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.

n-형 3C-SiC의 특성

이기암 단국대학교 1999 論文集 Vol.34 No.-

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 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.

n-형 3C-SiC의 특성

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).

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.

Neutral Electrolyzed Water for Prevention of Dental Caries

이기암 大韓小兒齒科學會 2016 大韓小兒齒科學會誌 Vol.43 No.3

Gargle solution has typically been used for the prevention of oral infectious disease such as dental caries and periodontitis. However, the use of most gargle solutions is controversial in application for children because some gargle solutions have harmful side effects. Electrolyzed water is generated by passed an electric current and has antimicrobial activity. The purpose of this study was to investigate and compare the efficacy of electrolyzed water in various conditions for eliminating cariogenic bacteria. Electrolyzed water was generated by a platinum electrode in the presence of sodium chloride at various concentrations. Streptococcus mutans and Streptococcus sobrinus were cultivated into a brain heart infusion broth. After harvesting planktonic bacteria, the pellets were treated with the electrolyzed water and commercial gargle solutions and plated on a mitis-salivarius agar plate. Also, the anti-biofilm activity of the electrolyzed water and commercial gargle solutions was investigated after biofilm formation of S. mutans and S. sobrinus. The bacteria in the biofilm were plated onto a mitis-salivarius agar plate. The plates were incubated, and the colony forming unit was measured. The electrolyzed water containing sodium chloride showed significant antibacterial activity against S. mutans and S. sobrinus as well as some gargle solutions. Furthermore, the electrolyzed water had more disruptive effect on the biofilm of S. mutans and S. sobrinus and killed more bacteria in the biofilm than commercial gargle solutions. The results demonstrate that electrolyzed water may be a useful gargle solution for prevention of dental caries. 치아우식은 Streptococcus mutans와 S. sobrinus가 주요 원인균이며, 이를 예방하기 위해서 구강 청결제를 사용한다. 그러나 구강청결제의 부작용 및 해로움으로 인하여 소아에게 권장하기에 주위를 요한다. 전기 분해수는 물을 전극을 통해서전류를 흘려주어 생성되는 용액으로 항균력을 갖는다. 본 연구에서는 전기 분해수를 구강 청결제 대용으로 사용하기 위해서치아 우식원성 세균 및 바이오 필름에 대한 항균력을 조사하였다. 염화나트륨이 포함된 증류수를 백금전극을 이용하여 전기 분해수를 생성하였다. 전기분해 수소수의 물리화학적 성분을 분석하고 S. mutans 및 S. sobrinus 배양액을 원심분리하여 세균을 얻고 전기 분해수, 알코올 및 불소가 포함된 구강 청결제를 처리하고 살아있는 세균 수를 배양을 통해서 조사하였다. 또한 치아우식균의 바이오 필름을 형성시킨 후, 전기 분해수 및구강 청결제를 처리하여 바이오 필름 제거능을 크리스탈 바이올렛 염색을 이용하여 분석하고, 바이오 필름 내 살아있는 세균수의 양은 배양을 통하여 분석하였다. 전기분해수는 높은 농도의 자유염소 (free chlorine)을 포함하고 중성 페하를 보였다. 전기 분해수는 유의하게 S. mutans 및 S. sobrinus에 대해서 항균력을 보였으며, 이 세균들의 바이오 필름 제거능 및 바이오 필름 내 세균에 대해서도 항균력을보였다. 전기 분해수는 부유세균에 대해서 알코올이 포함된 구강청결제보다 약한 항균력을 보였지만, 바이오 필름 세균에 대해서는 더 강한 항균력을 나타냈다. 이러한 결과를 바탕으로 중성 전기 분해수는 치아우식 예방을 위한 기존 구강 청결제의 대체 용액으로 사용이 가능할 것으로 사료된다.

Surface tension and foam properties of several surfactant solutions with diol

이기암,오성근,최정빈 한국공업화학회 2021 한국공업화학회 연구논문 초록집 Vol.2021 No.0

질소화합물에 관한 N14NQR(핵사중극공명)연구

이기암 단국대학교 1986 論文集 Vol.20 No.-

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.