• 멤브레인
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• 제21권3호
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• pp.236-246
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• 2011

본 연구에서는 기공의 크기가 $0.4{\mu}m$의 소수성 막인 폴리에틸렌 100가닥으로 모듈을 제작하여 직접접촉식과 동반기체식 막증류 과정에서 막의 양단의 온도차, 공급수의 염분농도, 그리고 냉각수/동반기체의 유량에 대해서 투과수의 플럭스를 측정하였다. 이론적으로는, 동반기체식 막증류는 직접접촉식 막증류 공정의 막의 투과측 표면과 냉각수 사이에 동반 기체층이 추가된 것으로 간주하였다. 이 동반기체층은 새로운 저항층과과 동반기체의 이동중 상변화된 수증기가 손실되는 것이 투과유속을 30% 정도 감소시키게 된다. 물질수지식을 이용하여, 기존의 식과는 다르게 보정계수(${\omega}$)를 넣어 직접접촉식 막증류와 동반기체식 막증류의 이론값을 실험값과 비교 분석하였다.

• KSBB Journal
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• 제31권2호
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• pp.120-125
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• 2016

Two-dimensional cultivation is typically used for cell growth, but the method reduces the characteristics of chondrocytes and stem cells, and limits culture area. Therefore, development of three-dimensional culture method is needed to mimic in vivo environment, improve quality of cells and scale-up efficiently. Improving proliferation and chondrogenesis is available by co-culture of chondrocytes and mesenchymal stem cells (MSCs) that leads to interaction between two kinds of cells. However, the co-culture has problems that permeability of sphere diminishes as aggregate size increased and ratio of two kinds of cells composing each spheres is different. In this work, co-cultivation method using controlled sphere composed of chondrocytes and MSCs was established and enhanced chondrogenesis. Periosteum-derived progenitor cells (PDPCs) that are appropriate for cell therapy source of articular cartilage were used as MSCs. Controlled spheres were formed in the hanging-drop plates and shifted for being induced chondrogenesis in 35-mm non-adhesive culture dishes at a rotation rate of 60 rpm. After inducing chondrogenesis, gene expressions related with chondrogenesis were found to be improved and it was apparent that the utilization of controlled spheres promoted chondrogenesis. As a result, available numbers of cells per unit area were increased and chondrogenic differentiation ability was improved compared to typical two-dimensional culture. This approach shows the potential in cartilage regeneration as it can provide sufficient numbers of chondrocytes.

• 전력전자학회논문지
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• 제18권1호
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• pp.45-53
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• 2013

Fuel cell power system is one of the most promising energy source for the alternative energy because it has unique advantages such as high energy density, no power drop during operation, and feasible to make compact size. However, due to very low response time, fuel cell is difficult to correspond to drastic load changes and start-up operation. For solving these problem, fuel cell power system must include energy storage device such as Li-Poly battery or super capacitor. Therefore, bi-directional DC-DC converter must be required for this storage device and fuel cell-PCS control. This paper presents a design and modeling of the bi-directional DC/DC converter. Firstly, we present modeling the boost and buck mode of the bi-directional converter through both PWM switch model and state space averaging technique. Secondly, in order to minimize output ripple and transient response overshoot, we have two identical DC-DC converters interleaved and adopt two-loop voltage-current controller. The proposed bi-directional DC-DC converter's modeling method and control design have been verified with computer simulation and experimentation.

• 한국응용과학기술학회지
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• 제31권4호
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• pp.623-627
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• 2014

에멀젼은 섞이지 않은 두 물질을 분산시스템으로 혼합시켜 놓은 것이다. 에멀젼의 점도에 영향을 미치는 인자는 유화입자 크기, 연속상 및 분산상 종류, 연속상과 분산상의 비, 유화제 종류 및 유화기기 등 다양한 요소들이 있다. 본 연구에서는 오일 극성도에 따라 에멀젼의 점도 변화를 관찰하였고 이를 유기개념도를 이용하여 해석하였다. 탄화수소계, 에스테르계 및 실리콘계 오일을 사용하여 에멀젼을 제조하여 점도를 측정하였다. 오일 극성도가 높을수록 계면에 위치하는 유화제 및 유화안정제의 양이 적어지기 때문에 점도는 감소하였다. 극성 오일간 극성도를 수치적으로 비교하기 위해 유기개념도 이용하였으며 유기개념도상의 해석과 에멀젼의 점도 측정 결과가 실리콘 오일을 제외하고는 모두 일치하였다.

• Journal of Microbiology and Biotechnology
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• 제18권1호
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• pp.43-47
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• 2008

The nickel and cobalt resistance of Cupriavidus metallidurans CH34 is mediated by the CnrCBA efflux pump encoded by the cnrYHXCBAT metal resistance determinant. The products of the three genes cnrYXH transcriptionally regulate expression of cnr. CnrY and CnrX are membrane-bound proteins, probably functioning as anti-sigma factors, whereas CnrH is a cnr-specific extracytoplasmic functions (ECF) sigma factor. The periplasmic domain of CnrX (residues 29-148) was cloned as a N-terminal His-tagged protein, expressed in Escherichia coli, and purified using affinity chromatography and gel filtration. The molecular mass was estimated to be about 13.6kDa by size exclusion chromatography, corresponding to a monomer. The tetragonal bipyramid crystals were obtained by mixing an equal volume of protein in 50mM Tris-HCl, pH 7.5, 1% glycerol, 100mM NaCl, 1mM DTT, and the reservoir solution of 15% w/v PEG 2000, 100mM lithium chloride at 277K in 2-4 days using hanging drop vapor diffusion. The protein concentration was 24mg/ml. The crystal that diffracted to $2.42{\AA}$ resolution belongs to space group $P4_1\;or\;P4_3$ with unit cell parameters of $a=b=32.14{\AA},\;c=195.31{\AA},\;{\alpha}={\beta}={\gamma}=90^{\circ}$, with one molecule of CnrX in the asymmetric unit.

• Journal of Biosystems Engineering
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• 제42권1호
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• pp.44-55
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• 2017

Background: Heat recovery is one of the prominent ways to save a considerable amount of conventional fossil fuel and minimize its adverse effects on the environment. The rotary heat exchanger is one of the most effective and efficient devices for heat recovery or heat exchanging purposes. It is a regenerative type of heat exchanger, which has been studied and used for many heat recovery purposes. However, regenerative thermal wheels have been mostly used as heat recovery systems in buildings. For modeling a rotary regenerator, it is very important to numerically consider all the factors involved, such as effectiveness, rotational speed, geometrical size and shape, and pressure drop (${\Delta}p$). In recent times, several researchers have actively studied the rotary heat exchangers, both theoretically and experimentally. Reviews: In this paper different advances in the numerical modeling of regenerative rotary heat exchangers in relation to fluid flow and heat transfer have been discussed. Researchers have indicated that the effectiveness of the regenerative rotary heat exchanger depends on various factors including, among many others, rotational speed, rotational period and combustion power. It is reported that with the increase of periodic rotation the deviation of theoretical results from the experimental result increases. The available literature indicates that regenerative heat exchangers are having relatively more effectiveness (60-80%), compared to other heat exchangers. It is also observed that the finite difference method and finite volume methods are mostly used for discretizing the heat transfer governing equations, under some assumptions. Research also indicates that for the effectiveness calculation the ${\varepsilon}-NTU$ method is the most popular and convenient.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.179-185
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• 2014

Average temperature and temperature uniformity in a battery cell are the important criteria of the thermal management of the battery pack for hybrid electric vehicles and electric vehicles (HEVs and EVs) because high power with large size cell is used for the battery pack. Thus, liquid cooling system is generally applied for the HEV/EV battery pack. The liquid cooling system is made of multiple cooling plates with coolant flow paths. The cooling plates are inserted between the battery cells to reject the heat from batteries to coolant. In this study, the cooling plate with U-shaped coolant flow paths is considered to evaluate the effects of coolant flow condition on the cooling performance of the system. The counter flow and parallel flow set up is compared and the effect of flow rate is evaluated using CFD tool (FLUENT). The number of counter-flows and flow rate are changed and the effect on the cooling performance including average temperature, differential temperature, and standard deviation of temperature are investigated. The results show that the parallel flow has better cooling performance compared with counter flow and it is also found that the coolant flow rate should be chosen with the consideration of trade-off between the cooling performance and pressure drop.

• 분석과학
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• 제8권1호
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• pp.17-23
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• 1995

$5.0{\times}10^{-2}M$ $LiClO_4$ 용액 중에서 펄스차이 폴라그래피로 2-mercapto-1-methyl-imidazole(MMI)의 정량방법을 조사하였다. 분석의 최적 조건은 초기전위 -0.9 volt vs. Ag/AgCl, 펄스높이 80mV, 주사속도 2mV/sec, 중간 크기 수은방울이었다. 검정곡선은 $1.0{\times}10^{-7}M$에서 $8.0{\times}10^{-5}M$ 범위까지 좋은 직선성을 보여 주었으며, 검출한계는 $2.2{\times}10^{-9}M$이었다. 이 방법은 다른 첨가제의 방해 없이 항갑상선 치료제 중의 MMI 정량에 응용할 수 있었다.

• 한국농공학회지
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• 제12권4호
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• pp.2078-2083
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• 1970

The purpose of this study is to give the data neccesary for improving the planning of drainage structures, specially inverted siphons, in irrigation channels. With the samples of 15 drainage inlets, one drainage flume, 16 drainage inverted siphons and 6 drainage culverts in the 3 lines of irrigation channel under Chong-Won Irrigation Association, author abtained the following results. 1. It is presumed that design drainage discharge should be determined with some additional reserves, on the basis of the maximum rainfall intensity in local area and the size of drainage area on the topographical map, avoiding the way of eye measure. 2. Location of drainage inlet should be kept away from the place where topography can make lots of wash load, but when unavoidably allowing the inflow into irrigation channel, wash load outlet with even the purpose of drainage, or drainage flume in stead of drainage inlet should be taken account of. 3. It is presumed that drainage flume may be the structure which can perform its function from a structural point of view as far as topography permits. 4. Drainage inverted siphon should be avoided at any place as much as possible; a) In case that location of the siphon would be permitted only at paddy field, drainage area hauing the amount of discharge which requires more than 90cm in diameter could only be allowed. b) In this case, crest elevation of the tank of both inlet and outlet, at least, should not be lower than the surface level of paddy field. c) As far as topography and stratum permit, ratio of depth of outlet tank to head drop should be decreased as much as possible so that discharging efficiency of wash load could increase. d) In case of avoiding the setting of the siphon, irrigation aqueduct, irrigation inverted siphon, or drainage flume should be recommended in accordance with topography. 5. Discharging capability of wash load by drainage culvert appeared to depend hardly upon the diameter of the culvert, but greatly upon the location, specially near village, for there stones and dirts dumped may considerably be piled up. So, a counter plan for that is required.

• 분석과학
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• 제15권3호
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• pp.256-262
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• 2002

평균입자크기가 200 ${\mu}m$인 코디어라이트 분말을 사용하여 다공성 필터를 제조한 후, 진공함침법으로 $V_2O_5$, CuO, $LaCoO_3$ 촉매를 담지시킨 후 NO와 $SO_2$ 기체를 촉매 담지 세라믹필터에 동시 통과시키면서 NOx/SOx의 동시제거효율을 측정하였다. 제조된 다공성 필터의 기공률은 61.6%였고, 압축강도는 12.3 MPa이었으며, 면속도 5 cm/sec에서의 차압은 147 Pa이었다. NO와 $SO_2$의 동시제거효율을 분석해 본 결과, 페로브스카이트계 $LaCoO_3$ 촉매의 동시제거효율이 가장 우수함을 확인하였으며, $LaCoO_3$ 촉매의 NO에 대한 제거효율은 90% 이상, $SO_2$에 대해서는 80% 이상이었다.