• 한국물환경학회지
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• 제32권3호
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• pp.243-252
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• 2016

In cases of water pollution accidents, accurate prediction for arrival time and concentration of contaminants in a river is essential to take proper measures and minimize their impact on downstream water intake facilities. It is critical to fully understand the behavior characteristics of contaminants on river surface, especially in case of oil spill accidents. Therefore, in this study, the effects of main parameters of advection and diffusion of contaminants were analyzed and validated by comparing the results of Lagrangian particle tracking (LPT) simulation of Environmental Fluid Dynamic Code (EFDC) model with those of Global Position System (GPS)-equipped drifter experiment. Prevention scenario modeling was accomplished by taking cases of movable weir operation into account. The simulated water level and flow velocity fluctuations agreed well with observations. There was no significant difference in the speed of surface particle movement between 5 and 10 layer modeling. Therefore, 5 layer modeling could be chosen to reduce computational time. It was found that full three dimensional modeling simulated wind effects on surface particle movements more sensitively than depth-averaged two dimensional modeling. The diffusion range of particles was linearly proportional to horizontal diffusivity by sensitivity analysis. Horizontal diffusivity estimated from the results of GPS-equipped drifter experiment was 0.096 m²/sec, which was considered to be valid for applying the LPT module in this area. Finally, the scenario analysis results showed that particle movements could be stagnant when discharge from the upstream weir was reduced, implying the possibility of securing time for mitigation actions such as oil boom installation and wiping oil contaminants. The outcomes of this study can help improve the prediction accuracy of particle tracking simulation to establish the most suitable mitigation plan considering the combination of movable weir operation.

• 대한간호학회지
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• 제42권1호
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• pp.56-65
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• 2012

Purpose: This study was done to evaluate the effects of cognitive behavioral therapy in a victimized community district and to determine if the program is an effective nursing intervention to reduce posttraumatic stress disorder symptom, depression and state anxiety. Methods: A nonequivalent control group design was used for the study. The participants, 32 elementary school students, were selected from grades 4, 5, 6 and each student was assigned to either the experimental (16) or control (16) group. Cognitive behavioral therapy was used as the experimental treatment from April 9 to May 28, 2009. The experimental group received cognitive behavior therapy intervention 8 times. Data analysis was done using ANCOVA with SPSS 17.0. Results: After the intervention, the experimental group showed significantly lower levels of posttraumatic stress disorder symptoms than the control group. Conclusion: The findings from this study suggest that cognitive behavioral therapy is an effective nursing intervention to decrease the level of mental health problems of children in victimized district. Further research is required in order to identify the continuous effects of cognitive behavioral therapy.

• 마이크로전자및패키징학회지
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• 제23권1호
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• pp.35-39
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• 2016

The flexible and superhydrophobic properties of silica aerogels are extremely important material for thermal insulation and oil spill cleanup applications for their long-term use. Flexible silica aerogels were synthesized by using a two-step sol-gel process with precursors, methyltrimethoxysilane (MTMS) followed by supercritical drying. Silica aerogels were prepared at different molar ratio of methanol to MTMS (M). It was observed that the silica aerogels prepared at M=28 were monolithic but inelastic in nature, however, for M=35, the obtained aerogels were monolithic, elastic in nature with less shrinkage. The microstructural studies were carried out using scanning electron microscopy and surface area measurements. The hydrophobicity was confirmed by Fourier transform Infrared spectroscopy and water contact angle measurements. The detailed insight mechanism for flexible nature of silica aerogels and hydrophobic behavior were studied.

• 대한조선학회논문집
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• 제32권2호
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• pp.22-31
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• 1995

본 연구에서는, 이미 개발된 3차원 해류유동 수치해석 기법을 불규칙한 해저지형과 복잡한 육지지형을 가지는 인천항 부근의 연안해역에 적용하였다. 3차원 다층기법에 의한 계산결과와 2차원 수심평균기법에 의한 계산결과를 비교하여 조류의 연직구조에 미치는 해저지형의 효과를 조사하였다. 또한, 해석해에 의한 결과와 본 연구에서 제안된 수치해석 기법에 의한 계산결과의 비교를 통하여 취송류의 연직구조를 조사하였다. 인천항부근 연안해역의 대표적인 단면을 택하여 해석해에 의한 결과 및 경험값에 의한 결과와 본 연구에서 제안된 수치해석 기법에 의한 계산결과를 비교하여 취송류에 미치는 해저지형의 효과를 조사하였으며, 경험값에 의한 결과와 본 수치해석기법에 의한 계산결과의 비교를 통하여 취송류에 미치는 육지지형의 효과도 조사하였다.

• 한국물환경학회지
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• 제29권3호
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• pp.383-392
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• 2013

In this research, mixing behavior of the floating pollutant such as oil spill accidents was analyzed by studying the advection-diffusion of GPS floaters at water surface. The LPT (Lagrangian Particle Tracking) model of EFDC (Environmental Fluid Dynamics Computer Code) was used to simulate the motion of the GPS floater tracer. In the field experiment, 35 GPS floaters were injected at the Samun Bridge of Nakdong River. GPS floaters traveled to downstream about 700 m for 90 minutes. The field data by the GPS floater experiments were compared with the simulation in order to calibrate the parameter of LPT model. The turbulent diffusion coefficient of LPT model was determined as $K_H/hu^*$ = 0.17 from the scatter diagram. The arrival time of peak concentration and transverse diffusion from the simulation results were similar with the experiments from the concentration curves. Numerical experiments for anticipation of damage from floating pollutant were conducted in the same reach of the Nakdong River and the results show that the pollutant cloud transported to the left bank where the Hwawon pumping station is located. For this reason, it is suggested that the proper action should be needed to maintain the safety of the water withdrawal at the Hwawon pumping station.