'to be in close relation' is correct and usable in written English.
You can use it when you want to express a strong connection between two people, places, or things. For example, "Our two families have been in close relation for generations."
Using Monte-Carlo simulations, prediction of genetic trend is shown to be in close relation with CD1.
"Why not make a place the whole family wants to come to a couple of times a year, more, not just once?" "The museum needs to be in close relation to the park," is how Zumthor chose to respond.
The types, magnitudes, areal extensions, and distributions of such sources are expected to be in close relation with the basement rocks (i.e., supra-basement features).
Lymphangiogenesis has been shown to be in close relation to fibrogenesis in different organs, including the kidney (Sakamoto et al., 2009; Zampell et al., 2012; El-Chemaly et al., 2009).
At last, our findings were in close relation with Bahlmann's findings.
These results might be in close relation to the known hypolipidemic and anti-inflammatory effects of the investigated medicinal fungus.
In a remedial street design plan the factor "environment" needs to be examined in close relation with road safety and traffic capacity at the design stage.
Within the individual handset usage patterns, temporal inhomogeneities due to circadian and weekly cycles were also reported [10], which are in close relation to the spatial inhomogeneities, such as nighttime at home and daytime in office.
However, the anterior/mandibular aspect is in close relation to the FOM muscles and FDG uptake to this part of the muscle can typically be distinguished from intrinsic muscle uptake of the tongue.
Other illustrative materials were in close relation to the earliest esoteric Daoist literature.
Engineering design problems involve meeting system's performance requirements such as reliability which is in close relation to appropriate selection of components and determination of a system level architecture.
