As Dawei suggests, the "complex change verb valency" part is the only part that gives me trouble. While I do not speak this jargon, his answer seems good.
or maybe ... simple or complex changes to verb latency ...
Was this you meaning?
You seem an expert at English? Yet you ask here? :)
In my field we do not publish in the past tense for describing the article.
In section 4 the text presents. When you write it, section 4 presents. A year later, the text is unchanged, so section 4 presents. Not presented.
Describing the paper uses the present.
Describing the work uses the past .
I understand that this may be different in your field.
These are publishing conventions, noticeably different from field to field. They differ as much, maybe, as citation styles differ.
So in this paper, we explore, or explored, depending on whether you are describing the work, or the paper.
section 2 we focus - as it is the paper you describe, not the work.
Finally we showed - could be the work, past, already done,or the paper, presnt.