• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.304-309
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• 2012

Size verification of small and large bubbles in a bubble column was investigated by employing the dynamic gas disengagement (DGD) method and dual electrical resistivity probe (DRP) method, simultancously. The holdups of large and small bubbles in the bubble column in a given operating condition were obtained by means of the DGD method by measuring the pressure drop variation in the column with a variation of time after stopping the gas input into the column. The size and frequency of bubbles were measured by the DRP method in the same operating condition, from which the bubble holdup of each range of size was obtained. The verification of size in determining the large or small bubbles was decided by comparing the holdups of large or small bubbles measured by the DGD method with that measured by the DRP method. Filtered compressed air and tap water were used as a gas and a continuous liquid medium. The diameter and height of the bubble column were 0.102 m and 1.5 m, respectively. The demarcation size between the large and the small bubbles in the bubble column was 4.0~5.0 mm; the demarcation size was about 5.0 mm when the gas velocity was in the relatively low range, but about 4.0 mm when the gas velocity was in the relatively high range, within this experimental conditions.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.201-213
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• 2017

Water is removed from crude oil containing water by using oil separator. This study aims to develop a three-dimensional (3D) Eulerian computational fluid dynamics (CFD) model to predict the separation efficiency of air-water-oil separator. In the incompressible, isothermal and unsteady-state CFD model, air is defined as continuous phase, and water and oil are given as dispersed phase. The momentum equation includes the drag force, lift force and resistance force of porous media. The standard k-${\varepsilon}$ model is used for turbulence flow. The exit pressures of water and oil play an important role in determining the liquid level of the oil separator. The exit pressures were identified to be 6.3 kPa and 5.1 kPa for water and oil, respectively, to keep a liquid level of 25 cm at a normal operating condition. The time evolution of volume fractions of air, water and oil was investigated. The settling velocities of water and oil along the longitudinal separator distance were analyzed, when the oil separator reached a steady-state. The oil separation efficiency obtained from the CFD model was 99.85%, which agreed well with experimental data. The relatively simple CFD model can be used for the modification of oil separator structure and finding optimal operating conditions.

• The KIPS Transactions:PartB
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• v.14B no.5
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• pp.321-328
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• 2007

In this paper, we propose a fast and dynamic Region-of-Interest coding method using the adaptive code-block discrimination algorithm in JPEG2000 images which complements the implicit ROI coding method and the modified implicit ROI coding method. For reducing the time of discriminating the code block, the proposed method estimates the characteristics of the shape of ROI and makes the shape of boundaries, and classifies the patterns of each code block. The method improves the preferred processing and loss of wavelet coefficients of background within the ROI code blocks by adaptively classifying the code blocks with the percentage of content of the wavelet coefficients using the thresholds of ROI and background. Also, the priority control of wavelet coefficients of background within ROI code block supports the rapid ROI coding by processing in batch based on patterns unlike the existing methods that process with unit of wavelet coefficients. To show the usefulness of this method, we compared this to the existing methods. There is no difference in performance, but we confirmed very speedy in processing time.

• Journal of the Korea Institute of Building Construction
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• v.16 no.2
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• pp.97-105
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• 2016

Recently, application case of the ultra rapid hardening concrete-polymer composite(URHCPC) are increasing to repair for the deterioration of pavement. But it is a major disadvantage that the main material is expensive and has environmental load. For these reasons, the development of the economic, eco-friendly materials is needed. Calcium Aluminate Composite (CAC), produced by rapid cooling of atomizing method with molten ladle furnace slag, is a material capable of improving the economic feasibility and reducing the environmental load of URHCPC. In this paper, the properties of CAC and gypsum mixed CAC (GC) as alternative materials of RSC according to the types of polymer dispersion were studied. The results were as follows; compressive strength, tensile strength, flexural strength, bonding strength and modulus of elasticity of the composites using CAC or GC showed higher values than those of plain proportion in 3 hour. In later age, they were at the same level as the general proportions. URHCPC using BPD as polymer dispersion had superior strength properties generally. But modulus of elasticity was the same level as the case of using a SBR latex. According to these results, CAC or GC can partially substituted for RSC to product the URHCPC. When URHCPC uses the BPD as the polymer dispersion, it can be improved performance.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.407-411
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• 2015

Dense ceramic membranes have been prepared using the commercial perovsikite $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$, powders synthesized by the solid state reaction method. The as-synthesized powders were compressed into disks with 1.0 mm of thickness and the disk was sintered at $1,100^{\circ}C$ for 2 hr. The oxygen permeation flux of $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ membrane increased with the increasing temperature and oxygen partial pressure. The activation energy for oxygen permeation was increased with the increasing oxygen partial pressure. Oxygen permeation flux at $950^{\circ}C$ were measured at various flow rates of feed and sweep gas. It has been demonstrated that oxygen permeability increased at elevated flow rates of both gases, but the sweep gas is more influential.

• Korean Journal of Agricultural Science
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• v.19 no.1
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• pp.65-78
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• 1992

The paper describes the comparison between observed and predicted stress-strain characteristics of marine silty clay in Dangjin district. For prediction, the hyperbolic model which is applied the parameters acquiring by physical and triaxial compression test was adopted, and the obtained results were summarized as follows: 1. The Young's modulus were increased with decreasing of moisture contents and increasing of dry density. 2. The most affective factor to hyperbolic model is lateral stress and dry density. and than cohesion and internal friction angle. 3. The comparision between the statistical and hyperbolic values of maximum deviator stress have few accordance. and the statisticals is lower than the hyperbolics. 4. Without. much labor and tiresome procedures, effective computer program was made and applied, but technical procedure for prevents test errors of parameter calculation is importants.

• Nuclear Engineering and Technology
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• v.17 no.4
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• pp.290-301
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• 1985

600MW(e) CANDU Primary Heat Transport System (PHTS) is composed of the two “figure-of-eight” loops and is designed to operate with the 4% Reactor Outlet Header (ROH) quality at its rated power. This existence of the two compressible regions and the positive flow-qualitly-void feedbacks are the sources of the PHTS flow instability. To ensure the PHTS stability, ROH-ROH interconnect pipes are installed as passive systems. This paper describes the investigation of the PHTS flow instability at its design full power condition. Also studied are the interconnect effect and the inherent system damping effect on the system stability. The time domain stability analyses are accessed by using the ATHER/MOD-I code which is the improved version of the KAERI developed ATHER code. Under the most adverse system modelling, the “figure-of-eight” symmetric loop shows divergent flow oscillations. Under with the interconnect, the PHTS stability is remarkably enhanced so that the system becomes stable. However, even under the conservative pressurizer modelling, the PHTS shows the more convergent flow oscillations. With the interconnect and the pressurizer modelling, its stability is highly credited. Conclusively, the inherent system damping by pressurizer itself can credit the PHTS stability without the interconnect.

• Proceedings of the Korean Society for the Gifted Conference
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• 2004.11a
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• pp.125-148
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• 2004

본 연구는 우수한 학업 성적을 보이는 재미 한인 영재 청소년들이 민족적 정체감을 어떻게 형성해 나가는지를 알아보는데 그 목적이 있다. 이를 위해 미국 뉴욕의 학업영재아를 위한 고등학교에 재학중인 25명의 한인 영재아들을 대상으로 Phinney의 민족적 정체감 평가지가 사용되었다. 민족적 정체감의 평가를 위해 3가지의 민족 정체감 구성요인들이 사용되었는데, 이들은 민족적 자기 정의, 민족집단에 대한 평가와 민족집단에 대한 참여이다. 개방형 문제에 응답을 한 학생들은 두 명의 독립적인 관찰자에 의해, 자신이 정의한 민족집단에 대한 탐구와 헌신의 정도에 따라, 3단계의 민족 정체감 발달 단계로 나누어졌다. 이 3단계 중 첫번째 단계는 자신이 속한 민족집단에 대한 무관심과 낮은 참여도를 보이는 민족 정체감 무관심의 시기이고, 두 번째 단계는 자신의 민족집단에 대한 관심을 가지고 그 집단의 역사와 철학, 문화, 그리고 주류사회 속에서 해당 민족집단의 사회적 위치와 편견 등에 대해 관심과 참여를 보여주는 민족 정체감 탐구의 시기이며, 마지막 단계는 민족 정체감 완성 시기로, 자신을 그 집단의 구성원으로 완전히 수용하면서, 민족적 정체감에 안정된 모습을 보이는 단계이다. 각 민족 정체감 구성요소들과 민족 정체감 발달 단계내의 집단차를 논의하기 위해 ANOVA가 사용되었다. 연구에 참여한 대부분의 영채아들은 자신을 재미아시아인이 아니라, 한국인 혹은 재미동포로 정의하였고, 이러한 민족적 자기 정의는 학생들의 민족집단에 대한 평가도와 참여도에 중요한 역할을 한다는 것을 알 수 있었다. 또한 민족집단에 대한 긍정적인 평가는 민족집단에 대한 활발한 참여와 밀접한 관련성을 가지고 있었다. 연구에서 나타난 결과들을 바탕으로 재미 한인 영재 청소년들이 높은 자아 존중감을 지닐 수 있도록, 현재 교육현장과 실생활에서 활용할 수 있는 여러 방안들과 함께, 앞으로 필요한 보다 많은 연구를 위한 제언이 제시되었다. 사고력 계발에 보다 충실할 수 있도록 내용의 폭을 넓히고 접근방법을 달리하는 심화 중심으로 교육과정을 구성하고 운영한다고 하였다. 그러나 현재 개발된 교육과정 편성과 운영은 창의성 교육의 구현보다는 압축형 속진 교육과정의 특성이 강하여, 이와 같은 운영지침을 실현하기 어려운 것이 현실이므로 교육과정 편제의 개선이나 운영지침에 적합한 교육내용의 개발이 시급히 이루어져야 할 것이다. 둘째, R&E(Research ＆ Education)는‘연구를 통한 교육’,‘교육을 통한 연구’를 의미하며 과학영재교육과정의 가장 큰 특징이라 할 수 있는 자율연구와 위탁교육을 위한 프로그램이다.여주는 것으로 나타났다.보였다. 5. L값은 살균처리의 경우 저장 30일 이후 약간 어두워지는 경향을 보였고, 121$^{\circ}C$ 살균처리에서 높은 값을 보였다. 대체로 저장온도가 높고 저장기간이 길어질수록 약간 밝아지는 경향을 보였다. 적색도는 인삼 첨가구의 경우 상온 및 냉장저장에서 10$0^{\circ}C$ 살균이 121$^{\circ}C$ 처리구 보다 약간 높은 값을 보였다. 저장기간에 따른 적색도의 변화는 인삼과 송이 첨가구에서 비교적 안정적이었다. 황색도는 상온 및 냉장저장에서 저장기간에 따라 약간 감소하는 경향을 보인 후 상온저장 50일 째, 냉장 60일 째 가장 높게 나타났다. 121$^{\circ}C$ 살균처리구가 10$0^{\circ}C$ 처리구보다 약간 높은 경향을 보였다.^{\circ}C$$,에서는 20시간 가열시 0.706$\mu\textrm{g}$/kg으로 가장 높게 생성된 후 서서히 감소하였다. 그러나 산값과 공액이중산값은 계속 증가하는 양상을 나타냈다. 즉 B(a)P생성과 산패도 변화사이에는 일정한 관계를 나타내지는 않았다.ve(+)의 상관관계가 있었다.l

• Journal of the Korea Institute of Building Construction
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• v.14 no.5
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• pp.379-388
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• 2014

The purpose of this study is to investigate the effect of capsulated slurry phase change material (PCM) on the thermal crack in mass concrete by experimental work and FEM analysis. In this study, three conditions of samples were prepared for evaluating the level of hydration heat, i.e., a material condition, a cement paste condition and a concrete condition. Also, a compressive strength test was conducted for FEM inverse analysis. Based on the results of the experiment, exothermic function coefficients of concrete with encapsulated slurry PCM were deducted by the inverse analysis. After that, they applied to FEM analysis of the mass scale concrete structures. From the results of this experiment, $31^{\circ}C$ capsulated slurry PCM had no super cooling phenomenon in the material condition. In the cement condition, hydration heat decreased by 34.61J when PCM of 1g was mixed. In the concrete condition, PCM of 6% was deducted as the best level in hydration heat absorption. In FEM inverse analysis, rate coefficient of reaction gradually decreased when PCM mixing ratio increased. But, temperature-rise coefficient increased when PCM mixing ratio exceeded 6%. For the inversed exothermic function coefficients applying to large scale concrete structures, a thermal cracking index increased by 0.05 when PCM of 1% was mixed.

• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.155-163
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• 1995

The primary purpose of this study is to hvestigate reusal techniques of high calclun-i fly ash in the construct.ion field, which may contribute to the savings of construction materials and consenratlng environment. Furt.hcrrnore, it can setup material properties or characteristics requiremi for development of new materials. Firstly, chemical and physical cahraci.eristics of liigh~calciurn fly ash is arialyseti. And then, the usability of the concrete is tcsted by investigating the flowablility and strength development through parameters of various replace ment r,itios with respect to different nuxing conditions. Finally, the durability and mechanical properties(e1astic nlodulus of the concrete is tested. As the result of the study, the following conclusions are derived : (1) the quaritii y of the CaO The primary purpose of this study is to hvestigate reusal techniques of high calclun-i fly ash in the co:lstruct.ion field, which may contribute to the savings of construction materials and consenratlng environment. Furt.hcrrnore, it can setup material properties or characteristics requiremi for development of new materials. Firstly, chemical and physical cahraci.eristics of liigh~calciurn fly ash is arialyseti. And then, the usability of the concrete is tcsted by investigating the flowablility and strength development through parameters of various replace ment r,itios with respect to different nuxing conditions. Finally, the durability and mechanical properties(e1astic nlodulus of the concrete is tested. As the result of the study, the following conclusions are derived : (1) the quaritii y of the CaO