• 한국물환경학회지
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• 제28권4호
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• pp.582-594
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• 2012

A simple ecohydorlogic model that simulates hydrologic components and vegetation dynamics simultaneously based on equations of soil water dynamics and vegetation's growth and mortality is discussed. In order to simulate ungauged watersheds, the proposed model is calibrated with indirected estimated observation data set; 1) empirically estimated annual vaporization, 2) monthly surface runoff estimated by NRCS-CN method, and 3) vegetation fraction estimated by SPOT/VEGETATION NDVI. In order to check whether the model is performed well with indirectly estimated data or not, four upper dam watersheds (Andong, Habcheon, Namgang, Milyang) in Nakdong River watershed are selected, and the model is verified.

• 상하수도학회지
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• 제21권1호
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• pp.65-73
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• 2007

To consider business-based requirements beyond the existing roles of water supply, water utilities need enough methodology to integrate lots of related issues and to introduce effective decision-makings. On these grounds, this study modeled and simulated water business system using system dynamics approach. It is expected that formalised model can describe the actual system structurally and statistically, help utilities to predict their business performance and make decisions to solve chronic issues. Moreover, the case study of Y city gave political measures objectively and practically.

• 대한기계학회논문집B
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• 제33권8호
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• pp.559-564
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• 2009

The variation in the shape of water droplet moving on atomistically smooth solid surface in the presence of a constant body force is simulated using molecular dynamics simulation. We investigated how the advancing and receding contact angle of the moving water droplet changes on a solid surface having various characteristic energies. From the MD simulation results, we obtained the density profile defined as the number of water molecules at a given position. Then, assuming the water droplet periphery to be a circle, we calculated the contact angles by using a nonlinear fitting of the half-density contour line. The present simulation clearly shows the different profile of the advancing and receding contact angle for these three different interaction potential between the water droplet and the solid surface.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2925-2930
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• 2013

We present results of molecular dynamics simulations for hydroxide ion in supercritical water of densities 0.22, 0.31, 0.40, 0.48, 0.61, and 0.74 g/cc using the SPC/E water potential with Ewald summation. The limiting molar conductance of $OH^-$ ion at 673 K monotonically increases with decreasing water density. It is also found that the hydration number of water molecules in the first hydration shells around the $OH^-$ ion decreases and the potential energy per hydrated water molecule also decreases in the whole water density region with decreasing water density. Unlike the case in our previous works on LiCl, NaCl, NaBr, and CsBr [Lee at al., Chem. Phys. Lett. 1998, 293, 289-294 and J. Chem. Phys. 2000, 112, 864-869], the number of hydrated water molecules around ions and the potential energy per hydrated water molecule give the same effect to cause a monotonically increasing of the diffusion coefficient with decreasing water density in the whole water density region. The decreasing residence times are consistent with the decreasing potential energy per hydrated water molecule.

• 상하수도학회지
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• 제20권2호
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• pp.187-196
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• 2006

Forecasting the long-term water demand is important in the plan of water supply system because the location and capacity of water facilities are decided according to it. To forecast the long-term water demand, the existing method based on lpcd and population has been usually used. But, these days the trend among the variation of water demand has been disappeared, so expressing other variation of it is needed to forecast correct water demand. To accomplish it, we introduced the System Dynamics method to consider total connections of water demand factor. Firstly, the factors connected with water demand were divided into three sectors(water demand, industry, and population sectors), and the connections of factors were set with multiple regression model. And it was compared to existing method. The results are as followings. The correlation efficients are 0.330 in existing model and 0.960 in SD model and MAE are 3.96% in existing model and 1.68% in SD model. So, it is proved that SD model is superior to the existing model. To forecast the long-term water demand, scenarios were made with variations of employment condition, economic condition and consumer price indexes and forecasted water demands in 2012. After all scenarios were performed, the results showed that it was not needed to increase the water supply ability in Seoul.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.52-56
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• 2009

In this study a dynamic modeling scheme is presented to derive the probabilistic structure of soil water and plant water stress when subject to stochastic precipitation conditions. The newly developed model has the form of the Fokker-Planck equation, and its applicability as a model for the probabilistic evolution of the soil water and plant water stress is investigated under climate change scenarios. This model is based on the cumulant expansion theory, and has the advantage of providing the probabilistic solution in the form of probability distribution function (PDF), from which one can obtain the ensemble average behavior of the dynamics. The simulation result of soil water confirms that the proposed soil water model can properly reproduce the results obtained from observations, and it also proves that the soil water behaves with consistent cycle based on the precipitation pattern. The plant water stress simulation, also, shows two different PDF patterns according to the precipitation. Moreover, with all the simulation results with climate change scenarios, it can be concluded that the future soil water and plant water stress dynamics will differently behave with different climate change scenarios.

• 상하수도학회지
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• 제20권1호
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• pp.104-114
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• 2006

Recently, the PPP (Public-Private-Participate) program on water and wastewater services in Korea has been under an active debate. However, the controversy has reached the limits of getting more valuable implications from past foreign experience beyond conceptual and/or qualitative case studies. This paper analyze scientifically and quantitatively the Buenos Aires Water Concession Project focused on propriety of the contract using system dynamics modeling. The results show that Buenos Aires's Project has several problems in the contract phase even though Argentina government spent much time to design it. Analysis results suggest that estimation of K factor considering delay effect and future uncertainty, reduction of the first fixed terms of contract, etc., are needed for a proper contract.

• 대한조선학회논문집
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• 제44권2호
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• pp.166-173
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• 2007

Collision analysis problems between ship to ship can be generally classified into the external mechanics(outer dynamics) and internal mechanics(inner dynamics). The former can be also dealt with the concept of fluid-structure interaction and the use of rigid body dynamic program, depending on the ways handling the hydrodynamic pressure due to surrounding water. In this study, full scale ship collision simulation was carried out, such as a DWT 75,000 ton striking ship collided at right angle to the middle of a DWT 150,000 struck ship with 10 knots velocity, coupling MCOL, a rigid body mechanics program for modeling the dynamics of ships, to hydrocode LS-DYNA. It could be confirmed that more suitable damage estimation would be performed in the case of the collision simulations with consideration of surrounding water through the comparison with the collision simulation results of fixed struck ships without it. Through this study, the opportunity could be obtained to establish a more effective ship collision simulation technique between ship to ship.

• 상하수도학회지
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• 제30권5호
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• pp.561-569
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• 2016

In this paper a concept of the paradigm shift in the operations of Water and Wastewater systems regarding the production and usage of water was introduced. Based on this concept the interrelationships between the water quality in the upper basin of NakDong River relative to Busan and the degree of satisfaction of the customers on the water supply service in Busan were modeled using the System Dynamics modeling methodology. SamRangJin basin area was determined as the upper basin of Busan after analyzing the relationships between the water quality of MoolGeum water intake point and water quality data of various mid- and upper water intake points along NakDong River. The amount of contaminants generated in SamRangJin basin was modeled using the Gross Regional Domestic Product in the area and the treated amount was calculated using the efficiency of wastewater treatment and the degree of improvement of environmental condition per investment. The water quality at MoolGeum water intake point was modeled to take the effects of the remaining amount of contaminants after treatment and the non-point source contaminants in SamRangJin basin. Using the developed System Dynamics model the effects of the investment for the improvement of environmental condition in SamRangJin basin were compared to the case of alternate water source development for Busan in terms of the degree of satisfaction of the customers on the water supply service in Busan.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.21-21
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• 2011

A series of Quasi-Elastic Neutron Scattering (QENS) experiments helps us to understand the single-particle (hydrogen atom) dynamics of a globular protein and its hydration water and strong coupling between them. We also performed Molecular Dynamics (MD) simulations on a realistic model of the hydrated hen-egg Lysozyme powder having two proteins in the periodic box. We found the existence of a Fragile-to-Strong dynamic Crossover (FSC) phenomenon in hydration water around a protein occurring at TL=$225{\pm}5K$ by analyzing Intermediate Scattering Function (ISF). On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the High Density Liquid (HDL) form, a more fluid state, to predominantly the Low Density Liquid (LDL) form, a less fluid state, derived from the existence of a liquid?liquid critical point at an elevated pressure. We showed experimentally and confirmed theoretically that this sudden switch in the mobility of the hydration water around a protein triggers the dynamic transition (so-called glass transition) of the protein, at a temperature TD=220 K. Mean Square Displacement (MSD) is the important factor to show that the FSC is the key to the strong coupling between a protein and its hydration water by suggesting TL${\fallingdotseq}$TD. MD simulations with TIP4P force field for water were performed to understand hydration level dependency of the FSC temperature. We added water molecules to increase hydration level of the protein hydration water, from 0.30, 0.45, 0.60 and 1.00 (1.00 is the bulk water). These confirm the existence of the FSC and the hydration level dependence of the FSC temperature: FSC temperature is decreased upon increasing hydration level. We compared the hydration water around Lysozyme, B-DNA and RNA. Similarity among those suggests that the FSC and this coupling be universal for globular proteins, biopolymers.