• Ocean and Polar Research
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• 제24권3호
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• pp.289-300
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• 2002

The Lago Sofia conglomerates encased in the Cretaceous Cerro Toro Formation, southern Chile, represent a gigantic submarine channel system developed along a foredeep trough. The channel system consists of several tributaries along the trough margin and a trunk channel along the trough axis. Voluminous debris flows were generated ubiquitously along the tract of the submarine channel mainly by the failure of nearby channel banks or slopes. The flows transformed immediately into multiphase flows and resulted in very thick-bedded mass-flow deposits with a peculiar structure sequence. The mass-flow deposits commonly overlie fluted or grooved surfaces and consist of a lower division of clast-supported and imbricated pebble-cobble conglomerate with common basal inverse grading, and an upper division of clast- to matrix-supported and disorganized pebble conglomerate or pebbly mudstone with abundant intraformational clasts. The structure sequence suggests a temporal succession of a turbidity current, a bipartite hyperconcentrapted flow with active clast collisions near the flow base, and a cohesive debris flow probably with a rigid plug. The multiphase flow is interpreted to have resulted from transformation of clast-rich but cohesive debris flows. Cohesive debris flows appear to transform more easily into dilute flow types in subaqueous environments because they are apt to hydroplane. This is in contrast to the flow transitions in subaerial environments where noncohesive debris flows are dominant and difficult to hydroplane.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.632-639
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• 2018

최근 플러그인 전기자동차에 대한 적극적인 보급 정책이 추진되고 있으나 플러그인 전기자동차는 전력계통에 직접 연계되어 충전수요를 공급받기 때문에 충전수요의 집중도에 따라서는 전력계통의 설비확충이 요구될 수도 있다. 반면 전력계통의 설비확충은 많은 시간과 투자가 소요되어 현실적으로 제한될 수밖에 없기 때문에 기존의 전력망을 효율적으로 이용하여 플러그인 전기자동차의 충전수요를 안정적으로 공급하는 것은 플러그인 전기자동차의 보급 확대에도 중요한 요소라고 할 수 있다. 따라서 본 논문에서는 주어진 전력계통에서 선로조류와 모선전압과 같은 제약조건을 만족하면서 플러그인 전기자동차의 충전수요를 공급하기 위한 충전계획 수립방안을 제안한다. 이를 위해 자동차의 주행 패턴과 충전 요금제를 기준으로 플러그인 전기자동차 충전수요의 요구량과 충전 시작시간을 전기자동차별로 모델링 한 후 이를 전력계통 모델에 연계하여 조류계산을 계산하여 전력계통의 운전 상태를 모의하였다. 또한 선로의 전력조류와 모선의 전압에 대한 제약 조건의 만족 여부를 확인하며 제약조건에 위반이 발생하는 경우 이를 완화하기 위해 제약조건에 직접 관련된 플러그인 전기자동차의 충전수요를 조정하여 계통제약의 만족여부를 재확인하는 과정을 반복함으로써 주어진 전력계통의 제약조건을 만족할 수 있는 플러그인 전기자동차의 충전계획을 수립하였다.

• 분석과학
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• 제10권1호
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• pp.66-74
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• 1997

지름 2.54cm, 길이 10cm인 유리관에 tyrosinase(EC. 1.14.18.1)를 입자의 크기 $550{\mu}m$인 탄소에 고정시켜 충진하고, 페놀과 산소를 기질로 사용하여 tyrosinase의 반응 특성을 조사하기 위해 axial dispersion 모델을 제안하였다. 본 논문에서 페놀의 농도는 55.5mM로 고정시키고 산소(2.7ppm, 5.4ppm, 그리고 9.5ppm)와 유속 (1~3mL/s)을 변화시키면서 탄소에 고정된 tyrosinase의 반응을 관찰하였다. 또한, Damkolher수를 계산하고 분산 특성과 식으로부터 효소반응 속도 및 분산의 영향을 예측하기 위해 수치적 해석을 하였다. 연구 결과 물질저항은 주로 외부 전달과 내부확산이었으며, 제안된 모델에서 Biot수는 64.25였다. 페놀은 1.0mL/s 정도의 느린 속도에서 산소의 농도가 높을수록 높은 전환율을 나타내었다. 한편, axial dispersion 모델과 plug flow 모델의 비교에서는 모두 같은 전환율을 나타내어 axial dispersion 모델이 반응속도와 무관함을 알 수 있었다.

• 한국물환경학회지
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• 제34권3호
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• pp.270-284
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• 2018

Paldang is a river reservoir located in the Midwest of Korea, with a water volume of $244{\cdot}10^6m^3$ and a water surface area of $36.5km^2$. It has eutrophied since the construction of a dam at the end of 1973, and the phosphorus concentration has decreased since 2001. Average hydraulic residence time of the Paldang reservoir is about 10 days during the spring season and 5.6 days as an annual level. The hydraulics and water quality of the reservoir can differ greatly, both temporally and spatially. For the spring period (March to May) in 2001 ~ 2017, the reservoir mean total phosphorus concentration calculated from the budget model based on a plug-flow system (PF) and a continuous stirred-tank reaction system (CSTR) was 13 % higher and 10 % lower than the observed concentration, respectively. A composite flow system (CF) was devised by assuming that the transition zone was plug flow, and that the lacustrine zone was completely mixed. The mean concentration calculated from the model based on CF was not skewed from the observed concentration, and showed just 6 % error. The retention coefficient of the phosphorus derived from the CF was 0.30, which was less than those of the natural lakes abroad or river reservoirs in Korea. The apparent settling velocity of total phosphorus was estimated to be $93m\;yr^{-1}$, which was 6 ~ 9 times higher than those of foreign natural lakes. Assuming CF, the critical load line for the total phosphorus concentration showed a hyperbolic relation to the hydraulic load in the Paldang reservoir. This is different from the previously known straight critical load line. The trophic state of the Paldang reservoir has recently been estimated to be mesotrophic based on the critical-load curve of the phosphorus budget model developed in this study. Although there is no theoretical error in the newly developed budget model, it is necessary to verify the validity of the portion below the inflection point of the critical-load curve afterwards.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 추계 학술대회논문집
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• pp.127-132
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• 2002

Numerical and experimental works have been made in order to figure out the physical mechanism of thermal storage system for the determination of optimal design and to enhance the thermal efficiency of the system. To this end a computer program is developed and evaluated successfully against experimental data measured with a bench scale facility. Considering the thermal efficiency of storage is critically impaired by the mixing effect, the minimum flow mixing situation is calculated by the assumption of uniform plug-type flow as a reference condition. Further a parametric systematic calculations have been made for a hypothetical full-scale storage system with Fr, storage dimension, diffuser type and loading hour, etc.

• 동력기계공학회지
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• 제17권1호
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• pp.27-35
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• 2013

SCR (Selective Catalytic Reduction) on DPF (Diesel Particulate Filter) is a multi-functional after-treatment device which integrates soot filtration and DeNOx function into a single can. Because of its advantage in package and cost, the SCR on DPF is considered as a potential candidate for future application. It inherently employes wall flow type monolithic reactor so ash included in exhaust gas may deposit inside the inlet channel of this device. This study is intended to identify the impact of ash deposit on SCR reaction under wall flow type monolithic reactor. Simulation approach is used so relevant species transport equations for wall flow type monolith is derived. These equations can be solved together with momentum conservation equations and give solution for conversion performance. Both ash deposit and clean catalyst case are simulated and comparison of these two cases gives an insight for the impact of ash deposit on conversion performance. Ash deposit can be classified as ash layer and ash plug. and impact of ash deposit is described along with different morphology of ash deposit.

• 한국전산유체공학회지
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• 제18권4호
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• pp.74-81
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• 2013

A numerical design analysis is conducted to search for an optimal shape of outlet in a rotating-disk CVD reactor. The goal is to suppress flow recirculation that has been found in a reactor having a sudden expansion of flow passage outside of the rotating disk. In order to streamline gas flow, the sidewall at which the flow in the Ekman layer is impinged, is tilted. The axisymmetric laminar flow and heat transfer in the reactor are simulated using the incompressible ideal gas model. For the conventional vertical sidewall, the flow recirculation forming in the corner region could be expanded into the interior to distort the upstream flow. The numerical results show that this unfavorable phenomenon inducing back flow could be dramatically suppressed by tilting the sidewall at a certain range of angle. The assessment of deviation in deposition rate based on the characteristic isotherm illustrates that the sidewall tilting may expand the domain of stable plug-like flow regime toward higher pressure. A physical interpretation is attempted to explain the mechanism to suppress flow recirculation.

• 한국대기환경학회지
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• 제6권1호
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• pp.57-72
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• 1990

The oxidation of carbon monoxide on a catalyst, $LaSrNiCoO_3$ was investigatigated with a plug flow system. Kinetic quantities such as reaction-rate, reaction order and Arhenius-parameters at various reactor temperature from 200$^\circ$C to 300$^\circ$C were determined. Also, the optimum condition for the oxidation of carbon monoxide with this catalyst was determined and are as follows. Partial pressure of oxigen ; 428mmHg Partial pressure of carbon monoxide ; 332mmHg Mixed moral ratio of oxigen and Carbon monoxide ; 1.3 : 1 Total gas flow ; 224ml/min Reaction temperature ; 340$^\circ$C The reaction kinetic equation at the optimum condition, temperature range from 200$^\circ$C to 340$^\circ$C, are as follow. $$ $v = Ae^{6.5Kcal/RT} [CO]^{0.93 \sim 0.98} [O_2]^{0.42 \sim 0.50}$ $$ In addition to this, numerical calculation were performed to evaluate the mass and heat transfer effect on this system.

• 대한기계학회논문집A
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• 제39권11호
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• pp.1123-1129
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• 2015

자동차부품 세척장비는 엔진과 변속기 블록 등의 가공과정에서 잔류하는 기름때를 제거하며, 잦은 수류방향 전환과 고압수의 분사를 위해 한 쌍의 2 방향 밸브를 사용한다. 그러나 정교한 밸브제어장치 없이 2 방향 밸브를 사용하는 경우 급격한 수류방향 전환에 따른 맥동현상이 발생하여 사용에 어려움이 따른다. 대안으로 하나의 3 방향 절환밸브를 사용하는 방법은 정교한 제어장치 없이도 정확한 수류방향 절환이 원활히 이루어져 이러한 문제점을 해결할 수 있다. 그러나 복잡한 유로 및 바텀플러그 형상으로 인해 유속변화가 심하게 발생하여 공동현상이 나타날 수 있다. 본 연구에서는 3 방향 절환밸브 내의 유동특성을 해석적으로 평가하였으며, 바텀플러그 하부에서 나타나는 공동현상을 공동화지표와 POC(Percent of cavitation)를 도입하여 정량화하였다. 공동현상의 저감을 위해 바텀플러그 형상을 매개변수화하고, 해석의 수렴성 개선과 해석시간을 단축시킬 수 있는 단순 유한요소모델을 이용하여 유동해석을 통한 형상최적설계를 실시하였다. 완전요인배치법을 통한 실험계획법과 인공신경망 기반 반응표면모델을 적용하여 공동현상이 발생하지 않는 POC 가 30% 미만인 바텀플러그의 형상을 제시하였다. 얻어진 최적해는 POC 27%에 대하여 바텀플러그의 허리길이와 꼬리길이가 각각 6.42mm 및 6.96mm 이다.

• 한국자동차공학회논문집
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• 제3권2호
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• pp.146-156
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• 1995

Growing international concern about environmental issues in recent years has led to new proposals for strengthening exhaust emission standards and fuel economy requirements throughout the world. The low emission vehicle(LEV) standards drawn up by the California Air Resources Board(CARB) in the U.S.A are noticeably stringent To cope with this regulation, a reduction of HC emission is the most important challenge for the automotive industry because HC emission levels are severer than any other components emission levels. In this paper, the apparatus for visulalizing the wall film flow in a intake manifold and the spark plug with optical fiber for detecting the signal from diffusion flame are developed to mal,e the HC formation mechanism clear. High speed camera system is also used to elucidate the correlation wall film flow and the diffusion flame. Using these methods, the effect of fuel injection systems such as injection direction, spray angle, atomised injection on HC emission levels is investigated. Consequently, the optimal fuel injection conditions for minimizing the wall film flow and reducing the HC emission are found through this research.