The influence of base oil properties on the efficiency of action of ZDDP-type additives

This paper deals with the analysis of the influence of base oil viscosity on the ability of ZDDP-containing lubricants to form protective layers (especially antiwear layers). The chemical structure of additives used was characterised according to their thermal stability, determined by differential scanning calorimetry (DSC). The additives were added to base oils of various viscosities. The prepared lubricants were tested using a four-ball machine, and analysed by DSC. The relationships between base oil viscosity and seizure load (P_t), weld load (P_w) and DSC test results are presented and discussed. The mechanism of interaction between ZDDP and the base oils was analysed by the use of a mathematical model.     

Assessment of lubricity of compositions of fuel oil with biocomponents derived from rape-seed

This paper presents an assessment of tribological properties of compositions of fuel oil containing fatty acid methyl esters derived from rape-seed oil. An HFRR (high-frequency reciprocating rig – ball-on-flat) apparatus was used in this investigation. The studies were carried out for a steel–steel pair in the concentrated contact.The tribological properties were determined by motion resistances, wear and lubricant film concentration. The surfaces were analysed after tribological tests. The aim of the investigation was an attempt to obtain a correlation between wear quantities being measured and percentage content of bioadditives in fuel oil. It was found that at as little as 5% of the additive the coefficient of friction decreases by about 20% while wear decreases twofold relative to fuel oil, which may result from an increase in the stability of the lubricant film.     

Examining how country-level science policy shapes publication patterns: the case of Poland

Scientometrics - This country case study describes how science policy instruments are designed to shape publication patterns and identifies the changes in researchers’ productivity that can...     

The correlation between results of different model friction tests in terms of an energy analysis of friction and lubrication

A general method for anticipating results of highly complex tests on the basis of simple measurements has not yet been worked out. An energy-based method for determining antiwear and extreme pressure (EP) properties of oils containing additives is described in the present paper. The method allows the parameters characterizing the ability of additive-containing oils to form boundary layers in the antiwear (α_AW) and EP (α_EP) regions to be determined.The parameters α_AW and α_EP make it possible to correlate the results of different friction tests. The correlation between seizure load P_t, welding load P_z, wear load index I_h, four-ball wear test results d₄₀ and results of the FZG tests is presented in this paper.     

Publication patterns in the social sciences and humanities: evidence from eight European countries

Scientometrics - The increasing number of open-access full-text scientific documents promotes the transformation from metadata- to content-based studies, which is more detailed and semantic. Along...     

Researchers publishing monographs are more productive and more local-oriented

Scientometrics - In this study, we investigate what share of researchers publish monographs across fields, gender and seniority. We acquired data from the Polish current research information system...     

Rotational motion control of a spacecraft

This note describes a systematic procedure for the control synthesis of a rigid spacecraft using the energy shaping method. The geometric concept of a mechanical system in a coordinate-independent form is used to derive a control algorithm for the Euler-Poincare equations. The main result of this note is a specialization of the method on the unit quaternion group. This note is concluded with the examples of the potential functions and implementation for the three-axis attitude control problem.     

Liapunov stability and adding machines revisited

We give a revised proof of a theorem originally due to Buescu and Stewart (1995). The new version of this theorem dispenses with the assumption that the space X is locally compact. The theorem is as follows: let X be a locally connected metric space, let f,:,X→X be a continuous map, and let A⊂X be a Liapunov stable compact transitive set that has infinitely many connected components. Then the map induced by f on the space of connected components of A is topologically conjugate to an adding machine.