao Li
This paper aims to improve the tribological properties of lithium complex greases using nanoparticles to investigate the tribological behavior of single additives (nano-TiO2 or…
Abstract
Purpose
This paper aims to improve the tribological properties of lithium complex greases using nanoparticles to investigate the tribological behavior of single additives (nano-TiO2 or nano-CeO2) and composite additives (nano-TiO2–CeO2) in lithium complex greases and to analyze the mechanism of their influence using a variety of characterization tools.
Design/methodology/approach
The morphology and microstructure of the nanoparticles were characterized by scanning electron microscopy and an X-ray diffractometer. The tribological properties of different nanoparticles, as well as compounded nanoparticles as greases, were evaluated. Average friction coefficients and wear diameters were analyzed. Scanning electron microscopy and three-dimensional topography were used to analyze the surface topography of worn steel balls. The elements present on the worn steel balls’ surface were analyzed using energy-dispersive spectroscopy and X-ray photoelectron spectroscopy.
Findings
The results showed that the coefficient of friction (COF) of grease with all three nanoparticles added was low. The grease-containing composite nanoparticles exhibited a lower COF and superior anti-wear properties. The sample displayed its optimal tribological performance when the ratio of TiO2 to CeO2 was 6:4, resulting in a 30.5% reduction in the COF and a 29.2% decrease in wear spot diameter compared to the original grease. Additionally, the roughness of the worn spot surface and the maximum depth of the wear mark were significantly reduced.
Originality/value
The main innovation of this study is the first mixing of nano-TiO2 and nano-CeO2 with different sizes and properties as compound lithium grease additives to significantly enhance the anti-wear and friction reduction properties of this grease. The results of friction experiments with a single additive are used as a basis to explore the synergistic lubrication mechanism of the compounded nanoparticles. This innovative approach provides a new reference and direction for future research and development of grease additives.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2023-0291/
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Jianming Wang, Guotao Ye and Jingshu Yang
Influencer marketing has emerged as a key strategy for brands to promote green products. The effectiveness of virtual influencers – a newer type of endorser – for these products…
Abstract
Purpose
Influencer marketing has emerged as a key strategy for brands to promote green products. The effectiveness of virtual influencers – a newer type of endorser – for these products remains unclear. This study aims to compare the effectiveness of virtual and human influencers in promoting green products and to uncover the key mechanisms that drive their influence.
Design/methodology/approach
In this research, the hypotheses were examined across three experimental studies. Study 1 initially investigated the effectiveness of virtual influencers in endorsing green products. Study 2 identified perceived altruistic motivation and perceived congruence of product and influencer as key mechanisms. Study 3 explored the moderating effect of language type (rational vs emotional).
Findings
The findings indicate that virtual influencers are generally less effective than human influencers in promoting green products, largely due to lower perceived altruistic motivation and congruence. Yet, using rational language in promotional posts can enhance the effectiveness of virtual influencers in endorsing these products.
Originality/value
This study combines the mind perception theory with the match-up hypothesis to explore the intrinsic mechanisms of perceived altruistic motivation and congruence, specifically from an emotional perspective, based on the unique attributes of virtual influencers and green products. These insights guide brands in selecting suitable endorsers for green products in the context of increasing environmental awareness and digitalization.
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Guotao Zhang, Yanguo Yin, Ting Xie, Dan Li, Ming Xu and Congmin Li
This paper aims to obtain high mechanical and good tribological properties of epoxy resin-based coatings under dry friction conditions.
Abstract
Purpose
This paper aims to obtain high mechanical and good tribological properties of epoxy resin-based coatings under dry friction conditions.
Design/methodology/approach
Bonded solid lubricant coatings containing Kevlar fibres were prepared by a spraying method. The friction and wear properties of the coatings were experimentally investigated with a face-to-face tribometre under dry friction conditions. Scanning electron microscopy, energy dispersive X-ray spectroscopy and 3D laser scanning technologies were used to characterise the tribological properties. The action mechanism of the Kevlar fibres on a solid lubricant transfer film was also analysed.
Findings
Adding Kevlar fibres can significantly improve the wear resistance of the coatings. When the Kevlar fibre content increases, the tribological properties of the coatings improve and then worsen. Superior properties are obtained with 0.03 g of Kevlar fibres. Appropriately increasing the load or speed is beneficial to the removal of the outer epoxy resin and the formation of a lubricant film. During friction, the solid lubricants wrapped in the epoxy resin accumulate on the surface to form a transfer film that shows a good self-lubricating performance. In the later friction stage, fatigue cracks occur on the solid lubricant film but cannot connect to one another because of the high wear resistance and the entanglement of the rod-like Kevlar fibres. Thus, no large-area film falls from the matrix, thereby ensuring the long-term functioning of solid lubricant coatings.
Originality/value
Epoxy resin-based solid lubricant coatings modified by Kevlar fibres were prepared, and their friction and wear properties were investigated. Their tribological mechanisms were also proposed. This work provided a basis for the analysis of the tribological properties and design of bonded solid lubricant coatings containing Kevlar fibres.
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Yanguo Yin, Rongrong Li, Guotao Zhang, Kaiyuan Zhang, Shuguang Ding and Qi Chen
This paper aims to fabricate a FeS/Cu-Bi copper-based lead-free bearing material to maintain good friction-reducing and anti-adhesive properties under boundary lubrication…
Abstract
Purpose
This paper aims to fabricate a FeS/Cu-Bi copper-based lead-free bearing material to maintain good friction-reducing and anti-adhesive properties under boundary lubrication conditions.
Design/methodology/approach
The materials were fabricated by mechanical alloying and powder metallurgy and tested under dry friction conditions using HDM-20 wear tester.
Findings
The results show that mechanical alloying can improve the antifriction and wear resistance of the materials. The 6 per cent FeS and 6 per cent Bi in the copper-based bearing materials fabricated by mechanical alloying have a better synergism which contributes to the friction and wear properties of copper matrix.
Originality/value
This new approach solves the problems of Bi and FeS mutual segmentation, mutual agglomeration and poor interface bonding.
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Guotao Zhang, Yanguo Yin, Ming Xu and Congmin Li
This paper aims to obtain high mechanical strength and good self-lubricating property of iron-based powder metallurgy materials. A new type of bilayer material with dense…
Abstract
Purpose
This paper aims to obtain high mechanical strength and good self-lubricating property of iron-based powder metallurgy materials. A new type of bilayer material with dense substrate and porous surface was proposed in this paper to obtain high strength and good self-lubricating property.
Design/methodology/approach
The materials were prepared by powder metallurgy. Their friction and wear properties were investigated with an end-face tribo-tester. Energy dispersive spectrometer, X-ray diffraction and the 3D laser scanning technologies were used to characterise the tribological properties of materials. The tribological and bearing mechanisms of the monolayer and bilayer materials were compared.
Findings
The results show that adding proper TiH2 can effectively improve the porosity and hardness. With the TiH2 content increased from 0 to 4 per cent, the average friction coefficients increase slowly, and the wearability decreases first and then increases. When containing 3.5 per cent TiH2, high strength and good self-lubrication characteristics are obtained. Besides, the tribological properties of monolayer materials are better than those of bilayer materials when the load is between 980 and 1,470 N, while the opposite result is obtained under the load varied from 1,470 to 2,450 N. In the bilayer material, the porous oil surface can lubricate well and the dense substrate can improve the mechanical property. So, its comprehensive tribological and mechanical properties are better than those of monolayer material.
Originality/value
The friction and wear properties of a new type bilayer materials were investigated. And their tribological mechanisms were proposed. This work can provide a theoretical reference for developing high-performance iron-based oil materials under boundary lubrication.
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Guotao Yang, Yue Wang, Huibin Chang and Qinghua Chen
This study examines the relative efficiencies of anti-poverty policies implemented in 28 Chinese provinces.
Abstract
Purpose
This study examines the relative efficiencies of anti-poverty policies implemented in 28 Chinese provinces.
Design/methodology/approach
This study uses meta-frontier undesirable dynamic two-stage data envelopment analysis. The authors divide the poverty reduction process into two stages: agricultural production and poverty reduction. Public expenditure is the input for the second stage, and the population below the poverty line is the undesirable output. The authors compute the efficiencies (overall efficiency, efficiency of each stage and the efficiencies of individual inputs and outputs) using meta-frontier analysis for the 28 provinces.
Findings
The results show that: (1) a significant imbalance exists between the eastern and western regions in terms of input-output efficiencies; (2) the poverty reduction stage generally fared better than the agricultural production stage did. In particular, most provinces saw increases in poverty reduction efficiencies between 2013 and 2017; (3) the place-based poverty relief policies introduced in recent years are effective at reducing the poverty rate and reaching the government-set goals and (4) while disposable income has increased steadily over the past few years, income inequality has been exacerbated.
Research limitations/implications
The results show that: (1) a significant imbalance exists between the eastern and western regions in terms of input-output efficiencies; (2) the poverty reduction stage generally fared better than the agricultural production stage did. In particular, most provinces saw increases in poverty reduction efficiencies between 2013 and 2017; (3) the place-based poverty relief policies introduced in recent years are effective at reducing the poverty rate and reaching the government-set goals and (4) while disposable income has increased steadily over the past few years, income inequality has exacerbated.
Originality/value
A large amount of attention and public resources are devoted to fighting poverty and associated market failures in China. The extant literature focuses either on the agricultural production itself or the relationship between human capital and productivity levels. Making use of recent developments of the DEA method, the authors propose a new framework for evaluating the efficiencies of the poverty reduction process. Such a framework has the advantage of giving researchers and policymakers a more detailed diagnosis with regard to the components in the endeavor to eliminate poverty and providing useful information for policymakers to optimize public funds use. Methodologically, the framework is flexible enough to be employed for future research in similar appraisals, at different geographic and scale aggregation levels, for public projects including but not limited to poverty reduction.
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Guotao Xie, Jing Zhang, Junfeng Tang, Hongfei Zhao, Ning Sun and Manjiang Hu
To the industrial application of intelligent and connected vehicles (ICVs), the robustness and accuracy of environmental perception are critical in challenging conditions…
Abstract
Purpose
To the industrial application of intelligent and connected vehicles (ICVs), the robustness and accuracy of environmental perception are critical in challenging conditions. However, the accuracy of perception is closely related to the performance of sensors configured on the vehicle. To enhance sensors’ performance further to improve the accuracy of environmental perception, this paper aims to introduce an obstacle detection method based on the depth fusion of lidar and radar in challenging conditions, which could reduce the false rate resulting from sensors’ misdetection.
Design/methodology/approach
Firstly, a multi-layer self-calibration method is proposed based on the spatial and temporal relationships. Next, a depth fusion model is proposed to improve the performance of obstacle detection in challenging conditions. Finally, the study tests are carried out in challenging conditions, including straight unstructured road, unstructured road with rough surface and unstructured road with heavy dust or mist.
Findings
The experimental tests in challenging conditions demonstrate that the depth fusion model, comparing with the use of a single sensor, can filter out the false alarm of radar and point clouds of dust or mist received by lidar. So, the accuracy of objects detection is also improved under challenging conditions.
Originality/value
A multi-layer self-calibration method is conducive to improve the accuracy of the calibration and reduce the workload of manual calibration. Next, a depth fusion model based on lidar and radar can effectively get high precision by way of filtering out the false alarm of radar and point clouds of dust or mist received by lidar, which could improve ICVs’ performance in challenging conditions.
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Hongbo Gao, Guanya Shi, Kelong Wang, Guotao Xie and Yuchao Liu
Over the past decades, there has been significant research effort dedicated to the development of autonomous vehicles. The decision-making system, which is responsible for driving…
Abstract
Purpose
Over the past decades, there has been significant research effort dedicated to the development of autonomous vehicles. The decision-making system, which is responsible for driving safety, is one of the most important technologies for autonomous vehicles. The purpose of this study is the use of an intensive learning method combined with car-following data by a driving simulator to obtain an explanatory learning following algorithm and establish an anthropomorphic car-following model.
Design/methodology/approach
This paper proposed car-following method based on reinforcement learning for autonomous vehicles decision-making. An approximator is used to approximate the value function by determining state space, action space and state transition relationship. A gradient descent method is used to solve the parameter.
Findings
The effect of car-following on certain driving styles is initially achieved through the simulation of step conditions. The effect of car-following initially proves that the reinforcement learning system is more adaptive to car following and that it has certain explanatory and stability based on the explicit calculation of R.
Originality/value
The simulation results show that the car-following method based on reinforcement learning for autonomous vehicle decision-making realizes reliable car-following decision-making and has the advantages of simple sample, small amount of data, simple algorithm and good robustness.
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Guotao Zhang, Baohong Tong, Shubao Yang, Liping Shi and Yanguo Yin
The purpose of this paper was to study the hydrodynamic lubrication of rough bilayer porous bearing to reveal the effect of percolation.
Abstract
Purpose
The purpose of this paper was to study the hydrodynamic lubrication of rough bilayer porous bearing to reveal the effect of percolation.
Design/methodology/approach
The seepage lubrication model of the circular bilayer porous bearing was established in polar coordinates. The digital filtering technique and Darcy’s law were used to simulate the rough surface and the percolation characteristic of the oil bearing, respectively. The influence of the structural parameters on the lubrication performance was analyzed.
Findings
Compared with the ordinary monolayer oil bearing with high porosity, the bilayer bearing can reduce the whole porosity, prevent oil infiltrating into the porous medium and have better lubrication performance. The lubrication performance of bilayer oil bearing is better than that of the single-layer oil bearing which has a higher porosity. With increasing root-mean-square roughness or decreasing surface porosity, the lubrication performance of the bilayer bearing improves. The lower the porosity of the surface layer, the better the lubrication performance.
Originality/value
This research provides a theoretical basis for clarifying the lubrication mechanism and influence the mechanism of the bilayer oil bearing.
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Cong Liu, Baohong Tong, Guotao Zhang, Wei Wang, Kun Liu and Peimin Xu
This paper aims to investigate the influence of oil–air lubrication flow behavior on point contact sliding wear characteristics.
Abstract
Purpose
This paper aims to investigate the influence of oil–air lubrication flow behavior on point contact sliding wear characteristics.
Design/methodology/approach
Oil–air lubrication equations between point contact counterparts were established on the basis of volume of fluid model. The effects of oil supply and injection azimuth on oil-phase volume fraction and its pressure distribution were simulated with commercial software Fluent. Characteristics of point contact sliding wear were then tested with an MFT-3000 friction tester under oil–air lubrication condition. The influence of flow behavior on wear characteristic was investigated combined with numerical and experimental results. The wear mechanism was revealed using SEM, EDS and ferrography.
Findings
When air supply speed is constant, the oil-phase volume fraction increases with the increase in oil supply, which helps form continuous oil film and decrease the sliding wear evidently. The injection angle and distance considerably influence the oil–air flow behavior. When injecting at a certain distance and angle, the oil-phase volume fraction reaches its maximum, and the abrasion loss is minimal. Under the test conditions in this study, abrasive particles are mainly debris and a few spiral cuttings. The wear mechanism is abrasive wear.
Originality/value
The influence of the behavior of oil–air lubrication flow on the characteristic of point contact sliding wear is analyzed. This work provides guidance for the application of oil–air lubrication technology in point contact friction pairs.