• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.13-21
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• 2005

이 논문은 발열 반응에서 상이 변화하는 물질의 연속 방정식에서 유도되는 안정된 파면의 구조를 고려했다. 특별히 액체와 기체, 고체와 액체 사이의 동적인 파면 구조를 수치적으로 연구하였다. 1차원 충격파 구조 분석에 근거한 본 연구에 의하면 연소 시 나노 사이즈의 파면이 존재한다고 추정한다. 설명을 위해, 증발과 응축에는 n-heptane이 사용되었고, 용해와 응고에는 HMX를 사용하였다. 이 개념의 확장은 로켓 추진제와 같이 액체, 고체 연료의 넓은 범위 모두를 포함한다.

• 전기학회논문지
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• 제60권11호
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• pp.2097-2102
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• 2011

Discharge analysis technique for dielectric liquid was presented by using the Finite Element Analysis (FEA) under a lightning impulse incorporating two-phase flow phenomena which described gas and liquid phases in discharge space. Until now, the response of step voltage has been extensively explored, but that of lightning impulse voltage was rarely viewed in the literature. We, therefore, developed an analyzing technique for dielectric liquid in a tip-sphere electrode stressed by a high electric field. To capture the bubble phase, the Heaviside function was introduced mathematically and the material functions for the ionization, dissociation, recombination, and attachment were defined in liquid and bubble, respectively. By using this numerical setup, the molecular dissociation and ionization mechanisms were tested under low and high electric fields resulted from the lightning impulse voltage of 1.2/50 ${\mu}s$. To verify our numerical results, the velocity of electric field wave was measured and compared to the previous experimental results which can be viewed in many papers. Those results had good agreement with each other.

• 한국식품과학회지
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• 제47권5호
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• pp.567-573
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• 2015

일본 증류식 소주인 본격소주 9종을 수거하여 시료의 휘발성 향기성분을 헤드스페이스-고체상미량추출법에 의해 추출한 후, 가스크로마토그래피-질량분석기를 이용하여 분석하였다. 총 76개의 성분이 동정되었고, 화학적 특성에 따라 분류하면 에스터 48종, 알코올 13종, 기타 15종의 성분이 동정되었다. 에스터와 알코올이 주요한 성분으로 분석되었으며 아세트산아이소아밀, 폼산아이소아밀, 헥산산에틸, 옥탄산에틸, 데카노산에틸, 아이소아밀알코올, 2-페닐에탄올이 주요 성분으로 나타났다. 주성분 분석 결과 제조원료에 따라 주성분1 선상에서 대맥국 원료 본격소주의 향기패턴이 큰 차이를 보이는 것으로 나타났으며 쌀과 보리 원료에 따른 향기패턴의 차이는 크게 나타나지 않았다. 본 연구의 일본 본격소주 휘발성 향기성분 분석 결과와 국내산 증류식 소주의 주요 향기성분 분석 결과를 비교분석하면 향후 국내산 증류식 소주의 품질관리에 주요한 향기성분 파악이 가능하고 이를 통해 다양한 원재료와 제조방법에 따른 증류식 소주 제품 개발이 가능하리라 여겨진다.

• 대한기계학회논문집B
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• 제32권7호
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• pp.529-535
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• 2008

The characteristics of combustion process in an internal combustion engine are affected by the mixing process between injected fuel and ambient gas. Therefore, it is necessary to understand the mixture formation process of diesel spray. In this study, the spray structure was visualized by the exciplex fluorescence method, which can provide the simultaneous 2-D images of vapor and liquid phase in inner spray. For accurate investigation, the liquid-phase images were recorded with a 35mm still camera and CCD camera. Consequentially, it could be confirmed that the high-concentration vapor phase is formed in the region of spray tip and the edge of the liquid phase where droplets exist in the evaporating diesel spray, and the formed vapor is spread by diffusion. Also, the distribution of vapor is determined by the motion of droplets that exist in the edge of the liquid phase and the spray-tip region.

• 한국추진공학회지
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• 제21권5호
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• pp.71-79
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• 2017

액체-기체의 2상 유동에 대한 수치해석 기법을 연구하였다. 비압축성 방정식에는 가상 압축성 기법을 적용하였으며 LS와 VOF를 합친 CLSVOF 기법을 적용하여 액체-기체 경계면을 추적하였다. CLSVOF의 격자 의존도를 파악하기 위해 h=1/64, 1/128, 1/128, 그리고 1/160의 격자로 Zalesak's disk 문제와 액체의 3차원 변형 문제의 수치해석을 실시했으며 격자가 최대 보존 오차에 미치는 영향을 조사하였다. 비압축성 2상 유동 방정식을 적용하여 Rayleigh-Taylor 불안정성에 대한 수치해석을 실시하였고 밀도 차에 의한 액체 표면 불안정성이 나타난다는 것을 알 수 있었다.

• 한국전산유체공학회지
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• 제14권4호
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• pp.13-22
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• 2009

A two-phase (gas and liquid) flow analysis solver, named CUPID, has been developed for a realistic simulation of transient two-phase flows in light water nuclear reactor components. In the CUPID solver, a two-fluid three-field model is adopted and the governing equations are solved on unstructured grids for flow analyses in complicated geometries. For the numerical solution scheme, the semi-implicit method of the RELAP5 code, which has been proved to be very stable and accurate for most practical applications of nuclear thermal hydraulics, was used with some modifications for an application to unstructured non-staggered grids. This paper is concerned with the effects of interpolation schemes on the simulation of two-phase flows. In order to stabilize a numerical solution and assure a high numerical accuracy, the second-order upwind scheme is implemented into the CUPID code in the present paper. Some numerical tests have been performed with the implemented scheme and the comparison results between the second-order and first-order upwind schemes are introduced in the present paper. The comparison results among the two interpolation schemes and either the exact solutions or the mesh convergence studies showed the reduced numerical diffusion with the second-order scheme.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.676-679
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• 2009

The bottom-simulating reflector (BSR) is the most commonly observed seismic indicator of gas hydrate in the Ulleung Basin, East Sea. We processed ten representative seismic reflection profiles, selected from a large data set, for amplitude variation with offset (AVO) analysis of the BSR to estimate gas-hydrate concentrations. First, BSRs were divided into five groups based on their seismic amplitudes and associated sediment types: (1) very high-amplitude BSRs in turbidite/hemipelagic sediments, (2) high-amplitude BSRs in debris-flow deposits, (3) moderate-amplitude BSRs in turbidite/hemipelagic sediments, (4) very low-amplitude BSRs in debris-flow deposits, and (5) very low-amplitude BSRs in seismic chimneys. The AVO responses of the group 1 and 3 BSRs are characterized by a rapid decrease and a relatively slow decrease in magnitude with offset, respectively. The AVO response of the group 2 BSR is characterized by a relatively slow increase in magnitude with offset. The AVO responses of the groups 4 and 5 BSRs are characterized by a flat AVO with very small zero-offset amplitude. Theoretical AVO curves, based on the three-phase Biot theory, suggest that the group 1 and 3 BSRs may be related to high (> 40%) concentrations of gas hydrate whereas the group 2 BSRs may indicate low (< 20%) concentrations of gas hydrate. The AVO responses of the group 4 and 5 BSRs cannot be compared with the theoretical models because of their very small zero-offset amplitudes. The comparison of the AVO response of the BSR at the UBGH-04 well with theoretical models suggests about 10% gas-hydrate concentration above the gas-hydrate stability zone.

• Journal of Advanced Marine Engineering and Technology
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• 제35권2호
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• pp.216-223
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• 2011

열압축기는 고압 증기를 이용하여 저압 증기를 중간압으로 이송하는 일종의 이젝터이다. 이젝터에 대한 기존의 수치해석 연구는 대부분 작동유체를 이상기체로 취급하고 있으나 상변화가 발생하는 경우 이상기체 거동에서 크게 벗어날 수 있다. 따라서 본 연구에서는 이상기체 상태방정식 대신 Redlich-Kwong 방정식을 적용하여 열압축기 내부 유동을 수치 해석하였고, realizable k-${\epsilon}$ 모델과 SST k-${\omega}$ 모델을 비교한 결과 SST k-${\omega}$ 모델이 shock diamond 패턴과 박리 및 난류경계층을 잘 예측하는 것을 확인할 수 있었다. 또한 실제기체 상태방정식을 사용한 경우가 이상기체 상태방정식을 사용한 경우에 비해 상대적으로 디퓨저 입구 부분과 디퓨저 목부분에서 에너지 손실이 많은 것을 알 수 있었으며, 디퓨저 출구부분에서 shock train에 의한 압력상승은 상대적으로 적으나 pseudo shock에 의한 압력상승은동일한 것으로 확인되었다.

• 한국축산식품학회지
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• 제34권5호
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• pp.700-708
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• 2014

The volatile composition of veal has yet to be reported and is one of the important factors determining meat character and quality. To identify the most important aroma compounds in veal from Holstein bull calves fed one of three diets, samples were subjected to solid-phase microextraction (SPME) combined with gas chromatography-quadrupole mass spectrometry (GC-MS). Most of the important odorants were aldehydes and alcohols. For group A (veal calves fed entirely on milk for 90 d before slaughter), the most abundant compound class was the aldehydes (52.231%), while that was alcohols (26.260%) in group C (veal calves fed starter diet for at least 60 d before slaughter). In both classes the absolute percentages of the volatile compounds in veal were different indicating that the veal diet significantly (p<0.05) affected headspace volatile composition in veal as determined by principal component analysis (PCA). Twenty three volatile compounds showed significance by using a partial least-squared discriminate analysis (PLS-DA) (VIP>1). The establishment of the global volatile signature of veal may be a useful tool to define the beef diet that improves the organoleptic characteristics of the meat and consequently impacts both its taste and economic value.

• 한국대기환경학회지
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• 제10권1호
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• pp.24-31
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• 1994

Hourly variation of gaseous nitrous acid( HNO$_2$) concentration in Seoul air was monitored from Jan. 11 to SeP. 12, Nitrous acid concentration was determined by DS/IC over nine months of observation, HNO$_2$ range from 0.04 ppb to 5.5 ppb. Gor-tex tube as gaseous HNO$_2$generator in this study is thought to be more convenient and reproducible device than previous generator. As a result of NaOH instead of Na$_2$ CO$_3$/NaHCO$_3$ solution as the IC eluent, we could obtain more stable baseline. The concentration of the NaOH eluent was 15 mM . The limit of detection(3$\sigma$) of the liquid- Phase and gas phase nitrous acid of this method are 1.1ng/$m\ell$ , 0.04 n $\ell$ / $\ell$, respectively. The precisions evaluated by 10 replicate analysis of standard solution and standard gas generated are $\pm$1.59, $\pm$2. 89% RSD, respectively. Due to the lack of standard material for air, direct assessment of the accuracy was not possible. This study was applied to the analysis of Seoul ambient air and their results are reported herein.