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?
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You seem an expert at English? Yet you ask here? :)
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In my field we do not publish in the past tense for describing the article.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 .
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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.
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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.
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