FC-25계 회주철의 Boro-Nitriding 복합 표면처리에 따른 표면특성과 고온산화거동에 관한 연구

허인창,손근수,윤재홍,조동율,박봉규,김현수,김인수 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.2

Surface properties and oxidation behavior were studied for FC-25 gray cast iron (GCI), ion nitrided CCI (N CCI), powder boronized CCI (B GCI) and powder boronized N CCI (B-N GCI). A boride (Fe2B and FeB) layer with a tooth shape was formed by boronizing GCI at 650℃. The thickness and hardness of the layer were proportional to boronizing temperature and time. The hardness was decreased as the depth of the boronized layer increased. The activation energy for boride formation was about 74 kJ/mol. The thickness of the graphite layer formed by boronizing was increased by increasing temperature and time. A silicon layer insoluble to borides accumulated beneath the boride layer. The major phases were Fe4N, Fe3N and FeN in the nitride layer formed by ion nitriding. The thickness and hardness of the layer increased with increasing nitriding temperature and time under the Fe4N decomposition temperature of 680℃. The hardness was maximum at the surface and decreased with increasing nitrided depth on B-N GCI at 700℃, above the Fe4N decomposition temperature. Hardness of B-N GCI at the layer depth of 10 μm was 1000 Hv, which was lower than that of the B GCI at the same condition. Also the layer thickness was 50 gm; 10 μm deeper than that of B GCI. The reason was that the nitrogen gas given off by the decomposition made the layer porous and facilitated the diffusion of oxygen and other reactants. The samples were oxidated at 800℃ for 48hrs under atmospheric air. Oxidation rate was in decreasing order of N GCI, GCI, B GCI and B-N GCI. Oxidation rates were greatly influenced by the diffusion of nitrogen gas formed by Fe4N decomposition over the decomposition temperature of 680℃ and the oxidation barrier of the less corrosive boride layer. (Received October 29, 2004)

이온 교환체로서 Quinine-금속thiocyanate착물을 이용한 Quinine의 정량

허문희,백광진,최현영,안문규 경성대학교 1997 論文集 Vol.18 No.1

The fabrication and performance characteristics of quinine sensitive poly(vinyl chloride) membrane electrodes based on the ion-association complex of quinine with an anionic counter ion, metal thiocyanates (Co(SCN)??, Cd(SCN)??, Fe((SCN)??, Hg(SCN)??, Mn(SCN)??, Ni(SCN)??, zn(SCN)??) was described. The sensing membrane was based on the quinine complex of cobalt thiocyanate plasticized with 65.3% (w/w) tris(2-ethylhexyl) phosphate (TEHP), ferric thiocyanate with 65.3% (w/w) TEHP, nickel thiocyanate with 65.3% (w/w) TEHP and zinc thiocyanate with 49% (w/w) TEHP. These electrodes show a linear response down to 1.2×10?, 1.0×10?, 9.6×10?, 2.0×10?M with Nernstian slope of 55.69, 54.96, 56.63, 55.80 mV/dec. for quinine with relative standard deviation of 3.1, .51, 2.26, 3.16% at pH 5.5∼7.6, respectively. Response time was 10∼20s. The quinine-nickel complex with 65.3% (w/w) TEHP was the optimal ion-exchanger for quinine selective electrode. The electrode exhibits good selectivity for the quinine in the presence of some inorganic cation and organic cations. The quinindine-nickel complex instead of quinine-nickel complex as an ion-exchanger was successfully applied to the direct potentiometric determination of quinidine pharmaceutical preparation giving an average recovery of 101.5% and relative standard deviation of 2.5%.

쐐기 형태의 5급와동에서 수복재료에 따른 변연 미세누출의 비교

허복,이희주,장현주 大韓齒科保存學會 2000 Restorative Dentistry & Endodontics Vol.25 No.1

상아질표면처리에 따른 글래스아이오노머 및 Compomer의 전단결합강도의 비교

허 복,이희주,정현숙 大韓齒科保存學會 1999 Restorative Dentistry & Endodontics Vol.24 No.2

중국 고추산업의 현황과 대응

허봉구,김현석,김주현 한국국제농업개발학회 2005 韓國國際農業開發學會誌 Vol.17 No.1

고추의 주된 수출국인 중국의 고추 품종, 재배, 유통 등 고추산업의 현황을 조사하고 이에 대한 몇가지 대응방안을 제시하면 다음과 같다. 1. 중국의 고추 총생산량은 전세계 생산량의 48%로서 최대 수출국은 인도네시아, 말레이시아, 한국 등지로 수출된다. 2. 중국 산동성의 고추 총생산량은 15만톤 정도이나 우리나라 고추와 비슷하고 색택이 좋은 건고추 益都椒가 숙주로 고춧가루 형태로 한국에 수출된다. 3. 경쟁력 강화를 위해서는 직파재배나 일시수확형, 붉은 색깔이 많은 고추품종의 개발이나 생산비 절감을 위찬 재배법의 개발이 필요하다. 4. 고품질 고춧가루 생산을 위한 가공기술의 개발과 고추가공 수출품의 규격화로 세계시장을 확대해야 할 것이다. Export of red pepper in China vs South Korea increased every year. Red pepper industry that is cultivars, cultivation method and distribution etc. were investigated and confrontation on the red pepper industry in South Korea were suggested as follows; The amount of red pepper production in China was possessed by 48% world production of red pepper. Presently red pepper exported to Indonesia, Malaysia and South Korea. The amount of red pepper production in Shandong district in China was 1.5 hundred thousand ton. Yi du jiao that is similiar to Korean red pepper is high ASTA value and export to South Korea. For the strengthen, cultivars for direct sowing, once of harvesting and high ASTA and also cultivation method for production cost saving will be developed. Manufactering techniques for production of red pepper powder in high quality will be develope. Standard on export products of red pepper will process and expand world market.

FC-25계 회주철의 이온질화처리에 따른 표면특성과 고온산화거동에 관한 연구

허인창,손근수,윤재홍,조동율,박봉규,김현수,김인수 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.4

Surface properties and high temperature oxidation behavior were investigated for FC-25 Gray Cast Iron(GCI) and the ion nitrided GCI(N-GCI). The GCI was pre-cleaned to improve hardness to the optimum pre-sputtering parameters with an Ar/H₂ ratio of 1/2, working pressure of 3 torr, working temperature of 550℃ and working time of 1hour. The optimum nitriding conditions for the maximum hardness of 560575 Hv were an N₂/H₂ ratio of 3/1, working pressure of 3 torr, and working temperature of 575℃. The thickness of graphite in the GCI was increased by increasing the working temperature from 525℃ to 595℃ for the nitriding time of 6-18hrs. XRD patterns showed FeO and Fe₂O₃ peaks for both the oxidized N-GCI and GCI at temperatures of 600℃ and 800℃ under atmospheric environment for both 24 and 60hours. At 800℃, above the Fe4N decomposition temperature of 680℃, the oxidation rate of N-GCI was greater than that of the GCI. The most abundant nitride, Fe4N, was decomposed and the nitrogen gas given off by the decomposition made the protective film porous by degassing through the film. But at 600℃, below the decomposition temperature, the degree of oxidation of N-GCI was lower than that of the GCI because the nitride film worked as protective barrier for oxidation. (Received October 29, 2004)

Dibucaine-금속 요오드 착물을 이온교환체로서 이용한 Dibucaine의 정량

최현영,이지연,허문회,안문규 慶星大學校 1998 論文集 Vol.19 No.1

Dibucaine-selective poly(vinyl chloride) menbrance electrodes were designed based on ion-association complex between dibucaine and metal iodide complex such as H??, Bil?? and CdI??. Stable potentiometric response was obtained with Meyer reagent at pH 3.0-5.5, with Dragendorff reagent at pH 3.0-5.0 and with Marume reagent at pH 3.0-5.5. The best plasticizer was 49 w/w% acetyl-tri-n-butly critrate for Meyer reagent, 65.3 w.w% for Marume reagent. The electrodes exhibited a linear response based on Meyer, Dragendorff and Marume complex were the concentration range of 2×10?4×10?M ,2×10×4×10?M, 2×10?1×10?M,respectively. The potentiometric response slope of optimized membrane electrodes based on Meyer, Dragendorff and Marume complex for dibucaine were 56.12,57.81 and 56.45?? with relative standard deviation of 2.75, 2.29 and 1.96%, respectively. This ISE methods are found to be sensitive, rapid, fairly accurate and are able to be empolyed successfully for the determination of dibucaine preparations.

여러 식품 및 사료로부터 분리된 미생물로부터 유용 박테리오신의 탐색

백현동,허지운 慶南大學校 附設 工業技術硏究所 1998 硏究論文集 Vol.15 No.3

박테리오신은 미생물로부터 생산되는 천연의 무독성 방부제로서 주목받고 있는 항균성 단백질이다. 단백질로 구성되어 있기 때문에 인체에 섭취되면 소화기관의 단백질 가수분해효소에 의해 분해되므로써, 인체에 무독하고 잔류성이 없다는 점에서 식품, 화장품, 농약 및 기타 분야에서의 천연 항생물질로서의 효용성이 증대되고 있다. 대부분의 박테리오신은 생산균주와 매우 가까운 그람 양성균만을 억제하는 매우 제한된 항균범위를 가지고 있어, 우수한 내열성에도 불구하고, 산업화하는데 문제점으로 지적되어 왔다. 따라서 본 연구에서는 여러 식품 및 사료로부터 GRAS로 인정받고 있는 유용 미생물을 분리하고, 이 분리균주들로부터 항균범위가 넓은 유용 박테리오신을 탐색하였다. 우선 각종 분리원에서 propionibacteria를 선택적으로 분리하기 위한 PAGSA배지를 확립하였다. 50종의 김치시료로부터 150종의 젖산균을 분리하였으며, 이 중에서 3종의 균주가 항균범위가 넓은 것으로 확인되었다. 그러나 주 항균효과가 젖산에 의한 가능성에 대해 향후 추가 실험이 필요하다. 치이즈로부터 15종의 미생물을 분리하고, 이 중 3종의 다른 propionibacteria를 확인하였고 많은 그람 음성균에 항균효과가 있슴이 확인되었다. Silage로부터 propionibacteria와 젖산균을 15종 분리하였으며, JWS15균주가 가장 항균범위가 넓은 균주로 밝혀졌고, 그람 음성균인 E. coli, Pseudomonas속균주에 항균효과가 있었다. 각종 식품으로부터 35종의 바실러스 균주를 분리하였으며, 이 중 SS704균주는 테스트한 대부분의 바실러스 균주와 대부분의 그람 음성균에 매우 큰 활성을 보였고, 주요 식물병원균인 Erwinia herbicola, Pseudomonas syringae, Xanthomonas campestris에 뚜렷한 항균활동을 보여 이 들 식물병원성균의 선택적인 방제에 활용이 가능하리라 판단된다. Bacteriocins are proteins produced by a heterogeneous group of bacteria have a bactericidal effect on closely related organisms. Because bacteriocins are natural products of many microorganisms associated with foods, there is currently an enhanced interest in their use as natural food preservatives. The GRAS microorganisms were isolated from various food and feed sources and the antibacterial activity of 215 isolates was determined by the deferred and a modified well diffusion assay. Bacillus strain SS704 showed a broad antibacterial spectrum of activity against all Gram-positive and Gram-negative bacteria tested, but not against yeasts tested. Especially, strain SS704 was active against major plant pathogens, such as Erwinia herbicola, Pseudomonas syringae, and Xanthomonas campestris. Thus, the exploitation of this strain in agriculture will be focused in the near future on the retardation of spoilage by plant pathogens and for grain preservation.

MOCVD법에 의해 제조된 Fe₂O₃-TiO₂계 산화물 박막의 내식특성에 관한 연구

李在鉉,杉本克久,許聖康,尹在弘,金顯洙,邊應善 國立 昌原大學校 産業技術硏究所 1998 産技硏論文集 Vol.12 No.-

Fe₂O₃-TiO₂artificial passive films were formed at the temperatures of 200-350℃ by low pressure MOCVD technique. The relationship between the formation temperature and corrosion resistance of the Fe₂O₃-TiO₂films was examined in acid solutions. Fe₂O₃-TiO₂films deposited above 300℃ were crystalline and the films deposited below 250℃ were amorphous. The dissolution rate of the Fe₂O₃-TiO₂films deposited at 200 and 250℃ decreased with increasing the formation temperature in 5 M HCl, but the films deposited at 300 and 350℃ hardly dissolved in the solution. The films deposited at 200 and 350℃ easily dissolved at cathodic potentials in 1 M H₂SO₄and HCl owing to te selective reduction of iron oxide components in the films. But, the selective reduction in the films deposited at 300 and 350℃ was suppressed. The Fe₂O₃-TiO₂films deposited above 300℃ have higher corrosion resistance than that of the films deposited below 250℃, because the former have high crystallinity and cotain high chemical resistant oxides.

만곡 근관에서 삼각 혹은 장방형 단면 구조의 니켈-티타늄 파일 응력 분포에 관한 3차원 유한요소 연구

김현주,이찬주,김병민,박정길,허복,김현철 대한치과보존학회 2009 Restorative Dentistry & Endodontics Vol.34 No.1

이 연구의 목적은 3차원 유한요소 모형 분석을 이용하여 삼각 대칭형과 S형태의 단면 및 변형된 사각 형태인 장방형 단면으로 분류되는 네 종류의 니켈티타늄 파일이 만곡 근관 적용 시의 응력 분포를 비교하는 것이다. 삼각 대칭형 단면 구조의 ProFile #30 / .06과 HeroShaper #30 / .06,장방형 단면구조의 Mtwo #30 / .05와 NRT #30 / .06 파일을 마이크로컴퓨터 단층촬영을 하고 reverse engineering을 통하여 파일의 구조를 얻고 삼차원 유한요소모형을 제작하였다. 모형 근관 내에서 파일이 근관장 끝까지 진입하여 회전할 때 발생하는 von Mises 응력 분포 및 파일의 제거후의 잔류 응력의 분포양상을 ABAQUS 프로그램을 이용하여 비교하였다. 근관 내 회전 시에 발생하는 응력을 관찰하였을 때 NRT 파일에서 가장 큰 응력을 나타냈으며 , 각 파일에서의 최고 응력과 최저 응력을 비교하였을 때 Mtwo파일에서 가장 큰 차이가 나타났다. 응력의 내부 분포 경향을 보았을때 장방형 구조의 단면을 가진 Mtwo 및 NRT 파일에서 불연속적인 응력의 집중 부위가 관찰되었으며 , 근관 외부로 파일을 제거하여 탄성 회복이 일어난 후의 잔류 응력도 NRT 파일에서 가장 높게 나타났다. 이상의 결과로 유추할 때, 삼각대칭 단면 구조를 가진 파일보다 S-형태의 단면과 변형된 사각 형태의 단면 등의 장방형 단면 구조의 파일이 파절의 위험성이 더 클 것으로 사료된다. The purpose of this study was to compare the stress distributions of NiTi rotary instruments bascd on their cross-sectional geometries of triangular shape-based cross-sectional design. S-shaped cross-sectional design and modified rectangular shape-based one using 3D FE models. NiTi rotary files of S-shaped and modified rectangular design of cross-section such as Mtwo or NRT showed larger stress change while file rotation during simulated shaping. The stress of files with rectangular cross-section design such as Mtwo, NRT was distributed as an intermittent pattern along the long axis of file. On the other hand, the stress of files with triangular cross-section design was distributed continuously. When the residual stresses which could increase the risk of file fatigue fracture were analyzed after their withdrawal, the NRT and Mtwo model also presented higher residual stresses. From this result, it can be inferred that S-shaped and modified rectangular shape-based files were more susceptible to file fracture than the files having triangular shape-based one.