检索结果-南通市图书馆

Quantitative simulation and verification of upgrade law of sustainable development in Beijing-Tianjin-Hebei urban agglomeration

引用

Science China Earth Sciences 2019年第12期62卷 2031-2049页

作者： Chuanglin FANG Longwu LIANG zhenbo wang Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China

The natural formation and development of urban agglomerations is a process in which core cities continue to unite their neighboring cities to enhance sustainability for their own sustainable *** upgrade mechanism of sustainable development urban agglomeration is a nonlinear composite upgrade curve that is a function of time,increasing with the number of *** this paper,the sustainable upgrade function curve,upgrade rate,and upgrade speed of urban agglomerations were solved using a geometrical derivation,and the index system for measuring the upgrade capability of sustainable development of urban agglomerations was *** dynamic change in economic sustainable upgrade capability,social sustainable upgrade capability,environmental sustainable upgrade capability,and comprehensive sustainable upgrade capability of a Beijing-Tianjin-Hebei urban agglomeration from 2000 to 2015 was measured by technique for order preference by similarity to an ideal solution and a grey correlation method,and a comprehensive,intercity unite strength model and a unite threshold calculation method for urban agglomerations were *** research shows that the economic sustainable upgrade capability,social sustainable upgrade capability,environmental sustainable upgrade capability,and comprehensive sustainable upgrade capability of the Beijing-Tianjin-Hebei urban agglomeration all show a wave-like rising *** average annual upgrade speeds during 2000-2015 are,respectively,2.4%.1.67%,1.1%,and 1.74%,with the intercity comprehensive unite strength of urban agglomerations maintaining a general increase;but there is a limit to the joint *** 2000 to 2015,as the core city of the Beijing-Tianjin-Hebei urban agglomeration,Beijing,to enhance its sustainable upgrade capability,jointly developed with Tianjin,Langfang,and Baoding before 2000,Tangshan in 2002,Cangzhou in 2009,Zhangjiakou and Shijiazhuang in 2012,and Chengde in *** 2015,the comprehensive u

关键词： Sustainable upgrade law of urban agglomeration Sustainable upgrade strength of urban agglomeration Quantitative simulation and verification Beijing-Tianjin-Hebei urban agglomeration

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Real-time trajectory optimization for powered planetary landings based on analytical shooting equations

引用

Chinese Journal of Aeronautics 2022年第7期35卷 91-99页

作者： Lin CHENG Peng SHI Shengping GONG zhenbo wang School of Astronautics Beihang UniversityBeijing 100191China Department of Mechanical Aerospaceand Biomedical EngineeringUniversity of TennesseeKnoxville 37996USA

Traditionally,numerical trajectory integration for shooting equation calculation and iterations for shooting with randomly guessed initial solutions deteriorate the real-time performance of indirect methods for on-board *** this study,the indirect method is improved to achieve real-time trajectory optimization of fuel-optimal powered planetary landings with the help of analytical shooting equation derivations and a practical homotopy ***,the contributions of this paper are ***,the analytical expressions for shooting equation calculation are derived to replace the traditional time-consuming trajectory ***,the computational efficiency is significantly ***,the original three-dimensional landing problem is connected with a simplified one-dimensional problem that only involves the vertical dynamics,and its analytical solution is obtained based on Pontryagin’s minimum ***,starting with the analytical solution,the accurate solution of the original landing problem can be obtained through an adaptive homotopy *** results of Earth landing scenarios are given to substantiate the effectiveness of the proposed techniques and illustrate that the developed method can obtain a fuel-optimal landing trajectory in 5 ms with 100%success rate.

关键词： Adaptive homotopy Analytical solution Fuel-optimal landings Indirect method Real-time control

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Identifying the scope of the Lhasa Metropolitan Area based on a spatial field energy model

引用

Journal of Geographical Sciences 2021年第2期31卷 245-264页

作者： wang zhenbo LI Jiaxin LIANG Longwu Institute of Geographic Sciences and Natural Resources Research CASBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China

The cultivation and development of modern metropolitan areas with the aim of establishing new regional centers with competitive edge is a key objective for the new-type urbanization directions in *** construction of the Lhasa Metropolitan Area is of great significance for the promotion of the South Asia Channel,the‘Belt and Road’initiative,the Bangladesh-China-India-Myanmar Economic Corridor,the Himalaya Economic Cooperation Zone,and for rapid development and long-term stability of the Qinghai-Tibet *** paper examines the scope of the Lhasa Metropolitan Area including Chengguanqu(Chengguan District),Doilungdeqen,Dagze,Lhunzhub,Damxung,Nyemo,Quxu,Maizhokunggar,Samzhubze Qu(Samzhubze District),Gyangze,Rinbung,Bainang,Nedong,Gonggar,and Zhanang using a spatial field energy model that combines nodality and accessibility indices and considers multiple indicators including traffic flow between *** combining factors such as the natural background,population agglomeration,the social economy,infrastructure construction,and the urban spatial structure of the Lhasa Metropolitan Area,it is proposed to build a bow-and-arrow-shaped urban system with‘one core,two centers,one axis,and two wings’along the valleys and the transportation trunk lines of the *** study advocates the construction of a pure land industrial system comprising a green cultural and tourism-oriented plateau.

关键词： Lhasa Metropolitan Area spatial scope spatial field energy model development path

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Aluminizing Low Carbon Steel at Lower Temperatures

引用

Journal of Materials Science & Technology 2009年第4期25卷 433-436页

作者： Xiao Si Bining Lu zhenbo wang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China The High School Affiliated to Renmin University of China Beijing 100080 China

This study reports the significantly enhanced aluminizing behaviors of a low carbon steel at temperatures far below the austenitizing temperature, with a nanostructured surface layer produced by surface mechanical attrition treatment （SMAT）. A much thicker iron aluminide compound layer with a much enhanced growth kinetics of η-Fe2Al5 in the SMAT sample has been observed relative to the coarse-grained steel sample. Compared to the coarse-grained sample, a weakened texture is formed in the aluminide layer in the SMAT sample. The aluminizing kinetics is analyzed in terms of promoted difusivity and nucleation frequency in the nanostructured surface layer.

关键词： Nanostructured materials Surface mechanical attrition treatment Aluminizing Diffusion Nucleation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Efficient high-accuracy north-south station-keeping strategy for geostationary satellites

引用

Science China(Technological Sciences) 2021年第11期64卷 2415-2426页

作者： HUANG XuXing YANG Bin LI Shuang wang zhenbo College of Astronautics Nanjing University of Aeronautics and AstronauticsNanjing 210016China Department of Mechanical Aerospaceand Biomedical EngineeringUniversity of TennesseeKnoxvilleTN 37996USA

Station-keeping(SK) is indispensable in actual geostationary(GEO) satellite missions. Due to the luni-solar gravity perturbations, the inclination of a GEO satellite suffers the issues of secular drift and long-period oscillation. Current north-south(NS)SK strategies maintain the GEO satellite’s orbit with high accuracy but low fuel efficiency. In this work, an efficient highaccuracy NS-SK strategy is developed for the GEO satellites. First, an averaging method is employed to decrease the accumulation of the secular drift within a one-solar-day SK cycle, while the long-period oscillation caused by the solar gravity is damped to further improve the orbital accuracy using the impulse and finite-thrust propulsions. Second, we contribute a fueloptimal cycle that reduces the fuel consumption and a fixed-interval cycle that executes SK control in fixed time interval every day to further enhance the proposed NS-SK strategy. Numerical simulations show that the improved strategy can achieve highaccuracy NS-SK with little fuel consumption. Moreover, results also demonstrate that the fixed-interval cycle can reach higher NS-SK accuracy while consuming less fuel.

关键词： geostationary orbit north-south station-keeping long-period oscillation fuel-optimal fixed-interval

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An identifier-actor-optimizer policy learning architecture for optimal control of continuous-time nonlinear systems

引用

Science China(Physics,Mechanics & Astronomy) 2020年第6期63卷 42-53页

作者： Lin Cheng zhenbo wang FangHua Jiang JunFeng Li School of Aerospace Engineering Tsinghua UniversityBeijing 100084China Department of Mechanical Aerospaceand Biomedical EngineeringUniversity of TennesseeKnoxville TN 37996USA

An intelligent solution method is proposed to achieve real-time optimal control for continuous-time nonlinear systems using a novel identifier-actor-optimizer(IAO)policy learning *** this IAO-based policy learning approach,a dynamical identifier is developed to approximate the unknown part of system dynamics using deep neural networks(DNNs).Then,an indirect-method-based optimizer is proposed to generate high-quality optimal actions for system control considering both the constraints and performance ***,a DNN-based actor is developed to approximate the obtained optimal actions and return good initial guesses to the *** this way,the traditional optimal control methods and state-of-the-art DNN techniques are combined in the IAO-based optimal policy learning *** to the reinforcement learning algorithms with actor-critic architectures that suffer hard reward design and low computational efficiency,the IAO-based optimal policy learning algorithm enjoys fewer user-defined parameters,higher learning speeds,and steadier convergence properties in solving complex continuous-time optimal control problems(OCPs).Simulation results of three space flight control missions are given to substantiate the effectiveness of this IAO-based policy learning strategy and to illustrate the performance of the developed DNN-based optimal control method for continuous-time OCPs.

关键词： continous-time nonlinear systems identifier-actor-optimizer architecture intelligent optimal control deep neural net-works

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Bubble behaviors of geldart B particle in a pseudo two-dimensional pressurized fluidized bed

引用

Particuology 2023年第8期79卷 121-132页

作者： Xiaoli Zhu Yibo Liu Yuehuan Li Haigang wang zhenbo wang College of New Energy China University of Petroleum(East China)Qingdao266580China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing100190China

Pressurized fluidized beds have been developed in quite a few industrial applications because of intensified heat and mass transfer and chemical *** bubble behaviors under elevated pressure,strongly influencing the fluidization and reaction conversion of the whole system,are of great research *** this work,the bubble behaviors of Geldart B particle in a pseudo two-dimensional(2D)pressurized fluidized bed were experimentally studied based on digital image analysis *** effects of pressure and fluidization gas velocity on the general bubble behaviors(i.e.,size,shape and spatial distribution)and the dynamic characteristics,such as the time-evolution of voidage distribution and local flow regimes,were comprehensively *** show that increasing pressure re-duces the stability of bubbles and facilitates gas passing through the emulsion phase,resulting in the"smoother"fluidization state with smaller bubbles and declined bubble fraction and standard *** equivalent bubble diameter and bubble aspect ratio increase with the increasing gas velocity while decrease as pressure *** elevated pressure reduces bubbles extension in the vertical direction,prohibits the"short pass"of fluidization gas in large oblong bubbles/slugs and benefits the gas-solid *** flow regimes variation with gas velocity is affected by the elevated pressure,and demonstrates different features in different local positions of the bed.

关键词： Pressurized fluidizedbed Bubble behaviors Geldart Bparticle Local flowregimes Digital image analysis

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Annealing-induced Grain Refinement in a Nanostructured Ferritic Steel

引用

Journal of Materials Science & Technology 2012年第1期28卷 41-45页

作者： Limin wang zhenbo wang Sheng Guo Ke Lu Sheng Guo and Ke Lu Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China

A nanostructured surface layer with a mean ferrite grain size of -8 nm was produced on a Fe-gCr steel by means of surface mechanical attrition treatment. Upon annealing, ferrite grains coarsen with increasing temperature and their sizes increase to -40 nm at 973 K. Further increasing annealing temperature leads to an obvious reduction of ferrite grain sizes, to -14 nm at 1173 K. The annealing-induced grain refinement is analyzed in terms of phase transformations in the nanostructured steel.

关键词： Nanostructured Surface mechanical attrition treatment (SMAT) Ferritic steel Grain refinement Austenitization

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Green economic efficiency in the Yangtze River Delta:spatiotemporal evolution and influencing factors

引用

Ecosystem Health and Sustainability 2019年第1期5卷 20-35,I0014页

作者： zhenbo wang Xinming wang Longwu Liang Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijingChina School of Resources and Environment University of Chinese Academy of SciencesBeijingChina School of Economics and Management Nanchang Aviation UniversityNanchangChina

Based on economic-social-resource-environment perspective,which people’s welfare was considered compared with the traditional perspective,using SSU and PP model,spatial analysis method,spatial econometric model to study green economy efficiency(GRE)of 26 Cities in the Yangtze River Delta from 2005 to *** results show the following:Corrected GRE is markedly lower than conventional efficiency;Stage characteristics are obvious of *** overall spatial pattern has emerged of lower efficiency in the east and higher efficiency in the west,and exist clear signs of spatial *** spatial Dubin model has abetter fitting *** biggest direct effect on local green economic efficiency and spatial spillover effects on nearby areas is proportion of tertiary industry.

关键词： Green economic efficiency measurement and calculation spatial characteristics influencing factors Yangtze River Delta urban agglomeration spatial econometrics

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Design optimization of guide vane for mitigating elbow erosion using computational fluid dynamics and response surface methodology

引用

Particuology 2022年第4期20卷 83-94页

作者： Anjun Li zhenbo wang Liyun Zhu Zengli wang Jingyuan Shi Wensan Yang School of New Energy China University of Petroleum(East China)266580 ShandongChina CNPC East China Design Institute Co. Ltd.266071 ShandongChina

A90°elbow equipped with guide vanes was developed with the intent of reducing elbow *** models were formed to predict the maximum erosion rate of elbow and Face-1,and the response surface methodology was used to study the relationship between the erosion rate and structural parameters of guide vane.A second-order response surface model was established to determine the relationship between R and variables,and a reduced cubic(RC)polynomial model was obtained to reveal the relation-ship between R2 and the three *** numerical results show that the low-speed region is expended and the maximum discrete particle matter(DPM)concentration is reduced after installing the guide *** internal component provides a shelter for the elbow from the direct impact of high-speed solids.

关键词： Elbow Particle erosion Guide vane Response surface methodology

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：