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: "a survey on state estimation techniques and challenges in smart distribution systems"
  Abstract: This paper presents a review of the literature on state estimation (SE) in power systems. While covering works related to SE in transmission systems, the main focus of this paper is distribution system SE (DSSE). The critical topics of DSSE, including mathematical problem formulation, application of pseudo-measurements, metering instrument placement, network topology issues, impacts of renewable penetration, and cyber-security are discussed. Both conventional and modern data-driven and probabilistic techniques have been reviewed. This paper can provide researchers and utility engineers with insights into the technical achievements, barriers, and future research directions of DSSE.

Connected through hyperedge HE-1 (induced by source paper "real time power system state estimation and forecasting via deep unrolled neural networks"):
  with members:
    - "a learning to infer method for real time power grid multi line outage identification"
    - "learning to optimize training deep neural networks for interference management"
    - "power system state estimation via feasible point pursuit algorithms and cramer rao bound"
    - "resnet with one neuron hidden layers is a universal approximator"
    - "robust and scalable power system state estimation via composite optimization"
    - "psse redux convex relaxation decentralized robust and dynamic approaches"
    - "a learning to infer method for real time power grid topology identification"
    - "identity mappings in deep residual networks"

Connected through hyperedge HE-2 (induced by source paper "a multi timescale data driven approach to enhance distribution system observability"):
  with members:
    - "a tutorial on spectral clustering"

Connected through hyperedge HE-3 (induced by source paper "a data driven framework for assessing cold load pick up demand in service restoration"):
  with members:
    - "review of smart meter data analytics applications methodologies and challenges"

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)