• 대한조선학회논문집
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• 제28권1호
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• pp.19-26
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• 1991

난류유동 지배 방정식인 타원형 레이놀즈 방정식을 수치계산에 의해 계산하였다. 계산 대상으로는 실험결과가 많이 알려진 축 대칭 물체를 택하였다. 수치적으로 얻어지는 물체접합 좌표계를 사용하였고, 난류모형으로는 $\kappa-\varepsilon$모형으로써 경계면 근처의 복잡한 유동특성을 추정할 수 있도록 영역을 2개로 나누어 계산하는 2층모형(two-layer model)을 사용하였다. 입구면의 경계조건을 사용하여 물체의 중앙부 이후부터 계산을 수행하였다. 입구면에서의 속도와 난류량 등은 경계층 방정식을 풀어 얻어진 결과와 평판의 경계층 자료로부터 얻어진 결과를 사용하였으며, 이로부터 입구면 조건이 점성유동 해석 결과에 미치는 영향을 조사하였다.

• International Journal of Advanced Culture Technology
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• 제3권2호
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• pp.138-143
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• 2015

This paper was aimed to study the drying kinetics of coffee and to investigate the thin-layer drying kinetics of coffee by using a convective air dryer. The coffee was dried for the temperatures of 40, 50 and $60^{\circ}C$ with relative humidity in the range of 14-25% the airflow rate fixed at 1 m/s. According to the experiment result, the drying rate curve showed that drying process took place only in the falling rate period. Seven thin layer drying models (Newton, Page, Henderson and Pabis, Logarithmic, Wang and Singh, Two terms, Modified Henderson and Pabis) were fitted to the experimental moisture content data. The Two-trem model was found to be a better model for describing the characteristics of coffee for the temperatures of 40, 50 and $60^{\circ}C$. The effective moisture diffusivity of coffee increased when the drying temperature increased. The value was in the range of $4.5028{\times}10^{-11}$ to $6.4803{\times}10^{-11}m^2/s$.

• 한국전산유체공학회지
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• 제10권4호통권31호
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• pp.12-17
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• 2005

A computational study of evaluation of current turbulence models is performed for a better prediction of thermal stratification in an upper plenum of a liquid metal reactor. The turbulence models tested in the present study are the two-layer model, the shear stress transport (SST) model, the v2-f model and the elliptic blending mode(EBM). The performances of the turbulence models are evaluated by applying them to the thermal stratification experiment conducted at JNC (Japan Nuclear Corporation). The algebraic flux model is used for treating the turbulent heat flux for the two-layer model and the SST model, and there exist little differences between the two turbulence models in predicting the temporal variation of temperature. The v2-f model and the elliptic blending model better predict the steep gradient of temperature at the interface of thermal stratification, and the v2-f model and elliptic blending model predict properly the oscillation of the ensemble-averaged temperature. In general the overall performance of the elliptic blending model is better than the v2-f model in the prediction of the amplitude and frequency of the temperature oscillation.

• Bulletin of the Korean Chemical Society
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• 제19권7호
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• pp.733-737
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• 1998

Using an atom superposition and electron delocalization molecular orbital (ASED-MO) method, we have compared adsorption properties of adsorbates on the Pt(Ill) surface with the Pt(lll)/γ-Al203 surface in the ethylene hydrogenation reaction. In two-layer thick model systems, the calculated activation energy of the hydrogenation by the surface platinum hydride is equal to the energy by the hydride over supported platinum/γ-alumina. The transition structure on platinum is very close to the structure on the supported platinum/γ-alumina surface. Hydrogenation by the surface hydride on platinum can take place easily because the activation energy is about 0.5 eV less than hydrogenation by ethylidene. On supported platinum/,y-alumina the activation energy of the hydride mechanism is about 0.61 eV less than that of ethylidene mechanism. In one-layer thick model systems, the activation energy of hydrogenation by ethylidene is about 0.13 eV less than the activation energy of hydride reaction. The calculated activation energy by the hydride over the supported platinum y-alumina is 0. 24 eV higher than the platinum surface. We have found from this result that the catalytic properties of one-layer thick model systems have been influenced by the support but the two-layer thick model systems have not been influenced by the support.

• 천문학회보
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• 제35권2호
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• pp.73.2-73.2
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• 2010

In order to understand internal dynamics of starless cores, molecular line emissions are usually observed. From profiles of the molecular lines, internal motions of starless cores have been deduced using a simple radiative transfer model such as the two-layer model (Myers et al.1996). This brings complexities arising from the chemical evolution. The motivation of this study is to follow the chemical evolution of a starless core that goes through gravitational contraction. For this purpose, we have performed hydrodynamical simulations with a marginally unstable Bonnor-Ebert sphere as an initial condition. We follow the chemical evolution of this core with changing conditions such as the chemical reaction rate at the dust surface and the strength of radiation field that penetrate into the core. At the core center, the molecules suffer from a higher degree of molecular depletion on the dust covered by ice rather than on the bare silicate dust. The stronger radiation field dissociates more molecules at the core envelope. From analysis on the line profile using the two-layer model, we found that the speed of inward motion deduced from the HCN F = 2-1 line adequately traces the true infall speed, when the dust is covered by ice and the core is exposed to the diffuse interstellar radiation field. Under different conditions, the two-layer model significantly underestimate the infall speed.

• Steel and Composite Structures
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• 제16권3호
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• pp.325-337
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• 2014

The strength and buckling problem of a five layer sandwich beam under axial compression or bending is presented. Two faces of the beam are thin aluminium sheets and the core is made of aluminium foam. Between the faces and the core there are two thin binding glue layers. In the paper a mathematical model of the field of displacements, which includes a share effect and a bending moment, is presented. The system of partial differential equations of equilibrium for the five layer sandwich beam is derived on the basis of the principle of stationary total potential energy. The equations are analytically solved and the critical load is obtained. For comparison reasons a finite element model of the beam is formulated. For the case of bended beam the static analysis has been performed to obtain the stress distribution across the height of the beam. For the axially compressed beam the buckling analysis was carried out to determine the buckling load and buckling shape. Moreover, experimental investigations are carried out for two beams. The comparison of the results obtained in the analytical and numerical (FEM) analysis is shown in graphs and figures. The main aim of the paper is to present an analytical model of the five layer beam and to compare the results of the theoretical, numerical and experimental analyses.

• 인터넷정보학회논문지
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• 제19권4호
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• pp.35-44
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• 2018

Monitoring through Synthesis Aperture Radar (SAR) is responsible for marine safety from floating icebergs. However, there are limits to distinguishing between icebergs and ships in SAR images. Convolutional Neural Network (CNN) is used to distinguish the iceberg from the ship. The goal of this paper is to increase the accuracy of identifying icebergs from SAR images. The metrics for performance evaluation uses the log loss. The two-layer CNN model proposed in research of C.Bentes et al.[1] is used as a benchmark model and compared with the four-layer CNN model using data augmentation. Finally, the performance of the final CNN model using the VGG-16 pre-trained model is compared with the previous model. This paper shows how to improve the benchmark model and propose the final CNN model.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 1997년도 International Symposium on Fire Science and Technology
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• pp.625-632
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• 1997

A two-dimensional zone-like model is developed to predict the interaction between hot gas layer and water droplets after sprinkler activation. The model combines the motion equations for each droplet with heat and mass transfer between the gas and water. The results indicate that negative buoyancy in the hot layer can only be obtained if the initial temperature profile is uniform. If an experimental profile Is used instead, positive buoyancy results. This conclusion has been confirmed with experimental data.

• 한국음향학회지
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• 제34권6호
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• pp.470-478
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• 2015

음선 모델링에서 다층 해저 바닥을 고려하는 경험적 방법 중 하나는 단일층 가정으로써, 다층 구조에 대한 평면파 반사계수를 사용하는 것이다. 본 연구자는 이층 해저 바닥에 대해 단일 층 가정의 유효성을 조사하고, 음속비, 송수신 거리 당 층 두께, 1차 반사파의 스침각의 함수로 표현되는 간단한 부등식 조건을 얻었다. 부등식 조건으로부터, 단일 층 가정이 실제 해양 환경의 중주파수 음선 모델링에 적용될 수 있음을 보였다. 마지막으로 한국 동해와 유사한 해양환경에 대해 수치실험을 수행하였다. 다층 해저 바닥에 대한 평면파 반사계수를 적용한 기하학적 빔 모델을 이용하여 비상관 전달손실을 계산하고, 서울대학교에서 개발한 포물선 방정식 패키지인 SNUPE 2.0의 결과와 비교하였다.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제11권6호
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• pp.185-192
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• 2022

다중모드 의료영상 융합(MMIF)은 각기 다른 특징들을 나타내는 여러 종류의 모드의 이미지를 풍부한 정보가 포함된 하나의 결과 이미지로 통합하는 것이다. 이러한 의료영상 융합은 의사가 환자의 병변을 정확하게 관찰하고 치료하는 것을 도와줄 수 있다. 이러한 목적에 영향을 받아 본 논문에서는 복층 분해기 및 미세구조 보존 모델에 기반한 새로운 방법을 제안한다. 첫째, 복층 분해기를 사용하여 소스 이미지를 미세정보 보존의 특성을 갖는 에너지 층과 구조적 층으로 분해하였다. 둘째, 구조 텐서 연산자와 max-abs를 결합하여 구조적 층을 융합한다. 에너지 층의 융합을 위해 미세구조 보존 모델을 제안하였으며 이미지 융합성능을 크게 향상시킬 수 있었다. 마지막으로, 융합규칙을 통해 형성된 두 개의 융합된 하위 이미지를 합산하여 구축하였다. 실험을 통하여 제안된 방법이 현재까지 최첨단 융합 방법들과 비교하여 우수한 성능을 나타내는 것을 검증하였다.