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A comprehensive research on wear resistance of GH4169 superalloy in longitudinal-torsional ultrasonic vibration side milling with tool wear and surface quality

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Chinese Journal of Aeronautics 2024年第4期37卷 556-573页

作者： Baoqi CHANG Zhaoxi YI Fen ZHANG Lian DUAN Ji-an DUAN School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China State Key Laboratory of High Performance and Complex Manufacturing Central South UniversityChangsha 410083China School of Physics and Electronics Central South UniversityChangsha 410083China

To improve the service and machining performance of the workpiece, the tool wear mechanisms, surface machining quality, and wear resistance in conventional side milling(CSM)and longitudinal-torsional ultrasonic vibration side milling(LTUVSM) of GH4169 superalloy at different cutting lengths are investigated systematically. Tool wear mechanisms are revealed and the correlation between machined surface quality with tool wear is analyzed correspondingly. Tool wear patterns mainly include adhesive wear, diffusion wear, abrasive wear, and chipping *** surface quality is achieved in LTUVSM due to a maximum reduction of flank wear bandwidth and wear rate by 71.9% and 71.5%, respectively, compared to CSM. The friction coefficient,initial wear stage time, and wear volume of dry sliding wear were measured to evaluate the workpiece wear resistance. The maximum reductions in friction coefficient and wear volume in LTUVSM are 18.2% and 15.8% compared to CSM. The regular ultrasonic vibration textures suppress the friction and the growth of contact nodes in the contact area, decreasing the degree of surface wear, which is demonstrated by a 38.8% increase in initial wear stage time compared to *** conclusion, the workpiece in LTUVSM exhibits higher wear resistance because of the improvement of tool wear and the guarantee of surface quality.

关键词： Dry sliding wear Surface quality Tool wear Ultrasonic vibration Wear resistance

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Pore opening and binder flow during initial stage of thermal debinding in MIM

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中国有色金属学会会刊：英文版 2003年第5期13卷 1194-1198页

作者：赵利刚李益民 State Key Laboratory for Powder Metallurgy Central South University Changsha 410083China State Key Laboratory for Powder Metallurgy Central South University Changsha 410083ChinaHunan Injection Hi Tech Ltd Changsha 410083China

Pore opening and binder flow during the initial stage of thermal debinding in metal injection molded parts was investigated. Scaning electron microscopy(SEM) pictures of 316 L stainless steel parts using wax based binder show that small particles will move to the surface with the process of debinding. SEM pictures of different mass loss rate specimens indicate that initial pores will emerge when as little as 4% binder removes. During the initial stage of thermal debinding, vapor tension varies in different place due to the difference of curvature. Thus more binders will be removed in places with smaller cavity between metal powders, and in these places small openings emerge.

关键词：金属注射成型热结合胶结剂流动注模成型

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Phase decomposition behavior and its effects on mechanical properties of TiNbTa0.5ZrAl0.5 refractory high entropy alloy

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Journal of Materials Science & Technology 2021年第7期66卷 10-20页

作者： Yuankui Cao Weidong Zhang Bin Liu Yong Liu Meng Du Ao Fu State Key Lab of Powder Metallurgy Central South UniversityChangsha410083China School of Materials Science and Engineering Hunan UniversityChangsha410083China

The mechanical properties of refractory high entropy alloys(RHEAs) strongly depend on their phase structures. In this work, the phase stability of a BCC TiNbTa0.5ZrAl0.5 refractory high entropy alloy subjected to thermomechanical processing was evaluated, and the effects of phase decomposition on room/high temperature mechanical properties were quantitatively studied. It was found that, the thermomechanical processing at 800℃and 1200℃ leads to phase decomposition in the TiNbTa0.5ZrAl0.5 alloy. The phase decomposition is caused by the rapid rising of free energy of the primary BCC phase. The effect of the precipitates on room temperature strength is determined by the competition between the increasing in precipitation strengthening and the decreasing in solid solution strengthening. But at high temperatures(800-1200℃), the phase decomposition causes significant reduction in strength, mainly due to the grain boundary sliding and the decreasing in solid solution strengthening.

关键词： High entropy alloy Thermomechanical processing Precipitation Mechanical property Strengthening mechanism

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The impact of political connections on firm pollution: New evidence based on heterogeneous environmental regulation

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Petroleum Science 2023年第1期20卷 636-647页

作者： Zong-Run Wang Hai-Qin Fu Xiao-Hang Ren School of Business Central South UniversityChangsha410083China

Increasing attention has been focused on the extent to which corporate political connections influence the growing pollution due to the rapid growth in the popularity of firm pollution in developing *** adopt a static threshold regression model to investigate the effects of heterogeneous environmental regulation on political connections and firm pollution based on the panel data from China’s A-share listed companies from 2012 to *** empirical results show a non-linear relationship between the degree of political connection of listed company executives and the level of firm *** the relationship between the two roughly presents a U-shaped relationship under the action of the marketincentive environmental regulation ***,it roughly presents an inverted N-shaped relationship under the action of the command-control environmental regulation ***,the group test results show that the existence of regional and ownership heterogeneity causes certain differences in the environmental behaviour of politically connected *** findings indicate that diverse environmental regulations are needed to promote sustainable green development and to further expand the theoretical and practical exploration of political connections on firm pollution.

关键词： Political connections Firm pollution Market-incentive environmental regulation Command-control environmental regulation Threshold model

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Analytic optimal pose tracking control in close-range proximity operations with a non-cooperative target

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Chinese Journal of Aeronautics 2024年第5期37卷 410-425页

作者： Caisheng WEI Guanhua HUANG Zeyang YIN Qifeng CHEN School of Automation Central South UniversityChangsha 410083China

This paper investigates an analytical optimal pose tracking control problem for chaser spacecraft during the close-range proximity operations with a non-cooperative space target subject to attitude tumbling and unknown orbital ***,the relative translational motion between the orbital target and the chaser spacecraft is described in the Line-of-Sight(LOS)coordinate frame along with attitude quaternion ***,based on the coupled 6-Degree of Freedom(DOF)pose dynamic model,an analytical optimal control action consisting of constrained optimal control value,application time and its duration are proposed via exploring the iterative sequential action control ***,the global closed-loop asymptotic stability of the proposed predictive control action is presented and *** with traditional proximity control schemes,the highlighting advantages are that the application time and duration of the devised controller is applied discretely in light of the influence of the instantaneous pose configuration on the pose tracking performance with less energy consumptions rather than at each sample ***,three groups of illustrative examples are organized to validate the effectiveness of the proposed analytical optimal pose tracking control scheme.

关键词： Optimal control Close-range proximity operation Non-cooperative space target Coupled attitude and orbit control Iterative sequential action control

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Automatic Diabetic Retinopathy Screening via Cascaded Framework Based on Image- and Lesion-Level Features Fusion

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Journal of Computer Science & Technology 2019年第6期34卷 1307-1318页

作者： Cheng-Zhang Zhu Rong Hu Bei-Ji Zou Rong-Chang Zhao Chang-Long Chen Ya-Long Xiao College of Literature and Journalism Central South UniversityChangsha 410083China Hunan Province Engineering Technology Research Center of Computer Vision and Intelligent Medical Treatment changsha 410083 China School of Computer Science and Engineering Central South UniversityChangsha 410083China

The early detection of diabetic retinopathy is crucial for preventing ***,it is time-consuming to analyze fundus images manually,especially considering the increasing amount of medical *** this paper,we propose an automatic diabetic retinopathy screening method using color fundus *** approach consists of three main components:edge-guided candidate microaneurysms detection,candidates classification using mixed features,and diabetic retinopathy prediction using fused features of image level and lesion *** divide a screening task into two sub-classification tasks:(1)verifying candidate microaneurysms by a naive Bayes classifier;(2)predicting diabetic retinopathy using a support vector machine *** approach can effectively alleviate the imbalanced class distribution *** evaluate our method on two public databases:Lariboisière and Messidor,resulting in an area under the curve of 0.908 on Lariboisière and 0.832 on *** scores demonstrate the advantages of our approach over the existing methods.

关键词： diabetic retinopathy feature fusion microaneurysm naive Bayes support vector machine

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Formation of sulfur oxide groups by SO_(2) and their roles in mercury adsorption on carbon-based materials

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Journal of Environmental Sciences 2022年第9期34卷 44-49页

作者： Fenghua Shen Shudan He Junyuan Li Cao Liu Kaisong Xiang Hui Liu School of Metallurgy and Environment Central South UniversityChangsha 410083China Chinese National Engineering Research Center for Control&Treatment of Heavy Metal Pollution Changsha 410083China School of Chemistry and Chemical Engineering Central South UniversityChangsha 410083China

The presence of SO_(2) display significant effect on the mercury(Hg) adsorption ability of carbon-based sorbent. Yet the adsorption and oxidation of SO_(2) on carbon with oxygen group, as well as the roles of different sulfur oxide groups in Hg adsorption have heretofore been unclear. The formation of sulfur oxide groups by SO_(2) and their effects on Hg adsorption on carbon was detailed examined by the density functional theory. The results show that SO_(2) can be oxidized into SO_(2) by oxygen group on carbon surface. Both C-SO_(2) and C-SO_(2)can improve Hg adsorption on carbon site, while the promotive effect of C-SO_(2) is stronger than C-SO_(2). Electron density difference analyses reveal that sulfur oxide groups enhance the charge transfer ability of surface unsaturated carbon atom, thereby improving Hg adsorption. The experimental results confirm that surface active groups formed by SO_(2) adsorption is more active for Hg adsorption than the groups generated by SO_(2).

关键词： Sulfur dioxide Mercury Carbon sorbent Adsorption mechanism

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Inhibiting segregation enabled outstanding combination of mechanical and corrosion properties in precipitation-strengthened aluminum alloys

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Journal of Materials Science & Technology 2024年第12期179卷 240-250页

作者： Fang Li Geng Chen Sijun Chen Changjun Zhu Kanghua Chen Powder Metallurgy Research Institute Central South UniversityChangsha 410083China Light Alloy Research Institute Central South UniversityChangsha 410083China

Segregation of solutes to grain boundary(GB)is the dominant restriction on enhancement of mechanical properties and corrosion resistance during aging in precipitation-strengthened aluminum ***,we innovatively introduce the cyclic deformation by the vibration during aging to eliminate the GB segre-gation,resulting in the formation of the narrow precipitate-free zone(PFZ)widths near the GB,as well as the fine and discontinuous grain boundary precipitations(GBPs).Compared with the traditional peak-aging,the 2014 aluminum alloy treated by thermal cooperative vibration aging(TCVA)exhibits a superb combination of impact toughness and corrosion resistance,and retains the strength and *** ad-dition,the atomic simulations show that TCVA generates numerous vacancies near the GB,but does not change the dislocation density with the increase of cycle *** results indicate that the vacancy significantly promotes the nucleation and growth of precipitates in the vicinity of GB,resulting in the narrow PFZs and fine discontinuous *** present work provides the fundamental knowledge and method to inhibit the equilibrium segregation of solutes to GB during aging,and further realizes the precipitation-strengthened aluminum alloys with excellent mechanical and corrosion properties.

关键词： Precipitation-strengthened aluminum alloys Precipitate-free zone Grain boundary precipitation Mechanical properties Corrosion resistance

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Synthesis and electrochemical characterization of layered Li[Ni_(1/3)Co_(1/3)Mn_(1/3)]O_2 cathode materialfor Li-ion batteries

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中国有色金属学会会刊：英文版 2005年第6期15卷 1425-1428页

作者：禹筱元胡国荣彭忠东肖劲刘业翔 School of Chemistry and Chemical Engineering Central South University Changsha 410083 ChinaSchool of Metallurgical Science and Engineering Central South University Changsha 410083 China School of Metallurgical Science and Engineering Central South University Changsha 410083 China

Layered LiNi1/3Co1/3Mn1/3O2 materials were synthesized using a nickel-cobalt-manganese carbonate precursor obtained by chemical co-precipitation. The [Ni1/3Co1/3Mn1/3]CO3 precursor and the LiNi1/3Co1/3Mn1/3O2 powders were characterized by X-ray diffraction（XRD） and scanning electron micrograph（SEM）. The SEM analysis shows that these particles possess uniform and spherical morphology. The electrochemical properties of the (LiNi1/3-)(Co1/3Mn1/3O2) cathode material for rechargeable lithium-ion batteries such as the galvanostatic charge-discharge performance and cyclic voltammetry（CV） were measured. The results show that an initial discharge capacity of 190.29mA·h·g-1 is obtained in the voltage range of 2.54.6V and at a current rate of 0.1C at 25℃.The discharge capacity increases linearly with the increase of the upper cut-off voltage limit.

关键词：锂离子电池电极材料电化学性能合成分层结构

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A froth velocity measurement method based on improved U-Net++semantic segmentation in flotation process

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International Journal of Minerals,Metallurgy and Materials 2024年第8期31卷 1816-1827页

作者： Yiwei Chen Degang Xu Kun Wan School of Automation Central South UniversityChangsha 410083China

During flotation,the features of the froth image are highly correlated with the concentrate grade and the corresponding working *** static features such as color and size of the bubbles and the dynamic features such as velocity have obvious differences between different working *** extraction of these features is typically relied on the outcomes of image segmentation at the froth edge,making the segmentation of froth image the basis for studying its visual ***,the absence of scientifically reliable training data with label and the necessity to manually construct dataset and label make the study difficult in the mineral *** solve this problem,this paper constructs a tungsten concentrate froth image dataset,and proposes a data augmentation network based on Conditional Generative Adversarial Nets(cGAN)and a U-Net++-based edge segmentation *** performance of this algorithm is also evaluated and contrasted with other algorithms in this *** the results of semantic segmentation,a phase-correlationbased velocity extraction method is finally suggested.

关键词： froth flotation froth segmentation froth image data augmentation velocity extraction image features

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