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Rolling stones with nonconvex sides II: all time regularity of interface and surface
이기암,이은재 대한수학회 2012 대한수학회지 Vol.49 No.3
In this paper we consider the evolution of the rolling stone with a rotationally symmetric nonconvex compact initial surface 0 under the Gauss curvature ow. Let X : Sn[0,1) ! Rn+1 be the embeddings of the sphere in Rn+1 such that (t) = X(Sn, t) is the surface at time t and (0) = 0. As a consequence the parabolic equation describing the motion of the hypersurface becomes degenerate on the interface sep-arating the nonconvex part from the strictly convex side, since one of the curvature will be zero on the interface. By expressing the strictly convex part of the surface near the interface as a graph of a function z = f(r, t)and the non-convex part of the surface near the interface as a graph of a function z = φ(r), we show that if at time t = 0, g = 1n fn-1r vanishes linearly at the interface, the g(r; t) will become smooth up to the interface for long time before focusing.
증착 후 열처리 조건에 따른 ITO박막의 광학적, 전기적 특성 연구
이기암 단국대학교 1998 論文集 Vol.33 No.-
Electronbeamevaporated Indium Tin Oxide(ITO) films were analyzed by investigation of transmittance. sheet resistance and crystalline structure with varying annealing temperature and oxygen partial pressure in air and vacuum. With increasing annealing temperature, ITO films showed two changes ; the transmittance increased and the sheet resistance became lower. In vacuum annealing, transmittance increased with increasing oxygen partial pressure. The best conditions for nonabsorbing ITO thin films are annealing temperature of 280℃ and oxygen partial pressure of 5×10^-5 torr. The crystalline structure of ITO films were more excellent at the vacuum annealing than the annealing in air, with the increase of annealing temperature and the decrease of oxygen partial pressure.
이기암,박국상 단국대학교 1999 論文集 Vol.34 No.-
High quality 3C-SiC epilayer was grown on Si(lll) at 1250 ℃ using chemical vapor deposition(CVD) technique by pyrolyzing tetramethylsilane(TMS). The crystallinity and electrical properties of 3C-SiC epilayer were investigated by X-ray diffraction. Fourier-transform infrared spectroscopy. Raman spectrum. Hall measurement and current-voltage characteristics(Ⅰ-Ⅴ).
Effects of Diols on the foaming and emulsion properties in surfactant solutions
이기암,오성근 한국응용과학기술학회 2022 한국응용과학기술학회지 Vol.39 No.4
The effects of 1,3-Butanediol, 1,2-Pentanediol, and 1,2-Hexanediol in surfactant solutions on cmc, surface tension, foaming and emulsifying properties were determined. The addition of diols in aqueous surfactant solution decreased cmc and surface tension, and enhanced the foaming and emulsifying power. This trend is more significant by the longer hydrocarbon chain length of the diols. This property was confirmed because the diol’s alkyl chain and the hydrophobic interaction with the surfactant reduce the cohesive force of water and increase the interaction between the head groups of the surfactant at interface. In addition, MIC test was conducted to determine the preservative power of each diol, and as a result, the antibacterial activity was effective in the order of 1,2-HDO > 1,2-PDO > 1,3-BDO. The results of this study show that diol can be applied to cosmetics as an auxiliary surfactant and antibacterial agent. 본 연구에서는 계면활성제 용액에서 1,3-Butanediol, 1,2-Pentanediol, 1,2 Hexanediol 들이cmc, 표면장력, 기포력 및 유화력에 미치는 영향을 연구 하였다. 계면활성제 수용액에 diol의 첨가는 cmc와 표면장력 저하를 초래 하였으며 기포력 및 유화력은 향상 되었다. 이러한 경향은 diol의 사슬길이가 길수록 현저 하였다. 이러한 특성은 diol의 알킬사슬과 계면활성제 분자간에 소수성 상호작용이 물분자간의 응집력을 감소시키고, 계면에서 계면활성제 headgroup간 상호작용을 증진시키기 때문이다. 또한 각 diol의 방부력을 평가하기 위하여 MIC 측정을 수행 하였으며 방부력은 1,2-HDO > 1,2-PDO > 1,3-BDO 순서였다. 본 연구의 결과들은 diol들이 화장품에서 보조 계면활성제와 방부제로 이용될 수있음을 확인 시켜 주웠다.
A financial market of a stochastic delay equation
이기암,이기섭,박상현 대한수학회 2019 대한수학회보 Vol.56 No.5
We propose a stochastic delay financial model which describes influences driven by historical events. The underlying is modeled by stochastic delay differential equation (SDDE), and the delay effect is modeled by a stopping time in coefficient functions. While this model makes good economical sense, it is difficult to mathematically deal with this. Therefore, we circumvent this model with similar delay effects but mathematically more tractable, which is by the backward time integration. We derive the option pricing equation and provide the option price and the perfect hedging portfolio.
Rolling Stones with nonconvex sides I: regularity theory
이기암,Eunjai Rhee 대한수학회 2012 대한수학회지 Vol.49 No.2
In this paper, we consider the regularity theory and the exis-tence of smooth solution of a degenerate fully nonlinear equation describ-ing the evolution of the rolling stones with nonconvex sides:{M(h) = ht - F(t, z, zhzz) in f 0 < z ≤ 1}× [0,T]ht(z, t) = H(hz(z, t), h) on f z = 0 g:We establish the Schauder theory for C2,α-regularity of h.