Effects of Cooling Rate on the Microstructure and Tensile Properties of Wire-Arc Additive Manufactured Ti–6Al–4V Alloy

Hui‑Jun Yi,Jin‑Woo Kim,Young‑Lak Kim,Sangyong Shin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.8

Wire-arc additive manufacturing has emerged as a technology that could replace the conventional manufacturing processof titanium alloys. However, it produces a coarse β grain, which can accumulate via several deposited materials, resulting isstrong texture and anisotropy. To investigate potential solutions, the effects of the cooling rate on the resulting microstructureand tensile properties were studied. The cooling rate of the deposited materials was adjusted by interpass temperaturecontrol. Under rapid cooling, fine α + α′ grain with a low aspect ratio were observed and tensile and hardness propertieswere also improved.

Effects of Quenching Methods and Aging Processes on the Crushing Properties and Microstructure of Al–Zn–Mg Alloy Thin-Walled Square Extrusions

Hui Guo,Jin Zhang,Cheng Wang,Yun‑lai Deng 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

In this study, the effects of different (online quenching and offline quenching) quenching methods and aging processes (T6and T73) on the crashworthiness and microstructural evolution of three Al–Zn–Mg alloys (G1–G3) were studied by conductingtensile test and axial compression tests at room temperature, combined with optical metallography, electron back scattereddiffraction, and transmission electron microscopy microstructural observations. The obtained results revealed that thecrushing properties of three different Al–Zn–Mg alloys subjected to different quenching methods and aging processes weresignificantly different. Their crushing energy absorption of are ranked as follows: G1 > G3 > G2. The highest total energyabsorption gap (between T6 and T73) is the G1 alloy, and the lowest one is the G3 alloy. The largest total energy absorptiongap between the two quenching methods is the G3 alloy, and the smallest one is the G1 alloy. The G2 alloy with the largesttotal amount of Zn + Mg has the highest number density of matrix precipitates, the largest precipitate gap (between T6 andT73) and the smallest precipitate gap between the two quenching methods. The G3 alloy with the largest Zn/Mg ratio hasthe smallest number density of matrix precipitates, the minimum precipitation gap (between T6 and T73) and the maximumprecipitation gap between the two quenching methods. The G1 alloy with the lowest Zn/Mg ratio has the smallest size ofgrain boundary precipitates and PFZ width, while their largest values are obtained for the G3 alloy with the maximum Zn/Mg ratio. As a crushing resistant structural material, the crushing properties is improved without reducing the strength. Theratio of Zn/Mg should be controlled within the range of 4.57–6.15, while the total amount of Zn + Mg should be controlledwithin the range of 6.18–7.01.

Four new compounds from the bulbs of Lycoris aurea with neuroprotective effects against CoCl2 and H2O2-induced SH-SY5Y cell injuries

An Jin,Xuelian Xiang,Yun-Yun Zhu,Heng-Yi Yu,Hui-Fang Pi,Peng Zhang,Han-Li Ruan 대한약학회 2014 Archives of Pharmacal Research Vol.37 No.3

Three new alkaloids, 2a-hydroxy-6-O-n-butyloduline,O-n-butyllycorenine, (-)-N-(chloromethyl)lycoramine(1–3), and a new phenolic compound, ((7S)-7-(4-hydroxyphenyl)-7-hydroxypropyl)-20-methylbenzene-30,60-diol (14), along with ten known alkaloids (4–13), wereisolated from the bulbs of Lycoris aurea collected fromHuaihua County of Hunan Province, China. Their structureswere elucidated by spectroscopic methods includingHRESIMS, UV, IR, and NMR. All the isolated compoundswere tested for their neuroprotective effects against CoCl2and H2O2-induced SH-SY5Y cell death. Compounds 1–7and 10 exhibited significant neuroprotective effects againstCoCl2-induced SH-SY5Y cell injury, while compounds1–5, 7, 10 and 12 showed obvious neuroprotective effectsagainst H2O2-induced SH-SY5Y cell death.

감초로부터 Glycyrrhizin 추출

이진휘,장향동,최하영,서동호,이성미,김경하 서울産業大學校 1998 논문집 Vol.47 No.1

Glycyrrhiza uralensis계의 원감초 뿌리에서 추출도는 감초는 여러가지 질병의 약제로 널리 이용되어 왔다. 그 주성분인 gliycyrrhizin은 항염증 활성 및 anti-allergic activity를 갖고 있으며 이러한 생리활성은 aglycone β-gliycyrrhetinic acid 의 활성에 의한 것으로 알려져 있고, β-gliycyrrhetinic acid는 steroid 구조와 유사하며, 면역조절 특성을 갖는 것으로 인식되고 있다. 이러한 β-gliycyrrhetinic acid 의 면역조절 활성에 기여하는 인자와 그 경로에 대하여 조사된 바 있다 Glycyrrhizin은 감초뿌리의 주성분중 하나이며, 그외에도 surgars(14%), starches(30%), flavonoids, saponoids, amonoacids, gums 및 essential oil 등을 포함하고 있다. Licorice, the root extract of Glycyrrhiza uralensis, is used as a medicine for various diseases. Antiinflammatory as well as anti-allergic activities have been attributed to one of its main constituents, glycyrrhizin. These activities are mainly ascribed to the action of the aglycome β-glycyrrhetinic acid. βGlyeyrrhetinic acid has a steroid-like structure and is believed to have immunomodulatory properties, To determine whether interference with complement functions may contribute to the immunomdulatory activity of β-glycyrrbetinic acid. its effect on the classical and alternative activation pathways of human complement were investigated. The main constituent found in the root is glycyrrhizin. The plant also contains various sugars(14%), starches(30%), flavonoids, saponoids, aminoacids, gums, and essential oil etc.

Sol-Gel법을 이용한 다공성 Silica Ceramic 합성에 있어서 물이 겔화시간 및 평형농도에 미치는 영향에 관한 연구

이진휘,김화중,이준 서울産業大學校 1992 논문집 Vol.35 No.1

본 연구에서는 sol-gel process에 의하여 silcon계 다공성 ceramic물질을 합성하고, 합성 과정에서 중요하게 작용하는 인자들을 조사하였다. 중요한 인자들로 여러가지를 들수 있는데, 본 연구에서는 gelation time과 FT-IR을 이용한 최종 생성물의 화학 구조 조사에 의하여, 반응이 평형 상태에 도달하는 데 요구되는 물의 영향에 대하여 조사하였다. 실험 결과 EtOH/TEOS molar ratio가 7.6일 때, 반응이 평형에 도달하는데 소요되는 물의 양은 약 11mole인 것으로 사료되었다. The synthesis of porous silica ceramic material using sol-gel process was performed and the influencing factors during the synthesis were evaluated. Among several influencing factors, however, in this research program, the equilibrium concentrations of H₂O during hydrolysis and poly-condensation were studied based on the investigations of gelation time and chemical structures for the final porous ceramic materials using FT-IR. The results suggested that the equilibrium concentration of H₂O was about 11 moles for 7.6 of EtOH/TEOS molar ratio.

Sol-Gel법을 이용한 Silica Ceramic합성에 있어서 화학 구조 변화에 관한 연구

이진휘,정은정 서울産業大學校 1995 논문집 Vol.42 No.1

Sol-gel공정에 의하여 TEOS를 이용하여 silica ceramic을 합성하는 공정중 건조 및 소성공정중의 중간생성물의 변화를 20℃, 40℃ 및 60℃로 반응시킨 시료에 대하여 TG/DTA, FT-IR 및 X-ray diffraction에 의하여 실험하였다. 실험 결과 반응온도가 높을수록 가수분해 속도가 증가되었으며 중간 생성물의 양도 증가하였다. 고립된 Si-OH중 -OH의 증발은 700∼800℃정도에서 일어나며, 60℃에서 건조한 시료의 경우 급격한 가수분해 및 축중합반응으로 인하여 역반응에 의한 약간의 불완전한 치환형태의 alkoxide가 잔류하는 것으로 사료된다. The chemical components produced by drying and sintering process during synthesizing of silica ceramic by sol-gel process were characterized by using TG/DTA, FT-IR and X-ray diffraction to evaluate the changing intermediates for the samples treated by three different drying temperatures, 20℃, 40℃ and 60℃. The results showed that the higher the reaction temperature, the faster the rate of hydrolysis and the large the concentration of intermediates. Dehydroxylation of Si-OH starts in the early stage of the thermal treatment and continues up to 700∼800℃. It is supposed that alkoxides might be formed by backward reaction derived by hydrolysis and condensation-polymerization abruptly in case of dried at 60℃.

Sol-gel법을 이용한 미세공 실리카 세라믹의 기공구조 변화에 관한 연구

이진휘,연만형,정은정,박노혁 서울産業大學校 1996 논문집 Vol.43 No.1

솔-젤법에 의하여 제조된 미세공 실리카 세라믹에 대하여 N₂-adsorption isotherm 및 TEM에 의하여 기공구조 변화를 조사하였다. Group 1, 2 및 3의 경우 물의 양이 각각 11, 5.5 및 3.8mole까지는 급격히 surface area의 증가를 보이다가 그 이후에는 완만한 상승을 보이는데, 이것은 앞의 실험에서 보인[4.5]gelation time 및 FT-IR의 실험결과와 일치하는 것이다. 서로 다른 물의 양에 대하여 BET surface area와 Cumulative surface area의 차이가 Group 1서 Group 3으로 옮아감에 따라 커지는 것은 용매의 양은 감소하는 반면 TEOS의 양 증가로 인하여 물과 TEOS의 반응이 원활하지 못한 결과로 덜 발달된 polymer에 기인한 작은 particle에 의하여 형성된 작은 기공들에 기인한 것으로 사료된다. 이와같은 기공구조는 TEM의 결과에 의하여 확인할 수 있다. Group A에서 E쪽으로 갈수록 물의 양의 증가에 기인하여 surface area는 증가하며, Group a에서 d쪽으로 갈수록 물의 양의 감소에 기인하여 surface area는 감소한다. N₂-adsorption isotherm and TEM were used to investigate the micro-porous silica ceramic prepared by sol-gel process to find the structural changes of pores. In the case of Group 1, 2 and 3, the drift of the surface area increased steeply till the amount of water 11, 5.5 and 3.8 moles individually and after that showed increased smoothly. It is the same results as the gelation time and the FT-IR[4.5]. It is the reason that the differences of BET and Cumulative surface area become larger proportionally as moving from Group 3 that the reaction of water and TEOS is less active, caused by using decreased quantity of water but increased TEOS, and therefore the smaller pores by the smaller particles were formed. It was identified by TEM. The surface area is increased by the increased water as moving from Group A to Group E, and decreased by the decreased water as moving from a to e.

전기분해에 의한 염색폐수의 탈색에 관한 연구

이진휘,이진희,연만형,조성국 서울産業大學校 1997 논문집 Vol.46 No.1

전기분해에 의한 염색폐수의 탈색효과를 규명하기 위하여 Fe, Al 및 Cu극판을 단일 또는 혼용하여 적색, 황색 및 청색산성염료 200ppm에 대하여 탈색실험을 수행한 결과 Fe(+)와 Al(-)전극을 혼용하고, 극간거리가 1.5㎝일 때 가장 제거율이 좋았다. 염색폐수의 농도 50∼250ppm에 대하여 전해질로써 NaCl을 0.1∼0.5% 사용하고 전류밀도 0.033∼0.166A/㎠로 실험한 결과 6분이상의 시간 경과후 95%이상 색도가 제거되었고, 전해질의 농도가 높을수록 소비전력은 높아지고 제거율은 향상되었으나 시간이 지남에 따라서 전력소비는 거의 일정하였다. This experiment is performed to investigate the decoloration of dye wastewater by using the same or different electrodes of Fe, Al and Cu. The waste solution consists of a single colored acidic dye of red, yellow or blue with a concentration of 200ppm. The results showed that the combination of Fe(+) and Al(-) electrodes and a distanced of 1.5㎝s between the electrodes was best for the decoloration process. It showed more than 95% decoloration occurred after 6 min. when we used NaCl solution of 0.1∼0.5% for electrolysis and current densities of 0.033∼0.166A/㎠ with solutions of 50∼250ppm. The higher the concentration of electrolyte, the higher the consumption of power becomes constant after a period of time.

실리콘 웨이퍼 공정용 알루미나 정전척의 제작과 특성에 관한 연구

천희곤,조동율,이영섭,박용균,최성호,정광진,Serguei Spoutai 울산대학교 기계부품 및 소재 특성평가연구센터 1999 연구보고서 Vol.1999 No.-

정전척의 유전체 물질로 열전도도와 유전특성 그리고 기계적 특성이 우수한 알루미나에 TiO₂첨가하여 유전체의 비저항을 변화시켜서 정전척(electrostatic chuck)에서 발생하는 정전력인 쿨롱힘(coulomb force)과 존슨-라벡힘(Johnsen-Fahbeck firce_의 영향을 규명하려 하였다. 그리고 비저항, 인가전압, 온도, 습도가 정전력에 어떠한 영향을 주는지 고찰하였으며, 인가전압에 따른 응답 특성에 관하여 고찰하였다. Alumina electrostatic chucks for silicon wafer process with wide range of electrical resistivity were fabricated by controlling the amount of TiO₂ addition (0 wt%, 1.3 wt%, 2 wt%, 2.8 wt%). The dependence of electrostatic force on applied voltage, temperature and humidity was investigated. In addition, response characteristics on applied voltage and relationship between electrical resistivity and electrostatic force characteristics such as Coulomb force and Johnsen-Rahbeck force were discussed

SPOT을 통한 문법항목의 난이도 고찰

최진희 배재대학교 주시경교양교육연구소 2017 대학교양교육연구 Vol.2 No.1

본 고에서는 전공 및 교양 초급 클래스에서 다양한 배경을 가진 일본어 학습자를 대상으로 SPOT 테스트를 이용하여 문법 항목의 난이도를 조사한 것이다. SPOT는 자연 발화 속도로 언어를 처리하는 능력이 있어야만 해답할 수 있는 테스트이다. 정답률이 50%이하인 경우는 8개(13.3%)로 で(お)いてください가 가장 정답률이 낮았다. 다음으로는 なに(が), どこに(も), (し)かない,(お)持ちする가 낮았다. 발음 상 듣기 어려운 표현과 부정 표현을 동반하는 관용 표현, 겸양 표현이 습득하기 어려운 항목으로 분류된다. 부정 표현과 동반하는 표현은 습득하지 못한 것으로 특히 주의하여 지도할 필요가 있겠다. 주로 초급 문법 항목 중 이른 시기에 도입되는 표현들이 잘 습득할 수 있도록 지도법을 개선 보완할 필요가 있겠다. In this paper, I have researched the level of difficulty on Japanese grammar in SPOT test, which is taken by Japanese learners who have various background. SPOT is a test which can be answered by the people who have capabilities to understand in natural discourse speed. As the result of the test, there were 8 questions which have less than 50 percents of the rate of correct answers. The question "deoitekudasai" had the lowest rate because listening to "de+oi" sound was very difficult. The correct answer rates of idiomatic expression and honorific expression were also pretty low compared to other questions. Even though the learners acquired the negative expression at the beginning stage, acquisition of the negative expressions was low. Therefore, teaching methods of negative grammar need to be revised.