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您的检索式：作者名="Zonghan SUN"
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| 1 | Branch values in Ahlfors’ theory of covering surfaces显示文摘In the study of the constant in Ahlfors’second fundamental theorem involving a set Eq consisting of q points,branch values of covering surfaces outside Eq bring a lot of troubles.To avoid this situation,for a given surfaceΣ0,it is useful to construct a new surfaceΣ1,such that L(■Σ1)≤L(■Σ0),and H(Σ1,Eq)≥H(Σ0,Eq).and all branch values ofΣ1 are contained in Eq.The goal of this paper is to prove the existence of suchΣ1,which generalizes a result found by Zhang(2013). | Zonghan Sun Guangyuan Zhang | 2020 | Science China Mathematics2020，63，8： | 1 |
| 2 | System Strength Assessment Based on Multi-task Learning显示文摘Increase in permeability of renewable energy sources(RESs)leads to the prominent problem of voltage stability in power system,so it is urgent to have a system strength evaluation method with both accuracy and practicability to control its access scale within a reasonable range.Therefore,a hybrid intelligence enhancement method is proposed by combining the advantages of mechanism method and data driven method.First,calculation of critical short circuit ratio(CSCR)is set as the direction of intelligent enhancement by taking the multiple renewable energy station short circuit ratio as the quantitative indicator.Then,the construction process of CSCR dataset is proposed,and a batch simulation program of samples is developed accordingly,which provides a data basis for subsequent research.Finally,a multi-task learning model based on progressive layered extraction is used to simultaneously predict CSCR of each RESs connection point,which significantly reduces evaluation error caused by weak links.Predictive performance and anti-noise performance of the proposed method are verified on the CEPRI-FS-102 bus system,which provides strong technical support for real-time monitoring of system strength. | Baoluo Li Shiyun Xu Huadong Sun Zonghan Li Lin Yu | 2024 | CSEE Journal of Power and Energy Systems2024，10，1： | 0 |
| 3 | Properties of Ahlfors constant in Ahlfors covering surface theory显示文摘This paper is a subsequent work of[Invent.Math.,2013,191:197-253].The second fundamental theorem in Ahlfors covering surface theory is that,for each set E_(q)of q(≥3)distinct points in the extended complex plane C,there is a minimal positive constant H_(0)(E_(q))(called Ahlfors constant with respect to E_(q)),such that the inequality(q-2)A(Σ)-4π#(f^(-1)(E_(q))∩U)≤H_(0)(E_(q))L(ЭΣ)holds for any simply-connected surfaceΣ=(f,U),where A(Σ)is the area ofΣ,L(ЭΣ)is the perimeter ofΣ,and#denotes the cardinality.It is difficult to compute H_(0)(E_(q))explicitly for general set E_(q),and only a few properties of H_(0)(E_(q))are known.The goals of this paper are to prove the continuity and differentiability of H_(0)(E_(q)),to estimate H_(0)(E_(q)),and to discuss the minimum of H_(0)(E_(q))for fixed q. | Wennan LI Zonghan SUN Guangyuan ZHANG | 2021 | Frontiers of Mathematics in China2021，16，4： | 0 |
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