Search results

To identify the typical multilevel issues in social science, as well as illustrate the theoretical basis, hierarchical models and empirical exemplars of multilevel paradigm.

Hierarchical and multilevel data are extremely common in social systems, but multilevel analysis is constrained by statistical techniques. With the development of social system theory and empirical methods such as hierarchical structure modeling and latent growth modeling, multilevel paradigm can be used to analyze multilevel data. So it is necessary to identify typical multilevel phenomena in social science and discuss multilevel modeling techniques.

This paper identifies four typical multilevel phenomena in social system study: hierarchical and clustered sampling, collective construct research, longitudinal repeated measures, and event history analysis. Hierarchical structure modeling and latent growth modeling are effective multilevel analysis techniques in social science because of their advantages in the integration of social system research.

The quality and availability of multilevel data are the main limitations regarding which model will be applied.

The paper can aid the provision of effective multilevel models to social workers.

This paper provides information on application of multilevel modeling in social science.

The purpose of this paper is to study the effects of team trust and individual trust on cooperative performance and to examine the role of relationship commitment.

Statistical analysis on questionnaire data from 245 team members was used to assess relationship between trust, relationship commitment and cooperative performance.

The results show that both the team trust and the individual trust are positively correlated with cooperative performance. The indirect effect of team trust on cooperative performance mediated by relationship commitment is significantly greater than its direct effect. However, the indirect effect of individual trust on cooperative performance mediated by relationship commitment is significantly less than its direct effect.

Previous researches about the trust between teams focused on the team trust which did not match with the reality, especially in China, a country that thinks highly of interpersonal relationship. The paper first considers the effects of both the team trust and the individual trust on cooperative performance and compares these effects with the effects mediated by relationship commitment.

This paper considers the use and application of the “grey system” modelling methodology for the prediction and characterisation of boiler water R‐values in electric power generating plants. It has been confirmed that the GM (1,1) model can pinpoint precisely the properties of the water chemistry cycle. It is considered that the grey system methodology can strengthen significantly the effectiveness of system diagnosis, thereby enabling the development and application of automated water chemistry management systems in power plants.

This paper aims to predict and evaluate the wear rate of TiAl-2 Wt.% MoO₃ tabular crystals (TMCs) using the Newton interpolation methods.

The friction and wear behaviors of TMC were examined using pin-on-disc apparatus at different times, namely, 1,200, 2,400, 3,600, 4,800 and 6,000 s. The wear rates of five different times as interpolation nodes were measured and calculated by electron probe microanalysis (EMPA) and field emission electron microscope (FESEM). Then, the prediction formula of wear rate was constructed using the Newton interpolation method. The accuracy of the prediction formula and the relationship with friction layer and worn surface are verified for evaluating the reliability of the prediction formula.

The prediction formula shows a similar variation trend of TMC as the experimental results, indicating that the prediction formula can forecast the wear rate and working condition of TMC. Moreover, the microstructures of friction layer and worn surface also have a strong impact on the prediction formulas.

The prediction formulas of the Newton interpolation polynomial can be adopted to predict working longevity in the mechanical components, which can guide the practical engineering application in industrial fields.

This paper aims to study the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti₃C₂ to improve the tribological properties of M50 bearing steel with microporous channels.

M50 matrix self-lubricating composites (MMSC) were designed and prepared by filling Sn–Ag–Cu and MXene–Ti₃C₂ in the microporous channels of M50 bearing steel. The tribology performance testing of as-prepared samples was executed with a multifunction tribometer. The optimum hole size and lubricant content, as well as self-lubricating mechanism of MMSC, were studied.

The tribological properties of MMSC are strongly dependent on the synergistic lubrication effect of MXene–Ti₃C₂ and Sn–Ag–Cu. When the hole size of microchannel is 1 mm and the content of MXene–Ti₃C₂ in mixed lubricant is 4 wt.%, MMSC shows the lowest friction coefficient and wear rate. The Sn–Ag–Cu and MXene–Ti₃C₂ are extruded from the microporous channels and spread to the friction interface, and a relatively complete lubricating film is formed at the friction interface. Meanwhile, the synergistic lubrication of Sn–Ag–Cu and MXene–Ti₃C₂ can improve the stability of the lubricating film, thus the excellent tribological property of MMSC is obtained.

The results help in deep understanding of the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti₃C₂ on the tribological properties of M50 bearing steel. This work also provides a useful reference for the tribological design of mechanical components by combining surface texture with solid lubrication.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0381/

This in vitro study aims to explore the effects of selective laser melting (SLM) process parameters on the accuracy of the intaglio surface of cobalt–chromium alloy (Co–Cr), commercially pure titanium (CP Ti) and titanium alloy (Ti–6Al–4V) maxillary removable partial denture (RPD) frameworks and optimize these process parameters.

Maxillary RPD framework specimens designed on a benchmark model were built. The process parameters, including contour scan speed and laser power, infill scan speed and laser power, hatch space, build orientation and metallic powder type, were arranged through the Taguchi design. Three-dimensional deviations of the clasps area, connector area and overall area of maxillary RPD frameworks were analyzed by using root mean square (RMS) as a metric. One-way analyses of variance with the above RMSs as the dependent variable were carried out (α = 0.05).

Maxillary RPD frameworks built horizontally had a more accurate intaglio surface than those built at other orientation angles; CP Ti or Ti–6Al–4V maxillary RPD frameworks had a more accurate intaglio surface than Co–Cr ones; the Maxillary RPD framework built with a higher infill scan speed and lower infill laser power had the more accurate intaglio surface than the one built with other levels of these two process parameters.

A novel benchmark model for evaluating the accuracy of the intaglio surface of maxillary RPD frameworks manufactured by SLM is proposed. The accuracy of the intaglio surface of maxillary RPD frameworks can be improved by adjusting SLM process parameters. The optimal setting of process parameters concerning the accuracy of the intaglio surface of maxillary RPD frameworks was given.

The purpose of this paper is to investigate the influence of binder effect on tribological behavior of brake friction composite materials: a case study of phenolic resin modified by N-Methylaniline.

Four different friction materials have been fabricated by varying modified phenolic resin content. The samples were prepared by the conventional powder metallurgy methods following ball milling, mixing, pre-forming, hot pressing and post-curing processes. Thermogravimetric analysis was used to determination of the degradation mechanism of organic components and study of thermal stability of the samples. A friction test was carried out in dry conditions using a vertical tribometer. Analysis of worn surfaces was performed using a scanning electron microscope.

The experimental results revealed that the sample containing 25 Wt.% phenolic resin has good mechanical and thermal properties with stable friction characteristics.

This paper presents the effect of N-methylaniline modified phenolic resin on friction composites to improve tribological performance by its thermal properties.

Dairy products are an essential part of a healthy diet, and dairy is an emerging food industry in China. Meanwhile, the dairy industry is one of the “disaster zones” with quality and safety issues occurring more frequently in its supply chain than in others. Based on qualitative research focused on consumers in the Northwest and South of China, the present study aims to understand and provide information on consumer perception of food safety in dairy products.

Nine focus group interviews were carried out from January to April 2018. Altogether, 61 participants (24 males, 37 females, aged 18–60 years) were recruited in four cities. Qualitative content analysis of the data was conducted using Nvivo version 11.4.0.

A high concern with the safety of dairy products is widespread, particularly among participants with children, who are especially worried about the safety of dairy products. High prevalence of food safety incidents causes consumers to lower their confidence in food safety, and make them pay more attention to the news about food safety incidents. Consumers tend to become less sensitive to price, focusing more on food safety and quality, while purchasing dairy products. Brand and purchase venue are the most important indicators for consumers to determine the quality of dairy products. Safety certification becomes increasingly important.

It has some limitations. The focus group interviews covered different two regions (Northwest and South of China). However, the number of focus groups was limited to nine because of budget constraints. The participants come from Northwest and South of the country, which means that the findings may not apply for another area of the country. A more representative sampling with a larger sample size would be necessary to increase the validity of the study. However, the results can serve as input for further research.

This paper explores the Chinese consumers' perception of food safety and dairy products, consumers' behaviour concerning dairy products based on focus group interviews with consumers. This study offers valuable insights to members of academia, food suppliers and policy-makers.