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: "unobservable false data injection attacks against pmus feasible conditions and multiplicative attacks"
  Abstract: This paper studies false data injection (FDI) attacks against phasor measurement units (PMUs). As compared to the conventional bad data detector (BDD), an enhanced BDD utilizing the effect of zero injection buses is proposed. Feasible conditions under which FDI attacks are unobservable to this enhanced BDD are discussed. In addition, a class of multiplicative FDI attacks that maintain the rank of the PMU measurement matrix is introduced. Simulation results on the IEEE RTS-24-bus system indicate that the these multiplicative unobservable attacks can avoid detection by both the enhanced BDD and a detector based on low-rank decomposition proposed in prior work.

Connected through hyperedge HE-1 (induced by source paper "can predictive filters detect gradually ramping false data injection attacks against pmus"):
  with members:
    - "vulnerability assessment of n 1 reliable power systems to false data injection attacks"
    - "false data injection attacks on phasor measurements that bypass low rank decomposition"
    - "evaluating power system vulnerability to false data injection attacks via scalable optimization"
    - "vulnerability analysis and consequences of false data injection attack on power system state estimation"

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)