Study on Microstructure and Mechanical Properties of the Al–25Cr–5Si (at%) Alloy Powder Using Gas-Atomization and SPS Process

Yong‑Ho Kim,Hyo‑Sang Yoo,Jeong‑Han Lee,Ik‑Hyun Oh,Hyun‑Kuk Park,Hyeon‑Taek Son 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

In order to investigate the microstructure and mechanical properties on Al–25Cr–5Si (at%) alloy, a mixed powder with pureelements and an alloy powder using a gas atomization process were used. Fine and high purity Al–25Cr–5Si (at%) alloypowder was successfully prepared by gas atomization and densified using a spark plasma sintering (SPS) process. The overallpowder size distribution of the mixed Al, Cr, and Si elemental powders was in the range of 10–15 μm. The atomized Al–Cr–Sialloy powder was fine and spherical in morphology and difficult to be formed by intermetallic formation. Densification wasclearly confirmed at 1000 °C, with almost isolated pores formed, by clear removal of pores between particles, deformationof particles, an increase in the number of contacts, and a change in size between particles. As a result of XRD analysis ofthe sintered compacts, single phase was observed using the mixed powder, but the compact using gas atomization remainedthe alloy phase even at the process temperature. The Vickers hardness of the compacts by mixed powder was observed at59.70 Hv and the compact using gas atomized powders on the temperature 1000 °C of the Vickers hardness increased to702.6 Hv. The compressive yield strength of the compact with mixed powder was 195.24 MPa and the compressive strengthof the compact with gas atomized powder increased to 802.07 MPa. It is considered not to be decomposed by the AlCrSi,Al13Cr4Si4and Al8Cr5phases sintering process, resulting from the improvement of mechanical properties.

일부 종합병원 병리조직실 공기 중 포름알데히드 농도

정규현,하안례,이용환 고신대학교 보건과학연구소 2002 보건과학연구소보 Vol.12 No.-

Formaldehyde irritiates mucous membranes in the eyes, nose, and upper respiratory tract, and it is a potential carcinogen. The purpose of this study was to assess the time-weighted average (TWA) and short-term exposure limit (STEL) concentration to formaldehyde exposure and to suggest proper improvement strategy to minimize exposure. This study was conducted at 3 histopathology laboratories in the hospitals located in Busan from January 20 to March 10, 2002. Formaldehyde and organic solvents (ethanol and xylene) were sampled by personal air sampler and analyzed by gas chromatography. The obtained results were as follows. 1. TWA concentrations of formaldehyde ranged from 0.28 to 10.64 ppm and those of two laboratories out of 3 were exceeded the threshold limit value (TLV). 2. In one laboratory, STEL concentrations was exceeded threshold limit value (TLV), as 2.39 ppm. 3. TWA concentrations of ethanol and xylene were under the TLVs. It is necessary to improve the local ventilation systems and other facilities to prevent the personnels in the laboratories from the diseases due to formaldehyde exposure.

소화성 궤양 환자에 대한Lansoprazole의 치료 효과

정현용,김진희 최신의학사 1997 最新醫學 Vol.40 No.6

혈액투석 환자에게서 발생한 재생불량성 빈혈 1예

정지용,윤나라,강대웅,오종찬,장재현,선길홍,박경희,정종훈,김현리 朝鮮大學校 附設 醫學硏究所 2005 The Medical Journal of Chosun University Vol.30 No.1

Aplastic anemia is a disease characterized by pancytopenia in the peripheral blood and hypocellular bone marrow with the fatty infiltration. The causes of the acquired aplastic anemia were usually related to drugs and immune-related diseases. A 34-years old man was admitted due to general weakness. He has been going hemodialysis for 2 years because of end stage renal disease (ESRD) due to chronic glomerulonephritis. At admission, laboratory tests showed hemoglobin 6.2 g/dL, hematocrit 18.0 %, WBC 5,710mm (neutrophil 71.8%, lymphocyte 19.1%, monocyte 5.9%), reticulocyte 1.9%, platelet 93,000/mm, Fe 12.8 ug/dL, TIBC 204 ug/dL, ferritin 941.47 ng /ml, haptoglobin 0.72 g/L, vitamin B12 508.17 pmol/L, folate 24 ng/mL, total protein 6.54 g/dL, albumin 3.76 g/dL, Alk. pohsphatase 79 IU/L, AST 30.0 IU/L, ALT 39.7 IU/L, total bilirubin 0.57 mg/dl, BUN 79.4 mg/dl and creatinine 10.18 mg/dl. Peripheral blood smear showed the normocytic normochromic anemia with anisocytosis. Anemia was diagnosed but it was irresponsive to the recombinant human erythropoietin (EPO) and blood transfusion. In the bone marrow aspiration smear were there the hypoplastic myeloid and erythroid precursors. The bone marrow biopsy section showed the hypoplasia of all components (10-20%) and the fatty infiltration. We have experienced one case of the idiopathic aplastic anemia in a patient going through hemodialysis and we just report it with documentary records. 저자들은 혈액 투석 중인 환자에서 약물, 면역계 이상등의 원인을 발견할 수 없었음에도 재생 불량성 빈혈이 발생한 1예를 경험하여 문헌 고찰과 함께 보고하는 바이다.

니페디핀이 암피실린의 흡수에 미치는 영향

정현정,용철순,최윤수,오두만 영남대학교 약품개발연구소 1997 영남대학교 약품개발연구소 연구업적집 Vol.7 No.-

Amino-β-lactam antibiotics are absorbed by the dipeptide transporter in the small intestine. These uptakes are coupled to a proton influx. The inward proton gradient is partly induced by the Na^(+)/H^(+) exchanger and cakium ion is involved in control of this antiport. Interaction between ampicillin which is one of the amino-β-lactam antibiotics and nifedipine which is one of calcium channel blocking agents was studied in rats in vivo and with rabbit jejunum mounted on the Sweetana/Grass diffusion cells in vitro. Bioavailability of ampicillin was increased significantly when nifedipine was co-administered orally in rats. There were no differences in the distribution phase and the elimination phase when ampicillin was given either alone or with nifedipine intravenously. Conditions for in vitro experiments were determined. The lift rate of O₂/CO₂ gas was controlled to 3 bubbles/sec and ampicillin was stable in the Kreb's buffer at pH6.0 Absorption of ampicillin was the greatest when the completely-stripped serosal membrane was used. Transport of ampicillin from mucosal to serosal side in the rabbit jejunum was enhanced by 32% in the presence of nifedipine (p=0.059). Above results suggest that nifedipine might increase the plasma level of ampicillin via the improved absorption in the intestine rather than the reduction in the elimination or/and alteration in the distribution.

위궤양에 대한 Teprenone(Selbex^�)의 임상효과

정현용,김병호,성자원,이기천,허승식,이종선,이헌영,김영건 충남대학교 의과대학 지역사회의학연구소 1991 충남의대잡지 Vol.18 No.2

The study objective was to assess the ulcer healing effects of Teprenone, stimulator of mucus production, given in dose of 50mg tid. We reviewed 25 cases of gastric ulcer proven endoscopically and treated by Teprenone. The results were follows; 1) The healing rate of gastric ulcer was 72% after 8 weeks treatment. 2) Subjective symptoms such as epigastric pain, belching, nausea, anorexia and vomiting were subsided at 86%. 3) There were not developed any symptoms, signs and laboratory abnormality (CBC, liver funtion test, urinalysis) suggesting side effect of drugs. In conclusion, Teprenone was considered an effective and safe drug in the treatment of gastric ulcer diseases.

신경회로망을 이용한 지능형 로봇 제어 시스템 설계

정동연,김용태,한성현 경남대학교 공업기술연구소 2000 硏究論文集 Vol.18 No.-

본 논문에서는 일반적으로 고정된 위치에서 검사하는 비젼 시스템이 아닌 카메라를 로봇의 말단효파부에 장착하여 렌덤하게 움직이는 물체를 추적하여 지능적으로 매니퓰레이터의 위치 및 속도를 제어하여 정확한 위치에 납땜 작업을 한 후 비젼 검사를 실시하는 로봇 비젼 시스템을 설계한다. 자동검사를 위한 비젼기술은 실시간 실현을 위해 디지털 신호 처리기를 사용한 새로운 고성능 비젼 알고리즘을 개발해서 S사의 전자부품 조립검사라인, 즉 카메라 조립검사라인에서 라인을 따라 흘러 들어오는 백커버(Back Cover)들을 정해진 위치를 따라 로봇을 이동하여 자동 인식한다. 인식된 백커버의 납땜상태를 다양한 위치 및 이동공정에서 대해서도 유연하게 검사를 자동으로 수행하고 품질기준 통과여부를 자동 판단할 수 있는, 이른바 다공정 제품의 형상인식 및 자동검사용 로봇 비젼 기술을 개발하기 위한 연구가 수행되었다. 그리고 제안된 로봇 비젼 시스템의 성능을 컴퓨터 시뮬레이션 및 실험을 통하여 S사의 조립라인중 5번 Cell의 유사공정을 모델링하여 그에 대한 유사한 실험을 통해 그 신뢰성을 입증하고자 한다. In this paper, we have proposed a new approach to the design of robot vision system to develop the technology for the automatic test and assembling of precision mechanical and electronic parts for the factory automation. In order to perform real time implementation of the automatic assembling tasks in the complex processes, we have developed an intelligent control algorithm based-on neural networks control theory to enhance the precise motion control. Implementing of the automatic test tasks has been performed by the real-time vision algorithm based-on TMS320C31 DSPs. It distinguishes correctly the difference between the acceptable and unacceptable defective item through pattern recognition of parts by the developed vision algorithm. Finally, the performance of proposed robot vision system has been illustrated by experiment for the similar model of fifth cell among the twelve cell for automatic test and assembling in S company.

上部胃腸管出血과 下部腸管出血에서의 BUN/Creatinine Ratio의 比較

鄭賢溶 충남대학교 의과대학 지역사회의학연구소 1990 충남의대잡지 Vol.17 No.1

To evaluate the relationship between BUN/creatinine ratio and sites of gastrointestinal bleeding, to investigate the mechanism of high BUN level in gastrointestinal bleeding. I reviewed 228 cases (UGI 189 cases, LGI 39 cases) of acute gastrointestinal hemorrhage. The results were follows: 1. In the sites of bleeding, upper parts were involved more 5 times than lower parts. 2. The causes of upper gastrointestinal bleeding were gastric ulcer(29.6%), esophageal varix(24.3%), hemorrhage gastritis(14.3%), duodenal ulcer(11.1%), stomach cancer(8.5%), Mallory-Weiss syndrome(4.8%) and others(7.4%). 3. The causes of lower gastrointestinal bleeding were colon cancer(13%), ulcerative colitis(10.3%), hemorrhoid(10.3%), intestinal tuberculosis(7.6%), malignant lymphoma(5.1%), diverticulitis(5.1%), colon polyp(5.1%), typhoid enteritis(5.1%), bacillary dysentery(5.1%), hemorrhagic colitis(5.1%), vascular malformation(5.1%), others(10.3%) and unknown causes(13%). 4. The BUN/creatinine ratio were significantly high in UGI bleeding than LGI bleeding at same hemoglobin levels. 5. High level of BUN/creatinine ratio(above 20) were noticed in 64% of UGI bleeding and 2.6% of LGI bleeding(1/39 cases). 6. The mechanism of increased BUN levels in gastrointestinal bleeding was considered chiefly high urea formation in liver by intestinal nitrogen overload.

DNA 감지를 위한 MOSFET형 전하검출센서의 제작 및 특성

정용택,김동선,류홍근,박혜정,신장규,최평,이종현,임근배 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1

농촌주민의 혈중 납과 카드뮴 농도에 관한 조사연구

정현숙,조영채,이동배 忠南大學校 環境問題硏究所 1991 環境硏究 Vol.9 No.-

The purpose of this study was to find out blood lead and cadmium concentration levels of rural residents. The blood samples were collected from 140 rural residents in 5 nonpolluted regions in Kunbuk-Myun, Kumsan-Gun, Chungnam province from August 31 to September 30, 1990 and analyzed by atomic absorption spectrophotometry. The results were summerized as follow : The mean concentration level(range) of blood lead was 0.240±0.060㎍/ml(0.130-0.390㎍/ml) for males and 0.237±0.056㎍ /ml(0.120-0.370㎍/m) for females. There was no statistically significant difference among age groups and sexes. The distributions were similar to normal distribution in both sexes. The mean concentration level(range) of blood cadmium was 0.066±0.099㎍/ml(0.012-0.582㎍/ ml) for males and 0.060±0.062㎍/ml(0.015-0.392㎍/ml) for females. There was no statistically significant difference among age groups and sexes. The distributions were skewed to the low level ranges in both sexes. The lead concentration level in whole blood did not show statistically sinificant difference among kinds of farming product. But the cadmium level of the rice-ginseng-tobacco farmers was statistically significantly high (p<0.005). The cadmium concentration level in whole blood was 0.040±0.027㎍/ml for the rice-ginseng farmers, 0.076±0.100㎍/ml ofr the rice-tobacco famers, and 0.158±0.171㎍/ ml for the rice-ginseng-to-bacco farmers. There were no statistically significant difference in blood lead and cadmuim concentration levels among groups classified by drinking habit, smoking habit and exposed years to pesticides. The correlation coefficent between the blood lead and cadmium concentration levels was statistically significant(R=0.2054, P<0.05).