Results 11 to 20 of about 11,809 (167)
Zhejiang Daxue xuebao. Lixue ban, 2012 研究了一类捕食种群、食饵种群同时具有收获率的Holling III类功能反应生态系统.其中食饵种群具有非线性密度制约，捕食者无密度制约.应用微分方程定性理论，讨论了该微分生态系统.研究了系统的平衡点，对中心焦点的阶数、稳定性做出了分析.得出当给定参数满足一定条件时，系统不存在极限环.利用Hopf分支理论和张芷芬唯一性定理，证明了该系统极限环的存在性和唯一性.结果表明，2种群的密度或产生周期性的变化，或都稳定在一组定值的附近，可以保持一种稳定状态.
LIUJuan(刘娟), LIYi-min(李医民)
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Power System Transient Stability Preventive Control Optimization Method Driven by Stacking Ensemble Learning [PDF]
, 2023 Aiming at the contradiction between the rapidity requirement of online calculation of transient stability preventive control and the computational complexity of time-domain equations, a stacking ensemable learning driven optimization method for power ...
HU Wei +7 more
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Zhejiang Daxue xuebao. Lixue ban, 2013 研究了一类区间时变时滞非线性广义系统的稳定性问题.基于Lyapunov稳定性理论，应用线性矩阵不等式和自由权矩阵方法，给出了使得系统正则、无脉冲且一致渐近稳定的时滞相关型稳定性新准则.结果表明，所给准则可有效判定区间时变时滞非线性广义系统的稳定性，它比已有的一些结果具有更小的保守性，并且通过数值实例进行了验证.
JIAOJian-min(焦建民)
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Kongjian kexue xuebao, 2023 为确保高温材料科学实验柜科学实验系统能够成功地进行空间材料科学实验，在空间进行高温材料科学实验的时候要求其温度稳定在±0.25℃范围内。面对如此之高的温度稳定度要求，提出一个新的解决方案：在实验输入和输出数据的基础上，确定一个与高温炉控制系统内部等价的模型，为获得满足实验要求的控制参数提供依据。本文将高温炉控制系统内部看作黑箱模型，基于XGBoost方法分别对四类样品实验的高温炉内部温区2和温区3进行建模，模型精确度全部可达到99.98%以上。与传统建模方式传递函数相对比，在传统方法表现最好的情况下 ...
任 俊竹, 肖 志刚, 于 强
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Research on mining plan of non-working high-level coal seam in open-pit mine with near-horizontal composite coal seam [PDF]
, 2023 In the extraction of subhorizontal multiple coal seams using open-pit mining in China, the problem of coal seam in the high wall is commonly existed, but studies usually focus on the lower coal seam mining problem only.
Bo CAO +5 more
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Doubts on the formula for the anti overturning stability coefficient of gravity retaining walls [PDF]
The recommended calculation method for the anti-overturning stability of gravity retaining walls in the current technical specifications of various engineering industries is problematic.
ZHANG Yongkang
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Characteristics and mechanism of overlying rock and surface damage in gently inclined thick coal seam mining [PDF]
In order to scientifically guide the disaster prevention and ecological environment protection of the gently coal seam mining in the west of Ordos Basin, and to realize the green and safe mining of coal.
Bingchao ZHAO +5 more
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, 2018 以某城市互通立交桥为例,采用有限元方法计算,分析了不同曲率半径对小半径匝道弯桥受力的影响以及对小半径匝道弯桥抗倾覆性能的影响,并分析了支座反力、支座脱空影响、梁体转角、抗倾覆稳定系数计算对比及关键状态。福建省交通运输科技项目 ...
李云州, 李绍松, 裘是
core
Migration characteristics of landslide considering particle morphology [PDF]
Considering the particle morphology of geotechnical materials is essential for accurately assessing slope stability and predicting landslide migration.
Changyu HAN +5 more
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Growing Demand and Uneven Supply: Eight Years of Nature Education in China 需求增长与供给不均:中国自然教育八年发展回顾
Integrative Conservation, EarlyView.ABSTRACT This study examines the role of nature education in advancing conservation and sustainability in China between 2014 and 2023. Drawing on national survey reports and historical–comparative methods, it analyses the dynamics of public demand, institutional supply, and practitioner capacity.
Qi Yunxi, Lyu Xiang, Huang Yu
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