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Degraded creep resistance induced by static precipitation strengthening in high-pressure die casting Mg-Al-Sm alloy

Journal of Materials Science & Technology 2024年第11期178卷 48-58页

作者： Qiang Yang Shuhui Lv Bo deng Norbert Hort Yuanding Huang wei Sun Xin qiu State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China School of Materials Science and Engineering Changchun University of Science and TechnologyChangchun 130022China MagIC-Magnesium Innovation Centre Helmholtz-Zentrum HereonMax-Planck Strasse 1Geesthacht 21502Germany Institute of Product Technology and Systems Leuphana University LüneburgUniversiättsalleLüneburg 121335Germany

Relationship between precipitation strengthening and creep resistance improvement has been an impor-tant topic for the widespread applications of magnesium ***,static precipitation strength-ening through thermal stable precipitates would generate satisfactory creep ***,an op-posite example is presented in this work and we propose that the size of precipitates plays a crucial role in controlling the operative creep *** addition,the precipitate components along with their crystal structures in the crept Mg-4Al-3Sm-0.4Mn samples with/without pre-aging were thor-oughly studied using Cs aberration-corrected high-angle annular dark-field scanning transmission elec-tron microscopy(HAADF-STEM).Previous aging generates a large density of fine precipitates(ling mechanisms are transferred from dislocation climb to dislocation slip after previous aging,thus leading to degradation of creep ***,there are mainly five types of precipitates/clusters,namelyβ"-(Al,Mg)3Sm,Al5Sm3,ordered Al-Sm cluster,ordered Al-Mn cluster and ordered/unordered AlMnSm *** crystal structures of the former two precipitates were discussed and the formation mechanisms of the precipitates/clusters were revealed.

关键词： Magnesium alloy Transmission electron microscopy Precipitation Creep resistance Segregation

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Distribution and mechanism of gently dipping fractures subjected to river incision: A case study from Nujiang River, China

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Journal of Mountain Science 2018年第1期15卷 211-224页

作者： zhu Lei HUANG Run-qiu YAN Ming CHEN Guo-qing wei wei State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology College of architecture and urban planning Sichuan Agricultural University

Gently dipping fractures subjected to river incision are widely distributed on rock *** this paper,a rock slope on the Nujiang River(China)is investigated to study the role of gently dipping fractures in the rock slopes *** field surveys indicate that gentle fractures are concentrated in four main ***,the kinematics of the fracture system suggest that the genesis of these fractures can be synthesized into a progressive evolution *** model indicates that the joints begin with the formation of an array of en echelon cracks that are subjected to continued crack elongation and shearing before ultimately approaching one another and interacting to form a complex joint *** analysis is performed to reveal the mechanisms of this genesis,and three main fracture patterns are identified based on the slope stress and are classified with respect to the slope *** on the detail field investigations and the evolutionary history of the river valley,we propose that intermittent incision by the river was the main factor contributing to the concentrated distribution of gently dipping joints.

关键词： Joints Rock slope Distribution Fracture mode Genesis mechanism

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Adsorption of humic acid from aqueous solution on bilayer hexadecyltrimethyl ammonium bromide-modified zeolite

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Frontiers of Environmental Science & Engineering 2011年第1期5卷 65-75页

作者： Yanhui ZHAN Jianwei lin Yanling qiu Naiyun GAO Zhiliang zhu State Key Laboratory of Pollution Control and Resource Reuse Tongji UniversityShanghai 200092China College of Marine Science Shanghai Ocean UniversityShanghai 201306China

Surfactant-modified natural zeolites(SMNZ)with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide(HTAB)onto the surface of a natural *** adsorption behavior of humic acid(HA)on SMNZ was *** indicate that the adsorbent SMNZ exhibited a higher affinity toward HA than the natural *** removal efficiency by SMNZ increased with HTAB *** Ca2+in solution favored HA adsorption onto *** capacity decreased with an increasing solution *** typical SMNZ with bilayer HTAB coverage,HA adsorption process is well described by a pseudo-second-order kinetic *** experimental isotherm data fitted well with the Langmuir *** maximum HA adsorption capacities for SMNZ with bilayer HTAB coverage at pH 5.5 and 7.5 were 63 and 41 mg·g^(-1),respectively.E2/E3(absorbance at 250 nm to that at 365 nm)and E4/E6(absorbance at 465 nm to that at 665 nm)ratios of the residual HA in solution were lower than that of the original HA *** indicates that the HA fractions with high polar functional groups,low molecular weight(MW),and aromaticity had a stronger tendency for adsorption onto SMNZ with bilayer HTAB *** show that HTABmodified natural zeolite is a promising adsorbent for removal of HA from aqueous solution.

关键词： bilayer surfactant-modified zeolite hexadecyltrimethyl ammonium bromide(HTAB) adsorption humic acid(HA)

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A Specification Test of Stochastic Diffusion Models

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Acta Mathematicae Applicatae Sinica 2013年第3期29卷 529-540页

作者： Shu-lin ZHANG Zheng-hong wei qiu-xiang BI School of Statistics Southwestern University of Finance and Economics College of Mathematics and Computational Science University of Shenzhen Department of Fixed Income Guangfa SecuritiesCo.Ltd.

In this paper, we propose a hypothesis testing approach to checking model mis-specification in continuous-time stochastic diffusion model. The key idea behind the development of our test statistic is rooted in the generalized information equality in the context of martingale estimating equations. We propose a bootstrap resampling method to implement numerically the proposed diagnostic procedure. Through intensive simulation studies, we show that our approach is well performed in the aspects of type I error control, power improvement as well as computational efficiency.

关键词： Stochastic diffusion model martingale estimating function generalized information equality

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Combinatorial screening via high-throughput preparation:Thermoelectric performance optimization for n-type Bi-Te-Se film with high average zT>1

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Journal of Materials Science & Technology 2023年第29期160卷 18-27页

作者： Guangyu Han wei zhu Siming Guo Jie Zhou Yutong Liu Yuan deng School of Materials Science and Engineering Beihang UniversityBeijing 100083China Research Institute for Frontier Science Beihang UniversityBeijing 100083China Key Laboratory of Intelligent Sensing Materials and Chip Integration Technology of Zhejiang Province(2021E10022) Hangzhou Innovation Institute of Beihang UniversityHangzhou 310052China

Thermoelectric materials have drawn extensive interest due to the direct conversion between electricity and heat,however,it is usually a time-consuming process for applying traditional“sequential”meth-ods to grow materials and investigate their properties,especially for thermoelectric films that typically require fine microstructure ***-throughput experimental approaches can effectively accelerate materials development,but the methods for high-throughput screening of the microstructures require further *** this work,a combinatorial high-throughput optimization solution of material properties is proposed for the parallel screening and optimizing of composition and microstructure,which involves two distinctive types of high-throughput fabrication approaches for thin films,along with a new portable multiple discrete masks based high-throughput preparation ***,Bi_(2)Te_(3-x)Se_(x)thin film library with 196 throughputs for locating the optimized composition is obtained in one growth *** addition,another thin film library composed of 31 materials with traceable process parameters is built to further investigate the relationship between microstructure,process,and thermoelectric *** high-throughput screening,the Bi_(2)Te_(2.9)Se_(0.1)film with(00l)orientation is prepared with a peak zT value of 1.303 at 353 K along with a high average zT value of 1.047 in the interval from 313 to 523 *** method can be also extended to the discovery of other functional thin films with a rapid combinatorial screening of the composition and structure to accelerate material optimization.

关键词： High-throughput preparation Thermoelectric performance Bi-Te-Se film Combinatorial screening

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Stress field interaction during propagation of adjacent tensile twinning nuclei in magnesium

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Rare Metals 2019年第8期38卷 721-732页

作者： Zhe Li Ben Xu Qi Sun qiu-lin Li wei Liu School of Materials Science and Engineering Tsinghua University Beijing 100084 China Daya Bay Nuclear Power Plant China Nuclear Power Engineering Co. Ltd Shenzhen 518000 China Joint Laboratory of Nuclear Materials and Service Safety Graduate School at Shenzhen Tsinghua University Shenzhen 518000 China

The shear stress field proximity to the twinning and prismatic/basal interfaces of {1012} tensile twins is shown by molecular dynamics *** stress field interacts and influences the twinning growth mode in the subsequent deformation process,which is simulated by changing the relative positions of the *** asymmetrical growth mode appears,in which the growth of one twin is predominant over the other when they are oriented at 45° to each *** growth mode is sensitive to the simulation temperature and strain rate and can be attributed to the interaction of the stress field proximity to the prismatic/basal interfaces and twinning planes.

关键词： Twinning Twin-twin interaction Stress field Molecular dynamics Magnesium

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Experimental study on pressure and aeration characteristics in stepped chute flows

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Science China(Technological Sciences) 2015年第4期58卷 720-726页

作者： XU wei lin LUO Shu Jing ZHENG qiu Wen LUO Jing State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University

The free flow on the step surfaces has received much attention for its representative body type,flow structure,water-air two phase flow,cavitation,and many complex *** experiments about the time-averaged pressure and aeration concentration distribution on the step surface show that the vertical plane of steps will inevitably experience negative pressure,which must rely on adequate aeration concentration to avoid cavitation ***,the self-aerated flow at the head section has a relatively low aeration concentration,and the concentration of the entire steps decreases with the increasing of weir head,the minimum appears in the vicinity of the corner,and the location is close to the minimum ***,it is necessary to set aerator in the upstream end of the step surfaces to avoid cavitation damage.

关键词： stepped spillway time-averaged pressure aerated flow cavitation erosion

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Peak compression technique in high-performance liquid chromatography

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Chinese Science Bulletin 2009年第16期54卷 2805-2809页

作者： wei YuXia WANG lin XIAO ShengYuan QING Hong zhu Yong HU GaoFei deng Yulin School of Life Science and Technology Beijing Institute of Technology Beijing 100081 China

Peak compression technique based on the difference of the solute migration velocity in two different mobile phases was described theoretically and confirmed using benzaldehyde and 4-hydroxyquinoline (4-HQ) as model compounds. After peak compression, the peak compression factors (the ratio of peak width at half-height under non-compression and that under compression condition) of benzaldehyde and 4-HQ were 0.19 and 0.13, respectively. By this application of the peak compression technique to the mixture, both enhanced peak height and good separation were obtained in one run cycle. This peak compression technique was introduced to determine benzaldehyde from semicarbazide-sensitive amine oxidase-catalyzed enzymetic reaction in order to illustrate the applicability of this technique to the real sample. As a result, the peak was compressed effectively, and 4.94-fold, 19.3-fold and 5.74-fold enhancement in peak height, plate number and signal to noise ratio were also achieved, respectively.

关键词：压缩技术高效液相色谱模型化合物脲甲醛迁移速度羟基喹啉压缩条件运行周期

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Dynamic mechanical behavior of ultra-high strength steel 30CrMnSiNi2A at high strain rates and elevated temperatures

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Journal of Iron and Steel Research International 2017年第7期24卷 724-729页

作者： qiu-lin Niu wei-wei Ming Ming Chen Si-wen Tang Peng-nan Li College of Mechanical and Electrical Engineering Hunan University of Science and Technology Hunan Provincial Key Laboratory of High Efficiency and Precision Machining of Difficult-to-Cut Material Hunan University of Science and Technology School of Mechanical Engineering Shanghai Jiao Tong University

During high speed machining in the field of manufacture,chip formation is a severe plastic deformation process including large strain,high strain rate and high *** the strain rate in high speed cutting process can be achieved to 105 s^（-1）.30CrMnSiNi2Asteel is a kind of important high-strength low-alloy structural steel with wide application *** the dynamic mechanical properties of30CrMnSiNi2Aunder the conditions of high strain rate and high temperature is necessary to construct the constitutive relation model for high speed *** dynamic compressive mechanical properties of30CrMnSiNi2Asteel were studied using split Hopkinson pressure bar（SHPB）tests at 30-700°C and3000-10000s^（-1）.The stress-strain curves of 30CrMnSiNi2Asteel at different temperatures and strain rates were investigated,and the strain hardening effect and temperature effect were *** results show that 30CrMnSiNi2Ahas obvious temperature sensitivity at 300°***,the flow stress decreased significantly with the increase of *** strain hardening effect of the material at high strain rate is not significant with the increase of *** strain rate hardening effect is obvious with increasing the *** to the experimental results,the established Johnson-Cook（J-C）constitutive model of 30CrMnSiNi2Asteel could be used at high strain rate and high temperature.

关键词： 30CrMnSiNi2A steel Dynamic mechanical behavior Split Hopkinson pressure bar High temperature High strain rate Ultra-high strength steel

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Accurate prediction of the critical heat flux for pool boiling on the heater substrate

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Chinese Physics B 2022年第6期31卷 476-482页

作者： Fengxun Hai wei zhu Xiaoyi Yang Yuan deng School of Energy and Power Engineering Beihang UniversityBeijing 100083China Research Institute for Frontier Science Beihang UniversityBeijing 100083China Beijing Advanced Innovation Center for Biomedical Engineering Beihang UniversityBeijing 100083China Hangzhou Innovation Institute Beihang UniversityHangzhou 310052China

While the influence of liquid qualities,surface morphology,and operating circumstances on critical heat flux(CHF)in pool boiling has been extensively studied,the effect of the heater substrate has *** on the force balance analysis,a theoretical model has been developed to accurately predict the CHF in pool boiling on a heater *** analytical expression for the CHF of a heater substrate is obtained in terms of the surface thermophysical *** is indicated that the ratio of thermal conductivity(k)to the product of density(ρ)and specific heat(cp)is an essential substrate property that influences the *** modifying the well-known force-balance-based CHF model(Kandlikar model),the thermal characteristics of the substrate are taken into *** bias of predicted CHF values are within 5%compared with the experimental results.

关键词： boiling heat transfer kandlikar model critical heat flux heater substrate

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