Microstructure and Tensile Properties in Low Pressure Cast Al-Si Alloy through Cooling Rate Control

Suh, Jun-Young,Park, Sung Jin,Lee, Hee-Kwon,Chang, Si Young Materials Research Society of Korea 2020 한국재료학회지 Vol.30 No.2

In this study, three kinds of metal chills such as SS400, AC4CH and brass, with different thicknesses of 40 ~ 80 mm, were applied for low pressure casting of Al-Si alloy to control cooling rate. The microstructural characteristics with increasing cooling rate were represented using factors including D₁, D₂, size of primary α phases and shape factor and size of eutectic Si. The tensile properties were investigated and additionally analyzed based on the microstructural characteristics. As the cooling rate increased, D₁, D₂, and sizes of primary α phases and eutectic Si apparently decreased and the shape factor of eutectic Si increased to over 0.8. The ultimate tensile strength (UTS) and yield strength (YS) increased with decreasing D₁, D₂, and size of primary α phases, while elongation increased with decreasing size of eutectic Si and concurrently increasing shape factor of eutectic Si. This indicated that the primary α phases and eutectic Si in Al-Si alloy were refined with increasing cooling rate, resulting in improvement of UTS and YS without sacrificing elongation. After the tensile test, preferential deformation of primary α phases was observed in the Al-Si alloy produced at higher cooling rates of more than 0.1 K/s.

Wire Saw 슬러리로부터 Si와 SiC의 선택적 회수

한승열,이종대,전진혁,박노국,이태진,류시옥 嶺南大學校 工業技術硏究所 2004 工業技術硏究所論文集 Vol.32 No.1

This study was focused on the recovery of Si and SiC from wire saw slurry in wire saw slicing process. In order to separate Si and SiC from wire saw slurry, alkali dissolution method was used and then Na₂O showed superior dissolution property of Si. At this time, SiC was separated as powder from alkali aqueous solution. Si was dissolved as a liquid in alkali aqueous solution. After removing SiC powder, the powder was obtained by drying alkali aqueous solution and then it's XRD analysis showed that it was the water glass (Na₂SiO₃).

석탄회분의 융착형성 연구

이시훈,박주식,임영준,김형택 한국화학공학회 1996 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.34 No.1

본 연구에서는 DTF를 이용하여 준역청탄인 Alaska탄의 회분과 deposit을 제조하고 조성을 분석하여 각각의 조성이 용융성에 미치는 영향을 고찰하였으며 ASTM 회분의 결과와 비교하였다. ASTM 회분은 alumina, silica, mullite, Ca-com-pound 등이 결정성으로 존재하는 반면 DTF 회분은 표면에 K, Fe, Ca 등이 농축된 구형의 drop이 만들어지는 것을 알 수 있었다. 또한 DTF 회분에는 mullite만이 결정성으로 존재하였다. Deposit은 용융후 고형화된 glass phase로 만들어 졌는데 Fe는 Fe^(3+) silicate로 전이되고 deposit하부에 Si가 농축되는 것으로부터 석탄 내의 무기물 조성 중에 용융을 지배하는 것은 Si인 것을 알 수 있었다. Alaska탄은 ASTM 회분분석결과로부터는 용융성이 강하게 예측되었으나 DTF에서 형성된 deposit 분석결과 표면에 부착강도를 낮게 하는 Ca가 농축되어 열전달면에서의 제거는 용이한 것으로 판단되었다. Ash and deposits were made using Alaska sub-bituminous coal in a drop tube furnace(DTF) and the effects of their compositions on fusion were compared with those of the ashes prepared from the ASTM aching procedure. It has been found that the ASTM ash includes alumina, silica, mullite, and Ca compounds as crystalline phases, whereas the DTF ash includes spherical drops with K, Fe, and Ca condensed on the surface. In a DTF ash, only mullite existed as crystalline phase. 'Che deposits existed as glass phases which were formed by solidification from melts, and Fe was transformed to Fe^(3+) silicate and Si was concentrated on the lower part of the deposit. This fact indicates that, among various inorganic elements in coal, Si controls the fusion. Although it was initially predicted that Alaska coal ash have strong slagging propensity based on the results of ASTM ash characterization, the results of analysis of the DTF deposits shows that the deposits can be easily removed from the heat transfer area because it is enriched with Ca which reduces the strength of its adhesion to the solid surface.

닭에서 오존수의 급여가 닭와포자충 감염에 미치는 영향

박배근,染谷梓,류시윤,김현수,조성환,전무형,손화영 충남대학교 수의과대학 동물의과학연구소 2001 動物醫科學硏究誌 Vol.9 No.-

Ozone is very effective in acute and chronic viral disease as a virucidal agent and in improving the general health of the animals. The effects of ozonized water supply against Cryptosporidium baileyi was studied in 2-day-old chicken. After oral inoculation of chicken with 1×10^6 oocysts, ozonized water(0.5ppm) and tap water were supplied to experimental and control group, respectively. The prepatent period of both group was 6 days postinoculation(PI). The patent period of experimental group was shorter(6-18 days) than that of control group(6-22 days). The number of oocysts in the feces were maximum on days 11 PI, indicating 1.99×10^6 oocysts/experimental chicken and 6.00×10^6 oocysts/control chicken. The number of discharged oocysts during experimental period was higher in control group than that of experimental group. In the view of febric bursa sections on 7 days PI, the number of endogenous development of C baileyi was smaller in experimental group that in control group. This results indicate that the autoinfected sporozoite were damaged by ozone. The ozonized water supply to chickens is alleviation cryptosporidiosis.

직접 황 회수 공정(DSRP)에 관한 연구

전진혁,한기보,박노국,이종대,류시옥,이태진 한국공업화학회 2004 응용화학 Vol.8 No.1

At Hot gas desulfurization, which is one of the unit process for Integrated coal Gasification Combined Cycle(IGCC) system, SO₂ was generated in the regeneration process of sorbents. SO₂ is a major atmospheric pollutant causing various ecological damages and health problems. Direct sulfur recovery process(DSRP) is the catalytic reduction of SO₂ to elemental sulfur by a reductant gas such as CO, H_(z) or CH₄. In this work, the optimization of reaction condition such as the reaction temperature, space velocity and CO/SO₂ molar ratio in DSRP was performed. Sn-Zr compound was used as catalyst in DSRP. Especially, in this process, at low temperature of 598 K, elemental sulfur yield was very high. Generally, DSRP was performed at high temperature above 673 K. Therefore, this process has many advantage from the viewpoint of economy.

암 환자의 혈장 Transforming Growth Factor-β1 농도

박병규,하우송,이시은,이수진,박순태,박찬후,전지현,장정순 THE KOREAN SOCIETY FOR BIOMEDICAL LABORATORY SCINE 1999 Journal of biomedical laboratory sciences Vol.5 No.2

한국인의 대표적인 성인 고형 종양인 위암, 간암, 유방암과 소아 백혈병 및 2종의 소아 고형 종양 환자로부터 혈장 transforming growth factor-ß1 (TGF-ß1) 농도를 sandwich ELISA 분석법을 이용해 측정함으로써 TGF-ß1을 이 질환들에 대한 새로운 종양표지자 (tumor marker)로 사용할 수 있는지 검토하였다. 또한 연령 및 성별에 따른 혈장 TGF-ß1 농도의 정상치를 조사하였다. 신생아에서 70대까지 혈장 TGF-ß1 농도의 차이는 없었고 남녀간의 차이도 없었다. 위암 환자의 혈장TCF-ß1 농도는 16.0±6.8 ng/ml (평균 ±표준편차)로 정상 대조군의 TGF-ß1 농도 (8.3 ±5.0 ng/ml) 보다 유의하게 높았으나 간암, 유방암 환자의 혈장 TGF-ß1 농도는 대조군과 차이가 없었다. 그리고 위암 환자 16명, 간암 환자 8명, 유방암 환자 7명 중 각각 7명 (43.7%), 1명 (12.5%), 1명 (14.3%)에서만 혈장 TGF-ß1 농도가 증가되었다. 5명의 소아 백혈병 환자에서는 관해 (remission) 여부와 상관없이 혈장 TGF-ßl 농도가 모두 정상 범위에 있었으나 2명의 소아 고형암 환자에서는 종양 절제 전에는 혈장TGF-ß1 농도가 높았다가 절제 후 정상으로 떨어졌다. 결론적으로 1)정상인의 혈장 TGF-ßl 농도는 연령 및 성별에 따른 차이가 없다는 것을 알 수 있었고, 2)성인 고형암인 위암, 간암, 유방암에서는 낮은 민감도로 인해 TGF-ß1을 진단을 위한 선별 검사로 이용하기에는 부적절한 것으로 판단되었으며, 3) 정상 대조군보다 혈장 TGF-ß1 농도가 높았던 위암 환자와 종양 절제 전후로 혈장 TGF-ß1 농도가 민감하게 변했던 소아 고형 암 환자에 대해서는 향후 표본 수를 늘려 부가적인 연구를 해 야 할 것으로 사료된다. To evaluate the usefulness of transforming growth factor-ß1 (TGF-ß1)as a new tumor marker, we determined the plasma TGF-ß1 levels using sandwich ELISA assay in cancer patients. Patients with three most common adult cancers in Korea (stomach, liver and breast cancer) and children's cancers (leukemia and two kinds of solid tumor) were enrolled for the study. Furthermore, 39 individuals were subjected to age and sex-stratified plasma TGF-ß1 analysis. No statistical difference was demonstrated with respect to age or sex. The mean plasma TGF-ß1 level (16.0 ng/ml) of stomach cancer patients was significantly higher than that (8.3ng/ml) of controls. However, there was no difference among the mean plasma TGF-ß1 levels of liver, breast cancer patients and controls. Seven of 16 patients (43.7%) with stomach cancer, one of 8 (12.5%) with liver cancer, and one of 7 (14.3%) with breast cancer showed higher TGF-ß1 levels compared to controls. Plasma TGF-ß1 concentrations of five leukemic children remained in the normal range regardless of the remission state. In contrast, initial high TGF-ß1 levels from two children with solid tumors returned to normal range on surgical resection of tumors. From the above results, we could conclude that plasma TGF-ß1 levels of apparently healthy individuals seem to be rather constant irrespective of difference in age or sex, and the plasma TGF-ß1 has the limited value as a screening test for the diagnosis of aforementioned adult cancers because of its low sensitivity. Finally, additional studies need to be pursed for the large number of stomach cancer and pediatric solid tumor patients in order to reach a secure conclusion on the usefulness of plasma TGF-ß1 as a tumor marker in these patients.

내시경적 조임근절개술후에 발생한 췌십이지장 가성동맥류 1예

박수영,김윤정,박진한,전현수,박시형,이영진,이은지,김지현 仁濟大學校 白病院 2010 仁濟醫學 Vol.31 No.-

We reported a case of pancreatic pseudoaneurysm, involving pancreaticoduodenal artery, developed after endoscopic retrograde cholangiopancreatography(ERCP) with endoscopic sphinterotomy. A 54 year old woman was transferred to our hospital due to sustained hematochezia and hypovolemia. A week before admission, she underwent ERCP with endoscopic sphinterotomy for acute cholangitis in local clinics. She developed abdominal pain and hematochezia at 12 hours after the procedures. A post procedure contrast enhanced computed tomography of abdomen demonstrated a pseudoaneurysm in inferior portion of pancreatic head. This was not present on the pre procedure contrast enhanced computed tomography of abdomen and was thought to arise from the pancreaticoduodenal artery as a complication of the pre sphincterotomy. She was brought to our emergency room in a state of hypovolemia. A upper endoscopy showed active bleeding from ampula of vater. An celiac angiography demonstrated pancreatic pseudoaneurysm involving inferior pancreaticoduodenal artery and selective coil embolization of was performed.

라벤더 에탄올 추출물의 피지생성 억제효과

박시준,김호민,한규수,성금수,신미란,문연자,우원홍 한국전통의학연구소 2006 한국전통의학지 Vol.15 No.1

Lavandula vera is indispensable member of the herb family, used for perfumes and potpourri. Androgens have profound effects on the physiology of the sebaceous gland. Sebum is secreted due to the effect of androgen, which starts to be secreted at puberty. Using the human sebocyte cell line SZ95, the author investigated the inhibitory effect of Lavandula vera on the lipid production. Light microscopic finding were examined numerous cytoplasmic lipid droplets SZ95 cells by Oil red staining and lipid droplets were increased markedly by testosterone. On the other hand, combined treatment with Lavandula vera and testosterone resulted in a lower lipid droplets than with testosterone alone in a dose-dependent manner. These findings indicate that Lavandula vera acts antagonistically to testosterone and inhibits the lipid synthesis of SZ95 cells at the cellular level.

마우스에서 오존수의 급여가 쥐와포자충 감염에 미치는 영향

박배근,김덕환,류시윤,김현수,조성환,전무형 충남대학교 수의과대학 동물의과학연구소 2000 動物醫科學硏究誌 Vol.8 No.-

Ozone is very effective in acute and chronic viral disease as a virucidal agent in reversing positive antibody tests and in improving the general health of the animals. The effects of ozonized water supply against Cryptosporidium muris was studied in 5-weeks-old mice. After oral inoculation of mice with 1×10^6 oocysts, ozonized water(0.5ppm) and tap water were supplied to experimental and control group, respectively. The prepatent period of both group was 8 days postinoculation(PI). The patent period of experimental group was longer(62days) than that of experimental group(57days). The number of oocysts in the feces were maxium on days 28 PI, indicating 3.54×10^6 oocysts/experimental mouse and 5.56×10^6 oocysts/ control mouse. The number of discharge oocysts during 12-33 PI was more in control group than that of experimental group. In the view of gastric gland section on days 28 PI, the number of endogenous development of C muris was smaller in experimental group than in control group. This results indicates that the autoinfected sporozoite were damaged by ozone.

PP/MMT 나노복합재료의 열안정성 및 기계적 계면 특성에 관한 연구

박수진,전병렬,송시용,이종문 한국공업화학회 2004 공업화학 Vol.15 No.1

본 연구에서는 몬모릴로나이트(Na^(-)-montmorillonite, MMT)를 dodecylammonium chloide로 유기적 개질하여 폴리프로필렌(PP) 나노복합재료의 열안정성과 기계적 계면 물성에 미치는 영향을 조사하였다. 나노복합재료의 구조 및 표면 특성은 각각 XRD와 FT-IR을 통해 알아보았고, 열안정성은 TGA를 통해 알아보았으며, 주조된 시편의 기계적 계면 물성은 K_(IC)와 G_(IC)를 통해 알아보았다. 실험 결과, dodecylammonium chloide을 이용한 MMT의 유기적 개질(DA-MMT)은 약 7.3 Å의 실리케이트 층간을 증가시켰고, DA-MMT 내의 CH_(2) 기에 의해 2800~2900 ㎝^(-1)에서 새로운 피크가 나타났다. PP/DA-MMT 나노복합재료의 열안정성은 순수한 PP 수지에 비해 향상되었는데, 이는 DA-MMT 입자와 PP 사이의 분자간 상호작용에 의한 것으로 판단된다. 또한, PP/DA-MMT 나노복합재료가 높은 기계적 계면 물성을 나타냈는데, 이러한 결과는 층간이 증가된 실리케이트에 PP가 쉽게 삽입되기 때문으로 판단된다. In this work. the effect of organic modification of Na-montmorillonite (MMT) with dodecylammonium chloride on thermal stabilities and mechanical interfacial properties of PP nanocomposites was investigated. The structure and surface properties of the nanocomposites were determined by XRD and FT-IR, respectively. The thermal stabilities of the nanocomposites were studied using a TGA analysis. Also, the mechanical interfacial properties were confirmed by KIC and GIC of casting specimens. As a result, the organic modification of MMT by dodecylammonium chloride(DA-MMT) led to the increase of the silicate layers to about 7.3 A, and the new peaks at 2800∼2900 cm^(-1) hand were shown in the presence of the CH groups on the DA-MMT. The thermal stahilities of PP/DA-MMT nanocomposites were higher than that of pure PP resin, which can be attributed to the increase of intermolecular interaction between DA-MMT particles and PP matrix. Also, the PP/DA-MMT nanocomposites had higher mechanical interfacial properties than those of pristime nanocomposites. These results explained that the pp was easily inserted in the spacing of the silcate interlayers of which were increased.