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Spheres of Urban Influence and Factors in Beijing-Tianjin-Hebei Metropolitan Region Based on Viewpoint of Administrative Division Adjustment

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Chinese Geographical Science 2017年第5期27卷 709-721页

作者： ZHU Jianhua chen Xi chen Tian School of Geographic Sciences Northeast Normal UniversityChangchun 130024China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Northeast Asian Studies College Jilin UniversityChangchun 130012China

The coordinated development of Beijing, Tianjin and Hebei has been elevated as China's important strategy. And, the priority in considering how to bring the maximum effect of their coordinated development into play is to delineate the spheres of urban influence with regard to the cities in the Beijing-Tianjin-Hebei Metropolitan Region. By building an evaluation index system of urban comprehensive strength, this paper applies the principal component analysis method to determine centrality strength of the cities, and the breakpoint theory and weighted Voronoi diagram to identify the spheres of urban influence in all central cities of the region. Results show that 13 central cities within the region greatly differ in strength, which can be classified into four tiers and that the spheres of urban influence do not have a high goodness of fit with administrative jurisdiction scope. Cities like Beijing, Tianjin, Shijiazhuang and Handan have larger spheres of urban, spheres of urban influence in Tangshan and Qinhuangdao are basically consistent with their administrative jurisdiction scopes, and seven cities including Langfang and Baoding have smaller spheres of urban influence. So according to these cities' comprehensive strength and spheres of influence, the region can be divided into five plates: Beijing, Tianjin, Shijiazhuang, Tangshan and Handan. The major influence factors for inconsistency between spheres of urban influence and spheres of jurisdiction include difference in urban administrative ranking, small number of central cities with weak strength, discrepancy in the number of counties under jurisdiction, unreasonable spheres of jurisdiction and diversity in topographical conditions. In order to solve the imbalance in the spheres of urban influence and those of jurisdiction and better facilitate the coordinated development of the region, it is advised to adjust administrative areas so as to obtain more optimized urban spatial layout and more reasonable urban scale

关键词： spheres of urban influence urban comprehensive strength adjustment of administrative divisions weighted Voronoi diagram Beijing-Tianjin-Hebei Metropolitan Region

Endpoint Estimates for Generalized Multilinear Fractional Integrals on the Non-homogeneous Metric Spaces

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Chinese Annals of Mathematics,Series B 2018年第4期39卷 721-738页

作者： Jiecheng chen Xiaoli chen Fangting JIN Department of Mathematics Zhejiang Normal University Jinhua 321004 Zhejiang China. Corresponding author. Department of Mathematics Jiangxi Normal University Nanchang 330022 China

In this paper, some endpoint estimates for the generalized multilinear fractional integrals Ia,m on the non-homogeneous metric spaces are established.

关键词： Generalized multilinear fractional integrals Lipschitz space RBMO s-pace Morrey space Non-homogeneous metric space

Topologically Correct Intersection Curves of Two Trimmed Quadrics with Tolerance Control

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Journal of Systems Science & Complexity 2024年第5期37卷 2207-2239页

作者： SHAO Wenbing chen Falai Department of Mathematics University of Science and Technology of ChinaHefei 230026China

Surface/surface intersection is a fundamental problem in Compute Aided Design and Geometric Modeling since it is essential to solid modeling,numerically controlled machining,feature recognition,computer animation,*** practical applications,quadric surfaces,which are the most basic type of surfaces,are typically bounded surfaces trimmed by a sequence of *** this paper,a robust algorithm is proposed for computing the intersection curve segments of two trimmed quadrics based on the parametric representation of the intersection curves of two *** proposed algorithm guarantees correct topology and ensures that the approximation errors of the end points of the intersection curve segments are less than a given *** error control is based on an effective solution to a set of polynomial inequality system using the root isolation *** examples are presented to validate the robustness and effectiveness of the proposed algorithm.

关键词： Polynomial inequality system root isolation surface/surface intersection tolerance control trimmed quadrics

Sliding-Mode-Based Attitude Tracking Control of Spacecraft Under Reaction Wheel Uncertainties

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IEEE/CAA Journal of Automatica Sinica 2023年第6期10卷 1475-1487页

作者： Wei chen Qinglei Hu the School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China. The Beihang Hangzhou Innovation Institute Yuhang Hangzhou 310023China

The attitude tracking operations of an on-orbit spacecraft with degraded performance exhibited by potential actuator uncertainties(including failures and misalignments) can be extraordinarily challenging. Thus, the control law development for the attitude tracking task of spacecraft subject to actuator(namely reaction wheel) uncertainties is addressed in this paper. More specially, the attitude dynamics model of the spacecraft is firstly established under actuator failures and misalignment(without a small angle approximation operation). Then, a new non-singular sliding manifold with fixed time convergence and anti-unwinding properties is proposed, and an adaptive sliding mode control(SMC) strategy is introduced to handle actuator uncertainties, model uncertainties and external disturbances simultaneously. Among this, an explicit misalignment angles range that could be treated herein is offered. Lyapunov-based stability analyses are employed to verify that the reaching phase of the sliding manifold is completed in finite time, and the attitude tracking errors are ensured to converge to a small region of the closest equilibrium point in fixed time once the sliding manifold enters the reaching phase. Finally, the beneficial features of the designed controller are manifested via detailed numerical simulation tests.

关键词： Actuator failures actuator misalignment angles finite time sliding mode control(SMC) spacecraft attitude tracking

Real-time electromagnetic transient simulation algorithm for integrated power systems based on network level and component level parallelism

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Science China(Technological Sciences) 2012年第11期55卷 3232-3241页

作者： chen LaiJun chen Ying MEI ShengWei State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments(Department of Electrical Engineering Tsinghua University)Beijing 100084China

The analysis and simulation of power system are becoming more and more challenging as the complexity of system topology and components has been increased. In this paper, a hybrid parallel algorithm is proposed for the real-time electromagnetic transient simulation （EMTS） of integrated power systems containing multiphase machines. The proposed algorithm is com- posed of a novel network partition method called component level parallelization and the Multi-Area Thevenin Equivalent （MATE） method, which extends the flexibility of the network partition in parallel simulation. Moreover, several methods are developed to enhance the efficiency of the communication and computation. Power systems with up to 410 single-phase elec- trical nodes and 336 switches are simulated in a time step of 50 ~ts to validate the proposed algorithm.

关键词： EMTP multiphase machine network partition parallel computing power system real-time simulation

Particle breakage of granular materials during sample preparation

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第2期11卷 417-422页

作者： Yifei Sun Sanjay Nimbalkar chen chen Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai University School of Civil and Environmental Engineering University of Technology Sydney

Particle breakage is commonly observed in granular materials when subjected to external loads. It was found that particle breakage would occur during both sample preparation and loading stages. However,main attention was usually paid to the particle breakage behaviour of samples during loading stage. This study attempts to explore the breakage behaviour of granular materials during sample *** samples of rockfill aggregates are prepared by layered compaction method to achieve different relative densities. Extents of particle breakage based on the gradings before and after test are presented and analysed. It is found that particle breakage during sample preparation cannot be ignored. Gradings after test are observed to shift away from the initial grading. Aggregates with larger size that appear to break are more than the smaller-sized ones. Irrespective of the initial gradings, an increase in the extent of particle breakage with the increasing relative density is observed during sample preparation.

关键词： Particle breakage Compaction Relative density Granular material

Novel three-body nano-abrasive wear mechanism

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Friction 2022年第5期10卷 677-687页

作者： Ruling chen Shaoxian LI College of Mechanical Engineering Donghua UniversityShanghai 201620China

Current three-body abrasive wear theories are based on a macroscale abrasive indentation process,and these theories claim that material wear cannot be achieved without damaging the hard mating *** this study,the process of three-body nano-abrasive wear of a system including a single crystalline silicon substrate,an amorphous silica cluster,and a polyurethane pad,based on a chemical mechanical polishing(CMP)process,is investigated via molecular dynamics *** cluster slid in a suspended state in smooth regions and underwent rolling impact in the asperity regions of the silicon surface,realizing non-damaging monoatomic material *** proves that indentation-plowing is not necessary when performing CMP material ***,a non-indentation rolling-sliding adhesion theory for three-body nano-abrasive wear between ultrasoft/hard mating surfaces is *** wear theory not only unifies current mainstream CMP material removal theories,but also clarifies that monoatomic material wear without damage can be realized when the indentation depth is less than zero,thereby perfecting the relationship between material wear and surface *** results provide new understanding regarding the CMP microscopic material removal mechanism as well as new research avenues for three-body abrasive wear theory at the monoatomic scale.

关键词： wear mechanism material removal mechanism three-body abrasive wear chemical mechanical polishing(CMP) molecular dynamics simulation

“吸纳型治理”:社会组织融入城市社区治理的路径选择

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理论导刊 2019年第2期 47-53页

作者：陈平青岛大学政治与公共管理学院山东青岛266101

社会组织参与社区治理基于多元治理的理论支撑、传统社区治理的博弈困境以及部分参与主体的冷漠态度。从社会组织的视角审视社区治理实践,治理主体力量差异明显、治理体制僵化、共同体意识淡漠等导致社区治理绩效低下;而基于利益激励、... 详细信息

社会组织参与社区治理基于多元治理的理论支撑、传统社区治理的博弈困境以及部分参与主体的冷漠态度。从社会组织的视角审视社区治理实践,治理主体力量差异明显、治理体制僵化、共同体意识淡漠等导致社区治理绩效低下;而基于利益激励、制度保障及价值引导的项目制、协同制和联动制都存在部分困境。"吸纳型治理"作为一种纳入利益因素、价值关切及制度考量的综合治理模式,应该是推动社区治理的有效路径。

关键词：社区治理社会组织 “吸纳型治理” 多元治理

Carbon nanotubes/graphitic carbon nitride nanocomposites for all-solid-state supercapacitors

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Science China(Technological Sciences) 2020年第9期63卷 1714-1720页

作者： LU Chao chen Xi Deparment of Earth and Environmental Engineering Columbia UniversityNew York 10027USA School of Chemical Engineering.Northwest University Xi'an 710069China

All-solid-state supercapacitors with high power density and working stability are high-efficiency energy storage devices for smart electronic equipment. Developing electrode materials with fast ions and electrons transport is critical to improving the energy storage capability. Here, we report carbon nanotubes/graphitic carbon nitride nanocomposites with large specific surface area, porous structure and high electrical conductivity toward high-performance supercapacitors. The large surface area with porosity provides reservoir for ion accommodation during charge-discharge processes, and the high conductivity facilitates electrons and ions transport. Furthermore, nitrogen sites in electrodes contribute significant pseudocapacitance for supercapacitors. The nanocomposites based device gives a high specific capacity of 148 F g^(–1) at current density of 1 A g^(–1) with good rate capability from 1 to 10 A g^(–1). Additionally, the device displays excellent working stability with capacitance retention of 93%even after 10000 cycles at 1 A g^(–1) under 0.8 V in air. This study sheds light on design of nanocomposites with highly efficient charge transfer and will accelerate development of next-generation solid state energy devices.

关键词： carbon nanotubes graphitic carbon nitride nanocomposite nitrogen doping high capacity supercapacitors