检索结果-南通市图书馆

ADJACENT MARTIX METHOD OF IDENTIFYING ISOMORPHISM TO PLANAR KINEMATIC CHAIN WITH MULTIPLE JOINTS AND HIGHER PAIRS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2006年第4期19卷 605-609页

作者： SONG Li HUANG yong cheng Ling Department of Mechanical Engineering Xiangtan University Xiangtan 411105 China

The adjacent matrix method for identifying isomorphism to planar kinematic chain with multiple joints and higher pairs is presented. The topological invariants of the planar kinematic chain can be calculated and compared by adjacent matrix. The quantity of calculation can be reduced effectively using the several divisions of bars and the reconfiguration of the adjacent matrix. As two structural characteristics of adjacent matrix, the number of division and division code are presented. It can be identified that two kinematic chains are isomorphic or not by comparing the structural characteristics of their adjacent matrixes using a method called matching row-to-row. This method may be applied to the planar linkage chain too. So, the methods of identifying isomorphism are unified in the planar kinematic chain that has or hasn＇t higher pairs with or without multiple joints. And it has some characters such as visual, simple and convenient for processing by computer, and so on.

关键词： Planar kinematic chain Higher pair Multiple joint Adjacent matrix Identifying isomorphism

基于原型校正时空网络的多步海表面高度时空预测

在线全文

学校读者我要写书评

暂无评论

海洋与湖沼 2024年第4期55卷 840-852页

作者：任甜周圆程永存陈克然李硕士天津大学电气自动化与信息工程学院天津300072 航天宏图信息技术股份有限公司北京100195

海表面高度作为一项重要的海洋观测指标,对海洋生态系统和气候变化研究具有重要影响。传统基于循环神经网络(recurrent neural network,RNN)的时空序列预测模型在更新记忆状态时,存在一个关键问题:旧的记忆状态会被立即刷新,模型无法有... 详细信息

海表面高度作为一项重要的海洋观测指标,对海洋生态系统和气候变化研究具有重要影响。传统基于循环神经网络(recurrent neural network,RNN)的时空序列预测模型在更新记忆状态时,存在一个关键问题:旧的记忆状态会被立即刷新,模型无法有效地保留时间序列的长期依赖关系和变化趋势。这导致在多步海洋预测中,模型无法充分挖掘时间域的重要特征,从而使预测误差随着预测步长的增加而严重累积。为解决这个问题,设计一种原型校正时空网络(prototype corrected spatiotemporal network,PCST-Net)来实现准确的端到端多步海表面高度时空预测。PCST-Net采用基于RNN的网络结构,并设计记忆状态更新(memory state update,MSU)单元作为模型的核心构建单元。MSU单元利用原型校正模块(prototype correction module,PCM)来学习海表面高度样本的原型特征,从而提取时间域中的关键信息,并校正当前时间步的海表面高度高维特征,有效缓解多步预测中的严重误差累积问题。此外,提出一种多步信息输入策略,使模型能够从更广泛的时间步长中获得更全面准确的上下文信息,进而提高预测性能。通过对热带太平洋日平均海表面高度异常(sea surface height anomaly,SSHA)数据的多步时空预测验证了所提出的模型。结果表明:PCST-Net模型对未来5 d多步SSHA时空预测的平均均方根误差、平均绝对误差和皮尔逊相关系数分别为0.634 cm、0.488 cm和0.995。研究表明,PCST-Net模型可以准确地预测SSHA的时空变化趋势,这为多步海表面高度时空预测模型提供了一种可行性方法。

关键词：海洋预测海表面高度时空预测深度学习卫星遥感数据

在线全文

学校读者我要写书评

暂无评论

颞下颌关节紊乱病的MRI临床应用进展

口腔医学 2024年第1期44卷 11-15页

作者：魏丽丽李波程勇口颌系统重建与再生全国重点实验室口腔生物医学教育部重点实验室口腔医学湖北省重点实验室武汉大学口腔医(学)院武汉大学口腔医院放射科湖北武汉430079

随着颞下颌关节影像检查手段的发展,磁共振成像逐渐成为颞下颌关节紊乱病的首选检查方法,由于其无电离辐射暴露风险且为非侵入性检查,可清晰显示关节盘、关节腔积液、髁突水肿、咀嚼肌、双板区及滑膜病变,在临床有较大应用价值。本文从... 详细信息

随着颞下颌关节影像检查手段的发展,磁共振成像逐渐成为颞下颌关节紊乱病的首选检查方法,由于其无电离辐射暴露风险且为非侵入性检查,可清晰显示关节盘、关节腔积液、髁突水肿、咀嚼肌、双板区及滑膜病变,在临床有较大应用价值。本文从关节盘位置及形态改变、关节腔积液、髁突水肿和翼外肌的磁共振成像表现及其相关性研究现状进行探讨,以期为颞下颌关节紊乱病影像诊断提供思路。

关键词：颞下颌关节紊乱病磁共振成像关节盘移位关节腔积液

乡村振兴背景下塔里木河流域农业节水问题与思考

在线全文

学校读者我要写书评

暂无评论

水利规划与设计 2024年第6期 1-3,25页

作者：程勇李江张环魏光辉新疆塔里木河流域管理局新疆库尔勒841000

水资源是支撑国民经济发展的关键要素。塔里木河流域土地资源、光热资源丰富,具备发展现代农业的良好基础。但农业用水比重过大、用水结构不合理的问题长期制约经济社会高质量发展。基于此,文章从农田基本条件、基础设施、节水机制、管... 详细信息

水资源是支撑国民经济发展的关键要素。塔里木河流域土地资源、光热资源丰富,具备发展现代农业的良好基础。但农业用水比重过大、用水结构不合理的问题长期制约经济社会高质量发展。基于此,文章从农田基本条件、基础设施、节水机制、管理机制4个方面论述了流域当前农业水资源高效利用存在的问题,之后从体制机制、工程建设、科学研究、运行管理等方面就做好新时期流域农业高效节水提出了几点思考。研究成果对于全面构建流域农业节水体制机制,指导实现流域水利高质量发展提供了参考借鉴。

关键词：水资源农业节水体制机制高质量发展塔里木河流域

Fatou Components and Julia Sets of Singularly Perturbed Rational Maps with Positive Parameter

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2012年第10期28卷 1937-1954页

作者： Wei Yuan QIU Lan XIE yong cheng YIN School of Mathematical Sciences Fudan University

In this paper, we discuss the rational maps Fλ（z）=z^n＋λ/z^n,n≥2with the positive real parameter ）λ. It is shown that the immediately attracting basin Bλ of ∞ for Fλ is always a Jordan domain if the Julia set of Fλ is not a Cantor set. Fuhermore, Bλ is a quasidisk if there is no parabolic fixed point on the boundary of Bλ. It is also shown that if the Julia set of Fλ is connected, then it is locally connected and all Fatou components are Jordan domains. Finally, a complete description to the problem when the Julia set is a Sierpirlski curve is given.

关键词： Julia set Fatou component Jordan domain local connectivity Sierpifiski curve

在线全文

学校读者我要写书评

暂无评论

新疆渭干河流域下游水生态问题与对策研究

水利技术监督 2024年第7期 214-217页

作者：程勇李江张环魏光辉新疆塔里木河流域管理局新疆库尔勒841000

开展绿洲水生态治理是实现绿洲高质量发展的必然选择。文章针对新疆渭干河流域下游存在的绿洲耕地扩张显著,水资源供需矛盾加剧,土壤盐渍化危害,农田排水存在面源污染等问题。针对性地提出了以水而定,合理确定绿洲适宜规模,优化绿洲水... 详细信息

开展绿洲水生态治理是实现绿洲高质量发展的必然选择。文章针对新疆渭干河流域下游存在的绿洲耕地扩张显著,水资源供需矛盾加剧,土壤盐渍化危害,农田排水存在面源污染等问题。针对性地提出了以水而定,合理确定绿洲适宜规模,优化绿洲水土资源管理;减少人为活动对荒漠-绿洲过渡带的扰动,促进过渡带植被自然恢复;坚持节水优先,统筹好节水、蓄水、调水与增水;系统推进流域退化生态系统保护与修复,开展山水林田湖草沙冰综合治理;综合应用盐渍化生态修复措施5个方面的意见建议。研究成果对于指导流域水生态系统治理、促进经济社会生态良好发展提供了思路。

关键词：水资源水生态盐渍化渭干河流域

Double Ramification Cycles with Orbifold Targets

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2022年第8期38卷 1333-1376页

作者： Bo Hui CHEN cheng yong DU Rui WANG Department of Mathematics Sichuan UniversityChengdu 610064P.R.China School of Mathematical Sciences V.C.&V.R.Key Lab and Laurent Mathematics CenterSichuan Normal UniversityChengdu 610068P.R.China Department of Mathematics University of CaliforniaBerkeleyCA 94720-3840USA

In this paper,we consider double ramification cycles with orbifold *** explicit formula for double ramification cycles with orbifold targets,which is parallel to and generalizes the one known for the smooth case,is **... 详细信息

关键词： Root of orbifold line bundles polynomiality double ramification cycle absolute/relative orbifold Gromov–Witten theory

Sn-based Intermetallic Compounds for Li-ion Batteries: Structures, Lithiation Mechanism, and Electrochemical Performances

在线全文

学校读者我要写书评

暂无评论

Energy & Environmental Materials 2018年第3期1卷 132-147页

作者： Zheng Yi Zhaomin Wang yong cheng Limin Wang State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryCASChangchun 130022China Department of Chemistry University of Science and Technology of ChinaHefei 230026China Key Laboratory of Preparation and Application of Environmental Friendly Materials Jilin Normal UniversityChangchun 130103China

On account of the lower theoretical capacity of the traditional graphite,the development of reliable anode materials with high capacity and energy density for application in lithium-ion batteries(LIBs)is zealously pur... 详细信息

关键词： anode materials lithiation mechanism lithium-ion batteries review Sn

A strategy to control microstructures of a Ni-based superalloy during hot forging based on particle swarm optimization algorithm

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

Advances in Manufacturing 2019年第2期7卷 238-247页

作者： Dong-Dong Chen yong-cheng Lin Xiao-Min Chen School of Mechanical and Electrical Engineering Central South University Changsha 410083 People's Republic of China State Key Laboratory of High Performance Complex Manufacturing Changsha 410083 People's Republic of China College of Automotive and Mechanical Engineering Changsha University of Science and Technology Changsha 410114 People's Republic of China

In this study, a strategy based on the particle swarm optimization (PSO) algorithm is developed to control the microstructures of a Ni-based superalloy during hot forging. This strategy is composed of three parts, namely, material models, optimality criterions, and a PSO algo rithm. The material models are utilized to predict microstructure information, such as recrystallization volume fraction and average grain size. The optimality crite? non can be determined by the designed target microstructures and random errors. The developed strategy is resolved using the PSO algorithm, which is an intelligent optimal algorithm. This algorithm does not need a derivable objective function, which renders it suitable for dealing with the complex hot forging process of alloy components. The optimal processing parameters (deformation temperature and strain rate) are obtained by the developed strategy and validated by the hot forging experiments. Uniform and fine target microstructures can be obtained using the optimized processing parameters, which indicates that the developed strategy is effective for controlling the microstructural evolution during the hot forging of the studied superalloy.

关键词： Processing parameters Microstructure Particle swarm optimization (PSO) algorithm Superalloy