• Membrane Journal
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• v.18 no.1
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• pp.53-64
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• 2008

Fouling behavior of polyethylene capillary membranes was examined by measuring the flux of bentonite colloidal suspensions through the cross flow micro filtration. The membrane fouling was due to the three mechanisms: the cake formation on the membrane surface, the standard pore blocking and the complete pore blocking by particles. These mechanisms were simultaneously responsible for the membrane fouling, being significantly governed by the cake filtration. In the total fouling at $1.0kg/cm^2$ TMP condition, the complete blocking was 3.36%, the standard blocking 3.18% and the cake filtration 96.05%. For 1000 ppm feed solution, the complete blocking was 1.71% compared with the standard blocking of 1.90% and the cake filtration of 96.39%. And 96.14% of the total fouling was generated at the initial period of filtration. The cake filtration effect was larger on $0.34{\mu}m$ pore membrane than on $0.24{\mu}m$ pore membrane. With the increase in cross flow velocity, the component fouling decreased by 10.20%, and the ratio of pore blocking to total fouling increased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.171-177
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• 1995

추진기관 연소관 제작시 발생하는 결함등에는 주로 표면결함의 형태의 것이 많은데 연소관 설계시 이러한 결함들의 영향을 고려하는 것이 구조물의 안정성에 있어 중요한 요소가 된다. 따라서 본 논문에서는 연소관에 발생할수 있는 결함들에 대한 파단하중 및 파단압력에 대한 탄성 및 탄소성해석을 통하여 파괴 매개변수인 J적분을 유한요소 프로그램인 ABAQUS를 이용하여 3차원 비선형해석을 수행하여 5가지의 균열모델을 사용하여 평판, 양단개방 압력용기(open tube) 및 양단막힘 압력용기 (closed tube)의 파단하중하에서의 J적분의 영향을 분석하였다. 평판 결함시편의 J적분으로부터 압력용기의 손상허용설계를 할 수 있는 방안을 조사 하였으며 추진기관 연소관에 적용하여 발생가능한 크기의 결함에 대한 안정성을 조사한결과 충분한 안정성을 확보하고 있음을 알수 있었다.

• Membrane Journal
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• v.15 no.1
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• pp.52-61
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• 2005

Permeate flux decline in a microfiltration was analyzed by measuring the permeability of bentonite colloidal solution through polyethylene capillary membranes. The flux decline with time was due to the growth of cake layer on the membrane surface and to the pore blocking by particles. As the time approaches to steady state, the permeate flux is almost controlled by the cake filtration model. Faster flux decline at high trans-membrane pressure was attributed to the formation of denser packed cake layer and pore blocking. The ratio of permeate flux to the initial permeate flux, J/J₁, decreased with increasing the trans-membrane pressure, from 45% for 0.5 kg/sub f//㎠ to 38% for 2.0 kg/sub f//㎠. In comparing the ratio of each fouling component to the total fouling for the 0.5 kg/sub f//㎠ TMP condition, complete blocking was 23.4%, standard blocking was about 14.6% and cake filtration was 62.0%, respectively. Permeate flux through the membrane increases with cross flow velocity, and the effect of the variation of velocity is more significant at 1.0 kg/sub f//㎠ rather than at 2.0 kg/sub f//㎠ of the operation pressure. Permeate flux for the membrane having the average pore diameter of 0.34 ㎛ was higher than that for the membrane of 0.24 ㎛ pore size, with the higher flux with the low concentration of feed. On the operation using the membrane of 0.34 ㎛ pore, the pore blocking in the low concentration of 200 ppm is negligible relative to the pore blocking in the 1000 ppm feed.

• Clinical and Experimental Pediatrics
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• v.45 no.3
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• pp.295-301
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• 2002

미세혈관의 모든 분절(세동맥, 모세혈관, 세정맥)에 있는 내피세포의 기능은 허혈-재관류(ischemia-reperfusion)에 노출시 장애가 발생하게 되는데, 세동맥에서는 혈관확장 능력이 떨어지고, 모세혈관에서는 체액 여과 및 백혈구에 의한 혈관의 막힘(leukocyte plugging)이 증가되며, 세정맥에서는 백혈구-내피세포 접착(leukocyte-endothelial cell adhesion)과 단백의 혈관 외 누출이 증가한다. 활성 산소(reactive oxygen species)와 nitric oxide의 생산의 불균형은 이들 반응을 촉진시키며, 심혈관 질환의 위험 인자인 hypercholesterolemia, 당뇨병, 고혈압 등은 I/R에 대한 미세혈관 반응을 더욱 악화시킨다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.5
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• pp.428-432
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• 2012

In the waste collection system, living waste is collected through the piping network. There are many confluent pipes in a piping network. These confluent pipes were often clogged up with waste. The optimal configuration of the confluent pipes has been defined by the design guide. However, nobody know how this design guide were determined. Therefore, in this paper, we found the design data for the confluent pipe configuration in order to avoid the waste clogging in a piping network. The distance between connected point on the confluent pipes should be longer than the previous design guide.

• Membrane Journal
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• v.15 no.4
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• pp.338-348
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• 2005

The permeate flux decline on microfiltration capillary membrane operation was investigated with inorganic colloidal solutions. The permeate flux of the alumina solution is two times higher in average than that of the bentonite solution. The flux decline with increase in operation time was less in the alumina solution than in the bentonite solution. The rate of initial flux decline until 10 min was higher on the bentonite solution over the alumina solution. The decline in permeate flux was due to both the cake formation and the pore blocking. The latter effect was higher in the operation of the bentonite solution. In comparing the ratio of each fouling component to the total fouling fur the $1.0\;kg_f/cm^2$ TMP condition, complete blocking was $9.35\%$, standard blocking was about $6.82\%$ and cake filtration was $83.83\%$, respectively. With the increase in cross flow velocity, the permeate flux increased by $6.0\%$ for the alumina solution and by 14.0 for the bentonite solution. With the increase in average pore size fromm $0.24\;{\mu}m\;to\;0.34\;{\mu}m$, the permeate flux increases 1.61 times for the alumina solution and 1.76 times far the bentonite solution.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.590-595
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• 2008

A new adaptive TMS variable area flow meter that is used to the environment measuring equipment is proposed. This system is consist of a ball moving within the tube line which corresponds to gas flow and photo sensor array which monitoring the movement of ball. This system can monitoring the position of bali in case of the very few gas flow in various levels. And it can automatically adjust the gas flow at the highest and the lowest level to prevent the tube line blockage.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.948-954
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• 2008

Membrane bioreactor(MBR) processes have been widely applied to wastewater treatment for last decades due to its excellent capability of solid-liquid separation. However, membrane fouling was considered as a limiting factor in wide application of the MBR process. Excess aeration into membrane surface is a common way to control membrane fouling in most MBR. However, the excessively supplied air is easily dissipated in the reactor, which results in consuming energy and thus, it should be modified for effective control of membrane fouling. In this study, cylindrical tube was introduced to MBR in order to use the supplied air effectively. Membrane fibers were immersed into the cylindrical tube. This makes the supplied air non-dissipated in the reactor so that membrane fouling could be controlled economically. Two different air supplying method was employed and compared each other; nozzle and porous diffuser which were located just beneath the membrane module. Transmembrane pressure(TMP) was monitored as a function of airflow rate, flux, and ratio of the tube area and cross-sectioned area of membrane fibers(A$_m$/A$_t$). Flow rate of air and liquid was regulated to obtain slug flow in the cylindrical tube. With the same flow of air supply, nozzle was more effective for controlling membrane fouling than porous diffuser. Accumulation of sludge was observed in the tube with the nozzle, if the air was not suppled sufficiently. Reduction of membrane fouling was dependent upon the ratio, A$_m$/A$_t$. For diffuser, membrane fouling was minimized when A$_m$/A$_t$ was 0.27, but 0.55 for nozzle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.633-643
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• 2015

In this study, we develop a highly efficient conical-air diffuser that generates fine bubble. By inserting a sufficient number of aerotropic microorganisms with dissolved oxygen from an air diffuser and minimizing the air-channel blockages within the air diffuser, we expect to improve the efficiency and durability of the decomposition process for organic waste. To upgrade the conventional air diffuser, we perform experiments and numerical analysis to develop a conical-type that generates fine bubble, and which is free from nozzle blockage. We complement the air-diffuser design by numerically analyzing the internal air-flow pattern within the diffuser. Then, by applying the diffuser to a mockup bioreactor, we experimentally and numerically study the bubble behavior observed in the diffuser and the 2-phase fluid flow in the bioreactor. The results obtained include statistics of the cord length and increased velocity, and we investigate the mechanisms of the fluid-flow characteristics including bubble clouds. Throughout the study, we systemize the design procedures for the design of efficient air diffusers, and we visualize the fluid-flow patterns caused by bubble generation within the mockup bioreactor. These results will provide a meaningful basis for further study as well as the detection of oxygen transfer and fluid-flow characteristics in real-scale bio-reactors using sets of air diffusers.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.331-337
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• 2016

Radial collector wells (RCWs) have been managed by Korea Rural Community Corporation (KRC) since 1983, installing 98 wells for agriculture in rural area over the country. Among them, 20 wells were installed upstream of 5 subsurface dams and the remaining were installed regardless of the subsurface dam. Most of RCWs have been developed in 1980s and 1990s, and 83 wells have been passed more than 20 years after construction. The number of horizontal arms for RCWs varies from 9 to 28, with length and diameter being 10~30 m and 65 mm, respectively. The central caisson with an inner diameter of 3.5 m was commonly constructed to a depth of 10 m. The maximum pumping rates in RCWs, which are located at distances of 10 to 1,200 m from the river, are 2,000~10,000 m³/day. RCW has a fundamental problem that reduced pumping capacity and degraded well efficiency, due to the physical and chemical clogging. From the feasibility test for improving RCW performance, specific capacity increased to 67% after rehabilitation. TV logging for RCW horizontal arm shows that near the caisson is more severe clogging. From the results of this study, KRC has established the guidebook for monitoring and improving well efficiency through physical/chemical treatment, well logging, and hydraulic tests and managed RCWs periodically with its rehabilitation methods.