어닐링 온도 변화가 Al/연강 클래드재의 계면 특성에 미치는 영향

정은욱,김희봉,김동용,김민중,조영래,Jeong, Eun-Wook,Kim, Hoi-Bong,Kim, Dong-Yong,Kim, Min-Jung,Cho, Young-Rae 한국재료학회 2012 한국재료학회지 Vol.22 No.11

For heat exchanger applications, 2-ply clad materials were fabricated by rolling of aluminum (Al) and mild steel sheets. Effects of annealing temperature on interface properties, especially on inter-layer formation and softening of strain hardened mild-steel, for Al/mild steel clad materials, were investigated. To obtain optimum annealing conditions for the Al/mild steel clad materials, annealing temperature was varied from room temperature to $600^{\circ}C$. At the annealing temperature about $450^{\circ}C$, an inter-layer was formed in an island-shape at the interface of the Al/mild steel clad materials; this island expanded along the interface at higher temperature. By analyzing the X-ray diffraction (XRD) peaks and the energy dispersive X-ray spectroscopy (EDX) results, it was determined that the exact chemical stoichiometry for the inter-layer was that of $Fe_2Al_5$. In some samples, an X-layer was formed between the Al and the inter-layer of $Fe_2Al_5$ at high annealing temperature of around $550^{\circ}C$. The existence of an X-layer enhanced the growth of the inter-layer, which resulted in the delamination of the Al/mild-steel clad materials. Hardness tests were also performed to examine the influence of the annealing temperature on the cold deformability, which is a very important property for the deep drawing process of clad materials. The hardness value of mild steel gradually decreased with increasing annealing temperature. Especially, the value of hardness sharply decreased in the temperature range between $525^{\circ}C$ and $550^{\circ}C$. From these results, we can conclude that the optimum annealing temperature is around $550^{\circ}C$ under condition of there being no X-layer creation.

노인요양시설 서비스 제공 수준의 관련 요인 분석

정은욱 ( Eun Wook Jung ),정승원 ( Seung Won Jeong ),서영준 ( Young Joon Seo ),최대봉 ( Dae Bong Choi ) 한국병원경영학회 2007 병원경영학회지 Vol.12 No.4

The objective of this study is to examine relevant factors of the service level of aged care facilities. The sample used in this study consisted of 357 aged care facilities in Korea. Data were collected with self-administered questionnaire and 140 returned questionnaire were analyzed by SPSS Version 12.0. The major findings of the study are as follows: First, there was no significant mean difference in the service level by the facility characteristics, except the length of operation. Second, it was found that both administrative characteristics and employer characteristics were positively associated with the level of nursing and supportive services. Third, the study results revealed that the following three variables of employee education and training, community networks, and employer`s philosophy and management principles had significant positive effects on the level of nursing services. Meanwhile, the following two variables of employee education and training, and community networks had significant positive effects on the level of supportive services. In conclusion, in order to improve their service level, the managers of aged care facilities in Korea should make efforts to provide more employee education and training, establish networks with the community stakeholders, for example, local clinics and hospitals. It is also recommended for the government to make a policy inducing more qualified private investors to enter the aged care market, as well as to strengthen the qualification of the managers of the public aged care facilities.

극저온 열처리가 7075 알루미늄 합금의 잔류응력과 기계적 특성에 미치는 영향

김회봉,정은욱,고대훈,김병민,조영래,Kim, Hoi-Bong,Jeong, Eun-Wook,Ko, Dae-Hoon,Kim, Byung-Min,Cho, Young-Rae 한국재료학회 2013 한국재료학회지 Vol.23 No.1

In this study, the effects of cryogenic treatment cycles on the residual stress and mechanical properties of 7075 aluminum alloy (Al7075) samples, in the form of a tube-shaped product with a diameter of 500 nm, were investigated. Samples were first subjected to solution treatment at $470^{\circ}C$, followed by cryogenic treatment and aging treatment. The residual stress and mechanical properties of the samples were systematically characterized. Residual stress was measured with a cutting method using strain gauges attached on the surface of the samples; in addition, tensile strength and Vickers hardness tests were performed. The detailed microstructure of the samples was investigated by transmission electron microscopy. Results showed that samples with 85 % relief in residual stress and 8% increase in tensile strength were achieved after undergoing three cycles of cryogenic treatments; this is in contrast to the samples processed by conventional solution treatment and natural aging (T4). The major reasons for the smaller residual stress and relatively high tensile strength for the samples fabricated by cryogenic treatment are the formation of very small-sized precipitates and the relaxation of residual stress during the low temperature process in uphill quenching. In addition, samples subjected to three cycles of cryogenic treatment demonstrated much lower residual stress than, and similar tensile strength compared to, those samples subjected to one cycle of cryogenic treatment or artificial aging treatment.

폴리머 기판에 스퍼터법으로 경사 증착한 Cr박막의 특성

배광진,최인균,정은욱,김동용,이태용,조영래,Bae, Kwang-Jin,Choi, In-Kyun,Jeong, Eun-Wook,Kim, Dong-Yong,Lee, Tae-Yong,Cho, Young-Rae 한국재료학회 2015 한국재료학회지 Vol.25 No.1

Glancing angle deposition (GLAD) is a powerful technique to control the morphology and microstructure of thin film prepared by physical vapor deposition. Chromium (Cr) thin films were deposited on a polymer substrate by a sputtering technique using GLAD. The change in thickness and Vickers microhardness for the samples was observed with a change in the glancing angle. The adhesion properties of the critical load (Lc) by a scratch tester for the samples were also measured with varying the glancing angle. The critical load, thickness and Vickers microhardness for the samples decreased with an increase in the glancing angle. However, the thickness of the Cr thin film prepared at a $90^{\circ}$ glancing angle showed a relatively large value of 50 % compared to that of the sample prepared at $0^{\circ}$. The results of X-ray diffraction and scanning electron microscopy demonstrated that the effect of GLAD on the microstructure of samples prepared by sputter technique was not as remarkable as the samples prepared by evaporation technique. The relatively small change in thickness and microstructure of the Cr thin film is due to the superior step-coverage properties of the sputter technique.

플라즈마 표면처리가 표면에너지와 Cr코팅층 / 기판의 부착 특성에 미치는 영향

김동용 ( Dong Yong Kim ),정은욱 ( Eun Wook Jeong ),후이 ( Kwun Nam Hui ),최영선 ( Young Son Choe ),한정호 ( Jung Ho Han ),조영래 ( Young Rae Cho ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.10

Atmospheric plasma surface treatment (APST) was applied on the soda-lime glass and silicon wafer(Si-wafer) substrates for surface modification. The surface energy for the surface treated samples was measured using the wetting angle. The effect of APST on surface energy and interface properties between sputtered chromium (Cr) coatings and substrates was investigated. The surface energy increased linearly and reached a maximum value of 74 mJ/m2 by APST. The increase in surface energy is due to the increased value of the polar component in surface energy. When the samples were exposed to the air, the increased surface energy decreased and tended to have hydrophobicity. The work of adhesion for the surface treated samples was calculated using the data of surface tension for water. We demonstrated that the trend of work of adhesion for the samples was similar to the change of adhesion strength between sputtered Cr coatings and the surface treated substrates. (Received March 13, 2013)

자동차보험과 건강보험의 의료기관 종별가산율 일원화 논리에 대한 고찰

김정덕 ( Jung Duck Kim ),정은욱 ( Eun Wook Jeong ),이종훈 ( Jong Hoon Lee ) 경희대학교 경영연구원 2012 의료경영학연구 Vol.6 No.4

Government has driven the unification of added-ratio by size of medical institution(below ``added-ratio``) between National Health Insurance(NHI) and Traffic Accident Insurance(TAI). And Some studies have supported the policy through arguing that length of stay(LOS) and medical expenditure per hospitalization care of TAI is longer or higher than that of NHI. There is added-ratio difference in tertiary hospital(TAI 15%p higher than NHI), general hospital(TAI 12%p higher than NHI) among medical institutions between NHI and TAI(below ``group A``). But there is no difference in hospital(TAI 1%p higher than NHI), clinic(TAI=NHI)(below ``group B``). The policy target for the unification of added-ratio is group A. But LOS and medical expenditure per hospitalization care(MEPC) of group A is very short in realty. And management strategy of group A is not MEPC but medical expenditure per day(MEPD). To compare 3 medical institutions(general hospital, hospital, clinic) with LOS and MEPC according to same ICD code between NHI`s inpatients and TAI`s inpatients. 3 general hospitals, 3 hospitals, 3 clinics. Treatment amount of 6 months for each medical institutions. TAI`s LOS and MEPC of General hospital is shorter than that of NHI. But THI`s LOS and MEPC of hospital and clinic is longer than that of NHI. TAI`s LOS and MEPC of Group A is shorter than that of NHI. But TAI`s LOS and MEPC of group B is longer than that of NHI.

다공성 AAO 템플릿의 기공에 금속 함유 수용액의 충진 거동에 대한 연구

김태식 ( Tae Sik Kim ),정은욱 ( Eun Wook Jeong ),최인균 ( In Kyun Choi ),박운익 ( Woon Ik Park ),조영래 ( Young Rae Cho ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.4

Anodic aluminum oxide (AAO) templates have drawn much interest because they can be applicable to form carbon nanotubes, nanowires and nanorods. For the aim of nanowire fabrication, infiltration behaviors of metal containing solution into pores in AAO template were investigated. In this paper, nickel nitrate solution [Ni(NO3)2·6H2O] was used as metal containing solution (marker solution). The infiltration behavior of marker solution into the pores (diameter: 30 nm) in AAO template was observed by scanning electron microscopy. The samples which had been processed by plasma treatment or pressure change showed a favorable influence on the infiltration properties of marker solution into the pores. Compared to plasma treatment, the pressure change in the chamber showed a little effect on infiltration behavior of marker solution. From this study, we conclude that the change in surface energy of the AAO surface is more effective than pressure change for the infiltration of marker solution into the holes in AAO template. The weak effect of pressure change on infiltration is due to large value of Knudsen number resulted from very small diameter of pores in the AAO template. (Received June 3, 2014)