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Microstructure evolution, mechanical properties and fracture behavior of Al-xSi/AZ91D bimetallic composites prepared by a compound casting

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Journal of Magnesium and Alloys 2024年第5期12卷 1944-1964页

作者： Guangyu Li Wenming Jiang Feng Guan junwen zhu Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology

In this paper, the effect of the Si content on microstructure evolution, mechanical properties, and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically. The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer（MRL）, whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites, while the hypereutectic Al-Si/AZ91D composites were opposite. The MRL included eutectic layer（E layer）,intermetallic compound layer（IMC layer） and transition region layer（T layer）. In the IMC layer, the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg2Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides, increasing Si content, the thickness proportion of the T layer increased, forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content, and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa, which was 73.4% higher than the Al-6Si/AZ91D composite. The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content. The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg2Si particle reinforcement, the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.

关键词： Al/Mg bimetallic composites Si content Mg 2 Si reinforcement Microstructure Mechanical properties Fracture behavior

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On-chip circulating tumor cells isolation based on membrane filtration and immuno-magnetic bead clump capture

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Nanotechnology and Precision Engineering 2022年第1期5卷 24-34页

作者： Shuai Zhang Yue Wang Chaoqiang Yang junwen zhu Xiongying Ye Wenhui Wang State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentsTsinghua UniversityBeijing 100084China

Isolating rare circulating tumor cells(CTCs)from blood is critical for the downstream analysis that is important in cancer-related research,diagnosis,and medicine,and efforts are ongoing to increase the efficiency and purity of CTC isolation in microfluidics.Reported in this paper is a two-stage integrated microfluidic chip for coarse-to-fine CTC isolation from whole blood.First,blood cells are removed by filtration using a micropore-array membrane,then CTCs and other cells that are trapped in the micropores are peeled off the membrane by a novel release method based on air–liquid interfacial tension,which significantly increases the recovery rate of CTCs.The second stage is CTC capture based on an on-chip dense immuno-magnetic-bead clump,which offers high capture efficiency and purity.Both the micropore filtration and immuno-magnetic-bead capture are validated and optimized experimentally.Overall,the integrated microfluidic chip can realize a recovery rate of 85.5%and a purity of 37.8%for rare cancer cells spiked in whole blood.

关键词： Circulating tumor cells Whole blood Isolation Filtration Magnetic-bead clump

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Improving mechanical properties of AZ91D magnesium/A356 aluminum bimetal prepared by compound casting via a high velocity oxygen fuel sprayed Ni coating

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Journal of Magnesium and Alloys 2022年第4期10卷 1075-1085页

作者： Guangyu Li Wenming Jiang Feng Guan junwen zhu Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

In this paper,a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound casting.The effects of the Ni coating as well as its thickness on microstructure and mechanical properties of the AZ91D/A356 bimetal were systematically researched for the first time.Results demonstrated that the Ni coating and its thickness had a significant effect on the interfacial phase compositions and mechanical properties of the AZ91D/A356 bimetal.The 10μm’s Ni coating cannot prevent the generation of the Al-Mg intermetallic compounds(IMCs)at the interface zone of the AZ91D/A356 bimetal,while the Ni coating with the thickness of 45μm and 190μm can avoid the formation of the Al-Mg IMCs.When the Ni coating was 45μm,the Ni coating disappeared and transformed into Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles at the interface zone.With a thickness of 190μm’s Ni coating,part of the Ni coating remained and the interface layer was composed of the Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles,Mg_(2)Ni layer,Ni solid solution(SS)layer,Al_(3)Ni_(2) layer,Al_(3)Ni layer and sporadic Al_(3)Ni+Al-Al_(3)Ni eutectic structures from AZ91D side to A356 side in sequence.The interface layer consisting of the Mg-Ni and Al-Ni IMCs obtained with the Ni coating had an obvious lower hardness than the Al-Mg IMCs.The shear strength of the AZ91D/A356 bimetal with a Ni coating of 45μm thickness enhanced 41.4%in comparison with that of the bimetal without Ni coating,and the fracture of the bimetal with 45μm’s Ni coating occurred between the Mg matrix and the interface layer with a mixture of brittle fracture and ductile fracture.

关键词： Magnesium/aluminum bimetal Microstructure Mechanical properties Ni coating Compound casting High velocity oxygen fuel spraying

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Effect of vibration on interfacial microstructure and mechanical properties of Mg/Al bimetal prepared by a novel compound casting

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Journal of Magnesium and Alloys 2022年第8期10卷 2296-2309页

作者： Feng Guan Wenming Jiang Guangyu Li junwen zhu Junlong Wang Guoliang Jie Zitian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated.The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal,but it did not change the phase compositions of the interface,which was composed of layerⅠ(Al3Mg2+Mg2Si),layerⅡ(Al_(12)Mg_(17)+Mg_(2)Si)and layerⅢ(Al_(12)Mg_(17)/δ-Mg).Without vibration,the Mg_(2)Si phase with a needle-like morphology mainly aggregated in the layerⅡof the interface.After the application of the vibration,the SEM and EBSD analysis results showed that the Mg_(2)Si and Al3Mg2phases in the interface were obviously refined,and the distribution of the Mg_(2)Si became more uniform,due to the strong forced convection of the molten metal resulting from the vibration.The TEM analysis indicated that the interface between the A_(l3)Mg_(2) and Mg_(2)Si phases was non-coherent,suggesting the Mg_(2)Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface.Compared to the Mg/Al bimetal without vibration,the shear strength of the Mg/Al bimetal with vibration increased by about 50%from 31.7 MPa on average to 47.5 MPa,and the hardness of the layer I of the interface increased,and the hardness of the layerⅢdecreased.The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.

关键词： Mg/Al bimetal Vibration Compound casting Interfacial microstructure Bonding properties

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Evaluation of Scientific and Technological Research in China’s Colleges: A Review of Policy Reforms, 2000–2020

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ECNU Review of Education 2020年第3期3卷 556-561页

作者： junwen zhu East China Normal University

Purpose:This study conducts a systematic review of policy reforms for the evaluation of scientific and technological research(E-STR)in China’s colleges.In doing so,it identifies changes to past policies,as well as the objectives and realizability of the most recent policy reform.Design/Approach/Methods:This study systematically reviews the contexts of E-STR policy reforms in China’s colleges post 2000 using three important related policy documents from 2003,2013,and 2020 as samples.Research findings were obtained via content analysis.Findings:Unlike previous attempts,the most recent policy reform has incorporated the lessons learned while introducing highly targeted measures and a monitoring mechanism.Such reform should accelerate the promotion of major original scientific research in China’s colleges,enhance the contribution of scientific research to socioeconomic development,and strengthen support for the cultivation of undergraduate talents.Originality/Value:Initiated in the early part of 2000,China’s latest E-STR policy reform constitutes an important turning point in the initiative to burst the research bubble and return to the essence of innovation.It will drive China’s colleges to embark on a research path that places value on original innovation and contribution to socioeconomic development.

关键词： China higher education policy reform research evaluation Science Citation Index

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The Composition and Evolution of China’s High-Level Talent Programs in Higher Education

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ECNU Review of Education 2019年第1期2卷 104-110页

作者： junwen zhu East China Normal University China

Purpose:This article provides an overview of the composition and evolution of China’s high-level talent programs in higher education.Design/Approach/Methods:This article reviews key talent policies adopted by the Chinese government since the 1990s,using content analysis methods to identify policy characteristics and reform trends.Findings:Talent programs in China operate at four levels:the national level,provincial level,city level,and institutional level.The main objectives of China’s high-level talent programs are to support and promote the development of young talent and to encourage overseas scholars to return to China.China’s high-level talent programs have undergone various changes since 1993.The evolution is characterized by the following five major aspects:individual program optimization;replacement,integration,and separation;preventing overlapping funding;mitigating the unbalanced impact the programs have on higher education institutions across regions;and strengthening risk assessment for programs focused on attracting overseas talent.Originality/Value:This article offers a comprehensive assessment of the talent programs implemented by Chinese universities and explores the key trends and content of recent policy changes.

关键词： China higher education talent programs

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涉罪人工智能刑罚的正当性——以东西方认识论互补视角为切入点

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华东理工大学学报（社会科学版） 2024年第2期39卷 106-119页

作者：王学光诸珺文华东政法大学刑事法学院上海200042

尽管孟德斯鸠、伏尔泰等学者从“犯罪人”角度讨论了刑罚正当性,但是他们的论述忽视罪与罚的实质而在人工智能刑罚领域无法适用。本文对古希腊哲学中的共相观进行总结,以破解当今人工智能刑法学者落入的“主观思维陷阱”。本文以生成式... 详细信息

尽管孟德斯鸠、伏尔泰等学者从“犯罪人”角度讨论了刑罚正当性,但是他们的论述忽视罪与罚的实质而在人工智能刑罚领域无法适用。本文对古希腊哲学中的共相观进行总结,以破解当今人工智能刑法学者落入的“主观思维陷阱”。本文以生成式人工智能为例,结合先秦时期、秦汉时期、唐宋时期和明清时期的儒家学说进行探讨,发现人工智能的自我意识可用“实在论”进行概括。基于向量技术生成的人工智能尽管拥有自我意识,但是其在一定程度上缺乏由感性认识到理性认识的升华,刑罚无法使其感到自内而外的痛苦,所以对人工智能施加的刑罚缺乏正当性。人类和人工智能的地位落入黑格尔所提出的主人意识与奴隶意识的辩证关系中,因此应以宋明理学的“以严为本,而以宽济之”的思想对涉罪人工智能进行行政立法规制。

关键词：人工智能刑罚观儒家学说共相概念认识论安塞姆学说

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Enhanced mechanical properties of 6082 aluminum alloy via SiC addition combined with squeeze casting

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Journal of Materials Science & Technology 2021年第29期88卷 119-131页

作者： Wenming Jiang junwen zhu Guangyu Li Feng Guan Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan430074China State Key Laboratory of High Performance Complex Manufacturing Central South University410083 ChangshaChina

In order to improve mechanical properties of 6082 aluminum alloy,the SiC_(p)/Al 6082 composites were prepared by the addition of the micron-sized SiC_(p)articles combined with the squeeze casting.The effects of the SiC_(p)content and squeeze casting on the microstructure and mechanical properties of the 6082 aluminum alloy were investigated by SEM,EDS,TEM,tensile testing and hardness testing analysis methods.Research results exhibited that the SiC_(p)content and squeeze casting had a significant impact on the microstructure and mechanical properties of the 6082 aluminum alloy.The addition of the SiC_(p)refined the grain size of the 6082 aluminum alloy while caused the increase of the porosity with increasing the SiC_(p)content,especially in the permanent mold casting condition.Compared to the permanent mold casting,the squeeze casting obviously reduced pore defects,refined grain size and made the SiC_(p)distribute evenly as well as bond tightly with the Al matrix.The tensile strength,yield strength,elongation,elastic modulus and hardness of the 6082 aluminum alloy obtained with the SiC_(p)and squeeze casting were remarkably improved,and the optimal mechanical properties were obtained with a 2 wt.%SiC_(p),and they increased 10.73%,72.7%,193.9%,23.5%and 25.2%,respectively,compared to those of the6082 aluminum alloy obtained without SiC_(p)and squeeze casting.The fracture surface of the SiC_(p)/Al 6082 composites obtained with the squeeze casting was dense and exhibited a ductile fracture mode.

关键词： 6082 aluminum alloy SiC_(p) Aluminum matrix composites Squeeze casting Microstructure Mechanical properties

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Cilia regulate meiotic recombination in zebrafish

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Journal of Molecular Cell Biology 2022年第7期14卷 37-48页

作者： Haibo Xie Xiaosi Wang Minjun Jin Lanqin Li junwen zhu Yunsi Kang Zhe Chen Yonghua Sun Chengtian Zhao Institute of Evolution&Marine Biodiversity Ocean University of ChinaQingdao 266003China State Key Laboratory of Freshwater Ecology and Biotechnology Institute of HydrobiologyInnovation Academy for Seed DesignHubei Hongshan LaboratoryChinese Academy of SciencesWuhan 430072China Laboratory for Marine Biology and Biotechnology Qingdao National Laboratory for Marine Science and TechnologyQingdao 266003China Sars-Fang Centre Ministry of Education Key Laboratory of Marine Genetics and BreedingCollege of Marine Life SciencesOcean University of ChinaQingdao 266003China College of Advanced Agricultural Sciences University of Chinese Academy of SciencesBeijing 100049China

Meiosis is essential for evolution and genetic diversity in almost all sexual eukaryotic organisms.The mechanisms of meiotic recombination,such as synapsis,have been extensively investigated.However,it is still unclear whether signals from the cytoplasm or even from outside of the cell can regulate the meiosis process.Cilia are microtubule-based structures that protrude from the cell surface and function as signaling hubs to sense extracellular signals.Here,we reported an unexpected and critical role of cilia during meiotic recombination.During gametogenesis of zebrafish,cilia were specifically present in the prophase stages of both primary spermatocytes and primary oocytes.By developing a germ cell-specific CRISPR/Cas9 system,we demonstrated that germ cell-specific depletion of ciliary genes resulted in compromised double-strand break repair,reduced crossover formation,and increased germ cell apoptosis.Our study reveals a previously undiscovered role for cilia during meiosis and suggests that extracellular signals may regulate meiotic recombination via this particular organelle.

关键词： cilia meiosis homologous recombination kif3a zebrafish

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A paper-based self-inductive folding displacement sensor for human respiration and motion signals measurement

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npj Flexible Electronics 2022年第1期6卷 653-663页

作者： junwen zhu Yanshen Jia Mengmeng Li Zhanxuan Zhou Yinghao Chen Qiang Liu Xing Yang The State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentTsinghua UniversityBeijing 100084China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China School of Electromechanical and Automobile Engineering Yantai UniversityYan Tai 264005China Key Laboratory of Photonic Control Technology Ministry of EducationTsinghua UniversityBeijing 100083China

Flexible sensors have recently attracted much attention for potential applications in motion measurement and wearable health monitoring.In this paper,an environment-friendly,economic,and high-performance paper-based self-inductive folding displacement sensor(PSIFS)was proposed,with displacement resolution of 20μm and wide measurement range of 43.2 mm.The sensor sensitivity could reach 4.44%mm^(−1) with the maximum deviation of 0.00904 in experiments.The sensing mechanism based on inductance variation due to three-dimensional deformation of planar inductor coil and structural design principle under two dimensions of sensitivity and size were proposed and studied.The folding method to enhance sensitivity was proposed and 3 times sensitivity enhancement could be achieved by once folding.Multiple breathing states and motion states of the human joints could be recognized.The proposed simple paper-based sensor,folding method to increase sensitivity,and structural design model may provide a way for the research of flexible sensors.

关键词： folding inductive motion

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