The phrase "are not so efficient" is correct and usable in written English.
It can be used when comparing the efficiency of two or more things, indicating that one is less efficient than the other.
Example: "While traditional methods have their merits, they are not so efficient as the new automated system we have implemented."
Alternatives: "are relatively inefficient" or "are not as effective".
Unfortunately, commonly used wavelet transforms are not so efficient on delta frame coding.
Surfactant solutions are not so efficient for better recovery of oil due to low viscosity compared to that of the oil.
Umbelliferone can be extracted with water [36], ethanol or aqueous ethanol [37], methanol [38], while solvents like ether or dichloromethane are not so efficient [39].
Since heuristic approaches are not so efficient for escaping local optimum values, the obtained solutions by them may have a large disparity compared to the best known or sub-optimal solutions.
There are some reports that Interleukin-28B, or other IFN-stimulated genes (ISGs) may influence the SVR during treatment with interferons or interferon plus ribavirin 17, 18 but this does not explain why they are not so efficient in treating those infected with other genotypes.
The police in this northeast corner of Slovakia aren't so efficient in the best of times, but in post-Communist Slovakia, open discrimination against the Roma, or Gypsies, is the norm.
However, collection of these carriers was not so efficient and a radical improvement in design of the device is required.
Although the addition of Mg was not so efficient for improving the activity of mesoporous catalyst, benefit for suppressing coke formation was observed.
Ramsey Nasser, who co-developed a programming language entirely from emoji, said that "emoji have less cultural baggage than a natural language," though he conceded that they're not so efficient for coding a Web site.
But it is not so efficient that it doesn't propagate, occasionally, titanic errors and absurdities.
