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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.
$ZnS_{0.24}Se_{0.76}$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 $GaAs/ZnS_{0.24}Se_{0.76}\;is\;2.153{\times}104\;V/cm$.
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.
The Impact of Expense Shocks on the Financial Distress of Korean Households
유재인 통계청 2014 통계연구 Vol.19 No.1
The main objective of this study is to examine the major determinants of householdfinancial distress, particularly expense shocks that increase the probability of failure in loan repayment. Using the survey of household finances published by Statistics Korea, the study investigates expense shocks that result in a large proportion of household income beingallocated to debt repayment, thus limiting the funds available for consuming goods and/orsaving. I use a bootstrapped random effect probit model and two-stage least squares model. In addition, in finding a variable’s optimal spit value and goodness of fit, I use an earlywarning signal methodology. The test results present the following three categories ofexpense shocks are sensitive to financial vulnerability: i) secured loans for debt repayment,medical expenses, and daily expenses; ii) unsecured credits for debt repayment, medicalexpenses and rents; iii) credit card loans for debt repayment, and rents.
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.
MBE법으로 성장한 ZnSe/GaAs 이종접합구조의 Photoreflectance 연구
유재인,배인호,손정식,김대년,김기홍,이승준 한국물리학회 2004 새물리 Vol.49 No.3
Using photoreflectance (PR), we investigated characteristics of ZnSe epilayers grown on SI-GaAs by using molecular beam epitaxy MBE). From the PR spectrum at room temperature, we observed the band gap energies of GaAs and ZnSe. From the Franze-Keldysh Oscillations(FKOs), we evaluated the interface electric field. In addition, the transition energy of ZnSe were observed to 2.6225 and 2.6684 eV for $E_{HH}$(heavy hole) and $E_{LH}$(light hole),respectively. 반절연성 GaAs 위에 분자선 에피텍시 (MBE)법으로 성장된 ZnSe 에피층의 특성을 광변조 분광(PR)법을 이용하여 연구 하였다. 상온에서 측정된 PR 스펙트럼에서 GaAs와 ZnSe의 밴드갭 에너지와 관측된 FKOs로부터 계면 전기장을 구하였다. 또한 상온에서 측정한 PR 스펙트럼에서 관측된 ZnSe의 {E}$_{HH}$와 {E}$_{LH}$의 전이 에너지는 각각 2.623와 2.669 eV 였다. 주파수 의존성에서 주파수가 낮을수록 시료내부에 들어가는 광량이 현저히 낮아지기 때문에 GaAs 관련 피크세기의 감소율이ZnSe의 감소율 보다 약 20 \% 더 크게 관측되었다.
Al0.21Ga0.79As/GaAs 와 Si3N4/Al0.21Ga0.79As/GaAs 이종접합구조의 Photoreflectance 특성 연구
유재인,배인호 한국물리학회 2004 새물리 Vol.49 No.1
Photoreflectance (PR) was measured to investigate the characteristices of Si$_3$N$_4$/Al$_{0.21}$Ga$_{0.79}$As\\/GaAs and Al$_{0.21}$Ga$_{0.79}$As/GaAs heterostructures. In the PR spectrum of the sample with a 170-nm-thick caping layer of Si$_3$N$_4$ the ``C'' peak was confirmed as being due to a residual carbon impurity defect. After the sample with the Si$_3$N$_4$ caping layer had beeb annealed, the band gap energy was shifted toward low energy. This result showed that the Si$_3$N$_4$ cappign layer controlled the evaporation of As. Si$_3$N$_4$/Al$_{0.21}$Ga$_{0.79}$As/GaAs와 Al$_{0.21}$Ga$_{0.79}$As/GaAs 이종접합구조 특성을 조사하기 위하여 Photoreflectance(PR) 방법으로 측정하였다. Si$_3$N$_4$ cap 층이 170 nm인 PR 스펙트럼에서, C 피크 신호는 시료 성장시 존재하는 불순물 carbon에 의한 것이다. 그리고 시료를 열처리를 했을 경우, Si$_3$N$_4$ cap 층이 존재할 때는 밴드갭 에너지의 이동이 적었다. 이러한 결과는 Si$_3$N$_4$ cap 층이 As의 evaporation를 억제하는 역할을 한다고 할 수 있다.