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Precision glass molding： Toward an optimal fabrication of optical lenses

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Frontiers of Mechanical Engineering 2017年第1期12卷 3-17页

作者： Liangchi ZHANG weidong liu Laboratory for Precision and Nano Processing Technologies School ofMechanical and Manufacturing Engineering The University of NewSouth Wales Sydney NSW 2052 Australia

It is costly and time consuming to use machining processes, such as grinding, polishing and lapping, to produce optical glass lenses with complex features. Precision glass molding （PGM） has thus been developed to realize an efficient manufacture of such optical components in a single step. However, PGM faces various technical challenges. For example, a PGM process must be carded out within the super-cooled region of optical glass above its glass transition temperature, in which the material has an unstable non-equilibrium structure. Within a narrow window of allowable tempera- ture variation, the glass viscosity can change from 10s to 10t2 Pa-s due to the kinetic fragility of the super-cooled liquid. This makes a PGM process sensitive to its molding temperature. In addition, because of the structural relaxa- tion in this temperature window, the atomic structure that governs the material properties is strongly dependent on time and thermal history. Such complexity often leads to residual stresses and shape distortion in a lens molded, causing unexpected changes in density and refractive index. This review will discuss some of the central issues in PGM processes and provide a method based on a manufacturing chain consideration from mold material selection, property and deformation characterization of optical glass to process optimization. The realization of such optimization is a necessary step for the Industry 4.0 of PGM.

关键词： precision glass molding optical lens consti-tutive modeling optimization manufacturing chain Indus-try 4.0

Geometric Deviation Modeling by Kinematic Matrix Based on Lagrangian Coordinate

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Chinese Journal of Mechanical Engineering 2015年第5期28卷 1056-1066页

作者： liu weidong HU Yueming liu Yu DAI Wanyi Guangzhou Institute of Modern Industrial Technology South China University of Technology Engineering Research Centre for Precision Electronic Manufacturing Equipment Ministry of EducationSouth China University of Technology

Typical representation of dimension and geometric accuracy is limited to the self-representation of dimension and geometric deviation based on geometry variation thinking, yet the interactivity affection of geometric variation and gesture variation of multi-rigid body is not included. In this paper, a kinematic matrix model based on Lagrangian coordinate is introduced, with the purpose of unified model for geometric variation and gesture variation and their interactive and integrated analysis. Kinematic model with joint, local base and movable base is built. The ideal feature of functional geometry is treated as the base body; the fitting feature of functional geometry is treated as the adjacent movable body; the local base of the kinematic model is fixed onto the ideal geometry, and the movable base of the kinematic model is fixed onto the fitting geometry. Furthermore, the geometric deviation is treated as relative location or rotation variation between the movable base and the local base, and it＇s expressed by the Lagrangian coordinate. Moreover, kinematic matrix based on Lagrangian coordinate for different types of geometry tolerance zones is constructed, and total freedom for each kinematic model is discussed. Finally, the Lagrangian coordinate library, kinematic matrix library for geometric deviation modeling is illustrated, and an example of block and piston fits is introduced. Dimension and geometric tolerances of the shaft and hole fitting feature are constructed by kinematic matrix and Lagrangian coordinate, and the results indicate that the proposed kinematic matrix is capable and robust in dimension and geometric tolerances modeling.

关键词： geometry deviation geometry deviation representation kinematic matrix Lagrangian coordinate virtual joint

Does the Belt and Road Initiative Promote Value Chain Connection Between China and the Silk Road Countries?

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Chinese Geographical Science 2021年第6期31卷 979-995页

作者： ZHENG Zhi liu weidong SONG Zhouying Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing100101China Key Laboratory of Regional Sustainable Development Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing100049China

The global value chains have become the core skeleton of the global *** a large-scale international cooperation initiative,the Belt and Road Initiative(BRI hereafter)may have a significant impact on the global economic *** this context,the spatiotemporal pattern and evolution of the value chain connection of the Silk Road countries and whether the BRI will promote the value chain connections between China and these countries are important research questions for understanding the changing global economic *** paper employs input-output analysis,network analysis and difference-in-differences based on Propensity Score Matching(PSM-DID)to conduct an in-depth quantitative study of these *** results show that,first,the overall value chain connection between China and the Silk Road countries has been rising since *** the perspective of geographical distribution,Southeast Asia is the highest value chain connection region with China,and the growth in the central and eastern Europe is the most significant,whereas the central Asia is the lowest value connection *** the perspective of complex network analysis,China’s position in the network of value flow among the Silk Road countries has been increasing continuously,and it has been in the lead position since ***,the implementation of the BRI has had a significant positive influence on the overall value chain connection between China and the Silk Road countries,but this positive influence is limited to the central and eastern Europe region,whereas it is not significant in other ***,this paper suggests that to promote the development of value chain connection,the Silk Road countries need to develop more specific policies related to value *** need to be able to correctly identify the comparative advantages of the region and the types of value chains that are compatible with them and then find suitable partners and formulate targeted promotion po

关键词： the Belt and Road Initiative global value chains input-output technique pattern evolution network analysis difference-in-differences based on Propensity Score Matching(PSM-DID)

Pathways to peak carbon emissions in China by 2030: An analysis in relation to the economic growth rate

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Science China Earth Sciences 2022年第6期65卷 1057-1072页

作者： weidong liu Wanbei JIANG Zhipeng TANG Mengyao HAN Key Laboratory of Regional Sustainable Development Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China

With less than ten years left to meet its pledge to peak carbon dioxide emissions(peak emissions hereafter) by 2030,China has entered a critical emissions reduction stage. How to meet this commitment in a context in which GDP per capita will double from 2020 by 2035 is a major decision-making issue for the Chinese government and people and one which warrants further study. To reveal the relationships between the GDP growth rate, the rate of decrease of carbon intensity and the time to reach peak emissions, this study translates the question as to “when China's carbon emissions peak will occur” into “how can one control the rate of carbon intensity decrease at a given GDP growth rate”. In the light of the results of a random forest algorithm used to identify and project the key drivers of carbon intensity in China, a mathematical model was developed to simulate different scenarios relating to decreases in carbon intensity. The date at which Chinese carbon emissions will peak is predicted by comparing the rate of decrease of carbon intensity with the GDP growth rate. The results show that the time to peak emissions depends on the relationship between the rate of decrease of carbon intensity and the GDP growth rate, where the former depends mainly on the energy structure and policy. If China's annual GDP growth rate were 5.0% during the 15th Five-Year Plan, and if the share of non-fossil energy in total energy consumption were 23.0% or above, China's carbon emissions will peak before2030. If the share of non-fossil fuels were 20.0% or less, China might not be able to reach its 2030 target. In this latter case an acceleration in the pace of energy restructuring would be required to reach peak emissions before 2030. The projected peak emissions scenarios suggest that the carbon peak will occur between 2025 to 2029, with average peak emissions of 11.2 billion tons and a distribution ranging from a minimum of 10.5 billion and a maximum of 11.9 billion tons. If the GDP grow

关键词： Carbon emissions Carbon emissions peak Carbon intensity Energy structure GDP growth rate

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Robust reduced rank regression in a distributed setting

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Science China Mathematics 2022年第8期65卷 1707-1730页

作者： Xi Chen weidong liu Xiaojun Mao Stern School of Business New York UniversityNew YorkNY 10012USA School of Mathematical Sciences and MoE Key Lab of Artificial Intelligence Shanghai Jiao Tong UniversityShanghai 200240China School of Data Science Fudan UniversityShanghai 200433China

This paper studies the reduced rank regression problem,which assumes a low-rank structure of the coefficient matrix,together with heavy-tailed *** address the heavy-tailed noise,we adopt the quantile loss function instead of commonly used squared ***,the non-smooth quantile loss brings new challenges to both the computation and development of statistical properties,especially when the data are large in size and distributed across different *** this end,we first transform the response variable and reformulate the problem into a trace-norm regularized least-square problem,which greatly facilitates the *** on this formulation,we further develop a distributed ***,we establish the convergence rate of the obtained estimator and the theoretical guarantee for rank *** simulation analysis is provided to demonstrate the effectiveness of our method.

关键词： reduced rank regression distributed estimation quantile loss rank recovery

Acoustic Emission Recognition Based on a Two-Streams Convolutional Neural Network

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Computers, Materials & Continua 2020年第7期64卷 515-525页

作者： Weibo Yang weidong liu Jinming liu Mingyang Zhang School of Information and Communication Engineering Nanjing Institute of TechnologyNanjing211167China School of Information and Control Engineering China University of Mining and TechnologyXuzhou221000China School of Information Science and Engineering Southeast UniversityNanjing211100China Department of Electrical and Computer Engineering National University of Singapore119077Singapore

The Convolutional Neural Network(CNN)is a widely used deep neural *** with the shallow neural network,the CNN network has better performance and faster computing in some image recognition *** can effectively avoid the problem that network training falls into local *** present,CNN has been applied in many different fields,including fault diagnosis,and it has improved the level and efficiency of fault *** this paper,a two-streams convolutional neural network(TCNN)model is *** on the short-time Fourier transform(STFT)spectral and Mel Frequency Cepstrum Coefficient(MFCC)input characteristics of two-streams acoustic emission(AE)signals,an AE signal processing and classification system is constructed and compared with the traditional recognition methods of AE signals and traditional CNN *** experimental results illustrate the effectiveness of the proposed *** with single-stream convolutional neural network and a simple Long Short-Term Memory(LSTM)network,the performance of TCNN which combines spatial and temporal features is greatly improved,and the accuracy rate can reach 100%on the current database,which is 12%higher than that of single-stream neural network.

关键词： Convolutional neural network acoustic emission fault detection

Analysis of the Flow Rate Characteristics of Valveless Piezoelectric Pump with Fractal-like Y-shape Branching Tubes

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Chinese Journal of Mechanical Engineering 2014年第3期27卷 628-634页

作者： HUANG Jun ZHANG Jianhui WANG Shouyin liu weidong State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences

Microchannel heat sink with high heat transfer coefficients has been extensively investigated due to its wide application prospective in electronic cooling. However, this cooling system requires a separate pump to drive the fluid transfer, which is uneasy to minimize and reduces their reliability and applicability of the whole system. In order to avoid these problems, valveless piezoelectric pump with fractal-like Y-shape branching tubes is proposed. Fractal-like Y-shape branching tube used in microchannel heat sinks is exploited as no-moving-part valve of the valveless piezoelectric pump. In order to obtain flow characteristics of the pump, the relationship between tube structure and flow rate of the pump is studied. Specifically, the flow resistances of fractal-like Y-shape branching tubes and flow rate of the pump are analyzed by using fractal theory. Then, finite element software is employed to simulate the flow field of the tube, and the relationships between pressure drop and flow rate along merging and dividing flows are obtained. Finally, valveless piezoelectric pumps with fractal-like Y-shape branching tubes with different fractal dimensions of diameter distribution are fabricated, and flow rate experiment is conducted. The experimental results show that the flow rate of the pump increases with the rise of fractal dimension of the tube diameter. When fractal dimension is 3, the maximum flow rate of the valveless pump is 29.16 mL/min under 100 V peak to peak （13 Hz） power supply, which reveals the relationship between flow rate and fractal dimensions of tube diameter distribution. This paper investigates the flow characteristics of valveless piezoelectric pump with fractal-like Y-shape branching tubes, which provides certain references for valveless piezoelectric pump with fractal-like Y-shape branching tubes in application on electronic chip cooling.

关键词： piezoelectric pump valveless fractal-like Y-shape branching tube

Theorizing Belt and Road construction mode from institutional and cultural perspectives

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Journal of Geographical Sciences 2021年第5期31卷 623-640页

作者： liu weidong YAO Qiuhui Key Laboratory of Regional Sustainable Development Modeling Institute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China

There is a gap between the great vision and high-quality targets of the Belt and Road Initiative(BRI) and Western recognition of them, which challenges Chinese and Western scholars. This gap should be narrowed by conducting in-depth case studies and comparative studies at the project level. In recent years, the international academic community has paid increasing attention to Chinese outward foreign direct investment(FDI), but Belt and Road construction is much broader in scope, comprising not only FDI projects but also China-financed projects and emerging mixed projects. Our investigation, observation, and examination of the BRI projects find that compared to their Western counterparts, Chinese enterprises have less experience in doing business in other countries and often pay less attention to institutional and cultural differences between China and the host countries. Thus, revisiting the institutional and cultural turn in economic geography and employing its ideas to analyze the BRI projects and summarize their construction modes may contribute to the development of both economic geography and the BRI. This paper first briefly reviews the background and research trends of the institutional and cultural turn and then summarizes three major modes of Belt and Road construction, namely, EPC(Engineering Procurement Construction)-based projects, concession-based projects, and FDI;finally, it draws on the institutional and cultural turn to classify the BRI projects according to the two indicators of "Breadth and Depth of Territorial Embeddedness" and "Destructive Effect of a Project and/or Technology" into four types: transformative, supportive, ordinary projects and overseas industrial cooperation parks. Different institutional and cultural sensitivity can be observed for each type of project. The preliminary theorization proposed in this paper may offer a potential framework for further research on the BRI.

关键词： Belt and Road Initiative institutional and cultural difference financing structure high-quality development territorial embeddedness

Phase Structure and Electrochemical Properties of Rare Earth Based Hydrogen Storage Alloys

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Journal of Rare Earths 2004年第z1期22卷 228-231页

作者： Chen weidong liu Xiangdong liu Xiao Che Guangdong School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China School of Material Science and Technology Inner Mongolia University of Technology Huhhot 010062 China

The rare earth based hydrogen storage alloys MmxM1 1 - x ( Ni3.55 Co0.75 Mn0.4 A10.3 ) ( x = 0 ～ 0.5 ) were investigated in this *** Ml: Mm ratio to change the content of La,Ce,Pr and Nd in the alloys and then to change the phase structure, the influences of phase structure on the electrochemical properties were *** results indicate that the main phase of all alloys is LaNi5 with CaCu5 type structure and the crystal lattices constants of LaNi5 are changed with increasing x value, i.e, decreased a-axis, increased c-axis and axis ratio and nonlinear decreased crystal *** crystal volume of the alloy with x = 0.3 is larger than *** is second phase A1LaNi4 in alloys when x≥0.3, which decrease the discharge capacity, but increase the cycling stability and high rate discharge *** comprehensively, the alloy with x = 0.3 shows the higher discharge capacity and the better cycling stability.

关键词： rare earth based hydrogen storage alloy phase structure activation discharge capacity cycling stability high rate discharge ability