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: "High-Efficiency Class E, $hboxEF_2$ , and $hboxE/F_3$ Inverters"
  Abstract: This paper investigates the new Class EF 2  inverter and the already known Class E and E/F 3  inverters. The purpose of this paper is to find the answer to the question: what should be added to a classic Class E inverter to improve its performance with minimum expenditure? Class EF 2  and E/F 3  inverters meet this requirement through operating under zero-voltage switching and zero-voltage slope switching conditions (as in Class E) with improved transistor waveforms (as in Class F and 1/F). Selected results of a numerical analysis of Class E, EF 2  and E/F 3  inverters are shown and discussed. The analysis is aimed at maximizing the power output capabilities of these inverters for soft-switching conditions and fixed voltage and current stresses on their transistors as constraints. Measurement results of the Class EF 2  and E inverters are given to verify the validity of the presented theory. The measured output power of the inverters was 526 and 366 W with the total efficiency of 97.1% and 96.6% at 1 MHz, respectively

Connected through hyperedge HE-1 (induced by source paper "A Push–Pull Class-E Inverter With Improved Efficiency"):
  with members:
    (none)

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