• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.99.1-99.1
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• 2011

Reactant mixing has a critical role in ensuring reformate quality and an important design objective is to achieve sufficiently complete mixture of reactants. For that purpose it is required to understand the coupled transport-kinetics phenomena in the mixing region. Three-dimensional computational fluid dynamics model was developed and validated in previous works. The mixing characteristics in various alternatives of a prototype mixing chamber were compared, and then a reduced reaction kinetics was applied to two extreme designs for investigating the impact of gas-phase reactions. Both designs did not reach threshold ethylene mole fraction of 0.001, but surprisingly more ethylene was generated in the design having better mixing characteristics. The presentation will deliver the development process of coupled transport and kinetics model briefly and the detailed information about the mixing characteristics and gas-phase reactions in two mixer designs.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.24-33
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• 1999

This paper investigate the effects of the variations of engine operation condition in the flame kernel formation and developmnet . A model for calculating the initial kernel development in spark ignition engines is formualted. It considered input of electrical energy, combustion energy release and heat transfer to the spark plyg, cylinder head, and unburned mixture. The model also takes into accounts strain rate of initial kernel and residual gas fraction. The breakdown process and the subsequent electrical power input initially control the kernel growth while intermediate growth is mainly dominated by diffusion or conduction. Then, the flame propagates by the chemical energy and turbulent flame expansion. Flame kernel development also influenced by engine operating conditions, for example, EGR rate, air-fuel ration and intake manifold pressure.

• 한국안전학회지
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• 제20권2호
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• pp.162-168
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• 2005

노말프로판올과 노말데칸의 가연성혼합물의 하부인화점을 Tag개방식 장치를 이용하여 측정하였다. 실험결과 인화점과 조성의 관계에서 혼합물 보다 낮은 인화점을 보여주었다. 노말 프로판올의 몰분율 0.71에서 $27^{\circ}C$였으며, 노말프로판올의 인화점은 $28^{\circ}C$였다. 실험 결과는 이상용액을 근거로 한 예측 값과 활동도계수 예측식인 van Laar식을 사용하여 계산된 값을 각각 비교하였다. 이상용액 개념을 이용한 예측 값은 실험 값과 차이를 보였으나, van Laar 식에 의한 예측 값은 실험 값과 일치하였으며, van Laar식에 의한 예측 값과 실험 값은 평균 $0.83^{\circ}C$차이를 보였다. 본 연구에서 제시된 방법론은 가연성물질에 대해 안전한 저장 및 취급하는 조건의 결정과 같은 화학공정 설계의 본질적 안전 설계에 적용할 수 있다.

• 한국물환경학회지
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• 제30권3호
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• pp.329-339
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• 2014

This study aims to estimate chlorophyll-a concentration in rivers using multi-spectral RapidEye imagery and Spectral Mixture Analysis (SMA) and assess the applicability of SMA for multi-temporal imagery analysis. Comparison between images (acquired on Oct. and Nov., 2013) predicted and ground reference chlorophyll-a concentration showed significant performance statistically with determination coefficients of 0.49 and 0.51, respectively. Two band (Red-RE) model for the October and November 2013 RapidEye images showed low performance with coefficient of determinations ($R^2$) of 0.26 and 0.16, respectively. Also Three band (Red-RE-NIR) model showed different performance with $R^2$ of 0.016 and 0.304, respectively. SMA derived Chlorophyll-a concentrations showed relatively higher accuracy than band ratio models based values. SMA was the most appropriate method to calculate Chlorophyll-a concentration using images which were acquired on period of low Chlorophyll-a concentrations. The results of SMA for multi-temporal imagery showed low performance because of the spatio-temporal variation of each end members. This approach provides the potential of providing a cost effective method of monitoring river water quality and management using multi-spectral imagery. In addition, the calculated Chlorophyll-a concentrations using multi-spectral RapidEye imagery can be applied to water quality modeling, enhancing the predicting accuracy.

• International Journal of Fluid Machinery and Systems
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• 제10권3호
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• pp.254-263
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• 2017

The cavitation erosion remains an industrial issue for many applications. This paper deals with the cavitation intensity, which can be described as the fluid mechanical loading leading to cavitation damage. The estimation of this quantity is a challenging problem both in terms of modeling the cavitating flow and predicting the erosion due to cavitation. For this purpose, a numerical methodology was proposed to estimate cavitation intensity from 3D unsteady cavitating flow simulations. CFD calculations were carried out using Code_Saturne, which enables U-RANS equations resolution for a homogeneous fluid mixture using the Merkle's model, coupled to a $k-{\varepsilon}$ turbulence model with the Reboud's correction. A post-process cavitation intensity prediction model was developed based on pressure and void fraction derivatives. This model is applied on a flow around a hydrofoil using different physical (inlet velocities) and numerical (meshes and time steps) parameters. The article presents the cavitation intensity model as well as the comparison of this model with experimental results. The numerical predictions of cavitation damage are in good agreement with experimental results obtained by pitting test.

• 대한기계학회논문집A
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• 제26권10호
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• pp.1971-1981
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• 2002

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocities and temperature fields during rheology forming process, the each governing equations correspondent to the liquid and solid region are adapted. Therefore, each numerical model considering the solid and liquid coexisting region within the semi-solid material have been developed to predict the defects of rheology forming parts. The Arbitrary Boundary Maker And Cell(ABMAC) method is employed to solve the two-Phase flow model of the Navier-Stokes equation. Theoretical model basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on using the liquid and solid viscosity. The Liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

• 한국화재소방학회논문지
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• 제25권5호
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• pp.93-99
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• 2011

본 연구에서는 환기부족 구획화재에서의 일산화탄소 발생에 대한 FDS의 예측성능을 평가하기 위해 수치해석 연구를 수행하였다. ISO-9705 표준 화재실의 2/5 크기의 모형 내부에 위치한 메탄과 헵탄 화염의 거동을 FDS Ver. 5.5를 이용하여 해석하였다. 해석 결과를 기존의 실험 결과와 비교함으로써 고온 상층부에서 연소가스 농도의 예측에 대한 FDS의 성능을 평가하고 CO 생성율이 국부 위치에서의 CO 농도 예측에 미치는 영향을 분석하였다. 해석 결과로부터 이단반응 혼합분율 모델이 적용된 FDS Ver. 5.5가 CO 농도의 예측에 있어 이전 버전의 FDS에 비해 효과적임을 알 수 있었다. 또한 환기부족 화재조건에서 CO 생성율을 조절함으로써 실험값에 보다 근접한 CO 농도를 얻을 수 있었다.

• Advances in nano research
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• 제16권5호
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• pp.509-519
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• 2024

In this study, the static analysis of carbon nanotube-reinforced composites (CNTRC) beams resting on a Winkler-Pasternak elastic foundation is presented. The developed theories account for higher-order variation of transverse shear strain through the depth of the beam and satisfy the stress-free boundary conditions on the top and bottom surfaces of the beam. To study the effect of carbon nanotubes distribution in functionally graded (FG-CNT), we introduce in the equation of CNT volume fraction a new exponent equation. The SWCNTs are assumed to be aligned and distributed in the polymeric matrix with different patterns of reinforcement. The rule of mixture is used to describe the material properties of the CNTRC beams. The governing equations were derived by employing Hamilton's principle. The models presented in this work are numerically provided to verify the accuracy of the present theory. The analytical solutions are presented, and the obtained results are compared with the existing solutions to verify the validity of the developed theories. Many parameters are investigated, such as the Pasternak shear modulus parameter, the Winkler modulus parameter, the volume fraction, and the order of the exponent in the volume fraction equation. New results obtained from bending and stresses are presented and discussed in detail. From the obtained results, it became clear the influence of the exponential CNTs distribution and Winkler-Pasternak model improved the mechanical properties of the CNTRC beams.

• 한국식품영양과학회지
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• 제22권5호
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• pp.565-569
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• 1993

동결건조한 양조간장의 분말로 부터 갈색물질을 Sephadex G-10으로 겔-여과 크로마토그라피법에 의하여 분획한 다음 이를 동결건조하여 분말로 만든 후, 동갈색물질의 항산화력을 다른 항산화제인 부틸히드록시아니졸(BHA) 및 ${\alpha}-토코패롤과$ 비교하여 보았다. 갈색물질 및 양조간장은 다 같이 지방산의 산화반응에 있어서 과산화물의 생성을 크게 저해시켰고, 갈색물질이 양조간장 자체보다 항산화 효과가 더 높았으며 농도에 비례하여 항산화성이 증대되었다. 그러나 갈색물질의 항산화력은 과산화물 생성억제 능력 그리고 conjugated dienoic acid 생성저해 능력 등에서 BHA 및 ${\alpha}-토코페롤$ 보다는 낮았다. 이와같은 양조간장의 갈색물질의 항산화성은 그 획분이 대량 섭취도고 있는 발효조미식품이라는 점에서 중요한 의의를 가질 것으로 판단된다.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.1009-1018
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• 2002

The Representative Interactive Flamelet (RIF) concept has been applied to numerically simulate the combustion processes and pollutant formation in the direct injection diesel engine. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF concept has the capabilities to predict the auto-ignition and subsequent flame propagation in the diesel engine combustion chamber as well as to effectively account for the detailed mechanisms of soot formation, NOx formation including thermal NO path, prompt and nitrous 70x formation, and reburning process. Special emphasis is given to the turbulent combustion model which properly accounts for vaporization effects on the mixture fraction fluctuations and the pdf model. The results of numerical modeling using the RIF concept are compared with experimental data and with numerical results of the commonly applied procedure which the low-temperature and high-temperature oxidation processes are represented by the Shell ignition model and the eddy dissipation model, respectively. Numerical results indicate that the RIF approach including the vaporization effect on turbulent spray combustion process successfully predicts the ignition delay time and location as well as the pollutant formation.