버블 칼럼 광생물반응기의 내부 유동분석을 위한 전산유체역학 시뮬레이션 모델의 이용

유재인,이인복,황현섭,홍세운,서일환,권경석,김용희,Yoo, J.I.,Lee, I.B.,Hwang, H.S.,Hong, S.W.,Seo, I.H.,Bitog, J.P.,Kwon, K.S.,Kim, Y.H. 한국농공학회 2009 한국농공학회논문집 Vol.51 No.5

Photobioreactor (PBR) that houses and cultivates microalgae providing a suitable environment for its growth, such as light, nutrients, CO2, heat, etc. is now getting more popular in the last decade. Among the many types of PBRs, the bubble column type is very attractive because of its simple construction and easy operation. However, despite the availability of these PBRs, only a few of them can be practically used for mass production. Many limitations still holdback their use especially during their scale-up. To enlarge the culture volume and productivity while supplying optimum environmental conditions, various PBR structures and process control are needed to be investigated. In this study, computational fluid dynamics (CFD) was economically used to design a bubble-column type PBR taking the place of field experiments. CFD is a promising technique which can simulate the growth and production of microalgae in the PBR. To study bubble column PBR with CFD, the most important factor is the possibility of realizing bubble. In this study, multi-phase models which are generally used to realize bubbles were compared by theoretical approaches and comparing in a 2D simulation. As a result, the VOF (volume of fluid) model was found to be the most effective model to realize the bubbles shape as well as the flow inside PBR which may be induced by bubble injection. Considering the accuracy and economical efficiency, 0.005 second time step size was chosen for 2.5 mm mesh size. These results will be used as criteria for scale-up in the PBR simulation.

Photoreflectance 방법에 의한 ZnS0.22Se0.78 /GaAs 이종접합 구조의 광학적 특성 연구

유재인,배인호,박성배 한국물리학회 2005 새물리 Vol.50 No.1

Photoreflectance(PR) spectroscopy was used to investigate a ZnS$_{0.22}$Se$_{0.78}$/GaAs heterostructure that hae been grown by using molecular beam epitaxy. The PR spectra exhibited sharp signatures, and the transition energies could be accurately determined by using a third derivate function form fit. Also, we calculated the variation in the interface electric field with increasing laser intensity. The interface electric filed was foung to saturate the laser intensity was increased gradually. MBE로 성장된 ZnS$_{0.22}$Se$_{0.78}$/GaAs 이종접합 구조의 특성을 photoreflectance (PR) 방법으로 조사하였다. 전이 에너지에 관련되는 PR 신호는 잘 관측되었으며, third derivate function form (TDFF) 피팅 방법으로 값을 구하였다. 또한 레이저 세기에 따른 계면 전기장 값은 증가하다가 포화되었는데 이는 레이저 세기가 증가할 수록 시료 표면에서 내부로 확산되는 전자의 증가로 계면에서 전자과도 현상이 일어나기 때문이다.

Cucker-Smale 메카니즘에 의한 코스피 변동성 네트워크에 관한 연구

유재인 한국응용경제학회 2017 응용경제 Vol.19 No.1

Cucker and Smale(2007)의 모형을 바탕으로 한국 주식 시장의 주식 수익률 변동성 간 상호 연결 강도를 측정하였다. GMM 모형 추정 결과 변동성 상호 연결 강도는 개별 변동성의 미래 값을 예측하는데 유의한 역할을 하는 것으로 나타났다. 평균 변동성 대비 개별 변동성 위치를 일별 자료로 구축하고 변동성 뭉침 지수 (Volatility Flocking Index, VFI)를 산출하였다. VFI와 코스피 평균 수익률 및 내재변동성 지수 (VKOSPI)의 벡터자기상관모형 결과 VFI는 코스피 내재변동성(VKOSPI)의 외부충격에 유의한 반응을 보였다. 업종 별 분석에 의하면 한국의 VFI의 증가에 소재, 필수 소비재 및 금융 관련 주식들의 역할이 큰 반면, 미국 VFI 증가에는 에너지, 유틸리티, 및 헬스케어 관련 주식들의 역할이 큰 것으로 나타났다. In this study, I analyze multi-volatility flocking phenomenon from a volatility network. Referring to Cucker and Smale (2007)’s flocking mechanism, I generate the Volatility Flocking Index (VFI) with volatilities of 30 companies that are listed on KOSPI. I examine the impulse response function from the results of vector autoregression model with the VFI, the average return of KOSPI, and the implied volatility index (VKOSPI). The results show that the VFI helps measuring risks and predicting changes in the KOSPI and VKOSPI. In the sector analysis, stocks in materials, consumer staples and financials play significant roles in changing the VFI.

만성기관지염에 대한 經氣管 吸引物 검사

유재인 가톨릭대학산업의학센타 산업의학연구소 1984 韓國의 産業醫學 Vol.23 No.1

Using the simple technique of transtracheal aspiration(TTA)in patients with chronic bronchitis,bacteria were found in 11 transtracheal aspirates from 14 patients. From 3 aspirates no bacteria were isolated.In 11 aspirates the isolated bacterium grew in pure culture. This preliminary report indicates that the bacterial flora in this condition is more complicated than hitherto appreciated.

Al_(0.24)Ga_(0.76)As/GaAs HEMT 구조에서의 표면 광전압에 관한 연구

유재인,김종수,배인호,신영남,박성배 대구대학교 기초과학연구소 2000 基礎科學硏究 Vol.16 No.2

We report a surface photovoltage(SPV) study of Al_(0.24)Ga_(0.76)As/GaAs HEMT structure grown by molecular beam epitaxy. The energies of Eo transition for GaAs and Al_(0.24)Ga_(0.76)As were 1.41 and 1.71 eV, respectively. These values were in good agreement with photo reflectance(PR) measurement. As the frequency is increased from 25 to 55 Hz, the intensity of SPV signal is gradually reduced. Meanwhille, the intensity of SPV signal gradually increased as the temperature increased from 100 K to room temperature. From the former, the surface photovoltage of Al_(0.24)Ga_(0.76)As layer is 8.61 mV, which is about 1.4 times smaller than that of GaAs. This is due to influence of carrier mobility.

Welfare effects of life annuities for an altruistic consumer in Korea

유재인 재단법인 경기연구원 2017 GRI 연구논총 Vol.19 No.1

In this paper I develop a simple overlapping generations model of a household who annuitizes income in an actuarially fair market. In this setup, I particularly model the strong motivation of Korean consumers in leaving bequests for their children or descendants. I have showed the optimal policies of lifetime consumption, and saving over the life cycle. The numerical solutions are contingent on the assumption of a household’s bequest motive parameter. I calculate that the indirect utility with the optimal policies without a public pension system differs from the welfare with a pay-as-you-go social security. Given the plausible values of parameters that can explain aggregate economic environment, and consumers’ preference, I show that the welfare increases when a consumer purchase individual life annuity with receiving public pension than without receiving the public pension. Given the negative population growth rates and high survival probabilities in Korea, the results show that a pay-as-you-go social security system increases the welfare. The gain is sensitive to how strongly a household want to leave bequests to the next generation. The welfare differences based on the numerical solutions can explain the easily observed pattern that there are only a few number of consumers in Korean life annuity market.

GaAs/In0.1Ga0.9As/GaAs 구조에서의 Photoreflectance 특성 연구

유재인,배인호,박성배,박헌보 한국물리학회 2006 새물리 Vol.52 No.4

We have studied the photoreflectance (PR) of GaAs/In$_{0.1}$Ga$_{0.9}$As/GaAs heterostructures with different thicknesses of InGaAs layers grown by using metal-organic chemical-vapor deposition (MOCVD). The room-temperature PR spectra show two typical signals, around 1.42 and 1.30 eV, which can be attributed to the band gap energies of GaAs and InGaAs, respectively. In addition, we observe Franz-Keldysh oscillations above the InGaAs fundamental band gap. From these oscillations, we calculate the electric fields at the In$_{0.1}$Ga$_{0.9}$As/GaAs interface. Also, the temperature dependence of the PR peak is investigated. GaAs/In$_{0.1}$Ga$_{0.9}$As/GaAs 이종접합 구조에서 InGaAs 층의 두께에 따른 광 특성을 photoreflectance (PR) 방법으로 조사하였다. 그리고 상온 PR 스펙트럼에서 GaAs의 밴드갭에 관련된 신호가 약 1.42 eV에서 관측되었으며, 그리고 In$_{0.1}$Ga$_{0.9}$As에 관계된 신호는 두께 70, 150 및 300 nm에 대해서 각각 1.311, 1.296 및 1.287 eV에서 관측되었다. 상온 및 저온에서 Franz-Keldysh oscillations (FKOs)이 In$_{0.1}$Ga$_{0.9}$As와 GaAs 밴드갭 에너지 사이에서 관측되었으며, FKO의 주기를 통해 In$_{0.1}$Ga$_{0.9}$As/GaAs의 계면 전기장 값을 구하였다.

마그네슘합금 판재 구이판 표면처리

유재인 한국표면공학회 2011 한국표면공학회 학술발표회 초록집 Vol.2011 No.11

$ZnS_{0.24}Se_{0.76}$의 photoreflectance 특성 연구

유재인,김동렬,이제훈,Yu J. I.,Kim D. L.,Lee J. H. 한국레이저가공학회 2004 한국레이저가공학회지 Vol.7 No.3

In this research, we investigated the characteristic of $ZnS_{0.24}Se_{0.76}/GaAs$ heterostructure by using photoreflectance sprctroscopy(PR). The oscillations observed above the 1.43 eV range were attributed Franze-Keldysh effect. The interface electric filed of $GaAs/ZnS_{0.24}Se_{0.76}\;is\;2.153{\times}104\;V/cm$.

Mg Alloy의 Burning과 Plasma Electrolyte Oxidation 표면처리에 대한 연구

유재인,최순돈,장호경,Yu, Jae-In,Choi, Soon-Don,Jang, Ho-Kyeoung 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.5

Plasma electrolyte oxidation (PEO) 표면처리된 Mg 합금을 scanning electron microscopy (SEM) 방법으로 표면에 형성된 산화 막을 조사 분석하였다. 측정은 상온에서 수행하였다. Burning 및 PEO 방식의 표면처리 방법을 통해 제작 된 시료의 산화막을 SEM, EDS 및 I-V 측정을 통해 분석하였다. 그 결과 burning 방식의 표면처리가 PEO보다 내식성이 떨어지는 단점이 있지만, 전도성이 부여되는 결과를 나타낸다. The surface oxidation of magnesium was performed by burning and PEO treatment method. The scanning electron microscopy (SEM), EDS, and I-V characteristics have been applied to the study of the oxidation status. The sample formed by buring method shows weaker corrosion-resistant property than that by PEO method, but this shows more conducting property.