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APPLICATION OF Ct-PARAMETER FOR CREEP-FATIGUE CRACK GROWTH WITH SLOW LOAD RISING CONDITION

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Acta Metallurgica Sinica(English Letters) 1999年第1期12卷 22-30页

作者： Lee, j.H. yoon, K.B. kim, y.j. Back, U.B. Korea Inst of Nuclear Safety Taejon South Korea

Most of the assessment equations for Ct which is a wellknown fracture parameter characterizing high temperature crack growth rates, have limited applicability to constant load conditions after sudden loading. However, crack growth due to creep can also occur under load varying conditions when load rising time is so long that accumulated creep deformation near the crack tip is not *** this paper, the estimation equation of the Ctparameter which can be applied to the case of slow load rising, i.e., (Ct)r, is explained. And the correlation between (Ct)r at the end of the load increasing period and Ct at the beginning of the succeeding load hold period is discussed. Finite element analyses of several cases with various loading conditions were performed and results were presented to show the effectiveness of the proposed Ct estimation scheme. The general applicability of the equation is also discussed.

关键词： creep fatigue crack time dependent fracture mechanics Ctparameter,C*integral

静力疲劳荷载作用下的带预制板的连续组合双肋桥的裂缝控制

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钢结构(中英文) 2008年第5期 73-74页

作者： Ryu, H.K. kim, y.j. Chang, S.P.

为研究裂缝控制,选取了一个带有预制板的两跨连续组合双肋梁的足尺模型,并对其进行试验及观察。在试验中,第一次荷载加到360kN,然后进行疲劳荷载试验。最后静力加载至900kN。试验结果证实了带预制板的双肋连续组合梁显示出了在静力疲劳... 详细信息

为研究裂缝控制,选取了一个带有预制板的两跨连续组合双肋梁的足尺模型,并对其进行试验及观察。在试验中,第一次荷载加到360kN,然后进行疲劳荷载试验。最后静力加载至900kN。试验结果证实了带预制板的双肋连续组合梁显示出了在静力疲劳荷载作用下的组合截面的强度和刚度特性。然而,在负弯矩作用区域,裂缝集中在内部支撑之上的桥面之间的接缝部位,初始的裂缝间距由接缝处间的距离决定,在使用荷载作用下,带有预制板的组合桥梁的桥面和横向接缝的裂缝宽度可以被控制在一个容许裂缝宽度之内。弯矩曲率曲线或者由欧洲规范4-2中规定的抗弯刚度仍可被用于评估考虑到在这种桥梁上拉伸硬化作用的有效刚度。

关键词：裂缝控制连续组合双肋梁预制板环式节点横向接缝静力疲劳荷载组合截面特性负弯矩区域裂缝宽度组合截面的抗弯刚度

Maximizing biomass utilization: An integrated strategy for coproducing multiple chemicals

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journal of Energy Chemistry 2025年第1期100卷 180-191页

作者： Byeongchan Ahn Sua jo jonggeol Na j.jay Liu young-ju kim Wangyun Won Department of Chemical and Biological Engineering Korea University Department of Chemical Engineering (Integrated process) Kyung Hee University Department of Chemical Engineering and Materials Science Ewha Womans University Department of Chemical Engineering Pukyong National University Resources Engineering Plant Research Department Korea Institute of Geoscience and Mineral Resources

Lignocellulosic biomass is one of the viable solutions to alleviate the global warming. However, the limited utilization of biomass majorly focused on cellulose and hemicellulose restricts the economic and environmental feasibilities. To cope with this issue, we proposed an integrated process of co-producing 1,6-hexanediol（1,6-HDO） with tetrahydrofuran and adipic acid from biomass, referred to as Strategy A. To compare the impacts of lignin upgrading and feedstock, Strategy B, which co-produces tetrahydrofuran alone, and Strategy C, which is the traditional route to produce 1,6-HDO from fossil fuels, were used. Heat networks are also designed to reduce operating costs and indirect carbon emissions due to energy consumption, saving 87% and 83% of the heat and cooling requirements, respectively, in Strategy A. The market competitiveness of Strategy A was evaluated by determining the minimum selling price through techno-economic analysis, and sustainability was thoroughly investigated by quantifying the environmental impacts through both midpoint and endpoint life-cycle assessments（LCAs）.Strategy A was found to be the most favorable both economically（USRDSCHARDOLLAR3,402/ton） and environmentally（-26.9 kg CO2eq.）. This indicates that lignin valorization is not only economically but also environmentally preferred. Finally, changes in economic and environmental feasibilities depending on economic, process, and environmental parameters were investigated using sensitivity and uncertainty analyses. The results of these analyses provide valuable insight into bio-based chemical production.

关键词： Biorefinery Carbon mitigation Climate change Global warming Lignin utilization Bioeconomy

氧化反应相关基因多态性与先兆子痫发病的风险

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世界核心医学期刊文摘（妇产科学分册） 2005年第7期1卷 23-23页

作者： kim y.j. Park H.S. Park M.H. 李跃萍 Dept. of Obstetrics and Gynecology Ewha Womans University 9111 MokDong Yangcheonku Seoul 151- 070 South Korea

Objective: The purpose of this study was to determine whether genetic variability in oxidative stress- related enzymes contributes to individual preeclampsia susceptibility differences. Study Design: Polymorphisms in the cytochrome P450 (CyP)1A1 (MspI), CyP1A1(Ile/Val), glutathione Stransferase (GST)M1, GSTT1, myeloperoxidase (MPO), and manganese superoxide dismutase (MnSOD) genes were evaluated by polymerase chain reaction (PCR) or PCR- restriction fragment length polymorphism (RFLP) in 214 healthy controls with an uncomplicated obstetric history, and in 121 preeclampsia patients. χ 2 analyses were used to statistically evaluate differences. Results: No significant differences in the CyP1A1(MspI) or CyP1A1(Ile/Val) genotypes were observed between the healthy controls and the preeclampsia patients (χ 2 = 1.43, P = 0.49 versus χ 2 = 1.54, P = 0.46). The GSTM1 homozygous null type and GSTT1 homozygous null type were no differences in the patients and controls (χ 2 = 0.01, P = 0.92 versus χ 2 = 0.31, P = 0.57), and no significant differences in the polymorphisms of the MPO and MnSOD genotypes were found between the patients and controls (χ 2 = 2.00, P = 0.37 versus χ 2 = 0.07, P = 0.96). Conclusion: Polymorphisms in the oxidative stress- related genes (CyP1A1, GSTM1, GSTT1, MPO, MnSOD) do not seem to be risk factors for preeclampsia.

关键词：先兆子痫氧化反应基因多态性过氧物酶健康孕妇纯合子谷胱甘肽转移酶无显著性差异细胞色素氧化酶遗传基因

Photoluminescence enhancement of red-emitting GdVO_4:Eu and yVO_4:Eu phosphors by adding zinc

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journal of Rare Earths 2013年第1期31卷 13-17页

作者： K.Park j.kim K.y.kim j.y.kim y.kim S.j.Dhoble Faculty of Nanotechnology and Advanced Materials Engineering Sejong University Department of Advanced Materials Engineering Hoseo University Department of Chemistry and Institute of Basic Sciences Dankook University Department of Physics R.T.M. Nagpur University

We synthesized the rare-earth activated Ro.94_xEuo.06ZnxVO4 （R： Gd and y; 0〈_x〈_0.08） phosphors with a spherical mor- phology and a smooth surface by the ultrasonic spray pyrolysis. The annealed Ro.94_xEuo.06ZnxVO4 crystallized in the tetragonal zircon type structure, belonging to the space group of I41/amd. The incorporation of a small amount of Zn to Ro.94Euo.06VO4 improved the emission characteristics. The emission intensities of the Gdo.88EUo.06Zno.06VO4 and yo.9Euo.06Zno.04VO4 phosphors at 619 nm were 72% and 2 1% stronger than those of the Gdo,94Euo.06VO4 and yo.94Euo.06VO4 phosphors, respectively. We demonstrated that the addi- tion of Zn to Ro.94Euo.06VO4 was quite effective for improving the photoluminescent properties.

关键词： rare earths photolurninescence vanadate ultrasonic spray pyrolysis

Computational study on influence of RF shielding box on inductance of coil

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Plasma Science and Technology 2019年第6期21卷 23-28页

作者： S j kim j j LEE y S LEE j H kim S j yOU Applied Physics lab for PLasma Engineering(APPLE) Department of Physics Chungnam National University Daejeon 34134 Republic of Korea Korea Research Institute of Standards and Science(KRISS) Daejeon 34113 Republic of Korea

Despite the fact that a radio frequency (RF) shielding box affects a coil inductance used in matching network,RF engineers have used a coil inductance measured in open space on designing matching networks since it is difficult to precisely measure the coil inductance within the RF shielding *** this work,we investigate the influences of the RF shielding box on the coil inductance via a 3D full electromagnetic wave *** results shows that the coil inductance decreases from-6.0% to-11.9% compared with its ideal inductance depending on coil positions within the RF shielding *** inductive and capacitive coupling between the coil and surfaces of the RF shielding box contribute to the reduction of the coil *** expect that these results would be useful for those who design RF matching networks.

关键词： 3D full EM wave simulation RF matching component RF shield inductive and capacitive coupling

Difference in the Hot Compressive Behavior and Processing Maps between the As-cast and Homogenized Al-Zn-Mg-Cu(7075) Alloys

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journal of Materials Science & Technology 2016年第7期32卷 660-670页

作者： S.y. Park W.j. kim Department of Materials Science and Engineering Hongik University 72-1 Sangsu-dong Mapo-gu Seoul 121-791 Republic of Korea Advanced Fusion Process R&D Group Korea Institute of Industrial Technology 994-32 Dongchun-dong Yeonsu-gu Incheon 406-130 Republic of Korea

The deformation mechanisms and processing maps of the as-cast Al-Zn-Mg-Cu （？0？5） aluminum （AI） alloy were studied and compared with those of the homogenized 7075 Al alloy in the temperature range of 573-723 K and in the strain rate range of 10 3-10 s-1 to explore a possibility for directly using the as- cast 7075 Al alloy as a billet for hot working. The as-cast and homogenized 7075 A1 alloys had similar grain sizes and showed similar high-temperature deformation behaviors. The as-cast 7075 Al alloy, however, exhibited higher power efficiencies and smaller unstable flow regions compared to the homogenized 7075 AI alloy because of the presence of secondary phases （MgZn2） segregated at the dendritic interfaces in the as-cast microstructure, which were formed during non-equilibrium solidification. These segregated phases provided nucleation sites for dynamic recovery or continuous dynamic recrystallization, and as a result a fine and more homogeneous （sub）grain structure could be obtained from the as-cast micro- structure compared to the homogenized microstructure. The current work suggested the possibility and advantage of using as-cast microstructures for hot working of aluminum alloys with high content of solutes.

关键词： Al-based alloysProcessing mapHot compressionAs-cast microstructureSegregationRecrystallization

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

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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

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

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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