Derek Young's research is in combinatorial matrix theory. Young uses linear algebra and mathematical software to construct matrices that realize the maximum nullity over a set of matrices. Young also uses graph theory to describe the maximum nullity. For instance, each set of matrices that are of interest corresponds to a unique graph. That graph has parameters which bound the maximum nullity above and below.
Young, D. (2021). Techniques for determining equality of the maximum nullity and the zero forcing number of a graph. The Electronic Journal of Linear Algebra, 37, 295–315. https://doi.org/10.13001/ela.2021.4967