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含水率对红层泥岩填料刚度劣化特性及微观结构影响研究

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岩土力学 2024年第7期45卷 1976-1986页

作者：陈康刘先峰袁胜洋马杰陈忆涵蒋关鲁西南交通大学高速铁路线路工程教育部重点实验室四川成都610031 西南交通大学土木工程学院四川成都610031 加拿大皇家军事学院加拿大金士顿K7K7B4 新疆工程学院新疆乌鲁木齐830023

为研究含水率对红层泥岩填料刚度劣化规律和微观结构的影响,开展了不同含水率下三轴不排水剪切试验、压汞试验和扫描电镜试验,基于能量守恒定律推导了填料刚度劣化与弹塑性应变能增量间的关系。结果表明:填料黏聚力随含水率增加而降低,... 详细信息

为研究含水率对红层泥岩填料刚度劣化规律和微观结构的影响,开展了不同含水率下三轴不排水剪切试验、压汞试验和扫描电镜试验,基于能量守恒定律推导了填料刚度劣化与弹塑性应变能增量间的关系。结果表明:填料黏聚力随含水率增加而降低,内摩擦角则随含水率增加先增加后降低。填料结构损伤由应变能转化引起,从宏观上表现为刚度劣化。归一化刚度比值随塑性应变能增量占比增加而线性降低,随应力发展呈非线性衰减。以最优含水率为界,当试样在干侧时,填料有较好的荷载抵抗能力;湿侧填料荷载抵抗能力远低于干侧。损伤应力等值线与等含水率线构成上下界为对数曲线的状态面。填料孔隙分布在干侧为单峰形态,粒间接触较为紧密,结构稳定性好。在湿侧呈双峰结构,团聚体排列定向性程度较低。填料应在干侧压实填筑,推荐采用5%~7%作为填筑目标含水率。

关键词：路基填料红层泥岩刚度劣化应变能微观结构

顺倾及反倾层状碎裂结构斜坡地震反应的大型振动台试验研究

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岩土力学 2024年第2期45卷 489-501页

作者：王通刘先峰袁胜洋蒋关鲁胡金山邵珠杰田士军西南交通大学土木工程学院四川成都610031 西南交通大学高速铁路线路工程教育部重点实验室四川成都610031 新疆工程学院土木工程学院新疆乌鲁木齐830023 中铁第一勘察设计院集团有限公司陕西西安710043

西南艰险山区分布着大量的不同倾向的层状碎裂结构斜坡,地震作用下极易发生崩塌、滑坡等灾害,对在建的川藏铁路造成严重威胁。通过大型振动台模型试验,研究了强震条件下顺倾、反倾层状碎裂结构斜坡的动力响应、失稳破坏模式以及能量传... 详细信息

西南艰险山区分布着大量的不同倾向的层状碎裂结构斜坡,地震作用下极易发生崩塌、滑坡等灾害,对在建的川藏铁路造成严重威胁。通过大型振动台模型试验,研究了强震条件下顺倾、反倾层状碎裂结构斜坡的动力响应、失稳破坏模式以及能量传递规律。试验结果表明:反倾斜坡的抗震性能显著优于顺倾斜坡;顺倾斜坡的破坏模式主要为拉裂-剪切-隆起-滑移型破坏,反倾斜坡的破坏模式主要为拉伸-弯曲-倾倒-崩塌型破坏;反倾斜坡的自振频率高于顺倾斜坡,顺倾斜坡的自振频率随震级的增加而逐渐降低,而反倾斜坡的自振频率在地震波幅值为0.4g~0.7g时出现反复震荡现象;顺倾斜坡存在明显的高程放大效应和趋表效应,反倾斜坡存在高程放大效应,其内部的加速度响应大于坡表。边际谱识别显示:顺倾斜坡的边际谱幅值(peak of marginal spectrum amplitude,简称PMSA)突变在坡腰上部最显著,说明该位置附近地震波的能量损失最大,反映出顺倾斜坡在坡腰上部附近形成了滑动破坏面;反倾斜坡的PMSA在坡肩处降低得最为显著,反映出坡肩部位损伤最为严重,易发生局部崩塌破坏。分析结果与试验现象能够较好地吻合,进一步揭示了不同结构类型层状碎裂结构斜坡在强震作用下的动力响应与失稳破坏模式,为川藏铁路的安全建设提供了依据。

关键词：顺倾斜坡反倾斜坡振动台试验地震加速度峰值(peak ground acceleration,简称PGA)放大系数破坏模式损伤识别

Microstructure and Mechanical Properties of CNT-Reinforced AZ91D Composites Fabricated by Ultrasonic Processing

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Acta Metallurgica Sinica(English Letters) 2016年第7期29卷 652-660页

作者： Fu-Ze Zhao Xiao-Hui Feng yuan-sheng yang Institute of Metal Research Chinese Academy of Sciences

Carbon nanotube （CNT）-reinforced AZ91D alloy composite was fabricated by ultrasonic processing. The microstructure and mechanical properties of the CNTs/AZ91D composites were investigated. Obvious grain refinement was achieved with the addition of 0.5 wt% CNTs. The SEM observation indicated that CNTs were distributed near the grain boundary or around the inter-grain β-Mg17A112 phase. No evident reaction product was found at the interface between CNTs and AZ91D matrix. Compared to the monolithic AZ91D alloy, the yield strength, ultimate tensile strength, and elongation of the 0.5 wt% CNTs/AZ91D composite were improved significantly. However, the poor interface bonding between CNTs and AZ91D matrix restricted further improvement in mechanical properties.

关键词： Carbon nanotubes (CNTs) Magnesium matrix composites Ultrasonic vibration Microstructure Mechanical properties

Microstructure Evolution and Growth Orientation of Directionally Solidified Mg–4 wt% Zn Alloy with Different Growth Rates

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Acta Metallurgica Sinica(English Letters) 2017年第12期30卷 1185-1191页

作者： Hong-Min Jia Xiao-Hui Feng yuan-sheng yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China University of Chinese Academy of Sciences Beijing 100039China Shandong Key Laboratory for High Strength Lightweight Metallic Materials Ji'nan 250014 China

The microstructure evolution and growth orientation of directionally solidified Mg-4 wt% Zn alloy in the growth rate range from 20 to 200μm/s were investigated. A typical cellular structure was observed with a growth rate of 20 μm/s, and the cellular spacing was 115 μm. When the growth rate increased to 60 μm/s, cellular structure with some developed perturbations was obtained and the cellular spacing was 145 μm, suggesting that the cell-to-dendrite transition happened at the growth rate lower than 60 μm/s. As the growth rate further increased, the microstructure was dendritic and the primary dendritic arm spacing decreased. The relationship between the primary dendritic arm spacings and the growth rates was in good agreement with Trivedi model during dendritic growth. Besides, X-ray diffraction and transmission electron microscopy analyses showed that the growth direction of directionally solidified Mg-4 wt% Zn alloy was （1120） lay in {0002} crystal plane, and the preferred orientation was explained with the lattice vibration model for one-dimensional monatomic chain.

关键词： Directional solidification Mg-Zn alloy Microstructure evolution Primary dendritic arm spacing Growth orientation

Resonance Light Scattering Spectra of Silver Thiocyanate System and its Application in Analysis

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Chinese Chemical Letters 2005年第8期16卷 1063-1066页

作者： Chang Yin LU Zhi Hui HAN sheng yuan yang School of Chemistry and Chemical Engineering Nanhua University School of Public Health Nanhua UniversityHengyang 421001 Institute of Labour Hygiene and Occupational Diseases of Human Province Changsha 410007

A novel determination method of Ag^＋ was established. In acetic acid-sodium acetate buffer （pH 5.0） medium, Ag^＋ reacts with SCN^- to form AgSCN in the presence of TritonX-100,which results in an increase of resonance light scattering （RLS）and giving a new RLS *** maximum RLS peak was at 585 nm,The enhancement of resonance light scattering at 585 nm was proportional to the concentration of Ag^＋ ranging from 0.0045-4.00μg mL^-1 （r=9991）,and the detection limit was 1.37 ng mL^-1 with the recovery of 97.70%- 104.80%。

关键词： Resonance light scattering silver silver thiocyanate.

Improved wear resistance of biodegradable Mg-1.5Zn-0.6Zr alloy by Sc addition

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Rare Metals 2021年第8期40卷 2206-2212页

作者： Tao Li Xi-Tao Wang Shou-Qiu Tang yuan-sheng yang Jian-Hua Wu Ji-Xue Zhou Shandong Provincial Key Laboratory of High Strength Lightweight Metallic Materials Advanced Materials InstituteQilu University of Technology(Shandong Academy of Sciences)Jinan250014China Institute of Metal Research Chinese Academy of SciencesShenyang110016China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing100083China Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing100083China

Magnesium alloys exhibit significant potential for use in next-generation biodegradable *** magnesium alloys are expected to exhibit good wear *** this work,the effects of rare earth metal Sc on the wear resistance of biodegradable magnesium alloys were *** average grain sizes of Mg-1.5 Zn-0.6 Zr-x Sc(ZK21-x Sc,x=0,0.2,0.5,1.0;wt%)alloys decreased with Sc content *** other rare earth metals,the grain refinement mechanism of Sc belongs to the heterogeneous nucleation *** yield tensile strengths and Vickers hardness of the ZK21-x Sc alloys markedly improved with the addition of Sc *** could be due to the grain refinement and enhanced bond energy resulting from Sc ***,the friction and wear tests showed that the friction coefficient of the alloys decreased and the weight loss reduced with Sc addition *** implies that Sc addition could enhance the wear resistance of magnesium *** the addition of Sc increasing,the peeling phenomenon weakened gradually and the worn surfaces of samples became *** major wear mechanisms of the as-cast ZK21-x Sc alloys were abrasion wear and delamination wear.

关键词： Magnesium Wear resistance Scandium Hardness Biodegradable

Recent Advances in Deciphering the Mechanisms and Biological Functions of DNA Demethylation

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Chinese Journal of Chemistry 2024年第6期42卷 645-651页

作者： yang Feng sheng-Jun Chen Bi-Feng yuan Key Laboratory of Aquatic Product Processing Ministry of Agriculture and Rural AffairsNational R&D Center for Aquatic Product ProcessingSouth China Sea Fisheries Research InstituteChinese Academy of Fishery SciencesGuangzhouGuangdong510300 China School of Public Health Research Center of Public HealthRenmin Hospital of Wuhan UniversityWuhan UniversityWuhanHubei430071 China

5-Methylcytosine (5mC) is a dynamic and reversible epigenetic modification in genomic DNA of higher *** has been well-established that the demethylation of 5mC occurs through the ten-eleven translocation (TET)-mediated oxidation of 5mC followed by thymine DNA glycosylase (TDG)-initiated base excision repair (BER).Recent findings also have identified an alternative pathway of DNA *** this pathway,TET enzymes directly oxidize 5mC to form 5-formylcytosine (5fC) or 5-carboxylcytosine (5caC).These modified bases can undergo direct deformylation or decarboxylation,***,DNA demethylation can also occur through the deamination of 5mC and 5hmC,resulting in the production of thymine and 5-hydroxymethyluracil (5hmU),*** DNA demethylation pathways possess critical functional implications and roles in biological *** Recent Advances article will focus on the studies of mechanisms and biological functions of DNA demethylation,shedding light on the reversible nature of the epigenetic modification of 5mC.

关键词： Epigenetics DNA DNA methylation 5-Methylcytosine Demethylation Mechanisms Biological functions C—C bond cleavage Mass spectrometry

Significant annealing-induced hardening effect in nanolaminate d-nanotwinne d(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)me dium-entropy alloy by severe cold rolling

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Journal of Materials Science & Technology 2024年第3期170卷 156-166页

作者： Shuqing yuan Hui Fu Lei Qian Chi Fai Cheung Xu-sheng yang State Key Laboratory of Ultra-precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518060China

Due to the easy coarsening caused by poor thermal stability,the verified annealing-induced hardening in nanograined metals can only maintain at a relatively low-temperature *** this study,a nanolam-inated(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)medium-entropy alloy with an average lamellae thickness of∼20 nm embedded by thinner nanotwins was fabricated by severe cold rolling to achieve superior thermal *** with the conventional nanotwinned CrCoNi with nanotwins inside ultra-fined grains,the hier-archical nanolaminated-nanotwinned(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8) exhibits a significant annealing-induced hard-ening effect,i.e.,hardness increasing from∼250 HV in the original specimen to∼500 HV in the cold-rolled status and finally∼630 HV after annealing at 600℃for 1 *** microstructure characterizations reveal that the reduced dislocation density and formation of L1_(2)ordered domain are mainly responsible for such hardening effect,which is facilitated by the effectively suppressed coarsening with annealing temperature,i.e.,slow detwinning process and well-retained low-angle nanolamellar *** coarsening mechanisms from the cold-rolled nanolamellae to the fully recrystallized micro-equiaxed structures under the annealing temperatures ranging from 400 to 800℃ were also elucidated by atomic observations.

关键词： Annealing-induced hardening Thermal stability Nanolaminated-nanotwinned structure CrCoNi Detwinning Grain boundary migration

Hot compression behavior and processing map of cast Mg-4Al-2Sn-Y-Nd alloy

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Transactions of Nonferrous Metals Society of China 2014年第3期24卷 626-631页

作者：王晶史宝良杨院生中国科学院金属研究所沈阳110016 山东省科学院新材料研究所济南250014

The plastic flow behavior of a newly developed high ductility magnesium alloy, Mg-4Al-2Sn-Y-Nd, was investigated by hot compression from 200 to 400 ℃ with a strain rate of 1.5×10-3 to 7.5 s-1. The results reveal that the strain rate sensitivity factor （m） of the alloy is much lower than that of the AZ31 alloy, which implies that the alloy should be more suitable for processing at high strain rate. The constitutive relationship of the alloy deformed at elevated temperature was obtained by plotting the experimental data. The stress exponent of the alloy is 10.33, which reveals that climb-controlled dislocations creep is the dominated deformation mechanism. The processing-map technique was used to determine the practical processing window. The proper deformation temperature and strain rate of the cast alloy were determined as 350-400 ℃ and 0.01-0.03 s-1, respectively.

关键词： magnesium alloy uniaxial compression apparent activation energy processing map