Search results

The CL60 steel wheels of subway vehicles operating on specific lines require frequent refurbishment due to rapid wear and tear. Considering this issue, MoS₂-based and graphite-based solid lubricants are used to reduce the wear rate of subway wheels and extend their service life.

Under laboratory conditions, the effect of MoS₂-based and graphite-based solid lubricants on the friction and wear performance of subway wheels and rails was evaluated using a modified GPM-60 wear testing machine.

Under laboratory conditions, MoS₂-based solid lubricants have the best effect in reducing wheel/rail wear, compared to the control group without lubrication, at 2 × 105 revolutions, the total wheel-rail wear decreased by 95.07%. However, when three types of solid lubricants are used separately, the hardness evolution of the wheel-rail contact surface exhibits different characteristics.

The research results provide important support for improving the lifespan of wheel and rail, extending the service cycle of wheel and rail, reducing the operating costs of subway systems, improving the safety of subway systems and providing wear reduction maintenance for other high wear mechanical components.

The experiment was conducted through the design and modification of a GPM-60 testing machine for wear testing. The experiment simulated the wheel-rail contact situation under actual subway operation and evaluated the effects of three different solid lubricants, MoS₂-based and graphite-based, on the wear performance and surface hardening evolution of subway wheel-rail.

The purpose of this paper is to compare the changes in the risk spillover effects between the copper spot and futures markets before and after the issuance of copper options, analyze the risk spillover effects between the three markets after the issuance of the options and can provide effective suggestions for regulators and investors who hedge risks.

The MV-CAViaR model is an extended form of the vector autoregressive model (VAR) to the quantile model, and it is also a special form of the MVMQ-CAViaR model. Based on the VAR quantile model, this model has undergone continuous promotion of the Conditional Autoregressive Value-at-Risk Model (CAViaR) and the Multi-quantile Conditional Autoregressive Value-at-Risk Model (MQ-CAViaR), and finally got the current form of the model.

The issuance of options has led to certain changes in the risk spillover effect between the copper spot and its derivative markets, and the risk aggregation effect in the futures market has always been significant. Therefore, when supervising the copper product market and investors using copper derivatives to avoid market risks, they need to pay attention to the impact of futures on the spot market, the impact of options on the futures market and the risk spillover effects of spot and futures on the options market.

The empirical results of this paper can be used to hedge market risk investment strategies, and the changes in market relationships also provide an effective basis for the supervision of the copper product market by the supervisory authority.

It is the first literature research to discuss the risk and the impact of spillover effects of copper options on China copper market and its derivative markets. The MV-CAViaR model can capture the mutual risk influence between markets by modeling multiple markets simultaneously.

The purpose of this paper is to obtain high-solids-content and low-viscosity starch adhesive, and improve bonding strength of the pure starch adhesive.

Maize starch was treated by hydrochloric acid solution with different concentrations, and acid-thinned starch adhesive was prepared. Polyisocyanate as a crosslinking agent was added to improve water resistance of the pure starch adhesive.

The physical and chemical properties of the acid-thinned starch adhesive were characterised. Acid hydrolysis did not change structure of starch granules, but increased its crystallinity. After acid modification, starch granules became less smooth and some fragments appeared. Acid treatment had little influence on thermal stability of starch, when acid hydrolysis was not strong. High concentration of HCl solution led to starch granules being destroyed, resulting in decrease in bonding strength. The optimal HCl concentration was 0.5 mol/L. Polyisocyanate addition was beneficial to improve the bonding strength of the acid-thinned starch adhesive.

Acid hydrolysis changed the properties of the starch adhesive.

Acid hydrolysis decreased viscosity of the starch adhesive and improved its solids content, which had a positive effect on the application of the starch adhesive.

It was helpful to develop an environment-friendly, natural polymer-based wood adhesive.

The properties of acid-thinned starch and acid-thinned starch adhesive were studied.

Fluorinated polyurethane combines some virtues of polyurethane and fluorinated polymer, such as low water absorption, attractive surface properties, good wearability and high weatherability. Fluorocarbon chains have been incorporated into polyurethanes by fluorinated diisocyanates, chain extenders, polyether glycols, polyester glycols and end-cappers. However, the fluorinated polyurethane, which is prepared with monohydric fluorocarbon alcohol, is seldom reported. The purpose of this research is to prepare and apply the novel fluorocarbon alcohols with side chain to modify polyurethane as the blocking agent.

The novel fluorocarbon alcohol with side chain 2-methoxy-3-nonene perfluorinated oxygen propanol (MNPOP) can be prepared via alcoholysis reaction of methanol and 2,3-epoxypropyl perfluorinated nonene ether (EPPNE), which was prepared with etherification of hexafluoropropene trimer (HFPT) and 2,3-glycidol. Structures of EPPNE and MNPOP are confirmed with FTIR and NMR. The polyurethane can be modified when MNPOP is used as blocking agent.

In comparison with the conventional polyurethane, the hydrophobic property of fluorinated polyurethane is improved. However, the increase of tensile strength of modified polyurethane is not obvious because MNPOP belongs to monohydric alcohol. And the function of MNPOP in the modified polyurethane is the blocking agent. The thermal stability of conventional and modified polyurethane is almost the same because MNPOP is de-blocked and fluorocarbon chains have not been incorporated into polyurethanes when the temperature is more than 150°C.

The polyurethane is modified with the novel fluorocarbon alcohols with side chain, which functions as the blocking agent. The hydrophobic property of fluorinated polyurethane is improved.

This paper aims to investigate the preparation of Nano-Al₂O₃ lubricant, as well as the effect of surface modification of Al₂O₃ on friction and wear properties.

The chemical parameters such as the energy levels of the Highest Occupied Molecular Orbital, the Lowest Unoccupied Molecular Orbital and the Fukui indices of seven modifiers, including myristic acid myristyl ester, glycerol trioleate, acetyl monoethanolamine, docosanamide, Tween-60, dodecyl dihydroxyethyl amine oxide and sodium dodecyl sulfate (SDS), are calculated by using the Materials Studio software. Meanwhile, the adsorption energies of these seven modifiers on Al₂O₃ nanoparticles are also calculated. Based on the simulation results, SDS and Tween-60 were identified as the most effective surface modifiers. Modified lubricants were prepared with Al₂O₃ nanoparticles at varying concentrations (0.1–0.4 Wt.%). Their tribological properties, including the maximum nonseizure load (P_B) and the coefficient of friction (COF), were evaluated using a four-ball wear tester. The worn surfaces were analyzed by scanning electron microscopy and three-dimensional profilometry.

The results indicate that SDS improves both the extreme pressure and anti-wear performance of the lubricant. The lubricant achieves optimal performance when combined with 1.0 Wt.% SDS and 0.2 Wt.% nano-Al₂O₃. At this combination, the value of PB reaches 209 N, and the value of COF is approximately 0.072. Compared to the unmodified Al₂O₃ lubricant with a COF of 0.086, this represents a 23% reduction in COF.

Modified Al₂O₃ lubricants demonstrate superior lubrication performance and effectively reduce the COF, providing valuable insights for the practical application of nanolubricants.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2024-0353/

The purpose of this study is to use liposome technology in the treatment of fabrics textiles because of its efficient energy saving, reducing time and temperature.

The newly prepared lecithin liposome was used to encapsulate dyes for the purpose of increasing dyeing affinity. Different ratios of commercially available lecithin liposomes (1%, 3%, 5% and 7%) were used simultaneously in the dyeing of cotton and wool fabrics. The treated fabrics (cotton and wool fabrics) were confirmed using different analytical procedures such as scanning electron microscope (SEM), Fourier-transition infrared spectroscopy, ultraviolet protection factor, colour strength (K|S) measurements and fastness measurements.

The results show that increasing liposome ratios in dyeing baths leads to increased dyeing affinity for cotton and wool fabrics compared with conventional dyeing without using liposomes. In addition to that, the colour strength values, infrared spectra, SEM and fastness properties of non-liposome-dyed fabrics and liposome-dyed fabrics were investigated.

The research paper provides broad spectrum of green encapsulation fabrics using liposome technology to perform the dye stability, dye strength and fastness.

The purpose of this paper is to review English-language publications about school principalship in China published between 1998 and 2013 and to present an overview of the authorship, topics, methodologies and key findings of these publications.

The methodology includes an exhaustive review of journal articles and book chapters about Chinese school principalship published in the English language. In total, 39 articles and 17 book chapters are identified for the 1998-2013 period. Qualitative analysis is conducted to determine the basic patterns of authorship, topics, methods and key findings. The changes or continuities in these patterns during the study period are also discerned.

The paper identifies several continuous and discontinuous patterns in each of the review categories and provides a better understanding of on-going research into the practice of school principalship in China. The results also suggest areas that require deeper exploration.

This paper explores the landscape of school principalship in China as reflected in the international literature and indicates the ways that this landscape has changed or remained the same over the years. As such, the paper contributes to the thin knowledge base concerning school principalship in China and sheds light on the enduring local-global tension in the evolution of education systems.

The purpose of this paper is to highlight state-of-the-art digital human modeling applications in aviation and aerospace industry, generate research interest and promote application of digital human modeling technology among audience of diverse background including researchers, students, trainees, etc. in academia and industry; designers; engineers; and ergonomists associated with aviation and aerospace sectors.

Comprehensive literature search was performed and, subsequently, all publications identified were studied thoroughly at least by abstracts. Available information has been segregated under different headings and depicted systematically for easy understanding by readers.

Virtual human modeling technology has been used in assessing reach and accessibility in aircraft cockpits, creating accurate posture libraries, performing vision analysis for pilots, determining design modifications to accommodate female users, predicting probable pilot behavior in proposed cockpit design, simulating air flow and heat transfer in fighter plane’s cockpit, assessing comfort of airplane passenger seats, maintenance studies, human spaceflight training, verifying component accessibility, investigating impact of space suit parts and harnesses, etc. Traditional approach for ergonomic investigations (involving costly physical mockups and trials with real humans) can be effectively replaced by evaluations facilitated by digital mockups and digital humans.

Being a review paper, the present manuscript is purely academic in nature.

The present paper represents critical review (with up to date references), leading to a comprehensive knowledge body about application of digital human modeling in aviation and aerospace industry. Avenues still to be explored have been identified and future research directions have been given aiming at aviation and aerospace completely human centric.