The phrase "are only efficient" is correct and usable in written English.
It can be used when discussing the effectiveness or productivity of a particular method, process, or system, emphasizing that efficiency is the sole characteristic being highlighted.
Example: "In this context, the new algorithms are only efficient when applied to large datasets."
Alternatives: "are solely efficient" or "are merely efficient".
However, these are only efficient with a small number of items in the database.
However, the orthogonalization-based processing schemes are only efficient when the interference has similar strength with the desired signal.
Methodologically, detailed microscopic in situ measurements of leaf deposition require intense resources and are only efficient close to the pollen source.
It is evident that the large number of parallel groups are only efficient when there are the large number of SUs in the system and vice versa.
As already mentioned, the scheduling algorithms obtained in the previous sections are only efficient when the throughput guarantees are promised over a long time-window T W containing many time-slots.
Table 3 also indicates that the second bank is more efficient than the third, tenth, and eleventh banks which are only efficient in one level, so that, it can be the advantages of coordination between players.
He notes, for example, that the simulated UAV the researchers developed is only efficient at relatively high speeds; at lower speeds, flight efficiency drops dramatically.
This method is only efficient, however, if there are more data elements than processors and one data element does not dominate all the others.
However, this algorithm requires a centralized control and is only efficient for problem instances of small size due to the computation complexity.
Taking the ion temperature gradient modes (ITG) as an example, the solution from the new finite element solver has been compared to the solution from the original GTC's iterative solver which is only efficient for adiabatic electrons.
