publications

How did one arrive at the red-underlined part in the equation (2) from differentiating equation (1)? Please see the picture:

https://imgur.com/a/FZBUaY6

The paper referred here:

Chen, Y., Zhuang, W., Wang, S., Lin, J., Balint, D., & Shan, D. (2012). Investigation of FE model size definition for surface coating application. Chinese Journal of Mechanical Engineering, 25(5), 860-867.

http://stephanebordas.blogspot.co.uk/

From the blogosphere

Nature 453, x (2008). doi:10.1038/7196xc

Does a scientist who has had three patents in the past five years,
but only three papers, each cited just three times, deserve more
recognition than one with five Nature papers and 1,000 citations? 

Can anyone download the full paper I have no access to Nature!!!!