• Particle and aerosol research
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• v.13 no.2
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• pp.79-85
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• 2017

This study identified the loss of minimum fluidization velocity and pressure in accordance with the superficial velocity of $NiO/MoO_3/MoS_2$, a rare metallic oxide and high value-added material in the lab-scale fluidized bed reactor (L=0.25 m, D=0.05 m). The average pressure loss in L/D 1, 2, and 3 of $NiO/MoO_3/MoS_2$ within the scope of superficial gas velocity between 0.07 and 0.45 m/s based on the L/D 1, 2, and 3 of the specimen was shown to be 290~1952 Pa at decreasing flux and 253~1925 Pa at increasing flux. The comparison between the theoretical value proposed by Wen and the test data showed a difference between 0.021~0.36 magnification. Based on these results, this study was able to determine the operation conditions where rare metallic oxides could be applied in real phenomena.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3274-3279
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• 2009

The elutriation characteristics of particle size distribution were investigated in a gas-solid fluidized bed. Experiments were carried out with the mulit-sized particles of Gaussian distributions. The elutriation rate constant obtained from the experiment was correlated with the standard deviation of particle size and the dimensionless group of the velocity ratio. The standard deviation of pressure fluctuation, mean pressure, major frequency and power spectrum density function were calculated by pressure fluctuation properties. Size distribution of elutriated particles and pressure fluctuations were measured for the particle size distribution of particle system depended largrly on the size distribution. Characteristics of fluidization and elutriation were greatly influenced by the particle size distribution and these characteristics could be interpreted with pressure fluctuation properties.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1756-1760
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• 2004

Circulating Fluidized-Bed (CFB) boilers which have been operated in Korea were manufactured by the design technology of foreign leading companies. As they are not active to transfer their technology, domestic companies don't have the enough ability to design it independently yet. Doosan Heavy Industries & Construction Co. Ltd. and Korean Institute of Energy Research are trying to develop and improve the particle re-circulating device among the components of CFB boiler. Our purpose is to control the amount of particles leaving the re-circulating system by adjusting utility air and reuse the heat of circulating particles. The results of experiments with cold model system show that a fluidization state in the particle re-circulating device is very stable when the amount of utility air is supplied to its wind box with 2.29 times of minimum fluidization velocity. Also the amount of particles entering the riser don't increase linearly when the amount of utility air is supplied over 2.5 times of minimum fluidization velocity. Now we are testing its functional run with the hotstate experiment set-up.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.2
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• pp.110-122
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• 1996

본 논문에서는 전기유동유체(Electro-Rheological Fluid : ERF)를 함유하는 지능구조물의 동적 모델링 및 진동제어를 수행하였다. 먼저 실리콘 오일을 기본용매로 하여 조성된 ERF의 복소 전단모듈러스를 전장부하와 가진 주파수의 함수로 동적 회전모드 실험을 통하여 도출한 후, 이를 샌드위치 보 이론과 연계하여 동적 모델링을 실시하였다. 도출된 6차 편미분방정식 형태의 지배 방정식을 유한요소 모델로 이산화하여 전장부하에 따른 지능구조물의 동탄성 특성값인 감쇠 고유 주파수 및 모달 손실계수를 주파수 영역에서 얻었다. 그리고 ERF를 함유한 샌드위치 형태의 지능구조물을 제작한 후 실험적으로 얻은 동탄성 특성값과 모델에 의해 예측된 동탄성 특성값을 비교 고찰하여 제시된 동적 모델에 대한 타당성을 입증하였다. 또한 모델을 통해 전장부하 함수로 예측된 주파수 응답곡선 중에서 각 주파수 대역에 대해 최소 변위가 되는 응답곡선을 요구응답으로 설정한 후, 그에 해당하는 전장부하를 선정하는 논리적인 능동 진동제어 알고리즘을 제안하였다. 제어알고리즘의 유용성을 입증하기 위해 실험적으로 수행된 능동 진동제어 결과를 주파수영역과 시간영역에서 제시하였다.

• KSBB Journal
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• v.8 no.5
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• pp.431-437
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• 1993

Active carbon which has the smallest bulk and wet density was found as the best support media among 4 different kinds of materials(celite, natural zeolite, Pusuk stone, active carbon) to make a proper fluidized-bed with small energy consumption. Its minimum and optimum fluidization velocity were found as 0.03cm/sec and 0.25cm/sec, respectively. As organic loading rate for methane fermentation was increased, CODcr removal efficiencies of all the media were decreased. But, CODcr, removal efficiencies of active carbon was maintained more than 90% in this experimental range of the organic loading rate. Larger amount of microorganism was adsorbed on the active carbon which has very high specific surface area. At the organic loading rate of 16g CODcr,/l day, its adsorbed cell mass was 157mg/g. Comparing natural zeolite with roast celite, adsorbed cell mass did not increase in proportion to specific surface area of the media. Even though roast celite has the same specific surface area as the Pusuk stone, its organic removal ability was superior to that of the Pusuk stone, which explains that the relatively great surface roughness and the positive surface charge are important for cell adsorption. It was concluded that the support media for anaerobic fluidized reactor should have small wet density and small fuidization velocity, if possible, in order to increase cell adsorption by reducing the fluid shear stress.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1994.06a
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• pp.56-64
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• 1994

탄성유체윤활 (elastohydrodynamic lubrication : EHL)이론은 구름 베어링, 기어 및 캠기구 등과 같이 집중 하중을 받는 기계 요소에서의 윤활 현상을 설명하는 이론으로서, 윤활부분에서 금속 접촉이 발생하지 않도록 기계요소를 설계하기 위하여 필요한 최소유막두께를 결정하는 데 사용된다. 그리이스는 대표적인 윤활제로서 구름 베어링의 윤활에 있어서 중요한 위치를 점하고 있다. 현재 집중 하중을 받는 기계 요소의 윤활에는 윤활 구조의 간편화, 보수의 용이성, 먼지나 이물의 침입 방지 등에 유리한 그리이스 윤활의 사용이 확대되고 있다. 현재 전동기, 가정용 전기기기, 측정기 등에 쓰이는 구름 베어링의 경우는 거의 전량 그리이스 윤활이 사용되고 있다. 지금까지의 연구는 유동특성상의 복잡성 때문에 무한장 선접촉 등온 EHL 문제에 대한 해석이었고, 아직까지는 그리이스 윤활 TEHL 해석에 관한 연구는 발표된 바 없다. 본 연구에는 Herschel-Bulkley 모델 그리이스 EHL문제를 열탄성유체윤활해석하여 보다 정확한 접촉부의 압력분포와 유막형상을 예측하고자 한다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.277-281
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• 2000

본 논문에서 생체실험용 대형 2축 자기장 발생장치를 설계하였다. 생체실험 대상이 유동적이지 않고 홀더(holder)내에 고정될 경우 이는 방향성(orientation)의 논란이 불가피하며 이 영향을 줄이기 위해 각 축에 4개씩 총 8개의 코일을 사용하여 2축 4중코일 구조로 장치를 설계하였다. 원하는 특정 자기장에 대한 권선수 및 전류치를 결정하기 위해 정육면체 구조의 자기장 발생장치를 원통형으로 근사화시켜 간소하게 수식을 유도하였으며 각 코일의 최적위치 및 최적 권선비는 별도의 최적화 시뮬레이션을 통하여 수치를 추출하였다. 이렇게 얻어진 수치들을 MATLAB으로 제작한 시뮬레이터에 적용하여 설계 조건과 동일하게 모델링한 발생장치 주변에서의 자기장 분포를 시뮬레이션 해보았으며, 각 축에서의 균일도를 평가하여 균인 자기장 분포영역 또는 사용가능영역을 도출하였다. 장치해석 결과, 임의의 기준 자기장에 대해 약 5%의 오차범위를 인정할 경우, 최소 60% 이상의 사용가능영역을 확보할 수 있었으며, 이 영역 내에서는 고도의 균일 자기장이 분포함을 확인할 수 있었다.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.4
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• pp.44-49
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• 2013

An establishment of dioxin-reduction operating skill for medium sized incineration facility is urgently needed in Korea with nearly 90% of medium sized incineration. Using lattice stoker incineration processing the capacity of 20 tons industrial general waste per day, similar properties of the household waste, dioxin-reduction is derived in optimum operating condition and parameters. As a result, CO haunting which is the minimization of frequency is found as the major parameter to minimize dioxin.

• Management & Information Systems Review
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• v.28 no.3
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• pp.161-189
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• 2009

The sub-prime crisis led to the collapse of US investment banks which were considered highly competitive during the Asian Financial Crisis. The event gave us a lesson on importance of the financial supervision. Additionally concerns rise over the fact that the role model of the Capital Market Law, created for the purpose of developing the capital market, is the US investment banks. This paper investigates if the prudential regulations, among them especially the capital regulation, are able to prevent the risk the arises from Korean financial firms operating investment bank business. The current capital requirement regulation, Net Capital Ratio(NCR), is not sufficient, because it's nature of being a ratio makes the NCR ineffective when assets and liabilities are concurrently rising. We also verified the internal model which measured the market risk, by comparing the US investment and Korean banks' diversification effect. The result of the test is that it is difficult to conclude the internal model has a critical defect. This paper's contribution is that it is not sufficient use only the capital regulation in supervising financial markets.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.499-505
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• 2010

In this study, hydrodynamics and reaction characteristic of K-based solid sorbents for $CO_2$ capture were investigated using a continuous system composed of two bubbling fluidized-bed reactors(1.2 m tall bed with 0.11 m i.d.). Potassium-based dry sorbents manufactured by the Korea Electric Power Research Institute were used, which were composed of $K_2CO_3$ of 35% for $CO_2$ absorption and supporters of 65% for mechanical strength. The continuous system consists of two bubbling fluidized-bed reactors, solid injection nozzle, riser, chiller, analyzer and heater for regeneration reaction. The minimum fluidizing velocity of the continuous system was 0.0088 m/s and the solid circulation rate measured was $10.3kg/m^2{\cdot}s$ at 1.05 m/s velocity of the solid injection nozzle. The $CO_2$ concentration of the simulated gas was about 10 vol% in dry basis. Reaction temperature in carbonator and regenerator were maintained about $70^{\circ}C$ and $200^{\circ}C$, respectively. Differential pressures, which were maintained in carbonator and regenerator, were about $415mmH_2O$ and $350mmH_2O$, respectively. In order to find out reaction characteristics of dry sorbents, several experiments were performed according to various experimental conditions such as $H_2O$ content(7.28~19.66%) in feed gas, velocity (0.053~0.103 m/s) of simulated gas, temperature($60{\sim}80^{\circ}C$) of a carbonator, temperature($150{\sim}200^{\circ}C$) of a regenerator and solid circulation rate($7.0{\sim}10.3kg/m^2{\cdot}s$). The respective data of operating variables were saved and analyzed after maintaining one hour in a stable manner. As a result of continuous operation, $CO_2$ removal tended to increase by increasing $H_2O$ content in feed gas, temperature of a regenerator and solid circulation rate and to decrease by increasing temperature of a carbonator and gas velocity in a carbonator.