检索结果-南通市图书馆

Effect of refinement of grains and icosahedral phase on hot compressive deformation and processing maps of Mg-Zn-y magnesium alloys with different volume fractions of icosahedral phase

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2019年第1期35卷 181-191页

作者： T.y.kwak W.J.kim Department of Materials Science and Engineering Hongik University

The effect of the volume fraction of I-phase on the hot compressive behavior and processing maps of the extruded Mg-Zn-y alloys was examined, and the obtained results were compared with those of the cast alloys in a previous work. The average grain sizes, fractions of dynamically recrystallized(DRXed) grains,and sizes of DRXed grains of the extruded alloys after compressive deformation were significantly smaller,higher and smaller, respectively, than those of the cast alloys after compressive deformation under the same experimental conditions. This was because the microstructures of the extruded alloys, having much more grain boundaries and more refined I-phase particles than the cast alloys, provided a larger number of nucleation sites for dynamic recrystallization than those of the cast alloys. The constitutive equations for high-temperature deformation of the extruded and cast alloys could be derived using the same activation energy for plastic flow, which was close to the activation energy for lattice diffusion in *** with the cast alloys, the onset of the power law breakdown(PLB) occurred at larger ZenerHolloman(Z) parameter values in the extruded alloys. This was because the extruded alloys had finer initial grain sizes and higher fractions of finer DRXed grains compared to the cast alloys, such that the onset of PLB caused by creation of excessive concentrations of deformation-induced vacancies was delayed to a higher strain rate and a lower temperature. The flow-stress difference between the extruded alloys and the cast alloys could be attributed to the difference in the fraction of DRXed grains. According to the processing maps, the extruded alloys exhibited higher power dissipation efficiency and flow stability than the cast alloys. This agreed with the microstructural observations.

关键词： Hot compression Magnesium alloy Processing map Grain refinement Dynamic recrystallization

Superplastic behavior of an ultrafine-grained Mg-13Zn-1.55y alloy with a high volume fraction of icosahedral phases prepared by high-ratio differential speed rolling

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2017年第9期33卷 919-925页

作者： T.y.kwak W.J.kim Rare Metal R&BD Group Korea Institute of Industrial Technology Department of Materials Science and Engineering Hongik University

An ultrafine-grained（UFG） Mg-13Zn-1.55 y alloy（ZW132） with a high volume fraction（7.4%） of icosahedral phase（I-phase, Mg;Zn;y） particles was prepared by applying high-ratio differential speed rolling（HRDSR） on the cast microstructure following homogenization. The alloy exhibited excellent superplasticity at low temperatures(tensile elongations of 455% and 1021% 473 k-10;s;and 523 k-10;s;,respectively). Compared with UFG Mg-9.25Zn-1.66 y alloy（ZW92） with a lower volume fraction of I-phase particles（4.1%）, which was prepared using the same processing routes, the UFG ZW132 alloy exhibited a higher thermal stability of grain size. Rapid grain coarsening, however, occurred at temperatures beyond523 k, leading to a loss of superplasticity. The high-temperature deformation behavior of the HRDSRprocessed ZW132 alloy could be well described assuming that the mechanisms of grain boundary sliding and dislocation climb creep competed with each other and considering that the grain-size was largely increased by accelerated grain growth at the temperatures beyond 523 k.

关键词： Magnesium alloy Superplastic deformation Ultrafine grain Icosahedral quasicrystal Grain growth

Thermal stress analysis method considering geometric effect of risers in sand mold casting process

在线全文

学校读者我要写书评

暂无评论

China Foundry 2014年第6期11卷 531-536页

作者： S.y.kwak H.y.Hwang C.Cho e-Design R&D Group Korea Institute of Industrial Technology (KITECH) Department of Virtual Engineering Korea University of Science and Technology(UST) Department of Mechanical Engineering Inha University

Solidif ication and f luid f low analysis using computer simulation is a current common practice. There is also a high demand for thermal stress analysis in the casting process because casting engineers want to control the defects related to thermal stresses, such as large deformation and crack generation during casting. The riser system is an essential part of preventing the shrinkage defects in the casting process, and it has a great inf luence on thermal phenomena. The analysis domain is dramatically expanded by attaching the riser system to a casting product due to its large volume, and it makes FEM mesh generation diff icult. However, it is diff icult to study and solve the above proposed problem caused by riser system using traditional analysis methods which use single numerical method such as FEM or FDM. In this paper, some research information is presented on the effects of the riser system on thermal stress analysis using a FDM/FEM hybrid method in the casting process simulation. The results show the optimal conditions for stress analysis of the riser model in order to save computation time and memory resources.

关键词： thermal stress sand mold casting riser numerical analysis hybrid method simulation

Effects of displacement boundary conditions on thermal deformation in thermal stress problems

在线全文

学校读者我要写书评

暂无评论

China Foundry 2013年第3期10卷 187-194页

作者： S.y.kwak C.H.Lim J.H.Nam e-Design Center Korea Institute of Industrial Technology Department of Virtual Engineering University of Science and Technology

Most computational structural engineers are paying more attention to applying loads rather than to DBCs (Displacement Boundary Conditions) because most static stable mechanical structures are working under already prescribed displacement boundary conditions. In all of the computational analysis of solving a system of algebraic equations, such as FEM (Finite Element Method), three translational and three rotational degrees of freedom (DOF) should be constrained (by applying DBCs) before solving the system of algebraic equation in order to prevent rigid body motions of the analysis results (singular problem). However, it is very difficult for an inexperienced engineer or designer to apply proper DBCs in the case of thermal stress analysis where no prescribed DBCs or constraints exist, for example in water quenching for heat treatment. Moreover, improper DBCs cause incorrect solutions in thermal stress analysis, such as stress concentration or unreasonable deformation phases. To avoid these problems, we studied a technique which performs the thermal stress analysis without any DBCs; and then removes rigid body motions from the deformation results in a post process step as the need arises. The proposed technique makes it easy to apply DBCs and prevent the error caused by improper DBCs. We proved it was mathematically possible to solve a system of algebraic equations without a step of applying DBCs. We also compared the analysis results with those of a

关键词：铸造工艺金属材料热处理钢材料

侧支图：急性前循环缺血性脑卒中后病变进展和缺血半暗带的预测

在线全文

学校读者我要写书评

暂无评论

国际医学放射学杂志 2024年第3期 371-371页

作者： J.S.yi H.J.ki y.S.Jeon J.J.Park T.J.Lee J.T.kwak 黄世豪

摘要目的旨在评估侧支图预测急性前循环缺血性脑卒中后病变进展和缺血半暗带的能力。方法从前瞻性收集的数据库中选定数据进行回顾性分析。基于扩散加权成像

关键词：

Runaway Electron Suppression by ECRH and RMP in kSTAR

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2013年第2期15卷 119-122页

作者： A. C. ENGLAND Z. y. CHEN D. C. SEO J. CHUNG y. S. LEEV J. W. yOO W. C. kIM y. S. BAE y. M. JEONV J. G. kwak M. kWON kSTAR Team National Fusion Research Institute Daejeon Republic of Korea Huazhong University of Science and Technology National Fusion Research Institute Daejeon Republic of Korea

We have observed reduction of the runaway electron synchrotron radiation, hard X-ray （HXR） intensity, and HXR energy after applying 110 GHz 2nd harmonic electron cyclotron resonant heating （ECRH） during runaway electron （RE） discharges at low density with startup runaway electrons. However, we did not see a significant reduction of X-rays from 170 GHz 2nd harmonic ECRH at a higher field. A recently installed IR TV camera was used to observe the forward cone of synchrotron radiation from high energy REs in kSTAR. We have observed changes to the synchrotron images and reduction of the HXR by application of resonant magnetic perturbations （RMP） from in-vessel control coils （IVCC） installed inside kSTAR in the n----1 configuration.

关键词： tokamak runaway electron suppression X-ray synchrotron radiation

ICRF Heated Long-Pulse Plasma Discharges in LHD

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2006年第1期8卷 28-32页

作者： R. kUMAZAWA T. SEkI T. MUTOH k. SAITO T. WATARI y. NAkAMURA M. SAkAMOTO T. WATANABE S. kUBO T. SHIMOZUMA y. yOSHIMURA H. IGAMI y. TAkEIRI y. OkA k. TSUMORI M. OSAkABE k. IkEDA k. NAGAOkA O. kANEkO J. MIyAZAWA S. MORITA k. NARIHARA M. SHOJI S. MASUZAkI M. GOTO T. MORISAkI B. J. PETERSON k. SATO T. TOkUZAWA N. ASHIkAWA k. NISHIMURA H. FUNABA H. CHIkARAISHI T. NOTAkE y. TORII H. OkADA M. ICHIMURA H. HIGAkI y. TAkASE H. kASAHARA F. SHIMPO G.NOMURA C.TAkAHASHI M.yOkOTA A. kATO 赵燕平 J. S. yOON J. G. kwak H. yAMADA k. kAWAHATA N. OHyABU k. IDA y. NAGAyAMA N. NODA A. kOMORI S. SUDO O. MOTOJIMA National Institute for Fusion Science Toki Japan kyusyu University Kasuga Japan Nagoya University Faculty of Engineering Nagoya Japan kyoto University Institute of Advanced Energy Uji Japan Tsukuba University Plasma Research Center Tsukuba Japan Tokyo University Graduate School of Frontier Sciences Tokyo Japan Institute of Plasma Physics Chinese Academy of Sciences Hefei 230031 China kAERI 150 Deogjin-dong Yuseong-gu Daejeon Korea Rep.

A long-pulse plasma discharge for more than 30 *** achieved on the LargeHelical Device(LHD).A plasma of n_e=0.8×10^(19)m^(-3)and T_(iO)=2.0 keV was sustained withP_(ICH)=0.52 MW,P_(ECH)=0.1 MW and averaged P_(NBI)=0.067 *** injected heatingenergy was 1.3 GJ,which was a quarter of the prepared RF heating *** of the keys to thesuccess of the experiment was a dispersion of the local plasma heat load to divertors,accomplishedby shifting the magnetic axis inward and outward.

关键词：长脉冲等离子体放电 LHD ICRF加热螺旋/仿星器构造稳定态操作

Massively parallel electro-optic sampling of space-encoded optical pulses for ultrafast multi-dimensional imaging

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2023年第2期12卷 304-313页

作者： yongjin Na Hyunsoo kwak Changmin Ahn Seung Eon Lee Woojin Lee Chu-Shik kang Jungchul Lee Junho Suh Hongki yoo Jungwon kim korea Advanced Institute of Science and Technology(kAIST) Daejeon 34141Korea korea Research Institute of Standards and Science(kRISS) Daejeon 34113Korea

High-speed and high-resolution imaging of surface profiles is critical for the investigation of various structures and mechanical dynamics of micro-and nano-scale *** particular,recent emergence of various nonlinear,transient and complex mechanical dynamics,such as anharmonic vibrations in mechanical resonators,has necessitated real-time surface deformation imaging with higher axial and lateral resolutions,speed,and dynamic ***,real-time capturing of fast and complex mechanical dynamics has been challenging,and direct time-domain imaging of displacements and mechanical motions has been a missing element in studying full-field structural and dynamic ***,by exploiting the electro-optic sampling with a frequency comb,we demonstrate a line-scan time-of-flight(TOF)camera that can simultaneously measure the TOF changes of more than 1000 spatial coordinates with hundreds megapixels/s pixel-rate and sub-nanometre axial resolution over several millimetres *** unique combination of performances enables fast and precise imaging of both complex structures and dynamics in three-dimensional devices and mechanical resonators.

关键词： deformation dimensional dynamics

Portable System for CWA Detection Using Micro Array Gas Sensor

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

稀有金属材料与工程 2006年第A3期35卷 124-128页

作者： J.H.kwak y.T.Lim G.H.kim N.J.Choi H.D.Park G.H.Rue J.S.Huh J.C.kim D.D.Lee School of Electrical Engineering and Computer Science Kyungpook National UniversityDaegu 1370Korea Electronics and Telecommunications Research Institute Future Technology Research Division New Functional Information Devices TeamGajeongYuseong-GuDaejeon 161 Korea korea Electronics Technology Institute Yatap-DongBundang-GuSeongnam-SiGyeonggi-Do #68Korea Department of Materials Science and Metallurgy Kyungpook National UniversityDaegu 1370Korea Department of Chemical Engineering Kyungpook National UniversityDaegu 1370Korea

Biochemistry weapon is raising new tools of war and *** research is an experiment about portable system for CWAs (chemical warfare agents) detection using micro array gas *** were divided into four types such as blood, nerve,vesicant,and choking *** detect various CWAs,semiconductor thick film sensor array based on tin oxide was fabricated and their gas responses were *** temperature was range of 250℃to 350℃and gas concentration was range of 0.1μg/g to 10μg/*** array was measured as operating temperatures,concentrations for four simulant agents of *** parameters from results were carried out classification among CWAs through the principal component analysis (PCA).Also,classification of gases is studied using adaptive resonance theory (ART) that is one of neural network *** displayed using PDA system.

关键词： SnO2 chemical warfare agents(CWAs) portable system ART array PCA