• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.549-552
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• 2009

Methane hydrate is crystalline ice-like compounds which formed methane gas enters within water molecules composed cavity at specially temperature and pressure condition, and water molecule and each other from physically-bond. $1m^3$ hydrate of pure methane can be decomposed to the maximum of $172m^3$ at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18~24% less than the liquefied transportation. However, when methane hydrate is formed artificially, the amount of consumed gas is relatively low due to a slow reaction rate between water and methane gas. In this study, for the better hydrate reaction rate, there is make nano fluid using ultrasonic dispersion of carbon nano tube. and then, Experiment with hydrate formation by nano fluid and methane gas reaction. The results show that when the carbon nano tubes of 0.004 wt% was added to pure water, the amount of consumed gas was about 300% higher than that in pure water and the hydrate formation time decreased.

• 한국측량학회지
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• 제30권6_2호
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• pp.631-642
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• 2012

This study aims to predict inundation and flood-stricken areas more accurately by simulating flood damage caused by reversible flow of rain water in the upper water system through precise 3D terrain model and backwater output. For the upstream of the South Han-River, precise 3D terrain model was established by using aerial LiDAR data and backwater by area was output by applying the storm events of 2002 including the history of flood damage. The 3D flood simulation was also performed by using GIS Tool and for occurrence of related rainfall events, inundation events of the upriver region of water system was analyzed. In addition, the results of flood simulation using backwater were verified by making the inundation damage map for the relevant area and comparing it with flood simulation's results. When comparing with the results of the flood simulation applying uniformly the gauging station's water surface elevation used for the existing flood simulation, it is found that the results of the flood simulation using backwater are close to the actual inundation damage status. Accordingly, the causes of flood occurred in downstream of water system and upstream that has different topographic characteristics could be investigated and applying the simulation with backwater is proved more proper in order to procure accuracy of the flood simulation for the upriver region.

• 한국해양공학회지
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• 제18권4호
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• pp.65-70
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• 2004

Many port states, such as New Zealand, U.S.A., Australia, and Canada, have strict regulations to prevent arriving ships from discharging polluted ballast water that contains harmful aquatic organisms and pathogens. They are notified that transfer of polluted ballast water can cause serious injury to public health and damage to property and environment. For this reason, ballast exchange in deep sea is perceived as the most effective method of emptying ballast water. The ballast management plan contains the effective exchange method, ballast system, and safety considerations. In this study, we pursued both nautical engineering analysis and optimization of the algorithm, in order to generate the sequence of stability and rapidity. A heuristic algorithm was chosen on the basis of optimality and applicability to a sequential exchange problem. We have built an optimized algorithm for the automatic exchange of ballast water, by redefining core elements of the A$\ast$ algorithm, such as node, operator, and evaluation function. The final version of the optimized algorithm has been applied to existing bulk carrier, and the performance of the algorithm has been successfully verified.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2008년도 춘계학술발표회
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• pp.61-67
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• 2008

본 연구에서는 부산신항과 낙동강 하구역의 접점인 연결잔교를 통해 소통되는 해수의 수리적인 특성을 파악하고 현장관측결과와 수치모형실험을 통해 연결잔교부를 통한 물질수송특성을 파악하였다. 그 결과를 요약하면 다음과 같다. 현장조사를 통한 해수수송량 관측결과는 1차 관측기간 동안 단위시간당 해수수송량은 $184.71m^3/sce$이고, 잔차해수수송량은 $59.74m^3/sec$로 신항만에서 낙동강 하구역 방향으로 유출되었다. 또한 2차 관측기간 동안 단위시간당 해수수송량은 $331.15m^3/sec$이고, 잔차해수수송량은 $28.88m^3/sec$로 낙동강 하구역에서 신항만 방향으로 유출되었다. 연결잔교 주변의 수심변화를 고려한 3가지 시나리오의 수치모의 결과에서 신항만 지역에 항내매몰로 수심이 저감된 경우에는 약 $0.7\sim18.4%$ 물질수송량이 저감하게 되며, 해수소통 향상을 위해 낙동강 하구역 지역에 수로준설(수심 5m 가정)을 할 경우 약 $3.5\sim21.9%$의 물질수송량이 증가하였다.

• Ocean Systems Engineering
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• 제5권4호
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• pp.319-329
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• 2015

Submerged breakwaters are used to prevent shore line erosion and sediment transportation. One of their advantages is low visual impact. In this paper, the effects of discontinuous submerged breakwaters over water surface elevation was numerically studied considering the extended Boussinesq equations as governing equations using MIKE21 software. The result of discontinuous breakwater was compared with a beach without breakwater. The results showed that the gap dramatically effects on surface elevation from shore line to offshore. It is also evident from results that with approaching the center of the gap, fluctuation of surface elevation is generated. It is because of passing longshore currents towards offshore through the gap which leads to an increase in sediment transportation rate. Nevertheless, transferring water mass from breakwater gap results in powerful rip currents leading to high changes on longshore wave profile.

• 한국환경과학회지
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• 제21권3호
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• pp.277-287
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• 2012

The MFFn(Mass First Flush) was analyzed for various rainy events(monitoring data from 2008 to 2009) in Transportation area(Highway, National road, Trunk road). Estimated MFFn using SWMM was evaluated by comparison with observed MFFn. MFFn was estimated by varying n-value from 10% to 90% on the rainy events. The n-value increases, MFFn is closed to '1'. As time passed, the rainfall runoff was getting similar to ratio of pollutants accumulation. The result of a measure of the strength of the linear relationship between observed data and expected data under model was good ($R^2$=0.89). Pollutants runoff loads by volume showed Highway 26.6%, National road 44.8%, Trunk road 35.0% at the MFF20(20% by total runoff). A case of MFF30, pollutants runoff loads by volume showed Highway 40.2%, National road 54.3%, Trunk road 46.8%. According to the results, Initial precipitation basis were Highway MFF30, National road MFF20, Trunk road MFF30 when the Non-Point source control facilities set up.

• 한국입자에어로졸학회지
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• 제17권3호
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• pp.43-54
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• 2021

Size distributions of atmospheric particulate matter (PM) and its water-soluble organic and inorganic components were measured between January and February 2021 at an urban site in Gwangju in order to identify the major factors that determine their size distributions. Their size distributions during the study period were mainly divided into two groups. In the first group, PM, NO₃^-, SO₄^2-, NH₄⁺ and water-soluble organic carbon (WSOC) exhibited bi-modal size distributions with a dominant condensation mode at a particle size of 0.32 ㎛. This group was dominated by local production of secondary water-soluble components under atmospheric stagnation and low relative humidity (RH) conditions, rather than long-range transportation of aerosol particles from China. On the other hand, in the second group, they showed tri-modal size distributions with a very pronounced droplet mode at a diameter of 1.0 ㎛. These size distributions were attributable to the local generation and accumulation of secondary aerosol particles under atmospheric conditions such as atmospheric stagnation and high RH, and an increase in the influx of atmospheric aerosol particles by long-distance transportation abroad. Contributions of droplet mode NO₃^-, SO₄^2-, NH₄⁺ and WSOC to fine particles in the second group were significantly higher than those in the first group period. However, their condensation mode contributions were about two-fold higher in the first group than in the second group. The significant difference in the size distribution of the accumulation mode of the WSOC and secondary ionic components between the two groups was due to the influx of aerosol particles with a long residence time by long-distance transport from China and local weather conditions (e.g., RH).

• 농업과학연구
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• 제23권1호
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• pp.159-176
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• 1996

This study is aimed at reviewing the methods of joint cost allocation and allocating the joint cost of estuary dam with specially repect to Kumgang Large-scale Agricultural Comprehensive Development Project. Apart from the water resource development project propelled by Water Resource Development Corporation in connection with Law of Multipurpose Dam Development, the Largescale Comprehensive Agricultural Development Projects couldn't ins-titutionally be carried out cost allocation of common facilities, even though it were concerned with irrigation, municipal and industrical water supply, flood control, sightseeing and industrial zone development components. To decrease farmer's burden of the project costs and, operation and maintenance costs, the joint costs of common facilities like estuary dam included in agricultural development projects have to be allocated by suitable method as alternative cost-remaining benefit method and the analytical activity should be supported by revising the concerned laws as Rural Development and Promotion and, Rural Rearrangement conpatible with the law for multipurpose dam development. Kumgang Agricultural Comprehensive Development Project was selected as a case study for the estimation of socio-economic benefits by project components and joint cost allocation of the estuary dam. The main results of the study are as follows; Joint cost allocation and unit charges by components 1. The project area will be 25,554ha with total project cost of 624,860 million won including the estuary dam cost of 120,843 million won. The project costs were ex-pressed by 1994 constant price. 2. Total quantity of water was estimated 365 million tons which were consisted of 245 million tons for irrigation, 73 million tons for municipal water and 47 million tons for industrial water. 3. The rates of joint cost allocation were amounted to 34.2% for agriculture, 2.5% for sightseeing, 45.7% for transportation, 11.8% for M & I water supply and 5.8% for flood control respectively. 4. The unit financial charges by project components were estimated at 7.88 won per ton for irrigation, 16.11won for M & I water, 1,686won per vehicle one pass, 977won per Pyeong according to the capital recovery method. The financial charges using straitline method for depreciation were estimated at 7.88won per ton for irrigation, 9.12won per ton for M & I water, 624won per vehicle one pass for transportation and 331won per Pyeong for sightseeing area. 5. The unit economic charges by project components were estimated at 21.1 won per ton for irrigation, 15.2won for M & I water, 977won per vehicle one pass, 977won per Pyeong according to the capital recovery method. The economic charges using straitline method for depreciation were estimated at 11.72won per ton for irrigation, 8.61won per ton for M & I water, 331won per vehicle one pass for transportation. Policy recommendation 1. The unit operation and maintenance costs for irrigation water in the paddy field couldn't be imposed as the water resource cost untreated. 2. The dam costs including investment cost and O & M cost, as a joint cost, had to be allocated by each benefited components as transportation, M & I water supply, flood control, irrigation and drainage, and sightseeing. But the agricultural comprehensive project have been dealt as an irrigation project without any appraisal socio-economic benefits and any allocating the joint cost of estuary dam. 3. All the associated project benefits and costs must be evaluated based on accounting principle and rent recovery rate of the project costs and O & M costs should be regulated by the laws concerned. 4. The rural development and promotion law and rural rearrangement law have to be revised comprising joint cost allocation considering free rider problems. 5. The government subsidy for the agricultural base development project has to be covered all the project costs. In case of common facilities representing joint cost allocation problems, all the allocated casts for other purposes like transportation and M & I water supply etc. should be recovered for formation in investment fund for agricultural base development and to procure O & M costs for irrigation facilities.

• 한국태양에너지학회 논문집
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• 제32권5호
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• pp.118-123
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• 2012

Water balance has a significant impact on the overall fuel cell performance. Maintenance of proper water management should provide an adequate membrane hydration and avoidance of water flooding in the catalyst layer and gas diffusion layer. Considering the important of advanced water management in PEM fuel cell, this study proposes a simple one dimensional water transportation model of PEM fuel cell for use in a dynamic condition. The model has been created by assumption that the output is the water liquid saturation difference. The liquid saturation change is the total difference between the additional water and the removal water on the system. The water addition is obtained from fuel cell reaction and the electro osmotic drag. The water removal is obtained from capillary transport and evaporation process. The result shows that the capillary water transport of low temperature fuel cell is high because the evaporation rate is low.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.281-283
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• 2005

Water management in polymer electrolyte membrane fuel cells(PEMFCs) is one of the most challenging issues. Freeze start-up in the automotive applications is also important research topic in the PEMFC field. Transportation of proton and separation of reactant gases are main roles of polymer electrolyte membranes. It has been known that water in the membrane conducts as a vehicle for the proton transportation. At sub-zero temperature, the frozen water blocks the access of reactant gases to the active sites of electrode as well as occurs the physical destruction of fuel cell structures. In this study, property changes of electrolyte membranes in the freeze conditions $(at\;-25^{\circ}C)$ were investigated. For the various amount of water contained membranes, the property changes, especially for the proton conductivity, were observed after several times of freeze/thaw$(-25\~80^{\circ}C)$ cycle.