• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.535-541
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• 2015

In this study, an approximate multi-objective optimization of a wall-mounted monitor bracket arm was performed. The rotation angle of the bracket arm was determined considering the inplane degree of freedom. We then formulated an optimization problem on maximum stress and deflection. Analyses of mean and design parameters were conducted for sensitivity regarding performance with orthogonal array and response surface method (RSM). RSM models of objective and constraint functions were generated using central composite (CCD) and D-optimal design. The accuracy of approximate models was evaluated through $R^2$ value. The obtained optimal solutions by non-dominant sorting genetic algorithm (NSGA-II) were validated through the finite element analysis and we compared the obtained optimal solution by CCD and D-optimal design.

• KSBB Journal
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• v.17 no.3
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• pp.235-240
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• 2002

The surface of polypropylene was modified by 1 keV $Ar^+$ ion beam in an $O_2$ environment in order to enhance wettability. Contact angle of deionized water on modified polypropylene was reduced from $78^{\circ}$to $22^{\circ}$. The enhanced wettability is originated from newly formed functional groups such as ether, carbonyl, and carbonyl groups. During immersion in deionized water, the enhanced wettability has remained nearly same. After washing in water, the hydrophilic functional groups on the polymer surface have been very stable. The modified polypropylene was adopted as bio-film media to remove organics in synthetic wastewater. Microbe adhesion on the polypropylene surface was improved due to the newly formed hydrophilic groups.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.149-156
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• 2011

This experimental design and response surface methodology (RSM) have been applied to the investigation of the electro-UV-ultrasonic complex process for the disinfection of E. coli in the water. The disinfection reactions of electro-UV-ultrasonic process were mathematically described as a function of parameters power of electrolysis ($X_1$), UV ($X_2$), and ultrasonic process ($X_3$) being modeled by use of the Box-Behnken technique, which was used for fitting 2nd order response surface model. The application of RSM yielded the following regression equation, which is empirical relationship between the residual E. coli number (Ln CFU) in water and test variables in coded unit: residual E. coli number (Ln CFU) = 23.69 - 3.75 Electrolysis - 0.67 UV - 0.26 Ultrasonic - 0.16 Electrolysis UV + 0.05 Electrolysis Ultrasonic + 0.27 $Electrolysis^2$ + 0.14 $UV^2$ - 0.01 $Ultrasonic^2$). The model predictions agreed well with the experimentally observed result ($R^2$ = 0.983). Graphical 2D contour and 3D response surface plots were used to locate the optimum range. The estimated ridge of maximum response and optimal conditions for residual E. coli number (Ln CFU) using 'numerical optimization' of Design-Expert software were 1.47 Ln CFU/L and 6.94 W of electrolysis, 6.72 W of UV and 14.23 W of ultrasonic process. This study clearly showed that response surface methodology was one of the suitable methods to optimize the operating conditions and minimize the residual E. coli number of the complex disinfection.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.375-380
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• 2003

In this study. we have intended to control the properties of surface reaction zone generated between pure titanium and oxide investment moulds. Commercially pure titanium was centrifugally casted and silica$.$alumina based phosphate bonded investment was used as the mould material. The effect of cooling methods after casting on the surface reaction zone and mechanical properties of casts were investigated. The resulting casts showed the multilayered surface reaction zone regardless of cooling method. Especially. water cooling method produced the titanium casts with thinner surface reaction zone. weaker strength. and higher elongation properties compared to air cooling. It can thus be known that the resulting casts had satisfactory mechanical properties as dental materials. From these results, the cooling rate dependence of interfacial and mechanical properties can be attributed to the diffusion of oxygen from casting environment, which control the reaction of titanium and mould.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.376-384
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• 2009

Purpose: The purpose of this study was to evaluate the response of osteoblast-like cells to Ca-P coated surface obtained via Ion beam-assisted deposition (IBAD) method and Sol-Gel process on anodized surface by cellular proliferation and differentiation. Material and methods: The surface of a commercially pure titanium (Grade IV) discs with dimension of 10mm diameter and 2 mm thickness was modified by anodic oxidation under a constant voltage of 300 V. The experimental groups were coated with Ca-P by the IBAD method and Sol-Gel process on anodized surface. The surface roughness (Ra) of specimens was measured by optical interferometer and each surface was examined by SEM. To evaluate cell response, MG63 cells were cultured and cell proliferation, ALP activity and the ability of cell differentiation were examined. Also, cell morphology was examined by SEM. The significant of each group was verified by Kruskal-Wallis Test ($\alpha$=.05). Results: The Ra value of Ca-P coated surface by IBAD method was significantly higher than Ca-P coated surface by Sol-gel process (P < .05). The level of cell proliferation and ALP activity was higher in Ca-P coated surface by IBAD method (P<.05). The expression of ALP showed higher level expression in Ca-P coated surface by IBAD method. Cells grown on Ca-P coated surface by IBAD method were uniformly distributed and developed a very close layer. Conclusion: These experiments showed better performances of Ca-P coated surface by IBAD method with respect to Ca-P coated surface by Sol-gel process. Ca-P coated surface by IBAD method appear to give rise more mature osteoblast characteristics and might result in increased bone growth and bone-implant contact.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.2
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• pp.76-82
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• 2009

In this papers, Study on the Bonding property and Strength Evaluation in Bonding interface Joints of Dissimilar material using DOE. We found optimal condition that uses experimental design method (Response Surface Analysis, DOE) used temperature, pressure, time on experiment factor. And we could get bonding condition and strength that break and crack do not happen in mechanical processing about united dissimilar material. And progress 3 point bending tests and verified result.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3044-3048
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• 2008

It is well known that Premixed Charge Compression Ignition (PCCI) diesel engines according to many technologies such a change in injection timing, multiple injection strategy, cooled EGR, intake charging and SCV have the potential to achieve homogeneous mixture in the cylinder which result in lower NOx and PM as well as performance improvements. This may generate merely the infinite number of experimental conditions. The use of Response Surface Methodology (RSM) technique can considerably pull down the number of experimental set and time demand. This paper presents the effects of both fuel injection and engine operation conditions on the combustion and emissions in the PCCI diesel engine system. The experimental results have revealed that a change in fuel injection timing and multiple injection strategy along with various operating conditions affect the combustion, emissions and BSFC characteristics in the PCCI engine.

• ETRI Journal
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• v.11 no.1
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• pp.89-96
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• 1989

$C_2F_6$/$CHF_6$ 플라즈마를 이용한 실리콘 산화막의 반응성이온 식각공정시 실리콘 표면에 형성되는 고분자 잔류막과 근표면 손상영역을 X-선 광전자분광법(x-ray photoelectron spectroscopy)과 러더포드 후방산란법(Rutherford backscattering)을 이용하여 연구하였다. 표면 잔류막은 CF, $CF_2$, $CF_3$, $C-CF_x$, 그리고 C-C/C-H 등의 결합을 가진 불화탄소 고분자로 구성되어 있으며, 또한 C 1s와 Si 2p X-선 광선자 스펙트럼으로부터 C-Si 결합이 존재함을 확인하였다. 반응성이온 식각을 거친 실리콘 표면 구조의 연구결과, 불소와 탄소로 구성된 고분자막($<20 \AA$)이 극표면에 존재하며, 식각 후 공기중에 노출됨에 따라 고분자 잔류층으로 산소가 통과하여 기판을 산화시킴으로써 실리콘 산화막( $~10\AA$)이 그 아래에 형성되었음을 알았다. 그리고 실리콘산화막 아래에 탄소-산소 결합영역이 관찰되었다. 플라즈마 가스의 조성에서 $CHF_3$의 량이 증가함에 따라 고분자 잔류막의 두께가 증가하였으며, 본 연구의 실험조건에서 2분간 overetching한 시편의 경우에도 실리콘 표면 영역의 손상정도가 매우 적음을 발견하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4378-4384
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• 2012

In LED chip packaging, die bonding is a very important process which fixes the LED chip on the lead frame to provide enough strength for the next process. This paper focuses on the process optimization of a LED die bonding, which attaches small zener diode chip on PLCC LED package frame, using response surface analysis. Design of experiment (DOE) of 5 factors, 3 levels and 5 responses are considered, and the results are investigated. As the results, optimal conditions those satisfy all response objects can be derived.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.121-121
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• 2016

치아는 인체중에서도 혹한 환경에서 부분으로 높은 하중과 타액과 같은 강 부식성 매체로 그 환경이 상상을 초월한다. 즉 반복적으로 가해지는 하중(응력)과 침식을 유발하는 타액과 음식물 등이다. 따라서 치아가 쉽게 파괴되거나 썩는 현상이 나타나게 된다. 이렇게 사용되다가 치아의 역할을 다하게 되면 인공치아를 사용하게 되는데 그 재료가 바로 타이타늄(Ti)이다. 생체매식재로 사용되는 Ti는 반응성이 높아 산소와 쉽게 결합하여 표면에 TiO, $TiO_2$, 및 $Ti_2O_3$와 같은 산화피막을 표면에 형성함으로써 뛰어난 부식저항성과 생체적합성을 가지며 생체에 독성이 없고 탄성계수가 골과 비슷하여 골과 임플란트 경계면에서 응력분산에 유리한 성질 등 물리적, 기계적 성질이 뛰어나 외과용 임플란트 재료로 가장 좋은 재료이다. 금속 임플란트의 생체적합도는 임플란트 재료 자체보다는 생체 내 산화막이 화학적으로 불안정할 때 부식이 발생하게 되고 그 결과 금속이온이 주위로 유리되어 조직반응을 일으키므로 금속의 표면을 덮고 있는 산화막에 의해 좌우된다. Ti는 생체불활성재료로서 매식재료로 사용할 경우 뼈와 잘 융합되는 골유착을 나타내나 골과 화학적결합은 하지 않고 골형성을 적극적으로 유도하지 못함으로 환자의 치유기간이 길어지게 된다. 이러한 이유로 골조직내 임플란트의 접합을 개선하기위한 연구가 이루어져 골과의 결합을 높이기 위해 골유착을 일으키는 Ti에 골성장을 유도하는 뼈성분인 하이드록시 아파타이트(HA)라는 물질을 플라즈마 코팅법을 사용하던가 아니면 Hanks' solution내에서 침적 후 HA도금을 하는 방법 등으로 처리하고 있다. 그러나 플라즈마 코팅법은 고온에서 처리를 행하고 Hanks' solution내에 침적할 경우 Ti표면에 밀착도가 저하되거나 합금의 상변화 등으로 인하여 표면처리 과정 중에서 내식성이 크게 감소될 수 있다. 이러한 여러 가지 코팅법을 통하여 골 유착을 증진시키기 위한 연구는 계속되고 있지만 임상적으로 사용 후 문제가 단시일에 발생되는 것도 아니고 수년이 지나야 나타나게 된다. 이러한 방법으로 코팅을 하게 되면 골과 잘 유착이 되어 자연차아와 같은 기능을 하게 된다. 따라서 이러한 문제를 최소화하는 방법이 나노구조를 표면에 형성시켜 골유착을 쉽게 함으로써 이를 개선할 수 있을 것으로 생각되어 본 강의에서는 임플란트의 문제와 사용되는 재료에 대하여 고찰하여 자연치아를 대체 할 수 있는지 알아보았다.