Regarding to the infinitive constructions, check the to-do-rules from https://github.com/opencog/opencog/blob/master/opencog/nlp/scm/relex-to-logic.scm

For "scientists try to understand science", the logic form is like:
```
EvaluationLink
    PredicateNode Try
    EvaluationLink
        PredicateNode Understand
        ConceptNode Scientists
        ConceptNode Science
```
Per embedded sentences, it's the similar mechanism as the "that/which/..." clauses. That is: apply the rules to the sub sentence first, with some temporary MarkerLink as an incomplete result marker. Then deal with the MarkerLink in the post processing part.   
        
The expected final result of RelEx2Logic for that example would be something like:

```
A scientist tries to understand how our world works.

SatisfySetLink 
    VariableNode "$qVar"
    EvaluationLink
        PredicateNode Try
        EvaluationLink
              PredicateNode Understand
              ListLink
                   ConceptNode Scientist
                   EvaluationLink 
                          PredicateNode "How"
                          ListLink
                               VariableNode "$qVar"
                               EvaluationLink 
                                       PredicateNode Work
                                       ConceptNode World
      
```
For "our world", possessive-rule that has been defined in https://github.com/opencog/opencog/blob/master/opencog/nlp/scm/relex-to-logic.scm would be applied as well...