The phrase "a difficult application" is correct and usable in written English.
You can use it when referring to an application process or software that is challenging to navigate or complete.
Example: "The job requires a difficult application that tests both technical skills and problem-solving abilities."
Alternatives: "a challenging application" or "a complex application".
And beyond scouting players for the Union's U-18, U-16 and U-14 teams, there's a difficult application process to get into YSC Academy.
Most of the formulations containing acetone, in Table 2, have apparent relaxation time near or above 1 min and their structure is particularly stable, thus resulting in a difficult application to surfaces.
It is well know that in the system of n-ZnO/p-Si, electron and hole recombination takes place mainly in Si rather than in ZnO, leading to a difficult application for lighting since Si has a narrow and indirect band gap.
Pathways other than linear slopes have been described, but require a rather difficult application of statistical modeling [ 12].
A slightly more difficult application of the Mayer Vietoris sequence is the calculation of the homology groups of the Klein bottle X.
EagleBurgmann Germany GmbH & Co Kg has developed a sealing strategy specifically for this difficult application, which provides a cost-effective, long-term solution, as this case study explains.
The design and function of steam drum manway doors present a difficult sealing application for plant personnel.
A new ATTRA publication, "Federal Conservation Resources for Sustainable Farming and Ranching," is an overview of those programs and acts as a guide for navigating the often complex and difficult application process.
The AAPF is probably the most difficult application out there, as it requires a ten-page research plan, in addition to about 10 auxiliary documents.
Although it has a long history, it did not draw much attention from researchers due to its complexity and difficult application.
In such situations where estimating ρ B is difficult, application of two generalised URMAs may be the most appropriate option available (Table 3), although specifically for diagnostic studies other methods may also be valuable [ 21].
