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Flat jet electrochemical milling of TC4 alloy with tailoring backward parallel flow

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Chinese Journal of Aeronautics 2024年第4期37卷 574-592页

作者： Huanghai KONG Ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool *** on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed ***, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.

关键词： Flat jet electrochemical milling TC4 alloy Surface roughness Micro-hardness Material removal rate

Pathways toward a pollution-free planet and challenges

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Frontiers of Environmental Science & Engineering 2024年第6期18卷 3-8页

作者： Jiuhui qu Jiaping Chen School of Environment Tsinghua UniversityBeijing 100084China College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518060China

The mission of“Establishment of Zero-Pollution Earth”defined by United Nations Environment Programme aims at creation of a clean,safe and prosperous home for all human *** is of rational choice from each individual to protect our environment and demonstrates our great ambition to achieve our *** key message given in this article is that,zero pollution does not mean no discharge of pollutants and instead it can be achievable through optimizing and controlling a sound balance between pollutants discharge and capacities of decontamination through treatment and natural environmental accumulation,which can be termed as“Principle of Equilibrium”between pollution and *** on this principle,we propose and illustrate several key factors and synergistic pathways toward a pollution-free planet:quantitative determination on purification and wastewater;source control through green measures;minimization of negative side-effects;precise management through digitalized systems;and keeping sound balance between pollutants and natural *** should be noted that we would face a series of difficulties and challenges in moving forward to“Zero-Pollution Earth”.We should further develop theories,principles and tools to achieve the balance between quantity of pollutants and decontamination *** should work together to break through the bottleneck limited by“Principle of equilibrium”to establish new environmental remediation systems leading to“Zero-Pollution Earth”.

关键词： Wastewater treatment Resources Recovery Greenhouse gases Energy Pollution-free

Design of a Passive Gait‑based Ankle‑foot Exoskeleton with Self‑adaptive Capability

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Chinese Journal of Mechanical Engineering 2020年第3期33卷 86-96页

作者： Xiangyang Wang Sheng Guo Bojian qu Majun Song Haibo qu Robotics Institute School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Key Laboratory of Vehicle Advanced Manufacturing Measuring and Control TechnologyMinistry of EducationBeijing Jiaotong UniversityBeijing 100044China School of Engineering Science KTH Royal Institute of Technology10044 StockholmSweden.

Propulsion during push-off is the key to realizing human *** have evolved a way of walking with high energy utilization,but it can be further *** inspiration from the muscle-tendon unit,a passive spring-actuated ankle-foot exoskeleton is designed to assist with human walking and to lengthen walking duration by mechanically enhancing walking *** of the gait events is realized using a smart clutch,which is designed to detect the contact states between the shoe sole and the ground,and automatically switch its working *** engagement of a suspended spring behind the human calf muscles is hence controlled and is in synchrony with *** device is completely passive and contains no external power *** is stored and returned passively using the *** our walking trials,the soleus electromyography activity is reduced by as much as 72.2%when the proposed ankle-foot exoskeleton is worn on the human *** influence of the exoskeleton on walking habits is also *** results show the potential use of the exoskeleton in humans’daily life.

关键词： Ankle-foot exoskeleton Energy cost Self-adaptiveness Human augmentation

In uence of Particle Size on Laser Absorption and Scanning Track Formation Mechanisms of Pure Tungsten Powder During Selective Laser Melting

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Engineering 2019年第4期5卷 736-745页

作者： jiayao Zhang Dongdong Gu Ying Yang Hongmei Zhang Hongyu Chen Donghuai Dai Kaijie Lin College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China Jiangsu Provincial Engineering Laboratory for Laser Additive Manufacturing of High-Performance Metallic Components Nanjing University of Aeronautics and AstronauticsNanjing 210016China

A three-dimensional laser absorption model based on ray tracing was established to describe the coupled interaction of a laser beam with particles in the powder layers of pure tungsten(W)material processed by selective laser melting(SLM).The influence of particle size on the powder-to-laser absorptivity and underlying absorption behavior was *** intrinsic relationship between the absorption,distribution of absorbed irradiance within the powder layers,and surface morphology and geometric characteristics(e.g.,contact angle,width and height of tracks,and remelted depth)of the laser scanning tracks is presented *** conclusions indicate that the absorptivity of the powder layers considerably exceeds the single powder particle value or the dense solid material *** an increase in particle size,the powder layer absorbs less laser *** maximum absorptivity of theWpowder layers reached 0.6030 at the particle size of 5 *** distribution of laser irradiance on the particle surface was sensitive to particle size,azimuthal angle,and the position of the powder particles on the *** maximum irradiance in the powder layers decreased from 1.117×10^–3 to 0.85×10^–3W·μm^-2 and the contour of the irradiance distribution in the center of the irradiated area gradually contracted when the particle size increased from 5 to 45 *** experimental study on the surface morphologies and cross-sectional geometric characteristics of SLM-fabricated W material was performed,and the experimental results validated the mechanisms of the powder-to-laser-absorption behavior that were obtained in *** work provides a scientific basis for the application of the ray-tracing model to predict the wetting and spreading ability of melted tracks during SLM additive manufacturing in order to yield a sound laser processability.

关键词： Selective laser melting(SLM) Tungsten Ray-tracing model Absorptivity Laser scanning tracks

Theoretical connection from the dielectric constant of films to the capacitance of capacitors under high temperature

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High Voltage 2023年第4期8卷 707-716页

作者： Yongxin Zhang Qikun Feng Shaolong Zhong jiayao Pei Fangyi Chen Lei Huang Zhe Yang Zhimin Dang Department of Electrical Engineering Tsinghua UniversityBeijingChina Department of Electrical and Computer Engineering Carnegie Mellon UniversityPittsburghPennsylvaniaUSA Department of Energy Technology Aalborg UniversityAalborgDenmark

In the process of coping with energy and environmental protection issues,technologies such as energy materials,energy devices,and energy systems have made great *** excellent performance,film capacitors play an increasingly important role in energyrelated *** the increase of application scenarios and the continuous development of film material technology,it is urgent to establish a better theoretical connection from films to ***,the main components of the capacitor including the film and the positional relationships among them are ***,from the two perspectives of indirect calculation according to the volume and the direct calculation according to the winding process,the equation between the dielectric constant of films and the corresponding capacitance of capacitors is ***,the measurement data and error analysis results of the built test platform prove the accuracy and great potential of the proposed calculation *** addition,error sources,including film thickness uniformity,are ***,the challenges faced by the proposed calculation methods and the paths that can be referenced for future research are summarised and discussed.

关键词： film dielectric capacitance

Additive manufacturing alumina components with lattice structures by digital light processing technique

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Journal of Materials Science & Technology 2019年第12期35卷 2751-2755页

作者： Qjngfeng Zeng Changhao Yang Dingyi Tang jiayao Li Zhiqiang Feng Jiantao Liu Kang Guan Science and Technology on Thermostructural Composite Materials Laboratory School of Materials Science and EngineeringNorthwestern Polytechnical University.Xi'an 710072China International Center for Materials Discovery School of Materials Science and EngineeringNorthwestern Polytechical UniversityXi'an 710072China MSEA International Institute for Materials Genome Gu'an065500China School of Mechanics and Engineering Southwest Jiaotong UniversityChengdu 610031China LMEE-UEVE Universiti Paris-SaclayEvry 91020France School of Mechanical Engineering Southwest Jiaotong UniversityChengdu 610031China School of Materials Science and Engineering South China University of TechnologyGuangzhou 510640China

Digital light processing technique was applied to manufacture alumina ceramic parts with two types of lattice structure units, i.e. vertex interconnect structure and edge structure. The internal porosity of the unit is 40%. The printed parts were sintered and the grain size is about 1.1 μm. The bending strength of the vertex interconnect structure is much larger than that of the edge structure. Materials genome initiative(MGI) aims to digital design and intelligent manufacture for advanced components. This research shows us an example to achieve this goal.

关键词： Additive manufacturing Ceramics DLP Lattice structure

Total Nitrogen and Total Phosphorus Pollution Reshaped the Relationship Between Water Supply and Demand in the Huaihe River Watershed, China

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Chinese Geographical Science 2023年第3期33卷 512-530页

作者： LU Yan LIU Lyuyi QIN Fen WANG jiayao LIU Jianzhong LI Yingjie WAN Luwen School of Geoscience and Technology Zhengzhou UniversityZhengzhou 450001China Henan Provincial Academy of Eco-Environmental Sciences Zhengzhou 450003China Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions Ministry of EducationHenan UniversityKaifeng 475000China Henan Industrial Technology Academy of Spatio-Temporal Big Data Henan UniversityKaifeng 475000China College of Geography and Environmental Science Henan UniversityKaifeng 475000China Environmental Science and Policy Program Michigan State UniversityEast LansingMI 48824USA

As total nitrogen(TN)and total phosphorus(TP)pollution is the main source of water pollution in the Huaihe River watershed in China,it is important to understand how TN and TP pollution affect the relationship between water supply and *** their impacts and describing the spatiotemporal distribution of these relationships are necessary for furtherly deepening the theory of TN and TP pollution on water bodies,and this information is also particularly essential for managing water resources *** this study,based on the potential water supply,the water demand and the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)water purification models,we estimated the TN and TP pollution from agricultural fertilizer,livestock and poultry breeding,and rural residents in the Huaihe River watershed and simulated TN and TP impacts on the relationship between water supply and *** found that if the impact of TN and TP pollution on water supply was not taken into account,on average,there was excess water supply in 79.20%of the watershed and excess demand in 20.80%of the rest during 1980–*** the TN concentration limit,Grade-Ⅱ(The water quality meets the secondary level of water body qualified in GB3838–2002,classified as Grade-II)water was the main watersupply type in 1980–2018,followed by Grade-Ⅰ and Grade-Ⅲ *** total water shortage showed an inverted V-shaped trend:first increasing and then decreasing at the same *** proportion of the water shortage of Grade-I water in the total water shortage was the largest,followed by Grade-Ⅱ and Grade-III *** with excess demand were located on the north bank of Wang-Beng,Yishuhe,and Huxi regions,although the water in these sub-watersheds met the water quality standards of Grade-Ⅰ *** the TP concentration limit,Grade-Ⅱ and Grade-Ⅰ water were the main water-supply *** overall water shortage trend first increased and then decreased,exhibiting an inverted V-shape from

关键词： watershed breeding poultry

Inclusion Size Effect on Mechanical Properties of Particle Hydrogel Composite

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Acta Mechanica Solida Sinica 2019年第5期32卷 643-651页

作者： Xiaocheng Hu Shaoxing qu State Key Laboratory of Fluid Power and Mechatronic System Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceDepartment of Engineering Mechanics38 Zheda RoadHangzhou 310027China

Particle hydrogel composite(PHC)combines the characteristics of at least two mat erials and has pot ential applications in many *** functions require the particle size to range from nanometer to millimeter,which has a noticeable effect on the mechanical properties of the hydrogel *** this paper,the mechanical properties of silica-inlaid PAAM hydrogel are measured with various particle diameters from 75 nm to 50|*** results show no obvious size effect on the mechanical properties of PHC when the particle diameter falls in micron ***,as the particle size decreases to nanoscale,the modulus of the PHC begins to increase *** size-irrelevant moduli and stress fields of PHCs with random and uniform particle distributions under different loading conditions are obtained based on the finite element ***,the toughening mechanism and the failure of the PHC are *** size-irrelevant modulus of the PHC is also predicted by the equivalent inclusion ***,the interaction between the hydrogel polymer chains and the particles is described from the microscopic point of view,requiring the nanoscale size-dependent theory and new experimental approach to further explore the mechanical proper ties of PHC.

关键词： Particle hydrogel composite Size effect Finite element method

Stochastic Iterative Learning Control With Faded Signals

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IEEE/CAA Journal of Automatica Sinica 2019年第5期6卷 1196-1208页

作者： Ganggui qu Dong Shen the College of Information Science and Technology Beijing University of Chemical TechnologyBeijing 100029China

Stochastic iterative learning control(ILC) is designed for solving the tracking problem of stochastic linear systems through fading channels. Consequently, the signals used in learning control algorithms are faded in the sense that a random variable is multiplied by the original signal. To achieve the tracking objective, a two-dimensional Kalman filtering method is used in this study to derive a learning gain matrix varying along both time and iteration axes. The learning gain matrix minimizes the trace of input error covariance. The asymptotic convergence of the generated input sequence to the desired input value is strictly proved in the mean-square sense. Both output and input fading are accounted for separately in turn, followed by a general formulation that both input and output fading *** examples are provided to verify the effectiveness of the proposed schemes.

关键词： Fading channels iterative learning control (ILC) Kalman filtering, mean-square convergence stochastic systems