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Analysis on phase selection and microstructure evolution in directionally solidified Zn-Al-Mg-Ce alloy

China Foundry 2023年第4期20卷 347-355页

作者： Ji-peng Li De-gao Qiao Shi-wen Dong peng peng Xian-tao Yan Xu-dong Zhang Gansu jiu Steel Group Hongxing Iron and Steel Co. Ltd.Jiayuguan 735199GansuChina School of Materials and Energy Lanzhou UniversityLanzhou 730000China School of Physics and Electronic Information Engineering Qinghai Normal UniversityXining 810016QinghaiChina

In the process of hot-dip Zn-Al-Mg alloy coating,the plating solution dissipates heat in the direction perpendicular to the steel plate,which is considered to be a process of directional solidification.To understand the relationship between microstructure and cooling rate of Zn-Al-Mg alloys,both the phase constitution and microstructure characteristic length scales of Zn-9.5Al-3Mg-0.01Ce(wt.%)alloy were investigated by the directional solidification experiments at different growth velocities(V=40,80,160,250μm·s^(-1)).The experimental results show that the microstructure of directionally solidified Zn-9.5Al-3Mg-0.01Ce alloy is composed of primary Al dendrites and(Zn-Al-Mg2Zn11)ternary eutectics at the growth velocities ranging from 40 to 250μm·s^(-1).The primary Al dendrites are aligned regularly along the growth direction,accompanied with obvious secondary dendrites.The relationship between the microstructure length scale and the thermal parameters of solidification is obtained:λ1=374.66V-0.383,andλ2=167.5V-0.563(λ1is the primary dendrite arm spacing,andλ2 is the secondary dendrit arm spacing).In addition,through the interface response function(IRF)and the nucleation and constitutional undercooling(NCU),the phase selection of Zn-9.5Al-3Mg-0.01Ce is obtained:(Zn+Al+Mg2Zn11)ternary eutectics in the Zn-9.5Al-3Mg-0.01Ce alloy will be replaced by ternary eutectics(Zn+Al+MgZn2)when the growth rate is lower than 7.53μm·s^(-1).

关键词： Zn-Al-Mg alloy directional solidification microstructure length scale phase selection

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Effects of cooling rate on microstructure and microhardness of directionally solidified Galvalume alloy

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China Foundry 2024年第3期21卷 213-220页

作者： Ji-peng Li De-gao Qiao jian li Xiao-yang Luo peng peng Xian-tao Yan Xu-dong Zhang Gansu jiu Steel Group Hongxing Iron and Steel Co. Ltd.Jiayuguan 735111GansuChina School of Materials and Energy Lanzhou UniversityLanzhou 730000China

The influences of cooling rate on the phase constitution,microstructural length scale,and microhardness of directionally solidified Galvalume(Zn-55Al-1.6Si)alloy were investigated by directional solidification experiments at different withdrawal speeds(5,10,20,50,100,200,and 400μm·s^(-1)).The results show that the microstructure of directionally solidified Galvalume alloys is composed of primary Al dendrites,Si-rich phase and(Zn-Al-Si)ternary eutectics at the withdrawal speed ranging from 5 to 400μm·s^(-1).As the withdrawal speed increases,the segregation of Si element intensifies,resulting in an increase in the area fraction of the Si-rich phase.In addition,the primary Al dendrites show significant refinement with an increase in the withdrawal speed.The relationship between the primary dendrite arm spacing(λ_(1))and the thermal parameters of solidification is obtained:λ_(1)=127.3V^(-0.31).Moreover,as the withdrawal speed increases from 5 to 400μm·s^(-1),the microhardness of the alloy increases from 90 HV to 151 HV.This is a combined effect of grain refinement and second-phase strengthening.

关键词： Galvalume alloy directional solidification microstructure length scale microhardness

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Changes in axial length after vitrectomy for rhegmatogenous retinal detachment combined with choroidal detachment

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International Journal of Ophthalmology(English edition) 2022年第8期15卷 1290-1295页

作者： Ji-peng Li Jun Xu Meng Zhao Beijing Tongren Eye Center Beijing Key Laboratory of Ophthalmology and Visual ScienceBeijing Tongren HospitalCapital Medical UniversityBeijing 100730China

AIM:To report the postoperative axial length(AL)changes in rhegmatogenous retinal detachment combined with choroidal detachment(RRD-CD)patients.METHODS:The medical records of 97 consecutive patients from January 2015 to December 2018 were reviewed.Patients included were divided into RRD-CD and RRD only groups.All patients had received AL measurements before pars plana vitrectomy(PPV)and before silicone oil removal(SOR).The changes in AL of the two groups were compared.In addition,the potential factors related to AL changes were analyzed.RESULTS:AL elongation after PPV was 1.01 mm[interquartile range(IQR):0.37,1.79;P=0.02]in the RRD-CD group,which was greater than in RRD only group(0.15 mm,IQR:0.04,0.41;Plikely to experience post-PPV AL elongation of more than 1 mm[Plikely to have a postoperative elongation of AL.The primary intraoclular lens implantation using presurgery AL data may cause a significant refractive error in RRD-CD patients who underwent PPV.

关键词： rhegmatogenous retinal detachment choroidal detachment axial length pars plana vitrectomy

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Synergistic effect of various elements in Fe_(41)Co_(7)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) amorphous alloy hollow ball on catalytic degradation of methylene blue

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Journal of Rare Earths 2022年第4期40卷 605-615,I0004页

作者： Wenhu Luo Qingjun Chen li ji Xinyuan peng Guosheng Huang School of Materials Science and Engineering Nanchang Hongkong UniversityNanchang 330063China State Key Laboratory for Marine Corrosion and Protection Luoyang Ship Material Research Institute(LSMRI)Qingdao 266237China

Metallic glasses have recently attracted great attention in terms of degrading dyes and other organic pollutants as an environmentally friendly material for wastewater remediation.Herein,we report a new type of amorphous catalyst Fe_(41)Co_(7)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) hollow balls.Results demonstrate that the catalyst can still completely decolorize the 20 mg/L methylene blue(MB)solution after reused for 50 times under conditions of pH=5,catalyst content 0.5 g/L,and temperature 80°C.The catalyst is easily broken during degradation,so the inner surface also provides additional active sites.The Fe_(41)Co_(7)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) amorphous alloy hollow balls were characterized by energy dispersive X-ray specroscopy(EDS),scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS),respectively.The elements in the catalytic system have a synergistic catalytic effect.Redox cycle Fe^(2+)/Fe^(3+),Co^(2+)/Co^(3+)and Mo^(4+)/Mo^(6+) promote mutual conversion and accelerate the catalytic process of their reaction with H_(2)O_(2),forming a self-stable redox cycle process.Among them,Fe^(2+)promotes the conversion of Co^(3+)to Co^(2+),and Mo^(4+) promotes the conversion of Fe^(3+)to Fe^(2+),mainly Fe^(2+)and Co^(2+)react with H_(2)O_(2) to generate•OH.Mo and Cr elements form MoO_(2) and Cr_(2)O_(3) plasma compounds on the surface,which act as a protective film to make the catalyst more stable and be repeated used more frequently.

关键词： Metallic glasses Methylene blue degradation Synergistic catalytic Repeatability Hollow ball Rare earths

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Bifurcation of limit Cycles for a Perturbed Piecewise Quadratic Diferential Systems

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Acta Mathematica Sinica,English Series 2022年第3期38卷 591-611页

作者： Gui lin ji Chang jian liU peng Heng li School of Mathematics(Zhuhai) Sun Yat-sen UniversityZhuhai519082P.R.China

In this paper,the bifurcation of limit cycles for planar piecewise smooth systems is studied which is separated by a straight line.We give a new form of Abelian integrals for piecewise smooth systems which is simpler than before.In application,for piecewise quadratic system the existence of 10 limit cycles and 12 small-amplitude limit cycles is proved respectively.

关键词： Piecewise system limit cycle Abelian integral

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A micro-investigation on water bridge effects for unsaturated granular materials with constant water content by discrete element method

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Particuology 2023年第12期83卷 50-62页

作者： Mengchen li jiyuan Luan Xuguang Gao ji-peng Wang Abdelali Dadda School of Civil Engineering Shandong University17922 Jingshi RoadJinan250061China

The most common state of surface soil is unsaturated.Changes in water content will substantially impact its strength,leading to geological and engineering catastrophes.This paper used liGGGHTS software to simulate the water bridge effect of unsaturated granular materials with constant water content and verify the rationality of the simplification of the stress-force-fabric(SFF)relationship.The results showed that the capillary force was not isotropic,which was different from the previous study,thus it cannot be overlooked in the simplification of the SFF relationship.Moreover,the influence of water content on the macroscopic mechanical behavior of unsaturated granular materials was interpreted through the evolutions of coordination number,interparticle force,fabric and force anisotropy,and other microscopic parameters.Compared to the literature,we found that different water bridge models would not change the characteristics of the solid skeleton.

关键词： Unsaturated granular material Water bridge effect Water content Discrete element method Stress-force-fabric(SFF)relationship

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Unknown system dynamics estimator-based impedance control for lower limb exoskeleton with enhanced performance

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Control Theory and Technology 2024年第1期22卷 56-68页

作者： Wenhao Zhang peng Song Mingying Wu Qiang li Xinmin Mo Pingxin ji Northwest Institute of Mechanical and Electrical Engineering Xianyang712099ShaanxiChina Xi’an Exo-Smart Dynamics Technology Ltd. Xi’an712046ShaanxiChina Department of Mechanical and Engineering Beijing Institute of TechnologyBeijing100081China

In this article, an unknown system dynamics estimator-based impedance control method is proposed for the lower limb exoskeleton to stimulate the tracking flexibility with the terminal target position when suffering parametric inaccuracies and unexpected disturbances. To reinforce the robust performance, via constructing the filtering operation-based dynamic relation, i.e., invariant manifold, the unknown system dynamics estimators are employed to maintain the accurate perturbation identification in both the hip and knee subsystem. Besides, a funnel control technique is designed to govern the convergence process within a minor overshoot and a higher steady-state precision. Meanwhile, an interactive complaint result can be obtained with the aid of the impedance control, where the prescribed terminal trajectory can be adjusted into the interaction variable-based target position by the force–position mapping, revealing the dynamic influence between the impedance coefficient (stiffness and damping) and the adjusted position magnitude. A sufficient stability analysis verifies the ultimately uniformly bounded results of all the error signals, and even the angle errors can be regulated within the predefined funnel boundary in the whole convergence. Finally, some simulations are provided to demonstrate the validity and superiority including the enhanced interaction flexibility and robustness.

关键词： Trajectory tracking Invariant manifold Funnel control Impedance control Lower limb exoskeleton

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Flume Experiment Investigation on Propagation Characteristics of Tidal Bore in A Curved Channel

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China Ocean Engineering 2023年第1期37卷 131-144页

作者： FAN Jun TAO Ai-feng SHI Mo-quan li Ying peng ji Key Laboratory of Ministry of Education for Coastal Disaster and Protection Hohai UniversityNanjing 210098China College of Harbour Coastal and Offshore EngineeringHohai UniversityNanjing 210098China The Adminstrative Committee of Nantong Haimen Sanchang Industrial Park Nantong 226121China Zhejiang University of Water Resources and Electric Power Hangzhou 310018China China Renewable Energy Engineering Institute Beijing 100120China

Tidal bore is a special and intensive form of flow movement induced by tidal effect in estuary areas, which has complex characteristics of profile, propagation and flow velocity. Although it has been widely studied for the generation mechanism, propagation features and influencing factors, the curved channel will complicate the characteristics of tidal bore propagation, which need further investigation compared with straight channel. In this study, the flume experiments for both undular and breaking bores’ propagation in curved channel are performed to measure the freesurface elevation and flow velocity by ultrasonic sensors and ADV respectively. The propagation characteristics,including tidal bore height, cross-section surface gradient, tidal bore propagation celerity, and flow velocity are obtained for both sides of the curved channel. And three bore intensities are set for each type of tidal bores. The freesurface gradients are consistently enlarged in high-curvature section for undular and breaking bores, but have distinct behaviors in low-curvature section. The spatial distributions of tidal bore propagation celerity and flow velocity are compared between concave and convex banks. This work will provide experimental reference for engineering design of beach and seawall protection, erosion reduction and siltation promotion in estuary areas with the existence of tidal bores.

关键词： tidal bore curved channel flume experiment propagation celerity bore intensity

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腹腔镜胃切除术治疗老年胃癌患者:与腹腔镜胃切除术治疗非老年患者以及与开腹手术治疗老年患者的对比分析

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Gastroenterology Report 2021年第2期9卷 146-153,I0002页

作者： Zheng-Yan li jie Chen Bin Bai Shuai Xu Dan Song Bo lian Ji-peng Li Gang ji Qing-Chuan Zhao Xijing Hospital of Digestive Diseases Fourth Military Medical UniversityXi’anShanxiP.R.China Department of General Surgery Southwest HospitalThird Military Medical UniversityChongqingP.R.China

背景:腹腔镜胃切除术对于老年胃癌患者的获益尚不明确。本研究旨在探讨腹腔镜胃切除术应用于老年胃癌患者的可行性和安全性。方法:回顾性分析2009年6月至2015年7月间于第四军医大学西京医院行胃切除术的胃癌患者的临床资料。老年(年龄... 详细信息

背景:腹腔镜胃切除术对于老年胃癌患者的获益尚不明确。本研究旨在探讨腹腔镜胃切除术应用于老年胃癌患者的可行性和安全性。方法:回顾性分析2009年6月至2015年7月间于第四军医大学西京医院行胃切除术的胃癌患者的临床资料。老年(年龄≥70岁)腹腔镜组114例,非老年(年龄<70岁)腹腔镜组740例,老年开腹组383例。比较老年腹腔镜组与其他两组患者术中情况、术后近期疗效及远期生存结局。结果:相较于非老年腹腔镜组,老年腹腔镜组除术后首次排气时间延长外,其他近期疗效指标差异无统计学意义。老年腹腔镜组5年总体生存率低于非老年腹腔镜组(57.0%vs 65.5%,P<0.001),而5年肿瘤特异生存率两组差异则无统计学意义(64.9%vs 66.2%,P=0.476)。相较于老年开腹组,老年腹腔镜手术时间延长[(236.4±77.3)vs(179±52.2)min,P<0.001],术中出血量减少[(174.0±88.4)vs(209.3±133.8)ml,P=0.008],术后住院时间缩短[(8.3±2.5)vs(9.2±4.5)d,P=0.048];两组术后并发症严重程度相当。多因素分析结果显示,腹腔镜手术不是发生术后并发症的危险因素。结论:腹腔镜胃切除术治疗老年胃癌患者安全可行,可获得较为满意的近期疗效和远期生存。

关键词： laparoscopic gastrectomy elderly patients gastric cancer

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Heterointerface engineering in hierarchical assembly of the Co/Co(OH)_(2)@carbon nanosheets composites for wideband microwave absorption

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Nano Research 2023年第2期16卷 2611-2621页

作者： Yuhan Wu Guodong Wang Xixi Yuan Gang Fang peng li Guangbin ji College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China Aerospace Research Institute of Material&Processing Technology Beijing 100076China

Heterogeneous interface engineering strategy is an effective method to optimize electromagnetic functional materials.However,the mechanism of heterogeneous interfaces on microwave absorption is still unclear.In this study,abundant heterointerfaces were customized in hierarchical structures via a collaborative strategy of lyophilization and hard templates.The impressive electromagnetic heterostructures and strong interfacial polarization were realized on the zero-dimensional(0D)hexagonal close-packed(hcp)-face-centered cubic(fcc)Co/two-dimensional(2D)Co(OH)_(2)nanosheets@three-dimensional(3D)porous carbon nanosheets(Co/Co(OH)_(2)@PCN).By controlling the carbonization temperature,the electromagnetic parameters were further adjusted to broaden the effective absorption bandwidth(EAB).Accordingly,the EAB of these absorbers were almost greater than 6 GHz(covering the entire Ku-band)in the thickness range of 2.0–2.2 mm except the sample S-1.0-800.As far as to the S-0.8-700 achieved an EAB up to 7.1 GHz at 2.2 mm and the minimum reflection loss(RLmin)value was−25.8 dB.Moreover,in the far-field condition,the radar cross section(RCS)of S-0.8-700 can be reduced to 19.6 dB·m^(2).We believe that this work will stimulate interest in interface engineering and provide a direction for achieving efficient absorbing materials.

关键词： microwave absorption wide bandwidth interface engineering hierarchical porous structure absorption mechanism

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