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Size Effect of Impact Abrasive Particles on Wear and Surface Hardening Behavior of High‑Manganese Steel

Acta Metallurgica Sinica(English Letters) 2023年第6期36卷 906-916页

作者： yongjin wang Chuansongxin Song Renbo Song Zetian Ma Tom Taylor School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Swansea University Swansea SA18EPUK

The size effect of impact abrasive particles on wear and surface hardening behavior of high-manganese steel was studied.Impact wear tests were carried out on MLD-10 tester with abrasive particle sizes of 6.0–0.75 mm,respectively.The results showed that the impact wear behavior and surface hardening mechanism of high-manganese steel were affected by the size of abrasive particles.A critical size of abrasive particle might exhibit to distinguish the impact wear behavior.When the abrasive particle size was larger than 0.75 mm,the wear mass loss generally showed a decreasing trend with the decrease of the abrasive particle size.Dislocation strengthening and mechanical twinning contributed to the good work hardening behavior.However,effective surface hardening layer could not be formed for sample tested with particle size of 0.75 mm and the wear mass loss was the highest among all the conditions.The weak hardening effect led to the sharp increase of the wear mass loss.Press-in abrasives could be observed on the wear surface when the abrasive particle size was larger than 0.75 mm.The press-in abrasives were peeled off from the wear surface and broken,leaving deep grooves and peeling pits.Material exchange with the sample would occur with the flow of abrasives.A large area of furrow was formed on the wear surface.For particle size of 0.75 mm,aggregated abrasives formed a dynamic buffer layer on the surface and the stress distribution was more even.The formation of buffer layer would lower the effect of the impact load and the work hardening effect could not be fully activated.The mutual extrusion among the abrasives,friction wheel and sample caused plastic deformation of the worn surface during impact test.The present study would help guiding to select the application field of high-manganese steel more precisely.

关键词： Abrasive particles Three-body impact wear High-manganese steel Wear mechanism Surface hardening behavior

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Ice-volume and insolation influences on hydroclimate changes in central eastern China during the antepenultimate glacial period

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Science China Earth Sciences 2023年第1期66卷 71-79页

作者： Quan wang Shayue YUAN Yijia LIANG Kan ZHAO Qingfeng SHAO Zhenqiu ZHANG Junji ZHU Xinggong KONG yongjin wang Jianghu LAN Hai CHENG Chengwei XIA Yi LI School of Geography and Tourism Chongqing Normal UniversityChongqing 401331China Chongqing Key Laboratory of Wetland Science Research of the Upper Reaches of the Yangtze River Chongqing 401331China School of Geographical Science Nantong UniversityNantong 226007China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application School of GeographyNanjing Normal UniversityNanjing 210023China State Key Laboratory of Loess and Quaternary Geology Institute of Earth EnvironmentChinese Academy of SciencesXi’an 710061China Institute of Global Environmental Change Xi’an Jiaotong UniversityXi’an 710054China

The rainfall changes in East Asian summer monsoon(EASM)regions on the orbital timescale remain controversial due to the lack of reliable rainfall records.Here,we present new multiproxy records(δ^(18)O,δ^(13)C,Sr/Ca and Mg/Ca)of a230Thdated stalagmite from Hulu Cave in central eastern China.Multiproxy records reconstruct a regional hydroclimate history from 340 to 261 kyr BP(thousand years before present),approximately covering the antepenultimate glacial period.Theδ^(18)O record is dominated by the precessional cycles,suggesting that EASM responds to changes in Northern Hemisphere summer insolation(NHSI)on the orbital timescale.Significant correlations amongst theδ^(13)C,Sr/Ca and Mg/Ca suggest that a common factor,i.e.,the local hydrological cycle,controlled their variability,and their leading principal component can be used as a proxy linked to regional rainfall.This composite record bears a good similarity to those from the Chinese Loess Plateau,showing a gradually decreasing rainfall during the antepenultimate glacial period,consistent with changes in global ice volume.Superimposed on the long-term trend,three relative wetter intervals were responding to the higher NHSI periods,suggesting that EASM rainfall variability was induced by integrated effects of global ice volume and NHSI.The increased ice sheets and lower NHSI resulted in an increased meridional temperature gradient and southward shift of the westerlies,which shortened the duration of Meiyu and midsummer rainfall.The differences between the rainfall record and the stalagmiteδ^(18)O record indicate that the latter represents the overall EASM intensity linked to monsoon circulation,but does not directly reflect the rainfall changes at the cave sites.

关键词： Hulu Cave Stalagmite records Antepenultimate glacial period East Asian summer monsoon rainfall

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Screening of Chemical Agents for Controlling Spodoptera frugiperda in Corn Fields of Panmao Township,Yunnan Province

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Plant Diseases and Pests 2022年第2期13卷 8-9,16页

作者： yongjin wang Economic Crop Workstation of Mouding County Mouding 675500China

[Objectives]The paper was to effectively prevent and control the damage of Spodoptera frugiperda and to screen effective agents.[Methods]The block test of drug control was carried out,and the insect pest situation was investigated five times.[Results]150 mL/hm^(2) of 5%emamectin benzoate+600 mL/hm 2 of 5%lufenuron had better comprehensive control effect on S.frugiperda,and the corn yield reached 10100.55 kg/hm^(2).[Conclusions]The study provides a basis for scientific control of S.frugiperda.

关键词： Panmao Township Corn Spodoptera frugiperda Control agent Screen

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数字技术会带来“技术奇点”吗?

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产业经济评论 2024年第2期 107-120页

作者：王永进南开大学经济学院国际经济贸易系

经济增长的本质是什么?人类是否能够实现经济的可持续增长?数字技术是否可能带来“技术奇点”,从而创造一个不需要人类且产出无限增长的世界?本文首先从经济学的角度系统梳理关于数字技术对经济增长影响的研究,在此基础上从限制经济增... 详细信息

经济增长的本质是什么?人类是否能够实现经济的可持续增长?数字技术是否可能带来“技术奇点”,从而创造一个不需要人类且产出无限增长的世界?本文首先从经济学的角度系统梳理关于数字技术对经济增长影响的研究,在此基础上从限制经济增长的物理因素角度对上述问题进行重新解读。本文认为:即便数字技术是人类历史的又一次革命,并且也可能创造一轮新的经济增长奇迹,但是,人类经济活动终究不能脱离有用物质有限、空间有限、物质不可无限分割以及地球承载能力有限的约束。而数字技术所带来的不平等以及其对生态环境的破坏,会进一步割裂GDP与人类福祉之间的关系。为此,从“技术奇点”转向“可持续的福祉增长”就成为一项迫在眉睫的关键任务。

关键词：经济增长经济发展物理约束技术奇点可持续的福祉增长

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国内供应链摩擦、中间品进口与生产率进步

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国际贸易问题 2024年第4期 103-120页

作者：刘卉王永进南开大学经济与社会发展研究院南开大学经济学院

如何破除由于地区封锁所导致的供应链摩擦,并形成国内国际双循环相互促进的新发展格局是中国进入高质量发展阶段的必然要求。本文提出了一个测度企业国内市场供应链摩擦的量化评估框架,并通过动态结构模型考察了国内市场供应链摩擦对企... 详细信息

如何破除由于地区封锁所导致的供应链摩擦,并形成国内国际双循环相互促进的新发展格局是中国进入高质量发展阶段的必然要求。本文提出了一个测度企业国内市场供应链摩擦的量化评估框架,并通过动态结构模型考察了国内市场供应链摩擦对企业进口决策和生产率进步的影响。研究发现:(1)与国企相比,民营企业在国内中间品市场面临更高的供应链摩擦,而且该现象在中西部地区更为明显;(2)国内供应链摩擦与进口产品质量之间存在显著的负向关系;(3)对无论何种所有制企业而言,其进口中间投入品质量和种类的提高所产生的即时静态收益,均显著高于生产率演变所引致的滞后动态收益;(4)反事实分析表明,民营企业面临的高供应链摩擦显著抑制了其生产率增长。通过对国内的供应链摩擦进行重塑,可以使民营企业的长期生产率、进口参与率以及企业价值分别提高8.48%、16.04%和9.24%,这为推动供应链的优化升级提供了全新的思路。

关键词：供应链摩擦中间品进口生产率进步

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Optimal portfolio and consumption selection with default risk

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Frontiers of Mathematics in China 2012年第6期7卷 1019-1042页

作者： Lijun BO yongjin wang Xuewei YANG Department of Mathematics Xidian University Xi'an 710071 China School of Business Nankai University Tianjin-300071 China School of Management and Engineering Nanjing University Nanjing 210093 China

我们与可默认的安全调查一个最佳的公事包和消费选择问题。在经过消费最大化一般水准的期望的打折的实用程序的目标下面，一个动态编程原则被使用导出一双秒顺序有坡度限制的寓言的 Hamilton-Jacobi-Bellman (HJB ) 方程。我们探索由一... 详细信息

我们与可默认的安全调查一个最佳的公事包和消费选择问题。在经过消费最大化一般水准的期望的打折的实用程序的目标下面，一个动态编程原则被使用导出一双秒顺序有坡度限制的寓言的 Hamilton-Jacobi-Bellman (HJB ) 方程。我们探索由一个粘性解决方案的方程接近并且描绘的这些 HJB 缺省以后并且预先默认作为 HJB 方程的抑制粘性答案的唯一的对珍视函数。

关键词：最优投资组合和消费违约 HJB方程风险效用最大化动态规划

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自由贸易试验区的出口溢出效应:基于共同机构持股视角

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财贸经济 2024年第4期45卷 157-172页

作者：王永进燕晓娟南开大学经济学院 300110

本文使用2007—2016年沪深A股上市公司数据和海关数据研究共同机构持股如何影响自由贸易试验区的出口溢出。研究发现,共同机构持股能够发挥促进信息溢出的作用,从而促进自由贸易试验区企业的出口溢出,提升非自由贸易试验区企业的出口水... 详细信息

本文使用2007—2016年沪深A股上市公司数据和海关数据研究共同机构持股如何影响自由贸易试验区的出口溢出。研究发现,共同机构持股能够发挥促进信息溢出的作用,从而促进自由贸易试验区企业的出口溢出,提升非自由贸易试验区企业的出口水平,且溢出效应对规模更大、生产力更高或者国有性质的非自由贸易试验区出口企业更加显著。异质性检验表明,非自由贸易试验区出口企业的吸收能力和地理位置、自由贸易试验区出口企业的其他国家经验、信息网络的完备性都是影响溢出效应的关键。此外,共同机构持股对新产品市场的出口溢出的促进效应更大。共同机构持股对非自由贸易试验区出口企业的出口集约边际和扩展边际均有积极作用,并且促进加工贸易向一般贸易转型。

关键词：自由贸易试验区共同机构持股出口溢出机构投资者

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Multiscale analysis of Asian Monsoon over the past 640 ka

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Science China Earth Sciences 2019年第5期62卷 843-852页

作者： Yalan ZENG Shitao CHEN Shaohua YANG Yijia LIANG yongjin wang Key Laboratory of Virtual Geographic Environment Ministry of Education School of Geography ScienceNanjing Normal University State Key Laboratory of Cultivation Base of Geographical Environment Evolution (Jiangsu Province) Jiangsu Center for Collaborative Innovation in Geographical Environment Resource Development and Application

The empirical mode decomposition(EMD) method is used to re-analyse the high-resolution and precisely-dated stalagmite record from Chinese caves over the past 640 ka. Results show that(1) the variation in the Asian Monsoon can be completely decomposed into ten quasiperiod oscillations, among which the precession and semiprecession band oscillations are the most prominent periodicities, with contribution rates of 31.1% and 30.7%, respectively;(2) the cross-spectrum analysis of the semiprecession component and bi-hemisphere insolation(BHI) are strongly correlated, indicating an amplified response of precipitation and temperature variability to the interhemispheric insolation in the low-latitude regions, thus further affecting the intensity of the Asian Monsoon;(3) on millennial timescales, obvious oscillations at the 5 ka and 1–2 ka bands roughly correspond to the classical Bond and Dansgaard-Oeschger(DO) cycles. Additionally, a strong correlation is found between the detrended stalagmite δ18 O records and Ca/Sr sequence from the North Atlantic(especially at the 5 ka band). This result means that the 5 ka cycle is characteristic of the glacial-interglacial cycle since the middle and late Pleistocene and may imply that climate change on the millennial timescale is the result of an interaction between global ice volume and insolation.

关键词： Empirical mode decomposition (EMD) Asian Monsoon Oxygen isotope records Semiprecession 5 ka cycle

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ENSO-Like Pacing of the Asian Summer Monsoon during the Early Holocene

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Journal of Meteorological Research 2020年第2期34卷 325-335页

作者： Xiaohua SHAO Tao wang yongjin wang Hai CHENG Kan ZHAO Xinggong KONG School of Geography Nanjing University of Information Science & TechnologyNanjing 210044China Public Meteorological Service Center of Anhui Province Hefei 230031China Key Laboratory of Virtual Geographic Environment Ministry of EducationNanjing Normal UniversityNanjing 210023China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing 210023China Institute of Global Environmental Change Xi’an Jiaotong UniversityXi’an 710049China Department of Geology and Geophysics University of MinnesotaMN 55455USA

We present a230Th-dated stalagmite oxygen isotope(δ^18O)record from Loushanguan Cave in the Yangtze River valley,China.The^δ18O record,if viewed as a proxy of the Asian summer monsoon(ASM)intensity,provides an ASM history for the early Holocene with clear centennial-scale variability.A significant approximately 200-yr cycle between 10.2 and 9.1 ka BP(before present,where"present"is defined as the year AD 1950),as revealed by spectral power analyses,is of global significance and is probably forced by the Suess or de Vries cycle of solar activity.Here,we explore a physical mechanism to explain the relationship between the solar activity and the ASM.A strong coherence between the ASM and El Ni?o–Southern Oscillation(ENSO)has been observed by performing crosswavelet analyses on this cycle.Our study suggests that a strong(weak)ASM state corresponds to a warm(cold)ENSO,which is consistent with modern meteorological observations but contrasts with previous studies on regions far from the Meiyu rainbelt.We argue that the centennial fluctuations of the ASM are a fundamental characteristic forced by the solar activity,with the ENSO variability as a mediator.The relationship between ENSO and the ASM displayed spatial heterogeneity on the centennial scale during the early Holocene,which is a more direct analogue to the observed modern interannual variability of the ASM.

关键词： isotope records Asian summer monsoon El Nino-Southern Oscillation centennial scale solar activity Yangtze River valley early Holocene

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Non-destructive corrosion study on a magnesium alloy with mechanical properties tailored for biodegradable cardiovascular stent applications

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Journal of Materials Science & Technology 2021年第7期66卷 128-138页

作者： Changhong Cai Marta M.Alves Renbo Song yongjin wang Jingyuan Li School of Materials Science and Engineering University of Science and Technology BeijingBeijing100083China Centro de Qufmica Estrutural Instituto Superior TecnicoUniversidade de LisboaAv.Rovisco Pais1049-001LisboaPortugal

AnMg-2Zn-0.6Zr-0.6Nd alloy for biodegradable cardiovascular stent applications was prepared through indirect extrusion. The alloy exhibited a superior combination of tensile yield strength(TYS), ultimate tensile strength(UTS) and elongation(EL) of about 269 MPa, 298 MPa and 25.6 %, respectively. In addition,the non-destructive electrochemical frequency modulation(EFM) technique was used for the first time to investigate the corrosion behavior of Mg alloys combined with electrochemical impedance spectroscopy(EIS) in Dulbecco’s Modified Eagle’s Medium(DMEM) and in Hank’s solution. Compared with the corrosion rate of 0.07 mm/year in Hank’s solution, lower corrosion rate of 0.03 mm/year was achieved in DMEM. The significant differences between the corrosion rate trends were discussed and related with the composition of the corrosion layer formed. Depending on the biomimetic fluids tested, different corrosion products were precipitated on the alloy’s surface: a compact and homogeneous layer of Mg_(x)Ca_(y)(PO_(4))_(z) and Zn(OH)_(2) and organic compounds was formed in DMEM, whereas a partial coverage of Mg_(x)Ca_(y)(PO_(4))_(z) and Zn(OH)_(2) was formed in Hank’s solution.

关键词： Mg-Zn-Zr-Nd alloy Mechanical property Corrosion EIS EFM

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