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전기화학적 분석을 통해 산출된 코팅 결함율이 트라이볼로지적 특성에 미치는 영향 평가
김우중(Woo-Jung Kim),안승호(Seung-Ho Ahn),김호건(Ho-Gun Kim),김정구(Jung-Gu Kim),조정우(Chung-Woo Cho),이영제(Young-Ze Lee) 한국트라이볼로지학회 2004 한국윤활학회지(윤활학회지) Vol.20 No.6
Many of the current development in surface modification engineering are focused on multilayered coatings, which have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel in this study. The prepared samples are designed as WC-Ti_(0.6)Al_(0.4)N, WCTi_(0.53)Al_(0.47)N, WC-Ti_(0.5)Al_(0.5)N and WC-Ti_(0.43)Al_(0.57)N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behaviors. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec and a normal load of 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (H_R = 66) having a diameter of 10 ㎜. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Also, wear mechanism was determined by using SEM coupled with energy-dispersive spectroscopy (EDS). Results have showed an improved wear resistance of the WC- Ti_(1-x)AlxN coatings with increasing of Al (aluminum) concentration.
전기화학적 분석을 통해 산출된 코팅 결함율이 트라이볼로지적 특성에 미치는 영향 평가
김우중(Woo-Jung Kim),안승호(Seung-Ho Ahn),김호건(Ho-Gun Kim),김정구(Jung-Gu Kim),조정우(Chung-Woo Cho),이영제(Young-Ze Lee) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.38 No.-
Recently, many of the current development in surface modification engineering are focused on multilayered coatings. Multilayered coatings have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel. The prepared samples are designed as WC-Ti0.6Al0.4N, WC-Ti0.6Al0.4N, WC-Ti0.53Al0.47N and WC-Ti0.43Al0.57N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behavior. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec, 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (HR = 66) having a diameter of 10 ㎜. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Also, wear mechanism was determined by using SEM coupled with EDS. Results have showed an improved wear resistance of the WC-Ti1-xAlxN coatings with increasing of Al concentration.
김우중(Woo Jung Kim),양유진(Yoo Jin Yang),정희정(Hee Jung Chung) 대한소아신경학회 2005 대한소아신경학회지 Vol.13 No.2
Purpose : Lactic acidosis is one of the most common forms of metabolic acidosis. It is hard to fine the cause of lactic acidosis, because in many cases the clinical features of this disorder are non-specific and overlap with those of other metabolic or non-metabolic diseases. In this report, we tried to identify the causes of lactic acidosis and classified them into four groups:primary and secondary lactic acidosis, neurodegenerative disorders and others. Methods : We analyzed the clinical characteristics of 22 patients who had arterial blood lactate levels over 2.5 mmol/L. They visited Ilsan Hospital because of seizures or delayed development. Clinical characteristics include laboratory findings, EEG, brain imaging study, chromosomal study and metabolic enzymatic evaluation. Results : The mean age of the patients was 3.4 years. Most of them complained of delayed development(21 cases) and seizures(14 cases). One of the patients was revealed as primary lactic acidosis, and the other one secondary lactic acidosis. Also, there was a case of neurodegenerative disease. Furthermore, the other ten patients were affected by other causes of lactic acidosis:7 cases of epilepsy, a case of Rett syndrome, a case of 4p deletion syndrome, and a case of cerebral palsy. However, the causes of lactic acidosis of the remaining 9 patients were unknown. But 5 of them were thought to be affected by respiratory chain disorders diagnosed by modified Walker’s criteria. Conclusion : There are numerous disorders in children which can produce lactic acidosis. Although metabolic work-ups of these patients are very complex and require coordinated efforts of clinicians and laboratory works, early diagnosis of the etiologic nature of the disease is essential to minimize the progression and the complications of the disease. 배 경 : 고젖산혈증은 여러 가지 원인에 의해 나타날 수 있지만, 대부분 비특이적인 임상양상을 보이기 때문에 진단이 쉽지 않다. 하지만, 이와 같은 질환들은 환아에서 심한 성장부전을 초래할 뿐 아니라 경련발작, 발달지연, 정신지체 및 뇌성마비 같은 운동기능저하 등의 심각한 문제를 야기시키므로, 가능한 조기에 원인을 찾아내는 것이 매우 중요하다. 이에 저자들은 발달지연이나 경련발작을 주소로 내원한 환아에서 고젖산혈증을 보인 경우 그 원인을 분석하고, 이들의 임상적 의의를 살펴보기 위하여 본 연구를 시행하였다. 방 법 : 2001년 2월부터 2004년 2월까지 국민건강보험공단 일산병원 소아과의 발달지연 클리닉을 방문한 환자 중 간질 발작과 발달지연의 원인 분석 시 동맥혈에서 채취한 젖산 농도가 2.5 mmol/L 이상인 22명을 대상으로 하여 임상양상, 가족력, 과거럭 등에 대한 후향적 연구를 시행하였다. 결 과 : 환자 중 발달지연을 보인 환자는 21례, 경련발작 14례였으며, 성장지연 8례, 근긴장도 저하 2례, 근력저하 5례로 나타났다. 남녀의 비는 14:8이었으며, 나이는 1개월부터 9년 11개월까지로 평균은 3년 5개월이었다. 16례에서 동맥혈 젖산농도 및 피루빅산 농도를 구했으며, 젖산/피루빅산 비율은 13부터 730까지 다양하였다. 뇌파검사상 17례, 뇌자기공명영상 검사상 8례, 뇌자기스펙트 검사상 4례에서 이상소견을 보였다. 피부섬유세포 검사상 1례(14%)에서 RCC Ⅰ-Ⅲ deficiency 소견을 보였다. 세포유전학적 염색체 검사상 1례(14%)에서 4번 염색체 단완의 결손 소견이 보였다. 분자유전학적 돌연변이 검사는 9례에서 시행하였으나, 이상 소견은 나오지 않았다. 결과적으로 고젖산혈증의 원인은 대사성질환이 8례(사립체질환 의중 5례, 일시적 고젖산혈증 1례 포함), 신경변성질환 1례, 전신질환과 동반된 경우가 10례, 미상 3례이었다. 결 론 : 사립체 질환과 같은 대사 이상 질환에 의해 발생하는 고젖산혈증의 경우는 환자의 성장 및 발달에도 영향을 미치며, 조기진단 및 그에 맞는 조기치료가 필수적이기 때문에, 고젖산혈증이 있을 때 그 원인을 조기진단 하는데 도움이 되는 단계적인 진단 체계를 확립하여 단계별로 진단 과정을 밟아가는 것이 중요하다.
S형상 점진기능재료 나노-스케일 판의 자유진동 특성에 미치는 비국소 탄성 효과
김우중(Kim, Woo-Jung),이원홍(Lee, Won-Hong),박원태(Park Weon-Tae),한성천(Han, Sung-Cheon) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.2
본 논문에서는 S형상함수를 이용한 점진기능재료 나노-스케일 판의 자유진동 특성에 미치는 비국소 탄성 이 론의 효과에 대하여 연구하였다. 비국소 탄성 이론은 미소 규모 효과를 고려할 수 있고 S형상함수는 점진기능재료의 정확한 특성변화를 고려할 수 있다. 이러한 이론을 이용하여 나노-스케일 판의 고유진동수에 미치는 비국소 이론의 효과를 제시하였고, 국소 탄성이론과의 관계를 수치해석 결과를 통하여 고찰하였다. 또한 (i) 거듭제곱 지수, (ii) 비국 소 계수, (iii) 탄성계수 비 그리고 (iv) 나노-스케일 판의 두께 및 형상 변화 등이 나노-스케일 판의 무차원 진동수에 미치는 효과에 대하여 관찰하였다. 본 연구의 결과를 검증하기 위해 참고문헌의 결과들과 비교 분석하였으며 해석결 과는 참고문헌의 결과들과 잘 일치함을 알 수 있었다. 비국소 이론에 의한 나노-스케일 판의 진동에 관한 연구는 향 후 관련연구에 비교자료로 활용될 수 있을 것이다. We study free vibration analysis of sigmoid functionally graded materials(S-FGM) nano-scale plates, using a nonlocal elasticity theory of Eringen in this paper. This theory has ability to capture the both small scale effects and sigmoid function in terms of the volume fraction of the constituents for material properties through the plate thickness. Numerical solutions of S-FGM nano-scale plate are presented using this theory to illustrate the effect of nonlocal theory on natural frequency of the S-FGM nano-scale plates. The relations between nonlocal and local theories are discussed by numerical results. Further, effects of (i) power law index (ii) nonlocal parameters, (iii) elastic modulus ratio and (iv) thickness and aspect ratios on nondimensional frequencies are investigated. In order to validate the present solutions, the reference solutions are compared and discussed. The results of S-FGM nano-scale plates using the nonlocal theory may be the benchmark test for the free vibration analysis.
김우중(Woo-Jung Kim),김재훈(Jae-Hoon Kim),장중철(Jung-Cheol Jang),김범수(Beom-Soo Kim),유근봉(Keun-Bong Yoo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
The Heat Recovery Steam Generator(HRSG) is device that uses exhaust gas of gas turbine to increase thermal efficiency. In order to requirements global needs saving energy, reducing emission of CO2, reducing cost, many power plant appled HRSG. Generally, High Cr steels are used in steam side tube because of its high temperature strength and oxidation resistance. This paper addresses creep-rupture test of 9Cr-1Mo steel at isothermal temperature with change thermal and stress condition. the results of date are plotting to Larson-Miller parameter. Through hardness test of specimens, fluctuation of hardness values are determined to interrelation between hardness and life. Finally, The test specimen of creep rupture is observed by Transmission Electron Microscope(TEM) to analyze higt temperature material behavior of Cr steels
김우중 ( Woo Joong Kim ),김재훈 ( Jae Hoon Ki ),장중철 ( Jung Cheol Jang ),김범수 ( Beom Soo Kim ),이기천 ( Gi Chun Lee ) 한국안전학회(구 한국산업안전학회) 2013 한국안전학회지 Vol.28 No.3
The Heat Recovery Steam Generator (HRSG) is a device recycling the exhaust gas of gas turbine in combined power and chemical plants. Since service temperatures was very high, the damage of HRSG tubes intensively occurred in superheater and reheater. The aim of this paper is to determine life and hardness relationship that addresses creep-rupture test and creep-interrupt test in modified 9Cr-1Mo steel. The measured life that consists of function of hardness was found to constant tendency.