• 한국가구학회지
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• 제28권3호
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• pp.248-258
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• 2017

A study was carried out to observe the 1% aqueous safranine solution flow speed in longitudinal and radial directions of softwood Thuja orientalis L., diffuse-porous wood Gmelina arborea Roxb., and ring-porous wood Phellodendron amurense Rupr., Longitudinal flow was considered from bottom to top while the radial flow was considered from bark to pith directions. In radial direction, ray cells and in longitudinal direction tracheids, vessel and wood fiber were considered for the measurement of liquid penetration speed at less than 12% moisture contents(MC). The variation of penetration speed for different species was observed and the reasons behind for this variation were explored. The highest radial penetration depth was found in ray parenchyma of T. orientalis but the lowest one was found in ray parenchyma of P. amurense. The average liquid penetration depth in longitudinal trachied of T. orientalis was found the highest among all the other cells. The penetration depth in fiber of G. arborea was found the lowest among the other longitudinal cells. It was found that cell dimension and also meniscus angle of safranine solution with cell walls were the prime factors for the variation of liquid flow speed in wood. Vessel was found to facilitate prime role in longitudinal penetration for hardwood species. The penetration depth in vessel of G. arborea was found highest among all vessels. Anatomical features like ray parenchyma cell length and diameter, end-wall pits number were found also responsible fluid flow differences. Initially liquid penetration speed was high and the nit gradually decreased in an uneven rate. Liquid flow was captured via video and the penetration depths in those cells were measured. It was found that even in presence of abundant rays in hardwood species, penetration depth of liquid in radial direction of softwood species was found high. Herein the ray length, lumen area, end wall pit diameter determined the radial permeability. On the other hand, vessel and fiber structure affected the longitudinal flow of liquids. Following a go-stop-go cycle, the penetration speed of a liquid decreased over time.

• 멤브레인
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• 제31권5호
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• pp.343-350
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• 2021

본 연구에서는 다공성 중공사형 분리막(multi-bore capillary membrane module)을 생물막 반응기(MBR)에 침지시켜 운전시간에 따른 흡입 압력을 측정하였다. 공칭 세공크기가 0.2㎛, 외경이 6.4 또는 4.2 mm이고 육각 형태인 중공사형모듈을 MLSS 8,000 mg/L 활성 슬러지 수용액에 각각 침지시키고 투과 유속, 공기량에 따른 변화를 확인하였다. 여과운전/정지이완(FR) 및 정지이완 시 역세척(FR/BW) 및 사인파형 투과유속 연속운전(SFCO) 방식으로 조작하였다. SFCO의 흡입 압력은 30 L/m²·hr에서 낮았으며, 50 L/m²·hr에서는 FR의 흡입 압력이 높게 나타났다. 또한 외경이 작은 모듈의 흡입 압력 상승이 비교적 낮았으며, 외경이 큰 모듈의 흡입 압력은 높게 상승하였지만 역세척으로 40% 이상 감소시킬 수 있었다.

• 대한화학회지
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• 제20권3호
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• pp.173-184
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• 1976

鋼製毛細管粘度計를 제작하여 윤활유의 流動性質을 연구하였다. 使用한 윤활유는 bentone 윤활유(thickener의 무게 농도 2.0, 4.0, 6.0, 8.0 및 $10.0{\%}$)와 Lime-soap윤활유(thickener의 무게농도 2.4, 7.0, 9.3, 12.1 및 15.2%)이었다. Lime-soap윤활유의 流動性質에 對하여 resident-time(毛細管內에 윤활유가 殘留하는 時間) 效果를 硏究하기 위하여 半徑(R)과 길이(L)를 달리하는 各種毛細管을 使用하였다. 그러나 bentone 윤활유의 流動性質의 仔細한 硏究를 위하여서는 單一種의 毛細管을 使用하였다. 實驗結果(流出量對 shear 速度)에 對하여 Ree-Eyring 式에 나타나는 $X_1{\beta}_1/{\alpha}_1$(Newton 單位에 對한 量), $X_2/{\alpha}_2$ 및 ${\beta}_2$(非 Newton 單位에 對한 量) 等의 係數가 thickener 농도와 溫度에 對하여 어떻게 變化하는가를 보았다. 이 硏究의 分析結果에 依하면 ${\Delta}H_1^{\neq}$와 ${\Delta}H_2^{\neq}$(각각 流動單位 type1과 type2의 流動活性化엔탈피)가 溶媒(base oil)의 流動活性化엔탈피(${\Delta}H_b^{\neq}$)에 近似的으로 一致한다. 이 事實로부터 thickener의 流動單位 (type 1, type 2 공히)는 溶媒分子의 移動으로 因하여 장만된 小孔에 뛰어드러감으로써 全體系의 流動이 이루어짐을 알 수 있다. Bentone 윤활유에 대하여 ${\beta}_2$는 어느 주어진 溫度에 있어서 thickener 농도에 無關함을 알아냈으니 이것은 旣往文獻에 發表된 事實과 一致한다. 殘留時間效果를 lime-soap 윤활유에 對하여 보려고 詩圖하였으나 그 結果는 分明하지 않았다. 그 理由는 lime-soap 윤활유 自身의 性質에도 依存하지만 著者들의 使用한 毛細管의 L/R 値(殘留時間에 比例하는 常數)가 너무 적었음에 原因이 있다고 생각된다.

• Journal of Nutrition and Health
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• 제11권1호
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• pp.33-37
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• 1978

The effect of heating time (0 to 30 hours at $180{\pm}5^{\circ}C$) on the change of flow properties, fatty acid compositions and some other characteristics such as acid value, iodine value, peroxide value and density of purified edible rice bran oil were observed. flow properties were measured with Maron-Belner type capillary viscometer. Newtonian motion was observed in non-heated oil and the oil heated for 5 hours but non-Newtonian motion was observed in the oil heated for more than 10 hours and at high shear stress. The fatty acid compositions were analyzed by gas liquid chromatography and all the components of fatty acids were reduced in amounts with extention of heating time. The acid value, peroxide value and density were increased but iodine value were decreased with extension of heating time.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1475-1483
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• 2004

Loop thermosyphon(LTS) has many good characteristics such as low thermal resistance, no power consumption, noiseless operation and small size. To investigate the overall performance of LTS, we have performed various experiments varying three parameters: input power of the heater, working fluid(water, ethanol, FC3283) and filling ratio of the working fluid. At a combination of these parameters, temperature measurements are made at many locations of the LTS. The temperature difference between the evaporator and the condenser is used to obtain the thermal resistance. In addition, flow visualization using a high speed camera is carried out. The thermal resistance is not constant. It is lower at higher input power, which is one of the distinct merits of LTS. Flow instabilities are frequently observed when changing the working fluid, the input power and the filling ratio. The results show that the LTS can be readily put into practical use. Future practical application in electronic cooling is recommended.

• 설비공학논문집
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• 제18권4호
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• pp.304-311
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• 2006

Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

• Korea-Australia Rheology Journal
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• 제20권3호
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• pp.109-116
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• 2008

The effect of intermolecular aggregation induced by hydrophobic and electrostatic interactions on shear and elongational flow properties of aqueous acrylic thickener solutions is discussed. Complex shear modulus is determined at frequencies up to $10^4$ rad/s employing oscillatory squeeze flow. Extensional flow behavior is characterized using Capillary Break-up Extensional Rheometry. Aqueous solutions of poly(acrylic acid)(PAA)/poly(vinylpyrrolidone-co-vinylimidazole) (PVP-VI) mixtures exhibit unusual rheological properties described here for the first time. Zero-shear viscosity of the mixtures increases with decreasing pH and can exceed that of the pure polymers in solution by more than two orders of magnitude. This is attributed to the formation of complexes induced by electrostatic interactions in the pH range, where both polymers are oppositely charged. PAA/PVP-VI mixtures are compared to the commercial thickener Sterocoll FD (BASF SE), which is a statistical co-polymer including (meth) acrylic acid and ethylacrylate (EA) forming aggregates in solution due to "sticky" contacts among hydrophobic EA-sequences. PAA/PVP-VI complexes are less compact and more deformable than the hydrophobic Sterocoll FD aggregates. Solutions of PAA/PVP-VI exhibit a higher zero-shear viscosity even at lower molecular weight of the aggregates, but are strongly shear-thinning in contrast to the weakly shear-thinning solutions of Sterocoll FD. The higher ratio of characteristic relaxation times in shear and elongation determined for PAA/PVP-VI compared to Sterocoll FD solutions reflects, that the charge-induced complexes provide a much stronger resistance to extensional flow than the aggregates formed by hydrophobic interactions. This is most likely due to a break-up of the latter in extensional flow, while there is no evidence for a break-up of complexes for PAA/PVP-VI mixtures. These flexible aggregates are more suitable for the stabilization of thin filaments in extensional flows.

• 한국식품과학회지
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• 제16권1호
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• pp.29-36
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• 1984

5 wt% 쌀전분 현탁액 및 호화된 쌀전분 $3{\sim}9wt%$ 용액을 시료로 한 쌀전분 수용액계의 유동거동을 $30{\sim}80^{\circ}C$ 범위에서 관형 리오메타를 사용하여 조사였다. 생전분의 현탁액은 딜라탄트유체거동을 보인 반면 호화액은 농도증가에 따라 의가소성으로부터 빙햄의 가소성의 유동거동을 보였다. 호화액의 유동거동지수 값은 모든 시료에서 약 1.2정도였으며 현탁액에서는 $0.87{\sim}0.90$범위였다. 3 및 5 % 호화액에서는 항복응력값을 무시할수 있었으나 이들 농도이상에서는 무시할 수없는 정도였고 농도증가에 따라 증가하였다. 점조도 지수값은 지수함수식에 따르는 농도 및 온도의존성을 나타내었다. 쌀전분 수용액계의 $30{\sim}80^{\circ}C$에서 측정한 활성화에너지는 현탁액과 호화액에서 각각 $0.13{\sim}2.71$ 및 $5.39{\sim}9.57\;Kcal/g\;mole$ 범위였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권3호
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• pp.140-150
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• 2007

A simple, label-free microfluidic cell purification method is presented for separation of cancer cells by exploiting difference in cell adhesion. To maximize the adhesion difference, three types of polymeric nanostructures (50nm pillars, 50nm perpendicular and 50nm parallel lines with respect to the direction of flow) were fabricated using UV-assisted capillary moulding and included inside a polydimethylsiloxane (PDMS) microfluidic channel bonded onto glass substrate. The adhesion force of human breast epithelial cells (MCF10A) and human breast carcinoma (MCF7) was measured independently by injecting each cell line into the microfluidic device followed by culture for a period of time (e.g., one, two, and three hours). Then, the cells bound to the floor of a microfluidic channel were detached by increasing the flow rate of medium in a stepwise fashion. It was found that the adhesion force of MCF10A was always higher than that of MCF cells regardless of culture time and surface nanotopography at all flow rates, resulting in a label-free detection and separation of cancer cells. For the cell types used in our study, the optimum separation was found for 2 hours culture on 50nm parallel line pattern followed by flow-induced detachment at a flow rate of $300{\mu}l/min$.

• 대한기계학회논문집
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• 제12권5호
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• pp.1189-1196
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• 1988

본 연구에서는 내경이 각각 8.5mm와 10.3mm이며 무차원길이가 각각 710과 1158인 두 개의 시험관을 사용하는 유동장치를 제작하여 시험관 입구에서부터 유체역 학적 경계층(hydrodynamic boundary layer)과 열적 경계층(thermal boundary layer)이 동시에 발달하기 시작하는 경계조건을 형성하고 관벽에서 일정한 열 플럭스(constant heat flux)를 발생하는 조건을 부여하였다. 퇴화현상(degradation)에 대하여 비교적 안정성을 가진 폴리아크라마이드(polyacrylamide) Separan Ap273을 수도물에 용해하여 제조한 폴리머용액으로 유동특성과 열전달특성을 실험하여 열적입구길이와 열전달특성 을 규명하고자 한다.