'unknown practice' is correct and usable in written English.
You can use it when referring to a practice that has not been identified. For example, "The researchers are still trying to uncover the effects of this unknown practice."
"It was a very new and unknown practice when I did the ad.
In recent years, the church has come up with a form of acknowledgment of controversial businessmen: awarding them with the title Archon, a hitherto unknown practice in the country.
In that case, they may forego the profit and encourage bidding to go up beyond the $80 million, with the knowledge that Arnault will win the top bid through a proxy a controversial but not unknown practice in the high-stakes art world.
"What may have been acceptable business practices or relatively unknown business practices 10, 15 years ago are liable to cause problems today," said Craig Varoga, a Democratic consultant who runs the Patriot Majority political action committee.
The reconstruction error, unknown in practice, is denoted (e = x^sharp - x_0).
In general, the a priori bound E is unknown in practice.
In general, the a-priori bound is unknown in practice, in this case, with (4.14).
Although Equation (28) minimizes (27), the major issue is that the image irradiance E i is unknown in practice.
(N_0) is the horizontal size of the whole object support, unknown in practice (for example, (N_0 = 512) in the case of the (512^2) Shepp Logan phantom).
Unfortunately, the rank K is generally unknown in practice; therefore, an algorithm used to estimate K is presented in this section.
Finally, we test the robustness of our method against the fluctuations of the size of PSF in the model, since the exact value is usually unknown in practice and is estimated.
