human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge groups authors who co-authored the same paper.

Details of the hypergraph:
Center hyperedge (induced by source paper "User, device and orientation independent human activity recognition on mobile phones: challenges and a proposal"):
  Abstract: Smart phones equipped with a rich set of sensors are explored as alternative platforms for human activity recognition in the ubiquitous computing domain. However, there exist challenges that should be tackled before the successful acceptance of such systems by the masses. In this paper, we particularly focus on the challenges arising from the differences in user behavior and in the hardware. To investigate the impact of these factors on the recognition accuracy, we performed tests with 20 different users focusing on the recognition of basic locomotion activities using the accelerometer, gyroscope and magnetic field sensors. We investigated the effect of feature types, to represent the raw data, and the use of linear acceleration for user, device and orientation-independent activity recognition.

Includes members:
  Member "Similar gait action recognition using an inertial sensor":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "Learning multi-level features for sensor-based human action recognition")
  Member "Online pose classification and walking speed estimation using handheld devices":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "Regularization Networks and Support Vector Machines")

Question: Please tell me which research area the co-authored paper (i.e., the source paper of the center hyperedge) belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Computer science