• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.1-11
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• 2008

To overcome the mid frequency limitation of geometrical acoustic techniques, the phased geometrical method was suggested by introducing the phase information into the sound propagation from the source. By virtue of phase information, the phased tracing method has a definite benefit in taking the interference phenomenon at mid frequencies into account. Still, this analysis technique has suffered from difficulties in dealing with low frequency phenomena, so called, wave nature of sound. At low frequencies, diffraction at corners, edges, and obstacles can cause errors in simulating the transfer function and the impulse response. Due to the use of real valued absorption coefficient, simulated results have shown a discrepancy with measured data. Thus, incorrect phase of the reflection characteristic of a wall should be corrected. In this work, the uniform theory of diffraction was integrated into the phased beam tracing method (PBTM) and the result was compared to the ordinary PBTM. By changing the phase of the reflection coefficient, effects of phase information were investigated. Incorporating such error compensation methods, the acoustic prediction by PBTM can be further extended to low frequency range with improved accuracy in the room acoustic field.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.229-238
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• 2006

This paper shows the analytic error caused by the inconsistency of the approximation order between the non local boundary condition (NLBC) and the parabolic governing equation. To obtain the analytic error, we first transform the NLBC to the half space domain using plane wave analysis. Then, the analytic error is derived on the boundary between the true numerical domain and the half space domain equivalent to the NLBC. The derived analytic error is physically expressed as the artificial reflection. We examine the characteristic of the analytic error for the grazing angle, the approximation order of the PE or the NLBC. Our main contribution is to present the analytic method of error estimation and the application limit for the high order parabolic equation and the NLBC.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.203-218
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• 2010

The site categorization and corresponding site amplification factors in the current Korean seismic design guideline are based on provisions for the western United States (US), although the site effects resulting in the amplification of earthquake ground motions are directly dependent on the regional and local site characteristic conditions. In these seismic codes, two amplification factors called site coefficients, $F_a$ and $F_v$, for the short-period band and midperiod band, respectively, are listed according to a criterion, mean shear wave velocity ($V_S$) to a depth of 30 m, into five classes composed of A to E. To suggest a site classification system reflecting Korean site conditions, in this study, systematic site characterization was carried out at four regional areas, Gyeongju, Hongsung, Haemi and Sacheon, to obtain the $V_S$ profiles from surface to bedrock in field and the non-linear soil properties in laboratory. The soil deposits in Korea, which were shallower and stiffer than those in the western US, were examined, and thus the site period in Korea was distributed in the low and narrow band comparing with those in western US. Based on the geotechnical characteristic properties obtained in the field and laboratory, various site-specific seismic response analyses were conducted for total 75 sites by adopting both equivalent-linear and non-linear methods. The analysis results showed that the site coefficients specified in the current Korean provision underestimate the ground motion in the short-period range and overestimate in the mid-period range. These differences can be explained by the differences in the local site characteristics including the depth to bedrock between Korea and western US. Based on the analysis results in this study and the prior research results for the Korean peninsula, new site classification system was developed by introducing the site period as representative criterion and the mean $V_S$ to a depth of shallower than 30 m as additional criterion, to reliably determine the ground motions and the corresponding design spectra taking into account the regional site characteristics in Korea.

• Journal of the Korean Wood Science and Technology
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• v.11 no.3
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• pp.58-69
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• 1983

This research is performed to compare lignin compounds isolated in Pinus koraiensis Sieb et Zucco, with those compounds which have been already isolated. and to elucidate IR spectra of functional groups and aromatic nucleus for chemical structure of lignin. In vanillin and dehydrodivanillin having carbonyl group ill ${\alpha}$-position. characteristic absorption band of carbonyl group was confirmed in 1665 $cm^{-1}$. Absorption band of vanillic and syringic acid with carboxyl group were indicated in 1675 and 1690 $cm^{-1}$ respectively. Syringic acid showed low wave number because this was affected by methoxyl group. Characteristic absorption bands of guaiacyl, syringly and guaiacyl-syringyl co-polymer nucleus were clearly disclosed in diarylpropane compounds. It were reconfirmed that absorption band of guaiacyl showed longer wave number than of syringly nucleus.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.279-299
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• 2019

Recently occurred earthquake Gyeongju and Pohang served as a momentum to remind that Korean peninsular is not a safety zone from earthquake anymore. The importance of seismic design, therefore, have been realized and researches regarding design response spectrum have been actively carried out by many researchers and engineers. Current tunnel seismic design method is conducted to check safety of tunnel structure by dynamic numerical analysis with condition of completed lining installation, so, it is impossible to consider safety of tunnel behavior under construction. In this study, therefore, dynamic numerical analysis considering seismic wave propagations has been performed after back analysis using results from field monitoring of tunnel under construction in fractured zone and 1st reinforcement (shotcrete, rockbolt) behaviour are analyzed. Waves are classified by period characteristic (short and long). As a result, the difference depending on period characteristic is minor, and increasements of displacement are obtained at crown displacement due to seismic wave is 28~31%, 14~16% at left side of tunnel in the fractured zone, 13~27% at right side of tunnel in the bed rock, respectively. In case of shotcrete axial force is increased 113~115% at tunnel crown, 102% at left side, 106~110% at right side, respectively. Displacement and axial force of rockbolts which are selected by type of anchored grounds (only fractured zone, fractured zone and bed rock, only bedrock) are analyzed, as a result, rockbolt which is anchored to fractured zone and bed rock at the same time are weaker than any other case.

• Journal of the Korean Institute of Landscape Architecture
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• v.47 no.1
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• pp.26-38
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• 2019

This study is based on the analysis of the characteristics of waterfront scenery. Recently, waterfront development has expanded residentially, commercially and into leisure space. In the development of the waterfront, it is necessary to apply designs suitable for urban and various other waterfront areas. In this study, the natural scenery of the waterfront was researched with respect to the Korean Jingyeong landscape paintings and the main elements of the scenery were analyzed. In this study, 105 painting of Korean Jingyeong landscapes paintings were selected for the analysis of the waterside scenery. The paintings of Jeong Seon were studied to categorize streams topographically into mountainous, upper, middle, lower, and ocean types. In addition, major micro-topography elements, which are 13 water image elements and 13 staffage elements were analyzed. The main waterfront landscape elements are divided into 13 types. The waterfalls were divided into long waterfalls, short waterfalls, cascading waterfalls, and other aspects considered were line stream, curve stream, multi-curve stream, pond, water surface, flow surface, wave surface, rock side, pile sandy side, sandy side. There are 13 kinds of staffage elements, include pine forest, pine trees, fir trees, bamboo trees, willow trees, broadleaf tree, villages, houses, gazebo, boat, bridges, and people. The waterfront landscape by a river area was explained according to each characteristic of the waterfront landscape and staffage, and their changes were analyzed in each area. The 105 paintings were divided into 35 pieces of mountainous streams, 9 upper streams, 5 middle streams, 35 lower streams, and 21 oceans, and the change of each waterfront landscape and staffage was analyzed. Based on the topographical analysis of the waterfront landscape and staffage, the results can be summarized into 5 types of the waterfront landscape. Based on the micro-topographical characteristics of the waterfront landscape styles are as follow. In the mountainous streams, long waterfall and deep forest type are apparent, which depicts deep mountain waterfall scenery, and a multi-stream forest is the scenery of a picnic in the mountains, which is a representative form of mountainous streams landscape. In the upper-middle stream, the water-surface and gazebo type is predominant. In the lower stream, the sandy-gazebo typ scenery is predominant and the sandy depiction is unique to lower stream landscape. Pile sandy-dock type is life scenes where human activity highlighted, is a representative form of the lower stream landscapes. The characteristic of the coastal landscape is the serpentine rock scenery on the beach and the wave-serpentine rock type that forms the main coastal landscape. The study aims to propose significant design elements for a natural waterfront landscape planning based on the analysis of landscape in the paintings of Jeong Seon.

• Journal of the Mineralogical Society of Korea
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• v.27 no.1
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• pp.1-15
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• 2014

Probing the electronic structures of crystalline Mg-silicates at high pressure is essential for understanding the various macroscopic properties of mantle materials in Earth's interior. Quantum chemical calculations based on the density functional theory are used to explore the atomic configuration and electronic structures of Earth materials at high pressure. Here, we calculate the partial density of states (PDOS) and O K-edge energy-loss near-edge structure (ELNES) spectra for $MgSiO_3$ perovskite at 25 GPa and 120 GPa using the WIEN2k program based on the full-potential linearized projected augmented wave (FP-LPAW) method. The calculated PDOS and O K-edge ELNES spectra for $MgSiO_3$ Pv show significant pressure-induced changes in their characteristic spectral features and relative peak intensity. These changes in spectral features of $MgSiO_3$ Pv indicate that the pressure-induced changes in local atomic configuration around O atoms such as Si-O, O-O, and Mg-O length can induce the significant changes on the local electronic structures around O atoms. The result also indicates that the significant changes in O K-edge features can results from the topological densification at constant Si coordination number. This study can provide a unique opportunity to understand the atomistic origins of pressure-induced changes in local electronic structures of crystalline and amorphous $MgSiO_3$ at high pressure more systematically.

• Atmosphere
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• v.28 no.3
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• pp.305-315
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• 2018

This study investigates the characteristic spatial patterns and dynamic processes associated with the summertime extreme temperature events in South Korea during the last 20 years (1995~2014) using Self-Organizing Map (SOM). The classified SOM patterns commonly have high temperature and anticyclonic circulation anomalies over South Korea. The two major teleconnection patterns are identified: one is from the subtropical western North Pacific (WNP) affecting to the north and the other is from the North Atlantic (NA) affecting downstream region. The meridional teleconnection pattern is related to the forcing of positive sea surface temperature (SST) anomaly over the WNP. The northward propagating Rossby wave generates the East Asia-Pacific (EAP) pattern to form an anticyclonic circulation anomaly over South Korea. On the other hand, NA SST anomalies generate an eastward Rossby wave train across the Eurasian continent, leading to the development of an anticyclonic circulation anomaly over South Korea. The EAP pattern occurs more frequently in July and August, whereas the midlatitude teleconnection pattern associated with NA SST anomalies develops more frequently in early summer (June).

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.45-51
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• 2003

Grouting materials in rock is grouted as vein type along the fault surface by the other way for soil and allow a change of characteristics in rock faults as a result of that. Therefore the deformation characteristics of rock faults after grouting differ as a direction and characteristic of grouted fault and stress condition of field rock. Thereby it must be analyzed the effect for deformation of rock according to characteristics of rock faults and characteristics of grouting materials to accurately evaluate the reinforced effect by grouting. But grouting method used in field until present depends on experience of workers, and inspection for those effects are evaluated by measurement of elastic wave velocity, permeability tests and etc. in field. In this study, it was investigated that the effects for shear characteristics of maximum shear strength, residual shear strength and etc. by comparison and analysis of test results which were worked by direct shear tests of rock faults with changing a type of grouting materials and the grouting depth(t) for average width(a) of fault surface roughness when OPC(Ordinary Portland Cement) and Micro cement was grouted in fault surface of field rock to evaluate characteristicsof the shear deformation for rock fault surface of dam by grouting.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.329-337
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• 2006

A small hydro-power plant operated by cooling water discharged from the power plant is under construction. In this study, the flow characteristics of the effluent channel and the outfall coastal zone in which the facilities are constructed have been measured and analysed. The flow pattern is highly dependent on the effluent discharge and clearly classified as these typical areas; the upstream and downstream areas of the weir, and the outfall coastal zone. The discharge and the width of the channel in the upstream area of the weir are increased step by step, so the water level fluctuation is small. The flow overtopping the weir is rapidly changing and has highly vertical fluctuation patterns after hydraulic jump just below the weir. The flow pattern in the outfall zone is directed toward the seaward direction and the velocity is dominated by the tidal level fluctuation. The mean tidal range in this area is about 10% greater than that of the Tongyeong tidal gauging station and the wave effects are negligible because of the sheltering effects of this area.