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Global assessment of terrestrial productivity in response to water stress

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Science Bulletin 2024年第15期69卷 2352-2356页

作者： Qi Liu Huadong Guo Jiahua Zhang Shijie Li Ji Li Fengmei Yao Miguel D.Mahecha Jian Peng School of Computer Engineering Jiangsu University of TechnologyChangzhou 213001China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 101408China Department of Remote Sensing Helmholtz Centre for Environmental ResearchUFZLeipzig 04318Germany Remote Sensing Centre for Earth System Research Leipzig UniversityLeipzig 04103Germany Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094China Remote Sensing and digital Earth Center School of Computer Science and TechnologyQingdao UniversityQingdao 266071China key laboratory of Earth Observation of Hainan Province Hainan Aerospace Information Research InstituteChinese Academy of SciencesSanya 572000China School of Geographical Sciences Nanjing University of Information Science and TechnologyNanjing 210044China key laboratory of Water Cycle and Related Land Surface Processes Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China German Centre for Integrative Biodiversity Research(iDiv) Halle-Jena-Leipzig 04103Germany

In recent decades, climate warming has led to an increase in atmospheric water demand, a potential reduction in soil moisture and a rise in the frequency and intensity of droughts. This has intensified the effects of water stress on plants, leading to more vegetated areas experiencing water stress [1,2]. Soil moisture (SM)and vapor pressure deficit (VPD) are considered the two main factors that exert water stress on vegetation activity and terrestrial productivity, thereby affecting the global carbon cycle [3].

关键词： soil moisture terrestrial

Quantitative study on interactions between interfacial misfit dislocation networks and matrix dislocations in Ni-based single crystal superalloys

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Acta Mechanica Solida Sinica 2017年第4期30卷 345-353页

作者： Jun Xiong Yaxin Zhu Zhenhuan Li Minsheng Huang Department of Mechanics Huazhong University of Science and Technology State key laboratory of digital manufacturing Equipment and technology Huazhong University of Science and Technology Hubei key laboratory of Engineering Structural Analysis and Safety Assessment

The interactions between the moving dislocation within matrix channel and the interfacial misfit dislocation networks on the two-phase interfaces in Ni-based single crystal superalloys are studied carefully via atomic modeling, with special focus on the factors influ- encing the critical bowing stress of moving dislocations in the matrix channel. The results show that the moving matrix dislocation type and its position with respect to the interfacial misfit dislocation segments have considerable influences on the interactions. If the moving matrix dislocation is pure screw, it reacts with the interracial misfit dislocation segments toward dislocation linear energy reduction, which decreases the critical bowing stress of screw dislocation due to dislocation linear energy release during the dislocation reactions. If the moving matrix dislocation is of 60^-mixed type, it is obstructed by the interaction between the mixed matrix dislocations and the misfit interfacial dislocation segments. As a result, the critical bowing stress increases significantly because extra interactive energy needs to be overcome. These two different effects on the critical bowing stress become in- creasingly significant when the moving matrix dislocation is very close to the interracial misfit dislocation segments. In addition, the matrix channel width also has a significant influence on the critical bowing stress, i.e. the narrower the matrix channel is, the higher the critical bowing stress is. The classical Orowan formula is modified to predict these effects on the critical bowing stress of moving matrix dislocation, which is in good agreement with the computational results.

关键词： Dislocation interaction Misfit dislocation networks Molecular dynamics Matrix dislocation Ni-based single crystal superalloys

Tensile Properties and Wear Resistance of Mg Alloy Containing High Si as Implant Materials

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Journal of Renewable Materials 2023年第4期11卷 1977-1989页

作者： Mengqi Cong Yang Zhang Yunlong Zhang Xiao Liu Yalin Lu Xiaoping Li key laboratory of Advanced Materials Design and Additive manufacturing of Jiangsu Province Jiangsu University of TechnologyChangzhou213001China

Magnesium alloy has been considered as one of the third-generation biomaterials for the regeneration and support of functional bone *** a regeneration implant material with great potential applications,in-situ Mg_(2)Si phase reinforced Mg-6Zn cast alloy was comprehensively studied and expected to possess excellent mechanical properties via the refining and modifying of Mg_(2)Si *** present study demonstrates that the primary and eutectic Mg_(2)Si phase can be greatly modified by the yttrium(Y)*** size of the primary Mg_(2)Si phases can be reduced to~20μm with an addition of 0.5 wt.%*** phenomenon is mainly attributed to the poisoning effect of the Y ***,wear resistance and tensile properties of the ternary alloy have also been improved by the Y ***-6Zn-4Si-0.5Y alloy exhibits optimal tensile properties and wears *** ultimate tensile strength and the elongation of the alloy with 0.5 wt.%Y are 50%and 65%higher than those of the ternary alloy,*** Y addition(1.0 wt.%)deteriorates the tensile properties of Mg-Zn-Si *** improvement of the tensile properties is mainly due to the modification of primary and eutectic Mg_(2)Si phases as well as the solid solution strengthening of the Y *** study provides a certain implication for the application of Mg-Zn-Si alloys containing Y elements as regeneration implants.

关键词： Magnesium alloys Mg2Si phase microstructure regeneration mechanical properties

IBEA-SVM: An Indicator-based Evolutionary Algorithm Based on Pre-selection with Classification Guided by SVM

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Applied Mathematics(A Journal of Chinese Universities) 2019年第1期34卷 1-26页

作者： LI Hao-ran HE Fa-zhi YAN Xiao-hu School of Computer Science and technology Wuhan University State key laboratory of digital manufacturing Equipment and technology Huazhong University

Multi-objective optimization has many important applications and becomes a challenging issue in applied science. In typical multi-objective optimization algorithms, such as Indicator-based Evolutionary Algorithm(IBEA), all of parents and offspring need to be evaluated in every generation, and then the better solutions of them are selected as the next generation candidates. This leads to a large amount of calculation and slows down convergence rate for IBEA related applications. Our discovery is that the evaluation of evolutionary algorithm is a binary classi?cation in nature and a meaningful preselection method will accelerate the convergence rate. Therefore this paper presents a novel preselection approach to improve the performance of the IBEA, in which a SVM(Support Vector Machine) classi?er is adopted to sort the promising solutions from unpromising solutions and then the newly generated solutions are conversely added as train sample to increase the accuracy of the classi?er. Firstly, we proposed an online and asynchronous training method for SVM model with empirical kernel. The initial population is randomly generated among population size, which is used as initial training. In the process of training, SVM classi?er is modi?ed and perfected to adapt to the evolutionary algorithm sample. Secondly, the classi?er divides all the new generated solutions from the whole solution spaces into promising solutions and unpromising ones. And only the promising ones are forwarded for evaluation. In this way, the evaluation time can be greatly reduced and the solution quality can be obviously improved. Thirdly, the promising and unpromising solutions are labeled as new train samples in next generation to re?ne classi?er model. A number of experiments on benchmark functions validates the proposed approach. The results show that IBEA-SVM can signi?cantly outperform previous works.

关键词： multi-objective optimization SVM IBEA training classification

Experimental study of laser lift-off of ultra-thin polyimide film for flexible electronics

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Science China(Technological Sciences) 2019年第2期62卷 233-242页

作者： BIAN Jing ZHOU LaoBoYang WAN XiaoDong LIU MinXiao ZHU Chen HUANG YongAn YIN ZhouPing State key laboratory of digital manufacturing Equipment and technology Huazhong University of Science and Technology Flexible Electronics Research Center Huazhong University of Science and Technology

It is increasingly crucial for flexible electronics to efficiently and reliably peel large-area, ultra-thin flexible films off from rigid substrate serving as substrates of flexible electronics device, especially in industrial production. This paper experimentally investigated the mechanism and technologic characteristics of laser lift-off(LLO) process of ultra-thin(～ 2 μm) polyimide(PI)film. It was found increasingly difficult to obtain desirable ultra-thin PI film by LLO with the decrease of the film thickness. The optimal process parameters were achieved considering laser fluence and accumulated irradiation times(AIT), which were found to be strongly correlative to the thickness of PI film. The process mechanism of LLO of PI film was disclosed that laser ablation of interfacial PI will result in the formation of gas products between the PI and glass substrate, enabling the change of interface microstructures to reduce the interface bond strength. The amount of gas products mainly determines the result of LLO process for ultra-thin PI film, from residual adhesion to wrinkles or cracking. The strategy of multi-scanning based on multiple irradiations of low-energy laser pulses was presented to effectively achieve a reliable LLO process of ultra-thin PI film. This study provides an attractive route to optimize the LLO process for large-scale production of ultra-thin flexible electronics.

关键词： laser lift-off interfacial peeling delamination flexible electronics thin film

Thermal and tilt effects on bearing characteristics of hydrostatic oil pad in rotary table

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Journal of Hydrodynamics 2016年第4期28卷 585-595页

作者：刘志峰湛承鹏程强赵永胜李小燕王义达 College of Mechanical Engineering and Applied Electronics technology Beijing University of Technology State key laboratory of digital manufacturing Equipment and technology Huazhong University of Science and Technology

Hydrostatic pads are key components of a constant flow compensation hydrostatic rotary table. The tilt and thermal effects due to the partial load, the manufacturing errors and the friction must be considered. However, designers are more likely inclined to ignore these effects. In this work, the coupled characteristics of the tilt and thermal effects are studied. A coupled mathematical model to calculate the bearing properties of the pads is built. This model takes into consideration of tilt and thermal effects and is used to solve the flow problem by the finite difference method. The characteristics of the oil pad, including, the recess pressures, the load carrying capacity and the damping coefficients, are obtained and the tilt and thermal effects are analyzed. It is observed that the tilt has a tremendous impact on the bearing characteristics of the hydrostatic pad. The recess pressure, the load carrying capacity and the stiffness are reduced by 50% and the pressure distribution and the temperature distribution of the oil film also change significantly. When the pads work under a tilt operation, a larger land width is better for its bearing properties. It is also observed that the thermal effect is significant and cannot be ignored.

关键词： thermo-hydrodynamic lubricant tilting Reynolds equations constant flow compensation

Real-time adaptive particle image velocimetry for accurate unsteady flow field measurements

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Science China(Technological Sciences) 2022年第9期65卷 2143-2155页

作者： OUYANG ZhenXing YANG Hua LU Jin HUANG YongAn YIN ZhouPing State key laboratory of digital manufacturing Equipment and technology School of Mechanical Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Almost all conventional open-loop particle image velocimetry(PIV) methods employ fixed-interval-time optical imaging technology and the time-consuming cross-correlation-based PIV measurement algorithm to calculate the velocity *** this study,a novel real-time adaptive particle image velocity(RTA-PIV) method is proposed to accurately measure the instantaneous velocity field of an unsteady flow *** the proposed closed-loop RTA-PIV method,a new correlation-filter-based PIV measurement algorithm is introduced to calculate the velocity field in real ***,a Kalman predictor model is established to predict the velocity of the next time instant and a suitable interval time can be *** adaptively adjust the interval time for capturing two particle images,a new high-speed frame-straddling vision system is developed for the proposed RTA-PIV *** fully analyze the performance of the RTA-PIV method,we conducted a series of numerical experiments on ground-truth image pairs and on real-world image sequences.

关键词： real-time adaptive particle image velocimetry flow field measurement high-speed vision correlation filter

Robotic cluster machining:manufacturing revolution for large and complex components

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Science China(Technological Sciences) 2022年第9期65卷 2215-2217页

作者： TAO Bo GONG ZeYu &DING Han State key laboratory of digital manufacturing Equipment and technology Huazhong University of Science and TechnologyWuhan 430074China

Large complex components, such as aircraft skins, aerospace hulls, ship and high-speed train shells, are key components for aviation, aerospace, marine and transportation *** high-efficiency and high-quality manufacturing of these products is not only a major need for industry, but also a frontier hotspot in the field of intelligent manufacturing.

关键词： frontier cluster aviation

An on-line tool path smoothing algorithm for 6R robot manipulator with geometric and dynamic constraints

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Science China(Technological Sciences) 2021年第9期64卷 1907-1919页

作者： SUN HongWei YANG JiXiang LI DingWei DING Han School of Mechanical Science and Engineering State Key Laboratory of Digital Manufacturing Equipment and TechnologyHuazhong University of Science and TechnologyWuhan 430074China

The tool path smoothness of the industrial robot directly influences the dynamic performance of its motion control. Therefore, it is important to smooth the path that is composed of small linear segments, in order to achieve continuous and smooth *** paper uses the FIR filter interpolation method to generate the smooth tool tip position and tool orientation trajectory for robot manipulators with 6 rotational(6R) joints. The geometric smoothness and motion interpolation are achieved in one *** maximum velocity and acceleration of joints are constrained when calculating the time parameters of the FIR filter. By specially designing the overlapping time at transition corners, the tool tip position and tool orientation deviations are all constrained in the workpiece coordinate system. Considering the complexity of the inverse kinematics of the robot, in order to constrain the velocity and acceleration of robot joints, this paper proposes a simplified method which directly establishes the relationship between joint motion and tool motion through the derivative of joint motion to tool motion without considering the inverse kinematics. Simulation and experiment results show that the algorithm can generate continuous acceleration commands of the tool tip position and tool orientation within the corner error tolerance. The preset velocity and acceleration limitations of six joints are all constrained well. Comparisons with existing algorithms demonstrate advantages of the proposed method.

关键词： robots tool path corner smooth FIR filter kinematics