• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.897-905
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• 2007

Approximately 70% of Korea is composed of forest areas. Especially 48% of agricultural field is practiced at highland areas over 400 m in elevation in Kangwon province. Over 90% of highland agricultural farming is located at Kangwon province. Runoff characteristics at the mountainous area such as Kangwon province are largely affected by steep slopes, thus runoff estimation considering field slopes needs to be utilized for accurate estimation of direct runoff. Although many methods for runoff estimation are available, the Soil Conservation Service (SCS), now Natural Resource Conservation Service (NRCS), Curve Number (CN)-based method is used in this study. The CN values were obtained from many plot-years dataset obtained from mid-west areas of the United States, where most of the areas have less than 5% in slopes. Thus, the CN method is not suitable for accurate runoff estimation where significant areas are over 5% in slopes. Therefore, the CN values were adjusted based on the average slopes (25.8% at Doam-dam watershed) depending on the 5-day Antecedent Moisture Condition (AMC). In this study, the CN-based Long-Term Hydrologic Impact Assessment (L-THIA) direct runoff estimation model used and the Web-based Hydrograph Analysis Tool (WHAT) was used for direct runoff separation from the stream flow data. The $R^2$ value was 0.65 and the Nash-Sutcliffe coefficient value was 0.60 when no slope adjustment was made in CN method. However, the $R^2$ value was 0.69 and the Nash-Sutcliffe value was 0.69 with slope adjustment. As shown in this study, it is strongly recommended the slope adjustment in the CN direct runoff estimation should be made for accurate direct runoff prediction using the CN-based L-THIA model when applied to steep mountainous areas.

• Ocean and Polar Research
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• v.42 no.1
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• pp.49-61
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• 2020

We analyzed the morphological characteristics of OCC (Ocean Core Complexes) in the middle part of the Central Indian Ridge (MCIR) using high-resolution geophysical data recorded on the Deep-Tow SideScan Sonar IMI-30 system. In terms of slope-gradient variations calculated from the high-resolution bathymetry data, the normal faults formed by seafloor spreading were associated generally with slopes > 30° and resulted in high backscatter intensities, which reflect more topographic effects than acoustic medium variation. However, the areas associated with gentle slopes < 10° tend to show the backscatter intensities reflecting the acoustic characteristic of the medium. We show that the detachment faults exposing the OCCs were initiated with high-angle normal faults (58°) exhibiting outward and inward dips of a breakaway zone. In order to examine the spatial distribution of OCC structures, we characterized the transition from magmatic-dominant seafloor with abyssal hills to tectonic-dominant seafloor with OCC using the down-slope direction variation. The slope direction of the seafloor generally tends to be perpendicular to the ridge azimuth in the magmatic-dominant zone, whereas it becomes parallel to the given ridge azimuth near the OCC structures. Therefore, this spatial change of seafloor slope directions indicates that the formation of OCC structures is causally associated with the tectonic-dominant spreading rather than magmatic extension. These results also suggest that the topographical characteristics of seafloor spreading and OCC structures can be distinguished using high-resolution geophysical data. Thus, we propose that the high-resolution bathymetry and backscatter intensity data can help select potential areas of exploitation of hydrothermal deposits in MCIR effectively.

• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.118-127
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• 2015

Because streams have a great diversity of morphological features according to their reaches, it is necessary to classify the types of streams in order to assess their characteristics of channel. In addition, a quantitative assessment system for channel characteristics should be reflected in the stream type properties. Therefore, this study compares two stream classification system (Rosgen's and Yamamoto's) to review their applicability on Korean streams, and the two classification systems were applied on the Nam River. In order for the mean bed slope and the longitudinal connectivity of the provincial and national streams to be reflected in the assessment system of channel characteristics, the Yamamoto system is considered highly adaptable in the stream geomorphology side. In addition, it has been found the Rosgen system has a low correlation of bed slope compared to the Yamamoto system in the view of bed materials. On the other hand, the Yamamoto system was found to be capable of reflecting sediment sorting (hydraulic sorting) of the bed slope. According to the results obtained at the Nam River, the Rosgen system could not classify a type of stream by relationship between bed material and bed slope, but the Yamamoto system can verify the correlation of stream type. However, further review is needed with respect to the applicability of natural rivers. Three types of stream that can be applied to the assessment system of channel characteristics were proposed.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.340-351
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• 2023

Landslides are major natural geological hazards that cause enormous property damage and human casualties annually. The vulnerability of mountainous areas to landslides is further exacerbated by the impacts of climate change. Soil depth is a crucial parameter in landslide and debris flow analysis, and plays an important role in the evaluation of watershed hydrological processes that affect slope stability. An accurate method of estimating soil depth is to directly investigate the soil strata in the field. However, this requires significant amounts of time and money; thus, numerous models for predicting soil depth have been proposed. However, they still have limitations in terms of practicality and accuracy. In this study, 71 seismic survey results were collected from domestic mountainous areas to estimate soil depth on hill slopes. Soil depth was estimated on the basis of a shear wave velocity of 700 m/s, and a database was established for slope angle, elevation, and soil depth. Consequently, the statistical characteristics of soil depth were analyzed, and the correlations between slope angle and soil depth, and between elevation and soil depth were investigated. Moreover, various soil depth prediction models based on slope angle were investigated, and corrected linear and exponential soil depth prediction models were proposed.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.65-73
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• 2008

In the current practice for slope stability problem in Japan, the shear strength, $\tau$, mobilized along the failure surface is usually estimated based on an empirical approximation in which the cohesion, c, is assumed to be equal to the soil thickness above the supposed slip surface, d(m). This approximation is advantageous in that the result of stability analysis is not influenced by the designers in charge. However, since the methodology has little theoretical background, the cohesion may often be grossly overestimated, and conversely the angle of shear resistance, $\phi$, is significantly underestimated, when the soil thickness above the supposed slip surface is quite large. In this paper, a case record of natural slope failure that took place in Hyogo Prefecture in 2007, is described in detail for the case in which the shear strength along the collapsed surface was carefully examined in a series of direct shear box (DSB) tests by considering the effects of in-situ shear stress along the slip surface. It is demonstrated that the factor of safety agrees with that of in-situ conditions when the shear strength from this kind of DSB test was employed for the back-analysis of the slope failure.

• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.347-355
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• 2002

We have constructed a high efficiency and broad tunable cw Ti:sapphire laser with a four-mirror symmetric Z-type laser cavity to increase the laser usability. From theoretical analyses and experimental data for a symmetric Z-type laser cavity containing a Kerr medium, the cavity mode size and the Kerr-lens mode-locking (KLM) strength for KLM lasers can be confirmed as function of the position in the cavity, the intracavity laser power, and the stability parameter. As a result, the slope efficiency and the maximum average output power of cw Ti:sapphire laser at 5 W pumping power of Ar-ion laser were 31.3% and 1420 ㎽ respectively. The tunablility was ranged from 730 ㎚ to 908 ㎚ with average output power above 700 ㎽. We obtained the KLM operation easily by self-aperturing effect in the Kerr medium and the slope efficiency and the maximum average output power of KLM Ti:sapphire laser was 16% and 550 ㎽ respectively. The spectral bandwidth was 33 ㎚ at the center wavelength of 807 ㎚ and the pulse width was 27 fs with a repetition rate of 82 ㎒.

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.323-332
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• 1988

The bacteria containing urease convert each molecule of urea into two molecules of ammonia and one molecule of carbon dioxide gas. Bacterial electrodes have been constructed by immobilizing the Proteus vulgaris on an ammonia and a carbon dioxide gas-sensors, and were investigated for the effects of pH, temperature, buffer solution, bacterial amounts and interferences, and life time. NH3-bacterial electrode based on ammonia gas-sensor had linearity in the range of $7.0{\times}10^{-4}\;-\;3.0{\times}10^{-2}$M urea in pH 7.4, 0.05M phosphate buffer at $25^{\circ}C$ with a slope of 116.7 mV/decade. While $CO_{2-}$bacterial electrode based on carbon dioxide gas-sensor bad linearity in the range of $7.0{\times}10^{-4}\;-\;5. 0{\times}10^{-2}$M urea in pH 7.0, 0.1M phosphate buffer at $30^{\circ}C$with a slope of $45.4{\times}45.7mV/decade$. As the clinical application, urea in urine was determined by these devices and this result was compared with spectrophotometric method. Consequently, these electrodes could be used for the analysis of many samples because of simplicity, rapidity and convenience of the experimental procedure.

• Korean Journal of Environment and Ecology
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• v.21 no.6
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• pp.559-564
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• 2007

This research is aimed at finding out the ecological change of Seunghwanglim through the examination of vegetational change of tree seedlings of old giant trees growing at Seunghwanglim [Seunghwang Forest designated as a Natural Monument No.93] after the installation of protective iron fence. The survey results are as follows: First, as a result of keeping out people by installing a protective iron fence in 1989, soil hardness of the plane forest was greatly improved except the area used as roads. The seedlings of the plane forest, whose damage index is 2,3,4, were found to have the highest 1,202 $individuals/400m^2$, and those of the plane forest, whose damage index is 1, were revealed to have 565 $individuals/400m^2$, and those of the slope forest were found to have 403 $individuals/400m^2$. The number of the young sapling[taller than 2 meters] individuals of the plane forest whose damage index is 1 was found to be the most $48/400m^2$, and that of the plane forest whose damage index is 2, 3, 4- was $31/400m^2$, and that of the slope forest proved to be $14/400m^2$. In the plane forest whose damage index is 2, 3, 4, the saplings of the Ulmus davidiana var. japonica and Acer triflorum are relatively much distributed, and in the plane forest whose damage index is 1, many saplings of the Prunus padus and Styrax obassia, were found to grow and in the slope forest, many saplings of the Acer pictum subsp. mono and Acer pseudo-sieboldianum. were found to grow. Many seedlings of Rubus spp. - R. oldhamii, R. coreanus and R. crataegifolius. - and Akebia quinata were growing vigorously on plane forest, but they might decrease in number with the increasing number of the tree saplings.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.3
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• pp.175-183
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• 2020

There have rarely been performed for the clay mineralogy of the East Sea sediments except for few studies about paleoenvironmental aspect. This study inferred the provenance of sediments based on the clay mineral characteristics and distribution pattern for the 120 sediment samples collected by the box corer from the Gangneung-Donghae area between 2017-2019. The relative proportions of the four major clay minerals are abundant in the order of illite, chlorite, kaolinite, and smectite. The continental shelf sediments below water depth 150 m have more chlorite and kaolinite content and better illite crystallinity, but less illite and smectite content, and S/I index than those of continental slope sediments. Clay mineral composition of the continental shelf sediments are influenced by the adjacent continental geology, because north site (Gangneung area) has more chlorite but south site (Donghae area) has more kaolinite. These characteristics and distribution pattern of clay minerals indicate that the provenance of sediments are different between continental shelf and continental slop. The continental shelf sediments may be introduced the study area by the adjacent small rivers whereas the continental slope sediment might be supplied by current from the south of the study area.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.51-61
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• 2016

New building methods are needed to aid increased inner-city redevelopment and industrial construction. A particular area of improvement is the efficient use of cut slopes, with the minimization of associated problems. A retaining wall of precast panels can resist the horizontal earth pressure by increasing the shear strength of the ground and reinforcing it through contact with the panels. Precast panels allow quick construction and avoid the problem of concrete deterioration. Other problems to be solved include the digging of borrow pits, the disposal of material cut from the slope, and degradation of the landscape caused by the exposed concrete retaining wall.This study suggest the methods of improvement of an existing precast panel wall system by changing the appearance of the panels to that of natural rock and improving the process of adhering the panel to a vertical slope. The panels were tested in the laboratory and in the field. The laboratory test verified their specific strength and behavior, and the field test assessed the panels' ground adherence at a vertical cutting. Reinforcement of the cutting slope was also measured and compared with the results of 3D numerical analysis. The results of laboratory test, identified that the shear bar increase the punching resistance of panel. And as a results of test construction, identified the construct ability and field applicability of the panel wall system adhered to in-situ ground. In addition to that, extended measurement and numerical analysis, identified the long-term stability of panel wall system adhered to in-situ ground.