The phrase "a difficult problem as" is not correct and usable in written English as it is incomplete and lacks context.
It could be used in a sentence where you are comparing or explaining a difficult problem, but it needs additional information to be clear.
Example: "A difficult problem as it relates to climate change is finding sustainable energy sources."
Alternatives: "a challenging issue as" or "a tough situation as".
When decisions are taken to engage in stabilization and reconstruction, ensuring the oversight of multiple federal agencies acting in the same space will continue to be a difficult problem, as will be the challenge of quickly deploying appropriate permanent agency oversight personnel.
Vehicle classification poses a difficult problem as vehicles have high intra-class variation and relatively low inter-class variation.
It can be seen that antenna is nowadays a crucial factor in wireless communication, though design-efficient and reliable antenna is a difficult problem as such design is a simulation-based time-consuming task [6].
However, choosing an ideal control set for a population study is a difficult problem, as the age, sex and ethnicity of the case and control groups should be matched to enable appropriate conclusions to be made.
Since pathway categorization is a difficult problem, as partition of the global interaction network in "parts" inevitably introduces artefacts, we also proceeded to a detailed, gene-by-gene inspection of the most discriminative genes based on inspection of literature data.
Although worldwide its incidence in childhood is falling, due to widespread immunization against hepatitis B, it remains a difficult problem as chemotherapy has made little or no impact on survival and most tumors are unresectable.
The evaluation of a key-frame extraction and video summarization systems has been considered a very difficult problem, as long as user-based systems are concerned.
Although we are concerned with the case where the reaction term is linear, the number of parameters involved, however, leads us to a relatively difficult problem as can be seen in our previous discussions.
It was a difficult problem, but as usual, Murphy had already found an answer working with other people.
Resource allocation is in general a difficult problem, and as a result the allocation of resources to multiple applications in a multimedia system has seen considerable research.
This seems to be a difficult problem, just as it is the case for SDEs and will probably require double integrals of compensated processes to be simulated.
