• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.640-655
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• 2013

The purpose of this study is to analyze the cognitive demands level of the description about 'changes of state' and 'kinetic theory' on the 'science 1' textbooks by the 2007 revised curriculum. The three types of curriculum analysis taxonomy have been used to analyze the cognitive demands level of those contents on the 6 kinds of 'science 1' textbooks. The most higher level of cognitive demands about the concepts have been discussed here due to the focus of the concepts. The first, the cognitive demand level about 'three states of substances' depending on the motion of their particles in 6 textbooks is a early formal operational stage because of using by the application of kinetic theory. The second, the cognitive demand level about 'diffusion' and 'evaporation' is a early formal operational stage, because the particles move around faster so they can change their position. The third, the cognitive level of the pressure and volume in a gas is a early formal operational stage because of explaining only phenomena in simple correspondence with formal model of kinetic theory. And simple functional relationships beyond linear on the graph of the volume and pressure of gas, the volume and temperature of gas is also a early formal operational stage. The fourth, the cognitive level of the energy of heat by a change of the state is also a early formal operational stage because kinetic theory picture accepted as providing explanation by the change of the state. And functional relationships beyond linear on the graph of the explanation of boiling point of water in water is also a early formal operational stage.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.174-183
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• 2014

Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field. In the condition of an irregular wave field, the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated. Simulation results were used as input data in a finite element computer program for elastoplastic seabed response. Simulations evaluated the time and spatial variations in excess pore water pressure, effective stress, and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the results of the analysis, the liquefaction potential at the seabed in front and rear of the composite breakwater was identified. Since the liquefied seabed particles have no resistance to force, scour potential could increase on the seabed. In addition, the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater. Due to limitations of allowable paper length, the studied results were divided into two portions; (I) focusing on the dynamic response of structure, acceleration, deformation of seabed, and (II) focusing on the time variation in excess pore water pressure, liquefaction, effective stress path in the seabed. This paper corresponds to (II).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.160-173
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• 2014

Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field. In the condition of an irregular wave field, the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated. Simulation results were used as input data in a finite element computer program for elastoplastic seabed response. Simulations evaluated the time and spatial variations in excess pore water pressure, effective stress, and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the results of the analysis, the liquefaction potential at the seabed in front and rear of the composite breakwater was identified. Since the liquefied seabed particles have no resistance to force, scour potential could increase on the seabed. In addition, the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater. Due to limitations of allowable paper length, the studied results were divided into two portions; (I) focusing on the dynamic response of structure, acceleration, deformation of seabed, and (II) focusing on the time variation in excess pore water pressure, liquefaction, effective stress path in the seabed. This paper corresponds to (I).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.49-64
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• 2014

Seabed beneath and near the coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If the liquefaction occurs in the seabed, the structure may sink, overturn, and eventually fail. Especially, the seabed liquefaction behavior beneath a gravity-based structure under wave loading should be evaluated and considered for design purpose. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using 2-dimensional numerical wave tank. The 2-dimensional numerical wave tank was expanded to account for irregular wave fields, and to calculate the dynamic wave pressure and water particle velocity acting on the seabed and the surface boundary of the structure. The simulation results of the wave pressure and the shear stress induced by water particle velocity were used as inputs to a FLIP(Finite element analysis LIquefaction Program). Then, the FLIP evaluated the time and spatial variations in excess pore water pressure, effective stress and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the analysis, when the shear stress was considered, the liquefaction at the seabed in front of the structure was identified. Since the liquefied seabed particles have no resistance force, scour can possibly occur on the seabed. Therefore, the strength decrease of the seabed at the front of the structure due to high wave loading for the longer period of time such as a storm can increase the structural motion and consequently influence the stability of the structure.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.374-385
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• 2013

Sediment particle motions have been numerically simulated over a sinusoidal ripple. Turbulent boundary layer flows are generated by Large Eddy Simulation, and the sediment particle motions are simulated using Lagrangian particle tracking method. Two unsteady flow conditions are used in the experiment by employing two different wave amplitudes while keeping other conditions such as wave period same. As expected, the amount of suspended sediment particles is clearly dependent on the wave amplitude as it is increasing with increasing flow intensity. However, it is also observed that the pattern of suspension may be different as well due to the only different condition caused by wave amplitude. Specially, the time of maximum sediment suspension within the wave period is not coincident between the two cases because sediment suspension is strongly affected by the existence of turbulent eddies that are formed at different times over the ripple between the two cases as well. The role of these turbulent eddies on sediment suspension is important as it is also confirmed in previous researches. However, it is also found the time of these eddies' formation may also dependent on the wave amplitude over rippled beds. Therefore, it has been proved that various flow as well as geometric conditions under waves has to be considered in order to have better understanding on the sediment suspension process over ripples. In addition, it is found that high turbulent energy and strong upward flow velocities occur during the time of eddy formation, which also supports high suspension rate at these time steps. The results indicate that the relationship between the structure of flows and bedforms has to be carefully examined in studying sediment suspension at coastal regions.