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北京城市儿童教育辅导机构的空间集聚及影响因素

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地理研究 2022年第4期41卷 1170-1182页

作者：窦晨晨谌丽解扬洋蒋雅卓北京联合大学应用文理学院北京100191

教育资源分布的空间均衡关乎社会公平。现有研究主要关注中小学等正规教育设施,对儿童教育辅导机构关注较少。随着教育培训现象越来越普遍,对城市空间功能和社会公平的影响日渐突出,有必要进一步分析其空间集聚特征及影响因素。本文基于... 详细信息

教育资源分布的空间均衡关乎社会公平。现有研究主要关注中小学等正规教育设施,对儿童教育辅导机构关注较少。随着教育培训现象越来越普遍,对城市空间功能和社会公平的影响日渐突出,有必要进一步分析其空间集聚特征及影响因素。本文基于2018年北京儿童教育辅导机构POI数据,综合使用核密度、Moran’s I指数等空间分析方法,分析北京城市儿童教育辅导机构的空间集聚特征,并构建格网,采用多元回归方法分析其影响因素。结果显示:北京城市儿童教育辅导机构集聚分布在二环至五环内向北延伸的半环状集聚带上;学科类辅导机构在海淀区更集聚分布,艺体类则集聚分布在朝阳区;不同规模儿童教育辅导机构具有不同的空间集聚特征。北京城市儿童教育辅导机构的空间集聚分布是学区、同业集聚程度、房价、交通便捷程度、人口状况等多种因素综合作用的结果;不同学科、不同规模辅导机构集聚的主导因素有显著差异。结果表明课外教育资源存在向重点学区、高级社区空间集聚的倾向,从而可能加剧教育资源的空间不均衡。

关键词：儿童教育教育辅导机构空间集聚影响因素北京

Output feedback stabilization of stochastic high-order planar nonlinear systems with stochastic inverse dynamics and output-constraint

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Science China(Information Sciences) 2024年第3期67卷 182-196页

作者： Ruiming xie Shengyuan XU Nanjing University of Science and Technology School of Automation

In this paper, we solve the output feedback control problem of stochastic high-order planar nonlinear systems with output constraint and stochastic integral input-to-state stability(SiISS) inverse dynamics. By employing a key coordinate transformation, a stochastic nonlinear system with output constraint and SiISS inverse dynamics is converted into an unconstrained system. By skillfully constructing an observer and adopting SiISS small-gain conditions, we develop a new output feedback control design and analysis method, and prove that all the closed-system signals are bounded almost surely, the output constraint is not violated almost surely, and the equilibrium point of the closed-loop system is stochastically asymptotically stable.

关键词： stochastic high-order planar nonlinear system outputconstraint stochastic inverse dynamics output feedbackstabilization stochastic integral input-to-state stability(SiISS)

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Fixed-time stabilization of output-constrained stochastic high-order nonlinear systems

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Science China(Information Sciences) 2024年第4期67卷 5-20页

作者： Ruiming xie Shengyuan XU Nanjing University of Science and Technology School of Automation

In this study, the fixed-time stabilization problem of stochastic high-order nonlinear systems with output constraint and high-order and low-order nonlinearities is addressed. A new coordinate transformation is employed to directly convert output-constrained stochastic systems into an equivalent unconstrained *** fully extracting the characteristics of system nonlinearities and using the stochastic fixed-time stability theorem, a new design and analysis method is constructed to guarantee that the trivial solution of the closed-loop system is stochastically fixed-time stable while fulfilling the output constraint.

关键词： stochastic high-order nonlinear system outputconstraint high-order and low-order nonlinearity fixed-timestabilization finite-time stabilization

Review of the research on the development and utilization of clay-type lithium resources

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Particuology 2024年第4期87卷 46-53页

作者： Ruiqi xie Zhihui Zhao Xiong Tong Xian xie Qiang Song Peiqiang Fan Faculty of Land Resource Engineering Kunming University of Science and TechnologyKunming650093China Yunnan Engineering Research Center for Metal Tailings Resource Utilization Kunming650093China

Since the demands for lithium have been in explosive growth recently and several great clay lithium resources were founded in China,the development and utilization of clay-type lithium resources become a hot *** order to provide a guidance for the concentration and extracting lithium of clay-type lithium resources,this review systematically summarized the main types and characteristics of clay-type lithium resources and the research status of lithium extraction from clay lithium ***,the flotation research status of the main mineral of clay lithium ore was also ***,we discussed the difficulties in the development and utilization of clay-type lithium ore and put forward the subsequent research *** paper can provide a guidance for the con-centration and extracting lithium of clay-type lithium resources in the future.

关键词： Clay lithium Clay mineral flotation Lithium extraction Leaching

Conductive and stable polyphenylene/CNT composite membrane for electrically enhanced membrane fouling mitigation

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Frontiers of Environmental Science & Engineering 2024年第1期18卷 35-47页

作者： Huijuan xie Haiguang Zhang Xu Wang Gaoliang Wei Shuo Chen xie Quan Key Laboratory of Industrial Ecology and Environmental Engineering(Ministry of Education) School of Environmental Science and TechnologyDalian University of TechnologyDalian 116024China

Nanocarbon-based conductive membranes, especially carbon nanotube (CNT)-based membranes, have tremendous potential for wastewater treatment and water purification because of their excellent water permeability and selectivity, as well as their electrochemically enhanced performance (e.g., improved antifouling ability). However, it remains challenging to prepare CNT membranes with high structural stability and high electrical conductivity. In this study, a highly electroconductive and structurally stable polyphenylene/CNT (PP/CNT) composite membrane was prepared by electropolymerizing biphenyl on a CNT hollow fiber membrane. The PP/CNT membrane showed 3.4 and 5.0 times higher electrical conductivity than pure CNT and poly(vinyl alcohol)/CNT (PVA/CNT) membranes, respectively. The structural stability of the membrane was superior to that of the pure CNT membrane and comparable to that of the PVA/CNT membrane. The membrane fouling was significantly alleviated under an electrical assistance of −2.0 V, with a flux loss of only 11.7% after 5 h filtration of humic acid, which is significantly lower than those of PP/CNT membranes without electro-assistance (56.8%) and commercial polyvinylidene fluoride (PVDF) membranes (64.1%). Additionally, the rejection of negatively charged pollutants (humic acid and sodium alginate) was improved by the enhanced electrostatic repulsion. After four consecutive filtration-cleaning cycle tests, the flux recovery rate after backwashing reached 97.2%, which was much higher than those of electricity-free PP/CNT membranes (67.0%) and commercial PVDF membranes (61.1%). This study offers insights into the preparation of stable conductive membranes for membrane fouling control in potential water treatment applications.

关键词： Polyphenylene CNTs Membrane Electro-assistance Membrane fouling mitigation

基于CA-Markov模型的淮河流域土地利用变化研究

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灌溉排水学报 2024年第1期43卷 52-59,96页

作者：刘赛艳张永江解阳阳张钦席海潮扬州大学水利科学与工程学院江苏扬州225009 扬州大学现代农村水利研究院江苏扬州225009

【目的】研究淮河流域土地利用变化特征并预测淮河流域2030年土地利用变化,实现流域土地资源的合理开发利用。【方法】基于淮河流域1990—2020年共7期的土地利用数据,采用土地利用转移矩阵和土地利用动态度分析淮河流域土地利用变化特... 详细信息

【目的】研究淮河流域土地利用变化特征并预测淮河流域2030年土地利用变化,实现流域土地资源的合理开发利用。【方法】基于淮河流域1990—2020年共7期的土地利用数据,采用土地利用转移矩阵和土地利用动态度分析淮河流域土地利用变化特征。基于元胞自动机-马尔科夫(CA-Markov)模型模拟淮河流域2010和2015年的土地利用格局,并在满足一定的精度条件下,预测淮河流域2030年的土地利用变化趋势。【结果】(1)耕地和建设用地面积占淮河流域土地利用面积的80%以上,是淮河流域最主要的两种土地利用类型;(2)耕地的减少和建设用地的持续扩张是淮河流域1990—2020年土地利用最为明显的变化特征;(3)基于CA-Markov模型模拟的2010年和2015年土地利用的Kappa系数分别为0.937和0.944,模拟精度较高;(4)预测的淮河流域2030年土地利用变化显示:耕地的减少和建设用地的扩张仍然是主要趋势,但二者变化幅度放缓,林地和草地的变化不显著,水域面积继续增加。【结论】淮河流域建设用地大幅度扩张以及耕地面积持续减少应引起重视,基于CA-Markov模型模拟的2030年土地利用变化可为流域未来土地利用开发提供参考。

关键词：土地利用 CA-Markov模型转移矩阵 Kappa系数淮河流域

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Transfer learning framework for multi-scale crack type classification with sparse microseismic networks

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International Journal of Mining Science and Technology 2024年第2期34卷 167-178页

作者： Arnold Yuxuan xie Bing QLi Department of Civil and Environmental Engineering Western UniversityLondon N6A 3K7Canada

Rock fracture mechanisms can be inferred from moment tensors(MT)inverted from microseismic ***,MT can only be inverted for events whose waveforms are acquired across a network of *** is limiting for underground mines where the microseismic stations often lack azimuthal ***,there is a need for a method to invert fracture mechanisms using waveforms acquired by a sparse microseismic ***,we present a novel,multi-scale framework to classify whether a rock crack contracts or dilates based on a single *** framework consists of a deep learning model that is initially trained on 2400000+manually labelled field-scale seismic and microseismic waveforms acquired across 692 *** learning is then applied to fine-tune the model on 300000+MT-labelled labscale acoustic emission waveforms from 39 individual experiments instrumented with different sensor layouts,loading,and rock types in *** optimal model achieves over 86%F-score on unseen waveforms at both the lab-and *** model outperforms existing empirical methods in classification of rock fracture mechanisms monitored by a sparse microseismic *** facilitates rapid assessment of,and early warning against,various rock engineering hazard such as induced earthquakes and rock bursts.

关键词： Multi-scale Fracture processes Microseismic Acoustic emission Source mechanism Deep learning

Influence characteristics of water penetration on fibre-reinforced polymer/rigid polyurethane foam interface of the composite cross-arm considering natural ageing

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High Voltage 2024年第1期9卷 81-93页

作者： Jun xie Zhe Zhou Ziqian Liu Haonan Tian Sigang Zhang Qing xie Hebei Provincial Key Laboratory of Power Transmission Equipment Security Defense North China Electric Power UniversityBaodingChina State Grid Gansu Electric Power Company LanzhouChina

Fibre-reinforced polymer(FRP)/rigid polyurethane foam(RPUF)interface is susceptible to moisture intrusion in addition to natural ageing during *** study investigated the influence of moisture intrusion on the FRP/RPUF interface under natural ageing using experiments and molecular dynamics(MD)*** absorption,shear strength,and leakage current tests were used to clarify the changes in the interface *** degradation mechanism of moisture intrusion at the interface under natural ageing was revealed by MD simulation and *** results show that the natural ageing of interfacial materials will slightly reduce the quality of the interface but will reduce the water resistance of the material and promote the process of water intrusion into the *** addition,water mainly invades the interface through *** water penetration,the interfacial bonding strength and insulation performance significantly *** and hydrolysis of interfacial materials are the main reasons for decreased interfacial *** can cause irreversible damage to the interface,increasing interface defects and water *** vicious cycle of material hydrolysis is the ultimate cause of interfacial *** polar molecules produced by this process and the water absorbed by the interface caused the degradation of the interface insulation performance.

关键词： interface polyurethane interfacial

Imprints of ultralight axions on the gravitational wave and pulsar timing measurement

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 23-29页

作者： Ning xie Fa Peng Huang MOE Key Laboratory of TianQin Mission TianQin Research Center for Gravitational Physics&School of Physics and AstronomyFrontiers Science Center for TianQinGravitational Wave Research Center of CNSASun Yat-sen University(Zhuhai Campus)Zhuhai 519082China

The axion or axion-like particle motivated from a natural solution of strong CP problem or string theory is a promising dark matter *** study the new observational effects of ultralight axion-like particles by the space-borne gravitational wave detector and the radio *** the neutron star-black hole binary as an example,we demonstrate that the gravitational waveform could be obviously modified by the slow depletion of the axion cloud around the black hole formed through the superradiance *** compare these new effects on the binary with the well-studied effects from dynamical friction with dark matter and dipole radiation in model-independent ***,we discuss the constraints from LIGO/Virgo and study the detectability of the ultralight axion particles at LISA and TianQin.

关键词： gravitational wave axion dark matter