• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.901-906
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• 1998

Gas and liquid flow characteristics were investigated in an internal circulation airlift reactor using a single nozzle for a gas distributor. In three reactors with different diameters of the downcomer and heights of the riser, the gas holdup in the individual flow zone and the impulseresponse curve of tracer for an air-water system were measured for various gas velocities and reactor heights. Experimental results showed that the flow behavior of bubbles in the riser was the slug flow due to strong coalescences of bubbles and that the bubble flow pattern in the downcomer was the transition bubble flow for the smaller diameter of the downcomer, however, it was the homogeneous bubble flow for the larger one. And mean gas holdups in the individual flow zone and the reactor were greatly increased with decreasing the diameter of the downcomer for the equal ratio of height of the top section to that of the riser. Also, the mixing time was much effected by the height of the top section of reactor and for the equal ratio of height of top section to that of the riser, it was increased with increasing the diameter of the downcomer and the height of the riser. Flow characteristics of liquid were mainly varied with the bubble flow pattern in the downcomer and the size of the top section of reactor. And circulation velocities of liquid in the riser were increased with increasing gas velocities and the size of the top section of reactor, and for the equal ratio of height of top section to that of the riser, they were increased with increasing the diameter of the downcomer and the height of the riser.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.522-526
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• 2012

New experimental method to measure solid descending velocity in a vertical downcomer was presented and effects of downcomer diameter and particle properties on descending velocities for Geldart group A, B, and D particle have been measured and investigated. The effect of initial solid inventory on solid descending velocity was negligible. However, solid flow rate, solid circulation rate and solid descending velocity increased as the downcomer diameter increased. Moreover, solid descending velocity increased linearly as the downcomer diameter increased and showed distinguishable trend for Geldart group D particle from Geldart group A and B particles. Empirical correlations of solid descending velocity for Geldart group D and Geldart group A and B particles have been derived based on the measured values. The correlations could predict well the solid descending velocities.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.665-674
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• 2020

Low-frequency pressure fluctuations in an external-loop airlift reactor were investigated. Low-frequency pressure fluctuations could be measured by shooting videos about liquid levels in the four piezometric tubes which were installed at the lower and upper parts of the riser and downcomer using a cellular phone. The periodic characteristics of pressure fluctuations were proved by the calculation of their auto-correlation function and cross-correlation function. Even if the riser superficial gas velocity was constant, the riser and downcomer gas holdups as well as wall pressures were periodically changed due to the inertia of circulating liquid. In general, the intensity of pressure fluctuations increased with an increase in the gas velocity. When the unaerated liquid height was 0.04 m, the maximum period of pressure fluctuations was found at the specific gas velocity (0.14 ms^-1). It was because the maximum inertia of circulating liquid resulted from a reduction in the increasing rate of the liquid circulation velocity and a decrease in the volume of the effectively circulating liquid with an increase in the gas velocity.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.816-821
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• 1997

The hydrodynamics and the liquid flow characteristics were investigated in an internal circulation airlift reactor with a single nozzle as a gas distributor. In an air-water system, the gas holdup in the individual flow zone and the impulse-response curve of tracer were measured at various gas velocities and reactor heights. Experimental results showed that for the higher gas velocity(>about 8 cm/s), the flow behavior of bubbles in the riser was turbulent flow due to strong bubble coalescences and the axial height of dispersion zone of large bubbles having uniform sizes in the downcomer was decreased with increasing gas velocity. And mean gas holdups in the individual flow zone and the reactor were increased with increasing gas velocities and were decreased with increasing heights of the top section of the reactor and it was decreased with increasing the height of the top section and gas velocity. Flow characteristics of liquid in the riser and the downcomer was tend to access to plug flow and the overall flow behavior of liquid was mainly varied with the size of the top section which it was assumed to be perfect mixing zone. In these conditions, liquid circulation velocities were increased with increasing gas velocities and they were higher than those by using other gas distributors.

• The Monthly Diabetes
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• s.188
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• pp.11-13
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• 2005

인슐린 저항성 증후군 환자나 당뇨병 발병 고위험군, 당뇨병 초기 환자에서는 인슐린 저항성 및 고인슐린혈증은 일반적으로 함께 나타나는 상황이다. 그러나 당뇨병이 이미 발병하여 매우 높은 혈당 상태에 있거나 당뇨병이 오래 진행되어 인슐린 분비능력이 매우 하강한 환자에서는 인슐린저항성이 심한데도 불구하고 고인슐린혈증은 나타나지 않을 수 있다.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.239-244
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• 2006

As an effective means to convey crushed materials from seabed to onboard ship, air-lift pump provides a reliable mechanism due to its simple configuration and easy-to-operate principle. The present study is focused on fundamental investigation of related performance through analysis program based on the gas-liquid two-phase flow in circular pipes. It is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates.

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.203-211
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• 1997

본 연구는 기온$15^{\circ}C{\pm}1^{\circ}C$ $26^{\circ}C{\pm}1^{\circ}C$,습도$55%{\pm}5%$ 환경조건에서 손가락 끝마디 부분을 얼음물에 침지시킨후 구강온과 4부위 피부온, 손가락끝 피부온, 전신온냉감, 전신쾌적감, 손가락 끝 동통감의 변화를 젊은 남자 피험자와 노인남자 피험자를 대상으로 비교측정하고자 하였다. 본 학회에서는 젊은 남자피험자 그룹에 대하여 보고하고자 한다. 결과는 다 음과 같다. $15^{\circ}C{\pm}1^{\circ}C$에서 4부위 피부온을 보면 가슴과 상완은 손가락끝 침지시 약간 하강하고 다시 상승하지만 대퇴와 하퇴에서는 하강하고 그 상태가 유지된다. 특히 하퇴의 경우는 급격히 하강하는 경향을 보이고 있다. 손가락끝 피부온은 손가락 침지와 동시에 급격한 하강을 나타내나 손가락을 꺼낸후에 손가락 침지전의 온도로 회복되지는 않았다. 평균피부온을 보면 손가락 침지시 하강하는 경향을 보이고 있다. 전신 쾌적감은 약간 불쾌하게 나타났고, 전신온냉감은 서늘하다고나타났고 손가락끝의 동통 감은 매우 아프다고 나타났다. $26^{\circ}C{\pm}1^{\circ}C$에서 4부위 피부온을 보면 가슴 상완대퇴 하퇴 모두 손가락끝 침지시 약간 하강하고 낮은 상태로 유지되는 경향을 보이고 있다. 손가락끝 피부온은 손가락 침지시 급격한 하강을 나타내었고 손가락을 꺼낸후에도 침지의 온도로 회복이 되었다. 평균피부온은 손가락 침지후에 약간 하강하였지만 큰 차이는 없었다. 전신쾌적감은 약간 쾌적하게 나타났고 전신온냉감은 약간 따뜻하다라고 나타났으며 손가락끝의 동통감은 약간 아프다고쪽으로 나타났다.때문에 이를 디자인에 곧바로 적용시키기 어려운 점이 있다. 이에 본 연구는 기존의 바용성 평가를 위한 분석도구들이 갖는 문제 점들 해결하여 제품의 사용자 인터페이스 디자인 개발과정에서 활용할 수 있는 평가 분석도구를 개발하는 것을 목표로 한다. 이를 위해 첫째, 다양한 유형의 정보를 포함하는 비디오 정보를 선정하였따. 둘째, 데이터를 다양한 측면에서 추출할 수 있는 Data logger를 개발하였다. 셋째, 데이터를 시각적으로 정리하고 분석할 수 있는 도구를 제안한다. 마지막으로 인터페이스 디자인에서 여러 가지 디자인안을 도출해 내는 작업에 이용할 수 있는 종합화과정을 개발한다. 이러한 일련의 과정이 통합된 컴퓨터 시스템 안에서 이루어지도록 프로그램을 개발하여 정보의 유용성을 높일 수 있도록 한다.at the entropy index as a measurement of inter-business relatedness is not significant but technological relatedness index is significant. OLS estimates on pooled data were considerably different from FEM or REM estimates on panel data. By introducing interaction effect among the three variables for business portfolio properties, we obtained three findings. First, only VI (Vertical integration) has a significant positive correlation with ROS. Second, when using TFP growth as an depende

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.2
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• pp.252-258
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• 1999

As an effective means to convey crushed materials from seabed to on board ship and to raise hazardous or abrasive liquids air-lift pump provides a reliable mechanism due to its simple config-uration and easy-to-operate principle. The present study is focused on fundamental investigation of related performance by the analysis program based on the gas-liquid two-phase flow in circular pipes. The program covers pump operating in isothermal and vertical two-phase flow with Newto-nian liquids. it is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates and furthermore attachment of downcomer gives little effects on riser performance the conveyed liquid flow rate increases with larger submergence rate.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.735-740
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• 1995

일체형 원자로에는 노심지지원통과 원자로용기 내벽사이의 환형 공간을 나선으로 감는 형태인 일체형 관류식 나선형 증기발생기와 증기발생기를 여러 개의 모듈로 나누어 환형 공간에 배치하는 형태인 모듈형 관류식 직관형증기 발생기가 가장 적합한 것으로 판단되어 두 가지 형태에 대한 개념을 설정하였다. 일체형 관류식 나선형 증기발생기는 전열관 집합체, 지지구조물, 하강유로, 그리고 증기 및 급수 헤더로 구성되어 있다. 모듈형 관류식 직관형 증기발생기는 개개의 모듈이 별도로 운전될 수 있는 12개의 모듈로 구성되며, 원자로용기를 관통하는 배관의 수를 줄이기 위해서 급수관이 증기관의 안쪽에 있는이중배관 개념을 사용한 것이 특징이다. 모듈형 관류식 직관헝 증기발생기가설계 및 제작이 용이하지만 높이를 줄이기 위한 방안으로 두 가지 개념이 조합된 모듈형 관류식 나선형 증기발생기도 검토하였다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2012.04a
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• pp.182-185
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• 2012

본 연구는 서울시민안전체험관 방문 유치원 및 초등학교 학생 183명을 대상으로 안전체험교육 실시 전후에 안전지식의 변화를 12문항의 연구도구지를 통해 측정하였다. 분석결과 안전교육 전에 비해 교육 후에 약 2.13점 상승하여 효과가 있었으며, 소방미끄럼틀의 안전한 하강자세 등 10개 문항에서 매우 유의미한 차이를 보였으나(p<0.001), 화재대피 시 몸을 낮추는 이유(p<0.001), 소화기 사용시 최초의 행동(p<0.05)에서는 부적으로 유의미한 차이를 보여 향후 안전교육 효과의 극대화를 위해 수요자중심 교육, 아동교육 전문가의 참여, 교육매뉴얼, 교육품평회 등을 통한 교육자 수준의 상향평준화 등이 필요한 것으로 나타났다.