Last night, I was reading this article:
Ok, probably you cannot download the paper then I toke a screenshot and uploaded it here for you:
Please read this paragraph(Highlighted in the above screenshot):
Park et al.  investigated sonic nozzles that are applied to gas flow rate measurements and determined that the critical pressure ratio is highly dependent on the Reynolds number rather than area ratio, especially in the cases with low flow velocity. Variation of discharge coefficients for sonic nozzles with flow geometry and Reynolds number was reported by Paik et al. , who determined higher discharge coefficients with increase of mass flow rate. Spotts et al.  performed a CFD study of the compressible flow through convergent–conical nozzles to investigate the effect of the nozzle pressure ratio and nozzle angle on the nozzle performance. They confirmed that for smaller nozzle angles, the discharge coefficient increases and the choked nozzle pressure ratio will be reduced.
Why didn't the bold words or phrases get any definite article "the"? Totally some parts of this paragraph is odd. e.g. There are two "Reynolds number" and the first one has got a definite article but the last one didn't get. Is it okay?