The phrase "a frequencies at which" is not correct in English.
It should be "the frequencies at which" or "frequencies at which." You can use it when discussing specific frequencies related to a topic, such as sound, radio waves, or other scientific measurements.
Example: "The study focused on the frequencies at which the material resonates."
Alternatives: "the rates at which" or "the levels at which."
The group tracked these fluctuations by passing the light through ethylene gas and tuning the laser so that its frequency was just at the edge of one of the gas's absorption peaks--a frequency at which ethylene absorbs light.
A natural frequency is a frequency at which the system will vibrate if initially disturbed from rest and not subjected to any external loads (De Silva 2007).
Therefore, the unit of the sum of fractions is, that is, every fraction signifies a frequency at which slots are scheduled.
What is more, in order to avoid being caught and grab network resources for maximizing attack effect, some malicious nodes would elaborately choose a frequency at which they participate in the cooperation to cheat normal nodes.
For a given level of muscle activation there exists a frequency at which the maximum speed is attained.
One possibility is that the initially poor ILD sensitivity that we observed at 1 kHz, a frequency at which ferrets are particularly sensitive to ITDs, might reflect the effects of prior experience concerning the relative usefulness of different spatial cues.
To accomplish this task, the program employs a database of frequencies at which typical emissions in meteor spectra appear.
We propose that skeletal muscle phenotype is tuned to this operational frequency, since each muscle has a limited range of frequencies at which power can be produced efficiently.
Thus, there exists a range of excitation frequencies at which the response can be controlled by modified SDOF system, and outside this range, the response can be controlled by 2-DOF system.
