Correlation Between Primary Si and Silicide Refinement Induced by Ultrasonic Treatment of Multicomponent Al–Si Alloy Containing Ti, Zr, V, and P

Jae‑Gil Jung,Young‑Hee Cho,Tae‑Young Ahn,Jae‑Hee Yoon,Sang‑Hwa Lee,Jung‑Moo Lee 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.5

The correlation between primary Si and silicide refinement induced by ultrasonic treatment (UST) of multicomponent Al–Sialloy containing Ti, Zr, V, and P was investigated. UST significantly refined the primary Si phase owing to cavitation-inducedwetting and deagglomeration of MgAl2O4particles. Lowering the UST finish temperature caused deterioration of the degreeof primary Si refinement, instead leading to silicide refinement. Cavitation-induced silicide nucleation on wetted MgAl2O4consumed the MgAl2O4particles, particularly in the case of primary Si nucleation. Similarly, the formation of an AlP phaseon the silicide phase reduced the nucleation efficiency of the AlP phase. Poisoning of the MgAl2O4and AlP phases by thesilicide phase was responsible for the deterioration in primary Si refinement. Room-temperature tensile strength and hightemperatureelongation were increased by UST and were dependent on the size of primary Si.

구리 지역에서 조사한 고혈압의 인지도, 치료률 및 관리률

홍철호,김순길,홍택원,이제,신진호,이재웅,김경수,김정현,임헌길,이방헌 대한간질학회 2003 대한간질학회지 Vol.9 No.1

수문지질 특성에 의한 갈수량의 변화

이길영,허재영,박승기 大田大學校 産業技術硏究所 1996 산업기술연구소 論文集 Vol.7 No.2

The regional unbalance of water quantity and the deterioration of water quality become pending problems that should be solved. Although monthly streamflow data have been used in most water resources plannings to cope with the problems, for more effective management of confined water resources the exact calculation of daily droughtflow is essential. In this study, the droughtflows at Backokpo watershed in Han River were measured from May 1993 to May 1994 and the relations between drogughtflow and the hydrogeological character of the watershed were figured out.

Al5083-O 용접부의 보호가스 혼합비율에 따른 저온 인성 평가

이동길,이상열,양훈승,정재강 朝鮮大學校 機械技術硏究所 2002 機械技術硏究 Vol.5 No.1

본 연구에서는 저온용기 등에 많이 사용되고 있는 알루미늄 합금 A15083-O재에 대한 보호가스 혼합비율과 저온인성과의 관계를 규명하고자 혼합가스 비율을 여러 가지로 달리 하여 GMA 용접을 하였다. 시험온도는 상온에서 극저온까지 단계적으로 낮추어가며 계장화 샬피충격시험을 실시하였다. 최대하중은 시험온도가 낮아질수록 증가하였으나 변위는 25℃부터 -85℃까지는 시험온도에 관계가 없었으나 -196℃에서는 크게 감소하였으며, 모든 시험온도 및 불활성가스 혼합비율에서 흡수에너지는 용착금속부, 용융선 및 HAZ 순으로 증가하였다. 용착금속부의 흡수에너지는 시험온도 및 불활성가스 혼합비율에 관계없이 매우 낮게 나타난 반면, 용융선 및 HAZ시험편의 흡수에너지는 모재와 거의 유사한 값을 나타내었다. 또한, 모든 시험온도에서 흡수에너지는 He의 혼합량이 증가할수록 증가하는 경향을 보여 Ar33%+He67%에서 가장 우수한 인성을 나타내었다. In this study, the low temperature toughness was evaluated by using the instrumented Charpy impact testing procedures for A15083-O aluminum alloy used in the LNG carrying and storing tank. The specimens were GMA(Gas Metal Arc) welded with four different mixing shield gas ratios (Ar100% + He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%), and tested at four different temperatures(+25, -30, -85, and -196℃) in order to investigate the influence of the mixing shielding gas ratio and the low temperature. The specimens were divided into base metal, weld metal, fusion line, and HAZ specimen according to the notch position. From experiment, the maximum load was increased a little up to -85℃, and the maximum load and maximum displacement were shown the highest and the lowest at -196℃ than the test temperatures because of the brittle behavior. The absorption energy of weld metal notched specimens was not nearly depends on test temperature and mixing shield gas ratio because the casting structure was formed in weld metal zone by melting welding wire. In the other hand, the others specimens was shown that the lower temperature, the higher absorption energy slightly up to -85℃ but the energy was decreased so much at -196℃.

혈액 및 비장조직에서 일산화탄소 헤모글로빈 농도에 관한 연구 : A Comparison of CO-Hb in Blood and Spleen Specimens

이진훈,오세진,김유나,이진숙,유재훈,장성길 內務部 國立科學搜査硏究所 2001 國立 科學 搜査 硏究所 年報 Vol.33 No.-

온도변화에 따른 알루미늄합금 용접부의 피로수명에 관한 연구

이동길,양승훈,김건호,정재강 朝鮮大學校 機械技術硏究所 2002 機械技術硏究 Vol.5 No.1

본 연구에서는 저온용기 등에 많이 사용되고 있는 알루미늄 합금 A15083-0재에 대한 보호가스 혼합비율과 피로수명과의 관계를 규명하고자 혼합가스 비율을 여러 가지로 달리하여 GMA 용접을 실시하였다. 시험온도는 상온에서 극저온까지 단계적으로 낮추어가며 실시하였다. 용접재의 피로수명은 모든 불활성가스 혼합비율 및 노치 가공위치에서 모재보다 높은 피로수명을 보였으며, 영향부, 용융선 및 용착금속부 순으로 피로수명이 증가하였다. 상온에서부터 -85℃까지는 온도가 낮아짐에 따라 피로수명은 모재 및 Ar33%+He67%의 경우 증가한 반면, 다른 불황성 가스혼합비에서는 감소하는 경향을 나타내었며, -196℃ 극저온에서는 피로수명 크게 증가하여 저온재료로서 유용한 성질이 나타났다. The influence of mixing shield gas ratio and test temperature on fatigue life of welding zone were examined experimentally for a AI5083-O aluminum alloy. The GMA(Gas Metal Arc) welding was carried out for weld specimen with various mixing gas ratio(Ar100% + He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%). The tested temperature range was from room temperature(+25℃) to cryogenic temperature(-192℃). The welding zone was divided into four sub-zones for analysis ; weld metal, fusion line, HAZ, and base metal. In the influence of mixing gas ration, fatigue life of weld metal was decreased with higher Argon gas ration, but fusion line and HAZ specimens were not influenced greatly, The fatigue life increased at lower temperatures, particularly at -196℃. It was known availability that the A15083-O is appropriate for used low temperature material.

肩胛骨과 목 및 腰痛의 捻挫 指壓占에 관한 硏究

李栽吉 群山大學校 1994 論文集 Vol.21 No.-

We often see man being embarrassed under the circumstances of no doctor(such as athletic field, mountain, sea, river, isolated place, etc.) when his unnatural physical excercise sprains a part of his body, such as muscle, joint, and ligament. This study suggests some methods of the first aid treatment that we can cure or improve his sprains with our finger pressure point.

미소원공결함을 갖는 차량 밸브용강재의 피로크랙진전거동에 관한 연구

이동길,이상열,정재강 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.1

본 연구에서는 자동차 밸브에 사용되고 있는 내열강 STR3과 STR35를 마찰용접한 후 모재, 열영향부 및 접합선(bond line)에 미소 인공결함을 가공하여 피로크랙 발생 및 전파 거동, 피로수명 및 기계적성질의 상관관계를 조사하는 연구를 수행하였다. 평활재의 피로한도시험 결과 STR3의 피로한도는 429.0MPa이며, STR35는 409.4MPa로서 항복강도가 높은 STR3의 피로한도가 약 20MPa이 높게 나타났다. 미소원공결함이 접합선으로부터 1.0mm떨어진 곳에 가공된 시험편의 피로수명은 모재보다 STR3은 약99%, STR35는 약 25%씩 증가한 반면 접합선에 미소원공결함이 가공된 시험편은 모재보다 STR3은 약 20%, STR35는 약 72% 감소하였으며 파괴전 관찰된 최종크랙길이도 크게 감소하였다. 또한 피로크랙길이와 파단수명비의 관계식에 본 시험재료를 적용한 결과 마찰용접 및 미소원공결함의 위치에 관계없이 비례관계가 있음을 알 수 있었다. The fatigue crack propagation characteristics were investigated for two kind of heat-resisting steel, STR3 and STR35, commonly using in valve material of vehicles, in order to evaluate the fatigue crack propagation behavior and fatigue life of dissimilar friction welding zone. The fatigue limits of the as-received specimens, STR3 and STR35, were 429MPa and 409.4MPa respectably. The fatigue life of the specimen showed about 99.1% for STR3, about 25.2% for STR35 higher than that of the base metal specimen. But the fatigue life of bond line notched specimen was shown about 20% for STR3 and about 72% for STR35 shorter than that of the base metal specimen.

水泳敎育에 適合한 補助體操의 硏究 : 2人1組의 體操를 中心으로

李栽吉 군산대학교 1985 群山水産專門大學 硏究報告 Vol.19 No.2

Man's muscle and articulation are developed well, if they receive the proper resistance according to the physical development condition. Before swimming, and preliminary gymnastics of a pair were conducted in order to relax the tonus of the muscles, to make good blood circulation and to increase the flexibility of skeletal joint structure. The effect investigation of preliminary gymnastics was made as the subject students the freshmen of 550 every year in Kunsan National Fisheries Junior College in summer from 1981 to 1985. This preliminary gymnastics includes the leg exercises, foot-joint exercises, foot-joint exercises, chaffing and tapping exercises on a foot sole, lifting and making a round posture under lying facing upward, leg spreading out and pulling exercises, back pressing exercises, breast exercises, trunk exercises, waist exercises, and back and abdomen exercises. As a result of investigation, this preliminary gymnastics are very effective on the precaustions of muscular paralysis due to the good blood circulation corresponding to the relaxation of muscular rigidity and the flexibility of articulations.

접촉각 측정을 통한 Alkanethiol로 표면 처리한 은 분말의 표면 특성 연구

이길재,신승일,오성근 한국공업화학회 2004 공업화학 Vol.15 No.1

은 분말을 alkanethiol로 표면 처리한 후, alkanethiol의 탄소 개수 변화에 따른 은 입자의 표면 특성변화를 접촉각 측정을 통해 연구하였다. 이때 은 입자 표면에 alkanethiol의 흡착여부를 DRIFT (diffuse reflectance infrared fourier transform) spectrum를 통해 확인하였다. 접촉각은 Washburn 식을 바탕으로 한 liquid penetration 방법으로 측정하였고, 이 측정법의 보완을 위해 분말에 압력을 가하여 원판형태로 만들어 그 표면에서 접촉각을 측정하는 sessile drop 방법을 함께 사용하였다. 그 결과 순수한 은 입자의 물에 대한 접촉각은 두 가지 방법에 대해 각각 58°, 40° 나왔고, 다양한 탄소개수(C_(4)-C_(12))의 alkanethiol로 표면 처리한 입자는 모두 90° 이상의 결과를 얻었다. 즉 alkanethiol로 처리한 은 입자의 표면이 소수성으로 변했음을 의미한다. 여기서 처리한 alkanethiol의 탄소개수가 증가할수록 접촉각은 계속 증가했으나, 접촉각의 증가 폭은 상대적으로 점차 감소하였다. Contact angles of silver powders were measured for investigation of surface properties of silver particles as changing alkyl chain length of alkanethiol. Silver powders were modified by various alkanethiol (C4∼C12). Adsorption of alkanethiol on silver particles was confirmed by DRIFT (diffuse reflectance infrared fourier transform) spectrum. Contact angles were measured by liquid penetration method based on Washbum equation and sessile drop method on tablet of compressed powder. In result. the value of contact angles on water were 53°, 40°about two method. Contact angles of surface treated particles by alkanethiol of varied alkyl chain length were larger than 90°. Because of bonding between silver and sulfur in alkanethiol, silver surface was surrounded by alkyl groups of alkanethiol. Surface properties of silver particles were increased on hydrophobicity with alkyl chain length of alkanethiol. In comparison with increase of contact angle accordingto increase of alkyl chain length of alkanethiol. the widths of increasing contact angle were relatively decreased.