human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "analytical studies of quasi steady state model in power system long term stability analysis"
  Abstract: In this paper, a theoretical foundation for the Quasi Steady-State (QSS) model in power system long-term stability analysis is developed. Sufficient conditions under which the QSS model gives accurate approximations of the long-term stability model in terms of trajectory and ω-limit set are derived. These sufficient conditions provide some physical insights regarding the reason for the failure of the QSS model. Additionally, several numerical examples are presented to illustrate the analytical results derived.

Connected through hyperedge HE-1 (induced by source paper "a framework for dynamic stability analysis of power systems with volatile wind power"):
  with members:
    - "long term stability analysis of power systems with wind power based on stochastic differential equations model development and foundations"
    - "numerical investigations on quasi steady state model for voltage stability limitations and nonlinear analysis"

Connected through hyperedge HE-2 (induced by source paper "pmu based estimation of dynamic state jacobian matrix"):
  with members:
    - "applying a formula for generator redispatch to damp interarea oscillations using synchrophasors"
    - "data driven diagnostics of mechanism and source of sustained oscillations"

Connected through hyperedge HE-3 (induced by source paper "data driven diagnostics of mechanism and source of sustained oscillations"):
  with members:
    - "quasi steady state model for power system stability limitations analysis and a remedy"

Connected through hyperedge HE-4 (induced by source paper "quasi steady state model for power system stability limitations analysis and a remedy"):
  with members:
    - "numerical investigations on quasi steady state model for voltage stability limitations and nonlinear analysis"
    - "some issues with quasi steady state model in long term stability"

Connected through hyperedge HE-5 (induced by source paper "application of pseudo transient continuation method in dynamic stability analysis"):
  with members:
    - "numerical investigations on quasi steady state model for voltage stability limitations and nonlinear analysis"
    - "some issues with quasi steady state model in long term stability"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.SY(Systems and Control)