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심형민,오근택,김경남 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.4
Titanium and its alloys are widely used in biomedical and dental fieds because of their excellent corrosion resistance, biocompatibility, high strength to weight ratio and good fatigue properties. It is well known that titanium is protected from corrosion due to the stability of passive film that controls and determines the corrosion resistance of titanium. The stability of passive film can also determine biocompatibility of titanium and its alloys. The purpose of this study was to evaluate the electrochomical properties of Ti-Ag alloys and the stavility of passive film in artificial saliva. We designed Ti-Ag alloys with silver contents ranging from zero to 5.0 at% in steps of 0.5 at%. The alloys were arc-melted, homogenized, hot-rolled to 2 mm in thickness, and finally solution heat-treated for 1hour and quenched in water. Potentiodynamic and poteniostatic testing were performed and open circuit potential of the Ti-Ag alloys was measured in artificial saliva 37℃. Passive film of the Ti-Ag alloys was analyzed by XPS(x-ray photoelectron spectroscopy). Ti-Ag alloys showed low passive current density and electrochemically stable behavior in the artificial saliva and passive film of the Ti-Ag alloys was composed of TiO_2, Ti_2O_3 and TiO. As Ag content increased, TiO_2 fraction increased and titanium oxide layer of the Ti-Ag alloys formedthicker than that of titanium.It is thought that Ti-Ag alloys can be adopted and used safely with good biocompatibility for dental application.
보수적 근사모델을 적용한 신뢰성기반 강건 최적설계 방법 기초연구
심형민(Hyoung Min Sim),송창용(Chang Yong Song),이종수(Jongsoo Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
The methods of robust design optimization (RDO) and reliability-based robust design optimization referred as RBRDO are implemented in the present study. The RBRDO is an integrated method that accounts for the design robustness in objective function and for the reliability in constraints. The objective function in RBRDO is expressed in terms of mean and standard deviation of an original objective function so that the multi-objective formulation is to be employed. The regressive approximate models are generated via moving least squares method (MLSM) and constraint-feasible moving least squares method (CF-MLSM) that is possible to realize the feasibility regardless of the multimodality/nonlinearity of the constraint function during the approximate optimization processes. The regression model based RBRDO is newly devised and its numerical characteristics are explored using the design of an actively controlled ten bar truss structure.
디젤 엔진 연료 분사량 예측을 위한 HCS기반 신경망 근사모델링
심형민(Hyoung Min Sim),박재인(Jae In Park),이준규(Joon Kyu Lee),이수홍(Soo Hong Lee),이종수(Jongsoo Lee) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
In this paper, we proposed the use of hermit cubic spline and back-propagation neural networks to predict rates of injection in diesel engine fuel injection system. The rate of injection in the diesel engine is described in terms of energizing time and rail pressure, and its time integration corresponds to the total fuel quantity. All results verified the possibility of neural network based rates of injection prediction and hermite cubic spline interpolation method as well.
보수적 근사모델을 적용한 신뢰성 기반 강건 최적설계 방법
심형민(Hyoung Min Sim),송창용(Chang Yong Song),이종수(Jongsoo Lee),최하영(Ha-Young Choi) 한국해양공학회 2012 韓國海洋工學會誌 Vol.26 No.6
The methods of robust design optimization(RDO) and reliability-based robust design optimization (RBRDO) were implemented in the present study. RBRDO is an integrated method that accounts for the design robustness of an objective function and for the reliability of constraints. The objective function in RBRDO is expressed in terms of the mean and standard deviation of an original objective function. Thus, a multi-objective formulation is employed. The regressive approximate models are generated via the moving least squares method(MLSM) and constraint-feasible moving least squares method (CF-MLSM), which make it possible to realize the feasibility regardless of the multimodality/nonlinearity of the constraint function during the approximate optimization processes. The regression model based RBRDO is newly devised and its numerical characteristics are explored using the design of an actively controlled ten bar truss structure.
치과 재료용 NiTi 합금의 특성에 대한 Ag 첨가의 영향
오근택,박기호,심형민,황충주,김경남 大韓齒科器材學會 2001 대한치과재료학회지 Vol.28 No.4
Equiatomic and near-equiatomic nickel-titanium alloys have shape memory effect and superelasticity. However nickel-titanium alloys are extremely sensitive to the precise nickel-titanium ratio and alloying additions. There are many reports on the alloying additions such as Fe, Al, Cr, Co, V, Pt, Pd, Zr, Hf, Nb and Cu. The purpose of this study was to investigate the effect of silver addition to nickel-titanium alloy for dental and medical application.Arc melting process was used to fabricate nickel-titanium alloys. The casts were heat-treated in a vacuum furnace at 950℃ for 72 hours to homogenize their composition. Subsequently, they were hot-rolled at 950℃ to obtain the plate samples and annealed in a vacuum furnace at 950℃. To investigate the properties of nickel-titanium alloys, phases, transformation temperature, compositions, corrosion resistance and hardness were evaluated using X-ray diffractometer, differential scanning calorimeter, energy dispersive spectroscopy or atomic absorption spectroscopy, potentiostat and micro-vickers hardness tester, respectively. NiTiAg alloys showed the low silver recovery rate for the cast due to its low evaporation temperature, and showed low silver solubility to NiTi alloy. Silver addition to NiTi alloy increased transition temperature range (TTR) above 100℃ and stabilized martensitic phase(monoclinic structure) at room temperature because Ms temperature was above room temperature. Martensitic and austenitic phase existed in x-ray diffraction pattern of solution annealed NiTiAg alloys. The Silver addition is considered to improve corrosion resistance and change largely the mechanical properties depending upon the amount of alloying addition and types of addition elements.