• 한국환경과학회지
• /
• 제25권7호
• /
• pp.927-935
• /
• 2016

Dissolved oxygen is necessary for many biological processes as well as many industrial practices. Dissolved oxygen released from water in dissolved air flotation (DAF) systems can be have many different applications. However, DAF systems are very costly to operate. To develop more efficient DAF systems, a deeper understanding of the process of oxygen being released from water is required. In this study, molecular dynamics (MD) simulations were used to simulate 100 oxygen molecules surrounded by 31002 water molecules at temperatures ranging from $0^{\circ}C$ to $100^{\circ}C$. Simulations were carried out for 10 ns, during which, in most cases, all the oxygen molecules were released from the water droplet. With MD simulations, visualization of the molecules escaping the water droplet was possible, which aided the understanding of the interactions between molecules at the nano-scale. The results showed that as the oxygen molecules moved near the edge of the water droplet that the oxygen molecules hesitated before escaping the water droplet or returned to the interior of the water droplet. This was because of the attractive forces between the water and oxygen molecules. Moreover, after most of the oxygen molecules were released from the droplet, some were found to return to the droplet's edge or even the interior of the droplet. It was also confirmed that oxygen molecules were released at a faster rate at higher temperatures.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2006년도 Asia Navigation Conference
• /
• pp.157-165
• /
• 2006

In February,2004, at International Maritime Organization (IMO), LONDON, a new international convention 'International Convention fur the Control and Management of Ship's Ballast Water and Sediment 2004' was adopted. It is called 'Ballast Water Management Convention (BWM)'. Ballast water means charged seawater or fresh water in ship's special tanks (ballast tank) to keep safety navigation and ship's maneuverability. However, from 1980, it was point out the serious problem for marine ecosystem and human life that ballast water includes harmful marine species (and small organisms) and these species are also discharged along with ballast water. These species were released with discharged ballast water in water areas, where species are different from discharged ballast water. The problem is that released species increase when released species are more powerful than native species and consequently, marine ecological system is destroyed in released water area. Authors have inspected the validity of the ballast water exchange using pumping-through method that is one of the methods of ballast water management. In this paper, the numerical simulation of the motion and density of the fluid at the time of exchange of the fluid in a 2-dimensional tank using the pumping-through method was carried out by using two different type numerical methods. One method is MPS method that is one of the particle methods. Other one is Finite Different Method (FDM). Authors were compared with result of two numerical method calculations and experiment result and reported some knowledge from these results.

• 한국태양에너지학회 논문집
• /
• 제37권5호
• /
• pp.39-47
• /
• 2017

In a hot water system using solar energy, solar heat is not simply collected by the heat collecting plate, but by heat exchange between the solar collector (flat or vacuum type) and the hot water storage tank. Therefore, the amount of collected solar energy depends on the hot water usage patterns that determine the temperature of the thermal storage tank. Also, if the temperature of the hot water stored in the storage tank exceeds the dangerous temperature during the summer, the heat must be released for safety. If the temperature of the hot water in the storage tank is low, it is necessary to heat by the auxiliary heat source. In this study, three buildings are defined as hotel, swimming pool, and school facilities. And we calculated the released heat energy, auxiliary heat source, and pure storage heat energy based on different hot water usage patterns and installation angle of the solar collectors.

• 한국환경과학회지
• /
• 제11권12호
• /
• pp.1333-1337
• /
• 2002

A significant fraction of nutrients, such as nitrogen and phosphorus released from sediment are utilized by primary production in the shallow water of coast and lake. The purpose of this study is to introduce the mechanism of nutrients release from sediment and to introduce the methods of the measurement of nutrient released from sediment. One approach is to calculate nutrients released from sediment by a concentration gradient between sediment pore waters and overlying water based on the Fick's law. The other approaches of measurement are the undisturbed sediment core experiments and measurement of nutrient released from sediment by the in situ chamber equipment.

• Journal of the Korean Wood Science and Technology
• /
• 제33권3호통권131호
• /
• pp.53-63
• /
• 2005

본 연구는 바다목장사업 소재로서 방부처리 목재의 사용 가능성에 대한 기초자료를 얻고자 실시하였다. CCA, CCFZ, ACQ 처리재 내 포함된 유해 중금속의 해수에 대한 용탈 안전성을 평가하기 위해 각각 2% 및 3% 방부제 수용액으로 처리한 목재를 증류수, 자연해수 및 인공적으로 염도를 조절한 인공해수에 41일간 폭로하여 기간 별 각 성분의 용탈량을 측정하였다. 바닷물에서 CCA 처리재의 구리 및 크롬의 용탈은 거의 일어나지 않았으며, 다소 많은 비소의 용탈이 있었으나 증류수에서의 용탈에 비해 적은 양을 나타내었다. CCFZ는 증류수에서 크롬과 아연의 용탈량이 매우 높았으나 바닷물에서는 훨씬 적은 용탈량을 나타내었다. 방부제 흡수량 및 인공해수의 염분 농도에 따른 용탈량에는 큰 차이가 없었다. ACQ 처리재는 CCA 및 CCFZ 처리재에 비해 많은 구리 용탈을 나타내었으며 용탈 매체에 따른 차이는 나타나지 않았다.

• 한국수산과학회지
• /
• 제36권4호
• /
• pp.365-371
• /
• 2003

The reared fries of black sea bream, Acanthopagrus schlegeli were released in Gamak Bay and initial adaptation to the environment was evaluated. Thirty thousand fries were marked with magnetic tag, released and recaptured and its stomach content were analysed; the neighboring zooplankton, beuthic algae and other young fishes were investigated. The fries were released on July 30, 2001 in summer season. Water temperature of surface and bottom were $24^{\circ}C\;and\;21^{\circ}C,$ respectively. $Chlorophyll\;\alpha$ content was 4.5 ${\mu}g/L$ with high primary production. Salinity was $32.0-32.5\%_{\circ}.$ Water depth of releasing site was about 30 m. The sea jungle was formed at the first point of releasing and it kept the fries for about 3 days in the bay with plenty of food organisms within 5 m depth. Stomach analysis of the fries revealed that real feeding started from the 15 days after releasing and full feeding took place after the tenth day.

• 한국세라믹학회지
• /
• 제51권6호
• /
• pp.584-590
• /
• 2014

Air-cooled slag showed grindability approximately twice as good as that of water-cooled slag. While the studied water-cooled slag was composed of glass as constituent mineral, the air-cooled slag was mainly composed of melilite. It is assumed that the sulfur in air-cooled slag is mainly in the form of CaS, which is oxidized into $CaS_2O_3$ when in contact with air. $CaS_2O_3$, then, is released mainly as $S_2O{_3}^{2-}$ion when in contact with water. However, the sulfur in water-cooled slag functioned as a constituent of the glass structure, so the$S_2O{_3}^{2-}$ ion was not released even when in contact with water. When no chemical admixture was added, the blended cement of air-cooled slag showed higher fluidity and retention effect than those of the blended cement of the water-cooled slag. It seems that these discrepancies are caused by the initial hydration inhibition effect of cement by the $S_2O{_3}^{2-}$ ion of air-cooled slag. When a superplasticizer is added, the air-cooled slag used more superplasticizer than did the blast furnace slag for the same flow because the air-cooled slag had higher specific surface area due to the presence of micro-pores. Meanwhile, the blended cement of the air-cooled slag showed a greater fluidity retention effect than that of the blended cement of the water-cooled slag. This may be a combined effect of the increased use of superplasticizer and the presence of released $S_2O{_3}^{2-}$ ion; however, further, more detailed studies will need to be conducted.

• Archives of Pharmacal Research
• /
• 제26권5호
• /
• pp.426-431
• /
• 2003

This study was carried out to investigate the addition of water-soluble isoflavone into milk by means of microencapsulation technique. The yield of microencapsulation, sensory attributes, and capsule stability of water-soluble isoflavone microcapsules in milk were measured. Coating materials used was polyglycerol monostearate (PGMS), and core material was water-soluble isoflavone. The encapsulation yield of water-soluble isoflavone with PGMS was 67.2% when the ratio of coating material to core material was 15 : 1. The rate of water-soluble isoflavone release from capsules was 18, 19, and 25% when stored at 4,20, and $30^{\circ}C$ for 12 days in milk, respectively. In sensory evaluation, beany flavor and color of microencapsuled water-soluble isoflavone added milk were significantly different from uncapsuled water-soluble isoflavone added milk, however, bitterness was not significantly different. In vitro study, micro-capsules of water-soluble isoflavone in simulated gastric fluid with the range of 3 to 6 pHs were released 3.0∼15.0%, however, the capsules in simulated intestinal fluid with pH 7 were released 95.7% for 40 min incubation time. In conclusion, this study provided that PGMS as coating materials was suitable for the microencapsulation of water-soluble isoflavone, and the capsule containing milk was almost not affected with sensory attribute.

• 한국농공학회논문집
• /
• 제55권3호
• /
• pp.51-62
• /
• 2013

The importance of environmental water has been risen in terms of river ecosystem soundness with preventing stream flow depletion in rural area, while enlarging agricultural reservoir project is conducted under the 4 main river restoration project for supplying more water to 4 main rivers. The aim of this study was to estimate the amount of environmental water release and analyze the release pattern during non-irrigation season in enlarged agricultural reservoirs. The 4 reservoirs (Dansan, Samga, Geumbong, Changpyeong) located on the upper region of Nakdong river were simulated applying the operation rule which was determined by release criteria curves. The simulated results indicated that the more environmental water could be released than the spillway release and continuous release was achieved with smaller range of fluctuation. In case of Changpyeong reservoir, average 506.0 thousand $m^3$ environmental water could be released on Feb., and it was about twice as much as the spillway release before the enlargement, and also, the 18 thousand $m^3$/day environmental water could be supplied to a stream consistently after enlargement. From the results, it was expected that the additional environmental water release will improve stream water flow during dry season in terms of quantity and quality of water.

• Nuclear Engineering and Technology
• /
• 제51권5호
• /
• pp.1345-1354
• /
• 2019

Clogging of sump strainers that filter the recirculation water in containment after a loss-of-coolant accident (LOCA) seriously impedes the continued cooling of nuclear reactor cores. In experiments examining the corrosion of aluminium alloy 6061, a common material in containment equipment, in borated solutions simulating the water chemistry of sump water after a LOCA, we found that Fe-bearing intermetallic particles, which were initially buried in the Al matrix, were progressively exposed as corrosion continued. Their cathodic nature $vis-{\grave{a}}-vis$ the Al matrix provoked continuous trenching around them until they were finally released into the test solution. Such particles released from Al alloy components in a reactor containment after a LOCA will be transported to the sump entrance with the recirculation flow and trapped by the debris bed that typically forms on the strainer surface, potentially aggravating strainer clogging. These Fe-bearing intermetallic particles, many of which had a rod or thin strip-like geometry, were identified to be mainly the cubic phase ${\alpha}_c-Al(Fe,Mn)Si$ with an average size of about $2.15{\mu}m$; 11.5 g of particles with a volume of about $3.2cm^3$ would be released with the dissolution of every 1 kg 6061 aluminium alloy.