human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "Classifier for Activities with Variations"
  Abstract: {}

Connected through hyperedge HE-1 (induced by source paper "Learning multi-level features for sensor-based human action recognition"):
  with members:
    - "Similar gait action recognition using an inertial sensor"

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Engineering