You have a very nice way to say 'I don't know'.
STFT means short time fourier transform, and when I find something about using it on rotordynamics, I will post it here .
heitor - OK I was being funny. I've been doing rotating machinery analysis for 20 years, so if I haven't seen an abbreviation I think it is fair to say it is a bit specialised.
Anyway, yes we use different resolutions for our FFTs, but frankly the use of very short frames of data is rarely used in the automotive world since we are often very interested in the exact frequencies, and our slew rates are not very high. If your slew rates are high enough that you need to use STFT then I suggest you probably need to think about a time domain analysis not an FFT. You should probably be thinking about using a gated sampling technique at the very least (the diesel guys use this to look at the combustion noise signature from each cylinder).
Incidentally anybody who hasn't read polikar's web page is in for a treat, it is the best discussion of ffts and wavelets I've seen.
I have been doing some research on non-stationary vibration analysis.STFT is one of useful time-frequency analysis tools to get the information of rotordynamic during run-up and coast down.
It's the one given in anands78 post. I've been usimg that website as a reference for guys at work for a couple of years, in fact just about every time wavelets come up. It has a great discussion of why the inherent limits that apply to ffts also apply to wavelet analysis.