• Journal of Pharmaceutical Investigation
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• 제37권5호
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• pp.275-280
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• 2007

A rapidly disintegration famotidine tablet formulation in the oral cavity was developed using microcrystalline cellulose (MCC) and low-substituted hydroxypropyl cellulose (L-HPC), or additionally cropovidone as an internal disintegrant. Effects of disintegrants on the disintegration time in vitro and hardness were evaluated. Average wetting time of the tablets prepared in scale-up manufacturing process was less than 15 sec. Among the formulations tested, the tablet prepared with crospovidone as an internal disintegrant and Emcocel $90M^{(R)}$ as an external disintegrant showed fastest disintegration. These results may suggest that crospovidone and Emcocel $90M^{(R)}$ possessed excellent wetting nature, which result in the rapid disintegration of tablet.

• 한국유체기계학회 논문집
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• 제18권6호
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• pp.27-30
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• 2015

In this study, we attempted to harvest energy using water droplet based on Reverse Electro Wetting On Dielectric (REWOD) phenomenon between water droplet and dielectric surface without external bias. REWOD device can be fabricated via simple coating process, which is highly economic and easy. We believe that our system is well-suited for IoT(Internet of Things) embedded electronics that require low but consistent electricity. Moreover, our device can be integrated with window to generate electricity upon raindrops.

• 한국분무공학회지
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• 제17권1호
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• pp.9-13
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• 2012

This study investigates experimentally evaporation characteristics of nanofluid droplets containing 50 nm alumina($Al_2O_3$) particles and the wettability changes on a hydrophilic glass surfaces. From the captured digital images by using a CMOS camera and a magnifying lens, we examined the effect of particle concentration on droplet evaporation rate which can be indirectly deduced from the measured droplet volumes varying with time. In particular, with the use of a digital image analysis technique, the present study measured droplet perimeters and the contact angles to study the wetting dynamics during evaporating process. In addition, we compared the measured total evaporation time with theoretically estimated values. It was found that as the volume fractions of nanofluid increased, the total evaporation time and the initial contact angles decreased, while the droplet perimeters increased.

• 한국재료학회지
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• 제5권2호
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• pp.191-196
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• 1995

비정질 PEEK 필름의 self-bonding강도는 접합시의 공정변수(시간, 온도, 그리고 압력)와 밀접한 관계가 있다. 본 연구에서는 이러한 공정변수의 효과를 규명하기 위하여 각기 다른 접합조건하에서 개발된 시편들의 self-bonding강도를 single lap-shear test를 통하여 측정된 각각의 전단 응력(shear strength)으로 나타내었다. 개발된 self-bonding강도는 접합온도가 증가함에 따라 증가하였으며, 접합시간의 1/4승에 일차함수적으로 비례증가하였다. 접합공정 중의 압력의 효과는 단지 초기 접합단계인 wetting에 기여하였을 뿐 self-bonding강도 자체에는 거의 영향을 미치지 않는 것으로 사려되었다. 결론적으로 비정질 PEEK 필름의 self-bonding현상은 현장에서의 실제 접합공정에서 어떠한 접착재료의 사용없이도 모재와 같은 강도를 개발하는데 무한한 가능성이 있는 것으로 판단되었다.

• 상하수도학회지
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• 제22권6호
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• pp.681-687
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• 2008

It is well known that the water infiltration rate depends on soil properties such as soil water content, water head, capillary suction, density, hydraulic conductivity, and porosity. However, most of proposed infiltration models assume that the air phase is continuous and in equilibrium with the atmosphere or air compression and air entrapment on infiltration was not considered. This study presents experimental results on unsaturated water infiltration to relate air entrapment and hydraulic conductivity function based on soil air properties. The objectives of this study were to measure change of soil air pressure ahead of wetting front under air drain and air confined condition to find the confined air effect on infiltration rate, to reduce the entrapped air volume related with soil air pressure to increase the soil permeability, and to make a basis of infiltration process model for the purpose of improvement of infiltration rate in the homogeneous soil column. The results of the work show that soil air pressure increases according to increasement of the saturated soil depth rather than the wetting front depth during infiltration process.

• Corrosion Science and Technology
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• 제7권5호
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• pp.243-251
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• 2008

Magnesium alloys become popular research topic in last decade due to its light weight and relatively high strength-to-weight ratio in the energy aspiration age. Almost all structure materials are supposed to suspend stress. Magnesium is quite sensitive to corrosive environment, and also sensitive to environmental assisted cracking. However, so far we have the limited knowledge about the environmental sensitive cracking of magnesium alloys. The corrosion fatigue (CF) test was conducted. Many factors' effects, like grain size, texture, heat treatment, loading frequency, stress ratio, strain rate, chemical composition of environment, pH value, relative humidity were investigated. The results showed that all these factors had obvious influence on the crack initiation and propagation. Especially the dependence of CF life on pH value and frequency is quite different to the other traditional structural metallic materials. In order to interpret the results, the electrochemistry tests by polarization dynamic curve and electrochemical impedance spectroscopy were conducted with and without stress. The corrosion of magnesium alloys was also studied by in-situ observation in environmental scanning electron microscopy (ESEM). The corrosion rate changed with the wetting time during the initial corrosion process. The pre-charging of hydrogen caused crack initiated at $\beta$ phase, and with the increase of wetting time the crack propagated, implying that hydrogen produced by corrosion reaction participated in the process.

• 한국기계가공학회지
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• 제18권11호
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• pp.35-40
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• 2019

Laser processing has been used in various fields. In this study, the feasibility of a hydrophobic surface was investigated through the laser cladding technique. A diode laser was used, and the output was set to 600-800 W. Seven different specimens were prepared with different cladding widths and spacings, and the contact angles for water droplets were evaluated. As a result, the contact angle of water droplets measured in the direction parallel to the cladding line was higher than that in the vertical direction. The wider the cladding width and the cladding space, the higher the contact angle in the parallel direction. It is thought that when a higher contact angle is formed in the parallel direction, more air can be placed in the valley between the cladding lines. In addition, for the hydrophobic coating effect, the contact angle of the coated cladding surface was increased by about $5-15^{\circ}$ as a whole compared to the coated smooth surface. It was confirmed that the wetting characteristics were improved through the cladding.

• 대한조선학회논문집
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• 제29권1호
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• pp.71-80
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• 1992

국제수조회의(ITTC) 내항성분과에서 회귀현상(rare event)레 대한 시험기법 확립 및 계측기간 결정을 목적으로 19차 ITTC 내항성분과의 공동사업으로 갑판침수 계측시험을 수행한 바 있다. 본 논문에는 공동연구에 참여한 수조시험연구회(KTTC)의 두 회원인 해사기술연구소(KRISO)와 현대선박해양연구소(HMRI)의 실험방법 및 결과를 비교 검토하였다. 선수상대운동과 갑판침수 사이의 상관관계 및 Poisson process에 근거한 계측시간의 추정에 촛점을 두어 결과를 고찰하였다. 동일한 특성을 갖는 입사파에 대해 계측된 갑판침수 빈도수는 두 기관 모두 계측시마다 큰 차이를 보였으며 이는 일반적인 선체운동 계측 보다 더 많은 계측시간이 필요한 것을 의미한다. 선수상대운동과 갑판침수사이의 상관관계는 선수형상, 선속 및 해상상태에 따라 달라지며 본 공동연구의 실험 조건하에서는 (유의파고 7.88m, 선속 22.15노트) 둘 사이의 상관관계가 매우 높은 것으로 나타났다. 또한 갑판침수 현상의 통계적 특성은 Poisson process로 해석될 수 있음을 보였다.

• 한국지반공학회논문집
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• 제21권5호
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• pp.59-64
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• 2005

불포화토를 연구하는데 있어 함수특성곡선과 투수계수방정식을 결정하는 것은 필수요소이나 이는 쉬운 일이 아니다. 본 연구에서는 함수특성곡선과 투수계수방정식을 얻기 위한 새로운 시험장치가 개발되었다. 개발된 시험장치를 사용하여 두 종류의 토사에 대해 포화투수계수시험과 함수특성곡선을 결정하기 위한 시험을 실시하였다. 시험진행순서는 먼저 포화투수계수시험을 실시한 후, 함수특성곡선의 건조과정에 대한 시험을 실시하고 다음으로 함수특성곡선의 습윤과정에 대한 시험순으로 진행하였다. 시험결과에 의하면 건조과정의 함수특성곡선과 습윤과정의 함수특성곡선 간에는 이력현상이 존재함을 알 수 있었다. 투수계수방정식의 결정은 시험으로부터 얻어진 포화투수계수와 함수특성곡선 이용하여 구하는 이론적인 방법을 사용하였다.

• Tribology and Lubricants
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• 제35권1호
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• pp.9-15
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• 2019

Graphene is a fascinating material for fabricating flexible and transparent devices owing to its thickness and mechanical properties. To utilize graphene as a core material for devices, the transfer process of graphene is an inevitable step. The transfer process can be classified into wet and dry methods depending on the surrounding environment. The adhesion between graphene and a target substrate determines the success or failure of the transfer process. As the surface energy of graphene is an important parameter that provides adhesion, it is useful to estimate the surface energy to understand the mechanisms of the transfer process. However, the exact surface energy of graphene is still disputed because the wetting transparency of graphene depends on the polarity of the liquid and target substrate. Previously reported results use graphene transferred by the wet method. However, there are few reports on the surface energy of graphene transferred by the dry method. In this study, the surface energy of graphene transferred by the wet and dry methods is estimated. Wetting transparency occurs for certain combinations of liquids and substrates. For graphene on a polar substrate, the surface energy decreases by 25 and 35% for the wet and dry transfer methods, respectively. However, the surface energy of graphene on dispersive substrates decreases by ~10% regardless of the transfer method. In conclusion, the surface energy of graphene is $36{\sim}38mJ/m^2$, and differs depending on the transfer method and polarity of the substrate.