• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.343-347
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• 2002

In this paper, we can easily update teaming information by using database built in web server system in implementation of a web courseware that a learner can effectively team the 'Digital Circuits' subject. Also, we offered multimedia elements such as graphics, animations, and voices etc. for increasing understanding and interaction of teaming and designed and implemented a simulation-type web courseware of practice-oriented. In result, it can encourage a learner with a motive of learning and increase effects of teaming. Also, a learner can learn various contents because we can add teaming contents to database according to needs. Furthermore, it can improve understanding for teaming by offering feedback on the result. In future, we need to design and implement circuits with more complex and many functions by adding circuit with function that can store.

• Structural Engineering and Mechanics
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• v.62 no.4
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• pp.381-389
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• 2017

In the present study, the advanced procedure has been proposed to estimate higher accuracy of embedment of pipes that are installed on soft clay seabed. Numerical simulation by OrcaFlex simulation code was performed to investigate dynamic seabed embedment, and two steps, i.e., static and dynamic analysis, were adopted. In total, four empirical curves were developed to estimate the seabed embedment including dynamic phenomena, i.e., behaviour of vessel, environmental condition, and behaviour of nonlinear soil. The obtained results were compared with existing methods (named general method) such as design code or guideline to examine the difference of seabed embedment for existing and advance methods. Once this process was carried out for each case, a diagram for estimating seabed embedment was established. The applicability of the proposed method was verified through applied examples with field survey data. This method will be very useful in predicting seabed embedment on soft clay, and the structural behaviours of installed subsea pipelines can be changed by the obtained seabed embedment in association with on-bottom stability, free span, and many others.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.445-452
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• 2002

In the field of civil and geotechnical engineering, students conduct a variety of soil tests to fulfill undergraduate soil mechanics course requirement. There is a range of problems in soil laboratory instruction, such as, some students not getting hands on experience of conducting tests because of inadequate number of apparatus, time constraints and inability in exciting students to seriously conduit the experiments, However when these laboratory soil tests are simulated with multimedia interaction ann visualization techniques, the students conceptual understanding of soil mechanics is enhanced. The simulation program for website teaching is a computer based instructional package intended to complement, and potentially replace, some physical testing in a real soil laboratory. The overall aim of this project is to develop an experimental simulation program toward active learning and development of critical thinking skills, including data interpretation, understanding of the precesses and influential factors, and problem solving. Therefore enable students to access website to team experimental procedure at any time or place.

• Journal of Korea Water Resources Association
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• v.38 no.6 s.155
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• pp.429-438
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• 2005

In this study, a couple of ordinary differential equations which can describe random waves are derived from the Boussinesq equations. Incident random waves are generated by using the TMA(TEXEL storm, MARSEN, ARSLOE) shallow-water spectrum. The governing equations are integrated with the 4-th order Runge-Kutta method. By using newly derived wave equations, nonlinear energy interaction of propagating waves in constant depth is studied. The characteristics of random waves propagate over a sinusoidally varying topography lying on a sloping beach are also investigated numerically. Transmission and reflection of random waves are considerably affected by nonlinearity.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.262-265
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• 2019

The effect of inter-band transition on surface plasmon resonance in gold thin film was investigated. We induced localized inter-band transition in the film by using incident light on its surface from a green laser (532 nm) source, and the surface plasmon resonance for inter-band transition was investigated at different wavelengths. It was determined that the reflectivity of blue light (450 nm) was significantly reduced in the region where the green laser was incident. We demonstrated that this decrease is mainly due to the coupling between the blue light and the surface plasmon resonance of excited electrons in higher energy states, based on experimental results for the incident and polarization angle-dependent reflectivity of the blue light.

• Safety and Health at Work
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• v.12 no.3
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• pp.317-323
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• 2021

Background: The surface mining industry has one of the highest fatality rates among private industries in the United States. Despite recent decreases in the fatality rates of comparable industries, the fatality rate in the surface mining industry has increased. Meanwhile, a lack of safety research in surface mining has hindered efforts to improve safety strategies in the surface mining workplace. Method: This study examined quarry workers' hazard identification skills by conducting a case study of a surface mining facility in the Mid-Atlantic region of the United States. Semistructured interviews were conducted with eight quarry workers who were employed at the mine facility. In addition to the interviews, data were collected through field notes, notes from an expert meeting with safety managers, and site photographs to explore quarry workers' safety behaviors in the workplace. Results: The results showed that quarry workers identified hazards and improved their safety performance by translating safety knowledge learned from training into practice, acquiring hands-on work experience, learning from coworkers, and sharing responsibilities among team members. Conclusion: This study contributes to understanding quarry workers' safe performance beyond what they have learned in safety training to include their interaction with other workers and hand-on experience in the workplace. This study informs practitioners in the surface mining industry to build a safe work environment as they design effective safety programs for employees.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.244-252
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• 2021

Wind plays an important role in cases of unexpected radioactive pollutant dispersion, deciding distribution and concentration of the leaked substance. The accurate prediction of wind has been challenging in numerical weather prediction models, especially near the surface because of the complex interaction between turbulent flow and topographic effect. In this study, we investigated the characteristics of atmospheric dispersion of radioactive material (i.e. ¹³⁷Cs) according to the simulated boundary layer around the HANARO research nuclear reactor in Korea using the Weather Research and Forecasting (WRF)-Mesoscale Model Interface (MMIF)-California Puff (CALPUFF) model system. We examined the impacts of orographic drag on wind field, stability calculation methods, and planetary boundary layer parameterizations on the dispersion of radioactive material under a radioactive leaking scenario. We found that inclusion of the orographic drag effect in the WRF model improved the wind prediction most significantly over the complex terrain area, leading the model system to estimate the radioactive concentration near the reactor more conservatively. We also emphasized the importance of the stability calculation method and employing the skillful boundary layer parameterization to ensure more accurate low atmospheric conditions, in order to simulate more feasible spatial distribution of the radioactive dispersion in leaking scenarios.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.121-130
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• 2021

In this study, a computational fluid dynamics (CFD) simulation based on an Eulerian-Eulerian approach was used to evaluate the mixing performance of a mud agitator through the distribution of bulk particles. Firstly, the commercial CFD software Star-CCM+ was verified by performing numerical simulations of single-phase water mixing problems in an agitator with various turbulence models, and the simulation results were compared with an experiment. The standard model was selected as an appropriate turbulence model, and a grid convergence test was performed. Then, a simulation of the liquid-solid multi-phase mixing in an agitator was simulated with different multi-phase interaction models, and lift and drag models were selected. In the case of the lift model, the results were not significantly affected, but Syamlal and O'Brien's drag model showed more reasonable results with respect to the experiment. Finally, with the properly determined simulation conditions, a multi-phase flow simulation of a mud agitator was performed to predict the mixing time and spatial distribution of solid particles. The applicability of the CFD multi-phase simulation for the practical design of a mud agitator was confirmed.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.3966-3978
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• 2021

ISFRA (Integrated SFR Analysis Program for PSA) computer program has been developed for simulating the response of the PGSFR pool design with metal fuel during a severe accident. This paper describes validation of the ISFRA aerosol model against the Aerosol Behavior Code Validation and Evaluation (ABCOVE) experiments undertaken in 1980s for radionuclide transport within a SFR containment. ABCOVE AB5, AB6, and AB7 tests are simulated using the ISFRA aerosol model and the results are compared against the measured data as well as with the simulation results of the MELCOR severe accident code. It is revealed that the ISFRA prediction of single-component aerosols inside a vessel (AB5) is in good agreement with the experimental data as well as with the results of the aerosol model in MELCOR. Moreover, the ISFRA aerosol model can predict the "washout" phenomenon due to the interaction between two aerosol species (AB6) and two-component aerosols without strong mutual interference (AB7). Based on the theory review of the aerosol correlation technique, it is concluded that the ISFRA aerosol model can provide fast, stable calculations with reasonable accuracy for most of the cases unless the aerosol size distribution is strongly deformed from log-normal distribution.

• Journal of Ocean Engineering and Technology
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• v.36 no.1
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• pp.11-20
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• 2022

Generally, tsunamis are generated by the rapid crustal movements of the ocean floor. Other factors of tsunami generation include landslides on coastal and ocean floor slopes, glacier collapses, and meteorite collisions. In this study, two numerical analyses were conducted to examine the formation, propagation, and deformation properties of landslide tsunamis. First, LS-DYNA was adopted to simulate the formation and propagation processes of tsunamis generated by dropping rigid bodies. The generated tsunamis had smaller wave heights and wider waveforms during their propagation, and their waveforms and flow velocities resembled those of theoretical solitary waves after a certain distance. Second, after the formation of the landslide tsunami, a tsunami based on the solitary wave approximation theory was generated in a numerical wave tank (NWT) with a computational domain that considered the stability/steady phase. The comparison of two numerical analysis results over a certain distance indicated that the waveform and flow velocity were approximately equal, and the maximum wave pressures acting on the upright wall also exhibited similar distributions. Therefore, an effective numerical model such as LS-DYNA was necessary to analyze the formation and initial deformations of the landslide tsunami, while an NWT with the wave generation method based on the solitary wave approximation theory was sufficient above a certain distance.