18.
In Winter, naturally, they closed the Shutters,
But in Kolomna,5 Summer Nights are hot,
And so they left them open; the Muse stutters
With Shame to mention “Pale Diana” (not,
I’m sure, that She is swarthy – my heart flutters
As fast as Any one’s, at her cold, fruitless Lot)
But while her Mama snored, our chaste Parasha
Prayed to the night6 to make her Life no harsher

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With D impeller for fan with guide vanes:
The axial fans with the D impeller is equipped with
guide vanes for higher pressures and efficiency.
The impeller is made of sea water resistant alum
and has variable pitch to easier suit different
capacities and pressures.
Due to the guide vanes the fan can achieve
pressures up to 1600 Pa.