• Journal of The Geomorphological Association of Korea
• /
• v.26 no.1
• /
• pp.1-14
• /
• 2019

Large landslide is a type of mass movement that causes drastic landform changesin a short period, and it causes huge human and property damage over a large area. The purpose of this study is to categorize the types and characteristics of large landslides around the Kokomeren River basin, Kyrgyzstan and to discuss the geomorphic development after the large landslides. The topographic analysis about a total of 20 landslides documented collapsed volumes of 0.01 to 1.10 km³, height drops of 180 to 1,770 m, and runout distances of 1,200 to 5,400 m. Rock avalanche and rockslide are identified as major types of large-scale landslides in the study area. Rock avalanches can be divided into P-type, J-type, and S-type based on the features of slope failure and kinematic characteristics of rock debris. Landslide synchronistic landforms such as trimlines, transverse ridges, longitudinal ridges, levees, and hummocks are well developed in the rock avalanche. The pieces of evidence of landslide dam, landslide-dammed lake, and remnant outburst flood deposits are observed in the upstream and downstream where the rockslides occurred. The Ak-Kiol landslide dam is the best example of a geomorphic development due to lake spillover and the large landslides were likely to be triggered by huge paleo-seismic events.

• Current Optics and Photonics
• /
• v.7 no.5
• /
• pp.529-536
• /
• 2023

The Morlet wavelet transform method is proposed to analyze a single interferogram with spatial carrier frequency that is captured by an optical interferometer. The method can retain low frequency components that contain the phase information of a measured optical surface, and remove high frequency disturbances by wavelet decomposition and reconstruction. The key to retrieving the phases from the low-frequency wavelet components is to extract wavelet ridges by calculating the maximum value of the wavelet transform amplitude. Afterwards, the wrapped phases can be accurately solved by multiple iterative calculations on wavelet ridges. Finally, we can reconstruct the wave-front of the measured optical element by applying two-dimensional discrete cosine transform to those wrapped phases. Morlet wavelet transform does not need to remove the spatial carrier frequency components manually in the processing of interferogram analysis, but the step is necessary in the Fourier transform algorithm. So, the Morlet wavelet simplifies the process of the analysis of interference fringe patterns compared to Fourier transform. Consequently, wavelet transform is more suitable for automated programming analysis of interference fringes and avoiding the introduction of additional errors compared with Fourier transform.

• Journal of the Korean Geographical Society
• /
• v.43 no.3
• /
• pp.276-295
• /
• 2008

Recent disputes on mountain ranges in Korea have partially been derived from the discordance of the spatial distribution and the extent of mountain ranges presented by different researchers and school textbooks. The lack of consensus on the definition and genesis of mountain ranges adds further confusion. In order to overcome these problems, it is necessary to provide genetically classified mountain range maps for different usages, map scales and educational purposes. This paper first argues that mountain ranges and mountain ridges should separately be used as different conceptual frameworks to explain complex spatial distribution of mountains in Korea. The new mountain range map (sanmaekdo) proposed in this research puts strong emphasis on tectonic movement and denudational processes to explain the spatial distribution of mountains. The new mountain range map has 15 mountain ranges (sanmaek: in total, which are further divided into 7 primary and 8 secondary mountain ranges. The new mountain range map eliminates Jeogyuryeongsanmaek, Myohyangsanmaek, Myeoraksanmaek, and Masingnyeongsanmaek from the existing map, since these have a vague definition and obscure spatial distribution. On the contrary, few new primary mountain ranges (Gilju-Myeongcheonsanmaek, Yangsansanmaek, Jirisanmaek) and secondary mountain ranges (Wolchulsanmaek and Buksubaeksanmaek) are added to the new mountain range map. Other mountain ranges also show a large difference both in their spatial distribution and the extent of mountain ranges, compared with the previous map. This is especially the case for Nangnimsanmaek, Hamgyeongsanmaek, Taebaeksanmaek, and Sobaeksanmaek. A few new names are also assigned to Macheollyeongsanmaek (Baekdusanmaek), Gwangjusanmaek (Hwaaksanmaek), Charyeongsanmaek (Chiaksanmaek), and Horyeongsanmaek (Naejangsanmaek), even though they show similar spatial distribution patterns with the ones in the existing map.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.20 no.2
• /
• pp.166-174
• /
• 1987

Distribution, bathymetry and textural parameters of the bottom sediment deposited between Geoje and Namhae Islands were studied to understand the depositional environment of the area. The study area is divided into three different provinces. Except for the Gwangyang Bay and Changseon Channel, mud dominates in the western part whereas sandy mud and muddy sand prevail in the southeastern part including the eastern area of the Yogji Island. The relict sediment is located in the eastern part of the area. Generally, the Holocene sediment, located in the northern part of the area, is considered to be transported and deposited by a pelagic suspension mode. Influence of strong tidal currents results in some depressions in the vicinity of Changseon Island and the eastern part of the Yogji Island, The Tsushima Warm Current is supposed to affect the southern part of the area. The two parallels sand ridges lying in the southeastern part of the area are covered with very thin Holocene mud. This seems to be caused by the winnowing effect of the current. The similarity between the two directions of the current and the ridges encourages this idea. The boundary between the Holocene and relict sediment, however, lies further south the ridges.

• Journal of the Korean earth science society
• /
• v.33 no.3
• /
• pp.242-258
• /
• 2012

The Yellow Sea has sensitively responded to high-amplitude sea-level fluctuations during the late Quaternary. The repeated inundation and exposure have produced distinct transgression-regression successions with extensive exposure surfaces in Kyeonggi Bay. The late Quaternary strata consist of four seismic stratigraphic units, considered as depositional sequences (DS-1, DS-2, DS-3, and DS-4). DS-1 was interpreted as ridge-forming sediments of tidal-flat and estuarine channel-fill facies, formed during the Holocene highstand. DS-2 consists of shallow-marine facies in offshore area, which was formed during the regression of Marine Isotope Stage (MIS)-3 period. DS-3 comprises the lower transgressive facies and the upper highstand tidal-flat facies in proximal ridges and forced regression facies in distal ridges and offshore area. The lowermost DS-4 rests on acoustic basement rocks, considered as the shallow-marine and shelf deposits formed before the MIS-6 lowstand. This study suggests six depositional stages. During the first stage-A, MIS-6 lowstand, the Yellow Sea shelf was subaerially exposed with intensive fluvial incision and weathering. The subsequent rapid and high amplitude rise of sea level in stage-B until the MIS-5e highstand produced transgressive deposits in the lowermost part of the MIS-5 sequence, and the successive regression during the MIS-5d to -5a and the MIS-4 lowstand formed the upperpart of the MIS-5 sequence in stage-C. During the stage-D, from the MIS-4 lowstand to MIS-3c highstand period, the transgressive MIS-3 sequence formed in a subtidal environment characterized by repetitive fluvial incision and channel-fill deposition in exposed area. The subsequent sea-level fall culminating the last glacial maximum (Stage-E) made shallow-marine regressive deposits of MIS-3 sequence in offshore distal area, whereas it formed fluvial channel-fills and floodplain deposits in the proximal area. After the last glacial maximum, the overall Yellow Sea shelf was inundated by the Holocene transgression and highstand (Stage-F), forming the Holocene transgressive shelf sands and tidal ridges.

• Applied Microscopy
• /
• v.32 no.1
• /
• pp.57-66
• /
• 2002

The structures of sucker of two Cobiidae; Common freshwater goby and Triden goby were observed by light and electron microscopy. Scanning electron microscopy revealed the characteristic narrow ridges and grooves on the apical portion of sucker of Common freshwater goby, and hexagonal structures similar to a honeycomb representing the intercellular junctional area on the middle and basal portions. Some ridges were present on the epithelial surface on the middle and basal portions. The openings of several mucus-secreting cells were present between main epithelial cells. Light and transmission electron microscopy revealed the core of the fin; soft rays with a surrounding dense collagen fiber layer. Some loosely arranged fibers (collagen fiber) radiated toward the surface epithelium. The surface epithelium was cuboidal or columnar in shape. Scanning electron microscopy revealed the coiled irregular ridges and grooves, which was less developed and had sparser distribution than in Common freshwater goby, on the apical portion of sucker of Triden goby. The middle and basal portions had honeycomb structures as in Common freshwater goby. Fewer mucoussecreting cells were present. Light and transmission electron microscopy showed the core of soft rays, dense collagen fiber layer, however, the radiating fibers observed in the Common freshwater goby was rarely present. The sucker was thinner because the epithelium is squamous or polygonal in shape and rare presence of the radiating fibers.

• Journal of the Korean Geophysical Society
• /
• v.2 no.3
• /
• pp.191-200
• /
• 1999

Analysis of chirp high-resolution seismic profiles from the central Yellow Sea reveals that depositional environments in this area can be divided into three distinctive zones from west to east: (1) subaqueous delta system near the Shandong Peninsula, (2) erosional zone in the central Yellow Sea, and (3) tidal sand ridges and sand waves near the Korean Peninsula. The Shandong subaqueous delta, extending southward from the Shandong Peninsula, changes gradually into prodelta southeastward. The sediments originated from the Yellow River are transported southward along the Chinese coastal area. The erosional zone in the central Yellow Sea contains numerous paleochannels and shows linear erosional features trending northwest-southeast. The erosional zone would be dominated by non-depositional or erosional processes during the Holocene. Tidal sand ridges and sand waves are well developed along the western coast of Korea. The residual sands, which were originally fluvial sediments at the sea-level lowstand, are interpreted as the result of winnowing process during the sea-level rise. Modern sand ridges generally migrates in a northeast-southwestern direction, which coincide with dominant tidal current direction.

• Journal of Bio-Environment Control
• /
• v.28 no.4
• /
• pp.388-395
• /
• 2019

The purpose of this study is to suggest structural model and analyze design factors for the development of small greenhouse standardization model. The average dimensions of small greenhouse desired by urban farmers were 3.3m in width, 1.9m in eaves height, 2.7m in ridge height, 5.7m in length. The cladding materials for small greenhouse were preferred to glass, PC board and plastic film, framework to aluminum alloy and steel, and heating method in electrical energy. In addition, it was analyzed that small greenhouses need to develop structural model by dividing them into entry-level type and high-level type. The roof type that was used for entry-level type was arch shape, framework was steel pipe, cladding material was plastic film. On the other hand, high-level type was used in even span or dutch light type, framework with square hollow steel, cladding materials with glass or PC board. In consideration of these findings and practicality, this study developed four types of small greenhouses. The width, eaves height, ridges height, and length of the small greenhouses of even span type, which were covered with 5mm thick glass and 6mm thick PC board were 3m, 2.2m, 2.9m, and 6m, respectively. The small greenhouse of dutch light type covered with 5mm thick glass was designed with 3.8m in with, 2.2m in eaves height, 2.9m in ridges height, and 6m in length. The width, eaves height, ridges height, and length of the arch shape small greenhouse covered with a 0.15mm PO film were 3m, 1.5m, 2.8m, and 6m, respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.27 no.1
• /
• pp.33-47
• /
• 2022

In this study, distribution of submarine sand ridges in the coastal waters of Korea was surveyed using multibeam echo sounder data, and the topographic characteristics of each region were identified. For this purpose, the DEM (Digital Elevation Model) data was generated using depth data obtained from the Yellow Sea and the South Sea by Korea Hydrographic and Oceanographic Agency, and then applied the TPI (Topographic Position Index) technique to precisely extract the boundary of the sand ridges. As a result, a total of 200 sand ridges distributed in the coastal waters were identified, and the characteristics of each region of the sedimentary sediments were analyzed by performing statistical analysis on the scale (width, length, perimeter, area, height) and shape (width/length ratio, height/width ratio, linear·branch type, exposure·non-exposure type). The results of this study are expected to be used not only for coastal navigational safety, but also for marine naming support, marine aggregate resource identification, and fisheries resource management.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.03a
• /
• pp.47-78
• /
• 1999

About 440,000 $\textrm{km}^2$, about twice the size of the Korean Peninsula is covered by loess deposits in China. Along the middle reaches of the Huanghe River, mainly in Shaanxi and in Gansu province loess plateau covers vast area amounting to 273,000 $\textrm{km}^2$ Chinese studies on loess and loessial slopes are summarized. And some of the U. S. study and others are also presented for comparison.