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.

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.

효과적인 다차원 분석을 지원하는 스프레드시트 방식의 OLAP 인터페이스 설계 및 구현

윤민희,김진호,문양세 강원대학교 정보통신연구소 2006 정보통신논문지 Vol.10 No.-

OLAP systems support effectively data analysis over a large volume of business data to make decisions for an enterprise. In order to process data analysis efficiently, OLAP systems pre-compute the summary of business data over various dimensions and store them into data warehouses. Several specialized tools have been developed to display and to browse the results of complex analytical queries on data warehouses. In this paper, we developed a spreadsheet-like tool to support OLAP operations and to browse the results of analytical queries. Spreadsheet is one of the most popular and user-friendly data analysis tool. It also has lots of advantages, which is interactive, easy to learn, etc. Thus this paper implemented an OLAP tool using spreadsheet-style interface to analyze large OLAP data on World-Wide Web. Through this tool, users can process OLAP activities easily and effectively by using the same ways as well-known shreadsheet tools like Microsoft Excel.

Sol-Gel법을 이용한 Silica Membrane의 제조 공정에 관한 조사연구

이진휘,이준,김화중 서울産業大學校 1990 논문집 Vol.32 No.1

졸 -겔 공정에 대한 일반적인 문헌들을 검토하였다. 이와같은 문헌들을 성공적으로 적용하려면 공정에 대한 여러가지 단계와, 영향을 미치는 인자들에 관한 체계적인 이해가 먼저 요구된다. 겔화하는 동안 구조 및 미세구조의 전개에 영향을 미치는 몇가지 인자와 더불어 건조 및 열처리 조건을 조사하였다. 혼합물, 다공성 고체 및 코팅분야에 적용하기 위한 몇가지 예들을 기술하였다. 현재 이 분야의 발전에 기여할 새로운 응용기회는 많다. The general informations of the sol-gel process are reviewed. Successful applications are dependent on sufficient scientific understanding of the various stages and factors of the process. A number of factors governing the development of the structure and microstructure during gelation and subsequent drying and firing conditions are mentioned. Examples are described for applications in the areas of composites, porous solids and coatings. Opportunities for many new applications are presently available for exploitations.

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.

하약골 수조작술에 의한 폐구성 과두걸림 환자의 치료

김진환,김희정 大韓顎顔面成形再建外科學會 2000 Maxillofacial Plastic Reconstructive Surgery Vol.22 No.1

In general, treatment of the patients with closed lock divides into a conservative and a surgical treatment. Surgical treatment has been often applied in case that occlusal splint therapy was not effective on the patient with closed lock. In recent, some clinicians reported good results with mandibular manipulation. Three patients complained limitation of month opening-(mean mouth opening was 22.3mm) and TMJ pain. Articular discs were displaced anteriorly on MRI. Two patients didn't improve the symptoms with long term occlusal splint therapy. We applied mandibular manipulation after injection with 2% lidocaine into the upper joint space of the affected TMJ and directly inserted occlusal splint to all patients. At the follow-up check, mean mouth opening was 41.7mm. TMJ pain decreased, condyle and disc relationship was improved functionally on MRI.

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.

고속의 GaAs SRAM 을 위한 새로운 센스 앰프의 설계 연구

조희철,김선옥,이웅호,윤진섭,이진구 동국대학교 산업기술대학원 1993 산업기술논문집 Vol.1 No.-

A new sense amplifier is designed in order to realize high-speed GaAs SRAM's. The Schematics are similar to "a source coupled differential amplifier" execept that two analyzed using basic FET current equations. The transconductance of the new sense amplifier is approximately 3.5 times larger than that of the conventional sense amplifier. Output high voltage is reduced to about 0.64V, therefore, the time which reached V_(max) are reduced also. The simulation results show that the access time of 0.9ns and the power dissipation of 12.2mW are achieved in GaAs 16bit SRAM's.

불국사 석탑의 물성 및 지반특성 조사

최희수,서만철,오진용 공주대학교 문화재보존과학연구소 2003 문화재과학기술 Vol.2 No.1

경주 불국사의 다보탑과 석가탑은 751년에 축조된 국보급 문화재이나 오늘날은 석재의 풍화 및 지대석의 어긋남 현상들이 관찰된다. 이에 대한 정확한 이해는 두 석탑의 안정성 진단에 필수적이며 따라서 석탑의 지반환경과 석재 물성에 관한 비파괴 정밀 조사가 필요로 한다. 이 연구에서는 석재의 역학적 성질을 위해 초음파 속도 측정을 실시하였고 천부지질구조를 위해 탄성파, 전기비저항, 지하레이더 등의 비파괴 복합 지구물리탐사를 석탑 주변에서 수행하였다. 초음파 속도범위는 석가탑에서는 1217~4403 m/s이며, 다보탑에서는 584~5845 m/s이며 이로부터 추정한 일축강도 평균치는 각각 463 kg/cm^(2), 409 kg/cm^(2)이다. 대체로 두 석탑 주변의 북서쪽 구역에서 낮은 탄성파 속도와 비저항 값이 나타나, 이 부분을 비교적 연약한 지반으로 해석한다. 그리고, 탄성파 속도분포에서는 다보탑 지반이 더 큰 속도를 보여 상대적으로 석가탑 지반보다 견고함을 보여준다. 대체로 석탑지반의 전기비저항은 최대 2200 Ωm이며 200 Ωm내외의 외부지반보다 더 높은 값을 보인다. 복합 지구물리탐사 결과를 종합하면 다보탑지반의 형태는 8각형(한 변은 6 m)으로 그 깊이는 약 4 m 이나, 석가탑지반은 약 8x10 m의 직사각형 형태로 깊이는 약 3 m 이다. Two three-story stone pagodas, Seokgatap and Dabotap, built in 791 at Bulkuksa temple, are well-known national treasures. However, they have experienced weathering process and an offset of the stone alignment is observed at the base part of Dabotap. Understanding of these phenomena is essential for the structural safety diagnosis for them, and therefore the nondestructive geophysical methods was applied. Direct measurements of ultrasonic velocities was introduced for the mechanical properties of the stone. Multidisciplinary geophysical prospectings including seismic, resistivity, ground-penetrating radar(GPR) methods were carried out around two pagodas for their site characteristics. The velocity ranges of ultrasonic waves for Dabotap and Seokgatap are 1217~4403m/s and 584~5845m/s, respectively, and the estimated averages of the uniaxial compressive strength are 463 kg/cm^(2) and 409 kg/cm^(2), respectively. At the northeast of each pagodas, the lower seismic velocities and resistivities are shown, which is interpreted to be weaker subsurface section. On the basis of the higher velocity structure, the site of Seokgatap appears to have solider stability than the Seokgatap site. Near the pagodas, higher(up to 2200 Ωm) resistivity is present whereas their outskirts have as low as 200 Ωm. By the combined results of each geophyscial methods, the subsurface boundaries of each stone pagodas are revealed. The Dabotap site is in the form of an octagon having 6-m-long side with the depth of ~4 m, whereas the Seokgatap site is the 8x10 m rectangle with the depth of 3 m.