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Improved creep aging response in Al-Cu alloy by applying pre-aging before pre-straining

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Chinese Journal of Aeronautics 2023年第7期36卷 518-530页

作者： Fangpu LYU chunhui liu Peipei MA Jianshi YANG Longhui CHEN Lihua ZHAN Minghui HUANG State Key Laboratory of Precision Manufacturing for Extreme Service Performance School of Mechanical and Electrical EngineeringCentral South UniversityChangsha 410083China Light Alloy Research Institute Central South UniversityChangsha 410083China Advanced Research Center Central South UniversityChangsha 410083China

The improvement of post-form properties without compromising creep formability has been a critical issue in creep age forming of aluminum alloy component. A pretreatment process incorporating artificial pre-aging at 165 °C for 6 h/12 h/24 h followed by pre-strain(3%–9%)has been developed. This method not only evidently improves the strength but also accelerates the creep deformation during creep aging of an Al-Cu alloy. A strength increase of 50 MPa with a slight decrease of ductility relative to the 9% pre-strained alloy is acquired in the alloy artificially pre-aged for 24 h regardless of the pre-strain level(3%–9%). Artificial aging for 24 h prior to 3%pre-strain enables an increase of creep strain by 30%. The creep strain in the alloy artificially preaged for 24 h and pre-strained by 6% is comparable to that in the alloy pre-strained by 9%. The strength and ductility in the alloy artificially pre-aged for 6 h/12 h and pre-strained by 3% are even slightly higher than those in the alloy purely pre-strained by 9%. The characterizations by transmission electron microscopy reveal that pre-aging at 165 °C could promote the accumulation of dislocations during pre-straining due to the pinning effect of pre-existing Guinier-Preston zones(GP zones)/θ’’phases and thus expedite the creep deformation in respect to the pure pre-straining treatment. The enhanced precipitation of θ’phases at these pinned dislocations contributes to the improved strength after creep aging. The results demonstrate applying artificial pre-aging before pre-straining is an efficient strategy to elevate the creep aging response in Al alloys.

关键词： Al-Cu alloy Creep aging Pre-aging Precipitation Pre-strain

Numerical modeling on strain energy evolution in rock system interaction with energy-absorbing prop and rock bolt

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International Journal of Mining Science and Technology 2023年第10期33卷 1273-1288页

作者： Yang Hao chunhui liu Yu Wu Hai Pu Yanlong Chen Lingling Shen Guichen Li State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou 221116China School of Mines China University of Mining and TechnologyXuzhou 221116China

The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to high geo-stress and strong disturbed effects. This paper is to investigate the strain energy evolution in the interaction between coal and rock masses with self-designed energy-absorbing props and rock bolts by numerical modeling with the finite difference method. The interaction between rock and rock bolt/prop is accomplished by the cables element and the interface between the inner and outer props. Roadway excavation and coal extraction conditions in deep mining are numerically employed to investigate deformation, plastic zone ranges, strain energy input, accumulation, dissipation,and release. The effect on strain energy input, accumulation, dissipation, and release with rock deformation, and the plastic zone is addressed. A ratio of strain energy accumulation, dissipation, and release with energy input a, β, γ is to assess the dynamic hazards. The effects on roadway excavation and coal extraction steps of a, β, γ are discussed. The results show that:(1) In deep high geo-stress roadways, the energyabsorbing support system plays a dual role in resisting deformation and reducing the scope of plastic zones in surrounding rock, as well as absorbing energy release in the surrounding rock, especially in the coal extraction state to mitigate disturbed effects.(2) The strain energy input, accumulation is dependent on roadway deformation, the strain energy dissipation is relied on plastic zone area and disturbed effects, and strain energy release density is the difference among the three. The function of energyabsorbing rock bolts and props play a key role to mitigate strain energy release density and amount, especially in coal extraction condition, with a peak density value from 4×10^(4) to 1×10^(4)J/m^(3), and amount value from 3.57×10^(8) to 1.90×10^(6)J.(3) When mining is advanced in small steps, the strai

关键词： Strain energy Coal and rock mass Energy-absorbing prop and rock bolt Strain energy evolution

Dislocation reconfiguration during creep deformation of an Al-Cu-Li alloy via electropulsing

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Journal of Materials Science & Technology 2022年第35期130卷 27-34页

作者： Chang Zhou Lihua Zhan He Li chunhui liu Yongqian Xu Bolin Ma Youliang Yang Minghui Huang College of Mechanical and Electrical Engineering Central South UniversityChangsha410083China State Key Laboratory of High Performance Complex Manufacturing Central South UniversityChangsha410083China Light Alloys Research Institute Central South UniversityChangsha410083China

Creep mechanism was well-known to be mainly dominated by the dislocation sliding and climbing during creep deformation. Here we study the creep deformation of an Al-Cu-Li alloy with the assistance of electropulsing and subsequent microstructural observations. We find that creep strain increased drastically under electropulsing and was almost twelve times as much as that of the non-pulsed sample. Microstructural observations confirmed that dislocation reconfiguration happens via electropulsing, namely helical dislocations being opened rapidly. This opened dislocation structure can possess a much higher mobility than the initial helical dislocation, which mostly responsible for the greatly increased creep strain. Our results revealed a new mechanism accountable for the distinctly electroplastic creep deformation.

关键词： Dislocation reconfiguration Electroplasticity Al-Cu-Li alloy Creep deformation

“使唤”的词汇化及其再发展:基于兼语脱落的跨层融合

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语文研究 2024年第2期 31-39页

作者：刘春卉四川大学文学与新闻学院四川成都610207

文章认为,“使唤”词汇化为动词的形式基础是表示“使使唤”“使人唤”的兼语框架“使唤(NP)”,此类兼语框架的产生则是兼语并入或脱落的结果。当兼语框架“使唤NP”中“使”与“唤”的支配对象同为NP时,“使唤”就可能被重新分析为动... 详细信息

文章认为,“使唤”词汇化为动词的形式基础是表示“使使唤”“使人唤”的兼语框架“使唤(NP)”,此类兼语框架的产生则是兼语并入或脱落的结果。当兼语框架“使唤NP”中“使”与“唤”的支配对象同为NP时,“使唤”就可能被重新分析为动词。这种基于兼语框架的词汇化明显不同于基于短语或其他非句法结构的词汇化,是经历了兼语并入或脱落的特殊缩合式再跨层融合的结果。“使唤”词汇化为动词后,其兼语框架义开始更多地由“遣使唤”“使人唤”等完整形式的同义兼语结构来表达以避免歧义。动词“使唤”可以通过转喻用作名词指称官职,还可以经由语法化发展为工具格介词。

关键词：词汇化使唤使使VP 兼语框架“使VP” 兼语脱落

Genomic footprints of Kam Sweet Rice domestication indicate possible migration routes of theDongpeople inChina andprovide resources for future rice breeding

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Molecular Plant 2023年第2期16卷 415-431页

作者： chunhui liu Tianyi Wang Huicha Chen Xiaoding Ma Chengzhi Jiao Di Cui Bing Han Xiaobing Li Aixia Jiao Renchao Ruan Dayuan Xue Yanjie Wang Longzhi Han Institute of Crop Sciences Chinese Academy of Agricultural SciencesBeijing 100081China College of Life and Environmental Sciences Minzu University of ChinaBeijing 100081China Smartgenomics Technology Institute Tianjin 301700China Institute of Crop Germplasm Resources Guizhou Academy of Agricultural SciencesGuiyang 550025China

The Dong people are one of China’s 55 recognized ethnic minorities,but there has been a long-standing debate about their origins.In this study,we performed whole-genome resequencing of Kam Sweet Rice(KSR),a valuable,rare,and ancient rice landrace unique to the Dong people.Through comparative genomic analyses of KSR and other rice landraces from south of the Yangtze River Basin in China,we provide evidence that the ancestors of the Dong people likely originated from the southeast coast of China at least 1000 years ago.Alien introgression and admixture in KSR demonstrated multiple migration events in the history of the Dong people.Genomic footprints of domestication demonstrated characteristics of KSR that arose from artificial selection and geographical adaptation by the Dong people.The key genes GS3,Hd1,and DPS1(related to agronomic traits)and LTG1 and MYBS3(related to cold tolerance)were identified as domestication targets,reflecting crop improvement and changes in the geographical environment of the Dong people during migration.A genome-wide association study revealed a candidate yield-associated gene,Os01g0923300,a specific haplotype in KSR that is important for regulating grain number per panicle.RNA-sequencing and quantitative reverse transcription-PCR results showed that this gene was more highly expressed in KSR than in ancestral populations,indicating that it may have great value in increasing yield potential in other rice accessions.In summary,our work develops a novel approach for studying human civilization and migration patterns and provides valuable genomic datasets and resources for future breeding of high-yield and climate-resilient rice varieties.

关键词： Dong ethnic group Kam Sweet Rice genomic evolution population genetics

Counting Multiplicities in a Hypersurface over Number Fields

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Algebra Colloquium 2018年第3期25卷 437-458页

作者： Hao Wen chunhui liu Department of iVlathematicM Sciences Tsinghua University Beijing 100084 China Department of Mathematics Faculty of Science Kyoto University Kyoto 606-8502 Japan

We fix a counting function of multiplicities of algebraic points in a projective hypersurface over a number field, and take the sum over all algebraic points of bounded height and fixed degree. An upper bound for the sum with respect to this counting function will be given in terms of the degree of the hypersurface, the dimension of the singular locus, the upper bounds of height, and the degree of the field of definition.

关键词：地上复合代数学

Additive manufacturing of a high strength Al-5Mg_(2)Si-2Mg alloy:Microstructure and mechanical properties

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Journal of Materials Science & Technology 2021年第32期91卷 215-223页

作者： Hailin Yang Yingying Zhang Jianying Wang Zhilin liu chunhui liu Shouxun Ji State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Light Alloy Research Institute College of Mechanical and Electrical EngineeringCentral South UniversityChangsha 410083China BCAST Brunel University LondonUxbridgeMiddlesex UB83PHUnited Kingdom

A novel Al-5 Mg2 Si-2 Mg alloy was processed by selective laser melting(SLM) to understand its representative features of microstructural evolution and mechanical properties during additive manufacturing(AM). The as-SLM fabricated Al-5 Mg_(2) Si-2 Mg alloy is found to deliver much less hot cracks and other defects. Meanwhile, excellent mechanical property is also achieved, i.e. 452 ± 11 MPa for ultimate tensile strength, 295 ± 14 MPa for yield strength, and 9.3 ± 2.5% for elongation. Clearly, these mechanical properties are better than that obtained by high pressure die casting(HPDC), and better than some other alloys obtained by SLM. The as-SLM fabricated Al-5 Mg_(2) Si-2 Mg alloy is featured by the significantly refined microstructures in the compact primary α-Al, the divorced Mg_(2) Si eutectic networks distributing atα-Al grain boundaries, and some α-Al Fe Mn Si phase in association with eutectic Mg_(2) Si phase. The high strength and ductility of the alloy are attributed to its unique features including(a) the reduced solidification range,(b) the possible increase of the eutectic level in the microstructure, and(c) the shift of eutectic point and the maximum solubility point of Mg2 Si in Al matrix.

关键词： Aluminium alloys Additive manufacturing Selective laser melting Microstructure Mechanical properties

Optimization of bits allocation and path planning with trajectory constraint in UAV-enabled mobile edge computing system

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Chinese Journal of Aeronautics 2020年第10期33卷 2716-2727页

作者： Yizhe LUO Wenrui DING Baochang ZHANG Wenqian HUANG chunhui liu School of Electronics and Information Engineering Beihang UniversityBeijing 100083China Institute of Unmanned System Beihang UniversityBeijing 100083China School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100083China

In this paper,an Unmanned Aerial Vehicle(UAV)enabled Mobile Edge Computing(MEC)system is studied,in which UAV acts as server to offer computing offloading service to the Mobile Users(MUs)with limited computing capability and energy budget.We aim to minimize the total energy consumption of MUs by jointly optimizing the bit allocation for uplink,computing at the UAV and downlink,along with the UAV trajectory in a unified framework.To this end,a trajectory constraint model is employed to avoid sudden changes of velocity and acceleration during flying.Due to high-order information in use,we lead to a more reasonable nonconvex optimization problem than prior arts.An Alternating Direction Method of Multipliers(ADMM)method is introduced to solve the optimization problem,which is decomposed into a set of easy subproblems,to meet the requirement on the efficiency in edge computing.Numerical results demonstrate that our approach leads a smoother UAV trajectory,significantly save the energy consumption for UAV during flying.

关键词： Constraint implementation Edge computing Energy consumption Optimization methodology Unmanned Aerial Vehicles(UAV)

Normal Bipolar Fuzzy Ideals in Non-involutive Residuated Lattices

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Journal of Mathematical Research with Applications 2020年第5期40卷 441-452页

作者： chunhui liu School of Mathematics and Computer Science Chifeng University

In this paper, the problem of bipolar fuzzy ideal is further studied in non-involutive residuated lattices. The notion of normal bipolar fuzzy ideal is introduced, some important properties and equivalent characterizations of normal bipolar fuzzy ideals are obtained. In addition, two special types of normal bipolar fuzzy ideals are defined, which are called maxima and completely normal bipolar fuzzy ideals, respectively, and their relationships are discussed.This work further expands the way for revealing the structural characteristics of non-involutive residuated lattices.

关键词： non-classical logic non-involutive residuated lattice bipolar fuzzy set normal bipolar fuzzy ideal