The phrase "are mainly discussed" is grammatically correct and can be used in written English.
You can use it when talking about a topic or subject that is frequently talked about or analyzed. Example: In this chapter, the effects of climate change are mainly discussed.
In this article the scheme theory, architecture, service process, and performance are mainly discussed.
Push/pull production mode used in CIMS and its application in refinery are mainly discussed in this paper.
The influences of warm water injection and the horizontal well placements on the gas production are mainly discussed.
The formation and the evolution of PTFE transfer films with bearing operation are mainly discussed according to the relevant analysis.
For the latter, the physical and chemical properties of both starting wafers and SOI structures are mainly discussed.
For electronic tongue, the potentiometric and voltammetric types are mainly discussed together with applications in food and pharmaceutical analyses.
However, people are mainly discussing the BBHMM video because it has a plot where a gangsta Rihanna is peeved with a male accountant (played by Hannibal's Mads Mikkelsen).
Design calculation methods under serviceability and bearing capacity limits were mainly discussed.
Here, it is mainly discussed the design method of the developed mechanical actuator based on SolidWorks features.
The sound field is mainly discussed in terms of instantaneous pressure fluctuations, frequency spectra, acoustic intensity and directivity.
At first, emotional and affective aspect of social intelligence is mainly discussed because the aspect is considered as more important in contrast with goal-oriented intelligence.
