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拟常曲率黎曼流形中卷积子流形的一些不等式
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作者 王佳慧 程丽鹃 朱业成 《中国科学技术大学学报》 CAS CSCD 北大核心 2022年第3期44-51,70,共9页
用最优化方法,研究了拟常曲率黎曼流形中的卷积子流形,讨论了广义标准δ-Casorati曲率,建立了内在不变量和外在不变量之间的两个不等式,推广了实空间形式中子流形的最优不等式。
关键词 Casorati曲率 最优化方法 数量曲率
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基于强化学习的高速列车群运行调整方法 被引量:4
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作者 代学武 程丽娟 +3 位作者 崔东亮 俞胜平 袁志明 应志鹏 《中国科学:信息科学》 CSCD 北大核心 2022年第5期890-906,共17页
随着我国高速铁路建设成网,行车密度不断提高,在出现突发事件导致列车晚点时,行车调度的复杂性和难度急剧增加,如何动态调整列车群运行,以减少晚点,提高准点率是运行调整的核心.本文提出了一种适用于突发事件下高速列车群运行调整的无... 随着我国高速铁路建设成网,行车密度不断提高,在出现突发事件导致列车晚点时,行车调度的复杂性和难度急剧增加,如何动态调整列车群运行,以减少晚点,提高准点率是运行调整的核心.本文提出了一种适用于突发事件下高速列车群运行调整的无模型强化学习方法.首先将多个列车在多个车站和闭塞区间的运行调整建模为受约束的资源占用和配置的多阶段序贯决策过程,提出了基于动态时空拓扑矩阵的车站和区间统一化建模方法.针对高铁列车群时空关联强的特点,首次提出了一种包含车辆位置、路网资源等时空分布信息的强化学习状态空间、动作空间和回报函数,构建了有效的奖励反馈机制.然后,针对高铁运行系统搜索空间巨大的难点,提出了启发式动作子空间自适应生成方法,利用部分显式静态约束构建启发式规则减少搜索空间,有效减少了无模型强化学习的试错次数,提高了求解效率,也保留了无模型通用性好的优点.最后,基于京广高铁实际案例的仿真分析表明,在发生不同时空范围的大风限速,导致多车延误的事件下,所提出的算法均能较好收敛,明显减少列车群内晚点传播,与MILP,ACO,FCFS方法相比,列车群的平均晚点时间可减少2%~20%. 展开更多
关键词 强化学习 时空拓扑矩阵 列车运行调整 FCFS算法 优化
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Seismic analysis of semi-gravity RC cantilever retaining wall with TDA backfill 被引量:2
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作者 II-Sang AHN lijuan cheng 《Frontiers of Earth Science》 SCIE CAS CSCD 2017年第4期455-469,共15页
The seismic behavior of Tire Derived Aggregate (TDA) used as backfill material of 6.10 m high retaining walls was investigated based on nonlinear time-history Finite Element Analysis (FEA). The retaining walls wer... The seismic behavior of Tire Derived Aggregate (TDA) used as backfill material of 6.10 m high retaining walls was investigated based on nonlinear time-history Finite Element Analysis (FEA). The retaining walls were semi- gravity reinforced concrete cantilever type. In the backfill, a 2.74 m thick conventional soil layer was placed over a 3.06 m thick TDA layer. For comparison purpose, a conventional all soil-backfill model was also developed, and the analysis results from the two models under the Northridge and Takatori earthquakes were compared. The FEA results showed that both models did not experience major damage in the backfill under the Northridge earthquake. However, under the Takatori earthquake, the TDA-backfiU model developed substantially large displacement in the retaining walls and in the backfill compared with the soil-backfill model. Regions of large plastic strain were mainly formed in the TDA layer, and the soil over the TDA layer did not experience such large plastic strain, suggesting less damage than the soil-backfill model. In addition, the acceleration on the backfill surface of the TDA-backfill model decreased substantially compared with the soil-backfill model. If an acceleration sensitive structure is placed on the surface of the backfill, the TDA backfill may induce less damage to it. 展开更多
关键词 TDA (Tire Derived Aggregate) scrap tires retaining wall seismic analysis Finite Element Analysis
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Hierarchical metal-phenolic-polyplex assembly toward superwetting membrane for high-flux and antifouling oil-water separation
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作者 Xueting Zhao Yuanyuan Jiang +4 位作者 lijuan cheng Youyou Lan Tingyuan Wang Jiefeng Pan Lifen Liu 《Chinese Chemical Letters》 SCIE CAS CSCD 2022年第8期3859-3864,共6页
Superwetting membranes have emerged as promising materials for the efficient treatment of oily wastewater.Typically,superwetting membranes can be developed by ingeniously chemical modification and topographical struct... Superwetting membranes have emerged as promising materials for the efficient treatment of oily wastewater.Typically,superwetting membranes can be developed by ingeniously chemical modification and topographical structuration of microporous membranes.Herein,we report the hierarchical assembly of metal-phenolic-polyplex coating to manipulate membrane surface superwettability by integrating metal-phenolic(Fe^(Ⅲ)-tannic acid(TA))assembly with polyplex(tannic acid-polyethylenimine(PEI))assembly.The proposed Fe-TA-PEI coating can be deposited on microporous membrane via simply dipping into Fe^(Ⅲ)-TA-PEI co-assembly solution.Based on the catechol chemistry,the coordination complexation of Fe^(Ⅲ)and TA develops metal-phenolic networks to provide hydrophilic chemistries,and the electrostatic complexation of TA and PEI generates nanoconjugates to impart hierarchical architectures.Benefiting from the synergy of hydrophilic chemistries and hierarchical architectures,the resulting PVDF/Fe-TA-PEI membrane exhibits excellent superhydrophilicity(~0°)underwater superoleophobicity(~150°)and superior anti-oil-adhesion capability.The superhydrophilicity of PVDF/Fe-TA-PEI membrane greatly promotes membrane permeability,featuring water fluxes up to 5860 L m^(-2)h^(-1).The underwater superoleophobicity of PVDF/Fe-TA-PEI membrane promises potential flux(3393 L m^(-2)h^(-1)),high separation efficiency(99.3%)and desirable antifouling capability for oil-in-water emulsion separation.Thus,we highlight the reported hierarchical metal-phenolic-polyplex assembly as a straightforward and effective strategy that enables the synchronous modulation of surface chemistry and topography toward superwetting membranes for promising high-flux and antifouling oil-water separation. 展开更多
关键词 Metal-phenolic POLYPLEX Superwetting MEMBRANE Oil-water separation
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Functional inequalities on manifolds with non-convex boundary
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作者 lijuan cheng Anton Thalmaier James Thompson 《Science China Mathematics》 SCIE CSCD 2018年第8期1421-1436,共16页
In this article, new curvature conditions are introduced to establish functional inequalities including gradient estimates, Harnack inequalities and transportation-cost inequalities on manifolds with non-convex boundary.
关键词 Ricci curvature gradient inequality log-Sobolev inequality geometric flow
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