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

흡입관에 부착된 이젝터내의 유동특성에 관한연구

이행남,박길문,모양우,이덕구,설재림,김건일 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.2

The ejector is used to get low pressure, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc. because there are not any problem even it is mixed with kinds of liquid, gas, and solid. The flow characteristics in diffuser are investigated by PIV and CFD. The agreement between numerical analysis and experiment shows the validity of this study and the results of this study would be useful to the engineers who design for the flow systems for heating, ventilation, air conditioning and wastewater purification plants.

미소원공결함을 갖는 자동차 전륜구동 축재의 피로수명 예측

이동길,오환교,정재강 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

본 연구에서는 현재 생산되고 있는 자동차의 전륜 구동축재료 S43C와 S50C를 대상으로 회전굽힘피로시험을 통해 고주파열처리와 온도조건에 따른 피로크랙 전파거동을 고찰하고, Nisitani가 제안한 역학적 변수에 의해 재료상수를 구한 후 그 적용성을 검토해 보았다. 비열처리재 S43C 및 S50C의 피로한도는 각각 98.1MPa, 107.9MPa이었으며, 열처리재는 각각 147.1MPa, 156.9MPa로서 열처리 후 두 재료 모두 피로한도가 약 49MPa씩 증가하였으며, 저온(-30℃)에서의 피로수명은 상온(25℃)에서보다 두 재료 모두 비열처리재는 약 110%, 열처리재는 약 120% 증가하였다. 또한 본 재료에 실험으로부터 얻어진 재료상수를 Nisitani의 피로크랙전파속도 예측식에 적용하여 피로수명을 예측한 결과 고주파 열처리 여부와 실험온도 조건에 관계없이 약 5% 내외의 낮은 오차를 보이며 잘 일치함을 알았다. In this study, the rotary bending fatigue test was carried out with two kinds of materials, S43C and S50C, using in the front engine and front drive shaft of vehicle. The specimens were heat-treated by high frequency induction method and tested at +25℃ and -30℃ in order to look over the influence of the heat treatment and the temperatures. The mechanical factor, C(2a)p, proposed by Nisitani was employed in the present study to compare the results of fatigue life obtained from experiment and prediction. The fatigue limit of the as-received specimens S43C and S50C were 98.1MPa and 107.7MPa, and that of the heat-treated S43C and S50C were shown 147.1MPa and 156.9MPa respectably. It means that the fatigue limit was increased about 49MPa by high frequency heat treatment. Fatigue lifes of the specimens tested at low temperature(-30℃) showed about 110% for as-received, 120% for heat-treated higher than at room temperature(25℃). It was found the crack length at onset or final fracture tested at low temperature was shorter than the crack length at room temperature(+25℃). The fatigue lifes were predicted with an equation of the fatigue crack propagation proposed by Nisitani, d(da/dN)=C(2a)p, the results were found to be within 5.0% error by comparison with experimented results.

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.

徒手體操에서 身體各部位의 可動性에 관한 硏究

李栽吉 군산대학교 1986 群山水産專門大學 硏究報告 Vol.20 No.2

The meaning of gymnastic originated from gymnos of Greek, namely nakedness. The worth of gymnastic was recognized to the world by Ling P.H., a originator of Swedish gymnastic, and F. L. Jahn, a representative of German gymnastic. The muscle and joint parts are remarkably developed, when the resisting force is properly inflicted on the body. This paper has been theoretically studied on the maxium movability and connective and mixed exercise. The purpose of this study is on the production of gymnastic exercise without apparatus.

구조용강의 유한요소해석 및 온도변화에 따른 피로수명 평가에 관한 연구

이동길,이상열,정재강 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.2

본 연구에서는 국산 승용차의 전륜구동축 재료인 S43C와 S5OC를 대상으로 유한요소해석과 회전굽힘피로실험을 통해 고주파열처리와 온도조건에 따른 피로크랙의 발생, 전파거동을 고찰하였다. 유한요소해석 결과 하중이 가해지는 방향에 따라 반복적으로발생되는 인장응격 및 압축응력은 미소원공결함 부분에서 가장 크게 나타났다. 이러한원인은 미소원공결함이 응력의 국부적인 집중원으로 작용했기 때문으로 생각되며, 이러한 응력의 반복으로 인하여 미소원공결함을 기점으로 크랙이 발생∙성장하였음을 알 수있다. 회전굽힘피로실험 결과 두가지 재료 모두 저온(-3O℃) 피로수명은 비열처리재의 경우 상온(25℃)보다 약 110% 증가하였고, 열처리재는 약 120% 증가함으로서 온도의 저하가 피로수명을 크게 증가시킨 반면 고온(80℃) 피로수명은 상온 피로수명과 비교시 비열처리재가 약 35%. 열처리재가 약 5%의 피로수명 감소를 나타냈다. In this study, the rotary bending fatigue test was carried out with two kind of material, S43C and S5OC, using in the front engine and front wheel drive shaft of vehicle. The specimens were heat-treated by high frequency induction method and tested at room(+25℃), high(+80) and low temperature(-3O℃) in order to look over the fatigue crack initiation and propagation behavior by the heat treatment and the temperatures. Based on the FEM result, the tensile and compressive stress repeatedly generated by load direction were largest on the small circular defect due to the stress concentration. So the small crack was initiated and grew from the defect Fatigue lifts of the specimens tested at low temperature showed about 110% for as-received. 120% for heat-treated higher than at room temperature, It was found that low temperature increased so much the fatigue life. At room and high temperature, the fatigue life of as-received specimens were decreased about 35%, but that of heat-treated specimens were decreased about only 5% at high temperature more than at room temperature, Therefore, fatigue life under high temperature will be considered at design of front engine and front wheel drive shaft materials of vehicle.

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.-

일차배양된 설치류 호흡기 상피세포로부터의 점액소 분비에 대한 수종 약물의 영향

이충재,석정호,이재흔,허강민,박지선,배소현,노삼길,박상철 충남대학교 의학연구소 2003 충남의대잡지 Vol.30 No.2

1. PKC activator인 PMA는 일차배양 HTSE세포로부터의 뮤신분비를 0.1μM 농도에서 30%, 1μM 농도에서 80% 가량 증가시켰다. 2. 식물 유래 성분으로, flavonoid의 일종인 TFR은 일치배양 HTSE 세포로부터의 뮤신분비를 10μM 농도에서 50%, 100μM 농도에서 80% 가량 증가시켰다. 3. 양이온성 폴리펩티드인 PLL 및 PLA는 일차 배양 HTSE 세포로부터의 뮤신분비를 0.01 - 10μM 농도에서 용량의존적으로 감소시켰다. 4. 결론적으로, 본 연구에서 얻어진 결과들은 새로운 거담제 및 점액용해제나 단백분해 효소제가 아닌 호흡기 류신의 생성/분비를 조절해 줄 수 있는 신개념의 약물을 개발함에 있어 극히 일부분이나마 단서를 제공하고 있다고 하루 수 있을 것이다. In the present study, we tried to investigate whether phorbol myristate acetate(PMA), trihydroxymethoxy-flavanone rutinoside(TFR) and cationic polypeptides significantly affect mucin release(secretion) from cultured hamster tracheal surface epithelial cells. Confluent primary hamster tracheal surface epithelial (HTSE) cells were metabolically radiolabeled with 3H-glucosamine for 24 hr and chased for 30 min in the presence of each agent to assess the effect on 3H-mucin release. The results were as follows : (1) Both PMA and TFR significantly increased mucin release from cultured HTSE cells ; (2) Cationic polypeptides including po1y-L-lysine(PLL, mw 7,500) and poly-L-arginine(PLA, mw 10,800) significantly inhibited mucin release from cultured HTSE cells, in a dose-dependent manner. This finding suggests us that PMA and TFR be further studied for the possible use as mild expectorants and cationic polypeptides might function as a regulator for hyper-secretion of mucus, both by direct acting on airway mucin-secreting cells, during the treatment of chronic airway diseases.

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.