• 한국산학기술학회논문지
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• 제10권5호
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• pp.1133-1140
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• 2009

본 이산화황이 잔류하는 한약재를 탕제로 달이는 방식에 따라 효율적으로 제거하는 방법을 찾기 위해 약 달이는 방식을 전통약탕기와 진자약탕기 2종류로 설정하였다. 전통약탕기로 156.4ppm을 함유하는 한약재를 1시간 달였을 때 96.7%의 제거효율을 보였으며, 2시간 달였을 때 100% 제거됨을 알 수 있었다. 전통약탕기 뚜껑을 전통한지, 일반한지, 거름종이, 일반종이를 사용하였을 경우 전통한지를 사용할 경우가 이산화황 제거효율이 가장 우수한 것으로 나타났다. 전통한지의 초기 pH는 10.03으로, 전통약탕기에 이산화황이 48ppm, 193ppm, 753ppm 및 1,506ppm 함유하는 한약재를 넣고 1시간 달인 후 pH 측정결과 9.37, 9.14, 8.9 및 8.03으로 각각 나타났다. 전자약탕기 파이롯트실험은, 전자약탕기로 1시간 약을 달일 경우 82.8%의 이산화황제거율을 보였으며, 약탕기 내부 중판부분에 전통한지, 거름종이, 활성탄, 참숯을 넣고 약을 달였을 때 73.6%, 72.8%, 73.9% 및 69.5%의 제거율을 보여 전자약탕기는 내부에 어떤 물체를 넣었을 경우 이산화황의 휘발을 방해하여 제거를 방해하는 것으로 나타났다.

• 동력기계공학회지
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• 제16권4호
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• pp.51-59
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• 2012

The computational flow analysis using LES technique was carried out to investigate the flow characteristics of a sirocco fan under the maximum flowrate condition. The commercial SC/Tetra software was used for this unsteady and three-dimensional numerical analysis. In consequence, because a flow is unstable within the range of about 50% of a housing depth from a bellmouth around the cutoff region, the passing flow through the blade cascade occurred on the X-Y plane is a slow or a reverse with approaching to the housing inlet. Also, the secondary flow shows on the radial plane of a housing, and its vortex center exists within about 33% of a housing depth from a bellmouth except the cutoff region. Moreover, the flow occurring on the exit plane of a sirocco fan shows a complex secondary flow.

• 대한설비공학회지:설비저널
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• 제12권4호
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• pp.264-274
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• 1983

Two-dimensional jet flows into a couple of confined rectangular enclosures such as an Ondol flue channel and their flow distributions were analyzed by numerical graphics : rectangular space in one enclosure is vacated and the other has 8 rectangular small posts. Both enclosures have a protruded inlet nozzle and on outlet on its center line. Steady state incompressible laminar viscous flow was assumed. The primitive forms of Navier-Stokes equations and continuity equation in a cartesian coordinate system were solved numerically by the Marker and Cell method for Reynolds numbers of 5, 10, 20, 30 and 40. From the numerical graphics it was found that the flow regions in both enclosures were devided into tow parts ; one part was the jet flow localized in a narrow center region of the enclosure and the other part was the very slow recirculating flow occupying the rest of the flow region in the enclosures. However there were a little differences in the shapes of jet flow in both enclosures for Reynolds numbers of 5 and 10 and also in the shapes of recirculating flows in both enclosures for all Reynolds number. Also it was found that waving flow appeared right before the outlet at Reynolds number of 20 and more.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.142-149
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• 2000

Two dimensional slow viscous flow around two counter-rotating equal cylinders is Investigated based on Stokes' approximation. An exact formal expression of the stream function is obtained by using the bipolar cylinder coordinates and Fourier series expansion. From the stream function obtained, the streamline patterns around the cylinders are shown and the pressure distribution In the flow field is determined. By Integrating the stress distribution on the cylinder, the force and the moment exerted on the cylinder are calculated. The flow rate through the gap between the two cylinders is determined as the distance between two cylinders vary. It Is also revealed that the velocity at the far field has finite non-zero value. Special attention is directed to the case of very small distances between two cylinders by way of the lubrication theory.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.549-558
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• 2017

DC distribution has several differences compared to AC distribution. DC distribution has a higher efficiency than AC distribution when distributing electricity at the same voltage level. Accordingly, power can be transferred further with low-voltage DC. In addition, power flow in a DC grid system is produced by only a voltage difference in magnitude. Owing to these differences, operation of a DC grid system significantly differs from that of an AC system. In this paper, the power flow problem in a bipolar-type DC grid with unbalanced load conditions is organized and solved. Control strategy of energy storage system on a slow time scale with power references obtained by solving an optimization problem regarding the DC grid is then proposed. The proposed strategy is verified with computer simulations.

• Journal of Advanced Marine Engineering and Technology
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• 제31권3호
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• pp.235-242
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• 2007

This paper discusses dynamic characteristics of a urea-SCR (Selective Catalytic Reduction) system. The urea flow rate to improve NOx conversion efficiency is generally determined by parameters such as catalyst temperature and space velocity. The urea-SCR system was tested in the various engine operating conditions governing the raw NOx emission levels, space velocity. and SCR catalyst temperature. These experiments include cold-transients to determine catalyst light-off temperature and urea flow rate transients. Likewise. ammonia storage dynamics was also investigated. The cold-transient results indicate the light-off temperature of the catalysts used in these experiments was $200-220^{\circ}C$. The ammonia storage and urea flow rate transients all indicate very slow dynamics (on the order of seconds) which presents control challenges for mobile applications. The results presented in this paper should provide an excellent starting point in developing a functional in-vehicle urea-SCR system.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.27-30
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• 2005

In a microfluidic chips pressure driven flow or electro-osmotic flow has been usually employed to deliver bio-samples. Flow in the chips is usually slow and the mixing performance is poor. A micro-mixer with a rapid mixing is important for practical applications. In this study a newly designed and electro-osmotic driven micro-mixer is proposed. This design is comprised of a channel and a series of metal electrodes periodically attached on the side surface. In this configuration electro-osmotic flows and the stirring effects are simulated three-dimensionally using a commercial code, CFD-ACE. Focus is given the effect on the electro-osmotic flow characteristics under the local variation of the electric field.

• 대한기계학회논문집
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• 제18권7호
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• pp.1840-1850
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• 1994

Enhancement of numerical algorithms for low speed compressible flow will be considered. Contemporary time-marching algorithm has been widely accepted and applied as the method of choice for transonic, supersonic and hypersonic flows. In the low Mach number regime, time-marching algorithms do not fare as well. When the velocity is small, eigenvalues of the system of compressible equations differ widely so that the system becomes very stiff and the convergence becomes very slow. This characteristic can lead to difficulties in computations of many practical engineering problems. In the present approach, the time-derivative preconditioning method will be used to control the eigenvalue stiffness and to extend computational capabilities over a wide range of flow conditions (from very low Mach number to supersonic flow). Computational capabilities of the above algorithm will be demonstrated through computation of a variety of practical engineering problems.

• 대한조선학회논문집
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• 제41권3호
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• pp.13-21
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• 2004

This paper deals with a theoretical and experimental method for the design of a biased asymmetric pre-swirl stator propulsion system which is an energy saving device by recovering a propeller rotational energy. In the case of slow-speed ships, the upward flow is generated along the afterbody hull form at the propeller plane. The generated upward flow cancels the rotating flow of the propeller at the starboard part while it increases at port part. The present biased asymmetric pre-swirl stator propulsion system consists of three blades at the port and one blade at the starboard which can recover the biased rotating flow effectively. This paper provides the design concept which gives more simple and a high degree of efficiency and the experimental results for the compound propulsion system.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제22권1호
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• pp.1-11
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• 2008

요즘 사회 현상학에선 몰입(flow)에 대한 관심이 매우 높다. 몰입이란 쉽지는 않지만 그렇다고 아주 버겁지도 않은 과제를 극복할 때 누구나 경험할 수 있는 황홀한 상태라고 한다. 누구나 몰입경험으로 인해 삶의 질을 높일 수 있다면 여러 교과분야에서도 학생들이 이를 활용할 수 있도록 돕고 안내하는 것은 미래에 더욱 능력 있는 문제해결자가 될 수 있도록 안내하는 것이 될 것이므로 매우 의미 있는 일이라 할 수 있다. 본 연구는 수학교육입장에서 몰입을 이해하고 이를 해석해보아 그 유용성을 인식하고, 또한, 앞으로의 몰입을 구체화할 수 있는 연구의 선행연구로써 활용될 수 있기를 기대한다.