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First the link to this week’s complete list as HTML and as PDF.
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Male faculty for STEM subjects tend to reject studies that assert gender bias in their fields. So this is proof for their own gender bias and prejudiced rejection of female colleagues – at least according to Handley et al. Maybe so. But if an article is frequently rejected as poorly done, if this rejection is strongest among STEM faculty as opposed to faculty from other fields and the general public, could it not just be the case, that this is a genuinely poor study? Admittedly the gender difference in evaluation is strongest among STEM faculty, but who says it has to be the men, who are biased here? It is a proven fact that all scientists tend to accept studies supporting their view less critically than those opposing them. So the valuation criticising a study should always carry more weight than one accepting it.
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Sina et al.’s result would be quite important if it were plausible. Their data are roughly identical to my typical calculations at about 20 kW for 110 km/h, of which three quarters are air and one quarter rolling resistance. Their 1.5 kW of slip loss equals 7–8 % of slip. At my typically far higher pressure (4 bar) and speed (150 km/h) this would result in at least this amount of error in the odometer counting and speedometer reading. Checking over distances long enough to allow this precision I have never found my odometer to be more wrong than about 1 %, which is half the difference expected between new and worn tyres. So I confidently predict slip on dry roads, high pressure and large speed to remain less than 2 % and its effect on losses thus lower than that of rolling resistance when raising tyre pressures. The same result is obtained from their figure 7. 20 kW at 110 km/h is a traction force of about 0.65 kN. The weight on both driven wheels is more than 6 kN and μp and μs are around 1 as seen from the limits for braking and cornering. Thus we find ourselves at around the 10 % mark or below on the force range.
Their stating rolling resistance not for one or for all four, but for two tyres is untypical and confusing and makes their data hard to read. Confusing kPa for MPa in the tyre pressure and using arcane non-SI units like PS, HP, cc, and psi does the same and is another example of Elsevier’s slipshod to non-existent editing.
Addendum:
Speedometers are nearly universally driven from the gearbox and thus from the driven wheels. 7 % slip at a constant 150 km/h would result in an instantaneous drop of 10 km/h in the reading on releasing the accelerator – something impossible to miss and yet never seen.
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Drijfhout et al. do not look at data but only at computer models with positive feedbacks and more parameters than independent data points. Modeling the future is a questionable exercise anyway that is certain to yield unreliable results when extrapolating way outside of the range of data fed into model construction. Projections like those are best ignored.
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Many of the issues discussed in El-Mouchan are specifically French, but most are far more general. As the same development of population composition is happening all over Europe but came to France much earlier, his observations paint a valuable picture of things to come.
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