Al 함유 13%Cr 스테인리스강의 표면 질소침투 열처리에 미치는 첨가원소 탄소의 영향 : 13%Cr 스테인리스강의 고질소 표면침투 열처리

성장현,주동원,김기돈,유대경,박진욱 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.3

This study aims to investigate the effect of carbon content on the surface nitrogen permeation of 13%Cr-1.8%Al alloyed stainless steels. The surface nitrogen permeation was performed at 1050℃-1200℃ in the 1㎏/㎠ nitrogen gas atmosphere. The nitrogen permeated surface layer of the specimen containing 0.03%C consists of AlN, martensite and retained austenite phases, while the surface layer of the specimen containing 0.14%C appears the AlFe₃C_x phase including former three phases. The specimen containing 0.14%C shows lower total case depth than that containing 0.03%C at the nitrogen permeation temperatures of 1050℃ and 1100℃, while the total case depth of the specimen containing 0.14%C is remarkably increased at the temperature of 1150℃ and 1200℃ due to the increase in the retained austenite content. Martensitic phase, AlN and AlFe₃C_x precipitate of the nitrogen permeated surface layer cause to increase the surface hardness of 550∼600Hv.

고온자전합성법에 의한 Ti/Al 복합판재의 미세조직 형성과정

박우진,안상호,정재영,김낙준,이원철 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.10

Microstructural evolution of Ti/Al layered structures annealed at various temperature has been investigated by using optical microscopy, scanning electron microscopy, and X-ray diffractometry. Ti/Al layered sheets have been produced by dipping two Ti sheets in Al melt. The Ti/Al interfaces showed good bonding characteristics in as-dipped sheet. Microstructure of the heat-treated Ti/Al sheet varies depending on the subsequent annealing temperature. In the Ti/Al layered composite annealed at temperature below Al melting point, thin TiAl₃ layer was formed by the diffusion process at the Ti/Al interfaces. In the case of composite exposed at temperature above Al melting point, the equiaxed TiAl₃particles protruded into Al matrix from the thin TiAl₃ layer as well as the formation of thin TiAl₃ layer. TiAl₃ particles become homogeneously distributed within the Al matrix away from the Ti/Al interface with increasing annealing time. The formation of TiAl₃ phase in Ti/Al sheet annealed at temperature above Al melting point is believed to be formed by the exothermic chemical reaction.

저농도의 Ethanol 이 Vibrio parahaemolyticus 의 증식과 생존에 미치는 영향

박찬성,카메론해커니 한국조리과학회 1995 한국식품조리과학회지 Vol.11 No.2

액체배지에 첨가한 저농도의 ethanol(3∼7%, v/v)이 Vibrio parahaemolyticus의 증식과 생존에 미치는 항균 작용 효과를 -20, 5, 35, 45, 50℃에서 조사하였다. 35℃ 에서의 V, parahaemolyticus 의 증식은 ethanol농도의 증가와 더불어 저해되었으며, 5% ethanol의 존재하에서는 긴 유도기를 거친 후에 증식이 시작되었으나 ethanol 7%에서는 생균수는 계속 감소하여 사멸하였다. 3∼7%의 ethanol을 함유한 액체배지에 10^6∼10^7 cells/㎖의 V. parahaemolyticus를 접종하여 저온(5℃∼-20℃)과 고온(45℃, 50℃)에 저장하였을 때 고온에 저장한 V. parahaemolyticus의 생균수는 급격히 감소하였으며 ethanol농도가 증가할수록 세균의 사멸율은 증가하였다. The effect of low concentrations of ethanol(3∼7%, v/v) in culture broth as an antibacterial agent against Vibrio parahaemolyticus was tested at -20, 5, 35, 45 and 50℃. Increasing concentrations of ethanol progressively inhibited initial growth of V. parahaemolyticus at 35℃. Growth occured at 5% ethanol, but only after a prolonged lag period. At 7% ethanol, the number of viable cells of V. parahaemolyticus declined during incubation. Culture broth containing 3∼7% ethanol was inoculated with 10^6∼10^7 cells/㎖ of V. parahaemolyticus and incubated at low temperatures(5℃, -20℃) and high temperatures(45℃, 50℃). In the presence of 5 or 7% of ethanol, the viability in the cells incubated at high temperatures decreased rapidly. Rate of death increased with increasing concentration of ethanol.

Fe-C-Mn-Si 계 열연 변태유기소성 복합조직강의 미세조직과 기계적 성질에 미치는 합금원소의 영향 (1) : 미세조직과 기계적 성질 Microstructure and Mechanical Properties

박성호,이순기,고향진,김낙준 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.6

The present study is aimed at developing the high strength, high formability low alloy steels having retained austenite as one of the constituents. The main emphasis has been put on understanding the effects of processing variables and alloying elements (Cu, Nb) on the microstructure and mechanical properties of hot-rolled Fe-C-Mn-Si base TRIP (Transformation Induced Plasticity) steels. Experimental results show that microstructure of hot-rolled alloys consists of ferrite, bainite, martensite and retained austenite, whose volume fraction and morphology vary depending on the hot-rolling conditions and alloy compositions. The increase in the quench-finish temperature results in a homogeneous distribution of fine granular particles of retained austenite and hard second phases in a ferrite matrix and accordingly a good combination of strength and ductility. The Cu-containing alloy has been found to improve mechanical properties over the base alloy due to the precipitation of fine ε-Cu in ferrite grains. Nb addition increases the dynamic recrystallization temperature of austenite, resulting in the formation of coarse pan-caked bainite packets. Based on these results, the optimum microstructure for a better combination of strength and ductility is suggested to be the one having granular particles of retained austenite and hard phase (martensite or bainite) in a fine ferrite matrix.

직접 메탄올 연료전지를 위한 anode 전극재료 개발

박경원,이설아,오인환,남석우,하홍용,임태훈,홍성안,성영은 한국공업화학회 1999 응용화학 Vol.3 No.2

Direct methanol fuel cell (DMFC) needs better anode electrocatalysts than Pt, which suffers from self CO poisoning phenomena. The improved oxidation kinetics enabled by Pt promoters such as Ru, Sn, Mo, W or Os has been attributed to a bifunctional and/or an electronic effect. The alloy electrode materials were prepared by reduction and colloidal methods. It was generally proved that binary system such as those based on Pt, these components are much more active in promoting DMFC reactions than pure platinum catalysts. The oxidation onset on pure Pt was 0.45 V and the potentials decreased with alloying. Pt-Ru showed the lowest onset potential. However, chronoamperometry provided high stability at Pt-Mo on CO poisoning, which shows a promising candidate as DMFC anode material. The strategy of ternary or quaternary electrocatalysts, the effects of synthesis and particle sizes will be discussed.

방사성 의약품 합성에 관한 연구(Ⅵ) : Auflatoxine-B1의 방사성 요오드 표지와 그 생리작용

박경배,유용운,성호경,김유선 대한핵의학회 1978 핵의학 분자영상 Vol.12 No.1

Carcinogen으로 알려져 있는 auflatoxine계통 화합물의 방사성 표지 반응을 연구하였다. Auflatoxine 계통 약품중에서 그 함유량이 가장 큰 auflatoxin-B1을 초산 촉매하에 chloroamine-T를 사용하여 125I로 표지한 결과 표지화합물을 방사화학적 수율 63.6%로 얻을 수 있었다. 생성물의 화학구조를 I.R. 및 N.M.R.로 검사한 결과 auflatoxine의 benzene고리에 표지되었음을 확인하였다. 쥐를 시험동물로 삼아 경구 투여후의 대사과정을 부검으로 조사한 결과 간 및 혈액에 방사능이 축적되고 요오드이온은 분리되지 않았음을 확인하였다. Labelling auflatoxines, the potential carcinogenic compounds, by radioactive iodine has been studied. The aufiatoxine-B1, which is known to be the most abundant components of auflatoxines in the nature, was labelled by radioactive iodine-125 through an acid catalyst chloroamine-T procedure. The radiochemical yield was amounted to 63.6%. The chemical structure of the labelled product was proved to be 6-iodo 5-methoxy coumarine structure of auflatoxine-B1 molecule by means of I.R. and N.M.R. spectroscopy. The labelled product was orally administered in a test animal (Rat) and examined the accumnulation of radioactivity in the body at the definite time interval. The accumnulation of the radioactivity was pronounced at the blood and the liver. There was no indication of the decomposition of auflatcxine-B1-125I in the organs of the test animal. $quot;

Dieulafoy 양 병변에 의한 십이지장게실 출혈 1 예

김상현,김경환,이동현,송철수,정노원,박상제,김은규,하홍성,나일환,황윤이,성은영,최익수,신영기 대한소화기내시경학회 2001 Clinical Endoscopy Vol.23 No.1

Duodenal diverticula are first reported by Chomel in 1710. Duodenal diverticula are relatively common in adults with a prevalence of 23% in SRCP. The most duodenal diverticulum is asymptomatic. Complications such as obstruction, cholangitis, blliary stones, ulceration, perforation and hemorrhage can occur in approximately 10%. However, relatively few cases of bleeding from a duodenal diverticulum have been reported. The cause of bleeding from a duodenal diverticulum is uncertain and various suspected etiologies were suggested, such as ectopic gastric mucosa, stasis-induced ulceration, erosion into major vessels, aortoenteric fistuias, intradiverticujar polyp, aspirin-induced erosion. We report a case of a bleeding duodenal diverticulum by a Dieulafoy-like lesion and suggest this 1esion as one of posslble causes of blee4ng in duodenal diverticulum.

교류-직류 변환오차 자동 측정시스템

권성원,박영태,조용명,강전홍,김규태 한국센서학회 1998 센서학회지 Vol.7 No.6

A dual-channel automatic ac-do voltage transfer error measurement system in which the output voltages of two thermal voltage converters which are ac voltage standard are directly measured at the same time to reduce the output voltage drift is described. Forward-reverse measurement method by using a two-channel scanner is used to cancel the offset voltage of the voltmeters. The agreements of the 4-V TVC comparison results between other national standards institute and Korea Research Institute of Standards and Science were less than about ±2 ppm in the frequency range of 40 Hz∼100 kHz, and were less than about ±4 ppm at 200 kHz∼1 MHz. Measurement uncertainty is reduced significantly from ?5 ppm of manual system to ±3 ppm of new system(up to 100 kHz) typically and great increase in comparison efficiency has been achieved by this system.

원자력용 HT9 강과 HT9M 강의 미세조직과 기계적 특성 변화

김성호,박순동,류우석,국일현,송병준 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.12

Microstructure and mechanical properties of HT9 and HT9M steels for liquid metal reactor(LMR) core materials have been investigated. The tempering temperature at which cell structure was formed by rearrangement of dislocations was same in two steels. More carbides were precipitated in HT9 steel due to high carbon content and precipitation of carbides was delayed in HT9M steel. Thus the decrease of hardness with tempering temperature in HT9M steel was lower than that of HT9 steel. The yield strength was decreased, the fine prior austenite grain was formed, and the formation of δ-ferrite was restricted in HT9M steel by decreasing the Cr and carbon content and increasing the Nb content. Thus the impact property of HT9M steel was improved.

목재분진의 독성에 의한 환경홀몬특성 연구

이내우,김성빈,박희련,디노피사니엘로 한국산업위생학회 2000 한국산업보건학회지 Vol.10 No.2

This study was performed to evaluate tannin exposure by woodcuts for workers in furniture factories and to investigate the relationship between tannin exposure and sino-nasal cancer risk. In order to explore possible cytological changes leading to nasal cancer, we have examined 50 male furniture workers and 50 matched controls using brush cytology. The results we have obtained in this study were as follows: 1. The tannin contents of woods used in woodworking factories have been measured and varied from 0.43 to 8.72 ㎎ tannic acid equivalent per gram wood, for reconstituted softwood and turpentine (Syncarpia glomuliferia) respectively. 2. Airborne tannins in woodcuts were also determined by area and personal exposure. The values of mean exposures for bath methods are ranged from 3.1 to 5.0 ㎍/㎥ and from 4.6 to 14.5 ㎍/㎥ in furniture manufactures. 3. Over nasal cytology scores 2, the scores of study group were slightly more than control group and this kind of metaplasias seemed to be occurred over 2 ㎎/㎥ woodcuts and 6 ㎍/㎥ tannin exposure. Keratinising squamous metaplasia was investigated at nasal cytology score 3 and 10 ㎍/㎥ tannin exposure. The nasal cytology score 4 was seemed to be atypical squamous metaplasia. 4. To find out contributing factors to nasal cytology change, odds ratio that is one of fundmental biostatistics was applied. Actually the relationship between woodcuts, tannin concentration and metaplasia were not meaningful, but the relationship between working experience more than 15 years and metaplasia was calculated as 1.83. This reveals that significant clinical abnormalities could be influenced from the years of woodworking experiences. However further research is required to evaluate the significance of the data, for the purposes of sino-nasal risk assessment, standard setting to prevent nasal cancer occurrences and possibility of changing workplace.