This equilibrium is difficult to attain and even more difficult to change.
But he conceded it would be difficult to attain that goal.
An empirically grounded, universally valid judgment on the impact of e-cigarettes may be difficult to attain.
In fact ηa is shown to be limiting, such that values over ηa > 50% are difficult to attain.
Due to the relatively thin concrete panel thickness, it is difficult to attain adequate ductility in connection system.
The large number of families needed in discovering genetic variants with modest effect sizes is difficult to attain.
Zirconia posts exhibit high strength and toughness, but reliable bonding with the resin core is difficult to attain.
Of course it is difficult to attain this degree of certitude, and the difficulty is enhanced by the restrictions of the criminal law.
While these regions are theoretically attractive for multi-stage snap-morphing, they are difficult to attain in practice by means of a single control parameter.
Although the H∞ control method is a powerful tool to design robust controller, it is difficult to attain the performances in time domain.
