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- Anderberg, Cecilia, et al.
(författare)
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Alternative descriptions of roughness for cylinder liner production
- 2009
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Ingår i: Journal of Materials Processing Technology. - Amsterdam : Elsevier. - 0924-0136 .- 1873-4774. ; 209:4, s. 1936-1942
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Tidskriftsartikel (refereegranskat)abstract
- The roughness of stratified surfaces such as cylinder liners, produced by plateau honing, is functionally important in their tribology but is notoriously difficult to characterise. An issue in manufacturing quality control related to their tribological function is the comparative ability of various roughness characterisation systems. In this paper the Rk family of parameters is compared with the Rq family as regards stability and discrimination. When coefficients of variation of the two parameter families are compared as a measure of stability, CVs of individual parameters vary between 8% and 20% but do not seem to indicate a clear advantage to either family. When the correlation of parameters within and between the two groups is computed as a measure of relative discriminative ability, many parameters are found to be highly correlated, to the point where values of Rpk and Rpq are effectively indistinguishable. The relative robustness of the parameters is also established by simulation of surface or measurement artefacts: outlying peaks and valleys, high-frequency noise, changes in stylus or skid radius, changes in high-pass filter and in assessment length. Outlying peaks cause a large increase in Rpk, while outlying valleys have little effect. The Rq parameters are more sensitive to high-frequency noise than the Rk parameters. Increasing the stylus radius reduced the valley parameters, while adding a 25 mm radius skid increased Rk and Rpq by as much as 15%. Increasing the short-wavelength cut-off from 2.5 m to 8 m reduced most parameters, particularly the peak parameters, while replacing the robust Gaussian filter used throughout by a valley-suppression filter had little effect. Finally reducing the assessment length from 17 mm to 4 mm decreased the values of many parameters by up to 11%. Increasing plateau honing time decreased plateau roughness, while increasing pressure during coarse honing increased valley roughness, but these changes could not be correlated with roughness parameters. This suggests that the optimum parameter set has not yet been found. 2008 Elsevier B.V. All rights reserved.
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- Baker-Austin, Craig, et al.
(författare)
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Extreme arsenic resistance by the acidophilic archaeon 'Ferroplasma acidarmanus' Fer1.
- 2007
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 11:3, s. 425-34
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Tidskriftsartikel (refereegranskat)abstract
- 'Ferroplasma acidarmanus' Fer1 is an arsenic-hypertolerant acidophilic archaeon isolated from the Iron Mountain mine, California; a site characterized by heavy metals contamination. The presence of up to 10 g arsenate per litre [As(V); 133 mM] did not significantly reduce growth yields, whereas between 5 and 10 g arsenite per litre [As(III); 67-133 mM] significantly reduced the yield. Previous bioinformatic analysis indicates that 'F. acidarmanus' Fer1 has only two predicted genes involved in arsenic resistance and lacks a recognizable gene for an arsenate reductase. Biochemical analysis suggests that 'F. acidarmanus' Fer1 does not reduce arsenate indicating that 'F. acidarmanus' Fer1 has an alternative resistance mechanism to arsenate other than reduction to arsenite and efflux. Primer extension analysis of the putative ars transcriptional regulator (arsR) and efflux pump (arsB) demonstrated that these genes are co-transcribed, and expressed in response to arsenite, but not arsenate. Two-dimensional polyacrylamide gel electrophoresis analysis of 'F. acidarmanus' Fer1 cells exposed to arsenite revealed enhanced expression of proteins associated with protein refolding, including the thermosome Group II HSP60 family chaperonin and HSP70 DnaK type heat shock proteins. This report represents the first molecular and proteomic study of arsenic resistance in an acidophilic archaeon.
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- Dimkovski, Zlate, 1974-, et al.
(författare)
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Quantification of Blechmantel Effect on Wear of Cylinder Bore Microtopography
- 2008
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Ingår i: Proceedings of the 13th Nordic Symposium on Tribology, Nordtrib 2008. - Tampere : Tampere University Press. - 9789521519611 ; , s. 13-
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Konferensbidrag (refereegranskat)abstract
- The presence of cold work material (blechmantel) smeared out on cylinder liners by faulty honing is undesirable as it seals the oil-bearing honing grooves. It is also believed to correlate with increased bore wear, presumably due to its loosening and together with the carbon build-up from the piston’s top land form an increased quantity of abrasive particles. An attempt has been made to estimate the extent of removal of blechmantel for different wear regimes present at the middle and top region (near the top dead centre) of the liner surface using the unworn bottom region as a reference for comparison. A number of truck cylinder liners were axially sectioned after varying periods of engine running under similar conditions of load, engine speed and lubrication. 3D surface measurements were taken at the three regions and a range of standard parameters was extracted. Combining the profile and image analysis, an algorithm was developed to identify and quantify the blechmantel covering the grooves that is most likely to break and act as abrasive wear particles and at the same time it represents the part of blechmantel which covers the most of the surface. It was found out that a mere portion of the blechmantel from the middle and bottom section was removed, while the blechmantel from the top section was greatly removed and thereby it represents one of the possible causes for wear. Axial wear scratches more emphasized on the thrust side of the liner were observed not only through the whole stroke area, but also in the bottom region. The fact that the most of the blechmantel is not removed from the running surface of the liner (except for the very small portion of the polished areas at the dead centres), points out that the blechmantel plays only a minor role on wear of the cylinder liner surfaces.
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- Fahlman, Andreas, et al.
(författare)
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Metabolic costs of foraging and the management of O2 and CO2 stores in Steller sea lions
- 2008
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Ingår i: The Journal of Experimental Biology. - Cambridge : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 211, s. 3573-3580
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Tidskriftsartikel (refereegranskat)abstract
- The metabolic costs of foraging and the management of O2 and CO2 stores during breath-hold diving was investigated in three female Steller sea lions (Eumetopias jubatus) trained to dive between 10 and 50 m (N=1142 dives). Each trial consisted of two to eight dives separated by surface intervals that were determined by the sea lion (spontaneous trials) or by the researcher (conditioned trials). During conditioned trials, surface intervals were long enough for O2 to return to pre-dive levels between each dive. The metabolic cost of each dive event (dive+surface interval; DMR) was measured using flow-through respirometry. The respiratory exchange ratio (O2/CO2) was significantly lower during spontaneous trials compared with conditioned trials. DMR was significantly higher during spontaneous trials and decreased exponentially with dive duration. A similar decrease in DMR was not as evident during conditioned trials. DMR could not be accurately estimated from the surface interval (SI) following individual dives that had short SIs (<50 s), but could be estimated on a dive by dive basis for longer SIs (>50 s). DMR decreased by 15%, but did not differ significantly from surface metabolic rates (MRS) when dive duration increased from 1 to 7 min. Overall, these data suggest that DMR is almost the same as MRS, and that Steller sea lions incur an O2 debt during spontaneous diving that is not repaid until the end of the dive bout. This has important consequences in differentiating between the actual and `apparent' metabolic rate during diving, and may explain some of the differences in metabolic rates reported in pinniped species.
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