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H<sub>2</sub>O<sub>2</sub>/HCl 처리한 Ti 임플란트의 생체활성 평가
유재선,권오성,이오연,이민호,송기홍,Yue J. S.,Kwon O. S.,Lee O. Y.,Lee M. H.,Song K. H. 한국재료학회 2005 한국재료학회지 Vol.15 No.5
Surface treatment play an important role in nucleating calcium phosphate deposition on surgical Ti implant. Therefore, the purpose of this study is to examine whether the precipitation of apatite on cp-Ti and Ti alloys are affected by surface modification in HCl and $H_2O_2$ solution. Specimens were then chemically treated with a solution containing 0.1 M HCl and 8.8M $H_2O_2$ at $80^{\circ}C$ for 30 mins, and subsequently heat-treated at $400^{\circ}C$ for 1 hour. All specimens were immersed in the HBSS with pH 7.4 at $36.5^{\circ}C$ for 15 days, and the surface was examined with XRD, SEM, EDX ana XPS. Also, pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloy specimens with and without surface treatment were implanted in the abdominal connective tissue of mice for 4 weeks. All specimens chemically treated with HCl and $H_2O_2$ solution have the ability to form a apatite layer in the HBSS which has inorganic ion composition similar to human blood plasma. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was $38.57\;{\mu}m,\;62.27\;{\mu}m\;and\;45.64\;{\mu}m$ in the cp-Ti, Ti-6Al-4V ana Ti-6Al-7Nb alloy specimens with the chemical treatment respectively, and $52.20\;{\mu}m,\;75.62\;{\mu}m\;and\;66.56\;{\mu}m$ in the commercial specimens of cp-Ti, Ti-6Al-4V and Ti-6Al-7Nb without any treatment respectively. The results of this evaluation indicate that the chemically treated cp-Ti, Ti-6Al-4V ana Ti-6Al-7Nb alloys have better bioactivity and biocompatibility compared to the other metals tested.
초전도 세라믹 Y-Ba-Cu-O계의 구조적 상전이와 분해거동에 관한 연구
이민호,이민상,김양수,진영철 ( M . H . Lee,M . S . Lee,Y . S . Kim,Y . C . Jin ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.3
In this study, the structural phase transition and decomposition of superconducting ceramic, Y-Ba-Cu-O system was studied. The results of the study are as follows. The high Tc superconductor Y₂Ba₂Cu₃O_(7-x) is made in solid state reaction of O₂atmosphere and the valve of X in Y₂Ba₂Cu₃O_(7-x) is 0.1∼0.2. The transition temperature of tetragonal-orthorhombic phase of Y₂Ba₂Cu₃O_(7-x) appear at 790℃-900℃. In the result of measuring the electrical resistance of sample annealed in O₂atmosphere, the electrical resistance show zero at 92K and the best superconductor, Y₂Ba₂Cu₃O_(7-x)(Y123) can be mabe.
MCFC 양극측에서 Al-Cr피복 스테인레스강 분리판의 내식성평가
이민호,윤재식,배인성,윤동주,김병일,박형호,Lee, M.H.,Yoon, J.S.,Bae, I.S.,Yoon, D.J.,Kim, B.I.,Park, H.H. 한국재료학회 2003 한국재료학회지 Vol.13 No.2
In order to evaluate the corrosion resistance at the anode side separator for molten carbonate fuel cell, STS316 and SACC-STS316 (chromium and aluminum were simultaneously deposited by diffusion into STS316 authentic stainless steel substrate by pack-cementation process) were applied as the separator material. In case of STS316, corrosion proceeded via three steps ; a formation step of corrosion product until stable corrosion product, a protection step against corrosion until breakaway occurs, a advance step of corrosion after breakaway. Especially, STS316 would be impossible to use the separator without suitable surface modification because of rapid corrosion rate after formation of corrosion product, occurs the severe problem on stability of cell during long-time operation. Whereas, SACC-STS316 was showed more effective corrosion resistance than the present separator, STS316 due to the intermetallic compound layer such as NiAl, Ni3Al formed on the surface of STS316 specimen. And it is anticipated that, in order to use SACC-STS316 alternative separator at the anode side, coating process, which can lead to dense coating layer, has to be developed, and by suitable pre-treatment before using it, very effective corrosion resistance will be achieved.
이민호,김항석,송영근,Lee, M.H.,Kim, H.S.,Song, Y.K. 한국전자통신연구원 2014 전자통신동향분석 Vol.29 No.2
전 세계의 인구와 도시가 점점 증가함에 따라 매년 각종 범죄를 비롯한 사건사고와 가상이변, 홍수, 지진 등과 같은 자연재해가 증가하고 있다. 따라서 공공의 안전과 재난상황에서 구조를 위한 새로운 통신의 필요성이 급증하게 되었다. 모바일 광대역 공공안전(Public Safety) 통신은 여러 지역에서 다양한 사고와 재난이 발생하였을 때, 응급현장에서의 지시나 관리의 책임을 지는 기관에서 사용하는 전파통신을 의미한다. 이를 활용하면 더욱 효율적이고 체계적으로 공공의 안전을 위협하는 상황에 대한 대응능력을 향상시킬 수 있을 것으로 보인다. 따라서 관련 시장 역시 급격히 성장할 것으로 전망되고 있다. 본고에서는 모바일 광대역 공공안전 통신시장의 규모와 흐름을 살펴보고 공공안전과 재난구조 활동의 발전을 위한 무선통신망 구축의 방안에 대해 살펴보고자 한다.
이민호(M. H. Lee),이지훈(J. H. Lee),장건희(G. H. Jang) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4
This research investigates the stability analysis for the rotating and the stationary grooved journal bearing. The dynamic coefficients of the journal bearing are calculated by using FEM and the perturbation method. When journal bearing is in whirling motion, the dynamic coefficients have time-varying components as a sine wave due to the reaction force of oil film toward the center of journal even in the steady state. The solutions for the equations of motion can be assumed as the Fourier series expansion. The equations of motion can be rewritten as the linear algebraic equations with respect to the Fourier coefficients. Then, stability of the grooved journal bearing can be calculated by Hills infinite determinant. The periodic function of dynamic coefficients is derived using Fourier Fast Transform(FFT).The stability of journal bearing is determined as rotating speed increases and the stability of rotating grooved journal bearing is compared and discussed with the stability of stationary grooved journal bearing.