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Component positioning is an important part of aircraft assembly, aiming at the problem that it is difficult to accurately fall into the corresponding ball socket for the ball head connected with aircraft component. This study aims to propose a ball head adaptive positioning method based on impedance control.

First, a target impedance model for ball head positioning is constructed, and a reference positioning trajectory is generated online based on the contact force between the ball head and the ball socket. Second, the target impedance parameters were optimized based on the artificial fish swarm algorithm. Third, to improve the robustness of the impedance controller in unknown environments, a controller is designed based on model reference adaptive control (MRAC) theory and an adaptive impedance control model is built in the Simulink environment. Finally, a series of ball head positioning experiments are carried out.

During the positioning of the ball head, the contact force between the ball head and the ball socket is maintained at a low level. After the positioning, the horizontal contact force between the ball head and the socket is less than 2 N. When the position of the contact environment has the same change during ball head positioning, the contact force between the ball head and the ball socket under standard impedance control will increase to 44 N, while the contact force of the ball head and the ball socket under adaptive impedance control will only increase to 19 N.

In this paper, impedance control is used to decouple the force-position relationship of the ball head during positioning, which makes the entire process of ball head positioning complete under low stress conditions. At the same time, by constructing an adaptive impedance controller based on MRAC, the robustness of the positioning system under changes in the contact environment position is greatly improved.

This paper aims to study almost Ricci–Yamabe soliton in the context of certain contact metric manifolds.

The paper is designed as follows: In Section 3, a complete contact metric manifold with the Reeb vector field ξ as an eigenvector of the Ricci operator admitting almost Ricci–Yamabe soliton is considered. In Section 4, a complete K-contact manifold admits gradient Ricci–Yamabe soliton is studied. Then in Section 5, gradient almost Ricci–Yamabe soliton in non-Sasakian (k, μ)-contact metric manifold is assumed. Moreover, the obtained result is verified by constructing an example.

We prove that if the metric g admits an almost (α, β)-Ricci–Yamabe soliton with α ≠ 0 and potential vector field collinear with the Reeb vector field ξ on a complete contact metric manifold with the Reeb vector field ξ as an eigenvector of the Ricci operator, then the manifold is compact Einstein Sasakian and the potential vector field is a constant multiple of the Reeb vector field ξ. For the case of complete K-contact, we found that it is isometric to unit sphere S²ⁿ⁺¹ and in the case of (k, μ)-contact metric manifold, it is flat in three-dimension and locally isometric to Eⁿ⁺¹ × Sⁿ(4) in higher dimension.

All results are novel and generalizations of previously obtained results.

The purpose of this paper is to reveal the dynamic contact characteristics of the slip ring. Dynamic contact resistance models considering wear and self-excited were established based on fractal theory.

The effects of tangential velocity, stiffness and damping coefficient on dynamic contact resistance are studied. The relationships between fractal parameters, wear time and contact parameters are revealed.

The results show that the total contact area decreases with the friction coefficient and fractal roughness under the same load. Self-excited vibration occurs at a low speed (less than 0.6 m/s). It transforms from stick-slip motion at 0.4 m/s to pure sliding at 0.5 m/s. A high stiffness makes contact resistance fluctuate violently, while increasing the damping coefficient can suppress the self-excited vibration and reduce the dynamic contact resistance. The fractal contact resistance model considering wear is established based on the fractal parameters models. The validity of the model is verified by the wear tests.

The results have a great significance to study the electrical contact behavior of conductive slip ring.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2023-0300/

The purpose of this study is to establish a thermal contact conductance model of rough surfaces with inclination based on three-dimensional fractal theory.

The effects of contact load, inclination angle, fractal dimensional and fractal roughness on thermal contact conductance of rough surfaces were studied using numerical simulation.

The results show that the thermal contact conductance of the rough surface increases with the increase of contact load and fractal dimension and decreases with the increase of fractal roughness and inclination angle. The inclination angle of the rough surface has an important influence on the thermal contact conductance of the rough, and it is a factor that cannot be ignored in the study of the thermal contact conductance of rough surfaces.

A thermal contact conductance model of rough surfaces with inclination based on three-dimensional fractal theory was established in this study. The achievements of this study provide some theoretical basis for the investigation of the thermal contact conductance of rough surfaces.

The Russian invasion of Ukraine in February 2022 has led to the displacement of many Ukrainians. The purpose of this study is to investigate the relationship between their contact with Dutch society and their mental health. To this end, 136 adult, mostly female, displaced Ukrainians in the Netherlands participated in an online survey to investigate the relationship between quality of host national contact and mental health, as moderated by quantity of host national contact. The survey had a Ukrainian, Russian and English version, and it consisted of single questions assessing various variables, including quality of host national contact, quantity of host national contact, amount of discrimination/prejudice as well as five questions assessing mental health (Mental Health Inventory 5 [MHI-5]; Berwick et al., 1991). Contrary to the hypotheses, no interaction was found between quality of host national contact and quantity of host national contact, and quality of host national contact did not have a significant main effect on mental health. However, there is a significant, yet nonlinear main effect of quantity of host national contact on mental health. Moreover, there is a significant correlation between quality of host national contact and quantity of host national contact. Finally, and interestingly, there is a positive relationship between the amount of discrimination/prejudice and mental health among people who chose to fill out the Ukrainian version of the survey. These results provide a nuanced view of the relationship between the host environment and mental health, and governmental policies should take into account the complexity of this relationship.

A total of 161 displaced, mostly female (90.40%), Ukrainians in the Netherlands with the average age of 35 agreed to participate in this online survey. The main variables measured were mental health (dependent variable), quality of host national contact (independent variable 1) and quantity of host national contact (independent variable 2/moderator). Additional variables, such as the level of perceived discrimination/prejudice, have been included in the analyses. The survey was available in three different languages: Ukrainian, Russian and English.

In this study, the role of host national contact in the mental health of displaced Ukrainians in the Netherlands was investigated. The results showed that there was no interaction between quality of host national contact and quantity of host national contact in the prediction of mental health. Moreover, quality of host national contact did not predict mental health. Thus, both of the (preregistered) hypotheses of this study were refuted. However, the amount of perceived discrimination/prejudice turned out to be linked to mental health. Surprisingly, the amount of perceived discrimination/prejudice predicted higher mental health scores among participants who chose to fill out the survey in Ukrainian. Moreover, of the respondents included in the analysis, 94.85% gave reason for mental health concerns, as expressed by a converted MHI-5 score below 60.

Even though this study does show a positive relationship between the level of discrimination/prejudice and mental health among displaced Ukrainians who filled out the Ukrainian version of the survey, it does not offer a definite explanation for why this seemingly unexpected result occurred. No causal conclusions can be drawn based on this study regarding the relationship between host national contact and mental health.

The results of this study show that certain occurrences in the contact with host society members relate to mental health in unexpected and seemingly complex ways. This might mean that this study has potential for nuancing the current scientific knowledge regarding the relationship between host national contact and mental health. Such nuances might be quite important, as scientific research often forms the basis for governmental policies aimed at improving the mental health of displaced people. Therefore, governmental policymakers should be aware of the fact that there is no easy, clear-cut answer yet to the complex host society factors that play a role in the mental health of various displaced groups. Moreover, an investigation of the role of host national contact might lead to valuable knowledge about factors that contribute to the mental health of refugees. As has been said, refugees are at risk of developing various mental health issues, so they might need help managing their mental health. To this end, policymakers might need evidence-based information to develop interventions targeted at specific refugee groups. By investigating the mental health of displaced Ukrainians in the Netherlands, new insights will be gained to optimize mental health care for this particular refugee group.

This study yields important information regarding the degree of participation and inclusion of displaced Ukrainians in Dutch society, which can inform policies targeted at improving the experiences of this new displaced group. Because displaced Ukrainians have to deal with the mental health consequences of war and displacement, they might be particularly in need of a safe haven in which they feel included.

To the best of the author’s knowledge, this is the first study in which the role of the host society context in the mental health of displaced Ukrainians in the Netherlands is assessed. The results are quite unexpected and can nuance the current research on the link between discrimination and mental health. Moreover, this study can inspire future research to be conducted in the reasons behind this nuance, by researching the role of identity and uncertainty. Also, the author believes that this study is particularly suitable for this journal because it really looks at the link between social inclusion in the Dutch context and mental health outcomes.

Tribological research is complex and multidisciplinary, with many parameters to consider. As traditional experimentation is time-consuming and expensive due to the complexity of tribological systems, researchers tend to use quantitative and qualitative analysis to monitor critical parameters and material characterization to explain observed dependencies. In this regard, numerical modeling and simulation offers a cost-effective alternative to physical experimentation but must be validated with limited testing. This paper aims to highlight advances in numerical modeling as they relate to the field of tribology.

This study performed an in-depth literature review for the field of modeling and simulation as it relates to tribology. The authors initially looked at the application of foundational studies (e.g. Stribeck) to understand the gaps in the current knowledge set. The authors then evaluated a number of modern developments related to contact mechanics, surface roughness, tribofilm formation and fluid-film layers. In particular, it looked at key fields driving tribology models including nanoparticle research and prosthetics. The study then sought out to understand the future trends in this research field.

The field of tribology, numerical modeling has shown to be a powerful tool, which is both time- and cost-effective when compared to standard bench testing. The characterization of tribological systems of interest fundamentally stems from the lubrication regimes designated in the Stribeck curve. The prediction of tribofilm formation, film thickness variation, fluid properties, asperity contact and surface deformation as well as the continuously changing interactions between such parameters is an essential challenge for proper modeling.

This paper highlights the major numerical modeling achievements in various disciplines and discusses their efficacy, assumptions and limitations in tribology research.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2023-0076/

The aim of this paper is to empirically investigate whether social contacts can mediate the way in which current unemployment impacts future unemployment.

We use 2006–2017 data from the Household Income and Labour Dynamics in Australia (HILDA) survey and a dynamic random-effects model to describe the evolution of individual unemployment status over time.

Once controlled for the local context where individuals live and create friendships, we find that above-average social contacts reduce unemployment persistence. However, social contacts seem to be slightly less effective in deprived neighborhoods. These findings are consistent with the idea that individuals obtain information about job opportunities through a network of social contacts, and unemployment may lead to a decay of social capital, making it more difficult to find employment in future periods. Our results also show that neighborhood deprivation increases individual unemployment risk, while above-average neighborhood cohesion reduces the probability of unemployment in deprived neighborhoods.

Although many studies have been published on unemployment persistence, to the best of the author's knowledge, this is the first study quantifying the impact of social contacts on unemployment persistence. The study also offers fresh empirical evidence on the impact of neighborhood characteristics on unemployment risk.

Job characteristics can potentially influence employees’ attitudes and behaviors. However, their impact on employees’ innovative behaviors, particularly in public sector organizations, has received little scholarly attention. Based on relational job design theory and the broaden-and-build theory of positive emotions, this study aims to examine the effect of job contact on public sector employees’ innovative work behavior through the mediator of happiness at work. It also assesses whether prosocial motivation strengthens the influence of job contact on innovative work behavior (via happiness at work).

The model was examined on a sample of 180 employee-supervisor dyads (90 supervisors and 180 employees) recruited from various government departments in the United Arab Emirates.

The findings support the proposed moderated mediation model in which job contact positively and significantly impacts innovative work behavior. The association between job contact and innovative behavior via happiness at work is found to be stronger for employees who are highly prosocially motivated.

The findings offer prescriptive insights into public sector employee happiness and prosocial motivation by illustrating when and how job contact influences innovative work behavior. The authors also present relevant managerial recommendations for promoting public sector employees’ innovative behavior.

The assembly simulation in tolerance analysis is one of the most important steps for the tolerance design of mechanical products. However, most assembly simulation methods are based on the rigid body assumption, and those assembly simulation methods considering deformation have a poor efficiency. This paper aims to propose a novel efficient and precise tolerance analysis method based on stable contact to improve the efficiency and reliability of assembly deformation simulation.

The proposed method comprehensively considers the initial rigid assembly state, the assembly deformation and the stability examination of assembly simulation to improve the reliability of tolerance analysis results. The assembly deformation of mating surfaces was first calculated based on the boundary element method with optimal initial assembly state, then the stability of assembly simulation results was assessed by the density-based spatial clustering of applications with noise algorithm to improve the reliability of tolerance analysis. Finally, combining the small displacement torsor theory, the tolerance scheme was statistically analyzed based on sufficient samples.

A case study of a guide rail model demonstrated the efficiency and effectiveness of the proposed method.

The present study only considered the form error when generating the skin model shape, and the waviness and the roughness of the matching surface were not considered.

To the best of the authors’ knowledge, the proposed method is original in the assembly simulation considering stable contact, which can effectively ensure the reliability of the assembly simulation while taking into account the computational efficiency.