• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1594-1605
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• 2001

In this study, a numerical simulation was developed which was capable of predicting the characteristics of NO formation in pilot scale combustor adopting the air-staged burner flame. The numerical calculation was constructed by means of establishing the mathematical models fur turbulence, turbulent combustion, radiation and turbulent nitric oxide chemistry. Turbulence was solved with standard k-$\xi$ model and the turbulent combustion model was incorporated using a two step reaction scheme together with an eddy dissipation model. The radiative transfer equation was calculated by means of the discrete ordinates method with the weighted sum of gray gases model for CO$_2$and H$_2$O. In the NO chemistry model, the chemical reaction rates for thermal and prompt NO were statistically averaged using the $\beta$ probability density function. The results were validated by comparison with measurements. For the experiment, a 0.2 MW pilot multi-air staged burner has been designed and fabricated. Only when the radiation was taken into account, the predicted gas temperature was in good agreement with the experimental one, which meant that the inclusion of radiation was indispensable for modeling multi-air staged gas flame. This was also true of the prediction of the NO formation, since it heavily depended on temperature. Subsequently, it was found that the multi-air staged combustion technique might be used as a practical tool in reducing the NO formation by controlling the peak flame temperature.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.577-588
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• 2017

There are many constraints, both economically and ethically that experimenting human evacuation behavior in situations such as fire. Therefore, the evacuation behavior is simulated based on the existing studies. In recent years, the foundation has been established as computer performance advances, models closer to reality can be studied. In this study, the evacuation time in the subway platform was analyzed from modeling human behavior and smoke propagation in a fire. The evacuation efficiency was also examined by dividing the shape of the subway station platform by the stair position and comparing the evacuation times for each platform. As a result, it was found that the side platform was longer than the island platform by 36.82% more time to evacuation. The shape of the stairs is most advantageous in terms of evacuation form side type platform was 210 seconds and island type platform was 186 seconds, when a fire occurs in the center of the platform. And most favorable in location of evacuation stairs were located at 2/5 point and 4/5 from depending on the step location.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.10
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• pp.4401-4408
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• 2015

Background: Cancer is a primary source of concern in Thailand and other countries around the world, including the Asian-Pacific region. Evidence supports that an important contributing cause of cancer and other chronic illnesses such as stroke, diabetes, and hypertension is excessive alcohol consumption. Studies conducted in Thailand reveal a worrisome rise in the number of new and regular drinkers in communities. Therefore, actions for primary, secondary and tertiary prevention of problem drinking are necessary. In recent years nurses in North East Thailand have been developing and implementing the Khon Kaen Family Health Nursing model to embed disease prevention in communities through the actions of family health nurses and local family health leaders. Aim: The aim of this qualitative research was to better understand the experiences of the local family health leaders using this model and to synthesize lessons learned. Materials and Methods: As part of a participatory action research approach involving analysis of focus group discussions and individual interviews, the experiences of 45 family health leaders were synthesized. Results: Four main themes were identified, namely: i) Family first: role modeling beginning at the personal and family level. ii) Local leverage: using village community forums to reduce alcohol drinking. iii) Gentle growth: making the first step and treading gently; and iv) Respect, Redemption, Rehabilitation: valuing the person to re-integrate them in the village society. Conclusions: As alcohol consumption in the village declined significantly following the prevention program, these findings illuminate how low-tech integrated prevention approaches may be very useful, particularly in rural communities. The lessons learned may have relevance not only in Thailand but in other countries seeking to prevent and mitigate behavior that conduces to diseases such as cancer.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.499-509
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• 2001

2-D transport model based on a discrete probability distribution for a particle displacement was developed too solve advection-diffusion problems in natural stream. In this proposed model, the probabilities expressed as an average and variance function were used to predict the mass transfer between cells in one time step. The proposed model produces solutions without numerical dispersion for constant velocity, diffusion coefficient, and cross-sectional area. When the stability and positivity restrictions were satisfied, the model produced excellent results compared to analytical solutions and other finite difference methods. The proposed model is tested against the dispersion data collected in the Grand River, Canada. The simulation results show that the proposed model can properly describe the two-dimensional mixing phenomena in the natural stream.

• Journal of Korea Water Resources Association
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• v.33 no.1
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• pp.61-72
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• 2000

The purpose of this study is to improve the method of evaluating groundwater recharge by using grid-based soil moisture routing technique. A model which predicts temporal variation and spatial distribution of soil moisture on a daily time step was developed. The model uses ASCII-formatted map data supported by the irregular gridded map of the GRASS(Geographic Resources Analysis Support System)-GIS and can generate daily and monthly spatial distribution map of surface runoff, soil moisture content, evapotranspiration within the watershed. The model was applied to Ipyunggyo watershed($75.6\;\textrm{km}^2$) located in the upstream of Bocheongchun watershed. Seven maps; DEM(Digital Elevation Mode]), stream, flow path, soil, land use, Thiessen network and free groundwater level, were used for input data. Predicted streamflows resulting from two years (l995, 1996) daily data were compared with the observed values at the watershed outlet. The results of temporal variations and spatial distributions of soil moisture are presented by using GRASS GIS. As a final result, the monthly predicted groundwater recharge was presented.sented.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.16 no.3
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• pp.197-207
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• 2016

It is very important to maintain a constant chlorine concentration in the post chlorination process, which is the final step in the water treatment process (hereafter WTP) before servicing water to citizens. Even though a flow meter between the filtration basin and clear well must be installed for the post chlorination process, it is not easy to install owing to poor installation conditions. In such a case, a raw water flow meter has been used as an alternative and has led to dosage errors due to detention time. Therefore, the inlet flow to the clear well is estimated by a time series neural network for the plant without a measurement value, a new residual chlorine meter is installed in the inlet of the clear well to decrease the control period, and the proposed modeling and controller to analyze the chlorine concentration change in the well is a neuro fuzzy algorithm and cascade method. The proposed algorithm led to post chlorination and chlorination improvements of 1.75 times and 1.96 times respectively when it was applied to an operating WTP. As a result, a hygienically safer drinking water is supplied with preemptive response for the time delay and inherent characteristics of the disinfection process.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.3
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• pp.1-12
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• 1985

The linear tracking theory has a great merit that its solution can be analytically obtained under the quadratic performance measure. However, this theory has not been applied to reservoir system operation yet, because the tracking assumes no boundness of the control and state vectors. This paper presents deriving the optimal control law and solving the Riccati equations for the discrete time horizon, and its application to the real system. And the additional necessary conditions for the saturated vectors of the control and/or state are also derived using the concept of the Pontryagin's minimum principle. The logic and its algorithm in this work are not so positive to give a general solution. In fact, it is a matter of modeling in terms of relative magnitude of disturbance and time-step size. However its application to the real environment of the Han river, which comprises six major reservoirs in series/parallel, demonstrated satisfactory results over 36 monthly stages.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.335-344
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• 2011

A curvilinear non-hydrostatic free surface model is developed to investigate nonlinear wave interactions in a circular channel. The proposed model solves the unsteady Navier-Stokes equations in a three-dimensional domain with a pressure correction method, which is one of fractional step methods. A hybrid staggered-grid layout in the vertical direction is implemented, which renders relatively simple resulting pressure equation as well as free surface closure. Numerical accuracy with respect to wave nonlinearity is tested against the fifth-order Stokes solution in a two-dimensional numerical wave tank. Numerical applications center on the evolution of nonlinear waves including diffraction and reflection affected by the curvature of side wall in a circular channel comparing with linear waves. Except for a highly nonlinear bichrmatic wave, the model's results are in good agreement with superimposed analytical solution that neglects nonlinear effects. Through the numerical simulation of the highly nonlinear bichramatic wave, the model shows its capability to investigate the evolution of nonlinear wave groups in a circular channel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.321-322
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• 2006

In many manufacturing processes such as web formation, manufacturing of paper and nonwoven, fabric weaving, etc., planar sheets are transported and at the same time appropriate tension is imposed. The input material rolled up on beams is fed by unwinding the beam and the processed is then taken up on beams by winding it. While processed, the planar sheets are thrown under the processing load of impulse form, which causes irregular thickness of the processed sheet. To improve the quality of the product, a dynamic model is needed and the dynamic characteristics is to be analyzed by simulation. This study shows that density variation dynamics of the in-process-sheet in the machine direction can be described at each moment of disturbing impacts in forms of difference equations, while the impacts and tension, the time-dependency of the material properties were taken into account. Simulation showed the most serious variation of the density occurred in the process starting phase. The starting velocity curve with step form showed the least variation of the density. As the time order of the function of the starting velocity cure becomes higher, the density variation gets greater.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.14-28
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• 2020

Future climate change may affect the hydro-thermal and biogeochemical characteristics of dam reservoirs, the most important water resources in Korea. Thus, scientific projection of the impact of climate change on the reservoir environment, factoring uncertainties, is crucial for sustainable water use. The purpose of this study was to predict the future water temperature and stratification structure of the Soyanggang Reservoir in response to a total of 42 scenarios, combining two climate scenarios, seven GCM models, one surface runoff model, and three wind scenarios of hydrodynamic model, and to quantify the uncertainty of each modeling step and scenario. Although there are differences depending on the scenarios, the annual reservoir water temperature tended to rise steadily. In the RCP 4.5 and 8.5 scenarios, the upper water temperature is expected to rise by 0.029 ℃ (±0.012)/year and 0.048 ℃ (±0.014)/year, respectively. These rise rates are correspond to 88.1 % and 85.7 % of the air temperature rise rate. Meanwhile, the lower water temperature is expected to rise by 0.016 ℃ (±0.009)/year and 0.027 ℃ (±0.010)/year, respectively, which is approximately 48.6 % and 46.3 % of the air temperature rise rate. Additionally, as the water temperatures rises, the stratification strength of the reservoir is expected to be stronger, and the number of days when the temperature difference between the upper and lower layers exceeds 5 ℃ increases in the future. As a result of uncertainty quantification, the uncertainty of the GCM models showed the highest contribution with 55.8 %, followed by 30.8 % RCP scenario, and 12.8 % W2 model.