检索结果-南通市图书馆

青藏高原及其周边志留纪综合地层、生物群与古地理演化

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中国科学：地球科学 2024年第4期54卷 1026-1057页

作者：陈中阳陈清王光旭方翔唐鹏闫冠州袁文伟黄冰张小乐燕夔张元动王怿中国科学院南京地质古生物研究所现代古生物学和地层学国家重点实验室南京210008 中国科学院大学北京100049

青藏高原志留纪的古生物学与地层学研究已有百余年的历史,随着第二次青藏高原综合科学考察研究项目的启动,对于青藏高原志留纪的地层系统和化石群的总结,及其与周边地区的对比亟待更新.本文在青藏高原及其周边选择了33条代表剖面,从地... 详细信息

青藏高原志留纪的古生物学与地层学研究已有百余年的历史,随着第二次青藏高原综合科学考察研究项目的启动,对于青藏高原志留纪的地层系统和化石群的总结,及其与周边地区的对比亟待更新.本文在青藏高原及其周边选择了33条代表剖面,从地层区划、岩石地层、年代地层和生物地层等方面,对已有的资料进行了总结,将青藏高原及其周边划为了4个地层区:西藏-滇西-川西地层区、昆仑-祁连地层区、华南地层区和塔里木地层区.其中青藏高原主体部分被划入了西藏-滇西-川西地层区,该地层区地层和生物组合发育基本完整,一定程度上弥补了我国其他地区志留系研究的不足.通过对志留纪青藏高原及其周边古生物地理研究的总结,尤其是对鱼类动物群、孢型植物组合和腕足动物群分布特征的梳理,指出华南、塔里木和印支等三大板块之间的关系应该比此前认为的更为密切.与研究程度较高的周边地区相比,青藏高原主体部分的志留系尚处于初步研究阶段,诸多问题和领域有待开展和深入研究.未来需要对志留系底部黑色岩系的时限、分布和资源量进行研究,为我国未来页岩气勘探开发提供新的方向.志留系中-上部浅海地层需要进行进一步的划分.由于青藏高原地区的志留系发育较完整,在生物地层学工作基础上,更有潜力补充和完善我国志留纪的碳同位素地层学研究.

关键词：青藏高原志留纪地层区划岩石地层生物地层古地理演化

High-Speed Friction Stir Welding of T6-Treated B4Cp/6061Al Composite

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 67-74页

作者： Y.z.Li Y.N.zan q.z.wa.g B.L.Xiao z.Y.Ma Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Science and Technology of China Shenyang 110016China

T6-treated 20 wt% B4 Cp/6061 Al sheets were joined under welding speeds of 400–1200 mm/min by friction stir welding(FSW) with a threaded cermet pin. The macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone(Nz) of the joints, the B4 C particles were broken up and uniformly redistributed. The Nz exhibited lower hardness than the base metal(BM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the BM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ~ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the Nz. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the Nz due to the kissing bond defects.

关键词： Metal-matrix composites Microstructures Mechanical properties Friction stir welding High-speed welding

Mechanical properties of cocoons constructed consecutively by a single silkworm caterpillar,Bombyx mori

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2008年第2期24卷 151-160页

作者： S.q.Huang H.P.zhao X.q.Feng W.Cui z.Lin M.q.Xu Department of Engineering Mechanics FML Tsinghua University Beijing 100084 China Department of Sericulture Shandong Agriculture University Tai'an 271018 China Department of Landscape Architecture Human Environment-Biological Polytechnic College. Hengyang 421005 China

Most animals have the ability to adapt, to some extends and in different ways, the variation or disturbance of environment. In our experiments, we forced a silkworm caterpillar to spin two, three or four thin cocoons by taking it out from the cocoon being constructed. The mechanical properties of these cocoons were studied by static tensile tests and dynamic mechanical thermal analysis. Though external disturbances may cause the decrease in the total weight of silk spun by the silkworm, a gradual enhancement was interestingly found in the mechanical properties of these thin cocoons. Scanning electron microscopy observations of the fractured specimens of the cocoons showed that there exist several different energy dissipation mechanisms occurred simultaneously at macro-, meso-, and micro-scales, yielding a superior capacity of cocoons to adsorb the energy of possible attacks from the outside and to protect efficiently its pupa against damage. Through evolution of millions of years, therefore, the silkworm Bombyx mori seems to have gained the ability to adapt external disturbances and to redesign a new cocoon with optimized protective function when its first cocoon has been damaged for some reasons.

关键词： Silk Silkworm cocoon Mechanical property Biomimetics

ground-state mass of ^(22)Al and test of state-of-the-art ab initio calculations

在线全文

学校读者我要写书评

暂无评论

Chinese Physics C 2024年第3期48卷 72-78页

作者：孙铭泽于越王新鹏王猛李健国张玉虎 K.Blaum 陈祖毅陈瑞九邓涵宇付超义葛文文黄文嘉焦红扬李红蕙李宏福罗胤芳廖挺 YuALitvinov 司敏帅鹏史金阳王茜邢元明徐星徐瑚珊许甫荣袁琪 T.Yamaguchi 颜鑫亮杨建成原有进周小红周旭张敏曾奇 CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern PhysicsChinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China Max-Planck-Institut für Kernphysik Saupfercheckweg 169117 HeidelbergGermany gSI Helmholtzzentrum für Schwerionenforschung Planckstraße 164291 DarmstadtGermany Advanced Energy Science and Technology guangdong Laboratory Huizhou516007China State Key Laboratory of Nuclear Physics and Technology School of PhysicsPeking UniversityBeijing 100871China Department of Physics Saitama UniversitySaitama 338-8570Japan School of Nuclear Science and Engineering East China University of TechnologyNanchang 330013China

The ground-state mass excess of the T_(z)=−2 drip-line nucleus ^(22)Al is measured for the first time as 18103(10)keV using the newly-developed Bρ-defined isochronous mass spectrometry method at the cooler storage ring in *** new mass excess value allowed us to determine the excitation energies of the two low-lying 1+states in ^(22)Al with significantly reduced uncertainties of 51 *** compared to the analogue states in its mirror nucleus ^(22)F,the mirror energy differences of the two 1^(+)states in the ^(22)Al-^(22)F mirror pair are determined to be−625(51)keV and−330(51)*** excitation energies and mirror energy differences are used to test the state-of-the-art ab initio valence-space in-medium similarity renormalization group calculations with four sets of interactions derived from the chiral effective field *** mechanism leading to the large mirror energy differences is investigated and attributed to the occupation of theπs_(1/2) orbital.

关键词： nuclear mass Bρ-defined IMS mirror energy difference ab initio VS-IMSRg calculations chiral interactions

A new model for the expansion tube considering the stress coupling:Theory,experiments and simulations

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2022年第7期18卷 1190-1204页

作者： M.z.Wu X.W.zhang q.M.zhang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyHaidian DistrictBeijing10081China

Based on the two-arc profile assumption,the expansion deformation and energy absorption of circular tubes compressed by conical-cylindrical dies were ***,the deformation of the two arcs was analyzed independently and an improved model denoted as Model-I was ***,by further involving the coupling between the bending moment and membrane forces,a more elaborate model,i.e.,Model-II was ***,experiments and simulations were conducted to verify the models,which show that,compared with previous theoretical models,Model-II could not only capture the prominent features of the deformation,but also improve the prediction accuracy of the steady driving force *** means of this model,it was found that the critical semi-conical angle,which makes the driving force minimum,increases with the increase of the friction coefficient,expansion ratio as well as the radius/thickness ratio of the ***,the energy dissipation due to stretching is always greater than that of bending,while the friction dissipation can account for the largest proportion at small semi-conical angle or large friction *** a certain friction and die conditions,the specific energy absorption of expanded tubes can be much higher than that under progressive collapse mode.

关键词： Expansion Circular tube Stress coupling Strain hardening Energy absorption

EXPERIMENTAL RESEARCH AND NUMERICAL SIMULATION OF LASER SHOCK FORMINg OF TA2 TITANIUM SHEET

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 347-354页

作者： F. wang z. q. Yao J. Hu q.L. Deng School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200030 China

Laser shock forming （ISF） was a new technique realized by applying an impulsive pressure generated by laser-induced shock wave on the surface of metal sheet. LSF of metal sheet was investigated with experiments and numerical simulation. The basic theories were introduced; the surface quality and deformation of the processed titanium sample （TA2） were examined; ABAqUS was used to simulate ISF and the central displacement of the shocked region was measured and compared with the simulation. Overlapped ISF treatment was experimentally carried out to produce groove and simulation. The results showed that the surface quality and the microstructure with single laser pulse had no remarkable change, and ablation was observed on the surface of the sample with overlapped pulses. The deformation observed in the numerical simulation agreeed with that observed in the experimental measurement quite well.

关键词： laser shock forming numerical simulation surface quality deformation

收缩压与脑皮质结构异常改变相关:孟德尔随机化研究证据

在线全文

学校读者我要写书评

暂无评论

中华高血压杂志（中英文） 2024年第5期32卷 446-446页

作者：袁源(译) 练桂丽(审校) 不详

高血压被认为是脑血管疾病和认知减退的重要危险因素。但是,高血压、收缩压/舒张压、脉压和平均动脉压对脑皮质结构的具体影响尚不清楚。孟德尔随机化为探究血压组分和脑皮质改变的因果关系提供了可靠的方法。方法:该研究为孟德尔随机... 详细信息

高血压被认为是脑血管疾病和认知减退的重要危险因素。但是,高血压、收缩压/舒张压、脉压和平均动脉压对脑皮质结构的具体影响尚不清楚。孟德尔随机化为探究血压组分和脑皮质改变的因果关系提供了可靠的方法。方法:该研究为孟德尔随机化研究,采用来自血压组分和神经影像学的大型全基因组关联研究数据进行分析。

关键词：脑皮质孟德尔随机化脑血管疾病全基因组关联研究危险因素平均动脉压神经影像学异常改变

Microstructure Evolution of in situ (Ti3AlC+Ti5Si3 )/Ti3Al Composite Sheet with a Novel quasi-continuous Chain Reinforcement Distribution Architecture Prepared by Using Roll Bonding and Reaction Annealing

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2013年第12期29卷 1191-1196页

作者： J.C.Pang g.H.Fan X.P.Cui A.B.Li L.geng z.z.zheng q.W.wang School of Materials Science and Engineering Harbin Institute of Technology

The Ti3Al matrix composite sheet with a novel quasi-continuous chain reinforcement distribution was prepared by using roll bonding and subsequent reaction annealing with pure Ti and SiCp/Al *** (Ti3AlC t Ti5Si3) reinforcements were produced by in situ reaction of the as-rolled Tie(SiC p/Al) laminated composite sheet after a two-stage annealing treatment including first annealing at 660 C and second annealing at 1250 *** microstructure evolution during the reaction annealing was *** the first reaction annealing,TiAl3was formed,and the SiC particles were pushed together due to the Kirkendall effect,and after the second reaction annealing,Ti3Al,Ti3AlC and Ti5Si3were *** addition,the reinforcement distribution presents a quasi-continuous chain microstructure in Ti3Al matrix composite sheet.

关键词： Composite Intermetallic Fabrication Reaction synthesis

On the mechanism of Si-promoted destabilization of TiC_(x)particles in Al alloys

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第34期165卷 17-26页

作者： H.Dong Y.C.guo Y.z.Chen F.Xia q.q.guo q.Chen g.L.Li J.Y.zhao Y.zhong J.P.Li School of Materials and Chemical Engineering Xi’an Technological UniversityXi’an 710021China State Key Lab.of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China School of Science Xi’an University of Science and TechnologyXi’an 710054China

TiC_(x)is an excellent composite strengthening particle and grain refiner for Al ***,the stability of TiC_(x)is poor when solute Si exists in Al alloy melts,which significantly depresses its strengthening and grain refining *** this work,the destabilization mechanisms of the TiC_(x)particles in Al-Si alloy melt with a composition of Al-7Si-7.5TiC were explored via experiments,first-principles calculations and thermodynamic *** experimental results show that Si atoms diffuse into TiC_(x)and Ti atoms are released into the Al melt to form a Ti-rich transition zone during the insulation of TiC_(x)in Al-Si melt,and the TiAlySiz and Al_(4)C_(3)phases are solidified in the Ti-rich zone and at Ti-rich zone/TiC_(x)interface,*** first principles calculations show that the low formation energy of C vacancies facilitates the rapid diffusion of Si atoms in TiC_(x),while the doping of Si atoms reduces the energy barrier of diffusion of Ti atoms in TiC_(x)and promotes the formation of Ti-rich *** thermodynamic calculations show that the wide crystallization temperature range of the destabilized product TiAlySiz phase is the key to continuous decomposition of TiC_(x)*** addition,the driving force of the main destabilization reaction of TiC_(x)in the Al-Si alloys is about 44 times higher than that in the Al alloys without Si *** indicates that the presence of solute Si remarkably promotes the subsequent decomposition process of TiC_(x)in the Al-Si alloy melts.

关键词： Al-Si alloy TiC_(x)particles Destabilization First principles calculations Thermodynamics