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Wear particles and contaminants are known to reduce lifetime of machine elements such as roller bearings. This can be avoided through fine filtration. However, oil filterability can change in service, and in case of exceeding the maximum pressure at the filter, contaminated oil can flow through a bypass, threatening the function of the lubricated components. The purpose of this study is to provide a cost-efficient method to estimate the long-term oil fine filterability.

The estimation of long-term oil fine filterability takes place in two steps. In the first step, oil in its original condition is subjected to different stresses to reproduce changes experienced in service within a relatively short period of time. In the second step, the resulting oil is subjected to filterability tests. Existing test methods were adapted to produce realistic oil changes and deliver a realistic evaluation of filterability.

Oils produced using metal-catalyzed thermal-oxidative stresses and humid air are similar to real oil samples from the point of view of nuclear magnetic resonance oil analyses and filterability tests. Test conditions suitable for highly viscous gear oils were derived considering operation at low and high temperatures.

The test method provides an estimate of deterioration of oil filterability in service through a comparison between the filterability of oil in original condition and the filterability of an artificially produced oil.

The purpose of this paper is to investigate the applicability of the quadratic failure hypothesis (QFH) on journal bearings coated with a white metal sliding layer on the prediction of safe and unsafe operating conditions. The hypothesis covers operation conditions under static and dynamical loading.

Material tests and elastohydrodynamic, as well as structural, simulations were conducted to provide the required input data for the failure hypothesis. Component samples were tested to verify the results of the QFH.

The load bearing capacity of journal bearings was analysed for different operating conditions by the use of the QFH. Results allow for the identification of critical and non-critical loading conditions and are in accordance with component test results.

Today’s design guidelines for journal bearings do not consider a multi-axial stress state and actual stress distribution. The applied hypothesis enables consideration of multiaxiality inside the sliding surface layer, as well as determining the location of bearing fatigue due to material overload.

This paper aims to study the lubrication mechanism of textured journal bearings.

CFD models for textured journal bearings are established. The effect of texture coverage on the pressure distribution is studied to find the proper texture distribution. To enhance the local load-carrying capacity at textures, the micro-hydrodynamic pressure and microflow at different texture depth ratios are captured. The interaction between the texture-induced microflow and the bearing lubrication film is analyzed from the microflow perspective.

The bearing performance is on the one hand enhanced by the micro-hydrodynamic pressure generated by textures. On the other hand, the main bearing land and maximum pressure can be interfered by textures, leading to the reduction of load-carrying capacity. To minimize the interference effect, textures are suggested to distribute downstream of the minimum film thickness location. As the lubrication film thickness increases, the corresponding optimum texture depth ratio rises. The vortices influence the local flow rate through the lubrication film at textures and further affect the micro-hydrodynamic pressure and local load-carrying capacity. The texture depth ratio, at which vortices begin to occur, generates the maximum micro-hydrodynamic pressure.

The proper texture distribution is introduced, which is capable to generate the micro-hydrodynamic pressure without interfering with the primary load-carrying capacity of the bearing. The microflow effect is found to considerably influence the local load-carrying capacity at textures. The necessity of sub-regional optimization in textured journal bearings is pointed out. This study provides the fundamental reference for the design and optimization of textured journal bearings.

To decrease wear and friction, zinc dialkyldithiophosphate (ZDDP) has been used in engine oil for several decades, but the mechanism of the tribofilm formation is still unclear. The purpose of this study is to characterize the chemical details of the tribofilm by using high-resolution approaching.

An ISO VG 100 mineral oil mixed with ZDDP was used in sliding tests on cylindrical roller bearings. Tribofilm formation was observed after 2 h of the sliding test. X-ray photoelectron spectroscopy (XPS) and atom probe tomography (APT) were used for chemical analysis of the tribofilm.

The results show that the ZDDP tribofilm consists of the common ZDDP elements along with iron oxides. A considerable amount of zinc and a small amount of sulfur were observed. In particular, an oxide interlayer with sulfur enrichment was revealed by APT between the tribofilm and the steel substrate. The depth profile of the chemical composition was obtained, and a tribofilm of approximately 40 nm thickness was identified by XPS.

A sulfur enrichment at the interface is observed by APT, which is beneath an oxygen enrichment. The clear evidence of the S interlayer confirms the hard and soft acids and bases principle.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0035/

Rolling bearing operation under mixed and boundary lubrication conditions may lead to heavy adhesive or abrasive wear, which may lead to wear-induced rolling bearing failure. The purpose of this paper is to investigate the wear protection capabilities of different grease compositions at varying temperatures. It is considered that the temperature influences the lubrication conditions, the behaviour of grease components, namely, bleed oil and thickener, as well as the tribofilm formation due to tribo-chemical interactions between additives and surfaces.

In this study, four different greases were produced on the basis of a mineral base oil by varying the thickener and the addition of ZDDP. Various grease-lubricated rolling bearing experiments were conducted in a wide temperature range from 0°C to 120°C. Subsequently, the wear pattern, tribofilm formation and grease structures were analysed. Thereby, the influence of the different grease thickeners and the performance of ZDDP as a common antiwear and extreme pressure additive was evaluated.

The results show a strong temperature-dependency and allow a classification of temperature ranges concerning wear protection. At low temperatures, all greases provide a very good wear protection without the evidence of additive-based tribofilm formation. In the experiments at elevated temperatures, ZDDP tribofilms were formed. The formation depends on the thickener type: in comparison to lithium thickener, polyurea thickener favours more protective tribofilms at the same temperature. The experimental results show that medium temperatures in the range of 40°C–60°C are critical concerning wear due to the insufficient tribolayer formation and limited load carrying capacity of the grease.

Temperature is a key operating parameter for grease lubrication in roller bearings. The experimental work enables consideration of different impact pathways of temperature by combining roller bearing tests and microanalysis.

In this paper, after an elucidation of several central concepts of the topic, the author focuses on the sales channels in tourism and clarifies the role retailers play in the market. He shows that the existence of institutional travel retailers is generally based on transaction costs, and that thanks to the automation the level of dependence on transaction costs can be reduced. This thesis induces the question to what extent the retailers' performances can be automated. In answer to this question the author creates a list of criteria including the following aspects; the general and occasional suitability of retail products (e g tickets, travel packages), the availability of technical equipment and information necessary for the automation at the points of sale and in the households (buyers), the level of complexity and acceptance regarding the handling of automated travel services. The paper comes to the conclusion that the automation of travel services will probably be used mainly by business travelers, whereas private customers will more likely keep their affinity for conventional retailers.

The purposes of the study are to compare the investment behavior of farmers in Kazakhstan as a transforming country and in Germany as a Western industrialized country as well as to analyze whether the investment behavior of farmers is consistent with the normative benchmarks of the net present value approach or the real options (RO) approach.

The paper conducted an experiment with 100 Kazakhstani and 106 German farmers. The first part of the experiment describes an investment opportunity in an agricultural and in a non-agricultural treatment. The second part refers to a Holt and Laury lottery to determine farmers' risk attitude that could influence the investment behavior.

The results show that both approaches do not provide an exact prediction of the investment behavior of farmers. However, German farmers invest later than Kazakhstani farmers meaning that the investment behavior of German farmers is closer to the RO approach. This might imply that German farmers are more likely to take into account the value of flexibility when making investment decisions than Kazakhstani farmers.

Since investment behavior is country-specific, it is worth investigating whether farmers from other transforming countries would show different investment behavior compared to farmers from other Western industrialized countries. Furthermore, decision-making behavior related to investments could be different from that related to disinvestments. Therefore, it may be interesting to analyze the disinvestment decisions of farmers in transforming and Western industrialized countries.

The results show that it is not acceptable to apply the results of experiments investigating the investment behavior of entrepreneurs in a transforming country to entrepreneurs in a Western industrialized country and vice versa. Furthermore, training for farmers is needed because there is still room for improvement in order to achieve the RO benchmark. Finally, taking into account RO effects could improve the results of policy impact analysis.

This is the first experimental study comparing the investment behavior of farmers from a transforming country and from a Western industrialized country.

In March 2014, the minister responsible for public housing in the state of New South Wales in Australia announced that all 600 public housing tenants living in the historic heritage-listed adjacent inner-city neighbourhoods of Millers Point and The Rocks in Sydney were to be moved and the homes sold to the highest bidder on the open market. There were to be no exceptions, and the last public housing resident was moved from the area in July 2018. A common view is that public housing areas in countries with a residualised welfare system are characterised by attenuated social ties, anomie and bleakness. This chapter examines neighbouring, social ties, mutual assistance and sense of community among public housing tenants in Millers Point and demonstrates that this is not always the case. Drawing on 48 in-depth interviews with residents, plus observation, I show that the social connections among public housing tenants in the area were unusually strong and enduring. I argue that in order to understand why this was so, we need to look at the physical and social features of the area. Following on from the seminal work of Jane Jacobs, the New Urbanism movement argues that compactness, mixed land use and walkability are crucial enablers of social interaction and neighbourliness. These physical features were present in Millers Point. There is now a recognition by New Urbanism scholars that physical elements in themselves rarely create community and that the social features of neighbourhoods also have to be taken into account. In the case of the public housing tenants in inner Sydney, the key social features were longevity of residence and homogeneity. Another crucial aspect was a strong sense of social obligation. This was partially due to the presence of strong trade unionism in the area historically and the intermittent nature of employment at certain periods, which ensured neighbours rallied round to help those who were less fortunate.

The purpose of this paper is to review the development of engagement research in pursuit of improved sustainability accounting and performance and to identify issues in the further development of this field. In particular, the authors consider the implications of this research for practice, policy and theory following the publication of a special issue on the topic in 2007 in the Accounting, Auditing and Accountability Journal.

The authors performed a systematic review of the relevant literature in selected accounting journals for the 11 year period 2007–2017 inclusive. The authors identified the methods, topics and theories addressed by researchers and the academic journals that are more likely to publish engagement research.

The authors found a significant increase in engagement work over the decade since publication of the special issue and a marked increase in the volume and complexity of data collected in studies. There is a marked difference in the openness of different journals to engagement research and the type of engagement research published across accounting journals. Contrary to the argument made by critics of engagement research the authors found that this field of research not only uses theory, but develops theory.

Through the examination of methods and theories used and topics considered, the authors identify avenues for further research – and the journals likely to be receptive to it.

The study demonstrates that the collective body of engagement research aimed at improving sustainability accounting and performance has significant potential to inform practice and policy developments with the same aim.

The study examines an emerging approach in an emerging field of research with significant academic, practice and policy potential.

Collegiality is the modus operandi of universities. Collegiality is central to academic freedom and scientific quality. In this way, collegiality also contributes to the good functioning of universities’ contribution to society and democracy. In this concluding paper of the special issue on collegiality, we summarize the main findings and takeaways from our collective studies. We summarize the main challenges and contestations to collegiality and to universities, but also document lines of resistance, activation, and maintenance. We depict varieties of collegiality and conclude by emphasizing that future research needs to be based on an appreciation of this variation. We argue that it is essential to incorporate such a variation-sensitive perspective into discussions on academic freedom and scientific quality and highlight themes surfaced by the different studies that remain under-explored in extant literature: institutional trust, field-level studies of collegiality, and collegiality and communication. Finally, we offer some remarks on methodological and theoretical implications of this research and conclude by summarizing our research agenda in a list of themes.