• The Journal of Engineering Geology
• /
• v.15 no.3
• /
• pp.257-268
• /
• 2005

In situ rock mass is generally heterogeneous and discontinuous, with varying degrees of strength along the planes of weakness. The planes of weakness such as joints, faults, cracks and bedding planes, control the strength and deformation characteristics of the rock mass. Subsequently, the stability of underground opening depends upon the spatial distribution of discontinuities and their mechanical properties in relation with geometrical shape of openins as well as the mechanical properties of intact rock materials. Understanding the behaviour of a discontinuous rock mass remains a key issue for improving excavation design in hiかy stressed environments. Although recent advances in rock mechanics have provided guidelines for the design of underground opening in isotropic rock mass, prediction and control of deformation in discontinuous rock masses are still unclear. In this study, parametric study was performed to investigate the plastic zone size, stress distribution and deformation behavior around underground opening in a discontinuous rock mass using a continuum joint model. The solutions were obtained by an elasto-plastic finite difference analysis, employing the Mohr-Coulomb failure criteria. Non-associated flow rule and perfectly plastic material behavior are also assumed.

• Journal of Radiation Protection and Research
• /
• v.39 no.2
• /
• pp.70-80
• /
• 2014

The interpretation on the diffusion of radiation contaminants in air is usually to apply a Gaussian plume equation that obtains normal distributions in stable air flow conditions to draw a conservative conclusion. In this study, a numerical study using computational fluid dynamics methods was performed to interpret the air flow pattern and the diffusion of the radiation contaminants at the Wolseong nuclear power plants, and a more detailed solution can be obtained than the Gaussian plume equation, which is difficult to use to simulate complex terrains. The results show that a significant fluctuation of air flow in the terrain appears in the case of a northwester and southeaster because of the mountain located in the northwest and the sea located in the south-east. The northwesterly air flow shows the most unstable flow in the vertical direction when it passes over the terrain of mountain. The stable southeasterly air flow enters into the nuclear power plant from the sea, but it becomes unstable rapidly because of the interference by the building and the terrain. On the other hand, in the case of a northeaster and southwester, a small interruption of air flow is caused by the terrain and wake behind the buildings of nuclear power plants.

• Geophysics and Geophysical Exploration
• /
• v.13 no.4
• /
• pp.323-329
• /
• 2010

Three deconvolution methods were applied to stacked seismic data obtained to investigate gas-hydrates in the Ulleung Basin, East Sea: (1) minimum-phase spiking deconvolution, (2) minimum-phase spiking deconvolution using an averaged wavelet from all traces, and (3) deterministic deconvolution using a wavelet with phases computed from well-logs. We analyzed the resolving property of these methods for lithological boundaries. The first deconvolution method increases temporal resolution but decreases lateral continuity. The second method shows, in an overall sense, similar results to the spiking deconvolution using a minimum phase wavelet for each trace; however, it results in a more consistent and continuous bottom-simulating reflector (BSR) and better resolved sub-BSR reflectors. The results from the third method reveal more detailed internal structures of debris-flow deposits and increased continuity of reflectors; in addition, the seafloor reflection and the BSR appear to have changed to a zero-phase waveform. These properties help more precisely estimate the distribution and reserves of gas hydrates in the exploration area by improving analysis of facies and amplitude of the BSR.

• Geophysics and Geophysical Exploration
• /
• v.11 no.2
• /
• pp.148-152
• /
• 2008

Multichannel seismic profiles reveal a strong bottom simulating reflector (BSR) occurring below the seafloor in the plain of the Ulleung Basin, East Sea (Japan Sea). The essential characteristics of the BSR include its cross-cutting relationship to strata, strong amplitude, and reverse polarity with respect to the seafloor reflection, representing the base of the gas hydrate stability zone (BHSZ). The BSR reflection coefficient ranging from -0.23 to -0.26 is 1.5${\sim}$1.7 times that of the seafloor reflection and interval velocities decrease to less than 700 m/s below the BSR. These features indicate the existence of free gas beneath the GHSZ. Heat flow, estimated from the BSR depth as $95{\sim}98mW/m^2$, is in good agreement with measured values. Therefore, the BSR can be efficiently used to estimate regional distribution of heat flow in the Ulleung Basin.

• Journal of The Korean Association For Science Education
• /
• v.26 no.7
• /
• pp.856-869
• /
• 2006

J. J. Schwab is usually considered as the founder of the concept of scientific enquiry, perhaps the most important key word of science education of the 20th century. Mainly through the method of literature review, this study reappraises Schwab's life as a science educator as well as a curriculum scholar, and his ideas concerning several important issues about science and science education. Like other eminent science educators, before the 1950s, who were originally talented scientists but later became engaged in educational activities, Schwab were trained and known as a genetic scientist, but later he concentrated on university reform, curriculum studies and science education. His academic interest was very diverse across different disciplines, from biology and science in general to history, philosophy and education. The essence of his theory of scientific enquiry was 'to teach science as science', and the best way to do it was 'to teach science as enquiry'. With enquiry, however, he tried to deliver some important but differentiated meanings, for example by distinguishing 'science as enquiry' and 'teaching as enquiry', and 'static enquiry' and 'fluid enquiry'. Scientific enquiry was the core concept upon which many of his ideas concerning science education and education in general were based, such as the diversity of science, textbooks, curriculum and roles of teachers. In summary, Schwab can be characterized as a rational reformist of science education, who tried to identify the very nature and goals of the discipline and to bring its substantial changes with concrete and practical guidelines. Nevertheless, some of his ideas, like the diversity of science and conceptual invention, have been handed down by his followers frequently with considerable distortion.

• Resources Recycling
• /
• v.23 no.2
• /
• pp.17-25
• /
• 2014

The thermal effect on the compositional change of the $SO_2$ absorption process product was investigated compared with the composition of raw material when dolomite is employed in place of lime in the scrubbing process based on thermodynamic estimation. It was considered that the equilibrium reactions which directly related with the formation of $CaSO_4$ and $MgSO_4$, the absorption process products, are those between $Ca^{2+}$ and $Ca(OH)_2$, $Mg^{2+}$ and $Mg(OH)_2$, and the secondary dissociation reaction of $H_2SO_4$. It was thought to be necessary to examine the enthalpy change for the formation reactions of $CaSO_4$ and $MgSO_4$ along with the thermal feature of the relative reactions to figure out the influence of temperature on the compositional change of absorption process products. The stable regions for $Ca(OH)_2$ and $Mg(OH)_2$ in Pourbaix diagram were found to be increased as temperature rises and the equilibrium reaction between $Ca^{2+}$ and $Ca(OH)_2$ was investigated to be more strongly influence by temperature change compared with the equilibrium reaction between $Mg^{2+}$ and $Mg(OH)_2$. The amounts of $CaSO_4$ and $MgSO_4$ were anticipated to be decreased with temperature considering the thermal characteristics for the equilibrium reactions regarding calcium, magnesium, and $H_2SO_4$. It was understood that the formation ratio between $CaSO_4$ and $MgSO_4$ is greater than the composition ratio between calcium and magnesium contained in dolomite at specific temperature and the decrease of the formation ratio of $CaSO_4$ and $MgSO_4$ with temperature was estimated to be diminished as the content of calcium in dolomite is increased. In addition, the extent of the change in the compositional ratio between absorption process products was examined to be reduced compared with the composition of raw material as the calcium content in dolomite is raised.